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In contact mode, the tip is "dragged" across the surface of the sample and the contours of the surface are measured either using the deflection of the cantilever directly or, more commonly, using the feedback signal required to keep the cantilever at a constant position. Because the measurement of a static signal is prone to noise and drift, low stiffness cantilevers (i.e. cantilevers with a low spring constant, k) are used to achieve a large enough deflection signal while keeping the interaction force low. Close to the surface of the sample, attractive forces can be quite strong, causing the tip to "snap-in" to the surface. Thus, contact mode AFM is almost always done at a depth where the overall force is repulsive, that is, in firm "contact" with the solid surface. | 0 | Theoretical and Fundamental Chemistry |
The magic bullet is a scientific concept developed by the German Nobel laureate Paul Ehrlich in 1907. While working at the Institute of Experimental Therapy (Institut für experimentelle Therapie), Ehrlich formed an idea that it could be possible to kill specific microbes (such as bacteria), which cause diseases in the body, without harming the body itself. He named the hypothetical agent as Zauberkugel, and used the English translation "magic bullet" in The Harben Lectures at London. The name itself is a reference to an old German myth about a bullet that cannot miss its target. Ehrlich had in mind Carl Maria von Webers popular 1821 opera Der Freischütz', in which a young hunter is required to hit an impossible target in order to marry his bride.
Ehrlich envisioned that just like a bullet fired from a gun to hit a specific target, there could be a way to specifically target invading microbes. His continued research to discover the magic bullet resulted in further knowledge of the functions of the body's immune system, and in the development of Salvarsan, the first effective drug for syphilis, in 1909. His works were the foundation of immunology, and for his contributions he shared the 1908 Nobel Prize in Physiology or Medicine with Élie Metchnikoff.
Ehrlich's discovery of Salvarsan in 1909 for the treatment of syphilis is termed as the first magic bullet. This led to the foundation of the concept of chemotherapy. | 1 | Applied and Interdisciplinary Chemistry |
BSi dissolution is controlled by:
* Thermodynamics of solubility: Temperature (0 to 25 °C - 50x increase).
* Sinking rate: Food web structure—grazers, fecal pellets, discarded feeding structures, Aggregation - rapid transport.
* Bacterial degradation of organic matrix (Bidle and Azam, 1999). | 1 | Applied and Interdisciplinary Chemistry |
The utilization of the difference between dielectrophoretic forces exerted on different particles in nonuniform electric fields is known as DEP separation. The exploitation of DEP forces has been classified into two groups: DEP migration and DEP retention. DEP migration uses DEP forces that exert opposite signs of force on different particle types to attract some of the particles and repel others. DEP retention uses the balance between DEP and fluid-flow forces. Particles experiencing repulsive and weak attractive DEP forces are eluted by fluid flow, whereas particles experiencing strong attractive DEP forces are trapped at electrode edges against flow drag.
Dielectrophoresis field-flow fractionation (DEP-FFF), introduced by Davis and Giddings, is a family of chromatographic-like separation methods. In DEP-FFF, DEP forces are combined with drag flow to fractionate a sample of different types of particles. Particles are injected into a carrier flow that passes through the separation chamber, with an external separating force (a DEP force) being applied perpendicular to the flow. By means of different factors, such as diffusion and steric, hydrodynamic, dielectric and other effects, or a combination thereof, particles (<1 μm in diameter) with different dielectric or diffusive properties attain different positions away from the chamber wall, which, in turn, exhibit different characteristic concentration profile. Particles that move further away from the wall reach higher positions in the parabolic velocity profile of the liquid flowing through the chamber and will be eluted from the chamber at a faster rate. | 0 | Theoretical and Fundamental Chemistry |
Transitions made by the free valence electrons of the molecules are responsible for the production of scintillation light in organic crystals. These electrons are associated with the whole molecule rather than any particular atom and occupy the so-called -molecular orbitals. The ground state S is a singlet state above which are the excited singlet states (S, the lowest triplet state (T), and its excited levels (T, A fine structure corresponding to molecular vibrational modes is associated with each of those electron levels. The energy spacing between electron levels is ≈1 eV; the spacing between the vibrational levels is about 1/10 of that for electron levels.
An incoming particle can excite either an electron level or a vibrational level. The singlet excitations immediately decay ( state without the emission of radiation (internal degradation). The S state then decays to the ground state S (typically to one of the vibrational levels above S) by emitting a scintillation photon. This is the prompt component or fluorescence. The transparency of the scintillator to the emitted photon is due to the fact that the energy of the photon is less than that required for an S → S transition (the transition is usually being to a vibrational level above S).
When one of the triplet states gets excited, it immediately decays to the T state with no emission of radiation (internal degradation). Since the T → S transition is very improbable, the T state instead decays by interacting with another T molecule:
and leaves one of the molecules in the S state, which then decays to S with the release of a scintillation photon. Since the T-T interaction takes time, the scintillation light is delayed: this is the slow or delayed component (corresponding to delayed fluorescence). Sometimes, a direct T → S transition occurs (also delayed), and corresponds to the phenomenon of phosphorescence. Note that the observational difference between delayed-fluorescence and phosphorescence is the difference in the wavelengths of the emitted optical photon in an S → S transition versus a T → S transition.
Organic scintillators can be dissolved in an organic solvent to form either a liquid or plastic scintillator. The scintillation process is the same as described for organic crystals (above); what differs is the mechanism of energy absorption: energy is first absorbed by the solvent, then passed onto the scintillation solute (the details of the transfer are not clearly understood). | 0 | Theoretical and Fundamental Chemistry |
tert-Butanesulfinamide has been used as an auxiliary in an asymmetric synthesis of cetirizine (more potent than the racemic mixture of the drug) starting from p-chlorobenzaldehyde and phenylmagnesium bromide. | 0 | Theoretical and Fundamental Chemistry |
Reagent testing is one of the processes used to identify substances contained within a pill, usually illicit substances.
With the increased prevalence of drugs being available in their pure forms, the terms "drug checking" or "pill testing" may also be used, although these terms usually refer to testing with a wider variety of techniques covered by drug checking. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry glycerolysis refers to any process in which chemical bonds are broken via a reaction with glycerol. The term refers almost exclusively to the transesterification reaction of glycerol with triglycerides (fats/oils) to form mixtures of monoglycerides and diglycerides. These find a variety of uses; as food emulsifiers (e.g. E471), low fat cooking oils (e.g. diacylglycerol oil) and surfactants (such as monolaurin).
The transesterification process gives a complex mixture of products, however not all of these are of equivalent use. This has led to the development of optimized processes able to produce better defined products; in particular by using enzymes, reactions in supercritical carbon dioxide and flow chemistry. The production of diglycerides (often called diacylglycerols or DAGs) have been investigated extensively due to their use in foods, with total annual sales of approximately US$200 million in Japan since its introduction in the late 1990s until 2009. | 0 | Theoretical and Fundamental Chemistry |
Nitrosoarenes typically participate in a monomer–dimer equilibrium. The azobenzene N,N-dioxide (Ar(O)N=N(O)Ar) dimers, which are often pale yellow, are generally favored in the solid state, whereas the deep-green monomers are favored in dilute solution or at higher temperatures. They exist as cis and trans' isomers.
When stored in protic media, primary and secondary nitrosoalkanes isomerize to oximes.
Due to the stability of the nitric oxide free radical, nitroso organyls tend to have very low C–N bond dissociation energies: nitrosoalkanes have BDEs on the order of , while nitrosoarenes have BDEs on the order of . As a consequence, they are generally heat- and light-sensitive. Compounds containing O–(NO) or N–(NO) bonds generally have even lower bond dissociation energies. For instance, N-nitrosodiphenylamine, PhN–N=O, has a N–N bond dissociation energy of only . Organonitroso compounds serve as a ligands giving transition metal nitroso complexes. | 0 | Theoretical and Fundamental Chemistry |
Princeton's conversion of the Model C stellarator to a tokamak produced results matching the Soviets. With an apparent solution to the magnetic bottle problem in-hand, plans begin for a larger machine to test scaling and methods to heat the plasma.
In 1972, John Nuckolls outlined the idea of fusion ignition, a fusion chain reaction. Hot helium made during fusion reheats the fuel and starts more reactions. Nuckolls's paper started a major development effort. LLNL built laser systems including Argus, Cyclops, Janus, the neodymium-doped glass (Nd:glass) laser Long Path, Shiva laser, and the 10 beam Nova in 1984. Nova would ultimately produce 120 kilojoules of infrared light during a nanosecond pulse.
The UK built the Central Laser Facility in 1976.
The "advanced tokamak" concept emerged, which included non-circular plasma, internal diverters and limiters, superconducting magnets, and operation in the so-called "H-mode" island of increased stability. Two other designs became prominent; the compact tokamak sited the magnets on the inside of the vacuum chamber, and the spherical tokamak with as small a cross section as possible.
In 1974 J.B. Taylor re-visited ZETA and noticed that after an experimental run ended, the plasma entered a short period of stability. This led to the reversed field pinch concept. On May 1, 1974, the KMS fusion company (founded by Kip Siegel) achieved the world's first laser induced fusion in a deuterium-tritium pellet.
The Princeton Large Torus (PLT), the follow-on to the Symmetrical Tokamak, surpassed the best Soviet machines and set temperature records that were above what was needed for a commercial reactor. Soon after it received funding with the target of breakeven.
In the mid-1970s, Project PACER, carried out at LANL explored the possibility of exploding small hydrogen bombs (fusion bombs) inside an underground cavity. As an energy source, the system was the only system that could work using the technology of the time. It required a large, continuous supply of nuclear bombs, however, with questionable economics.
In 1976, the two beam Argus laser became operational at LLNL. In 1977, the 20 beam Shiva laser there was completed, capable of delivering 10.2 kilojoules of infrared energy on target. At a price of $25 million and a size approaching that of a football field, Shiva was the first megalaser.
At a 1977 workshop at the Claremont Hotel in Berkeley Dr. C. Martin Stickley, then Director of the Energy Research and Development Agency ’s Office of Inertial Fusion, claimed that "no showstoppers" lay on the road to fusion energy.
The DOE selected a Princeton design Tokamak Fusion Test Reactor (TFTR) and the challenge of running on deuterium-tritium fuel.
The 20 beam Shiva laser at LLNL became capable of delivering 10.2 kilojoules of infrared energy on target. Costing $25 million and nearly covering a football field, Shiva was the first "megalaser" at LLNL. | 0 | Theoretical and Fundamental Chemistry |
In heterogeneous electron transfer, an electron moves between a chemical species and a solid-state electrode. Theories addressing heterogeneous electron transfer have applications in electrochemistry and the design of solar cells. | 0 | Theoretical and Fundamental Chemistry |
STRENDA DB
STRENDA DB is a web-based storage and search platform that has incorporated the Guidelines and automatically checks the submitted data on compliance with the STRENDA Guidelines thus ensuring that the manuscript data sets are complete and valid. A valid data set is awarded a STRENDA Registry Number (SRN) and a fact sheet (PDF) is created containing all submitted data. Each dataset is registered at [https://datacite.org Datacite] and assigned a DOI to refer and track the data. After the publication of the manuscript in a peer-reviewed journal the data in STRENDA DB are made open accessible.
STRENDA DB is a repository recommended by re3data and OpenDOAR. It is harvested by OpenAIRE.
The database service is recommended in the authors' instructions of more than 10 biochemistry journals, including [https://nature.com Nature], [https://www.jbc.org The Journal of Biological Chemistry], [https://elifesciences.org eLife], and [https://www.plos.org PLoS]. It has been referred as a standard tool for the validation and storage of enzyme kinetics data in multifold publications
A recent study examining eleven publications, including Supporting Information, from two leading journals revealed that at least one omission was found in every one of these papers. The authors concluded that using STRENDA DB in the current version would ensure that about 80% auf the relevant information would be made available.
Data Management
STRENDA DB is considered a tool for research data management by the research community (e.g. EU project CARBAFIN). | 1 | Applied and Interdisciplinary Chemistry |
A 250 kilowatt methane synthesis plant was constructed by the Center for Solar Energy and Hydrogen Research (ZSW) at Baden-Württemberg and the Fraunhofer Society in Germany and began operating in 2010. It is being upgraded to 10 megawatts, scheduled for completion in autumn 2012.
The George Olah carbon dioxide recycling plant operated by Carbon Recycling International in Grindavík, Iceland, has been producing 2 million liters of methanol transportation fuel per year from flue exhaust of the Svartsengi Power Station since 2011. It has the capacity to produce 5 million liters per year.
Audi has constructed a carbon-neutral liquefied natural gas (LNG) plant in Werlte, Germany. The plant is intended to produce transportation fuel to offset LNG used in their A3 Sportback g-tron automobiles, and can keep 2,800 metric tons of CO out of the environment per year at its initial capacity.
Zero, a British-based company set up by former F1 engineer Paddy Lowe, has developed a process it terms petrosynthesis to develop synthetic fuels from atmospheric carbon dioxide and water using renewable energy. In 2022 it began work on a demonstration production plant at Bicester Heritage near Oxford.
Commercial developments are taking place in Columbia, South Carolina, Camarillo, California, and Darlington, England. A demonstration project in Berkeley, California, proposes synthesizing both fuels and food oils from recovered flue gases. | 0 | Theoretical and Fundamental Chemistry |
There are many signals that control catabolism. Most of the known signals are hormones and the molecules involved in metabolism itself. Endocrinologists have traditionally classified many of the hormones as anabolic or catabolic, depending on which part of metabolism they stimulate. The so-called classic catabolic hormones known since the early 20th century are cortisol, glucagon, and adrenaline (and other catecholamines). In recent decades, many more hormones with at least some catabolic effects have been discovered, including cytokines, orexin (known as hypocretin), and melatonin. | 1 | Applied and Interdisciplinary Chemistry |
These can be used to create pulses of neutrons, they have been used for some activation work where the decay of the target isotope is very rapid. For instance in oil wells. | 0 | Theoretical and Fundamental Chemistry |
The discussion above describes relaxation of nuclear magnetization in the presence of a constant magnetic field B. This is called relaxation in the laboratory frame.
Another technique, called relaxation in the rotating frame, is the relaxation of nuclear magnetization in the presence of the field B together with a time-dependent magnetic field B. The field B rotates in the plane perpendicular to B at the Larmor frequency of the nuclei in the B. The magnitude of B is typically much smaller than the magnitude of B. Under these circumstances the relaxation of the magnetization is similar to laboratory frame relaxation in a field B. The decay constant for the recovery of the magnetization component along B is called the spin-lattice relaxation time in the rotating frame and is denoted T.
Relaxation in the rotating frame is useful because it provides information on slow motions of nuclei. | 0 | Theoretical and Fundamental Chemistry |
The mechanism for transition metal-catalyzed olefin metathesis has been widely researched over the past forty years. RCM undergoes a similar mechanistic pathway as other olefin metathesis reactions, such as cross metathesis (CM), ring-opening metathesis polymerization (ROMP), and acyclic diene metathesis (ADMET). Since all steps in the catalytic cycle are considered reversible, it is possible for some of these other pathways to intersect with RCM depending on the reaction conditions and substrates. In 1971, Chauvin proposed the formation of a metallacyclobutane intermediate through a [2+2] cycloaddition which then cycloeliminates to either yield the same alkene and catalytic species (a nonproductive pathway), or produce a new catalytic species and an alkylidene (a productive pathway). This mechanism has become widely accepted among chemists and serves as the model for the RCM mechanism.
Initiation occurs through substitution of the catalyst’s alkene ligand with substrate. This process occurs via formation of a new alkylidene through one round of [2+2] cycloaddition and cycloelimination. Association and dissociation of a phosphine ligand also occurs in the case of Grubbs catalysts. In an RCM reaction, the alkylidene undergoes an intramolecular [2+2] cycloaddition with the second reactive terminal alkene on the same molecule, rather than an intermolecular addition of a second molecule of starting material, a common competing side reaction which may lead to polymerization Cycloelimination of the metallacyclobutane intermediate forms the desired RCM product along with a [M]=CH, or alkylidene, species which reenters the catalytic cycle. While the loss of volatile ethylene is a driving force for RCM, it is also generated by competing metathesis reactions and therefore cannot be considered the only driving force of the reaction. | 0 | Theoretical and Fundamental Chemistry |
An eluotropic series is listing of various compounds in order of eluting power for a given adsorbent. The "eluting power" of a solvent is largely a measure of how well the solvent can "pull" an analyte off the adsorbent to which it is attached. This often happens when the eluent adsorbs onto the stationary phase, displacing the analyte. Such series are useful for determining necessary solvents needed for chromatography of chemical compounds. Normally such a series progresses from non-polar solvents, such as n-hexane, to polar solvents such as methanol or water. The order of solvents in an eluotropic series depends both on the stationary phase as well as on the compound used to determine the order. | 0 | Theoretical and Fundamental Chemistry |
The advantage of nanofluidic devices is from its feasibility to be integrated with electronic circuitry. Because they are built using the same manufacturing technology, it is possible to make a nanofluidic system with digital integrated circuit on a single chip. Therefore, the control and manipulation of particles in the electrolyte can be achieved in a real-time.
Fabrication of nano-channels is categorized into top-down and bottom-up methods. Top-down methods are the conventional processes utilized in the IC industry and Microelectromechanical systems research. It begins with photolithography on a bulk silicon wafer. Bottom-up methods, in contrast, starts with atoms or molecules with intrinsic nano-scaled dimension. By organize and combine these building blocks together, it is able to form a nanostructures as small as only a few nanometers. | 0 | Theoretical and Fundamental Chemistry |
The formula for dimensions can be derived assuming an -dimensional real vector space with a basis and an inner product . The reciprocal lattice vectors are uniquely determined by the formula . Using the permutation
they can be determined with the following formula:
Here, is the volume form, is the inverse of the vector space isomorphism defined by and denotes the inner multiplication.
One can verify that this formula is equivalent to the known formulas for the two- and three-dimensional case by using the following facts: In three dimensions, and in two dimensions, , where is the rotation by 90 degrees (just like the volume form, the angle assigned to a rotation depends on the choice of orientation). | 0 | Theoretical and Fundamental Chemistry |
The methylglyoxal pathway is activated by the increased intercellular uptake of carbon containing molecules such as glucose, glucose-6-phosphate, lactate, or glycerol. Methylglyoxal is formed from dihydroxyacetone phosphate (DHAP) by the enzyme methylglyoxal synthase, giving off a phosphate group.
Methylglyoxal is then converted into two different products, either D-lactate, and L-lactate. Methylglyoxal reductase and aldehyde dehydrogenase convert methylglyoxal into lactaldehyde and, eventually, L-lactate. If methylglyoxal enters the glyoxylase pathway, it is converted into lactoylguatathione and eventually D-lactate. Both D-lactate, and L-lactate are then converted into pyruvate. The pyruvate that is created most often goes on to enter the Krebs cycle ([http://mic.sgmjournals.org/cgi/reprint/151/3/707 Weber] 711–13). | 1 | Applied and Interdisciplinary Chemistry |
The concept of additive effect is derived from the concept of drug synergy. Thus, the origin of additive effect dates back to the early twentieth century when the search for synergy started. During the search for synergy, the models of Loewe additivity and Bliss independence were proposed. These models are capable of measuring the effects of drug combinations. Hence, Loewe additivity and Bliss independence were developed to determine whether an effect of a drug combination is synergistic or antagonistic. During the construction of these models, the concept of additive effect was introduced as the baseline for the determination of synergy and antagonism. | 1 | Applied and Interdisciplinary Chemistry |
A thermal diode in this sense is a device whose thermal resistance is different for heat flow in one direction than for heat flow in the other direction. I.e., when the thermal diode's first terminal is hotter than the second, heat will flow easily from the first to the second, but when the second terminal is hotter than the first, little heat will flow from the second to the first.
Such an effect was first observed in a copper–cuprous-oxide interface by Chauncey Starr in the 1930s. Beginning in 2002, theoretical models were proposed to explain this effect. In 2006 the first microscopic solid-state thermal diodes were built. In April 2015 Italian researchers at CNR announced development of a working thermal diode, publishing results in Nature Nanotechnology.
Thermal siphons can act as a one-way heat flow.
Heat pipes operating in [https://www.1-act.com/resources/heat-pipe-fundamentals/different-types-of-heat-pipes/diode-heat-pipes/ gravity] may also have this effect. | 0 | Theoretical and Fundamental Chemistry |
Dip pen nanolithography (DPN) is a scanning probe lithography technique where an atomic force microscope (AFM) tip is used to create patterns directly on a range of substances with a variety of inks. A common example of this technique is exemplified by the use of alkane thiolates to imprint onto a gold surface. This technique allows surface patterning on scales of under 100 nanometers. DPN is the nanotechnology analog of the dip pen (also called the quill pen), where the tip of an atomic force microscope cantilever acts as a "pen", which is coated with a chemical compound or mixture acting as an "ink", and put in contact with a substrate, the "paper".
DPN enables direct deposition of nanoscale materials onto a substrate in a flexible manner. Recent advances have demonstrated massively parallel patterning using two-dimensional arrays of 55,000 tips.
Applications of this technology currently range through chemistry, materials science, and the life sciences, and include such work as ultra high density biological nanoarrays, and additive photomask repair. | 1 | Applied and Interdisciplinary Chemistry |
In France, an extensive, cable-supported green roof has been created on the International School in Lyon. Another huge green roof of roughly has been incorporated into the new museum L'Historial de la Vendée which opened in June 2006 at Les Lucs-sur-Boulogne. | 1 | Applied and Interdisciplinary Chemistry |
Neurophysins are acidic proteins with a molecular weight of approximately 10,000 Da that are rich in cysteine, glycine, and proline residues . The protein is double domain with a polypeptide chain of 93-95 residues with 14 cysteine residues forming 7 disulfide bridges . Domain I contains a COOH terminal with a disulfide loop; domain II lacks this COOH terminal disulfide loop . Based on the resemblance of the disulfide loop present on vasopressin and oxytocin, it is suggested that the hormones form covalent linkages to this disulfide loop present on the COOH terminal of domain I. | 1 | Applied and Interdisciplinary Chemistry |
A Chemical and Physical Foundations
Thermodynamics and kinetics
Redox states
Water, pH, acid-base reactions and buffers
Solutions and equilibria
Solute-solvent interactions
Chemical interactions and bonding
Chemical reaction mechanisms
B Structural Biology: Structure, Assembly, Organization and Dynamics
Small molecules
Macromolecules (e.g., nucleic acids, polysaccharides, proteins and complex lipids)
Supramolecular complexes (e.g., membranes, ribosomes and multienzyme complexes)
C Catalysis and Binding
Enzyme reaction mechanisms and kinetics
Ligand-protein interaction (e.g., hormone receptors, substrates and effectors, transport proteins and antigen-antibody interactions)
D Major Metabolic Pathways
Carbon, nitrogen and sulfur assimilation
Anabolism
Catabolism
Synthesis and degradation of macromolecules
E Bioenergetics (including respiration and photosynthesis)
Energy transformations at the substrate level
Electron transport
Proton and chemical gradients
Energy coupling (e.g., phosphorylation and transport)
F Regulation and Integration of Metabolism
Covalent modification of enzymes
Allosteric regulation
Compartmentalization
Hormones
G Methods
Biophysical approaches (e.g., spectroscopy, x-ray, crystallography, mass spectroscopy)
Isotopes
Separation techniques (e.g., centrifugation, chromatography and electrophoresis)
Immunotechniques | 1 | Applied and Interdisciplinary Chemistry |
PDE5 is expressed in clitoral corpus cavernosum and in vaginal smooth muscle and epithelium. Therefore, it is possible that PDE5 inhibitors could affect female sexual arousal disorder but further research is needed. Increased levels of cGMP have been shown to occur in human-cultured vaginal smooth muscle cells treated with a PDE5 inhibitor suggesting involvement of the NO/cGMP axis in the female sexual response. | 1 | Applied and Interdisciplinary Chemistry |
The free acid () and monohydrated calcium salt () forms of HMB have different pharmacokinetics. HMB-FA is more readily absorbed into the bloodstream and has a longer elimination half-life (3 hours) relative to HMB-Ca (2.5 hours). Tissue uptake and utilization of HMB-FA is higher than for HMB-Ca. The fraction of an ingested dose that is excreted in urine does not differ between the two forms. | 1 | Applied and Interdisciplinary Chemistry |
Aggregation in colloidal dispersions (or stable suspensions) has been characterized by the degree of interparticle attraction. For attractions strong relative to the thermal energy (given by kT), Brownian motion produces irreversibly flocculated structures with growth rates limited by the rate of particle diffusion. This leads to a description using such parameters as the degree of branching, ramification or fractal dimensionality. A reversible growth model has been constructed by modifying the cluster-cluster aggregation model with a finite inter-particle attraction energy.
In systems where forces of attraction forces are buffered to some degree, a balance of forces leads to an equilibrium phase separation, that is particles coexist with equal chemical potential in two distinct structural phases. The role of the ordered phase as an elastic colloidal solid has been evidenced by the elastic (or reversible) deformation due to the force of gravity. This deformation can be quantified by the distortion of the lattice parameter, or inter-particle spacing. | 0 | Theoretical and Fundamental Chemistry |
Most natural waters contain small quantities of organic compounds. Aquatic microorganisms have evolved to use some of these compounds as food. Microorganisms living in oxygenated waters use dissolved oxygen to oxidatively degrade the organic compounds, releasing energy which is used for growth and reproduction. Populations of these microorganisms tend to increase in proportion to the amount of food available. This microbial metabolism creates an oxygen demand proportional to the amount of organic compounds useful as food. Under some circumstances, microbial metabolism can consume dissolved oxygen faster than atmospheric oxygen can dissolve into the water or the autotrophic community (algae, cyanobacteria and macrophytes) can produce. Fish and aquatic insects may die when oxygen is depleted by microbial metabolism.
Biochemical oxygen demand is the amount of oxygen required for microbial metabolism of organic compounds in water. This demand occurs over some variable period of time depending on temperature, nutrient concentrations, and the enzymes available to indigenous microbial populations. The amount of oxygen required to completely oxidize the organic compounds to carbon dioxide and water through generations of microbial growth, death, decay, and cannibalism is total biochemical oxygen demand (total BOD). Total BOD is of more significance to food webs than to water quality. Dissolved oxygen depletion is most likely to become evident during the initial aquatic microbial population explosion in response to a large amount of organic material. If the microbial population deoxygenates the water, however, that lack of oxygen imposes a limit on population growth of aerobic aquatic microbial organisms resulting in a longer term food surplus and oxygen deficit.
A standard temperature at which BOD testing should be carried out was first proposed by the Royal Commission on Sewage Disposal in its eighth report in 1912:
This was later standardised at 68 °F and then 20 °C. This temperature may be significantly different from the temperature of the natural environment of the water being tested.
Although the Royal Commission on Sewage Disposal proposed 5 days as an adequate test period for rivers of the United Kingdom of Great Britain and Ireland, longer periods were investigated for North American rivers. Incubation periods of 1, 2, 5, 10 and 20 days were being used into the mid-20th century. Keeping dissolved oxygen available at their chosen temperature, investigators found up to 99 percent of total BOD was exerted within 20 days, 90 percent within 10 days, and approximately 68 percent within 5 days. Variable microbial population shifts to nitrifying bacteria limit test reproducibility for periods greater than 5 days. The 5-day test protocol with acceptably reproducible results emphasizing carbonaceous BOD has been endorsed by the United States Environmental Protection Agency (EPA). This 5-day BOD test result may be described as the amount of oxygen required for aquatic microorganisms to stabilize decomposable organic matter under aerobic conditions. Stabilization, in this context, may be perceived in general terms as the conversion of food to living aquatic fauna. Although these fauna will continue to exert biochemical oxygen demand as they die, that tends to occur within a more stable evolved ecosystem including higher trophic levels. | 0 | Theoretical and Fundamental Chemistry |
Pinoresinol biosynthesis involved a protein called a dirigent protein. The first dirigent protein was discovered in Forsythia intermedia. This protein has been found to direct the stereoselective biosynthesis of (+)-pinoresinol from coniferyl alcohol monomers. Recently, a second, enantiocomplementary dirigent protein was identified in Arabidopsis thaliana, which directs enantioselective synthesis of (−)-pinoresinol. | 0 | Theoretical and Fundamental Chemistry |
1.5th order derivative of a voltammogram hits the abscissa exactly at the point where the formal potential of the electrode reaction is found. | 0 | Theoretical and Fundamental Chemistry |
Immunoscintigraphy incorporates Tc into a monoclonal antibody, an immune system protein, capable of binding to cancer cells. A few hours after injection, medical equipment is used to detect the gamma rays emitted by the Tc; higher concentrations indicate where the tumor is. This technique is particularly useful for detecting hard-to-find cancers, such as those affecting the intestines. These modified antibodies are sold by the German company Hoechst (now part of Sanofi-Aventis) under the name Scintimun. | 0 | Theoretical and Fundamental Chemistry |
The central solenoid and toroidal field superconducting magnets for the planned experimental ITER fusion reactor use niobium–tin as a superconductor. The central solenoid coil will produce a field of . The toroidal field coils will operate at a maximum field of 11.8 T. Estimated use is of NbSn strands and 250 metric tonnes of NbTi strands.
At the Large Hadron Collider at CERN, extra-strong quadrupole magnets (for focussing beams) made with niobium–tin are being installed in key points of the accelerator between late 2018 and early 2020. Niobium tin had been proposed in 1986 as an alternative to niobium–titanium, since it allowed coolants less complex than superfluid helium, but this was not pursued in order to avoid delays while competing with the then-planned US-led Superconducting Super Collider. | 1 | Applied and Interdisciplinary Chemistry |
Phosphorus is an essential nutrient for plants and animals. Phosphorus is a limiting nutrient for aquatic organisms. Phosphorus forms parts of important life-sustaining molecules that are very common in the biosphere. Phosphorus does enter the atmosphere in very small amounts when dust containing phosphorus is dissolved in rainwater and sea spray, but the element mainly remains on land and in rock and soil minerals. Phosphates which are found in fertilizers, sewage and detergents, can cause pollution in lakes and streams. Over-enrichment of phosphate in both fresh and inshore marine waters can lead to massive algae blooms. In fresh water, the death and decay of these blooms leads to eutrophication. An example of this is the Canadian Experimental Lakes Area.
Freshwater algal blooms are generally caused by excess phosphorus, while those that take place in saltwater tend to occur when excess nitrogen is added. However, it is possible for eutrophication to be due to a spike in phosphorus content in both freshwater and saltwater environments.
Phosphorus occurs most abundantly in nature as part of the orthophosphate ion (PO), consisting of a P atom and 4 oxygen atoms. On land most phosphorus is found in rocks and minerals. Phosphorus-rich deposits have generally formed in the ocean or from guano, and over time, geologic processes bring ocean sediments to land. Weathering of rocks and minerals release phosphorus in a soluble form where it is taken up by plants, and it is transformed into organic compounds. The plants may then be consumed by herbivores and the phosphorus is either incorporated into their tissues or excreted. After death, the animal or plant decays, and phosphorus is returned to the soil where a large part of the phosphorus is transformed into insoluble compounds. Runoff may carry a small part of the phosphorus back to the ocean. Generally with time (thousands of years) soils become deficient in phosphorus leading to ecosystem retrogression. | 0 | Theoretical and Fundamental Chemistry |
There are 30 isoforms of FAM227B and one paralog, FAM227A. The conserved domains in these isoforms (as well as the paralog) are of various sizes and encode the protein FWWh (pfam14922) of unknown function, which all contain the distinctive motif FWW with a hydrophobic residue h. The main isoform used for analysis of FAM227B is isoform 1 (NM_152647.3). The next most reliable isoform of FAM227B is isoform 2 ( NM_001330293.2). The second isoform is shorter and has a distinct C-terminus.
Below are cartoons depicting the different lengths and cutting patterns of the isoforms*:
The cartoons do not precisely depict differences between all the isoforms, but instead act as a simple depiction of a larger pattern between the isoforms. | 1 | Applied and Interdisciplinary Chemistry |
Liquation requires that the silver-rich copper first be melted with approximately three times its weight in lead; as silver has a greater affinity with lead, most of the silver would end up within this rather than the copper. If the copper is assayed and found to contain too little silver for liquation to be financially viable (around 0.31% is the minimum required,) it is melted and allowed to settle so that much of the silver sinks towards the bottom. The ‘tops’ are then drawn off and used to produce copper while the silver-rich ‘bottoms’ are used in the liquation process. The copper-lead alloy created can be tapped off and cast into large plano-convex ingots known as ‘liquation cakes’. As the metals cool and solidify the copper and the silver-containing lead separate as they are immiscible with each other.
The ratio of lead to copper in these cakes is an important factor for the process to work efficiently. Agricola recommended 3 parts copper to 8–12 parts lead. The copper must be assayed to accurately determine how much silver it contains; for copper rich in silver the top end of this ratio was used to make sure the maximum amount of silver possible would end up within the lead. However, there also needs to be enough copper to allow the cakes to keep their shape once most of the lead has drained away; too much copper and it would trap some of the lead within and the process would be very inefficient.
The size of these cakes remained consistent from when Agricola wrote of them in 1556 to the 19th century when the process became obsolete. They were usually thick, about in diameter and weighed from . This consistency is not without reason as the size of the cakes is very important to the smooth running of the liquation process. If the cakes are too small, the product would not be worth the time and costs spent on the process, if they are too large then the copper would begin to melt before the maximum amount of lead has drained away.
The cakes are heated in a liquation furnace, usually four or five at once, to a temperature above the melting point of lead (327°C), but below that of copper (1084 °C), so that the silver-rich lead melts and flows away. As the melting point of lead is so low a high-temperature furnace is not required and it can be fuelled with wood. It is important that this takes place in a reducing atmosphere, i.e. one with little oxygen, to avoid the lead oxidising; the cakes are therefore well covered by charcoal and little air is allowed into the furnace. It is impossible to stop some of the lead oxidising, however, and this drops down and forms spiky projections known as ‘liquation thorns’ in the channel underneath the hearth.
The older and relatively simple method of cupellation can then be used to separate the silver from the lead. If the lead is assayed and found not to contain enough silver to make the cupellation process worthwhile it is reused in liquation cakes until it has sufficient silver.
The ‘exhausted liquation cakes’ which still contain some lead and silver are ‘dried’ in a special furnace which is heated to a higher temperature under oxidising conditions. This is essentially just another stage of liquation and most of the remaining lead is expelled and oxidised to form liquation thorns, though some remains as lead metal. The copper can then be refined to remove other impurities and produce copper metal.
Waste products can be reused to produce new liquation cakes to try to minimise loss of metals, especially silver. The waste products are mostly in the form of liquation thorns from the liquation and the drying process but there are also some slags produced. | 1 | Applied and Interdisciplinary Chemistry |
A shuttle vector is a vector (usually a plasmid) constructed so that it can propagate in two different host species. Therefore, DNA inserted into a shuttle vector can be tested or manipulated in two different cell types. The main advantage of these vectors is they can be manipulated in E. coli, then used in a system which is more difficult or slower to use (e.g. yeast).
Shuttle vectors include plasmids that can propagate in eukaryotes and prokaryotes (e.g. both Saccharomyces cerevisiae and Escherichia coli) or in different species of bacteria (e.g. both E. coli and Rhodococcus erythropolis). There are also adenovirus shuttle vectors, which can propagate in E. coli and mammals.
Shuttle vectors are frequently used to quickly make multiple copies of the gene in E. coli (amplification). They can also be used for in vitro experiments and modifications (e.g. mutagenesis, PCR).
One of the most common types of shuttle vectors is the yeast shuttle vector. Almost all commonly used S. cerevisiae vectors are shuttle vectors. Yeast shuttle vectors have components that allow for replication and selection in both E. coli cells and yeast cells. The E. coli component of a yeast shuttle vector includes an origin of replication and a selectable marker, e.g. antibiotic resistance, beta lactamase, beta galactosidase. The yeast component of a yeast shuttle vector includes an autonomously replicating sequence (ARS), a yeast centromere (CEN), and a yeast selectable marker (e.g. URA3, a gene that encodes an enzyme for uracil synthesis, Lodish et al. 2007). | 1 | Applied and Interdisciplinary Chemistry |
In SARS-CoV-2 (COVID-19) infected Caco-2 cells, the phosphorylase activity of CK2 is increased resulting in phosphorylation of several cytoskeletal proteins. These infected cells also display CK2-containing filopodia protrusions associated with budding viral particles. Hence the protrusions may assist the virus in infecting adjacent cells. In these same cells, the CK2 inhibitor silmitasertib displayed potent antiviral activity. Senhwa Biosciences and the US National Institutes of Health have announced that they will evaluate the efficacy of silmitasertib in treating COVID-19 infections. | 1 | Applied and Interdisciplinary Chemistry |
For a compound to reach a tissue, it usually must be taken into the bloodstream – often via mucous surfaces like the digestive tract (intestinal absorption) – before being taken up by the target cells. Factors such as poor compound solubility, gastric emptying time, intestinal transit time, chemical instability in the stomach, and inability to permeate the intestinal wall can all reduce the extent to which a drug is absorbed after oral administration. Absorption critically determines the compound's bioavailability. Drugs that absorb poorly when taken orally must be administered in some less desirable way, like intravenously or by inhalation (e.g. zanamivir). Routes of administration are an important consideration. | 1 | Applied and Interdisciplinary Chemistry |
In many cases, the Benesi–Hildebrand method provides excellent linear plots, and reasonable values for K and ε. However, various problems arising from experimental data have been noted from time to time. Some of these issues include: different values of ε with different concentration scales, lack of consistency between the Benesi–Hildebrand values and those obtained from other methods (e.g. equilibrium constants from partition measurements), and zero and negative intercepts. Concerns have also surfaced over the accuracy of the Benesi–Hildebrand method as certain conditions cause these calculations to become invalid. For instance, the reactant concentrations must always obey the assumption that the initial concentration of the guest ([G]) is much larger than the initial concentration of the host ([H]). In the case when this breaks down, the Benesi–Hildebrand plot deviates from its linear nature and exhibits scatter plot characteristics. Also, in the case of determining the equilibrium constants for weakly bound complexes, it is common for the formation of 2:1 complexes to occur in solution. It has been observed that the existence of these 2:1 complexes generate inappropriate parameters that significantly interfere with the accurate determination of association constants. Due to this fact, one of the criticisms of this method is the inflexibility of only being able to study reactions with 1:1 product complexes.
These limitations can be overcome by using a computational method which is more generally applicable, a non-linear least-squares minimization method. The two parameters, K or ε are determined by using the Solver module a spreadsheet, by minimizing a sum of squared differences between observed and calculated quantities with respect to the equilibrium constant and molar absorbance or chemical shift values of the individual chemical species involved. The use of this and more sophisticated methods have the additional advantage that they are not limited to systems where a single complex is formed. | 0 | Theoretical and Fundamental Chemistry |
In the [Mn(HO)] metal complex, manganese has an oxidation state of +2, thus it is a d ion. HO is a weak field ligand (spectrum shown below), and according to the Tanabe–Sugano diagram for d ions, the ground state is A. Note that there is no sextet spin multiplicity in any excited state, hence the transitions from this ground state are expected to be spin-forbidden and the band intensities should be low. From the spectra, only very low intensity bands are observed (low molar absorptivity (ε) values on y-axis). | 0 | Theoretical and Fundamental Chemistry |
Selegiline is a selective inhibitor of MAO-B, irreversibly inhibiting it by binding to it covalently. It is generally believed to exert its effects by blocking the breakdown of dopamine, thus increasing its activity; however, recent evidence suggests that MAO-A is solely or almost entirely responsible for the metabolism of dopamine. Its possible neuroprotective properties may be due to protecting nearby neurons from the free oxygen radicals that are released by MAO-B activity. At higher doses, selegiline loses its selectivity for MAO-B and inhibits MAO-A as well.
Selegiline potentiates the release of catecholamines independent of its MAO-B inhibiting action. As such, it has been called the "first synthetic catecholaminergic activity enhancer substance".
Selegiline also inhibits CYP2A6 and can increase the effects of nicotine as a result. Selegiline also appears to activate σ receptors, having a relatively high affinity for these receptors of approximately 400 nM. | 0 | Theoretical and Fundamental Chemistry |
The class Duplopiviricetes is the second clade of dsRNA viruses and is in the phylum Pisuviricota, which also contains positive-sense single-stranded RNA viruses. Duplopiviricetes mostly contains plant and fungal viruses and includes the following four families: Amalgaviridae, Hypoviridae, Partitiviridae, and Picobirnaviridae. | 1 | Applied and Interdisciplinary Chemistry |
It is semisynthetic and in the same class as penicillin. Cloxacillin is used against staphylococci that produce beta-lactamase, due to its large R chain, which does not allow the beta-lactamases to bind. This drug has a weaker antibacterial activity than benzylpenicillin, and is devoid of serious toxicity except for allergic reactions. | 0 | Theoretical and Fundamental Chemistry |
The electromigration degradation of the on-chip power grid network/interconnect depends on the IR drop noise of the power grid interconnect.
The electromigration-aware lifetime of the power grid interconnects as well as the chip decreases if the chip suffers from a high value of the IR drop noise. | 0 | Theoretical and Fundamental Chemistry |
A pitch drop experiment is a long-term experiment which measures the flow of a piece of pitch over many years. "Pitch" is the name for any of a number of highly viscous liquids which appear solid, most commonly bitumen, also known as asphalt. At room temperature, tar pitch flows at a very low rate, taking several years to form a single drop. | 1 | Applied and Interdisciplinary Chemistry |
Sinistral and dextral, in some scientific fields, are the two types of chirality ("handedness") or relative direction. The terms are derived from the Latin words for "left" (sinister) and "right" (dexter). Other disciplines use different terms (such as dextro- and laevo-rotary in chemistry, or clockwise and anticlockwise in physics) or simply use left and right (as in anatomy).
Relative direction and chirality are distinct concepts. Relative direction is from the point of view of the observer; a completely symmetric object has a left side and a right side, from the observer's point of view, if the top and bottom and direction of observation are defined. Chirality, however, is observer-independent: no matter how one looks at a right-hand screw thread, it remains different from a left-hand screw thread. Therefore, a symmetric object has sinistral and dextral directions arbitrarily defined by the position of the observer, while an asymmetric object that shows chirality may have sinistral and dextral directions defined by characteristics of the object, regardless of the position of the observer. | 0 | Theoretical and Fundamental Chemistry |
Secreted by leukocytes, respectively fibroblasts, IFNα IFNβ together regulate antiviral immunity, cell proliferation and anti-tumor effects. In viral infection signalling pathway, either of IFNα or β binds to IFN receptor (IFNAR), composed of IFNAR1 and IFNAR2, immediately followed by the phosphorylation of STAT1, STAT4 and IFN target genes. During the initial phase of viral infection in NK cells, STAT1 activation is replaced by the activation of STAT4. | 1 | Applied and Interdisciplinary Chemistry |
The term advection often serves as a synonym for convection, and this correspondence of terms is used in the literature. More technically, convection applies to the movement of a fluid (often due to density gradients created by thermal gradients), whereas advection is the movement of some material by the velocity of the fluid. Thus, although it might seem confusing, it is technically correct to think of momentum being advected by the velocity field in the Navier-Stokes equations, although the resulting motion would be considered to be convection. Because of the specific use of the term convection to indicate transport in association with thermal gradients, it is probably safer to use the term advection if one is uncertain about which terminology best describes their particular system. | 1 | Applied and Interdisciplinary Chemistry |
At room temperature, anhydrous cobalt chloride has the cadmium chloride structure () (Rm) in which the cobalt(II) ions are octahedrally coordinated. At about 706 °C (20 degrees below the melting point), the coordination is believed to change to tetrahedral. The vapor pressure has been reported as 7.6 mmHg at the melting point. | 0 | Theoretical and Fundamental Chemistry |
Having reads of 400-500 base pairs length is sufficient to determine the species or strain of the organism where the DNA comes from, provided its genome is already known, by using for example a k-mer based taxonomic classifier software. With millions of reads from next generation sequencing of an environmental sample, it is possible to get a complete overview of any complex microbiome with thousands of species, like the gut flora. Advantages over 16S rRNA amplicon sequencing are: not being limited to bacteria; strain-level classification where amplicon sequencing only gets the genus; and the possibility to extract whole genes and specify their function as part of the metagenome.
The sensitivity of metagenomic sequencing makes it an attractive choice for clinical use.
It however emphasizes the problem of contamination of the sample or the sequencing pipeline. | 1 | Applied and Interdisciplinary Chemistry |
In the case of magic angle spinning DNP (MAS-DNP), the mechanism is different but to understand it, a two spins system can still be used. The polarization process of the nucleus still occurs when the microwave irradiation excites the double quantum or zero quantum transition, but due to the fact that the sample is spinning, this condition is only met for a short time at each rotor cycle (which makes it periodical). The DNP process in that case happens step by step and not continuously as in the static case. | 0 | Theoretical and Fundamental Chemistry |
Researchers have found spongin to be useful in the photocatalytic degradation and removal of bisphenols (such as BPA) in wastewater. A heterogeneous catalyst consisting of a spongin scaffold for iron phthalocyanine (SFe) in conjunction with peroxide and UV radiation has been shown to remove phenolic wastes more quickly and efficiently than conventional methods. Other research using spongin scaffolds for the immobilization of Trametes versicolor Laccase has shown similar results in phenol degradation. | 1 | Applied and Interdisciplinary Chemistry |
In 1942 Professor Friedrich Paneth was recruiting young chemists for the nuclear energy project. Wilkinson joined and was sent out to Canada, where he stayed in Montreal and later Chalk River Laboratories until he could leave in 1946. For the next four years he worked with Professor Glenn T. Seaborg at University of California, Berkeley, mostly on nuclear taxonomy. He then became a research associate at the Massachusetts Institute of Technology and began to return to his first interest as a student – transition metal complexes of ligands such as carbon monoxide and olefins.
He was at Harvard University from September 1951 until he returned to England in December 1955, with a sabbatical break of nine months in Copenhagen. At Harvard, he still did some nuclear work on excitation functions for protons in cobalt, but had already begun to work on olefin complexes.
In June 1955 he was appointed to the chair of Inorganic Chemistry at Imperial College London, and from then on worked almost entirely on the complexes of transition metals.
Wilkinson is well known for his popularisation of the use of Wilkinsons catalyst RhCl(PPh) in catalytic hydrogenation, and for the discovery of the structure of ferrocene. Wilkinsons catalyst is used industrially in the hydrogenation of alkenes to alkanes.
He supervised PhD students and postdoctoral researchers including John A. Osborn, Alan Davison and Malcolm Green. | 0 | Theoretical and Fundamental Chemistry |
Jean Lynch-Stieglitz is a paleoceanographer known for her research on reconstructing changes in ocean circulation over the last 100,000 years. | 0 | Theoretical and Fundamental Chemistry |
Many different proteins bind to particular TET enzymes and recruit the TETs to specific genomic locations. In some studies, further analysis is needed to determine whether the interaction per se mediates the recruitment or instead the interacting partner helps to establish a favourable chromatin environment for TET binding. TET1‑depleted and TET2‑depleted cells revealed distinct target preferences of these two enzymes, with TET1‑preferring promoters and TET2‑preferring gene bodies of highly expressed genes and enhancers.
The three mammalian DNA methyltransferases (DNMTs) show a strong preference for adding a methyl group to the 5 carbon of a cytosine where a cytosine nucleotide is followed by a guanine nucleotide in the linear sequence of bases along its 5 → 3 direction (at CpG sites). This forms a 5mCpG site. More than 98% of DNA methylation occurs at CpG sites in mammalian somatic cells. Thus TET enzymes largely initiate demethylation at 5mCpG sites.
Oxoguanine glycosylase (OGG1) is one example of a protein that recruits a TET enzyme. TET1 is able to act on 5mCpG if an ROS has first acted on the guanine to form 8-hydroxy-2'-deoxyguanosine (8-OHdG or its tautomer 8-oxo-dG), resulting in a 5mCp-8-OHdG dinucleotide (see Figure). After formation of 5mCp-8-OHdG, the base excision repair enzyme OGG1 binds to the 8-OHdG lesion without immediate excision (see Figure). Adherence of OGG1 to the 5mCp-8-OHdG site recruits TET1, allowing TET1 to oxidize the 5mC adjacent to 8-OHdG. This initiates the demethylation pathway.
EGR1 is another example of a protein that recruits a TET enzyme. EGR1 has an important role in learning and memory. When a new event such as fear conditioning causes a memory to be formed, EGR1 messenger RNA is rapidly and selectively up-regulated in subsets of neurons in specific brain regions associated with learning and memory formation. TET1s is the predominant isoform of TET1 that is expressed in neurons. When EGR1 proteins are expressed, they appear to bring TET1s to about 600 sites in the neuron genome. Then EGR1 and TET1 appear to cooperate in demethylating and thereby activating the expression of genes downstream of the EGR1 binding sites in DNA. | 1 | Applied and Interdisciplinary Chemistry |
A coalescer is a device which induces coalescence in a medium. They are primarily used to separate emulsions into their components via various processes, operating in reverse to an emulsifier.
Coalescers are of two main types: mechanical and electrostatic. Mechanical coalescers use filters or baffles to make droplets coalesce, while electrostatic coalescers use DC or AC electric fields (or combinations). | 0 | Theoretical and Fundamental Chemistry |
Hemichromes form an insoluble macromolecule (macromolecular aggregate) by copolymerization with the cytoplasm of band 3. Covalent bonds reinforce the aggregate interactions of the hemichromes which are accumulated on the surface of the membrane. However, hemichromes are less stable than their native form. | 1 | Applied and Interdisciplinary Chemistry |
In 1898, Scientific American published an article called Bessemer Steel and its Effect on the World explaining the significant economic effects of the increased supply in cheap steel. They noted that the expansion of railroads into previously sparsely inhabited regions of the country had led to settlement in those regions, and had made the trade of certain goods profitable, which had previously been too costly to transport.
The Bessemer process revolutionized steel manufacture by decreasing its cost, from £40 per long ton to £6–7 per long ton, along with greatly increasing the scale and speed of production of this vital raw material. The process also decreased the labor requirements for steel-making. Before it was introduced, steel was far too expensive to make bridges or the framework for buildings and thus wrought iron had been used throughout the Industrial Revolution. After the introduction of the Bessemer process, steel and wrought iron became similarly priced, and some users, primarily railroads, turned to steel. Quality problems, such as brittleness caused by nitrogen in the blowing air, prevented Bessemer steel from being used for many structural applications. Open-hearth steel was suitable for structural applications.
Steel greatly improved the productivity of railroads. Steel rails lasted ten times longer than iron rails. Steel rails, which became heavier as prices fell, could carry heavier locomotives, which could pull longer trains. Steel rail cars were longer and were able to increase the freight to car weight from 1:1 to 2:1. | 1 | Applied and Interdisciplinary Chemistry |
Pharmacology and pharmacotherapy (like health care generally) are universally relevant around the world, making translingual communication about them an important goal. An interlingual perspective is thus useful in drug nomenclature. The WHO issues INNs in English, Latin, French, Russian, Spanish, Arabic, and Chinese. A drugs INNs are often cognates across most or all of the languages, but they also allow small inflectional, diacritic, and transliterational differences that are usually transparent and trivial for nonspeakers (as is true of most international scientific vocabulary). For example, although paracetamolum (la) has an inflectional difference from paracetamol (en), and although paracétamol (fr) has a diacritic difference, the differences are trivial; users can easily recognize the "same word" (although Americans will likely not recognize the word paracetamol in the first place, because that medicine is known as "acetaminophen" in the United States, even among most healthcare professionals, illustrating that the INN system is not perfect in its functioning). And although парацетамол (ru) and paracetamol' (en) have a transliterational difference, they sound similar, and for Russian speakers who can recognize Latin script or English speakers who can recognize Cyrillic script, they look similar; users can recognize the "same word". Thus, INNs make medicines bought anywhere in the world as easily identifiable as possible to people who do not speak that language. Notably, the "same word" principle allows health professionals and patients who do not speak the same language to communicate to some degree and to avoid potentially life-threatening confusions from drug interactions. | 1 | Applied and Interdisciplinary Chemistry |
Saturation binding measures the specific binding of a radioligand at varying concentrations while at equilibrium. Through this method, the number of receptors can be determined as well as affinity of the ligand to these receptors. Saturation binding experiments are often called "Scatchard experiments" as they can be graphed as a Scatchard plot. | 1 | Applied and Interdisciplinary Chemistry |
In thermodynamics and fluid mechanics, stagnation temperature is the temperature at a stagnation point in a fluid flow. At a stagnation point the speed of the fluid is zero and all of the kinetic energy has been converted to internal energy and is added to the local static enthalpy. In both compressible and incompressible fluid flow, the stagnation temperature is equal to the total temperature at all points on the streamline leading to the stagnation point. See gas dynamics. | 1 | Applied and Interdisciplinary Chemistry |
PDE5 inhibitors are generally well tolerated, with side effects including transient headaches, flushing, dyspepsia, congestion and dizziness. There have also been reports of temporary vision disturbances with sildenafil and, to a lesser extent, vardenafil, and back and muscle pain with tadalafil. These side effects may be attributed to the unintended effects of PDE5 inhibitors against other PDE isozymes, such as PDE1, PDE6 and PDE11. It is theorised that improved selectivity of PDE5 inhibitors may lead to fewer side effects. For example, vardenafil and tadalafil have demonstrated reduced adverse effects probably due to improved selectivity for PDE5. However, no highly selective PDE5 inhibitors are currently in development.
Patients who take nitrates, alpha blockers or sGC stimulators within 24 hours of PDE5 inhibitor administration (or 48 hours for tadalafil) may experience symptomatic hypotension, so concurrent use is contraindicated. PDE5 inhibitors are also contraindicated in patients with hereditary eye conditions such as retinitis pigmentosa due to the small increased risk of nonarteritic ischaemic optic neuropathy in patients taking the medication.
Hearing impairment is one risk factor for those who are using PDE5 inhibitors and it has been reported for all available drugs on the market. This problem may be due to high level effect cGMP on cochlear hair cells. It has been reported that PDE5 inhibitors (sildenafil & vardenafil) cause transient visual disturbances likely due to PDE6 inhibition.
Several reports are about approaches to improve PDE5 inhibitors, where as chemical groups have been switched out to increase potency and selectivity, which should potentially lead to drugs with fewer side effects. | 1 | Applied and Interdisciplinary Chemistry |
Polyoxins are a group of nucleoside antibiotics composed of heterocyclic moieties containing nitrogen. An example is Polyoxin B.
Polyoxins work by inhibiting the biosynthesis of chitin. | 1 | Applied and Interdisciplinary Chemistry |
The mathematical similarities between the expressions for shear viscocity, thermal conductivity and diffusion coefficient of the ideal (dilute) gas is not a coincidence; It is a direct result of the Onsager reciprocal relations (i.e. the detailed balance of the reversible dynamics of the particles), when applied to the convection (matter flow due to temperature gradient, and heat flow due to pressure gradient) and advection (matter flow due to the velocity of particles, and momentum transfer due to pressure gradient) of the ideal (dilute) gas. | 0 | Theoretical and Fundamental Chemistry |
Allyltrimethylsilane is the organosilicon compound with the formula (CH)SiCHCH=CH. The molecule consists of the trimethylsilyl group attached to allyl group. This colorless liquid is used in organic synthesis. | 0 | Theoretical and Fundamental Chemistry |
Born in Kobe, Japan, Yamamoto earned a B.S. at Kyoto University in 1967 and a Ph.D. at Harvard University in 1971.
He was a professor at Nagoya University from 1983 until 2002 and has since been a professor within the Department of Chemistry at the University of Chicago. His research work is largely in the chemistry of acid catalysts that play an important role in triggering or driving chemical reactions, specifically Lewis and Brønsted acid catalysts used in selective organic synthesis. Yamamoto has authored or co-authored several books on topics in modern synthetic organic chemistry. As of 2021, his h-index equals to 120 with more than 64,000 citations. | 0 | Theoretical and Fundamental Chemistry |
Ajith Chrysantha Stephen Perera, JP, CChem., FRSC (29 February 1956 – 29 October 2020) was a Chartered Chemist by profession, a scholar, a former senior manager in industry, a qualified training instructor, also a former test-match-panel cricket umpire.
The international admiration Perera has won and the national recognition he has gained have come through his achievements, acquired both in Sri Lanka and in England in different fields: cricket, analytical chemistry and quality assurance, in all of which he was academically and professionally well qualified and widely experienced.
Almost on the eve of umpiring his first cricket test match in Colombo, Sri Lanka vs New Zealand, a large wayside tree crashed on and straddled his moving car, killing his chauffeur and leaving him instantaneously a paraplegic for life.
He was a writer, speaker, author and a disability rights activist - as a fervent advocate for inclusion of all people by design - most importantly as a widely experienced and highly competent accessibility adviser and assessor, recognised by three learned societies and several reputed bodies overseas.
He was the founder and, as of 10 June 2020, held the honorary position of Chief Executive / Secretary-General]] of Idiriya, a registered, not-for-profit humanitarian service organisation in Sri Lanka. | 0 | Theoretical and Fundamental Chemistry |
Due to the constant perfusion of the microdialysis probe with fresh perfusate, a total equilibrium cannot be established. This results in dialysate concentrations that are lower than those measured at the distant sampling site. In order to correlate concentrations measured in the dialysate with those present at the distant sampling site, a calibration factor (recovery) is needed. The recovery can be determined at steady-state using the constant rate of analyte exchange across the microdialysis membrane. The rate at which an analyte is exchanged across the semipermeable membrane is generally expressed as the analyte’s extraction efficiency. The extraction efficiency is defined as the ratio between the loss/gain of analyte during its passage through the probe (C−C) and the difference in concentration between perfusate and distant sampling site (C−C).
In theory, the extraction efficiency of a microdialysis probe can be determined by: 1) changing the drug concentrations while keeping the flow rate constant or 2) changing the flow rate while keeping the respective drug concentrations constant. At steady-state, the same extraction efficiency value is obtained, no matter if the analyte is enriched or depleted in the perfusate. Microdialysis probes can consequently be calibrated by either measuring the loss of analyte using drug-containing perfusate or the gain of analyte using drug-containing sample solutions. To date, the most frequently used calibration methods are the low-flow-rate method, the no-net-flux method, the dynamic (extended) no-net-flux method, and the retrodialysis method. The proper selection of an appropriate calibration method is critically important for the success of a microdialysis experiment. Supportive in vitro experiments prior to the use in animals or humans are therefore recommended. In addition, the recovery determined in vitro may differ from the recovery in humans. Its actual value therefore needs to be determined in every in vivo experiment. | 1 | Applied and Interdisciplinary Chemistry |
The identity of the repeat units (monomer residues, also known as "mers") comprising a polymer is its first and most important attribute. Polymer nomenclature is generally based upon the type of monomer residues comprising the polymer. A polymer which contains only a single type of repeat unit is known as a homopolymer, while a polymer containing two or more types of repeat units is known as a copolymer. A terpolymer is a copolymer which contains three types of repeat units.
Polystyrene is composed only of styrene-based repeat units, and is classified as a homopolymer. Polyethylene terephthalate, even though produced from two different monomers (ethylene glycol and terephthalic acid), is usually regarded as a homopolymer because only one type of repeat unit is formed. Ethylene-vinyl acetate contains more than one variety of repeat unit and is a copolymer. Some biological polymers are composed of a variety of different but structurally related monomer residues; for example, polynucleotides such as DNA are composed of four types of nucleotide subunits.
A polymer containing ionizable subunits (e.g., pendant carboxylic groups) is known as a polyelectrolyte or ionomer, when the fraction of ionizable units is large or small respectively. | 0 | Theoretical and Fundamental Chemistry |
Pinealon is a tripeptide composed of -glutamic acid, -aspartic acid, and -arginine and is notated as Glu-Asp-Arg or EDR. | 1 | Applied and Interdisciplinary Chemistry |
Full article: Iron Fertilization
Iron fertilization is a facet of geoengineering, which purposefully manipulates the Earth's climate system, typically in aspects of the carbon cycle or radiative forcing. Of current geoengineering interest is the possibility of accelerating the biological pump to increase export of carbon from the surface ocean. This increased export could theoretically remove excess carbon dioxide from the atmosphere for storage in the deep ocean. Ongoing investigations regarding artificial fertilization exist. Due to the scale of the ocean and the fast response times of heterotrophic communities to increases in primary production, it is difficult to determine whether limiting-nutrient fertilization results in an increase in carbon export. However, the majority of the community does not believe this is a reasonable or viable approach. | 0 | Theoretical and Fundamental Chemistry |
* In non-homogeneous media, the diffusion coefficient varies in space, . This dependence does not affect Fick's first law but the second law changes:
* In anisotropic media, the diffusion coefficient depends on the direction. It is a symmetric tensor . Fick's first law changes to it is the product of a tensor and a vector: For the diffusion equation this formula gives The symmetric matrix of diffusion coefficients should be positive definite. It is needed to make the right hand side operator elliptic.
* For inhomogeneous anisotropic media these two forms of the diffusion equation should be combined in
* The approach based on Einsteins mobility and Teorell formula gives the following generalization of Ficks equation for the multicomponent diffusion of the perfect components: where are concentrations of the components and is the matrix of coefficients. Here, indices and are related to the various components and not to the space coordinates.
The Chapman–Enskog formulae for diffusion in gases include exactly the same terms. These physical models of diffusion are different from the test models which are valid for very small deviations from the uniform equilibrium. Earlier, such terms were introduced in the Maxwell–Stefan diffusion equation.
For anisotropic multicomponent diffusion coefficients one needs a rank-four tensor, for example , where refer to the components and correspond to the space coordinates. | 0 | Theoretical and Fundamental Chemistry |
The success of DNA based markers lead to the development of PCR. PCR (polymerase chain reaction) is a DNA amplification technique that can be applied to various types of fragments. Prior to this development, to amplify DNA, it had to be cloned or isolated. Shortly after the discovery of PCR came the idea of using PCR-based markers for gel electrophoresis. These type of markers are based on PCR primers and are categorized as DNA sequence polymorphism. | 1 | Applied and Interdisciplinary Chemistry |
The stoichiometric name is followed by the number of hydrogen atoms in brackets. For example BH, diborane(6). More structural information can be conveyed by adding the "structural descriptor" closo-, nido-, arachno-, hypho-, klado- prefixes.<br />
There is a fully systematic method of numbering the atoms in the boron hydride clusters, and a method of describing the position of bridging hydrogen atoms using the μ symbol. | 0 | Theoretical and Fundamental Chemistry |
The mycofactocin biosynthesis pathway is one of the most abundant of any RiPP system in the collection of bacterial genomes sequenced to date. However, its species distribution is heavily skewed towards the Actinomycetota, including Mycobacterium tuberculosis, which is the causative agent of tuberculosis and therefore the number one killer among bacterial pathogens of humans. The system is virtually absent from the normal human microbiome, although common in soil bacteria.
# The biosynthesis of mycofactocin from its precursor peptide MftA begins with decarboxylation of the C-terminal tyrosine residue by the radical SAM enzyme MftC, with help from the precursor-binding protein MftB.
# However, MftC appears next to perform a further modification to the MftA precursor peptide, an easily missed isomerization, by introducing a tyramine-valine cross-link, and consuming another S-adenosylmethionine in the process. The need for two modifications to MftA by MftC might explain the high degree of amino acid conservation in the last eight residues of MftA, as compared to the level of conservation seen for PqqA, precursor of PQQ.
# Next, the creatininase homolog MftE releases the C-terminal dipeptide, VY* (valine-tyrosine, where * indicates that the tyrosine was previously modified).
# Next, MftD converts the VY-derived dipeptide to premycofactocin, which has a biologically active redox center.
# And lastly, the glycosyltransferase MftF builds onto premycofactocin a variably sized, beta-1,4 linked oligomeric chain of glucose (i.e. cellulose), sometimes substituting derivatives such as 2-O-methylglucose.
Mycofactocin, therefore, is not a single compound, but instead a mixture of closely related electron carriers that differ in the nature of their attached oligosaccharides. | 1 | Applied and Interdisciplinary Chemistry |
Brain-derived neurotrophic factor (BDNF) is also a myokine, though BDNF produced by contracting muscle is not released into circulation. Rather, BDNF produced in skeletal muscle appears to enhance the oxidation of fat. Skeletal muscle activation through exercise also contributes to an increase in BDNF secretion in the brain. A beneficial effect of BDNF on neuronal function has been noted in multiple studies. Dr. Pedersen writes, "Neurotrophins are a family of structurally related growth factors, including brain-derived neurotrophic factor (BDNF), which exert many of their effects on neurons primarily through Trk receptor tyrosine kinases. Of these, BDNF and its receptor TrkB are most widely and abundantly expressed in the brain. However, recent studies show that BDNF is also expressed in non-neurogenic tissues, including skeletal muscle. BDNF has been shown to regulate neuronal development and to modulate synaptic plasticity. BDNF plays a key role in regulating survival, growth and maintenance of neurons, and BDNF has a bearing on learning and memory. However, BDNF has also been identified as a key component of the hypothalamic pathway that controls body mass and energy homeostasis.
With respect to studies of exercise and brain function, a 2010 report is of particular interest. Erickson et al. have shown that the volume of the anterior hippocampus increased by 2% in response to aerobic training in a randomized controlled trial with 120 older adults. The authors also summarize several previously-established research findings relating to exercise and brain function: (1) Aerobic exercise training increases grey and white matter volume in the prefrontal cortex of older adults and increases the functioning of key nodes in the executive control network. (2) Greater amounts of physical activity have been associated with sparing of prefrontal and temporal brain regions over a 9-y period, which reduces the risk for cognitive impairment. (3) Hippocampal and medial temporal lobe volumes are larger in higher-fit older adults (larger hippocampal volumes have been demonstrated to mediate improvements in spatial memory). (4) Exercise training increases cerebral blood volume and perfusion of the hippocampus.
Regarding the 2010 study, the authors conclude: "We also demonstrate that increased hippocampal volume is associated with greater serum levels of BDNF, a mediator of neurogenesis in the dentate gyrus. Hippocampal volume declined in the control group, but higher preintervention fitness partially attenuated the decline, suggesting that fitness protects against volume loss. Caudate nucleus and thalamus volumes were unaffected by the intervention. These theoretically important findings indicate that aerobic exercise training is effective at reversing hippocampal volume loss in late adulthood, which is accompanied by improved memory function." | 1 | Applied and Interdisciplinary Chemistry |
Antibody-vaccine engineered construct abbreviated AVEC is an anti cancer drug in clinical trials that enables the immune system to detect and naturally eliminate malignant cells. It is a biomolecularly engineered molecule consisting of the two main components: (1) antibody; (2) vaccine. (1) The antibody component binds AVEC to the targeted molecule, e.g., to epidermal growth factor receptor 2 (HER2) on breast cancer cells. (2) The vaccine component elicits an immune response, directed against the cancer cells bound by the antibody component, e.g., immune response to the HBV vaccine mounted by the prophylactic immunity gained by vaccination.
It has the potential to be used to treat a variety of types of cancer, including breast cancer, ovarian cancer, colorectal cancer and leukemias. | 1 | Applied and Interdisciplinary Chemistry |
The allyl ligand is commonly found in organometallic chemistry. Most commonly, allyl ligands bind to metals via all three carbon atoms, the η-binding mode. The η-allyl group is classified as an LX-type ligand in the Green LXZ ligand classification scheme, serving as a 3e donor using neutral electron counting and 4e donor using ionic electron counting. More common are complexes with allyl and other ligands. Examples include (η-allyl)Mn(CO) and CpPd(allyl). | 0 | Theoretical and Fundamental Chemistry |
Pepscan is a procedure for mapping and characterizing epitopes involving the synthesis of overlapping peptides and analysis of the peptides in enzyme-linked immunosorbent assays (ELISAs). The method is based on combinatorial chemistry and was pioneered by Mario Geysen and coworkers.
Rob Meloen was one of Geysen's co-workers. He also played an important role in the development of numerous other new technologies, including vaccine and diagnostic product development for several viral diseases. From 1994 to 2010, Meloen was Professor of Special Appointment (Chair: Biomolecular Recognition) at Utrecht University. He was one of the co-founders of the company Pepscan (Lelystad, the Netherlands) and became Scientific Director (CSO). Pepscan is now part of the Biosynth Group.
Twenty-five years later, the Pepscan methodology, evolved and modernized with the latest insights, is still an important part of Pepscan’s epitope mapping platform, which is instrumental in therapeutic antibody development. | 1 | Applied and Interdisciplinary Chemistry |
Scientists began to wonder about the energetic of cluster formation early in the 19th century. Henry Eyring developed the activated-complex theory describing kinetics of reactions. Interest in studying the weak interactions of molecules and ions(e.g. van der Waals) in clusters encouraged gas phase spectroscopy, in 1962 D.H. Rank studied weak interactions in the gas phase using traditional infrared spectroscopy. D.S. Bomse used IRPD with an ICR to study isotopic compounds in 1980 at California Institute of Technology. Spectroscopy for weak bonding clusters was limited by low cluster concentration and the variety of accessible cluster states. Cluster states vary in part due to frequent collisions with other species, to reduce collisions in gas phase IRPD forms clusters in low pressure ion traps (e.g. FT-ICR). Nitrogen and water were one of the first complexes studied with the aid of a mass spectrometer by A. Good at University of Alberta in the 1960s. | 0 | Theoretical and Fundamental Chemistry |
The citrate-malate shuttle is a series of chemical reactions, commonly referred to as a biochemical cycle or system, that transports acetyl-CoA in the mitochondrial matrix across the inner and outer mitochondrial membranes for fatty acid synthesis. Mitochondria are enclosed in a double membrane. As the inner mitochondrial membrane is impermeable to acetyl-CoA, the shuttle system is essential to fatty acid synthesis in the cytosol. It plays an important role in the generation of lipids in the liver (hepatic lipogenesis).
The name of the citrate-malate shuttle is derived from the two intermediates – short-lived chemicals that are generated in a reaction step and consumed entirely in the next – citrate and malate that carry the acetyl-CoA molecule across the mitochondrial double membrane.
The citrate–malate shuttle is present in humans and other higher eukaryotic organisms and is closely related to the Krebs cycle. The system is responsible for the transportation of malate into the mitochondrial matrix to serve as an intermediate in the Krebs cycle and the transportation of citrate into the cytosol for secretion in Aspergillus niger, a fungus used in the commercial production of citric acid. | 1 | Applied and Interdisciplinary Chemistry |
*Gene fusion
** Recurrent somatic fusions of the two genes, NGFI-A–binding protein 2 (NAB2) and STAT6, located at chromosomal region 12q13, have been identified in solitary fibrous tumors.
*Amplification
**STAT6 is amplified in a subset of dedifferentiated liposarcoma. | 1 | Applied and Interdisciplinary Chemistry |
Hydrophobicity scales can also be obtained by calculating the solvent accessible surface areas for amino acid residues in the expended polypeptide chain or in alpha-helix and multiplying the surface areas by the empirical solvation parameters for the corresponding types of atoms.
A differential solvent accessible surface area hydrophobicity scale based on proteins as compacted networks near a critical point, due to self-organization by evolution, was constructed based on asymptotic power-law (self-similar) behavior. This scale is based on a bioinformatic survey of 5526 high-resolution structures from the Protein Data Bank. This differential scale has two comparative advantages: (1) it is especially useful for treating changes in water-protein interactions that are too small to be accessible to conventional force-field calculations, and (2) for homologous structures, it can yield correlations with changes in properties from mutations in the amino acid sequences alone, without determining corresponding structural changes, either in vitro or in vivo. | 0 | Theoretical and Fundamental Chemistry |
Organic nitroso complexes can be prepared from preformed organic nitroso precursors. These precursors usually exist as N-N bonded dimers, but the dimer dissociates readily. This direct method is used to give W(CO)(tert-BuNO) (where tert-Bu is ). The Fe-porphyrin complex depicted below is prepared by this route. More complicated but more biorelevant routes involve degradation of precursors such as nitrobenzene and phenylhydroxylamine.
: (Et = CH, i-Pr = (CH)CH)
The coupling of organic ligands and nitric oxide is yet another route. | 0 | Theoretical and Fundamental Chemistry |
Hemispherical transmittance of a surface, denoted T, is defined as
where
*Φ is the radiant flux transmitted by that surface;
*Φ is the radiant flux received by that surface. | 0 | Theoretical and Fundamental Chemistry |
* The larvae of the berothid lacewing Lomamyia latipennis feed on termites which they subdue with an aggressive allomone. The first instar approaches a termite and waves the tip of its abdomen near the termite's head. The termite becomes immobile after 1 to 3 minutes, and completely paralysed very soon after this, although it may live for up to 3 hours. The berothid then feeds on the paralysed prey. The third instar feeds in a similar manner and may kill up to six termites at a time. Contact between the termite and the berothid is not necessary for subduing, and other insects present are not affected by the allomone.
* Bark beetles communicate via pheromones to announce a new food resource (i.e. dead trees, roots, living trees, etc.) ultimately resulting in the accumulation of a large concentration of bark beetles. Select species of bark beetles have the capability to emit pheromones that can negatively affect the behavioral response of another competing species of bark beetles when both species are attempting to inhabit the loblolly pine tree. A certain molecular compound within the released pheromone of one species can interfere with a competing species ability to respond its own species pheromone in the environment. This interaction aides the emitter by decreasing its local bark beetle competition. A competitive interaction occurring between two species of bark beetles is seen when the pheromones of G. sulcates interferes with the behavioral feedback of G. retusus. The impact of interactions between competing species fighting for food and space within an environment is seen when observing the California I. pini. The I. pinihave two receptors in which one is used to receive the pheromone of their own species and the other receptor receives the pheromone of their competing species. The presence of these two receptors makes sure that pheromones from their own species, I. pini, are not being interrupted by their competing species, I. paraconfusus.
* Arthropods that travel alone, like beetles and cockroaches, have evolved to emit pheromones when in the presence of ants in which the emitted pheromone is identical to the ant's alarm pheromone. The alarm pheromone of the worker ants causes the ants to stop what they are doing and to return to their nest till the alarm pheromone ceases in their environment. This release of an ant alarm pheromone by an arthropod causes the ants to go into alarm and allows the arthropod to escape its predators before the ants are able to recruit more workers. | 1 | Applied and Interdisciplinary Chemistry |
A retention basin, sometimes called a retention pond, wet detention basin, or storm water management pond (SWMP), is an artificial pond with vegetation around the perimeter and a permanent pool of water in its design. It is used to manage stormwater runoff, for protection against flooding, for erosion control, and to serve as an artificial wetland and improve the water quality in adjacent bodies of water.
It is distinguished from a detention basin, sometimes called a "dry pond", which temporarily stores water after a storm, but eventually empties out at a controlled rate to a downstream water body. It also differs from an infiltration basin which is designed to direct stormwater to groundwater through permeable soils.
Wet ponds are frequently used for water quality improvement, groundwater recharge, flood protection, aesthetic improvement, or any combination of these. Sometimes they act as a replacement for the natural absorption of a forest or other natural process that was lost when an area is developed. As such, these structures are designed to blend into neighborhoods and viewed as an amenity.
In urban areas, impervious surfaces (roofs, roads) reduce the time spent by rainfall before entering into the stormwater drainage system. If left unchecked, this will cause widespread flooding downstream. The function of a stormwater pond is to contain this surge and release it slowly. This slow release mitigates the size and intensity of storm-induced flooding on downstream receiving waters. Stormwater ponds also collect suspended sediments, which are often found in high concentrations in stormwater water due to upstream construction and sand applications to roadways. | 1 | Applied and Interdisciplinary Chemistry |
For the subsequent reaction at high temperatures, it is necessary to choose a suitable container material which is chemically inert to the reactants under the heating conditions used. The noble metals, platinum and gold, are usually suitable. Containers may be crucibles or boats made from foil. For low temperature reactions, other metals like Nickel (below 600–700 °C) can be used. | 1 | Applied and Interdisciplinary Chemistry |
In a polyrotaxane, unlike a conventional polymer, the molecules are linked by mechanical bonding, such as hydrogen boding or charge transfer, not covalent bonds. Also, the rings are capable of rotating on or shuttling around the axles, resulting in the large amount of freedom of polyrotaxanes. This unconventional combination of molecules leads to the distinctive properties of polyrotaxanes. | 0 | Theoretical and Fundamental Chemistry |
In matrix-assisted laser desorption and ionization (MALDI), the sample is incorporated in a chemical matrix that is capable of absorbing energy from a laser. Similar to SIMS, ionization happens in vacuum. Laser irradiation ablates the matrix material from the surface and results in charged gas phase matrix particles, the analyte molecules are ionized from this charged chemical matrix. Liu et al. used MALDI-MS to detect eight phospholipids from single A549 cells. MALDI MS imaging can be used for spatial metabolomics and single cell analysis. | 1 | Applied and Interdisciplinary Chemistry |
An amidate/imidate anion is formed upon deprotonation of an amide or imidic acid. Since amides and imidic acids are tautomers, they form the same anion upon deprotonation. The two names are thus synonyms describing the same anion, although arguably, imidate refers to the resonance contributor on the left, while amidate refers to the resonance contributor on the right. However, they are distinguished when they act as ligands for transition metals, with O-bound species referred to as imidates and N-bound species referred to as amidates. They can be considered aza-substituted analogues of enolates with the formula R-N=C(O)R. | 0 | Theoretical and Fundamental Chemistry |
Many human-made chemicals are derived from fossil fuels (such as petroleum or coal) in which is greatly depleted because the age of fossils far exceeds the half-life of . The relative absence of is therefore used to determine the relative contribution (or mixing ratio) of fossil fuel oxidation to the total carbon dioxide in a given region of the Earth's atmosphere.
Dating a specific sample of fossilized carbonaceous material is more complicated. Such deposits often contain trace amounts of carbon-14. These amounts can vary significantly between samples, ranging up to 1% of the ratio found in living organisms, a concentration comparable to an apparent age of 40,000 years. This may indicate possible contamination by small amounts of bacteria, underground sources of radiation causing the (n,p) reaction, direct uranium decay (although reported measured ratios of /U in uranium-bearing ores would imply roughly 1 uranium atom for every two carbon atoms in order to cause the / ratio, measured to be on the order of 10), or other unknown secondary sources of carbon-14 production. The presence of carbon-14 in the isotopic signature of a sample of carbonaceous material possibly indicates its contamination by biogenic sources or the decay of radioactive material in surrounding geologic strata. In connection with building the Borexino solar neutrino observatory, petroleum feedstock (for synthesizing the primary scintillant) was obtained with low content. In the Borexino Counting Test Facility, a / ratio of 1.94×10 was determined; probable reactions responsible for varied levels of in different petroleum reservoirs, and the lower levels in methane, have been discussed by Bonvicini et al. | 0 | Theoretical and Fundamental Chemistry |
In the Hooker reaction (1936) an alkyl chain in a certain naphthoquinone (phenomenon first observed in the compound lapachol) is reduced by one methylene unit as carbon dioxide in each potassium permanganate oxidation.
:Mechanistically oxidation causes ring-cleavage at the alkene group, extrusion of carbon dioxide in decarboxylation with subsequent ring-closure. | 0 | Theoretical and Fundamental Chemistry |
Synergetics is an interdisciplinary science explaining the formation and self-organization of patterns and structures in open systems far from thermodynamic equilibrium. It is founded by Hermann Haken, inspired by the laser theory. Hakens interpretation of the laser principles as self-organization of non-equilibrium systems paved the way at the end of the 1960s to the development of synergetics. One of his successful popular books is Erfolgsgeheimnisse der Natur, translated into English as The Science of Structure: Synergetics'.
Self-organization requires a macroscopic system, consisting of many nonlinearly interacting subsystems. Depending on the external control parameters (environment, energy fluxes) self-organization takes place. | 0 | Theoretical and Fundamental Chemistry |
*An Excellent Nickel Boride Catalyst for the Cis-Selective Semihydrogenation of Acetylenes Tetrahedron (J. Choi and N. M. Yoon), Tetrahedron Lett. Vol.37 p. 1057 (1996)
*A New Coupling Reaction of Alkyl Iodides with Electron Deficient Alkenes Using Nickel Boride(cat.)- Borohydride Exchange Resin in Methanol (T. B. Sim, J. Choi, M. J. Joung and N. M. Yoon), J. Org. Chem. Vol.62 p. 2357 (1997)
*Sodium Diethyldialkynylaluminate A New Chemoselective Alkynylating Agent (J. H. Ahn, M. J. Joung, and N. M. Yoon) J. Org. Chem. Vol.60 p. 6173 (1995)
*Synthesis of Disulfides by Copper Catalyzed Disproportionation of Thiols (J. Choi and N. M. Yoon), J. Org. Chem. Vol.60 p. 3266 (1995)
*Monoisopinocampheylborane- A New Chiral Hydroborating Agent for Relatively Hindered (Trisubstituted) Olefins (H. C. Brown and N. M. Yoon), J. Am. Chem. Soc. Vol.99 p. 5514 (1977)
*Diisopinocampheylborane of high Optical Purity. Asymmetric Synthesis via Hydroboration with Essentially Complete Asymmetric Induction (H. C. Brown and N. M. Yoon), Israel J. Chem Vol.15 p. 12 (1976~1977)
*Lithium Trimethylethynylaluminate A New Chemoselective Ethynylating Agent (M. J. Joung, J. H. Ahn and N. M. Yoon), J. Org. Chem. Vol.61 p. 4472 (1996)
*The Rapido Reaction of Carboxylic Acids with Borane-Tetrahydrofuran. A Remarkably Convenient Procedure for the Selective Conversion of Carboxylic Acids to the Corresponding Alcohols in the Presence of Other Functional Groups (N. M. Yoon, C. S. Park, H. C. Brown, S. Krishnamurthy, and T. P. Stoky), J. Org. Chem. Vol.38 p. 2786 (1973) | 0 | Theoretical and Fundamental Chemistry |
Dietmar Seyferth (January 11, 1929 – June 6, 2020) was an emeritus professor of chemistry at the Massachusetts Institute of Technology. He published widely on topics in organometallic chemistry and was the founding editor of the journal Organometallics. | 0 | Theoretical and Fundamental Chemistry |
The frequency of light scattered by particles undergoing electrophoresis is shifted by the amount of the Doppler effect, from that of the incident light, : .
The shift can be detected by means of heterodyne optics in which the scattering light is mixed with the reference light.
The autocorrelation function of intensity of the mixed light, , can be approximately described by the following damped cosine function [7].
where is a decay constant and A, B, and C are positive constants dependent on the optical system.
Damping frequency is an observed frequency, and is the frequency difference between scattered and reference light.
where is the frequency of scattered light, the frequency of the reference light,
the frequency of incident light (laser light),
and the modulation frequency.
The power spectrum of mixed light, namely the Fourier transform of , gives a couple of Lorenz functions at having a half-width of at the half maximum.
In addition to these two, the last term in equation (1) gives another Lorenz function at
The Doppler shift of frequency and the decay constant are dependent on the geometry of the optical system and are expressed respectively by the equations.
and
where is velocity of the particles, is the amplitude of the scattering vector, and is the translational diffusion constant of particles.
The amplitude of the scattering vector is given by the equation
Since velocity is proportional to the applied electric field, , the apparent electrophoretic mobility is define by the equation
Finally, the relation between the Doppler shift frequency and mobility is given for the case of the optical configuration of Fig. 3 by the equation
where is the strength of the electric field, the refractive index of the medium, , the wavelength of the incident light in vacuum, and the scattering angle.
The sign of is a result of vector calculation and depends on the geometry of the optics.
The spectral frequency can be obtained according to Eq. (2).
When , Eq. (2) is modified and expressed as
The modulation frequency can be obtained as the damping frequency without an electric field applied.
The particle diameter is obtained by assuming that the particle is spherical. This is called the hydrodynamic diameter, .
where is Boltzmann coefficient, is the absolute temperature, and the dynamic viscosity of the surrounding fluid. | 0 | Theoretical and Fundamental Chemistry |
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