text
stringlengths 105
4.57k
| label
int64 0
1
| label_text
stringclasses 2
values |
|---|---|---|
The stomach is a major organ of the gastrointestinal tract and digestive system. It is a consistently J-shaped organ joined to the esophagus at its upper end and to the duodenum at its lower end.
Gastric acid (informally gastric juice), produced in the stomach plays a vital role in the digestive process, and mainly contains hydrochloric acid and sodium chloride. A peptide hormone, gastrin, produced by G cells in the gastric glands, stimulates the production of gastric juice which activates the digestive enzymes. Pepsinogen is a precursor enzyme (zymogen) produced by the gastric chief cells, and gastric acid activates this to the enzyme pepsin which begins the digestion of proteins. As these two chemicals would damage the stomach wall, mucus is secreted by innumerable gastric glands in the stomach, to provide a slimy protective layer against the damaging effects of the chemicals on the inner layers of the stomach.
At the same time that protein is being digested, mechanical churning occurs through the action of peristalsis, waves of muscular contractions that move along the stomach wall. This allows the mass of food to further mix with the digestive enzymes. Gastric lipase secreted by the chief cells in the fundic glands in the gastric mucosa of the stomach, is an acidic lipase, in contrast with the alkaline pancreatic lipase. This breaks down fats to some degree though is not as efficient as the pancreatic lipase.
The pylorus, the lowest section of the stomach which attaches to the duodenum via the pyloric canal, contains countless glands which secrete digestive enzymes including gastrin. After an hour or two, a thick semi-liquid called chyme is produced. When the pyloric sphincter, or valve opens, chyme enters the duodenum where it mixes further with digestive enzymes from the pancreas, and then passes through the small intestine, where digestion continues.
The parietal cells in the fundus of the stomach, produce a glycoprotein called intrinsic factor which is essential for the absorption of vitamin B12. Vitamin B12 (cobalamin), is carried to, and through the stomach, bound to a glycoprotein secreted by the salivary glands – transcobalamin I also called haptocorrin, which protects the acid-sensitive vitamin from the acidic stomach contents. Once in the more neutral duodenum, pancreatic enzymes break down the protective glycoprotein. The freed vitamin B12 then binds to intrinsic factor which is then absorbed by the enterocytes in the ileum.
The stomach is a distensible organ and can normally expand to hold about one litre of food. This expansion is enabled by a series of gastric folds in the inner walls of the stomach. The stomach of a newborn baby will only be able to expand to retain about 30 ml. | 1 | Applied and Interdisciplinary Chemistry |
In fluid dynamics, Green's law, named for 19th-century British mathematician George Green, is a conservation law describing the evolution of non-breaking, surface gravity waves propagating in shallow water of gradually varying depth and width. In its simplest form, for wavefronts and depth contours parallel to each other (and the coast), it states:
: or
where and are the wave heights at two different locations – 1 and 2 respectively – where the wave passes, and and are the mean water depths at the same two locations.
Greens law is often used in coastal engineering for the modelling of long shoaling waves on a beach, with "long" meaning wavelengths in excess of about twenty times the mean water depth. Tsunamis shoal (change their height) in accordance with this law, as they propagate – governed by refraction and diffraction – through the ocean and up the continental shelf. Very close to (and running up) the coast, nonlinear effects become important and Greens law no longer applies. | 1 | Applied and Interdisciplinary Chemistry |
miR-324-5p likely regulates cell growth and survival through interaction with multiple pathways. Published research demonstrates that this miRNA interacts with the Hedgehog (HH) signaling pathway via interactions with HH transcription factor Gli1 and HH protein receptor Smo, often contributing to tumorigenesis. miR-324-5p's activating interaction with the protein NfkB also regulates numerous components of cell survival, including cell cycle control, enzyme synthesis, and cell adhesion. In addition, miR-324-5p regulates components of the MAPK pathway, influencing cell growth, proliferation, and survival. Specifically, miR-324-5p downregulates RAF and ERK and is necessary for normal levels of cell growth. Reduced expression leads to increased cell growth and proliferation, and overexpression limits growth, leading to its role in oncogenesis. | 1 | Applied and Interdisciplinary Chemistry |
Under the molecular orbital formalism, a typical ground-state molecule has electrons in the lowest possible energy levels. According to the Pauli principle, at most two electrons can occupy a given orbital, and if an orbital contains two electrons they must be in opposite spin states. The highest occupied molecular orbital is called the HOMO and the lowest unoccupied molecular orbital is called the LUMO; the energy gap between these two states is known as the HOMO–LUMO gap. If the molecule absorbs light whose energy is equal to this gap, an electron in the HOMO may be excited to the LUMO. This is called the molecule's excited state.
Excimers are only formed when one of the dimer components is in the excited state. When the excimer returns to the ground state, its components dissociate and often repel each other. The wavelength of an excimers emission is longer (smaller energy) than that of the excited monomers emission. An excimer can thus be measured by fluorescent emissions.
Because excimer formation is dependent on a bimolecular interaction, it is promoted by high monomer density. Low-density conditions produce excited monomers that decay to the ground state before they interact with an unexcited monomer to form an excimer. | 0 | Theoretical and Fundamental Chemistry |
Fluoroantimonic acid solution is so reactive that it is challenging to identify media with which it is unreactive. Materials compatible with fluoroantimonic acid as a solvent include SOClF, and sulfur dioxide; some chlorofluorocarbons have also been used. Containers for HF/SbF are made of PTFE.
Fluoroantimonic acid solutions decompose when heated, generating free hydrogen fluoride gas and liquid antimony pentafluoride at a temperature of 40 °C.
As a superacid, fluoroantimonic acid solutions protonate nearly all organic compounds, often causing dehydrogenation, or dehydration. In 1967, Bickel and Hogeveen showed that 2HF·SbF reacts with isobutane and neopentane to form carbenium ions:
:(CH)CH + H → (CH)C + H
:(CH)C + H → (CH)C + CH
It is also used in the synthesis of tetraxenonogold complexes. | 0 | Theoretical and Fundamental Chemistry |
Piperidine is produced by hydrogenation of pyridine with a nickel-, cobalt-, or ruthenium-based catalyst at elevated temperatures. The hydrogenation of pyridine to piperidine releases 193.8 kJ·mol, which is slightly less than the energy of the hydrogenation of benzene (205.3 kJ·mol).
Partially hydrogenated derivatives are obtained under milder conditions. For example, reduction with lithium aluminium hydride yields a mixture of 1,4-dihydropyridine, 1,2-dihydropyridine, and 2,5-dihydropyridine. Selective synthesis of 1,4-dihydropyridine is achieved in the presence of organometallic complexes of magnesium and zinc, and (Δ3,4)-tetrahydropyridine is obtained by electrochemical reduction of pyridine. Birch reduction converts pyridine to dihydropyridines. | 0 | Theoretical and Fundamental Chemistry |
UV-induced RNA-antibody crosslinking was added on top of m6A-seq to produce PA-m6A-seq (photo-crosslinking-assisted m6A-seq) which increases resolution up to ~23nt. First, 4-thiourodine (4SU) is incorporated into the RNA by adding 4SU in growth media, some incorporation sites presumably near m6A location. Immunoprecipitation is then performed on full-length RNA using m6A-specific antibody [36]. UV light at 365 nm is then shined onto RNA to activate the crosslinking to the antibody with 4SU. Crosslinked RNA was isolated via competition elution and fragmented further to ~25-30nt; proteinase K was used to dissociate the covalent bond between crosslinking site and antibody. Peptide fragments that remain after antibody removal from RNA cause the base to be read as a C as opposed to a T during reverse transcription, effectively inducing a point mutation at the 4SU crosslinking site. The short fragments are subjected to library construction and Illumina sequencing, followed by finding the consensus methylation sequence.
The presence of the T to C mutation helps increase the signal to noise ratio of methylation site detection as well as providing greater resolution to the methylation sequence.
One shortcoming of this method is that m6A sites that did not incorporate 4SU can't be detected.
Another caveat is that position of 4SU incorporation can vary relative to any single m6A residue, so it still remains challenging to precisely locate m6A site using the T to C mutation. | 1 | Applied and Interdisciplinary Chemistry |
In surface science, a tensiometer is a measuring instrument used to measure the surface tension () of liquids or surfaces. Tensiometers are used in research and development laboratories to determine the surface tension of liquids like coatings, lacquers or adhesives. A further application field of tensiometers is the monitoring of industrial production processes like parts cleaning or electroplating. | 0 | Theoretical and Fundamental Chemistry |
Between World War I and World War II, many new aspirin brands and aspirin-based products entered the market. The Australian company Nicholas Proprietary Limited, through the aggressive marketing strategies of George Davies, built Aspro into a global brand, with particular strength in Australia, New Zealand, and the U.K. American brands such as Burtons Aspirin, Molloys Aspirin, Cal-Aspirin and St. Joseph Aspirin tried to compete with the American Bayer, while new products such Cafaspirin (aspirin with caffeine) and Alka-Seltzer (a soluble mix of aspirin and bicarbonate of soda) put aspirin to new uses. In 1925, the German Bayer became part of IG Farben, a conglomerate of former dye companies; IG Farbens brands of Aspirin and, in Latin America, the caffeinated Cafiaspirina (co-managed with Sterling Products) competed with less expensive aspirins such as Geniol'. | 1 | Applied and Interdisciplinary Chemistry |
For a mathematical definition of a dilution assay an observation space is defined and a function so that the responses are mapped to the set of real numbers. It is now assumed that a function exists which relates the dose to the response
in which is an error term with expectation 0. is usually assumed to be continuous and monotone. In situations where a standard preparation is included it is furthermore assumed that the test preparation behaves like a dilution (or concentration) of the standard
:, for all
where is the relative potency of . This is the fundamental assumption of similarity of dose-response curves which is necessary for a meaningful and unambiguous definition of the relative potency. In many cases it is convenient to apply a power transformation with or a logarithmic transformation . The latter can be shown to be a limit case of so if is written for the log transformation the above equation can be redefined as
:, for all .
Estimates of are usually restricted to be member of a well-defined parametric family of functions, for example the family of linear functions characterized by an intercept and a slope. Statistical techniques such as optimization by Maximum Likelihood can be used to calculate estimates of the parameters. Of notable importance in this respect is the theory of Generalized Linear Models with which a wide range of dilution assays can be modelled. Estimates of may describe satisfactorily over the range of doses tested, but they do not necessarily have to describe beyond that range. However, this does not mean that dissimilar curves can be restricted to an interval where they happen to be similar.
In practice, itself is rarely of interest. More of interest is an estimate of or an estimate of the dose that induces a specific response. These estimates involve taking ratios of statistically dependent parameter estimates. Fieller's theorem can be used to compute confidence intervals of these ratios.
Some special cases deserve particular mention because of their widespread use: If is linear and this is known as a slope-ratio model. If is linear and this is known as a parallel line model. Another commonly applied model is the probit model where is the cumulative normal distribution function, and follows a binomial distribution. | 1 | Applied and Interdisciplinary Chemistry |
The permanent Venusian clouds produce a concentrated acid rain, as the clouds in the atmosphere of Earth produce water rain. Jupiter's moon Europa is also thought to have an atmosphere containing sulfuric acid hydrates. | 0 | Theoretical and Fundamental Chemistry |
Hammond's postulate (or alternatively the Hammond–Leffler postulate), is a hypothesis in physical organic chemistry which describes the geometric structure of the transition state in an organic chemical reaction. First proposed by George Hammond in 1955, the postulate states that:
Therefore, the geometric structure of a state can be predicted by comparing its energy to the species neighboring it along the reaction coordinate. For example, in an exothermic reaction the transition state is closer in energy to the reactants than to the products. Therefore, the transition state will be more geometrically similar to the reactants than to the products. In contrast, however, in an endothermic reaction the transition state is closer in energy to the products than to the reactants. So, according to Hammond’s postulate the structure of the transition state would resemble the products more than the reactants. This type of comparison is especially useful because most transition states cannot be characterized experimentally.
Hammonds postulate also helps to explain and rationalize the Bell–Evans–Polanyi principle. Namely, this principle describes the experimental observation that the rate of a reaction, and therefore its activation energy, is affected by the enthalpy of that reaction. Hammonds postulate explains this observation by describing how varying the enthalpy of a reaction would also change the structure of the transition state. In turn, this change in geometric structure would alter the energy of the transition state, and therefore the activation energy and reaction rate as well.
The postulate has also been used to predict the shape of reaction coordinate diagrams. For example, electrophilic aromatic substitution involves a distinct intermediate and two less well defined states. By measuring the effects of aromatic substituents and applying Hammond's postulate it was concluded that the rate-determining step involves formation of a transition state that should resemble the intermediate complex. | 0 | Theoretical and Fundamental Chemistry |
These predicted editing sites result in the translation of an Arginine instead of a Glutamine at the Q/R site and an Alanine instead of a Threonine at the T/A site. These codon changes are nonsynomonous. Since the editing sites are located just before a collagen like trimerization domain, editing may effect protein oligomerization. This region is also likely to be a protease domain. It is not known if the amino acid changes caused by editing could have an effect on these domains. | 1 | Applied and Interdisciplinary Chemistry |
p53 - package - palindromic sequence - palmitoyl acyltransferase - Parkinson's disease - pBR322 - PCR - pedigree - peptide - peptide-transporting ATPase - peptide bond - phage - phagemid - phenotype - phenylacetaldoxime dehydratase - PhIP-Seq - phosphatase, alkaline - phosphatidylcholine 12-monooxygenase - phosphatidylcholine desaturase - phosphatidylinositol a-mannosyltransferase - phosphodiester bond - phospholipid acyltransferase - phosphonate-transporting ATPase - phosphorylation - physical map - plant calmodulin-binding domain - plasmid - plastoquinol/plastocyanin reductase - point mutation - poly-A track - polyA tail - polyacrylamide gel - polyclonal antibodies - polydactyly - polymerase - polymerase chain reaction - polymorphism - polynucleotide kinase - polypeptide - polyvinyl-alcohol dehydrogenase (acceptor) - positional cloning - positional sequencing - post-transcriptional regulation - post-translational modification - post-translational processing - post-translational regulation - PRE - precursor mRNA - primary immunodeficiency - primary transcript - primer - primer extension - probe - processivity - progesterone 5alpha-reductase - promoter - pronucleus - prostate cancer - protease - proteasome - proteasome ATPase - protein - Protein translocation - proto-oncogene - pseudobaptigenin synthase - pseudogene - pseudoknot - pseudorevertant - pulse sequence database - pulsed field gel electrophoresis - purine - PyrC leader - PyrD leader - pyrimidine | 1 | Applied and Interdisciplinary Chemistry |
Aldehydes participate in many reactions. From the industrial perspective, important reactions are:
* condensations, e.g., to prepare plasticizers and polyols, and
* reduction to produce alcohols, especially "oxo-alcohols". From the biological perspective, the key reactions involve addition of nucleophiles to the formyl carbon in the formation of imines (oxidative deamination) and hemiacetals (structures of aldose sugars). | 0 | Theoretical and Fundamental Chemistry |
Most analytical techniques use a calibration curve. There are a number of advantages to this approach. First, the calibration curve provides a reliable way to calculate the uncertainty of the concentration calculated from the calibration curve (using the statistics of the least squares line fit to the data).
Second, the calibration curve provides data on an empirical relationship. The mechanism for the instrument's response to the analyte may be predicted or understood according to some theoretical model, but most such models have limited value for real samples. (Instrumental response is usually highly dependent on the condition of the analyte, solvents used and impurities it may contain; it could also be affected by external factors such as pressure and temperature.)
Many theoretical relationships, such as fluorescence, require the determination of an instrumental constant anyway, by analysis of one or more reference standards; a calibration curve is a convenient extension of this approach. The calibration curve for a particular analyte in a particular (type of) sample provides the empirical relationship needed for those particular measurements.
The chief disadvantages are (1) that the standards require a supply of the analyte material, preferably of high purity and in known concentration, and (2) that the standards and the unknown are in the same matrix. Some analytes - e.g., particular proteins - are extremely difficult to obtain pure in sufficient quantity. Other analytes are often in complex matrices, e.g., heavy metals in pond water. In this case, the matrix may interfere with or attenuate the signal of the analyte. Therefore, a comparison between the standards (which contain no interfering compounds) and the unknown is not possible. The method of standard addition is a way to handle such a situation. | 1 | Applied and Interdisciplinary Chemistry |
The majority of observed interactions between promoters and enhancers do not cross TAD boundaries. Removing a TAD boundary (for example, using CRISPR to delete the relevant region of the genome) can allow new promoter-enhancer contacts to form. This can affect gene expression nearby - such misregulation has been shown to cause limb malformations (e.g. polydactyly) in humans and mice.
Computer simulations have shown that transcription-induced supercoiling of chromatin fibres can explain how TADs are formed and how they can assure very efficient interactions between enhancers and their cognate promoters located in the same TAD. | 1 | Applied and Interdisciplinary Chemistry |
Tellurium-128 and -130 are essentially stable. They only decay by double beta decay, with half lives >10 years. They constitute the major fraction of natural occurring tellurium at 32 and 34% respectively.
Tellurium-132 and its daughter I are important in the first few days after a criticality. It was responsible for a large fraction of the dose inflicted on workers at Chernobyl in the first week.
The isobar forming Te/I is: Tin-132 (half-life 40 s) decaying to antimony-132 (half-life 2.8 minutes) decaying to tellurium-132 (half-life 3.2 days) decaying to iodine-132 (half-life 2.3 hours) which decays to stable xenon-132.
The creation of tellurium-126 is delayed by the long half-life (230 k years) of tin-126. | 0 | Theoretical and Fundamental Chemistry |
Desorption is the physical process where adsorbed atoms or molecules are released from a surface into the surrounding vacuum or fluid. This occurs when a molecule gains enough energy to overcome the activation barrier and the binding energy that keep it attached to the surface.
Desorption is the reverse of the process of adsorption, which differs from absorption in that adsorption it refers to substances bound to the surface, rather than being absorbed into the bulk.
Desorption can occur from any of several processes, or a combination of them: it may result from heat (thermal energy); incident light such as infrared, visible, or ultraviolet photons; or a incident beam of energetic particles such as electrons. It may also occur following chemical reactions such as oxidation or reduction in an electrochemical cell or after a chemical reaction of a adsorbed compounds in which the surface may act as a catalyst. | 0 | Theoretical and Fundamental Chemistry |
NURF was first purified from the model organism Drosophila melanogaster by Toshio Tsukiyama and Carl Wu in 1995. Tsukiyama and Wu described NURF’s chromatin remodeling activity on the hsp70 promoter. It was later discovered that NURF regulates transcription in this manner for hundreds of genes. A human ortholog of NURF, called hNURF, was isolated in 2003. | 1 | Applied and Interdisciplinary Chemistry |
Typically, computation inference methods are primarily used to predict protein targets for small molecule drugs based on computer based pattern recognition. However, this method could also be used for finding new targets for existing or newly developed drugs. By identifying the pharmacophore of the drug molecule, the profiling method of pattern recognition can be carried out where a new target is identified. This provides an insight at a possible mechanism of action since it is known what certain functional components of the drug are responsible for when interacting with a certain area on a protein, thus leading to a therapeutic effect. | 1 | Applied and Interdisciplinary Chemistry |
The relevance of observations from fission yeast mating-type regions and centromeres to mammals is not clear, as some evidence suggests that heterochromatin maintenance in mammalian cells is independent of the components of the RNAi pathway. It is known, however, that plants and animals have analogous mechanism for small RNA-guided heterochromatin formation, and it is believed that the mechanisms described above for S. pombe are highly conserved and play some role in heterochromatin formation in mammals as well. In higher eukaryotes, RNAi-dependent heterochromatic silencing appears to play a larger role in germline cells than in primary cells or cell lines, and is only one of the many different forms of gene silencing used throughout the genome, making it more difficult to study.
The role of RNAi in transcriptional gene silencing in plants has been characterized fairly well, and functions primarily through DNA methylation via the RdDM pathway. In this process, which is distinct from the process described above, argonaut-bound siRNA recognizes nascent RNA transcripts or the target DNA to guide the methylation and silencing of the target genomic region. | 1 | Applied and Interdisciplinary Chemistry |
Ordered Two-Template Relay (OTTR) is a library preparation technique used to improve quantitation of highly modified non-coding RNA (ncRNA) species, which have been difficult to characterize using traditional cDNA sequencing approaches. OTTR leverages a retroelement reverse transcriptase (RT), termed BoMoC, with template jumping properties and high processivity across modified RNA templates, to generate cDNA products for next-generation sequencing (NGS). Overall, OTTR offers a streamlined approach for cDNA library production of full-length and modified ncRNA targets. | 1 | Applied and Interdisciplinary Chemistry |
The main advantages to using emulsified fuels instead of the fuel itself are environmental and economic benefits. Addition of water to the diesel process decreases combustion temperatures and lowers NO emissions. A paper compares water injection and emulsified fuels into diesel engines (marine and stationary engines) and discusses the emissions and mechanisms involved. It concludes that emulsified fuels are singularly effective in simultaneously reducing NO and PM emissions. Another paper has examined the effects of EGR and Emulsion Fuels. | 0 | Theoretical and Fundamental Chemistry |
12-Crown-4, also called 1,4,7,10-tetraoxacyclododecane and lithium ionophore V, is a crown ether with the formula CHO. It is a cyclic tetramer of ethylene oxide which is specific for the lithium cation. | 0 | Theoretical and Fundamental Chemistry |
It is produced by thermal reactions of compounds of the type HNCHCHX (X = OH, NH, or NHR) in the presence of zeolitic catalysts. An idealized conversion is shown for the conversion from ethanolamine:
:3 HNCHCHOH → N(CHCH)N + NH + 3 HO | 0 | Theoretical and Fundamental Chemistry |
The manufacture of nuclei on the island of stability proves to be very difficult because the nuclei available as starting materials do not deliver the necessary sum of neutrons. Radioactive ion beams (such as S) in combination with actinide targets (such as Cm) may allow the production of more neutron rich nuclei nearer to the center of the island of stability, though such beams are not currently available in the required intensities to conduct such experiments. Several heavier isotopes such as Cm and Es may still be usable as targets, allowing the production of isotopes with one or two more neutrons than known isotopes, though the production of several milligrams of these rare isotopes to create a target is difficult. It may also be possible to probe alternative reaction channels in the same Ca-induced fusion-evaporation reactions that populate the most neutron-rich known isotopes, namely those at a lower excitation energy (resulting in fewer neutrons being emitted during de-excitation), or those involving evaporation of charged particles (pxn, evaporating a proton and several neutrons, or αxn, evaporating an alpha particle and several neutrons). This may allow the synthesis of neutron-enriched isotopes of elements 111–117. Although the predicted cross sections are on the order of 1–900 fb, smaller than when only neutrons are evaporated (xn channels), it may still be possible to generate otherwise unreachable isotopes of superheavy elements in these reactions. Some of these heavier isotopes (such as Mc, Fl, and Nh) may also undergo electron capture (converting a proton into a neutron) in addition to alpha decay with relatively long half-lives, decaying to nuclei such as Cn that are predicted to lie near the center of the island of stability. However, this remains largely hypothetical as no superheavy nuclei near the beta-stability line have yet been synthesized and predictions of their properties vary considerably across different models.
The process of slow neutron capture used to produce nuclides as heavy as Fm is blocked by short-lived isotopes of fermium that undergo spontaneous fission (for example, Fm has a half-life of 370 µs); this is known as the "fermium gap" and prevents the synthesis of heavier elements in such a reaction. It might be possible to bypass this gap, as well as another predicted region of instability around A = 275 and Z = 104–108, in a series of controlled nuclear explosions with a higher neutron flux (about a thousand times greater than fluxes in existing reactors) that mimics the astrophysical r-process. First proposed in 1972 by Meldner, such a reaction might enable the production of macroscopic quantities of superheavy elements within the island of stability; the role of fission in intermediate superheavy nuclides is highly uncertain, and may strongly influence the yield of such a reaction.
It may also be possible to generate isotopes in the island of stability such as Fl in multi-nucleon transfer reactions in low-energy collisions of actinide nuclei (such as U and Cm). This inverse quasifission (partial fusion followed by fission, with a shift away from mass equilibrium that results in more asymmetric products) mechanism may provide a path to the island of stability if shell effects around Z = 114 are sufficiently strong, though lighter elements such as nobelium and seaborgium (Z = 102–106) are predicted to have higher yields. Preliminary studies of the U + U and U + Cm transfer reactions have failed to produce elements heavier than mendelevium (Z = 101), though the increased yield in the latter reaction suggests that the use of even heavier targets such as Es (if available) may enable production of superheavy elements. This result is supported by a later calculation suggesting that the yield of superheavy nuclides (with Z ≤ 109) will likely be higher in transfer reactions using heavier targets. A 2018 study of the U + Th reaction at the Texas A&M Cyclotron Institute by Sara Wuenschel et al. found several unknown alpha decays that may possibly be attributed to new, neutron-rich isotopes of superheavy elements with 104 < Z < 116, though further research is required to unambiguously determine the atomic number of the products. This result strongly suggests that shell effects have a significant influence on cross sections, and that the island of stability could possibly be reached in future experiments with transfer reactions. | 0 | Theoretical and Fundamental Chemistry |
Robert Sidney Cahn (9 June 1899 – 15 June 1981) was a British chemist, best known for his contributions to chemical nomenclature and stereochemistry, particularly by the Cahn–Ingold–Prelog priority rules, which he proposed in 1956 with Christopher Kelk Ingold and Vladimir Prelog. Cahn was the first to report the structure of Cannabinol (CBN) found in Cannabis in the early 1930s.
Cahn was born in Hampstead, London. He became a fellow of the Royal Institute of Chemistry and was editor of the Journal of the Chemical Society from 1949 until 1963, and he remained with the Society as Director of Publications Research until his retirement in 1965. | 0 | Theoretical and Fundamental Chemistry |
K and U move together during geochemical processes and have long-lived radioisotopes that emit gamma rays. It is calculated as a ratio of one to the other on an equal mass basis which is often .
This creates a compelling explanation for the evolution of the solar system.
This result is consistent with an increasing temperature toward the sun during its early protoplanetary nebula phase.
The temperature at the early stage of solar system formation was in excess of 1,000K at the distance of Earth from the sun, and as low as 200–100K at the distances of Jupiter and Saturn. | 0 | Theoretical and Fundamental Chemistry |
Normality can be used for acid-base titrations. For example, sulfuric acid (HSO) is a diprotic acid. Since only 0.5 mol of HSO are needed to neutralize 1 mol of OH, the equivalence factor is:
:f(HSO) = 0.5
If the concentration of a sulfuric acid solution is c(HSO) = 1 mol/L, then its normality is 2 N. It can also be called a "2 normal" solution.
Similarly, for a solution with c(HPO) = 1 mol/L, the normality is 3 N because phosphoric acid contains 3 acidic H atoms. | 0 | Theoretical and Fundamental Chemistry |
*Help to insulate a building for sound; the soil helps to block lower frequencies and the plants block higher frequencies
*If installed correctly many living roofs can contribute to LEED points
*Increase agricultural space
*Green roofs not only retain rainwater, but also moderate the temperature of the water and act as natural filters for any of the water that happens to run off. | 1 | Applied and Interdisciplinary Chemistry |
The main advantage of locating a space power station in geostationary orbit is that the antenna geometry stays constant, and so keeping the antennas lined up is simpler. Another advantage is that nearly continuous power transmission is immediately available as soon as the first space power station is placed in orbit, LEO requires several satellites before they are producing nearly continuous power.
Power beaming from geostationary orbit by microwaves carries the difficulty that the required optical aperture sizes are very large. For example, the 1978 NASA SPS study required a 1 km diameter transmitting antenna and a 10 km diameter receiving rectenna for a microwave beam at 2.45 GHz. These sizes can be somewhat decreased by using shorter wavelengths, although they have increased atmospheric absorption and even potential beam blockage by rain or water droplets. Because of the thinned array curse, it is not possible to make a narrower beam by combining the beams of several smaller satellites. The large size of the transmitting and receiving antennas means that the minimum practical power level for an SPS will necessarily be high; small SPS systems will be possible, but uneconomic.
A collection of LEO (low earth orbit) space power stations has been proposed as a precursor to GEO (geostationary orbit) space-based solar power. | 0 | Theoretical and Fundamental Chemistry |
In microbial communities like soil, the C:N ratio is a key indicator as it describes a balance between energetic foods (represented by carbon) and material to build protein with (represented by nitrogen). An optimal C:N ratio of around 24:1 provides for higher microbial activity.
The C:N ratio of soil can be modified by the addition of materials such as compost, manure, and mulch. A feedstock with a near-optimal C:N ratio will be consumed quickly. Any excess C will cause the N originally in the soil to be consumed, competing with the plant for nutrients (immobilization) – at least temporarily until the microbes die. Any excess N, on the other hand, will usually just be left behind (mineralization), but too much excess may result in losses to leaching. The recommended C:N ratio for soil materials is therefore 30:1. A soil test may be done to find the C:N ratio of soil itself.
The C:N ratio of microbes themselves is generally around 10:1. A lower ratio is correlated with higher soil productivity. | 0 | Theoretical and Fundamental Chemistry |
Discovered by Tillett and Francis in 1930, it was initially thought that CRP might be a pathogenic secretion since it was elevated in a variety of illnesses, including cancer. The later discovery of hepatic synthesis (made in the liver) demonstrated that it is a native protein. Initially, CRP was measured using the quellung reaction which gave a positive or a negative result. More precise methods nowadays use dynamic light scattering after reaction with CRP-specific antibodies.
CRP was so named because it was first identified as a substance in the serum of patients with acute inflammation that reacted with the cell wall polysaccharide (C-polysaccharide) of pneumococcus. | 1 | Applied and Interdisciplinary Chemistry |
The WGSR is a highly valuable industrial reaction that is used in the manufacture of ammonia, hydrocarbons, methanol, and hydrogen. Its most important application is in conjunction with the conversion of carbon monoxide from steam reforming of methane or other hydrocarbons in the production of hydrogen. In the Fischer–Tropsch process, the WGSR is one of the most important reactions used to balance the H/CO ratio. It provides a source of hydrogen at the expense of carbon monoxide, which is important for the production of high purity hydrogen for use in ammonia synthesis.
The water–gas shift reaction may be an undesired side reaction in processes involving water and carbon monoxide, e.g. the rhodium-based Monsanto process. The iridium-based Cativa process uses less water, which suppresses this reaction. | 0 | Theoretical and Fundamental Chemistry |
Other experts have proposed building reservoirs to prevent the movement of algae downstream. However, that can lead to the growth of algae within the reservoir, which become sediment traps with a resultant buildup of nutrients. Some researchers found that intensive blooms in reservoirs were the primary source of toxic algae observed downstream, but the movement of algae has so far been less studied, although it is considered a likely cause of algae transport. | 0 | Theoretical and Fundamental Chemistry |
Siderophores have applications in medicine for iron and aluminum overload therapy and antibiotics for improved targeting. Understanding the mechanistic pathways of siderophores has led to opportunities for designing small-molecule inhibitors that block siderophore biosynthesis and therefore bacterial growth and virulence in iron-limiting environments.
Siderophores are useful as drugs in facilitating iron mobilization in humans, especially in the treatment of iron diseases, due to their high affinity for iron. One potentially powerful application is to use the iron transport abilities of siderophores to carry drugs into cells by preparation of conjugates between siderophores and antimicrobial agents. Because microbes recognize and utilize only certain siderophores, such conjugates are anticipated to have selective antimicrobial activity. An example is the cephalosporin antibiotic cefiderocol.
Microbial iron transport (siderophore)-mediated drug delivery makes use of the recognition of siderophores as iron delivery agents in order to have the microbe assimilate siderophore conjugates with attached drugs. These drugs are lethal to the microbe and cause the microbe to apoptosise when it assimilates the siderophore conjugate. Through the addition of the iron-binding functional groups of siderophores into antibiotics, their potency has been greatly increased. This is due to the siderophore-mediated iron uptake system of the bacteria. | 1 | Applied and Interdisciplinary Chemistry |
Phenanthroline may be prepared by two successive Skraup reactions of glycerol with o-phenylenediamine, catalyzed by sulfuric acid, and an oxidizing agent, traditionally aqueous arsenic acid or nitrobenzene. Dehydration of glycerol gives acrolein which condenses with the amine followed by a cyclization. | 0 | Theoretical and Fundamental Chemistry |
Radiocarbon is a scientific journal devoted to the topic of radiocarbon dating.
It was founded in 1959 as a supplement to the American Journal of Science, and is an important source of data and information about radiocarbon dating. It publishes many radiocarbon results, and since 1979 it has published the proceedings of the international conferences on radiocarbon dating. The journal is published six times per year. it is published by Cambridge University Press. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, photocatalysis is the acceleration of a photoreaction in the presence of a photocatalyst, the excited state of which "repeatedly interacts with the reaction partners forming reaction intermediates and regenerates itself after each cycle of such interactions." In many cases, the catalyst is a solid that upon irradiation with UV- or visible light generates electron–hole pairs that generate free radicals. Photocatalysts belong to three main groups; heterogeneous, homogeneous, and plasmonic antenna-reactor catalysts. The use of each catalysts depends on the preferred application and required catalysis reaction. | 0 | Theoretical and Fundamental Chemistry |
This book describes how an official, the Bergmeister, is in charge of mining. He marks out the land into areas called meers when a vein is discovered. The rest of the book covers the laws of mining. There is a section on how the mine can be divided into shares. The roles of various other officials in regulating mines and taxing the production are stated. The shifts of the miners are fixed. The chief trades in the mine are listed and are regulated by both the Bergmeister and their foremen. | 1 | Applied and Interdisciplinary Chemistry |
As stated previously, Darken's first equation allows the calculation of the marker velocity in respect to a binary system where the two components have different diffusion coefficients. For this equation to be applicable, the analyzed system must have a constant concentration and can be modeled by the Boltzmann–Matano solution.
For the derivation, a hypothetical case is considered where two homogeneous binary alloy rods of two different compositions are in contact. The sides are protected, so that all of the diffusion occurs parallel to the length of the rod. In establishing the coordinate axes to evaluate the derivation, Darken sets the x-axis to be fixed at the far ends of the rods, and the origin at the initial position of the interface between the two rods. In addition this choice of a coordinate system allows the derivation to be simplified, whereas Smigelskas and Kirkendall's coordinate system was considered to be the non-optimal choice for this particular calculation as can be seen in the following section. At the initial planar interface between the rods, it is considered that there are infinitely small inert markers placed in a plane which is perpendicular to the length of the rods. Here, inert markers are defined to be a group of particles that are of a different elemental make-up from either of the diffusing components and move in the same fashion. For this derivation, the inert markers are assumed to be following the motion of the crystal lattice. The motion relative to the marker is associated with diffusion, , while the motion of the markers is associated with advection, . Fick’s first law, the previous equation stated for diffusion, describes the entirety of the system for only small distances from the origin, since at large distances advection needs to be accounted for. This results in the total rate of transport for the system being influenced by both factors, diffusion and advection. | 0 | Theoretical and Fundamental Chemistry |
The enzyme-linked immunosorbent spot (ELISpot) is a type of assay that focuses on quantitatively measuring the frequency of cytokine secretion for a single cell. The ELISpot Assay is also a form of immunostaining since it is classified as a technique that uses antibodies to detect a protein analyte, with the word analyte referring to any biological or chemical substance being identified or measured.
The FluoroSpot Assay is a variation of the ELISpot assay. The FluoroSpot Assay uses fluorescence in order to analyze multiple analytes, meaning it can detect the secretion of more than one type of protein. | 1 | Applied and Interdisciplinary Chemistry |
A survey of glass objects at the Victoria and Albert Museum in London, in 1992, found that more than 1 in 10 objects in the collection were affected by crizzling, ranging from 16th century Venetian to 20th century Scandinavian glass.
Venetian glass is particularly susceptible because artisans minimized the use of lime, to make the glass as clear as possible.
The works of modern glassmakers who experiment with their glass formulas, such as Ettore Sottsass, can also be at high risk for damage.
Museums such as the National Museum of the American Indian may find glass disease an issue of great importance because many of the Native American cultural materials in their collections incorporate glass beads.
Small ornamental glass beads were often made cheaply, using recipes with a high flux to silica ratio. This makes them more susceptible to glass disease. Blues, reds, and black are often affected by glass disease. The combination of glass beads with other materials (cordage, fabric, leather, metal, bone, surface colorants, ceremonial substances, and kaolin) complicates deterioration and conservation of ethnographic objects. | 0 | Theoretical and Fundamental Chemistry |
As a response to gunpowder artillery, European fortifications began displaying architectural principles such as lower and thicker walls in the mid-1400s. Cannon towers were built with artillery rooms where cannons could discharge fire from slits in the walls. However this proved problematic as the slow rate of fire, reverberating concussions, and noxious fumes produced greatly hindered defenders. Gun towers also limited the size and number of cannon placements because the rooms could only be built so big. Notable surviving artillery towers include a seven layer defensive structure built in 1480 at Fougères in Brittany, and a four layer tower built in 1479 at Querfurth in Saxony.
The star fort, also known as the bastion fort, tracé à litalienne, or renaissance fortress, was a style of fortification that became popular in Europe during the 16th century. The bastion and star fort was developed in Italy, where the Florentine engineer Giuliano da Sangallo (1445–1516) compiled a comprehensive defensive plan using the geometric bastion and full tracé à litalienne that became widespread in Europe.
The main distinguishing features of the star fort were its angle bastions, each placed to support their neighbor with lethal crossfire, covering all angles, making them extremely difficult to engage with and attack. Angle bastions consisted of two faces and two flanks. Artillery positions positioned at the flanks could fire parallel into the opposite bastion's line of fire, thus providing two lines of cover fire against an armed assault on the wall, and preventing mining parties from finding refuge. Meanwhile, artillery positioned on the bastion platform could fire frontally from the two faces, also providing overlapping fire with the opposite bastion. Overlapping mutually supporting defensive fire was the greatest advantage enjoyed by the star fort. As a result, sieges lasted longer and became more difficult affairs. By the 1530s the bastion fort had become the dominant defensive structure in Italy.
Outside Europe, the star fort became an "engine of European expansion", and acted as a force multiplier so that small European garrisons could hold out against numerically superior forces. Wherever star forts were erected the natives experienced great difficulty in uprooting European invaders.
In China, Sun Yuanhua advocated for the construction of angled bastion forts in his Xifashenji so that their cannons could better support each other. The officials Han Yun and Han Lin noted that cannons on square forts could not support each side as well as bastion forts. Their efforts to construct bastion forts and their results were inconclusive. Ma Weicheng built two bastion forts in his home county, which helped fend off a Qing incursion in 1638. By 1641, there were ten bastion forts in the county. Before bastion forts could be spread any further, the Ming dynasty fell in 1644, and they were largely forgotten as the Qing dynasty was on the offensive most of the time and had no use for them. | 1 | Applied and Interdisciplinary Chemistry |
*The Morison equation is a heuristic formulation of the force fluctuations in an oscillatory flow. The first assumption is that the flow acceleration is more-or-less uniform at the location of the body. For instance, for a vertical cylinder in surface gravity waves this requires that the diameter of the cylinder is much smaller than the wavelength. If the diameter of the body is not small compared to the wavelength, diffraction effects have to be taken into account.
*Second, it is assumed that the asymptotic forms: the inertia and drag force contributions, valid for very small and very large Keulegan–Carpenter numbers respectively, can just be added to describe the force fluctuations at intermediate Keulegan–Carpenter numbers. However, from experiments it is found that in this intermediate regime—where both drag and inertia are giving significant contributions—the Morison equation is not capable of describing the force history very well. Although the inertia and drag coefficients can be tuned to give the correct extreme values of the force.
*Third, when extended to orbital flow which is a case of non uni-directional flow, for instance encountered by a horizontal cylinder under waves, the Morison equation does not give a good representation of the forces as a function of time. | 1 | Applied and Interdisciplinary Chemistry |
Agents that break disulfide bonds by reduction include:
* 2-Mercaptoethanol
* Dithiothreitol
* TCEP (tris(2-carboxyethyl)phosphine) | 1 | Applied and Interdisciplinary Chemistry |
Plants produce secondary metabolites known as allelochemicals. Rather than participating in basic metabolic processes, they mediate interactions between a plant and its environment, often attracting, repelling, or poisoning insects. They also help produce secondary cell wall components such as those that require amino acid modification.
In a tritrophic system, volatiles, which are released into the air, are superior to surface chemicals in drawing foraging natural enemies from afar. Plants also produce root volatiles which will drive tritrophic interactions between below-ground herbivores and their natural enemies. Some plant volatiles can be smelled by humans and give plants like basil, eucalyptus, and pine their distinctive odors. The mixture and ratios of individual volatiles emitted by a plant under given circumstances (also referred to as synomones in the context of natural enemy attraction) is referred to as a volatile profile. These are highly specific to certain plant species and are detectable meters from the source. Predators and parasitoids exploit the specificity of volatile profiles to navigate the complex infochemical signals presented by plants in their efforts to locate a particular prey species.
The production of volatiles is likely to be beneficial given two conditions: that they are effective in attracting natural enemies and that the natural enemies are effective in removing or impeding herbivores. However, volatile chemicals may not have evolved initially for this purpose; they act in within-plant signaling, attraction of pollinators, or repulsion of herbivores that dislike such odors. | 1 | Applied and Interdisciplinary Chemistry |
Nuclear fission was discovered in December 1938 by chemists Otto Hahn and Fritz Strassmann and physicists Lise Meitner and Otto Robert Frisch. Fission is a nuclear reaction or radioactive decay process in which the nucleus of an atom splits into two or more smaller, lighter nuclei and often other particles. The fission process often produces gamma rays and releases a very large amount of energy, even by the energetic standards of radioactive decay. Scientists already knew about alpha decay and beta decay, but fission assumed great importance because the discovery that a nuclear chain reaction was possible led to the development of nuclear power and nuclear weapons. Hahn was awarded the 1944 Nobel Prize in Chemistry for the discovery of nuclear fission.
Hahn and Strassmann at the Kaiser Wilhelm Institute for Chemistry in Berlin bombarded uranium with slow neutrons and discovered that barium had been produced. Hahn suggested a bursting of the nucleus, but he was unsure of what the physical basis for the results were. They reported their findings by mail to Meitner in Sweden, who a few months earlier had fled Nazi Germany. Meitner and her nephew Frisch theorised, and then proved, that the uranium nucleus had been split and published their findings in Nature. Meitner calculated that the energy released by each disintegration was approximately 200 megaelectronvolts, and Frisch observed this. By analogy with the division of biological cells, he named the process "fission".
The discovery came after forty years of investigation into the nature and properties of radioactivity and radioactive substances. The discovery of the neutron by James Chadwick in 1932 created a new means of nuclear transmutation. Enrico Fermi and his colleagues in Rome studied the results of bombarding uranium with neutrons, and Fermi concluded that his experiments had created new elements with 93 and 94 protons, which his group dubbed ausenium and hesperium. Fermi won the 1938 Nobel Prize in Physics for his "demonstrations of the existence of new radioactive elements produced by neutron irradiation, and for his related discovery of nuclear reactions brought about by slow neutrons". However, not everyone was convinced by Fermis analysis of his results. Ida Noddack suggested that instead of creating a new, heavier element 93, it was conceivable that the nucleus had broken up into large fragments, and Aristid von Grosse suggested that what Fermis group had found was an isotope of protactinium.
This spurred Hahn and Meitner, the discoverers of the most stable isotope of protactinium, to conduct a four-year-long investigation into the process with their colleague Strassmann. After much hard work and many discoveries, they determined that what they were observing was fission, and that the new elements that Fermi had found were fission products. Their work overturned long-held beliefs in physics and paved the way for the discovery of the real elements 93 (neptunium) and 94 (plutonium), for the discovery of fission in other elements, and for the determination of the role of the uranium-235 isotope in that of uranium. Niels Bohr and John Wheeler reworked the liquid drop model to explain the mechanism of fission. | 0 | Theoretical and Fundamental Chemistry |
Scientists studying strangeness as signature of quark gluon plasma present and discuss their results at specialized meetings. Well established is the series International Conference on Strangeness in Quark Matter, first organized in Tucson, Arizona, in 1995. The latest edition, 10–15 June 2019, of the conference was held in Bari, Italy, attracting about 300 participants. A more general venue is the Quark Matter conference, which last time took place from 3–9 September 2023 in Houston, USA, attracting about 800 participants. | 0 | Theoretical and Fundamental Chemistry |
Expanded polyethylene copolymers (EPC) are also known - such as 50:50 (weight) materials with polystyrene. Though other properties are intermediate between the two bases, toughness for the copolymer exceeds either, with good tensile and puncture resistance. It is particularly applicable for re-usable products. | 0 | Theoretical and Fundamental Chemistry |
In general, the Gibbs free energy of micellization can be approximated as:
where is the change in Gibbs free energy of micellization, is the universal gas constant, is the absolute temperature, and is the critical micelle concentration. | 0 | Theoretical and Fundamental Chemistry |
Researchers produced an artificial tooth whose microstructure mimicked that of a real tooth. The outer layers, corresponding to enamel, were hard and structurally complex. The outer layers contained glass nanoparticles and aluminium oxide plates were aligned perpendicular to the surface. After the outer layers hardened, a second suspension was poured. It contained no glass, and the plates were aligned horizontally to the surface of the tooth. These deeper layers were tougher, resembling dentine. The tooth was then cooked at 1,600 degrees to compact and harden the material — a process known as sintering. The last step involved filling remaining pores with a synthetic monomer used in dentistry, which polymerizes after treatment. Hardness and durability approximated that of both the enamel and dentine of a tooth. | 0 | Theoretical and Fundamental Chemistry |
Alkaline water electrolysis is a type of electrolyzer that is characterized by having two electrodes operating in a liquid alkaline electrolyte. Commonly, a solution of potassium hydroxide (KOH) or sodium hydroxide (NaOH) at 25-40 wt% is used. These electrodes are separated by a diaphragm, separating the product gases and transporting the hydroxide ions (OH) from one electrode to the other. A recent comparison showed that state-of-the-art nickel based water electrolyzers with alkaline electrolytes lead to competitive or even better efficiencies than acidic polymer electrolyte membrane water electrolysis with platinum group metal based electrocatalysts.
The technology has a long history in the chemical industry. The first large-scale demand for hydrogen emerged in late 19th century for lighter-than-air aircraft, and before the advent of steam reforming in the 1930s, the technique was competitive. | 0 | Theoretical and Fundamental Chemistry |
Until the late 1960s, soil chemistry focused primarily on chemical reactions in the soil that contribute to pedogenesis or that affect plant growth. Since then, concerns have grown about environmental pollution, organic and inorganic soil contamination and potential ecological health and environmental health risks. Consequently, the emphasis in soil chemistry has shifted from pedology and agricultural soil science to an emphasis on environmental soil science. | 0 | Theoretical and Fundamental Chemistry |
In molecular biology, hybridization (or hybridisation) is a phenomenon in which single-stranded deoxyribonucleic acid (DNA) or ribonucleic acid (RNA) molecules anneal to complementary DNA or RNA. Though a double-stranded DNA sequence is generally stable under physiological conditions, changing these conditions in the laboratory (generally by raising the surrounding temperature) will cause the molecules to separate into single strands. These strands are complementary to each other but may also be complementary to other sequences present in their surroundings. Lowering the surrounding temperature allows the single-stranded molecules to anneal or “hybridize” to each other.
DNA replication and transcription of DNA into RNA both rely upon nucleotide hybridization, as do molecular biology techniques including Southern blots and Northern blots, the polymerase chain reaction (PCR), and most approaches to DNA sequencing. | 1 | Applied and Interdisciplinary Chemistry |
María del Coral Barbas Arribas (or Arriba) is a professor at the Universidad CEU San Pablo in Madrid, Spain who is known for her research on metabolomics and integration of chemical data. | 0 | Theoretical and Fundamental Chemistry |
The complex adopts a trigonal bipyramidal geometry with trans CO and hydrido ligands, resulting in pseudo-C symmetry. The Rh-P, Rh-C, and Rh-H distances are 2.32, 1.83, and 1.60 Å, respectively. This complex is one of a small number of stable pentacoordinate rhodium hydrides. | 0 | Theoretical and Fundamental Chemistry |
*Van Wylen, G.J., and Sonntag, R.E. (1965), Fundamentals of Classical Thermodynamics, John Wiley & Sons, Inc., New York | 1 | Applied and Interdisciplinary Chemistry |
The system was originally developed by Richard Anthony Jefferson during his Ph.D. at the University of Colorado at Boulder. He adapted the technique for the use with plants as he worked in the Plant Breeding Institute of Cambridge, between 1985 and 1987. Since then thousands of labs have used the system, making it one of the most widely used tools in plant molecular biology, as underlined by thousands of citations in scientific literature. | 1 | Applied and Interdisciplinary Chemistry |
Peptidoglycan recognition is an evolutionarily conserved process. The overall structure is similar between bacterial species, but various modifications can increase the diversity. These include modifications of the length of sugar polymers, modifications in the sugar structures, variations in cross-linking or substitutions of amino acids (primarily at the third position). The aim of these modifications is to alter the properties of the cell wall, which plays a vital role in pathogenesis.
Peptidoglycans can be degraded by several enzymes (lysozyme, glucosaminidase, endopeptidase...), producing immunostimulatory fragments (sometimes called muropeptides) that are critical for mediating host-pathogen interactions. These include MDP (muramyl dipeptide), NAG (N-acetylglucosamine) or iE-DAP (γ-d-glutamyl-meso-diaminopimelic acid).
Peptidoglycan from intestinal bacteria (both pathogens and commensals) crosses the intestinal barrier even under physiological conditions. Mechanisms through which peptidoglycan or its fragments enter the host cells can be direct (carrier-independent) or indirect (carrier-dependent), and they are either bacteria-mediated (secretion systems, membrane vesicles) or host cell-mediated (receptor-mediated, peptide transporters). Bacterial secretion systems are protein complexes used for the delivery of virulence factors across the bacterial cell envelope to the exterior environment. Intracellular bacterial pathogens invade eukaryotic cells (which may lead to the formation of phagolysosomes and/or autophagy activation), or bacteria may be engulfed by phagocytes (macrophages, monocytes, neutrophils...). The bacteria-containing phagosome may then fuse with endosomes and lysosomes, leading to degradation of bacteria and generation of polymeric peptidoglycan fragments and muropeptides. | 1 | Applied and Interdisciplinary Chemistry |
Rotavirus is the most common cause of acute gastroenteritis in infants and young children worldwide. This virus contains a dsRNA genome and is a member of the Reoviridae family. The genome of rotavirus consists of eleven segments of dsRNA. Each genome segment codes for one protein with the exception of segment 11, which codes for two proteins. Among the twelve proteins, six are structural and six are non-structural proteins.
It is a double-stranded RNA non-enveloped virus. | 1 | Applied and Interdisciplinary Chemistry |
Initially process simulation was used to simulate steady state processes. Steady-state models perform a mass and energy balance of a steady state process (a process in an equilibrium state) independent of time.
Dynamic simulation is an extension of steady-state process simulation whereby time-dependence is built into the models via derivative terms i.e. accumulation of mass and energy. The advent of dynamic simulation means that the time-dependent description, prediction and control of real processes in real time has become possible. This includes the description of starting up and shutting down a plant, changes of conditions during a reaction, holdups, thermal changes and more.
Dynamic simulation require increased calculation time and are mathematically more complex than a steady state simulation. It can be seen as a multiple repeated steady state simulation (based on a fixed time step) with constantly changing parameters.
Dynamic simulation can be used in both an online and offline fashion. The online case being model predictive control, where the real-time simulation results are used to predict the changes that would occur for a control input change, and the control parameters are optimised based on the results. Offline process simulation can be used in the design, troubleshooting and optimisation of process plant as well as the conduction of case studies to assess the impacts of process modifications. Dynamic simulation is also used for operator training. | 1 | Applied and Interdisciplinary Chemistry |
Sonar flowmeters are non-intrusive clamp-on devices that measure flow in pipes conveying slurries, corrosive fluids, multiphase fluids and flows where insertion type flowmeters are not desired. Sonar flowmeters have been widely adopted in mining, metals processing, and upstream oil and gas industries where traditional technologies have certain limitations due to their tolerance to various flow regimes and turn down ratios.
Sonar flowmeters have the capacity of measuring the velocity of liquids or gases non-intrusively within the pipe and then leverage this velocity measurement into a flow rate by using the cross-sectional area of the pipe and the line pressure and temperature. The principle behind this flow measurement is the use of underwater acoustics.
In underwater acoustics, to locate an object underwater, sonar uses two knowns:
* The speed of sound propagation through the array (i.e., the speed of sound through seawater)
* The spacing between the sensors in the sensor array
and then calculates the unknown:
* The location (or angle) of the object.
Likewise, sonar flow measurement uses the same techniques and algorithms employed in underwater acoustics, but applies them to flow measurement of oil and gas wells and flow lines.
To measure flow velocity, sonar flowmeters use two knowns:
* The location (or angle) of the object, which is 0 degrees since the flow is moving along the pipe, which is aligned with the sensor array
* The spacing between the sensors in the sensor array
and then calculates the unknown:
* The speed of propagation through the array (i.e. the flow velocity of the medium in the pipe). | 1 | Applied and Interdisciplinary Chemistry |
Cadmium sulfide is the inorganic compound with the formula CdS. Cadmium sulfide is a yellow salt. It occurs in nature with two different crystal structures as the rare minerals greenockite and hawleyite, but is more prevalent as an impurity substituent in the similarly structured zinc ores sphalerite and wurtzite, which are the major economic sources of cadmium. As a compound that is easy to isolate and purify, it is the principal source of cadmium for all commercial applications. Its vivid yellow color led to its adoption as a pigment for the yellow paint "cadmium yellow" in the 18th century. | 0 | Theoretical and Fundamental Chemistry |
A Gamow–Teller transition is a beta decay in which the spins of the emitted electron (positron) and anti-neutrino (neutrino) couple to total spin , leading to an angular momentum change between the initial and final states of the nucleus (assuming an allowed transition).
In this case, the nuclear part of the operator is given by
with the weak axial-vector coupling constant, and the spin Pauli matrices, which can produce a spin-flip in the decaying nucleon. | 0 | Theoretical and Fundamental Chemistry |
A small fraction of metabolism – less than 5% in all tissues except the testes where it accounts for about 33% – is initially catalyzed by leucine aminomutase, producing β-leucine, which is subsequently metabolized into (β-KIC), β-ketoisocaproyl-CoA, and then acetyl-CoA by a series of uncharacterized enzymes. | 1 | Applied and Interdisciplinary Chemistry |
This concept was first postulated by Funk and Reinstrom (1966) as a maximally efficient way to produce fuels (e.g. hydrogen, ammonia) from stable and abundant species (e.g. water, nitrogen) and heat sources. Although fuel availability was scarcely considered before the oil crisis efficient fuel generation was an issue in important niche markets. As an example, in the military logistics field, providing fuels for vehicles in remote battlefields is a key task. Hence, a mobile production system based on a portable heat source (a nuclear reactor was considered) was being investigated with utmost interest.
Following the oil crisis, multiple programs (Europe, Japan, United States) were created to design, test and qualify such processes for purposes such as energy independence. High-temperature (around operating temperature) nuclear reactors were still considered as the likely heat sources. However, optimistic expectations based on initial thermodynamics studies were quickly moderated by pragmatic analyses comparing standard technologies (thermodynamic cycles for electricity generation, coupled with the electrolysis of water) and by numerous practical issues (insufficient temperatures from even nuclear reactors, slow reactivities, reactor corrosion, significant losses of intermediate compounds with time...). Hence, the interest for this technology faded during the next decades, or at least some tradeoffs (hybrid versions) were being considered with the use of electricity as a fractional energy input instead of only heat for the reactions (e.g. Hybrid sulfur cycle). A rebirth in the year 2000 can be explained by both the new energy crisis, demand for electricity, and the rapid pace of development of concentrated solar power technologies whose potentially very high temperatures are ideal for thermochemical processes, while the environmentally friendly side of thermochemical cycles attracted funding in a period concerned with a potential peak oil outcome. | 0 | Theoretical and Fundamental Chemistry |
Like OCT, the early implementations of a/LCI relied on physically changing the optical path length (OPL) to control the depth in the sample from which data are acquired. However, it has been demonstrated that it is possible to use a Fourier domain implementation to yield depth resolution in a single data acquisition. A broadband light source is used to produce a spectrum of wavelengths at once, and the backscattered light is collected by a coherent optical fiber in the return path to capture different scattering angles simultaneously. Intensity is then measured via a spectrometer: a single frame from the spectrometer contains scattering intensity as a function of wavelength and angle. Finally the data is Fourier transformed on a line-by-line basis to generate scattering intensity as a function of OPL and angle. In the resulting image, the x axis represents the OPL and the y axis the angle of reflection, thus yielding a 2D map of reflection intensities.
Using this method, the acquisition speed is limited only by the integration time of the spectrometer and can be as short at 20 ms. The same data that initially required tens of minutes to acquire can be acquired ~10 times faster. | 0 | Theoretical and Fundamental Chemistry |
To enhance carbon sequestration processes in oceans the following technologies have been proposed but none have achieved large scale application so far: Seaweed farming, ocean fertilisation, artificial upwelling, basalt storage, mineralization and deep sea sediments, adding bases to neutralize acids. The idea of direct deep-sea carbon dioxide injection has been abandoned. | 0 | Theoretical and Fundamental Chemistry |
*Massachusetts Institute of Technology (MIT)
*Carnegie Institute
*Westinghouse Electric Corporation
*Gould-National Batteries, Inc.
*General Electrical Company | 0 | Theoretical and Fundamental Chemistry |
Anti-nuclear ribonucleoprotein (anti-nRNP) antibodies, also known as anti-U1-RNP antibodies, are found in 30–40% of SLE. They are often found with anti-Sm antibodies, but they may be associated with different clinical associations. In addition to SLE, these antibodies are highly associated with mixed connective tissue disease. Anti-nRNP antibodies recognise the A and C core units of the snRNPs and because of this they primarily bind to the U1-snRNP. The immune response to RNP may be caused by the presentation of the nuclear components on the cell membrane in apoptotic blebs. Molecular mimicry has also been suggested as a possible mechanism for the production of antibodies to these proteins because of similarity between U1-RNP polypeptides and Epstein-Barr virus polypeptides. | 1 | Applied and Interdisciplinary Chemistry |
The Gilman test is a chemical test for the detection of Grignard reagents and organolithium reagents.
A 0.5 mL sample is added to a 1% solution of Mischler's ketone in benzene or toluene. To this solution is added 1 mL of water for hydrolysis to take place and then several drops of 0.2% iodine in glacial acetic acid. If the color of the resulting solution becomes a greenish-blue then the original sample did contain the organometallic species. | 0 | Theoretical and Fundamental Chemistry |
In two-dimensional space there are 5 Bravais lattices, grouped into four lattice systems, shown in the table below. Below each diagram is the Pearson symbol for that Bravais lattice.
Note: In the unit cell diagrams in the following table the lattice points are depicted using black circles and the unit cells are depicted using parallelograms (which may be squares or rectangles) outlined in black. Although each of the four corners of each parallelogram connects to a lattice point, only one of the four lattice points technically belongs to a given unit cell and each of the other three lattice points belongs to one of the adjacent unit cells. This can be seen by imagining moving the unit cell parallelogram slightly left and slightly down while leaving all the black circles of the lattice points fixed.
The unit cells are specified according to the relative lengths of the cell edges (a and b) and the angle between them (θ). The area of the unit cell can be calculated by evaluating the norm , where a and b are the lattice vectors. The properties of the lattice systems are given below: | 0 | Theoretical and Fundamental Chemistry |
In chemistry and chemical physics, a mesophase or mesomorphic phase is a phase of matter intermediate between solid and liquid. Gelatin is a common example of a partially ordered structure in a mesophase. Further, biological structures such as the lipid bilayers of cell membranes are examples of mesophases. Mesophases with long-range positional order but no orientational order are plastic crystals, whereas those with long-range orientational order but only partial or no positional order are liquid crystals.
Georges Friedel (1922) called attention to the "mesomorphic states of matter" in his scientific assessment of observations of the so-called liquid crystals. Conventionally a crystal is solid, and crystallization converts liquid to solid. The oxymoron of the liquid crystal is resolved through the notion of mesophases. The observations noted an optic axis persisting in materials that had been melted and had begun to flow. The term liquid crystal persists as a colloquialism, but use of the term was criticized in 1993: In The Physics of Liquid Crystals the mesophases are introduced from the beginning:
:...certain organic materials do not show a single transition from solid to liquid, but rather a cascade of transitions involving new phases. The mechanical properties and the symmetry properties of these phases are intermediate between those of a liquid and those of a crystal. For this reason they have often been called liquid crystals. A more proper name is ‘mesomorphic phases’ (mesomorphic: intermediate form)
Further, "The classification of mesophases (first clearly set out by G. Friedel in 1922) is essentially based on symmetry."
Molecules that demonstrate mesophases are called mesogens.
In technology, molecules in which the optic axis is subject to manipulation during a mesophase have become commercial products as they can be used to manufacture display devices, known as liquid-crystal displays (LCDs). The susceptibility of the optical axis, called a director, to an electric or magnetic field produces the potential for an optical switch that obscures light or lets it pass. Methods used include the Freedericksz transition, the twisted nematic field effect and the in-plane switching effect. From early liquid crystal displays the buying public has embraced the low-power optical switch facility of mesophases with director.
Consider a solid consisting of a single molecular species and subjected to melting. Ultimately it is rendered to an isotropic state classically referred to as liquid. Mesophases occur before then when an intermediate state of order is still maintained as in the nematic, smectic, and columnar phases of liquid crystals. Mesophases thus exhibit anisotropy. LCD devices work as an optical switch which is turned off and on by an electric field applied to the mesogen with director. The response of the director to the field is expressed with viscosity parameters, as in the Ericksen-Leslie theory in continuum mechanics developed by Jerald Ericksen and Frank Matthews Leslie. LCD devices work only up to the transition temperature when the mesophase changes to the isotropic liquid phase at the so-called clearing point.
Mesophase phenomena are important in many scientific fields. The publishing arms of professional societies have academic journals as needed. For instance, the American Chemical Society has both Macromolecules and Langmuir, while Royal Society of Chemistry has Soft Matter, and American Physical Society has Physical Review E, and Elsevier has Advances in Colloid and Interface Science. | 0 | Theoretical and Fundamental Chemistry |
There are a huge number of industries and applications which benefit from induction shrink fitting or removal using solid state RF and MF heaters. In practice, the methodology employed can vary from a simple manual approach where an operator assembles or disassembles the parts to fully automatic pneumatic and hydraulic press arrangements.
* Automotive starter rings onto flywheels
* Timing gears to crankshafts
* Motor stators into motor bodies
* Motor shafts into stators
* Removal and re-fitting of a gas turbine impeller
* Removal and re-fitting of hollow bolts in electrical generators
* Assembly of high precision roller bearings
* Shrink fitting of 2-stroke crankshafts for ship engines | 1 | Applied and Interdisciplinary Chemistry |
Trials have demonstrated lower vitamin D levels are highly prevalent in people with schizophrenia, particularly those with acute episodes. | 1 | Applied and Interdisciplinary Chemistry |
Mixtures can be either homogeneous or heterogeneous: a mixture of uniform composition and in which all components are in the same phase, such as salt in water, is called homogeneous, whereas a mixture of non-uniform composition and of which the components can be easily identified, such as sand in water, it is called heterogeneous.
In addition, "uniform mixture" is another term for homogeneous mixture and "non-uniform mixture" is another term for heterogeneous mixture. These terms are derived from the idea that a homogeneous mixture has a uniform appearance, or only one visible phase, because the particles are evenly distributed. However, a heterogeneous mixture has non-uniform composition, and its constituent substances are easily distinguishable from one another (often, but not always, in different phases).
Several solid substances, such as salt and sugar, dissolve in water to form a special type of homogeneous mixture called a solution, in which there is both a solute (dissolved substance) and solvent (dissolving medium) present. Air is an example of a solution as well: a homogeneous mixture of gaseous nitrogen solvent, in which oxygen and smaller amounts of other gaseous solutes are dissolved. Mixtures are not limited in either their number of substances or the amounts of those substances, though in a homogeneous mixture the solute-to-solvent proportion can only reach a certain point before the mixture separates and becomes heterogeneous.
A homogeneous mixture is characterized by uniform dispersion of its constituent substances throughout; the substances exist in equal proportion everywhere within the mixture. Differently put, a homogeneous mixture will be the same no matter from where in the mixture it is sampled. For example, if a solid-liquid solution is divided into two halves of equal volume, the halves will contain equal amounts of both the liquid medium and dissolved solid (solvent and solute).
In physical chemistry and materials science, "homogeneous" more narrowly describes substances and mixtures which are in a single phase. | 0 | Theoretical and Fundamental Chemistry |
An example of a YES logic gate comprises a benzo-crown-ether connected to a cyano-substituted anthracene unit. An output of 1 (fluorescence) is obtained only when sodium ions are present in the solution (indicating an input of 1). Sodium ions are encapsulated by the crown ether, resulting in a quenching of the PET process, and causing the anthracene unit to fluoresce. | 0 | Theoretical and Fundamental Chemistry |
In non-competitive inhibition the binding of the inhibitor to the enzyme reduces its activity but does not affect the binding of substrate. This type of inhibitor binds with equal affinity to the free enzyme as to the enzyme-substrate complex. It can be thought of as having the ability of competitive and uncompetitive inhibitors, but with no preference to either type. As a result, the extent of inhibition depends only on the concentration of the inhibitor. V will decrease due to the inability for the reaction to proceed as efficiently, but K will remain the same as the actual binding of the substrate, by definition, will still function properly. | 1 | Applied and Interdisciplinary Chemistry |
Since the introduction of pertussis vaccines in the 1940s and 1950s, different genetic changes have been described surrounding the pertussis toxin. | 1 | Applied and Interdisciplinary Chemistry |
LPA is the result of phospholipase A2 action on phosphatidic acid. The SN-1 position can contain either an ester bond or an ether bond, with ether LPA being found at elevated levels in certain cancers. LPA binds the high-affinity G-protein coupled receptors LPA1, LPA2, and LPA3 (also known as EDG2, EDG4, and EDG7, respectively). | 1 | Applied and Interdisciplinary Chemistry |
The NZIC is a member of the Federation of Asian Chemical Societies (FACS) and a constituent organisation of Royal Society Te Apārangi. | 1 | Applied and Interdisciplinary Chemistry |
The Yukawa–Tsuno equation, first developed in 1959, is a linear free-energy relationship in physical organic chemistry. It is a modified version of the Hammett equation that accounts for enhanced resonance effects in electrophilic reactions of para- and meta-substituted organic compounds. This equation does so by introducing a new term to the original Hammett relation that provides a measure of the extent of resonance stabilization for a reactive structure that builds up charge (positive or negative) in its transition state. The Yukawa–Tsuno equation can take the following forms:
where and represent the rate constants for an X-substituted and unsubstituted compound, respectively; represents the Hammett reaction constant; represents the Hammett substituent constant; and represent the Hammett substituent constants for reactions in which positive or negative charges are built up at the reactive center, respectively; and represents the Yukawa–Tsuno parameter. | 0 | Theoretical and Fundamental Chemistry |
A kinetic exclusion assay (KinExA) is a type of bioassay in which a solution containing receptor, ligand, and receptor-ligand complex is briefly exposed to additional ligand immobilized on a solid phase. | 1 | Applied and Interdisciplinary Chemistry |
The most synthetically useful aminations of enolate anions employ N-acyloxazolidinone substrates. The chiral auxiliaries on these compounds are easily removed after hydrazine formation (with azo compounds) or azidation (with trisyl azide). Azidation using the latter reagent is more efficient than bromination followed by nucleophilic substitution by the azide anion Palladium on carbon and hydrogen gas reduce both azide and hydrazide products (the latter only after conversion to the hydrazine). | 0 | Theoretical and Fundamental Chemistry |
Lateral flow assays have played a critical role in COVID-19 testing as they have the benefit of delivering a result in 15–30 minutes. The systematic evaluation of lateral flow assays during the COVID-19 pandemic was initiated at Oxford University as part of a UK collaboration with Public Health England. A study that started in June 2020 in the United Kingdom, FALCON-C19, confirmed the sensitivity of some lateral flow devices (LFDs) in this setting. Four out of 64 LFDs tested had desirable performance characteristics according to these early tests; the Innova SARS-CoV-2 Antigen Rapid Qualitative Test performed moderately in viral antigen detection/sensitivity with excellent specificity, although kit failure rates and the impact of training were potential issues. The Innova test's specificity is more widely publicised, but sensitivity in phase 4 trials was 50.1%. This describes a device for which one out of every two patients infected with COVID-19 and tested in real-world conditions would receive a false-negative result. After closure of schools in January 2021, biweekly LFTs were introduced in England for teachers, pupils, and households of pupils when schools re-opened on March 8, 2021 for asymptomatic testing. Biweekly LFT were made universally available to everyone in England on April 9, 2021. LFTs have been used for mass testing for COVID-19 globally and complement other public health measures for COVID-19.
Some scientists outside government expressed serious misgivings in late 2020 about the use of Innova LFDs for screening for Covid. According to Jon Deeks, a professor of biostatistics at the University of Birmingham, England, the Innova test is "entirely unsuitable" for community testing: "as the test may miss up to half of cases, a negative test result indicates a reduced risk of Covid, but does not exclude Covid".
Sensitivity of tests used in 2022 was around 70%. | 1 | Applied and Interdisciplinary Chemistry |
* In patients with hyperthyroidism, there will be fewer available binding sites on TBG (due to the increased circulating T3 / T4). This will lead to an increased thyroid hormone binding ratio.
* In patients with hypothyroidism, there will be more free binding sites on TBG (due to the decreased amount of circulating T3 / T4) and as such the THBR will be decreased.
* In general, High with High thyroid activity and Low with Low thyroid activity. | 1 | Applied and Interdisciplinary Chemistry |
Historically, the theory of rotational energy levels was developed to account for observations of vibration-rotation spectra of gases in infrared spectroscopy, which was used before microwave spectroscopy had become practical. To a first approximation, the rotation and vibration can be treated as separable, so the energy of rotation is added to the energy of vibration. For example, the rotational energy levels for linear molecules (in the rigid-rotor approximation) are
In this approximation, the vibration-rotation wavenumbers of transitions are
where and are rotational constants for the upper and lower vibrational state respectively, while and are the rotational quantum numbers of the upper and lower levels. In reality, this expression has to be modified for the effects of anharmonicity of the vibrations, for centrifugal distortion and for Coriolis coupling.
For the so-called R branch of the spectrum, so that there is simultaneous excitation of both vibration and rotation. For the P branch, so that a quantum of rotational energy is lost while a quantum of vibrational energy is gained. The purely vibrational transition, , gives rise to the Q branch of the spectrum. Because of the thermal population of the rotational states the P branch is slightly less intense than the R branch.
Rotational constants obtained from infrared measurements are in good accord with those obtained by microwave spectroscopy, while the latter usually offers greater precision. | 0 | Theoretical and Fundamental Chemistry |
Chlorophyll fluorescence is light re-emitted by chlorophyll molecules during return from excited to non-excited states. It is used as an indicator of photosynthetic energy conversion in plants, algae and bacteria. Excited chlorophyll dissipates the absorbed light energy by driving photosynthesis (photochemical energy conversion), as heat in non-photochemical quenching or by emission as fluorescence radiation. As these processes are complementary processes, the analysis of chlorophyll fluorescence is an important tool in plant research with a wide spectrum of applications. | 0 | Theoretical and Fundamental Chemistry |
The existence of charged particles causes the plasma to generate, and be affected by, magnetic fields. Plasma with a magnetic field strong enough to influence the motion of the charged particles is said to be magnetized. A common quantitative criterion is that a particle on average completes at least one gyration around the magnetic-field line before making a collision, i.e., , where is the electron gyrofrequency and is the electron collision rate. It is often the case that the electrons are magnetized while the ions are not. Magnetized plasmas are anisotropic, meaning that their properties in the direction parallel to the magnetic field are different from those perpendicular to it. While electric fields in plasmas are usually small due to the plasma high conductivity, the electric field associated with a plasma moving with velocity in the magnetic field is given by the usual Lorentz formula , and is not affected by Debye shielding. | 0 | Theoretical and Fundamental Chemistry |
Delamanid, a drug used to treat multi-drug-resistant tuberculosis (MDRTB) in combination with other antituberculosis medications, is activated in the mycobacterium by deazaflavin-dependent nitroreductase (Ddn), an enzyme which uses dihydro-F (reduced form). The activated form of the drug is highly reactive and attacks cell wall synthesis enzymes such as DprE2. Pretomanid works in the same way. Clinical isolates resistant to these two drugs tend to have mutations in the biosynthetic pathway for F. | 1 | Applied and Interdisciplinary Chemistry |
An operon is made up of 3 basic DNA components:
* Promoter – a nucleotide sequence that enables a gene to be transcribed. The promoter is recognized by RNA polymerase, which then initiates transcription. In RNA synthesis, promoters indicate which genes should be used for messenger RNA creation – and, by extension, control which proteins the cell produces.
* Operator – a segment of DNA to which a repressor binds. It is classically defined in the lac operon as a segment between the promoter and the genes of the operon. The main operator (O1) in the lac operon is located slightly downstream of the promoter; two additional operators, O2 and O3 are located at -82 and +412, respectively. In the case of a repressor, the repressor protein physically obstructs the RNA polymerase from transcribing the genes.
* Structural genes – the genes that are co-regulated by the operon.
Not always included within the operon, but important in its function is a regulatory gene, a constantly expressed gene which codes for repressor proteins. The regulatory gene does not need to be in, adjacent to, or even near the operon to control it.
An inducer (small molecule) can displace a repressor (protein) from the operator site (DNA), resulting in an uninhibited operon.
Alternatively, a corepressor can bind to the repressor to allow its binding to the operator site. A good example of this type of regulation is seen for the trp operon. | 1 | Applied and Interdisciplinary Chemistry |
Brandt was born in Riddarhyttan, Skinnskatteberg parish, Västmanland to Jurgen Brandt, a mineowner and pharmacist, and Katarina Ysing. He was professor of chemistry at Uppsala University, and died in Stockholm. He was able to show that cobalt was the source of the blue color in glass, which previously had been attributed to the bismuth found with cobalt. He died on April 29, 1768, of prostate cancer.
About 1741 he wrote: "As there are six kinds of metals, so I have also shown with reliable experiments... that there are also six kinds of half-metals: a new half-metal, namely Cobalt regulus in addition to Mercury, Bismuth, Zinc, and the reguluses of Antimony and Arsenic". He gave six ways to distinguish bismuth and cobalt which were typically found in the same ores:
#Bismuth fractures while Cobalt is more like a true metal.
#The regulus of Shetz fuses with flint and fixed alkali giving a blue glass known as zaffera, sasre, or smalt. Bismuth does not.
#Bismuth melts easily and if kept melted, calcinates forming a yellow powder.
#Bismuth amalgamates with Mercury; the regulus of Cobalt does not at all.
#Bismuth dissolved in nitric acid and with aqua regia and gives a white precipitate when put in pure water. The regulus of Cobalt needs alkalies to precipitate, and then forms dark or black precipitates. | 1 | Applied and Interdisciplinary Chemistry |
In order to access the nucleosomal DNA, the bonds between it and the histone octamer must be broken. This change takes place periodically in the cell as specific regions are transcribed, and it happens genome-wide during replication. Remodeling proteins work in three distinct ways: they can slide the DNA along the surface of the octamer, replace the one histone dimer with a variant, or remove the histone octamer entirely. No matter the method, in order to modify the nucleosomes, the remodeling complexes require energy from ATP hydrolysis to drive their actions.
Of the three techniques, sliding is the most common and least extreme. The basic premise of the technique is to free up a region of DNA that the histone octamer would normally tightly bind. While the technique is not well defined, the most prominent hypothesis is that the sliding is done in an “inchworm” fashion. In this method, using ATP as an energy source, the translocase domain of the nucleosome-remodeling complex detaches a small region of DNA from the histone octamer. This “wave” of DNA, spontaneously breaking and remaking the hydrogen bonds as it goes, then propagates down the nucleosomal DNA until it reaches the last binding site with the histone octamer. Once the wave reaches the end of the histone octamer the excess that was once at the edge is extended into the region of linker DNA. In total, one round of this method moves the histone octamer several base pairs in a particular direction—away from the direction the “wave” propagated. | 1 | Applied and Interdisciplinary Chemistry |
In the Euclidean plane, reflections and glide reflections are the only two kinds of indirect (orientation-reversing) isometries.
For example, there is an isometry consisting of the reflection on the x-axis, followed by translation of one unit parallel to it. In coordinates, it takes
This isometry maps the x-axis to itself; any other line which is parallel to the x-axis gets reflected in the x-axis, so this system of parallel lines is left invariant.
The isometry group generated by just a glide reflection is an infinite cyclic group.
Combining two equal glide reflections gives a pure translation with a translation vector that is twice that of the glide reflection, so the even powers of the glide reflection form a translation group.
In the case of glide-reflection symmetry, the symmetry group of an object contains a glide reflection, and hence the group generated by it. If that is all it contains, this type is frieze group p11g.
Example pattern with this symmetry group:
A typical example of glide reflection in everyday life would be the track of footprints left in the sand by a person walking on a beach.
Frieze group nr. 6 (glide-reflections, translations and rotations) is generated by a glide reflection and a rotation about a point on the line of reflection. It is isomorphic to a semi-direct product of Z and C.
Example pattern with this symmetry group:
For any symmetry group containing some glide-reflection symmetry, the translation vector of any glide reflection is one half of an element of the translation group. If the translation vector of a glide reflection is itself an element of the translation group, then the corresponding glide-reflection symmetry reduces to a combination of reflection symmetry and translational symmetry. | 0 | Theoretical and Fundamental Chemistry |
The main technological driver for the exploration of multiferroics has been their potential for controlling magnetism using electric fields via their magneto electric coupling. Such a capability could be technologically transformative, since the production of electric fields is far less energy intensive than the production of magnetic fields (which in turn require electric currents) that are used in most existing magnetism-based technologies. There have been successes in controlling the orientation of magnetism using an electric field, for example in heterostructures of conventional ferromagnetic metals and multiferroic BiFeO, as well as in controlling the magnetic state, for example from antiferromagnetic to ferromagnetic in FeRh.
In multiferroic thin films, the coupled magnetic and ferroelectric order parameters can be exploited for developing magnetoelectronic devices. These include novel spintronic devices such as tunnel magnetoresistance (TMR) sensors and spin valves with electric field tunable functions. A typical TMR device consists of two layers of ferromagnetic materials separated by a thin tunnel barrier (~2 nm) made of a multiferroic thin film. In such a device, spin transport across the barrier can be electrically tuned. In another configuration, a multiferroic layer can be used as the exchange bias pinning layer. If the antiferromagnetic spin orientations in the multiferroic pinning layer can be electrically tuned, then magnetoresistance of the device can be controlled by the applied electric field. One can also explore multiple state memory elements, where data are stored both in the electric and the magnetic polarizations. | 0 | Theoretical and Fundamental Chemistry |
[Co(NH)] is a component of some structural biology methods (especially for DNA or RNA, where positive ions stabilize tertiary structure of the phosphate backbone), to help solve their structures by X-ray crystallography or by nuclear magnetic resonance. In the biological system, the counterions would more probably be Mg, but the heavy atoms of cobalt (or sometimes iridium, as in ) provide anomalous scattering to solve the phase problem and produce an electron-density map of the structure.
[Co(NH)] is used to investigate DNA. The cation induces the transition of DNA structure from the classical B-form to the Z-form. | 0 | Theoretical and Fundamental Chemistry |
Experimental data of high pressure jets have to be limited in terms of size and complexity of the scenario due to the inherit dangers and expenses correlated to the experiment itself. Alternative methods to gather data, such as representative models, can be used in order to predict what the maximum extend of the gas cloud at its LFL concentration can reach. Simpler models like a gaussian gas dispersion model (e.g., SCREEN3 - a dispersion model) or integral model (e.g., PHAST- an integral model) can be useful to have a quick and qualitative overview on how the jet may extend. Unfortunately, their inability to properly simulate jet-obstacle interactions make them impossible to use beyond preliminary calculations. This is the reason why Computational Fluid Dynamic (CFD) simulations are generally preferred for more complex scenarios.
Although there exists several approaches for CFD simulations, a common approach is the use of a finite volume method that discretizes the volume into smaller cells of varying shapes. Every single cell will represent a fluid-filled volume where the scenarios parameters will be applied. Every cell that was modeled solves a set of conservation equations of mass, momentum and energy, along with the continuity equation. Fluid-obstacle interaction is then modeled with varying algorithms based on the closure turbulent model used.
Depending on the number of total cells within the volume, the better the quality of the simulation, the longer the simulation time. Convergence problems can arise within the simulation as large momentum, mass and energy gradients appear in the volume. The points where these problems are expected to appear (like in the nearfield zone of the jet) need to have a higher number of cells to achieve gradual changes between one cell and another. Ideally, through CFD simulations, a simpler model can be derived which, for a specific set of scenarios, allows to have results with an accuracy and precision level similar to the CFD simulation itself. | 1 | Applied and Interdisciplinary Chemistry |
These different definitions have true physical meaning because different techniques in physical polymer chemistry often measure just one of them. For instance, osmometry measures number average molar mass and small-angle laser light scattering measures mass average molar mass. is obtained from viscosimetry and by sedimentation in an analytical ultra-centrifuge. The quantity a in the expression for the viscosity average molar mass varies from 0.5 to 0.8 and depends on the interaction between solvent and polymer in a dilute solution. In a typical distribution curve, the average values are related to each other as follows:
The dispersity (also known as the polydispersity index) of a sample is defined as divided by and gives an indication just how narrow a distribution is.
The most common technique for measuring molecular mass used in modern times is a variant of high-pressure liquid chromatography (HPLC) known by the interchangeable terms of size exclusion chromatography (SEC) and gel permeation chromatography (GPC). These techniques involve forcing a polymer solution through a matrix of cross-linked polymer particles at a pressure of up to several hundred bar. The limited accessibility of stationary phase pore volume for the polymer molecules results in shorter elution times for high-molecular-mass species. The use of low dispersity standards allows the user to correlate retention time with molecular mass, although the actual correlation is with the Hydrodynamic volume. If the relationship between molar mass and the hydrodynamic volume changes (i.e., the polymer is not exactly the same shape as the standard) then the calibration for mass is in error.
The most common detectors used for size exclusion chromatography include online methods similar to the bench methods used above. By far the most common is the differential refractive index detector that measures the change in refractive index of the solvent. This detector is concentration-sensitive and very molecular-mass-insensitive, so it is ideal for a single-detector GPC system, as it allows the generation of mass v's molecular mass curves. Less common but more accurate and reliable is a molecular-mass-sensitive detector using multi-angle laser-light scattering - see static light scattering. These detectors directly measure the molecular mass of the polymer and are most often used in conjunction with differential refractive index detectors. A further alternative is either low-angle light scattering, which uses a single low angle to determine the molar mass, or Right-angle-light laser scattering in combination with a viscometer, although this latter technique does not give an absolute measure of molar mass but one relative to the structural model used.
The molar mass distribution of a polymer sample depends on factors such as chemical kinetics and work-up procedure. Ideal step-growth polymerization gives a polymer with dispersity of 2. Ideal living polymerization results in a dispersity of 1. By dissolving a polymer an insoluble high molar mass fraction may be filtered off resulting in a large reduction in and a small reduction in , thus reducing dispersity. | 0 | Theoretical and Fundamental Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.