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Azines are a functional class of organic compounds with the connectivity RRC=N-N=CRR. These compounds are the product of the condensation of hydrazine with ketones and aldehydes, although in practice they are often made by alternative routes. Ketazines are azines derived from ketones. For example, acetone azine is the simplest ketazine. Aldazines are azines derived from aldehydes. | 0 | Theoretical and Fundamental Chemistry |
Haplotype refers to a group of genetic variants inherited together on a chromosome from one parent due to their genetic linkage. Haplotype phasing (also called haplotype estimation) refers to the process of reconstructing individual haplotypes, important for determining the genetic basis of diseases. Linked-read sequencing allows consistent coverage of genes related to different diseases, helping scientists to obtain all the regions carrying mutations from targeted genes. For example, in 2018, a group of researchers used linked-read sequencing technology to sequence genetic information from a pregnant woman who was a carrier of Duchenne muscular dystrophy (DMD) mutation. Linked-read sequencing allows them to identify the maternal haplotypes and determine the presence of the mutant alleles in the foetal DNA. This non-invasive prenatal diagnosis of DMD demonstrates the clinical applicability of linked-read sequencing. | 1 | Applied and Interdisciplinary Chemistry |
His parents emigrated from Switzerland to the United States, where Nef studied chemistry at Harvard University until 1884. Upon graduation, he joined Adolf von Baeyer at the University of Munich, where he received his Ph.D. in 1887.
He was a professor at Purdue University from 1887 till 1889 and at Clark University from 1889 till 1892. In 1892 Nef joined the newly formed University of Chicago as professor of chemistry, where he spent the rest of his academic career.
His son John Ulric Nef (1899–1988) became a professor of economic history and published several books. | 0 | Theoretical and Fundamental Chemistry |
During drug discovery, lipophilicity and molecular weight are often increased in order to improve the affinity and selectivity of the drug candidate. Hence it is often difficult to maintain drug-likeness (i.e., RO5 compliance) during hit and lead optimization. Hence it has been proposed that members of screening libraries from which hits are discovered should be biased toward lower molecular weight and lipophilicity so that medicinal chemists will have an easier time in delivering optimized drug development candidates that are also drug-like. Hence the rule of five has been extended to the rule of three (RO3) for defining lead-like compounds.
A rule of three compliant compound is defined as one that has:
* octanol-water partition coefficient log P not greater than 3
* molecular mass less than 300 daltons
* not more than 3 hydrogen bond donors
* not more than 3 hydrogen bond acceptors
* not more than 3 rotatable bonds | 1 | Applied and Interdisciplinary Chemistry |
Oil-based defoamers have an oil carrier. The oil might be mineral oil, vegetable oil or any other oil that is insoluble in the foaming medium, except silicone oil. An oil-based defoamer also contains a wax and/or hydrophobic silica to boost the performance. Typical waxes are ethylene bis stearamide (EBS), paraffin waxes, ester waxes and fatty alcohol waxes. These products might also have surfactants to improve emulsification and spreading in the foaming medium.
These are heavy duty defoamers and are normally best at knocking down surface foam. | 0 | Theoretical and Fundamental Chemistry |
The NDUFAF6 gene encodes a protein that localizes to mitochondria. The encoded protein plays an important role in the assembly of complex I (NADH-ubiquinone oxidoreductase) of the mitochondrial respiratory chain through regulation of subunit ND1 biogenesis. | 1 | Applied and Interdisciplinary Chemistry |
# Removal of the smear layer and etching of dentine
# Priming of the dentine surface
# Bonding of the primed dentine surface to the restorative material | 0 | Theoretical and Fundamental Chemistry |
A changed migratory potential of cells has relatively high importance in the development of several clinical symptoms and syndromes.
Altered chemotactic activity of extracellular (e.g., Escherichia coli) or intracellular (e.g., Listeria monocytogenes) pathogens itself represents a significant clinical target. Modification of endogenous chemotactic ability of these microorganisms by pharmaceutical agents can decrease or inhibit the ratio of infections or spreading of infectious diseases.
Apart from infections, there are some other diseases wherein impaired chemotaxis is the primary etiological factor, as in Chédiak–Higashi syndrome, where giant intracellular vesicles inhibit normal migration of cells. | 1 | Applied and Interdisciplinary Chemistry |
The orbit width can be estimated by considering the variation in over an orbit period . Using the conservation of and ,</blockquote>The orbit widths can then be estimated, which gives
* Passing width:
* Banana width:
The bounce angle at which becomes zero for the trapped particles is</blockquote> | 1 | Applied and Interdisciplinary Chemistry |
The carbon–fluorine bond length is typically about 1.35 ångström (1.39 Å in fluoromethane). It is shorter than any other carbon–halogen bond, and shorter than single carbon–nitrogen and carbon–oxygen bonds. The short length of the bond can also be attributed to the ionic character of the bond (the electrostatic attractions between the partial charges on the carbon and the fluorine). The carbon–fluorine bond length varies by several hundredths of an ångstrom depending on the hybridization of the carbon atom and the presence of other substituents on the carbon or even in atoms farther away. These fluctuations can be used as indication of subtle hybridization changes and stereoelectronic interactions. The table below shows how the average bond length varies in different bonding environments (carbon atoms are sp-hybridized unless otherwise indicated for sp or aromatic carbon).
The variability in bond lengths and the shortening of bonds to fluorine due to their partial ionic character are also observed for bonds between fluorine and other elements, and have been a source of difficulties with the selection of an appropriate value for the covalent radius of fluorine. Linus Pauling originally suggested 64 pm, but that value was eventually replaced by 72 pm, which is half of the fluorine–fluorine bond length. However, 72 pm is too long to be representative of the lengths of the bonds between fluorine and other elements, so values between 54 pm and 60 pm have been suggested by other authors. | 0 | Theoretical and Fundamental Chemistry |
The Hinsberg reaction is a chemical test for the detection of primary, secondary and tertiary amines. The reaction was first described by Oscar Hinsberg in 1890. In this test, the amine is shaken well with the Hinsberg reagent (benzenesulfonyl chloride) in the presence of aqueous alkali (either KOH or NaOH). A primary amine will form a soluble sulfonamide salt. Acidification of this salt then precipitates the sulfonamide of the primary amine. A secondary amine in the same reaction will directly form an insoluble sulfonamide. A tertiary amine will not react with the original reagent (benzene sulfonyl chloride) and will remain insoluble. After adding dilute acid this insoluble amine is converted to a soluble ammonium salt. In this way the reaction can distinguish between the three types of amines.
Tertiary amines are able to react with benzenesulfonyl chloride under a variety of conditions; the test described above is not absolute. The Hinsberg test for amines is valid only when reaction speed, concentration, temperature, and solubility are taken into account. | 0 | Theoretical and Fundamental Chemistry |
Catherine E. Costello is the William Fairfield Warren distinguished professor in the department of biochemistry, Cell Biology and Genomics, and the director of the Center for Biomedical Mass Spectrometry at the Boston University School of Medicine. | 1 | Applied and Interdisciplinary Chemistry |
In 1999, the Dioxin Affair occurred when 50 kg of PCB transformer oils were added to a stock of recycled fat used for the production of 500 tonnes of animal feed, eventually affecting around 2,500 farms in several countries. The name Dioxin Affair was coined from early misdiagnosis of dioxins as the primary contaminants, when in fact they turned out to be a relatively small part of the contamination caused by thermal reactions of PCBs. The PCB congener pattern suggested the contamination was from a mixture of Aroclor 1260 and 1254. Over 9 million chickens, and 60,000 pigs were destroyed because of the contamination. The extent of human health effects has been debated, in part because of the use of differing risk assessment methods. One group predicted increased cancer rates, and increased rates of neurological problems in those exposed as neonates. A second study suggested carcinogenic effects were unlikely and that the primary risk would be associated with developmental effects due to exposure in pregnancy and neonates. Two businessmen who knowingly sold the contaminated feed ingredient received two-year suspended sentences for their role in the crisis. | 1 | Applied and Interdisciplinary Chemistry |
In 2020 a team at the University Hospital Heidelberg (Germany) re-gained the antibacterial power of vancomycin by modifying the molecule with a cationic oligopeptide. The oligopeptide consists of six arginin units in Position V. In comparison to the unmodified vancomycin the activity against vancomycin-resistant bacteria could be enhanced by a factor of 1,000. This pharmacon is still in preclinical development. | 0 | Theoretical and Fundamental Chemistry |
* Plumbing
* Tap water
* Irrigation
* Pipelines transporting gas or liquid over long distances
* Compressed air systems
* Casing for concrete pilings used in construction projects
* High-temperature or high-pressure manufacturing processes
* The petroleum industry:
** Oil well casing
** Oil refinery equipment
* Delivery of fluids, either gaseous or liquid, in a process plant from one point to another point in the process
* Delivery of bulk solids, in a food or process plant from one point to another point in the process
* The construction of high pressure storage vessels (large pressure vessels are constructed from plate, not pipe owing to their wall thickness and size).
Additionally, pipes are used for many purposes that do not involve conveying fluid. Handrails, scaffolding, and support structures are often constructed from structural pipes, especially in an industrial environment. | 1 | Applied and Interdisciplinary Chemistry |
In many countries, pesticides must be approved for sale and use by a government agency.
Worldwide, 85% of countries have pesticide legislation for the proper storage of pesticides and 51% include provisions to ensure proper disposal of all obsolete pesticides.
Though pesticide regulations differ from country to country, pesticides, and products on which they were used are traded across international borders. To deal with inconsistencies in regulations among countries, delegates to a conference of the United Nations Food and Agriculture Organization adopted an International Code of Conduct on the Distribution and Use of Pesticides in 1985 to create voluntary standards of pesticide regulation for different countries. The Code was updated in 1998 and 2002. The FAO claims that the code has raised awareness about pesticide hazards and decreased the number of countries without restrictions on pesticide use.
Three other efforts to improve regulation of international pesticide trade are the United Nations London Guidelines for the Exchange of Information on Chemicals in International Trade and the United Nations Codex Alimentarius Commission. The former seeks to implement procedures for ensuring that prior informed consent exists between countries buying and selling pesticides, while the latter seeks to create uniform standards for maximum levels of pesticide residues among participating countries. | 1 | Applied and Interdisciplinary Chemistry |
Like other organolithium compounds, tert-butyllithium is a cluster compound. Whereas n-butyllithium exists both as a hexamer and a tetramer, tert-butyllithium exists exclusively as a tetramer with a cubane structure. Bonding in organolithium clusters involves sigma delocalization and significant Li−Li bonding. Despite its complicated structure, tert-butyllithium is usually depicted in equations as a monomer.
The lithium–carbon bond in tert-butyllithium is highly polarized, having about 40 percent ionic character. The molecule reacts like a carbanion, as is represented by these two resonance structures: | 0 | Theoretical and Fundamental Chemistry |
Changing the fish population of bodies of water as a part of watershed management can facilitate desirable changes in aquatic ecosystems suffering from eutrophication characterized by domination by phytoplankton aiding ecosystem restoration, an application of restoration ecology. In ponds or lakes alternative stable conditions, one with high algae populations, little other plant life, and turbid water, another with low algae populations, a diverse plant population, and clear water, may exist. In addition to prevention of excess nutrients such as phosphorus and nitrates, removal of certain fish species adapted to turbid water may facilitate change from one steady state to the other, an application of dynamical systems theory. Fish species may be removed by means of poison, harvesting, or introduction of predatory species. As a different fish community will result from the process it will affect recreational and commercial fishermen whose cooperation or opposition is important.
Lake Zwemlust, a hypertrophic pond used as a swimming pool in The Netherlands with an area of 1.5 hectares and an average depth of 1.5 meters, was treated in March 1987. The initial Secchi disk transparency was only 0.3 meters, less than the 1 meter maximum permitted for swimming pools in The Netherlands. In the first summer Secchi disk transparency increased to at least 2.5 meters, the maximum depth of the lake. The lake was drained and 1,500 kilograms of planktivorous and benthivorous fish such as common bream were removed by seining and electrofishing. The pond was stocked with 1500 northern pike fingerlings and some mature rudd whose offspring served as food for the pike. Willow branches, nuphar lutea roots, and starts of Chara globularis were added as vegetation and shelter. Expenses were met by the local water authority which was compensated by increased patronage by swimmers. In the summer of the second year, 1988, there was considerable plant growth and, possibly due to lack of predation by carp or minnows, an explosion in the number of snails, including Radix peregra var. ovata a host of Trichobilharzia ocellata the cause of schistosome dermatitis, swimmer's itch.
In addition to grazing by zooplankton the lush growth of macrophytes removed sufficient nutrients from the water to prevent algal bloom by phytoplanktons. | 1 | Applied and Interdisciplinary Chemistry |
* 7th International Thai Institute of Chemical Engineering and Applied Chemistry Conference (ITIChE 2017) and The 27th National Thai Institute of Chemical Engineering and Applied Chemistry Conference (TIChE 2017)
** 18–20 October 2017 Shangri-La Hotel, Bangkok
* The 18th Thailand Chemical Engineering and Applied Chemistry Conference.
** 20–21 October 2008 at Jomtien Palm Beach Resort, Cholburi.
** Host: Department of Chemical Engineering, Mahidol University, Nakhon Pathom.
* The 17th Thailand Chemical Engineering and Applied Chemistry Conference.
** 29–30 October 2007 at The Empress Hotel, Chiang Mai.
** Host: Department of Industrial Chemistry, Chiang Mai University, Chiang Mai.
* The 16th Thailand Chemical Engineering and Applied Chemistry Conference.
** 26–27 October 2006 at Rama Garden Hotel, Bangkok.
** Host: Department of Chemical Engineering, Kasetsart University, Bangkok.
* The 15th Thailand Chemical Engineering and Applied Chemistry Conference.
** 27–28 October 2005 at Jomtien Palm Beach Resort, Cholburi.
** Host: Department of Chemical Engineering, Burapha University, Cholburi.
* The 14th Thailand Chemical Engineering and Applied Chemistry Conference.
** Host: Department of Chemical Engineering, King Mongkut's Institute of Technology North Bangkok, Bangkok.
* The 13th Thailand Chemical Engineering and Applied Chemistry Conference.
** 30–31 October 2003 at Royal Hill Resort and Golf Course, Nakhon Nayok.
** Host: Department of Chemical Engineering, Srinakharinwirot University, Nakhon Nayok. | 1 | Applied and Interdisciplinary Chemistry |
Mutations in the subunits of complex I can cause mitochondrial diseases, including Leigh syndrome. Point mutations in various complex I subunits derived from mitochondrial DNA (mtDNA) can also result in Lebers Hereditary Optic Neuropathy.There is some evidence that complex I defects may play a role in the etiology of Parkinsons disease, perhaps because of reactive oxygen species (complex I can, like complex III, leak electrons to oxygen, forming highly toxic superoxide).
Although the exact etiology of Parkinsons disease is unclear, it is likely that mitochondrial dysfunction, along with proteasome inhibition and environmental toxins, may play a large role. In fact, the inhibition of complex I has been shown to cause the production of peroxides and a decrease in proteasome activity, which may lead to Parkinsons disease. Additionally, Esteves et al. (2010) found that cell lines with Parkinson's disease show increased proton leakage in complex I, which causes decreased maximum respiratory capacity.
Brain ischemia/reperfusion injury is mediated via complex I impairment. Recently it was found that oxygen deprivation leads to conditions in which mitochondrial complex I lose its natural cofactor, flavin mononucleotide (FMN) and become inactive. When oxygen is present the enzyme catalyzes a physiological reaction of NADH oxidation by ubiquinone, supplying electrons downstream of the respiratory chain (complexes III and IV). Ischemia leads to dramatic increase of succinate level. In the presence of succinate mitochondria catalyze reverse electron transfer so that fraction of electrons from succinate is directed upstream to FMN of complex I. Reverse electron transfer results in a reduction of complex I FMN, increased generation of ROS, followed by a loss of the reduced cofactor (FMNH) and impairment of mitochondria energy production. The FMN loss by complex I and I/R injury can be alleviated by the administration of FMN precursor, riboflavin.
Recent studies have examined other roles of complex I activity in the brain. Andreazza et al. (2010) found that the level of complex I activity was significantly decreased in patients with bipolar disorder, but not in patients with depression or schizophrenia. They found that patients with bipolar disorder showed increased protein oxidation and nitration in their prefrontal cortex. These results suggest that future studies should target complex I for potential therapeutic studies for bipolar disorder. Similarly, Moran et al. (2010) found that patients with severe complex I deficiency showed decreased oxygen consumption rates and slower growth rates. However, they found that mutations in different genes in complex I lead to different phenotypes, thereby explaining the variations of pathophysiological manifestations of complex I deficiency.
Exposure to pesticides can also inhibit complex I and cause disease symptoms. For example, chronic exposure to low levels of dichlorvos, an organophosphate used as a pesticide, has been shown to cause liver dysfunction. This occurs because dichlorvos alters complex I and II activity levels, which leads to decreased mitochondrial electron transfer activities and decreased ATP synthesis. | 1 | Applied and Interdisciplinary Chemistry |
In cerebral infarction, the penumbra has decreased perfusion. Besides acute and chronic neurovascular diseases, the value of ASL has been demonstrated in brain tumors, epilepsy and neurodegenerative disease, such as Alzheimer's disease, frontotemporal dementia and Parkinson disease. Additionally, DP-pCASL has promising potential for assessing blood-brain barrier integrity in patients with ischemic stroke.
Although the primary form of fMRI uses the blood-oxygen-level dependent (BOLD) contrast, ASL is another method of obtaining contrast.
There have been research to apply ASL to renal imaging, pancreas imaging, and placenta imaging. A challenge to these sort of non-cerebral perfusion is motion due to breathing. Additionally, there is a lot less development on the segmentation of theses specific organs, so the studies are relatively small scale. | 0 | Theoretical and Fundamental Chemistry |
Cross-polarization (CP), originally published as proton-enhanced nuclear induction spectroscopy is a solid-state nuclear magnetic resonance (ssNMR) technique to transfer nuclear magnetization from different types of nuclei via heteronuclear dipolar interactions. The H-X cross-polarization dramatically improves the sensitivity of ssNMR experiments of most experiments involving spin-1/2 nuclei, capitalizing on the higher H polarisation, and shorter T(H) relaxation times. It was developed by Michael Gibby, Alexander Pines and Professor John S. Waugh at the Massachusetts Institute of Technology.
In this technique the natural nuclear polarization of an abundant spin (typically H) is exploited to increase the polarization of a rare spin (such as C, N, P) by irradiating the sample with radio waves at the frequencies matching the Hartmann–Hahn condition:
where are the gyromagnetic ratios, is the spinning rate, and is an integer. This process is sometimes referred to as "spin-locking". The power of one contact pulse is typically ramped to achieve a more broadband and efficient magnetisation transfer.
The evolution of the X NMR signal intensity during the cross polarisation is a build-up and decay process whose time axis is usually referred to as the "contact time". At short CP contact times, a build-up of X magnetisation occurs, during which the transfer of H magnetisation from nearby spins (and remote spins through proton spin diffusion) to X occurs. For longer CP contact times, the X magnetisation decreases from T(X) relaxation, i.e. the decay of the magnetisation during a spin lock. | 0 | Theoretical and Fundamental Chemistry |
Berylliosis, or chronic beryllium disease (CBD), is a chronic allergic-type lung response and chronic lung disease caused by exposure to beryllium and its compounds, a form of beryllium poisoning. It is distinct from acute beryllium poisoning, which became rare following occupational exposure limits established around 1950. Berylliosis is an occupational lung disease.
While there is no cure, symptoms can be treated. | 1 | Applied and Interdisciplinary Chemistry |
Residual chemical shift anisotropy (RCSA) is the difference between the chemical shift anisotropy (CSA) of aligned and non-aligned molecules. It is normally three orders of magnitude smaller than the static CSA, with values on the order of parts-per-billion (ppb). RCSA is useful for structural determination and it is among the new developments in NMR spectroscopy. | 0 | Theoretical and Fundamental Chemistry |
A ternary rhodium-centered bipyramidal dibismuth complex is an example of subhalide complexes with interesting geometry and unusual electronic properties, particularly what has been reported as an example of Möbius aromaticity. The complex exhibits a 4-electron-5-centered bond in the central plane occupied by a Bi equatorial pentagon with the rhodium center in the middle. Based on the electronic analysis carried out by Ruck (2003), the bismuth bonding consists of 2-centered-2-electron bonds, namely, Bi-Rh and Bi-Br one (see structure on the right).
The electronic analysis was carried out starting with counting the available skeletal electrons. Each of the 7 bismuth atoms contribute a total of 3x7=21 electrons (3 per each atom), while Rh gives all of its 9 electrons and the 8 bridging bromide atoms yield 3 electrons each. The total skeletal electron count is thus 54. The total skeletal electron count gets distributed as follows: 2 electrons per each of the 16 2c-2e Bi-Br bond, 2 electrons per each of the 7 2c-2e Rh-Bi metallic bond, 2 rhodium lone pairs remaining on the Rh centre (total of 4e), and 4 electrons for 5c-4e bond pertaining to the central pentagon. The sum of electrons used in bonding is therefore 54. Hence, the subhalide complex is electron-precise, i.e., with all of its skeletal electrons involved in chemical bonding.
The bonding in such a system was compared to the aromatic cyclopentadienyl aromatic anion. Contrary to the π-type all in-phase orbital overlap exhibited by the organic cyclopentadienyl anion, σ-type bonding of the RhBi unit yields a phase change for an orbital pair (see figure).
The relative orbital energy diagram is rationalized for each of the systems relying on the Frost-Musulin mnemonic. The two lone pairs stemming from the rhodium metallic center are localized on the lowest-lying twicely degenerate set of molecular orbitals, consistent with the Möbius-type aromaticity. For reference, the electronics of the aromatic organice cyclopentadienyl unit is shown to the right of the rhodium-centered pentagonal Bi unit. As can be seen, Hückel rules dictate the molecular orbital splitting is inverted compared to its metallic counterpart, the highest-occupied molecular orbitals this time being twicely degenerate. | 0 | Theoretical and Fundamental Chemistry |
Some acetylides are notoriously explosive. Formation of acetylides poses a risk in handling of gaseous acetylene in presence of metals such as mercury, silver or copper, or alloys with their high content (brass, bronze, silver solder). | 0 | Theoretical and Fundamental Chemistry |
Quinone-interacting membrane-bound oxidoreductase is a membrane-bound protein complex present in the electron transport chain of sulfate reducers (e.g. Desulfovibrio species) and some sulfur oxidizers.
It was first described by Pires et al. (2003). | 1 | Applied and Interdisciplinary Chemistry |
Acoustic foam is a lightweight material made from polyurethane (either polyether or polyester) or extruded melamine foam. It is usually cut into tiles. One surface of these tiles often features pyramid, cone, wedge, or uneven cuboid shapes. Acoustic foam tiles are suited to placing on sonically reflective surfaces to act as sound absorbers, thus enhancing or changing the sound properties of a room.
This type of sound absorption is different from soundproofing, which is typically used to keep sound from escaping or entering a room rather than changing the properties of sound within the room itself.
Acoustic foam panels typically suppress reverberations in the mid and high frequencies. To deal with lower frequencies, much thicker pieces of acoustic foam (often in metal or wood enclosures) can be placed in the corners of a room and are called acoustic foam bass traps. | 0 | Theoretical and Fundamental Chemistry |
Light irradiation can initiate the reaction while avoiding exerting additional physical effects on the monomer crystal. It can be used in topochemical polymerization based on free radical mechanism such as 1,4-polymerization of diacetylene or diene polymerization. UV light is widely used as initiation method as it does in conventional polymerization. In some circumstances, however, the polymerization initiated by UV light is so slow that unbalanced pressure will accumulate more easily as previously stated. γ-irradiation can trigger the reaction faster due to the shorter wavelength. Thus, it was proved to be a better choice than UV in various reactions such as topochemical polymerization of 1,3-diene carboxylic acid derivatives. | 0 | Theoretical and Fundamental Chemistry |
A plasma is matter in which charges are screened due to the presence of other mobile charges. For example: Coulomb's Law is suppressed by the screening to yield a distance-dependent charge, , i.e., the charge Q is reduced exponentially with the distance divided by a screening length α. In a QGP, the color charge of the quarks and gluons is screened. The QGP has other analogies with a normal plasma. There are also dissimilarities because the color charge is non-abelian, whereas the electric charge is abelian. Outside a finite volume of QGP the color-electric field is not screened, so that a volume of QGP must still be color-neutral. It will therefore, like a nucleus, have integer electric charge.
Because of the extremely high energies involved, quark-antiquark pairs are produced by pair production and thus QGP is a roughly equal mixture of quarks and antiquarks of various flavors, with only a slight excess of quarks. This property is not a general feature of conventional plasmas, which may be too cool for pair production (see however pair instability supernova). | 0 | Theoretical and Fundamental Chemistry |
In spectral scanning, each 2-D sensor output represents a monochromatic (single-colored), spatial (x, y) map of the scene. HSI devices for spectral scanning are typically based on optical band-pass filters (either tunable or fixed). The scene is spectrally scanned by exchanging one filter after another while the platform remains stationary. In such staring, wavelength scanning systems, spectral smearing can occur if there is movement within the scene, invalidating spectral correlation/detection. Nonetheless, there is the advantage of being able to pick and choose spectral bands, and having a direct representation of the two spatial dimensions of the scene. If the imaging system is used on a moving platform, such as an airplane, acquired images at different wavelengths corresponds to different areas of the scene. The spatial features on each of the images may be used to realign the pixels. | 0 | Theoretical and Fundamental Chemistry |
Microcoils have found usefulness in telemetry systems, where planar microcoils are used to supply energy to miniaturized implants. | 0 | Theoretical and Fundamental Chemistry |
Through the use of magnetic traps, constant magnetic force can be applied to millions of DNA hairpin-tethered magnetic beads in parallel. The magnetic force can be easily adjusted by changing the distance between the trap and the magnetic beads. The number of eads that can be simultaneously monitored, which determines the read throughput of this platform, is limited by the bead size, length of the tethered DNA hairpin, and the optical resolution limit. Currently, a density of 750 K/mm (comparable to an Illumina HiSeq 2000) can be achieved. | 1 | Applied and Interdisciplinary Chemistry |
Phosphodiester bonds make up the backbones of DNA and RNA. In the phosphodiester bonds of nucleic acids, a phosphate is attached to the 5 carbon of one nucleoside and to the 3 carbon of the adjacent nucleoside. Specifically, it is the phosphodiester bonds that link the 3 carbon atom of one sugar molecule and the 5 carbon atom of another (hence the name 3, 5 phosphodiester linkage used with reference to this kind of bond in DNA and RNA chains). The involved saccharide groups are deoxyribose in DNA and ribose in RNA. In order for the phosphodiester bond to form, joining the nucleosides, the tri-phosphate or di-phosphate forms of the nucleotide building blocks are broken apart to give off energy required to drive the enzyme-catalyzed reaction. In DNA replication, for example, formation of the phosphodiester bonds is catalyzed by a DNA polymerase enzyme, using a pair of magnesium cations and other supporting structures. Formation of the bond occurs not only in DNA and RNA replication, but also in the repair and recombination of nucleic acids, and may require the involvement of various polymerases, primers, and/or ligases. During the replication of DNA, for example, the DNA polymerase I leaves behind a hole between the phosphates in the newly formed backbone. DNA ligase is able to form a phosphodiester bond between the nucleotides on each side of the gap.
Phosphodiesters are negatively charged at pH 7. The negative charge attracts histones, metal cations such as magnesium, and polyamines [needs citation]. Repulsion between these negative charges influences the conformation of the polynucleic acids. | 1 | Applied and Interdisciplinary Chemistry |
-Deprenyl, also known as or dextro-N-propargyl-N-methylamphetamine, is an MAO-B inhibitor that metabolizes into -amphetamine and -methamphetamine and is therefore also a norepinephrine–dopamine releasing agent. It is the opposite enantiomer of -deprenyl (selegiline).
-Deprenyl, also an MAO-B inhibitor, metabolizes to -amphetamine and -methamphetamine, which are both norepinephrine releasing agents. In contrast, -deprenyl additionally has dopaminergic effects and has been found to be reinforcing in scientific research, whereas -deprenyl is not known to have any appreciable psychological reinforcement.
In addition to its actions as an MAO-B inhibitor and NDRA, -deprenyl has been found to bind with high affinity to the σ receptor (K = 79 nM) similarly to various other amphetamine derivatives. Its -isomer, selegiline, binds with 3.5-fold lower affinity in comparison. | 0 | Theoretical and Fundamental Chemistry |
Both steps are producing energy to be coupled to ATP synthesis. Nitrifying organisms are chemoautotrophs, and use carbon dioxide as their carbon source for growth. Some AOB possess the enzyme, urease, which catalyzes the conversion of the urea molecule to two ammonia molecules and one carbon dioxide molecule. Nitrosomonas europaea, as well as populations of soil-dwelling AOB, have been shown to assimilate the carbon dioxide released by the reaction to make biomass via the Calvin Cycle, and harvest energy by oxidizing ammonia (the other product of urease) to nitrite. This feature may explain enhanced growth of AOB in the presence of urea in acidic environments.
In most environments, organisms are present that will complete both steps of the process, yielding nitrate as the final product. However, it is possible to design systems in which nitrite is formed (the Sharon process).
Nitrification is important in agricultural systems, where fertilizer is often applied as ammonia. Conversion of this ammonia to nitrate increases nitrogen leaching because nitrate is more water-soluble than ammonia.
Nitrification also plays an important role in the removal of nitrogen from municipal wastewater. The conventional removal is nitrification, followed by denitrification. The cost of this process resides mainly in aeration (bringing oxygen in the reactor) and the addition of an external carbon source (e.g., methanol) for the denitrification.
Nitrification can also occur in drinking water. In distribution systems where chloramines are used as the secondary disinfectant, the presence of free ammonia can act as a substrate for ammonia-oxidizing microorganisms. The associated reactions can lead to the depletion of the disinfectant residual in the system. The addition of chlorite ion to chloramine-treated water has been shown to control nitrification.
Together with ammonification, nitrification forms a mineralization process that refers to the complete decomposition of organic material, with the release of available nitrogen compounds. This replenishes the nitrogen cycle. | 1 | Applied and Interdisciplinary Chemistry |
Most alkenes are prochiral, meaning in this context that their hydrocyanation generates chiral nitriles. Conventional hydrocyanation catalysts, e.g. , catalyse the formation of racemic mixtures. When however the supporting ligands are chiral, the hydrocyanation can be highly enantioselective. For asymmetric hydrocyanation, popular chiral ligands are chelating aryl diphosphite complexes. | 0 | Theoretical and Fundamental Chemistry |
Many plants acquire sulfur through gaseous atmospheric compounds. Leaves of trees have δS values lying between those of air and soil, suggesting that there is uptake occurring from atmospheric and soil sources. The δS values of trees has also been demonstrated to be height dependent, with the foliage at the tops of conifers, bull rushes and deciduous trees having δS values more reflective of the atmosphere and lower foliage having δS values closer to that of soil. It has been proposed that this is due to upper foliage exerting a canopy action on the lower branches, taking up atmospheric sulfur before it can reach lower levels. This is further supported with the epiphytic lichens and mosses having δS values close to atmospheric S compounds. This occurs due to lichens and mosses having no access to soil and relying on the direct uptake of gaseous sulfur, dissolved sulfur through rainfall and dry fall accumulation, providing a cumulative record of atmospheric sulfur isotope composition.
Main forms of atmospheric sulfur come from the natural sulfur emissions formed biologically and emitted as HS or organic sulfur gases such as DMS (dimethyl sulfide), COS (carbonyl sulfide), and CS (carbon disulfide). These gases are predominantly formed over oceans, wetlands, salt marshes, and estuaries by algae and bacteria. Anthropogenic emissions have increased the concentration of sulfur in the atmosphere mainly through emissions of SO, from coal, oil, industrial processes, and biomass burning. In 2000, global anthropogenic emission of sulfur was estimated of 55.2–68 Tg S per year, which is much higher than the natural sulfur emissions estimated to be 34 Tg S per year. In the event of excess sulfur in plant tissue, it has been demonstrated that when exposed to high doses of sulfur dioxide, plants emit hydrogen sulfide (HS) and possibly other reduced sulfur compounds in response to high sulfur loading | 0 | Theoretical and Fundamental Chemistry |
When two or more types of ligands (L, L, ...) are coordinated to an octahedral metal centre (M), the complex can exist as isomers. The naming system for these isomers depends upon the number and arrangement of different ligands. | 0 | Theoretical and Fundamental Chemistry |
Filter aid selection: filter aid are recoat cake that act as the actual filter media and there two different types which are diatomaceous earth or perlite.
Important parameter to consider is the solid penetration into the pre coat cake and its limits 0.002 to 0.005 inch penetration thickness.
Large amount of filter aid is used i.e. “open”, more filter aid is aid removed which lead to higher disposal cost. If little amount of filter aid is used i.e. “tight” will lead to no flow rate into the drum. This comparison can be illustrated in figure 5 as below. | 0 | Theoretical and Fundamental Chemistry |
Alzheimers disease affects forty-five million people and is the fifth leading cause of death in the 65 plus population. There is no complete cure for the disease, currently. However, lithium is being evaluated for its effectiveness as a potential therapeutic measure. One of the leading causes of Alzheimers is the hyperphosphorylation of the tau protein by the enzyme GSK-3, which leads to the overproduction of amyloid peptides that cause cell death. To combat this toxic amyloid aggregation, lithium upregulates the production of neuroprotectors and neurotrophic factors, as well as inhibiting the GSK-3 enzyme. Lithium also stimulates neurogenesis within the hippocampus, making it thicker. Yet another cause of Alzheimer's disease is the dysregulation of calcium ions within the brain. Too much or too little calcium within the brain can lead to cell death. Lithium is able to restore the intracellular calcium homeostasis through inhibiting the wrongful influx of calcium upstream. It also promotes the redirection of the influx of the calcium ions into the lumen of the endoplasmic reticulum of the cells to reduce the oxidative stress within the mitochondria.
In 2009, a study was performed by Hampel and colleagues that asked patients with Alzheimers to take a low dose of lithium daily for three months; it resulted in a significant slowing of cognitive decline, benefitting patients being in the prodromal stage the most. Upon a secondary analysis, the brains of the Alzheimers patients were studied and shown to have an increase in BDNF markers, meaning they had actually shown cognitive improvement. Another study, a population study this time by Kessing et al., showed a negative correlation between Alzheimer's disease deaths and the presence of lithium in drinking water. Areas with increased lithium in their drinking water showed less dementia overall in their population. | 1 | Applied and Interdisciplinary Chemistry |
The diagnosis of SR deficiency is based on the analysis of the pterins and biogenic amines found in the cerebrospinal fluid (CSF) of the brain. The pterin compound functions as a cofactor in enzyme catalysis and biogenic amines which include adrenaline, dopamine, and serotonin have functions that vary from the control of homeostasis to the management of cognitive tasks. This analysis reveals decreased concentrations of homovanillic acid (HVA), 5-hydroxyindolacetic acid (HIAA), and elevated levels of 7,8-dihydrobiopterin, a compound produced in the synthesis of neurotransmitters. Sepiapterin is not detected by the regularly used methods applied in the investigation of biogenic monoamine metabolites in the cerebrospinal fluid. It must be determined by specialized methods that work by indicating a marked and abnormal increase of sepiapterin in cerebrospinal fluid. Confirmation of the diagnosis occurs by demonstrating high levels of CSF sepiapterin and a marked decrease of SR activity of the fibroblasts along with SPR gene molecular analysis. | 1 | Applied and Interdisciplinary Chemistry |
Invasion percolation is a mathematical model of realistic fluid distributions for slow immiscible fluid invasion in porous media, in percolation theory.
It "explicitly takes into account the transport process taking place". A wetting fluid such as water takes over from a non-wetting fluid such as oil, and capillary forces are taken into account. It was introduced by Wilkinson and Willemsen (1983). | 1 | Applied and Interdisciplinary Chemistry |
The sorbent tube and the focusing trap may be packed with one or more sorbents. The type and number of sorbents depends on a number of factors including the sampling setup, the analyte volatility range, analyte concentration, and the humidity of the sample.
One of the most versatile and popular sorbents for thermal desorption is poly(2,6-diphenyl-p-phenylene oxide), known by its trademark Tenax. | 0 | Theoretical and Fundamental Chemistry |
Protein inhibition by inhibitor binding may induce obstruction in pathway regulation, homeostatic regulation and physiological function.
Competitive inhibitors compete with substrate to bind to free enzymes at active sites and thus impede the production of the enzyme-substrate complex upon binding. For example, carbon monoxide poisoning is caused by the competitive binding of carbon monoxide as opposed to oxygen in hemoglobin.
Uncompetitive inhibitors, alternatively, bind concurrently with substrate at active sites. Upon binding to an enzyme substrate (ES) complex, an enzyme substrate inhibitor (ESI) complex is formed. Similar to competitive inhibitors, the rate at product formation is decreased also.
Lastly, mixed inhibitors are able to bind to both the free enzyme and the enzyme-substrate complex. However, in contrast to competitive and uncompetitive inhibitors, mixed inhibitors bind to the allosteric site. Allosteric binding induces conformational changes that may increase the proteins affinity for substrate. This phenomenon is called positive modulation. Conversely, allosteric binding that decreases the proteins affinity for substrate is negative modulation. | 1 | Applied and Interdisciplinary Chemistry |
Although most plasmids are double-stranded DNA molecules, some consist of single-stranded DNA, or predominantly double-stranded RNA. RNA plasmids are non-infectious extrachromosomal linear RNA replicons, both encapsidated and unencapsidated, which have been found in fungi and various plants, from algae to land plants. In many cases, however, it may be difficult or impossible to clearly distinguish RNA plasmids from RNA viruses and other infectious RNAs. | 1 | Applied and Interdisciplinary Chemistry |
Nitrolic acids are organic compounds with the functional group RC(NO)=NOH. They are prepared by the reaction of nitroalkanes with base and nitrite sources:
:RCHNO + HNO → RC(NO)=NOH + HO
The conversion was first demonstrated by Victor Meyer using nitroethane. The reaction proceeds via the intermediacy of the nitronate anion. | 0 | Theoretical and Fundamental Chemistry |
Although the concentration of the ozone in the ozone layer is very small, it is vitally important to life because it absorbs biologically harmful ultraviolet (UV) radiation coming from the Sun. Extremely short or vacuum UV (10–100 nm) is screened out by nitrogen. UV radiation capable of penetrating nitrogen is divided into three categories, based on its wavelength; these are referred to as UV-A (400–315 nm), UV-B (315–280 nm), and UV-C (280–100 nm).
UV-C, which is very harmful to all living things, is entirely screened out by a combination of dioxygen (< 200 nm) and ozone (> about 200 nm) by around altitude. UV-B radiation can be harmful to the skin and is the main cause of sunburn; excessive exposure can also cause cataracts, immune system suppression, and genetic damage, resulting in problems such as skin cancer. The ozone layer (which absorbs from about 200 nm to 310 nm with a maximal absorption at about 250 nm) is very effective at screening out UV-B; for radiation with a wavelength of 290 nm, the intensity at the top of the atmosphere is 350 million times stronger than at the Earths surface. Nevertheless, some UV-B, particularly at its longest wavelengths, reaches the surface, and is important for the skins production of vitamin D in mammals.
Ozone is transparent to most UV-A, so most of this longer-wavelength UV radiation reaches the surface, and it constitutes most of the UV reaching the Earth. This type of UV radiation is significantly less harmful to DNA, although it may still potentially cause physical damage, premature aging of the skin, indirect genetic damage, and skin cancer. | 0 | Theoretical and Fundamental Chemistry |
Cleavage forms parallel to crystallographic planes:
*Basal, pinacoidal, or planar cleavage occurs when there is only cleavage plane. Talc has basal cleavage. Mica (like muscovite or biotite) also has basal cleavage; this is why mica can be peeled into thin sheets.
*Prismatic cleavage occurs when there are cleavage planes in a crystal that intersect at 90 degrees. Spodumene exhibits prismatic cleavage.
*Non-Prismatic cleavage occurs when there are cleavage planes in a crystal that do not intersect at 90 degrees (two non-perpendicular directions of cleavage, e.g 60 & 120 degrees).
*Cubic cleavage occurs when there are cleavage planes intersecting at 90 degrees. Halite (or salt) has cubic cleavage, and therefore, when halite crystals are broken, they will form more cubes.
*Rhombohedral cleavage occurs when there are cleavage planes intersecting at angles that are not 90 degrees. Calcite has rhombohedral cleavage.
*Octahedral cleavage occurs when there are cleavage planes in a crystal. Fluorite exhibits perfect octahedral cleavage. Octahedral cleavage is common for semiconductors. Diamond also has octahedral cleavage.
*Dodecahedral cleavage occurs when there are cleavage planes in a crystal. Sphalerite has dodecahedral cleavage. | 0 | Theoretical and Fundamental Chemistry |
This variant of the AnMBR combines the previous two variants, keeping the membrane unit external, but submerged within an external chamber. The anaerobic process takes place first, and then subsequently enters the membrane unit for filtration. Here, the influent(wastewater) is pumped into the externally submerged chamber where it is then filtered into the permeate(effluent) and the retentate(organic load). This variant, similar to the submerged AnMBR, also utilizes low negative pressure to separate the permeate and retentate. Following this process, the effluent leaves the system while the organic load recirculates into the bioreactor unit to then turn into biogas. | 1 | Applied and Interdisciplinary Chemistry |
René Marcelin (12 June 1885 – 24 September 1914) was a French physical chemist, who died in World War I at a young age. He was a pupil of Jean Baptiste Perrin at the Faculty of Sciences in Paris and performed theoretical studies in the field of chemical kinetics. | 0 | Theoretical and Fundamental Chemistry |
Retro (or reverse) screening (RS) is a relatively new approach to determine the specificity and selectivity of a therapeutic drug molecule against a target protein or another macromolecule. It proceeds in the opposite direction to the so-called virtual screening (VS). In VS, the goal is to use a protein target to identify a high-affinity ligand from a search library typically containing hundreds of thousands of small molecules. In contrast, RS employs a known drug molecule to screen a protein library containing hundreds of thousands of individual structures (obtained from both experimental and modeling techniques). Accordingly, the extent to which this drug cross-reacts with the human proteome provides a measure of its efficacy and the potential long-term side-effects. RS is expected to play a key role in providing an additional layer of quality control in drug discovery. | 1 | Applied and Interdisciplinary Chemistry |
In the buffer layer, between 5 wall units and 30 wall units, neither law holds, such that:
:For
with the largest variation from either law occurring approximately where the two equations intersect, at . That is, before 11 wall units the linear approximation is more accurate and after 11 wall units the logarithmic approximation should be used, though neither are relatively accurate at 11 wall units.
The mean streamwise velocity profile is improved for with an eddy viscosity formulation based on a near-wall turbulent kinetic energy function and the van Driest mixing length equation. Comparisons with DNS data of fully developed turbulent channel flows for showed good agreement. | 1 | Applied and Interdisciplinary Chemistry |
Darcy's law can be expressed very generally as:
where q is the volume flux vector of the fluid at a particular point in the medium, h is the total hydraulic head, and K is the hydraulic conductivity tensor, at that point. The hydraulic conductivity can often be approximated as a scalar. (Note the analogy to Ohm's law in electrostatics. The flux vector is analogous to the current density, head is analogous to voltage, and hydraulic conductivity is analogous to electrical conductivity.) | 1 | Applied and Interdisciplinary Chemistry |
Wolfgang Pauli was the first to suggest the idea of a particle such as the neutrino existing in our universe in 1930. He believed such a particle to be completely massless. This was the belief amongst the astrophysics community until the solar neutrino problem was solved.
Frederick Reines, from the University of California at Irvine, and George A. Cowan were the first astrophysicists to detect neutrinos in 1956. They won a Nobel Prize in Physics for their work in 1995.
Raymond Davis and John Bahcall are the pioneers of solar neutrino studies. While Bahcall never won a Nobel Prize, Davis along with Masatoshi Koshiba won the Nobel Prize in Physics in 2002 after the solar neutrino problem was solved for their contributions in helping solve the problem.
Pontecorvo, known as the first astrophysicist to suggest the idea neutrinos have some mass and can oscillate, never received a Nobel Prize for his contributions due to his passing in 1993.
Arthur B. McDonald, a Canadian physicist, was a key contributor in building the Sudbury Neutrino Observatory (SNO) in the mid 1980s and later became the director of the SNO and leader of the team that solved the solar neutrino problem. McDonald, along with Japanese physicist Kajita Takaaki both received a Nobel Prize for their work discovering the oscillation of neutrinos in 2015. | 0 | Theoretical and Fundamental Chemistry |
In SKP the probe and sample are held parallel to each other and electrically connected to form a parallel plate capacitor. The probe is selected to be of a different material to the sample, therefore each component initially has a distinct Fermi level. When electrical connection is made between the probe and the sample electron flow can occur between the probe and the sample in the direction of the higher to the lower Fermi level. This electron flow causes the equilibration of the probe and sample Fermi levels. Furthermore, a surface charge develops on the probe and the sample, with a related potential difference known as the contact potential (V). In SKP the probe is vibrated along a perpendicular to the plane of the sample. This vibration causes a change in probe to sample distance, which in turn results in the flow of current, taking the form of an ac sine wave. The resulting ac sine wave is demodulated to a dc signal through the use of a lock-in amplifier. Typically the user must select the correct reference phase value used by the lock-in amplifier. Once the dc potential has been determined, an external potential, known as the backing potential (V) can be applied to null the charge between the probe and the sample. When the charge is nullified, the Fermi level of the sample returns to its original position. This means that V is equal to -V, which is the work function difference between the SKP probe and the sample measured.
The cantilever in the AFM is a reference electrode that forms a capacitor with the surface, over which it is scanned laterally at a constant separation. The cantilever is not piezoelectrically driven at its mechanical resonance frequency ω as in normal AFM although an alternating current (AC) voltage is applied at this frequency.
When there is a direct-current (DC) potential difference between the tip and the surface, the AC+DC voltage offset will cause the cantilever to vibrate. The origin of the force can be understood by considering that the energy of the capacitor formed by the cantilever and the surface is
plus terms at DC. Only the cross-term proportional to the V·V product is at the resonance frequency ω. The resulting vibration of the cantilever is detected using usual scanned-probe microscopy methods (typically involving a diode laser and a four-quadrant detector). A null circuit is used to drive the DC potential of the tip to a value which minimizes the vibration. A map of this nulling DC potential versus the lateral position coordinate therefore produces an image of the work function of the surface.
A related technique, electrostatic force microscopy (EFM), directly measures the force produced on a charged tip by the electric field emanating from the surface. EFM operates much like magnetic force microscopy in that the frequency shift or amplitude change of the cantilever oscillation is used to detect the electric field. However, EFM is much more sensitive to topographic artifacts than KPFM. Both EFM and KPFM require the use of conductive cantilevers, typically metal-coated silicon or silicon nitride. Another AFM-based technique for the imaging of electrostatic surface potentials, scanning quantum dot microscopy, quantifies surface potentials based on their ability to gate a tip-attached quantum dot. | 0 | Theoretical and Fundamental Chemistry |
For , advection is relatively unimportant, and so
the magnetic field will tend to relax towards a purely diffusive state, determined by the boundary conditions rather than the flow.
For , diffusion is relatively unimportant on the length scale L. Flux lines of the magnetic field are then advected with the fluid flow, until such time as gradients are concentrated into regions of short enough length scale that diffusion can balance advection. | 1 | Applied and Interdisciplinary Chemistry |
After free falling through a height in a vacuum from an initial velocity of 0, a mass will have reached a speed
where is the acceleration due to gravity. Rearranged as a head:
The term is called the velocity head, expressed as a length measurement. In a flowing fluid, it represents the energy of the fluid due to its bulk motion.
The total hydraulic head of a fluid is composed of pressure head and elevation head. The pressure head is the equivalent gauge pressure of a column of water at the base of the piezometer, and the elevation head is the relative potential energy in terms of an elevation. The head equation, a simplified form of the Bernoulli principle for incompressible fluids, can be expressed as:
where
* is the hydraulic head (Length in m or ft), also known as the piezometric head.
* is the pressure head, in terms of the elevation difference of the water column relative to the piezometer bottom (Length in m or ft), and
* is the elevation at the piezometer bottom (Length in m or ft)
In an example with a 400 m deep piezometer, with an elevation of 1000 m, and a depth to water of 100 m: z = 600 m, ψ = 300 m, and h = 900 m.
The pressure head can be expressed as:
where
is the gauge pressure (Force per unit area, often Pa or psi),
* is the unit weight of the liquid (Force per unit volume, typically N·m or lbf/ft),
* is the density of the liquid (Mass per unit volume, frequently kg·m), and
* is the gravitational acceleration (velocity change per unit time, often m·s) | 1 | Applied and Interdisciplinary Chemistry |
Neurotrophins are a family of proteins that induce the survival, development, and function of neurons.
They belong to a class of growth factors, secreted proteins that can signal particular cells to survive, differentiate, or grow. Growth factors such as neurotrophins that promote the survival of neurons are known as neurotrophic factors. Neurotrophic factors are secreted by target tissue and act by preventing the associated neuron from initiating programmed cell death – allowing the neurons to survive. Neurotrophins also induce differentiation of progenitor cells, to form neurons.
Although the vast majority of neurons in the mammalian brain are formed prenatally, parts of the adult brain (for example, the hippocampus) retain the ability to grow new neurons from neural stem cells, a process known as neurogenesis. Neurotrophins are chemicals that help to stimulate and control neurogenesis. | 1 | Applied and Interdisciplinary Chemistry |
A world effort was triggered in the 1960s to study magnetohydrodynamic converters in order to bring MHD power conversion to market with commercial power plants of a new kind, converting the kinetic energy of a high velocity plasma into electricity with no moving parts at a high efficiency. Research was also conducted in the field of supersonic and hypersonic aerodynamics to study plasma interaction with magnetic fields to eventually achieve passive and even active flow control around vehicles or projectiles, in order to soften and mitigate shock waves, lower thermal transfer and reduce drag.
Such ionized gases used in "plasma technology" ("technological" or "engineered" plasmas) are usually weakly ionized gases in the sense that only a tiny fraction of the gas molecules are ionized. These kinds of weakly ionized gases are also nonthermal "cold" plasmas. In the presence of magnetics fields, the study of such magnetized nonthermal weakly ionized gases involves resistive magnetohydrodynamics with low magnetic Reynolds number, a challenging field of plasma physics where calculations require dyadic tensors in a 7-dimensional phase space. When used in combination with a high Hall parameter, a critical value triggers the problematic electrothermal instability which limited these technological developments. | 0 | Theoretical and Fundamental Chemistry |
Polymers with thermally induced shape-memory effect are those polymers that respond to external stimuli and because of this have the ability to change their shape. The thermally induced shape-memory effect results from a combination of proper processing and programming of the system.
This effect can be observed in polymers with very different chemical composition, which opens a great possibility of applications. | 0 | Theoretical and Fundamental Chemistry |
The term spiral separator can refer to either a device for separating slurry components by density (wet spiral separators), or for a device for sorting particles by shape (dry spiral separators). | 0 | Theoretical and Fundamental Chemistry |
Richard Robert Ernst (14 August 1933 – 4 June 2021) was a Swiss physical chemist and Nobel laureate.
Ernst was awarded the Nobel Prize in Chemistry in 1991 for his contributions towards the development of Fourier transform nuclear magnetic resonance (NMR) spectroscopy while at Varian Associates and ETH Zurich. These underpin applications to both to chemistry with NMR spectroscopy and to medicine with magnetic resonance imaging (MRI).
He humbly referred to himself as a "tool-maker" rather than a scientist. | 0 | Theoretical and Fundamental Chemistry |
Polluted effluent is added into the bottom of the cell and mixed with the adsorbent in the adsorption zone 1.1 where adsorption of the pollutants onto the surface of the adsorbent occurs. Mixing between the adsorbent and the polluted effluent is promoted by air spargers at the base of the cell which also facilitate the migration of the adsorbent upwards and into the cell's sedimentation zone. | 0 | Theoretical and Fundamental Chemistry |
Channels differ with respect to the ion they let pass (for example, Na, K, Cl), the ways in which they may be regulated, the number of subunits of which they are composed and other aspects of structure. Channels belonging to the largest class, which includes the voltage-gated channels that underlie the nerve impulse, consists of four or sometimes five subunits with six transmembrane helices each. On activation, these helices move about and open the pore. Two of these six helices are separated by a loop that lines the pore and is the primary determinant of ion selectivity and conductance in this channel class and some others. The existence and mechanism for ion selectivity was first postulated in the late 1960s by Bertil Hille and Clay Armstrong. The idea of the ionic selectivity for potassium channels was that the carbonyl oxygens of the protein backbones of the "selectivity filter" (named by Bertil Hille) could efficiently replace the water molecules that normally shield potassium ions, but that sodium ions were smaller and cannot be completely dehydrated to allow such shielding, and therefore could not pass through. This mechanism was finally confirmed when the first structure of an ion channel was elucidated. A bacterial potassium channel KcsA, consisting of just the selectivity filter, "P" loop, and two transmembrane helices was used as a model to study the permeability and the selectivity of ion channels in the Mackinnon lab. The determination of the molecular structure of KcsA by Roderick MacKinnon using X-ray crystallography won a share of the 2003 Nobel Prize in Chemistry.
Because of their small size and the difficulty of crystallizing integral membrane proteins for X-ray analysis, it is only very recently that scientists have been able to directly examine what channels "look like." Particularly in cases where the crystallography required removing channels from their membranes with detergent, many researchers regard images that have been obtained as tentative. An example is the long-awaited crystal structure of a voltage-gated potassium channel, which was reported in May 2003. One inevitable ambiguity about these structures relates to the strong evidence that channels change conformation as they operate (they open and close, for example), such that the structure in the crystal could represent any one of these operational states. Most of what researchers have deduced about channel operation so far they have established through electrophysiology, biochemistry, gene sequence comparison and mutagenesis.
Channels can have single (CLICs) to multiple transmembrane (K channels, P2X receptors, Na channels) domains which span plasma membrane to form pores. Pore can determine the selectivity of the channel. Gate can be formed either inside or outside the pore region. | 1 | Applied and Interdisciplinary Chemistry |
The parameters for water quality are determined by the intended use. Work in the area of water quality tends to be focused on water that is treated for potability, industrial/domestic use, or restoration (of an environment/ecosystem, generally for health of human/aquatic life). | 0 | Theoretical and Fundamental Chemistry |
Photo-reflectance is a highly sensitive measurement technique and provides unmatched capability for characterizing the material and electronic properties of thin films. Photo-reflectance has been particularly important in basic research on semiconductors due to its ability to precisely determine semiconductor bandstructures (even at room temperature). As an optical technique, photo-reflectance would appear suited to industrial applications because it is non-contact, and because it has good spatial resolution. However, the need for spectroscopic information limits measurement speed, and consequently the adoption of spectroscopic photo-reflectance in industrial applications such as process control of microelectronics manufacturing.
Nevertheless, where spectroscopic information is not required, photo-reflectance techniques have been implemented in semiconductor manufacturing process control. For example, in the late 1980s, Therma-Wave, Inc. introduced the "Therma-Probe" photo-modulated reflectance system to the market for semiconductor process control equipment. The original Therma-Probe focused an intensity modulated pump laser beam onto a spot on a silicon sample, modulating the sample reflectance. The reflectance changes were detected by a coincident laser probe beam of 633 nanometer wavelength. At this wavelength no electro-reflectance signal is present, since it is far removed from any interband transitions in silicon. Rather, the mechanisms responsible for the Therma-Probe signal are thermo-modulation and the Drude free carrier effect. The Therma-Probe was used primarily for monitoring of the ion implantation process in silicon semiconductor manufacturing. Measurement systems such as the Therma-Probe are particularly desirable in process control of microelectronics manufacturing because they provide the ability to quickly verify the correct execution of process steps, without contacting the wafer or removing the wafer from the clean room. Generally a number of measurements will be made on certain areas of the wafer and compared with expected values. As long as the measured values are within a certain range, the wafers are passed for continued processing. (This is known as statistical process control.) Other photo-modulated reflectance systems marketed for process control of implant processes are the "TWIN" metrology system marketed by [http://www.pvatepla.com/en/home PVA TePla AG], and the "PMR-3000" marketed by [https://www.semilab.hu/ Semilab Co. Ltd] (originally Boxer-Cross, Inc.).
However, by the mid 2000s, new manufacturing processes were requiring new process control capabilities, for example the need for control of new "diffusion-less" annealing processes and advanced strained silicon processes. To address these new process control requirements, in 2007, [https://xcalipr.com Xitronix Corporation] introduced a photo-reflectance system to the semiconductor process control market. Like the Therma-Probe, the Xitronix metrology system utilized a fixed wavelength probe beam generated by a laser. However, the probe beam of the Xitronix system had a wavelength of approximately 375 nanometers, near the first major interband transition in silicon. At this wavelength the electro-modulation signal is dominant, which enabled the Xitronix system to precisely measure active doping concentration in diffusion-less annealing processes. This probe beam wavelength also provided excellent sensitivity to strain in strained silicon processes. More recently, the use of laser photo-reflectance technology for precision measurement of carrier diffusion lengths, recombination lifetimes, and mobilities has been demonstrated. | 0 | Theoretical and Fundamental Chemistry |
Dioxygen complexes are coordination compounds that contain O as a ligand. The study of these compounds is inspired by oxygen-carrying proteins such as myoglobin, hemoglobin, hemerythrin, and hemocyanin. Several transition metals form complexes with O, and many of these complexes form reversibly. The binding of O is the first step in many important phenomena, such as cellular respiration, corrosion, and industrial chemistry. The first synthetic oxygen complex was demonstrated in 1938 with cobalt(II) complex reversibly bound O. | 0 | Theoretical and Fundamental Chemistry |
An old-standing topic in grain growth is the evolution of the grains size distribution. Inspired by the work of Lifshitz and Slyozov on Ostwald ripening, Hillert has suggested that in a normal grain growth process the size distribution function must converge to a self-similar solution, i.e. it becomes invariant when the grain size is scaled with a characteristic length of the system that is proportional to the average grain size .
Several simulation studies, however, have shown that the size distribution deviates from the Hillerts self-similar solution. Hence a search for a new possible self-similar solution was initiated that indeed led to a new class of self-similar distribution functions. Large-scale phase field simulations have shown that there is indeed a self-similar behavior possible within the new distribution functions. It was shown that the origin of the deviation from Hillerts distribution is indeed the geometry of grains specially when they are shrinking. | 1 | Applied and Interdisciplinary Chemistry |
MFGM lipid components such as sphingomyelin and gangliosides are highly concentrated in the brain and support synaptogenesis and myelination. In the central nervous system, sphingomyelin is a key component of the myelin sheath, which insulates axons and supports efficient transmission of nerve impulses. During myelination, nerve axons are wrapped with multiple layers of cell membrane by oligodendrocyte glial cells, a process that accounts for a large portion of brain growth during late gestation and the first two years of life, but which can also continue up to 5–10 years of age. Meanwhile, gangliosides are concentrated within the brain’s gray matter and constitute approximately 6% to 10% of the total human brain lipid mass. Additionally, gangliosides are enriched at the synaptic membrane of neurons, and are functionally involved in neurotransmission and synapse formation. Brain ganglioside accretion occurs at an accelerated rate in the early years of life, coinciding with the most active period of myelination, axonal outgrowth, and synaptogenesis.
Alongside the growth of brain size, total brain ganglioside concentration also increases 3-fold from early fetal development to 5 years of age. | 1 | Applied and Interdisciplinary Chemistry |
For a circular bleach spot of radius and diffusion-dominated recovery, the fluorescence is described by an equation derived by Soumpasis (which involves modified Bessel functions and )
with the characteristic timescale for diffusion, and is the time. is the normalized fluorescence (goes to 1 as goes to infinity). The diffusion timescale for a bleached spot of radius is , with D the diffusion coefficient.
Note that this is for an instantaneous bleach with a step function profile, i.e., the fraction of protein assumed to be bleached instantaneously at time is , and , for is the distance from the centre of the bleached area. It is also assumed that the recovery can be modelled by diffusion in two dimensions, that is also both uniform and isotropic. In other words, that diffusion is occurring in a uniform medium so the effective diffusion constant D is the same everywhere, and that the diffusion is isotropic, i.e., occurs at the same rate along all axes in the plane.
In practice, in a cell none of these assumptions will be strictly true.
#Bleaching will not be instantaneous. Particularly if strong bleaching of a large area is required, bleaching may take a significant fraction of the diffusion timescale . Then a significant fraction of the bleached protein will diffuse out of the bleached region actually during bleaching. Failing to take account of this will introduce a significant error into D.
#The bleached profile will not be a radial step function. If the bleached spot is effectively a single pixel then the bleaching as a function of position will typically be diffraction limited and determined by the optics of the confocal laser scanning microscope used. This is not a radial step function and also varies along the axis perpendicular to the plane.
#Cells are of course three-dimensional not two-dimensional, as is the bleached volume. Neglecting diffusion out of the plane (we take this to be the xy plane) will be a reasonable approximation only if the fluorescence recovers predominantly via diffusion in this plane. This will be true, for example, if a cylindrical volume is bleached with the axis of the cylinder along the z axis and with this cylindrical volume going through the entire height of the cell. Then diffusion along the z axis does not cause fluorescence recovery as all protein is bleached uniformly along the z axis, and so neglecting it, as Soumpasis equation does, is harmless. However, if diffusion along the z' axis does contribute to fluorescence recovery then it must be accounted for.
#There is no reason to expect the cell cytoplasm or nucleoplasm to be completely spatially uniform or isotropic.
Thus, the equation of Soumpasis is just a useful approximation, that can be used when the assumptions listed above are good approximations to the true situation, and when the recovery of fluorescence is indeed limited by the timescale of diffusion . Note that just because the Soumpasis can be fitted adequately to data does not necessarily imply that the assumptions are true and that diffusion dominates recovery. | 1 | Applied and Interdisciplinary Chemistry |
In January researchers reported that six choroideremia patients had been treated with adeno-associated virus with a copy of REP1. Over a six-month to two-year period all had improved their sight. By 2016, 32 patients had been treated with positive results and researchers were hopeful the treatment would be long-lasting. Choroideremia is an inherited genetic eye disease with no approved treatment, leading to loss of sight.
In March researchers reported that 12 HIV patients had been treated since 2009 in a trial with a genetically engineered virus with a rare mutation (CCR5 deficiency) known to protect against HIV with promising results.
Clinical trials of gene therapy for sickle cell disease were started in 2014.
In February LentiGlobin BB305, a gene therapy treatment undergoing clinical trials for treatment of beta thalassemia gained FDA "breakthrough" status after several patients were able to forgo the frequent blood transfusions usually required to treat the disease.
In March researchers delivered a recombinant gene encoding a broadly neutralizing antibody into monkeys infected with simian HIV; the monkeys' cells produced the antibody, which cleared them of HIV. The technique is named immunoprophylaxis by gene transfer (IGT). Animal tests for antibodies to ebola, malaria, influenza, and hepatitis were underway.
In March, scientists, including an inventor of CRISPR, Jennifer Doudna, urged a worldwide moratorium on germline gene therapy, writing "scientists should avoid even attempting, in lax jurisdictions, germline genome modification for clinical application in humans" until the full implications "are discussed among scientific and governmental organizations".
In December, scientists of major world academies called for a moratorium on inheritable human genome edits, including those related to CRISPR-Cas9 technologies but that basic research including embryo gene editing should continue. | 1 | Applied and Interdisciplinary Chemistry |
The Florida Everglades is located in southern Florida. The ecosystem is essentially a subtropical fresh water marsh composed of a variety of flora and fauna. Of particular note is the saw grass and ridge slough formations that make the Everglades unique. Over the course of the past century mankind has had a rising presence in this region. Currently, all of the eastern shore of Florida is developed and the population has increased to over 6 million residents. This increased presence over the years has resulted in the channeling and redirecting of water from its traditional path through the Everglades and into the Gulf of Mexico and Atlantic Ocean. With this there have been a variety of deleterious effects upon the Florida Everglades. | 1 | Applied and Interdisciplinary Chemistry |
:Automated diffraction tomography (ADT) uses software to collect diffraction patterns over a series of slight tilt increments. In this way, a three-dimensional (tomographic) data set of reciprocal lattice intensities can be generated and used for structure determination. By coupling this technique with PED, the range and quality of the data set can be improved. The combination of ADT-PED has been employed effectively to investigate complex framework structures and beam-sensitive organic crystals | 0 | Theoretical and Fundamental Chemistry |
The expansion of gold mining in the Rand of South Africa began to slow down in the 1880s, as the new deposits being found tended to contain pyritic ore. The gold could not be extracted from this compound with any of the then available chemical processes or technologies.
In 1887, John Stewart MacArthur, working in collaboration with brothers Robert and William Forrest for the Tennant Company in Glasgow, Scotland, developed the MacArthur–Forrest process for the extraction of gold from gold ores. Several patents were issued in the same year. By suspending the crushed ore in a cyanide solution, a separation of up to 96 percent pure gold was achieved.
The process was first used on the Rand in 1890 and, despite operational imperfections, led to a boom of investment as larger gold mines were opened up.
By 1891, Nebraska pharmacist Gilbert S. Peyton had refined the process at his Mercur Mine in Utah, "the first mining plant in the United States to make a commercial success of the cyanide process on gold ores." In 1896, Bodländer confirmed that oxygen was necessary for the process, something that had been doubted by MacArthur, and discovered that hydrogen peroxide was formed as an intermediate.
Around 1900, the American metallurgist Charles Washington Merrill (1869–1956) and his engineer Thomas Bennett Crowe improved the treatment of the cyanide leachate, by using vacuum and zinc dust. Their process is the Merrill–Crowe process. | 1 | Applied and Interdisciplinary Chemistry |
MLPA quantifies the presence of particular sequences in a sample of DNA, using a specially designed probe pair for each target sequence of interest. The process consists of multiple steps:
# The sample DNA is denatured, resulting in single-stranded sample DNA.
# Pairs of probes are hybridized to the sample DNA, with each probe pair designed to query for the presence of a particular DNA sequence.
# Ligase is applied to the hybridized DNA, combining probe pairs that are hybridized immediately next to each other into a single strand of DNA that can be amplified by PCR.
# PCR amplifies all probe pairs that have been successfully ligated, using fluorescently labeled PCR primers.
# The PCR products are quantified, typically by (capillary) electrophoresis.
Each probe pair consists of two oligonucleotides, with sequence that recognizes adjacent sites of the target DNA, a PCR priming site, and optionally a "stuffer" to give the PCR product a unique length when compared to other probe pairs in the MLPA assay. Each complete probe pair must have a unique length, so that its resulting amplicons can be uniquely identified during quantification, avoiding the resolution limitations of multiplex PCR. Because the forward primer used for probe amplification is fluorescently labeled, each amplicon generates a fluorescent peak which can be detected by a capillary sequencer. Comparing the peak pattern obtained on a given sample with that obtained on various reference samples, the relative quantity of each amplicon can be determined. This ratio is a measure for the ratio in which the target sequence is present in the sample DNA.
Various techniques including DGGE (Denaturing Gradient Gel Electrophoresis), DHPLC (Denaturing High Performance Liquid Chromatography), and SSCA (Single Strand Conformation Analysis) effectively identify SNPs and small insertions and deletions. MLPA, however, is one of the only accurate, time-efficient techniques to detect genomic deletions and insertions (one or more entire exons), which are frequent causes of cancers such as hereditary non-polyposis colorectal cancer (HNPCC), breast, and ovarian cancer. MLPA can successfully and easily determine the relative copy number of all exons within a gene simultaneously with high sensitivity. | 1 | Applied and Interdisciplinary Chemistry |
Dentistry is one field in which free radical photopolymers have found wide usage as adhesives, sealant composites, and protective coatings. These dental composites are based on a camphorquinone photoinitiator and a matrix containing methacrylate oligomers with inorganic fillers such as silicon dioxide. Resin cements are utilized in luting cast ceramic, full porcelain, and veneer restorations that are thin or translucent, which permits visible light penetration in order to polymerize the cement. Light-activated cements may be radiolucent and are usually provided in various shades since they are utilized in esthetically demanding situations.
Conventional halogen bulbs, argon lasers and xenon arc lights are currently used in clinical practice. A new technological approach for curing light-activated oral biomaterials using a light curing unit (LCU) is based on blue light-emitting diodes (LED). The main benefits of LED LCU technology are the long lifetime of LED LCUs (several thousand hours), no need for filters or a cooling fan, and virtually no decrease of light output over the lifetime of the unit, resulting in consistent and high quality curing. Simple depth of cure experiments on dental composites cured with LED technology show promising results. | 0 | Theoretical and Fundamental Chemistry |
Doppler cooling, which is usually accompanied by a magnetic trapping force to give a magneto-optical trap, is by far the most common method of laser cooling. It is used to cool low density gases down to the Doppler cooling limit, which for rubidium-85 is around 150 microkelvins.
In Doppler cooling, initially, the frequency of light is tuned slightly below an electronic transition in the atom. Because the light is detuned to the "red" (i.e., at lower frequency) of the transition, the atoms will absorb more photons if they move towards the light source, due to the Doppler effect. Thus if one applies light from two opposite directions, the atoms will always scatter more photons from the laser beam pointing opposite to their direction of motion. In each scattering event the atom loses a momentum equal to the momentum of the photon. If the atom, which is now in the excited state, then emits a photon spontaneously, it will be kicked by the same amount of momentum, but in a random direction. Since the initial momentum change is a pure loss (opposing the direction of motion), while the subsequent change is random, the probable result of the absorption and emission process is to reduce the momentum of the atom, and therefore its speed—provided its initial speed was larger than the recoil speed from scattering a single photon. If the absorption and emission are repeated many times, the average speed, and therefore the kinetic energy of the atom, will be reduced. Since the temperature of a group of atoms is a measure of the average random internal kinetic energy, this is equivalent to cooling the atoms. | 0 | Theoretical and Fundamental Chemistry |
Two structural components are necessary for integrase binding: a hydrophobic benzyl moiety that buries into a highly hydrophobic pocket near the active site; and chelating triad that binds with two Mg ions in a rather hydrophilic region, anchoring the inhibitor onto the protein surface (see figure 3). In fact, all potent integrase inhibitors possess a substituted benzyl component that is critical for maintaining 3‘end joining potency. Removal of the benzyl group prevents inhibitory function. Lipophylic substituents are therefore beneficial for the strand transfer inhibition, in particular the thiophenyl, furanyl and (thiophen-2-yl)phenyl substitutions. Heteroaromatic amine and amide also cause increase in 3‘ processing inhibitory action.
When catechol-based inhibitors of IN were researched it was observed that maintaining a planar relationship with the bis-hydroxylated aryl ring increases potency. The inhibitory activity could be further optimized by including a meta-chloro substituent, enhancing the interaction of the benzyl group with the adjacent hydrophobic pocket (see figure 4: Structures A-G).
A benzyl substituted hydroxyl group (fig. 4 H) improves metal-chelating capability (compared to structure J in fig. 4) while a methoxy group (I) is much less potent due to steric clash by the additional methyl group with the catalytic metals.
When researching diketo derivates, the central pyrrole ring of structure K in fig. 4 was replaced by a series of aromatic systems having various substitution patterns. That provided optimum relative orientation of the benzyl and diketoacid (DKA) site chain. Structure L in fig. 4 resulted in 100 fold increase in potency.
Benard et al (2004) synthesized INIs with a quinoline subunit and an ancillary aromatic ring linked by functionalized spacers such as amide, hydrazide, urea and hydroxyprop-1-en-3-one moiety. They found that the amide group containing derivatives were the most promising ones. By synthesizing series of styrylquinones researchers found out that a carboxyl group at C-7, a hydroxylgroup at C-8 in the quinoline subunit and an ancillary phenyl ring (Figure 4: Structure M) are required for inhibition, although alterations of the ring are tolerated. Two hydroxyl groups on the ancillary phenyl ring are also required for inhibitory potency. | 1 | Applied and Interdisciplinary Chemistry |
Most genes considered master regulators code for transcription factor proteins, which in turn alter the expression of downstream genes in the pathway. Canonical examples of master regulators include Oct-4 (also called POU5F1), SOX2, and NANOG, all transcription factors involved in maintaining pluripotency in stem cells. Master regulators involved in development and morphogenesis can also appear as oncogenes relevant to tumorigenesis and metastasis, as with the Twist transcription factor.
Other genes reported as master regulators code for SR proteins, which function as splicing factors, and some noncoding RNAs. | 1 | Applied and Interdisciplinary Chemistry |
The stability of emulsions can be characterized using techniques such as light scattering, focused beam reflectance measurement, centrifugation, and rheology. Each method has advantages and disadvantages. | 0 | Theoretical and Fundamental Chemistry |
In polymer chemistry, the equivalent weight of a reactive polymer is the mass of polymer which has one equivalent of reactivity (often, the mass of polymer which corresponds to one mole of reactive side-chain groups). It is widely used to indicate the reactivity of polyol, isocyanate, or epoxy thermoset resins which would undergo crosslinking reactions through those functional groups.
It is particularly important for ion-exchange polymers (also called ion-exchange resins): one equivalent of an ion-exchange polymer will exchange one mole of singly charged ions, but only half a mole of doubly charged ions.
Nevertheless, given the decline in use of the term "equivalent weight" in the rest of chemistry, it has become more usual to express the reactivity of a polymer as the inverse of the equivalent weight, that is in units of mmol/g or meq/g. | 0 | Theoretical and Fundamental Chemistry |
: The codon AUG both codes for methionine and serves as an initiation site: the first AUG in an mRNA's coding region is where translation into protein begins. | 1 | Applied and Interdisciplinary Chemistry |
An hydrological transport model is a mathematical model used to simulate the flow of rivers, streams, groundwater movement or drainage front displacement, and calculate water quality parameters. These models generally came into use in the 1960s and 1970s when demand for numerical forecasting of water quality and drainage was driven by environmental legislation, and at a similar time widespread access to significant computer power became available. Much of the original model development took place in the United States and United Kingdom, but today these models are refined and used worldwide.
There are dozens of different transport models that can be generally grouped by pollutants addressed, complexity of pollutant sources, whether the model is steady state or dynamic, and time period modeled. Another important designation is whether the model is distributed (i.e. capable of predicting multiple points within a river) or lumped. In a basic model, for example, only one pollutant might be addressed from a simple point discharge into the receiving waters. In the most complex of models, various line source inputs from surface runoff might be added to multiple point sources, treating a variety of chemicals plus sediment in a dynamic environment including vertical river stratification and interactions of pollutants with in-stream biota. In addition watershed groundwater may also be included. The model is termed "physically based" if its parameters can be measured in the field.
Often models have separate modules to address individual steps in the simulation process. The most common module is a subroutine for calculation of surface runoff, allowing variation in land use type, topography, soil type, vegetative cover, precipitation and land management practice (such as the application rate of a fertilizer). The concept of hydrological modeling can be extended to other environments such as the oceans, but most commonly (and in this article) the subject of a river watershed is generally implied. | 1 | Applied and Interdisciplinary Chemistry |
Diazirines have been used in photoaffinity labeling experiments involving nucleic acids as well. Examples include:
* Incorporation of a diazirine moiety on a nucleoside sugar in a DNA polymer to investigate interactions between the minor groove of DNA and DNA polymerases.
* Incorporation of a diazirine moiety on a nucleoside base in a DNA polymer to investigate the mode of DNA repair by proteins.
Diazirines have also been used to study protein lipid interactions, for example the interaction of various sphingolipids with proteins in vivo. | 0 | Theoretical and Fundamental Chemistry |
Coelenterazine is a luciferin, a molecule that emits light after reaction with oxygen, found in many aquatic organisms across eight phyla. It is the substrate of many luciferases such as Renilla reniformis luciferase (Rluc), Gaussia luciferase (Gluc), and photoproteins, including aequorin, and obelin. All these proteins catalyze the oxidation of this substance, a reaction catalogued EC 1.13.12.5. | 1 | Applied and Interdisciplinary Chemistry |
The core was probably originally compiled around AD 600, perhaps in Alexandria in Egypt, in Greek. The core contains items traceable to earlier Alexandrian Greek texts, particularly the Stockholm papyrus and Leiden Papyrus X, which are Greek texts dated to the 2nd or 3rd century AD that contain some of the same and similar recipes. The first few recipes in the Phillipps-Corning manuscript of the Mappae clavicula were long considered integral, but they form a distinct separate entity, the De coloribus et mixtionibus, which survives (in whole or in part) in at least 62 manuscripts. The core of the Latin Mappae clavicula is very likely a translation of a Greek text, although the original Greek text (if it existed) does not exist today.
The best manuscripts of the Mappae clavicula date from the eighth to the twelfth century.
One of the fullest collections of recipes is in a certain manuscript dated late 12th century in which about 300 recipes are presented. In this manuscript, called the Phillipps-Corning manuscript, some of the names for some materials are Arabic names (e.g. alquibriz from the Arabic for sulphur, atincar from the Arabic for borax, alcazir from the Arabic for tin). The recipes containing the Arabic names are historically later, and are in all likelihood no earlier than the 12th century. Certain earlier manuscripts have about 200 recipes. | 1 | Applied and Interdisciplinary Chemistry |
If a drop is placed on a smooth, horizontal surface, it is generally not in the equilibrium state. Hence, it spreads until an equilibrium contact radius is reached (partial wetting). While taking into account capillary, gravitational, and viscous contributions, the drop radius as a function of time can be expressed as
For the complete wetting situation, the drop radius at any time during the spreading process is given by
where
:*γ is surface tension of the fluid
:*V is drop volume
:*η is viscosity of the fluid
:*ρ is density of the fluid
:*g is gravitational constant
:*λ is shape factor, 37.1m
:*t is experimental delay time
:*r is drop radius in equilibrium | 0 | Theoretical and Fundamental Chemistry |
* 1983: Humboldt Prize.
* 1997: The Advisory Committee on Antarctic Names (US-ACAN) named Stuiver Valley in Antarctica after Minze Stuiver for his work on radiocarbon dating Antarctic samples.
* 1993: The 13th Pomerance Award of the Archaeological Institute of America for Scientific Contributions to Archaeology went to Minze Stuiver along with Michael G. L. Baillie, Bernd Becker, Gordon W. Pearson, Jonathan R. Pilcher, and Hans Suess.
* 2000: Received The American Quaternary Association Distinguished Career Award.
* 2001: Thomson Reuters most cited paper in geosciences for the 1990s.
* 2005: Awarded the Geological Society of America's Penrose Gold Medal for outstanding original contributions or achievements that mark a major advance in the science of geology.
* 2009: Awarded an honorary doctorate at Queen's University Belfast. | 0 | Theoretical and Fundamental Chemistry |
The relative amount of fading can be measured and studied by using standard test strips. In the workflow of the Blue Wool test, one reference strip set shall be stored protected from any exposure to light. Simultaneously, another equivalent test strip set is exposed under a light source defined in the standard. For example, if the lightfastness of the colourant is indicated to be 5 on the Blue Wool scale, it can be expected to fade by a similar amount as the strip number 5 in the Blue Wool test strip set. The success of the test can be confirmed by comparing the test strip set with the reference set that was stored protected from the light. | 0 | Theoretical and Fundamental Chemistry |
Different thermogalvanic cells have been constructed attending to their uses and properties. Usually they are classified according to the electrolyte employed in each specific type of cell. | 0 | Theoretical and Fundamental Chemistry |
Phosphine (IUPAC name: phosphane) is a colorless, flammable, highly toxic compound with the chemical formula PH, classed as a pnictogen hydride. Pure phosphine is odorless, but technical grade samples have a highly unpleasant odor like rotting fish, due to the presence of substituted phosphine and diphosphane (). With traces of present, is spontaneously flammable in air (pyrophoric), burning with a luminous flame. Phosphine is a highly toxic respiratory poison, and is immediately dangerous to life or health at 50 ppm. Phosphine has a trigonal pyramidal structure.
Phosphines are compounds that include and the organophosphines, which are derived from by substituting one or more hydrogen atoms with organic groups. They have the general formula . Phosphanes are saturated phosphorus hydrides of the form , such as triphosphane. Phosphine, PH, is the smallest of the phosphines and the smallest of the phosphanes. | 0 | Theoretical and Fundamental Chemistry |
Above 973K, the Deacon reaction is reversed, yielding hydrogen chloride and oxygen from water and chlorine:
::HO + Cl → 2 HCl + 1/2 O | 0 | Theoretical and Fundamental Chemistry |
Although small in terms of power, the disposal of waste heat from microchips and other electronic components, represents a significant engineering challenge. This necessitates the use of fans, heatsinks, etc. to dispose of the heat.
For example, data centers use electronic components that consume electricity for computing, storage and networking. The French CNRS explains a data center is like a resistor and most of the energy it consumes is transformed into heat and requires cooling systems. | 0 | Theoretical and Fundamental Chemistry |
After periods of post-doctoral research at the University of Newcastle upon Tyne and the University of Manchester in 1965 and 1966, Robinson was a faculty member in the Department of Chemistry at the University of Otago in Dunedin from 1967 to 2006. He became a professor in 1985 and the Mellor Professor of Chemistry in 1996, and served as the head of the Department of Chemistry from 1986 to 1998. When he retired in 2006 he was made a professor emeritus.
Building on his doctoral research, Robinson proposed that metal carbonyl clusters could participate in electron transfer reactions, and demonstrated that clusters are able to be reversibly reduced. Other research areas that he pursued included the design of organometallic compounds for use in biomedical research, and the development of molecular switches. | 0 | Theoretical and Fundamental Chemistry |
In 1938, Emilio Segrè and Glenn T. Seaborg isolated for the first time the metastable isotope technetium-99m, after bombarding natural molybdenum with 8 MeV deuterons in the cyclotron of Ernest Orlando Lawrence's Radiation laboratory. In 1970 Seaborg explained that:
Later in 1940, Emilio Segrè and Chien-Shiung Wu published experimental results of an analysis of fission products of uranium-235, including molybdenum-99, and detected the presence of an isomer of element 43 with a 6-hour half life, later labelled as technetium-99m. | 0 | Theoretical and Fundamental Chemistry |
Source:
* HL: With agents to enhance corrosion protection and age resistance. Used in hydraulic systems that do not pose any requirements as to wear protection.
* HLP: With agents to enhance corrosion protection and age resistance. Suitable for most fields of application and components.
* HLPD: As HLP but also used in systems where solid or liquid contamination need to be kept temporarily suspended.
* HVLP: With agents to enhance corrosion protection, age resistance, to reduce scuffing wear in mixed friction areas, and to improve the viscosity-temperature behavior. Used in system operated over a wide temperature range.
* HVLPD: As HVLP but also used in systems where solid or liquid contamination need to be kept temporarily suspended. | 1 | Applied and Interdisciplinary Chemistry |
The bond angles in aziridine are approximately 60°, considerably less than the normal hydrocarbon bond angle of 109.5°, which results in angle strain as in the comparable cyclopropane and ethylene oxide molecules. A banana bond model explains bonding in such compounds. Aziridine is less basic than acyclic aliphatic amines, with a pKa of 7.9 for the conjugate acid, due to increased s character of the nitrogen free electron pair. Angle strain in aziridine also increases the barrier to nitrogen inversion. This barrier height permits the isolation of separate invertomers, for example the cis and trans invertomers of N-chloro-2-methylaziridine. | 0 | Theoretical and Fundamental Chemistry |
Another level of complexity comes from the existence of slow redox-driven reactions that may change the activity of the enzyme and make the response depart from steady-state. Here, slow means that the time scale of the (in)activation is similar to the voltammetric time scale . If a RDE is used, these slow (in)activations are detected by a hysteresis in the catalytic voltammogram that is not due to mass-transport. The hysteresis may disappear at very fast scan rates (if the inactivation has no time to proceed) or at very slow scan rates (if the (in)activation reaction reaches a steady-state). | 0 | Theoretical and Fundamental Chemistry |
Source:
Consider a semi-infinite fuel surface with leading edge located at and let the free stream oxidizer velocity be . Through the solution of Blasius equation ( is the self-similar Howarth–Dorodnitsyn coordinate), the mass flux ( is density and is vertical velocity) in the vertical direction can be obtained
where
In deriving this, it is assumed that the density and the viscosity , where is the temperature. The subscript describes the values far away from the fuel surface. The main interest in combustion process is the fuel burning rate, which is obtained by evaluating at , as given below, | 1 | Applied and Interdisciplinary Chemistry |
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