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The reaction steps are reversible reactions and the reaction is driven to completion by removal of water e.g. by azeotropic distillation, molecular sieves or titanium tetrachloride. Primary amines react through an unstable hemiaminal intermediate which then splits off water.
Secondary amines do not lose water easily because they do not have a proton available and instead they often react further to an aminal:
or when an α-carbonyl proton is present to an enamine:
In acidic environment the reaction product is an iminium salt by loss of water.
This reaction type is found in many Heterocycle preparations for example the Povarov reaction and the Friedländer-synthesis to quinolines. | 0 | Theoretical and Fundamental Chemistry |
* From Small Disturbances
: (subsonic)
* From Divergence Theorem
* Let Velocity U be a twice continuously differentiable function in a region of volume V in space. This function is the stream function .
* Let P be a point in the volume V
* Let S be the surface boundary of the volume V.
* Let Q be a point on the surface S, and .
As Q goes from inside V to the surface of V,
* Therefore:
For :, where the surface normal points inwards.
This equation can be broken down into both a source term and a doublet term.
The Source Strength at an arbitrary point Q is:
The Doublet Strength at an arbitrary point Q is:
The simplified potential flow equation is:
With this equation, along with applicable boundary conditions, the potential flow problem may be solved. | 1 | Applied and Interdisciplinary Chemistry |
Iron minerals can active for dechlorination. These minerals use . Particular minerals that can be used include green rust, magnetite, pyrite, and glauconite. The most reactive of the iron minerals are the iron sulfides and oxides. Pyrite, an iron sulfide, is able to dechlorinate carbon tetrachloride in suspension. | 1 | Applied and Interdisciplinary Chemistry |
In the study of the structure of mercury b- , lead- and organotin derivatives of nitrosophenols, Nesmeyanov discovered the phenomenon of metallotropy, that is, a special tautomerism in which a reversible transfer of an organometallic group occurs. Joint studies by A. N. Nesmeyanov and I. F. Lutsenko discovered heteroatomic tautomerism (between carbon and oxygen atoms) in keto-enol systems of tin , o- and germanium compounds. Nesmeyanov, together with Yu. A. and N. A. Ustynyuk, discovered a new type of metallotropy: it was found that in fluorenylchromium tricarbonyl anions, η 6 -complexes are equilibrium and reversibly isomerized into η 5 -complexes. | 0 | Theoretical and Fundamental Chemistry |
Emeléus was born in Poplar, London on 22 June 1903, the son of Karl Henry Emeléus (1869–1948), a pharmacist who was born in Vaasa, Finland. The family moved to the Old Pharmacy in Battle, Sussex shortly after Emeléus was born. His elder brother Karl George Emeléus (1901–1989) went on to become professor of physics at the Queen's University of Belfast.
Emeléus was educated at St Leonards Collegiate School, Hastings, and Hastings Grammar School followed by the Royal College of Science, Imperial College, London, graduating in 1923. He gained his PhD in 1926 and a DSc three years later. During his post-graduate studies he spent time at the University of Karlsruhe as a student of Alfred Stock and two years at Princeton University with Professor Hugh Stott Taylor. Among his many students and research colleagues, notable are Norman Greenwood, Ken McTaggart and F. Gordon A. Stone. | 0 | Theoretical and Fundamental Chemistry |
The VICARTE – Vidro e Cerâmica para as Artes (Glass and Ceramic for the Arts) is a research unit composed of the Faculty of Sciences and Technology of the Universidade Nova de Lisboa and the Faculty of Fine Arts of the Universidade de Lisboa which works to further the research of glass and ceramics. In partnership with cultural heritage institutions across the country, they offer a Master's program in Glass and Ceramic Art and Science with an interdisciplinary approach to the coursework. | 0 | Theoretical and Fundamental Chemistry |
Like its counterpart, RB-E2F, the DREAM complex is also affected by similar growth stimuli and subsequent cyclin-CDK activity. Increasing cyclin D-CDK4 and cyclin E-CDK2 activity dissociates the DREAM complex from the promoter by phosphorylation of p130. Hyper-phosphorylated p130 is subsequently degraded and E2F4 exported from the nucleus. Once the repressive E2Fs are vacated, activating E2Fs bind to the promoter to up-regulate G1/S genes that promote DNA synthesis and transition of the cell cycle. BMYB is also up-regulated during this time, which then binds to genes that peak at G2/M phase. Binding of BMYB to late cell cycle genes is dependent on its association with the MuvB core to form the BMYB-MuvB complex, which is then able to up-regulate genes in the G2/M phase. | 1 | Applied and Interdisciplinary Chemistry |
Thiolactones can be prepared by dehydration of thiol-containing carboxylic acids. Thiolactones can be hydrolyzed back to the thiol acids under basic conditions. β-Thiolactones can be opened by reaction at the 4-position via S2 nucleophilic reactions. | 0 | Theoretical and Fundamental Chemistry |
The availability of phosphorus in an ecosystem is restricted by the rate of release of this element during weathering. The release of phosphorus from apatite dissolution is a key control on ecosystem productivity. The primary mineral with significant phosphorus content, apatite [Ca(PO)OH] undergoes carbonation.
Little of this released phosphorus is taken up by biota (organic form), whereas a larger proportion reacts with other soil minerals. This leads to precipitation into unavailable forms in the later stage of weathering and soil development. Available phosphorus is found in a biogeochemical cycle in the upper soil profile, while phosphorus found at lower depths is primarily involved in geochemical reactions with secondary minerals. Plant growth depends on the rapid root uptake of phosphorus released from dead organic matter in the biochemical cycle. Phosphorus is limited in supply for plant growth. Phosphates move quickly through plants and animals; however, the processes that move them through the soil or ocean are very slow, making the phosphorus cycle overall one of the slowest biogeochemical cycles.
Low-molecular-weight (LMW) organic acids are found in soils. They originate from the activities of various microorganisms in soils or may be exuded from the roots of living plants. Several of those organic acids are capable of forming stable organo-metal complexes with various metal ions found in soil solutions. As a result, these processes may lead to the release of inorganic phosphorus associated with aluminum, iron, and calcium in soil minerals. The production and release of oxalic acid by mycorrhizal fungi explain their importance in maintaining and supplying phosphorus to plants.
The availability of organic phosphorus to support microbial, plant and animal growth depends on the rate of their degradation to generate free phosphate. There are various enzymes such as phosphatases, nucleases and phytase involved for the degradation. Some of the abiotic pathways in the environment studied are hydrolytic reactions and photolytic reactions. Enzymatic hydrolysis of organic phosphorus is an essential step in the biogeochemical phosphorus cycle, including the phosphorus nutrition of plants and microorganisms and the transfer of organic phosphorus from soil to bodies of water. Many organisms rely on the soil derived phosphorus for their phosphorus nutrition. | 0 | Theoretical and Fundamental Chemistry |
PTEN is a tumor suppressor that inhibits the PI3K/AKT pathway. PTEN inhibitors, such as bisperoxovanadium, can enhance the PI3K/AKT pathway to promote cell migration, survival and proliferation. While there are some concerns over possible cell cycle dysregulation and tumorigenesis, temporary and moderate PTEN inhibition may confer neuroprotection against traumatic brain injury and improve CNS recovery by reestablishing lost connections by axonogenesis. Medicinal value of PTEN inhibitors remains to be determined. | 1 | Applied and Interdisciplinary Chemistry |
Modafinil is generally well-tolerated but can have potential risks and side effects. Common adverse effects of modafinil, experienced by less than 10% of users, include headaches, nausea, and reduced appetite. Anxiety, insomnia, dizziness, diarrhea, and rhinitis are also reported in 5% to 10% of users. Psychiatric reactions have occurred in individuals with and without a preexisting psychiatric history.
No significant changes in body weight have been observed in clinical trials, although decreased appetite and weight loss have been noted in children and adolescents. Modafinil can cause a slight increase in aminotransferase enzymes, indicative of liver function, but there is no evidence of serious liver damage when levels are within reference ranges.
Rare but serious adverse effects include severe skin rashes and allergy-related symptoms. Between December 1998 and January 2007, the FDA received reports of six cases of severe cutaneous adverse reactions, including erythema multiforme, Stevens–Johnson syndrome, toxic epidermal necrolysis, and DRESS syndrome. The FDA has issued alerts regarding these risks and also noted reports of angioedema and multi-organ hypersensitivity reactions in postmarketing surveillance. In 2007, the FDA required Cephalon to modify the Provigil leaflet to include warnings about these serious conditions. The long-term safety and effectiveness of modafinil have not been conclusively established.
The FDA does not endorse modafinil for children's medical conditions due to an increased risk of rare but serious dermatological toxicity (Stevens–Johnson syndrome). However, in Europe, modafinil may be prescribed for treating narcolepsy in children. | 0 | Theoretical and Fundamental Chemistry |
Lactic acid fermentation is used in many areas of the world to produce foods that cannot be produced through other methods. The most commercially important genus of lactic acid-fermenting bacteria is Lactobacillus, though other bacteria and even yeast are sometimes used. Two of the most common applications of lactic acid fermentation are in the production of yogurt and sauerkraut. | 1 | Applied and Interdisciplinary Chemistry |
The non-dimensional energy equation for fluid flow in a boundary layer can simplify to the following, when heating from viscous dissipation and heat generation can be neglected:
Where and are the velocities in the x and y directions respectively normalized by the free stream velocity, and are the x and y coordinates non-dimensionalized by a relevant length scale, is the Reynolds number, is the Prandtl number, and is the non-dimensional temperature, which is defined by the local, minimum, and maximum temperatures:
The non-dimensional species transport equation for fluid flow in a boundary layer can be given as the following, assuming no bulk species generation:
Where is the non-dimensional concentration, and is the Schmidt number.
Transport of heat is driven by temperature differences, while transport of species is due to concentration differences. They differ by the relative diffusion of their transport compared to the diffusion of momentum. For heat, the comparison is between viscous diffusivity () and thermal diffusion (), given by the Prandtl number. Meanwhile for mass transfer, the comparison is between viscous diffusivity () and mass Diffusivity (), given by the Schmidt number.
In some cases direct analytic solutions can be found from these equations for the Nusselt and Sherwood numbers. In cases where experimental results are used, one can assume these equations underlie the observed transport.
At an interface, the boundary conditions for both equations are also similar. For heat transfer at an interface, the no-slip condition allows us to equate conduction with convection, thus equating Fouriers law and Newtons law of cooling:
Where q” is the heat flux, is the thermal conductivity, is the heat transfer coefficient, and the subscripts and compare the surface and bulk values respectively.
For mass transfer at an interface, we can equate Ficks Law with Newtons law for convection, yielding:
Where is the mass flux [kg/s ], is the diffusivity of species a in fluid b, and is the mass transfer coefficient. As we can see, and are analogous, and are analogous, while and are analogous. | 1 | Applied and Interdisciplinary Chemistry |
Dendrimers have been prepared via click chemistry, employing Diels-Alder reactions, thiol-ene and thiol-yne reactions and azide-alkyne reactions.
There are ample avenues that can be opened by exploring this chemistry in dendrimer synthesis. | 0 | Theoretical and Fundamental Chemistry |
The set of strategies that comprise biosorption, bioaccumulation and biomineralization are closely related to each other, because one way or another have a direct contact between the cell and radionuclide. These mechanisms are evaluated accurately using advanced analysis technologies such as electron microscopy, X-ray diffraction and XANES, EXAFS and X-ray spectroscopies.
Biosorption and bioaccumulation are two metabolic actions that are based on the ability to concentrate radionuclides over a thousand times the concentration of the environment. They consist of complexation of radioactive waste with phosphates, organic compounds and sulfites so that they become insoluble and less exposed to radiotoxicity. They are particularly useful in biosolids for agricultural purposes and soil amendments, although most properties of these biosolids are unknown.
Biosorption method is based on passive sequestration of positively charged radioisotopes by lipopolysaccharides (LPS) on the cell membrane (negatively charged), either live or dead bacteria. Its efficiency is directly related to the increase in temperature and can last for hours, being a much faster method than direct bioreduction. It occurs through the formation of slimes and capsules, and with a preference for binding to the phosphate and phosphoryl groups (although it also occurs with carboxyl, amine or sulfhydryl groups). Bacillota and other bacteria like Citrobacter freudii have significant biosorption capabilities; Citrobacter does it through electrostatic interaction of uranium with phosphates of their LPS.
Quantitative analyzes determine that, in the case of uranium, biosorption may vary within a range between 45 and 615 milligrams per gram of cell dry weight. However, it is a technique that requires a high amount of biomass to affect bioremediation; it presents problems of saturation and other cations that compete for binding to the bacterial surface.
Bioaccumulation refers to uptake of radionuclides into the cell, where they are retained by complexations with negatively charged intracellular components, precipitation or granules formations. Unlike biosorption, this is an active process: it depends on an energy-dependent transport system. Some metals or radionuclides can be absorbed by bacteria accidentally because of its resemblance to dietary elements for metabolic pathways. Several radioisotopes of strontium, for example, are recognized as analogs of calcium and incorporated within Micrococcus luteus. Uranium, however, has no known function and is believed that its entry into the cell interior may be due to its toxicity (it is able to increase membrane permeability).
Furthermore, biomineralization —also known as bioprecipitation— is the precipitation of radionuclides through the generation of microbial ligands, resulting in the formation of stable biogenic minerals. These minerals have a very important role in the retention of radioactive contaminants. A very localized and produced enzymatically ligand concentration is involved and provides a nucleation site for the onset of biomineral precipitation. This is particularly relevant in precipitations of phosphatase activity-derivate biominerals, which cleavage molecules such as glycerol phosphate on periplasm. In Citrobacter and Serratia genera, this cleavage liberates inorganic phosphates (HPO) that precipitates with uranyl ion (UO) and cause deposition of polycrystalline minerals around the cell wall. Serratia also form biofilms that promote precipitation of chernikovite (rich in uranium) and additionally, remove up to 85% of cobalt-60 and 97% of cesium-137 by proton substitution of this mineral. In general, biomineralization is a process in which the cells do not have limitations of saturation and can accumulate up to several times its own weight as precipitated radionuclides.
Investigations of terrestrial and marine bacterial isolates belonging to the genera Aeromonas, Bacillus, Myxococcus, Pantoea, Pseudomonas, Rahnella and Vibrio have also demonstrated the removal of uranium radioisotopes as phosphate biominerals in both oxic and anoxic growth conditions. | 1 | Applied and Interdisciplinary Chemistry |
Contributors to the field of fluid dynamics in turn come from a wide array of fields, and in addition to their other titles, each is also a fluid dynamicist. Following is a list of notable fluid dynamicists: | 1 | Applied and Interdisciplinary Chemistry |
Ion-exchange chromatography separates molecules based on their respective charged groups. Ion-exchange chromatography retains analyte molecules on the column based on coulombic (ionic) interactions. The ion exchange chromatography matrix consists of positively and negatively charged ions. Essentially, molecules undergo electrostatic interactions with opposite charges on the stationary phase matrix. The stationary phase consists of an immobile matrix that contains charged ionizable functional groups or ligands. The stationary phase surface displays ionic functional groups (R-X) that interact with analyte ions of opposite charge. To achieve electroneutrality, these immobilized charges couple with exchangeable counterions in the solution. Ionizable molecules that are to be purified, compete with these exchangeable counterions, for binding to the immobilized charges on the stationary phase. These ionizable molecules are retained or eluted based on their charge. Initially, molecules that do not bind or bind weakly to the stationary phase are first to be washed away. Altered conditions are needed for the elution of the molecules that bind to the stationary phase. The concentration of the exchangeable counterions, which competes with the molecules for binding, can be increased, or the pH can be changed to affect the ionic charge of the eluent or the solute. A change in pH affects the charge on the particular molecules and, therefore, alter their binding. When reducing the net charge of the solute's molecules, they start eluting out. This way, such adjustments can be used to release the proteins of interest. Additionally, concentration of counterions can be gradually varied to affect the retention of the ionized molecules, thus separate them. This type of elution is called gradient elution. On the other hand, step elution can be used, in which the concentration of counterions are varied in steps. This type of chromatography is further subdivided into cation exchange chromatography and anion-exchange chromatography. Positively charged molecules bind to cation exchange resins, while negatively charged molecules bind to anion exchange resins. The ionic compound consisting of the cationic species M+ and the anionic species B− can be retained by the stationary phase.
Cation exchange chromatography retains positively charged cations because the stationary phase displays a negatively charged functional group:
Anion exchange chromatography retains anions using positively charged functional group:
Note that the ion strength of either C+ or A− in the mobile phase can be adjusted to shift the equilibrium position, thus retention time.
The ion chromatogram shows a typical chromatogram obtained with an anion exchange column. | 0 | Theoretical and Fundamental Chemistry |
Chromatographic peak resolution is given by
where t is the retention time and w is the peak width at baseline. Here compound 1 elutes before compound 2.
If the peaks have the same width | 0 | Theoretical and Fundamental Chemistry |
Buddhist atomism is a school of atomistic Buddhist philosophy that flourished on the Indian subcontinent during two major periods. During the first phase, which began to develop prior to the 6th century CE, Buddhist atomism had a very qualitative, Aristotelian-style atomic theory. This form of atomism identifies four kinds of atoms, corresponding to the standard elements. Each of these elements has a specific property, such as solidity or motion, and performs a specific function in mixtures, such as providing support or causing growth. Like the Hindus and Jains, the Buddhists were able to integrate a theory of atomism with their logical presuppositions.
According to Noa Ronkin, this kind of atomism was developed in the Sarvastivada and Sautrantika schools for whom material reality can be: The second phase of Buddhist atomism, which flourished in the 7th century CE, was very different from the first. Indian Buddhist philosophers, including Dharmakirti and Dignāga, considered atoms to be point-sized, durationless, and made of energy. In discussing Buddhist atomism, Stcherbatsky writes: | 1 | Applied and Interdisciplinary Chemistry |
CeCoIn ("Cerium-Cobalt-Indium 5") is a heavy-fermion superconductor with a layered crystal structure, with somewhat two-dimensional electronic transport properties. The critical temperature of 2.3 K is the highest among all of the Ce-based heavy-fermion superconductors. | 1 | Applied and Interdisciplinary Chemistry |
Esmirtazapine (ORG-50,081) is a tetracyclic antidepressant drug that was under development by Organon for the treatment of insomnia and vasomotor symptoms (e.g., hot flashes) associated with menopause. Esmirtazapine is the (S)-(+)-enantiomer of mirtazapine and possesses similar overall pharmacology, including inverse agonist actions at H and 5-HT receptors and antagonist actions at α-adrenergic receptors.
Notably, esmirtazapine has a shorter half life of around 10 hours, compared to R-mirtazapine and racemic mixture, which has a half-life of 18–40 hours. Merck has run several studies on low dose (3–4.5 mg) esmirtazapine for the treatment of insomnia. It is attractive for treating insomnia since it is a potent H-inhibitor and a 5-HT antagonist. Unlike low-dose mirtazapine, the half life (10 hours) is short enough that next-day sedation may be manageable, however, for people with CYP2D6 polymorphisms, which constitute a sizable fraction of the population, the half-life is expected to be quite a bit longer. Merck researchers claimed that the incidence of next-day sedation was not a problem in one of their studies, but this claim has been challenged (15% of patients complained of daytime sleepiness vs 3.5% in the placebo group).
In March 2010, Merck terminated its internal clinical development program for esmirtazapine for hot flashes and insomnia, "for strategic reasons". | 0 | Theoretical and Fundamental Chemistry |
Radionuclides are incorporated either into compounds normally used by the body such as glucose (or glucose analogues), water, or ammonia, or into molecules that bind to receptors or other sites of drug action. Such labelled compounds are known as radiotracers. PET technology can be used to trace the biologic pathway of any compound in living humans (and many other species as well), provided it can be radiolabeled with a PET isotope. Thus, the specific processes that can be probed with PET are virtually limitless, and radiotracers for new target molecules and processes are continuing to be synthesized. As of this writing there are already dozens in clinical use and hundreds applied in research. In 2020 by far the most commonly used radiotracer in clinical PET scanning is the carbohydrate derivative FDG. This radiotracer is used in essentially all scans for oncology and most scans in neurology, thus makes up the large majority of radiotracer (>95%) used in PET and PET-CT scanning.
Due to the short half-lives of most positron-emitting radioisotopes, the radiotracers have traditionally been produced using a cyclotron in close proximity to the PET imaging facility. The half-life of fluorine-18 is long enough that radiotracers labeled with fluorine-18 can be manufactured commercially at offsite locations and shipped to imaging centers. Recently rubidium-82 generators have become commercially available. These contain strontium-82, which decays by electron capture to produce positron-emitting rubidium-82.
The use of positron-emitting isotopes of metals in PET scans has been reviewed, including elements not listed above, such as lanthanides. | 1 | Applied and Interdisciplinary Chemistry |
Ionic micelles are typically very affected by the salt concentration. In ionic micelles the monomers are typically fully ionized, but the high electric field strength at the surface of the micelles will cause adsorption of some proportion of the free counter-ions. In this case a chemical equilibrium process can be assumed between the charged micelles and its constituents, the bile salt monomers, and bound counter-ions :
where is the average aggregation number and is the average degree of counter-ion binding to the micelle. In this case, the Gibbs free energy is given by:
where is the Gibbs energy of micellization and is the free counter-ion concentration at CMC. For large , that is in the limit when then the micelles becomes a true macroscopic phase, the Gibbs free energy is usually approximated by: | 0 | Theoretical and Fundamental Chemistry |
The Salvinia effect defines surfaces which are able to permanently keep relatively thick air layers as a result of their hydrophobic chemistry, in combination with a complex architecture in nano- and microscopic dimensions.
This phenomenon was discovered during a systematic research on aquatic plants and animals by Wilhelm Barthlott and his colleagues at the University of Bonn between 2002 and 2007. Five criteria have been defined, they enable the existence of stable air layers under water and as of 2009 define the Salvinia effect: (1) hydrophobic surfaces chemistry in combination with (2) nanoscalic structures generate superhydrophobicity, (3) microscopic hierarchical structures ranging from a few mirco- to several millimeters with (4) undercuts and (5) elastic properties. Elasticity appears to be important for the compression of the air-layer in dynamic hydrostatic conditions. An additional optimizing criterion is the chemical heterogeneity of the hydrophilic tips (Salvinia Paradox). This is a prime example of a hierarchical structuring on several levels.
In plants and animals, air retaining salvinia effect surfaces are always fragmented in small compartments with a length of 0.5 to 8 cm and the borders are sealed against loss of air by particular microstructures. Compartments with sealed edges are also important for technical applications.
The working principle is illustrated in for the Giant Salvinia. The leaves of S. molesta are capable of keeping an air layer on its surfaces for a long time when submerged in water. If a leaf is pulled under water, the leaf surface shows a silvery shine. The distinctive feature of S. molesta lies in the long term stability. While the air layer on most hydrophobic surfaces vanishes shortly after submerging, S. molesta is able to stabilize the air for several days to several weeks. The time span is thereby just limited by the lifetime of the leaf.
The high stability is a consequence of a seemingly paradoxical combination of a superhydrophobic (extremely water repellent) surface with hydrophilic (water attractive) patches on the tips of the structures.
When submerged under water, no water can penetrate the room between the hairs due to the hydrophobic character of the surfaces. However, the water is pinned to the tip of each hair by the four wax free (hydrophilic) end cells. This fixation results in a stabilization of the air layer under water. The principle is shown in the figure.
Two submerged, air retaining surfaces are schematically shown: on the left hand side: a hydrophobic surface. On the right hand side: a hydrophobic surface with hydrophilic tips.
If negative pressure is applied, a bubble is quickly formed on the purely hydrophobic surfaces (left) stretching over several structures. With increasing negative pressure the bubble grows and can detach from the surface. The air bubble rises to the surface and the air layer decreases until it vanishes completely.
In case of the surface with hydrophilic anchor cells (right) the water is pinned to the tips of every structure by the hydrophilic patch on top. These linkages allow the formation of a bubble stretching over several structures; bubble release is suppressed because several links have to be broken first. This results in a higher energy input for the bubble formation. Therefore, an increased negative pressure is needed to form a bubble able to detach from the surface and rise upwards. | 0 | Theoretical and Fundamental Chemistry |
Fat suppression is useful for example to distinguish active inflammation in the intestines from fat deposition such as can be caused by long-standing (but possibly inactive) inflammatory bowel disease, but also obesity, chemotherapy and celiac disease. Without fat suppression techniques, fat and fluid will have similar signal intensities on fast spin-echo sequences.
Techniques to suppress fat on MRI mainly include:
* Identifying fat by the chemical shift of its atoms, causing different time-dependent phase shifts compared to water.
* Frequency-selective saturation of the spectral peak of fat by a "fat sat" pulse before imaging.
* Short tau inversion recovery (STIR), a T1-dependent method
* Spectral presaturation with inversion recovery (SPIR) | 0 | Theoretical and Fundamental Chemistry |
was a Japanese organic chemist and marine biologist, and professor emeritus at Marine Biological Laboratory (MBL) in Woods Hole, Massachusetts and Boston University School of Medicine. He was awarded the Nobel Prize in Chemistry in 2008 for the discovery and development of green fluorescent protein (GFP) with two American scientists: Martin Chalfie of Columbia University and Roger Tsien of the University of California-San Diego. | 0 | Theoretical and Fundamental Chemistry |
A plasmid is a double stranded circular DNA molecule commonly used for molecular cloning. Plasmids are generally 2 to 4 kilobase-pairs (kb) in length and are capable of carrying inserts up to 15kb. Plasmids contain an origin of replication allowing them to replicate inside a bacterium independently of the host chromosome. Plasmids commonly carry a gene for antibiotic resistance that allows for the selection of bacterial cells containing the plasmid. Many plasmids also carry a reporter gene that allows researchers to distinguish clones containing an insert from those that do not. | 1 | Applied and Interdisciplinary Chemistry |
The expression of tides as a bounded Kelvin wave is well observable in enclosed shelf seas around the world (e.g. the English channel, the North Sea or the Yellow sea). Animation 1 shows the behaviour of a simplified case of a Kelvin wave in an enclosed shelf sea for the case with (lower panel) and without friction (upper panel). The shape of an enclosed shelf sea is represented as a simple rectangular domain in the Northern Hemisphere which is open on the left hand side and closed on the right hand side. The tidal wave, a Kelvin wave, enters the domain in the lower left corner and travels to the right with the coast on its right. The sea surface height (SSH, left panels of animation 1), the tidal elevation, is maximum at the coast and decreases towards the centre of the domain. The tidal currents (right panels of animation 1) are in the direction of wave propagation under the crest and in the opposite direction under the through. They are both maximum under the crest and the trough of the waves and decrease towards the centre. This was expected as the equations for and are in phase as they both depend on the same arbitrary function describing the wave motion and exponential decay term.
On the enclosed right hand side, the Kelvin wave is reflected and because it always travels with the coast on its right, it will now travel in the opposite direction. The energy of the incoming Kelvin wave is transferred through Poincare waves along the enclosed side of the domain to the outgoing Kelvin wave. The final pattern of the SSH and the tidal currents is made up of the sum of the two Kelvin waves. These two can amplify each other and this amplification is maximum when the length of the shelf sea is a quarter wavelength of the tidal wave. Next to that, the sum of the two Kelvin waves result in several static minima's in the centre of the domain which hardly experience any tidal motion, these are called Amphidromic points. In the upper panel of figure 2, the absolute time averaged SSH is shown in red shading and the dotted lines show the zero tidal elevation level at roughly hourly intervals, also known as cotidal lines. Where these lines intersect the tidal elevation is zero during a full tidal period and thus this is the location of the Amphidromic points.
In the real world, the reflected Kelvin wave has a lower amplitude due to energy loss as a result of friction and through the transfer via Poincare waves (lower left panel of animation 1). The tidal currents are proportional to the wave amplitude and therefore also decrease on the side of the reflected wave (lower right panel of animation 1). Finally, the static minima's are no longer in the centre of the domain as wave amplitude is no longer symmetric. Therefore, the Amphidromic points shift towards the side of the reflected wave (lower panel figure 2).
The dynamics of a tidal Kelvin wave in enclosed shelf sea is well manifested and studied in the North Sea. | 1 | Applied and Interdisciplinary Chemistry |
PCR works readily with a DNA template of up to two to three thousand base pairs in length. However, above this size, product yields often decrease, as with increasing length stochastic effects such as premature termination by the polymerase begin to affect the efficiency of the PCR. It is possible to amplify larger pieces of up to 50,000 base pairs with a slower heating cycle and special polymerases. These are polymerases fused to a processivity-enhancing DNA-binding protein, enhancing adherence of the polymerase to the DNA.
Other valuable properties of the chimeric polymerases [http://www.fidelitysystems.com/TopoTaq.html TopoTaq] and PfuC2 include enhanced thermostability, specificity and resistance to contaminants and inhibitors. They were engineered using the unique helix-hairpin-helix (HhH) DNA binding domains of topoisomerase V from hyperthermophile Methanopyrus kandleri. Chimeric polymerases overcome many limitations of native enzymes and are used in direct PCR amplification from cell cultures and even food samples, thus by-passing laborious DNA isolation steps. A robust strand-displacement activity of the hybrid TopoTaq polymerase helps solve PCR problems that can be caused by hairpins and G-loaded double helices. Helices with a high G-C content possess a higher melting temperature, often impairing PCR, depending on the conditions. | 1 | Applied and Interdisciplinary Chemistry |
A blank value in analytical chemistry is a measurement of a blank. The reading does not originate from a sample, but the matrix effects, reagents and other residues. These contribute to the sample value in the analytical measurement and therefore have to be subtracted.
The limit of blank is defined by the Clinical And Laboratory Standards Institute as the highest apparent analyte concentration expected to be found when replicates of a sample containing no analyte are tested. | 0 | Theoretical and Fundamental Chemistry |
In the region known as the viscous sublayer, below 5 wall units, the variation of to is approximately 1:1, such that:
:For
where,
This approximation can be used farther than 5 wall units, but by the error is more than 25%. | 1 | Applied and Interdisciplinary Chemistry |
The dehydration theory explains why mucoadhesion can arise rapidly. When two gels capable of rapid gelation in an aqueous environment are brought into contact, movement occurs between the two gels until a state of equilibrium is reached. Gels associated with a strong affinity for water will have high osmotic pressures and large swelling forces. The difference in osmotic pressure when these gels contact mucus gels will draw water into the formulation and quickly dehydrate the mucus gel, forcing intermixing and consolidation until equilibrium results.
This mixture of formulation and mucus can increase contact time with the mucous membrane, leading to the consolidation of the adhesive bond. However, the dehydration theory does not apply to solid formulations or highly hydrated forms. | 1 | Applied and Interdisciplinary Chemistry |
By the historical periods of the Pharaohs in Egypt, the Vedic Kings in India, the Tribes of Israel, and the Maya civilization in North America, among other ancient populations, precious metals began to have value attached to them. In some cases rules for ownership, distribution, and trade were created, enforced, and agreed upon by the respective peoples. By the above periods metalworkers were very skilled at creating objects of adornment, religious artifacts, and trade instruments of precious metals (non-ferrous), as well as weaponry usually of ferrous metals and/or alloys. These skills were well executed. The techniques were practiced by artisans, blacksmiths, atharvavedic practitioners, alchemists, and other categories of metalworkers around the globe. For example, the granulation technique was employed by numerous ancient cultures before the historic record shows people traveled to far regions to share this process. Metalsmiths today still use this and many other ancient techniques.
As time progressed, metal objects became more common, and ever more complex. The need to further acquire and work metals grew in importance. Skills related to extracting metal ores from the earth began to evolve, and metalsmiths became more knowledgeable. Metalsmiths became important members of society. Fates and economies of entire civilizations were greatly affected by the availability of metals and metalsmiths. The metalworker depends on the extraction of precious metals to make jewelry, build more efficient electronics, and for industrial and technological applications from construction to shipping containers to rail, and air transport. Without metals, goods and services would cease to move around the globe on the scale we know today. | 1 | Applied and Interdisciplinary Chemistry |
Photobiology is the scientific study of the beneficial and harmful interactions of non-ionizing radiation in living organisms, conventionally demarcated around 10 eV, the first ionization energy of oxygen. UV ranges roughly from 3 to 30 eV in energy. Hence photobiology entertains some, but not all, of the UV spectrum. | 0 | Theoretical and Fundamental Chemistry |
In 2020, the FDA granted orphan drug designation RT001 for the treatment of patients with progressive supranuclear palsy (PSP). PSP is a disease involving modification and dysfunction of tau protein; RT001's mechanism of action both lowers lipid peroxidation and prevents mitochondrial cell death of neurons which is associated with disease onset and progression. | 1 | Applied and Interdisciplinary Chemistry |
The contact stage is the initial wetting that occurs between the adhesive and membrane. This can occur mechanically by bringing together the two surfaces, or through the bodily systems, like when particles are deposited in the nasal cavity by inhalation. The principles of initial adsorption of small molecule adsorbates can be described by DLVO theory. | 1 | Applied and Interdisciplinary Chemistry |
One can characterise a surface that has undergone certain finishing operations by three main properties of: roughness, waviness, and fractal dimension. Among these, roughness and fractality are of most importance, with roughness often indicated in terms of a rms value, and surface fractality denoted generally by D. The effect of surface structures on thermal conductivity at interfaces is analogous to the concept of electrical contact resistance, also known as ECR, involving contact patch restricted transport of phonons rather than electrons. | 0 | Theoretical and Fundamental Chemistry |
In addition to being manipulated for medical and energy applications, capillary pressure is the cause behind various natural phenomena as well. For example, needle ice, seen in cold soil, occurs via capillary action. The first major contributions to the study of needle ice, or simply, frost heaving were made by Stephen Taber (1929) and Gunnar Beskow (1935), who independently aimed to understand soil freezing. Taber’s initial work was related to understanding how the size of pores within the ground influenced the amount of frost heave. He also discovered that frost heave is favorable for crystal growth and that a gradient of soil moisture tension drives water upward toward the freezing front near the top of the ground. In Beskow’s studies, he defined this soil moisture tension as “capillary pressure” (and soil water as “capillary water”). Beskow determined that the soil type and effective stress on the soil particles influenced frost heave, where effective stress is the sum of pressure from above ground and the capillary pressure.
In 1961, D.H. Everett elaborated on Taber and Beskow’s studies to understand why pore spaces filled with ice continue to experience ice growth. He utilized thermodynamic equilibrium principles, a piston cylinder model for ice growth and the following equation to understand the freezing of water in porous media (directly applicable to the formation of needle ice):
where:
: is the pressure of the solid crystal
: is the pressure in the surrounding liquid
: is the interfacial tension between the solid and the liquid
: is the surface area of the phase boundary
: is the volume of the crystal
: is the mean curvature of the solid/liquid interface
With this equation and model, Everett noted the behavior of water and ice given different pressure conditions at the solid-liquid interface. Everett determined that if the pressure of the ice is equal to the pressure of the liquid underneath the surface, ice growth is unable to continue into the capillary. Thus, with additional heat loss, it is most favorable for water to travel up the capillary and freeze in the top cylinder (as needle ice continues to grow atop itself above the soil surface). As the pressure of the ice increases, a curved interface between the solid and liquid arises and the ice will either melt, or equilibrium will be reestablished so that further heat loss again leads to ice formation. Overall, Everett determined that frost heaving (analogous to the development of needle ice) occurs as a function of the pore size in the soil and the energy at the interface of ice and water. Unfortunately, the downside to Everett's model is that he did not consider soil particle effects on the surface. | 1 | Applied and Interdisciplinary Chemistry |
The major steps in the Sulfo-TK pathway are:
* isomerization of sulfoquinovose to sulfofructose (catalyzed by sulfoquinovose isomerase);
* transketol reaction of sulfofructose to release erythrose (catalyzed by sulfofructose transketolase, a thiamine diphosphate dependent enzyme), and transfer of the C2-moiety to glyceraldehyde phosphate, yielding xylulose-5-phosphate (Xu5P).
* 4-Sulfoerythrose is isomerized to 4-sulfoerythrulose (SEu), whereupon a second round of transketolase catalyzed reaction cleaves SE to sulfoacetaldehyde, while the C2-moiety is again transferred to an acceptor molecule, glyceraldehyde phosphate (GAP), yielding a second molecule of xylulose-5-phosphate (Xu5P).
* Finally, the sulfoacetaldehyde is reduced to isethionate and excreted.
The sulfoacetaldehyde may be oxidized to sulfoacetate. | 1 | Applied and Interdisciplinary Chemistry |
Alpha-cleavage (α-cleavage) in organic chemistry refers to the act of breaking the carbon-carbon bond adjacent to the carbon bearing a specified functional group. | 0 | Theoretical and Fundamental Chemistry |
Technically, Hammonds postulate only describes the geometric structure of a chemical reaction. However, Hammonds postulate indirectly gives information about the rate, kinetics, and activation energy of reactions. Hence, it gives a theoretical basis for the understanding the Bell-Evans-Polanyi principle, which describes the experimental observation that the enthalpy change and rate of similar reactions were usually correlated.
The relationship between Hammond's postulate and the BEP principle can be understood by considering a S1 reaction. Although two transition states occur during a S1 reaction (dissociation of the leaving group and then attack by the nucleophile), the dissociation of the leaving group is almost always the rate-determining step. Hence, the activation energy and therefore rate of the reaction will depend only upon the dissociation step.
First, consider the reaction at secondary and tertiary carbons. As the BEP principle notes, experimentally S1 reactions at tertiary carbons are faster than at secondary carbons. Therefore, by definition, the transition state for tertiary reactions will be at a lower energy than for secondary reactions. However, the BEP principle cannot justify why the energy is lower.
Using Hammond's postulate, the lower energy of the tertiary transition state means that its structure is relatively closer to its reactants R(tertiary)-X than to the carbocation "product" when compared to the secondary case. Thus, the tertiary transition state will be more geometrically similar to the R(tertiary)-X reactants than the secondary transition state is to its R(secondary)-X reactants. Hence, if the tertiary transition state is close in structure to the (low energy) reactants, then it will also be lower in energy because structure determines energy. Likewise, if the secondary transition state is more similar to the (high energy) carbocation "product," then it will be higher in energy. | 0 | Theoretical and Fundamental Chemistry |
Many S-N compounds are prepared from . Reaction with piperidine generates :
A related cation is also known, i.e. .
Treatment with tetramethylammonium azide produces the heterocycle :
Cyclo- has 10 pi-electrons.
In a related reaction, the use of the bis(triphenylphosphine)iminium azide gives a salt containing the blue anion:
The anion has a chain structure described using the resonance .
reacts with electron-poor alkynes.
Chlorination of gives thiazyl chloride.
Passing gaseous over silver metal yields the low temperature superconductor polythiazyl or polysulfurnitride (transition temperature (0.26±0.03) K), often simply called "(SN)". In the conversion, the silver first becomes sulfided, and the resulting silver sulfide| catalyzes the conversion of the into the four-membered ring , which readily polymerizes. | 0 | Theoretical and Fundamental Chemistry |
The Histone code hypothesis suggests the idea that patterns of post-translational modifications on histones, collectively, can direct specific cellular functions. Chemical modifications of histone proteins often occur on particular amino acids. This specific addition of single or multiple modifications on histone cores can be interpreted by transcription factors and complexes which leads to functional implications. This process is facilitated by enzymes such as HATs and HDACs that add or remove modifications on histones, and transcription factors that process and "read" the modification codes. The outcome can be activation of transcription or repression of a gene. For example, the combination of acetylation and phosphorylation have synergistic effects on the chromosomes overall structural condensation level and, hence, induces transcription activation of immediate early gene.
Experiments investigating acetylation patterns of H4 histones suggested that these modification patterns are collectively maintained in mitosis and meiosis in order to modify long-term gene expression. The acetylation pattern is regulated by HAT and HADC enzymes and, in turn, sets the local chromatin structure. In this way, acetylation patterns are transmitted and interconnected with protein binding ability and functions in subsequent cell generation. | 0 | Theoretical and Fundamental Chemistry |
The dominant luminous component in a cluster of galaxies is the 10 to 10 kelvin intracluster medium. The emission from the intracluster medium is characterized by thermal bremsstrahlung. This radiation is in the energy range of X-rays and can be easily observed with space-based telescopes such as Chandra X-ray Observatory, XMM-Newton, ROSAT, ASCA, EXOSAT, Suzaku, RHESSI and future missions like IXO [https://web.archive.org/web/20080303062108/http://constellation.gsfc.nasa.gov/] and Astro-H [https://web.archive.org/web/20071112015825/http://www.astro.isas.ac.jp/future/NeXT/].
Bremsstrahlung is also the dominant emission mechanism for H II regions at radio wavelengths. | 0 | Theoretical and Fundamental Chemistry |
Different blocking agents for isocyanates have different unblocking temperatures.
* Sodium bisulfite
* Diethyl malonate =
* 3,5-Dimethylpyrazole =
* MEKO =
* Phenol =
* Caprolactam = | 0 | Theoretical and Fundamental Chemistry |
Tollmien (1931) and Schlichting (1929) theorized that viscosity-induced grabbing and releasing of laminae created long-crested simple harmonic (SH) oscillations (vibrations) along a smooth flat boundary, at a flow rate approaching the onset of turbulence. These T-S waves would gradually increase in amplitude until they broke up into the vortices, noise and high resistance that characterize turbulent flow. Contemporary wind tunnels failed to show T-S waves.
In 1943, Schubauer and Skramstad (S and S) created a wind tunnel that went to extremes to damp mechanical vibrations and sounds that might affect the airflow studies along a smooth flat plate. Using a vertical array of evenly spaced hot wire anemometers in the boundary layer (BL) airflow, they substantiated the existence of T-S oscillations by showing SH velocity fluctuations in the BL laminae. The T-S waves gradually increased in amplitude until a few random spikes of in-phase amplitude appeared, triggering focal vortices (turbulent spots), with noise. A further increase in flow rate resulted suddenly in many vortices, aerodynamic noise and a great increase in resistance to flow. An oscillation of a mass in a fluid creates a sound wave; SH oscillations of a mass of fluid, flowing in that same fluid along a boundary, must result in SH sound, reflected off the boundary, transversely into the fluid.
S and S found foci of in-phase spiking amplitude in the T-S waves; these must create bursts of high amplitude sound, with high energy oscillation of fluid molecules transversely through the BL laminae. This has the potential to freeze laminar slip (laminar interlocking) in these spots, transferring the resistance to the boundary: this breaking at the boundary could rip out pieces of T-S long-crested waves which would tumble head-over-heels downstream in the boundary layer as the vortices of turbulent spots. With further increase in flow rate, there is an explosion into turbulence, with many random vortices and the noise of aerodynamic sound.
Schubauer and Skramstad overlooked the significance of the co-generation of transverse SH sound by the T-S waves in transition and turbulence. However, John Tyndall (1867) in his transition-to-turbulence flow studies using flames, deduced that SH waves were created during transition by viscosity acting around the walls of a tube and these could be amplified by blending with similar SH sound waves (from a whistle), triggering turbulence at lower flow rates. Schubauer and Skramstad introduced SH sound into the boundary layer by creating SH fluttering vibrations of a BL ferromagnetic ribbon in their 1941 experiments, similarly triggering turbulence at lower flow rates.
Tyndall’s contribution towards explaining the mystery of transition to turbulence 150 years ago is beginning to gain recognition. | 1 | Applied and Interdisciplinary Chemistry |
″There was once a time when sawmill operators could barely give away their sawdust. They dumped it in the woods or incinerated it just to get rid of the stuff. These days, they have ready markets for sawdust…″, according to a report in 2008. For example, sawdust is used by biomass power plants as fuel or is sold to dairy farmers as animal bedding. | 1 | Applied and Interdisciplinary Chemistry |
Iron is an essential bioelement for most forms of life, from bacteria to mammals. Its importance lies in its ability to mediate electron transfer. In the ferrous state (Fe), iron acts as an electron donor, while in the ferric state (Fe) it acts as an acceptor. Thus, iron plays a vital role in the catalysis of enzymatic reactions that involve electron transfer (reduction and oxidation, redox). Proteins can contain iron as part of different cofactors, such as iron–sulfur clusters (Fe-S) and heme groups, both of which are assembled in mitochondria. | 1 | Applied and Interdisciplinary Chemistry |
The main subprocesses of sensor-based sorting are material conditioning, material presentation, detection, data processing and separation.
* Material conditioning includes all operations which prepare the particles for being detected by the sensor. All optical sensors need clean material to be able to detect optical characteristics. Conditioning includes screening and cleaning of the feed material.
* The aim of the material presentation is the isolation of the particles by creating a single particle layer with the densest surface cover possible without particles touching each other and enough distance to each other allowing for a selective detection and rejection of each single particle.
There are two types of sensor-based sorters: the chute type and the belt type. For both types the first step in acceleration is spreading out the particles by a vibrating feeder followed by either a fast belt or a chute. On the belt type the sensor usually detects the particles horizontally while they pass it on the belt. For the chute type the material detection is usually done vertically while the material passes the sensor in a free fall. The data processing is done in real time by a computer. The computer transfers the result of the data processing to an ultra fast ejection unit which, depending on the sorting decision, ejects a particle or lets it pass. | 0 | Theoretical and Fundamental Chemistry |
Quantitative PCR (Q-PCR) is used to measure the quantity of a PCR product (preferably real-time, QRT-PCR). It is the method of choice to quantitatively measure amounts of transgene DNA in a food or feed sample. Q-PCR is commonly used to determine whether a DNA sequence is present in a sample and the number of its copies in the sample. The method with currently the highest level of accuracy is quantitative real-time PCR. QRT-PCR methods use fluorescent dyes, such as Sybr Green, or fluorophore-containing DNA probes, such as TaqMan, to measure the amount of amplified product in real time. If the targeted genetic sequence is unique to a certain GMO, a positive PCR test proves that the GMO is present in the sample. | 1 | Applied and Interdisciplinary Chemistry |
In the 1960s and 1970s various groups reported the ring-opening polymerization of norbornene catalyzed by hydrated trichlorides of ruthenium and other late transition metals in polar, protic solvents. This prompted Robert H. Grubbs and coworkers to search for well-defined, functional group tolerant catalysts based on ruthenium. The Grubbs group successfully polymerized the 7-oxo norbornene derivative using ruthenium trichloride, osmium trichloride as well as tungsten alkylidenes. They identified a Ru(II) carbene as an effective metal center and in 1992 published the first well-defined, ruthenium-based olefin metathesis catalyst, (PPh)ClRu=CHCH=CPh:
The corresponding tricyclohexylphosphine complex (PCy)ClRu=CHCH=CPh was also shown to be active. This work culminated in the now commercially available 1st generation Grubbs catalyst. | 0 | Theoretical and Fundamental Chemistry |
Wide varieties of aromatic compounds are enzymatically reduced to form free radicals that contain one more electron than their parent compounds. In general, the electron donor is any of a wide variety of flavoenzymes and their coenzymes. Once formed, these anion free radicals reduce molecular oxygen to superoxide and regenerate the unchanged parent compound. The net reaction is the oxidation of the flavoenzyme's coenzymes and the reduction of molecular oxygen to form superoxide. This catalytic behavior has been described as a futile cycle or redox cycling. | 0 | Theoretical and Fundamental Chemistry |
Since 2011, the MOSE control centre and management functions for the lagoon system have been located in the Venice Arsenal, symbol of the former trading and military might of the historic Serenissima or "Serene Republic". Numerous historical buildings, in a state of decay and abandonment for decades, have already been restored and reorganisation of the area is underway to accommodate these new activities.
Restoration has enabled a heritage of extraordinary historical and architectural value to be safeguarded and allowed buildings to be recovered and re-utilised. As home to MOSE management and control the arsenal will receive a new lease of life after years of abandonment, allowing its renaissance as a place of innovation and production, with important economic repercussions for the city and local area.
The historic arsenal buildings before and after restoration and construction of infrastructure to accommodate the new functions are shown below.
In the control centre, key decisions will be taken on raising and lowering the mobile barriers according to measurements made by tide gauges positioned in front of the lagoon inlets to record the rising tide in real time. The command to raise the gate will be given when water reaches the level established by the procedure to begin the manoeuvre and guarantee that the water level in the lagoon does not exceed the requisite safe level. | 1 | Applied and Interdisciplinary Chemistry |
In fluid dynamics, a blast wave is the increased pressure and flow resulting from the deposition of a large amount of energy in a small, very localised volume. The flow field can be approximated as a lead shock wave, followed by a self-similar subsonic flow field. In simpler terms, a blast wave is an area of pressure expanding supersonically outward from an explosive core. It has a leading shock front of compressed gases. The blast wave is followed by a blast wind of negative gauge pressure, which sucks items back in towards the center. The blast wave is harmful especially when one is very close to the center or at a location of constructive interference. High explosives that detonate generate blast waves. | 1 | Applied and Interdisciplinary Chemistry |
Gene symbols are italicised and all letters are in lowercase (shh). Protein designations are the same as the gene symbol, but are not italicised; the first letter is in uppercase and the remaining letters are in lowercase (Shh). | 1 | Applied and Interdisciplinary Chemistry |
A half-life often describes the decay of discrete entities, such as radioactive atoms. In that case, it does not work to use the definition that states "half-life is the time required for exactly half of the entities to decay". For example, if there is just one radioactive atom, and its half-life is one second, there will not be "half of an atom" left after one second.
Instead, the half-life is defined in terms of probability: "Half-life is the time required for exactly half of the entities to decay on average". In other words, the probability of a radioactive atom decaying within its half-life is 50%.
For example, the accompanying image is a simulation of many identical atoms undergoing radioactive decay. Note that after one half-life there are not exactly one-half of the atoms remaining, only approximately, because of the random variation in the process. Nevertheless, when there are many identical atoms decaying (right boxes), the law of large numbers suggests that it is a very good approximation to say that half of the atoms remain after one half-life.
Various simple exercises can demonstrate probabilistic decay, for example involving flipping coins or running a statistical computer program. | 0 | Theoretical and Fundamental Chemistry |
Surface or ground water abstracted for the supply of drinking water must be capable of meeting rigorous chemical standards following treatment. This requires a detailed knowledge of the water entering the treatment plant. In addition to the normal suite of environmental chemical parameters, other parameters such as hardness, phenol, oil and in some cases a real-time organic profile of the incoming water as in the River Dee regulation scheme. | 0 | Theoretical and Fundamental Chemistry |
The clinical use of most antibiotics result in a mutation of the pathogen organism leading to their resistance against the drug. Therefore, development of new drugs is always needed. A potential first step in developing new drugs against currently threatening diseases (e.g. tuberculosis) is to find new drug targets in the causative agent of the disease, i.e. the pathogen microorganism, let it be either a bacterium, or a protozoan parasite. After finding the target protein in the bacterium (or protozoan parasite), one could design small molecular drug compounds that bind to the protein and inhibit it.
Public availability of biological network data makes the process of searching for new drug targets easier than it was before. By using the available metabolic networks, it is possible to find important nodes with link analysis algorithms, like PageRank. In a recently published paper, biochemical reactions are treated as nodes of the metabolic network. In this directed network, reaction A has a directed edge towards reaction B if the product of the former enters the latter reaction as a substrate or co-factor.
To select important nodes that could serve as drug targets, we might think of selecting high in-degree nodes (hubs; nodes with many incoming edges). It was shown however[2], that targeting hub proteins with many vital functions may unintentionally harm the living cell as well. A PageRank-based scoring method could detect important nodes that are not hubs and therefore might be better drug targets.
The PageRank of a node A is the stationary limit probability distribution that the random walker is at node A. In its original application, the personalization vector w captured the personal interest of a web-surfer: interesting websites to a surfer appeared with a higher probability in the distribution given in vector w. In this metabolic network, w is personalized to proteins; w is larger for those proteins that appear in higher concentrations in the proteomics analysis of certain diseases. This personalized PageRank may identify other related proteins to the disease.
However, by using only the personalized PageRank to identify important nodes, hubs still get a high score on average. To find non-hub important nodes instead, we should consider scoring the nodes by their "relativized personalized PageRank"; i.e. their personalized PageRank scores over the number of edges pointing towards them (over their in-degree):
The relativized personalized PageRank (rPPR(v)) for a node v is given by:
where PpageRank(v) is the personalized PageRank score of node v, and d_(v) is its in-degree. It was shown, that by using this method, numerous already validated drug targets can be found (e.g. in the Mycobacterium tuberculosis), therefore, new, currently unknown targets might be detected as well. | 1 | Applied and Interdisciplinary Chemistry |
*Materials Performance magazine
*CoatingsPro magazine
*CORROSION journal
*technical and reference books
*podcasts and webcasts | 1 | Applied and Interdisciplinary Chemistry |
The term agostic, derived from the Ancient Greek word for "to hold close to oneself", was coined by Maurice Brookhart and Malcolm Green, on the suggestion of the classicist Jasper Griffin, to describe this and many other interactions between a transition metal and a C−H bond. Often such agostic interactions involve alkyl or aryl groups that are held close to the metal center through an additional σ-bond.
Short interactions between hydrocarbon substituents and coordinatively unsaturated metal complexes have been noted since the 1960s. For example, in tris(triphenylphosphine) ruthenium dichloride, a short interaction is observed between the ruthenium(II) center and a hydrogen atom on the ortho position of one of the nine phenyl rings. Complexes of borohydride are described as using the three-center two-electron bonding model.
The nature of the interaction was foreshadowed in main group chemistry in the structural chemistry of trimethylaluminium. | 0 | Theoretical and Fundamental Chemistry |
The outbreak of hostilities in eastern Ukraine in 2014 complicated the activities of the enterprise. As a result, the plant ended 2014 with a net loss of UAH 4,871.533 million. In the first nine months of 2015, the plant produced 426 thousand tons of pig iron and 1.664 million tons of grade K coal concentrate, but losses continued to increase.
In June 2016, the leadership of the unrecognized DPR introduced external management at the plant, by which time its communications and a significant part of the equipment had become unusable due to repeated shutdowns and long downtime.
Also in June 2016, on the basis of the Donetsk Electrometallurgical Plant (DEMP), the state enterprise Yuzovsky Metallurgical Plant was opened. The YuMZ industrial complex is located on the same territory as the Donetsk Metallurgical Plant, which, in turn, is located in three districts of the DPR capital at once - Voroshilovsky, Budenovsky, Leninsk.
It was Re-launched on October 5, 2017.
In 2018 YuMZ began to supply products to Turkey, Iran and Syria.
Since May 1, 2019, blast-furnace production has been stopped. The company does not manufacture products. During the heating period of 2019–2020, only the factory CHPP-PVS and related power plants worked, in order to supply heat to part of the above three districts of the city of Donetsk.
From March to August 2020, the plant suspended work due to a shortage of raw materials. As of November 2020, the YuMZ complex, separated from the main part of the plant, continues to produce steel, specializing in the production of continuously cast square billets. The workforce consists of 858 people.
At the DMZ, there are energy workshops that provide transit and supply to factory consumers and sub-consumers of drinking and industrial water, electricity, natural gas, steam and hot water. | 1 | Applied and Interdisciplinary Chemistry |