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Some bacteria such as enteropathogenic E. coli and enterohemorrhagic E. coli can induce membrane ruffling by secreting toxins via the type three secretion system and modifying the host cytoskeleton. Such toxins include EspT, Map, and SopE, which mimic RhoGEF and activate endogenous Rho GTPases to manipulate actin polymerisation in the infected cell. | 1 | Applied and Interdisciplinary Chemistry |
Rapamycin and rapalogs (rapamycin derivatives) are small molecule inhibitors, which have been evaluated as anticancer agents. The rapalogs have more favorable pharmacokinetic profile compared to rapamycin, the parent drug, despite the same binding sites for mTOR and FKBP12. | 1 | Applied and Interdisciplinary Chemistry |
In 1921, Meitner accepted an invitation from Manne Siegbahn to come to Sweden and give a series of lectures on radioactivity as a visiting professor at Lund University. She found that very little research had been done on radioactivity in Sweden, but she was eager to learn about X-ray spectroscopy, which was Siegbahns specialty. At his laboratory, she met a Dutch doctoral candidate, Dirk Coster, who was studying X-ray spectroscopy, and his wife Miep, who was working on her doctorate in Indonesian language and culture. Armed with her newly acquired knowledge of X-ray spectroscopy, Meitner took a fresh look at the beta-ray spectra when she returned to Berlin. It was known that some beta emission was primary, with electrons being ejected directly from the nucleus, and some was secondary, in which alpha particles from the nucleus knocked electrons out of orbit. Meitner was sceptical of Chadwicks claim that the spectral lines were entirely due to secondary electrons, while the primary ones formed a continuous spectrum. Using techniques developed by Jean Danysz, she examined the spectra of lead-210, radium-226 and thorium-238. Meitner discovered the cause of the emission of electrons from surfaces of atoms with "signature" energies, now known as the Auger effect. The effect is named for Pierre Victor Auger, who independently discovered it in 1923.
Women were granted the right of habilitation in Prussia in 1920, and in 1922 Meitner was granted her habilitation and became a Privatdozentin. She was the first woman to receive her habilitation in physics in Prussia, and only the second in Germany after Hedwig Kohn. Since Meitner had already published over 40 papers, she was not required to submit a thesis, but Max von Laue recommended that the requirement for an inaugural lecture not be waived, since he was interested in what she had to say. She therefore gave an inaugural lecture on "Problems of Cosmic Physics". From 1923 to 1933, she taught a colloquium or tutorial at Friedrich Wilhelm University each semester, and supervised doctoral students at the KWI for Chemistry. These included Arnold Flammersfeld, Kan-Chang Wang and Nikolaus Riehl. In 1926, she became an außerordentlicher Professor (extraordinary professor), the first woman university physics professor in Germany. Her physics section became larger, and she acquired a permanent assistant. Scientists from Germany and around the world came to the KWI for Chemistry to conduct research under her supervision. In 1930, Meitner taught a seminar on "Questions of Atomic Physics and Atomic Chemistry" with Leó Szilárd.
Meitner had a Wilson cloud chamber constructed at the KWI for Chemistry, the first one in Berlin, and with her student Kurt Freitag studied the tracks of alpha particles that did not collide with a nucleus. With her assistant Kurt Philipp she later used it to take the first images of positron traces from gamma radiation. She proved Chadwicks assertion that the discrete spectral lines were entirely the result of secondary electrons, and the continuous spectra were therefore indeed entirely caused by the primary ones. In 1927, Charles Drummond Ellis and William Alfred Wooster measured the energy of the continuous spectrum produced by the beta decay of bismuth-210 at 0.34 MeV where the energy of each disintegration was 0.35 MeV. Thus, the spectrum accounted for nearly all of the energy. Meitner was so stunned by this result that she repeated the experiment with Wilhelm Orthmann using an improved method, and verified Ellis and Woosters results. It appeared that the law of conservation of energy did not hold for beta decay, something Meitner regarded as unacceptable. In 1930, Wolfgang Pauli wrote an open letter to Meitner and Hans Geiger in which he proposed that the continuous spectrum was caused by the emission of a second particle during beta decay, one that had no electric charge and little or no rest mass. The idea was taken up by Enrico Fermi in his 1934 theory of beta decay, and he gave the name "neutrino" to the hypothetical neutral particle. At the time there was scant hope of detecting neutrinos, but in 1956 Clyde Cowan and Frederick Reines did just that. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, coordination number, defined originally in 1893 by Alfred Werner, is the total number of neighbors of a central atom in a molecule or ion. The concept is most commonly applied to coordination complexes. | 0 | Theoretical and Fundamental Chemistry |
The surface of a metal oxide consists of ordered arrays of acid–base centres. The cationic metal centres act as Lewis acid sites while the anionic oxygen centres act as Lewis bases. Surface hydroxyl groups can serve as Brønsted acid or base sites as they can give up or accept a proton. The surface of most metal oxides will be, to some extent, hydroxylated under normal conditions when water vapor is present. The strength and the amount of Lewis And Brønsted acid–base sites will determine the catalytic activity of many metal oxides. Due to this there is a great need to develop standard methods for the characterization of the strength, concentration, and distribution of surface acid–base sites.
The concepts of Lewis acid–base theory and Brønsted–Lowry acid–base theory may be applied to surfaces, however there is no general theory that serves to determine surface acidity or basicity. The qualitative treatment of Brønsted acid base theory is based on the thermodynamic equilibrium constant (K) of acid–base reactions between individual molecules in homogeneous systems. This treatment requires measurement of equilibrium concentrations of reactants and products. The presence of two phases also provides a problem for the quantitative acid–base determination of solids. When an acid or base is adsorbed on to an oxide surface it will perturb neighbouring acid–base sites. This perturbation will inevitably influence the relaxation of the surface and make it impossible to have acid–base reactions at the surface which only involve a single surface site. | 0 | Theoretical and Fundamental Chemistry |
The sources of the energy required for the formation of magma oceans in the early Solar System were the radioactive decay of aluminium-26, accretionary impacts, and core formation. The abundance and short half life of aluminium-26 allowed it to function as one of the sources of heat for the melting of planetesimals. With aluminium-26 as a heat source, planetesimals that had accreted within 2 Ma after the formation of the first solids in the Solar System could melt. Melting in the planetesimals began in the interior and the interior magma ocean transported heat via convection. Planetesimals larger than 20 km in radius that accreted within 2 Ma are expected to have melted, although not completely.
The kinetic energy provided by accretionary impacts and the loss of potential energy from a planet during core formation are also large heat sources for planet melting. Core formation, also referred to as metal-silicate differentiation, is the separation of metallic components from silicate in the magma that sink to form a planetary core. Accretionary impacts that produce heat for the melting of planet embryos and large terrestrial planets have an estimated timescale of tens to hundreds of millions of years. A prime example would be the Moon-forming impact on Earth, that is thought to have formed a magma ocean with a depth of up to 2000 km. The energy of accretionary impacts foremost melt the exterior of the planetary body, and the potential energy provided by core differentiation and the sinking of metals melts the interior. | 0 | Theoretical and Fundamental Chemistry |
The dystrophin-associated protein complex, also known as the dystrophin-associated glycoprotein complex is a multiprotein complex that includes dystrophin and the dystrophin-associated proteins. It is one of the two protein complexes that make up the costamere in striated muscle cells. The other complex is the integrin-vinculin-talin complex. | 1 | Applied and Interdisciplinary Chemistry |
Hydrolysis of xenon hexafluoride or xenon tetrafluoride yields a solution from which colorless XeO crystals can be obtained by evaporation. The crystals are stable for days in dry air, but readily absorb water from humid air to form a concentrated solution. The crystal structure is orthorhombic with a = 6.163 Å, b = 8.115 Å, c = 5.234 Å, and 4 molecules per unit cell. The density is 4.55 g/cm. | 0 | Theoretical and Fundamental Chemistry |
Polymers contain different morphologies on the molecular level which give rise to their macro properties. Long range disorder in the polymer chain is representative of amorphous solids, and the chain segments are considered amorphous. Long range polymer order is similar to crystalline material, and chain segments are considered crystalline.
The thermal characteristics of polymers are fundamentally different from those of most solid materials. Solid materials typically have one melting point, the T, above which the material loses internal molecular ordering and becomes a liquid. Polymers have both a melting temperature T and a glass transition temperature T. Above the T, the polymer chains lose their molecular ordering and exhibit reptation, or mobility. Below the T, but still above the T, the polymer chains lose some of their long-range mobility and can form either crystalline or amorphous regions. In this temperature range, as the temperature decreases, amorphous regions can transition into crystalline regions, causing the bulk material to become more crystalline over all. Below the T, molecular motion is stopped and the polymer chains are essentially frozen in place. In this temperature range, amorphous regions can no longer transition into crystalline regions, and the polymer as a whole has reached its maximum crystallinity.
Hoffman nucleation theory addresses the amorphous to crystalline polymer transition, and this transition can only occur in the temperature range between the T and T. The transition from an amorphous to a crystalline single polymer chain is related to the random thermal energy required to align and fold sections of the chain to form ordered regions titled lamellae, which are a subset of even bigger structures called spherulites. The crystallization of polymers can be brought about by several different methods, and is a complex topic in itself. | 0 | Theoretical and Fundamental Chemistry |
Many polymer chemists are concerned with limiting the rate of disproportionation during polymerization. Although disproportionation results in formation of one new double bond which may react with the polymer chain, a saturated hydrocarbon is also formed, and thus the chain reaction does not readily proceed. During living free radical polymerization, termination pathways for a growing polymer chain are removed. This can be achieved through several methods, one of which is reversible termination with stable radicals. Nitroxide radicals and other stable radicals reduce recombination and disproportionation rates and control the concentration of polymeric radicals. | 0 | Theoretical and Fundamental Chemistry |
The lactate shuttle hypothesis also explains the balance of lactate production in the cytosol, via glycolysis or glycogenolysis, and lactate oxidation in the mitochondria (described below). | 1 | Applied and Interdisciplinary Chemistry |
According to an ancient Hawaiian legend, on the island of Maui near the harbor of Hana there was a village of fishermen haunted by a curse. Upon their return from the sea, one of the fishermen would go missing. One day, enraged by another loss, the fishermen assaulted a hunchbacked hermit deemed to be the culprit of the town's misery. While ripping the cloak off the hermit the villagers were shocked because they uncovered rows of sharp and triangular teeth within huge jaws. A shark god had been caught. It was clear that the missing villagers had been eaten by the god on their journeys to the sea. The men mercilessly tore the shark god into pieces, burned him and threw the ashes into a tide pool near the harbor of Hana. Shortly after, a thick brown "moss" started to grow on the walls of the tide pool causing instant death to victims hit by spears smeared with the moss. Thus was the evil of the demon. The moss growing in the cursed tide pool became known as "limu-make-o-Hana" which literally means "seaweed of death from Hana." The Hawaiians believed that an ill curse came over them if they tried to collect the deadly "seaweed". | 0 | Theoretical and Fundamental Chemistry |
Hemiaminals form from the reaction of an amine and a ketone or aldehyde. The hemiaminal is sometimes isolable, but often they spontaneously dehydrate to give imines. | 0 | Theoretical and Fundamental Chemistry |
When one substance is dissolved into another, a solution is formed. This is opposed to the situation when the compounds are insoluble like sand in water. In a solution, all of the ingredients are uniformly distributed at a molecular level and no residue remains. A solvent-solute mixture consists of a single phase with all solute molecules occurring as solvates (solvent-solute complexes), as opposed to separate continuous phases as in suspensions, emulsions and other types of non-solution mixtures. The ability of one compound to be dissolved in another is known as solubility; if this occurs in all proportions, it is called miscible.
In addition to mixing, the substances in a solution interact with each other at the molecular level. When something is dissolved, molecules of the solvent arrange around molecules of the solute. Heat transfer is involved and entropy is increased making the solution more thermodynamically stable than the solute and solvent separately. This arrangement is mediated by the respective chemical properties of the solvent and solute, such as hydrogen bonding, dipole moment and polarizability. Solvation does not cause a chemical reaction or chemical configuration changes in the solute. However, solvation resembles a coordination complex formation reaction, often with considerable energetics (heat of solvation and entropy of solvation) and is thus far from a neutral process.
When one substance dissolves into another, a solution is formed. A solution is a homogeneous mixture consisting of a solute dissolved into a solvent. The solute is the substance that is being dissolved, while the solvent is the dissolving medium. Solutions can be formed with many different types and forms of solutes and solvents. | 1 | Applied and Interdisciplinary Chemistry |
Protein analysis using microPIXE allow for the determination of the elemental composition of liquid and crystalline proteins. microPIXE can quantify the metal content of protein molecules with a relative accuracy of between 10% and 20%.
The advantage of microPIXE is that given a protein of known sequence, the X-ray emission from sulfur can be used as an internal standard to calculate the number of metal atoms per protein monomer. Because only relative concentrations are calculated there are only minimal systematic errors, and the results are totally internally consistent.
The relative concentrations of DNA to protein (and metals) can also be measured using the phosphate groups of the bases as an internal calibration. | 0 | Theoretical and Fundamental Chemistry |
A system's internal state of thermodynamic equilibrium should be distinguished from a "stationary state" in which thermodynamic parameters are unchanging in time but the system is not isolated, so that there are, into and out of the system, non-zero macroscopic fluxes which are constant in time.
Non-equilibrium thermodynamics is a branch of thermodynamics that deals with systems that are not in thermodynamic equilibrium. Most systems found in nature are not in thermodynamic equilibrium because they are changing or can be triggered to change over time, and are continuously and discontinuously subject to flux of matter and energy to and from other systems. The thermodynamic study of non-equilibrium systems requires more general concepts than are dealt with by equilibrium thermodynamics. Many natural systems still today remain beyond the scope of currently known macroscopic thermodynamic methods.
Laws governing systems which are far from equilibrium are also debatable. One of the guiding principles for these systems is the maximum entropy production principle. It states that a non-equilibrium system evolves such as to maximize its entropy production. | 0 | Theoretical and Fundamental Chemistry |
Sorption reactions of inner sphere complexes are applicable in the transport and retention of trace elements in soil systems. In particular, the sorbent materials found in nature are often metal-oxide inner sphere complexes.
In nature, this is particularly important for iron and manganese cycling, as both are effected by the redox potential of their environments for weathering to occur. Oxyanions such as can hinder the dissolution and weathering of these metals. Reductive dissolution in these environments may take longer or be non-existent as a result. However, an understanding of this has led to greater usage of oxyanions in built environments where corrosion and weathering needs to be limited.
Ion size of the central metal and of inorganic ligands also play a role in the weathering. Alkali earth metals have reduced sorption as their ion size increases due to decreased affinity to anionic charges, which increases their mobility through weathering as a result.
For nonpolar ligands, van der Waals forces instead play a larger role in sorption interactions. Hydrogen bonding does also occur, but is not a part of the adsorption process itself. Due to these factors, the soil quality influences the retention and depletion of nutrients, pollutants, and other ligands that perform sorption with the soil.
Generally, the charged surface of a metallic ion can become charged via crystalline imperfections, chemical reactions at the surface, or sorption at the surface-active ion. Clay minerals are an example of these interactions, and as such can explain chemical homeostasis in the ocean, biogeochemical cycling of metals, and even radioactive waste disposal.
In engineering applications, the clay minerals can promote sodium ion adsorption in petroleum extraction, alongside the creation of environmental liners through the development of a stern layer.
Additionally, water remediation can also be considered a by-product of inner sphere complexes found in clay and other mineral complexes. This is theorized to occur due to metal-metal precipitation, such as in the case of iron-arsenic. However, pH can greatly affect the surface binding effectiveness in this case as well. | 0 | Theoretical and Fundamental Chemistry |
The volatilome (sometimes termed volatolome or volatome) contains all of the volatile metabolites as well as other volatile organic and inorganic compounds that originate from an organism, super-organism, or ecosystem. The atmosphere of a living planet could be regarded as its volatilome. While all volatile metabolites in the volatilome can be thought of as a subset of the metabolome, the volatilome also contains exogenously derived compounds that do not derive from metabolic processes (e.g. environmental contaminants), therefore the volatilome can be regarded as a distinct entity from the metabolome. The volatilome is a component of the aura of molecules and microbes (the microbial cloud) that surrounds all organisms. | 1 | Applied and Interdisciplinary Chemistry |
Rubredoxin is an electron-carrier found in sulfur-metabolizing bacteria and archaea. The active site contains an iron ion coordinated by the sulfur atoms of four cysteine residues forming an almost regular tetrahedron. Rubredoxins perform one-electron transfer processes. The oxidation state of the iron atom changes between the +2 and +3 states. In both oxidation states the metal is high spin, which helps to minimize structural changes. | 1 | Applied and Interdisciplinary Chemistry |
To obtain a rough idea of what phases might occur, one can use a model that has some of the same properties as QCD, but is easier to manipulate. Many physicists use Nambu–Jona-Lasinio models, which contain no gluons, and replace the strong interaction with a four-fermion interaction. Mean-field methods are commonly used to analyse the phases. Another approach is the bag model, in which the effects of confinement are simulated by an additive energy density that penalizes unconfined quark matter. | 0 | Theoretical and Fundamental Chemistry |
There are two functionally different classes of disaccharides:
*Reducing disaccharides, in which one monosaccharide, the reducing sugar of the pair, still has a free hemiacetal unit that can perform as a reducing aldehyde group; lactose, maltose and cellobiose are examples of reducing disaccharides, each with one hemiacetal unit, the other occupied by the glycosidic bond, which prevents it from acting as a reducing agent. They can easily be detected by the Woehlk test or Fearon's test on methylamine.
*Non-reducing disaccharides, in which the component monosaccharides bond through an acetal linkage between their anomeric centers. This results in neither monosaccharide being left with a hemiacetal unit that is free to act as a reducing agent. Sucrose and trehalose are examples of non-reducing disaccharides because their glycosidic bond is between their respective hemiacetal carbon atoms. The reduced chemical reactivity of the non-reducing sugars, in comparison to reducing sugars, may be an advantage where stability in storage is important. | 0 | Theoretical and Fundamental Chemistry |
Constructed wetlands can be used to treat raw sewage, storm water, agricultural and industrial effluent. Constructed wetlands mimic the functions of natural wetlands to capture stormwater, reduce nutrient loads, and create diverse wildlife habitat. Constructed wetlands are used for wastewater treatment or for greywater treatment.
Many regulatory agencies list treatment wetlands as one of their recommended "best management practices" for controlling urban runoff. | 1 | Applied and Interdisciplinary Chemistry |
Silicon in nature is typically bonded to oxygen, in a tetravalent oxidation state. The major forms of solid Si are silicate minerals and amorphous silica, whereas in aqueous solutions the dominant forms are orthosilicic acid and its dissociated species. There are three stable isotopes of Si, associated with the following mean natural abundances: Si– 92.23%, Si– 4.67%, and Si– 3.10%. The isotopic composition of Si is often formulated by the delta notation, as the following:
The reference material (standard) for defining the δSi of a sample is the National Bureau of Standards (NBS) 28 Sand Quartz, which has been certified and distributed by the National Institute of Standards and Technology (NIST), and is also named NIST RM 8546. Currently, there are four main analytical methods for the measurement of Si isotopes: Gas Source Isotope-Ratio Mass Spectrometry (GC-IRMS), Secondary Ion Mass Spectrometry (SIMS), Multi-Collector Inductively Coupled Plasma Mass Spectrometry (MC–IPC–MS), and Laser Ablation MC–ICP–MS. | 0 | Theoretical and Fundamental Chemistry |
Diazomethane is a popular methylating agent in the laboratory, but it is too hazardous (explosive gas with a high acute toxicity) to be employed on an industrial scale without special precautions. Use of diazomethane has been significantly reduced by the introduction of the safer and equivalent reagent trimethylsilyldiazomethane. | 0 | Theoretical and Fundamental Chemistry |
Semiconductors are usually studied in a photoelectrochemical cell. Different configurations exist with a three electrode device. The phenomenon to study happens at the working electrode WE while the differential potential is applied between the WE and a reference electrode RE (saturated calomel, Ag/AgCl). The current is measured between the WE and the counter electrode CE (carbon vitreous, platinum gauze). The working electrode is the semiconductor material and the electrolyte is composed of a solvent, an electrolyte and a redox specie.
A UV-vis lamp is usually used to illuminate the working electrode. The photoelectrochemical cell is usually made with a quartz window because it does not absorb the light. A monochromator can be used to control the wavelength sent to the WE. | 0 | Theoretical and Fundamental Chemistry |
Ḥarbī al-Ḥimyarī () is a semi-legendary Himyarite sage that occurs several times in the writings attributed to the Islamic alchemist Jābir ibn Ḥayyān (died c. 806−816). He is said there to have been one of Jabirs teachers, and to have been 463 years old when Jabir met him. One of Jabirs lost works was dedicated to Harbi al-Himyaris contributions to alchemy, a fact which may point to the existence in Jabirs time of a written work attributed to him. | 1 | Applied and Interdisciplinary Chemistry |
In experimental fluid mechanics, Lagrangian Particle Tracking refers to the process of determining trajectories of small neutrally buoyant particles (flow tracers) that are freely suspended within a turbulent flow field. These are usually obtained by 3-D Particle Tracking Velocimetry. A collection of such particle trajectories can be used for analyzing the Lagrangian dynamics of the fluid motion, for performing Lagrangian statistics of various flow quantities etc.
In computational fluid dynamics, the Lagrangian particle tracking (or in short LPT method) is a numerical technique for simulated tracking of particle paths Lagrangian within an Eulerian phase. It is also commonly referred to as Discrete Particle Simulation (DPS). Some simulation cases for which this method is applicable are: sprays, small bubbles, dust particles, and is especially optimal for dilute multiphase flows with large Stokes number. | 1 | Applied and Interdisciplinary Chemistry |
In a cosolvent system, two miscible fluids with different boiling points are mixed to create a zeotropic mixture. The first fluid is a solvating agent that dissolves soil in the cleaning process. This fluid is an organic solvent with a low-boiling point and a flash point greater than the system's operating temperature. After the solvent mixes with the oil, the second fluid, a hydrofluoroether rinsing agent (HFE), rinses off the solvating agent. The solvating agent can be flammable because its mixture with the HFE is nonflammable. In bisolvent cleaning processes, the rinsing agent is separated from the solvating agent. This makes the solvating and rinsing agents more effective because they are not diluted.
Cosolvent systems are used for heavy oils, waxes, greases and fingerprints, and can remove heavier soils than processes that use pure or azeotropic solvents. Cosolvent systems are flexible in that different proportions of substances in the zeotropic mixture can be used to satisfy different cleaning purposes. For example, increasing the proportion of solvating agent to rinsing agent in the mixture increases the solvency, and thus is used for removing heavier soils.
The operating temperature of the system depends on the boiling point of the mixture, which in turn depends on the compositions of these agents in zeotropic mixture. Since zeotropic mixtures have different boiling points, the cleaning and rinse sump have different ratios of cleaning and solvating agents. The lower-boiling point solvating agent is not found in the rinse sump due to the large difference in boiling points between the agents. | 1 | Applied and Interdisciplinary Chemistry |
The Ernst Schering Prize is awarded annually by the Ernst Schering Foundation for especially outstanding basic research in the fields of medicine, biology or chemistry anywhere in the world. Established in 1991 by the Ernst Schering Research Foundation, and named after the German apothecary and industrialist, Ernst Christian Friedrich Schering, who founded the Schering Corporation, the prize is now worth €50,000. | 1 | Applied and Interdisciplinary Chemistry |
Metabolites produced by marine algae have been found to have many antimicrobial properties. This is because they are produced by the marine organisms as chemical deterrents and as such contain bioactive compounds. The principal classes of marine algae that produce these types of secondary metabolites are Cyanophyceae, Chlorophyceae and Rhodophyceae. Observed biogenic products include polyketides, amides, alkaloids, fatty acids, indoles and lipopeptides. For example, over 10% of compounds isolated from Lyngbya majuscula, which is one of the most abundant cyanobacteria, have antifungal and antimicrobial properties. Additionally, a study by Ren et al. (2002) tested halogenated furanones produced by Delisea pulchra from the Rhodophyceae class against the growth of Bacillus subtilis. When applied at a 40 µg/mL concentration, the furanone inhibited the formation of a biofilm by the bacteria and reduced the biofilm's thickness by 25% and the number of live cells by 63%.
These characteristics then have the potential to be utilised in man-made materials, such as making anti-fouling paints without the environment-damaging chemicals. Environmentally safe alternatives are needed to TBT (tin-based antifouling agent) which releases toxic compounds into water and the environment and has been banned in several countries. A class of biogenic compounds that has had a sizeable effect against the bacteria and microalgae that cause fouling are acetylene sesquiterpenoid esters produced by Caulerpa prolifera (from the Chlorophyceae class), which Smyrniotopoulos et al. (2003) observed inhibiting bacterial growth with up to 83% of the efficacy of TBT oxide.
Current research also aims to produce these biogenic substances on a commercial level using metabolic engineering techniques. By pairing these techniques with biochemical engineering design, algae and their biogenic substances can be produced on a large scale using photobioreactors. Different system types can be used to yield different biogenic products. | 0 | Theoretical and Fundamental Chemistry |
In 1994, Donald and Kevin Dahm began using numerical techniques to calculate remission and transmission from samples of varying numbers of plane parallel layers from absorption and remission fractions for a single layer. Their plan was to "start with a simple model, treat the problem numerically rather than analytically, then look for analytical functions that describe the numerical results. Assuming success with that, the model would be made more complex, allowing more complex analytical expressions to be derived, eventually, leading to an understanding of diffuse reflection at a level that appropriately approximated particulate samples." They were able to show the fraction of incident light remitted, , and transmitted, , by a sample composed of layers, each absorbing a fraction and remitting a fraction of the light incident upon it, could be quantified by an Absorption/Remission function (symbolized and called the ART function), which is constant for a sample composed of any number of identical layers. | 0 | Theoretical and Fundamental Chemistry |
The Collaborative Computing Project for NMR (CCPN) is a project that aims to bring together computational aspects of the scientific community involved in NMR spectroscopy, especially those who work in the field of protein NMR. The general aims are to link new and existing NMR software via a common data standard and provide a forum within the community for the discussion of NMR software and the scientific methods it supports. CCPN was initially started in 1999 in the United Kingdom but collaborates with NMR and software development groups worldwide. | 0 | Theoretical and Fundamental Chemistry |
The underlying principle corresponds to that of the Fabry-Pérot interferometer, which is also the underlying principle for the white-light interferometry. | 0 | Theoretical and Fundamental Chemistry |
*Ebbing, Darrell D. and Gammon, Steven D. [https://books.google.com/books?id=_vRm5tiUJcsC&pg=PA837 General Chemistry] (2007) ,
*[https://books.google.com/books?id=NaVq4ztgsD8C&pg=PA59 Nobel Lectures in Chemistry], Volume 1, World Scientific (1999)
*Swaddle, Thomas Wilson [https://books.google.com/books?id=hXpOtkYS5X4C&pg=PA316 Inorganic chemistry: an industrial and environmental perspective], Academic Press (1997)
*Brett CMA, Brett AMO, ELECTROCHEMISTRY, Principles, methods, and applications, Oxford University Press, (1993)
*Wiberg, Egon; Wiberg, Nils and Holleman, Arnold Frederick [https://books.google.com/books?id=Mtth5g59dEIC&pg=PA65 Inorganic chemistry], Academic Press (2001) | 0 | Theoretical and Fundamental Chemistry |
What makes this magnesium blockade of the NMDAR channel particularly significant in terms of LTP induction is that the block is membrane voltage-dependent. The basis of this voltage dependence is relatively straightforward. The NMDAR channel is a transmembrane protein; that is, it spans the cell membrane. As such, it also spans the electric field generated by the membrane potential. The magnesium binding site within the NMDAR channel is physically located within this electric field. Magnesium ions carrying a double positive charge can be acted upon by the field. When the cell is hyperpolarized, magnesium is stabilized inside the channel (i.e. the two positive charges on the magnesium ion are attracted toward the negative pole of the electric field, which points toward the inside of the cell). As a cell is depolarized, the field effect on the magnesium ion weakens, and the dwell time of magnesium ions within the channel decreases. Thus, the kinetics of the binding reaction between magnesium and the NMDAR channel are such that magnesium periodically unbinds and leaves the channel, only to be replaced by another magnesium ion. During the (very brief) time that the magnesium is absent from the open channel, other ions (such as sodium and calcium) can flow through the channel. However, when the cell is more hyperpolarized, the bound state of magnesium is stabilized and it leaves the channel less often and for a shorter period of time (on average). When the cell is less hyperpolarized, the magnesium leaves the channel more often and stays away for longer (on average). Hence, the magnesium blockade of the open NMDAR channel is membrane voltage-dependent.
While the NMDAR channel itself displays little or no voltage dependence (its open channel I/V curve is more or less linear), the voltage dependence of the magnesium block effectively, if indirectly, confers voltage dependence to this channel. Thus, in effect, the NMDAR channel is both a ligand-gated and voltage-gated channel at the same time. This fact is critical to the function of the NMDAR as a Hebbian coincidence detector. More strictly speaking, inward cationic current (sodium or calcium) through the open unblocked NMDAR does decrease with depolarization (because of the decreased electrochemical "driving force"), but the voltage-dependent unblocking seems to outweigh this decrease in driving force, so the calcium influx into the spine caused by a pair of appropriately timed pre- and postsynaptic spikes significantly exceeds the sum of the influxes due to the individual spikes alone. This extra, or "nonlinear", calcium entry triggers the strength change. | 1 | Applied and Interdisciplinary Chemistry |
In his presentation at a 2019 chemometrics conference in France, Steven Brown called Kowalski the "father" of the following areas of chemometrics: NAS methods (with K. Booksh), multiway methods (with E. Sanchez), heuristics in chemistry (with C. Bender), multi-algorithms in chemistry for “big data” ( > 16 kb).
Responding to a question posed during a 1988 interview, Kowalski felt that his most impactful paper to date was the one he wrote with C. Bender, published in the Journal of the American Chemical Society in 1972, "Pattern recognition. A Powerful approach to interpreting chemical data". Wold categorized this publication as a "seminal" paper in pattern recognition in chemistry.
Kowalski's areas of interest outside of chemometrics were analytical instrumentation, remote sensing, process modeling, and chemical sensors in process analysis and control. | 0 | Theoretical and Fundamental Chemistry |
The atomic structure of human uncoupling protein 1 UCP1 has been solved by cryogenic-electron microscopy. The structure has the typical fold of a member of the SLC25 family. UCP1 is locked in a cytoplasmic-open state by guanosine triphosphate in a pH-dependent manner, preventing proton leak. | 1 | Applied and Interdisciplinary Chemistry |
Once the precursor oligosaccharide is formed, the completed glycan is then transferred to the nascent polypeptide in the lumen of the ER membrane. This reaction is driven by the energy released from the cleavage of the pyrophosphate bond between the dolichol-glycan molecule.
There are three conditions to fulfill before a glycan is transferred to a nascent polypeptide:
*Asparagine must be located in a specific consensus sequence in the primary structure (Asn–X–Ser or Asn–X–Thr or in rare instances Asn–X–Cys).
*Asparagine must be located appropriately in the three-dimensional structure of the protein (Sugars are polar molecules and thus need to be attached to asparagine located on the surface of the protein and not buried within the protein)
*Asparagine must be found in the luminal side of the endoplasmic reticulum for N-linked glycosylation to be initiated. Target residues are either found in secretory proteins or in the regions of transmembrane protein that face the lumen.
Oligosaccharyltransferase is the enzyme responsible for the recognition of the consensus sequence and the transfer of the precursor glycan to a polypeptide acceptor which is being translated in the endoplasmic reticulum lumen. N-linked glycosylation is, therefore, a co-translational event | 0 | Theoretical and Fundamental Chemistry |
Sublimation is historically used as a generic term to describe a two-step phase transition ― a solid-to-gas transition (sublimation in a more precise definition) followed by a gas-to-solid transition (deposition). (See below) | 0 | Theoretical and Fundamental Chemistry |
The Korteweg–de Vries equation (KdV equation) can be used to describe the uni-directional propagation of weakly nonlinear and long waves—where long wave means: having long wavelengths as compared with the mean water depth—of surface gravity waves on a fluid layer. The KdV equation is a dispersive wave equation, including both frequency dispersion and amplitude dispersion effects. In its classical use, the KdV equation is applicable for wavelengths λ in excess of about five times the average water depth h, so for λ > 5 h; and for the period τ greater than with g the strength of the gravitational acceleration. To envisage the position of the KdV equation within the scope of classical wave approximations, it distinguishes itself in the following ways:
* Korteweg–de Vries equation — describes the forward propagation of weakly nonlinear and dispersive waves, for long waves with λ > 7 h.
* Shallow water equations — are also nonlinear and do have amplitude dispersion, but no frequency dispersion; they are valid for very long waves, λ > 20 h.
* Boussinesq equations — have the same range of validity as the KdV equation (in their classical form), but allow for wave propagation in arbitrary directions, so not only forward-propagating waves. The drawback is that the Boussinesq equations are often more difficult to solve than the KdV equation; and in many applications wave reflections are small and may be neglected.
* Airy wave theory — has full frequency dispersion, so valid for arbitrary depth and wavelength, but is a linear theory without amplitude dispersion, limited to low-amplitude waves.
* Stokes wave theory — a perturbation-series approach to the description of weakly nonlinear and dispersive waves, especially successful in deeper water for relative short wavelengths, as compared to the water depth. However, for long waves the Boussinesq approach—as also applied in the KdV equation—is often preferred. This is because in shallow water the Stokes perturbation series needs many terms before convergence towards the solution, due to the peaked crests and long flat troughs of the nonlinear waves. While the KdV or Boussinesq models give good approximations for these long nonlinear waves.
The KdV equation can be derived from the Boussinesq equations, but additional assumptions are needed to be able to split off the forward wave propagation. For practical applications, the Benjamin–Bona–Mahony equation (BBM equation) is preferable over the KdV equation, a forward-propagating model similar to KdV but with much better frequency-dispersion behaviour at shorter wavelengths. Further improvements in short-wave performance can be obtained by starting to derive a one-way wave equation from a modern improved Boussinesq model, valid for even shorter wavelengths. | 1 | Applied and Interdisciplinary Chemistry |
In a recent study, used 20% enriched uranium dispersed in a range of different matrices was examined to determine the physical locations of different isotopes and chemical elements.
* A solid solution of urania in yttria-stabilized zirconia (YSZ) (Y:Zr atom ratio of 1:4).
* Urania particles in an inert matrix formed by a mixture of YSZ and spinel (MgAlO).
* Urania particles dispersed in the inert matrix formed by a mixture of YSZ and alumina.
The fuels varied in their ability to retain the fission xenon; the first of the three fuels retained 97% of the Xe, the second retained 94% while the last fuel only retained 76% of this xenon isotope. The Xe is a long-lived radioactive isotope which can diffuse slowly out of the pellet before being neutron activated to form Cs. The more short-lived Xe was less able to leach out of the pellets; 99%, 98% and 95% of the Xe was retained within the pellets. It was also found that the Cs concentration in the core of the pellet was much lower than the concentration in the rim of the pellet, while the less volatile Ru was spread more evenly throughout the pellets.
The following fuel is particles of solid solution of urania in yttria-stabilized zirconia dispersed in alumina which had burnt up to 105 GW-days per cubic meter. The scanning electron microscope (SEM) is of the interface between the alumina and a fuel particle. It can be seen that the fission products are well confined to within the fuel, little of the fission products have entered the alumina matrix. The neodymium is spread throughout the fuel in a uniform manner, while the caesium is almost homogenously spread out throughout the fuel. The caesium concentration is slightly higher at two points where xenon bubbles are present. Much of the xenon is present in bubbles, while almost all of the ruthenium is present in the form of nanoparticles. The ruthenium nanoparticles are not always colocated with the xenon bubbles. | 0 | Theoretical and Fundamental Chemistry |
A chemical transport model (CTM) is a type of computer numerical model which typically simulates atmospheric chemistry and may give air pollution forecasting. | 1 | Applied and Interdisciplinary Chemistry |
The three-level-amplifier is the template of a quantum device. It operates by employing a hot and cold bath
to maintain population inversion between two energy levels which is used to amplify light by stimulated emission
The ground state level (1-g) and the excited level (3-h) are coupled to a hot bath of temperature .
The energy gap is . When the population on the levels equilibrate
where is the Planck constant and is the Boltzmann constant.
The cold bath of temperature couples the ground (1-g) to an intermediate level (2-c)
with energy gap .
When levels 2-c and 1-g equilibrate then
The device operates as an amplifier when levels (3-h) and (2-c) are coupled to an external field of frequency .
For optimal resonance conditions .
The efficiency of the amplifier in converting heat to power is the ratio of work output to heat input:
Amplification of the field is possible only for positive gain (population inversion)
This is equivalent to .
Inserting this expression into the efficiency formula leads to:
where is the Carnot cycle efficiency.
Equality is obtained under a zero gain condition .
The relation between the quantum amplifier and the Carnot efficiency was first pointed out by Scovil and Schultz-DuBois:
Reversing the operation driving heat from the cold bath to the hot bath by consuming power constitutes a refrigerator.
The efficiency of the refrigerator defined as the coefficient of performance (COP) for the reversed device is: | 0 | Theoretical and Fundamental Chemistry |
Plithotaxis, from the Greek word "πλήΘος", denotes a crowd, swarm, or throng. In collective cellular migration, plithotaxis is the tendency for each individual cell within a monolayer to migrate along the local orientation of the maximal principal stress, or equivalently, minimal intercellular shear stress. Plithotaxis requires force transmission across many cell-cell junctions and therefore is an emergent property of the cell group.
Plithotaxis is found to hold at the level of both a subcellular grid point and an individual cell of a confluent monolayer, and the stresses must be tensile. | 1 | Applied and Interdisciplinary Chemistry |
Pepper spray designed to be used against people is considered a prohibited weapon in Canada. The definition under regulation states "any device designed to be used for the purpose of injuring, immobilizing or otherwise incapacitating any person by the discharge therefrom of (a) tear gas, Mace or other gas, or (b) any liquid, spray, powder or other substance that is capable of injuring, immobilizing or otherwise incapacitating any person" is a prohibited weapon.
Only law enforcement officers may legally carry or possess pepper spray labeled for use on persons. Any similar canister with the labels reading "dog spray" or "bear spray" is regulated under the Pest Control Products Act—while legal to be carried by anyone, it is against the law if its use causes "a risk of imminent death or serious bodily harm to another person" or harming the environment and carries a penalty up to a fine of $500,000 and jail time of maximum 3 years. Carrying bear spray in public, without justification, may also lead to charges under the Criminal Code. | 1 | Applied and Interdisciplinary Chemistry |
Bioswales experience short, potentially intense, periods of rain, flooding and pollutant loading followed by dry seasons. It is important to take into account how the vegetation selected for the bioswales will grow and understanding what types of plants are considered the best fit.
There are four types of bioswales that can be constructed based on the needs of the location.
* Low grass bioswales utilize low growing grass that can be landscaped, similar to lawns. These types of bioswales tend to be less effective than vegetated bioswales in treating stormwater runoff and sustaining an adequate collection time.
* Vegetated bioswales are created with taller growing plants, ornamental vegetations, shrubs, and even trees. These types can also be lined with rocks to slow down the velocity of stormwater runoff that is flowing through bioswales to increase collection time for decontamination. Vegetated bioswales can also include vegetation that is highly useful in removing certain chemicals in runoffs very efficiently.
* Low water use bioswales are helpful in areas that tend to be drier with hotter climate. Xeriscape bioswales are populated with runoff generally only after rain and storms and stay dry otherwise.
* Wet bioswales are similar to wetlands in which they retain water for a much longer period of time that allows for infiltration of stormwater instead of simply emptying the water at the end of the bioswale into storm drain inlets.
Bioswales require a certain soil composition that does not contain more than 5% clay. The soil itself before implementation should not be contaminated. Bioswales should be constructed with a longitudinal slope to allow sediments to settle. Maximum slope of bioswales is 3:1. A minimum clearance is required to ensure that other infrastructure would not be damaged. The overfill drain should be located at least 6 inches above the ground plane to allow for maximum concentration time of stormwater runoff in the bioswales. Rocks can also be used to slow down the runoff velocity. The use of filters is important to prevent inlets from becoming blocked by sediments or trash. | 1 | Applied and Interdisciplinary Chemistry |
TRC105 is an experimental antibody targeted at endoglin as an anti-angiogenesis treatment for soft-tissue sarcoma. | 1 | Applied and Interdisciplinary Chemistry |
Minerals that have the same structure (isomorphic minerals) may have epitaxic relations. An example is albite on microcline . Both these minerals are triclinic, with space group , and with similar unit cell parameters, a = 8.16 Å, b = 12.87 Å, c = 7.11 Å, α = 93.45°, β = 116.4°, γ = 90.28° for albite and a = 8.5784 Å, b = 12.96 Å, c = 7.2112 Å, α = 90.3°, β = 116.05°, γ = 89° for microcline. | 0 | Theoretical and Fundamental Chemistry |
TEOS-10 covers all thermodynamic properties of liquid water, seawater, ice, water vapour and humid air within their particular ranges of validity as well as their mutual equilibrium composites such as sea ice or cloudy (wet and icy) air.
Additionally, TEOS-10 covers derived properties, for example the potential temperature and Conservative Temperature, the buoyancy frequency, the planetary vorticity and the Montgomery and Cunningham geostrophic streamfunctions. A complete list of featured properties can be found in the [http://www.teos-10.org/pubs/TEOS-10_Manual.pdf TEOS-10 Manual].
The handling of salinity was one of the novelties in TEOS-10. It defines the relationship between Reference Salinity and Practical Salinity, Chlorinity or Absolute Salinity and accounts for the different chemical compositions by adding a regionally variable 𝛿S (see Figure). TEOS-10 is valid for Vienna Standard Mean Ocean Water which accounts for different hydrogen- and oxygen-isotope compositions in water which affects the triple point and therefore phase transitions of water. | 0 | Theoretical and Fundamental Chemistry |
To measure the rate constants, known concentrations of receptor and ligand are mixed in solution and the quantity of free receptor is repeatedly measured over time as the solution phase reaction occurs. The time course of the free receptor depletion is then fit with a standard bimolecular rate equation.
(4) dLR/dt = k∙R∙L - K∙k∙RL
where K * k has been substituted for k . | 1 | Applied and Interdisciplinary Chemistry |
The following definition differentiates an aerobic granule from a simple floc with relatively good settling properties and came out of discussions which took place at the 1st IWA-Workshop Aerobic Granular Sludge in Munich (2004): | 1 | Applied and Interdisciplinary Chemistry |
In particle physics and astrophysics, the term strange matter is used in two different contexts, one broader and the other more specific and hypothetical:
# In the broader context, our current understanding of the laws of nature predicts that strange matter could be created when nuclear matter (made of protons and neutrons) is compressed beyond a critical density. At this critical pressure and density, the protons and neutrons dissociate into quarks, yielding quark matter and potentially strange matter.
# A more specific hypothesis is that quark matter is the true ground state of all matter, and thus more stable than ordinary nuclear matter. This idea is known as the "strange matter hypothesis", or the Bodmer–Witten assumption. Under this hypothesis, the nuclei of the atoms we see around us are only metastable, even when the external critical pressure is zero, and given enough time (or the right stimulus) the nuclei would decay into stable droplets of strange matter. Droplets of strange matter are also referred to as strangelets. | 0 | Theoretical and Fundamental Chemistry |
Veige received a Ph.D. degree in chemistry from Cornell University in 2003 under the direction of Peter T. Wolczanski. He pursued postdoctoral research under the direction of Daniel G. Nocera at Massachusetts Institute of Technology. | 0 | Theoretical and Fundamental Chemistry |
pRb is a multifunctional protein with many binding and phosphorylation sites. Although its common function is seen as binding and repressing E2F targets, pRb is likely a multifunctional protein as it binds to at least 100 other proteins.
pRb has three major structural components: a carboxy-terminus, a "pocket" subunit, and an amino-terminus. Within each domain, there are a variety of protein binding sites, as well as a total of 15 possible phosphorylation sites. Generally, phosphorylation causes interdomain locking, which changes pRb's conformation and prevents binding to target proteins. Different sites may be phosphorylated at different times, giving rise to many possible conformations and likely many functions/activity levels. | 1 | Applied and Interdisciplinary Chemistry |
For glass containers, the goal of surface dealkalization is to render the inside surface of the container more resistant to interactions with liquid products later put inside it. Since the treatment is directed primarily at changing the properties of the inside surface in contact with the product, it is also referred to as "internal treatment".
The most common example of its use with containers is on bottles intended to hold alcoholic spirits. The reason for this is that some alcoholic spirits such as vodka and gin have an approximately neutral pH and a high alcohol content, but are not buffered in any way against changes in pH. If alkali is leached from the glass into the product, the pH will begin to rise (i.e. become more alkaline), can eventually reach a pH high enough that the solution begins to attack the glass itself quite effectively. By this mechanism, initially neutral alcohol products can achieve a pH where the glass container itself begins to slowly dissolve, leaving thin, siliceous glass flakes or particles in the fluid. Dealkalization treatment hinders this process by removing alkali from the inside surface. Not only does this mean less extractable alkali in the glass surface directly contacting the product, but it also creates a barrier for the diffusion of alkali from the underlying bulk glass into the product.
The same logic applies in pharmaceutical glass items such as vials that are intended to hold medicinal products. While many of these items are composed of more durable borosilicate glass, they are also at times dealkalized in order to minimize the possibility of alkali leaching from the glass into the product. This action helps to avoid undesired changes in pH or ionic strength of the solution, which not only inhibits eventual attack of the glass as previously described, but can also be important in maintaining the efficacy or stability of sensitive product formulations. | 0 | Theoretical and Fundamental Chemistry |
Ultraviolet sterilizers are often used to help control unwanted microorganisms in aquaria and ponds. UV irradiation ensures that pathogens cannot reproduce, thus decreasing the likelihood of a disease outbreak in an aquarium.
Aquarium and pond sterilizers are typically small, with fittings for tubing that allows the water to flow through the sterilizer on its way from a separate external filter or water pump. Within the sterilizer, water flows as close as possible to the ultraviolet light source. Water pre-filtration is critical as water turbidity lowers UV-C penetration.
Many of the better UV sterilizers have long dwell times and limit the space between the UV-C source and the inside wall of the UV sterilizer device. | 0 | Theoretical and Fundamental Chemistry |
One can also plot the dihedral angles in polysaccharides (e.g. with [http://glycosciences.de/tools/carp/ CARP]). | 1 | Applied and Interdisciplinary Chemistry |
The fission process can be understood when a nucleus with some equilibrium deformation absorbs energy (through neutron capture, for example), becomes excited and deforms to a configuration known as the "transition state" or "saddle point" configuration. As the nucleus deforms, the nuclear Coulomb energy decreases while the nuclear surface energy increases. At the saddle point, the rate of change of the Coulomb energy is equal to the rate of change of the nuclear surface energy. The formation and eventual decay of this transition state nucleus is the rate-determining step in the fission process and corresponds to the passage over an activation energy barrier to the fission reaction. When this occurs, the neck between the nascent fragments disappears and the nucleus divides into two fragments. The point at which this occurs is called the "scission point". | 0 | Theoretical and Fundamental Chemistry |
The radio spectrum scope (also radio panoramic receiver, panoramic adapter, pan receiver, pan adapter, panadapter, panoramic radio spectroscope, panoramoscope, panalyzor and band scope) was invented by Marcel Wallace - and measures and shows the magnitude of an input signal versus frequency within one or more radio bands - e.g. shortwave bands. A spectrum scope is normally a lot cheaper than a spectrum analyzer, because the aim is not high quality frequency resolution - nor high quality signal strength measurements.
The spectrum scope use can be to:
* find radio channels quickly of known and unknown signals when receiving.
* find radio amateurs activity quickly e.g. with the intent of communicating with them.
Modern spectrum scopes, like the Elecraft P3, also plot signal frequencies and amplitudes over time, in a rolling format called a waterfall plot. | 0 | Theoretical and Fundamental Chemistry |
The PROX process allows for the reaction of CO with oxygen, reducing CO concentration from approximately 0.5–1.5% in the feed gas to less than 10 ppm.
:2CO + O → 2CO
Due to the prevalent presence of hydrogen in the feed gas, the competing, undesired combustion of hydrogen will also occur to some degree:
:2H + O → 2HO
The selectivity of the process is a measure of the quality of the reactor, and is defined as the ratio of consumed carbon monoxide to the total of consumed hydrogen and carbon monoxide.
The disadvantage of this technology is its very strong exothermic nature, coupled with a very narrow optimal operation temperature window, and is best operated between 353 and 450 K, yielding a hydrogen loss of around one percent. Effective cooling is therefore required. In order to minimize steam generation, excessive dilution with nitrogen is used. Additionally the reaction is interrupted with an intermediary cooler before proceeding to a second stage.
In the first reaction an excess of oxygen is provided, at around a factor of two, and about 90% of the CO is transformed. In the second step a substantially higher oxygen excess is used, at approximately a factor of 4, which is then processed with the remaining CO, in order to reduce the CO concentration to less than 10 ppm. To also avoid excess CO-fraction loading, the transient operation of a CO adsorber may be important.
The instrumentation and process control complexity requirements are relatively high. The advantage of this technique over selective methanation is the higher space velocity, which reduces the required reactor size. For the case of strong temperature rises, the feed of air can simply be broken.
The technical origins for CO-PROX lies in the synthesis of ammonia (Haber process). Ammonia synthesis also has a strict requirement of CO-free hydrogen, as CO is a strong catalyst poison for the usual catalysts used in this process. | 0 | Theoretical and Fundamental Chemistry |
Methylene blue is also a photosensitizer used to create singlet oxygen when exposed to both oxygen and light. It is used in this regard to make organic peroxides by a Diels-Alder reaction which is spin forbidden with normal atmospheric triplet oxygen. | 0 | Theoretical and Fundamental Chemistry |
While the two previous models implied that eRNAs were not functionally relevant, this mechanism states that eRNAs are functional molecules that exhibit cis activity. In this model, eRNAs can locally recruit regulatory proteins at their own site of synthesis. Supporting this hypothesis, transcripts originating from enhancers upstream of the Cyclin D1 gene are thought to serve as adaptors for the recruitment of histone acetyltransferases. It was found that depletion of these eRNAs led to Cyclin D1 transcriptional silencing. | 1 | Applied and Interdisciplinary Chemistry |
In the Newman-Kwart rearrangement O-thiocarbamates can isomerise to S-thiocarbamates. This reaction, which generally requires high temperatures, is an important method for the synthesis of thiophenols. | 0 | Theoretical and Fundamental Chemistry |
MoOPH is synthesized from molybdenum trioxide by oxidation with hydrogen peroxide and addition of the HMPA and pyridine ligands: | 0 | Theoretical and Fundamental Chemistry |
Structural variations, such as deletions, duplications, inversions, translocations, and other rearrangements, are common in human genomes. These variations can have significant impacts on genome functions, and have been implicated in many diseases. Linked-read sequencing technology labels all reads that originate from the same long DNA fragment with the same barcode, so it enables the detection of a large number of structural variants. Complexity of structural variants can be resolved with linked-read sequencing, and provide a complete picture of the genomic landscape. Many scientists have already been using linked-read sequencing to identify and characterise structural variants in diverse populations, including people with genetic disorders or cancers | 1 | Applied and Interdisciplinary Chemistry |
Sum-frequency generation (SFG) is a second order nonlinear optical process based on the mixing of two input photons at frequencies and to generate a third photon at frequency . As with any optical phenomenon in nonlinear optics, this can only occur under conditions where:
the light is interacting with matter, that lacks centrosymmetry (for example, surfaces and interfaces);
the light has a very high intensity (typically from a pulsed laser).
Sum-frequency generation is a "parametric process", meaning that the photons satisfy energy conservation, leaving the matter unchanged: | 0 | Theoretical and Fundamental Chemistry |
The nonradiative process for heat generation of organic PTAs is different from that of inorganic PTAs such as metals and semiconductors which is related with surface plasmon resonance. As shown in the figure, conjugated polymers are first activated to the excited state (S1) under light irradiation and then excited state (S1) decays back to the ground state (S0) via three processes: (I) emitting a photon (fluorescence), (II) intersystem crossing, and (III) nonradiative relaxation (heat generation). Because these three pathways of the S1 decaying back to the S0 are usually competitive in photosensitive materials, light emitting and intersystem crossing must be efficiently reduced in order to increase the heat generation and improve the photothermal conversion efficiency. For conjugated polymers, on the one hand, their unique structures lead to closed stacking of the molecular sensitizers with highly frequent intermolecular collisions which can efficiently quench the fluorescence and intersystem crossing, and thus enhance the yield of nonradiative relaxation. On the other hand, compared with monomeric phototherapeutic molecules, conjugated polymers possess higher stability in vivo against disassembly and photobleaching, longer blood circulation time, and more accumulation at tumor site due to the enhanced permeability and retention (EPR) effect. Therefore, conjugated polymers have high photothermal conversion efficiency and a large amount of heat generation. One of the most widely used equations to calculate photothermal conversion efficiency (η) of organic PTAs is as follows:
η = (hAΔΤ-Qs)/I(1-10)
where h is the heat transfer coefficient, A is the container surface area, ΔΤ means the maximum temperature change in the solution, A means the light absorbance, I is the laser power density, and Qs is the heat associated with the light absorbance of the solvent.
Furthermore, various efficient methods, especially donor-acceptor (D-A) strategy, have been designed to enhance the photothermal conversion efficiency and heat generation of conjugated polymers. The D-A assembly system in the conjugated polymers contributes to strong intermolecular electron transfer from the donor to the acceptor, thus bringing efficient fluorescence and intersystem crossing quenching, and improved heat generation. In addition, the HOMO-LUMO gap of the D−A conjugated polymers can be easily tuned through changing the selection of electron donor (ED) and electron acceptor (EA) moieties, and thus D−A structured polymers with extremely low band gap can be developed to improve the NIR absorption and photothermal conversion efficiency of CPs. | 0 | Theoretical and Fundamental Chemistry |
In mass transfer, the sieving coefficient is a measure of equilibration between the concentrations of two mass transfer streams. It is defined as the mean pre- and post-contact concentration of the mass receiving stream divided by the pre- and post-contact concentration of the mass donating stream.
where
* S is the sieving coefficient
* C is the mean concentration mass receiving stream
* C is the mean concentration mass donating stream
A sieving coefficient of unity implies that the concentrations of the receiving and donating stream equilibrate, i.e. the out-flow concentrations (post-mass transfer) of the mass donating and receiving stream are equal to one another. Systems with sieving coefficient that are greater than one require an external energy source, as they would otherwise violate the laws of thermodynamics.
Sieving coefficients less than one represent a mass transfer process where the concentrations have not equilibrated.
Contact time between mass streams is important in consider in mass transfer and affects the sieving coefficient. | 1 | Applied and Interdisciplinary Chemistry |
Geometric Dynamic Recrystallization (GDR) is a recrystallization mechanism that has been proposed to occur in several alloys, particularly aluminium, at high temperatures and low strain rates. It is a variant of dynamic recrystallization.
The basic mechanism is that during deformation the grains will be increasingly flattened until the boundaries on each side are separated by only a small distance. The deformation is accompanied by the serration of the grain boundaries due to surface tension effects where they are in contact with low-angle grain boundaries belonging to sub-grains.
Eventually the points of the serrations will come into contact. Since the contacting boundaries are defects of opposite sign they are able to annihilate and so reduce the total energy in the system. In effect the grain will pinch in two new grains.
The grain size is known to decrease as the applied stress is increased. However, high stresses require a high strain rate and at some point statically recrystallized grains will begin to nucleate and consume the GDRX microstructure.
There are features that are unique to GDRX:
* The recrystallisation spreads throughout the specimen over a strain range (0.5-1 in Al-Mg-Mn alloys) without any change in flow stress. This is in contrast to discontinuous mechanisms where the flow stress normally decreases by ~25% as the recrystallized grains form.
* GDRX results in grains that are around 3 times the sub-grain size. Statically recrystallized grains are normally 20-30 times the sub-grain size. | 1 | Applied and Interdisciplinary Chemistry |
Along with the related organotantalum species, niobium alkylidenes were among the first Scrock carbenes studied. The first syntheses of these complexes involved addition of organolithium reagents lacking β-hydrogens into hindered Nb(V) complexes followed by α-proton elimination. As compared to tantalum alkylidenes, niobium alkylidenes are less thermally and hydrolytically stable. | 0 | Theoretical and Fundamental Chemistry |
In liquid chromatography:
* Charged aerosol detector electrically charged aerosol is used for the detection of non-UV-absorbing chargeable molecules, especially saccharides and lipids
* Evaporative light scattering detector evaporating non volatile solutes inside a volatile mobile phase for universal detection. used for saccharides and lipids and other non-UV-absorbing molecules
In gas chromatography:
* Flame ionization detector which uses ionizing flame to detect most hydrocarbon molecules
* Flame photometric detector which uses atomizing flame to get light emitted from specific elements to detect and quantify them
* Nitrogen Phosphorus Detector a thermionic detector with photometeric detection, sensitive specifically to nitrogen and phosphorus hydrocarbons
* Atomic-emission detector is a hyphenation between gas chromatography and atomic emission spectrophotometer for detection of elements.
In all types of chromatography:
* Mass spectrometer is in fact hyphenation between the separative instrument and a mass spectrometry instrument to get information on the molecular weight or atomic weight of the solute. In the advanced mass spectrometry technologies there is information on solutes structure and even chemical properties. The hyphenation between ultra high performance chromatography with high resolution mass spectrometers revolutionalized entire new scientific fields of research and application, such as toxicology, proteomics, lipidomics, genomics, metabolomics and metabonomics. | 0 | Theoretical and Fundamental Chemistry |
The backscattering method is also employed in fiber optics applications to detect optical faults. Light propagating through a fiber-optic cable gradually attenuates due to Rayleigh scattering. Faults are thus detected by monitoring the variation of part of the Rayleigh backscattered light. Since the backscattered light attenuates exponentially as it travels along the optical fiber cable, the attenuation characteristic is represented in a logarithmic scale graph. If the slope of the graph is steep, then power loss is high. If the slope is gentle, then optical fiber has a satisfactory loss characteristic.
The loss measurement by the backscattering method allows measurement of a fiber-optic cable at one end without cutting the optical fiber hence it can be conveniently used for the construction and maintenance of optical fibers. | 0 | Theoretical and Fundamental Chemistry |
The earliest gunpowder recipe and primitive weaponry date to Chinas Song dynasty and the oldest extant guns appear in the Mongol-led Yuan dynasty of China. However, historian Tonio Andrade notes that there is a surprising scarcity of reliable evidence of firearms in Iran or Central Asia prior to the late 14th century. He argues that, in the Middle East, no guns are mentioned prior to the 1360s, while Russian records do not contain reliable mentions of firearms until 1382, after the guns arrival in western Europe, despite their closer proximity and interactions with the Mongol empires. | 1 | Applied and Interdisciplinary Chemistry |
The four phosphorus atoms are at the corners of a tetrahedron surrounding the palladium(0) center. This structure is typical for four-coordinate 18 e complexes. The corresponding complexes Ni(PPh) and Pt(PPh) are also well known. Such complexes reversibly dissociate PPh ligands in solution, so reactions attributed to Pd(PPh) often in fact arise from Pd(PPh) or even Pd(PPh). | 0 | Theoretical and Fundamental Chemistry |
Decipium was the proposed name for a new chemical element isolated by Marc Delafontaine from the mineral samarskite. He published his discovery in 1878 and later published a follow-up paper in 1881.
Decipium was considered to be in the cerium group of rare earths.
In 1880, spectral analysis proved that decipium had a high samarium content. It is now believed that Delafontaine's decipium sample was a mixture of samarium with traces of other rare earth elements. | 1 | Applied and Interdisciplinary Chemistry |
Many metals, such as arsenic, cadmium, chromium, nickel and their compounds may be mutagenic, but they may act, however, via a number of different mechanisms. Arsenic, chromium, iron, and nickel may be associated with the production of ROS, and some of these may also alter the fidelity of DNA replication. Nickel may also be linked to DNA hypermethylation and histone deacetylation, while some metals such as cobalt, arsenic, nickel and cadmium may also affect DNA repair processes such as DNA mismatch repair, and base and nucleotide excision repair. | 0 | Theoretical and Fundamental Chemistry |
Comparative genomics approaches were used to predict the function-relevant variants under the assumption that the functional genetic locus should be conserved across different species at an extensive phylogenetic distance. On the other hand, some adaptive traits and the population differences are driven by positive selections of advantageous variants, and these genetic mutations are functionally relevant to population specific phenotypes. Functional prediction of variants’ effect in different biological processes is pivotal to pinpoint the molecular mechanism of diseases/traits and direct the experimental validation. | 1 | Applied and Interdisciplinary Chemistry |
Herbert Charles Brown (May 22, 1912 – December 19, 2004) was an American chemist and recipient of the 1979 Nobel Prize in Chemistry for his work with organoboranes. | 0 | Theoretical and Fundamental Chemistry |
Retrotransposons (also called Class I transposable elements or transposons via RNA intermediates) are a type of genetic component that copy and paste themselves into different genomic locations (transposon) by converting RNA back into DNA through the reverse transcription process using an RNA transposition intermediate.
Through reverse transcription, retrotransposons amplify themselves quickly to become abundant in eukaryotic genomes such as maize (49–78%) and humans (42%). They are only present in eukaryotes but share features with retroviruses such as HIV, for example, discontinuous reverse transcriptase-mediated extrachromosomal recombination.
These retrotransposons are regulated by a family of short non-coding RNAs termed as PIWI [P-element induced wimpy testis]-interacting RNAs (piRNAs). piRNA is a recently discovered class of ncRNAs, which are in the length range of ~24-32 nucleotides. Initially, piRNAs were described as repeat-associated siRNAs (rasiRNAs) because of their origin from the repetitive elements such as transposable sequences of the genome. However, later it was identified that they acted via PIWI-protein. In addition to having a role in the suppression of genomic transposons, various roles of piRNAs have been recently reported like regulation of 3’ UTR of protein-coding genes via RNAi, transgenerational epigenetic inheritance to convey a memory of past transposon activity, and RNA-induced epigenetic silencing.
There are two main types of retrotransposons, long terminal repeats (LTRs) and non-long terminal repeats (non-LTRs). Retrotransposons are classified based on sequence and method of transposition. Most retrotransposons in the maize genome are LTR, whereas in humans they are mostly non-LTR. Retrotransposons (mostly of the LTR type) can be passed onto the next generation of a host species through the germline.
The other type of transposon is the DNA transposon. DNA transposons encode a transposase which, when translated, catalyses the excision of the transposase gene and its flanking region and its insertion into a different genomic location: a jumping DNA element. Hence retrotransposons can be thought of as replicative, whereas DNA transposons are non-replicative. Due to their replicative nature, retrotransposons can increase eukaryotic genome size quickly and survive in eukaryotic genomes permanently. It is thought that staying in eukaryotic genomes for such long periods gave rise to special insertion methods that do not affect eukaryotic gene function drastically. | 1 | Applied and Interdisciplinary Chemistry |
In 1961, Smith was honored for his teaching by the Manufacturing Chemists' Association. He received the 1982 Wig Distinguished Professor award for excellence in teaching from Pomona College. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, the chloromethyl group is a functional group that has the chemical formula . The naming of this group is derived from the methyl group (which has the formula ), by replacing one hydrogen atom by a chlorine atom. Compounds with this group are a subclass of the organochlorines.
The way of introducing a chloromethyl group into aromatic compounds is the chloromethylation by the Blanc reaction. | 0 | Theoretical and Fundamental Chemistry |
1,3-BPG has a very similar role in the Calvin cycle to its role in the glycolytic pathway. For this reason both reactions are said to be analogous. However the reaction pathway is effectively reversed. The only other major difference between the two reactions is that NADPH is used as an electron donor in the calvin cycle whilst NAD is used as an electron acceptor in glycolysis. In this reaction cycle 1,3BPG originates from 3-phosphoglycerate and is made into glyceraldehyde 3-phosphate by the action of specific enzymes.
Contrary to the similar reactions of the glycolytic pathway, 1,3BPG in the Calvin cycle does not produce ATP but instead uses it. For this reason it can be considered to be an irreversible and committed step in the cycle. The outcome of this section of the cycle is an inorganic phosphate is removed from 1,3BPG as a hydrogen ion and two electrons are added to the compound.
In complete reverse of the glycolytic pathway reaction, the enzyme phosphoglycerate kinase catalyses the reduction of the carboxyl group of 1,3BPG to form an aldehyde instead. This reaction also releases an inorganic phosphate molecule which is subsequently used as energy for the donation of electrons from the conversion of NADPH to NADP. Overseeing this latter stage of the reaction is the enzyme glyceraldehyde-phosphate dehydrogenase. | 0 | Theoretical and Fundamental Chemistry |
The areas of scientific interests of Igor V. Komarov are medicinal chemistry and synthesis of model compounds, which can be used to obtain new knowledge in biochemistry, stereochemistry, theoretical chemistry, catalysis. Igor has over 125 peer reviewed research papers, h-index 31, has guided 8 PhD students to date. Igors scientific group puts the main focus on developing of novel synthetic methods and design of theoretically interesting molecules, part of which were created and synthesized in tight collaboration with Prof. Anthony J. [http://www.ch.cam.ac.uk/person/ajk1 Kirby] from the University of Cambridge (United Kingdom). One of such collaborative projects was synthesis, study of stereochemistry and chemical properties of 1-aza-2-adamantanone and its derivatives. A trimethyl-substituted derivative ("the most twisted amide", "Kirbys amide") was designed in the Prof. Kirbys laboratory and synthesized by Igor in 1997 during his postdoctoral stay in Cambridge. In 2014, a parent molecule was made in Igors group in collaboration with Prof. Kirby. The compound modelled the transition state of cis-trans isomerization of amides and allowed obtaining fundamental knowledge about the amide bond.
Igor V. Komarov started his research in the area of synthetic organic chemistry at the beginning of 1990th, working on phosphorylation of aromatic heterocyclic compounds by phosphorus(V) acid halides. At that time, convenient phosphorylation methods were developed, which now find use, for example, for synthesis of materials applicable for uranium extraction. Later, working in Rostock, Igor V. Komarov changed the direction of his research and got interested in homogenous asymmetric catalysis. The study of catalysis was carried out using model compounds: functionalized camphor- and tartaric acid-derived chiral ligands were synthesized such as monophosphines, diphosphines, and then Rhodium(I) complexes with them. The complexes were used for asymmetric homogenous hydrogenation of prochiral substrates, and the obtained results allowed elucidating the effects of oxo- and oxy-functional groups in ligands on efficiency and selectivity of the catalysts. These works led to introduction of efficient catalysts to synthetic practice, like catASium, some of them bearing a camphor-derived ligand ROCKYPhos (named after the cities ROstok and KYiv).
Although Igors interest to the synthesis of chiral ligands has not been faded, he changed the general direction of his research once more, and now he works in the area of drug design. One of the main design principle is restriction of conformational mobility of the drug candidate molecules. Prof. Komarovs research group developed many approaches to synthesis of conformationally restricted amines and amino acids - the building blocks for drug design. Numerous conformationally restricted fluorine-containing amino acids were also designed and synthesized, with a purpose of using them as labels to study peptides in lipid bilayers by solid-state NMR spectroscopy.
Igor V. Komarov's group made a contribution to design and synthesis of light-controllable biologically active compounds - photocontrollable peptides - potential candidates for photopharmacology drugs. Photopharmacology drugs can be administered in the inactive, non-toxic form, and then activated ("switched on") by light only when and where required to treat localized lesions (e.g.in solid tumors). The activation by light can be done with very high spatiotemporal precision in the lesion site, leaving the rest of the patient body unaffected. After the treatment, the photopharmacology drugs can be inactivated ("switched off") by light in order to diminish side-effects and environmental burden.
Another research direction in the Igor V. Komarov's scientific group is navigation of chemical space. A method of structural comparison for organic molecules was developed which employed exit vector plot analysis. Enumeration of molecules (exhaustive generation of all theoretically possible structures) was carried out for some classes of organic compounds, for example, for conformationally restricted diamines.
In the area of nanotechnology, Igor V. Komarov's research group studied cell-penetrating peptides as carriers for carbon-based fluorescent nanoparticles, shuttling them inside eukaryotic cells with the purpose of bioimaging.
Igor V. Komarov has a Ukrainian patent, 2 international patents, is a co-authors of text-books on NMR spectroscopy. | 0 | Theoretical and Fundamental Chemistry |
The term co-receptor is prominent in literature regarding signal transduction, the process by which external stimuli regulate internal cellular functioning. The key to optimal cellular functioning is maintained by possessing specific machinery that can carry out tasks efficiently and effectively. Specifically, the process through which intermolecular reactions forward and amplify extracellular signals across the cell surface has developed to occur by two mechanisms.
First, cell surface receptors can directly transduce signals by possessing both serine and threonine or simply serine in the cytoplasmic domain. They can also transmit signals through adaptor molecules through their cytoplasmic domain which bind to signalling motifs. Secondly, certain surface receptors lacking a cytoplasmic domain can transduce signals through ligand binding. Once the surface receptor binds the ligand it forms a complex with a corresponding surface receptor to regulate signalling. These categories of cell surface receptors are prominently referred to as co-receptors. Co-receptors are also referred to as accessory receptors, especially in the fields of biomedical research and immunology.
Co-receptors are proteins that maintain a three-dimensional structure. The large extracellular domains make up approximately 76–100% of the receptor. The motifs that make up the large extracellular domains participate in ligand binding and complex formation.
The motifs can include glycosaminoglycans, EGF repeats, cysteine residues or ZP-1 domains. The variety of motifs leads to co-receptors being able to interact with two to nine different ligands, which themselves can also interact with a number of different co-receptors.
Most co-receptors lack a cytoplasmic domain and tend to be GPI-anchored, though a few receptors have been identified which contain short cytoplasmic domains that lack intrinsic kinase activity. | 1 | Applied and Interdisciplinary Chemistry |
Waterfowl and boats moving across the surface of water produce a wake pattern, first explained mathematically by Lord Kelvin and known today as the Kelvin wake pattern.
This pattern consists of two wake lines that form the arms of a chevron, V, with the source of the wake at the vertex of the V. For sufficiently slow motion, each wake line is offset from the path of the wake source by around arcsin(1/3) = 19.47° and is made up of feathery wavelets angled at roughly 53° to the path. | 1 | Applied and Interdisciplinary Chemistry |
The following issues are commonly observed during acid-base extraction and typically have simple solutions
* Only one layer is observed in the separatory funnel.
** This is due to using an organic solvent with significant miscibility with water (e.g. acetonitrile). The organic solvent used must be water-insoluble to observe phase separation and perform an acid-base extraction.
* Three layers form in the separatory funnel.
** Often this is a result of insufficient mixing, and light stirring will solve the issue.
* The boundary between the organic layer and aqueous layer is not observed.
** Ice can be used to identify the boundary as it will float between the two layers.
* An emulsion forms and one layer is suspended in the other as tiny droplets.
** This can be solved by using a glass stirring rod to gently "push" the tiny droplets into each other, eventually resulting in separation and causing the two layers to appear. Adding a small amount of brine solution can also be used to break up the emulsion; this process is termed "salting out". Emulsions can be prevented by mixing the solutions gently rather than vigorously.
* The relative positions of the aqueous/organic layers are unknown.
** A small amount of water can be added to the separatory funnel. Whichever layer these droplets go into is identified as the aqueous layer. | 0 | Theoretical and Fundamental Chemistry |
Prokaryotic photoautotrophs include Cyanobacteria, Pseudomonadota, Chloroflexota, Acidobacteriota, Chlorobiota, Bacillota, Gemmatimonadota, and Eremiobacterota.
Cyanobacteria is the only prokaryotic group that performs oxygenic photosynthesis. Anoxygenic photosynthetic bacteria use PSI- and PSII-like photosystems, which are pigment protein complexes for capturing light. Both of these photosystems use bacteriochlorophyll. There are multiple hypotheses for how oxygenic photosynthesis evolved. The loss hypothesis states that PSI and PSII were present in anoxygenic ancestor cyanobacteria from which the different branches of anoxygenic bacteria evolved. The fusion hypothesis states that the photosystems merged later through horizontal gene transfer. The most recent hypothesis suggests that PSI and PSII diverged from an unknown common ancestor with a protein complex that was coded by one gene. These photosystems then specialized into the ones that are found today. | 0 | Theoretical and Fundamental Chemistry |
Classic organic reactions exist for the synthesis of acyloins.
* The acyloin condensation is a reductive coupling of esters
* The benzoin condensation is condensation reaction between aldehydes catalyzed by a nucleophile
* Oxidation of carbonyls is possible with molecular oxygen but not selective
* Better alternative is oxidation of corresponding silyl enol ethers with mCPBA in the Rubottom oxidation
* MoOPH oxidation of carbonyls is a system with molybdenum peroxide, pyridine and hexamethylphosphoramide. | 0 | Theoretical and Fundamental Chemistry |
Nickel-based superalloys are used in load-bearing structures requiring the highest homologous temperature of any common alloy system (Tm = 0.9, or 90% of their melting point). Among the most demanding applications for a structural material are those in the hot sections of turbine engines (e.g. turbine blade). They comprise over 50% of the weight of advanced aircraft engines. The widespread use of superalloys in turbine engines coupled with the fact that the thermodynamic efficiency of turbine engines is a function of increasing turbine inlet temperatures has provided part of the motivation for increasing the maximum-use temperature of superalloys. From 1990-2020, turbine airfoil temperature capability increased on average by about 2.2 °C/year. Two major factors have made this increase possible:
* Processing techniques that improved alloy cleanliness (thus improving reliability) and/or enabled the production of tailored microstructures such as directionally solidified or single-crystal material.
* Alloy development resulting in higher temperature materials primarily through the additions of refractory elements such as Re, W, Ta, and Mo.
About 60% of the temperature increases related to advanced cooling, while 40% have resulted from material improvements. State-of-the-art turbine blade surface temperatures approach 1,150 C. The most severe stress and temperature combinations correspond to an average bulk metal temperature approaching 1,000 C..
Although Ni-based superalloys retain significant strength to 980 C, they tend to be susceptible to environmental attack because of the presence of reactive alloying elements. Surface attack includes oxidation, hot corrosion, and thermal fatigue. | 1 | Applied and Interdisciplinary Chemistry |
In some countries, as Poland, Denmark, India, Indonesia prior to 1997 element 104 had a Soviet proposal kurchatovium and element 105 had an American proposal hahnium. | 1 | Applied and Interdisciplinary Chemistry |
The Intronerator is a database of alternatively spliced genes and a database of introns for Caenorhabditis elegans. | 1 | Applied and Interdisciplinary Chemistry |
For US food and dietary supplement labeling purposes the amount in a serving is expressed as a percent of Daily Value (%DV). For selenium labeling purposes 100% of the Daily Value was 70 μg, but as of May 27, 2016 it was revised to 55 μg. A table of the old and new adult daily values is provided at Reference Daily Intake. | 1 | Applied and Interdisciplinary Chemistry |
Dendrimers have the potential to completely change the pharmacokinetic and pharmacodynamic (PK/PD) profiles of a drug. As carriers, the PK/PD is no longer determined by the drug itself but by the dendrimer’s localization, drug release, and dendrimer excretion. ADME properties are very highly tunable by varying dendrimer size, structure, and surface characteristics. While G9 dendrimers biodistribute very heavily to the liver and spleen, G6 dendrimers tend to biodistribute more broadly. As molecular weight increases, urinary clearance and plasma clearance decrease while terminal half-life increases. | 0 | Theoretical and Fundamental Chemistry |
SU-8 is a commonly used epoxy-based negative photoresist. Negative refers to a photoresist whereby the parts exposed to UV become cross-linked, while the remainder of the film remains soluble and can be washed away during development.
As shown in the structural diagram, SU-8 derives its name from the presence of 8 epoxy groups. This is a statistical average per moiety. It is these epoxies that cross-link to give the final structure.
It can be made into a viscous polymer that can be spun or spread over a thickness ranging from below 1 micrometer up to above 300 micrometers, or Thick Film Dry Sheets (TFDS) for lamination up to above 1 millimetre thick. Up to 500 µm, the resist can be processed with standard contact lithography. Above 500 µm, absorption leads to increasing sidewall undercuts and poor curing at the substrate interface. It can be used to pattern high aspect ratio structures. An aspect ratio of (> 20) has been achieved with the solution formulation and (> 40) has been demonstrated from the dry resist. Its maximum absorption is for ultraviolet light with a wavelength of the i-line: 365 nm (it is not practical to expose SU-8 with g-line ultraviolet light). When exposed, SU-8's long molecular chains cross-link, causing the polymerisation of the material. SU-8 series photoresists use gamma-butyrolactone or cyclopentanone as the primary solvent.
SU-8 was originally developed as a photoresist for the microelectronics industry, to provide a high-resolution mask for fabrication of semiconductor devices.
It is now mainly used in the fabrication of microfluidics (mainly via soft lithography, but also with other imprinting techniques such as nanoimprint lithography) and microelectromechanical systems parts. It is also one of the most biocompatible materials known and is often used in bio-MEMS for life science applications. | 0 | Theoretical and Fundamental Chemistry |
Effusion from an equilibrated container into outside vacuum can be calculated based on kinetic theory. The number of atomic or molecular collisions with a wall of a container per unit area per unit time (impingement rate) is given by:
assuming mean free path is much greater than pinhole diameter and the gas can be treated as an ideal gas.
If a small area on the container is punched to become a small hole, the effusive flow rate will be
where is the molar mass, is the Avogadro constant, and is the gas constant.
The average velocity of effused particles is
Combined with the effusive flow rate, the recoil/thrust force on the system itself is
An example is the recoil force on a balloon with a small hole flying in vacuum. | 0 | Theoretical and Fundamental Chemistry |
Methods for predicting liquid properties can be organized by their "scale" of description, that is, the length scales and time scales over which they apply.
*Macroscopic methods use equations that directly model the large-scale behavior of liquids, such as their thermodynamic properties and flow behavior.
*Microscopic methods use equations that model the dynamics of individual molecules.
*Mesoscopic methods fall in between, combining elements of both continuum and particle-based models. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, T-shaped molecular geometry describes the structures of some molecules where a central atom has three ligands. Ordinarily, three-coordinated compounds adopt trigonal planar or pyramidal geometries. Examples of T-shaped molecules are the halogen trifluorides, such as ClF.
According to VSEPR theory, T-shaped geometry results when three ligands and two lone pairs of electrons are bonded to the central atom, written in AXE notation as AXE. The T-shaped geometry is related to the trigonal bipyramidal molecular geometry for AX molecules with three equatorial and two axial ligands. In an AXE molecule, the two lone pairs occupy two equatorial positions, and the three ligand atoms occupy the two axial positions as well as one equatorial position. The three atoms bond at 90° angles on one side of the central atom, producing the T shape.
The trifluoroxenate(II) anion, , has been investigated as a possible first example of an AXE molecule, which might be expected by VSEPR reasoning to have six electron pairs in an octahedral arrangement with both the three lone pairs and the three ligands in a mer or T-shaped orientations. Although this anion has been detected in the gas phase, attempts at synthesis in solution and experimental structure determination were unsuccessful. A computational chemistry study showed a distorted planar Y-shaped geometry with the smallest F–Xe–F bond angle equal to 69°, rather than 90° as in a T-shaped geometry. | 0 | Theoretical and Fundamental Chemistry |
Carbohydrate Polymers is a peer-reviewed scientific journal that covers the entire scope of carbohydrate polymers and the research and exploitation of polysaccharides. The journal is published by Elsevier. | 0 | Theoretical and Fundamental Chemistry |
* [http://www.piercenet.com/cat/dialysis-tubing-cassettes-devices Thermo Scientific]
* [http://www.spectrumlabs.com/dialysis/MembraneDialysis.html Spectrum Laboratories]
* [https://web.archive.org/web/20131113175438/http://www.fishersci.com/categories/life-science/proteomics/dialysis-and-desalting Fisher Scientific]
* [https://web.archive.org/web/20131113181441/http://www.emdmillipore.com/life-science-research/d-tube-dialyzers/c_C3Cb.s1OuKYAAAEjKBp9.zLX%3Bsid%3DUYhkIlFoOZF4IgMRWnYJdfmo1gt20jvPaaZ6dOLFc_zaQd_mfWgHiFdWRtPpn3oR0ft0PlKxrLBNJdih8wzRyf4icHx9Zp24YhLcA-lxCSSMFDvPaaZ6dOLF EMD Millipore]
* [https://www.sigmaaldrich.com/US/en/products/labware Sigma-Aldrich]
* [http://www.harvardapparatus.com/ Harvard Apparatus]
* [http://www.membrane-mfpi.com/ Membrane Filtration Products, Inc.]
* [http://www.HTDialysis.com] | 1 | Applied and Interdisciplinary Chemistry |
The addition of resin to glass ionomers improves them significantly, allowing them to be more easily mixed and placed. Resin-modified glass ionomers allow equal or higher fluoride release and there is evidence of higher retention, higher strength and lower solubility. Resin-based glass ionomers have two setting reactions: an acid-base setting and a free-radical polymerisation. The free-radical polymerisation is the predominant mode of setting, as it occurs more rapidly than the acid-base mode. Only the material properly activated by light will be optimally cured. The presence of resin protects the cement from water contamination. Due to the shortened working time, it is recommended that placement and shaping of the material occurs as soon as possible after mixing. | 0 | Theoretical and Fundamental Chemistry |
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