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In special relativity, an observer moving with uniform proper acceleration through Minkowski spacetime is conveniently described with Rindler coordinates, which are related to the standard (Cartesian) Minkowski coordinates by
The line element in Rindler coordinates, i.e. Rindler space is
where , and where is related to the observer's proper time by (here ).
An observer moving with fixed traces out a hyperbola in Minkowski space, therefore this type of motion is called hyperbolic motion. The coordinate is related to the Schwarzschild spherical coordinate by the relation
An observer moving along a path of constant is uniformly accelerating, and is coupled to field modes which have a definite steady frequency as a function of . These modes are constantly Doppler shifted relative to ordinary Minkowski time as the detector accelerates, and they change in frequency by enormous factors, even after only a short proper time.
Translation in is a symmetry of Minkowski space: it can be shown that it corresponds to a boost in x, t coordinate around the origin. Any time translation in quantum mechanics is generated by the Hamiltonian operator. For a detector coupled to modes with a definite frequency in , we can treat as "time" and the boost operator is then the corresponding Hamiltonian. In Euclidean field theory, where the minus sign in front of the time in the Rindler metric is changed to a plus sign by multiplying to the Rindler time, i.e. a Wick rotation or imaginary time, the Rindler metric is turned into a polar-coordinate-like metric. Therefore any rotations must close themselves after 2 in a Euclidean metric to avoid being singular. So
A path integral with real time coordinate is dual to a thermal partition function, related by a Wick rotation. The periodicity of imaginary time corresponds to a temperature of in thermal quantum field theory. Note that the path integral for this Hamiltonian is closed with period 2. This means that the modes are thermally occupied with temperature . This is not an actual temperature, because is dimensionless. It is conjugate to the timelike polar angle , which is also dimensionless. To restore the length dimension, note that a mode of fixed frequency in at position has a frequency which is determined by the square root of the (absolute value of the) metric at , the redshift factor. This can be seen by transforming the time coordinate of a Rindler observer at fixed to an inertial, co-moving observer observing a proper time. From the Rindler-line-element given above, this is just . The actual inverse temperature at this point is therefore
It can be shown that the acceleration of a trajectory at constant in Rindler coordinates is equal to , so the actual inverse temperature observed is
Restoring units yields
The temperature of the vacuum, seen by an isolated observer accelerating at the Earth's gravitational acceleration of = , is only . For an experimental test of the Unruh effect it is planned to use accelerations up to , which would give a temperature of about .
The Rindler derivation of the Unruh effect is unsatisfactory to some, since the detector's path is super-deterministic. Unruh later developed the Unruh–DeWitt particle detector model to circumvent this objection. | 0 | Theoretical and Fundamental Chemistry |
PCLake is a dynamic, mathematical model used to study eutrophication effects in shallow lakes and ponds. PCLake models explicitly the most important biotic groups and their interrelations, within the general framework of nutrient cycles. PCLake is used both by scientist and water managers. PCLake is in 2019 extended to PCLake+, which can be applied to stratifying lakes. | 1 | Applied and Interdisciplinary Chemistry |
Together with H.G. Moseley, Rutherford developed the atomic numbering system in 1913. Rutherford and Moseley's experiments used cathode rays to bombard various elements with streams of electrons and observed that each element responded in a consistent and distinct manner. Their research was the first to assert that each element could be defined by the properties of its inner structures – an observation that later led to the discovery of the atomic nucleus. This research led Rutherford to theorize that the hydrogen atom (at the time the least massive entity known to bear a positive charge) was a sort of "positive electron" – a component of every atomic element.
It was not until 1919 that Rutherford expanded upon his theory of the "positive electron" with a series of experiments beginning shortly before the end of his time at Manchester. He found that nitrogen, and other light elements, ejected a proton, which he called a "hydrogen atom", when hit with α (alpha) particles. In particular, he showed that particles ejected by alpha particles colliding with hydrogen have unit charge and 1/4 the momentum of alpha particles.
Rutherford returned to the Cavendish Laboratory in 1919, succeeding J. J. Thomson as the Cavendish professor and the laboratorys director, posts that he held until his death in 1937. During his tenure, Nobel prizes were awarded to James Chadwick for discovering the neutron (in 1932), John Cockcroft and Ernest Walton for an experiment that was to be known as splitting the atom' using a particle accelerator, and Edward Appleton for demonstrating the existence of the ionosphere. | 1 | Applied and Interdisciplinary Chemistry |
In 1957, Ronald Breslow proposed that a relatively stable nucleophilic carbene, a thiazol-2-ylidene derivative of vitamin B (thiamine), was the catalyst involved in the benzoin condensation that yields furoin from furfural.
In this cycle, the vitamin's thiazolium ring exchanges a hydrogen atom (attached to carbon 2 of the ring) for a furfural residue. In deuterated water, the C2-proton was found to rapidly exchange for a deuteron in a statistical equilibrium.
This exchange was proposed to proceed via intermediacy of a thiazol-2-ylidene. In 2012 the isolation of the so-called Breslow intermediate was reported.
In 1960, Hans-Werner Wanzlick and coworkers conjectured that carbenes derived from dihydroimidazol-2-ylidene were produced by vacuum pyrolysis of the corresponding 2-trichloromethyl dihydroimidazole compounds with the loss of chloroform.
They conjectured that the carbene existed in equilibrium with its dimer, a tetraaminoethylene derivative, the so-called Wanzlick equilibrium. This conjecture was challenged by Lemal and coworkers in 1964, who presented evidence that the dimer did not dissociate; and by Winberg in 1965. However, subsequent experiments by Denk, Herrmann and others have confirmed this equilibrium, albeit in specific circumstances. | 0 | Theoretical and Fundamental Chemistry |
Biological scaffolds can be created from human donor tissue or from animals; however, animal tissue is often more popular since it is more widely accessible and more plentiful. Xenograft, from a donor of a different species from the recipient, heart valves can be from either pigs, cows, or sheep. If either human or animal tissue is used, the first step in creating useful scaffolds is decellularization, which means to remove the cellular contents all the while preserving the ECM matrix, which is advantageous compared to manufacturing synthetic scaffolds from scratch. Many decellularization methods have been used such as the use of nonionic and ionic detergents that disrupt cellular material interactions or the use of enzymes to cleave peptide bonds, RNA, and DNA. | 1 | Applied and Interdisciplinary Chemistry |
In viscous fluid dynamics, the Archimedes number (Ar), is a dimensionless number used to determine the motion of fluids due to density differences, named after the ancient Greek scientist and mathematician Archimedes.
It is the ratio of gravitational forces to viscous forces and has the form:
where:
* is the local external field (for example gravitational acceleration), ,
* is the characteristic length of body, .
* is the submerged specific gravity,
* is the density of the fluid, ,
* is the density of the body, ,
* is the kinematic viscosity, ,
* is the dynamic viscosity, , | 1 | Applied and Interdisciplinary Chemistry |
Sigma hole interactions exhibit a strong preference for linearity. Theoretical studies have shown that the interaction is most stabilizing when the negative site is colinear with the bond that gives rise to the sigma hole. As the angle between this bond and the sigma hole interaction is decreased, the strength of the interaction is generally found to decrease rapidly. This finding is consistent with the hypothesis that the sigma hole arises from electronic anisotropy. There are cases in which the angle of interaction does differ somewhat from 180° - in these cases, the influence of additional intermolecular interactions are implicated in determining the overall geometry. | 0 | Theoretical and Fundamental Chemistry |
One famous intercalation host is graphite, which intercalates potassium as a guest. Intercalation expands the van der Waals gap between sheets, which requires energy. Usually this energy is supplied by charge transfer between the guest and the host solid, i.e., redox. Two potassium graphite compounds are KC and KC. Carbon fluorides (e.g., (CF) and (CF)) are prepared by reaction of fluorine with graphitic carbon. The color is greyish, white, or yellow. The bond between the carbon and fluorine atoms is covalent, thus fluorine is not intercalated. Such materials have been considered as a cathode in various lithium batteries.
Treating graphite with strong acids in the presence of oxidizing agents causes the graphite to oxidise. Graphite bisulfate, [C][HSO], is prepared by this approach using sulfuric acid and a little nitric acid or chromic acid. The analogous graphite perchlorate can be made similarly by reaction with perchloric acid. | 0 | Theoretical and Fundamental Chemistry |
The Earth, as a system, is open to radiation from the sun and space, but is practically closed with regard to matter. As all closed systems, it follows the law of conservation of mass which states that matter cannot be created nor destroyed, thus, the matter, although transformed and migrated, remains the same as when the Earth was formed. The Earth system contains seven different reservoirs that are separated into surface reservoirs, which include atmosphere, hydrosphere, biosphere, pedosphere, and lithosphere and the isolated reservoirs that include deep Earth and outer space. Geochemical cycles are concerned with the interactions between deep earth which consists of Earths mantle and core, and the lithosphere which consists of the Earths crust. | 0 | Theoretical and Fundamental Chemistry |
Lyngbyastatins 1 and 3 are cytotoxic cyclic depsipeptides that possess antiproliferative activity against human cancer cell lines. These compounds, first isolated from the extract of a Lyngbya majuscula/Schizothrix calcicola assemblage and from L. majuscula Harvey ex Gomont (Oscillatoriaceae) strains, respectively, target the actin cytoskeleton of eukaryotic cells. | 1 | Applied and Interdisciplinary Chemistry |
* Gottfried Münzenberg: "Stigmatisch fokussierendes Teilchenspektrometer mit Massen- und Energiedispersion", Ph.D. thesis, Giessen, 1971 | 1 | Applied and Interdisciplinary Chemistry |
Many important chemical compounds are derived from benzene by replacing one or more of its hydrogen atoms with another functional group. Examples of simple benzene derivatives are phenol, toluene, and aniline, abbreviated PhOH, PhMe, and PhNH, respectively. Linking benzene rings gives biphenyl, CH–CH. Further loss of hydrogen gives "fused" aromatic hydrocarbons, such as naphthalene, anthracene, phenanthrene, and pyrene. The limit of the fusion process is the hydrogen-free allotrope of carbon, graphite.
In heterocycles, carbon atoms in the benzene ring are replaced with other elements. The most important variations contain nitrogen. Replacing one CH with N gives the compound pyridine, CHN. Although benzene and pyridine are structurally related, benzene cannot be converted into pyridine. Replacement of a second CH bond with N gives, depending on the location of the second N, pyridazine, pyrimidine, or pyrazine. | 1 | Applied and Interdisciplinary Chemistry |
DNP was first realized using the concept of the Overhauser effect, which is the perturbation of nuclear spin level populations observed in metals and free radicals when electron spin transitions are saturated by microwave irradiation. This effect relies on stochastic interactions between an electron and a nucleus. The "dynamic" initially meant to highlight the time-dependent and random interactions in this polarization transfer process.
The DNP phenomenon was theoretically predicted by Albert Overhauser in 1953
and initially drew some criticism from Norman Ramsey, Felix Bloch and other renowned physicists of the time on the grounds of being "thermodynamically improbable". The experimental confirmation by Carver and Slichter as well as an apologetic letter from Ramsey both reached Overhauser in the same year.
The so-called electron-nucleus cross-relaxation, which is responsible for the DNP phenomenon is caused by rotational and translational modulation of the electron-nucleus hyperfine coupling. The theory of this process is based essentially on the second-order time-dependent perturbation theory solution of the von Neumann equation for the spin density matrix.
While the Overhauser effect relies on time-dependent electron-nuclear interactions, the remaining polarizing mechanisms rely on time-independent electron-nuclear and electron-electron interactions. | 0 | Theoretical and Fundamental Chemistry |
All bioluminescent bacteria share a common gene sequence: the lux operon characterized by the luxCDABE gene organization. LuxAB codes for luciferase while luxCDE codes for a fatty-acid reductase complex that is responsible for synthesizing aldehydes for the bioluminescent reaction. Despite this common gene organization, variations, such as the presence of other lux genes, can be observed among species. Based on similarities in gene content and organization, the lux operon can be organized into the following four distinct types: the Aliivibrio/Shewanella type, the Photobacterium type, theVibrio/Candidatus Photodesmus type, and the Photorhabdus type. While this organization follows the genera classification level for members of Vibrionaceae (Aliivibrio, Photobacterium, and Vibrio), its evolutionary history is not known.
With the exception of the Photorhabdus operon type, all variants of the lux operon contain the flavin reductase-encoding luxG gene. Most of the Aliivibrio/Shewanella type operons contain additional luxI/luxR regulatory genes that are used for autoinduction during quorum sensing. The Photobacterum operon type is characterized by the presence of rib genes that code for riboflavin, and forms the lux-rib operon. TheVibrio/Candidatus Photodesmus operon type differs from both the Aliivibrio/Shewanella and the Photobacterium operon types in that the operon has no regulatory genes directly associated with it. | 1 | Applied and Interdisciplinary Chemistry |
Multidisciplinary observations are still needed in the deep water column to properly understand the biological pump:
* Physics: stratification affects particle sinking; understanding the origin of the particles and the residence time of the DIC from particle remineralization in the deep ocean requires measurement of advection and mixing.
* Biogeochemistry: export/mixing down of particulate and dissolved organic matter from the surface layer determines labile organic matter arriving at the seafloor, which is either respired by seafloor biota or stored for longer times in the sediment.
* Biology and ecosystems: zooplankton and microorganisms break down and remineralize sinking particles in the water column. Exported organic matter feeds all water column and benthic biota (zooplankton, benthic invertebrates, microbes) sustaining their biomass, density, and biodiversity. | 0 | Theoretical and Fundamental Chemistry |
In 2004, separate civil suits alleging illegal marketing of citalopram and escitalopram for use by children and teenagers by Forest were initiated by two whistleblowers: a physician named Joseph Piacentile and a Forest salesman named Christopher Gobble. In February 2009, the suits were joined. Eleven states and the District of Columbia filed notices of intent to intervene as plaintiffs in the action.
The suits alleged that Forest illegally engaged in off-label promotion of Lexapro for use in children; hid the results of a study showing lack of effectiveness in children; paid kickbacks to physicians to induce them to prescribe Lexapro to children; and conducted so-called "seeding studies" that were, in reality, marketing efforts to promote the drug's use by doctors. Forest denied the allegations but ultimately agreed to settle with the plaintiffs for over $313 million. | 0 | Theoretical and Fundamental Chemistry |
All RiPPs are synthesized first at the ribosome as a precursor peptide. This peptide consists of a core peptide segment which is typically preceded (and occasionally followed) by a leader peptide segment and is typically ~20-110 residues long. The leader peptide is usually important for enabling enzymatic processing of the precursor peptide via aiding in recognition of the core peptide by biosynthetic enzymes and for cellular export. Some RiPPs also contain a recognition sequence C-terminal to the core peptide; these are involved in excision and cyclization. Additionally, eukaryotic RiPPs may contain a signal segment of the precursor peptide which helps direct the peptide to cellular compartments.
During RiPP biosynthesis, the unmodified precursor peptide (containing an unmodified core peptide, UCP) is recognized and chemically modified sequentially by biosynthetic enzymes (PRPS). Examples of modifications include dehydration (i.e. lanthipeptides, thiopeptides), cyclodehydration (i.e. thiopeptides), prenylation (i.e. cyanobactins), and cyclization (i.e. lasso peptides), among others. The resulting modified precursor peptide (containing a modified core peptide, MCP) then undergoes proteolysis, wherein the non-core regions of the precursor peptide are removed. This results in the mature RiPP. | 1 | Applied and Interdisciplinary Chemistry |
Sodium and potassium nitrates are commonly used as fertilizers. As they are also strong oxidizers, they enter pyrotechnic compositions and the manufacturing of explosives.
Eutectic mixtures of alkali metal nitrates are used as molten salts. For example, a 40:7:53 mixture of NaNO: NaNO:KNO melts at 142 °C and is stable to about 600 °C.
A minor use is for coloring the light emitted by fireworks:
* lithium nitrate produces a red color,
* sodium nitrate produces a yellow/orange color,
* potassium nitrate and rubidium nitrate produce violet colors,
* caesium nitrate produces an indigo color.
In a general way, the emitted color progressively turns from the red to the violet in the visible spectrum of light when going down in the column of the alkaline metals in the periodic table of Mendeleev. It corresponds to a decrease of the wavelength of the light emitted during the electrons de-excitation step in the atoms brought at high temperature. The photons emitted by caesium are more energetic than these of lithium. | 0 | Theoretical and Fundamental Chemistry |
The first reported method of methylation analysis using bisulfite-treated DNA utilized PCR and standard dideoxynucleotide DNA sequencing to directly determine the nucleotides resistant to bisulfite conversion. Primers are designed to be strand-specific as well as bisulfite-specific (i.e., primers containing non-CpG cytosines such that they are not complementary to non-bisulfite-treated DNA), flanking (but not involving) the methylation site of interest. Therefore, it will amplify both methylated and unmethylated sequences, in contrast to methylation-specific PCR. All sites of unmethylated cytosines are displayed as thymines in the resulting amplified sequence of the sense strand, and as adenines in the amplified antisense strand. By incorporating high throughput sequencing adaptors into the PCR primers, PCR products can be sequenced with massively parallel sequencing. Alternatively, and labour-intensively, PCR product can be cloned and sequenced. Nested PCR methods can be used to enhance the product for sequencing.
All subsequent DNA methylation analysis techniques using bisulfite-treated DNA is based on this report by Frommer et al. (Figure 2). Although most other modalities are not true sequencing-based techniques, the term "bisulfite sequencing" is often used to describe bisulfite-conversion DNA methylation analysis techniques in general. | 1 | Applied and Interdisciplinary Chemistry |
The Prix Wilder-Penfield is an award by the government of Quebec that is part of the Prix du Québec, which "goes to scientists whose research aims fall within the field of biomedicine. These fields include the medical sciences, the natural sciences, and engineering". It is named in honour of Wilder Penfield. | 1 | Applied and Interdisciplinary Chemistry |
There are several methods termed natural cycle IVF:
* IVF using no drugs for ovarian hyperstimulation, while drugs for ovulation suppression may still be used.
* IVF using ovarian hyperstimulation, including gonadotropins, but with a GnRH antagonist protocol so that the cycle initiates from natural mechanisms.
* Frozen embryo transfer; IVF using ovarian hyperstimulation, followed by embryo cryopreservation, followed by embryo transfer in a later, natural, cycle.
IVF using no drugs for ovarian hyperstimulation was the method for the conception of Louise Brown. This method can be successfully used when people want to avoid taking ovarian stimulating drugs with its associated side-effects. HFEA has estimated the live birth rate to be approximately 1.3% per IVF cycle using no hyperstimulation drugs for women aged between 40 and 42.
Mild IVF is a method where a small dose of ovarian stimulating drugs are used for a short duration during a natural menstrual cycle aimed at producing 2–7 eggs and creating healthy embryos. This method appears to be an advance in the field to reduce complications and side-effects for women, and it is aimed at quality, and not quantity of eggs and embryos. One study comparing a mild treatment (mild ovarian stimulation with GnRH antagonist co-treatment combined with single embryo transfer) to a standard treatment (stimulation with a GnRH agonist long-protocol and transfer of two embryos) came to the result that the proportions of cumulative pregnancies that resulted in term live birth after 1 year were 43.4% with mild treatment and 44.7% with standard treatment. Mild IVF can be cheaper than conventional IVF and with a significantly reduced risk of multiple gestation and OHSS. | 1 | Applied and Interdisciplinary Chemistry |
Phlorizin consists of glucose moiety and two aromatic rings (aglycone moiety) joined by an alkyl spacer. Initially, phlorizin was isolated for treatment of fever and infectious diseases, particularly malaria. According to Michael Nauck and his partners, studies were made in the 1950s on phlorizin that showed that it could block sugar transport in the kidney, small intestine, and a few other tissues. In the early 1990s, sodium/glucose cotransporter 2 was fully characterized, so the mechanism of phlorizin became of real interest. In later studies it was said that sugar-blocking effects of phlorizin was due to inhibition of the sodium/glucose cotransporter proteins.
Most of the reported SGLT-2 inhibitors are glucoside analogs that can be tracked to the o-aryl glucoside found in the nature. The problem with using o-glucosides as SGLT-2 inhibitors is instability that can be tracked to degradation by β-glucosidase in the small intestine. Because of that, o-glucosides given orally have to be prodrug esters. These prodrugs go through changes in the body leading to carbon–carbon bond between the glucose and the aglycone moiety so c-glucoside are formed from the o-glucosides. C-glucosides have a different pharmacokinetic profile than o-glucosides (e.g. half-life and duration of action) and are not degraded by the β-glucosidase. The first discovered c-glucoside was the drug dapagliflozin. Dapagliflozin was the first highly selective SGLT-2-inhibitor approved by the European Medicines Agency. All SGLT-2 inhibitors in clinical development are prodrugs that have to be converted to its active ‘A’ form for activity. | 1 | Applied and Interdisciplinary Chemistry |
Phosphopantetheine, also known as 4'-phosphopantetheine, is a prosthetic group of several acyl carrier proteins including the acyl carrier proteins (ACP) of fatty acid synthases, ACPs of polyketide synthases, the peptidyl carrier proteins (PCP), as well as aryl carrier proteins (ArCP) of nonribosomal peptide synthetases (NRPS). It is also present in formyltetrahydrofolate dehydrogenase.
Subsequent to the expression of the apo acyl carrier protein, 4-phosphopantetheine moiety is attached to a serine residue. The coupling involves formation of a phosphodiester linkage. This coupling is mediated by acyl carrier protein synthase (ACPS), a 4-phosphopantetheinyl transferase.
Phosphopantetheine prosthetic group covalently links to the acyl group via a high energy thioester bond. The flexibility and length of the phosphopantetheine chain (approximately 2 nm) allows the covalently tethered intermediates to access spatially distinct enzyme-active sites. This accessibility increases the effective molarity of the intermediate and allows an assembly line-like process. | 1 | Applied and Interdisciplinary Chemistry |
The three Laves phases are intermetallic compounds composed of CN12 and CN16 polyhedra with AB stoichiometry, commonly seen in binary metal systems like MgZn. Due to the small solubility of AB structures, Laves phases are almost line compounds, though sometimes they can have a wide homogeneity region. | 1 | Applied and Interdisciplinary Chemistry |
The reagent removes pairs of H atoms from organic molecules. The stoichiometry of its action is illustrated by the conversion of tetralin to naphthalene:
:2 CCl(CN)O + CH → 2 CCl(CN)(OH) + CH
The resulting hydroquinone is poorly soluble in typical reaction solvents (dioxane, benzene, alkanes), which facilitates workup.
Solutions of DDQ in benzene are red, due to the formation of a charge-transfer complex. | 0 | Theoretical and Fundamental Chemistry |
Stereochemistry is conveniently denoted in skeletal formulae:
The relevant chemical bonds can be depicted in several ways:
* Solid lines represent bonds in the plane of the paper or screen.
* Solid wedges represent bonds that point out of the plane of the paper or screen, towards the observer.
* Hashed wedges or dashed lines (thick or thin) represent bonds that point into the plane of the paper or screen, away from the observer.
* Wavy lines represent either unknown stereochemistry or a mixture of the two possible stereoisomers at that point.
*An obsolescent depiction of hydrogen stereochemistry that used to be common in steroid chemistry is the use of a filled circle centered on a vertex (sometimes called H-dot/H-dash/H-circle, respectively) for an upward pointing hydrogen atom and two hash marks next to vertex or a hollow circle for a downward pointing hydrogen atom.
An early use of this notation can be traced back to Richard Kuhn who in 1932 used solid thick lines and dotted lines in a publication. The modern solid and hashed wedges were introduced in the 1940s by Giulio Natta to represent the structure of high polymers, and extensively popularised in the 1959 textbook Organic Chemistry by Donald J. Cram and George S. Hammond.
Skeletal formulae can depict cis and trans isomers of alkenes. Wavy single bonds are the standard way to represent unknown or unspecified stereochemistry or a mixture of isomers (as with tetrahedral stereocenters). A crossed double-bond has been used sometimes; it is no longer considered an acceptable style for general use but may still be required by computer software. | 0 | Theoretical and Fundamental Chemistry |
The journal is abstracted and indexed in EBSCOHost, Gale Database of Publications & Broadcast Media, and Scopus. | 1 | Applied and Interdisciplinary Chemistry |
In organometallic chemistry, acetylide refers to chemical compounds with the chemical formulas and , where M is a metal. The term is used loosely and can refer to substituted acetylides having the general structure (where R is an organic side chain). Acetylides are reagents in organic synthesis. The calcium acetylide commonly called calcium carbide is a major compound of commerce. | 0 | Theoretical and Fundamental Chemistry |
Foldit attempts to apply the human brain's three-dimensional pattern matching and spatial reasoning abilities to help solve the problem of protein structure prediction. 2016 puzzles are based on well-understood proteins. By analysing how humans intuitively approach these puzzles, researchers hope to improve the algorithms used by protein-folding software.
Foldit includes a series of tutorials where users manipulate simple protein-like structures and a periodically updated set of puzzles based on real proteins. It shows a graphical representation of each protein which users can manipulate using a set of tools. | 1 | Applied and Interdisciplinary Chemistry |
From 1974 to 2010 Denmark required premarket approval of microbial food cultures. The positive list of microbial food cultures is available on the website of the Danish Veterinary and Food Administration.
In 2010, the regulation changed. Approval is no longer needed but a notification should be made to the Veterinary and Food Administration. | 1 | Applied and Interdisciplinary Chemistry |
The composition of the solar system is similar to that of many other stars, and aside from small anomalies it can be assumed to have formed from a solar nebula that had a uniform composition, and the composition of the Suns photosphere is similar to that of the rest of the Solar System. The composition of the photosphere is determined by fitting the absorption lines in its spectrum to models of the Suns atmosphere. By far the largest two elements by fraction of total mass are hydrogen (74.9%) and helium (23.8%), with all the remaining elements contributing just 1.3%. There is a general trend of exponential decrease in abundance with increasing atomic number, although elements with even atomic number are more common than their odd-numbered neighbors (the Oddo–Harkins rule). Compared to the overall trend, lithium, boron and beryllium are depleted and iron is anomalously enriched.
The pattern of elemental abundance is mainly due to two factors. The hydrogen, helium, and some of the lithium were formed in about 20 minutes after the Big Bang, while the rest were created in the interiors of stars. | 0 | Theoretical and Fundamental Chemistry |
It is useful to recognize that the only states within ~ of the Fermi level contribute significantly to the entropy. Other states are either fully occupied, , or completely unoccupied, . In either case, these states do not contribute to the entropy. If one assumes that the density of states is constant within of the Fermi level, one can derive that the electron heat capacity, equal to:
where is the density of states (number of levels per unit energy) at the Fermi level. Several other approximations can be made, but they all indicate that the electronic entropy should, to first order, be proportional to the temperature and the density of states at the Fermi level. As the density of states at the Fermi level varies widely between systems, this approximation is a reasonable heuristic for inferring when it may be necessary to include electronic entropy in the thermodynamic description of a system; only systems with large densities of states at the Fermi level should exhibit non-negligible electronic entropy (where large may be approximately defined as ). | 0 | Theoretical and Fundamental Chemistry |
Plate-type fuel has fallen out of favor over the years. Plate-type fuel is commonly composed of enriched uranium sandwiched between metal cladding. Plate-type fuel is used in several research reactors where a high neutron flux is desired, for uses such as material irradiation studies or isotope production, without the high temperatures seen in ceramic, cylindrical fuel. It is currently used in the Advanced Test Reactor (ATR) at Idaho National Laboratory, and the nuclear research reactor at the University of Massachusetts Lowell Radiation Laboratory. | 0 | Theoretical and Fundamental Chemistry |
Phosphinooxazolines are used as ligands in allylic substitution reactions as both enantio- and regioselectivity is required to give an enantiomerically pure product due to the transition state being highly symmetric. In the example below all additions are enantioselective however the symmetric complex has no regiocontrol, resulting in a racemic product. The asymmetric complex is both regioselective and enantioselective, resulting in a single enantiomer.
The primary application of PHOX ligands is in palladium catalysts used for enantioselective allylic substitutions. They are able to effect a wide range of substitutions including allylic alkylations (Tsuji-Trost reaction), aminations and sulfonylations. | 0 | Theoretical and Fundamental Chemistry |
The dry distillation of calcium acetate to give acetone was reported by Charles Friedel in 1858 and until World War I ketonization was the premier commercial method for its production.
Ketonic decarboxylation of propanoic acid over a manganese(II) oxide catalyst in a tube furnace affords 3-pentanone. Of commercial interest are related ketonizations using cerium(IV) oxide and manganese dioxide on alumina as the catalysts. 5-Nonanone, which is potentially of interest as a diesel fuel, can be produced from valeric acid. Stearone is prepared by heating magnesium stearate.
An example of intramolecular ketonization is the conversion of adipic acid to cyclopentanone with barium hydroxide.
The synthesis of 4-heptanone illustrates the production of the metal carboxylate in situ. Iron powder and butyric acid are converted to iron butyrate. Pyrolysis of that salt gives the ketone. | 0 | Theoretical and Fundamental Chemistry |
A system of vibrations in a crystalline solid lattice can be modeled as an Einstein solid, i.e. by considering N quantum harmonic oscillator potentials along each degree of freedom. Then, the free energy of the system can be written as
where the index α sums over all the degrees of freedom. In the 1907 Einstein model (as opposed to the later Debye model) we consider only the high-energy limit:
Then
and we have
Define geometric mean frequency by
where g measures the total number of spatial degrees of freedom of the system.
Thus we have
Using energy
we have
This gives heat capacity at constant volume
which is independent of the temperature.
For another more precise derivation, see Debye model. | 0 | Theoretical and Fundamental Chemistry |
* [http://www.jove.com/video/3532/synthesis-of-nine-atom-deltahedral-zintl-ions-of-germanium-and-their-functionalization-with-organic-groups Video of preparation of KGe (subscription required)] | 0 | Theoretical and Fundamental Chemistry |
Polymer melts exhibit different deformation mechanisms when subjected to shear or tensile stresses. For example, a polymer melt’s ductility can increase when a stimulus, such as light, causes fragmentation of the polymer chains through bond breaking. This process is known as chain scission. In the low temperature regime of a polymer melt (T < Tg), crazing or shear banding can occur. The former mechanism resembles crack formation, but this deformation mechanism actually involves the formation of fibrils separated by porous domains or voids. The latter mechanism (shear banding) involves the formation of localized regions of plastic deformation, which typically arise near the position of the maximal shear point in a polymer melt. It is important to note that crazing and shear banding are deformation mechanisms observed in glassy polymers.
For crystalline polymers, the deformation mechanism is best described by a stress-strain curve for a crystalline polymer, such as nylon. The stress-strain behavior exhibits four characteristic regions. The first region is the linear-elastic regime, where the stress-strain behavior is elastic with no plastic deformation. The characteristic deformation mechanism in the second region is yielding, where plastic deformation can occur in the form phenomena such as twinning. The third region shows the formation of a neck, and the fourth region is characterized as a steep increase in stress due to viscous flow. Additionally, region four corresponds to alignment and elongation of the polymer backbone from its coiled or folded state—eventually leading to fracture. | 1 | Applied and Interdisciplinary Chemistry |
Emerin is a 29.0 kDa (34 kDa observed MW) protein composed of 254 amino acids. Emerin is a serine-rich protein with an N-terminal 20-amino acid hydrophobic region that is flanked by charged residues; the hydrophobic region may be important for anchoring the protein to the membrane, with the charged terminal tails being cytosolic. In cardiac, skeletal, and smooth muscle, emerin localizes to the inner nuclear membrane; expression of emerin is highest in skeletal and cardiac muscle. In cardiac muscle specifically, emerin also resides at adherens junctions within intercalated discs. | 1 | Applied and Interdisciplinary Chemistry |
Administration of neuromuscular blocking agents (NMBA) during anesthesia can facilitate endotracheal intubation. This can decrease the incidence of postintubation hoarseness and airway injury.
Short-acting neuromuscular blocking agents are chosen for endotracheal intubation for short procedures (< 30minutes), and neuromonitoring is required soon after intubation. Options include succinylcholine, rocuronium or vecuronium if sugammadex is available for rapid reversal block.
Any short or intermediate acting neuromuscular blocking agents can be applied for endotracheal intubation for long procedures (≥ 30 minutes). Options include succinylcholine, rocuronium, vecuronium, mivacurium, atracurium and cisatracurium. The choice among these NMBA depends on availability, cost and patient parameters that affect drug metabolism.
Intraoperative relaxation can be maintained as necessary with additional dose of nondepolarizing NMBA.
Among all NMBA, Succinylcholine establish the most stable and fastest intubating conditions, thus is considered as the preferred NMBA for rapid sequence induction and intubation (RSII). Alternatives for succinylcholine for RSII include high dose rocuronium (1.2mg/kg which is a 4 X ED95 dose), or avoidance of NMBAs with a high dose remifentanil intubation. | 1 | Applied and Interdisciplinary Chemistry |
This enzyme is often listed in medical literature under incorrect name "creatinine kinase". Creatinine is not a substrate or a product of the enzyme. | 1 | Applied and Interdisciplinary Chemistry |
Labourers working in the smelting industry have reported respiratory illnesses inhibiting their ability to perform the physical tasks demanded by their jobs. | 1 | Applied and Interdisciplinary Chemistry |
A typical dialysis procedure for protein samples is as follows:
# Prepare the membrane according to instructions
# Load the sample into dialysis tubing, cassette or device
# Place sample into an external chamber of dialysis buffer (with gentle stirring of the buffer)
# Dialyze for 2 hours (at room temperature or 4 °C)
# Change the dialysis buffer and dialyze for another 2 hours
# Change the dialysis buffer and dialyze for 2 hours or overnight
The total volume of sample and dialysate determine the final equilibrium concentration of the small molecules on both sides of the membrane. By using the appropriate volume of dialysate and multiple exchanges of the buffer, the concentration of small contaminants within the sample can be decreased to acceptable or negligible levels.
For example, when dialyzing 1mL of sample against 200mL of dialysate, the concentration of unwanted dialyzable substances will be decreased 200-fold when equilibrium is attained. Following two additional buffer changes of 200mL each, the contaminant level in the sample will be reduced by a factor of 8 x 10 (200 x 200 x 200). | 1 | Applied and Interdisciplinary Chemistry |
Nonsense mutations include stop-gain and start-loss. Stop-gain is a mutation that results in a premature termination codon (a stop was gained), which signals the end of translation. This interruption causes the protein to be abnormally shortened. The number of amino acids lost mediates the impact on the proteins functionality and whether it will function whatsoever. Stop-loss is a mutation in the original termination codon (a stop was lost), resulting in abnormal extension of a proteins carboxyl terminus. Start-gain creates an AUG start codon upstream of the original start site. If the new AUG is near the original start site, in-frame within the processed transcript and downstream to a ribosomal binding site, it can be used to initiate translation. The likely effect is additional amino acids added to the amino terminus of the original protein. Frame-shift mutations are also possible in start-gain mutations, but typically do not affect translation of the original protein. Start-loss is a point mutation in a transcript's AUG start codon, resulting in the reduction or elimination of protein production.
Missense mutations code for a different amino acid. A missense mutation changes a codon so that a different protein is created, a non-synonymous change. Conservative mutations result in an amino acid change. However, the properties of the amino acid remain the same (e.g., hydrophobic, hydrophilic, etc.). At times, a change to one amino acid in the protein is not detrimental to the organism as a whole. Most proteins can withstand one or two point mutations before their function changes. Non-conservative mutations result in an amino acid change that has different properties than the wild type. The protein may lose its function, which can result in a disease in the organism. For example, sickle-cell disease is caused by a single point mutation (a missense mutation) in the beta-hemoglobin gene that converts a GAG codon into GUG, which encodes the amino acid valine rather than glutamic acid. The protein may also exhibit a "gain of function" or become activated, such is the case with the mutation changing a valine to glutamic acid in the BRAF gene; this leads to an activation of the RAF protein which causes unlimited proliferative signalling in cancer cells. These are both examples of a non-conservative (missense) mutation.
Silent mutations code for the same amino acid (a "synonymous substitution"). A silent mutation does not affect the functioning of the protein. A single nucleotide can change, but the new codon specifies the same amino acid, resulting in an unmutated protein. This type of change is called synonymous change since the old and new codon code for the same amino acid. This is possible because 64 codons specify only 20 amino acids. Different codons can lead to differential protein expression levels, however. | 1 | Applied and Interdisciplinary Chemistry |
* 2013 Biotechnology Heritage Award, from the Biotechnology Industry Organization (BIO) and the Chemical Heritage Foundation
*2004 Winthrop-Sears Medal, from the Chemical Heritage Foundation and The Chemists' Club, with Alexander Zaffaroni
*2001 Condecoracion Eduardo Liceaga, Mexican highest award for contributions to the health field.
*1994 Dr. Leopoldo Rio de la Loza, Mexican National Prize in Pharmaceutical Sciences
* Leadership Award of the Mexican Health Federation | 0 | Theoretical and Fundamental Chemistry |
Unable to pursue his career, Schwab emigrated from Nazi Germany to Greece in 1939, He and Elly married in Athens in the same year. With the connections of his wife, both started research work in the industrial chemistry laboratory of the recently founded Kanellopoulos Institute of Chemistry and Agriculture in Piraeus.
For the following years he spent in Greece, Schwab (known in Greek as Γεώργιος Σβαμπ, ) came to view Greece as "his second fatherland".
While in the Kanellopoulos Institute, a sui generis research institution for contemporary Greece, he was allowed to pursue purely scientific work; indeed Schwab had a fruitful 11-year stay marked by a series of incidental discoveries as well as systematic studies continuing his previous work on catalysis.
Schwab was in a difficult situation during the Axis occupation of Greece, when he once again faced danger from the German occupying forces due to his Jewish background. In 1942, the German authorities refused to renew his German passport. Georg-Maria escaped the fate of his brother, Josef-Maria Schwab – who died as a forced labourer in Organisation Todt, by keeping a low profile in Greece and getting an exemption from the 1943 order for German citizens to return to Germany with the help of an official at the German Embassy in Athens.
After the liberation of Greece (1944), Schwab was able to resume his research at the Kanellopoulos Institute, until he was offered the Professorship of Physical Chemistry at the Technical University of Athens in 1949. He kept the position and taught the subject for the next 10 years. | 0 | Theoretical and Fundamental Chemistry |
*Savannah Pulp and Paper Laboratory (now Herty Advanced Materials Development Center), founded by Charles H. Herty Sr. in 1932
*Commercialization of the Hall-Héroult process for producing aluminum by the Pittsburgh Reduction Company in 1888
*John William Draper and the founding of the American Chemical Society in 1876
*The National Bureau of Standards (now National Institute of Standards and Technology), founded in 1901 | 1 | Applied and Interdisciplinary Chemistry |
Enhanced Atmospheric Methane Oxidation is the concept of enhancing the overall oxidative methane sink in the atmosphere, through generating additional hydroxyl or chlorine atmospheric radicals. | 1 | Applied and Interdisciplinary Chemistry |
The cyclooctane derivative OCT was the first one developed for Cu-free click chemistry; it had only ring strain to drive the reaction forward, and the kinetics were barely improved over the Staudinger ligation. After OCT and MOFO (monofluorinated cyclooctyne), the difluorinated cyclooctyne (DIFO) was developed. An improved synthetic approach to a monofluorosubstituted cyclooctyne (MFCO) was introduced that could easily be converted to a useful reactive intermediate for bioconjugation applications, although the reactivity was somewhat slower than DIFO. The MFCO demonstrated excellent stability characteristics for long-term storage.
The substituted cyclooctyne is activated for a 1,3-dipolar cycloaddition by its ring strain and electron-withdrawing fluorine substituents, which allows the reaction to take place with kinetics comparable to the Cu-catalyzed Huisgen cycloaddition. Ring strain (~18 kcal/mol) arises from the deviation of the bond angles from the ideal 180° to form an eight-membered ring, the smallest of all cycloalkynes. The electron-withdrawing fluorine substituents were chosen due to their synthetic ease and compatibility with living biological systems. Additionally, the group cannot produce cross-reacting Michael acceptors that could act as alkylating agents toward nucleophilic species within cells.
Like most cyclooctynes, DIFO prefers the chair conformation in both the ground state and the minimum energy traction path, although boat transition states may also be involved. Gas phase regioselectivity is calculated to favor 1,5 addition over 1,4 addition by up to 2.9 kcal/mol in activation energy in the gas phase; solvation corrections give the same energy barriers for both regioisomers, explaining the regioisomeric mix that results from DIFO cycloadditions. While the 1,4 isomer is disfavored by its larger dipole moment (all electron-rich substituents on one side), solvation stabilizes it more strongly than the 1,5 isomer, eroding regioselectivity. Experimental studies by Carolyn R. Bertozzi report a nearly 1:1 ratio of regioisomers, confirming the predicted lack of regioselectivity in the addition.
Furthermore, nearly all of the distortion energy (92%) arises from the distortion of the 1,3 dipole rather than the cyclooctyne, which has a pre-distorted ground state geometry that increases its reactivity. Fluorination decreases the distortion energy by allowing the transition state to be achieved with a lesser distortion of the 1,3-dipole during a reaction, resulting in a larger dipole angle. | 0 | Theoretical and Fundamental Chemistry |
On July 9, 2007, a purple, hybrid orchid was named Dendrobium Tuanku Zara Salim in honour of her visit to the 7th Ipoh International Orchid Festival.
She is the current Chancellor of the Sultan Idris Education University (UPSI), and was proclaimed on 1 January 2012.
She has been awarded an Honorary Fellowship by the Institution of Chemical Engineers (IChemE) in April 2014 in recognition of her interest in the continued improvement of Malaysia's education and academic performance.
She then was made as the first Royal Patron of the IChemE in Malaysia in October 2016. On accepting the honour, Tuanku Zara said that chemical engineering can be a challenging career, but rewarding as well. Chemical engineers are highly employable, have wide and diverse career options, and can make a big impact in society and the environment. She intends to, as Royal Patron of the IChemE, do her part to inspire the younger generation to consider chemical engineering as a viable career choice.
She is also a patron of the Family Health Society of Perak, Convent Girls Alumni and Perak Girl Guides. | 1 | Applied and Interdisciplinary Chemistry |
Self-heating cans of military food rations developed during WWII used a thermite-like mixture of 1:1 iron(II,III) oxide and calcium silicide. Such mixture, when ignited, generates moderate amount of heat and no gaseous products. | 1 | Applied and Interdisciplinary Chemistry |
1,1-Difluoroethane, or DFE, is an organofluorine compound with the chemical formula CHF. This colorless gas is used as a refrigerant, where it is often listed as R-152a (refrigerant-152a) or HFC-152a (hydrofluorocarbon-152a). It is also used as a propellant for aerosol sprays and in gas duster products. As an alternative to chlorofluorocarbons, it has an ozone depletion potential of zero, a lower global warming potential (124) and a shorter atmospheric lifetime (1.4 years). | 1 | Applied and Interdisciplinary Chemistry |
Water vapor plays a key role in lightning production in the atmosphere. From cloud physics, usually clouds are the real generators of static charge as found in Earth's atmosphere. The ability of clouds to hold massive amounts of electrical energy is directly related to the amount of water vapor present in the local system.
The amount of water vapor directly controls the permittivity of the air. During times of low humidity, static discharge is quick and easy. During times of higher humidity, fewer static discharges occur. Permittivity and capacitance work hand in hand to produce the megawatt outputs of lightning.
After a cloud, for instance, has started its way to becoming a lightning generator, atmospheric water vapor acts as a substance (or insulator) that decreases the ability of the cloud to discharge its electrical energy. Over a certain amount of time, if the cloud continues to generate and store more static electricity, the barrier that was created by the atmospheric water vapor will ultimately break down from the stored electrical potential energy. This energy will be released to a local oppositely charged region, in the form of lightning. The strength of each discharge is directly related to the atmospheric permittivity, capacitance, and the source's charge generating ability. | 1 | Applied and Interdisciplinary Chemistry |
Ferrara graduated from Syracuse University and State University of New York College of Environmental Science and Forestry with doctorate degree in organic chemistry. | 0 | Theoretical and Fundamental Chemistry |
He is a nuclear chemist who worked at Los Alamos National Lab for more than 30 years. He established Kiva Labs in Santa Fe where he continues exploration of evidence of his model of cold fusion. Storms is also a Science Advisor to Cold Fusion Now.
Storm's work is listed in the Atomic Energy of Canada Ltd. 2013 Report on cold fusion, which identifies 25 theories on the mechanisms behind cold fusion, but notes that "What was apparent from this review is that there has been a plethora of investigations and theories for CF/LENR/CMNS over the last 20 years, but a relative shortage of credible, peer-reviewed information sources." | 0 | Theoretical and Fundamental Chemistry |
As a flow in a channel becomes supersonic, one significant change takes place. The conservation of mass flow rate leads one to expect that contracting the flow channel would increase the flow speed (i.e. making the channel narrower results in faster air flow) and at subsonic speeds this holds true. However, once the flow becomes supersonic, the relationship of flow area and speed is reversed: expanding the channel actually increases the speed.
The obvious result is that in order to accelerate a flow to supersonic, one needs a convergent-divergent nozzle, where the converging section accelerates the flow to sonic speeds, and the diverging section continues the acceleration. Such nozzles are called de Laval nozzles and in extreme cases they are able to reach hypersonic speeds ( at 20 °C).
An aircraft Machmeter or electronic flight information system (EFIS) can display Mach number derived from stagnation pressure (pitot tube) and static pressure. | 1 | Applied and Interdisciplinary Chemistry |
Methylglyoxal is a component of some kinds of honey, including manuka honey; it appears to have activity against E. coli and S. aureus and may help prevent formation of biofilms formed by P. aeruginosa.
Research suggests that methylglyoxal contained in honey does not cause an increased formation of advanced glycation end products (AGEs) in healthy persons. | 1 | Applied and Interdisciplinary Chemistry |
In coal-fired power stations, the raw feed coal from the coal storage area is first crushed into small pieces and then conveyed to the coal feed hoppers at the boilers. The coal is next pulverized into a very fine powder. The pulverizers may be ball mills, rotating drum grinders, or other types of grinders.
Some power stations burn fuel oil rather than coal. The oil must kept warm (above its pour point) in the fuel oil storage tanks to prevent the oil from congealing and becoming unpumpable. The oil is usually heated to about 100 °C before being pumped through the furnace fuel oil spray nozzles.
Boilers in some power stations use processed natural gas as their main fuel. Other power stations may use processed natural gas as auxiliary fuel in the event that their main fuel supply (coal or oil) is interrupted. In such cases, separate gas burners are provided on the boiler furnaces. | 1 | Applied and Interdisciplinary Chemistry |
* F: Formylation (optional)
* A: Adenylation (required in a module)
* PCP: Thiolation and peptide carrier protein with attached 4'-phospho-pantetheine (required in a module)
* C: Condensation forming the amide bond (required in a module)
* Cy: Cyclization into thiazoline or oxazolines (optional)
* Ox: Oxidation of thiazolines or oxazolines to thiazoles or oxazoles (optional)
* Red: Reduction of thiazolines or oxazolines to thiazolidines or oxazolidines (optional)
* E: Epimerization into D-amino acids (optional)
* NMT: N-methylation (optional)
* TE: Termination by a thio-esterase (only found once in a NRPS)
* R: Reduction to terminal aldehyde or alcohol (optional)
* X: Recruits cytochrome P450 enzymes (optional) | 1 | Applied and Interdisciplinary Chemistry |
Considering an isothermal flow without mass transfer, the Unsteady Reynolds Average Navier-Stokes equations (URANS) are:
Where:
* is the phasic volume fraction and it represents the space occupied by the k-phase.
* is the momentum source term. | 1 | Applied and Interdisciplinary Chemistry |
Nitrobenzyl-based PPGs are often considered the most commonly used PPGs. These PPGs are traditionally identified as Norrish Type II reaction as their mechanism was first described by Norrish in 1935. Norrish elucidated that an incident photon (200 nm –10 s. Following resonance of the π-electrons, a five-membered ring is formed before the PPG is cleaved yielding 2-nitrosobenzaldehyde and a carboxylic acid.
Overall, nitrobenzyl-based PPGs are highly general. The list of functional groups that can be protected include, but are not limited to, phosphates, carboxylates, carbonates, carbamates, thiolates, phenolates and alkoxides. Additionally, while the rate varies with a number of variables, including choice of solvent and pH, the photodeprotection has been exhibited in both solution and in the solid-state. Under optimal conditions, the photorelease can proceed with >95% yield. Nevertheless, the photoproducts of this PPG are known to undergo imine formation when irradiated at wavelengths above 300 nm. This side product often competes for incident radiation, which may lead to decreased chemical and quantum yields. | 0 | Theoretical and Fundamental Chemistry |
He is a professor in the Department of Applied Chemistry at the University of Tokyo. He has published extensively on the multicomponent assembly of large coordination cages. Compounds designed and prepared in his research group are variously described as three-dimensional synthetic receptors, coordination assemblies, molecular paneling, molecular flasks, crystalline sponges, and coordination capsules.
He shared the 2018 Wolf Prize in Chemistry with Omar Yaghi "for conceiving metal-directed assembly principles leading to large highly porous complexes". | 0 | Theoretical and Fundamental Chemistry |
L1 activity has been observed in numerous types of cancers, with particularly extensive insertions found in colorectal and lung cancers. It is currently unclear if these insertions are causes or secondary effects of cancer progression. However, at least two cases have found somatic L1 insertions causative of cancer by disrupting the coding sequences of genes APC and PTEN in colon and endometrial cancer, respectively.
Quantification of L1 copy number by qPCR or L1 methylation levels with bisulfite sequencing are used as diagnostic biomarkers in some types of cancers. L1 hypomethylation of colon tumor samples is correlated with cancer stage progression. Furthermore, less invasive blood assays for L1 copy number or methylation levels are indicative of breast or bladder cancer progression and may serve as methods for early detection. | 1 | Applied and Interdisciplinary Chemistry |
One study conducted by investigators at the University of North Carolina Chapel Hill looked into donated sperm utilization within the United States from 1995 to 2017. Cross-sectional studies recorded that an estimated 170,701 individuals during 1995 used donated sperm, while the 2011 to 2013 cohort had a decreased amount of donated sperm use of 37,385. Most recently, in the 2015 to 2017 cohort, 440,986 individuals were reported to use donated sperm. When looking at 200,197 individuals across 2011–2017, 76% had a 4-year college degree or further while 24% had high school or 2-year college degree. In terms of household percent of poverty, 71% of the sperm bank users were at or above 400% of the household poverty level while only 11% were between 200 and 399% of the household poverty levels. Although the household income levels were not explicit, there seems to be an obvious trend that higher education level attainment (such as finishing college or higher) and being at much higher income level above the household poverty levels were the common tendencies in the sperm bank users. | 1 | Applied and Interdisciplinary Chemistry |
Promoters are important gene regulatory elements used in tuning synthetically designed genetic circuits and metabolic networks. For example, to overexpress an important gene in a network, to yield higher production of target protein, synthetic biologists design promoters to upregulate its expression. Automated algorithms can be used to design neutral DNA or insulators that do not trigger gene expression of downstream sequences. | 1 | Applied and Interdisciplinary Chemistry |
Dicloxacillin is insensitive to beta-lactamase (also known as penicillinase) enzymes secreted by many penicillin-resistant bacteria. The presence of the isoxazolyl group on the side chain of the penicillin nucleus facilitates the β-lactamase resistance, since they are relatively intolerant of side-chain steric hindrance. Thus, it is able to bind to penicillin-binding proteins (PBPs) and inhibit peptidoglycan crosslinking, but is not bound by or inactivated by β-lactamase | 0 | Theoretical and Fundamental Chemistry |
The chemical composition of a mixture can be defined as the distribution of the individual substances that constitute the mixture, called "components". In other words, it is equivalent to quantifying the concentration of each component. Because there are different ways to define the concentration of a component, there are also different ways to define the composition of a mixture. It may be expressed as molar fraction, volume fraction, mass fraction, molality, molarity or normality or mixing ratio.
Chemical composition of a mixture can be represented graphically in plots like ternary plot and quaternary plot. | 0 | Theoretical and Fundamental Chemistry |
In science fiction, mutagens are often represented as substances that are capable of completely changing the form of the recipient or granting them superpowers. Powerful radiations are the agents of mutation for the superheroes in Marvel Comicss Fantastic Four, Daredevil, and Hulk, while in the Teenage Mutant Ninja Turtles franchise the mutagen is a chemical agent also called "ooze", and for Inhumans the mutagen is the Terrigen Mist. Mutagens are also featured in video games such as Cyberia, System Shock, The Witcher, Metroid Prime: Trilogy, Resistance: Fall of Man, Resident Evil, Infamous, Freedom Force, Command & Conquer, Gears of War 3, StarCraft, BioShock, Fallout, Underrail, and Maneater'.
In the "nuclear monster" films of the 1950s, nuclear radiation mutates humans and common insects often to enormous size and aggression; these films include Godzilla, Them!, Attack of the 50 Foot Woman, Tarantula!, and The Amazing Colossal Man. | 0 | Theoretical and Fundamental Chemistry |
The stationary convection–diffusion equation describes the steady-state behavior of a convective-diffusive system. In a steady state, , so the equation to solve becomes the second order equation: | 1 | Applied and Interdisciplinary Chemistry |
The Lucas test in alcohols is a test to differentiate between primary, secondary, and tertiary alcohols. It is based on the difference in reactivity of the three classes of alcohols with hydrogen halides via an S1 reaction:
: tert-BuOH + HCl → tert-BuCl + HO
The differing reactivity reflects the differing ease of formation of the corresponding carbocations. Tertiary carbocations are far more stable than secondary carbocations, and primary carbocations are the least stable(due to hyperconjugation).
An equimolar mixture of ZnCl and concentrated HCl is the reagent. The alcohol is protonated, the HO group formed leaves, forming a carbocation, and the nucleophile Cl (which is present in excess) readily attacks the carbocation, forming the chloroalkane. Tertiary alcohols react immediately with Lucas reagent as evidenced by turbidity owing to the low solubility of the organic chloride in the aqueous mixture. Secondary alcohols react within five or so minutes (depending on their solubility). Primary alcohols do not react appreciably with Lucas reagent at room temperature. Hence, the time taken for turbidity to appear is a measure of the reactivity of the class of alcohol, and this time difference is used to differentiate among the three classes of alcohols:
* no visible reaction at room temperature and forming an oily layer only on heating: primary, such as 1-pentanol
* solution forms oily layer in 3–5 minutes: secondary, such as 2-pentanol
* solution forms an oily layer immediately: tertiary, such as 2-methyl-2-butanol
The Lucas test is usually an alternative to the oxidation test - which is used to identify primary and secondary alcohols. | 0 | Theoretical and Fundamental Chemistry |
In the Earths magnetic field, NMR frequencies are in the audio frequency range, or the very low frequency and ultra low frequency bands of the radio frequency spectrum. Earths field NMR (EFNMR) is typically stimulated by applying a relatively strong dc magnetic field pulse to the sample and, after the end of the pulse, analyzing the resulting low frequency alternating magnetic field that occurs in the Earth's magnetic field due to free induction decay (FID). These effects are exploited in some types of magnetometers, EFNMR spectrometers, and MRI imagers. Their inexpensive portable nature makes these instruments valuable for field use and for teaching the principles of NMR and MRI.
An important feature of EFNMR spectrometry compared with high-field NMR is that some aspects of molecular structure can be observed more clearly at low fields and low frequencies, whereas other aspects observable at high fields are not observable at low fields. This is because:
* Electron-mediated heteronuclear J-couplings (spin-spin couplings) are field independent, producing clusters of two or more frequencies separated by several Hz, which are more easily observed in a fundamental resonance of about 2 kHz."Indeed it appears that enhanced resolution is possible due to the long spin relaxation times and high field homogeneity which prevail in EFNMR."
* Chemical shifts of several ppm are clearly separated in high field NMR spectra, but have separations of only a few millihertz at proton EFNMR frequencies, so are usually not resolved. | 0 | Theoretical and Fundamental Chemistry |
Partition chromatography was one of the first kinds of chromatography that chemists developed, and is barely used these days. The partition coefficient principle has been applied in paper chromatography, thin layer chromatography, gas phase and liquid–liquid separation applications. The 1952 Nobel Prize in chemistry was earned by Archer John Porter Martin and Richard Laurence Millington Synge for their development of the technique, which was used for their separation of amino acids. Partition chromatography uses a retained solvent, on the surface or within the grains or fibers of an "inert" solid supporting matrix as with paper chromatography; or takes advantage of some coulombic and/or hydrogen donor interaction with the stationary phase. Analyte molecules partition between a liquid stationary phase and the eluent. Just as in hydrophilic interaction chromatography (HILIC; a sub-technique within HPLC), this method separates analytes based on differences in their polarity. HILIC most often uses a bonded polar stationary phase and a mobile phase made primarily of acetonitrile with water as the strong component. Partition HPLC has been used historically on unbonded silica or alumina supports. Each works effectively for separating analytes by relative polar differences. HILIC bonded phases have the advantage of separating acidic, basic and neutral solutes in a single chromatographic run.
The polar analytes diffuse into a stationary water layer associated with the polar stationary phase and are thus retained. The stronger the interactions between the polar analyte and the polar stationary phase (relative to the mobile phase) the longer the elution time. The interaction strength depends on the functional groups part of the analyte molecular structure, with more polarized groups (e.g., hydroxyl-) and groups capable of hydrogen bonding inducing more retention. Coulombic (electrostatic) interactions can also increase retention. Use of more polar solvents in the mobile phase will decrease the retention time of the analytes, whereas more hydrophobic solvents tend to increase retention times. | 0 | Theoretical and Fundamental Chemistry |
The Deborah number (De) is a dimensionless number, often used in rheology to characterize the fluidity of materials under specific flow conditions. It quantifies the observation that given enough time even a solid-like material might flow, or a fluid-like material can act solid when it is deformed rapidly enough. Materials that have low relaxation times flow easily and as such show relatively rapid stress decay. | 1 | Applied and Interdisciplinary Chemistry |
Throughout human history, fungi have been utilized as a source of food and harnessed to ferment and preserve foods and beverages. In the 20th century, humans have learned to harness fungi to protect human health (antibiotics, anti-cholesterol statins, and immunosuppressive agents), while industry has utilized fungi for large scale production of enzymes, acids, and biosurfactants. With the advent of modern nanotechnology in the 1980s, fungi have remained important by providing a greener alternative to chemically synthesized nanoparticle. | 0 | Theoretical and Fundamental Chemistry |
For an optically thin plasma composed of a single, neutral atomic species in local thermal equilibrium (LTE), the density of photons emitted by a transition from level i to level j is
where :
* is the emission rate density of photons (in m sr s)
* is the number of neutral atoms in the plasma (in m)
* is the transition probability between level i and level j (in s)
* is the degeneracy of the upper level i (2J+1)
* is the partition function (unitless)
* is the energy level of the upper level i (in eV)
* is the Boltzmann constant (in eV/K)
* is the temperature (in K)
* is the line profile such that
* is the wavelength (in nm)
The partition function is the statistical occupation fraction of every level of the atomic species : | 0 | Theoretical and Fundamental Chemistry |
He studied at the University of Kazan where he graduated in mathematics but he started teaching chemistry in 1835. To improve his skills he was asked to study in Europe for some time, which he did between 1838 and 1841. He studied with Justus Liebig in Giessen, where he finished his research on the benzoin condensation, which was discovered by Liebig several years before. He presented his research results at the University of Saint Petersburg, where he received his Ph.D. He became Professor for Chemistry in the same year at the University of Kazan and left for the University of Saint Petersburg in 1847 where he also became a member of the St. Petersburg Academy of Sciences and first president of the Russian Physical and Chemical Society (1868–1877).
In St. Petersburg, professor Zinin was a private teacher of chemistry to the young Alfred Nobel. | 0 | Theoretical and Fundamental Chemistry |
Based on the principle of counter-current piston flow, these processes are the closest to the blast furnace or, more accurately, the stückofen. Hot reducing gases are obtained from natural gas, in a separate unit from the shaft, and injected at the bottom of the shaft, while the ore is charged at the top. The pre-reduced materials are extracted hot, but in solid form, from the bottom of the shaft. This similarity to a blast furnace without its crucible made it one of the first processes explored by metallurgists, but the failures of the German Gurlt in 1857, and the French Eugène Chenot (son of Adrien) around 1862, led to the conclusion that "the reduction of iron ore [...] is therefore [not] possible in large quantities by gas alone".
Developed in the 1970s, the Midrex process is the best example of a continuous direct reduction process. As much a technical success as a commercial one, since 1980 it has accounted for around two-thirds of the world's production of pre-reduced materials. Its similarity to the blast furnace means that it shares some of its advantages, such as high production capacity, and some disadvantages, such as the relative difficulty of controlling several simultaneous reactions in a single reactor (since the nature of the product changes considerably as it travels through the vessel). The strategy of selling turnkey units, combined with a cautious increase in production capacity, has given this process good financial and technical visibility... compared with the often dashed hopes of competing processes.
Its direct competitor, the HYL III process, is the result of a research effort by the Tenova Group (de), heir to the Mexican Hylsa pioneers. Accounting for almost 20% of pre-reduced product production, it differs from the Midrex process in that it features an in-house reforming unit for the production of reducing gases.
Other processes have been developed based on this continuous reactor principle. Some, like ULCORED, are still at the study stage. Most have only been developed in a single country, or by a single company. Others were failures, such as the NSC process, of which a single plant was built in 1984 and converted to HYL III in 1993, ARMCO (a single unit commissioned in 1963 and shut down in 1982) or PUROFER (3 units operational from 1970 to 1979, small-scale production resumed in 1988).
Coal-fired processes are variants of natural gas processes, where the gas can be synthesized from coal in an additional unit. Among these variants, the MXCOL, of which one unit has been operational since 1999 and two are under construction, is a Midrex fed by a coal gasification unit. Technically mature but more complex, they are at a disadvantage compared with equivalent gas-fired processes, which require slightly less investment. | 1 | Applied and Interdisciplinary Chemistry |
The spines of sea urchins are composed of mesocrystals of calcite nano-crystals (92%) in a matrix of non-crystalline calcium carbonate (8%). This structure makes the spines hard but also shock-absorbing, which special property makes them effective defences against predators. Mesocrystals also appear in the shells of some eggs, coral, chitin, and the shells of mussels. | 0 | Theoretical and Fundamental Chemistry |
Eukaryotes belonging to some divergent lineages have very special organizations of the ATP synthase. A euglenozoa ATP synthase forms a dimer with a boomerang-shaped F head like other mitochondrial ATP synthases, but the F subcomplex has many unique subunits. It uses cardiolipin. The inhibitory IF also binds differently, in a way shared with trypanosomatida. | 0 | Theoretical and Fundamental Chemistry |
The relationship between linear momentum and deformable fluid bodies is well explored, as are the Navier–Stokes equations for incompressible flow. However, exploring the relationships foundational to the Chézy formula can be helpful towards understanding the formula in full.
To understand the Chézy similarity parameter, a simple can help summarize the conservation of momentum of a control volume uniformly flowing through an open channel:
Where the sum of forces on the contents of a control volume in the open channel is equal to the sum of the time rate of change of the linear momentum of the contents of the control volume, plus the net rate of flow of linear momentum through the control surface. The momentum principle may always be used for hydrodynamic force calculations.
As long as uniform flow can be assumed, applying the linear momentum equation to a river channel flowing in one dimension means that momentum remains conserved and the forces are balanced in the direction of flow:
Here, the hydrostatic pressure forces are F and F, the component (τPl) represents the shear force of friction acting on the control volume, and the component (ω sin θ) represents the gravitational force of the fluid's weight acting on the sloped channel bottom are held in balance in the flow direction. The free-body diagram below illustrates this equilibrium of forces in open channel flow with uniform flow conditions.
Most open-channel flows are turbulent and characterized by very large Reynolds numbers. Due to the large Reynolds numbers characteristic in open channel flow, the channel shear stress proves to be proportional to the density and velocity of the flow. This can be illustrated in a series of advanced formulas which identify a shear stress similarity parameter characteristic of all turbulent open channels. Combining this parameter with channel components and the conservation of momentum in an open channel flow results with the Chézy formula that explains this relationship: .
Chézy's similarity parameter and formula explain how the velocity of water flowing through a channel has a relationship with the slope and sheer stress of the channel bottom, the hydraulic radius of flow, and the Chézy coefficient, which empirically incorporates several other parameters of the flowing water. This relationship is driven by the conservation of momentum present during uniform flow conditions. | 1 | Applied and Interdisciplinary Chemistry |
Aliphatic metal alkoxides decompose in water: where R is an organic substituent and L is an unspecified ligand (often an alkoxide). A well-studied case is the irreversible hydrolysis of titanium isopropoxide:
By controlling the stoichiometry and steric properties of the alkoxide, such reactions can be arrested leading to metal-oxy-alkoxides, which usually are oligonuclear. Other alcohols can be employed in place of water. In this way one alkoxide can be converted to another, and the process is properly referred to as alcoholysis (although there is an issue of terminology confusion with transesterification, a different process - see below). The position of the equilibrium can be controlled by the acidity of the alcohol; for example phenols typically react with alkoxides to release alcohols, giving the corresponding phenoxide. More simply, the alcoholysis can be controlled by selectively evaporating the more volatile component. In this way, ethoxides can be converted to butoxides, since ethanol (b.p. 78 °C) is more volatile than butanol (b.p. 118 °C). | 0 | Theoretical and Fundamental Chemistry |
The Reactor Materials Laboratory was established at Culcheth in 1950. The UKAEA's Safety and Reliability Directorate (SRD) stayed at Culcheth until 1995. | 1 | Applied and Interdisciplinary Chemistry |
SPIDR (scaffold protein involved in DNA repair) regulates the stability or assembly of RAD51 and DMC1 on single-stranded DNA. RAD51 and DMC1 are recombinases that act during mammalian meiosis to mediate strand exchange during the repair of DNA double-strand breaks by homologous recombination. | 1 | Applied and Interdisciplinary Chemistry |
Depending on the arrangement of the three nitrogen atoms in triazol-5-ylidene, there are two possible isomers, namely 1,2,3-triazol-5-ylidenes and 1,2,4-triazol-5-ylidenes.
The triazol-5-ylidenes based on the 1,2,4-triazole ring are pictured below and were first prepared by Enders and coworkers by vacuum pyrolysis through loss of methanol from 2-methoxytriazoles. Only a limited range of these molecules have been reported, with the triphenyl substituted molecule being commercially available.
Triazole-based carbenes are thermodynamically stable and have diagnostic C NMR chemical shift values between 210 and 220 ppm for the carbenic carbon. The X-ray structure of the triphenyl substituted carbene above shows an N–C–N bond angle of around 101°. The 5-methoxytriazole precursor to this carbene was made by the treatment of a triazolium salt with sodium methoxide, which attacks as a nucleophile. This may indicate that these carbenes are less aromatic than imidazol-2-ylidenes, as the imidazolium precursors do not react with nucleophiles due to the resultant loss of aromaticity. | 0 | Theoretical and Fundamental Chemistry |
Worthy of note is that in 2013, a structural prediction of the Au (SCH) cluster, based on Density Functional Theory (DFT) was confirmed in 2015. This result represents the maturity of this field where calculations are able to guide the experimental work.
The following table features some sizes. | 0 | Theoretical and Fundamental Chemistry |
The choice of infrared wavelengths used for the measurement largely defines the detector's suitability for a particular applications. Not only must the target gas (or gases) have a suitable absorption spectrum, the wavelengths must lie within a spectral window so the air in the beam path is itself transparent. These wavelength regions have been used:
* 3.4 μm region. All hydrocarbons and their derivatives absorb strongly, due to the C-H stretch mode of molecular vibration. It is commonly used in infrared point detectors where path lengths are necessarily short, and for open-path detectors requiring parts-per-million sensitivity. A disadvantage for many applications is that methane absorbs relatively weakly compared to heavier hydrocarbons, leading to large inconsistencies of calibration. For open-path detection of flammable concentrations the absorption for non-methane hydrocarbons is so strong that the measurement saturates, a significant gas cloud appearing black. This wavelength region is beyond the transmission range of borosilicate glass, so windows and lenses must be made of more expensive materials and tend to be small in aperture.
* 2.3 μm region. All hydrocarbons and their derivatives have absorption coefficients appropriate for open path detection at flammable concentrations. A useful advantage in practical applications is that the detector's response to many different gases and vapours is relatively uniform when expressed in terms of the lower flammable limit. Borosilicate glass retains useful transmission in this wavelength region, allowing large aperture optics to be produced at moderate cost.
* 1.6 μm region. A wide range of gases absorb in the near-infrared. Typically the absorption coefficients are relatively weak, but light molecules show narrow, individually resolved spectral lines rather than broad bands. This results in relatively large values of the gradient and curvature of the absorption with respect to wavelength, enabling semiconductor laser-based systems to distinguish gas molecules very specifically; for instance hydrogen sulfide, or methane to the exclusion of heavier hydrocarbons. | 1 | Applied and Interdisciplinary Chemistry |
One limitation of EPIC-seq is its reliance on prior knowledge of genes associated with specific cancers. The effectiveness of the EPIC-seq model hinges on the availability of comprehensive gene expression profiles for the targeted cancer types. This dependency may restrict its applicability to cancers with well-characterized gene expression patterns, limiting its utility in cancers with less understood molecular signatures. | 1 | Applied and Interdisciplinary Chemistry |
The specific heat capacity of LAGP materials with general formula fits into the Maier-Kelley polynomial law in the temperature range from room temperature to 700 °C:
where
: is the absolute temperature,
: are fitting constants.
Typical values are in the range of 0.75 - 1.5 J⋅g⋅K in the temperature interval 25 - 100 °C. The constants increase with the x value, i.e. with both the aluminium and the lithium content, while the constant does not follow a precise trend. As a result, the specific heat capacity of LAGP is expected to increase as the Al content grows and the Ge content decreases, which is consistent with data about the relative specific heats of aluminium and germanium compounds.
In addition, the thermal diffusivity of LAGP follows a decreasing trend with increasing temperature, irrespective of the aluminium content:
The aluminium level affects the exponent , which varies from 0.08 (high Al content) to 0.11 (low Al content). Such small values suggest the presence of a large number of point defects in the material, which is highly beneficial for solid ionic conductors. Finally, the expression for the thermal conductivity can be written:
where
: is the heat capacity per unit volume,
: is the average phonon group velocity,
: is the phonon mean free path,
: is the density of the material.
Taking everything into account, as the aluminium content in LAGP increases, the ionic conductivity increases as well, while the thermal conductivity decreases, since a larger number of lithium ions enhances the phonon scattering, thus reducing the phonon mean free path and the thermal transport in the material. Therefore, thermal and ionic transports in LAGP ceramics are not correlated: the corresponding conductivities follow opposite trends as a function of the aluminium content and are affected in a different way by temperature variations (e.g., the ionic conductivity increases by one order of magnitude upon an increase from room temperature to 100 °C, while the thermal conductivity increases by only 6%). | 0 | Theoretical and Fundamental Chemistry |
Robert Emerson described the eponymous effect in 1957. In his paper he observed that:
# When plants are exposed to light having wavelength greater than 680 nm, then only one photosystem is activated; i.e. PS700 resulting in formation of ATP only.
# When plants are exposed to light having wavelength less than 680 nm, the rate of photosynthesis was very low.
# On giving both shorter and higher wavelengths of light, the efficiency of the process increased, because both photosystems were working together at the same time, resulting in higher yield. | 0 | Theoretical and Fundamental Chemistry |
Diargon or the argon dimer is a molecule containing two argon atoms. Normally, this is only very weakly bound together by van der Waals forces (a van der Waals molecule). However, in an excited state, or ionised state, the two atoms can be more tightly bound together, with significant spectral features. At cryogenic temperatures, argon gas can have a few percent of diargon molecules. | 0 | Theoretical and Fundamental Chemistry |
Reverse transcriptase creates double-stranded DNA from an RNA template.
In virus species with reverse transcriptase lacking DNA-dependent DNA polymerase activity, creation of double-stranded DNA can possibly be done by host-encoded DNA polymerase δ, mistaking the viral DNA-RNA for a primer and synthesizing a double-stranded DNA by a similar mechanism as in primer removal, where the newly synthesized DNA displaces the original RNA template.
The process of reverse transcription, also called retrotranscription or retrotras, is extremely error-prone, and it is during this step that mutations may occur. Such mutations may cause drug resistance. | 1 | Applied and Interdisciplinary Chemistry |
Grain boundary sliding is a plastic deformation mechanism where crystals can slide past each other without friction and without creating significant voids as a result of diffusion. The deformation process associated with this mechanism is referred to as granular flow. The absence of voids results from solid-state diffusive mass transfer, locally enhanced crystal plastic deformation, or solution and precipitation of a grain boundary fluid. This mechanism operates at a low strain rate produced by neighbor switching. Grain boundary sliding is grain size- and temperature-dependent. It is favored by high temperatures and the presence of very fine-grained aggregates where diffusion paths are relatively short. Large strains operating in this mechanism do not result in the development of a lattice preferred orientation or any appreciable internal deformation of the grains, except at the grain boundary to accommodate the grain sliding; this process is called superplastic deformation. | 1 | Applied and Interdisciplinary Chemistry |
Expansion joints are required in large ducted air systems to allow fixed pieces of piping to be largely free of stress as thermal expansion occurs. Bends in elbows also can accommodate this. Expansion joints also isolate pieces of equipment such as fans from the rigid ductwork, thereby reducing vibration to the ductwork as well as allowing the fan to “grow” as it comes up to the operating air system temperature without placing stress on the fan or the fixed portions of ductwork.
An expansion joint is designed to allow deflection in the axial (compressive), lateral (shear), or angular (bending) deflections. Expansion joints can be non-metallic or metallic (often called bellows type). Non-metallic can be a single ply of rubberized material or a composite made of multiple layers of heat and erosion resistant flexible material. Typical layers are: outer cover to act a gas seal, a corrosion-resistant material such as Teflon, a layer of fiberglass to act as an
insulator and to add durability, several layers of insulation to ensure that the heat transfer from the flue gas is reduced to the required temperature and an inside layer.
A bellows is made up of a series of one or more convolutions of metal to allow the axial, lateral, or angular deflection. | 1 | Applied and Interdisciplinary Chemistry |
Radiation is produced owing to the spontaneous transition of an excimer molecule from an excited electronic state to the ground state. Excimer and exciplex molecules are not long-living formations. They rapidly decompose, typically within a few nanoseconds, releasing their excitation energy in the form of a UV photon:
: emission by an excimer molecule:
: emission by an exciplex molecule:
where Rg* is an excimer molecule, RgX* is an exciplex molecule, Rg is an atom of rare gas, and X is an atom of halogen. | 0 | Theoretical and Fundamental Chemistry |
SHIFTCOR is an automated protein chemical shift correction program that uses statistical methods to compare and correct predicted NMR chemical shifts (derived from the 3D structure of the protein) relative to an input set of experimentally measured chemical shifts. SHIFTCOR uses several simple statistical approaches and pre-determined cut-off values to identify and correct potential referencing, assignment and typographical errors. SHIFTCOR identifies potential chemical shift referencing problems by comparing the difference between the average value of each set of observed backbone (1Hα, 13Cα, 13Cβ, 13CO, 15N and 1HN) shifts and their corresponding predicted chemical shifts. The difference between these two averages results in a nucleus-specific chemical shift offset or reference correction (i.e. one for 1H, one for 13C and one for 15N). In order to ensure that certain extreme outliers do not unduly bias these average offset values, the average of the observed shifts is only calculated after excluding potential mis-assignments or typographical errors. | 0 | Theoretical and Fundamental Chemistry |
Barbara Cannon is a British-Swedish biochemist, physiologist and an academic. She is an emeritus professor at Stockholm University as well as the chairman of the scientific advisory board at The Helmholtz Centre. She is also a consultant at Combigene.
Cannon is most known for her work on mammalian thermogenesis, primarily focusing on the function of brown adipose tissue. She is the recipient of the 2014 King's Medal from the Order of the Seraphims, Sweden.
Cannon is a Fellow of the Royal Swedish Academy of Sciences. | 1 | Applied and Interdisciplinary Chemistry |
HDS systems should be sized based on treatment objectives including desired level of pollutant removal, drainage basin characteristics, climate of the region, and particle size to be targeted. Performance is also sensitive to water temperature, i.e. season. Care must be taken to avoid routing excess flow through the device and compromising performance. Each vendor’s product has different pollutant removal rates that should be evaluated before selecting the system.
The Technology Assessment Protocol-Ecology (TAPE) and Technology Acceptance and Reciprocity Partnership (TARP) are evaluation programs sponsored by several state agencies in the U.S. These programs include lab and field testing and provide specific sizing criteria for hydrodynamic separation systems.
Currently, the Environmental & Water Resources Institute (a component of the American Society of Civil Engineers) and ASTM International are developing comprehensive verification guidelines and standard test methods for assessing the performance of these devices. | 1 | Applied and Interdisciplinary Chemistry |
The Fineman-Ross method can be biased towards points at low or high monomer concentration, so Kelen and Tüdős introduced an arbitrary constant,
where and are the highest and lowest values of from the Fineman-Ross method. The data can be plotted in a linear form
where and . Plotting against yields a straight line that gives when and when . This distributes the data more symmetrically and can yield better results. | 0 | Theoretical and Fundamental Chemistry |
Slow strain rate testing (SSRT), also called constant extension rate tensile testing (CERT), is a popular test used by research scientists to study stress corrosion cracking. It involves a slow (compared to conventional tensile tests) dynamic strain applied at a constant extension rate in the environment of interest. These test results are compared to those for similar tests in a, known to be inert, environment. A 50-year history of the SSRT has recently been published by its creator. The test has also been standardized and two ASTM symposia devoted to it. | 1 | Applied and Interdisciplinary Chemistry |
The hexol cation exists as two optical isomers that are mirror images of each other, depending on the arrangement of the bonds between the central cobalt atom and the three bidentate peripheral units [Co(NH)(HO)]. It belongs to the D point group. The nature of chirality can be compared to that of the ferrioxalate anion .
In a historic set of experiments, a salt of hexol with an optically active anion — specifically, its -(+)-bromocamphorsulfonate – was resolved into separate salts of the two cation isomers by fractional crystallisation. A more efficient resolution involves the bis(tartrato)diantimonate(III) anion. The hexol hexacation has a high specific rotation of 2640°. | 0 | Theoretical and Fundamental Chemistry |
Subsets and Splits