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The mathematical definition given by H.T. Odum is formally analogous to the definition provided on the maximum power theorem article. (For a brief explanation of Odums approach to the relationship between ecology and electronics see Ecological Analog of Ohms Law) | 0 | Theoretical and Fundamental Chemistry |
This is used for area monitoring of penetrating radiation and is usually expressed as the quantity H*(10). This means the radiation is equivalent to that found 10 mm within the ICRU sphere phantom in the direction of origin of the field. An example of penetrating radiation is gamma rays. | 0 | Theoretical and Fundamental Chemistry |
In the mid 19th century, investigators proposed several possible structures for benzene which were consistent with its empirical formula, CH, which had been determined by combustion analysis. The first, which was proposed by Kekulé in 1865, later proved to be closest to the true structure of benzene. This structure inspired several others to draw structures that were consistent with benzenes empirical formula; for example, Ladenburg proposed prismane, Dewar proposed Dewar benzene, and Koerner and Claus proposed Claus benzene. Some of these structures would be synthesized in the following years. Prismane, like the other proposed structures for benzene, is still often cited in the literature, because it is part of the historical struggle toward understanding the mesomeric structures and resonance of benzene. Some computational chemists still research the differences between the possible isomers of CH. | 0 | Theoretical and Fundamental Chemistry |
Bioactivation is a crucial step in the activity of certain pharmaceuticals. Often, the parent form of the drug is not the active form and it needs to be metabolized in order to produce its therapeutic effects. In other cases, bioactivation is not necessarily needed for drugs to be active and can instead produce reactive intermediates that initiate stronger adverse effects than the original form of the drug. Bioactivation can occur through the action Phase I metabolic enzymes, such as cytochrome P450 or peroxidases. Reactive intermediates can cause a loss of function in some enzymatic pathways or can promote the production of reactive oxygen species, both of which can increase stress levels and alter homeostasis. | 1 | Applied and Interdisciplinary Chemistry |
During calibration with the no-net-flux-method, the microdialysis probe is perfused with at least four different concentrations of the analyte of interest (C) and steady-state concentrations of the analyte leaving the probe are measured in the dialysate (C). The recovery for this method can be determined by plotting C−C over C and computing the slope of the regression line. If analyte concentrations in the perfusate are equal to concentrations at the sampling site, no-net flux occurs. Respective concentrations at the no-net-flux point are represented by the x-intercept of the regression line. The strength of this method is that, at steady-state, no assumptions about the behaviour of the compound in the vicinity of the probe have to be made, since equilibrium exists at a specific time and place. However, under transient conditions (e.g. after drug challenge), the probe recovery may be altered resulting in biased estimates of the concentrations at the sampling site. To overcome this limitation, several approaches have been developed that are also applicable under non-steady-state conditions. One of these approaches is the dynamic no-net-flux method. | 1 | Applied and Interdisciplinary Chemistry |
It is a precursor to trifluoromethyltrimethylsilane, a popular trifluoromethylating reagent in organic synthesis. | 1 | Applied and Interdisciplinary Chemistry |
Examples of oxygen nucleophiles are water (HO), hydroxide anion, alcohols, alkoxide anions, hydrogen peroxide, and carboxylate anions.
Nucleophilic attack does not take place during intermolecular hydrogen bonding. | 0 | Theoretical and Fundamental Chemistry |
Package inserts mention that levofloxacin is to be avoided in patients with a known hypersensitivity to levofloxacin or other quinolone drugs.
Like all fluoroquinolines, levofloxacin is contraindicated in patients with epilepsy or other seizure disorders, and in patients who have a history of quinolone-associated tendon rupture.
Levofloxacin may prolong the QT interval in some people, especially the elderly, and levofloxacin should not be used for people with a family history of Long QT syndrome, or who have long QT, chronic low potassium, it should not be prescribed with other drugs that prolong the QT interval.
Unlike ciprofloxacin, levofloxacin does not appear to deactivate the drug metabolizing enzyme CYP1A2. Therefore, drugs that use that enzyme, like theophylline, do not interact with levofloxacin. It is a weak inhibitor of CYP2C9, suggesting potential to block the breakdown of warfarin and phenprocoumon. This can result in more action of drugs like warfarin, leading to more potential side effects, such as bleeding.
The use of non-steroidal anti-inflammatory drugs (NSAIDs) in combination with high dose fluoroquinolone therapy may lead to seizures.
When levofloxacin is taken with anti-acids containing magnesium hydroxide or aluminum hydroxide, the two combine to form insoluble salts that are difficult to absorb from the intestines. Peak serum concentrations of levofloxacin may be reduced by 90% or more, which can prevent the levofloxacin from working. Similar results have been reported when levofloxacin is taken with iron supplements and multi-vitamins containing zinc.
A 2011 review examining musculoskeletal complications of fluoroquinolones proposed guidelines with respect to administration to athletes, that called for avoiding all use of fluoroquinolone antibiotics if possible, and if they are used: ensure there is informed consent about the musculoskeletal risks, and inform coaching staff; do not use any corticosteroids if fluoroquinolones are used; consider dietary supplements of magnesium and antioxidants during treatment; reduce training until the course of antibiotic is finished and then carefully increase back to normal; and monitor for six months after the course is finished, and stop all athletic activity if symptoms emerge. | 0 | Theoretical and Fundamental Chemistry |
For isotopes occurring at extremely low levels, accelerator mass spectrometry (AMS) can be used. For example, the decay rate of the radioisotope C is widely used to date organic materials, but this approach was once limited to relatively large samples no more than a few thousand years old. AMS extended the range of C dating to about 60,000 years BP, and is about 10 times more sensitive than conventional IRMS.
AMS works by accelerating negative ions through a large (mega-volt) potential, followed by charge exchange and acceleration back to ground. During charge exchange, interfering species can be effectively removed. In addition, the high energy of the beam allows the use of energy-loss detectors, that can distinguish between species with the same mass/charge ratio. Together, these processes allow the analysis of extreme isotope ratios above 10. | 0 | Theoretical and Fundamental Chemistry |
As the density increases, the Gamow peak increases in height and shifts towards lower energy, while the potential barriers are depressed. If the potential barriers are depressed by the amount of , the Gamow peak is shifted across the origin, making the reactions density-dependent, as the Gamow peak energy is much larger than the thermal energy. The material becomes a degenerate gas at such densities. Harrison proposed that models fully independent of temperature be called cryonuclear.
Pycnonuclear reactions can proceed in two ways: direct ( or ) or through chain of electron capture reactions (). | 0 | Theoretical and Fundamental Chemistry |
Escitalopram, like other SSRIs, has been shown to affect sexual function, causing side effects such as decreased libido, delayed ejaculation, and anorgasmia.
There is also evidence that SSRIs may cause an increase in suicidal ideation. An analysis conducted by the FDA found a statistically insignificant 1.5 to 2.4-fold (depending on the statistical technique used) increase of suicidality among the adults treated with escitalopram for psychiatric indications. The authors of a related study note the general problem with statistical approaches: due to the rarity of suicidal events in clinical trials, it is hard to draw firm conclusions with a sample smaller than two million patients.
Citalopram and escitalopram are associated with dose-dependent QT interval prolongation and should not be used in those with congenital long QT syndrome or known pre-existing QT interval prolongation, or in combination with other medicines that prolong the QT interval. ECG measurements should be considered for patients with cardiac disease, and electrolyte disturbances should be corrected before starting treatment. In December 2011, the UK implemented new restrictions on the maximum daily doses at 20 mg for adults and 10 mg for those older than 65 years or with liver impairment. There are concerns of higher rates of QT prolongation and torsades de pointes compared with other SSRIs. The US Food and Drug Administration and Health Canada did not similarly order restrictions on escitalopram dosage, only on its predecessor citalopram. | 0 | Theoretical and Fundamental Chemistry |
The problem of finding a reaction centre in a protein matrix is formally equivalent to many problems in computing. Mapping computing problems onto reaction center searches may allow light harvesting to work as a computational device, improving computational speeds at room temperature, yielding 100-1000x efficiency. | 0 | Theoretical and Fundamental Chemistry |
Suksin Lee was born in P'yŏngannam-do, Korea, the son of I Myŏngse and a woman of the Koksan Kang family. He earned his medical degree from Kyŏngsŏng Medical College (now Seoul National University) in 1921, and obtained his medical license in August of that year. After graduation, he studied pathology for several months at Tokyo Imperial University in Japan. He then traveled to Germany in 1922 to pursue additional studies.
After completing preliminary language instruction and various coursework in chemistry and physiological chemistry at the Friedrich Wilhelm University of Berlin, he earned a doctorate of medicine in 1926. Lees inaugural dissertation, Ueber Glykolyse', was a study of inorganic phosphates during blood glycolysis. His thesis advisors at the time included Otto Lubarsch of the Chemistry Department at the Pathological Institute, University of Berlin.
While in his final year of studies, Lee obtained a position as a research assistant at a national hospital in Berlin, where he worked until 1927. During this time he published and co-published several papers on the effects of photosensitive substances on glucose metabolism and cellular respiration. | 1 | Applied and Interdisciplinary Chemistry |
Hydraulic structures like weirs or locks often contain moveable steel structures like valves or gates, which are submerged under water. These steel structures are often constructed with thin steel plates mounted on girders. When the steel structures are accelerated or decelerated, substantial amounts of water are moved, too. This added mass must e.g. be taken into account when designing the drive systems for these steel structures. | 1 | Applied and Interdisciplinary Chemistry |
The concept of isotopes developed from radioactivity. The pioneering work on radioactivity by Henri Becquerel, Marie Curie and Pierre Curie was awarded the [https://www.nobelprize.org/nobel_prizes/physics/laureates/1903/ Nobel Prize in Physics in 1903]. Later Frederick Soddy would take radioactivity from physics to chemistry and shed light on the nature of isotopes, something with rendered him the [https://www.nobelprize.org/nobel_prizes/chemistry/laureates/1921/ Nobel Prize in Chemistry in 1921] (awarded in 1922).
The question of stable, non-radioactive isotopes was more difficult and required the development by Francis Aston of a high-resolution mass spectrograph, which allowed the separation of different stable isotopes of one and the same element. Francis Aston was awarded the [https://www.nobelprize.org/nobel_prizes/chemistry/laureates/1922/ 1922 Nobel Prize in Chemistry] for this achievement. With his enunciation of the whole-number rule, Aston solved a problem that had riddled chemistry for a hundred years. The understanding was that different isotopes of a given element would be chemically identical.
It was discovered in the 1930s by Harold Urey in 1932 (awarded the Nobel Prize in Chemistry in 1934). It was early on found that the deuterium content had a profound effect on chemistry and biochemistry.
In the linear approximation, the effect of isotopic substitution is proportional to the mass ratio of the heavy and light isotope. Thus chemical and biological effects of heavier isotopes of the “biological” atoms C, N and O are expected to be much smaller since the mass ratios for the normal to heavier isotopes are much closer to unity than the factor two for hydrogen to deuterium. However, it has been reported in 1930s, and then again in 1970s and 1990s, as well as recently, that relatively small changes in the content of the heavy isotope of hydrogen, deuterium, has profound effects on biological systems. These strong nonlinear effects could not be fully rationalized based on the known concepts of the isotopic effects. These and other observations make it possible that isotopes have a much more profound importance than could ever have been imagined by the pioneers.
In 2011 [http://chem1.mbb.ki.se/?page_id=10 Roman Zubarev] formulated the isotope resonance hypothesis. It originated in the following, unexpected observation. Define ΔM = M - M, where M is the monoisotopic mass (e.g. O = 15.994915 Da) and M is the nominal (integer) mass, i.e., the number of nucleons (e.g. O = 16). ΔM is a constant in the whole Universe. Define ΔM = M - M, where M is the average isotopic mass (e.g. O = 15.999 Da on Earth). Obviously ΔM depends on the precise isotopic composition for a given molecule. Finally define NMD = 1000ΔM/M and NIS = 1000ΔM/M, where NMD [in units of ‰] and NIS [in units of ‰] are the normalized isotopic defect and shift, respectively. If NIS is plotted as a function of NMD for a large number of terrestrial peptides, one would anticipate a homogenous distribution of data points (as in Fig. 1B). This is not what was found by Zubarev's team, instead they found band gap in the distribution with a narrow line in the middle (Fig. 1A).
This serendipitous discovery led Zubarev to formulate the isotope resonance hypothesis. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, acetylation is an organic esterification reaction with acetic acid. It introduces an acetyl group into a chemical compound. Such compounds are termed acetate esters or simply acetates. Deacetylation is the opposite reaction, the removal of an acetyl group from a chemical compound. | 0 | Theoretical and Fundamental Chemistry |
Based on structural features and the phylogeny of the essential protein ORF2p, LINEs can be separated into six main groups, referred to as R2, RanI, L1, RTE, I and Jockey. These groups can further be subdivided into at least 28 clades.
In plant genomes, so far only LINEs of the L1 and RTE clade have been reported. Whereas L1 elements diversify into several subclades, RTE-type LINEs are highly conserved, often constituting a single family.
In fungi, Tad, L1, CRE, Deceiver and Inkcap-like elements have been identified, with Tad-like elements appearing exclusively in fungal genomes.
All LINEs encode a least one protein, ORF2, which contains an RT and an endonuclease (EN) domain, either an N-terminal APE or a C-terminal RLE or rarely both. A ribonuclease H domain is occasionally present. Except for the evolutionary ancient R2 and RTE superfamilies, LINEs usually encode for another protein named ORF1, which may contain an Gag-knuckle, a L1-like RRM (), and/or an esterase. LINE elements are relatively rare compared to LTR-retrotransposons in plants, fungi or insects, but are dominant in vertebrates and especially in mammals, where they represent around 20% of the genome. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, a suspension is a heterogeneous mixture of a fluid that contains solid particles sufficiently large for sedimentation. The particles may be visible to the naked eye, usually must be larger than one micrometer, and will eventually settle, although the mixture is only classified as a suspension when and while the particles have not settled out. | 0 | Theoretical and Fundamental Chemistry |
EXPOSE is a multi-user facility mounted outside the International Space Station (ISS) dedicated to astrobiology. EXPOSE was developed by the European Space Agency (ESA) for long-term spaceflights and was designed to allow exposure of chemical and biological samples to outer space while recording data during exposure.
The results will contribute to our understanding of photobiological processes in simulated radiation climates of planets (e.g. early Earth, early and present Mars, and the role of the ozone layer in protecting the biosphere from harmful UV-B radiation), as well as studies of the probabilities and limitations for life to be distributed beyond its planet of origin. EXPOSE data support long-term in situ studies of microbes in artificial meteorites, as well as of microbial communities from special ecological niches. Some EXPOSE experiments investigated to what extent particular terrestrial organisms are able to cope with extraterrestrial environmental conditions. Others tested how organic molecules react when subjected for a prolonged period of time to unfiltered solar light. | 1 | Applied and Interdisciplinary Chemistry |
In 2008, the installed costs of sprinkler systems ranged from US$0.31 – $3.66 per square foot, depending on type and location. Residential systems, installed at the time of initial home construction and utilizing municipal water supplies, average about US$0.35/square foot.
Systems can be installed during initial construction, or retrofitted. Some communities have laws requiring residential sprinkler systems, especially where large municipal hydrant water supplies ("fire flows") are not available. Nationwide in the United States, one and two-family homes generally do not require fire sprinkler systems, although the overwhelming loss of life due to fires occurs in these spaces. Residential sprinkler systems are inexpensive (about the same per square foot as carpeting or floor tiling), but require larger water supply piping than is normally installed in homes, so retrofitting is usually cost prohibitive.
According to the National Fire Protection Association (NFPA), fires in hotels with sprinklers averaged 78% less damage than fires in hotels without them (1983–1987). The NFPA says the average loss per fire in buildings with sprinklers was $2,300, compared to an average loss of $10,300 in unsprinklered buildings. However, in a purely economic comparison, this is not a complete picture; the total costs of fitting, and the costs arising from non-fire triggered release must be factored.
The NFPA states that it "has no record of a fire killing more than two people in a completely sprinklered building where a sprinkler system was properly operating, except in an explosion or flash fire or where industrial fire brigade members or employees were killed during fire suppression operations." Elsewhere it has stated, "NFPA has no record of a multiple fatality in a fully sprinklered building where the system operated."
The world's largest fire sprinkler manufacturer is the Fire Protection Products division of Tyco International. | 1 | Applied and Interdisciplinary Chemistry |
In medieval warfare, sturdy stakes were stuck into the ground at the bottom of long lines of ditches, positioned with a sharp end pointing up diagonally, in order to prevent cavalry charges in a given area. Even if the stakes were spotted, horsemen would be forced to dismount and effectively give up their advantage as cavalry, and become easier targets. The correct layout of these extensive lines of ditches and the control of stake size, form and placement were part of the craft of war.
An alternative cavalry deterrent, allowing quicker dispersal and providing the advantage of being hidden more easily, was the deployment of, for example, small balls with spikes, used during most of antiquity. Many variants were used, such as boards with metal hooks, as described as used by Julius Caesar. A more modern version of this are caltrops.
Passive fortification—ditches and obstacles such as dragon's teeth and Czech hedgehogs—were used as anti-tank measures during World War II. | 1 | Applied and Interdisciplinary Chemistry |
In a crystal containing different cations, those of high valency and small coordination number tend not to share polyhedron elements with one another. This rule tends to increase the distance between highly charged cations, so as to reduce the electrostatic repulsion between them.
One of Pauling's examples is olivine, , where M is a mixture of at some sites and at others. The structure contains distinct tetrahedra which do not share any oxygens (at corners, edges or faces) with each other. The lower-valence and cations are surrounded by polyhedra which do share oxygens. | 0 | Theoretical and Fundamental Chemistry |
By combining topographic image formation with tomographic image reconstruction, distributions of defects can be resolved in three dimensions. Unlike "classical" computed tomography (CT), image contrast is not based on differences in absorption (absorption contrast), but on the usual contrast mechanisms of topography (diffraction contrast). In this way, three-dimensional distributions of dislocations in crystals have been imaged.
Literature: | 0 | Theoretical and Fundamental Chemistry |
Extinct isotopes of superheavy elements are isotopes of superheavy elements whose half-lives were too short to have lasted through the formation of the Solar System, and because they are not replenished by natural processes, can nowadays only be found as their decay products (from alpha decay, cluster decay or spontaneous fission) trapped within sediment and meteorite samples dating billions of years ago. | 0 | Theoretical and Fundamental Chemistry |
Some countries require or recommend fortification of foods. As of January 2022, 37 countries, mostly in Sub-Saharan Africa, require food fortification of cooking oil, rice, wheat flour or maize (corn) flour with vitamin A, usually as retinyl palmitate or retinyl acetate. Examples include Pakistan, oil, 11.7 mg/kg and Nigeria, oil, 6 mg/kg; wheat and maize flour, 2 mg/kg. An additional 12 countries, mostly in southeast Asia, have a voluntary fortification program. For example, the government of India recommends 7.95 mg/kg in oil and 0.626 mg/kg for wheat flour and rice. However, compliance in countries with voluntary fortification is lower than countries with mandatory fortification. No countries in Europe or North America fortify foods with vitamin A.
Separated from fortification via addition of synthetic vitamin A to foods, means of fortifying foods via genetic engineering have been explored. Research on rice began in 1982. The first field trials of golden rice cultivars were conducted in 2004. The result was "Golden Rice", a variety of Oryza sativa rice produced through genetic engineering to biosynthesize beta-carotene, a precursor of retinol, in the edible parts of rice. In May 2018, regulatory agencies in the United States, Canada, Australia and New Zealand had concluded that Golden Rice met food safety standards. On 21 July 2021, the Philippines became the first country to officially issue the biosafety permit for commercially propagating Golden Rice. However, in April 2023, the Supreme Court of the Philippines issued a Writ of Kalikasan ordering the Department of Agriculture to stop the commercial distribution of genetically modified rice in the country. | 1 | Applied and Interdisciplinary Chemistry |
Characteristics of fecal sludge may vary widely due to climate, toilet type, diet and other variables. Fecal sludge can be grouped by consistency as "liquid" (total solids or TS <5%), "slurry" (TS 5–15%), "semi-solid" (TS 15–25%), and "solid" (TS >25%). Quantities and qualities of fecal sludge and wastewater are very different, with the range of fecal sludge characteristics being 1–2 orders of magnitude higher than wastewater.
The result of the demographic, environmental, and technical factors that influence characteristics of fecal sludge is a high level of heterogeneity that complicates characterization.
In the absence of actual data, designers often use default values, such as 2,000 mg/L for BOD and 5,000 mg/L of TSS in order to size the treatment system. However, this often results in over-design or under-design of fecal sludge treatment plants. This is because there is often no "standard range of variation" for particular properties, and findings from one study cannot necessarily be used as a base of comparison to another.
Research has shown that correlations to spatially available data can help predict quantities and qualities of fecal sludge. The relevant indicators for the prediction include income level, users, volume, emptying frequency, and truck size. Using these correlations in characteristics could provide a way to reduce analytical costs for fecal sludge analysis.
Performing a waste characterization study helps to understand local conditions and provides data that factors into treatment plant sizing. It can also help to estimate the value of the products that can be derived from the treatment process.
The main physico-chemical parameters commonly measured to characterize fecal sludge include: BOD, total suspended solids, % solids, indication of sand, COD, ammonium, total nitrogen and total phosphorus, Fats, Oil and Grease (FOG), Sludge Volume Index (SVI), pH, alkalinity.
Relatively little data exists on pathogen content in fecal sludge. One study from rural Bangladesh determined 41 helminth eggs per g of fecal sludge from pit latrines.
The characteristics of fecal sludge may be influenced by:
* Methods, techniques and the skill levels of personnel conducting the desludging;
* The efficiency of the different types of equipment used in desludging;
* Seasonality – presence of groundwater or flood water that may infiltrate into tanks and dilute the contents;
* The last time the tank was desludged (age of fecal sludge). | 1 | Applied and Interdisciplinary Chemistry |
Robinson was awarded the 2010 Geological Society of London President's Award for her contributions to geosciences. In 2011 Robinson moved back to the United Kingdom, where she was appointed to the faculty of the University of Bristol. She was awarded a European Research Council Starting Grant studying changes in chemistry and circulation of the Atlantic Ocean. She makes use of an Agassiz Trawl to collect samples from the floor of the ocean, with a particular focus on deep-sea corals. Robinson was involved with a British Antarctic Survey mission to the South Orkney Islands. The mission took place on the RRS James Clark Ross and investigated the biodiversity in and outside of the South Orkney Islands. For this work she was awarded the Antarctic Service Medal.
In 2016 she delivered a Ted Talk on the secrets she discovers on the ocean floor. | 0 | Theoretical and Fundamental Chemistry |
The choice of species is based on which will give the best correlation to human trials. Differences in the gut, enzyme activity, circulatory system, or other considerations make certain models more appropriate based on the dosage form, site of activity, or noxious metabolites. For example, canines may not be good models for solid oral dosage forms because the characteristic carnivore intestine is underdeveloped compared to the omnivores, and gastric emptying rates are increased. Also, rodents can not act as models for antibiotic drugs because the resulting alteration to their intestinal flora causes significant adverse effects. Depending on a drugs functional groups, it may be metabolized in similar or different ways between species, which will affect both efficacy and toxicology.
Medical device studies also use this basic premise. Most studies are performed in larger species such as dogs, pigs and sheep which allow for testing in a similar sized model as that of a human. In addition, some species are used for similarity in specific organs or organ system physiology (swine for dermatological and coronary stent studies; goats for mammary implant studies; dogs for gastric and cancer studies; etc.).
Importantly, the regulatory guidelines of FDA, EMA, and other similar international and regional authorities usually require safety testing in at least two mammalian species, including one non-rodent species, prior to human trials authorization. | 1 | Applied and Interdisciplinary Chemistry |
The basic method is to produce sacrificial anodes through a casting process. However, two casting methods can be distinguished.
The high pressure die-casting process for sacrificial anodes is widespread. It is a fully automated machine process. In order for the manufacturing process to run reliably and in a repeatable manner, a modification of the processed sacrificial anode alloy is required. Alternatively, the gravity casting process is used for the production of the sacrificial anodes. This process is performed manually or partially automated. The alloy does not have to be adapted to the manufacturing process, but is designed for 100% optimum corrosion protection. | 0 | Theoretical and Fundamental Chemistry |
Examples of siderophores produced by various bacteria and fungi:
Hydroxamate siderophores
Catecholate siderophores
Mixed ligands
Amino carboxylate ligands
A comprehensive list of siderophore structures (over 250) is presented in Appendix 1 in reference. | 1 | Applied and Interdisciplinary Chemistry |
It may cause dizziness, and patients should not, therefore, drive or operate heavy machinery or vehicles until they are familiar with how dexketoprofen affects them. Concomitant use of alcohol and other sedatives may potentiate this effect. In a small subset of individuals the dizziness may be intolerable and require transition to an alternative treatment. | 0 | Theoretical and Fundamental Chemistry |
Anticoagulation therapy has a long history. In 1884 John Berry Haycraft described a substance found in the saliva of leeches, Hirudo medicinalis, that had anticoagulant effects. He named the substance ‘Hirudine’ from the Latin name. The use of medicinal leeches can be dated back all the way to ancient Egypt. In the early 20th century Jay McLean, L. Emmet Holt Jr. and William Henry Howell discovered the anticoagulant heparin, which they isolated from the liver (hepar). Heparin remains one of the most effective anticoagulants and is still used today, although it has its disadvantages, such as requiring intravenous administration and having a variable dose-response curve due to substantial protein binding. In the 1980s low molecular-weight heparin (LMWH) were developed. They are derived from heparin by enzymatic or chemical depolymerization and have better pharmacokinetic properties than heparin. In 1955 the first clinical use of warfarin, a vitamin K antagonist, was reported. Warfarin was originally used as a rat poison in 1948 and thought to be unsafe for humans, but a suicide attempt suggested that it was relatively safe for humans. Vitamin K antagonists are the most commonly used oral anticoagulants today and warfarin was the 11th most prescribed drug in the United States in 1999 and is actually the most widely prescribed oral anticoagulant worldwide. Warfarin has its disadvantages though, just like heparin, such as a narrow therapeutic index and multiple food and drug interactions and it requires routine anticoagulation monitoring and dose adjustment. Since both heparin and warfarin have their downsides the search for alternative anticoagulants has been ongoing and DTIs are proving to be worthy competitors. The first DTI was actually hirudin, which became more easily available with genetic engineering. It is now available in a recombinant form as lepirudin (Refludan) and desirudin (Revasc, Iprivask). Development of other DTIs followed with the hirudin analog, bivalirudin, and then the small molecular DTIs. However, such DTIs were also having side effects such as bleeding complications and liver toxicity, and their long-term effects were in doubt. | 1 | Applied and Interdisciplinary Chemistry |
Soldiers can be exposed to a wide variety of chemical hazards. These threats are mostly invisible but detectable by hyperspectral imaging technology. The Telops Hyper-Cam, introduced in 2005, has demonstrated this at distances up to 5 km. | 0 | Theoretical and Fundamental Chemistry |
A key concept in interpreting radiocarbon dates is archaeological association: what is the true relationship between two or more objects at an archaeological site? It frequently happens that a sample for radiocarbon dating can be taken directly from the object of interest, but there are also many cases where this is not possible. Metal grave goods, for example, cannot be radiocarbon dated, but they may be found in a grave with a coffin, charcoal, or other material which can be assumed to have been deposited at the same time. In these cases, a date for the coffin or charcoal is indicative of the date of deposition of the grave goods, because of the direct functional relationship between the two. There are also cases where there is no functional relationship, but the association is reasonably strong: for example, a layer of charcoal in a rubbish pit provides a date which has a relationship to the rubbish pit.
Contamination is of particular concern when dating very old material obtained from archaeological excavations and great care is needed in the specimen selection and preparation. In 2014, Thomas Higham and co-workers suggested that many of the dates published for Neanderthal artifacts are too recent because of contamination by "young carbon".
As a tree grows, only the outermost tree ring exchanges carbon with its environment, so the age measured for a wood sample depends on where the sample is taken from. This means that radiocarbon dates on wood samples can be older than the date at which the tree was felled. In addition, if a piece of wood is used for multiple purposes, there may be a significant delay between the felling of the tree and the final use in the context in which it is found. This is often referred to as the old wood problem. One example is the Bronze Age trackway at Withy Bed Copse, in England; the trackway was built from wood that had clearly been worked for other purposes before being re-used in the trackway. Another example is driftwood, which may be used as construction material. It is not always possible to recognize re-use. Other materials can present the same problem: for example, bitumen is known to have been used by some Neolithic communities to waterproof baskets; the bitumen's radiocarbon age will be greater than is measurable by the laboratory, regardless of the actual age of the context, so testing the basket material will give a misleading age if care is not taken. A separate issue, related to re-use, is that of lengthy use, or delayed deposition. For example, a wooden object that remains in use for a lengthy period will have an apparent age greater than the actual age of the context in which it is deposited. | 0 | Theoretical and Fundamental Chemistry |
Modern applications use the analytical ultracentrifuge. The theoretical basis for the measurements is developed from the Mason-Weaver equation. The advantage of using analytical sedimentation equilibrium analysis for Molecular Weight of proteins and their interacting mixtures is the avoidance of need for derivation of a frictional coefficient, otherwise required for interpretation of dynamic sedimentation.
Sedimentation equilibrium can be used to determine molecular mass. It forms the basis for an analytical ultracentrifugation method for measuring molecular masses, such as those of proteins, in solution. | 1 | Applied and Interdisciplinary Chemistry |
The main processes involved in secondary sewage treatment are designed to remove as much of the solid material as possible. They use biological processes to digest and remove the remaining soluble material, especially the organic fraction. This can be done with either suspended-growth or biofilm processes. The microorganisms that feed on the organic matter present in the sewage grow and multiply, constituting the biological solids, or biomass. These grow and group together in the form of flocs or biofilms and, in some specific processes, as granules. The biological floc or biofilm and remaining fine solids form a sludge which can be settled and separated. After separation, a liquid remains that is almost free of solids, and with a greatly reduced concentration of pollutants.
Secondary treatment can reduce organic matter (measured as biological oxygen demand) from sewage, using aerobic or anaerobic processes. The organisms involved in these processes are sensitive to the presence of toxic materials, although these are not expected to be present at high concentrations in typical municipal sewage. | 1 | Applied and Interdisciplinary Chemistry |
In the table below, the dispersion relation ω = [Ω(k)] between angular frequency ω = 2π / T and wave number k = 2π / λ is given, as well as the phase and group speeds.
Deep water corresponds with water depths larger than half the wavelength, which is the common situation in the ocean. In deep water, longer period waves propagate faster and transport their energy faster. The deep-water group velocity is half the phase velocity. In shallow water, for wavelengths larger than twenty times the water depth, as found quite often near the coast, the group velocity is equal to the phase velocity. | 1 | Applied and Interdisciplinary Chemistry |
Monocyte distribution width (MDW) is a cytometry-based parameter that measures the range of variation of monocytes. If the parameter is available, it is reported as part of the standard complete blood count (CBC) with differential.
The parameter was FDA cleared as an early sepsis indicator for ER patients in 2019 for Beckman Coulter.
MDW serves as an indicator for early screening of sepsis in conjunction with CRP and PCT and for differentiating false positive blood cultures. | 1 | Applied and Interdisciplinary Chemistry |
Adaptive cells change their absorption/reflection characteristics depending on environmental conditions. An adaptive material responds to the intensity and angle of incident light. At the part of the cell where the light is most intense, the cell surface changes from reflective to adaptive, allowing the light to penetrate the cell. The other parts of the cell remain reflective increasing the retention of the absorbed light within the cell.
In 2014, a system was developed that combined an adaptive surface with a glass substrate that redirect the absorbed to a light absorber on the edges of the sheet. The system also includes an array of fixed lenses/mirrors to concentrate light onto the adaptive surface. As the day continues, the concentrated light moves along the surface of the cell. That surface switches from reflective to adaptive when the light is most concentrated and back to reflective after the light moves along. | 0 | Theoretical and Fundamental Chemistry |
This term is also used in the field of gene synthesis—for example "40-base synthetic oligonucleotides are built into 500- to 800-bp synthons". | 0 | Theoretical and Fundamental Chemistry |
Sometimes adding an ion other than the ones that are part of the precipitated salt itself can increase the solubility of the salt. This "salting in" is called the "uncommon-ion effect" (also "salt effect" or the "diverse-ion effect"). It occurs because as the total ion concentration increases, inter-ion attraction within the solution can become an important factor. This alternate equilibrium makes the ions less available for the precipitation reaction. This is also called odd ion effect. | 0 | Theoretical and Fundamental Chemistry |
Clinical trials recruit study subjects to sign a document representing their "informed consent". The document includes details such as its purpose, duration, required procedures, risks, potential benefits, key contacts and institutional requirements. The participant then decides whether to sign the document. The document is not a contract, as the participant can withdraw at any time without penalty.
Informed consent is a legal process in which a recruit is instructed about key facts before deciding whether to participate. Researchers explain the details of the study in terms the subject can understand. The information is presented in the subject's native language. Generally, children cannot autonomously provide informed consent, but depending on their age and other factors, may be required to provide informed assent. | 1 | Applied and Interdisciplinary Chemistry |
This is an expansion of stereoscopic PIV by adding a second plane of investigation directly offset from the first one. Four cameras are required for this analysis. The two planes of laser light are created by splitting the laser emission with a beam splitter into two beams. Each beam is then polarized orthogonally with respect to one another. Next, they are transmitted through a set of optics and used to illuminate one of the two planes simultaneously.
The four cameras are paired into groups of two. Each pair focuses on one of the laser sheets in the same manner as single-plane stereoscopic PIV. Each of the four cameras has a polarizing filter designed to only let pass the polarized scattered light from the respective planes of interest. This essentially creates a system by which two separate stereoscopic PIV analysis setups are run simultaneously with only a minimal separation distance between the planes of interest.
This technique allows the determination of the three velocity gradient components single-plane stereoscopic PIV could not calculate: , , and . With this technique, the entire velocity gradient tensor of the fluid at the 2-dimensional plane of interest can be quantified. A difficulty arises in that the laser sheets should be maintained close enough together so as to approximate a two-dimensional plane, yet offset enough that meaningful velocity gradients can be found in the z-direction. | 1 | Applied and Interdisciplinary Chemistry |
*"Conference Paper: Opportunities in energy storage due to the paradigm shift fueled by the mobile and clean tech revolutions"
*"A Consumer Revolution"
*"Benchmark study on high performing carbon anode material"
*"Conference Paper: Safety studies of Li-ion key components by ARC"
*"Conference Paper: Safety studies on lithium-ion batteries by accelerating rate calorimetry"
*Uppsala University Dissertation<br>"Chemical and Electrochemical Intercalation of Lithium Into a V6O13 Host" | 0 | Theoretical and Fundamental Chemistry |
In this approach, the sample is spiked with a species (internal standard) which is used to normalise the response of analyte, compensating for variables at any stage of the sample preparation and analysis, including ion suppression.
It is important that the internal standard displays very similar (ideally identical) properties, with respect to detector response (i.e. ionisation), as the analyte of interest. To simplify the selection of internal standard, most laboratories use an analogous stable isotope in an isotope dilution type analysis. The stable isotope is almost guaranteed to be chemically and physically as close as possible to the analyte of interest, hence producing an almost identical detector response in addition to behaving identically during sample preparation and chromatographic resolution. To this end, the ion suppression experienced by both the analyte and the internal standard should be identical. It is important to note that an excessively high concentration of stable isotope internal standard may cause ion suppression itself, since it will co-elute with the analyte of interest. Hence, the internal standard should be added at an appropriate concentration. | 0 | Theoretical and Fundamental Chemistry |
The optimization of the particle size distribution facilitates the pumping, mixing and transportation of foodstuff. Particle size analysis is usually done with any milled food, such as coffee, flour, cocoa powder. It is especially helpful with chocolate quality to ensure there is a consistent taste and feeling when eaten. Furthermore, in the case of food emulsions, particle size analysis is relevant to predict stability and shelf-life, and optimize homogenization. | 0 | Theoretical and Fundamental Chemistry |
Fluxes have several serious drawbacks:
* Corrosivity, which is mostly due to the aggressive compounds of the activators; hygroscopic properties of the flux residues may aggravate the effects
* Interference with test equipment, which is due to the insulating residues deposited on the test contacts on electronic circuit boards
* Interference with machine vision systems when the layer of flux or its remains is too thick or improperly located
* Contamination of sensitive parts, e.g. facets of laser diodes, contacts of connectors and mechanical switches, and MEMS assemblies
* Deterioration of electrical properties of printed circuit boards, as soldering temperatures are above the glass transition temperature of the board material and flux components (e.g. glycols, or chloride and bromide ions) can diffuse into its matrix; e.g. water-soluble fluxes containing polyethylene glycol were demonstrated to have such impact
* Deterioration of high-frequency circuit performance by flux residues
* Deterioration of surface insulation resistance, which tends to be as much as three orders of magnitude lower than the bulk resistance of the material
* Electromigration and growth of whiskers between nearby traces, aided by ionic residues, surface moisture and a bias voltage
* The fumes liberated during soldering have adverse health effects, and volatile organic compounds can be outgassed during processing
* The solvents required for post-soldering cleaning of the boards are expensive and may have adverse environmental impact
In special cases the drawbacks are sufficiently serious to warrant using fluxless techniques. | 1 | Applied and Interdisciplinary Chemistry |
The emitted photons from excited lanthanides are detected by highly sensitive devices and techniques such as single-photon detection. If the lifetime of the excited emitting level is long enough, then time-resolved detection (TRD) can be used to enhance the signal-to-noise ratio. The instrumentation used to perform LRET is relatively simple, although slightly more complex than conventional fluorimeters. The general requirements are a pulsed UV excitation source and time-resolved detection.
Light sources which emit short duration pulses can be divided into the following categories:
* Flash tubes
* Mechanically or electronically chopped discharge lamps
* Spark gaps
* Pulsed lasers
The most important factors in the selection of the pulsed light source for are the duration and intensity of the light. Pulsed lasers for the 300 to 500 nm range have now replaced spark caps in fluorescence spectroscopy. There are four general types of pulsing lasers used: lasers with pulsed excitation, lasers with G-switching, mode locked lasers and cavity dumped lasers. Pulsed nitrogen lasers (337 nm) have often been used as an excitation source in time resolved fluorometry.
In time resolved fluorometry the fast photomultiplier tube is the only practical single photon detector. Good single photon resolution is also an advantage in counting photons from long decay fluorescent probes, such as lanthanide chelates.
These commercial instruments are available in the market today: Perkin-Elmer Micro Filter Fluorometer LS-2, Perkin-Elmer Luminescence Spectrometer Model LS 5, and LKB-Wallac Time-Resolved Fluorometer Model 1230. | 1 | Applied and Interdisciplinary Chemistry |
Measuring isotopic ratios by mass spectrometry includes multiple steps in which samples can undergo cross-contamination, including during sample preparation, leakage of gas through instrument valves, the generic category of phenomena called memory effects, and the introduction of blanks (foreign analyte measured as part of the sample). As a result of these instrument-specific effects the range in measured δ values can be lower than the true range in the original samples. To correct for such scale compression researchers calculate a "stretching factor" by measuring two isotopic reference materials (Coplen, 1988). For the hydrogen system the two reference materials are commonly VSMOW2 and SLAP2, where δH = 0 and δH = -427.5 vs. VSMOW. If the measured difference between the two references is less than 427.5‰, all measured H/H ratios are multiplied by the stretching factor required to bring the difference between the two reference materials in line with expectations. After this scaling, a factor is added to all measured isotopic ratios so that the reference materials attain their defined isotopic values. The carbon system also uses two anchoring reference materials (Coplen et al., 2006a; 2006b). | 0 | Theoretical and Fundamental Chemistry |
Fermentation is a specific type of heterotrophic metabolism that uses organic carbon instead of oxygen as a terminal electron acceptor. This means that these organisms do not use an electron transport chain to oxidize NADH to and therefore must have an alternative method of using this reducing power and maintaining a supply of for the proper functioning of normal metabolic pathways (e.g. glycolysis). As oxygen is not required, fermentative organisms are anaerobic. Many organisms can use fermentation under anaerobic conditions and aerobic respiration when oxygen is present. These organisms are facultative anaerobes. To avoid the overproduction of NADH, obligately fermentative organisms usually do not have a complete citric acid cycle. Instead of using an ATP synthase as in respiration, ATP in fermentative organisms is produced by substrate-level phosphorylation where a phosphate group is transferred from a high-energy organic compound to ADP to form ATP. As a result of the need to produce high energy phosphate-containing organic compounds (generally in the form of Coenzyme A-esters) fermentative organisms use NADH and other cofactors to produce many different reduced metabolic by-products, often including hydrogen gas (). These reduced organic compounds are generally small organic acids and alcohols derived from pyruvate, the end product of glycolysis. Examples include ethanol, acetate, lactate, and butyrate. Fermentative organisms are very important industrially and are used to make many different types of food products. The different metabolic end products produced by each specific bacterial species are responsible for the different tastes and properties of each food.
Not all fermentative organisms use substrate-level phosphorylation. Instead, some organisms are able to couple the oxidation of low-energy organic compounds directly to the formation of a proton motive force or sodium-motive force and therefore ATP synthesis. Examples of these unusual forms of fermentation include succinate fermentation by Propionigenium modestum and oxalate fermentation by Oxalobacter formigenes. These reactions are extremely low-energy yielding. Humans and other higher animals also use fermentation to produce lactate from excess NADH, although this is not the major form of metabolism as it is in fermentative microorganisms. | 1 | Applied and Interdisciplinary Chemistry |
Normal–phase chromatography was one of the first kinds of HPLC that chemists developed, but has decreased in use over the last decades. Also known as normal-phase HPLC (NP-HPLC), this method separates analytes based on their affinity for a polar stationary surface such as silica; hence it is based on analyte ability to engage in polar interactions (such as hydrogen-bonding or dipole-dipole type of interactions) with the sorbent surface. NP-HPLC uses a non-polar, non-aqueous mobile phase (e.g., chloroform), and works effectively for separating analytes readily soluble in non-polar solvents. The analyte associates with and is retained by the polar stationary phase. Adsorption strengths increase with increased analyte polarity. The interaction strength depends not only on the functional groups present in the structure of the analyte molecule, but also on steric factors. The effect of steric hindrance on interaction strength allows this method to resolve (separate) structural isomers.
The use of more polar solvents in the mobile phase will decrease the retention time of analytes, whereas more hydrophobic solvents tend to induce slower elution (increased retention times). Very polar solvents such as traces of water in the mobile phase tend to adsorb to the solid surface of the stationary phase forming a stationary bound (water) layer which is considered to play an active role in retention. This behavior is somewhat peculiar to normal phase chromatography because it is governed almost exclusively by an adsorptive mechanism (i.e., analytes interact with a solid surface rather than with the solvated layer of a ligand attached to the sorbent surface; see also reversed-phase HPLC below). Adsorption chromatography is still somewhat used for structural isomer separations in both column and thin-layer chromatography formats on activated (dried) silica or alumina supports.
Partition- and NP-HPLC fell out of favor in the 1970s with the development of reversed-phase HPLC because of poor reproducibility of retention times due to the presence of a water or protic organic solvent layer on the surface of the silica or alumina chromatographic media. This layer changes with any changes in the composition of the mobile phase (e.g., moisture level) causing drifting retention times.
Recently, partition chromatography has become popular again with the development of Hilic bonded phases which demonstrate improved reproducibility, and due to a better understanding of the range of usefulness of the technique. | 0 | Theoretical and Fundamental Chemistry |
A variety of methods for the generation of diimide exist. The most synthetically useful methods are:
* Oxidation of hydrazine with oxygen, in the presence of a copper(II) catalyst and/or a carboxylic acid
* Decarboxylation of dipotassium azodicarboxylate in the presence of an acid
* Thermal decomposition of sulfonylhydrazides
Procedures (particularly those employing air as an oxidant) are typically straightforward and do not require special handling techniques. | 0 | Theoretical and Fundamental Chemistry |
The ligand chosen for the application depends on the target site selected and it is responsible for cellular interaction. The target site contains the binding sites that the ligands target to deliver the LTL to the desired area. Favorable target site characteristics are determined by what is commonly expressed by tissues of the pathology of interest. Determinants can include histones, basement membrane fibrinogen, selectins, adhesion molecules, or other ligand targets. For example, in some human cancer tumors such as ovarian carcinomas, folate is over-expressed. Ligand-targeted liposomes for targeting cancer often use this over-expression of folate and a ligand that targets this vitamin to localize drug delivery to the desired area. Ligand-targeted liposomes utilize active targeting to interact with the desired cells.
Once administered intravenously into blood circulation, ligand-targeted liposomes must travel to reach the target area to deliver their contents. LTLs retain the contained agent until the process of cellular uptake. LTLs are taken into cells through the process of receptor-mediated endocytosis. The ligand chosen for each application also depends on the target site selected. The target site contains the binding sites that the ligands target to deliver the LTL to the desired area. In some human tumors such as ovarian carcinomas, folate is over-expressed. Ligand-targeted liposomes for use in this application use this over-expression to folate and a ligand that targets folate to localize drug delivery to the desired area. The tumor microenvironment of solid tumor cancers is also a unique targeting site. Tumor endothelial cells are important for angiogenesis which is key to tumor growth, therefore using LTLs to target these cells can limit the growth and vascularization of a tumor.
Receptor-mediated endocytosis is the most common way LTLs deliver material to the cell. The targeting ligand attached to the liposome attaches to the binding site found on the cell of interest. The particles are transported to lysosomes to be processed. This process allows the molecules to cross the blood-brain barrier, which allows the drug to be delivered to tissue that is relatively difficult to reach without a specific mechanism. Less commonly, pinocytosis or phagocytosis may be used for cellular uptake of the liposome. Certain recognition sites, such as ecto-NAD+oglycohydro|ase, mediate uptake to aid in the internalization and effectiveness of the LTLs.
The remainder of LTLs in circulation after binding to the target site are mainly cleared through the reticuloendothelial system (RES). The RES includes different organs including the kidneys, lungs, spleen, liver, bone marrow, and lymph nodes. The liver is the primary organ for the clearance of LTLs. The RES is most likely able to clear LTLS due to fenestrations in their microvasculature that allow for extravasation. Phagocytic cells within the RES break down LTLs. | 1 | Applied and Interdisciplinary Chemistry |
* Irvine, Geoffrey J., MJ Gerald Lesley, Todd B. Marder, Nicholas C. Norman, Craig R. Rice, Edward G. Robins, Warren R. Roper, George R. Whittell, and L. James Wright. "Transition metal− boryl compounds: synthesis, reactivity, and structure." Chemical reviews 98, no. 8 (1998): 2685–2722.
* Gallop, Mark A., and Warren R. Roper. "Carbene and carbyne complexes of ruthenium, osmium, and iridium." Adv. Organomet. Chem 25 (1986): 121–198.
* Gallop, Mark A., and Warren R. Roper. "Carbene and carbyne complexes of ruthenium, osmium, and iridium." Adv. Organomet. Chem 25 (1986): 121–198.
* Brothers, Penelope J., and Warren R. Roper. "Transition-metal dihalocarbene complexes." Chemical Reviews 88, no. 7 (1988): 1293–1326.
* Hill, Anthony F., Warren R. Roper, Joyce M. Waters, and Anthony H. Wright. "A mononuclear, low-valent, electron-rich osmium methylene complex." Journal of the American Chemical Society 105, no. 18 (1983): 5939–5940. | 0 | Theoretical and Fundamental Chemistry |
Carbamoyl chlorides are prepared by the reaction of an amine with phosgene:
:2 RNH + COCl → RNCOCl + [RNH]Cl
They also arise by the addition of hydrogen chloride to isocyanates:
:RNCO + HCl → RNHCOCl
In this way, carbamoyl chlorides can be prepared with N-H functionality. | 0 | Theoretical and Fundamental Chemistry |
In an alternative technique to interphase or metaphase preparations, fiber FISH, interphase chromosomes are attached to a slide in such a way that they are stretched out in a straight line, rather than being tightly coiled, as in conventional FISH, or adopting a chromosome territory conformation, as in interphase FISH. This is accomplished by applying mechanical shear along the length of the slide, either to cells that have been fixed to the slide and then lysed, or to a solution of purified DNA. A technique known as chromosome combing is increasingly used for this purpose. The extended conformation of the chromosomes allows dramatically higher resolution – even down to a few kilobases. The preparation of fiber FISH samples, although conceptually simple, is a rather skilled art, and only specialized laboratories use the technique routinely. | 1 | Applied and Interdisciplinary Chemistry |
Although the input vector field and the result image are discretized, it pays to look at it from a continuous viewpoint. Let be the vector field given in some domain . Although the input vector field is typically discretized, we regard the field as defined in every point of , i.e. we assume an interpolation. Streamlines, or more generally field lines, are tangent to the vector field in each point. They end either at the boundary of or at critical points where . For the sake of simplicity, in the following critical points and boundaries are ignored. A field line , parametrized by arc length , is defined as . Let be the field line that passes through the point for . Then the image gray value at is set to
where is the convolution kernel, is the noise image, and is the length of field line segment that is followed.
has to be computed for each pixel in the LIC image. If carried out naively, this is quite expensive. First, the field lines have to be computed using a numerical method for solving ordinary differential equations, like a Runge–Kutta method, and then for each pixel the convolution along a field line segment has to be calculated.
The output image will normally be colored in some way. Typically some scalar field in is used, like the vector length, to determine the hue, while the gray-scale LIC image determines the brightness of the color.
Different choices of convolution kernels and random noise produce different textures: for example pink noise produces a cloudy pattern where areas of higher flow stand out as smearing, suitable for weather visualization. Further refinements in the convolution can improve the quality of the image. | 1 | Applied and Interdisciplinary Chemistry |
Other plasma processing methods exist, but generally do not provide the resolution or purity of chromatographic methods.
Two-phase liquid extraction may be performed using polyethylene glycol (PEG)-phosphate Aqueous two-phase systems, with a PEG-rich top layer and a phosphate-rich bottom layer. Although this method is somewhat useful for protein recovery, it does not work as well for the recovery of other blood components.
Membrane fractionation has the advantage of minimal protein loss yet high removal of pathological plasma components. This method incorporates processes such as thermofiltration and applying pulsate flow. The latest two-stage membrane system utilizes a high flow recirculation circuit that is effective for removal of LDL cholesterol. It may prove useful for patients that have clogged arteries and other cardiovascular problems involving cholesterol.
Batch adsorption, e.g. onto ion exchange media, is only useful when dealing with smaller samples of plasma, typically 200 mL or less. Batch adsorption recovers the product in a larger volume of elution buffer than does column chromatography or frontal chromatography, and the resulting more dilute product requires concentration, typically on a membrane system, which can lead to loss of product by irreversible adsorption to the membrane. | 0 | Theoretical and Fundamental Chemistry |
The first step in analysis is the introduction of the sample. This has been achieved in ICP-MS through a variety of means.
The most common method is the use of analytical nebulizers. Nebulizer converts liquids into an aerosol, and that aerosol can then be swept into the plasma to create the ions. Nebulizers work best with simple liquid samples (i.e. solutions). However, there have been instances of their use with more complex materials like a slurry. Many varieties of nebulizers have been coupled to ICP-MS, including pneumatic, cross-flow, Babington, ultrasonic, and desolvating types. The aerosol generated is often treated to limit it to only smallest droplets, commonly by means of a Peltier cooled double pass or cyclonic spray chamber. Use of autosamplers makes this easier and faster, especially for routine work and large numbers of samples. A Desolvating Nebuliser (DSN) may also be used; this uses a long heated capillary, coated with a fluoropolymer membrane, to remove most of the solvent and reduce the load on the plasma. Matrix removal introduction systems are sometimes used for samples, such as seawater, where the species of interest are at trace levels, and are surrounded by much more abundant contaminants.
Laser ablation is another method. While being less common in the past, is rapidly becoming popular has been used as a means of sample introduction, thanks to increased ICP-MS scanning speeds. In this method, a pulsed UV laser is focused on the sample and creates a plume of ablated material which can be swept into the plasma. This allows geochemists to spacially map the isotope composition in cross-sections of rock samples, a tool which is lost if the rock is digested and introduced as a liquid sample. Lasers for this task are built to have highly controllable power outputs and uniform radial power distributions, to produce craters which are flat bottomed and of a chosen diameter and depth.
For both Laser Ablation and Desolvating Nebulisers, a small flow of Nitrogen may also be introduced into the Argon flow. Nitrogen exists as a dimer, so has more vibrational modes and is more efficient at receiving energy from the RF coil around the torch.
Other methods of sample introduction are also utilized. Electrothermal vaporization (ETV) and in torch vaporization (ITV) use hot surfaces (graphite or metal, generally) to vaporize samples for introduction. These can use very small amounts of liquids, solids, or slurries. Other methods like vapor generation are also known. | 0 | Theoretical and Fundamental Chemistry |
The earliest polymerizations of fluorene were oxidative polymerization with AlCl or FeCl, and more commonly electropolymerization. Electropolymerization is an easy route to obtain thin, insoluble conducting polymer films. However, this technique has a few disadvantages in that it does not provide controlled chain growth polymerizations, and processing and characterization are difficult as a result of its insolubility. Oxidative polymerization produces a similarly poor site-selectivity on the monomer for chain growth resulting in poor control over the regularity of the polymers structure. However, oxidative polymerization does produce soluble polymers (from side-chain containing monomers) which are more easily characterized with nuclear magnetic resonance. | 0 | Theoretical and Fundamental Chemistry |
Downspout disconnection is a form of green infrastructure that separates roof downspouts from the sewer system and redirects roof water runoff into permeable surfaces. It can be used for storing stormwater or allowing the water to penetrate the ground. Downspout disconnection is especially beneficial in cities with combined sewer systems. With high volumes of rain, downspouts on buildings can send 12 gallons of water a minute into the sewer system, which increases the risk of basement backups and sewer overflows. | 1 | Applied and Interdisciplinary Chemistry |
Distortionless enhancement by polarization transfer (DEPT) is an NMR method used for determining the presence of primary, secondary and tertiary carbon atoms. The DEPT experiment differentiates between CH, CH and CH groups by variation of the selection angle parameter (the tip angle of the final H pulse): 135° angle gives all CH and CH in a phase opposite to CH; 90° angle gives only CH groups, the others being suppressed; 45° angle gives all carbons with attached protons (regardless of number) in phase.
Signals from quaternary carbons and other carbons with no attached protons are always absent (due to the lack of attached protons).
The polarization transfer from H to C has the
secondary advantage of increasing the sensitivity over the normal C
spectrum (which has a modest enhancement from the nuclear overhauser effect (NOE) due to the H decoupling). | 0 | Theoretical and Fundamental Chemistry |
CoQ is metabolized in all tissues, with the metabolites being phosphorylated in cells. CoQ10 is reduced to ubiquinol during or after absorption in the small intestine. It is absorbed by chylomicrons, and redistributed in the blood within lipoproteins. Its elimination occurs via biliary and fecal excretion. | 1 | Applied and Interdisciplinary Chemistry |
While slight variations on the standard genetic code had been predicted earlier, none was discovered until 1979, when researchers studying human mitochondrial genes determined that they used an alternative code. Nonetheless, the mitochondria of many other eukaryotes, including most plants, use the standard code. Many slight variants have been discovered since, including various alternative mitochondrial codes. Further, the AUA, AUC, and AUU codons are all allowable start codons.
Some of these differences should be regarded as pseudo-changes in the genetic code due to the phenomenon of RNA editing, which is common in mitochondria. In higher plants, it was thought that CGG encoded for tryptophan and not arginine; however, the codon in the processed RNA was discovered to be the UGG codon, consistent with the standard genetic code for tryptophan. Of note, the arthropod mitochondrial genetic code has undergone parallel evolution within a phylum, with some organisms uniquely translating AGG to lysine. | 1 | Applied and Interdisciplinary Chemistry |
Zinc coatings are generally not employed in the US. In order to protect ductile iron pipe prior to installation, pipe is instead supplied with a temporary 1 mil or 25 μm thick bituminous coating. This coating is not intended to provide protection once the pipe is installed. | 1 | Applied and Interdisciplinary Chemistry |
TRPV1 is primarily expressed on, small myelinated and unmyelinated medium size, sensory neurons in dorsal root and trigeminal ganglia, where sensory neurons cluster. TRPV1 receptors are also found in muscles, joints, the urinary bladder and kidneys. The functional activity of TRPV1 has been demonstrated, within the central nervous system, in the spinal cord and specific sites in the brain including the hypothalamus, cerebellum, locus coeruleus, periaqueductal grey and cortex. Activation of TRPV1 sets off an influx of calcium and sodium ions which in turn initiates a cascade of events that result in membrane depolarization, neuronal firing and transduction of neural impulses. TRPV1 phosphorylates as a response to several algesic agents, resulting in a lower threshold of channel activation. Some substances such as bradykinin, nerve growth factor and protons have been reported to sensitize the TRPV1 receptor. Activation of TRPV1 results in the release of pro-nociceptive peptides, which decreases when treated with TRPV1 antagonists. In general, most channel antagonists bind in the pore region, interacting with residues from all four monomers of the tetrameric channel. | 1 | Applied and Interdisciplinary Chemistry |
Underwater corrosion engineers apply the same principals used in underground corrosion control but use specially trained and certified scuba divers for condition assessment, and corrosion control system installation and commissioning. The main difference being in the type of reference cells used to collect voltage readings. Corrosion of piles and the legs of oil and gas rigs are of particular concern. This includes rigs in the North Sea off the coast of the United Kingdom and the Gulf of Mexico. | 1 | Applied and Interdisciplinary Chemistry |
The Cleveland open-cup method is one of three main methods in chemistry for determining the flash point of a petroleum product using a Cleveland open-cup apparatus, also known as a Cleveland open-cup tester. First, the test cup of the apparatus (usually brass) is filled to a certain level with a portion of the product. Then, the temperature of this chemical is increased rapidly and then at a slow, constant rate as it approaches the theoretical flash point. The increase in temperature will cause the chemical to begin to produce flammable vapor in increasing quantities and density. The lowest temperature at which a small test flame passing over the surface of the liquid causes the vapor to ignite is considered the chemicals flash point. This apparatus may also be used to determine the chemicals fire point which is considered to have been reached when the application of the test flame produces at least five continuous seconds of ignition. Temperature range of this apparatus is 120 to 250 degree c
The other principal methods of establishing chemical flash points are the Pensky–Martens closed-cup test and the Tagliabue cup method (often called simply the "Tag method"). | 0 | Theoretical and Fundamental Chemistry |
Due to its ease of operation and its usefulness in polishing irregularly-shaped objects, electropolishing has become a common process in the production of semiconductors.
As electropolishing can also be used to sterilize workpieces, the process plays an essential role in the food, medical, and pharmaceutical industries.
It is commonly used in the post-production of large metal pieces such as those used in drums of washing machines, bodies of ocean vessels and aircraft, and automobiles.
While nearly any metal may be electropolished, the most-commonly polished metals are 300- and 400-series stainless steel, aluminum, copper, titanium, and nickel- and copper-alloys.
Ultra-high vacuum (UHV) components are typically electropolished in order to have a smoother surface for improved vacuum pressures, out-gassing rates, and pumping speed.
Electropolishing is commonly used to prepare thin metal samples for transmission electron microscopy and atom probe tomography because the process does not mechanically deform surface layers like mechanical polishing does. | 1 | Applied and Interdisciplinary Chemistry |
* Estimating dissolved organic carbon concentration
* Specific ultraviolet absorbance for metric of aromaticity
* Bial's test for concentration of pentoses | 0 | Theoretical and Fundamental Chemistry |
The ideal case of distillation uses zeotropic mixtures. Zeotropic fluid and gaseous mixtures can be separated by distillation due to the difference in boiling points between the component mixtures. This process involves the use of vertically-arranged distillation columns (see Figure 2). | 1 | Applied and Interdisciplinary Chemistry |
A multitude of organ structures have been recapitulated using organoids. This section aims to outline the state of the field as of now through providing an abridged list of the organoids that have been successfully created, along with a brief outline based on the most recent literature for each organoid, and examples of how it has been utilized in research. | 1 | Applied and Interdisciplinary Chemistry |
LFV is sought to be extended to all fluid or solid materials, providing that they are electrical conductors. As shown before, the Lorentz force generated by the flow depend linearly on the conductivity of the fluid. Typically, the electrical conductivity of molten metals is of the order of so the Lorentz force is in the range of some mN. However, equally important liquids as glass melts and electrolytic solutions have a conductivity of giving rise to a Lorentz force of the order of micronewtons or even smaller. | 1 | Applied and Interdisciplinary Chemistry |
There are four disciplines within the DnaA protein. An initial comparison of Escherichia coli and Bacillus subtilis proteins led to the discovery of a sphere structure, which revealed a relatively conserved N-terminus and a largely conserved large C-terminus separated by a region that was mostly variable. As an example, the Enterobacterial proteins have nearly identical N- and C-terminal sequences, however they are characterized by numerous amino acid adjustments, elisions, and insertions in the variable regions. There is an AAA+ family ATPase motif and an independent DNA binding sphere in the C-terminal region. It was determined by NMR that Escherichia coli sphere IV had a crystal-clear structure when complexed with a DnaA- box. As a result, it was confirmed that the DNA list is intermediated by a combination of a helix-turn-helix motif and an introductory circle. When bound to ATP, but not to ADP, DnaA forms a super-helical structure with four monomers per turn. The structure of sphere I has been determined from three additional bacterial species and Escherichia coli by NMR. | 1 | Applied and Interdisciplinary Chemistry |
There is also an emergent perspective called The Scholarship of Teaching and Learning (SoTL). Although there is debate on how to best define SoTL, one of the primary practices is for mainstream faculty members (organic, inorganic, biochemistry, etc.) to develop a more informed view of their practices, how to carry out research and reflection on their own teaching, and about what constitutes deep understanding in student learning. | 1 | Applied and Interdisciplinary Chemistry |
There are two main types of inorganic carbon that are found in the oceans. Dissolved inorganic carbon (DIC) is made up of bicarbonate (HCO), carbonate (CO) and carbon dioxide (including both dissolved CO and carbonic acid HCO). DIC can be converted to particulate inorganic carbon (PIC) through precipitation of CaCO (biologically or abiotically). DIC can also be converted to particulate organic carbon (POC) through photosynthesis and chemoautotrophy (i.e. primary production). DIC increases with depth as organic carbon particles sink and are respired. Free oxygen decreases as DIC increases because oxygen is consumed during aerobic respiration.
Particulate inorganic carbon (PIC) is the other form of inorganic carbon found in the ocean. Most PIC is the CaCO that makes up shells of various marine organisms, but can also form in whiting events. Marine fish also excrete calcium carbonate during osmoregulation.
Some of the inorganic carbon species in the ocean, such as bicarbonate and carbonate, are major contributors to alkalinity, a natural ocean buffer that prevents drastic changes in acidity (or pH). The marine carbon cycle also affects the reaction and dissolution rates of some chemical compounds, regulates the amount of carbon dioxide in the atmosphere and Earth's temperature. | 0 | Theoretical and Fundamental Chemistry |
As the world attempts to move towards a low-carbon economy, the technique of using carbon capture by using carbon dioxide from the atmosphere is gaining attention and research being done. Using carbon dioxide in PUD production is being researched. High bio-based content is similarly prized. Coating materials that are vegetable based, waterborne and UV curable are considered very green and have been studied. | 0 | Theoretical and Fundamental Chemistry |
Following are tables of commonly occurring expressions in physics, related to the dimensions of energy, momentum, and force. | 1 | Applied and Interdisciplinary Chemistry |
A new, effective and economical concept in pheromone delivery using a flowable formulation to create long lasting monolithic pheromone dispensers has been brought to the market in the past decade. These novel SPLAT pheromone mating disruption formulations can provide effective season long suppression effect (e.g., depending on the target pest a single application of SPLAT controls the target pest for a complete reproductive cycle, or for the entire season) and can be manually or mechanically applied. Although mechanical dispersal techniques require specialized off-the-shelf application technology and/or equipment, once the application system is made to work it allows protection of extensive areas using pheromones, one of the most benign and effective pest management techniques available today. A benefit of SPLAT is that the dollop anchors where it lands, avoiding unwanted drift of the formulation once applied in the field, and, depending on the mode of application, the cured dollops are retrievable. | 1 | Applied and Interdisciplinary Chemistry |
Autoantibodies may be produced against the body's own snRNPs, most notably the anti-Sm antibodies targeted against the Sm protein type of snRNP specifically in systemic lupus erythematosus (SLE). | 1 | Applied and Interdisciplinary Chemistry |
From the very early stages of structural studies of DNA by X-ray diffraction and biochemical means, molecular models such as the Watson-Crick nucleic acid double helix model were successfully employed to solve the puzzle of DNA structure, and also find how the latter relates to its key functions in living cells. The first high quality X-ray diffraction patterns
of A-DNA were reported by Rosalind Franklin and Raymond Gosling in 1953. Rosalind Franklin made the critical observation that DNA exists in two distinct forms, A and B, and produced the sharpest pictures of both through X-ray diffraction technique. The first calculations of the Fourier transform of an atomic helix were reported one year earlier by Cochran, Crick and Vand, and were followed in 1953 by the computation of the Fourier transform of a coiled-coil by Crick.
Structural information is generated from X-ray diffraction studies of oriented DNA fibers with the help of molecular models of DNA that are combined with crystallographic and mathematical analysis of the X-ray patterns.
The first reports of a double helix molecular model of B-DNA structure were made by James Watson and Francis Crick in 1953. That same year, Maurice F. Wilkins,
A. Stokes and H.R. Wilson, reported the first X-ray patterns
of in vivo B-DNA in partially oriented salmon sperm heads.
The development of the first correct double helix molecular model of DNA by Crick and Watson may not have been possible without the biochemical evidence for the nucleotide base-pairing ([A---T]; [C---G]), or Chargaffs rules. Although such initial studies of DNA structures with the help of molecular models were essentially static, their consequences for explaining the in vivo functions of DNA were significant in the areas of protein biosynthesis and the quasi-universality of the genetic code. Epigenetic transformation studies of DNA in vivo' were however much slower to develop despite their importance for embryology, morphogenesis and cancer research. Such chemical dynamics and biochemical reactions of DNA are much more complex than the molecular dynamics of DNA physical interactions with water, ions and proteins/enzymes in living cells. | 0 | Theoretical and Fundamental Chemistry |
Precession electron diffraction (PED) is a specialized method to collect electron diffraction patterns in a transmission electron microscope (TEM). By rotating (precessing) a tilted incident electron beam around the central axis of the microscope, a PED pattern is formed by integration over a collection of diffraction conditions. This produces a quasi-kinematical diffraction pattern that is more suitable as input into direct methods algorithms to determine the crystal structure of the sample. | 0 | Theoretical and Fundamental Chemistry |
Different from electrostatics, sterically stabilized suspensions rely on the physical interaction of polymer chains attached to the surface of the particles to keep the suspension stabilized; the adsorbed polymer chains act as a spacer to keep the suspended particles separated at a sufficient distance to prevent the Hamaker attraction from dominating and pulling the particles out of suspension. The polymers are typically either grafted or adsorbed onto the surface of the particle. With grafted polymers, the backbone of the polymer chain is covalently bonded to the particle surface. Whereas an adsorbed polymer is a copolymer composed of lyophobic and lyophilic region, where the lyophobic region non-covalently adheres to the particle surface and the lyophilic region forms the steric boundary or spacer. | 1 | Applied and Interdisciplinary Chemistry |
Caesium-137 reacts with water, producing a water-soluble compound (caesium hydroxide). The biological behaviour of caesium is similar to that of potassium and rubidium. After entering the body, caesium gets more or less uniformly distributed throughout the body, with the highest concentrations in soft tissue. However, unlike group 2 radionuclides like radium and strontium-90, caesium does not bioaccumulate and is excreted relatively quickly. The biological half-life of caesium is about 70 days.
A 1961 experiment showed that mice dosed with 21.5 μCi/g had a 50% fatality within 30 days (implying an LD of 245 μg/kg). A similar experiment in 1972 showed that when dogs are subjected to a whole body burden of 3800 μCi/kg (140 MBq/kg, or approximately 44 μg/kg) of caesium-137 (and 950 to 1400 rads), they die within 33 days, while animals with half of that burden all survived for a year. Important researches have shown a remarkable concentration of Cs in the exocrine cells of the pancreas, which are those most affected by cancer. In 2003, in autopsies performed on 6 children who died in the polluted area near Chernobyl (of reasons not directly linked to the Chernobyl disaster; mostly sepsis), where they also reported a higher incidence of pancreatic tumors, Bandazhevsky found a concentration of Cs 3.9 times higher than in their livers (1359 vs 347 Bq/kg, equivalent to 36 and 9.3 nCi/kg in these organs, 600 Bq/kg = 16 nCi/kg in the body according to measurements), thus demonstrating that pancreatic tissue is a strong accumulator and secretor in the intestine of radioactive cesium.
Accidental ingestion of caesium-137 can be treated with Prussian blue (Fe[Fe(CN)]), which binds to it chemically and reduces the biological half-life to 30 days. | 0 | Theoretical and Fundamental Chemistry |
Virus survival through inclusion of AMGs is governed by the laws of natural selection and has been made highly selective through co-evolution with their hosts. As such, the AMGs that confer a fitness advantage to the virus's ability to infect a host and reproduce will be more abundant. AMG abundance is largely dictated by the lifestyle of the virus, environmental conditions surrounding it, and host characteristics. | 1 | Applied and Interdisciplinary Chemistry |
RuCl(PPh) facilitates oxidations, reductions, cross-couplings, cyclizations, and isomerization. It is used in the Kharasch addition of chlorocarbons to alkenes.
Dichlorotris(triphenylphosphine)ruthenium(II) serves as a precatalyst for the hydrogenation of alkenes, nitro compounds, ketones, carboxylic acids, and imines. On the other hand, it catalyzes the oxidation of alkanes to tertiary alcohols, amides to t-butyldioxyamides, and tertiary amines to α-(t-butyldioxyamides) using tert-butyl hydroperoxide. Using other peroxides, oxygen, and acetone, the catalyst can oxidize alcohols to aldehydes or ketones. Using dichlorotris(triphenylphosphine)ruthenium(II) the N-alkylation of amines with alcohols is also possible (see "borrowing hydrogen").
RuCl(PPh) efficiently catalyzes carbon-carbon bond formation from cross couplings of alcohols through C-H activation of sp carbon atoms in the presence of a Lewis acid. | 0 | Theoretical and Fundamental Chemistry |
This is often the fuel of choice for reactor designs that NASA produces, one advantage is that uranium nitride has a better thermal conductivity than UO. Uranium nitride has a very high melting point. This fuel has the disadvantage that unless N was used (in place of the more common N), a large amount of C would be generated from the nitrogen by the (n,p) reaction. As the nitrogen needed for such a fuel would be so expensive it is likely that the fuel would require pyroprocessing to enable recovery of the N. It is likely that if the fuel was processed and dissolved in nitric acid that the nitrogen enriched with N would be diluted with the common N. Fluoride volatility is a method of reprocessing that does not rely on nitric acid, but it has only been demonstrated in relatively small scale installations whereas the established PUREX process is used commercially for about a third of all spent nuclear fuel (the rest being largely subject to a "once through fuel cycle"). All nitrogen-fluoride compounds are volatile or gaseous at room temperature and could be fractionally distilled from the other gaseous products (including recovered uranium hexafluoride) to recover the initially used nitrogen. If the fuel could be processed in such a way as to ensure low contamination with non-radioactive carbon (not a common fission product and absent in nuclear reactors that don't use it as a moderator) then fluoride volatility could be used to separate the produced by producing carbon tetrafluoride. is proposed for use in particularly long lived low power nuclear batteries called diamond batteries. | 0 | Theoretical and Fundamental Chemistry |
In 1940, after completing the first year of his PhD studies, Hurst volunteered as a civilian experimental scientist with the Ministry of Supply, undertaking bomb disposal and mine detection duties. In 1944 he was part of the team, led by John Pilkington Hudson, that defused the first V-1 flying bomb found intact in Britain. It took the team a week of painstaking work to successfully complete the task, made more difficult by toxic fumes from the explosive and ongoing bombing raids. As a result, Hurst was awarded the George Medal: his citation noted his "sustained courage when engaged in hazardous operations".
At the end of the war, Hurst saw service in Berlin, assisting with defusing unexploded Allied bombs. | 0 | Theoretical and Fundamental Chemistry |
Jet aerators are applied across a wide range of water, wastewater and biosolids treatment applications. Their primary purpose is to transfer oxygen to the liquid or sludge. A Jet aerator works through aspirating technology by simultaneously introducing large volumes of high kinetic energy liquid and air through one or more jet nozzles. The high velocity liquid exits the inner, primary jet and rapidly mixes with the incoming air in the outer jet. This intense mixing and high degree of turbulence in the gas/liquid cloud travels outward from the jet along the basin floor prior to the vertical rise of the gas bubble column to the liquid surface. | 1 | Applied and Interdisciplinary Chemistry |
Chlorophyll a is found in all chloroplasts, as well as their cyanobacterial ancestors. Chlorophyll a is a blue-green pigment partially responsible for giving most cyanobacteria and chloroplasts their color. Other forms of chlorophyll exist, such as the accessory pigments chlorophyll b, chlorophyll c, chlorophyll d, and chlorophyll f.
Chlorophyll b is an olive green pigment found only in the chloroplasts of plants, green algae, any secondary chloroplasts obtained through the secondary endosymbiosis of a green alga, and a few cyanobacteria. It is the chlorophylls a and b together that make most plant and green algal chloroplasts green.
Chlorophyll c is mainly found in secondary endosymbiotic chloroplasts that originated from a red alga, although it is not found in chloroplasts of red algae themselves. Chlorophyll c is also found in some green algae and cyanobacteria.
Chlorophylls d and f are pigments found only in some cyanobacteria. | 0 | Theoretical and Fundamental Chemistry |
The fundamental properties of currents mediated by ion channels were analyzed by the British biophysicists Alan Hodgkin and Andrew Huxley as part of their Nobel Prize-winning research on the action potential, published in 1952. They built on the work of other physiologists, such as Cole and Bakers research into voltage-gated membrane pores from 1941. The existence of ion channels was confirmed in the 1970s by Bernard Katz and Ricardo Miledi using noise analysis . It was then shown more directly with an electrical recording technique known as the "patch clamp", which led to a Nobel Prize to Erwin Neher and Bert Sakmann, the techniques inventors. Hundreds if not thousands of researchers continue to pursue a more detailed understanding of how these proteins work. In recent years the development of automated patch clamp devices helped to increase significantly the throughput in ion channel screening.
The Nobel Prize in Chemistry for 2003 was awarded to Roderick MacKinnon for his studies on the physico-chemical properties of ion channel structure and function, including x-ray crystallographic structure studies. | 1 | Applied and Interdisciplinary Chemistry |
Radiological materials emit gamma photons, which gamma radiation detectors, also called radiation portal monitors (RPM), are good at detecting. Systems currently used in US ports (and steel mills) use several (usually 4) large PVT panels as scintillators and can be used on vehicles moving up to 16 km/h.
They provide very little information on energy of detected photons, and as a result, they were criticized for their inability to distinguish gammas originating from nuclear sources from gammas originating from a large variety of benign cargo types that naturally emit radioactivity, including bananas, cat litter, granite, porcelain, stoneware, etc. Those naturally occurring radioactive materials, called NORMs account for 99% of nuisance alarms. Some radiation, like in the case of large loads of bananas is due to potassium and its rarely occurring (0.0117%) radioactive isotope potassium-40, other is due to radium or uranium that occur naturally in earth and rock, and cargo types made out of them, like cat litter or porcelain.
Radiation originating from earth is also a major contributor to background radiation.
Another limitation of gamma radiation detectors is that gamma photons can be easily suppressed by high-density shields made from lead or steel, preventing detection of nuclear sources. Those types of shields do not stop fission neutrons produced by plutonium sources, however. As a result, radiation detectors usually combine gamma and neutron detectors, making shielding only effective for certain uranium sources. | 0 | Theoretical and Fundamental Chemistry |
The alkaline sulfur liquid battery is an interesting concept due to the simplicity, low cost, durability, thermal stability (no thermal runaway), low carbon foot print, eliminating the need of rare earth minerals for storage and its applicability to transportation systems. The internal electrolytes and the catholyte gets refreshed continuously making the life time very long. This storage technology has a low carbon footprint per kWh of energy storage medium. A BEIS Report describes this technology as a novel flow battery technology that is low-cost, long lasting and easily scalable. Can be used for very long term storage economically and sustainably.
A demonstrator which has been operational since 2017 has shown an overall AC-AC roundtrip efficiency of 93.15%, which is comparatively higher other comparable battery storage systems with online references. This technology is based on lithium-sulfur battery technology which have a high theoretical energy density of 2600 Wh kg and theoretical energy capacity of 1675 mAh g. Therefore the theoretical energy density and theoretical energy capacity of SLIQ technology can be very close to 2600 Wh kg and 1675 mAh g respectively. This alkali sulphur liquid battery has been chosen to be included in an ARPA-E report on ‘The Cost and Performance Requirements for “Flexible” Advanced Nuclear Plants in Future Power Markets’ published in the official ARPA-E website. This ARPA-E report indicates that the SLIQ technology has a cost lower than $94/kWh with a life time exceeding 20 years, which makes this technology a definite candidate as an electrical storage technology for the fight against climate crisis. | 1 | Applied and Interdisciplinary Chemistry |
In 1957, R. Gordon Wasson, the vice president of J.P. Morgan, published an article in Life magazine extolling the virtues of magic mushrooms. This prompted Albert Hofmann to isolate psilocybin in 1958 for distribution by Sandoz with its product LSD in the U.S., further raising interest in LSD in the mass media. Following Wasson's report, Timothy Leary visited Mexico to experience the mushrooms. | 1 | Applied and Interdisciplinary Chemistry |
In general, acidity of donor sites correlates well with the strength of the donor. For example, it is a common strategy to add electron-withdrawing aryl substituents on a thiourea catalyst, which can increase its acidity and thus the strength of its hydrogen bonding. However, it is still unclear how donor strength correlates with desired reactivity. Importantly, more acidic catalysts are not necessarily more effective. For instance, ureas are less acidic than thioureas by roughly 6 pKa units, but it is not generally true that ureas are significantly worse are catalyzing reactions.
Furthermore, the effect of varying substituents on the catalyst is rarely well understood. Small substituent changes can completely change reactivity or selectivity. An example of this was in the optimization studies of a bifunctional Strecker reaction catalyst, one of the first well-studied thiourea catalysts. Specifically, varying the X substituent on the salicylaldimine substituent, it was found that typical electron-withdrawing or electron-donating substituents had little effect on the rate, but ester substituents such as acetate or pivaloate seemed to cause noticeable rate acceleration. This observation is difficult to rationalize given that the X group is far from the reactive center during the course of the reaction and electronics do not seem to be the cause. In general, despite the relative ease of electronic tuning with organic catalysts, chemists have not yet reached a useful understanding of these modifications. | 0 | Theoretical and Fundamental Chemistry |
Ring-closing metathesis (RCM) is a widely used variation of olefin metathesis in organic chemistry for the synthesis of various unsaturated rings via the intramolecular metathesis of two terminal alkenes, which forms the cycloalkene as the E- or Z- isomers and volatile ethylene.
The most commonly synthesized ring sizes are between 5-7 atoms; however, reported syntheses include 45- up to 90- membered macroheterocycles. These reactions are metal-catalyzed and proceed through a metallacyclobutane intermediate. It was first published by Dider Villemin in 1980 describing the synthesis of an Exaltolide precursor, and later become popularized by Robert H. Grubbs and Richard R. Schrock, who shared the Nobel Prize in Chemistry, along with Yves Chauvin, in 2005 for their combined work in olefin metathesis. RCM is a favorite among organic chemists due to its synthetic utility in the formation of rings, which were previously difficult to access efficiently, and broad substrate scope. Since the only major by-product is ethylene, these reactions may also be considered atom economic, an increasingly important concern in the development of green chemistry.
There are several reviews published on ring-closing metathesis. | 0 | Theoretical and Fundamental Chemistry |
Base conditions, also known as standard conditions, consist of a specified absolute pressure and temperature. To ensure accuracy, it is important to refer to base conditions when measuring the volume of a sample of liquid or gas. This applies to both static measurement and flow measurement. | 1 | Applied and Interdisciplinary Chemistry |
A common treatment method for preventing iodine-131 exposure is by saturating the thyroid with regular, stable iodine-127, as an iodide or iodate salt. | 0 | Theoretical and Fundamental Chemistry |
Dynamic reserve, in the context of the dynamic energy budget theory, refers to the set of metabolites (mostly polymers and lipids) that an organism can use for metabolic purposes. These chemical compounds can have active metabolic functions, however. They are not just "set apart for later use." Reserve differs from structure in the first place by its dynamics. Reserve has an implied turnover, because it is synthesized from food (or other substrates in the environment) and used by metabolic processes occurring in cells. The turnover of structure depends on the maintenance of an organism. Maintenance is not required for reserve. A freshly laid egg consists almost exclusively of reserve, and hardly respires. The chemical compounds in the reserve have the same turnover, while that in the structure can have a different turnover, and so it depends on the compound. | 1 | Applied and Interdisciplinary Chemistry |
*[https://web.archive.org/web/20060528050505/http://www.beckman.com/literature/Bioresearch/ar-409.pdf Thoria-based Cermet Nuclear Fuel: Sintered Microsphere Fabrication by Spray Drying] | 0 | Theoretical and Fundamental Chemistry |
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