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The use of chlorofluorocarbons as aerosols in medicine, such as USP-approved salbutamol, has been phased out by the U.S. Food and Drug Administration. A different propellant known as hydrofluoroalkane, or HFA, which was not known to harm the environment, was chosen to replace it.
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Applied and Interdisciplinary Chemistry
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In organic chemistry, spherical aromaticity is formally used to describe an unusually stable nature of some spherical compounds such as fullerenes and polyhedral boranes.
In 2000, Andreas Hirsch and coworkers in Erlangen, Germany, formulated a rule to determine when a fullerene would be aromatic. They found that if there were 2(n+1) π-electrons, then the fullerene would display aromatic properties. This follows from the fact that an aromatic fullerene must have full icosahedral (or other appropriate) symmetry, so the molecular orbitals must be entirely filled. This is possible only if there are exactly 2(n+1) electrons, where n is a nonnegative integer. In particular, for example, buckminsterfullerene, with 60 π-electrons, is non-aromatic, since 60/2 = 30, which is not a perfect square.
In 2011, Jordi Poater and Miquel Solà, expanded the rule to determine when an open-shell fullerene species would be aromatic. They found that if there were 2n+2n+1 π-electrons, then the fullerene would display aromatic properties. This follows from the fact that a spherical species having a same-spin half-filled last energy level with the whole inner levels being fully filled is also aromatic. It is similar to Baird's rule.
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Theoretical and Fundamental Chemistry
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The subject of bubble size is important because the aeration system in a wastewater or sewage treatment plant consumes an average of 50 to 70 percent of the energy of the entire plant. Increasing the oxygen transfer efficiency decreases the power the plant requires to provide the same quality of effluent water. Furthermore, fine bubble diffusers evenly spread out (often referred to as a grid arrangement) on the floor of a tank, provide the operator of the plant a great deal of operational flexibility. This can be used to create zones with high oxygen concentrations (oxic or aerobic), zones with minimal oxygen concentration (anoxic) and zones with no oxygen (anaerobic). This allows for more precise targeting and removal of specific contaminants.
The importance of achieving ever smaller bubble sizes has been a hotly debated subject in the industry as ultra fine bubbles (micrometre size) are generally perceived to rise too slowly and provide too little "pumpage" to provide adequate mixing of sewage in an aeration tank. On the other hand, the industry standard "fine bubble" with a typical discharge diameter of 2 mm is probably larger than it needs to be for many plants. Average bubble diameters of 0.9 mm are possible nowadays, using special polyurethane (PUR) or special recently developed EPDM membranes.
Fine bubble diffusers have largely replaced coarse bubble diffusers and mechanical aerators in most of the developed world and in much of the developing world. The exception would be in secondary treatment phases, such as activated sludge processing tanks, where 85 to 90 percent of any remaining solid materials (floating on the surface) are removed through settling or biological processes. The biological process uses air to encourage bacterial growth that would consume many of these waste materials, such as phosphorus and nitrogen that are dissolved in the wastewater. The larger air release openings of a coarse bubble diffuser helps to facilitate a higher oxygen transfer rate and bacterial growth. One disadvantage of using fine bubble diffusers in activated sludge tanks is the tendency of floc (particle) clogging the small air release holes.
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Applied and Interdisciplinary Chemistry
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A hypothetical azeotrope of constituents X and Y is shown in the adjacent diagram. Two sets of curves on a phase diagram one at an arbitrarily chosen low pressure and another at an arbitrarily chosen, but higher, pressure. The composition of the azeotrope is substantially different between the high- and low-pressure plots: higher in X for the high-pressure system. The goal is to separate X in as high a concentration as possible starting from point A. At the low pressure, it is possible by progressive distillation to reach a distillate at the point, B, which is on the same side of the azeotrope as A. Successive distillation steps near the azeotropic composition exhibit very little difference in boiling temperature. If this distillate is now exposed to the high pressure, it boils at point C. From C, by progressive distillation it is possible to reach a distillate at the point D, which is on the same side of the high-pressure azeotrope as C. If that distillate is then exposed again to the low pressure, it boils at point E, which is on the opposite side of the low-pressure azeotrope to A. So, by means of the pressure swing, it is possible to cross over the low-pressure azeotrope.
When the solution is boiled at point E, the distillate is poorer in X than the residue at point E. This means that the residue is richer in X than the distillate at point E. Indeed, progressive distillation can produce a residue as rich in X as is required.
In summary:
# Low-pressure rectification (A to B)
# High-pressure rectification (C to D)
# Low-pressure stripping (E to target purity)
* Rectification: the distillate, or "tops", is retained and exhibits an increasingly lower boiling point.
* Stripping: the residue, or "bottoms", is retained and exhibits an increasingly higher boiling point.
A mixture of 5% water with 95% tetrahydrofuran is an example of an azeotrope that can be economically separated using a pressure swing: a swing in this case between 1 atm and 8 atm. By contrast the composition of the water to ethanol azeotrope discussed earlier is not affected enough by pressure to be easily separated using pressure swings and instead, an entrainer may be added that either modifies the azeotropic composition and exhibits immiscibility with one of the components, or extractive distillation may be used.
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Applied and Interdisciplinary Chemistry
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Energy homeostasis is the homeostatic control of energy balance – the difference between energy obtained through food consumption and energy expenditure – in living systems.
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Applied and Interdisciplinary Chemistry
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Due to MoOPH's steric bulk, preferential attack at the O–O bond occurs from the less hindered enolate face in the absence of stereoelectronic factors.
In addition, nitriles with acidic alpha protons can be converted directly to cyanohydrins; however, in the case of branched nitriles, this reaction directly affords the ketone.
In the case of sulfones, alpha-hydroxylation leads directly to the ketone or aldehyde.
Common byproducts of the alpha-hydroxylation tend to include overoxidation to the corresponding dicarbonyl or intermolecular aldol reaction of the starting material. Procedures to prevent side reactions include the inverse addition of the enolate to MoOPH or careful control of the temperature (-78 to -20 °C). Notable miscellaneous reactions include MoOPH’s ability to oxidize alkylboranes directly to the alcohol with net stereo-retention.
MoOPH has also been shown to oxidize N-trimethylsilyl amides directly to the hydroxamic acid.
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Theoretical and Fundamental Chemistry
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Some enzymatic nitrification inhibitors, such as nitrapyrin, can also inhibit the oxidation of methane in methanotrophic bacteria. AMO shows similar kinetic turnover rates to methane monooxygenase (MMO) found in methanotrophs, indicating that MMO is a similar catalyst to AMO for the purpose of methane oxidation. Furthermore, methanotrophic bacteria share many similarities to oxidizers such as Nitrosomonas. The inhibitor profile of particulate forms of MMO (pMMO) shows similarity to the profile of AMO, leading to similarity in properties between MMO in methanotrophs and AMO in autotrophs.
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Applied and Interdisciplinary Chemistry
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Chemokines are functionally divided into two groups:
*Homeostatic: are constitutively produced in certain tissues and are responsible for basal leukocyte migration. These include: CCL14, CCL19, CCL20, CCL21, CCL25, CCL27, CXCL12 and CXCL13. This classification is not strict; for example, CCL20 can act also as pro-inflammatory chemokine.
*Inflammatory: these are formed under pathological conditions (on pro-inflammatory stimuli, such as IL-1, TNF-alpha, LPS, or viruses) and actively participate in the inflammatory response attracting immune cells to the site of inflammation. Examples are: CXCL-8, CCL2, CCL3, CCL4, CCL5, CCL11, CXCL10.
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Applied and Interdisciplinary Chemistry
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*1999 - Outstanding Faculty Award, State Council of Higher Education of Virginia (SCHEV)
*2007 - Jabir Ibn Hyyan (Geber) Award, Saudi Chemical Society
*2008 - SAE International Award for Research on Automotive Lubricants, Society of Automotive Engineering
*2012–13 - Jefferson Science Fellow (JSF), U.S. Department of State and USAID
*2012 - Fellow, American Physical Society (APS) "For pioneering contributions to the fields of ion-induced nucleation, ion mobility, thermochemistry and structures of molecular cluster ions, gas phase cluster polymerization, nanostructured materials and nanocatalysis"
*2013 - Fellow, American Association for the Advancement of Science (AAAS) "For Distinguished contributions to the fields of clusters, nucleation, nanostructured materials and nanocatalysis, particularly for the novel synthesis of advanced nanomaterials"
*2018 - Virginia Outstanding Scientist, Awarded by the Virginia Governor
*2021 - Distinguished Service Award, Virginia Section of the American Chemical Society
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Theoretical and Fundamental Chemistry
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Homogeneous metallocene catalysts, e.g., derived from or related to zirconocene dichloride introduced a level of microstructural control that was unavailable with heterogeneous systems. Metallocene catalysts are homogeneous single-site systems, implying that a uniform catalyst is present in the solution. In contrast, commercially important Ziegler-Natta heterogeneous catalysts contain a distribution of catalytic sites. The catalytic properties of single-site catalysts can be controlled by modification of the ligand. Initially ligand modifications focused on various cyclopentadienyl derivatives, but great diversity was uncovered through high throughput screening. These post-metallocene catalysts employ a range of chelating ligands, often including pyridine and amido (RN). These ligands are available in great diversity with respect to their steric and electronic properties. Such postmetallocene catalysts enabled the introduction of Chain shuttling polymerization.
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Theoretical and Fundamental Chemistry
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The corrosive effect of polluted, acidic city air on limestone and marble was noted in the 17th century by John Evelyn, who remarked upon the poor condition of the Arundel marbles.
Since the Industrial Revolution, emissions of sulfur dioxide and nitrogen oxides into the atmosphere have increased. In 1852, Robert Angus Smith was the first to show the relationship between acid rain and atmospheric pollution in Manchester, England. Smith coined the term "acid rain" in 1872.
In the late 1960s, scientists began widely observing and studying the phenomenon. At first, the main focus in this research lay on local effects of acid rain. Waldemar Christofer Brøgger was the first to acknowledge long-distance transportation of pollutants crossing borders from the United Kingdom to Norway – a problem systematically studied by Brynjulf Ottar in the 1970s. Ottars work was strongly influenced by Swedish soil scientist Svante Odén, who had drawn widespread attention to Europes acid rain problem in popular newspapers and wrote a landmark paper on the subject in 1968.
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Applied and Interdisciplinary Chemistry
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The gauche effect is very sensitive to solvent effects, due to the large difference in polarity between the two conformers. For example, 2,3-dinitro-2,3-dimethylbutane, which in the solid state exists only in the gauche conformation, prefers the gauche conformer in benzene solution by a ratio of 79:21, but in carbon tetrachloride, it prefers the anti conformer by a ratio of 58:42. Another case is trans-1,2 difluorocyclohexane, which has a larger preference for the di-equatorial conformer, rather than the anti-diaxial conformer, in more polar solvents.
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Theoretical and Fundamental Chemistry
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Anionic and cationic surfactants can be determined thermometrically by titrating one type against the other. For instance, benzalkonium chloride (a quaternary-type cationic surfactant) may be determined in cleaners and algaecides for swimming pools and spas by titrating with a standard solution of sodium dodecyl sulfate. Alternatively, anionic surfactants such as sodium lauryl sulfate can be titrated with cetyl pyridinium chloride.
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Theoretical and Fundamental Chemistry
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The origins of the field date back to the 1950s, when Yehuda Hirshberg developed the photochromic spiropyrans and suggested their use in data storage. In the 1970s, Valerii Barachevskii demonstrated that this photochromism could be produced by two-photon excitation, and at the end of the 1980s Peter M. Rentzepis showed that this could lead to three-dimensional data storage. A wide range of physical phenomena for data reading and recording have been investigated, large numbers of chemical systems for the medium have been developed and evaluated, and extensive work has been carried out in solving the problems associated with the optical systems required for the reading and recording of data. Currently, several groups remain working on solutions with various levels of development and interest in commercialization.
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Theoretical and Fundamental Chemistry
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Depending on the polymerization technique applied, two different types of poly(phthalaldehyde) can be acquired, linear and cyclic.
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Theoretical and Fundamental Chemistry
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Mixed-mode chromatography (MMC), or multimodal chromatography, refers to chromatographic methods that utilize more than one form of interaction between the stationary phase and analytes in order to achieve their separation. What is distinct from conventional single-mode chromatography is that the secondary interactions in MMC cannot be too weak, and thus they also contribute to the retention of the solutes.
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Theoretical and Fundamental Chemistry
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Coupling magnetic nanoparticles to gene vectors results in hundreds-fold increase of the uptake of these vectors on a time scale of minutes, thus leading to high transfection efficiency. Gene vector and magnetic nanoparticle complexes are transfected into cells after 10–15 minutes, which is faster than the 2–4 hours that other transfection methods require. After 24, 48 or 72 hours, most of the particles are localized in the cytoplasm, in vacuoles (membranes surrounded structure into cells) and occasionally in the cell nucleus.
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Applied and Interdisciplinary Chemistry
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*Thomas Edison's work in chemistry, including the development of carbon filaments and the nickel-iron battery and research into domestic sources of rubber at the Thomas Edison National Historical Park in West Orange, New Jersey, The Henry Ford in Dearborn, Michigan, and the Edison and Ford Winter Estates in Fort Myers, Florida.
*Izaak Maurits Kolthoff's role in establishing the modern discipline of analytical chemistry at the University of Minnesota in Minneapolis, Minnesota.
*The research and professional contributions of Rachel Holloway Lloyd, the first American woman to receive a Ph.D. in chemistry (awarded by the University of Zurich in 1887), at the University of Nebraska-Lincoln where she taught.
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Applied and Interdisciplinary Chemistry
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Denitrification is the reduction of nitrates back into nitrogen gas (), completing the nitrogen cycle. This process is performed by bacterial species such as Pseudomonas and Paracoccus, under anaerobic conditions. They use the nitrate as an electron acceptor in the place of oxygen during respiration. These facultatively (meaning optionally) anaerobic bacteria can also live in aerobic conditions. Denitrification happens in anaerobic conditions e.g. waterlogged soils. The denitrifying bacteria use nitrates in the soil to carry out respiration and consequently produce nitrogen gas, which is inert and unavailable to plants. Denitrification occurs in free-living microorganisms as well as obligate symbionts of anaerobic ciliates.
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Applied and Interdisciplinary Chemistry
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Mixtures containing HFC-43-10mee can replace CFC-113 and perfluorocarbon (PFC) as solvents in cleaning systems because HFC-43-10mee does not harm the ozone layer, unlike CFC-113 and PFC. Various mixtures of HFC-43-10mee are commercially available for a variety of cleaning purposes. Examples of zeotropic solvents in cleaning processes include:
* Zeotropic mixtures of HFC-43-10mee and hexamethyldisiloxane can dissolve silicones and are highly compatible with polycarbonates and polyurethane. They can be used to remove silicone lubricant from medical devices.
* Zeotropic mixtures of HFC-43-10mee and isopropanol can remove ions and water from materials without porous surfaces. This zeotropic mixture helps with absorption drying.
* Zeotropic mixtures of HFC-43-10mee, fluorosurfactant, and antistatic additives are energy-effiicient and environmentally safe drying fluids that provide spot-free drying.
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Applied and Interdisciplinary Chemistry
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In Nyāya Sūtra's Book 4, Chapter 1, verses 19–21, postulates God exists, states a consequence, then presents contrary evidence, and from contradiction concludes that the postulate must be invalid.
A literal interpretation of the three verses suggests that Nyāya school rejected the need for a God for the efficacy of human activity. Since human action and results do not require assumption or need of the existence of God, sutra IV.1.21 is seen as a criticism of the "existence of God and theism postulate". The context of the above verses includes various efficient causes. Nyāya Sūtra verses IV.1.22 to IV.1.24, for example, examine the hypothesis that "random chance" explains the world, after these Indian scholars had rejected God as the efficient cause.
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Applied and Interdisciplinary Chemistry
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The leakage current of logic switching transistors increases with temperature. In rare instances, this may lead to thermal runaway in digital circuits. This is not a common problem, since leakage currents usually make up a small portion of overall power consumption, so the increase in power is fairly modest — for an Athlon 64, the power dissipation increases by about 10% for every 30 degrees Celsius. For a device with a TDP of 100 W, for thermal runaway to occur, the heat sink would have to have a thermal resistivity of over 3 K/W (kelvins per watt), which is about 6 times worse than a stock Athlon 64 heat sink. (A stock Athlon 64 heat sink is rated at 0.34 K/W, although the actual thermal resistance to the environment is somewhat higher, due to the thermal boundary between processor and heatsink, rising temperatures in the case, and other thermal resistances.) Regardless, an inadequate heat sink with a thermal resistance of over 0.5 to 1 K/W would result in the destruction of a 100 W device even without thermal runaway effects.
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Applied and Interdisciplinary Chemistry
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Stable isotopes have become a popular method for understanding aquatic ecosystems because they can help scientists in understanding source links and process information in marine food webs. These analyses can also be used to a certain degree in terrestrial systems. Certain isotopes can signify distinct primary producers forming the bases of food webs and trophic level positioning. The stable isotope compositions are expressed in terms of delta values (δ) in permil (‰), i.e. parts per thousand differences from a standard. They express the proportion of an isotope that is in a sample. The values are expressed as:
: δX = [(R / R) – 1] × 10
where X represents the isotope of interest (e.g., C) and R represents the ratio of the isotope of interest and its natural form (e.g., C/C). Higher (or less negative) delta values indicate increases in a samples isotope of interest, relative to the standard, and lower (or more negative) values indicate decreases. The standard reference materials for carbon, nitrogen, and sulfur are Pee Dee Belamnite limestone, nitrogen gas in the atmosphere, and Cañon Diablo meteorite respectively. Analysis is usually done using a mass spectrometer, detecting small differences between gaseous elements. Analysis of a sample can cost anywhere from $30 to $100. Stable isotopes assist scientists in analyzing animal diets and food webs by examining the animal tissues that bear a fixed isotopic enrichment or depletion vs. the diet. Muscle or protein fractions have become the most common animal tissue used to examine the isotopes because they represent the assimilated nutrients in their diet. The main advantage to using stable isotope analysis as opposed to stomach content observations is that no matter what the status is of the animals stomach (empty or not), the isotope tracers in the tissues will give us an understanding of its trophic position and food source. The three major isotopes used in aquatic ecosystem food web analysis are C, N and S. While all three indicate information on trophic dynamics, it is common to perform analysis on at least two of the previously mentioned 3 isotopes for better understanding of marine trophic interactions and for stronger results.
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Theoretical and Fundamental Chemistry
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Quark–gluon plasma (QGP or quark soup) is an interacting localized assembly of quarks and gluons at thermal (local kinetic) and (close to) chemical (abundance) equilibrium. The word plasma signals that free color charges are allowed. In a 1987 summary, Léon van Hove pointed out the equivalence of the three terms: quark gluon plasma, quark matter and a new state of matter. Since the temperature is above the Hagedorn temperature—and thus above the scale of light u,d-quark mass—the pressure exhibits the relativistic Stefan-Boltzmann format governed by temperature to the fourth power () and many practically massless quark and gluon constituents. It can be said that QGP emerges to be the new phase of strongly interacting matter which manifests its physical properties in terms of nearly free dynamics of practically massless gluons and quarks. Both quarks and gluons must be present in conditions near chemical (yield) equilibrium with their colour charge open for a new state of matter to be referred to as QGP.
In the Big Bang theory, quark–gluon plasma filled the entire Universe before matter as we know it was created. Theories predicting the existence of quark–gluon plasma were developed in the late 1970s and early 1980s. Discussions around heavy ion experimentation followed suit and the first experiment proposals were put forward at CERN and BNL in the following years. Quark–gluon plasma was detected for the first time in the laboratory at CERN in the year 2000.
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Theoretical and Fundamental Chemistry
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Titanium powder metallurgy (P/M) offers the possibility of creating net shape or near net shape parts without the material loss and cost associated with having to machine intricate components from wrought billet. Powders can be produced by the blended elemental technique or by pre-alloying and then consolidated by metal injection moulding, hot isostatic pressing, direct powder rolling or laser engineered net shaping.
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Applied and Interdisciplinary Chemistry
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Besides trying to re-activate the tumor suppressive function of pRb, one other distinct approach to treat dysregulated pRb pathway cancers is to take advantage of certain cellular consequences induced by pRb loss. It has been shown that E2F stimulates expression of pro-apoptotic genes in addition to G1/S transition genes, however, cancer cells have developed defensive signaling pathways that protect themselves from death by deregulated E2F activity. Development of inhibitors of these protective pathways could thus be a synthetically lethal method to kill cancer cells with overactive E2F.
In addition, it has been shown that the pro-apoptotic activity of p53 is restrained by the pRb pathway, such that pRb deficient tumor cells become sensitive to p53 mediated cell death. This opens the door to research of compounds that could activate p53 activity in these cancer cells and induce apoptosis and reduce cell proliferation.
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Applied and Interdisciplinary Chemistry
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Solvents can affect rates through equilibrium-solvent effects that can be explained on the basis of the transition state theory. In essence, the reaction rates are influenced by differential solvation of the starting material and transition state by the solvent. When the reactant molecules proceed to the transition state, the solvent molecules orient themselves to stabilize the transition state. If the transition state is stabilized to a greater extent than the starting material then the reaction proceeds faster. If the starting material is stabilized to a greater extent than the transition state then the reaction proceeds slower. However, such differential solvation requires rapid reorientational relaxation of the solvent (from the transition state orientation back to the ground-state orientation). Thus, equilibrium-solvent effects are observed in reactions that tend to have sharp barriers and weakly dipolar, rapidly relaxing solvents.
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Theoretical and Fundamental Chemistry
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A new chapter was opened when Max Lewandowsky in 1899 in Berlin observed that adrenal extracts acted on the smooth muscle of the eye and orbit of cats — such as the iris dilator muscle and nictitating membrane — in the same way as sympathetic nerve stimulation. The correspondence was extended by John Newport Langley and, under his supervision, Thomas Renton Elliott in Cambridge. In four papers in volume 31, 1904, of the Journal of Physiology Elliott described the similarities organ by organ. His hypothesis stands in the abstract of a presentation to the Physiological Society of May 21, 1904, a little over ten years after Oliver and Schafer's presentation: ″Adrenalin does not excite sympathetic ganglia when applied to them directly, as does nicotine. Its effective action is localized at the periphery. I find that even after complete denervation, whether of three days’ or ten months’ duration, the plain muscle of the dilatator pupillae will respond to adrenalin, and that with greater rapidity and longer persistence than does the iris whose nervous relations are uninjured. Therefore, it cannot be than adrenalin excites any structure derived from, and dependent for its persistence on, the peripheral neurone. ... The point at which the stimulus of the chemical excitant is received, and transformed into what may cause the change of tension of the muscle fiber, is perhaps a mechanism developed out of the muscle cell in response to its union with the synapsing sympathetic fiber, the function of which is to receive and transform the nervous impulse. "Adrenalin" might then be the chemical stimulant liberated on each occasion when the impulse arrives at the periphery.″ The abstract is the ″birth certificate″ of chemical neurotransmission. Elliott was never so explicit again. It seems he was discouraged by the lack of a favorable response from his seniors, Langley in particular, and a few years later he left physiological research.
The breakthrough for chemical neurotransmission came when, in 1921, Otto Loewi in Graz demonstrated the ″humorale Übertragbarkeit der Herznervenwirkung″ in amphibians. Vagusstoff transmitted inhibition from the vagus nerves, and Acceleransstoff transmitted stimulation from the sympathetic nerves to the heart. Loewi took some years to commit himself with respect to the nature of the Stoffe, but in 1926 he was sure that Vagusstoff was acetylcholine, writing in 1936 ″I no longer hesitate to identify the Sympathicusstoff with adrenaline.″
He was correct in the latter statement. In most amphibian organs including the heart, the concentration of adrenaline far exceeds that of noradrenaline, and adrenaline is indeed the main transmitter. In mammals, however, difficulties arose. In a comprehensive structure-activity study of adrenaline-like compounds, Dale and the chemist George Barger in 1910 found that Elliotts hypothesis assumed a stricter parallelism between the effects of sympathetic nerve impulses and adrenaline than actually existed. For example, sympathetic impulses shared with adrenaline contractile effects in the trigone but not relaxant effects in the fundus of the cats urinary bladder. In this respect, ″amino-ethanol-catechol″ – noradrenaline – mimicked sympathetic nerves more closely than adrenaline did. The Harvard Medical School physiologist Walter Bradford Cannon, who had popularized the idea of a sympatho-adrenal system preparing the body for fight and flight, and his colleague Arturo Rosenblueth developed an elaborate but ″queer″ theory of two sympathins, sympathin E (excitatory) and sympathin I (inhibitory). The Belgian pharmacologist Zénon Bacq as well as Canadian and US-American pharmacologists between 1934 and 1938 suggested that noradrenaline might be the – or at least one – postganglionic sympathetic transmitter. However, nothing definite was brought to light till after the war. In the meantime, Dale created a terminology that has since imprinted the thinking of neuroscientists: nerve cells should be named after their transmitter, i.e. cholinergic if the transmitter was ″a substance like acetylcholine", and adrenergic if it was ″some substance like adrenaline″.
In 1936, the year when Loewi accepted adrenaline as the (amphibian) sympathetic transmitter, Dale and Loewi received the Nobel Prize in Physiology or Medicine ″for their discoveries relating to chemical transmission of nerve impulses″.
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Applied and Interdisciplinary Chemistry
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In organic chemistry, a primary carbon is a carbon atom which is bound to only one other carbon atom. It is thus at the end of a carbon chain. In case of an alkane, three hydrogen atoms are bound to a primary carbon (see propane in the figure on the right). A hydrogen atom could also be replaced by a hydroxy group (), which would make the molecule a primary alcohol.
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Theoretical and Fundamental Chemistry
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The simplest theoretical model is that of a homogeneous sphere surrounded by a conducting dielectric medium. For a homogeneous sphere of radius and complex permittivity in a medium with complex permittivity the (time-averaged) DEP force is:
The factor in curly brackets is known as the complex Clausius-Mossotti function and contains all the frequency dependence of the DEP force. Where the particle consists of nested spheres – the most common example of which is the approximation of a spherical cell composed of an inner part (the cytoplasm) surrounded by an outer layer (the cell membrane) – then this can be represented by nested expressions for the shells and the way in which they interact, allowing the properties to be elucidated where there are sufficient parameters related to the number of unknowns being sought.
For a more general field-aligned ellipsoid of radius and length with complex dielectric constant in a medium with complex dielectric constant the time-dependent dielectrophoretic force is given by:
The complex dielectric constant is , where is the dielectric constant, is the electrical conductivity, is the field frequency, and is the imaginary unit. This expression has been useful for approximating the dielectrophoretic behavior of particles such as red blood cells (as oblate spheroids) or long thin tubes (as prolate ellipsoids) allowing the approximation of the dielectrophoretic response of carbon nanotubes or tobacco mosaic viruses in suspension.
These equations are accurate for particles when the electric field gradients are not very large (e.g., close to electrode edges) or when the particle is not moving along an axis in which the field gradient is zero (such as at the center of an axisymmetric electrode array), as the equations only take into account the dipole formed and not higher order polarization. When the electric field gradients are large, or when there is a field null running through the center of the particle, higher order terms become relevant, and result in higher forces.
To be precise, the time-dependent equation only applies to lossless particles, because loss creates a lag between the field and the induced dipole. When averaged, the effect cancels out and the equation holds true for lossy particles as well. An equivalent time-averaged equation can be easily obtained by replacing E with E, or, for sinusoidal voltages by dividing the right hand side by 2.
These models ignores the fact that cells have a complex internal structure and are heterogeneous. A multi-shell model in a low conducting medium can be used to obtain information of the membrane conductivity and the permittivity of the cytoplasm.
For a cell with a shell surrounding a homogeneous core with its surrounding medium considered as a layer, as seen in Figure 2, the overall dielectric response is obtained from a combination of the properties of the shell and core.
where 1 is the core (in cellular terms, the cytoplasm), 2 is the shell (in a cell, the membrane). r1 is the radius from the centre of the sphere to the inside of the shell, and r2 is the radius from the centre of the sphere to the outside of the shell.
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Theoretical and Fundamental Chemistry
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In iron and steel metallurgy, ledeburite is a mixture of 4.3% carbon in iron and is a eutectic mixture of austenite and cementite. Ledeburite is not a type of steel as the carbon level is too high although it may occur as a separate constituent in some high carbon steels. It is mostly found with cementite or pearlite in a range of cast irons.
It is named after the metallurgist Karl Heinrich Adolf Ledebur (1837–1906). He was the first professor of metallurgy at the Bergakademie Freiberg and discovered ledeburite in 1882.
Ledeburite arises when the carbon content is between 2.06% and 6.67%. The eutectic mixture of austenite and cementite is 4.3% carbon, FeC:2Fe, with a melting point of 1147 °C.
Ledeburite-II (at ambient temperature) is composed of cementite-I with recrystallized secondary cementite (which separates from austenite as the metal cools) and (with slow cooling) of pearlite. The pearlite results from the eutectoidal decay of the austenite that comes from the ledeburite-I at 723 °C. During more rapid cooling, bainite can develop instead of pearlite, and with very rapid cooling martensite can develop.
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Applied and Interdisciplinary Chemistry
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Crystals can be classified in three ways: lattice systems, crystal systems and crystal families. The various classifications are often confused: in particular the trigonal crystal system is often confused with the rhombohedral lattice system, and the term "crystal system" is sometimes used to mean "lattice system" or "crystal family".
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Theoretical and Fundamental Chemistry
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The Stokes radius or Stokes–Einstein radius of a solute is the radius of a hard sphere that diffuses at the same rate as that solute. Named after George Gabriel Stokes, it is closely related to solute mobility, factoring in not only size but also solvent effects. A smaller ion with stronger hydration, for example, may have a greater Stokes radius than a larger ion with weaker hydration. This is because the smaller ion drags a greater number of water molecules with it as it moves through the solution.
Stokes radius is sometimes used synonymously with effective hydrated radius in solution. Hydrodynamic radius, R, can refer to the Stokes radius of a polymer or other macromolecule.
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Applied and Interdisciplinary Chemistry
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The nuclear Overhauser effect (NOE) is the transfer of nuclear spin polarization from one population of spin-active nuclei (e.g. H, C, N etc.) to another via cross-relaxation. A phenomenological definition of the NOE in nuclear magnetic resonance spectroscopy (NMR) is the change in the integrated intensity (positive or negative) of one NMR resonance that occurs when another is saturated by irradiation with an RF field. The change in resonance intensity of a nucleus is a consequence of the nucleus being close in space to those directly affected by the RF perturbation.
The NOE is particularly important in the assignment of NMR resonances, and the elucidation and confirmation of the structures or configurations of organic and biological molecules. The H two-dimensional NOE spectroscopy (NOESY) experiment and its extensions are important tools to identify stereochemistry of proteins and other biomolecules in solution, whereas in solid form crystal x-ray diffraction typically used to identify stereochemistry. The heteronuclear NOE is particularly important in C NMR spectroscopy to identify carbons bonded to protons, to provide polarization enhancements to such carbons to increase signal-to-noise, and to ascertain the extent the relaxation of these carbons is controlled by the dipole-dipole relaxation mechanism.
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Theoretical and Fundamental Chemistry
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Autoproteolysis takes place in some proteins, whereby the peptide bond is cleaved in a self-catalyzed intramolecular reaction. Unlike zymogens, these autoproteolytic proteins participate in a "single turnover" reaction and do not catalyze further reactions post-cleavage. Examples include cleavage of the Asp-Pro bond in a subset of von Willebrand factor type D (VWD) domains and Neisseria meningitidis FrpC self-processing domain, cleavage of the Asn-Pro bond in Salmonella FlhB protein, Yersinia YscU protein, as well as cleavage of the Gly-Ser bond in a subset of sea urchin sperm protein, enterokinase, and agrin (SEA) domains. In some cases, the autoproteolytic cleavage is promoted by conformational strain of the peptide bond.
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Applied and Interdisciplinary Chemistry
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Nomenclature of Inorganic Chemistry, IUPAC Recommendations 2005 is the 2005 version of Nomenclature of Inorganic Chemistry (which is informally called the Red Book). It is a collection of rules for naming inorganic compounds, as recommended by the International Union of Pure and Applied Chemistry (IUPAC).
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Theoretical and Fundamental Chemistry
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The karat (US spelling, symbol k or Kt) or carat (UK spelling, symbol c or Ct) is a fractional measure of purity for gold alloys, in parts fine per 24 parts whole. The karat system is a standard adopted by US federal law.
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Applied and Interdisciplinary Chemistry
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In Mesopotamia, from –2750 BC, the lost-wax technique was used for small-scale, and then later large-scale copper and bronze statues. One of the earliest surviving lost-wax castings is a small lion pendant from Uruk IV. Sumerian metalworkers were practicing lost-wax casting from approximately –3200 BC. Much later examples from northeastern Mesopotamia/Anatolia include the Great Tumulus at Gordion (late 8th century BC), as well as other types of Urartian cauldron attachments.
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Applied and Interdisciplinary Chemistry
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In organic chemistry, a guaianolide is a type of sesquiterpene lactone consisting of a gamma-lactone and either a cyclopentane or cyclopentene, both fused to a central cycloheptane or cycloheptene structure. There are two subclasses, structural isomers differing in the location that part of the lactone is bonded to the central ring, known as 6,12-guaianolides and 8,12-guaianolides.
Because some of the natural products in this class of tricyclic phytochemical have been found to be potentially biologically active, there has been interest in their chemical syntheses. The full biosynthetic origin of most of the known guaianolides has not been established, but the pathway is generally presumed to begin with the formation of a germacrene lactone derived from farnesyl pyrophosphate.
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Theoretical and Fundamental Chemistry
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The luteinizing hormone/choriogonadotropin receptor (LHCGR), also lutropin/choriogonadotropin receptor (LCGR) or luteinizing hormone receptor (LHR), is a transmembrane receptor found predominantly in the ovary and testis, but also many extragonadal organs such as the uterus and breasts. The receptor interacts with both luteinizing hormone (LH) and chorionic gonadotropins (such as hCG in humans) and represents a G protein-coupled receptor (GPCR). Its activation is necessary for the hormonal functioning during reproduction.
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Applied and Interdisciplinary Chemistry
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In a conventional oil refinery, isobutane is alkylated with low-molecular-weight alkenes (primarily a mixture of propene and butene) in the presence of a Brønsted acid catalyst, which can include solid acids (zeolites). The catalyst protonates the alkenes (propene, butene) to produce carbocations, which alkylate isobutane. The product, called "alkylate", is composed of a mixture of high-octane, branched-chain paraffinic hydrocarbons (mostly isoheptane and isooctane). Alkylate is a premium gasoline blending stock because it has exceptional antiknock properties and is clean burning. Alkylate is also a key component of avgas. By combining fluid catalytic cracking, polymerization, and alkylation, refineries can obtain a gasoline yield of 70 percent. The widespread use of sulfuric acid and hydrofluoric acid in refineries poses significant environmental risks. Ionic liquids are used in place of the older generation of strong Bronsted acids.
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Theoretical and Fundamental Chemistry
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The simplest method of obtaining 1,2-, 1,4-, and 1,6- heteroatom substitution patterns is to start with them. Biochemical and industrial processes can provide inexpensive sources of chemicals that have normally inaccessible substitution patterns. For example, amino acids, oxalic acid, succinic acid, adipic acid, tartaric acid, and glucose are abundant and provide nonroutine substitution patterns.
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Theoretical and Fundamental Chemistry
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*SSC, Noakhali R.K. Zilla H.E. School, 1945
*HSC, Comilla Victoria College, 1947
*BSc (Hons), Department of Chemistry, University of Dhaka, First in the First Class
*MSc, Department of Chemistry, University of Dhaka, First in the First Class, 1951
*PhD, Manchester University, UK (Thesis entitled "The Acid Behaviour of Carboxylic Derivatives", 5 July 1956) Awarded "Royal Commission for the Exhibition of 1851" to pursue PhD studies.
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Theoretical and Fundamental Chemistry
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Invalid if other proteins or immunoglobulins compete with TBG, including familial dysalbuminemic hyperthyroxinemia
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Applied and Interdisciplinary Chemistry
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* Deepening of the voice
* Growth of facial and body hair
* Male-pattern baldness
* Enlargement of the clitoris
* Breast atrophy – possible shrinking and/or softening of breasts
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Applied and Interdisciplinary Chemistry
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Push–pull technology was developed at the International Centre of Insect Physiology and Ecology (ICIPE) in Kenya in collaboration with Rothamsted Research, UK. and national partners in the 1990s. Research and development for the push-pull strategy was funded by a number of partners including the Gatsby Charitable Foundation of the UK, the Rockefeller Foundation, the UK’s Department for International Development, and the Global Environment Facility of the UNEP, among others.
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Applied and Interdisciplinary Chemistry
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mTOR integrates the input from upstream pathways, including insulin, growth factors (such as IGF-1 and IGF-2), and amino acids. mTOR also senses cellular nutrient, oxygen, and energy levels. The mTOR pathway is a central regulator of mammalian metabolism and physiology, with important roles in the function of tissues including liver, muscle, white and brown adipose tissue, and the brain, and is dysregulated in human diseases, such as diabetes, obesity, depression, and certain cancers. Rapamycin inhibits mTOR by associating with its intracellular receptor FKBP12. The FKBP12–rapamycin complex binds directly to the FKBP12-Rapamycin Binding (FRB) domain of mTOR, inhibiting its activity.
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Applied and Interdisciplinary Chemistry
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Polymer-protein conjugates can also form a higher ordered supramolecular structure via self-assembly of amphiphilic polymers into micelles and microcapsules, which is one of the most promising strategies to generate drug delivery systems. Such systems have the innate advantage of rapid preparation, a high drug loading capacity, ease of surface decoration, and the potential to be stimuli responsive.
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Applied and Interdisciplinary Chemistry
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The plot reveals whether hydrophobic amino acids are concentrated on one side of the helix, usually with polar or hydrophilic amino acids on the other. This arrangement is common in alpha helices within globular proteins, where one face of the helix is oriented toward the hydrophobic core and one face is oriented toward the solvent-exposed surface. Specific patterns characteristic of protein folds and protein docking motifs are also revealed, as in the identification of leucine zipper dimerization regions and coiled coils. This projection diagram is often called and "Edmundson wheel" after its inventor.
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Applied and Interdisciplinary Chemistry
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The ortho effect also occurs when a meta-directing group is positioned in a meta arrangement relative to an ortho–para-directing group, a new substituent introduced into the molecule tends to preferentially occupy the ortho position relative to the meta-directing group rather than the para position. Currently, there is no definitive explanation for the ortho effect, but it is hypothesized that there may be intramolecular assistance from the meta-directing group influencing the positioning of the incoming substituent. For example, the electrophilic aromatic nitration of 1-methyl-3-nitrobenzene affords 4-methyl-1,2-dinitrobenzene and 1-methyl-2,3-dinitrobenzene in 60.1% and 28.4% yields, respectively. In contrast, 2-methyl-1,4-dinitrobenzene (2c) is isolated in only 9.9% yield. As witnessed in the above example, when a π-acceptor substituent (πAS) is meta to a π-donor substituent (πDS), the electrophilic aromatic nitration occurs ortho to the πAS rather than para.
Similar results were also observed on the nitration of 3-methylbenzoic acid in which 5-methyl-2-nitrobenzoic acid and 3-methyl-2-nitrobenzoic acid were obtained as the major compounds, whereas 3-methyl-4-nitrobenzoic acid was reported as a minor compound. Also in nitration of the nitration of 3-bromobenzoic acid 5-bromo-2-nitrobenzoic acid (83%yield) was obtained as major product and 3-bromo-2-nitrobenzoic acid (13% yield) as minor. On an interesting note the potential isomer 3-bromo-4-nitrobenzoic acid was not detected.
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Theoretical and Fundamental Chemistry
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Shadowing and blocking are important concepts in almost all types of ion-surface interactions and result from the repulsive nature of the ion-nucleus interaction. As shown at right, when a flux of ions flows in parallel towards a scattering center (nucleus), they are each scattered according to the force of the Coulomb repulsion. This effect is known as shadowing. In a simple Coulomb repulsion model, the resulting region of “forbidden” space behind the scattering center takes the form of a paraboloid with radius at a distance L from the scattering center. The flux density is increased near the edge of the paraboloid.
Blocking is closely related to shadowing, and involves the interaction between scattered ions and a neighboring scattering center (as such it inherently requires the presence of at least two scattering centers). As shown, ions scattered from the first nucleus are now on diverging paths as they undergo interaction with the second nucleus. This interaction results in another “shadowing cone” now called a blocking cone where ions scattered from the first nucleus are blocked from exiting at angles below . Focusing effects again result in an increased flux density near .
In both shadowing and blocking, the "forbidden" regions are actually accessible to trajectories when the mass of incoming ions is greater than that of the surface atoms (e.g. Ar impacting Si or Al). In this case the region will have a finite but depleted flux density.
For higher energy ions such as those used in MEIS and RBS the concepts of shadowing and blocking are relatively straightforward since ion-nucleus interactions dominate and electron screening effects are insignificant. However, in the case of LEIS these screening effects do interfere with ion-nucleus interactions and the repulsive potential becomes more complicated. Also, multiple scattering events are very likely which complicates analysis. Importantly, due to the lower energy ions used LEIS is typically characterized by large interaction cross-sections and shadow cone radii. For this reason penetration depth is low and the method has much higher first-layer sensitivity than MEIS or RBS. Overall, these concepts are essential for data analysis in impact collision LEIS experiments (see below).
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Theoretical and Fundamental Chemistry
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A synonym for such neutron emission is "prompt neutron" production, of the type that is best known to occur simultaneously with induced nuclear fission. Induced fission happens only when a nucleus is bombarded with neutrons, gamma rays, or other carriers of energy. Many heavy isotopes, most notably californium-252, also emit prompt neutrons among the products of a similar spontaneous radioactive decay process, spontaneous fission.
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Theoretical and Fundamental Chemistry
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There are several other report types that have some resemblance in name or degree of detail to the Phase I Environmental Site Assessment:
Phase II Environmental Site Assessment is an "intrusive" investigation which collects original samples of soil, groundwater or building materials to analyze for quantitative values of various contaminants. This investigation is normally undertaken when a Phase I ESA determines a likelihood of site contamination. The most frequent substances tested are petroleum hydrocarbons, heavy metals, pesticides, solvents, asbestos and mold.
Phase III Environmental Site Assessment is an investigation involving remediation of a site. Phase III investigations aim to delineate the physical extent of contamination based on recommendations made in Phase II assessments. Phase III investigations may involve intensive testing, sampling, and monitoring, "fate and transport" studies and other modeling, and the design of feasibility studies for remediation and remedial plans. This study normally involves assessment of alternative cleanup methods, costs and logistics. The associated reportage details the steps taken to perform site cleanup and the follow-up monitoring for residual contaminants.
Limited Phase I Environmental Site Assessment is a truncated Phase I ESA, normally omitting one or more work segments such as the site visit or certain of the file searches. When the field visit component is deleted the study is sometimes called a Transaction Screen.
Environmental Assessment has little to do with the subject of hazardous substance liability, but rather is a study preliminary to an Environmental Impact Statement, which identifies environmental impacts of a land development action and analyzes a broad set of parameters including biodiversity, environmental noise, water pollution, air pollution, traffic, geotechnical risks, visual impacts, public safety issues and also hazardous substance issues.
SBA Phase I Environmental Site Assessment means properties purchased through the United States Small Business Administration's 504 Fixed Asset Financing Program require specific and often higher due diligence requirements than regular Real Estate transactions. Due diligence requirements are determined according to the NAICS codes associated with the prior business use of the property. There are 58 specific NAICS codes that require Phase I Investigations. These include, but are not limited to: Funeral Homes, Dry Cleaners, and Gas Stations. The SBA also requires Phase II Environmental Site Assessment to be performed on any Gas Station that has been in operation for more than 5 years. The additional cost to perform this assessment cannot be included in the amount requested in the loan and adds significant costs to the borrower.
Freddie Mac/Fannie Mae Phase I Environmental Site Assessments are two specialized types of Phase I ESAs that are required when a loan is financed through Freddie Mac or Fannie Mae. The scopes of work are based on the ASTM E1527-05 Standard but have specific requirements including the following: the percent and scope of the property inspection; requirements for radon testing; asbestos and lead-based paint testing and operations-and-maintenance (O&M) plans to manage the hazards in place; lead in drinking water; and mold inspection. For condominiums, Fannie Mae requires a Phase I ESA anytime the initial underwriting analysis indicates environmental concerns.
HUD Phase I Environmental Site Assessment
The U.S. Department of Housing and Urban Development also requires a Phase I ESA for any condominium under construction that wishes to offer an FHA insured loan to potential buyers.
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Applied and Interdisciplinary Chemistry
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Hydrothermal ore minerals, which typically form from high temperature aqueous solutions, trap tiny bubbles of liquids or gases when cooling and forming solid rock. The trapped fluid in an inclusion preserves a record of the composition, temperature and pressure of the mineralizing environment. An inclusion often contains two or more phases. If a vapor bubble is present in the inclusion along with a liquid phase, simple heating of the inclusion to the point of resorption of the vapor bubble gives a likely temperature of the original fluid. If minute crystals, such as halite, sylvite, hematite or sulfides, are present in the inclusion, they provide direct clues as to the composition of the original fluid.
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Theoretical and Fundamental Chemistry
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In 1964 Hisatsune and Surez investigated the infrared spectrum of metaborate anions in dilute solid solutions of potassium salt in alkali halides such as potassium chloride KCl.
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Theoretical and Fundamental Chemistry
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No laninamivir resistance has been reported. However it is a concern that resistance to laninamivir is similar to that of zanamivir because of the similarity in binding properties with the NA protein. Laninamivir octanoate (CS-8958), which is a prodrug of laninamivir (another inhaled NAI with long-acting properties), has also been approved in Japan and is commercially available under the name of Inavir (Daiichi Sankyo Company Ltd.
| 1 |
Applied and Interdisciplinary Chemistry
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Earl Sutherland of Vanderbilt University won a Nobel Prize in Physiology or Medicine in 1971 "for his discoveries concerning the mechanisms of the action of hormones", especially epinephrine, via second messengers (such as cyclic adenosine monophosphate, cyclic AMP).
| 1 |
Applied and Interdisciplinary Chemistry
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There are two principal signal transduction pathways involving the G protein-linked receptors: the cAMP signal pathway and the phosphatidylinositol signal pathway.
| 1 |
Applied and Interdisciplinary Chemistry
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Upon treatment with a standard acid, fluoride salts convert to hydrogen fluoride and metal salts. With strong acids, it can be doubly protonated to give fluoronium|. Oxidation of fluoride gives fluorine. Solutions of inorganic fluorides in water contain F and bifluoride . Few inorganic fluorides are soluble in water without undergoing significant hydrolysis. In terms of its reactivity, fluoride differs significantly from chloride and other halides, and is more strongly solvated in protic solvents due to its smaller radius/charge ratio. Its closest chemical relative is hydroxide, since both have similar geometries.
| 1 |
Applied and Interdisciplinary Chemistry
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This book is a description of the various types of veins that can be found. There are 30 illustrations of different forms of these veins, forming the majority of Book III. Agricola also describes a compass to determine the direction of veins and mentions that some writers claim that veins lying in certain directions are richer, although he provides counter-examples. He also mentions the theory that the sun draws the metals in veins to the surface, although he himself doubts this. Finally he explains that gold is not generated in the beds of streams and rivers and east-west streams are not more productive than others inherently. Gold occurs in streams because it is torn from veins by the water.
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Applied and Interdisciplinary Chemistry
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The Newton loop-node method is based on Kirchhoff’s first and second laws. The Newton loop-node method is the combination of the Newton nodal and loop methods and does not solve loop equations explicitly. The loop equations are transformed to an equivalent set of nodal equations, which are then solved to yield the nodal pressures. The nodal pressures are used then to calculate the corrections to the chord flows (which is synonymous to loop flows), and the tree branch flows are obtained from them.
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Applied and Interdisciplinary Chemistry
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An enyne is an organic compound containing a double bond (alkene) and a triple bond (alkyne). It is called a conjugated enyne when the double and triple bonds are conjugated.
The term is a contraction of the terms alkene and alkyne.
The simplest enyne is vinylacetylene.
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Theoretical and Fundamental Chemistry
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Adverse effects of dextromethorphan in overdose at doses 3 to 10 times the recommended therapeutic dose:
At doses 11 to 75 times the recommended therapeutic dose:
Episodic acute psychosis can occur when high doses of dextromethorphan are taken for recreational use, and an abundance of psychiatric symptoms can result, including dissociation and other PCP-like symptoms.
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Theoretical and Fundamental Chemistry
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Jean Brachets research in Brussel demonstrated the localization and relative abundance between RNA and DNA in the cells of both animals and plants opened up the door into the research of cytochemistry. The work by Moller and Holter in 1976 about endocytosis which discussed the relationship between a cells structure and function had established the needs of cytochemical research.
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Applied and Interdisciplinary Chemistry
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Hormones derived from the modification of amino acids are referred to as amine hormones. Typically, the original structure of the amino acid is modified such that a –COOH, or carboxyl, group is removed, whereas the , or amine, group remains. Amine hormones are synthesized from the amino acids tryptophan or tyrosine.
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Theoretical and Fundamental Chemistry
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In genetics, coverage is one of several measures of the depth or completeness of DNA sequencing, and is more specifically expressed in any of the following terms:
*Sequence coverage (or depth) is the number of unique reads that include a given nucleotide in the reconstructed sequence. Deep sequencing refers to the general concept of aiming for high number of unique reads of each region of a sequence.
*Physical coverage, the cumulative length of reads or read pairs expressed as a multiple of genome size.
*Genomic coverage, the percentage of all base pairs or loci of the genome covered by sequencing.
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Applied and Interdisciplinary Chemistry
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Open flow microperfusion (OFM) is a sampling method for clinical and preclinical drug development studies and biomarker research. OFM is designed for continuous sampling of analytes from the interstitial fluid (ISF) of various tissues. It provides direct access to the ISF by insertion of a small, minimally invasive, membrane-free probe with macroscopic openings. Thus, the entire biochemical information of the ISF becomes accessible regardless of the analyte's molecular size, protein-binding property or lipophilicity.
OFM is capable of sampling lipophilic and hydrophilic compounds, protein bound and unbound drugs, neurotransmitters, peptides and proteins, antibodies, nanoparticles and nanocarriers, enzymes and vesicles.
| 1 |
Applied and Interdisciplinary Chemistry
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The electron distribution around an atom or molecule undergoes fluctuations in time. These fluctuations create instantaneous electric fields which are felt by other nearby atoms and molecules, which in turn adjust the spatial distribution of their own electrons. The net effect is that the fluctuations in electron positions in one atom induce a corresponding redistribution of electrons in other atoms, such that the electron motions become correlated. While the detailed theory requires a quantum-mechanical explanation (see quantum mechanical theory of dispersion forces), the effect is frequently described as the formation of instantaneous dipoles that (when separated by vacuum) attract each other. The magnitude of the London dispersion force is frequently described in terms of a single parameter called the Hamaker constant, typically symbolized . For atoms that are located closer together than the wavelength of light, the interaction is essentially instantaneous and is described in terms of a "non-retarded" Hamaker constant. For entities that are farther apart, the finite time required for the fluctuation at one atom to be felt at a second atom ("retardation") requires use of a "retarded" Hamaker constant.
While the London dispersion force between individual atoms and molecules is quite weak and decreases quickly with separation like , in condensed matter (liquids and solids), the effect is cumulative over the volume of materials, or within and between organic molecules, such that London dispersion forces can be quite strong in bulk solid and liquids and decay much more slowly with distance. For example, the total force per unit area between two bulk solids decreases by where is the separation between them. The effects of London dispersion forces are most obvious in systems that are very non-polar (e.g., that lack ionic bonds), such as hydrocarbons and highly symmetric molecules like bromine (Bra liquid at room temperature) or iodine (I a solid at room temperature). In hydrocarbons and waxes, the dispersion forces are sufficient to cause condensation from the gas phase into the liquid or solid phase. Sublimation heats of e.g. hydrocarbon crystals reflect the dispersion interaction. Liquification of oxygen and nitrogen gases into liquid phases is also dominated by attractive London dispersion forces.
When atoms/molecules are separated by a third medium (rather than vacuum), the situation becomes more complex. In aqueous solutions, the effects of dispersion forces between atoms or molecules are frequently less pronounced due to competition with polarizable solvent molecules. That is, the instantaneous fluctuations in one atom or molecule are felt both by the solvent (water) and by other molecules.
Larger and heavier atoms and molecules exhibit stronger dispersion forces than smaller and lighter ones. This is due to the increased polarizability of molecules with larger, more dispersed electron clouds. The polarizability is a measure of how easily electrons can be redistributed; a large polarizability implies that the electrons are more easily redistributed. This trend is exemplified by the halogens (from smallest to largest: F, Cl, Br, I). The same increase of dispersive attraction occurs within and between organic molecules in the order RF, RCl, RBr, RI (from smallest to largest) or with other more polarizable heteroatoms. Fluorine and chlorine are gases at room temperature, bromine is a liquid, and iodine is a solid. The London forces are thought to arise from the motion of electrons.
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Theoretical and Fundamental Chemistry
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Caesium carbonate facilitates the N-alkylation of compounds such as sulfonamides, amines, β-lactams, indoles, heterocyclic compounds, N-substituted aromatic imides, phthalimides, and other similar compounds. Research on these compounds has focused on their synthesis and biological activity. In the presence of sodium tetrachloroaurate (), caesium carbonate is very efficient mechanism for aerobic oxidation of different kinds of alcohols into ketones and aldehydes at room temperature without additional polymeric compounds. There is no acid formation produced when primary alcohols are used. The process of selective oxidation of alcohols to carbonyls had been quite difficult due to the nucleophilic character of the carbonyl intermediate. In the past Cr(VI) and Mn(VII) reagents have been used to oxidize alcohols, however, these reagents are toxic and comparatively expensive. Caesium carbonate can also be used in Suzuki, Heck, and Sonogashira synthesis reactions. Caesium carbonate produces carbonylation of alcohols and carbamination of amines more efficiently than some of the mechanisms that have been introduced in the past. Caesium carbonate can be used for sensitive synthesis when a balanced strong base is needed.
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Theoretical and Fundamental Chemistry
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Many biochemists predicted when examining K. C. Nicolaou's biomimetic synthesis of the endiandric acid cascade that enzymes aided this reaction in the biosynthesis. The biomimetic series determined that this process took place synthetically through a series of Diels-Alder cyclization reactions and therefore led researches to believe that Diels-Alderase assisted the formation of endiandric acid C.
Although it has been discovered since then that many famous cyclization reactions like that of lovastatin do result from the Diels-Alderase they have determine that the endiandric acid cascade does not involve enzymes but rather spontaneously undergoes ring formation from a derivative of bisnoryangonin 5, which results from both the shikimate and acetic pathways. The 4-hydroxycinnamoyl-CoA, compound 2, is the precursor that comes from the shikimate pathway. Two units of malonyl CoA are then added to through the acetate pathway 3. Compound 3 is then reduced to the di-enol form that tautomerizes to give the bisnoryangonin 5. A small amount of compound 5 can be isolated, however S-adenosyl methionine methylates most of it and gives yangonin 6. It has been proposed that a bisnoryangonin derivative 7, is then reduced by dehydrogenase to give the polyene precursor 8, that goes through spontaneous 8π conrotatory, 6π disrotatory, and [4+2] cyclization reactions to form endiandric acid C. This proposal is supported by the fact that endiandric acids naturally occur as racemic mixtures and not in an enantiomerically pure form, which should happen if enzymes mediate this process. The Diels-Alder reaction itself is a powerful reaction that can give cyclic compounds with many stereogenic centers.
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Theoretical and Fundamental Chemistry
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Since stringent environmental regulations limiting emissions have been enacted in many countries, is being removed from flue gases by a variety of methods. Common methods used:
*Wet scrubbing using a slurry of alkaline sorbent, usually limestone or lime, or seawater to scrub gases;
*Spray-dry scrubbing using similar sorbent slurries;
*Wet sulfuric acid process recovering sulfur in the form of commercial quality sulfuric acid;
*SNOX Flue gas desulfurization removes sulfur dioxide, nitrogen oxides and particulates from flue gases;
*Dry sorbent injection systems that introduce powdered hydrated lime (or other sorbent material) into exhaust ducts to eliminate and from process emissions.
For a typical coal-fired power station, flue-gas desulfurization (FGD) may remove 90 per cent or more of the in the flue gases.
| 1 |
Applied and Interdisciplinary Chemistry
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Some members of the Heidelberg-Moscow collaboration claimed a detection of neutrinoless beta decay in Ge in 2001. This claim was criticized by outside physicists as well as other members of the collaboration. In 2006, a refined estimate by the same authors stated the half-life was 2.3 years. This half-life has been excluded at high confidence by other experiments, including in Ge by GERDA.
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Theoretical and Fundamental Chemistry
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In a crystal, a superstructure manifests itself through additional reflections in diffraction patterns, e.g., in low energy electron diffraction (LEED) or X-ray diffraction experiments. Often a set of weak diffraction spots appears between the stronger spots belonging to what is referred to as the substructure. In some cases a phase transition occurs, e.g., at higher temperatures, where the superstructure disappears and the material reverts to the simpler substructure. Not all compounds exhibit a superstructure.
The superspots in diffraction patterns represent a modulation of the substructure that causes the inherent translation symmetry of the (substructure) lattice to be violated slightly or the size of the repeat motif of the structure to be increased. One could speak of symmetry breaking of the translation symmetry of the lattice, although rotational symmetry may be lost simultaneously.
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Theoretical and Fundamental Chemistry
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In 1945 there were 38 furnaces worldwide, each with a capacity of 1 Mt/year. The process was favored in Germany due to the autarky policy of the Nazi regime, which prioritized the use of low-quality domestic iron ore. The transfer of technology between Nazi Germany and Imperial Japan led to the Japanese Empire benefiting from this process. Furnaces were installed in the co-prosperity sphere and operated by Japanese technicians. By the eve of the Pacific War, the process was being used in four steelworks in Japan.
After World War II all installations in Germany, China, and North Korea were dismantled, with 29 furnaces sent to the USSR as war reparations. Only the Japanese and Czechoslovakian plants remained functional.
In the 1950s Krupp rebuilt several large furnaces in Spain, Greece, and Germany. The Czechoslovakians were the primary drivers, constructing 16 furnaces and increasing process efficiency. The Great Soviet Encyclopedia reports that over 65 industrial plants, ranging from 60 to 110 meters in length and 3.6 to 4.6 meters in diameter, were constructed between 1930 and 1950. By 1960, 50 furnaces were producing 2 million tons per year in several countries.
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Applied and Interdisciplinary Chemistry
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Hybrid Fusion FISH ([http://www.prevnos.com/hybrid-fusion-fish HF-FISH]) uses primary additive excitation/emission combination of fluorophores to generate additional spectra through a labeling process known as dynamic optical transmission (DOT). Three primary fluorophores are able to generate a total of 7 readily detectable emission spectra as a result of combinatorial labeling using DOT. Hybrid Fusion FISH enables highly multiplexed FISH applications that are targeted within clinical oncology panels. The technology offers faster scoring with efficient probesets that can be readily detected with traditional fluorescent microscopes.
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Applied and Interdisciplinary Chemistry
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In the United States, modern MRFs began in the 1970s. Peter Karter established Resource Recovery Systems, Inc. in Branford, Connecticut, the "first materials recovery facility (MRF)" in the US.
| 1 |
Applied and Interdisciplinary Chemistry
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Steam locomotives and the steam engines used on ships and stationary applications such as power plants also require feedwater pumps. In this situation, though, the pump was often powered using a small steam engine that ran using the steam produced by the boiler. A means had to be provided, of course, to put the initial charge of water into the boiler (before steam power was available to operate the steam-powered feedwater pump). The pump was often a positive displacement pump that had steam valves and cylinders at one end and feedwater cylinders at the other end; no crankshaft was required.
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Applied and Interdisciplinary Chemistry
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Alpha hydroxy acids can be converted into amino acids directly using aqueous ammonia solution, hydrogen gas and a heterogeneous metallic ruthenium catalyst.
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Theoretical and Fundamental Chemistry
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The following assumptions are made regarding the problem in the vortex lattice method:
*The flow field is incompressible, inviscid and irrotational. However, small-disturbance subsonic compressible flow can be modeled if the general 3D Prandtl-Glauert transformation is incorporated into the method.
*The lifting surfaces are thin. The influence of thickness on aerodynamic forces are neglected.
*The angle of attack and the angle of sideslip are both small, small angle approximation.
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Applied and Interdisciplinary Chemistry
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Phosphites, sometimes called phosphite esters, have the general structure P(OR) with oxidation state +3. Such species arise from the alcoholysis of phosphorus trichloride:
:PCl + 3 ROH → P(OR) + 3 HCl
The reaction is general, thus a vast number of such species are known. Phosphites are employed in the Perkow reaction and the Michaelis–Arbuzov reaction. They also serve as ligands in organometallic chemistry.
Intermediate between phosphites and phosphines are phosphonites (P(OR)R) and phosphinite (P(OR)R). Such species arise via alcoholysis reactions of the corresponding phosphonous and phosphinous chlorides ((PClR) and (PClR) , respectively). The latter are produced by reaction of a phosphorus trichloride with a poor metal-alkyl complex, e.g. organomercury, organolead, or a mixed lithium-organoaluminum compound.
| 0 |
Theoretical and Fundamental Chemistry
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Addition polymers are generally chemically inert, involving strong C-C bonds. For this reason they are non-biodegradable and difficult to recycle. In contrast, condensation polymers tend to be more readily bio-degradable because their backbones contain weaker bonds.
| 0 |
Theoretical and Fundamental Chemistry
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There exist multiple transcription and translation mechanisms to prevent lethality due to deleterious mutations in the coding region. Such measures include proofreading by some DNA Polymerases during replication, mismatch repair following replication, and the Wobble Hypothesis which describes the degeneracy of the third base within an mRNA codon.
| 1 |
Applied and Interdisciplinary Chemistry
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Cp metal complexes are mainly used as stoichiometric reagents in chemical research. Ferrocenium reagents are oxidants. Cobaltocene is a strong, soluble reductant.
Derivatives of CpTiCl and CpZrCl are the basis of some reagents in organic synthesis. Upon treatment with aluminoxane, these dihalides give catalysts for olefin polymerization. Such species are called Kaminsky-type catalysts.
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Theoretical and Fundamental Chemistry
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Normally, angiotensin I is converted to angiotensin II by an angiotensin-converting enzyme (ACE). Angiotensin II constricts blood vessels, increasing blood pressure. Enalaprilat, the active metabolite of enalapril, inhibits ACE. Inhibition of ACE decreases levels of angiotensin II, leading to less vasoconstriction and decreased blood pressure.
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Theoretical and Fundamental Chemistry
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There are many design components of MBBR that come together to make the technology highly efficient. First, the process occurs in a basin (or aeration tank). The overall size of this tank is dependent on both the type and volume of wastewater being processed. The influent enters the basin at the beginning of treatment. Second component being the media. The media consists of the free-floating biocarriers mentioned earlier and can occupy as much as 70 percent of the tank. Third, an aeration grid is responsible for helping the media move through the basin and ensure the carriers come into contact with as much waste as possible, in addition to introducing more oxygen into the basin. Lastly, a sieve keeps all the carriers in the tank to prevent the plastic carriers from escaping the aeration.
Though there are a few different methods, they all use the same design components. The continuous flow method involves continuous flow of wastewater into the basin, with an equal flow of treated water exiting through the sieve. Intermittent aeration method operating in cycles of aeration and non-aeration, allowing for both aerobic conditions and anoxic conditions. Sequencing batch reactor (SBR) method is completed in a single reactor where several treatment steps occur in a sequence, where the treated water is removed before the cycle begins again. Large diameter submersible mixers are commonly used as a method for mixing in these systems.
| 1 |
Applied and Interdisciplinary Chemistry
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The material has the unusual property of changing to ammonium thiocyanate upon heating above . Upon cooling, the ammonium salt converts back to thiourea.
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Theoretical and Fundamental Chemistry
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Injectors or ejectors are made of carbon steel, stainless steel, brass, titanium, PTFE, carbon, and other materials.
| 1 |
Applied and Interdisciplinary Chemistry
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The needs of navigation may also require that a stable, continuous, navigable channel is prolonged from the navigable river to deep water at the mouth of the estuary. The interaction of river flow and tide needs to be modeled by computer or using scale models, moulded to the configuration of the estuary under consideration and reproducing in miniature the tidal ebb and flow and fresh-water discharge over a bed of very fine sand, in which various lines of training walls can be successively inserted. The models should be capable of furnishing valuable indications of the respective effects and comparative merits of the different schemes proposed for works.
| 1 |
Applied and Interdisciplinary Chemistry
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An evanescent field is a residue optical field that "leaks" during total internal reflection. This "leaking" of light fades off at an exponential rate. The evanescent field has found a number of applications in nanometer resolution imaging (microscopy); optical micromanipulation (optical tweezers) are becoming ever more relevant in research.
In optical tweezers, a continuous evanescent field can be created when light is propagating through an optical waveguide (multiple total internal reflection). The resulting evanescent field has a directional sense and will propel microparticles along its propagating path. This work was first pioneered by S. Kawata and T. Sugiura, in 1992, who showed that the field can be coupled to the particles in proximity on the order of 100 nanometers. This direct coupling of the field is treated as a type of photon tunnelling across the gap from prism to microparticles. The result is a directional optical propelling force.
A recent updated version of the evanescent field optical tweezers makes use of extended optical landscape patterns to simultaneously guide a large number of particles into a preferred direction without using a waveguide. It is termed as Lensless Optical Trapping ("LOT"). The orderly movement of the particles is aided by the introduction of Ronchi Ruling that creates well-defined optical potential wells (replacing the waveguide). This means that particles are propelled by the evanescent field while being trapped by the linear bright fringes. At the moment, there are scientists working on focused evanescent fields as well.
In recent studies, the evanescent field generated by mid-infrared laser has been used to sort particles by molecular vibrational resonance selectively. Mid-infrared light is commonly used to identify molecular structures of materials because the vibrational modes exist in the mid-infrared region. A study by Statsenko et al. described optical force enhancement by molecular vibrational resonance by exciting the stretching mode of Si-O-Si bond at 9.3 μm. It is shown that silica microspheres containing significant Si-O-Si bond move up to ten times faster than polystyrene microspheres due to molecular vibrational resonance. Moreover, this same group also investigated the possibility of optical force chromatography based on molecular vibrational resonance.
Another approach that has been recently proposed makes use of surface plasmons, which is an enhanced evanescent wave localized at a metal/dielectric interface. The enhanced force field experienced by colloidal particles exposed to surface plasmons
at a flat metal/dielectric interface has been for the first time measured using a photonic force microscope, the total force magnitude being found 40 times stronger compared to a normal evanescent wave. By patterning the surface with gold microscopic islands it is possible to have selective and parallel trapping in these islands. The forces of the latter optical tweezers lie in the femtonewton range.
The evanescent field can also be used to trap cold atoms and molecules near the surface of an optical waveguide or optical nanofiber.
| 1 |
Applied and Interdisciplinary Chemistry
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If one dimension is very large compared to the others, the principal strain in the direction of the longest dimension is constrained and can be assumed as constant, that means there will be effectively zero strain along it, hence yielding a plane strain condition (Figure 7.2). In this case, though all principal stresses are non-zero, the principal stress in the direction of the longest dimension can be disregarded for calculations. Thus, allowing a two dimensional analysis of stresses, e.g. a dam analyzed at a cross section loaded by the reservoir.
The corresponding strain tensor is:
and the corresponding stress tensor is:
in which the non-zero term arises from the Poisson's effect. However, this term can be temporarily removed from the stress analysis to leave only the in-plane terms, effectively reducing the analysis to two dimensions.
| 1 |
Applied and Interdisciplinary Chemistry
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There are mainly two types of mathematical models to predict the dynamic stall behaviour: semi-empirical models and computational fluid dynamics method. With regard to the latter method, because of the sophisticated flow field during the process of the dynamic stall, the full Navier-Stokes equations and proper models are adopted, and some promising results have been presented in the literature. However, to utilize this method precisely, proper turbulence models and transition models should be carefully selected. Furthermore, this method is also sometimes too computationally costly for research purposes as well as the pre-design of a helicopter rotor. On the other hand, to date some semi-empirical models have shown their capability of providing adequate precision, which contains sets of linear and nonlinear equations, based on classical unsteady thin-airfoil theory and parameterized by empirical coefficients. Therefore, a large number of experimental results are demanded to correct the empirical coefficients, and it is foreseeable that these models cannot be generally adapted to a wide range of conditions such as different airfoils, Mach numbers, and so on.
Here, two typical semi-empirical methods are presented to give insights into the modelling of dynamic stall.
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Applied and Interdisciplinary Chemistry
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In chemistry, sparging, also known as gas flushing in metallurgy, is a technique in which a gas is bubbled through a liquid in order to remove other dissolved gas(es) and/or dissolved volatile liquid(s) from that liquid. It is a method of degassing. According to Henry's law, the concentration of each gas in a liquid is proportional to the partial pressure of that gas (in the gaseous state) in contact with the liquid. Sparging introduces a gas that has little or no partial pressure of the gas(es) to be removed, and increases the area of the gas-liquid interface, which encourages some of the dissolved gas(es) to diffuse into the sparging gas before the sparging gas escapes from the liquid. Many sparging processes, such as solvent removal, use air as the sparging gas. To remove oxygen, or for sensitive solutions or reactive molten metals, a chemically inert gas such as nitrogen, argon, or helium is used.
| 1 |
Applied and Interdisciplinary Chemistry
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Magnesium can be removed either thermally or by reactive measures through the dissolution in acid.
Esen & Bor found a critical content of magnesium as a space holder to be 55-60%, above which compacts shrink excessively during sintering. Foams ranging in porosity from 45 to 70% with a bimodal pore distribution and compressive strength of 15 MPa (for 70% porosity) were demonstrated. Kim et al. fabricated foams with anisotropic pores through the intentional deformation of Mg particles during compaction in an effort to enhance mechanical properties. A final porosity of 70% equated to a yield strength of 38 MPa for normal orientation of pores and 59 MPa when pores were aligned with the direction of compression.
| 0 |
Theoretical and Fundamental Chemistry
|
Control of flux through a metabolic pathway requires that
*The degree to which metabolic steps determine the metabolic flux varies based on the organisms' metabolic needs.
*The change in flux that occurs due to the above requirement being communicated to the rest of the metabolic pathway in order to maintain a steady-state.
Control of flux in a metabolic pathways:
*The control of flux is a systemic property, that is it depends, to varying degrees, on all interactions in the system.
*The control of flux is measured by the flux control coefficient
*In a linear chain of reactions, the flux control coefficient will have values between zero and one.
*A step with a flux control coefficient of zero means that, that particular step, has no influence over the steady-state flux.
*A step in a linear chain with a flux control coefficient of one means that that particular step has complete control over the steady-state flux.
*A flux control coefficient can only be measured in the intact system and cannot for example be determined by inspection of an isolated enzyme in vitro.
| 1 |
Applied and Interdisciplinary Chemistry
|
After a hiatus, Norşuntepe was again occupied during the Early Bronze Age. During this period, the site was surrounded by a mudbrick city wall built on a stone foundation. There is evidence for copper production and some sort of palace or large, central building appears at the site in the final phases. In terms of material culture and architecture, there are clear parallels with Transcaucasia, and the Kura–Araxes culture. The latest Early Bronze Age phase in Norşuntepe ends in fire.
| 1 |
Applied and Interdisciplinary Chemistry
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The sphere packing problem is the three-dimensional version of a class of ball-packing problems in arbitrary dimensions. In two dimensions, the equivalent problem is packing circles on a plane. In one dimension it is packing line segments into a linear universe.
In dimensions higher than three, the densest lattice packings of hyperspheres are known up to 8 dimensions. Very little is known about irregular hypersphere packings; it is possible that in some dimensions the densest packing may be irregular. Some support for this conjecture comes from the fact that in certain dimensions (e.g. 10) the densest known irregular packing is denser than the densest known regular packing.
In 2016, Maryna Viazovska announced a proof that the E lattice provides the optimal packing (regardless of regularity) in eight-dimensional space, and soon afterwards she and a group of collaborators announced a similar proof that the Leech lattice is optimal in 24 dimensions. This result built on and improved previous methods which showed that these two lattices are very close to optimal.
The new proofs involve using the Laplace transform of a carefully chosen modular function to construct a radially symmetric function such that and its Fourier transform both equal 1 at the origin, and both vanish at all other points of the optimal lattice, with negative outside the central sphere of the packing and positive. Then, the Poisson summation formula for is used to compare the density of the optimal lattice with that of any other packing. Before the proof had been formally refereed and published, mathematician Peter Sarnak called the proof "stunningly simple" and wrote that "You just start reading the paper and you know this is correct."
Another line of research in high dimensions is trying to find asymptotic bounds for the density of the densest packings. It is known that for large , the densest lattice in dimension has density between (for some constant ) and . to
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Theoretical and Fundamental Chemistry
|
The acid converts deoxyribose to a molecule that binds with diphenylamine to form a blue substance. The reagent does not interact with RNA, so can be used to distinguish DNA from RNA.
| 0 |
Theoretical and Fundamental Chemistry
|
Lagrangian coherent structures (LCSs) are distinguished surfaces of trajectories in a dynamical system that exert a major influence on nearby trajectories over a time interval of interest. The type of this influence may vary, but it invariably creates a coherent trajectory pattern for which the underlying LCS serves as a theoretical centerpiece. In observations of tracer patterns in nature, one readily identifies coherent features, but it is often the underlying structure creating these features that is of interest.
As illustrated on the right, individual tracer trajectories forming coherent patterns are generally sensitive with respect to changes in their initial conditions and the system parameters. In contrast, the LCSs creating these trajectory patterns turn out to be robust and provide a simplified skeleton of the overall dynamics of the system. The robustness of this skeleton makes LCSs ideal tools for model validation, model comparison and benchmarking. LCSs can also be used for now-casting and even short-term forecasting of pattern evolution in complex dynamical systems.
Physical phenomena governed by LCSs include floating debris, oil spills, surface drifters and chlorophyll patterns in the ocean; clouds of volcanic ash and spores in the atmosphere; and coherent crowd patterns formed by humans and animals.
While LCSs generally exist in any dynamical system, their role in creating coherent patterns is perhaps most readily observable in fluid flows.
| 1 |
Applied and Interdisciplinary Chemistry
|
SINEs are much shorter (300bp) than LINEs. They share similarity with genes transcribed by RNA polymerase II, the enzyme that transcribes genes into mRNA transcripts, and the initiation sequence of RNA polymerase III, the enzyme that transcribes genes into ribosomal RNA, tRNA and other small RNA molecules. SINEs such as mammalian MIR elements have tRNA gene at the start and adenine-rich at the end like in LINEs.
SINEs do not encode a functional reverse transcriptase protein and rely on other mobile transposons, especially LINEs. SINEs exploit LINE transposition components despite LINE-binding proteins prefer binding to LINE RNA. SINEs cannot transpose by themselves because they cannot encode SINE transcripts. They usually consist of parts derived from tRNA and LINEs. The tRNA portion contains an RNA polymerase III promoter which the same kind of enzyme as RNA polymerase II. This makes sure the LINE copies would be transcribed into RNA for further transposition. The LINE component remains so LINE-binding proteins can recognise the LINE part of the SINE.
| 1 |
Applied and Interdisciplinary Chemistry
|
(lead(II) dicarbonate) can be formed at 30 GPa and 2000K from PbCO and CO. It forms white monoclinic crystals, with space group P2/c and four formula units per unit cell. At 30 GPa the unit cell has a=4.771 b=8.079 c=7.070 Å and β=91.32°. The unit cell volume is 272.4 Å and density 7.59.
(strontium dicarbonate) is very similar to the lead compound, and also has monoclinic structure with space group P2/c and four formula units per unit cell. At 30 GPa the unit cell has a=4.736 b=8.175 c=7.140 Å and β=91.34°. The unit cell volume is 276.3 Å and density 4.61. The double Sr=O bonds have lengths of 1.22, 1.24, and 1.25 Å. The single Sr-O bonds have lengths of 1.36 and 1.41 Å. The angles subtended at the carbon atoms are slightly less than 120°, and the angle at the C-O-C is larger.
| 0 |
Theoretical and Fundamental Chemistry
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