text
stringlengths 105
4.57k
| label
int64 0
1
| label_text
stringclasses 2
values |
|---|---|---|
Since late 2000s, propanephosphonic acid anhydride, sold commercially under various names such as "T3P", has become a useful reagent for amide bond formation in commercial applications. It converts the oxygen of the carboxylic acid into a leaving group, whose peptide-coupling byproducts are water-soluble and can be easily washed away. In a performance comparison between propanephosphonic acid anhydride and other peptide coupling reagents for the preparation of a nonapeptide drug, it was found that this reagent was superior to other reagents with regards to yield and low epimerization. | 1 | Applied and Interdisciplinary Chemistry |
Bulkier than IMes is the NHC ligand IPr (CAS 244187-81-3). IPr features diisopropylphenyl in place of the mesityl substituents.
Some variants of IMes and IPr have saturated backbones, two such ligands are SIMes and SIPr. They are prepared by alkylation of substituted anilines with dibromoethane followed by ring closure and dehydrohalogenation of the dihydroimidazolium salt. | 0 | Theoretical and Fundamental Chemistry |
High levels of molybdenum can interfere with the body's uptake of copper, producing copper deficiency. Molybdenum prevents plasma proteins from binding to copper, and it also increases the amount of copper that is excreted in urine. Ruminants that consume high levels of molybdenum suffer from diarrhea, stunted growth, anemia, and achromotrichia (loss of fur pigment). These symptoms can be alleviated by copper supplements, either dietary or injection. The effective copper deficiency can be aggravated by excess sulfur.
Copper reduction or deficiency can also be deliberately induced for therapeutic purposes by the compound ammonium tetrathiomolybdate, in which the bright red anion tetrathiomolybdate is the copper-chelating agent. Tetrathiomolybdate was first used therapeutically in the treatment of copper toxicosis in animals. It was then introduced as a treatment in Wilson's disease, a hereditary copper metabolism disorder in humans; it acts both by competing with copper absorption in the bowel and by increasing excretion. It has also been found to have an inhibitory effect on angiogenesis, potentially by inhibiting the membrane translocation process that is dependent on copper ions. This is a promising avenue for investigation of treatments for cancer, age-related macular degeneration, and other diseases that involve a pathologic proliferation of blood vessels.
In some grazing livestock, most strongly in cattle, molybdenum excess in the soil of pasturage can produce scours (diarrhea) if the pH of the soil is neutral to alkaline; see teartness. | 1 | Applied and Interdisciplinary Chemistry |
The generation of CIDNP in a typical photochemical system (target + photosensitizer, flavin in this example) is a cyclic photochemical process shown schematically in Figure 1. The chain of reactions is initiated by a blue light photon, which excites the flavin mononucleotide (FMN) photosensitizer to the singlet excited state. The fluorescence quantum yield of this state is rather low, and approximately half of the molecules undergo intersystem crossing into the long-lived triplet state. Triplet FMN has a remarkable electron affinity. If a molecule with a low ionization potential (e.g. phenols, polyaromatics) is present in the system, the diffusion-limited electron transfer reaction forms a spin-correlated triplet electron transfer state – a radical pair. The kinetics are complicated and may involve multiple protonations and deprotonations, and hence exhibit pH dependence.
The radical pair may either cross over to a singlet electron state and then recombine, or separate and perish in side reactions. The relative probability of these two pathways for a given radical pair depends on the nuclear spin state and leads to the nuclear spin state sorting and observable nuclear polarization. | 0 | Theoretical and Fundamental Chemistry |
One of the typical uses of additive effect is to detect synergy. Additive effect can be considered as the baseline effect in methods of determining the presence of synergistic effect between two or more drugs. Synergistic effect is similar to additive effect. The only difference is it has a combination effect greater than additive effect. To be brief, synergy can produce an effect of 2 + 2 > 4 when drugs are used in combination. The combination of angiotensin II receptor antagonist (ARB), Candesartan-cilexetil , and angiotensin-converting enzyme inhibitor (ACEI), Ramipril, demonstrates a synergistic effect in reducing systolic blood pressure. | 1 | Applied and Interdisciplinary Chemistry |
Cation-exchange capacity (CEC) is a measure of how many cations can be retained on soil particle surfaces. Negative charges on the surfaces of soil particles bind positively-charged atoms or molecules (cations), but allow these to exchange with other positively charged particles in the surrounding soil water. This is one of the ways that solid materials in soil alter the chemistry of the soil. CEC affects many aspects of soil chemistry, and is used as a measure of soil fertility, as it indicates the capacity of the soil to retain several nutrients (e.g. K, NH, Ca) in plant-available form. It also indicates the capacity to retain pollutant cations (e.g. Pb). | 0 | Theoretical and Fundamental Chemistry |
Similar to Cu(I) chemistry mentioned above, Rh(I) complexes can also transmetallate with arylboronic esters to get aryl rhodium intermediates, to which CO is inserted giving carboxylic acids. Later, Iwasawa et al. described C-H carboxylation strategy. Rh(I) undergoes oxidative addition to aryl C-H bond followed by transmetallation with alkyl aluminum species. Ar-Rh(I) regenerates by reductive elimination releasing methane. Ar-Rh(I) attacks CO then transmetallates with aryl boronic acid to release the boronic acid of product, giving final carboxylic acid by hydrolysis. Directed and non-directed versions are both achieved.
Iwasawa and co-workers developed Rh(I) catalyzed carbonation reaction initiated by Rh-H insertion to vinylarenes. In order to regenerate reactive Rh-H after nucleophilic addition to CO, photocatalytic proton-coupled electron transfer approach was adopted. In this system, excess amount of diethylpropylethylamine works as sacrificial electron donor (Scheme 5). | 0 | Theoretical and Fundamental Chemistry |
While the cytosolic fermentation pathway of lactate is well established, a novel feature of the lactate shuttle hypothesis is the oxidation of lactate in the mitochondria. Baba and Sherma (1971) were the first to identify the enzyme lactate dehydrogenase (LDH) in the mitochondrial inner membrane and matrix of rat skeletal and cardiac muscle. Subsequently, LDH was found in the rat liver, kidney, and heart mitochondria. It was also found that lactate could be oxidized as quickly as pyruvate in rat liver mitochondria. Because lactate can either be oxidized in the mitochondria (back to pyruvate for entry into the Krebs’ cycle, generating NADH in the process), or serve as a gluconeogenic precursor, the intracellular lactate shuttle has been proposed to account for the majority of lactate turnover in the human body (as evidenced by the slight increases in arterial lactate concentration). Brooks et al. confirmed this in 1999, when they found that lactate oxidation exceeded that of pyruvate by 10-40% in rat liver, skeletal, and cardiac muscle.
In 1990, Roth and Brooks found evidence for the facilitated transporter of lactate, monocarboxylate transport protein (MCT), in the sarcolemma vesicles of rat skeletal muscle. Later, MCT1 was the first of the MCT super family to be identified. The first four MCT isoforms are responsible for pyruvate/lactate transport. MCT1 was found to be the predominant isoform in many tissues including skeletal muscle, neurons, erythrocytes, and sperm. In skeletal muscle, MCT1 is found in the membranes of the sarcolemma, peroxisome, and mitochondria. Because of the mitochondrial localization of MCT (to transport lactate into the mitochondria), LDH (to oxidize the lactate back to pyruvate), and COX (cytochrome c oxidase, the terminal element of the electron transport chain), Brooks et al. proposed the possibility of a mitochondrial lactate oxidation complex in 2006. This is supported by the observation that the ability of muscle cells to oxidize lactate was related to the density of mitochondria. Furthermore, it was shown that training increases MCT1 protein levels in skeletal muscle mitochondria, and that corresponded with an increase in the ability of muscle to clear lactate from the body during exercise. The affinity of MCT for pyruvate is greater than lactate, however two reactions will ensure that lactate will be present in concentrations that are orders of magnitude greater than pyruvate: first, the equilibrium constant of LDH(3.6 x 104) greatly favors the formation of lactate. Secondly, the immediate removal of pyruvate from the mitochondria (either via the Krebs’ cycle or gluconeogenesis) ensures that pyruvate is not present in great concentrations within the cell.
LDH isoenzyme expression is tissue-dependent. It was found that in rats, LDH-1 was the predominant form in the mitochondria of myocardium, but LDH-5 was predominant in the liver mitochondria. It is suspected that this difference in isoenzyme is due to the predominant pathway the lactate will take - in liver it is more likely to be gluconeogenesis, whereas in the myocardium it is more likely to be oxidation. Despite these differences, it is thought that the redox state of the mitochondria dictates the ability of the tissues to oxidize lactate, not the particular LDH isoform. | 1 | Applied and Interdisciplinary Chemistry |
Since the original discovery by Dan Shechtman, hundreds of quasicrystals have been reported and confirmed. Quasicrystals are found most often in aluminium alloys (Al–Li–Cu, Al–Mn–Si, Al–Ni–Co, Al–Pd–Mn, Al–Cu–Fe, Al–Cu–V, etc.), but numerous other compositions are also known (Cd–Yb, Ti–Zr–Ni, Zn–Mg–Ho, Zn–Mg–Sc, In–Ag–Yb, Pd–U–Si, etc.).
Two types of quasicrystals are known. The first type, polygonal (dihedral) quasicrystals, have an axis of 8-, 10-, or 12-fold local symmetry (octagonal, decagonal, or dodecagonal quasicrystals, respectively). They are periodic along this axis and quasiperiodic in planes normal to it. The second type, icosahedral quasicrystals, are aperiodic in all directions. Icosahedral quasicrystals have a three dimensional quasiperiodic structure and possess fifteen 2-fold, ten 3-fold and six 5-fold axes in accordance with their icosahedral symmetry.
Quasicrystals fall into three groups of different thermal stability:
* Stable quasicrystals grown by slow cooling or casting with subsequent annealing,
* Metastable quasicrystals prepared by melt spinning, and
* Metastable quasicrystals formed by the crystallization of the amorphous phase.
Except for the Al–Li–Cu system, all the stable quasicrystals are almost free of defects and disorder, as evidenced by X-ray and electron diffraction revealing peak widths as sharp as those of perfect crystals such as Si. Diffraction patterns exhibit fivefold, threefold, and twofold symmetries, and reflections are arranged quasiperiodically in three dimensions.
The origin of the stabilization mechanism is different for the stable and metastable quasicrystals. Nevertheless, there is a common feature observed in most quasicrystal-forming liquid alloys or their undercooled liquids: a local icosahedral order. The icosahedral order is in equilibrium in the liquid state for the stable quasicrystals, whereas the icosahedral order prevails in the undercooled liquid state for the metastable quasicrystals.
A nanoscale icosahedral phase was formed in Zr-, Cu- and Hf-based bulk metallic glasses alloyed with noble metals.
Most quasicrystals have ceramic-like properties including high thermal and electrical resistance, hardness and brittleness, resistance to corrosion, and non-stick
properties. Many metallic quasicrystalline substances are impractical for most applications due to their thermal instability; the Al–Cu–Fe ternary system and the Al–Cu–Fe–Cr and Al–Co–Fe–Cr quaternary systems, thermally stable up to 700 °C, are notable exceptions.
The quasi-ordered droplet crystals could be formed under Dipolar forces in the Bose Einstein condensate. While the softcore Rydberg dressing interaction has forms triangular droplet-crystals, adding a Gaussian peak to the plateau type interaction would form multiple roton unstable points in the Bogoliubov spectrum. Therefore, the excitation around the roton instabilities would grow exponentially and form multiple allowed lattice constants leading to quasi-ordered periodic droplet crystals. | 0 | Theoretical and Fundamental Chemistry |
Recombinant human insulin has almost completely replaced insulin obtained from animal sources (e.g. pigs and cattle) for the treatment of type 1 diabetes. A variety of different recombinant insulin preparations are in widespread use. Recombinant insulin is synthesized by inserting the human insulin gene into E. coli, or yeast (Saccharomyces cerevisiae) which then produces insulin for human use. Insulin produced by E. coli requires further post translational modifications (e.g. glycosylation) whereas yeasts are able to perform these modifications themselves by virtue of being more complex host organisms. The advantage of recombinant human insulin is after chronic use patients don't develop an immune defence against it the way animal sourced insulin stimulates the human immune system. | 1 | Applied and Interdisciplinary Chemistry |
Biomaterials can be constructed using only materials sourced from plants and animals in order to alter, replace, or repair human tissue/organs. Use of natural biomaterials were used as early as ancient Egypt, where indigenous people used animal skin as sutures. A more modern example is a hip replacement using ivory material which was first recorded in Germany 1891.
Valuable criteria for viable natural biomaterials:
* Biodegradable
* Biocompatible
* Able to promote cell attachment and growth
* Non-toxic
Examples of natural biomaterials:
* Alginate
* Matrigel
* Fibrin
* Collagen
* Myocardial tissue engineering | 1 | Applied and Interdisciplinary Chemistry |
Transformation infections is limited to abortive or restrictive infections. This constitutes the broadest category of infections as it can include both cytocidal and persistent infection. Viral transformation is most commonly understood as transforming infections, so the remainder of the article focuses on detailing transforming infections. | 1 | Applied and Interdisciplinary Chemistry |
The consolidation stage of mucoadhesion involves the establishment of adhesive interactions to reinforce strong or prolonged adhesion. When moisture is present, mucoadhesive materials become activated and the system becomes plasticized. This stimulus allows the mucoadhesive molecules to separate and break free while proceeding to link up by weak van der Waals and hydrogen bonds. Consolidation factors are essential for the surface when exposed to significant dislodging stresses. Multiple mucoadhesion theories exist that explain the consolidation stage, the main two which focus on macromolecular interpenetration and dehydration. | 1 | Applied and Interdisciplinary Chemistry |
The term is often used without a definition. Some authors define the term "high-energy" to be equivalent to "chemically unstable", while others reserve the term for high-energy phosphates, such as the Great Soviet Encyclopedia which defines the term "high-energy compounds" to refer exclusively to those.
The IUPAC glossary of terms used in ecotoxicology defines a primary producer as an "organism capable of using the energy derived from light or a chemical substance in order to manufacture energy-rich organic compounds". However, IUPAC does not formally define the meaning of "energy-rich". | 1 | Applied and Interdisciplinary Chemistry |
Microscopically, liquids consist of a dense, disordered packing of molecules. This contrasts with the other two common phases of matter, gases and solids. Although gases are disordered, the molecules are well-separated in space and interact primarily through molecule-molecule collisions. Conversely, although the molecules in solids are densely packed, they usually fall into a regular structure, such as a crystalline lattice (glasses are a notable
exception). | 0 | Theoretical and Fundamental Chemistry |
The need for this theory arises from the need to derive activity coefficients of solutes when their concentrations are too high to be predicted accurately by Debye–Hückel theory. These activity coefficients are needed because an equilibrium constant is defined in thermodynamics as a quotient of activities but is usually measured using concentrations. The protonation of a monobasic acid will be used to simplify the exposition. The equilibrium for protonation of the conjugate base, A of the acid, may be written as
for which
where {HA} signifies an activity of the chemical species HA etc.. The role of water in the equilibrium has been ignored as in all but the most concentrated solutions the activity of water is a constant. K is defined here as an association constant, the reciprocal of an acid dissociation constant.
Each activity term can be expressed as the product of a concentration and an activity coefficient. For example,
where the square brackets signify a concentration and γ is an activity coefficient. Thus the equilibrium constant can be expressed as a product of a concentration quotient and an activity coefficient quotient.
Taking logarithms.
K is the hypothetical value that the equilibrium constant would have if the solution of the acid were so dilute that the activity coefficients were all equal to one.
It is common practise to determine equilibrium constants in solutions containing an electrolyte at high ionic strength such that the activity coefficients are effectively constant. However, when the ionic strength is changed the measured equilibrium constant will also change, so there is a need to estimate individual (single ion) activity coefficients. Debye–Huckel theory provides a means to do this, but it is accurate only at very low concentrations. Hence the need for an extension to Debye–Hückel theory. Two main approaches have been used. SIT theory, discussed here and Pitzer equations. | 0 | Theoretical and Fundamental Chemistry |
Like many other energy generation technologies, the manufacture of solar cells, especially its rapid expansion, has many environmental and supply-chain implications. Global mining may adapt and potentially expand for sourcing the needed minerals which vary per type of solar cell. Recycling solar panels could be a source for materials that would otherwise need to be mined. | 0 | Theoretical and Fundamental Chemistry |
A pipefitter or steamfitter is a tradesman who installs, assembles, fabricates, maintains, and repairs mechanical piping systems. Pipefitters usually begin as helpers or apprentices. Journeyman pipefitters deal with industrial/commercial/marine piping and heating/cooling systems. Typical industrial process pipe is under high pressure, which requires metals such as carbon steel, stainless steel, and many different alloy metals fused together through precise cutting, threading, grooving, bending, and welding. A plumber concentrates on lower pressure piping systems for sewage and potable tap water in the industrial, commercial, institutional, or residential atmosphere. Utility piping typically consists of copper, PVC, CPVC, polyethylene, and galvanized pipe, which is typically glued, soldered, or threaded. Other types of piping systems include steam, ventilation, hydraulics, chemicals, fuel, and oil.
In Canada, pipefitting is classified as a compulsory trade, and carries a voluntary "red seal" inter-provincial standards endorsement. Pipefitter apprenticeships are controlled and regulated provincially, and in some cases allow for advance standing in similar trades upon completion.
In the United States, many states require pipefitters to be licensed. Requirements differ from state to state, but most include a four- to five-year apprenticeship. Union pipefitters are required to pass an apprenticeship test (often called a "turn-out exam") before becoming a licensed journeyman. Others can be certified by NCCER (formerly the National Center for Construction Education and Research). | 1 | Applied and Interdisciplinary Chemistry |
There is a mode of polymerization referred to as reversible-deactivation polymerization which is distinct from living polymerization, despite some common features. Living polymerization requires a complete absence of termination reactions, whereas reversible-deactivation polymerization may contain a similar fraction of termination as conventional polymerization with the same concentration of active species. Some important aspects of these are compared in the table: | 0 | Theoretical and Fundamental Chemistry |
A hydrogen carrier is an organic macromolecule that transports atoms of hydrogen from one place to another inside a cell or from cell to cell for use in various metabolical processes. Examples include NADPH, NADH, and FADH. The main role of these is to transport hydrogen atom to electron transport chain which will change ADP to ATP by adding one phosphate during metabolic processes (e.g. photosynthesis and respiration). Hydrogen carrier participates in an oxidation-reduction reaction by getting reduced due to the acceptance of a Hydrogen. The enzyme used in Glycolysis, Dehydrogenase is used to attach the hydrogen to one of the hydrogen carrier. | 1 | Applied and Interdisciplinary Chemistry |
D-dimer (or D dimer) is a dimer that is a fibrin degradation product (or FDP), a small protein fragment present in the blood after a blood clot is degraded by fibrinolysis. It is so named because it contains two D fragments of the fibrin protein joined by a cross-link, hence forming a protein dimer.
D-dimer concentration may be determined by a blood test to help diagnose thrombosis. Since its introduction in the 1990s, it has become an important test performed in people with suspected thrombotic disorders, such as venous thromboembolism. While a negative result practically rules out thrombosis, a positive result can indicate thrombosis but does not exclude other potential causes. Its main use, therefore, is to exclude thromboembolic disease where the probability is low.
D-dimer levels are used as a predictive biomarker for the blood disorder disseminated intravascular coagulation and in the coagulation disorders associated with COVID-19 infection. A four-fold increase in the protein is an indicator of poor prognosis in people hospitalized with COVID-19. | 1 | Applied and Interdisciplinary Chemistry |
Z-Cote was studied to evaluate hypothetical agricultural impacts if it were to contaminate irrigated water. In the study it was found that Z-Cote had a negligible impact on bean (Phaseolus vulgaris) pod production and increased root length and the concentration of more nutritional elements. | 1 | Applied and Interdisciplinary Chemistry |
Continuous network models of GRNs are an extension of the Boolean networks described above. Nodes still represent genes and connections between them regulatory influences on gene expression. Genes in biological systems display a continuous range of activity levels and it has been argued that using a continuous representation captures several properties of gene regulatory networks not present in the Boolean model. Formally most of these approaches are similar to an artificial neural network, as inputs to a node are summed up and the result serves as input to a sigmoid function, e.g., but proteins do often control gene expression in a synergistic, i.e. non-linear, way. However, there is now a continuous network model that allows grouping of inputs to a node thus realizing another level of regulation. This model is formally closer to a higher order recurrent neural network. The same model has also been used to mimic the evolution of cellular differentiation and even multicellular morphogenesis. | 1 | Applied and Interdisciplinary Chemistry |
# Yang, Dong, Xijun Chang, Yongwen Liu, and Sui Wang. "Synthesis and Efficiency of a Spherical Macroporous Epoxy-Polyamide Chelating Resin for Preconcentrating and Separating Trace Noble Metal Ions." Annali di Chimica 95.1-2 (2005): 111-14.
# Zougagh, Mohammed, J. M. Cano Pav N, and A. Garcia De Torres. "Chelating Sorbents Based on Silica Gel and Their Application in Atomic Spectrometry." Anal Bioanal Chem Analytical and Bioanalytical Chemistry 381.6 (2005): 1103-113.
# R. R. Greenberg" and H. M. Kingston. “Trace Element Analysis of Natural Water Samples by Neutron Activation Analysis with Chelating Resin.” Center for Analytical Chemistry, National Bureau of Standards, Washington, D.C. 20234. | 0 | Theoretical and Fundamental Chemistry |
These codes typically use regular grids (cubical or rectangular cuboid), conjugate gradient method to solve large system of linear equations, and FFT-acceleration of the matrix-vector products which uses convolution theorem. Complexity of this approach is almost linear in number of dipoles for both time and memory. | 0 | Theoretical and Fundamental Chemistry |
There is a complete kiln in the restored Tsalapatas brick Factory in Volos Greece that has been converted to an industrial museum.
There are two in New Zealand.
Kaohsiung city in Taiwan is also home to a Hoffman kiln, built by the Japanese government in 1899. | 1 | Applied and Interdisciplinary Chemistry |
In June 2010, the first case report appeared of a progressive multifocal leukoencephalopathy being successfully treated with mefloquine. Mefloquine can also act against the JC virus. Administration of mefloquine seemed to eliminate the virus from the patient's body and prevented further neurological deterioration.
Mefloquine alters cholinergic synaptic transmission through both postsynaptic and presynaptic actions. The postsynaptic action to inhibit acetylcholinesterase changes transmission across synapses in the brain. | 0 | Theoretical and Fundamental Chemistry |
* Dicerandrol A
* Dicerandrol B
* Dicerandrol C
* Penexanthone A
* Phomolactonexanthone A
* Phomolactonexanthone B
* Phomoxanthone A and its derivatives:
** 1-acetylphomoxanthone A
** 1,1′-diacetylphomoxanthone A
** 1,1′,8-triacetylphomoxanthone A
** 1,1′,8,8′-tetraacetylphomoxanthone A
** 12-deacetylphomoxanthone A
** 12,12′-dideacetylphomoxanthone A (deacetylphomoxanthone C)
** 12,12′,13,13′-tetradeacetylphomoxanthone A (deacetylphomoxanthone A)
* Phomoxanthone B and its derivatives:
** 12-deacetylphomoxanthone B
** 12,12′,13,13′-tetradeacetylphomoxanthone B (deacetylphomoxanthone B) | 1 | Applied and Interdisciplinary Chemistry |
A duplex steam pump has two sets of steam and water cylinders. They are not physically connected but the steam valves on the first pump are operated by the movement of the second pump's piston rod, and vice versa. The result is that there are no "dead spots" and the pump is always self-starting. | 1 | Applied and Interdisciplinary Chemistry |
Initial biological evaluation of (+)-discodermolide by the Longley group showed that it has immunosuppressive properties both in vitro and in vivo. The immunosuppression response was observed at a relatively low concentration that (+)-discodermolide was non-toxic in vitro. In both human peripheral blood leukocytes and murine splenocytes, (+)-discodermolide was found to suppress the two-way mixed lymphocyte reaction. In addition, mitogenic response of peripheral blood leukocytes was also suppressed by the (+)-discodermolide. Follow up experiments demonstrated that (+)-discodermolide also has anti-proliferative effects in several other non-lymphoid cell lines. | 0 | Theoretical and Fundamental Chemistry |
The Semipalatinsk Test Site, also known as "The Polygon", was the primary testing venue for the Soviet Union's nuclear weapons. It is located on the steppe in northeast Kazakhstan (then the Kazakh SSR), south of the valley of the Irtysh River. The scientific buildings for the test site were located around 150 km west of the town of Semipalatinsk (later renamed Semey), near the border of East Kazakhstan Province and Pavlodar Province with most of the nuclear tests taking place at various sites further to the west and south, some as far as into Karagandy Province.
The Soviet Union conducted 456 nuclear tests at Semipalatinsk from 1949 until 1989 with little regard for their effect on the local people or environment. The full impact of radiation exposure was hidden for many years by Soviet authorities and has only come to light since the test site closed in 1991.
From 1996 to 2012, a secret joint operation of Kazakh, Russian, and American nuclear scientists and engineers secured the waste plutonium in the tunnels of the mountains. | 1 | Applied and Interdisciplinary Chemistry |
Fischer graduated from TUM in 1949. He then started his doctoral thesis as an assistant to Professor Walter Hieber in the Inorganic Chemistry Institute, His thesis was entitled "The Mechanisms of Carbon Monoxide Reactions of Nickel(II) Salts in the Presence of Dithionites and Sulfoxylates". | 0 | Theoretical and Fundamental Chemistry |
A common example of galvanic corrosion occurs in galvanized iron, a sheet of iron or steel covered with a zinc coating. Even when the protective zinc coating is broken, the underlying steel is not attacked. Instead, the zinc is corroded because it is less "noble". Only after it has been consumed can rusting of the base metal occur. By contrast, with a conventional tin can, the opposite of a protective effect occurs: because the tin is more noble than the underlying steel, when the tin coating is broken, the steel beneath is immediately attacked preferentially. | 1 | Applied and Interdisciplinary Chemistry |
A screw flowmeter is composed of a set of screws (also called spindles) which form with the internal structure of the flowmeters' casing a measurement chamber.
The screw will get into rotation thanks to the medium passing through the device, which will then be transferred by the-said screws from one end to the other end of the measuring device. For this to be done, the pressure drop is essential and seen as a "necessary evil". This rotation can then be recorded by a sensor which, combined with the processing unit (software and hardware), will be able to deliver a measurement according to the flowrate, viscosity and size of the measurement chamber. ft
Screw flowmeters are well-acknowledged for their excellent linearity (±0.001%), excellent repeatability (up to 0,006%) and accuracy (±0.1%). They have the propensity to be used as metrological international reference and/or standard by metrological institutes, due to their outstanding features and reliability. Thanks to screw meters, public and independent institutes of metrology worldwide can compare their respective work, facilities, or calibrate other flowmeters (e.g., master metering) or compare flowmeters' performance according to different measurement principles.
List of public and independent institutes of metrology using screw flow meters as international reference and/or standard:
*Australia
*Austria
*Belgium
*Canada
*Czech Republic
*Denmark
*France
*Germany
*Japan
*Mexico
*Scotland
*Sweden
*Switzerland
*Taiwan R.O.C.
*The Netherlands
*The United Kingdom
*Vietnam | 1 | Applied and Interdisciplinary Chemistry |
According to Web of Science the three most cited papers in the journal are:
# Chiappe C, Pieraccini D. Ionic liquids: solvent properties and organic reactivity, 18(4): 275–297, 2005
# Carmichael AJ, Seddon KR. Polarity study of some 1-alkyl-3-methylimidazolium ambient-temperature ionic liquids with the solvatochromic dye, Nile Red, 13(10): 591–595, 2000
# Matyjaszewski K, Ziegler MJ, Arehart SV, et al. Gradient copolymers by atom transfer radical copolymerization, 13(12): 775–786, 2000 | 0 | Theoretical and Fundamental Chemistry |
Pipe bursting is a trenchless method of replacing buried pipelines (such as sewer, water, or natural gas pipes) without the need for a traditional construction trench. "Launching and receiving pits" replace the trench needed by conventional pipe-laying. | 1 | Applied and Interdisciplinary Chemistry |
In a chemical analysis, the internal standard method involves adding the same amount of a chemical substance to each sample and calibration solution. The internal standard responds proportionally to changes in the analyte and provides a similar, but not identical, measurement signal. It must also be absent from the sample matrix to ensure there is no other source of the internal standard present. Taking the ratio of analyte signal to internal standard signal and plotting it against the analyte concentrations in the calibration solutions will result in a calibration curve. The calibration curve can then be used to calculate the analyte concentration in an unknown sample.
Selecting an appropriate internal standard accounts for random and systematic sources of uncertainty that arise during sample preparation or instrument fluctuation. This is because the ratio of analyte relative to the amount of internal standard is independent of these variations. If the measured value of the analyte is erroneously shifted above or below the actual value, the internal standard measurements should shift in the same direction.
Ratio plot provides good way of compensation of detector sensitivity variation, but may be biased and should be replaced by Relative concentration/Relative calibration calculations if the reason of response variability is in different mass of analysed sample and traditional (not internal standard) calibration curve of any analyte is not linear through origin. | 0 | Theoretical and Fundamental Chemistry |
Tenebrescence, also known as reversible photochromism, is the ability of minerals to change color when exposed to light. The effect can be repeated indefinitely, but is destroyed by heating.
Tenebrescent minerals include hackmanite, spodumene and tugtupite. | 0 | Theoretical and Fundamental Chemistry |
Since there is continuous withdrawal of steam and continuous return of condensate to the boiler, losses due to blowdown and leakages have to be made up to maintain a desired water level in the boiler steam drum. For this, continuous make-up water is added to the boiler water system. Impurities in the raw water input to the plant generally consist of calcium and magnesium salts which impart hardness to the water. Hardness in the make-up water to the boiler will form deposits on the tube water surfaces which will lead to overheating and failure of the tubes. Thus, the salts have to be removed from the water, and that is done by a water demineralising treatment plant (DM). A DM plant generally consists of cation, anion, and mixed bed exchangers. Any ions in the final water from this process consist essentially of hydrogen ions and hydroxide ions, which recombine to form pure water. Very pure DM water becomes highly corrosive once it absorbs oxygen from the atmosphere because of its very high affinity for oxygen.
The capacity of the DM plant is dictated by the type and quantity of salts in the raw water input. However, some storage is essential as the DM plant may be down for maintenance. For this purpose, a storage tank is installed from which DM water is continuously withdrawn for boiler make-up. The storage tank for DM water is made from materials not affected by corrosive water, such as PVC. The piping and valves are generally of stainless steel. Sometimes, a steam blanketing arrangement or stainless steel doughnut float is provided on top of the water in the tank to avoid contact with air. DM water make-up is generally added at the steam space of the surface condenser (i.e., the vacuum side). This arrangement not only sprays the water but also DM water gets deaerated, with the dissolved gases being removed by a de-aerator through an ejector attached to the condenser. | 1 | Applied and Interdisciplinary Chemistry |
Metallurgy in China has a long history, with the earliest metal objects in China dating back to around 3,000 BCE. The majority of early metal items found in China come from the North-Western Region (mainly Gansu and Qinghai, 青海). China was the earliest civilization to use the blast furnace and produce cast iron. | 1 | Applied and Interdisciplinary Chemistry |
A fraction in chemistry is a quantity collected from a batch of a substance in a fractionating separation process. In such a process, a mixture is separated into fractions, which have compositions that vary according to a gradient. A fraction can be defined as a group of chemicals that have similar boiling points. A common fractionating process is fractional distillation, in which separation is achieved by condensing a vapor over a range of temperatures. It is used to produce liquor and various hydrocarbon fuels, such as gasoline, kerosene and diesel.
A fraction is the product of a fractionating column, a vast chamber designed to separate different substances (such as crude oil) based on their boiling point.
Fraction could also refer to a description of the composition of a mixture, e.g. mass fraction or mole fraction.
For a simpler definition a fraction is a part of the fractionating column where a compound with one boiling point can be separated from other compounds with different boiling points. | 0 | Theoretical and Fundamental Chemistry |
Thermal spraying techniques are coating processes in which melted (or heated) materials are sprayed onto a surface. The "feedstock" (coating precursor) is heated by electrical (plasma or arc) or chemical means (combustion flame).
Thermal spraying can provide thick coatings (approx. thickness range is 20 microns to several mm, depending on the process and feedstock), over a large area at high deposition rate as compared to other coating processes such as electroplating, physical and chemical vapor deposition. Coating materials available for thermal spraying include metals, alloys, ceramics, plastics and composites. They are fed in powder or wire form, heated to a molten or semimolten state and accelerated towards substrates in the form of micrometer-size particles. Combustion or electrical arc discharge is usually used as the source of energy for thermal spraying. Resulting coatings are made by the accumulation of numerous sprayed particles. The surface may not heat up significantly, allowing the coating of flammable substances.
Coating quality is usually assessed by measuring its porosity, oxide content, macro and micro-hardness, bond strength and surface roughness. Generally, the coating quality increases with increasing particle velocities. | 1 | Applied and Interdisciplinary Chemistry |
RNA polymerase binding in bacteria involves the sigma factor recognizing the core promoter region containing the −35 and −10 elements (located before the beginning of sequence to be transcribed) and also, at some promoters, the α subunit C-terminal domain recognizing promoter upstream elements. There are multiple interchangeable sigma factors, each of which recognizes a distinct set of promoters. For example, in E. coli, σ is expressed under normal conditions and recognizes promoters for genes required under normal conditions ("housekeeping genes"), while σ recognizes promoters for genes required at high temperatures ("heat-shock genes"). In archaea and eukaryotes, the functions of the bacterial general transcription factor sigma are performed by multiple general transcription factors that work together. The RNA polymerase-promoter closed complex is usually referred to as the "transcription preinitiation complex."
After binding to the DNA, the RNA polymerase switches from a closed complex to an open complex. This change involves the separation of the DNA strands to form an unwound section of DNA of approximately 13 bp, referred to as the "transcription bubble". Supercoiling plays an important part in polymerase activity because of the unwinding and rewinding of DNA. Because regions of DNA in front of RNAP are unwound, there are compensatory positive supercoils. Regions behind RNAP are rewound and negative supercoils are present. | 1 | Applied and Interdisciplinary Chemistry |
In acoustics, Stokess law of sound attenuation is a formula for the attenuation of sound in a Newtonian fluid, such as water or air, due to the fluids viscosity. It states that the amplitude of a plane wave decreases exponentially with distance traveled, at a rate given by
where is the dynamic viscosity coefficient of the fluid, is the sound's angular frequency, is the fluid density, and is the speed of sound in the medium.
The law and its derivation were published in 1845 by the Anglo-Irish physicist G. G. Stokes, who also developed Stokes's law for the friction force in fluid motion. A generalisation of Stokes attenuation taking into account the effect of thermal conductivity was proposed by the German physicist Gustav Kirchhoff in 1868.
Sound attenuation in fluids is also accompanied by acoustic dispersion, meaning that the different frequencies are propagating at different sound speeds. | 1 | Applied and Interdisciplinary Chemistry |
For example, one could use a cation exchange (negatively charged) surface chemistry for ERLIC separations to reduce the influence on retention of anionic (negatively charged) groups (the phosphates of nucleotides or of phosphonyl antibiotic mixtures; or sialic acid groups of modified carbohydrates) to now allow separation based more on the basic and/or neutral functional groups of these molecules. Modifying the polarity of a weakly ionic group (e.g. carboxyl) on the surface is easily accomplished by adjusting the pH to be within two pH units of that groups pKa. For strongly ionic functional groups of the surface (i.e. sulfates or phosphates) one could instead use a lower amount of buffer so the residual charge is not completely ion paired. An example of this would be the use of a 12.5mM (rather than the recommended >20mM buffer), pH 9.2 mobile phase on a polymeric, zwitterionic, betaine-sulfonate surface to separate phosphonyl antibiotic mixtures (each containing a phosphate group). This enhances the influence of the columns sulfonic acid functional groups of its surface chemistry over its, slightly diminished (by pH), quaternary amine. Commensurate with this, these analytes will show a reduced retention on the column eluting earlier, and in higher amounts of organic solvent, than if a neutral polar HILIC surface were used. This also increases their detection sensitivity by negative ion mass spectrometry. | 1 | Applied and Interdisciplinary Chemistry |
A Levich constant (B) is often used in order to simplify the Levich equation. Furthermore, B is readily extracted from rotating disk electrode experimental data.
The B can be defined as:
where
* n is the number of moles of electrons transferred in the half reaction (number)
* F is the Faraday constant (C/mol)
* A is the electrode area (cm)
* D is the diffusion coefficient (see Fick's law of diffusion) (cm/s)
* v is the kinematic viscosity (cm/s)
* C is the analyte concentration (mol/cm) | 0 | Theoretical and Fundamental Chemistry |
Over the years, Antibody Solutions has had strategic agreements with a range of life science companies, including Open Monoclonal Technology, Inc. (OMT), Reflexion Pharmaceuticals, Guava Technologies, Single-Cell Technologies, [https://www.trianni.com Trianni], Harbour Antibodies, OmniAb and Alloy Therapeutics. | 1 | Applied and Interdisciplinary Chemistry |
The African crested rat (Lophiomys imhausi) has a broad, white-bordered strip of hairs covering an area of glandular skin on the flank. When the animal is threatened or excited, the mane on its back erects and this flank strip parts, exposing the glandular area. The hairs in this flank area are highly specialised; at the tips they are like ordinary hairs, but are otherwise spongy, fibrous, and absorbent. The rat is known to deliberately chew the roots and bark of the Poison-arrow tree (Acokanthera schimperi), which contains ouabain. After the rat has chewed the tree, instead of swallowing the poison it slathers the resulting masticate onto its specialised flank hairs which are adapted to absorb the poisonous mixture. It thereby creates a defense mechanism that can sicken or even kill predators which attempt to bite it. | 0 | Theoretical and Fundamental Chemistry |
In dry air, the color of produced light (e.g. by lightning) is dominated by the emission lines of nitrogen, yielding the spectrum with primarily blue emission lines. The lines of neutral nitrogen (NI), neutral oxygen (OI), singly ionized nitrogen (NII) and singly ionized oxygen (OII) are the most prominent features of a lightning emission spectrum.
Neutral nitrogen radiates primarily at one line in the red part of the spectrum. Ionized nitrogen radiates primarily as a set of lines in the blue part of the spectrum.
A violet hue can occur when the spectrum contains emission lines of atomic hydrogen. This may happen when the air contains high amount of water, e.g. with lightnings in low altitudes passing through rain thunderstorms. Water vapor and small water droplets ionize and dissociate easier than large droplets, therefore have higher impact on color.
The hydrogen emission lines at 656.3 nm (the strong H-alpha line) and at 486.1 nm (H-beta) are characteristic for lightnings.
Rydberg atoms, generated by low-frequency lightnings, emit at red to orange color and can give the lightning a yellowish to greenish tint.
Generally, the radiant species present in atmospheric plasma are N, N, O, NO (in dry air) and OH (in humid air). The temperature, electron density, and electron temperature of the plasma can be inferred from the distribution of rotational lines of these species. At higher temperatures, atomic emission lines of N and O, and (in presence of water) H, are present. Other molecular lines, e.g. CO and CN, mark the presence of contaminants in the air. | 0 | Theoretical and Fundamental Chemistry |
Magnetic material synthesis and characterization technology continue to improve, allowing for the production of various shapes, sizes, and compositions of magnetic material to be studied and tuned for improved properties. One of the places which has seen great advancement is in the synthesis of magnetic materials at nanometer length scales. Nanoparticle research has seen a great deal of interest in a number of fields as many phenomena can be explained by what is occurring on the nanoscale, which can be probed more effectively using nanometer sized materials. One unique type of materials which have seen a recent surge in research interest have been known as "nanoflakes" where they resemble flakes or discs of nanometer thickness and micrometer dimensions. Nanomaterials of this shape have seen use in a number of fields including energy storage, as [electrodes] of electrochemical cells, and in cancer therapy to kill cancer cells. | 0 | Theoretical and Fundamental Chemistry |
Hückels rule is not valid for many compounds containing more than one ring. For example, pyrene and trans-bicalicene contain 16 conjugated electrons (8 bonds), and coronene contains 24 conjugated electrons (12 bonds). Both of these polycyclic molecules are aromatic, even though they fail the 4n + 2 rule. Indeed, Hückels rule can only be theoretically justified for monocyclic systems. | 0 | Theoretical and Fundamental Chemistry |
* In acids: violet
* At equivalence point (pH 5.2): grey
* In bases: green
Methylene blue functions to change the red-yellow shift of methyl red to a more distinct violet-green shift. | 0 | Theoretical and Fundamental Chemistry |
In biochemistry, a cross-linked enzyme aggregate is an immobilized enzyme prepared via cross-linking of the physical enzyme aggregates with a difunctional cross-linker. They can be used as stereoselective industrial biocatalysts. | 0 | Theoretical and Fundamental Chemistry |
While telomeres play an important role in cellular senescence, the intricate biological details of telomeres still require further investigation. The complex interactions between telomeres, different proteins and the cellular environment must be fully understood in order to develop precise and safe interventions to change it. Understanding the long-term effects of telomere extension on the body is complex and risky. Prediction of long-term consequences, including potential unanticipated side effects or interactions with other cellular processes, requires thorough and long-term investigation. | 1 | Applied and Interdisciplinary Chemistry |
FK1012 is a dimer consisting of two molecules of tacrolimus (FK506) linked via their vinyl groups. It is used as a research tool in chemically induced dimerization applications. FK1012 is a chemical inducer of dimerization (CID) which makes the protein capable of dimerization or oligomerization of fusion proteins containing one or more FKBP12 domains. It is used in pharmacology to act as a mediator in the formation of FK506 dimer. FK506 binding proteins (FKBPs) do not normally form dimers but can be caused to dimerize in the presence of FK1012. Genetically engineered proteins based on FKBPs can be used to manipulate protein localization, signaling pathways and protein activation. | 1 | Applied and Interdisciplinary Chemistry |
As mentioned above, G-proteins may terminate their own activation due to their intrinsic GTP→GDP hydrolysis capability. However, this reaction proceeds at a slow rate (≈0.02 times/sec) and, thus, it would take around 50 seconds for any single G-protein to deactivate if other factors did not come into play. Indeed, there are around 30 isoforms of RGS proteins that, when bound to Gα through their GAP domain, accelerate the hydrolysis rate to ≈30 times/sec. This 1500-fold increase in rate allows for the cell to respond to external signals with high speed, as well as spatial resolution due to limited amount of second messenger that can be generated and limited distance a G-protein can diffuse in 0.03 seconds. For the most part, the RGS proteins are promiscuous in their ability to deactivate G-proteins, while which RGS is involved in a given signaling pathway seems more determined by the tissue and GPCR involved than anything else. In addition, RGS proteins have the additional function of increasing the rate of GTP-GDP exchange at GPCRs, (i.e., as a sort of co-GEF) further contributing to the time resolution of GPCR signaling.
In addition, the GPCR may be desensitized itself. This can occur as:
# a direct result of ligand occupation, wherein the change in conformation allows recruitment of GPCR-Regulating Kinases (GRKs), which go on to phosphorylate various serine/threonine residues of IL-3 and the C-terminal tail. Upon GRK phosphorylation, the GPCR's affinity for β-arrestin (β-arrestin-1/2 in most tissues) is increased, at which point β-arrestin may bind and act to both sterically hinder G-protein coupling as well as initiate the process of receptor internalization through clathrin-mediated endocytosis. Because only the liganded receptor is desensitized by this mechanism, it is called homologous desensitization
# the affinity for β-arrestin may be increased in a ligand occupation and GRK-independent manner through phosphorylation of different ser/thr sites (but also of IL-3 and the C-terminal tail) by PKC and PKA. These phosphorylations are often sufficient to impair G-protein coupling on their own as well.
# PKC/PKA may, instead, phosphorylate GRKs, which can also lead to GPCR phosphorylation and β-arrestin binding in an occupation-independent manner. These latter two mechanisms allow for desensitization of one GPCR due to the activities of others, or heterologous desensitization. GRKs may also have GAP domains and so may contribute to inactivation through non-kinase mechanisms as well. A combination of these mechanisms may also occur.
Once β-arrestin is bound to a GPCR, it undergoes a conformational change allowing it to serve as a scaffolding protein for an adaptor complex termed AP-2, which in turn recruits another protein called clathrin. If enough receptors in the local area recruit clathrin in this manner, they aggregate and the membrane buds inwardly as a result of interactions between the molecules of clathrin, in a process called opsonization. Once the pit has been pinched off the plasma membrane due to the actions of two other proteins called amphiphysin and dynamin, it is now an endocytic vesicle. At this point, the adapter molecules and clathrin have dissociated, and the receptor is either trafficked back to the plasma membrane or targeted to lysosomes for degradation.
At any point in this process, the β-arrestins may also recruit other proteins—such as the non-receptor tyrosine kinase (nRTK), c-SRC—which may activate ERK1/2, or other mitogen-activated protein kinase (MAPK) signaling through, for example, phosphorylation of the small GTPase, Ras, or recruit the proteins of the ERK cascade directly (i.e., Raf-1, MEK, ERK-1/2) at which point signaling is initiated due to their close proximity to one another. Another target of c-SRC are the dynamin molecules involved in endocytosis. Dynamins polymerize around the neck of an incoming vesicle, and their phosphorylation by c-SRC provides the energy necessary for the conformational change allowing the final "pinching off" from the membrane. | 1 | Applied and Interdisciplinary Chemistry |
This book describes the miner and the finding of veins. Agricola assumes that his audience is the mine owner, or an investor in mines. He advises owners to live at the mine and to appoint good deputies. It is recommended to buy shares in mines that have not started to produce as well as existing mines to balance the risks. The next section of this book recommends areas where miners should search. These are generally mountains with wood available for fuel and a good supply of water. A navigable river can be used to bring fuel, but only gold or gemstones can be mined if no fuel is available. The roads must be good and the area healthy. Agricola describes searching streams for metals and gems that have been washed from the veins. He also suggests looking for exposed veins and also describes the effects of metals on the overlying vegetation. He recommends trenching to investigate veins beneath the surface. He then describes dowsing with a forked twig although he rejects the method himself. The passage is the first written description of how dowsing is done. Finally he comments on the practice of naming veins or shafts. | 1 | Applied and Interdisciplinary Chemistry |
Confusion between inversion domains and antiphase domains is common, even in the published literature, and particularly in the case of GaAs grown on silicon. (Similar defects form in GaN on silicon, where they are correctly identified as inversion domains). An example is illustrated in the diagram below.
Figure 4. Highlighted area showing an inversion domain, incorrectly called an antiphase domain, in GaAs on Si.
The shaded region, B, is an example of an APD. In the figure, GaAs is grown on a misoriented surface of Si (details are not discussed here). The misorientation causes the Ga and As atoms in region B to be on opposite sites compared to the crystal matrix. The presence of the APD results in Ga sites 1, 1’, 2, 2’, 3, 3’ being bonded to Ga atoms in the APD to form an APB.
In mixed oxidation state materials like magnetite, antiphase domains and antiphase domain boundaries can occur as a result of charge-ordering even though there are no changes in atom locations. For example, the reconstructed magnetite (100) surface contains alternating Fe pairs and Fe pairs in the first subsurface layer. An antiphase domain boundary can form if two subsurface Fe pairs meet when two terraces grow together. | 0 | Theoretical and Fundamental Chemistry |
By the addition of yttria to pure zirconia (e.g., fully stabilized YSZ) Y ions replace Zr on the cationic sublattice. Thereby, oxygen vacancies are generated due to charge neutrality:
meaning that two Y ions generate one vacancy on the anionic sublattice. This facilitates moderate conductivity of yttrium-stabilized zirconia for O ions (and thus electrical conductivity) at elevated and high temperature. This ability to conduct O ions makes yttria-stabilized zirconia well suited for application as solid electrolyte in solid oxide fuel cells.
For low dopant concentrations, the ionic conductivity of the stabilized zirconias increases with increasing YO content. It has a maximum around 8–9 mol% almost independent of the temperature (800–1200 °C). Unfortunately, 8–9 mol% YSZ (8YSZ, 8YDZ) also turned out to be situated in the 2-phase field (c+t) of the YSZ phase diagram at these temperatures, which causes the material's decomposition into Y-enriched and depleted regions on the nanometre scale and, consequently, the electrical degradation during operation. The microstructural and chemical changes on the nanometre scale are accompanied by the drastic decrease of the oxygen-ion conductivity of 8YSZ (degradation of 8YSZ) of about 40% at 950 °C within 2500 hours. Traces of impurities like Ni, dissolved in the 8YSZ, e.g., due to fuel-cell fabrication, can have a severe impact on the decomposition rate (acceleration of inherent decomposition of the 8YSZ by orders of magnitude) such that the degradation of conductivity even becomes problematic at low operation temperatures in the range of 500–700 °C.
Nowadays, more complex ceramics like co-doped zirconia (e.g., with scandia) are in use as solid electrolytes. | 0 | Theoretical and Fundamental Chemistry |
Fujita and coworkers discovered a self-assemble ML (6 palladium ions and 4 ligands in each complex) supramolecular container that could be enhanced into a chiral supramolecule by an addition of peripheral chiral auxiliary. In this case, the auxiliary diethyldiaminocyclohexane does not directly activate the catalytic site but induces a slight deformation of the triazine plane to create chiral cavity inside the container molecule. This container could then be used to asymmetrically catalyze a [2+2] photoaddition of maleimide and inert aromatic compound fluoranthene, which previously have not been shown to undergo thermal or photochemical pericyclic reaction. The catalyst yields an enantiomeric excess of 40%. | 0 | Theoretical and Fundamental Chemistry |
"Amoxicillin" is the International Nonproprietary Name (INN), British Approved Name (BAN), and United States Adopted Name (USAN), while "amoxycillin" is the Australian Approved Name (AAN).
Amoxicillin is one of the semisynthetic penicillins discovered by former pharmaceutical company Beecham Group. The patent for amoxicillin has expired, thus amoxicillin and co-amoxiclav preparations are marketed under various brand names across the world. | 0 | Theoretical and Fundamental Chemistry |
A year and a half after his execution, Lavoisier was completely exonerated by the French government. During the White Terror, his belongings were delivered to his widow. A brief note was included, reading "To the widow of Lavoisier, who was falsely convicted". | 1 | Applied and Interdisciplinary Chemistry |
Devapamil is a calcium channel blocker. It is also known as desmethoxyverapamil, which is a phenylalkylamine (PAA) derivative. Devapamil not only inhibits by blocking the calcium gated channels, but also by depolarizing the membrane during the sodium-potassium exchanges. | 1 | Applied and Interdisciplinary Chemistry |
In 2007, the European Commission gave authorization for the marketing of trabectedin, under the trade name Yondelis, "for the treatment of patients with advanced soft tissue sarcoma, after failure of anthracyclines and ifosfamide, or who are unsuited to receive these agents". The European Medicine Agency's evaluating committee, the Committee for Medicinal Products for Human Use (CHMP), observed that trabectedin had not been evaluated in an adequately designed and analyzed randomized controlled trial against current best care, and that the clinical efficacy data were mainly based on patients with liposarcoma and leiomyosarcoma. However, the pivotal study did show a significant difference between two different trabectedin treatment regimens, and due to the rarity of the disease, the CHMP considered that marketing authorization could be granted under exceptional circumstances. As part of the approval PharmaMar agreed to conduct a further trial to identify whether any specific chromosomal translocations could be used to predict responsiveness to trabectedin.
Trabectedin is also approved in South Korea and Russia.
In 2015, (after a phase III study comparing trabectedin with dacarbazine), the US FDA approved trabectedin (Yondelis) for the treatment of liposarcoma and leiomyosarcoma that is either unresectable or has metastasized. Patients must have received prior chemotherapy with an anthracycline. | 0 | Theoretical and Fundamental Chemistry |
In RT-PCR, the RNA template is first converted into a complementary DNA (cDNA) using a reverse transcriptase (RT). The cDNA is then used as a template for exponential amplification using PCR. The use of RT-PCR for the detection of RNA transcript has revolutionized the study of gene expression in the following important ways:
* Made it theoretically possible to detect the transcripts of practically any gene
* Enabled sample amplification and eliminated the need for abundant starting material required when using northern blot analysis
* Provided tolerance for RNA degradation as long as the RNA spanning the primer is intact | 1 | Applied and Interdisciplinary Chemistry |
When genotypes grown together in a diverse population have different profiles of resource use they complement each other in the exploitation of the limiting resource and therefore are subject to smaller between-plant competition.
In case of disease or environmental change some plants will take over when others fail. Yield stability over years and environments can be better than pure lines due to compensation.
Participatory plant breeding (PPB) methods represent alternatives aimed to improve local adaptation breeding, to promote genetic diversity, to empower farmers and rural communities. In PPB farmers are actively participating in developing new cultivars or populations, e.g. by performing selection. | 1 | Applied and Interdisciplinary Chemistry |
Tropinone is an alkaloid, famously synthesised in 1917 by Robert Robinson as a synthetic precursor to atropine, a scarce commodity during World War I. Tropinone and the alkaloids cocaine and atropine all share the same tropane core structure. Its corresponding conjugate acid at pH 7.3 major species is known as tropiniumone. | 0 | Theoretical and Fundamental Chemistry |
This integral may be evaluated by defining the wave function over the complex E plane and closing the E contour using a semicircle on which the wavefunctions vanish. The integral over the closed contour may then be evaluated, using the Cauchy integral theorem, as a sum of the residues at the various poles. We will now argue that the residues of approach those of at time and so the corresponding wavepackets are equal at temporal infinity.
In fact, for very positive times t the factor in a Schrödinger picture state forces one to close the contour on the lower half-plane. The pole in the from the Lippmann–Schwinger equation reflects the time-uncertainty of the interaction, while that in the wavepackets weight function reflects the duration of the interaction. Both of these varieties of poles occur at finite imaginary energies and so are suppressed at very large times. The pole in the energy difference in the denominator is on the upper half-plane in the case of , and so does not lie inside the integral contour and does not contribute to the integral. The remainder is equal to the wavepacket. Thus, at very late times , identifying as the asymptotic noninteracting out state.
Similarly one may integrate the wavepacket corresponding to at very negative times. In this case the contour needs to be closed over the upper half-plane, which therefore misses the energy pole of , which is in the lower half-plane. One then finds that the and wavepackets are equal in the asymptotic past, identifying as the asymptotic noninteracting in state. | 0 | Theoretical and Fundamental Chemistry |
The Rigveda refers to ayas, and also states that the Dasyus had ayas (RV 2.20.8). In RV 4.2.17, "the gods [are] smelting like copper/metal ore the human generations".
The references to ayas in the Rig Veda probably refer to bronze or copper rather than to iron. Scholars like Bhargava maintain that Rigveda was written in the Vedic state of Brahmavarta and Khetri Copper mines formed an important location in Brahmavarta. Vedic people had used Copper extensively in agriculture, Water purification, tools, utensils etc., D. K. Chakrabarti (1992) argued: "It should be clear that any controversy regarding the meaning of ayas in the Rgveda or the problem of the Rgvedic familiarity or unfamiliarity with iron is pointless. There is no positive evidence either way. It can mean both copper-bronze and iron and, strictly on the basis of the contexts, there is no reason to choose between the two." | 1 | Applied and Interdisciplinary Chemistry |
QuEChERS is a solid phase extraction method for detection of biocide residues in food. The name is a portmanteau word formed from "quick, easy, cheap, effective, rugged, and safe".
__TOC__ | 0 | Theoretical and Fundamental Chemistry |
The mathematical resolution to Loschmidt's paradox is called the (steady state) fluctuation theorem (FT), which is a generalisation of the second law of thermodynamics. The FT shows that as a system gets larger or the trajectory duration becomes longer, entropy-consuming trajectories become more unlikely, and the expected second law behaviour is recovered.
The FT was first put forward by and much of the work done in developing and extending the theorem was accomplished by theoreticians and mathematicians interested in nonequilibrium statistical mechanics.
The first observation and experimental proof of Evan's fluctuation theorem (FT) was performed by | 0 | Theoretical and Fundamental Chemistry |
This is the point at which the rotating wave approximation is made. The dipole approximation has been assumed, and for this to remain valid the electric field must be near resonance with the atomic transition. This means that and the complex exponentials multiplying and can be considered to be rapidly oscillating. Hence on any appreciable time scale, the oscillations will quickly average to 0. The rotating wave approximation is thus the claim that these terms may be neglected and thus the Hamiltonian can be written in the interaction picture as
Finally, transforming back into the Schrödinger picture, the Hamiltonian is given by
Another criterion for rotating wave approximation is the weak coupling condition, that is, the Rabi frequency should be much less than the transition frequency.
At this point the rotating wave approximation is complete. A common first step beyond this is to remove the remaining time dependence in the Hamiltonian via another unitary transformation. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, the Craik–Leibovich (CL) vortex force describes a forcing of the mean flow through wave–current interaction, specifically between the Stokes drift velocity and the mean-flow vorticity. The CL vortex force is used to explain the generation of Langmuir circulations by an instability mechanism. The CL vortex-force mechanism was derived and studied by Sidney Leibovich and Alex D. D. Craik in the 1970s and 80s, in their studies of Langmuir circulations (discovered by Irving Langmuir in the 1930s). | 1 | Applied and Interdisciplinary Chemistry |
Historically, displacement chromatography was applied to preparative separations of amino acids and rare earth elements and has also been investigated for isotope separation. | 0 | Theoretical and Fundamental Chemistry |
Ortho lithiation can be used to generate many of the same structures as lateral lithiation; however, reactivity differences between aryl- and benzyllithium species may suggest the use of one method over the other. A useful alternative method for stereoselective functionalization of the benzylic position involves the use of chromium arene complexes. Substitution at the benzylic position is much better tolerated in methods that employ benzylic lithiation of chromium arene complexes than lateral lithiations; however, the chromium byproducts of these reactions pose waste disposal difficulties. The use of mixed zinc/copper organometallic reagents generated from benzyl bromides represents a second alternative to lateral lithiation. The functional group compatibility of this method is greater than lateral lithiation, but more steps are required to generate the reactive organometallic species from an unfunctionalized benzylic position. | 0 | Theoretical and Fundamental Chemistry |
Drug metabolism is the metabolic breakdown of drugs by living organisms, usually through specialized enzymatic systems. More generally, xenobiotic metabolism (from the Greek xenos "stranger" and biotic "related to living beings") is the set of metabolic pathways that modify the chemical structure of xenobiotics, which are compounds foreign to an organism's normal biochemistry, such as any drug or poison. These pathways are a form of biotransformation present in all major groups of organisms and are considered to be of ancient origin. These reactions often act to detoxify poisonous compounds (although in some cases the intermediates in xenobiotic metabolism can themselves cause toxic effects). The study of drug metabolism is called pharmacokinetics.
The metabolism of pharmaceutical drugs is an important aspect of pharmacology and medicine. For example, the rate of metabolism determines the duration and intensity of a drug's pharmacologic action. Drug metabolism also affects multidrug resistance in infectious diseases and in chemotherapy for cancer, and the actions of some drugs as substrates or inhibitors of enzymes involved in xenobiotic metabolism are a common reason for hazardous drug interactions. These pathways are also important in environmental science, with the xenobiotic metabolism of microorganisms determining whether a pollutant will be broken down during bioremediation, or persist in the environment. The enzymes of xenobiotic metabolism, particularly the glutathione S-transferases are also important in agriculture, since they may produce resistance to pesticides and herbicides.
Drug metabolism is divided into three phases. In phase I, enzymes such as cytochrome P450 oxidases introduce reactive or polar groups into xenobiotics. These modified compounds are then conjugated to polar compounds in phase II reactions. These reactions are catalysed by transferase enzymes such as glutathione S-transferases. Finally, in phase III, the conjugated xenobiotics may be further processed, before being recognised by efflux transporters and pumped out of cells. Drug metabolism often converts lipophilic compounds into hydrophilic products that are more readily excreted. | 1 | Applied and Interdisciplinary Chemistry |
Heat engines have been known since antiquity but were only made into useful devices at the time of the industrial revolution in the 18th century. They continue to be developed today. | 0 | Theoretical and Fundamental Chemistry |
Power spectra are needed for each of the points on the surface; this encapsulates information about the turbulence intensity for each point. Under IEC standards, only one power spectrum is used; that is, all points have the same turbulence intensity.
With the power spectra, the spectral matrix can be formed. This a -by- matrix. The main diagonal of the spectral matrix contains the previously defined spectra for all points on the surface. The off-main diagonal elements contain all the cross spectra between the points. The cross spectra are determined by the following function:
Due to the symmetry of the coherence matrix, only elements are independent. This property can be exploited to lighten memory requirements when writing a programme to simulate the Sandia method.
The spectral matrix, , can be written as the matrix product of a matrix, , and its transpose. That is,
is ultimately needed to obtain the complex Fourier co-efficients of the Fourier transforms of the time series of the wind speeds at all the points on the surface. Note - if the Fourier transform of a time domain function, , is , then the resultant spectrum is ; for multiple time domain functions, the Fourier co-efficients can be stored in a matrix, which then means that the above equation is applicable.
Obviously, there are an infinite number of solutions to the above expression; consequently, the assumption that is a lower triangular matrix is made such that only one solution exists. The solution can be found via a Cholesky decomposition. The resultant matrix can be thought of as the weighting factors for the
linear combination of N independent, unit-magnitude, white-noise inputs that will
yield N correlated outputs with the correct spectral matrix.
To get the complex Fourier co-efficients associated with the Fourier transform of the time series of the wind speeds, a column vector, is obtained by multiply the matrix by a column vector containing values of Gaussian white noise, , as shown below:
The column vector gives the Fourier co-efficients for all points on the grid at a given frequency. This is then built up into a two dimensional matrix which covers the complex Fourier co-efficients for all points across all frequencies. Then, an inverse fast Fourier transform is performed to get the time series. That is, | 1 | Applied and Interdisciplinary Chemistry |
A naturally occurring predator to coral reefs in the Great Barrier Reef is the Crown of Thorns sea star (Acanthaster planci). Population outbreaks of the Crown of Thorns sea star are one of the major causes of coral decline across the Great Barrier Reef, as an adult crown-of-thorns starfish is capable of consuming up to 10 m2 of reef building coral a year. However, each species of coral is not equally impacted, as the sea star has been observed to favor branching species of coral, Acropora, followed by a sub branching species. This results in a sequential and ordered eradication of coral reef species.
Crown of Thorns Sea Star outbreaks on the Great Barrier Reef have become more frequent in recent years, which scientists predict could be linked to human activities. Any increase in nutrients, possibly from river run-off, can positively affect starfish populations, leading to detrimental outbreaks. As pressures from climate change increase, the time between reef disturbances is becoming shorter, leaving less time for reef recovery. | 0 | Theoretical and Fundamental Chemistry |
Experimentally the first examples of mechanically interlocked molecular architectures appeared in the 1960s with catenanes being synthesized by Wasserman and Schill and rotaxanes by Harrison and Harrison. The chemistry of MIMAs came of age when Sauvage pioneered their synthesis using templating methods. In the early 1990s the usefulness and even the existence of MIMAs were challenged. The latter concern was addressed by X ray crystallographer and structural chemist David Williams. Two postdoctoral researchers who took on the challenge of producing [5]catenane (olympiadane) pushed the boundaries of the complexity of MIMAs that could be synthesized their success was confirmed in 1996 by a solid‐state structure analysis conducted by David Williams. | 0 | Theoretical and Fundamental Chemistry |
Sheath air is clean filtered air that surrounds the aerosol stream to prevent particulates from circulating or depositing within the optic chamber. Sheath air prevents contamination caused by build-up and deposits, improves response time by containing the sample, and improves maintenance by keeping the optic chamber clean. The nephelometer creates the sheath air by passing air through a zero filter before beginning the sample. | 0 | Theoretical and Fundamental Chemistry |
Escitalopram was developed in cooperation between Lundbeck and Forest Laboratories. Its development was initiated in 1997, and the resulting new drug application was submitted to the US FDA in March 2001. The short time (3.5 years) it took to develop escitalopram can be attributed to the previous experience of Lundbeck and Forest with citalopram, which has similar pharmacology. | 0 | Theoretical and Fundamental Chemistry |
Coenzyme F is synthesized via a multi-step pathway:
* 7,8-didemethyl-8-hydroxy-5-deazariboflavin synthase (FbiC) produces Coenzyme FO (also written F0), itself a cofactor of DNA photolyase (antenna). This is the head portion of the molecule.
* 2-phospho-L-lactate transferase (FbiA) produces Coenzyme F-0, the portion containing the head, the diphosphate bridge, and ending with a carboxylic acid group.
* Coenzyme F420-0:L-glutamate ligase (one part of FbiB) puts a glutamate residue at the -COOH end, producing Coenzyme F-1.
* Coenzyme F420-1:gamma-L-glutamate ligase (other part of FbiB) puts a gamma-glutamate residue at the -COOH end, producing Coenzyme F-2, the final compound (in its oxidized form). Also responsible for adding additional units.
Oxidized F can be converted to reduced F-H by multiple enzymes such as Glucose-6-phosphate dehydrogenase (coenzyme-F420) (Fgd1). | 1 | Applied and Interdisciplinary Chemistry |
According to a study done by the Mayo Clinic, miscarriage rates for IVF are somewhere between 15 and 25% for those under the age of 35. In naturally conceived pregnancies, the rate of miscarriage is between 10 and 20% for those under the age of 35. Risk of miscarriage, regardless of the method of conception, does increase with age. | 1 | Applied and Interdisciplinary Chemistry |
The LiMCA method measures the total concentration and size distribution of inclusions present in aluminum alloys. Its measuring principle is based on an objective and user-independent method. The LiMCA CM system can characterize the cleanliness of a melt at time intervals in the order of one minute. It can therefore monitor, in real-time, the evolution of cleanliness along a cast as a function of process parameters and melt-handling practices.
The heart of the LiMCA measuring system consists of a closed glass tube (electrically insulating material) bearing a small orifice at its bottom. The tube is positioned in liquid metal. By creating a vacuum inside the tube, the metal with the suspended inclusions to be detected is forced through the small orifice. Two electrodes are necessary: one inside the tube and the other outside. Both electrodes are immersed in the liquid metal. A constant electric current is applied between the electrodes. The current flows through the
liquid metal by the small orifice in the tube. When an inclusion enters the orifice, it displaces its volume of conducting fluid, temporarily raising the electrical resistance. The increase of resistance generates a voltage pulse. The magnitude of the voltage pulse is a function of the volume of the particle. The duration of the pulse is related to the
transit time of the inclusion. The voltage pulses are amplified and their amplitude measured digitally. The size distribution and total concentration are displayed in real-time on a computer screen. | 1 | Applied and Interdisciplinary Chemistry |
The ancient world lacked standardized forensic practices, which enabled criminals to escape punishment. Criminal investigations and trials relied heavily on forced confessions and witness testimony. However, ancient sources do contain several accounts of techniques that foreshadow concepts in forensic science developed centuries later.
The first written account of using medicine and entomology to solve criminal cases is attributed to the book of Xi Yuan Lu (translated as Washing Away of Wrongs), written in China in 1248 by Song Ci (, 1186–1249), a director of justice, jail and supervision, during the Song dynasty.
Song Ci introduced regulations concerning autopsy reports to court, how to protect the evidence in the examining process, and explained why forensic workers must demonstrate impartiality to the public. He devised methods for making antiseptic and for promoting the reappearance of hidden injuries to dead bodies and bones (using sunlight and vinegar under a red-oil umbrella); for calculating the time of death (allowing for weather and insect activity); described how to wash and examine the dead body to ascertain the reason for death. At that time the book had described methods for distinguishing between suicide and faked suicide. He wrote the book on forensics stating that all wounds or dead bodies should be examined, not avoided. The book became the first form of literature to help determine the cause of death.
In one of Song Cis accounts (Washing Away of Wrongs'), the case of a person murdered with a sickle was solved by an investigator who instructed each suspect to bring his sickle to one location. (He realized it was a sickle by testing various blades on an animal carcass and comparing the wounds.) Flies, attracted by the smell of blood, eventually gathered on a single sickle. In light of this, the owner of that sickle confessed to the murder. The book also described how to distinguish between a drowning (water in the lungs) and strangulation (broken neck cartilage), and described evidence from examining corpses to determine if a death was caused by murder, suicide or accident.
Methods from around the world involved saliva and examination of the mouth and tongue to determine innocence or guilt, as a precursor to the Polygraph test. In ancient India, some suspects were made to fill their mouths with dried rice and spit it back out. Similarly, in ancient China, those accused of a crime would have rice powder placed in their mouths. In ancient middle-eastern cultures, the accused were made to lick hot metal rods briefly. It is thought that these tests had some validity since a guilty person would produce less saliva and thus have a drier mouth; the accused would be considered guilty if rice was sticking to their mouths in abundance or if their tongues were severely burned due to lack of shielding from saliva. | 0 | Theoretical and Fundamental Chemistry |
For a Maclaurin spheroid of eccentricity greater than 0.812670, a Jacobi ellipsoid of the same angular momentum has lower total energy. If such a spheroid is composed of a viscous fluid (or in the presence of gravitational radiation reaction), and if it suffers a perturbation which breaks its rotational symmetry, then it will gradually elongate into the Jacobi ellipsoidal form, while dissipating its excess energy as heat (or gravitational waves). This is termed secular instability; see Roberts–Stewartson instability and Chandrasekhar–Friedman–Schutz instability. However, for a similar spheroid composed of an inviscid fluid (or in the absence of radiation reaction), the perturbation will merely result in an undamped oscillation. This is described as dynamic (or ordinary) stability.
A Maclaurin spheroid of eccentricity greater than 0.952887 is dynamically unstable. Even if it is composed of an inviscid fluid and has no means of losing energy, a suitable perturbation will grow (at least initially) exponentially. Dynamic instability implies secular instability (and secular stability implies dynamic stability). | 1 | Applied and Interdisciplinary Chemistry |
Lu grew up in Miami, Florida, the daughter of immigrants from Taiwan. She studied chemistry at the Massachusetts Institute of Technology, earning her B.S. in 2000. As an undergraduate, she conducted research under Prof. Vernon Ingram on peptides that ameliorate amyloid beta neurotoxicity.
She then went on to graduate studies at the California Institute of Technology, where she studied novel coordination chemistry and small molecule reactivity with Prof. Jonas C. Peters. Lus doctoral work focused on the reactivity of zwitterionic palladium(II) complexes with CO, ethylene and amines, as well as tetrahedral manganese complexes and reductive cleavage of CO with an iron(I) complex. She earned her Ph.D. in 2006, with a thesis entitled The Chemistry of Tris(phosphino)borate Manganese and Iron Platforms'.
Lu conducted postdoctoral studies at the Max Planck Institute for Bioinorganic Chemistry from 2006 to 2009, under the mentorship of Prof. Karl Wieghardt. Under Wieghardt, Lu studied first-row transition metal complexes synthesized with redox non-innocent α-iminopyridine ligands. Lu also reported the synthesis and characterization of a chromium iminyl radical complex, using the α-iminopyridine ligand system. | 0 | Theoretical and Fundamental Chemistry |
Gestonorone caproate is a potent, long-acting, and pure progestogen, possessing no androgenic, anabolic, antiandrogenic, estrogenic, antiestrogenic, glucocorticoid, mineralocorticoid, or teratogenic effects. It is approximately 20 to 25 times more potent than progesterone or hydroxyprogesterone caproate in animal bioassays when all are given by subcutaneous injection. In humans, 100 or 200 mg intramuscular gestonorone caproate has been said to be equivalent to 1,000 mg intramuscular hydroxyprogesterone caproate. Hence, gestonorone caproate is approximately 5- to 10-fold more potent than hydroxyprogesterone caproate in humans. The biological effects of gestonorone caproate in women have been studied.
Like other potent progestins, gestonorone caproate possesses potent antigonadotropic activity and is capable of markedly suppressing the gonadal production and circulating levels of sex hormones such as testosterone and estradiol. A clinical study found that 400 mg/week intramuscular gestonorone caproate suppressed testosterone levels by 75% in men, while orchiectomy as a comparator reduced testosterone levels by 91%. Levels of luteinizing hormone, conversely, remained unchanged. In general, progestogens can maximally suppress testosterone levels by about 70 to 80%. In accordance with its lack of glucocorticoid activity, gestonorone caproate has no anticorticotropic effects, and does not influence the secretion of adrenocorticotropic hormone.
17α-Hydroxyprogesterone has weak progestogenic activity, but C17α esterification results in higher progestogenic activity. Of a variety of different esters, the caproate (hexanoate) ester was found to have the strongest progestogenic activity, and this formed the basis for the development of gestonorone caproate, as well as other caproate progestogen esters such as hydroxyprogesterone caproate.
Gestonorone caproate has been found to decrease the weights of the prostate gland and seminal vesicles by 40 to 70% in adult male rats. It has been shown in canines to mediate these effects both via its antigonadotropic effects and by direct actions in these tissues. Gestonorone caproate decreases the uptake of testosterone into the prostate gland. It has also been found to have direct antiproliferative effects on human ovarian cancer cells in vitro.
Gestonorone caproate has been reported to act to some extent as a 5α-reductase inhibitor, similarly to progesterone. | 0 | Theoretical and Fundamental Chemistry |
One would want the errors on the stability constants to be roughly commensurate with experimental error. For example, with pH titration data, if pH is measured to 2 decimal places, the errors of should not be much larger than 0.01. In exploratory work where the nature of the species present is not known in advance, several different chemical models may be tested and compared. There will be models where the uncertainties in the best estimate of an equilibrium constant may be somewhat or even significantly larger than , especially with those constants governing the formation of comparatively minor species, but the decision as to how large is acceptable remains subjective. The decision process as to whether or not to include comparatively uncertain equilibria in a model, and for the comparison of competing models in general, can be made objective and has been outlined by Hamilton. | 0 | Theoretical and Fundamental Chemistry |
A Xe atom that does not capture a neutron undergoes beta decay to Cs, one of the 7 long-lived fission products, while a Xe that does capture a neutron becomes almost-stable Xe.
The probability of capturing a neutron before decay varies with the neutron flux, which itself depends on the kind of reactor, fuel enrichment and power level; and the Cs / Xe ratio switches its predominant branch very near usual reactor conditions.
Estimates of the proportion of Xe during steady-state reactor operation that captures a neutron include 90%, 39%–91% and "essentially all".
For instance, in a (somewhat high) neutron flux of 10 n·cm·s, the xenon cross section of σ = cm ( barn) would lead to a capture probability of s, which corresponds to a half-life of about one hour. Compared to the 9.17 hour half-life of Xe, this nearly ten-to-one ratio means that under such conditions, essentially all Xe would capture a neutron before decay. But if the neutron flux is lowered to one-tenth of this value, like in CANDU reactors, the ratio would be 50-50, and half the Xe would decay to Cs before neutron capture.
Xe from neutron capture ends up as part of the eventual stable fission xenon which also includes Xe, Xe, and Xe produced by fission and beta decay rather than neutron capture.
Nuclei of Xe, Xe, and Xe that have not captured a neutron all beta decay to isotopes of caesium. Fission produces Xe, Xe, and Xe in roughly equal amounts but, after neutron capture, fission caesium contains more stable Cs (which however can become Cs on further neutron activation) and highly radioactive Cs than Cs. | 0 | Theoretical and Fundamental Chemistry |
Purinergic signalling has an essential role at interactions between neurons and glia cells, allowing these to detect action potentials and modulate neuronal activity, contributing for intra and extracellular homeostasis regulation. Besides purinergic neurotransmitter, ATP acts as a trophic factor at cellular development and growth, being involved on microglia activation and migration, and also on axonal myelination by oligodendrocytes. There are two main types of purinergic receptors, P1 binding to adenosine, and P2 binding to ATP or ADP, presenting different signalling cascades.
The Nrf2/ARE signalling pathway has a fundamental role at fighting against oxidative stress, to which neurons are especially vulnerable due to its high oxygen consumption and high lipid content. This neuroprotective pathway involves control of neuronal activity by perisynaptic astrocytes and neuronal glutamate release, with the establishment of tripartite synapses. The Nrf2/ARE activation leads to a higher expression of enzymes involved in glutathione syntheses and metabolism, that have a key role in antioxidant response.
The LKB1/NUAK1 signalling pathway regulates terminal axon branching at cortical neurons, via local immobilized mitochondria capture. Besides NUAK1, LKB1 kinase acts under other effectors enzymes as SAD-A/B and MARK, therefore regulating neuronal polarization and axonal growth, respectively. These kinase cascades implicates also Tau and others MAP.
An extended knowledge of these and others neuronal pathways could provide new potential therapeutic targets for several neurodegenerative chronic diseases as Alzheimers, Parkinsons and Huntington's disease, and also amyotrophic lateral sclerosis. | 0 | Theoretical and Fundamental Chemistry |
Three conditions must be present for oil reservoirs to form:
* A source rock rich in hydrocarbon material buried deeply enough for subterranean heat to cook it into oil,
* A porous and permeable reservoir rock where it can accumulate,
* A caprock (seal) or other mechanism to prevent the oil from escaping to the surface. Within these reservoirs, fluids will typically organize themselves like a three-layer cake with a layer of water below the oil layer and a layer of gas above it, although the different layers vary in size between reservoirs. Because most hydrocarbons are less dense than rock or water, they often migrate upward through adjacent rock layers until either reaching the surface or becoming trapped within porous rocks (known as reservoirs) by impermeable rocks above. However, the process is influenced by underground water flows, causing oil to migrate hundreds of kilometres horizontally or even short distances downward before becoming trapped in a reservoir. When hydrocarbons are concentrated in a trap, an oil field forms, from which the liquid can be extracted by drilling and pumping.
The reactions that produce oil and natural gas are often modeled as first order breakdown reactions, where hydrocarbons are broken down to oil and natural gas by a set of parallel reactions, and oil eventually breaks down to natural gas by another set of reactions. The latter set is regularly used in petrochemical plants and oil refineries.
Petroleum has mostly been recovered by oil drilling (natural petroleum springs are rare). Drilling is carried out after studies of structural geology (at the reservoir scale), sedimentary basin analysis, and reservoir characterisation (mainly in terms of the porosity and permeability of geologic reservoir structures). Wells are drilled into oil reservoirs to extract the crude oil. "Natural lift" production methods that rely on the natural reservoir pressure to force the oil to the surface are usually sufficient for a while after reservoirs are first tapped. In some reservoirs, such as in the Middle East, the natural pressure is sufficient over a long time. The natural pressure in most reservoirs, however, eventually dissipates. Then the oil must be extracted using "artificial lift" means. Over time, these "primary" methods become less effective and "secondary" production methods may be used. A common secondary method is "waterflood" or injection of water into the reservoir to increase pressure and force the oil to the drilled shaft or "wellbore." Eventually "tertiary" or "enhanced" oil recovery methods may be used to increase the oil's flow characteristics by injecting steam, carbon dioxide and other gases or chemicals into the reservoir. In the United States, primary production methods account for less than 40 percent of the oil produced on a daily basis, secondary methods account for about half, and tertiary recovery the remaining 10 percent. Extracting oil (or "bitumen") from oil/tar sand and oil shale deposits requires mining the sand or shale and heating it in a vessel or retort, or using "in-situ" methods of injecting heated liquids into the deposit and then pumping the liquid back out saturated with oil. | 0 | Theoretical and Fundamental Chemistry |
In 1991, a specific high affinity sodium pump inhibitor indistinguishable from ouabain was first discovered in the human circulation and proposed as one of the potential mediators of long term blood pressure and the enhanced salt excretion following salt and volume loading. This agent was an inhibitor of the sodium pump that acted similarly to digitalis. A number of analytical techniques led to the conclusion that this circulating molecule was ouabain and that humans were producing it as an endogenous hormone. A large portion of the scientific community agreed that this inhibitor was endogenous ouabain and that there was strong evidence to indicate that it was synthesized in the adrenal gland. One early speculative interpretation of the analytical data led to the proposal that endogenous ouabain may have been the 11 epimer, i.e., an isomer of plant ouabain. However, this possibility was excluded by various methods including the synthesis of the 11 epimer and the demonstration that it has different chromatographic behavior from ouabain. Critically, the primary observations concerning the identification of ouabain in mammals were repeated and confirmed using a variety of tissue sources on three different continents with advanced analytical methods as summarized elsewhere
Despite widespread analytical confirmation, some questioned whether or not this endogenous substance is ouabain. The arguments were based less upon rigorous analytical data but more on the fact that immunoassays are neither entirely specific nor reliable. Hence, it was suggested that some assays for endogenous ouabain detected other compounds or failed to detect ouabain at all. Additionally, it was suggested that rhamnose, the L-sugar component of ouabain, could not be synthesized within the body despite published data to the contrary. Yet another argument against the existence of endogenous ouabain was the lack of effect of rostafuroxin (a first generation ouabain receptor antagonist) on blood pressure in an unselected population of hypertensive patients. | 0 | Theoretical and Fundamental Chemistry |
The École nationale supérieure de chimie de Paris was founded in 1896 by Charles Friedel, a chemist and mineralogist who headed the school until 1899. At the time, the school was called the Laboratoire de chimie pratique et industrielle. It was located in the 6th arrondissement (rue Michelet), where it stayed until 1923.
After the death of Friedel, Henri Moissan took the reins of the school. He was awarded the Nobel Prize for chemistry in 1906, while he was director. Moissan made student admission subject to competitive exams and renamed the school Institut de chimie appliquée (Institute of Applied Chemistry).
In 1907, the school began delivering a prestigious masters of engineering. In the same year, Moissan died and a transitional directorate was created. Soon thereafter, Camille Chabrié was named director. The school closed when World War I started and reopened in 1916. This was also the first year a female student was admitted; the ENSCP was one of the first engineering schools in France to do so.
In 1923, the school moved to its current location, on the rue Pierre et Marie Curie (in the 5th arrondissement). The buildings were designed and built by Henri-Paul Nénot, architect of the Sorbonne. In 1932, the school became l'Institut de Chimie de Paris (Paris Institute of Chemistry). Finally, in 1948, it became the École nationale supérieure de chimie de Paris (ENSCP). | 1 | Applied and Interdisciplinary Chemistry |
Apart from mass spectrometry and chromatography, other two validation techniques have been developed, namely
#Pre- and post-labelling techniques:
*Pre-labelling → involves the use of P: cells are grown in P containing medium, thus allowing the incorporation of [α-P]NTPs during transcription by T7 RNA polymerase. The modified RNA is then extracted, and each RNA species is isolated and subsequently digested by T2 RNase. Next, RNA is hydrolyzed into 5' nucleoside monophosphates, which are analyzed 2D-TLC (two-dimensional thin-layer chromatography). This method is able to detect and quantify every modification but will not contribute to the characterization of the sequence.
*Post-labelling → implicates the selective labelling of a specific position within the sequence: these techniques rely on the Stanley-Vassilenko approach principles, that has been adjusted to achieve a better validation quality. First, RNA is cleaved into free 5’-OH fragments either by RNase H or DNAzymes, by sequence specific hydrolysis. The polynucleotide kinase (PKN) then performs the 5’ radioactive post-labelling phosphorylation using [γ-P]ATP. At this point, the labelled fragments undergo a size fragmentation, that can be performed either by Nuclease P1 or according to the SCARLET method. In both cases, the final product is a group of 5’ nucleoside monophosphates (5’ NMPs) that will be analyzed by TLC.
**SCARLET: this recent approach exploits not just one, but two sequence selection steps, the last of which is obtained during the splinted ligation of the radioactive-labelled fragments with a long DNA oligonucleotide, at its 3’-end. After degradation, the labelled residue is purified together with the ligated DNA oligonucleotide and finally hydrolyzed and therefore released thanks to the activity of the Nuclease P1.
This method has proven to be very useful in the validation of modified residues in mRNAs and lncRNAs, such as m6A and Ψ
#Oligonucleotide-based techniques: this method includes several variants
*Splinted ligation of particular modified DNAs, that exploits the ligase sensitivity to 3’ and 5’ nucleotides (so far used for m6A, 2’-O-Me, Ψ)
*Microarray modification identification through a DNA-chip, that exploits the decrease in duplex stability of cDNA oligonucleotides, due to the impediment in conventional base-pairing caused by modifications (ex. m1A, m1G, m22G)
*RT primer extension at low dNTPs concentration, for mapping of RT arrest signals. | 1 | Applied and Interdisciplinary Chemistry |
The fundamental interacting force of physisorption is Van der Waals force. Even though the interaction energy is very weak (~10–100 meV), physisorption plays an important role in nature. For instance, the van der Waals attraction between surfaces and foot-hairs of geckos (see Synthetic setae) provides the remarkable ability to climb up vertical walls. Van der Waals forces originate from the interactions between induced, permanent or transient electric dipoles.
In comparison with chemisorption, in which the electronic structure of bonding atoms or molecules is changed and covalent or ionic bonds form, physisorption does not result in changes to the chemical bonding structure. In practice, the categorisation of a particular adsorption as physisorption or chemisorption depends principally on the binding energy of the adsorbate to the substrate, with physisorption being far weaker on a per-atom basis than any type of connection involving a chemical bond. | 0 | Theoretical and Fundamental Chemistry |
Favipiravir is sold under the brand names , Avifavir, Avipiravir, Areplivir, FabiFlu, Favipira, Reeqonus, and Qifenda. | 0 | Theoretical and Fundamental Chemistry |
Forestal is a solvent used in chromatography, composed of acetic acid, water, and hydrochloric acid in a 30:10:3 ratio by volume. It is useful for isolating anthocyanins in room-temperature chromatography using standard filter paper. | 0 | Theoretical and Fundamental Chemistry |
* Hellman Fellow, Chris & Warren Hellman Young Faculty Award, 2002
* Faculty Career Development Award, Academic Senate, UCSD, 2003
* Alfred P. Sloan Research Fellowship, 2004
* Lifetime Honorary Member, Israel Chemical Society, 2009
* Visiting Professor at the University of Manchester, since 2009
* Japan Society for the Promotion of Science (JSPS) Award, 2009
* Dalton Transactions European / African Lectureship Award, 2010
* Fellow of the Royal Society of Chemistry, 2011
* JSPS Professorship, "Brain Circulation Project", Nagoya Institute of Technology, 2015
* Elhuyar-Goldschmidt Award, Spanish Royal Society of Chemistry, 2017
* Ludwig Mond Award, Royal Society of Chemistry, 2017
* L.A. Chugaev Commemorative Medal, Russian Academy of Sciences, 2017 | 0 | Theoretical and Fundamental Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.