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Some metal carbynes dimerize to give dimetallacyclobutadienes. In these complexes, the carbyne ligand serves as a bridging ligand.
Several cluster-bound carbyne complexes are known, typically with CO ligands. These compounds do not feature MC triple bonds; instead the carbyne carbon is tetrahedral. Tricobalt derivatives are prepared by treating cobalt carbonyl with haloforms:
:2 HCBr + Co(CO) → 2 HCCo(CO) + 18 CO + 3 CoBr | 0 | Theoretical and Fundamental Chemistry |
The Green Infrastructure approach analyses the natural environment in a way that highlights its function and subsequently seeks to put in place, through regulatory or planning policy, mechanisms that safeguard critical natural areas. Where life support functions are found to be lacking, plans may propose how these can be put in place through landscaped and/or engineered improvements.
Within an urban context, this can be applied to re-introducing natural waterways and making a city self-sustaining particularly with regard to water, for example, to harvest water locally, recycle it, re-use it and integrate stormwater management into everyday infrastructure.
The multi-functionality of this approach is key to the efficient and sustainable use of land, especially in a compact and bustling country such as England where pressures on land are particularly acute. An example might be an urban edge river floodplain which provides a repository for flood waters, acts as a nature reserve, provides a recreational green space and could also be productively farmed (probably through grazing). There is growing evidence that the natural environment also has a positive effect on human health. | 1 | Applied and Interdisciplinary Chemistry |
The initial condition is assumed to be a smooth and divergence-free function (see smooth function) such that, for every multi-index (see multi-index notation) and any , there exists a constant such that
: for all
The external force is assumed to be a smooth function as well, and satisfies a very analogous inequality (now the multi-index includes time derivatives as well):
: for all
For physically reasonable conditions, the type of solutions expected are smooth functions that do not grow large as . More precisely, the following assumptions are made:
# There exists a constant such that for all
Condition 1 implies that the functions are smooth and globally defined and condition 2 means that the kinetic energy of the solution is globally bounded. | 1 | Applied and Interdisciplinary Chemistry |
Similar to liquid metal embrittlement (LME), solid metal-induced embrittlement results in a decrease in fracture strength of a material. In addition, a decrease in tensile ductility over a temperature range is indicative of metal-induced embrittlement. Although SMIE is greatest just below the embrittler’s melting temperature, the range over which SMIE occurs ranges from to T, where T is the melting temperature of the embrittler. The reduction in ductility is caused by formation and propagation of stable, subcritical intergranular cracks. SMIE produces both intergranular and transgranular fracture surfaces in otherwise ductile materials. | 1 | Applied and Interdisciplinary Chemistry |
Many very hydrophobic materials found in nature rely on Cassie's law and are biphasic on the submicrometer level. The fine hairs on some plants are hydrophobic, designed to exploit the solvent properties of water to attract and remove sunlight-blocking dirt from their photosynthetic surfaces. Inspired by this lotus effect, many functional superhydrophobic surfaces have been developed.
Water striders are insects that live on the surface film of water, and their bodies are effectively unwettable due to specialized hairpiles called hydrofuge; many of their body surfaces are covered with these specialized "hairpiles", composed of tiny hairs spaced so closely that there are more than one thousand microhairs per mm, which creates a hydrophobic surface. Similar hydrofuge surfaces are known in other insects, including aquatic insects that spend most of their lives submerged, with hydrophobic hairs preventing entry of water into their respiratory system. The skin surface of some species of lizards, such as geckos and anoles, has also been documented as highly hydrophobic, and may facilitate self-cleaning or underwater breathing.
Some birds are great swimmers, due to their hydrophobic feather coating. Penguins are coated in a layer of air and can release that trapped air to accelerate rapidly when needing to jump out of the water and land on higher ground. Wearing an air coat when swimming reduces the drag and also acts as a heat insulator. | 0 | Theoretical and Fundamental Chemistry |
Nod factors (nodulation factors or NF), are signaling molecules produced by soil bacteria known as rhizobia in response to flavonoid exudation from plants under nitrogen limited conditions. Nod factors initiate the establishment of a symbiotic relationship between legumes and rhizobia by inducing nodulation. Nod factors produce the differentiation of plant tissue in root hairs into nodules where the bacteria reside and are able to fix nitrogen from the atmosphere for the plant in exchange for photosynthates and the appropriate environment for nitrogen fixation. One of the most important features provided by the plant in this symbiosis is the production of leghemoglobin, which maintains the oxygen concentration low and prevents the inhibition of nitrogenase activity. | 1 | Applied and Interdisciplinary Chemistry |
Involved in the earliest step for the formation of the active cleavage complex, the CFIm complex is formed by three proteins of 25, 59 and 68 kDa, respectively:
*CFIm25 (or CPSF5/NUDT21)
*CFIm59 (or CPSF7)
*CFIm68 (or CPSF6)
CFIm25 and CFIm68 are sufficient for the activity of the complex, proving the expected redundancy of CFIm68 and CFIm59, which share great sequence similarity. | 1 | Applied and Interdisciplinary Chemistry |
In most dewetting studies a thin polymer film is spin-cast onto a substrate. Even in the case of the film does not dewet immediately if it is in a metastable state, e.g. if the temperature is below the glass transition temperature of the polymer. Annealing such a metastable film above its glass transition temperature increases the mobility of the polymer-chain molecules and dewetting takes place.
The process of dewetting occurs by the nucleation and growth of randomly formed holes, which coalesce to form a network of filaments, before breaking into droplets. When starting from a continuous film, an irregular pattern of droplets is formed. The droplet size and droplet spacing may vary over several orders of magnitude, since the dewetting starts from randomly formed holes in the film. There is no spatial correlation between the dry patches that develop. These dry patches grow and the material is accumulated in the rim surrounding the growing hole. In the case where the initially homogeneous film is thin (in the range of 100 nm), a polygon network of connected strings of material is formed, like a Voronoi pattern of polygons. These strings then can break up into droplets, a process which is known as the Plateau-Rayleigh instability. At other film thicknesses, other complicated patterns of droplets on the substrate can be observed, which stem from a fingering instability of the growing rim around the dry patch. | 0 | Theoretical and Fundamental Chemistry |
Palmitoylcarnitine is an ester derivative of carnitine involved in the metabolism of fatty acids. During the tricarboxylic acid cycle (TCA), fatty acids undergo a process known as β-oxidation to produce energy in the form of ATP. β-oxidation occurs primarily within mitochondria, however the mitochondrial membrane prevents the entry of long chain fatty acids (>C10), so the conversion of fatty acids such as palmitic acid is key. Palmitic acid is brought to the cell and once inside the cytoplasm is first converted to Palmitoyl-CoA. Palmitoyl-CoA has the ability to freely pass the outer mitochondrial membrane, but the inner membrane is impermeable to the Acyl-CoA and thioester forms of various long-chain fatty acids such as palmitic acid. The palmitoyl-CoA is then enzymatically transformed into palmitoylcarnitine via the Carnitine O-palmitoyltransferase family. The palmitoylcarnitine is then actively transferred into the inner membrane of the mitochondria via the carnitine-acylcarnitine translocase. Once inside the inner mitochondrial membrane, the same Carnitine O-palmitoyltransferase family is then responsible for transforming the palmitoylcarnitine back to the palmitoyl-CoA form. | 1 | Applied and Interdisciplinary Chemistry |
In the detection sub-process location and property vectors are recorded to allow particle localization for ejection and material classification for discrimination purposes. All detection technologies applied have in common to be cheap, contactless and fast. The technologies are subdivided in transmitting and reflecting groups, the first measuring the inner content of a particle while the later only uses the surface reflection for discrimination. Surface, or reflection technologies have the disadvantage that the surfaces need to be representing the content, thus need to be clean from clay and dust adhesions. But by default surface reflection technologies violate the Fundamental Sampling Principle because not all components of a particle have the same probability of being detected.
The main transmitting technologies are EM (Electromagnetics) and XRT (X-ray-Transmission). EM detection is based on the conductivity of the material passing an alternating electromagnetic field. The principle of XRT is widely known through the application in medical diagnostics and airport luggage scanners. The main surface or reflection technologies are traditionally X-ray luminescence detectors capturing the fluorescence of diamonds under the excitation of X-ray radiation and color cameras detecting brightness and colour difference. Spectroscopic methods such as near-infrared spectroscopy known from remote sensing in exploration in mining for decades, have found their way into industrial scale sensor-based sorters. Advantage of the application of near-infrared spectroscopy is that the evidence can be measured on the presence of specific molecular bonds, thus minerals composition of the near-infrared active minerals. There is more detection technologies available on industrial scale sensor-based ore sorters. Readers that want to go into detail can find more in the literature. | 0 | Theoretical and Fundamental Chemistry |
The majority of bitumen used commercially is obtained from petroleum. Nonetheless, large amounts of bitumen occur in concentrated form in nature. Naturally occurring deposits of bitumen are formed from the remains of ancient, microscopic algae (diatoms) and other once-living things. These natural deposits of bitumen have been formed during the Carboniferous period, when giant swamp forests dominated many parts of the Earth. They were deposited in the mud on the bottom of the ocean or lake where the organisms lived. Under the heat (above 50 °C) and pressure of burial deep in the earth, the remains were transformed into materials such as bitumen, kerogen, or petroleum.
Natural deposits of bitumen include lakes such as the Pitch Lake in Trinidad and Tobago and Lake Bermudez in Venezuela. Natural seeps occur in the La Brea Tar Pits and the McKittrick Tar Pits in California, as well as in the Dead Sea.
Bitumen also occurs in unconsolidated sandstones known as "oil sands" in Alberta, Canada, and the similar "tar sands" in Utah, US.
The Canadian province of Alberta has most of the world's reserves, in three huge deposits covering , an area larger than England or New York state. These bituminous sands contain of commercially established oil reserves, giving Canada the third largest oil reserves in the world. Although historically it was used without refining to pave roads, nearly all of the output is now used as raw material for oil refineries in Canada and the United States.
The world's largest deposit of natural bitumen, known as the Athabasca oil sands, is located in the McMurray Formation of Northern Alberta. This formation is from the early Cretaceous, and is composed of numerous lenses of oil-bearing sand with up to 20% oil. Isotopic studies show the oil deposits to be about 110 million years old. Two smaller but still very large formations occur in the Peace River oil sands and the Cold Lake oil sands, to the west and southeast of the Athabasca oil sands, respectively. Of the Alberta deposits, only parts of the Athabasca oil sands are shallow enough to be suitable for surface mining. The other 80% has to be produced by oil wells using enhanced oil recovery techniques like steam-assisted gravity drainage.
Much smaller heavy oil or bitumen deposits also occur in the Uinta Basin in Utah, US. The Tar Sand Triangle deposit, for example, is roughly 6% bitumen.
Bitumen may occur in hydrothermal veins. An example of this is within the Uinta Basin of Utah, in the US, where there is a swarm of laterally and vertically extensive veins composed of a solid hydrocarbon termed Gilsonite. These veins formed by the polymerization and solidification of hydrocarbons that were mobilized from the deeper oil shales of the Green River Formation during burial and diagenesis.
Bitumen is similar to the organic matter in carbonaceous meteorites. However, detailed studies have shown these materials to be distinct. The vast Alberta bitumen resources are considered to have started out as living material from marine plants and animals, mainly algae, that died millions of years ago when an ancient ocean covered Alberta. They were covered by mud, buried deeply over time, and gently cooked into oil by geothermal heat at a temperature of . Due to pressure from the rising of the Rocky Mountains in southwestern Alberta, 80 to 55 million years ago, the oil was driven northeast hundreds of kilometres and trapped into underground sand deposits left behind by ancient river beds and ocean beaches, thus forming the oil sands. | 0 | Theoretical and Fundamental Chemistry |
Acridine has been obtained as eight polymorphs and aripiprazole has nine. The record for the largest number of well-characterised polymorphs is held by a compound known as ROY. Glycine crystallizes as both monoclinic and hexagonal crystals. Polymorphism in organic compounds is often the result of conformational polymorphism. | 0 | Theoretical and Fundamental Chemistry |
The organization of the DNA that is achieved by the nucleosome cannot fully explain the packaging of DNA observed in the cell nucleus. Further compaction of chromatin into the cell nucleus is necessary, but it is not yet well understood. The current understanding is that repeating nucleosomes with intervening "linker" DNA form a 10-nm-fiber, described as "beads on a string", and have a packing ratio of about five to ten. A chain of nucleosomes can be arranged in a 30 nm fiber, a compacted structure with a packing ratio of ~50 and whose formation is dependent on the presence of the H1 histone.
A crystal structure of a tetranucleosome has been presented and used to build up a proposed structure of the 30 nm fiber as a two-start helix.
There is still a certain amount of contention regarding this model, as it is incompatible with recent electron microscopy data. Beyond this, the structure of chromatin is poorly understood, but it is classically suggested that the 30 nm fiber is arranged into loops along a central protein scaffold to form transcriptionally active euchromatin. Further compaction leads to transcriptionally inactive heterochromatin. | 1 | Applied and Interdisciplinary Chemistry |
Hirudin derivatives are all bivalent DTIs, they block both the active site and exosite 1 in an irreversible 1:1 stoichiometric complex. The active site is the binding site for the globular amino-terminal domain and exosite 1 is the binding site for the acidic carboxy-terminal domain of hirudin. Native hirudin, a 65-amino-acid polypeptide, is produced in the parapharyngeal glands of medicinal leeches. Hirudins today are produced by recombinant biotechnology using yeast. These recombinant hirudins lack a sulfate group at Tyr-63 and are therefore called desulfatohirudins. They have a 10-fold lower binding affinity to thrombin compared to native hirudin, but remain a highly specific inhibitor of thrombin and have an inhibition constant for thrombin in the picomolar range. Renal clearance and degradation account for the most part for the systemic clearance of desulfatohirudins and there is accumulation of the drug in patients with chronic kidney disease. These drugs should not be used in patients with impaired renal function, since there is no specific antidote available to reverse the effects. Hirudins are given parenterally, usually by intravenous injection. 80% of hirudin is distributed in the extravascular compartment and only 20% is found in the plasma. The most common desulfatohirudins today are lepirudin and desirudin. | 1 | Applied and Interdisciplinary Chemistry |
The nature of chemical reactions and their description is one of the most fundamental problems in chemistry. The concepts of covalent and ionic bonds which emerged in the beginning of the 20th century specify the profound differences between their electronic structures. These differences, in turn, lead to dramatically different behavior of covalent and ionic compounds both in the solution and solid phase. In the solid phase, ionic compounds, e.g. salts, are prone to formation of crystal lattices; in polar solvents, they dissociate into ions surrounded by solvate shells, thus rendering the solution highly ionic conductive. In contrast to covalent bonds, ionic interactions demonstrate flexible, dynamic behavior, which allows tuning ionic compounds to obtain desired properties. | 1 | Applied and Interdisciplinary Chemistry |
Buccianti was born on 7 August 1960 in Florence. She earned a master's degree in stratigraphy from the University of Florence in 1988, including work done as a student with Agip, and completed a PhD at the University of Florence in 1994. She obtained a permanent research position at the university in 2001. | 0 | Theoretical and Fundamental Chemistry |
In dynamic covalent chemistry covalent bonds are broken and formed in a reversible reaction under thermodynamic control. While covalent bonds are key to the process, the system is directed by non-covalent forces to form the lowest energy structures. | 0 | Theoretical and Fundamental Chemistry |
In order to provide a good minigene model, the gene fragment should have all of the necessary elements to ensure it exhibits the same alternative splicing (AS) patterns as the wild type gene, i.e., the length of the fragment must include all upstream and downstream sequences which can affect its splicing. Therefore, most minigene designs begin with a thorough in silico analysis of the requirements of the experiment before any "wet" lab work is conducted. With the advent of Bioinformatics and widespread use of computers, several good programs now exist for the identification of cis-acting control regions that affect the splicing outcomes of a gene and advanced programs can even consider splicing outcomes in various tissue types. Differences in minigenes are usually reflected in the final size of the fragment, which is in turn a reflection of the complexity of the minigene itself. The number of foreign DNA elements (exon and introns) inserted into the constitutive exons and introns of a given fragment varies with the type of experiment and the information being sought. A typical experiment might involve wild type minigenes which are expected to express genes normally in a comparison run against genetically engineered allelic variations which replace the wild-type gene and have been cloned into the same flanking sequences as the original fragment. These types of experiments help to determine the effect of various mutations on pre-mRNA splicing. | 1 | Applied and Interdisciplinary Chemistry |
In coordination chemistry, Tanabe–Sugano diagrams are used to predict absorptions in the ultraviolet (UV), visible and infrared (IR) electromagnetic spectrum of coordination compounds. The results from a Tanabe–Sugano diagram analysis of a metal complex can also be compared to experimental spectroscopic data. They are qualitatively useful and can be used to approximate the value of 10Dq, the ligand field splitting energy. Tanabe–Sugano diagrams can be used for both high spin and low spin complexes, unlike Orgel diagrams, which apply only to high spin complexes. Tanabe–Sugano diagrams can also be used to predict the size of the ligand field necessary to cause high-spin to low-spin transitions.
In a Tanabe–Sugano diagram, the ground state is used as a constant reference, in contrast to Orgel diagrams. The energy of the ground state is taken to be zero for all field strengths, and the energies of all other terms and their components are plotted with respect to the ground term. | 0 | Theoretical and Fundamental Chemistry |
Hull speed can be calculated by the following formula:
where
: is the length of the waterline in feet, and
: is the hull speed of the vessel in knots
If the length of waterline is given in metres and desired hull speed in knots, the coefficient is 2.43 kn·m. The constant may be given as 1.34 to 1.51 knot·ft in imperial units (depending on the source), or 4.50 to 5.07 km·h·m in metric units, or 1.25 to 1.41 m·s·m in SI units.
The ratio of speed to is often called the "speed/length ratio", even though it is a ratio of speed to the square root of length. | 1 | Applied and Interdisciplinary Chemistry |
Small-molecule anti-genomic therapeutics, or SMAT, refers to a biodefense technology that targets DNA signatures found in many biological warfare agents. SMATs are new, broad-spectrum drugs that unify antibacterial, antiviral and anti-malarial activities into a single therapeutic that offers substantial cost benefits and logistic advantages for physicians and the military. | 1 | Applied and Interdisciplinary Chemistry |
Two types of quantum efficiency of a solar cell are often considered:
*External quantum efficiency (EQE) is the ratio of the number of charge carriers collected by the solar cell to the number of photons of a given energy shining on the solar cell from outside (incident photons).
*Internal quantum efficiency (IQE) is the ratio of the number of charge carriers collected by the solar cell to the number of photons of a given energy that shine on the solar cell from outside and are absorbed by the cell.
The IQE is always larger than the EQE in the visible spectrum. A low IQE indicates that the active layer of the solar cell is unable to make good use of the photons, most likely due to poor carrier collection efficiency. To measure the IQE, one first measures the EQE of the solar device, then measures its transmission and reflection, and combines these data to infer the IQE.
The external quantum efficiency therefore depends on both the absorption of light and the collection of charges. Once a photon has been absorbed and has generated an electron-hole pair, these charges must be separated and collected at the junction. A "good" material avoids charge recombination. Charge recombination causes a drop in the external quantum efficiency.
The ideal quantum efficiency graph has a square shape, where the QE value is fairly constant across the entire spectrum of wavelengths measured. However, the QE for most solar cells is reduced because of the effects of recombination, where charge carriers are not able to move into an external circuit. The same mechanisms that affect the collection probability also affect the QE. For example, modifying the front surface can affect carriers generated near the surface. Highly doped front surface layers can also cause free carrier absorption which reduces QE in the longer wavelengths. And because high-energy (blue) light is absorbed very close to the surface, considerable recombination at the front surface will affect the "blue" portion of the QE. Similarly, lower energy (green) light is absorbed in the bulk of a solar cell, and a low diffusion length will affect the collection probability from the solar cell bulk, reducing the QE in the green portion of the spectrum. Generally, solar cells on the market today do not produce much electricity from ultraviolet and infrared light (<400 nm and >1100 nm wavelengths, respectively); these wavelengths of light are either filtered out or are absorbed by the cell, thus heating the cell. That heat is wasted energy, and could damage the cell. | 0 | Theoretical and Fundamental Chemistry |
The species problem in non-eukaryotic taxonomy has led to various suggestions in classifying bacteria, and the ad hoc committee on reconciliation of approaches to bacterial systematics of 1987 has recommended use of GC-ratios in higher-level hierarchical classification. For example, the Actinomycetota are characterised as "high GC-content bacteria". In Streptomyces coelicolor A3(2), GC-content is 72%. With the use of more reliable, modern methods of molecular systematics, the GC-content definition of Actinomycetota has been abolished and low-GC bacteria of this clade have been found. | 1 | Applied and Interdisciplinary Chemistry |
FPIA quantifies the change in fluorescence polarization of reaction mixtures of fluorescent-labelled tracer, sample antigen, and defined antibody. Operating under fixed temperature and viscosity allows for the fluorescence polarization to be directly proportional to the size of the fluorophore. Free tracer in solution has a lower fluorescence polarization than antibody-bound tracer with slower Brownian motion. The tracer and the specific antigen will compete to bind to the antibody and if the antigen is low in concentration, more tracer will be bound to the antibody resulting in a higher fluorescence polarization and vice versa.
A conventional FPIA follows the procedure below:
# A specific quantity of sample is added to reaction buffer.
# The solution is allowed to equilibrate at room temperature for approximately two minutes.
# The solution is evaluated in a fluorescence polarization analyzer to gather a baseline measurement.
# A specific quantity of antigen conjugated with fluorophore is added to the solution.
# The solution again equilibrates for approximately two minutes.
# The solution is evaluated again by the fluorescence polarization analyzer.
# The fluorescence polarization value for the tracer containing solution is compared to the baseline and magnitude of difference is proportional to quantity of target analyte in sample. | 1 | Applied and Interdisciplinary Chemistry |
Viral transformation is the change in growth, phenotype, or indefinite reproduction of cells caused by the introduction of inheritable material. Through this process, a virus causes harmful transformations of an in vivo cell or cell culture. The term can also be understood as DNA transfection using a viral vector.
Viral transformation can occur both naturally and medically. Natural transformations can include viral cancers, such as human papillomavirus (HPV) and T-cell Leukemia virus type I. Hepatitis B and C are also the result of natural viral transformation of the host cells. Viral transformation can also be induced for use in medical treatments.
Cells that have been virally transformed can be differentiated from untransformed cells through a variety of growth, surface, and intracellular observations. The growth of transformed cells can be impacted by a loss of growth limitation caused by cell contact, less oriented growth, and high saturation density. Transformed cells can lose their tight junctions, increase their rate of nutrient transfer, and increase their protease secretion. Transformation can also affect the cytoskeleton and change in the quantity of signal molecules. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, coprecipitation (CPT) or co-precipitation is the carrying down by a precipitate of substances normally soluble under the conditions employed. Analogously, in medicine, coprecipitation (referred to as immunoprecipitation) is specifically "an assay designed to purify a single antigen from a complex mixture using a specific antibody attached to a beaded support".
Coprecipitation is an important topic in chemical analysis, where it can be undesirable, but can also be usefully exploited. In gravimetric analysis, which consists on precipitating the analyte and measuring its mass to determine its concentration or purity, coprecipitation is a problem because undesired impurities often coprecipitate with the analyte, resulting in excess mass. This problem can often be mitigated by "digestion" (waiting for the precipitate to equilibrate and form larger and purer particles) or by redissolving the sample and precipitating it again.
On the other hand, in the analysis of trace elements, as is often the case in radiochemistry, coprecipitation is often the only way of separating an element. Since the trace element is too dilute (sometimes less than a part per trillion) to precipitate by conventional means, it is typically coprecipitated with a carrier, a substance that has a similar crystalline structure that can incorporate the desired element. An example is the separation of francium from other radioactive elements by coprecipitating it with caesium salts such as caesium perchlorate. Otto Hahn is credited for promoting the use of coprecipitation in radiochemistry.
There are three main mechanisms of coprecipitation: inclusion, occlusion, and adsorption. An inclusion (incorporation in the crystal lattice) occurs when the impurity occupies a lattice site in the crystal structure of the carrier, resulting in a crystallographic defect; this can happen when the ionic radius and charge of the impurity are similar to those of the carrier. An adsorbate is an impurity that is weakly, or strongly, bound (adsorbed) to the surface of the precipitate. An occlusion occurs when an adsorbed impurity gets physically trapped inside the crystal as it grows.
Besides its applications in chemical analysis and in radiochemistry, coprecipitation is also important to many environmental issues related to water resources, including acid mine drainage, radionuclide migration around waste repositories, toxic heavy metal transport at industrial and defense sites, metal concentrations in aquatic systems, and wastewater treatment technology.
Coprecipitation is also used as a method of magnetic nanoparticle synthesis. | 0 | Theoretical and Fundamental Chemistry |
The cold work produced from this process is typically minimal, similar to the cold work produced by laser peening, only a few percent, but a great deal less than shot peening, gravity peening or, deep rolling. Cold work is particularly important because the higher the cold work at the surface of a component, the more vulnerable to elevated temperatures and mechanical overload that component will be and the easier the beneficial surface residual compression will relax, rendering the treatment pointless. In other words, a component that has been highly cold worked will not hold the compression if it comes into contact with extreme heat, like an engine, and will be just as vulnerable as it was to start. Therefore, LPB and laser peening stand out in the surface enhancement industry because they are both thermally stable at high temperatures. The reason LPB produces such low percentages of cold work is because of the aforementioned closed-loop process control. Conventional shot peening processes have some guesswork involved and are not exact at all, causing the procedure to have to be performed multiple times on one component. For example, shot peening, in order to make sure every spot on the component is treated, typically specifies coverage of between 200% (2T) and 400% (4T). This means that at 200% coverage (2T), 5 or more impacts occur at 84% of locations and at 400% coverage (4T), it is significantly more. The problem is that one area will be hit several times while the area next to it is hit fewer times, leaving uneven compression at the surface. This uneven compression results in the whole process being easily "undone", as was mentioned above. LPB requires only one pass with the tool and leaves a deep, even, beneficial compressive stress.
The LPB process can be performed on-site in the shop or in situ on aircraft using robots, making it easy to incorporate into everyday maintenance and manufacturing procedures. The method is applied under continuous closed loop process control (CLPC), creating accuracy within 0.1% and alerting the operator and QA immediately if the processing bounds are exceeded. The limitation of this process is that different CNC processing codes need to be developed for each application, just like any other machining task. The other issue is that because of dimensional restrictions, it may not be possible to create the tools necessary to work on certain geometries, although that has yet to be a problem. | 1 | Applied and Interdisciplinary Chemistry |
The Archimedes number is applied often in the engineering of packed beds, which are very common in the chemical processing industry. A packed bed reactor, which is similar to the ideal plug flow reactor model, involves packing a tubular reactor with a solid catalyst, then passing incompressible or compressible fluids through the solid bed. When the solid particles are small, they may be "fluidized", so that they act as if they were a fluid. When fluidizing a packed bed, the pressure of the working fluid is increased until the pressure drop between the bottom of the bed (where fluid enters) and the top of the bed (where fluid leaves) is equal to the weight of the packed solids. At this point, the velocity of the fluid is just not enough to achieve fluidization, and extra pressure is required to overcome the friction of particles with each other and the wall of the reactor, allowing fluidization to occur. This gives a minimum fluidization velocity, , that may be estimated by:
where:
* is the diameter of sphere with the same volume as the solid particle and can often be estimated as , where is the diameter of the particle. | 1 | Applied and Interdisciplinary Chemistry |
The input data on irrigation, evaporation, and surface runoff are to be specified per season for three kinds of agricultural practices, which can be chosen at the discretion of the user:
:A: irrigated land with crops of group A
:B: irrigated land with crops of group B
:U: non-irrigated land with rain-fed crops or fallow land
The groups, expressed in fractions of the total area, may consist of combinations of crops or just of a single kind of crop. For example, as the A-type crops one may specify the lightly irrigated cultures, and as the B type the more heavily irrigated ones, such as sugarcane and rice. But one can also take A as rice and B as sugar cane, or perhaps trees and orchards. A, B and/or U crops can be taken differently in different seasons, e.g. A=wheat plus barley in winter and A=maize in summer while B=vegetables in winter and B=cotton in summer. Non-irrigated land can be specified in two ways: (1) as U = 1−A−B and (2) as A and/or B with zero irrigation. A combination can also be made.
Further, a specification must be given of the seasonal rotation of the different land uses over the total area, e.g. full rotation, no rotation at all, or incomplete rotation. This occurs with a rotation index. The rotations are taken over the seasons within the year. To obtain rotations over the years it is advisable to introduce annual input changes as explained
When a fraction A1, B1 and/or U1 differs from the fraction A2, B2 and/or U2 in another season, because the irrigation regime changes in the different seasons, the program will detect that a certain rotation occurs. If one wishes to avoid this, one may specify the same fractions in all seasons (A2=A1, B2=B1, U2=U1) but the crops and irrigation quantities may be different and may need to be proportionally adjusted. One may even specify irrigated land (A or B) with zero irrigation, which is the same as un-irrigated land (U).
Cropping rotation schedules vary widely in different parts of the world. Creative combinations of area fractions, rotation indexes, irrigation quantities and annual input changes can accommodate many types of agricultural practices.
Variation of the area fractions and/or the rotational schedule gives the opportunity to simulate the effect of different agricultural practices on the water and salt balance. | 0 | Theoretical and Fundamental Chemistry |
The generation of a transmembrane electrical potential through ion movement across a cell membrane drives biological processes like nerve conduction, muscle contraction, hormone secretion, and sensation. By convention, physiological voltages are measured relative to the extracellular region; a typical animal cell has an internal electrical potential of (−70)–(−50) mV.
An electrochemical gradient is essential to mitochondrial oxidative phosphorylation. The final step of cellular respiration is the electron transport chain, composed of four complexes embedded in the inner mitochondrial membrane. Complexes I, III, and IV pump protons from the matrix to the intermembrane space (IMS); for every electron pair entering the chain, ten protons translocate into the IMS. The result is an electric potential of more than . The resulting flux of protons back into the matrix powers the efforts of ATP synthase to combine inorganic phosphate and ADP.
Similar to the electron transport chain, the light-dependent reactions of photosynthesis pump protons into the thylakoid lumen of chloroplasts to drive the synthesis of ATP. The proton gradient can be generated through either noncyclic or cyclic photophosphorylation. Of the proteins that participate in noncyclic photophosphorylation, photosystem II (PSII), plastiquinone, and cytochrome bf complex directly contribute to generating the proton gradient. For each four photons absorbed by PSII, eight protons are pumped into the lumen.
Several other transporters and ion channels play a role in generating a proton electrochemical gradient. One is TPK, a potassium channel that is activated by Ca and conducts K from the thylakoid lumen to the stroma, which helps establish the electric field. On the other hand, the electro-neutral K efflux antiporter (KEA) transports K into the thylakoid lumen and H into the stroma, which helps establish the pH gradient. | 0 | Theoretical and Fundamental Chemistry |
Catherine E. Costello attended the Emmanuel College in Boston for her undergraduate studies in chemistry, and minors in mathematics and physics. She received a Master of Science (1967) and a PhD from Georgetown University (1971). After graduation, she did post-doctoral research with Klaus Biemann at Massachusetts Institute of Technology. | 1 | Applied and Interdisciplinary Chemistry |
The North Pacific Gyre, one of the largest ecosystem on Earth, is bordered to the south by the Intertropical Convergence Zone and extending north to roughly 50°N. At the southern boundary of the North Pacific Gyre, the North Equatorial Current flows west along the equator towards southeast Asia. The Kuroshio Current is the western boundary current of the North Pacific Gyre, flowing northeast along the coast of Japan. At roughly 50°N, the flow turns east and becomes the North Pacific Current. The North Pacific Current flows east, eventually bifurcating near the west coast of North America into the northward flowing Alaska Current and the southward flowing California Current. The Alaska Current is the eastern boundary current of the subpolar Alaska Gyre, while the California Current is the eastern boundary current that completes the North Pacific Gyre circulation. Within the North Pacific Gyre is the Great Pacific garbage patch, an area of increased plastic waste concentration. | 1 | Applied and Interdisciplinary Chemistry |
Reddi is the founder of the International Conference on Bone Morphogenetic Proteins (BMPs). He organized the first conference at the Johns Hopkins University School of Medicine in 1994. The conference is held every two years rotating between the United States and an international venue. | 1 | Applied and Interdisciplinary Chemistry |
Over the course of Earth's geologic history concentrations have played a role in biological evolution. The first photosynthetic organisms probably evolved early in the evolutionary history of life and most likely used reducing agents such as hydrogen or hydrogen sulfide as sources of electrons, rather than water. Cyanobacteria appeared later, and the excess oxygen they produced contributed to the oxygen catastrophe, which rendered the evolution of complex life possible. In recent geologic times, low concentrations below 600 parts per million might have been the stimulus that favored the evolution of C4 carbon fixation| plants which increased greatly in abundance between 7 and 5 million years ago over plants that use the less efficient C3 carbon fixation| metabolic pathway. At current atmospheric pressures photosynthesis shuts down when atmospheric concentrations fall below 150 ppm and 200 ppm although some microbes can extract carbon from the air at much lower concentrations. | 1 | Applied and Interdisciplinary Chemistry |
2,4,6-Trichlorobenzoyl chloride or Yamaguchi's reagent is an chlorinated aromatic compound that is commonly used in a variety of organic syntheses. | 0 | Theoretical and Fundamental Chemistry |
The first observations of intracellular structures that probably represented mitochondria were published in 1857, by the physiologist Albert von Kolliker. Richard Altmann, in 1890, established them as cell organelles and called them "bioblasts." In 1898, Carl Benda coined the term "mitochondria" from the Greek , , "thread", and , , "granule." Leonor Michaelis discovered that Janus green can be used as a supravital stain for mitochondria in 1900. In 1904, Friedrich Meves made the first recorded observation of mitochondria in plants in cells of the white waterlily, Nymphaea alba, and in 1908, along with Claudius Regaud, suggested that they contain proteins and lipids. Benjamin F. Kingsbury, in 1912, first related them with cell respiration, but almost exclusively based on morphological observations. In 1913, Otto Heinrich Warburg linked respiration to particles which he had obtained from extracts of guinea-pig liver and which he called "grana". Warburg and Heinrich Otto Wieland, who had also postulated a similar particle mechanism, disagreed on the chemical nature of the respiration. It was not until 1925, when David Keilin discovered cytochromes, that the respiratory chain was described.
In 1939, experiments using minced muscle cells demonstrated that cellular respiration using one oxygen molecule can form four adenosine triphosphate (ATP) molecules, and in 1941, the concept of the phosphate bonds of ATP being a form of energy in cellular metabolism was developed by Fritz Albert Lipmann. In the following years, the mechanism behind cellular respiration was further elaborated, although its link to the mitochondria was not known. The introduction of tissue fractionation by Albert Claude allowed mitochondria to be isolated from other cell fractions and biochemical analysis to be conducted on them alone. In 1946, he concluded that cytochrome oxidase and other enzymes responsible for the respiratory chain were isolated to the mitochondria. Eugene Kennedy and Albert Lehninger discovered in 1948 that mitochondria are the site of oxidative phosphorylation in eukaryotes. Over time, the fractionation method was further developed, improving the quality of the mitochondria isolated, and other elements of cell respiration were determined to occur in the mitochondria.
The first high-resolution electron micrographs appeared in 1952, replacing the Janus Green stains as the preferred way to visualize mitochondria. This led to a more detailed analysis of the structure of the mitochondria, including confirmation that they were surrounded by a membrane. It also showed a second membrane inside the mitochondria that folded up in ridges dividing up the inner chamber and that the size and shape of the mitochondria varied from cell to cell.
The popular term "powerhouse of the cell" was coined by Philip Siekevitz in 1957.
In 1967, it was discovered that mitochondria contained ribosomes. In 1968, methods were developed for mapping the mitochondrial genes, with the genetic and physical map of yeast mitochondrial DNA completed in 1976. | 1 | Applied and Interdisciplinary Chemistry |
The popularization of NHC ligands can be traced to Arduengo, who reported the deprotonation of dimesitylimidazolium cation to give IMes. IMes is a free NHC that can be used as a ligand. Other NHCs have been isolated as the free ligands. Aside from IMes, another important NHC ligand is IPr, which features diisopropylphenyl groups in place of the mesityl groups. NHCs with saturated backbones include SIMes and SIPr. | 0 | Theoretical and Fundamental Chemistry |
The Cornforth Medal for the most outstanding PhD thesis submitted by a member. It is named after the Australian Nobel Prize in Chemistry winner, Sir John Cornforth.
The Rennie Memorial Medal for the member of less than 8 years of professional experience since completing their most recent relevant qualification who has contributed most towards the development of some branch of chemical science.
The Leighton Memorial Medal is awarded to individuals in recognition of eminent services to chemistry in Australia.
The Ollé Prize for a member of the institute who submits the "best treatise, writing or paper" on any subject relevant to the institute's interests.
The Adrien Albert award recognises the enormous contributions made by Prof. Adrien Albert to medicinal chemistry. It is the premier award of the Medicinal Chemistry and Chemical Biology Division and is given for sustained, outstanding research in the field of medicinal or agricultural chemistry or chemical biology. The research upon which the award is made must be conducted wholly, or largely, within Australia and New Zealand. | 1 | Applied and Interdisciplinary Chemistry |
Each dislocation is associated with a strain field which contributes some small but finite amount to the materials stored energy. When the temperature is increased - typically below one-third of the absolute melting point - dislocations become mobile and are able to glide, cross-slip and climb. If two dislocations of opposite sign meet then they effectively cancel out and their contribution to the stored energy is removed. When annihilation is complete then only excess dislocation of one kind will remain. | 1 | Applied and Interdisciplinary Chemistry |
Traditionally the level of multiplexing in SILAC was limited due to the number of SILAC isotopes available. Recently, a new technique called NeuCode (neutron encoding) SILAC, has augmented the level of multiplexing achievable with metabolic labeling (up to 4). The NeuCode amino acid method is similar to SILAC but differs in that the labeling only utilizes heavy amino acids. The use of only heavy amino acids eliminates the need for 100% incorporation of amino acids needed for SILAC. The increased multiplexing capability of NeuCode amino acids is from the use of mass defects from extra neutrons in the stable isotopes. These small mass differences however need to be resolved on high-resolution mass spectrometers. | 1 | Applied and Interdisciplinary Chemistry |
Proteins, DNAs, RNAs, and other polymer folding dynamics have been measured using FRET. Usually, these systems are under equilibrium whose kinetics is hidden. However, they can be measured by measuring single-molecule FRET with proper placement of the acceptor and donor dyes on the molecules. See single-molecule FRET for a more detailed description. | 1 | Applied and Interdisciplinary Chemistry |
Although only being able to produce short hydrogel fibers, production of hydrogel fiber by polymerizing the hydrogel network inside a tubular mold and push out the fiber forcefully can also be achieved. But the friction will increase with the increasing length, and only short hydrogel fibers are feasible.
A case would be the production of poly(acrylamide-co-poly(ethylene glycol) diacrylate) fiber reported by yun et al. The pregel solution was a mixture of AAM, [https://www.sigmaaldrich.com/catalog/product/aldrich/455008?lang=en®ion=US poly(ethylene glycol) diacrylate] (PEGDA, crosslinker), and [https://www.sigmaaldrich.com/catalog/product/aldrich/405655?lang=en®ion=US&cm_sp=Insite-_-caSrpResults_srpRecs_srpModel_2-hydroxy-2-methylpropiophenone-_-srpRecs3-1 2-hydroxy-2-methylpropiophenone] (photoinitiator). The mixture was injected into a tubular mold and extracted through hydrostatic force afterwards. | 0 | Theoretical and Fundamental Chemistry |
Lipid droplets, also referred to as lipid bodies, oil bodies or adiposomes, are lipid-rich cellular organelles that regulate the storage and hydrolysis of neutral lipids and are found largely in the adipose tissue. They also serve as a reservoir for cholesterol and acyl-glycerols for membrane formation and maintenance. Lipid droplets are found in all eukaryotic organisms and store a large portion of lipids in mammalian adipocytes. Initially, these lipid droplets were considered to merely serve as fat depots, but since the discovery in the 1990s of proteins in the lipid droplet coat that regulate lipid droplet dynamics and lipid metabolism, lipid droplets are seen as highly dynamic organelles that play a very important role in the regulation of intracellular lipid storage and lipid metabolism. The role of lipid droplets outside of lipid and cholesterol storage has recently begun to be elucidated and includes a close association to inflammatory responses through the synthesis and metabolism of eicosanoids and to metabolic disorders such as obesity, cancer, and atherosclerosis. In non-adipocytes, lipid droplets are known to play a role in protection from lipotoxicity by storage of fatty acids in the form of neutral triacylglycerol, which consists of three fatty acids bound to glycerol. Alternatively, fatty acids can be converted to lipid intermediates like diacylglycerol (DAG), ceramides and fatty acyl-CoAs. These lipid intermediates can impair insulin signaling, which is referred to as lipid-induced insulin resistance and lipotoxicity. Lipid droplets also serve as platforms for protein binding and degradation. Finally, lipid droplets are known to be exploited by pathogens such as the hepatitis C virus, the dengue virus and Chlamydia trachomatis among others. | 1 | Applied and Interdisciplinary Chemistry |
An amino acid neurotransmitter is an amino acid which is able to transmit a nerve message across a synapse. Neurotransmitters (chemicals) are packaged into vesicles that cluster beneath the axon terminal membrane on the presynaptic side of a synapse in a process called endocytosis.
Amino acid neurotransmitter release (exocytosis) is dependent upon calcium Ca and is a presynaptic response. | 1 | Applied and Interdisciplinary Chemistry |
TIA1 or Tia1 cytotoxic granule-associated rna binding protein is a 3UTR mRNA binding protein that can bind the 5TOP sequence of 5'TOP mRNAs. It is associated with programmed cell death (apoptosis) and regulates alternative splicing of the gene encoding the Fas receptor, an apoptosis-promoting protein. Under stress conditions, TIA1 localizes to cellular RNA-protein conglomerations called stress granules. It is encoded by the TIA1 gene.
Mutations in the TIA1 gene have been associated with amyotrophic lateral sclerosis, frontotemporal dementia, and Welander distal myopathy. It also plays a crucial role in the development of toxic oligomeric tau in Alzheimer's disease. | 1 | Applied and Interdisciplinary Chemistry |
Photodissociation is used to detect electromagnetic activity of ions, compounds, and clusters when spectroscopy cannot be directly applied. Low concentrations of analyte can be one inhibiting factor to spectroscopy esp. in the gas phase. Mass spectrometers, time-of-flight and ion cyclotron resonance have been used to study hydrated ion clusters. Instruments are able to use ESI to effectively form hydrated ion clusters. Laser ablation and corona discharge have also been used to form ion clusters. Complexes are directed through a mass spectrometer where they are irradiated with infrared light, Nd:YAG laser. | 0 | Theoretical and Fundamental Chemistry |
He grew up with his brother and two sisters in Shelby, North Carolina, where their father was a community leader. After graduating from Shelby High School, Homer E. Le Grand Jr. matriculated at the University of North Carolina at Chapel Hill. With a joint major in chemistry and history, he graduated there in 1966 with a B.A. In June 1966 in Cleveland County, North Carolina, he married Brenda Ann Lefler (born 1943). At the University of Wisconsin he graduated in 1970 with a Ph.D. in the history of science. His Ph.D. thesis is entitled Berthollet and the Oxygen Theory of Acidity. He became a member of the history department of Virginia Tech and for the academic year 1975–1976 went on sabbatical with his wife and their three small children to the University of Melbourne. From 1976 to 1999 he was a faculty member in the history department of the University of Melbourne and was there also the Dean of Arts for several years. From 1999 to 2006 at Monash University, he was a professor in the history department and also Dean of the Faculty of Arts. In 2007 he retired as professor emeritus.
In his research on the history of chemistry, Le Grand argued that Humphry Davys discoveries enabled 19th-century chemists to fully realize the value of Lavoisiers operational definition of chemical elements as those irreducible elements which validate conservation of mass before and after a chemical transformation. The 2003 book Plate Tectonics: An Insiders History of the Modern Theory of the Earth', edited by Naomi Oreskes with the assistance of Le Grand, contains chapters by some of the most important scientists who developed plate tectonics.
In his honour, Monash University sponsors the Homer Le Grand Student Assistance Scholarship.
Upon his death he was survived by his widow, a daughter, two sons, and eight grandchildren. One son, Alexander Benton, became an orthopedic surgeon in Bozeman, Montana, and the other son, nicknamed "Chip", became a journalist employed by The Australian and The Age. | 1 | Applied and Interdisciplinary Chemistry |
Many peripheral membrane proteins bind to the membrane primarily through interactions with integral membrane proteins. But there is a diverse group of proteins which interact directly with the surface of the lipid bilayer. Some, such as myelin basic protein, and spectrin have mainly structural roles. A number of water-soluble proteins can bind to the bilayer surface transiently or under specific conditions.
Misfolding processes, typically exposing hydrophobic regions of proteins, often are associated with binding to lipid membranes and subsequent aggregation, for example, during neurodegenerative disorders, neuronal stress and apoptosis. | 1 | Applied and Interdisciplinary Chemistry |
Drill stems must be designed to transfer drilling torque for combined lengths that often exceed several miles down into the Earth's crust, and also must be able to resist pressure differentials between inside and outside (or vice versa), and have sufficient strength to suspend the total weight of deeper components. For deep wells this requires tempered steel tubes that are expensive, and owners spend considerable efforts to reuse them after finishing a well.
A used drill stem is inspected on site, or off location. Ultrasonic testing and modified instruments similar to the spherometer are used at inspection sites to identify defects from metal fatigue, in order to preclude fracture of the drill stem during future wellboring. Drill pipe is most often considered premium class, which is 80% remaining body wall (RBW). After inspection determines that the RBW is below 80%, the pipe is considered to be Class 2 or "yellow band" pipe. Eventually the drill pipe will be graded as scrap and marked with a red band.
Drill pipe is a portion of the overall drill string. The drill string consists of both drill pipe and the bottom hole assembly (BHA), which is the tubular portion closest to the bit. The BHA will be made of thicker walled heavy weight drill pipe (HWDP) and drill collars, which have a larger outside diameter and provide weight to the drill bit and stiffness to the drilling assembly. Other BHA components can include a mud motor, measurement while drilling (MWD) apparatus, stabilizers, and various specialty downhole tools. The drill stem includes the entire drill string, plus the kelly that imparts rotation and torque to the drill pipe at the top.
See Drilling rig (petroleum) for a diagram of a drilling rig. | 1 | Applied and Interdisciplinary Chemistry |
Steel superalloys are of interest because some present creep and oxidation resistance similar to Ni-based superalloys, at far less cost.
Gamma (γ): Fe-based alloys feature a matrix phase of austenite iron (FCC). Alloying elements include: Al, B, C, Co, Cr, Mo, Ni, Nb, Si, Ti, W, and Y. Al (oxidation benefits) must be kept at low weight fractions (wt.%) because Al stabilizes a ferritic (BCC) primary phase matrix, which is undesirable, as it is inferior to the high temperature strength exhibited by an austenitic (FCC) primary phase matrix.
Gamma-prime (γ): This phase is introduced as precipitates to strengthen the alloy. γ-Ni3Al precipitates can be introduced with the proper balance of Al, Ni, Nb, and Ti additions. | 1 | Applied and Interdisciplinary Chemistry |
Clinical trials of vitamin D supplementation for depressive symptoms have generally been of low quality and show no overall effect, although subgroup analysis showed supplementation for participants with clinically significant depressive symptoms or depressive disorder had a moderate effect. | 1 | Applied and Interdisciplinary Chemistry |
Hormones have the following effects on the body:
* stimulation or inhibition of growth
* wake-sleep cycle and other circadian rhythms
* mood swings
* induction or suppression of apoptosis (programmed cell death)
* activation or inhibition of the immune system
* regulation of metabolism
* preparation of the body for mating, fighting, fleeing, and other activity
* preparation of the body for a new phase of life, such as puberty, parenting, and menopause
* control of the reproductive cycle
* hunger cravings
A hormone may also regulate the production and release of other hormones. Hormone signals control the internal environment of the body through homeostasis. | 1 | Applied and Interdisciplinary Chemistry |
The simple relationship between amino acid sequence and DNA recognition of the TALE binding domain allows for the efficient engineering of proteins. In this case, artificial gene synthesis is problematic because of improper annealing of the repetitive sequence found in the TALE binding domain. One solution to this is to use a publicly available software program (DNAWorks) to calculate oligonucleotides suitable for assembly in a two step PCR oligonucleotide assembly followed by whole gene amplification. A number of modular assembly schemes for generating engineered TALE constructs have also been reported. Both methods offer a systematic approach to engineering DNA binding domains that is conceptually similar to the modular assembly method for generating zinc finger DNA recognition domains. | 1 | Applied and Interdisciplinary Chemistry |
There are two general pathways that explain EDH
* Diffusible factors are endothelium-derived substances that are able to pass through internal elastic layer (IEL), reach underlying vascular smooth muscle cells at a concentration sufficient to activate ion channels, and initiate smooth muscle hyperpolarization and relaxation.
* Contact-mediated mechanisms bestow endothelial hyperpolarization that passively spreads to the smooth muscle through inter-cellular coupling, and, therefore, EDH is considered as a solely electrical event. | 1 | Applied and Interdisciplinary Chemistry |
The ionic activity coefficient is connected to the ionic diameter by the formula obtained from Debye–Hückel theory of electrolytes:
where A and B are constants, z is the valence number of the ion, and I is ionic strength. | 0 | Theoretical and Fundamental Chemistry |
While the Kastle–Meyer test has been reported as being able to detect blood dilutions down to 1:10, there are a number of important limitations to the test. Chemical oxidants such as copper and nickel salts will cause the Kastle–Meyer reagent to turn pink before the addition of the hydrogen peroxide, thus it is vitally important to add the reagent first, then wait a few seconds, then add the hydrogen peroxide.
The Kastle–Meyer test has the same reaction with human blood as it does with any other hemoglobin-based blood, so a confirmatory test such as the Ouchterlony test must be performed to definitively conclude from which species the blood originated.
Color catalytic tests are very sensitive, but not specific. The positive color test alone should not be interpreted as positive proof of blood. A negative result is generally proof of the absence of detectable quantities of heme, however a false negative can be generated in the presence of a reducing agent. The test is unable to give specific evidence as to what is in the blood. | 0 | Theoretical and Fundamental Chemistry |
Oligonucleotidase (, oligoribonuclease) is an exoribonuclease derived from Flammulina velutipes. This enzyme catalyses the following chemical reaction
: 3'-end directed exonucleolytic cleavage of viral RNA-DNA hybrid | 1 | Applied and Interdisciplinary Chemistry |
In Sri Lanka, every candidate for the award of the status of Chartered Chemist (C.Chem.) shall
* C1 be more than 30 years of age
AND
* C2 (a) have passed parts I and II of the Graduateship Examination conducted by the Institute of Chemistry, Ceylon.
OR
(b) have obtained a Special Degree with Chemistry as the principal subject from a recognized university.<br />
OR
(c) have obtained a bachelors degree from a recognized university with an adequate coverage of Chemistry, acceptable to the Council and at least a masters degree in a branch of Chemistry from a recognized university. <br />
OR
(d) have obtained a bachelor's degree from a recognized university, with an adequate coverage of Chemistry and has had sufficient experience and/or attainments in the Chemical Sciences for the period of at least 10 years acceptable to the Council. <br />
OR
(f) have obtained any other equivalent qualifications acceptable to the Council,
AND
* C3 (a) have passed Part II (C) of the Graduateship Examination conducted by the Institute
OR (b) have an equivalent attainment acceptable to the Council.
AND
* C4 be able to demonstrate a high level of competence and professionalism in the practice of Chemistry and show his commitment to maintain his expertise for a period of at least 5 years subsequent to obtaining the qualifications and experience referred to in C 2 above.
AND
* C5 Such a person should provide evidence of possessing one or more of the following at a level acceptable to the Council.
(a) has specialist chemical skills relevant to their practice <br />
(b) has in– depth knowledge of the specialist areas of chemistry<br />
(c) has responsibilities based upon chemistry and has made a significant personal contribution.<br />
(d) demonstrates professionalism in the workplace<br />
(e) has maintained chemical expertise through continuing professional development. | 1 | Applied and Interdisciplinary Chemistry |
The potential theory of Polanyi, also called Polanyi adsorption potential theory, is a model of adsorption proposed by Michael Polanyi where adsorption can be measured through the equilibrium between the chemical potential of a gas near the surface and the chemical potential of the gas from a large distance away. In this model, he assumed that the attraction largely due to Van Der Waals forces of the gas to the surface is determined by the position of the gas particle from the surface, and that the gas behaves as an ideal gas until condensation where the gas exceeds its equilibrium vapor pressure. While the adsorption theory of Henry is more applicable in low pressure and BET adsorption isotherm equation is more useful at from 0.05 to 0.35 P/Po, the Polanyi potential theory has much more application at higher P/Po (~0.1–0.8). | 0 | Theoretical and Fundamental Chemistry |
Beryllium halides are formed by a combination of halogen with a beryllium atom. Beryllium halides are mostly covalent in nature except for the fluoride which is more ionic. They can be used as Lewis acid catalysts. Preparation for these compounds varies by the halogen. Beryllium halides are among the most common starting points to form complexes with other types of ligand. Halides can donate 2 electrons into the beryllium center with a charge of −1. | 0 | Theoretical and Fundamental Chemistry |
The United Nations, through the World Health Organization (WHO) together with the International Labour Organization (ILO) and United Nations Environment Programme (UNEP), collaborate on the International Programme on Chemical Safety (IPCS) to publish summary documents on chemicals. The IPCS published one such document in 2000 summarizing the status of scientific knowledge on MDI.
The IARC evaluates the hazard data on chemicals and assigns a rating on the risk of carcinogenesis. In the case of TDI, the final evaluation is possibly carcinogenic to humans (Group 2B). For MDI, the final evaluation is not classifiable as to its carcinogenicity to humans (Group 3).
The International Isocyanate Institute is an international industry consortium that seeks promote the safe utilization of isocyanates by promulgating best practices. | 0 | Theoretical and Fundamental Chemistry |
*Post-translational modification of proteins in proteins generated by cell-free protein synthesis is still limited compared to the traditional methods, and may not be as biologically relevant. | 1 | Applied and Interdisciplinary Chemistry |
The intense coloring of the molecule is generated by the absorption of specific wavelengths of light by the pi bonds. These bonds are ordinarily excited by light in the orange region of the spectrum, causing the molecule to appear blue. When the molecule interacts with protons from an acid the bonds become harder to excite and thus absorb green light which has a shorter wavelength. This is what causes the molecule to appear red in the presence of an acid. | 0 | Theoretical and Fundamental Chemistry |
The stereochemical structure of a cyclic monosaccharide can be represented in a Haworth projection. In this diagram, the α-isomer for the pyranose form of a -aldohexose has the −OH of the anomeric carbon below the plane of the carbon atoms, while the β-isomer has the −OH of the anomeric carbon above the plane. Pyranoses typically adopt a chair conformation, similar to that of cyclohexane. In this conformation, the α-isomer has the −OH of the anomeric carbon in an axial position, whereas the β-isomer has the −OH of the anomeric carbon in equatorial position (considering -aldohexose sugars). | 0 | Theoretical and Fundamental Chemistry |
Bottromycin is a macrocyclic peptide with antibiotic activity. It was first discovered in 1957 as a natural product isolated from Streptomyces bottropensis. It has been shown to inhibit methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococci (VRE) among other Gram-positive bacteria and mycoplasma. Bottromycin is structurally distinct from both vancomycin, a glycopeptide antibiotic, and methicillin, a beta-lactam antibiotic.
Bottromycin binds to the A site of the ribosome and blocks the binding of aminoacyl-tRNA, therefore inhibiting bacterial protein synthesis. Although bottromycin exhibits antibacterial activity in vitro, it has not yet been developed as a clinical antibiotic, potentially due to its poor stability in blood plasma. To increase its stability in vivo, some bottromycin derivatives have been explored.
The structure of bottromycin contains a macrocyclic amidine as well as a thiazole ring. The absolute stereochemistry at several chiral centers has been determined as of 2009. In 2012, a three-dimensional solution structure of bottromycin was published. The solution structure revealed that several methyl groups are on the same face of the structure.
Bottromycin falls within the ribosomally synthesized and post-translationally modified peptide class of natural product. | 0 | Theoretical and Fundamental Chemistry |
In 1982 the British PDRM82 was issued for civil defence. This model is lightweight, with an LCD display and a plastic case, and has all the electronics, including miniature Geiger tube (shielded against beta particles), on a single, EMP-hardened, PCB. It was designed by Plessey to use three standard 1.5 volt cells, and is microprocessor controlled with digital readout.
For use by the Royal Observer Corps, the instrument was also provided in the fixed version designated the PDRM82(F). The fixed version had an external coaxial socket mounted on its rear that accepted a cable from the above ground ionisation detector under a polycarbonate dome. For training purposes, timed simulated readings could be fed to the meter from an EPROM. | 0 | Theoretical and Fundamental Chemistry |
The theoretical framework underpinning FTMW spectroscopy is analogous to that used to describe FT-NMR spectroscopy. The behaviour of the evolving system is described by optical Bloch equations. First, a short (typically 0-3 microsecond duration) microwave pulse is introduced on resonance with a rotational transition. Those molecules that absorb the energy from this pulse are induced to rotate coherently in phase with the incident radiation. De-activation of the polarisation pulse is followed by microwave emission that accompanies decoherence of the molecular ensemble. This free induction decay occurs on a timescale of 1-100 microseconds depending on instrument settings. Following pioneering work by Dicke and co-workers in the 1950s, the first FTMW spectrometer was constructed by Ekkers and Flygare in 1975. | 0 | Theoretical and Fundamental Chemistry |
In 1969, the Avon Products executive Girard B. Henderson relocated to Las Vegas, Nevada, and embarked on the construction of the Dawson buildings on Spencer Street and an underground house across the street, which took from 1974 to 1978 to build. Oswald Gutsche, the president of Alexander Dawson Inc., oversaw the building of a new underground residence. This dwelling was inspired by the designs of Jay Swayze and served as a model. He enlisted Frank Zupancic, a private contractor who had previously constructed Oswald Gutsche's home, to undertake the construction. Henderson and his wife chose to reside in this subterranean abode, located on 3970 Spencer Street.
To access the underground home, a stairwell or a elevator descent takes people below ground level, opening into the entry of the residence. The underground property consists of several key features, including the home centered in the space.
After Henderson died on November 16, 1983, his wife Mary lived in the underground house for a short while. Following her death on October 1, 1988, businessman Thomas "Tex" Edmonson (1908–2003) acquired the underground property. As the second husband of Lucy Henderson, Tex Edmonson purchased the property under the Tex-Tex Corporation, becoming the new owner of the underground dwelling.
An article appeared in the The New Yorker magazine, which talked about Susan Roy, a magazine editor and architecture historian, who saw images of family fallout shelters including this one back in 2003, in Nest magazine (published from 1997 to 2004). The experience resulted in a book she wrote, Bamboozled: How the U.S. Government Misled Itself and Its People into Believing They Could Survive a Nuclear Attack. | 0 | Theoretical and Fundamental Chemistry |
Participants in Phase I drug trials do not gain any direct health benefit from taking part. They are generally paid a fee for their time, with payments regulated and not related to any risk involved. Motivations of healthy volunteers is not limited to financial reward and may include other motivations such as contributing to science and others. In later phase trials, subjects may not be paid to ensure their motivation for participating with potential for a health benefit or contributing to medical knowledge. Small payments may be made for study-related expenses such as travel or as compensation for their time in providing follow-up information about their health after the trial treatment ends. | 1 | Applied and Interdisciplinary Chemistry |
A pair of diazonium cations can be coupled to give biaryls. This conversion is illustrated by the coupling of the diazonium salt derived from anthranilic acid to give diphenic acid (). In a related reaction, the same diazonium salt undergoes loss of and to give benzyne. | 0 | Theoretical and Fundamental Chemistry |
Axial-flow fans have blades that force air to move parallel to the shaft about which the blades rotate. This type of fan is used in a wide variety of applications, ranging from small cooling fans for electronics to the giant fans used in cooling towers. Axial flow fans are applied in air conditioning and industrial process applications. Standard axial flow fans have diameters of 300–400 mm or 1,800–2,000 mm and work under pressures up to 800 Pa. Special types of fans are used as low-pressure compressor stages in aircraft engines.
Examples of axial fans are:
* Table fan: Basic elements of a typical table fan include the fan blade, base, armature, and lead wires, motor, blade guard, motor housing, oscillator gearbox, and oscillator shaft. The oscillator is a mechanism that motions the fan from side to side. The armature axle shaft comes out on both ends of the motor, one end of the shaft is attached to the blade and the other is attached to the oscillator gearbox. The motor case joins to the gearbox to contain the rotor and stator. The oscillator shaft combines the weighted base and the gearbox. A motor housing covers the oscillator mechanism. The blade guard joins to the motor case for safety.
* Domestic extractor fan: Wall- or ceiling-mounted, the domestic extractor fan is employed to remove moisture and stale air from domestic dwellings. Bathroom extractor fans typically utilize a four-inch (100 mm) impeller, whilst kitchen extractor fans typically use a six-inch (150 mm) impeller as the room itself is often bigger. Axial fans with five-inch (125 mm) impellers are also used in larger bathrooms though are much less common. Domestic axial extractor fans are not suitable for duct runs over 3 m or 4 m, depending on the number of bends in the run, as the increased air pressure in longer pipework inhibits the performance of the fan. [https://extractorfans.shop/pages/bathroom-fans-a-comprehensive-guide]
* Continuous running extractor fans run continuously at a very slow rate, running fast when necessary, for example when a bathroom light is switched on. At working speed they are just normal extractor fans. At continuous speed they extract typically 5 to 10 l/sec and use little electricity, 1 or 2 watts, for low annual cost. Some have humidity sensors to control trickle operation. They have the advantage of ensuring ventilation and preventing build-up of humidity. Alternatively, a normal extractor fan may be fitted to operate intermittently at full power for the same purpose. In cold weather they may have noticeably cool the room they are in, or, if the door is open, the house.
* Electro-mechanical fans: Among collectors, are rated according to their condition, size, age, and number of blades. Four-blade designs are the most common. Five-blade or six-blade designs are rare. The materials from which the components are made, such as brass, are important factors in fan desirability.
* Ceiling fan is a fan suspended from the ceiling of a room. Most ceiling fans rotate at relatively low speeds and, being inaccessible to reach, do not have blade guards. Ceiling fans are used in both residential and industrial/commercial settings.
* In automobiles, a mechanical or electrically driven fan provides engine cooling and prevents the engine from overheating by blowing or drawing air through a coolant-filled radiator. The fan may be driven with a belt and pulley off the engine's crankshaft or an electric motor switched on or off by a thermostatic switch.
* Computer fan for cooling electrical components and in laptop coolers
* Fans inside audio power amplifiers help to draw heat away from the electrical components.
* Variable pitch fan: A variable-pitch fan is used where precise control of static pressure within supply ducts is required. The blades are arranged to rotate upon a control-pitch hub. The fan wheel will spin at a constant speed. The blades follow the control pitch hub. As the hub moves toward the rotor, the blades increase their angle of attack and an increase in flow results. | 0 | Theoretical and Fundamental Chemistry |
Levonorgestrel, also known as 17α-ethynyl-18-methyl-19-nortestosterone or as 17α-ethynyl-18-methylestr-4-en-17β-ol-3-one, is a synthetic estrane steroid and a derivative of testosterone. It is the C13β or levorotatory stereoisomer and enantiopure form of norgestrel, the C13α or dextrorotatory isomer being inactive. Levonorgestrel is more specifically a derivative of norethisterone (17α-ethynyl-19-nortestosterone) and is the parent compound of the gonane (18-methylestrane or 13β-ethylgonane) subgroup of the 19-nortestosterone family of progestins. Besides levonorgestrel itself, this group includes desogestrel, dienogest, etonogestrel, gestodene, norelgestromin, norgestimate, and norgestrel. Levonorgestrel acetate and levonorgestrel butanoate are C17β esters of levonorgestrel. Levonorgestrel has a molecular weight of 312.45 g/mol and a partition coefficient (log P) of 3.8. | 0 | Theoretical and Fundamental Chemistry |
Runaway thermonuclear reactions can occur in stars when nuclear fusion is ignited in conditions under which the gravitational pressure exerted by overlying layers of the star greatly exceeds thermal pressure, a situation that makes possible rapid increases in temperature through gravitational compression. Such a scenario may arise in stars containing degenerate matter, in which electron degeneracy pressure rather than normal thermal pressure does most of the work of supporting the star against gravity, and in stars undergoing implosion. In all cases, the imbalance arises prior to fusion ignition; otherwise, the fusion reactions would be naturally regulated to counteract temperature changes and stabilize the star. When thermal pressure is in equilibrium with overlying pressure, a star will respond to the increase in temperature and thermal pressure due to initiation of a new exothermic reaction by expanding and cooling. A runaway reaction is only possible when this response is inhibited. | 1 | Applied and Interdisciplinary Chemistry |
On the faculty of Indiana University, Bloomington, since 1971. 1978 – Professor of Chemistry. 1980 – Visiting Scientist, Department of Immunogenetics, Max Planck Institute for Biology, Tübingen, Germany. 1988 – James H. Rudy Professor of Chemistry. 1999 – Distinguished Professor of Chemistry. 1999 – Director of the Institute for Pheromone Research. 2000–2015 – Lilly Chemistry Alumni Chair. 2004 – Adjunct Professor of Medicine, Indiana University School of Medicine. 2004–2009 – Director of the National Center for Glycomics and Glycoproteomics. 2010 – Director of the Novotny Glycoscience Laboratory. 2011 – Distinguished Professor Emeritus of Chemistry. | 0 | Theoretical and Fundamental Chemistry |
Quorum sensing is used by bacteria to form biofilms. Quorum sensing is used by bacteria to form biofilms because the process determines if the minimum number of bacteria necessary for biofilm formation are present. The criteria to form a biofilm is dependent on a certain density of bacteria rather than a certain number of bacteria being present. When aggregated in high enough densities, some bacteria may form biofilms to protect themselves from biotic or abiotic threats. Quorum sensing is used by both Gram-positive and Gram-negative bacteria because it aids cellular reproduction. Once in a biofilm, bacteria can communicate with other bacteria of the same species. Bacteria can also communicate with other species of bacteria. This communication is enabled through autoinducers used by the bacteria.
Additionally, certain responses can be generated by the host organism in response to the certain bacterial autoinducers. Despite the fact that specific bacterial quorum sensing systems are different, for example the target genes, signal relay mechanisms, and chemical signals used between bacteria, the ability to coordinate gene expression for a specific species of bacteria remains the same. This ability alludes to the larger idea that bacteria have potential to become a multicellular bacterial body.
Secondly, biofilms may also serve to transport nutrients into the microbial community or transport toxins out by means of channels that permeate the extracellular polymeric matrix (like cellulose) that holds the cells together. Finally, biofilms are an ideal environment for horizontal gene transfer through either conjugation or environmental DNA (eDNA) that exists in the biofilm matrix.
The process of biofilm development is often triggered by environmental signals, and bacteria are proven to require flagella to successfully approach a surface, adhere to it, and form the biofilm. As cells either replicate or aggregate in a location, the concentration of autoinducers outside of the cells increases until a critical mass threshold is reached. At this point, it is energetically unfavorable for intracellular autoinducers to leave the cell and they bind to receptors and trigger a signaling cascade to initiate gene expression and begin secreting an extracellular polysaccharide to encase themselves inside. | 1 | Applied and Interdisciplinary Chemistry |
The structure and dispersion relation of internal waves in a uniformly stratified fluid is found through the solution of the linearized conservation of mass, momentum, and internal energy equations assuming the fluid is incompressible and the background density varies by a small amount (the Boussinesq approximation). Assuming the waves are two dimensional in the x-z plane, the respective equations are
in which is the perturbation density, is the pressure, and is the velocity. The ambient density changes linearly with height as given by and , a constant, is the characteristic ambient density.
Solving the four equations in four unknowns for a wave of the form gives the dispersion relation
in which is the buoyancy frequency and is the angle of the wavenumber vector to the horizontal, which is also the angle formed by lines of constant phase to the vertical.
The phase velocity and group velocity found from the dispersion relation predict the unusual property that they are perpendicular and that the vertical components of the phase and group velocities have opposite sign: if a wavepacket moves upward to the right, the crests move downward to the right. | 1 | Applied and Interdisciplinary Chemistry |
The main parameters that characterize the rotating magnetic field created by a three-phase inductor in the working area of the apparatus in the absence of ferromagnetic particles include: the number of pairs of magnetic poles, the angular speed of their rotation; magnitude and speed of rotation of the magnetic induction vector hodograph, which in real devices is an ellipse with eccentricity increasing when approaching the surface of the working chamber. It is advisable to characterize the magnetic properties of the vortex layer by volume-averaged values;a convenient parameter for energy control of the operation of the vortex layer is itspower density.
Devices АВС - 100, АВС - 150, etc. are focused on uniform distribution of ferromagnetic particles throughout the working area and have a bipolar inductor. When developing an inductor for these devices, the salient-pole design of liquid steel induction rotators was chosen as an analogue. The choice of salient-pole inductor design was associated mainly with simplified manufacturing technology, ease of operation, repair and cooling.
In the central part of the working area of these devices, the magnetic field in the absence of ferromagnetic particles is close to uniform: the hodograph of the magnetic induction vector in this area is close to a circle, coinciding with it in the center of the working area of these devices; the module of the magnetic induction vector is approximately 0.12 T (in various devices from 0.1 to 0.15 T); the angular speed of its rotation is 314 radians per second, which corresponds to a rotation speed of 3000 rpm.
In a working vortex layer, the modulus of the averaged magnetic induction vector reaches values of 0.2 T and lags behind the external field strength by a certain phase angle.
The specific power of the vortex layer in various modes for these devices ranges from 0.1 to 1.5 kW per cubic decimeter of the working area.
The devices have dual-circuit oil-water cooling, power capacitors to compensate for the reactive power of the inductor and are powered from a 380V, 50 Hz network. Other design features of the devices are described in detail in the monograph.
Subsequently, the line of these and similar devices was mastered, modified and expanded by other manufacturers and developers. Currently, devices use both salient-pole inductors and inductors with distributed windings, similar to the stators of electric motors; different types of cooling, different types of power capacitors are used. If necessary, the device includes power converters of voltage and frequency of the supply network. Methods for monitoring and controlling the operation of the vortex layer and technological lines based on it are also being improved.
In scientific and technical developments related to issues of electromechanics of devices of the class under consideration, it is sometimes usedcomputer modellinginductor and behavior of ferromagnetic particles. An analytical model of the force effect of a circular rotating magnetic field on a magnetic particle in devices with an external electric inductor with a different number of magnetic poles is considered in the work | 1 | Applied and Interdisciplinary Chemistry |
The design of a complex pressure containment system involves much more than the application of Barlow's formula. For example, in 100 countries the ASME BPVCcode stipulates the requirements for design and testing of pressure vessels.
The formula is also common in the pipeline industry to verify that pipe used for gathering, transmission, and distribution lines can safely withstand operating pressures. The design factor is multiplied by the resulting pressure which gives the maximum operating pressure (MAOP) for the pipeline. In the United States, this design factor is dependent on Class locations which are defined in DOT Part 192. There are four class locations corresponding to four design factors: | 1 | Applied and Interdisciplinary Chemistry |
In the Romance speaking part of Europe the scruple was divided in 24 grains, in the rest of Europe in 20 grains. Notable exceptions were Venice and Sicily, where the scruple was also divided in 20 grains.
The Sicilian apothecaries ounce was divided into 10 drachms. Since the scruple was divided into only 20 grains, like in the northern countries, an ounce consisted of 600 grains. This was not too different from the situation in most of the other Mediterranean countries, where an ounce consisted of 576 grains.
In France, at some stage the apothecaries' pound of 12 ounces was replaced by the larger civil pound of 16 ounces. The subdivisions of the apothecaries ounce were the same as in the other Romance countries, however, and were different from the subdivisions of the otherwise identical civil ounce. | 1 | Applied and Interdisciplinary Chemistry |
Alarm photosynthesis represents an unknown photosynthetic variation to be added to the already known C4 and CAM pathways. However, alarm photosynthesis, in contrast to these pathways, operates as a biochemical pump that collects carbon from the organ interior (or from the soil) and not from the atmosphere. | 0 | Theoretical and Fundamental Chemistry |
There was a quarterly report on each research topic presented to the individual research committee and an annual one circulated also to members on request. Final results were compiled as a report that was immediately available to members. After about two years the commercial confidentiality was dropped and a paper was presented at a meeting of the Institute of Metals or other organisation and subsequently published in their Journal. Some researches that had resulted in valuable definitive advancements were then published in book form. | 1 | Applied and Interdisciplinary Chemistry |
The specific weight, also known as the unit weight (symbol , the Greek letter gamma), is a volume-specific quantity defined as the weight per unit volume of a material.
A commonly used value is the specific weight of water on Earth at , which is . | 0 | Theoretical and Fundamental Chemistry |
In photonics, band gaps or stop bands are ranges of photon frequencies where, if tunneling effects are neglected, no photons can be transmitted through a material. A material exhibiting this behaviour is known as a photonic crystal. The concept of hyperuniformity has broadened the range of photonic band gap materials, beyond photonic crystals. By applying the technique in supersymmetric quantum mechanics, a new class of optical disordered materials has been suggested, which support band gaps perfectly equivalent to those of crystals or quasicrystals.
Similar physics applies to phonons in a phononic crystal. | 0 | Theoretical and Fundamental Chemistry |
The second weighting factor is the tissue factor W, but it is used only if there has been non-uniform irradiation of a body. If the body has been subject to uniform irradiation, the effective dose equals the whole body equivalent dose, and only the radiation weighting factor W is used. But if there is partial or non-uniform body irradiation the calculation must take account of the individual organ doses received, because the sensitivity of each organ to irradiation depends on their tissue type. This summed dose from only those organs concerned gives the effective dose for the whole body. The tissue weighting factor is used to calculate those individual organ dose contributions.
The ICRP values for W are given in the table shown here.
The article on effective dose gives the method of calculation. The absorbed dose is first corrected for the radiation type to give the equivalent dose, and then corrected for the tissue receiving the radiation. Some tissues like bone marrow are particularly sensitive to radiation, so they are given a weighting factor that is disproportionally large relative to the fraction of body mass they represent. Other tissues like the hard bone surface are particularly insensitive to radiation and are assigned a disproportionally low weighting factor.
In summary, the sum of tissue-weighted doses to each irradiated organ or tissue of the body adds up to the effective dose for the body. The use of effective dose enables comparisons of overall dose received regardless of the extent of body irradiation. | 0 | Theoretical and Fundamental Chemistry |
Each cell division cycle triggers a new round of chromosome replication by DnaA, the initiator protein. It is crucial to regulate DnaA-ATP monomer interactions with oriC during helicase loading and unwinding of origin DNA for precise timing. DnaA recognition sites in Escherichia coli are arranged in OriC to facilitate staged pre-replication complex assembling, with DnaA interacting with low affinity sites at it oligomerizes to fill the gaps between high affinity sites as it oligomerizes. There may be numerous gap-filling strategies to link OriC functions to bacterial lifestyles in nature, which may account for the wide variability of OriC DnaA recognition site patterns. The two forms of DnaA, the active ATP- and ADP-form are regulated. The ATP-form is converted to the ADP-form through either Regulatory inactivation of DnaA (RIDA), which in turn consists of the Hda protein and the β sliding clamp (DnaN) and datA-dependent DnaA-ATP hydrolysis. The ADP-form is converted to the ATP-form by DnaA-reactivating sequences 1 and 2 (DARS1 and DARS2). | 1 | Applied and Interdisciplinary Chemistry |
Whereas traditional bioinformatics is a wide subject it has a large focus on molecular biology, pharmaceutical bioinformatics more specifically targets chemical-biological interaction and exploratory focus of chemical and biological interactors using e.g. cheminformatics and chemometrics methods. Methods include, apart from many general bioinformatics methods, ligand-based modeling such as Quantitative structure–activity relationship (QSAR) and proteochemometrics, computer-aided molecular design, chembioinformatics databases, algorithms for chemical software, and biopharmaceutical chemistry including analyses of biological activity and other issues related to drug discovery. | 1 | Applied and Interdisciplinary Chemistry |
Catalytic triads perform covalent catalysis using a residue as a nucleophile. The reactivity of the nucleophilic residue is increased by the functional groups of the other triad members. The nucleophile is polarised and oriented by the base, which is itself bound and stabilised by the acid.
Catalysis is performed in two stages. First, the activated nucleophile attacks the carbonyl carbon and forces the carbonyl oxygen to accept an electron pair, leading to a tetrahedral intermediate. The build-up of negative charge on this intermediate is typically stabilized by an oxyanion hole within the active site. The intermediate then collapses back to a carbonyl, ejecting the first half of the substrate, but leaving the second half still covalently bound to the enzyme as an acyl-enzyme intermediate. Although general-acid catalysis for breakdown of the First and Second tetrahedral intermediate may occur by the path shown in the diagram, evidence supporting this mechanism with chymotrypsin has been controverted.
The second stage of catalysis is the resolution of the acyl-enzyme intermediate by the attack of a second substrate. If this substrate is water then the result is hydrolysis; if it is an organic molecule then the result is transfer of that molecule onto the first substrate. Attack by this second substrate forms a new tetrahedral intermediate, which resolves by ejecting the enzyme's nucleophile, releasing the second product and regenerating free enzyme. | 1 | Applied and Interdisciplinary Chemistry |
At 62 °C and atmospheric pressure, phosphonium iodide sublimates and dissociates reversibly into phosphine and hydrogen iodide (HI). It oxidizes slowly in air to give iodine and phosphorus oxides; it is hygroscopic and is hydrolyzed into phosphine and HI:
Phosphine gas may be devolved from phosphonium iodide by mixing an aqueous solution with potassium hydroxide:
It reacts with elemental iodine and bromine in a nonpolar solution to give phosphorus halides; for example:
Phosphonium iodide is a powerful substitution reagent in organic chemistry; for example, it can convert a pyrilium into a phosphinine via substitution. In 1951, Glenn Halstead Brown found that PHI reacts with acetyl chloride to produce an unknown phosphine derivative, possibly . | 0 | Theoretical and Fundamental Chemistry |
One major feature found in protein structures is the addition of sugars (glycosylation) to specific amino acid residues by post translational modification. Complex sugar structures can be connected to these sites, and this can substantially modify the properties of these proteins, a main reason for their presence. Attached sugars can assist in folding some proteins to their correct shape; so, affecting a proteins’ structure is a possible outcome. SRCD is ideally well suited to determining any conformational differences that might arise from different ambient environments directly because of the extended wavelength range into the VUV region which provides greater information content. However, attached sugars can contribute to the SRCD signal because their transitions are located more towards the VUV end of the spectrum. This means that their presence can cause a problem in obtaining an accurate measure of the secondary structure content of the protein as a result. Matsuo. and Gekko produced the landmark study of VUVCD spectra of selected saccharides, thereby demonstrating that glycoproteins would have a contribution to their spectra from their sugar content. From this and further studies they demonstrated that the SRCD spectral characteristics that arose from sugars could be attributed to many factors within their conformations: the configuration of the hydroxyl group about the C1 atom of the saccharide (alpha or beta conformation, or almost axial or equatorial to the plane of the sugar ring respectively), the axial or equatorial positioning of the remaining hydroxyl groups, the trans or gauche nature of the C5 hydroxymethyl group, and the glycosidic linkage (either 1-4 or 1-6) between sugar monomers. Utilising this information, the Wallace group investigated the glycosylation of the voltage-gated sodium channel in experiments that relied on the fact that a CD(SRCD) spectrum of a mixture of components is the sum of all those components present. The aim was to establish if there were differences in the three-dimensional structure of the channel with and without sugars attached to the structure; did glycosylation play any significant role in the function of these channels when sugars were attached? Three experimental sets of SRCD spectra were collected; the non-glycosylated and glycosylated channel structures and a further one of the isolated sugar components that combined to form those attached to the channel. Taking away the spectrum of the non-glycosylated channel from that of the glycosylated they demonstrated that the resultant difference spectrum corresponded to that of the sugar components. This meant that there were no structural differences between the glycosylated and non-glycosylated channel structures, so sugar attachment played no key role in their function | 0 | Theoretical and Fundamental Chemistry |
The topology of an interactome makes certain predictions how a network reacts to the perturbation (e.g. removal) of nodes (proteins) or edges (interactions). Such perturbations can be caused by mutations of genes, and thus their proteins, and a network reaction can manifest as a disease. A network analysis can identify drug targets and biomarkers of diseases. | 1 | Applied and Interdisciplinary Chemistry |
Due to its high fission yield, relatively long half-life, and mobility in the environment, technetium-99 is one of the more significant components of nuclear waste. Measured in becquerels per amount of spent fuel, it is the dominant producer of radiation in the period from about 10 to 10 years after the creation of the nuclear waste. The next shortest-lived fission product is samarium-151 with a half-life of 90 years, though a number of actinides produced by neutron capture have half-lives in the intermediate range. | 0 | Theoretical and Fundamental Chemistry |
The other process of primary production is lithoautotrophy. Lithoautotrophs use reduced chemical compounds such as hydrogen gas, hydrogen sulfide, methane, or ferrous ion to fix carbon and participate in primary production. Lithoautotrophic organisms are prokaryotic and are represented by members of both the bacterial and archaeal domains. Lithoautotrophy is the only form of primary production possible in ecosystems without light such as ground-water ecosystems, hydrothermal vent ecosystems, soil ecosystems, and cave ecosystems. | 0 | Theoretical and Fundamental Chemistry |
Alastair Ian Scott (10 April 1928 in Glasgow – 18 April 2007) was a British-American organic chemist who achieved international renown for elucidating the biosynthetic pathway of vitamin B12.
He occupied successive chairs of organic chemistry at the universities of British Columbia, Sussex, and Yale before moving to Texas A&M University in 1977. In 1980 he occupied the [http://ourhistory.is.ed.ac.uk/index.php/Chemistry#Forbes_Chair_of_Organic_Chemistry Forbes chair of organic Chemistry] at the University of Edinburgh. He was named a distinguished professor of chemistry and biochemistry in 1981 at Texas A&M University, and remained there until the end of his career.
In 1964 he won the Corday-Morgan Medal of the Royal Society of Chemistry (RSC). He was awarded the 1975 Ernest Guenther Award and the 1994 Arthur C. Cope Scholar Award by the American Chemical Society (ACS). He gave the RSC Centenary Lecture in 1994 and the Royal Society Bakerian Lecture in 1996. He took the Tetrahedron Prize (1995), the RSC Natural Products Award (1996), the Welch Award in Chemistry (2000), the Royal Societys Davy Medal (2001), the Queens Royal Medal of the Royal Society of Edinburgh (2001), and the ACS Nakanishi Prize (2003). He was Texas Scientist of the Year in 2002.
He was a Fellow of the Royal Society and the Royal Society of Edinburgh, the American Association for the Advancement of Science and the European Academy of Sciences. In addition, he was an honorary member of the Japanese Pharmacological Society. | 0 | Theoretical and Fundamental Chemistry |
The existence of the Kelvin-Helmholtz instability was first discovered by German physiologist and physicist Hermann von Helmholtz in 1868. Helmholtz identified that "every perfect geometrically sharp edge by which a fluid flows must tear it asunder and establish a surface of separation". Following that work, in 1871, collaborator William Thomson (later Lord Kelvin), developed a mathematical solution of linear instability whilst attempting to model the formation of ocean wind waves.
Throughout the early 20th Century, the ideas of Kelvin-Helmholtz instabilities were applied to a range of stratified fluid applications. In the early 1920s, Lewis Fry Richardson developed the concept that such shear instability would only form where shear overcame static stability due to stratification, encapsulated in the Richardson Number.
Geophysical observations of the Kelvin-Helmholtz instability were made through the late 1960s/early 1970s, for clouds, and later the ocean. | 1 | Applied and Interdisciplinary Chemistry |
Johann Schröder (1600, Bad Salzuflen – 1664) was a German physician and pharmacologist who was the first person to recognise that arsenic was an element. In 1649, he produced the elemental form of arsenic by heating its oxide, and published two methods for its preparation. | 1 | Applied and Interdisciplinary Chemistry |
Water has a higher heat capacity than most other substances. This quality makes it an ideal raw material for boiler operations. Boilers are part of a closed system as compared to open systems in a gas turbine. The closed system that is used is the Rankine cycle. This means that the water is recirculated throughout the system and is never in contact with the atmosphere. The water is reused and needs to be treated to continue efficient operations. Boiler water must be treated in order to be proficient in producing steam. Boiler water is treated to prevent scaling, corrosion, foaming, and priming. Chemicals are put into boiler water through the chemical feed tank to keep the water within chemical range. These chemicals are mostly oxygen scavengers and phosphates. The boiler water also has frequent blowdowns in order to keep the chloride content down. The boiler operations also include bottom blows in order to get rid of solids. Scale is precipitated impurities out of the water and then forms on heat transfer surfaces. This is a problem because scale does not transfer heat very well and causes the tubes to fail by getting too hot. Corrosion is caused by oxygen in the water. The oxygen causes the metal to oxidize which lowers the melting point of the metal. Foaming and priming are aused when the boiler water does not have the correct amount of chemicals and there are suspended solids in the water which carry over in the dry pipe. The dry pipe is where the steam and water mixtures are separated. | 1 | Applied and Interdisciplinary Chemistry |
The physical processes that fall under the designations of recovery, recrystallization and grain growth are often difficult to distinguish in a precise manner. Doherty et al. (1998) stated:
Thus the process can be differentiated from recrystallization and grain growth as both feature extensive movement of high-angle grain boundaries.
If recovery occurs during deformation (a situation that is common in high-temperature processing) then it is referred to as dynamic while recovery that occurs after processing is termed static. The principal difference is that during dynamic recovery, stored energy continues to be introduced even as it is decreased by the recovery process - resulting in a form of dynamic equilibrium. | 1 | Applied and Interdisciplinary Chemistry |
Freiherr Christian Johann Dietrich Theodor von Grotthuss (20 January 1785 – 26 March 1822) was a Baltic German scientist known for establishing the first theory of electrolysis in 1806 and formulating the first law of photochemistry in 1817. His theory of electrolysis is considered the first description of the so-called Grotthuss mechanism. | 0 | Theoretical and Fundamental Chemistry |
Positron emission, beta plus decay, or β decay is a subtype of radioactive decay called beta decay, in which a proton inside a radionuclide nucleus is converted into a neutron while releasing a positron and an electron neutrino (). Positron emission is mediated by the weak force. The positron is a type of beta particle (β), the other beta particle being the electron (β) emitted from the β decay of a nucleus.
An example of positron emission (β decay) is shown with magnesium-23 decaying into sodium-23:
Because positron emission decreases proton number relative to neutron number, positron decay happens typically in large "proton-rich" radionuclides. Positron decay results in nuclear transmutation, changing an atom of one chemical element into an atom of an element with an atomic number that is less by one unit.
Positron emission occurs only very rarely naturally on earth, when induced by a cosmic ray or from one in a hundred thousand decays of potassium-40, a rare isotope, 0.012% of that element on earth.
Positron emission should not be confused with electron emission or beta minus decay (β decay), which occurs when a neutron turns into a proton and the nucleus emits an electron and an antineutrino.
Positron emission is different from proton decay, the hypothetical decay of protons, not necessarily those bound with neutrons, not necessarily through the emission of a positron, and not as part of nuclear physics, but rather of particle physics. | 0 | Theoretical and Fundamental Chemistry |
Response regulators can be divided into at least three broad classes, based on the features of effector domains: regulators with a DNA-binding effector domain, regulators with an enzymatic effector domain, and single-domain response regulators. More comprehensive classifications based on more detailed analysis of domain architecture are possible. Beyond these broad categorizations, there are response regulators with other types of effector domains, including RNA-binding effector domains.
Regulators with a DNA-binding effector domain are the most common response regulators, and have direct impacts on transcription. They tend to interact with their cognate regulators at an N-terminus receiver domain, and contain the DNA-binding effector towards the C-terminus. Once phosphorylated at the receiver domain, the response regulator dimerizes, gains enhanced DNA binding capacity and acts as a transcription factor. The architecture of DNA binding domains are characterized as being variations on helix-turn-helix motifs. One variation, found on the response regulator OmpR of the EnvZ/OmpR two-component system and other OmpR-like response regulators, is a "winged helix" architecture. OmpR-like response regulators are the largest group of response regulators and the winged helix motif is widespread. Other subtypes of DNA-binding response regulators include FixJ-like and NtrC-like regulators. DNA-binding response regulators are involved in various uptake processes, including nitrate/nitrite (NarL, found in most prokaryotes).
The second class of multidomain response regulators are those with enzymatic effector domains. These response regulators can participate in signal transduction, and generate secondary messenger molecules. Examples include the chemotaxis regulator CheB, with a methylesterase domain that is inhibited when the response regulator is in the inactive unphosphorylated conformation. Other enzymatic response regulators include c-di-GMP phosphodiesterases (e.g. VieA in V. cholerae), protein phosphatases and histidine kinases.
A relatively small number of response regulators, single-domain response regulators, only contain a receiver domain, relying on protein-protein interactions to exert their downstream biological effects. The receiver domain undergoes a conformational change as it interacts with an autophosphorylated histidine kinase, and consequently, the response regulator can initiate further reactions along a signaling cascade. Prominent examples include the chemotaxis regulator CheY, which interacts with flagellar motor proteins directly in its phosphorylated state.
Sequencing has so far shown that the distinct classes of response regulators are unevenly distributed throughout various taxa, including across domains. While response regulators with DNA-binding domains are the most common in bacteria, single-domain response regulators are more common in archaea, with other major classes of response regulators seemingly absent from archaeal genomes. | 1 | Applied and Interdisciplinary Chemistry |
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