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In scattering theory, a scattering channel is a quantum state of the colliding system before or after the collision (). The Hilbert space spanned by the states before collision (in states) is equal to the space spanned by the states after collision (out states) which are both Fock spaces if there is a mass gap. This is the reason why the S matrix which maps the in states onto the out states must be unitary. The scattering channel are also called scattering asymptotes. The Møller operators are mapping the scattering channels onto the corresponding states which are solution of the Schrödinger equation taking the interaction Hamiltonian into account. The Møller operators are isometric. | 0 | Theoretical and Fundamental Chemistry |
Ecological sanitation, commonly abbreviated as ecosan (also spelled eco-san or EcoSan), is an approach to sanitation provision which aims to safely reuse excreta in agriculture. It is an approach, rather than a technology or a device which is characterized by a desire to "close the loop", mainly for the nutrients and organic matter between sanitation and agriculture in a safe manner. One of the aims is to minimise the use of non-renewable resources. When properly designed and operated, ecosan systems provide a hygienically safe system to convert human excreta into nutrients to be returned to the soil, and water to be returned to the land. Ecosan is also called resource-oriented sanitation. | 1 | Applied and Interdisciplinary Chemistry |
Reflection high energy electron diffraction - total reflection angle X-ray spectroscopy is a technique for monitoring the chemical composition of crystals. RHEED-TRAXS analyzes X-ray spectral lines emitted from a crystal as a result of electrons from a RHEED gun colliding with the surface.
RHEED-TRAXS is preferential to X-ray microanalysis (XMA)(such as EDS and WDS) because the incidence angle of the electrons on the surface is very small, typically less than 5°. As a result, the electrons do not penetrate deeply into the crystal, meaning the X-ray emission is restricted to the top of the crystal, allowing for real-time, in-situ monitoring of surface stoichiometry.
The experimental setup is fairly simple. Electrons are fired onto a sample causing X-ray emission. These X-rays are then detected using a silicon-lithium Si-Li crystal placed behind beryllium windows, used to maintain vacuum. | 0 | Theoretical and Fundamental Chemistry |
Hydrotesting of pipes, pipelines and vessels is performed to expose defective materials that have missed prior detection, ensure that any remaining defects are insignificant enough to allow operation at design pressures, expose possible leaks and serve as a final validation of the integrity of the constructed system. ASME B31.3 requires this testing to ensure tightness and strength.
Buried high pressure oil and gas pipelines are tested for strength by pressurising them to at least 125% of their maximum allowable working pressure (MAWP) at any point along their length. Since many long distance transmission pipelines are designed to have a steel hoop stress of 80% of specified minimum yield strength (SMYS) at Maximum allowable operating pressure MAOP, this means that the steel is stressed to SMYS and above during the testing, and test sections must be selected to ensure that excessive plastic deformation does not occur.
For piping built to ASME B31.3, if the design temperature is greater than the test temperature, then the test pressure must be adjusted for the related allowable stress at the design temperature. This is done by multiplying 1.5 MAWP by the ratio of the allowable stress at the test temperature to allowable stress at the design temperature per ASME B31.3 Section 345.4.2 Equation 24. Test pressures need not exceed a value that would produce a stress higher than yield stress at test temperature. ASME B31.3 section 345.4.2 (c)
Other codes require a more onerous approach. BS PD 8010-2 requires testing to 150% of the design pressure – which should not be less than the MAOP plus surge and other incidental effects that will occur during normal operation.
Leak testing is performed by balancing changes in the measured pressure in the test section against the theoretical pressure changes calculated from changes in the measured temperature of the test section.
Australian standard AS2885.5 "Pipelines – Gas and liquid petroleum: Part 5: Field pressure testing" gives an excellent explanation of the factors involved.
In the aerospace industry, depending on the airline, company or customer, certain codes will need to be followed. For example, Bell Helicopter has a certain specification that will have to be followed for any parts that will be used in their helicopters. | 1 | Applied and Interdisciplinary Chemistry |
Chain initiation is the initial generation of a chain carrier, which is an intermediate such as a radical or an ion which can continue the reaction by chain propagation. Initiation steps are classified according to the way that energy is provided: thermal initiation, high energy initiation, and chemical initiation, etc. Thermal initiation uses molecular thermal motion to dissociate a molecule and form active centers. High energy initiation refers to the generation of chain carriers by radiation. Chemical initiation is due to a chemical initiator.
For the case of radical polymerization as an example, chain initiation involves the dissociation of a radical initiator molecule (I) which is easily dissociated by heat or light into two free radicals (2 R°). Each radical R° then adds a first monomer molecule (M) to start a chain which terminates with a monomer activated by the presence of an unpaired electron (RM°).
* I → 2 R°
* R° + M → RM° | 0 | Theoretical and Fundamental Chemistry |
There are many mechanisms by which pharmaceutical drugs can have toxic implications. A very common mechanism is covalent binding of either the drug or its metabolites to specific enzymes or receptor in tissue-specific pathways that then will elicit toxic responses. Covalent binding can occur during both on-target and off-target situations and after biotransformation. | 1 | Applied and Interdisciplinary Chemistry |
In France a facility exists in which a fuel melting incident can be made to happen under strictly controlled conditions. In the PHEBUS research program fuels have been allowed to heat up to temperatures in excess of the normal operating temperatures, the fuel in question is in a special channel which is in a toroidal nuclear reactor. The nuclear reactor is used as a driver core to irradiate the test fuel. While the reactor is cooled as normal by its own cooling system the test fuel has its own cooling system, which is fitted with filters and equipment to study the release of radioactivity from the damaged fuel. Already the release of radioisotopes from fuel under different conditions has been studied. After the fuel has been used in the experiment it is subject to a detailed examination (PIE), In the 2004 annual report from the ITU some results of the PIE on PHEBUS (FPT2) fuel are reported in section 3.6. | 0 | Theoretical and Fundamental Chemistry |
In the course of evolution, leaves have adapted to different environments in the following ways:
* Waxy micro- and nanostructures on the surface reduce wetting by rain and adhesion of contamination (See Lotus effect).
* Divided and compound leaves reduce wind resistance and promote cooling.
* Hairs on the leaf surface trap humidity in dry climates and create a boundary layer reducing water loss.
* Waxy plant cuticles reduce water loss.
* Large surface area provides a large area for capture of sunlight.
* In harmful levels of sunlight, specialized leaves, opaque or partly buried, admit light through a translucent leaf window for photosynthesis at inner leaf surfaces (e.g. Fenestraria).
* Kranz leaf anatomy in plants which perform carbon fixation
* Succulent leaves store water and organic acids for use in CAM photosynthesis.
* Aromatic oils, poisons or pheromones produced by leaf borne glands deter herbivores (e.g. eucalypts).
* Inclusions of crystalline minerals deter herbivores (e.g. silica phytoliths in grasses, raphides in Araceae).
* Petals attract pollinators.
* Spines protect the plants from herbivores (e.g. cacti).
* Stinging hairs to protect against herbivory, e.g. in Urtica dioica and Dendrocnide moroides (Urticaceae).
* Special leaves on carnivorous plants are adapted for trapping food, mainly invertebrate prey, though some species trap small vertebrates as well (see carnivorous plants).
* Bulbs store food and water (e.g. onions).
* Tendrils allow the plant to climb (e.g. peas).
* Bracts and pseudanthia (false flowers) replace normal flower structures when the true flowers are greatly reduced (e.g. spurges, spathes in the Araceae and floral heads in the Asteraceae). | 0 | Theoretical and Fundamental Chemistry |
Thermal desorption first appeared as an environmental treatment technology in 1985 when it was specified in the Record of Decision for the McKin Company Superfund site within the Royal River watershed in Maine.
It is frequently referred to as "low temp" thermal desorption to differentiate it from high temperature incineration. An early direct fired thermal desorption project was the treatment of 8000 tons of toxaphene (a chlorinated pesticide) contaminated sandy soil at the S&S Flying Services site in Marianna Florida in 1990, with later projects exceeding 170,000 tons at the Cape Fear coal tar site in 1999. A status report from the United States Environmental Protection Agency shows that thermal desorption has been used at 69 Superfund sites through FY2000. In addition, hundreds of remediation projects have been completed using thermal desorption at non-Superfund sites.
For in-situ on-site treatment options, only incineration and stabilization have been used at more Superfund sites. Incineration suffers from poor public acceptance. Stabilization does not provide a permanent remedy, since the contaminants are still on site. Thermal desorption is a widely accepted technology that provides a permanent solution at an economically competitive cost.
The world’s first large-scale thermal desorption for treatment of mercury-containing wastes was erected in Wölsau, for the remediation of the Chemical Factory Marktredwitz (founded in 1788) was considered to be the oldest in Germany. Operation commenced in October 1993 including the first optimising phase. 50,000 tons of mercury-contaminated solid wastes were treated successfully between August 1993 and June 1996. 25 metric tons of mercury had been recovered from soil and rubble. Unfortunately the Marktredwitz plant is often misunderstood in the literature as a pilot-scale plant only. | 1 | Applied and Interdisciplinary Chemistry |
In the episode "A No-Rough-Stuff-Type Deal" of the crime drama television series Breaking Bad, Walter White uses thermite to burn through a security lock in order to steal a methylamine drum from a chemical plant. | 0 | Theoretical and Fundamental Chemistry |
Mammalian expression vectors offer considerable advantages for the expression of mammalian proteins over bacterial expression systems - proper folding, post-translational modifications, and relevant enzymatic activity. It may also be more desirable than other eukaryotic non-mammalian systems whereby the proteins expressed may not contain the correct glycosylations. It is of particular use in producing membrane-associating proteins that require chaperones for proper folding and stability as well as containing numerous post-translational modifications. The downside, however, is the low yield of product in comparison to prokaryotic vectors as well as the costly nature of the techniques involved. Its complicated technology, and potential contamination with animal viruses of mammalian cell expression have also placed a constraint on its use in large-scale industrial production.
Cultured mammalian cell lines such as the Chinese hamster ovary (CHO), COS, including human cell lines such as HEK and HeLa may be used to produce protein. Vectors are transfected into the cells and the DNA may be integrated into the genome by homologous recombination in the case of stable transfection, or the cells may be transiently transfected. Examples of mammalian expression vectors include the adenoviral vectors, the pSV and the pCMV series of plasmid vectors, vaccinia and retroviral vectors, as well as baculovirus. The promoters for cytomegalovirus (CMV) and SV40 are commonly used in mammalian expression vectors to drive gene expression. Non-viral promoter, such as the elongation factor (EF)-1 promoter, is also known. | 1 | Applied and Interdisciplinary Chemistry |
Fmoc carbamate is frequently used as a protecting group for amines, where the Fmoc group can be introduced by reacting the amine with fluorenylmethyloxycarbonyl chloride (Fmoc-Cl), e.g.:
The other common method for introducing the Fmoc group is through 9-fluorenylmethylsuccinimidyl carbonate (Fmoc-OSu), which may itself be obtained by the reaction of Fmoc-Cl with the dicyclohexylammonium salt of N-hydroxysuccinimide.
Reacting with 9-fluorenylmethyloxycarbonyl azide (itself made by reacting Fmoc-Cl with sodium azide) in sodium bicarbonate and aqueous dioxane is also a method to install Fmoc group.
Because the fluorenyl group is highly fluorescent, certain UV-inactive compounds may be reacted to give the Fmoc derivatives, suitable for analysis by reversed phase HPLC. Analytical uses of Fmoc-Cl that do not use chromatography may be limited by the requirement that excess Fmoc-Cl be removed before an analysis of fluorescence. | 1 | Applied and Interdisciplinary Chemistry |
The concept of structural-metabolic cellular complexes was first conceived in 1970 by A. M. Kuzin of the USSR Academy of Sciences, and adopted in 1972 by Paul A. Srere of the University of Texas for the enzymes of the citric acid cycle. This hypothesis was well accepted in the former USSR and further developed for the complex of glycolytic enzymes (Embden-Meyerhof-Parnas pathway) by B.I. Kurganov and A.E. Lyubarev. In the mid-1970s, the group of F.M. Clarke at the University of Queensland, Australia also worked on the concept. The name "metabolon" was first proposed in 1985 by Paul Srere during a lecture in Debrecen, Hungary. | 1 | Applied and Interdisciplinary Chemistry |
Stream restoration or river restoration, sometimes called river reclamation in the United Kingdom, is a set of activities that aim to improve the environmental health of a river or stream. These activities aim to restore rivers and streams to their original states or to a reference state, in support of biodiversity, recreation, flood management, landscape development, or a combination of these phenomena. Stream restoration is generally associated with environmental restoration and ecological restoration. In that sense, stream restoration differs from:
* river engineering, a term which typically refers to physical alterations of a water body, for purposes that include navigation, flood control or water supply diversion and are not necessarily related to ecological restoration;
* waterway restoration, a term used in the United Kingdom describing alterations to a canal or river to improve navigability and related recreational amenities.
Improved stream health may be indicated by expanded habitat for diverse species (e.g. fish, aquatic insects, other wildlife) and reduced stream bank erosion, although bank erosion is increasingly generally recognized as contributing to the ecological health of streams. Enhancements may also include improved water quality (i.e., reduction of pollutant levels and increase of dissolved oxygen levels) and achieving a self-sustaining, resilient stream system that does not require periodic human intervention, such as dredging or construction of flood or erosion control structures. Stream restoration projects can also yield increased property values in adjacent areas.
In the past decades, stream restoration has emerged as a significant discipline in the field of water-resources management, due to the degradation of many aquatic and riparian ecosystems related to human activities. In the U.S. alone, it was estimated in the early 2000s that more than one billion U.S. dollars were spent each year to restore rivers and that close to 40,000 restoration projects had been conducted in the continental part of the country. | 1 | Applied and Interdisciplinary Chemistry |
Hydroxylamine yields via oxidation to azinic acid. Further attempted oxidation yields nitric acid, and finally orthonitrate.
More hydroxyl radicals substitute the hydrogen atoms to yield azonous acid & azorous acid. | 0 | Theoretical and Fundamental Chemistry |
There are three optical ways via which these tagged molecules can be visualized: fluorescence, phosphorescence and laser-induced fluorescence (LIF). In all three cases molecules relax to a lower state and their excess energy is released as photons. In fluorescence this energy decay occurs rapidly (within s to s at atmospheric pressure), thus making "direct" fluorescence impractical for tagging. In phosphorescence the decay is slower, because the transition is quantum-mechanically forbidden.
In some "writing" schemes, the tagged molecule ends up in an excited state. If the molecule relaxes through phosphorescence, lasting long enough to see line displacement, this can be used to track the written line and no additional visualisation step is needed. If during tagging the molecule did not reach a phosphorescing state, or relaxed before the molecule was "read", a second step is needed. The tagged molecule is then excited using a second laser beam, employing a wavelength such that it specifically excites the tagged molecule. The molecule will fluoresce and this fluorescence is captured by means of a camera. This manner of visualisation is called laser induced fluorescence (LIF).
Optical techniques are frequently used in modern fluid velocimetry but most are opto-mechanical in nature. Opto-mechanical techniques do not rely on photonics alone for flow measurements but require macro-size seeding. The best known and often used examples are particle image velocimetry (PIV) and laser Doppler velocimetry (LDV). Within the field of all-optical techniques we can distinguish analogous techniques but using molecular tracers. In Doppler schemes, light quasi-elastically scatters off molecules and the velocity of the molecules convey a Doppler shift to the frequency of the scattered light. In molecular tagging techniques, like in PIV, velocimetry is based on visualizing the tracer displacements. | 1 | Applied and Interdisciplinary Chemistry |
Sarıçiftçi has published more than 500 scientific publications in scientific journals. He is one of the most cited scientists in his field. In a global ranking of the best materials scientists Sarıçiftçi was classified as 14th. | 0 | Theoretical and Fundamental Chemistry |
The peptidoglycan layer within the bacterial cell wall is a crystal lattice structure formed from linear chains of two alternating amino sugars, namely N-acetylglucosamine (GlcNAc or NAG) and N-acetylmuramic acid (MurNAc or NAM). The alternating sugars are connected by a β-(1,4)-glycosidic bond. Each MurNAc is attached to a short (4- to 5-residue) amino acid chain, containing -alanine, -glutamic acid, meso-diaminopimelic acid, and -alanine in the case of Escherichia coli (a Gram-negative bacterium) or -alanine, -glutamine, -lysine, and -alanine with a 5-glycine interbridge between tetrapeptides in the case of Staphylococcus aureus (a Gram-positive bacterium). Peptidoglycan is one of the most important sources of D-amino acids in nature.
By enclosing the inner membrane, the peptidoglycan layer protects the cell from lysis caused by the turgor pressure of the cell. When the cell wall grows, it retains its shape throughout its life, so a rod shape will remain a rod shape, and a spherical shape will remain a spherical shape for life. This happens because the freshly added septal material of synthesis transforms into a hemispherical wall for the offspring cells.
Cross-linking between amino acids in different linear amino sugar chains occurs with the help of the enzyme DD-transpeptidase and results in a 3-dimensional structure that is strong and rigid. The specific amino acid sequence and molecular structure vary with the bacterial species.
The different peptidoglycan types of bacterial cell walls and their taxonomic implications have been described. Archaea (domain Archaea) do not contain peptidoglycan (murein). Some Archaea contain pseudopeptidoglycan (pseudomurein, see below).
Peptidoglycan is involved in binary fission during bacterial cell reproduction. L-form bacteria and mycoplasmas, both lacking peptidoglycan cell walls, do not proliferate by binary fission, but by a budding mechanism.
In the course of early evolution, the successive development of boundaries (membranes, walls) protecting first structures of life against their environment must have been essential for the formation of the first cells (cellularisation).
The invention of rigid peptidoglycan (murein) cell walls in bacteria (domain Bacteria) was probably the prerequisite for their survival, extensive radiation and colonisation of virtually all habitats of the geosphere and hydrosphere. | 1 | Applied and Interdisciplinary Chemistry |
Bioorganometallic chemistry is the study of biologically active molecules that contain carbon directly bonded to metals or metalloids. The importance of main-group and transition-metal centers has long been recognized as important to the function of enzymes and other biomolecules. However, only a small subset of naturally-occurring metal complexes and synthetically prepared pharmaceuticals are organometallic; that is, they feature a direct covalent bond between the metal(loid) and a carbon atom. The first, and for a long time, the only examples of naturally occurring bioorganometallic compounds were the cobalamin cofactors (vitamin B) in its various forms. In the 21st century, as a result of the discovery of new systems containing carbon–metal bonds in biology, bioorganometallic chemistry is rapidly emerging as a distinct subdiscipline of bioinorganic chemistry that straddles organometallic chemistry and biochemistry. Naturally occurring bioorganometallics include enzymes and sensor proteins. Also within this realm are synthetically prepared organometallic compounds that serve as new drugs and imaging agents (technetium-99m sestamibi) as well as the principles relevant to the toxicology of organometallic compounds (e.g., methylmercury). Consequently, bioorganometallic chemistry is increasingly relevant to medicine and pharmacology. | 0 | Theoretical and Fundamental Chemistry |
Trimethyl orthoformate is prepared on an industrial scale by the methanolysis of hydrogen cyanide:
:HCN + 3 HOCH → HC(OCH) + NH
Trimethyl orthoformate can also be prepared from the reaction between chloroform and sodium methoxide, an example of the Williamson ether synthesis. | 0 | Theoretical and Fundamental Chemistry |
The carbothermic route to magnesium has been recognized as a low energy, yet high productivity path to magnesium extraction. The chemistry is as follow:
The reaction between magnesia and carbon produces a magnesium and carbon monoxide vapour. A disadvantage of this method is that slow cooling the vapour can cause the reaction to quickly revert back. To prevent this from happening, the magnesium can be dissolved directly in a suitable metal solvent before reversion starts happening. Rapid quenching of the vapour can also be performed to prevent reversion.
The Bolzano process is very similar to the Pidgeon process. The difference between the Pidgeon process and the Bolzano process is that the heating process is done through electric heating conductors, and retorts are placed vertically into large blocks in the Bolzano process. A complete reaction takes about 20–24 hours. The Pidgeon method is less technologically complex and because of distillation/vapour deposition conditions, a high purity product is easily achievable.
Besides the Pigeon process, the second most used process for magnesium production is electrolysis. This is a two step process. The first step is to prepare feedstock containing magnesium chloride and the second step is to dissociate the compound in electrolytic cells as magnesium metal and chlorine gas. The basic reaction is as follows:
The magnesium chloride can be obtained using the Dow process, a process that mixes sea water and dolomite in a flocculator or by dehydration of magnesium chloride brines. The electrolytic cells are partially submerged in a molten salt electrolyte to which the produced magnesium chloride is added in concentrations between 6-18%. The temperatures at which this reaction is operated is between 680 and 750 degrees Celsius. This process does have its fair share of disadvantages including production of harmful chlorine gas and the overall reaction being very energy intensive, creating environmental risks. The Pidgeon process is more advantageous regarding its simplicity, shorter construction period, low power consumption and overall good magnesium quality compared to the electrolysis method. | 1 | Applied and Interdisciplinary Chemistry |
Toxicokinetics (often abbreviated as TK) is the description of both what rate a chemical will enter the body and what occurs to excrete and metabolize the compound once it is in the body. | 1 | Applied and Interdisciplinary Chemistry |
Iron can be stored in ferritin as ferric iron due to the ferroxidase activity of the ferritin heavy chain. Dysfunctional ferritin may accumulate as hemosiderin, which can be problematic in cases of iron overload. The ferritin storage iron pool is much larger than the labile iron pool, ranging in concentration from 0.7 mM to 3.6 mM. | 1 | Applied and Interdisciplinary Chemistry |
The investigation of Mg in animals, including humans, has lagged behind that in bacteria and yeast. This is largely because of the complexity of the systems involved, but also because of the impression within the field that Mg was maintained at high levels in all cells and was unchanged by external influences. Only in the last 25 years has a series of reports begun to challenge this view, with new methodologies finding that free Mg content is maintained at levels where changes might influence cellular metabolism. | 1 | Applied and Interdisciplinary Chemistry |
Synthetic perovskites are possible materials for high-efficiency photovoltaics – they showed a conversion efficiency of up to 26.3% and can be manufactured using the same thin-film manufacturing techniques as that used for thin film silicon solar cells. Methylammonium tin halides and methylammonium lead halides are of interest for use in dye-sensitized solar cells. Some perovskite PV cells reach a theoretical peak efficiency of 31%.
Among the methylammonium halides studied so far the most common is the methylammonium lead triiodide (). It has a high charge carrier mobility and charge carrier lifetime that allow light-generated electrons and holes to move far enough to be extracted as current, instead of losing their energy as heat within the cell. effective diffusion lengths are some 100 nm for both electrons and holes.
Methylammonium halides are deposited by low-temperature solution methods (typically spin-coating). Other low-temperature (below 100 °C) solution-processed films tend to have considerably smaller diffusion lengths. Stranks et al. described nanostructured cells using a mixed methylammonium lead halide () and demonstrated one amorphous thin-film solar cell with an 11.4% conversion efficiency, and another that reached 15.4% using vacuum evaporation. The film thickness of about 500 to 600 nm implies that the electron and hole diffusion lengths were at least of this order. They measured values of the diffusion length exceeding 1 μm for the mixed perovskite, an order of magnitude greater than the 100 nm for the pure iodide. They also showed that carrier lifetimes in the mixed perovskite are longer than in the pure iodide. Liu et al. applied Scanning Photo-current Microscopy to show that the electron diffusion length in mixed halide perovskite along (110) plane is in the order of 10 μm.
For , open-circuit voltage (V) typically approaches 1 V, while for with low Cl content, V > 1.1 V has been reported. Because the band gaps (E) of both are 1.55 eV, V-to-E ratios are higher than usually observed for similar third-generation cells. With wider bandgap perovskites, V up to 1.3 V has been demonstrated.
The technique offers the potential of low cost because of the low temperature solution methods and the absence of rare elements. Cell durability is currently insufficient for commercial use. However, the solar cells are prone to degradation due to volatility of the organic [CHNH]I salt. The all-inorganic perovskite cesium lead iodide perovskite (CsPbI) circumvents this problem, but is itself phase-unstable, the low temperature solution methods of which have only been recently developed.
Planar heterojunction perovskite solar cells can be manufactured in simplified device architectures (without complex nanostructures) using only vapor deposition. This technique produces 15% solar-to-electrical power conversion as measured under simulated full sunlight. | 0 | Theoretical and Fundamental Chemistry |
Eslicarbazepine acetate (ESL), sold under the brand names Aptiom and Zebinix among others, is an anticonvulsant medication approved for use in Europe and the United States as monotherapy or as additional therapy for partial-onset seizures epilepsy.
Similarly to oxcarbazepine, ESL behaves as a prodrug to (S)-(+)-licarbazepine. As such, their mechanisms of action are identical. | 0 | Theoretical and Fundamental Chemistry |
The FCC lattice is a Bravais lattice, and its Fourier transform is a body-centered cubic lattice. However to obtain without this shortcut, consider an FCC crystal with one atom at each lattice point as a primitive or simple cubic with a basis of 4 atoms, at the origin and at the three adjacent face centers, , and . Equation () becomes
with the result
The most intense diffraction peak from a material that crystallizes in the FCC structure is typically the (111). Films of FCC materials like gold tend to grow in a (111) orientation with a triangular surface symmetry. A zero diffracted intensity for a group of diffracted beams (here, of mixed parity) is called a systematic absence. | 0 | Theoretical and Fundamental Chemistry |
Aquametry in analytical chemistry refer to analytical processes to measure the water present in materials.
The methods widely used in aquametry encompasses Karl Fischer titration, distillation, chromatography etc. | 0 | Theoretical and Fundamental Chemistry |
Over the years, concerns over population declines of the northern white rhinoceros (Ceratotherium simum cottoni) have increased with the increasing value of their horns to poachers. Specifically, the population has declined nearly seventy percent from 2011 to 2019. Processes like SCNT can help aid in conservation efforts towards the revival of their population. Researchers are looking towards induced pluripotent stem cells (iPSC), as they hold limitless possibilities. With the lack of natural mating occurring within the species due to the limited number of them, this sub-species provides researchers the opportunity for iPSC intervention. Other methods, including artificial insemination with fresh semen (AI), have been used successfully in another sub-species, the Southern White Rhinoceros (Ceratotherium simum simum). Frozen-thawed semen has been tested and has seen some successes, helping solve issues with reproduction of the species as a whole. | 1 | Applied and Interdisciplinary Chemistry |
Agamous (AG) is a homeotic gene and MADS-box transcription factor from Arabidopsis thaliana. The TAIR AGI number is AT4G18960.
The identity of a floral organ is determined by particular combinations of homeotic genes, these genes derive from a group of undifferentiated cells known as the floral meristem. The presence of the homeotic gene in Arabidopsis ceases all meristem activity and proceeds to facilitate the development of stamens and carpels. | 1 | Applied and Interdisciplinary Chemistry |
TADs have been reported to be relatively constant between different cell types (in stem cells and blood cells, for example), and even between species in specific cases. | 1 | Applied and Interdisciplinary Chemistry |
Figure 2 shows the positions of the BBOC at various stages of the operating cycle.
The BBOC is held in an upright position during the charging stage. A solid or liquid charge is added using an overhead crane. The furnace is then tilted forward so that the lance is above the charge, and the charge is melted using an oil or natural gas burner that is inserted near the top of the furnace. Once the charge has been melted, the furnace is tilted back into the blowing position and oxygen is blown into the bath. Slag formed from the oxidation of lead and zinc is removed periodically by tilting the furnace forward again and pouring it off.
The oxygen flow rate during blowing for a three tonne capacity furnace is 20–30 Nm/h. Zinc is initially oxidized to form a zinc oxide dross on the surface of the charge, but as lead oxide subsequently forms, a fluid slag of zinc and lead oxides is created. Most of the copper is removed at the same time as the lead. The final removal of copper to a level of 0.04% is undertaken at the end of the process by further additions of lead to collect the copper.
If the lance needs to be replaced at any time during operation, this is done by tilting the furnace forward until the lance is above the surface of the bath, where it can be removed and replaced without the contents of the furnace draining through the hole in the furnace lining.
The cupellation process finishes when the silver is about 99.7% pure. At this point, the silver is poured from the furnace and transferred to another furnace, where a flux is added to upgrade and remove the oxygen from the silver to produce market bullion of 99.9% purity. | 1 | Applied and Interdisciplinary Chemistry |
Computational approaches have been regarded as a useful tool to elucidate the mechanism of action of enzymes. Molecular mechanics itself can not predict the electron transfer which is the fundamental of organic reaction but the molecular dynamics simulation provide sufficient information considering the flexibility of protein during catalytic reaction. The complementary method would be combined molecular mechanics/ quantum mechanics simulation (QM/MM)methods. With this approach, only the atoms responsible for enzymatic reaction in the catalytic region will be reared with quantum mechanics and the rest of the atoms were treated with molecular mechanics. | 1 | Applied and Interdisciplinary Chemistry |
The Crabbé reaction (or Crabbé allene synthesis, Crabbé–Ma allene synthesis) is an organic reaction that converts a terminal alkyne and aldehyde (or, sometimes, a ketone) into an allene in the presence of a soft Lewis acid catalyst (or stoichiometric promoter) and secondary amine. Given continued developments in scope and generality, it is a convenient and increasingly important method for the preparation of allenes, a class of compounds often viewed as exotic and synthetically challenging to access. | 0 | Theoretical and Fundamental Chemistry |
Antibiotics, sympathomimetics, antihistamines, anticholinergics, NSAIDs, corticosteroids, antiseptics, local anesthetics, antifungals, and cerumenolytics. | 1 | Applied and Interdisciplinary Chemistry |
Via the process known as spontaneous resolution, 5-10% of all racemates crystallize as mixtures of enantiopure crystals. This phenomenon allowed Louis Pasteur to separate left-handed and right-handed sodium ammonium tartrate crystals. These experiments underpinned his discovery of optical activity. In 1882 he went on to demonstrate that by seeding a supersaturated solution of sodium ammonium tartrate with a d-crystal on one side of the reactor and a l-crystal on the opposite side, crystals of opposite handedness will form on the opposite sides of the reactor.
Spontaneous resolution has also been demonstrated with racemic methadone. In a typical setup 50 grams dl-methadone is dissolved in petroleum ether and concentrated. Two millimeter-sized d- and l-crystals are added and after stirring for 125 hours at 40 °C two large d- and l-crystals are recovered in 50% yield.
Another form of direct crystallization is preferential crystallization also called resolution by entrainment of one of the enantiomers. For example, seed crystals of (−)- induce crystallization of this enantiomer from an ethanol solution of (±)-. | 0 | Theoretical and Fundamental Chemistry |
One line of evidence for ion transport comes from macroscopic examination of statistical ensembles. All these techniques use intact vesicles with an entrapped volume, with ion channel activities reported by different spectroscopic methods.
In a typical case, a dye is entrapped within the population of vesicles. This dye is selected to be respond colorimetrically or fluorometrically to the presence of an ion; this ion is typically absent from the inside of the vesicle but present in the outside. Without an ion transporter, the lipid bilayer as a kinetic barrier to block ion flux, and the dye remains "dark" indefinitely.
As an ion transporter allows ions on the outside to diffuse in, its addition will affect the color/fluorescence property of the dye. By macroscopically monitoring the dye's properties over time, and controlling outside factors, the ability of a compound to act as an ion transporter can be measured.
Observing ion transport, however, does not pin down ion channel as the mechanism. Any class of transporter can lead to the same observation, and additional corroborating evidence is usually required. Sophisticated experiments intended to probe selectivity, gating, and other channel parameters have been developed over the past two decades and recently summarized. | 0 | Theoretical and Fundamental Chemistry |
Decantation is a process for the separation of mixtures of immiscible liquids or of a liquid and a solid mixture such as a suspension. The layer closer to the top of the container—the less dense of the two liquids, or the liquid from which the precipitate or sediment has settled out—is poured off, leaving denser liquid or the solid behind. The process typically is unable to remove all of the top layer, meaning the separation is incomplete or at least one of the two separated components is still contaminated by the other one. | 0 | Theoretical and Fundamental Chemistry |
Brain tissue swelling, known as cerebral oedema, results from brain injury and other traumatic head injuries that can increase intracranial pressure (ICP). Negatively charged molecules within cells create a fixed charge density, which increases intracranial pressure through the Donnan effect. ATP pumps maintain a negative membrane potential even though negative charges leak across the membrane; this action establishes a chemical and electrical gradient.
The negative charge in the cell and ions outside the cell creates a thermodynamic potential; if damage occurs to the brain and cells lose their membrane integrity, ions will rush into the cell to balance chemical and electrical gradients that were previously established. The membrane voltage will become zero, but the chemical gradient will still exist. To neutralize the negative charges within the cell, cations flow in, which increases the osmotic pressure inside relative to the outside of the cell. The increased osmotic pressure forces water to flow into the cell and tissue swelling occurs. | 0 | Theoretical and Fundamental Chemistry |
When a body of material starts from a non-equilibrium state of inhomogeneity or chemical non-equilibrium, and is then isolated, it spontaneously evolves towards its own internal state of thermodynamic equilibrium. It is not necessary that all aspects of internal thermodynamic equilibrium be reached simultaneously; some can be established before others. For example, in many cases of such evolution, internal mechanical equilibrium is established much more rapidly than the other aspects of the eventual thermodynamic equilibrium. Another example is that, in many cases of such evolution, thermal equilibrium is reached much more rapidly than chemical equilibrium. | 0 | Theoretical and Fundamental Chemistry |
On the basis of Mössbauer spectroscopic analysis, green rust minerals are suspected to occur as minerals in certain bluish-green soils that are formed in alternating redox conditions, and turn ochre once exposed to air. The green rust has been conjectured to be present in the form of the mineral fougerite. | 1 | Applied and Interdisciplinary Chemistry |
The final stage in the production of copper is refining. Refining is achieved by electrolysis, which exploits the easy (low potential) and selective conversion of copper(II) solutions to the metal. The anodes cast from processed blister copper are placed into an aqueous solution of 3–4% copper sulfate and 10–16% sulfuric acid. Cathodes are thin rolled sheets of highly pure copper or, more commonly these days, reusable stainless steel starting sheets (as in the IsaKidd process). A potential of only 0.2–0.4 volts is required for the process to commence. In industrial plants current densities up to 420 A/m are possible.
At the anode (oxidation reaction), copper and less noble metals dissolve. More noble metals and less soluble elements such as silver, gold, selenium, and tellurium settle to the bottom of the cell as anode slime, which forms a salable by-product. Copper(II) ions migrate through the electrolyte to the cathode. At the cathode (reduction reaction), ions are reduced in copper metal and Cu plates out, but less noble constituents such as arsenic and zinc remain in solution unless a higher voltage is used.
The reactions involving metallic copper and ions at the electrodes are the following: | 1 | Applied and Interdisciplinary Chemistry |
Monomers with aromatic motifs such as bis(merocyanine), oligo(para-phenylenevinylene) (OPV), perylene bisimide (PBI) dye, cyanine dye, corannulene and nano-graphene derivatives have been employed to prepare supramolecular polymers. In some cases, hydrogen bonding side chains appended onto the core aromatic motif help to hold the monomer strongly in the supramolecular polymer. A notable system in this category is a nanotubular supramolecular polymer formed by the supramolecular polymerization of amphiphilic hexa-peri-hexabenzocoronene (HBC) derivatives. Generally, nanotubes are categorized as 1D objects morphologically, however, their walls adopt a 2D geometry and therefore require a different design strategy. HBC amphiphiles in polar solvents solvophobically assemble into a 2D bilayer membrane, which roles up into a helical tape or a nanotubular polymer. Conceptually similar amphiphilic design based on cyanine dye and zinc chlorin dye also polymerize in water resulting in nanotubular supramolecular polymers. | 0 | Theoretical and Fundamental Chemistry |
As early as 1147 in Troyes in Champagne (in the Middle Ages an important trading town) a unit of weight called was used.
The national French standard until 1799 was based on a famous artifact called the , which probably dates back to the second half of the 15th century. It is an elaborate set of nesting weight pieces, with a total metric weight of 12.238 kg. The set is now shown in the Musée des Arts et Métiers in Paris. The total nominal value of the set is 50 or , a mark being 8 ounces. The ounce had therefore a metric equivalent of 30.59 g. The was used as a national French standard for trading, for gold, silver, and jewels, and for weighing medicine. It was also used in international communications between scientists. In the time before the French Revolution, the civil pound also played the role of the apothecaries pound in the French apothecaries system, which otherwise remained a standard system of the Romance (24 grains per scruple) type.
In Bruges, Amsterdam, Antwerp and other Flemish cities, a "troy" unit ("") was also in use as a standard for valuable materials and medicine. As in France, the way in which the Flemish troy ounce was subdivided depended on what was weighed. Unlike the French, the Flemish apothecaries divided the scruple into 20 grains. The Flemish troy pound became the standard for the gold and apothecaries system in the United Kingdom of the Netherlands; it was also used in this way in Lübeck. (The London troy pound was referred to as the ', after metrification.)
The Dutch troy mark consisted of 8 Flemish troy ounces, with each ounce of 20 engels, and each engel divided into 32 assen. The Amsterdam Pound of two marks, used in commerce, weighed 10,280 assen, while the Amsterdam Troy pound weighed 10,240 assen, i.e. exactly two troy marks.
In 1414, six years before the Treaty of Troyes, a statute of Henry V of England gave directions to the goldsmiths in terms of the troy pound. (In 1304 it had apparently not yet been introduced, since it did not appear in the statute of weights and measures.) There is evidence from the 15th century that the troy pound was used for weighing metals and spices. After the abolishment of the Tower pound in 1527 by Henry VIII of England, the troy pound was the official basis for English coin weights. The British apothecaries' system was based on the troy pound until metrication, and it survived in the United States and Australia well into the 20th century.
Since the modern (English, American and Imperial) troy ounces are roughly 1.5% heavier than the late Paris ounce, the exact historical relations between the original , the French , the Flemish and the English troy pound are unclear. It is known, however, that the numerical relation between the English and French troy ounces was exactly 64:63 in the 14th century. | 1 | Applied and Interdisciplinary Chemistry |
RNA sequencing is a next-generation sequencing technology; as such it requires only a small amount of RNA and no previous knowledge of the genome. It allows for both qualitative and quantitative analysis of RNA transcripts, the former allowing discovery of new transcripts and the latter a measure of relative quantities for transcripts in a sample.
The three main steps of sequencing transcriptomes of any biological samples include RNA purification, the synthesis of an RNA or cDNA library and sequencing the library. The RNA purification process is different for short and long RNAs. This step is usually followed by an assessment of RNA quality, with the purpose of avoiding contaminants such as DNA or technical contaminants related to sample processing. RNA quality is measured using UV spectrometry with an absorbance peak of 260 nm. RNA integrity can also be analyzed quantitatively comparing the ratio and intensity of 28S RNA to 18S RNA reported in the RNA Integrity Number (RIN) score. Since mRNA is the species of interest and it represents only 3% of its total content, the RNA sample should be treated to remove rRNA and tRNA and tissue-specific RNA transcripts.
The step of library preparation with the aim of producing short cDNA fragments, begins with RNA fragmentation to transcripts in length between 50 and 300 base pairs. Fragmentation can be enzymatic (RNA endonucleases), chemical (trismagnesium salt buffer, chemical hydrolysis) or mechanical (sonication, nebulisation). Reverse transcription is used to convert the RNA templates into cDNA and three priming methods can be used to achieve it, including oligo-DT, using random primers or ligating special adaptor oligos. | 1 | Applied and Interdisciplinary Chemistry |
* Handbook of Nanostructured Materials and Nanotechnology; Nalwa, H.S., Ed.; Academic Press: New York, NY, USA, 2000; Volume 5, pp. 501–575 | 0 | Theoretical and Fundamental Chemistry |
In biochemistry, the molar absorption coefficient of a protein at depends almost exclusively on the number of aromatic residues, particularly tryptophan, and can be predicted from the sequence of amino acids. Similarly, the molar absorption coefficient of nucleic acids at can be predicted given the nucleotide sequence.
If the molar absorption coefficient is known, it can be used to determine the concentration of a protein in solution. | 0 | Theoretical and Fundamental Chemistry |
UV rays also treat certain skin conditions. Modern phototherapy has been used to successfully treat psoriasis, eczema, jaundice, vitiligo, atopic dermatitis, and localized scleroderma. In addition, UV light, in particular UV‑B radiation, has been shown to induce cell cycle arrest in keratinocytes, the most common type of skin cell. As such, sunlight therapy can be a candidate for treatment of conditions such as psoriasis and exfoliative cheilitis, conditions in which skin cells divide more rapidly than usual or necessary. | 0 | Theoretical and Fundamental Chemistry |
After the introduction of CrO cassettes, Japanese companies began developing a royalty-free alternative to DuPonts patent, based on an already established cobalt doping process. A controlled increase in cobalt content causes an almost linear increase in coercivity, thus a Type II "pseudochrome" tape can be made by simply adding around 3% cobalt to a Type I ferricobalt tape. By 1974 the technology was ready for mass production, and TDK and Maxell introduced their classic "pseudochromes" (TDK SA and Maxell UD-XL), while killing their true chrome lines (TDK KR and Maxell CR). By 1976, ferricobalt formulations took over the video tape market, and eventually they became the dominant high-performance tape for audio cassette. Chromium dioxide disappeared from the Japanese domestic market, although chrome remained the tape of choice for high fidelity cassette duplication among the music labels. In consumer markets, chrome coexisted as a distant second with "pseudochromes" until the very end of the cassette era. Ferricobalt technology developed continuously: in the 1980s Japanese companies introduced premium' double-layered ferricobalts with exceptionally high MOL and SOL; in the middle of the 1990s TDK launched the first and only triple-coated ferricobalt, the SA-XS.
The electromagnetic properties of Type II ferricobalts are very close to those of their Type I cousins. Owing to the use of replay equalization, the hiss level is lower, but so is the treble saturation level. The dynamic range of Type II ferricobalts, according to the 1990 tests, lies between 60 and 65dB. The coercivity of 580700Oe and remanence of 13001550G are close to the CrO reference tape, but the difference is big enough to cause compatibility problems. TDK SA was the informal reference in Japan. TDK advertisements boasted that "more decks are aligned to SA than any other tape", but there is very little first-hand information on which tapes were actually used at the factories. Japanese manufacturers provided lists of recommended tapes but did not disclose their reference tapes. There is, however, enough indirect information converging on TDK SA. For example, in 1982, when Japanese-owned Harman Kardon sent samples for Dolby certification, they were aligned to the IEC CrO reference. However, production copies of the same models were aligned to TDK SA. Since the Japanese already dominated both the cassette and hi-fi equipment markets, incompatibility further undermined the market share of European-made cassette decks and CrO cassettes. In 1987, the IEC resolved the compatibility issue by appointing a new Type II reference tape U 564 W, a BASF ferricobalt with properties that were very close to contemporary TDK tapes. With the short-lived 1988 Reference Super, even BASF started the manufacture and sale of Type II ferricobalt tapes. | 0 | Theoretical and Fundamental Chemistry |
Understanding the mechanisms and purposes of lactonase activity could lead to potential applied roles for these lactonases to control bacterial infections by inhibiting quorum-sensing activity and bring about profound effects on human health and the environment. However, in both the chemical and enzymatic lactonolysis, the reaction is reversible, complicating direct therapeutic application of lactonases.
Pseudomonas aeruginosa, is an AHL-producing bacteria an opportunistic pathogen that infects immuno-compromised patients, and is found in lung infections of cystic fibrosis patients. P. aeruginosa relies on quorum sensing via production of lactones N-butanoyl--homoserine (C4-HSL) and N-(3-oxododecanoyl)-l-HSL (3-oxo-C12-HSL) to regulate swarming, toxin and protease production, and proper biofilm formation. The absence of one or more components of the quorum-sensing system results in a significant reduction in virulence of the pathogen.
Erwinia carotovora is a plant pathogen that causes soft rot in a number of crops such as potatoes and carrots by using N-hexanoyl-l-HSL (C6-HSL) quorum sensing to evade the plant's defense systems and coordinate its production of pectate lyase during the infection process.
Plants expressing AHL-Lactonase were shown to demonstrate enhanced resistance to infection from the pathogen Erwinia carotovora. Expression of virulence genes in E. Carotovora is regulated by N-(3-oxohexanoyl)--homoserine lactone (OHHL). Presumably, OHHL-hydrolysis via lactonase reduced OHHL levels, inhibiting the quorum-sensing systems driving virulence gene expression. | 1 | Applied and Interdisciplinary Chemistry |
Bone ash is a white material produced by the calcination of bones. Typical bone ash consists of about 55.82% calcium oxide, 42.39% phosphorus pentoxide, and 1.79% water. The exact composition of these compounds varies depending upon the type of bones being used, but generally the formula for bone ash is Ca(OH)(PO). Bone ash usually has a density around 3.10 g/mL and a melting point of 1670 °C (3038 °F). Most bones retain their cellular structure through calcination. | 0 | Theoretical and Fundamental Chemistry |
In 1987 Parker was a fellow of the John Simon Guggenheim Foundation. In 2009 the Parker was elected a fellow of the American Chemical Society and she received the Francis P. Garvan-John M. Olin Medal from the American Chemical Society. In 2017 she received the Arthur C. Cope Scholar Award in recognition of her work synthesizing organic compounds. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, slosh refers to the movement of liquid inside another object (which is, typically, also undergoing motion).
Strictly speaking, the liquid must have a free surface to constitute a slosh dynamics problem, where the dynamics of the liquid can interact with the container to alter the system dynamics significantly. Important examples include propellant slosh in spacecraft tanks and rockets (especially upper stages), and the free surface effect (cargo slosh) in ships and trucks transporting liquids (for example oil and gasoline).
However, it has become common to refer to liquid motion in a completely filled tank, i.e. without a free surface, as "fuel slosh".
Such motion is characterized by "inertial waves" and can be an important effect in spinning spacecraft dynamics. Extensive mathematical and empirical relationships have been derived to describe liquid slosh. These types of analyses are typically undertaken using computational fluid dynamics and finite element methods to solve the fluid-structure interaction problem, especially if the solid container is flexible. Relevant fluid dynamics non-dimensional parameters include the Bond number, the Weber number, and the Reynolds number.
Slosh is an important effect for spacecraft, ships, some land vehicles and some aircraft. Slosh was a factor in the Falcon 1 second test flight anomaly, and has been implicated in various other spacecraft anomalies, including a near-disaster with the Near Earth Asteroid Rendezvous (NEAR Shoemaker) satellite. | 1 | Applied and Interdisciplinary Chemistry |
Glyceraldehyde 3-phosphate, also known as triose phosphate or 3-phosphoglyceraldehyde and abbreviated as G3P, GA3P, GADP, GAP, TP, GALP or PGAL, is a metabolite that occurs as an intermediate in several central pathways of all organisms. With the chemical formula H(O)CCH(OH)CHOPO</sup>, this anion is a monophosphate ester of glyceraldehyde. | 0 | Theoretical and Fundamental Chemistry |
Cyrus Eaton (1883–1979) in 1925 purchased the small Trumbull Steel Company of Warren, Ohio, for $18 million. In the late 1920s he purchased undervalued steel and rubber companies. In 1930, Eaton consolidated his steel holdings into the Republic Steel, based in Cleveland; it became the third-largest steel producer in the U.S., after US Steel and Bethlehem Steel. | 1 | Applied and Interdisciplinary Chemistry |
Most of the methyl chloride present in the environment ends up being released to the atmosphere. After being released into the air, the atmospheric lifetime of this substance is about 10 months with multiple natural sinks, such as ocean, transport to the stratosphere, soil, etc.
On the other hand, when the methyl chloride emitted is released to water, it will be rapidly lost by volatilization. The half-life of this substance in terms of volatilization in the river, lagoon and lake is 2.1 h, 25 h and 18 days, respectively.
The amount of methyl chloride in the stratosphere is estimated to be 2 x 10 tonnes per year, representing 20-25% of the total amount of chlorine that is emitted to the stratosphere annually. | 1 | Applied and Interdisciplinary Chemistry |
Spiro structures contain chiral molecules with no say asymmetric center. The rings of a spiro structure lie at right angles to each other. It's important to note that the mirror images of spiro structures are non-superimposable and are enantiomers. | 0 | Theoretical and Fundamental Chemistry |
Hair multiplication or hair cloning is a proposed technique to counter hair loss. The technology to clone hair is in its early stages, but multiple groups have demonstrated pieces of the technology at a small scale with a few in commercial development.
Scientists previously assumed that in the case of complete baldness, follicles are completely absent from the scalp, so they cannot be regenerated. However, it was discovered that the follicles are not entirely absent, as there are stem cells in the bald scalp from which the follicles naturally arise. The abnormal behavior of these follicles is suggested to be the result of progenitor cell deficiency in these areas. One recently discovered molecule (SCUBE3), may aid in activating these cells and regrowing hair.
The basic idea of hair cloning is that healthy follicle cells or dermal papillae can be extracted from the subject from areas that are not bald and are not suffering hair loss. They can be multiplied (cloned) by various culturing methods and the new cells can be injected back into the bald scalp, where they would produce healthy hair. In 2015, initial trials for human hair were successful in generating new follicles, but the hairs grew in various different directions, giving an unnatural look. Scientists believe they may have solved this problem by using nearly microscopic 3D-printed shafts to assist follicles growing upward through the scalp. This technique however is still in the research phase and is not available for public or commercial use.
As of 2023, estimates for when there will be successful hair cloning for humans are around 2030-2035; recent advancements in stem cell research and follicle generation mean that balding may be solved in around 10 years. | 1 | Applied and Interdisciplinary Chemistry |
The theology in Tattvartha Sutra presents seven categories of truth in sutra 1.4:
#Souls exist ()
#Non-sentient matter exists ()
#Karmic particles exist that inflow to each soul ()
#Karmic particles bind to the soul {which transmigrate with rebirth} ()
#Karmic particles inflow can be stopped ()
#Karmic particles can fall away from soul ()
#Complete release of karmic particles leads to liberation from worldly bondage ()
Umaswami categorizes the types of knowledge to be empirical, attained through one's sense of perception. He adds that knowledge is also acquired through literature, clairvoyance, and omniscience. In chapter 2, Umaswati presents sutras on soul. He asserts that soul is distinguished by suppression of deluding karma, or elimination of eight types of karmas, or partial presence of destructive karmas, or arising of eight types of new karmas, or those that are innate to the soul, or a combination of these. In chapter 3 through 6, Umaswati presents sutras for his first three categories of truth. | 1 | Applied and Interdisciplinary Chemistry |
Nickel allergy is typically diagnosed by patch testing – applying a patch with 2.5% (in North America) or 5% (in Europe) nickel sulfate to the upper back and looking for irritation on the skin. As with other causes of allergic contact dermatitis, patches containing several common allergens are typically applied to the back for 48 hours, removed, then the spots examined for allergic reactions 2 to 5 days later.
SNAS can often mimic IBS and may be more common than is widely appreciated. It therefore should be considered as a differential diagnosis item when a doctor is considering a diagnosis of IBS, and nickel allergy testing is advisable as a means to exclude or confirm SNAS. Even before such testing, some differentiating factors in the medical history are if certain foods prompt the symptoms (for example, peanuts or shellfish), whereas IBS is not specific to those foods. | 1 | Applied and Interdisciplinary Chemistry |
Consider a small variation in the velocity potential . Then the resulting variation in the Lagrangian is:
Using Leibniz integral rule, this becomes, in case of constant density :
The first integral on the right-hand side integrates out to the boundaries, in and , of the integration domain and is zero since the variations are taken to be zero at these boundaries. For variations which are zero at the free surface and the bed, the second integral remains, which is only zero for arbitrary in the fluid interior if there the Laplace equation holds:
with the Laplace operator.
If variations are considered which are only non-zero at the free surface, only the third integral remains, giving rise to the kinematic free-surface boundary condition:
Similarly, variations only non-zero at the bottom result in the kinematic bed condition: | 1 | Applied and Interdisciplinary Chemistry |
Soil is well developed in the forest as suggested by the thick humus layers, rich diversity of large trees and animals that live there. Forest soils can form a thick soil carbon sponge. In forests, precipitation exceeds evapotranspiration which results in an excess of water that percolates downward through the soil layers. Slow rates of decomposition leads to large amounts of fulvic acid, greatly enhancing chemical weathering. The downward percolation, in conjunction with chemical weathering leaches Mg, Fe, and aluminium (Al) from the soil and transports them downward, a process known as podzolization. This process leads to marked contrasts in the appearance and chemistry of the soil layers. | 0 | Theoretical and Fundamental Chemistry |
A not often used definition of glaze is the highly sintered compacted oxide layer formed due to the sliding of either two metallic surfaces (or sometimes a metal surface and ceramic surface) at high temperatures (normally several hundred degrees Celsius) in oxidizing conditions. The sliding or tribological action generates oxide debris that can be compacted against one or both sliding surfaces and, under the correct conditions of load, sliding speed and oxide chemistry as well as (high) temperature, sinter together to form a glaze layer. The glaze formed in such cases is actually a crystalline oxide, with a very small crystal or grain size having been shown to approach nano-scale levels. Such glaze layers were originally thought to be amorphous oxides of the same form as ceramic glazes, hence the name glaze is still currently used.
Such glazes have attracted limited attention due to their ability to protect the metallic surfaces on which they may form, from wear under the high temperature conditions in which they are generated. This high temperature wear protection allows potential use at temperatures beyond the range of conventional hydrocarbon-based, silicone-based or even solid lubricants such as molybdenum disulfide (the latter useful up to about short term). Once they form, little further damage occurs unless there is a dramatic change in sliding conditions.
Such glazes work by providing a mechanically resistant layer, which prevents direct contact between the two sliding surfaces. For example, when two metals slide against each other, there can be a high degree of adhesion between the surfaces. The adhesion may be sufficient to result in metallic transfer from one surface to the other (or removal and ejection of such material) - effectively adhesive wear (also referred to as severe wear). With the glaze layer present, such severe adhesive interactions cannot occur and wear may be greatly reduced. The continued generation of oxidized debris during the more gradual wear that results (entitled mild wear) can sustain the glaze layer and maintain this low wear regime.
However, their potential application has been hampered as they have only successfully been formed under the very sliding conditions where they are meant to offer protection. A limited amount of sliding damage (referred to as run in wear - actually a brief period of adhesive or severe wear) needs to occur before the oxides are generated and such glaze layers can form. Efforts at encouraging their early formation have met with very limited success, and the damage inflicted during the run in period is one factor preventing this technique being used for practical applications.
As oxide generated is effectively the result of the tribochemical decay of one or both of the metallic (or ceramic) surfaces in contact, the study of compacted oxide layer glazes is sometimes referred to as part of the more general field of high temperature corrosion.
The generation of oxides during high temperature sliding wear does not automatically lead to the production of a compacted oxide layer glaze. Under certain conditions (potentially due to non-ideal conditions of sliding speed, load, temperature or oxide chemistry / composition), the oxide may not sinter together and instead the loose oxide debris may assist or enhance the removal of material by abrasive wear. A change in conditions may also see a switch from the formation of a loose, abrasive oxide to the formation of wear protective compacted oxide glaze layers and vice versa, or even the reappearance of adhesive or severe wear. Due to the complexities of the conditions controlling the types of wear observed, there have been a number of attempts to map types of wear with reference to sliding conditions in order to help better understand and predict them. | 1 | Applied and Interdisciplinary Chemistry |
1,2 carboboration delivers the carbon-carbon bond and the carbon-boron bond to adjacent carbons in the substrate. It is typically facilitated by transition metal catalysis, but transition-metal-free 1,2 carboborations have been developed and continue to be of interest to synthetic chemists. The benefit of utilizing transition metals is that the reactions can often have enantioselective control based on the ligands used on the metal complex. Common metals used are palladium, nickel, and copper, which are often coupled with an organoborane or a boron source with an electrophile or nucleophile. | 0 | Theoretical and Fundamental Chemistry |
SMA is subject to structural fatigue – a failure mode by which cyclic loading results in the initiation and propagation of a crack that eventually results in catastrophic loss of function by fracture. The physics behind this fatigue mode is accumulation of microstructural damage during cyclic loading. This failure mode is observed in most engineering materials, not just SMAs.
SMAs are also subject to functional fatigue, a failure mode not typical of most engineering materials, whereby the SMA does not fail structurally but loses its shape-memory/superelastic characteristics over time. As a result of cyclic loading (both mechanical and thermal), the material loses its ability to undergo a reversible phase transformation. For example, the working displacement in an actuator decreases with increasing cycle numbers. The physics behind this is gradual change in microstructure—more specifically, the buildup of accommodation slip dislocations. This is often accompanied by a significant change in transformation temperatures. Design of SMA actuators may also influence both structural and functional fatigue of SMA, such as the pulley configurations in SMA-Pulley system. | 1 | Applied and Interdisciplinary Chemistry |
Andrei Nikolaevich Khlobystov () is a Russian-British scientist who is the Professor of Nanomaterials at the University of Nottingham. He serves as Director for Research for the School of Chemistry in the Faculty of Science and has received several awards during his career, including the European Young Investigator award and the Corday–Morgan Prize in 2015. Khlobystov is currently the Director and principal investigator of the [http://www.masi.ac.uk Metal Atoms on Surfaces and Interfaces EPSRC Programme Grant]. | 0 | Theoretical and Fundamental Chemistry |
The nuclease hybridization assay, also called S1 nuclease cutting assay, is a nuclease protection assay-based hybridization ELISA. The assay is using S1 nuclease, which degrades single-stranded DNA and RNA into oligo- or mononucleotides, leaving intact double-stranded DNA and RNA.
In the nuclease hybridization assay, the oligonucleotide analyte is captured onto the solid support such as a 96-well plate via a fully complementary cutting probe. After enzymatic processing by S1 nuclease, the free cutting probe and the cutting probe hybridized to metabolites, i.e. shortmers of the analyte are degraded, allowing signal to be generated only from the full-length cutting probe-analyte duplex.
The assay is well tolerant to diverse chemistries, as exemplified by the development of a nuclease assay for morpholino oligonucleotides.
This assay set-up can lack robustness and is not suitable for validation following the FDA's guidelines for [https://www.fda.gov/files/drugs/published/Bioanalytical-Method-Validation-Guidance-for-Industry.pdf bioanalytical method validation]. This is demonstrated by an absence of published method that have been validated to the standards outlined by the FDA for bioanalytical methods. | 1 | Applied and Interdisciplinary Chemistry |
A newer chiral derivatizing agent (CDA), α-cyano-α-fluoro (2-naphthyl)-acetic acid (2-CFNA) was prepared in optically pure form by the chiral HPLC separation of a racemic 2-CFNA methyl ester. This ester was obtained by fluorination of methyl α-cyano (2-naphthyl) acetate with FClO3. 2-CFNA has been shown to be a superior CDA than Mosher's agent to determine the enantiomeric excess of a primary alcohol. | 0 | Theoretical and Fundamental Chemistry |
In spectroscopy and radiometry, vector radiative transfer (VRT) is a method of modelling the propagation of polarized electromagnetic radiation in low density media. In contrast to scalar radiative transfer (RT), which models only the first Stokes component, the intensity, VRT models all four components through vector methods.
For a single frequency, , the VRT equation for a scattering media can be written as follows:
where s is the path, is the propagation vector, K is the extinction matrix, is the absorption vector, B is the Planck function and Z is the scattering phase matrix.
All the coefficient matrices, K, and Z, will vary depending on the density of absorbers/scatterers present and must be calculated from their density-independent quantities, that is the attenuation coefficient vector, , is calculated from the mass absorption coefficient vector times the density of the absorber.
Moreover, it is typical for media to have multiple species causing extinction, absorption and scattering, thus these coefficient matrices must be summed up over all the different species.
Extinction is caused both by simple absorption as well as from scattering out of the line-of-sight, , therefore we calculate the extinction matrix from the combination of the absorption vector and the scattering phase matrix:
where I is the identity matrix.
The four-component radiation vector, where I, Q, U and V are the first through fourth elements of the Stokes parameters, respectively, fully describes the polarization state of the electromagnetic radiation.
It is this vector-nature that considerably complicates the equation.
Absorption will be different for each of the four components, moreover, whenever the radiation is scattered, there can be a complex transfer between the different Stokes components—see polarization mixing—thus the scattering phase function has 4*4=16 components. It is, in fact, a rank-two tensor. | 0 | Theoretical and Fundamental Chemistry |
An agitation rack is a special form of agitator used to store platelets. It is composed of a series of clasps attached to motorised bars, that rock the specimens of platelets gently back-and-forth. This prevents them from becoming activated and adhering to one another, which cannot be reversed by any current means. | 1 | Applied and Interdisciplinary Chemistry |
IHC staining for FH is used to detect lack of this protein in patients with papillary renal cell carcinoma type 2. The lack of FH in renal carcinoma cells induces pro-survival metabolic adaptations where several cascades are affected. | 1 | Applied and Interdisciplinary Chemistry |
A Josiphos ligand is a type of chiral diphosphine which has been modified to be substrate-specific; they are widely used for enantioselective synthesis. They are widely used in asymmetric catalysis. | 0 | Theoretical and Fundamental Chemistry |
Modafinil's patent history involves several key developments. The original patent, , was granted to Laboratoire L. Lafon in 1990, covering the chemical compound of modafinil. This patent expired in 2010. In 1994, Cephalon filed a patent for modafinil in the form of particles of a defined size, represented by , which expired in 2015.
Following the nearing expiration of marketing rights in 2002, generic manufacturers, including Mylan and Teva, applied for FDA approval to market a generic form of modafinil, leading to legal challenges by Cephalon regarding the particle size patent. The patent RE 37,516 was declared invalid and unenforceable in 2011.
In addition, Cephalon entered agreements with several generic drug manufacturers to delay the sale of generic modafinil in the US. These agreements were subject to legal scrutiny and antitrust investigations, culminating in a ruling by the Court of Appeals in 2016, which found that the settlements did not violate antitrust laws. | 0 | Theoretical and Fundamental Chemistry |
Photodynamic therapy utilizes Type II photosensitizers to harvest light to degrade tumors or cancerous masses. This discovery was first observed back in 1907 by Hermann von Tappeiner when he utilized eosin to treat skin tumors. The photodynamic process is predominantly a noninvasive technique wherein the photosensitizers are put inside a patient so that it may accumulate on the tumor or cancer. When the photosensitizer reaches the tumor or cancer, wavelength specific light is shined on the outside of the patients affected area. This light (preferably near infrared frequency as this allows for the penetration of the skin without acute toxicity) excites the photosensitizers electrons into the triplet state. Upon excitation, the photosensitizer begins transferring energy to neighboring ground state triplet oxygen to generate excited singlet oxygen. The resulting excited oxygen species then selectively degrades the tumor or cancerous mass.
In February 2019, medical scientists announced that iridium attached to albumin, creating a photosensitized molecule, can penetrate cancer cells and, after being irradiated with light (a process called photodynamic therapy), destroy the cancer cells. | 0 | Theoretical and Fundamental Chemistry |
In the late 19th and early 20th centuries the town of Waratah in Gippsland, Victoria, Australia produced a majority of the quicklime used in the city of Melbourne as well as around other parts of Gippsland. The town, now called Walkerville, was set on an isolated part of the Victorian coastline and exported the lime by ship. When this became unprofitable in 1926 the kilns were shut down. The present-day area, though having no town amenities as such, markets itself as a tourist destination. The ruins of the lime kilns can still be seen today.
A lime kiln also existed in Wool Bay, South Australia. | 1 | Applied and Interdisciplinary Chemistry |
Dendrosomes are vesicular, spherical, supramolecular entities wherein the dendrimer–nucleic acid complex is encapsulated within a lipophilic shell. They possess negligible hemolytic toxicity and higher transfection efficiency, and they are better tolerated in vivo than are dendrimers. The word " Dendrosome" came from the Greek word "Dendron" meaning tree and " some" means vesicles. Thus dendrosomes are vesicular structures composed of dendrimers. | 0 | Theoretical and Fundamental Chemistry |
The mucoadhesive process will differ greatly depending on the surface and properties of the adhesive. However, two general steps of the process have been identified: the contact stage and the consolidation stage. | 1 | Applied and Interdisciplinary Chemistry |
The lower boundary of the model domain coincides with the ground. Because of the inhomogeneity of the terrain, it is not possible to impose boundary conditions at that boundary with respect to Cartesian coordinates. Therefore, a transformation of the vertical coordinate to a terrain-following one is performed. Hence, the originally irregularly bounded physical domain is mapped onto one consisting of unit cubes. | 1 | Applied and Interdisciplinary Chemistry |
From biblical times until the 1950s the pesticides used were inorganic compounds and plant extracts. The inorganic compounds were derivatives of copper, arsenic, mercury, sulfur, among others, and the plant extracts contained pyrethrum, nicotine, and rotenone among others. The less toxic of these are still in use in organic farming. In the 1940s the insecticide DDT, and the herbicide 2,4-D, were introduced. These synthetic organic (i.e. non inorganic) compounds were widely used and were very profitable. They were followed in the 1950s and 1960s by numerous other synthetic pesticides, which led to the growth of the pesticide industry. During this period, it became increasing evident that DDT, which had been sprayed widely in the environment to combat the vector, had accumulated in the food chain, and become a global pollutant, as summarised in the well-known book Silent Spring. Finally, DDT was banned in the 1970s in several countries, and subsequently all persistent pesticides were banned worldwide, an exception being spraying on interior walls for vector control.
Resistance to a pesticide was first seen in the 1920s with inorganic pesticides, and later it was found that development of resistance is to be expected, and measures to delay it are important. Integrated pest management (IPM) was introduced in the 1950s. By careful analysis and spraying only when an economical or biological threshold of crop damage is reached, pesticide application is reduced. This became in the 2020s the official policy of international organisations, industry, and many governments. With the introduction of high yielding varieties in the 1960s in the green revolution, more pesticides were used. Since the 1980s genetically modified crops were introduced, which resulted in lower amounts of insecticides used on them. Organic agriculture, which uses only non-synthetic pesticides, has grown and in 2020 represents about 1.5 per cent of the world’s total agricultural land.
Pesticides have become more effective. Application rates fell from 1,000–2,500 grams of active ingredient per hectare (g/ha) in the 1950s to 40–100 g/ha in the 2000s. Despite this, amounts used have increased. In high income countries over 20 years between the 1990s and 2010s amounts used increased 20%, while in the low income countries amounts increased 1623%. | 1 | Applied and Interdisciplinary Chemistry |
Denaturing gradient gel electrophoresis (DGGE) works by applying a small sample of DNA (or RNA) to an electrophoresis gel that contains a denaturing agent. Researchers have found that certain denaturing gels are capable of inducing DNA to melt at various stages. As a result of this melting, the DNA spreads through the gel and can be analyzed for single components, even those as small as 200-700 base pairs.
What is unique about the DGGE technique is that as the DNA is subjected to increasingly extreme denaturing conditions, the melted strands fragment completely into single strands. The process of denaturation on a denaturing gel is very sharp: "Rather than partially melting in a continuous zipper-like manner, most fragments melt in a step-wise process. Discrete portions or domains of the fragment suddenly become single-stranded within a very narrow range of denaturing conditions" (Helms, 1990). This makes it possible to discern differences in DNA sequences or mutations of various genes: sequence differences in fragments of the same length often cause them to partially melt at different positions in the gradient and therefore "stop" at different positions in the gel. By comparing the melting behavior of the polymorphic DNA fragments side by side on denaturing gradient gels, it is possible to detect fragments that have mutations in the first melting domain (Helms, 1990). Placing two samples side by side on the gel and allowing them to denature together, researchers can easily see even the smallest differences in two samples or fragments of DNA.
There are a number of disadvantages to this technique: "Chemical gradients such as those used in DGGE are not as reproducible, are difficult to establish and often do not completely resolve heteroduplexes" (Westburg, 2001). These problems are addressed by TGGE, which uses a temperature, rather than chemical, gradient to denature the sample. | 1 | Applied and Interdisciplinary Chemistry |
In a compressible fluid, it is convenient to define the total conditions (also called stagnation conditions) for all thermodynamic state properties (such as total temperature, total enthalpy, total speed of sound). These total flow conditions are a function of the fluid velocity and have different values in frames of reference with different motion.
To avoid potential ambiguity when referring to the properties of the fluid associated with the state of the fluid rather than its motion, the prefix "static" is commonly used (such as static temperature and static enthalpy). Where there is no prefix, the fluid property is the static condition (so "density" and "static density" mean the same thing). The static conditions are independent of the frame of reference.
Because the total flow conditions are defined by isentropically bringing the fluid to rest, there is no need to distinguish between total entropy and static entropy as they are always equal by definition. As such, entropy is most commonly referred to as simply "entropy". | 1 | Applied and Interdisciplinary Chemistry |
Paracetamol powder has poor compression properties, which poses difficulty in making tablets. A second polymorph was found with more suitable compressive properties. | 0 | Theoretical and Fundamental Chemistry |
Krypton-85 is used in arc discharge lamps commonly used in the entertainment industry for large HMI film lights as well as high-intensity discharge lamps. The presence of krypton-85 in discharge tube of the lamps can make the lamps easy to ignite. Early experimental krypton-85 lighting developments included a railroad signal light designed in 1957 and an illuminated highway sign erected in Arizona in 1969. A 60 μCi (2.22 MBq) capsule of krypton-85 was used by the random number server HotBits (an allusion to the radioactive element being a quantum mechanical source of entropy), but was replaced with a 5 μCi (185 kBq) Cs-137 source in 1998.
Krypton-85 is also used to inspect aircraft components for small defects. Krypton-85 is allowed to penetrate small cracks, and then its presence is detected by autoradiography. The method is called "krypton gas penetrant imaging". The gas penetrates smaller openings than the liquids used in dye penetrant inspection and fluorescent penetrant inspection.
Krypton-85 was used in cold-cathode voltage regulator electron tubes, such as the type 5651.
Krypton-85 is also used for Industrial Process Control mainly for thickness and density measurements as an alternative to Sr-90 or Cs-137.
Krypton-85 is also used as a charge neutralizer in aerosol sampling systems. | 0 | Theoretical and Fundamental Chemistry |
Aminolevulinic acid utilization is promising in the field of cancer delineation, particularly in the context of fluorescence-guided surgery. This compound is utilized to enhance the visualization of malignant tissues during surgical procedures. When administered to patients, 5-ALA is metabolized to protoporphyrin IX (PpIX) preferentially in cancer cells, leading to their fluorescence under specific light wavelengths. This fluorescence aids surgeons in real-time identification and precise removal of cancerous tissue, reducing the likelihood of leaving residual tumor cells behind. This innovative approach has shown success in various cancer types, including brain and spine gliomas, bladder cancer, and oral squamous cell carcinoma. | 1 | Applied and Interdisciplinary Chemistry |
When retroviruses have integrated their own genome into the germ line, their genome is passed on to a following generation. These endogenous retroviruses (ERVs), contrasted with exogenous ones, now make up 5–8% of the human genome. Most insertions have no known function and are often referred to as "junk DNA". However, many endogenous retroviruses play important roles in host biology, such as control of gene transcription, cell fusion during placental development in the course of the germination of an embryo, and resistance to exogenous retroviral infection. Endogenous retroviruses have also received special attention in the research of immunology-related pathologies, such as autoimmune diseases like multiple sclerosis, although endogenous retroviruses have not yet been proven to play any causal role in this class of disease.
While transcription was classically thought to occur only from DNA to RNA, reverse transcriptase transcribes RNA into DNA. The term "retro" in retrovirus refers to this reversal (making DNA from RNA) of the usual direction of transcription. It still obeys the central dogma of molecular biology, which states that information can be transferred from nucleic acid to nucleic acid but cannot be transferred back from protein to either protein or nucleic acid. Reverse transcriptase activity outside of retroviruses has been found in almost all eukaryotes, enabling the generation and insertion of new copies of retrotransposons into the host genome. These inserts are transcribed by enzymes of the host into new RNA molecules that enter the cytosol. Next, some of these RNA molecules are translated into viral proteins. The proteins encoded by the gag and pol genes are translated from genome-length mRNAs into Gag and Gag–Pol polyproteins. In example, for the gag gene; it is translated into molecules of the capsid protein, and for the pol gene; it is translated into molecules of reverse transcriptase. Retroviruses need a lot more of the Gag proteins than the Pol proteins and have developed advanced systems to synthesize the required amount of each. As an example, after Gag synthesis nearly 95 percent of the ribosomes terminate translation, while other ribosomes continue translation to synthesize Gag–Pol. In the rough endoplasmic reticulum glycosylation begins and the env gene is translated from spliced mRNAs in the rough endoplasmic reticulum, into molecules of the envelope protein. When the envelope protein molecules are carried to the Golgi complex, they are divided into surface glycoprotein and transmembrane glycoprotein by a host protease. These two glycoprotein products stay in close affiliation, and they are transported to the plasma membrane after further glycosylation.
It is important to note that a retrovirus must "bring" its own reverse transcriptase in its capsid, otherwise it is unable to utilize the enzymes of the infected cell to carry out the task, due to the unusual nature of producing DNA from RNA.
Industrial drugs that are designed as protease and reverse-transcriptase inhibitors are made such that they target specific sites and sequences within their respective enzymes. However these drugs can quickly become ineffective due to the fact that the gene sequences that code for the protease and the reverse transcriptase quickly mutate. These changes in bases cause specific codons and sites with the enzymes to change and thereby avoid drug targeting by losing the sites that the drug actually targets.
Because reverse transcription lacks the usual proofreading of DNA replication, a retrovirus mutates very often. This enables the virus to grow resistant to antiviral pharmaceuticals quickly, and impedes the development of effective vaccines and inhibitors for the retrovirus.
One difficulty faced with some retroviruses, such as the Moloney retrovirus, involves the requirement for cells to be actively dividing for transduction. As a result, cells such as neurons are very resistant to infection and transduction by retroviruses. This gives rise to a concern that insertional mutagenesis due to integration into the host genome might lead to cancer or leukemia. This is unlike Lentivirus, a genus of Retroviridae, which are able to integrate their RNA into the genome of non-dividing host cells. | 1 | Applied and Interdisciplinary Chemistry |
Source:
When hemoglobin is exposed to certain conditions, reversible or irreversible hemichromes are formed.
Reversible hemichrome formation occurs in the presence of:
* Fatty acids
* Aliphatic alcohol (n-butanol)
* Dehydration
* High concentration of glycerol
* Polyethylene glycol
Irreversible hemichrome formation occurs in the presence of:
* Phenylhydrazine
* Sodium dodecyl sulphate (SDS) | 1 | Applied and Interdisciplinary Chemistry |
Explosophores are functional groups in organic chemistry that give organic compounds explosive properties. | 0 | Theoretical and Fundamental Chemistry |
The cecum is a pouch marking the division between the small intestine and the large intestine. It lies below the ileocecal valve in the lower right quadrant of the abdomen. The cecum receives chyme from the last part of the small intestine, the ileum, and connects to the ascending colon of the large intestine. At this junction there is a sphincter or valve, the ileocecal valve which slows the passage of chyme from the ileum, allowing further digestion. It is also the site of the appendix attachment. | 1 | Applied and Interdisciplinary Chemistry |
Anti-double stranded DNA (anti-dsDNA) antibodies are highly associated with SLE. They are a very specific marker for the disease, with some studies quoting nearly 100%. Data on sensitivity ranges from 25 to 85%. Anti-dsDNA antibody levels, known as titres, correlate with disease activity in SLE; high levels indicate more active lupus. The presence of anti-dsDNA antibodies is also linked with lupus nephritis and there is evidence they are the cause. Some anti-dsDNA antibodies are cross reactive with other antigens found on the glomerular basement membrane (GBM) of the kidney, such as heparan sulphate, collagen IV, fibronectin and laminin. Binding to these antigens within the kidney could cause inflammation and complement fixation, resulting in kidney damage. Presence of high DNA-binding and low C3 levels have been shown to have extremely high predictive value (94%) for the diagnosis of SLE. It is also possible that the anti-dsDNA antibodies are internalised by cells when they bind membrane antigens and then are displayed on the cell surface. This could promote inflammatory responses by T-cells within the kidney. It is important to note that not all anti-dsDNA antibodies are associated with lupus nephritis and that other factors can cause this symptom in their absence. The antigen of anti-dsDNA antibodies is double stranded DNA. | 1 | Applied and Interdisciplinary Chemistry |
Once again, the conformation and position of groups (ie. substituents) larger than a singular hydrogen are critical to the overall stability of the molecule. The larger the group, the less likely to prefer the axial position on its respective carbon. Maintaining said position with a larger size costs more energy from the molecule as a whole because of steric repulsion between the large groups' nonbonded electron pairs and the electrons of the smaller groups (ie. hydrogens). Such steric repulsions are absent for equatorial groups. The cyclohexane model thus assesses steric size of functional groups on the basis of gauche interactions. The gauche interaction will increase in energy as the size of the substituent involved increases. For example, a t-butyl substituent would sustain a higher energy gauche interaction as compared to a methyl group, and therefore, contribute more to the instability of the molecule as a whole.
In comparison, a staggered conformation is thus preferred; the larger groups would maintain the equatorial position and lower the energy of the entire molecule. This preference for the equatorial position among bulkier groups lowers the energy barriers between different conformations of the ring. When the molecule is activated, there will be a loss in entropy due to the stability of the larger substituents. Therefore, the preference of the equatorial positions by large molecules (such as a methyl group) inhibits the reactivity of the molecule and thus makes the molecule more stable as a whole. | 0 | Theoretical and Fundamental Chemistry |
The first known racemic mixture was racemic acid, which Louis Pasteur found to be a mixture of the two enantiomeric isomers of tartaric acid. He manually separated the crystals of a mixture, starting from an aqueous solution of the sodium ammonium salt of racemate tartaric acid. Pasteur benefited from the fact that ammonium tartrate salt gives enantiomeric crystals with distinct crystal forms (at 77 °F). Reasoning from the macroscopic scale down to the molecular, he reckoned that the molecules had to have non-superimposable mirror images.
A sample with only a single enantiomer is an enantiomerically pure or enantiopure compound. | 0 | Theoretical and Fundamental Chemistry |
Grewe's cyclization is easier to handle in terms of the chemicals used, produces higher yields and higher purity of the product. | 0 | Theoretical and Fundamental Chemistry |
An introduction to Landau theory can be found here.
Based on Ginzburg–Landau theory, the free energy of a ferroelectric material, in the absence of an electric field and applied stress may be written as a Taylor expansion in terms of the order parameter, P. If a sixth order expansion is used (i.e. 8th order and higher terms truncated), the free energy is given by:
where P, P, and P are the components of the polarization vector in the x, y, and z directions respectively, and the coefficients, must be consistent with the crystal symmetry. To investigate domain formation and other phenomena in ferroelectrics, these equations are often used in the context of a phase field model. Typically, this involves adding a gradient term, an electrostatic term and an elastic term to the free energy. The equations are then discretized onto a grid using the finite difference method or finite element method and solved subject to the constraints of Gauss's law and Linear elasticity.
In all known ferroelectrics, and . These coefficients may be obtained experimentally or from ab-initio simulations. For ferroelectrics with a first order phase transition, , whereas for a second order phase transition.
The spontaneous polarization, P of a ferroelectric for a cubic to tetragonal phase transition may be obtained by considering the 1D expression of the free energy which is:
This free energy has the shape of a double well potential with two free energy minima at , the spontaneous polarization. We find the derivative of the free energy, and set it equal to zero in order to solve for :
Since the P = 0 solution of this equation rather corresponds to a free energy maxima in the ferroelectric phase, the desired solutions for P correspond to setting the remaining factor to zero:
whose solution is:
and eliminating solutions which take the square root of a negative number (for either the first or second order phase transitions) gives:
If , the solution for the spontaneous polarization reduces to:
The hysteresis loop (P versus E) may be obtained from the free energy expansion by including the term -E P corresponding to the energy due to an external electric field E interacting with the polarization P, as follows:
We find the stable polarization values of P under the influence of the external field, now denoted as P, again by setting the derivative of the energy with respect to P to zero:
Plotting E (on the X axis) as a function of P (but on the Y axis) gives an S-shaped curve which is multi-valued in P for some values of E. The central part of the S corresponds to a free energy local maximum (since ). Elimination of this region, and connection of the top and bottom portions of the S curve by vertical lines at the discontinuities gives the hysteresis loop of internal polarization due to an external electric field. | 0 | Theoretical and Fundamental Chemistry |
The Ranch-style house one-level underground earth shelter was designed to blend with the surroundings with earth against the walls and on the roof. It had a brick veneer siding but was enclosed in a waterproof concrete shell and covered with a compacted earth berm. The entrance was created to look like an opening to a mineshaft. To make the house functional, over $104,000 () was spent on the hydroelectric system that supplied the underground dwelling with power. Water for the system flowed from glacial snowpack on Mt. Audubon. More than $200,000 ( was spent in total to make the house livable.
To imitate the comforts of above-ground living, the wood-frame home had three-bedrooms, a swimming pool, and fake "outdoor" patio. Because the house had no window, artist Jewell Smith painted Trompe-lœil murals depicting the New York City skyline from the living room and the Golden Gate Bridge from a bedroom. Windows within the structure revealed a narrow corridor that served as a separation between the "exterior" wall and the concrete retaining wall. As noted by architecture historian Beatriz Colomina in her book, Domesticity at War,' this architectural element disrupted the conventional notions of inside and outside. The house had a remote-controlled lighting system that could imitate the night sky and sunrise. Additionally, a fireplace channeled smoke through a fake tree trunk to the surface. | 0 | Theoretical and Fundamental Chemistry |
The identification of the genetic basis for the causative agent of a disease can be an important component of understanding its effects and spread. Location and content of structural genes can elucidate the evolution of virulence, as well as provide necessary information for treatment. Likewise understanding the specific changes in structural gene sequences underlying a gain or loss of virulence aids in understanding the mechanism by which diseases affect their hosts.
For example, Yersinia pestis (the bubonic plague) was found to carry several virulence and inflammation-related structural genes on plasmids. Likewise, the structural gene responsible for tetanus was determined to be carried on a plasmid as well. Diphtheria is caused by a bacterium, but only after that bacterium has been infected by a bacteriophage carrying the structural genes for the toxin.
In Herpes simplex virus, the structural gene sequence responsible for virulence was found in two locations in the genome despite only one location actually producing the viral gene product. This was hypothesized to serve as a potential mechanism for strains to regain virulence if lost through mutation.
Understanding the specific changes in structural genes underlying a gain or loss of virulence is a necessary step in the formation of specific treatments, as well the study of possible medicinal uses of toxins. | 1 | Applied and Interdisciplinary Chemistry |
Moiseev was born in Moscow. He studied organic chemistry at Moscow State University of Fine Chemical Technologies (MITHT). After graduating in 1952, his first jobs were as an engineer, a junior researcher in physical chemistry, then a senior researcher in organic chemistry. From 1963, he worked at the N. S. Kurnakov (IGIC) of the Russian Academy of Sciences (RAS), Moscow, as head of the laboratory of metal-complex catalysis and coordination chemistry. From 2003 onward, he was a professor at the Gubkin Russian State University of Oil and Gas (RGUNG Gubkin).
He also served as chairman of the Scientific Council for Gas Chemistry, RAS, and vice-president of the Russian Chemical Society. | 0 | Theoretical and Fundamental Chemistry |
Epitaxial wafers of crystalline silicon can be grown on a monocrystalline silicon "seed" wafer by chemical vapor deposition (CVD), and then detached as self-supporting wafers of some standard thickness (e.g., 250 µm) that can be manipulated by hand, and directly substituted for wafer cells cut from monocrystalline silicon ingots. Solar cells made with this "kerfless" technique can have efficiencies approaching those of wafer-cut cells, but at appreciably lower cost if the CVD can be done at atmospheric pressure in a high-throughput inline process. The surface of epitaxial wafers may be textured to enhance light absorption.
In June 2015, it was reported that heterojunction solar cells grown epitaxially on n-type monocrystalline silicon wafers had reached an efficiency of 22.5% over a total cell area of 243.4 cm. | 0 | Theoretical and Fundamental Chemistry |
Lithophile elements are those that remain on or close to the surface because they combine readily with oxygen, forming compounds that do not sink into the Earth's core. The lithophile elements include Al, B, Ba, Be, Br, Ca, Cl, Cr, Cs, F, I, Hf, K, Li, Mg, Na, Nb, O, P, Rb, Sc, Si, Sr, Ta, Th, Ti, U, V, Y, Zr, W and the lanthanides or rare earth elements (REE).
Lithophile elements mainly consist of the highly reactive metals of the s- and f-blocks. They also include a small number of reactive nonmetals, and the more reactive metals of the d-block such as titanium, zirconium and vanadium. Lithophile derives from "lithos" which means "rock", and "phileo" which means "love".
Most lithophile elements form very stable ions with an electron configuration of a noble gas (sometimes with additional f-electrons). The few that do not, such as silicon, phosphorus and boron, form extremely strong covalent bonds with oxygen – often involving pi bonding. Their strong affinity for oxygen causes lithophile elements to associate very strongly with silica, forming relatively low-density minerals that thus float to the Earth's crust. The more soluble minerals formed by the alkali metals tend to concentrate in seawater or extremely arid regions where they can crystallise. The less soluble lithophile elements are concentrated on ancient continental shields where all soluble minerals have been weathered.
Because of their strong affinity for oxygen, most lithophile elements are enriched in the Earths crust relative to their abundance in the solar system. The most reactive s- and f-block metals, which form either saline or metallic hydrides, are known to be extraordinarily enriched on Earth as a whole relative to their solar abundances. This is because during the earliest stages of the Earths formation the reaction that controlled the stable form of each chemical element was its ability to form compounds with hydrogen. Under these conditions, the s- and f-block metals were strongly enriched during the formation of the Earth. The most enriched elements are rubidium, strontium and barium, which between them account for over 50 percent by mass of all elements heavier than iron in the Earth's crust.
The nonmetallic lithophiles – phosphorus and the halogens – exist on Earth as ionic salts with s-block metals in pegmatites and seawater. With the exception of fluorine, whose hydride forms hydrogen bonds and is therefore of relatively low volatility, these elements have had their concentrations on Earth significantly reduced through escape of volatile hydrides during the Earths formation. Although they are present in the Earths crust in concentrations quite close to their solar abundances, phosphorus and the heavier halogens are probably significantly depleted on Earth as a whole relative to their solar abundances.
Several transition metals, including chromium, molybdenum, iron and manganese, show both lithophile and siderophile characteristics and can be found in both these two layers. Although these metals form strong bonds with oxygen and are never found in the Earth's crust in the free state, metallic forms of these elements are thought very likely to exist in the core of the earth as relics from when the atmosphere did not contain oxygen. Like the "pure" siderophiles, these elements (except iron) are considerably depleted in the crust relative to their solar abundances.
Owing to their strong affinity for oxygen, lithophile metals, although they form the great bulk of the metallic elements in Earth's crust, were never available as free metals before the development of electrolysis. With this development, many lithophile metals are of considerable value as structural metals (magnesium, aluminium, titanium, vanadium) or as reducing agents (sodium, magnesium, calcium).
The non-metals phosphorus and the halogens were also not known to early chemists, though production of these elements is less difficult than of metallic lithophiles since electrolysis is required only with fluorine. Elemental chlorine is particularly important as an oxidizing agent – usually being made by electrolysis of sodium chloride. | 0 | Theoretical and Fundamental Chemistry |
For a weakly collisional plasma, Debye shielding can be introduced in a very intuitive way by taking into account the granular character of such a plasma. Let us imagine a sphere about one of its electrons, and compare the number of electrons crossing this sphere with and without Coulomb repulsion. With repulsion, this number is smaller. Therefore, according to Gauss theorem, the apparent charge of the first electron is smaller than in the absence of repulsion. The larger the sphere radius, the larger is the number of deflected electrons, and the smaller the apparent charge: this is Debye shielding. Since the global deflection of particles includes the contributions of many other ones, the density of the electrons does not change, at variance with the shielding at work next to a Langmuir probe (Debye sheath). Ions bring a similar contribution to shielding, because of the attractive Coulombian deflection of charges with opposite signs.
This intuitive picture leads to an effective calculation of Debye shielding (see section II.A.2 of ). The assumption of a Boltzmann distribution is not necessary in this calculation: it works for whatever particle distribution function. The calculation also avoids approximating weakly collisional plasmas as continuous media. An N-body calculation reveals that the bare Coulomb acceleration of a particle by another one is modified by a contribution mediated by all other particles, a signature of Debye shielding (see section 8 of ). When starting from random particle positions, the typical time-scale for shielding to set in is the time for a thermal particle to cross a Debye length, i.e. the inverse of the plasma frequency. Therefore in a weakly collisional plasma, collisions play an essential role by bringing a cooperative self-organization process: Debye shielding. This shielding is important to get a finite diffusion coefficient in the calculation of Coulomb scattering (Coulomb collision).
In a non-isothermic plasma, the temperatures for electrons and heavy species may differ while the background medium may be treated as the vacuum and the Debye length is
where
* λ is the Debye length,
* ε is the permittivity of free space,
* k is the Boltzmann constant,
* q is the charge of an electron,
* T and T are the temperatures of the electrons and ions, respectively,
* n is the density of electrons,
* n is the density of atomic species j, with positive ionic charge zq
Even in quasineutral cold plasma, where ion contribution virtually seems to be larger due to lower ion temperature, the ion term is actually often dropped, giving
although this is only valid when the mobility of ions is negligible compared to the process's timescale. | 0 | Theoretical and Fundamental Chemistry |
While enantioselective epoxidations have been successfully achieved utilizing Sharpless epoxidation, Shi epoxidation, and Jacobsen epoxidation, none of these methods allows for the efficient asymmetric synthesis of terminal epoxides, which are key chiral building blocks. Due to the inexpensiveness of most racemic terminal epoxides and their inability to generally be subjected to classical resolution, an effective kinetic resolution of terminal epoxides would serve as a highly important synthetic methodology. In 1996, Jacobsen and coworkers developed a methodology for the kinetic resolution of epoxides via nucleophilic ring-opening with attack by an azide anion. The (R,R) catalyst is shown.
The catalyst could effectively, with loadings as low as 0.5 mol%, open the epoxide at the terminal position enantioselectively, yielding enantioenriched epoxide starting material and 1,2-azido alcohols. Yields are nearly quantitative and ee's were excellent (≥95% in nearly all cases). The 1,2-azido alcohols can be hydrogenated to give 1,2-amino alcohols, as shown below.
In 1997, Jacobsens group published a methodology which improved upon their earlier work, allowing for the use of water as the nucleophile in the epoxide opening. Utilizing a nearly identical catalyst, ees in excess of 98% for both the recovered starting material epoxide and 1,2-diol product were observed. In the example below, hydrolytic kinetic resolution (HKR) was carried out on a 58 gram scale, resulting in 26 g (44%) of the enantioriched epoxide in >99% ee and 38 g (50%) of the diol in 98% ee.
A multitude of other substrates were examined, with yields of the recovered epoxide ranging from 36-48% for >99% ee. Jacobsen hydrolytic kinetic resolution can be used in tandem with Jacobsen epoxidation to yield enantiopure epoxides from certain olefins, as shown below. The first epoxidation yields a slightly enantioenriched epoxide, and subsequent kinetic resolution yields essentially a single enantiomer. The advantage of this approach is the ability to reduce the amount of hydrolytic cleavage necessary to achieve high enantioselectivity, allowing for overall yields up to approximately 90%, based on the olefin.
Ultimately, the Jacobsen epoxide opening kinetic resolutions produce high enantiomeric purity in the epoxide and product, in solvent-free or low-solvent conditions, and have been applicable on a large scale. The Jacobsen methodology for HKR in particular is extremely attractive since it can be carried out on a multiton scale and utilizes water as the nucleophile, resulting in extremely cost-effective industrial processes.
Despite impressive achievements, HKR has generally been applied to the resolution of simple terminal epoxides with one stereocentre. Quite recently, D. A. Devalankar et al. reported an elegant protocol involving a two-stereocentered Co-catalyzed HKR of racemic terminal epoxides bearing adjacent C–C binding substituents. | 0 | Theoretical and Fundamental Chemistry |
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