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An equation of state (for gases) is a mathematical model used to roughly describe or predict the state properties of a gas. At present, there is no single equation of state that accurately predicts the properties of all gases under all conditions. Therefore, a number of much more accurate equations of state have been developed for gases in specific temperature and pressure ranges. The "gas models" that are most widely discussed are "perfect gas", "ideal gas" and "real gas". Each of these models has its own set of assumptions to facilitate the analysis of a given thermodynamic system. Each successive model expands the temperature range of coverage to which it applies. | 0 | Theoretical and Fundamental Chemistry |
The European Association of Geochemistry (EAG) is a pan-European organization founded to promotes geochemical research. The EAG organizes conferences, meetings and educational courses for geochemists in Europe, including the Goldschmidt Conference which it co-sponsors with the North American Geochemical Society. | 0 | Theoretical and Fundamental Chemistry |
In 1925, a study on the phenomena of oxidation and reaeration in the Ohio River in the US was published by the sanitary engineer, Harold Warner Streeter and the consultant, Earle Bernard Phelps (1876–1953). The study was based on data obtained from May 1914 to April 1915 by the United States Public Health Service under supervision of Surg. W.H. Frost.
More complex versions of the Streeter–Phelps model were introduced during the 1960s, where computers made it possible to include further contributions to the oxygen development in streams. At the head of this development were OConnor (1960) and Thomann (1963). OConnor added the contributions from photosynthesis, respiration and sediment oxygen demand (SOD). Thomann expanded the Streeter–Phelps model to allow for multi segment systems. | 1 | Applied and Interdisciplinary Chemistry |
The operation of the diamond anvil cell relies on a simple principle:
where is the pressure, the applied force, and the area. Typical culet sizes for diamond anvils are 100–250 micrometres (µm), such that a very high pressure is achieved by applying a moderate force on a sample with a small area, rather than applying a large force on a large area. Diamond is a very hard and virtually incompressible material, thus minimising the deformation and failure of the anvils that apply the force. | 0 | Theoretical and Fundamental Chemistry |
An innovative use of the diamond anvil cell is testing the sustainability and durability of life under high pressures, including the search for life on extrasolar planets. Testing portions of the theory of panspermia (a form of interstellar travel) is one application of DAC. When interstellar objects containing life-forms impact a planetary body, there is high pressure upon impact and the DAC can replicate this pressure to determine if the organisms could survive. Another reason the DAC is applicable for testing life on extrasolar planets is that planetary bodies that hold the potential for life may have incredibly high pressure on their surface.
In 2002, scientists at the Carnegie Institution of Washington examined the pressure limits of life processes. Suspensions of bacteria, specifically Escherichia coli and Shewanella oneidensis, were placed in the DAC, and the pressure was raised to 1.6 GPa, which is more than 16,000 times Earth's surface pressure (985 hPa). After 30 hours, only about 1% of the bacteria survived. The experimenters then added a dye to the solution. If the cells survived the squeezing and were capable of carrying out life processes, specifically breaking down formate, the dye would turn clear. 1.6 GPa is such great pressure that during the experiment the DAC turned the solution into ice-IV, a room-temperature ice. When the bacteria broke down the formate in the ice, liquid pockets would form because of the chemical reaction. The bacteria were also able to cling to the surface of the DAC with their tails.
Skeptics debated whether breaking down formate is enough to consider the bacteria living. Art Yayanos, an oceanographer at the Scripps Institute of Oceanography in La Jolla, California, believes an organism should only be considered living if it can reproduce. Subsequent results from independent research groups have shown the validity of the 2002 work. This is a significant step that reiterates the need for a new approach to the old problem of studying environmental extremes through experiments. There is practically no debate whether microbial life can survive pressures up to 600 MPa, which has been shown over the last decade or so to be valid through a number of scattered publications.
Similar tests were performed with a low-pressure (0.1–600 MPa) diamond anvil cell, which has better imaging quality and signal collection. The studied microbes, Saccharomyces cerevisiae (baker's yeast), continued to grow at pressures of 15–50 MPa, and died at 200 MPa. | 0 | Theoretical and Fundamental Chemistry |
*Aza-Cope rearrangement
*Beckmann rearrangement
*Duff reaction
*Mannich reaction
*Pictet-Spengler reaction
*Stephen aldehyde synthesis
*Stork enamine alkylation
*Vilsmeier-Haack reaction and Vilsmeier reagent | 0 | Theoretical and Fundamental Chemistry |
Galvanic corrosion (also called bimetallic corrosion) is an electrochemical process in which one metal (more active one) corrodes preferentially when it is in electrical contact with another dissimilar metal, in the presence of an electrolyte. A similar galvanic reaction is exploited in primary cells to generate a useful electrical voltage to power portable devices – a classic example being a cell with zinc and copper electrodes. Galvanic corrosion is also exploited when a sacrificial metal is used in cathodic protection. Galvanic corrosion happens when there are an active metal and a more noble metal in contact in the presence of electrolyte. | 1 | Applied and Interdisciplinary Chemistry |
Reynolds transport theorem can be expressed as follows:
in which is the outward-pointing unit normal vector, is a point in the region and is the variable of integration, and are volume and surface elements at , and is the velocity of the area element (not the flow velocity). The function may be tensor-, vector- or scalar-valued. Note that the integral on the left hand side is a function solely of time, and so the total derivative has been used. | 1 | Applied and Interdisciplinary Chemistry |
Calmodulin is an example of a signal-transduction protein. It is a small protein that contains four EF-hand motifs, each of which is able to bind a Ca ion.
In an EF-hand loop protein domain, the calcium ion is coordinated in a pentagonal bipyramidal configuration. Six glutamic acid and aspartic acid residues involved in the binding are in positions 1, 3, 5, 7 and 9 of the polypeptide chain. At position 12, there is a glutamate or aspartate ligand that behaves as a (bidentate ligand), providing two oxygen atoms. The ninth residue in the loop is necessarily glycine due to the conformational requirements of the backbone. The coordination sphere of the calcium ion contains only carboxylate oxygen atoms and no nitrogen atoms. This is consistent with the hard nature of the calcium ion.
The protein has two approximately symmetrical domains, separated by a flexible "hinge" region. Binding of calcium causes a conformational change to occur in the protein. Calmodulin participates in an intracellular signaling system by acting as a diffusible second messenger to the initial stimuli. | 1 | Applied and Interdisciplinary Chemistry |
Neuropeptidergic means "related to neuropeptides".
A neuropeptidergic agent (or drug) is a chemical which functions to directly modulate the neuropeptide systems in the body or brain. An example is opioidergics. | 1 | Applied and Interdisciplinary Chemistry |
*On 2 August 1970, three people aboard the BC Ferry Queen of Victoria perished and the ship itself suffered close to $1 million damage when a Russian freighter, the Sergey Yesenin, struck it in Active Pass.
*On 9 August 1979, the BC Ferry Queen of Alberni ran aground at Collinson Reef in Active Pass, causing the vessel to tip dramatically to one side. Extensive vehicle and ship damage occurred, as well as the casualty of a racehorse.
*On 6 November 2015, a man jumped from the deck of a BC Ferry in Active Pass and swam to Galiano Island. He was later arrested after breaking into a cabin. | 1 | Applied and Interdisciplinary Chemistry |
Cascade impactors – particulate matter is withdrawn isokinetically from a source and segregated by size in a cascade impactor at the sampling point exhaust conditions of temperature, pressure, etc. Cascade impactors use the principle of inertial separation to size segregate particle samples from a particle laden gas stream. The mass of each size fraction is determined gravimetrically. The California Air Resources Board Method 501 is currently the most widely accepted test method for particle size distribution emissions measurements. | 0 | Theoretical and Fundamental Chemistry |
The clipping method is similar to the capping reaction except that in this case the dumbbell shaped molecule is complete and is bound to a partial macrocycle. The partial macrocycle then undergoes a ring closing reaction around the dumbbell-shaped molecule, forming the rotaxane. | 0 | Theoretical and Fundamental Chemistry |
Another ancient idea dating back to Anaxagoras in the 5th century BC is panspermia, the idea that life exists throughout the universe, distributed by meteoroids, asteroids, comets and planetoids. It does not attempt to explain how life originated in itself, but shifts the origin of life on Earth to another heavenly body. The advantage is that life is not required to have formed on each planet it occurs on, but rather in a more limited set of locations (potentially even a single location), and then spread about the galaxy to other star systems via cometary or meteorite impact. | 0 | Theoretical and Fundamental Chemistry |
He worked as a chemist for the Clinton Laboratories (now Oak Ridge National Laboratory) during the World War II Manhattan Project, engaged in separating, identifying and characterizing the radioactive elements produced by nuclear fission. In 1945, he, together with Jacob A. Marinsky and Charles D. Coryell, isolated the previously undocumented rare-earth element 61 (promethium). Marinsky and Glendenin produced it both by extraction from fission products and by bombarding neodymium with neutrons. They isolated it using ion-exchange chromatography. Publication of the finding was delayed until later due to the war. In September 1947, Marinsky and Glendenin announced the discovery at a meeting of the American Chemical Society. Upon the suggestion of Coryell's wife, the team named the new element for the titan god Prometheus, who stole fire from the gods and was punished for the act by Zeus. They had also considered naming it "clintonium" for the facility where it was isolated. | 1 | Applied and Interdisciplinary Chemistry |
To achieve these objectives, the Association will make use, amongst others, of the following activities:
* Organisation of scientific and technical seminars and of international meetings between members and with other actors within the sector
* Production of statistical, scientific and legal studies for the benefit of its members
* Publication of information for the benefit of the public and the users of the products
* Liaising with the European and national institutions. | 1 | Applied and Interdisciplinary Chemistry |
*Publications from the International Energy Agency (IEA) Energy in Buildings and Communities Programme (EBC) ventilation-related research projects-annexes:
**[https://www.iea-ebc.org/projects/project?AnnexID=9 EBC Annex 9 Minimum Ventilation Rates]
**[https://www.iea-ebc.org/projects/project?AnnexID=18 EBC Annex 18 Demand Controlled Ventilation Systems]
**[https://www.iea-ebc.org/projects/project?AnnexID=26 EBC Annex 26 Energy Efficient Ventilation of Large Enclosures]
**[https://www.iea-ebc.org/projects/project?AnnexID=27 EBC Annex 27 Evaluation and Demonstration of Domestic Ventilation Systems]
**[https://www.iea-ebc.org/projects/project?AnnexID=35 EBC Annex 35 Control Strategies for Hybrid Ventilation in New and Retrofitted Office Buildings (HYBVENT)]
**[https://www.iea-ebc.org/projects/project?AnnexID=62 EBC Annex 62 Ventilative Cooling] | 1 | Applied and Interdisciplinary Chemistry |
Oriented Line Integral Convolution (OLIC)
* Fast Rendering of Oriented Line Integral Convolution ( FROLIC) | 1 | Applied and Interdisciplinary Chemistry |
Heart muscle primarily metabolizes fat for energy and Acyl-CoA metabolism has been identified as a critical molecule in early stage heart muscle pump failure.
Cellular acyl-CoA content correlates with insulin resistance, suggesting that it can mediate lipotoxicity in non-adipose tissues. Acyl-CoA: diacylglycerol acyltransferase (DGAT) plays an important role in energy metabolism on account of key enzyme in triglyceride biosynthesis. The synthetic role of DGAT in adipose tissue such as the liver and the intestine, sites where endogenous levels of its activity and triglyceride synthesis are high and comparatively clear. Also, any changes in the activity levels might cause changes in systemic insulin sensitivity and energy homeostasis.
A rare disease called multiple acyl-CoA dehydrogenase deficiency (MADD) is a fatty acid metabolism disorder. Acyl-CoA is important because this enzyme helps make Acyl-CoA from free fatty acids, and this activates the fatty acid to be metabolized. This compromised fatty acid oxidation leads to many different symptoms, including severe symptoms such as cardiomyopathy and liver disease and mild symptoms such as episodic metabolic decomposition, muscle weakness and respiratory failure. MADD is a genetic disorder, caused by a mutation in the ETFA, ETFB, and ETFDH genes. MADD is known as an "autosomal recessive disorder" because for one to get this disorder, one must receive this recessive gene from both parents. | 1 | Applied and Interdisciplinary Chemistry |
The valley of stability can be helpful in interpreting and understanding properties of nuclear decay processes such as decay chains and nuclear fission.
Radioactive decay often proceeds via a sequence of steps known as a decay chain. For example, U decays to Th which decays to Pa and so on, eventually reaching Pb:
With each step of this sequence of reactions, energy is released and the decay products move further down the valley of stability towards the line of beta stability. Pb is stable and lies on the line of beta stability.
The fission processes that occur within nuclear reactors are accompanied by the release of neutrons that sustain the chain reaction. Fission occurs when a heavy nuclide such as uranium-235 absorbs a neutron and breaks into nuclides of lighter elements such as barium or krypton, usually with the release of additional neutrons. Like all nuclides with a high atomic number, these uranium nuclei require many neutrons to bolster their stability, so they have a large neutron-proton ratio (N/Z). The nuclei resulting from a fission (fission products) inherit a similar N/Z, but have atomic numbers that are approximately half that of uranium. Isotopes with the atomic number of the fission products and an N/Z near that of uranium or other fissionable nuclei have too many neutrons to be stable; this neutron excess is why multiple free neutrons but no free protons are usually emitted in the fission process, and it is also why many fission product nuclei undergo a long chain of β decays, each of which converts a nucleus N/Z to (N − 1)/(Z + 1), where N and Z are, respectively, the numbers of neutrons and protons contained in the nucleus.
When fission reactions are sustained at a given rate, such as in a liquid-cooled or solid fuel nuclear reactor, the nuclear fuel in the system produces many antineutrinos for each fission that has occurred. These antineutrinos come from the decay of fission products that, as their nuclei progress down a β decay chain toward the valley of stability, emit an antineutrino along with each β particle. In 1956, Reines and Cowan exploited the (anticipated) intense flux of antineutrinos from a nuclear reactor in the design of an experiment to detect and confirm the existence of these elusive particles. | 0 | Theoretical and Fundamental Chemistry |
The LIFT fast repetition rate (FRR) fluorescence technique is a method for measuring plant fluorescence. It uses a series of short bursts of blue light pulses from a LED to excite photosystem II in the plant. When the quinone acceptor A (Q) reaches its capacity for binding electrons, the system becomes saturated and consequently red fluorescence is emitted. This is regulated by a precise excitation protocol, which consists of a saturation sequence (SQA) and a relaxation sequence (RQA) with a set of short excitation flashes (1 μs).
The fluorescence can then be measured with FRR fluorometry. For that purpose, the LIFT instrument has a built-in optical interference filter to separate the red chlorophyll fluorescence from reflected light, with a wavelength of 685 ± 10 nm.
The fluorescence transient resulting from this excitation protocol shows the kinetics of the reduction of Q and its subsequent re-oxidation, and can be used to calculate various photosynthetic indicators. These indicators provide information on the level of photosynthetic activity, such as the efficiency of light utilization, the quantum yield of photochemical conversion, and the rate of electron transport. | 0 | Theoretical and Fundamental Chemistry |
Intermolecular forces are repulsive at short distances and attractive at long distances (see the Lennard-Jones potential). In a gas, the repulsive force chiefly has the effect of keeping two molecules from occupying the same volume. This gives a real gas a tendency to occupy a larger volume than an ideal gas at the same temperature and pressure. The attractive force draws molecules closer together and gives a real gas a tendency to occupy a smaller volume than an ideal gas. Which interaction is more important depends on temperature and pressure (see compressibility factor).
In a gas, the distances between molecules are generally large, so intermolecular forces have only a small effect. The attractive force is not overcome by the repulsive force, but by the thermal energy of the molecules. Temperature is the measure of thermal energy, so increasing temperature reduces the influence of the attractive force. In contrast, the influence of the repulsive force is essentially unaffected by temperature.
When a gas is compressed to increase its density, the influence of the attractive force increases. If the gas is made sufficiently dense, the attractions can become large enough to overcome the tendency of thermal motion to cause the molecules to disperse. Then the gas can condense to form a solid or liquid, i.e., a condensed phase. Lower temperature favors the formation of a condensed phase. In a condensed phase, there is very nearly a balance between the attractive and repulsive forces. | 0 | Theoretical and Fundamental Chemistry |
Duplex sequencing is a new method and its efficiency was studied in limited applications such as detecting point mutations using targeted capture sequencing. More studies need to be performed to expand the application and feasibility of duplex sequencing to more complex samples with larger numbers of mutations, indels, and copy number variations. | 1 | Applied and Interdisciplinary Chemistry |
Siddiquis first breakthrough in research came when he successfully isolated an antiarrhythmic agent in 1931 from the roots of Rauvolfia serpentina. He named the newly discovered chemical compound as Ajmaline, after his mentor Hakim Ajmal Khan who was one of the illustrious practitioners of Unani system of medicine in South Asia. Later on, Siddiqui also extracted other alkaloids from Rauvolfia serpentina that included Ajmalinine, Ajmalicine (CHNO), Isoajmaline, Neoajmaline, Serpentine and Serpentinine'. Many of these are still used worldwide for treatment of mental disorders and cardiovascular ailments, especially as antiarrhythmic agents in Brugada syndrome. | 0 | Theoretical and Fundamental Chemistry |
In metallurgy, selective leaching, also called dealloying, demetalification, parting and selective corrosion, is a corrosion type in some solid solution alloys, when in suitable conditions a component of the alloys is preferentially leached from the initially homogenous material. The less noble metal is removed from the alloy by a microscopic-scale galvanic corrosion mechanism. The most susceptible alloys are the ones containing metals with high distance between each other in the galvanic series, e.g. copper and zinc in brass. The elements most typically undergoing selective removal are zinc, aluminium, iron, cobalt, chromium, and others. | 1 | Applied and Interdisciplinary Chemistry |
In 2018, the atmospheric concentration of CFC-11 was noted by researchers to be declining more slowly than expected, and it subsequently emerged that it remains in widespread use as a blowing agent for polyurethane foam insulation in the construction industry of China. In 2021, researchers announced that emissions declined by 20,000 U.S. tons from 2018 to 2019, which mostly reversed the previous spike in emissions. In 2022, the European Commission announced an updated regulation that mandates the recovery and prevention of emissions of CFC-11 blowing agents from foam insulation in demolition waste, which is still emitted at significant scale. | 1 | Applied and Interdisciplinary Chemistry |
In the early 1930s, 90 percent of the urban population of the United States had electric power, in comparison to only 10 percent of rural homes. At the time, power companies did not feel that extending power to rural areas (rural electrification) would produce enough profit to make it worth their while. However, in the midst of the Great Depression, President Franklin D. Roosevelt realized that rural areas would continue to lag behind urban areas in both poverty and production if they were not electrically wired. On May 11, 1935, the president signed an executive order called the Rural Electrification Administration, also known as REA. The agency provided loans to fund electric infrastructure in the rural areas. In just a few years, 300,000 people in rural areas of the United States had received power in their homes.
While electricity dramatically improved working conditions on farms, it also had a large impact on the safety of food production. Refrigeration systems were introduced to the farming and food distribution processes, which helped in food preservation and kept food supplies safe. Refrigeration also allowed for shipment of perishable commodities throughout the United States. As a result, United States farmers quickly became the most productive in the world, and entire new food systems arose. | 0 | Theoretical and Fundamental Chemistry |
Cyanobacterial CCMs are similar in principle to those found in eukaryotic algae and hornworts, but the compartment into which carbon dioxide is concentrated has several structural differences. Instead of the pyrenoid, cyanobacteria contain carboxysomes, which have a protein shell, and linker proteins packing RuBisCO inside with a very regular structure.
Cyanobacterial CCMs are much better understood than those found in eukaryotes, partly due to the ease of genetic manipulation of prokaryotes. | 0 | Theoretical and Fundamental Chemistry |
Bartter syndrome, infantile, with sensorineural deafness (Barttin), also known as BSND, is a human gene which is associated with Bartter syndrome.
This gene encodes an essential beta subunit for CLC chloride channels. These heteromeric channels localize to basolateral membranes of renal tubules and of potassium-secreting epithelia of the inner ear. Mutations in this gene have been associated with Bartter syndrome with sensorineural deafness. | 1 | Applied and Interdisciplinary Chemistry |
Phenolphthalein can be synthesized by condensation of phthalic anhydride with two equivalents of phenol under acidic conditions. It was discovered in 1871 by Adolf von Baeyer.
The reaction can also be catalyzed by a mixture of zinc chloride and thionyl chloride. | 0 | Theoretical and Fundamental Chemistry |
*[https://archivesearch.lib.cam.ac.uk/repositories/9/resources/1699 The Papers of Alfred Maddock] held at the Churchill Archives Centre
* ; from the Periodic Videos series, dated 5 September 2008; in which Professor Sir Martyn Poliakoff, who studied under Maddock, recounts the laboratory bench anecdote. | 0 | Theoretical and Fundamental Chemistry |
The Bradford assay is linear over a short range, typically from 0 µg/mL to 2000 µg/mL, often making dilutions of a sample necessary before analysis. In making these dilutions, error in one dilution is compounded in further dilutions resulting in a linear relationship that may not always be accurate.
Basic conditions and detergents, such as SDS, can interfere with the dye's ability to bind to the protein through its side chains.
The reagents in this method tend to stain the test tubes. Same test tubes cannot be used since the stain would affect the absorbance reading. This method is also time sensitive. When more than one solution is tested, it is important to make sure every sample is incubated for the same amount of time for accurate comparison.
It is also inhibited by the presence of detergents, although this problem can be alleviated by the addition of cyclodextrins to the assay mixture.
Much of the non-linearity stems from the equilibrium between two different forms of the dye which is perturbed by adding the protein. The Bradford assay linearizes by measuring the ratio of the absorbances, 595 over 450 nm. This modified Bradford assay is approximately 10 times more sensitive than the conventional one.
The Coomassie Blue G250 dye used to bind to the proteins in the original Bradford method readily binds to arginine and lysine groups of proteins. This is a disadvantage because the preference of the dye to bind to these amino acids can result in a varied response of the assay between different proteins. Changes to the original method, such as increasing the pH by adding NaOH or adding more dye have been made to correct this variation. Although these modifications result in a less sensitive assay, a modified method becomes sensitive to detergents that can interfere with sample. | 0 | Theoretical and Fundamental Chemistry |
As the compound contains the peroxydisulfate ion as the counter anion, this compound should be treated as an explosive even though its explosive properties were not well established. The complex also releases tiny amounts of pyridine vapor which is a possible carcinogen. | 0 | Theoretical and Fundamental Chemistry |
A variety of substituted derivatives of phen have been examined as ligands. Substituents at the 2,9 positions confer protection for the attached metal, inhibiting the binding of multiple equivalents of the phenanthroline. Such bulky ligands also favor trigonal or tetrahedral coordination at the metal. Phen itself form complexes of the type [M(phen)]Cl when treated with metal dihalides (M = Fe, Co, Ni). By contrast, neocuproine and bathocuproine form 1:1 complexes such as [Ni(neocuproine)Cl]. | 0 | Theoretical and Fundamental Chemistry |
Back pressure is the term used for the hydraulic pressure required to create a flow through a chromatography column in high-performance liquid chromatography, the term deriving from the fact that it is generated by the resistance of the column, and exerts its influence backwards on the pump that must supply the flow. Back-pressure is a useful diagnostic feature of problems with the chromatography column. Rapid chromatography is favoured by columns packed with very small particles, which create high back-pressures. Column designers use "kinetic plots" to show the performance of a column at a constant back-pressure, usually selected as the maximum that a system's pump can reliably produce. | 1 | Applied and Interdisciplinary Chemistry |
Titanium and titanium alloys have been wide usage in aerospace, medical, and maritime applications. The most known titanium alloy that adopts solid solution strengthening is Ti-6Al-4V. Also, the addition of oxygen to pure Ti alloy adopts a solid solution strengthening as a mechanism to the material, while adding it to Ti-6Al-4V alloy doesn’t have the same influence. | 1 | Applied and Interdisciplinary Chemistry |
A chemical clock (or clock reaction) is a complex mixture of reacting chemical compounds in which the onset of an observable property (discoloration or coloration) occurs after a predictable induction time due to the presence of clock species at a detectable amount.
In cases where one of the reagents has a visible color, crossing a concentration threshold can lead to an abrupt color change after a reproducible time lapse. | 0 | Theoretical and Fundamental Chemistry |
BMP is a panel of tests that measures eight analytes in the bloods fluid portion (plasma). The results of the BMP provide valuable information about a patients kidney function, blood sugar level, electrolyte levels, and the acid-base balance. Abnormal changes in one or more of these analytes can be a sign of serious health issues:
* Sodium, Potassium, Chloride, and Carbon Dioxide: they are electrolytes that have electrical charges that manage the body’s water level, acid-base balance in the blood, and kidney function.
* Calcium: This charged electrolyte is essential for the proper functions of nerve, muscle, blood clotting, and bone health. Changes in the calcium level can be signs of bone disease, muscle cramps/ spasms, thyroid disease, or other conditions.
* Glucose: This measures the blood sugar levels, which is a crucial energy for your body and brain. High glucose levels can be a sign of diabetes or insulin resistance.
* Urea and Creatinine: These are waste products that the kidney filters out from blood. Urea measurements are helpful in detecting and treating kidney failure and related metabolic disorders, whereas creatinine measurements give information on kidney’s health, tracking renal dialysis treatment, and monitor hospitalized patients that are on diuretics. | 1 | Applied and Interdisciplinary Chemistry |
In the Southern Ocean, the use of relative wind stress is important because eddies are crucial in the Antarctic Circumpolar Circulation, and the damping of these eddies with relative wind stress will affect the overturning circulation. The Residual Meridional Overturning Circulation (RMOC), is a streamfunction that quantifies the transport of tracers across isopycnals. Wind stress is taken into account through the formulation of the RMOC, which is the sum of the Eulerian mean MOC and eddy-induced bolus overturning . The Eulerian mean MOC is dependent on the meridional winds that drive Ekman transport in zonal direction. The eddy-induced bolus overturning acts to restore sloping isopycnals to the horizontal, which are induced by eddies. The formulation of the RMOC is given by:
with being the zonal mean wind stress, the reference density, the Coriolis parameter (negative in Southern Hemisphere), the quasi-Stokes eddy diffusivity field, equal to being the length and the velocity of the eddy, respectively, and the slope of the isopycnals.
Inserting a lower wind stress, by using relative wind stress instead of resting ocean wind stress, directly leads to lower residual overturning, by reducing the Eulerian mean MOC (). Furthermore, it affects the eddy-induced bolus overturning () by damping eddies which results in reduced length and velocity scale ( & ) of eddies. The sum of this thus leads to a lower . | 1 | Applied and Interdisciplinary Chemistry |
The histidine phosphotransfer function can be carried out by proteins with at least two different architectures, both composed of a four-helix bundle but differing in the way the bundle is assembled. Most structurally characterized HPt proteins, such as the Hpt domain from the Escherichia coli protein ArcB and the Saccharomyces cerevisiae protein Ypd1, form the bundle as monomers. In the less common type, such as the Bacillus subtilis sporulation factor Spo0B or the Caulobacter crescentus protein ChpT, the bundle is assembled as a protein dimer, with similarity to the structure of histidine kinases. Monomeric HPt domains possess only one phosphorylatable histidine residue and interact with one response regulator, whereas dimers have two phosphorylation sites and can interact with two response regulators at the same time. Monomeric HPt domains have no enzymatic activity of their own and act purely as phosphate shuttles, while the dimeric Spo0B is catalytic; its phosphotransfer rate to the recipient response regulator is dramatically accelerated compared to histidine phosphate. Despite possessing a second domain with some similarity to ATPase domains, dimeric HPt proteins have not been shown to bind or hydrolyze ATP and lack key residues present in other ATPases.
The monomeric and dimeric forms do not have detectable sequence similarity and are most likely not evolutionarily related; they are instead examples of convergent evolution. Although dimeric HPts likely originate from degenerate histidine kinases, it is possible that monomeric HPts have a number of distinct origins, as there are few evolutionary constraints on the structure. | 1 | Applied and Interdisciplinary Chemistry |
Firefly luciferin is the luciferin found in many Lampyridae species. It is the substrate of beetle luciferases (EC 1.13.12.7) responsible for the characteristic yellow light emission from fireflies, though can cross-react to produce light with related enzymes from non-luminous species. The chemistry is unusual, as adenosine triphosphate (ATP) is required for light emission, in addition to molecular oxygen. | 1 | Applied and Interdisciplinary Chemistry |
Woven wire cloth, typically produced from stainless steel, is commonly employed as a filtration medium for sieving in a wide range of industries. Most often woven with a plain weave, or a twill weave for the lightest of meshes, apertures can be produced from a few microns upwards (e.g. 25 microns), employing wires with diameters from as little as 25 microns. A twill weave allows a mesh to be woven when the wire diameter is too thick in proportion to the aperture. Other, less commonplace, weaves, such as Dutch/Hollander, allow the production of meshes that are stronger and/or having smaller apertures.
Today wire cloth is woven to strict international standards, e.g. ISO1944:1999, which dictates acceptable tolerance regarding nominal mesh count and blemishes. The nominal mesh count, to which mesh is generally defined is a measure of the number of openings per lineal inch, determined by counting the number of openings from the centre of one wire to the centre of another wire one lineal inch away. For example, a 2 mesh woven with a wire of 1.6mm wire diameter has an aperture of 11.1mm (see picture below of a 2 mesh with an intermediate crimp). The formula for calculating the aperture of a mesh, with a known mesh count and wire diameter, is as follows:
where a = aperture, b = mesh count and c = wire diameter.
Other calculations regarding woven wire cloth/mesh can be made including weight and open area determination. Of note, wire diameters are often referred to by their standard wire gauge (swg); e.g. a 1.6mm wire is a 16 swg.
Traditionally, screen cloth was made with metal wires woven with a loom. Today, woven cloth is still widely used primarily because they are less expensive than other types of screen media. Over the years, different weaving techniques have been developed; either to increase the open area percentage or add wear-life. Slotted opening woven cloth is used where product shape is not a priority and where users need a higher open area percentage. Flat-top woven cloth is used when the consumer wants to increase wear-life. On regular woven wire, the crimps (knuckles on woven wires) wear out faster than the rest of the cloth resulting in premature breakage. On flat-top woven wire, the cloth wears out equally until half of the wire diameter is worn, resulting in a longer wear life. Unfortunately flat-top woven wire cloth is not widely used because of the lack of crimps that causes a pronounced reduction of passing fines resulting in premature wear of con crushers. | 1 | Applied and Interdisciplinary Chemistry |
Add master mix which contains buffer, dNTP mix, MgCl, Taq polymerase and nuclease-free water to each PCR tube. Then add the necessary primer to the tubes. Next, place the PCR tubes in a thermal cycler for 30 cycles of the amplification program. This includes: denaturation, annealing, and elongation. The products of RT-PCR can be analyzed with gel electrophoresis. | 1 | Applied and Interdisciplinary Chemistry |
Sanitary sewers evolved from combined sewers built where water was plentiful. Animal feces accumulated on city streets while animal-powered transport moved people and goods. Accumulations of animal feces encouraged dumping chamber pots into streets where night soil collection was impractical. Combined sewers were built to use surface runoff to flush waste off streets and move it underground to places distant from populated areas. Sewage treatment became necessary as population expanded, but increased volumes and pumping capacity required for treatment of diluted waste from combined sewers is more expensive than treating undiluted sewage.
Communities that have urbanized in the mid-20th century or later generally have built separate systems for sewage (sanitary sewers) and stormwater, because precipitation causes widely varying flows, reducing sewage treatment plant efficiency.
In the UK, the term "foul sewer" was also in use for a sanitary sewer. | 1 | Applied and Interdisciplinary Chemistry |
The term GM ("genetically modified") is often used as a synonym of transgenic to refer to plants modified using recombinant DNA technologies. Plants with transgenic/GM disease resistance against insect pests have been extremely successful as commercial products, especially in maize and cotton, and are planted annually on over 20 million hectares in over 20 countries worldwide (see also genetically modified crops). Transgenic plant disease resistance against microbial pathogens was first demonstrated in 1986. Expression of viral coat protein gene sequences conferred virus resistance via small RNAs. This proved to be a widely applicable mechanism for inhibiting viral replication. Combining coat protein genes from three different viruses, scientists developed squash hybrids with field-validated, multiviral resistance. Similar levels of resistance to this variety of viruses had not been achieved by conventional breeding.
A similar strategy was deployed to combat papaya ringspot virus, which by 1994 threatened to destroy Hawaii's papaya industry. Field trials demonstrated excellent efficacy and high fruit quality. By 1998 the first transgenic virus-resistant papaya was approved for sale. Disease resistance has been durable for over 15 years. Transgenic papaya accounts for ~85% of Hawaiian production. The fruit is approved for sale in the U.S., Canada and Japan.
Potato lines expressing viral replicase sequences that confer resistance to potato leafroll virus were sold under the trade names NewLeaf Y and NewLeaf Plus, and were widely accepted in commercial production in 1999–2001, until McDonald's Corp. decided not to purchase GM potatoes and Monsanto decided to close their NatureMark potato business. NewLeaf Y and NewLeaf Plus potatoes carried two GM traits, as they also expressed Bt-mediated resistance to Colorado potato beetle.
No other crop with engineered disease resistance against microbial pathogens had reached the market by 2013, although more than a dozen were in some state of development and testing. | 1 | Applied and Interdisciplinary Chemistry |
A galactosylceramide, or galactocerebroside is a type of cerebroside consisting of a ceramide with a galactose residue at the 1-hydroxyl moiety.
The galactose is cleaved by galactosylceramidase.
Galactosylceramide is a marker for oligodendrocytes in the brain, whether or not they form myelin. | 1 | Applied and Interdisciplinary Chemistry |
The role of TLRs in direct recognition of peptidoglycan is controversial. In some studies, has been reported that peptidoglycan is sensed by TLR2. But this TLR2-inducing activity could be due to cell wall lipoproteins and lipoteichoic acids that commonly co-purify with peptidoglycan. Also variation in peptidoglycan structure in bacteria from species to species may contribute to the differing results on this topic. | 1 | Applied and Interdisciplinary Chemistry |
Die swell, also known as extrudate swell or Barus effect, is a common phenomenon in polymer processing. Die swell occurs in instances of polymer extrusion, in which a stream of polymeric material is forced through a die, a specialized tool in manufacturing to shape or cut polymeric materials. Die swell is an instance where a polymer stream is compressed by entrance into a die, and is followed by a partial recovery or "swell" back to the former shape and volume of the polymer after exiting the die, hence the term die swell.
Die swell is a phenomenon directly related to entropy and the relaxation of the polymer within the flow stream. Initially, a flow stream has a constant rate before entering the die, and the polymers within the stream occupy a roughly spherical conformation, maximizing entropy. Extrusion through the die causes an increase in flow rate through the polymer flow stream. As the polymer spends time inside the die and is subject to the much increased flow rate, the polymers lose the spherical shape, becoming longer due to the increased flow rate. Physical entanglements may relax, if the time scale of the polymer within the die is long enough. When the polymer stream leaves the die, the remaining physical entanglements cause the polymers in the die stream to regain a portion of its former shape and spherical volume, in order to return to the roughly spherical conformation that maximizes entropy.
The disentanglement of polymer chains is a kinetic process, and so the longer the die is, the more time is given for the physical entanglements within the polymer stream to disentangle. With a longer die and a slower polymer flow stream, less pronounced die swell will be observed. This is due to the longer die providing a longer time period for polymer, when subject to the increase flow rate, to disentangle. This characteristic relaxation time determines the length of time the polymer must spend inside the die to minimize die swell. | 0 | Theoretical and Fundamental Chemistry |
HVAF coating technology is the combustion of propane in a compressed air stream. Like HVOF, this produces a uniform high velocity jet. HVAF differs by including a heat baffle to further stabilize the thermal spray mechanisms. Material is injected into the air-fuel stream and coating particles are propelled toward the part. HVAF has a maximum flame temperature of 3,560° to 3,650 °F and an average particle velocity of 3,300 ft/sec. Since the maximum flame temperature is relatively close to the melting point of most spray materials, HVAF results in a more uniform, ductile coating. This also allows for a typical coating thickness of 0.002–0.050". HVAF coatings also have a mechanical bond strength of greater that 12,000 psi. Common HVAF coating materials include, but are not limited to; tungsten carbide, chrome carbide, stainless steel, hastelloy, and inconel. Due to its ductile nature hvaf coatings can help resist cavitation damage. | 1 | Applied and Interdisciplinary Chemistry |
After separation, an additional separation method may then be used, such as isoelectric focusing or SDS-PAGE. The gel will then be physically cut, and the protein complexes extracted from each portion separately. Each extract may then be analysed, such as by peptide mass fingerprinting or de novo peptide sequencing after in-gel digestion. This can provide a great deal of information about the identities of the proteins in a complex. | 1 | Applied and Interdisciplinary Chemistry |
Before mass separation, a beam of positive ions has to be extracted from the plasma and focused into the mass-analyzer. It is important to separate the ions from UV photons, energetic neutrals and from any solid particles that may have been carried into the instrument from the ICP. Traditionally, ICP-MS instruments have used transmitting ion lens arrangements for this purpose. Examples include the Einzel lens, the Barrel lens, Agilents Omega Lens and Perkin-Elmers Shadow Stop. Another approach is to use ion guides (quadrupoles, hexapoles, or octopoles) to guide the ions into mass analyzer along a path away from the trajectory of photons or neutral particles. Yet another approach is Varian patented used by Analytik Jena ICP-MS 90 degrees reflecting parabolic "Ion Mirror" optics, which are claimed to provide more efficient ion transport into the mass-analyzer, resulting in better sensitivity and reduced background. Analytik Jena ICP-MS PQMS is the most sensitive instrument on the market.
A sector ICP-MS will commonly have four sections: an extraction acceleration region, steering lenses, an electrostatic sector and a magnetic sector. The first region takes ions from the plasma and accelerates them using a high voltage. The second uses may use a combination of parallel plates, rings, quadrupoles, hexapoles and octopoles to steer, shape and focus the beam so that the resulting peaks are symmetrical, flat topped and have high transmission. The electrostatic sector may be before or after the magnetic sector depending on the particular instrument, and reduces the spread in kinetic energy caused by the plasma. This spread is particularly large for ICP-MS, being larger than Glow Discharge and much larger than TIMS. The geometry of the instrument is chosen so that the instrument the combined focal point of the electrostatic and magnetic sectors is at the collector, known as Double Focussing (or Double Focussing).
If the mass of interest has a low sensitivity and is just below a much larger peak, the low mass tail from this larger peak can intrude onto the mass of interest. A Retardation Filter might be used to reduce this tail. This sits near the collector, and applies a voltage equal but opposite to the accelerating voltage; any ions that have lost energy while flying around the instrument will be decelerated to rest by the filter. | 0 | Theoretical and Fundamental Chemistry |
SDS-PAGE, sodium dodecyl sulfate polyacrylamide gel electrophoresis, describes a collection of related techniques to separate proteins according to their electrophoretic mobility (a function of the molecular weight of a polypeptide chain) while in the denatured (unfolded) state. In most proteins, the binding of SDS to the polypeptide chain imparts an even distribution of charge per unit mass, thereby resulting in a fractionation by approximate size during electrophoresis.
SDS is a strong detergent agent used to denature native proteins to unfolded, individual polypeptides. When a protein mixture is heated to 100 °C in presence of SDS, the detergent wraps around the polypeptide backbone. In this process, the intrinsic charges of polypeptides becomes negligible when compared to the negative charges contributed by SDS. Thus polypeptides after treatment become rod-like structures possessing a uniform charge density, that is same net negative charge per unit length. The electrophoretic mobilities of these proteins will be a linear function of the logarithms of their molecular weights. | 1 | Applied and Interdisciplinary Chemistry |
Heinz Falk is married to Rotraud Falk since 1966 and they have one son:
*Alexander Falk (August 13, 1967) is the CEO of Altova. | 0 | Theoretical and Fundamental Chemistry |
Several types of cells support an action potential, such as plant cells, muscle cells, and the specialized cells of the heart (in which occurs the cardiac action potential). However, the main excitable cell is the neuron, which also has the simplest mechanism for the action potential.
Neurons are electrically excitable cells composed, in general, of one or more dendrites, a single soma, a single axon and one or more axon terminals. Dendrites are cellular projections whose primary function is to receive synaptic signals. Their protrusions, known as dendritic spines, are designed to capture the neurotransmitters released by the presynaptic neuron. They have a high concentration of ligand-gated ion channels. These spines have a thin neck connecting a bulbous protrusion to the dendrite. This ensures that changes occurring inside the spine are less likely to affect the neighboring spines. The dendritic spine can, with rare exception (see LTP), act as an independent unit. The dendrites extend from the soma, which houses the nucleus, and many of the "normal" eukaryotic organelles. Unlike the spines, the surface of the soma is populated by voltage activated ion channels. These channels help transmit the signals generated by the dendrites. Emerging out from the soma is the axon hillock. This region is characterized by having a very high concentration of voltage-activated sodium channels. In general, it is considered to be the spike initiation zone for action potentials, i.e. the trigger zone. Multiple signals generated at the spines, and transmitted by the soma all converge here. Immediately after the axon hillock is the axon. This is a thin tubular protrusion traveling away from the soma. The axon is insulated by a myelin sheath. Myelin is composed of either Schwann cells (in the peripheral nervous system) or oligodendrocytes (in the central nervous system), both of which are types of glial cells. Although glial cells are not involved with the transmission of electrical signals, they communicate and provide important biochemical support to neurons. To be specific, myelin wraps multiple times around the axonal segment, forming a thick fatty layer that prevents ions from entering or escaping the axon. This insulation prevents significant signal decay as well as ensuring faster signal speed. This insulation, however, has the restriction that no channels can be present on the surface of the axon. There are, therefore, regularly spaced patches of membrane, which have no insulation. These nodes of Ranvier can be considered to be "mini axon hillocks", as their purpose is to boost the signal in order to prevent significant signal decay. At the furthest end, the axon loses its insulation and begins to branch into several axon terminals. These presynaptic terminals, or synaptic boutons, are a specialized area within the axon of the presynaptic cell that contains neurotransmitters enclosed in small membrane-bound spheres called synaptic vesicles. | 0 | Theoretical and Fundamental Chemistry |
For the majority of eukaryotic messenger RNAs (mRNAs), translation initiates from a methionine-encoding AUG start codon following the molecular processes of cap-binding and scanning by ribosomal pre-initiation complexes (PICs). In rare exceptions, such as translation by viral IRES-containing mRNAs, cap-binding and/or scanning are not required for initiation, although AUG is still typically used as the first codon. RAN translation is an exception to the canonical rules as it uses variable start site selection and initiates from a non-AUG codon, but may still depend on cap-binding and scanning. | 1 | Applied and Interdisciplinary Chemistry |
Tin pest is an autocatalytic, allotropic transformation of the element tin, which causes deterioration of tin objects at low temperatures. Tin pest has also been called tin disease, tin blight or tin leprosy (lèpre détain').
It was observed in medieval Europe that the pipes of pipe organs were affected in cool climates. As soon as the tin began decomposing, the process accelerated.
With the adoption of the Restriction of Hazardous Substances Directive (RoHS) regulations in Europe, and similar regulations elsewhere, traditional lead/tin solder alloys in electronic devices have been replaced by nearly pure tin, introducing tin pest and related problems such as tin whiskers. | 1 | Applied and Interdisciplinary Chemistry |
Each bacterial gene is denoted by a mnemonic of three lower case letters which indicate the pathway or process in which the gene-product is involved, followed by a capital letter signifying the actual gene. In some cases, the gene letter may be followed by an allele number. All letters and numbers are underlined or italicised. For example, leuA is one of the genes of the leucine biosynthetic pathway, and leuA273 is a particular allele of this gene.
Where the actual protein coded by the gene is known then it may become part of the basis of the mnemonic, thus:
*rpoA encodes the α-subunit of RNA polymerase
*rpoB encodes the β-subunit of RNA polymerase
*polA encodes DNA polymerase I
*polC encodes DNA polymerase III
*rpsL encodes ribosomal protein, small S12
Some gene designations refer to a known general function:
*dna is involved in DNA replication | 1 | Applied and Interdisciplinary Chemistry |
Seemingly ambiguous oxidation states are derived from a set of resonance formulas of equal weights for a molecule having heteronuclear bonds where the atom connectivity does not correspond to the number of two-electron bonds dictated by the 8 − N rule. An example is SN where four resonance formulas featuring one S=N double bond have oxidation states +2 and +4 for the two sulfur atoms, which average to +3 because the two sulfur atoms are equivalent in this square-shaped molecule. | 0 | Theoretical and Fundamental Chemistry |
The glass version of these lenses achieves their photochromic properties through the embedding of microcrystalline silver halides (usually silver chloride) in a glass substrate. Plastic photochromic lenses use organic photochromic molecules (for example oxazines and naphthopyrans) to achieve the reversible darkening effect. These lenses darken when exposed to ultraviolet light of the intensity present in sunlight, but not in artificial light. In the presence of UV-A light (wavelengths of 320–400 nm), electrons from the glass combine with the colourless silver cations to form elemental silver. Because elemental silver is visible, the lenses appear darker.
Back in the shade, this reaction is reversed. The silver returns to its original ionic state, and the lenses become clear.
With the photochromic material dispersed in the glass substrate, the degree of darkening depends on the thickness of glass, which poses problems with variable-thickness lenses in prescription glasses. With plastic lenses, the material is typically embedded into the surface layer of the plastic in a uniform thickness of up to 150 µm. | 0 | Theoretical and Fundamental Chemistry |
Acidic protein denaturants include:
* Acetic acid
* Trichloroacetic acid 12% in water
* Sulfosalicylic acid | 1 | Applied and Interdisciplinary Chemistry |
While Newton explained the tides by describing the tide-generating forces and Daniel Bernoulli gave a description of the static reaction of the waters on Earth to the tidal potential, the dynamic theory of tides, developed by Pierre-Simon Laplace in 1775, describes the oceans real reaction to tidal forces. Laplaces theory of ocean tides takes into account friction, resonance and natural periods of ocean basins. It predicts the large amphidromic systems in the world's ocean basins and explains the oceanic tides that are actually observed.
The equilibrium theory—based on the gravitational gradient from the Sun and Moon but ignoring the Earth's rotation, the effects of continents, and other important effects—could not explain the real ocean tides. Since measurements have confirmed the dynamic theory, many things have possible explanations now, like how the tides interact with deep sea ridges, and chains of seamounts give rise to deep eddies that transport nutrients from the deep to the surface. The equilibrium tide theory calculates the height of the tide wave of less than half a meter, while the dynamic theory explains why tides are up to 15 meters. <br>
Satellite observations confirm the accuracy of the dynamic theory, and the tides worldwide are now measured to within a few centimeters. Measurements from the CHAMP satellite closely match the models based on the TOPEX data. Accurate models of tides worldwide are essential for research since the variations due to tides must be removed from measurements when calculating gravity and changes in sea levels. | 1 | Applied and Interdisciplinary Chemistry |
Embrittlement is a significant decrease of ductility of a material, which makes the material brittle. Embrittlement is used to describe any phenomena where the environment compromises a stressed material's mechanical performance, such as temperature or environmental composition. This is oftentimes undesirable as brittle fracture occurs quicker and can much more easily propagate than ductile fracture, leading to complete failure of the equipment. Various materials have different mechanisms of embrittlement, therefore it can manifest in a variety of ways, from slow crack growth to a reduction of tensile ductility and toughness. | 1 | Applied and Interdisciplinary Chemistry |
The octadecanoid pathway is a biosynthetic pathway for the production of the phytohormone jasmonic acid (JA), an important hormone for induction of defense genes. JA is synthesized from alpha-linolenic acid, which can be released from the plasma membrane by certain lipase enzymes. For example, in the wound defense response, phospholipase C will cause the release of alpha-linolenic acid for JA synthesis.
In the first step, alpha-linolenic acid is oxidized by the enzyme lipoxygenase. This forms 13-hydroperoxylinolenic acid, which is then modified by a dehydrase and undergoes cyclization by allene oxide cyclase to form 12-oxo-phytodienoic acid. This undergoes reduction and three rounds of beta oxidation to form jasmonic acid. | 1 | Applied and Interdisciplinary Chemistry |
Most commonly used post treatment, where chlorine is dissolved in water to form and hydrochloric acid hypochlorous acid. The latter act as a disinfectant that is able to eliminate pathogens such as bacteria, viruses and protozoa by penetrating the cell walls. | 0 | Theoretical and Fundamental Chemistry |
In recent years a variety of double and triple bonds between the semi-metallic elements have been reported, including silicon, germanium, arsenic, bismuth and so on. The ability of certain main group elements to catenate is currently the subject of research into inorganic polymers. | 0 | Theoretical and Fundamental Chemistry |
One viral epitranscriptome modification that has been identified is the 5-methylcytidine (mC). HIV-1 and MLV transcriptomes contain elevated levels of these residues by approximately 14-30 fold when compared to a cell’s normal levels. NSUN2 is the complex that codes the cytidine methyltransferases credited with mC formation in cells and amplification in viral epitranscriptomes. The NSUN2 affects the translational aspect of the mRNA in the viral cells, boosting the expression of the viral genome. It has also been found that the mC alters the splicing pattern and locations in the viral transcriptome. This affected the HIV-1 transcript in both early and late infection. | 1 | Applied and Interdisciplinary Chemistry |
Statistical mechanics, also known as statistical thermodynamics, emerged with the development of atomic and molecular theories in the late 19th century and early 20th century, and supplemented classical thermodynamics with an interpretation of the microscopic interactions between individual particles or quantum-mechanical states. This field relates the microscopic properties of individual atoms and molecules to the macroscopic, bulk properties of materials that can be observed on the human scale, thereby explaining classical thermodynamics as a natural result of statistics, classical mechanics, and quantum theory at the microscopic level. | 0 | Theoretical and Fundamental Chemistry |
Culture techniques and media vary depending upon the requirements of the fungal isolate involved, however the general procedure consist of the following: fungal hyphae are typically placed in liquid growth media and placed in shake culture until the fungal culture has increased in biomass. The fungal hyphae are removed from the growth media, washed with distilled water to remove the growth media, placed in distilled water and incubated on shake culture for 24 to 48 hours. The fungal hyphae are separated from the supernatant, and an aliquot of the supernatant is added to 1.0 mM ion solution. The ion solution is then monitored for 2 to 3 days for the formation of nanoparticles. Another common culture technique is to add washed fungal hyphae directly into 1.0 mM ion solution instead of utilizing the fungal filtrate. Silver nitrate is the most widely used source of silver ions, but silver sulfate has also been utilized. Choloroauric acid is generally used as the source of gold ions at various concentrations (1.0 mM and 250 mg to 500 mg of Au per liter). Cadmium sulfide nanoparticle synthesis for F. oxysporum was conducted using a 1:1 ratio of Cd and SO at a 1 mM concentration. Gold nanoparticles can vary in shape and size depending on the pH of the ion solution. Gericke and Pinches (2006) reported that for V. luteoalbum small (cc.10 nm) spherical gold nanoparticles are formed at pH 3, larger (spherical, triangular, hexagon and rods) gold nanoparticles are formed at pH 5, and at pH 7 to pH 9 the large nanoparticles tend to lack a defined shape. Temperature interactions for both silver and gold nanoparticles were similar; a lower temperature resulted in larger nanoparticles while higher temperatures produced smaller nanoparticles. | 0 | Theoretical and Fundamental Chemistry |
The most commonly observed health effects in people exposed to extremely high levels of PCBs are skin conditions, such as chloracne and rashes, but these were known to be symptoms of acute systemic poisoning dating back to 1922. Studies in workers exposed to PCBs have shown changes in blood and urine that may indicate liver damage. In Japan in 1968, 280 kg of PCB-contaminated rice bran oil was used as chicken feed, resulting in a mass poisoning, known as Yushō disease, in over 1800 people. Common symptoms included dermal and ocular lesions, irregular menstrual cycles and lowered immune responses. Other symptoms included fatigue, headaches, coughs, and unusual skin sores. Additionally, in children, there were reports of poor cognitive development. Women exposed to PCBs before or during pregnancy can give birth to children with lowered cognitive ability, immune compromise, and motor control problems.
There is evidence that crash dieters that have been exposed to PCBs have an elevated risk of health complications. Stored PCBs in the adipose tissue become mobilized into the blood when individuals begin to crash diet.
PCBs have shown toxic and mutagenic effects by interfering with hormones in the body. PCBs, depending on the specific congener, have been shown to both inhibit and imitate estradiol, the main sex hormone in females. Imitation of the estrogen compound can feed estrogen-dependent breast cancer cells, and possibly cause other cancers, such as uterine or cervical. Inhibition of estradiol can lead to serious developmental problems for both males and females, including sexual, skeletal, and mental development issues. In a cross-sectional study, PCBs were found to be negatively associated with testosterone levels in adolescent boys.
High PCB levels in adults have been shown to result in reduced levels of the thyroid hormone triiodothyronine, which affects almost every physiological process in the body, including growth and development, metabolism, body temperature, and heart rate. It also resulted in reduced immunity and increased thyroid disorders. | 1 | Applied and Interdisciplinary Chemistry |
Both the legacy NACE and SSPC organizations were ANSI-accredited standards developers, which AMPP plans to continue. The merged standards program includes 25 standing standards committees that develop technical standards for industries including cathodic protection, coatings, defense, highways and bridges, rail, maritime, oil and gas, power and utilities, research and testing, tanks and pipelines, and water and wastewater. | 1 | Applied and Interdisciplinary Chemistry |
A microbial desalination cell (MDC) is a biological electrochemical system that implements the use of electro-active bacteria to power desalination of water in situ, resourcing the natural anode and cathode gradient of the electro-active bacteria and thus creating an internal supercapacitor. Available water supply has become a worldwide endemic as only .3% of the Earth's water supply is usable for human consumption, while over 99% is sequestered by oceans, glaciers, brackish waters, and biomass. Current applications in electrocoagulation, such as microbial desalination cells, are able to desalinate and sterilize formerly unavailable water to render it suitable for safe water supply. Microbial desalination cells stem from microbial fuel cells, deviating by no longer requiring the use of a mediator and instead relying on the charged components of the internal sludge to power the desalination process. Microbial desalination cells therefore do not require additional bacteria to mediate the catabolism of the substrate during biofilm oxidation on the anodic side of the capacitor. MDCs and other bio-electrical systems are favored over reverse osmosis, nanofiltration and other desalination systems due to lower costs, energy and environmental impacts associated with bio-electrical systems. | 0 | Theoretical and Fundamental Chemistry |
There are several, largely empirical laws of recrystallization:
* Thermally activated. The rate of the microscopic mechanisms controlling the nucleation and growth of recrystallized grains depend on the annealing temperature. Arrhenius-type equations indicate an exponential relationship.
* Critical temperature. Following from the previous rule it is found that recrystallization requires a minimum temperature for the necessary atomic mechanisms to occur. This recrystallization temperature decreases with annealing time.
* Critical deformation. The prior deformation applied to the material must be adequate to provide nuclei and sufficient stored energy to drive their growth.
* Deformation affects the critical temperature. Increasing the magnitude of prior deformation, or reducing the deformation temperature, will increase the stored energy and the number of potential nuclei. As a result, the recrystallization temperature will decrease with increasing deformation.
* Initial grain size affects the critical temperature. Grain boundaries are good sites for nuclei to form. Since an increase in grain size results in fewer boundaries this results in a decrease in the nucleation rate and hence an increase in the recrystallization temperature
* Deformation affects the final grain size. Increasing the deformation, or reducing the deformation temperature, increases the rate of nucleation faster than it increases the rate of growth. As a result, the final grain size is reduced by increased deformation. | 1 | Applied and Interdisciplinary Chemistry |
Diffuse clouds are of astronomical interest because they play a primary role in the evolution and thermodynamics of ISM. Observation of the abundant atomic hydrogen in 21 cm has shown good signal-to-noise ratio in both emission and absorption. Nevertheless, HI observations have a fundamental difficulty when are directed to low mass regions of the hydrogen nucleus, as the center part of a diffuse cloud: Thermal width of hydrogen lines are the same order as the internal velocities structures of interest, so clouds components of various temperatures and central velocities are indistinguishable in the spectrum. Molecular lines observations in principle doesnt suffer from these problems. Unlike HI, molecules generally have excitation temperature T , so that emission is very weak even from abundant species. CO and HO are considered to be the most easily studied candidate molecules. CO has transitions in a region of the spectrum (wavelength HO has the 18 cm emission, line convenient for absorption observations. Observation studies provide the most sensitive means of detections of molecules with sub thermal excitation, and can give the opacity of the spectral line, which is a central issue to model the molecular region.
Studies based in the kinematic comparison of HO and HI absorption lines from diffuse clouds are useful in determining their physical conditions, especially because heavier elements provide higher velocity resolution. | 1 | Applied and Interdisciplinary Chemistry |
If one could observe a gas under a powerful microscope, one would see a collection of particles without any definite shape or volume that are in more or less random motion. These gas particles only change direction when they collide with another particle or with the sides of the container. This microscopic view of gas is well-described by statistical mechanics, but it can be described by many different theories. The kinetic theory of gases, which makes the assumption that these collisions are perfectly elastic, does not account for intermolecular forces of attraction and repulsion. | 0 | Theoretical and Fundamental Chemistry |
DDM is based on an algorithm proposed in Croccolo et al. and Alaimo et al., which is conveniently named differential dynamic algorithm (DDA). DDA works by subtracting images acquired at different times and taking advantage that, as the delay between two subtracted images gets large, the energy content of the difference image increases correspondingly. A two-dimensional fast Fourier transform (FFT) analysis of the difference images allows to quantify the growth of the signal contains for each wave vector and one can calculate the Fourier power spectrum of the difference images for different delays to obtain the so-called image structure function . Calculation shows that for both scattering- and fluorescence-based DDM
where is the normalized intermediate scattering function that would be measured in a dynamic light scattering (DLS) experiment, the sample scattering intensity that would be measured in a static light scattering (SLS) experiment, a background term due to the noise along the detection chain a transfer function that depends on the microscope details. Equation () shows that DDM can be used for DLS experiments, provided that a model for the normalized intermediate scattering function is available. For instance, in the case of Brownian motion one has where is the diffusion coefficient of the Brownian particles. If the transfer function is determined by calibrating the microscope with a suitable sample, DDM can be employed also for SLS experiments. Alternative algorithms for data analysis are suggested in.
Running DDM on a series of frames smaller than the full-frame has been called multi-DDM. This is analogous to changing the scattering volume in a light scattering experiment, but is readily carried out by selecting out of the full-frame movie. The coherence lengthscale of the dynamics can be picked up from a multi-DDM analysis. | 0 | Theoretical and Fundamental Chemistry |
Polymersomes that contain active enzymes and that provide a way to selectively transport substrates for conversion by those enzymes have been described as nanoreactors.
Polymersomes have been used to create controlled release drug delivery systems. Similar to coating liposomes with polyethylene glycol, polymersomes can be made invisible to the immune system if the hydrophilic block consists of polyethylene glycol. Thus, polymersomes are useful carriers for targeted medication.
For in vivo applications, polymersomes are de facto limited to the use of FDA-approved polymers, as most pharmaceutical firms are unlikely to develop novel polymers due to cost issues. Fortunately, there are a number of such polymers available, with varying properties, including:
Hydrophilic blocks
* Poly(ethylene glycol) (PEG/PEO)
* Poly(2-methyloxazoline)
Hydrophobic blocks
* Polydimethylsiloxane (PDMS)
* Poly(caprolactone (PCL)
* Poly(lactide) (PLA)
* Poly(methyl methacrylate) (PMMA)
If enough of the block copolymer molecules that make up a polymersome are cross-linked, the polymersome can be made into a transportable powder.
Polymersomes can be used to make an artificial cell if hemoglobin and other components are added. The first artificial cell was made by Thomas Chang. | 1 | Applied and Interdisciplinary Chemistry |
In the United States, sperm banks maintain lists or catalogs of donors which provide basic information about the donor such as racial origin, skin color, height, weight, color of eyes, and blood group. Some of these catalogs are available for browsing on the Internet, while others are made available to patients only when they apply to a sperm bank for treatment. Some sperm banks make additional information about each donor available for an additional fee, and others make additional basic information known to children produced from donors when those children reach the age of 18. Some clinics offer "exclusive donors" whose sperm is used to produce pregnancies for only one recipient woman. How accurate this is, or can be, is not known, and neither is it known whether the information produced by sperm banks, or by the donors themselves, is true. Many sperm banks will, however, carry out whatever checks they can to verify the information they request, such as checking the identity of the donor and contacting his own doctor to verify medical details.
In the United Kingdom, most donors are anonymous at the point of donation and recipients can see only non-identifying information about their donor (height, weight, ethnicity etc.). Donors need to provide identifying information to the clinic and clinics will usually ask the donors doctor to confirm any medical details they have been given. Donors are asked to provide a pen portrait of themselves which is held by the HFEA and can be obtained by the adult conceived from the donation at the age of 18, along with identifying information such as the donors name and last known address. Known donation is permitted and it is not uncommon for family or friends to donate to a recipient couple.
Qualities that potential recipients typically prefer in donors include the donors being tall, college educated, and with a consistently high sperm count.
A review came to the result that 68% of donors had given information to the clinical staff regarding physical characteristics and education but only 16% had provided additional information such as hereditary aptitudes and temperament or character. | 1 | Applied and Interdisciplinary Chemistry |
In order to achieve its objectives EFDA conducts the following group of activities:
* Collective use of JET, the world's largest fusion experiment
* Reinforced coordination of fusion physics and technology research and development in EU laboratories.
* Training and carrier development of researchers, promoting links to universities and carrying out support actions for the benefit of the fusion programme.
* EU contributions to international collaborations outside F4E
EFDA coordinates a range of activities to be carried out by the Associations in 7 key physics and technology areas. The implementation of these activities benefits from structures so called Task Forces and Topical Groups. The European Task Forces on [https://web.archive.org/web/20091222223222/http://www.efda.org/about_efda/activities-plasma_wall_interaction.htm Plasma Wall Interaction] (PWI) and on [https://web.archive.org/web/20091222223205/http://www.efda.org/about_efda/activities-integrated_tokamak_modelling.htm Integrated Tokamak Modelling] (ITM) set up respectively in 2002 and 2003. To strengthen the co-ordination in other key areas five Topical Groups have been set up in 2008: on [https://web.archive.org/web/20090419230108/http://www.efda.org/about_efda/activities-fusion_materials.htm Fusion Materials Development], [https://web.archive.org/web/20091222223153/http://www.efda.org/about_efda/activities-diagnostics.htm Diagnostics], [https://web.archive.org/web/20091222223159/http://www.efda.org/about_efda/activities-heating_and_current_drive.htm Heating and Current Drive], [https://web.archive.org/web/20091222223242/http://www.efda.org/about_efda/activities-transport.htm Transport] and [https://web.archive.org/web/20091222223217/http://www.efda.org/about_efda/activities-magnetohydrodinamics.htm Plasma Stability and Control]. | 0 | Theoretical and Fundamental Chemistry |
An oxyanion, or oxoanion, is an ion with the generic formula (where A represents a chemical element and O represents an oxygen atom). Oxyanions are formed by a large majority of the chemical elements. The formulae of simple oxyanions are determined by the octet rule. The corresponding oxyacid of an oxyanion is the compound . The structures of condensed oxyanions can be rationalized in terms of AO polyhedral units with sharing of corners or edges between polyhedra. The oxyanions (specifically, phosphate and polyphosphate esters) adenosine monophosphate (AMP), adenosine diphosphate (ADP) and adenosine triphosphate (ATP) are important in biology. | 0 | Theoretical and Fundamental Chemistry |
The Hiyama coupling is a palladium-catalyzed cross-coupling reaction of organosilanes with organic halides used in organic chemistry to form carbon–carbon bonds (C-C bonds). This reaction was discovered in 1988 by Tamejiro Hiyama and Yasuo Hatanaka as a method to form carbon-carbon bonds synthetically with chemo- and regioselectivity. The Hiyama coupling has been applied to the synthesis of various natural products.
:* : aryl, alkenyl or alkynyl
:* : aryl, alkenyl, alkynyl or alkyl
:* : Cl, F or alkyl
:* : Cl, Br, I or OTf | 0 | Theoretical and Fundamental Chemistry |
SDS is a common ingredient in toothpastes due to its low cost, its lack of impact on taste, and its desirable action as a foaming agent. | 1 | Applied and Interdisciplinary Chemistry |
The enantiopure synthesis of levopropylhexedrine may be accomplished in a two step reaction. The first step is the Wenker synthesis of the relevant aziridine. The second step is the simple catalytic hydrogenation of the propylhexedrine-aziridine. | 0 | Theoretical and Fundamental Chemistry |
2,3-Bisphosphoglycerate or 2,3-BPG (formerly named 2,3-diphosphoglycerate or 2,3-DPG) is an organophosphate formed in red blood cells during glycolysis and is the conjugate base of 2,3-bisphosphoglyceric acid. The production of 2,3-BPG is likely an important adaptive mechanism, because the production increases for several conditions in the presence of diminished peripheral tissue O availability, such as hypoxemia, chronic lung disease, anemia, and congestive heart failure, among others, which necessitate easier oxygen unloading in the peripheral tissue. High levels of 2,3-BPG shift the curve to the right (as in childhood), while low levels of 2,3-BPG cause a leftward shift, seen in states such as septic shock, and hypophosphataemia. In the absence of 2,3-BPG, hemoglobins affinity for oxygen increases. 2,3-BPG acts as a heteroallosteric effector of hemoglobin, lowering hemoglobins affinity for oxygen by binding preferentially to deoxyhemoglobin. An increased concentration of BPG in red blood cells favours formation of the T (taut or tense), low-affinity state of hemoglobin and so the oxygen-binding curve will shift to the right. | 1 | Applied and Interdisciplinary Chemistry |
In a nozzle or other constriction, the discharge coefficient (also known as coefficient of discharge or efflux coefficient) is the ratio of the actual discharge to the ideal discharge, i.e., the ratio of the mass flow rate at the discharge end of the nozzle to that of an ideal nozzle which expands an identical working fluid from the same initial conditions to the same exit pressures.
Mathematically the discharge coefficient may be related to the mass flow rate of a fluid through a straight tube of constant cross-sectional area through the following:
Where:
:, discharge coefficient through the constriction (dimensionless).
:, mass flow rate of fluid through constriction (mass per time).
:, density of fluid (mass per volume).
:, volumetric flow rate of fluid through constriction (volume per time).
:, cross-sectional area of flow constriction (area).
: , velocity of fluid through constriction (length per time).
:, pressure drop across constriction (force per area).
This parameter is useful for determining the irrecoverable losses associated with a certain piece of equipment (constriction) in a fluid system, or the "resistance" that piece of equipment imposes upon the flow.
This flow resistance, often expressed as a dimensionless parameter, , is related to the discharge coefficient through the equation:
which may be obtained by substituting in the aforementioned equation with the resistance, , multiplied by the dynamic pressure of the fluid, . | 1 | Applied and Interdisciplinary Chemistry |
The organometallic chemistry of titanium typically starts from . An important reaction involves sodium cyclopentadienyl to give titanocene dichloride, . This compound and many of its derivatives are precursors to Ziegler–Natta catalysts. Tebbe's reagent, useful in organic chemistry, is an aluminium-containing derivative of titanocene that arises from the reaction of titanocene dichloride with trimethylaluminium. It is used for the "olefination" reactions.
Arenes, such as react to give the piano-stool complexes (R = H, ; see figure above). This reaction illustrates the high Lewis acidity of the entity, which is generated by abstraction of chloride from by aluminium trichloride|. | 0 | Theoretical and Fundamental Chemistry |
Glyoxalase I, which is part of the glyoxalase system present in the cytosol, catalyzes the conversion of α-oxoaldehyde (RC(O)CHO) and the thiol glutathione (abbreviated GSH) to S-2-hydroxyacylglutathione derivatives [RCH(OH)CO-SG]. The catalytic mechanism involves an intermediate hemithioacetal adduct [RCOCH(OH)-SG]. The spontaneous reaction forms methylglyoxal-glutathione hemithioacetal and human glyoxalase I.
A hemithioacetal is also invoked in the mechanism of prenylcysteine lyase. In catalytic mechanism, S-farnesylcysteine is oxidized by a flavin to a thiocarbenium ion. The thiocarbenium ion hydrolyzes to form the hemithioacetal:
After formation, the hemithioacetal breaks into hydrogen peroxide, farnesal, and cysteine. | 0 | Theoretical and Fundamental Chemistry |
Element 43 was named masurium (after Masuria in Eastern Prussia). The group bombarded columbite with a beam of electrons and deduced element 43 was present by examining X-ray diffraction spectrograms. The wavelength of the X-rays produced is related to the atomic number by a formula derived by Henry Moseley. The team claimed to detect a faint X-ray signal at a wavelength produced by element 43. Contemporary experimenters could not replicate the discovery, and in fact it was dismissed as an error for many years.
It was not until 1998 that this dismissal began to be questioned. John T. Armstrong of the National Institute of Standards and Technology ran computer simulations of the experiments and obtained results very close to those reported by the 1925 team; the claim was further supported by work published by David Curtis of the Los Alamos National Laboratory measuring the (tiny) natural occurrence of technetium. Debate still exists as to whether the 1925 team actually did discover element 43. | 1 | Applied and Interdisciplinary Chemistry |
Flash photolysis is a pump-probe laboratory technique, in which a sample is first excited by a strong pulse of light from a pulsed laser of nanosecond, picosecond, or femtosecond pulse width or by another short-pulse light source such as a flash lamp. This first strong pulse is called the pump pulse and starts a chemical reaction or leads to an increased population for energy levels other than the ground state within a sample of atoms or molecules. Typically the absorption of light by the sample is recorded within short time intervals (by a so-called test or probe pulses) to monitor relaxation or reaction processes initiated by the pump pulse.
Flash photolysis was developed shortly after World War II as an outgrowth of attempts by military scientists to build cameras fast enough to photograph missiles in flight. The technique was developed in 1949 by Manfred Eigen, Ronald George Wreyford Norrish and George Porter, who won the 1967 Nobel Prize in Chemistry for this invention. Over the next 40 years the technique became more powerful and sophisticated due to developments in optics and lasers. Interest in this method grew considerably as its practical applications expanded from chemistry to areas such as biology, materials science, and environmental sciences. Today, flash photolysis facilities are extensively used by researchers to study light-induced processes in organic molecules, polymers, nanoparticles, semiconductors, photosynthesis in plants, signaling, and light-induced conformational changes in biological systems. | 0 | Theoretical and Fundamental Chemistry |
The Late Bronze Age remains at Norşuntepe was heavily disturbed by later Iron Age activity, but some larger buildings have been excavated. | 1 | Applied and Interdisciplinary Chemistry |
In his main work Ungar made rats choose to enter either a ligthed or a dark box. Normally nocturnal animals, upon entering the dark, rats were given an electric shock, and the rats were quickly trained to enter the lighted box. After a prolonged training, an extract was prepared from their brains, which was injected into mice which were tested in the same lighted/dark setup. By measuring time spent by the mice in the boxes, it was found that the mice injected with an extract from the treated rats could be distinguished from the ones injected with the extract from the untreated rats. | 1 | Applied and Interdisciplinary Chemistry |
Researchers work in the Chesapeake Bay to collect information about water quality, plant and animal abundances, shoreline erosion, tides, waves, and harmful algal blooms. For example, the Virginia Institute of Marine Science monitors the abundance of submerged aquatic vegetation in the shallow areas of the Chesapeake Bay each summer. Many organizations run continuous monitoring programs. Monitoring programs set out instruments at fixed stations on buoys, moorings, and docks throughout the Bay to record things like temperature, salinity, chlorophyll-a concentration, dissolved oxygen, and turbidity over time.
Organizations actively collecting data in the Chesapeake Bay include, but are not limited to:
*Chesapeake Bay National Estuarine Research Reserve in Maryland
*Chesapeake Bay National Estuarine Research Reserve in Virginia
*Chesapeake Bay Program
*Hampton Roads Sanitation District
*Maryland Department of Natural Resources
*NASA GSFC Ocean Biology group
*NASA GSFC Applied Sciences group (Water Resources and Human Health areas)
*NOAA Chesapeake Bay Office
*Old Dominion University’s Earth and Ocean Sciences Department
*Smithsonian Environmental Research Center
*United States Geological Survey
*University of Maryland Center for Environmental Science
*Virginia Department of Environmental Quality
*Virginia Department of Health
*Virginia Institute of Marine Science
*Virginia Marine Resources Commission | 1 | Applied and Interdisciplinary Chemistry |
Arsenic can cause oxidative stress through the formation of reactive oxygen species (ROS), and reactive nitrogen species (RNS). Reactive oxygen species are produced by the enzyme NADPH oxidase, which transfers electrons from NADPH to oxygen, synthesizing a superoxide, which is a reactive free radical. This superoxide can react to form hydrogen peroxide and a reactive oxygen species. The enzyme NADPH oxidase is able to generate more reactive oxygen species in the presence of arsenic, due to the subunit p22phax, which is responsible for the electron transfer, being upregulated by arsenic. The reactive oxygen species are capable of stressing the endoplasmic reticulum, which increases the amount of the unfolded protein response signals. This leads to inflammation, cell proliferation, and eventually to cell death. Another mechanism in which reactive oxygen species cause cell death would be through the cytoskeleton rearrangement, which affects the contractile proteins.
The reactive nitrogen species arise once the reactive oxygen species destroy the mitochondria. This leads to the formation of the reactive nitrogen species, which are responsible for damaging DNA in arsenic poisoning. Mitochondrial damage is known to cause the release of reactive nitrogen species, due to the reaction between superoxides and nitric oxide (NO). Nitric oxide (NO) is a part of cell regulation, including cellular metabolism, growth, division and death. Nitric oxide (NO) reacts with reactive oxygen species to form peroxynitrite. In cases of chronic arsenic exposure, the nitric oxide levels are depleted, due to the superoxide reactions. The enzyme NO synthase (NOS) uses L-arginine to form nitric oxide, but this enzyme is inhibited by monomethylated arsenic (III) compounds. | 1 | Applied and Interdisciplinary Chemistry |
Torricellis law, also known as Torricellis theorem, is a theorem in fluid dynamics relating the speed of fluid flowing from an orifice to the height of fluid above the opening. The law states that the speed of efflux of a fluid through a sharp-edged hole at the bottom of the tank filled to a depth is the same as the speed that a body would acquire in falling freely from a height , i.e. , where is the acceleration due to gravity. This expression comes from equating the kinetic energy gained, , with the potential energy lost, , and solving for . The law was discovered (though not in this form) by the Italian scientist Evangelista Torricelli, in 1643. It was later shown to be a particular case of Bernoulli's principle. | 1 | Applied and Interdisciplinary Chemistry |
Gessner et al. first revealed a synthetic route for stabilized ketenyl anion using metalated ylides in 2022. In their paper, upon introducing CO, metalated ylide with posassium cation exchange CO with phosphine group R, also known for carbonylation of ylide. Their isolated ketenyl anion [K(PPh(=S)CCO] is stable solid for a week under inert atmosphere, and its crystal structure was characterized. An alternate synthetic pathway for synthesizing ketenyl anion from ylide, shown in Figure 2, includes sulfuration on diphenylphosphine group, deprotonation on carbon center, and CO substitution in exchange of triphenylphosphine leaving. This synthesis resulted in 88% isolation of the product. Later in their studies, the ketenyl anion product upon carbonylation can be selective by changing electron-withdrawing ability on a certain leaving group and Lewis acidity of coordinated alkali metal cation. In their example with ylide containing phosphine group and tosyl group (Ts), Gessner et al. was able to produce the ketenyl anion product more selective by modifying those parameters, shown in Figure 2. As R group is more electron-withdrawing group, it becomes more likely to leave than tosyl group. For example, changing R group from cyclohexyl group (Cy) to phenyl group (Ph) favored the ketenyl anion product with R group leaving by 76%. This is because phenyl group is less electron rich and less nucleophilic compared to cyclohexyl group, resulting in more stable by itself. For alkali metal cation trend, when triphenylphosphine group is present, changing from M = Li to M = K favored in phosphine group leaving by 9%. Although it is a small effect compared to leaving group effect, this is due to Lewis acidity on metal cations because a stronger Lewis acidic metal cation (Li > K in Lewis acidity) attracts tosyl group to interact, resulting in increasing leaving group ability.
Inoue et al. presented synthetic route of stabilizing ketene via silica-carbonyl anion, silicon analogue of ketene. They motivated this goals from recent reactivity study of silylene and disilane activating CO and isolating intermediate, hypothesizing that silica-ketenyl anion is also capable to stabilize ketene. While Gessner et al. uses ylides to accept CO, Inoue et al. uses silylene anion with another silyl group substituted to afford insertion of CO or carbonylation at room temperature in exchange of silyl group.
Liu et al. had another approach to stabilize and isolate ketene by using carbene coordinated by phosphinidene. Carbene coordinated by 2,6-diisopropylphenyl(Dipp)-substituted phosphinidene and dinitrogen (N) perform N/CO ligand exchange. The starting material is similar to N-heterocyclic carbene with bulky substituents, invented by Bertrand. In their studies, this reaction is concerted and thermodynamically favorable (-47.4 kcal/mol relative to N-coordinated carbene) on coordinating CO ligand to NHC. This product is stable at room temperature inert atmosphere for a month, and no decomposition while heating in THF at 80 °C for 12 hours was observed. | 0 | Theoretical and Fundamental Chemistry |
The correct (extensive) formulas for systems A and B were obtained because we included all the possible ways that the two systems could exchange particles. The use of combinations (i.e. N particles choose N) was used to ascertain the number of ways N particles can be divided into system A containing n particles and system B containing n particles. This counting is not justified on physical grounds, but on the need to integrate over phase space. As will be illustrated below, phase space contains not a single n-sphere and a single n-sphere, but instead
pairs of n-spheres, all situated in the same -dimensional velocity space. The integral over accessible phase space must include all of these n-spheres, as can be seen in the figure, which shows the actual velocity phase space associated with a gas that consists of three particles. Moreover, this gas has been divided into two systems, A and B.
If we ignore the spatial variables, the phase space of a gas with three particles is three dimensional, which permits one to sketch the n-spheres over which the integral over phase space must be taken. If all three particles are together, the split between the two gases is 3|0. Accessible phase space is delimited by an ordinary sphere (2-sphere) with a radius that is either or (depending which system has the particles).
If the split is 2|1, then phase space consists of circles and points. Each circle occupies two dimensions, and for each circle, two points lie on the third axis, equidistant from the center of the circle. In other words, if system A has 2 particles, accessible phase space consists of 3 pairs of n-spheres, each pair being a 1-sphere and a 0-sphere:
Note that | 0 | Theoretical and Fundamental Chemistry |
One of the methods of synthesis is the reaction of direct neutralization of oxalic acid with lithium hydroxide: | 0 | Theoretical and Fundamental Chemistry |
Lappert was born in Czechoslovakia and came to the UK as a Kindertransport refugee. He received his PhD in 1951 at the Northern Polytechnic, London. | 0 | Theoretical and Fundamental Chemistry |
Chetsanga was born in Murewa, Zimbabwe on 22 August 1935, and was baptised in 1948. In his youth, he was educated at Nhowe Mission, and went on to study at University of California, Berkeley where he received his BSc in 1965. Chetsanga also studied for a period at Pepperdine University. In 1969, he received his MSc and PhD in biochemistry and molecular biology from University of Toronto before becoming a post doctoral fellow at Harvard University between 1969 and 1972. Between 1972 and 1983 he became a professor at the University of Michigan, then in 1983 he left to become the senior lecturer in Biochemistry for University of Zimbabwe. In 1990, President Robert Mugabe awarded him President’s Award for Distinguished Contribution to Science and Technology. Has also awarded the Order of the Star of Zimbabwe. He is presently the vice chancellor at Zimbabwe Ezekiel Guti University.
In 2004, when the Zimbabwe Academy of Sciences was formed, Chetsanga was appointed the first president of the academy. Chetsanga advocated the use of genetically modified food sources as a possible solution for food shortages in Africa in 2020. | 1 | Applied and Interdisciplinary Chemistry |
In mixed inhibition the inhibitor may bind to the enzyme whether or not the substrate has already bound. Hence mixed inhibition is a combination of competitive and noncompetitive inhibition. Furthermore, the affinity of the inhibitor for the free enzyme and the enzyme-substrate complex may differ. By increasing concentrations of substrate [S], this type of inhibition can be reduced (due to the competitive contribution), but not entirely overcome (due to the noncompetitive component). Although it is possible for mixed-type inhibitors to bind in the active site, this type of inhibition generally results from an allosteric effect where the inhibitor binds to a different site on an enzyme. Inhibitor binding to this allosteric site changes the conformation (that is, the tertiary structure or three-dimensional shape) of the enzyme so that the affinity of the substrate for the active site is reduced.
These four types of inhibition can also be distinguished by the effect of increasing the substrate concentration [S] on the degree of inhibition caused by a given amount of inhibitor. For competitive inhibition the degree of inhibition is reduced by increasing [S], for noncompetitive inhibition the degree of inhibition is unchanged, and for uncompetitive (also called anticompetitive) inhibition the degree of inhibition increases with [S]. | 1 | Applied and Interdisciplinary Chemistry |
When we stretch a piece of rubber, e.g. a rubber band, we notice that it deforms uniformly, lengthwise. Every element along its length experiences the same extension factor as the entire sample. If we release one end, the sample snaps back to its original length very rapidly, too fast for our eye to resolve the process. Our intuitive expectation is that it returns to its original length in the same manner as when it was stretched, i. e. uniformly. However, this is not what happens. Experimental observations by Mrowca et al. show a surprising behavior. To capture the extremely fast retraction dynamics, they utilized a clever experimental method devised by Exner and Stefan in 1874, well before high-speed electronic measuring devices were invented. Their method consisted of a rapidly rotating glass cylinder which, after being coated with lamp black, was placed next to the stretched rubber sample. Styli, attached to the mid-point and free end of the rubber sample, were held in contact with the glass cylinder. Then, as the free end of the rubber snapped back, the styli traced out helical paths in the lamp black coating of the rotating cylinder. By adjusting the rotation speed of the cylinder, they could record the position of the styli in less than one complete rotation. The trajectories were transferred to a graph by rolling the cylinder on a piece of damp blotter paper. The mark left by a stylus appeared as a white line (no lamp black) on the paper.
Their data, plotted as the graph in Fig. 5, shows the position of end and midpoint styli as the sample rapidly retracts to its original length. The sample was initially stretched 9.5” beyond its unstrained length and then released. The styli returned to their original positions (displacement of 0”) in a little over 6 ms. The linear behavior of the displacement vs. time indicates that, after a brief acceleration, both the end and the midpoint of the sample snapped back at a constant velocity of about 50 m/s or 112 mph. However, the midpoint stylus did not start to move until about 3 ms after the end was released. Evidently, the retraction process travels as a wave, starting at the free end.
At high extensions some of the energy stored in the stretched network chain is due to a change in its entropy, but most of the energy is stored in bond distortions (regime II, above) which do not involve an entropy change. If one assumes that all of the stored energy is converted to kinetic energy, the retraction velocity may be calculated directly from the familiar conservation equation E = mv. Numerical simulations, based on the Molecular Kink paradigm, predict velocities consistent with this experiment. | 0 | Theoretical and Fundamental Chemistry |
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