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Rotation of the reduction furnace may be a design choice intended to circulate the ore through the furnace. It can also play an active part in the chemical reaction by ensuring mixing between the reactants present. Rotary hearth processes, where the ore rests on a fixed bed and travels through a tunnel, fall into the first category. Rotary kiln processes, where the ore is mixed with coal at high temperature, constitute the second category. | 1 | Applied and Interdisciplinary Chemistry |
The activity coefficient , which is also a dimensionless quantity, relates the activity to a measured mole fraction (or in the gas phase), molality , mass fraction , molar concentration (molarity) or mass concentration :
The division by the standard molality (usually 1 mol/kg) or the standard molar concentration (usually 1 mol/L) is necessary to ensure that both the activity and the activity coefficient are dimensionless, as is conventional.
The activity depends on the chosen standard state and composition scale; for instance, in the dilute limit it approaches the mole fraction, mass fraction, or numerical value of molarity, all of which are different. However, the activity coefficients are similar.
When the activity coefficient is close to 1, the substance shows almost ideal behaviour according to Henrys law (but not necessarily in the sense of an ideal solution). In these cases, the activity can be substituted with the appropriate dimensionless measure of composition , or . It is also possible to define an activity coefficient in terms of Raoults law: the International Union of Pure and Applied Chemistry (IUPAC) recommends the symbol for this activity coefficient, although this should not be confused with fugacity. | 0 | Theoretical and Fundamental Chemistry |
As aircraft performance increased in the mid-20th century, the amount of force required to operate mechanical flight controls became excessive, and hydraulic systems were introduced to reduce pilot effort. The hydraulic actuators are controlled by valves; these in turn are operated directly by input from the aircrew (hydro-mechanical) or by computers obeying control laws (fly by wire).
Hydraulic power is used for other purposes. It can be stored in accumulators to start an auxiliary power unit (APU) for self-starting the aircraft's main engines. Many aircraft equipped with the M61 family of cannon use hydraulic power to drive the gun system, permitting reliable high rates of fire.
The hydraulic power itself comes from pumps driven by the engines directly, or by electrically-driven pumps. In modern commercial aircraft these are electrically-driven pumps; should all the engines fail in flight the pilot will deploy a propeller-driven electric generator called a Ram-Air Turbine (RAT) which is concealed under the fuselage. This provides electrical power for the hydraulic pumps and control systems as power is no longer available from the engines. In that system and others, electric pumps can provide both redundancy and the means of operating hydraulic systems without the engines operating, which can be very useful during maintenance. | 1 | Applied and Interdisciplinary Chemistry |
Foodomics was defined in 2009 as "a discipline that studies the Food and Nutrition domains through the application and integration of advanced -omics technologies to improve consumer's well-being, health, and knowledge". Foodomics requires the combination of food chemistry, biological sciences, and data analysis.
The study of foodomics became under the spotlight after it was introduced in the first international conference in 2009 at Cesena, Italy. Many experts in the field of omics and nutrition were invited to this event in order to find the new approach and possibility in the area of food science and technology. However, research and development of foodomics today are still limited due to high throughput analysis required. The American Chemical Society journal called Analytical Chemistry dedicated its cover to foodomics in December 2012.
Foodomics involves four main areas of omics:
* Genomics, which involves investigation of genome and its pattern.
* Transcriptomics, which explores a set of gene and identifies the difference among various conditions, organisms, and circumstance, by using several techniques including microarray analysis;
* Proteomics, studies every kind of proteins that is a product of the genes. It covers how protein functions in a particular place, structures, interactions with other proteins, etc.;
* Metabolomics, includes chemical diversity in the cells and how it affects cell behavior; | 1 | Applied and Interdisciplinary Chemistry |
A system akin to the Bessemer process has existed since the 11th century in East Asia. Economic historian Robert Hartwell writes that the Chinese of the Song Dynasty (960–1279 CE) innovated a "partial decarbonization" method of repeated forging of cast iron under a cold blast. Sinologist Joseph Needham and historian of metallurgy Theodore A. Wertime have described the method as a predecessor to the Bessemer process of making steel. This process was first described by the prolific scholar and polymath government official Shen Kuo (1031–1095) in 1075, when he visited Cizhou. Hartwell states that perhaps the earliest center where this was practiced was the great iron-production district along the Henan–Hebei border during the 11th century. | 1 | Applied and Interdisciplinary Chemistry |
Red mud is composed of a mixture of solid and metallic oxides. The red colour arises from iron oxides, which can comprise up to 60% of the mass. The mud is highly basic with a pH ranging from 10 to 13. In addition to iron, the other dominant components include silica, unleached residual aluminium compounds, and titanium oxide.
The main constituents of the residue after the extraction of the aluminium component are insoluble metallic oxides. The percentage of these oxides produced by a particular alumina refinery will depend on the quality and nature of the bauxite ore and the extraction conditions. The table below shows the composition ranges for common chemical constituents, but the values vary widely:
Mineralogically expressed the components present are:
In general, the composition of the residue reflects that of the non-aluminium components, with the exception of part of the silicon component: crystalline silica (quartz) will not react but some of the silica present, often termed, reactive silica, will react under the extraction conditions and form sodium aluminium silicate as well as other related compounds. | 1 | Applied and Interdisciplinary Chemistry |
When synthesizing simple organolithium reagents, the reduction of one equivalent of a simple alkyl or aryl halide with two equivalents of lithium metal produces one equivalent of a simple alkyl- or aryl-lithium and one equivalent of lithium halide with good yield.
This reaction is known to proceed via a radical pathway that is likely initiated through a single-electron-transfer mechanism of the type shown below.
Magnesium similarly metalates organohalides to give Grignard reagents. | 0 | Theoretical and Fundamental Chemistry |
The calculations to be performed on the measurements taken depend on the technology used, since beta counters measure the sample's radioactivity whereas AMS determines the ratio of the three different carbon isotopes in the sample.
To determine the age of a sample whose activity has been measured by beta counting, the ratio of its activity to the activity of the standard must be found. To determine this, a blank sample (of old, or dead, carbon) is measured, and a sample of known activity is measured. The additional samples allow errors such as background radiation and systematic errors in the laboratory setup to be detected and corrected for. The most common standard sample material is oxalic acid, such as the HOxII standard, of which was prepared by the National Institute of Standards and Technology (NIST) in 1977 from French beet harvests.
The results from AMS testing are in the form of ratios of , , and , which are used to calculate Fm, the "fraction modern". This is defined as the ratio between the / ratio in the sample and the / ratio in modern carbon, which is in turn defined as the / ratio that would have been measured in 1950 had there been no fossil fuel effect.
Both beta counting and AMS results have to be corrected for fractionation. This is necessary because different materials of the same age, which because of fractionation have naturally different / ratios, will appear to be of different ages because the / ratio is taken as the indicator of age. To avoid this, all radiocarbon measurements are converted to the measurement that would have been seen had the sample been made of wood, which has a known δ value of −25‰.
Once the corrected / ratio is known, a "radiocarbon age" is calculated using:
The calculation uses 8,033 years, the mean-life derived from Libbys half-life of 5,568 years, not 8,267 years, the mean-life derived from the more accurate modern value of 5,730 years. Libbys value for the half-life is used to maintain consistency with early radiocarbon testing results; calibration curves include a correction for this, so the accuracy of final reported calendar ages is assured. | 0 | Theoretical and Fundamental Chemistry |
A Langmuir monolayer can be compressed or expanded by modifying its area with a moving barrier in a Langmuir film balance. If the surface tension of the interface is measured during the compression, a compression isotherm is obtained. This isotherm shows the variation of surface pressure (, where is the surface tension of the interface before the monolayer is formed) with the area (the inverse of surface concentration ). It is analogous with a 3D process in which pressure varies with volume.
A variety of bidimensional phases can be detected, each separated by a phase transition. During the phase transition, the surface pressure doesnt change, but the area does, just like during normal phase transitions volume changes but pressure doesnt.
The 2D phases, in increasing pressure order:
* Bidimensional gas: there are few molecules per area unit, and they have few interactions, therefore, analogous of the equations of state for 3D gases can be used: ideal gas law , where is the area per mole. As the surface pressure increases, more complex equations are needed (Van der Waals, virial...)
* Expanded liquid
* Compressed liquid
* Solid
If the area is further reduced once the solid phase has been reached, collapse occurs, the monolayer breaks and soluble aggregates and multilayers are formed
Gibbs monolayers also follow equations of state, which can be deduced from Gibbs isotherm.
* For very dilute solutions , through Gibbs isotherm another analogous of ideal gas law is reached
* For more concentrated solutions and applying Langmuir isotherm , thus | 0 | Theoretical and Fundamental Chemistry |
The advection equation is the partial differential equation that governs the motion of a conserved scalar field as it is advected by a known velocity vector field. It is derived using the scalar fields conservation law, together with Gausss theorem, and taking the infinitesimal limit.
One easily visualized example of advection is the transport of ink dumped into a river. As the river flows, ink will move downstream in a "pulse" via advection, as the water's movement itself transports the ink. If added to a lake without significant bulk water flow, the ink would simply disperse outwards from its source in a diffusive manner, which is not advection. Note that as it moves downstream, the "pulse" of ink will also spread via diffusion. The sum of these processes is called convection. | 1 | Applied and Interdisciplinary Chemistry |
Power spectral-analysis have been used to examine the spatial structures for climate research. These results suggests atmospheric turbulence link climate change to more local regional volatility in weather conditions. | 0 | Theoretical and Fundamental Chemistry |
Given that there is no need for restriction enzymes other than for generating the linearized vector, the procedure is much simpler and faster than traditional subcloning. There is also no need to add restriction sites when designing primers and thus shorter primers can be used saving time and money. In addition, in instances where there are no viable restriction sites that can be used for traditional cloning, TA cloning is often used as an alternative. The major downside of TA cloning is that directional cloning is not possible, so the gene has a 50% chance of getting cloned in the reverse direction. | 1 | Applied and Interdisciplinary Chemistry |
A telluroxide is a type of organotellurium compound with the formula RTeO. These compounds are analogous to sulfoxides in some respects. Reflecting the decreased tendency of Te to form multiple bonds, telluroxides exist both the monomer and the polymer, which are favored in solution and the solid state, respectively:
:(RTeO) n RTeO
Telluroxides are prepared from the telluroethers by halogenation followed by base hydrolysis:
:RTe + Br → RTeBr
:RTeBr + 2 NaOH → RTeO + 2 NaBr + HO | 0 | Theoretical and Fundamental Chemistry |
Sustainable drainage systems (also known as SuDS, SUDS, or sustainable urban drainage systems) are a collection of water management practices that aim to align modern drainage systems with natural water processes and are part of a larger green infrastructure strategy. SuDS efforts make urban drainage systems more compatible with components of the natural water cycle such as storm surge overflows, soil percolation, and bio-filtration. These efforts hope to mitigate the effect human development has had or may have on the natural water cycle, particularly surface runoff and water pollution trends.
SuDS have become popular in recent decades as understanding of how urban development affects natural environments, as well as concern for climate change and sustainability, have increased. SuDS often use built components that mimic natural features in order to integrate urban drainage systems into the natural drainage systems or a site as efficiently and quickly as possible. SUDS infrastructure has become a large part of the Blue-Green Cities demonstration project in Newcastle upon Tyne. | 1 | Applied and Interdisciplinary Chemistry |
Many discoveries of precolonial gold artifacts go unreported because the gold is found or stolen by treasure hunters, who simply melt the gold down for profit. Among the most important gold artifact discoveries are the "Surigao Treasure" found by construction worker Berto Morales in 1991, the Agusan image found by Manobo woman Belay Campos in 1917, the Bolinao Skull discovered by the National Museum of the Philippines at the Balingasay Archaeological Site in Bolinao, Pangasinan,and the Oton Death Mask excavated rom San Antonio, Iloilo on Panay Island by a team from the National Museum of the Philippines and the University of the Philippines Diliman in the 1960s. | 1 | Applied and Interdisciplinary Chemistry |
Changes in the RNA processing machinery may lead to mis-splicing of multiple transcripts, while single-nucleotide alterations in splice sites or cis-acting splicing regulatory sites may lead to differences in splicing of a single gene, and thus in the mRNA produced from a mutant gene's transcripts. A study in 2005 involving probabilistic analyses indicated that greater than 60% of human disease-causing mutations affect splicing rather than directly affecting coding sequences. A more recent study indicates that one-third of all hereditary diseases are likely to have a splicing component. Regardless of exact percentage, a number of splicing-related diseases do exist. As described below, a prominent example of splicing-related diseases is cancer.
Abnormally spliced mRNAs are also found in a high proportion of cancerous cells. Combined RNA-Seq and proteomics analyses have revealed striking differential expression
of splice isoforms of key proteins in important cancer pathways. It is not always clear whether such aberrant patterns of splicing contribute to the cancerous growth, or are merely consequence of cellular abnormalities associated with cancer. For certain types of cancer, like in colorectal and prostate, the number of splicing errors per cancer has been shown to vary greatly between individual cancers, a phenomenon referred to as transcriptome instability. Transcriptome instability has further been shown to correlate grealty with reduced expression level of splicing factor genes. Mutation of DNMT3A has been demonstrated to contribute to hematologic malignancies, and that DNMT3A-mutated cell lines exhibit transcriptome instability as compared to their isogenic wildtype counterparts.
In fact, there is actually a reduction of alternative splicing in cancerous cells compared to normal ones, and the types of splicing differ; for instance, cancerous cells show higher levels of intron retention than normal cells, but lower levels of exon skipping. Some of the differences in splicing in cancerous cells may be due to the high frequency of somatic mutations in splicing factor genes, and some may result from changes in phosphorylation of trans-acting splicing factors. Others may be produced by changes in the relative amounts of splicing factors produced; for instance, breast cancer cells have been shown to have increased levels of the splicing factor SF2/ASF. One study found that a relatively small percentage (383 out of over 26000) of alternative splicing variants were significantly higher in frequency in tumor cells than normal cells, suggesting that there is a limited set of genes which, when mis-spliced, contribute to tumor development. It is believed however that the deleterious effects of mis-spliced transcripts are usually safeguarded and eliminated by a cellular posttranscriptional quality control mechanism termed nonsense-mediated mRNA decay [NMD].
One example of a specific splicing variant associated with cancers is in one of the human DNMT genes. Three DNMT genes encode enzymes that add methyl groups to DNA, a modification that often has regulatory effects. Several abnormally spliced DNMT3B mRNAs are found in tumors and cancer cell lines. In two separate studies, expression of two of these abnormally spliced mRNAs in mammalian cells caused changes in the DNA methylation patterns in those cells. Cells with one of the abnormal mRNAs also grew twice as fast as control cells, indicating a direct contribution to tumor development by this product.
Another example is the Ron (MST1R) proto-oncogene. An important property of cancerous cells is their ability to move and invade normal tissue. Production of an abnormally spliced transcript of Ron has been found to be associated with increased levels of the SF2/ASF in breast cancer cells. The abnormal isoform of the Ron protein encoded by this mRNA leads to cell motility.
Overexpression of a truncated splice variant of the FOSB gene – ΔFosB – in a specific population of neurons in the nucleus accumbens has been identified as the causal mechanism involved in the induction and maintenance of an addiction to drugs and natural rewards.
Recent provocative studies point to a key function of chromatin structure and histone modifications in alternative splicing regulation. These insights suggest that epigenetic regulation determines not only what parts of the genome are expressed but also how they are spliced. | 1 | Applied and Interdisciplinary Chemistry |
In the early 1900s, chemical messengers were crudely extracted from whole animal brains and tissues and studied for their physiological effects. In 1931, von Euler and Gaddum, used a similar method to try and isolate acetylcholine but instead discovered a peptide substance that induced physiological changes including muscle contractions and depressed blood pressure. These effects were not abolished using atropine, ruling out the substance as acetylcholine.
In insects, proctolin was the first neuropeptide to be isolated and sequenced. In 1975, Alvin Starratt and Brian Brown extracted the peptide from hindgut muscles of the cockroach and found that its application enhanced muscle contractions. While Starratt and Brown initially thought of proctolin as an excitatory neurotransmitter, proctolin was later confirmed as a neuromodulatory peptide.
David de Wied first used the term "neuropeptide" in the 1970s to delineate peptides derived from the nervous system. | 1 | Applied and Interdisciplinary Chemistry |
With a relatively low global warming potential (GWP) index of 124 and favorable thermophysical properties, 1,1-difluoroethane has been proposed as an environmentally friendly alternative to R134a. Despite its flammability, R152a also presents operating pressures and volumetric cooling capacity (VCC) similar to R134a so it can be used in large chillers or in more particular applications like heat pipe finned heat exchangers.
Furthermore, 1,1-difluoroethane is also commonly used in gas dusters and numerous other retail aerosol products, particularly those subject to stringent volatile organic compound (VOC) requirements.
The molecular weight of difluoroethane is 66, making it a useful and convenient tool for detecting vacuum leaks in Gas chromatography–mass spectrometry (GC-MS) systems. The cheap and freely available gas has a molecular weight and fragmentation pattern (base peak 51 m/z in typical EI-MS, major peak at 65 m/z) distinct from anything in air. If mass peaks corresponding to 1,1-difluoroethane are observed immediately after spraying a suspect leak point, leaks may be identified. | 1 | Applied and Interdisciplinary Chemistry |
Mixer settlers are a class of mineral process equipment used in the solvent extraction process. A mixer settler consists of a first stage that mixes the phases together followed by a quiescent settling stage that allows the phases to separate by gravity. | 0 | Theoretical and Fundamental Chemistry |
An alternative approach for applying the Hellmann–Feynman theorem is to promote a fixed or discrete parameter which appears in a Hamiltonian to be a continuous variable solely for the mathematical purpose of taking a derivative. Possible parameters are physical constants or discrete quantum numbers. As an example, the radial Schrödinger equation for a hydrogen-like atom is
which depends upon the discrete azimuthal quantum number . Promoting to be a continuous parameter allows for the derivative of the Hamiltonian to be taken:
The Hellmann–Feynman theorem then allows for the determination of the expectation value of for hydrogen-like atoms:
In order to compute the energy derivative, the way depends on has to be known. These quantum numbers are usually independent, but here the solutions must be varied so as to keep the number of nodes in the wavefunction fixed. The number of nodes is , so . | 0 | Theoretical and Fundamental Chemistry |
PDC electrolysis was first considered theoretically in 1952, and experimental research began as early as 1960 however it was originally focused on its technical applications to industry and the possibilities of improving the quality and rate of metal deposition. It partially succeeded, providing promising results its ability to create smoother, denser deposits, and reducing the amount of metal required in electroplating.
The first instance it was considered to initialise the electrolysis of water was from the perspective of magnetolysis in 1985, where high strength magnets, or in this case electromagnets, are used in conjunction with homopolar propellers. Ghoroghichian and Bockris conducted this experimental research to determine how a pulsed current can impact the rate of hydrogen production and provide economic advantages. A current density ratio of 2.07 was observed, demonstrating, for the first time, that a pulsed current can double the production of hydrogen, in comparison to a steady state current.
Since hydrogen gas cannot be collected in its free form, and it can be used to provide a source of renewable and clean energy through fuel cells, discovering an electrolysis method with the greatest efficiency is valued. With early experimental and theoretical success, many patents began to be developed until as recent as 2002, but since 1985, it has only been researched intermittently with varying levels of success. | 0 | Theoretical and Fundamental Chemistry |
1-Arseno-3-phosphoglycerate can be derived from the glycolytic pathway via the bonding of Arsenate and glyceraldehyde-3-phosphate, which is catalyzed by glyceraldehyde phosphate dehydrogenase (GAPDH). The net production of ATP is zero as a result of the formation of the intermediate, 1-arseno-3-phosphoglycerate, as opposed to the conventional pathway, which produces a net result of two ATP molecules. | 1 | Applied and Interdisciplinary Chemistry |
In order to combat the potential global warming effects of F-gases, and as part of the EU's Kyoto protocol commitments, in 2006 the European Union passed two pieces of legislation controlling their use: the [http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2006:161:0001:0011:EN:PDF F-gas Regulation (EC) No 842/2006] and the Mobile Air Conditioning Directive [http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2006:161:0012:0018:en:PDF Directive 2006/40/EC]. The F-gas Regulation adopts an approach based on containment and recovery of F-gases as well as imposing obligations on reporting, training and labeling on those using F-gases.
On 26 September 2011, the Commission issued a [http://ec.europa.eu/clima/policies/f-gas/docs/report_en.pdf report] on the application, effects and adequacy of the Regulation, drawing from the results of an analytical [http://ec.europa.eu/clima/policies/f-gas/docs/2011_study_en.pdf study] it commissioned from German environmental research institute, Öko-Recherche. A further [https://web.archive.org/web/20130720143224/http://www.epeeglobal.org/epeedocs/internet/docs/ERIE__Armines_study_-_Executive_Summary_-_October_2011_5889.pdf study], conducted by the Armines Centre energétique et procédés and by Energy Research Innovation Engineering (ERIE) found that emissions reductions of up to 60% can be achieved by improving containment measures and accelerating the changeover from high GWP refrigerants to ones with lower GWP.
On 7 November 2012, the European Commission published the [http://ec.europa.eu/clima/policies/f-gas/legislation/docs/com_2012_643_en.pdf proposal] to revise the F-gas Regulation. In December 2013, the European Parliament and the Council of the EU agreed the [http://www.eu2013.lt/en/news/pressreleases/member-states-approve-the-agreement-by-the-co-legislators-on-the-regulation-on-reduction-of-emissions-of-fluorinated-greenhouse-gases-f-gases- text of the revised regulation], which shall be applied from 1 January 2015. | 1 | Applied and Interdisciplinary Chemistry |
Xiang et al. found a new approach in inhibiting tumour growth and metastasis by simultaneously attacking both the tumour and its vasculature by a cytotoxic T cell (CTL) response against the survivin protein, which will later result in the activation of apoptosis in tumour cells.
The idea and general principle behind his technique is described below. Mice were immunized with the oral vaccination and then subjected to tumour challenges by injecting them in the chest with a certain number of tumour cells and a Matrigel pre-formed extracellular matrix to hold the tumour cells together. The mice were sacrificed and the endothelium tissue was stained with a fluorescent dye that would aid in the quantification of tumour neovascularisation using a Matrigel assay. There was found to be a significant difference between the control and test groups, whereby mice given the vaccine had less angiogenesis from the tumour challenge than the control mice that were not given any of the vaccine prior to tumour challenge. In vitro assays and other tests were also performed to validate the idea of the occurrence of an actual immune response to support what they observed in the mice. For example, the spleen on the challenged mice were isolated and measured for the presence of any cytokines, and specifically activated immune cell groups that would indicative that a specific immune response did occur upon vaccination. The isolated CTLs specific for the survivin protein after vaccination of the mice were used in cytoxicity assays where mice tumour cells expressing survivin were shown to be killed upon incubation with the specific CTLs.
By using an oral DNA vaccine carried in an attenuated non-virulent form of Salmonella typhimurium, which co-encoded secretory chemokine CCL21 and survivin protein in C57BL/6J mice, Xiang et al. have been able to elicit an immune response carried out by dendritic cells (DCs) and CTLs to eliminate and suppress the pulmonary metastases of non-small cell lung carcinoma. The activation of the immune response is most likely taking place in the secondary lymphoid organ called the Peyer's Patch in the small intestine where DCs take up the survivin protein by phagocytosis and present them on their surface receptors to naive CD8+ T cells (uninactivated CTL) to achieve a specific immune response targeting survivin exclusively. Activated CTLs specific for a particular antigen kill their target cells by first recognizing parts of the survivin protein expressed on MHC I (immunohistocompatability) proteins presented on the surface of tumour cells and vasculature and then releasing granules that induce the tumour cells to undergo apoptosis. The DNA vaccine contained the CCL21 secretory chemokine as a way to enhance the likelihood of eliciting the immune response by better mediating the physical interaction of the antigen-presenting DCs and the naive CD8+ T cells, resulting in a greater likelihood of immune activation. | 1 | Applied and Interdisciplinary Chemistry |
* Positions of the CBED disks are the same as the positions of the Bragg peaks and are given approximately by the relation:
where is the distance between the crystallographic planes , is the Bragg angle, is an integer, and is the wavelength of the probing electrons.
* The beam convergence semi-angle - is controlled by the C2 aperture. The probing beam convergence semi-angle, , is of the order of milliradians, ranging from 0.1˚ to 1˚. For small convergence semi-angle, the CBED disks do not overlap with each other, whereas for larger semi-convergence angles, the disks overlap.
* The diameter of a CBED disk is given by the beam convergence semi-angle :
* Defocus : The distance between the crossover of the probing beam and the position of the specimen is called the defocus distance . The sample can be moved along the axis. At a defocus distance, both the direct space and reciprocal space information are visible in the CBED pattern. | 0 | Theoretical and Fundamental Chemistry |
When two streams or rivers merge or water is discharged to a stream it is possible to determine the BOD and DO after mixing assuming steady state conditions and instantaneous mixing. The two streams are considered as dilutions of each other thus the initial BOD and DO will be
and
where
* is the initial concentration of BOD in the river downstream of the mixing, also called BOD(0). The unit of is .
* is the background BOD of the concentration in the river .
* is the BOD of the content of the merging river .
* is the initial concentration of the dissolved oxygen in the river downstream of the conjoining point .
* is the background concentration of the dissolved oxygen content in the river .
* is the background concentration of the dissolved oxygen content in the merging river .
* is the flow in the river upstream from the mixing point .
* is the flow in the merging river upstream from the mixing point . | 1 | Applied and Interdisciplinary Chemistry |
Generally, the Koenigs–Knorr reaction refers to the use of glycosyl chlorides, bromides and more recently iodides as glycosyl donors. The Koenigs–Knorr reaction can be performed with alternative promoters such as various heavy metal salts including mercuric bromide/mercuric oxide, mercuric cyanide and silver triflate. When mercury salts are used, the reaction is normally called the Helferich method.
Other glycosidation methods are Fischer glycosidation, use of glycosyl acetates, thioglycosides, glycosyl trichloroacetimidates, glycosyl fluorides or n-pentenyl glycosides as glycosyl donors, or intramolecular aglycon delivery. | 0 | Theoretical and Fundamental Chemistry |
Arachidonoyl serotonin (N-arachidonoyl-serotonin, AA-5-HT) is an endogenous lipid signaling molecule. It was first described in 1998 as being an inhibitor of fatty acid amide hydrolase (FAAH). In 2007, it was shown to have analgesic properties and to act as an antagonist of the TRPV1 receptor. In 2011, it was shown to be present in the ileum and jejunum of the gastrointestinal tract and modulate glucagon-like peptide-1 (GLP-1) secretion. In addition to this, in 2016, AA-5-HT was also found to affect the signaling mechanisms responsible for anxiety, by inhibiting dopamine release from the Basolateral amygdala following fear behavior. In 2017, AA-5-HT was tested in its effects on the sleep wake cycle, where it was found to affect the sleep homeostasis when used in conjunction with molecules and chemicals that affect wake-related neurotransmitters. | 1 | Applied and Interdisciplinary Chemistry |
Oxidative deamination is a form of deamination that generates α-keto acids and other oxidized products from amine-containing compounds, and occurs primarily in the liver. Oxidative deamination is stereospecific, meaning it contains different stereoisomers as reactants and products; this process is either catalyzed by L or D- amino acid oxidase and L-amino acid oxidase is present only in the liver and kidney. Oxidative deamination is an important step in the catabolism of amino acids, generating a more metabolizable form of the amino acid, and also generating ammonia as a toxic byproduct. The ammonia generated in this process can then be neutralized into urea via the urea cycle.
Much of the oxidative deamination occurring in cells involves the amino acid glutamate, which can be oxidatively deaminated by the enzyme glutamate dehydrogenase (GDH), using NAD or NADP as a coenzyme. This reaction generates α-ketoglutarate (α-KG) and ammonia. Glutamate can then be regenerated from α-KG via the action of transaminases or aminotransferase, which catalyze the transfer of an amino group from an amino acid to an α-keto acid. In this manner, an amino acid can transfer its amine group to glutamate, after which GDH can then liberate ammonia via oxidative deamination. This is a common pathway during amino acid catabolism.
Another enzyme responsible for oxidative deamination is monoamine oxidase, which catalyzes the deamination of monoamines via addition of oxygen. This generates the corresponding ketone- or aldehyde-containing form of the molecule, and generates ammonia. Monoamine oxidases MAO-A and MAO-B play vital roles in the degradation and inactivation of monoamine neurotransmitters such as serotonin and epinephrine. Monoamine oxidases are important drug targets, targeted by MAO inhibitors (MAOIs) such as selegiline. Glutamate dehydrogenase play an important role in oxidative deamination. | 1 | Applied and Interdisciplinary Chemistry |
The basic idea of the DDA was introduced in 1964 by DeVoe who applied it to study the optical properties of molecular aggregates; retardation effects were not included, so DeVoe's treatment was limited to aggregates that were small compared with the wavelength. The DDA, including retardation effects, was proposed in 1973 by Purcell and Pennypacker
who used it to study interstellar dust grains. Simply stated, the DDA is an approximation of the continuum target by a finite array of polarizable points. The points acquire dipole moments in response to the local electric field. The dipoles interact with one another via their electric fields, so the DDA is also sometimes referred to as the coupled dipole approximation.
Nature provides the physical inspiration for the DDA - in 1909 Lorentz
showed that the dielectric properties of a substance could be directly related to the polarizabilities of the individual atoms of which it was composed, with a particularly simple and exact relationship, the Clausius-Mossotti relation (or Lorentz-Lorenz), when the atoms are located on a cubical lattice. We may expect that, just as a continuum representation of a solid is appropriate on length scales that are large compared with the interatomic spacing, an array of polarizable points can accurately approximate the response of a continuum target on length scales that are large compared with the interdipole separation.
For a finite array of point dipoles the scattering problem may be solved exactly, so the only approximation that is present in the DDA is the replacement of the continuum target by an array of N-point dipoles. The replacement requires specification of both the geometry (location of the dipoles) and the dipole polarizabilities. For monochromatic incident waves the self-consistent solution for the oscillating dipole moments may be found; from these the absorption and scattering cross sections are computed. If DDA solutions are obtained for two independent polarizations of the incident wave, then the complete amplitude scattering matrix can be determined.
Alternatively, the DDA can be derived from volume integral equation for the electric field. This highlights that the approximation of point dipoles is equivalent to that of discretizing the integral equation, and thus decreases with decreasing dipole size.
With the recognition that the polarizabilities may be tensors, the DDA can readily be applied to anisotropic materials. The extension of the DDA to treat materials with nonzero magnetic susceptibility is also straightforward, although for most applications magnetic effects are negligible.
There are several reviews of DDA method. | 0 | Theoretical and Fundamental Chemistry |
Vaska published ca. eighty journal articles on the coordination chemistry of transition metals, homogeneous catalysis, and both organometallic and bioinorganic chemistry. His years at Mellon were especially productive. With J.W. Di Luzio in 1962 he first described the iridium compound which became known as Vaskas complex, trans-IrCl(CO)[P(CH)] Working with a series of coworkers, he demonstrated that this iridium(I) complex undergoes a variety of reactions with small molecules. For example, it oxidatively adds H to give a dihydride. He subsequently discovered that his complex reversibly bound O, which was then a startling achievement. He discovered the main reactions of oxidative addition, a process that is central to homogeneous catalysis in organometallic chemistry. He demonstrated a number of important substituent effects on the oxidative addition, such as the greater reactivity of Ir(I) vs. Rh(I) and the stabilization of oxidative adducts by iodide vs.' chloride. | 0 | Theoretical and Fundamental Chemistry |
Latticial metal complex or grid complex is a supramolecular complex of several metal atoms and coordinating ligands which form a grid-like structural motif. The structure formation usually occurs while on thermodynamic molecular self-assembly. They have properties that make them interesting for information technology as the future storage materials.
Chelate ligands are used as ligands in tetrahedral or octahedral structures, which mostly use nitrogen atoms in pyridine like ring systems other than donor centers. Suitable metal ions are in accordance with octahedral coordinating transition metal ions such as Mn or rare tetrahedral Coordinating such as Ag used. | 0 | Theoretical and Fundamental Chemistry |
Some subfields of geochemistry are:
*Aqueous geochemistry studies the role of various elements in watersheds, including copper, sulfur, mercury, and how elemental fluxes are exchanged through atmospheric-terrestrial-aquatic interactions.
*Biogeochemistry is the field of study focusing on the effect of life on the chemistry of the Earth.
*Cosmochemistry includes the analysis of the distribution of elements and their isotopes in the cosmos.
*Isotope geochemistry involves the determination of the relative and absolute concentrations of the elements and their isotopes in the Earth and on Earth's surface.
*Organic geochemistry, the study of the role of processes and compounds that are derived from living or once-living organisms.
*Photogeochemistry is the study of light-induced chemical reactions that occur or may occur among natural components of the Earth's surface.
*Regional geochemistry includes applications to environmental, hydrological and mineral exploration studies. | 0 | Theoretical and Fundamental Chemistry |
Covalent bonds can be polarized depending on the relative electronegativity of the two atoms forming the bond. The electron cloud in a σ-bond between two unlike atoms is not uniform and is slightly displaced towards the more electronegative of the two atoms. This causes a permanent state of bond polarization, where the more electronegative atoms has a fractional negative charge (δ) and the less electronegative atom has a fractional positive charge (δ).
For example, the water molecule has an electronegative oxygen atom that attracts a negative charge. This is indicated by δ in the water molecule in the vicinity of the O atom, as well as by a δ next to each of the two H atoms. The vector addition of the individual bond dipole moments results in a net dipole moment for the molecule. A polar bond is a covalent bond in which there is a separation of charge between one end and the other - in other words in which one end is slightly positive and the other slightly negative. Examples include most covalent bonds. The hydrogen-chlorine bond in HCl or the hydrogen-oxygen bonds in water are typical. | 0 | Theoretical and Fundamental Chemistry |
The Markstein number with respect to the unburnt gas mixture for a one step reaction in the limit of large activation energy asymptotics was derived by Paul Clavin and Forman A. Williams in 1982. The Markstein number then is
where
* is the heat release parameter defined with density ratio,
* is the Zel'dovich number,
* is the Lewis number of the deficient reactant (either fuel or oxidizer)
* is the dilogarithm function.
and the Markstein number with respect to the burnt gas mixture is derived by Clavin (1985) | 1 | Applied and Interdisciplinary Chemistry |
Like esters, most carboxylic acids can be reduced to alcohols by hydrogenation, or using hydride transferring agents such as lithium aluminium hydride. Strong alkyl transferring agents, such as organolithium compounds but not Grignard reagents, will reduce carboxylic acids to ketones along with transfer of the alkyl group.
Vilsmaier reagent (N,N-Dimethyl(chloromethylene)ammonium chloride [ClHC\dN+(CH3)2]Cl−) is a highly chemoselective agent for carboxylic acid reduction. It selectively activates the carboxylic acid to give the carboxymethyleneammonium salt, which can be reduced by a mild reductant like lithium tris(t-butoxy)aluminum hydride to afford an aldehyde in a one pot procedure. This procedure is known to tolerate reactive carbonyl functionalities such as ketone as well as moderately reactive ester, olefin, nitrile, and halide moieties. | 0 | Theoretical and Fundamental Chemistry |
In humans, about 70% of promoters located near the transcription start site of a gene (proximal promoters) contain a CpG island. CpG islands are generally 200 to 2000 base pairs long, have a C:G base pair content >50%, and have regions of DNA where a cytosine nucleotide is followed by a guanine nucleotide and this occurs frequently in the linear sequence of bases along its 5′ → 3′ direction.
Genes may also have distant promoters (distal promoters) and these frequently contain CpG islands as well. An example is the promoter of the DNA repair gene ERCC1, where the CpG island-containing promoter is located about 5,400 nucleotides upstream of the coding region of the ERCC1 gene. CpG islands also occur frequently in promoters for functional noncoding RNAs such as microRNAs. | 1 | Applied and Interdisciplinary Chemistry |
Elmer V. McCollum, the Department’s first Professor and Chair, discovered vitamins A, B and D, as well as the importance of trace metals in diets. McCollum was the chair of the department for 27 years, from 1917 until 1944. After stepping down as the Chair of the Department, McCollum went on to help establish the McCollum-Pratt Institute at the Johns Hopkins University Homewood Campus. | 1 | Applied and Interdisciplinary Chemistry |
* TsOH may be converted to p-toluenesulfonic anhydride by heating with phosphorus pentoxide.
* When heated with acid and water, TsOH undergoes hydrolysis to toluene:
:CHCHSOH + HO → CHCH + HSO
This reaction is general for aryl sulfonic acids. | 0 | Theoretical and Fundamental Chemistry |
The converting process occurs in a converter. Two kinds of converters are widely used: horizontal and vertical.
Horizontal (which are an improvement of the ) prevail in the metallurgy of non-ferrous metals. Such a converter is a horizontal barrel lined with refractory material inside. A hood for the purpose of the loading/unloading operations is located on the upper side of the converter. Two belts of tuyeres come along the axis on either sides of the converter.
Molten sulfide material, referred to as matte, is poured through the hood into the converter during the operation of loading. Air is distributed to tuyeres from the two tuyere collectors which are located on opposite sides of the converter. Collector pipes vary in diameter with distance from the connection to air supplying trunk; this is to provide equal pressure of air in each tuyere.
This high temperature roasting allows oxygen in the air to replace sulfide compounds in the minerals. Unless carefully captured, these oxidized sulfur compounds such as sulfur trioxide leave the converter as a noxious acidic vapor, along with other dangerous volatile elements such as arsenic trioxide. | 1 | Applied and Interdisciplinary Chemistry |
Rhazinilam is an alkaloid first isolated in 1965 by Linde from the Melodinus australis plant. It was later isolated from the shrub Rhazya stricta as well as from other organisms. | 0 | Theoretical and Fundamental Chemistry |
Many of the non-metals that could make mixed-anion compounds may have greatly varying volatilities. This makes it more difficult to combine the elements together. Compounds may be produced in a solid state reaction, by heating solids together, either in a vacuum or a gas. Common gases used include, oxygen, hydrogen, ammonia, chlorine, fluorine, hydrogen sulfide, or carbon disulfide. Soft chemical approaches to manufacture include solvothermal synthesis, or substituting atoms in a structure by others, including by water, oxygen, fluorine, or nitrogen. Teflon pouches can be used to separate different formulations. Thin film deposits can yield strained layers. High pressures can be used to prevent evaporation of volatiles. High pressure can result in different crystal forms, perhaps with higher coordination number. | 0 | Theoretical and Fundamental Chemistry |
Different applications move over their particular map along different paths. An example map with no operating lines is shown as a pictorial reference with the stall/surge line on the left and the steepening speed lines towards choke and overload on the right.
Maps have similar features and general shape because they all apply to machines with spinning vanes which use similar principles for pumping a compressible fluid. Not all machines have stationary vanes (centrifugal compressors may have either vaned or vaneless diffusers). However a compressor operating as part of a gas turbine or turbocharged engine behaves differently to an industrial compressor because its flow and pressure characteristics have to match those of its driving turbine and other engine components, such as power turbine or jet nozzle for a gas turbine, and, for a turbocharger the engine airflow which depends on engine speed and charge pressure. A link between a gas turbine compressor and its engine can be shown with lines of constant engine temperature ratio, ie the effect of fuelling/increased turbine temperature which raises the running line as the temperature ratio increases.
One manifestation of different behaviour appears in the choke region on the right-hand side of a map. It is a no-load condition in a gas turbine, turbocharger or industrial axial compressor but overload in an industrial centrifugal compressor. Hiereth et al. shows a turbocharger compressor full-load, or maximum fuelling, curve runs up close to the surge line. A gas turbine compressor full-load line also runs close to the surge line. The industrial compressor overload is a capacity limit and requires high power levels to pass the high flow rates required. Excess power is available to inadvertently take the compressor beyond the overload limit to a hazardous condition on cold days if it is driven by a gas turbine. | 0 | Theoretical and Fundamental Chemistry |
Le Chatelier's principle refers to states of thermodynamic equilibrium. The latter are stable against perturbations that satisfy certain criteria; this is essential to the definition of thermodynamic equilibrium.
OR
It states that changes in the temperature, pressure, volume, or concentration of a system will result in predictable and opposing changes in the system in order to achieve a new equilibrium state.
For this, a state of thermodynamic equilibrium is most conveniently described through a fundamental relation that specifies a cardinal function of state, of the energy kind, or of the entropy kind, as a function of state variables chosen to fit the thermodynamic operations through which a perturbation is to be applied.
In theory and, nearly, in some practical scenarios, a body can be in a stationary state with zero macroscopic flows and rates of chemical reaction (for example, when no suitable catalyst is present), yet not in thermodynamic equilibrium, because it is metastable or unstable; then Le Chatelier's principle does not necessarily apply. | 0 | Theoretical and Fundamental Chemistry |
Supercritical water gasification is a process of exploiting the beneficial effect of supercritical water to convert aqueous biomass streams into clean water and gases like H, CH, CO, CO etc. | 0 | Theoretical and Fundamental Chemistry |
Coverage (read depth or depth) is the average number of reads representing a given nucleotide in the reconstructed sequence. It can be calculated from the length of the original genome (G), the number of reads(N), and the average read length(L) as . For example, a hypothetical genome with 2,000 base pairs reconstructed from 8 reads with an average length of 500 nucleotides will have 2x redundancy. This parameter also enables one to estimate other quantities, such as the percentage of the genome covered by reads (sometimes also called coverage). A high coverage in shotgun sequencing is desired because it can overcome errors in base calling and assembly. The subject of DNA sequencing theory addresses the relationships of such quantities.
Sometimes a distinction is made between sequence coverage and physical coverage. Sequence coverage is the average number of times a base is read (as described above). Physical coverage is the average number of times a base is read or spanned by mate paired reads. | 1 | Applied and Interdisciplinary Chemistry |
Nicotinamide adenine dinucleotide has several essential roles in metabolism. It acts as a coenzyme in redox reactions, as a donor of ADP-ribose moieties in ADP-ribosylation reactions, as a precursor of the second messenger molecule cyclic ADP-ribose, as well as acting as a substrate for bacterial DNA ligases and a group of enzymes called sirtuins that use NAD to remove acetyl groups from proteins. In addition to these metabolic functions, NAD emerges as an adenine nucleotide that can be released from cells spontaneously and by regulated mechanisms, and can therefore have important extracellular roles. | 0 | Theoretical and Fundamental Chemistry |
Virokines are proteins encoded by some large DNA viruses that are secreted by the host cell and serve to evade the host's immune system. Such proteins are referred to as virokines if they resemble cytokines, growth factors, or complement regulators; the term viroceptor is sometimes used if the proteins resemble cellular receptors. A third class of virally encoded immunomodulatory proteins consists of proteins that bind directly to cytokines. Due to the immunomodulatory properties of these proteins, they have been proposed as potentially therapeutically relevant to autoimmune diseases. | 1 | Applied and Interdisciplinary Chemistry |
Bacterial recombination is a type of genetic recombination in bacteria characterized by DNA transfer from one organism called donor to another organism as recipient. This process occurs in three main ways:
* Transformation, the uptake of exogenous DNA from the surrounding environment.
* Transduction, the virus-mediated transfer of DNA between bacteria.
* Conjugation, the transfer of DNA from one bacterium to another via cell-to-cell contact.
The final result of conjugation, transduction, and/or transformation is the production of genetic recombinants, individuals that carry not only the genes they inherited from their parent cells but also the genes introduced to their genomes by conjugation, transduction, and/or transformation.
Recombination in bacteria is ordinarily catalyzed by a RecA type of recombinase. These recombinases promote repair of DNA damages by homologous recombination.
The ability to undergo natural transformation is present in at least 67 bacterial species. Natural transformation is common among pathogenic bacterial species. In some cases, the DNA repair capability provided by recombination during transformation facilitates survival of the infecting bacterial pathogen. Bacterial transformation is carried out by numerous interacting bacterial gene products. | 1 | Applied and Interdisciplinary Chemistry |
Cosmic inflation is phase of accelerated cosmic expansion just after the Big Bang. It explains the origin of the large-scale structure of the cosmos. It is believed quantum vacuum fluctuations caused by zero-point energy arising in the microscopic inflationary period, later became magnified to a cosmic size, becoming the gravitational seeds for galaxies and structure in the Universe (see galaxy formation and evolution and structure formation). Many physicists also believe that inflation explains why the Universe appears to be the same in all directions (isotropic), why the cosmic microwave background radiation is distributed evenly, why the Universe is flat, and why no magnetic monopoles have been observed.
The mechanism for inflation is unclear, it is similar in effect to dark energy but is a far more energetic and short lived process. As with dark energy the best explanation is some form of vacuum energy arising from quantum fluctuations. It may be that inflation caused baryogenesis, the hypothetical physical processes that produced an asymmetry (imbalance) between baryons and antibaryons produced in the very early universe, but this is far from certain. | 0 | Theoretical and Fundamental Chemistry |
In practice, the Joule–Thomson effect is achieved by allowing the gas to expand through a throttling device (usually a valve) which must be very well insulated to prevent any heat transfer to or from the gas. No external work is extracted from the gas during the expansion (the gas must not be expanded through a turbine, for example).
The cooling produced in the Joule–Thomson expansion makes it a valuable tool in refrigeration. The effect is applied in the Linde technique as a standard process in the petrochemical industry, where the cooling effect is used to liquefy gases, and in many cryogenic applications (e.g. for the production of liquid oxygen, nitrogen, and argon). A gas must be below its inversion temperature to be liquefied by the Linde cycle. For this reason, simple Linde cycle liquefiers, starting from ambient temperature, cannot be used to liquefy helium, hydrogen, or neon. They must first be cooled to their inversion temperatures, which are -233 C (helium), -71 C (hydrogen), and -42 C (neon). | 0 | Theoretical and Fundamental Chemistry |
In viruses this phenomenon may be programmed to occur at particular sites and allows the virus to encode multiple types of proteins from the same mRNA. Notable examples include HIV-1 (human immunodeficiency virus), RSV (Rous sarcoma virus) and the influenza virus (flu), which all rely on frameshifting to create a proper ratio of 0-frame (normal translation) and "trans-frame" (encoded by frameshifted sequence) proteins. Its use in viruses is primarily for compacting more genetic information into a shorter amount of genetic material.
In eukaryotes it appears to play a role in regulating gene expression levels by generating premature stops and producing nonfunctional transcripts. | 1 | Applied and Interdisciplinary Chemistry |
The Yukawa–Tsuno equation allows for treatment of both para- and meta- substituents, and it also better correlates data from reactions with high electron demand than the original Hammett equation. However, this equation does not take into account the effects of various solvents on organic reactions. Also, Yukawa and Tsuno note that, even within a group of similar reactions, -values for more electron-withdrawing substituents tend to be higher than predicted—seen as a slight increase in slope on a Yukawa–Tsuno plot—and thus, are not as strongly correlated with the remainder of the data. | 0 | Theoretical and Fundamental Chemistry |
The bromodomain is a motif that is responsible for acetylated lysine recognition on histones by nucleosome remodelling proteins. Posttranslational modifications of N- and C-terminal histone tails attracts various transcription initiation factors that contain bromodomains, including human transcriptional coactivator PCAF, TAF1, GCN5 and CREB-binding protein (CBP), to the promoter and have a significance in regulating gene expression. Structural analysis of transcription factors has shown that highly conserved bromodomains are essential for protein to bind to acetylated lysine. This suggests that specific histone site acetylation has a regulatory role in gene transcriptional activation. | 0 | Theoretical and Fundamental Chemistry |
In 1992, Canadian authorities determined that eating fish contaminated with malachite green posed a significant health risk. Malachite green was classified a Class II Health Hazard. Due to its low manufacturing cost, malachite green is still used in certain countries with less restrictive laws for non aquaculture purposes. In 2005, analysts in Hong Kong found traces of malachite green in eels and fish imported from China. In 2006, the United States Food and Drug Administration (FDA) detected malachite green in seafood from China, among others, where the substance is also banned for use in aquaculture. In June 2007, the FDA blocked the importation of several varieties of seafood due to continued malachite green contamination.
Malachite green has been banned in the United States since 1983 in food-related applications. The substance is also banned in the United Kingdom. It is prohibited from the use in food in Macao.
Animals metabolize malachite green to its leuco form. Being lipophillic (the leuco form has a log P of 5.70), the metabolite is retained in catfish muscle longer (HL = 10 days) than is the parent molecule (HL = 2.8 days). | 0 | Theoretical and Fundamental Chemistry |
The hybrid sulfur cycle (HyS) is a two-step water-splitting process intended to be used for hydrogen production. Based on sulfur oxidation and reduction, it is classified as a hybrid thermochemical cycle because it uses an electrochemical (instead of a thermochemical) reaction for one of the two steps. The remaining thermochemical step is shared with the sulfur-iodine cycle.
The Hybrid sulphur cycle (HyS)was initially proposed and developed by Westinghouse Electric Corp. in the 1970s, so it is also known as the "Westinghouse" cycle. Current development efforts in the United States are being led by the Savannah River National Laboratory. | 0 | Theoretical and Fundamental Chemistry |
Cannabinoid binding sites exist throughout the central and peripheral nervous systems. The two most relevant receptors for cannabinoids are the CB and CB receptors, which are expressed predominantly in the brain and immune system respectively. Density of expression varies based on species and correlates with the efficacy that cannabinoids will have in modulating specific aspects of behavior related to the site of expression. For example, in rodents, the highest concentration of cannabinoid binding sites are in the basal ganglia and cerebellum, regions of the brain involved in the initiation and coordination of movement. In humans, cannabinoid receptors exist in much lower concentration in these regions, which helps explain why cannabinoids possess a greater efficacy in altering rodent motor movements than they do in humans.
A recent analysis of cannabinoid binding in CB and CB receptor knockout mice found cannabinoid responsiveness even when these receptors were not being expressed, indicating that an additional binding receptor may be present in the brain. Binding has been demonstrated by 2-arachidonoylglycerol (2-AG) on the TRPV1 receptor suggesting that this receptor may be a candidate for the established response.
In addition to CB1 and CB2, certain orphan receptors are known to bind endocannabinoids as well, including GPR18, GPR55 (a regulator of neuroimmune function), and GPR119. CB1 has also been noted to form a functional human receptor heterodimer in orexin neurons with OX1, the CB1–OX1 receptor, which mediates feeding behavior and certain physical processes such as cannabinoid-induced pressor responses which are known to occur through signaling in the rostral ventrolateral medulla. | 1 | Applied and Interdisciplinary Chemistry |
Relativistic heat conduction refers to the modelling of heat conduction (and similar diffusion processes) in a way compatible with special relativity. In special (and general) relativity, the usual heat equation for non-relativistic heat conduction must be modified, as it leads to faster-than-light signal propagation. Relativistic heat conduction, therefore, encompasses a set of models for heat propagation in continuous media (solids, fluids, gases) that are consistent with relativistic causality, namely the principle that an effect must be within the light-cone associated to its cause. Any reasonable relativistic model for heat conduction must also be stable, in the sense that differences in temperature propagate both slower than light and are damped over time (this stability property is intimately intertwined with relativistic causality). | 0 | Theoretical and Fundamental Chemistry |
First steps towards solving the paradox were made by Saint-Venant, who modelled viscous fluid friction. Saint-Venant states in 1847:
:"But one finds another result if, instead of an ideal fluid – object of the calculations of the geometers of the last century – one uses a real fluid, composed of a finite number of molecules and exerting in its state of motion unequal pressure forces or forces having components tangential to the surface elements through which they act; components to which we refer as the friction of the fluid, a name which has been given to them since Descartes and Newton until Venturi."
Soon after, in 1851, Stokes calculated the drag on a sphere in Stokes flow, known as Stokes' law. Stokes flow is the low Reynolds-number limit of the Navier–Stokes equations describing the motion of a viscous liquid.
However, when the flow problem is put into a non-dimensional form, the viscous Navier–Stokes equations converge for increasing Reynolds numbers towards the inviscid Euler equations, suggesting that the flow should converge towards the inviscid solutions of potential flow theory – having the zero drag of the d'Alembert paradox. Of this, there is no evidence found in experimental measurements of drag and flow visualisations. In the second half of the 19th century this again raised questions concerning the applicability of fluid mechanics. | 1 | Applied and Interdisciplinary Chemistry |
The concept of a nanocar built out of molecular "tinkertoys" was first hypothesized by M.T. Michalewicz at the Fifth Foresight Conference on Molecular Nanotechnology (November 1997). Subsequently, an expanded version was published in Annals of Improbable Research. These papers were supposed to be a not-so-serious contribution to a fundamental debate on the limits of bottom-up Drexlerian nanotechnology and conceptual limits of how far mechanistic analogies advanced by Eric Drexler could be carried out. The important feature of this nanocar concept was the fact that all molecular component tinkertoys were known and synthesized molecules (alas, some very exotic and only recently discovered, e.g. staffanes, and notably – ferric wheel, 1995), in contrast to some Drexlerian diamondoid structures that were only postulated and never synthesized; and the drive system that was embedded in a ferric wheel and driven by inhomogeneous or time-dependent magnetic field of a substrate – an "engine in a wheel" concept. | 0 | Theoretical and Fundamental Chemistry |
The frequency at which vortex shedding takes place for an infinite cylinder is related to the Strouhal number by the following equation:
Where is the dimensionless Strouhal number, is the vortex shedding frequency (s), is the diameter of the cylinder (m), and is the flow velocity (m s).
The Strouhal number depends on the Reynolds number , but a value of 0.22 is commonly used. Over four orders of magnitude in Reynolds number, from 100 to 100000, the Strouhal number varies only between 0.18 and 0.22. | 1 | Applied and Interdisciplinary Chemistry |
The Walden reductor can be used to obtain chemical species in their low valence state if required for chemical analyses or to obtain small amounts of the compound in the appropriate form. | 0 | Theoretical and Fundamental Chemistry |
Side effects are mild, usually at the start of treatment; they include:
*Cough
*Fatigue
*Weakness/Asthenia
*Headache
*Disturbances of mood and/or sleep
Less often
*Taste impairment
*Epigastric discomfort
*Nausea
*Abdominal pain
*Rash
Reversible increases in blood urea and creatinine may be observed. Proteinuria has occurred in some patients. Rarely, angioneurotic edema and decreases in hemoglobin, red cells, and platelets have been reported. | 0 | Theoretical and Fundamental Chemistry |
A mutation in genes encoding 11β-hydroxylase is associated with congenital adrenal hyperplasia due to 11β-hydroxylase deficiency.
11β-hydroxylase is involved in the metabolism of 17α-hydroxyprogesterone to 21-deoxycortisol, in cases of congenital adrenal hyperplasia due to 21-hydroxylase deficiency. | 1 | Applied and Interdisciplinary Chemistry |
In the past, devices with controlled strain or strain rate (CR rheometers) were distinguished from rheometers with controlled stress (CS rheometers) depending on the measuring principle.
In a controlled strain (CR) rheometer, the sample is subjected to displacement or speed (strain or strain rate) using a DC motor, and the resulting torque (stress) is measured separately using an additional force-torque sensor (torque compensation transducer). The electric current used to generate the displacement or speed of the motor is not used as a measure of the torque acting in the sample. This mode of operation is also referred to as separate motor transducer mode (SMT).
* Deflection angle/strain and shear rate are set by the motor based on the position control of the optical encoder in the lower part.
* Sample reaction (the stress acting within the sample) is measured by an additional force-torque transducer (torque re-balance transducer)
* The separation of drive and torque measurement has advantages in strain-controlled tests, since the motor's moment of inertia has no influence on the measured torque.
* Limitations of the SMT mode can be found in stress-controlled measurements (e.g. creep tests)
In a controlled-stress (CS) rheometer, the torque acting in the sample is determined directly from the electrical torque generated in the motor. With such a design, no separate torque sensor is required. Usually, this mode of operation is described as combined motor-transducer mode (CMT).
* The stress acting in the sample is determined directly from the torque generated in the motor, which is required to deform the sample.
* Deflection angle/strain and shear rate are determined by the use of an optical encoder.
* Single-motor rheometers allow characterization of samples in either strain/shear rate or shear stress-controlled tests
* Since only one actor (motor) is required, the single-motor rheometer can be easily combined with additional application-specific accessories that enable the study of material properties in a variety of different applications.
* Limitations may occur from less precise data evaluation in the transient regime of start-up shear tests.
Nowadays, there are device concepts that allow both working modes, the combined motor transducer mode and the separate motor transducer mode, by using two motors in one device. The use of only one motor enables measurements to be made in the combined motor transducer mode. Using both motors allows working in the separate motor transducer mode, where one motor is used to deform the sample while the other motor is used to record the torque acting in the sample. Furthermore, this concept allows for additional modes of operation, such as counter-rotating mode, where both motors can rotate or oscillate in opposite directions. This mode of operation is used, for example, to increase the maximum achievable shear rate range or for advanced rheooptical characterization of samples. | 1 | Applied and Interdisciplinary Chemistry |
Primary (1°) phosphines, with the formula RPH, are typically prepared by alkylation of phosphine. Simple alkyl derivatives such as methylphosphine (CHPH) are prepared by alkylation of alkali metal derivatives MPH (M is Li, Na, or K). Another synthetic route involves treatment of the corresponding chlorophosphines with hydride reagents. For example, reduction of dichlorophenylphosphine with lithium aluminium hydride affords phenylphosphine (PhPH).
Primary (RPH) and secondary phosphines (RRPH and RPH) add to alkenes in presence of a strong base (e.g., KOH in DMSO). Markovnikov's rules apply. Similar reactions occur involving alkynes. Base is not required for electron-deficient alkenes (e.g., derivatives of acrylonitrile) and alkynes. | 0 | Theoretical and Fundamental Chemistry |
An assay is an analytic tool often used in a laboratory setting in order to assess or measure some quality of a target entity. In virology, assays can be used to differentiate between transformed and non-transformed cells. Varying the assay used, changes the selective pressure on the cells and therefore can change what properties are selected in the transformed cells.
Three common assays used are the focus forming assay, the Anchorage independent growth assay, and the reduced serum assay.
The focus forming assay (FFA) is used to grow cells containing a transforming oncogene on a monolayer of non-transformed cells. The transformed cells will form raised, dense spots on the sample as they grow without contact inhibition. This assay is highly sensitive compared to other assays used for viral analysis, such as the yield reduction assay.
An example of the Anchorage independent growth assay is the soft agar assay. The assay is assessing the cells' ability to grow in a gel or viscous fluid. Transformed cells can grow in this environment and are considered anchorage independent. Cells that can only grow when attached to a solid surface are anchorage dependent untransformed cells. This assay is considered one of the most stringent for detection of malignant transformation
In a reduced serum assay, cells are assayed by exploiting the changes in cell serum requirements. Non-transformed cells require at least a 5% serum medium in order to grow; however, transformed cells can grow in an environment with significantly less serum. | 1 | Applied and Interdisciplinary Chemistry |
Sodium amide induces the loss of two equivalents of hydrogen bromide from a vicinal dibromoalkane to give a carbon–carbon triple bond, as in a preparation of phenylacetylene.
Usually two equivalents of sodium amide yields the desired alkyne. Three equivalents are necessary in the preparation of a terminal alkynes because the terminal CH of the resulting alkyne protonates an equivalent amount of base.
Hydrogen chloride and ethanol can also be eliminated in this way, as in the preparation of 1-ethoxy-1-butyne. | 0 | Theoretical and Fundamental Chemistry |
A Bancroft point is the temperature where an azeotrope occurs in a binary system. Although vapor liquid azeotropy is impossible for binary systems which are rigorously described by Raoult's law, for real systems, azeotropy is inevitable at temperatures where the saturation vapor pressure of the components are equal. Such a temperature is called a Bancroft point. However, not all azeotropic binary systems exhibit such a point. Also, a Bancroft point must lie in the valid temperature ranges of the Antoine equation.
Bancroft point is named after Wilder Dwight Bancroft. | 0 | Theoretical and Fundamental Chemistry |
Sulfide minerals such as pyrite (FeS) and pyrrhotite (FeS) occur in many ore deposits. Pyrite and its polymorph marcasite also are important in many coal deposits and shales. These sulfide minerals form in environments more reducing than that of the Earth's surface. When in contact with oxidizing surface waters, sulfides react: sulfate (SO) forms, and the water becomes acidic and charged with a variety of elements, some potentially toxic. Consequences can be environmentally harmful, as discussed in the entry for acid mine drainage.
Sulfur oxidation to sulfate or sulfur dioxide also is important in generating sulfur-rich volcanic eruptions, like those of Pinatubo in 1991 and El Chichon in 1982. These eruptions contributed unusually large quantities of sulfur dioxide to the Earth's atmosphere, with consequent effects on atmospheric quality and on climate. The magmas were unusually oxidizing, almost two log units more so than the NiNiO buffer. The calcium sulfate, anhydrite, was present as phenocrysts in the erupted tephra. In contrast, sulfides contain most of the sulfur in magmas more reducing than the FMQ buffer. | 0 | Theoretical and Fundamental Chemistry |
In 1987 the private New York laboratory, Lifecodes, began assisting Dr. Ferrara in his efforts to establish a DNA laboratory for the state of Virginia.
In 1988 Timothy Spencer, the "Southside Strangler", became first serial killer in the United States to be convicted on the basis of DNA evidence. Spencer committed three rapes and murders in Richmond Virginia, and one in Arlington, Virginia in the fall of 1987.
Ferrara recognized the potential utility of the precedent that had been set in Spencer case, and immediately focused his political savvy on convincing the Virginia General Assembly to fund the creation of the first State DNA Database in the country.
In 1989 under his leadership, Virginia became the first state laboratory capable of performing DNA fingerprinting. The FBI had started its limited DNA laboratory operations just four months earlier.
In addition to his directorship of the Virginia Department of Forensic Science (VA-DFS), Dr. Ferrara was an honorary professor at Virginia Commonwealth University. Through his passion for teaching and research, as well as his commitment to developing a nationally recognized Forensic Science educational program at VCU, the program officially became a department in 2005. | 0 | Theoretical and Fundamental Chemistry |
An inexact differential or imperfect differential is a differential whose integral is path dependent. It is most often used in thermodynamics to express changes in path dependent quantities such as heat and work, but is defined more generally within mathematics as a type of differential form. In contrast, an integral of an exact differential is always path independent since the integral acts to invert the differential operator. Consequently, a quantity with an inexact differential cannot be expressed as a function of only the variables within the differential. I.e., its value cannot be inferred just by looking at the initial and final states of a given system. Inexact differentials are primarily used in calculations involving heat and work because they are path functions, not state functions. | 0 | Theoretical and Fundamental Chemistry |
BJP-led NDA government of Atal Bihari Vajpayee had propagated the idea of interlinking of rivers to deal with the problem of drought and different parts of the country at the same time.
The Congress general secretary Rahul Gandhi said in 2009 that the entire idea of interlinking of rivers was dangerous and that he was opposed to interlinking of rivers as it would have "severe" environmental implications. Jairam Ramesh, a cabinet minister in former UPA government, said the idea of interlinking India's rivers was a "disaster", putting a question mark on the future of the ambitious project.
Karunanidhi, whose DMK has been a key ally of the Congress-led UPA at the centre, wrote that linking rivers at the national level perhaps is the only permanent solution to the water scarcity problem in the country. Karunanidhi said the government should make an assessment of the project's feasibility starting with the south-bound rivers. DMK for 2014 general elections added Nationalisation and inter-linking of rivers to its manifesto.
Kalpasar Project is an irrigation project which envisages storing Narmada River water in an offshore freshwater reservoir located in Gulf of Khambhat sea for further pumping to arid Sourashtra region for irrigation use. | 1 | Applied and Interdisciplinary Chemistry |
In physical organic chemistry, the Swain–Lupton equation is a linear free energy relationship (LFER) that is used in the study of reaction mechanisms and in the development of quantitative structure activity relationships for organic compounds. It was developed by C. Gardner Swain and Elmer C. Lupton Jr. in 1968 as a refinement of the Hammett equation to include both field effects and resonance effects. | 0 | Theoretical and Fundamental Chemistry |
Fast Sulphon Black is purple when complexed with copper, and turns green when titrated against EDTA, as the EDTA displaces it, being the better complexing agent due to the chelate effect. | 0 | Theoretical and Fundamental Chemistry |
The cell used in this process consists of an iron tank lined with carbon at the bottom.
A molten alloy of copper, crude aluminium and silicon is used as the anode. It forms the lowermost layer in the cell.
The middle layer consists of molten mixture of fluorides of sodium, aluminium and barium (cryolite + BaF).
The uppermost layer consists of molten aluminium.
A set of graphite rods dipped in molten aluminium serve as the cathode.
During electrolysis, Al ions from the middle layer migrate to the upper layer, where they are reduced to aluminum by gaining 3 electrons.
Equal numbers of Al ions are produced in the lower layer. These ions migrate to the middle layer. Pure aluminium is tapped off from time to time. The Hoopes process gives about 99.99% pure aluminium. | 1 | Applied and Interdisciplinary Chemistry |
Functional groups containing heteroatoms in low oxidation states can be oxidised by trifluoroperacetic acid. Common cases include the oxidation of iodine (for example, the formation of the hypervalent iodine compound from iodobenzene mentioned earlier), nitrogen, sulfur, and selenium.
In the case of nitrogen-containing compounds, known transformations include oximes and aromatic primary amines to nitro compounds (even with electron-withdrawing substituents, for example, pentafluoroaniline to pentafluoronitrobenzene), nitrosamines to nitramines, formation of aromatic N-oxides and aromatic azine N-oxides, and conversion of nitroso compounds to nitro compounds or nitramines. For example, a mixture of hydrogen peroxide and trifluoroperacetic acid oxidises the nitroso-substituted pyrimidine 4,6-diamino-5-nitrosopyrimidine-2-thiol to its nitro analogue while also removing the thiol moiety by oxidative hydrolytic desulfurization:
In the case of chalcogen elements, sulfide moieties (R–S–R) can be oxidised by trifluoroperacetic acid to sulfoxide (R–S(O)–R) and/or sulfone (R–S(O)–R) forms, depending on the conditions used. In the analogous selenium system, trifluoroperacetic acid oxidation of selenoethers (R–Se–R) produces selones (R–Se(O)–R) without the formation of the related selenoxides (R–Se(O)–R) as an isolable product, a reaction which is particularly effective when the R is an aryl group. A general approach to the formation of sulfinyl chlorides (RS(O)Cl) is the reaction of the corresponding thiol with sulfuryl chloride (). In cases where the sulfenyl chloride (RSCl) results instead, a subsequent trifluoroperacetic acid oxidation affords the desired product, as in the case of 2,2,2-trifluoro-1,1-diphenylethanethiol:
The trifluoroperacetic acid oxidation of thiophene illustrates competing pathways for reaction, with both S-oxidation and epoxidation being possible. The major pathway initially forms the sulfoxide, but this chemical promptly undergoes a Diels-Alder-type dimerisation before any further oxidation occurs—neither thiophene-S-oxide or thiophene-S,S-dioxide are found among the products of the reaction. The dimer can then be oxidized further, converting one of the S-oxide moieties to an S,S-dioxide. In the minor reaction pathway, a Prilezhaev epoxidation results in the formation of thiophene-2,3-epoxide that rapidly rearranges to the isomer thiophene-2-one. Trapping experiments demonstrate that this epoxide pathway is not an alternative reaction of the S-oxide intermediate, and isotopic labeling experiments demonstrate that a 1,2-hydride shift (an NIH shift) occurs and thus that a cationic intermediate is involved. The choice of trifluoroperacetic acid preparation method is important as water suppresses the minor reaction pathway, likely because it acts as a competing base. | 0 | Theoretical and Fundamental Chemistry |
Analytical quality control (AQC) refers to all those processes and procedures designed to ensure that the results of laboratory analysis are consistent, comparable, accurate and within specified limits of precision. Constituents submitted to the analytical laboratory must be accurately described to avoid faulty interpretations, approximations, or incorrect results. The qualitative and quantitative data generated from the laboratory can then be used for decision making. In the chemical sense, quantitative analysis refers to the measurement of the amount or concentration of an element or chemical compound in a matrix that differs from the element or compound. Fields such as industry, medicine, and law enforcement can make use of AQC. | 1 | Applied and Interdisciplinary Chemistry |
The core idea is to create a noise texture on a regular grid and then bend this grid according to the flow (the vector field). The bent grid is then sampled at the original grid locations. Thus, the output is a version of the noise, that is displaced according to the flow.
The advantage of this approach is that it can be accelerated on modern graphics hardware, thus allowing for real-time or almost real-time simulation of 2D flow data. This is particularly handy if one wants to visualise multiple scaled versions of the vector field to first gain an overview and then concentrate on the details. | 1 | Applied and Interdisciplinary Chemistry |
The space-holder technique is the most commonly employed method for producing titanium foams. The space-holder technique allows for the fabrication of higher porosity foams (35–80% ) than other techniques, while also giving the engineer more control over pore fraction, shape and connectivity. Mechanical properties can be adjusted through the size, shape and quantity of space-holders employed. The space-holder technique was first demonstrated by Zhao and Sun for the fabrication of aluminum foams in a powder metallurgical method, which consisted of the incorporation of NaCl as a space-holder. The space-holder was mixed into the powder mixture and dissolved prior to sintering. The same method was used to create titanium foams for the first time when Wen et al. utilized ammonium hydrogen carbonate spacers. | 0 | Theoretical and Fundamental Chemistry |
The South Atlantic Gyre is located in the southern hemisphere in the Atlantic Ocean, between the Intertropical Convergence Zone in the north and the Antarctic Circumpolar Current to the south. The South Equatorial Current brings water west towards South America, forming the northern boundary of the South Atlantic gyre. Here, the water moves south in the Brazil Current, the western boundary current of the South Atlantic Gyre. The Antarctic Circumpolar Current forms both the southern boundary of the gyre and the eastward component of the gyre circulation. Eventually, the water reaches the west coast of Africa, where it is brought north along the coast as a part of the eastern boundary Benguela Current, completing the gyre circulation. The Benguela Current experiences the Benguela Niño event, an Atlantic Ocean analogue to the Pacific Ocean's El Niño, and is correlated with a reduction in primary productivity in the Benguela upwelling zone. | 1 | Applied and Interdisciplinary Chemistry |
Embrittlement is a series complex mechanism that is not completely understood. The mechanisms can be driven by temperature, stresses, grain boundaries, or material composition. However, by studying the embrittlement process, preventative measures can be put in place to mitigate the effects. There are several ways to study the mechanisms. During metal embrittlement (ME), crack-growth rates can be measured. Computer simulations can also be used to enlighten the mechanisms behind embrittlement. This is helpful for understanding hydrogen embrittlement (HE), as the diffusion of hydrogen through materials can be modeled. The embrittler does not play a role in final fracture; it is mostly responsible for crack propagation. Cracks must first nucleate. Most embrittlement mechanisms can cause fracture transgranularly or intergranularly. For metal embrittlement, only certain combinations of metals, stresses, and temperatures are susceptible. This is contrasted to stress-corrosion cracking where virtually any metal can be susceptible given the correct environment. Yet this mechanism is much slower than that of liquid metal embrittlement (LME), suggesting that it directs a flow of atoms both towards and away from the crack. For neutron embrittlement, the main mechanism is collisions within the material from the fission byproducts. | 1 | Applied and Interdisciplinary Chemistry |
Pressure–volume work (or PV or P-V work) occurs when the volume of a system changes. PV work is often measured in units of litre-atmospheres where . However, the litre-atmosphere is not a recognized unit in the SI system of units, which measures P in pascals (Pa), V in m, and PV in joules (J), where 1 J = 1 Pa·m. PV work is an important topic in chemical thermodynamics.
For a process in a closed system, occurring slowly enough for accurate definition of the pressure on the inside of the systems wall that moves and transmits force to the surroundings, described as quasi-static', work is represented by the following equation between differentials:
where
* (inexact differential) denotes an infinitesimal increment of work done by the system, transferring energy to the surroundings;
* denotes the pressure inside the system, that it exerts on the moving wall that transmits force to the surroundings. In the alternative sign convention the right hand side has a negative sign.
* (exact differential) denotes an infinitesimal increment of the volume of the system.
Moreover,
where denotes the work done by the system during the whole of the reversible process.
The first law of thermodynamics can then be expressed as
(In the alternative sign convention where W = work done on the system, . However, is unchanged.) | 0 | Theoretical and Fundamental Chemistry |
In the mid 2010s several techniques combined with Next Generation Sequencing were developed that employ the "tag" principle for "digital gene expression profiling" but without the use of the tagging enzyme. The "MACE" approach, (=Massive Analysis of cDNA Ends) generates tags somewhere in the last 1500 bps of a transcript. The technique does not depend on restriction enzymes anymore and thereby circumvents bias that is related to the absence or location of the restriction site within the cDNA. Instead, the cDNA is randomly fragmented and the 3ends are sequenced from the 5 end of the cDNA molecule that carries the poly-A tail. The sequencing length of the tag can be freely chosen. Because of this, the tags can be assembled into contigs and the annotation of the tags can be drastically improved. Therefore, MACE is also use for the analyses of non-model organisms. In addition, the longer contigs can be screened for polymorphisms. As UTRs show a large number of polymorphisms between individuals, the MACE approach can be applied for allele determination, allele specific gene expression profiling and the search for molecular markers for breeding. In addition, the approach allows determining alternative polyadenylation of the transcripts. Because MACE does only require 3’ ends of transcripts, even partly degraded RNA can be analyzed with less degradation dependent bias. The MACE approach uses unique molecular identifiers to allow for identification of PCR bias. | 1 | Applied and Interdisciplinary Chemistry |
In the pre-modern chemistry of Paracelsus, a clyssus, or clissus, was one of the effects, or productions of that art; consisting of the most efficacious principles of any body, extracted, purified, and then remixed.
Or, a clyssus is when the several constituents of a body are prepared and purified separately, and then combined again. Thus, the five principles, reassembled into one body, by long digestion, make a clyssus. So, clyssus of antimony is produced by distillation from antimony, nitre, and sulfur mixed together. There is also clyssus of vitriol, which is a spirit drawn by distillation from vitriol dissolved in vinegar; this was used by pre-modern physicians in treating various diseases, and to extract the tinctures of several vegetables.
Clyssus is used among some authors for a kind of sapa, or extract, made with eight parts of the juice of a plant, and one of sugar, seethed together into the consistency of honey. | 1 | Applied and Interdisciplinary Chemistry |
Brain-derived neurotrophic factor (BDNF) is a neurotrophic factor found originally in the brain, but also found in the periphery. To be specific, it is a protein that has activity on certain neurons of the central nervous system and the peripheral nervous system; it helps to support the survival of existing neurons, and encourage the growth and differentiation of new neurons and synapses through axonal and dendritic sprouting. In the brain, it is active in the hippocampus, cortex, cerebellum, and basal forebrain – areas vital to learning, memory, and higher thinking. BDNF was the second neurotrophic factor to be characterized, after NGF and before neurotrophin-3.
BDNF is one of the most active substances to stimulate neurogenesis. Mice born without the ability to make BDNF suffer developmental defects in the brain and sensory nervous system, and usually die soon after birth, suggesting that BDNF plays an important role in normal neural development.
Despite its name, BDNF is actually found in a range of tissue and cell types, not just the brain. Expression can be seen in the retina, the CNS, motor neurons, the kidneys, and the prostate. Exercise has been shown to increase the amount of BDNF and therefore serve as a vehicle for neuroplasticity. | 1 | Applied and Interdisciplinary Chemistry |
Molded and laser-ablated shark skin replicas have been fabricated, and shown to be oleophobic in water. The molded replicas use a negative made of polyvinylsiloxane dental wax and the positive replica was made of epoxy. These replicas have also shown that the structure of shark skin reduces the fluid drag caused by turbulent flow. The fluid dynamic properties of sharkskin have been mimicked in swimsuit, nautical, and aerospace applications. | 0 | Theoretical and Fundamental Chemistry |
Oxidation state is an important index to evaluate the charge distribution within molecules. The most common definition of oxidation state was established by IUPAC, which let the atom with higher electronegativity takes all the bonding electrons and calculated the difference between the number of electrons and protons around each atom to assign the oxidation states. However, the definition doesn't thoroughly consider the distribution of the bonding electrons and further restricts the applicability of oxidation states.
To precisely assign the oxidation state for each component in the molecule, especially for organometallic complexes, several different research groups, including Pedro Salvador and Martin Head-Gordon, have developed different methods to determine the oxidation states. In 2009, Martin Head-Gordon group established a new method called localized orbitals bonding analysis (LOBA) to assign the electrons associated with each localized orbitals. However, this method failed to provide reasonable oxidation states since the orbitals cannot be localized for some complicated systems.
To overcome this problem to get the correct assignment of oxidation states, in 2022, Martin Head-Gordon and Pedro Salvador decide to localize the electrons based on different fragments rather than atoms. Thus, they developed the method known as oxidation state localized orbitals (OSLOs), which can accurately assign electrons to different fragments to obtain the oxidation states of each fragment. | 0 | Theoretical and Fundamental Chemistry |
Bottromycin is produced naturally as a series of products differing in methylation patterns. All products contain valine and phenylalanine methylation. Bottromycin A2 is singly methylated on proline, bottromycin B lacks methylation on proline, and bottromycin C contains a doubly methylated proline.
A partial structure of bottromycin was reported shortly after the initial discovery of bottromycin. The first structural studies relied on traditional methods of analysis. Its peptide-like structure, including the presence of glycine and valine, was first suggested by a combination of acidic hydrolysis, acetylation, ninhydrin staining, and paper chromatography, among other experiments. The presence of a thiazole ring, along with an adjacent β-methylated phenylalanine, was established by ninhydrin staining, potassium permanganate oxidation, and comparison to synthetic standards. A methyl ester substituent was reported in 1958. The same study also reported that the Kunz hydrolysis product lacking a methyl ester was biologically inactive. Nakamura and colleagues later reported that bottromycin contained tert-leucine and cis-3-methylproline. They also proposed a linear iminohexapeptide structure.
These early structural studies were not followed up until recent years with the renewed interest in bottromycin. The structure was confirmed in the 1980s and 1990s to be a cyclic iminopeptide based on NMR studies, with a linear side chain connected to the macrocycle via an amidine linkage.
Its absolute stereochemistry, however, was not characterized until 2009. Stereochemistry at carbon 18 and 25 was proposed by comparing predicted conformers obtained using molecular dynamics to experimental constraints obtained through NMR experiments. Stereochemistry at carbon 43 was confirmed by comparing H NMR of authentic hydrolysis product to a chemically synthesized sample of the same fragment. Finally, optical rotation, H NMR, and HRMS experiments of chemically synthesized bottromycin matched that of biologically produced bottromycin.
The three-dimensional solution structure of bottromycin A2 was solved by NMR in 2012. The overall structure was obtained with good resolution (RMSD 0.74±0.59 Å), with a RMSD of 0.09±0.06 Å for the macrocycle. In this study, it was proposed that the methylated proline residue contributed to the restricted conformation of the macrocycle. The methylated proline and β-OMe alanine residues were found to be on the same face of bottroymycin A2 and it was suggested that this characteristic contributed to binding of bottromycin to the ribosomal A site. | 0 | Theoretical and Fundamental Chemistry |
Although the International Bureau of Weights and Measures (an international standards organization known also by its French-language initials BIPM) recognizes the use of parts-per notation, it is not formally part of the International System of Units (SI). Note that although "percent" (%) is not formally part of the SI, both the BIPM and the International Organization for Standardization (ISO) take the position that "in mathematical expressions, the internationally recognized symbol % (percent) may be used with the SI to represent the number 0.01" for dimensionless quantities. According to IUPAP, "a continued source of annoyance to unit purists has been the continued use of percent, ppm, ppb, and ppt". Although SI-compliant expressions should be used as an alternative, the parts-per notation remains nevertheless widely used in technical disciplines. The main problems with the parts-per notation are set out below. | 1 | Applied and Interdisciplinary Chemistry |
This occurs when the rate of rainfall on a surface exceeds the rate at which water can infiltrate the ground, and any depression storage has already been filled. This is also called Hortonian overland flow (after Robert E. Horton), or unsaturated overland flow. This more commonly occurs in arid and semi-arid regions, where rainfall intensities are high and the soil infiltration capacity is reduced because of surface sealing, or in urban areas where pavements prevent water from infiltrating. | 1 | Applied and Interdisciplinary Chemistry |
The RT instability can be seen as the result of baroclinic torque created by the misalignment of the pressure and density gradients at the perturbed interface, as described by the two-dimensional inviscid vorticity equation, , where ω is vorticity, ρ density and p is the pressure. In this case the dominant pressure gradient is hydrostatic, resulting from the acceleration.
When in the unstable configuration, for a particular harmonic component of the initial perturbation, the torque on the interface creates vorticity that will tend to increase the misalignment of the gradient vectors. This in turn creates additional vorticity, leading to further misalignment. This concept is depicted in the figure, where it is observed that the two counter-rotating vortices have velocity fields that sum at the peak and trough of the perturbed interface. In the stable configuration, the vorticity, and thus the induced velocity field, will be in a direction that decreases the misalignment and therefore stabilizes the system.
A much simpler explanation of the basic physics of the Rayleigh-Taylor instability can be found in Ref.20. | 1 | Applied and Interdisciplinary Chemistry |
Many metabolites found in nature contain alkyne or enyne moieties, and therefore, the Sonogashira reaction has found frequent utility in their syntheses. Several of the most recent and promising applications of this coupling methodology toward the total synthesis of natural products exclusively employed the typical copper-cocatalyzed reaction.
An example of the coupling of an aryl iodide to an aryl acetylene can be seen in the reaction of an iodinated alcohol and tris(isopropyl)silylacetylene, which gave an alkyne, an intermediate in the total synthesis of the benzindenoazepine alkaloid bulgaramine.
There are other recent examples of the use of aryl iodides for the preparation of intermediates under typical Sonogashira conditions, which, after cyclization, yield natural products such as benzylisoquinoline or indole alkaloids An example is the synthesis of the benzylisoquinoline alkaloids (+)-(S)-laudanosine and (–)-(S)-xylopinine. The synthesis of these natural products involved the use of Sonogashira cross-coupling to build the carbon backbone of each molecule. | 0 | Theoretical and Fundamental Chemistry |
Some molecules, such as XeF or , have a lone pair that distorts the symmetry of the molecule from O to C. The specific geometry is known as a monocapped octahedron, since it is derived from the octahedron by placing the lone pair over the centre of one triangular face of the octahedron as a "cap" (and shifting the positions of the other six atoms to accommodate it). These both represent a divergence from the geometry predicted by VSEPR, which for AXE predicts a pentagonal pyramidal shape. | 0 | Theoretical and Fundamental Chemistry |
Hydron is a generic term for hydrogen cation; protons, deuterons and tritons are all hydrons.
The hydrons are not found in heavier isotopes, however. | 0 | Theoretical and Fundamental Chemistry |
They are mild acylating agents. With aqueous base, acyl cyanides break down to cyanide and the carboxylate:
With azides, acyl cyanides undergo the click reaction to give acyl tetrazoles. | 0 | Theoretical and Fundamental Chemistry |
The earliest compelling evidence for human habitation of the Americas comes from the Clovis complex, between 11,050 and 10,800 C yr B.P. However, a series of human tracks were identified at White Sands National Park, New Mexico, which have been dated contentiously dated to between 23,000 and 21,000 years ago - during the Last Glacial Maximum. Alongside anatomically modern humans, the trackway shows impressions created by a Columbian mammoth and a giant ground sloth. The upper biostratigraphic limit for when the impressions were made could therefore be determined by consideration of the extinction dates of mammoths and ground sloths. More precise dates were able to be gained via radiocarbon dating of ditch grass (ruppia cirrhosa) embedded in the prints. These seeds produced a date of 23,000-21,000 years ago.
However, C dates are not infallible, and this remains a topic of debate. A recent counterproposal posits that the trackways were, in fact, created by the Clovis culture and the pre-existing proposed dates of first habitation should not be moved. False dates may have been produced as older strata containing the seeds could have been eroded and displaced onto the damp clay, before being impressed in by footsteps. Alternatively, aquatic plants like ditch grass reflect the C levels in their environment when living, if C was deficient in the habitat, this could imply a false date. | 0 | Theoretical and Fundamental Chemistry |
Optical data from satellites and from aircraft are increasingly being used to inform application decisions. | 1 | Applied and Interdisciplinary Chemistry |
Levonorgestrel is a hormonal medication which is used in a number of birth control methods. It is combined with an estrogen to make combination birth control pills. As an emergency birth control, sold under the brand names Plan B One-Step and Julie, among others, it is useful within 72 hours of unprotected sex. The more time that has passed since sex, the less effective the medication becomes, and it does not work after pregnancy (implantation) has occurred. Levonorgestrel works by preventing ovulation or fertilization from occurring. It decreases the chances of pregnancy by 57–93%. In an intrauterine device (IUD), such as Mirena among others, it is effective for the long-term prevention of pregnancy. A levonorgestrel-releasing implant is also available in some countries.
Common side effects include nausea, breast tenderness, headaches, and increased, decreased, or irregular menstrual bleeding. When used as an emergency contraceptive, if pregnancy occurs, there is no evidence that its use harms the fetus. It is safe to use during breastfeeding. Birth control that contains levonorgestrel will not change the risk of sexually transmitted infections. It is a progestin and has effects similar to those of the hormone progesterone. It works primarily by preventing ovulation and closing off the cervix to prevent the passage of sperm.
Levonorgestrel was patented in 1960 and introduced for medical use together with ethinylestradiol in 1970. It is on the World Health Organization's List of Essential Medicines. It is available as a generic medication. In the United States, levonorgestrel-containing emergency contraceptives are available over the counter (OTC) for all ages. In 2020, it was the 323rd most commonly prescribed medication in the United States, with more than 800thousand prescriptions. | 0 | Theoretical and Fundamental Chemistry |
Helmut Cölfen discovered and named mesocrystals in 2005 during his studies on biominerals. He suggested that their growth was due to a non-classical, self-assembly based process. | 0 | Theoretical and Fundamental Chemistry |
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