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Dendrimers are unique hyper-branched synthetic polymers with monodispersed size, well-defined structure, and a highly functionalized terminal surface. They are typically composed of synthetic or natural amino acid, nucleic acids, and carbohydrates. Therapeutics can be loaded with relative ease onto the interior of the dendrimers or the terminal surface of the branches via electrostatic interaction, hydrophobic interactions, hydrogen bonds, chemical linkages, or covalent conjugation. Drug-dendrimer conjugation can elongate the half-life of drugs. Currently, dendrimer use in biological systems is limited due to dendrimer toxicity and limitations in their synthesis methods. Dendrimers are also confined within a narrow size range (<15 nm) and current synthesis methods are subject to low yield. The surface groups will reach the de Gennes dense packing limit at high generation level, which seals the interior from the bulk solution – this can be useful for encapsulation of hydrophobic, poorly soluble drug molecules. The seal can be tuned by intramolecular interactions between adjacent surface groups, which can be varied by the condition of the solution, such as pH, polarity, and temperature, a property which can be utilized to tailor encapsulation and controlled release properties. | 0 | Theoretical and Fundamental Chemistry |
The SAW chemosensor is nonionic and nonspecific. It directly measures the total mass of each chemical compound as it exits the gas chromatography column and condenses on the crystal surface, thus causing a change in the fundamental acoustic frequency of the crystal. Odor concentration is directly measured with this integrating type of detector. Column flux is obtained from a microprocessor that continuously calculates the derivative of the SAW frequency. | 0 | Theoretical and Fundamental Chemistry |
Jerry March, Ph.D. (August 1, 1929 – December 25, 1997) was an American organic chemist and a professor of chemistry at Adelphi University.
March authored the Marchs Advanced Organic Chemistry' text, which is considered to be a pillar of graduate-level organic chemistry texts. The book was prepared in its fifth edition at the time of his death. | 0 | Theoretical and Fundamental Chemistry |
Sediment chemistry provides information on contamination, however it does not provide information of biological effects (Chapman, 1990). Sediment chemistry is used as a screening tool to determine the contaminants that are most likely to be destructive to organisms present in the benthic community at a specific site. During analysis, sediment chemistry data does not depend strictly on comparisons to sediment quality guidelines when utilizing the triad approach. Rather, sediment chemistry data, once collected for the specific site, is compared to the most relevant guide values, based on site characteristics, to assess which chemicals are of the greatest concern. This technique is used because no one set of data is adequate for all situations. This allows you to identify the chemicals of concern, which most frequently exceed effects-based guidelines. Once the chemical composition of the sediment is determined and the most concerning contaminants have been identified, toxicity tests are conducted to link environmental concentrations to potential adverse effects. | 1 | Applied and Interdisciplinary Chemistry |
In Gross-Pitaevskii mean field theory, one replaces the field operators with c-number functions:
. To find the mean-field
ground states, one then minimises the resulting energy with respect to these c-number functions.
For a spatially uniform system spin-one system, there are two possible mean-field ground states.
When , the ground state is
while for the ground state is
The former expression is referred to as the polar state while the latter is the
ferromagnetic state.
Both states are unique up to overall spin rotations. Importantly,
cannot be rotated into .
The Majorana stellar representation
provides a particularly insightful description of the mean-field phases of spinor
condensates with larger spin. | 0 | Theoretical and Fundamental Chemistry |
Bioleaching is in general simpler and, therefore, cheaper to operate and maintain than traditional processes, since fewer specialists are needed to operate complex chemical plants. And low concentrations are not a problem for bacteria because they simply ignore the waste that surrounds the metals, attaining extraction yields of over 90% in some cases. These microorganisms actually gain energy by breaking down minerals into their constituent elements. The company simply collects the ions out of the solution after the bacteria have finished.
Bioleaching can be used to extract metals from low concentration ores such as gold that are too poor for other technologies. It can be used to partially replace the extensive crushing and grinding that translates to prohibitive cost and energy consumption in a conventional process. Because the lower cost of bacterial leaching outweighs the time it takes to extract the metal.
High concentration ores, such as copper, are more economical to smelt rather bioleach due to the slow speed of the bacterial leaching process compared to smelting. The slow speed of bioleaching introduces a significant delay in cash flow for new mines. Nonetheless, at the largest copper mine of the world, Escondida in Chile the process seems to be favorable.
Economically it is also very expensive and many companies once started can not keep up with the demand and end up in debt. | 1 | Applied and Interdisciplinary Chemistry |
*Beridze TG, Odintsova MS, Sissakian NM (1967) Distribution of bean leaf DNA components in the cell organelle fractions. Molek.Biol.USSR. 1,142-153
*Beridze TG (1972) DNA nuclear satellites of the genus Phaseolus. Biochim. Biophys. Acta 262,393-396
*Beridze TG (1975) DNA nuclear satellites of the genus Brassica: variation between species. Biochim.Biophys.Acta. 395,274-279
*Beridze T. Satellite DNA, 1986, Springer-Verlag, Berlin, Heidelberg, New York, Tokio
*Beridze T, Pipia I, Beck J., Hsu S.-CT, Gamkrelidze M, Gogniashvili M, Tabidze V, This R,Bacilieri P, Gotsiridze V, Glonti M, Schaal B (2011). Plastid DNA sequence diversity in a worldwide set of grapevine cultivars (Vitis vinifera L. subsp. vinifera). Bulletin of the Georgian National Academy of Sciences. 5, 2011, 98–103.
*Pipia I, Gogniashvili M, Tabidze V, Beridze T, Gamkrelidze M, Gotsiridze V, Melyan G, Musayev M, Salimov V, Beck J, Schaal B (2012) Plastid DNA sequence diversity in wild grapevine samples (Vitis vinifera subsp. sylvestris) from the Caucasus region. Vitis 51 (3), 119–124
*Tabidze V, Baramidze G, Pipia I, Gogniashvili M, Ujmajuridze L, Beridze T, Hernandez AG, Schaal B (2014) The Complete Chloroplast DNA Sequence of Eleven Grape Cultivars. Simultaneous Resequencing Methodology. Journal International des Sciences de la Vigne et du Vin J Int Sci Vigne Vin. 48, 99-109
*Tabidze V, Pipia I, Gogniashvili M, Kunelauri N, Ujmajuridze L, Pirtskhalava M, Vishnepolsky B, Hernandez AG, Fields CJ, BeridzeT (2017) Whole genome comparative analysis of four Georgian grape cultivars. Molecular Genetics and Genomics. 292, 1377-1389
*Gogniashvili M., Naskidashvili P., Bedoshvili D., Kotorashvili A., Kotaria N., Beridze T. (2015) Complete chloroplast DNA sequences of Zanduri wheat (Triticum spp.) Genet Resour Crop Evol
*Gogniashvili M, Jinjikhadze T, Maisaia M, Akhalkatsi M, Kotorashvili A, Kotaria N, Beridze T, Dudnikov AJ (2016) Complete chloroplast genomes of Aegilops tauschii Coss. and Ae.cylindrica Host sheds light on plasmon D evolution. Current Genetics.
*Gogniashvili M, Maisaia I, Kotorashvili A, Kotaria N, Beridze T (2018) Complete chloroplast DNA sequences of Georgian indigenous polyploid wheats (Triticum spp.) and B plasmon evolution. Genet Resour Crop Evol 65:1995–2002 | 1 | Applied and Interdisciplinary Chemistry |
Scanning electron microscopy is a useful tool to employ before any of the above analyses that may result in loss of the original material since it can be used to check for daughter minerals or vapor bubbles and help determine the best technique that should be chosen for melt inclusion analysis. | 0 | Theoretical and Fundamental Chemistry |
Spot tests are performed by placing a small amount of the desired reagent on the portion of the lichen to be tested. Often, both the cortex and medulla of the lichen are tested, and at times it is useful to test other structures such as soralia. One method is to draw up a small amount of the chemical into a glass capillary and touch it to the lichen thallus; a small paint brush is also used for this purpose. Reactions are best visualised with a hand lens or a stereo microscope. A razor blade may be used to remove the cortex and access the medulla. Alternatively, the solution can be applied to lichen features that lack a cortex or that leave the medulla exposed, such as soralia, pseudocyphellae, or the underside of squamules.
In a variation of this technique, suggested by the Swedish chemist Johan Santesson, a piece of filter paper is used to try to make the colour reaction more readily observable. The lichen fragment is pressed on the paper, and lichen substances are extracted with 10–20 drops of acetone. After evaporating the acetone, the lichen substances are left on the paper in a ring around the lichen fragment. The filter paper can then be spot tested in the usual way. In cases where the results of a spot test on the thallus are uncertain, it is possible to squash a thin section of the tissue on a microscope slide in a minimal amount of water and reagent under a cover slip. A colour change is visible under a low-power microscope objective, or when the slide placed against a white background. This technique is useful when testing lichens with dark pigments, such as Bryoria.
Spot tests may be used individually or in combination. The results of a spot tests are typically represented with a short code that includes, in order, (1) a letter indicating the reagent used, (2) a "+" or "−" sign indicating a colour change or lack of colour change, respectively, and (3) a letter or word indicating the colour observed. In addition, care should be taken to indicate which part of the lichen was tested. For example, "Cortex K+ orange, C−, P−" means the cortex of the test specimen turned orange with application of KOH and did not change under bleach or para-phenylenediamine. Similarly, "Medulla K−, KC+R" would indicate the medulla of the lichen was insensitive to application of KOH, but application of KOH followed immediately by bleach caused the medulla to turn red.
Occasionally, it takes some time for the colour reaction to develop. For example, in certain Cladonia species, the PD reaction with fumarprotocetraric acid can take up to half a minute. In contrast, the reactions with C and KC are usually fleeting and occur within a second of applying the reagent, so a colour change can easily be missed. There are several possible reasons that an anticipated test result does not occur. Causes include old and chemically inactive reagents, and low concentrations of lichen substances in the sample. If the colour of the thallus is dark, a colour change might be obscured, and other techniques are more appropriate, like the filter paper technique. | 0 | Theoretical and Fundamental Chemistry |
The soil is a rich source of bacterial and fungal genera. Common Gram-positive species are those belonging to the Actinomycetales and species of the genera Bacillus, Arthrobacter and Nocardia. Many of these organisms produce and secrete ferrioxamines which lead to growth promotion of not only the producing organisms, but also other microbial populations that are able to utilize exogenous siderophores. Soil fungi include Aspergillus and Penicillium predominantly produce ferrichromes. This group of siderophores consist of cyclic hexapeptides and consequently are highly resistant to environmental degradation associated with the wide range of hydrolytic enzymes that are present in humic soil. Soils containing decaying plant material possess pH values as low as 3–4. Under such conditions organisms that produce hydroxamate siderophores have an advantage due to the extreme acid stability of these molecules. The microbial population of fresh water is similar to that of soil, indeed many bacteria are washed out from the soil. In addition, fresh-water lakes contain large populations of Pseudomonas, Azomonas, Aeromonas and Alcaligenes species. As siderophores are secreted into the surroundings, siderophores can be detected by bacterivorous predators, including Caenorhabditis elegans, resulting in the nematode migration to the bacterial prey. | 1 | Applied and Interdisciplinary Chemistry |
The phenomenon is generally named un mascaret in French. but some other local names are preferred.
* Seine had a significant bore until the 1960s, locally named la barre. Since then, it has been practically eliminated by dredging and river training.
* Bay of Mont-Saint-Michel including Couesnon, Sélune, and Sée
* Arguenon
* Vire
*Sienne
* Vilaine, locally named le mascarin
* Dordogne
* Garonne | 1 | Applied and Interdisciplinary Chemistry |
On 3 and 4 March 2016, unusually high levels of caesium-137 were detected in the air in Helsinki, Finland. According to STUK, the country's nuclear regulator, measurements showed 4,000 μBq/m – about 1,000 times the usual level. An investigation by the agency traced the source to a building from which STUK and a radioactive waste treatment company operate. | 0 | Theoretical and Fundamental Chemistry |
PGC-1α is thought to be a master integrator of external signals. It is known to be activated by a host of factors, including:
# Reactive oxygen species and reactive nitrogen species, both formed endogenously in the cell as by-products of metabolism but upregulated during times of cellular stress.
#Fasting can also increase gluconeogenic gene expression, including hepatic PGC-1α.
# It is strongly induced by cold exposure, linking this environmental stimulus to adaptive thermogenesis.
# It is induced by endurance exercise and recent research has shown that PGC-1α determines lactate metabolism, thus preventing high lactate levels in endurance athletes and making lactate as an energy source more efficient.
# cAMP response element-binding (CREB) proteins, activated by an increase in cAMP following external cellular signals.
# Protein kinase B (Akt) is thought to downregulate PGC-1α, but upregulate its downstream effectors, NRF1 and NRF2. Akt itself is activated by PIP, often upregulated by PI3K after G protein signals. The Akt family is also known to activate pro-survival signals as well as metabolic activation.
# SIRT1 binds and activates PGC-1α through deacetylation inducing gluconeogenesis without affecting mitochondrial biogenesis.
PGC-1α has been shown to exert positive feedback circuits on some of its upstream regulators:
# PGC-1α increases Akt (PKB) and Phospho-Akt (Ser 473 and Thr 308) levels in muscle.
# PGC-1α leads to calcineurin activation.
Akt and calcineurin are both activators of NF-kappa-B (p65). Through their activation, PGC-1α seems to activate NF-kappa-B. Increased activity of NF-kappa-B in muscle has recently been demonstrated following induction of PGC-1α. The finding seems to be controversial. Other groups found that PGC-1s inhibit NF-kappa-B activity. The effect was demonstrated for PGC-1 alpha and beta.
PGC-1α has also been shown to drive NAD biosynthesis to play a large role in renal protection in acute kidney injury. | 1 | Applied and Interdisciplinary Chemistry |
The name Aspirin was derived from the name of the chemical ASA—Acetylspirsäure in German. Spirsäure (salicylic acid) was named for the meadowsweet plant, Spirea ulmaria, from which it could be derived. Aspirin took a- for the acetylation, -spir- from Spirsäure, and added -in as a typical drug name ending to make it easy to say. In the final round of naming proposals that circulated through Bayer, it came down to Aspirin and Euspirin; Aspirin, they feared, might remind customers of aspiration, but Arthur Eichengrün argued that Eu- (meaning "good") was inappropriate because it usually indicated an improvement over an earlier version of a similar drug. Since the substance itself was already known, Bayer intended to use the new name to establish their drug as something new; in January 1899 they settled on Aspirin. | 1 | Applied and Interdisciplinary Chemistry |
Leaves which have a petiole (leaf stalk) are said to be petiolate.
Sessile (epetiolate) leaves have no petiole and the blade attaches directly to the stem. Subpetiolate leaves are nearly petiolate or have an extremely short petiole and may appear to be sessile.
In clasping or decurrent leaves, the blade partially surrounds the stem.
When the leaf base completely surrounds the stem, the leaves are said to be perfoliate, such as in Eupatorium perfoliatum.
In peltate leaves, the petiole attaches to the blade inside the blade margin.
In some Acacia species, such as the koa tree (Acacia koa), the petioles are expanded or broadened and function like leaf blades; these are called phyllodes. There may or may not be normal pinnate leaves at the tip of the phyllode.
A stipule, present on the leaves of many dicotyledons, is an appendage on each side at the base of the petiole, resembling a small leaf. Stipules may be lasting and not be shed (a stipulate leaf, such as in roses and beans), or be shed as the leaf expands, leaving a stipule scar on the twig (an exstipulate leaf).
The situation, arrangement, and structure of the stipules is called the "stipulation".
;Free, lateral: As in Hibiscus.
;Adnate: Fused to the petiole base, as in Rosa.
;Ochreate: Provided with ochrea, or sheath-formed stipules, as in Polygonaceae; e.g., rhubarb.
;Encircling the petiole base: | 0 | Theoretical and Fundamental Chemistry |
A selenonic acid is an organoselenium compound containing the SeOH functional group. Selenonic acids are the selenium analogs of sulfonic acids. Examples of the acid are rare. Benzeneselenonic acid is a white solid. It can be prepared by the oxidation of benzeneselenol. | 0 | Theoretical and Fundamental Chemistry |
Flucloxacillin was developed in the 1960s following an increase in penicillin-resistant (beta-lactamase producing) staphylococcal infections due to the widespread use of benzylpenicillin by 1960. All the natural penicillins and first semi-synthetic penicillins were destroyed by staphylococcal beta-lactamase, leading Beecham (later GlaxoSmithKline) to search for more stable antibiotics. By 1962, a series of similarly structured acid-stable penicillins (oxacillin, cloxacillin, dicloxacillin and flucloxacillin), with the potential for being taken by mouth, were developed. Flucloxacillin and dicloxacillin showed particular stability against the beta-lactamase enzyme of Staph. aureus and could withstand acid. Beecham further developed cloxacillin and popularised flucloxacillin in the UK, while Bristol Laboratories concentrated on marketing oxacillin and dicloxacillin in the United States, leading to the difference in use in both countries. Flucloxacillin was first marketed in Europe in the 1970s. | 0 | Theoretical and Fundamental Chemistry |
Oxidised copper ores include carbonates such as azurite and malachite, the silicate chrysocolla, and sulfates such as atacamite. In some cases, sulfide ores are allowed to degrade to oxides. Such ores are amenable to hydrometallurgy. Specifically, such oxide ores are usually extracted into aqueous sulfuric acid, usually in a heap leaching or dump leaching. The resulting pregnant leach solution is purified by solvent extraction (SX). It is treated with an organic solvent and an organic chelators. The chelators bind the copper ions (and no other ions, ideally), the resulting complexes dissolve in the organic phase. This organic solvent is evaporated, leaving a residue of the copper complexes. The copper ions are liberated from the residue with sulfuric acid. The barred (denuded) sulfuric acid recycled back on to the heaps. The organic ligands are recovered and recycled as well. Alternatively, the copper can be precipitated out of the pregnant solution by contacting it with scrap iron; a process called cementation. Cement copper is normally less pure than SX-EW copper. | 1 | Applied and Interdisciplinary Chemistry |
Phosgene reacts with water to release hydrogen chloride and carbon dioxide:
Analogously, upon contact with ammonia, it converts to urea:
Halide exchange with nitrogen trifluoride and aluminium tribromide gives carbonyl fluoride| and carbonyl bromide|, respectively. | 0 | Theoretical and Fundamental Chemistry |
Born in Christchurch on 24 April 1940, Robinson was the son of Jack Robinson and Lurline Robinson (née Cross). He was educated at Christchurch Boys High School, and then studied at the University of Canterbury, graduating Master of Science with second-class honours in chemistry in 1962. He completed a PhD at the same institution in 1964. His thesis, titled Studies in the coordination chemistry of certain transition metals', elucidated the first structure of a cluster compound and its unusual delocalised bonding.
On 12 May 1962, Robinson married Judith Rae, and they went on to have four children. | 0 | Theoretical and Fundamental Chemistry |
Twice a year the EBF brings together representatives all member companies to discuss subjects well prepared in advance. The topics range from procedural to regulatory often resulting in internal benchmarking or surveys. Next to these general meetings, topic specific specialists meetings are also organized. All member companies assign one representative to these closed meetings. | 0 | Theoretical and Fundamental Chemistry |
Phase separation is the creation of two distinct phases from a single homogeneous mixture. The most common type of phase separation is between two immiscible liquids, such as oil and water. This type of phase separation is known as liquid-liquid equilibrium. Colloids are formed by phase separation, though not all phase separations forms colloids - for example oil and water can form separated layers under gravity rather than remaining as microscopic droplets in suspension. | 0 | Theoretical and Fundamental Chemistry |
If the quasi-steady-state hypothesis is assumed in addition to BFEI hypothesis, then the complex concentration can be assumed to be in a stationary (steady) state according to the Briggs–Haldane hypothesis, and the GEBIK equations become
which are written in a form similar to the classical Micaelis-Menten equations for any substrate and product. Here, the equations also show that the various isotopologue and isotopomer substrates appear as competing species. Eqs. () for isotopic compositions, Eq. () for the fractionation factor and Eq. () for the enrichment factor equally applies to the GEBIK equations under the BFEI and QSS hypothesis. | 0 | Theoretical and Fundamental Chemistry |
Transcription is when RNA is copied from DNA. During transcription, RNA polymerase makes a copy of a gene from the DNA to mRNA as needed. This process differs slightly in eukaryotes and prokaryotes. One notable difference is that prokaryotic RNA polymerase associates with DNA-processing enzymes during transcription so that processing can proceed during transcription. Therefore, this causes the new mRNA strand to become double stranded by producing a complementary strand known as the tRNA strand, which when combined are unable to form structures from base-pairing. Moreover, the template for mRNA is the complementary strand of tRNA, which is identical in sequence to the anticodon sequence that the DNA binds to. The short-lived, unprocessed or partially processed product is termed precursor mRNA, or pre-mRNA; once completely processed, it is termed mature mRNA. | 1 | Applied and Interdisciplinary Chemistry |
Many physicists simply give up on a microscopic approach, and make informed guesses of the expected phases (perhaps based on NJL model results). For each phase, they then write down an effective theory for the low-energy excitations, in terms of a small number of parameters, and use it to make predictions that could allow those parameters to be fixed by experimental observations. | 0 | Theoretical and Fundamental Chemistry |
The partial specific volume express the variation of the extensive volume of a mixture in respect to composition of the masses. It is the partial derivative of volume with respect to the mass of the component of interest.
where is the partial specific volume of a component defined as:
The PSV is usually measured in milliLiters (mL) per gram (g), proteins > 30 kDa can be assumed to have a partial specific volume of 0.708 mL/g. Experimental determination is possible by measuring the natural frequency of a U-shaped tube filled successively with air, buffer and protein solution. | 1 | Applied and Interdisciplinary Chemistry |
All atoms bigger than hydrogen are formed in stars or supernovae through nucleosynthesis, when gravity, temperature and pressure reach levels high enough to fuse protons and neutrons together. Protons and neutrons form the atomic nucleus, which accumulates electrons to form atoms. The number of protons in the nucleus, called atomic number, uniquely identifies a chemical element. | 0 | Theoretical and Fundamental Chemistry |
Due to the similarity in mass and nuclear properties between the proton and neutron, they are sometimes considered as two symmetric types of the same object, a nucleon. While only the proton has an electric charge, this is often negligible due to the weakness of the electromagnetic interaction relative to the strong nuclear interaction. The symmetry relating the proton and neutron is known as isospin and denoted I (or sometimes T).
Isospin is an SU(2) symmetry, like ordinary spin, so is completely analogous to it. The proton and neutron, each of which have isospin-, form an isospin doublet (analogous to a spin doublet), with a "down" state (↓) being a neutron and an "up" state (↑) being a proton. A pair of nucleons can either be in an antisymmetric state of isospin called singlet, or in a symmetric state called triplet. In terms of the "down" state and "up" state, the singlet is
:, which can also be written :
This is a nucleus with one proton and one neutron, i.e. a deuterium nucleus. The triplet is
and thus consists of three types of nuclei, which are supposed to be symmetric: a deuterium nucleus (actually a highly excited state of it), a nucleus with two protons, and a nucleus with two neutrons. These states are not stable. | 0 | Theoretical and Fundamental Chemistry |
The first boundary condition is
which constrains the sum of a and b. The second equation is
with the notable limit as (and ) of
The mixing rules become
The cross term still must be specified by a combining rule, either
or | 0 | Theoretical and Fundamental Chemistry |
Plant defenses can be classified as constitutive or induced. Constitutive defenses are always present, while induced defenses are produced or mobilized to the site where a plant is injured. There is wide variation in the composition and concentration of constitutive defenses; these range from mechanical defenses to digestibility reducers and toxins. Many external mechanical defenses and quantitative defenses are constitutive, as they require large amounts of resources to produce and are costly to mobilize. A variety of molecular and biochemical approaches are used to determine the mechanisms of constitutive and induced defensive responses.
Induced defenses include secondary metabolites and morphological and physiological changes. An advantage of inducible, as opposed to constitutive defenses, is that they are only produced when needed, and are therefore potentially less costly, especially when herbivory is variable. Modes of induced defence include systemic acquired resistance and plant-induced systemic resistance. | 1 | Applied and Interdisciplinary Chemistry |
Current Organic Chemistry is indexed in the following databases:
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* Scilit
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* TOC Premier
* Ulrich's Periodicals Directory | 0 | Theoretical and Fundamental Chemistry |
A lot of research has been conducted on Vectorette PCR and the applications it has in the field of biology. Scientists used Vectorette PCR to take the transgene flanking DNA and isolate it. They used this technique on the DNA belonging to mice that was next to transgene sections. From this the scientists were able to show that the use of Vectorettes is capable of facilitating the recovery and mapping of sequences in complex genomes. They have also found that Vectorette PCR can help in the analysis of sequences by subvectoretting when PCR products of a large size are the subject at hand.
Other work has looked at developing a method using Vectorette PCR in order to accomplish genomic walking. By using Vectorette PCR, scientists were able to acquire single-stranded DNA which were obtained from PCR products in order to sequence them. From this an approach was identified in which the amplification of sequences which were previously uncharacterized was possible. This research demonstrates how novel sequences can be rapidly developed when only a known sequence of DNA is used to start.
Further research has experimented with the creation of a method that progresses the isolation of microsatellite repeats. By using Vectorette PCR, researchers have found a rapid technique to accomplish this with novel, microsatellite repeats. They have attempted and succeeded in using this technique to isolate an amount of six microsatellite repeats.
Vectorette PCR has also been used to not only identify genomic positions of insertion sequences (IS) but also to map them. Research on this has shed light on a way to complete the typing of microbial stains and the identification and mapping of things like IS insertion sites that reside in microbial genomes. Vectorette PCR proves useful when it comes to rapidly and simply surveying genomes’ IS elements.
Transposable element, transposon, or TE is a variation of genetic elements that is capable of changing its location in a genome by a process called “jumping”. TE display is designed to present the different variations of TE insertion sites which helps to make numerous dominant markers. A problem that arose in the original method was finding a PCR method that was capable of being specific and efficient in its output of the transposon within the genome. Researchers have found a solution for this problem by using Vectorette PCR as the PCR method. Since Vectorette PCR is capable of being specific with its isolation and amplification of genes, this helped with their research and aided in improving the method of TE display by saving both time and costs. The researchers were then able to produce numerous dominant markers with the use of Vectorette PCR that is based on a TE display that is nonradioactive.
Thyroid lymphoma is an illness which leads to the transformation of the lymphocytes belonging to the thyroid into cells of a cancerous nature. Researchers have tested a new method that aids in the diagnosis of this condition. The use of Vectorette PCR was combined with restriction enzyme digestion, and it was found that Vectorette PCR proved to be useful in their study and aided in the diagnosis of thyroid lymphoma.
Researchers have looked into the potential use of Vectorette PCR in the examination of the genes of diseases. They have taken two methods, trinucleotide repeats which are specifically used for the targeting of transcribed regions and Vectorette PCR, to obtain simple sequence repeats or SSRs. It is believed that genetic markers can be made from these SSRs. The outcome from this research is hoped to aid researchers attempt the derivation of genetic markers which are transportable from unknown genomes. Vectorette PCR was used to uncover SSRs which flank the trinucleotide repeat that was targeted for testing. This is also known as TNR or trinucleotide Vectorette PCR. They believe that their TNR method combined with the amplification provided by Vectorette PCR can be used in eukaryotes to create molecular markers that are based on simple repeat sequences. The researchers also think that this method will be of value when attempting to isolate genes that are able to bring about diseases. | 1 | Applied and Interdisciplinary Chemistry |
Volatility itself has no defined numerical value, but it is often described using vapor pressures or boiling points (for liquids). High vapor pressures indicate a high volatility, while high boiling points indicate low volatility. Vapor pressures and boiling points are often presented in tables and charts that can be used to compare chemicals of interest. Volatility data is typically found through experimentation over a range of temperatures and pressures. | 0 | Theoretical and Fundamental Chemistry |
Some systems in fluid dynamics involve a fluid being subject to conservative body forces. Since a conservative body force is the gradient of some potential function, it has the same effect as a gradient in fluid pressure. It is often convenient to define a modified pressure equal to the true fluid pressure plus the potential.
Examples of conservative body forces include gravity and the centrifugal force in a rotating reference frame. | 1 | Applied and Interdisciplinary Chemistry |
Fatty acids also affect insulin secretion. In type 2 diabetes, fatty acids are able to potentiate insulin release to compensate the increment need of insulin. It was found that the β-cells express free fatty acid receptors at their surface, through which fatty acids can impact the function of β-cells. Long-chain acyl-CoA and DAG are the metabolites resulting from the intracellular metabolism of fatty acids. Long-chain acyl-CoA has the ability to acylate proteins that are essential in the insulin granule fusion. On the other hand, DAG activates PKC that is involved in the insulin secretion. | 1 | Applied and Interdisciplinary Chemistry |
Some such phenomena resisting the tendency to thermalize include (see, e.g., a quantum scar):
* Conventional quantum scars, which refer to eigenstates with enhanced probability density along unstable periodic orbits much higher than one would intuitively predict from classical mechanics.
* Perturbation-induced quantum scarring: despite the similarity in appearance to conventional scarring, these scars have a novel underlying mechanism stemming from the combined effect of nearly-degenerate states and spatially localized perturbations, and they can be employed to propagate quantum wave packets in a disordered quantum dot with high fidelity.
* Many-body quantum scars.
*Many-body localisation (MBL), quantum many-body systems retaining memory of their initial condition in local observables for arbitrary amounts of time.
Other systems that resist thermalisation and are better understood are quantum integrable systems and systems with dynamical symmetries. | 0 | Theoretical and Fundamental Chemistry |
According to the Greek-Russian archaeologist, Sarianidi, who explored the tepes, Gonurtepe was the "capital or the imperial city of a complex Bronze Age state, one that stretched at least a thousand square miles and encompassing hundreds of satellite settlements". He also called it the "worlds fifth center of ancient civilization" with its refined society called the "Turkmenistans Morghab River society", formally called the "Bactria-Margiana Archaeological Complex". It is said to be in league with the "cultural cradles of antiquity" of Egypt, Mesopotamia, India, and China.
The meandering Morghab River along which the Morghab civilization developed by Gonurdepe and Merv, which was once an important place along the Silk Route. But the river flows through the regional capital city of Mary, about 40 miles away from the exploration site of Gonurtepe.
The site is dated to late 3rd millennium BC. Excavations have taken place for more than 35 years and still continue at a slow pace due to a lack of adequate funding. The main findings of the excavations are that the site was "an agricultural and herding community who grew grain, raised sheep, built sophisticated irrigation and sewage systems, and produced ceramics in the many kilns that dot the landscape."
A fort had been built with thick walls and the enclosed area within the fort had single storied houses, and also a palace, two observatories and cremation grounds. The excavation of the cemeteries revealed many objects, both local and imported (from Indus Valley and Egypt).
Religious practices indicated that it was the birthplace of the Zoroastrian religion, a monolithic religion. The practices of sheep sacrifices, temples dedicated to fire and water, drinking of soma-haoma (a brew presumed to be made of opium, ephedra, and a local narcotic) have been deduced as practices followed by Zoroastrians. | 1 | Applied and Interdisciplinary Chemistry |
Fluorenylmethyloxycarbonyl chloride (Fmoc-Cl) is a chloroformate ester. It is used to introduce the fluorenylmethyloxycarbonyl protecting group as the Fmoc carbamate. | 0 | Theoretical and Fundamental Chemistry |
In biophysics, the Kautsky effect (also fluorescence transient, fluorescence induction or fluorescence decay) is a phenomenon consisting of a typical variation in the behavior of a plant fluorescence when exposed to light. It was discovered in 1931 by H. Kautsky and A. Hirsch.
When dark-adapted photosynthesising cells are illuminated with continuous light, chlorophyll fluorescence displays characteristic changes in intensity accompanying the induction of photosynthetic activity. | 0 | Theoretical and Fundamental Chemistry |
Automation is an essential element in HTSs usefulness. Typically, an integrated robot system consisting of one or more robots transports assay-microplates from station to station for sample and reagent addition, mixing, incubation, and finally readout or detection. An HTS system can usually prepare, incubate, and analyze many plates simultaneously, further speeding the data-collection process. HTS robots that can test up to 100,000 compounds per day currently exist. Automatic colony pickers pick thousands of microbial colonies for high throughput genetic screening. The term uHTS or ultra-high-throughput screening' refers (circa 2008) to screening in excess of 100,000 compounds per day. | 1 | Applied and Interdisciplinary Chemistry |
Because they operate at low pressure and rely on gravity to move fluids (and entrained solids), drain-waste-vent systems use fittings whose interior surfaces are as smooth as possible. The fittings may be "belled" (expanded slightly in diameter) or otherwise shaped to accommodate the insertion of pipe or tubing without forming a sharp interior ridge that might catch debris or accumulate material, and cause a clog or blockage. Freshly cut ends of pipe segments are carefully deburred to remove projecting slivers of material which may snag debris (such as hair or fibers) which can build up to cause blockages. This internal smoothness also makes it easier to "snake out" or "rod out" a clogged pipe with a plumber's snake.
Underground piping systems for landscaping drainage or the disposal of stormwater or groundwater also use low-pressure gravity flow, so fittings for these systems resemble larger-scale DWV fittings. With high peak-flow volumes, the design and construction of these systems may resemble those of storm sewers.
Fittings for central vacuum systems are similar to DWV fittings but usually have thinner and lighter construction because the weight of the materials conveyed is less. Vacuum-system designs share with DWV designs the need to eliminate internal ridges, burrs, sharp turns, or other obstructions which might create clogs. | 1 | Applied and Interdisciplinary Chemistry |
The Tipson–Cohen reaction is a name reaction first discovered by Stuart Tipson and Alex Cohen at the National Bureau of Standards in Washington D.C. The Tipson–Cohen reaction occurs when two neighboring secondary sulfonyloxy groups in a sugar molecule are treated with zinc dust (Zn) and sodium iodide (NaI) in a refluxing solvent such as N,N-dimethylformamide (DMF) to give an unsaturated carbohydrate. | 0 | Theoretical and Fundamental Chemistry |
The process of splat quenching involves rapid quenching or cooling of molten metal. A typical procedure for splat quenching involves pouring the molten metal between two cooled copper rollers that are circulated with water to transfer the heat away from the metal, causing it to almost instantaneously solidify.
A more efficient splat quenching technique is Duwezs and Willens gun technique. Their technique produces higher rates of cooling of the droplet of metal because the sample is propelled at high velocities and hits a quencher plate causing its surface area to increase which immediately solidifies the metal. This allows for a wider range of metals that can be quenched and be given amorphous-like features instead of the general iron alloy.
Another technique involves the consecutive spraying of the molten metal onto a chemical vapor deposition surface. However, the layers do not fuse together as desired and this causes oxides to be contained in the structure and pores to form around the structure. Manufacturing companies take an interest in the resultant products because of their near-net shaping capabilities. | 1 | Applied and Interdisciplinary Chemistry |
* Can be made from any organic material using proven technology going through syngas. There is no need to use food crops and compete with food production. The amount of methanol that can be generated from biomass is much greater than ethanol.
* Can compete with and complement ethanol in a diversified energy marketplace. Methanol obtained from fossil fuels has a lower price than ethanol.
* Can be blended in gasoline like ethanol. In 2007, China blended more than of methanol into fuel and will introduce methanol fuel standard by mid-2008. M85, a mixture of 85% methanol and 15% gasoline can be used much like E85 sold in some gas stations today. | 1 | Applied and Interdisciplinary Chemistry |
Quantitative measures of exposure are used: in risk assessment, together with inputs from toxicology, to determine risk from substances released to the environment, to establish protective standards, in epidemiology, to distinguish between exposed and control groups, and to protect workers from occupational hazards. | 1 | Applied and Interdisciplinary Chemistry |
TET dioxygenase isoforms include at least two isoforms of TET1, one of TET2 and three isoforms of TET3. The full-length canonical TET1 isoform appears virtually restricted to early embryos, embryonic stem cells and primordial germ cells (PGCs). The dominant TET1 isoform in most somatic tissues, at least in the mouse, arises from alternative promoter usage which gives rise to a short transcript and a truncated protein designated TET1s. The isoforms of TET3 are the full length form TET3FL, a short form splice variant TET3s, and a form that occurs in oocytes and neurons designated TET3o. TET3o is created by alternative promoter use and contains an additional first N-terminal exon coding for 11 amino acids. TET3o only occurs in oocytes and neurons and is not expressed in embryonic stem cells or in any other cell type or adult mouse tissue tested. Whereas TET1 expression can barely be detected in oocytes and zygotes, and TET2 is only moderately expressed, the TET3 variant TET3o shows extremely high levels of expression in oocytes and zygotes, but is nearly absent at the 2-cell stage. It is possible that TET3o, high in neurons, oocytes and zygotes at the one cell stage, is the major TET enzyme utilized when very large scale rapid demethylations occur in these cells. | 1 | Applied and Interdisciplinary Chemistry |
Isobutyryl chloride (2-methylpropanoyl chloride) is the organic compound with the formula . A colorless liquid, it the simplest branched-chain acyl chloride. It is prepared by chlorination of isobutyric acid. | 0 | Theoretical and Fundamental Chemistry |
Flow focusing in fluid dynamics is a technology whose aim is the production of drops or bubbles by straightforward hydrodynamic means. The output is a dispersed liquid or gas, frequently in the form of a fine aerosol or an emulsion. No other driving force is required, apart from traditional pumping, a key difference with other comparable technologies, such as electrospray (where an electric field is needed). Both flow focusing and electrospray working in their most extensively used regime produce high quality sprays composed by homogeneous and well-controlled-size droplets. Flow focusing was invented by Prof. Alfonso M. Gañan-Calvo (who now teaches at ETSI in Seville) in 1994, patented in 1996, and published for the first time in 1998. | 1 | Applied and Interdisciplinary Chemistry |
Anisotropic terahertz microspectrosopy (ATM) has found applications in structural biology and molecular fingerprinting of DNA and proteins. The technique is also suitable for drug discovery and studying THz frequency properties of thin film solid state materials.
Special attention is given to molecular motions in proteins where many structural changes occur at frequencies in the terahertz range of the spectrum (0.3 THz to 3 THz). These structural changes include hinge motions in which two regions of molecules are connected together by a flexible molecular structure that bends like a mechanical hinge or elbow. ATM is uniquely capable of measuring the spatial direction in which hinge motions occur because of its use of linearly polarized electric fields. | 0 | Theoretical and Fundamental Chemistry |
To the published books of Ernst Homburg belong:
* (dissertation)
In his dissertation, Homburg described the important transformations during the first half of the nineteenth century in the character and the organization of the chemical industries in Europe. The leading positions in the management of the factories were then for the first time taken by industrial chemists. This process, together with the formation of an occupational group of high social prestige, was especially visible in Germany. There was an important relation with the development of polytechnic education. Homburg considers the transformation of polytechnic and university chemical education more as a cause than as a consequence of the emergence of the occupation of the chemist.
Many scholars, that wrote about the development of the chemist's occupation in the context of the development of university education, like Joseph Ben-David, Bernard Henry Gustin, Erica Hickel, Ingunn Possehl, R. Steven Turner and Ulrike Köster, had created the impression that the emergence of the chemical occupation was the exclusive result of the work of Justus von Liebig (1803-1873). The broader social perspective was lacking. No reference was made to the interplay between events in this particular domain of work and knowledge and the development of the social division of labour as a whole. Homburg tries to fill this gap in the main body of his dissertation. Especially the short period between 1830 and 1850 marked a radical change in the organisation of education. Apart from the changes in the German educational system, a "veritable revolution of the laboratory" occurred. Especially the emergence of analytical chemistry caused the development of new laboratories, with smaller apparatuses, and the possibility to give laboratory instruction a more prominent place in chemical education.
The last part of the dissertation summarizes the new functions in which the chemically trained found their occupation.
* (The history of chemistry in the Netherlands; published in 3 vols. 1993, 1997, 2004)
* (Growth by Fertilizer : DSM Agro 1929-2004)
Ernst Homburg was one of the chemistry editors of: | 1 | Applied and Interdisciplinary Chemistry |
For example, the skeletal formula of hexane (top) is shown below. The carbon atom labeled C appears to have only one bond, so there must also be three hydrogens bonded to it, in order to make its total number of bonds four. The carbon atom labelled C has two bonds to other carbons and is therefore bonded to two hydrogen atoms as well. A Lewis structure (middle) and ball-and-stick model (bottom) of the actual molecular structure of hexane, as determined by X-ray crystallography, are shown for comparison.
It does not matter which end of the chain one starts numbering from, as long as consistency is maintained when drawing diagrams. The condensed formula or the IUPAC name will confirm the orientation. Some molecules will become familiar regardless of the orientation. | 0 | Theoretical and Fundamental Chemistry |
PIV can also be used to measure the velocity field of the free surface and basal boundary in a granular flows such as those in shaken containers, tumblers and avalanches.
This analysis is particularly well-suited for nontransparent media such as sand, gravel, quartz, or other granular materials that are common in geophysics. This PIV approach is called "granular PIV". The set-up for granular PIV differs from the usual PIV setup in that the optical surface structure which is produced by illumination of the surface of the granular flow is already sufficient to detect the motion. This means one does not need to add tracer particles in the bulk material. | 1 | Applied and Interdisciplinary Chemistry |
A bumblebee nest differs in size and structure from that of a honeybee. Bumblebee nests are smaller and contain far fewer individuals which is mostly due to differences in the method of colony reproduction. Honeybee colonies can contain up to 50,000 individuals, whereas bumblebee colonies usually only contain a few hundred. This means the number of bees available for foraging is low and resources must be allocated accordingly. Assessing the level of food stores is not seen in honeybees, likely because the large colonies make such assessment inefficient. Bumblebees only store enough honey for a few days. By monitoring the levels of the honey pots a bumblebee colony can either up or down regulate the number of bees out foraging. Lab experiments by Anna Dornhaus and Lars Chittka in 2005 showed evidence of this up or down regulation by monitoring the activity level of the hive after the addition of nectar to the honey pots. Hive activity increased when high quality nectar was injected into the honey pots, provided the wells werent already full. When the honey pots were full, there was no significant change in activity regardless of whether the nectar imported was from a high or low quality source. They hypothesized that either the foraging bee does not signal the nest or the nest bees ignore the signal because the demand for food is low. The tropical bumblebee Bombus transversalis' has also been shown to respond to honey pot levels in a similar way. | 1 | Applied and Interdisciplinary Chemistry |
The foundations of the oxy-hydrogen blowpipe were laid down by Carl Wilhelm Scheele and Joseph Priestley around the last quarter of the eighteenth century. The oxy-hydrogen blowpipe itself was developed by the Frenchman Bochard-de-Saron, the English mineralogist Edward Daniel Clarke and the American chemist Robert Hare in the late 18th and early 19th centuries. It produced a flame hot enough to melt such refractory materials as platinum, porcelain, fire brick, and corundum, and was a valuable tool in several fields of science. It is used in the Verneuil process to produce synthetic corundum. | 0 | Theoretical and Fundamental Chemistry |
There are three observations that can be made when looking at a generalized compressibility chart. These observations are:
# Gases behave as an ideal gas regardless of temperature when the reduced pressure is much less than one (P ≪ 1).
# When reduced temperature is greater than two (T > 2), ideal-gas behavior can be assumed regardless of pressure, unless pressure is much greater than one (P ≫ 1).
# Gases deviate from ideal-gas behavior the most in the vicinity of the critical point. | 0 | Theoretical and Fundamental Chemistry |
Cannabinoid CP55,940 and △-tetrahydrocannabinol (△-THC) can induce the release of dynorphin B, which in return acts as an agonist of κ-opioid receptors, resulting in the production of antinociception. Similarly, Tyr-D-Arg-Phe-Sar (TAPS) is capable of promoting a release of dynorphin B through the simulation of μ-opioid receptors, causing a production of antinociception. The antinociceptive effect produced by dynorphin B allows for spinal analgesia. | 1 | Applied and Interdisciplinary Chemistry |
Paredes and Quiles concluded that chloroplasts under stress from water deficit rely on processes like the opening of stomata to disperse excess heat accumulated via metabolic processes within plant cells. These metabolic processes are responsible for chemical energy synthesis that can be achieved via chlororespiratory ETCs when a reduction in photosynthesis activity is evident. | 1 | Applied and Interdisciplinary Chemistry |
Certain species of plants are considered indicators of high selenium content of the soil, since they require high levels of selenium to thrive. The main selenium indicator plants are Astragalus species (including some locoweeds), princes plume (Stanleya sp.), woody asters (Xylorhiza sp.), and false goldenweed (Oonopsis' sp.) | 1 | Applied and Interdisciplinary Chemistry |
Photochemical reactions require a light source that emits wavelengths corresponding to an electronic transition in the reactant. In the early experiments (and in everyday life), sunlight was the light source, although it is polychromatic. Mercury-vapor lamps are more common in the laboratory. Low-pressure mercury-vapor lamps mainly emit at 254 nm. For polychromatic sources, wavelength ranges can be selected using filters. Alternatively, laser beams are usually monochromatic (although two or more wavelengths can be obtained using nonlinear optics), and LEDs have a relatively narrow band that can be efficiently used, as well as Rayonet lamps, to get approximately monochromatic beams.
The emitted light must reach the targeted functional group without being blocked by the reactor, medium, or other functional groups present. For many applications, quartz is used for the reactors as well as to contain the lamp. Pyrex absorbs at wavelengths shorter than 275 nm. The solvent is an important experimental parameter. Solvents are potential reactants, and for this reason, chlorinated solvents are avoided because the C–Cl bond can lead to chlorination of the substrate. Strongly-absorbing solvents prevent photons from reaching the substrate. Hydrocarbon solvents absorb only at short wavelengths and are thus preferred for photochemical experiments requiring high-energy photons. Solvents containing unsaturation absorb at longer wavelengths and can usefully filter out short wavelengths. For example, cyclohexane and acetone "cut off" (absorb strongly) at wavelengths shorter than 215 and 330 nm, respectively.
Typically, the wavelength employed to induce a photochemical process is selected based on the absorption spectrum of the reactive species, most often the absorption maximum. Over the last years, however, it has been demonstrated that, in the majority of bond-forming reactions, the absorption spectrum does not allow selecting the optimum wavelength to achieve the highest reaction yield based on absorptivity. This fundamental mismatch between absorptivity and reactivity has been elucidated with so-called photochemical action plots. | 0 | Theoretical and Fundamental Chemistry |
The dissolution of cellulose by ILs has attracted interest. A patent application from 1930 showed that 1-alkylpyridinium chlorides dissolve cellulose. Following in the footsteps of the lyocell process, which uses hydrated N-Methylmorpholine N-oxide as a solvent for pulp and paper. The "valorization" of cellulose, i.e. its conversion to more valuable chemicals, has been achieved by the use of ionic liquids. Representative products are glucose esters, sorbitol, and alkylgycosides. IL 1-butyl-3-methylimidazolium chloride dissolves freeze dried banana pulp and with an additional 15% dimethyl sulfoxide, lends itself to Carbon-13 NMR analysis. In this way the entire complex of starch, sucrose, glucose, and fructose can be monitored as a function of banana ripening.
Beyond cellulose, ILs have also shown potential in the dissolution, extraction, purification, processing and modification of other biopolymers such as chitin/chitosan, starch, alginate, collagen, gelatin, keratin, and fibroin. For example, ILs allow for the preparation of biopolymer materials in different forms (e.g. sponges, films, microparticles, nanoparticles, and aerogels) and better biopolymer chemical reactions, leading to biopolymer-based drug/gene-delivery carriers. Moreover, ILs enable the synthesis of chemically modified starches with high efficiency and degrees of substitution (DS) and the development of various starch-based materials such as thermoplastic starch, composite films, solid polymer electrolytes, nanoparticles and drug carriers. | 0 | Theoretical and Fundamental Chemistry |
In jaundice owing to hemolysis (prehepatic, or hemolytic, jaundice), the pathophysiology is that overproduction of bilirubin from the extravascular or intravascular hemolysis overwhelms the capacity of the liver to excrete it. The bilirubin present in the plasma is largely unconjugated in this setting as they haven't been taken up and conjugated by the liver. In this case, total serum bilirubin increases while the ratio of direct bilirubin to indirect bilirubin remains 96 to 4 as up to 96%-99% of bilirubin in the bile are conjugated mentioned above. | 1 | Applied and Interdisciplinary Chemistry |
In a meta-analysis of 11 randomized trials involving hirudin and other DTIs versus heparin in the treatment of acute coronary syndrome (ACS) it was found that hirudin has a significantly higher incidence of bleeding compared with heparin. Hirudin is therefore not recommended for treatment of ACS and currently it has no clinical indications. | 1 | Applied and Interdisciplinary Chemistry |
These isotopes are used in positron emission tomography, a technique used for medical imaging. The energy emitted depends on the isotope that is decaying; the figure of applies only to the decay of carbon-11.
The short-lived positron emitting isotopes C (T = ), N (T = ), O (T = ), and F (T = ) used for positron emission tomography are typically produced by proton irradiation of natural or enriched targets. | 0 | Theoretical and Fundamental Chemistry |
Methyl chloroformate is a chemical compound with the chemical formula . It is the methyl ester of chloroformic acid. It is an oily colorless liquid, although aged samples appear yellow. It is also known for its pungent odor. | 0 | Theoretical and Fundamental Chemistry |
The physical properties of the isomers of xylene differ slightly. The melting point ranges from (m-xylene) to (p-xylene)—as usual, the para isomer's melting point is much higher because it packs more readily in the crystal structure. The boiling point for each isomer is around . The density of each isomer is around and thus is less dense than water. The odor of xylene is detectable at concentrations as low as 0.08 to 3.7 ppm (parts of xylene per million parts of air) and can be tasted in water at 0.53 to 1.8 ppm.
Xylenes form azeotropes with water and a variety of alcohols. The azeotrope with water consists of 60% xylenes and boils at 94.5 °C. As with many alkylbenzene compounds, xylenes form complexes with various halocarbons. The complexes of different isomers often have dramatically different properties from each other. | 1 | Applied and Interdisciplinary Chemistry |
GEOTRACES is an international research programme that aims to improve an understanding of biogeochemical cycles in the oceans.
The concept of cycle describes the pathway by which a chemical element moves through the three major compartments of Earth (such as continents, atmosphere, and ocean). Because these cycles are directly related to climate dynamics and are heavily impacted by global change, it is essential to quantify them.
GEOTRACES focuses on the oceanic part of the cycles, with the ambition to map the distribution of trace elements and isotopes in the ocean and to understand the processes controlling this distribution. Some of these trace elements are directly linked to climate via, for example, their role as essential nutrients for life; others allow quantification of ocean processes (origin and dynamics of matter, age of water masses, etc.); some of them are pollutants (for example, lead or mercury). Modelling based on the data collected will thus achieve substantial progress in understanding the current and past of the ocean and improve projections of the ocean’s response to global change.
GEOTRACES is organised internationally under the auspices of the [http://www.scor-int.org/ Scientific Committee for Oceanic Research] (of the International Council for Science). Its management is overseen by a Scientific Steering Committee (SSC), with representatives of 15 nations from across the globe, and the programme involves active participation of more than 30 nations.
The GEOTRACES SSC was initially led by co-chairs, Prof. Robert F. Anderson of the Lamont–Doherty Earth Observatory (Columbia University) and Prof. Gideon M. Henderson from University of Oxford. Current co-chairs are Dr. Maeve Lohan of the University of Southampton and Dr. Karen Casciotti from Stanford University. | 0 | Theoretical and Fundamental Chemistry |
Kyoung-Shin Choi () is a professor of chemistry at the University of Wisconsin-Madison. Choi's research focuses on the electrochemical synthesis of electrode materials, for use in electrochemical and photoelectrochemical devices. | 0 | Theoretical and Fundamental Chemistry |
Heterocyclic analogs of cyclohexane are pervasive in sugars, piperidines, dioxanes, etc. They exist generally follow the trends seen for cyclohexane, i.e. the chair conformer being most stable. The axial–equatorial equilibria (A values) are however strongly affected by the replacement of a methylene by O or NH. Illustrative are the conformations of the glucosides. 1,2,4,5-Tetrathiane ((SCH)) lacks the unfavorable 1,3-diaxial interactions of cyclohexane. Consequently its twist-boat conformation is populated; in the corresponding tetramethyl structure, 3,3,6,6-tetramethyl-1,2,4,5-tetrathiane, the twist-boat conformation dominates. | 0 | Theoretical and Fundamental Chemistry |
Water coats particles in aerosols, making them activated, usually in the context of forming a cloud droplet (such as natural cloud seeding by aerosols from trees in a forest). Following the Kelvin equation (based on the curvature of liquid droplets), smaller particles need a higher ambient relative humidity to maintain equilibrium than larger particles do. The following formula gives relative humidity at equilibrium:
where is the saturation vapor pressure above a particle at equilibrium (around a curved liquid droplet), p is the saturation vapor pressure (flat surface of the same liquid) and S is the saturation ratio.
Kelvin equation for saturation vapor pressure above a curved surface is:
where r droplet radius, σ surface tension of droplet, ρ density of liquid, M molar mass, T temperature, and R molar gas constant. | 0 | Theoretical and Fundamental Chemistry |
Joseph Chatt (6 November 1914 – 19 May 1994) was a renowned British researcher in the area of inorganic and organometallic chemistry. His name is associated with the description of the pi-bond between transition metals and alkenes, the Dewar–Chatt–Duncanson model.
Chatt received his Ph.D. at the University of Cambridge under the direction of F. G. Mann for research on organoarsenic and organophosphorus compounds and their complexes with transition metals. He was employed at Imperial Chemical Industries from 1949 to 1962, during which time he, often in collaboration with Bernard L. Shaw, published influential work on the metal hydrides and metal alkene complexes. During this period, he reported the first example of C-H bond activation by a transition metal and one of the first examples of a transition metal hydride.
In the 1960s, Chatt moved to a professorship at the University of Sussex and subsequently assumed directorship of the Nitrogen Fixation Unit under the Agricultural Research Council. Using the transition metal dinitrogen complex W(N)(dppe), his group first demonstrated the conversion of a dinitrogen ligand into ammonia. This work provided some of the first molecular models for nitrogen fixation. Chatt authored or co-authored over 300 peer-reviewed publications.
Among his many awards, he was recognized with the 1981 Wolf Prize "for pioneering and fundamental contributions to synthetic transition metal chemistry, particularly transition metal hydrides and dinitrogen complexes." He was elected a Fellow of the Royal Society in 1961 and was made a Commander of the Order of the British Empire.
In 1995, a year after his death, the Unit of Nitrogen Fixation moved to Norwich and became part of the John Innes Centre. The new building, as well as an annual lecture at the Centre, were named in his honour. | 0 | Theoretical and Fundamental Chemistry |
Cells observed under the electron microscope after a technique involving rapid freezing of the cells followed by substitution of water with a polymer (Fast-freeze Fixation/Freeze Substitution) contain a large number of electron dense bodies around the cell periphery. These structures correspond in size and location to the fluorescent bodies confirmed to be scintillons by their light emission, and they show colocalization of anti-luciferase and anti-LBP labeling meaning both bioluminescence proteins are found in the structures. Scintillons appear as cytoplasmic drops hanging in the vacuolar space, as they are almost completely surrounded by the vacuolar membrane. This structure led to the proposal that a voltage gated proton channel in the vacuolar membrane could allow an action potential to be propagated along the vacuolar membrane. This would in turn let protons enter into the cytoplasm around all the scintillons in the cells virtually simultaneously producing an intense but brief flash of light. Voltage gated proton channels were subsequently identified in a dinoflagellate confirming their predicted existence. | 1 | Applied and Interdisciplinary Chemistry |
This involves sampling first onto a sorbent tube. The most widely used tubes are those following the pattern laid out by WG5 (see above). After sampling (for which a variety of accessories are available), the tube is desorbed to transfer the analytes to the focusing trap before the second desorption stage transfers them to the GC. The greater sensitivity of this method has made it increasingly popular for sampling dilute gas streams, or in exploratory work where the target atmosphere is unknown.
*Diffusive (or passive) sampling – A tube is packed with a single sorbent bed and allowed to adsorb analytes from the air diffusively. It is suitable for sampling known compounds over a period of hours (for analyte concentrations of 2–10 μg/m) to weeks (for analyte concentrations of 0.3–300 μg/m).
*Pumped (or active) sampling – A tube is packed with up to three sorbent beds and a flow of the sample gas passed through it. It is suitable for sampling high and low concentrations of known and unknown compounds over timescales of minutes to hours.
*Direct desorption – This is used for sampling emissions from small pieces of solid or semi-solid materials. The material is placed inside a tube and heated to release the vapours directly into the focusing trap.
*Headspace – The material is placed in a (micro-)chamber or other sampling container, and a flow of gas passed through it to transfer the headspace dynamically onto a sorbent tube. | 0 | Theoretical and Fundamental Chemistry |
In viruses and bacteriophages, the DNA or RNA is surrounded by a protein capsid, sometimes further enveloped by a lipid membrane. Double-stranded DNA is stored inside the capsid in the form of a spool, which can have different types of coiling leading to different types of liquid-crystalline packing. This packing can change from hexagonal to cholesteric to isotropic at different stages of the phage functioning. Although the double helices are always locally aligned, the DNA inside viruses does not represent real liquid crystals, because it lacks fluidity. On the other hand, DNA condensed in vitro, e.g., with the help of polyamines also present in viruses, is both locally ordered and fluid. | 1 | Applied and Interdisciplinary Chemistry |
The depolarized voltage opens additional voltage-dependent potassium channels, and some of these do not close right away when the membrane returns to its normal resting voltage. In addition, further potassium channels open in response to the influx of calcium ions during the action potential. The intracellular concentration of potassium ions is transiently unusually low, making the membrane voltage V even closer to the potassium equilibrium voltage E. The membrane potential goes below the resting membrane potential. Hence, there is an undershoot or hyperpolarization, termed an afterhyperpolarization, that persists until the membrane potassium permeability returns to its usual value, restoring the membrane potential to the resting state. | 0 | Theoretical and Fundamental Chemistry |
MIKE SHE is an integrated hydrological modelling system for building and simulating surface water flow and groundwater flow. MIKE SHE can simulate the entire land phase of the hydrologic cycle and allows components to be used independently and customized to local needs. MIKE SHE emerged from Système Hydrologique Européen (SHE) as developed and extensively applied since 1977 onwards by a consortium of three European organizations: the Institute of Hydrology (the United Kingdom), SOGREAH (France) and DHI (Denmark). Since then, DHI has continuously invested resources into research and development of MIKE SHE. MIKE SHE can be used for the analysis, planning and management of a wide range of water resources and environmental problems related to surface water and groundwater, especially surface-water impact from groundwater withdrawal, conjunctive use of groundwater and surface water, wetland management and restoration, river basin management and planning, impact studies for changes in land use and climate.
The program is offered in both 32-bit and 64-bit versions for Microsoft Windows operating systems. | 1 | Applied and Interdisciplinary Chemistry |
Thin films are thin material layers ranging from fractions of a nanometer to several micrometers in thickness. Thin-film thermoelectric materials are grown by conventional semiconductor deposition methods and fabricated using conventional semiconductor micro-fabrication techniques.
Thin-film thermoelectrics have been demonstrated to provide high heat pumping capacity that far exceeds the capacities provided by traditional bulk pellet TE products. The benefit of thin-films versus bulk materials for thermoelectric manufacturing is expressed in Equation 1. Here the Qmax (maximum heat pumped by a module) is shown to be inversely proportional to the thickness of the film, L.
Eq. 1
As such, TE coolers manufactured with thin-films can easily have 10x – 20x higher Qmax values for a given active area A. This makes thin-film TECs ideally suited for applications involving high heat-flux flows. In addition to the increased heat pumping capability, the use of thin films allows for truly novel implementation of TE devices. Instead of a bulk module that is 1–3 mm in thickness, a thin-film TEC can be fabricated less than 100 um in thickness.
In its simplest form, the P or N leg of a TE couple (the basic building block of all thin-film TE devices) is a layer of thin-film TE material with a solder layer above and below, providing electrical and thermal functionality. | 0 | Theoretical and Fundamental Chemistry |
An acetyl group of acetyl-CoA combines with oxaloacetate to form citrate, releasing the coenzyme group (CoA) in the mitochondrial matrix. | 1 | Applied and Interdisciplinary Chemistry |
Organophosphorus chemistry is the scientific study of the synthesis and properties of organophosphorus compounds, which are organic compounds containing phosphorus. They are used primarily in pest control as an alternative to chlorinated hydrocarbons that persist in the environment. Some organophosphorus compounds are highly effective insecticides, although some are extremely toxic to humans, including sarin and VX nerve agents.
Phosphorus, like nitrogen, is in group 15 of the periodic table, and thus phosphorus compounds and nitrogen compounds have many similar properties. The definition of organophosphorus compounds is variable, which can lead to confusion. In industrial and environmental chemistry, an organophosphorus compound need contain only an organic substituent, but need not have a direct phosphorus-carbon (P-C) bond. Thus a large proportion of pesticides (e.g., malathion), are often included in this class of compounds.
Phosphorus can adopt a variety of oxidation states, and it is general to classify organophosphorus compounds based on their being derivatives of phosphorus(V) vs phosphorus(III), which are the predominant classes of compounds. In a descriptive but only intermittently used nomenclature, phosphorus compounds are identified by their coordination number σ and their valency λ. In this system, a phosphine is a σλ compound. | 0 | Theoretical and Fundamental Chemistry |
Carboximidates (or more general imidates) are organic compounds, which can be thought of as esters formed between a imidic acid (R-C(=NR)OH) and an alcohol, with the general formula R-C(=NR)OR".
They are also known as imino ethers, since they resemble imines (>C=N-) with an oxygen atom connected to the carbon atom of the C=N double bond. | 0 | Theoretical and Fundamental Chemistry |
The plot of the Hammett equation is typically seen as being linear, with either a positive or negative slope correlating to the value of rho. However, nonlinearity emerges in the Hammett plot when a substituent affects the rate of reaction or changes the rate-determining step or reaction mechanism of the reaction. For the reason of the former case, new sigma constants have been introduced to accommodate the deviation from linearity otherwise seen resulting from the effect of the substituent. σ+ takes into account positive charge buildup occurring in the transition state of the reaction. Therefore, an electron donating group (EDG) will accelerate the rate of the reaction by resonance stabilization and will give the following sigma plot with a negative rho value.
σ- is designated in the case where negative charge buildup in the transition state occurs, and the rate of the reaction is consequently accelerated by electron withdrawing groups (EWG). The EWG withdraws electron density by resonance and effectively stabilizes the negative charge that is generated. The corresponding plot will show a positive rho value.
In the case of a nucleophilic acyl substitution the effect of the substituent, X, of the non-leaving group can in fact accelerate the rate of the nucleophilic addition reaction when X is an EWG. This is attributed to the resonance contribution of the EWG to withdraw electron density thereby increasing the susceptibility for nucleophilic attack on the carbonyl carbon. A change in rate occurs when X is EDG, as is evidenced when comparing the rates between X = Me and X = OMe, and nonlinearity is observed in the Hammett plot.
The effect of the substituent may change the rate-determining step (rds) in the mechanism of the reaction. A certain electronic effect may accelerate a certain step so that it is no longer the rds.
A change in the mechanism of a reaction also results in nonlinearity in the Hammett plot. Typically, the model used for measuring the changes in rate in this instance is that of the SN2 reaction. However, it has been observed that in some cases of an SN2 reaction that an EWG does not accelerate the reaction as would be expected and that the rate varies with the substituent. In fact, the sign of the charge and degree to which it develops will be affected by the substituent in the case of the benzylic system.
For example, the substituent may determine the mechanism to be an SN1 type reaction over a SN2 type reaction, in which case the resulting Hammett plot will indicate a rate acceleration due to an EDG, thus elucidating the mechanism of the reaction.
Another deviation from the regular Hammett equation is explained by the charge of nucleophile. Despite nonlinearity in benzylic SN2 reactions, electron withdrawing groups could either accelerate or retard the reaction. If the nucleophile is negatively charged (e.g. cyanide) the electron withdrawing group will increase the rate due to stabilization of the extra charge which is put on the carbon in the transition state. On the other hand, if the nucleophile is not charged (e.g. triphenylphosphine), electron withdrawing group is going to slow down the reaction by decreasing the electron density in the anti bonding orbital of leaving group in the transition state. | 0 | Theoretical and Fundamental Chemistry |
The oxygen blast furnace (OBF) process has been extensively studied theoretically because of the potentials of promising energy conservation and emission reduction. This type may be the most suitable for use with CCS. The main blast furnace has of three levels; the reduction zone (), slag formation zone (), and the combustion zone ().
Blast furnaces are currently rarely used in copper smelting, but modern lead smelting blast furnaces are much shorter than iron blast furnaces and are rectangular in shape. Modern lead blast furnaces are constructed using water-cooled steel or copper jackets for the walls, and have no refractory linings in the side walls. The base of the furnace is a hearth of refractory material (bricks or castable refractory). Lead blast furnaces are often open-topped rather than having the charging bell used in iron blast furnaces.
The blast furnace used at the Nyrstar Port Pirie lead smelter differs from most other lead blast furnaces in that it has a double row of tuyeres rather than the single row normally used. The lower shaft of the furnace has a chair shape with the lower part of the shaft being narrower than the upper. The lower row of tuyeres being located in the narrow part of the shaft. This allows the upper part of the shaft to be wider than the standard. | 1 | Applied and Interdisciplinary Chemistry |
After granulation, a final lubrication step is used to ensure that the tableting blend does not stick to the equipment during the tableting process. This usually involves low shear blending of the granules with a powdered lubricant, such as magnesium stearate or stearic acid. | 1 | Applied and Interdisciplinary Chemistry |
Even though μ-opioid receptor (MOR) targeting drugs have been used for a long time, not much is known about the structure-activity relationship and the ligand-receptor interactions on the basis of well-defined biological effects on receptor activation or inhibition. Also, the distinction in the receptor-ligand interaction patterns of agonists and antagonists is not known for sure. One theory states that the morphinans biological activity could be determined by the size of the N-substituents. For example, antagonists usually have larger substituents, such as allyl- or [https://pubchem.ncbi.nlm.nih.gov/compound/11029756 cyclopropyl methyl] at the morphinan nitrogen, while agonists generally contain a methyl group. On the other hand, agonist activity is also shown in ligands with larger groups at the morphinan nitrogen, and therefore this hypothesis is challenged. | 1 | Applied and Interdisciplinary Chemistry |
Electrical steel is one material that uses decarburization in its production. To prevent the atmospheric gases from reacting with the metal itself, electrical steel is annealed in an atmosphere of nitrogen, hydrogen, and water vapor, where oxidation of the iron is specifically prevented by the proportions of hydrogen and water vapor so that the only reacting substance is carbon being oxidized into carbon monoxide (CO). | 1 | Applied and Interdisciplinary Chemistry |
The central dogma of molecular biology deals with the flow of genetic information within a biological system. It is often stated as "DNA makes RNA, and RNA makes protein", although this is not its original meaning. It was first stated by Francis Crick in 1957, then published in 1958:
He re-stated it in a Nature paper published in 1970: "The central dogma of molecular biology deals with the detailed residue-by-residue transfer of sequential information. It states that such information cannot be transferred back from protein to either protein or nucleic acid."
A second version of the central dogma is popular but incorrect. This is the simplistic DNA → RNA → protein pathway published by James Watson in the first edition of The Molecular Biology of the Gene (1965). Watsons version differs from Cricks because Watson describes a two-step (DNA → RNA and RNA → protein) process as the central dogma. While the dogma as originally stated by Crick remains valid today, Watson's version does not. | 1 | Applied and Interdisciplinary Chemistry |
Spans:
* Sorbitan monolaurate
* Sorbitan monostearate
* Sorbitan tristearate
Tweens:
* Tween 20
* Tween 40
* Tween 60
* Tween 80 | 0 | Theoretical and Fundamental Chemistry |
Anisomycin is used as a component of Martin Lewis agar, an in vitro diagnostic product which is used extensively in the United States for the selective isolation of Neisseria gonorrhoeae and Neisseria meningitidis. The antimicrobial can also be used in buffered charcoal yeast extract media for the selective isolation of Legionella species. | 1 | Applied and Interdisciplinary Chemistry |
Scientists in Amsterdam, the Netherlands, took cubes of bioactive glass and implanted them into the tibias of guinea pigs in 1986. After 8, 12, and 16 weeks of implantation, the guinea pigs were euthanized and their tibias were harvested. The implants and tibias were then subjected to a shear strength test to determine the mechanical properties of the implant to bone boundary, where it was found to have a shear strength of 5 N/mm. Electron microscopy showed the ceramic implants had bone remnants firmly adhered to them. Further optical microscopy revealed bone cell and blood vessel growth within the area of the implant which was proof of biocompatibility between the bone and implant.
Bioactive glass was the first material found to create a strong bond with living bone tissue. | 0 | Theoretical and Fundamental Chemistry |
Botanical gardens, zoos, and aquariums are the most conventional methods of ex situ conservation. Also in ex situ conservation, all of which house whole, protected specimens for breeding and reintroduction into the wild when necessary and possible. These facilities provide not only housing and care for specimens of endangered species, but also have an educational value. They inform the public of the threatened status of endangered species and of those factors which cause the threat, with the hope of creating public interest in stopping and reversing those factors which jeopardize a species survival in the first place. They are the most publicly visited ex situ' conservation sites, with the WZCS (World Zoo Conservation Strategy) estimating that the 1,100 organized zoos in the world receive more than 600 million visitors annually. Globally there is an estimated total of 2,107 aquaria and zoos in 125 countries. Additionally many private collectors or other not-for-profit groups hold animals and they engage in conservation or reintroduction efforts. Similarly there are approximately 2,000 botanical gardens in 148 counties cultivating or storing an estimated 80,000 taxa of plants. | 1 | Applied and Interdisciplinary Chemistry |
GESTIS Substance Database is a freely accessible online information system on chemical compounds. It is maintained by the Institut für Arbeitsschutz der Deutschen Gesetzlichen Unfallversicherung (IFA, Institute for Occupational Safety and Health of the German Social Accident Insurance). Information on occupational medicine and first aid is compiled by Henning Heberer and his team (TOXICHEM, Leuna).
The database contains information for the safe handling of hazardous substances and other chemical substances at work:
* toxicology/ecotoxicology
* important physical and chemical properties
* application and handling
* health effects
* protective measures and such in case of danger (incl. first aid)
* special regulations e.g. GHS classification and labelling according to CLP Regulation (pictograms, H phrases, P phrases).
The available information relates to about 9,400 substances. Data are updated immediately after publication of new official regulations or after the issue of new scientific results.
A mobile version of the GESTIS Substance Database, suitable for smartphones and tablets, is also available. | 1 | Applied and Interdisciplinary Chemistry |
Mice were first used systematically to determine a drug's central nervous system side effects by S. Irwin in 1962 and then again in 1968. Its use in the pharmaceutical industry has become ingrained since then, as below.
The National Academy of Sciences issued in 1975 a position paper on the "Principles for Evaluating Chemicals in the Environment." This paper influenced government and academic circles, and was adopted by e.g. Brimblecombe for his study of atmospheric arsenic levels. The critical review in 1982 by Mitchell and Tilson, caused the US EPA to develop guidelines for several behavioural tests including a test series based on the Irwin Screen, named the Functional Observational Battery (FOB) by Sette in 1989. In 1998, the FOB was published in the late 1990s as EPA Human Health 870 Series Test Guidelines, and in praxis the Irwin screen and the FOB "overlap and to some extent are interchangeable."
The American batteries were harmonised with the OECD's from the same era. Similar tests on food chemicals were recommended by the FDA in their Red Book. Behavioural test batteries are now required for new drugs by the S7A group of the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH). | 1 | Applied and Interdisciplinary Chemistry |
Survivin has been a target of attention in recent years for cancer immunotherapy, as it is an antigen that is expressed mostly in cancer cells and absent in normal cells. This is because survivin is deemed to be a crucial player in tumour survival. There has been much evidence accumulated over the years that shows survivin as a strong T-cell-activating antigen, and clinical trials have already been initiated to prove its usefulness in the clinic. | 1 | Applied and Interdisciplinary Chemistry |
The Blake number in fluid mechanics is a nondimensional number showing the ratio of inertial force to viscous force.
It is used in momentum transfer in general and in particular for flow of a fluid through beds of solids. It is a generalisation of the Reynolds number for flow through porous media.
Expressed mathematically the Blake number is:
where | 1 | Applied and Interdisciplinary Chemistry |
The Comins' reagent is a triflyl-donating reagent that is used to synthesize vinyl triflates from the corresponding ketone enolates or dienolates.
It was first reported in 1992 by Daniel Comins. The vinyl triflates prepared are useful as substrates in the Suzuki reaction. | 0 | Theoretical and Fundamental Chemistry |
The proton-motive force is derived from the Gibbs free energy. Let N denote the inside of a cell, and P denote the outside. Then
where
* is the Gibbs free energy change per unit amount of cations transferred from P to N;
* is the charge number of the cation ;
* is the electric potential of N relative to P;
* and are the cation concentrations at P and N, respectively;
* is the Faraday constant;
* is the gas constant; and
* is the temperature.
The molar Gibbs free energy change is frequently interpreted as a molar electrochemical ion potential .
For an electrochemical proton gradient and as a consequence:
where
Mitchell defined the proton-motive force (PMF) as
For example, implies . At this equation takes the form:
Note that for spontaneous proton import from the P side (relatively more positive and acidic) to the N side (relatively more negative and alkaline), is negative (similar to ) whereas PMF is positive (similar to redox cell potential ).
It is worth noting that, as with any transmembrane transport process, the PMF is directional. The sign of the transmembrane electric potential difference is chosen to represent the change in potential energy per unit charge flowing into the cell as above. Furthermore, due to redox-driven proton pumping by coupling sites, the proton gradient is always inside-alkaline. For both of these reasons, protons flow in spontaneously, from the P side to the N side; the available free energy is used to synthesize ATP (see below). For this reason, PMF is defined for proton import, which is spontaneous. PMF for proton export, i.e., proton pumping as catalyzed by the coupling sites, is simply the negative of PMF(import).
The spontaneity of proton import (from the P to the N side) is universal in all bioenergetic membranes. This fact was not recognized before the 1990s, because the chloroplast thylakoid lumen was interpreted as an interior phase, but in fact it is topologically equivalent to the exterior of the chloroplast. Azzone et al. stressed that the inside phase (N side of the membrane) is the bacterial cytoplasm, mitochondrial matrix, or chloroplast stroma; the outside (P) side is the bacterial periplasmic space, mitochondrial intermembrane space, or chloroplast lumen. Furthermore, 3D tomography of the mitochondrial inner membrane shows its extensive invaginations to be stacked, similar to thylakoid disks; hence the mitochondrial intermembrane space is topologically quite similar to the chloroplast lumen.:
The energy expressed here as Gibbs free energy, electrochemical proton gradient, or proton-motive force (PMF), is a combination of two gradients across the membrane:
* the concentration gradient (via ) and
* electric potential gradient .
When a system reaches equilibrium, ; nevertheless, the concentrations on either side of the membrane need not be equal. Spontaneous movement across the potential membrane is determined by both concentration and electric potential gradients.
The molar Gibbs free energy of ATP synthesis
is also called phosphorylation potential. The equilibrium concentration ratio can be calculated by comparing and , for example in case of the mammalian mitochondrion:
H / ATP = ΔG / (Δp / 10.4 kJ·mol/mV) = 40.2 kJ·mol / (173.5 mV / 10.4 kJ·mol/mV) = 40.2 / 16.7 = 2.4. The actual ratio of the proton-binding c-subunit to the ATP-synthesizing beta-subunit copy numbers is 8/3 = 2.67, showing that under these conditions, the mitochondrion functions at 90% (2.4/2.67) efficiency.
In fact, the thermodynamic efficiency is mostly lower in eukaryotic cells because ATP must be exported from the matrix to the cytoplasm, and ADP and phosphate must be imported from the cytoplasm. This "costs" one "extra" proton import per ATP, hence the actual efficiency is only 65% (= 2.4/3.67). | 1 | Applied and Interdisciplinary Chemistry |
Solar energy production in the U.S. has doubled from 2013 to 2019. This was driven first by the falling price of quality silicon, and later simply by the globally plunging cost of photovoltaic modules. In 2018, the U.S. added 10.8GW of installed solar photovoltaic energy, an increase of 21%.
Latin America : Latin America has emerged as a promising region for solar energy development in recent years, with over 10 GW of installations in 2020. The solar market in Latin America has been driven by abundant solar resources, falling costs, competitive auctions and growing electricity demand. Some of the leading countries for solar energy in Latin America are Brazil, Mexico, Chile and Argentina. However, the solar market in Latin America also faces some challenges, such as political instability, financing gaps and power transmission bottlenecks.
Middle East and Africa : The Middle East and Africa has also experienced significant growth in solar energy deployment in recent years, with over 8 GW installations in 2020. The solar market in the Middle East and Africa has been driven by the low-cost generation of solar energy, the diversification of energy sources, the fight against climate change and rural electrification are motivated. Some of the notable countries for solar energy in the Middle East and Africa are Saudi Arabia, United Arab Emirates, Egypt, Morocco and South Africa. However, the solar market in the Middle East and Africa also faces several obstacles, including social unrest, regulatory uncertainty and technical barriers. | 0 | Theoretical and Fundamental Chemistry |
Combining an adsorbent with a refrigerant, adsorption chillers use heat to provide a cooling effect. This heat, in the form of hot water, may come from any number of industrial sources including waste heat from industrial processes, prime heat from solar thermal installations or from the exhaust or water jacket heat of a piston engine or turbine.
Although there are similarities between adsorption chillers and absorption refrigeration, the former is based on the interaction between gases and solids. The adsorption chamber of the chiller is filled with a solid material (for example zeolite, silica gel, alumina, active carbon or certain types of metal salts), which in its neutral state has adsorbed the refrigerant. When heated, the solid desorbs (releases) refrigerant vapour, which subsequently is cooled and liquefied. This liquid refrigerant then provides a cooling effect at the evaporator from its enthalpy of vaporization. In the final stage the refrigerant vapour is (re)adsorbed into the solid. As an adsorption chiller requires no compressor, it is relatively quiet. | 0 | Theoretical and Fundamental Chemistry |
Turbofans differ from turbojets in that they have an additional fan at the front of the engine, which accelerates air in a duct bypassing the core gas turbine engine. Turbofans are the dominant engine type for medium and long-range airliners.
Turbofans are usually more efficient than turbojets at subsonic speeds, but at high speeds their large frontal area generates more drag. Therefore, in supersonic flight, and in military and other aircraft where other considerations have a higher priority than fuel efficiency, fans tend to be smaller or absent.
Because of these distinctions, turbofan engine designs are often categorized as low-bypass or high-bypass, depending upon the amount of air which bypasses the core of the engine. Low-bypass turbofans have a bypass ratio of around 2:1 or less. | 1 | Applied and Interdisciplinary Chemistry |
Helium-3 nuclear magnetic resonance (He-NMR) is an analytical technique used to identify helium-containing compounds. Because a helium atom, or even two helium atoms, can be encased in fullerene-like cages, the nuclear magnetic resonance spectroscopy of this element can be a sensitive probe for changes of the carbon framework around it. Using carbon-13 NMR to analyze fullerenes themselves is complicated by so many subtle differences among the carbons in anything but the simplest, highly-symmetric structures. The technique is limited by the need to use the rare helium-3 isotope: the vast majority of naturally occurring helium is helium-4, which does not have suitable magnetic properties for NMR detection. | 0 | Theoretical and Fundamental Chemistry |
In the United States, Valeant raised the cost of the medication from about US$500 to US$24,000 per month in 2016. | 0 | Theoretical and Fundamental Chemistry |
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