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The Cauchy–Born rule or Cauchy–Born approximation is a basic hypothesis used in the mathematical formulation of solid mechanics which relates the movement of atoms in a crystal to the overall deformation of the bulk solid. It states that in a crystalline solid subject to a small strain, the positions of the atoms within the crystal lattice follow the overall strain of the medium. The currently accepted form is Max Borns refinement of Cauchys original hypothesis which was used to derive the equations satisfied by the Cauchy stress tensor. The approximation generally holds for face-centered and body-centered cubic crystal systems. For complex lattices such as diamond, however, the rule has to be modified to allow for internal degrees of freedom between the sublattices. The approximation can then be used to obtain bulk properties of crystalline materials such as stress-strain relationship.
For crystalline bodies of finite size, the effect of surface stress is also significant. However, the standard Cauchy–Born rule cannot deduce the surface properties. To overcome this limitation, Park et al. (2006) proposed a surface Cauchy–Born rule. Several modified forms of the Cauchy–Born rule have also been proposed to cater to crystalline bodies having special shapes. Arroyo & Belytschko (2002) proposed an exponential Cauchy Born rule for modeling of mono-layered crystalline sheets as two-dimensional continuum shells. Kumar et al. (2015) proposed a helical Cauchy–Born rule for modeling slender bodies (such as nano and continuum rods) as special Cosserat continuum rods. | 0 | Theoretical and Fundamental Chemistry |
Hot cutting is performed by means of a thermal torch (plasma or oxyfuel) and is mounted to the last axis of a multi-axis machine. The axes of the multi-axis machine are powered by electric motors and are synchronized to create a path for the torch and pipe that yield a desired profile. The synchronization of axes is accomplished either mechanically, via cams, levers and gears, or electronically, via microprocessors and controllers. | 1 | Applied and Interdisciplinary Chemistry |
The indigenous people of Mono Lake are from a band of the Northern Paiute, called the Kutzadikaa. They speak the Northern Paiute language. The Kutzadikaa traditionally forage alkali fly pupae, called kutsavi in their language.
The term "Mono" is derived from "Monachi", a Yokuts term for the tribes that live on both the east and west side of the Sierra Nevada.
During early contact, the first known Mono Lake Paiute chief was Captain John.
The Mono tribe has two bands: Eastern and Western. The Eastern Mono joined the Western Mono bands' villages annually at Hetch Hetchy Valley, Yosemite Valley, and along the Merced River to gather acorns, different plant species, and to trade. The Western Mono and Eastern mono traditionally lived in the south-central Sierra Nevada foothills, including Historical Yosemite Valley.
Present day Mono Reservations are currently located in Big Pine, Bishop, and several in Madera County and Fresno County, California. | 1 | Applied and Interdisciplinary Chemistry |
Anhydrous zinc chloride is able to melt and boil without any decomposition until 900 °C in an inert atmosphere. However, in the presence of oxygen, zinc chloride oxidizes to zinc oxide above 400 °C.
When hydrated zinc chloride is heated, Zn(OH)Cl is produced instead of anhydrous zinc chloride: | 0 | Theoretical and Fundamental Chemistry |
Unique distributions of compounds across one or many plates can be employed either to increase the number of assays per plate or to reduce the variance of assay results, or both. The simplifying assumption made in this approach is that any N compounds in the same well will not typically interact with each other, or the assay target, in a manner that fundamentally changes the ability of the assay to detect true hits.
For example, imagine a plate wherein compound A is in wells 1-2-3, compound B is in wells 2-3-4, and compound C is in wells 3-4-5. In an assay of this plate against a given target, a hit in wells 2, 3, and 4 would indicate that compound B is the most likely agent, while also providing three measurements of compound B's efficacy against the specified target. Commercial applications of this approach involve combinations in which no two compounds ever share more than one well, to reduce the (second-order) possibility of interference between pairs of compounds being screened. | 1 | Applied and Interdisciplinary Chemistry |
Molasses-based distilleries all over the world generate large amount of effluent termed as spent wash or vinasse. For each liter of alcohol produced, around 8 liters of effluent is generated. This effluent has chemical oxygen demand (COD) of 1,50,000 PPM and biochemical oxygen demand (BOD) of 60,000 PPM and even more. This effluent needs to be treated and the only effective method for conclusive disposal is by composting.
Sugar factories generate pressmud / cachaza during the process and the same has about 30% fibers as carbon and has large amounts of water. This pressmud is dumped on prepared land in the form of 100 meters long windrows of 3 meters x 1.5 meters and spent wash is sprayed on the windrow while the windrow is being turned. These machines help consume spent wash of about 2.5 times of the volume of the pressmud, which means that 100 meters of windrow accommodates about 166 MT of pressmud and uses about 415 m³ of spent wash in 50 days.
Microbial Culture (organic solution) TRIO COM-CULT is used about 1 kg per MT of pressmud for fast de-composing of the spent wash. Hundreds of thousands of square meters of spent wash is being composted all over the world in countries like India, Colombia, Brazil, Thailand, Indonesia, South Africa etc.
The compost yard has to be prepared in such a way that the land is impervious and does not allow the liquid effluent to pass down into the earth. The compost thus generated is of excellent quality and is rich in nutrients. | 1 | Applied and Interdisciplinary Chemistry |
In 1985, the United States Congress passed legislation requiring the disposal of the stockpile chemical agents and munitions consisting of over 3 million chemical weapons, adding up to 31,000 tons of chemical weapons needing to be disposed of. This was ordered because a timely and safe disposal of chemical weapons is far safer than chemical weapon storage. Between the years of 1982 and 1992, the United States army reported approximately 1,500 leaking chemical weapons munitions, and in 1993 a 100-gallon chemical spill was reported at the Tooele Army Depot in Utah consisting of mustard agents. When chemical weapons are leaked or spilled into the ground, an insidious process follows where the condition of the agent is unknown. This occurs because the process of chemical agents degrading in soil is a complex process that is affected by many factors such as temperature, acidity, alkalinity, meteorological conditions, and the types of organisms present in the soil. This complexity causes persistent agents such as sulfur mustards to be harmful for decades. | 1 | Applied and Interdisciplinary Chemistry |
Proline-catalyzed aldol additions proceed via a six-membered enamine transition state according to the Zimmerman-Traxler model. Addition of 20-30 mol% proline to acetone or hydroxyacetone catalyzes their addition to a diverse set of aldehydes with high (>99%) enantioselectivity yielding diol products.
Proline and proline derivatives have been implemented as organocatalysts to promote asymmetric condensation reactions. An example of such a reaction proceeding through a six membered transition state is modelled as follows.
Intramolecular aldolization reactions that are catalyzed by proline likewise go through six-membered transition states. These transition states can enable the formation of either the enolexo or the enolendo product. | 0 | Theoretical and Fundamental Chemistry |
There has been a general trend towards converting existing resin systems to waterborne resins, for ease of use and environmental considerations. Particularly, their development was driven by increased demand for solventless systems since the manufacture of coatings and adhesives entailed the increasing release of solvents into the atmosphere from numerous sources. Using VOC exempt solvents is not a panacea as they have their own weaknesses.
The problem has always been that polyurethanes in water are not stable, reacting to produce a urea and carbon dioxide. Many papers and patents have been published on the subject. For environmental reasons there is even a push to have PUD available both water-based and bio-based or made from renewable raw materials. PUDs are used because of the general desire to formulate coatings, adhesives, sealants and elastomers based on water rather than solvent, and because of the perceived or assumed benefits to the environment. | 0 | Theoretical and Fundamental Chemistry |
Especially when in concentrated form, organic peroxides can decompose by self-oxidation, since organic peroxides contain both an oxidizer (the O-O bond) and fuel (C-H and C-C bonds). A "self-accelerating decomposition" occurs when the rate of peroxide decomposition generates heat at a faster rate than it can be dissipated to the environment. Temperature is the main factor in the rate of decomposition. The lowest temperature at which a packaged organic peroxide will undergo a self-accelerating decomposition within a week is defined as the self-accelerating decomposition temperature (SADT). A large fire at the Arkema Chemical Plant in Crosby, Texas (USA) in 2017 was caused by the decomposition of various organic peroxides following power failure and subsequent loss of cooling systems. This occurred due to extreme flooding from Hurricane Harvey, which destroyed main and back-up power generators at the site. | 0 | Theoretical and Fundamental Chemistry |
A foaming agent is a material such as a surfactant or a blowing agent that facilitates the formation of foam. A surfactant, when present in small amounts, reduces surface tension of a liquid (reduces the work needed to create the foam) or increases its colloidal stability by inhibiting coalescence of bubbles. A blowing agent is a gas that forms the gaseous part of the foam. | 0 | Theoretical and Fundamental Chemistry |
The National Atmospheric Deposition Program (NADP) is a Cooperative Research Support Program of the State Agricultural Experiment Stations (NRSP-3). Housed at the Wisconsin State Laboratory of Hygiene at the University of Wisconsin–Madison, the NADP is a collaborative effort between many different groups, such as: Federal, state, tribal, local governmental agencies, educational institutions, private companies, and non-governmental agencies. These organizations work together in order to operate monitoring sites and report deposition data. The NADP provides free access to all of its data, including seasonal and annual averages, trend plots, deposition maps, reports, manuals, and educational brochures. | 1 | Applied and Interdisciplinary Chemistry |
Although initially used in conjunction with UV/Vis spectroscopy, many modifications have been made that allow the B–H method to be applied to other spectroscopic techniques involving fluorescence, infrared, and NMR.
Modifications have also been done to further improve the accuracy in the determination of K and ε based on the Benesi–Hildebrand equations. One such modification was done by Rose and Drago. The equation that they developed is as follows:
Their method relied on a set of chosen values of ε and the collection of absorbance data and initial concentrations of the host and guest. This would thus allow the calculation of K. By plotting a graph of ε versus K, the result would be a linear relationship. When the procedure is repeated for a series of concentrations and plotted on the same graph, the lines intersect at a point giving the optimum value of ε and K. However, some problems have surfaced with this modified method as some examples displayed an imprecise point of intersection or no intersection at all.
More recently, another graphical procedure has been developed in order to evaluate K and ε independently of each other. This approach relies on a more complex mathematical rearrangement of the Benesi–Hildebrand method but has proven to be quite accurate when compared to standard values. | 0 | Theoretical and Fundamental Chemistry |
One type of organelle can turn nitrogen gas into a biologically available form. This nitroplast was discovered in algae. | 1 | Applied and Interdisciplinary Chemistry |
Hydrothermal liquefaction (HTL) is a thermal depolymerization process used to convert wet biomass, and other macromolecules, into crude-like oil under moderate temperature and high pressure. The crude-like oil has high energy density with a lower heating value of 33.8-36.9 MJ/kg and 5-20 wt% oxygen and renewable chemicals. The process has also been called hydrous pyrolysis.
The reaction usually involves homogeneous and/or heterogeneous catalysts to improve the quality of products and yields. Carbon and hydrogen of an organic material, such as biomass, peat or low-ranked coals (lignite) are thermo-chemically converted into hydrophobic compounds with low viscosity and high solubility. Depending on the processing conditions, the fuel can be used as produced for heavy engines, including marine and rail or upgraded to transportation fuels, such as diesel, gasoline or jet-fuels.
The process may be significant in the creation of fossil fuels. Simple heating without water, anhydrous pyrolysis has long been considered to take place naturally during the catagenesis of kerogens to fossil fuels. In recent decades it has been found that water under pressure causes more efficient breakdown of kerogens at lower temperatures than without it. The carbon isotope ratio of natural gas also suggests that hydrogen from water has been added during creation of the gas. | 0 | Theoretical and Fundamental Chemistry |
The compound is prepared by treatment of solid tetra-n-butylammonium bromide with bromine vapor:
:[N(CH)]Br + Br → [N(CH)]Br
Instead of bromine, tetra-n-butylammonium bromide can also be reacted with vanadium pentoxide and aqueous hydrogen peroxide, or alternatively with ceric ammonium nitrate. This molecule is commonly used as a catalyst in reactions involving the Fischer–Speier esterification mechanism and was heavily tested on by Dr Divyam Shard and Dr Arnav Mohammed, co-workers at Hustlers' University while working with Mr Atul Gowande. | 0 | Theoretical and Fundamental Chemistry |
While the standard addition method is effective in reducing the interference of most matrix effects on the analyte signal, it cannot correct for the translational matrix effects. These effects are caused by other substances present in the unknown sample that are often independent of the analyte concentration. They are commonly referred to as background and can impact the intercept of the regression line without affecting the slope. This results in bias towards the unknown concentration. In other words, standard addition will not correct for these backgrounds or other spectral interferences.
Analysts also needs to evaluate the precision of the determined unknown concentration by calculating for the standard deviation, . Lower indicates greater precision of the measurements. The value of is given by
where the calculation involves the following variables:
* standard deviation of the residuals,
* absolute value of the slope of the least-squares line,
* y-intercept of the linear curve,
* number of standards,
* average measurement of the standards,
* concentrations of the standards,
* average concentration of the standards, | 0 | Theoretical and Fundamental Chemistry |
FIDYST is a proprietary simulation tool developed by the Fraunhofer Institute for Industrial Mathematics that simulates fibers in turbulent flows. The name FIDYST is an acronym and means Fiber Dynamics Simulation Tool. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, pyramidal inversion (also umbrella inversion) is a fluxional process in compounds with a pyramidal molecule, such as ammonia (NH) "turns inside out". It is a rapid oscillation of the atom and substituents, the molecule or ion passing through a planar transition state. For a compound that would otherwise be chiral due to a stereocenter, pyramidal inversion allows its enantiomers to racemize. The general phenomenon of pyramidal inversion applies to many types of molecules, including carbanions, amines, phosphines, arsines, stibines, and sulfoxides. | 0 | Theoretical and Fundamental Chemistry |
Ceramic fuels other than oxides have the advantage of high heat conductivities and melting points, but they are more prone to swelling than oxide fuels and are not understood as well. | 0 | Theoretical and Fundamental Chemistry |
In 2014, media reported that a pitch drop experiment had been recently rediscovered at Aberystwyth University in Wales. Dating from 1914, it predates the Queensland experiment by 13 years. But as the pitch is more viscous (or the average temperature lower) this experiment has not yet produced its first drop and is not expected to for over 1,000 years. | 1 | Applied and Interdisciplinary Chemistry |
On superhydrophobic surfaces, liquid drops are observed to bounce off of the solid surface. Richard and Quéré showed that a small liquid drop was able to bounce off of a solid surface over 20 times before coming to rest. Of particular interest is the length of time that the drop remains in contact with the solid surface. This is important in applications such as heat transfer and aircraft icing. To find a relationship between drop size and contact time for low Weber number impacts (We ) and capillarity () can be used, as follows:
where is the drop density, R is the drop radius, is the characteristic time scale, and is the drop surface tension.
This yields
The contact time is independent of velocity in this regime. The minimum contact time for a low deformation drop (We << 1) is approximated by the lowest-order oscillation period for a spherical drop., giving the characteristic time a prefactor of approximately 2.2. For large-deformation drops (We > 1), similar contact times are seen even though dynamics of impact are different, as discussed below. If the droplet is split into multiple droplets, the contact time is reduced.
By creating tapered surfaces with large spacing, the impacting droplet will exhibit the counterintuitive pancake bouncing, characterized by the droplet bouncing off at the end of spreading without retraction, resulting in ~80% contact time reduction. | 1 | Applied and Interdisciplinary Chemistry |
Immersion chillers work by circulating a cooling fluid (usually tap water from a garden hose or faucet) through a copper/stainless steel coil that is placed directly in the hot wort. As the cooling fluid runs through the coil it absorbs and carries away heat until the wort has cooled to the desired temperature.
The advantage of using a copper or stainless steel immersion chiller is the lower risk of contamination versus other methods when used in an amateur or homebrewing environment. The clean chiller is placed directly in the still boiling wort and thus sanitized before the cooling process begins. | 1 | Applied and Interdisciplinary Chemistry |
Examples of photochemical organic reactions are electrocyclic reactions, radical reactions, photoisomerization, and Norrish reactions.
Alkenes undergo many important reactions that proceed via a photon-induced π to π* transition. The first electronic excited state of an alkene lacks the π-bond, so that rotation about the C–C bond is rapid and the molecule engages in reactions not observed thermally. These reactions include cis-trans isomerization and cycloaddition to other (ground state) alkene to give cyclobutane derivatives. The cis-trans isomerization of a (poly)alkene is involved in retinal, a component of the machinery of vision. The dimerization of alkenes is relevant to the photodamage of DNA, where thymine dimers are observed upon illuminating DNA with UV radiation. Such dimers interfere with transcription. The beneficial effects of sunlight are associated with the photochemically-induced retro-cyclization (decyclization) reaction of ergosterol to give vitamin D. In the DeMayo reaction, an alkene reacts with a 1,3-diketone reacts via its enol to yield a 1,5-diketone. Still another common photochemical reaction is Howard Zimmerman's di-π-methane rearrangement.
In an industrial application, about 100,000 tonnes of benzyl chloride are prepared annually by the gas-phase photochemical reaction of toluene with chlorine. The light is absorbed by chlorine molecules, the low energy of this transition being indicated by the yellowish color of the gas. The photon induces homolysis of the Cl-Cl bond, and the resulting chlorine radical converts toluene to the benzyl radical:
:Cl + hν → 2 Cl·
:CHCH + Cl· → CHCH· + HCl
:CHCH· + Cl· → CHCHCl
Mercaptans can be produced by photochemical addition of hydrogen sulfide (HS) to alpha olefins. | 0 | Theoretical and Fundamental Chemistry |
Dyesol and Tata Steel Europe announced in June the development of the world's largest dye sensitized photovoltaic module, printed onto steel in a continuous line.
Dyesol and CSIRO announced in October a Successful Completion of Second Milestone in Joint Dyesol / CSIRO Project.
Dyesol Director Gordon Thompson said, "The materials developed during this joint collaboration have the potential to significantly advance the commercialisation of DSC in a range of applications where performance and stability are essential requirements.
Dyesol is extremely encouraged by the breakthroughs in the chemistry allowing the production of the target molecules. This creates a path to the immediate commercial utilisation of these new materials."
Dyesol and Tata Steel Europe announced in November the targeted development of Grid Parity Competitive BIPV solar steel that does not require government subsidised feed in tariffs. TATA-Dyesol "Solar Steel" Roofing is currently being installed on the Sustainable Building Envelope Centre (SBEC) in Shotton, Wales. | 0 | Theoretical and Fundamental Chemistry |
The initiation of the transcription is a multistep sequential process that involves several mechanisms: promoter location, initial reversible binding of RNA polymerase, conformational changes in RNA polymerase, conformational changes in DNA, binding of nucleoside triphosphate (NTP) to the functional RNA polymerase-promoter complex, and nonproductive and productive initiation of RNA synthesis.
The promoter binding process is crucial in the understanding of the process of gene expression. Tuning synthetic genetic systems relies on precisely engineered synthetic promoters with known levels of transcription rates. | 1 | Applied and Interdisciplinary Chemistry |
To stop the electron transfer chain completing, producing output signals, the input of a photon, , is used to produce a pump probe spectroscopy effect by promoting an electron in an electron transfer chain. The fall of the pump probe promoted electron produces an output that is quenched down an electron transfer chain.
An alternative is similar to the AND gate alternative; an input causes a change in molecule structure breaking the electron transfer chain by not allowing the smooth energy transfer of electrons. | 0 | Theoretical and Fundamental Chemistry |
Normal glass does not transmit below 350 nm, so it is not used for optics in solar-blind systems. Instead calcium fluoride, fused silica, and magnesium fluoride are used as they are transparent to shorter wavelengths. | 0 | Theoretical and Fundamental Chemistry |
In plants, potassium plays a key role in maintaining plant health. High concentrations of potassium in plants play a key role in synthesis of essential proteins in plants as well as development of plant organelles like cell walls to prevent damage from viruses and insects. It also lowers the concentration of low molecular weight molecules like sugars and amino acids and increases the concentration of high weight molecular weight molecules like protein which also prevent the development and propagation of viruses. Potassium absorption has a positive correlation with aquaporins and the uptake of water in plant cells via cell membrane proteins. Because of this correlation, it has been noted that potassium also plays a key part in stomatal movement and regulation as high concentrations of potassium are moved into the plant stomata to keep them open and promote photosynthesis. In animals, potassium also plays a key part along with sodium in maintaining resting cell membrane potential and in cell-cell communication via repolarization of axon pathways after an action potential between neurons. Potassium may also play a key part in maintaining blood pressure in animals as shown in a study where increased severity of periodontal disease and hypertension were inversely correlated to urinary potassium excretion (a telltale sign of low potassium intake). | 1 | Applied and Interdisciplinary Chemistry |
Molar concentration (also called molarity, amount concentration or substance concentration) is a measure of the concentration of a chemical species, in particular, of a solute in a solution, in terms of amount of substance per unit volume of solution. In chemistry, the most commonly used unit for molarity is the number of moles per liter, having the unit symbol mol/L or mol/dm in SI units. A solution with a concentration of 1 mol/L is said to be 1 molar, commonly designated as 1 M or 1 . Molarity is often depicted with square brackets around the substance of interest; for example, the molarity of the hydrogen ion is depicted as [H]. | 0 | Theoretical and Fundamental Chemistry |
;AIME
*Sir Henry Ayers foundation president, 1893
*Uriah Dudley foundation general secretary 1893–1897
*David Lauder Stirling (c. 1871 – 30 August 1949); president 1894, secretary 1906–1941 or later; also secretary, Victorian Chamber of Mines 1898–1945
*H. W. Ferd Kayser (mine manager Mount Bischoff Tin Mining Company), vice-president 1894, president 1898, 1899
*Alexander Montgomery (government geologist in New Zealand, Tasmania, and Western Australia), president 1895
*Ernest Lidgey geological surveyor in Victoria; conducted Australia's first geophysical surveys; president 1901
*Samuel Henry McGowan (c. 1845 – 13 May 1921), accountant specializing in gold mining companies, mayor of Bendigo 1899–1900; president 1902
*F. Danvers Power, lecturer at Sydney University, president 1897, 1904.
*Robert C. Sticht general manager, Mount Lyell Mining & Railway Company, president 1905, 1915, vice-president 1909
*G. D. Delprat (manager of the Broken Hill mine), president 1906
*Dr. Alfred William Howitt, C.M.G., F.G.S., the eminent naturalist, was president 1907
*Frank A. Moss, (general manager of Kalgurli Gold Mines), president 1907
*C. F. Courtney (general manager of the Sulphide Corporation), president 1908
*Richard Hamilton, (general manager of the Great Boulder Proprietary mine), president 1909, vice-president 1910
*G. A. Richard (of Mount Morgan, Queensland), president 1910
*Herman Carl Bellinger from US; mine manager, Cobar 1909–1914, president 1912
*James Hebbard (manager of the Central Mine, Broken Hill), president 1913
*John Warren (mining) (manager of Block 10, Broken Hill), vice-president 1894, president 1902
*Hyman Herman (director of the Victorian geological survey), joined 1897, president 1914, remained councillor to 1959.
*Robert Silvers Black, (general manager of Kalgurli Gold Mines), president 1917
*J. W. Sutherland metallurgist at Lake View Consols and Golden Horse Shoe gold mines; president 1918
*Professor D. B. Waters of Otago, New Zealand, vice-president 1917,1918 (absent for most of this period — he was with New Zealand Tunnelling Company in France).
;AIMM
*R. W. Chapman, vice-president 1906, president 1920
*Colin Fraser (later Sir Colin), president 1923
*H. W. Gepp, later Sir Herbert William Gepp, president 1924
*Ernest W. Skeats (professor of geology, University of Melbourne), vice-president 1924, president 1925
*David Lauder Stirling, general secretary 1922–45
*R. M. Murray (general manager, Mount Lyell Mining & Railway Company), president 1927
*Alfred Stephen Kenyon, treasurer 1897, secretary 1906, president 1928
*E. C. Andrews (New South Wales Government Geologist), president 1929
*William Edward Wainwright (general manager of Broken Hill South), president 1919, 1930, vice-president 1916–18, 1933, 1934
*Wiliam Harley Wainwright son of W. E. Wainwright, (chief metallurgist, BHP) life member
*Essington Lewis (managing director of BHP) vice-president 1932, president 1935
*Andrew Fairweather, president 1932 (succeeded W. E. Mainwright at Broken Hill South mine and as General Manager)
*Professor J. Neill Greenwood (dean of Melbourne University Faculty of Applied Science), president 1936,1937
*Donald Yates, superintendent of Broken Hill Associated Smelters Pty., president 1937
*Julius Kruttschnitt (general manager, Mount Isa Mines) president 1939
*Oliver H. Woodward (general manager, North Mine, Broken Hill) active in tunnelling operations WWI, president 1940
*Arthur H. P. Moline (1877–1965) (succeeded R. M. Murray as general manager, Mount Lyell, in 1944), president 1945
*Asdruebal James Keast (general manager, Zinc Corporation; Australian Aluminium Production Commission 1951–55), president 1946, vice-president 1947
*Frank R. Hockey / Francis Richard Hockey (general superintendent, BHP), president 1947, vice-president 1949,1950
*F. F. Espie / Frank Fancett Espie (general superintendent, Western Mining Corporation), president 1948
*Godfrey Bernard O'Malley, vice-president 1943–46
*Maurice Alan Edgar Mawby (director of exploration, Zinc Corporation, Limited), vice-president 1950,1951, president 1953,1954
*Ian Munro McLennan (General Manager, BHP), president 1951
*Beryl Elaine Jacka MBE, typist 1936; assistant general secretary 1945–52, secretary 1952–1976
*Gordon Colvin Lindesay Clark CMG | 1 | Applied and Interdisciplinary Chemistry |
In the late 1950s, ductile iron pipe was introduced to the marketplace, featuring higher strength and similar corrosion resistance compared to cast iron. According to a 2004 study, an expected lifespan of 100 years is likely for ductile iron pipe, based on test results, field inspections and in-service operations over 50 years. In 2012, the American Water Works Association reported that ductile iron pipes in benign soil or installed in more aggressive soils using "evolved laying practices" had an estimated life up to 110 years, based on a nationwide analysis of water pipes in the US.
Like most ferrous materials, ductile iron is susceptible to corrosion, therefore its useful life depends on the impact of corrosion. Corrosion can occur in two ways in ductile iron pipes: graphitization, the leaching away of iron content through corrosion leading to a generally weakened pipe structure, and corrosion pitting, which is a more localized effect also causing weakening of the pipe structure.
Over the last 100 years, the average thickness of iron pipes has decreased due to increased metal strength, through metallurgical advancements as well as improved casting technique. | 1 | Applied and Interdisciplinary Chemistry |
Gates' total synthesis of morphine provided a proof of the structure of morphine proposed by Robinson in 1925. This synthesis of morphine features one of the first examples of the Diels-Alder reaction in the context of total synthesis. | 0 | Theoretical and Fundamental Chemistry |
Most methods of lipid extraction and isolation from biological samples exploit the high solubility of hydrocarbon chains in organic solvents. Given the diversity in lipid classes, it is not possible to accommodate all classes with a common extraction method. The traditional Bligh/Dyer procedure
uses chloroform/methanol-based protocols that include phase partitioning into the organic layer. However, several protocols now exist, with newer methods overcoming the shortcomings of older ones and solving problems associated with, for example, targeted lipid isolation or high throughput data collection
. Most protocols work relatively well for a variety of physiologically relevant lipids but they have to be adapted for species with particular properties and low-abundance and labile lipid metabolites. | 1 | Applied and Interdisciplinary Chemistry |
The inorganic carbon species include carbon dioxide, carbonic acid, bicarbonate anion, and carbonate. It is customary to express carbon dioxide and carbonic acid simultaneously as . C is a key parameter when making measurements related to the pH of natural aqueous systems, and carbon dioxide flux estimates.
where,
* C is the total inorganic carbon
* is the sum of carbon dioxide and carbonic acid concentrations ()
* is the bicarbonate concentration
* is the carbonate concentration
Each of these species are related by the following pH-driven chemical equilibria:
The concentrations of the different species of DIC (and which species is dominant) depends on the pH of the solution, as shown by a Bjerrum plot.
Total inorganic carbon is typically measured by the acidification of the sample which drives the equilibria to . This gas is then sparged from solution and trapped, and the quantity trapped is then measured, usually by infrared spectroscopy. | 0 | Theoretical and Fundamental Chemistry |
The foundational axioms of fluid dynamics are the conservation laws, specifically, conservation of mass, conservation of linear momentum, and conservation of energy (also known as the First Law of Thermodynamics). These are based on classical mechanics and are modified in quantum mechanics and general relativity. They are expressed using the Reynolds transport theorem.
In addition to the above, fluids are assumed to obey the continuum assumption. Fluids are composed of molecules that collide with one another and solid objects. However, the continuum assumption assumes that fluids are continuous, rather than discrete. Consequently, it is assumed that properties such as density, pressure, temperature, and flow velocity are well-defined at infinitesimally small points in space and vary continuously from one point to another. The fact that the fluid is made up of discrete molecules is ignored.
For fluids that are sufficiently dense to be a continuum, do not contain ionized species, and have flow velocities that are small in relation to the speed of light, the momentum equations for Newtonian fluids are the Navier–Stokes equations—which is a non-linear set of differential equations that describes the flow of a fluid whose stress depends linearly on flow velocity gradients and pressure. The unsimplified equations do not have a general closed-form solution, so they are primarily of use in computational fluid dynamics. The equations can be simplified in several ways, all of which make them easier to solve. Some of the simplifications allow some simple fluid dynamics problems to be solved in closed form.
In addition to the mass, momentum, and energy conservation equations, a thermodynamic equation of state that gives the pressure as a function of other thermodynamic variables is required to completely describe the problem. An example of this would be the perfect gas equation of state:
where is pressure, is density, and is the absolute temperature, while is the gas constant and is molar mass for a particular gas. A constitutive relation may also be useful. | 1 | Applied and Interdisciplinary Chemistry |
Modern classification of meteorites and micrometeorites is complex; the 2007 review paper of Krot et al. summarizes modern meteorite taxonomy. Linking individual micrometeorites to meteorite classification groups requires a comparison of their elemental, isotopic and textural characteristics. | 0 | Theoretical and Fundamental Chemistry |
An unexpected series of experimental results for the rate of decay of heavy highly charged radioactive ions circulating in a storage ring has provoked theoretical activity in an effort to find a convincing explanation. The rates of weak decay of two radioactive species with half lives of about 40 s and 200 s are found to have a significant oscillatory modulation, with a period of about 7 s.
The observed phenomenon is known as the GSI anomaly, as the storage ring is a facility at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany. As the decay process produces an electron neutrino, some of the proposed explanations for the observed rate oscillation invoke neutrino properties. Initial ideas related to flavour oscillation met with skepticism. A more recent proposal involves mass differences between neutrino mass eigenstates. | 0 | Theoretical and Fundamental Chemistry |
When treating infection, whether bacterial or viral, there is always a risk of the infectious agent to develop drug resistance. The treatment of HIV infection is especially susceptible to drug resistance which is a serious clinical concern in the chemotherapeutic treatment of the infection. Drug resistant HIV-strains emerge if the virus is able to replicate in the presence of the antiretroviral drugs.
NNRTI-resistant HIV-strains have the occurring mutations mainly in and around the NNIBP affecting the NNRTI binding directly by altering the size, shape and polarity on different areas of the pocket or by affecting, indirectly, the access to the pocket. Those mutations are primarily noted in domains which span amino acids 98-108, 178-190 or 225-238 of the p66 subunit. The most frequent mutations observed in viruses isolated from patients who have been on a failing NNRTI containing chemotherapy are Lys-103N and Tyr-181C. NNRTI resistance has been linked to over 40 amino acid substitutions in vitro and in vivo.
Antiretroviral drugs are never used in monotherapy due to rapid resistance development. The highly active antiretroviral therapy (HAART) was introduced in 1996. The treatment regimen combines three drugs from at least two different classes of antiretroviral drugs.
The advance of etravirine over other NNRTIs is that multiple mutations are required for the development of drug resistance. The drug has also shown activity against viruses with common NNRTI resistance associated mutations and cross-resistance mutations. | 1 | Applied and Interdisciplinary Chemistry |
The quantum tunneling dynamics in water was reported as early as 1992. At that time it was known that there are motions which destroy and regenerate the weak hydrogen bond by internal rotations of the substituent water monomers. On 18 March 2016, it was reported that the hydrogen bond can be broken by quantum tunneling in the water hexamer. Unlike previously reported tunneling motions in water, this involved the concerted breaking of two hydrogen bonds. Later in the same year, the discovery of the quantum tunneling of water molecules was reported. | 1 | Applied and Interdisciplinary Chemistry |
Normally, ice crystals grown in solution only exhibit the basal (0001) and prism faces (1010), and appear as round and flat discs. However, it appears the presence of AFPs exposes other faces. It now appears the ice surface 2021 is the preferred binding surface, at least for AFP type I. Through studies on type I AFP, ice and AFP were initially thought to interact through hydrogen bonding (Raymond and DeVries, 1977). However, when parts of the protein thought to facilitate this hydrogen bonding were mutated, the hypothesized decrease in antifreeze activity was not observed. Recent data suggest hydrophobic interactions could be the main contributor. It is difficult to discern the exact mechanism of binding because of the complex water-ice interface. Currently, attempts to uncover the precise mechanism are being made through use of molecular modelling programs (molecular dynamics or the Monte Carlo method). | 1 | Applied and Interdisciplinary Chemistry |
Thalidomide is provided as a racemic mixture of two enantiomers; while there are reports that only one of the enantiomers may cause birth defects, the body converts each enantiomer into the other through mechanisms that are not well understood. The (R)-enantiomer has the desired sedative effect while the (S)-enantiomer harbors embryo-toxic and teratogenic effect. Attempting to extract solely R-thalidomide does not remove the risk of birth defects, as it was demonstrated that the "safe" R-thalidomide undergoes an in vivo chiral inversion to the "teratogenic" S-thalidomide. Under biological conditions, the enantiomers interconvert (bidirectional chiral inversion – (R)- to (S)- and vice versa). | 0 | Theoretical and Fundamental Chemistry |
To measure the hydration band, a small slice of material is typically cut from an artifact. This sample is ground down to about 30 micrometers thick and mounted on a petrographic slide (this is called a thin section). The hydration rind is then measured under a high-power microscope outfitted with some method for measuring distance, typically in tenths of micrometers. The technician measures the microscopic amount of water absorbed on freshly broken surfaces. The principle behind obsidian hydration dating is simple–the longer the artifact surface has been exposed, the thicker the hydration band will be. | 0 | Theoretical and Fundamental Chemistry |
SP-D is a type of lectin, more specifically they are a collagen-containing C-type (calcium dependent) lectin which are named collectins. The collectins are responsible for immune and inflammatory control. They have a very basic structure,
* triple-helical collagen region
* C-terminal homotrimeric lectin or carbohydrate recognition domain (CRD).
SP-D is actually a monomer, these monomers assist in high affinity saccharide binding. Three of the same type of monomers associate to form a homotrimer.
SP-D has a complex quaternary structure in which monomers (43 kDa) are assembled into tetramers of trimers thus forming dodecamers. Dodecamers are further assembled into large multimeric structures. The oligomerization of SP-D results in the burial of the tail domains while the head domains are exposed. Oligomerization is dependent upon the cysteine residues at positions 15 and 20 within the N-terminal tail region. | 0 | Theoretical and Fundamental Chemistry |
The term host cell reactivation or HCR was first used to describe the survival of UV-irradiated bacteriophages, that were transfected to UV-pretreated cells. This phenomenon was first thought to be the result of homologous recombination between both bacteria and phage, but later recognized as enzymatic repair. Modifications of the assay were later developed, using transient expression plasmid DNA vectors on immortalized fibroblasts, and lately on human lymphocytes.
The HCR assay known also as plasmid reactivation assay, indirectly monitors cellular transcriptional repair system, that is activated by the transcriptional-inhibited damage inflicted by UV-Radiation into the plasmid. Given that UV-induced DNA damage is used as mutagen, the cell uses nucleotide excision repair NER pathway, that is activated by distortion in the DNA helix.
The Host-Cell Reactivation Assay or HCR is a technique used to measure the DNA repair capacity of cell of a particular DNA alteration. In the HCR assay the ability of an intact cell to repair exogenous DNA is measured The host cell is transfected with a damaged plasmid containing a reporter gene, usually luciferase, which has been deactivated due to the damage. The ability of the cell to repair the damage in the plasmid, after it has been introduced to the cell, allows the reporter gene to be reactivated. Earlier versions of this assay were based on the chloramphenicol acetyltransferase [http://www.wikigenes.org/e/gene/e/2847485.html (CAT)] gene, but the version of the assay using luciferase as reporter gene is as much as 100-fold more sensitive. | 1 | Applied and Interdisciplinary Chemistry |
The term optical activity is derived from the interaction of chiral materials with polarized light. In a solution, the (−)-form, or levorotatory form, of an optical isomer rotates the plane of a beam of linearly polarized light counterclockwise. The (+)-form, or dextrorotatory form, of an optical isomer does the opposite. The rotation of light is measured using a polarimeter and is expressed as the optical rotation.
Enantiomers can be separated by chiral resolution. This often involves forming crystals of a salt composed of one of the enantiomers and an acid or base from the so-called chiral pool of naturally occurring chiral compounds, such as malic acid or the amine brucine. Some racemic mixtures spontaneously crystallize into right-handed and left-handed crystals that can be separated by hand. Louis Pasteur used this method to separate left-handed and right-handed sodium ammonium tartrate crystals in 1849. Sometimes it is possible to seed a racemic solution with a right-handed and a left-handed crystal so that each will grow into a large crystal.
Liquid chromatography (HPLC and TLC) may also be used as an analytical method for the direct separation of enantiomers and the control of enantiomeric purity, e.g. active pharmaceutical ingredients (APIs) which are chiral. | 0 | Theoretical and Fundamental Chemistry |
By maximizing with respect to Z, one would find the best neutron–proton ratio N/Z for a given atomic weight A. We get
This is roughly 1 for light nuclei, but for heavy nuclei the ratio grows in good agreement with experiment.
By substituting the above value of Z back into , one obtains the binding energy as a function of the atomic weight, .
Maximizing with respect to A gives the nucleus which is most strongly bound, i.e. most stable. The value we get is A = 63 (copper), close to the measured values of A = 62 (nickel) and A = 58 (iron).
The liquid-drop model also allows the computation of fission barriers for nuclei, which determine the stability of a nucleus against spontaneous fission. It was originally speculated that elements beyond atomic number 104 could not exist, as they would undergo fission with very short half-lives, though this formula did not consider stabilizing effects of closed nuclear shells. A modified formula considering shell effects reproduces known data and the predicted island of stability (in which fission barriers and half-lives are expected to increase, reaching a maximum at the shell closures), though also suggests a possible limit to existence of superheavy nuclei beyond Z = 120 and N = 184. | 0 | Theoretical and Fundamental Chemistry |
2-O-methylation refers to the methylation of the 2 hydroxyl group of the ribose within an RNA nucleotide. 2'-O-methylation is found in the five-prime cap of mRNAs in higher eukaryotes. It is involved in differentiating between self and non-self mRNA. Without the 2′-O-methylation mark the immune system triggers higher levels of type 1 interferon activity. While this modification is not currently known to be a response to any particular phenomenon, not everything is fully understood about the mechanisms of this modification due to the difficulty of studying small RNA molecules. However, the effect on RNA stability this modification has could be regulated to modulate transcript levels. | 1 | Applied and Interdisciplinary Chemistry |
The application of kinetic theory to ideal gases makes the following assumptions:
* The gas consists of very small particles. This smallness of their size is such that the sum of the volume of the individual gas molecules is negligible compared to the volume of the container of the gas. This is equivalent to stating that the average distance separating the gas particles is large compared to their size, and that the elapsed time during a collision between particles and the container's wall is negligible when compared to the time between successive collisions.
* The number of particles is so large that a statistical treatment of the problem is well justified. This assumption is sometimes referred to as the thermodynamic limit.
* The rapidly moving particles constantly collide among themselves and with the walls of the container, and all these collisions are perfectly elastic.
* Interactions (i.e. collisions) between particles are strictly binary and uncorrelated, meaning that there are no three-body (or higher) interactions, and the particles have no memory.
* Except during collisions, the interactions among molecules are negligible. They exert no other forces on one another.
Thus, the dynamics of particle motion can be treated classically, and the equations of motion are time-reversible.
As a simplifying assumption, the particles are usually assumed to have the same mass as one another; however, the theory can be generalized to a mass distribution, with each mass type contributing to the gas properties independently of one another in agreement with Daltons Law of partial pressures. Many of the models predictions are the same whether or not collisions between particles are included, so they are often neglected as a simplifying assumption in derivations (see below).
More modern developments, such as Revised Enskog Theory and the Extended BGK model, relax one or more of the above assumptions. These can accurately describe the properties of dense gases, and gases with internal degrees of freedom, because they include the volume of the particles as well as contributions from intermolecular and intramolecular forces as well as quantized molecular rotations, quantum rotational-vibrational symmetry effects, and electronic excitation. While theories relaxing the assumptions that the gas particles occupy negligible volume and that collisions are strictly elastic have been successful, it has been shown that relaxing the requirement of interactions being binary and uncorrelated will eventually lead to divergent results. | 0 | Theoretical and Fundamental Chemistry |
Several hnRNPs interact with telomeres, which protect the ends of chromosomes from deterioration and are often associated with cell longevity. hnRNP D associates with the G-rich repeat region of the telomeres, possibly stabilizing the region from secondary structures which would inhibit telomere replication.
hnRNP has also been shown to interact with telomerase, the protein responsible for elongating telomeres and prevent their degradation. hnRNPs C1 and C2 associate with the RNA component of telomerase, which improves its ability to access the telomere. | 1 | Applied and Interdisciplinary Chemistry |
Crystallization is largely over when reaches values close to 1, which will be at a crystallization time defined by , as then the exponential term in the above expression for will be small. Thus crystallization takes a time of order
i.e., crystallization takes a time that decreases as one over the one-quarter power of the nucleation rate per unit volume, , and one over the three-quarters power of the growth velocity . Typical crystallites grow for some fraction of the crystallization time and so have a linear dimension , or
i.e., the one quarter power of the ratio of the growth velocity to the nucleation rate per unit volume. Thus the size of the final crystals only depends on this ratio, within this model, and as we should expect, fast growth rates and slow nucleation rates result in large crystals. The average volume of the crystallites is of order this typical linear size cubed.
This all assumes an exponent of , which is appropriate for the uniform (homogeneous) nucleation in three dimensions. Thin films, for example, may be effectively two-dimensional, in which case if nucleation is again uniform the exponent . In general, for uniform nucleation and growth, , where is the dimensionality of space in which crystallization occurs. | 0 | Theoretical and Fundamental Chemistry |
Metal ions are often used for diagnostic medical imaging. Metal complexes can be used either for radioisotope imaging (from their emitted radiation) or as contrast agents, for example, in magnetic resonance imaging (MRI). Such imaging can be enhanced by manipulation of the ligands in a complex to create specificity so that the complex will be taken up by a certain cell or organ type.
Examples of metals used for diagnosis include:
* Technetium. Tc is the most commonly used radioisotope agent for imaging purposes. It has a short half-life, emits only gamma ray photons, and does not emit beta or alpha particles (which are more damaging to surrounding cells), and thus is particularly suitable as an imaging radioisotope.
* Gadolinium(III), Iron(III), Manganese(II): For MRI imaging paramagnetic metals are needed for contrast imaging. Gadolinium(III), Iron(III), and Manganese(II) are all paramagnetic metals that are able to alter the tissue relaxation times and produce a contrast image.
* Gallium-68 is useful as a positron source for Positron emission tomography.
* Cobalt(III): Cobalt(III) is used with the compound bleomycin (BLM) (Figure 1), which is an antibiotic, to selectively be taken up by tumor cells. The use of cobalt results in the best blood-to-tumor distribution ratio, but its half-life is too long to be conducive for imaging purposes. A solution has been proposed to attach an EDTA moiety to the terminal thiazole ring of bleomycin, radiolabeled so that the entire complex can then be traceable. This system could provide tumor locations accurately, leading to earlier detection and more non-invasive procedures in the future. | 1 | Applied and Interdisciplinary Chemistry |
*Order of the Sacred Treasure, 6th class (1940)
*Majima Award for Organic Chemistry of the Chemical Society of Japan (1944)
*Order of the Sacred Treasure, 5th class (1944)
*Order of the Sacred Treasure, 4th class (1945)
*Asahi Prize (1952)
*Japan Academy Award (1953)
*Order of Culture (1958)
*Person of Cultural Merit (1958)
*Dark-blue Ribbon Medal and Imperial Cup of the Government of Japan (1967)
*Order of the Sacred Treasure, 1st class (1972)
*Cultural Medal of the Republic of China (1979)
*August Wilhelm von Hofmann Memorial Medal of the German Chemical Society (1981)
*Special Award of the Society of Synthetic Organic Chemistry of Japan (1984) | 0 | Theoretical and Fundamental Chemistry |
Local bans have been enacted elsewhere, including in many large and small cities within the US:
* Alaska — In Alaska, the towns of Bethel, Cordova, and Seward have enacted bans.
* California — At least 128 cities in California have an existing polystyrene ban in some form. As of 2023, 12 counties — namely Alameda, Contra Costa, Los Angeles, Marin, Mendocino, Monterey, San Francisco, San Luis Obispo, San Mateo, Santa Clara, Santa Cruz, and Sonoma have bans affecting the general public. Additionally, 27 municipalities in other counties, namely Arcata, Camarillo, Carlsbad, Carpinteria, Dana Point, Davis, Del Mar, Encinitas, Goleta, Imperial Beach, Laguna Beach, Newport Beach, Oceanside, Ojai, Oxnard, Palm Springs, Port Hueneme, San Clemente, San Diego, Santa Barbara, Solana Beach, South Lake Tahoe, Thousand Oaks, Truckee, Ventura, Vista, and Yountville have bans. Together these laws cover over 20.6 million people, or about 53% of the states population. The city of Berkeley passed the nations first polystyrene foodware ban in 1988, while also requiring all disposable foodware to be degradable or recyclable.
* Connecticut — Hamden, Groton, Norwalk, Stamford, and Westport have all enacted bans. Hamden enacted the state's first ban in 1989, and continues to retain its original ordinance.
* Georgia — South Fulton banned single-use plastics in 2019. Atlanta banned polystyrene at city-owned buildings, including Hartsfield–Jackson Atlanta International Airport.
* Illinois — Oak Park and River Forest have enacted bans. In 2023, the state legislature passed a ban affecting state agencies and universities.
* Massachusetts — At least 66 municipalities have bans on polystyrene, including Abington, Acton, Amherst, Andover, Arlington, Athol, Attleboro, Brookline, Buckland, Cambridge, Chatham, Chelmsford, Concord, Dennis, Eastham, Easthampton, Essex, Fairhaven, Falmouth, Georgetown, Gloucester, Grafton, Great Barrington, Greenfield, Hadley, Hamilton, Hanson, Ipswich, Lee, Lenox, Lexington, Lincoln, Manchester-by-the-Sea, Marblehead, Maynard, Medford, Melrose, Nantucket, Newton, Northborough, Northampton, Orleans, Pittsfield, Provincetown, Raynham, Reading, Revere, Rockport, Salem, Saugus, Shrewsbury, Somerville, South Hadley, Stockbridge, Sudbury, Swampscott, Upton, Wayland, Wellfleet, Westborough, Westfield, Westford, Whitman, Williamstown, Winthrop, and Yarmouth.
* Minnesota — Minneapolis enacted a ban in 1989, and amended the largely unenforced ban in 2015. In 2017, the city of St. Louis Park effectively banned single-use polystyrene after mandating compostable, reusable, or locally recyclable packaging. Saint Paul enacted a similar provision in 2022.
* New Hampshire — Portsmouth enacted the first ban in New Hampshire in 2020.
* New Mexico — Santa Fe County passed a ban on serving food, or packing eggs, baked goods, or produce in polystyrene containers, affecting unincorporated parts of the county.
* Pennsylvania — The Boroughs of Ambler, Newtown, Swarthmore, and Townships of Montgomery, Newtown, Solebury, Tredyffrin, Upper Merion, Upper Moreland, and Uwchlan enacted bans.
* South Carolina — The city of Charleston adopted an ordinance in 2018, with the surrounding Charleston County adopting a similar ordinance the year after. | 0 | Theoretical and Fundamental Chemistry |
In static methods a mixture is brought to equilibrium and the concentration of a species in the solution phase is determined by chemical analysis. This usually requires separation of the solid and solution phases. In order to do this the equilibration and separation should be performed in a thermostatted room. Very low concentrations can be measured if a radioactive tracer is incorporated in the solid phase.
A variation of the static method is to add a solution of the substance in a non-aqueous solvent, such as dimethyl sulfoxide, to an aqueous buffer mixture. Immediate precipitation may occur giving a cloudy mixture. The solubility measured for such a mixture is known as "kinetic solubility". The cloudiness is due to the fact that the precipitate particles are very small resulting in Tyndall scattering. In fact the particles are so small that the particle size effect comes into play and kinetic solubility is often greater than equilibrium solubility. Over time the cloudiness will disappear as the size of the crystallites increases, and eventually equilibrium will be reached in a process known as precipitate ageing. | 0 | Theoretical and Fundamental Chemistry |
Dislocations in a crystal lattice are line defects that are associated with local stress fields. Dislocations allow shear at lower stress than that needed for a perfect crystal structure. The local stress fields result in interactions between the dislocations which then result in strain hardening or cold working. | 0 | Theoretical and Fundamental Chemistry |
emissions have also led to the stratosphere contracting by 400 meters since 1980, which could affect satellite operations, GPS systems and radio communications. | 1 | Applied and Interdisciplinary Chemistry |
Coal-tar creosote is the most widely used wood treatment today; both industrially, processed into wood using pressure methods such as "full-cell process" or "empty-cell process", and more commonly applied to wood through brushing. In addition to toxicity to fungi, insects, and marine borers, it serves as a natural water repellent. It is commonly used to preserve and waterproof railroad ties, pilings, telephone poles, power line poles, marine pilings, and fence posts. Although suitable for use in preserving the structural timbers of buildings, it is not generally used that way because it is difficult to apply. There are also concerns about the environmental impact of the leaching of creosote into aquatic ecosystems.
Due to its carcinogenic character, the European Union has regulated the quality of creosote for the EU market and requires that the sale of creosote be limited to professional users. The United States Environmental Protection Agency regulates the use of coal-tar creosote as a wood preservative under the provisions of the Federal Insecticide, Fungicide, and Rodenticide Act. Creosote is considered a restricted-use pesticide and is only available to licensed pesticide applicators. | 0 | Theoretical and Fundamental Chemistry |
Bioplastics are plastic materials produced from renewable biomass sources, such as vegetable fats and oils, corn starch, straw, woodchips, sawdust, recycled food waste, etc. Some bioplastics are obtained by processing directly from natural biopolymers including polysaccharides (e.g., starch, cellulose, chitosan, and alginate) and proteins (e.g., soy protein, gluten, and gelatin), while others are chemically synthesised from sugar derivatives (e.g., lactic acid) and lipids (oils and fats) from either plants or animals, or biologically generated by fermentation of sugars or lipids. In contrast, common plastics, such as fossil-fuel plastics (also called petro-based polymers) are derived from petroleum or natural gas.
One advantage of bioplastics is their independence from fossil fuel as a raw material, which is a finite and globally unevenly distributed resource linked to petroleum politics and environmental impacts. Life cycle analysis studies show that some bioplastics can be made with a lower carbon footprint than their fossil counterparts, for example when biomass is used as raw material and also for energy production. However, other bioplastics' processes are less efficient and result in a higher carbon footprint than fossil plastics.
The distinction between non-fossil-based (bio)plastic and fossil-based plastic is of limited relevance since materials such as petroleum are themselves merely fossilized biomass. As such, whether any kind of plastic is degradable or non-degradable (durable) depends on its molecular structure, not on whether or not the biomass constituting the raw material is fossilized. Both durable bioplastics, such as Bio-PET or biopolyethylene (bio-based analogues of fossil-based polyethylene terephthalate and polyethylene), and degradable bioplastics, such as polylactic acid, polybutylene succinate, or polyhydroxyalkanoates, exist. Bioplastics must be recycled similar to fossil-based plastics to avoid plastic pollution; "drop-in" bioplastics (such as biopolyethylene) fit into existing recycling streams. On the other hand, recycling biodegradable bioplastics in the current recycling streams poses additional challenges, as it may raise the cost of sorting and decrease the yield and the quality of the recyclate. However, biodegradation is not the only acceptable end-of-life disposal pathway for biodegradable bioplastics, and mechanical and chemical recycling are often the preferred choice from the environmental point of view.
Biodegradability may offer an end-of-life pathway in certain applications, such as agricultural mulch, but the concept of biodegradation is not as straightforward as many believe. Susceptibility to biodegradation is highly dependent on the chemical backbone structure of the polymer, and different bioplastics have different structures, thus it cannot be assumed that bioplastic in the environment will readily disintegrate. Conversely, biodegradable plastics can also be synthesized from fossil fuels.
As of 2018, bioplastics represented approximately 2% of the global plastics output (>380 million tons). With continued research on bioplastics, investment in bioplastic companies and rising scrutiny on fossil-based plastics, bioplastics are becoming more dominant in some markets, while the output of fossil plastics also steadily increases. | 0 | Theoretical and Fundamental Chemistry |
* CPPs have been used to transport a variety of biomolecules into cells in both vitro and in vivo. One must be cautious of which CPPs are used. For example, different CPPs promote movement into different cell types and cellular components.
* If the TIVA tag is not used within 3 months of synthesis, the FRET signal is weakened.
* The storage of TIVA tag requires a -80 °C freezer and should be in dried form. | 1 | Applied and Interdisciplinary Chemistry |
In a suspension roaster, the concentrates are blown into a combustion chamber very similar to that of a pulverized coal furnace. The roaster consists of a refractory-lined cylindrical steel shell, with a large combustion space at the top and 2 to 4 hearths in the lower portion, similar to those of a multiple hearth furnace. Additional grinding, beyond that required for a multiple hearth furnace, is normally required to ensure that heat transfer to the material is sufficiently rapid for the desulfurization and oxidation reactions to occur in the furnace chamber. Suspension roasters are unpressurized and operate at about . | 1 | Applied and Interdisciplinary Chemistry |
A barb (or hose barb), which connects flexible hose or tubing to pipes, typically has a male-threaded end which mates with female threads. The other end of the fitting has a single- or multi-barbed tube—a long tapered cone with ridges, which is inserted into a flexible hose. | 1 | Applied and Interdisciplinary Chemistry |
A reconstruction is built by compiling data from the resources above. Database tools such as KEGG and BioCyc can be used in conjunction with each other to find all the metabolic genes in the organism of interest. These genes will be compared to closely related organisms that have already developed reconstructions to find homologous genes and reactions. These homologous genes and reactions are carried over from the known reconstructions to form the draft reconstruction of the organism of interest. Tools such as ERGO, Pathway Tools and Model SEED can compile data into pathways to form a network of metabolic and non-metabolic pathways. These networks are then verified and refined before being made into a mathematical simulation.
The predictive aspect of a metabolic reconstruction hinges on the ability to predict the biochemical reaction catalyzed by a protein using that protein's amino acid sequence as an input, and to infer the structure of a metabolic network based on the predicted set of reactions. A network of enzymes and metabolites is drafted to relate sequences and function. When an uncharacterized protein is found in the genome, its amino acid sequence is first compared to those of previously characterized proteins to search for homology. When a homologous protein is found, the proteins are considered to have a common ancestor and their functions are inferred as being similar. However, the quality of a reconstruction model is dependent on its ability to accurately infer phenotype directly from sequence, so this rough estimation of protein function will not be sufficient. A number of algorithms and bioinformatics resources have been developed for refinement of sequence homology-based assignments of protein functions:
* [http://inparanoid.sbc.su.se/cgi-bin/index.cgi InParanoid]: Identifies eukaryotic orthologs by looking only at in-paralogs.
* [https://www.ncbi.nlm.nih.gov/cdd CDD]: Resource for the annotation of functional units in proteins. Its collection of domain models utilizes 3D structure to provide insights into sequence/structure/function relationships.
* [http://www.ebi.ac.uk/interpro/ InterPro]: Provides functional analysis of proteins by classifying them into families and predicting domains and important sites.
* [http://string.embl.de/ STRING]: Database of known and predicted protein interactions.
Once proteins have been established, more information about the enzyme structure, reactions catalyzed, substrates and products, mechanisms, and more can be acquired from databases such as [http://www.kegg.jp/ KEGG], [http://www.metacyc.org/ MetaCyc] and [http://www.chem.qmul.ac.uk/iubmb/enzyme/ NC-IUBMB]. Accurate metabolic reconstructions require additional information about the reversibility and preferred physiological direction of an enzyme-catalyzed reaction which can come from databases such as [https://web.archive.org/web/20150506193454/http://www.brenda-enzymes.org/ BRENDA] or [http://www.metacyc.org/ MetaCyc] database. | 1 | Applied and Interdisciplinary Chemistry |
Although not as nutritious as other organs such as fruit, leaves provide a food source for many organisms. The leaf is a vital source of energy production for the plant, and plants have evolved protection against animals that consume leaves, such as tannins, chemicals which hinder the digestion of proteins and have an unpleasant taste. Animals that are specialized to eat leaves are known as folivores.
Some species have cryptic adaptations by which they use leaves in avoiding predators. For example, the caterpillars of some leaf-roller moths will create a small home in the leaf by folding it over themselves. Some sawflies similarly roll the leaves of their food plants into tubes. Females of the Attelabidae, so-called leaf-rolling weevils, lay their eggs into leaves that they then roll up as means of protection. Other herbivores and their predators mimic the appearance of the leaf. Reptiles such as some chameleons, and insects such as some katydids, also mimic the oscillating movements of leaves in the wind, moving from side to side or back and forth while evading a possible threat. | 0 | Theoretical and Fundamental Chemistry |
There are two basic forms of devolatilization to a vacuum. In foam devolatilization, bubbles inside the polymer solution nucleate and grow, finally bursting and releasing their volatile content to the surroundings. This requires sufficient vapor pressure. If possible, this is a very efficient method because the volatiles only need to diffuse a short way.
Film devolatilization occurs when there is no longer sufficient vapor pressure to generate bubbles, and requires on sufficient surface area and good mixing. In this case, stripping agent such as nitrogen may be added to the polymer to induce improved mass transfer through bubbles. | 1 | Applied and Interdisciplinary Chemistry |
* The results are aesthetically pleasing.
* Creates a clean, smooth surface that is easier to sterilise.
* Can polish areas that are inaccessible by other polishing methods.
* Removes a small amount of material (typically 20-40 micrometre in depth in the case of stainless steel) from the surface of the parts, while also removing small burrs or high spots. It can be used to reduce the size of parts when necessary.
* Stainless steel preferentially removes iron from the surface and enhances the chromium/nickel content for the most superior form of passivation for stainless steel.
* Electropolishing can be used on a wide range of metals including stainless steel, aluminum, copper, brass and titanium. | 1 | Applied and Interdisciplinary Chemistry |
Tris(cyclooctatetraene)triiron or Fe(COT), also referred to as the Lavallo-Grubbs compound (after its discoverers) is an organoiron compound with the formula Fe(CH). It is a pyrophoric, black crystalline solid, which is insoluble in common organic solvents.The compound represents a rare example of a hydrocarbon analogue of the well-known Triiron dodecacarbonyl (Fe(CO)), originally prepared by Dewar and Jones in the early 20th century. | 0 | Theoretical and Fundamental Chemistry |
Four members of 2A peptides family are frequently used in life science research. They are P2A, E2A, F2A, and T2A. F2A is derived from foot-and-mouth disease virus 18; E2A is derived from equine rhinitis A virus; P2A is derived from porcine teschovirus-1 2A; T2A is derived from thosea asigna virus 2A.
The following table shows the sequences of four members of 2A peptides. Adding the optional linker “GSG” (Gly-Ser-Gly) on the N-terminal of a 2A peptide helps with efficiency. | 1 | Applied and Interdisciplinary Chemistry |
Higher selectivity: for example, positive, negative and neutral substances could be separated by a reversed phase (RP)/anion-cation exchange (ACE) column in a single run.
Higher loading capacity,
for example, loading capacity of ACE/ hydrophilic interaction chromatography (HILIC) increased 10-100 times when compared with RPLC,
which offered a new selection and idea for developing semi-preparative and preparative chromatography.
One mixed-mode column can replace two or even more single mode columns, which is economic and eco-friendly for employing the stationary phase more sufficiently and reducing the consuming and ‘waste’ of raw materials.
Single mixed-mode column can be applied for on-line two-dimensional (2D) analysis in a sealed system via establishing corresponding chromatographic system or off-line 2D analysis as two columns. | 0 | Theoretical and Fundamental Chemistry |
Oxygen has three stable isotopes, O, O, and O. Oxygen ratios are measured relative to Vienna Standard Mean Ocean Water (VSMOW) or Vienna Pee Dee Belemnite (VPDB). Variations in oxygen isotope ratios are used to track both water movement, paleoclimate, and atmospheric gases such as ozone and carbon dioxide. Typically, the VPDB oxygen reference is used for paleoclimate, while VSMOW is used for most other applications. Oxygen isotopes appear in anomalous ratios in atmospheric ozone, resulting from mass-independent fractionation. Isotope ratios in fossilized foraminifera have been used to deduce the temperature of ancient seas. | 0 | Theoretical and Fundamental Chemistry |
The residence time of a fluid parcel is the total time that the parcel has spent inside a control volume (e.g.: a chemical reactor, a lake, a human body). The residence time of a set of parcels is quantified in terms of the frequency distribution of the residence time in the set, which is known as residence time distribution (RTD), or in terms of its average, known as mean residence time.
Residence time plays an important role in chemistry and especially in environmental science and pharmacology. Under the name lead time or waiting time it plays a central role respectively in supply chain management and queueing theory, where the material that flows is usually discrete instead of continuous. | 0 | Theoretical and Fundamental Chemistry |
The Vital Question is a book by the English biochemist Nick Lane about the way the evolution and origin of life on Earth was constrained by the provision of energy.
The book was well received by critics; The New York Times, for example, found it "seductive and often convincing" though the reviewer considered much of it speculative beyond the evidence provided. The Guardian wrote that the book presented hard evidence and tightly interlocking theory on a question once thought inaccessible to science, the origin of life. New Scientist found the books arguments powerful and persuasive with many testable ideas; that it was not easy to read was compensated by the "incredible, epic story" that it told. The Telegraph wrote that the book succeeded brilliantly as science writing, expanding the readers horizons with a gripping narrative. | 1 | Applied and Interdisciplinary Chemistry |
Ommochrome (or visual pigment) refers to several biological pigments that occur in the eyes of crustaceans and insects. The eye color is determined by the ommochromes. Ommochromes are also found in the chromatophores of cephalopods, and in spiders.
Ommochromes are metabolites of tryptophan, via kynurenine and 3-hydroxykynurenine. They are responsible for a wide variety of colors, ranging from yellow over red and brown to black. Lighter colors tend to be generated by ommatins, while mixtures of ommatin and ommins are responsible for darker colors.
In spiders, ommochromes are usually deposited as pigment granules within the cells of the hypodermis, immediately beneath the cuticle.
A study on various insects showed that ommochromes in their eyes have high antioxidant activity. The ommochromes were found to have the ability to suppress the Maillard reaction. | 1 | Applied and Interdisciplinary Chemistry |
One of Salas primary areas of study concerned chemical identity and change. In 1610 Sala accompanied Count Johann von Nassau as a field doctor and between 1612 and 1617 he worked in The Hague. His experiments at this time with silver nitrate and silver salts were an important step towards the invention of the photographic process; He introduced the alchemical name "magisterium argenti," or "crystalli Dianae," for silver nitrate, which he also called "lapis lunearis" and described in his Opera medica chimicae' the smelting of silver nitrate.
In Septem planetarum terrestrium spagirica recensio (1614) he reported that "Si lapidem lunearem pulveratum ad solem exponas instar atramenti niggerimus" (When you expose powdered silver nitrate to sunlight, it turns black as ink), and also its effect on paper; silver nitrate wrapped in paper for a year turned black This discovery of the sun’s effect on powdered silver nitrate was not replicated by then "respected" scientists and was subsequently disregarded as having “no practical application," despite the use of silver nitrate in the practice of alchemy.
Robert Boyle made a similar observation later, but mistakenly believed that the darkening resulted from exposure to air, rather than light. | 1 | Applied and Interdisciplinary Chemistry |
Owing to the presence of covalently bonded fluorine, halothane absorbs in the atmospheric window and is therefore a greenhouse gas. However, it is much less potent than most other chlorofluorocarbons and bromofluorocarbons due to its short atmospheric lifetime, estimated at only one year vis-à-vis over 100 years for many perfluorocarbons. Despite its short lifespan, halothane still has a global warming potential 47 times that of carbon dioxide, although this is over 100 times smaller than the most abundant fluorinated gases, and about 800 times smaller than the GWP of sulfur hexafluoride over 500 years. Halothane is believed to make a negligible contribution to global warming. | 0 | Theoretical and Fundamental Chemistry |
Purified extracts of the sweet chili pepper containing capsinoids have been extensively studied through rigorous safety tests, including evaluation of chronic toxicity, reproduction, genotoxicity, and teratology in animals, single oral administration and pharmacokinetics in humans.
Capsinoids are hydrolyzed before absorption and break down to fatty acids and to vanillyl alcohol. According to human studies conducted to date, intact capsinoids are not present in the bloodstream following oral administration, suggesting minimal concern about untoward activation of TRPV1 receptors in other parts of the body. Single dose oral administration of up to 30 mg capsinoids did not raise blood pressure or heart rate in healthy volunteers, nor did administration of CH-19 Sweet. | 1 | Applied and Interdisciplinary Chemistry |
Inputs to the marine carbon cycle are numerous, but the primary contributions, on a net basis, come from the atmosphere and rivers. Hydrothermal vents generally supply carbon equal to the amount they consume. | 0 | Theoretical and Fundamental Chemistry |
If Germanium-75 is produced, it quickly decays to Arsenic. Germanium-76 is essentially stable, only decaying via extremely slow double beta decay to . | 0 | Theoretical and Fundamental Chemistry |
The speed of sound in seawater is about 1,500 m/s (whereas the speed of sound is usually around 330 m/s in air at roughly 101.3 kPa pressure, 1 atmosphere), and varies with water temperature, salinity, and pressure. The thermal conductivity of seawater is 0.6 W/mK at 25 °C and a salinity of 35 g/kg.
The thermal conductivity decreases with increasing salinity and increases with increasing temperature. | 0 | Theoretical and Fundamental Chemistry |
RAN translation produces a variety of dipeptide repeat proteins by translation of expanded hexanucleotide repeats present in an intron of the C9orf72 gene. The expansion of the hexanucleotide repeats and thus accumulation of dipeptide repeat proteins are thought to cause cellular toxicity that leads to neurodegeneration in ALS disease. | 1 | Applied and Interdisciplinary Chemistry |
In electrochemistry, a half-cell is a structure that contains a conductive electrode and a surrounding conductive electrolyte separated by a naturally occurring Helmholtz double layer. Chemical reactions within this layer momentarily pump electric charges between the electrode and the electrolyte, resulting in a potential difference between the electrode and the electrolyte. The typical anode reaction involves a metal atom in the electrode being dissolved and transported as a positive ion across the double layer, causing the electrolyte to acquire a net positive charge while the electrode acquires a net negative charge. The growing potential difference creates an intense electric field within the double layer, and the potential rises in value until the field halts the net charge-pumping reactions. This self-limiting action occurs almost instantly in an isolated half-cell; in applications two dissimilar half-cells are appropriately connected to constitute a Galvanic cell.
A standard half-cell consists of a metal electrode in an aqueous solution where the concentration of the metal ions is 1 molar (1 mol/L) at 298 kelvins (25 °C). In the case of the standard hydrogen electrode (SHE), a platinum electrode is used and is immersed in an acidic solution where the concentration of hydrogen ions is 1M, with hydrogen gas at 1atm being bubbled through solution. The electrochemical series, which consists of standard electrode potentials and is closely related to the reactivity series, was generated by measuring the difference in potential between the metal half-cell in a circuit with a standard hydrogen half-cell, connected by a salt bridge.
The standard hydrogen half-cell:
:2H(aq) + 2e → H(g)
The half-cells of a Daniell cell:
:Original equation
::Zn + Cu → Zn + Cu
:Half-cell (anode) of Zn
::Zn → Zn + 2e
:Half-cell (cathode) of Cu
::Cu + 2e → Cu | 0 | Theoretical and Fundamental Chemistry |
*Antimony potassium tartrate, an anion, that forms diastereomeric salts with chiral cations.
*Camphorsulfonic acid, an acid that forms diastereomeric salts with chiral amines
*1-Phenylethylamine, a base that forms diastereomeric salts with chiral acids. Many related chiral amines have been demonstrated.
The chiral pool consists of many widely available resolving agents. | 0 | Theoretical and Fundamental Chemistry |
The SSA can be measured by adsorption using the BET isotherm. This has the advantage of measuring the surface of fine structures and deep texture on the particles. However, the results can differ markedly depending on the substance adsorbed. The BET theory has inherent limitations but has the advantage to be simple and to yield adequate relative answers when the solids are chemically similar. In relatively rare cases, more complicated models based on thermodynamic approaches, or even quantum chemistry, may be applied to improve the consistency of the results, but at the cost of much more complex calculations requiring advanced knowledge and a good understanding from the operator. | 0 | Theoretical and Fundamental Chemistry |
The alpha effect is also dependent on solvent but not in a predictable way: it can increase or decrease with solvent mix composition or even go through a maximum. At least in some cases, the alpha effect has been observed to vanish if the reaction is conducted in the gas phase, leading some to conclude that it is primarily a solvation effect. However, this explanation has limitations since similar alpha effects could be found in different solvent systems and also because the solvation affects both the basicity and the nucleophilicity of the nucleophile. | 0 | Theoretical and Fundamental Chemistry |
Electropositive metals such as sodium, potassium, magnesium, zinc, etc. can insert into alkyl halides, breaking the carbon-halide bond
( halide could be chlorine, bromine, iodine ) and forming a carbon-metal bond. This reaction happens via a SET mechanism ( single-electron-transfer mechanism ). If magnesium reacts with an alkyl halide, it forms a Grignard reagent, or if lithium reacts, an organolithium reagent is formed. Thus, this type of insertion reactions has important applications in chemical synthesis. | 0 | Theoretical and Fundamental Chemistry |
The journal included reviews of research, books, and academic conferences, as well as primary results in the form of brief reports. It also reviewed what it considered to be notable aspects of patents and relevant scientific literature. Occasionally articles on the history, geological occurrences, and exploitation of platinum group metals were also published. | 1 | Applied and Interdisciplinary Chemistry |
Electrophoresis is the process of separating nucleic acid species based on their length by applying an electric field to them. As nucleic acids are negatively charged, they are pushed by an electric field through a matrix, usually an agarose gel, with the smaller molecules being pushed farther, faster. Capillary electrophoresis is a technique whereby small amounts of a nucleic acid sample can be run on a gel in a very thin tube. There is a detector in the machine that can tell when nucleic acid samples pass through a specific point in the tube, with smaller samples passing through first. This can produce an electropherogram such as the one in Figure 1, where length is related to time at which the samples pass the detector.
A marker is a sample of known size run along with the sample so that the actual size of the rest of the sample can be known by comparing their running distance/time to be relative to this marker.
RNA is a biological macromolecule made of sugars and nitrogenous bases that plays a number of crucial roles in all living cells. There are several subtypes of RNA, with the most prominent in the cell being tRNA (transfer RNA), rRNA (ribosomal RNA), and mRNA (messenger RNA). All three of these are involved in the process of translation, with the most prominent species (~85%) of cellular RNA being rRNA. As a result, this is the most immediately visible species when RNA is analyzed via electrophoresis and is thus used for determining RNA quality (see Computation, below). rRNA comes in various sizes, with those in mammals belonging to the sizes 5S, 18S, and 28S. The 28S and 5S rRNAs form the large subunit and the 18S forms the small subunit of the ribosome, the molecular machinery responsible for synthesizing proteins. | 1 | Applied and Interdisciplinary Chemistry |
NMR tubes are hard to clean because of their small bore. They are cleaned best before the sample has dried.
Cleaning is performed usually by rinsing with the same (non-deuterated) solvent used to dissolve the initial sample. Dichloromethane or acetone are good choices because dichloromethane is similar in polarity to chloroform, a common NMR solvent, while acetone dissolves many organic compounds. Sonication and scrubbing with a pipe cleaner may be helpful in removing traces of solid contaminants. If necessary, the tube may be filled with an oxidizing solution of aqua regia or piranha solution (HO/HSO). Care should be taken with these solutions, as they can unexpectedly and violently erupt from the NMR tube due to pressure build-up (aqua regia) or explosion (piranha). Chromic acid solutions are never used, due to traces of paramagnetic chromium left behind on the tubes causing interference with NMR experiments.
When the NMR tube is determined to be clean, it is triple-rinsed with distilled water and left to air-dry or dry in an oven at low temperature. It is best not to exceed 60 °C. At higher temperatures, slight tube distortion can occur which will affect tube camber. If NMR tubes are washed, a final rinse is recommended with a solvent that easily evaporates at 60 °C and that has no residue such as methanol. Avoid acetone, which leaves a residue. | 0 | Theoretical and Fundamental Chemistry |
* Small Footprint
* Proven enhanced nutrient removal (ENR)
* Up to 50-percent energy savings
* Excellent settling
* No chemical addition
* Resilient to fluctuations in pH, toxic shocks, loadings, and flows
* Easy operation with fully automated controls | 1 | Applied and Interdisciplinary Chemistry |
The hepatocyte is a complex and multifunctional differentiated cell whose cell response will be influenced by the zone in hepatic lobule, because concentrations of oxygen and toxic substances present in the hepatic sinusoids change from periportal zone to centrilobular zone10. The hepatocytes of the intermediate zone have the appropriate morphological and functional features since they have the environment with average concentrations of oxygen and other substances.
This specialized cell is capable of:
* Regulate glucose metabolism
# Via cAMP/PKA/TORC (transducers of regulated CREB)/CRE, PIP3 /PKB and PLC /IP3
# Expression of enzymes for synthesis, storage and distribution of glucose
* Synthesis of acute phase proteins
# Via JAK /STAT /APRE (acute phase response element)
# Expression of C-reactive protein, globulin protease inhibitors, complement, coagulation and fibrinolytic systems and iron homeostasis
* Regulate iron homeostasis (acute phase independent)
# Via Smads /HAMP
# Hepcidin expression
* Regulate lipid metabolism
# Via LXR /LXRE (LXR response element)
# Expression of ApoE CETP, FAS and LPL
* Exocrine production of bile salts and other compounds
# Via LXR /LXRE
# Expression of CYP7A1 and ABC transporters
* Degradate of toxic substances
# Via LXR /LXRE
# Expression of ABC transporters
* Endocrine production
# Via JAK/STAT /GHRE (growth hormone response element)
:IGF-1 and IGFBP-3 expression
# Via THR/THRE (thyroid hormone response element)
:Angiotensinogen expression
* Regenerate itself by hepatocyte mitosis
# Via STAT and Gab1: RAS/MAPK, PLC/IP3 and PI3K/FAK
# Cell growth, proliferation, survival, invasion and motility
The hepatocyte also regulates other functions for constitutive synthesis of proteins (albumin, ALT and AST) that influences the synthesis or activation of other molecules (synthesis of urea and essential amino acids), activate vitamin D, utilization of vitamin K, transporter expression of vitamin A and conversion of thyroxine. | 0 | Theoretical and Fundamental Chemistry |
The total dose is fractionated (spread out over time) for several important reasons. Fractionation allows normal cells time to recover, while tumor cells are generally less efficient in repair between fractions. Fractionation also allows tumor cells that were in a relatively radio-resistant phase of the cell cycle during one treatment to cycle into a sensitive phase of the cycle before the next fraction is given. Similarly, tumor cells that were chronically or acutely hypoxic (and therefore more radioresistant) may reoxygenate between fractions, improving the tumor cell kill.
Fractionation regimens are individualised between different radiation therapy centers and even between individual doctors. In North America, Australia, and Europe, the typical fractionation schedule for adults is 1.8 to 2 Gy per day, five days a week. In some cancer types, prolongation of the fraction schedule over too long can allow for the tumor to begin repopulating, and for these tumor types, including head-and-neck and cervical squamous cell cancers, radiation treatment is preferably completed within a certain amount of time. For children, a typical fraction size may be 1.5 to 1.8 Gy per day, as smaller fraction sizes are associated with reduced incidence and severity of late-onset side effects in normal tissues.
In some cases, two fractions per day are used near the end of a course of treatment. This schedule, known as a concomitant boost regimen or hyperfractionation, is used on tumors that regenerate more quickly when they are smaller. In particular, tumors in the head-and-neck demonstrate this behavior.
Patients receiving palliative radiation to treat uncomplicated painful bone metastasis should not receive more than a single fraction of radiation. A single treatment gives comparable pain relief and morbidity outcomes to multiple-fraction treatments, and for patients with limited life expectancy, a single treatment is best to improve patient comfort. | 0 | Theoretical and Fundamental Chemistry |
Hydroxylamine and its salts are commonly used as reducing agents in myriad organic and inorganic reactions. They can also act as antioxidants for fatty acids.
High concentrations of hydroxylamine are used by biologists to introduce mutations by acting as a DNA nucleobase amine-hydroxylating agent. In is thought to mainly act via hydroxylation of cytidine to hydroxyaminocytidine, which is misread as thymidine, thereby inducing C:G to T:A transition mutations. But high concentrations or over-reaction of hydroxylamine in vitro are seemingly able to modify other regions of the DNA & lead to other types of mutations. This may be due to the ability of hydroxylamine to undergo uncontrolled free radical chemistry in the presence of trace metals and oxygen, in fact in the absence of its free radical affects Ernst Freese noted hydroxylamine was unable to induce reversion mutations of its C:G to T:A transition effect & even considered hydroxylamine to be the most specific mutagen known. Practically, it has been largely surpassed by more potent mutagens such as EMS, ENU, or nitrosoguanidine, but being a very small mutagenic compound with high specificity, it found some specialized uses such as mutation of DNA packed within bacteriophage capsids, & mutation of purified DNA in vitro.
An alternative industrial synthesis of paracetamol developed by Hoechst–Celanese involves the conversion of ketone to a ketoxime with hydroxylamine.
Some non-chemical uses include removal of hair from animal hides and photographic developing solutions. In the semiconductor industry, hydroxylamine is often a component in the "resist stripper", which removes photoresist after lithography.
Hydroxylamine can also be used to better characterize the nature of a post-translational modification onto proteins. For example, poly(ADP-Ribose) chains are sensitive to hydroxylamine when attached to glutamic or aspartic acids but not sensitive when attached to serines. Similarly, Ubiquitin molecules bound to serines or threonines residues are sensitive to hydroxylamine, but those bound to lysine (isopeptide bond) are resistant. | 0 | Theoretical and Fundamental Chemistry |
Potassium thioacetate is an organosulfur compound and a salt with the formula . This white, water-soluble solid is used as a reagent for preparing thioacetate esters and other derivatives. | 0 | Theoretical and Fundamental Chemistry |
Strained alkenes also utilize strain-relief as a driving force that allows for their participation in click reactions. Trans-cycloalkenes (usually cyclooctenes) and other strained alkenes such as oxanorbornadiene react in click reactions with a number of partners including azides, tetrazines and tetrazoles. These reaction partners can interact specifically with the strained alkene, staying bioorthogonal to endogenous alkenes found in lipids, fatty acids, cofactors and other natural products. | 0 | Theoretical and Fundamental Chemistry |
This is another factor which slows the motion of ions within a solution. It is the tendency of the applied potential to move the ionic atmosphere itself. This drags the solvent molecules along because of the attractive forces between ions and solvent molecules. As a result, the central ion at the centre of the ionic atmosphere is influenced to move towards the pole opposite its ionic atmosphere. This inclination retards its motion. | 0 | Theoretical and Fundamental Chemistry |
* Nitinol is highly biocompatible and has properties suitable for use in orthopedic implants. Due to nitinol's unique properties it has seen a large demand for use in less invasive medical devices. Nitinol tubing is commonly used in catheters, stents, and superelastic needles.
* In colorectal surgery, the material is used in devices for reconnecting the intestine after removing the pathogens.
* Nitinol is used for devices developed by Franz Freudenthal to treat patent ductus arteriosus, blocking a blood vessel that bypasses the lungs and has failed to close after birth in an infant.
* In dentistry, the material is used in orthodontics for brackets and wires connecting the teeth. Once the SMA wire is placed in the mouth its temperature rises to ambient body temperature. This causes the nitinol to contract back to its original shape, applying a constant force to move the teeth. These SMA wires do not need to be retightened as often as other wires because they can contract as the teeth move unlike conventional stainless steel wires. Additionally, nitinol can be used in endodontics, where nitinol files are used to clean and shape the root canals during the root canal procedure. Because of the high fatigue tolerance and flexibility of nitinol, it greatly decreases the possibility of an endodontic file breaking inside the tooth during root canal treatment, thus improving safety for the patient.
* Another significant application of nitinol in medicine is in stents: a collapsed stent can be inserted into an artery or vein, where body temperature warms the stent and the stent returns to its original expanded shape following removal of a constraining sheath; the stent then helps support the artery or vein to improve blood flow. It is also used as a replacement for sutures—nitinol wire can be woven through two structures then allowed to transform into its preformed shape, which should hold the structures in place.
* Similarly, collapsible structures composed of braided, microscopically-thin nitinol filaments can be used in neurovascular interventions such as stroke thrombolysis, embolization, and intracranial angioplasty.
* A more recent application of nitinol wire is in female contraception, specifically in intrauterine devices. | 1 | Applied and Interdisciplinary Chemistry |
The preinitiation complex, which contains a mediator, transcription factors, a nucleosome and RNA polymerase II, is important to position the polymerase for the start of transcription. Before RNA synthesis can occur, the polymerase must dissociate from mediator. This appears to be accomplished by phosphorylation of part of the polymerase by a kinase. Importantly, mediator and transcription factors do not dissociate from the DNA at the time polymerase begins transcription. Rather, the complex remains at the promoter to recruit another RNA polymerase to begin another round of transcription.
There is some evidence to suggest that mediator in a yeast is involved in regulating RNA polymerase III (Pol III) transcripts of tRNAs In support of that evidence, an independent report showed specific association of mediator with Pol III in Saccharomyces cerevisiae. Those authors also reported specific associations with RNA polymerase I and proteins involved in transcription elongation and RNA processing, supporting other evidence of mediator's involvement in elongation and processing. | 1 | Applied and Interdisciplinary Chemistry |
Deprotonation of carbene precursor salts with strong bases has proved a reliable route to almost all stable carbenes:
Imidazol-2-ylidenes and dihydroimidazol-2-ylidenes, such IMes, have been prepared by the deprotonation of the respective imidazolium and dihydroimidazolium salts. The acyclic carbenes and the tetrahydropyrimidinyl based carbenes were prepared by deprotonation using strong homogeneous bases.
Several bases and reaction conditions have been employed with varying success. The degree of success has been principally dependent on the nature of the precursor being deprotonated. The major drawback with this method of preparation is the problem of isolation of the free carbene from the metals ions used in their preparation. | 0 | Theoretical and Fundamental Chemistry |
Water is amphoteric: it has the ability to act as either an acid or a base in chemical reactions. According to the Brønsted-Lowry definition, an acid is a proton () donor and a base is a proton acceptor. When reacting with a stronger acid, water acts as a base; when reacting with a stronger base, it acts as an acid. For instance, water receives an ion from HCl when hydrochloric acid is formed:
In the reaction with ammonia, , water donates a ion, and is thus acting as an acid:
Because the oxygen atom in water has two lone pairs, water often acts as a Lewis base, or electron-pair donor, in reactions with Lewis acids, although it can also react with Lewis bases, forming hydrogen bonds between the electron pair donors and the hydrogen atoms of water. HSAB theory describes water as both a weak hard acid and a weak hard base, meaning that it reacts preferentially with other hard species:
When a salt of a weak acid or of a weak base is dissolved in water, water can partially hydrolyze the salt, producing the corresponding base or acid, which gives aqueous solutions of soap and baking soda their basic pH:
: + NaOH + | 1 | Applied and Interdisciplinary Chemistry |
While obtaining qualitative information about the elemental composition of a surface is relatively straightforward, it is necessary to understand the statistical cross-section of interaction between ion and surface atoms in order to obtain quantitative information. Stated another way, it is easy to find out if a particular species is present, but much more difficult to determine how much of this species is there.
The two-body collision model fails to give quantitative results as it ignores the contributions of coulomb repulsion as well as the more complicated effects of charge screening by electrons. This is generally less of a problem in MEIS and RBS experiments but presents issues in LEIS. Coulomb repulsion occurs between positively charged primary ions and the nuclei of surface atoms. The interaction potential is given as:
Where and are the atomic numbers of the primary ion and surface atom, respectively, is the elementary charge, is the interatomic distance, and is the screening function. accounts for the interference of the electrons orbiting each nucleus. In the case of MEIS and RBS, this potential can be used to calculate the Rutherford scattering cross section (see Rutherford scattering) :
As shown at right, represents a finite region for an incoming particle, while represents the solid scattering angle after the scattering event. However, for LEIS is typically unknown which prevents such a clean analysis. Additionally, when using noble gas ion beams there is a high probability of neutralization on impact (which has strong angular dependence) due to the strong desire of these ions to be in a neutral, closed shell state. This results in poor secondary ion flux. See AISS and TOF-SARS below for approaches to avoiding this problem. | 0 | Theoretical and Fundamental Chemistry |
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