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Entropy-vorticity waves (or sometimes entropy-vortex waves) refer to small-amplitude waves carried by the gas within which entropy, vorticity, density but not pressure perturbations are propagated. Entropy-vortivity waves are essentially isobaric, incompressible, rotational perturbations along with entropy perturbations. This wave differs from the other well-known small-amplitude wave that is a sound wave, which propagates with respect to the gas within which density, pressure but not entropy perturbations are propagated. The classification of small disturbances into acoustic, entropy and vortex modes was introduced by Leslie S. G. Kovasznay.
Entropy-vorticity waves are ubiquitous in supersonic problems, particularly those involving shock waves. Since these perturbations are carried by the gas, they are convected by the flow downstream of the shock wave, but they cannot be propagates in the upstream direction (behind the shock wave) unlike the acoustic wave, which can propagate upstream and can catch up the shock wave. As such, they are useful in understadning many high speed flows and are important in many applications such as in solid-propellant rockets and detonations. | 1 | Applied and Interdisciplinary Chemistry |
Explosive boiling can be best described by a p-T phase diagram. Figure on right shows a typical p-T phase diagram of a substance. The binodal line or the coexistence curve is a thermodynamic state where at that specific temperature and pressure, liquid and vapor can coexist. The spinodal line on right is the boundary of absolute instability of a solution to decomposition into multiple phases. A typical heating process is shown using red ink.
If the heating process is relatively slow, the liquid has enough time to relax to an equilibrium state and the liquid follows the binodal curve, the Clausius–Clapeyron relation is still valid. During this time heterogeneous evaporation occurs in the substance with bubbles nucleating from impurity sites, surfaces, grain boundaries etc.
On the other hand, if the heating process is fast enough that the substance cannot reach binodal curve through heterogeneous boiling, the liquid becomes superheated with its temperature above boiling point at a given pressure. System then shifts away from the binodal and continues to follow the red curve and thus approaches towards spinodal. Near the critical temperature thermodynamic properties like specific heat, density varies rapidly as shown on the figure at right. Density and entropy undergoes largest fluctuation. During this time it is possible to have a large density fluctuation in a very small volume. This fluctuation of density results in the nucleation of a bubble. The bubble nucleation process occurs homogeneously everywhere in the substance. The rate of bubble nucleation and vapor sphere growth rate increases exponentially closer to the critical temperature. The increasing nucleation prevents the system from going to the spinodal. When the bubble radius reaches the critical size it continues to expand and eventually explodes resulting a mixture of gas and droplets which is termed as explosive boiling or phase explosion.
At the beginning, explosive boiling was used by Martynyuk to calculate the critical temperature of metals. He used electric resistance to heat up metal wire. Later explosive boiling was found to occur while using ultra fast femtosecond laser ablation. Although this kind of explosive boiling should occur by any mechanism whereby the temperature of the liquid is rapidly raised close to the critical temperature of the substance. | 0 | Theoretical and Fundamental Chemistry |
Type N (Nicrosil–Nisil) thermocouples are suitable for use between −270 °C and +1300 °C, owing to its stability and oxidation resistance. Sensitivity is about 39 μV/°C at 900 °C, slightly lower compared to type K.
Designed at the Defence Science and Technology Organisation (DSTO) of Australia, by Noel A. Burley, type-N thermocouples overcome the three principal characteristic types and causes of thermoelectric instability in the standard base-metal thermoelement materials:
#A gradual and generally cumulative drift in thermal EMF on long exposure at elevated temperatures. This is observed in all base-metal thermoelement materials and is mainly due to compositional changes caused by oxidation, carburization, or neutron irradiation that can produce transmutation in nuclear reactor environments. In the case of type-K thermocouples, manganese and aluminium atoms from the KN (negative) wire migrate to the KP (positive) wire, resulting in a down-scale drift due to chemical contamination. This effect is cumulative and irreversible.
#A short-term cyclic change in thermal EMF on heating in the temperature range about 250–650 °C, which occurs in thermocouples of types K, J, T, and E. This kind of EMF instability is associated with structural changes such as magnetic short-range order in the metallurgical composition.
#A time-independent perturbation in thermal EMF in specific temperature ranges. This is due to composition-dependent magnetic transformations that perturb the thermal EMFs in type-K thermocouples in the range about 25–225 °C, and in type J above 730 °C.
The Nicrosil and Nisil thermocouple alloys show greatly enhanced thermoelectric stability relative to the other standard base-metal thermocouple alloys because their compositions substantially reduce the thermoelectric instabilities described above. This is achieved primarily by increasing component solute concentrations (chromium and silicon) in a base of nickel above those required to cause a transition from internal to external modes of oxidation, and by selecting solutes (silicon and magnesium) that preferentially oxidize to form a diffusion-barrier, and hence oxidation-inhibiting films.
Type N thermocouples are suitable alternative to type K for low-oxygen conditions where type K is prone to green rot. They are suitable for use in vacuum, inert atmospheres, oxidizing atmospheres, or dry reducing atmospheres. They do not tolerate the presence of sulfur. | 1 | Applied and Interdisciplinary Chemistry |
Other perfluorocarbon emulsions have been tested as oxygen therapeutics. When perfluorocarbons are exposed to high concentrations of oxygen, large amounts of oxygen dissolve into the perfluorocarbons. If the perfluorocarbon/oxygen solution is then exposed to a low oxygen environment, then oxygen diffuses out of the solution. Three different approaches sought to utilize this characteristic to improve oxygen delivery to tissue.
Early perfluorocarbon emulsions for oxygen delivery were developed as blood substitutes. They used large-molecule perfluorocarbons with boiling points higher than body temperature which were formed into liquid emulsion droplets. The emulsions were injected intravenously and circulated through the bloodstream, and the droplets picked up oxygen when passing through the lungs and offloaded oxygen when passing through the capillaries in other tissues. The primary form of excretion of the perfluorocarbon was through the reticulo-endothelial system - the droplets would remain in the bloodstream until they were recognized by the immune system, would be taken up by phagocytes, and broken down thereby releasing the perfluorocarbon molecules which eventually pass through the lungs and be exhaled. These high boiling point perfluorocarbons typically had half-lives measured in hours or days. Relatively large doses were required, but such doses could have side effects including pneumonia. Despite these challenges, Fluosol-DA was approved by the FDA and was marketed as a blood substitute in the United States from 1989 through 1994 when it was withdrawn from the market due to poor sales. Perftoran was approved in the Soviet Union in 1994 and remained in limited use in Russia at least as late as 2019.
The second approach to oxygen delivery tested a perfluorocarbon emulsion not as a blood substitute, but rather as a cerebrospinal fluid (CSF) substitute. In order to increase oxygen delivery to the brains of patients that had reduced blood flow due to acute ischemic stroke, artificial CSF mixed with pre-oxygenated perfluorocarbon emulsion was continuously added into the skull by a ventricular catheter while CSF was continuously removed by a lumbar catheter. Animal studies in cats with acute ischemic stroke showed very strong results, so a clinical trial in four humans was conducted. All four patients survived for 30 days to 2 years before dying of other causes. Enrollment in the trial was slow however, which caused the funding for the project to be cut.
A third approach to oxygen delivery is to move perfluorocarbon molecules into positions where they can enhance the flow of oxygen through the lower parts of the oxygen cascade. While it is difficult to observe the positioning of the perfluorocarbon molecules directly, molecules positioned in the right places between red blood cells and mitochondria may reduce resistance to oxygen flow. In cases where the oxygen tension at the mitochondria are very low, this would expose nearby red blood cells to lower oxygen tensions and cause them to offload more oxygen as described by the oxygen–hemoglobin dissociation curve. The most notable example is dodecafluoropentane emulsion (DDFPe, formerly EchoGen, now NanO). The drug is injected intravenously then the perfluorocarbon molecules spread widely before eventually passing through the lungs whey they are evaporated and exhaled. The drug showed very strong results in animal studies of acute ischemic stroke, heart attack and other indications. The drug was tested in a Phase Ib/II clinical trial in 24 patients who had reduced blood flow to the brain due to acute ischemic stroke, where it was intended to increase oxygen delivery to the brain to keep the tissue alive until blood flow could be normalized. The high dose group of patients in the clinical trial had improved functional independence compared to placebo, though the number of patients tested was small and there were confounding factors including differences in stroke severity, so larger clinical trials are needed to confirm the effect. Another perfluorocarbon, perfluorooctyl bromide, has been shown in animal studies to collect in tumor tissue and increase oxygenation of those tumors, potentially by improving the flow of oxygen from red blood cells. | 0 | Theoretical and Fundamental Chemistry |
Ellipsometric porosimetry measures the change of the optical properties and thickness of the materials during adsorption and desorption of a volatile species at atmospheric pressure or under reduced pressure depending on the application. The EP technique is unique in its ability to measure porosity of very thin films down to 10 nm, its reproducibility and speed of measurement. Compared to traditional porosimeters, Ellipsometer porosimeters are well suited to very thin film pore size and pore size distribution measurement. Film porosity is a key factor in silicon based technology using low-κ materials, organic industry (encapsulated organic light-emitting diodes) as well as in the coating industry using sol gel techniques. | 0 | Theoretical and Fundamental Chemistry |
Werner Rolfinck (15 November 1599 – 6 May 1673) was a German physician, scientist and botanist. He was a medical student in Leiden, Oxford, Paris, and Padua. | 1 | Applied and Interdisciplinary Chemistry |
RNA Pol II-mediated gene transcription induces a local opening of chromatin state through the recruitment of histone acetyltransferases and other histone modifiers that promote euchromatin formation. It was proposed that the presence of these enzymes could also induce an opening of chromatin at enhancer regions, which are usually present at distant locations but can be recruited to target genes through looping of DNA. In this model, eRNAs are therefore expressed in response to RNA Pol II transcription and therefore carry no biological function. | 1 | Applied and Interdisciplinary Chemistry |
When either the laser intensity is further increased or a longer wavelength is applied as compared with the regime in which multi-photon ionization takes place, a quasi-stationary approach can be used and results in the distortion of the atomic potential in such a way that only a relatively low and narrow barrier between a bound state and the continuum states remains. Then, the electron can tunnel through or for larger distortions even overcome this barrier. These phenomena are called tunnel ionization and over-the-barrier ionization, respectively. | 0 | Theoretical and Fundamental Chemistry |
As DNA printing and DNA assembly methods have allowed commercial gene synthesis to become progressively and exponentially cheaper over the past years, artificial gene synthesis represents a powerful and flexible engineering tool for creating and designing new DNA sequences and protein functions. Besides synthetic biology, various research areas like those involving heterologous gene expression, vaccine development, gene therapy and molecular engineering, would benefit greatly from having fast and cheap methods to synthesise DNA to code for proteins and peptides. The methods used for DNA printing and assembly have even enabled the use of DNA as an information storage medium. | 1 | Applied and Interdisciplinary Chemistry |
Functional selectivity has been proposed to broaden conventional definitions of pharmacology.
Traditional pharmacology posits that a ligand can be either classified as an agonist (full or partial), antagonist or more recently an inverse agonist through a specific receptor subtype, and that this characteristic will be consistent with all effector (second messenger) systems coupled to that receptor. While this dogma has been the backbone of ligand-receptor interactions for decades now, more recent data indicates that this classic definition of ligand-protein associations does not hold true for a number of compounds; such compounds may be termed as mixed agonist-antagonists.
Functional selectivity posits that a ligand may inherently produce a mix of the classic characteristics through a single receptor isoform depending on the effector pathway coupled to that receptor. For instance, a ligand can not easily be classified as an agonist or antagonist, because it can be a little of both, depending on its preferred signal transduction pathways. Thus, such ligands must instead be classified on the basis of their individual effects in the cell, instead of being either an agonist or antagonist to a receptor.
It is also important to note that these observations were made in a number of different expression systems and therefore functional selectivity is not just an epiphenomenon of one particular expression system. | 1 | Applied and Interdisciplinary Chemistry |
Hevesy György was born in Budapest, Hungary, to a wealthy and ennobled family of Hungarian-Jewish descent, the fifth of eight children to his parents Lajos Bischitz and Baroness Eugénia (Jenny) Schossberger (ennobled as "De Tornya"). Grandparents from both sides of the family had provided the presidents of the Jewish community of Pest. His parents converted to Roman Catholicism. George grew up in Budapest and graduated high school in 1903 from Piarist Gimnázium. The family's name in 1904 was Hevesy-Bischitz, and Hevesy later changed his own.
De Hevesy began his studies in chemistry at the University of Budapest for one year, and at the Technical University of Berlin for several months, but transferred to the University of Freiburg. There he met Ludwig Gattermann. In 1906, he started his Ph.D. thesis with Georg Franz Julius Meyer, acquiring his doctorate in physics in 1908. In 1908, Hevesy was offered a position at the ETH Zürich, Switzerland, yet being independently wealthy, he was able to choose his research environment. He worked first with Fritz Haber in Karlsruhe, Germany, then with Ernest Rutherford in Manchester, England, where he also met Niels Bohr. Back at home in Budapest, he was appointed professor in physical chemistry in 1918. In 1920, he settled in Copenhagen. | 1 | Applied and Interdisciplinary Chemistry |
To separate nucleic acids by TGGE, the following steps must be performed: preparing and pouring the gels, electrophoresis, staining, and elution of DNA. Because a buffered system must be chosen, it is important that the system remain stable within the context of increasing temperature. Thus, urea is typically utilized for gel preparation; however, researchers need to be aware that the amount of urea used will affect the overall temperature required to separate the DNA. The gel is loaded, the sample is placed on the gel according to the type of gel that is being run—i.e. parallel or perpendicular—the voltage is adjusted and the sample can be left to run. Depending on which type of TGGE is to be run, either perpendicular or parallel, varying amounts of sample need to be prepared and loaded. A larger amount of one sample is used with perpendicular, while a smaller amount of many samples are used with parallel TGGE. Once the gel has been run, the gel must be stained to visualize the results. While there are a number of stains that can be used for this purpose, silver staining has proven to be the most effective tool. The DNA can be eluted from the silver stain for further analysis through PCR amplification. | 1 | Applied and Interdisciplinary Chemistry |
A microfibril is a very fine fibril, or fiber-like strand, consisting of glycoproteins and cellulose. It is usually, but not always, used as a general term in describing the structure of protein fiber, e.g. hair and sperm tail. Its most frequently observed structural pattern is the 9+2 pattern in which two central protofibrils are surrounded by nine other pairs. Cellulose inside plants is one of the examples of non-protein compounds that are using this term with the same purpose. Cellulose microfibrils are laid down in the inner surface of the primary cell wall. As the cell absorbs water, its volume increases and the existing microfibrils separate and new ones are formed to help increase cell strength. | 1 | Applied and Interdisciplinary Chemistry |
Oxyntomodulin (often abbreviated OXM) is a naturally occurring 37-amino acid peptide hormone found in the colon, produced by the oxyntic (fundic) cells of the oxyntic (fundic) mucosa. It has been found to suppress appetite.
The mechanism of action of oxyntomodulin is not well understood. It is known to bind both the GLP-1 receptor and the glucagon receptor, but it is not known whether the effects of the hormone are mediated through these receptors or through an unidentified receptor.
Oxyntomodulin has been linked to entrainment of the liver's circadian clock.
Oxyntomodulin has been investigated as a blood-glucose regulation agent in connection with diabetes. | 1 | Applied and Interdisciplinary Chemistry |
There are two common measures of photosynthetically active radiation: photosynthetic photon flux (PPF) and yield photon flux (YPF). PPF values all photons from 400 to 700 nm equally, while YPF weights photons in the range from 360 to 760 nm based on a plant's photosynthetic response.
PAR as described with PPF does not distinguish between different wavelengths between 400 and 700 nm, and assumes that wavelengths outside this range have zero photosynthetic action. If the exact spectrum of the light is known, the photosynthetic photon flux density (PPFD) values in μmol⋅s⋅m) can be modified by applying different weighting factors to different wavelengths. This results in a quantity called the yield photon flux (YPF). The red curve in the graph shows that photons around 610 nm (orange-red) have the highest amount of photosynthesis per photon. However, because short-wavelength photons carry more energy per photon, the maximum amount of photosynthesis per incident unit of energy is at a longer wavelength, around 650 nm (deep red).
It has been noted that there is considerable misunderstanding over the effect of light quality on plant growth. Many manufacturers claim significantly increased plant growth due to light quality (high YPF). The YPF curve indicates that orange and red photons between 600 and 630 nm can result in 20 to 30% more photosynthesis than blue or cyan photons between 400 and 540 nm.
But the YPF curve was developed from short-term measurements made on single leaves in low light. More recent longer-term studies with whole plants in higher light indicate that light quality may have a smaller effect on plant growth rate than light quantity. Blue light, while not delivering as many photons per joule, encourages leaf growth and affects other outcomes.
The conversion between energy-based PAR and photon-based PAR depends on the spectrum of the light source (see Photosynthetic efficiency). The following table shows the conversion factors from watts for black-body spectra that are truncated to the range 400–700 nm. It also shows the luminous efficacy for these light sources and the fraction of a real black-body radiator that is emitted as PAR.
For example, a light source of 1000 lm at a color temperature of 5800 K would emit approximately 1000/265 = 3.8 W of PAR, which is equivalent to 3.8 × 4.56 = 17.3 μmol/s. For a black-body light source at 5800 K, such as the sun is approximately, a fraction 0.368 of its total emitted radiation is emitted as PAR. For artificial light sources, that usually do not have a black-body spectrum, these conversion factors are only approximate.
The quantities in the table are calculated as
where is the black-body spectrum according to Planck's law, is the standard luminosity function, represent the wavelength range (400–700 nm) of PAR, and is the Avogadro constant. | 0 | Theoretical and Fundamental Chemistry |
The potential value of pincer ligands in catalysis has been investigated, although no process has been commercialized. Aspirational applications are motivated by the high thermal stability and rigidity. Disadvantages include the cost of the ligands. | 0 | Theoretical and Fundamental Chemistry |
The basic principle of LID to use nature as a model and manage rainfall at the source is accomplished through sequenced implementation of runoff prevention strategies, runoff mitigation strategies, and finally, treatment controls to remove pollutants. Although Integrated Management Practices (IMPs) — decentralized, microscale controls that infiltrate, store, evaporate, and detain runoff close to the source — get most of the attention by engineers, it is crucial to understand that LID is more than just implementing a new list of practices and products. It is a strategic design process to create a sustainable site that mimics the undeveloped hydrologic properties of the site. It requires a prescriptive approach that is appropriate for the proposed land use.
Design using LID principles follows four simple steps.
# Determine pre-developed conditions and identify the hydrologic goal (some jurisdictions suggest going to wooded conditions).
# Assess treatment goals, which depend on site use and local keystone pollutants.
# Identify a process that addresses the specific needs of the site.
# Implement a practice that utilizes the chosen process and that fits within the site's constraints.
The basic processes used to manage stormwater include pretreatment, filtration, infiltration, and storage and reuse. | 1 | Applied and Interdisciplinary Chemistry |
In biology, actinic light denotes light from solar or other sources that can cause photochemical reactions such as photosynthesis in a species. | 0 | Theoretical and Fundamental Chemistry |
An action potential pulse is a mathematically and experimentally correct Synchronized Oscillating Lipid Pulse coupled with an Action Potential. This is a continuation of Hodgkin Huxley's work in 1952 with the inclusion of accurately modelling ion channel proteins, including their dynamics and speed of activation.
The action potential pulse is a model of the speed an action potential that is dynamically dependent upon the position and number of ion channels, and the shape and make up of the axon. The action potential pulse model takes into account entropy and the conduction speed of the action potential along an axon. It is an addition to the Hodgkin Huxley model.
Investigation into the membranes of axons have shown that the spaces in between the channels are sufficiently large, such that cable theory cannot apply to them, because it depends upon the capacitance potential of a membrane to be transferred almost instantly to other areas of the membrane surface. In electrical circuits this can happen because of the special properties of electrons, which are negatively charged, whereas in membrane biophysics potential is defined by positively charged ions instead. These ions are usually Na or Ca, which move slowly by diffusion and have limited ionic radii in which they can affect adjacent ion channels. It is mathematically impossible for these positive ions to move from one channel to the next, in the time required by the action potential flow model, due to instigated depolarization. Furthermore entropy measurements have long demonstrated that an action potentials flow starts with a large increase in entropy followed by a steadily decreasing state, which does not match the Hodgkin Huxley theory. In addition a soliton pulse is known to flow at the same rate and follow the action potential. From measurements of the speed of an action potential, hyperpolarization must have a further component of which the soliton' mechanical pulse is the only candidate.
The resulting action potential pulse therefore is a synchronized, coupled pulse with the entropy from depolarization at one channel providing sufficient entropy for a pulse to travel to sequential channels and mechanically open them.
This mechanism explains the speed of transmission through both myelinated and unmyelinated axons.
This is a timed pulse, that combines the entropy from ion transport with the efficiency of a flowing pulse.
The action potential pulse model has many advantages over the simpler Hodgkin Huxley version including evidence, efficiency, timing entropy measurements, and the explanation of nerve impulse flow through myelinated axons.
Myelinated axons
This model replaces saltatory conduction, which was a historical theory that relied upon cable theory to explain conduction, and was an attempt at a model that has no basis is either physiology or membrane biophysics.
In myelinated axons the myelin acts as a mechanical transducer preserving the entropy of the pulse and insulating against mechanical loss. In this model the nodes of Ranvier (where ion channels are highly concentrated) concentrate the ion channels providing maximum entropy to instigate a pulse that travels from node to node along the axon with the entropy being preserved by the shape and dynamics of the myelin sheath. | 0 | Theoretical and Fundamental Chemistry |
Particularly when two-photon absorption is utilized, high-powered lasers may be required that can be bulky, difficult to cool, and pose safety concerns. Existing optical drives utilize continuous wave diode lasers operating at 780 nm, 658 nm, or 405 nm. 3D optical storage drives may require solid-state lasers or pulsed lasers, and several examples use wavelengths easily available by these technologies, such as 532 nm (green). These larger lasers can be difficult to integrate into the read/write head of the optical drive. | 0 | Theoretical and Fundamental Chemistry |
Georg Jacob Tysland (13 February 1890 – 14 February 1932) was a Norwegian engineer and metallurgist. Tysland is known as the originator of a successful electric smelting furnace for the production of pig iron, a semi-finished product for the production of steel. | 1 | Applied and Interdisciplinary Chemistry |
In physical organic chemistry, the Grunwald–Winstein equation is a linear free energy relationship between relative rate constants and the ionizing power of various solvent systems, describing the effect of solvent as nucleophile on different substrates. The equation, which was developed by Ernest Grunwald and Saul Winstein in 1948, could be written
where the and are the solvolysis rate constants for a certain compound in different solvent systems and in the reference solvent, 80% aqueous ethanol, respectively. The parameter is a parameter measuring the sensitivity of the solvolysis rate with respect to , the measure of ionizing power of the solvent. | 0 | Theoretical and Fundamental Chemistry |
Molecular physics is the study of the physical properties of molecules and molecular dynamics. The field overlaps significantly with physical chemistry, chemical physics, and quantum chemistry. It is often considered as a sub-field of atomic, molecular, and optical physics. Research groups studying molecular physics are typically designated as one of these other fields. Molecular physics addresses phenomena due to both molecular structure and individual atomic processes within molecules. Like atomic physics, it relies on a combination of classical and quantum mechanics to describe interactions between electromagnetic radiation and matter. Experiments in the field often rely heavily on techniques borrowed from atomic physics, such as spectroscopy and scattering. | 0 | Theoretical and Fundamental Chemistry |
CAF-1 is required for the spatial organization and epigenetic marking of heterochromatin domains in pluripotent embryonic cells, creating a cellular memory of somatic cell identity during cellular differentiation.
Cells resembling 2-cell-stage mouse embryos (totipotent cells) can be induced in vitro through downregulation of the chromatin-assembly activity of CAF-1 in embryonic stem cells.
CAF-1 forms a deadenylase complex with CCR4-Not, which should not be confused with the unrelated CCR4. The CAF-1/CCR4-Not complex cooperates with the release factor eRF3 and PABPC1 to shorten the poly(A) tail of mRNA during translation. | 1 | Applied and Interdisciplinary Chemistry |
Natural sources of gamma rays on Earth include gamma decay from naturally occurring radioisotopes such as potassium-40, and also as a secondary radiation from various atmospheric interactions with cosmic ray particles. Some rare terrestrial natural sources that produce gamma rays that are not of a nuclear origin, are lightning strikes and terrestrial gamma-ray flashes, which produce high energy emissions from natural high-energy voltages. Gamma rays are produced by a number of astronomical processes in which very high-energy electrons are produced. Such electrons produce secondary gamma rays by the mechanisms of bremsstrahlung, inverse Compton scattering and synchrotron radiation. A large fraction of such astronomical gamma rays are screened by Earth's atmosphere. Notable artificial sources of gamma rays include fission, such as occurs in nuclear reactors, as well as high energy physics experiments, such as neutral pion decay and nuclear fusion.
A sample of gamma ray-emitting material that is used for irradiating or imaging is known as a gamma source. It is also called a radioactive source, isotope source, or radiation source, though these more general terms also apply to alpha and beta-emitting devices. Gamma sources are usually sealed to prevent radioactive contamination, and transported in heavy shielding. | 0 | Theoretical and Fundamental Chemistry |
Starfish is a set of software tools developed in 2019 by a consortium of scientists to analyze data from nine different variations of FISH, since all variations produce the same set of data—gene expression values mapped to x and y coordinates in a cell. The software, created for all scientists, not just bioinformaticians, reads a set of images, removes noise, and identifies RNA molecules. This approach has set out to define a standard analysis scheme of FISH datasets in a similar way to single-cell transcriptomics analysis. | 1 | Applied and Interdisciplinary Chemistry |
Dextroamphetamine is the active metabolite of the prodrug lisdexamfetamine (L-lysine-dextroamphetamine), available by the brand name Vyvanse (Elvanse in the European market) (Venvanse in the Brazil market) (lisdexamfetamine dimesylate). Dextroamphetamine is liberated from lisdexamfetamine enzymatically following contact with red blood cells. The conversion is rate-limited by the enzyme, which prevents high blood concentrations of dextroamphetamine and reduces lisdexamfetamine's drug liking and abuse potential at clinical doses. Vyvanse is marketed as once-a-day dosing as it provides a slow release of dextroamphetamine into the body. Vyvanse is available as capsules, and chewable tablets, and in seven strengths; 10 mg, 20 mg, 30 mg, 40 mg, 50 mg, 60 mg, and 70 mg. The conversion rate between lisdexamfetamine dimesylate (Vyvanse) to dextroamphetamine base is 29.5%. | 0 | Theoretical and Fundamental Chemistry |
The anthocyanin biosynthesis pathway is now well known and most of the enzymes are characterised. In the formation of blue pigments a few enzymes have particularly important roles, in particular flavonoid 35-hydroxylase (F35H) and dihydroflavonol 4-reductase (DFR).
The flavonoid 35H-hydroxylase is responsible for the introduction of the second and third hydroxyl group in the B-ring of dihydrokaempferol (DHK) or naringenin which are regarded as the main substrates of the reaction. Product of the reaction with DHK is dihydromyricetin (DHM), precursor for synthesis of all delphinidin type anthocyanin. Enzyme is a member of cytochrome P450 protein family (P450s). It is a very diverse group of heme-containing oxidases, which catalyse NADPH- or NADH-dependent oxidation. F35H was classified into CYP75A subfamily. This enzyme this is regarded as necessary for the blue pigment formation.
Dihydroflavonol 4-reductase is the oxidoreductase that catalyses in the presence of NADPH the stereospecific reduction of the keto group in position 4 of dihydroflavonols producing colourless leucoanthocyanidins as a precursor for anthocyanin formation. Enzyme can show substrate specificity with respect to the B-ring hydroxylation pattern of the dihydroflavonol and can therefore have an influence on the type of formed anthocyanin. For the blue pigment formation, necessary is enzyme, which accept dihydromyricetin (DHM) as a substrate. Product of DFR reaction with DHM in the following steps of the pathway is converted to delphinidin type blue pigments. | 1 | Applied and Interdisciplinary Chemistry |
Transition state theory requires a value of the transmission coefficient, called in that theory. This value is often taken to be unity (i.e., the species passing through the transition state always proceed directly to products and never revert to reactants and ). To avoid specifying a value of , the rate constant can be compared to the value of the rate constant at some fixed reference temperature (i.e., ) which eliminates the factor in the resulting expression if one assumes that the transmission coefficient is independent of temperature. | 0 | Theoretical and Fundamental Chemistry |
Various biomaterials, whether they are biological, synthetic, or a combination of both, can be used to create scaffolds, which when implanted in a human body can promote host tissue regeneration. First, cells from the patient in which the scaffold will be implanted in are harvested. These cells are expanded and seeded into the created scaffold, which is then inserted inside the human body. The human body serves as a bioreactor, which allows the formation of an extracellular matrix (ECM) along with fibrous proteins around the scaffold to provide the necessary environment for the heart and circulatory system. The initial implantation of the foreign scaffold triggers various signaling pathways guided by the foreign body response for cell recruitment from neighboring tissues. The new nanofiber network surrounding the scaffold mimics the native ECM of the host body. Once cells begin to populate the cell, the scaffold is designed to gradually degrade, leaving behind a constructed heart valve made of the host body's own cells that is fully capable of cell repopulation and withstanding environmental changes within the body. The scaffold designed for tissue engineering is one of the most crucial components because it guides tissue construction, viability, and functionality long after implantation and degradation. | 1 | Applied and Interdisciplinary Chemistry |
Amalgamation with mercury can be used to recover very small gold particles, and mercury is still widely used in small-scale artisanal mining across the world. Mercury forms a mercury-gold amalgam with smaller gold particles, and then the gold is concentrated by boiling away the mercury from the amalgam. This is effective in extracting very small gold particles, but the process is hazardous due to the toxicity of mercury vapour. Large-scale use of mercury stopped in the 1960s. However, mercury is still used in artisanal and small-scale gold mining (ASGM). One mechanism by which mercury is employed in hydraulic mining is as an "undercurrent", in which the flow of smaller grains is diverted over mercury-coated copper plates. High flow velocities associated with hydraulic mining cause flouring of mercury, the wearing down of mercury particles that contributes to mercury loss into the environment.
Over of mercury contaminated the environment in California as a result of placer mining in the late nineteenth and early twentieth centuries. Stamp mill mining contributed an additional of mercury contamination. Mercury contamination in California waterways is a major contemporary environmental issue, as is groundwater pollution, mostly by inorganic mercury. | 1 | Applied and Interdisciplinary Chemistry |
In the physical sciences, an interface is the boundary between two spatial regions occupied by different matter, or by matter in different physical states. The interface between matter and air, or matter and vacuum, is called a surface, and studied in surface science. In thermal equilibrium, the regions in contact are called phases, and the interface is called a phase boundary. An example for an interface out of equilibrium is the grain boundary in polycrystalline matter.
The importance of the interface depends on the type of system: the bigger the quotient area/volume, the greater the effect the interface will have. Consequently, interfaces are very important in systems with large interface area-to-volume ratios, such as colloids.
Interfaces can be flat or curved. For example, oil droplets in a salad dressing are spherical but the interface between water and air in a glass of water is mostly flat.
Surface tension is the physical property which rules interface processes involving liquids. For a liquid film on flat surfaces, the liquid-vapor interface keeps flat to minimize interfacial area and system free energy. For a liquid film on rough surfaces, the surface tension tends to keep the meniscus flat, while the disjoining pressure makes the film conformal to the substrate. The equilibrium meniscus shape is a result of the competition between the capillary pressure and disjoining pressure.
Interfaces may cause various optical phenomena, such as refraction. Optical lenses serve as an example of a practical application of the interface between glass and air.
One topical interface system is the gas-liquid interface between aerosols and other atmospheric molecules. | 0 | Theoretical and Fundamental Chemistry |
Reverse transcription is the transfer of information from RNA to DNA (the reverse of normal transcription). This is known to occur in the case of retroviruses, such as HIV, as well as in eukaryotes, in the case of retrotransposons and telomere synthesis.
It is the process by which genetic information from RNA gets transcribed into new DNA. The family of enzymes involved in this process is called Reverse Transcriptase. | 1 | Applied and Interdisciplinary Chemistry |
At first his work appeared as that of his master and patron Fourcroy, then in their joint names; in 1790 he began to publish on his own, and between that year and 1833 his name is associated with 376 papers. Most of these were simple records of patient and laborious analytical operations, and it is perhaps surprising that among all the substances he analysed he detected only two new elements, beryllium in 1798 in beryl and chromium in 1797 in a red lead ore from Siberia. He also managed to get liquid ammonia at atmospheric pressure.
Later with Fourcroy, he identified a metal in a platinum residue they called ‘ptène’, This name ‘ptene’ or ‘ptène’ was reported as an early synonym for osmium.
Either together or successively he held the offices of inspector of mines, professor at the School of Mines and at the Polytechnic School, assayer of gold and silver articles, professor of chemistry in the College de France and at the Jardin des Plantes, member of the Council of Industry and Commerce, commissioner on the pharmacy laws, and finally professor of chemistry to the Medical Faculty, to which he succeeded on Fourcroy's death in 1809. His lectures, which were supplemented with practical laboratory teaching, were attended by many chemists who subsequently attained distinction.
A lesser-known contribution and finding of his included the study of hens fed a known amount of mineral. "Having calculated all the lime in oats fed to a hen, found still more in the shells of its eggs. Therefore, there is a creation of matter. In what way, no one knows." | 1 | Applied and Interdisciplinary Chemistry |
Choosing to run a chemical reaction using flow chemistry, either in a microreactor or other mixing device offers a variety of pros and cons. | 1 | Applied and Interdisciplinary Chemistry |
A quantity of sample is weighed, placed in a crucible, and subjected to destructive distillation. During a fixed period of severe heating, the residue undergoes cracking and coking reactions . At the termination of the heating period, the crucible containing the carbonaceous residue is cooled in a desiccator and weighed. The residue remaining is calculated as a percentage of the original sample, and reported as Conradson carbon residue. | 0 | Theoretical and Fundamental Chemistry |
Amyotrophic lateral sclerosis ALS is a neurodegenerative disease characterized by progressive muscular paralysis reflecting degeneration of motor neurons in the primary motor cortex, corticospinal tracts, brainstem and spinal cord. One study using the superoxide dismutase 1 (SOD1) mutant mouse, an ALS model which develops severe neurodegeneration, the expression of p75NTR correlated with the extent of degeneration and p75NTR knockdown delayed disease progression. | 1 | Applied and Interdisciplinary Chemistry |
A clathrate is a chemical substance consisting of a lattice that traps or contains molecules. The word clathrate is derived from the Latin (), meaning with bars, latticed. Most clathrate compounds are polymeric and completely envelop the guest molecule, but in modern usage clathrates also include host–guest complexes and inclusion compounds. According to IUPAC, clathrates are inclusion compounds "in which the guest molecule is in a cage formed by the host molecule or by a lattice of host molecules." The term refers to many molecular hosts, including calixarenes and cyclodextrins and even some inorganic polymers such as zeolites.
Clathrates can be divided into two categories: clathrate hydrates and inorganic clathrates. Each clathrate is made up of a framework and guests that reside the framework. Most common clathrate crystal structures can be composed of cavities such as dodecahedral, tetrakaidecahedral, and hexakaidecahedral cavities.
The molar fraction of water of most clathrate hydrates is 85%. Clathrate hydrates are derived from organic hydrogen-bonded frameworks. These frameworks are prepared from molecules that "self-associate" by multiple hydrogen-bonding interactions. Small molecules or gases (i.e. methane, carbon dioxide, hydrogen) can be encaged as a guest in hydrates. The ideal guest/host ratio for clathrate hydrates range from 0.8 to 0.9. The guest interaction with the host is limited to van der Waals forces. Certain exceptions exist in semiclathrates where guests incorporate into the host structure via hydrogen bonding with the host structure. Hydrates form often with partial guest filling and collapse in the absence of guests occupying the water cages. Like ice, clathrate hydrates are stable at low temperatures and high pressure and possess similar properties like electrical resistivity. Clathrate hydrates are naturally occurring and can be found in the permafrost and oceanic sediments. Hydrates can also be synthesized through seed crystallization or using amorphous precursors for nucleation.
Unlike hydrates, inorganic clathrates have a covalently bonded framework of inorganic atoms with guests typically consisting of alkali or alkaline earth metals. Due to the stronger covalent bonding, the cages are often smaller than hydrates. Guest atoms interact with the host by ionic or covalent bonds. Therefore, partial substitution of guest atoms follow Zintl rules so that the charge of the overall compound is conserved. Most inorganic clathrates have full occupancy of its framework cages by a guest atom to be in stable phase. Inorganic clathrates can be synthesized by direct reaction using ball milling at high temperatures or high pressures. Crystallization from melt in another common synthesis route. Due to the wide variety of composition of host and guest species, inorganic clathrates are much more chemically diverse and possess a wide range of properties. Most notably, inorganic clathrates can be found to be both an insulator and a superconductor (BaSi). A common property of inorganic clathrates that has attracted researchers is low thermal conductivity. Low thermal conductivity is attributed to the ability of the guest atom to "rattle" within the host framework. The freedom of movement of the guest atoms scatters phonons that transport heat. | 0 | Theoretical and Fundamental Chemistry |
Barium azide is an inorganic azide with the formula . It is a barium salt of hydrazoic acid. Like most azides, it is explosive. It is less sensitive to mechanical shock than lead azide. | 0 | Theoretical and Fundamental Chemistry |
Selenium has a protective effect towards mercury toxicity. Mercury binds to selenium with high affinity, so this metal can inhibit selenium-dependent enzymes. However, increased selenium intake can preserve the enzyme activities, reducing the adverse effects caused by mercury exposure. | 1 | Applied and Interdisciplinary Chemistry |
Mach tuck is usually caused by two things: a rearward movement of the centre of pressure of the wing, and a decrease in wing downwash velocity at the tailplane, both of which cause a nose down pitching moment. For a particular aircraft design only one of these may be significant in causing a tendency to for example, a delta-winged aircraft with no foreplane or tailplane in the first case, and the Lockheed P-38 in the second case. Alternatively, a particular design may have no significant tendency, such as the Fokker F28 Fellowship.
As an aerofoil generating lift moves through the air, the air flowing over the top surface accelerates to a higher local speed than the air flowing over the bottom surface. When the aircraft speed reaches its critical Mach number the accelerated airflow locally reaches the speed of sound and creates a small shock wave, even though the aircraft is still travelling below the speed of sound. The region in front of the shock wave generates high lift. As the aircraft itself flies faster, the shock wave over the wing gets stronger and moves rearwards, creating high lift further back along the wing. It is this rearward movement of lift which causes the aircraft to tuck or pitch nose-down.
The severity of Mach tuck on any given design is affected by the thickness of the aerofoil, the sweep angle of the wing, and the location of the tailplane relative to the main wing.
A tailplane which is positioned further aft can provide a larger stabilizing pitch-up moment.
The camber and thickness of the aerofoil affect the critical Mach number, with a more highly curved upper surface causing a lower critical Mach number.
On a swept wing the shock wave typically forms first at the wing root, especially if it is more cambered than the wing tip. As speed increases, the shock wave and associated lift extend outwards and, because the wing is swept, backwards.
The changing airflow over the wing can reduce the downwash over a conventional tailplane, promoting a stronger nose-down pitching moment.
Another problem with a separate horizontal stabilizer is that it can itself achieve local supersonic flow with its own shock wave. This can affect the operation of a conventional elevator control surface.
Aircraft without enough elevator authority to maintain trim and fly level can enter a steep, sometimes unrecoverable dive. Until the aircraft is supersonic, the faster top shock wave can reduce the authority of the elevator and horizontal stabilizers.
Mach tuck may or may not occur depending on aircraft design. Many modern aircraft have little or no effect. | 1 | Applied and Interdisciplinary Chemistry |
Thermodynamic equilibrium is characterized by the free energy for the whole (closed) system being a minimum. For systems at constant temperature and pressure the Gibbs free energy is minimum. The slope of the reaction free energy with respect to the extent of reaction, ξ, is zero when the free energy is at its minimum value.
The free energy change, dG, can be expressed as a weighted sum of change in amount times the chemical potential, the partial molar free energy of the species. The chemical potential, μ, of the ith species in a chemical reaction is the partial derivative of the free energy with respect to the number of moles of that species, N
A general chemical equilibrium can be written as
where n are the stoichiometric coefficients of the reactants in the equilibrium equation, and m are the coefficients of the products. At equilibrium
The chemical potential, μ, of the ith species can be calculated in terms of its activity, a.
μ is the standard chemical potential of the species, R is the gas constant and T is the temperature. Setting the sum for the reactants j to be equal to the sum for the products, k, so that δG(Eq) = 0
Rearranging the terms,
This relates the standard Gibbs free energy change, ΔG</sup> to an equilibrium constant, K, the reaction quotient of activity values at equilibrium. | 0 | Theoretical and Fundamental Chemistry |
Many environmental protection agencies have issued regulations that limit the concentration of pollutants in gaseous emissions and define the reference conditions applicable to those concentration limits. For example, such a regulation might limit the concentration of Nitrogen oxide| to 55 ppmv in a dry combustion exhaust gas (at a specified reference temperature and pressure) corrected to 3 volume percent O in the dry gas. As another example, a regulation might limit the concentration of total particulate matter to 200 mg/m of an emitted gas (at a specified reference temperature and pressure) corrected to a dry basis and further corrected to 12 volume percent CO in the dry gas.
Environmental agencies in the USA often use the terms "dscf" or "scfd" to denote a "standard" cubic foot of dry gas. Likewise, they often use the terms "dscm" or "scmd" to denote a "standard" cubic meter of gas. Since there is no universally accepted set of "standard" temperature and pressure, such usage can be and is very confusing. It is strongly recommended that the reference temperature and pressure always be clearly specified when stating gas volumes or gas flow rates. | 1 | Applied and Interdisciplinary Chemistry |
Passing–Bablok regression is a method from robust statistics for nonparametric regression analysis suitable for method comparison studies introduced by Wolfgang Bablok and Heinrich Passing in 1983. The procedure is adapted to fit linear errors-in-variables models. It is symmetrical and is robust in the presence of one or few outliers.
The Passing-Bablok procedure fits the parameters and of the linear equation using non-parametric methods. The coefficient is calculated by taking the shifted median of all slopes of the straight lines between any two points, disregarding lines for which the points are identical or . The median is shifted based on the number of slopes where to create an approximately consistent estimator. The estimator is therefore close in spirit to the Theil-Sen estimator. The parameter is calculated by .
In 1986, Passing and Bablok extended their method introducing an equivariant extension for method transformation which also works when the slope is far from 1.
It may be considered a robust version of reduced major axis regression. The slope estimator is the median of the absolute values of all pairwise slopes.
The original algorithm is rather slow for larger data sets as its computational complexity is . However, fast quasilinear algorithms of complexity ln have been devised.
Passing and Bablok define a method for calculating a 95% confidence interval (CI) for both and in their original paper, which was later refined, though bootstrapping the parameters is the preferred method for in vitro diagnostics (IVD) when using patient samples. The Passing-Bablok procedure is valid only when a linear relationship exists between and , which can be assessed by a CUSUM test. Further assumptions include the error ratio to be proportional to the slope and the similarity of the error distributions of the and distributions.
The results are interpreted as follows. If 0 is in the CI of , and 1 is in the CI of , the two methods are comparable within the investigated concentration range. If 0 is not in the CI of there is a systematic difference and if 1 is not in the CI of then there is a proportional difference between the two methods.
However, the use of Passing–Bablok regression in method comparison studies has been criticized because it ignores random differences between methods. | 0 | Theoretical and Fundamental Chemistry |
Double-stranded nucleic acids are made up of complementary sequences, in which extensive Watson-Crick base pairing results in a highly repeated and quite uniform Nucleic acid double-helical three-dimensional structure. In contrast, single-stranded RNA and DNA molecules are not constrained to a regular double helix, and can adopt highly complex three-dimensional structures that are based on short stretches of intramolecular base-paired sequences including both Watson-Crick and noncanonical base pairs, and a wide range of complex tertiary interactions.
Nucleic acid molecules are usually unbranched and may occur as linear and circular molecules. For example, bacterial chromosomes, plasmids, mitochondrial DNA, and chloroplast DNA are usually circular double-stranded DNA molecules, while chromosomes of the eukaryotic nucleus are usually linear double-stranded DNA molecules. Most RNA molecules are linear, single-stranded molecules, but both circular and branched molecules can result from RNA splicing reactions. The total amount of pyrimidines in a double-stranded DNA molecule is equal to the total amount of purines. The diameter of the helix is about 20 Å. | 1 | Applied and Interdisciplinary Chemistry |
Most models of the CD V-700 are constructed using a two-piece case made of die-cast and stamped aluminum with a distinctive yellow paint (John Deere Yellow), a Civil Defense “CD” decal and check source. The upper, die-cast part of the case contains a groove around the outer edge for a rubber gasket that renders the case water-tight. These have often deteriorated over the years but can be replaced with a section of rubber bead as used for mounting household screen windows in their frames. This section of the case also houses the meter, the printed circuit board and the battery holders. Mounted to the top of the upper case is a carry handle in which the probe clips in for storage, a connector for a headphone and the control knob.
The inside of the unit contains high voltage electronics of up to 900 volts, so care is recommended when operating with the case open. Inside the lower, stamped aluminum portion of the case is a printed diagram corresponding to the make and model of the unit that the lower case shipped with. In the decades since these units were made, it is common to find case bottoms have been switched between different makes and models, so the diagram may not match the actual mechanical and electrical properties of the unit.
Power is typically supplied by 2–5 D cell batteries, though early models used three B batteries in conjunction with two D-cell batteries. The most common cells employed are common alkaline primary batteries but rechargeable batteries can also be used. The common alkaline batteries have the disadvantage of a good chance of leakage of corrosive fluids when the unit is placed into storage for long periods, so it is advisable to remove the batteries for storage.
The units were shipped with a packet containing a silica gel to absorb any moisture inside the container and maintain the electronic components of the device. This packet should either be replaced or regenerated in an oven annually.
Unlike many newer devices of this type, the CD V-700s are not equipped with a visual or audible alarm for excessively high levels of radiation. | 0 | Theoretical and Fundamental Chemistry |
During G2 phase of the cell cycle, Cdk1 and cyclin B1 makes a complex and forms maturation promoting factor (MPF). The complex accumulates in the nucleus due to phosphorylation of the cyclin B1 at multiple sites, which inhibits nuclear export of the complex. Phosphorylation of Thr19 and Tyr15 residues of Cdk1 by Wee1 and MYT1 keeps the complex inactive and inhibits entry into mitosis whereas dephosphorylation of Cdk1 by CDC25C phosphatase at Thr19 and Tyr15 residues, activates the complex which is necessary in order to enter mitosis. Cdc25C phosphatase is present in the cytoplasm and in late G2 phase it is translocated into the nucleus by signaling such as PIK1, PIK3. The regulated translocation and accumulation of the multiple required signaling cascade components, MPF and its activator Cdc25, in the nucleus generates efficient activation of the MPF and produces switch-like, ultrasensitive entry into mitosis.
The figure shows different possible mechanisms for how increased regulation of the localization of signaling components by the stimulus (input signal) shifts the output from Michaelian response to ultrasensitive response. When stimulus is regulating only inhibition of Cdk1-cyclinB1 nuclear export, the outcome is Michaelian response, Fig (a). But if the stimulus can regulate localization of multiple components of the signaling cascade, i.e. inhibition of Cdk1-cyclinB1 nuclear export and translocation of the Cdc25C to nucleus, then the outcome is ultrasensitive response, Fig (b). As more components of the signaling cascade are regulated and localized by the stimulus—i.e. inhibition of Cdk1-cyclinB1 nuclear export, translocation of the Cdc25C to the nucleus, and activation of Cdc25C—the output response becomes more and more ultrasensitive, Fig(c). | 1 | Applied and Interdisciplinary Chemistry |
As their natural analogues, synthetic biopolymers find applications in numerous fields, including materials for commodities, drug delivery, tissue engineering, therapeutic and diagnostic applications. | 1 | Applied and Interdisciplinary Chemistry |
Hydrofluorocarbons (HFCs) contain no chlorine. They are composed entirely of carbon, hydrogen, and fluorine. They have no known effects on the ozone layer; fluorine itself is not ozone-toxic. However, HFCs and perfluorocarbons (PFCs) are greenhouse gases, which cause global warming. Two groups of haloalkanes, hydrofluorocarbons (HFCs) and perfluorocarbons, are targets of the Kyoto Protocol. Allan Thornton, President of the Environmental Investigation Agency, a non-governmental, environmental watchdog, says that HFCs are up to 12,500 times as potent as carbon dioxide in global warming. The higher global warming potential has two causes: HFCs remain in the atmosphere for long periods of time, and they have more chemical bonds than , which means that they are able to absorb more solar energy per molecule than carbon dioxide. Wealthy countries are clamping down on these gases. Thornton says that many countries are needlessly producing these chemicals just to get the carbon credits. Thus, as a result of carbon trading rules under the Kyoto Protocol, nearly half the credits from developing countries are from HFCs, with China scoring billions of dollars from catching and destroying HFCs that would be in the atmosphere as industrial byproducts. | 1 | Applied and Interdisciplinary Chemistry |
Mairanovsky was born to a Jewish family in Batumi in 1899.
Mairanovsky was the head of several secret laboratories in the Bach Institute of Biochemistry in Moscow (1928–1935). As the head of Laboratory No. 1 (1938–1946), he initiated the secret poison program conducted by the NKVD. He used political prisoners for experiments with poisons. His classified PhD thesis defended in 1940 was entitled "Biological activity of the products of interaction of mustard gas with [human] skin tissues".
Mairanovsky participated personally in political assassinations as a member of Pavel Sudoplatov's team in the 1940s, including assassination of Isaiah Oggins.
He was arrested as a part of the doctors' plot in 1951, in connection with the case of Viktor Abakumov, and spent 10 years in prison. After his release, he headed a biochemical laboratory in Makhachkala, Dagestan ASSR. | 1 | Applied and Interdisciplinary Chemistry |
The effect of electroreflectence was first written of in a review letter from 1965 by B. O. Seraphin and R. B. Hess from Michelson Laboratory, China Lake, California where they were studying the Franz-Keldysh effect above the fundamental edge in germanium. They found that it was not only possible for the material to absorb the electrons, but also re-emit them. Following this discovery Seraphin has written numerous articles on the new found phenomenon. | 0 | Theoretical and Fundamental Chemistry |
The measurement of heat changes is performed using calorimetry, usually an enclosed chamber within which the change to be examined occurs. The temperature of the chamber is monitored either using a thermometer or thermocouple, and the temperature plotted against time to give a graph from which fundamental quantities can be calculated. Modern calorimeters are frequently supplied with automatic devices to provide a quick read-out of information, one example being the differential scanning calorimeter. | 0 | Theoretical and Fundamental Chemistry |
inflammation induced by cholesterol loading into immune cells causes heart disease. A class of drugs called statins blocks cholesterol synthesis and is used extensively in treating heart disease. | 1 | Applied and Interdisciplinary Chemistry |
Heat transfer physics describes the kinetics of energy storage, transport, and energy transformation by principal energy carriers: phonons (lattice vibration waves), electrons, fluid particles, and photons. Heat is thermal energy stored in temperature-dependent motion of particles including electrons, atomic nuclei, individual atoms, and molecules. Heat is transferred to and from matter by the principal energy carriers. The state of energy stored within matter, or transported by the carriers, is described by a combination of classical and quantum statistical mechanics. The energy is different made (converted) among various carriers.
The heat transfer processes (or kinetics) are governed by the rates at which various related physical phenomena occur, such as (for example) the rate of particle collisions in classical mechanics. These various states and kinetics determine the heat transfer, i.e., the net rate of energy storage or transport. Governing these process from the atomic level (atom or molecule length scale) to macroscale are the laws of thermodynamics, including conservation of energy. | 0 | Theoretical and Fundamental Chemistry |
Phosgene oxime is classified as a vesicant even though it does not produce blisters. It is toxic by inhalation, ingestion, or skin contact. The effects of the poisoning occur almost immediately. No antidote for phosgene oxime poisoning is known. Generally, any treatment is supportive. Typical physical symptoms of CX exposure are as follows:
*Skin: Blanching surrounded by an erythematous ring can be observed within 30 seconds of exposure. A wheal develops on exposed skin within 30 minutes. The original blanched area acquires a brown pigmentation by 24 hours. An eschar forms in the pigmented area by 1 week and sloughs after approximately 3 weeks. Initially, the effects of CX can easily be misidentified as mustard gas exposure. However, the onset of skin irritation resulting from CX exposure is a great deal faster than mustard gas, which typically takes several hours or more to cause skin irritation.
*Eyes: Eye examination typically demonstrates conjunctivitis, lacrimation, lid edema, and blepharospasm after even minute exposures. More severe exposures can result in keratitis, iritis, corneal perforation, and blindness.
*Respiratory: Irritation of the mucous membranes may be observed on examination of the oropharynx and nose. Evidence of pulmonary edema, including rales and wheezes, may be noted on auscultation. Pulmonary thromboses are prominent features of severe CX exposure.
*Gastrointestinal: Some animal data suggest that CX may cause hemorrhagic inflammatory changes in the GI tract. | 1 | Applied and Interdisciplinary Chemistry |
A promising strategy for the construction of DNA-encoded libraries is represented by the use of multifunctional building blocks covalently conjugated to an oligonucleotide serving as a “core structure” for library synthesis. In a ‘pool-and-split’ fashion a set of multifunctional scaffolds undergo orthogonal reactions with series of suitable reactive partners. Following each reaction step, the identity of the modification is encoded by an enzymatic addition of DNA segment to the original DNA “core structure”. The use of N-protected amino acids covalently attached to a DNA fragment allow, after a suitable deprotection step, a further amide bond formation with a series of carboxylic acids or a reductive amination with aldehydes. Similarly, diene carboxylic acids used as scaffolds for library construction at the 5’-end of amino modified oligonucleotide, could be subjected to a Diels-Alder reaction with a variety of maleimide derivatives. After completion of the desired reaction step, the identity of the chemical moiety added to the oligonucleotide is established by the annealing of a partially complementary oligonucleotide and by a subsequent Klenow fill-in DNA-polymerization, yielding a double stranded DNA fragment. The synthetic and encoding strategies described above enable the facile construction of DNA-encoded libraries of a size up to 10 member compounds carrying two sets of “building blocks”. However the stepwise addition of at least three independent sets of chemical moieties to a tri-functional core building block for the construction and encoding of a very large DNA-encoded library (comprising up to 10 compounds) can also be envisaged.(Fig.2) | 1 | Applied and Interdisciplinary Chemistry |
The substituent parameter is now defined by field and resonance effects, F and R, which are dependent on the individual substituent. Constants r and f account for the importance of each of the two effects. These constants do not depend on the substituent but instead depend on the set of Hammett substituent parameters (σ, σ, σ, σ, etc.).
In order to find the weighted constants, r and f, for each set of substituent parameters, one would need to establish the fact that each new substituent parameter σ could be written as a linear combination of specific reaction substituent parameters, i.e.
where σ and σ are specific substituent parameters (i.e. σ, σ, etc.) and c and c are constants independent of the substituent (depend on the reaction conditions, i.e. temperature, solvent, and individual reaction being studied). This can be expressed more generically as:
where i is an intercept to keep from fixing the origin at (0,0). If this was not done, the equation would give exceedingly more weight to the unsubstituted compounds that one is trying to make a comparison to using this equation.
A linear least-squares analysis is used to determine the coefficients/constants a, b, and i (Swain and Lupton used a procedure called DOVE: Dual Obligate Vector Evaluation).
Constants were first based on three previous reactions (σ, σ, σ), which leads to more possible errors since the compiled data is only a minimal combination of a much larger pool. Seeing possible error in this limited pool, the data pool was increased by assigning a scale to begin with. A zero-scale is used for hydrogen, because it is known to neither readily donate or accept electron density when attached to a carbon atom due to similar electronegativities. A value of 1 was assigned to NO, because previous research determined the effect of this substituent was predominantly due to resonance. Lastly, F was set equal to R for both components so that the field effects could be compared directly to the resonance effects. This then leads to:
:F = R = 0 for H (Hydrogen).
:F = R = 1 for NO (Nitrogen Dioxide).
Fig. 2 shows some relative F and R values that Swain and Lupton founded. | 0 | Theoretical and Fundamental Chemistry |
Imidoyl chlorides react readily with water, hydrogen sulfide, amines, and hydrogen halides. Treating imidoyl chlorides with water forms the corresponding amide:
:RC(NR’)Cl + HO → RCONHR’ + HCl
Aliphatic imidoyl chlorides are more sensitive toward hydrolysis than aryl derivatives. Electron-withdrawing substituents decrease the reaction rate. Imidoyl chlorides react with hydrogen sulfide to produce thioamides:
:RC(NR’)Cl + HS → RC(S)NHR’ + HCl
When amines are treated with imidoyl chlorides, amidines are obtained.
:RC(NR’)Cl + 2R”NH → RC(NR’)NHR” + R”NHCl
When R' ≠ R", two isomers are possible.
Upon heating, imidoyl chlorides also undergo dehydrohalogenation to form nitriles:
:RC(NR’)Cl → RC≡N + R’Cl
Treatment of imidoyl chloride with hydrogen halides, such as HCl, forms the corresponding iminium chloride cations:
:RC(NR’)Cl + HCl → [RC(NHR’)Cl]Cl | 0 | Theoretical and Fundamental Chemistry |
Newly synthesized DNA, otherwise known as Okazaki fragments, are bound by DNA ligase, which forms a new strand of DNA. There are two strands that are created when DNA is synthesized. The leading strand is continuously synthesized and is elongated during this process to expose the template that is used for the lagging strand (Okazaki fragments). During the process of DNA replication, DNA and RNA primers are removed from the lagging strand of DNA to allow Okazaki fragments to bind to. Since this process is so common, Okazaki maturation will take place around a million times during one completion of DNA replication. For Okazaki maturation to occur, RNA primers must create segments on the fragments to be ligated. This is used as a building block for the synthesis of DNA in the lagging strand. On the template strand, polymerase will synthesize in the opposite direction from the replication fork. Once the template becomes discontinuous, it will create an Okazaki fragment. Defects in the maturation of Okazaki fragments can potentially cause strands in the DNA to break and cause different forms of chromosome abnormality. These mutations in the chromosomes can affect the appearance, the number of sets, or the number of individual chromosomes. Since chromosomes are fixed for each specific species, it can also change the DNA and cause defects in the genepool of that species. | 1 | Applied and Interdisciplinary Chemistry |
The effective volume of a cluster is considered much larger than the volume of the particles due to the lower packing fraction of the cluster. Since, heat can be transferred rapidly within the such clusters, the volume fraction of the highly conductive phase is larger than the volume of solid, thus increasing its thermal conductivity | 0 | Theoretical and Fundamental Chemistry |
There has been some controversy about AstraZenecas behaviour in creating, patenting, and marketing the drug. Esomeprazoles successful predecessor, omeprazole, is a mixture of two mirror-imaged molecules (esomeprazole which is the S-enantiomer, and R-omeprazole); critics said the company was trying to "evergreen" its omeprazole patent by patenting the pure esomeprazole and aggressively marketing to doctors that it is more effective than the mixture. | 0 | Theoretical and Fundamental Chemistry |
A ketone or aldehyde can be attached to a protein through the oxidation of N-terminal serine residues or transamination with PLP. Additionally, they can be introduced by incorporating unnatural amino acids via the Tirrell method or Schultz method. They will then selectively condense with an alkoxyamine and a hydrazine, producing oxime and hydrazone derivatives (shown in the first and second reactions, respectively, in Figure 6). This reaction is highly chemoselective in terms of protein bioconjugation, but the reaction rate is slow. The mechanistic studies show that the rate determining step is the dehydration of tetrahedral intermediate, so a mild acidic solution is often employed to accelerate the dehydration step.
The introduction of nucleophilic catalyst can significantly enhance reaction rate (shown in Figure 7). For example, using aniline as a nucleophilic catalyst, a less populated protonated carbonyl becomes a highly populated protonated Schiff base. In other words, it generates a high concentration of reactive electrophile. The oxime ligation can then occur readily, and it has been reported that the rate increased up to 400 times under mild acidic condition. The key of this catalyst is that it can generate a reactive electrophile without competing with desired product.
Recent developments that exploit proximal functional groups have enabled hydrazone condensations to operate at 20 Ms at neutral pH while oxime condensations have been discovered which proceed at 500-10000 Ms at neutral pH without added catalysts. | 1 | Applied and Interdisciplinary Chemistry |
Using mesophilic bacteria requires the fermentation process to occur below 40 °C, which can cause bacterial contamination due to the low temperature. On the industrial scale, this requires sterilization steps which means a special facility must be built, more employees are needed to run this extra step, and more energy is consumed at the plant. A novel aerobic Geobacillus strain XT15 has been shown to produce 2,3-butanediol at a temperature between 45 and 55 °C. This higher temperature will avoid the risk of contamination because microorganisms that live in normal environments cannot reproduce above 45 °C. The Geobacillus strain XT15 is thermophilic, which allows it to be able to operate fermentation at this higher temperature. Sterilization would not be necessary using this alternative strain making the manufacturing process more efficient and cost-effective. | 1 | Applied and Interdisciplinary Chemistry |
In two-dimensional plane flow, the vorticity vector, defined as , reduces to , where
or
These are forms of Poisson's equation. | 1 | Applied and Interdisciplinary Chemistry |
World Health Organization Guidelines for Drinking Water Quality state that as an indicator organism Escherichia coli provides conclusive evidence of recent fecal pollution and should not be present in water meant for human consumption. In the U.S., the EPA Total Coliform Rule states that a public water system is out of compliance if more than 5 percent of its monthly water samples contain coliforms. | 0 | Theoretical and Fundamental Chemistry |
The working principle of molography is illustrated in Figure 1. Molography is based on diffraction of laser light at a special 2D nanopattern of molecular binding sites on the surface of a sensor chip, termed mologram. A mologram is a coherent assembly of binding sites on a chip that form the blueprint of molecular hologram. The hologram has the shape of a focusing diffractive lens and is illuminated by an evanescent wave. Evanescent waves occur when light is totally internally reflected at an interface of two dielectrics. Biomolecules that bind to the mologram diffract laser light into a diffraction-limited focal spot in three dimensional space, the focal point of the mologram. The intensity of the focused light correlates quadratically with the amount of bound molecules on the mologram and therefore also the number of biomolecular interactions that take place.
In complex biological samples, the concentration of off-target molecules is usually significantly higher than the target molecules. Therefore, even in the absence of recognition elements the off-target molecules readily adsorb to the surface of the sensor. However, this a random process and the off-target molecules do not bind to the ordered binding sites of the mologram. Thus, scattering of off-target molecules is uniform in all spatial directions and therefore off-target molecules hardly contribute to the measured light intensity in the narrow solid angle of the focal spot. In essence, focal molography forms a high-frequency spatial affinity lock-in that only measures the Fourier component of the refractive index distribution that corresponds to the binding modulation of the mologram. Since the environmental noise (temperature gradients, buffer changes and nonspecific binding of off-target molecules) is inversely proportional to the spatial frequency and therefore situated mostly at "long" spatial periods most of the noise can be rejected. This property makes molography extremely robust and renders temperature stabilization or sensor equilibration obsolete. | 1 | Applied and Interdisciplinary Chemistry |
Diphenylamine is used as a pre- or postharvest scald inhibitor for apples applied as an indoor drench treatment. Its anti-scald activity is the result of its antioxidant properties, which protect the apple skin from the oxidation products of α-farnesene during storage. Apple scald is physical injury that manifests in brown spots after fruit is removed from cold storage. | 0 | Theoretical and Fundamental Chemistry |
AEP was founded in the State of California in 1974 and held its first organization wide meeting of members in Palo Alto, California, on the Stanford University campus. At that meeting the first directors and officers were elected and by-laws adopted. From then on the board of directors has met quarterly to establish governance, coordinate legislative liaison and plan annual meeting. There are nine AEP chapters, covering the California geographical regions of: Channel Counties, Inland Empire, Los Angeles County, Monterey Bay-Silicon Valley, Orange County, San Diego, San Francisco Bay Area, Superior, and Central. | 1 | Applied and Interdisciplinary Chemistry |
In genetics, a transcription terminator is a section of nucleic acid sequence that marks the end of a gene or operon in genomic DNA during transcription. This sequence mediates transcriptional termination by providing signals in the newly synthesized transcript RNA that trigger processes which release the transcript RNA from the transcriptional complex. These processes include the direct interaction of the mRNA secondary structure with the complex and/or the indirect activities of recruited termination factors. Release of the transcriptional complex frees RNA polymerase and related transcriptional machinery to begin transcription of new mRNAs. | 1 | Applied and Interdisciplinary Chemistry |
Block copolymers comprise two or more homopolymer subunits linked by covalent bonds. The union of the homopolymer subunits may require an intermediate non-repeating subunit, known as a junction block. Diblock copolymers have two distinct blocks; triblock copolymers have three. Technically, a block is a portion of a macromolecule, comprising many units, that has at least one feature which is not present in the adjacent portions. A possible sequence of repeat units A and B in a triblock copolymer might be ~A-A-A-A-A-A-A-B-B-B-B-B-B-B-A-A-A-A-A~.
Block copolymers are made up of blocks of different polymerized monomers. For example, polystyrene-b-poly(methyl methacrylate) or PS-b-PMMA (where b = block) is usually made by first polymerizing styrene, and then subsequently polymerizing methyl methacrylate (MMA) from the reactive end of the polystyrene chains. This polymer is a "diblock copolymer" because it contains two different chemical blocks. Triblocks, tetrablocks, multiblocks, etc. can also be made. Diblock copolymers are made using living polymerization techniques, such as atom transfer free radical polymerization (ATRP), reversible addition fragmentation chain transfer (RAFT), ring-opening metathesis polymerization (ROMP), and living cationic or living anionic polymerizations. An emerging technique is chain shuttling polymerization.
The synthesis of block copolymers requires that both reactivity ratios are much larger than unity (r >> 1, r >> 1) under the reaction conditions, so that the terminal monomer unit of a growing chain tends to add a similar unit most of the time.
The "blockiness" of a copolymer is a measure of the adjacency of comonomers vs their statistical distribution. Many or even most synthetic polymers are in fact copolymers, containing about 1-20% of a minority monomer. In such cases, blockiness is undesirable. A block index has been proposed as a quantitative measure of blockiness or deviation from random monomer composition. | 0 | Theoretical and Fundamental Chemistry |
NBS is commercially available. It can also be synthesized in the laboratory. To do so, sodium hydroxide and bromine are added to an ice-water solution of succinimide. The NBS product precipitates and can be collected by filtration.
Crude NBS gives better yield in the Wohl–Ziegler reaction. In other cases, impure NBS (slightly yellow in color) may give unreliable results. It can be purified by recrystallization from 90 to 95 °C water (10 g of NBS for 100 mL of water). | 0 | Theoretical and Fundamental Chemistry |
One of the first DREADDs was based on the human M muscarinic receptor (hM). Only two point mutations of hM were required to achieve a mutant receptor with nanomolar potency for CNO, insensitivity to acetylcholine and low constitutive activity and this DREADD receptor was named hM3Dq. M and M muscarinic receptors have been mutated to create DREADDs hM1Dq and hM5Dq respectively.
The most commonly used inhibitory DREADD is hM4Di, derived from the M muscarinic receptor that couples with the G protein. Another G coupled human muscarinic receptor, M, was also mutated to obtain the DREADD receptor hM2D. Another inhibitory G-DREADD is the kappa-opioid-receptor (KOR) DREADD (KORD) which is selectively activated by salvinorin B (SalB).
G-coupled DREADDs have also been developed. These receptors are also known as GD and are chimeric receptors containing intracellular regions of the turkey erythrocyte β-adrenergic receptor substituted into the rat M DREADD. | 1 | Applied and Interdisciplinary Chemistry |
Ro-vibrational spectroscopy concerns molecules in the gas phase. There are sequences of quantized rotational levels associated with both the ground and excited vibrational states. The spectra are often resolved into lines due to transitions from one rotational level in the ground vibrational state to one rotational level in the vibrationally excited state. The lines corresponding to a given vibrational transition form a band.
In the simplest cases the part of the infrared spectrum involving vibrational transitions with the same rotational quantum number (ΔJ = 0) in ground and excited states is called the Q-branch. On the high frequency side of the Q-branch the energy of rotational transitions is added to the energy of the vibrational transition. This is known as the R-branch of the spectrum for ΔJ = +1. The P-branch for ΔJ = −1 lies on the low wavenumber side of the Q branch. The appearance of the R-branch is very similar to the appearance of the pure rotation spectrum (but shifted to much higher wavenumbers), and the P-branch appears as a nearly mirror image of the R-branch. The Q branch is sometimes missing because of transitions with no change in J being forbidden.
The appearance of rotational fine structure is determined by the symmetry of the molecular rotors which are classified, in the same way as for pure rotational spectroscopy, into linear molecules, spherical-, symmetric- and asymmetric- rotor classes. The quantum mechanical treatment of rotational fine structure is the same as for pure rotation.
The strength of an absorption line is related to the number of molecules with the initial values of the vibrational quantum number ν and the rotational quantum number , and depends on temperature. Since there are actually states with rotational quantum number , the population with value increases with initially, and then decays at higher . This gives the characteristic shape of the P and R branches.
A general convention is to label quantities that refer to the vibrational ground and excited states of a transition with double prime and single prime, respectively. For example, the rotational constant for the ground state is written as and that of the excited state as
Also, these constants are expressed in the molecular spectroscopist's units of cm. so that in this article corresponds to in the definition of rotational constant at Rigid rotor. | 0 | Theoretical and Fundamental Chemistry |
The ion is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a formal charge of −1. This charge results from a combination formal charge in which each of the three oxygens carries a − charge, whereas the nitrogen carries a +1 charge, all these adding up to formal charge of the polyatomic nitrate ion. This arrangement is commonly used as an example of resonance. Like the isoelectronic carbonate ion, the nitrate ion can be represented by resonance structures: | 0 | Theoretical and Fundamental Chemistry |
* Does not require extra computation to produce and optimize a set of loops.
* Can easily be adapted for optimization tasks. | 1 | Applied and Interdisciplinary Chemistry |
In metallurgy, recovery is a process by which a metal or alloys deformed grains can reduce their stored energy by the removal or rearrangement of defects in their crystal structure. These defects, primarily dislocations, are introduced by plastic deformation of the material and act to increase the yield strength of a material. Since recovery reduces the dislocation density, the process is normally accompanied by a reduction in a materials strength and a simultaneous increase in the ductility. As a result, recovery may be considered beneficial or detrimental depending on the circumstances.
Recovery is related to the similar processes of recrystallization and grain growth, each of them being stages of annealing. Recovery competes with recrystallization, as both are driven by the stored energy, but is also thought to be a necessary prerequisite for the nucleation of recrystallized grains. It is so called because there is a recovery of the electrical conductivity due to a reduction in dislocations. This creates defect-free channels, giving electrons an increased mean free path. | 1 | Applied and Interdisciplinary Chemistry |
The Lotka–Volterra equations describe dynamics of the predator-prey systems. The rate of predation upon the prey is assumed to be proportional to the rate at which the predators and the prey meet; this rate is evaluated as xy, where x is the number of prey, y is the number of predator. This is a typical example of the law of mass action. | 0 | Theoretical and Fundamental Chemistry |
Specific weight can be used in civil engineering and mechanical engineering to determine the weight of a structure designed to carry certain loads while remaining intact and remaining within limits regarding deformation. | 0 | Theoretical and Fundamental Chemistry |
In conventional DLTS the capacitance transients are investigated by using a lock-in amplifier or double box-car averaging technique when the sample temperature is slowly varied (usually in a range from liquid nitrogen temperature to room temperature 300 K or above). The equipment reference frequency is the voltage pulse repetition rate. In the conventional DLTS method this frequency multiplied by some constant (depending on the hardware used) is called the "rate window". During the temperature scan, peaks appear when the emission rate of carriers from some defect equals the rate window. By setting up different rate windows in subsequent DLTS spectra measurements one obtains different temperatures at which some particular peak appears. Having a set of the emission rate and corresponding temperature pairs one can make an Arrhenius plot, which allows for the deduction of defect activation energy for the thermal emission process. Usually this energy (sometimes called the defect energy level) together with the plot intercept value are defect parameters used for its identification or analysis. On samples with low free carrier density conductance transients have also been used for a DLTS analysis.
In addition to the conventional temperature scan DLTS, in which the temperature is swept while pulsing the device at a constant frequency, the temperature can be kept constant and sweep the pulsing frequency. This technique is called the frequency scan DLTS. In theory the frequency and temperature scan DLTS should yield same results. Frequency scan DLTS is specifically useful when an aggressive change in temperature might damage the device. An example when frequency scan is shown to be useful is for studying modern MOS devices with thin and sensitive gate oxides.
DLTS has been used to study quantum dots and perovskite solar cells. | 0 | Theoretical and Fundamental Chemistry |
Levonorgestrel is the generic name of the drug and its , , , , , and , while lévonorgestrel is its . It is also known as d-norgestrel, d(–)-norgestrel, or -norgestrel, as well as by its developmental code names WY-5104 (Wyeth) and SH-90999 (Schering AG). | 0 | Theoretical and Fundamental Chemistry |
Positive and negative controls should be run after preparation of each lot of medium.
Positive control: Klebsiella
Negative control: Escherichia coli | 0 | Theoretical and Fundamental Chemistry |
Chloroform reacts photochemically with oxygen to form chlorine, phosgene and hydrogen chloride. To slow this process and reduce the acidity of the solvent, chloroform-d is stored in brown-tinted bottles, often over copper chips or silver foil as stabilizer. Instead of metals, a small amount of a neutralizing base like potassium carbonate may be added. It is less toxic to the liver and kidneys than due to the presence of a bond which is stronger than a bond. The bond is stronger than a bond, making it somewhat less prone to form the destructive trichloromethyl radical (). | 0 | Theoretical and Fundamental Chemistry |
AllBusiness.com defines a limiting (constraining) factor as an "item that restricts or limits production or sale of a given product". The examples provided include: "limited machine hours and labor-hours and shortage of materials and skilled labor. Other limiting factors may be cubic feet of display or warehouse space, or working capital." The term is also frequently used in technology literature.
The analysis of limiting business factors is part of the program evaluation and review technique, critical path analysis, and theory of constraints as presented in the novel The Goal. | 0 | Theoretical and Fundamental Chemistry |
Complexometric titration (sometimes chelatometry) is a form of volumetric analysis in which the formation of a colored complex is used to indicate the end point of a titration. Complexometric titrations are particularly useful for the determination of a mixture of different metal ions in solution. An indicator capable of producing an unambiguous color change is usually used to detect the end-point of the titration. Complexometric titration are those reactions where a simple ion is transformed into a complex ion and the equivalence point is determined by using metal indicators or electrometrically. | 0 | Theoretical and Fundamental Chemistry |
The Liebermann reagent named after Hungarian chemist Leo Liebermann (1852-1926) is used as a simple spot-test to presumptively identify alkaloids as well as other compounds. It is composed of a mixture of potassium nitrite and concentrated sulfuric acid. 1 g of potassium nitrite is used for every 10 mL of sulfuric acid. Potassium nitrite may also be substituted by sodium nitrite. It is used to test for cocaine, morphine, PMA and PMMA.
The test is performed by scraping off a small amount of the substance and adding a drop of the reagent (which is initially clear and colorless). The results are analyzed by viewing the color of the resulting mixture, and by the time taken for the change in color to become apparent. | 0 | Theoretical and Fundamental Chemistry |
HIV-1 integration occurs through a multistep process that includes two catalytic reactions: 3´endonucleolytic processing of proviral DNA ends (termed 3´processing) and integration of 3´-processed viral DNA into cellular DNA (referred to as strand transfer). In 3´processing IN binds to a short sequence located at either end of the long terminal repeat (LTR) of the viral DNA and catalyzes endonucleotide cleavage. This results in elimination of a dinucleotide from each of the 3´ends of the LTR. Cleaved DNA is then used as a substrate for integration or strand transfer. Strand transfer is a trans-esterification reaction involving a direct nucleophilic attack of the 3´hydroxy group of the two newly processed viral 3´-DNA ends on the phosphodiester backbone of the host target DNA. This leads to covalent insertion of viral DNA into the genome of the infected cell. Strand transfer occurs simultaneously at both ends of the viral DNA molecule, with an offset of precisely five base pairs between the two opposite points of insertion. The integration reaction is completed by removal of unpaired dinucleotides from the 5- ends of the viral DNA, repair of the single-stranded gaps created between the viral and target DNA molecules and ligation of 3-ends to 5-ends of the host DNA. Divalent metals, Mg or Mn, are required for 3-processing and strand transfer steps as well as for assembly of IN onto specific viral donor DNA to form a complex that is competent to carry out either function. Because the abundance of magnesium (Mg) versus manganese (Mn ) in human cells is 1,000,000-fold, magnesium seems a more readily available divalent cofactor for integration. | 1 | Applied and Interdisciplinary Chemistry |
In a conjugated pi-system, electrons are able to capture certain photons as the electrons resonate along a certain distance of p-orbitals - similar to how a radio antenna detects photons along its length. Typically, the more conjugated (longer) the pi-system is, the longer the wavelength of photon can be captured. Compounds whose molecules contain a sufficient number of conjugated bonds can absorb light in the visible region, and therefore appear colorful to the eye, usually appearing yellow or red.
Many dyes make use of conjugated electron systems to absorb visible light, giving rise to strong colors. For example, the long conjugated hydrocarbon chain in beta-carotene leads to its strong orange color. When an electron in the system absorbs a photon of light of the right wavelength, it can be promoted to a higher energy level. A simple model of the energy levels is provided by the quantum-mechanical problem of a one-dimensional particle in a box of length L, representing the movement of a π electron along a long conjugated chain of carbon atoms. In this model the lowest possible absorption energy corresponds to the energy difference between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). For a chain of n C=C bonds or 2n carbon atoms in the molecular ground state, there are 2n π electrons occupying n molecular orbitals, so that the energy gap is
Since the box length L increases approximately linearly with the number of C=C bonds n, this means that the energy ΔE of a photon absorbed in the HOMO–LUMO transition is approximately proportional to 1/n. The photon wavelength λ = hc/ΔE is then approximately proportional to n. Although this model is very approximate, λ does in general increase with n (or L) for similar molecules. For example, the HOMO–LUMO absorption wavelengths for conjugated butadiene, hexatriene and octatetraene are 217 nm, 252 nm and 304 nm respectively. However, for good numerical agreement of the particle in a box model with experiment, the single-bond/double-bond bond length alternations of the polyenes must be taken into account. Alternatively, one can use the Hückel method which is also designed to model the electronic structure of conjugated systems.
Many electronic transitions in conjugated π-systems are from a predominantly bonding molecular orbital (MO) to a predominantly antibonding MO (π to π), but electrons from non-bonding lone pairs can also be promoted to a π-system MO (n to π) as often happens in charge-transfer complexes. A HOMO to LUMO transition is made by an electron if it is allowed by the selection rules for electromagnetic transitions. Conjugated systems of fewer than eight conjugated double bonds absorb only in the ultraviolet region and are colorless to the human eye. With every double bond added, the system absorbs photons of longer wavelength (and lower energy), and the compound ranges from yellow to red in color. Compounds that are blue or green typically do not rely on conjugated double bonds alone.
This absorption of light in the ultraviolet to visible spectrum can be quantified using ultraviolet–visible spectroscopy, and forms the basis for the entire field of photochemistry.
Conjugated systems that are widely used for synthetic pigments and dyes are diazo and azo compounds and phthalocyanine compounds. | 0 | Theoretical and Fundamental Chemistry |
Disturbing potential acid sulfate soils can have a destructive effect on plant and fish life, and on aquatic ecosystems. Flushing of acidic leachate to groundwater and surface waters can cause a number of impacts, including:
* Ecological damage to aquatic and riparian ecosystems through fish kills, increased fish disease outbreaks, dominance of acid-tolerant species, precipitation of iron, etc.
* Effects on estuarine fisheries and aquaculture projects (increased disease, loss of spawning area, etc.).
* Contamination of groundwater and surface water with arsenic, aluminium and other metals.
* Reduction in agricultural productivity through metal contamination of soils (predominantly by aluminium).
* Damage to infrastructure through the corrosion of concrete and steel pipes, bridges and other sub-surface assets. | 0 | Theoretical and Fundamental Chemistry |
What is claimed to be the world's first green roof botanical garden was set up in Augustenborg, Malmö in May 1999. The International Green Roof Institute (IGRI) opened to the public in April 2001 as a research station and educational facility. (It has since been renamed the Scandinavian Green Roof Institute (SGRI), in view of the increasing number of similar organisations around the world.) Green roofs are well-established in Malmö: the Augustenborg housing development near the SGRI botanical garden incorporates green roofs and extensive landscaping of streams, ponds, and soak-ways between the buildings to deal with storm water run-off.
The new Bo01 urban residential development (in the Västra Hamnen (Western Harbour) close to the foot of the Turning Torso office and apartment block, designed by Santiago Calatrava) is built on the site of old shipyards and industrial areas, and incorporates many green roofs.
In 2012, the shopping mall Emporia with its roof garden, was opened. The size of the roof garden is approximately equivalent to 4 soccer fields, which makes it one of the biggest green roof parks in Europe that is accessible to the public. | 1 | Applied and Interdisciplinary Chemistry |
Alkoxyaluminium and closely related hydride reagents reduce a wide variety of functional groups, often with good selectivity. This section, organized by functional group, covers the most common or synthetically useful methods for alkoxyaluminium hydride reduction of organic compounds.
Many selective reductions of carbonyl compounds can be effected by taking advantage of the unique reactivity profiles of metal alkoxylaluminium hydrides. For instance, lithium tri-tert-butoxy)aluminium hydride (LTBA) reduces aldehydes and ketones selectively in the presence of esters, with which it reacts extremely slowly.
α,β-Unsaturated ketones may be reduced selectively in a 1,2 or 1,4 sense by a judicious choice of reducing agent. Use of relatively unhindered lithium trimethoxyaluminium hydride results in nearly quantitative direct addition to the carbonyl group (Eq. ()). On the other hand, use of the bulky reagent LTBA leads to a high yield of the conjugate addition product (Eq. ()).
Ether cleavage is difficult to accomplish with most hydride reagents. However, debenzylation of benzyl aryl ethers may be accomplished with SMEAH. This protocol is a useful alternative to methods requiring acid or hydrogenolysis (e.g., Pd/C and hydrogen gas).
Epoxides are generally attacked by alkoxyaluminium hydrides at the less substituted position. A nearby hydroxyl group may facilitate intramolecular delivery of the hydride reagent, allowing for selective opening of 1,2-disubstituted epoxides at the position closer to the hydroxyl group. The configuration at the untouched epoxide carbon is preserved.
Unsaturated carbonyl compounds may be reduced either to saturated or unsaturated alcohols by alkoxyaluminium hydride reagents. Addition of an unsaturated aldehyde to a solution of Red-Al afforded the saturated alcohol; inverse addition yielded the unsaturated alcohol product.
Alkenes undergo hydroalumination in the presence of some alkoxyaluminium hydrides. In a related application, NaAlH(OCHCHOCH) (sodium bis(methoxyethoxy) aluminium dihydride, SMEAH or Red-Al) reacts with zirconocene dichloride to afford zirconocene chloride hydride (Schwartz's reagent). Alkenes undergo hydrozirconation in the presence of this reagent, affording functionalized products after quenching with an electrophile.
Functional groups containing heteroatoms other than oxygen may also be reduced to the corresponding hydrocarbons in the presence of an alkoxyaluminium hydride reagent. Primary alkyl halides undergo reduction to the corresponding alkanes in the presence of NaAlH(OH)(OCHCHOCH). Secondary halides are less reactive, but afford alkanes in reasonable yield.
Sulfoxides are reduced to the corresponding sulfides in good yield in the presence of SMEAH.
Imines are reduced by metal alkoxyaluminium hydrides to the corresponding amines. In the example below, use of the exo amine forms with high diastereoselectivity. The selectivity of hydride reduction in this case is higher than that of catalytic hydrogenation. | 0 | Theoretical and Fundamental Chemistry |
ACE inhibitors inhibit the actions of angiotensin converting enzyme (ACE), thereby lowering the production of angiotensin II and decreasing the breakdown of bradykinin. The decrease in angiotensin II results in relaxation of arteriole smooth muscle leading to a decrease in total peripheral resistance, reducing blood pressure as the blood is pumped through widened vessels. Its effect on bradykinin is responsible for the dry cough side effect.
Ramipril, a prodrug or precursor drug, is converted to the active metabolite ramiprilat by carboxylesterase 1. Ramiprilat is mostly excreted by the kidneys. Its half-life is variable (3–16 hours), and is prolonged by heart and liver failure, as well as kidney failure. Peak effect occurs between 3 and 6 hours after dosing, with approximately 50% of this effect retained after 24 hours. | 0 | Theoretical and Fundamental Chemistry |
A DNA-binding dye binds to all double-stranded (ds) DNA in PCR, increasing the fluorescence quantum yield of the dye. An increase in DNA product during PCR therefore leads to an increase in fluorescence intensity measured at each cycle. However, dsDNA dyes such as SYBR Green will bind to all dsDNA PCR products, including nonspecific PCR products (such as primer dimer). This can potentially interfere with, or prevent, accurate monitoring of the intended target sequence.
In real-time PCR with dsDNA dyes the reaction is prepared as usual, with the addition of fluorescent dsDNA dye. Then the reaction is run in a real-time PCR instrument, and after each cycle, the intensity of fluorescence is measured with a detector; the dye only fluoresces when bound to the dsDNA (i.e., the PCR product).
This method has the advantage of only needing a pair of primers to carry out the amplification, which keeps costs down; multiple target sequences can be monitored in a tube by using different types of dyes. | 1 | Applied and Interdisciplinary Chemistry |
Consider the interface as a curve for where is a free parameter. The free energy to be minimized is
with the constraints which we can write as and fixed volume .
The modified Lagrangian, taking into account the constraints is therefore
where are Lagrange multipliers. By definition, the momentum and the Hamiltonian which is computed to be:
Now, we recall that the boundary is free in the direction and is a free parameter. Therefore, we must have:
At the boundary and , therefore we recover the Young equation. | 0 | Theoretical and Fundamental Chemistry |
Green algae have been taken up by the euglenids, chlorarachniophytes, a lineage of dinoflagellates, and possibly the ancestor of the CASH lineage (cryptomonads, alveolates, stramenopiles and haptophytes) in three or four separate engulfments. Many green algal derived chloroplasts contain pyrenoids, but unlike chloroplasts in their green algal ancestors, storage product collects in granules outside the chloroplast. | 0 | Theoretical and Fundamental Chemistry |
For planar vessel, there is an exact solution. Here , then
If the transformations and , where is the maximum temperature which occurs at due to symmetry, are introduced
Integrating once and using the second boundary condition, the equation becomes
and integrating again
The above equation is the exact solution, but maximum temperature is unknown, but we have not used the boundary condition of the wall yet. Thus using the wall boundary condition at , the maximum temperature is obtained from an implicit expression,
Critical is obtained by finding the maximum point of the equation (see figure), i.e., at .
So the critical Frank-Kamentskii parameter is . The system has no steady state (or explodes) for and for , the system goes to a steady state with very slow reaction. | 1 | Applied and Interdisciplinary Chemistry |
OVERFLOW - the OVERset grid FLOW solver - is a software package for simulating fluid flow around solid bodies using computational fluid dynamics (CFD). It is a compressible 3-D flow solver that solves the time-dependent, Reynolds-averaged, Navier–Stokes equations using multiple overset structured grids. | 1 | Applied and Interdisciplinary Chemistry |
Once a nucleic acid sequence has been obtained from an organism, it is stored in silico in digital format. Digital genetic sequences may be stored in sequence databases, be analyzed (see Sequence analysis below), be digitally altered and be used as templates for creating new actual DNA using artificial gene synthesis. | 1 | Applied and Interdisciplinary Chemistry |
It can be seen in some studies that biodegradation accounts for the absence of creosote preservatives on the initial surface of the sediment. In a study from Pensacola, Florida, PAHs were not detected on the surface on the aquatic sediment, but the highest concentrations were detected at a depth of 8-13 centimeters. A form an anaerobic biodegradation of m-cresol was seen in a study using sulfate-reducing and nitrate-reducing enriched environments. The reduction of m-cresol in this study was seen in under 144 hours, while additional chemical intermediates were being formed. The chemical intermediates were formed in the presence of bicarbonate. The products included 4-hydroxy-2-methylbenzoic acid and acetate compounds. Although the conditions were enriched with the reducing anaerobic compounds, sulfate and nitrate reducing bacteria are commonly found in the environment. For further information, see sulfate-reducing bacteria. The type of anaerobic bacteria ultimately determines the reduction of the creosote preservative compounds, while each individual compound may only go through reduction under certain conditions. BTEX is a mixture of benzene, toluene, ethylbenzene, and xylene, that was studied in the presence of four different anaerobic-enriched sediments. Though the compound, BTEX, is not found in creosote preservatives, the products of creosote preservatives' oxidation-reduction reactions include some of these compounds. For oxidation-reduction reactions, see the following section. In this study, it was seen that certain compounds such as benzene were only reduced under sulfate-enriched environments, while toluene was reduced under a variety of bacteria-enriched environments, not just sulfate. The biodegradation of a creosote preservative in an anaerobic enrichment depends not only on the type of bacteria enriching the environment, but also the compound that has been released from the preservative. In aerobic environments, preservative compounds are limited in the biodegradation process by the presence of free oxygen. In an aerobic environment, free oxygen comes from oxygen saturated sediments, sources of precipitation, and plume edges. The free oxygen allows for the compounds to be oxidized and decomposed into new intermediate compounds. Studies have shown that when BTEX and PAH compounds were placed in aerobic environments, the oxidation of the ring structures caused cleavage in the aromatic ring and allowed for other functional groups to attach. When an aromatic hydrocarbon was introduced to the molecular oxygen in experimental conditions, a dihydrodiol intermediate was formed, and then oxidation occurred transforming the aromatic into a catechol compound. Catechol allows for cleavage of the aromatic ring to occur, where functional groups can then add in an ortho- or meta- position. | 0 | Theoretical and Fundamental Chemistry |
Kernel
* Component based architecture
* Dynamic loading of external plugins
* Interpolation and integration on arbitrary elements
* Transparent MPI parallelization
* Parallel writing and reading from solution files
* Support for XML case files
* Unstructured 2D/3D hybrid meshes in many formats
Numerical Methods
* Cell Center finite volume solver
* Residual distribution solver
* High order finite element solver
* Spectral Finite Volume solver
* Spectral Finite Difference solver
* Discontinuous Galerkin method solver
* Residual Distribution solver (dedicated to incompressible flow)
Physical Models
* Compressible Euler and Navier-Stokes Equations
** Perfect and Real Gas (from low Mach to hypersonic)
** Chemical reacting mixtures
** Thermal and Chemical non-equilibrium flows
* Incompressible Navier-Stokes
* Linearized Euler (for Aeroacoustics)
* Ideal Magnetohydrodynamics
* Structural Elasticity
* Multi-ion Electrochemistry
* Heat transfer
* Multiple Scalar Advection models | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, a phosphoric acid, in the general sense, is a phosphorus oxoacid in which each phosphorus (P) atom is in the oxidation state +5, and is bonded to four oxygen (O) atoms, one of them through a double bond, arranged as the corners of a tetrahedron. Two or more of these tetrahedra may be connected by shared single-bonded oxygens, forming linear or branched chains, cycles, or more complex structures. The single-bonded oxygen atoms that are not shared are completed with acidic hydrogen atoms. The general formula of a phosphoric acid is , where n is the number of phosphorus atoms and x is the number of fundamental cycles in the molecule's structure, between 0 and .
Removal of protons () from k hydroxyl groups –OH leaves anions generically called phosphates (if ) or hydrogen phosphates (if k is between 1 and ), with general formula . The fully dissociated anion () has formula . The term phosphate is also used in organic chemistry for the functional groups that result when one or more of the hydrogens are replaced by bonds to other groups.
These acids, together with their salts and esters, include some of the best-known compounds of phosphorus, of high importance in biochemistry, mineralogy, agriculture, pharmacy, chemical industry, and chemical research. | 0 | Theoretical and Fundamental Chemistry |
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