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Nearly two billion people in the developing world are deficient in zinc. Groups at risk include children in developing countries and the elderly with chronic illnesses. In children, it causes an increase in infection and diarrhea and contributes to the death of about 800,000 children worldwide per year. The World Health Organization advocates zinc supplementation for severe malnutrition and diarrhea. Zinc supplements help prevent disease and reduce mortality, especially among children with low birth weight or stunted growth. However, zinc supplements should not be administered alone, because many in the developing world have several deficiencies, and zinc interacts with other micronutrients. While zinc deficiency is usually due to insufficient dietary intake, it can be associated with malabsorption, acrodermatitis enteropathica, chronic liver disease, chronic renal disease, sickle cell disease, diabetes, malignancy, and other chronic illnesses.
In the United States, a federal survey of food consumption determined that for women and men over the age of 19, average consumption was 9.7 and 14.2 mg/day, respectively. For women, 17% consumed less than the EAR, for men 11%. The percentages below EAR increased with age. The most recent published update of the survey (NHANES 2013–2014) reported lower averages – 9.3 and 13.2 mg/day – again with intake decreasing with age.
Symptoms of mild zinc deficiency are diverse. Clinical outcomes include depressed growth, diarrhea, impotence and delayed sexual maturation, alopecia, eye and skin lesions, impaired appetite, altered cognition, impaired immune functions, defects in carbohydrate utilization, and reproductive teratogenesis. Zinc deficiency depresses immunity, but excessive zinc does also.
Despite some concerns, western vegetarians and vegans do not suffer any more from overt zinc deficiency than meat-eaters. Major plant sources of zinc include cooked dried beans, sea vegetables, fortified cereals, soy foods, nuts, peas, and seeds. However, phytates in many whole-grains and fibers may interfere with zinc absorption and marginal zinc intake has poorly understood effects. The zinc chelator phytate, found in seeds and cereal bran, can contribute to zinc malabsorption. Some evidence suggests that more than the US RDA (8 mg/day for adult women; 11 mg/day for adult men) may be needed in those whose diet is high in phytates, such as some vegetarians. The European Food Safety Authority (EFSA) guidelines attempt to compensate for this by recommending higher zinc intake when dietary phytate intake is greater. These considerations must be balanced against the paucity of adequate zinc biomarkers, and the most widely used indicator, plasma zinc, has poor sensitivity and specificity. | 1 | Applied and Interdisciplinary Chemistry |
The model was initially developed by Beddoes and Leishman&Beddoes and refined by Leishman and Tyler&Leishman.
The model consists of three distinct sub-systems for describing the dynamic stall physics:
* Attached flow model for the unsteady (linear) airloads (with compressibility effects included) using the compressible indicial response functions;
* Separated flow model for the nonlinear airloads (Kirchhoff-Helmholtz theory);
* Dynamic stall model for the leading edge vortex-induced airloads.
One significant advantage of the model is that it uses relatively few empirical coefficients, with all but four at each Mach number being derived from static airfoil data. | 1 | Applied and Interdisciplinary Chemistry |
Human chorionic gonadotropin is a glycoprotein composed of 237 amino acids with a molecular mass of 36.7 kDa, approximately 14.5kDa αhCG and 22.2kDa βhCG.
It is heterodimeric, with an α (alpha) subunit identical to that of luteinizing hormone (LH), follicle-stimulating hormone (FSH), thyroid-stimulating hormone (TSH), and a β (beta) subunit that is unique to hCG.
* The α (alpha) subunit is 92 amino acids long.
* The β-subunit of hCG gonadotropin (beta-hCG) contains 145 amino acids, encoded by six highly homologous genes that are arranged in tandem and inverted pairs on chromosome 19q13.3 - CGB (1, 2, 3, 5, 7, 8). It is known that CGB7 has a sequence slightly different from that of the others.
The two subunits create a small hydrophobic core surrounded by a high surface area-to-volume ratio: 2.8 times that of a sphere. The vast majority of the outer amino acids are hydrophilic.
beta-hCG is mostly similar to beta-LH, with the exception of a Carboxy Terminus Peptide (beta-CTP) containing four glycosylated serine residues that is responsible for hCG's longer half-life. | 1 | Applied and Interdisciplinary Chemistry |
An explicit distinction between thermal equilibrium and thermodynamic equilibrium is made by B. C. Eu. He considers two systems in thermal contact, one a thermometer, the other a system in which there are several occurring irreversible processes, entailing non-zero fluxes; the two systems are separated by a wall permeable only to heat. He considers the case in which, over the time scale of interest, it happens that both the thermometer reading and the irreversible processes are steady. Then there is thermal equilibrium without thermodynamic equilibrium. Eu proposes consequently that the zeroth law of thermodynamics can be considered to apply even when thermodynamic equilibrium is not present; also he proposes that if changes are occurring so fast that a steady temperature cannot be defined, then "it is no longer possible to describe the process by means of a thermodynamic formalism. In other words, thermodynamics has no meaning for such a process." This illustrates the importance for thermodynamics of the concept of temperature.
Thermal equilibrium is achieved when two systems in thermal contact with each other cease to have a net exchange of energy. It follows that if two systems are in thermal equilibrium, then their temperatures are the same.
Thermal equilibrium occurs when a system's macroscopic thermal observables have ceased to change with time. For example, an ideal gas whose distribution function has stabilised to a specific Maxwell–Boltzmann distribution would be in thermal equilibrium. This outcome allows a single temperature and pressure to be attributed to the whole system. For an isolated body, it is quite possible for mechanical equilibrium to be reached before thermal equilibrium is reached, but eventually, all aspects of equilibrium, including thermal equilibrium, are necessary for thermodynamic equilibrium. | 0 | Theoretical and Fundamental Chemistry |
This intuitive picture is not quite right, because is an eigenfunction of the Hamiltonian and so at different times only differs by a phase. Thus, in particular, the physical state does not evolve and so it cannot become noninteracting. This problem is easily circumvented by assembling and into wavepackets with some distribution of energies over a characteristic scale . The uncertainty principle now allows the interactions of the asymptotic states to occur over a timescale and in particular it is no longer inconceivable that the interactions may turn off outside of this interval. The following argument suggests that this is indeed the case.
Plugging the Lippmann–Schwinger equations into the definitions
and
of the wavepackets we see that, at a given time, the difference between the and wavepackets is given by an integral over the energy . | 0 | Theoretical and Fundamental Chemistry |
FEBS activities include: publishing journals; providing grants for scientific meetings such as an annual Congress, Young Scientists’ Forum and FEBS Advanced Courses; offering travel awards to early-stage scientists to participate in these events; offering research Fellowships for pre- and post-doctoral bioscientists; promoting molecular life science education; encouraging integration of scientists working in economically disadvantaged countries of the FEBS area; and awarding prizes and medals for research excellence. FEBS collaborates with related scientific societies such as its Constituent Societies, the International Union of Biochemistry and Molecular Biology (IUBMB) and the European Molecular Biology Organization (EMBO).
Awards presented by FEBS include the Sir Hans Krebs Medal, the FEBS/EMBO Women in Science Award (presented jointly with EMBO), the Datta medal and the Theodor Bücher medal. | 1 | Applied and Interdisciplinary Chemistry |
MicroRNAs (miRNAs) appear to regulate the expression of more than 60% of protein coding genes of the human genome. If an miRNA is abundant it can behave as a "switch", turning some genes on or off. However, altered expression of many miRNAs only leads to a modest 1.5- to 4-fold change in protein expression of their target genes. Individual miRNAs often repress several hundred target genes. Repression usually occurs either through translational silencing of the mRNA or through degradation of the mRNA, via complementary binding, mostly to specific sequences in the 3 untranslated region of the target genes mRNA. The mechanism of translational silencing or degradation of mRNA is implemented through the RNA-induced silencing complex (RISC). | 1 | Applied and Interdisciplinary Chemistry |
Ceration is a chemical process, a common practice in alchemy. It is performed by continuously adding a liquid by imbibition to a hard, dry substance while it is heated. Typically, this treatment makes the substance softer, more like molten wax (cera in Latin). Pseudo-Gebers Summa Perfectionis' explains that ceration is "the mollification of an hard thing, not fusible unto liquefaction", and stresses the importance of correct humidity in the process.
Antoine-Joseph Pernety's 1787 mytho-Hermetic dictionary defines it somewhat differently as the time when matter passes from black to gray, and then to white. Continuous cooking effects this change. Ceration may be synonymous with similar terms for alchemical burning processes. Incineration, for example is listed by Manly P. Hall. | 1 | Applied and Interdisciplinary Chemistry |
A primary advantage of curing with ultraviolet light is the speed at which a material can be processed. Speeding up the curing, or drying step, in a process can reduce flaws and errors by decreasing time that an ink or coating spends as wet. This can increase the quality of a finished item, and potentially allow for greater consistency. Another benefit to decreasing manufacturing time is that less space needs to be devoted to storing items which can not be used until the drying step is finished.
Because UV energy has unique interactions with many different materials, UV curing allows for the creation of products with characteristics not achievable via other means. This has led to UV curing becoming fundamental in many fields of manufacturing and technology, where changes in strength, hardness, durability, chemical resistance, and many other properties are required. | 0 | Theoretical and Fundamental Chemistry |
G.V. Pigulevsky was born on December 10, 1888 (November 28, old style) in Kovno (nowadays Kaunas, Lithuania) in the family of a lawyer Vasily Ivanovich Pigulevsky. There were two other sons in the family - Boris and Vladimir. In 1906, after graduating from the Vilna Gymnasium, he entered the Faculty of Physics and Mathematics of the Saint Petersburg Imperial University. After graduation in 1911, he stayed at the Department of Chemistry at the suggestion of Professor L.A. Chugaev. Since 1912 he simultaneously became a laboratory assistant in the Agricultural Scientific Committee of the Ministry of Agriculture, in 1914-23 he worked as a scientific specialist of the same committee. At the same time, he lectured at the Psychoneurological Institute (1914-1918). In 1919, he taught analytical chemistry at the Women's Medical Institute.
In 1920 Pigulevsky became a lecturer (since 1929 - associate professor) at Petrograd University (later - Leningrad State University). In 1924-1928, he worked as the head of the laboratory of labor protection of the People's Commissariat for Labour of the North-Western Region. In 1929, Pigulevsky was elected as a professor of the Institute of Chemical Technology. In the same year, he headed the Department of fats and oils of this Institute (1929-1930). In 1931-1934 while continuing to teach at Leningrad State University, Pigulevsky headed the Department of Organic Chemistry at the Arkhangelsk Forestry Engineering Institute. In 1934, he became a professor of organic chemistry at Leningrad State University. At the same time, he headed the laboratory of bioproducts of this University. In 1935, he obtained Doctor of Science in chemistry degree without thesis defense.
In 1941-1942, as a part of a group of chemists Pigulevsky organized the production of medicines (streptocide, phenamine, glucose, sulfidine and sulfazol) in besieged Leningrad. In the summer of 1942, he was evacuated to Kazan. In 1942-1943, he served as a senior researcher at the I.P. Pavlov Physiological Institute of the Academy of Sciences of the USSR. In 1943, Pigulevsky accepted an invitation to head the biochemical laboratory of the V.L. Komarov Botanical Institute and led it until the end of his life. In 1944, Pigulevsky returned to Leningrad.
After coming back to Leningrad, he again headed the laboratory of bioproducts at Leningrad State University. In 1957, this laboratory was reorganized as the problematic laboratory of natural compounds of the Faculty of Chemistry of the Leningrad State University. Pigulevsky headed it until the end of his life. He died in 1964 in Leningrad. | 0 | Theoretical and Fundamental Chemistry |
The etymology of the words "urethane" and "carbamate" are highly similar but not the same. The word "urethane" was first coined in 1833 by French chemist Jean-Baptiste Dumas. Dumas states "Urethane. The new ether, brought into contact with liquid and concentrated ammonia, exerts on this substance a reaction so strong that the mixture boils, and sometimes even produces a sort of explosion. If the ammonia is in excess, all the ether disappears. It forms ammonium hydrochlorate and a new substance endowed with interesting properties." Dumas appears to be naming this compound urethane. However, later Dumas states "While waiting for opinion to settle on the nature of this body, I propose to designate by the names of urethane and oxamethane the two materials which I have just studied, and . These names which, in my eyes, do not prejudge anything in the question of alcohol and ethers, will at least have the advantage of satisfying chemists who still refuse to accept our theory." The word urethane is derived from the words "urea" and "ether" with the suffix "-ane" as a generic chemical suffix, making it specific for the R2NC(=O)OR (R not = H) bonding structure.
The use of the word "carbamate" appears to come later only being traced back to at least 1849, in a description of Dumas's work by Henry Medlock. Medlock states "It is well known that the action of ammonia on chloro-carbonate (phosgene) of ethyl gives rise to the formation of the substance which Dumas, the discoverer, called urethane, and which we are now in the habit of considering as the ether of carbamic acid." This suggests that instead of continuing with the urethane family naming convention Dumas coined, they altered the naming convention to ethyl ether of carbamic acid. Carbamate is derived from the words "carbamide", otherwise known as urea, and "-ate" a suffix which indicates the salt or ester of an acid.
Both words have roots deriving from urea. Carbamate is less-specific because the -ate suffix is ambiguous for either the salt or ester of a carbamic acid. However, the -ate suffix is also more specific because it suggests carbamates must be derived from the acid of carbamate, or carbamic acids. Although, a urethane has the same chemical structure as a carbamate ester moiety, a urethane not derived from a carbamic acid is not a carbamate ester. In other words, any synthesis of the R2NC(=O)OR (R not = H) moiety that does not derive from carbamic acids is not a carbamate ester but instead a urethane. Furthermore, carbamate esters are urethanes but not all urethanes are carbamate esters. This further suggests that polyurethanes are not simply polycarbamate-esters because polyurethanes are not typically synthesized using carbamic acids.
IUPAC states "The esters are often called urethanes or urethans, a usage that is strictly correct only for the ethyl esters." But also states, "An alternative term for the compounds R2NC(=O)OR (R not = H), esters of carbamic acids, R,NC(=O)OH, in strict use limited to the ethyl esters, but widely used in the general sense". IUPAC provides these statements without citation. | 0 | Theoretical and Fundamental Chemistry |
Strontium is naturally deposited in hydroxyapatite, the mineral component of bones and teeth, following its consumption in food and water. Each locale has a unique Sr isotope ratio and, therefore, the ratio found in a bone or enamel sample can be cross referenced against a record of environmental Sr ratios and assigned to a region. Dental enamel forms in childhood, therefore, Sr extracted from dental enamel reflects the environment in which an individual lived during infancy and childhood. Bone, however, is constantly being renewed and can therefore be used to infer the adult diet and location of the individual. As such, if the Sr ratios are the analogous in the bones and teeth, it can be inferred that an individual remained in the same general region throughout their life. If the ratios differ, the individual's birthplace and death place can be mapped, allowing inference of their movements. This has been applied to determine the functionality and significance of Stonehenge, finding that both the visitors and cattle used in feasting travelled great distances, with Sr ratios attributed to both Scotland and Wales. | 0 | Theoretical and Fundamental Chemistry |
Polyanionic and featuring a potentially chelating polyphosphate group, ATP binds metal cations with high affinity. The binding constant for is (). The binding of a divalent cation, almost always magnesium, strongly affects the interaction of ATP with various proteins. Due to the strength of the ATP-Mg interaction, ATP exists in the cell mostly as a complex with bonded to the phosphate oxygen centers.
A second magnesium ion is critical for ATP binding in the kinase domain. The presence of Mg regulates kinase activity. It is interesting from an RNA world perspective that ATP can carry a Mg ion which catalyzes RNA polymerization. | 1 | Applied and Interdisciplinary Chemistry |
Centrifugal partition chromatography does not uses any solid stationary phase, so it guarantees a cost-effective separation for the highest industrial levels. As opposed to countercurrent chromatography, it is possible to get very high flow rates (for example 10 liters / min) with active stationary phase ratio of >80%, which guarantees good separation and high productivity. As in centrifugal partition chromatography, material is dissolved, and loaded the column in mass / volume units, loading capability can be much higher than standard solid-liquid chromatographic techniques, where material is loaded to the active surface area of the stationary phase, which takes up less than 10% of the column.
Industrial instrument like Gilson (Armen Instrument), Kromaton (Rousselet Robatel) and RotaChrom Technologies (RotaChrom) differ from laboratory scale instruments by the applicable flow rate with satisfactory stationary phase retention (70–90%). Industrial instruments have flow rates of multiple liter / minutes, while able to purify materials from 10 kg to tonnes per month.
Operating the production scale equipment requires industrial volume solvent preparation (mixer/settler) and solvent recovery equipment. | 0 | Theoretical and Fundamental Chemistry |
Substrate-level phosphorylation is a metabolism reaction that results in the production of ATP or GTP supported by the energy released from another high-energy bond that leads to phosphorylation of ADP or GDP to ATP or GTP (note that the reaction catalyzed by creatine kinase is not considered as "substrate-level phosphorylation"). This process uses some of the released chemical energy, the Gibbs free energy, to transfer a phosphoryl (PO) group to ADP or GDP. Occurs in glycolysis and in the citric acid cycle.
Unlike oxidative phosphorylation, oxidation and phosphorylation are not coupled in the process of substrate-level phosphorylation, and reactive intermediates are most often gained in the course of oxidation processes in catabolism. Most ATP is generated by oxidative phosphorylation in aerobic or anaerobic respiration while substrate-level phosphorylation provides a quicker, less efficient source of ATP, independent of external electron acceptors. This is the case in human erythrocytes, which have no mitochondria, and in oxygen-depleted muscle. | 1 | Applied and Interdisciplinary Chemistry |
The gal operon of E. coli consists of 4 structural genes: galE (epimerase), galT (galactose transferase), galK (galactokinase), and galM (mutarotase) which are transcribed from two overlapping promoters, PG1 (+1) and PG2 (-5), upstream from galE. GalE encodes for an epimerase that converts UDP-glucose into UDP-galactose. This is required for the formation of UDP-galactose for cell wall biosynthesis, in particular the cell wall component lipopolysaccharide, even when cells are not using galactose as a carbon/energy source. GalT encodes for the protein galactosyltransferase which catalyzes the transfer of a galactose sugar to an acceptor, forming a glycosidic bond. GalK encodes for a kinase that phosphorylates α-D-galactose to galactose 1-phosphate. Lastly, galM catalyzes the conversion of β-D-galactose to α-D-galactose as the first step in galactose metabolism.
The gal operon contains two operators, O (for external) and O (for internal). The former is just upstream of the promoter, and the latter is just after the galE gene (the first gene in the operon). These operators bind the repressor, GalR, which is encoded from outside the operator region. For this repressor protein to function properly, the operon also contains a histone binding site to facilitate this process.
An additional site, known as the activating site, is found following the external operator, but upstream of PG2. This site serves as the binding region for the cAMP-CRP complex, which modulates the activity of the promoters and thus, gene expression. | 1 | Applied and Interdisciplinary Chemistry |
Interference of two sinusoidal waves with slightly different wavelengths, but the same amplitude and propagation direction, results in a beat pattern, called a wave group. As can be seen in the animation, the group moves with a group velocity c different from the phase velocity c, due to frequency dispersion.
The group velocity is depicted by the red lines (marked B) in the two figures above.
In shallow water, the group velocity is equal to the shallow-water phase velocity. This is because shallow water waves are not dispersive. In deep water, the group velocity is equal to half the phase velocity: c = ½ c.
The group velocity also turns out to be the energy transport velocity. This is the velocity with which the mean wave energy is transported horizontally in a narrow-band wave field.
In the case of a group velocity different from the phase velocity, a consequence is that the number of waves counted in a wave group is different when counted from a snapshot in space at a certain moment, from when counted in time from the measured surface elevation at a fixed position. Consider a wave group of length Λ and group duration of τ. The group velocity is:
The number of waves in a wave group, measured in space at a certain moment is: Λ / λ. While measured at a fixed location in time, the number of waves in a group is: τ / T. So the ratio of the number of waves measured in space to those measured in time is:
So in deep water, with c = ½ c, a wave group has twice as many waves in time as it has in space.
The water surface elevation η(x,t), as a function of horizontal position x and time t, for a bichromatic wave group of full modulation can be mathematically formulated as:
with:
* a the wave amplitude of each frequency component in metres,
* k and k the wave number of each wave component, in radians per metre, and
* ω and ω the angular frequency of each wave component, in radians per second.
Both ω and k, as well as ω and k, have to satisfy the dispersion relation:
: and
Using trigonometric identities, the surface elevation is written as:
The part between square brackets is the slowly varying amplitude of the group, with group wave number ½ ( k − k ) and group angular frequency ½ ( ω − ω ). As a result, the group velocity is, for the limit k → k :
Wave groups can only be discerned in case of a narrow-banded signal, with the wave-number difference k − k small compared to the mean wave number ½ (k + k). | 1 | Applied and Interdisciplinary Chemistry |
Most nitrolic acids are laboratory curiosities. One exception is the compound HOC(CH)C(NO)=NOH, which is produced by the oxidation of cyclohexanone with nitric acid. This species decomposes to adipic acid and nitrous oxide:
:HOC(CH)C(NO)=NOH → HOC(CH)COH + NO
This conversion is thought to be the largest anthropogenic route to NO, which, on a molecule-to-molecule basis, has 298 times the atmospheric heat-trapping ability of carbon dioxide. Adipic acid is a precursor to many nylon polymers. In the end, nitrous oxide is produced in about one to one mole ratio to the adipic acid. | 0 | Theoretical and Fundamental Chemistry |
A description of the structure of reticulated foams is still being developed. While Plateau's laws, the rules governing the shape of soap films in foams were developed in the 19th century, a mathematical description of the structure is still debated. The computer-generated Weaire–Phelan structure is the most recent. In a reticulated foam only the edges of the polyhedra remain; the faces are missing. In commercial reticulated foam, up to 98% of the faces are removed. The dodecahedron is sometimes given as the basic unit for these foams, but the most representative shape is a polyhedron with 13 faces. Cell size and cell size distribution are critical parameters for most applications. Porosity is typically 95%, but can be as high as 98%. Reticulation affects many of the physical properties of a foam. Typically resistance to compression is decreased while tensile properties like elongation and resistance to tearing are increased. | 0 | Theoretical and Fundamental Chemistry |
Explosive antimony is an allotrope of the chemical element antimony that is so sensitive to shock that it explodes when scratched or subjected to sudden heating. The allotrope was first described in 1855.
Chemists form the allotrope through electrolysis of a concentrated solution of antimony trichloride in hydrochloric acid, which forms an amorphous glass.
This glass contains significant amounts of halogen impurity at its boundaries.
When it explodes, the allotrope releases 24 calories (100 J) per gram. White fumes of antimony trichloride are produced and the elemental antimony reverts to its metallic form. | 0 | Theoretical and Fundamental Chemistry |
Careful selection of the reaction tank material is essential along with control of the current, flow rate and pH. Electrodes can be made of iron, aluminum, titanium, graphite or other materials, depending upon the wastewater to be treated and the contaminants to be removed. Temperature and pressure appear to have only a minor effect on the process.
In the EC process the water-contaminant mixture separates into a floating layer, a mineral-rich flocculated sediment, and clear water. The floating layer is generally removed by means of an overflow weir or similar removal method. The aggregated flocculent mass settles either in the reaction vessel or in subsequent settling tanks due to gravitational force.
Following removal to a sludge collection tank, it is typically dewatered to a semi-dry cake using a mechanical screw press. The clear, treated (supernatant) water is typically then pumped to a buffer tank for later disposal and/or reuse in the plant's designated process. | 1 | Applied and Interdisciplinary Chemistry |
Elizabeth Gooking Greenleaf was the first female apothecary in the Thirteen Colonies. She is considered to be the first female pharmacist in the United States.
Mary Corinna Putnam Jacobi graduated from the New York College of Pharmacy in 1863, which made her the first woman to graduate from a United States school of pharmacy.
Susan Hayhurst was the first woman to receive a pharmacy degree in the United States, which occurred in 1883.
Cora Dow (1868–1915), a pharmacist in Cincinnati, Ohio, was the leading female pharmacist of her time, with eleven stores under her name when she died.
Julia Pearl Hughes (1873–1950) was the first African-American female pharmacist to own and operate her own drug store.
Anna Louise James (1886–1977) was the first African-American female pharmacist in Connecticut. | 1 | Applied and Interdisciplinary Chemistry |
Instrumentation in time-domain diffuse optics consists of three fundamental components namely, a pulsed laser source, a single photon detector and a timing electronics. | 0 | Theoretical and Fundamental Chemistry |
The atmosphere is 21% oxygen by volume, which equates to a total of roughly 34 × 10 mol of oxygen. Other oxygen-containing molecules in the atmosphere include ozone (O), carbon dioxide (CO), water vapor (HO), and sulphur and nitrogen oxides (SO, NO, NO, etc.). | 0 | Theoretical and Fundamental Chemistry |
Some of the job skills and abilities that one needs to attain to be successful in this field of work include science, mathematics, reading comprehension, writing, and critical thinking. These skills are critical because of the nature of the experimental techniques of the occupation. One will also need to convey trends found in research in written and oral forms.
A degree in biochemistry or a related science such as chemistry is the minimum requirement for any work in this field. This is sufficient for a position as a technical assistant in industry or in academic settings. A Ph.D. (or equivalent) is generally required to pursue or direct independent research. To advance further in commercial environments, one may need to acquire skills in management.
Biochemists must pass a qualifying exam or a preliminary exam to continue their studies when receiving a Ph.D. in biochemistry.
Biochemistry requires an understanding of organic and inorganic chemistry. All types of chemistry are required, with emphasis on biochemistry, organic chemistry and physical chemistry. Basic classes in biology, including microbiology, molecular biology, molecular genetics, cell biology, and genomics, are focused on. Some instruction in experimental techniques and quantification is also part of most curricula.
In the private industries for businesses, it is imperative to possess strong business management skills as well as communication skills. Biochemists must also be familiar with regulatory rules and management techniques.
Biochemistry Blog publishes high quality research articles, papers, posts and jobs related to biochemistry. Biochemistry 2019, biochemistry papers latest.
Due to the reliance on most principles of the basic science of Biochemistry, early contemporary physicians were informally qualified to perform research on their own in mainly this (today also related biomedical sciences) field. | 1 | Applied and Interdisciplinary Chemistry |
The word ketone is derived from Aketon, an old German word for acetone.
According to the rules of IUPAC nomenclature, ketone names are derived by changing the suffix -ane of the parent alkane to -anone. Typically, the position of the carbonyl group is denoted by a number, but traditional nonsystematic names are still generally used for the most important ketones, for example acetone and benzophenone. These nonsystematic names are considered retained IUPAC names, although some introductory chemistry textbooks use systematic names such as "2-propanone" or "propan-2-one" for the simplest ketone () instead of "acetone".
The derived names of ketones are obtained by writing separately the names of the two alkyl groups attached to the carbonyl group, followed by "ketone" as a separate word. Traditionally the names of the alkyl groups were written in order of increasing complexity, for example methyl ethyl ketone. However, according to the rules of IUPAC nomenclature, the alkyl groups are written alphabetically, for example ethyl methyl ketone. When the two alkyl groups are the same, the prefix "di-" is added before the name of alkyl group. The positions of other groups are indicated by Greek letters, the α-carbon being the atom adjacent to carbonyl group.
Although used infrequently, oxo is the IUPAC nomenclature for the oxo group (=O) and used as prefix when the ketone does not have the highest priority. Other prefixes, however, are also used. For some common chemicals (mainly in biochemistry), keto refer to the ketone functional group. | 0 | Theoretical and Fundamental Chemistry |
In thermodynamics and chemical engineering, the vapor–liquid equilibrium (VLE) describes the distribution of a chemical species between the vapor phase and a liquid phase.
The concentration of a vapor in contact with its liquid, especially at equilibrium, is often expressed in terms of vapor pressure, which will be a partial pressure (a part of the total gas pressure) if any other gas(es) are present with the vapor. The equilibrium vapor pressure of a liquid is in general strongly dependent on temperature. At vapor–liquid equilibrium, a liquid with individual components in certain concentrations will have an equilibrium vapor in which the concentrations or partial pressures of the vapor components have certain values depending on all of the liquid component concentrations and the temperature. The converse is also true: if a vapor with components at certain concentrations or partial pressures is in vapor–liquid equilibrium with its liquid, then the component concentrations in the liquid will be determined dependent on the vapor concentrations and on the temperature. The equilibrium concentration of each component in the liquid phase is often different from its concentration (or vapor pressure) in the vapor phase, but there is a relationship. The VLE concentration data can be determined experimentally or approximated with the help of theories such as Raoults law, Daltons law, and Henry's law.
Such vapor–liquid equilibrium information is useful in designing columns for distillation, especially fractional distillation, which is a particular specialty of chemical engineers. Distillation is a process used to separate or partially separate components in a mixture by boiling (vaporization) followed by condensation. Distillation takes advantage of differences in concentrations of components in the liquid and vapor phases.
In mixtures containing two or more components, the concentrations of each component are often expressed as mole fractions. The mole fraction of a given component of a mixture in a particular phase (either the vapor or the liquid phase) is the number of moles of that component in that phase divided by the total number of moles of all components in that phase.
Binary mixtures are those having two components. Three-component mixtures are called ternary mixtures. There can be VLE data for mixtures with even more components, but such data is often hard to show graphically. VLE data is a function of the total pressure, such as 1 atm or at the pressure the process is conducted at.
When a temperature is reached such that the sum of the equilibrium vapor pressures of the liquid components becomes equal to the total pressure of the system (it is otherwise smaller), then vapor bubbles generated from the liquid begin to displace the gas that was maintaining the overall pressure, and the mixture is said to boil. This temperature is called the boiling point of the liquid mixture at the given pressure. (It is assumed that the total pressure is held steady by adjusting the total volume of the system to accommodate the specific volume changes that accompany boiling.) The boiling point at an overall pressure of 1 atm is called the normal boiling point of the liquid mixture. | 0 | Theoretical and Fundamental Chemistry |
The most frequently reported mechanical property of titanium foams is compressive strength. It was generally accepted that the compressive properties of metal foams depended on the properties of the cell wall rather than on pore size. However, more recent research has indicated that smaller pore sizes equate to higher compressive strength. As pore sizes reach nano-dimensions, the relationship is even more clear due to changes in deformation mechanism.
Tuncer & Arslan fabricated titanium foams via the space-holder method using various shaped space-holders to elucidate the effect of cell morphology on mechanical properties. They found that foams created with needle-like urea space-holders exhibited a decrease in elastic modulus and yield strength when compared to spherical pores. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, the amino radical, , also known as the aminyl radical or azanyl radical, is the neutral form of the amide ion (). Aminyl radicals are highly reactive and consequently short-lived, like most radicals; however, they form an important part of nitrogen chemistry. In sufficiently high concentration, amino radicals dimerise to form hydrazine. While as a functional group is common in nature, forming a part of many compounds (e.g. the phenethylamines), the radical cannot be isolated in its free form. | 0 | Theoretical and Fundamental Chemistry |
Ions can be non-chemically prepared using various ion sources, usually involving high voltage or temperature. These are used in a multitude of devices such as mass spectrometers, optical emission spectrometers, particle accelerators, ion implanters, and ion engines.
As reactive charged particles, they are also used in air purification by disrupting microbes, and in household items such as smoke detectors.
As signalling and metabolism in organisms are controlled by a precise ionic gradient across membranes, the disruption of this gradient contributes to cell death. This is a common mechanism exploited by natural and artificial biocides, including the ion channels gramicidin and amphotericin (a fungicide).
Inorganic dissolved ions are a component of total dissolved solids, a widely known indicator of water quality. | 0 | Theoretical and Fundamental Chemistry |
Nikolaev Institute of Inorganic Chemistry of the Siberian Branch of the RAS () is a research institute in Akademgorodok of Novosibirsk, Russia. It was founded in 1957. | 0 | Theoretical and Fundamental Chemistry |
There are five key pieces of equipment used in a pipebursting operation: the expander head, pulling rods, a pulling machine, a retaining device, and a hydraulic power pack.
Today's expander heads have a leading end much smaller in diameter than the trailing (bursting) end, small enough to fit through the pipe that will be replaced. The smaller leading end is designed to guide the expander head through the existing pipe; earlier models did not have this feature and lost course at times, resulting in incomplete pipe bursts and project failures.
The transition from the leading end to the trailing end can include "fins" that make first contact with the existing pipe. Using these fins as the primary breaking point is a very effective way to ensure that the pipe is broken along the entire circumference.
A machine is set in the receiving pit to pull the expander head and new pipe into the line. The head is pulled by heavy, interlocking links that form a chain. Each link weighs several hundred pounds.
All of the equipment used in a pipe bursting operation is powered by one or multiple hydraulic power generators. | 1 | Applied and Interdisciplinary Chemistry |
Ca ions are usually kept at nanomolar levels in the cytosol of plant cells, and act in a number of signal transduction pathways as second messengers. | 1 | Applied and Interdisciplinary Chemistry |
Infragravity waves are surface gravity waves with frequencies lower than the wind waves – consisting of both wind sea and swell – thus corresponding with the part of the wave spectrum lower than the frequencies directly generated by forcing through the wind.
Infragravity waves are ocean surface gravity waves generated by ocean waves of shorter periods. The amplitude of infragravity waves is most relevant in shallow water, in particular along coastlines hit by high amplitude and long period wind waves and ocean swells. Wind waves and ocean swells are shorter, with typical dominant periods of 1 to 25 s. In contrast, the dominant period of infragravity waves is typically 80 to 300 s, which is close to the typical periods of tsunamis, with which they share similar propagation properties including very fast celerities in deep water. This distinguishes infragravity waves from normal oceanic gravity waves, which are created by wind acting on the surface of the sea, and are slower than the generating wind.
Whatever the details of their generation mechanism, discussed below, infragravity waves are these subharmonics of the impinging gravity waves.
Technically infragravity waves are simply a subcategory of gravity waves and refer to all gravity waves with periods greater than 30 s. This could include phenomena such as tides and oceanic Rossby waves, but the common scientific usage is limited to gravity waves that are generated by groups of wind waves.
The term "infragravity wave" appears to have been coined by Walter Munk in 1950. | 1 | Applied and Interdisciplinary Chemistry |
Some new instrumentations techniques exist that allow zeta potential to be measured. The Zeta Potential Analyzer can measure solid, fibers, or powdered material. The motor found in the instrument creates an oscillating flow of electrolyte solution through the sample. Several sensors in the instrument monitor other factors, so the software attached is able to do calculations to find the zeta potential. Temperature, pH, conductivity, pressure, and streaming potential are all measured in the instrument for this reason.
Zeta potential can also be calculated using theoretical models, and an experimentally-determined electrophoretic mobility or dynamic electrophoretic mobility.
Electrokinetic phenomena and electroacoustic phenomena are the usual sources of data for calculation of zeta potential. (See Zeta potential titration.) | 0 | Theoretical and Fundamental Chemistry |
The nucleophilic lysine residue is commonly targeted site in protein bioconjugation, typically through amine-reactive N-hydroxysuccinimidyl (NHS) esters. To obtain optimal number of deprotonated lysine residues, the pH of the aqueous solution must be below the pKa of the lysine ammonium group, which is around 10.5, so the typical pH of the reaction is about 8 and 9. The common reagent for the coupling reaction is NHS-ester (shown in the first reaction below in Figure 1), which reacts with nucleophilic lysine through a lysine acylation mechanism. Other similar reagents are isocyanates and isothiocyanates that undergo a similar mechanism (shown in the second and third reactions in Figure 1 below). Benzoyl fluorides (shown in the last reaction below in Figure 1), which allows for lysine modification of proteins under mild conditions (low temperature, physiological pH), were recently proposed as an alternative to classically used lysine specific reagents. | 1 | Applied and Interdisciplinary Chemistry |
Phosphoramide is a chemical compound with the molecular formula . It is a derivative of phosphoric acid in which each of the hydroxyl groups have been replaced with an amino group. In bulk, the compound is a white solid, soluble in polar solvents. | 0 | Theoretical and Fundamental Chemistry |
Organic Reactions is a peer-reviewed book series that was established in 1942. It publishes detailed descriptions of useful organic reactions. Each article (called a chapter) is an invited review of the primary source material for the given reaction, and is written under tight editorial control, making it a secondary to tertiarylevel source. Each chapter explores the practical and theoretical aspects of the reaction, including its selectivity and reproducibility. The longest chapter runs to 1,303 pages. While individual articles are not open access, the journal's wiki maintains a repository of summaries of reactions. The series is abstracted and indexed in Scopus. | 0 | Theoretical and Fundamental Chemistry |
The most famous case of polyamorphism is amorphous ice. Pressurizing conventional hexagonal ice crystals to about 1.6 GPa at liquid nitrogen temperature (77 K) converts them to the high-density amorphous ice. Upon releasing the pressure, this phase is stable and has density of 1.17 g/cm at 77 K and 1 bar. Consequent warming to 127 K at ambient pressure transforms this phase to a low-density amorphous ice (0.94 g/cm at 1 bar). Yet, if the high-density amorphous ice is warmed up to 165 K not at low pressures but keeping the 1.6 GPa compression, and then cooled back to 77 K, then another amorphous ice is produced, which has even higher density of 1.25 g/cm at 1 bar. All those amorphous forms have very different vibrational lattice spectra and intermolecular distances.
A similar abrupt liquid-amorphous phase transition is predicted in liquid silicon when cooled under high pressures. This observation is based on first principles molecular dynamics computer simulations, and might be expected intuitively since tetrahedral amorphous carbon, silicon, and germanium are known to be structurally analogous to water. | 0 | Theoretical and Fundamental Chemistry |
Direct photophoresis is caused by the transfer of photon momentum to a particle by refraction and reflection. Movement of particles in the forward direction occurs when the particle is transparent and has an index of refraction larger compared to its surrounding medium. Indirect photophoresis occurs as a result of an increase in the kinetic energy of molecules when particles absorb incident light only on the irradiated side, thus creating a temperature gradient within the particle. In this situation the surrounding gas layer reaches temperature equilibrium with the surface of the particle. Molecules with higher kinetic energy in the region of higher gas temperature impinge on the particle with greater momenta than molecules in the cold region; this causes a migration of particles in a direction opposite to the surface temperature gradient. The component of the photophoretic force responsible for this phenomenon is called the radiometric force. This comes as a result of uneven distribution of radiant energy (source function within a particle).
Indirect photophoretic force depends on the physical properties of the particle and the surrounding medium.
For pressures , where the free mean path of the gas is much larger than the characteristic size of the suspended particle (direct photophoresis), the longitudinal force is
where the mean temperature of the scattered gas is (thermal accommodation coefficient , momentum accommodation coefficient )
and the black body temperature of the particle (net light flux , Stefan Boltzmann constant , temperature of the radiation field )
is the thermal conductivity of the particle.
The asymmetry factor for spheres is usually (positive longitudinal photophoresis).
For non-spherical particles, the average force exerted on the particle is given by the same equation where the radius is now the radius of the respective volume-equivalent sphere. | 0 | Theoretical and Fundamental Chemistry |
In the brewing industry flocculation has a different meaning. It is a very important process in fermentation during the production of beer where cells form macroscopic flocs. These flocs cause the yeast to sediment or rise to the top of a fermentation at the end of the fermentation. Subsequently, the yeast can be collected (cropped) from the top (ale fermentation) or the bottom (lager fermentation) of the fermenter in order to be reused for the next fermentation.
Yeast flocculation is primarily determined by the calcium concentration, often in the 50-100ppm range. Calcium salts can be added to cause flocculation, or the process can be reversed by removing calcium by adding phosphate to form insolubable calcium phosphate, adding excess sulfate to form insoluble calcium sulfate, or adding EDTA to chelate the calcium ions. While it appears similar to sedimentation in colloidal dispersions, the mechanisms are different. | 1 | Applied and Interdisciplinary Chemistry |
Kikuchi lines, first observed by Seishi Kikuchi in 1928, are linear features created by electrons scattered both inelastically and elastically. As the electron beam interacts with matter, the electrons are diffracted via elastic scattering, and also scattered inelastically losing part of their energy. These occur simultaneously, and cannot be separated – according to the Copenhagen interpretation of quantum mechanics, only the probabilities of electrons at detectors can be measured. These electrons form Kikuchi lines which provide information on the orientation.
Kikuchi lines come in pairs forming Kikuchi bands, and are indexed in terms of the crystallographic planes they are connected to, with the angular width of the band equal to the magnitude of the corresponding diffraction vector . The position of Kikuchi bands is fixed with respect to each other and the orientation of the sample, but not against the diffraction spots or the direction of the incident electron beam. As the crystal is tilted, the bands move on the diffraction pattern. Since the position of Kikuchi bands is quite sensitive to crystal orientation, they can be used to fine-tune a zone-axis orientation or determine crystal orientation. They can also be used for navigation when changing the orientation between zone axes connected by some band, an example of such a map produced by combining many local sets of experimental Kikuchi patterns is in Figure 8; Kikuchi maps are available for many materials. | 0 | Theoretical and Fundamental Chemistry |
Although any device that promotes contact between air and water strips some volatile compounds, air strippers are usually packed towers or tray towers operated with countercurrent flow of water and air. The countercurrent flow removes particles from the water and into the air. This process is known as volatization or air stripping. Water is deposited into the system through the top and air is ventilated in through the bottom. Water that reaches the bottom of the system is typically considered treated, but additional testing may be done to determine if it is safe for consumption. Since many of the compounds stripped are hazardous air pollutants, the air exiting a stripper may require emissions control. Carbon adsorption is often used and catalytic oxidation is another option. There are mainly two different types of air strippers: Packed tower systems and sieve tray systems. Different types of air strippers are used depending on the type and amount of contaminants found in the water source being extracted. | 1 | Applied and Interdisciplinary Chemistry |
Initial salting in at low concentrations is explained by the Debye–Huckel theory. Proteins are surrounded by the salt counterions (ions of opposite net charge) and this screening results in decreasing electrostatic free energy of the protein and increasing activity of the solvent, which in turn leads to increasing solubility. This theory predicts that the logarithm of solubility is proportional to the square root of the ionic strength.
The behavior of proteins in solutions at high salt concentrations is explained by John Gamble Kirkwood. The abundance of the salt ions decreases the solvating power of salt ions, resulting in the decrease in the solubility of the proteins and precipitation results.
At high salt concentrations, the solubility is given by the following empirical expression.
:log S = B − KI
where S is the solubility of the protein, B is a constant (function of protein, pH and temperature), K is the salting out constant (function of pH, mixing and salt), and I is the ionic strength of the salt. This expression is an approximation to that proposed by Long and McDevit. | 0 | Theoretical and Fundamental Chemistry |
In 1982 The Electrochemical Society created the [https://web.archive.org/web/20150721022447/http://www.electrochem.org/awards/ecs/ecs_awards.htm#k Norman Hackerman Young Author Award] to honor the best paper published in the Journal of the Electrochemical Society for a topic in the field of electrochemical science and technology by a young author or authors. In 2000 the Welch Foundation created the Norman Hackerman Award in Chemical Research to recognize the work of young researchers in Texas. The Rice Board of Trustees established the Norman Hackerman Fellowship in Chemistry in honor of Hackermans 90th birthday in 2002. In 2008, the original Experimental Science Building at the University of Texas at Austin campus was demolished and rebuilt as the Norman Hackerman Experimental Science Building in his name and honor. The building was completed in late 2010, with the opening and dedication ceremony on March 2, 2011, which was both Hackermans 99th Birthday and the 175th Anniversary of Texas Independence. The main building at the J. Erik Jonsson Center of the National Academy of Sciences is Hackerman House, named in his honor. Hackerman House overlooks Quissett Harbor in Woods Hole MA, on Cape Cod. | 0 | Theoretical and Fundamental Chemistry |
The mobile phase or eluent is a solvent or a mixture of solvents used to move the compounds through the column. It is chosen so that the retention factor value of the compound of interest is roughly around 0.2 - 0.3 in order to minimize the time and the amount of eluent to run the chromatography. The eluent has also been chosen so that the different compounds can be separated effectively. The eluent is optimized in small scale pretests, often using thin layer chromatography (TLC) with the same stationary phase, using solvents of different polarity until a suitable solvent system is found. Common mobile phase solvents, in order of increasing polarity, include hexane, dichloromethane, ethyl acetate, acetone, and methanol. A common solvent system is a mixture of hexane and ethyl acetate, with proportions adjusted until the target compound has a retention factor of 0.2 - 0.3. Contrary to common misconception, methanol alone can be used as an eluent for highly polar compounds, and does not dissolve silica gel.
There is an optimum flow rate for each particular separation. A faster flow rate of the eluent minimizes the time required to run a column and thereby minimizes diffusion, resulting in a better separation. However, the maximum flow rate is limited because a finite time is required for the analyte to equilibrate between the stationary phase and mobile phase, see Van Deemter's equation. A simple laboratory column runs by gravity flow. The flow rate of such a column can be increased by extending the fresh eluent filled column above the top of the stationary phase or decreased by the tap controls. Faster flow rates can be achieved by using a pump or by using compressed gas (e.g. air, nitrogen, or argon) to push the solvent through the column (flash column chromatography).
The particle size of the stationary phase is generally finer in flash column chromatography than in gravity column chromatography. For example, one of the most widely used silica gel grades in the former technique is mesh 230 – 400 (40 – 63 µm), while the latter technique typically requires mesh 70 – 230 (63 – 200 µm) silica gel.
A spreadsheet that assists in the successful development of flash columns has been developed. The spreadsheet estimates the retention volume and band volume of analytes, the fraction numbers expected to contain each analyte, and the resolution between adjacent peaks. This information allows users to select optimal parameters for preparative-scale separations before the flash column itself is attempted. | 0 | Theoretical and Fundamental Chemistry |
Coagulation or blood clotting relies on, in addition to the production of fibrin, interactions between platelets. When the endothelium or the lining of a blood vessel is damaged, connective tissue including collagen fibers is locally exposed. Initially, platelets stick to the exposed connective tissue through specific cell-surface receptors. This is followed by platelet activation and aggregation in which platelets become firmly attached and release chemicals that recruit neighboring platelets to the site of vascular injury. A meshwork of fibrin then forms around this aggregation of platelets to increase the strength of the clot. | 1 | Applied and Interdisciplinary Chemistry |
In 1787, part-time chemist Carl Axel Arrhenius found a heavy black rock in an old quarry near the Swedish village of Ytterby (now part of the Stockholm Archipelago). Thinking it was an unknown mineral containing the newly discovered element tungsten, he named it ytterbite and sent samples to various chemists for analysis.
Johan Gadolin at the University of Åbo identified a new oxide (or "earth") in Arrhenius sample in 1789, and published his completed analysis in 1794. Anders Gustaf Ekeberg confirmed the identification in 1797 and named the new oxide yttria. In the decades after Antoine Lavoisier developed the first modern definition of chemical elements, it was believed that earths could be reduced to their elements, meaning that the discovery of a new earth was equivalent to the discovery of the element within, which in this case would have been yttrium'.
Friedrich Wöhler is credited with first isolating the metal in 1828 by reacting a volatile chloride that he believed to be yttrium chloride with potassium.
In 1843, Carl Gustaf Mosander found that samples of yttria contained three oxides: white yttrium oxide (yttria), yellow terbium oxide (confusingly, this was called erbia at the time) and rose-colored erbium oxide (called terbia at the time). A fourth oxide, ytterbium oxide, was isolated in 1878 by Jean Charles Galissard de Marignac. New elements were later isolated from each of those oxides, and each element was named, in some fashion, after Ytterby, the village near the quarry where they were found (see ytterbium, terbium, and erbium). In the following decades, seven other new metals were discovered in "Gadolin's yttria". Since yttria was found to be a mineral and not an oxide, Martin Heinrich Klaproth renamed it gadolinite in honor of Gadolin.
Until the early 1920s, the chemical symbol Yt was used for the element, after which Y came into common use.
In 1987, yttrium barium copper oxide was found to achieve high-temperature superconductivity. It was only the second material known to exhibit this property, and it was the first-known material to achieve superconductivity above the (economically important) boiling point of nitrogen. | 1 | Applied and Interdisciplinary Chemistry |
The carbon:nutrient balance hypothesis, also known as the environmental constraint hypothesis or Carbon Nutrient Balance Model (CNBM), states that the various types of plant defenses are responses to variations in the levels of nutrients in the environment. This hypothesis predicts the Carbon/Nitrogen ratio in plants determines which secondary metabolites will be synthesized. For example, plants growing in nitrogen-poor soils will use carbon-based defenses (mostly digestibility reducers), while those growing in low-carbon environments (such as shady conditions) are more likely to produce nitrogen-based toxins. The hypothesis further predicts that plants can change their defenses in response to changes in nutrients. For example, if plants are grown in low-nitrogen conditions, then these plants will implement a defensive strategy composed of constitutive carbon-based defenses. If nutrient levels subsequently increase, by for example the addition of fertilizers, these carbon-based defenses will decrease. | 1 | Applied and Interdisciplinary Chemistry |
Like any mineral extraction practices, there are environmental advantages and disadvantages. Cobalt and Lithium are two key metals that can be used for aiding with more environmentally friendly technologies above ground, such as powering batteries that energize electric vehicles or creating wind power. An environmentally friendly approach to mining that allows for more sustainability would be to extract these metals from the seafloor. Lithium mining from the seafloor at mass quantities could provide a substantial amount of renewable metals to promote more environmentally friendly practices in society to reduce humans' carbon footprint. Lithium mining from the seafloor could be successful, but its success would be dependent on more productive recycling practices above ground.
There are also risks that come with extracting from the seafloor. Many biodiverse species have long lifespans on the seafloor, which means that their reproduction takes more time. Similarly to fish harvesting from the seafloor, the extraction of minerals in large amounts, too quickly, without proper protocols, can result in a disruption of the underwater ecosystems. Contrarily, this would have the opposite effect and prevent mineral extractions from being a long-term sustainable practice, and would result in a shortage of required metals. Any seawater mineral extractions also risk disrupting the habitat of the underwater life that is dependent on the uninterrupted ecosystem within their environment as disturbances can have significant disturbances on animal communities. | 0 | Theoretical and Fundamental Chemistry |
The molecular formula NO (molar mass: 72.03 g/mol, exact mass: 72.0072 u) may refer to:
* Nitrosylazide
* Oxatetrazole | 0 | Theoretical and Fundamental Chemistry |
Thymidylate synthase inhibitors are chemical agents which inhibit the enzyme thymidylate synthase and have potential as an anticancer chemotherapy. This inhibition prevents the methylation of C5 of deoxyuridine monophosphate (dUMP) thereby inhibiting the synthesis of deoxythymidine monophosphate (dTMP). The downstream effect is promotion of cell death because cells would not be able to properly undergo DNA synthesis if they are lacking dTMP, a necessary precursor to dTTP.
Five agents were in clinical trials in 2002: raltitrexed, pemetrexed, nolatrexed, Plevitrexed( ZD9331/BGC9331), and GS7904L.
Examples include
* Raltitrexed, used for colorectal cancer since 1998
* Fluorouracil, used for colorectal cancer
* BGC 945/ ONX-0801
* OSI-7904L | 1 | Applied and Interdisciplinary Chemistry |
Linkage isomerism was first noted for nitropentaamminecobalt(III) chloride, . This cationic cobalt complex can be isolated as either of two linkage isomers. In the yellow-coloured isomer, the nitro ligand is bound through nitrogen. In the red linkage isomer, the nitrito is bound through one oxygen atom. The O-bonded isomer is often written as . Although the existence of the isomers had been known since the late 1800s, only in 1907 was the difference explained. It was later shown that the red isomer converted to the yellow isomer upon UV-irradiation. In this particular example, the formation of the nitro isomer () from the nitrito isomer () occurs by an intramolecular rearrangement. | 0 | Theoretical and Fundamental Chemistry |
Primase adds RNA primers onto the lagging strand, which allows synthesis of Okazaki fragments from 5 to 3. However, primase creates RNA primers at a much lower rate than that at which DNA polymerase synthesizes DNA on the leading strand. DNA polymerase on the lagging strand also has to be continually recycled to construct Okazaki fragments following RNA primers. This makes the speed of lagging strand synthesis much lower than that of the leading strand. To solve this, primase acts as a temporary stop signal, briefly halting the progression of the replication fork during DNA replication. This molecular process prevents the leading strand from overtaking the lagging strand. | 1 | Applied and Interdisciplinary Chemistry |
A Langmuir–Blodgett (LB) film is a nanostructured system formed when Langmuir films—or Langmuir monolayers (LM)—are transferred from the liquid-gas interface to solid supports during the vertical passage of the support through the monolayers. LB films can contain one or more monolayers of an organic material, deposited from the surface of a liquid onto a solid by immersing (or emersing) the solid substrate into (or from) the liquid. A monolayer is adsorbed homogeneously with each immersion or emersion step, thus films with very accurate thickness can be formed. This thickness is accurate because the thickness of each monolayer is known and can therefore be added to find the total thickness of a Langmuir–Blodgett film.
The monolayers are assembled vertically and are usually composed either of amphiphilic molecules (see chemical polarity) with a hydrophilic head and a hydrophobic tail (example: fatty acids) or nowadays commonly of nanoparticles.
Langmuir–Blodgett films are named after Irving Langmuir and Katharine B. Blodgett, who invented this technique while working in Research and Development for General Electric Co. | 0 | Theoretical and Fundamental Chemistry |
Modern coupling chemistries allow other properties of polyfluorenes to be controlled through implementation of complex molecular designs.
The above polymer structure pictured has excellent photoluminescent quantum yields (partly due to its fluorene monomer) excellent stability (due to its oxadiazole comonomer) good solubility (due to its many and branched alkyl side chains) and has an amine functionalized side chain for ease of tethering to other molecules or to a substrate.
The luminescent color of polyfluorenes can be changed, for example, (from blue to green-yellow) by adding functional groups which participate in excited state intramolecular proton transfer. Exchanging the alkoxy side chains for alcohol side groups allows for energy dissipation (and a red-shift in emission) through reversible transfer of a proton from the alcohol to the nitrogen (on the oxadiazole). These complicated molecular structures were engineered to have these properties and were only able to be realized through careful control of their ordering and side group functionality. | 0 | Theoretical and Fundamental Chemistry |
Glycosylation is the reaction in which a carbohydrate (or glycan), i.e. a glycosyl donor, is attached to a hydroxyl or other functional group of another molecule (a glycosyl acceptor) in order to form a glycoconjugate. In biology (but not always in chemistry), glycosylation usually refers to an enzyme-catalysed reaction, whereas glycation (also non-enzymatic glycation and non-enzymatic glycosylation) may refer to a non-enzymatic reaction.
Glycosylation is a form of co-translational and post-translational modification. Glycans serve a variety of structural and functional roles in membrane and secreted proteins. The majority of proteins synthesized in the rough endoplasmic reticulum undergo glycosylation. Glycosylation is also present in the cytoplasm and nucleus as the O-GlcNAc modification. Aglycosylation is a feature of engineered antibodies to bypass glycosylation. Five classes of glycans are produced:
* N-linked glycans attached to a nitrogen of asparagine or arginine side-chains. N-linked glycosylation requires participation of a special lipid called dolichol phosphate.
* O-linked glycans attached to the hydroxyl oxygen of serine, threonine, tyrosine, hydroxylysine, or hydroxyproline side-chains, or to oxygens on lipids such as ceramide.
* Phosphoglycans linked through the phosphate of a phosphoserine.
*C-linked glycans, a rare form of glycosylation where a sugar is added to a carbon on a tryptophan side-chain. Aloin is one of the few naturally occurring substances.
* Glypiation, which is the addition of a GPI anchor that links proteins to lipids through glycan linkages. | 0 | Theoretical and Fundamental Chemistry |
Low levels of vitamin D are associated with two major forms of human inflammatory bowel disease: Crohn's disease and ulcerative colitis. Deficiencies in vitamin D have been linked to the severity of the case of inflammatory bowel disease, however, whether vitamin D deficiency causes inflammatory bowel disease or is a symptom of the disease is not clear.
There is some evidence that vitamin D supplementation therapy for people with inflammatory bowel disease may be associated with improvements in scores for clinical inflammatory bowel disease activity and biochemical markers. Vitamin D treatment may be associated with less frequent relapse of symptoms in IBD. It is not clear if this treatment improves the person's quality of life or what the clinical response to vitamin D treatment. The ideal treatment regime and dose of vitamin D therapy has not been well enough studied. | 1 | Applied and Interdisciplinary Chemistry |
Mixtures with air of the gas 1,1,1,2-tetrafluoroethane are not flammable at atmospheric pressure and temperatures up to 100 °C (212 °F). However, mixtures with high concentrations of air at elevated pressure and/or temperature can be ignited. Contact of 1,1,1,2-tetrafluoroethane with flames or hot surfaces in excess of 250 °C (482 °F) may cause vapor decomposition and the emission of toxic gases including hydrogen fluoride and carbonyl fluoride, however the decomposition temperature has been reported as above 370 °C. 1,1,1,2-Tetrafluoroethane itself has an of 1,500 g/m in rats, making it relatively non-toxic, apart from the dangers inherent to inhalant abuse. Its gaseous form is denser than air and will displace air in the lungs. This can result in asphyxiation if excessively inhaled. This contributes to most deaths by inhalant abuse.
Aerosol cans containing 1,1,1,2-tetrafluoroethane, when inverted, become effective freeze sprays. Under pressure, 1,1,1,2-tetrafluoroethane is compressed into a liquid, which upon vaporization absorbs a significant amount of thermal energy. As a result, it will greatly lower the temperature of any object it contacts as it evaporates. | 1 | Applied and Interdisciplinary Chemistry |
Promoter activity is a term that encompasses several meanings around the process of gene expression from regulatory sequences —promoters and enhancers. Gene expression has been commonly characterized as a measure of how much, how fast, when and where this process happens. Promoters and enhancers are required for controlling where and when a specific gene is transcribed.
Traditionally the measure of gene products (i.e. mRNA, proteins, etc.) has been the major approach of measure promoter activity. However, this method confront with two issues: the stochastic nature of the gene expression and the lack of mechanistic interpretation of the thermodynamical process involved in the promoter activation.
The actual developments in metabolomics product of developments of next-generation sequencing technologies and molecular structural analysis have enabled the development of more accurate models of the process of promoter activation (e.g. the sigma structure of the polymerase holoenzyme domains) and a better understanding of the complexities of the regulatory factors involved. | 1 | Applied and Interdisciplinary Chemistry |
Sand rammer consists of calibrated sliding weight actuated by cam, a shallow cup to accommodate specimen tube below ram head, a specimen stripper to strip compacted specimen out of specimen tube, a specimen tube to prepare the standard specimen of 50 mm diameter by 50 mm height or 2 inch diameter by 2 inch height for an AFS standard specimen. | 1 | Applied and Interdisciplinary Chemistry |
For the one-decay solution :
the equation indicates that the decay constant has units of , and can thus also be represented as 1/, where is a characteristic time of the process called the time constant.
In a radioactive decay process, this time constant is also the mean lifetime for decaying atoms. Each atom "lives" for a finite amount of time before it decays, and it may be shown that this mean lifetime is the arithmetic mean of all the atoms' lifetimes, and that it is , which again is related to the decay constant as follows:
This form is also true for two-decay processes simultaneously , inserting the equivalent values of decay constants (as given above)
into the decay solution leads to: | 0 | Theoretical and Fundamental Chemistry |
Once the substrate is bound and oriented to the active site, catalysis can begin. The residues of the catalytic site are typically very close to the binding site, and some residues can have dual-roles in both binding and catalysis.
Catalytic residues of the site interact with the substrate to lower the activation energy of a reaction and thereby make it proceed faster. They do this by a number of different mechanisms including the approximation of the reactants, nucleophilic/electrophilic catalysis and acid/base catalysis. These mechanisms will be explained below. | 1 | Applied and Interdisciplinary Chemistry |
Lactic acid bacteria (LAB) already exists as part of the natural flora in most vegetables. Lettuce and cabbage were examined to determine the types of lactic acid bacteria that exist in the leaves. Different types of LAB will produce different types of silage fermentation, which is the fermentation of the leafy foliage. Silage fermentation is an anaerobic reaction that reduces sugars to fermentation byproducts like lactic acid. | 1 | Applied and Interdisciplinary Chemistry |
Deuterium is produced for industrial, scientific and military purposes, by starting with ordinary water—a small fraction of which is naturally-occurring heavy water—and then separating out the heavy water by the Girdler sulfide process, distillation, or other methods.
In theory, deuterium for heavy water could be created in a nuclear reactor, but separation from ordinary water is the cheapest bulk production process.
The world's leading supplier of deuterium was Atomic Energy of Canada Limited until 1997, when the last heavy water plant was shut down. Canada uses heavy water as a neutron moderator for the operation of the CANDU reactor design.
Another major producer of heavy water is India. All but one of India's atomic energy plants are pressurised heavy water plants, which use natural (i.e., not enriched) uranium. India has eight heavy water plants, of which seven are in operation. Six plants, of which five are in operation, are based on D–H exchange in ammonia gas. The other two plants extract deuterium from natural water in a process that uses hydrogen sulfide gas at high pressure.
While India is self-sufficient in heavy water for its own use, India also exports reactor-grade heavy water. | 0 | Theoretical and Fundamental Chemistry |
Chromatography is a method chemists use to separate compounds. This type of filter paper has specific water flow rate and absorption speed to maximize the result of paper chromatography. The absorption speed of this type of filter paper is from 6 cm to 18 cm and the thickness is from 0.17 mm from 0.93 mm. | 0 | Theoretical and Fundamental Chemistry |
The main advantages of excimer lamps over other sources of UV and VUV radiation are as follows:
* high average specific power of UV radiation (up to 1 Watt per cubic centimeter of active medium);
* high energy of an emitted photon (from 3.5 to 11.5 eV);
* quasimonochromatic radiation with the spectral full-width at half maximum from 2 to 15 nm;
* high power spectral density of UV radiation;
* choice of the wavelength of the spectral maximum of UV radiation for specific purposes (see table);
* availability of multi-wave UV radiation owing to simultaneous excitation of several kinds of working excimer molecules;
* absence of visible and IR radiation;
* instant achievement of the operating mode;
* low heating of radiating surface;
* absence of mercury. | 0 | Theoretical and Fundamental Chemistry |
Longuet-Higgins and E. W. Abrahamson showed that the Woodward–Hoffmann rules can best be derived by examining the correlation diagram of a given reaction. A symmetry element is a point of reference (usually a plane or a line) about which an object is symmetric with respect to a symmetry operation. If a symmetry element is present throughout the reaction mechanism (reactant, transition state, and product), it is called a conserved symmetry element. Then, throughout the reaction, the symmetry of molecular orbitals with respect to this element must be conserved. That is, molecular orbitals that are symmetric with respect to the symmetry element in the starting material must be correlated to (transform into) orbitals symmetric with respect to that element in the product. Conversely, the same statement holds for antisymmetry with respect to a conserved symmetry element. A molecular orbital correlation diagram correlates molecular orbitals of the starting materials and the product based upon conservation of symmetry. From a molecular orbital correlation diagram one can construct an electronic state correlation diagram that correlates electronic states (i.e. ground state, and excited states) of the reactants with electronic states of the products. Correlation diagrams can then be used to predict the height of transition state barriers.
Although orbital "symmetry" is used as a tool for sketching orbital and state correlation diagrams, the absolute presence or absence of a symmetry element is not critical for the determination of whether a reaction is allowed or forbidden. That is, the introduction of a simple substituent that formally disrupts a symmetry plane or axis (e.g., a methyl group) does not generally affect the assessment of whether a reaction is allowed or forbidden. Instead, the symmetry present in an unsubstituted analog is used to simplify the construction of orbital correlation diagrams and avoid the need to perform calculations. Only the phase relationships between orbitals are important when judging whether a reaction is "symmetry"-allowed or forbidden. Moreover, orbital correlations can still be made, even if there are no conserved symmetry elements (e.g., 1,5-sigmatropic shifts and ene reactions). For this reason, the Woodward–Hoffmann, Fukui, and Dewar–Zimmerman analyses are equally broad in their applicability, though a certain approach may be easier or more intuitive to apply than another, depending on the reaction one wishes to analyze. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, crystallography, and materials science, the coordination number, also called ligancy, of a central atom in a molecule or crystal is the number of atoms, molecules or ions bonded to it. The ion/molecule/atom surrounding the central ion/molecule/atom is called a ligand. This number is determined somewhat differently for molecules than for crystals.
For molecules and polyatomic ions the coordination number of an atom is determined by simply counting the other atoms to which it is bonded (by either single or multiple bonds). For example, [Cr(NH)ClBr] has Cr as its central cation, which has a coordination number of 6 and is described as hexacoordinate. The common coordination numbers are 4, 6 and 8. | 0 | Theoretical and Fundamental Chemistry |
Electrophilic alkylating agents deliver the equivalent of an alkyl cation. Alkyl halides are typical alkylating agents. Trimethyloxonium tetrafluoroborate and triethyloxonium tetrafluoroborate are particularly strong electrophiles due to their overt positive charge and an inert leaving group (dimethyl or diethyl ether). Dimethyl sulfate is intermediate in electrophilicity. | 0 | Theoretical and Fundamental Chemistry |
Dimethylallyl pyrophosphate (DMAPP; or alternatively, dimethylallyl diphosphate (DMADP); also isoprenyl pyrophosphate) is an isoprenoid precursor. It is a product of both the mevalonate pathway and the MEP pathway of isoprenoid precursor biosynthesis. It is an isomer of isopentenyl pyrophosphate (IPP) and exists in virtually all life forms. The enzyme isopentenyl pyrophosphate isomerase catalyzes isomerization between DMAPP and IPP.
In the mevalonate pathway DMAPP is synthesised from mevalonic acid. In contrast, DMAPP is synthesised from HMBPP in the MEP pathway.
At present, it is believed that there is crossover between the two pathways in organisms
that use both pathways to create terpenes and terpenoids, such as in plants, and that DMAPP is the crossover product. | 1 | Applied and Interdisciplinary Chemistry |
Video spectroscopy combines spectroscopic measurements with video technique. This technology has resulted from recent developments in hyperspectral imaging. A video capable imaging spectrometer can work like a camcorder and provide full frame spectral images in real-time that enables advanced (vehicle based) mobility and hand-held imaging spectroscopy. Unlike hyperspectral line scanners, a video spectrometer can spectrally capture randomly and quickly moving objects and processes. The product of a conventional hyperspectral line scanner has typically been called a hyperspectral data cube. A video spectrometer produces a spectral image data series at much higher speeds (1 ms) and frequencies (25 Hz) that is called a hyperspectral video. This technology can initiate novel solutions and challenges in spectral tracking, field spectroscopy, spectral mobile mapping, real-time spectral monitoring and many other applications. | 0 | Theoretical and Fundamental Chemistry |
CIP is commonly used for cleaning bioreactors, fermenters, mix vessels, and other equipment used in biotech manufacturing, pharmaceutical manufacturing and food and beverage manufacturing. CIP is performed to remove or obliterate previous mammalian cell culture batch components. It is used to remove in-process residues, control bioburden, and reduce endotoxin levels within processing equipment and systems. Residue removal is accomplished during CIP with a combination of heat, chemical action, and turbulent flow.
The U.S. Food and Drug Administration published a CIP regulation in 1978 applicable to pharmaceutical manufacturing. The regulation states, "Equipment and utensils shall be cleaned, maintained, and sanitized at appropriate intervals to prevent malfunctions or contamination that would alter the safety, identity, strength, quality or purity of the drug product beyond the official or other established requirements."
Repeatable, reliable, and effective cleaning is of the utmost importance in a manufacturing facility. Cleaning procedures are validated to demonstrate that they are effective, reproducible, and under control. In order to adequately clean processing equipment, the equipment must be designed with smooth stainless steel surfaces and interconnecting piping that has cleanable joints. The chemical properties of the cleaning agents must properly interact with the chemical and physical properties of the residues being removed.
A typical CIP cycle consists of many steps which often include (in order):
* Pre-rinse with WFI (water for injection) or PW (purified water) which is performed to wet the interior surface of the tank and remove residue. It also provides a non-chemical pressure test of the CIP flow path.
* Caustic solution single pass flush through the vessel to drain. Caustic is the main cleaning solution.
* Caustic solution re-circulation through the vessel.
* Intermediate WFI or PW rinse
* Acid solution wash – used to remove mineral precipitates and protein residues.
* Final rinse with WFI or PW – rinses to flush out residual cleaning agents.
* disinfectant solution wash or hot water circulation to kill all microbes. The disinfectant can be cold disinfectant like [https://www.ecocaretech.com/peracetic-acid Eko Power PAA Sterized Forte] which peractic Acid which is approved as no-rinse disinfectant if used as per the manufacturer recommendation.
* Final air blow – used to remove moisture remaining after CIP cycle.
Critical parameters must be met and remain within the specification for the duration of the cycle. If the specification is not reached or maintained, cleaning will not be ensured and will have to be repeated. Critical parameters include temperature, flow rate/supply pressure, chemical concentration, chemical contact time, and final rinse conductivity (which shows that all cleaning chemicals have been removed). | 1 | Applied and Interdisciplinary Chemistry |
The purine nucleotide cycle occurs in the cytosol (a gel-like substance) of the sarcoplasm of skeletal muscle, and in the myocyte's cytosolic compartment of the cytoplasm of cardiac and smooth muscle. The cycle occurs when ATP reservoirs run low (ADP > ATP), such as strenuous exercise, fasting or starvation.
Proteins catabolize into amino acids, and amino acids are precursors for purines, nucleotides and nucleosides which are used in the purine nucleotide cycle. The amino acid glutamate is used to neutralize the ammonia produced when AMP is converted into IMP. Another amino acid, aspartate, is used along with IMP to produce S-AMP in the cycle. Skeletal muscle contains amino acids for use in catabolism, known as the free amino acid pool; however, inadequate carbohydrate supply and/or strenuous exercise requires protein catabolism to sustain the free amino acids.
When the phosphagen system (ATP-PCr) has been depleted of phosphocreatine (creatine phosphate), the purine nucleotide cycle also helps to sustain the myokinase reaction by reducing accumulation of AMP produced after muscle contraction in the below reaction.
During muscle contraction:
: HO + ATP → H + ADP + P (Mg assisted, utilization of ATP for muscle contraction by ATPase)
: H + ADP + CP → ATP + Creatine (Mg assisted, catalyzed by creatine kinase, ATP is used again in the above reaction for continued muscle contraction)
: 2 ADP → ATP + AMP (catalyzed by adenylate kinase/myokinase when CP is depleted, ATP is again used for muscle contraction)
Muscle at rest:
: ATP + Creatine → H + ADP + CP (Mg assisted, catalyzed by creatine kinase)
: ADP + P → ATP (during anaerobic glycolysis and oxidative phosphorylation)
AMP can dephosphorylate to adenosine and diffuse out of the cell; the purine nucleotide cycle may therefore also reduce the loss of adenosine from the cell since nucleosides permeate cell membranes, whereas nucleotides do not. | 1 | Applied and Interdisciplinary Chemistry |
In condensed matter physics and inorganic chemistry, the cation-anion radius ratio can be used to predict the crystal structure of an ionic compound based on the relative size of its atoms. It is defined as the ratio of the ionic radius of the positively charged cation to the ionic radius of the negatively charged anion in a cation-anion compound. Anions are larger than cations. Large sized anions occupy lattice sites, while small sized cations are found in voids.
In a given structure, the ratio of cation radius to anion radius is called the radius ratio. This is simply given by . | 0 | Theoretical and Fundamental Chemistry |
A direct fluorescent antibody (DFA or dFA), also known as "direct immunofluorescence", is an antibody that has been tagged in a direct fluorescent antibody test. Its name derives from the fact that it directly tests the presence of an antigen with the tagged antibody, unlike western blotting, which uses an indirect method of detection, where the primary antibody binds the target antigen, with a secondary antibody directed against the primary, and a tag attached to the secondary antibody.
Commercial DFA testing kits are available, which contain fluorescently labelled antibodies, designed to specifically target unique antigens present in the bacteria or virus, but not present in mammals (Eukaryotes). This technique can be used to quickly determine if a subject has a specific viral or bacterial infection.
In the case of respiratory viruses, many of which have similar broad symptoms, detection can be carried out using nasal wash samples from the subject with the suspected infection. Although shedding cells in the respiratory tract can be obtained, it is often in low numbers, and so an alternative method can be adopted where compatible cell culture can be exposed to infected nasal wash samples, so if the virus is present it can be grown up to a larger quantity, which can then give a clearer positive or negative reading.
As with all types of fluorescence microscopy, the correct absorption wavelength needs to be determined in order to excite the fluorophore tag attached to the antibody, and detect the fluorescence given off, which indicates which cells are positive for the presence of the virus or bacteria being detected.
Direct immunofluorescence can be used to detect deposits of immunoglobulins and complement proteins in biopsies of skin, kidney and other organs. Their presence is indicative of an autoimmune disease. When skin not exposed to the sun is tested, a positive direct IF (the so-called Lupus band test) is an evidence of systemic lupus erythematosus. Direct fluorescent antibody can also be used to detect parasitic infections, as was pioneered by Sadun, et al. (1960). | 1 | Applied and Interdisciplinary Chemistry |
When sequencing RNA other than mRNA, the library preparation is modified. The cellular RNA is selected based on the desired size range. For small RNA targets, such as miRNA, the RNA is isolated through size selection. This can be performed with a size exclusion gel, through size selection magnetic beads, or with a commercially developed kit. Once isolated, linkers are added to the 3 and 5 end then purified. The final step is cDNA generation through reverse transcription. | 1 | Applied and Interdisciplinary Chemistry |
The usefulness of TD Diffuse optics lies in its ability to continually and noninvasive monitor optical properties of tissue. Making it a powerful diagnostic tool for long-term bedside monitoring in infants and adults alike. It has already been demonstrated that TD diffuse optics can be successfully applied to various biomedical applications such as cerebral monitoring, optical mammography, muscle monitoring, etc. | 0 | Theoretical and Fundamental Chemistry |
Solar cells are commonly encapsulated in a transparent polymeric resin to protect the delicate solar cell regions for coming into contact with moisture, dirt, ice, and other conditions expected either during operation or when used outdoors. The encapsulants are commonly made from polyvinyl acetate or glass. Most encapsulants are uniform in structure and composition, which increases light collection owing to light trapping from total internal reflection of light within the resin. Research has been conducted into structuring the encapsulant to provide further collection of light. Such encapsulants have included roughened glass surfaces, diffractive elements, prism arrays, air prisms, v-grooves, diffuse elements, as well as multi-directional waveguide arrays. Prism arrays show an overall 5% increase in the total solar energy conversion. Arrays of vertically aligned broadband waveguides provide a 10% increase at normal incidence, as well as wide-angle collection enhancement of up to 4%, with optimized structures yielding up to a 20% increase in short circuit current. Active coatings that convert infrared light into visible light have shown a 30% increase. Nanoparticle coatings inducing plasmonic light scattering increase wide-angle conversion efficiency up to 3%. Optical structures have also been created in encapsulation materials to effectively "cloak" the metallic front contacts. | 0 | Theoretical and Fundamental Chemistry |
The structure of a polymeric material can be described at different length scales, from the sub-nm length scale up to the macroscopic one. There is in fact a hierarchy of structures, in which each stage provides the foundations for the next one.
The starting point for the description of the structure of a polymer is the identity of its constituent monomers. Next, the microstructure essentially describes the arrangement of these monomers within the polymer at the scale of a single chain. The microstructure determines the possibility for the polymer to form phases with different arrangements, for example through crystallization, the glass transition or microphase separation.
These features play a major role in determining the physical and chemical properties of a polymer. | 0 | Theoretical and Fundamental Chemistry |
The Ford viscosity cup is a simple gravity device that permits the timed flow of a known volume of liquid passing through an orifice located at the bottom. Under ideal conditions, this rate of flow would be proportional to the kinematic viscosity (expressed in stokes and centistokes) that is dependent upon the specific gravity of the draining liquid. However, the conditions in a simple flow cup are seldom ideal for making true measurements of viscosity. It is important when using a Ford Cup and when retesting liquids that the temperature of the cup and the liquid is maintained, as ambient temperature makes a significant difference to viscosity and thus flow rate.
Many other types of flow cups are used, depending on the industry or region:
* Din Cup 4 mm, standard DIN 53211 (cancelled)
* ISO Cup 2–6, 8 mm, standard ISO 2431
* AFNOR Cup 2, 4–6, 8 mm, standard NF T30-014
* ASTM Cup 1–5, standard ASTM D1200 | 1 | Applied and Interdisciplinary Chemistry |
The pH of an alkaline soil can be reduced by adding acidifying agents or acidic organic materials. Elemental sulfur (90–99% S) has been used at application rates of – it slowly oxidizes in soil to form sulfuric acid. Acidifying fertilizers, such as ammonium sulfate, ammonium nitrate and urea, can help to reduce the pH of a soil because ammonium oxidises to form nitric acid. Acidifying organic materials include peat or sphagnum peat moss.
However, in high-pH soils with a high calcium carbonate content (more than 2%), it can be very costly and/or ineffective to attempt to reduce the pH with acids. In such cases, it is often more efficient to add phosphorus, iron, manganese, copper and/or zinc instead, because deficiencies of these nutrients are the most common reasons for poor plant growth in calcareous soils. | 0 | Theoretical and Fundamental Chemistry |
Calculations of the IMFP are mostly based on the algorithm (full Penn algorithm, FPA) developed by Penn, experimental optical constants or calculated optical data (for compounds). The FPA considers an inelastic scattering event and the dependence of the energy-loss function (EFL) on momentum transfer which describes the probability for inelastic scattering as a function of momentum transfer. | 0 | Theoretical and Fundamental Chemistry |
Synthetic zeolites have complex structures and examples (with structural formulae) are:
* NaAlSiO·27HO, zeolite A (Linde type A sodium form, NaA), used in laundry detergents
* NaAlSiO·16HO, Analcime, IUPAC code ANA
* NaAlSiO·q HO, Losod
* NaAlSiO·518HO, Linde type N | 0 | Theoretical and Fundamental Chemistry |
Coupling of RNA polymerase II (pol II) transcription can influence processing reactions in three ways.
# localization
#* positions mRNA processing factors at the elongation complex, which raises their local concentration in the vicinity of the nascent transcript
# kinetic coupling
#* the rate of transcript can have profound effects on RNA folding and the assembly of RNA-protein complexes
# allosteric
#* contact between the pol II elongation complex and mRNA processing factors can allosterically inhibit or activate mRNA processing factors | 1 | Applied and Interdisciplinary Chemistry |
In general, EPIC-seq analysis results showed a significant correlation between the inspected biological effect and the developed score. For the classification tasks Area Under the ROC (receiver operating characteristic curve) Curve (AUC) scores were over 90% with a sufficient significance interval. Also, for these tasks, cfDNA levels did not change the performance unfavourably even when the levels were below 1%. So, the method shows a good robustness against cfDNA levels as well. Finally, EPIC-seq did not show any significant changes under different pre-analytical factors, which proves that the method is robust under different circumstances that can be caused by the instruments and tools used before the analysis. | 1 | Applied and Interdisciplinary Chemistry |
The Migma device is perhaps the first significant attempt to solve the recirculation problem. It uses a storage system that was, in effect, an infinite number of storage rings arranged at different locations and angles. This is not done by added components or hardware configurations, but via careful arrangement of the magnetic fields within a wide but flat cylindrical vacuum chamber. Only ions undergoing very high angle scattering events would be lost, and calculations suggest that the rate of these events was such that any given ion would pass through the reaction area 10 times before scattering out. This would be enough to sustain positive energy output.
Several Migma devices were built and showed some promise, but it did not progress beyond moderately sized devices. Several theoretical concerns were raised based on space charge limit considerations, which suggested that increasing the density of the fuel to useful levels would require enormous magnets to confine it. During funding rounds the system became mired in an acrimonious debate with the various energy agencies and further development ended in the 1980s. | 0 | Theoretical and Fundamental Chemistry |
After his return to England in 1815, Davy began experimenting with lamps that could be used safely in coal mines. The Revd Dr Robert Gray of Bishopwearmouth in Sunderland, founder of the Society for Preventing Accidents in Coalmines, had written to Davy suggesting that he might use his extensive stores of chemical knowledge to address the issue of mining explosions caused by firedamp, or methane mixed with oxygen, which was often ignited by the open flames of the lamps then used by miners. Incidents such as the Felling mine disaster of 1812 near Newcastle, in which 92 men were killed, not only caused great loss of life among miners but also meant that their widows and children had to be supported by the public purse. The Revd Gray and a fellow clergyman also working in a north-east mining area, the Revd John Hodgson of Jarrow, were keen that action should be taken to improve underground lighting and especially the lamps used by miners.
Davy conceived of using an iron gauze to enclose a lamps flame, and so prevent the methane burning inside the lamp from passing out to the general atmosphere. Although the idea of the safety lamp had already been demonstrated by William Reid Clanny and by the then unknown (but later very famous) engineer George Stephenson, Davys use of wire gauze to prevent the spread of flame was used by many other inventors in their later designs. George Stephenson's lamp was very popular in the north-east coalfields, and used the same principle of preventing the flame reaching the general atmosphere, but by different means. Unfortunately, although the new design of gauze lamp initially did seem to offer protection, it gave much less light, and quickly deteriorated in the wet conditions of most pits. Rusting of the gauze quickly made the lamp unsafe, and the number of deaths from firedamp explosions rose yet further.
There was some discussion as to whether Davy had discovered the principles behind his lamp without the help of the work of Smithson Tennant, but it was generally agreed that the work of the two men had been independent. Davy refused to patent the lamp, and its invention led to his being awarded the Rumford medal in 1816. | 1 | Applied and Interdisciplinary Chemistry |
Persistent carbenes tend to exist in the singlet, dimerizing when forced into triplet states. Nevertheless, Hideo Tomioka and associates used electron delocalization to produce a comparatively stable triplet carbene (bis(9-anthryl)carbene) in 2001. It has an unusually long half-life of 19 minutes.
Although the figure below shows the two parts of the molecule in one flat plane, molecular geometry puts the two aromatic parts in orthogonal positions with respect to each other.
In 2006 a triplet carbene was reported by the same group with a half-life of 40 minutes. This carbene is prepared by a photochemical decomposition of a diazomethane precursor by 300 nm light in benzene with expulsion of nitrogen gas.
Again the figure below is not an adequate representation of the actual molecular structure: both phenyl rings are positioned orthogonal with respect to each other. The carbene carbon has an sp-hybridisation, the two remaining orthogonal p-orbitals each conjugating with one of the aromatic rings.
Exposure to oxygen (a triplet diradical) converts this carbene to the corresponding benzophenone. The diphenylmethane compound is formed when it is trapped by cyclohexa-1,4-diene. As with the other carbenes, this species contains large bulky substituents, namely bromine and the trifluoromethyl groups on the phenyl rings, that shield the carbene and prevent or slow down the process of dimerization to a 1,1,2,2-tetra(phenyl)alkene. Based on computer simulations, the distance of the divalent carbon atom to its neighbors is claimed to be 138 picometers with a bond angle of 158.8°. The planes of the phenyl groups are almost at right angles to each other (the dihedral angle being 85.7°). | 0 | Theoretical and Fundamental Chemistry |
Etoricoxib, that is used for patients with chronic arthropathies and musculoskeletal and dental pain, is absorbed moderately when given orally. A study on its pharmacokinetics showed that the plasma peak concentration of etoricoxib occurs after approximately 1 hour. It has shown to be extensively bound to plasma albumin (about 90%), and has an apparent volume of distribution (V) of 120 L in humans. The area under the plasma concentration-time curve (AUC) increases in proportion to increased dosage (5–120 mg). The elimination half-life is about 20 hours in healthy individuals, and such long half-life enables the choice to have once-daily dosage. Etoricoxib, like the other coxibs, is excreted in urine and feces and also metabolized in likewise manner. CYP3A4 is mostly responsible for biotransformation of etoricoxib to carboxylic acid metabolite, but a non CYP450 metabolism pathway to glucuronide metabolite is also at hand. A very small portion of etoricoxib (<1%) is eliminated unchanged in the urine. Patients with chronic kidney disease do not appear to have different plasma concentration curve (AUC) compared to healthy individuals. It has though been reported that patients with moderate hepatic impairment have increased plasma concentration curve (AUC) by approximately 40%. It has been stated that further study is necessary to describe precisely the relevance of pharmacokinetic properties in terms of the clinical benefits and risks of etoricoxib compared to other clinical options. | 1 | Applied and Interdisciplinary Chemistry |
As evidenced by a decreased fluorescence, OCP in its red form is capable of dissipating absorbed light energy from the phycobilisome antenna complex. According to Rakhimberdieva and coworkers, about 30-40% of the energy absorbed by phycobilisomes does not reach the reaction centers when the carotenoid-induced NPQ is active.
The exact mechanism and quenching site in both the carotenoid as well as the phycobilisome still remain uncertain. The linker polypeptide ApcE in the allophycocyanin (APC) core of the phycobilisomes is known to be important, but is not the site of quenching. Several lines of evidence suggest that it is the 660 nm fluorescence emission band of the APC core which is quenched by OCP.
The temperature dependence of the rate of fluorescence quenching is similar to that of soluble protein folding, supporting the hypothesis that OCP slightly unfolds when it converts to OCP. | 0 | Theoretical and Fundamental Chemistry |
ATSDR prides itself on using "the best science." And in 2003, BBC News described ATSDR as "widely regarded as the world's leading agency on public health and the environment."
However, ATSDR has also been the focus of scrutiny from Congress and other groups. Much of the criticism is due to the fact that the agency has been overtasked yet understaffed and underfunded for much of its history.
* In August 1991, the General Accounting Office (now the Government Accountability Office) published a report that faulted the quality of ATSDR's original public health assessments and questioned their usefulness. It also placed part of the blame on the deadlines and requirements that Congress imposed with SARA: "SARA’s requirement that ATSDR quickly assess 951 Superfund sites came at a time when the agency was still relatively new and ... not staffed or organized for the job." The report also noted that after meeting the SARA deadline, ATSDR was able to increase the rigor of its public health assessments.
* In May 1992, the Environmental Health Network and the National Toxics Campaign Fund published "Inconclusive by Design," a report which noted structural limitations to the work of CDC and ATSDR.
* In April 2008, the United States House of Representatives Committee on Science and Technology Subcommittee on Investigations and Oversight held a hearing on formaldehyde exposures in trailers that the Federal Emergency Management Agency (FEMA) provided as temporary housing to people displaced by Hurricane Katrina. A report based on the hearing, issued by the subcommittee's Democratic majority staff in September 2008, noted shortcomings in the agency’s original health consultation that examined the health risks of formaldehyde in the FEMA trailers.
* In March 2009, the Democratic majority staff of the Subcommittee on Investigations and Oversight issued another report on ATSDR, which called for leadership changes within the agency. The report stated: "Time and time again ATSDR appears to avoid clearly and directly confronting the most obvious toxic culprits that harm the health of local communities throughout the nation. Instead, they deny, delay, minimize, trivialize or ignore legitimate concerns and health considerations of local communities and well respected scientists and medical professionals."
In the March 12, 2009, congressional hearing, the subcommittee chairman, Congressman Brad Miller, characterized ATSDR as keen to "please industries and government agencies" and referred to ATSDRs reports as "jackleg assessments saying not to worry." In defense of ATSDRs work, director Howard Frumkin noted that ATSDR's staff has declined from 500 to about 300, and that often communities expect "definitive answers about the links between exposures and illnesses," but expectations can be unmet due to scientific uncertainty. However, Dr. Frumkin also acknowledged the possibility that some assessments did not use the best data or monitoring techniques. | 1 | Applied and Interdisciplinary Chemistry |
The application of nanoparticles (NPs) are one of novel promising techniques to target biofilms due to their high surface-area-to-volume ratio, their ability to penetrate to the deeper layers of biofilms and the capacity to releasing antimicrobial agents in a controlled way. Studying NP-EPS interactions could provide deeper understanding on how to develop more effective nanoparticles. "smart release" nanocarriers that can penetrate biofilms and be triggered by pathogenic microenvironments to deliver drugs or multifunctional compounds, such as catalytic nanoparticles to aptamers, dendrimers, and bioactive peptides) have been developed to disrupt the EPS and the viability or metabolic activity of the embedded bacteria. Some factors that would alter the potentials of the NP to transport antimicrobial agents into the biofilm include physicochemical interactions of the NPs with EPS components, the characteristics of the water spaces (pores) within the EPS matrix and the EPS matrix viscosity. Size and surface properties (charge and functional groups) of the NPs are the major determinants of the penetration in and the interaction with the EPS. Another potential antibiofilm strategy is phage therapy. Bacteriophages, viruses that invade specific bacterial host cells, were suggested to be effective agents in penetrating biofilms. In order to reach the maximum efficacy to eradicate biofilms, therapeutic strategies need to target both the biofilm matrix components as well as the embedded microorganisms to target the complex biofilm microenvironment. | 1 | Applied and Interdisciplinary Chemistry |
VMAT research began in 1958 when Nils-Åke Hillarp discovered secretory vesicles. In the 1970s, scientists like Arvid Carlsson recognized the need to understand how transport systems and ion gradients work in different organisms in order to explore new treatment options such as reserpine (RES). Researchers discovered inhibitors that blocked the uptake of neurotransmitters into vesicles, suggesting the existence of VMATs. A decade later, molecular genetic tools have improved methods for protein identification. Scientists have used these tools to analyze DNA and amino acid sequences, and discovered that transporters in bacteria and humans were very similar, which emphasized the importance and universality of transporters. The transporters were first structurally identified by cloning VMATs in rats. The VMAT were first isolated and purified in bovine chromaffin granules, in both its native and denatured forms. | 1 | Applied and Interdisciplinary Chemistry |
In the basic electroforming process, an electrolytic bath is used to deposit nickel or other electroformable metal onto a conductive surface of a model (mandrel). Once the deposited material has been built up to the desired thickness, the electroform is parted from the substrate. This process allows precise replication of the mandrel surface texture and geometry at low unit cost with high repeatability and excellent process control.
If the mandrel is made of a non-conductive material it can be coated with a thin conductive layer. | 1 | Applied and Interdisciplinary Chemistry |
Bloch was born in Zürich, Switzerland to Jewish parents Gustav and Agnes Bloch. Gustav Bloch, his father, was financially unable to attend University and worked as a wholesale grain dealer in Zürich. Gustav moved to Zürich from Moravia in 1890 to become a Swiss citizen. Their first child was a girl born in 1902 while Felix was born three years later.
Bloch entered public elementary school at the age of six and is said to have been teased, in part because he "spoke Swiss German with a somewhat different accent than most members of the class". He received support from his older sister during much of this time, but she died at the age of twelve, devastating Felix, who is said to have lived a "depressed and isolated life" in the following years. Bloch learned to play the piano by the age of eight and was drawn to arithmetic for its "clarity and beauty". Bloch graduated from elementary school at twelve and enrolled in the Cantonal Gymnasium in Zürich for secondary school in 1918. He was placed on a six-year curriculum here to prepare him for University. He continued his curriculum through 1924, even through his study of engineering and physics in other schools, though it was limited to mathematics and languages after the first three years. After these first three years at the Gymnasium, at age fifteen Bloch began to study at the Eidgenössische Technische Hochschule (ETHZ), also in Zürich. Although he initially studied engineering he soon changed to physics. During this time he attended lectures and seminars given by Peter Debye and Hermann Weyl at ETH Zürich and Erwin Schrödinger at the neighboring University of Zürich. A fellow student in these seminars was John von Neumann.
Bloch graduated in 1927, and was encouraged by Debye to go to Leipzig to study with Werner Heisenberg. Bloch became Heisenberg's first graduate student, and gained his doctorate in 1928. His doctoral thesis established the quantum theory of solids, using waves to describe electrons in periodic lattices.
On March 14, 1940, Bloch married Lore Clara Misch (1911–1996), a fellow physicist working on X-ray crystallography, whom he had met at an American Physical Society meeting. They had four children, twins George Jacob Bloch and Daniel Arthur Bloch (born January 15, 1941), son Frank Samuel Bloch (born January 16, 1945), and daughter Ruth Hedy Bloch (born September 15, 1949). | 0 | Theoretical and Fundamental Chemistry |
If two substituents on an atom are geometric isomers of each other, the Z-isomer has higher priority than the E-isomer. A stereoisomer that contains two higher priority groups on the same face of the double bond (cis) is classified as "Z." The stereoisomer with two higher priority groups on opposite sides of a carbon-carbon double bond (trans) is classified as "E." | 0 | Theoretical and Fundamental Chemistry |
Big dynorphin is an endogenous opioid peptide of the dynorphin family that is composed of both dynorphin A and dynorphin B. Big dynorphin has the amino acid sequence: Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Ile-Arg-Pro-Lys-Leu-Lys-Trp-Asp-Asn-Gln-Lys-Arg-Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Gln-Phe-Lys-Val-Val-Thr. It has nociceptive and anxiolytic-like properties, as well as effects on memory in mice.
Big dynorphin is a principal endogenous, agonist at the human kappa-opioid receptor. | 1 | Applied and Interdisciplinary Chemistry |
5β-coprostanol has a low water solubility, and consequently a high octanol-water partition coefficient . In other words, 5β-coprostanol has an affinity nearly 1 billion times higher for octanol than for water. This means that in most environmental systems, 5β-coprostanol will be associated with the solid phase. | 1 | Applied and Interdisciplinary Chemistry |
In general, there are two different formats of genome-wide CRISPR knockout screens: arrayed and pooled. In an arrayed screen, each well contains a specific and known sgRNA targeting a specific gene. Since the sgRNA responsible for each phenotype is known based on well location, phenotypes can be identified and analysed without requiring genetic sequencing. This format allows for the measurement of more specific cellular phenotypes, perhaps by fluorescence or luminescence, and allows researchers to use more library types and delivery methods. For large-scale LOF screens, however, arrayed formats are considered low-efficiency, and expensive in terms of financial and material resources because cell populations have to be isolated and cultured individually.
In a pooled screen, cells grown in a single vessel are transduced in bulk with viral vectors collectively containing the entire sgRNA library. To ensure that the amount of cells infected by more than one sgRNA-containing particle is limited, a low multiplicity of infection (MOI) (typically 0.3-0.6) is used. Evidence so far has suggested that each sgRNA should be represented in a minimum of 200 cells. Transduced cells will be selected for, followed by positive or negative selection for the phenotype of interest, and genetic sequencing will be necessary to identify the integrated sgRNAs. | 1 | Applied and Interdisciplinary Chemistry |
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