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SpliceInfo is a database for the four major alternative-splicing modes (exon skipping, 5-alternative splicing, 3-alternative splicing and intron retention) in the human genome.
This resource appears to be no longer available. | 1 | Applied and Interdisciplinary Chemistry |
Absolute configuration refers to the spatial arrangement of atoms within a chiral molecular entity (or group) and its resultant stereochemical description. Absolute configuration is typically relevant in organic molecules where carbon is bonded to four different substituents. This type of construction creates two possible enantiomers. Absolute configuration uses a set of rules to describe the relative positions of each bond around the chiral center atom. The most common labeling method uses the descriptors R or S and is based on the Cahn–Ingold–Prelog priority rules. R and S refer to rectus and sinister, Latin for right and left, respectively.
Chiral molecules can differ in their chemical properties, but are identical in their physical properties, which can make distinguishing enantiomers challenging. Absolute configurations for a chiral molecule (in pure form) are most often obtained by X-ray crystallography, although with some important limitations. All enantiomerically pure chiral molecules crystallise in one of the 65 Sohncke groups (chiral space groups). Alternative techniques include optical rotatory dispersion, vibrational circular dichroism, ultraviolet-visible spectroscopy, the use of chiral shift reagents in proton NMR and Coulomb explosion imaging. | 0 | Theoretical and Fundamental Chemistry |
Reactions that reduce Fd include the oxidation of aldehydes to acids like the glyceraldehyde to glycerate reaction (-580 mV), the carbon monoxide dehydrogenase reaction (-520 mV), and the 2-oxoacid:Fd Oxidoreductase reactions (-500 mV) like the reaction carried out by pyruvate synthase. | 0 | Theoretical and Fundamental Chemistry |
The School of Chemistry was established as a part of the Faculty of Science in 1882. However, chemistry was taught at the University of Sydney since 1852. A purpose-built building was constructed on what was later named Science Road starting in 1888 and was completed in 1890. The building was designed largely by Archibald Liversidge, Professor of Chemistry and the first Dean of the Faculty of Science. The original Chemistry Building is now used by the Sydney Pharmacy School.
In 1945, a large fibro-cement building (known as "Tramsheds") was constructed for use by chemistry students until the current Chemistry Building opened in 1958. The current Chemistry Building is notable in architectural history as one of the first structures in Australia with a curtain wall design. | 1 | Applied and Interdisciplinary Chemistry |
Macromolecules often have unusual physical properties that do not occur for smaller molecules.
Another common macromolecular property that does not characterize smaller molecules is their relative insolubility in water and similar solvents, instead forming colloids. Many require salts or particular ions to dissolve in water. Similarly, many proteins will denature if the solute concentration of their solution is too high or too low.
High concentrations of macromolecules in a solution can alter the rates and equilibrium constants of the reactions of other macromolecules, through an effect known as macromolecular crowding. This comes from macromolecules excluding other molecules from a large part of the volume of the solution, thereby increasing the effective concentrations of these molecules. | 0 | Theoretical and Fundamental Chemistry |
F is a water insoluble protein with eight subunits and a transmembrane ring. The ring has a tetrameric shape with a helix-loop-helix protein that goes through conformational changes when protonated and deprotonated, pushing neighboring subunits to rotate, causing the spinning of F which then also affects conformation of F, resulting in switching of states of alpha and beta subunits. The F region of ATP synthase is a proton pore that is embedded in the mitochondrial membrane. It consists of three main subunits, a, b, and c. Six c subunits make up the rotor ring, and subunit b makes up a stalk connecting to F OSCP that prevents the αβ hexamer from rotating. Subunit a connects b to the c ring. Humans have six additional subunits, d, e, f, g, F6, and 8 (or A6L). This part of the enzyme is located in the mitochondrial inner membrane and couples proton translocation to the rotation that causes ATP synthesis in the F region.
In eukaryotes, mitochondrial F forms membrane-bending dimers. These dimers self-arrange into long rows at the end of the cristae, possibly the first step of cristae formation. An atomic model for the dimeric yeast F region was determined by cryo-EM at an overall resolution of 3.6 Å. | 0 | Theoretical and Fundamental Chemistry |
In the year 1975, timoprazole was found to inhibit acid secretion irrespective of stimulus, extracellular or intracellular. Studies on timoprazole revealed enlargement of the thyroid gland due to inhibition of iodine uptake as well as atrophy of the thymus gland. A literature search showed that some substituted mercapto-benzimidazoles had no effect on iodine uptake and introduction of such substituents into timoprazole resulted in an elimination of the toxic effects, without reducing the antisecretory effect. A derivative of timoprazole, omeprazole, was discovered in 1979, and was the first of a new class of drug that control acid secretion in the stomach, a proton pump inhibitor (PPI). Addition of 5-methoxy-substitution to the benzimidazole moiety of omeprazole was also made and gave the compound much more stability at neutral pH. In 1980, an Investigational New Drug (IND) application was filed and omeprazole was taken into Phase III human trials in 1982. A new approach for the treatment of acid-related diseases was introduced, and omeprazole was quickly shown to be clinically superior to the histamine H receptor antagonists, and was launched in 1988 as Losec in Europe, and in 1990 as Prilosec in the United States. In 1996, Losec became the world's biggest ever selling pharmaceutical, and by 2004 over 800 million patients had been treated with the drug worldwide. During the 1980s, about 40 other companies entered the PPIs area, but few achieved market success: Takeda with lansoprazole, Byk Gulden (now Nycomed) with pantoprazole, and Eisai with rabeprazole, all of which were analogues of omeprazole. | 1 | Applied and Interdisciplinary Chemistry |
On the news of Lulu and Nana having been born, the Peoples Daily announced the experimental result as "a historical breakthrough in the application of gene editing technology for disease prevention." But scientists at the Second International Summit on Human Genome Editing immediately developed serious concerns. Robin Lovell-Badge, head of the Laboratory of Stem Cell Biology and Developmental Genetics at the Francis Crick Institute, who moderated the session on 28 November, recalled that He Jiankui did not mention human embryos in the draft summary of the presentation. He received an urgent message on 25 November through Jennifer Doudna of the University of California, Berkeley, a pioneer of the CRISPR/Cas9 technology, to whom he had confided the news earlier that morning. As the news already broke out before the day of the presentation, he had to be brought in by the University of Hong Kong security from his hotel. Nobel laureate David Baltimore, the chair of the organizing committee of the summit, was the first to react after Hes speech, and declared his horror and dismay at his work.
He did not disclose the parents names (other than their pseudonyms Mark and Grace) and they did not make themselves available to be interviewed, so their reaction to this experiment and the ensuing controversy is not known. There was widespread criticism in the media and scientific community over the conduct of the clinical project and its secrecy, and concerns raised for the long term well-being of Lulu and Nana. Bioethicist Henry T. Greely of Stanford Law School declared, "I unequivocally condemn the experiment," and later, "He Jiankui’s experiment was, amazingly, even worse than I first thought." Kiran Musunuru, one of the experts called on to review Hes manuscript and who later wrote a book on the scandal, called it a "historic ethical fiasco, a deeply flawed experiment".
On the night of 26 November 122 Chinese scientists issued a statement criticizing his research. They declared that the experiment was unethical, "crazy" and "a huge blow to the global reputation and development of Chinese science". The Chinese Academy of Medical Sciences made a condemnation statement on 5 January 2019 saying that:
A series of investigations was opened by Hes university, local authorities, and the Chinese government. On 26 November 2018, SUSTech released a public notification on its website condemning Hes conduct, mentioning the key points as:
* The research work was conducted off-campus by Associate Professor He Jiankui without reporting to the university and the Department of Biology, and the university and the Department of Biology were unaware of it.
* The Academic Committee of the Department of Biology considers that Associate Professor He Jiankui's use of gene editing technology for human embryo research is a serious violation of academic ethics and academic standards.
* SUSTech strictly requires scientific research to comply with national laws and regulations and to respect and abide by international academic ethics and academic norms. The university will immediately hire authoritative experts to set up an independent committee to conduct an in-depth investigation, and will publish relevant information after the investigation.
On 28 November 2018, the organising committee of the Second International Summit on Human Genome Editing, led by Baltimore, issued a statement, declaring:On 29 January 2019, it was learned that a U.S. Nobel laureate Craig Mello interviewed He about his experiment with gene-edited babies. In February 2019, He's claims were reported to have been confirmed by Chinese investigators, according to NPR News. Around that time, news reported that the Chinese government may have helped fund the CRISPR babies experiment, at least in part, based on newly uncovered documents. | 1 | Applied and Interdisciplinary Chemistry |
Atomic physics is the field of physics that studies atoms as an isolated system of electrons and an atomic nucleus. Atomic physics typically refers to the study of atomic structure and the interaction between atoms. It is primarily concerned with the way in which electrons are arranged around the nucleus and
the processes by which these arrangements change. This comprises ions, neutral atoms and, unless otherwise stated, it can be assumed that the term atom includes ions.
The term atomic physics can be associated with nuclear power and nuclear weapons, due to the synonymous use of atomic and nuclear in standard English. Physicists distinguish between atomic physics—which deals with the atom as a system consisting of a nucleus and electrons—and nuclear physics, which studies nuclear reactions and special properties of atomic nuclei.
As with many scientific fields, strict delineation can be highly contrived and atomic physics is often considered in the wider context of atomic, molecular, and optical physics. Physics research groups are usually so classified. | 0 | Theoretical and Fundamental Chemistry |
Pulmonary surfactant is a surface-active complex of phospholipids and proteins formed by type II alveolar cells. The proteins and lipids that make up the surfactant have both hydrophilic and hydrophobic regions. By adsorbing to the air-water interface of alveoli, with hydrophilic head groups in the water and the hydrophobic tails facing towards the air, the main lipid component of surfactant, dipalmitoylphosphatidylcholine (DPPC), reduces surface tension.
As a medication, pulmonary surfactant is on the WHO Model List of Essential Medicines, the most important medications needed in a basic health system. | 0 | Theoretical and Fundamental Chemistry |
By the early 19th century the puddling process was widespread. Until technological advances made it possible to work at higher heats, slag impurities could not be removed entirely, but the reverberatory furnace made it possible to heat iron without placing it directly in the fire, offering some degree of protection from the impurity of the fuel source. Thus, with the advent of this technology, coal began to replace charcoal fuel. The Bessemer process allowed steel to be produced without fuel, using the impurities of the iron to create the necessary heat. This drastically reduced the costs of steel production, but raw materials with the required characteristics could be difficult to find.
High-quality steel was made by the reverse process of adding carbon to carbon-free wrought iron, usually imported from Sweden. The manufacturing process, called the cementation process, consisted of heating bars of wrought iron together with charcoal for periods of up to a week in a long stone box. This produced blister steel. The blister steel was put in a crucible with wrought iron and melted, producing crucible steel. Up to 3 tons of expensive coke was burnt for each ton of steel produced. Such steel when rolled into bars was sold at £50 to £60 (approximately £3,390 to £4,070 in 2008) a long ton. The most difficult and work-intensive part of the process, however, was the production of wrought iron done in finery forges in Sweden.
This process was refined in the 18th century with the introduction of Benjamin Huntsman's crucible steel-making techniques, which added an additional three hours firing time and required additional large quantities of coke. In making crucible steel, the blister steel bars were broken into pieces and melted in small crucibles, each containing 20 kg or so. This produced higher quality crucible steel but increased the cost. The Bessemer process reduced the time needed to make lower-grade steel to about half an hour while requiring only the coke needed initially to melt the pig iron. The earliest Bessemer converters produced steel for £7 a long ton, although it initially sold for around £40 a ton. | 1 | Applied and Interdisciplinary Chemistry |
Flow injection techniques have proven very useful in marine science for both organic and inorganic analytes in marine animal samples/seafood. Flow Injection methods applied to the determination of amino acids (histidine, L-lysine and tyrosine), DNA/RNA, formaldehyde, histamine, hypoxanthine, polycyclic aromatic hydrocarbons, diarrheic shellfish poisoning, paralytic shellfish poisoning, succinate/glutamate, trimethylamine/ total volatile basic nitrogen, total lipid hydroperoxides, total volatile acids, uric acid, vitamin B12, silver, aluminium, arsenic, boron, calcium, cadmium, cobalt, chromium, copper, iron, gallium, mercury, indium, lithium, manganese, molibdenum, nickel, lead, antimony, selenium, tin, strontium, thallium, vanadium, zinc, nitrate/nitrite, phosphorus/phosphate and silicate. | 0 | Theoretical and Fundamental Chemistry |
Duplornaviricota contains most dsRNA viruses, including reoviruses, which infect a diverse range of eukaryotes, and cystoviruses, which are the only dsRNA viruses known to infect prokaryotes. Apart from RdRp, viruses in Duplornaviricota also share icosahedral capsids that contain 60 homo- or heterodimers of the capsid protein organized on a pseudo T=2 lattice. The phylum is divided into three classes: Chrymotiviricetes, which primarily contains fungal and protozoan viruses, Resentoviricetes, which contains reoviruses, and Vidaverviricetes, which contains cystoviruses. | 1 | Applied and Interdisciplinary Chemistry |
If creating an mRNA library (i.e. with cDNA clones), there are several possible protocols for isolating full length mRNA. To extract DNA for genomic DNA (also known as gDNA) libraries, a DNA mini-prep may be useful. | 1 | Applied and Interdisciplinary Chemistry |
Some words common in spectroscopy, optical microscopy and photography have been adapted or their scope modified for their use in chemical imaging. They include: resolution, field of view and magnification. There are two types of resolution in chemical imaging. The spectral resolution refers to the ability to resolve small energy differences; it applies to the spectral axis. The spatial resolution is the minimum distance between two objects that is required for them to be detected as distinct objects. The spatial resolution is influenced by the field of view, a physical measure of the size of the area probed by the analysis. In imaging, the field of view is a product of the magnification and the number of pixels in the detector array. The magnification is a ratio of the physical area of the detector array divided by the area of the sample field of view. Higher magnifications for the same detector image a smaller area of the sample. | 0 | Theoretical and Fundamental Chemistry |
Borane dimethylsulfide is flammable and reacts readily with water to produce a flammable gas. It also has an unpleasant smell. | 0 | Theoretical and Fundamental Chemistry |
Best polymerization conditions for acrylamide gels are obtained at 25–30 °C and polymerization seems terminated after 20–30 min of reaction although residual monomers (10–30%) are detected after this time. The co-polymerization of acrylamide (AA) monomer/N,N'-Methylenebisacrylamide (Bis-AA) cross-linker initiated by ammonium persulfate (APS)/tetramethylethylenediamine (TEMED) reactions, is most efficient at alkaline pH of the acrylamide solution. Thereby, acrylamide chains are created and cross-linked at a time. Due to the properties of the electrophoresis buffer, the gel polymerization is conducted at pH 10.00 making sure an efficient use of TEMED and APS as catalysts of the polymerization reaction, and concurrently, suppressing a competitive hydrolysis of the produced acrylamide polymer network. Polymer networks are three-dimensionally linked polymer chains. Otherwise, proteins could be modified by reaction with unpolymerized monomers of acrylamide, forming covalent acrylamide adduction products that may result in multiple bands.
Additionally, the time of polymerization of a gel may directly affect the peak-elution times of separated metalloproteins in the electropherogram due to the compression and dilatation of the gels and their pores if the incubation times for the reaction mixture (gel solution) used to prepare a gel are not optimized (cf. fig. Electropherogram, see sect. Reproducibility and recovery). In order to ensure maximum reproducibility in gel pore size and to obtain a fully polymerized and non-restrictive large pore gel for a PAGE run, the polyacrylamide gel is polymerized for a time period of 69 hr at room temperature (RT) in a gel column located on the casting stand. The exothermic heat generated by the polymerization processes is dissipated constantly while the temperature may rise rapidly to over 75 °C in the first minutes, after which it falls slowly. After 69 hr, the gel has reached room temperature and is in its lowest energy state, as the basic chemical reactions and gelation are complete. Gelation means that the
solvent (water) gets immobilized within the polymer network by means of hydrogen bonds and also van der Waals forces. As a result, the prepared gel is homogeneous (in terms of homogeneous distribution of cross-links throughout the gel sample), inherently stable and free of monomers or radicals. Fresh polyacrylamide gels are further hydrophilic, electrically neutral and do not bind proteins. Sieving effects due to gravity-induced compression of the gel can be excluded for the same reasons. Thus, in a medium without molecular sieving properties a high-resolution can be expected.
Before an electrophoretic run is started the prepared 4% T (total polymer content (T)), 2.67% C (cross-linker concentration (C)) gel is pre-run to equilibrate it. It is essentially non-sieving and optimal for electrophoresis of proteins greater than or equal to 200 ku. Proteins migrate in it more or less on the basis of their free mobility. For these reasons interactions of the gel with the biomolecules are negligibly low, and thus, the proteins separate cleanly and predictably at a polymerization time of 69 hr (cf. fig. Electropherogram). The separated metalloproteins including biomolecules ranging from approximately < 1 ku to greater than 30 ku (e.g., metal chaperones, prions, metal transport proteins, amyloids, metalloenzymes, metallopeptides, metallothionein, phytochelatins) are not dissociated into apoproteins and metal cofactors. | 0 | Theoretical and Fundamental Chemistry |
The AFM has three major abilities: force measurement, topographic imaging, and manipulation.
In force measurement, AFMs can be used to measure the forces between the probe and the sample as a function of their mutual separation. This can be applied to perform force spectroscopy, to measure the mechanical properties of the sample, such as the samples Youngs modulus, a measure of stiffness.
For imaging, the reaction of the probe to the forces that the sample imposes on it can be used to form an image of the three-dimensional shape (topography) of a sample surface at a high resolution. This is achieved by raster scanning the position of the sample with respect to the tip and recording the height of the probe that corresponds to a constant probe-sample interaction (see for more). The surface topography is commonly displayed as a pseudocolor plot.
Although the initial publication about atomic force microscopy by Binnig, Quate and Gerber in 1986 speculated about the possibility of achieving atomic resolution, profound experimental challenges needed to be overcome before atomic resolution of defects and step edges in ambient (liquid) conditions was demonstrated in 1993 by Ohnesorge and Binnig. True atomic resolution of the silicon 7x7 surface—the atomic images of this surface obtained by STM had convinced the scientific community of the spectacular spatial resolution of scanning tunneling microscopy—had to wait a little longer before it was shown by Giessibl.
In manipulation, the forces between tip and sample can also be used to change the properties of the sample in a controlled way. Examples of this include atomic manipulation, scanning probe lithography and local stimulation of cells.
Simultaneous with the acquisition of topographical images, other properties of the sample can be measured locally and displayed as an image, often with similarly high resolution. Examples of such properties are mechanical properties like stiffness or adhesion strength and electrical properties such as conductivity or surface potential. In fact, the majority of SPM techniques are extensions of AFM that use this modality. | 0 | Theoretical and Fundamental Chemistry |
Similar reactivity has also been observed for other hypervalent structures such as the miscellany of phosphorus compounds, for which hexacoordinated transition states have been proposed.
Hydrolysis of phosphoranes and oxyphosphoranes have been studied and shown to be second order in water. Belskii et al.'. have proposed a prerate determining nucleophilic attack by water resulting in an equilibrium between the penta- and hexacoordinated phosphorus species, which is followed by a proton transfer involving the second water molecule in a rate determining ring-opening step, leading to the hydroxylated product.
Alcoholysis of pentacoordinated phosphorus compounds, such as trimethoxyphospholene with benzyl alcohol, have also been postulated to occur through a similar octahedral transition state, as in hydrolysis, however without ring opening.
It can be understood from these experiments that the increased reactivity observed for hypervalent molecules, contrasted with analogous nonhypervalent compounds, can be attributed to the congruence of these species to the hypercoordinated activated states normally formed during the course of the reaction. | 0 | Theoretical and Fundamental Chemistry |
The nitroso group has both a +M and -M effect, but the -M effect is more favorable.
Nitrogen has a lone pair of electrons. However, the lone pair of its monomer form is unfavourable to donate through resonance. Only the dimer form is available for +M effect. However, the dimer form is less stable in a solution. Therefore, the nitroso group is less available to donate electrons.
Oppositely, withdrawing electron density is more favourable: (see the picture on the right).As a result, the nitroso group is a deactivator. However, it has available to donate electron density to the benzene ring during the Wheland intermediate, making it still being an ortho / para director. | 0 | Theoretical and Fundamental Chemistry |
K2.3 contains 6 transmembrane domains, a pore-forming region, and intracellular N- and C- termini and is readily blocked by apamin. The gene for K2.3, KCNN3, is located on chromosome 1q21. | 1 | Applied and Interdisciplinary Chemistry |
The increased complexity of the phosphorelay system compared to orthodox two-component signaling provides additional opportunities for regulation and improves the specificity of the response. Although there is very little cross-talk between orthodox two-component systems, phosphorelays allow more complex signaling pathways; examples include a bifurcated pathway with multiple downstream outputs, as in the case of the Caulobacter crescentus ChpT HPt involved in cell cycle regulation, or, alternatively, pathways in which more than one histidine kinase controls a single response regulator, such as the sporulation pathway in Bacillus subtilis, which can give rise to complex temporal variations. In some known cases, there is an additional form of regulation in phosphohistidine phosphatase enzymes that act on HPt, such as the Escherichia coli protein SixA which targets ArcB. | 1 | Applied and Interdisciplinary Chemistry |
Between 1857 and 1865, Macadam served as honorary secretary to the Exploration Committee of the Royal Society of Victoria, which organised the Burke and Wills expedition.
The expedition was organised by the society with the aim of crossing the continent of Australia from the south to the north coasts, map it, and collect scientific data and specimens. At that time, most of the interior of Australia had not been explored by the European settlers and was unknown to them.
In 1860–61, Robert O'Hara Burke and William John Wills led the expedition of 19 men with that intention, crossing Australia from Melbourne in the south, to the Gulf of Carpentaria in the north, a distance around 2,000 miles.
Three men ultimately travelled over 3,000 miles from Melbourne to the shores of the Gulf of Carpentaria and back to the Depot Camp at Cooper Creek. Seven men died in the attempt, including the leaders Burke and Wills. Of the four men who reached the north coast, only one, John King, survived with the help of the indigenous people to return to Melbourne.
This expedition became the first to cross the Australian continent. It was of great importance to the subsequent development of Australia and could be compared in importance to the Lewis and Clark Expedition overland to the North American Pacific Coast to the development of the United States.
After the heavy death toll of the expedition, initial criticism fell on the Royal Society, but it became clear that their foresight could not have prevented the deaths and this was then widely recognised when it became known that as Secretary of the Exploration Committee of the Burke and Wills expedition, Dr. Macadam had insisted on adequate provisions for their safety. | 0 | Theoretical and Fundamental Chemistry |
Microbubble contrast agents are generally used in contrast-enhanced ultrasound applications to enhance the acoustic impact of ultrasound. For sonoporation specifically, microbubbles are used to significantly enhance membrane translocation of molecular therapeutics. | 1 | Applied and Interdisciplinary Chemistry |
Fish exhibit a wide range of tactics to counteract aquatic hypoxia, but when escape from the hypoxic stress is not possible, maintaining oxygen extraction and delivery becomes an essential component to survival. Except for the Antarctic ice fish that does not, most fish use hemoglobin (Hb) within their red blood cells to bind chemically and deliver 95% of the oxygen extracted from the environment to the working tissues. Maintaining oxygen extraction and delivery to the tissues allows continued activity under hypoxic stress and is in part determined by modifications in two different blood parameters: hematocrit and the binding properties of hemoglobin. | 0 | Theoretical and Fundamental Chemistry |
The chair conformation of six-membered rings have a dihedral angle of 60° between adjacent substituents thus usually making it the most stable conformer. Since there are two possible chair conformation steric and stereoelectronic effects such as the anomeric effect, 1,3-diaxial interactions, dipoles and intramolecular hydrogen bonding must be taken into consideration when looking at relative energies. Conformations with 1,3-diaxial interactions are usually disfavored due to steric congestion and can shift equilibrium to the other chair form (example: C to C).
The size of the substituents greatly affects this equilibrium. However, intramolecular hydrogen bonding can be an example of a stabilizing 1,3-diaxial interaction. Dipoles also play a role in conformer stability, aligned dipoles lead to an increase in energy while opposed dipoles lead to a lowering of energy hence a stabilizing effect, this can be complicated by solvent effects. Polar solvents tend to stabilize aligned dipoles. All interaction must be taken into account when determining a preferred conformation.
Conformations of five-membered rings are limited to two, envelope and twist. The envelope conformation has four atoms in a plane while the twist form only has three. In the envelope form two different scenarios can be envisioned; one where the ring oxygen is in the four atom plane and one where it is puckered above or below the plane. When the ring oxygen is not in the plane the substituents eclipse and when it is in the plane torsional strain is relieved. Conformational analysis for the twist form is similar thus leading to the two forms being very close in energy. | 0 | Theoretical and Fundamental Chemistry |
In a hydraulic engineering application, it is typical for the volumetric flow within a pipe (that is, its productivity) and the head loss per unit length (the concomitant power consumption) to be the critical important factors. The practical consequence is that, for a fixed volumetric flow rate , head loss decreases with the inverse fifth power of the pipe diameter, . Doubling the diameter of a pipe of a given schedule (say, ANSI schedule 40) roughly doubles the amount of material required per unit length and thus its installed cost. Meanwhile, the head loss is decreased by a factor of 32 (about a 97% reduction). Thus the energy consumed in moving a given volumetric flow of the fluid is cut down dramatically for a modest increase in capital cost. | 1 | Applied and Interdisciplinary Chemistry |
Brazil's National Health Surveillance Agency banned the use of tanning beds for cosmetic purposes in 2009, making that country the first to enact a ban. It followed a 2002 ban on minors using the beds. | 0 | Theoretical and Fundamental Chemistry |
Following the total synthesis of bottromycin, Kobayashi and colleagues synthesized a series of bottromycin derivatives and evaluated their anti-MRSA and anti-VRE activity. Only derivatives of the methyl ester moiety were explored, as they found that the methyl ester was both important for antibacterial activity and unstable in blood plasma. A series of seventeen derivatives were synthesized, with derivatives falling into three general categories: amide derivatives, urea derivatives, and ketone derivatives. All analogs except the carboxylic acid and hydrazide analogs were derivatized from isolated bottromycin A2 using an activated azide ester. The derivatives were tested against six Gram-positive bacterial strains: Staphylococcus aureus FDA209P, S. aureus Smith, MRSA HH-1, MRSA 92-1191, Enterococcus faecalis NCTC12201, and E. faecalis NCTC12203 (both VRE).
Bottromycin A2 had low micromolar activity against all the strains tested, ranging from an MIC of 0.5 μg/mL in E. faecalis NCTC12203 to 2 μg/mL in MRSA HH-1. The amide and urea derivative families were found to have weaker antibacterial activity than bottromycin A2 against S. aureus, MRSA, and VRE. The MIC values for the amide and urea derivatives were generally four times greater than those for bottromycin A2. They were, however, significantly more stable in mouse plasma than bottromycin A2. Bottromycin A2 completely degraded in mouse plasma after 10 minutes and exhibited 0% residual activity after exposure to rat serum. Only one derivative had lower than 50% residual activity. In contrast, many derivatives retained a significant percentage of residual anti-MRSA activity following exposure to serum. Thioester intermediates to the ketone derivatives were found to be unstable, exhibiting 0% residual activity, although they had improved antibacterial activity, exhibiting sub-micromolar MIC values. The propyl ketone was found to be the most promising derivative of all the analogs obtained, both exhibiting antibacterial activity against the bacterial strains tested and stability in plasma, retaining 100% residual activity. The MIC values obtained for the propyl derivative were the same as those found for bottromycin A2 except in the case of NCTC12201, which had an MIC of 2 μg/mL for the derivative and an MIC of 1 μg/mL for bottromycin A2. A summary of MIC values for tested bacterial strains is shown below.
Even the least active bottromycin derivatives exhibited greater anti-VRE activity than vancomycin, which was used as a control antibiotic in this study. The propyl derivative and bottromycin A2 had similar antimicrobial activity to linezolid, a synthetic antibiotic active against Gram-positive bacteria including MRSA and VRE, across all the bacterial strains studied. Overall, the results of this study suggested that further modifications of bottromycin may lead to a more stable, effective antibiotic.
A natural derivative of bottromycin, bottromycin D, has also been identified. It is produced in a marine Streptomyces species, strain WMMB272. Although the methyl ester is still present in bottromycin D, one of the macrocyclic valines is mutated to an alanine. The minimum inhibitory concentration (MIC) for bottromycin D was determined and found to be only slightly less active than bottromycin A2 (2 μg/mL for bottromycin D vs. 1 μg/mL for bottromycin A2). The authors postulated that greater conformational flexibility of bottromycin D may be responsible for its lower activity.
No further antibacterial studies of synthetic or biosynthetic bottromycin derivatives have been reported in the literature as of 2013. The search for efficacious analogs will be enabled by bottromycin’s status as a ribosomal peptide. Analogs may be explored biosynthetically by changing the sequence of the precursor peptide; a change in amino acid sequence will lead directly to a modified bottromycin structure. | 0 | Theoretical and Fundamental Chemistry |
Ram Charan Mehrotra was born in a middle-class family on 16 February 1922 in Kanpur in the Indian state of Uttar Pradesh to Ram Bharose Mehrotra, a small-time cloth merchant and his homemaker wife, Chameli Devi. He lost both his parents before he turned 10 and had to continue his studies depending on merit scholarships and part-time jobs like private tuition. His primary schooling was at Municipal School, Kanpur and later he joined Christ Church School (present-day Christ Church College, Kanpur) from where he passed the intermediate course, standing first in the state. Joining the University of Allahabad in 1939 for his graduate studies, he completed the course on the strength of three scholarships and passed BSc with Mathematics, Physics and Chemistry as optional subjects. He continued at the university for MSc in chemistry which he passed with first rank in 1943. During this period, he was also involved in student politics in connection with the Quit India Movement of 1942 and had to stay away from studies for four months.
Before starting his formal academic career by joining Allahabad University in 1944 as a member of faculty of inorganic chemistry, Mehrotra worked at Vigyan Kala Bhawan, Daurala, a local learning centre involved in teaching science to prospective young entrepreneurs, for ten months during 1943–44 and was also associated with Vigyan Pragati, a science magazine published by National Institute of Science Communication and Information Resources (NISCAIR) of the Council of Scientific and Industrial Research. He served the university till 1954; in between, he had a short stint of two years at Birkbeck College from 1950 to 1952 as a British Council Fellow and part-time faculty, working with Donald Charlton Bradley; he utilised this period to secure a PhD from the University of London in 1952. He returned to India the same year and resumed his service at Allahabad University when he was offered the position of a reader at Lucknow University in 1954. After serving four years there, he moved to Gorakhpur University in 1958 as a professor where, a year later, he was promoted as the dean of the faculty of science. It was during this time, he served as a member of the Review Committee in Chemistry of the University Grants Commission of India under the chairmanship of T. R. Seshadri, where his colleagues included Asima Chatterjee, a noted chemist.
In 1962, on invitation of Mohan Sinha Mehta, the then vice chancellor of the University of Rajasthan, he took up the post of a professor and head of the newly formed chemistry department and served the institution for two decades. In between, he had a five-year stint as the vice chancellor of Delhi University (from 1974 to 1979) and a short assignment as a UGC National Fellow in December 1979 but on completion of those assignments, he returned to Rajasthan University, where he stayed till 1982; on his move from the university, he was made an emeritus professor. That year, he became associated with the activities of the University Grants Commission, first as the chairman of the Commission on Revision of Pay Scales to Teachers which submitted its report to UGC in 1986. Simultaneously, when the National Commission on Teachers was constituted by the Government of India in 1983 under the chairmanship of D. P. Chattopadhyaya, he was appointed as a member of the Research Advisory Committee. After his assignment with the committee, he took up the chair of the Book Writing Project of the National Council of Educational Research and Training (NCERT) and in 1991, he was appointed as the vice chancellor of the University of Allahabad, a position he held in 1993.
Mehrotra was married to Suman, a Hindi scholar, whom he married in 1944 around the same time when he joined Allahabad University. The couple had two daughters, Rashmi and Shalini and one son, Piyush Mehrotra, in between. He died on 11 July 2004, reportedly due to chronic obstructive pulmonary disease, at the age of 82. | 0 | Theoretical and Fundamental Chemistry |
The acidity of boric acid solutions is greatly increased in the presence of cis-vicinal diols (organic compounds containing similarly oriented hydroxyl groups in adjacent carbon atoms, ) such as glycerol and mannitol.
The tetrahydroxyborate anion formed in the dissolution spontaneously reacts with these diols to form relatively stable anion esters containing one or two five-member rings. For example, the reaction with mannitol , whose two middle hydroxyls are in cis orientation, can be written as
Giving the overall reaction
The stability of these mannitoborate ester anions shifts the equilibrium of the right and thus increases the acidity of the solution by 5 orders of magnitude compared to that of pure boric oxide, lowering the pK from 9 to below 4 for sufficient concentration of mannitol. The resulting solution has been called mannitoboric acid.
The addition of mannitol to an initially neutral solution containing boric acid or simple borates lowers its pH enough for it to be titrated by a strong base as NaOH, including with an automated a potentiometric titrator. This property is used in analytical chemistry to determine the borate content of aqueous solutions, for example to monitor the depletion of boric acid by neutrons in the water of the primary circuit of light-water reactor when the compound is added as a neutron poison during refueling operations. | 0 | Theoretical and Fundamental Chemistry |
A powerful demonstration of stacking is found in the buckycatcher. This molecular tweezer is based on two concave buckybowls with a perfect fit for one convex fullerene molecule. Complexation takes place simply by evaporating a toluene solution containing both compounds. In solution an association constant of 8600 M is measured based on changes in NMR chemical shifts.
Pi stacking is prevalent in protein crystal structures, and also contributes to the interactions between small molecules and proteins. As a result, pi–pi and cation–pi interactions are important factors in rational drug design. One example is the FDA-approved acetylcholinesterase (AChE) inhibitor tacrine which is used in the treatment of Alzheimer's disease. Tacrine is proposed to have a pi stacking interaction with the indolic ring of Trp84, and this interaction has been exploited in the rational design of novel AChE inhibitors. | 0 | Theoretical and Fundamental Chemistry |
The electronic transitions of the water molecule lie in the vacuum ultraviolet region. For water vapor the bands have been assigned as follows.
*65 nm band — many different electronic transitions, photoionization, photodissociation
*discrete features between 115 and 180 nm
**set of narrow bands between 115 and 125 nm (n) → many different Rydberg states and 3a (n) → 3sa Rydberg state
**128 nm band (n) → 3sa Rydberg state and 1b (n) → 3sa Rydberg state
**166.5 nm band (n) → 4a (σ*-like orbital)
:At least some of these transitions result in photodissociation of water into H+OH. Among them the best known is that at 166.5 nm. | 0 | Theoretical and Fundamental Chemistry |
Except for fluorine that can only form unstable polyfluorides at low temperature, all other stable halogens (Cl, Br, I) can form several isopolyhalogen anions that are stable at room temperature, of which the most prominent example being triiodide. In all these anions, the halogen atoms of the same element bond to each other. | 0 | Theoretical and Fundamental Chemistry |
Bioceramics properties of being anticorrosive, biocompatible, and aesthetic make them quite suitable for medical usage. Zirconia ceramic has bioinertness and noncytotoxicity. Carbon is another alternative with similar mechanical properties to bone, and it also features blood compatibility, no tissue reaction, and non-toxicity to cells. Bioinert ceramics do not exhibit bonding with the bone, known as osseointegration. However, bioactivity of bioinert ceramics can be achieved by forming composites with bioactive ceramics. Bioactive ceramics, including bioglasses must be non-toxic, and form a bond with bone. In bone repair applications, i.e. scaffolds for bone regeneration, the solubility of bioceramics is an important parameter, and the slow dissolution rate of most bioceramics relative to bone growth rates remains a challenge in their remedial usage. Unsurprisingly, much focus is placed on improving dissolution characteristics of bioceramics while maintaining or improving their mechanical properties. Glass ceramics elicit osteoinductive properties, with higher dissolution rates relative to crystalline materials, while crystalline calcium phosphate ceramics also exhibit non-toxicity to tissues and bioresorption. The ceramic particulate reinforcement has led to the choice of more materials for implant applications that include ceramic/ceramic, ceramic/polymer, and ceramic/metal composites. Among these composites ceramic/polymer composites have been found to release toxic elements into the surrounding tissues. Metals face corrosion related problems, and ceramic coatings on metallic implants degrade over time during lengthy applications. Ceramic/ceramic composites enjoy superiority due to similarity to bone minerals, exhibiting biocompatibility and a readiness to be shaped. The biological activity of bioceramics has to be considered under various in vitro and in vivo' studies. Performance needs must be considered in accordance with the particular site of implantation. | 0 | Theoretical and Fundamental Chemistry |
Source:
PICS is a powerful analysis tool that resolves correlations on the nanometer length and millisecond timescale. Adapted from methods of spatio-temporal image correlation spectroscopy, it exploits the high positional accuracy of single-particle tracking. While conventional tracking methods break down if multiple particle trajectories intersect, this method works in principle for arbitrarily large molecule densities and dynamical parameters (e.g. diffusion coefficients, velocities) as long as individual molecules can be identified. It is computationally cheap and robust and allows one to identify and quantify motions (e.g. diffusion, active transport, confined diffusion) within an ensemble of particles, without any a priori knowledge about the dynamics.
A particle image cross-correlation spectroscopy (PICCS) extension is available for biological processes that involve multiple interaction partners, as can observed by two-color microscopy. | 0 | Theoretical and Fundamental Chemistry |
Compositional names impart little structural information and are recommended for use when structural information is not available or does not need to be conveyed.
Stoichiometric names are the simplest and reflect either the empirical formula or the molecular formula. The ordering of the elements follows the formal electronegativity list for binary compounds and electronegativity list to group the elements into two classes which are then alphabetically sequenced. The proportions are specified by di-, tri-, etc. (See IUPAC numerical multiplier.) Where there are known to be complex cations or anions these are named in their own right and then these names used as part of the compound name. | 0 | Theoretical and Fundamental Chemistry |
Electron-positron pairs will form in the high charge field via the Schwinger mechanism when the electric charge of udQM is larger than 163, at which the baryon number is 609. The smallest stable udQM against neutron emission would be at baryon number 39. | 0 | Theoretical and Fundamental Chemistry |
Davy was born in Penzance, Cornwall, in the Kingdom of Great Britain on 17 December 1778, the eldest of the five children of Robert Davy, a woodcarver, and his wife Grace Millett. According to his brother and fellow chemist John Davy, their hometown was characterised by "an almost unbounded credulity respecting the supernatural and monstrous ... Amongst the middle and higher classes, there was little taste for literature, and still less for science ... Hunting, shooting, wrestling, cockfighting, generally ending in drunkenness, were what they most delighted in." | 1 | Applied and Interdisciplinary Chemistry |
The National Acid Precipitation Assessment Program (NAPAP) was a cooperative federal program that was first authorized in 1981 in order to coordinate acid rain research and report those findings to the U.S. Congress. The research, monitoring, and assessment efforts of NAPAP, and other groups in the 1980s, culminated in Title IV of the 1990 Clean Air Act Amendments (CAAA), also known as the Acid Deposition Control Program. Title IX of the CAAA reauthorized NAPAP to conduct acid rain research and monitoring, and to periodically assess the costs, benefits, and effectiveness of Title IV. The NAPAP member agencies were the U.S. Environmental Protection Agency, the U.S. Department of Energy, the U.S. Department of Agriculture, the U.S. Department of Interior, the National Aeronautics and Space Administration, and the National Oceanic and Atmospheric Administration.
The NAPAP published a total of four reports: 1991 (multiple volumes), 1998, 2005, and 2011. The Program was able to describe and document strong reductions in sulfur dioxide and nitrogen oxide emissions, as well as the resulting atmospheric deposition from 1980 to 2010 as various elements of the CAAA were implemented. The NAPAP officially ended with publication of the last report in 2011. To reflect the federal NAPAP role in the NADP, the network name was changed to NADP National Trends Network (NTN) | 1 | Applied and Interdisciplinary Chemistry |
According to the National Geographic, the Chesapeake Bay was one of the first hypoxic zones to be identified in the 1970s. The Chesapeake Bay experiences seasonal hypoxia due to high nitrogen levels. These nitrogen levels are caused by urbanization, there are multiple factories that pollute the atmosphere with nitrogen, and agriculture, the opposite side of the bay is used for poultry farming, which produces a lot of manure that ends up running off into the Chesapeake Bay.
From 1985 - 2019, there were efforts from the caretakers of Chesapeake Bay to reduce the annual hypoxic volumes. There was significant improvement in 2016-2017 that gave assurance to the caretakers that the efforts were successful, however recent data has shown that further efforts are needed to continuously curb the effects of global warming. | 0 | Theoretical and Fundamental Chemistry |
The phenomenon was discovered in 1832 by Friedrich Wöhler and Justus von Liebig. They observed that the silky needles of freshly crystallized benzamide slowly converted to rhombic crystals. Present-day analysis identifies three polymorphs for benzamide: the least stable one, formed by flash cooling is the orthorhombic form II. This type is followed by the monoclinic form III (observed by Wöhler/Liebig). The most stable form is monoclinic form I. The hydrogen bonding mechanisms are the same for all three phases; however, they differ strongly in their pi-pi interactions. | 0 | Theoretical and Fundamental Chemistry |
The multiple hearth furnaces consist of several circular hearths or kilns superimposed on each other. Material is fed from the top and is moved by the action of rotating "rabble arms", and the revolving mechanical rabbles attached to the arms move over the surface of each hearth to continuously shift the ore. The arms are attached to a rotating central shaft that passes through the center of the roaster. As the material is moved, the ore that is charged at the top hearth gradually moves downward as it passes through windows in the floor of each hearth or through alternate passages around the shaft and the periphery until it finally emerges at the bottom. | 1 | Applied and Interdisciplinary Chemistry |
Eukaryotic cells are composed of the following organelles:
* Nucleus: The nucleus of the cell functions as the genome and genetic information storage for the cell, containing all the DNA organized in the form of chromosomes. It is surrounded by a nuclear envelope, which includes nuclear pores allowing for the transportation of proteins between the inside and outside of the nucleus. This is also the site for replication of DNA as well as transcription of DNA to RNA. Afterwards, the RNA is modified and transported out to the cytosol to be translated to protein.
* Nucleolus: This structure is within the nucleus, usually dense and spherical. It is the site of ribosomal RNA (rRNA) synthesis, which is needed for ribosomal assembly.
* Endoplasmic reticulum (ER): This functions to synthesize, store, and secrete proteins to the Golgi apparatus. Structurally, the endoplasmic reticulum is a network of membranes found throughout the cell and connected to the nucleus. The membranes are slightly different from cell to cell and a cell's function determines the size and structure of the ER.
* Mitochondria: Commonly known as the powerhouse of the cell is a double membrane bound cell organelle. This functions for the production of energy or ATP within the cell. Specifically, this is the place where the Krebs cycle or TCA cycle for the production of NADH and FADH occurs. Afterwards, these products are used within the electron transport chain (ETC) and oxidative phosphorylation for the final production of ATP.
* Golgi apparatus: This functions to further process, package, and secrete the proteins to their destination. The proteins contain a signal sequence that allows the Golgi apparatus to recognize and direct it to the correct place. Golgi apparatus also produce glycoproteins and glycolipids.
* Lysosome: The lysosome functions to degrade material brought in from the outside of the cell or old organelles. This contains many acid hydrolases, proteases, nucleases, and lipases, which break down the various molecules. Autophagy is the process of degradation through lysosomes which occurs when a vesicle buds off from the ER and engulfs the material, then, attaches and fuses with the lysosome to allow the material to be degraded.
* Ribosomes: Functions to translate RNA to protein. it serves as a site of protein synthesis.
* Cytoskeleton: Cytoskeleton is a structure that helps to maintain the shape and general organization of the cytoplasm. It anchors organelles within the cells and makes up the structure and stability of the cell. The cytoskeleton is composed of three principal types of protein filaments: actin filaments, intermediate filaments, and microtubules, which are held together and linked to subcellular organelles and the plasma membrane by a variety of accessory proteins.
* Cell membrane: The cell membrane can be described as a phospholipid bilayer and is also consisted of lipids and proteins. Because the inside of the bilayer is hydrophobic and in order for molecules to participate in reactions within the cell, they need to be able to cross this membrane layer to get into the cell via osmotic pressure, diffusion, concentration gradients, and membrane channels.
* Centrioles: Function to produce spindle fibers which are used to separate chromosomes during cell division.
Eukaryotic cells may also be composed of the following molecular components:
* Chromatin: This makes up chromosomes and is a mixture of DNA with various proteins.
* Cilia: They help to propel substances and can also be used for sensory purposes. | 1 | Applied and Interdisciplinary Chemistry |
The regioselectivity of water elimination is highly influenced by ring size. When water is eliminated from cyclic tertiary alcohols by an E1 route, three major products are formed. The semicyclic isomer (so-called because the double bond is shared by a ring atom and an exocyclic atom) and the (E) endocyclic isomer are expected to predominate; the (Z) endocyclic isomer is not expected to be formed until the ring size is large enough to accommodate the awkward angles of the trans configuration. The exact population of each product relative to the others differs considerably depending upon the size of the ring involved. As the ring size increases, the semicyclic isomer decreases rapidly and the (E) endocyclic isomer increases, but after a certain point, the semicyclic isomer begins to increase again. This can be attributed to transannular strain; this strain is significantly reduced in the (E) endocyclic isomer because it has one less substituent in the ring than the semicyclic isomer. | 0 | Theoretical and Fundamental Chemistry |
The MLN can provide an important component of mercury dry deposition to a forested landscape. The importance of litterfall mercury data for quantifying atmospheric mercury deposition to forests was demonstrated with studies at NADP sites in the eastern USA from 2007-2009 and 2007 to 2014. | 1 | Applied and Interdisciplinary Chemistry |
Many terms are used to denote constructed wetlands, such as reed beds, soil infiltration beds, treatment wetlands, engineered wetlands, man-made or artificial wetlands. A biofilter has some similarities with a constructed wetland, but is usually without plants.
The term of constructed wetlands can also be used to describe restored and recultivated land that was destroyed in the past through draining and converting into farmland, or mining. | 1 | Applied and Interdisciplinary Chemistry |
A mixture of bromo acetal 1 (549 mg, 1.78 mmol), AIBN (30.3 mg, 0.185 mmol), and BuSnH (0.65 mL, 2.42 mmol) in dry benzene (12 mL) was heated under reflux for 1 hour and then evaporated under reduced pressure. Silicagel column chromatography of the crude product with hexane–EtOAc (92:8) as eluant gave tetrahydropyran 2 (395 mg, 97%) as an oily mixture of two diastereomers. (c 0.43, CHCl); IR (CHCl):1732 cm–1;1H NMR (CDCl)δ 4.77–4.89 (m, 0.6H), 4.66–4.69 (m, 0.4H), 3.40–4.44 (m, 4H), 3.68 (s, 3H), 2.61 (dd, J = 15.2, 4.2 Hz, 1H), 2.51 (dd, J = 15.2, 3.8 Hz, 1H), 0.73–1.06 (m, 3H); mass spectrum: m/z 215 (M+–Me); Anal. Calcd for CHO: C, 62.6; H, 9.65. Found: C, 62.6; H, 9.7. | 0 | Theoretical and Fundamental Chemistry |
Compounds with double bonds between carbon and sulfur are relatively uncommon, but include the important compounds carbon disulfide, carbonyl sulfide, and thiophosgene. Thioketones (RC(=S)R′) are uncommon with alkyl substituents, but one example is thiobenzophenone. Thioaldehydes are rarer still, reflecting their lack of steric protection ("thioformaldehyde" exists as a cyclic trimer). Thioamides, with the formula RC(=S)N(R)R are more common. They are typically prepared by the reaction of amides with Lawesson's reagent. Isothiocyanates, with formula R−N=C=S, are found naturally. Vegetable foods with characteristic flavors due to isothiocyanates include wasabi, horseradish, mustard, radish, Brussels sprouts, watercress, nasturtiums, and capers. | 0 | Theoretical and Fundamental Chemistry |
The injector consists of a body filled with a secondary fluid, into which a motive fluid is injected. The motive fluid induces the secondary fluid to move. Injectors exist in many variations, and can have several stages, each repeating the same basic operating principle, to increase their overall effect.
It uses the Venturi effect of a converging-diverging nozzle on a steam jet to convert the pressure energy of the steam to velocity energy, reducing its pressure to below that of the atmosphere, which enables it to entrain a fluid (e.g., water). After passing through the convergent "combining cone", the mixed fluid is fully condensed, releasing the latent heat of evaporation of the steam which imparts extra velocity to the water. The condensate mixture then enters a divergent "delivery cone" which slows the jet, converting kinetic energy back into static pressure energy above the pressure of the boiler enabling its feed through a non-return valve.
Most of the heat energy in the condensed steam is returned to the boiler, increasing the thermal efficiency of the process. Injectors are therefore typically over 98% energy-efficient overall; they are also simple compared to the many moving parts in a feed pump. | 1 | Applied and Interdisciplinary Chemistry |
The European Association of Geochemistry publishes, co-publishes, or sponsors the following:
* [http://www.geochemicalperspectives.org/ Geochemical Perspectives] – 4 issues a year
* Geochemical Perspectives Letters – an open access journal
* Elements: An International Magazine of Mineralogy, Geochemistry, and Petrology – 6 issues a year
* Chemical Geology – 24 issues a year | 0 | Theoretical and Fundamental Chemistry |
The first step in the NADP-ME type pathway is the conversion of pyruvate (Pyr) to phosphoenolpyruvate (PEP), by the enzyme Pyruvate phosphate dikinase (PPDK). This reaction requires inorganic phosphate and ATP plus pyruvate, producing PEP, AMP, and inorganic pyrophosphate (PP). The next step is the carboxylation of PEP by the PEP carboxylase enzyme (PEPC) producing oxaloacetate. Both of these steps occur in the mesophyll cells:
:pyruvate + P + ATP → PEP + AMP + PP
:PEP + → oxaloacetate
PEPC has a low K for — and, hence, high affinity, and is not confounded by O thus it will work even at low concentrations of .
The product is usually converted to malate (M), which diffuses to the bundle-sheath cells surrounding a nearby vein. Here, it is decarboxylated by the NADP-malic enzyme (NADP-ME) to produce and pyruvate. The is fixed by RuBisCo to produce phosphoglycerate (PGA) while the pyruvate is transported back to the mesophyll cell, together with about half of the phosphoglycerate (PGA). This PGA is chemically reduced in the mesophyll and diffuses back to the bundle sheath where it enters the conversion phase of the Calvin cycle. For each molecule exported to the bundle sheath the malate shuttle transfers two electrons, and therefore reduces the demand of reducing power in the bundle sheath. | 0 | Theoretical and Fundamental Chemistry |
Zinc serves a purely structural role in zinc fingers, twists and clusters. Zinc fingers form parts of some transcription factors, which are proteins that recognize DNA base sequences during the replication and transcription of DNA. Each of the nine or ten ions in a zinc finger helps maintain the finger's structure by coordinately binding to four amino acids in the transcription factor.
In blood plasma, zinc is bound to and transported by albumin (60%, low-affinity) and transferrin (10%). Because transferrin also transports iron, excessive iron reduces zinc absorption, and vice versa. A similar antagonism exists with copper. The concentration of zinc in blood plasma stays relatively constant regardless of zinc intake. Cells in the salivary gland, prostate, immune system, and intestine use zinc signaling to communicate with other cells.
Zinc may be held in metallothionein reserves within microorganisms or in the intestines or liver of animals. Metallothionein in intestinal cells is capable of adjusting absorption of zinc by 15–40%. However, inadequate or excessive zinc intake can be harmful; excess zinc particularly impairs copper absorption because metallothionein absorbs both metals.
The human dopamine transporter contains a high affinity extracellular zinc binding site which, upon zinc binding, inhibits dopamine reuptake and amplifies amphetamine-induced dopamine efflux in vitro. The human serotonin transporter and norepinephrine transporter do not contain zinc binding sites. Some EF-hand calcium binding proteins such as S100 or NCS-1 are also able to bind zinc ions. | 1 | Applied and Interdisciplinary Chemistry |
Nanofuidic triode is a three-terminal double junction nanofluidic device composed of positive-charged alumina and negative-charged silica nanochannels. The device is essentially a three-terminal bipolar junction transistor. By controlling the voltage across emitter and collector terminals, one can regulate the ion current from base terminal to one of the other two terminals, functioning as an ionic single-pole, double-throw switch. | 0 | Theoretical and Fundamental Chemistry |
Hematological abnormalities often associate with chronic liver diseases. Both iron overload and iron deficient anemia have been reported in patients with liver cirrhosis. The former is mainly due to reduced hepcidin level caused by the decreased synthetic capacity of the liver, while the latter is due to acute and chronic bleeding caused by portal hypertension. Inflammation is also present in patients with advanced chronic liver disease. As a consequence, elevated hepatic and serum ferritin levels are consistently reported in chronic liver diseases.
Studies showed association between high serum ferritin levels and increased risk of short-term mortality in cirrhotic patients with acute decompensation and acute-on-chronic liver failure. An other study found association between high serum ferritin levels and increased risk of long-term mortality in compensated and stable decompensated cirrhotic patients. The same study demonstrated that increased serum ferritin levels could predict the development of bacterial infection in stable decompensated cirrhotic patients, while in compensated cirrhotic patients the appearance of the very first acute decompensation episode showed higher incidence in patients with low serum ferritin levels. This latter finding was explaind by the association between chronic bleeding and increased portal pressure. | 1 | Applied and Interdisciplinary Chemistry |
The gal operon is a prokaryotic operon, which encodes enzymes necessary for galactose metabolism. Repression of gene expression for this operon works via binding of repressor molecules to two operators. These repressors dimerize, creating a loop in the DNA. The loop as well as hindrance from the external operator prevent RNA polymerase from binding to the promoter, and thus prevent transcription. Additionally, since the metabolism of galactose in the cell is involved in both anabolic and catabolic pathways, a novel regulatory system using two promoters for differential repression has been identified and characterized within the context of the gal operon. | 1 | Applied and Interdisciplinary Chemistry |
One of the classic structures of resorcinarenes and pyrogallolarenes is shown below. Because of the phenol group, some hydrogen bonds are foromed among the molecules. Sometimes, the binding ratio of the host and guest could reach 2 : 1. | 0 | Theoretical and Fundamental Chemistry |
Rotation around the C-5/C-6 bond is described by the angle ω. Three possible staggered conformations are possible:: gauche–trans (gt), gauche–gauche (gg), and trans–gauche (tg). The name indicates the interaction between O-5 and OH-6 first followed by the interaction between OH-6 and C-4. | 0 | Theoretical and Fundamental Chemistry |
The measurement time required for a single impedance measurement point strongly depends on the frequency of interest. While frequencies above about 1 Hz can be measured within seconds, the measurement time increases significantly in the lower frequency range.
Although the exact duration for measuring a complete impedance spectrum depends on the measauring device as well as on internal settings, the following measurement times can be considered as rules of thumb when measuring the frequency measurement points sequentially, with the upper frequency assumed as 100 kHz or 1 MHz:
* Down to approx. 1 Hz, the measuring time is approx. 1 minute
* Down to 0.1 Hz approx. 5 minutes
* Down to 0.05 Hz approx. 10 minutes
* Down to 0.02 Hz approx. 15 minutes
* Down to 0.01 Hz approx. 30 minutes
Measurements down to or below 0.01 Hz are typically associated with measurement times in the range of several hours. Therefore, a spectrum can be roughly divided into three sub-ranges with regard to the occurrence of artifacts: in the high-frequency domain (approx. > 100 to 1000 Hz), induction or mutual induction can dominate. In the low frequency region (< 1 Hz), drift can occur due to noticeable change in the system. The range between about 1 Hz and 1000 Hz is usually not affected by high- or low-frequency artifacts. However, the mains frequency (50/60 Hz) may come into play as distorting artifact in this region. | 0 | Theoretical and Fundamental Chemistry |
The law can be written as:
or
where
*V is the volume of the gas;
*n is the amount of substance of the gas (measured in moles);
*k is a constant for a given temperature and pressure.
This law describes how, under the same condition of temperature and pressure, equal volumes of all gases contain the same number of molecules. For comparing the same substance under two different sets of conditions, the law can be usefully expressed as follows:
The equation shows that, as the number of moles of gas increases, the volume of the gas also increases in proportion. Similarly, if the number of moles of gas is decreased, then the volume also decreases. Thus, the number of molecules or atoms in a specific volume of ideal gas is independent of their size or the molar mass of the gas. | 0 | Theoretical and Fundamental Chemistry |
In general, vitamin D is found in animal source foods, particularly fish, meat, offal, egg and dairy.
Vitamin D is found in fungi and is produced by ultraviolet irradiation of ergosterol. The vitamin D content in mushrooms and Cladina arbuscula, a lichen, increases with exposure to ultraviolet light, and is stimulated by industrial ultraviolet lamps for fortification. The United States Department of Agriculture reports D and D content combined in one value. | 1 | Applied and Interdisciplinary Chemistry |
Phred is often used together with another software program called Phrap, which is a program for DNA sequence assembly. Phrap was routinely used in some of the largest sequencing projects in the Human Genome Sequencing Project and is currently one of the most widely used DNA sequence assembly programs in the biotech industry. Phrap uses Phred quality scores to determine highly accurate consensus sequences and to estimate the quality of the consensus sequences. Phrap also uses Phred quality scores to estimate whether discrepancies between two overlapping sequences are more likely to arise from random errors, or from different copies of a repeated sequence. | 1 | Applied and Interdisciplinary Chemistry |
Dissimilatory metal reducers are a diverse group of microorganisms, which is reflected in the factors that affect the different forms of metal reduction. The process of dissimilatory metal reduction occurs in the absence of oxygen (O), but dissimilatory metal reducers include both obligate (strict) anaerobes, such as the family Geobacteraceae, and facultative anaerobes, such as Shewanella spp. As well, across the dissimilatory metal reducers species, various electron donors are used in the oxidative reaction that is coupled to metal reduction. For instance, some species are limited to small organic acids and hydrogen (H), whereas others may oxidize aromatic compounds. In certain instances, such as Cr(VI) reduction, the use of small organic compounds can optimize the rate of metal reduction. Another factor that influences metal respiration is environmental acidity. Although acidophilic and alkaliphilic dissimilatory metal reducers exist, the neutrophilic metal reducers group contains the most well-characterized genera. In soil and sediment environments, where the pH is often neutral, metals like iron are found in their solid oxidized forms, and exhibit variable reduction potential, which can affect their use by microorganisms.
Due to the impermeability of the cell wall to minerals and the insolubility of metal oxides, dissimilatory metal reducers have developed ways to reduce metals extracellularly via electron transfer. Cytochromes c, which are transmembrane proteins, play an important role in transporting electrons from the cytosol to enzymes attached to the outside of the cell. The electrons are then further transported to the terminal electron acceptor via direct interaction between the enzymes and the metal oxide. In addition to establishing direct contact, dissimilatory metal reducers also display the ability to perform ranged metal reduction. For instance, some species of dissimilatory metal reducers produce compounds that can dissolve insoluble minerals or act as electron shuttles, enabling them to perform metal reduction from a distance. Other organic compounds frequently found in soils and sediments, such as humic acids, may also act as electron shuttles. In biofilms, nanowires and multistep electron hopping (in which electrons jump from cell to cell towards the mineral) have also been suggested as methods for reducing metals without requiring direct cell contact. It has been proposed that cytochromes c are involved in both of these mechanisms. In nanowires, for instance, cytochromes c function as the final component that transfers electrons to the metal oxide. | 1 | Applied and Interdisciplinary Chemistry |
One can show that a given vector field can be decomposed as
Different than the usual Helmholtz decomposition, the
Helmholtz–Leray decomposition of is unique (up to an
additive constant for ). Then we can define as
The Leray projector is defined similarly on function spaces other than the Schwartz space, and on different domains with different boundary conditions. The four properties listed below will continue to hold in those cases. | 1 | Applied and Interdisciplinary Chemistry |
When surfactants are present above the critical micelle concentration (CMC), they can act as emulsifiers that will allow a compound that is normally insoluble (in the solvent being used) to dissolve. This occurs because the insoluble species can be incorporated into the micelle core, which is itself solubilized in the bulk solvent by virtue of the head groups' favorable interactions with solvent species. The most common example of this phenomenon is detergents, which clean poorly soluble lipophilic material (such as oils and waxes) that cannot be removed by water alone. Detergents clean also by lowering the surface tension of water, making it easier to remove material from a surface. The emulsifying property of surfactants is also the basis for emulsion polymerization.
Micelles may also have important roles in chemical reactions. Micellar chemistry uses the interior of micelles to harbor chemical reactions, which in some cases can make multi-step chemical synthesis more feasible. Doing so can increase reaction yield, create conditions more favorable to specific reaction products (e.g. hydrophobic molecules), and reduce required solvents, side products, and required conditions (e.g. extreme pH). Because of these benefits, Micellular chemistry is thus considered a form of green chemistry. However, micelle formation may also inhibit chemical reactions, such as when reacting molecules form micelles that shield a molecular component vulnerable to oxidation.
The use of cationic micelles of cetrimonium chloride, benzethonium chloride, and cetylpyridinium chloride can accelerate chemical reactions between negatively charged compounds (such as DNA or Coenzyme A) in an aqueous environment up to 5 million times. Unlike conventional micellar catalysis, the reactions occur solely on the charged micelles' surface.
Micelle formation is essential for the absorption of fat-soluble vitamins and complicated lipids within the human body. Bile salts formed in the liver and secreted by the gall bladder allow micelles of fatty acids to form. This allows the absorption of complicated lipids (e.g., lecithin) and lipid-soluble vitamins (A, D, E, and K) within the micelle by the small intestine.
During the process of milk-clotting, proteases act on the soluble portion of caseins, κ-casein, thus originating an unstable micellar state that results in clot formation.
Micelles can also be used for targeted drug delivery as gold nanoparticles. | 0 | Theoretical and Fundamental Chemistry |
In 1874, Cleve married Carolina Alma "Caralma" Öhbom (known as Alma Cleve), a teacher and author; the couple had three daughters. The first daughter, Astrid Maria Cleve (born 22 January 1875), became a botanist. His son-in-law and grandson, Hans von Euler-Chelpin and Ulf von Euler, both won Nobel Prizes. Cleve was friends with Thomas Edward Thorpe. The second daughter, Agnes Cleve-Jonand (born Agnes Elisabet Cleve) (1876-1951), was a visual artist and pioneer of Modernism in Sweden. The third and last daughter, Célie Brunius (born Gerda Cecilia Afrodite Cleve) (1882-1980), was a journalist. His daughter Agnes was married to illustrator, set designer and artist John Jon-And. His daughter Célie was married to writer August Brunius and was the mother of artist Göran Brunius, journalist Clas Brunius and associate professor Teddy Brunius. The television host and politician Lisette Schulman was his great-granddaughter.
Per Teodore Cleve was a supporter of women's equality and Ellen Fries, the first Swedish woman to receive a PhD, was one of his students.
Cleve began experiencing pleurisy in December 1904 and it affected his heart. He thought that he had recovered by the spring of 1905, and he returned home to Uppsala, Sweden,. but he died there on 18 June 1905. | 1 | Applied and Interdisciplinary Chemistry |
Tumor development is a complex process that requires cell division, growth, and survival. One approach used by tumors to upregulate growth and survival is through autocrine production of growth and survival factors. Autocrine signaling plays critical roles in cancer activation and also in providing self-sustaining growth signals to tumors. | 1 | Applied and Interdisciplinary Chemistry |
Newer developments of estimation methods have shown that the quality of the Joback method is limited. The original authors already stated themselves in the original article abstract: "High accuracy is not claimed, but the proposed methods are often as or more accurate than techniques in common use today."
The list of groups does not cover many common molecules sufficiently. Especially aromatic compounds are not differentiated from normal ring-containing components. This is a severe problem because aromatic and aliphatic components differ strongly.
The data base Joback and Reid used for obtaining the group parameters was rather small and covered only a limited number of different molecules. The best coverage has been achieved for normal boiling points (438 components), and the worst for heats of fusion (155 components). Current developments that can use data banks, like the Dortmund Data Bank or the DIPPR data base, have a much broader coverage.
The formula used for the prediction of the normal boiling point shows another problem. Joback assumed a constant contribution of added groups in homologous series like the alkanes. This doesn't describe the real behavior of the normal boiling points correctly. Instead of the constant contribution, a decrease of the contribution with increasing number of groups must be applied. The chosen formula of the Joback method leads to high deviations for large and small molecules and an acceptable good estimation only for mid-sized components. | 0 | Theoretical and Fundamental Chemistry |
Remote surface-enhanced Raman spectroscopy (SERS) consists of using metallic nanowaveguides supporting propagating surface plasmon polaritons (SPPs) to perform SERS at a distant location different to the one of the incident laser.
Propagating SPPs supported by nanowires has been used to show the remote excitation., as well as the remote detection of SERS. A silver nanowire was also used to show remote excitation and detection using graphene as Raman scatterer
Applications
Different plasmonic systems have already been used to show Raman detection of biomolecules in vivo in cells and remote excitation of surface catalytic reactions. | 0 | Theoretical and Fundamental Chemistry |
Given a thermodynamic system at an absolute temperature , the average thermal energy carried by each microscopic degree of freedom in the system is (i.e., about , or , at room temperature). This is generally true only for classical systems with a large number of particles, and in which quantum effects are negligible.
In classical statistical mechanics, this average is predicted to hold exactly for homogeneous ideal gases. Monatomic ideal gases (the six noble gases) possess three degrees of freedom per atom, corresponding to the three spatial directions. According to the equipartition of energy this means that there is a thermal energy of per atom. This corresponds very well with experimental data. The thermal energy can be used to calculate the root-mean-square speed of the atoms, which turns out to be inversely proportional to the square root of the atomic mass. The root mean square speeds found at room temperature accurately reflect this, ranging from for helium, down to for xenon.
Kinetic theory gives the average pressure for an ideal gas as
Combination with the ideal gas law
shows that the average translational kinetic energy is
Considering that the translational motion velocity vector has three degrees of freedom (one for each dimension) gives the average energy per degree of freedom equal to one third of that, i.e. .
The ideal gas equation is also obeyed closely by molecular gases; but the form for the heat capacity is more complicated, because the molecules possess additional internal degrees of freedom, as well as the three degrees of freedom for movement of the molecule as a whole. Diatomic gases, for example, possess a total of six degrees of simple freedom per molecule that are related to atomic motion (three translational, two rotational, and one vibrational). At lower temperatures, not all these degrees of freedom may fully participate in the gas heat capacity, due to quantum mechanical limits on the availability of excited states at the relevant thermal energy per molecule. | 0 | Theoretical and Fundamental Chemistry |
Sheldon Cooper, a fictional physicist from the television series The Big Bang Theory, appeared on the cover of a fictional issue of the journal. | 0 | Theoretical and Fundamental Chemistry |
Non ideal compressible fluid dynamics (NICFD), or non ideal gas dynamics, is a branch of fluid mechanics studying the dynamic behavior of fluids not obeying ideal-gas thermodynamics. It is for example the case of dense vapors, supercritical flows and compressible two-phase flows. With the term dense vapors, we indicate all fluids in the gaseous state characterized by thermodynamic conditions close to saturation and the critical point. Supercritical fluids feature instead values of pressure and temperature larger than their critical values, whereas two-phase flows are characterized by the simultaneous presence of both liquid and gas phases.
In all these cases, the fluid requires to be modelled as a real gas, since its thermodynamic behavior considerably differs from that of an ideal gas, which by contrast appears for dilute thermodynamic conditions. The ideal-gas law can be employed in general as a reasonable approximation of the fluid thermodynamics for low pressures and high temperatures. Otherwise, intermolecular forces and dimension of fluid particles, which are neglected in the ideal-gas approximation, become relevant and can significantly affect the fluid behavior. This is extremely valid for gases made of complex and heavy molecules, which tend to deviate more from the ideal model.
While the fluid dynamics of compressible flows in ideal conditions is well-established and is characterized by several analytical results, when non-ideal thermodynamic conditions are considered, peculiar phenomena possibly occur. This is particularly valid in supersonic conditions, namely for flow velocities larger than the speed of sound in the fluid considered. All typical features of supersonic flows are affected by non-ideal thermodynamics, resulting in both quantitative and qualitative differences with respect to the ideal gas dynamics. | 0 | Theoretical and Fundamental Chemistry |
Fumonisin B2 is a fumonisin mycotoxin produced by the fungi Fusarium verticillioides (formerly Fusarium moniliforme) and Aspergillus niger.
It is a structural analog of fumonisin B3, while it is lacking one hydroxy group compared to fumonisin B1.
Fumonisin B2 is more cytotoxic than fumonisin B1. Fumonisin B2 inhibits sphingosine acyltransferase.
Fumonisin B2 and other fumonisins frequently contaminate maize and other crops, while recently it has been shown using LC–MS/MS that FB2 can contaminate coffee beans as well. | 1 | Applied and Interdisciplinary Chemistry |
A class of tetradentate ligands with the generic name acacen are obtained by the condensation of derivatives of acetylacetone and ethylenediamine. Cobalt complexes [Co(acacen)L], selectively inhibit the activities of histidine-containing proteins through exchange of the axial ligands. These compounds show promise for the inhibition of oncogenesis.
The salan and salalen ligands are similar in structure to salen ligands, but have one or two saturated nitrogen-aryl bonds (amines rather than imines). They tend to be less rigid and more electron rich at the metal center than the corresponding salen complexes. Salans can be synthesized by the alkylation of an appropriate amine with a phenolic alkyl halide. The “half-salen” ligands have only one salicylimine group. They are prepared from a salicylaldehyde and a monoamine.
The name “salen” or “salen-type” may be used for other ligands that have similar environment around the chelating site, namely two acidic hydroxyls and two Schiff base (aryl-imine) groups. These include the ligands abbreviated as salph, from the condensation of 1,2-phenylenediamine and salicylaldehyde, and salqu, from the condensation of salicylaldehyde and 2-quinoxalinol. | 0 | Theoretical and Fundamental Chemistry |
Sand particles range in size (about 0.05–2 mm). Sand is the most coarse of the particle groups. Sand has the largest pores and soil particles of the particle groups. It also drains the most easily. These particles become more involved in chemical reactions when coated with clay. | 0 | Theoretical and Fundamental Chemistry |
Due to the unfavoured bond angles (60°), cyclopropyl groups are highly strained. Two orbital models were proposed to describe the bonding situation. The Coulson-Moffit model uses bent bonds. The C-C bonds are formed by overlap of two sp-hybrid orbitals. To adapt to the small bond angle, there is some rehybridization resulting in sp-hybrids for the ring bonds and sp for the C-H bonds. This model resembles the banana bond model for C=C double bonds (τ bonds).
Alternatively the structure can be explained with the Walsh model. Here the two sp-hybrids forming the ring bond are separated into one sp-hybrid and one pure p-orbital. This corresponds to the π bond description of C=C double bonds.
Cyclopropyl groups are good donors in hyperconjugation resulting in a considerable stabilization of carbocations. In contrast to double bonds, stabilization of radicals is weaker and stabilization of carbanions is negligible. This is explained by the occupation of the π system with two more electrons, making the cyclopropyl methyl cations HOMO isolobal to the allyl anions HOMO. | 0 | Theoretical and Fundamental Chemistry |
Fluorofluids are generally of very low toxicity, so much that they have been evaluated as synthetic blood. | 1 | Applied and Interdisciplinary Chemistry |
It has been observed that the development of hormone resistance in prostate cancer may be due to the upregulation of antiapoptotic genes, one of which is survivin.
Zhang et al. hypothesize that, if survivin is a significant contributor to the development of hormonal therapy resistance in prostate cancer cells, targeting survivin and blocking it would enhance prostate cancer cell susceptibility to anti-androgen therapy. (Anti-androgen therapy uses drugs to eliminate the presence of androgens in the cell and cellular environment, since such androgens are known to enhance tumour immortality in prostate cancer cells.) Zhang et al. first assessed the level of survivin expression of LNCaP (an androgen-dependent prostate cancer cell line that expresses intact androgen receptors) using quantitative Western analysis and found high expression of survivin in these cells. Cells exposed to dihydrotestosterone (DHT) showed increased levels of survivin expression only and not other IAP family members. This result suggests that androgens may upregulate survivin, which contributes to the resistance to apoptosis observed in the tumour cells. Next, with the addition of flutamide (an antiandrogen) to the cells, survivin levels were observed to significantly decrease. The LNCaP cells were transduced separately with the different constructs of the survivin gene (mutant or wild-type) and subjected to flutamide treatment and assessed for the apoptosis level. Flutamide-treated survivin mutant-transduced cells were shown to significantly increase apoptosis by double that of flutamide treatment alone. On the other end, overexpression of the wild-type survivin was found to significantly reduce the apoptosis levels from flutamide treatment compared to flutamide treatment alone. Therefore, these results support the hypothesis that survivin plays a role in the anti-apoptotic nature of the LNCaP cancer cell line and that inhibiting survivin in prostate cancer cells appears to enhance the therapeutic effect of flutamide. | 1 | Applied and Interdisciplinary Chemistry |
The main focus of George's research was centered on the mechanical implications of the thermal and photochemical organic reactions. His studies covered different areas of organometallic chemistry and he worked on electron transfer processes, organic reactions and functional group transformations. Thus he studied the organic reactions and functional group transformations, heterohexa-1, 3, 5-triene systems with regard to its electrocyclic reactions and the synthetic utility and phototransformations of dibenzobarrelenes. He also studied the picosecond laser flash photolysis techniques and the transient intermediates involved in photoreactions. He was noted for the original approach in his studies of hetero-aromatic systems.
George published his research through over 200 articles in peer-reviewed journals and guided a number of doctoral and post-doctoral scholars in their researches. He has contributed chapters to the Handbook of Chemistry and Physics, edited by C. N. R. Rao and his works have been cited by various authors in their publications. He pioneered photochemistry research at the National Institute for Interdisciplinary Science and Technology and established the Photochemistry Research Unit at the institution. He was a collaborator of C. N. R. Rao in popularizing science education at academic levels and is associated, as the executive director, with the Foundation for Capacity Building in Science (FCBS) initiative which promotes science education among Indian students through seminars and workshops. He also served as a member of the council of the Indian National Science Academy from 1989 to 1991. | 0 | Theoretical and Fundamental Chemistry |
Work analysing gravity currents propagating within a single fluid host was broadened to consider intrusions within sharply stratified fluids by Hoyler & Huppert in 1980. Since then there have been further significant analytical and experimental advancements into understanding specifically particle laden intrusions by researchers including Bonnecaze, et al., (1993, 1995, 1996), Rimoldi et al. (1996), and Rooij, et al. (1999). As of 2012 the most recent rigorous analytical analysis, designed to determine the propagation speed of a classically extending intrusion, was performed by Flynn and Linden. Practical experimentation into intrusions has typically employed a lock exchange to study intrusion dynamics. | 1 | Applied and Interdisciplinary Chemistry |
1-(4-Chlorophenyl)silatrane is an extremely toxic organosilicon compound which was developed by M&T Chemicals as a single-dose rodenticide. It was never registered as rodenticide, except for experimental use. 1-(4-Chlorophenyl)silatrane was one of the chemicals studied in the Project Coast. | 1 | Applied and Interdisciplinary Chemistry |
An important characteristic of Mono Lake is that it is a closed lake, meaning it has no outflow. Water can only escape the lake if it evaporates or is lost to groundwater. This may cause closed lakes to become very saline. The reconstruction of historical Mono Lake levels through carbon and oxygen isotopes have also revealed a correlation with well-documented changes in climate.
In the recent past, Earth experienced periods of increased glaciation known as ice ages. This geological period of ice ages is known as the Pleistocene, which lasted until ~11 ka. Lake levels in Mono Lake can reveal how the climate fluctuated. For example, during the cold climate of the Pleistocene the lake level was higher because there was less evaporation and more precipitation. Following the Pleistocene, the lake level was generally lower due to increased evaporation and decreased precipitation associated with a warmer climate.
The lake level has fluctuated during the Holocene, since the end of the ice ages. The Holocene high point is at elevation , reached in approximately 1820 BCE. The low point before modern diversions is at elevation , reached in 143 CE. The lowest modern level due to diversions is at , reached in 1980. | 1 | Applied and Interdisciplinary Chemistry |
Another method to create nanoparticles is to turn a suitable precursor substance, such as a gas (e.g. methane) or aerosol, into solid particles by combustion or pyrolysis. This is a generalization of the burning of hydrocarbons or other organic vapors to generate soot.
Traditional pyrolysis often results in aggregates and agglomerates rather than single primary particles. This inconvenience can be avoided by ultrasonic nozzle spray pyrolysis, in which the precursor liquid is forced through an orifice at high pressure. | 0 | Theoretical and Fundamental Chemistry |
Trichloroacetimidates were first introduced and explored by Schmidt in 1980 and since then have become very popular for glycoside synthesis. The use of trichloroacetimidates provides many advantages including ease of formation, reactivity and stereochemical outcome.
O-Glycosyl trichloroacetimidates are prepared via the addition of trichloroacetonitrile () under basic conditions to a free anomeric hydroxyl group.
Typical activating groups for glycosylation reactions using trichloroacetimidates are or TMSOTf.
Column chromatographic purification of the reaction mixture can sometimes be challenging due to the trichloroacetamide by-product. This can, however, be overcome by washing the organic layer with 1 M NaOH solution in a separatory funnel prior to chromatography. Acetyl protecting groups were found to be stable during this procedure. | 0 | Theoretical and Fundamental Chemistry |
Platinum-195 nuclear magnetic resonance spectroscopy (platinum NMR or Pt NMR) is a spectroscopic technique which is used for the detection and characterisation of platinum compounds. The sensitivity of the technique and therefore its diagnostic utility have increased significantly starting from the 1970s, with Pt NMR nowadays considered the method of choice for structural elucidation of Pt species in solution.
Examples of compounds routinely characterised with the method include platinum clusters and organoplatinum species such as Pt-based antitumour agents. Additional applications of Pt NMR include kinetic and mechanistic studies or investigations on drug binding. | 0 | Theoretical and Fundamental Chemistry |
The evolution of photosynthesis refers to the origin and subsequent evolution of photosynthesis, the process by which light energy is used to assemble sugars from carbon dioxide and a hydrogen and electron source such as water. The process of photosynthesis was discovered by Jan Ingenhousz, a Dutch-born British physician and scientist, first publishing about it in 1779.
The first photosynthetic organisms probably evolved early in the evolutionary history of life and most likely used reducing agents such as hydrogen rather than water. There are three major metabolic pathways by which photosynthesis is carried out: C photosynthesis, C photosynthesis, and CAM photosynthesis. C photosynthesis is the oldest and most common form. A C3 plant uses the Calvin cycle for the initial steps that incorporate into organic material. A C4 plant prefaces the Calvin cycle with reactions that incorporate into four-carbon compounds. A CAM plant uses crassulacean acid metabolism, an adaptation for photosynthesis in arid conditions. C4 and CAM plants have special adaptations that save water. | 0 | Theoretical and Fundamental Chemistry |
A microchannel plate (MCP) is used to detect single particles (electrons, ions and neutrons) and photons (ultraviolet radiation and X-rays). It is closely related to an electron multiplier, as both intensify single particles or photons by the multiplication of electrons via secondary emission. Because a microchannel plate detector has many separate channels, it can provide spatial resolution. | 0 | Theoretical and Fundamental Chemistry |
The applications of DNA walkers include nanomedicine, diagnostic sensing of biological samples, nanorobotics and much more. In late 2015, Yehl et al. improved the DNA walker's function by increasing its velocity, and it has been proposed as the basis for a low-cost, low-tech diagnostics machine capable of detecting single nucleotide mutations and heavy-metal contamination in water. In 2018 Nils Walter and his team designed a DNA walker that is capable of moving at a speed of 300 nanometres per minute. This is an order of magnitude faster than the pace of other types of DNA walker. | 0 | Theoretical and Fundamental Chemistry |
ATP synthase consists of a F and F subunit. The F subunit contains alpha and beta subunits of its own which can assist in the formation of ATP, or hydrolyze it to serve as a proton pump. Though most catalytic actions happen on the beta subunits, the alpha subunits each contain an arginine finger. The role of the arginine finger in ATP synthase is akin to the function of the arginine finger residues of G proteins; to help split ATP. For example, if the arginine of the arginine finger is substituted by lysine, possibly due to a missense mutation, the αR364K mutant results. In the αR364K mutant, the ability of ATP synthase to hydrolyze ATP is decreased around a thousandfold compared to the wild type. | 1 | Applied and Interdisciplinary Chemistry |
Many chemical compounds are aromatic rings with other functional groups attached. Examples include trinitrotoluene (TNT), acetylsalicylic acid (aspirin), paracetamol, and the nucleotides of DNA. | 0 | Theoretical and Fundamental Chemistry |
The Merrill–Crowe Process is a separation technique for removing gold from the solution obtained by the cyanide leaching of gold ores. It is an improvement of the MacArthur-Forrest process, where an additional vacuum is managed to remove air in the solution (invention of Crowe), and zinc dust is used instead of zinc shavings (improvement of Merrill).
The solution is separated from the ore by methods such as filtration (e.g. vertical leaf type clarifier filters) and counter current decantation (CCD). Afterwards a very clear solution is achieved by using pre-coated filters applying diatomaceous earth. Oxygen is then removed by passing the solution through a vacuum de-aeration column. Zinc dust is added to the clarified, de-aerated solution which precipitates the gold; zinc having a higher affinity for the cyanide ion than gold. Other precious metals, silver, and base metals, like copper, will also precipitate, if present.
Automated membrane filtration offers a cost savings alternative to CCD. Both applications are compared in detail by [http://www.tonsperhour.com/wp-content/uploads/Kent-McGrew_CCD-vs-AFP_Final.pdf K. McGrew, 2016.]
The gold precipitate (mixed with zinc dust) is then filtered out of the solution, and the zinc dust and gold are mixed with sulfuric acid to dissolve the zinc. The solution is filtered, and the remaining solids are smelted to a gold dore bar. These bars are sent to a refinery to remove the copper and silver, the specific process used depending upon the impurities in the gold.
The basic process was discovered and patented by Charles Washington Merrill around 1900, and later refined by Thomas Bennett Crowe, working for the Merrill Company. | 1 | Applied and Interdisciplinary Chemistry |
Ceramics are now commonly used in the medical fields as dental and bone implants. Surgical cermets are used regularly. Joint replacements are commonly coated with bioceramic materials to reduce wear and inflammatory response. Other examples of medical uses for bioceramics are in pacemakers, kidney dialysis machines, and respirators. | 0 | Theoretical and Fundamental Chemistry |
Aerobic digestion is typically used in an activated sludge treatment plant. Waste activated sludge and primary sludge are combined, where appropriate, and passed to a thickener where the solids content is increased. This substantially reduces the volume that is required to be treated in the digester. The process is usually run as a batch process with more than one digester tank in operation at any one time.
Air is pumped through the tank and the contents are stirred to keep the contents fully mixed. Carbon dioxide, waste air and small quantities of other gases including hydrogen sulfide are given off. These waste gases require treatment to reduce odours in works close to housing or capable of generating public nuisance. The digestion is continued until the percentage of degradable solids is reduced to between 20% and 10% depending on local conditions.
Where non-sewage waste is being processed, organic waste such as food, cardboard and horticultural waste can be significantly reduced in volume leaving an output that can be used as soil improver or biomass fuel. | 1 | Applied and Interdisciplinary Chemistry |
The recent discovery of the reversibility of many reactions catalyzed by inverting glycosyltransferases served as a paradigm shift in the field and raises questions regarding the designation of sugar nucleotides as activated donors. | 0 | Theoretical and Fundamental Chemistry |
The DMACA is any of a number of acidified DMACA solutions:
* 0.117 g of DMACA, 39 mL of ethanol, 5 mL of conc hydrochloric acid and diluted to 50mL with water
* 1 g DMACA, 1 mL conc. hydrochloric acid and 99 mL water
* 1 g DMACA in 99 mL conc. hydrochloric acid.
It is primarily used as a histological dye used to detect indoles, particularly for production in cells. It is used for the rapid identification of bacteria containing tryptophanase enzyme systems. It is also particularly useful for localization of proanthocyanidins compounds in plants, resulting in a blue staining. It has been used for grapevine fruit or for legumes foliage histology.
A colorimetric assay based upon the reaction of A-rings with the chromogen. p-Dimethylaminocinnamaldehyde has been developed for flavanoids in beer that can be compared with the vanillin procedure. The DMACA reagent may be superior to the vanillin procedure for the detection of catechins.
The DMACA reagent changes color over several days when exposed to air but when refrigerated can be stored for up to two weeks.
The DMACA reagent may also be referred to as the Renz and Loew reagent. | 0 | Theoretical and Fundamental Chemistry |
Gel electrophoresis is a technique which separates molecules by their size using an agarose or polyacrylamide gel. This technique is one of the principal tools of molecular biology. The basic principle is that DNA fragments can be separated by applying an electric current across the gel - because the DNA backbone contains negatively charged phosphate groups, the DNA will migrate through the agarose gel towards the positive end of the current. Proteins can also be separated on the basis of size using an SDS-PAGE gel, or on the basis of size and their electric charge by using what is known as a 2D gel electrophoresis. | 1 | Applied and Interdisciplinary Chemistry |
Original FutureGen project was intended to combine and test several new technologies in a single location, including coal gasification, emissions controls, hydrogen production, electricity generation, and carbon dioxide capture and storage (CCS).
Integrated Gasification Combined Cycle (IGCC) was the core technology behind FutureGen. IGCC power plants use two turbines – a gas and a steam turbine – to produce electric power more efficiently than pulverized coal plants. IGCC plants also make it easier to capture carbon dioxide for carbon sequestration.
FutureGen was to capture carbon dioxide produced during the gasification process and pump it into deep rock formations thousands of feet under ground. FutureGen specifically targeted rock formations containing saline water, as these are one of the most abundant types of geologic formations that can be used to store carbon dioxide worldwide. A study by the Global Energy Technology Strategy Program estimates the storage capacity of these saline rock formations in the U.S. to be 2,970 gigatons of carbon dioxide, compared to a capacity of 77 gigatons of carbon dioxide for all other types of reservoirs, such as depleted gas fields. Focusing on rock formations with saline water was intended to help ensure that the lessons learned from the project are broadly transferable throughout the U.S. and around the world. | 1 | Applied and Interdisciplinary Chemistry |
Data analysis methods for chemical imaging data sets typically employ mathematical algorithms common to single point spectroscopy or to image analysis. The reasoning is that the spectrum acquired by each detector is equivalent to a single point spectrum; therefore pre-processing, chemometrics and pattern recognition techniques are utilized with the similar goal to separate chemical and physical effects and perform a qualitative or quantitative characterization of individual sample components. In the spatial dimension, each chemical image is equivalent to a digital image and standard image analysis and robust statistical analysis can be used for feature extraction. | 0 | Theoretical and Fundamental Chemistry |
Praseodymium(III) nitride can be prepared by the reaction of nitrogen and metallic praseodymium on heating:
It can also be prepared from the reaction of ammonia and praseodymium metal on heating: | 0 | Theoretical and Fundamental Chemistry |
As posited in a "Thioester World", thioesters are possible precursors to life. As Christian de Duve explains:
However, due to the high free energy change of thioester's hydrolysis and correspondingly their low equilibrium constants, it is unlikely that these compounds could have accumulated abiotically to any significant extent especially in hydrothermal vent conditions. | 0 | Theoretical and Fundamental Chemistry |
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