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For the flux density received from a remote unresolvable "point source", the measuring instrument, usually telescopic, though not able to resolve any detail of the source itself, must be able to optically resolve enough details of the sky around the point source, so as to record radiation coming from it only, uncontaminated by radiation from other sources. In this case, spectral flux density is the quantity that describes the rate at which energy transferred by electromagnetic radiation is received from that unresolved point source, per unit receiving area facing the source, per unit wavelength range.
At any given wavelength λ, the spectral flux density, F, can be determined by the following procedure:
*An appropriate detector of cross-sectional area 1 m is pointed directly at the source of the radiation.
*A narrow band-pass filter is placed in front of the detector so that only radiation whose wavelength lies within a very narrow range, Δλ, centred on λ, reaches the detector.
*The rate at which EM energy is detected by the detector is measured.
*This measured rate is then divided by Δλ to obtain the detected power per square metre per unit wavelength range.
Spectral flux density is often used as the quantity on the y-axis of a graph representing the spectrum of a light-source, such as a star. | 0 | Theoretical and Fundamental Chemistry |
The alkynylation reaction of aryl halides using aromatic acetylenes was reported in 1975 in three independent contributions by Cassar, Dieck and Heck as well as Sonogashira, Tohda and Hagihara. All of the reactions employ palladium catalysts to afford the same reaction products. However, the protocols of Cassar and Heck are performed solely by the use of palladium and require harsh reaction conditions (i.e. high reaction temperatures). The use of copper-cocatalyst in addition to palladium complexes in Sonogashiras procedure enabled the reactions to be carried under mild reaction conditions in excellent yields. A rapid development of the Pd/Cu systems followed and enabled myriad synthetic applications, while Cassar-Heck conditions were left, maybe unjustly, all but forgotten. The reactions remarkable utility can be evidenced by the amount of research still being done on understanding and optimizing its synthetic capabilities as well as employing the procedures to prepare various compounds of synthetic, medicinal or material/industrial importance. Among the cross-coupling reactions it follows in the number of publications right after Suzuki and Heck reaction and a search for the term "Sonogashira" in SciFinder provides over 1500 references for journal publications between 2007 and 2010.
The Sonogashira reaction has become so well known that often all reactions that use modern organometallic catalyst to couple alkyne motifs are termed some variant of "Sonogashira reaction", despite the fact that these reactions are not carried out under true Sonogashira reaction conditions. | 0 | Theoretical and Fundamental Chemistry |
The first commercial primary-lead ISASMELT furnace was installed at the Yunnan Chihong Zinc and Germanium Company Limited (YCZG) greenfield zinc and lead smelting complex at Qujing in Yunnan Province in China. This furnace was part of a plant consisting of the ISASMELT furnace and a blast furnace specially designed to treat high-lead ISASMELT slag. The ISASMELT furnace was designed to produce both the slag and lead bullion, with about 40% of the lead in the concentrate being converted to lead bullion in the ISASMELT furnace.
The ISASMELT–blast furnace combination was designed to treat 160,000 t/y of lead concentrate.
The second commercial primary-lead ISASMELT furnace was commissioned at Kazzinc's smelting complex at Ust-Kamenogorsk in Kazakhstan in 2012. It is designed to treat 300,000 t/y of lead concentrate, again using an ISASMELT–blast furnace combination.
YCZG is constructing another lead ISASMELT at a new greenfield smelter in Huize in China, and this is due to be commissioned in 2013.
In June 2017, Glencore announced that Nyrstar NV had acquired an Isasmelt licence for its new Ausmelt furnace in Port Pirie. As part of the agreement, Nyrstar engaged training and ramp-up support services for the Ausmelt furnace and blast furnace by personnel from Glencore's Kazzinc operations in Kazakhstan. This involved training Nyrstar personnel at Ust-Kamenogorsk operations and site support by Kazzinc personnel during the commissioning and ramp-up stages of the Ausmelt plant. | 1 | Applied and Interdisciplinary Chemistry |
Tetrakis(pyridine)silver(II) peroxydisulfate is a chemical compound which contains silver in the rare oxidation state of +2. | 0 | Theoretical and Fundamental Chemistry |
* The Zelinsky Institute of Organic Chemistry of Russian Academy of Sciences is named after him since 1953;
* In 1961, a postage stamp was issued in honor of N. D. Zelinsky in the USSR;
* One of the Moscow streets is named after him, as well as streets in the cities of Voskresensk (Moscow region), Tiraspol, Chisinau, Tyumen, Yaroslavl, Veliky Novgorod, Orsk, Karaganda, Daugavpils, Alma-Ata and Mariupol;
* On the occasion of the 150th anniversary of the birth of the scientist, the State Unitary Enterprise “Marka Pridnestrovya” issued a series of stamps and envelopes;
* The large chemical auditorium of the Faculty of Chemistry of Moscow State University is named after Zelinsky;
* The crater Zelinskiy on the Moon is named in his honor (since 1970);
* On June 2, 2014, the name of Nikolai Dmitrievich Zelinsky was given to an enterprise producing personal and collective protective equipment - JSC Elektrostal Chemical and Mechanical Plant;
* May 19, 2016 in St. Petersburg on the building of the Research Institute of Metrology. D. I. Mendeleev (Moskovsky Prospekt, 19) a commemorative plaque was installed (sculptor-artist V. A. Sivakov) with the text: “Here, in 1915, the outstanding scientist Nikolai Dmitrievich Zelinsky invented a coal gas mask” | 0 | Theoretical and Fundamental Chemistry |
Tramadol and desmetramadol may be quantified in blood, plasma, serum, or saliva to monitor for abuse, confirm a diagnosis of poisoning or assist in the forensic investigation of a sudden death. Most commercial opiate immunoassay screening tests do not cross-react significantly with tramadol or its major metabolites, so chromatographic techniques must be used to detect and quantitate these substances. The concentration of desmetramadol in the blood or plasma of a person who has taken tramadol is generally 10–20% those of the parent drug. | 0 | Theoretical and Fundamental Chemistry |
It has been reported that mammalian glycosylation can improve the therapeutic efficacy of biotherapeutics. For example, therapeutic efficacy of recombinant human interferon gamma, expressed in HEK 293 platform, was improved against drug-resistant ovarian cancer cell lines. | 0 | Theoretical and Fundamental Chemistry |
Blowout panels, also called blow-off panels, areas with intentionally weakened structure, are used in enclosures, buildings or vehicles where a sudden overpressure may occur. By failing in a predictable manner, they channel the overpressure or pressure wave in the direction where it causes controlled, directed minimal harm, instead of causing a catastrophic failure of the structure. An alternative example is a deliberately weakened wall in a room used to store compressed gas cylinders; in the event of a fire or other accident, the tremendous energy stored in the (possibly flammable) compressed gas is directed into a "safe" direction, rather than potentially collapsing the structure in a similar manner to a thermobaric weapon. | 1 | Applied and Interdisciplinary Chemistry |
Title 15, Chapter 8, Section 291 of the United States Code makes it unlawful to stamp goods in the United States with "United States assay" or any similar stamp which gives the impression that the item has been officially assayed by the United States government. | 0 | Theoretical and Fundamental Chemistry |
Flotation is used for the purification of potassium chloride from sodium chloride and clay minerals. The crushed mineral is suspended in brine in the presence of fatty ammonium salts. Because the ammonium head group and K have very similar ionic radii (ca. 0.135, 0.143 nm respectively), the ammonium centers exchange for the surface potassium sites on the particles of KCl, but not on the NaCl particles. The long alkyl chains then confer Hydrophobicity to the particles, which enable them to form foams. | 1 | Applied and Interdisciplinary Chemistry |
The LDR is being studied as a byproduct of a concept using a fluid stream for momentum transfer between an approaching spacecraft and another spacecraft, station or Moon base. This method could reduce spacecraft mass while increasing space flight efficiency.
A Liquid Sheet Radiator (LRS), adapted for planetary surfaces, is essentially a fountain enclosed in a transparent envelope. The liquid flows down on the inside of this envelope. The liquid sheet radiator concept is exceptionally stable and does not require special machining of the orifice to achieve its performance. | 0 | Theoretical and Fundamental Chemistry |
The Bradford assay is a colorimetric assay that measures protein concentration. The reagent Coomassie brilliant blue turns blue when it binds to arginine and aromatic amino acids present in proteins, thus increasing the absorbance of the sample. The absorbance is measured using a spectrophotometer, at the maximum absorbance frequency (A) of the blue dye (which is 595 nm). In this case, the greater the absorbance, the higher the protein concentration.
Data for known concentrations of protein are used to make the standard curve, plotting concentration on the X axis, and the assay measurement on the Y axis. The same assay is then performed with samples of unknown concentration. To analyze the data, one locates the measurement on the Y-axis that corresponds to the assay measurement of the unknown substance and follows a line to intersect the standard curve. The corresponding value on the X-axis is the concentration of substance in the unknown sample. | 1 | Applied and Interdisciplinary Chemistry |
An organoid is a miniaturised and simplified version of an organ produced in vitro in three dimensions that mimics the key functional, structural and biological complexity of that organ. They are derived from one or a few cells from a tissue, embryonic stem cells or induced pluripotent stem cells, which can self-organize in three-dimensional culture owing to their self-renewal and differentiation capacities. The technique for growing organoids has rapidly improved since the early 2010s, and The Scientist names it as one of the biggest scientific advancements of 2013. Scientists and engineers use organoids to study development and disease in the laboratory, drug discovery and development in industry, personalized diagnostics and medicine, gene and cell therapies, tissue engineering and regenerative medicine. | 1 | Applied and Interdisciplinary Chemistry |
Free triiodothyronine (fT or free T3) is generally elevated in hyperthyroidism and decreased in hypothyroidism.
Reference ranges depend on the method of analysis. Results should always be interpreted using the range from the laboratory that performed the test. Example values are: | 1 | Applied and Interdisciplinary Chemistry |
Prior to entering politics, Jones was a high pressure liquid chromatographer. She worked at the Washington University School of Medicine and KV Pharmaceutical before becoming a sales director with Mary Kay. In April 2015, Jones was the first African-American elected to the Ferguson City Council, where she represented the city's first ward. In February 2020, Jones was selected to serve on the United States Environmental Protection Agency Local Government Advisory Committee.
In the 2017 municipal election, Jones ran for mayor, receiving 42.77% of the vote. It was the city's first election after the shooting of Michael Brown and subsequent Ferguson unrest.
In the June 2, 2020 mayoral election, Jones defeated fellow council member Heather Robinett. Jones succeeded incumbent James Knowles III, a Republican who was unable to seek re-election due to term limits. On June 17, 2020, Jones was sworn in as the first black and female mayor of Ferguson.
She is also a pastor in the African Methodist Episcopal Church. | 0 | Theoretical and Fundamental Chemistry |
The process of selecting appropriate deep final repositories for high-level waste and spent fuel is now underway in several countries with the first expected to be commissioned sometime after 2010. The basic concept is to locate a large, stable geologic formation and use mining technology to excavate a tunnel, or large-bore tunnel boring machines (similar to those used to drill the Channel Tunnel from England to France) to drill a shaft to below the surface where rooms or vaults can be excavated for disposal of high-level radioactive waste. The goal is to permanently isolate nuclear waste from the human environment. Many people remain uncomfortable with the immediate stewardship cessation of this disposal system, suggesting perpetual management and monitoring would be more prudent.
Because some radioactive species have half-lives longer than one million years, even very low container leakage and radionuclide migration rates must be taken into account. Moreover, it may require more than one half-life until some nuclear materials lose enough radioactivity to cease being lethal to living things. A 1983 review of the Swedish radioactive waste disposal program by the National Academy of Sciences found that country's estimate of several hundred thousand years—perhaps up to one million years—being necessary for waste isolation "fully justified."
The proposed land-based subductive waste disposal method disposes of nuclear waste in a subduction zone accessed from land and therefore is not prohibited by international agreement. This method has been described as the most viable means of disposing of radioactive waste, and as the state-of-the-art as of 2001 in nuclear waste disposal technology.
Another approach termed Remix & Return would blend high-level waste with uranium mine and mill tailings down to the level of the original radioactivity of the uranium ore, then replace it in inactive uranium mines. This approach has the merits of providing jobs for miners who would double as disposal staff, and of facilitating a cradle-to-grave cycle for radioactive materials, but would be inappropriate for spent reactor fuel in the absence of reprocessing, due to the presence of highly toxic radioactive elements such as plutonium within it.
Deep borehole disposal is the concept of disposing of high-level radioactive waste from nuclear reactors in extremely deep boreholes. Deep borehole disposal seeks to place the waste as much as beneath the surface of the Earth and relies primarily on the immense natural geological barrier to confine the waste safely and permanently so that it should never pose a threat to the environment. The Earths crust contains 120 trillion tons of thorium and 40 trillion tons of uranium (primarily at relatively trace concentrations of parts per million each adding up over the crusts 3 × 10 ton mass), among other natural radioisotopes. Since the fraction of nuclides decaying per unit of time is inversely proportional to an isotope's half-life, the relative radioactivity of the lesser amount of human-produced radioisotopes (thousands of tons instead of trillions of tons) would diminish once the isotopes with far shorter half-lives than the bulk of natural radioisotopes decayed.
In January 2013, Cumbria county council rejected UK central government proposals to start work on an underground storage dump for nuclear waste near to the Lake District National Park. "For any host community, there will be a substantial community benefits package and worth hundreds of millions of pounds" said Ed Davey, Energy Secretary, but nonetheless, the local elected body voted 7–3 against research continuing, after hearing evidence from independent geologists that "the fractured strata of the county was impossible to entrust with such dangerous material and a hazard lasting millennia."
Horizontal drillhole disposal describes proposals to drill over one km vertically, and two km horizontally in the earth's crust, for the purpose of disposing of high-level waste forms such as spent nuclear fuel, Caesium-137, or Strontium-90. After the emplacement and the retrievability period, drillholes would be backfilled and sealed. A series of tests of the technology were carried out in November 2018 and then again publicly in January 2019 by a U.S. based private company. The test demonstrated the emplacement of a test-canister in a horizontal drillhole and retrieval of the same canister. There was no actual high-level waste used in this test.
European Commission Joint Research Centre report of 2021 (see above) concluded: | 0 | Theoretical and Fundamental Chemistry |
** George Paget Thomson of Imperial College, London designs the toroidal solenoid, a simple fusion device. With Moses Blackman, he further develops the concept and files for a patent. This becomes the first fusion device to receive a patent. Repeated attempts to get development funding fail.
** A meeting at Harwell on the topic of fusion raises new concerns with the concept. On his return to London, Thomson gets graduate students James L. Tuck and Alan Alfred Ware to build a prototype device out of old radar parts.
** Peter Thonemann comes up with a similar idea, but uses a different method of heating the fuel. This seems much more practical and finally gains the mild interest of the UK nuclear establishment. Not aware of who he is talking to, Thonemann describes the concept to Thomson, who adopts the same concept.
** Herbert Skinner begins to write a lengthy report on the entire fusion concept, pointing out several areas of little or no knowledge.
** The Ministry of Supply (MoS) asks Thomson about the status of his patent filing, and he describes the problems he has getting funding. The MoS forces Harwell to provide some money, and Thomson releases his rights to the patent. It is granted late that year.
** Skinner publishes his report, calling for some experimental effort to explore the areas of concern. Along with the MoS's calls for funding of Thomson, this event marks the beginning of formal fusion research in the UK. | 0 | Theoretical and Fundamental Chemistry |
The atmospheric properties of exoplanets are of particular importance, as atmospheres provide the most likely observables for the near future, including habitability indicators and biosignatures. Over billions of years, the processes of life on a planet would result in a mixture of chemicals unlike anything that could form in an ordinary chemical equilibrium. For example, large amounts of oxygen and small amounts of methane are generated by life on Earth.
An exoplanet's color—or reflectance spectrum—can also be used as a biosignature due to the effect of pigments that are uniquely biologic in origin such as the pigments of phototrophic and photosynthetic life forms. Scientists use the Earth as an example of this when looked at from far away (see Pale Blue Dot) as a comparison to worlds observed outside of our solar system. Ultraviolet radiation on life forms could also induce biofluorescence in visible wavelengths that may be detected by the new generation of space observatories under development.
Some scientists have reported methods of detecting hydrogen and methane in extraterrestrial atmospheres. Habitability indicators and biosignatures must be interpreted within a planetary and environmental context. For example, the presence of oxygen and methane together could indicate the kind of extreme thermochemical disequilibrium generated by life. Two of the top 14,000 proposed atmospheric biosignatures are dimethyl sulfide and chloromethane (). An alternative biosignature is the combination of methane and carbon dioxide.
The detection of phosphine in the atmosphere of Venus is being investigated as a possible biosignature. | 1 | Applied and Interdisciplinary Chemistry |
The liver is the second largest organ (after the skin) and is an accessory digestive gland which plays a role in the body's metabolism. The liver has many functions some of which are important to digestion. The liver can detoxify various metabolites; synthesise proteins and produce biochemicals needed for digestion. It regulates the storage of glycogen which it can form from glucose (glycogenesis). The liver can also synthesise glucose from certain amino acids. Its digestive functions are largely involved with the breaking down of carbohydrates. It also maintains protein metabolism in its synthesis and degradation. In lipid metabolism it synthesises cholesterol. Fats are also produced in the process of lipogenesis. The liver synthesises the bulk of lipoproteins. The liver is located in the upper right quadrant of the abdomen and below the diaphragm to which it is attached at one part, the bare area of the liver. This is to the right of the stomach and it overlies the gall bladder. The liver synthesises bile acids and lecithin to promote the digestion of fat. | 1 | Applied and Interdisciplinary Chemistry |
One may derive the Taylor equation using method of averages, first introduced by Aris. The result can also be derived from large-time asymptotics, which is more intuitively clear. In the dimensional coordinate system , consider the fully-developed Poiseuille flow flowing inside a pipe of radius , where is the average velocity of the fluid. A species of concentration with some arbitrary distribution is to be released at somewhere inside the pipe at time . As long as this initial distribution is compact, for instance the species/solute is not released everywhere with finite concentration level, the species will be convected along the pipe with the mean velocity . In a frame moving with the mean velocity and scaled with following non-dimensional scales
where is the time required for the species to diffuse in the radial direction, is the diffusion coefficient of the species and is the Peclet number, the governing equations are given by
Thus in this moving frame, at times (in dimensional variables, ), the species will diffuse radially. It is clear then that when (in dimensional variables, ), diffusion in the radial direction will make the concentration uniform across the pipe, although however the species is still diffusing in the direction. Taylor dispersion quantifies this axial diffusion process for large .
Suppose (i.e., times large in comparison with the radial diffusion time ), where is a small number. Then at these times, the concentration would spread to an axial extent . To quantify large-time behavior, the following rescalings
can be introduced. The equation then becomes
If pipe walls do not absorb or react with the species, then the boundary condition must be satisfied at . Due to symmetry, at .
Since , the solution can be expanded in an asymptotic series, Substituting this series into the governing equation and collecting terms of different orders will lead to series of equations. At leading order, the equation obtained is
Integrating this equation with boundary conditions defined before, one finds . At this order, is still an unknown function. This fact that is independent of is an expected result since as already said, at times , the radial diffusion will dominate first and make the concentration uniform across the pipe.
Terms of order leads to the equation
Integrating this equation with respect to using the boundary conditions leads to
where is the value of at , an unknown function at this order.
Terms of order leads to the equation
This equation can also be integrated with respect to , but what is required is the solvability condition of the above equation. The solvability condition is obtained by multiplying the above equation by and integrating the whole equation from to . This is also the same as averaging the above equation over the radial direction. Using the boundary conditions and results obtained in the previous two orders, the solvability condition leads to
This is the required diffusion equation. Going back to the laboratory frame and dimensional variables, the equation becomes
By the way in which this equation is derived, it can be seen that this is valid for in which changes significantly over a length scale (or more precisely on a scale . At the same time scale , at any small length scale about some location that moves with the mean flow, say , i.e., on the length scale , the concentration is no longer independent of , but is given by | 1 | Applied and Interdisciplinary Chemistry |
Elimination, bimolecular reactions are one step, concerted reaction where both base and substrate participate in the rate limiting step. In an E2 mechanism, a base takes a proton near the leaving group, forcing the electrons down to make a double bond, and forcing off the leaving group-all in one concerted step. The rate law depends on the first order concentration of two reactants, making it a 2nd order (bimolecular) elimination reaction. Factors that affect the rate determining step are stereochemistry, leaving groups, and base strength.
A theory, for an E2 reaction, by Joseph Bunnett suggests the lowest pass through the energy barrier between reactants and products is gained by an adjustment between the degrees of C-H and C-X rupture at the transition state. The adjustment involves much breaking of the bond more easily broken, and a small amount of breaking of the bond which requires more energy. This conclusion by Bunnett is a contradiction from the Hammond postulate. The Hammond postulate is the opposite of what Bunnett theorized. In the transition state of a bond breaking step it involves little breaking when the bond is easily broken and much breaking when it is difficult to break. Despite these differences, the two postulates are not in conflict since they are concerned with different sorts of processes. Hammond focuses on reaction steps where one bond is made or broken, or the breaking of two or more bonds is done with no time taken occur simultaneously. The E2 theory transition state concerns a process when bond formation or breaking are not simultaneous. | 0 | Theoretical and Fundamental Chemistry |
ACME are not common among antibiotic sensitive S. aureus (MSSA). The elements for the most prominent MRSA ACME appear to have assembled recently in S. epidermidis into the speG-positive ACME which was transferred to virulent S. aureus during the evolution of the epidemic USA300 MRSA strain. This broadened the ability of S. aureus to colonize sites other than a specific part of the nose. This strain is able to persist on intact skin and is spread rapidly person-to-person. As a result, the speG-positive ACME is a particularly important element of MRSA pathogenesis. | 1 | Applied and Interdisciplinary Chemistry |
For polyatomic molecules, progressions are most often observed when the change in bond lengths upon electronic excitation coincides with the change due to a ″totally symmetric″ vibration. This is the same process that occurs in resonance Raman spectroscopy. For example, in formaldehyde (methanal), HCO, the n → π* transition involves excitation of an electron from a non-bonding orbital to an antibonding pi orbital which weakens and lengthens the C-O bond. This produces a long progression in the C-O stretching vibration. Another example is furnished by benzene, CH. In both gas and liquid phase the band around 250 nm shows a progression in the symmetric ring-breathing vibration.
As an example from inorganic chemistry the permanganate ion, , in aqueous solution has an intense purple colour due to an O → Mn ligand-to-metal charge transfer band (LMCT) in much of the visible region. This band shows a progression in the symmetric Mn-O stretching vibration. The individual lines overlap each other extensively, giving rise to a broad overall profile with some coarse structure.
Progressions in vibrations which are not totally symmetric may also be observed.
d-d electronic transitions in atoms in a centrosymmetric environment are electric-dipole forbidden by the Laporte rule. This will apply to octahedral coordination compounds of the transition metals. The spectra of many of these complexes have some vibronic character. The same rule also applies to f-f transitions in centrosymmetric complexes of lanthanides and actinides. In the case of the octahedral actinide chloro-complex of uranium(IV), UCl the observed electronic spectrum is entirely vibronic. At the temperature of liquid helium, 4K, the vibronic structure was completely resolved, with zero intensity for the purely electronic transition, and three side-lines corresponding to the asymmetric U-Cl stretching vibration and two asymmetric Cl-U-Cl bending modes. Later studies on the same anion were also able to account for vibronic transitions involving low-frequency lattice vibrations. | 0 | Theoretical and Fundamental Chemistry |
The inversion of ligand fields has interesting implications on the nature of reactivity of organometallic complexes. This sigma non-innocence of ligands arising from inverted ligand fields could therefore be used to tune reactivity of complexes and open space in understanding the mechanisms of existing reactions.
In an analysis of the [ZnF] , it was found that due to ligand field inversion displayed in this species, core ionization removes an electron from the metal-rich bonding t orbital, lengthening the Zn-F bonds. This is contrary to the classical ligand field where ionization would remove an electron from the antibonding t orbital shortening the Zn-F bonds.
The presence of electron-deficient ligands also result in an inverted ligand field. Calculations have shown that the large O 2p contribution into the LUMO/LUMO in [(LCu)(O)] should make the complex highly oxidizing as it contains electron deficient O ligands. Studies have corroborated this property as this complex has shown to be able to undergo C-H and C-F activation and aromatic hydroxylation.
There is evidence showing that reductive elimination on species displaying ligand field inversion do not undergo a redox event at the metal center. The C-CF bond formation by "Ni(IV)" complexes was completed without redox participation of the Nickel. The metal appears to remain Ni(II) throughout the reaction. The mechanism is thought to be through the attack of a masked electrophilic cation by anionic CF. The electron deficiency here is due to the inverted ligand field. | 0 | Theoretical and Fundamental Chemistry |
This disorder occurs through a mutation in the SPR gene, which is responsible for encoding the sepiapterin reductase enzyme. The enzyme is involved in the last step of producing tetrahydrobiopterin, better known as BH. BH is involved in the processing of amino acids and the production of neurotransmitters, specifically that of dopamine and serotonin which are primarily used in transmission of signals between nerve cells in the brain. The mutation in the SPR gene interferes with the production of the enzyme by producing enzymes with little or no function at all. This interference results in a lack of BH specifically in the brain. The lack of BH only occurs in the brain because other parts of the body adapt and utilize alternate pathways for the production of BH. The mutation in the SPR gene leads to nonfunctional sepiapterin reductase enzymes, which results in a lack of BH and ultimately disrupts the production of dopamine and serotonin in the brain. The disruption of dopamine and serotonin production leads to the visible symptoms present in patients suffering from sepiapterin reductase deficiency. SR deficiency is considered an inherited autosomal recessive condition disorder because each parent carries one copy of the mutated gene, but typically do not show any signs or symptoms of the condition. | 1 | Applied and Interdisciplinary Chemistry |
The Streptamer staining principle combines the classic method of T cell isolation by MHC-multimers with the Strep-tag/Strep-Tactin technology. The Strep-tag is a short peptide sequence that displays moderate binding affinity for the biotin-binding site of a mutated streptavidin molecule, called Strep-Tactin. For the Streptamer technology, the Strep-Tactin molecules are multimerized and form the "backbone", thus creating a platform for binding to strep-tagged proteins. Additionally, the Strep-Tactin backbone has a fluorescent label to allow flow cytometry analysis. Incubation of MHC-Strep-tag fusion proteins with the Strep-Tactin backbone results in the formation of a MHC-multimer, which is capable for antigen-specific staining of T cells. | 1 | Applied and Interdisciplinary Chemistry |
Although generally considered less-than-lethal when properly used (targets should exclude the face, eyes, throat or spine), one death has occurred when they have been fired at inappropriate areas. In one well-publicized incident in 2004, the Boston Police Department's use of an FN 303 during a crowd control situation resulted in the fatal shooting of Victoria Snelgrove, when the projectile struck her in the eye.
Also in 2004, University of California, Davis (UC Davis) police who wanted to break up a block party shot a pepperball at an unarmed student and damaged his eye—the student subsequently lost his athletic scholarship and dropped out of college. In 2012, a federal appeals court ruled that the police could be sued over the incident. In 2013, the student was awarded $774,000. | 1 | Applied and Interdisciplinary Chemistry |
Type S (90%Pt/10%Rh–Pt, by weight) thermocouples, similar to type R, are used up to 1600 °C. Before the introduction of the International Temperature Scale of 1990 (ITS-90), precision type-S thermocouples were used as the practical standard thermometers for the range of 630 °C to 1064 °C, based on an interpolation between the freezing points of antimony, silver, and gold. Starting with ITS-90, platinum resistance thermometers have taken over this range as standard thermometers. | 1 | Applied and Interdisciplinary Chemistry |
Biofluid dynamics may be considered as the discipline of biological engineering or biomedical engineering in which the fundamental principles of fluid dynamics are used to explain the mechanisms of biological flows and their interrelationships with physiological processes, in health and in diseases/disorder. It can be considered as the conjuncture of mechanical engineering and biological engineering. It spans from cells to organs, covering diverse aspects of the functionality of systemic physiology, including cardiovascular, respiratory, reproductive, urinary, musculoskeletal and neurological systems etc. Biofluid dynamics and its simulations in computational fluid dynamics (CFD) apply to both internal as well as external flows. Internal flows such as cardiovascular blood flow and respiratory airflow, and external flows such as flying and aquatic locomotion (i.e., swimming). Biological fluid Dynamics (or Biofluid Dynamics) involves the study of the motion of biological fluids (e.g. blood flow in arteries, animal flight, fish swimming, etc.). It can be either circulatory system or respiratory systems. Understanding the circulatory system is one of the major areas of research. The respiratory system is very closely linked to the circulatory system and is very complex to study and understand. The study of Biofluid Dynamics is also directed towards finding solutions to some of the human body related diseases and disorders. The usefulness of the subject can also be understood by seeing the use of Biofluid Dynamics in the areas of physiology in order to explain how living things work and about their motions, in developing an understanding of the origins and development of various diseases related to human body and diagnosing them, in finding the cure for the diseases related to cardiovascular and pulmonary systems. | 1 | Applied and Interdisciplinary Chemistry |
Photobromination with elemental bromine proceeds analogous to photochlorination also via a radical mechanism. In the presence of oxygen, the hydrogen bromide formed is partly oxidised back to bromine, resulting in an increased yield. Because of the easier dosage of the elemental bromine and the higher selectivity of the reaction, photobromination is preferred over photochlorination at laboratory scale. For industrial applications, bromine is usually too expensive (as it is present in sea water in small quantities only and produced from oxidation with chlorine). Instead of elemental bromine, N-bromosuccinimide is also suitable as a brominating agent. The quantum yield of photobromination is usually much lower than that of photochlorination. | 0 | Theoretical and Fundamental Chemistry |
Extracellular binding of cytokines or growth factors induce activation of receptor-associated Janus kinases, which phosphorylate a specific tyrosine residue within the STAT protein promoting dimerization via their SH2 domains. The phosphorylated dimer is then actively transported to the nucleus via an importin α/β ternary complex. Originally, STAT proteins were described as latent cytoplasmic transcription factors as phosphorylation was thought to be required for nuclear retention. However, unphosphorylated STAT proteins also shuttle between the cytosol and nucleus, and play a role in gene expression. Once STAT reaches the nucleus, it binds to a consensus DNA-recognition motif called gamma-activated sites (GAS) in the promoter region of cytokine-inducible genes and activates transcription. The STAT protein can be dephosphorylated by nuclear phosphatases, which leads to inactivation of STAT and subsequent transport out of the nucleus by an exportin-RanGTP complex. | 1 | Applied and Interdisciplinary Chemistry |
Following a suggestion by Jöns Jacob Berzelius, Mulder used the term protein in his 1838 paper, "On the composition of some animal substances" (originally in French but translated in 1839 to German). In the same publication, he also proposed that animals draw most of their protein from plants.
Mulder "was the first to propose a theory concerning the causes of the differences between albumin, casein, and fibrin, and other substances more or less similar to them in physical properties and in their chemical behavior when exposed to reagents. Analyses of these substances showed that their percentage contribution with respect to carbon, hydrogen, nitrogen and oxygen were so similar as to suggest that they contain one common radical."
This radical, a macromolecule, had formula and was known as protein. The variations in albuminous substances were attributed to peripheral bonds of protein to sulfur and/or phosphorus. Justus Liebig and his students sought to determine the structure of proteins, but until the methods of Emil Fischer and Franz Hofmeister became available, the amino acid decompositions were unknown.
Augustus Voelcker was Mulder's assistant for a year from 1846.
In 1850, Mulder was elected a foreign member of the Royal Swedish Academy of Sciences. He died in Bennekom. | 0 | Theoretical and Fundamental Chemistry |
The School of Chemistry (now School of Chemical Sciences) established in 1972, is one of the Schools of Devi Ahilya University Indore. The School was founded with the services of Prof. W. V. Bhagwat, along with Later Prof. M. B. Antia, Late Prof. R. Kaushal and Prof. S. G. Harmalkar. Subsequently, many members became the faculty of this school. Ever since its international status. It is the only School of the State which was honoured two times with the prestigious Katju award (Prof. N. S. Poonia for the year 1983 and Prof. K. K. Pandey for the year 1990). | 1 | Applied and Interdisciplinary Chemistry |
Like other crown ethers, 12-crown-4 complexes with alkali metal cations. The cavity diameter of 1.2-1.5 Å gives it a high selectivity towards the lithium cation (ionic diameter 1.36 Å)
Its point group is S. The dipole moment of 12-crown-4 varies with solvent and temperature. At 25 °C, the dipole moment of 12-crown-4 was determined as 2.33 ± 0.03 D in cyclohexane and 2.46 ± 0.01 D in benzene. | 0 | Theoretical and Fundamental Chemistry |
Alpha-emitting radionuclides are presently being used in three different ways to eradicate cancerous tumors: as an infusible radioactive treatment targeted to specific tissues (Radium-223), as a source of radiation inserted directly into solid tumors (Radium-224), and as an attachment to an tumor-targeting molecule, such as an antibody to a tumor-associated antigen.
Radium-223 is an alpha emitter that is naturally attracted to the bone because it is a calcium mimetic. Radium-223 (as radium-223 dichloride) can be infused into a cancer patient's veins, after which it migrates to parts of the bone where there is rapid turnover of cells due to the presence of metastasized tumors. Once within the bone, Ra-223 emits alpha radiation that can destroy tumor cells within a 100-micron distance. This approach has been in use since 2013 to treat prostate cancer which has metastasized to the bone. Radionuclides infused into the circulation are able to reach sites that are accessible to blood vessels. This means, however, that the interior of a large tumor that is not vascularized (i.e. is not well penetrated by blood vessels) may not be effectively eradicated by the radioactivity.
Radium-224 is a radioactive atom that is utilized as a source of alpha radiation in a cancer treatment device called DaRT (Diffusing Alpha-emitters Radiation Therapy). Each radium-224 atom undergoes a decay process producing 6 daughter atoms. During this process, 4 alpha particles are emitted. The range of an alpha particle—up to 100 microns—is insufficient to cover the width of many tumors. However, radium-224's daughter atoms can diffuse up to 2–3 mm in the tissue, thus creating a "kill region" with enough radiation to potentially destroy an entire tumor, if the seeds are placed appropriately.
Radium-224's half-life is short enough at 3.6 days to produce a rapid clinical effect while avoiding the risk of radiation damage due to overexposure. At the same time, the half-life is long enough to allow for handling and shipping the seeds to a cancer treatment center at any location across the globe.
Targeted alpha therapy for solid tumors involves attaching an alpha-particle-emitting radionuclide to a tumor-targeting molecule such as an antibody, that can be delivered by intravenous administration to a cancer patient. | 0 | Theoretical and Fundamental Chemistry |
Acidic solutions of fluoride (including hydrofluoric acid) can be determined by a simple thermometric titration with boric acid.
: B(OH) + 3F + 3H ↔ BF + 3HO
The titration plot illustrated in Figure 19 shows that the endpoint is quite rounded, suggesting that the reaction might not proceed to stoichiometric equilibrium. However, since the regions of the temperature curve immediately before and after the endpoint are quite linear, the second derivative of this curve (representing the intersection of tangents) will accurately locate the endpoint. Indeed, excellent precision can be obtained with this titration, with a CV of less than 0.1. | 0 | Theoretical and Fundamental Chemistry |
Extended aeration package plants use separate basins for aeration and settling, and are somewhat larger than SBR plants with reduced timing sensitivity. | 1 | Applied and Interdisciplinary Chemistry |
Following his completion of his PhD, Schoell began working for the German Geological Survey focusing on hyper saline hydrothermal vents in the Red Sea. From 1984 to 2001, Schoell worked for Chevron Oil Field Research Company in La Habra. During this time, he published his most cited paper, "Biogenic methane formation in marine and freshwater environments: CO reduction vs. acetate fermentation—Isotope evidence". In this paper, Schoell et al. discussed how hydrogen and carbon isotope composition analysis can be used to identify different biogenic methane production pathways from its water and CO precursors. This paper went on to win the 1995 AAPG Best Paper Award. In addition to this, while working for Chevron in 1984 Schoell requested funding from Chevron to fund John Hayes of Indiana University to develop continuous-flow compound-specific isotope analysis. This development allowed Schoell to make a variety of discoveries including the ability of steranes and hopanes in the Lacustrine Green River Formation could be used as a proxy for water paleo-depths.
During his time with Chevron, Schoell introduced Mudgas isotope analysis to Chevron and the natural gas industry, and worked in a variety of international locations including locations throughout the Americas, Southeast Asia and Africa as well as parts of Oceania.
In 2001, Schoell went on to establish a natural gas consulting company, GasConsult International, Inc. of which he was the CEO and president of until 2015. GasConsult specializes in ZR-LNG (zero-refrigeration liquified natural gas), LH2 (liquid hydrogen) and OHL (optimized liquid hydrogen) technologies and offers clients opportunities to transition to these technologies, and is now under the direction of Bill Howe.
In 2019, Schoell founded GasXpse which applies geochemical fundamentals to provide natural gas related consulting services and provide scientific advising for natural gas-related subjects. Further, Schoell has co-authored 76 publications in the field of geochemistry. | 0 | Theoretical and Fundamental Chemistry |
Cavity ring-down spectroscopy is a form of laser absorption spectroscopy. In CRDS, a laser pulse is trapped in a highly reflective (typically R > 99.9%) detection cavity. The intensity of the trapped pulse will decrease by a fixed percentage during each round trip within the cell due to absorption, scattering by the medium within the cell, and reflectivity losses. The intensity of light within the cavity is then determined as an exponential function of time.
The principle of operation is based on the measurement of a decay rate rather than an absolute absorbance. This is one reason for the increased sensitivity over traditional absorption spectroscopy, as the technique is then immune to shot-to-shot laser fluctuations. The decay constant, τ, which is the time taken for the intensity of light to fall to 1/e of the initial intensity, is called the ring-down time and is dependent on the loss mechanism(s) within the cavity. For an empty cavity, the decay constant is dependent on mirror loss and various optical phenomena like scattering and refraction:
where n is the index of refraction within the cavity, c is the speed of light in vacuum, l is the cavity length, R is the mirror reflectivity, and X takes into account other miscellaneous optical losses. This equation uses the approximation that ln(1+x) ≈ x for x close to zero, which is the case under cavity ring-down conditions. Often, the miscellaneous losses are factored into an effective mirror loss for simplicity. An absorbing species in the cavity will increase losses according to the Beer-Lambert law. Assuming the sample fills the entire cavity,
where α is the absorption coefficient for a specific analyte concentration at the cavitys resonance wavelength. The decadic absorbance, A', due to the analyte can be determined from both ring-down times.
Alternatively, the molar absorptivity, ε, and analyte concentration, C, can be determined from the ratio of both ring-down times. If X can be neglected, one obtains
When a ratio of species' concentrations is the analytical objective, as for example in carbon-13 to carbon-12 measurements in carbon dioxide, the ratio of ring-down times measured for the same sample at the relevant absorption frequencies can be used directly with extreme accuracy and precision. | 0 | Theoretical and Fundamental Chemistry |
Exogenous antigens are antigens that have entered the body from the outside, for example, by inhalation, ingestion or injection. The immune system's response to exogenous antigens is often subclinical. By endocytosis or phagocytosis, exogenous antigens are taken into the antigen-presenting cells (APCs) and processed into fragments. APCs then present the fragments to T helper cells (CD4) by the use of class II histocompatibility molecules on their surface. Some T cells are specific for the peptide:MHC complex. They become activated and start to secrete cytokines, substances that activate cytotoxic T lymphocytes (CTL), antibody-secreting B cells, macrophages and other particles.
Some antigens start out as exogenous and later become endogenous (for example, intracellular viruses). Intracellular antigens can be returned to circulation upon the destruction of the infected cell. | 1 | Applied and Interdisciplinary Chemistry |
In Earth science, a geochemical cycle is the pathway that chemical elements take in the surface and crust of the Earth. The term "geochemical" tells us that geological and chemical factors are all included. The migration of heated and compressed chemical elements and compounds such as silicon, aluminium, and general alkali metals through the means of subduction and volcanism is known in the geological world as geochemical cycles.
The geochemical cycle encompasses the natural separation and concentration of elements and heat-assisted recombination processes. Changes may not be apparent over a short term, such as with biogeochemical cycles, but over a long term changes of great magnitude occur, including the evolution of continents and oceans. | 0 | Theoretical and Fundamental Chemistry |
Anti-SSA autoantibodies (anti–Sjögrens-syndrome-related antigen A autoantibodies, also called anti-Ro, or similar names including anti-SSA/Ro, anti-Ro/SSA, anti–SS-A/Ro, and anti-Ro/SS-A) are a type of anti-nuclear autoantibodies that are associated with many autoimmune diseases, such as systemic lupus erythematosus (SLE), SS/SLE overlap syndrome, subacute cutaneous lupus erythematosus (SCLE), neonatal lupus and primary biliary cirrhosis. They are often present in Sjögrens syndrome (SS). Additionally, Anti-Ro/SSA can be found in other autoimmune diseases such as systemic sclerosis (SSc), polymyositis/dermatomyositis (PM/DM), rheumatoid arthritis (RA), and mixed connective tissue disease (MCTD), and are also associated with heart arrhythmia.
Anti-SSA/Ro autoantibodies are classified as extractable nuclear antigens. The Anti-SSA/Ro autoantibody targets Ro proteins, namely Ro52 and Ro60. Ro52 and Ro60 were originally thought to be one protein, however current findings show that they are two functionally distinct proteins encoded by genes on separate chromosomes. Anti-SSA/Ro autoantibodies are used in clinical settings as a diagnostic tool to identify patients with SLE and Sjögren's syndrome. In clinical tests for autoimmune disease, Anti-Ro antibodies are some of the most consistently and frequently detected among autoantibodies.
Anti-Ro autoantibodies are often found in conjunction with a similar antibody, Anti-La/SSB (also called anti–SS-B or anti–SS-B/La), in patients with SS. These two antibodies share pathological characteristics. | 1 | Applied and Interdisciplinary Chemistry |
Phase inversion membranes are typically characterized by their mean pore diameter and pore diameter distribution. This can be measured using a number of established analytical techniques such as the analysis of gas adsorption-desorption isotherms, porosimetry, or more niche approaches such as Evapoporometry. A Scanning electron microscope (SEM) can be used to characterize membranes with larger pore sizes, such as microfiltration and ultrafiltration membranes, while Transmission electron microscopy (TEM) can be used for all membrane types, including small pore membranes such as nanofiltration and reverse osmosis, though optical techniques tend to analyze only a small sample area that may not be representative of the sample as a whole. | 0 | Theoretical and Fundamental Chemistry |
NAIL-MS is used to study RNA modification mechanisms. Therefore, cells in culture are first fed with stable isotope labeled nutrients and the cells incorporate these into their biomolecules. After purification of the nucleic acids, most often RNA, analysis is done by mass spectrometry. Mass spectrometry is an analytical technique that measures the mass-to-charge ratio of ions. Pairs of chemically identical nucleosides of different stable-isotope composition can be differentiated in a mass spectrometer due to their mass difference. Unlabeled nucleosides can therefore be distinguished from their stable isotope labeled isotopologues. For most NAIL-MS approaches it is crucial that the labeled nucleosides are more than 2 Da heavier than the unlabeled ones. This is because 1.1% of naturally occurring carbon atoms are C isotopes. In the case of nucleosides this leads to a mass increase of 1 Da in ~10% of the nucleosides. This signal would disturb the final evaluation of the measurement.
NAIL-MS can be used to investigate RNA modification dynamics by changing the labeled nutrients of the corresponding growth medium during the experiment. Furthermore, cell populations can be compared directly with each other without effects of purification bias. Furthermore, it can be used for the production of biosynthetic isotopologues of most nucleosides which are needed for quantification by mass spectrometry and even for the discovery of yet unknown RNA modifications. | 0 | Theoretical and Fundamental Chemistry |
Salinosporamide A (Marizomib) is a potent proteasome inhibitor being studied as a potential anticancer agent. It entered phase I human clinical trials for the treatment of multiple myeloma, only three years after its discovery in 2003. This marine natural product is produced by the obligate marine bacteria Salinispora tropica and Salinispora arenicola, which are found in ocean sediment. Salinosporamide A belongs to a family of compounds, known collectively as salinosporamides, which possess a densely functionalized γ-lactam-β-lactone bicyclic core. | 0 | Theoretical and Fundamental Chemistry |
As stated above, BGIT can be used to calculate heats of formation, which are important in understanding the strengths of bonds and entire molecules. Furthermore, the method can be used to quickly estimate whether a reaction is endothermic or exothermic. These values are for gas-phase thermodynamics and typically at 298 K. Benson and coworkers have continued collecting data since their 1958 publication and have since published even more group increments, including strained rings, radicals, halogens, and more. Even though BGIT was introduced in 1958 and would seem to be antiquated in the modern age of advanced computing, the theory still finds practical applications. In a 2006 article, Gronert states: "Aside from molecular mechanics computer packages, the best known additivity scheme is Benson's." Fishtik and Datta also give credit to BGIT: "Despite their empirical character, GA methods continue to remain a powerful and relatively accurate technique for the estimation of thermodynamic properties of the chemical species, even in the era of supercomputers"
When calculating the heat of formation, all the atoms in the molecule must be accounted for (hydrogen atoms are not included as specific groups). The figure above displays a simple application for predicting the standard enthalpy of isobutylbenzene. First, it is usually very helpful to start by numbering the atoms. It is much easier then to list the specific groups along with the corresponding number from the table. Each individual atom is accounted for, where C−(H) accounts for one benzene carbon bound to a hydrogen atom. This would be multiplied by five, since there are five C−(H) atoms. The C−(C) molecule further accounts for the other benzene carbon attached to the butyl group. The C−(C)(C)(H)2 accounts for the carbon linked to the benzene group on the butyl moiety. The 2 carbon of the butyl group would be C−(C)(H) because it is a tertiary carbon (connecting to three other carbon atoms). The final calculation comes from the CH groups connected to the 2 carbon; C−(C)(H). The total calculations add to −5.15 kcal/mol (−21.6 kJ/mol), which is identical to the experimental value, which can be found in the National Institute of Standards and Technology Chemistry WebBook
Another example from the literature is when the BGIT was used to corroborate experimental evidence of the enthalpy of formation of benzo[k]fluoranthene. The experimental value was determined to be 296.6 kJ/mol with a standard deviation of 6.4 kJ/mol. This is within the error of the BGIT and is in good agreement with the calculated value. Notice that the carbons at the fused rings are treated differently than regular benzene carbons. Not only can the BGIT be used to confirm experimental values, but can also to confirm theoretical values.
BGIT also can be used for comparing the thermodynamics of simplified hydrogenation reactions for alkene (2-methyl-1-butene) and ketone(2-butanone). This is a thermodynamic argument, and kinetics are ignored. As determined by the enthalpies below the corresponding molecules, the enthalpy of reaction for 2-methyl-1-butene going to 2-methyl-butane is −29.07 kcal/mol, which is in great agreement with the value calculated from NIST, −28.31 kcal/mol. For 2-butanone going to 2-butanol, enthalpy of reaction is −13.75 kcal/mol, which again is in excellent agreement with −14.02 kcal/mol. While both reactions are thermodynamically favored, the alkene will be far more exothermic than the corresponding ketone. | 0 | Theoretical and Fundamental Chemistry |
Wavy single bonds are the standard way to represent unknown or unspecified stereochemistry or a mixture of isomers (as with tetrahedral stereocenters). A crossed double-bond has been used sometimes; it is no longer considered an acceptable style for general use by IUPAC but may still be required by computer software. | 0 | Theoretical and Fundamental Chemistry |
Bacteria are often viewed as the main consumers of DOC, but they can also produce DOC during cell division and viral lysis. The biochemical components of bacteria are largely the same as other organisms, but some compounds from the cell wall are unique and are used to trace bacterial derived DOC (e.g., peptidoglycan). These compounds are widely distributed in the ocean, suggesting that bacterial DOC production could be important in marine systems. Viruses are the most abundant life forms in the oceans infecting all life forms including algae, bacteria and zooplankton. After infection, the virus either enters a dormant (lysogenic) or productive (lytic) state. The lytic cycle causes disruption of the cell(s) and release of DOC. | 1 | Applied and Interdisciplinary Chemistry |
Several mathematical models of chemotaxis were developed depending on the type of
* Migration (e.g., basic differences of bacterial swimming, movement of unicellular eukaryotes with cilia/flagellum and amoeboid migration)
* Physico-chemical characteristics of the chemicals (e.g., diffusion) working as ligands
* Biological characteristics of the ligands (attractant, neutral, and repellent molecules)
* Assay systems applied to evaluate chemotaxis (see incubation times, development, and stability of concentration gradients)
* Other environmental effects possessing direct or indirect influence on the migration (lighting, temperature, magnetic fields, etc.)
Although interactions of the factors listed above make the behavior of the solutions of mathematical models of chemotaxis rather complex, it is possible to describe the basic phenomenon of chemotaxis-driven motion in a straightforward way. Indeed, let us denote with the spatially non-uniform concentration of the chemo-attractant and as its gradient. Then the chemotactic cellular flow (also called current) that is generated by the chemotaxis is linked to the above gradient by the law:where is the spatial density of the cells and is the so-called Chemotactic coefficient - is often not constant, but a decreasing function of the chemo-attractant. For some quantity that is subject to total flux and generation/destruction term , it is possible to formulate a continuity equation:
where is the divergence. This general equation applies to both the cell density and the chemo-attractant. Therefore, incorporating a diffusion flux into the total flux term, the interactions between these quantities are governed by a set of coupled reaction-diffusion partial differential equations describing the change in and :where describes the growth in cell density, is the kinetics/source term for the chemo-attractant, and the diffusion coefficients for cell density and the chemo-attractant are respectively and .
Spatial ecology of soil microorganisms is a function of their chemotactic sensitivities towards substrate and fellow organisms. The chemotactic behavior of the bacteria was proven to lead to non-trivial population patterns even in the absence of environmental heterogeneities. The presence of structural pore scale heterogeneities has an extra impact on the emerging bacterial patterns. | 1 | Applied and Interdisciplinary Chemistry |
In 2013, Diebold was the sole recipient of Austrias highest research award across all disciplines, the Wittgenstein Award. The award, which comes with substantial unrestricted research funds, is bestowed in support of the notion that scientists should be guaranteed the greatest possible freedom and flexibility in the performance of their research. It enabled Diebolds research activities to flourish without restriction. Other honors include:
* 2004 Fellow, American Physical Society, "For groundbreaking research on the role of defects in the interplay between bulk and surface properties of transition-metal oxides and on STM imaging of their surface structure.",
* 2005 Fellow of the American Vacuum Society
* 2007 Fellow, American Association for the Advancement of Science
* 2011, 2019 Advanced Grants by the European Research Council, for work on "Microscopic Processes and Phenomena at Oxide Surfaces and Interfaces" (2011), and "Water at Oxide Surfaces: a Fundamental Approach" (2019).
* 2013 Arthur W. Anderson Award of the American Chemical Society, for Distinguished Service in the Advancement of Surface Chemistry.
* 2013 Wittgenstein Award
*2014 European Academy of Sciences
*2014 Elected as a Full Member of the Austrian Academy of Sciences.
* 2015 Blaise Pascal medal in Materials Sciences by the European Academy of Sciences, for "Surfaces of Metal Oxides, Studied at the Atomic Scale".
* 2015 Debye Lecturer at Utrecht University, The Netherlands, entitled "Surface Science Studies of an Iron Oxide Model Catalyst" .
* 2015 21st Annual Schrödinger Lecturer at Trinity College Dublin, Ireland, with the title "An Atomic-Scale View at Oxide Surfaces".
* 2015 R. Brdička memorial lecturer at the J. Heyrovský Institute of Physical Chemistry, Prague, entitled "Surface Science of Metal Oxides".
*2015 Elected to the Leopoldina, the national academy of sciences in Germany,
*2019 Science award of the city of Vienna.
*2020 Gerhard Ertl Lecture Award
*2021 International Honorary Member of the American Academy of Arts and Sciences
*2022 Fellow of the Royal Society of Chemistry | 0 | Theoretical and Fundamental Chemistry |
The sulfur colloid of Tc is scavenged by the spleen, making it possible to image the structure of the spleen. | 0 | Theoretical and Fundamental Chemistry |
There is evidence that use during pregnancy may result in harm to the baby. Teratogenic and embryotoxic effects were shown on four animal species. In one case report, a 6-month old infant developed benign bright blue discolouration of the cornea after treatment with favipiravir which resolved after treatment cessation. | 0 | Theoretical and Fundamental Chemistry |
In dilatational interfacial rheology, the size of the interface is changing over time. The change in the surface stress or surface tension of the interface is being measured during this deformation. Based on the response, interfacial viscoelasticity is calculated according to well established theories:
where
* |E| is the complex surface dilatational modulus
* γ is the surface tension or interfacial tension of the interface
* A is the interfacial area
* δ is the phase angle difference between the surface tension and area
* E’<nowiki/>' is the elastic (storage) modulus
* E’ is the viscous (loss) modulus
Most commonly, the measurement of dilational interfacial rheology is conducted with an optical tensiometer combined to a pulsating drop module. A pendant droplet with surface active molecules in it is formed and pulsated sinusoidally. The changes in the interfacial area causes changes in the molecular interactions which then changes the surface tension. Typical measurements include performing a frequency sweep for the solution to study the kinetics of the surfactant.
In another measurement method suitable especially for insoluble surfactants, a Langmuir trough is used in an oscillating barrier mode. In this case, two barriers that limit the interfacial area are being oscillated sinusoidally and the change in surface tension measured. | 0 | Theoretical and Fundamental Chemistry |
A solution that shows greater positive deviation from Raoults law forms a minimum boiling azeotrope at a specific composition. In general, a positive azeotrope boils at a lower temperature than any other ratio of its constituents. Positive azeotropes are also called minimum boiling mixtures or pressure maximum azeotropes'. A well-known example of a positive azeotrope is an ethanol–water mixture (obtained by fermentation of sugars) consisting of 95.63% ethanol and 4.37% water (by mass), which boils at 78.2 °C. Ethanol boils at 78.4 °C, water boils at 100 °C, but the azeotrope boils at 78.2 °C, which is lower than either of its constituents. Indeed, 78.2 °C is the minimum temperature at which any ethanol/water solution can boil at atmospheric pressure. Once this composition has been achieved, the liquid and vapour have the same composition, and no further separation occurs.
The boiling and recondensation of a mixture of two solvents are changes of chemical state; as such, they are best illustrated with a phase diagram. If the pressure is held constant, the two variable parameters are the temperature and the composition.
The adjacent diagram shows a positive azeotrope of hypothetical constituents, X and Y. The bottom trace illustrates the boiling temperature of various compositions. Below the bottom trace, only the liquid phase is in equilibrium. The top trace illustrates the vapor composition above the liquid at a given temperature. Above the top trace, only the vapor is in equilibrium. Between the two traces, liquid and vapor phases exist simultaneously in equilibrium: for example, heating a 25% X : 75% Y mixture to temperature AB would generate vapor of composition B over liquid of composition A. The azeotrope is the point on the diagram where the two curves touch. The horizontal and vertical steps show the path of repeated distillations. Point A is the boiling point of a nonazeotropic mixture. The vapor that separates at that temperature has composition B. The shape of the curves requires that the vapor at B be richer in constituent X than the liquid at point A. The vapor is physically separated from the VLE (vapor-liquid equilibrium) system and is cooled to point C, where it condenses. The resulting liquid (point C) is now richer in X than it was at point A. If the collected liquid is boiled again, it progresses to point D, and so on. The stepwise progression shows how repeated distillation can never produce a distillate that is richer in constituent X than the azeotrope. Note that starting to the right of the azeotrope point results in the same stepwise process closing in on the azeotrope point from the other direction. | 1 | Applied and Interdisciplinary Chemistry |
The heat collected from this process generates steam, which can be used in a conventional steam turbine system to make electricity. In contrast to the low-temperature solar thermal systems that are used for air or water heating in domestic or commercial buildings, these solar thermal electricity plants operate at high temperatures, requiring both concentrated sunlight and a large collection area, making the Moroccan desert an ideal location.
This is an alternative approach to the more widely used “photovoltaic” technology for producing electricity from sunlight. In a photovoltaic system, the sunlight is absorbed in the photovoltaic device (commonly called a solar cell) and energy is passed to electrons in the material, converting the solar energy directly into electricity. Sometimes, solar thermal electricity and photovoltaics are portrayed as competing technologies and, while this may be true when deciding on the way forward for a specific site, in general they are complementary, using solar energy as extensively as possible. | 0 | Theoretical and Fundamental Chemistry |
*[http://www.efunda.com/ Diffusion Treatment Hardening]. eFunda. Retrieved 19 April 2008.
*[http://steel.keytometals.com Surface Hardening of Steels]. Key to Metals. Retrieved 19 April 2008. | 1 | Applied and Interdisciplinary Chemistry |
Bluing is a technique that can provide limited resistance to rusting for small steel items, such as firearms; for it to be successful, a water-displacing oil is rubbed onto the blued steel and other steel . | 1 | Applied and Interdisciplinary Chemistry |
Devolatilizers for polymer melts are classified as static or moving, also called "still" and "rotating" in the literature. | 1 | Applied and Interdisciplinary Chemistry |
In FRAP, a region is briefly exposed to intense light, irrecoverably photobleaching fluorophores, and the fluorescence recovery due to diffusion of nearby (non-bleached) fluorophores is imaged. A primary advantage of FRAP over FCS is the ease of interpreting qualitative experiments common in cell biology. Differences between cell lines, or regions of a cell, or before and after application of drug, can often be characterized by simple inspection of movies. FCS experiments require a level of processing and are more sensitive to potentially confounding influences like: rotational diffusion, vibrations, photobleaching, dependence on illumination and fluorescence color, inadequate statistics, etc. It is much easier to change the measurement volume in FRAP, which allows greater control. In practice, the volumes are typically larger than in FCS. While FRAP experiments are typically more qualitative, some researchers are studying FRAP quantitatively and including binding dynamics. A disadvantage of FRAP in cell biology is the free radical perturbation of the cell caused by the photobleaching. It is also less versatile, as it cannot measure concentration or rotational diffusion, or co-localization. FRAP requires a significantly higher concentration of fluorophores than FCS. | 0 | Theoretical and Fundamental Chemistry |
When a rock melts to form a liquid, the liquid is known as a primary melt. Primary melts have not undergone any differentiation and represent the starting composition of a magma. In nature, primary melts are rarely seen. Some leucosomes of migmatites are examples of primary melts. Primary melts derived from the mantle are especially important and are known as primitive melts or primitive magmas. By finding the primitive magma composition of a magma series, it is possible to model the composition of the rock from which a melt was formed, which is important because we have little direct evidence of the Earth's mantle. | 0 | Theoretical and Fundamental Chemistry |
Taxol resulted from the tail addition of the Ojima lactam to alcohol 51, which is baccatin III (the original target molecule of the Danishefsky synthesis). Alcohol 51 was derived from the allylic oxidation of α-acylketone 49. Compound 49 was ultimately derived from the Heck reaction of enol triflate 38, which was used to close the B-ring. Enol triflate 38 resulted from a rearrangement of compound 31 after protection of its hydroxyl group. Compound 31 was derived from the connection of the A and C rings with aldehyde 21 combining with the vinyllithium reagent derived from cyanohydrin 29. Cyanohydrin 29 originated as the ethyl isopropyl ketone (22). Aldehyde 21 was obtained from compound 17, which was the product of the opening of ketal 12. Ketal 12 was ultimately derived from the Wieland-Miescher ketone (1). | 0 | Theoretical and Fundamental Chemistry |
* To promote and support the chemical engineering and chemical technology profession.
* To promote and support the educational standard of chemical engineering and chemical technology.
* To encourage cooperation and industrial development including research and knowledge.
* To disseminate knowledge and consulting in chemical engineering and chemical technology.
* To be an agent of chemical engineering and chemical technology profession to cooperate with other organizations. | 1 | Applied and Interdisciplinary Chemistry |
Tracers are also used extensively in oceanography to study a wide array of processes. The isotopes used are typically naturally occurring with well-established sources and rates of formation and decay. However, anthropogenic isotopes may also be used with great success. The researchers measure the isotopic ratios at different locations and times to infer information about the physical processes of the ocean. | 0 | Theoretical and Fundamental Chemistry |
Jung et al. also describe a molecular mechanism for fibrinogen displacement involving pH cycling. Here the αC domains of fibrinogen change charge after pH cycling which results in conformational changes to the protein that leads to stronger interactions with the protein and the biomaterial. | 0 | Theoretical and Fundamental Chemistry |
In molecular geometry, bond length or bond distance is defined as the average distance between nuclei of two bonded atoms in a molecule. It is a transferable property of a bond between atoms of fixed types, relatively independent of the rest of the molecule. | 0 | Theoretical and Fundamental Chemistry |
Especially in proteins, electron transfer often involves hopping of an electron from one redox-active center to another. The hopping pathway, which is viewed as a vector, guides and facilitates ET within an insulating matrix. Typical redox centers are iron-sulfur clusters, e.g. the 4Fe-4S ferredoxins. These site are often separated by 7-10 Å, a distance compatible with fast outer-sphere ET. | 0 | Theoretical and Fundamental Chemistry |
What is the amount of ? The number of ionization depends upon the probability that an electron hits a gas molecule. This probability is the relation of the cross-sectional area of a collision between electron and ion in relation to the overall area that is available for the electron to fly through:
As expressed by the second part of the equation, it is also possible to express the probability as relation of the path traveled by the electron to the mean free path (distance at which another collision occurs).
is the number of molecules which electrons can hit. It can be calculated using the equation of state of the ideal gas
:: pressure, : volume, : Boltzmann constant, : temperature)</small>
The adjoining sketch illustrates that . As the radius of an electron can be neglected compared to the radius of an ion it simplifies to . Using this relation, putting () into () and transforming to one gets
where the factor was only introduced for a better overview.
The alteration of the current of not yet collided electrons at every point in the path can be expressed as
This differential equation can easily be solved:
The probability that (that there was not yet a collision at the point ) is
According to its definition is the number of ionizations per length of path and thus the relation of the probability that there was no collision in the mean free path of the ions, and the mean free path of the electrons:
It was hereby considered that the energy that a charged particle can get between a collision depends on the electric field strength and the charge : | 0 | Theoretical and Fundamental Chemistry |
The involvement of miRNAs in diseases has led scientists to become more interested in the role of additional protein complexes, like microprocessor, that have the ability to influence or modulate the function and expression of miRNAs. Microprocessor complex component, DGCR8, is affected through the micro-deletion of 22q11.2, a small portion of chromosome 22. This deletion causes irregular processing of miRNAs which leads to DiGeorge Syndrome. | 1 | Applied and Interdisciplinary Chemistry |
Covalent organic frameworks are crystalline porous polymers assembled from organic monomers linked through covalent bonds. | 0 | Theoretical and Fundamental Chemistry |
The synthesis of ionic carbonyl complexes is possible by oxidation or reduction of the neutral complexes. Anionic metal carbonylates can be obtained for example by reduction of dinuclear complexes with sodium. A familiar example is the sodium salt of iron tetracarbonylate (NaFe(CO), Collmans reagent'), which is used in organic synthesis.
The cationic hexacarbonyl salts of manganese, technetium and rhenium can be prepared from the carbonyl halides under carbon monoxide pressure by reaction with a Lewis acid.
:Mn(CO)Cl + AlCl + CO → [][]
The use of strong acids succeeded in preparing gold carbonyl cations such as [Au(CO)], which is used as a catalyst for the carbonylation of alkenes. The cationic platinum carbonyl complex [Pt(CO)] can be prepared by working in so-called superacids such as antimony pentafluoride. Although CO is considered generally as a ligand for low-valent metal ions, the tetravalent iron complex [Cp*Fe] (16-valence electron complex) quantitatively binds CO to give the diamagnetic Fe(IV)-carbonyl [Cp*FeCO] (18-valence electron complex). | 0 | Theoretical and Fundamental Chemistry |
A typical optical transfection protocol is as follows:
1) Build an optical tweezers system with a high NA objective
2) Culture cells to 50-60% confluency
3) Expose cells to at least 10 µg/ml of plasmid DNA
4) Dose the plasma membrane of each cell with 10-40 ms of focussed laser, at a power of <100 mW at focus
5) Observe transient transfection 24-96h later
6) Add selective medium if the generation of stable colonies is desired | 1 | Applied and Interdisciplinary Chemistry |
Filter paper is a semi-permeable paper barrier placed perpendicular to a liquid or air flow. It is used to separate fine solid particles from liquids or gases.
The raw materials are typically different paper pulps. The pulp may be made from softwood, hardwood, fiber crops, or mineral fibers. | 0 | Theoretical and Fundamental Chemistry |
Swamy and Jurjees (1986) have pointed out the limitations of sulfur concrete. They questioned the stability and the long-term durability of sulfur concrete beams with steel reinforcement, especially for sulfur concrete modified with dicyclopentadiene and dipentene. Even when dry, modified concrete beams show strength loss with ageing. Ageing in a wet environment leads to softening of sulfur concrete and loss of strength. It causes structural damages in sulfur concrete beams leading to shear failures and cracking. Swamy and Jurjees (1986) also observed severe corrosion of steel reinforcements. They concluded that the stability of reinforced sulfur concrete beams can only be guaranteed when they are unmodified and kept dry.
Being based on the use of elemental sulfur (S, or S) as a binder, sulfur concrete applications are expected to suffer the same limitations as those of elemental sulfur which is not a really inert material, can burn, and is also known to be a potent corrosive agent.
In case of fire, this concrete is flammable and will generate toxic and corrosive fumes of sulfur dioxide (), and sulfur trioxide (), ultimately leading to the formation of sulfuric acid ().
According to Maldonado-Zagal and Boden (1982), the hydrolysis of elemental sulfur (octa-atomic sulphur, S) in water is driven by its disproportionation into oxidised and reduced forms in the ratio / = 3/1. Hydrogen sulfide () causes sulfide stress cracking (SSC) and in contact with air is also easily oxidized into thiosulfate (), responsible for pitting corrosion.
Like pyrite (, iron(II) disulfide), in the presence of moisture, sulfur is also sensitive to oxidation by atmospheric oxygen and could ultimately produce sulfuric acid (), sulfate (), and intermediate chemical species such as thiosulfates (), or tetrathionates (), which are also strongly corrosive substances (pitting corrosion), as all the reduced species of sulfur. Therefore, long-term corrosion problems of steels and other metals (aluminium, copper...) need to be anticipated, and correctly addressed, before selecting sulfur concrete for specific applications.
The formation of sulfuric acid could also attack and dissolve limestone () and concrete structures while also producing expansive gypsum (), aggravating the formation of cracks and fissures in these materials.
If the local physico-chemical conditions are conducive (sufficient space and water available for their growth), sulfur-oxidizing bacteria (microbial oxidation of sulfur) could also thrive at the expense of concrete sulfur and contribute to aggravate potential corrosion problems.
The degradation rate of elemental sulfur depends on its specific surface area. The degradation reactions are the fastest with sulfur dust, or crushed powder of sulfur, while intact compact blocks of sulfur concrete are expected to react more slowly. The service life of components made of sulfur concrete depends thus on the degradation kinetics of elemental sulfur exposed to atmospheric oxygen, moisture and microorganisms, on the density/concentration of microcracks in the material, and on the accessibility of the carbon-steel surface to the corrosive degradation products present in aqueous solution in case of macrocracks or technical voids exposed to water ingress. All these factors need to be taken into account when designing structures, systems and components (SSC) based on sulfur concrete, certainly if they are reinforced, or pre-stressed, with steel elements (rebar or tensioning cables respectively).
While the process of elemental sulfur oxidation will also lower the pH value, aggravating carbon steel corrosion, in contrast to ordinary Portland cement and classical concrete, fresh sulfur concrete does not contain alkali hydroxides (KOH, NaOH), nor calcium hydroxide (), and therefore does not provide any buffering capacity to maintain a high pH passivating the steel surface. In other words, intact sulfur concrete does not chemically protect steel reinforcement bars (rebar) against corrosion. The corrosion of steel elements embedded into sulfur concrete will thus depends on water ingress through cracks and to their exposure to aggressive chemical species of sulfur dissolved in the seeping water. The presence of microorganisms fuelled by elemental sulfur could also play a role and accelerate the corrosion rate. | 1 | Applied and Interdisciplinary Chemistry |
Typically the presence of an amine functional group is deduced by a combination of techniques, including mass spectrometry as well as NMR and IR spectroscopies. H NMR signals for amines disappear upon treatment of the sample with DO. In their infrared spectrum primary amines exhibit two N-H bands, whereas secondary amines exhibit only one. In their IR spectra, primary and secondary amines exhibit distinctive N-H stretching bands near 3300 cm. Somewhat less distinctive are the bands appearing below 1600 cm, which are weaker and overlap with C-C and C-H modes. For the case of propyl amine, the H-N-H scissor mode appears near 1600 cm, the C-N stretch near 1000 cm, and the RN-H bend near 810 cm. | 0 | Theoretical and Fundamental Chemistry |
Merrilactone A occurs naturally in Illicium merrillianum, a plant indigenous to southern China and Myanmar. The genus Illicium belongs to the family Illiciaceae and is an evergreen shrub or tree. Approximately 40 species are disjunctively distributed in eastern North America, Mexico, the West Indies, and eastern Asia. The highest concentration of species is in northern Myanmar and southern China, where nearly 35 species have been described. The fruits of the Illicium species are distinctive star-shaped follicles that have a characteristic refreshing flavour. The fruits of Illicium merrillianum also have an aromatic odor, bland taste and cause numbness of the tongue when chewed.
The only economically important product from this genus is the fruit of Illicium verum, or Chinese star anise, which is widely used as a spice for flavouring food and beverages. In contrast, the fruit of Japanese star anise, Illicium anisatum, have been known to be very toxic for several centuries. | 0 | Theoretical and Fundamental Chemistry |
As early as 1976 a short-term, relatively small, dead zone off the coasts of New York and New Jersey cost commercial and recreational fisheries over $500 million. In 1998 a HAB in Hong Kong killed over $10 million in high-value fish.
In 2009, the economic impact for the state of Washington's coastal counties dependent on its fishing industry was estimated to be $22 million. In 2016, the U.S. seafood industry expected future lost revenue could amount to $900 million annually.
NOAA has provided a few cost estimates for various blooms over the past few years: $10.3 million in 2011 due to a HAB at Texas oyster landings; $2.4 million lost income by tribal commerce from 2015 fishery closures in the pacific northwest; $40 million from Washington state's loss of tourism from the same fishery closure.
Along with damage to businesses, the toll from human sickness results in lost wages and damaged health. The costs of medical treatment, investigation by health agencies through water sampling and testing, and the posting of warning signs at effected locations is also costly.
The closures applied to areas where this algae bloom occurs has a big negative impact of the fishing industries, add to that the high fish mortality that follows, the increase in price due to the shortage of fish available and decrease in the demand for seafood due to the fear of contamination by toxins. This causes a big economic loss for the industry.
Economic costs are estimated to rise. In June 2015, for instance, the largest known toxic HAB forced the shutdown of the west coast shellfish industry, the first time that has ever happened. One Seattle NOAA expert commented, "This is unprecedented in terms of the extent and magnitude of this harmful algal bloom and the warm water conditions we're seeing offshore...." The bloom covered a range from Santa Barbara, California northward to Alaska.
The negative impact on fish can be even more severe when they are confined to pens, as they are in fish farms. In 2007 a fish farm in British Columbia lost 260 tons of salmon as a result of blooms, and in 2016 a farm in Chile lost 23 million salmon after an algal bloom. | 0 | Theoretical and Fundamental Chemistry |
They are often prepared by reaction of the acid or the ester with halogen:
A related method is the Hell-Volhard-Zelinsky halogenation.
Amino acids are susceptible to diazotization in the presence of chloride, a process that affords chiral 2-chloro carboxylic acids and esters. | 0 | Theoretical and Fundamental Chemistry |
There are around 94 naturally occurring elements on earth. The atoms of each element have a nucleus containing a specific number of protons (always the same number for a given element), and some number of neutrons, which is often roughly a similar number. Two atoms of the same element having different numbers of neutrons are known as isotopes of the element. Different isotopes may have different properties – for example one might be stable and another might be unstable, and gradually undergo radioactive decay to become another element.
The hydrogen nucleus contains just one proton. Its isotope deuterium, or heavy hydrogen, contains a proton and a neutron. Helium contains two protons and two neutrons, and carbon, nitrogen and oxygen – six, seven and eight of each particle, respectively. However, a helium nucleus weighs less than the sum of the weights of the two heavy hydrogen nuclei which combine to make it. The same is true for carbon, nitrogen and oxygen. For example, the carbon nucleus is slightly lighter than three helium nuclei, which can combine to make a carbon nucleus. This difference is known as the mass defect. | 0 | Theoretical and Fundamental Chemistry |
Static fatigue tests can estimate a material’s lifetime and hardness to different environments. However, measuring a static fatigue limit can take a long time, and it is hard to measure a material’s true static fatigue limit with full certainty. | 1 | Applied and Interdisciplinary Chemistry |
Hysteresis, in this case, refers to the restructuring of the adhesive interface over some period of time, with the result being that the work needed to separate two surfaces is greater than the work that was gained by bringing them together (W > γ + γ). For the most part, this is a phenomenon associated with diffusive bonding. The more time is given for a pair of surfaces exhibiting diffusive bonding to restructure, the more diffusion will occur, the stronger the adhesion will become. The aforementioned reaction of certain polymer-on-polymer surfaces to ultraviolet radiation and oxygen gas is an instance of hysteresis, but it will also happen over time without those factors.
In addition to being able to observe hysteresis by determining if W > γ + γ is true, one can also find evidence of it by performing “stop-start” measurements. In these experiments, two surfaces slide against one another continuously and occasionally stopped for some measured amount of time. Results from experiments on polymer-on-polymer surfaces show that if the stopping time is short enough, resumption of smooth sliding is easy. If, however, the stopping time exceeds some limit, there is an initial increase of resistance to motion, indicating that the stopping time was sufficient for the surfaces to restructure. | 0 | Theoretical and Fundamental Chemistry |
In this type of substitution reaction, one group of the substrate participates initially in the reaction and thereby affects the reaction. Due to NGP, the reaction rate gets increased by many folds.
A classic example of NGP is the reaction of a sulfur or nitrogen mustard with a nucleophile, the rate of reaction is much higher for the sulfur mustard and a nucleophile than it would be for a primary or secondary alkyl chloride without a heteroatom.
reacts with water 650 times faster than . | 0 | Theoretical and Fundamental Chemistry |
Since an axon can be unmyelinated or myelinated, the action potential has two methods to travel down the axon. These methods are referred to as continuous conduction for unmyelinated axons, and saltatory conduction for myelinated axons. Saltatory conduction is defined as an action potential moving in discrete jumps down a myelinated axon.
This process is outlined as the charge passively spreading to the next node of Ranvier to depolarize it to threshold which will then trigger an action potential in this region which will then passively spread to the next node and so on.
Saltatory conduction provides one advantage over conduction that occurs along an axon without myelin sheaths. This is that the increased speed afforded by this mode of conduction assures faster interaction between neurons. On the other hand, depending on the average firing rate of the neuron, calculations show that the energetic cost of maintaining the resting potential of oligodendrocytes can outweigh the energy savings of action potentials. So, axon myelination does not necessarily save energy. | 1 | Applied and Interdisciplinary Chemistry |
Aside from bioreduction, biosorption, bioaccumulation and biomineralization, which are bacterial strategies for natural attenuation of radioactive contamination, there are also human methods that increase the efficiency or speed of microbial processes. This accelerated natural attenuation involves an intervention in the contaminated area to improve conversion rates of radioactive waste, which tend to be slow. There are two variants: biostimulation and bioaugmentation.
Biostimulation is the addition of nutrients with trace elements, electron donors or electron acceptors to stimulate activity and growth of natural indigenous microbial communities. It can range from simple fertilization or infiltration (called passive biostimulation) to more aggressive injections to the ground, and is widely used at US DOE sites. Nitrate is used as nutrient to biostimulate the reduction of uranium, because it serves as very energetically favorable electron acceptor for metal-reducing bacteria. However, many of these microorganisms (Geobacter, Shewanella or Desulfovibrio) exhibit resistance genes to heavy metals that limit their ability to bioremediate radionuclides. In these particular cases, a carbon source such as ethanol is added to the medium to promote the reduction of nitrate at first, and then of uranium. Ethanol is also used in soil injection systems with hydraulic recirculations: it raises the pH and promotes the growth of denitrifying and radionuclide-reducing bacteria, that produce biofilms and achieve almost 90% decrease in the concentration of radioactive uranium.
A number of geophysical techniques have been used to monitor the effects of in situ biostimulation trials including measurement of: spectral ionization potential, self potentials, current density, complex resistivity and also reactive transport modelling (RTM), which measures hydrogeological and geochemical parameters to estimate chemical reactions of the microbial community.
Bioaugmentaton, on the other hand, is the deliberated addition to the environment of microorganisms with desired traits to accelerate bacterial metabolic conversion of radioactive waste. They are often added when necessary species for bioremediation do not exist in the treatment place. This technique has shown in field trials over the years that it does not offer better results than biostimulation; neither it is clear that introduced species can be distributed effectively through the complex geological structures of most subsurface environments or that can compete long term with the indigenous microbiota. | 1 | Applied and Interdisciplinary Chemistry |
Below are listed some symbols of chemical apparatus and equipment normally used in a P&ID, according to ISO 10628 and ISO 14617. | 1 | Applied and Interdisciplinary Chemistry |
The concept of magic numbers in the field of chemistry refers to a specific property (such as stability) for only certain representatives among a distribution of structures. It was first recognized by inspecting the intensity of mass-spectrometric signals of rare gas cluster ions. Then, the same effect was observed with sodium clusters.
In case a gas condenses into clusters of atoms, the number of atoms in these clusters that are most likely to form varies between a few and hundreds. However, there are peaks at specific cluster sizes, deviating from a pure statistical distribution. Therefore, it was concluded that clusters of these specific numbers of atoms dominate due to their exceptional stability. The concept was also successfully applied to explain the monodispersed occurrence of thiolate-protected gold clusters; here the outstanding stability of specific cluster sizes is connected with their respective electronic configuration.
The term magic numbers is also used in the field of nuclear physics. In this context, magic numbers refer to a specific number of protons or neutrons that forms complete nucleon shells. | 0 | Theoretical and Fundamental Chemistry |
As well as circulating coins, where they are generally restricted to high-denomination coins, bi-metallic coins are often used in commemorative issues, often made of precious metals. For example, the only bi-metallic coin issued by the United States is the $10 Library of Congress commemorative, made of a gold ring around a platinum center. They are used primarily as a way of securing against coin counterfeiting. | 1 | Applied and Interdisciplinary Chemistry |
Thermal inductance refers to the phenomenon wherein a thermal change of an object surrounded by a fluid will induce a change in convection currents within that fluid, thus inducing a change in the kinetic energy of the fluid. It is considered the thermal analogue to electrical inductance in system equivalence modeling; its unit is the thermal henry.
Thus far, few studies have reported on the inductive phenomenon in the heat-transfer behaviour of a system. In 1946, Bosworth demonstrated that heat flow can have an inductive nature through experiments with a fluidic system. He claimed that the measured transient behaviour of the temperature change cannot be explained by merely the combination of the thermal resistance and the thermal capacitance. Bosworth later extended the experiments to study the thermal mutual inductance; however, he did not report on the thermal inductance in a heat-transfer system with the exception of a fluid flow. | 0 | Theoretical and Fundamental Chemistry |
Anisomycin, also known as flagecidin, is an antibiotic produced by Streptomyces griseolus which inhibits eukaryotic protein synthesis. Partial inhibition of DNA synthesis occurs at anisomycin concentrations that effect 95% inhibition of protein synthesis. Anisomycin can activate stress-activated protein kinases, MAP kinase and other signal transduction pathways. | 1 | Applied and Interdisciplinary Chemistry |
In the case of a non-circular cross-section of a pipe, the same formula can be used to find the entry length with a little modification. A new parameter “hydraulic diameter” relates the flow in non-circular pipe to that of circular pipe flow. This is valid as long as the cross-sectional area shape is not too exaggerated. Hydraulic Diameter is defined as:
where is the area of cross-section and is the Perimeter of the wet part of the pipe | 1 | Applied and Interdisciplinary Chemistry |
From 2000 to 2010, the U.S. Army Research Laboratory (ARL) researched potential extensions to LIBS technology, which focused on hazardous material detection. Applications investigated at ARL included the standoff detection of explosive residues and other hazardous materials, plastic landmine discrimination, and material characterization of various metal alloys and polymers. Results presented by ARL suggest that LIBS may be able to discriminate between energetic and non-energetic materials. | 0 | Theoretical and Fundamental Chemistry |
Milky seas (Somali: Kaluunka iftiima; English: Milky seas), also called mareel, is a luminous phenomenon in the ocean in which large areas of seawater (up to ) appear to glow translucently (in varying shades of blue). Such occurrences glow brightly enough at night to be visible from satellites orbiting Earth.
Mariners and other seafarers have reported that the ocean often emits a visible glow which extends for miles at night. In 2005, scientists announced that for the first time, they had obtained photographic evidence of this glow. It is most likely caused by bioluminescence. | 1 | Applied and Interdisciplinary Chemistry |
The model proposed by Roberto Germano and his collaborators, who have first observed the effect is based on the known concept of the exclusion zone.
The first observations of a different behaviour of water molecules close to the walls of its container date back to late ‘60s and early ‘70s, when Drost-Hansen, upon reviewing many experimental articles, came to the conclusion that interfacial water shows structural difference with respect to the bulk liquid water.
In 2006 Gerald Pollack published a seminal work on the exclusion zone and those observations were subsequently reported by several other groups, in which a hydrophilic material creates a coherent water region at the boundary between its surface and the water.
Further elaborating on the work of Pollack, the model describes liquid water as a system made of two phases: a matrix of non-coherent water molecules hosting many “Coherence Domains” (CDs), about 0.1 um in size, found in the exclusion zone, but also in the bulk volume.
In this model the behaviour of the coherence domains is also considered as the cause for the formation of xerosydryle.
The two phases, are characterized by different thermodynamic parameters, and are in a stable non-equilibrium state.
The coherent phase should be described by a quantum state, and in particular a state oscillating between a fundamental state, where electrons are firmly bound (ionization energy of 12.60 eV), and an excited state characterized by a quasi-free electron configuration. The energy of the excited state is 12.06 eV, which means that only a small amount of energy as small as (12.60 - 12.06) eV = 0.54 eV (Infrared range) is sufficient to extract an electron.
Then, at a fixed temperature and for molecules density exceeding a threshold, the transition of the non-coherent water molecules to the coherence state is spontaneous because it is driving the system to a lower energy configuration.
More exactly, the almost free electrons have to cross an energy barrier of (0.54 - Χ) eV, where Χ ~ 0.1 eV is the electric potential difference at the CD boundary with the non-coherent water.
This small amount of energy, ~ 0.44 eV, necessary for the electron extraction, makes the coherent water a reservoir of quasi-free electrons that can be easily released by Infrared stimulation, or quantum tunnel effect or by small external perturbation.
The two water phases, with their different potentials behave as the two components of a photovoltaic cell based on semiconductors.
Then, in the cell described in the patent, one of the two sectors has sheets of hydrophilic material, which create (more) coherent domains in that sector, with respect to the other sector. | 0 | Theoretical and Fundamental Chemistry |
In analytical chemistry, potentiometric titration is a technique similar to direct titration of a redox reaction. It is a useful means of characterizing an acid. No indicator is used; instead the electric potential is measured across the analyte, typically an electrolyte solution. To do this, two electrodes are used, an indicator electrode (the glass electrode and metal ion indicator electrode) and a reference electrode. Reference electrodes generally used are hydrogen electrodes, calomel electrodes, and silver chloride electrodes. The indicator electrode forms an electrochemical half-cell with the interested ions in the test solution. The reference electrode forms the other half-cell.
The overall electric potential is calculated as
is the potential drop over the test solution between the two electrodes. is recorded at intervals as the titrant is added. A graph of potential against volume added can be drawn and the end point of the reaction is halfway between the jump in voltage.
depends on the concentration of the interested ions with which the indicator electrode is in contact. For example, the electrode reaction may be
As the concentration of changes, the changes correspondingly. Thus the potentiometric titration involve measurement of with the addition of titrant. Types of potentiometric titration include acid–base titration (total alkalinity and total acidity), redox titration (HI/HY and cerate), precipitation titration (halides), and complexometric titration (free EDTA and Antical #5). | 0 | Theoretical and Fundamental Chemistry |
Zeldovich–Taylor flow (also known as Zeldovich–Taylor expansion wave) is the fluid motion of gaseous detonation products behind Chapman–Jouguet detonation wave. The flow was described independently by Yakov Zeldovich in 1942 and G. I. Taylor in 1950, although G. I. Taylor carried out the work in 1941 that being circulated in the British Ministry of Home Security. Since naturally occurring detonation waves are in general a Chapman–Jouguet detonation wave, the solution becomes very useful in describing real-life detonation waves. | 1 | Applied and Interdisciplinary Chemistry |
In the history of food, ancient fermented food processes, such as making bread, wine, cheese, curds, idli, dosa, etc., can be dated to more than seven thousand years ago. They were developed long before humanity had any knowledge of the existence of the microorganisms involved. Some foods such as Marmite are the byproduct of the fermentation process, in this case in the production of beer. | 1 | Applied and Interdisciplinary Chemistry |
Elly Agallidis was born in 1914 to a middle class family of Athens; she was the first child of Ioannis Agallidis and Maria-Edith Agallidis (née Zannou). She graduated with a degree in Physics from the University of Athens in 1934 and continued with postgraduate studies in the Physical Chemistry Laboratory of the University of Munich, then under the direction of Heinrich Otto Wieland. It was there that she met Georg-Maria Schwab, her future husband, who suggested that she examine parahydrogen and supervised her experimental work.
Schwab was banned from teaching in Nazi Germany due to his half-Jewish origin. With the increasing fear of prosecution, he decided in 1930 to emigrate to Elly's homeland, Greece. Agallidis and Schwab married in Athens the same year. Schwab-Agallidis was able to find work for both in the chemical laboratory of the Kanellopoulos Institute of Chemistry and Agriculture, where the couple collaborated on various topics of physico-chemical research for the next ten years (1939–1949). Among those topics Schwab-Agallidis continued her work on the properties of parahydrogen, for which she received her PhD by the Department of Physics of the University of Athens in 1939 and published multiple relevant papers in the following years. At the same period she also delivered lectures on Physical Chemistry at the University of Athens.
After a difficult period for the couple during the Axis occupation of Greece and the resumption of their research after the liberation of Greece, the two scientists eventually returned to West Germany when Schwab was offered the Professorship of Physical Chemistry at the University of Munich in 1951.
Elly Schwab-Agallidis died in Essen at the age of 92 in 2006. | 0 | Theoretical and Fundamental Chemistry |
Zinc is present in almost 3,000 human proteins, and thus is essential for nearly all cellular functions. Zn is also a key constituent of enzymes involved in cell regulation. Consistent with its ubiquitous presence, total cellular Zn concentrations are typically very high (~200 μM), while the concentrations of free Zn ions in the cytoplasms of cells can be as low as a few hundred picomolar, maintained within a narrow range to avoid deficiency and toxicity. One feature of Zn that makes it so critical in cellular biology is its flexibility in coordination to different numbers and types of ligands. Zn can coordinate with anywhere between three and six N-, O- and S-containing ligands (such as histidine, glutamic acid, aspartic acid and cysteine), resulting in a large number of possible coordination chemistries. Zn tends to bind to metal sites of proteins with relatively high affinities compared to other metal ions which, aside from its important functions in enzymatic reactions, partly explains its ubiquitous presence in cellular enzymes. | 0 | Theoretical and Fundamental Chemistry |
Réaumur, a French chemist, made early attempts to produce polycrystalline materials from glass, demonstrating that if glass bottles were packed into a mixture of sand and gypsum, and subjected to red heat for several days, the glass bottles turned opaque and porcelain-like. Although Réaumur was successful in the conversion of glass to a polycrystalline material, he was unsuccessful in achieving the control of the crystallization process, which is a key step in producing true practical glass ceramics with the improved properties mentioned above.
The discovery of glass-ceramics is credited to a man named Donald Stookey, a renowned glass scientist who worked at Corning Inc. for 47 years. The first iteration stemmed from a glass material, Fotoform, which was also discovered by Stookey while he was searching for a photo-etch-able material to be used in television screens. Soon after the beginning of Fotoform, the first ceramic material was discovered when Stookey overheated a Fotoform plate in a furnace at 900 degrees Celsius and found an opaque, milky-white plate inside the furnace rather than the molten mess that was expected. While examining the new material, which Stookey aptly named Fotoceram, he took note that it was much stronger than the Fotoform that it was created from as it survived a short fall onto concrete.
In the late 1950s two more glass-ceramic materials would be developed by Stookey, one found use as the radome in the nose cone of missiles, while the other led to the line of consumer kitchenware known as Corningware. Corning executives announced Stookey's discovery of the latter "new basic material" called Pyroceram which was touted as light, durable, capable of being an electrical insulator and yet thermally shock resistant. At the time, there were only few materials which offered the specific combination of characteristics that Pyroceram did and the material was rolled out as the Corningware kitchen line August 7, 1958.
Some of the success that Pyroceram brought inspired Corning to put an effort towards strengthening glass which became an effort by the technical directors of Corning titled Project Muscle. A lesser known "ultrastrong" glass-ceramic material developed in 1962 called Chemcor (now known as Gorilla Glass) was produced by Cornings glass team due to the Project Muscle effort. Chemcor would even be used to innovate the Pyroceram line of products as in 1961 Corning launched Centura Ware, a new line of Pyroceram that was lined with a glass laminate (invented by John MacDowell) and treated with the Chemcor process. Stookey continued to forge ahead in the discovery of the properties of glass-ceramics as he discovered how to make the material transparent in 1966. Though Corning would not release a product with his new innovation, for fear of cannibalizing Pyrex sales, until the late 1970s under the name Visions. | 0 | Theoretical and Fundamental Chemistry |
In thermodynamics, the compressibility factor (Z), also known as the compression factor or the gas deviation factor, describes the deviation of a real gas from ideal gas behaviour. It is simply defined as the ratio of the molar volume of a gas to the molar volume of an ideal gas at the same temperature and pressure. It is a useful thermodynamic property for modifying the ideal gas law to account for the real gas behaviour. In general, deviation from ideal behaviour becomes more significant the closer a gas is to a phase change, the lower the temperature or the larger the pressure. Compressibility factor values are usually obtained by calculation from equations of state (EOS), such as the virial equation which take compound-specific empirical constants as input. For a gas that is a mixture of two or more pure gases (air or natural gas, for example), the gas composition must be known before compressibility can be calculated. <br />
Alternatively, the compressibility factor for specific gases can be read from generalized compressibility charts that plot as a function of pressure at constant temperature.
The compressibility factor should not be confused with the compressibility (also known as [http://glossary.ametsoc.org/wiki/Coefficient_of_compressibility coefficient of compressibility] or [http://petrowiki.org/Isothermal_compressibility_of_gases isothermal compressibility]) of a material, which is the measure of the relative volume change of a fluid or solid in response to a pressure change. | 0 | Theoretical and Fundamental Chemistry |
More recently Yamago et al. reported stibine-mediated polymerization, using an organostibine transfer agent with the general structure Z(Z')-Sb-R (where Z= activating group and R= free radical leaving group). A wide range of monomers (styrenics, (meth)acrylics and vinylics) can be controlled, giving narrow molecular weight distributions and predictable molecular weights under thermally initiated conditions. Yamago has also published a patent indicating that bismuth alkyls can also control radical polymerizations via a similar mechanism. | 0 | Theoretical and Fundamental Chemistry |
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