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* In boronic ester homologization an alkyl group shifts from boron in a boronate to carbon:
In this reaction dichloromethyllithium converts the boronic ester into a boronate. A Lewis acid then induces a rearrangement of the alkyl group with displacement of the chlorine group. Finally an organometallic reagent such as a Grignard reagent displaces the second chlorine atom effectively leading to insertion of an RCH group into the C-B bond. Another reaction featuring a boronate alkyl migration is the Petasis reaction. | 0 | Theoretical and Fundamental Chemistry |
If the process of converting one type of energy into another takes place inside a thermodynamic system, for example, in chemical reactions, in electric or pneumatic motors, when one solid body rubs against another, then the processes of energy release or absorption will occur, and the thermodynamic system will always tend to a non-equilibrium state with respect to the environment. | 0 | Theoretical and Fundamental Chemistry |
In 1964, William Zisman published an article in the ACS publications on the "Relation of the Equilibrium Contact Angle to Liquid and Solid Constitution". It was in this article where he used what we call today as the Zisman plot. The Zisman plot is used to very quickly give a quantitative measurement of wettability, also known as the critical surface tension, γ , of a solid surface by measuring the liquid contact angle as shown in Figure 1. Taking the cosine of said angle and then graphing it against the surface tension of the liquid wetting the solid substrate yields the critical surface tension. Wettability is a measure of how well a liquid spreads and how complete the contact of the liquid is across the surface of a solid interface. A small contact angle indicates good wettability, while a large contact angle indicates poor wettability. The critical surface tension is the highest liquid surface tension that can completely wet a specific solid surface. For adhesive bonding complete wetting is used to maximize the adhesive joint strength.
Even though this relationship is empirical and less precise than the surface tension of a homologous series of liquids, it is very useful considering it is a parameter of the solid surface. This method is especially used to compare and measure the critical surface tension of low-energy solids (mainly plastics) very quickly and easily. Figure 4 in ZIsmans published article from 1964 shows the critical surface tension as a measure of wettability of Polyethylene. Zisman published this analysis in 1964 and used a variety of nonhomologous liquids to measure the critical surface tension of Polyethylene to be around 35 dynes per centimeter as shown by the intercept at x=1 in Figure 4. Figure 12 in Zismans 1964 article shows that different solids can also be plotted on the same graph to easily compare the critical solid surface tensions of a variety of plastic substrates including very different polymers such as teflon, acid monolayers, and esters. The ZIsman Plot proved to be a breakthrough which allowed for a very efficient way to measure wettability of a solid which helped to spawn the work of Dann in the late 1960s. Dann characterized the critical surface tensions of a variety of polymeric materials using the Zisman Plot. In modern days, David and Neumann in an investigation of contact angle on low-energy surfaces. However, today some different variations of the Zisman plot exist because the dependent variable is unitless being since it is cosine of the contact angle for the liquid. | 0 | Theoretical and Fundamental Chemistry |
Different average values can be defined, depending on the statistical method applied. In practice, four averages are used, representing the weighted mean taken with the mole fraction, the weight fraction, and two other functions which can be related to measured quantities:
*Number average molar mass (), also loosely referred to as number average molecular weight (NAMW).
*Mass average molar mass (), where stands for weight; also commonly referred to as weight average or weight average molecular weight (WAMW).
*Z-average molar mass (), where stands for centrifugation ().
*Viscosity average molar mass ().
Here, is the exponent in the Mark–Houwink equation that relates the intrinsic viscosity to molar mass. | 0 | Theoretical and Fundamental Chemistry |
Pressure drops seen for fully developed flow of fluids through pipes can be predicted using the Moody diagram which plots the Darcy–Weisbach friction factor against Reynolds number and relative roughness . The diagram clearly shows the laminar, transition, and turbulent flow regimes as Reynolds number increases. The nature of pipe flow is strongly dependent on whether the flow is laminar or turbulent. | 1 | Applied and Interdisciplinary Chemistry |
Copper was the first metal in common use for tools and containers since it is one of the few metals available in non-oxidized form, not requiring the smelting of an ore. Copper is easily softened by heating and then cooling (it does not harden by quenching, e.g., quenching in cool water). In this annealed state it may then be hammered, stretched and otherwise formed, progressing toward the desired final shape but becoming harder and less ductile as work progresses. If work continues beyond a certain hardness the metal will tend to fracture when worked and so it may be re-annealed periodically as shaping continues. Annealing is stopped when the workpiece is near its final desired shape, and so the final product will have a desired strength and hardness. The technique of repoussé exploits these properties of copper, enabling the construction of durable jewelry articles and sculptures (such as the Statue of Liberty). | 1 | Applied and Interdisciplinary Chemistry |
To first order, δCu values in organisms are driven by the δCu values of source materials. The δCu values of various soils from different regions have been found to vary from -0.34 to +0.33‰ depending on the biogeochemical processes taking place in the soil and the ligands with which Cu complexes. Organic-rich soils generally have lighter δCu values than mineral soils because the organic layers result from plant litter, which is isotopically light.
In plants, δCu values vary between the different components (seeds, roots, stem and leaves). The δCu values the roots of rice, lettuce, tomato and durum wheat plants were found to be 0.5 to 1.0‰ Cu-depleted relative to their source, while their shoots were up to 0.5‰ lighter than the roots. Seeds appear to be the most isotopically light component of plants, followed by leaves, then stems.
Rivers sampled throughout the world have a range of dissolved δCu values from +0.02 to +1.45‰. The average δCu values of the Amazon, Brahmaputra and Nile rivers are 0.69, 0.64 and 0.58‰, respectively. The average δCu value of the Chang Jiang river is 1.32‰, while that of the Missouri river is 0.13‰. | 0 | Theoretical and Fundamental Chemistry |
The standard heat of formation (ΔH°) of a compound is described as the enthalpy change when the compound is formed from its separated elements. When the heat of formation for a compound is different from either a prediction or a reference compound, this difference can often be attributed to strain. For example, ΔH° for cyclohexane is -29.9 kcal mol while ΔH° for methylcyclopentane is -25.5 kcal mol. Despite having the same atoms and number of bonds, methylcyclopentane is higher in energy than cyclohexane. This difference in energy can be attributed to the ring strain of a five-membered ring which is absent in cyclohexane. Experimentally, strain energy is often determined using heats of combustion which is typically an easy experiment to perform.
Determining the strain energy within a molecule requires knowledge of the expected internal energy without the strain. There are two ways do this. First, one could compare to a similar compound that lacks strain, such as in the previous methylcyclohexane example. Unfortunately, it can often be difficult to obtain a suitable compound. An alternative is to use Benson group increment theory. As long as suitable group increments are available for the atoms within a compound, a prediction of ΔH° can be made. If the experimental ΔH° differs from the predicted ΔH°, this difference in energy can be attributed to strain energy. | 0 | Theoretical and Fundamental Chemistry |
The terminus of the double bond in enols is nucleophilic. Its reactions with electrophilic organic compounds is important in biochemistry as well as synthetic organic chemistry. In the former area, the fixation of carbon dioxide involves addition of CO to an enol. | 0 | Theoretical and Fundamental Chemistry |
The birth of the theory of chaotic advection is usually traced back to a 1984 paper
by Hassan Aref. In this work, Aref studied the mixing induced by two vortices switched alternately on and off inside an inviscid fluid. This seminal work had been made possible by earlier developments in the fields of dynamical Systems and fluid mechanics in the previous decades. Vladimir Arnold
and Michel Hénon
had already noticed that the trajectories advected by area-preserving three-dimensional flows could be chaotic. However, the practical interest of chaotic advection for fluid mixing applications remained unnoticed until the work of Aref in the 80's. Since then, the whole toolkit of dynamical systems and chaos theory has been used to characterize fluid mixing by chaotic advection. Recent work has for example employed topological methods to characterize the stretching of fluid particles. Other recent directions of research concern the study of chaotic advection in complex flows, such as granular flows. | 1 | Applied and Interdisciplinary Chemistry |
RNAi intersects with a number of other pathways; as of 2010 it was not surprising that on occasion, nonspecific effects are triggered by the experimental introduction of an siRNA. When a mammalian cell encounters a double-stranded RNA such as an siRNA, it may mistake it as a viral by-product and mount an immune response. Furthermore, because structurally related microRNAs modulate gene expression largely via incomplete complementarity base pair interactions with a target mRNA, the introduction of an siRNA may cause unintended off-targeting. Chemical modifications of siRNA may alter the thermodynamic properties that also result in a loss of single nucleotide specificity. | 1 | Applied and Interdisciplinary Chemistry |
The word "transcriptome" was first used in the 1990s. In 1995, one of the earliest sequencing-based transcriptomic methods was developed, serial analysis of gene expression (SAGE), which worked by Sanger sequencing of concatenated random transcript fragments. Transcripts were quantified by matching the fragments to known genes. A variant of SAGE using high-throughput sequencing techniques, called digital gene expression analysis, was also briefly used. However, these methods were largely overtaken by high throughput sequencing of entire transcripts, which provided additional information on transcript structure such as splice variants. | 1 | Applied and Interdisciplinary Chemistry |
For single cation systems like SiO and TiO, hydrolysis and condensation processes naturally give rise to homogenous compositions. For systems involving multiple cations, such as strontium titanate, SrTiO and other perovskite systems, the concept of steric immobilisation becomes relevant. To avoid the formation of multiple phases of binary oxides as the result of differing hydrolysis and condensation rates, the entrapment of cations in a polymer network is an effective approach, generally termed the Pechini process. In this process, a chelating agent is used, most often citric acid, to surround aqueous cations and sterically entrap them. Subsequently, a polymer network is formed to immobilize the chelated cations in a gel or resin. This is most often achieved by poly-esterification using ethylene glycol. The resulting polymer is then combusted under oxidising conditions to remove organic content and yield a product oxide with homogeneously dispersed cations. | 0 | Theoretical and Fundamental Chemistry |
Heat can be provided for the endothermic calcination step either directly or indirectly.
Direct provision of heat involves the combustion of fuel in the calciner itself (fluidised bed combustion). This is generally assumed to be done under oxy-fuel conditions; i.e. oxygen rather than air is used to burn the fuel to prevent dilution of the CO with nitrogen. The provision of oxygen for the combustion uses much electricity; other air separation processes are being developed.
Indirect provision of heat to the calciner involves either:
* Combustion of fuel outside the vessel and conduction of energy in to the vessel
* Combustion of fuel in another vessel and use of a heat transfer medium.
Indirect methods are generally less efficient but do not require the provision of oxygen for combustion within the calciner to prevent dilution. The flue gas from the combustion of fuel in the indirect method could be mixed with the flue gas from the process that the CaL plant is attached to and passed through the carbonator to capture the CO. | 1 | Applied and Interdisciplinary Chemistry |
The existence of frigorific mixtures can be viewed as a consequence of the Gibbs phase rule, which describes the relationship at equilibrium between the number of components, the number of coexisting phases, and the number of degrees of freedom permitted by the conditions of heterogeneous equilibrium. Specifically, at constant atmospheric pressure, in a system containing linearly independent chemical components, if +1 phases are specified to be present in equilibrium, then the system is fully determined (there are no degrees of freedom). That is, the temperature and the compositions of all phases are determined. Thus, in for example the chemical system HO-NaCl, which has two components, the simultaneous presence of the three phases liquid, ice, and hydrohalite can exist only at atmospheric pressure at the unique temperature of –21.2 °C
. The approach to equilibrium of a frigorific mixture involves spontaneous temperature change driven by the conversion of latent heat into sensible heat as the phase proportions adjust to accommodate the decrease in thermodynamic potential associated with the approach to equilibrium. | 0 | Theoretical and Fundamental Chemistry |
For fission of uranium-235, the predominant radioactive fission products include isotopes of iodine, caesium, strontium, xenon and barium. The threat becomes smaller with the passage of time. Locations where radiation fields once posed immediate mortal threats, such as much of the Chernobyl Nuclear Power Plant on day one of the accident and the ground zero sites of U.S. atomic bombings in Japan (6 hours after detonation) are now relatively safe because the radioactivity has decreased to a low level.
Many of the fission products decay through very short-lived isotopes to form stable isotopes, but a considerable number of the radioisotopes have half-lives longer than a day.
The radioactivity in the fission product mixture is initially mostly caused by short lived isotopes such as I and Ba; after about four months Ce, Zr/Nb and Sr take the largest share, while after about two or three years the largest share is taken by Ce/Pr, Ru/Rh and Pm. Later Sr and Cs are the main radioisotopes, being succeeded by Tc. In the case of a release of radioactivity from a power reactor or used fuel, only some elements are released; as a result, the isotopic signature of the radioactivity is very different from an open air nuclear detonation, where all the fission products are dispersed. | 0 | Theoretical and Fundamental Chemistry |
In physics, the terms order and disorder designate the presence or absence of some symmetry or correlation in a many-particle system.
In condensed matter physics, systems typically are ordered at low temperatures; upon heating, they undergo one or several phase transitions into less ordered states.
Examples for such an order-disorder transition are:
* the melting of ice: solid–liquid transition, loss of crystalline order;
* the demagnetization of iron by heating above the Curie temperature: ferromagnetic–paramagnetic transition, loss of magnetic order.
The degree of freedom that is ordered or disordered can be translational (crystalline ordering), rotational (ferroelectric ordering), or a spin state (magnetic ordering).
The order can consist either in a full crystalline space group symmetry, or in a correlation. Depending on how the correlations decay with distance, one speaks of long range order or short range order.
If a disordered state is not in thermodynamic equilibrium, one speaks of quenched disorder. For instance, a glass is obtained by quenching (supercooling) a liquid. By extension, other quenched states are called spin glass, orientational glass. In some contexts, the opposite of quenched disorder is annealed disorder. | 0 | Theoretical and Fundamental Chemistry |
Choren Industries has built a plant in Germany that converts biomass to syngas and fuels using the Shell FT process structure. The company went bankrupt in 2011 due to impracticalities in the process.
Biomass gasification (BG) and Fischer–Tropsch (FT) synthesis can in principle be combined to produce renewable transportation fuels (biofuels). | 0 | Theoretical and Fundamental Chemistry |
Lakes and oceans appear cyan for several reasons. One is that the surface of the water reflects the color of the sky, which ranges from cyan to light azure. It is a common misconception that this reflection is the sole reason bodies of water appear cyan, though it can contribute. This contribution usually makes the body of water appear more a shade of azure rather than cyan depending on how bright the sky is.
Water in swimming pools with white-painted sides and bottom will appear cyan, even in indoor pools where there is no sky to be reflected. The deeper the pool, the more intense the cyan color becomes.
Some of the light hitting the surface of ocean is reflected but most of it penetrates the water surface, interacting with water molecules and other substances in the water. Water molecules can vibrate in three different modes when they interact with light. The red, orange, and yellow wavelengths of light are absorbed so the remaining light seen is composed of green, cyan, and blue wavelengths. This is the main reason the ocean's color is cyan. The relative contribution of reflected skylight and the light scattered back from the depths is strongly dependent on observation angle.
Scattering from suspended particles also plays an important role in the color of lakes and oceans, causing the water to look greener or bluer in different areas. A few tens of meters of water will absorb all light, so without scattering, all bodies of water would appear black. Because most lakes and oceans contain suspended living matter and mineral particles, light from above is scattered and some of it is reflected upwards. Scattering from suspended particles would normally give a white color, as with snow, but because the light first passes through many meters of cyan-colored liquid, the scattered light appears cyan. In extremely pure water—as is found in mountain lakes, where scattering from particles is very low—the scattering from water molecules themselves also contributes a cyan color.
Diffuse sky radiation due to Rayleigh scattering in the atmosphere along one's line of sight gives distant objects a cyan or light azure tint. This is most commonly noticed with distant mountains, but also contributes to the cyanness of the ocean in the distance. | 0 | Theoretical and Fundamental Chemistry |
Polyester resin offers the following advantages:
# Adequate resistance to water and variety of chemicals.
# Adequate resistance to weathering and ageing.
# Low cost.
# Polyesters can withstand a temperature up to 80 °C.
# Polyesters have good wetting to glass fibres.
# Relatively low shrinkage at between 4–8% during curing.
# Linear thermal expansion ranges from 100–200 x 10 K. | 0 | Theoretical and Fundamental Chemistry |
Fish scales are calcium phosphate composites coated with a mucus layer. Fish scale properties have been mimicked by polyacrylamide hydrogels, which are both hydrophilic and mimic the mucus’ retention of water. Additionally, fish scales have been used as a template for a casting technique, and as a model for a lithography and chemical etching techniques on silicon wafers that exhibited oleophobic contact angles of oil in water of 163° and 175°, respectively. | 0 | Theoretical and Fundamental Chemistry |
(AD 900–1500)
Objects of personal adornment and ceremonial objects
#Cerro Montoso, Veracruz
#Chachalacas, Veracruz
#El Tajin, Veracruz
#Isla de Sacrificios, Veracruz
#Pánuco, Veracruz
#Tampico, Veracruz | 1 | Applied and Interdisciplinary Chemistry |
Turkevich moved to the Department of Physics at the University of Chicago as a research assistant with Robert Mulliken where he studied molecular spectroscopy and nuclear fission products.
In 1942, during World War II, he joined the Manhattan Project, working initially at Columbia University. The Columbia laboratory group was asked to move to Chicago as part of the project and from 1943 to 1945 he worked at the Metallurgical Laboratory or "Met Lab", at the University of Chicago. He investigated the separation of uranium isotopes by gaseous diffusion of uranium hexafluoride and the radiochemistry of reactor products, such as plutonium, that are generated by neutron capture in uranium. In 1945, he transferred to Los Alamos, and was involved with the Trinity test, the first detonation of a nuclear device, near Alamogordo, New Mexico, on July 16, 1945. Turkevich was one of several scientists who estimated the amount of energy released in the explosion. He then transferred to Edward Teller's theory group to study nuclear fusion and establish whether producing a thermonuclear weapon was feasible, one of many challenges faced by scientists at Los Alamos that led to the development and use of the Monte Carlo method. He worked with Nicholas Metropolis and Stanley Frankel using the ENIAC computer.
Turkevich returned to the Department of Chemistry at the University of Chicago as an assistant professor in 1946. In July 1946, Turkevich and Seymour Katcoff suggested that nuclear explosions could be monitored by measuring the atmospheric concentration of the radioactive isotope krypton-85, a fission product. Turkevich wrote a letter to Philip Morrison proposing that atmospheric sampling could be used to estimate the number of fissions that had occurred in nuclear reactors and atmospheric atom bomb tests. The history of this aspect of Turkevichs work didnt become public until it was declassified in 1997.
He also worked on the peaceful uses of nuclear energy. For this latter work, he received the 1969 Atoms for Peace Award. | 0 | Theoretical and Fundamental Chemistry |
Because of their sequence similarity and operon structure, many two-component systems – particularly histidine kinases – are relatively easy to identify through bioinformatics analysis. (By contrast, eukaryotic kinases are typically easily identified, but they are not easily paired with their substrates.) A database of prokaryotic two-component systems called P2CS has been compiled to document and classify known examples, and in some cases to make predictions about the cognates of "orphan" histidine kinase or response regulator proteins that are genetically unlinked to a partner. | 1 | Applied and Interdisciplinary Chemistry |
The transesterification reaction is base catalyzed. Any strong base capable of deprotonating the alcohol will work (e.g. NaOH, KOH, sodium methoxide, etc.), but the sodium and potassium hydroxides are often chosen for their cost. The presence of water causes undesirable base hydrolysis, so the reaction must be kept dry.
In the transesterification mechanism, the carbonyl carbon of the starting ester (RCOOR) undergoes nucleophilic attack by the incoming alkoxide (RO) to give a tetrahedral intermediate, which either reverts to the starting material, or proceeds to the transesterified product (RCOOR). The various species exist in equilibrium, and the product distribution depends on the relative energies of the reactant and product. | 0 | Theoretical and Fundamental Chemistry |
Enolase next converts 2-phosphoglycerate to phosphoenolpyruvate. This reaction is an elimination reaction involving an E1cB mechanism.
Cofactors: 2 Mg: one "conformational" ion to coordinate with the carboxylate group of the substrate, and one "catalytic" ion that participates in the dehydration | 1 | Applied and Interdisciplinary Chemistry |
Myzocytosis (from Greek: myzein, () meaning "to suck" and kytos () meaning "container", hence referring to "cell") is a method of feeding found in some heterotrophic organisms. It is also called "cellular vampirism" as the predatory cell pierces the cell wall and/or cell membrane of the prey cell with a feeding tube, the conoid, sucks out the cellular content and digests it.
Myzocytosis is found in Myzozoa and also in some species of Ciliophora (both comprise the alveolates). A classic example of myzocytosis is the feeding method of the infamous predatory ciliate, Didinium, where it is often depicted devouring a hapless Paramecium. The suctorian ciliates were originally thought to have fed exclusively through myzocytosis, sucking out the cytoplasm of prey via superficially drinking straw-like pseudopodia. It is now understood that suctorians do not feed through myzocytosis, but actually, instead, manipulate and envenomate captured prey with their tentacle-like pseudopodia. | 1 | Applied and Interdisciplinary Chemistry |
Knowledge of charge carrier mobility in semiconductors is important for understanding the electronic and materials properties of a system. It is also valuable in device design and optimization. This is particularly true for thin film solar cells and thin film transistors, where charge extraction and amplification, respectively, are highly dependent upon mobility. TRMC has been used to study electron and hole dynamics in hydrogenated amorphous silicon, organic semiconductors, metal halide perovskites, metal oxides, dye sensitized systems, quantum dots, carbon nanotubes, chalcogenides, metal organic frameworks, and the interfaces between various systems.
Because charges are normally generated using a green (~2.3 eV) or ultraviolet (~3 eV) laser, this restricts materials to those with comparable or smaller bandgaps. The technique is hence well suited to the study of solar absorbers, but not to wide bandgap semiconductors such as metal oxides.
While it is very similar, and has the same dimensions, the parameter is not the same a charge carrier mobility. contains contributions from both holes and electrons, which cannot conventionally be resolved using TRMC. This is in contrast to Hall Measurements or transistor measurements, where hole and electron mobility can easily be separated. Additionally, the mobility is not directly extracted from the measurements, it is measured multiplied by the carrier generation yield, . The carrier generation yield is the number of electron hole pairs generated per absorbed photon. Because some absorbed photons can lead to bound neutral excitons, not all absorbed photons will lead to detectable free carriers. This can make interpretation of more complicated than mobility. However, generally both mobility and are parameters which one wishes to maximize when developing solar cells.
As a time-resolved technique, TRMC also provides information on the timescale of carrier recombination in solar cells. Unlike time resolved photoluminescence measurements, TRMC is not sensitive to the lifetime of excitons. | 0 | Theoretical and Fundamental Chemistry |
Much gold jewelry is produced by casting, with little or no cold working; which, depending on the alloy grade, may leave the metal relatively soft and bendable. However, a jeweler may intentionally use work hardening to strengthen wearable objects that are exposed to stress, such as rings. | 1 | Applied and Interdisciplinary Chemistry |
pSK1 is a plasmid from Staphylococcus aureus. This plasmid has a partition system determined by a single gene, par, previously known as orf245. This gene does not effect the plasmid copy number nor the grow rate (excluding its implication in a post-segregational killing system). A centromere-like binding sequence is present upstream of the par gene, and is composed of seven direct repeats and one inverted repeat. | 1 | Applied and Interdisciplinary Chemistry |
Consider a hydrogel made of polyelectrolytes decorated with weak acid groups that can ionize according to the reaction
is immersed in a salt solution of physiological concentration. The degree of ionization of the polyelectrolytes is then controlled by the and due to the charged nature of and , electrostatic interactions with other ions in the systems. This is effectively a reacting system governed by acid-base equilibrium modulated by electrostatic effects, and is relevant in drug delivery, sea water desalination and dialysis technologies. Due to the elastic nature of the gel, the dispersion of in the system is constrained and hence, there will be a partitioning of salts ions and inside and outside the gel, which is intimately coupled to the polyelectrolyte degree of ionization. This ion partitioning inside and outside the gel is analogous to the partitioning of ions across a semipemerable membrane in classical Donnan theory, but a membrane is not needed here because the gel volume constraint imposed by network elasticity effectively acts its role, in preventing the macroions to pass through the fictitious membrane while allowing ions to pass.
The coupling between the ion partitioning and polyelectrolyte ionization degree is only partially by the classical Donnan theory. As a starting point we can neglect the electrostatic interactions among ions. Then at equilibrium, some of the weak acid sites in the gel would dissociate to form that electrostatically attracts positive charged and salt cations leading to a relatively high concentration of and salt cations inside the gel. But because the concentration of is locally higher, it suppresses the further ionization of the acid sites. This phenomenon is the prediction of the classical Donnan theory. However, with electrostatic interactions, there are further complications to the picture. Consider the case of two adjacent, initially uncharged acid sites are both dissociated to form . Since the two sites are both negatively charged, there will be a charge-charge repulsion along the backbone of the polymer than tends to stretch the chain. This energy cost is high both elastically and electrostatically and hence suppress ionization. Even though this ionization suppression is qualitatively similar to that of Donnan prediction, it is absent without electrostatic consideration and present irrespective of ion partitioning. The combination of both effects as well as gel elasticity determines the volume of the gel at equilibrium. Due to the complexity of the coupled acid-base equilibrium, electrostatics and network elasticity, only recently has such system been correctly recreated in computer simulations. | 0 | Theoretical and Fundamental Chemistry |
Source:
n-Butyllithium (14.0 mL of a 2.5 M solution in hexane, 35 mmol) was added dropwise to a solution of 2,6-dimethylanisole (4.95 mL, 35 mmol) in 60 mL of tetrahydrofuran at 0°, and the resulting solution was stirred at 0° for 1 hour and then at ambient temperature for 4 hours. The reaction mixture was cooled to 0°, treated with cyclohexanecarboxaldehyde (4.2 mL, 35 mmol), allowed to warm to ambient temperature again, and poured into saturated aqueous ammonium chloride solution. The mixture was extracted with ether and the ether extract was washed with water and brine and concentrated in vacuo. The residue was purified by silica gel chromatography (hexane-ether, 5:1 v/v) to give 4.2 g (48%) of the product as a colorless oil; H NMR (CDCl) δ 1.05–1.50 (m, 6H), 1.64–1.82 (m, 4H), 1.92 (m, 1H), 2.28 (d, 1H, J = 3 Hz), 2.31 (s, 3H), 2.68 (dd, 1H, J = 10, 13 Hz), 2.85 (dd, 1H, J = 3, 13 Hz), 3.57 (m, 1H), 3.75 (s, 3H), 6.95–7.10 (m, 3H). | 0 | Theoretical and Fundamental Chemistry |
Most metal carbonyl complexes contain a mixture of ligands. Examples include the historically important IrCl(CO)(P(CH)) and the antiknock agent (CHCH)Mn(CO). The parent compounds for many of these mixed ligand complexes are the binary carbonyls, those species of the formula [M(CO)], many of which are commercially available. The formulae of many metal carbonyls can be inferred from the 18-electron rule. | 0 | Theoretical and Fundamental Chemistry |
While the presence of any symmetry element within a ligand intended for asymmetric induction might appear counterintuitive, asymmetric induction only requires that the ligand be chiral (i.e. have no improper rotation axis). Asymmetry (i.e. absence of any symmetry elements) is not required. C symmetry improves the enantioselectivity of the complex by reducing the number of unique geometries in the transition states. Steric and kinetic factors then usually favor the formation of a single product. | 0 | Theoretical and Fundamental Chemistry |
Modern-day boilers, such as those in coal-fired power stations, are still fitted with economizers which are descendants of Green's original design. In this context they are often referred to as feedwater heaters and heat the condensate from turbines before it is pumped to the boilers.
Economizers are commonly used as part of a heat recovery steam generator (HRSG) in a combined cycle power plant. In an HRSG, water passes through an economizer, then a boiler and then a superheater. The economizer also prevents flooding of the boiler with liquid water that is too cold to be boiled given the flow rates and design of the boiler.
A common application of economizers in steam power plants is to capture the waste heat from boiler stack gases (flue gas) and transfer it to the boiler feedwater. This raises the temperature of the boiler feedwater, lowering the needed energy input, in turn reducing the firing rates needed for the rated boiler output. Economizers lower stack temperatures which may cause condensation of acidic combustion gases and serious equipment corrosion damage if care is not taken in their design and material selection. | 0 | Theoretical and Fundamental Chemistry |
When an alien pathway is installed in a host (chassis) organism, and even when a native pathway is massively upregulated, reactive intermediates may accumulate to levels that negatively impact viability, growth, and flux through the pathway because a matching damage-control system is absent or has been overwhelmed. Engineering damage-control systems may thus be needed to support synthetic biology and metabolic engineering projects. | 1 | Applied and Interdisciplinary Chemistry |
The properties molar internal energy, , and entropy, , defined by the first and second laws of thermodynamics, hence all thermodynamic properties of a simple compressible substance, can be specified, up to a constant of integration, by two measurable functions, a mechanical equation of state, , and a constant volume specific heat, . | 0 | Theoretical and Fundamental Chemistry |
Mixtures are another common issue faced by forensic scientists when they are analyzing unknown or questionable DNA samples. A mixture is defined as a DNA sample that contains two or more individual contributors. That can often occur when a DNA sample is swabbed from an item that is handled by more than one person or when a sample contains both the victims and the assailants DNA. The presence of more than one individual in a DNA sample can make it challenging to detect individual profiles, and interpretation of mixtures should be performed only by highly trained individuals. Mixtures that contain two or three individuals can be interpreted with difficulty. Mixtures that contain four or more individuals are much too convoluted to get individual profiles. One common scenario in which a mixture is often obtained is in the case of sexual assault. A sample may be collected that contains material from the victim, the victim's consensual sexual partners, and the perpetrator(s).
Mixtures can generally be sorted into three categories: Type A, Type B, and Type C. Type A mixtures have alleles with similar peak-heights all around, so the contributors cannot be distinguished from each other. Type B mixtures can be deconvoluted by comparing peak-height ratios to determine which alleles were donated together. Type C mixtures cannot be safely interpreted with current technology because the samples were affected by DNA degradation or having too small a quantity of DNA present.
When looking at an electropherogram, it is possible to determine the number of contributors in less complex mixtures based on the number of peaks located in each locus. In comparison to a single source profile, which will only have one or two peaks at each locus, a mixture is when there are three or more peaks at two or more loci. If there are three peaks at only a single locus, then it is possible to have a single contributor who is tri-allelic at that locus. Two person mixtures will have between two and four peaks at each locus, and three person mixtures will have between three and six peaks at each locus. Mixtures become increasingly difficult to deconvolute as the number of contributors increases.
As detection methods in DNA profiling advance, forensic scientists are seeing more DNA samples that contain mixtures, as even the smallest contributor can now be detected by modern tests. The ease in which forensic scientists have in interpenetrating DNA mixtures largely depends on the ratio of DNA present from each individual, the genotype combinations, and the total amount of DNA amplified. The DNA ratio is often the most important aspect to look at in determining whether a mixture can be interpreted. For example, if a DNA sample had two contributors, it would be easy to interpret individual profiles if the ratio of DNA contributed by one person was much higher than the second person. When a sample has three or more contributors, it becomes extremely difficult to determine individual profiles. Fortunately, advancements in probabilistic genotyping may make that sort of determination possible in the future. Probabilistic genotyping uses complex computer software to run through thousands of mathematical computations to produce statistical likelihoods of individual genotypes found in a mixture.
Plant DNA profiling (fingerprinting) is a method for identifying cultivars that uses molecular marker techniques. This method is gaining attention due to Trade Related Intellectual property rights (TRIPs) and the Convention on Biological Diversity (CBD).
Identification, authentication, specific distinction, detecting adulteration and identifying phytoconstituents are all possible with DNA fingerprinting in medical plants.
DNA based markers are critical for these applications, determining the future of scientific study in pharmacognosy.
It also helps with determining the traits (such as seed size and leaf color) are likely to improve the offspring or not. | 1 | Applied and Interdisciplinary Chemistry |
Single photons in the infrared spectral range usually are not energetic enough for direct photodissociation of molecules. However, after absorption of multiple infrared photons a molecule may gain internal energy to overcome its barrier for dissociation. Multiple-photon dissociation (MPD; IRMPD with infrared radiation) can be achieved by applying high-power lasers, e.g. a carbon dioxide laser, or a free-electron laser, or by long interaction times of the molecule with the radiation field without the possibility for rapid cooling, e.g. by collisions. The latter method allows even for MPD induced by black-body radiation, a technique called blackbody infrared radiative dissociation (BIRD). | 0 | Theoretical and Fundamental Chemistry |
The Weber number may be written as:
where
* is the drag coefficient of the body cross-section.
* is the density of the fluid (kg/m).
* is its velocity (m/s).
* is its characteristic length, typically the droplet diameter (m).
* is the surface tension (N/m).
The modified Weber number,
equals the ratio of the kinetic energy on impact to the surface energy,
where
and | 1 | Applied and Interdisciplinary Chemistry |
A foam water fire sprinkler system is a special application system, discharging a mixture of water and low expansion foam concentrate, resulting in a foam spray from the sprinkler. These systems are usually used with special hazards occupancies associated with high challenge fires, such as flammable liquids, such as in aircraft hangars. | 1 | Applied and Interdisciplinary Chemistry |
After a period of post-doctoral research with George Sheldrick at the University of Göttingen, Brooker returned to New Zealand to take up a lectureship in chemistry at the University of Otago in 1991. She rose to become a full professor in 2006.
Brooker's research is in the fields of transition-metal and macrocyclic chemistry. Her work has included the development of molecular switches and molecular magnets, with potential application in nanodevices. | 0 | Theoretical and Fundamental Chemistry |
While it is important to note that the process of remineralization is a series of complex biochemical pathways [within microbes], it can often be simplified as a series of one-step processes for ecosystem-level models and calculations. A generic form of these reactions is shown by:
The above generic equation starts with two reactants: some piece of organic matter (composed of organic carbon) and an oxidant. Most organic carbon exists in a reduced form which is then oxidized by the oxidant (such as ) into and energy that can be harnessed by the organism. This process generally produces , water and a collection of simple nutrients like nitrate or phosphate that can then be taken up by other organisms. The above general form, when considering as the oxidant, is the equation for respiration. In this context specifically, the above equation represents bacterial respiration though the reactants and products are essentially analogous to the short-hand equations used for multi-cellular respiration. | 0 | Theoretical and Fundamental Chemistry |
Purple bacteria contain a single photosystem that is structurally related to PSII in cyanobacteria and chloroplasts:
: P870 → P870 → ubiquinone → cyt bc → cyt c → P870
This is a cyclic process in which electrons are removed from an excited chlorophyll molecule (bacteriochlorophyll; P870), passed through an electron transport chain to a proton pump (cytochrome bc complex; similar to the chloroplastic one), and then returned to the chlorophyll molecule. The result is a proton gradient that is used to make ATP via ATP synthase. As in cyanobacteria and chloroplasts, this is a solid-state process that depends on the precise orientation of various functional groups within a complex transmembrane macromolecular structure.
To make NADPH, purple bacteria use an external electron donor (hydrogen, hydrogen sulfide, sulfur, sulfite, or organic molecules such as succinate and lactate) to feed electrons into a reverse electron transport chain. | 0 | Theoretical and Fundamental Chemistry |
Chlorprothixene is an antagonist of the following receptors:
* 5-HT, 5-HT, 5-HT: antipsychotic effects, sedation/anxiolysis, antidepressant effect, weight gain
* D, D, D, D, D: antipsychotic effects, sedation, extrapyramidal side effects, prolactin increase, depression, apathy/anhedonia, weight gain
* H: sedation, weight gain
* Muscarinic acetylcholine receptors: anticholinergic effects, inhibition of extrapyramidal side effects
* α-Adrenergic: hypotension, sedation, anxiolysis
Because of its potent serotonin 5-HT and muscarinic acetylcholine receptor antagonism, chlorprothixene causes relatively mild extrapyramidal symptoms. This is in contrast to most other typical antipsychotics. For this reason, chlorprothixene has sometimes been described instead as an atypical antipsychotic.
Chlorprothixene has also been found to act as FIASMA (functional inhibitor of acid sphingomyelinase). | 0 | Theoretical and Fundamental Chemistry |
Subpolar gyres form at high latitudes (around 60°). Circulation of surface wind and ocean water is cyclonic, counterclockwise in the northern hemisphere and clockwise in the southern hemisphere, around a low-pressure area, such as the persistent Aleutian Low and the Icelandic Low. The wind stress curl in this region drives the Ekman suction, which creates an upwelling of nutrient-rich water from the lower depths.
Subpolar circulation in the southern hemisphere is dominated by the Antarctic Circumpolar Current, due to the lack of large landmasses breaking up the Southern Ocean. There are minor gyres in the Weddell Sea and the Ross Sea, the Weddell Gyre and Ross Gyre, which circulate in a clockwise direction. | 1 | Applied and Interdisciplinary Chemistry |
The charge modulation spectroscopy signal can be defined as the differential transmission divided by the total transmission . By modulating the mobile carriers, an increase transmission and decrease transmission features could be both observed. The former relates to the bleaching and the latter to the charge absorption and electrically induced absorption (electro-absorption). The charge modulation spectroscopy spectra is an overlap of charge-induced and electro-absorption features. In transistors, the electro-absorption is more significant during the high voltage drop. There are several ways to identify the electro-absorption contribution, such as get the second harmonic , or probe it at the depletion region. | 0 | Theoretical and Fundamental Chemistry |
Since all TOC analyzers only actually measure total carbon, TOC analysis always requires some accounting for the inorganic carbon that is always present. One analysis technique involves a two-stage process commonly referred to as TOC differential method. It measures the amount of inorganic carbon (IC) evolved from an acidified aliquot of a sample and also the amount of total carbon (TC) present in the sample. TOC is calculated by subtraction of the IC value from the TC of the sample. Another method directly measures TOC in the sample by acidifying the sample to a pH value of two or less to release the CO gas by decomposition of the carbonates and vent these gases to the air by a purge step. The remaining non-purgeable organic carbon (NPOC) contained in the liquid aliquot is then oxidized releasing the CO gases. These gases are then sent to the detector for measurement. This method is also referred to as the direct TOC method. A further variant employs acidification of the sample to evolve carbon dioxide and measuring it as inorganic carbon (IC), then oxidizing and measuring the remaining non-purgeable organic carbon (NPOC). This is called TIC-NPOC analysis. TC oxidizes in a combustion chamber at 1000 degrees Celsius; if no supporting catalyst is used to allow full combustion at temperatures lower than 1000 degrees C; while the combustion chamber for IC heats only to 150 degrees Celsius. The reason for this is because inorganic is decomposed at lower temperatures than organic carbons.
Whether the analysis of TOC is by TC-IC or NPOC methods, it may be broken into three main stages:
#Acidification
#Oxidation
#Detection and Quantification | 0 | Theoretical and Fundamental Chemistry |
Acidic nucleic acid denaturants include:
* Acetic acid
* HCl
* Nitric acid
Basic nucleic acid denaturants include:
* NaOH
Other nucleic acid denaturants include:
* DMSO
* Formamide
* Guanidine
* Sodium salicylate
* Propylene glycol
* Urea | 1 | Applied and Interdisciplinary Chemistry |
Sink flow is the opposite of source flow. The streamlines are radial, directed inwards to the line source. As we get closer to the sink, area of flow decreases. In order to satisfy the continuity equation, the streamlines get bunched closer and the velocity increases as we get closer to the source. As with source flow, the velocity at all points equidistant from the sink is equal.
The velocity of the flow around the sink can be given by –
The stream function associated with sink flow is –
The flow around a line sink is irrotational and can be derived from velocity potential. The velocity potential around a sink can be given by – | 1 | Applied and Interdisciplinary Chemistry |
A 1996 study by McPhee et al. suggested that stercobilin and other related pyrrolic pigments — including urobilin, biliverdin, and xanthobilirubic acid — has potential to function as a new class of HIV-1 protease inhibitors when delivered at low micromolar concentrations. These pigments were selected due to a similarity in shape to the successful HIV-1 protease inhibitor Merck L-700,417 (N,N-bis(2-hydroxy-1-indanyl)-2,6-diphenylmethyl-4-hydroxy-1,7-heptandiamide). Further research is suggested to study the pharmacological efficacy of these pigments. | 1 | Applied and Interdisciplinary Chemistry |
The thermospray (TSP) interface was developed in 1980 by Marvin Vestal and co-workers at the University of Houston. It was commercialized by Vestec and several of the major mass spectrometer manufacturers. The interface resulted from a long-term research project intended to find a LC–MS interface capable of handling high flow rates (1 ml/min) and avoiding the flow split in DLI interfaces. The TSP interface was composed of a heated probe, a desolvation chamber, and an ion focusing skimmer. The LC effluent passed through the heated probe and emerged as a jet of vapor and small droplets flowing into the desolvation chamber at low pressure. Initially operated with a filament or discharge as the source of ions (thereby acting as a CI source for vapourized analyte), it was soon discovered that ions were also observed when the filament or discharge was off. This could be attributed to either direct emission of ions from the liquid droplets as they evaporated in a process related to electrospray ionization or ion evaporation, or to chemical ionization of vapourized analyte molecules from buffer ions (such as ammonium acetate). The fact that multiply-charged ions were observed from some larger analytes suggests that direct analyte ion emission was occurring under at least some conditions. The interface was able to handle up to 2 ml/min of eluate from the LC column and would efficiently introduce it into the MS vacuum system. TSP was also more suitable for LC–MS applications involving reversed phase liquid chromatography (RT-LC). With time, the mechanical complexity of TSP was simplified, and this interface became popular as the first ideal LC–MS interface for pharmaceutical applications comprising the analysis of drugs, metabolites, conjugates, nucleosides, peptides, natural products, and pesticides. The introduction of TSP marked a significant improvement for LC–MS systems and was the most widely applied interface until the beginning of the 1990s, when it began to be replaced by interfaces involving atmospheric pressure ionization (API). | 0 | Theoretical and Fundamental Chemistry |
Enhancements for improving the effectiveness of SVE can include directional drilling, pneumatic and hydraulic fracturing, and thermal enhancement (e.g., hot air or steam injection). Directional drilling and fracturing enhancements are generally intended to improve the gas flow through the subsurface, especially in lower permeability zones. Thermal enhancements such as hot air or steam injection increase the subsurface soil temperature, thereby improving the volatility of the contamination. In addition, injection of hot (dry) air can remove soil moisture and thus improve the gas permeability of the soil. Additional thermal technologies (such as electrical resistance heating, six-phase soil heating, radio-frequency heating, or thermal conduction heating) can be applied to the subsurface to heat the soil and volatilize/desorb contaminants, but these are generally viewed as separate technologies (versus a SVE enhancement) that may use vacuum extraction (or other methods) for collecting soil gas. | 1 | Applied and Interdisciplinary Chemistry |
eIF2 is the main protein complex responsible for delivering the initiator tRNA to the P-site of the preinitiation complex, as a ternary complex containing Met-tRNA and GTP (the eIF2-TC). eIF2 has specificity for the methionine-charged initiator tRNA, which is distinct from other methionine-charged tRNAs used for elongation of the polypeptide chain. The eIF2 ternary complex remains bound to the P-site while the mRNA attaches to the 40s ribosome and the complex begins to scan the mRNA. Once the AUG start codon is recognized and located in the P-site, eIF5 stimulates the hydrolysis of eIF2-GTP, effectively switching it to the GDP-bound form via gated phosphate release. The hydrolysis of eIF2-GTP provides the conformational change to change the scanning complex into the 48S Initiation complex with the initiator tRNA-Met anticodon base paired to the AUG. After the initiation complex is formed the 60s subunit joins and eIF2 along with most of the initiation factors dissociate from the complex allowing the 60S subunit to bind. eIF1A and eIF5B-GTP remain bound to one another in the A site and must be hydrolyzed to be released and properly initiate elongation.
eIF2 has three subunits, eIF2-α, β, and γ. The former α-subunit is a target of regulatory phosphorylation and is of particular importance for cells that may need to turn off protein synthesis globally as a response to cell signaling events. When phosphorylated, it sequesters eIF2B (not to be confused with eIF2β), a GEF. Without this GEF, GDP cannot be exchanged for GTP, and translation is repressed. One example of this is the eIF2α-induced translation repression that occurs in reticulocytes when starved for iron. In the case of viral infection, protein kinase R (PKR) phosphorylates eIF2α when dsRNA is detected in many multicellular organisms, leading to cell death.
The proteins eIF2A and eIF2D are both technically named eIF2 but neither are part of the eIF2 heterotrimer and they seem to play unique functions in translation. Instead, they appear to be involved in specialized pathways, such as eIF2-independent translation initiation or re-initiation, respectively. | 1 | Applied and Interdisciplinary Chemistry |
Regioselective and stereoselective formation of carbon-carbon bonds adjacent to carbonyl group is an important procedure in organic chemistry. Alkylation reaction of enolates has been the main focus of the field. Both A. G. Myers and D. A. Evans developed asymmetric alkylation reactions for enolates.
The apparent shortcoming for enolate alkylation reactions is over-alkylation, even if the amount of base added for enolization as well as the reaction temperature are carefully controlled. The ketene formation during the deprotonation process for substrates possessing Evans' oxazolidinone is also a main side reaction for the related alkylation reactions. Development in the field of enamine chemistry and the utilization of imine derivatives of enolates managed to provide an alternative for enolate alkylation reactions.
In 1963, G. Stork reported the first enamine alkylation reaction for ketones - Stork enamine alkylation reaction.
In 1976, Meyers reported the first alkylation reaction of metallated azaenolates of hydrazones with an acyclic amino acid-based auxiliary. Compared with the free carbonyl compounds and the chiral enamine species reported previously, the hydrazones exhibit higher reactivity, regioselectivity and stereoselectivity.
The combination of cyclic amino acid derivatives (SAMP and RAMP) and the powerful hydrazone techniques were pioneered by E. J. Corey and D. Enders in 1976, and were independently developed by D. Enders later. Both SAMP and RAMP are synthesized from amino acids. The detailed synthesis of these two auxiliaries are shown below. | 0 | Theoretical and Fundamental Chemistry |
For the preservation of shorter fragment reads, barcode removal and adapter trimming need to be done. After read preprocessing, the alignment of reads to the human genome reference should be performed. Original EPIC-seq used hg19 but for better results, an updated version of human genome reference can be used. One should be careful about their aligner's options since some aligners can interfere with the inclusion of shorter reads paired with longer ones. For the deduplication, attached molecular customized barcodes should be exploited. These barcodes include endogenous and exogenous unique molecular identifiers (UMIs) and are handy for distinguishing Polymerase Chain Reaction (PCR) duplicates from real duplicates and hence for PCR duplicate cleansing. This portion is especially important for oncologic applications since the low mutation abundance can be suppressed by PCR duplicates. | 1 | Applied and Interdisciplinary Chemistry |
It was found that pyruvate dehydrogenase enzyme found in the mitochondria of eukaryotic cells closely resembles an enzyme from Geobacillus stearothermophilus, which is a species of gram-positive bacteria. Despite similarities of the pyruvate dehydrogenase complex with gram-positive bacteria, there is little resemblance with those of gram-negative bacteria. Similarities of the quaternary structures between pyruvate dehydrogenase and enzymes in gram-positive bacteria point to a shared evolutionary history which is distinctive from the evolutionary history of corresponding enzymes found in gram-negative bacteria. Through an endosymbiotic event, pyruvate dehydrogenase found in the eukaryotic mitochondria points to ancestral linkages dating back to gram-positive bacteria.
Pyruvate dehydrogenase complexes share many similarities with branched chain 2-oxoacid dehydrogenase (BCOADH), particularly in their substrate specificity for alpha-keto acids. Specifically, BCOADH catalyzes the degradation of amino acids and these enzymes would have been prevalent during the periods on prehistoric Earth dominated by rich amino acid environments. The E2 subunit from pyruvate dehydrogenase evolved from the E2 gene found in BCOADH while both enzymes contain identical E3 subunits due to the presence of only one E3 gene. Since the E1 subunits have a distinctive specificity for particular substrates, the E1 subunits of pyruvate dehydrogenase and BCOADH vary but share genetic similarities. The gram-positive bacteria and cyanobacteria that would later give rise to mitochondria and chloroplast found in eukaryotic cells retained the E1 subunits that are genetically related to those found in the BCOADH enzymes. | 1 | Applied and Interdisciplinary Chemistry |
When arriving at a site of a surface, an adatom has three options. There is a probability that it will adsorb to the surface (), a probability that it will migrate to another site on the surface (), and a probability that it will desorb from the surface and return to the bulk gas (). For an empty site (θ=0) the sum of these three options is unity.
For a site already occupied by an adatom (θ>0), there is no probability of adsorbing, and so the probabilities sum as:
For the first site visited, the P of migrating overall is the P of migrating if the site is filled plus the P of migrating if the site is empty. The same is true for the P of desorption. The P of adsorption, however, does not exist for an already filled site.
The P of migrating from the second site is the P of migrating from the first site and then migrating from the second site, and so we multiply the two values.
Thus the sticking probability () is the P of sticking of the first site, plus the P of migrating from the first site and then sticking to the second site, plus the P of migrating from the second site and then sticking at the third site etc.
There is an identity we can make use of.
The sticking coefficient when the coverage is zero can be obtained by simply setting . We also remember that
If we just look at the P of migration at the first site, we see that it is certainty minus all other possibilities.
Using this result, and rearranging, we find: | 0 | Theoretical and Fundamental Chemistry |
ChiRP-Seq (Chromatin Isolation by RNA purification) is a high-throughput sequencing method to discover regions of the genome which are bound by a specific RNA (or by a ribonucleoprotein containing the RNA of interest).
Recent studies have shown that a significant proportion of some genomes (including mouse and human genomes) synthesize RNA that apparently do not code for proteins. The function of most of these non-coding RNA still has to be ascertained. Various genomic methods are being developed to map the functional association of these novel RNA to distinct regions of the genome to gain a better understanding of their function. ChiRP-Seq is one of these new methods which uses the massively parallel sequencing capability of 2nd generation sequencers to catalog the binding sites of these novel RNA molecules on a genome.
Although many have believed that RNAs mainly encode for proteins a very large portion of the eukaryotic genome is composed of RNAs that do not. These RNAs were originally considered junk until new advancements lead to the realization that they may indeed have a biological purpose. Over the last few years lncRNAs have been the least explored and functionally characterized emerging regulatory molecules, especially in comparison to their short counterparts, small ncRNAs. ChiRP-Seq is a new technique that has allowed us to map long RNA occupancy across the genome at a higher resolution than ever before. ChiRP-Seq works via affinity capture of a target complex of lncRNA and chromatin by tiling antisense-oligos. This technique will allow scientists to generate a map of genomic binding sites of several hundred bases very accurately due to high sensitivity and low background. | 1 | Applied and Interdisciplinary Chemistry |
Sulfuryl fluoride (also spelled sulphuryl fluoride) is an inorganic compound with the formula SOF. It is an easily condensed gas and has properties more similar to sulfur hexafluoride than sulfuryl chloride, being resistant to hydrolysis even up to 150 °C. It is neurotoxic and a potent greenhouse gas, but is widely used as a fumigant insecticide to control termites. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, functionality is often used as a synonym for functional group. For example, a hydroxyl group can also be called a HO-function.
Functionalisation means the introduction of functional groups, for example
* the functionalisation of a surface (e.g. silanization for the specific modification of the adhesion of a surface)
* the functionalization of nanoparticles of a metal or metal oxide to stabilize such nanoparticles or
* the so-called C-H functionalization, which means the substitution of a C-H bond by a functional group, bonded at the same carbon atom | 0 | Theoretical and Fundamental Chemistry |
Carbon sequestration is the process of storing carbon in a carbon pool. It plays a crucial role in mitigating climate change by reducing the amount of carbon dioxide in the atmosphere. There are two main types of carbon sequestration: biologic (also called biosequestration) and geologic. Biologic carbon sequestration is a naturally occurring process as part of the carbon cycle. Humans can enhance it through deliberate actions and use of technology. Carbon dioxide () is naturally captured from the atmosphere through biological, chemical, and physical processes. These processes can be accelerated for example through changes in land use and agricultural practices, called carbon farming. Artificial processes have also been devised to produce similar effects. This approach is called carbon capture and storage. It involves using technology to capture and sequester (store) that is produced from human activities underground or under the sea bed.
Forests, kelp beds, and other forms of plant life absorb carbon dioxide from the air as they grow, and bind it into biomass. However, these biological stores are considered impermanent carbon sinks as the long-term sequestration cannot be guaranteed. For example, natural events, such as wildfires or disease, economic pressures and changing political priorities can result in the sequestered carbon being released back into the atmosphere.
Carbon dioxide that has been removed from the atmosphere can also be stored in the Earths crust by injecting it into the subsurface, or in the form of insoluble carbonate salts. The latter process is called mineral sequestration. These methods are considered non-volatile' because they not only remove carbon dioxide from the atmosphere but also sequester it indefinitely. This means the carbon is "locked away" for thousands to millions of years.
To enhance carbon sequestration processes in oceans the following technologies have been proposed: Seaweed farming, ocean fertilization, artificial upwelling, basalt storage, mineralization and deep sea sediments, adding bases to neutralize acids. However, none have achieved large scale application so far. | 0 | Theoretical and Fundamental Chemistry |
In early 2004, Schadler, Garde, and Siegel were awarded a U.S. National Science Foundation grant to make a new Molecularium show exclusively for an immersive dome based video display environment, also known as a fulldome medium. They recruited filmmaker, and experience designer, V. Owen Bush to bring the idea to life. Bush founded the production company Nanotoon Entertainment with writer/producer Kurt Przybilla to realize the new project. Bush and Przybilla proposed an adventure story of personified atoms flying a ship called the Molecularium through nanoscale materials including a snowflake, a penny, a stick of gum and the human body.
In February 2005, the team debuted "Molecularium - Riding Snowflakes" a 23-minute digital planetarium show at the Children's Museum of Science and Technology. In 2005, "Molecularium - Riding Snowflakes" won the Domie award at Domefest, a festival for immersive dome films, in Albuquerque New Mexico. "Molecularium - Riding Snowflakes" has shown at Chabot Space and Science Center in Oakland, California, the Newark Museum Planetarium in Newark, New Jersey, Dubai Children’s City, UAE, and Thinktank, Birmingham, UK, among other digital planetariums. It has been translated and versioned in Arabic, Korean and Turkish. It is Distributed by E&S, Spitz, Sky-Skan, and e-Planetarium.
In 2010, the American Library Association (ALA) selected the Molecularium Kid's Site for inclusion to its Great Websites for Kids. | 1 | Applied and Interdisciplinary Chemistry |
In E. coli, the biosynthesis begins with phosphorylation of 5-phosphoribosyl-pyrophosphate (PRPP), catalyzed by ATP-phosphoribosyl transferase. Phosphoribosyl-ATP converts to phosphoribosyl-AMP (PRAMP). His4 then catalyzes the formation of phosphoribosylformiminoAICAR-phosphate, which is then converted to phosphoribulosylformimino-AICAR-P by the His6 gene product. His7 splits phosphoribulosylformimino-AICAR-P to form -erythro-imidazole-glycerol-phosphate. After, His3 forms imidazole acetol-phosphate releasing water. His5 then makes -histidinol-phosphate, which is then hydrolyzed by His2 making histidinol. His4 catalyzes the oxidation of -histidinol to form -histidinal, an amino aldehyde. In the last step, -histidinal is converted to -histidine.
In general, the histidine biosynthesis is very similar in plants and microorganisms.
HisG → HisE/HisI → HisA → HisH → HisF → HisB → HisC → HisB → HisD (HisE/I and HisB are both bifunctional enzymes)
The enzymes are coded for on the His operon. This operon has a distinct block of the leader sequence, called block 1:
Met-Thr-Arg-Val-Gln-Phe-Lys-His-His-His-His-His-His-His-Pro-Asp
This leader sequence is important for the regulation of histidine in E. coli. The His operon operates under a system of coordinated regulation where all the gene products will be repressed or depressed equally. The main factor in the repression or derepression of histidine synthesis is the concentration of histidine charged tRNAs. The regulation of histidine is actually quite simple considering the complexity of its biosynthesis pathway and, it closely resembles regulation of tryptophan. In this system the full leader sequence has 4 blocks of complementary strands that can form hairpin loops structures. Block one, shown above, is the key to regulation. When histidine charged tRNA levels are low in the cell the ribosome will stall at the string of His residues in block 1. This stalling of the ribosome will allow complementary strands 2 and 3 to form a hairpin loop. The loop formed by strands 2 and 3 forms an anti-terminator and translation of the his genes will continue and histidine will be produced. However, when histidine charged tRNA levels are high the ribosome will not stall at block 1, this will not allow strands 2 and 3 to form a hairpin. Instead strands 3 and 4 will form a hairpin loop further downstream of the ribosome. The hairpin loop formed by strands 3 and 4 is a terminating loop, when the ribosome comes into contact with the loop, it will be “knocked off” the transcript. When the ribosome is removed the His genes will not be translated and histidine will not be produced by the cell. | 1 | Applied and Interdisciplinary Chemistry |
The Deborah number is the ratio of fundamentally different characteristic times. The Deborah number is defined as the ratio of the time it takes for a material to adjust to applied stresses or deformations, and the characteristic time scale of an experiment (or a computer simulation) probing the response of the material:
where stands for the relaxation time and for the "time of observation", typically taken to be the time scale of the process.
The numerator, relaxation time, is the time needed for a reference amount of deformation to occur under a suddenly applied reference load (a more fluid-like material will therefore require less time to flow, giving a lower Deborah number relative to a solid subjected to the same loading rate).
The denominator, material time, is the amount of time required to reach a given reference strain (a faster loading rate will therefore reach the reference strain sooner, giving a higher Deborah number).
Equivalently, the relaxation time is the time required for the stress induced, by a suddenly applied reference strain, to reduce by a certain reference amount. The relaxation time is actually based on the rate of relaxation that exists at the moment of the suddenly applied load.
This incorporates both the elasticity and viscosity of the material. At lower Deborah numbers, the material behaves in a more fluidlike manner, with an associated Newtonian viscous flow. At higher Deborah numbers, the material behavior enters the non-Newtonian regime, increasingly dominated by elasticity and demonstrating solidlike behavior.
For example, for a Hookean elastic solid, the relaxation time will be infinite and it will vanish for a Newtonian viscous fluid. For liquid water, is typically 10 s, for lubricating oils passing through gear teeth at high pressure it is of the order of 10 s and for polymers undergoing plastics processing, the relaxation time will be of the order of a few seconds. Therefore, depending on the situation, these liquids may exhibit elastic properties, departing from purely viscous behavior.
While is similar to the Weissenberg number and is often confused with it in technical literature, they have different physical interpretations. The Weissenberg number indicates the degree of anisotropy or orientation generated by the deformation, and is appropriate to describe flows with a constant stretch history, such as simple shear. In contrast, the Deborah number should be used to describe flows with a non-constant stretch history, and physically represents the rate at which elastic energy is stored or released. | 1 | Applied and Interdisciplinary Chemistry |
Photoinhibition occurs continuously when plants or cyanobacteria are exposed to light, and the photosynthesizing organism must, therefore, continuously repair the damage. The PSII repair cycle, occurring in chloroplasts and in cyanobacteria, consists of degradation and synthesis of the D1 protein of the PSII reaction centre, followed by activation of the reaction center. Due to the rapid repair, most PSII reaction centers are not photoinhibited even if a plant is grown in strong light. However, environmental stresses, for example, extreme temperatures, salinity, and drought, limit the supply of carbon dioxide for use in carbon fixation, which decreases the rate of repair of PSII.
In photoinhibition studies, repair is often stopped by applying an antibiotic (lincomycin or chloramphenicol) to plants or cyanobacteria, which blocks protein synthesis in the chloroplast. Protein synthesis occurs only in an intact sample, so lincomycin is not needed when photoinhibition is measured from isolated membranes. The repair cycle of PSII recirculates other subunits of PSII (except for the D1 protein) from the inhibited unit to the repaired one. | 0 | Theoretical and Fundamental Chemistry |
The vapor of cesium metaborate has neutral monomers and dimers as well as ionized versions thereof. The same situation holds for thallium metaborate . | 0 | Theoretical and Fundamental Chemistry |
Ming Wu, a UC Berkeley Professor of electrical engineering and computer sciences invented the new optoelectronic tweezers.
Wu transformed the optical energy from low powered light emitting diodes (LED) into electrical energy via a photoconductive surface. The idea is to allow the LED to switch on and off the photoconductive material via its fine projection. As the optical pattern can be easily transformable through optical projection, this method allows a high flexibility of switching different optical landscapes.
The manipulation/tweezing process is done by the variations between the electric field actuated by the light pattern. The particles will be either attracted or repelled from the actuated point due to its induced electrical dipole. Particles suspended in a liquid will be susceptible to the electrical field gradient, this is known as dielectrophoresis.
One clear advantage is that the electrical conductivity is different between different kinds of cells. Living cells have a lower conductive medium while the dead ones have minimum or no conductive medium. The system may be able to manipulate roughly 10,000 cells or particles at the same time.
See comments by Professor Kishan Dholakia on this new technique, K. Dholakia, Nature Materials 4, 579–580 (01 Aug 2005) News and Views.
"The system was able to move live E. coli bacteria and 20-micrometre-wide particles, using an optical power output of less than 10 microwatts. This is one-hundred-thousandth of the power needed for [direct] optical tweezers".
Another notably new type of optical tweezers is optothermal tweezers invented by Yuebing Zheng at The University of Texas at Austin. The strategy is to use light to create a temperature gradient and exploit the thermophoretic migration of matter for optical trapping. The team further integrated thermophoresis with laser cooling to develop opto-refrigerative tweezers to avoid thermal damages for noninvasive optical trapping and manipulation. | 1 | Applied and Interdisciplinary Chemistry |
Spectroradiometers, which operate almost like the visible region spectrophotometers, are designed to measure the spectral density of illuminants. Applications may include evaluation and categorization of lighting for sales by the manufacturer, or for the customers to confirm the lamp they decided to purchase is within their specifications. Components:
# The light source shines onto or through the sample.
# The sample transmits or reflects light.
# The detector detects how much light was reflected from or transmitted through the sample.
# The detector then converts how much light the sample transmitted or reflected into a number. | 0 | Theoretical and Fundamental Chemistry |
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convention. The net charge of an ion is not zero because its total number of electrons is unequal to its total number of protons.
A cation is a positively charged ion with fewer electrons than protons while an anion is a negatively charged ion with more electrons than protons. Opposite electric charges are pulled towards one another by electrostatic force, so cations and anions attract each other and readily form ionic compounds.
Ions consisting of only a single atom are termed atomic or monatomic ions, while two or more atoms form molecular ions or polyatomic ions. In the case of physical ionization in a fluid (gas or liquid), "ion pairs" are created by spontaneous molecule collisions, where each generated pair consists of a free electron and a positive ion. Ions are also created by chemical interactions, such as the dissolution of a salt in liquids, or by other means, such as passing a direct current through a conducting solution, dissolving an anode via ionization. | 0 | Theoretical and Fundamental Chemistry |
siRNAs act in the nucleus and the cytoplasm and are involved in RNAi as well as CDGS. siRNAs come from long dsRNA precursors derived from a variety of single-stranded RNA (ssRNA) precursors, such as sense and antisense RNAs. siRNAs also come from hairpin RNAs derived from transcription of inverted repeat regions. siRNAs may also arise enzymatically from non-coding RNA precursors. The volume of literature on siRNA within the framework of RNAi is extensive. One of the potent applications of siRNAs is the ability to distinguish the target versus non-target sequence with a single-nucleotide difference. This approach has been considered as therapeutically crucial for the silencing dominant gain-of-function (GOF) disorders,where mutant allele causing disease is differed from wt-allele by a single nucleotide (nt). This type of siRNAs with capability to distinguish a single-nt difference are termed as allele-specific siRNAs. | 1 | Applied and Interdisciplinary Chemistry |
Since the forces of water on a dam are hydrostatic forces, they vary linearly with depth. The total force on the dam is then the integral of the pressure multiplied by the width of the dam as a function of the depth. The center of pressure is located at the centroid of the triangular shaped pressure field from the top of the water line. The hydrostatic force and tipping moment on the dam about some point can be computed from the total force and center of pressure location relative to the point of interest. | 1 | Applied and Interdisciplinary Chemistry |
Zervas was born in 1902 in the rural town of Megalopolis in Arcadia, southern Greece. He was the first of 7 children of lawyer and parliamentarian Theodoros Zervas with Vasiliki Zerva (née Gyftaki). After finishing secondary education at the local Gymnasion of Kalamata in 1918, he went to study Chemistry at the University of Athens. Before finishing his studies there, he moved to Berlin in 1921 where he graduated with a degree in chemistry from the University of Berlin in 1924.
Under the supervision of Max Bergmann, he finished his doctoral thesis on the reactions of amino acids with aldehydes and was awarded his Dr. rer. nat. from the University of Berlin in 1926. He proceeded to work with Bergmann in the Kaiser Wilhelm Institute for Leather Research in Dresden, of which Bergmann was the founder and director. From 1926 to 1929 Zervas was a research associate and eventually rose to head of the organic chemistry division and vice-director of the institute (1929–1934). It was at this period that the two men developed the Bergmann-Zervas oligopeptide synthesis which brought them international fame within academic circles.
Zervas, by that point a close personal friend of Bergmann, decided to follow the latter to the US in 1934 after Bergmann emigrated from Nazi Germany in 1933 under pressure due to his Jewish origin. In New York, Zervas spent 3 years as lecturer and researcher at the Rockefeller Institute for Medical Research.
In 1930, he married Hildegard Lange, and they remained together until his death. | 0 | Theoretical and Fundamental Chemistry |
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In classical field theories, the Lagrangian specification of the flow field is a way of looking at fluid motion where the observer follows an individual fluid parcel as it moves through space and time. Plotting the position of an individual parcel through time gives the pathline of the parcel. This can be visualized as sitting in a boat and drifting down a river.
The Eulerian specification of the flow field is a way of looking at fluid motion that focuses on specific locations in the space through which the fluid flows as time passes. This can be visualized by sitting on the bank of a river and watching the water pass the fixed location.
The Lagrangian and Eulerian specifications of the flow field are sometimes loosely denoted as the Lagrangian and Eulerian frame of reference. However, in general both the Lagrangian and Eulerian specification of the flow field can be applied in any observer's frame of reference, and in any coordinate system used within the chosen frame of reference.
These specifications are reflected in computational fluid dynamics, where "Eulerian" simulations employ a fixed mesh while "Lagrangian" ones (such as meshfree simulations) feature simulation nodes that may move following the velocity field. | 1 | Applied and Interdisciplinary Chemistry |
Chaudhry Abdul Majeed (born:1937; Urdu: چودہری عبد لمجيد ) was a Pakistani nuclear chemist, nuclear weapon and reactor expert. He is known as one of the pioneers of Pakistans nuclear weapon programme, and has worked closely with former Pakistan Atomic Energy Commission (PAEC) Chairman Munir Ahmad Khans plutonium reprocessing project. He rose to prominence when he was apprehended by Pakistans intelligence agencies in a joint operation in late October 2001. Majeed was also one of the founding members of Sultan Bashiruddin Mahmoods Ummah Tameer-e-Nau organisation; an NGO which caused an international embarrassment for Pakistan. | 0 | Theoretical and Fundamental Chemistry |
The Kutta condition allows an aerodynamicist to incorporate a significant effect of viscosity while neglecting viscous effects in the underlying conservation of momentum equation. It is important in the practical calculation of lift on a wing.
The equations of conservation of mass and conservation of momentum applied to an inviscid fluid flow, such as a potential flow, around a solid body result in an infinite number of valid solutions. One way to choose the correct solution would be to apply the viscous equations, in the form of the Navier–Stokes equations. However, these normally do not result in a closed-form solution. The Kutta condition is an alternative method of incorporating some aspects of viscous effects, while neglecting others, such as skin friction and some other boundary layer effects.
The condition can be expressed in a number of ways. One is that there cannot be an infinite change in velocity at the trailing edge. Although an inviscid fluid can have abrupt changes in velocity, in reality viscosity smooths out sharp velocity changes. If the trailing edge has a non-zero angle, the flow velocity there must be zero. At a cusped trailing edge, however, the velocity can be non-zero although it must still be identical above and below the airfoil. Another formulation is that the pressure must be continuous at the trailing edge.
The Kutta condition does not apply to unsteady flow. Experimental observations show that the stagnation point (one of two points on the surface of an airfoil where the flow speed is zero) begins on the top surface of an airfoil (assuming positive effective angle of attack) as flow accelerates from zero, and moves backwards as the flow accelerates. Once the initial transient effects have died out, the stagnation point is at the trailing edge as required by the Kutta condition.
Mathematically, the Kutta condition enforces a specific choice among the infinite allowed values of circulation. | 1 | Applied and Interdisciplinary Chemistry |
Zuclopenthixol antagonises both dopamine D and D receptors, α-adrenoceptors and 5-HT receptors with a high affinity, but has no affinity for muscarinic acetylcholine receptors. It weakly antagonises the histamine (H) receptor but has no α-adrenoceptor blocking activity .
Evidence from in vitro work and clinical sources (i.e. therapeutic drug monitoring databases) suggests that both CYP2D6 and CYP3A4 play important roles in zuclopenthixol metabolism. | 0 | Theoretical and Fundamental Chemistry |
A stabilized liquid membrane device or SLMD is a type of passive sampling device which allows for the in situ, integrative collection of waterborne, labile ionic metal contaminants. By capturing and sequestering metal ions onto its surface continuously over a period of days to weeks, an SLMD can provide an integrative measurement of bioavailable toxic metal ions present in the aqueous environment. As such, they have been used in conjunction with other passive samplers in ecological field studies. | 0 | Theoretical and Fundamental Chemistry |
The Zeeman effect (; ) is the effect of splitting of a spectral line into several components in the presence of a static magnetic field. It is named after the Dutch physicist Pieter Zeeman, who discovered it in 1896 and received a Nobel prize for this discovery. It is analogous to the Stark effect, the splitting of a spectral line into several components in the presence of an electric field. Also similar to the Stark effect, transitions between different components have, in general, different intensities, with some being entirely forbidden (in the dipole approximation), as governed by the selection rules.
Since the distance between the Zeeman sub-levels is a function of magnetic field strength, this effect can be used to measure magnetic field strength, e.g. that of the Sun and other stars or in laboratory plasmas. | 0 | Theoretical and Fundamental Chemistry |
Ali Akbar Moosavi-Movahedi was born in Shiraz, Iran, in 1953. He attended Alborz High School in 1968, graduated from the National University of Iran (now known as Shahid Beheshti University) with a BSc in chemistry in 1975, earned his MSc in Bioanalytical Chemistry at the Eastern Michigan University in 1979, and obtained his Ph.D. in Biophysical Chemistry at the University of Manchester in 1986. | 0 | Theoretical and Fundamental Chemistry |
Keith Fagnou (June 27, 1971 – November 11, 2009) was a Canadian organic chemist and studied education and was a professor of chemistry at University of Saskatchewan and associate professor of organic chemistry at the University of Ottawa. His research focused on developing new reactions that avoid unnecessary activation of substrates and that can instead directly functionalize C–H bonds of simple molecules and introduce C–C bonds. | 0 | Theoretical and Fundamental Chemistry |
Canuel has a B.S. in Chemistry from Stonehill College (1981) and earned her Ph.D.in Marine Science (1992) from the University of North Carolina at Chapel Hill. Following her Ph.D. she was a postdoctoral researcher at the United States Geological Survey until 1994 when she joined the faculty at the College of William & Mary. She was promoted to professor in 2006, and named Chancellor Professor in 2018.
From 2018 until 2020 Canuel was a program officer at the National Science Foundation, and she returned there in 2021. | 0 | Theoretical and Fundamental Chemistry |
Cytochrome c was also discovered in 1996 by Xiaodong Wang to have an intermediate role in apoptosis, a controlled form of cell death used to kill cells in the process of development or in response to infection or DNA damage.
Cytochrome c binds to cardiolipin in the inner mitochondrial membrane, thus anchoring its presence and keeping it from releasing out of the mitochondria and initiating apoptosis. While the initial attraction between cardiolipin and cytochrome c is electrostatic due to the extreme positive charge on cytochrome c, the final interaction is hydrophobic, where a hydrophobic tail from cardiolipin inserts itself into the hydrophobic portion of cytochrome c.
During the early phase of apoptosis, mitochondrial ROS production is stimulated, and cardiolipin is oxidized by a peroxidase function of the cardiolipin–cytochrome c complex. The hemoprotein is then detached from the mitochondrial inner membrane and can be extruded into the soluble cytoplasm through pores in the outer membrane.
The sustained elevation in calcium levels precedes cyt c release from the mitochondria. The release of small amounts of cyt c leads to an interaction with the IP3 receptor (IP3R) on the endoplasmic reticulum (ER), causing ER calcium release. The overall increase in calcium triggers a massive release of cyt c, which then acts in the positive feedback loop to maintain ER calcium release through the IP3Rs. This explains how the ER calcium release can reach cytotoxic levels. This release of cytochrome c in turn activates caspase 9, a cysteine protease. Caspase 9 can then go on to activate caspase 3 and caspase 7, which are responsible for destroying the cell from within. | 1 | Applied and Interdisciplinary Chemistry |
In 1960, Qureshi found employment with the Pakistan Atomic Energy Commission (PAEC), and was posted to the Atomic Energy Center in Lahore where his interest built in radiochemistry. Upon returning to Pakistan from Denmark in 1971, he joined the Institute of Nuclear Science and Technology (the national lab) in Nilore, working at the Nuclear Chemistry Division (NCD).
As early as 1972, Qureshi joined the team of scientists that began working on the equation of state of the radioactive decay element plutonium, while he established the computerized radiation detection chemical analysis laboratories at the Pakistan Institute of Nuclear Science and Technology in 1973. In 1974, Qureshi and his team was instrumental at the national laboratory when he was the first to confirm the detection of radiation emissions coming from Rajasthan in India. Hence, by using neutron activation analysis, confirming Pokhran-I the first Indian nuclear test, which India later announced was indeed conducted at the Pokhran Test Range. Notably, he led the team that balanced the chemical equation required for the exothermic chemical reaction in fission devices. By 1977, he discovered the technique for balancing the nuclear Q-value and energy balance in a boosted fission weapon.
Eventually, Qureshi headed the Nuclear Chemistry Division (NCD) at the Institute of Nuclear Science and Technology which was responsible for the multi-stage chemical process that separated, concentrated and isolated plutonium from uranium. At NCD, he also played a supervisory role in developing the Analytical Chemistry Group comprising modern and state of the art analytical chemistry laboratories such as the Analytical Chemistry Laboratory, Atomic Absorption Spectroscopy lab, Emission Spectrography lab, Chromatography lab, Electrochemical Analysis lab and radioisotope production labs. The Analytical Chemistry Laboratory was later certified by the International Atomic Energy Agency (IAEA), and oversaw the successful commissioning of the PARR-III reactor that went phase critical in 1973.
Qureshi engaged in research about copper-nickel alloys after introducing the lattice dynamical method to evaluate the Cu/Ni alloys. Key and fundamental research on understanding neutron flux was carried out by Qureshi, for which he managed to secure patents from the IAEA. After the conclusion of the Pakistan's clandestine atomic bomb projects, he was appointed chief technical officer at the Pakistan Atomic Energy Commission (PAEC) in 1991; though he was more eager to return to academia.
Throughout his time at PAEC, Qureshi earned several scientific honors, including the Gold Medal and a Fellowship of the Pakistan Academy of Sciences in 1994. He was a recipient of the Sitara-i-Imtiaz (Star of Excellence) from the Government of Pakistan in 1992. In 1997, from the Iranian Government, he received the Khwarizmi International Award for advancing and understanding the "Nuclear analytical techniques development and application in Pakistan". | 0 | Theoretical and Fundamental Chemistry |
The book was first published by Profile Books in 2015. The British edition was subtitled with the question of the title, "Why is Life the Way it is?", whereas the American edition was subtitled with the explanation "Energy, Evolution, and the Origins of Complex Life". A paperback edition came out in 2016. The book has been translated into at least seven languages: Chinese, German, Japanese, Korean, Polish, Spanish, and Turkish. | 1 | Applied and Interdisciplinary Chemistry |
The Rayleigh number can also be used as a criterion to predict convectional instabilities, such as A-segregates, in the mushy zone of a solidifying alloy. The mushy zone Rayleigh number is defined as:
where:
* is the mean permeability (of the initial portion of the mush)
*L is the characteristic length scale
*α is the thermal diffusivity
*ν is the kinematic viscosity
*R is the solidification or isotherm speed.
A-segregates are predicted to form when the Rayleigh number exceeds a certain critical value. This critical value is independent of the composition of the alloy, and this is the main advantage of the Rayleigh number criterion over other criteria for prediction of convectional instabilities, such as Suzuki criterion.
Torabi Rad et al. showed that for steel alloys the critical Rayleigh number is 17. Pickering et al. explored Torabi Rad's criterion, and further verified its effectiveness. Critical Rayleigh numbers for lead–tin and nickel-based super-alloys were also developed. | 1 | Applied and Interdisciplinary Chemistry |
The 2nd analytical group of cations consists of ions which form acid-insoluble sulfides. Cations in the 2nd group include: Cd, Bi, Cu, As, As, Sb, Sb, Sn, Sn and Hg. Pb is usually also included here in addition to the first group. Although these methods refer to solutions that contain sulfide (S), these solutions actually only contain HS and bisulfide (HS). Sulfide (S) does not exist in appreciable concentrations in water.
The reagent used can be any substance that gives S ions in such solutions; most commonly used are hydrogen sulfide (at 0.2-0.3 M), thioacetamide (at 0.3-0.6 M), addition of hydrogen sulfide can often prove to be a lumbersome process and therefore sodium sulfide can also serve the purpose. The test with the sulfide ion must be conducted in the presence of dilute HCl. Its purpose is to keep the sulfide ion concentration at a required minimum, so as to allow the precipitation of 2nd group cations alone. If dilute acid is not used, the early precipitation of 4th group cations (if present in solution) may occur, thus leading to misleading results. Acids beside HCl are rarely used. Sulfuric acid may lead to the precipitation of the 5th group cations, whereas nitric acid oxidises the sulfide ion in the reagent, forming colloidal sulfur.
The precipitates of these cations are almost indistinguishable, except for CdS, which is yellow. All the precipitates, except for HgS, are soluble in dilute nitric acid. HgS is soluble only in aqua regia, which can be used to separate it from the rest. The action of ammonia is also useful in differentiating the cations. CuS dissolves in ammonia forming an intense blue solution, whereas CdS dissolves forming a colourless solution. The sulfides of As, As, Sb, Sb, Sn, Sn are soluble in yellow ammonium sulfide, where they form polysulfide complexes.
This group is determined by adding the salt in water and then adding dilute hydrochloric acid (to make the medium acidic) followed by hydrogen sulfide gas. Usually it is done by passing hydrogen sulfide over the test tube for detection of 1st group cations. If it forms a reddish-brown or black precipitate then Bi, Cu, Hg or Pb is present. Otherwise, if it forms a yellow precipitate, then Cd or Sn is present; or if it forms a brown precipitate, then Sn must be present; or if a red orange precipitate is formed, then Sb is present.
:Pb + KCrO → PbCrO + 2 K
Confirmation test for copper:
:2 Cu + K[Fe(CN)] + CHCOOH → Cu[Fe(CN)] + 4 K
:Cu + 2 NaOH → Cu(OH) + 2 Na
:Cu(OH) → CuO + HO (endothermic)
Confirmation test for bismuth:
:Bi + 3 KI (in excess) → BiI + 3 K
:BiI + KI → K[BiI]
:Bi + HO (in excess) → BiO + 2 H
Confirmation test for mercury:
:Hg + 2 KI (in excess) → HgI + 2 K
:HgI + 2 KI → K[HgI] (red precipitate dissolves)
:2 Hg + SnCl → 2 Hg + SnCl (white precipitate turns gray) | 0 | Theoretical and Fundamental Chemistry |
:This type of reactor contains two banks of heat exchangers which remove heat; the remainder of which is removed by the products and recycled in the system. The formation of heavy waxes should be avoided, since they condense on the catalyst and form agglomerations. This leads to fluidization. Hence, risers are operated over 297 °C (570 K). | 0 | Theoretical and Fundamental Chemistry |
The SI definition given by the International Committee for Weights and Measures (CIPM) says:
"The quantity dose equivalent H is the product of the absorbed dose D of ionizing radiation and the dimensionless factor Q (quality factor) defined as a function of linear energy transfer by the ICRU"
:H = Q × D
The value of Q is not defined further by CIPM, but it requires the use of the relevant ICRU recommendations to provide this value.
The CIPM also says that "in order to avoid any risk of confusion between the absorbed dose D and the dose equivalent H, the special names for the respective units should be used, that is, the name gray should be used instead of joules per kilogram for the unit of absorbed dose D and the name sievert instead of joules per kilogram for the unit of dose equivalent H".
In summary:
:gray: quantity D – absorbed dose
::1 Gy = 1 joule/kilogram – a physical quantity. 1 Gy is the deposit of a joule of radiation energy per kilogram of matter or tissue.
:sievert: quantity H – equivalent dose
::1 Sv = 1 joule/kilogram – a biological effect. The sievert represents the equivalent biological effect of the deposit of a joule of radiation energy in a kilogram of human tissue. The ratio to absorbed dose is denoted by Q. | 0 | Theoretical and Fundamental Chemistry |
Iron or steel, when heated to above 460 °C (900 °F), glows with a red color. The color of heated iron changes predictably (due to black-body radiation) from dull red through orange and yellow to white, and can be a useful indicator of its temperature. Good quality iron or steel at and above this temperature becomes increasingly malleable and plastic. Iron or steel having too much sulfur, on the other hand, becomes crumbly and brittle. This is due to the sulfur forming iron sulfide/iron mixtures in the grain boundaries of the metal which have a lower melting point than the steel.
When the steel is heated up and worked, the mechanical energy added to the workpiece increases the temperature further. The iron sulfide (FeS) or iron/iron sulfide alloy (which has an even lower melting point) begins to melt, and the steel starts to separate at the grain boundaries. Steelmakers add manganese (Mn) to the steel when it is produced, to form manganese sulfide (MnS). Manganese sulfide inclusions have a higher melting point and do not concentrate at the grain boundaries. Thus, when the steel is later heated up and worked, the melting at the grain boundaries does not occur. | 1 | Applied and Interdisciplinary Chemistry |
Particulate inorganic carbon (PIC) usually takes the form of calcium carbonate (CaCO), and plays a key part in the ocean carbon cycle. This biologically fixed carbon is used as a protective coating for many planktonic species (coccolithophores, foraminifera) as well as larger marine organisms (mollusk shells). Calcium carbonate is also excreted at high rates during osmoregulation by fish, and can form in whiting events. While this form of carbon is not directly taken from the atmospheric budget, it is formed from dissolved forms of carbonate which are in equilibrium with CO and then responsible for removing this carbon via sequestration.
:CO + HO → HCO → H + HCO
:Ca + 2HCO → CaCO + CO + HO
While this process does manage to fix a large amount of carbon, two units of alkalinity are sequestered for every unit of sequestered carbon. The formation and sinking of CaCO therefore drives a surface to deep alkalinity gradient which serves to raise the pH of surface waters, shifting the speciation of dissolved carbon to raise the partial pressure of dissolved CO in surface waters, which actually raises atmospheric levels. In addition, the burial of CaCO in sediments serves to lower overall oceanic alkalinity, tending to raise pH and thereby atmospheric CO levels if not counterbalanced by the new input of alkalinity from weathering. The portion of carbon that is permanently buried at the sea floor becomes part of the geologic record. Calcium carbonate often forms remarkable deposits that can then be raised onto land through tectonic motion as in the case with the White Cliffs of Dover in Southern England. These cliffs are made almost entirely of the plates of buried coccolithophores. | 0 | Theoretical and Fundamental Chemistry |
Bioprinting also has possible uses in the future in assisting in wastewater treatment and in corrosion control. When humans come in contact with environmental biofilms, it is possible for infections and long-term health hazards to occur. Antibiotic penetration and expansion within a biofilm is an area of research which can benefit from bioprinting techniques, to further explore the effect of environmental biofilms on human health. Biofilm printing requires further research due to limited published data and complex protocols. | 1 | Applied and Interdisciplinary Chemistry |
Common biosurfactants include:
* Bile salts are mixtures of micelle-forming compounds that encapsulate food, enabling absorption through the small intestine.
* Lecithin, which can be obtained either from soybean or from egg yolk, is a common food ingredient.
* Rhamnolipids, which can be produced by some species of Pseudomonas, e.g., Pseudomonas aeruginosa.
* Sophorolipids are produced by various nonpathogenic yeasts.
* Emulsan produced by Acinetobacter calcoaceticus.
Microbial biosurfactants are obtained by including immiscible liquids in the growth medium. | 0 | Theoretical and Fundamental Chemistry |
Optimization involves both structural optimization of the flow sheet itself as well as optimization of parameters in a given flowsheet. In the former one may alter the equipment used and/or its connections with other equipment. In the latter one can change the values of parameters such as temperature and pressure. Parameter Optimization is a more advanced stage of theory than process flowsheet optimization. | 1 | Applied and Interdisciplinary Chemistry |
A radiogenic nuclide is a nuclide that is produced by a process of radioactive decay. It may itself be radioactive (a radionuclide) or stable (a stable nuclide).
Radiogenic nuclides (more commonly referred to as radiogenic isotopes) form some of the most important tools in geology. They are used in two principal ways:
#In comparison with the quantity of the radioactive parent isotope in a system, the quantity of the radiogenic daughter product is used as a radiometric dating tool (e.g. uranium–lead geochronology).
#In comparison with the quantity of a non-radiogenic isotope of the same element, the quantity of the radiogenic isotope is used to define its isotopic signature (e.g. Pb/Pb). This technique is discussed in more detail under the heading isotope geochemistry. | 0 | Theoretical and Fundamental Chemistry |
As reagent testing has become more popular, vendors have begun to offer a greater range of tests. This increases the likelihood that a substance might have a unique profile of results, making the tests more useful.
Other reagents are discussed in scientific literature, but limited applications mean they may not be sold for consumer testing.
The National Institute of Justice provides information about "Color Test Reagents/Kits for Preliminary Identification
of Drugs of Abuse" in NIJ Standard–0604.01.
Several products are in early phases of development that are intended to allow their users to covertly detect (without using droppers, etc.) date-rape drugs, for instance reusable straws with components that change color in the presence of GHB, Rohypnol, or ketamine – see . | 0 | Theoretical and Fundamental Chemistry |
Numerous drugs can raise GGT levels, including barbiturates and phenytoin. GGT elevation has also been occasionally reported following nonsteroidal anti-inflammatory drugs (including aspirin), St. John's wort and kava. | 1 | Applied and Interdisciplinary Chemistry |
Mini-Reviews in Medicinal Chemistry is a monthly peer-reviewed medical journal covering all aspects of medicinal chemistry. It is published by Bentham Science Publishers and the editors-in-chief are Atta-ur-Rahman (University of Cambridge), M. Iqbal Choudhary (University of Karachi), and George Perry (University of Texas at San Antonio). | 1 | Applied and Interdisciplinary Chemistry |
Rewriting the above result for the pressure as , we may combine it with the ideal gas law
where is the Boltzmann constant and the absolute temperature defined by the ideal gas law, to obtain
which leads to a simplified expression of the average translational kinetic energy per molecule,
The translational kinetic energy of the system is times that of a molecule, namely . The temperature, is related to the translational kinetic energy by the description above, resulting in
which becomes
Equation () is one important result of the kinetic theory:
The average molecular kinetic energy is proportional to the ideal gas laws absolute temperature'.
From equations () and (), we have
Thus, the product of pressure and volume per mole is proportional to the average
translational molecular kinetic energy.
Equations () and () are called the "classical results", which could also be derived from statistical mechanics;
for more details, see:
The equipartition theorem requires that kinetic energy is partitioned equally between all kinetic degrees of freedom, D. A monotatomic gas is axially symmetric about each spatial axis, so that D = 3 comprising translational motion along each axis. A diatomic gas is axially symmetric about only one axis, so that D = 5, comprising translational motion along three axes and rotational motion along two axes. A polyatomic gas, like water, is not radially symmetric about any axis, resulting in D = 6, comprising 3 translational and 3 rotational degrees of freedom.
Because the equipartition theorem requires that kinetic energy is partitioned equally, the total kinetic energy is
Thus, the energy added to the system per gas particle kinetic degree of freedom is
Therefore, the kinetic energy per kelvin of one mole of monatomic ideal gas (D = 3) is
where is the Avogadro constant, and R is the ideal gas constant.
Thus, the kinetic energy per unit kelvin of an ideal monoatomic gas can be calculated easily:
* per mole: 12.47 J / K
* per molecule: 20.7 yJ / K = 129 μeV / K
At standard temperature (273.15 K), the kinetic energy can also be obtained:
* per mole: 3406 J
* per molecule: 5.65 zJ = 35.2 meV.
At higher temperatures (typically thousands of kelvins), vibrational modes become active to provide additional degrees of freedom, creating a temperature-dependence on D and the total molecular energy. Quantum statistical mechanics is needed to accurately compute these contributions. | 0 | Theoretical and Fundamental Chemistry |
* Biochemistry of phenolic compounds, by J. B. Harborne, 1964, Academic Press ([https://books.google.com/books?id=_-lqAAAAMAAJ Google Books])
* Plant phenolics, by Pascal Ribéreau-Gayon, 1972, Oliver and Boyd Editions ([https://books.google.com/books?id=EHzwAAAAMAAJ Google Books], , )
* The Biochemistry of plant phenolics, by C. F. van Sumere and P. J. Lea, Phytochemical Society of Europe, 1985, Clarendon Press ([https://books.google.com/books?id=YwmLAAAAIAAJ Google Books], )
* Biochemistry of Phenolic Compounds, by Wilfred Vermerris and Ralph Nicholson, 2006, Springer ([https://books.google.com/books?id=uLzdv8fsRxYC&dq=Biochemistry+of+Phenolic+Compounds&pg=PA3 Google book]) | 0 | Theoretical and Fundamental Chemistry |
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