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The Imd pathway appears to have evolved in the last common ancestor of centipedes and insects. However certain lineages of insects have since lost core components of Imd signalling. The first-discovered and most famous example is the pea aphid Acyrthosiphon pisum. It is thought that plant-feeding aphids have lost Imd signalling as they bear a number of bacterial endosymbionts, including both nutritional symbionts that would be disrupted by aberrant expression of antimicrobial peptides, and defensive symbionts that cover for some of the immune deficiency caused by loss of Imd signalling. It has also been suggested that antimicrobial peptides, the downstream components of Imd signalling, may be detrimental to fitness and lost by insects with exclusively plant-feeding ecologies. | 1 | Applied and Interdisciplinary Chemistry |
Symmetry–adapted coordinates may be created by applying a projection operator to a set of internal coordinates. The projection operator is constructed with the aid of the character table of the molecular point group. For example, the four (un–normalized) C–H stretching coordinates of the molecule ethene are given by
where are the internal coordinates for stretching of each of the four C–H bonds.
Illustrations of symmetry–adapted coordinates for most small molecules can be found in Nakamoto. | 0 | Theoretical and Fundamental Chemistry |
Norvaline is used as a dietary supplement for bodybuilding.
Recently, it was suggested in the treatment of Alzheimer's disease. | 1 | Applied and Interdisciplinary Chemistry |
Observations of supercritical adsorption reported before 1930 was covered in studies by McBain and Britton. All of the important articles on this subject published between 1930 and 1966 have been reviewed by Menon. During the last 20 years, a growing interest in supercritical adsorption research under the impetus of the quest for clean alternative fuels has been observed. Considerable progress has been made in both adsorption measurement techniques and molecular simulation of adsorption on computers, rendering new insights into the nature of supercritical adsorption. | 0 | Theoretical and Fundamental Chemistry |
An ectodomain is the domain of a membrane protein that extends into the extracellular space (the space outside a cell). Ectodomains are usually the parts of proteins that initiate contact with surfaces, which leads to signal transduction. A notable example of an ectodomain is the S protein, commonly known as the spike protein, of the viral particle responsible for the COVID-19 pandemic. The ectodomain region of the spike protein (S) is essential for attachment and eventual entry of the viral protein into the host cell.
Ectodomains play a crucial part in the signaling pathways of viruses. Recent findings have indicated that certain antibodies including the anti-receptor binding domain (anti-RBD) or anti-spike ectodomain (anti-ECD) IgG titers can act as virus neutralization titers (VN titers) which can be identified in individuals with diseases, dyspnea and hospitalizations. In perspective of severe acute respiratory syndrome corona virus 2 (SARS-Cov-2) these specific ectodomains may detect antibody efficacy against SARS-Cov-2, in which VN titers can classify eligible plasma donors. Protective measures against diseases and respiratory conditions can further be advanced through ongoing research on ectodomains. Ectodomain's play a crucial part in the signaling pathways of viruses. In perspective of severe acute respiratory syndrome corona virus 2 (SARS-Cov-2) these specific ectodomains may detect antibody efficacy against SARS-Cov-2, in which VN titers can classify eligible plasma donors. Protective measures against diseases and respiratory conditions can further be advanced through ongoing research on ectodomains.
Ectodomains also interact with membrane systems inducing vesicle aggregation, lipid mixing and liposome leakage which provides information as to how certain viruses spread infection throughout the cellular domain. Specifically, the hepatitis C virus (HCV) utilize a fusion process in which the ectodomain of HCV E2 envelope protein confers fusogenic properties to membrane systems implying HCV infection proceeds throughout the cell through receptor mediated endocytosis. These findings in the role of the ectodomains interacting with target membranes give insight into virus destabilization and mechanism of the fusion of viral and cellular membrane which is yet to be further characterized. | 1 | Applied and Interdisciplinary Chemistry |
Compounds with carbon phosphorus(III) multiple bonds are called phosphaalkenes (RC=PR) and phosphaalkynes (RC≡P). They are similar in structure, but not in reactivity, to imines (RC=NR) and nitriles (RC≡N), respectively. In the compound phosphorine, one carbon atom in benzene is replaced by phosphorus. Species of this type are relatively rare but for that reason are of interest to researchers. A general method for the synthesis of phosphaalkenes is by 1,2-elimination of suitable precursors, initiated thermally or by base such as DBU, DABCO, or triethylamine:
Thermolysis of MePH generates CH=PMe, an unstable species in the condensed phase. | 0 | Theoretical and Fundamental Chemistry |
Cyclins are a group of proteins that activate kinases involved in cell division. The degradation of cyclins is the key step that governs the exit from mitosis and progress into the next cell cycle. Cyclins accumulate in the course the cell cycle, then abruptly disappear just before the anaphase of mitosis. The cyclins are removed via a ubiquitin-mediated proteolytic pathway. | 1 | Applied and Interdisciplinary Chemistry |
Protactinium was first identified in 1913 by Kasimir Fajans and Oswald Helmuth Göhring at the University of Karlsruhe. The new element was named brevium due to the brief half-life of the isotope specific studied, Protactinium-234 (234 Pa).
Fajans and Göhring also worked to identify as many isotopes of the new element as possible, and also to publicize their discovery—a process that was hampered by the beginning of World War I.
In 1914, Göhring was conscripted into the army. Presumably he perished during the war; he is listed as the author of no further scientific articles or publications after 1915.
A stable isotope of this element was discovered in 1918, and thus the name was changed to protoactinium, which was abbreviated in 1949 to its present name, protactinium. | 1 | Applied and Interdisciplinary Chemistry |
The mean lifespan of methane in the atmosphere was estimated in a range between 9.6 years and twelve years. These differences are caused by the uncertainties about hydroxyl radical (-OH) concentrations and formation processes. When -OH reacts with methane, it is removed from the atmosphere, so changes in its concentration would also affect the concentration of methane. An increase in methane emissions greater than the regeneration rate of OH radicals would reduce their concentrations and so increase methane's mean atmospheric lifetime.
The reaction of methane and chlorine atoms acts as a primary sink of Cl atoms and is a primary source of hydrochloric acid (HCl) in the stratosphere.
CH + Cl → CH + HCl
The HCl produced in this reaction leads to catalytic ozone destruction in the stratosphere. | 1 | Applied and Interdisciplinary Chemistry |
Bicyclic molecules are described by IUPAC nomenclature. The root of the compound name depends on the total number of atoms in all rings together, possibly followed by a suffix denoting the functional group with the highest priority. Numbering of the carbon chain always begins at one bridgehead atom (where the rings meet) and follows the carbon chain along the longest path, to the next bridgehead atom. Then numbering is continued along the second longest path and so on. Fused and bridged bicyclic compounds get the prefix bicyclo, whereas spirocyclic compounds get the prefix spiro. In between the prefix and the suffix, a pair of brackets with numerals denotes the number of carbon atoms between each of the bridgehead atoms. These numbers are arranged in descending order and are separated by periods.
For example, the carbon frame of norbornane contains a total of 7 atoms, hence the root name heptane. This molecule has two paths of 2 carbon atoms and a third path of 1 carbon atom between the two bridgehead carbons, so the brackets are filled in descending order: [2.2.1]. Addition of the prefix bicyclo gives the total name bicyclo[2.2.1]heptane.
The carbon frame of camphor also counts 7 atoms, but is substituted with a carbonyl in this case, hence the suffix heptanone. We start with numbering the carbon frame at the bridgehead atom with the highest priority (methyl goes before proton), hence the bridgehead carbon in front gets number 1, the carbonyl gets number 2 and numbering continues along the carbon chain following the longest path, until the doubly substituted top carbon (number 7). Equal to norbornane, this molecule also has two paths of 2 carbon atoms and one path of 1 carbon atom between the two bridgehead carbons, so the numbers within the brackets stay [2.2.1]. Combining the brackets and suffix (now filling in the position of the carbonyl as well) gives us [2.2.1]heptan-2-one. Besides bicyclo, the prefix should also specify the positions of all methyl substituents so the complete, official name becomes 1,7,7-trimethylbicyclo[2.2.1]heptan-2-one.
When naming simple fused bicyclic compounds, the same method as for bridged bicyclic compounds is applied, except the third path between the two bridgehead atoms now consists of zero atoms. Therefore, fused bicyclic compounds have a "0" included in the brackets. For example, decalin is named bicyclo[4.4.0]decane. The numbers are sometimes omitted in unambiguous cases. For example, bicyclo[1.1.0]butane is typically called simply bicyclobutane.
The heterocyclic molecule DABCO has a total of 8 atoms in its bridged structure, hence the root name octane. Here the two bridgehead atoms are nitrogen instead of carbon atoms. Therefore, the official name gets the additional prefix 1,4-diaza and the total name becomes 1,4-diazabicyclo[2.2.2]octane. | 0 | Theoretical and Fundamental Chemistry |
A Dutch biochemist and physicist Anthonie Muller wrote many papers on thermosynthesis since 1983.
He defined thermosynthesis as:
"Biological heat engines working on thermal cycling."
also as:
"Theoretical biological mechanism for free energy gain from thermal cycling, tentatively stated as the energy source for origin of life."
The thermosynthesis concept, biological free energy gain from thermal cycling, is combined with the concept of the RNA World. The resulting overall origin of life model suggests new explanations for the emergence of the genetic code and the ribosome. It is proposed that the first protein named pF(1) obtained the energy to support the RNA World by a thermal variation of F(1) ATP synthases binding change mechanism. It is further proposed that this pF(1) was the single translation product during the emergence of the genetic machinery. During thermal cycling pF(1) condensed many substrates with broad specificity, yielding NTPs and randomly constituted protein and RNA libraries that contained self-replicating RNA. The smallness of pF(1) permitted the emergence of the genetic machinery by selection of RNA that increased the fraction of pF(1)s in the protein library: (1) an amino acids concatenating progenitor of rRNA bound to (2) a chain of positional tRNAs' linked by mutual recognition, and yielded a pF(1) (or its main motif); this positional tRNA set gradually evolved to a set of regular tRNAs functioning according to the genetic code, with concomitant emergence of (3) an mRNA coding for pF(1). | 1 | Applied and Interdisciplinary Chemistry |
Protoplasts can be used to study membrane biology, including the uptake of macromolecules and viruses . These are also used in somaclonal variation.
Protoplasts are widely used for DNA transformation (for making genetically modified organisms), since the cell wall would otherwise block the passage of DNA into the cell. In the case of plant cells, protoplasts may be regenerated into whole plants first by growing into a group of plant cells that develops into a callus and then by regeneration of shoots (caulogenesis) from the callus using plant tissue culture methods. Growth of protoplasts into callus and regeneration of shoots requires the proper balance of plant growth regulators in the tissue culture medium that must be customized for each species of plant. Unlike protoplasts from vascular plants, protoplasts from mosses, such as Physcomitrella patens, do not need phytohormones for regeneration, nor do they form a callus during regeneration. Instead, they regenerate directly into the filamentous protonema, mimicking a germinating moss spore.
Protoplasts may also be used for plant breeding, using a technique called protoplast fusion. Protoplasts from different species are induced to fuse by using an electric field or a solution of polyethylene glycol. This technique may be used to generate somatic hybrids in tissue culture.
Additionally, protoplasts of plants expressing fluorescent proteins in certain cells may be used for Fluorescence Activated Cell Sorting (FACS), where only cells fluorescing a selected wavelength are retained. Among other things, this technique is used to isolate specific cell types (e.g., guard cells from leaves, pericycle cells from roots) for further investigations, such as transcriptomics. | 1 | Applied and Interdisciplinary Chemistry |
Pyroelectric fusion has previously been observed in erbium hydrides. A high-energy beam of deuterium ions generated by pyroelectric crystals was directed at a stationary, room-temperature or target, and fusion was observed.
In previous fusion research, such as inertial confinement fusion (ICF), fuel such as the rarer tritium is subjected to high pressure for a nano-second interval, triggering fusion. In magnetic confinement fusion (MCF), the fuel is heated in a plasma to temperatures much higher than those at the center of the Sun. In LCF, conditions sufficient for fusion are created in a metal lattice that is held at ambient temperature during exposure to high-energy photons. ICF devices momentarily reach densities of 10 cc, while MCF devices momentarily achieve 10.
Lattice confinement fusion requires energetic deuterons and is therefore not cold fusion.
Lattice confinement fusion is used as a method to increase the cathode fuel density of inertial electrostatic fusion devices such as a Farnsworth-Hirsch fusor. This increases the probability of fusion events occurring and therefore the radiation output produced. In applications where fusors are used as X-ray, neutron, or proton radiation source, lattice confinement fusion improves the energy efficiency of the device. | 0 | Theoretical and Fundamental Chemistry |
The Journal of Photochemistry and Photobiology B: Biology is published monthly. The editors are Robert Carpentier and Dominic J. Robinson. Carpentier covers the fields of biophysics, biomolecular spectroscopy, photosynthesis, environmental photobiology, oxygen radicals, DNA repair, and UV-/VIS effects. Robinson covers photomedicine, photodynamic therapy, photosensitisers and dermatology. | 0 | Theoretical and Fundamental Chemistry |
Laser Doppler velocimetry is used in the analysis of vibration of MEMS devices, often to compare the performance of devices such as accelerometers-on-a-chip with their theoretical (calculated) modes of vibration. As a specific example in which the unique features of Laser Doppler velocimetry are important, the measurement of velocity of a MEMS watt balance device has allowed greater accuracy in the measurement of small forces than previously possible, through directly measuring the ratio of this velocity to the speed of light. This is a fundamental, traceable measurement that now allows traceability of small forces to the S.I. System. | 1 | Applied and Interdisciplinary Chemistry |
Durrant's research focuses on a range of photochemical applications including solar cells, solar fuel production and photocatalysis, nanomaterials and plastic electronics. Durrant has authored over 400 publications, focusing on the charge carrier kinetics which determine materials and device function.
Durrant teaches physical chemistry at Imperial College London and is involved in the SPECIFIC Innovation and Knowledge Centre (IKC) at Swansea University. | 0 | Theoretical and Fundamental Chemistry |
Metal-alkene complexes can be viewed as the smallest metallacycles, but they usually are not classified as metallacycles. In the Dewar–Chatt–Duncanson model, one resonance structure for the M(η-alkene) center is the metallacyclopropane. | 0 | Theoretical and Fundamental Chemistry |
The field of oxidative phosphorylation began with the report in 1906 by Arthur Harden of a vital role for phosphate in cellular fermentation, but initially only sugar phosphates were known to be involved. However, in the early 1940s, the link between the oxidation of sugars and the generation of ATP was firmly established by Herman Kalckar, confirming the central role of ATP in energy transfer that had been proposed by Fritz Albert Lipmann in 1941. Later, in 1949, Morris Friedkin and Albert L. Lehninger proved that the coenzyme NADH linked metabolic pathways such as the citric acid cycle and the synthesis of ATP. The term oxidative phosphorylation was coined by in 1939.
For another twenty years, the mechanism by which ATP is generated remained mysterious, with scientists searching for an elusive "high-energy intermediate" that would link oxidation and phosphorylation reactions. This puzzle was solved by Peter D. Mitchell with the publication of the chemiosmotic theory in 1961. At first, this proposal was highly controversial, but it was slowly accepted and Mitchell was awarded a Nobel prize in 1978. Subsequent research concentrated on purifying and characterizing the enzymes involved, with major contributions being made by David E. Green on the complexes of the electron-transport chain, as well as Efraim Racker on the ATP synthase. A critical step towards solving the mechanism of the ATP synthase was provided by Paul D. Boyer, by his development in 1973 of the "binding change" mechanism, followed by his radical proposal of rotational catalysis in 1982. More recent work has included structural studies on the enzymes involved in oxidative phosphorylation by John E. Walker, with Walker and Boyer being awarded a Nobel Prize in 1997. | 1 | Applied and Interdisciplinary Chemistry |
Besides making pioneering contribution in the domain of Soil Science, Dr Mukherjee played a key role in the development of agricultural research and education in the country. Soon after his appointment as Director of the Imperial (now Indian Agricultural Research Institute, New Delhi), in 1945, Dr Mukherjee began to
reorganise the research and educational activities of the Institute in the country as a whole. Under his direction the Institute expanded considerably in terms
of its academic activities and scientific performance. He initiated research in the area of soil-plant studies. Some of the sections he created in the Division of Soil Science and Agricultural Chemistry are Soil Survey, Soil Physics, Agricultural Chemistry, Soil Fertility, Soil Microbiology, Biochemistry, Organic Chemistry and Spectroscopy. Recent expansion of some of the sections such as Soil Survey, Microbiology, Biochemistry, Agricultural Chemicals, Agricultural Physics were credited to him.
The credit for initiating systematic studies on micronutrient elements in soils and plants and also on clay mineralogy of soils with the help of sophisticated instruments and modern techniques goes to him. He initiated work in the Institute on the nutritive value of foods, feeds and fodders, on insecticides and fungicides, and on the chemistry of plant products.
He was the first in the country to lay great emphasis on the importance of soil surveys for agricultural development and underlined the importance of uniformity in the methods of survey, classification and nomenclature of the soils of India. At his suggestion the Ministry of Agriculture, Government of India established in 1949 the Central Committee on Soil Science with him as chairman. The terms and reference of the Committee were practically in conformity with the objectives of the All India Soil and Land Use Survey Organization established in 1956 with 4 regional centres.
The soil map of India revised under his guidance (scale 1" --- 70 miles) showing 20 soil classes was published in 1954. He also developed the concept of the
basic soil regions in the classifications of the soils of India based on similar characteristics of land viz.., the climate, topography, vegetation and soils. | 0 | Theoretical and Fundamental Chemistry |
Classical invariant manifolds are invariant sets in the phase space of an autonomous dynamical system. In contrast,
LCSs are only required to be invariant in the extended phase space. This means that even if the underlying dynamical system is autonomous, the LCSs of the system over the interval will generally be time-dependent, acting as the evolving skeletons of observed coherent trajectory patterns. Figure 2b shows the difference between an attracting LCS and a classic unstable manifold of a saddle point, for evolving times, in an autonomous dynamical system. | 1 | Applied and Interdisciplinary Chemistry |
Mitogens act primarily by influencing a set of proteins which are involved in the restriction of progression through the cell cycle. The G1 checkpoint is controlled most directly by mitogens: further cell cycle progression does not need mitogens to continue. The point where mitogens are no longer needed to move the cell cycle forward is called the "restriction point" and depends on cyclins to be passed. One of the most important of these is TP53, a gene which produces a family of proteins known as p53. It, combined with the Ras pathway, downregulate cyclin D1, a cyclin-dependent kinase, if they are not stimulated by the presence of mitogens. In the presence of mitogens, sufficient cyclin D1 can be produced. This process cascades onwards, producing other cyclins which stimulate the cell sufficiently to allow cell division. While animals produce internal signals that can drive the cell cycle forward, external mitogens can cause it to progress without these signals. | 1 | Applied and Interdisciplinary Chemistry |
Because SuDS describe a collection of systems with similar components or goals, there is a large crossover between SuDS and other terminologies dealing with sustainable urban development. The following are examples generally accepted as components in a SuDS system:
Bioswales
Permeable pavement
Wetlands
Artificial wetlands can be constructed in areas that see large volumes of storm water surges or runoff. Built to replicate shallow marshes, wetlands as BMPs gather and filter water at scales larger than bioswales or rain gardens. Unlike bioswales, artificial wetlands are designed to replicate natural wetlands processes as opposed to having an engineered mechanism within the artificial wetland. Because of this, the ecology of the wetland (soil components, water, vegetation, microbes, sunlight processes, etc.) becomes the primary system to remove pollutants. Water in an artificial wetland tends to be filtered slowly in comparison to systems with mechanized or explicitly engineered components.
Wetlands can be used to concentrate large volumes of runoff from urban areas and neighborhoods. In 2012, the South Los Angeles Wetlands Park was constructed in a densely populated inner-city district as a renovation for a former LA Metro bus yard. The park is designed to capture runoff from surrounding surfaces as well as storm water overflow from the city's current drainage system.
Retention basins
Green roofs | 1 | Applied and Interdisciplinary Chemistry |
The enteric nervous system consists of some one hundred million neurons that are embedded in the peritoneum, the lining of the gastrointestinal tract extending from the esophagus to the anus. These neurons are collected into two plexuses – the myenteric (or Auerbachs) plexus that lies between the longitudinal and the smooth muscle layers, and the submucosal (or Meissners) plexus that lies between the circular smooth muscle layer and the mucosa.
Parasympathetic innervation to the ascending colon is supplied by the vagus nerve. Sympathetic innervation is supplied by the splanchnic nerves that join the celiac ganglia. Most of the digestive tract is innervated by the two large celiac ganglia, with the upper part of each ganglion joined by the greater splanchnic nerve and the lower parts joined by the lesser splanchnic nerve. It is from these ganglia that many of the gastric plexuses arise. | 1 | Applied and Interdisciplinary Chemistry |
At the end of World War II, the Allies occupied Germany and found large stockpiles of chemical weapons that they did not know how to dispose of or deal with. Ultimately, the Allies disposed large quantities of these chemical weapons into the Baltic Sea, including 32 000 tonnes of chemical munitions and chemical warfare agents dumped into the Bornholm Basin, and another 2000 tonnes of chemical weapons in the Gotland Basin.
The majority of these chemical munitions were dumped into the sea while contained in simple wooden crates, leading to a rapid proliferation of chemicals. Chemical Weapons being disposed in the ocean during the 20th century is not unique to the Baltic Sea, and other heavily contaminated areas where disposal occurred are the European, Japanese, Russian, and United States coasts. These chemical weapons dumped in the ocean pose a continual environmental and human health risk, and chemical agents and breakdown products from said agents have been recently been identified in ocean sediment near historical dumping sites. When chemical weapons are dumped or otherwise improperly disposed of, the chemical agents are quickly distributed over a wide range. The long term impacts of this wide-scale distribution are unknown, but known to be negative. In the Vietnam War of 1955–1975, a chemical weapon called agent orange was widely used by United States forces. The United States utilized agent orange as a type of tactical herbicide, aiming to destroy Vietnamese foliage and plant life to ease military access. This usage of agent orange has left lasting impacts that are still observable today in the Vietnamese environment, causing disease, stunted growth, and deformities. | 1 | Applied and Interdisciplinary Chemistry |
The compound is typically prepared by heating thin layers of urea, the thin layers facilitating escape of ammonia:
:3 (HN)CO → [HNC(O)NH]CO + 2 NH
It can also prepared by treatment of urea with phosgene:
:2 (HN)CO + COCl → [HNC(O)NH]CO + 2 HCl
A similar synthesis employs urea and dimethyl carbonate with potassium methoxide as a catalyst:
:2 (HN)CO + CO(OCH) → [HNC(O)NH]CO + 2 MeOH
The original synthesis entailed oxidation of uric acid with hydrogen peroxide.
Triuret is a complicating by-product in the industrial synthesis of melamine from urea. | 0 | Theoretical and Fundamental Chemistry |
In molecular cloning and biology, a gene knock-in (abbreviation: KI) refers to a genetic engineering method that involves the one-for-one substitution of DNA sequence information in a genetic locus or the insertion of sequence information not found within the locus. Typically, this is done in mice since the technology for this process is more refined and there is a high degree of shared sequence complexity between mice and humans. The difference between knock-in technology and traditional transgenic techniques is that a knock-in involves a gene inserted into a specific locus, and is thus a "targeted" insertion. It is the opposite of gene knockout.
A common use of knock-in technology is for the creation of disease models. It is a technique by which scientific investigators may study the function of the regulatory machinery (e.g. promoters) that governs the expression of the natural gene being replaced. This is accomplished by observing the new phenotype of the organism in question. The BACs and YACs are used in this case so that large fragments can be transferred. | 1 | Applied and Interdisciplinary Chemistry |
The Hildebrand solubility parameter is the square root of the cohesive energy density:
The cohesive energy density is the amount of energy needed to completely remove unit volume of molecules from their neighbours to infinite separation (an ideal gas). This is equal to the heat of vaporization of the compound divided by its molar volume in the condensed phase. In order for a material to dissolve, these same interactions need to be overcome, as the molecules are separated from each other and surrounded by the solvent. In 1936 Joel Henry Hildebrand suggested the square root of the cohesive energy density as a numerical value indicating solvency behavior. This later became known as the "Hildebrand solubility parameter". Materials with similar solubility parameters will be able to interact with each other, resulting in solvation, miscibility or swelling. | 0 | Theoretical and Fundamental Chemistry |
Earth absorbs some of the radiant energy received from the sun, reflects some of it as light and reflects or radiates the rest back to space as heat. A planets surface temperature depends on this balance between incoming and outgoing energy. When Earths energy balance is shifted, its surface becomes warmer or cooler, leading to a variety of changes in global climate. Radiative forcing is a metric calculated in watts per square meter, which characterizes the impact of an external change in a factor that influences climate. It is calculated as the difference in top-of-atmosphere (TOA) energy balance immediately caused by such an external change A positive forcing, such as from increased concentrations of greenhouse gases, means more energy arriving than leaving at the top-of-atmosphere, which causes additional warming, while negative forcing, like from sulfates forming in the atmosphere from sulfur dioxide, leads to cooling.
Within the lower atmosphere, greenhouse gases exchange thermal radiation with the surface and limit radiative heat flow away from it, which reduces the overall rate of upward radiative heat transfer. The increased concentration of greenhouse gases is also cooling the upper atmosphere, as it is much thinner than the lower layers, and any heat re-emitted from greenhouse gases is more likely to travel further to space than to interact with the fewer gas molecules in the upper layers. The upper atmosphere is also shrinking as the result. | 1 | Applied and Interdisciplinary Chemistry |
Pleuran is an insoluble polysaccharide (β-(1,3/1,6)-D-glucan), isolated from Pleurotus ostreatus.
Pleuran belongs to a group of glucose polymers commonly called beta-glucans demonstrating biological response modifier properties. These immunomodulating properties render the host more resistant to infections and neoplasms.
In a study published in December 2010, pleuran demonstrated to have a protective effect against exercise-induced suppression of immune cell activity (NK cells) in subjects taking 100 mg per day.
In another study published in 2011, pleuran reduced the incidence of upper respiratory tract infections and increased the number of circulating NK cells.
Pleuran is also being studied as a potential immunologic adjuvant. | 1 | Applied and Interdisciplinary Chemistry |
A general material surface experiences shear and strain in its deformation, both of which depend continuously on initial conditions by the continuity of the map .
The averaged strain and shear within a strip of -close material lines, therefore, typically show variation within such a strip.
The two-dimensional geodesic theory of LCSs seeks exceptionally coherent locations where this general trend fails, resulting in an order of magnitude smaller variability in shear or strain than what is normally expected across an strip. Specifically, the geodesic theory searches for LCSs as special material lines around which material strips show no variability either in the material-line
averaged shear (Shearless LCSs) or in the material-line averaged strain (Strainless or Elliptic LCSs). Such LCSs turn out to be null-geodesics of appropriate metric tensors defined by the deformation field—hence the name of this theory.
Shearless LCSs are found to be null-geodesics of a Lorentzian metric tensor defined as
Such null-geodesics can be proven to be tensorlines of the Cauchy–Green strain tensor, i.e., are tangent to the direction field formed by the strain eigenvector fields . Specifically, repelling LCSs are trajectories of starting from local maxima of the eigenvalue field. Similarly, attracting LCSs are trajectories of starting from local minims of the eigenvalue field. This agrees with the conclusion of the local variational theory of LCSs. The geodesic approach, however, also sheds more light on the robustness of hyperbolic LCSs: hyperbolic LCSs only prevail as stationary curves of the averaged shear functional under variations that leave their endpoints fixed. This is to be contrasted with parabolic LCSs (see below), which are also shearless LCSs but prevail as stationary curves to the shear functional even under arbitrary variations. As a consequence, individual trajectories are objective, and statements about the coherent structures they form should also be objective.
A sample application is shown in Fig. 9, where the sudden appearance of a hyperbolic core (strongest attracting part of a stretchline) within the oil spill caused the notable Tiger-Tail instability in the shape of the oil spill. | 1 | Applied and Interdisciplinary Chemistry |
These are strong but flexible springs inserted into a pipe to support the pipe walls during manual bending. They have diameters only slightly less than the internal diameter of the pipe to be bent. They are only suitable for bending soft copper pipe (typically used in household plumbing) or PVC pipe.
The spring is pushed into the pipe until its center is roughly where the bend is to be. A length of flexible wire can be attached to the end of the spring to facilitate its removal. The pipe is generally held against the flexed knee, and the ends of the pipe are pulled up to create the bend. To make it easier to retrieve the spring from the pipe, it is a good idea to bend the pipe slightly more than required, and then slacken it off a little. Springs are less cumbersome than rotary benders, but are not suitable for bending short lengths of piping when it is difficult to get the required leverage on the pipe ends.
Bending springs for smaller diameter pipes (10 mm copper pipe) slide over the pipe instead of inside. | 1 | Applied and Interdisciplinary Chemistry |
Malonyl-CoA plays a special role in the mitochondrial clearance of toxic malonic acid in the metabolic disorder combined malonic and methylmalonic aciduria (CMAMMA). In CMAMMA due to ACSF3, malonyl-CoA synthetase is decreased, which can generate malonyl-CoA from malonic acid, which can then be converted to acetyl-CoA by malonyl-CoA decarboxylase. In contrast, in CMAMMA due to malonyl-CoA decarboxylase deficiency, malonyl-CoA decarboxylase is decreased, which converts malonyl-CoA to acetyl-CoA. | 1 | Applied and Interdisciplinary Chemistry |
The database user interface is web-based and can be queried using text or accession numbers/identifiers. Since its integration with the other components of BOND, sequences have been added to interactions, molecular complexes and pathways in the results. Records include information on: BIND ID, description of the interaction/complex/pathway, publications, update records, organism, OntoGlyphs, ProteoGlyphs, and links to other databases where additional information can be found. BIND records include various viewing formats (e.g. HTML, ASN.1, XML, FASTA), various formats for exporting results (e.g. ASN.1, XML, GI list, PDF), and visualizations (e.g. Cytoscape). The exact viewing and exporting options vary depending on what type of data has been retrieved. | 1 | Applied and Interdisciplinary Chemistry |
The primordial radionuclides have been included for comparison; they are italicised and offset from the list of stable nuclides proper.
Abbreviations for predicted unobserved decay:
A for alpha decay, B for beta decay, 2B for double beta decay, E for electron capture, 2E for double electron capture, IT for isomeric transition, SF for spontaneous fission, * for the nuclides whose half-lives have lower bound. Double beta decay has only been listed when beta decay is not also possible.
^ Tantalum-180m is a "metastable isotope" meaning that it is an excited nuclear isomer of tantalum-180. See isotopes of tantalum. However, the half-life of this nuclear isomer is so long that it has never been observed to decay, and it thus occurs as an "observationally nonradioactive" primordial nuclide, as a minor isotope of tantalum. This is the only case of a nuclear isomer which has a half-life so long that it has never been observed to decay. It is thus included in this list.
^^ Bismuth-209 had long been believed to be stable, due to its half-life of 2.01 · 10 years, which is more than a billion times the age of the universe.
§ Europium-151 and samarium-147 are primordial nuclides with very long half-lives of 4.62 · 10 years and 1.066 · 10 years, respectively. | 0 | Theoretical and Fundamental Chemistry |
In the treatment of epilepsy, drugs such as vigabatrin that target both GABA transporters and the GABA metabolizing enzyme GABA-transaminase have been marketed, providing proof of principle for the neurotransmitter cycling systems as pharmacological targets. However, with regard to glutamate transport and metabolism, no such drugs have been developed, because glutamatergic synapses are abundant, and the neurotransmitter glutamate is an important metabolite in metabolism, making interference capable of adverse effects. So far, most of the drug development directed at the glutamatergic system seems to have been focused on ionotropic glutamate receptors as pharmacological targets, although G-protein coupled receptors have been attracting increased attention over the years. | 1 | Applied and Interdisciplinary Chemistry |
The mathematical equation for Boyle's law is:
where denotes the pressure of the system, denotes the volume of the gas, is a constant value representative of the temperature and volume of the system.
So long as temperature remains constant the same amount of energy given to the system persists throughout its operation and therefore, theoretically, the value of will remain constant. However, due to the derivation of pressure as perpendicular applied force and the probabilistic likelihood of collisions with other particles through collision theory, the application of force to a surface may not be infinitely constant for such values of , but will have a limit when differentiating such values over a given time. Forcing the volume of the fixed quantity of gas to increase, keeping the gas at the initially measured temperature, the pressure must decrease proportionally. Conversely, reducing the volume of the gas increases the pressure. Boyle's law is used to predict the result of introducing a change, in volume and pressure only, to the initial state of a fixed quantity of gas.
The initial and final volumes and pressures of the fixed amount of gas, where the initial and final temperatures are the same (heating or cooling will be required to meet this condition), are related by the equation:
Here and represent the original pressure and volume, respectively, and and represent the second pressure and volume.
Boyles law, Charless law, and Gay-Lussacs law form the combined gas law. The three gas laws in combination with Avogadros law can be generalized by the ideal gas law. | 0 | Theoretical and Fundamental Chemistry |
There are two common methods in which to construct a DNA molecular-weight size marker. One such method employs the technique of partial ligation. DNA ligation is the process by which linear DNA pieces are connected to each other via covalent bonds; more specifically, these bonds are phosphodiester bonds. Here, a 100bp duplex DNA piece is partially ligated. The consequence of this is that dimers of 200bp, trimers of 300bp, tetramers of 400bp, pentamers of 500bp, etc. will form. Additionally, a portion of the 100bp dsDNA will remain. As a result, a DNA "ladder" composed of DNA pieces of known molecular mass is created on the gel.
The second method employs the use of restriction enzymes and a recognized DNA sequence. The DNA is digested by a particular restriction enzyme, resulting in DNA pieces of varying molecular masses. One of the advantages of this method is that more marker can readily be created simply by digesting more of the known DNA. On the other hand, the size of the DNA pieces are based on the sites where the restriction enzyme cuts. This makes it more difficult to control the size of the fragments in the marker.
More recently, another method for constructing DNA molecular-weight size markers is being employed by laboratories. This strategy involves the use of Polymerase Chain Reaction (PCR). This is achieved one or two ways: 1) a DNA target is amplified at the same time via primer sets, or 2) different DNA targets are amplified independently via particular primers. | 1 | Applied and Interdisciplinary Chemistry |
The hardenability of a ferrous alloy is measured by a Jominy test: a round metal bar of standard size (indicated in the top image) is transformed to 100% austenite through heat treatment, and is then quenched on one end with room-temperature water. The cooling rate will be highest at the end being quenched, and will decrease as distance from the end increases. Subsequent to cooling a flat surface is ground on the test piece and the hardenability is then found by measuring the hardness along the bar. The farther away from the quenched end that the hardness extends, the higher the hardenability. This information is plotted on a hardenability graph.
The Jominy end-quench test was invented by Walter E. Jominy (1893-1976) and A.L. Boegehold, metallurgists in the Research Laboratories Division of General Motors Corp., in 1937. For his pioneering work in heat treating, Jominy was recognized by the American Society for Metals (ASM) with its Albert Sauveur Achievement Award in 1944. Jominy served as president of ASM in 1951. | 1 | Applied and Interdisciplinary Chemistry |
Mating in yeast is stimulated by the presence of a pheromone which binds to either the Ste2 receptor (in a-cells) or the Ste3 receptor (in α-cells). The binding of this pheromone then leads to the activation of a heterotrimeric G protein. The dimeric portion of this G-protein recruits Ste5 (and its related MAPK cascade components) to the membrane, and ultimately results in the phosphorylation of Fus3.
The switching mechanism arises as a result of competition between the Fus3 protein (a MAPK protein) and the phosphatase Ptc1. These proteins both attempt to control the 4 phosphorylation sites of Ste5, a scaffold protein with Fus3 attempting to phosphorylate the phosphosites, and Ptc1 attempting to dephosphorylate them.
Presence of α-factor induces recruitment of Ptc1 to Ste5 via a 4 amino acid motif located within the Ste5 phosphosites. Ptc1 then dephosphorylates Ste5, ultimately resulting in the dissociation of the Fus3-Ste5 complex. Fus3 dissociates in a switch-like manner, dependent on the phosphorylation state of the 4 phosphosites. All 4 phosphosites must be dephosphorylated in order for Fus3 to dissociate. Fus3's ability to compete with Ptc1 decreases as Ptc1 is recruited, and thus the rate of dephosphorylation increases with the presence of pheromone.
Kss1, a homologue of Fus3, does not affect shmooing, and does not contribute to the switch-like mating decision.
In yeast, mating as well as the production of shmoos occur via an all-or-none, switch-like mechanism. This switch-like mechanism allows yeast cells to avoid making an unwise commitment to a highly demanding procedure. However, not only does the mating decision need to be conservative (in order to avoid wasting energy), but it must also be fast to avoid losing the potential mate.
The decision to mate is extremely sensitive. There are 3 ways in which this ultrasensitivity is maintained:
#Multi-site phosphorylation – Fus3 only dissociates from Ste5 and becomes fully active when all 4 of the phosphosites are dephosphorylated. Even one phosphorylated site will result in immunity to α-factor.
#Two-stage binding – Fus3 and Ptc1 bind to separate docking sites on Ste5. Only after docking can they bind to, and act on, the phosphosites.
#Steric hindrance – competition between Fus3 and Ptc1 to control the 4 phosphosites on Ste3
[a and α yeast share the same mating response pathway, with the only difference being the type of receptor each mating type possesses. Thus the above description, given for a-type yeast stimulated with α-factor, works equally well for α-type yeast stimulated with a-factor.] | 1 | Applied and Interdisciplinary Chemistry |
There is currently some interest in developing air cars. Several engines have been proposed for these, although none have demonstrated the performance and long life needed for personal transport. | 1 | Applied and Interdisciplinary Chemistry |
The nines scale is also used in other contexts, such as describing the purity of gases. The purity of a gas is an indication of the ratio of it to other gases in its mixture, as measured by volume. Thus, a high purity refers to a low amount of other gases, or impurities. Gases of higher purity are in many contexts considered to be of better quality and are usually more expensive.
The purity of a gas is generally expressed as a grade prefixed with the letter N (rather than postfixed), indicating the "number of nines" in the percentage or decimal fraction. For example, a N2.0 gas is 99% (two nines) pure and 1% impurities by volume; a N6.0 gas is 99.9999% (six nines) pure, with 1 part per million (1 ppm or 1 vpm, volume per million) impurities.
Intermediate values indicate the digit following the last nine. For example, N4.6 estimates a purity level of 99.996% (four nines followed by a six). An alternative representation uses the common logarithm: for example, a gas which is 99.97% pure would be described as N3.5, since log(0.03%) = −3.523. | 1 | Applied and Interdisciplinary Chemistry |
The term sublimation refers specifically to a physical change of state and is not used to describe the transformation of a solid to a gas in a chemical reaction. For example, the dissociation on heating of solid ammonium chloride into hydrogen chloride and ammonia is not sublimation but a chemical reaction. Similarly the combustion of candles, containing paraffin wax, to carbon dioxide and water vapor is not sublimation but a chemical reaction with oxygen. | 0 | Theoretical and Fundamental Chemistry |
The two types of beta decay are known as beta minus and beta plus. In beta minus (β) decay, a neutron is converted to a proton, and the process creates an electron and an electron antineutrino; while in beta plus (β) decay, a proton is converted to a neutron and the process creates a positron and an electron neutrino. β decay is also known as positron emission.
Beta decay conserves a quantum number known as the lepton number, or the number of electrons and their associated neutrinos (other leptons are the muon and tau particles). These particles have lepton number +1, while their antiparticles have lepton number −1. Since a proton or neutron has lepton number zero, β decay (a positron, or antielectron) must be accompanied with an electron neutrino, while β decay (an electron) must be accompanied by an electron antineutrino.
An example of electron emission (β decay) is the decay of carbon-14 into nitrogen-14 with a half-life of about 5,730 years:
In this form of decay, the original element becomes a new chemical element in a process known as nuclear transmutation. This new element has an unchanged mass number , but an atomic number that is increased by one. As in all nuclear decays, the decaying element (in this case ) is known as the parent nuclide while the resulting element (in this case ) is known as the daughter nuclide.
Another example is the decay of hydrogen-3 (tritium) into helium-3 with a half-life of about 12.3 years:
An example of positron emission (β decay) is the decay of magnesium-23 into sodium-23 with a half-life of about 11.3 s:
β decay also results in nuclear transmutation, with the resulting element having an atomic number that is decreased by one.
The beta spectrum, or distribution of energy values for the beta particles, is continuous. The total energy of the decay process is divided between the electron, the antineutrino, and the recoiling nuclide. In the figure to the right, an example of an electron with 0.40 MeV energy from the beta decay of Bi is shown. In this example, the total decay energy is 1.16 MeV, so the antineutrino has the remaining energy: . An electron at the far right of the curve would have the maximum possible kinetic energy, leaving the energy of the neutrino to be only its small rest mass. | 0 | Theoretical and Fundamental Chemistry |
The expressome is a supramolecular complex consisting of RNA polymerase and a trailing ribosome linked by a shared mRNA transcript. It is supported by the transcription factors NusG and NusA, which interact with both RNA polymerase and the ribosome to couple the complexes together. When coupled by transcription factor NusG, the ribosome binds newly synthesized mRNA and prevents formation of secondary structures that inhibit transcription. Formation of an expressome complex also aids transcription elongation by the trailing ribosome opposing back-tracking of RNA polymerase. Three-dimensional models of ribosome-RNA polymerase expressome complexes have been determined by cryo-electron microscopy. | 1 | Applied and Interdisciplinary Chemistry |
The photoacoustic effect or optoacoustic effect is the formation of sound waves following light absorption in a material sample. In order to obtain this effect the light intensity must vary, either periodically (modulated light) or as a single flash (pulsed light). The photoacoustic effect is quantified by measuring the formed sound (pressure changes) with appropriate detectors, such as microphones or piezoelectric sensors. The time variation of the electric output (current or voltage) from these detectors is the photoacoustic signal. These measurements are useful to determine certain properties of the studied sample. For example, in photoacoustic spectroscopy, the photoacoustic signal is used to obtain the actual absorption of light in either opaque or transparent objects. It is useful for substances in extremely low concentrations, because very strong pulses of light from a laser can be used to increase sensitivity and very narrow wavelengths can be used for specificity. Furthermore, photoacoustic measurements serve as a valuable research tool in the study of the heat evolved in photochemical reactions (see: photochemistry), particularly in the study of photosynthesis.
Most generally, electromagnetic radiation of any kind can give rise to a photoacoustic effect. This includes the whole range of electromagnetic frequencies, from gamma radiation and X-rays to microwave and radio. Still, much of the reported research and applications, utilizing the photoacoustic effect, is concerned with the near ultraviolet/visible and infrared spectral regions. | 0 | Theoretical and Fundamental Chemistry |
A sequence in biology is the one-dimensional ordering of monomers, covalently linked within a biopolymer; it is also referred to as the primary structure of a biological macromolecule. While it can refer to many different molecules, the term sequence is most often used to refer to a DNA sequence. | 1 | Applied and Interdisciplinary Chemistry |
In the context of radiation protection, activity median aerodynamic diameter (AMAD) is the MAD for the airborne activity in a given aerosol. Internal dosimetry uses it as a means of simplifying the true distribution of aerodynamic diameters of a given aerosol. | 0 | Theoretical and Fundamental Chemistry |
The thermal stability of PPA is highly dependent on whether the polymer is end-capped or isolated without end groups. Cyclic PPA, in addition to functionalized linear PPA chains are known to be thermally stable for up to 150C as determined by both Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). Moreover, the polymer is known for its long-term shelf life wherein it can be stored at room-temperature for a significant amount of time. Various chemists have studied substitution effects on the thermal stability of PPA. For instance, scientists at The International Business Machines Corporation (IBM) concluded, after extensive studies, that o-phthalaldehyde monomers functionalized with chloro, bromo, and 4-trimethylsilyl functional groups result in highly stable PPA compared to the unsubstituted polymer. Similarly, Phillips et al. proved that the substituted and end-capped poly(4,5-dichlorophthalaldehyde) possesses higher thermal degradation temperatures than its unsubstituted counterparts. | 0 | Theoretical and Fundamental Chemistry |
Physical lipolysis involves destruction of fat cells containing the fat droplets and can be used as part of cosmetic body contouring procedures. Currently there are four main non-invasive body contouring techniques in aesthetic medicine for reducing localized subcutaneous adipose tissue in addition to the standard minimally invasive liposuction: low-level laser therapy (LLLT), cryolipolysis, radio frequency (RF) and high-intensity focused ultrasound (HIFU). However, they are less effective with shorter lasting benefits and can remove significantly smaller amounts of fat compared to traditional surgical liposuction or lipectomy. However, future drug developments can be potentially combined with smaller procedures to augment the result. | 1 | Applied and Interdisciplinary Chemistry |
An inductively coupled plasma (ICP) or transformer coupled plasma (TCP) is a type of plasma source in which the energy is supplied by electric currents which are produced by electromagnetic induction, that is, by time-varying magnetic fields. | 0 | Theoretical and Fundamental Chemistry |
Martha spent much of her scientific career interested in the quantitative analysis of various elements. Specifically, she studied the composition of ammonium phosphates in magnesium, zinc, and cadmium. Her study of ammonium phosphates was later used as a tool in her later analytical work. Martha spent much of her research career developing several analytical procedures for metal estimations and separations, with a special focus on gravimetric estimations of manganese and magnesium. Her other work included the analysis of prehistoric bronzes without major disruption to the metal composition and the study of organic esters.
While in graduate school at Yale, she worked for Andrew Gooch in the Kent Chemical Laboratory. Throughout her time in graduate school, she published nine papers in the American Journal of Science and in Zeitschrift für anorganische und allgemeine Chemie for her work in analytical chemistry. Four of the nine papers she published individually and the other five in collaboration with Gooch. After her marriage to Issac King Phelps in 1904, she collaborated with her husband to study ester synthesis. The work resulted in six more publications. In total, she published fifteen papers throughout the span of her ten year career as a chemist.
Martha's work is primarily recognized for her development of a protocol estimating arsenic as ammonium magnesium arsenate. The paper detailing the procedure was published in 1900. The protocol became a standard method of arsenic estimation in quantitative analysis studies and was written into textbooks for several years. | 0 | Theoretical and Fundamental Chemistry |
Journal of Biological Inorganic Chemistry (JBIC) is a peer-reviewed scientific journal. It is an official publication of the Society of Biological Inorganic Chemistry and published by Springer Science+Business Media.
Biological inorganic chemistry is a growing field of science that embraces the principles of biology and inorganic chemistry and impacts other fields ranging from medicine to the environment. JBIC seeks to promote this field internationally. The journal is primarily concerned with advances in understanding the role of metal ions within a biological matrix—be it a protein, DNA/RNA, or a cell, as well as appropriate model studies. Manuscripts describing high-quality original research on the above topics in English are invited for submission to this journal. The journal publishes original articles, minireviews, and commentaries on debated issues.
Follow JBIC Journal of Biological Inorganic Chemistry on Twitter: [https://twitter.com/JBIC_Journal @JBIC_Journal] | 0 | Theoretical and Fundamental Chemistry |
Avogadros law provides a way to calculate the quantity of gas in a receptacle. Thanks to this discovery, Johann Josef Loschmidt, in 1865, was able for the first time to estimate the size of a molecule. His calculation gave rise to the concept of the Loschmidt constant, a ratio between macroscopic and atomic quantities. In 1910, Millikans oil drop experiment determined the charge of the electron; using it with the Faraday constant (derived by Michael Faraday in 1834), one is able to determine the number of particles in a mole of substance. At the same time, precision experiments by Jean Baptiste Perrin led to the definition of the Avogadro number as the number of molecules in one gram-molecule of oxygen. Perrin named the number to honor Avogadro for his discovery of the namesake law. Later standardization of the International System of Units led to the modern definition of the Avogadro constant. | 0 | Theoretical and Fundamental Chemistry |
The following table shows radiation quantities in SI and non-SI units:
Although the United States Nuclear Regulatory Commission permits the use of the units curie, rad, and rem alongside SI units, the European Union European units of measurement directives required that their use for "public health ... purposes" be phased out by 31 December 1985. | 0 | Theoretical and Fundamental Chemistry |
While RPKA allows observation of rates over the course of the entire reaction, conducting only same-excess experiments does not provide sufficient information for determination of the corresponding rate constants. In order to construct enough independent relationships to solve for all of the unknown rate constants, it is necessary to examine systems with different-excess.
Consider again the simple example discussed above where the catalyst associates with substrate A, followed by reaction with B to form product P and free catalyst. Regardless of the approximation applied, multiple independent parameters (k and K in the case of pre-equilibrium; k, k, and k in the case of steady-state) are required to define the system. While one could imagine constructing multiple equations to describe the unknowns at different concentrations, when the data is obtained from a same-excess experiment [A] and [B] are not independent:
:e = [B] − [A]
Multiple experiments using different values of e are necessary to establish multiple independent equations defining the multiple independent rate constants in terms of experimental rates and concentrations. Non-linear least squares analysis may then be employed to obtain best fit values of the unknown rate constants to those equations. | 0 | Theoretical and Fundamental Chemistry |
*Winkler test for dissolved oxygen: Used to determine oxygen concentration in water. Oxygen in water samples is reduced using manganese(II) sulfate, which reacts with potassium iodide to produce iodine. The iodine is released in proportion to the oxygen in the sample, thus the oxygen concentration is determined with a redox titration of iodine with thiosulfate using a starch indicator.
*Vitamin C: Also known as ascorbic acid, vitamin C is a powerful reducing agent. Its concentration can easily be identified when titrated with the blue dye Dichlorophenolindophenol (DCPIP) which becomes colorless when reduced by the vitamin.
*Benedicts reagent: Excess glucose in urine may indicate diabetes in a patient. Benedicts method is the conventional method to quantify glucose in urine using a prepared reagent. During this type of titration, glucose reduces cupric ions to cuprous ions which react with potassium thiocyanate to produce a white precipitate, indicating the endpoint.
*Bromine number: A measure of unsaturation in an analyte, expressed in milligrams of bromine absorbed by 100 grams of sample.
*Iodine number: A measure of unsaturation in an analyte, expressed in grams of iodine absorbed by 100 grams of sample. | 0 | Theoretical and Fundamental Chemistry |
The ability of a surface to self-clean commonly depends on the hydrophobicity or hydrophilicity of the surface. Whether cleaning aqueous or organic matter from a surface, water plays an important role in the self-cleaning process. Specifically, the contact angle of water on the surface is an important characteristic that helps determine the ability of a surface to self-clean. This angle is affected by the roughness of the surface and the following models have been developed to describe the "stickiness" or wettability of a self-cleaning surface. | 0 | Theoretical and Fundamental Chemistry |
Gas chromatography-olfactometry (GC-O) is a technique that integrates the separation of volatile compounds using a gas chromatograph with the detection of odour using an olfactometer (human assessor). It was first invented and applied in 1964 by Fuller and co-workers. While GC separates volatile compounds from an extract, human olfaction detects the odour activity of each eluting compound. In this olfactometric detection, a human assessor may qualitatively determine whether a compound has odour activity or describe the odour perceived, or quantitatively evaluate the intensity of the odour or the duration of the odour activity. The olfactometric detection of compounds allows the assessment of the relationship between a quantified substance and the human perception of its odour, without instrumental detection limits present in other kinds of detectors. Compound identification still requires use of other detectors, such as mass spectrometry, with analytical standards. | 0 | Theoretical and Fundamental Chemistry |
Isolated chloroplasts placed under light conditions but in the absence of CO, reduce and then oxidize artificial electron acceptors, allowing the process to proceed. Oxygen (O) is released as a byproduct, but not sugar (CHO).
Chloroplasts placed under dark conditions and in the absence of CO, oxidize the artificial acceptor but do not reduce it, terminating the process, without production of oxygen or sugar. | 0 | Theoretical and Fundamental Chemistry |
The dose rate from a single uptake decays over time due to both radioactive decay, and biological decay (i.e. excretion from the body). The combined radioactive and biological half-life, called the effective half-life of the material, may range from hours for medical radioisotopes to decades for transuranic waste. Committed dose is the integral of this decaying dose rate over the presumed remaining lifespan of the organism. Most regulations require this integral to be taken over 50 years for uptakes during adulthood or over 70 years for uptakes during childhood. In dosimetry accounting, the entire committed dose is conservatively assigned to the year of uptake, even though it may take many years for the tissues to actually accumulate this dose. | 0 | Theoretical and Fundamental Chemistry |
Tropospheric ozone depletion events are phenomena that reduce the concentration of ozone in the earth's troposphere. Ozone (O3) is a trace gas which has been of concern because of its unique dual role in different layers of the lower atmosphere. Apart from absorbing UV-B radiation and converting solar energy into heat in the stratosphere, ozone in the troposphere provides greenhouse effect and controls the oxidation capacity of the atmosphere. | 1 | Applied and Interdisciplinary Chemistry |
Some molecular compounds that adopt square pyramidal geometry are XeOF, and various halogen pentafluorides (XF, where X = Cl, Br, I). Complexes of vanadium(IV), such as vanadyl acetylacetonate, [VO(acac)], are square pyramidal (acac = acetylacetonate, the deprotonated anion of acetylacetone (2,4-pentanedione)). | 0 | Theoretical and Fundamental Chemistry |
Ken Kesey was born in 1935 in La Junta, Colorado to dairy farmers Frederick A. Kesey and Ginevra Smith. In 1946, the family moved to Springfield, Oregon. A champion wrestler in both high school and college, he graduated from Springfield High School in 1953.
Kesey attended the University of Oregons School of Journalism, where he received a degree in speech and communication in 1957, where he was also a brother of Beta Theta Pi. He was awarded a Woodrow Wilson National Fellowship in 1958 to enroll in the creative writing program at Stanford University, which he did the following year. While at Stanford, he studied under Wallace Stegner and began the manuscript that would become One Flew Over the Cuckoos Nest.
At Stanford in 1959, Kesey volunteered to take part in a CIA-financed study named Project MKULTRA at the Menlo Park Veterans Hospital. The project studied the effects on the patients of psychoactive drugs, particularly LSD, psilocybin, mescaline, cocaine, AMT, and DMT. Kesey wrote many detailed accounts of his experiences with these drugs, both during the Project MKULTRA study and in the years of private experimentation that followed. Keseys role as a medical guinea pig inspired him to write the book One Flew Over the Cuckoos Nest in 1962. The success of the book, as well as the sale of his residence at Stanford, allowed him to move to La Honda, California in the mountains west of Stanford University. He frequently entertained friends and many others with parties he called "Acid Tests" involving music (such as Keseys favorite band, The Warlocks, later known as the Grateful Dead), black lights, fluorescent paint, strobes and other "psychedelic" effects, and, of course, LSD. These parties were noted in some of Allen Ginsbergs poems and are also described in the books The Electric Kool-Aid Acid Test by Tom Wolfe, Hells Angels: The Strange and Terrible Saga of the Outlaw Motorcycle Gangs by Hunter S. Thompson, and Freewheelin Frank, Secretary of the Hells Angels by Frank Reynolds. Ken Kesey was also said to have experimented with LSD with Ringo Starr in 1965 and that he influenced the setup for future performances with The Beatles in the UK.
In the summer of 1964, Kesey's Merry Pranksters customized a bus named "Furthur" and set out on a tour to propagate LSD use. | 1 | Applied and Interdisciplinary Chemistry |
Colonies of the ant Temnothorax albipennis nest in small crevices between rocks. When the rocks shift and the nest is broken up, these ants must quickly choose a new nest to move into. During the first phase of the decision-making process, a small portion of the workers leave the destroyed nest and search for new crevices. When one of these scout ants finds a potential nest, she assesses the quality of the crevice based on a variety of factors including the size of the interior, the number of openings (based on light level), and the presence or absence of dead ants. The worker then returns to the destroyed nest, where she waits for a short period before recruiting other workers to follow her to the nest that she has found, using a process called tandem running. The waiting period is inversely related to the quality of the site; for instance, a worker that has found a poor site will wait longer than a worker that encountered a good site. As the new recruits visit the potential nest site and make their own assessment of its quality, the number of ants visiting the crevice increases. During this stage, ants may be visiting many different potential nests. However, because of the differences in the waiting period, the number of ants in the best nest will tend to increase at the greatest rate. Eventually, the ants in this nest will sense that the rate at which they encounter other ants has exceeded a particular threshold, indicating that the quorum number has been reached. Once the ants sense a quorum, they return to the destroyed nest and begin rapidly carrying the brood, queen, and fellow workers to the new nest. Scouts that are still tandem-running to other potential sites are also recruited to the new nest, and the entire colony moves. Thus, although no single worker may have visited and compared all of the available options, quorum sensing enables the colony as a whole to quickly make good decisions about where to move. | 1 | Applied and Interdisciplinary Chemistry |
Of the 32 crystallographic point groups, 10 are polar:
The space groups associated with a polar point group do not have a discrete set of possible origin points that are unambiguously determined by symmetry elements.
When materials having a polar point group crystal structure are heated or cooled, they may temporarily generate a voltage called pyroelectricity.
Molecular crystals which have symmetry described by one of the polar space groups, such as sucrose, may exhibit triboluminescence. | 0 | Theoretical and Fundamental Chemistry |
Since microsphere beads are easily suspended in solution and each microsphere retains its identity when hybridized to the test sample, a typical suspension array experiment can analyze a wide range of biological analysis in a single reaction, called "multiplexing". In general, each type of microsphere used in an array is individually prepared in bulk. For example, the commercially available microsphere arrays from Luminex xMAP technology uses a 10X10 element array. This array involves beads with red and infrared dyes, each with ten different intensities, to give a 100-element array. Thus, the array size would increase exponentially if multiple dyes are used. For example, five different dyes with 10 different intensities per dye will give rise to 100,000 different array elements. | 1 | Applied and Interdisciplinary Chemistry |
Amino radicals can be produced by reacting OH radical with ammonia in irradiated aqueous solutions. This reaction is formulated as a hydrogen abstraction reaction.
The rate constant (k) for this reaction was determined to be , while the parallel reaction of OH with was found to be much slower. This rate was redetermined by using two-pulse radiolysis competition methods with benzoate and thiocyanate ions at pH 11.4. A value of k = was obtained from both systems. While in acidic solution, the corresponding reaction of with is too slow to be observed by pulse radiolysis. | 0 | Theoretical and Fundamental Chemistry |
By definition, antagonists display no efficacy to activate the receptors they bind. Antagonists do not maintain the ability to activate a receptor. Once bound, however, antagonists inhibit the function of agonists, inverse agonists, and partial agonists. In functional antagonist assays, a dose-response curve measures the effect of the ability of a range of concentrations of antagonists to reverse the activity of an agonist. The potency of an antagonist is usually defined by its half maximal inhibitory concentration (i.e., IC value). This can be calculated for a given antagonist by determining the concentration of antagonist needed to elicit half inhibition of the maximum biological response of an agonist. Elucidating an IC value is useful for comparing the potency of drugs with similar efficacies, however the dose-response curves produced by both drug antagonists must be similar. The lower the IC the greater the potency of the antagonist, and the lower the concentration of drug that is required to inhibit the maximum biological response. Lower concentrations of drugs may be associated with fewer side-effects. | 1 | Applied and Interdisciplinary Chemistry |
A fuel element failure is a rupture in a nuclear reactor's fuel cladding that allows the nuclear fuel or fission products, either in the form of dissolved radioisotopes or hot particles, to enter the reactor coolant or storage water.
The de facto standard nuclear fuel is uranium dioxide or a mixed uranium/plutonium dioxide. This has a higher melting point than the actinide metals. Uranium dioxide resists corrosion in water and provides a stable matrix for many of the fission products; however, to prevent fission products (such as the noble gases) from leaving the uranium dioxide matrix and entering the coolant, the pellets of fuel are normally encased in tubes of a corrosion-resistant metal alloy (normally Zircaloy for water-cooled reactors).
Those elements are then assembled into bundles to allow good handling and cooling. As the fuel fissions, the radioactive fission products are also contained by the cladding, and the entire fuel element can then be disposed of as nuclear waste when the reactor is refueled.
If, however, the cladding is damaged, those fission products (which are not immobile in the uranium dioxide matrix) can enter the reactor coolant or storage water and can be carried out of the core, into the rest of the primary cooling circuit, increasing contamination levels there.
In the EU, some work has been done in which fuel is overheated in a special research reactor named PHEBUS. During these experiments the emissions of radioactivity from the fuel are measured and afterwards the fuel is subjected to Post Irradiation Examination to discover more about what happened to it. | 0 | Theoretical and Fundamental Chemistry |
A variation of the heat flow technique is called power compensation calorimetry. This method uses a cooling jacket operating at constant flow and temperature. The process temperature is regulated by adjusting the power of the electrical heater. When the experiment is started, the electrical heat and the cooling power (of the cooling jacket) are in balance. As the process heat load changes, the electrical power is varied in order to maintain the desired process temperature. The heat liberated or absorbed by the process is determined from the difference between the initial electrical power and the demand for electrical power at the time of measurement. The power compensation method is easier to set up than heat flow calorimetry but it suffers from the similar limitations since any change in product composition, liquid level, process temperature, agitation rate or viscosity will upset the calibration. The presence of an electrical heating element is also undesirable for process operations. The method is further limited by the fact that the largest heat it can measure is equal to the initial electrical power applied to the heater.
: = current supplied to heater
: = voltage supplied to heater
: = current supplied to heater at equilibrium (assuming constant voltage / resistance) | 1 | Applied and Interdisciplinary Chemistry |
A hypersonic wind tunnel is designed to generate a hypersonic flow field in the working section, thus simulating the typical flow features of this flow regime - including compression shocks and pronounced boundary layer effects, entropy layer and viscous interaction zones and most importantly high total temperatures of the flow. The speed of these tunnels vary from Mach 5 to 15. The power requirement of a wind tunnel increases linearly with its cross section and flow density, but cubically with the test velocity required. Hence installation of a continuous, closed circuit wind tunnel remains a costly affair. The first continuous Mach 7-10 wind tunnel with 1x1 m test section was planned at Kochel am See, Germany during WW II and finally put into operation as Tunnel A in the late 1950s at AEDC Tullahoma, TN, USA for an installed power of 57 MW. In view of these high facility demands, also intermittently operated experimental facilities like blow-down wind tunnels are designed and installed to simulate the hypersonic flow. A hypersonic wind tunnel comprises in flow direction the main components: heater/cooler arrangements, dryer, convergent/divergent nozzle, test section, second throat and diffuser. A blow-down wind tunnel has a low vacuum reservoir at the back end, while a continuously operated, closed circuit wind tunnel has a high power compressor installation instead. Since the temperature drops with the expanding flow, the air inside the test section has the chance of becoming liquefied. For that reason, preheating is particularly critical (the nozzle may require cooling). | 1 | Applied and Interdisciplinary Chemistry |
The terms resin flux and rosin flux are ambiguous and somewhat interchangeable, with different vendors using different assignments. Generally, fluxes are labeled as rosin if the vehicle they are based on is primarily natural rosin. Some manufactures reserve "rosin" designation for military fluxes based on rosin (R, RMA and RA compositions) and label others as "resin".
Rosin has good flux properties. A mixture of organic acids (resin acids, predominantly abietic acid, with pimaric acid, isopimaric acid, neoabietic acid, dihydroabietic acid, and dehydroabietic acid), rosin is a glassy solid, virtually nonreactive and noncorrosive at normal temperature, but liquid, ionic and mildly reactive to metal oxides at molten state. Rosin tends to soften between 60–70 °C and is fully fluid at around 120 °C; molten rosin is weakly acidic and is able to dissolve thinner layers of surface oxides from copper without further additives. For heavier surface contamination or improved process speed, additional activators can be added.
There are several possible activator groups for rosins:
* halide activators (organic halide salts, e.g. dimethylammonium chloride and diethylammonium chloride)
* organic acids (monocarboxylic, e.g. formic acid, acetic acid, propionic acid, and dicarboxylic, e.g. oxalic acid, malonic acid, sebacic acid)
There are three types of rosin: gum rosin (from pine tree oleoresin), wood rosin (obtained by extraction of tree stumps), and tall oil rosin (obtained from tall oil, a byproduct of kraft paper process). Gum rosin has a milder odor and lower tendency to crystallize from solutions than wood rosin, and is therefore preferred for flux applications. Tall oil rosin finds increased use due to its higher thermal stability and therefore lower tendency to form insoluble thermal decomposition residues. The composition and quality of rosin differs by the tree type, and also by location and even by year. In Europe, rosin for fluxes is usually obtained from a specific type of Portuguese pine; in America a North Carolina variant is used.
Natural rosin can be used as is, or can be chemically modified by e.g. esterification, polymerization, or hydrogenation. The properties being altered are increased thermal stability, better cleanability, altered solution viscosity, and harder residue (or conversely, softer and more tacky residue). Rosin can be also converted to a water-soluble rosin flux, by formation of an ethoxylated rosin amine, an adduct with a polyglycol and an amine.
One of the early fluxes was a mixture of equal amounts of rosin and vaseline. A more aggressive early composition was a mixture of saturated solution of zinc chloride, alcohol, and glycerol.
Fluxes can be also prepared from synthetic resins, often based on esters of polyols and fatty acids. Such resins have improved fume odor and lower residue tack, but their fluxing activity and solubility tend to be lower than that of natural resins. | 1 | Applied and Interdisciplinary Chemistry |
At the appropriate Krafft temperature and critical micelle concentration these molecules will form individual tear-drop loops, where the hydrophobic ends are attracted to one another, to other molecules, and also to the similarly hydrophobic QDs. This forms a loaded micelle with a hydrophilic outer shell and a hydrophobic core.
When encapsulating hydrophobes in this way it is important to ensure the particle size is appropriate for the PEG backbone being utilized, as the number of PEG mer units (generally with a molecular weight of 6 kDa or 10 kDa) determines the maximum particle size that can be successfully contained at the core of the micelle.
To determine the average diameter, D, of the QDs, the following empirical equation is used:
Where
* is the diameter of the CdSe QD in nm
* is the wavelength of the first absorption peak in nm | 0 | Theoretical and Fundamental Chemistry |
Grain boundaries can cause failure mechanically by embrittlement through solute segregation (see Hinkley Point A nuclear power station) but they also can detrimentally affect the electronic properties. In metal oxides it has been shown theoretically that at the grain boundaries in AlO and MgO the insulating properties can be significantly diminished. Using density functional theory computer simulations of grain boundaries have shown that the band gap can be reduced by up to 45%. In the case of metals grain boundaries increase the resistivity as the size of the grains relative to the mean free path of other scatters becomes significant. | 1 | Applied and Interdisciplinary Chemistry |
The Kurnakov test, also known as Kurnakovs reaction, is a chemical test that distinguishes pairs of cis- and trans-isomers of [PtAX] (A = NH, X = halogen or pseudohalide). Upon treatment with thiourea, the trans-dihalides give less soluble white products, whereas the cis'-dihalides give more soluble yellow products. The test is still used to assay samples of the drug cisplatin, but it is mainly of pedagogical interest, as it illustrates the trans effect.
The test was devised by Soviet chemist Nikolai Kurnakov. | 0 | Theoretical and Fundamental Chemistry |
Organolithium reagents, including n-BuLi are used in synthesis of specific aldehydes and ketones. One such synthetic pathway is the reaction of an organolithium reagent with disubstituted amides:
: RLi + RCONMe → LiNMe + RC(O)R | 0 | Theoretical and Fundamental Chemistry |
Iron can also enter cells via CD44 in complexes bound to hyaluronic acid during epithelial–mesenchymal transition (EMT). In this process, epithelial cells transform into mesenchymal cells with detachment from the basement membrane, to which they’re normally anchored, paving the way for the newly differentiated motile mesenchymal cells to begin migration away from the epithelial layer.
While EMT plays a crucial role in physiological processes like implantation, where it enables the embryo to invade the endometrium to facilitate placental attachment, its dysregulation can also fuel the malignant spread of tumors empowering them to invade surrounding tissues and establish distant colonies (metastasis).
Malignant cells often exhibit a heightened demand for iron, fueling their transition towards a more invasive mesenchymal state. This iron is necessary for the expression of mesenchymal genes, like those encoding transforming growth factor beta (TGF-β), crucial for EMT. Notably, iron’s unique ability to catalyze protein and DNA demethylation plays a vital role in this gene expression process.
Conventional iron uptake pathways, such as those using the transferrin receptor 1 (TfR1), often prove insufficient to meet these elevated iron demands in cancer cells. As a result, various cytokines and growth factors trigger the upregulation of CD44, a surface molecule capable of internalizing iron bound to the hyaluronan complex. This alternative pathway, relying on CD44-mediated endocytosis, becomes the dominant iron uptake mechanism compared to the traditional TfR1-dependent route. | 1 | Applied and Interdisciplinary Chemistry |
Gay-Lussac was born at Saint-Léonard-de-Noblat in the present-day department of Haute-Vienne.
His father, Anthony Gay, son of a doctor, was a lawyer and prosecutor and worked as a judge in Noblat Bridge. Father of two sons and three daughters, he owned much of the Lussac village and began to add the name of this hamlet to his name, following a custom of the Ancien Régime. Towards the year 1803, father and son formally adopted the name Gay-Lussac. During the Revolution, under the Law of Suspects, his father, former king's attorney, was imprisoned in Saint Léonard from 1793 to 1794.
Gay-Lussac received his early education at the hands of the Catholic Abbey of Bourdeix. In the care of the Abbot of Dumonteil, he began his education in Paris, finally entering the École Polytechnique in 1798.
Three years later, Gay-Lussac transferred to the École des Ponts et Chaussées, and shortly afterward was assigned to C. L. Berthollet as his assistant. In 1804 he was appointed répétiteur (demonstrator) to Antoine François Fourcroy at the École Polytechnique, whom he succeeded in 1809 as professor of chemistry. From 1809 to 1832, he was also the professor of physics at the Sorbonne, a post which he only resigned for the chair of chemistry at the Jardin des Plantes. In 1821, he was elected a foreign member of the Royal Swedish Academy of Sciences. In 1831 he was elected to represent Haute-Vienne in the chamber of deputies, and in 1839 he entered the chamber of peers. He was elected a Foreign Honorary Member of the American Academy of Arts and Sciences in 1832.
Gay-Lussac married Geneviève-Marie-Joseph Rojot in 1809. He had first met her when she worked as a linen drapers shop assistant; he noticed she was studying a chemistry textbook under the counter, which led to their acquaintance. The couple had five children, of whom the eldest (Jules) became a student of Justus Liebig in Giessen. Some publications by Jules are mistaken as his fathers today since they share the same first initial (J. Gay-Lussac).
Gay-Lussac had a reputation as one of the greatest European scientists of his day, well justified by his innumerable discoveries in both chemistry and physics. The restored royalty made him a Peer of France, although he worked politically with the anti-clerical party. He was closely associated with François Arago.
Gay-Lussac died in Paris, and his grave is there at Père Lachaise Cemetery. His name is one of the 72 names inscribed on the Eiffel Tower. | 1 | Applied and Interdisciplinary Chemistry |
Pioneer factors can also affect transcription and differentiation through the control of DNA methylation. Pioneer factors that bind to CpG islands and cytosine residues block access to methyltransferases. Many eukaryotic cells have CpG islands in their promoters that can be modified by methylation having adverse effects on their ability to control transcription. This phenomenon is also present in promoters without CpG islands where single cytosine residues are protected from methylation until further cell differentiation. An example is FoxD3 preventing methylation of a cytosine residue in Alb1 enhancer, acting as a place holder for FoxA1 later in hepatic as well as in CpG islands of genes in chronic lymphocytic leukemia. For stable control of methylation state the cytosine residues are covered during mitosis, unlike most other transcription factors, to prevent methylation. Studies have shown that during mitosis 15% of all interphase FoxA1 binding sites were bound. The protection of cytosine methylation can be quickly removed allowing for rapid induction when a signal is present. | 1 | Applied and Interdisciplinary Chemistry |
Bitumen is a commonly recycled material in the construction industry. The two most common recycled materials that contain bitumen are reclaimed asphalt pavement (RAP) and reclaimed asphalt shingles (RAS). RAP is recycled at a greater rate than any other material in the United States, and typically contains approximately 5–6% bitumen binder. Asphalt shingles typically contain 20–40% bitumen binder.
Bitumen naturally becomes stiffer over time due to oxidation, evaporation, exudation, and physical hardening. For this reason, recycled asphalt is typically combined with virgin asphalt, softening agents, and/or rejuvenating additives to restore its physical and chemical properties. | 0 | Theoretical and Fundamental Chemistry |
The parent boroxine (cyclo-(HBO)) is prepared in small quantities as a low pressure gas by high temperature reaction of water and elemental boron or reaction of various boranes (BH or BH) with O. It is thermodynamically unstable with respect to disproportionation to diborane and boron oxide. Some reactivity studies and an IR spectrum are reported, but it is otherwise not well characterized.
As discovered in the 1930s, substituted boroxines (cyclo-(RBO), R = alkyl or aryl) are generally produced from their corresponding boronic acids by dehydration. This dehydration can be done either by a drying agent or by heating under a high vacuum.
Trimethylboroxine can be synthesized by reacting carbon monoxide with diborane (BH) and lithium borohydride (LiBH) as a catalyst (or reaction of borane–tetrahydrofuran or borane–(dimethyl sulfide) in the presence of sodium borohydride): | 0 | Theoretical and Fundamental Chemistry |
The other analogues of the phosphaethynolate anion all obey the general formulae E-C-X and are made by varying E and X. When changing either atom, unique trends amongst the different analogues become apparent. | 0 | Theoretical and Fundamental Chemistry |
Aging Research and Drug Discovery (ARDD) is a non-profit conference which is organized by University of Copenhagen and Columbia University every year at University of Copenhagen. | 1 | Applied and Interdisciplinary Chemistry |
Ephaptic coupling is a form of communication within the nervous system and is distinct from direct communication systems like electrical synapses and chemical synapses. The phrase may refer to the coupling of adjacent (touching) nerve fibers caused by the exchange of ions between the cells, or it may refer to coupling of nerve fibers as a result of local electric fields. In either case ephaptic coupling can influence the synchronization and timing of action potential firing in neurons. Research suggests that myelination may inhibit ephaptic interactions. | 1 | Applied and Interdisciplinary Chemistry |
The added mass can be incorporated into most physics equations by considering an effective mass as the sum of the mass and added mass. This sum is commonly known as the "virtual mass".
A simple formulation of the added mass for a spherical body permits Newton's classical second law to be written in the form
: becomes
One can show that the added mass for a sphere (of radius ) is , which is half the volume of the sphere times the density of the fluid. For a general body, the added mass becomes a tensor (referred to as the induced mass tensor), with components depending on the direction of motion of the body. Not all elements in the added mass tensor will have dimension mass, some will be mass × length and some will be mass × length.
All bodies accelerating in a fluid will be affected by added mass, but since the added mass is dependent on the density of the fluid, the effect is often neglected for dense bodies falling in much less dense fluids. For situations where the density of the fluid is comparable to or greater than the density of the body, the added mass can often be greater than the mass of the body and neglecting it can introduce significant errors into a calculation.
For example, a spherical air bubble rising in water has a mass of but an added mass of Since water is approximately 800 times denser than air (at RTP), the added mass in this case is approximately 400 times the mass of the bubble. | 1 | Applied and Interdisciplinary Chemistry |
The risk of opioid-related adverse effects such as respiratory depression, falls, cognitive impairment and sedation is increased. Tramadol may interact with other medications and increase the risk for adverse events. | 0 | Theoretical and Fundamental Chemistry |
Non-aqueous acid–base titrations can be carried out advantageously by thermometric means.
Acid leach solutions from some copper mines can contain large quantities of Fe(III) as well as Cu(II). The "free acid" (sulfuric acid) content of these leach solutions is a critical process parameter. While thermometric titrimetry can determine the free acid content with modest amounts of Fe(III), in some solutions the Fe(III) content is so high as to cause serious interference. Complexation with necessarily large amounts of oxalate is undesirable due to the toxicity of the reagent. A thermometric titration was devised by diluting the aliquot with propan-2-ol and titration with standard KOH in propan-2-ol. Most of the metal content precipitated prior to the commencement of the titration, and a clear, sharp endpoint for the sulfuric acid content was obtained. | 0 | Theoretical and Fundamental Chemistry |
There are a great variety of techniques to generate THz radiation and to detect THz fields. One can, e.g., use an antenna, a quantum-cascade laser, a free-electron laser, or optical rectification to produce well-defined THz sources. The resulting THz field can be characterized via its electric field E(t). Present-day experiments can already output E(t) that has a peak value in the range of MV/cm (megavolts per centimeter). To estimate how strong such fields are, one can compute the level of energy change such fields induce to an electron over microscopic distance of one nanometer (nm), i.e., L = 1 nm. One simply multiplies the peak E(t) with elementary charge e and L to obtain e E(t) L = 100 meV. In other words, such fields have a major effect on electronic systems because the mere field strength of E(t) can induce electronic transitions over microscopic scales. One possibility is to use such THz fields to study Bloch oscillations where semiconductor electrons move through the Brillouin zone, just to return to where they started, giving rise to the Bloch oscillations.
The THz sources can be also extremely short, down to single cycle of THz fields oscillation. For one THz, that means duration in the range of one picosecond (ps). Consequently, one can use THz fields to monitor and control ultrafast processes in semiconductors or to produce ultrafast switching in semiconductor components. Obviously, the combination of ultrafast duration and strong peak E(t') provides vast new possibilities to systematic studies in semiconductors.
Besides the strength and duration of E(t), the THz field's photon energy plays a vital role in semiconductor investigations because it can be made resonant with several intriguing many-body transitions. For example, electrons in conduction band and holes, i.e., electronic vacancies, in valence band attract each other via the Coulomb interaction. Under suitable conditions, electrons and holes can be bound to excitons that are hydrogen-like states of matter. At the same time, the exciton binding energy is few to hundreds of meV that can be matched energetically with a THz photon. Therefore, the presence of excitons can be uniquely detected based on the absorption spectrum of a weak THz field. Also simple states, such as plasma and correlated electron–hole plasma can be monitored or modified by THz fields. | 0 | Theoretical and Fundamental Chemistry |
A dispersion is a system in which distributed particles of one material are dispersed in a continuous phase of another material. The two phases may be in the same or different states of matter.
Dispersions are classified in a number of different ways, including how large the particles are in relation to the particles of the continuous phase, whether or not precipitation occurs, and the presence of Brownian motion. In general, dispersions of particles sufficiently large for sedimentation are called suspensions, while those of smaller particles are called colloids and solutions. | 0 | Theoretical and Fundamental Chemistry |
There are several methods for preparing aldehydes, but the dominant technology is hydroformylation. Illustrative is the generation of butyraldehyde by hydroformylation of propene: | 0 | Theoretical and Fundamental Chemistry |
The International Association for the Properties of Water and Steam (IAPWS) is an international non-profit association of national organizations concerned with the properties of water and steam, particularly thermophysical properties and other aspects of high-temperature steam, water and aqueous mixtures that are relevant to thermal power cycles and other industrial applications.
The organization publishes a range of releases. Specifically, these relate to the thermal and expansion properties of steam.
Both free software and commercial software implementations of the IAPWS correlations are available. | 0 | Theoretical and Fundamental Chemistry |
Monoclonal antibodies are structurally identical immunoglobulin molecules with identical epitope-specificity (all of them bind with the same epitope with same affinity) as against their polyclonal counterparts which have varying affinities for the same epitope.
They are usually not produced in a natural immune response, but only in diseased states like multiple myeloma, or through specialized laboratory techniques. Because of their specificity, monoclonal antibodies are used in certain applications to quantify or detect the presence of substances (which act as antigen for the monoclonal antibodies), and for targeting individual cells (e.g. cancer cells). Monoclonal antibodies find use in various diagnostic modalities (see: western blot and immunofluorescence) and therapies—particularly of cancer and diseases with autoimmune component. But, since virtually all responses in nature are polyclonal, it makes production of immensely useful monoclonal antibodies less straightforward. | 1 | Applied and Interdisciplinary Chemistry |
MDS has been used to characterise interactions between biomolecules under native conditions, and has been demonstrated to detect specific interactions within complex mixtures. It has also been used in detecting and quantifying protein-ligand interactions and protein-lipid interactions. | 1 | Applied and Interdisciplinary Chemistry |
The commercially most important system is the LiO × AlO × nSiO system (LAS system). The LAS system mainly refers to a mix of lithium, silicon, and aluminum oxides with additional components, e.g., glass-phase-forming agents such as NaO, KO and CaO and refining agents. As nucleation agents most commonly zirconium(IV) oxide in combination with titanium(IV) oxide is used. This important system was studied first and intensively by Hummel, and Smoke.
After crystallization the dominant crystal phase in this type of glass-ceramic is a high-quartz solid solution (HQ s.s.). If the glass-ceramic is subjected to a more intense heat treatment, this HQ s.s. transforms into a keatite-solid solution (K s.s., sometimes wrongly named as beta-spodumene). This transition is non-reversible and reconstructive, which means bonds in the crystal-lattice are broken and new arranged. However, these two crystal phases show a very similar structure as Li could show.
An interesting property of these glass-ceramics is their thermomechanical durability. Glass-ceramic from the LAS system is a mechanically strong material and can sustain repeated and quick temperature changes up to 800–1000 °C. The dominant crystalline phase of the LAS glass-ceramics, HQ s.s., has a strong negative coefficient of thermal expansion (CTE), keatite-solid solution as still a negative CTE but much higher than HQ s.s. These negative CTEs of the crystalline phase contrasts with the positive CTE of the residual glass. Adjusting the proportion of these phases offers a wide range of possible CTEs in the finished composite. Mostly for today's applications a low or even zero CTE is desired. Also a negative CTE is possible, which means, in contrast to most materials when heated up, such a glass-ceramic contracts. At a certain point, generally between 60% [m/m] and 80% [m/m] crystallinity, the two coefficients balance such that the glass-ceramic as a whole has a thermal expansion coefficient that is very close to zero. Also, when an interface between material will be subject to thermal fatigue, glass-ceramics can be adjusted to match the coefficient of the material they will be bonded to.
Originally developed for use in the mirrors and mirror mounts of astronomical telescopes, LAS glass-ceramics have become known and entered the domestic market through its use in glass-ceramic cooktops, as well as cookware and bakeware or as high-performance reflectors for digital projectors. | 0 | Theoretical and Fundamental Chemistry |
The standard ISO 228 - Pipe threads where pressure-tight joints are not made on the threads consists of the following parts:
* ISO 228-1:2000 Dimensions, tolerances and designation
* ISO 228-2:1987 Verification by means of limit gauges | 1 | Applied and Interdisciplinary Chemistry |
The limiting factor for fish undergoing hypoxia is the availability of fermentable substrate for anaerobic metabolism; once substrate runs out, ATP production ceases. Endogenous glycogen is present in tissue as a long term energy storage molecule. It can be converted into glucose and subsequently used as the starting material in glycolysis.
A key adaptation to long-term survival during hypoxia is the ability of an organism to store large amounts of glycogen. Many hypoxia-tolerant species, such as carp, goldfish, killifish, and oscar contain the largest glycogen content (300-2000 μmol glocosyl units/g) in their tissue compared to hypoxia-sensitive fish, such as rainbow trout, which contain only 100 μmol glocosyl units/g. The more glycogen stored in a tissue indicates the capacity for that tissue to undergo glycolysis and produce ATP. | 0 | Theoretical and Fundamental Chemistry |
Robert A. Volz is credited with discovering the first process for making reticulated polyurethane foam in 1956 while working for the Scott Paper Company. Production of reticulated polyurethane foam is a two-step process that begins with the creation of conventional (closed-cell) polyurethane foam, after which cell faces (or "windows") are removed. To do so, the fact that the higher surface area and lower mass of cell faces compared with cell struts (or edges) makes them much more susceptible to both combustion and chemical degradation is exploited. Thus, closed-cell foam is either filled with a combustible gas like hydrogen and ignited under controlled conditions, or it is exposed to a sodium hydroxide solution to chemically degrade the foam, which will remove cell windows whilst sparing the edges.
Reticulated ceramic foams are made by coating a reticulated polyurethane foam with an aqueous suspension of a ceramic powder then heating the material to first evaporate the water then fuse the ceramic particles and finally to burn off the organic polymer.
Reticulated metal foam can also be made using polyurethane foam as a template similar to its use in ceramic foams. Metals can be vapor deposited onto the polyurethane foam and then the organic polymer burned off. | 0 | Theoretical and Fundamental Chemistry |
pRb acts as a recruiter that allows for the binding of proteins that alter chromatin structure onto the site E2F-regulated promoters. Access to these E2F-regulated promoters by transcriptional factors is blocked by the formation of nucleosomes and their further packing into chromatin. Nucleosome formation is regulated by post-translational modifications to histone tails. Acetylation leads to the disruption of nucleosome structure. Proteins called histone acetyltransferases (HATs) are responsible for acetylating histones and thus facilitating the association of transcription factors on DNA promoters. Deacetylation, on the other hand, leads to nucleosome formation and thus makes it more difficult for transcription factors to sit on promoters. Histone deacetylases (HDACs) are the proteins responsible for facilitating nucleosome formation and are therefore associated with transcriptional repressors proteins.
pRb interacts with the histone deacetylases HDAC1 and HDAC3. pRb binds to HDAC1 in its pocket domain in a region that is independent to its E2F-binding site. pRb recruitment of histone deacetylases leads to the repression of genes at E2F-regulated promoters due to nucleosome formation. Some genes activated during the G1/S transition such as cyclin E are repressed by HDAC during early to mid-G1 phase. This suggests that HDAC-assisted repression of cell cycle progression genes is crucial for the ability of pRb to arrest cells in G1. To further add to this point, the HDAC-pRb complex is shown to be disrupted by cyclin D/Cdk4 which levels increase and peak during the late G1 phase. | 1 | Applied and Interdisciplinary Chemistry |
In instances in which DNA samples are degraded, like if there are intense fires or all that remains are bone fragments, standard STR testing on those samples can be inadequate. When standard STR testing is done on highly degraded samples, the larger STR loci often drop out, and only partial DNA profiles are obtained. Partial DNA profiles can be a powerful tool, but the probability of a random match is larger than if a full profile was obtained. One method that has been developed to analyse degraded DNA samples is to use miniSTR technology. In the new approach, primers are specially designed to bind closer to the STR region.
In normal STR testing, the primers bind to longer sequences that contain the STR region within the segment. MiniSTR analysis, however, targets only the STR location, which results in a DNA product that is much smaller.
By placing the primers closer to the actual STR regions, there is a higher chance that successful amplification of this region will occur. Successful amplification of those STR regions can now occur, and more complete DNA profiles can be obtained. The success that smaller PCR products produce a higher success rate with highly degraded samples was first reported in 1995, when miniSTR technology was used to identify victims of the Waco fire. | 1 | Applied and Interdisciplinary Chemistry |
In molecular biology, a two-component regulatory system serves as a basic stimulus-response coupling mechanism to allow organisms to sense and respond to changes in many different environmental conditions. Two-component systems typically consist of a membrane-bound histidine kinase that senses a specific environmental stimulus, and a corresponding response regulator that mediates the cellular response, mostly through differential expression of target genes. Although two-component signaling systems are found in all domains of life, they are most common by far in bacteria, particularly in Gram-negative and cyanobacteria; both histidine kinases and response regulators are among the largest gene families in bacteria. They are much less common in archaea and eukaryotes; although they do appear in yeasts, filamentous fungi, and slime molds, and are common in plants, two-component systems have been described as "conspicuously absent" from animals. | 1 | Applied and Interdisciplinary Chemistry |
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