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Marine outfalls for partially treated or untreated wastewater remain controversial. The design calculation and computer models for pollution modeling have been criticized, arguing that dilution has been overemphasized and that other mechanisms work in the opposite direction, such as bioaccumulation of toxins, sedimentation of sludge particles and agglomeration of sewage particles with grease. Accumulative mechanisms include slick formation, windrow formation, flocculate formation and agglomerated formation. Grease or wax can interfere with dispersion, so that bacteria and viruses could be carried to remote locations where the concentration of bacterial predators would be low and the die-off rate much lower. | 1 | Applied and Interdisciplinary Chemistry |
Bottles of di-tert-butyl dicarbonate buildup of internal pressure in sealed containers caused by its slow decomposition to di-tert-butyl carbonate and ultimately tert-butanol and CO in the presence of moisture. For this reason, it is usually sold and stored in plastic bottles rather than glass ones.
The main hazard of the reagent is its inhalational toxicity. Its median lethal concentration of 100 mg/m over 4 hours in rats is comparable to that of phosgene (49 mg/m over 50 min in rats). | 0 | Theoretical and Fundamental Chemistry |
The structure of P700 consists of a heterodimer with two distinct chlorophyll molecules, most notably chlorophyll a and chlorophyll a’, giving it an additional name of “special pair”. Inevitably, however, the special pair of P700 behaves as if it were just one unit. This species is vital due to its ability to absorb light energy with a wavelength approximately between 430 nm-700 nm, and transfer high-energy electrons to a series of acceptors that are situated near it, like Fe-S complex, Ferridoxyn(FD), which have a . | 0 | Theoretical and Fundamental Chemistry |
Ben Goldacre has argued that regulators – such as the Medicines and Healthcare products Regulatory Agency (MHRA) in the UK, or the Food and Drug Administration (FDA) in the United States – advance the interests of the drug companies rather than the interests of the public due to revolving door exchange of employees between the regulator and the companies and friendships develop between regulator and company employees. He argues that regulators do not require that new drugs offer an improvement over what is already available, or even that they be particularly effective.
Others have argued that excessive regulation suppresses therapeutic innovation and that the current cost of regulator-required clinical trials prevents the full exploitation of new genetic and biological knowledge for the treatment of human disease. A 2012 report by the Presidents Council of Advisors on Science and Technology made several key recommendations to reduce regulatory burdens to new drug development, including 1) expanding the FDAs use of accelerated approval processes, 2) creating an expedited approval pathway for drugs intended for use in narrowly defined populations, and 3) undertaking pilot projects designed to evaluate the feasibility of a new, adaptive drug approval process. | 1 | Applied and Interdisciplinary Chemistry |
The overall reaction catalyzed by ETF-QO is as follows:
ETF-QO(red) + ubiquinone ↔ ETF-QO(ox) + ubiquinol
Enzymatic activity is usually assayed spectrophotometrically by reaction with octanoyl-CoA as the electron donor and ubiquinone-1 as the electron acceptor. The enzyme can also be assayed via disproportionation of ETF semiquinone. Both reactions are below:
Octanoyl-CoA + Q ↔ QH + Oct-2-enoyl-CoA
2 ETF ↔ ETF + ETF | 1 | Applied and Interdisciplinary Chemistry |
There are a number of natural products with neurotrophic activity, which results from several mechanisms including enhancing BDNF gene transcription, upregulating the expression of BDNF and TrkB, and extracellular signal-regulated kinase (ERK) and CREB signalling.
The first discovered non-protein neurotrophic natural product was lactacystin, isolated from a culture broth of Streptomyces sp. Magnolol and honokiol, the main constituents of Magnolia officinalis and Magnolia obovata stem bark, have been reported to have neurotrophic activity in primary cultured rat cortical by enhancing the BDNF expression. Merrilactone A, jiadifenin, jiadifenolide, (1R,10S)-2-oxo-3,4-dehydroxyneomajucin, jiadifenoxolane A, (2R)-hydroxynorneomajucin, 11-O-debenzoyltashironin,tricycloillicinone, and bicycloillicinone, natural products of the Illicium family have been shown to promote neurite outgrowth in primary cultures of cortical neurons of fetal rats. Neurotrophic properties are also possessed by several members of the Lycopodium alkaloids (huperzine A, lyconadins, complanadine A and B, and nankakurine A and B). Studies have shown that huperazine A can elevate the levels of NGF and BDNF. Synthesis of NGF can be upregulated by administration of cyathanediterpenoids specifically erinacines, scabronines and cyrneines.
Some flavonoids, Isoflavonoids and neoflavonoids were found to have neuroprotective activity. Among the effective flavonoids, luteolin from Lonicera japonica sp., isorhamnetin from Opuntia ficus-indica, genistein from Genista tinctoria, and calycosin from Astragalus membranaceus showed the most promising effects by increasing the mRNA expression and protein secretion of NGF, GDNF, and BDNF. Paecilomycine A and spirotenuipesines A and B, members of the trichothecenes, isolated from the fruiting bodies of Paecilomycestenuipes, have significant neurotrophic profiles especially paecilomycine A which can stimulate the synthesis of neurotrophic factors. Polyprenylatedacylphloroglucinols (PPAPs) represented by hyperforin, hypericin and garsubellin A, have neurotrophic like properties. Hyperforin, isolated from the herb St. Johns wort (Hypericum perforatum'), can stimulate the upregulation of the TrkB receptor.
Beside natural products, there are some small molecules of natural origin that exert neurotrophic activities such as: Panaxytriol (promotes NGF-induced neurite outgrowth in PC-12 cells); 7,8-dihydroxyflavone (TrkB activator); Deoxygedunin (BDNF mimetic); Kansuinin E (promotes neurotrophic activity, most likely through TrkA activation); Tripchlorolide (stimulates expression of BDNF mRNA); Fucoxanthin (increases BDNF production and activates PKA/CREB pathway); Silibinin (Activate hippocampal ROS-BDNF-TrkB patway). | 1 | Applied and Interdisciplinary Chemistry |
Isadore Perlman (April 12, 1915 – August 3, 1991) was an American nuclear chemist noted for his research of Alpha particle decay.
The National Academy of Sciences called Perlman "a world leader on the systematics of alpha decay".
He was also recognized for his research of nuclear structure of the heavy elements.
He was also noted for his isolation of Curium,
as well as for fission of tantalum, bismuth, lead, thallium and platinum.
Perlman discovered uses of radioactive iodine and phosphorus for medical purposes.
He played a key role in Manhattan Project's plutonium production. | 0 | Theoretical and Fundamental Chemistry |
In quantum mechanics, ionized impurity scattering is the scattering of charge carriers by ionization in the lattice. The most primitive models can be conceptually understood as a particle responding to unbalanced local charge that arises near a crystal impurity; similar to an electron encountering an electric field. This effect is the mechanism by which doping decreases mobility.
In the current quantum mechanical picture of conductivity the ease with which electrons traverse a crystal lattice is dependent on the near perfectly regular spacing of ions in that lattice. Only when a lattice contains perfectly regular spacing can the ion-lattice interaction (scattering) lead to almost transparent behavior of the lattice. Impurity atoms in a crystal have an effect similar to thermal vibrations where conductivity has a direct relationship with temperature.
A crystal with impurities is less regular than a pure crystal, and a reduction in electron mean free paths occurs. Impure crystals have lower conductivity than pure crystals with less temperature sensitivity in that lattice. | 0 | Theoretical and Fundamental Chemistry |
*Albert Brahms (1692–1758)
*Antoine de Chézy (1718–1798)
*Henry Darcy (1803–1858)
*Julius Ludwig Weisbach (1806-1871)
*Robert Manning (1816–1897)
*Wilhelm Rudolf Kutter (1818–1888)
*Henri Bazin (1843–1917)
*Ludwig Prandtl (1875–1953)
*Paul Richard Heinrich Blasius (1883–1970)
*Albert Strickler (1887–1963)
*Cyril Frank Colebrook (1910–1997) | 1 | Applied and Interdisciplinary Chemistry |
Pheromone programs are most effective when controlling low to moderate pest population densities. MD has also been identified as a pest control method in which the insect does not become resistant. The scientific community, together with governmental agencies throughout the world, understands the benefits of mating disruption using species-specific sex pheromones, and consider sex-pheromone-based insect control programs among the most environmentally friendly treatments to be used to manage and control insect pest populations. Insect pheromone has been successfully used as an effective tool to slow the spread and to eradicate pests from very large areas in the US; for example to control the spongy moth (Lymantria dispar), a devastating forestry pest, and to eradicate the boll weevil and pink bollworm, two of the most damaging pest of cotton. Conventional pesticide based control methods, kill insects directly, whereas mating disruption confuses male insects from accurately locating a mating partner, leading to the eventual collapse of the mating cycle. Mating disruption, due to the specificity of the sex pheromone of the insect species, has the benefit of only affecting the males of that species, while leaving other non target species unaffected. This allows for very targeted pest management, promoting the suppression of a single pest species, leaving the populations of beneficial insects (pollinators and natural enemies) intact. Mating disruption, like most pest management strategies, is a useful technique, but should not be considered a stand-alone treatment program for it targets only a single species in plant production systems that usually have several pests of concern. Mating disruption is a valuable tool that should be used in Integrated Pest Management(IPM) programs.
Pheromone programs have been used for several decades around the globe and to date (2009) there is no documented public health evidence to suggest that agricultural use of synthetic pheromones is harmful to humans or to any other non-target species. However, continuing research is being conducted. | 1 | Applied and Interdisciplinary Chemistry |
Cyclic salt is salt that is carried by the wind when it comes in contact with breaking waves. It is estimated that more than 300 million tons of cyclic salt is deposited on the Earths surface each year, and it is considered to be a significant factor in the chlorine content of the Earths river water. In general, cyclic salt deposits are lower at sites further inland and are most abundant along the shoreline, although this pattern varies depending on the given environmental conditions.
Use of the term "cyclic" refers to the cycle in which the salt moves from sea to land and is then washed by rainwater back to the sea. The salt (and other solid matter) cannot evaporate as water does. Instead it leaves the ocean surface in fine droplets of drop impacts or bubble bursts. Wave-crests and other turbulence form foam. When drops splash or bubbles burst, fine droplets of solute are ejected from the water or bubble surface into the air. Some of the droplets are small enough to allow the water to evaporate before it falls back into the sea, leaving in the air a mote of the light enough to stay suspended by Brownian motion and be carried away on the wind. | 0 | Theoretical and Fundamental Chemistry |
Above the interface between the liquid and the surface, the pressure is equal to the atmospheric pressure . At the meniscus interface, due to the surface tension, there is a pressure difference of , where is the pressure on the convex side; and is known as Laplace pressure. If the tube has a circular section of radius , and the meniscus has a spherical shape, the radius of curvature is , where is the contact angle. The Laplace pressure is then calculated according to the Young-Laplace equation:where is the surface tension. | 1 | Applied and Interdisciplinary Chemistry |
Spectrometers are kept at a very low temperature using helium as the coolant. This allows for minimal background flux in far-infrared readings. Some of the designs for the spectrometers may be simple, but even the frame is at its warmest less than 20 Kelvin. These devices are not commonly used as it is very expensive to use superfluid helium over other coolants.
Superfluid helium has a very high thermal conductivity, which makes it very useful for cooling superconductors. Superconductors such as the ones used at the LHC (Large Hadron Collider) are cooled to temperatures of approximately 1.9 Kelvin. This temperature allows the niobium-titanium magnets to reach a superconductor state. Without the use of the superfluid helium, this temperature would not be possible. Using helium to cool to these temperatures is very expensive and cooling systems that use alternative fluids are more numerous.
Another application of the superfluid helium is its uses in understanding quantum mechanics. Using lasers to look at small droplets allows scientists to view behaviors that may not normally be viewable. This is due to all the helium in each droplet being at the same quantum state. This application does not have any practical uses by itself, but it helps us better understand quantum mechanics which has its own applications. | 1 | Applied and Interdisciplinary Chemistry |
Data resulting from toxicity studies that is integrated in to the ECOTOX database is subjected to a screening and quality assurance criteria developed by the EPA and the Office of Pesticide Programs (OPP). In order for study results to be accepted by the EPA and OPP the toxicity study must follow or consist of the following:
* The toxic effects are related to single chemical exposure;
* The toxic effects are on an aquatic or terrestrial plant or animal species;
* There is a biological effect on live, whole organisms;
* A concurrent environmental chemical concentration/dose or application rate is reported; and
* There is an explicit duration of exposure.
In addition to the criteria listed above, the following criteria, which are discussed in further detail in Attachment I, are applied by OPP as a further screen of acceptability:
* Toxicology information is reported for a chemical of concern to OPP;
* The article is published in the English language;
* The study is presented as a full article;
* The paper is a publicly available document;
* The paper is the primary source of the data
* A calculated endpoint is reported;
* Treatment(s) are compared to an acceptable control;
* The location of the study (e.g., laboratory vs. field) is reported; and
* The tested species is reported and verified. | 1 | Applied and Interdisciplinary Chemistry |
A catalyst's function is to increase the speed of the electron transfer (redox) reaction. Plastocyanin is believed to work less like an enzyme where enzymes decrease the transition energy needed to transfer the electron. Plastocyanin works more on the principles of entatic states where it increases the energy of the reactants, decreasing the amount of energy needed for the redox reaction to occur. Another way to rephrase the function of plastocyanin is that it can facilitate the electron transfer reaction by providing a small reorganization energy, which has been measured to about .
To study the properties of the redox reaction of plastocyanin, methods such as quantum mechanics / molecular mechanics (QM/MM) molecular dynamics simulations. This method was used to determine that plastocyanin has an entatic strain energy of about .
Four-coordinate copper complexes often exhibit square planar geometry, however plastocyanin has a trigonally distorted tetrahedral geometry. This distorted geometry is less stable than ideal tetrahedral geometry due to its lower ligand field stabilization as a result of the trigonal distortion. This unusual geometry is induced by the rigid “pre-organized” conformation of the ligand donors by the protein, which is an entatic state. Plastocyanin performs electron transfer with the redox between Cu(I) and Cu(II), and it was first theorized that its entatic state was a result of the protein imposing an undistorted tetrahedral geometry preferred by ordinary Cu(I) complexes onto the oxidized Cu(II) site. However, a highly distorted tetrahedral geometry is induced upon the oxidized Cu(II) site instead of a perfectly symmetric tetrahedral geometry. A feature of the entatic state is a protein environment that is capable of preventing ligand dissociation even at a high enough temperature to break the metal-ligand bond. In the case of plastocyanin, it has been experimentally determined through absorption spectroscopy that there is a long and weak Cu(I)-S bond that should dissociate at physiological temperature due to increased entropy. However, this bond does not dissociate due to the constraints of the protein environment dominating over the entropic forces.
In ordinary copper complexes involved in Cu(I)/Cu(II) redox coupling without a constraining protein environment, their ligand geometry changes significantly, and typically corresponds to the presence of a Jahn-Teller distorting force. However, the Jahn-Teller distorting force is not present in plastocyanin due to a large splitting of the d and d orbitals (See Blue Copper Protein Entatic State). Additionally, the structure of plastocyanin exhibits a long Cu(I)-S bond (2.9Å) with decreased electron donation strength. This bond also shortens the Cu(I)-S bond (2.1Å), increasing its electron donating strength. Overall, plastocyanin exhibits a lower reorganization energy due to the entatic state of the protein ligand enforcing the same distorted tetrahedral geometry in both the Cu(II) and Cu(I) oxidation states, enabling it to perform electron transfer at a faster rate. The reorganization energy of blue copper proteins such as plastocyanin from 0.7 to 1.2 eV (68-116 kJ/mol) compared to 2.4 eV (232 kJ/mol) in an ordinary copper complex such as [Cu(phen)]. | 0 | Theoretical and Fundamental Chemistry |
The danger of radiation from fallout also decreases rapidly with time due in large part to the exponential decay of the individual radionuclides. A book by Cresson H. Kearny presents data showing that for the first few days after the explosion, the radiation dose rate is reduced by a factor of ten for every seven-fold increase in the number of hours since the explosion. He presents data showing that "it takes about seven times as long for the dose rate to decay from 1000 roentgens per hour (1000 R/hr) to 10 R/hr (48 hours) as to decay from 1000 R/hr to 100 R/hr (7 hours)." This is a rule of thumb based on observed data, not a precise relation. | 0 | Theoretical and Fundamental Chemistry |
Also in 2006 the group of Masakatsu Shibasaki of the University of Tokyo published a synthesis again bypassing shikimic acid.
An improved method published in 2007 starts with the enantioselective desymmetrization of aziridine 1 with trimethylsilyl azide (TMSN) and a chiral catalyst to the azide 2. The amide group is protected as a BOC group with Boc anhydride and DMAP in 3 and iodolactamization with iodine and potassium carbonate first gives the unstable intermediate 4 and then stable cyclic carbamate 5 after elimination of hydrogen iodide with DBU.
The amide group is reprotected as BOC 6 and the azide group converted to the amide 7 by reductive acylation with thioacetic acid and 2,6-lutidine. Caesium carbonate accomplishes the hydrolysis of the carbamate group to the alcohol 8 which is subsequently oxidized to ketone 9 with Dess-Martin periodinane. Cyanophosphorylation with diethyl phosphorocyanidate (DEPC) modifies the ketone group to the cyanophosphate 10 paving the way for an intramolecular allylic rearrangement to unstable β-allyl phosphate 11 (toluene, sealed tube) which is hydrolyzed to alcohol 12 with ammonium chloride. This hydroxyl group has the wrong stereochemistry and is therefore inverted in a Mitsunobu reaction with p-nitrobenzoic acid followed by hydrolysis of the p-nitrobenzoate to 13.
A second Mitsunobu reaction then forms the aziridine 14 available for ring-opening reaction with 3-pentanol catalyzed by boron trifluoride to ether 15. In the final step the BOC group is removed (HCl) and phosphoric acid added to objective 16. | 0 | Theoretical and Fundamental Chemistry |
Pervious concrete has a common strength of though strengths up to can be reached. There is no standardized test for compressive strength. Acceptance is based on the unit weight of a sample of poured concrete using ASTM standard no. C1688. An acceptable tolerance for the density is plus or minus of the design density. Slump and air content tests are not applicable to pervious concrete because of the unique composition. The designer of a storm water management plan should ensure that the pervious concrete is functioning properly through visual observation of its drainage characteristics prior to opening of the facility. | 1 | Applied and Interdisciplinary Chemistry |
The developers of Ion Torrent semiconductor sequencing have marketed it as a rapid, compact and economical sequencer that can be utilized in a large number of laboratories as a bench top machine. The company hopes that their system will take sequencing outside of specialized centers and into the reach of hospitals and smaller laboratories. A January 2011 New York Times article, [https://www.nytimes.com/2011/01/05/health/05gene.html?pagewanted=1&_r=1&ref=hospitals "Taking DNA Sequencing to the Masses"], underlines these ambitions.
Due to the ability of alternative sequencing methods to achieve a greater read length (and therefore being more suited to whole genome analysis) this technology may be best suited to small scale applications such as microbial genome sequencing, microbial transcriptome sequencing, targeted sequencing, amplicon sequencing, or for quality testing of sequencing libraries. | 1 | Applied and Interdisciplinary Chemistry |
Marine debris and marine aerosols refer to particulates suspended in a liquid, usually water on the Earth's surface. Particulates in water are a kind of water pollution measured as total suspended solids, a water quality measurement listed as a conventional pollutant in the U.S. Clean Water Act, a water quality law. Notably, some of the same kinds of particles can be suspended both in air and water, and pollutants specifically may be carried in the air and deposited in water, or fall to the ground as acid rain. The majority of marine aerosols are created through the bubble bursting of breaking waves and capillary action on the ocean surface due to the stress exerted from surface winds. Among common marine aerosols, pure sea salt aerosols are the major component of marine aerosols with an annual global emission between 2,000-10,000 teragrams annually. Through interactions with water, many marine aerosols help to scatter light, and aid in cloud condensation and ice nuclei (IN); thus, affecting the atmospheric radiation budget. When they interact with anthropogenic pollution, marine aerosols can affect biogeochemical cycles through the depletion of acids such as nitric acid and halogens. | 1 | Applied and Interdisciplinary Chemistry |
TRMS is typically implemented to monitor processes that occur on second to millisecond time scale. However, there exist reports from studies in which sub-millisecond resolutions were achieved. | 1 | Applied and Interdisciplinary Chemistry |
After the reactants have been weighed out in the required amounts, they are mixed. For manual mixing of small quantities, usually an agate mortar and pestle are employed. Sufficient amount of some volatile organic liquid – preferably acetone or alcohol – is added to the mixture to aid homogenization. This forms a paste which is mixed thoroughly. During the process of grinding and mixing, the organic liquid gradually volatilizes and has usually evaporated completely after 10 to 15 minutes. For quantities much larger than ~20g, mechanical mixing is usually adopted using a ball mill and the pro | 1 | Applied and Interdisciplinary Chemistry |
RNA Pol II elongation promoters can be summarised in three classes:
# Drug/sequence-dependent arrest affected factors, e.g., SII (TFIIS) and P-TEFb protein families.
# Chromatin structure oriented factors. Based on histone post translational modifications – phosphorylation, acetylation, methylation and ubiquination.
#: See: chromatin, histone, and nucleosome
# RNA Pol II catalysis improving factors. Improve the Vmax or Km of RNA Pol II, so improving the catalytic quality of the polymerase enzyme. E.g. TFIIF, Elongin and ELL families.
#: See: Enzyme kinetics, Henri–Michaelis–Menten kinetics, Michaelis constant, and Lineweaver–Burk plot
As for initiation, protein interference, seen as the "drug/sequence-dependent arrest affected factors" and "RNA Pol II catalysis improving factors" provide a very rapid response and is used for fine level individual gene control. Elongation downregulation is also possible, in this case usually by blocking polymerase progress or by deactivating the polymerase.
Chromatin structure-oriented factors are more complex than for initiation control. Often the chromatin-altering factor becomes bound to the polymerase complex, altering the histones as they are encountered and providing a semi-permanent memory of previous promotion and transcription. | 1 | Applied and Interdisciplinary Chemistry |
A wide range of cellular secretions (say, a specific antibody or cytokine) can be detected using the ELISA technique. The number of cells which secrete those particular substances can be determined using a related technique, the ELISPOT assay. | 1 | Applied and Interdisciplinary Chemistry |
According to the label on consumer products TarnX and Silver Dip, the liquid silver cleaning products contain thiourea along with a warning that thiourea is a chemical on California's list of carcinogens. A lixiviant for gold and silver leaching can be created by selectively oxidizing thiourea, bypassing the steps of cyanide use and smelting. | 0 | Theoretical and Fundamental Chemistry |
The definitions of VOCs used for control of precursors of photochemical smog used by the U.S. Environmental Protection Agency (EPA) and state agencies in the US with independent outdoor air pollution regulations include exemptions for VOCs that are determined to be non-reactive, or of low-reactivity in the smog formation process. Prominent is the VOC regulation issued by the South Coast Air Quality Management District in California and by the California Air Resources Board (CARB). However, this specific use of the term VOCs can be misleading, especially when applied to indoor air quality because many chemicals that are not regulated as outdoor air pollution can still be important for indoor air pollution.
Following a public hearing in September 1995, Californias ARB uses the term "reactive organic gases" (ROG) to measure organic gases. The CARB revised the definition of "Volatile Organic Compounds" used in their consumer products regulations, based on the committees findings.
In addition to drinking water, VOCs are regulated in pollutant discharges to surface waters (both directly and via sewage treatment plants) as hazardous waste, but not in non-industrial indoor air. The Occupational Safety and Health Administration (OSHA) regulates VOC exposure in the workplace. Volatile organic compounds that are classified as hazardous materials are regulated by the Pipeline and Hazardous Materials Safety Administration while being transported. | 0 | Theoretical and Fundamental Chemistry |
One study in mice demonstrated dose-related carcinogenic potential at several different organ sites. The Food and Drug Administration in the US (FDA) has determined that gentian violet has not been shown by adequate scientific data to be safe for use in animal feed. Use of gentian violet in animal feed causes the feed to be adulterated and is a violation of the Federal Food, Drug, and Cosmetic Act in the US. On June 28, 2007, the FDA issued an "import alert" on farm raised seafood from China because unapproved antimicrobials, including gentian violet, had been consistently found in the products. The FDA report states:
"Like MG (malachite green), CV (crystal violet) is readily absorbed into fish tissue from water exposure and is reduced metabolically by fish to the leuco moiety, leucocrystal violet (LCV). Several studies by the National Toxicology Program reported the carcinogenic and mutagenic effects of crystal violet in rodents. The leuco form induces renal, hepatic and lung tumor in mice."
Health Canada recently found medical devices that use gentian violet to be safe for use but recommended to stop using all drug products that contain gentian violet, including on animals, causing Canadian engineering schools to revisit the usage of this dye during orientation. | 0 | Theoretical and Fundamental Chemistry |
The catalytically active species is the anions cis-[Rh(CO)I] (top of scheme). The first organometallic step is the oxidative addition of methyl iodide to cis-[Rh(CO)I] to form the hexacoordinate species [(CH)Rh(CO)I]. This anion rapidly transforms, via the migration of a methyl group to an adjacent carbonyl ligand, affording the pentacoordinate acetyl complex [(CHCO)Rh(CO)I]. This five-coordinate complex then reacts with carbon monoxide to form the six-coordinate dicarbonyl complex, which undergoes reductive elimination to release acetyl iodide (CHC(O)I). The catalytic cycle involves two non-organometallic steps: conversion of methanol to methyl iodide and the hydrolysis of the acetyl iodide to acetic acid and hydrogen iodide.
The reaction has been shown to be first-order with respect to methyl iodide and [Rh(CO)I]. Hence the oxidative addition of methyl iodide is proposed as the rate-determining step. | 0 | Theoretical and Fundamental Chemistry |
The primary physical advantage of thorium fuel is that it uniquely makes possible a breeder reactor that runs with slow neutrons, otherwise known as a thermal breeder reactor. These reactors are often considered simpler than the more traditional fast-neutron breeders. Although the thermal neutron fission cross section (σ) of the resulting is comparable to and , it has a much lower capture cross section (σ) than the latter two fissile isotopes, providing fewer non-fissile neutron absorptions and improved neutron economy. The ratio of neutrons released per neutron absorbed (η) in is greater than two over a wide range of energies, including the thermal spectrum. A breeding reactor in the uranium–plutonium cycle needs to use fast neutrons, because in the thermal spectrum one neutron absorbed by on average leads to less than two neutrons.
Thorium is estimated to be about three to four times more abundant than uranium in Earth's crust, although present knowledge of reserves is limited. Current demand for thorium has been satisfied as a by-product of rare-earth extraction from monazite sands. Notably, there is very little thorium dissolved in seawater, so seawater extraction is not viable, as it is with uranium. Using breeder reactors, known thorium and uranium resources can both generate world-scale energy for thousands of years.
Thorium-based fuels also display favorable physical and chemical properties that improve reactor and repository performance. Compared to the predominant reactor fuel, uranium dioxide (), thorium dioxide () has a higher melting point, higher thermal conductivity, and lower coefficient of thermal expansion. Thorium dioxide also exhibits greater chemical stability and, unlike uranium dioxide, does not further oxidize.
Because the produced in thorium fuels is significantly contaminated with in proposed power reactor designs, thorium-based used nuclear fuel possesses inherent proliferation resistance. cannot be chemically separated from and has several decay products that emit high-energy gamma radiation. These high-energy photons are a radiological hazard that necessitate the use of remote handling of separated uranium and aid in the passive detection of such materials.
The long-term (on the order of roughly to ) radiological hazard of conventional uranium-based used nuclear fuel is dominated by plutonium and other minor actinides, after which long-lived fission products become significant contributors again. A single neutron capture in is sufficient to produce transuranic elements, whereas five captures are generally necessary to do so from . 98–99% of thorium-cycle fuel nuclei would fission at either or , so fewer long-lived transuranics are produced. Because of this, thorium is a potentially attractive alternative to uranium in mixed oxide (MOX) fuels to minimize the generation of transuranics and maximize the destruction of plutonium. | 0 | Theoretical and Fundamental Chemistry |
Wood flour is commonly used as a filler in thermosetting resins such as bakelite, and in linoleum floor coverings. Wood flour is also the main ingredient in wood/plastic composite building products such as decks and roofs. Prior to 1920, wood flour was used as the filler in ¼-inch thick Edison Diamond Discs.
Wood flour has found a use in plugging small through-wall holes in leaking main condenser (heat exchanger) tubes at electrical power generating stations via injecting small quantities of the wood flour into the cooling water supply lines. Some of the injected wood flour clogs the small holes while the remainder exits the station in a relatively environmentally benign fashion.
Because of its adsorbent properties it has been used as a cleaning agent for removing grease or oil in various occupations. It has also been noted for its ability to remove lead contamination from water.
Wood flour can be used as a binder in grain filler compounds. | 1 | Applied and Interdisciplinary Chemistry |
The nomenclature is based on [n × m] G, n corresponds to the number of ligands above the metal ion level, m the number below ones. In case of using only one ligand type, the homoleptic grid is formed in a square [nxn] structure. When using different ligands arise heteroleptic complexes, however, compete with the homoleptic. The number of metal ions is always n + m. | 0 | Theoretical and Fundamental Chemistry |
Chemical oxidation analysers inject the sample into a chamber with phosphoric acid followed by persulfate. The analysis is separated into two steps. One removes inorganic carbon by acidification and purging. After removal of inorganic carbon persulfate is added and the sample is either heated or bombarded with UV light from a mercury vapor lamp. Free radicals form persulfate and react with any carbon available to form carbon dioxide. The carbon from both determination (steps) is either run through membranes which measure the conductivity changes that result from the presence of varying amounts of carbon dioxide, or purged into and detected by a sensitive NDIR detector. Same as the combustion analyser, the total carbon formed minus the inorganic carbon gives a good estimate of the total organic carbon in the sample.
This method is often used in online applications because of its low maintenance requirements. | 0 | Theoretical and Fundamental Chemistry |
Egyptian reliefs from 1500 BC depict siphons used to extract liquids from large storage jars.
Physical evidence for the use of siphons by Greeks are the Justice cup of Pythagoras in Samos in the 6th century BC and usage by Greek engineers in the 3rd century BC at Pergamon.
Hero of Alexandria wrote extensively about siphons in the treatise Pneumatica.
The Banu Musa brothers of 9th-century Baghdad invented a double-concentric siphon, which they described in their Book of Ingenious Devices. The edition edited by Hill includes an analysis of the double-concentric siphon.
Siphons were studied further in the 17th century, in the context of suction pumps (and the recently developed vacuum pumps), particularly with an eye to understanding the maximum height of pumps (and siphons) and the apparent vacuum at the top of early barometers. This was initially explained by Galileo Galilei via the theory of ("nature abhors a vacuum"), which dates to Aristotle, and which Galileo restated as , but this was subsequently disproved by later workers, notably Evangelista Torricelli and Blaise Pascal – see barometer: history. | 1 | Applied and Interdisciplinary Chemistry |
Copper metallurgy in Africa encompasses the study of copper production across the continent and an understanding of how it influenced aspects of African archaeology. | 1 | Applied and Interdisciplinary Chemistry |
Minze Stuiver (25 October 1929 – 26 December 2020) was a Dutch geochemist who was at the forefront of geoscience research from the 1960s until his retirement in 1998. He helped transform radiocarbon dating from a simple tool for archaeology and geology to a precise technique with applications in solar physics, oceanography, geochemistry, and carbon dynamics. Minze Stuiver's research encompassed the use of radiocarbon (C) to understand solar cycles and radiocarbon production, ocean circulation, lake carbon dynamics and archaeology as well as the use of stable isotopes to document past climate changes. | 0 | Theoretical and Fundamental Chemistry |
Current Medicinal Chemistry is indexed in the following databases:
*Chemical Abstracts Service/CASSI
*EMBASE
*EMBiology
*MEDLINE
*Science Citation Index Expanded
*Scopus
According to the Journal Citation Reports, the journal has a 2019 impact factor of 4.184, ranking it 16th out of 59 journals in the category "Chemistry, Medicinal". | 1 | Applied and Interdisciplinary Chemistry |
Chalconatronite is a carbonate mineral and rare secondary copper mineral that contains copper, sodium, carbon, oxygen, and hydrogen, its chemical formula is NaCu(CO)•3(HO). Chalconatronite is partially soluble in water, and only decomposes, although chalconatronite is soluble while cold, in dilute acids. The name comes from the minerals compounds, copper ("chalcos'" in Greek) and natron, naturally forming sodium carbonate. The mineral is thought to be formed by water carrying alkali carbonates (possibly from soil) reacting with bronze. Similar minerals include malachite, azurite, and other copper carbonates. Chalconatronite has also been found and recorded in Australia, Germany, and Colorado. | 1 | Applied and Interdisciplinary Chemistry |
Film-forming agents are a group of chemicals that leave a pliable, cohesive, and continuous covering over the hair or skin when applied to their surface. This film has strong hydrophilic properties and leaves a smooth feel on skin.
Film-forming agents include polyvinylpyrrolidone (PVP), acrylates, acrylamides, and copolymers.
They are commonly found as ingredients of cosmetics, particular hair-care products, but also moisturizers and other skin-care products. | 1 | Applied and Interdisciplinary Chemistry |
*Development of the Varian A-60 NMR Spectrometer in 1960, and the development of MRI by Paul Lauterbur at Stony Brook University in the 1970s | 1 | Applied and Interdisciplinary Chemistry |
Initiation of transcription requires promoter regions, which are specific nucleotide consensus sequences that tell the σ-factor on RNA polymerase where to bind to the DNA. The promoters are usually located 15 to 19 bases apart and are most commonly found upstream of the genes they control. RNA polymerase is made up of 4 subunits, which include two alphas, a beta, and a beta prime (α, α, β, and β). A fifth subunit, sigma (called the σ-factor), is only present during initiation and detaches prior to elongation. Each subunit plays a role in the initiation of transcription, and the σ-factor must' be present for initiation to occur. When all σ-factor is present, RNA polymerase is in its active form and is referred to as the holoenzyme. When the σ-factor detaches, it is in core polymerase form. The σ-factor recognizes promoter sequences at -35 and -10 regions and transcription begins at the start site (+1). The sequence of the -10 region is TATAAT and the sequence of the -35 region is TTGACA.
* The σ-factor binds to the -35 promoter region. At this point, the holoenzyme is referred to as the closed complex because the DNA is still double stranded (connected by hydrogen bonds).
*Once the σ-factor binds, the remaining subunits of the polymerase attach to the site. The high concentration of adenine-thymine bonds at the -10 region facilitates the unwinding of the DNA. At this point, the holoenzyme is called the open complex. This open complex is also called the transcription bubble. Only one strand of DNA, called the template strand (also called the noncoding strand or nonsense/antisense strand), gets transcribed.
*Transcription begins and short "abortive" nucleotide sequences approximately 10 base pairs long are produced. These short sequences are nonfunctional pieces of RNA that are produced and then released. Generally, this nucleotide sequence consists of about twelve base pairs and aids in contributing to the stability of RNA polymerase so it is able to continue along the strand of DNA.
* The σ-factor is needed to initiate transcription but is not needed to continue transcribing the DNA. The σ-factor dissociates from the core enzyme and elongation proceeds. This signals the end of the initiation phase and the holoenzyme is now in core polymerase form.
The promoter region is a prime regulator of transcription. Promoter regions regulate transcription of all genes within bacteria. As a result of their involvement, the sequence of base pairs within the promoter region is significant; the more similar the promoter region is to the consensus sequence, the tighter RNA polymerase will be able to bind. This binding contributes to the stability of elongation stage of transcription and overall results in more efficient functioning. Additionally, RNA polymerase and σ-factors are in limited supply within any given bacterial cell. Consequently, σ-factor binding to the promoter is affected by these limitations. All promoter regions contain sequences that are considered non-consensus and this helps to distribute σ-factors across the entirety of the genome. | 1 | Applied and Interdisciplinary Chemistry |
All the graphical symbols used in the SBGN languages are associated with an SBO term. This permits, for instance, to help generate SBGN maps from SBML models. | 1 | Applied and Interdisciplinary Chemistry |
*Melanopsin: in vertebrate retina, mediates pupillary reflex, involved in regulation of circadian rhythms
*Photopsin: reception of various colors of light in the cone cells of vertebrate retina
*Rhodopsin: green-blue light reception in the rod cells of vertebrate retina
*Protein Kinase C: mediates photoreceptor deactivation, and retinal degeneration
*OPN5: sensitive to UV-light | 1 | Applied and Interdisciplinary Chemistry |
Initially, the RNA or DNA of interest is purified and denoted as the input template (IT). The OTTR library preparation protocol require the IT is incubated with BoMoC, which uses terminal transferase or ‘tailing’ activity' to add a chain-terminating dideoxynucleotide base, ddRTP (ddATP or ddGTP), to the 3’ end of the IT, in the presence of manganese (Mn). To promote cDNA synthesis in the steps to follow, the divalent cation source is switched to magnesium (Mg), free ddRTPs are inactivated and dNTPs are added. Next, a RNA-DNA duplex, containing a 3’ +1Y (dTTP or dCTP) base overhang is added, allowing the RNA-DNA duplex to base pair with the ddRTP-containing IT. BoMoC extends from the 3’ of the +1Y base across the IT. Following this, dNTP concentrations are altered to encourage the addition of dGTP to the 3’ end of the cDNA IT through the non-template nucleotide addition (NTA) activity of BoMoC. A 3’ adaptor template (AT) containing a 3’ dCTP is added to the reaction, promoting base pairing between the cDNA 3’ G overhang and the 3’C base of the AT and subsequent extension by BoMoC. When using RNA as the input template, addition of RNase A and RNase H is needed to degrade remaining RNA, leaving only the cDNA template. | 1 | Applied and Interdisciplinary Chemistry |
A simple and widely used model for molecular interactions is the Hill equation, which provides a way to quantify cooperative binding by describing the fraction of saturated ligand binding sites as a function of the ligand concentration. | 1 | Applied and Interdisciplinary Chemistry |
Eukaryotic initiation factor 4F (eIF4F) is a heterotrimeric protein complex that binds the 5' cap of messenger RNAs (mRNAs) to promote eukaryotic translation initiation. The eIF4F complex is composed of three non-identical subunits: the DEAD-box RNA helicase eIF4A, the cap-binding protein eIF4E, and the large "scaffold" protein eIF4G. The mammalian eIF4F complex was first described in 1983, and has been a major area of study into the molecular mechanisms of cap-dependent translation initiation ever since. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, the Conia-ene reaction is an intramolecular cyclization reaction between an enolizable carbonyl such as an ester or ketone and an alkyne or alkene, giving a cyclic product with a new carbon-carbon bond. As initially reported by J. M. Conia and P. Le Perchec, the Conia-ene reaction is a heteroatom analog of the ene reaction that uses an enol as the ene component. Like other pericyclic reactions, the original Conia-ene reaction required high temperatures to proceed, limiting its wider application. However, subsequent improvements, particularly in metal catalysis, have led to significant expansion of reaction scope. Consequently, various forms of the Conia-ene reaction have been employed in the synthesis of complex molecules and natural products. | 0 | Theoretical and Fundamental Chemistry |
In combustion, Frank-Kamenetskii theory explains the thermal explosion of a homogeneous mixture of reactants, kept inside a closed vessel with constant temperature walls. It is named after a Russian scientist David A. Frank-Kamenetskii, who along with Nikolay Semenov developed the theory in the 1930s. | 1 | Applied and Interdisciplinary Chemistry |
Its use in children is generally advised against, although it may be done under the supervision of a specialist. On 21 September 2015, the FDA started investigating the safety of tramadol in use in persons under the age of 17. The investigation was initiated because some of these people have experienced slowed or difficult breathing. The FDA lists age under 12 years old as a contraindication. | 0 | Theoretical and Fundamental Chemistry |
The interactions that lead to the assembly of the chlorophylls in chlorosomes are rather simple and the results may one day be used to build artificial photosynthetic systems that convert solar energy to electricity or biofuel. | 0 | Theoretical and Fundamental Chemistry |
Humphrey Rang (born 1936) held the Chair of Pharmacology from 1979 to 1983.
Rang qualified in medicine at UCL and had worked in H.O.Schilds laboratory while a medical student. He was the author of the first successful ligand-binding experiment of the modern era. This was based on his PhD work in Oxford, under William D.M. Paton. Rang had previously been the Professor of Pharmacology at Southampton and at St. Georges Hospital Medical School. He brought with him David Colquhoun who was also returning to the department, having been appointed in 1964 as an assistant lecturer by H.O. Schild. These appointments greatly strengthened the interests and achievements of the department in fundamental aspects of pharmacology, particularly the study of ion channels and receptors.
In collaboration with M. Maureen Dale (also appointed during Schilds Headship), Rang prepared the first edition of Pharmacology, the successor to Wilson & Schilds Applied Pharmacology.
In 1983 Rang was offered and accepted the Directorship of the Sandoz Institute of Medical Research, a division of Sandoz, then an independent pharmaceutical company. The new Institute was located in UCL and developed a close relationship with the department, both in teaching, to which members of the Institute contributed, and in research. | 1 | Applied and Interdisciplinary Chemistry |
Polywater was a hypothesized polymerized form of water that was the subject of much scientific controversy during the late 1960s, first described by Soviet scientist Nikolai Fedyakin. By 1969 the popular press had taken notice of Western attempts to recreate the substance and sparked fears of a "polywater gap" between the United States and Soviet Union. Increased press attention also brought with it increased scientific attention, and as early as 1970 doubts about its authenticity were being circulated. By 1973 it was found to be illusory, being just water with any number of common compounds contaminating it. Today, polywater is best known as an example of pathological science. | 1 | Applied and Interdisciplinary Chemistry |
Alkyl groups form homologous series. The simplest series have the general formula . Alkyls include methyl, (), ethyl (), propyl (), butyl (), pentyl (), and so on. Alkyl groups that contain one ring have the formula , e.g. cyclopropyl and cyclohexyl. The formula of alkyl radicals are the same as alkyl groups, except the free valence "" is replaced by the dot "•" and adding "radical" to the name of the alkyl group (e.g. methyl radical ).
The naming convention is taken from IUPAC nomenclature:
The prefixes taken from IUPAC nomenclature are used to name branched chained structures by their substituent groups, for example 3-methylpentane:
The structure of 3-methylpentane is viewed as consisting of two parts. First, five atoms comprise the longest straight chain of carbon centers. The parent five-carbon compound is named pentane (highlighted blue). The methyl "substituent" or "group" is highlighted red. According to the usual rules of nomenclature, alkyl groups are included in the name of the molecule before the root, as in methylpentane. This name is, however, ambiguous, as the methyl branch could be on various carbon atoms. Thus, the name is 3-methylpentane to avoid ambiguity: The 3- is because the methyl is attached to the third of the five carbon atoms.
If there is more than one of the same alkyl group attached to a chain, then the prefixes are used on the alkyl groups to indicate multiples (i.e., di, tri, tetra, etc.)
This compound is known as 2,3,3-trimethylpentane. Here three identical alkyl groups attached to carbon atoms 2, 3, and 3. The numbers are included in the name to avoid ambiguity about the position of the groups, and "tri" indicates that there are three identical methyl groups. If one of the methyl groups attached to the third carbon atom were instead an ethyl group, then the name would be 3-ethyl-2,3-dimethylpentane. When there are different alkyl groups, they are listed in alphabetical order.
In addition, each position on an alkyl chain can be described according to how many other carbon atoms are attached to it. The terms primary, secondary, tertiary, and quaternary refer to a carbon attached to one, two, three, or four other carbons respectively. | 0 | Theoretical and Fundamental Chemistry |
Magneto-optic generalized ellipsometry (MOGE) is an advanced infrared spectroscopic ellipsometry technique for studying free charge carrier properties in conducting samples. By applying an external magnetic field it is possible to determine independently the density, the optical mobility parameter and the effective mass parameter of free charge carriers. Without the magnetic field only two out of the three free charge carrier parameters can be extracted independently. | 0 | Theoretical and Fundamental Chemistry |
*5'-nuclease TaqMan assay
*Exciton-controlled hybridization-sensitive fluorescent oligonucleotide (ECHO) probes.
*Dual Hybridization (LightCycler®) probes
*Scorpions® Probes
*LUX (Light Upon Extension) Probes
*DNA binding dye assays (e.g., SYBR Green, SYTO9, Melt Doctor, LCGreen Plus, etc.) | 1 | Applied and Interdisciplinary Chemistry |
Brown adipose tissue stores free fatty acids rather than triglycerides, and is especially abundant in newborn and hibernating mammals. Brown adipose tissue is involved in thermogenesis, and has a considerably higher glyceroneogenesis activity. Brown adipose tissue contains more glyceroneogenesis-related enzymes, in particular PEPC-K and glycerol kinase. PEPC-K is around 10 times more active than in white adipose tissue, and is the key regulatory enzyme that controls the activity of the pathway. Glycerol kinase phosphorylates glycerol to generate glycerol 3-phosphate, which is used to build triglycerides. An increase in the activity of glycerol kinase will increase the production of glycerol 3-phosphate.
Glyceroneogenesis in brown adipose tissue contributes to thermogenesis, a process that generates heat in warm-blooded animals by delivering free fatty acids to the mitochondria. In normal conditions, thermogenesis is down-regulated by the low concentration of free fatty acids in the cytosol, because glyceroneogenesis re-esterifies fatty acids to triglycerides. When exposed to cold, a neurotransmitter hormone called norepinephrine suppresses the activity of PEPC-K and thus the glyceroneogenesis re-esterification, increasing the availability of free fatty acids within the cell. Excess free fatty acids in the cytosol will consequently be delivered to the mitochondria for thermogenesis. | 1 | Applied and Interdisciplinary Chemistry |
The silicon α and β effects arise because 3rd period heteroatoms can stabilize adjacent carbanions charges via (negative) hyperconjugation.
In the α effect, reactions that develop negative charge adjacent to the silicon, such as metalations, exhibit accelerated rates. The C–M σ orbital partially overlaps the C–Si σ* anti-bonding orbital, which stabilizes the C–M bond. More generally, (i.e. even for "naked" carbanions) the Si σ* orbitals help stabilize the electrons on the α carbon.
In the β effect, reactions that develop positive charge on carbon atoms β to the silicon accelerate. The C–Si σ orbital partially overlaps the with the C–X (leaving group) σ* orbital (2b): This electron-density donation into the anti-bonding orbital weakens the C–X bond, decreasing the barrier to the cleavage indicated 3, and favoring formation of the carbenium 4. | 0 | Theoretical and Fundamental Chemistry |
Indigo carmine in a 0.2% aqueous solution is blue at pH 11.4 and yellow at 13.0. Indigo carmine is also a redox indicator, turning yellow upon reduction. Another use is as a dissolved ozone indicator through the conversion to isatin-5-sulfonic acid. This reaction has been shown not to be specific to ozone, however: it also detects superoxide, an important distinction in cell physiology. It is also used as a dye in the manufacturing of capsules. | 0 | Theoretical and Fundamental Chemistry |
Germacranolides are a group of natural chemical compounds classified as sesquiterpene lactones. They are found in a variety of plant sources. | 0 | Theoretical and Fundamental Chemistry |
In the United States, the Federal Ocean Acidification Research And Monitoring Act of 2009 supports government coordination, such as the National Oceanic Atmospheric Administration's (NOAA) "Ocean Acidification Program". In 2015, USEPA denied a citizens petition that asked EPA to regulate under the Toxic Substances Control Act of 1976 in order to mitigate ocean acidification. In the denial, the EPA said that risks from ocean acidification were being "more efficiently and effectively addressed" under domestic actions, e.g., under the Presidential Climate Action Plan, and that multiple avenues are being pursued to work with and in other nations to reduce emissions and deforestation and promote clean energy and energy efficiency. | 0 | Theoretical and Fundamental Chemistry |
In a sufficiently narrow (i.e., low Bond number) tube of circular cross-section (radius a), the interface between two fluids forms a meniscus that is a portion of the surface of a sphere with radius R. The pressure jump across this surface is related to the radius and the surface tension γ by
This may be shown by writing the Young–Laplace equation in spherical form with a contact angle boundary condition and also a prescribed height boundary condition at, say, the bottom of the meniscus. The solution is a portion of a sphere, and the solution will exist only for the pressure difference shown above. This is significant because there isn't another equation or law to specify the pressure difference; existence of solution for one specific value of the pressure difference prescribes it.
The radius of the sphere will be a function only of the contact angle, θ, which in turn depends on the exact properties of the fluids and the container material with which the fluids in question are contacting/interfacing:
so that the pressure difference may be written as:
In order to maintain hydrostatic equilibrium, the induced capillary pressure is balanced by a change in height, h, which can be positive or negative, depending on whether the wetting angle is less than or greater than 90°. For a fluid of density ρ:
where g is the gravitational acceleration. This is sometimes known as the Jurin's law or Jurin height after James Jurin who studied the effect in 1718.
For a water-filled glass tube in air at sea level:
*γ = 0.0728 J/m at 20 °C
*θ = 20° (0.35 rad)
*ρ = 1000 kg/m
*g = 9.8 m/s
and so the height of the water column is given by:
Thus for a 2 mm wide (1 mm radius) tube, the water would rise 14 mm. However, for a capillary tube with radius 0.1 mm, the water would rise 14 cm (about 6 inches). | 1 | Applied and Interdisciplinary Chemistry |
Many salts of [Fe(o-phen)]2+ have been characterized by X-ray crystallography. The structures of [Fe(o-phen)] and [Fe(o-phen)] are almost identical, consistent with both being low-spin. These cations are octahedral with D symmetry group. The Fe-N distances are 197.3 pm. | 0 | Theoretical and Fundamental Chemistry |
Artwork consists of many pigments with a wide range of spectral absorption properties, which determine their color. Due to the broad spectral features of these pigments, the identification of a specific pigment in a mixture is difficult. Pump–probe imaging can provide accurate, high-resolution, molecular information and distinguish between pigments that may even have the same visual color. | 0 | Theoretical and Fundamental Chemistry |
The A coupling (also known as A coupling reaction or the aldehyde-alkyne-amine reaction), coined by Prof. Chao-Jun Li of McGill University, is a type of multicomponent reaction involving an aldehyde, an alkyne and an amine which react to give a propargylamine.
The reaction proceeds via direct dehydrative condensation and requires a metal catalyst, typically based on ruthenium/copper, gold or silver. Chiral catalyst can be used to give an enantioselective reaction, yielding a chiral amine. The solvent can be water. In the catalytic cycle the metal activates the alkyne to a metal acetylide, the amine and aldehyde combine to form an imine which then reacts with the acetylide in a nucleophilic addition. The reaction type was independently reported by three research groups in 2001 -2002; one report on a similar reaction dates back to 1953.
If the amine substituents have an alpha hydrogen present and provided a suitable zinc or copper catalyst is used, the A coupling product may undergo a further internal hydride transfer and fragmentation to give an allene in a Crabbé reaction. | 0 | Theoretical and Fundamental Chemistry |
The photoconversion property of Kaede does not only contribute to the application on protein labeling and cell tracking, it is also responsible for the vast variation in the colour of stony corals, Trachyphyllia geoffroyi. Under sunlight, due to the photoconversion of Kaede, the tentacles and disks will turn red. As green fluorescent Kaede is synthesized continuously, these corals appear green again as more unconverted Kaede is created. By the different proportion of photoconverted and unconverted Kaede, great diversity of colour is found in corals. | 1 | Applied and Interdisciplinary Chemistry |
According to the radioactive element and the specific site conditions, bacteria can enzymatically immobilize radionuclides directly or indirectly. Their redox potential is exploited by some microbial species to carry out reductions that alter the solubility and hence, mobility, bioavailability and radiotoxicity. This waste treatment technique called bioreduction or enzymatic biotransformation is very attractive because it can be done in mild conditions for the environment, does not produce hazardous secondary waste and has potential as a solution for waste of various kinds.
Direct enzymatic reduction is the change of radionuclides of a higher oxidation state to a lower one made by facultative and obligate anaerobes. The radioisotope interact with binding sites of metabolically active cells and is used as terminal electron acceptor in the electron transport chain where compounds such as ethyl lactate act as electron donors under anaerobic respiration.
The periplasm plays a very important role in these bioreductions. In the reduction of uranium (VI) to insoluble uranium (IV), made by Shewanella putrefaciens, Desulfovibrio vulgaris, Desulfovibrio desulfuricans and Geobacter sulfurreducens, the activity of periplasmic cytochromes is required. The reduction of technetium (VII) to technetium (IV) made by S. putrefaciens, G. sulfurreducens, D. desulfuricans, Geobacter metallireducens and Escherichia coli, on the other hand, requires the presence of the complex formate hydrogenlyase, also placed in this cell compartment.
Other radioactive actinides such as thorium, plutonium, neptunium and americium are enzymatically reduced by Rhodoferax ferrireducens, S. putrefaciens and several species of Geobacter, and directly form an insoluble mineral phase.
The phenomenon of indirect enzymatic reduction is carried out by sulfate-reducing and dissimilatory metal-reducing bacteria on excretion reactions of metabolites and breakdown products. There is a coupling of the oxidation of organic acids —produced by the excretion of these heterotrophic bacteria— with the reduction of iron or other metals and radionuclides, which forms insoluble compounds that can precipitate as oxide and hydroxide minerals. In the case of sulfate-reducing bacteria hydrogen sulfide is produced, promoting increased solubility of polluting radionuclides and their bioleaching (as liquid waste that can then be recovered).
There are several species of reducing microorganisms that produce indirect sequestering agents and specific chelators, such as siderophores. These sequestering agents are crucial in the complexation of radionuclides and increasing their solubility and bioavailability. Microbacterium flavescens, for example, grows in the presence of radioisotopes such as plutonium, thorium, uranium or americium and produces organic acids and siderophores that allow the dissolution and mobilization of radionuclides through the soil. It seems that siderophores on bacterial surface could also facilitate the entry of these elements within the cell as well. Pseudomonas aeruginosa also secretes chelating agents out that meet uranium and thorium when grown in a medium with these elements. In general, it has also been found that enterobactin siderophores are extremely effective in solubilizing actinide oxides of plutonium. | 1 | Applied and Interdisciplinary Chemistry |
This book is extensively illustrated and describes the tools and machinery associated with mining. Handtools and different sorts of buckets, wheelbarrows and trucks on wooded plankways are described. Packs for horses and sledges are used to carry loads above ground. Agricola then provides details of various kinds of machines for lifting weights. Some of these are man-powered and some powered by up to four horses or by waterwheels. Horizontal drive shafts along tunnels allow lifting in shafts not directly connected to the surface. If this is not possible, treadmills will be installed underground. Instead of lifting weights, similar machines use chains of buckets to lift water. Agricola also describes several designs of piston force pumps, which are either man or animal-powered, or powered by water wheels. Because these pumps can only lift water about 24 feet, batteries of pumps are required for the deepest mines. Water pipe designs are also covered in this section. Designs of wind scoop for ventilating shafts or forced air using fans or bellows are also described. Finally, ladders and lifts using wicker cages are used to get miners up and down shafts. | 1 | Applied and Interdisciplinary Chemistry |
Aside from its environmental impacts, R12, like most chlorofluoroalkanes, forms phosgene gas when exposed to a naked flame. | 1 | Applied and Interdisciplinary Chemistry |
The Borda–Carnot equation is
where
: ΔE is the fluid's mechanical energy loss,
: ξ is an empirical loss coefficient, which is dimensionless and has a value between zero and one, 0 ≤ ξ ≤ 1,
: ρ is the fluid density,
: v and v are the mean flow velocities before and after the expansion.
In case of an abrupt and wide expansion, the loss coefficient is equal to one. In other instances, the loss coefficient has to be determined by other means, most often from empirical formulae (based on data obtained by experiments). The Borda–Carnot loss equation is only valid for decreasing velocity, v > v, otherwise the loss ΔE is zero without mechanical work by additional external forces there cannot be a gain in mechanical energy of the fluid.
The loss coefficient ξ can be influenced by streamlining. For example, in case of a pipe expansion, the use of a gradual expanding diffuser can reduce the mechanical energy losses. | 1 | Applied and Interdisciplinary Chemistry |
In the Langmuir-Blodgett method, the nanoparticles are injected at air-water interphase in a special Langmuir-Blodgett Trough. The floating particles are compressed closer to each other with motorized barriers which allow to control the packing density of the particles. After compressing the particles to the desired packing density, they are transferred on a solid substrate using vertical (Langmuir-Blodgett) or horizontal (Langmuir-Schaefer) dipping to create a monolayer coating. Controlled multilayer coatings can be made repeating the dipping procedure multiple times.
The benefits of the Langmuir-Blodgett method include a firm control over the packing density and the layer thickness achieved that have been shown to be better than with other methods, the ability to use different shapes and materials of substrates and particles and the possibility to characterize the particle layer during deposition for example a Brewster Angle Microscope. As a disadvantage, a successful Langmuir-Blodgett deposition requires optimization of multiple measurement parameters such as dipping speed, temperature and dipping packing density. | 0 | Theoretical and Fundamental Chemistry |
Immobilized enzymes have important application uses as they reduce costs and improve the outcome of the reaction they catalyze. Advantages include:
;Convenience: Minuscule amounts of protein dissolve in the reaction, so workup can be much easier. Upon completion, reaction mixtures typically contain only solvent and reaction products.
;Economy: The immobilized enzyme is easily removed from the reaction making it easy to recycle the biocatalyst. This is particularly useful in processes such as the production of Lactose Free Milk, as the milk can be drained from a container leaving the enzyme (Lactase) inside ready for the next batch.
;Stability: Immobilized enzymes typically have greater thermal and operational stability than the soluble form of the enzyme.
In the past, biological washing powders and detergents contained many proteases and lipases that broke down dirt. However, when the cleaning products contacted human skin, they created allergic reactions. This is why immobilization of enzymes is important, for many application fields.
Immobilized enzymes are used in various applications including: food, chemical, pharmaceutical, and medical industry. In the food industry for example, Immobilized enzymes are used for the manufacturing of several types of zero-calorie sweetners, Allulose for instance is an epimer of fructose, which is different structurally, resulting in it not being absorbable by human bodies when ingested. Another example of immobilized-enzyme-based sweetners include: Tagatose (immobilized β-galactosidase).
In the chemical (cosmetics) industry as well, immobilized enzymes are used for the production of emollient esters by utilizing immobilized CalB enzyme. The first company to use such method is Evonik company in 2000. The enzyme Lipase-CalB in its immobilized state is actually used in other pharmaceutical applications for the production of Odanacatib, and Sofosbuvir. | 0 | Theoretical and Fundamental Chemistry |
Contraceptive implants are primarily used to prevent unintended pregnancy and treat conditions such as non-pathological forms of menorrhagia. Examples include copper- and hormone-based intrauterine devices. | 1 | Applied and Interdisciplinary Chemistry |
Following the laser cooling proposals, in 1978 two research groups that Wineland, Drullinger and Walls of NIST, and Neuhauser, Hohenstatt, Toscheck and Dehmelt of the University of Washington succeeded in laser cooling atoms. The NIST group wanted to reduce the effect of Doppler broadening on spectroscopy. They cooled magnesium ions in a Penning trap to < 40 Kelvin. The Washington group cooled barium ions.
The research from both groups served to illustrate the mechanical properties of light. Around this time, laser cooling techniques had allowed for temperatures lowered to around 40 kelvins.
Influenced by the Wineland's work on laser cooling ions, William Phillips applied the same principles to laser cool neutral atoms. In 1982, he published the first paper where neutral atoms were laser cooled. The process used is now known as the Zeeman slower and is a standard technique for slowing an atomic beam. | 0 | Theoretical and Fundamental Chemistry |
Without the aid of the whole-genome sequences, pre-genomics investigations looked at select regions of the genome, often with only minimal knowledge of the gene sequences they were looking at. Genetic techniques capable of providing this sort of information include Restriction Fragment Length Polymorphism (RFLP) analysis and microsatellite analysis. | 1 | Applied and Interdisciplinary Chemistry |
Since constructed wetlands are self-sustaining their lifetime costs are significantly lower than those of conventional treatment systems. Often their capital costs are also lower compared to conventional treatment systems. They do take up significant space, and are therefore not preferred where real estate costs are high. | 1 | Applied and Interdisciplinary Chemistry |
Relative wind stress is a shear stress that is produced by wind blowing over the surface of the ocean, or another large body of water. Relative wind stress is related to wind stress but takes the difference between the surface ocean current velocity and wind velocity into account. The units are Newton per meter squared or Pascal . Wind stress over the ocean is important as it is a major source of kinetic energy input to the ocean which in turn drives large scale ocean circulation. The use of relative wind stress instead of wind stress, where the ocean current is assumed to be stationary, reduces the stress felt over the ocean in models. This leads to a decrease in the calculation of power input into the ocean of 20–35% and thus, results in a different simulation of the large scale ocean circulation. | 1 | Applied and Interdisciplinary Chemistry |
Red litmus contains a weak diprotic acid. When it is exposed to a basic compound, the hydrogen ions react with the added base. The conjugate base formed from the litmus acid has a blue color, so the wet red litmus paper turns blue in an alkaline solution. | 0 | Theoretical and Fundamental Chemistry |
Recent developments in light-emitting diode (LED) technology have led to the commercial availability of UVC LED sources.
UVC LEDs use semiconductor materials to produce light in a solid-state device. The wavelength of emission is tuneable by adjusting the chemistry of the semiconductor material, giving a selectivity to the emission profile of the LED across, and beyond, the germicidal wavelength band. Advances in understanding and synthesis of the AlGaN materials system led to significant increases in the output power, device lifetime, and efficiency of UVC LEDs in the early 2010s.
The reduced size of LEDs opens up options for small reactor systems allowing point-of-use applications and integration into medical devices. Low power consumption of semiconductors introduce UV disinfection systems that utilized small solar cells in remote or Third World applications.
By 2019, LEDs made up 41.4% of UV light sales, up from 19.2% in 2014 The UV-C LED global market is expected to rise from $223m in 2017 to US$991m in 2023. | 0 | Theoretical and Fundamental Chemistry |
YwIE is a member of the low-molecular-weight protein tyrosine phosphatase (LMW-PTP). It is the only active PAP present in B.subtilis, and PAPs exhibits almost no activity against Protein Serine, Protein Tyrosine, and Protein Threonine peptides. Also, YwIE has been shown to play a role in B.Subtilis's resistance to stress. Elsholz et al. (2012), reported in their paper that protein arginine phosphorylation likely plays a critical physiological and regulatory role in bacteria. They showed that protein arginine phosphorylation is involved in the regulation of homeostasis, biofilm formation, motility, competence, stress, and stringent responses by regulating gene expression and protein activity in Bacillus Subtilis. Their results suggested that the combined action of protein arginine phosphatase and kinase allows for rapid and reversible regulation of protein activity. Also, that protein-arginine-phosphatases reverse the effect of protein arginine kinases (PAKs) in living organisms. In B.Subtilis, YwIE, a PAP, counteracts the action of McsB, a protein arginine kinase (PAK). McsB phosphorylates arginine residues in the winged helix-turn-helix domain of CtsR4, preventing it from binding to DNA, allowing for the expression of the repressed gene. However, YwIE is capable of restoring the DNA-binding ability of the CtsR repressor, a stress response & heat shock regulator in B.Subtilis, by reversing the McsB-mediated phosphorylation4. It accomplishes this by dephosphorylating the CtsR Protein. Additionally, McsB and YwIE are capable of differentiating between phosphoarginine and other amino acid residues | 1 | Applied and Interdisciplinary Chemistry |
C5a is a protein fragment released from cleavage of complement component C5 by protease C5-convertase into C5a and C5b fragments. C5b is important in late events of the complement cascade, an orderly series of reactions which coordinates several basic defense mechanisms, including formation of the membrane attack complex (MAC), one of the most basic weapons of the innate immune system, formed as an automatic response to intrusions from foreign particles and microbial invaders. It essentially pokes microscopic pinholes in these foreign objects, causing loss of water and sometimes death. C5a, the other cleavage product of C5, acts as a highly inflammatory peptide, encouraging complement activation, formation of the MAC, attraction of innate immune cells, and histamine release involved in allergic responses. The origin of C5 is in the hepatocyte, but its synthesis can also be found in macrophages, where it may cause local increase of C5a. C5a is a chemotactic agent and an anaphylatoxin; it is essential in the innate immunity but it is also linked with the adaptive immunity. The increased production of C5a is connected with a number of inflammatory diseases. | 1 | Applied and Interdisciplinary Chemistry |
There are several variations of the MALDI technology and comparable instruments are today produced for very different purposes, from more academic and analytical, to more industrial and high throughput. The mass spectrometry field has expanded into requiring ultrahigh resolution mass spectrometry such as the FT-ICR instruments as well as more high-throughput instruments. As many MALDI MS instruments can be bought with an interchangeable ionization source (electrospray ionization, MALDI, atmospheric pressure ionization, etc.) the technologies often overlap and many times any soft ionization method could potentially be used. For more variations of soft ionization methods see: Soft laser desorption or Ion source. | 1 | Applied and Interdisciplinary Chemistry |
Earth systems engineering is essentially the use of systems analysis methods in the examination of environmental problems. When analyzing complex environmental systems, there are numerous data sets, stakeholders and variables. It is therefore appropriate to approach such problems with a systems analysis method. Essentially there are "six major phases of a properly-conducted system study". The six phases are as follows:
#Determine goals of system
#Establish criteria for ranking alternative candidates
#Develop alternatives solutions
#Rank alternative candidates
#Iterate
#Act
Part of the systems analysis process includes determining the goals of the system. The key components of goal development include the development of a Descriptive Scenario, a Normative Scenario and Transitive Scenario. Essentially, the Descriptive Scenario "describe[s] the situation as it is [and] tell[s] how it got to be that way" (Gibson, 1991). Another important part of the Descriptive Scenario is how it "point[s] out the good features and the unacceptable elements of the status quo". Next, the Normative Scenario shows the final outcome or the way the system should operate under ideal conditions once action has been taken. For the earth systems approach, the "Normative Scenario" will involve the most complicated analysis. The Normative Scenario will deal with stakeholders, creating a common trading zone or location for the free exchange of ideas to come up with a solution of where a system may be restored to or just how exactly a system should be modified. Finally the Transitive scenario comes up with the actual process of changing a system from a Descriptive state to a Normative state. Often, there is not one final solution, as noted in adaptive management. Typically an iterative process ensues as variables and inputs change and the system coevolves with the analysis. | 1 | Applied and Interdisciplinary Chemistry |
Clinical Chemistry and Laboratory Medicine is a monthly peer-reviewed scientific journal that is published by De Gruyter. | 1 | Applied and Interdisciplinary Chemistry |
When the box contains N non-interacting fermions of spin ½, it is interesting to calculate the energy in the thermodynamic limit, where N is so large that the quantum numbers n, n, n can be treated as continuous variables.
With the vector , each quantum state corresponds to a point in n-space with energy
With denoting the square of the usual Euclidean length .
The number of states with energy less than E + E is equal to the number of states that lie within a sphere of radius in the region of n-space where n, n, n are positive. In the ground state this number equals the number of fermions in the system:
The factor of two expresses the two spin states, and the factor of 1/8 expresses the fraction of the sphere that lies in the region where all n are positive.
The Fermi energy is given by
Which results in a relationship between the Fermi energy and the number of particles per volume (when L is replaced with V):
This is also the energy of the highest-energy particle (the th particle), above the zero point energy . The th particle has an energy of
The total energy of a Fermi sphere of fermions (which occupy all energy states within the Fermi sphere) is given by:
Therefore, the average energy per particle is given by: | 0 | Theoretical and Fundamental Chemistry |
The commercial manufacture of wood pulp grade chemical cellulose using the kraft chemical pulping processes releases resin acids. The Kraft process is conducted under strongly basic conditions of sodium hydroxide, sodium sulfide and sodium hydrosulfide, which neutralizes these resin acids, converting them to their respective sodium salts, sodium abietate, ((CH)CHCOONa) sodium pimarate ((CH)(CH)CHCOONa) and so on. In this form, the sodium salts are insoluble and, being of lower density than the spent pulping process liquor, float to the surface of storage vessels during the process of concentration, as a somewhat gelatinous pasty fluid called kraft soap, or resin soap.
Kraft soap can be reneutralized with sulfuric acid to restore the acidic forms abietic acid, palmitic acid, and related resin acid components. This refined mixture is called tall oil. Other major components include fatty acids and unsaponifiable sterols.
Resin acids, because of the same protectant nature they provide in the trees where they originate, also impose toxic implications on the effluent treatment facilities in pulp manufacturing plants. Furthermore, any residual resin acids that pass the treatment facilities add toxicity to the stream discharged to the receiving waters. | 1 | Applied and Interdisciplinary Chemistry |
While insulin is secreted by the pancreas to lower blood glucose levels, glucagon is secreted to raise blood glucose levels. This is why glucagon has been known for decades as a counter-regulatory hormone. When blood glucose levels are low, the pancreas secretes glucagon, which in turn causes the liver to convert stored glycogen polymers into glucose monomers, which is then released into the blood. This process is called glycogenolysis. Liver cells, or hepatocytes, have glucagon receptors which allow for glucagon to attach to them and thus stimulate glycogenolysis. Contrary to insulin, which is produced by pancreatic β-cells, glucagon is produced by pancreatic α-cells. It is also known that an increase in insulin suppresses glucagon secretion, and a decrease in insulin, along with low glucose levels, stimulates the secretion of glucagon. | 1 | Applied and Interdisciplinary Chemistry |
Chain shuttling polymerization makes use of two catalysts and a chain shuttling agent (CSA) to generate copolymers of alternating tacticity. Catalyst 1 (Cat1) propagates a polyolefin of a desired tacticity. Catalyst 2 (Cat2) generates another chain of a different tacticity. The two chains are allowed to co-propagate in a single reactor in the same living polymer fashion as before. To alternate the tacticity, a CSA will transfer the polymer chain from its respective catalyst. The CSA can then bind to Cat2 and attach the chain to Cat2. When the chain attaches to Cat2, the polymerization of that chain continues, except it now propagates with the tacticity dictated by Cat2, not Cat1. The general result is that the chain will alternate between two different tacticities. As the forward and reverse reactions occur, the polymer chain is “shuttled” back and forth between the two catalysts and a block copolymer is formed.
The shuttling of chains back and forth from catalysts via a CSA can be viewed as a competing chemical equilibrium. Note that the forward and reverse reactions of CSA binding and leaving either Cat1 or Cat2 are possible. This competition means that a chain can leave Cat1 via a CSA and the reattach to Cat1, polymerizing the same tacticity. The rate at which the reattachment of Cat1 occurs can be controlled by altering the relative concentrations of Cat1, Cat2 and CSA. For example, if one wanted to produce a polymer with the properties mainly resulting from the use of Cat1 and only wanted to influence its properties slightly by the presence of Cat2, a greater concentration of Cat1 would be used than for Cat2. The rate of alternation between tacticity can be controlled by altering the concentration of CSA relative to Cat1 and Cat2; having a higher concentration of CSA means that the chains will shuttle back and forth more rapidly, creating shorter units of alternating tacticity. | 0 | Theoretical and Fundamental Chemistry |
Ethanol fermentation causes bread dough to rise. Yeast organisms consume sugars in the dough and produce ethanol and carbon dioxide as waste products. The carbon dioxide forms bubbles in the dough, expanding it to a foam. Less than 2% ethanol remains after baking.
In a contemporary advancement, a group in Germany has been doing the opposite and converting stale bread into ethanol. | 1 | Applied and Interdisciplinary Chemistry |
Clay is a very fine-grained geologic material that develops plasticity when wet, but becomes hard, brittle and non–plastic upon drying or firing. It is a very common material, and is the oldest known ceramic. Prehistoric humans discovered the useful properties of clay and used it for making pottery. The chemistry of clay, including its capacity to retain nutrient cations such as potassium and ammonium, is important to soil fertility.
Because the individual particles in clay are less than in size, they cannot be characterized by ordinary optical or physical methods. The crystallographic structure of clay minerals became better understood in the 1930s with advancements in the x-ray diffraction (XRD) technique indispensable to deciphering their crystal lattice. Clay particles were found to be predominantly sheet silicate (phyllosilicate) minerals, now grouped together as clay minerals. Their structure is based on flat hexagonal sheets similar to those of the mica group of minerals. Standardization in terminology arose during this period as well, with special attention given to similar words that resulted in confusion, such as sheet and plane.
Because clay minerals are usually (but not necessarily) ultrafine-grained, special analytical techniques are required for their identification and study. In addition to X-ray crystallography, these include electron diffraction methods, various spectroscopic methods such as Mössbauer spectroscopy, infrared spectroscopy, Raman spectroscopy, and SEM-EDS or automated mineralogy processes. These methods can be augmented by polarized light microscopy, a traditional technique establishing fundamental occurrences or petrologic relationships. | 0 | Theoretical and Fundamental Chemistry |
*Thermodynamics, University of Colorado-Boulder, 2011
**[https://www.youtube.com/watch?v=fkqmf_QR4Yg Introduction to fugacity: Where did it come from?]
**[https://www.youtube.com/watch?v=AMBoLiQJMFQ What is fugacity?]
**[https://www.youtube.com/watch?v=OZFB48wVtjw What is fugacity in mixtures?] | 0 | Theoretical and Fundamental Chemistry |
Pigments absorb light. Soap bubbles show a prism of different colors on their surfaces. These colors result from the way light interacts with differing thicknesses of the bubble's film, a phenomenon called structural color. Part of Qingchen Shen and Silvia Vignolini’s research focuses on identifying the causes behind different types of structural colors in nature. In one case, her group found that cellulose nanocrystals (CNCs), which are derived from the cellulose found in plants, could be made into iridescent, colorful films without any added pigment. They made films with vibrant blue, green and red colors that, when placed under sunlight, were an average of nearly 7 F cooler than the surrounding air. A square meter of the film generated over 120 Watts of cooling power. | 0 | Theoretical and Fundamental Chemistry |
Oxygen-17 (O) is a low-abundance, natural, stable isotope of oxygen (0.0373% in seawater; approximately twice as abundant as deuterium).
As the only stable isotope of oxygen possessing a nuclear spin (+5/2) and a favorable characteristic of field-independent relaxation in liquid water, O enables NMR studies of oxidative metabolic pathways through compounds containing O (i.e. metabolically produced HO water by oxidative phosphorylation in mitochondria) at high magnetic fields.
Water used as nuclear reactor coolant is subjected to intense neutron flux. Natural water starts out with 373 ppm of O; heavy water starts out incidentally enriched to about 550 ppm of oxygen-17. The neutron flux slowly converts O in the cooling water to O by neutron capture, increasing its concentration. The neutron flux slowly converts O (with much greater cross section) in the cooling water to carbon-14, an undesirable product that can escape to the environment:
: O (n,α) → C
Some tritium removal facilities make a point of replacing the oxygen of the water with natural oxygen (mostly O) to give the added benefit of reducing C production. | 0 | Theoretical and Fundamental Chemistry |
Robert Boyle (; 25 January 1627 – 31 December 1691) was an Anglo-Irish natural philosopher, chemist, physicist, alchemist and inventor. Boyle is largely regarded today as the first modern chemist, and therefore one of the founders of modern chemistry, and one of the pioneers of modern experimental scientific method. He is best known for Boyles law, which describes the inversely proportional relationship between the absolute pressure and volume of a gas, if the temperature is kept constant within a closed system. Among his works, The Sceptical Chymist' is seen as a cornerstone book in the field of chemistry. He was a devout and pious Anglican and is noted for his writings in theology. | 1 | Applied and Interdisciplinary Chemistry |
When a switch is closed in an electrical circuit containing a capacitor or inductor, the component draws out the resulting change in voltage or current, causing the system to take a substantial amount of time to reach a new steady state. This period of time is known as the transient state.
A capacitor acts as a short circuit immediately after the switch is closed, increasing its impedance during the transient state until it acts as an open circuit in its steady state.
An inductor is the opposite, behaving as an open circuit until reaching a short circuit steady state. | 1 | Applied and Interdisciplinary Chemistry |
An alternative disposal method, transmutation, has been demonstrated at CERN for technetium-99. This transmutation process bombards the technetium ( as a metal target) with neutrons, forming the short-lived (half-life 16 seconds) which decays by beta decay to stable ruthenium (). Given the relatively high market value of Ruthenium and the particularly undesirable properties of Technetium, this type of nuclear transmutation appears particularly promising. | 0 | Theoretical and Fundamental Chemistry |
According to Carman Drahl of Forbes magazine, "Chemists will quickly recognize the life stories of giants in their field. This show wasn’t designed just for chemists, however. The target audience includes teachers, students, and curious TV viewers." The series, based on a National Science Foundation project description, tells "a detective story of chemistry, stretching from the ancient alchemists to todays efforts to find stable new forms of matter". Mark Dawidziak, of the Cleveland Plain Dealer', quotes the historical advisor, Alan Rocke: "[The series] portrays science as [a] very human process. People see it is a very mechanical process. A great humanity is revealed by these stories, but also the unfolding process of how science actually comes to these understandings of nature." Erica K. Jacobsen, of the Chemical Education Division of the American Chemical Society, found the series to be "an excellent tool for bringing students a different view of the periodic table and those involved in its history". | 1 | Applied and Interdisciplinary Chemistry |
Select filter cloth to obtain good wear and solid binding characteristics. Use moderate blowback pressure to avoid high wear. Adjust duration of blow back pressure short enough to remove the cake from the filter cloth. The tuning of valve body is important for the blow back to prevent the excess filtrated being force back out of the pipe to with the release cake solid as this minimises wear and filter media maintenance. | 0 | Theoretical and Fundamental Chemistry |
The Radiation Protection Division of the Health Protection Agency was formed on 1 April 2005, due to the Health Protection Agency Act 2004, directly superseding the NRPB. This became the CRCE due to the Health and Social Care Act 2012, when Public Health England was formed. | 1 | Applied and Interdisciplinary Chemistry |
It has been proposed that COX-2 selectivity could cause imbalance of prostaglandins in the vasculature. If this were the explanation for the increased cardiovascular risk then low-dose aspirin should negate this effect, which was not the case in the APPROVe trial. Also, the non-selective COX inhibitors, have also shown increase in cardiovascular events.
Another possible explanation was studied by Li H. et al. (2008). They showed that in spontaneously hypertensive rats (SHR) non-selective NSAIDs and the coxibs produce oxidative stress, indicated by enhanced vascular superoxide(O) content and elevated peroxide in plasma, which is in tune with enhanced expression of NADPH oxidase, which was noticed with use of diclofenac and naproxen and, to a lesser degree, rofecoxib and celecoxib. Nitrite in plasma was also decreased suggesting a diminished synthesis of vascular nitric oxide (NO). This decrease in NO synthesis did not result from decreased expression of endothelial nitric oxide synthase (eNOS) because expression of eNOS mRNA was not reduced, and even upregulated for some products. The decrease in NO synthesis could, rather, be explained by loss of eNOS function. For eNOS to be normally functional, it needs to form a dimer and to have its cofactor BH, which is one of the most potent naturally occurring reducing agents. BH is sensitive to oxidation by peroxynitrite (ONOO), which is produced when NO reacts with O, so it has been hypothesized that depletion of BH can occur with excessive oxidative stress (that can be caused by NSAIDs) and, hence, be the cause of eNOS dysfunction. This dysfunction, which is referred to as eNOS uncoupling, causes the production of O by eNOS, thereby leading to more oxidative stress produced by eNOS. In a study, both the selective COX-2 inhibitors and the non-selective NSAIDs produced oxidative stress, with greater effects seen with non-selective NSAIDs use. This could fit with the hypothesis concerning the prostacyclin/thromboxane imbalance. That is, although the non-selective NSAIDs produce more oxidative stress, they prevent platelet aggregation, whereas the COX-2 inhibitors reduce prostacyclin production, and, hence, the cardiovascular risk for the non-selective NSAIDs is not higher than for the coxibs.
Among other hypotheses are increased blood pressure, decreased production of epi-lipoxins (which have anti-inflammatory effects), and inhibition of vascular remodeling when using selective COX-2 inhibitors. | 1 | Applied and Interdisciplinary Chemistry |
Amides are usually prepared by coupling a carboxylic acid with an amine. The direct reaction generally requires high temperatures to drive off the water:
Esters are far superior substrates relative to carboxylic acids.
Further "activating" both acid chlorides (Schotten-Baumann reaction) and anhydrides (Lumière–Barbier method) react with amines to give amides:
Peptide synthesis use coupling agents such as HATU, HOBt, or PyBOP. | 0 | Theoretical and Fundamental Chemistry |
Resistance, , is proportional to the distance, , between the electrodes and is inversely proportional to the cross-sectional area of the sample, (noted on the Figure above). Writing (rho) for the specific resistance, or resistivity.
In practice the conductivity cell is calibrated by using solutions of known specific resistance, , so the individual quantities and need not be known precisely, but only their ratio. If the resistance of the calibration solution is , a cell-constant, defined as the ratio of and ( = ), is derived.
The specific conductance (conductivity), (kappa) is the reciprocal of the specific resistance.
Conductivity is also temperature-dependent.
Sometimes the conductance (reciprocical of the resistance) is denoted as = . Then the specific conductance (kappa) is: | 0 | Theoretical and Fundamental Chemistry |
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