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Water vapor will only condense onto another surface when that surface is cooler than the dew point temperature, or when the water vapor equilibrium in air has been exceeded. When water vapor condenses onto a surface, a net warming occurs on that surface. The water molecule brings heat energy with it. In turn, the temperature of the atmosphere drops slightly. In the atmosphere, condensation produces clouds, fog and precipitation (usually only when facilitated by cloud condensation nuclei). The dew point of an air parcel is the temperature to which it must cool before water vapor in the air begins to condense. Condensation in the atmosphere forms cloud droplets.
Also, a net condensation of water vapor occurs on surfaces when the temperature of the surface is at or below the dew point temperature of the atmosphere. Deposition is a phase transition separate from condensation which leads to the direct formation of ice from water vapor. Frost and snow are examples of deposition.
There are several mechanisms of cooling by which condensation occurs:
1) Direct loss of heat by conduction or radiation.
2) Cooling from the drop in air pressure which occurs with uplift of air, also known as adiabatic cooling.
Air can be lifted by mountains, which deflect the air upward, by convection, and by cold and warm fronts.
3) Advective cooling - cooling due to horizontal movement of air. | 1 | Applied and Interdisciplinary Chemistry |
The prognosis is good for paracetamol overdoses if treatment is initiated up to 8 hours after the drug has been taken. Most hospitals stock the antidote (acetylcysteine), which replenishes the liver's supply of glutathione, allowing the NAPQI to be metabolized safely. Without early administration of the antidote, fulminant liver failure follows, often in combination with kidney failure, and death generally occurs within several days. | 1 | Applied and Interdisciplinary Chemistry |
Thermal decomposition of concrete produces water vapor and carbon dioxide, which may further react with the metals in the melt, oxidizing the metals, and reducing the gases to hydrogen and carbon monoxide. The decomposition of the concrete and volatilization of its alkali components is an endothermic process. Aerosols released during this phase are primarily based on concrete-originating silicon compounds; otherwise volatile elements, for example, caesium, can be bound in nonvolatile insoluble silicates.
Several reactions occur between the concrete and the corium melt. Free and chemically bound water is released from the concrete as steam. Calcium carbonate is decomposed, producing carbon dioxide and calcium oxide. Water and carbon dioxide penetrate the corium mass, exothermically oxidizing the non-oxidized metals present in the corium and producing gaseous hydrogen and carbon monoxide; large amounts of hydrogen can be produced. The calcium oxide, silica, and silicates melt and are mixed into the corium. The oxide phase, in which the nonvolatile fission products are concentrated, can stabilize at temperatures of for a considerable period of time. An eventually present layer of more dense molten metal, containing fewer radioisotopes (Ru, Tc, Pd, etc., initially composed of molten zircaloy, iron, chromium, nickel, manganese, silver, and other construction materials and metallic fission products and tellurium bound as zirconium telluride) than the oxide layer (which concentrates Sr, Ba, La, Sb, Sn, Nb, Mo, etc. and is initially composed primarily of zirconium dioxide and uranium dioxide, possibly with iron oxide and boron oxides), can form an interface between the oxides and the concrete farther below, slowing down the corium penetration and solidifying within a few hours. The oxide layer produces heat primarily by decay heat, while the principal heat source in the metal layer is exothermic reaction with the water released from the concrete. Decomposition of concrete and volatilization of the alkali metal compounds consumes a substantial amount of heat.
The fast erosion phase of the concrete basemat lasts for about an hour and progresses to about one meter in depth, then slows to several centimeters per hour, and stops completely when the melt cools below the decomposition temperature of concrete (about ). Complete melt-through can occur in several days even through several meters of concrete; the corium then penetrates several meters into the underlying soil, spreads around, cools and solidifies.
During the interaction between corium and concrete, very high temperatures can be achieved. Less volatile aerosols of Ba, Ce, La, Sr, and other fission products are formed during this phase and introduced into the containment building at a time when most of the early aerosols are already deposited. Tellurium is released with the progress of zirconium telluride decomposition. Bubbles of gas flowing through the melt promote aerosol formation.
The thermal hydraulics of corium-concrete interactions (CCI, or also MCCI, "molten core-concrete interactions") is sufficiently understood.
The dynamics of the movement of corium in and outside the reactor vessel is highly complex, however, and the number of possible scenarios is wide; slow drip of melt into an underlying water pool can result in complete quenching, while the fast contact of a large mass of corium with water may result in a destructive steam explosion. Corium may be completely retained by the reactor vessel, or the reactor floor or some of the instrument penetration holes can be melted through.
The thermal load of corium on the floor below the reactor vessel can be assessed by a grid of fiber optic sensors embedded in the concrete. Pure silica fibers are needed as they are more resistant to high radiation levels.
Some reactor building designs, for example, the EPR, incorporate dedicated corium spread areas (core catchers), where the melt can deposit without coming in contact with water and without excessive reaction with concrete.
Only later, when a crust is formed on the melt, limited amounts of water can be introduced to cool the mass.
Materials based on titanium dioxide and neodymium(III) oxide seem to be more resistant to corium than concrete.
Deposition of corium on the containment vessel inner surface, e.g. by high-pressure ejection from the reactor pressure vessel, can cause containment failure by direct containment heating (DCH). | 0 | Theoretical and Fundamental Chemistry |
[https://thebiogrid.org/ BioGRID] is an open public resource containing manually curated molecular interaction data. In addition to its extensive catalogue of genetic and protein interactions, BioGRID also curates chemical interactions including experimentally-determined [https://thebiogrid.org/chemsearch.php?chemSearch=Bivalent* PROTACs and PROTAC-related molecules] with accompanying [https://wiki.thebiogrid.org/doku.php/protac_curation target and E3 information]. Additional resources include [https://protacpedia.weizmann.ac.il/ptcb/main PROTACpedia], a manually curated and user-contributed PROTAC-specific public access database, and [https://hanlaboratory.com/E3Atlas/ E3 Atlas], a comprehensive E3 database that characterizes the potential for specific E3 ligases to be employed for PROTAC design. | 1 | Applied and Interdisciplinary Chemistry |
When measuring water treated with water softeners, high levels of total dissolved solids do not correlate to hard water, as water softeners do not reduce TDS; rather, they replace magnesium and calcium ions, which cause hard water, with an equal charge of sodium or potassium ions, e.g. Ca ⇌ 2 Na, leaving overall TDS unchanged or even increased. Hard water can cause scale buildup in pipes, valves, and filters, reducing performance and adding to system maintenance costs. These effects can be seen in aquariums, spas, swimming pools, and reverse osmosis water treatment systems. Typically, in these applications, total dissolved solids are tested frequently, and filtration membranes are checked in order to prevent adverse effects.
In the case of hydroponics and aquaculture, TDS is often monitored in order to create a water quality environment favorable for organism productivity. For freshwater oysters, trouts, and other high value seafood, highest productivity and economic returns are achieved by mimicking the TDS and pH levels of each species' native environment. For hydroponic uses, total dissolved solids is considered one of the best indices of nutrient availability for the aquatic plants being grown.
Because the threshold of acceptable aesthetic criteria for human drinking water is 500 mg/L, there is no general concern for odor, taste, and color at a level much lower than is required for harm. A number of studies have been conducted and indicate various species' reactions range from intolerance to outright toxicity due to elevated TDS. The numerical results must be interpreted cautiously, as true toxicity outcomes will relate to specific chemical constituents. Nevertheless, some numerical information is a useful guide to the nature of risks in exposing aquatic organisms or terrestrial animals to high TDS levels. Most aquatic ecosystems involving mixed fish fauna can tolerate TDS levels of 1000 mg/L.
The fathead minnow (Pimephales promelas), for example, realizes an concentration of 5600 ppm based upon a 96-hour exposure. LD50 is the concentration required to produce a lethal effect on 50 percent of the exposed population. Daphnia magna, a good example of a primary member of the food chain, is a small planktonic crustacean, about 0.5 mm in length, having an LD50 of about 10,000 ppm TDS for a 96-hour exposure.
Spawning fishes and juveniles appear to be more sensitive to high TDS levels. For example, it was found that concentrations of 350 mg/L TDS reduced spawning of Striped bass (Morone saxatilis) in the San Francisco Bay-Delta region, and that concentrations below 200 mg/L promoted even healthier spawning conditions. In the Truckee River, EPA found that juvenile Lahontan cutthroat trout were subject to higher mortality when exposed to thermal pollution stress combined with high total dissolved solids concentrations.
For terrestrial animals, poultry typically possess a safe upper limit of TDS exposure of approximately 2900 mg/L, whereas dairy cattle are measured to have a safe upper limit of about 7100 mg/L. Research has shown that exposure to TDS is compounded in toxicity when other stressors are present, such as abnormal pH, high turbidity, or reduced dissolved oxygen with the latter stressor acting only in the case of Animalia.
In countries with often-unsafe/unclean tap water supplies, the TDS of drinking water is often checked by technicians to gauge how effectively their RO/Water Filtration devices are working. While TDS readings will not give an answer as to the amount of microorganisms present in a sample of water, they can get a good idea as to the efficiency of the filter by how much TDS is present. | 1 | Applied and Interdisciplinary Chemistry |
The molecular composition of a biomaterial determines the physical and chemical properties of a biomaterial. These compositions create complex structures that allow the biomaterial to function, and therefore are necessary to define and understand in order to develop a biomaterial. biomaterials can be designed to replicate natural organisms, a process known as biomimetics. The structure of a biomaterial can be observed at different at different levels to better understand a materials properties and function. | 1 | Applied and Interdisciplinary Chemistry |
Geostandards and Geoanalytical Research is a quarterly peer-reviewed scientific journal covering reference materials, analytical techniques, and data quality relevant to the chemical analysis of geological and environmental samples. The journal was established in 1977 as Geostandards Newsletter and modified its title in 2004. The editors-in-chief are Thomas C. Meisel, Jacinta Enzweiler, Mary F. Horan, Kathryn L. Linge, Christophe R. Quétel and Paul J. Sylvester. It is published by Wiley-Blackwell on behalf of the International Association of Geoanalysts. The journal is a hybrid open-access journal, publishing both subscription and open access articles. | 0 | Theoretical and Fundamental Chemistry |
It has been stated that Elias James Corey, also a Nobel Prize winner, feels he is responsible for the ideas that laid the foundation for this research, and that Woodward unfairly neglected to credit him in the discovery. In a 2004 memoir published in the Journal of Organic Chemistry, Corey makes his claim to priority of the idea: "On May 4, 1964, I suggested to my colleague R. B. Woodward a simple explanation involving the symmetry of the perturbed (HOMO) molecular orbitals for the stereoselective cyclobutene to 1,3-butadiene and 1,3,5-hexatriene to cyclohexadiene conversions that provided the basis for the further development of these ideas into what became known as the Woodward–Hoffmann rules".
Corey, then 35, was working into the evening on Monday, May 4, as he and the other driven chemists often did. At about 8:30 p.m., he dropped by Woodward's office, and Woodward posed a question about how to predict the type of ring a chain of atoms would form. After some discussion, Corey proposed that the configuration of electrons governed the course of the reaction. Woodward insisted the solution would not work, but Corey left drawings in the office, sure that he was on to something.
"I felt that this was going to be a really interesting development and was looking forward to some sort of joint undertaking," he wrote. But the next day, Woodward flew into Coreys office as he and a colleague were leaving for lunch and presented Coreys idea as his own – and then left. Corey was stunned.
In a 2004 rebuttal published in the Angewandte Chemie, Roald Hoffmann denied the claim: he quotes Woodward from a lecture given in 1966 saying: "I REMEMBER very clearly—and it still surprises me somewhat—that the crucial flash of enlightenment came to me in algebraic, rather than in pictorial or geometric form. Out of the blue, it occurred to me that the coefficients of the terminal terms in the mathematical expression representing the highest occupied molecular orbital of butadiene were of opposite sign, while those of the corresponding expression for hexatriene possessed the same sign. From here it was but a short step to the geometric, and more obviously chemically relevant, view that in the internal cyclisation of a diene, the top face of one terminal atom should attack the bottom face of the other, while in the triene case, the formation of a new bond should involve the top (or pari passu, the bottom) faces of both terminal atoms."
In addition, Hoffmann points out that in two publications from 1963 and 1965, Corey described a total synthesis of the compound dihydrocostunolide. Although they describe an electrocyclic reaction, Corey has nothing to offer with respect to explaining the stereospecificity of the synthesis.
This photochemical reaction involving 6 = 4×1 + 2 electrons is now recognized as conrotatory. | 0 | Theoretical and Fundamental Chemistry |
A consequence of the toroidal geometry to the guiding-center orbits is that some particles can be reflected on the trajectory from the outboard side to the inboard side due to the presence of magnetic field gradients, similar to a magnetic mirror. The reflected particles cannot do a full turn in the poloidal plane and are trapped which follow the banana orbits.
This can be demonstrated by considering tokamak equilibria for low- and large aspect ratio which have nearly circular cross sections, where polar coordinates centered at the magnetic axis can be used with approximately describing the flux surfaces. The magnitude of the total magnetic field can be approximated by the following expression: indicates value at the magnetic axis , is the major radius, is the inverse aspect ratio, and is the magnetic field. The parallel component of the drift-ordered guiding-center orbits in this magnetic field, assuming no electric field, is given by:
where is the particle mass, is the velocity, and is the magnetic moment (first adiabatic invariant). The direction in the subscript indicates parallel or perpendicular to the magnetic filed. is the effective potential reflecting the conservation of kinetic energy .
The parallel trajectory experiences a mirror force where the particle moving into a magnetic field of increasing magnitude can be reflected by this force. If a magnetic field has a minimum along a field line, the particles in this region of weaker field can be trapped. This is indeed true given the form of we use. The particles are reflected (trapped particles) for sufficiently large or complete their poloidal turn (passing particles) otherwise.
To see this in detail, the maximum and minimum of the effective potential can be identified as and . The passing particles have and the trapped particles have . Recognising this and define a constant of motion , we have
* Passing:
* Trapped: | 1 | Applied and Interdisciplinary Chemistry |
The following limitations were acknowledged by Charles Hansen:
* The parameters will vary with temperature
* The parameters are an approximation. Bonding between molecules is more subtle than the three parameters suggest. Molecular shape is relevant, as are other types of bonding such as induced dipole, metallic and electrostatic interactions.
* The size of the molecules also plays a significant role in whether two molecules actually dissolve in a given period.
* The parameters are hard to measure.
* 2008 work by Abbott and Hansen has helped address some of the above issues. Temperature variations can be calculated, the role of molar volume ("kinetics versus thermodynamics") is clarified, new chromatographic ways to measure HSP are available, large datasets for chemicals and polymers are available, Sphere software for determining HSP values of polymers, inks, quantum dots etc. is available (or easy to implement in one's own software) and the new Stefanis-Panayiotou method for estimating HSP from Unifac groups is available in the literature and also automated in software. All these new capabilities are described in the e-book, software, datasets described in the external links but can be implemented independently of any commercial package.
* Sometimes Hildebrand solubility parameters are used for similar purposes. Hildebrand parameters are not suitable for use outside their original area which was non-polar, non-hydrogen-bonding solvents. The Hildebrand parameter for such non-polar solvents is usually close to the Hansen value. A typical example showing why Hildebrand parameters can be unhelpful is that two solvents, butanol and nitroethane, which have the same Hildebrand parameter, are each incapable of dissolving typical epoxy polymers. Yet a 50:50 mix gives a good solvency for epoxies. This is easily explainable knowing the Hansen parameter of the two solvents and that the Hansen parameter for the 50:50 mix is close to the Hansen parameter of epoxies. | 0 | Theoretical and Fundamental Chemistry |
The Elementary Osmotic Pump (EOP) was developed by ALZA in 1974, and was the first practical example of an osmotic pump based drug release system for oral use. It was introduced to the market in the early 1980s in Osmosin (indomethacin) and Acutrim (phenylpropanolamine), but unexpectedly severe issues with GI irritation and cases of GI perforation led to the withdrawal of Osmosin.
Merck & Co. later developed the Controlled-Porosity Osmotic Pump (CPOP) with the intention of addressing some of the issues that led to Osmosins withdrawal via a new approach to the final stage of the release mechanism. Unlike the EOP, the CPOP had no pre-formed hole in the outer shell for the drug to be expelled out of. Instead, the CPOPs semipermeable membrane was designed to form numerous small pores upon contact with water through which the drug would be expelled via osmotic pressure. The pores were formed via the use of a pH insensitive leachable or dissolvable additive such as sorbitol. | 1 | Applied and Interdisciplinary Chemistry |
Magnesium is the most abundant free cation in plant cytosol, is the central atom in chlorophyll and offers itself as a bridging ion for the aggregation of ribosomes in plants. Even small changes in the concentration of magnesium in plant cytosol or chloroplasts can drastically affect the key enzymes present in the chloroplasts. It is most commonly used as a co-factor in eukaryotes and functions as an important functional key in enzymes like RNA Polymerase and ATPase. In phosphorylating enzymes like ATPase or kinases and phosphates, magnesium acts as a stabilizing ion in polyphosphate compounds due its Lewis acidity. Magnesium has also been noted as a possible secondary messenger for neural transmissions. Magnesium acts as an allosteric inhibitor for the enzyme vacuolar pyrophosphatase (V-PPase). In vitro, the concentration of free magnesium acts as a strict regulator and stabilizer for the enzyme activity of V-PPase. | 1 | Applied and Interdisciplinary Chemistry |
There are many metrics used for hit selection in primary screens without replicates.
The easily interpretable ones are fold change, mean difference, percent inhibition, and percent activity. However, the drawback common to all of these metrics is that they do not capture data variability effectively. To address this issue, researchers then turned to the z-score method or SSMD, which can capture data variability in negative references.
The z-score method is based on the assumption that the measured values (usually fluorescent intensity in log scale) of all investigated compounds in a plate have a normal distribution. SSMD also works the best under the normality assumption. However, true hits with large effects should behave very different from the majority of the compounds and thus are outliers. Strong assay artifacts may also behave as outliers. Thus, outliers are not uncommon in HTS experiments. The regular versions of z-score and SSMD are sensitive to outliers and can be problematic. Consequently, robust methods such as the z*-score method, SSMD*, B-score method, and quantile-based method have been proposed and adopted for hit selection in primary screens without replicates.
In a primary screen without replicates, every compound is measured only once. Consequently, we cannot directly estimate the data variability for each compound. Instead, we indirectly estimate data variability by making a strong assumption that every compound has the same variability as a negative reference in a plate in the screen. The z-score, z*-score and B-score relies on this strong assumption; so are the SSMD and SSMD* for cases without replicates. | 1 | Applied and Interdisciplinary Chemistry |
While the sequence that constitutes the 3′-UTR contributes greatly to gene expression, the structural characteristics of the 3′-UTR also play a large role. In general, longer 3′-UTRs correspond to lower expression rates since they often contain more miRNA and protein binding sites that are involved in inhibiting translation. Human transcripts possess 3′-UTRs that are on average twice as long as other mammalian 3′-UTRs. This trend reflects the high level of complexity involved in human gene regulation. In addition to length, the secondary structure of the 3′-untranslated region also has regulatory functions. Protein factors can either aid or disrupt folding of the region into various secondary structures. The most common structure is a stem-loop, which provides a scaffold for RNA binding proteins and non-coding RNAs that influence expression of the transcript. | 1 | Applied and Interdisciplinary Chemistry |
In South Africa, the terms "bobbejaan spanner" and "baboon spanner" are commonly used, especially for large pipe wrenches. Bobbejaan is the Afrikaans term for a baboon.
In Spain and Morocco, they are called grifa.
In Mexico they are known and called "stillson" without even using the word llave ("wrench").
In Turkey they are known as "English Keys". | 1 | Applied and Interdisciplinary Chemistry |
UnitVelo is a statistical framework of RNA velocity that models the dynamics of spliced and unspliced RNAs via flexible transcription activities. UnitVelo supports the inference of a unified latent time across the transcriptome. | 1 | Applied and Interdisciplinary Chemistry |
In plasma physics, the distribution function for a particle species , , takes the place of the probability density function. The corresponding Boltzmann equation is given by
where the third term includes the particle acceleration due to the Lorentz force and the Fokker–Planck term at the right-hand side represents the effects of particle collisions. The quantities and are the average change in velocity a particle of type experiences due to collisions with all other particle species in unit time. Expressions for these quantities are given elsewhere. If collisions are ignored, the Boltzmann equation reduces to the Vlasov equation. | 1 | Applied and Interdisciplinary Chemistry |
A linear biochemical pathway is a chain of enzyme-catalyzed reaction steps where the product of one reaction becomes the substrate for the next reaction. The molecules progress through the pathway sequentially from the starting substrate to the final product. Each step in the pathway is usually facilitated by a different specific enzyme that catalyzes the chemical transformation. An example includes DNA replication, which connects the starting substrate and the end product in a straightforward sequence.
Biological cells consume nutrients to sustain life. These nutrients are broken down to smaller molecules. Some of the molecules are used in the cells for various biological functions, and others are reassembled into more complex structures required for life. The breakdown and reassembly of nutrients is called metabolism. An individual cell will contain thousands of different kinds of small molecules, such as sugars, lipids, and amino acids. The interconversion of these molecules is carried out by catalysts called enzymes. For example, E. coli contains 2,338 metabolic enzymes. These enzymes form a complex web of reactions forming pathways by which nutrients are converted.
The figure below shows a four step pathway, with intermediates, and . To sustain a steady-state, the boundary species and are fixed. Each step is catalyzed by an enzyme, .
Linear pathways follow a step-by-step sequence, where each enzymatic reaction results in the transformation of a substrate into an intermediate product. This intermediate is processed by subsequent enzymes until the final product is synthesized.
A linear pathway can be studied in various ways. Multiple computer simulations can be run to try to understand the pathway's behavior. Another way to understand the properties of a linear pathway is to take a more analytical approach. Analytical solutions can be derived for the steady-state if simple mass-action kinetics are assumed. Analytical solutions for the steady-state when assuming Michaelis-Menten kinetics can be obtained but are quite often avoided. Instead, such models are linearized. The three approaches that are usually used are therefore:
* Computer simulation
* Analytical solutions using a linear mathematical model
* Linearization of a non-linear model | 1 | Applied and Interdisciplinary Chemistry |
Pitting corrosion is defined by localized attack, ranging from microns to millimeters in diameter, in an otherwise passive surface and only occurs for specific alloy and environmental combinations. Thus, this type of corrosion typically occurs in alloys that are protected by a tenacious (passivating) oxide film such as stainless steels, nickel alloys, aluminum alloys in environments that contain an aggressive species such as chlorides (Cl) or thiosulfates (SO). In contrast, alloy/environment combinations where the passive film is not very protective usually will not produce pitting corrosion. A good example of the importance of alloy/environment combinations is carbon steel. In environments where the pH value is lower than 10, carbon steel does not form a passivating oxide film and the addition of chloride results in uniform attack over the entire surface. However, at pH greater than 10 (alkaline) the oxide is protective and the addition of chloride results in pitting corrosion.
Besides chlorides, other anions implicated in pitting include thiosulfates (SO), fluorides and iodides. Stagnant water conditions with low concentrations of dissolved oxygen also favor pitting. Thiosulfates are particularly aggressive species and are formed by partial oxidation of pyrite (pyrite|, a ferrous disulfide), or partial sulfate reduction by microorganisms, a.o. by sulfate reducing bacteria (SRB). Thiosulfates are a concern for corrosion in many industries handling sulfur-derived compounds: sulfide ores processing, oil wells and pipelines transporting soured oils, kraft paper production plants, photographic industry, methionine and lysine factories. | 1 | Applied and Interdisciplinary Chemistry |
Studies of individual transcripts were being performed several decades before any transcriptomics approaches were available. Libraries of silkmoth mRNA transcripts were collected and converted to complementary DNA (cDNA) for storage using reverse transcriptase in the late 1970s. In the 1980s, low-throughput sequencing using the Sanger method was used to sequence random transcripts, producing expressed sequence tags (ESTs). The Sanger method of sequencing was predominant until the advent of high-throughput methods such as sequencing by synthesis (Solexa/Illumina). ESTs came to prominence during the 1990s as an efficient method to determine the gene content of an organism without sequencing the entire genome. Amounts of individual transcripts were quantified using Northern blotting, nylon membrane arrays, and later reverse transcriptase quantitative PCR (RT-qPCR) methods, but these methods are laborious and can only capture a tiny subsection of a transcriptome. Consequently, the manner in which a transcriptome as a whole is expressed and regulated remained unknown until higher-throughput techniques were developed. | 1 | Applied and Interdisciplinary Chemistry |
Scientists have devised a large number of nanowire compositions with controlled length, diameter, doping, and surface structure by using vapor and solution phase strategies. These oriented single crystals are being used in semiconductor nanowire devices such as diodes, transistors, logic circuits, lasers, and sensors. Since nanowires have a one-dimensional structure, meaning a large surface-to-volume ratio, the diffusion resistance decreases. In addition, their efficiency in electron transport which is due to the quantum confinement effect, makes their electrical properties be influenced by minor perturbation. Therefore, the use of these nanowires in nanosensor elements increases the sensitivity in electrode response. As mentioned above, the one-dimensionality and chemical flexibility of the semiconductor nanowires make them applicable in nanolasers. Peidong Yang and his co-workers have done some research on the room-temperature ultraviolet nanowires used in nanolasers. They have concluded that using short wavelength nanolasers has applications in different fields such as optical computing, information storage, and microanalysis. | 0 | Theoretical and Fundamental Chemistry |
In chemical kinetics, the pre-exponential factor or A factor is the pre-exponential constant in the Arrhenius equation (equation shown below), an empirical relationship between temperature and rate coefficient. It is usually designated by A when determined from experiment, while Z is usually left for collision frequency. The pre-exponential factor can be thought of as a measure of the frequency of properly oriented collisions. It is typically determined experimentally by measuring the rate constant at a particular temperature and fitting the data to the Arrhenius equation. The pre-exponential factor is generally not exactly constant, but rather depends on the specific reaction being studied and the temperature at which the reaction is occurring.
The units of the pre-exponential factor A are identical to those of the rate constant and will vary depending on the order of the reaction. For a first-order reaction, it has units of s. For that reason, it is often called frequency factor.
According to collision theory, the frequency factor, A, depends on how often molecules collide when all concentrations are 1 mol/L and on whether the molecules are properly oriented when they collide. Values of A for some reactions can be found at Collision theory.
According to transition state theory, A can be expressed in terms of the entropy of activation of the reaction. | 0 | Theoretical and Fundamental Chemistry |
Cementation is a type of precipitation, a heterogeneous process in which ions are reduced to zero valence at a solid metallic interface. The process is often used to refine leach solutions.
Cementation of copper is a common example. Copper ions in solution, often from an ore leaching process, are precipitated out of solution in the presence of solid iron. The iron oxidizes, and the copper ions are reduced through the transfer of electrons. The reaction is spontaneous because copper is higher on the galvanic series than iron.
: Cu(aq) + Fe(s) → Cu(s) + Fe(aq)
This was a historically useful process for the production of copper, where the precipitated solid copper metal was recovered as flakes or powder on the surface of scrap iron.
Cementation is used industrially to recover a variety of heavy metals including cadmium, and the cementation of gold by zinc in the Merrill-Crowe process accounts for a substantial fraction of world gold production. | 1 | Applied and Interdisciplinary Chemistry |
Diphosphines are also available in primary, secondary, and tertiary phosphorus substituents. Triphosphines etc. are similar. | 0 | Theoretical and Fundamental Chemistry |
In contrast to the other components of breast milk that are absorbed by the infant through breastfeeding, HMOs are indigestible for the nursing child. However, they have a prebiotic effect and serve as food for intestinal bacteria, especially bifidobacteria. The dominance of these intestinal bacteria in the gut reduces the colonization with pathogenic bacteria (probiosis) and thereby promotes a healthy intestinal microbiota and reduces the risk of dangerous intestinal infections. Recent studies suggest that HMOs significantly lower the risk of viral and bacterial infections and thus diminish the chance of diarrhoea and respiratory diseases.
This protective function of the HMOs is activated when in contact with specific pathogens, such as certain bacteria or viruses. These have the ability to bind themselves to the glycan receptors (receptors for long chains of connected sugar molecules on the surface of human cells) located on the surface of the intestinal cells and can thereby infect the cells of the intestinal mucosa. Researchers have discovered that HMOs mimic these glycan receptors so the pathogens bind themselves to the HMOs rather than the intestinal cells. This reduces the risk of an infection with a pathogen. It has also been demonstrated that HMOs can bind to several intestinal viruses, such as norovirus and Norwalk virus, moreover they can reduce the virus load from influenza and RSV.
In addition to this, HMOs seem to influence the reaction of specific cells of the immune system in a way that reduces inflammatory responses. It is also suspected that HMOs reduce the risk of premature infants becoming infected with the potentially life-threatening disease necrotizing enterocolitis (NEC).
Some of the metabolites directly affect the nervous system or the brain and can sometimes influence the development and behavior of children in the long term. There are studies that indicate certain HMOs supply the child with sialic acid residues. Sialic acid is an essential nutrient for the development of the child’s brain and mental abilities.
In experiments designed to test the suitability of HMOs as a prebiotic source of carbon for intestinal bacteria it was discovered that they are highly selective for a commensal bacteria known as Bifidobacteria longum biovar infantis. The presence of genes unique to B. infantis, including co-regulated glycosidases, and its efficiency at using HMOs as a carbon source may imply a co-evolution of HMOs and the genetic capability of select bacteria to utilize them. | 0 | Theoretical and Fundamental Chemistry |
The Hiyama–Denmark coupling is the modification of the Hiyama coupling that does not require a fluoride additive to utilize organosilanols and organic halides as coupling partners. The general reaction scheme is shown below, showcasing the utilization of a Brønsted base as the activating agent as opposed to fluoride, phosphine ligands are also used on the metal center.
A specific example of this reaction is shown with reagents. If fluoride had been used, as in the original Hiyama protocol, the tert-butyldimethylsilyl (TBS) ether would have likely been destroyed. | 0 | Theoretical and Fundamental Chemistry |
The equation describing the fluorescence as a function of time is particularly simple in another limit. If a large number of proteins bind to sites in a small volume such that there the fluorescence signal is dominated by the signal from bound proteins, and if this binding is all in a single state with an off rate k, then the fluorescence as a function of time is given by
Note that the recovery depends on the rate constant for unbinding, k, only. It does not depend on the on rate for binding. Although it does depend on a number of assumptions
#The on rate must be sufficiently large in order for the local concentration of bound protein to greatly exceed the local concentration of free protein, and so allow us to neglect the contribution to f of the free protein.
#The reaction is a simple bimolecular reaction, where the protein binds to localised sites that do not move significantly during recovery
#Exchange is much slower than diffusion (or whatever transport mechanism is responsible for mobility), as only then does the diffusing fraction recovery rapidly and then acts as the source of fluorescent protein that binds and replaces the bound bleached protein and so increases the fluorescence. With r the radius of the bleached spot, this means that the equation is only valid if the bound lifetime .
If all these assumptions are satisfied, then fitting an exponential to the recovery curve will give the off rate constant, k. However, other dynamics can give recovery curves similar to exponentials, so fitting an exponential does not necessarily imply that recovery is dominated by a simple bimolecular reaction. One way to distinguish between recovery with a rate determined by unbinding and recovery that is limited by diffusion, is to note that the recovery rate for unbinding-limited recovery is independent of the size of the bleached area r, while it scales as , for diffusion-limited recovery. Thus if a small and a large area are bleached, if recovery is limited by unbinding then the recovery rates will be the same for the two sizes of bleached area, whereas if recovery is limited by diffusion then it will be much slower for the larger bleached area. | 1 | Applied and Interdisciplinary Chemistry |
Low-speed rear-stage turbining occurs with excessive negative incidence leading to a pressure ratio less than one and the compressor stage absorbing power from the airflow.
Two examples where crossing the surge line prevented accelerating to high speed occurred with the first designs of the Rolls-Royce Avon and the IAE V2500 and required major compressor redesigns. Rotating stall at low corrected speeds caused blade failures on early axial compressors. | 0 | Theoretical and Fundamental Chemistry |
The sulfonyl functional group (RS(O)R') has become an important electron-withdrawing group for modern organic chemistry. α-Sulfonyl carbanions may be used as nucleophiles in alkylation reactions, Michael-type additions, and other processes. After having served their synthetic purpose, sulfonyl groups are often removed. In the presence of certain reducing agents, one of the sulfur-carbon bonds of the sulfonyl group is cleaved, leading to sulfur-free organic products. Depending on the nature of the substrate and reaction conditions, alkyl sulfones afford either the corresponding alkanes or olefins (the Julia olefination). Reductive desulfonylation is typically accomplished with active metals or salts (sodium amalgam, aluminium amalgam, magnesium, samarium(II) iodide), tin hydrides (tributyltin hydride), or transition metal complexes with reducing agents or nucleophiles (PdCl(dppp)/LiHBEt, Pd(PPh)/LiHBEt, Pd(PPh)/NaHC(COEt)). Alkyl, alkenyl, and allylic sulfones may be reduced using one or more of these methods. | 0 | Theoretical and Fundamental Chemistry |
It has been demonstrated by Cummins and coworkers that thermolysis of compounds of the general form CHPC(=PPh)R leads to the extrusion of CH (anthracene), triphenylphosphine, and the corresponding substituted phosphaacetylene: R-C≡P. Unlike the previous method, which derives the phosphaalkyne substituent from an acyl chloride, this method derives the substituent from a Wittig reagent. | 0 | Theoretical and Fundamental Chemistry |
The International Union of Pure and Applied Chemistry (IUPAC) recommends the use of numeric prefixes to indicate the position of substituents, generally by identifying the parent hydrocarbon chain and assigning the carbon atoms based on their substituents in order of precedence. For example, there are at least two isomers of the linear form of pentanone, a ketone that contains a chain of exactly five carbon atoms. There is an oxygen atom bonded to one of the middle three carbons (if it were bonded to an end carbon, the molecule would be an aldehyde, not a ketone), but it is not clear where it is located.
In this example, the carbon atoms are numbered from one to five, which starts at one end and proceeds sequentially along the chain. Now the position of the oxygen atom can be defined as on carbon atom number two, three or four. However, atoms two and four are exactly equivalent - which can be shown by turning the molecule around by 180 degrees.
The locant is the number of the carbon atom to which the oxygen atom is bonded. If the oxygen is bonded to the middle carbon, the locant is 3. If the oxygen is bonded to an atom on either side (adjacent to an end carbon), the locant is 2 or 4; given the choice here, where the carbons are exactly equivalent, the lower number is always chosen. So the locant is either 2 or 3 in this molecule.
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The locant is incorporated into the name of the molecule to remove ambiguity. Thus the molecule is named either pentan-2-one or pentan-3-one, depending on the position of the oxygen atom.
Any side chains can be present in the place of oxygen and it can be defined as simply the number on the carbon to which any thing other than a hydrogen is attached. | 0 | Theoretical and Fundamental Chemistry |
Operando spectroscopy is widely applicable to heterogeneous catalysis, which is largely used in industrial chemistry.
An example of operando methodology to monitor heterogeneous catalysis is the dehydrogenation of propane with molybdenum catalysts commonly used in industrial petroleum. Mo/SiO and Mo/AlO were studied with an operando setup involving EPR/UV-Vis, NMR/UV-Vis, and Raman. The study examined the solid molybdenum catalyst in real time. It was determined that the molybdenum catalyst exhibited propane dehydrogenation activity, but deactivated over time. The spectroscopic data showed that the most likely catalytic active state was in the production of propene. The deactivation of the catalyst was determined to be the result of coke formation and the irreversible formation of crystals, which were difficult to reduce back to . The dehydrogenation of propane can also be achieved with chromium catalysts, through the reduction of to . Propylene is one of the most important organic starting materials is used globally, particularly in the synthesis of various plastics. Therefore, the development of effective catalysts to produce propylene is of great interest. Operando spectroscopy is of great value to the further research and development of such catalysts. | 0 | Theoretical and Fundamental Chemistry |
Though his birth was not registered until 1918, Frederick Kenneth McTaggart (known as Ken) was born on 30 November 1917 at Elsternwick, to Victorian Railways industrial chemist Cyril (1881 – 1966), and teacher Hilda Theresa McTaggart (née Daniel, 1882 – 1966), and his sole sibling was an older sister, Jean.
Due to childhood illness his primary education started late; aged eight he entered Grade 4 at Ormond State School, then he was educated from age 13 at Melbourne Boys High School 1931–1936. He joined a school debating team, and the orchestra, of which he was leader in 1934, and was elected a prefect in 1935. He was a ham radio enthusiast, and in his 3rd year at the school was involved in the Wireless Club, of which he became vice-president, and built his own set, the MHS Twin, when in 1934 he was issued an Amateur Radio Licence,. It was an interest that he continued into adulthood and one he maintained throughout his life.
Aged 18 he commenced a Bachelor of Science in Chemistry at Melbourne University and in April 1939 was conferred Bachelor of Science in Wilson Hall, when he had already commenced a Master of Science with John Stuart Anderson working on the separation of hydrogen fluoride and zirconium for which he received 1st Class Honours in 1940. A Doctor of Science was conferred on him in 1965 by Melbourne University in recognition of his work on the chemistry of titanium and zirconium, and on reactions in low pressure discharges. | 0 | Theoretical and Fundamental Chemistry |
Solutions of simple aldehydes in alcohols mainly consist of the hemiacetal. The equilibrium is easily reversed and dynamic. The equilibrium is sensitive to steric effects. | 0 | Theoretical and Fundamental Chemistry |
Yield equilibration of strangeness yield in QGP is only possible due to a new process, gluon fusion, as shown by Rafelski and Müller. The top section of the Feynman diagrams figure, shows the new gluon fusion processes: gluons are the wavy lines; strange quarks are the solid lines; time runs from left to right. The bottom section is the process where the heavier quark pair arises from the lighter pair of quarks shown as dashed lines. The gluon fusion process occurs almost ten times faster than the quark-based strangeness process, and allows achievement of the high thermal yield where the quark based process would fail to do so during the duration of the "micro-bang".
The ratio of newly produced pairs with the normalized light quark pairs —the Wroblewski ratio—is considered a measure of efficacy of strangeness production. This ratio more than doubles in heavy ion collisions, providing a model independent confirmation of a new mechanism of strangeness production operating in collisions that are producing QGP.
Regarding charm and bottom flavour: the gluon collisions here are occurring within the thermal matter phase and thus are different from the high energy processes that can ensue in the early stages of the collisions when the nuclei crash into each other. The heavier, charm and bottom quarks are produced there dominantly. The study in relativistic nuclear (heavy ion) collisions of charmed and soon also bottom hadronic particle production—beside strangeness—will provide complementary and important confirmation of the mechanisms of formation, evolution and hadronization of quark–gluon plasma in the laboratory. | 0 | Theoretical and Fundamental Chemistry |
The etiology of hyperthecosis is unknown, however evidence suggests a possibility of genetic transmission. Hyperthecosis has been documented in familiar patterns. Insulin resistance may also play a role in the pathogenesis of hyperthecosis. Women with hyperthecosis have a significant degree of insulin resistance and insulin may stimulate the ovarian stromal androgen synthesis. | 1 | Applied and Interdisciplinary Chemistry |
Suppose the concentration of glutamine in an unknown sample needs to be measured. To do so, a series of standard solutions containing glutamine is prepared to create a calibration curve. A table summarizing a method for creating these solutions is shown below:
Here, a stock solution of glutamine is added in increasing increments with a high-accuracy instrument, such as a volumetric pipette, and diluted to the same volume in volumetric flasks. The resulting concentration is calculated using the formula for molar concentration. The result is 4 standard solutions with varying known concentrations plus a blank for instrument calibration. | 0 | Theoretical and Fundamental Chemistry |
In spectroscopy, bathochromic shift (; hence less common alternate spelling "bathychromic") is a change of spectral band position in the absorption, reflectance, transmittance, or emission spectrum of a molecule to a longer wavelength (lower frequency). Because the red color in the visible spectrum has a longer wavelength than most other colors, the effect is also commonly called a red shift.
Hypsochromic shift is a change to shorter wavelength (higher frequency). | 0 | Theoretical and Fundamental Chemistry |
A mutation in this gene has been associated with hyperimmunoglobulin E syndrome (HIES), a primary immunodeficiency characterized by elevated serum immunoglobulin E.
TYK2 appears to play a central role in the inflammatory cascade responses in the pathogenesis of immune-mediated inflammatory diseases such as psoriasis. The drug deucravacitinib (marketed as Sotyktu), a small-molecule TYK2 inhibitor, was approved for moderate-to-severe plaque psoriasis in 2022.
The P1104A allele of TYK2 has been shown to increase risk of tuberculosis when carried as a homozygote; population genetic analyses suggest that the arrival of tuberculosis in Europe drove the frequency of that allele down three-fold about 2,000 years before present. | 1 | Applied and Interdisciplinary Chemistry |
The above problem raises the question for α > 1: if a Bose gas with a fixed number of particles is lowered down below the critical temperature, what happens?
The problem here is that the Thomas–Fermi approximation has set the degeneracy of the ground state to zero, which is wrong. There is no ground state to accept the condensate and so particles simply disappear from the continuum of states. It turns out, however, that the macroscopic equation gives an accurate estimate of the number of particles in the excited states, and it is not a bad approximation to simply "tack on" a ground state term to accept the particles that fall out of the continuum:
where N is the number of particles in the ground state condensate.
Thus in the macroscopic limit, when T , the value of z is pinned to 1 and N takes up the remainder of particles. For T > T there is the normal behaviour, with N = 0. This approach gives the fraction of condensed particles in the macroscopic limit: | 0 | Theoretical and Fundamental Chemistry |
Atoms and molecules of gas or liquid can be trapped on a solid surface in a process called adsorption. This is an exothermic process involving a release of heat, and heating the surface increases the probability that an atom will escape within a given time. At a given temperature , the residence time of an adsorbed atom is given by
where is the gas constant, is an activation energy, and is a prefactor that is correlated with the vibration times of the surface atoms (generally of the order of seconds).
In vacuum technology, the residence time of gases on the surfaces of a vacuum chamber can determine the pressure due to outgassing. If the chamber can be heated, the above equation shows that the gases can be "baked out"; but if not, then surfaces with a low residence time are needed to achieve ultra-high vacuums. | 0 | Theoretical and Fundamental Chemistry |
If no bulk flow occurs in an element of length dx, the rates of diffusion of two ideal gases (of similar molar volume) A and B must be equal and opposite, that is .
The partial pressure of A changes by dP over the distance dx. Similarly, the partial pressure of B changes dP. As there is no difference in total pressure across the element (no bulk flow), we have
For an ideal gas the partial pressure is related to the molar concentration by the relation
where n is the number of moles of gas A in a volume V. As the molar concentration C is equal to n/ V therefore
Consequently, for gas A,
where D is the diffusivity of A in B. Similarly,
Considering that dP/dx=-dP/dx, it therefore proves that D=D=D. If the partial pressure of A at x is P is P</sub>, integration of above equation,
A similar equation may be derived for the counterdiffusion of gas B. | 1 | Applied and Interdisciplinary Chemistry |
Bowen's Kale was a reference material produced by British chemist Humphry Bowen and used for the calibration of early scientific instruments intended to measure trace elements during the 1960s.
With Peter Cawse, Bowen grew, dried, and crushed a large amount of marrow-stem kale (Brassica oleracea var. medullosa) into of a homogeneous and stable powder in 1960 that was subsequently freely distributed to researchers around the world for over two decades. This was probably the first successful example of such a de facto standard. Bowen's Kale stimulated preparation of further materials by other organizations for similar use. | 1 | Applied and Interdisciplinary Chemistry |
Intravenous magnesium sulphate is used in treating pre-eclampsia. For other than pregnancy-related hypertension, a meta-analysis of 22 clinical trials with dose ranges of 120 to 973 mg/day and a mean dose of 410 mg, concluded that magnesium supplementation had a small but statistically significant effect, lowering systolic blood pressure by 3–4 mm Hg and diastolic blood pressure by 2–3 mm Hg. The effect was larger when the dose was more than 370 mg/day. | 1 | Applied and Interdisciplinary Chemistry |
Fermentation of sugar to ethanol and can also be done by Zymomonas mobilis, however the path is slightly different since formation of pyruvate does not happen by glycolysis but instead by the Entner–Doudoroff pathway.
Other microorganisms can produce ethanol from sugars by fermentation but often only as a side product. Examples are
* Heterolactic acid fermentation in which Leuconostoc bacteria produce lactate + ethanol +
* Mixed acid fermentation where Escherichia produce ethanol mixed with lactate, acetate, succinate, formate, , and H
* 2,3-butanediol fermentation by Enterobacter producing ethanol, butanediol, lactate, formate, , and H | 1 | Applied and Interdisciplinary Chemistry |
In carbohydrate chemistry, a pair of anomers () is a pair of near-identical stereoisomers or diastereomers that differ at only the anomeric carbon, the carbon that bears the aldehyde or ketone functional group in the sugar's open-chain form. However, in order for anomers to exist, the sugar must be in its cyclic form, since in open-chain form, the anomeric carbon is planar and thus achiral. More formally stated, then, an anomer is an epimer at the hemiacetal/hemiketal carbon in a cyclic saccharide. Anomerization is the process of conversion of one anomer to the other. As is typical for stereoisomeric compounds, different anomers have different physical properties, melting points and specific rotations. | 0 | Theoretical and Fundamental Chemistry |
*Bailyn, M. (1994). A Survey of Thermodynamics, American Institute of Physics Press, New York, .
*Callen, H.B. (1960/1985). Thermodynamics and an Introduction to Thermostatistics, (1st edition 1960) 2nd edition 1985, Wiley, New York, .
* A translation may be found [http://neo-classical-physics.info/uploads/3/0/6/5/3065888/caratheodory_-_thermodynamics.pdf here]. A mostly reliable translation is to be found at Kestin, J. (1976). The Second Law of Thermodynamics, Dowden, Hutchinson & Ross, Stroudsburg PA.
*Eu, B.C. (2002). Generalized Thermodynamics. The Thermodynamics of Irreversible Processes and Generalized Hydrodynamics, Kluwer Academic Publishers, Dordrecht, .
*Jaynes, E.T. (1965). Gibbs vs. Boltzmann entropies, Am. J. Phys., 33: 391–398.
*Marsland, R. , Brown, H.R., Valente, G. (2015). [https://aapt.scitation.org/doi/abs/10.1119/1.4914528 Time and irreversibility in axiomatic thermodynamics], Am. J. Phys., 83(7): 628–634.
*Planck, M., (1923/1927). Treatise on Thermodynamics, translated by A. Ogg, third English edition, Longmans, Green and Co., London.
*Prigogine, I., Defay, R. (1950/1954). Chemical Thermodynamics, Longmans, Green & Co, London.
*Tisza, L. (1966). Generalized Thermodynamics, M.I.T. Press, Cambridge MA.
*Zemanksy, M.W., Dittman, R.H. (1937/1981). Heat and Thermodynamics. An Intermediate Textbook, sixth edition, McGraw-Hill Book Company, New York, ISNM 0-07-072808-9. | 0 | Theoretical and Fundamental Chemistry |
Per IUPAC, the term biaryl refers to an assembly of two aromatic rings joined by a single bond, starting with the simplest, biphenyl. Biaryls constitute an important structural motif of physical organic, synthetic, and catalytic interest—for instance, underlying the area of atropisomers in enantioselective synthesis—and they appear in many pharmaceutical, agrochemical, and materials (e.g. LCD) applications. The example of a coupling reaction reaction used in their preparation is an alternative to the traditional Suzuki and Stille cross-coupling reactions, and various catalysts have been employed for this transformation; Goossen et al. reported the formation of biaryls from palladium and copper-catalzyed cross-coupling reactions of an aryl or heteroaryl carboxylic acid and an aryl halide (I, Br, or Cl) in the presence of a base. | 0 | Theoretical and Fundamental Chemistry |
Methanesulfonyl chloride is a precursor to many compounds because it is highly reactive. It is an electrophile, functioning as a source of the "CHSO" synthon. | 0 | Theoretical and Fundamental Chemistry |
The eFS assay could be used to analyze other cell or tissue types. By assessing enrichment in GFP-expressing CD2-negative as well as CD2-positive cells, and by crossing a common pool of reporter transformant male flies to females expressing CD2 in different cell types, it is possible to assay specificity as well as activity. Accelerating the annotation of the regulatory genome in Drosophila should in principle generate the kind of large-scale regulatory interaction data that would allow exploring the network properties of transcriptional regulation. | 1 | Applied and Interdisciplinary Chemistry |
After a surface has been abrasion blasted and/or machined a thin layer of molybdenum, nickel-chromium alloys or nickel aluminide can be spayed before the final detonation spray coating to improve the bond strength. This is known as a bond coating. Bond coatings are often used when spray coating materials of ceramic composites are being applied. The component may need to be machined and/or abrasion blasted slightly deeper for the purpose of allowing space for the bond coating and spray coating to fit flush on the component surface.
Areas that are not to be sprayed must be covered in stop-off chemicals (chemicals that stop the spay from bonding) or tape. The chemicals and tape are then removed after the coating has cooled. | 1 | Applied and Interdisciplinary Chemistry |
The first to investigate trifluoromethyl groups in relationship to biological activity was F. Lehmann in 1927. An early review appeared in 1958. An early synthetic method was developed by Frédéric Swarts in 1892, based on antimony fluoride. In this reaction benzotrichloride was reacted with SbF to form PhCFCl and
PhCF. In the 1930s Kinetic Chemicals and IG Farben replaced SbF with HF.
The McLoughlin-Thrower reaction (1968) is an early coupling reaction using iodofluoroalkanes, iodoaromatic compounds and copper. In 1969 Kobayashi & Kumadaki adapted their protocol for trifluoromethylations. | 0 | Theoretical and Fundamental Chemistry |
2-Methoxyethoxymethyl chloride is an organic compound with formula . A colorless liquid, it is classified as a chloroalkyl ether. It is used as an alkylating agent. In organic synthesis, it is used for introducing the methoxyethoxy ether (MEM) protecting group. MEM protecting groups are generally preferred to methoxymethyl (MOM) protecting groups, both in terms of formation and removal.
Typically, the alcohol to be protected is deprotonated with a non-nucleophilic base such as N,N-diisopropylethylamine (DIPEA) in dichloromethane followed by addition of 2-methoxyethoxymethyl chloride.
The MEM protecting group can be cleaved (deprotection) with a range of Lewis and Bronsted acids. | 0 | Theoretical and Fundamental Chemistry |
Addition of a Grignard reagent to a tert-butanesulfinyl aldimine or ketimine results in asymmetric addition to give the branched sulfinamide. The observed stereoselectivity can be rationalized by a six-membered ring transition structure, wherein both oxygen and nitrogen of the sulfinyl imine coordinate magnesium.
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In a panel of healthy adults, negative associations were found between total DNA methylation and exposure to traffic related air pollution. DNA methylation levels were associated both with recent and chronic exposure to Black Carbon as well as benzene. | 1 | Applied and Interdisciplinary Chemistry |
Clarification is a name for the method of separating fluid from solid particles. Often clarification is used along with flocculation to make the solid particles sink faster to the bottom of the clarification pool while fluid is obtained from the surface which is free of solid particles.
Thickening is the same as clarification except reverse. Solids that sink to the bottom are obtained and fluid is rejected from the surface.
The difference of these methods could be demonstrated with the methods used in waste water processing: in the clarification phase, sludge sinks to the bottom of the pool and clear water flows over the clear water grooves and continues its journey. The obtained sludge is then pumped into the thickeners, where sludge thickens farther and is then obtained to be pumped into digestion to be prepared into fertilizer. | 0 | Theoretical and Fundamental Chemistry |
In 2009, Lu began her independent career at the University of Minnesota, Twin Cities as an assistant professor in the department of chemistry. She was promoted to associate professor with tenure in 2015, and full professor in 2020. She moved her laboratory to the University of Bonn in 2022.
Her research focuses on the synthesis and characterization of bimetallic complexes, especially those that contain a metal-metal bond. The Lu group has developed a series of trianionic, tripodal ligands that can coordinate two metals at close proximity, allowing for the formation for a metal-metal bond in a coordination complex. The metal-metal bond order can range from bond orders of less than one to a quintuple bond, as between manganese and chromium in a complex reported in 2013, and between two chromium atoms in a complex reported in 2015.
These coordination complexes are also active for catalytic reactions of small molecules, such as the silylation of nitrogen by a dicobalt complex, and alkene hydrogenation by nickel-group 13 element complexes. | 0 | Theoretical and Fundamental Chemistry |
Sodium hexanitritocobaltate(III) is inorganic compound with the formula . The anion of this yellow-coloured salt consists of the transition metal nitrite complex . It was a reagent for the qualitative test for potassium and ammonium ions. | 0 | Theoretical and Fundamental Chemistry |
Modified aldol tandem reaction is a sequential chemical transformation that combines aldol reaction with other chemical reactions that generate enolates. Enolates are a common building block in chemical syntheses and are typically formed by the addition of base to a ketone or aldehyde. Modified Aldol tandem reactions allow similar reactivity to be produced without the need for a base which may have adverse effects in a given chemical synthesis. A representative example is the decarboxylative aldol reaction (Figure "Modified aldol tandem reaction, decarboxylative aldol reaction as an example"), where the enolate is generated via decarboxylation reaction mediated by either transition metals or organocatalysts. Key advantage of this reaction over other types of aldol reaction is the selective generation of an enolate in the presence of aldehydes. This allows for the directed aldol reaction to produce a desired cross aldol.
Transition metals have been used to mediate the modified aldol tandem reaction. Allyl β-keto carboxylates can be used as substrate for palladium-mediated decarboxylative aldol reaction (Figure "Palladium-mediated decarboxylative aldol reaction with allyl β-keto carboxylates"). The allyl group can be removed by palladium, following decarboxylation reaction selectively generates the enolate at the β-keto group, which could further react with aldehyde to generate aldols.
Using decarboxylation reaction to generate enolate is a common strategy in biosynthetic pathways such as polyketide synthesis, where malonic acid half thioester can be converted to the corresponding enolate for Claisen condensation reaction. Inspired by this, a modified tandem aldol reaction has been developed using the malonic acid half thioester as the enolate source. A copper based catalyst system has been developed for efficient aldol generation at mild conditions (Figure "Decarboxylative aldol reaction with malonic acid half thioester"). | 0 | Theoretical and Fundamental Chemistry |
He was born in Moscow. He had two brothers Vasily (1904) and Andrei (1911) and a sister Tatyana (1908) (two born sisters died in infancy). His father (Nikolai Vasilyevich Nesmeyanov), graduated with excellence Vladimir Gymnasium, and then the Faculty of Law of Moscow University. He became interested in enlightenment and was working as a public teacher in the village of Bushov (Tula province) for 10 years. He had married in 1898 and worked at the Moscow city government, then he was a director Bakhrushinsky orphanage in Moscow (1901 – 1917). Alexander's mother, Lyudmila Danilovna (1878 – 1958), was a multi-talented teacher. At ten years Alexander became a vegetarian, and in 1913 he stopped eating fish. It was not easy to follow this conviction, especially in the famine years of 1918 – 1921, when roach and herring were an essential food product. He had become interested in various branches of biology: entomology, hydrobiology, ornithology and from the age of thirteen became interested in chemistry. | 0 | Theoretical and Fundamental Chemistry |
* The Seine divides in the historical center of Paris, flowing around two river islands, the Île Saint-Louis and the Île de la Cité. At the downstream confluence, where the river becomes a single channel again, the Île de la Cité is crossed by the famous Pont Neuf, adjacent to an equestrian statue of King Henri IV and the historically more recent Vert Galant park. The site has repeatedly been portrayed by artists including Monet, Renoir, and Pissarro.
* Further upstream, the Marne empties into the Seine at Charenton-le-Pont and Alfortville, just southeast of the Paris city limits. The site is dominated by the Huatian Chinagora, a four-star hotel under Chinese management. | 1 | Applied and Interdisciplinary Chemistry |
Because they are used for domestic water measurement, piston meters, also known as rotary piston or semi-positive displacement meters, are the most common flow measurement devices in the UK and are used for almost all meter sizes up to and including 40 mm ( in). The piston meter operates on the principle of a piston rotating within a chamber of known volume. For each rotation, an amount of water passes through the piston chamber. Through a gear mechanism and, sometimes, a magnetic drive, a needle dial and odometer type display are advanced. | 1 | Applied and Interdisciplinary Chemistry |
These adenylyl cyclases are the most familiar based on extensive study due to their important roles in human health. They are also found in some bacteria, notably Mycobacterium tuberculosis where they appear to have a key role in pathogenesis. Most AC-III's are integral membrane proteins involved in transducing extracellular signals into intracellular responses. A Nobel Prize was awarded to Earl Sutherland in 1971 for discovering the key role of AC-III in human liver, where adrenaline indirectly stimulates AC to mobilize stored energy in the "fight or flight" response. The effect of adrenaline is via a G protein signaling cascade, which transmits chemical signals from outside the cell across the membrane to the inside of the cell (cytoplasm). The outside signal (in this case, adrenaline) binds to a receptor, which transmits a signal to the G protein, which transmits a signal to adenylyl cyclase, which transmits a signal by converting adenosine triphosphate to cyclic adenosine monophosphate (cAMP). cAMP is known as a second messenger.
Cyclic AMP is an important molecule in eukaryotic signal transduction, a so-called second messenger. Adenylyl cyclases are often activated or inhibited by G proteins, which are coupled to membrane receptors and thus can respond to hormonal or other stimuli. Following activation of adenylyl cyclase, the resulting cAMP acts as a second messenger by interacting with and regulating other proteins such as protein kinase A and cyclic nucleotide-gated ion channels.
Photoactivated adenylyl cyclase (PAC) was discovered in Euglena gracilis and can be expressed in other organisms through genetic manipulation. Shining blue light on a cell containing PAC activates it and abruptly increases the rate of conversion of ATP to cAMP. This is a useful technique for researchers in neuroscience because it allows them to quickly increase the intracellular cAMP levels in particular neurons, and to study the effect of that increase in neural activity on the behavior of the organism. A green-light activated rhodopsin adenylyl cyclase (CaRhAC) has recently been engineered by modifying the nucleotide binding pocket of rhodopsin guanylyl cyclase. | 1 | Applied and Interdisciplinary Chemistry |
Crystallography is used by materials scientists to characterize different materials. In single crystals, the effects of the crystalline arrangement of atoms is often easy to see macroscopically because the natural shapes of crystals reflect the atomic structure. In addition, physical properties are often controlled by crystalline defects. The understanding of crystal structures is an important prerequisite for understanding crystallographic defects. Most materials do not occur as a single crystal, but are poly-crystalline in nature (they exist as an aggregate of small crystals with different orientations). As such, powder diffraction techniques, which take diffraction patterns of samples with a large number of crystals, play an important role in structural determination.
Other physical properties are also linked to crystallography. For example, the minerals in clay form small, flat, platelike structures. Clay can be easily deformed because the platelike particles can slip along each other in the plane of the plates, yet remain strongly connected in the direction perpendicular to the plates. Such mechanisms can be studied by crystallographic texture measurements.
In another example, iron transforms from a body-centered cubic (bcc) structure called ferrite to a face-centered cubic (fcc) structure called austenite when it is heated. The fcc structure is a close-packed structure unlike the bcc structure; thus the volume of the iron decreases when this transformation occurs.
Crystallography is useful in phase identification. When manufacturing or using a material, it is generally desirable to know what compounds and what phases are present in the material, as their composition, structure and proportions will influence the material's properties. Each phase has a characteristic arrangement of atoms. X-ray or neutron diffraction can be used to identify which structures are present in the material, and thus which compounds are present. Crystallography covers the enumeration of the symmetry patterns which can be formed by atoms in a crystal and for this reason is related to group theory. | 0 | Theoretical and Fundamental Chemistry |
A general d-orbital splitting diagram for square planar (D) transition metal complexes can be derived from the general octahedral (O) splitting diagram, in which the d−y, d and d orbitals. When the two axial ligands are removed to generate a square planar geometry, the d, d and d orbitals because of the torus shaped lobe of the d, d and d orbitals are generally presented as degenerate but they have to split into two different energy levels with respect to the irreducible representations of the point group D. Their relative ordering depends on the nature of the particular complex. Furthermore, the splitting of d-orbitals is perturbed by π-donating ligands in contrast to octahedral complexes. In the square planar case strongly π-donating ligands can cause the d and d orbitals to be higher in energy than the d</sub> orbital, whereas in the octahedral case π-donating ligands only affect the magnitude of the d-orbital splitting and the relative ordering of the orbitals is conserved. | 0 | Theoretical and Fundamental Chemistry |
Pathogenic bacteria commonly produce a bacterial capsule, a thick, mucous-like, layer of polysaccharide. The capsule cloaks antigenic proteins on the bacterial surface that would otherwise provoke an immune response and thereby lead to the destruction of the bacteria. Capsular polysaccharides are water-soluble, commonly acidic, and have molecular weights on the order of 100,000 to 2,000,000 daltons. They are linear and consist of regularly repeating subunits of one to six monosaccharides. There is enormous structural diversity; nearly two hundred different polysaccharides are produced by E. coli alone. Mixtures of capsular polysaccharides, either conjugated or native, are used as vaccines.
Bacteria and many other microbes, including fungi and algae, often secrete polysaccharides to help them adhere to surfaces and to prevent them from drying out. Humans have developed some of these polysaccharides into useful products, including xanthan gum, dextran, welan gum, gellan gum, diutan gum and pullulan.
Most of these polysaccharides exhibit useful visco-elastic properties when dissolved in water at very low levels. This makes various liquids used in everyday life, such as some foods, lotions, cleaners, and paints, viscous when stationary, but much more free-flowing when even slight shear is applied by stirring or shaking, pouring, wiping, or brushing. This property is named pseudoplasticity or shear thinning; the study of such matters is called rheology.
Aqueous solutions of the polysaccharide alone have a curious behavior when stirred: after stirring ceases, the solution initially continues to swirl due to momentum, then slows to a standstill due to viscosity and reverses direction briefly before stopping. This recoil is due to the elastic effect of the polysaccharide chains, previously stretched in solution, returning to their relaxed state.
Cell-surface polysaccharides play diverse roles in bacterial ecology and physiology. They serve as a barrier between the cell wall and the environment, mediate host-pathogen interactions. Polysaccharides also play an important role in formation of biofilms and the structuring of complex life forms in bacteria like Myxococcus xanthus.
These polysaccharides are synthesized from nucleotide-activated precursors (called nucleotide sugars) and, in most cases, all the enzymes necessary for biosynthesis, assembly and transport of the completed polymer are encoded by genes organized in dedicated clusters within the genome of the organism. Lipopolysaccharide is one of the most important cell-surface polysaccharides, as it plays a key structural role in outer membrane integrity, as well as being an important mediator of host-pathogen interactions.
The enzymes that make the A-band (homopolymeric) and B-band (heteropolymeric) O-antigens have been identified and the metabolic pathways defined. The exopolysaccharide alginate is a linear copolymer of β-1,4-linked -mannuronic acid and -guluronic acid residues, and is responsible for the mucoid phenotype of late-stage cystic fibrosis disease. The pel and psl loci are two recently discovered gene clusters that also encode exopolysaccharides found to be important for biofilm formation. Rhamnolipid is a biosurfactant whose production is tightly regulated at the transcriptional level, but the precise role that it plays in disease is not well understood at present. Protein glycosylation, particularly of pilin and flagellin, became a focus of research by several groups from about 2007, and has been shown to be important for adhesion and invasion during bacterial infection. | 0 | Theoretical and Fundamental Chemistry |
The ordinary range of chemical shifts ranges from about δ250 to −δ250, which is much wider than typical for H-NMR. Unlike H-NMR spectroscopy, P-NMR shifts are primarily not determined by the magnitude of the diamagnetic shielding, but are dominated by the so-called paramagnetic shielding tensor (unrelated to paramagnetism). The paramagnetic shielding tensor, σ, includes terms that describe the radial expansion (related to charge), energies of excited states, and bond overlap. Illustrative of the effects lead to big changes in chemical shifts, the chemical shifts of the two phosphate esters (MeO)PO (δ2.1) and (t-BuO)PO (δ-13.3). More dramatic are the shifts for phosphine derivatives HP (δ-240), (CH)P (δ-62), (i-Pr)P (δ20), and (t-Bu)P (δ61.9). | 0 | Theoretical and Fundamental Chemistry |
Mechanistic evidence was provided by Denham Harmans free radical theory of aging, created in the 1950s. This theory stated that organisms age over time due to the accumulation of damage from free radicals in the body. It also showed that metabolic processes, specifically the mitochondria, are prominent producers of free radicals. This provided a mechanistic link between Rubners initial observations of decreased lifespan in conjunction with increased metabolism. | 1 | Applied and Interdisciplinary Chemistry |
* Thure Cerling; Iain Douglas-Hamilton; Lee Siegel: "Elephant Tracks" University of Utah News Release, January 2, 2006. | 0 | Theoretical and Fundamental Chemistry |
It can be used in practical applications such as malting, to represent the grain–air–moisture system.
The underlying property data for the Mollier diagram is identical to a psychrometric chart. At first inspection, there may appear little resemblance between the charts, but if the user rotates a chart ninety degrees and looks at it in a mirror, the resemblance is apparent. The Mollier diagram coordinates are enthalpy h and humidity ratio x. The enthalpy coordinate is skewed and the constant enthalpy lines are parallel and evenly spaced. | 0 | Theoretical and Fundamental Chemistry |
Sybren Otto (Groningen, 3 August 1971) is Professor of Systems chemistry at the Stratingh Institute for Chemistry, University of Groningen. | 0 | Theoretical and Fundamental Chemistry |
Biomarkers can be classified based on different criteria.
Based on their characteristics they can be classified as imaging biomarkers (CT, PET, MRI) or molecular biomarkers with three subtypes: volatile, like breath, body fluid, or biopsy biomarkers.
Molecular biomarkers refer to non-imaging biomarkers that have biophysical properties, which allow their measurements in biological samples (e.g., plasma, serum, cerebrospinal fluid, bronchoalveolar lavage, biopsy) and include nucleic acids-based biomarkers such as gene mutations or polymorphisms and quantitative gene expression analysis, peptides, proteins, lipids metabolites, and other small molecules.
Biomarkers can also be classified based on their application such as diagnostic biomarkers (i.e., cardiac troponin for the diagnosis of myocardial infarction), staging of disease biomarkers (i.e., brain natriuretic peptide for congestive heart failure), disease prognosis biomarkers (cancer biomarkers), and biomarkers for monitoring the clinical response to an intervention (HbAlc for antidiabetic treatment).
Another category of biomarkers includes those used in decision making in early drug development. For instance, pharmacodynamic (PD) biomarkers are markers of a certain pharmacological response, which are of special interest in dose optimization studies. | 1 | Applied and Interdisciplinary Chemistry |
2C-B was first sold commercially in 5 mg pills as a purported aphrodisiac under the trade name "Erox", which was manufactured by the German pharmaceutical company Drittewelle. While being primarily a psychedelic it is also a mild entactogen. 5-MeO-MiPT is another psychedelic that some users find to be euphoric and tactile in low to moderate doses of 4-8 milligrams. | 1 | Applied and Interdisciplinary Chemistry |
It is not always possible to unequivocally determine the direction of intensity change, such as is for example the case for highly overlapping signals next to each other and of which the intensity changes in the opposite direction. This is where the off diagonal peaks in the synchronous 2D spectrum are used for:
#if there is a positive cross-peak at (x, y) in the synchronous 2D spectrum, the intensity of the signals at x and y changes in the same direction
#if there is a negative cross-peak at (x, y) in the synchronous 2D spectrum, the intensity of the signals at x and y changes in the opposite direction
As can be seen in the 2D synchronous spectrum on the right, the intensity changes of the peaks at 10 and 30 are related and the intensity of the peak at 10 and 30 changes in the opposite direction (negative cross-peak at (10,30)). The same is true for the peaks at 20 and 40. | 0 | Theoretical and Fundamental Chemistry |
He has been shown to form van der Waals compounds with other atoms forming bigger clusters such as MgHe and CaHe.
The helium-4 trimer (He), a cluster of three helium atoms, is predicted to have an excited state which is an Efimov state. This has been confirmed experimentally in 2015. | 0 | Theoretical and Fundamental Chemistry |
Mill scale is a complex oxide that contains around 70% iron with traces of nonferrous metals and alkaline compounds. Reduced iron powder may be obtained by conversion of mill scale into a single highest oxide i.e. hematite () followed by reduction with hydrogen. Shahid and Choi reported the reverse co-precipitation method for the synthesis of magnetite () from mill scale and used for multiple environmental applications such as nutrient recovery, ballasted coagulation in activated sludge process, and heavy metal remediation in an aqueous environment. | 1 | Applied and Interdisciplinary Chemistry |
Ring and Ball Apparatus is used to determine the softening point of bitumen, waxes, LDPE, HDPE/PP blend granules, rosin and solid hydrocarbon resins. The apparatus was first designed in the 1910s while ASTM adopted a test method in 1916. This instrument is ideally used for materials having softening point in the range of 30 °C to 157 °C. | 0 | Theoretical and Fundamental Chemistry |
Neurons in the olfactory system are unmyelinated and densely packed and thus the often small effects of ephaptic coupling are more easily seen. A number of studies have shown how inhibition among neurons in the olfactory system work to fine-tune integration of signals in response to odor. This inhibition has been shown to occur from changes in electrical potentials alone. The addition of ephaptic coupling to olfactory neuron models adds further support to the "dedicated-line" model in which each olfactory receptor sends its signal to one neuron. The inhibition due to ephaptic coupling would help account for the integration of signals that gives rise to more nuanced perception of smells. | 1 | Applied and Interdisciplinary Chemistry |
A concern usually addressed in catalyst design is efficiency, in particular how much of the incident light can be used in a system in practice. This is comparable with photosynthetic efficiency, where light-to-chemical-energy conversion is measured. Photosynthetic organisms are able to collect about 50% of incident solar radiation, however the theoretical limit of photosynthetic efficiency is 4.6 and 6.0% for C3 and C4 plants respectively. In reality, the efficiency of photosynthesis is much lower and is usually below 1%, with some exceptions such as sugarcane in tropical climate. In contrast, the highest reported efficiency for artificial photosynthesis lab prototypes is 22.4%. However, plants are efficient in using CO at atmospheric concentrations, something that artificial catalysts still cannot perform. | 0 | Theoretical and Fundamental Chemistry |
Protective forms of chemical mimicry work to benefit the mimicking species by preventing harm. In most cases this achieved by acting as a deterrent to other organisms by mimicking the chemicals emitted by another species that has a mechanism to deter predators. This can be either Batesian Mimicry or Müllerian mimicry. | 1 | Applied and Interdisciplinary Chemistry |
Magma contains dissolved volatile components, as described above. The solubilities of the different volatile constituents are dependent on pressure, temperature and the composition of the magma. As magma ascends towards the surface, the ambient pressure decreases, which decreases the solubility of the dissolved volatiles. Once the solubility decreases below the volatile concentration, the volatiles will tend to come out of solution within the magma (exsolve) and form a separate gas phase (the magma is super-saturated in volatiles).
The gas will initially be distributed throughout the magma as small bubbles, that cannot rise quickly through the magma. As the magma ascends the bubbles grow through a combination of expansion through decompression and growth as the solubility of volatiles in the magma decreases further causing more gas to exsolve. Depending on the viscosity of the magma, the bubbles may start to rise through the magma and coalesce, or they remain relatively fixed in place until they begin to connect and form a continuously connected network. In the former case, the bubbles may rise through the magma and accumulate at a vertical surface, e.g. the roof of a magma chamber. In volcanoes with an open path to the surface, e.g. Stromboli in Italy, the bubbles may reach the surface and as they pop small explosions occur. In the latter case, the gas can flow rapidly through the continuous permeable network towards the surface. This mechanism has been used to explain activity at Santiaguito, Santa Maria volcano, Guatemala and Soufrière Hills Volcano, Montserrat. If the gas cannot escape fast enough from the magma, it will fragment the magma into small particles of ash. The fluidised ash has a much lower resistance to motion than the viscous magma, so accelerates, causing further expansion of the gases and acceleration of the mixture. This sequence of events drives explosive volcanism. Whether gas can escape gently (passive eruptions) or not (explosive eruptions) is determined by the total volatile contents of the initial magma and the viscosity of the magma, which is controlled by its composition.
The term closed system degassing refers to the case where gas and its parent magma ascend together and in equilibrium with each other. The composition of the emitted gas is in equilibrium with the composition of the magma at the pressure, temperature where the gas leaves the system. In open system degassing, the gas leaves its parent magma and rises up through the overlying magma without remaining in equilibrium with that magma. The gas released at the surface has a composition that is a mass-flow average of the magma exsolved at various depths and is not representative of the magma conditions at any one depth.
Molten rock (either magma or lava) near the atmosphere releases high-temperature volcanic gas (>400 °C).
In explosive volcanic eruptions, the sudden release of gases from magma may cause rapid movements of the molten rock. When the magma encounters water, seawater, lake water or groundwater, it can be rapidly fragmented. The rapid expansion of gases is the driving mechanism of most explosive volcanic eruptions. However, a significant portion of volcanic gas release occurs during quasi-continuous quiescent phases of active volcanism. | 1 | Applied and Interdisciplinary Chemistry |
Hydrolysis is related to energy metabolism and storage. All living cells require a continual supply of energy for two main purposes: the biosynthesis of micro and macromolecules, and the active transport of ions and molecules across cell membranes. The energy derived from the oxidation of nutrients is not used directly but, by means of a complex and long sequence of reactions, it is channeled into a special energy-storage molecule, adenosine triphosphate (ATP). The ATP molecule contains pyrophosphate linkages (bonds formed when two phosphate units are combined) that release energy when needed. ATP can undergo hydrolysis in two ways: Firstly, the removal of terminal phosphate to form adenosine diphosphate (ADP) and inorganic phosphate, with the reaction:
Secondly, the removal of a terminal diphosphate to yield adenosine monophosphate (AMP) and pyrophosphate. The latter usually undergoes further cleavage into its two constituent phosphates. This results in biosynthesis reactions, which usually occur in chains, that can be driven in the direction of synthesis when the phosphate bonds have undergone hydrolysis. | 0 | Theoretical and Fundamental Chemistry |
The acetyltransferase activity and cellular location of PCAF are regulated through acetylation of PCAF itself. PCAF may be autoacetylated (acetylated by itself) or by p300. Acetylation leads to migration to the nucleus and enhances its acetyltransferase activity. PCAF interacts with and is deacetylated by HDAC3, leading to a reduction in PCAF acetyltransferase activity and cytoplasmic localisation. | 1 | Applied and Interdisciplinary Chemistry |
Elgiloy (Co-Cr-Ni Alloy) is a "super-alloy" consisting of 39-41% cobalt, 19-21% chromium, 14-16% nickel, 11.3-20.5% iron, 6-8% molybdenum, 1.5-2.5% manganese and 0.15% max. carbon.
It is used to make springs that are corrosion resistant and exhibit high strength, ductility, and good fatigue life. These same properties led to it being used for control cables in the Lockheed SR-71 Blackbird airplane, as they needed to cope with repeated stretching and contracting.
Elgiloy meets specifications AMS 5876, AMS 5833, and UNS R30003.
Due to its chemical composition, Elgiloy is highly resistant to sulfide stress corrosion cracking and pitting, and can operate at temperatures up to 454 °C.
Elgiloy is a trade name for this super alloy. Phynox is another trade name for the same super alloy. | 1 | Applied and Interdisciplinary Chemistry |
* US Human Proteome Organization Catherine E. Costello Lifetime Achievement in Proteomics Award (from 2020)
* Females in Mass Spectrometry Catherine E. Costello Award (from 2020) | 1 | Applied and Interdisciplinary Chemistry |
Phase inversion or phase separation is a chemical phenomenon exploited in the fabrication of artificial membranes. It is performed by removing the solvent from a liquid-polymer solution, leaving a porous, solid membrane. | 0 | Theoretical and Fundamental Chemistry |
The formose reaction, discovered by Aleksandr Butlerov in 1861, and hence also known as the Butlerov reaction, involves the formation of sugars from formaldehyde. The term formose is a portmanteau of formaldehyde and aldose. | 0 | Theoretical and Fundamental Chemistry |
The Benjamin–Bona–Mahony equation (BBM equation), or regularised long wave (RLW) equation, is in dimensional form given by:
All quantities have the same meaning as for the KdV equation. The BBM equation is often preferred over the KdV equation because it has a better short-wave behaviour.
; Derivation
The derivation is analogous to the one for the KdV equation. The dimensionless BBM equation is, non-dimensionalised using mean water depth h and gravitational acceleration g:
This can be brought into the standard form
through the transformation:
: and
but this standard form will not be used here.
Analogue to the derivation of the cnoidal wave solution for the KdV equation, periodic wave solutions η(ξ), with ξ = x−ct are considered Then the BBM equation becomes a third-order ordinary differential equation, which can be integrated twice, to obtain:
: with
Which only differs from the equation for the KdV equation through the factor c in front of () in the left hand side. Through a coordinate transformation β = ξ / the factor c may be removed, resulting in the same first-order ordinary differential equation for both the KdV and BBM equation. However, here the form given in the preceding equation is used. This results in a different formulation for Δ as found for the KdV equation:
The relation of the wavelength λ, as a function of H and m, is affected by this change in
For the rest, the derivation is analogous to the one for the KdV equation, and will not be repeated here.
; Résumé
The results are presented in dimensional form, for water waves on a fluid layer of depth h.
The cnoidal wave solution of the BBM equation, together with the associated relationships for the parameters is:
The only difference with the cnoidal wave solution of the KdV equation is in the equation for the wavelength λ. For practical applications, usually the water depth h, wave height H, gravitational acceleration g, and either the wavelength λ, or—most often—the period (physics) τ are provided. Then the elliptic parameter m has to be determined from the above relations for λ, c and τ through some iterative method. | 1 | Applied and Interdisciplinary Chemistry |
A Ni-BHT MOF nanosheet has been obtained using liquid-liquid interfacial synthesis. For the synthesis, organic linker is dissolved in dichloromethane upon which HO is added and then metal salt (Ni(OAc)) along with sodium bromide is added to the aqueous layer. | 0 | Theoretical and Fundamental Chemistry |
As an extension of the refocussing pulse treated above, consider a set of two pulses with arbitrary flip angles and , that is sequence
where again is a time interval. Liberally dropping irrelevant terms, the evolution for a single spin with offset up to just after the second pulse is
Now consider an ensemble of spins in a magnetic field that is sufficiently inhomogeneous to completely dephase the spins in the interval between the pulses. After the second pulse, we can decompose the remaining terms into a sum of two spin populations differing only in the sign of the term, in the sense that for an individual spin we have
where we used the identities and .
It is the spins in the new population that has been generated by the second pulse, namely the one with , that will lead to the formation of an echo after evolution for the next interval. Therefore, remembering to include the introduced by the first pulse, the amplitude of the resulting Hahn echo relative to that produced by an ideal 90°—180° refocussing pulse sequence is roughly
Note that this is not an exact result, because it considers only the refocussing of polarisation that was transverse immediately before the second pulse. In reality there will be further transverse components originating from the tipping of the longitudinal magnetisation that remained after the first pulse. However, for many tip angles, this is a good rule of thumb.
To instead arrive at this result using the state formalism, we would have had to non-trivially evaluate the rotation propagator as
and then evaluate a transition probability by considering the result of applying this to a state representing polarisation in the transverse plane. | 0 | Theoretical and Fundamental Chemistry |
Eliminate the sequences that are more than r% identical. There are two ways to eliminate the sequences. It can be done either by removing sequences from the block or just by finding similar sequences and replace them by new sequences which could represent the cluster. Elimination is done to remove protein sequences that are more similar than the specified threshold. | 1 | Applied and Interdisciplinary Chemistry |
When the surfaces are sufficiently far apart, the potential profiles originating from each individual surface will not be much perturbed by the presence of the other surface. This approximation thus suggests that one can simply add (superpose) the potentials profiles originating from each surface as illustrated the figure. Since the potential profile passes through a minimum at the mid-plane, it is easiest to evaluate the disjoining pressure at the midplane. The solution of the DH equation for an isolated wall reads
where z is the distance from the surface and ψ the surface potential. The potential at the midplane is thus given by twice the value of this potential at a distance z = h/2. The disjoining pressure becomes
The electrostatic double layer force decays in an exponential fashion. Due to the screening by the electrolyte, the range of the force is given by the Debye length and its strength by the surface potential (or surface charge density). This approximation turns out to be exact provided the plate-plate separation is large compared to the Debye length and the surface potentials are low.
This result can be simply generalized to highly charged surfaces, but only at larger separations. Even if the potential is large close to the surface, it will be small at larger distances, and can be described by the DH equation. However, in this case one has to replace the actual diffuse layer potential ψ with the effective potential ψ. Within the PB model, this effective potential can be evaluated analytically, and reads
The superposition approximation can be easily extended to asymmetric systems. Analogous arguments lead to the expression for the disjoining pressure
where the super-scripted quantities refer to properties of the respective surface. At larger distances, oppositely charged surfaces repel and equally charged ones attract. | 0 | Theoretical and Fundamental Chemistry |
* Morawetz, Herbert Polymers: The Origins and Growth of a Science John Wiley and Sons, 1985.
* Utracki, L. A. Commercial Polymer Blends London: Chapman and Hall, 1998.
* https://books.google.com/books?id=aLrrCAAAQBAJ&pg=PA14 | 0 | Theoretical and Fundamental Chemistry |
It is commonly known that drug addiction involves permanent synaptic plasticity of various neuronal circuits. Neuroproteomics is being applied to study the effect of drug addiction across the synapse. Research is being conducted by isolating distinct regions of the brain in which synaptic transmission takes place and defining the proteome for that particular region. Different stages of drug abuse must be studied, however, in order to map out the progression of protein changes along the course of the drug addiction. These stages include enticement, ingesting, withdrawal, addiction, and removal. It begins with the change in the genome through transcription that occurs due to the abuse of drugs. It continues to identify the most likely proteins to be affected by the drugs and focusing in on that area.
For drug addiction, the synapse is the most likely target as it involves communication between neurons. Lack of sensory communication in neurons is often an outward sign of drug abuse, and so neuroproteomics is being applied to find out what proteins are being affected to prevent the transport of neurotransmitters. In particular, the vesicle releasing process is being studied to identify the proteins involved in the synapse during drug abuse. Proteins such as synaptotagmin and synaptobrevin interact to fuse the vesicle into the membrane. Phosphorylation also has its own set of proteins involved that work together to allow the synapse to function properly. Drugs such as morphine change properties such as cell adhesion, neurotransmitter volume, and synaptic traffic. After significant morphine application, tyrosine kinases received less phosphorylation and thus send fewer signals inside the cell. These receptor proteins are unable to initiate the intracellular signaling processes that enable the neuron to live, and necrosis or apoptosis may be the result. With more and more neurons affected along this chain of cell death, permanent loss of sensory or motor function may be the result. By identifying the proteins that are changed with drug abuse, neuroproteomics may give clinicians even earlier biomarkers to test for to prevent permanent neurological damage.
Recently, a novel terminology (Psychoproteomics) has been coined by the University of Florida researchers from Dr. Mark S Gold Lab. Kobeissy et al. defined Psychoproteomics as integral proteomics approach dedicated to studying proteomic changes in the field of psychiatric disorders, particularly substance-and drug-abuse neurotoxicity. | 1 | Applied and Interdisciplinary Chemistry |
The max , or maximum dynamic pressure, condition is the point when an aerospace vehicle's atmospheric flight reaches the maximum difference between the fluid dynamics total pressure and the ambient static pressure. For an airplane, this occurs at the maximum speed at minimum altitude corner of the flight envelope. For a space vehicle launch, this occurs at the crossover point between dynamic pressure increasing with speed and static pressure decreasing with increasing altitude. This is an important design factor of aerospace vehicles, since the aerodynamic structural load on the vehicle is proportional to dynamic pressure. | 1 | Applied and Interdisciplinary Chemistry |
This definition is not however standardized, and MWCOs can also be defined as the molecular weight at which 80% of the analytes (or solutes) are prohibited from membrane diffusion.
Commercially available microdialysis probes typically have molecular weight cutoffs that range from 1,000 to 300,000 Da, and larger thresholds of filtration are measured in µm. Microdialysis may also be used to separate nanoparticles from the solutions in which they were formed. In such a separation, the eluate will consist of non-complexed reactants and components.
Ultrafiltration membrane manufacturers commonly produce and offer MWCO's of 2k, 5k, 10k, 30k, 50k, 100k, and 1,000k. Devices offered range from laboratory focused centrifugal devices (100ul to 100ml) to laboratory and bioprocessing relevant tangential flow filtration (TFF) devices (50ml to hundreds of litres). | 0 | Theoretical and Fundamental Chemistry |
As seen in the diagram below, impure titanium, zirconium, hafnium, vanadium, thorium or protactinium is heated in an evacuated vessel with a halogen at 50–250 °C. The patent specifically involved the intermediacy of TiI and ZrI, which were volatilized (leaving impurities as solid). At atmospheric pressure TiI melts at 150 °C and boils at 377 °C, while ZrI melts at 499 °C and boils at 600 °C. The boiling points are lower at reduced pressure. The gaseous metal tetraiodide is decomposed on a white hot tungsten filament (1400 °C). As more metal is deposited the filament conducts better and thus a greater electric current is required to maintain the temperature of the filament. The process can be performed in the span of several hours or several weeks, depending on the particular setup.
Generally, the crystal bar process can be performed using any number of metals using whichever halogen or combination of halogens is most appropriate for that sort of transport mechanism, based on the reactivities involved. The only metals it has been used to purify on an industrial scale are titanium, zirconium and hafnium, and in fact is still in use today on a much smaller scale for special purity needs. | 1 | Applied and Interdisciplinary Chemistry |
SIDIS measurements were pioneered at DESY by the HERMES experiment. They are currently (2021) being carried out at CERN by the COMPASS experiment and several experiments at Jefferson Lab. SIDIS will be an important technique used in the future Electron Ion Collider scientific program. | 0 | Theoretical and Fundamental Chemistry |
For small diameter pipes there may not be enough room for the tractor mechanism. Instead, a somewhat rigid "fish" is pushed through the pipe and attached to a rope at the access point near the truck. The fish is then pulled to place the rope along the pipe. The rope is then used to pull the inspection pig and cable through the pipe. Detaching the rope, the cable is then used to pull the pig backwards as the pipe is inspected on the monitor (this is the method shown in the illustrations below). | 1 | Applied and Interdisciplinary Chemistry |
A primary application of defoliants is the selective killing of plants. Two of the oldest chemical herbicides used as defoliants are 2,4-Dichlorophenoxyacetic acid (2,4-D) and 2,4,5-Trichlorophenoxyacetic acid (2,4,5-T). 2,4-D and 2,4,5-T are absorbed by broad-leafed plants, killing them by causing excessive hormonal growth. These phenoxy herbicides were designed to selectively kill weeds and unwanted plants in croplands. They were first introduced at the beginning of World War II and became widespread in use in agriculture following the end of the War.
Defoliants have a practical use in the harvesting of certain crops, particularly cotton, in the United States as well as a number of other cotton-producing countries. The use of defoliants aids in the effective harvesting of cotton and finer lint quality. The effectiveness of defoliant use in cotton harvesting depends on the type of defoliant(s) used, the number of applications, the amount applied, and environmental variables. Common harvest-aiding chemical defoliants include tribufos, dimethipin, and thidiazuron. According to a 1998 report by the U.S. Department of Agriculture National Agricultural Statistics Service (NASS), tribufos and thidiazuron accounted for 60% of crop area that was treated by defoliants during that crop year. | 1 | Applied and Interdisciplinary Chemistry |
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