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# flowfield must contain molecular species with an optical resonance wavelength that can be accessed by laser
# temperature measurements typically require two laser sources
# velocity measurements typically practical only for high Mach number flows (near sonic or supersonic)
# signal-to-noise ratio often limited by detector shot-noise
# fluorescence interferences from other species, especially from hydrocarbons in high pressure reacting flows
# attenuation of laser sheet across flow field or reabsorption of fluorescence before it reaches detector can lead to systematic errors | 1 | Applied and Interdisciplinary Chemistry |
Fluorine is relatively rare in the universe compared to other elements of nearby atomic weight. On Earth, fluorine is essentially found only in mineral compounds because of its reactivity. The main commercial source, fluorite, is a common mineral. | 0 | Theoretical and Fundamental Chemistry |
Glycolysis, which means “sugar splitting,” is the initial process in the cellular respiration pathway. Glycolysis can be either an aerobic or anaerobic process. When oxygen is present, glycolysis continues along the aerobic respiration pathway. If oxygen is not present, then ATP production is restricted to anaerobic respiration. The location where glycolysis, aerobic or anaerobic, occurs is in the cytosol of the cell. In glycolysis, a six-carbon glucose molecule is split into two three-carbon molecules called pyruvate. These carbon molecules are oxidized into NADH and ATP. For the glucose molecule to oxidize into pyruvate, an input of ATP molecules is required. This is known as the investment phase, in which a total of two ATP molecules are consumed. At the end of glycolysis, the total yield of ATP is four molecules, but the net gain is two ATP molecules. Even though ATP is synthesized, the two ATP molecules produced are few compared to the second and third pathways, Krebs cycle and oxidative phosphorylation. | 1 | Applied and Interdisciplinary Chemistry |
According to equation (10), the minimum required entropy change (right term) for the summation of the positive entropy changes decreases when T increases. As an example, performing the same numerical application but with T equals to 2000K would give a twice lower value (around 140 kJ/mol), which allows thermochemical cycles with only two reactions. Such processes can be realistically coupled with concentrated solar power technologies like Solar Updraft Tower. As an example in Europe, this is the goal of the Hydrosol-2 project (Greece, Germany (German Aerospace Center), Spain, Denmark, England) and of the researches of the solar department of the ETH Zurich and the Paul Scherrer Institute (Switzerland).
Examples of reactions satisfying high entropy changes are metal oxide dissociations, as the products have more excitation levels due to their gaseous state (metal vapors and oxygen) than the reactant (solid with crystalline structure, so symmetry dramatically reduces the number of different excitation levels). Consequently, these entropy changes can often be larger than the water-splitting one and thus a reaction with a negative entropy change is required in the thermochemical process so that Eq.(5) is satisfied. Furthermore, assuming similar stabilities of the reactant (ΔH°) for both thermolysis and oxide dissociation, a larger entropy change in the second case explained again a lower reaction temperature (Eq.(3)).
Let us assume two reactions, with positive (1 subscript, at T) and negative (2 subscript, at T°) entropy changes. An extra property can be derived in order to have T strictly lower than the thermolysis temperature: The standard thermodynamic values must be unevenly distributed among the reactions .
Indeed, according to the general equations (2) (spontaneous reaction), (4) and (5), one must satisfy,
Hence, if ΔH° is proportional to ΔH° by a given factor, and if ΔS° and ΔS° follow a similar law (same proportionality factor), the inequality (17) is broken (equality instead, so T equals to the water thermolysis temperature). | 0 | Theoretical and Fundamental Chemistry |
Electron donating groups are typically divided into three levels of activating ability (The "extreme" category can be seen as "strong".) Electron withdrawing groups are assigned to similar groupings. Activating substituents favour electrophilic substitution about the ortho and para positions. Weakly deactivating groups direct electrophiles to attack the benzene molecule at the ortho- and para- positions, while strongly and moderately deactivating groups direct attacks to the meta- position. This is not a case of favoring the meta- position like para- and ortho- directing functional groups, but rather disfavouring the ortho- and para-positions more than they disfavour the meta- position. | 0 | Theoretical and Fundamental Chemistry |
By combining substances with pK values differing by only two or less and adjusting the pH, a wide range of buffers can be obtained. Citric acid is a useful component of a buffer mixture because it has three pK values, separated by less than two. The buffer range can be extended by adding other buffering agents. The following mixtures (McIlvaine's buffer solutions) have a buffer range of pH 3 to 8.
A mixture containing citric acid, monopotassium phosphate, boric acid, and diethyl barbituric acid can be made to cover the pH range 2.6 to 12.
Other universal buffers are the Carmody buffer and the Britton–Robinson buffer, developed in 1931. | 0 | Theoretical and Fundamental Chemistry |
* Decorative stone artifacts, arts and decoration;
* Cultural heritage, archaeology and history of sciences. | 0 | Theoretical and Fundamental Chemistry |
The Qubit fluorometer is a laboratory instrument developed and distributed by Invitrogen, which is now a part of Thermo Fisher. It is used for the quantification of DNA, RNA, and protein. | 0 | Theoretical and Fundamental Chemistry |
The allows for visualization of two misoriented materials and their interface such as crystal twins or grain boundaries. The user interface provides three views: two smaller views, each depicting one unit cell of selected material and orientation, and a larger view depicting an appropriate interface of the two structures. The interface can be visualized in four modes:
* 3D model of both unit cells,
* wire-frame model of both unit cells,
* cross section of the interface,
* bulk representation (up to several hundred atoms).
All three views in the user interface are functionally interconnected. If the content of one view is rotated by the user, the other views follow. If a crystallographic plane or direction is selected in one view, it is shown in other views and corresponding crystallographic indices are stated. The tool also allows to highlight coincident site lattice or calculate the list of planes and directions which are parallel or nearly parallel in the two misoriented materials. | 0 | Theoretical and Fundamental Chemistry |
The quality of an SKP measurement is affected by a number of factors. This includes the diameter of the SKP probe, the probe to sample distance, and the material of the SKP probe. The probe diameter is important in the SKP measurement because it affects the overall resolution of the measurement, with smaller probes leading to improved resolution. On the other hand, reducing the size of the probe causes an increase in fringing effects which reduces the sensitivity of the measurement by increasing the measurement of stray capacitances. The material used in the construction of the SKP probe is important to the quality of the SKP measurement. This occurs for a number of reasons. Different materials have different work function values which will affect the contact potential measured. Different materials have different sensitivity to humidity changes. The material can also affect the resulting lateral resolution of the SKP measurement. In commercial probes tungsten is used, though probes of platinum, copper, gold, and NiCr has been used. The probe to sample distance affects the final SKP measurement, with smaller probe to sample distances improving the lateral resolution and the signal-to-noise ratio of the measurement. Furthermore, reducing the SKP probe to sample distance increases the intensity of the measurement, where the intensity of the measurement is proportional to 1/d, where d is the probe to sample distance. The effects of changing probe to sample distance on the measurement can be counteracted by using SKP in constant distance mode. | 0 | Theoretical and Fundamental Chemistry |
In January 1963, Bartlett and his graduate student, P. R. Rao, were hospitalized after an explosion in the laboratory. As they looked at what they thought might be the first crystals of XeF, the compound exploded, getting shards of glass in the eyes of both men. According to Bartlett, he thought that the compound may have contained water molecules, and he and Rao took off their glasses to get a better look. They were both taken to the hospital for four weeks, and Bartlett was left with damaged vision in one eye. The last piece of glass from this accident was removed 27 years later. | 0 | Theoretical and Fundamental Chemistry |
Anomers can be interconverted through a process known as mutarotation. The anomeric effect more accurately called the endo-anomeric effect is the propensity for heteroatoms at C-1 to be oriented axially. This is counter intuitive as one would expect the equatorially anomer to be the thermodynamic product. This effect has been rationalized through dipole–dipole repulsion and n–σ* arguments. | 0 | Theoretical and Fundamental Chemistry |
Immersed in water, extremely water repellent (super-hydrophobic), structured surfaces trap air between the structures and this air-layer is maintained for a period of time. A silvery shine, due to the reflection of light at the interface of air and water, is visible on the submerged surfaces.
Long lasting air layers also occur in aquatic arthropods which breathe via a physical gill (plastron) e. g. the water spider (Argyroneta) and the saucer bug (Aphelocheirus) Air layers are presumably also conducive to the reduction of friction in fast moving animals under water, as is the case for the back swimmer Notonecta.
The best known examples for long term air retention under water are the floating ferns of genus Salvinia. About ten species of very diverse sizes are found in lentic water in all warmer regions of the earth, one widely spread species (S. natans) found in temperate climates can be even found in Central Europe. The ability to retain air is presumably a survival technique for these plants. The upper side of the floating leaves is highly water repellent and possesses highly complex and species-specific very distinctive hairs. Some species present multicellular free-standing hairs of 0.3–3 mm length (e. g. S. cucullata) while on others, two hairs are connected at the tips (e.g. S. oblongifolia). S. minima and S. natans have four free standing hairs connected at a single base. The Giant Salvinia (S. molesta), as well as S. auriculata, and other closely related species, display the most complex hairs: four hairs grow on a shared shaft; they are connected at their tips. These structures resemble microscopic eggbeaters and are therefore referred to as “eggbeater trichomes”. The entire leaf surface, including the hairs, is covered with nanoscale wax crystals which are the reason for the water repellent properties of the surfaces. These leaf surfaces are therefore a classical example of a “hierarchical structuring“.
The egg-beater hairs of Salvinia molesta and closely related species (e.g. S. auriculata) show an additional remarkable property. The four cells at the tip of each hair (the anchor cells), as opposed to the rest of the hair, are free of wax and therefore hydrophilic; in effect, wettable islands surrounded by a super-hydrophobic surface. This chemical heterogeneity, the Salvinia paradox, enables a pinning of the air water interface to the plant and increases the pressure and longtime stability of the air layer.
The air retaining surface of the floating fern does not lead to a reduction in friction. The ecological extremely adaptable Giant Salvinia (S. molesta) is one of the most important invasive plants in all tropical and subtropical regions of the earth and is the cause of economic as well as ecological problems. Its growth rate might be the highest of all vascular plants. In the tropics and under optimal conditions, S. molesta can double its biomass within four days. The Salvinia effect, described here, most likely plays an essential role in its ecological success; the multilayered floating plant mats presumably maintain their function of gas exchange within the air-layer. | 0 | Theoretical and Fundamental Chemistry |
Distinct cracks may appear on the surface of the glass, and surface material may flake or chip, a process referred to as spalling. | 0 | Theoretical and Fundamental Chemistry |
Monopolin is composed of a 4 CSM1:2 LRS4 complex which forms a V-shaped structure with two globular heads at the ends, which are responsible for directly crosslinking sister kinetochores. Bound to each CSM1 head is a MAM1 protein which recruits one copy of the HRR25 kinase. The hydrophobic cavity on the CSM1 subunit allows the hydrophobic regions of Monopolin receptor and kinetochore protein, DSN1, to bind to and fuse the sister kinetochores. Microtubules can then attach to the kinetochores on the homologous centromeres and pull them toward opposite mitotic spindles to complete anaphase of meiosis I. | 1 | Applied and Interdisciplinary Chemistry |
Baldwins rules also apply to aldol cyclizations involving enolates. Two new descriptors need to be defined: enolendo and enolexo', which refer to whether both carbons of the enolate C-C fragment are incorporated into the ring formed or not, respectively.
The rules are the following: | 0 | Theoretical and Fundamental Chemistry |
Coproporphyrinogens are tetrapyrroles with four propionic acid groups and an equal number of substituted methyls.
Coproporphyrinogen III is the most common variance. In the metabolism of porphyrin, it is formed from uroporphyrinogen III by the enzyme uroporphyrinogen III decarboxylase, and it is converted into protoporphyrinogen IX by coproporphyrinogen III oxidase. | 1 | Applied and Interdisciplinary Chemistry |
The process flow diagram below is an example of a schematic or block flow diagram and depicts the various unit processes within a typical oil refinery: | 1 | Applied and Interdisciplinary Chemistry |
NTA and related technologies were developed by Bob Carr. Along with John Knowles, Carr founded NanoSight Ltd in 2003. This United Kingdom-based company, of which Knowles is the chairman and Carr is the chief technology officer, manufactures instruments that use NTA to detect and analyze small particles in industrial and academic laboratories. In 2004 Particle Metrix GmbH was founded in Germany by Hanno Wachernig. Particle Metrix makes the ZetaView which operates on the same NTA principle but uses different optics and fluidics in an attempt to improve sampling, zeta potential, and fluorescence detection. | 0 | Theoretical and Fundamental Chemistry |
He is a member of: Società Chimica Italiana; Accademia delle Scienze di Bologna; Accademia delle Scienze di Torino; Società Nazionale di Scienze, Lettere ed Arti in Napoli; Accademia Nazionale delle Scienze detta dei XL; Accademia Nazionale dei Lincei; European Photochemistry Association; ChemPubSoc Europe; Academia Europaea; European Academy of Sciences, European Academy of Sciences and Arts; American Association for the Advancement of Science. | 0 | Theoretical and Fundamental Chemistry |
Three angles are described by φ, ψ and ω (in the case of glycosidic linkages via O-6). Steric considerations and anomeric effects need to be taken into consideration when looking at preferred angles. | 0 | Theoretical and Fundamental Chemistry |
Nowadays, several Calphad softwares are available - in a framework of computational thermodynamics - to simulate solidification in systems with more than two components; these have recently been defined as Calphad Tools for the Metallurgy of Solidification. In recent years, Calphad-based methodologies have reached maturity in several important fields of metallurgy, and especially in solidification-related processes such as semi-solid casting, 3d printing, and welding, to name a few. While there are important studies devoted to the progress of Calphad methodology, there is still space for a systematization of the field, which proceeds from the ability of most Calphad-based software to simulate solidification curves and includes both fundamental and applied studies on solidification, to be substantially appreciated by a wider community than today. The three applied fields mentioned above could be widened by specific successful examples of simple modeling related to the topic of this issue, with the aim of widening the application of simple and effective tools related to Calphad and Metallurgy. See also "Calphad Tools for the Metallurgy of Solidification" in an ongoing issue of an Open Journal. https://www.mdpi.com/journal/metals/special_issues/Calphad_Solidification
Given a specific chemical composition, using a software for computational thermodynamics - which might be open or commercial - the calculation of the Scheil curve is possible if a thermodynamic database is available. A good point in favour of some specific commercial softwares is that the install is easy indeed and you can use it on a windows based system - for instance with students or for self training.
One should get some open, chiefly binary, databases (extension *.tdb), one could find - after registering - at Computational Phase Diagram Database (CPDDB) of the National Institute for Materials Science of Japan, NIMS https://cpddb.nims.go.jp/index_en.html. They are available - for free - and the collection is rather complete; in fact currently 507 binary systems are available in the thermodynamic data base (tdb) format.
Some wider and more specific alloy systems partly open - with tdb compatible format - are available with minor corrections for Pandat use at Matcalc https://www.matcalc.at/index.php/databases/open-databases. | 1 | Applied and Interdisciplinary Chemistry |
A Stirling cycle is like an Otto cycle, except that the adiabats are replaced by isotherms. It is also the same as an Ericsson cycle with the isobaric processes substituted for constant volume processes.
# TOP and BOTTOM of the loop: a pair of quasi-parallel isothermal processes
# LEFT and RIGHT sides of the loop: a pair of parallel isochoric processes
Heat flows into the loop through the top isotherm and the left isochore, and some of this heat flows back out through the bottom isotherm and the right isochore, but most of the heat flow is through the pair of isotherms. This makes sense since all the work done by the cycle is done by the pair of isothermal processes, which are described by Q=W. This suggests that all the net heat comes in through the top isotherm. In fact, all of the heat which comes in through the left isochore comes out through the right isochore: since the top isotherm is all at the same warmer temperature and the bottom isotherm is all at the same cooler temperature , and since change in energy for an isochore is proportional to change in temperature, then all of the heat coming in through the left isochore is cancelled out exactly by the heat going out the right isochore. | 0 | Theoretical and Fundamental Chemistry |
Orthophosphate ion can be conveniently thermometrically titrated with magnesium ions in the presence of ammonium ion. An aliquot of sample is buffered to approximately pH10 with an NH/NHCl solution.
The reaction:
: Mg + NH + PO ↔ MgNHPO↓
Is exothermic. CV's of under 0.1 have been achieved in test applications. The procedure is suitable for the determination of orthophosphate in fertilizers and other products. | 0 | Theoretical and Fundamental Chemistry |
Promiscuity is not only a primordial trait, but also a very widespread property in modern genomes. A series of experiments have been conducted to assess the distribution of promiscuous enzyme activities in E. coli. In E. coli 21 out of 104 single-gene knockouts tested (from the Keio collection) could be rescued by overexpressing a noncognate E. coli protein (using a pooled set of plasmids of the ASKA collection). The mechanisms by which the noncognate ORF could rescue the knockout can be grouped into eight categories: isozyme overexpression (homologues), substrate ambiguity, transport ambiguity (scavenging), catalytic promiscuity, metabolic flux maintenance (including overexpression of the large component of a synthase in the absence of the amine transferase subunit), pathway bypass, regulatory effects and unknown mechanisms. Similarly, overexpressing the ORF collection allowed E. coli to gain over an order of magnitude in resistance in 86 out 237 toxic environment. | 1 | Applied and Interdisciplinary Chemistry |
Accurate interpretation takes a variety of factors into account, such as the thyroid hormones i.e. thyroxine (T) and triiodothyronine (T), current medical status (such as pregnancy), certain medications like propylthiouracil, temporal effects including circadian rhythm and hysteresis, and other past medical history. | 1 | Applied and Interdisciplinary Chemistry |
The use of bracken fern as human food is mainly a historical question. The rhizomes of these plants served as human food in Scotland during the First World War. In America (USA, Canada), Russia, China and Japan, fern is grown commercially for human use. The usual procedure that is performed before eating the plant is to pre-treat the fern with boiling water in the presence of different chemicals, such as sodium bicarbonate and wood ash, to degrade or inactivate ptaquiloside and other toxic agents. Nevertheless, some carcinogenic activity persists even after the treatment. As shown by Kamon and Hirayama, the risk of oesophageal cancer was increased approximately by 2.1 in men and 3.7 in women who regularly consume bracken in Japan. Recent researches have suggested that sulfur-containing amino acids can potentially be used under appropriate conditions as detoxifying agents for ptaquiloside and selenium supplementation can prevent as well as reverse the immunotoxic effects induced by ptaquiloside.
Ptaquiloside in the aqueous extract of bracken can be detected using different instrumental methods: thin-layer chromatography–densitometry (TLC-densitometry), high-performance liquid chromatography (HPLC), gas chromatography–mass spectrometry (GCMS), and liquid chromatography–mass spectrometry (LC-MS). The diagnostic tests of ptaquiloside inside cells include gene mutation detection, immunohistochemical detection of tumor biomarkers, chromosomal aberrations, oxidative stress for EBH, PCR, real-time PCR and DNase-SISPA (sequence-independent single primer amplification). | 0 | Theoretical and Fundamental Chemistry |
Consider the sum
where >0 for all N. Since all the terms are positive, the value of S must be greater than the value of the largest term, , and less than the product of the number of terms and the value of the largest term. So we have
Taking logarithm gives
In statistical mechanics often will be : see Big O notation.
Here we have
For large M, is negligible with respect to M itself, and so we can see that ln S is bounded from above and below by , and so | 0 | Theoretical and Fundamental Chemistry |
The Repligen Award in Chemistry of Biological Processes was established in 1985 and consists of a silver medal and honorarium. Its purpose is to acknowledge and encourage outstanding contributions to the understanding of the chemistry of biological processes, with particular emphasis on structure, function, and mechanism. The Award is administered by the Division of Biological Chemistry of the American Chemical Society.
The award was suspended in 2018 until a patron can be found. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl group (e.g., alkyl, alkenyl, aryl), or hydrogen, or other groups. Carboxylic acids occur widely. Important examples include the amino acids and fatty acids. Deprotonation of a carboxylic acid gives a carboxylate anion. | 0 | Theoretical and Fundamental Chemistry |
In summary, in order to find a standard curve, one must use varying concentrations of BSA (Bovine Serum Albumin) in order to create a standard curve with concentration plotted on the x-axis and absorbance plotted on the y-axis. Only a narrow concentration of BSA is used (2-10 ug/mL) in order to create an accurate standard curve. Using a broad range of protein concentration will make it harder to determine the concentration of the unknown protein. This standard curve is then used to determine the concentration of the unknown protein. The following elaborates on how one goes from the standard curve to the concentration of the unknown.
First, add a line of best fit, or Linear regression and display the equation on the chart. Ideally, the R value will be as close to 1 as possible. R represents the sum of the square values of the fit subtracted from each data point. Therefore, if R is much less than one, consider redoing the experiment to get one with more reliable data.
The equation displayed on the chart gives a means for calculating the absorbance and therefore concentration of the unknown samples. In Graph 1, x is concentration and y is absorbance, so one must rearrange the equation to solve for x and enter the absorbance of the measured unknown. It is likely that the unknown will have absorbance numbers outside the range of the standard. These should not be included calculations, as the equation given cannot apply to numbers outside of its limitations.
In a large scale, one must compute the extinction coefficient using the Beer-Lambert Law A=εLC in which A is the measured absorbance, ε is the slope of the standard curve, L is the length of the cuvette, and C is the concentration being determined. In a micro scale, a cuvette may not be used and therefore one only has to rearrange to solve for x.
In order to attain a concentration that makes sense with the data, the dilutions, concentrations, and units of the unknown must be normalized (Table 1). To do this, one must divide concentration by volume of protein in order to normalize concentration and multiply by amount diluted to correct for any dilution made in the protein before performing the assay. | 0 | Theoretical and Fundamental Chemistry |
An androgen conjugate is a conjugate of an androgen, such as testosterone. They occur naturally in the body as metabolites of androgens. Androgen conjugates include sulfate esters and glucuronide conjugates and are formed by sulfotransferase and glucuronosyltransferase enzymes, respectively. In contrast to androgens, conjugates of androgens do not bind to the androgen receptor and are hormonally inactive. However, androgen conjugates can be converted back into active androgens through enzymes like steroid sulfatase.
Examples of androgen conjugates include the sulfates testosterone sulfate, dehydroepiandrosterone sulfate, androstenediol sulfate, dihydrotestosterone sulfate, and androsterone sulfate, and the glucuronides testosterone glucuronide, dihydrotestosterone glucuronide, androsterone glucuronide, and androstanediol glucuronide.
Androgen conjugates are conjugated at the C3 and/or C17β positions, where hydroxyl groups are available. | 1 | Applied and Interdisciplinary Chemistry |
A particle may diffuse to a surface in quiescent conditions, but this process is inefficient as a thick depletion layer develops, which leads to a progressive slowing down of the deposition. When particle deposition is efficient, it proceeds almost exclusively in a system under flow. In such conditions, the hydrodynamic flow will transport the particles close to the surface. Once a particle is situated close to the surface, it will attach spontaneously, when the particle-surface interactions are attractive. In this situation, one refers to favorable deposition conditions. When the interaction is repulsive at larger distances, but attractive at shorter distances, deposition will still occur but it will be slowed down. One refers to unfavorable deposition conditions here. The initial stages of the deposition process can be described with the rate equation
where ; is the number density of deposited particles, is the time, the particle number concentration, and the deposition rate coefficient. The rate coefficient depends on the flow velocity, flow geometry, and the interaction potential of the depositing particle with the substrate. In many situations, this potential can be approximated by a superposition of attractive van der Waals forces and repulsive electrical double layer forces and can be described by DLVO theory. When the charge of the particles is of the same sign as the substrate, deposition will be favorable at high salt levels, while it will be unfavorable at lower salt levels. When the charge of the particles is of the opposite sign as the substrate, deposition is favorable for all salt levels, and one observes a small enhancement of the deposition rate with decreasing salt level due to attractive electrostatic double layer forces. Initial stages of the deposition process are relatively similar to the early stages of particle heteroaggregation, whereby one of the particles is much larger than the other. | 0 | Theoretical and Fundamental Chemistry |
Peter Bernard David de la Mare (3 September 1920 – 13 December 1989) was a New Zealand physical organic chemist.
Born in Hamilton in 1920, he was the son of Sophia Ruth de la Mare (née Child), a medical practitioner, and Frederick Archibald de la Mare, a lawyer. He was educated at Hamilton High School, and then attended Victoria University College, from where he graduated in 1942 with an MSc in chemistry, winning the Shirtcliffe Fellowship and the Jacob Joseph Scholarship. His master's research was supervised by Philip Robertson. He worked at the Department of Scientific and Industrial Research in the agricultural department at Wellington and Ruakura, before undertaking PhD studies at University College London between 1946 and 1948, supervised by Christopher Ingold.
He was appointed as an assistant lecturer in the University College London department of chemistry in 1948, and was promoted to lecturer in 1949 and reader in 1957. In 1960 he moved to Bedford College, University of London, becoming professor and head of chemistry. He was appointed professor and head of chemistry at the University of Auckland in 1967, stepping down as head of department in 1980 and retiring in 1981.
De la Mare was awarded a DSc by thesis from the University of London in 1955. He was elected a Fellow of the Royal Society of New Zealand in 1970, and in 1985 he won the society's Hector Medal, then the highest award in New Zealand science. In 1983 he was awarded an honorary DSc by Victoria University of Wellington. | 0 | Theoretical and Fundamental Chemistry |
Secondary antibodies can be conjugated to enzymes such as horseradish peroxidase (HRP) or alkaline phosphatase (AP); or fluorescent dyes such as fluorescein isothiocyanate (FITC), rhodamine derivatives, Alexa Fluor dyes; or other molecules to be used in various applications. Secondary antibodies are used in many biochemical assays including:
* ELISA, including many HIV tests
* Western blot
* Immunostaining
* Immunohistochemistry
* Immunocytochemistry | 1 | Applied and Interdisciplinary Chemistry |
Acidic, sandy, or coarse soils often contain less calcium. Uneven soil moisture and overuse of fertilizers can also cause calcium deficiency. At times, even with sufficient calcium in the soil, it can be in an insoluble form and is then unusable by the plant or it could be attributed to a "transport protein". Soils containing high phosphorus are particularly susceptible to creating insoluble forms of calcium.
Calcium and magnesium are opposed within the plant cells, and have antagonistic interactions. As a result, a homeostatic balance between Ca and Mg within the plant is necessary for optimal growth and proper development. | 1 | Applied and Interdisciplinary Chemistry |
Due to the presence of vanabins, concentration of vanadium found in the blood cells of Ascidia gemmata belonging to the suborder Phlebobranchia is 10,000,000 times higher than that in the surrounding seawater. A similar biological process might have played a role in the formation of vanadium ores.
Vanadium is also present in fossil fuel deposits such as crude oil, coal, oil shale, and oil sands. In crude oil, concentrations up to 1200 ppm have been reported. | 0 | Theoretical and Fundamental Chemistry |
To extract quantities of interest, the autocorrelation data can be fitted, typically using a nonlinear least squares algorithm. The fit's functional form depends on the type of dynamics (and the optical geometry in question). | 0 | Theoretical and Fundamental Chemistry |
Smith worked on the development of technically and environmentally sound mineral and waste processing technologies. He laid the groundwork for various technical innovations, including the carbochlorination technique used in the processing of lunar anorthite. Alongside colleagues, he confirmed graphite's ability, with or without catalysts, to selectively reduce iron oxide in synthetic ilmenite, observed through isothermal weight loss over time from 850 °C to 1200 °C under argon atmosphere. Additionally, he explored reduction roasting processes using various reductants and desulfurizers to convert sulfide minerals to metallic form without sulfur dioxide emissions, capturing sulfur as either calcium sulfide or sodium sulfide. | 1 | Applied and Interdisciplinary Chemistry |
The second variant of the method construct the approximations to the Green's operator
now with vectors
The chain fraction for T-matrix now also holds, with little bit different definition of coefficients . | 0 | Theoretical and Fundamental Chemistry |
Accumulation of excess homogentisic acid and its oxide, named alkapton, is a result of the failure of the enzyme homogentisic acid 1,2-dioxygenase (typically due to a mutation) in the degradative pathway of tyrosine, consequently associated with alkaptonuria. | 1 | Applied and Interdisciplinary Chemistry |
The vortex tube was invented in 1931 by French physicist Georges J. Ranque. It was rediscovered by Paul Dirac in 1934 while he was searching for a device to perform isotope separation, leading to development of the Helikon vortex separation process. German physicist improved the design and published a widely read paper in 1947 on the device, which he called a Wirbelrohr (literally, whirl pipe).
In 1954, Westley published a comprehensive survey entitled "A bibliography and survey of the vortex tube", which included over 100 references. In 1951 Curley and McGree, in 1956 Kalvinskas, in 1964 Dobratz, in 1972 Nash, and in 1979 Hellyar made important contribution to the RHVT literature by their extensive reviews on the vortex tube and its applications.
From 1952 to 1963, C. Darby Fulton, Jr. obtained four U.S. patents relating to the development of the vortex tube. In 1961, Fulton began manufacturing the vortex tube under the company name Fulton Cryogenics. Fulton sold the company to Vortec, Inc. The vortex tube was used to separate gas mixtures, oxygen and nitrogen, carbon dioxide and helium, carbon dioxide and air in 1967 by Linderstrom-Lang.
Vortex tubes also seem to work with liquids to some extent, as demonstrated by Hsueh and Swenson in a laboratory experiment where free body rotation occurs from the core and a thick boundary layer at the wall. Air is separated causing a cooler air stream coming out the exhaust hoping to chill as a refrigerator. In 1988 R. T. Balmer applied liquid water as the working medium. It was found that when the inlet pressure is high, for instance 20-50 bar, the heat energy separation process exists in incompressible (liquids) vortex flow as well. Note that this separation is only due to heating; there is no longer cooling observed since cooling requires compressibility of the working fluid. | 0 | Theoretical and Fundamental Chemistry |
The Brønsted–Lowry definition, formulated in 1923, independently by Johannes Nicolaus Brønsted in Denmark and Martin Lowry in England, is based upon the idea of protonation of bases through the deprotonation of acids – that is, the ability of acids to "donate" hydrogen ions () otherwise known as protons to bases, which "accept" them.
An acid–base reaction is, thus, the removal of a hydrogen ion from the acid and its addition to the base. The removal of a hydrogen ion from an acid produces its conjugate base, which is the acid with a hydrogen ion removed. The reception of a proton by a base produces its conjugate acid, which is the base with a hydrogen ion added.
Unlike the previous definitions, the Brønsted–Lowry definition does not refer to the formation of salt and solvent, but instead to the formation of conjugate acids and conjugate bases, produced by the transfer of a proton from the acid to the base. In this approach, acids and bases are fundamentally different in behavior from salts, which are seen as electrolytes, subject to the theories of Debye, Onsager, and others. An acid and a base react not to produce a salt and a solvent, but to form a new acid and a new base. The concept of neutralization is thus absent. Brønsted–Lowry acid–base behavior is formally independent of any solvent, making it more all-encompassing than the Arrhenius model. The calculation of pH under the Arrhenius model depended on alkalis (bases) dissolving in water (aqueous solution). The Brønsted–Lowry model expanded what could be pH tested using insoluble and soluble solutions (gas, liquid, solid).
The general formula for acid–base reactions according to the Brønsted–Lowry definition is:
where HA represents the acid, B represents the base, represents the conjugate acid of B, and represents the conjugate base of HA.
For example, a Brønsted–Lowry model for the dissociation of hydrochloric acid (HCl) in aqueous solution would be the following:
The removal of from the produces the chloride ion, , the conjugate base of the acid. The addition of to the (acting as a base) forms the hydronium ion, , the conjugate acid of the base.
Water is amphoteric that is, it can act as both an acid and a base. The Brønsted–Lowry model explains this, showing the dissociation of water into low concentrations of hydronium and hydroxide ions:
This equation is demonstrated in the image below:
Here, one molecule of water acts as an acid, donating an and forming the conjugate base, , and a second molecule of water acts as a base, accepting the ion and forming the conjugate acid, .
As an example of water acting as an acid, consider an aqueous solution of pyridine, .
In this example, a water molecule is split into a hydrogen ion, which is donated to a pyridine molecule, and a hydroxide ion.
In the Brønsted–Lowry model, the solvent does not necessarily have to be water, as is required by the Arrhenius Acid–Base model. For example, consider what happens when acetic acid, , dissolves in liquid ammonia.
An ion is removed from acetic acid, forming its conjugate base, the acetate ion, . The addition of an ion to an ammonia molecule of the solvent creates its conjugate acid, the ammonium ion, .
The Brønsted–Lowry model calls hydrogen-containing substances (like ) acids. Thus, some substances, which many chemists considered to be acids, such as or , are excluded from this classification due to lack of hydrogen. Gilbert N. Lewis wrote in 1938, "To restrict the group of acids to those substances that contain hydrogen interferes as seriously with the systematic understanding of chemistry as would the restriction of the term oxidizing agent to substances containing oxygen." Furthermore, and are not considered Brønsted bases, but rather salts containing the bases and . | 0 | Theoretical and Fundamental Chemistry |
Synthetic foams are based on synthetic surfactants. They provide better flow and spreading over the surface of hydrocarbon-based liquids, for faster knockdown of flames. They have limited post-fire security and are toxic groundwater contaminants.
* Aqueous film forming foams (AFFF) are water-based and frequently contain hydrocarbon-based surfactants such as sodium alkyl sulfate, and fluorosurfactants, such as fluorotelomers, perfluorooctanoic acid (PFOA), or perfluorooctanesulfonic acid (PFOS).
* Alcohol-resistant aqueous film-forming foams (AR-AFFF) are foams resistant to the action of alcohols and can form a protective film.
*Fluorine-free foams (FFF, also called F3) are mostly based on hydrocarbon surfactants and are free of any fluorosurfactant. | 0 | Theoretical and Fundamental Chemistry |
Molecular diffusion, often simply called diffusion, is the thermal motion of all (liquid or gas) particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size (mass) of the particles. Diffusion explains the net flux of molecules from a region of higher concentration to one of lower concentration. Once the concentrations are equal the molecules continue to move, but since there is no concentration gradient the process of molecular diffusion has ceased and is instead governed by the process of self-diffusion, originating from the random motion of the molecules. The result of diffusion is a gradual mixing of material such that the distribution of molecules is uniform. Since the molecules are still in motion, but an equilibrium has been established, the result of molecular diffusion is called a "dynamic equilibrium". In a phase with uniform temperature, absent external net forces acting on the particles, the diffusion process will eventually result in complete mixing.
Consider two systems; S and S at the same temperature and capable of exchanging particles. If there is a change in the potential energy of a system; for example μ>μ (μ is Chemical potential) an energy flow will occur from S to S, because nature always prefers low energy and maximum entropy.
Molecular diffusion is typically described mathematically using Fick's laws of diffusion. | 1 | Applied and Interdisciplinary Chemistry |
Chemical weathering of igneous minerals leads to the formation of secondary minerals, which constitute the weathering products of the parent minerals. Secondary weathering minerals of igneous rocks can be classified mainly as iron oxides, salts, and phyllosilicates. The chemistry of the secondary minerals is controlled in part by the chemistry of the parent rock. Mafic rocks tends to contain higher proportions of magnesium and ferric and ferrous iron, which can lead to secondary minerals high in abundance of these cations, including serpentine, Al-, Mg- and Ca-rich clays, and iron oxides such as hematite. Felsic rocks tends to have relatively higher proportions of potassium and sodium, which can lead to secondary minerals rich in these ions, including Al-, Na- and K-rich clays such as kaolinite, montmorillonite and illite. | 0 | Theoretical and Fundamental Chemistry |
From the 17th century onwards, several European travelers observed the steel manufacturing in South India, at Mysore, Malabar and Golconda. The word "wootz" appears to have originated as a mistranscription of wook; the Tamil language root word for the alloy is urukku. Anothertheory says that the word is a variation of uchcha or ucha ("superior"). According to one theory, the word ukku is based on the meaning "melt, dissolve". Other Dravidian languages have similar-sounding words for steel: ukku in Kannada and Telugu, and urukku in Malayalam. When Benjamin Heyne inspected the Indian steel in Ceded Districts and other Kannada-speaking areas, he was informed that the steel was ucha kabbina ("superior iron"), also known as ukku tundu in Mysore.
Legends of wootz steel and Damascus swords aroused the curiosity of the European scientific community from the 17th to the 19th century. The use of high-carbon alloys was little known in Europe previously and thus the research into wootz steel played an important role in the development of modern English, French and Russian metallurgy.
In 1790, samples of wootz steel were received by Sir Joseph Banks, president of the British Royal Society, sent by Helenus Scott. These samples were subjected to scientific examination and analysis by several experts.
Specimens of daggers and other weapons were sent by the Rajas of India to the Great Exhibition in London in 1851 and 1862 International Exhibition. Though the arms of the swords were beautifully decorated and jeweled, they were most highly prized for the quality of their steel. The swords of the Sikhs were said to bear bending and crumpling, and yet be fine and sharp. | 1 | Applied and Interdisciplinary Chemistry |
* Benzaldehyde, for bees
* Butopyronoxyl (trade name Indalone). Widely used in a "6-2-2" mixture (60% Dimethyl phthalate, 20% Indalone, 20% Ethylhexanediol) during the 1940s and 1950s before the commercial introduction of DEET
* DEET (N,N-diethyl-m-toluamide)
* Dimethyl carbate
* Dimethyl phthalate, not as common as it once was but still occasionally an active ingredient in commercial insect repellents
* Ethyl butylacetylaminopropionate (IR3535 or 3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester)
* Ethylhexanediol, also known as Rutgers 612 or "6–12 repellent," discontinued in the US in 1991 due to evidence of causing developmental defects in animals
* Icaridin, also known as picaridin, Bayrepel, and KBR 3023
* Methyl anthranilate and other anthranilate-based insect repellents
* Metofluthrin
* Permethrin is a contact insecticide rather than a repellent
* SS220 is a repellent being researched that has shown promise to provide significantly better protection than DEET
* Tricyclodecenyl allyl ether, a compound often found in synthetic perfumes | 1 | Applied and Interdisciplinary Chemistry |
Electron acceptors participate in electron-transfer reactions. In this context, the oxidizing agent is called an electron acceptor and the reducing agent is called an electron donor. A classic oxidizing agent is the ferrocenium ion , which accepts an electron to form Fe(CH). One of the strongest acceptors commercially available is "Magic blue", the radical cation derived from N(CH-4-Br).
Extensive tabulations of ranking the electron accepting properties of various reagents (redox potentials) are available, see Standard electrode potential (data page). | 0 | Theoretical and Fundamental Chemistry |
On-target toxicity is also referred to as mechanism-based toxicity. This type of adverse effect that results from pharmaceutical drug exposure is commonly due to interactions of the drug with its intended target. In this case, both the therapeutic and toxic targets are the same. To avoid toxicity during treatment, many times the drug needs to be changed to target a different aspect of the illness or symptoms. Statins are an example of a drug class that can have toxic effects at the therapeutic target (HMG CoA reductase). | 1 | Applied and Interdisciplinary Chemistry |
Radium and radon are in the environment because they are decay products of uranium and thorium.
The radon (Rn) released into the air decays to Pb and other radioisotopes, and the levels of Pb can be measured. The rate of deposition of this radioisotope is dependent on the weather. Below is a graph of the deposition rate observed in Japan. | 0 | Theoretical and Fundamental Chemistry |
Carbocyclic analogues of dideoxyadenosine were investigated for their anti-HIV activity. Minimal activity was first observed. Many nucleoside analogues were prepared and examined but only one had significant activity and satisfied the requirements for clinical use. That was 2´,3´-didehydro analogue of dideoxyadenosine. Insertion of a cyclopropyl group on its 6-amino nitrogen of the adenine ring increased lipophilicity and thus enhanced brain penetration. The resulting compound is known as abacavir (see table 3). Abacavir was approved by the FDA for use in therapy of HIV-1 infections in December 1998.
This drug is the only approved antiretroviral that is active as a guanosine analogue in vivo. First it is monophosphorylated by adenosine phosphotransferase and then the monophosphate is converted to carbovir 3´-monophosphate. Subsequently, it is fully phosphorylated and the carbovir is incorporated by the RT into the DNA chain and acts as a chain terminator. Carbovir is a related guanosine analogue that had poor oral bioavailability and thus was withdrawn from clinical development. | 1 | Applied and Interdisciplinary Chemistry |
The greatest danger of tailings ponds is dam failure, with the most publicized failure in the U.S. being the failure of a coal slurry dam in the West Virginia Buffalo Creek Flood of 1972, which killed 125 people; other collapses include the Ok Tedi environmental disaster in New Guinea, which destroyed the fishery of the Ok Tedi River. On average, worldwide, there is one big accident involving a tailings dam each year.
Other disasters caused by tailings dam failures are, the 2000 Baia Mare cyanide spill and the Ajka alumina plant accident. In 2015, the iron ore tailings dam failure at the Germano mine complex in Minas Gerais, Brazil, was the country's biggest environmental disaster. The dam breach caused the death of 19 people due to flooding of tailings slime downstream and affected some 400 km of the Doce river system with toxic effluence and out into the Atlantic Ocean. | 1 | Applied and Interdisciplinary Chemistry |
All bacterial species that have been reported to possess bioluminescence belong within the families Vibrionaceae, Shewanellaceae, or Enterobacteriaceae, all of which are assigned to the class Gammaproteobacteria.
(List from Dunlap and Henryk (2013), "Luminous Bacteria", The Prokaryotes ) | 1 | Applied and Interdisciplinary Chemistry |
The hydrogen storage density per unit volume (crystal) of LaNiH at 2 bar is equal to the density of gaseous molecular hydrogen at 1800 bar, and all hydrogen can be desorbed at 2 bar. Although the hydrogen storage density in practical applications is reduced due to the aggregation of some LaNi powders, it is still higher than the density of liquid hydrogen. This allows safe operation of hydrogen fuel. In order to improve its hydrogen storage performance, metals such as lead or manganese are often used to partially replace nickel. Currently, LaNi is commonly used in storage and transportation of hydrogen, hydrogen vehicle power, fuel cells, separation and purification of hydrogen, propylene hydrogenation catalysts, etc. | 1 | Applied and Interdisciplinary Chemistry |
Gun-type fission weapons are fission-based nuclear weapons whose design assembles their fissile material into a supercritical mass by the use of the "gun" method: shooting one piece of sub-critical material into another. Although this is sometimes pictured as two sub-critical hemispheres driven together to make a supercritical sphere, typically a hollow projectile is shot onto a spike, which fills the hole in its center. Its name is a reference to the fact that it is shooting the material through an artillery barrel as if it were a projectile.
Since it is a relatively slow method of assembly, plutonium cannot be used unless it is purely the 239 isotope. Production of impurity-free plutonium is very difficult and is impractical. The required amount of uranium is relatively large, and thus the overall efficiency is relatively low. The main reason for this is the uranium metal does not undergo compression (and resulting density increase) as does the implosion design. Instead, gun type bombs assemble the supercritical mass by amassing such a large quantity of uranium that the overall distance through which daughter neutrons must travel has so many mean free paths it becomes very probable most neutrons will find uranium nuclei to collide with, before escaping the supercritical mass.
The first time gun-type fission weapons were discussed was as part of the British Tube Alloys nuclear bomb development program, the world's first nuclear bomb development program. The British MAUD Report of 1941 laid out how "an effective uranium bomb which, containing some 25 lb of active material, would be equivalent as regards destructive effect to 1,800 tons of T.N.T". The bomb would use the gun-type design "to bring the two halves together at high velocity and it is proposed to do this by firing them together with charges of ordinary explosive in a form of double gun".
The method was applied in four known US programs. First, the "Little Boy" weapon which was detonated over Hiroshima and several additional units of the same design prepared after World War II, in 40 Mark 8 bombs, and their replacement, 40 Mark 11 bombs. Both the Mark 8 and Mark 11 designs were intended for use as earth-penetrating bombs (see nuclear bunker buster), for which the gun-type method was preferred for a time by designers who were less than certain that early implosion-type weapons would successfully detonate following an impact. The second program was a family of 11-inch (280 mm) nuclear artillery shells, the W9 and its derivative W19, plus a repackaged W19 in a 16-inch (406 mm) shell for US Navy battleships, the W23. The third family was an 8-inch (203 mm) artillery shell, the W33.
South Africa also developed six nuclear bombs based on the gun-type principle, and was working on missile warheads using the same basic design – See South Africa and weapons of mass destruction.
There are currently no known gun-type weapons in service: advanced nuclear weapon states tended to abandon the design in favor of the implosion-type weapons, boosted fission weapons, and thermonuclear weapons. New nuclear weapon states tend to develop boosted fission and thermonuclear weapons only. All known gun-type nuclear weapons previously built worldwide have been dismantled. | 0 | Theoretical and Fundamental Chemistry |
The strip mill was a major innovation, with the first being erected at Ashland, Kentucky in 1923. This provided a continuous process, eliminating the need to pass the plates over the rolls and to double them. At the end the strip was cut with a guillotine shear or rolled into a coil. Early (hot rolling) strip mills did not produce strip suitable for tinplate, but in 1929 cold rolling began to be used to reduce the gauge further. The first strip mill in Great Britain was opened at Ebbw Vale in 1938 with an annual output of 200,000 tons.
The strip mill had several advantages over pack mills:
* It was cheaper due to having all parts of the process, starting with blast furnaces, on the same site.
* Softer steel could be used.
* Larger sheets could be produced at lower cost; this reduced cost and enabled tinplate and steel sheet to be used for more purposes.
* It was capital-intensive, rather than labour-intensive. | 1 | Applied and Interdisciplinary Chemistry |
El-Sayed was born in Zifta, Egypt and spent his early life in Cairo. He earned his B.Sc. in chemistry from Ain Shams University Faculty of Science, Cairo in 1953. El-Sayed earned his doctoral degree in chemistry from Florida State University working with Michael Kasha, the last student of the legendary G. N. Lewis. While attending graduate school he met and married Janice Jones, his wife of 48 years. He spent time as a post-doctoral researcher at Harvard University, Yale University and the California Institute of Technology before joining the faculty of the University of California at Los Angeles in 1961. In 1994, he retired from UCLA and accepted the position of Julius Brown Chair and Regents Professor of Chemistry and Biochemistry at the Georgia Institute of Technology. He led the [http://www.ldl.gatech.edu/ Laser Dynamics Lab] there until his full retirement in 2020.
El-Sayed is a former editor-in-chief of the Journal of Physical Chemistry (1980–2004). | 1 | Applied and Interdisciplinary Chemistry |
High-light grown plants generally have somewhat larger seeds, but produce many more flowers, and therefore there is a large increase in seed production per plant. Sturdy plants with short internodes and many flowers are important for horticulture, and hence a minimum amount of DLI is required for marketable horticultural plants. Measuring DLI over a growing season and comparing it to results can help determine which varieties of plants will thrive in a specific location. | 0 | Theoretical and Fundamental Chemistry |
Photosystem II is damaged by light irrespective of light intensity. The quantum yield of the damaging reaction in typical leaves of higher plants exposed to visible light, as well as in isolated thylakoid membrane preparations, is in the range of 10 to 10 and independent of the intensity of light. This means that one PSII complex is damaged for every 10-100 million photons that are intercepted. Therefore, photoinhibition occurs at all light intensities and the rate constant of photoinhibition is directly proportional to light intensity. Some measurements suggest that dim light causes damage more efficiently than strong light. | 0 | Theoretical and Fundamental Chemistry |
Specific characters may be used to create a suitable (ambigraphic) nucleic acid notation for complementary bases (i.e. guanine = b, cytosine = q, adenine = n, and thymine = u), which makes it is possible to complement entire DNA sequences by simply rotating the text "upside down". For instance, with the previous alphabet, (GTCA) would read as (TGAC, reverse complement) if turned upside down.
Ambigraphic notations readily visualize complementary nucleic acid stretches such as palindromic sequences. This feature is enhanced when utilizing custom fonts or symbols rather than ordinary ASCII or even Unicode characters. | 1 | Applied and Interdisciplinary Chemistry |
Difficulties have been encountered in the definition of the technological parameters that drive the process.
Two broad categories of generators, also known as power supplies, are in use on EDM machines commercially available: the group based on RC circuits and the group based on transistor-controlled pulses.
In both categories, the primary parameters at setup are the current and frequency delivered. In RC circuits, however, little control is expected over the time duration of the discharge, which is likely to depend on the actual spark-gap conditions (size and pollution) at the moment of the discharge. Also, the open circuit voltage (i.e. the voltage between the electrodes when the dielectric is not yet broken) can be identified as steady state voltage of the RC circuit.
In generators based on transistor control, the user is usually able to deliver a train of pulses of voltage to the electrodes. Each pulse can be controlled in shape, for instance, quasi-rectangular. In particular, the time between two consecutive pulses and the duration of each pulse can be set. The amplitude of each pulse constitutes the open circuit voltage. Thus, the maximum duration of discharge is equal to the duration of a pulse of voltage in the train. Two pulses of current are then expected not to occur for a duration equal or larger than the time interval between two consecutive pulses of voltage.
The maximum current during a discharge that the generator delivers can also be controlled. Because other sorts of generators may also be used by different machine builders, the parameters that may actually be set on a particular machine will depend on the generator manufacturer. The details of the generators and control systems on their machines are not always easily available to their user. This is a barrier to describing unequivocally the technological parameters of the EDM process. Moreover, the parameters affecting the phenomena occurring between tool and electrode are also related to the controller of the motion of the electrodes.
A framework to define and measure the electrical parameters during an EDM operation directly on inter-electrode volume with an oscilloscope external to the machine has been recently proposed by Ferri et al. These authors conducted their research in the field of μ-EDM, but the same approach can be used in any EDM operation. This would enable the user to estimate directly the electrical parameters that affect their operations without relying upon machine manufacturer's claims. When machining different materials in the same setup conditions, the actual electrical parameters of the process are significantly different. | 1 | Applied and Interdisciplinary Chemistry |
An ideal, defect-free semiconductor quantum well structure is a useful model system to illustrate the fundamental processes in typical PL experiments. The discussion is based on results published in Klingshirn (2012) and Balkan (1998).
The fictive model structure for this discussion has two confined quantized electronic and two hole subbands, e, e and h, h, respectively.
The linear absorption spectrum of such a structure shows the exciton resonances of the first (e1h1) and the second quantum well subbands (e, h), as well as the absorption from the corresponding continuum states and from the barrier. | 0 | Theoretical and Fundamental Chemistry |
Researchers in the field do not agree on a theory for cold fusion. One proposal considers that hydrogen and its isotopes can be absorbed in certain solids, including palladium hydride, at high densities. This creates a high partial pressure, reducing the average separation of hydrogen isotopes. However, the reduction in separation is not enough to create the fusion rates claimed in the original experiment, by a factor of ten. It was also proposed that a higher density of hydrogen inside the palladium and a lower potential barrier could raise the possibility of fusion at lower temperatures than expected from a simple application of Coulomb's law. Electron screening of the positive hydrogen nuclei by the negative electrons in the palladium lattice was suggested to the 2004 DOE commission, but the panel found the theoretical explanations not convincing and inconsistent with current physics theories. | 0 | Theoretical and Fundamental Chemistry |
Population genetics is essentially a study of the causes and effects of genetic variation within and between populations, and in the past, isozymes have been amongst the most widely used molecular markers for this purpose. Although they have now been largely superseded by more informative DNA-based approaches (such as direct DNA sequencing, single nucleotide polymorphisms and microsatellites), they are still among the quickest and cheapest marker systems to develop, and remain () an excellent choice for projects that only need to identify low levels of genetic variation, e.g. quantifying mating systems. | 1 | Applied and Interdisciplinary Chemistry |
A blotting matrix, in molecular biology and genetics, is the substrate onto which macromolecules, such as proteins, are transferred in a blot method. The matrices are generally chemically modified paper filters or microporous membrane filters. In a dot blot, macromolecules are applied directly to the matrix. Macromolecules can also be separated and transferred via gel electrophoresis.
One of the most common blotting matrices for protein analysis is nitrocellulose, which has a high affinity for proteins due to hydrophobic interactions. However, proteins with low molecular weight have a small affinity for nitrocellulose, limiting potential applications. This defect may be remedied by glutaraldehyde, which can covalently bond proteins to nitrocellulose. Another matrix is cellulose paper modified with diazophenylthiother, which can also facilitate covalent bonding of proteins. Nylon membranes are also used for protein blotting, although they may result in the binding of anionic dyes such as Coomassie blue and Amido black. Polyvinylidene fluoride membranes are also commonly used, due to their hydrophobicity. | 1 | Applied and Interdisciplinary Chemistry |
The conversion of nitrogen gas () into nitrates and nitrites through atmospheric, industrial and biological processes is called nitrogen fixation. Atmospheric nitrogen must be processed, or "fixed", into a usable form to be taken up by plants. Between 5 and 10 billion kg per year are fixed by lightning strikes, but most fixation is done by free-living or symbiotic bacteria known as diazotrophs. These bacteria have the nitrogenase enzyme that combines gaseous nitrogen with hydrogen to produce ammonia, which is converted by the bacteria into other organic compounds. Most biological nitrogen fixation occurs by the activity of molybdenum (Mo)-nitrogenase, found in a wide variety of bacteria and some Archaea. Mo-nitrogenase is a complex two-component enzyme that has multiple metal-containing prosthetic groups. An example of free-living bacteria is Azotobacter. Symbiotic nitrogen-fixing bacteria such as Rhizobium usually live in the root nodules of legumes (such as peas, alfalfa, and locust trees). Here they form a mutualistic relationship with the plant, producing ammonia in exchange for carbohydrates. Because of this relationship, legumes will often increase the nitrogen content of nitrogen-poor soils. A few non-legumes can also form such symbioses. Today, about 30% of the total fixed nitrogen is produced industrially using the Haber-Bosch process, which uses high temperatures and pressures to convert nitrogen gas and a hydrogen source (natural gas or petroleum) into ammonia. | 1 | Applied and Interdisciplinary Chemistry |
In 1984, a retrovirus vector system was designed that could efficiently insert foreign genes into mammalian chromosomes. | 1 | Applied and Interdisciplinary Chemistry |
Fuchter serves on the editorial board of MedChemComm. He is an elected council member of the Royal Society of Chemistry organic division. Fuchter is co-Director of the Imperial College London Centre for Drug Discovery Science. | 1 | Applied and Interdisciplinary Chemistry |
Current applications for syntactic foam include buoyancy modules for marine riser tensioners, remotely operated underwater vehicles (ROVs), autonomous underwater vehicles (AUVs), deep-sea exploration, boat hulls, and helicopter and airplane components.
Cementitious syntactic foams have also been investigated as a potential lightweight structural composite material. These materials include glass microspheres dispersed in a cement paste matrix to achieve a closed cell foam structure, instead of a metallic or a polymeric matrix. Cementitious syntactic foams have also been tested for their mechanical performance under high strain rate loading conditions to evaluate their energy dissipation capacity in crash cushions, blast walls, etc. Under these loading conditions, the glass microspheres of the cementitious syntactic foams did not show progressive crushing. Ultimately, unlike the polymeric and metallic syntactic foams, they did not emerge as suitable materials for energy dissipation applications. Structural applications of syntactic foams include use as the intermediate layer (that is, the core) of sandwich panels.
Though the cementitious syntactic foams demonstrate superior specific strength values in comparison to most conventional cementitious materials, it is challenging to manufacture them. Generally, the hollow inclusions tend to buoy and segregate in the low shear strength and high-density fresh cement paste. Therefore, maintaining a uniform microstructure across the material must be achieved through a strict control of the composite rheology. In addition, certain glass types of microspheres may lead to an alkali silica reaction. Therefore, the adverse effects of this reaction must be considered and addressed to ensure the long-term durability of these composites.
Other applications include;
*Deep-sea buoyancy foams. A method of creating submarine hulls by 3D printing was developed in 2018.
*Thermoforming plug assist
*Radar transparent materials
*Acoustically attenuating materials
*Cores for sandwich composites
*Blast mitigating materials
*Sporting goods such as bowling balls, tennis rackets, and soccer balls. | 0 | Theoretical and Fundamental Chemistry |
Vitrification (, via French ) is the full or partial transformation of a substance into a glass, that is to say, a non-crystalline amorphous solid. Glasses differ from liquids structurally and glasses possess a higher degree of connectivity with the same Hausdorff dimensionality of bonds as crystals: dim = 3. In the production of ceramics, vitrification is responsible for their impermeability to water.
Vitrification is usually achieved by heating materials until they liquidize, then cooling the liquid, often rapidly, so that it passes through the glass transition to form a glassy solid. Certain chemical reactions also result in glasses.
In terms of chemistry, vitrification is characteristic for amorphous materials or disordered systems and occurs when bonding between elementary particles (atoms, molecules, forming blocks) becomes higher than a certain threshold value. Thermal fluctuations break the bonds; therefore, the lower the temperature, the higher the degree of connectivity. Because of that, amorphous materials have a characteristic threshold temperature termed glass transition temperature (T): below T amorphous materials are glassy whereas above T they are molten.
The most common applications are in the making of pottery, glass, and some types of food, but there are many others, such as the vitrification of an antifreeze-like liquid in cryopreservation.
In a different sense of the word, the embedding of material inside a glassy matrix is also called vitrification. An important application is the vitrification of radioactive waste to obtain a substance that is thought to be safer and more stable for disposal.
One study suggests during the eruption of Mount Vesuvius in 79 AD, a victim's brain was vitrified by the extreme heat of the volcanic ash; however, this has been strenuously disputed. | 1 | Applied and Interdisciplinary Chemistry |
When DNA is damaged such as due to a lesion, a complex signal transduction pathway is activated which is responsible for recognizing the damage and instigating the cell's response for repair. Compared to the other lesion repair mechanisms, DDR is the highest level of repair and is employed for the most complex lesions. DDR consists of various pathways, the most common of which are the DDR kinase signaling cascades. These are controlled by phosphatidylinositol 3-kinase-related kinases (PIKK), and range from DNA-dependent protein kinase (DNA-PKcs) and ataxia telangiectasia-mutated (ATM) most involved in repairing DSBs to the more versatile Rad3-related (ATR). ATR is crucial to human cell viability, while ATM mutations cause the severe disorder ataxia-telangiectasia leading to neurodegeneration, cancer, and immunodeficiency. These three DDR kinases all recognize damage via protein-protein interactions which localize the kinases to the areas of damage. Next, further protein-protein interactions and posttranslational modifications (PTMs) complete the kinase activation, and a series of phosphorylation events takes place. DDR kinases perform repair regulation at three levels - via PTMs, at the level of chromatin, and at the level of the nucleus. | 1 | Applied and Interdisciplinary Chemistry |
Two kinds of complexes of molecules exist: the collisional complexes discussed
above, which are short lived. Besides, bound (i.e. relatively stable) complexes
of two or more molecules exist, the so-called van der Waals molecules. These
exist usually for much longer times than the collisional complexes and, under
carefully chosen experimental conditions (low temperature, moderate gas density),
their rotovibrational band spectra show "sharp" (or resolvable) lines (Heisenberg
uncertainty principle), much like ordinary molecules. If the parent molecules
are nonpolar, the same induced dipole mechanisms, which are discussed above,
are responsible for the observable spectra of van der Waals molecules.
Figure 1 (to be included) | 0 | Theoretical and Fundamental Chemistry |
Most of the solid blanket materials that surround the fusion chamber in conventional designs are replaced by a fluorine lithium beryllium (FLiBe) molten salt that can easily be circulated/replaced, reducing maintenance costs.
The liquid blanket provides neutron moderation and shielding, heat removal, and a tritium breeding ratio ≥ 1.1. The large temperature range over which FLiBe is liquid permits blanket operation at with single-phase fluid cooling and a Brayton cycle. | 0 | Theoretical and Fundamental Chemistry |
More than 100 immune system disorders affect humans, including inflammatory bowel diseases, multiple sclerosis, systemic lupus erythematosus, bloom syndrome, familial cold autoinflammatory syndrome, and dyskeratosis congenita. The Shapiro–Senapathy algorithm has been used to discover genes and mutations involved in many immune disorder diseases, including Ataxia telangiectasia, B-cell defects, epidermolysis bullosa, and X-linked agammaglobulinemia.
Xeroderma pigmentosum, an autosomal recessive disorder is caused by faulty proteins formed due to new preferred splice donor site identified using S&S algorithm and resulted in defective nucleotide excision repair.
Type I Bartter syndrome (BS) is caused by mutations in the gene SLC12A1. S&S algorithm helped in disclosing the presence of two novel heterozygous mutations c.724 + 4A > G in intron 5 and c.2095delG in intron 16 leading to complete exon 5 skipping.
Mutations in the MYH gene, which is responsible for removing the oxidatively damaged DNA lesion are cancer-susceptible in the individuals. The IVS1+5C plays a causative role in the activation of a cryptic splice donor site and the alternative splicing in intron 1, S&S algorithm shows, guanine (G) at the position of IVS+5 is well conserved (at the frequency of 84%) among primates. This also supported the fact that the G/C SNP in the conserved splice junction of the MYH gene causes the alternative splicing of intron 1 of the β type transcript.
Splice site scores were calculated according to S&S to find EBV infection in X-linked lymphoproliferative disease. Identification of Familial tumoral calcinosis (FTC) is an autosomal recessive disorder characterized by ectopic calcifications and elevated serum phosphate levels and it is because of aberrant splicing. | 1 | Applied and Interdisciplinary Chemistry |
Laser diffraction analysis has been used to measure particle-size objects in situations such as:
* observing distribution of soil texture and sediments such as clay and mud, with an emphasis on silt and the sizes of bigger samples of clay.
* determining in situ measurements of particles in estuaries. Particles in estuaries are important as they allow for natural or pollutant chemical species to move around with ease. The size, density, and stability of particles in estuaries are important for their transportation. Laser diffraction analysis is used here to compare particle size distributions to support this claim as well as find cycles of change in estuaries that occur because of different particles.
* soil and its stability when wet. The stability of soil aggregation (clumps held together by moist clay) and clay dispersion (clay separating in moist soil), the two different states of soil in the Cerrado savanna region, were compared with laser diffraction analysis to determine if plowing had an effect on the two. Measurements were made before plowing and after plowing for different intervals of time. Clay dispersion turned out to not be affected by plowing while soil aggregation did.
* erythrocyte deformability under shear. Due to a special phenomenon called tank treading, the membrane of the erythrocyte (red blood cell, RBC) rotates relative to the shear force and the cells cytoplasm causing RBCs to orient themselves. Oriented and stretched red blood cells have a diffraction pattern representing the apparent particle size in each direction, making it possible to measure the erythrocyte deformability and the orientability of the cells. In an ektacytometer' erythrocyte deformability can be measured under changing osmotic stress or oxygen tension and is used in the diagnosis and follow up of congenital hemolytic anemias. | 0 | Theoretical and Fundamental Chemistry |
The most reactive metals, such as sodium, will react with cold water to produce hydrogen and the metal hydroxide:
:2 Na (s) + 2 HO (l) →2 NaOH (aq) + H (g)
Metals in the middle of the reactivity series, such as iron, will react with acids such as sulfuric acid (but not water at normal temperatures) to give hydrogen and a metal salt, such as iron(II) sulfate:
:Fe (s) + HSO (l) → FeSO (aq) + H (g)
There is some ambiguity at the borderlines between the groups. Magnesium, aluminium and zinc can react with water, but the reaction is usually very slow unless the metal samples are specially prepared to remove the surface passivation layer of oxide which protects the rest of the metal. Copper and silver will react with nitric acid; but because nitric acid is an oxidizing acid, the oxidizing agent is not the H ion as in normal acids, but the NO ion. | 0 | Theoretical and Fundamental Chemistry |
In contrast to photoautotrophs, photoheterotrophs are organisms that depend solely on light for their energy and principally on organic compounds for their carbon. Photoheterotrophs produce ATP through photophosphorylation but use environmentally obtained organic compounds to build structures and other bio-molecules. | 0 | Theoretical and Fundamental Chemistry |
The range of applications for SMAs has grown over the years, a major area of development being dentistry. One example is the prevalence of dental braces using SMA technology to exert constant tooth-moving forces on the teeth; the nitinol archwire was developed in 1972 by orthodontist George Andreasen. This revolutionized clinical orthodontics. Andreasen's alloy has a patterned shape memory, expanding and contracting within given temperature ranges because of its geometric programming.
Harmeet D. Walia later utilized the alloy in the manufacture of root canal files for endodontics. | 1 | Applied and Interdisciplinary Chemistry |
The concept derives from Newton's Second Law when applied to a fluid parcel in the presence of a background stratification (in which the density changes in the vertical - i.e. the density can be said to have multiple vertical layers). The parcel, perturbed vertically from its starting position, experiences a vertical acceleration. If the acceleration is back towards the initial position, the stratification is said to be stable and the parcel oscillates vertically. In this case, and the angular frequency of oscillation is given . If the acceleration is away from the initial position (), the stratification is unstable. In this case, overturning or convection generally ensues.
The Brunt–Väisälä frequency relates to internal gravity waves: it is the frequency when the waves propagate horizontally; and it provides a useful description of atmospheric and oceanic stability. | 1 | Applied and Interdisciplinary Chemistry |
Micropollutants such as pharmaceuticals, ingredients of household chemicals, chemicals used in small businesses or industries, environmental persistent pharmaceutical pollutants (EPPP) or pesticides may not be eliminated in the commonly used sewage treatment processes (primary, secondary and tertiary treatment) and therefore lead to water pollution. Although concentrations of those substances and their decomposition products are quite low, there is still a chance of harming aquatic organisms. For pharmaceuticals, the following substances have been identified as toxicologically relevant: substances with endocrine disrupting effects, genotoxic substances and substances that enhance the development of bacterial resistances. They mainly belong to the group of EPPP.
Techniques for elimination of micropollutants via a fourth treatment stage during sewage treatment are implemented in Germany, Switzerland, Sweden and the Netherlands and tests are ongoing in several other countries. Such process steps mainly consist of activated carbon filters that adsorb the micropollutants. The combination of advanced oxidation with ozone followed by granular activated carbon (GAC) has been suggested as a cost-effective treatment combination for pharmaceutical residues. For a full reduction of microplasts the combination of ultrafiltration followed by GAC has been suggested. Also the use of enzymes such as laccase secreted by fungi is under investigation. Microbial biofuel cells are investigated for their property to treat organic matter in sewage.
To reduce pharmaceuticals in water bodies, source control measures are also under investigation, such as innovations in drug development or more responsible handling of drugs. In the US, the National Take Back Initiative is a voluntary program with the general public, encouraging people to return excess or expired drugs, and avoid flushing them to the sewage system. | 1 | Applied and Interdisciplinary Chemistry |
The "seat" is the interior surface of the body which contacts the disc to form a leak-tight seal. In discs that move linearly or swing on a hinge or trunnion, the disc comes into contact with the seat only when the valve is shut. In disks that rotate, the seat is always in contact with the disk, but the area of contact changes as the disc is turned. The seat always remains stationary relative to the body.
Seats are classified by whether they are cut directly into the body, or if they are made of a different material:
*Hard seats are integral to the valve body. Nearly all hard seated metal valves have a small amount of leakage.
*Soft seats are fitted to the valve body and made of softer materials such as PTFE or various elastomers such as NBR, EPDM, or FKM depending on the maximum operating temperature.
A closed soft seated valve is much less liable to leak when shut while hard seated valves are more durable. Gate, globe, and check valves are usually hard seated while butterfly, ball, plug, and diaphragm valves are usually soft seated. | 1 | Applied and Interdisciplinary Chemistry |
Cronstedt initiated the use of the blowpipe for the analysis of minerals. Originally a goldsmiths tool, it became widely used for the identification of small ore samples, particularly in Sweden where his contemporaries had seen Cronstedt use it. Use of the blowpipe enabled mineralogists to discover eleven new elements, beginning with Cronstedts discovery of nickel.
John Joseph Griffin credits Cronstedt as "the first person of eminence who used the blowpipe" and "the founder of Mineralogy" in A Practical Treatise on the Use of the Blowpipe (1827).
Cronstedt discovered the mineral now known as scheelite in 1751 at Bispberg Klack, later obtaining samples from the Kuhschacht mine in Freiberg, Germany. He gave it the name tungsten, meaning "heavy stone" in Swedish. Thirty years later, Carl Wilhelm Scheele determined that scheelite was in fact an ore, and that a new metal could be extracted from it. This element then became known by Cronstedt's name, tungsten.
Cronstedt also extracted the element nickel from ores in the cobalt mines of Los, Sweden. The ore was described by miners as kupfernickel because it had a similar appearance to copper (kupfer) and a mischievous sprite (nickel) was supposed by miners to be the cause of their failure to extract copper from it. Cronstedt presented his research on nickel to the Swedish Academy of Sciences in 1751 and 1754. Decades later, some scientists still argued that it was a mixture, and not a new metal, but its nature was eventually accepted.
In 1756, Cronstedt coined the term zeolite after heating the mineral stilbite with a blowpipe flame. He was the first to describe its distinctive properties, having observed the "frothing" when heated with a blowpipe.
Cronstedts book Försök til mineralogie, eller mineral-rikets upställning (“An attempt at mineralogy or arrangement of the Mineral Kingdom”, 1758) was originally published anonymously. In it, Cronstedt proposed that minerals be classified on the basis of chemical analysis of their composition. He was surprised that others supported his ideas and put them into practice. It was translated into English by Gustav Von Engeström (1738-1813) as An essay towards a system of mineralogy (1770). Engeström added an appendix, "Description and Use of a Mineralogical Pocket Laboratory; and especially the Use of the Blow-pipe in Mineralogy", which brought considerable attention to Cronstedts use of the blowpipe.
Cronstedt noted in Försök til mineralogie, eller mineral-rikets upställning that he had observed an “unidentified earth” in a heavy red stone from the Bastnäs mine in Riddarhyttan. Forty-five years later, Jöns Jacob Berzelius and Wilhelm Hisinger isolated the first element of the lanthanide series of the rare earth elements, cerium, in ore from the mine. | 1 | Applied and Interdisciplinary Chemistry |
For a monodisperse aerosol, a single number—the particle diameter—suffices to describe the size of the particles. However, more complicated particle-size distributions describe the sizes of the particles in a polydisperse aerosol. This distribution defines the relative amounts of particles, sorted according to size. One approach to defining the particle size distribution uses a list of the sizes of every particle in a sample. However, this approach proves tedious to ascertain in aerosols with millions of particles and awkward to use. Another approach splits the size range into intervals and finds the number (or proportion) of particles in each interval. These data can be presented in a histogram with the area of each bar representing the proportion of particles in that size bin, usually normalised by dividing the number of particles in a bin by the width of the interval so that the area of each bar is proportionate to the number of particles in the size range that it represents. If the width of the bins tends to zero, the frequency function is:
where
:is the diameter of the particles
: is the fraction of particles having diameters between and +
: is the frequency function
Therefore, the area under the frequency curve between two sizes a and b represents the total fraction of the particles in that size range:
It can also be formulated in terms of the total number density N:
Assuming spherical aerosol particles, the aerosol surface area per unit volume (S) is given by the second moment:
And the third moment gives the total volume concentration (V) of the particles:
The particle size distribution can be approximated. The normal distribution usually does not suitably describe particle size distributions in aerosols because of the skewness associated with a long tail of larger particles. Also for a quantity that varies over a large range, as many aerosol sizes do, the width of the distribution implies negative particles sizes, which is not physically realistic. However, the normal distribution can be suitable for some aerosols, such as test aerosols, certain pollen grains and spores.
A more widely chosen log-normal distribution gives the number frequency as:
where:
: is the standard deviation of the size distribution and
: is the arithmetic mean diameter.
The log-normal distribution has no negative values, can cover a wide range of values, and fits many observed size distributions reasonably well.
Other distributions sometimes used to characterise particle size include: the Rosin-Rammler distribution, applied to coarsely dispersed dusts and sprays; the Nukiyama–Tanasawa distribution, for sprays of extremely broad size ranges; the power function distribution, occasionally applied to atmospheric aerosols; the exponential distribution, applied to powdered materials; and for cloud droplets, the Khrgian–Mazin distribution. | 0 | Theoretical and Fundamental Chemistry |
ICOS has currently 13 member states and is in operational mode, with stations being certified for the operation according to the strict protocols and quality parameters. By the end of 2020 ICOS had 68 out of the 148 stations certified (labelled as either Class 1,2 or associated station), with greenhouse gas concentrations and fluxes determined on a routine basis.
ICOS member states | 1 | Applied and Interdisciplinary Chemistry |
Semiconductors are materials that have an electrical resistivity (and conductivity) between that of metallic conductors and non-metallic insulators. They can be found in the periodic table moving diagonally downward right from boron. They separate the electrical conductors (or metals, to the left) from the insulators (to the right).
Devices made from semiconductor materials are the foundation of modern electronics, including radio, computers, telephones, etc. Semiconductor devices include the transistor, solar cells, diodes and integrated circuits. Solar photovoltaic panels are large semiconductor devices that directly convert light into electrical energy.
In a metallic conductor, current is carried by the flow of electrons, but in semiconductors, current can be carried either by electrons or by the positively charged "holes" in the electronic band structure of the material. Common semiconductor materials include silicon, germanium and gallium arsenide. | 0 | Theoretical and Fundamental Chemistry |
Many coordination complexes catalyze electrochemical reactions, but only heterogeneous catalysts are of commercial value. | 0 | Theoretical and Fundamental Chemistry |
Three-dimensional structures of proteins involved in quorum sensing were first published in 2001, when the crystal structures of three LuxS orthologs were determined by X-ray crystallography. In 2002, the crystal structure of the receptor LuxP of Vibrio harveyi with its inducer AI-2 (which is one of the few biomolecules containing boron) bound to it was also determined. Many bacterial species, including E. coli, an enteric bacterium and model organism for gram-negative bacteria, produce AI-2. A comparative genomic and phylogenetic analysis of 138 genomes of bacteria, archaea, and eukaryotes found that "the LuxS enzyme required for AI-2 synthesis is widespread in bacteria, while the periplasmic binding protein LuxP is present only in Vibrio strains," leading to the conclusion that either "other organisms may use components different from the AI-2 signal transduction system of Vibrio strains to sense the signal of AI-2 or they do not have such a quorum sensing system at all." Vibrio species utilize Qrr RNAs, small non-coding RNAs, that are activated by these autoinducers to target cell density master regulators. Farnesol is used by the fungus Candida albicans as a quorum sensing molecule that inhibits filamentation.
A database of quorum-sensing peptides is available under the name Quorumpeps.
Certain bacteria can produce enzymes called lactonases that can target and inactivate AHLs.
Researchers have developed novel molecules which block the signalling receptors of bacteria ("Quorum quenching"). mBTL is a compound that has been shown to inhibit quorum sensing and decrease the amount of cell death by a significant amount.
Additionally, researchers are also examining the role of natural compounds (such as caffeine) as potential quorum sensing inhibitors. Research in this area has been promising and could lead to the development of natural compounds as effective therapeutics. | 1 | Applied and Interdisciplinary Chemistry |
In China, a number of incidents have occurred where state limits were exceeded by large amounts or where the wrong pesticide was used. In August 1994, a serious incident of pesticide poisoning of sweet potato crops occurred in Shandong province, China. Because local farmers were not fully educated in the use of insecticides, they used the highly-toxic pesticide named parathion instead of trichlorphon. It resulted in over 300 cases of poisoning and 3 deaths. Also, there was a case where a large number of students were poisoned and 23 of them were hospitalized because of vegetables that contained excessive pesticide residues. | 1 | Applied and Interdisciplinary Chemistry |
A skeletal isomer of a compound is a structural isomer that differs from it in the atoms and bonds that are considered to comprise the "skeleton" of the molecule. For organic compounds, such as alkanes, that usually means the carbon atoms and the bonds between them.
For example, there are three skeletal isomers of pentane: n-pentane (often called simply "pentane"), isopentane (2-methylbutane) and neopentane (dimethylpropane).
If the skeleton is acyclic, as in the above example, one may use the term chain isomerism. | 0 | Theoretical and Fundamental Chemistry |
Stone wool or rock wool is a spun mineral fibre used as an insulation product and in hydroponics. It is manufactured in a blast furnace fed with diabase rock which contains very low levels of metal oxides. The resultant slag is drawn off and spun to form the rock wool product. Very small amounts of metals are also produced which are an unwanted by-product. | 1 | Applied and Interdisciplinary Chemistry |
Composite metal foam has been tested in a puncture test. Puncture tests were conducted on S-S CMF-CSP with different thicknesses of stainless steel face sheets and CMF core. The bonding of the S-S CMF core and face sheets was done via adhesive bonding and diffusion bonding. Various thicknesses of the CMF core and face sheets created a variety of target areal densities from about 6.7 to about 11.7 kg per each tile of 30 x 30 cm. Targets were impacted using 2.54 and 3.175 cm diameter steel balls fired at velocities ranging from 120 to 470 m per second, resulting in puncture energies from 488 to 14 500 J over a 5.06–7.91 cm2 impact area for the two size sphere balls. None of the panels, even those with the lowest areal densities, showed complete penetration/puncture through their thickness. This was mostly due to the energy absorption capacity of the S-S CMF core in compression, whereas the face sheets strengthen the CMF core to better handle tensile stresses. Sandwich panels with thicker face sheets show less effectiveness, and a thin face sheet seemed to be sufficient to support the S-S CMF core for absorbing such puncture energies. Panels assembled using adhesive bonding showed debonding of the face sheets from the CMF core upon the impact of the projectile while the diffusion bonded panels showed more flexibility at the interface and better accommodated the stresses. Most diffusion bonded panels did not show a debonding of face sheets from the S-S CMF core. This study proved CMF's energy absorption abilities, indicating that CMF can be used to simultaneously increase protections and decrease weight. | 0 | Theoretical and Fundamental Chemistry |
For a complete list of the 209 PCB congeners, see PCB congener list. Note that biphenyl, while not technically a PCB congener because of its lack of chlorine substituents, is still typically included in the literature. | 1 | Applied and Interdisciplinary Chemistry |
Murexide is prepared by treating alloxantin with ammonia to 100 °C, or by treating uramil (5-aminobarbituric acid) with mercury oxide. It may also be prepared by digesting alloxan with alcoholic ammonia. | 0 | Theoretical and Fundamental Chemistry |
X-ray structures of DPP-4 that have been published since 2003 give rather detailed information about the structural characteristics of the binding site. Many structurally diverse DPP-4 inhibitors have been discovered and it is not that surprising considering the properties of the binding site:
1. A deep lipophilic pocket combined with several exposed aromatic side chains for achieving high affinity small molecule binding.
2. A significant solvent access that makes it possible to tune the physico-chemical properties of the inhibitors that leads to better pharmacokinetic behavior.
DPP-4 is a 766-amino acid transmembrane glycoprotein that belongs to the prolyloligopeptidase family. It consists of three parts; a cytoplasmic tail, a transmembrane region and an extracellular part. The extracellular part is divided into a catalytic domain and an eight-bladed β-propeller domain. The latter contributes to the inhibitor binding site. The catalytic domain shows an α/β-hydrolase fold and contains the catalytic triad Ser630 - Asp708 - His740. The S1-pocket is very hydrophobic and is composed of the side chains: Tyr631, Val656, Trp662, Tyr666 and Val711. Existing X-ray structures show that there is not much difference in size and shape of the pocket that indicates that the S1-pocket has high specificity for proline residues | 1 | Applied and Interdisciplinary Chemistry |
A selective surface can be used when energy is being extracted from the sun. Selective surfaces can also be used on solar collectors. We can find out how much help a selective surface coating is by looking at the equilibrium temperature of a plate that is being heated through solar radiation. If the plate is receiving a solar irradiation of 1350 W/m (minimum is 1325 W/m on 4 July and maximum is 1418 W/m on 3 January) from the sun the temperature of the plate where the radiation leaving is equal to the radiation being received by the plate is 393 K (248 °F). If the plate has a selective surface with an emissivity of 0.9 and a cut off wavelength of 2.0 μm, the equilibrium temperature is approximately 1250 K (1790 °F). The calculations were made neglecting convective heat transfer and neglecting the solar irradiation absorbed in the clouds/atmosphere for simplicity, the theory is still the same for an actual problem. | 0 | Theoretical and Fundamental Chemistry |
In 1901, Joseph Hoeing Kastle and Oliver March Shedd in the U.S. found that biological material could cause the oxidation of phenolphthalin to phenolphthalein in slightly alkaline solutions. In 1903, Erich Meyer in Germany found that blood cells could also trigger the reaction. In 1906, Kastle and Amoss found that chick hemoglobin in blood triggered the reaction. In 1909, Kastle found that the test was sensitive to very dilute samples of blood. However, in 1908, Pozzi-Escot (who by then was living in Lima, Peru) found that the test produced false positive reactions in response to a number of substances besides blood. | 0 | Theoretical and Fundamental Chemistry |
The target groups currently included on the Guide to PHARMACOLOGY are:
* Catalytic receptors
* Enzymes
* G protein-coupled receptors
* Ion channels
* Kinases
* Nuclear receptors
* Transporters
* Other protein targets including fatty acid-binding proteins, sigma receptors and adiponectin receptors
Information for each target group is subdivided into families based on classification, with a separate data page for each family. Within each page, targets are arranged into lists of tables, with each table including the protein and gene nomenclature for the target with links to gene nomenclature databases, and listing selected ligands with activity at the target, including agonists, antagonists, inhibitors and radioligands. Pharmacological data and references are given and each ligand is hyperlinked to a ligand page displaying nomenclature and a chemical structure or peptide sequence, along with synonyms and relevant database links. The Guide to PHARMACOLOGY also includes a list of all ligand molecules included on the site, subdivided into categories including small organic molecules (including mammalian metabolites, hormones and neurotransmitters), synthetic organic molecules, natural products, peptides, inorganic molecules and antibodies. A complete list of all the approved drugs included on the website is also available via the ligand list. The Guide to PHARMACOLOGY is being expanded to include clinical information on targets and ligands, in addition to educational resources.
Search features on the website include quick and advanced search options, and receptor and ligand searches, including support for ligand structures using chemical structures. Other features include Hot topic news items and a recent receptor-ligand pairing list. | 1 | Applied and Interdisciplinary Chemistry |
Ketones that have at least one alpha-hydrogen, undergo keto-enol tautomerization; the tautomer is an enol. Tautomerization is catalyzed by both acids and bases. Usually, the keto form is more stable than the enol. This equilibrium allows ketones to be prepared via the hydration of alkynes. | 0 | Theoretical and Fundamental Chemistry |
Some bacteria, such as E. coli, have several flagella per cell (4–10 typically). These can rotate in two ways:
# Counter-clockwise rotation aligns the flagella into a single rotating bundle, causing the bacterium to swim in a straight line; and
# Clockwise rotation breaks the flagella bundle apart such that each flagellum points in a different direction, causing the bacterium to tumble in place.
The directions of rotation are given for an observer outside the cell looking down the flagella toward the cell. | 1 | Applied and Interdisciplinary Chemistry |
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