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In order for a cell to be transformed by a virus, the viral DNA must be entered into the host cell. The simplest consideration is viral transformation of a bacterial cell. This process is called lysogeny. As shown in Figure 2, a bacteriophage lands on a cell and pins itself to the cell. The phage can then penetrate the cell membrane and inject the viral DNA into the host cell. The viral DNA can then either lay dormant until stimulated by a source such as UV light or it can be immediately taken up by the hosts genome. In either case the viral DNA will replicate along with the original host DNA during cell replication causing two cells to now be infected with the virus. The process will continue to propagate more and more infected cells. This process is in contrast to the lytic cycle where a virus only uses the host cells replication machinery to replicate itself before destroying the host cell.
The process is similar in animal cells. In most cases, rather than viral DNA being injected into an animal cell, a section of the membrane encases the virus and the cell then absorbs both the virus and the encasing section of the membrane into the cell. This process, called endocytosis, is shown in Figure 3. | 1 | Applied and Interdisciplinary Chemistry |
AR gene mutations in the LBD that alter ligand specificity and/or functional activity exist and are thought to contribute to the conversion of some AR antagonists into agonists, which explains the paradoxical temporary improvement sometimes observed in patients when antiandrogen therapy is stopped. These mutations can have great effect on the antagonist activities of current small molecule antiandrogens and make them less efficient in blocking AR function via indirect modulation from inside of the LBP. Recent studies with circulating tumor cells, suggest that the mutation frequency is higher than previously assumed based on tumor biopsies.
The T877A, W741L and W741C mutations are examples of known AR LBD mutations. The LNCaP prostate cancer cell line expresses AR with a T877A point mutation that causes proliferation in the presence of the antiandrogens hydroxyflutamide and cyproterone acetate. This mutation has also been discovered in patients with antiandrogen withdrawal syndrome being treated with these compounds. In another study, bicalutamide treatment of LNCaP cells resulted in two LBD mutations, W741L and W741C, causing bicalutamide to acquire agonist activity to both mutant ARs. The W741L mutation generates additional space such that the sulfonyl-linked phenyl ring of bicalutamide is accommodated at the location of the missing indole ring of W741. In non-mutant AR, the presence of the W741 side chain probably forces bicalutamide to protrude out thus precluding the active position of H12 on the AR receptor.
However, hydroxyflutamide worked as an antagonist for W741 mutant ARs. This concurs with the theory that flutamide and nilutamide antagonize AR through the mechanism of “passive antagonism”, as they are of a more modest size then bicalutamide. These drugs may therefore be effective as a second-line therapy for refractory prostate cancer previously treated with bicalutamide. | 1 | Applied and Interdisciplinary Chemistry |
The measurement of the angles can be used to determine crystal structure, see x-ray crystallography for more details. As a simple example, Bragg's law, as stated above, can be used to obtain the lattice spacing of a particular cubic system through the following relation:
where is the lattice spacing of the cubic crystal, and , , and are the Miller indices of the Bragg plane. Combining this relation with Bragg's law gives:
One can derive selection rules for the Miller indices for different cubic Bravais lattices as well as many others, a few of the selection rules are given in the table below.
These selection rules can be used for any crystal with the given crystal structure. KCl has a face-centered cubic Bravais lattice. However, the K and the Cl ion have the same number of electrons and are quite close in size, so that the diffraction pattern becomes essentially the same as for a simple cubic structure with half the lattice parameter. Selection rules for other structures can be referenced elsewhere, or derived. Lattice spacing for the other crystal systems can be found here. | 0 | Theoretical and Fundamental Chemistry |
In addition to minimising construction cost, other factors influence the placement of cut or filled sections.
For example, air pollutants can concentrate in the valleys created by the cut section. Conversely, noise pollution is mitigated by cut sections since an effective blockage of line-of-sight sound propagation is created by the depressed roadway design.
The environmental effects of fill sections are typically favorable with respect to air pollution dispersal, but in respect to sound propagation, exposure of nearby residents is generally increased, since sound walls and other forms of sound path blockage are less effective in this geometry.
The reasons for creating fills include the reduction of grade along a route or the elevation of the route above water, swampy ground, or areas where snow drifts frequently collect. Fills can also be used to cover tree stumps, rocks, or unstable soil, in which case material with a higher bearing capacity is placed on top of the obstacle in order to carry the weight of the roadway or railway and reduce differential settlement. | 1 | Applied and Interdisciplinary Chemistry |
The ore is comminuted and the cobalt rich oxides are separated by froth flotation. The cobalt-bearing concentrate is then mixed with lime and coal, and then melted in a reducing atmosphere. Iron and lighter impurities float to the surface as solid dross or are expelled from the melt as gas. The remaining liquid is composed of a heavier copper smelt containing approximately 5% cobalt that is processed for its copper and a lighter slag that is approximately 40% cobalt that is further refined by hydrometallurgical and electrolytic processing. Concentrations of cobalt oxide (CoO) may also be reduced by the aluminothermic reaction or with carbon in a blast furnace. | 1 | Applied and Interdisciplinary Chemistry |
Stochastic effects do not have a threshold of irradiation, are coincidental, and cannot be avoided. They can be divided into somatic and genetic effects. Among the somatic effects, secondary cancer is the most important. It develops because radiation causes DNA mutations directly and indirectly. Direct effects are those caused by ionizing particles and rays themselves, while the indirect effects are those that are caused by free radicals, generated especially in water radiolysis and oxygen radiolysis. The genetic effects confer the predisposition of radiosensitivity to the offspring. The process is not well understood yet. | 0 | Theoretical and Fundamental Chemistry |
DNA-directed RNA interference (ddRNAi) is a gene-silencing technique that utilizes DNA constructs to activate an animal cell's endogenous RNA interference (RNAi) pathways. DNA constructs are designed to express self-complementary double-stranded RNAs, typically short-hairpin RNAs, that bring about the silencing of a target gene or genes once processed. Any RNA, including endogenous messenger RNA (mRNAs) or viral RNAs, can be silenced by designing constructs to express double-stranded RNA complementary to the desired mRNA target.
This mechanism has been demonstrated to work as a novel therapeutic technique to silence disease-causing genes across a range of disease models, including viral diseases such as HIV, hepatitis B or hepatitis C, or diseases associated with altered expression of endogenous genes such as drug-resistant lung cancer, neuropathic pain, advanced cancer, and retinitis pigmentosa. | 1 | Applied and Interdisciplinary Chemistry |
Liu Yuanfang (; born February 1931) is a Chinese nuclear chemist. He is a chemist at the Chinese Academy of Sciences (CAS), who is now Professor of Chemistry at Shanghai University. He has studied nuclear chemistry and radiochemistry for forty years and pioneered education in that field in China. | 0 | Theoretical and Fundamental Chemistry |
Combination therapy or polytherapy is therapy that uses more than one medication or modality. Typically, the term refers to using multiple therapies to treat a single disease, and often all the therapies are pharmaceutical (although it can also involve non-medical therapy, such as the combination of medications and talk therapy to treat depression). Pharmaceutical combination therapy may be achieved by prescribing/administering separate drugs, or, where available, dosage forms that contain more than one active ingredient (such as fixed-dose combinations).
Polypharmacy is a related term, referring to the use of multiple medications (without regard to whether they are for the same or separate conditions/diseases). Sometimes "polymedicine" is used to refer to pharmaceutical combination therapy. Most of these kinds of terms lack a universally consistent definition, so caution and clarification are often advisable. | 1 | Applied and Interdisciplinary Chemistry |
A southwestern blot is based on Southern blot and is used to identify and characterize DNA-binding proteins by their ability to bind to specific oligonucleotide probes. The proteins are separated by gel electrophoresis and are subsequently transferred to nitrocellulose membranes similar to other types of blotting. | 1 | Applied and Interdisciplinary Chemistry |
Quinapril is indicated for the treatment of high blood pressure (hypertension) and as adjunctive therapy in the management of heart failure. It may be used for the treatment of hypertension by itself or in combination with thiazide diuretics, and with diuretics and digoxin for heart failure. | 0 | Theoretical and Fundamental Chemistry |
When looking at data related to individual molecules, one usually can construct propagators, and jumping time probability density functions, of the first order, the second order and so on, whereas from bulk experiments, one usually obtains the decay of a correlation function. From the information contained in these unique functions (obtained from individual molecules), one can extract a relatively clear picture on the way the system behaves; e.g. its kinetic scheme, or its potential of activity, or its reduced dimensions form. In particular, one can construct (many properties of) the reaction pathway of an enzyme when monitoring the activity of an individual enzyme. Additionally, significant aspects regarding the analysis of single molecule data—such as fitting methods and tests for homogeneous populations—have been described by several authors. On the other hand, there are several issues with the analysis of single molecule data including construction of a low noise environment and insulated pipet tips, filtering some of the remaining unwanted components (noise) found in recordings, and the length of time required for data analysis (pre-processing, unambiguous event detection, plotting data, fitting kinetic schemes, etc.). | 0 | Theoretical and Fundamental Chemistry |
As first shown in 2003, the auxiliary function of carotenoids as quenchers of singlet oxygen contributes to the photoprotective role of OCP has also been demonstrated under strong orange-red light, which are conditions where OCP cannot be photoactivated for its energy-quenching role. This is significant because all oxygenic phototrophs have a particular risk of oxidative damage initiated by singlet oxygen (O), which is produced when their own light-harvesting pigments act as photosensitizers. | 0 | Theoretical and Fundamental Chemistry |
* Fellow of the Royal Society (1869)
* Rumford Medal, Royal Society of London (1874)
* Janssen Medal, Paris Academy of Sciences (1889)
* Knight Commander of the Order of the Bath (1897)
* President, British Association (1903 – 1904)
* The crater Lockyer on the Moon and the crater Lockyer on Mars are both named after him, as is Norman Lockyer Island in Nunavut, Canada. | 1 | Applied and Interdisciplinary Chemistry |
In sensory neurons, an external signal such as pressure, temperature, light, or sound is coupled with the opening and closing of ion channels, which in turn alter the ionic permeabilities of the membrane and its voltage. These voltage changes can again be excitatory (depolarizing) or inhibitory (hyperpolarizing) and, in some sensory neurons, their combined effects can depolarize the axon hillock enough to provoke action potentials. Some examples in humans include the olfactory receptor neuron and Meissner's corpuscle, which are critical for the sense of smell and touch, respectively. However, not all sensory neurons convert their external signals into action potentials; some do not even have an axon. Instead, they may convert the signal into the release of a neurotransmitter, or into continuous graded potentials, either of which may stimulate subsequent neuron(s) into firing an action potential. For illustration, in the human ear, hair cells convert the incoming sound into the opening and closing of mechanically gated ion channels, which may cause neurotransmitter molecules to be released. In similar manner, in the human retina, the initial photoreceptor cells and the next layer of cells (comprising bipolar cells and horizontal cells) do not produce action potentials; only some amacrine cells and the third layer, the ganglion cells, produce action potentials, which then travel up the optic nerve. | 0 | Theoretical and Fundamental Chemistry |
Recently, LIBS has been investigated as a fast, micro-destructive food analysis tool. It is considered a potential analytical tool for qualitative and quantitative chemical analysis, making it suitable as a PAT (Process Analytical Technology) or portable tool. Milk, bakery products, tea, vegetable oils, water, cereals, flour, potatoes, palm date and different types of meat have been analyzed using LIBS. Few studies have shown its potential as an adulteration detection tool for certain foods. LIBS has also been evaluated as a promising elemental imaging technique in meat.
In 2019, researchers of the University of York and of the Liverpool John Moores University employed LIBS for studying 12 European oysters (Ostrea edulis, Linnaeus, 1758) from the Late Mesolithic shell midden at Conors Island (Republic of Ireland). The results highlighted the applicability of LIBS to determine prehistoric seasonality practices as well as biological age and growth at an improved rate and reduced cost than was previously achievable. | 0 | Theoretical and Fundamental Chemistry |
In addition to a material being certified as biocompatible, biomaterials must be engineered specifically to their target application within a medical device. This is especially important in terms of mechanical properties which govern the way that a given biomaterial behaves. One of the most relevant material parameters is the Youngs Modulus, E, which describes a materials elastic response to stresses. The Youngs Moduli of the tissue and the device that is being coupled to it must closely match for optimal compatibility between device and body, whether the device is implanted or mounted externally. Matching the elastic modulus makes it possible to limit movement and delamination at the biointerface between implant and tissue as well as avoiding stress concentration that can lead to mechanical failure. Other important properties are the tensile and compressive strengths which quantify the maximum stresses a material can withstand before breaking and may be used to set stress limits that a device may be subject to within or external to the body. Depending on the application, it may be desirable for a biomaterial to have high strength so that it is resistant to failure when subjected to a load, however in other applications it may be beneficial for the material to be low strength. There is a careful balance between strength and stiffness that determines how robust to failure the biomaterial device is. Typically, as the elasticity of the biomaterial increases, the ultimate tensile strength will decrease and vice versa. One application where a high-strength material is undesired is in neural probes; if a high-strength material is used in these applications the tissue will always fail before the device does (under applied load) because the Youngs Modulus of the dura mater and cerebral tissue is on the order of 500 Pa. When this happens, irreversible damage to the brain can occur, thus the biomaterial must have an elastic modulus less than or equal to brain tissue and a low tensile strength if an applied load is expected.
For implanted biomaterials that may experience temperature fluctuations, e.g., dental implants, ductility is important. The material must be ductile for a similar reason that the tensile strength cannot be too high, ductility allows the material to bend without fracture and also prevents the concentration of stresses in the tissue when the temperature changes. The material property of toughness is also important for dental implants as well as any other rigid, load-bearing implant such as a replacement hip joint. Toughness describes the material's ability to deform under applied stress without fracturing and having a high toughness allows biomaterial implants to last longer within the body, especially when subjected to large stress or cyclically loaded stresses, like the stresses applied to a hip joint during running.
For medical devices that are implanted or attached to the skin, another important property requiring consideration is the flexural rigidity, D. Flexural rigidity will determine how well the device surface can maintain conformal contact with the tissue surface, which is especially important for devices that are measuring tissue motion (strain), electrical signals (impedance), or are designed to stick to the skin without delaminating, as in epidermal electronics. Since flexural rigidity depends on the thickness of the material, h, to the third power (h), it is very important that a biomaterial can be formed into thin layers in the previously mentioned applications where conformality is paramount. | 1 | Applied and Interdisciplinary Chemistry |
TET enzymes are dioxygenases in the family of alpha-ketoglutarate-dependent hydroxylases. A TET enzyme is an alpha-ketoglutarate (α-KG) dependent dioxygenase that catalyses an oxidation reaction by incorporating a single oxygen atom from molecular oxygen (O) into its substrate, 5-methylcytosine in DNA (5mC), to produce the product 5-hydroxymethylcytosine in DNA. This conversion is coupled with the oxidation of the co-substrate α-KG to succinate and carbon dioxide (see Figure).
The first step involves the binding of α-KG and 5-methylcytosine to the TET enzyme active site. The TET enzymes each harbor a core catalytic domain with a double-stranded β-helix fold that contains the crucial metal-binding residues found in the family of Fe(II)/α-KG- dependent oxygenases. α-KG coordinates as a bidentate ligand (connected at two points) to Fe(II) (see Figure), while the 5mC is held by a noncovalent force in close proximity. The TET active site contains a highly conserved triad motif, in which the catalytically-essential Fe(II) is held by two histidine residues and one aspartic acid residue (see Figure). The triad binds to one face of the Fe center, leaving three labile sites available for binding α-KG and O (see Figure). TET then acts to convert 5-methylcytosine to 5-hydroxymethylcytosine while α-ketoglutarate is converted to succinate and CO. | 1 | Applied and Interdisciplinary Chemistry |
Beginning in 1927, researchers attempted to apply quantum mechanics to fields instead of single particles, resulting in quantum field theories. Early workers in this area include P.A.M. Dirac, W. Pauli, V. Weisskopf, and P. Jordan. This area of research culminated in the formulation of quantum electrodynamics by R.P. Feynman, F. Dyson, J. Schwinger, and S. Tomonaga during the 1940s. Quantum electrodynamics describes a quantum theory of electrons, positrons, and the electromagnetic field, and served as a model for subsequent quantum field theories.
The theory of quantum chromodynamics was formulated beginning in the early 1960s. The theory as we know it today was formulated by Politzer, Gross and Wilczek in 1975.
Building on pioneering work by Schwinger, Higgs and Goldstone, the physicists Glashow, Weinberg and Salam independently showed how the weak nuclear force and quantum electrodynamics could be merged into a single electroweak force, for which they received the 1979 Nobel Prize in Physics. | 1 | Applied and Interdisciplinary Chemistry |
Biuret is also used as a non-protein nitrogen source in ruminant feed, where it is converted into protein by gut microorganisms. It is less favored than urea, due to its higher cost and lower digestibility but the latter characteristic also slows down its digestion and so decreases the risk of ammonia toxicity. | 0 | Theoretical and Fundamental Chemistry |
Taking the natural logarithm of Arrhenius equation yields:
Rearranging yields:
This has the same form as an equation for a straight line:
where x is the reciprocal of T.
So, when a reaction has a rate constant that obeys the Arrhenius equation, a plot of ln k versus T gives a straight line, whose gradient and intercept can be used to determine E and A. This procedure has become so common in experimental chemical kinetics that practitioners have taken to using it to define the activation energy for a reaction. That is, the activation energy is defined to be (−R) times the slope of a plot of ln k vs. (1/T): | 0 | Theoretical and Fundamental Chemistry |
Captopril's main uses are based on its vasodilation and inhibition of some renal function activities. These benefits are most clearly seen in:
* Hypertension
* Cardiac conditions such as congestive heart failure and after myocardial infarction
* Preservation of kidney function in diabetic nephropathy.
Additionally, it has shown mood-elevating properties in some patients. This is consistent with the observation that animal screening models indicate putative antidepressant activity for this compound, although one study has been negative. Formal clinical trials in depressed patients have not been reported.
It has also been investigated for use in the treatment of cancer. Captopril stereoisomers were also reported to inhibit some metallo-β-lactamases. | 0 | Theoretical and Fundamental Chemistry |
A reducing sugar is any sugar that is capable of acting as a reducing agent. In an alkaline solution, a reducing sugar forms some aldehyde or ketone, which allows it to act as a reducing agent, for example in Benedict's reagent. In such a reaction, the sugar becomes a carboxylic acid.
All monosaccharides are reducing sugars, along with some disaccharides, some oligosaccharides, and some polysaccharides. The monosaccharides can be divided into two groups: the aldoses, which have an aldehyde group, and the ketoses, which have a ketone group. Ketoses must first tautomerize to aldoses before they can act as reducing sugars. The common dietary monosaccharides galactose, glucose and fructose are all reducing sugars.
Disaccharides are formed from two monosaccharides and can be classified as either reducing or nonreducing. Nonreducing disaccharides like sucrose and trehalose have glycosidic bonds between their anomeric carbons and thus cannot convert to an open-chain form with an aldehyde group; they are stuck in the cyclic form. Reducing disaccharides like lactose and maltose have only one of their two anomeric carbons involved in the glycosidic bond, while the other is free and can convert to an open-chain form with an aldehyde group.
The aldehyde functional group allows the sugar to act as a reducing agent, for example, in the Tollens test or Benedicts test. The cyclic hemiacetal forms of aldoses can open to reveal an aldehyde, and certain ketoses can undergo tautomerization to become aldoses. However, acetals, including those found in polysaccharide linkages, cannot easily become free aldehydes.
Reducing sugars react with amino acids in the Maillard reaction, a series of reactions that occurs while cooking food at high temperatures and that is important in determining the flavor of food. Also, the levels of reducing sugars in wine, juice, and sugarcane are indicative of the quality of these food products. | 0 | Theoretical and Fundamental Chemistry |
The software imports 3-D geometry from CAD data in the form of STL files. It has geometry Conformal Adaptive Binary-Tree mesh generation tool which creates 3-D grid from CAD surfaces. For liquid devices, PumpLinx has a cavitation model to account for the effect of liquid vapor, free/dissolved gas, and liquid compressibility.
PumpLinx provides templates for different categories of devices, including:
axial piston pumps,
centrifugal pumps,
gerotors,
gear pumps,
progressive cavity pumps,
propellers,
radial piston pumps,
rotary vane pumps,
submersible pumps, and
valves.
Those templates create an initial grid for special rotors; for example, grids around gears of a gear pump, and then re-meshes the grid for a moving simulation, and provide device specific input and output. The output from the code include velocities, pressures, temperatures, and gas volume fractions of the flow field, together with integrated engineering data such as loads and torques.
PumpLinx uses a single Graphical User Interface (GUI) for grid generation, model set-up, execution, and post processing. | 1 | Applied and Interdisciplinary Chemistry |
The du Noüy–Padday method is a minimized version of the du Noüy ring method replacing the large platinum ring with a thin rod that is used to measure equilibrium surface tension or dynamic surface tension at an air–liquid interface. In this method, the rod is oriented perpendicular to the interface, and the force exerted on it is measured. Based on the work of Padday, this method finds wide use in the preparation and monitoring of Langmuir–Blodgett films, ink & coating development, pharmaceutical screening, and academic research. | 0 | Theoretical and Fundamental Chemistry |
AOAC International has 18 active [https://www.aoac.org/membership/sections/ sections]; eight in North America, and ten in the rest of the world, China, India, Japan, Southeast Asia (excluding Thailand), Taiwan, Thailand, Europe (excluding Belgium, Netherlands, and Luxembourg), the Low Countries, Sub-Saharan Africa, and Latin America and the Caribbean. | 0 | Theoretical and Fundamental Chemistry |
In the case of two mirrors, in planes at an angle α, looking through both from the sector which is the intersection of the two halfspaces, is like looking at a version of the world rotated by an angle of 2α; the points of observations and directions of looking for which this applies correspond to those for looking through a frame like that of the first mirror, and a frame at the mirror image with respect to the first plane, of the second mirror. If the mirrors have vertical edges then the left edge of the field of view is the plane through the right edge of the first mirror and the edge of the second mirror which is on the right when looked at directly, but on the left in the mirror image.
In the case of two parallel mirrors, looking through both at once is like looking at a version of the world which is translated by twice the distance between the mirrors, in the direction perpendicular to them, away from the observer. Since the plane of the mirror in which one looks directly is beyond that of the other mirror, one always looks at an oblique angle, and the translation just mentioned has not only a component away from the observer, but also one in a perpendicular direction. The translated view can also be described by a translation of the observer in opposite direction. For example, with a vertical periscope, the shift of the world is away from the observer and down, both by the length of the periscope, but it is more practical to consider the equivalent shift of the observer: up, and backward.
It is also possible to create a non-reversing mirror by placing two first surface mirrors at 90º to give an image which is not reversed. | 0 | Theoretical and Fundamental Chemistry |
The boat conformations have higher energy than the chair conformations. The interaction between the two flagpole hydrogens, in particular, generates steric strain. Torsional strain also exists between the C2–C3 and C5–C6 bonds (carbon number 1 is one of the two on a mirror plane), which are eclipsed — that is, these two bonds are parallel one to the other across a mirror plane. Because of this strain, the boat configuration is unstable (i.e. is not a local energy minimum).
The molecular symmetry is C.
The boat conformations spontaneously distorts to twist-boat conformations. Here the symmetry is D, a purely rotational point group with three twofold axes. This conformation can be derived from the boat conformation by applying a slight twist to the molecule so as to remove eclipsing of two pairs of methylene groups. The twist-boat conformation is chiral, existing in right-handed and left-handed versions.
The concentration of the twist-boat conformation at room temperature is less than 0.1%, but at it can reach 30%. Rapid cooling of a sample of cyclohexane from to will freeze in a large concentration of twist-boat conformation, which will then slowly convert to the chair conformation upon heating. | 0 | Theoretical and Fundamental Chemistry |
Euxinic conditions have nearly vanished from Earth's open-ocean environments, but a few small scale examples still exist today. Many of these locations share common biogeochemical characteristics. For example, low rates of overturning and vertical mixing of the total water column is common in euxinic bodies of water. Small surface area to depth ratios allow multiple stable layers to form while limiting wind-driven overturning and thermohaline circulation. Furthermore, restricted mixing enhances stratified layers of high nutrient density which are reinforced by biological recycling. Within the chemocline, highly specialized organisms such as green sulfur bacteria take advantage of the strong redox potential gradient and minimal sunlight. | 0 | Theoretical and Fundamental Chemistry |
One of the primary uses of shock polars is in the field of shock wave reflection. A shock polar is plotted for the conditions before the incident shock, and a second shock polar is plotted for the conditions behind the shock, with its origin located on the first polar, at the angle through which the incident shock wave deflects the flow. Based on the intersections between the incident shock polar and the reflected shock polar, conclusions as to which reflection patterns are possible may be drawn. Often, it is used to graphically determine whether regular shock reflection is possible, or whether Mach reflection occurs. | 1 | Applied and Interdisciplinary Chemistry |
Epigenetic Therapy is the use of drugs or other epigenome-influencing techniques to treat medical conditions.
It is recently regarded as promising therapy to NSCLC.
As can be seen in the above, SFRP1 was downregulated epigenetically in NSCLC and was recently proposed as one of epigenetic therapy target. | 1 | Applied and Interdisciplinary Chemistry |
T7 DNA helicase (gp4) is a hexameric motor protein encoded by T7 phages that uses energy from dTTP hydrolysis to process unidirectionally along single stranded DNA, separating (helicase) the two strands as it progresses. It is also a primase, making short stretches of RNA that initiates DNA synthesis. It forms a complex with T7 DNA polymerase. Its homologs are found in mitochondria (as Twinkle) and chloroplasts. | 1 | Applied and Interdisciplinary Chemistry |
Niludipine is a calcium channel blocker of the dihydropyridine class. It is a vasodilator that acts upon the coronary arteries of the heart-lung. It was found to produce a calcium antagonistic effect on the smooth muscle of hearts of canines and guinea pigs inhibiting myocardial oxidative metabolism. | 1 | Applied and Interdisciplinary Chemistry |
Illicit use of the drug is thought to be a major factor in the success of the Boko Haram terrorist organization. When used at higher doses, the drug "can produce similar effects to heroin." One former member said, "whenever we took tramadol, nothing mattered to us anymore except what we were sent to do because it made us very high and very bold, it was impossible to go on a mission without taking it." Tramadol is also used as a coping mechanism in the Gaza Strip. It is also abused in the United Kingdom, inspiring the title of the TV show Frankie Boyles Tramadol Nights' (2010).
From March 2019, the Union Cycliste Internationale (UCI) banned the drug, after riders were using the painkiller to improve their performance. | 0 | Theoretical and Fundamental Chemistry |
The main tools are proton and carbon-13 NMR spectroscopy, IR Spectroscopy, Mass spectrometry, UV/Vis Spectroscopy and X-ray crystallography. | 0 | Theoretical and Fundamental Chemistry |
The biosphere is 22% oxygen by volume, present mainly as a component of organic molecules (CHNO) and water. | 0 | Theoretical and Fundamental Chemistry |
MFA is a convulsant poison. It causes severe convulsions in poisoned victims. Death results from respiratory failure.
For a variety of animals, the toxicity of methyl fluoroacetate has been determined orally and through subcutaneous injection. The dosage ranges from 0.1 mg/kg in dogs to 10–12 mg/kg in monkeys indicating considerable variation. An order of decreasing susceptibility has been determined within these animals which is: dog, guinea-pig, cat, rabbit, goat, and then likely horse, rat, mouse, and monkey. For the rat and mouse, the toxicity by inhalation has been investigated more fully than for other animals. The LD for the rat and mouse are 450 mg/m and above 1,000 mg/m for 5 minutes, respectively. In dogs, guinea-pigs, cats, rabbits, goats, horses, rats, mice, and monkeys, the pharmacological effects of this substance have been investigated by mouth and by injection. Methyl fluoroacetate causes progressive depression of respiration and is a convulsant poison in most animals. When applied to the skin it is not toxic, yet through inhalation, injection and by mouth it is. For the rat, cat and the rhesus monkey, the effects of methyl fluoroacetate have been determined similar to those of nicotine, strychnine, leptazol, picrotoxin, and electrically induced convulsions. The convulsive pattern is considered to be similar to that of leptazol. Little besides signs of asphyxia is found post-mortem in these animals. Estimations have been made for blood sugar, hemoglobin, plasma proteins, non-protein nitrogen, and serum potassium, calcium, chloride, and inorganic phosphate in a small number of rabbits, dogs, and goats. Blood changes include a rise of 20 to 60% in hemoglobin, a rise of up to 90% in blood sugar, a rise of 70 to 130% in inorganic phosphate, and a less significant rise in serum potassium with a terminal rise in non-protein nitrogen and potassium. The whole central nervous system is affected by methyl fluoroacetate just like with leptazol, with the higher centers being more sensitive than the lower ones. Small doses of methyl fluoroacetate have little effect on blood pressure yet in large doses it has an action similar to nicotine. It further stimulates the rate and volume of respiration and then causes failure of the respiration, probably central in origin as seen through graphic records. The knee jerk reaction appears to be accentuated through methyl fluoroacetate until convulsions occur due to the irradiation of the stimuli being so facilitated. Nervous conduction is increased and the threshold stimulus lessened in the reflex arc of a spinal cat. Methyl fluoroacetate reduces the electric convulsive threshold about 10 times in rats. The difficulties of treatments are stressed as methyl fluoroacetate is both a powerful convulsant and a respiratory depressant, yet suggestions for treatment in man are made. Methyl fluoroacetate presents a serious hazard as a food and water contaminant in the case that it is used as a poison against rodents and other vermin, as it is not easily detected or destroyed and is equally toxic by mouth and by injection. | 1 | Applied and Interdisciplinary Chemistry |
* Rapid/high throughput: In multiplex analysis, a 100-plex assay can be analyzed in every 30 seconds. The recent reported high-throughput flow cytometry can sample a 96-well plate in 1 minute, and theoretically, the 100-plex assay with this system can be analyzed in less than 1 second, or potentially deliver 12 million samples per day.
* High array density/multiplex: Compared to flat microarrays, SAT allows one to perform parallel measurements. A few microliters of microspheres could contain thousands of array elements and each array element is represented by hundreds of individual microspheres. Thus, the measurement by flow cytometry represents a replicate analysis of each array element.
* Effective gathering of information: One of the benefits of using SAT is that it allows you to take one sample from a patient or research organism and simultaneously test for multiple gene variants. Thus, from a single sample you can determine which virus from a series of viruses a patient has, or which base pair mutation is present in the organism with a unique phenotype.
* Cost-effective: Currently, commercially available suspension array kits costs $0.10-$0.25 per sequence tested. | 1 | Applied and Interdisciplinary Chemistry |
Photoexcitation is the first step in a photochemical process where the reactant is elevated to a state of higher energy, an excited state. The first law of photochemistry, known as the Grotthuss–Draper law (for chemists Theodor Grotthuss and John W. Draper), states that light must be absorbed by a chemical substance in order for a photochemical reaction to take place. According to the second law of photochemistry, known as the Stark–Einstein law (for physicists Johannes Stark and Albert Einstein), for each photon of light absorbed by a chemical system, no more than one molecule is activated for a photochemical reaction, as defined by the quantum yield. | 0 | Theoretical and Fundamental Chemistry |
Metals have been used in treatments since ancient times. The Ebers Papyrus from 1500BC is the first written account of the use of metals for treatment and describes the use of Copper to reduce inflammation and the use of iron to treat anemia. Sodium vanadate has been used since the early 20th century to treat rheumatoid arthritis. Recently metals have been used to treat cancer, by specifically attacking cancer cells and interacting directly with DNA. The positive charge on most metals can interact with the negative charge of the phosphate backbone of DNA. Some drugs developed that include metals interact directly with other metals already present in protein active sites, while other drugs can use metals to interact with amino acids with the highest reduction potential.
Examples of metals used in treatment include:
* Platinum: Platinum based compounds have been shown to specifically affect head and neck tumors. These coordination complexes are thought to act to cross-link DNA in tumor cells (Figure 2).
* Gold: Gold salt complexes have been used to treat rheumatoid arthritis (Figure 3). The gold salts are believed to interact with albumin and eventually be taken up by immune cells, triggering anti-mitochondrial effects and eventually cell apoptosis. This is an indirect treatment of arthritis, mitigating the immune response.
* Lithium: LiCO can be used to treat prophylaxis of manic depressive disorder.
* Zinc: Zinc can be used topically to heal wounds. Zn can be used to treat the herpes virus.
* Silver: Silver has been used to prevent infection at the burn site for burn wound patients.
* Platinum, Titanium, Vanadium, Iron: cis DDP (cis-diaminedichoroplatinum), titanium, vanadium, and iron have been shown to react with DNA specifically in tumor cells to treat patients with cancer.
* Gold, Silver, Copper: Phosphine ligand compounds containing gold, silver, and copper have anti-cancer properties.
* Lanthanum: Lanthanum Carbonate often used under the trade-name Fosrenol is used as a phosphate binder in patients with chronic kidney disease.
* Bismuth: Bismuth subsalicylate is used as an antacid.
* Zirconium: Sodium zirconium cyclosilicate is a potassium binder used in people with chronic kidney disease
* Arsenic: Arsenic trioxide is a chemotherapeutic used to treat acute promyelocytic leukemia | 1 | Applied and Interdisciplinary Chemistry |
Measuring floral scent both qualitatively (identification of VOCs) and quantitatively (absolute and/or relative emission of VOCs) requires the use of analytical chemistry techniques. It requires collecting floral VOCs, and then analyzing them. | 1 | Applied and Interdisciplinary Chemistry |
In 1999, an Austin, Texas, woman was awarded $32 million when she sued her insurer over mold damage in her 22-room mansion.
In 2001, a jury awarded a couple and their eight-year-old son $2.7 million, plus attorney's fees and costs, in a toxic mold-related personal injury lawsuit against the owners and managers of their apartment in Sacramento, California.
In 2002, the U.S. International Trade Commission reported that, according to one estimate, US insurers paid over $3 billion in mold-related lawsuits, more than double the previous year's total.
In 2003, there were over 10,000 mold-related lawsuits pending in US state courts according to the Insurance Information Institute. Most were filed in states with high humidity, but suits were on the rise in other states as well. Notably that year, The Tonight Show co-host Ed McMahon received $7.2 million from insurers and others to settle his lawsuit alleging that toxic mold in his Beverly Hills home made him and his wife ill and killed their dog. Also that year, environmental activist Erin Brockovich received settlements of $430,000 from two parties and an undisclosed amount from a third party to settle her lawsuit alleging toxic mold in her Agoura Hills, California, home.
By 2004, many mold litigation settlements were for amounts well past $100,000.
In 2005, the U.S. International Trade Commission reported that toxic mold showed signs of being the "new asbestos" in terms of claims paid.
In 2006, a Manhattan Beach, California family received a $22.6 million settlement in a toxic mold case. The family had asserted that moldy lumber had caused severe medical problems in their child. That same year, Hilton Hotels received $25 million in settlement of its lawsuit over mold growth in the Hilton Hawaiian Village's Kalia Tower.
In 2010, a jury awarded $1.2 million in damages in a lawsuit against a landlord for neglecting to repair a mold-infested house in Laguna Beach, California. The lawsuit asserted that a child in the home had severe respiratory problems for several years as a result of the mold.
In 2011, in North Pocono, Pennsylvania, a jury awarded two homeowners $4.3 million in a toxic mold verdict.
In 2012, a key appellate court in Manhattan found a consensus in the scientific literature for a causal relationship between the presence of mold and resultant illness. | 1 | Applied and Interdisciplinary Chemistry |
Unsteady forces due to a change of the relative velocity of a body submerged in a fluid can be divided into two parts: the virtual mass effect and the Basset force.
The origin of the force is that the fluid will gain kinetic energy at the expense of the work done by an accelerating submerged body.
It can be shown that the virtual mass force, for a spherical particle submerged in an inviscid, incompressible fluid is
where bold symbols denote vectors, is the fluid flow velocity, is the spherical particle velocity, is the mass density of the fluid (continuous phase), is the volume of the particle, and D/Dt denotes the material derivative.
The origin of the notion "virtual mass" becomes evident when we take a look at the momentum equation for the particle.
where is the sum of all other force terms on the particle, such as gravity, pressure gradient, drag, lift, Basset force, etc.
Moving the derivative of the particle velocity from the right hand side of the equation to the left we get
so the particle is accelerated as if it had an added mass of half the fluid it displaces, and there is also an additional force contribution on the right hand side due to acceleration of the fluid. | 1 | Applied and Interdisciplinary Chemistry |
When sufficient salt export is not taking place from a river basin to the sea in an attempt to harness the river water fully, it leads to river basin closure, and the available water in the downstream area of the river basin closer to the sea becomes saline and/ or alkaline water. Land irrigated with saline or alkaline water gradually turns into saline or alkali soils. The water percolation in alkali soils is very poor leading to waterlogging problems. Proliferation of alkali soils would compel the farmers to cultivate rice or grasses only as the soil productivity is poor with other crops and tree plantations. Cotton is the preferred crop in saline soils compared to many other crops. Interlinking water surplus rivers with water deficit rivers is needed for the long-term sustainable productivity of the river basins and for mitigating the anthropogenic influences on the rivers by allowing adequate salt export to the sea in the form of environmental flows. | 1 | Applied and Interdisciplinary Chemistry |
*The Inorganic Crystal Structure Database (ICSD) in its definition of "inorganic" carbon compounds, states that such compounds may contain either C-H or C-C bonds, but not both.
*The book series Inorganic Syntheses does not define inorganic compounds. The majority of its content deals with metal complexes of organic ligands.
*IUPAC does not offer a definition of "inorganic" or "inorganic compound" but does define inorganic polymer as "...skeletal structure that does not include carbon atoms." | 0 | Theoretical and Fundamental Chemistry |
The Krüppel associated box (KRAB) domain is a category of transcriptional repression domains present in approximately 400 human zinc finger protein-based transcription factors (KRAB zinc finger proteins). The KRAB domain typically consists of about 75 amino acid residues, while the minimal repression module is approximately 45 amino acid residues. It is predicted to function through protein-protein interactions via two amphipathic helices. The most prominent interacting protein is called TRIM28 initially visualized as SMP1, cloned as KAP1 and TIF1-beta. Substitutions for the conserved residues abolish repression.
Over 10 independently encoded KRAB domains have been shown to be effective repressors of transcription, suggesting this activity to be a common property of the domain. KRAB domains can be fused with dCas9 CRISPR tools to form even stronger repressors. | 1 | Applied and Interdisciplinary Chemistry |
In the US, tolerances for the amount of pesticide residue that may remain on food are set by the EPA, and measures are taken to keep pesticide residues below the tolerances. The US EPA has a web page for the allowable tolerances. In order to assess the risks associated with pesticides on human health, the EPA analyzed individual pesticide active ingredients as well as the common toxic effect that groups of pesticides have, called the cumulative risk assessment. Limits that the EPA sets on pesticides before approving them includes a determination of how often the pesticide should be used and how it should be used, in order to protect the public and the environment. In the US, the Food and Drug Administration (FDA) and USDA also routinely check food for the actual levels of pesticide residues.
A US organic food advocacy group, the Environmental Working Group, is known for creating a list of fruits and vegetables referred to as the Dirty Dozen; it lists produce with the highest number of distinct pesticide residues or most samples with residue detected in USDA data. This list is generally considered misleading and lacks scientific credibility because it lists detections without accounting for the risk of the usually small amount of each residue with respect to consumer health. In 2016, over 99% of samples of US produce had no pesticide residue or had residue levels well below the EPA tolerance levels for each pesticide. | 1 | Applied and Interdisciplinary Chemistry |
The Maxwell Garnett equation reads:
where is the effective dielectric constant of the medium, of the inclusions, and of the matrix; is the volume fraction of the inclusions.
The Maxwell Garnett equation is solved by:
so long as the denominator does not vanish. A simple MATLAB calculator using this formula is as follows. | 0 | Theoretical and Fundamental Chemistry |
In general, the spontaneity of a process only determines whether or not a process can occur and makes no indication as to whether or not the process will occur. In other words, spontaneity is a necessary, but not sufficient, condition for a process to actually occur. Furthermore, spontaneity makes no implication as to the speed at which as spontaneous may occur.
As an example, the conversion of a diamond into graphite is a spontaneous process at room temperature and pressure. Despite being spontaneous, this process does not occur since the energy to break the strong carbon-carbon bonds is larger than the release in free energy. | 0 | Theoretical and Fundamental Chemistry |
In 2018 the New Jersey Department of Environmental Protection (NJDEP) published a drinking water standard for PFNA. Public water systems in New Jersey are required to meet an MCL standard of 13 ppt. In 2020 the state set a PFOA standard at 14 ppt and a PFOS standard at 13 ppt.
In 2019 NJDEP filed lawsuits against the owners of two plants that had manufactured PFASs, and two plants that were cited for water pollution from other chemicals. The companies cited are DuPont, Chemours and 3M. NJDEP also declared five companies to be financially responsible for statewide remediation of the chemicals. Among the companies accused were Arkema and Solvay regarding a West Deptford Facility in Gloucester County, where Arkema manufactured PFASs, but Solvay claims to have never manufactured but only handled PFASs. The companies denied liability and contested the directive. In June 2020, the U.S. Environmental Protection Agency and New Jersey Department of Environmental Protection published a paper reporting that a unique family of PFAS used by Solvay, chloroperfluoropolyether carboxylates (ClPFPECAs), were contaminating the soils of New Jersey as far from the Solvay facility as 150 km. and the ClPFPECAs were found in water as well.
Later in 2020, the New Jersey state attorney general filed suit in the New Jersey Superior Court against Solvay regarding PFAS contamination of the state's environment. In May 2021, Solvay issued a press release that the company is "discontinuing the use of fluorosurfactants in the U.S.". | 0 | Theoretical and Fundamental Chemistry |
Unsaturated carbohydrates are desired as they are versatile building blocks that can be used in a variety of reactions. For example, they can be used as intermediates in the synthesis of natural products, or as dienophiles in the Diels-Alder reaction, or as precursors in the synthesis of oligosaccharides. The Tipson–Cohen reaction goes through a syn or anti elimination mechanism to produce an alkene in high to moderate yields. The reaction depends on the neighboring substituents. A mechanism for glucopyranosides and mannooyranosides is shown below.
Scheme 1: Syn elimination occurs with the glucopyranosides. Galactopyranosides follows a similar syn mechanism. Whereas, anti elimination occurs with mannopyranosides. Note that R could be a methanesulfonyl CHOS (Ms), or a toluenesulfonyl CHCHOS (Ts). | 0 | Theoretical and Fundamental Chemistry |
Humans and other mammals have chitinase and chitinase-like proteins that can degrade chitin; they also possess several immune receptors that can recognize chitin and its degradation products, initiating an immune response.
Chitin is sensed mostly in the lungs or gastrointestinal tract where it can activate the innate immune system through eosinophils or macrophages, as well as an adaptive immune response through T helper cells. Keratinocytes in skin can also react to chitin or chitin fragments. | 1 | Applied and Interdisciplinary Chemistry |
Medications can adjust the release of brain neurotransmitters in cases of depression, anxiety disorder, schizophrenia and other mental disorders because an imbalance within neurotransmitter systems can emerge as consistent characteristics in behaviour compromising people's lives. All people have a weaker form of such imbalance in at least one of such neurotransmitter systems that make each of us distinct from one another. The impact of this weak imbalance in neurochemistry can be seen in the consistent features of behaviour in healthy people (temperament). In this sense temperament (as neuro-chemically-based individual differences) and mental illness represents varying degrees along the same continuum of neurotransmitter imbalance in neurophysiological systems of behavioural regulation.
In fact, multiple temperament traits (such as Impulsivity, sensation seeking, neuroticism, endurance, plasticity, sociability or extraversion) have been linked to brain neurotransmitters and hormone systems.
By the end of the 20th century, it became clear that the human brain operates with more than a dozen neurotransmitters and a large number of neuropeptides and hormones. The relationships between these different chemical systems are complex as some of them suppress and some of them induce each other's release during neuronal exchanges. This complexity of relationships devalues the old approach of assigning "inhibitory vs. excitatory" roles to neurotransmitters: the same neurotransmitters can be either inhibitory or excitatory depending on what system they interact with. It became clear that an impressive diversity of neurotransmitters and their receptors is necessary to meet a wide range of behavioural situations, but the links between temperament traits and specific neurotransmitters are still a matter of research. Several attempts were made to assign specific (single) neurotransmitters to specific (single) traits. For example, dopamine was proposed to be a neurotransmitter of the trait of Extraversion, noradrenaline was linked to anxiety, and serotonin was thought to be a neurotransmitter of an inhibition system. These assignments of neurotransmitter functions appeared to be an oversimplification when confronted by the evidence of much more diverse functionality.
Research groups led by Petra Netter in Germany, Lars Farde in Karolinska Institute in Sweden and Trevor Robbins in Cambridge, UK had most extensive studies of the links between temperament/personality traits or dynamical properties of behavior and groups of neurotransmitters. | 1 | Applied and Interdisciplinary Chemistry |
Thermal irradiation is the rate at which radiation is incident upon a surface per unit area. It is measured in watts per square meter. Irradiation can either be reflected, absorbed, or transmitted. The components of irradiation can then be characterized by the equation
where, represents the absorptivity, reflectivity and transmissivity. These components are a function of the wavelength of the electromagnetic wave as well as the material properties of the medium. | 0 | Theoretical and Fundamental Chemistry |
Hydroxide mineralizers are also used to control the alumina/silica ratio of zeolites. A typical recipe for the production of a zeolite includes the mineralizer, the solvent, the seed crystal, a nutrient consisting of silica (SiO) and alumina (AlO), and a template. Templates are cations that direct the polymerization of the anionic building blocks to form a certain zeolite structure. Different templating cations lead to different zeolite structures. Typical templates include tetramethylammonium (TMA), sodium (Na) and potassium (K). Different zeolites can also be formed by changing the ratios of the nutrient source, the type of mineralizer or the temperature and pH of the reaction. At high pH, zeolites with high alumina content are formed, because hydroxides prevent the ability of silica to condense and oligomerize through the reaction shown above. At lower pH, zeolites with high silica content are favored. | 0 | Theoretical and Fundamental Chemistry |
*2021, Holds 80+ patents
*2021, Women of Technology Award, Connected World magazine
*2018, Technology Pioneer Award, World Economic Forum
*2018, INC. Top 100 Female Founders
*2018, Frost & Sullivan North American Lithium-Ion Industrial and Electric Vehicle Battery Technology Innovation Award
* 2015, CT Technology Council 2015 Women of Innovation: Entrepreneurial Innovation and Leadership Award
*2013, Elected Lifetime Ambassador of Honor, Dalarna, Sweden
*2011, Important Women in Mobile Tech
*2011, Swedish woman of the year (Årets svenska kvinna), Swedish Women's Educational Association.
* 2010, Elected Lifetime Member of the Royal Swedish Academy of Engineering Sciences (Kungliga ingenjörsvetenskapsakademien)
* 2010, Private Company CEO of the Year from the MassTLC Leadership Awards
* 2010, Technology Pioneer Award, World Economic Forum
* 2010, Sustainable Leadership Award, Swedish Association of Environmental Managers
* 2009, Entrepreneur Hall of Fame
*2009, Ernst & Young Entrepreneur of the Year for Clean Tech, New England region
* 2008, Stevie Award for Women in Business as Best Entrepreneur
* 2008, Top Innovators of 2008, EDN Magazine
* 2007, Mass High Tech Women to Watch
* 2007, DEMOgod™
* 2006, Top 100 Woman-Led Businesses in MA
*2002, 100 Top Young Innovators, MITs Technology Review'
*1998, Bell Labs Spot Innovation Award
*1994, Amelia Earhart International Fellowship
*1989, Nobel Foundation Student Award | 0 | Theoretical and Fundamental Chemistry |
Most naturally occurring nuclides are stable (about 251; see list at the end of this article), and about 35 more (total of 286) are known to be radioactive with sufficiently long half-lives (also known) to occur primordially. If the half-life of a nuclide is comparable to, or greater than, the Earth's age (4.5 billion years), a significant amount will have survived since the formation of the Solar System, and then is said to be primordial. It will then contribute in that way to the natural isotopic composition of a chemical element. Primordially present radioisotopes are easily detected with half-lives as short as 700 million years (e.g., U). This is the present limit of detection, as shorter-lived nuclides have not yet been detected undisputedly in nature except when recently produced, such as decay products or cosmic ray spallation.
Many naturally occurring radioisotopes (another 53 or so, for a total of about 339) exhibit still shorter half-lives than 700 million years, but they are made freshly, as daughter products of decay processes of primordial nuclides (for example, radium from uranium) or from ongoing energetic reactions, such as cosmogenic nuclides produced by present bombardment of Earth by cosmic rays (for example, C made from nitrogen).
Some isotopes that are classed as stable (i.e. no radioactivity has been observed for them) are predicted to have extremely long half-lives (sometimes as high as 10 years or more). If the predicted half-life falls into an experimentally accessible range, such isotopes have a chance to move from the list of stable nuclides to the radioactive category, once their activity is observed. For example, Bi and W were formerly classed as stable, but were found to be alpha-active in 2003. However, such nuclides do not change their status as primordial when they are found to be radioactive.
Most stable isotopes on Earth are believed to have been formed in processes of nucleosynthesis, either in the Big Bang, or in generations of stars that preceded the formation of the Solar System. However, some stable isotopes also show abundance variations in the earth as a result of decay from long-lived radioactive nuclides. These decay-products are termed radiogenic isotopes, in order to distinguish them from the much larger group of non-radiogenic isotopes. | 0 | Theoretical and Fundamental Chemistry |
Some metals, such as platinum, readily adsorb carbon monoxide, which is usually undesirable as it results in catalyst poisoning.
However, the strong affinity of CO to such catalysts also presents an opportunity: since carbon monoxide is a small molecule with a strong affinity to the catalyst, a large enough amount of CO will adsorb to the entire available surface area of the catalyst. That, in turn, means that by evaluating the amount of CO adsorbed, the catalyst's available surface area can be indirectly measured.
That surface area - also known as "real surface area" or "electrochemically active surface area" - can be measured by electrochemically oxidizing the adsorbed carbon monoxide, as the charge expended in oxidizing CO is directly proportional to the amount of CO adsorbed on the surface and therefore, the surface area of the catalyst. | 0 | Theoretical and Fundamental Chemistry |
Photoinhibition occurs in all organisms capable of oxygenic photosynthesis, from vascular plants to cyanobacteria. In both plants and cyanobacteria, blue light causes photoinhibition more efficiently than other wavelengths of visible light, and all wavelengths of ultraviolet light are more efficient than wavelengths of visible light. Photoinhibition is a series of reactions that inhibit different activities of PSII, but there is no consensus on what these steps are. The activity of the oxygen-evolving complex of PSII is often found to be lost before the rest of the reaction centre loses activity. However, inhibition of PSII membranes under anaerobic conditions leads primarily to inhibition of electron transfer on the acceptor side of PSII. Ultraviolet light causes inhibition of the oxygen-evolving complex before the rest of PSII becomes inhibited. Photosystem I (PSI) is less susceptible to light-induced damage than PSII, but slow inhibition of this photosystem has been observed. Photoinhibition of PSI occurs in chilling-sensitive plants and the reaction depends on electron flow from PSII to PSI. | 0 | Theoretical and Fundamental Chemistry |
X-ray analysis indicates certain important bond lengths and angles of the first diphosphene, bis(2,4,6-tri-tert-butylphenyl)diphosphene: P-P = 2.034 (2) Å; P-C = 1.826 (2) Å; P-P-C = 102.8 (1); C-P-P-C = 172.2 (1). Compared with the bond length of a P-P single bond in HPPH (2.238 Å), the P-P bond distance is much shorter, which reveals double bond character. The orientation of the substituents about the P-P double bond in bis(2,4,6-tri-tert-butylphenyl)diphosphene exhibits an E (trans) configuration. But by visible irradiation of the trans isomer, an interconversion between cis isomer and trans isomers would occur. In 1984, M. Koening et al. noticed a different splitting mode and chemical shift in H NMR and P NMR under a direct irradiation of a toluene solution of E-bis(2,4,6-tri-tert-butylphenyl)diphosphene, which suggesting a cis-trans isomerization. | 0 | Theoretical and Fundamental Chemistry |
This method is an acid heap leaching method like that of the copper method in that it utilises sulfuric acid instead of cyanide solution to dissolve the target minerals from crushed ore. The amount of sulfuric acid required is much higher than for copper ores, as high as 1,000 kg of acid per tonne of ore, but 500 kg is more common. The method was originally patented by Australian miner BHP and is being commercialized by Cerro Matoso in Colombia, a wholly owned subsidiary of BHP; Vale in Brazil; and European Nickel for the rock laterite deposits of Turkey, Talvivaara mine in Finland, the Balkans, and the Philippines. There currently are no operating commercial scale nickel laterite heap leach operations, but there is a sulphide HL operating in Finland.
Nickel recovery from the leach solutions is much more complex than for copper and requires various stages of iron and magnesium removal, and the process produces both leached ore residue ("ripios") and chemical precipitates from the recovery plant (principally iron oxide residues, magnesium sulfate and calcium sulfate) in roughly equal proportions. Thus, a unique feature of nickel heap leaching is the need for a tailings disposal area.
The final product can be nickel hydroxide precipitates (NHP) or mixed metal hydroxide precipitates (MHP), which are then subject to conventional smelting to produce metallic nickel. | 1 | Applied and Interdisciplinary Chemistry |
Each school of Hinduism has its own treatises on epistemology, with different number of Pramanas. For example, compared to Nyāya schools four pramanas', Carvaka school has just one (perception), while Advaita Vedanta school recognizes six means to reliable knowledge. | 1 | Applied and Interdisciplinary Chemistry |
One program that has integrated green infrastructure into construction projects worldwide is the Leadership in Energy and Environmental Design (LEED) certification. This system offers a benchmark rating for green buildings and neighborhoods, credibly quantifying a project's environmental responsibility. The LEED program incentivizes development that uses resources efficiently. For example, it offers specific credits for reducing indoor and outdoor water use, optimizing energy performance, producing renewable energy, and minimizing or recycling project waste. Two LEED initiatives that directly promote the use of green infrastructure include the rainwater management and heat island reduction credits. An example of a successfully LEED-certified neighborhood development is the 9th and Berks Street transit-oriented development (TOD) in Philadelphia, Pennsylvania, which achieved a Platinum level rating on October 12, 2017.
Another approach to implementing green infrastructure has been developed by the International Living Future Institute. Their Living Community Challenge assesses a community or city in twenty different aspects of sustainability. Notably, the Challenge considers whether the development achieves net positive water and energy uses and utilizes replenishable materials. | 1 | Applied and Interdisciplinary Chemistry |
The Great Oxygenation Event (GOE) is characterized by the disappearance of sulfur isotope mass-independent fractionation (MIF) in the sedimentary records at around 2.45 billion years ago (Ga). The MIF of sulfur isotope (ΔS) is defined by the deviation of measured δS value from the δS value inferred from the measured δS value according to the mass dependent fractionation law. The Great Oxidation Event represented a massive transition of global sulfur cycles. Before the Great Oxidation Event, the sulfur cycle was heavily influenced by the ultraviolet (UV) radiation and the associated photochemical reactions, which induced the sulfur isotope mass-independent fractionation (ΔS ≠ 0). The preservation of sulfur isotope mass-independent fractionation signals requires the atmospheric O lower than 10 of present atmospheric level (PAL). The disappearance of sulfur isotope mass-independent fractionation at ~2.45 Ga indicates that atmospheric pO exceeded 10 present atmospheric level after the Great Oxygenation Event. Oxygen played an essential role in the global sulfur cycles after the Great Oxygenation Event, such as oxidative weathering of sulfides. The burial of pyrite in sediments in turn contributes to the accumulation of free O in Earth's surface environment. | 0 | Theoretical and Fundamental Chemistry |
An open-label clinical study for infantile neuroaxonal dystrophy evaluating long-term evaluation of efficacy, safety, tolerability, and pharmacokinetics of deulinoleate ethyl, which, when taken with food, can protect the neuronal cells from degeneration, started in the Summer 2018. | 1 | Applied and Interdisciplinary Chemistry |
This book consists of the arguments used against the art and Agricolas counter arguments. He explains that mining and prospecting are not just a matter of luck and hard work; there is specialized knowledge that must be learned. A miner should have knowledge of philosophy, medicine, astronomy, surveying, arithmetic, architecture, drawing and law, though few are masters of the whole craft and most are specialists. This section is full of classical references and shows Agricolas classical education to its fullest. The arguments range from philosophical objections to gold and silver as being intrinsically worthless, to the danger of mining to its workers and its destruction of the areas in which it is carried out. He argues that without metals, no other activity such as architecture or agriculture are possible. The dangers to miners are dismissed, noting that most deaths and injuries are caused by carelessness, and other occupations are hazardous too. Clearing forests for timber is advantageous as the land can be farmed. Mines tend to be in mountains and gloomy valleys with little economic value. The loss of food from the forests destroyed can be replaced by purchase from profits, and metals have been placed underground by God and man is right to extract and use them. Finally, Agricola argues that mining is an honorable and profitable occupation. | 1 | Applied and Interdisciplinary Chemistry |
Atomic-scale imaging of graphene, semiconductor surfaces and adsorbed organic molecules were obtained in ultra high-vacuum. Angstrom-resolution images of hydration layers formed on proteins and Young's modulus map of a metal-organic frame work, purple membrane and a lipid bilayer were reported in aqueous solutions. | 0 | Theoretical and Fundamental Chemistry |
Exome sequencing is especially effective in the study of rare Mendelian diseases, because it is an efficient way to identify the genetic variants in all of an individual's genes. These diseases are most often caused by very rare genetic variants that are only present in a tiny number of individuals; by contrast, techniques such as SNP arrays can only detect shared genetic variants that are common to many individuals in the wider population. Furthermore, because severe disease-causing variants are much more likely (but by no means exclusively) to be in the protein coding sequence, focusing on this 1% costs far less than whole genome sequencing but still detects a high yield of relevant variants.
In the past, clinical genetic tests were chosen based on the clinical presentation of the patient (i.e. focused on one gene or a small number known to be associated with a particular syndrome), or surveyed only certain types of variation (e.g. comparative genomic hybridization) but provided definitive genetic diagnoses in fewer than half of all patients. Exome sequencing is now increasingly used to complement these other tests: both to find mutations in genes already known to cause disease as well as to identify novel genes by comparing exomes from patients with similar features. | 1 | Applied and Interdisciplinary Chemistry |
Targeted drug delivery is one of many ways researchers seek to improve drug delivery systems' overall efficacy, safety, and delivery. Within this medical field is a special reversal form of drug delivery called chemotactic drug targeting. By using chemical agents to help guide a drug carrier to a specific location within the body, this innovative approach seeks to improve precision and control during the drug delivery process, decrease the risk of toxicity, and potentially lower the required medical dosage needed. The general components of the conjugates are designed as follows: (i) carrier – regularly possessing promoter effect also on internalization into the cell; (ii) chemotactically active ligands acting on the target cells; (iii) drug to be delivered in a selective way and (iv) spacer sequence which joins drug molecule to the carrier and due to it enzyme labile moiety makes possible the intracellular compartment specific release of the drug. Careful selection of chemotactic component of the ligand not only the chemoattractant character could be expended, however, chemorepellent ligands are also valuable as they are useful to keep away cell populations degrading the conjugate containing the drug. In a larger sense, chemotactic drug-targeting has the potential to improve cancer, inflammation, and arthritis treatment by taking advantage of the difference in environment between the target site and its surroundings. Therefore, this Wikipedia article aims to provide a brief overview of chemotactic drug targeting, the principles behind the approach, possible limitations and advantages, and its application to cancer and inflammation. | 1 | Applied and Interdisciplinary Chemistry |
The functionality of a monomer molecule is the number of functional groups which participate in the polymerization. Monomers with functionality greater than two will introduce branching into a polymer, and the degree of polymerization will depend on the average functionality f per monomer unit. For a system containing N molecules initially and equivalent numbers of two functional groups A and B, the total number of functional groups is Nf.
And the modified Carothers equation is
: , where p equals to | 0 | Theoretical and Fundamental Chemistry |
In order to link sequence read abundance to the expression of a particular gene, transcript sequences are aligned to a reference genome or de novo aligned to one another if no reference is available. The key challenges for alignment software include sufficient speed to permit billions of short sequences to be aligned in a meaningful timeframe, flexibility to recognise and deal with intron splicing of eukaryotic mRNA, and correct assignment of reads that map to multiple locations. Software advances have greatly addressed these issues, and increases in sequencing read length reduce the chance of ambiguous read alignments. A list of currently available high-throughput sequence aligners is maintained by the EBI.
Alignment of primary transcript mRNA sequences derived from eukaryotes to a reference genome requires specialised handling of intron sequences, which are absent from mature mRNA. Short read aligners perform an additional round of alignments specifically designed to identify splice junctions, informed by canonical splice site sequences and known intron splice site information. Identification of intron splice junctions prevents reads from being misaligned across splice junctions or erroneously discarded, allowing more reads to be aligned to the reference genome and improving the accuracy of gene expression estimates. Since gene regulation may occur at the mRNA isoform level, splice-aware alignments also permit detection of isoform abundance changes that would otherwise be lost in a bulked analysis.
De novo assembly can be used to align reads to one another to construct full-length transcript sequences without use of a reference genome. Challenges particular to de novo assembly include larger computational requirements compared to a reference-based transcriptome, additional validation of gene variants or fragments, and additional annotation of assembled transcripts. The first metrics used to describe transcriptome assemblies, such as N50, have been shown to be misleading and improved evaluation methods are now available. Annotation-based metrics are better assessments of assembly completeness, such as contig reciprocal best hit count. Once assembled de novo, the assembly can be used as a reference for subsequent sequence alignment methods and quantitative gene expression analysis. | 1 | Applied and Interdisciplinary Chemistry |
Pyroelectric materials have been used to generate large electric fields necessary to steer deuterium ions in a nuclear fusion process. This is known as pyroelectric fusion. | 0 | Theoretical and Fundamental Chemistry |
After hits are identified from a high throughput screen, the hits are confirmed and evaluated using the following methods:
* Confirmatory testing: compounds that were found active against the selected target are re-tested using the same assay conditions used during the HTS to make sure that the activity is reproducible.
* Dose response curve: the compound is tested over a range of concentrations to determine the concentration that results in half maximal binding or activity (IC or EC value respectively).
* Orthogonal testing: confirmed hits are assayed using a different assay which is usually closer to the target physiological condition or using a different technology.
* Secondary screening: confirmed hits are tested in a functional cellular assay to determine efficacy.
* Synthetic tractability: medicinal chemists evaluate compounds according to their synthesis feasibility and other parameters such as up-scaling or cost of goods.
* Biophysical testing: nuclear magnetic resonance (NMR), isothermal titration calorimetry (ITC), dynamic light scattering (DLS), surface plasmon resonance (SPR), dual polarisation interferometry (DPI), microscale thermophoresis (MST) are commonly used to assess whether the compound binds effectively to the target, the kinetics, thermodynamics, and stoichiometry of binding, any associated conformational change and to rule out promiscuous binding.
* Hit ranking and clustering: Confirmed hit compounds are then ranked according to the various hit confirmation experiments.
* Freedom to operate evaluation: hit structures are checked in specialized databases to determine if they are patentable. | 1 | Applied and Interdisciplinary Chemistry |
In crystallography, goniometers are used for measuring angles between crystal faces. They are also used in X-ray diffraction to rotate the samples. The groundbreaking investigations of physicist Max von Laue and colleagues into the atomic structure of crystals in 1912 involved a goniometer. | 0 | Theoretical and Fundamental Chemistry |
*Ferrocene: bis(η-cyclopentadienyl)iron
*Uranocene: bis(η-1,3,5,7-cyclooctatetraene)uranium
*W(CO)(PPr)(η-H): the first compound to be synthesized with a dihydrogen ligand.
*IrCl(CO)[P(CH)](η-O): the dioxygen derivative which forms reversibly upon oxygenation of Vaska's complex. | 0 | Theoretical and Fundamental Chemistry |
Phosgene was synthesized by the Cornish chemist John Davy (1790–1868) in 1812 by exposing a mixture of carbon monoxide and chlorine to sunlight. He named it "phosgene" from Greek (, light) and (, to give birth) in reference of the use of light to promote the reaction. It gradually became important in the chemical industry as the 19th century progressed, particularly in dye manufacturing. | 0 | Theoretical and Fundamental Chemistry |
The term was first coined by Russian chemist V. Pletz in 1935 and originally mistranslated in some articles as plosophore. Also of note is an auxoexplose concept (similar to chromophore and auxochrome concept), which is a group that modifies the explosive capability of the molecule.
The term explosophore has been used more frequently after its use in books such as Organic Chemistry of Explosives by J. Agrawal and R. Hodgson (2007)'. | 0 | Theoretical and Fundamental Chemistry |
Plants growing at high light invest less of their biomass in leaves and stems, and more in roots. They grow faster, per unit leaf area (ULR) and per unit total plant mass (RGR), and therefore high-light grown plants generally have more biomass. They have shorter internodes, with more stem biomass per unit stem length, but plant height is often not strongly affected. High-light plants do show more branches or tillers. | 0 | Theoretical and Fundamental Chemistry |
In developed urban areas, naturally occurring depressions where storm water would pool are typically covered by impermeable surfaces, such as asphalt, pavement, or concrete, and are leveled for automobile use. Stormwater is directed into storm drains which may cause overflows of combined sewer systems or pollution, erosion, or flooding of waterways receiving the storm water runoff. Redirected stormwater is often warmer than the groundwater normally feeding a stream, and has been linked to upset in some aquatic ecosystems primarily through the reduction of dissolved oxygen (DO). Stormwater runoff is also a source of a wide variety of pollutants washed off hard or compacted surfaces during rain events. These pollutants may include volatile organic compounds, pesticides, herbicides, hydrocarbons and trace metals. | 1 | Applied and Interdisciplinary Chemistry |
oligo - oligodeoxyribonucleotide - oligonucleotide - oligosaccharide-transporting ATPase - oncogene - oncovirus - open reading frame - operator - operon - origin of replication - ornithine(lysine) transaminase - osteomimicry | 1 | Applied and Interdisciplinary Chemistry |
In some simplest cases, the state of condensed particles can be described with a nonlinear Schrödinger equation, also known as Gross–Pitaevskii or Ginzburg–Landau equation. The validity of this approach is actually limited to the case of ultracold temperatures, which fits well for the most alkali atoms experiments.
This approach originates from the assumption that the state of the BEC can be described by the unique wavefunction of the condensate . For a system of this nature, is interpreted as the particle density, so the total number of atoms is
Provided essentially all atoms are in the condensate (that is, have condensed to the ground state), and treating the bosons using mean-field theory, the energy (E) associated with the state is:
Minimizing this energy with respect to infinitesimal variations in , and holding the number of atoms constant, yields the Gross–Pitaevski equation (GPE) (also a non-linear Schrödinger equation):
where:
In the case of zero external potential, the dispersion law of interacting Bose–Einstein-condensed particles is given by so-called Bogoliubov spectrum (for ):
The Gross-Pitaevskii equation (GPE) provides a relatively good description of the behavior of atomic BEC's. However, GPE does not take into account the temperature dependence of dynamical variables, and is therefore valid only for .
It is not applicable, for example, for the condensates of excitons, magnons and photons, where the critical temperature is comparable to room temperature. | 0 | Theoretical and Fundamental Chemistry |
A major issue is how many embryos should be transferred, since placement of multiple embryos carries a risk of multiple pregnancy. While the past physicians placed multiple embryos to increase the chance of pregnancy, this approach has fallen out of favor. Professional societies, and legislatures in many countries, have issued guidelines or laws to curtail the practice. There is low to moderate evidence that making a double embryo transfer during one cycle achieves a higher live birth rate than a single embryo transfer; but making two single embryo transfers in two cycles has the same live birth rate and would avoid multiple pregnancies.
The appropriate number of embryos to be transferred depends on the age of the woman, whether it is the first, second or third full IVF cycle attempt and whether there are top-quality embryos available. According to a guideline from The National Institute for Health and Care Excellence (NICE) in 2013, the number of embryos transferred in a cycle should be chosen as in following table: | 1 | Applied and Interdisciplinary Chemistry |
Compared to concentration dependent bactericidal antibiotics like aminoglycosides and fluoroquinolones, the antibacterial activity of β-lactam antibiotics are generally more time dependent. Unlike the former, when piperacillin-tazobactam concentrations exceed minimum inhibitory concentrations (MIC) of a pathogen by five folds, the exponential relationship between concentration and activity begins to level off. Otherwise, piperacillin-tazobactam bactericidal efficacy is shown to consist of a strong association with the duration of time the concentration exceeds minimum inhibitory concentrations (T). When the T in the serum equates to 60–70% of the frequency for drug administration (dosing interval), maximal activity is achieved against Gram-negative bacteria, while for Gram-positive bacteria it occurs at around 40–50%.
Within a 24-hour period in one clinical study, a T surpassing 60% was found for piperacillin-susceptible bacteria including Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus in two dosing regimes (4.5 g every 8 hours and 3.375 g every 8 hours).
The evidence for this was obtained through Monte Carlo experiments procured by a special program (OPTAMA), where for several different scenarios (e.g. hospital acquired infections, secondary peritonitis, skin or soft tissue infections), the probability of attaining those figures were in the ranges of 85–95% and 90–89% respectively for the two regimes. In addition, two similar dosing regimes (3.375 g and 4.5 g every 6 hours) both had lower chances of reaching the 90% T threshold compared to the 50% threshold against hospital acquired pneumonia pathogens.
The optimization of piperacillin-tazobactam drug efficiency has been covered by various studies, limiting the focus down to two types of infusions; continuous and intermittent. A comparison using the two administration methods under the same dosage regime of 13.5 g per day highlighted no major differences when treating complex intra-abdominal infections. Furthermore, a follow-up analysis of this trial deduced that both methods of administration lead to higher concentrations compared to the MIC of the pathogens that were used. Similar results are found in a study where a select number of β-lactam susceptible pathogens consisting of Enterococcus faecalis, Klebsiella pneumoniae and Citrobacter freundii were used to test a ~10 g every 24 hour dosing interval for continuous infusion.
Organisms with a piperacillin-tazobactam MIC values equal to 32 or less than 16 μg/mL lead to 50% T when extended-interval intermittent administrations under two different dosing intervals (8.1 g and 6.75 g every 12 hours) were used against them. The pharmacodynamic target attainments corresponding to pathogens with MIC values of 16 μg/mL are found to reach 92% when a more traditional 4 hour dosing regime is utilized to administer at irregular intervals. One study using the Monte Carlo simulation produced contradicting results to the previous studies, deducing that inadequate pharmacodynamic targets were achieved (T > 50%) for similar ESBL-producing bacteria, applying to both continuous and high dosage intermittent infusion. | 0 | Theoretical and Fundamental Chemistry |
In physics, emission is the process by which a higher energy quantum mechanical state of a particle becomes converted to a lower one through the emission of a photon, resulting in the production of light. The frequency of light emitted is a function of the energy of the transition.
Since energy must be conserved, the energy difference between the two states equals the energy carried off by the photon. The energy states of the transitions can lead to emissions over a very large range of frequencies. For example, visible light is emitted by the coupling of electronic states in atoms and molecules (then the phenomenon is called fluorescence or phosphorescence). On the other hand, nuclear shell transitions can emit high energy gamma rays, while nuclear spin transitions emit low energy radio waves.
The emittance of an object quantifies how much light is emitted by it. This may be related to other properties of the object through the Stefan–Boltzmann law.
For most substances, the amount of emission varies with the temperature and the spectroscopic composition of the object, leading to the appearance of color temperature and emission lines. Precise measurements at many wavelengths allow the identification of a substance via emission spectroscopy.
Emission of radiation is typically described using semi-classical quantum mechanics: the particles energy levels and spacings are determined from quantum mechanics, and light is treated as an oscillating electric field that can drive a transition if it is in resonance with the systems natural frequency. The quantum mechanics problem is treated using time-dependent perturbation theory and leads to the general result known as Fermi's golden rule. The description has been superseded by quantum electrodynamics, although the semi-classical version continues to be more useful in most practical computations. | 0 | Theoretical and Fundamental Chemistry |
An important reaction is the acid/base equilibrium, yielding transition metal nitrite complexes:
:[LMNO] + 2OH LMNO + HO
This equilibrium serves to confirm that the linear nitrosyl ligand is, formally, NO, with nitrogen in the oxidation state +3
:NO + 2 OH NO + HO
Since nitrogen is more electronegative than carbon, metal-nitrosyl complexes tend to be more electrophilic than related metal carbonyl complexes. Nucleophiles often add to the nitrogen. The nitrogen atom in bent metal nitrosyls is basic, thus can be oxidized, alkylated, and protonated, e.g.:
:(PhP)(CO)ClOsNO + HCl → (PhP)(CO)ClOsN(H)O
In rare cases, NO is cleaved by metal centers:
: CpNbMe + NO → Cp(Me)Nb(O)NMe
: 2 Cp(Me)Nb(O)NMe → 2 CpNb(O)Me + ½MeN=NMe | 0 | Theoretical and Fundamental Chemistry |
Wursters blue is the trivial name given to the radical cation of the colorless chemical N,N,N′,N′-tetramethyl-p'-phenylenediamine, also known as TMPD. This is an easily oxidised phenylenediamine, which loses two electrons in one-electron oxidation steps; the radical cation is a characteristic blue-violet colour, which gives the compound part of its name. The remaining part of its name comes from its discoverer, the German chemist Casimir Wurster (7 August 1854 – 29 November 1913).
The hydrochloride salt of TMPD finds use as a redox indicator in the oxidase test and is also used in electron transport chain analysis as it is capable of donating electrons to cytochrome c.
The midpoint potential for titration of the first electron is given as 0.276 V vs Standard hydrogen electrode, and this transition is useful in potentiometric titrations as both a redox mediator and indicator. The two electron-oxidized colourless p-quinone-diiminium cation is unstable in aqueous solutions, therefore highly oxidizing conditions should be avoided in titrations relying on TMPD, or reached only during the final stage of the titration. The second oxidation step is not well separated from the first on the redox scale, so some instability will be encountered on the oxidizing side of 0.276, and it is impossible to prepare pure aqueous solutions of Wurster's Blue due to its dismutation to the unstable di-iminium ion and TMPD. | 0 | Theoretical and Fundamental Chemistry |
Professor Reddi discovered that bone induction is a sequential multistep cascade involving chemotaxis, mitosis, and differentiation. Early studies in his laboratory at the University of Chicago and National Institutes of Health unraveled the sequence of events involved in bone matrix-induce bone morphogenesis. Using a battery of in vitro and in vivo bioassays for bone formation, a systematic study was undertaken in his laboratory to isolate and purify putative bone morphogenetic proteins. Reddi and colleagues were the first to identify BMPs as pleiotropic regulators, acting in a concentration dependent manner. They demonstrated first that BMPs bind the extracellular matrix, are present at the apical ectodermal ridge in the developing limb bud, are chemotactic for human monocytes, and have neurotropic potential. His laboratory pioneered the use of BMPs in regenerative orthopedics and dentistry. | 1 | Applied and Interdisciplinary Chemistry |
The melting point of iron is experimentally well defined for pressures less than 50 GPa.
For greater pressures, published data (as of 2007) put the γ-ε-liquid triple point at pressures that differ by tens of gigapascals and 1000 K in the melting point. Generally speaking, molecular dynamics computer simulations of iron melting and shock wave experiments suggest higher melting points and a much steeper slope of the melting curve than static experiments carried out in diamond anvil cells.
The melting and boiling points of iron, along with its enthalpy of atomization, are lower than those of the earlier group 3d elements from scandium to chromium, showing the lessened contribution of the 3d electrons to metallic bonding as they are attracted more and more into the inert core by the nucleus; however, they are higher than the values for the previous element manganese because that element has a half-filled 3d subshell and consequently its d-electrons are not easily delocalized. This same trend appears for ruthenium but not osmium. | 1 | Applied and Interdisciplinary Chemistry |
By the late 18th century, the useful practices of engineering and technology began to influence philosophical explanations of the composition of matter. Those who speculated on the ultimate nature of matter began to verify their "thought experiments" with some repeatable demonstrations, when they could.
Ragusan polymath Roger Boscovich (1711–1787) provided the first general mathematical theory of atomism based on the ideas of Newton and Leibniz, but transforming them so as to provide a programme for atomic physics. | 1 | Applied and Interdisciplinary Chemistry |
Upon graduation, Floriana completed her postdoctoral research in Molecular Magnetism with Dr. Jean-Pascal Sutter at Institut de Chimie de la Matière Condensée de Bordeauxwith (ICMCB), France and also as a visiting Deutscher Akademischer Austauschdienst (DAAD) Fellow at University of Heidelberg, Germany. She then received a Marie Curie Individual Fellowship at University of Warwick to work in supramolecular chemistry before moving to University of Manchester in 2003 as a Researcher. She was later promoted to the position of Senior Researcher. She is currently part of the Molecular Magnetism group at University of Manchester, working along with Prof. David Collison, Nicholas F. Chilton, Grigore Timco and Richard Winpenny.
Floriana's research in general is based on inorganic chemistry and magnetochemistry, specifically on molecular magnetism, EPR spectroscopy and quantum computing. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, an anti-Bredt molecule is a bridged molecule with a double bond at the bridgehead. Bredts rule is the empirical observation that such molecules can only form in large enough ring systems. For example, two of the following norbornene isomers violate Bredts rule, and are too unstable to prepare:
The rule is named after Julius Bredt, who first discussed it in 1902 and codified it in 1924.
Bredts rule results from geometric strain: a double bond at a bridgehead atom necessarily must be trans in at least one ring. For small rings (fewer than eight atoms), a trans alkene cannot be achieved without substantial ring and angle strain (the p orbitals are improperly aligned for a π bond). Bredts rule also applies to carbocations and, to a lesser degree, via free radicals, because these intermediates also prefer a planar geometry with 120° angles and sp hybridization. It generally does not apply to hypervalent heteroatoms, although they are commonly written with a formal double bond.
There has been an active research program to seek anti-Bredt molecules, with success quantified in S, the non-bridgehead atom count. The above norbornene system has S = 5, and Fawcett originally postulated that stability required S ≥ 9 in bicyclic systems and S ≥ 11 in tricyclic systems. For bicyclic systems examples now indicate a limit of S ≥ 7, with several such compounds having been prepared. Bridgehead double bonds can be found in some natural products.
Bredt's rule can predict the viability of competing elimination reactions in a bridged system. For example, the metal alkyl complexes usually decompose quickly via beta elimination, but Bredt strain prevents tetranorbornyl complexes from doing so. Bicyclo[5.3.1]undecane-11-one-1-carboxylic acid undergoes decarboxylation on heating to 132 °C, but the similar compound bicyclo[2.2.1]heptan-7-one-1-carboxylic acid remains stable beyond 500 °C, because the decarboxylation proceeds through an anti-Bredt enol.
Bredt's rule may also prevent a molecule from resonating with certain valence bond isomers. 2-Quinuclidonium does not exhibit the usual reactivity of an amide, because the iminoether tautomer would violate the rule. | 0 | Theoretical and Fundamental Chemistry |
Drospirenone is marketed in combination with an estrogen under a variety of brand names throughout the world. Among others, it is marketed in combination with ethinylestradiol under the brand names Yasmin and Yaz, in combination with estetrol under the brand name Nextstellis, and in combination with estradiol under the brand name Angeliq. | 0 | Theoretical and Fundamental Chemistry |
The main use of pyridine is as a precursor to the herbicides paraquat and diquat. The first synthesis step of insecticide chlorpyrifos consists of the chlorination of pyridine. Pyridine is also the starting compound for the preparation of pyrithione-based fungicides. Cetylpyridinium and laurylpyridinium, which can be produced from pyridine with a Zincke reaction, are used as antiseptic in oral and dental care products. Pyridine is easily attacked by alkylating agents to give N-alkylpyridinium salts. One example is cetylpyridinium chloride.
It is also used in the textile industry to improve network capacity of cotton. | 0 | Theoretical and Fundamental Chemistry |
Gap junctions are the main site of cell-cell signaling or communication that allow small molecules to diffuse between adjacent cells. In vertebrates, gap junctions are composed of transmembrane proteins called connexins. They form hexagonal pores or channels through which ions, sugars, and other small molecules can pass. Each pore is made of 12 connexin molecules; 6 form a hemichannel on one cell membrane and interact with a hemichannel on an adjacent cell membrane. The permeability of these junctions is regulated by many factors including pH and Ca concentration. | 1 | Applied and Interdisciplinary Chemistry |
The values of I, I, R, and R are dependent upon the physical size of the solar cell. In comparing otherwise identical cells, a cell with twice the junction area of another will, in principle, have double the I and I because it has twice the area where photocurrent is generated and across which diode current can flow. By the same argument, it will also have half the R of the series resistance related to vertical current flow; however, for large-area silicon solar cells, the scaling of the series resistance encountered by lateral current flow is not easily predictable since it will depend crucially on the grid design (it is not clear what "otherwise identical" means in this respect). Depending on the shunt type, the larger cell may also have half the R because it has twice the area where shunts may occur; on the other hand, if shunts occur mainly at the perimeter, then R will decrease according to the change in circumference, not area.
Since the changes in the currents are the dominating ones and are balancing each other, the open-circuit voltage is practically the same; V starts to depend on the cell size only if R becomes too low. To account for the dominance of the currents, the characteristic equation is frequently written in terms of current density, or current produced per unit cell area:
where
*J, current density (ampere/cm)
*J, photogenerated current density (ampere/cm)
*J, reverse saturation current density (ampere/cm)
*r, specific series resistance (Ω·cm)
*r, specific shunt resistance (Ω·cm).
This formulation has several advantages. One is that since cell characteristics are referenced to a common cross-sectional area they may be compared for cells of different physical dimensions. While this is of limited benefit in a manufacturing setting, where all cells tend to be the same size, it is useful in research and in comparing cells between manufacturers. Another advantage is that the density equation naturally scales the parameter values to similar orders of magnitude, which can make numerical extraction of them simpler and more accurate even with naive solution methods.
There are practical limitations of this formulation. For instance, certain parasitic effects grow in importance as cell sizes shrink and can affect the extracted parameter values. Recombination and contamination of the junction tend to be greatest at the perimeter of the cell, so very small cells may exhibit higher values of J or lower values of R than larger cells that are otherwise identical. In such cases, comparisons between cells must be made cautiously and with these effects in mind.
This approach should only be used for comparing solar cells with comparable layout. For instance, a comparison between primarily quadratical solar cells like typical crystalline silicon solar cells and narrow but long solar cells like typical thin film solar cells can lead to wrong assumptions caused by the different kinds of current paths and therefore the influence of, for instance, a distributed series resistance contribution to r. Macro-architecture of the solar cells could result in different surface areas being placed in any fixed volume - particularly for thin film solar cells and flexible solar cells which may allow for highly convoluted folded structures. If volume is the binding constraint, then efficiency density based on surface area may be of less relevance. | 0 | Theoretical and Fundamental Chemistry |
Jean Rey (c. 1583 – c. 1645) or (in English) John Rey was a French physician and chemist.
Born in Le Bugue, in the Périgord (Dordogne département), he studied medicine at the University of Montpellier. He practised medicine in his native town and corresponded with René Descartes and Marin Mersenne.
He discovered that the weight of lead and tin increases when they are calcinated, and attributed this phenomenon to the weight of air, which he believed to become denser when heated (Essays, 1630). He explained the greater weight of calcinated lead and tin by supposing that calcination involves the incorporation of air in the metal. This hypothesis would later be confirmed by Antoine Lavoisier, over a century later in 1789.
His discovery of the weight of air also made possible the invention of the barometer by Evangelista Torricelli in 1643. He also developed a device called a "Thermoscope", a precursor of the thermometer.
Jean Rey died in Le Bugue, where he had lived all his life. The exact date of his death is disputed. | 1 | Applied and Interdisciplinary Chemistry |
A RecQ helicase is one of a family of helicases that helps reduce sister chromatid exchange during meiosis to lower mutation rates. RecQ helicases are found in many organisms, ranging from E. coli to humans. One of these helicases, the Bloom syndrome protein, contains an arginine finger which assists in its hydrolysis of ATP. In humans, the arginine finger of the Bloom syndrome protein is Arg982. The RecQ helicase, along with most proteins containing arginine fingers, is inhibited by sodium orthovanadate, which interferes with the arginine finger residue. | 1 | Applied and Interdisciplinary Chemistry |
Electrodeionization (EDI) is a water treatment technology that utilizes DC power, ion exchange membranes, and ion exchange resin to deionize water. EDI is typically employed as a polishing treatment following reverse osmosis (RO), and is used in the production of ultrapure water. It differs from other RO polishing methods, like chemically regenerated mixed beds, by operating continuously without chemical regeneration.
Electrodeionization can be used to produce high purity water, reaching electrical resistivity values as high as 18.2 MΩ/cm.
Electrodeionization (EDI) integrates three distinct processes:
# Electrolysis: A continuous DC current directs positive and negative ions toward electrodes with opposing electrical charges. The electrical potential draws anions and cations from diluting chambers, through cation or anion exchange membranes, into concentrating chambers.
# Ion exchange: An ion exchange resin fills the diluting chambers. As water flows through the resin bed, cations and anions become affixed to resin sites.
# Electrochemical regeneration: Unlike chemically regenerated mixed beds, EDI accomplishes regeneration through water splitting induced by the continuous electric current. Water splits from H and OH to effectively regenerate the resin without the need for external chemical additives.
EDI is sometimes labeled "continuous electrodeionization" (CEDI) because the electric current continually regenerates the ion exchange resin mass. | 0 | Theoretical and Fundamental Chemistry |
DGGE of small ribosomal subunit coding genes was first described by Gerard Muyzer, while he was Post-doc at Leiden University, and has become a widely used technique in microbial ecology.
PCR amplification of DNA extracted from mixed microbial communities with PCR primers specific for 16S rRNA gene fragments of bacteria and archaea, and 18S rRNA gene fragments of eukaryotes results in mixtures of PCR products.
Because these amplicons all have the same length, they cannot be separated from each other by agarose gel electrophoresis. However, sequence variations (i.e. differences in GC content and distribution) between different microbial rRNAs result in different denaturation properties of these DNA molecules.
Hence, DGGE banding patterns can be used to visualize variations in microbial genetic diversity and provide a rough estimate of the richness of abundance of predominant microbial community members. This method is often referred to as community fingerprinting. Recently, several studies have shown that DGGE of functional genes (e.g. genes involved in sulfur reduction, nitrogen fixation, and ammonium oxidation) can provide information about microbial function and phylogeny simultaneously. For instance, Tabatabaei et al. (2009) applied DGGE and managed to reveal the microbial pattern during the anaerobic fermentation of palm oil mill effluent (POME) for the first time. | 1 | Applied and Interdisciplinary Chemistry |
Solvent extraction – electrowinning (often referred to as "SX–EW") is a process frequently applied for recovering copper from low-grade and/or oxidised copper ore. It involves leaching the copper from the ore using an acidic solution, collecting the leach liquor containing the copper and contacting this solution with an organic extractant. The copper ions in the leach liquor transfer to the organic extractant, moving from a relatively low concentration to a higher concentration. The extractant is subsequently brought into contact with a second aqueous solution that is more acid than the original leach liquor, and the copper again moves, this time from the extractant into the aqueous solution. The result is an acidic solution of copper in which the copper concentration is high enough for it to be recovered by electrowinning. The solution destined for electrowinning is known as the electrolyte.
The electrolyte solution usually contains traces of the organic extractant that exist as tiny droplets within it. These need to be removed before the copper can be recovered in the electrowinning process, as the presence of minimal amounts of the extractant can cause difficulties by stripping and damaging the cathodes with a subsequent loss of cathode copper quality.
In the late 1980s, MIM built an SX–EW plant at Mount Isa to recover copper leached from low grade ore stockpiled while mining its Black Rock open cut in the 1960s. In a world first, a Jameson Cell was used to clean the electrolyte solution by removing the remaining organic solvent. This replaced the sand filters traditionally used.
The cell was 3 m high, twice the height of the early Cells used in MIM's lead–zinc concentrators, as it was thought that additional residence time would enhance recovery. It used a single downcomer. The downcomer was used to contact the electrolyte with air and the droplets of the organic extractant attached themselves to the air bubbles created in the downcomer.
After some initial modifications to the orifice size, the Cell was able to remove 70–90% of the entrained organic extractant. | 1 | Applied and Interdisciplinary Chemistry |
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