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Nitrogen and phosphorus grow a K. brevis red tide. Although K. brevis is initiated off shore, it will grow from nutrients (phosphorus and nitrogen) found on the shore. Along the southwest coast of Florida, when surface summer south winds blow phosphorus, nitrogen, green algae, and cyanobacteria into K. brevis that has come close to shore, there is a massive growth in the K. brevis red tide. The waves crashing break the cells open aerosolizing the subsequent brevetoxins which cause respiratory illnesses in humans. In 2018, MOTE Marine in Sarasota, FL updated their frequently asked questions to make it more clear that nutrients (nitrogen is a nutrient found in fertilizer) can grow K. brevis.
Along the west coast of Florida, the early phase of K. brevis blooms are initiated by northerly winds, resulting in upwelling events that cause nutrients to rise towards the surface of the water and transport multiple Karenia cell species towards the shore. Here they concentrate and either continue to grow or are taken up by onshore winds that spread the cells over beaches and near shore communities. It has been shown that K. brevis blooms are limited by available nitrogen (N) or phosphorus (P), but until recently it was not clear what sources K. brevis was utilizing for these key developmental nutrients. The most likely proposition is some combination of the upwelling of subsurface nutrients, land runoff (agricultural and sugar plantations, cattle ranches, golf courses, theme parks, septic systems, etc.) N2-fixation, drainage from phosphate mines and atmospheric deposition provides the necessary support for the blooms.
In addition to the breaking of the cells by waves, K. brevis cells can die because N-limitation directly affects the growth potential of blooms and the toxicity of K. brevis cells that comprise them. When N-limitation is present, intracellular brevetoxin concentrations (fg/μm) increased up to 2.5-fold in laboratory cultures, implying that during periods of N-limitation of algal growth, there is a higher chance of brevetoxin influx into the marine food web. The toxin content per cell increases when algal growth becomes P-limited. Various field measurements collected in the Gulf of Mexico have shown that the brevetoxin content of K. brevis cells is between 1 and 68 pg/cell; however, Hardison et al. discovered that during periods of transient P- and N-limitation, there is a 2- to 5-fold increase in brevetoxins per mole of cell carbon or unit of cell volume. Hardison concluded that this data suggest that the exposure of marine ecosystems to significantly different toxin levels depends on the nutrient status of the K. brevis cells. While brevetoxins remain intracellular during early stages of bloom development, the triggering of apoptosis and cell lysis with age release the toxins into the surrounding waters, implying that greater P-limitation that results in more cell death ultimately elevates brevetoxin levels. These high levels may persist in a food chain long after a bloom has subsided due to brevetoxin's high affinity for adsorbing to biological surfaces like sea grass fronds, and thereby accumulating in consuming organisms.
Overall, brevetoxins seem to increase under N- and P-limitation, however, the concentration of brevetoxins per cell under P-limitation has been reported to be roughly twice that under N-limitation. One major concern of this is that management of shellfish bed closures operating under the assumption that brevetoxin concentrations per cell do not vary may compromise public safety if a bloom became nutrient limited. | 0 | Theoretical and Fundamental Chemistry |
Much palladium forms during the fission process. In nuclear reprocessing, not all of the fission palladium dissolves; also some palladium that dissolves at first comes out of solution later. Palladium-rich dissolver fines (particles) are often removed as they interfere with the solvent extraction process by stabilising the third phase.
The fission palladium can separate during the process in which the PUREX raffinate is combined with glass and heated to form the final high level waste form. The palladium forms an alloy with the fission tellurium. This alloy can separate from the glass.
Pd is the only long-living radioactive isotope among the fission products and its beta decay has a long half life and low energy, this allows industrial use of extracted palladium without isotope separation.
Palladium-109 will most likely have decayed to stable silver-109 by the time reprocessing happens. Before reaching silver-109, a nuclear isomer will be reached; . However, unlike for there is no current use for . | 0 | Theoretical and Fundamental Chemistry |
De Hevesy married Pia Riis in 1924. They had one son and three daughters together, one of whom (Eugenie) married a grandson of the Swedish Nobel laureate Svante Arrhenius. De Hevesy died in 1966 at the age of eighty and was buried in Freiburg. In 2000, his body was moved to the Kerepesi Cemetery in Budapest, Hungary. He had published a total of 397 scientific documents, one of which was the Becquerel-Curie Memorial Lecture, in which he had reminisced about the careers of pioneers of radiochemistry. At his family's request, his ashes were interred at his birthplace in Budapest on 19 April 2001.
On 10 May 2005 the Hevesy Laboratory was founded at Risø National Laboratory for Sustainable Energy, now Technical University of Denmark, DTU Nutech. It was named after George de Hevesy as the father of the isotope tracer principle under the initiative of the lab's first director, Prof. Mikael Jensen. | 1 | Applied and Interdisciplinary Chemistry |
Two-step thermochemical cycles, often involving metal oxides, can be divided into two categories depending on the nature of the reaction: volatile and non-volatile. Volatile cycles utilize metal species that sublime during the reduction of the metal oxides, and non-volatile cycles can be further categorized into stoichiometric cycles and non-stoichiometric cycles. During the reduction half-cycle of the stochiometric cycle, the metal oxide is reduced and forms a new metal oxide with different oxidation states (FeO → 3FeO + 1/2 O); a non-stochiometric cycle's reduction of the metal oxide will produce vacancies, often oxygen vacancies, but the crystal structure remains stable and only a portion of the metal atoms change their oxidation state (CeO → CeO + δ/2 O). | 0 | Theoretical and Fundamental Chemistry |
A bioinformatic search of the sequence databases identified one homologue of the MRS2 gene of yeast in a range of metazoans. The protein has a very similar sequence and predicted TM topology to the yeast protein, and the GMN motif is intact at the end of the first TM domain. The human protein, hsaMrs2p, has been localised to the mitochondrial membrane in mouse cells using a GFP fusion protein.
Very little is known about the Mg transport characteristics of the protein in mammals, but Zsurka et al. (2001) has shown that the human Mrs2p complements the mrs2 mutants in the yeast mitochondrial Mg uptake system. | 1 | Applied and Interdisciplinary Chemistry |
For MLLL, a total of five geometric isomers and six stereoisomers are possible.
# One isomer in which all three pairs of identical ligands are trans
# Three isomers in which one pair of identical ligands (L or L or L) is trans while the other two pairs of ligands are mutually cis.
# Two enantiomeric pair in which all three pairs of identical ligands are cis. These are equivalent to the Δ vs Λ isomers mentioned above.
The number of possible isomers can reach 30 for an octahedral complex with six different ligands (in contrast, only two stereoisomers are possible for a tetrahedral complex with four different ligands). The following table lists all possible combinations for monodentate ligands:
Thus, all 15 diastereomers of MLLLLLL are chiral, whereas for MLLLLL, six diastereomers are chiral and three are not (the ones where L are trans). One can see that octahedral coordination allows much greater complexity than the tetrahedron that dominates organic chemistry. The tetrahedron MLLLL exists as a single enantiomeric pair. To generate two diastereomers in an organic compound, at least two carbon centers are required. | 0 | Theoretical and Fundamental Chemistry |
The general equation can then be written as
where the "force" term corresponds to the forces exerted on the particles by an external influence (not by the particles themselves), the "diff" term represents the diffusion of particles, and "coll" is the collision term – accounting for the forces acting between particles in collisions. Expressions for each term on the right side are provided below.
Note that some authors use the particle velocity instead of momentum ; they are related in the definition of momentum by . | 1 | Applied and Interdisciplinary Chemistry |
In fluid mechanics, dewetting is one of the processes that can occur at a solid–liquid, solid–solid or liquid–liquid interface. Generally, dewetting describes the process of retraction of a fluid from a non-wettable surface it was forced to cover. The opposite process—spreading of a liquid on a substrate—is called wetting. The factor determining the spontaneous spreading and dewetting for a drop of liquid placed on a solid substrate with ambient gas, is the so-called spreading coefficient :
where is the solid-gas surface tension, is the solid-liquid surface tension and is the liquid-gas surface tension (measured for the mediums before they are brought in contact with each other).
When , the spontaneous spreading occurs, and if , partial wetting is observed, meaning the liquid will only cover the substrate to some extent.
The equilibrium contact angle is determined from the Young–Laplace equation.
Spreading and dewetting are important processes for many applications, including adhesion, lubrication, painting, printing, and protective coating. For most applications, dewetting is an unwanted process, because it destroys the applied liquid film.
Dewetting can be inhibited or prevented by photocrosslinking the thin film prior to annealing, or by incorporating nanoparticle additives into the film.
Surfactants can have a significant effect on the spreading coefficient. When a surfactant is added, its amphiphilic properties cause it to be more energetically favorable to migrate to the surface, decreasing the interfacial tension and thus increasing the spreading coefficient (i.e. making S more positive). As more surfactant molecules are absorbed into the interface, the free energy of the system decreases in tandem to the surface tension decreasing, eventually causing the system to become completely wetting.
In biology, by analogy with the physics of liquid dewetting, the process of tunnel formation through endothelial cells has been referred to as cellular dewetting. | 0 | Theoretical and Fundamental Chemistry |
Cultivation practices include polyculture (growing multiple types of plants), crop rotation, planting crops in areas where the pests that damage them do not live, timing planting according to when pests will be least problematic, and use of trap crops that attract pests away from the real crop. Trap crops have successfully controlled pests in some commercial agricultural systems while reducing pesticide usage. In other systems, trap crops can fail to reduce pest densities at a commercial scale, even when the trap crop works in controlled experiments. | 1 | Applied and Interdisciplinary Chemistry |
The APPI interface for LC–MS was developed simultaneously by Bruins and Syage in 2000. APPI is another LC–MS ion source/ interface for the analysis of neutral compounds that cannot be ionized using ESI. This interface is similar to the APCI ion source, but instead of a corona discharge, the ionization occurs by using photons coming from a discharge lamp. In the direct-APPI mode, singly charged analyte molecular ions are formed by absorption of a photon and ejection of an electron. In the dopant-APPI mode, an easily ionizable compound (Dopant) is added to the mobile phase or the nebulizing gas to promote a reaction of charge-exchange between the dopant molecular ion and the analyte. The ionized sample is later transferred to the mass analyzer at high vacuum as it passes through small orifice skimmers. | 0 | Theoretical and Fundamental Chemistry |
EBSD is conducted using an SEM equipped with an EBSD detector containing at least a phosphor screen, compact lens and low-light Charge-coupled device (CCD) or Complementary metal–oxide–semiconductor (CMOS) camera. , commercially available EBSD systems typically come with one of two different CCD cameras: for fast measurements, the CCD chip has a native resolution of 640×480 pixels; for slower, and more sensitive measurements, the CCD chip resolution can go up to 1600×1200 pixels.
The biggest advantage of the high-resolution detectors is their higher sensitivity, and therefore the information within each diffraction pattern can be analysed in more detail. For texture and orientation measurements, the diffraction patterns are binned to reduce their size and computational times. Modern CCD-based EBSD systems can index patterns at a speed of up to 1800 patterns/second. This enables rapid and rich microstructural maps to be generated. | 0 | Theoretical and Fundamental Chemistry |
An organophosphinic acid is an organophosphorus compound with the formula RHPOH (R = alkyl, aryl). One or both P-H bonds in the parent hypophosphorous acid (aka phosphinic acid) are replaced by organic groups. The Cyanex family of dialkylphosphinic acids are used in hydrometallurgy to extract metals from ores. | 0 | Theoretical and Fundamental Chemistry |
For fully developed internal laminar flow, the Nusselt numbers tend towards a constant value for long pipes.
For internal flow:
where:
:D = Hydraulic diameter
:k = thermal conductivity of the fluid
:h = convective heat transfer coefficient | 1 | Applied and Interdisciplinary Chemistry |
A "photoelectrochemical cell" is one of two distinct classes of device. The first produces electrical energy similarly to a dye-sensitized photovoltaic cell, which meets the standard definition of a photovoltaic cell. The second is a photoelectrolytic cell, that is, a device which uses light incident on a photosensitizer, semiconductor, or aqueous metal immersed in an electrolytic solution to directly cause a chemical reaction, for example to produce hydrogen via the electrolysis of water.
Both types of device are varieties of solar cell, in that a photoelectrochemical cell's function is to use the photoelectric effect (or, very similarly, the photovoltaic effect) to convert electromagnetic radiation (typically sunlight) either directly into electrical power, or into something which can itself be easily used to produce electrical power (hydrogen, for example, can be burned to create electrical power, see photohydrogen). | 0 | Theoretical and Fundamental Chemistry |
Recombinant subunit vaccines are safe for administration. However, mild local reactions, including induration and swelling of the injection site, along with fever, fatigue and headache may be encountered after vaccination. Occurrence of severe hypersensitivity reactions and anaphylaxis is rare, but can possibly lead to deaths of individuals. Adverse effects can vary among populations depending on their physical health condition, age, gender and genetic predisposition.
Recombinant subunit vaccines are contraindicated to people who have experienced allergic reactions and anaphylaxis to antigens or other components of the vaccines previously. Furthermore, precautions should be taken when administering vaccines to people who are in diseased state and during pregnancy, in which their injections should be delayed until their conditions become stable and after childbirth respectively. | 1 | Applied and Interdisciplinary Chemistry |
Senapathy discovered that stop codons occur as key parts in every genetic element in eukaryotic genes. The table and figure show that the key parts of the core promoter elements, the lariat signal, the donor and acceptor splice signals, and the poly-A addition signal consist of one or more stop codons. This finding corroborates the split gene theory's claim that the underlying reason for the complete split gene paradigm is the origin of split genes from random DNA sequences, wherein random distribution of an extremely high frequency of stop codons were used by nature to define these genetic elements. | 1 | Applied and Interdisciplinary Chemistry |
The advantage of TEC-RED over SAGE is that no restriction endonuclease is needed for the initial linker binding. This prevents bias associated with restriction site sequences that will be missing from some genes, as is seen in SAGE. The ability to have a snapshot of specific RNA isoforms allows the deduction of differential regulation of isoforms through alternative selection of promoters. This may also aid in the discernment of expression patterns unique to the SL1 or SL2 sequence. TEC-RED also allows characterization of the 5’ ends of RNA produced and therefore of isoforms that differ by the amino terminal splicing. The technology permits the determination and verification of all known and unknown genes that may be predicted as well as the 5’ splice isoforms or 5’ RNA ends that may be produced. Using TEC-RED in conjunction with SAGE or a modified protocol will allow discernment of the 5’ and 3’ ends of transcripts, respectively. The identification of alternative splice variants, and possibly the relative quantities, containing a trans-spliced leader sequence is therefore possible. | 1 | Applied and Interdisciplinary Chemistry |
Hydrogen cyanide has been discussed as a precursor to amino acids and nucleic acids, and is proposed to have played a part in the origin of life. Although the relationship of these chemical reactions to the origin of life theory remains speculative, studies in this area have led to discoveries of new pathways to organic compounds derived from the condensation of HCN (e.g. Adenine). | 0 | Theoretical and Fundamental Chemistry |
A more general Couette flow includes a constant pressure gradient in a direction parallel to the plates. The Navier–Stokes equations are
where is the dynamic viscosity. Integrating the above equation twice and applying the boundary conditions (same as in the case of Couette flow without pressure gradient) gives
The pressure gradient can be positive (adverse pressure gradient) or negative (favorable pressure gradient). In the limiting case of stationary plates (), the flow is referred to as Plane Poiseuille flow, and has a symmetric (with reference to the horizontal mid-plane) parabolic velocity profile. | 1 | Applied and Interdisciplinary Chemistry |
From the 18th to the mid-19th century, the whaling industry prospered. By some reports, nearly 50,000 whales, including sperm whales, were killed each year. Throughout the 19th century, "millions of whales were killed for their oil, whalebone, and ambergris" to fuel profits, and they soon became endangered as a species as a result. Due to studies showing that the whale populations were being threatened, the International Whaling Commission instituted a moratorium on commercial whaling in 1982. Although ambergris is not harvested from whales, many countries also ban the trade of ambergris as part of the more general ban on the hunting and exploitation of whales.
Urine, faeces, and ambergris (that has been naturally excreted by a sperm whale) are waste products not considered parts or derivatives of a CITES species and are therefore not covered by the provisions of the convention.
Countries where ambergris trade is illegal include:
* Australia – Under federal law, the export and import of ambergris for commercial purposes is banned by the Environment Protection and Biodiversity Conservation Act 1999. The various states and territories have additional laws regarding ambergris.
* United States – The possession and trade of ambergris is prohibited by the Endangered Species Act of 1973.
* India – Sale or possession is illegal under the Wild Life (Protection) Act, 1972.
Countries where trade of ambergris is legal include:
* United Kingdom
* France
* Switzerland
* Maldives | 1 | Applied and Interdisciplinary Chemistry |
Assembly of the SNAREs into the "trans" complexes likely bridges the opposing lipid bilayers of membranes belonging to cell and secretory granule, bringing them in proximity and inducing their fusion. The influx of calcium into the cell triggers the completion of the assembly reaction, which is mediated by an interaction between the putative calcium sensor, synaptotagmin, with membrane lipids and/or the partially assembled SNARE complex.
One hypothesis implicates the molecule Complexin within the SNARE complex and its interaction with the molecule synaptotagmin. Known as the "clamp" hypothesis, the presence of complexin normally inhibits the fusion of the vesicle to the cell membrane. However, binding of calcium ions to synaptotagmin triggers the complexin to be released or inactivated, so that the vesicle is then free to fuse.
According to the "zipper" hypothesis, the complex assembly starts at the N-terminal parts of SNARE motifs and proceeds towards the C-termini that anchor interacting proteins in membranes. Formation of the "trans"-SNARE complex proceeds through an intermediate complex composed of SNAP-25 and syntaxin-1, which later accommodates synaptobrevin-2 (the quoted syntaxin and synaptobrevin isotypes participate in neuronal neuromediator release).
Based on the stability of the resultant cis-SNARE complex, it has been postulated that energy released during the assembly process serves as a means for overcoming the repulsive forces between the membranes. There are several models that propose explanation of a subsequent step – the formation of stalk and fusion pore, but the exact nature of these processes remains debated. Two of the most prominent models on fusion pore formation are the lipid-lined and protein-lined fusion pore theories. | 1 | Applied and Interdisciplinary Chemistry |
Nucleofection is an electroporation-based transfection method which enables transfer of nucleic acids such as DNA and RNA into cells by applying a specific voltage and reagents. Nucleofection, also referred to as nucleofector technology, was invented by the biotechnology company Amaxa. "Nucleofector" and "nucleofection" are trademarks owned by Lonza Cologne AG, part of the Lonza Group. | 1 | Applied and Interdisciplinary Chemistry |
Lactols can participate in a variety of chemical reactions including:
* Oxidation to form lactones
* Reaction with alcohols to form acetals
** The reaction of sugars with alcohols or other nucleophiles leads to the formation of glycosides
* Reduction (deoxygenation) to form cyclic ethers | 0 | Theoretical and Fundamental Chemistry |
* Milorganite is the trademark of a biosolids fertilizer produced by the Milwaukee Metropolitan Sewerage District. The recycled organic nitrogen fertilizer from the Jones Island Water Reclamation Facility in Milwaukee, Wisconsin, is sold throughout North America, reduces the need for manufactured nutrients.
* Loop is the trademark of a biosolids soil amendment produced by the King County Wastewater Treatment Division. Loop has been blended into GroCo, a commercially available compost product, since 1976. Several local farms and forests also use Loop directly.
* TAGRO is short for "Tacoma Grow" and is produced by the City of Tacoma, Washington, since 1991.
* Dillo Dirt has been produced by the City of Austin, Texas, since 1989.
* Biosolids are applied as fertilizer in the Central Wheatbelt of Australia as a recycling program by the Water Corporation. | 1 | Applied and Interdisciplinary Chemistry |
The photoelectric effect is the emission of electrons from a material caused by electromagnetic radiation (light). Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physics, solid state, and quantum chemistry to draw inferences about the properties of atoms, molecules and solids. The effect has found use in electronic devices specialized for light detection and precisely timed electron emission.
The experimental results disagree with classical electromagnetism, which predicts that continuous light waves transfer energy to electrons, which would then be emitted when they accumulate enough energy. An alteration in the intensity of light would theoretically change the kinetic energy of the emitted electrons, with sufficiently dim light resulting in a delayed emission. The experimental results instead show that electrons are dislodged only when the light exceeds a certain frequency—regardless of the lights intensity or duration of exposure. Because a low-frequency beam at a high intensity does not build up the energy required to produce photoelectrons, as would be the case if lights energy accumulated over time from a continuous wave, Albert Einstein proposed that a beam of light is not a wave propagating through space, but a swarm of discrete energy packets, known as photons—term coined by Gilbert N. Lewis in 1926.
Emission of conduction electrons from typical metals requires a few electron-volt (eV) light quanta, corresponding to short-wavelength visible or ultraviolet light. In extreme cases, emissions are induced with photons approaching zero energy, like in systems with negative electron affinity and the emission from excited states, or a few hundred keV photons for core electrons in elements with a high atomic number. Study of the photoelectric effect led to important steps in understanding the quantum nature of light and electrons and influenced the formation of the concept of wave–particle duality. Other phenomena where light affects the movement of electric charges include the photoconductive effect, the photovoltaic effect, and the photoelectrochemical effect. | 0 | Theoretical and Fundamental Chemistry |
Organic esters, ketones, and aldehydes with an α-hydrogen ( bond adjacent to the carbonyl group) often form enols. The reaction involves migration of a proton () from carbon to oxygen:
In the case of ketones, the conversion is called a keto-enol tautomerism, although this name is often more generally applied to all such tautomerizations. Usually the equilibrium constant is so small that the enol is undetectable spectroscopically.
In some compounds with two (or more) carbonyls, the enol form becomes dominant. The behavior of 2,4-pentanedione illustrates this effect:
Enols are derivatives of vinyl alcohol, with a connectivity. Deprotonation of organic carbonyls gives the enolate anion, which are a strong nucleophile. A classic example for favoring the keto form can be seen in the equilibrium between vinyl alcohol and acetaldehyde (K = [enol]/[keto] ≈ 3). In 1,3-diketones, such as acetylacetone (2,4-pentanedione), the enol form is favored.
The acid-catalyzed conversion of an enol to the keto form proceeds by proton transfer from O to carbon. The process does not occur intramolecularly, but requires participation of solvent or other mediators. | 0 | Theoretical and Fundamental Chemistry |
Surface tension is visible in other common phenomena, especially when surfactants are used to decrease it:
* Soap bubbles have very large surface areas with very little mass. Bubbles in pure water are unstable. The addition of surfactants, however, can have a stabilizing effect on the bubbles (see Marangoni effect). Surfactants actually reduce the surface tension of water by a factor of three or more.
* Emulsions are a type of colloidal dispersion in which surface tension plays a role. Tiny droplets of oil dispersed in pure water will spontaneously coalesce and phase separate. The addition of surfactants reduces the interfacial tension and allow for the formation of oil droplets in the water medium (or vice versa). The stability of such formed oil droplets depends on many different chemical and environmental factors. | 0 | Theoretical and Fundamental Chemistry |
Schematic view and experimental setups of the RIC wettability testing method is described in Figure 1. Core plugs are divided into 3–4 core samples, each of 3.8 cm average diameter and 1.5 cm length. The lateral area of each core sample is sealed by epoxy resin to ensure one-dimensional liquid penetration into the core by imbibition. A hook is mounted on top side of the core sample.
The RIC setup includes a beaker to host the imbibing fluid. A thin rope connects the core sample to a high-precision balance (0.001 gm accurate). A hanging core sample is positioned with the bottom part of the sample barely touching the imbibing fluid in the beaker. Relative saturation as well as mass of core samples starts to change during imbibition. A computer connected to a balance continuously monitors the core sample mass change over time. Plots of squared mass change versus time are generated. | 1 | Applied and Interdisciplinary Chemistry |
Petrobactin is a bis-catechol siderophore found in M. hydrocarbonoclasticus, A. macleodii, and the anthrax-producing B. anthracis. Like other siderophores petrobactin is a highly specific iron(III) transport ligand, contributing to the marine microbial uptake of environmental iron.
The iron-chelated petrobactin complex readily undergoes a photolytic oxidative decarboxylation due to its α-hydroxy carboxylate group, converting iron(III) to the more biologically useful iron(II). | 1 | Applied and Interdisciplinary Chemistry |
It was clear to many scientists at Columbia that they should try to detect the energy released in the nuclear fission of uranium from neutron bombardment. On 25 January 1939, a Columbia University group conducted the first nuclear fission experiment in the United States, which was done in the basement of Pupin Hall. The experiment involved placing uranium oxide inside of an ionization chamber and irradiating it with neutrons, and measuring the energy thus released. The next day, the Fifth Washington Conference on Theoretical Physics began in Washington, D.C., under the joint auspices of The George Washington University and the Carnegie Institution of Washington. From there, the news on nuclear fission spread even further, which fostered many more experimental demonstrations.
Bohr and Wheeler overhauled the liquid drop model to explain the mechanism of nuclear fission, with conspicuous success. Their paper appeared in Physical Review on 1 September 1939, the day Germany invaded Poland, starting World War II in Europe. As the experimental physicists studied fission, they uncovered more puzzling results. George Placzek asked Bohr why uranium fissioned with both very fast and very slow neutrons. Walking to a meeting with Wheeler, Bohr had an insight that the fission at low energies was due to the uranium-235 isotope, while at high energies it was mainly due to the far more abundant uranium-238 isotope. This was based on Meitner's 1937 measurements of the neutron capture cross-sections. This would be experimentally verified in February 1940, after Alfred Nier was able to produce sufficient pure uranium-235 for John R. Dunning, Aristid von Grosse and Eugene T. Booth to test.
Other scientists resumed the search for the elusive element 93, which seemed to be straightforward, as they now knew it resulted from the 23-minute half-life. At the Radiation Laboratory in Berkeley, California, Emilio Segrè and Edwin McMillan used the cyclotron to create the isotope. They then detected a beta activity with a 2-day half-life, but it had rare-earth element chemical characteristics, and element 93 was supposed to have chemistry akin to rhenium. It was therefore overlooked as just another fission product. Another year passed before McMillan and Philip Abelson determined that the 2-day half-life element was that of the elusive element 93, which they named "neptunium". They paved the way for the discovery by Glenn Seaborg, Emilio Segrè and Joseph W. Kennedy of element 94, which they named "plutonium" in 1941.
Another avenue of research, spearheaded by Meitner, was to determine if other elements could fission after being irradiated with neutrons. It was soon determined that thorium and protactinium could. Measurements were also made of the amount of energy released. Hans von Halban, Frédéric Joliot-Curie and Lew Kowarski demonstrated that uranium bombarded by neutrons emitted more neutrons than it absorbed, suggesting the possibility of a nuclear chain reaction. Fermi and Anderson did so too a few weeks later. It was apparent to many scientists that, in theory at least, an extremely powerful energy source could be created, although most still considered an atomic bomb an impossibility. | 0 | Theoretical and Fundamental Chemistry |
Due to the ability to introduce diverse functionality into COFs’ structure, catalytic sites can be fine-tuned in conjunction with other advantageous properties like conductivity and stability to afford efficient and selective catalysts. COFs have been used as heterogeneous catalysts in organic, electrochemical, as well as photochemical reactions. | 0 | Theoretical and Fundamental Chemistry |
*marsh gas/air
*carburetted hydrogen
*light carburetted hydrogen
*heavy inflammable air
*dicarburet of hydrogen
*fire-damp
*gas of the acetates | 1 | Applied and Interdisciplinary Chemistry |
As the combustion flue gas exits the boiler it is routed through a rotating flat basket of metal mesh which picks up heat and returns it to incoming fresh air as the basket rotates. This is called the air preheater. The gas exiting the boiler is laden with fly ash, which are tiny spherical ash particles. The flue gas contains nitrogen along with combustion products carbon dioxide, sulfur dioxide, and nitrogen oxides. The fly ash is removed by fabric bag filters in baghouses or electrostatic precipitators. Once removed, the fly ash byproduct can sometimes be used in the manufacturing of concrete. This cleaning up of flue gases, however, only occurs in plants that are fitted with the appropriate technology. Still, the majority of coal-fired power stations in the world do not have these facilities. Legislation in Europe has been efficient to reduce flue gas pollution. Japan has been using flue gas cleaning technology for over 30 years and the US has been doing the same for over 25 years. China is now beginning to grapple with the pollution caused by coal-fired power stations.
Where required by law, the sulfur and nitrogen oxide pollutants are removed by stack gas scrubbers which use a pulverized limestone or other alkaline wet slurry to remove those pollutants from the exit stack gas. Other devices use catalysts to remove nitrous oxide compounds from the flue-gas stream. The gas travelling up the flue-gas stack may by this time have dropped to about . A typical flue-gas stack may be tall to disperse the remaining flue gas components in the atmosphere. The tallest flue-gas stack in the world is tall at the Ekibastuz GRES-2 Power Station in Kazakhstan.
In the United States and a number of other countries, atmospheric dispersion modeling studies are required to determine the flue-gas stack height needed to comply with the local air pollution regulations. The United States also requires the height of a flue-gas stack to comply with what is known as the "good engineering practice" (GEP) stack height. In the case of existing flue gas stacks that exceed the GEP stack height, any air pollution dispersion modeling studies for such stacks must use the GEP stack height rather than the actual stack height. | 1 | Applied and Interdisciplinary Chemistry |
The stereochemistry of macromolecules can be defined even more precisely with the introduction of triads. An isotactic triad (mm) is made up of two adjacent meso diads, a syndiotactic triad (also spelled syndyotactic) (rr) consists of two adjacent racemo diads, and a heterotactic triad (rm) is composed of a racemo diad adjacent to a meso diad. The mass fraction of isotactic (mm) triads is a common quantitative measure of tacticity.
When the stereochemistry of a macromolecule is considered to be a Bernoulli process, the triad composition can be calculated from the probability P of a diad being meso. For example, when this probability is 0.25 then the probability of finding:
*an isotactic triad is P, or 0.0625
*an heterotactic triad is 2P(1–P), or 0.375
*a syndiotactic triad is (1–P), or 0.5625
with a total probability of 1. Similar relationships with diads exist for tetrads. | 0 | Theoretical and Fundamental Chemistry |
A number of processes of surface growth in areas ranging from mechanics of growing gravitational bodies through propagating fronts of phase transitions, epitaxial growth of nanostructures and 3D printing, growth of plants, and cell mobility require non-Euclidean description because of incompatibility of boundary conditions and different mechanisms of developing stresses at interfaces. Indeed, these mechanisms result in the curving of initially flat elements of the body and changing separation between different elements of it (especially in the soft matter). Gradual accumulation of deformations under the influx of accumulating mass results in the memory-conscious grows of the body and makes strains the subject of long-range forces. As a result of all above factors, generic non-Euclidean growth is described in terms of Riemannian geometry with a space- and time-dependent curvature. | 0 | Theoretical and Fundamental Chemistry |
The degree of dissociation α (also known as degree of ionization), is a way of representing the strength of an acid. It is defined as the ratio of the number of ionized molecules and the number of molecules dissolved in water. It can be represented as a decimal number or as a percentage. One can classify strong acids as those having ionization degrees above 30%, weak acids as those with α below 30%, and the rest as moderate acids, at a specified molar concentration. | 0 | Theoretical and Fundamental Chemistry |
Recently, there had been discussion connecting copy number variations to gene families. Gene families are defined as a set of related genes that serve similar functions but have minor temporal or spatial differences and these genes likely derived from one ancestral gene. The main reason copy number variations are connected to gene families is that there is a possibility that genes in a family may have derived from one ancestral gene which got duplicated into different copies. Mutations accumulate through time in the genes and with natural selection acting on the genes, some mutations lead to environmental advantages allowing those genes to be inherited and eventually clear gene families are separated out. An example of a gene family that may have been created due to copy number variations is the globin gene family. The globin gene family is an elaborate network of genes consisting of alpha and beta globin genes including genes that are expressed in both embryos and adults as well as pseudogenes. These globin genes in the globin family are all well conserved and only differ by a small portion of the gene, indicating that they were derived from a common ancestral gene, perhaps due to duplication of the initial globin gene.
Research has shown that copy number variations are significantly more common in genes that encode proteins that directly interact with the environment than proteins that are involved in basic cellular activities. It was suggested that the gene dosage effect accompanying copy number variation may lead to detrimental effects if essential cellular functions are disrupted, therefore proteins involved in cellular pathways are subjected to strong purifying selection. In addition, proteins function together and interact with proteins of other pathways, therefore it is important to view the effects of natural selection on bio-molecular pathways rather than on individual proteins. With that being said, it was found that proteins in the periphery of the pathway are enriched in copy number variations whereas proteins in the center of the pathways are depleted in copy number variations. It was explained that proteins in the periphery of the pathway interact with fewer proteins and so a change in protein dosage affected by a change in copy number may have a smaller effect on the overall outcome of the cellular pathway.
In the past few years, researchers seem to have shifted their focus from detecting, locating, and sequencing copy number variations to in depth analyses of the role of these copy number variations in the human genome and in nature in general. Evidence is needed to further validate the relationship between copy number variations and gene families as well as the role that natural selection plays in shaping these relationships and changes. Furthermore, researchers are also aiming to elucidate the molecular mechanisms involved in copy number variations as it may reveal essential information regarding structural variations in general. Taking a step back, the area of structural variation in the human genome seems to be a rapidly growing research topic. Not only can these research data provide additional evidence for evolution and natural selection, it can also be used to develop treatments for a wide range of genetic diseases. | 1 | Applied and Interdisciplinary Chemistry |
Recently, a nickel-catalyzed Sonogashira coupling has been developed which allows for the coupling of non-activated alkyl halides to acetylene without the use of palladium, although a copper co-catalyst is still needed. It has also been reported that gold can be used as a heterogeneous catalyst, which was demonstrated in the coupling of phenylacetylene and iodobenzene with an Au/CeO catalyst. In this case, catalysis occurs heterogeneously on the Au nanoparticles, with Au(0) as the active site. Selectivity to the desirable cross coupling product was also found to be enhanced by supports such as CeO and LaO. Additionally, iron-catalyzed Sonogashira couplings have been investigated as relatively cheap and non-toxic alternatives to palladium. Here, FeCl is proposed to act as the transition-metal catalyst and CsCO as the base, thus theoretically proceeding through a palladium-free and copper-free mechanism.
While the copper-free mechanism has been shown to be viable, attempts to incorporate the various transition metals mentioned above as less expensive alternatives to palladium catalysts have shown a poor track record of success due to contamination of the reagents with trace amounts of palladium, suggesting that these theorized pathways are extremely unlikely, if not impossible, to achieve.
Studies have shown that organic and inorganic starting materials can also contain enough (ppb level) palladium for the coupling. | 0 | Theoretical and Fundamental Chemistry |
where is the velocity of the fluid just after interacting with the rotor. This can be written as . The radial component of the velocity will be zero; this must be true if we are to use the annular ring approach; to assume otherwise would suggest interference between annular rings at some point downstream. Since we assume that there is no change in axial velocity across the disc, . Angular momentum must be conserved in an isolated system. Thus the rotation of the wake must not die away. Thus in the downstream section is constant. Thus Bernoulli simplifies in the downstream section:
In other words, the Bernoulli equations up and downstream of the rotor are the same as the Bernoulli expressions in the Betz model. Therefore, we can use results such as power extraction and wake speed that were derived in the Betz model i.e.
This allows us to calculate maximum power extraction for a system that includes a rotating wake. This can be shown to give the same value as that of the Betz model i.e. 0.59. This method involves recognising that the torque generated in the rotor is given by the following expression:
with the necessary terms defined immediately below. | 1 | Applied and Interdisciplinary Chemistry |
Polymerization is the process of combining many small molecules known as monomers into a covalently bonded chain or network. During the polymerization process, some chemical groups may be lost from each monomer. This happens in the polymerization of PET polyester. The monomers are terephthalic acid (HOOCCHCOOH) and ethylene glycol (HOCHCHOH) but the repeating unit is OCCHCOOCHCHO, which corresponds to the combination of the two monomers with the loss of two water molecules. The distinct piece of each monomer that is incorporated into the polymer is known as a repeat unit or monomer residue.
Synthetic methods are generally divided into two categories, step-growth polymerization and chain polymerization. The essential difference between the two is that in chain polymerization, monomers are added to the chain one at a time only, such as in polystyrene, whereas in step-growth polymerization chains of monomers may combine with one another directly, such as in polyester. Step-growth polymerization can be divided into polycondensation, in which low-molar-mass by-product is formed in every reaction step, and polyaddition.
Newer methods, such as plasma polymerization do not fit neatly into either category. Synthetic polymerization reactions may be carried out with or without a catalyst. Laboratory synthesis of biopolymers, especially of proteins, is an area of intensive research. | 0 | Theoretical and Fundamental Chemistry |
Relative entropy is directly related to the Fisher information metric. This can be made explicit as follows. Assume that the probability distributions and are both parameterized by some (possibly multi-dimensional) parameter . Consider then two close by values of and so that the parameter differs by only a small amount from the parameter value . Specifically, up to first order one has (using the Einstein summation convention)
with a small change of in the direction, and the corresponding rate of change in the probability distribution. Since relative entropy has an absolute minimum 0 for , i.e. , it changes only to second order in the small parameters . More formally, as for any minimum, the first derivatives of the divergence vanish
and by the Taylor expansion one has up to second order
where the Hessian matrix of the divergence
must be positive semidefinite. Letting vary (and dropping the subindex 0) the Hessian defines a (possibly degenerate) Riemannian metric on the parameter space, called the Fisher information metric. | 0 | Theoretical and Fundamental Chemistry |
The CSI method is not without some shortcomings. In particular, its performance drops if chemical shift assignments are mis-referenced or incomplete. It is also quite sensitive to the choice of random coil shifts used to calculate the secondary shifts and it generally identifies alpha helices (>85% accuracy) better than beta strands (<75% accuracy) regardless of the choice of random coil shifts. Furthermore, the CSI method does not identify other kinds of secondary structures, such as β-turns. Because of these shortcomings, a number of alternative CSI-like approaches have been proposed. These include: 1) a prediction method that employs statistically derived chemical shift/structure potentials (PECAN); 2) a probabilistic approach to secondary structure identification (PSSI); 3) a method that combines secondary structure predictions from sequence data and chemical shift data (PsiCSI), 4) a secondary structure identification approach that uses pre-specified chemical shift patterns (PLATON) and 5) a two-dimensional cluster analysis method known as 2DCSi. The performance of these newer methods is generally slightly better (2-4%) than the original CSI method. | 0 | Theoretical and Fundamental Chemistry |
There are no expected pharmacokinetic interactions between thalidomide and other medicines due to its neutral effects on P-glycoprotein and the cytochrome P450 family. It may interact with sedatives due to its sedative action and bradycardic agents, like beta-blockers, due to its bradycardia-inducing effects. Risk of peripheral neuropathy may be increased by concomitant treatment of thalidomide with other agents known to cause peripheral neuropathy. The risk of venous thromboembolisms with thalidomide seems to be increased when patients are treated with oral contraceptives or other cytotoxic agents (including doxorubicin and melphalan) concurrently. Thalidomide may interfere with various contraceptives, and hence it is advised that women of reproductive age use at least two different means of contraception to ensure that no child will be conceived while they are taking thalidomide. | 0 | Theoretical and Fundamental Chemistry |
The Chichibabin pyridine synthesis was reported in 1924 and the basic approach underpins several industrial routes. In its general form, the reaction involves the condensation reaction of aldehydes, ketones, α,β-unsaturated carbonyl compounds, or any combination of the above, in ammonia or ammonia derivatives. Application of the Chichibabin pyridine synthesis suffer from low yields, often about 30%, however the precursors are inexpensive. In particular, unsubstituted pyridine is produced from formaldehyde and acetaldehyde. First, acrolein is formed in a Knoevenagel condensation from the acetaldehyde and formaldehyde. The acrolein then condenses with acetaldehyde and ammonia to give dihydropyridine, which is oxidized to pyridine. This process is carried out in a gas phase at 400–450 °C. Typical catalysts are modified forms of alumina and silica. The reaction has been tailored to produce various methylpyridines. | 0 | Theoretical and Fundamental Chemistry |
The glycosylation reaction involves the coupling of a glycosyl donor and a glycosyl acceptor via initiation using an activator under suitable reaction conditions.
* A glycosyl donor is a sugar with a suitable leaving group at the anomeric position. This group, under the reaction conditions, is activated and via the formation of an oxocarbenium is eliminated leaving an electrophilic anomeric carbon.
* A glycosyl acceptor is a sugar with an unprotected nucleophilic hydroxyl group which may attack the carbon of the oxocarbenium ion formed during the reaction and allow for the formation of the glycosidic bond.
An activator is commonly a Lewis acid which enables the leaving group at the anomeric position to leave and results in the formation of the oxocarbenium ion. | 0 | Theoretical and Fundamental Chemistry |
The Candelabro Trivulzio in the Milan Cathedral, a seven-branch bronze candlestick measuring 5 meters in height, has a base and lower part decorated with intricately designed ornament which is considered by many to be French work of the 13th century; the upper part with the branches was added in the second half of the 16th century. A portion of a similar object showing the same intricate decoration existed formerly at Reims, but was unfortunately destroyed during World War I.
In the 16th century the names of Germain Pilon and Jean Goujon are sufficient evidence of the ability to work in bronze. A great outburst of artistic energy is seen from the beginning of the 17th century, when works in ormolu or gilt bronze were produced in huge quantities. The craftsmanship is magnificent and of the highest quality, the designs at first refined and symmetrical; but later, under the influence of the rococo style, introduced in 1723, aiming only at gorgeous magnificence. It was all in keeping with the spirit of the age, and in their own sumptuous setting these fine candelabra, sconces, vases, clocks and rich mountings of furniture are entirely harmonious. The "ciseleur" and the "fondeur", such as Pierre Gouthière and Jacques Caffieri, associated themselves with the makers of fine furniture and of delicate Sèvres porcelain, the result being extreme richness and handsome effect. The style was succeeded after the French Revolution by a stiff, classical manner which, although having a charm of its own, lacks the life and freedom of earlier work. In London the styles may be studied in the Wallace collection, Manchester Square, and at the Victoria and Albert Museum, South Kensington; in New York at the Metropolitan Museum. | 1 | Applied and Interdisciplinary Chemistry |
Amongst members of the ETS family, there is extensive conservation in the DNA-binding ETS domain and, therefore, a lot of redundancy in DNA binding. It is thought that interactions with other proteins (eg: Modulator of the activity of Ets called Mae) is one way in which specific binding to DNA is achieved. Transcription factor Ets are a site of signalling convergence.
ETS factors act as transcriptional repressors, transcriptional activators, or both. | 1 | Applied and Interdisciplinary Chemistry |
Long-term use of high doses of tramadol causes physical dependence and withdrawal syndrome. These include both symptoms typical of opioid withdrawal and those associated with serotonin–norepinephrine reuptake inhibitor (SNRI) withdrawal; symptoms include numbness, tingling, paresthesia, and tinnitus. Psychiatric symptoms may include hallucinations, paranoia, extreme anxiety, panic attacks, and confusion. In most cases, tramadol withdrawal will set in 12–20 hours after the last dose, but this can vary. Tramadol withdrawal typically lasts longer than that of other opioids. Seven days or more of acute withdrawal symptoms can occur as opposed to typically 3 or 4 days for other codeine analogs. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, potential flow or irrotational flow refers to a description of a fluid flow with no vorticity in it. Such a description typically arises in the limit of vanishing viscosity, i.e., for an inviscid fluid and with no vorticity present in the flow.
Potential flow describes the velocity field as the gradient of a scalar function: the velocity potential. As a result, a potential flow is characterized by an irrotational velocity field, which is a valid approximation for several applications. The irrotationality of a potential flow is due to the curl of the gradient of a scalar always being equal to zero.
In the case of an incompressible flow the velocity potential satisfies Laplace's equation, and potential theory is applicable. However, potential flows also have been used to describe compressible flows and Hele-Shaw flows. The potential flow approach occurs in the modeling of both stationary as well as nonstationary flows.
Applications of potential flow include: the outer flow field for aerofoils, water waves, electroosmotic flow, and groundwater flow. For flows (or parts thereof) with strong vorticity effects, the potential flow approximation is not applicable. | 1 | Applied and Interdisciplinary Chemistry |
* Boden und Bodenbildung Kolloidchemischer Betrachtung, 1918
* Anleitung zum quantitativischen agrikulturchemischen Praktikum, 1919 | 0 | Theoretical and Fundamental Chemistry |
Eutrophication, an influx of nutrients (phosphate/nitrate), often a byproduct of agricultural run-off and sewage discharge, can result in large but short-lived algae blooms. Upon a bloom's conclusion, the dead algae sink to the bottom and are broken down until all oxygen is expended. Such a case is the Gulf of Mexico where a seasonal dead zone occurs, which can be disturbed by weather patterns such as hurricanes and tropical convection. Sewage discharge, specifically that of nutrient concentrated "sludge", can be especially damaging to ecosystem diversity. Species sensitive to anoxic conditions are replaced by fewer hardier species, reducing the overall variability of the affected area.
Gradual environmental changes through eutrophication or global warming can cause major oxic-anoxic regime shifts. Based on model studies this can occur abruptly, with a transition between an oxic state dominated by cyanobacteria, and an anoxic state with sulfate-reducing bacteria and phototrophic sulfur bacteria. | 0 | Theoretical and Fundamental Chemistry |
Signal transducer and activator of transcription 6 (STAT6) is a transcription factor that belongs to the Signal Transducer and Activator of Transcription (STAT) family of proteins. The proteins of STAT family transmit signals from a receptor complex to the nucleus and activate gene expression. Similarly as other STAT family proteins, STAT6 is also activated by growth factors and cytokines. STAT6 is mainly activated by cytokines interleukin-4 and interleukin-13. | 1 | Applied and Interdisciplinary Chemistry |
SK channels are expressed throughout the central nervous system. They are highly conserved in mammals as well as in other organisms such as Drosophila melanogaster and Caenorhabditis elegans. SK channels are specifically involved in the medium afterhyperpolarizing potential (mAHP). They affect both the intrinsic excitability of neurons and synaptic transmission. They are also involved in calcium signaling. SK channel activation can mediate neuroprotection in various models of cell death. SK channels control action potential discharge frequency in hippocampal neurons, midbrain dopaminergic neurons, dorsal vagal neurons, sympathetic neurons, nucleus reticularis thalamic neurons, inferior olive neurons, spinal and hypoglossal motoneurons, mitral cells in the olfactory bulb, and cortical neurons. | 1 | Applied and Interdisciplinary Chemistry |
Homozygosity/Autozygosity mapping is a powerful technique, but is only valid when searching for a mutation segregating within a small, closed population. Such a small population, possibly created by the founder effect, will have a limited gene pool, and thus any inherited disease will probably be a result of two copies of the same mutation segregating on the same haplotype. Since affected individuals will probably be homozygous in the regions, looking at SNPs in a region is an adequate marker of regions of homozygosity and heterozygosity. Modern day SNP arrays are used to survey the genome and identify large regions of homozygosity. Homozygous blocks in the genomes of affected individuals can then be laid on top of each other, and the overlapping region should contain the disease gene.
This analysis is often extended by analyzing autozygosity, an extension of homozygosity, in the genomes of affected individuals. This can be accomplished by plotting a cumulative LOD score alongside the overlaid blocks of homozygosity. By taking into consideration the population allele frequencies for all SNPs via autozygosity mapping, the results of homozygosity can be confirmed. Furthermore, if two suspicious regions appear as a result of homozygosity mapping, autozygosity mapping may be able to distinguish between the two (ex. If one block of homozygosity is a result of a very non-diverse region of the genome, the LOD score will be very low).
Tools for Homozygosity Mapping
# HomSI: a homozygous stretch identifier from next-generation sequencing data A tool that identifies homozygous regions using deep sequence data. | 1 | Applied and Interdisciplinary Chemistry |
The dysfunction of potassium channels, including SK channels, is thought to play a role in the pathogenesis of Parkinson's disease (PD), a progressive neurodegenerative disorder.
SK channel blockers control the firing rate (the number of action potentials produced by a neuron in a given time) and the firing pattern (the way action potentials are allocated throughout time) through their production of m-AHP. SK channel activators decrease the firing rate, neuron sensitivity to excitatory stimuli, mediating neuroprotection, whereas SK channel blockers increase the firing rate and sensitivity to excitatory stimuli. This has important implications as to the function of dopaminergic neurons. For example, the amount of dopamine released by midbrain dopaminergic neurons is much higher when the frequency of firing increases than when they fire at a constant rate.
SK channels are widely expressed in midbrain dopaminergic neurons. Multiple pharmacological techniques have been used to adjust SK affinity for calcium ions, thereby modulating the excitability of substantia nigra dopaminergic neurons. Blockage of SK channels in vivo increases the firing rate of substantia nigra cells, which increases the amount of dopamine released from the synaptic terminals. When a large amount of dopamine accumulates in the cytosol, cell damage is induced due to the build-up of free radicals and damage to mitochondria.
In addition, techniques have been used to modulate SK channels in order to alter the dopamine phenotype of neurons. After the loss of TH+ (tyrosine hydroxylase-positive) substantia nigra compacta (SNc) neurons due to Parkinson’s-induced neurodegeneration, the number of these neurons can partially recover via a cell phenotype "shift" from TH- (tyrosine hydroxylase-negative) to TH+. The number of TH+ neurons can be altered by SK channel modulation; to be specific, the infusion of SK agonists into substantia nigra increases the number of TH+ neurons, whereas the infusion of SK antagonist decreases the number of TH+ neurons. The reason for this relationship between SK channels and TH expression may be due to neuroprotection against dopamine toxicity.
Two contradictory methods have been suggested as therapeutic options for the improvement of PD symptoms:
Inhibition of SK channels
*Inhibition of SK channels, to be specific the blockage of SK3 channels, increases the frequency of firing in dopaminergic neurons, thereby increasing the release of dopamine. It is, therefore, thought that the application of SK3 channels blockers in PD patients may alleviate short-term motor symptoms.
*However, inhibition also results in a decreased number of TH+ substantia nigra compacta (SNc) neurons in the cell, which results in a decrease in dopamine synthesis over the long term.
Facilitation of SK channels
*Enhancing the function of SK channels increases the number of TH+ substantia nigra compacta (SNc) neurons in the cell, thereby maintaining dopamine synthesis over the long term.
*However, the facilitation of SK channels decreases the firing frequency in dopaminergic neurons over the short term. | 1 | Applied and Interdisciplinary Chemistry |
Noncompetitive inhibitors of CYP2C9 enzyme include nifedipine, tranylcypromine, phenethyl isothiocyanate, and 6-hydroxyflavone. Computer docking simulation and constructed mutants substituted indicate that the noncompetitive binding site of 6-hydroxyflavone is the reported allosteric binding site of CYP2C9 enzyme. | 1 | Applied and Interdisciplinary Chemistry |
#Microinject the embryo with DNA coding for transposase and a plasmid with the reporter gene and transposase recognition sequences (and often the E. coli reporter gene and origin of replication, etc.).
#Random transposition occurs, inserting the reporter gene randomly. The insertion tends to occur near actively transcribed genes, as this is where the chromatin structure is loosest, so the DNA is most accessible.
#Grow flies and cross to remove genetic variation between the cells of the organism (see above).
#Look for flies expressing the reporter gene. These have experienced a successful transposition, so can be investigated to determine the phenotype due to mutation of existing genes.
Possible mutations:
#Insertion in a translated region => hybrid protein/truncated protein. Usually causes loss of protein function, although more complex effects are seen.
#Insertion in an intron => altered splicing pattern/splicing failure. Usually results in protein truncation or the production of inactive mis-spliced products, although more complex effects are common.
#Insertion in 5 (the sequence that will become the mRNA 5 UTR) untranslated region => truncation of transcript. Usually results in failure of the mRNA to contain a 5' cap, leading to less efficient translation.
#Insertion in promoter => reduction/complete loss of expression. Always results in greatly reduced protein production levels. The most useful type of insertion for analysis due to the simplicity of the situation.
#Insertion between promoter and upstream enhancers => loss of enhancer function/hijack of enhancer function for reporter gene.† Generally reduces the level of protein specificity to cell type, although complex effects are often seen. | 1 | Applied and Interdisciplinary Chemistry |
The complete breakdown of glucose releasing its energy is called cellular respiration. The last steps of this process occur in mitochondria. The reduced molecules NADH and FADH are generated by the Krebs cycle, glycolysis, and pyruvate processing. These molecules pass electrons to an electron transport chain, which releases the energy of oxygen to create a proton gradient across the inner mitochondrial membrane. ATP synthase then uses the energy stored in this gradient to make ATP. This process is called oxidative phosphorylation because it uses energy released by the oxidation of NADH and FADH to phosphorylate ADP into ATP. | 1 | Applied and Interdisciplinary Chemistry |
In addition to chlorophylls, another group of yellow–orange pigments called carotenoids are also found in the photosystems. There are about thirty photosynthetic carotenoids. They help transfer and dissipate excess energy, and their bright colors sometimes override the chlorophyll green, like during the fall, when the leaves of some land plants change color. β-carotene is a bright red-orange carotenoid found in nearly all chloroplasts, like chlorophyll a. Xanthophylls, especially the orange-red zeaxanthin, are also common. Many other forms of carotenoids exist that are only found in certain groups of chloroplasts. | 0 | Theoretical and Fundamental Chemistry |
Striations or string-like structures, also known as Birkeland currents, are seen in many plasmas, like the plasma ball, the aurora, lightning, electric arcs, solar flares, and supernova remnants. They are sometimes associated with larger current densities, and the interaction with the magnetic field can form a magnetic rope structure. (See also Plasma pinch)
Filamentation also refers to the self-focusing of a high power laser pulse. At high powers, the nonlinear part of the index of refraction becomes important and causes a higher index of refraction in the center of the laser beam, where the laser is brighter than at the edges, causing a feedback that focuses the laser even more. The tighter focused laser has a higher peak brightness (irradiance) that forms a plasma. The plasma has an index of refraction lower than one, and causes a defocusing of the laser beam. The interplay of the focusing index of refraction, and the defocusing plasma makes the formation of a long filament of plasma that can be micrometers to kilometers in length. One interesting aspect of the filamentation generated plasma is the relatively low ion density due to defocusing effects of the ionized electrons. (See also Filament propagation) | 0 | Theoretical and Fundamental Chemistry |
Galvanic cells are extensions of spontaneous redox reactions, but have been merely designed to harness the energy produced from said reaction. For example, when one immerses a strip of zinc metal (Zn) in an aqueous solution of copper sulfate (CuSO), dark-colored solid deposits will collect on the surface of the zinc metal and the blue color characteristic of the Cu ion disappears from the solution. The depositions on the surface of the zinc metal consist of copper metal, and the solution now contains zinc ions. This reaction is represented by
: Zn (s) + Cu (aq) → Zn (aq) + Cu (s)
In this redox reaction, Zn is oxidized to Zn and Cu is reduced to Cu. When electrons are transferred directly from Zn to Cu , the enthalpy of reaction is lost to the surroundings as heat. However, the same reaction can be carried out in a galvanic cell, allowing some of the chemical energy released to be converted into electrical energy. In its simplest form, a half-cell consists of a solid metal (called an electrode) that is submerged in a solution; the solution contains cations (+) of the electrode metal and anions (−) to balance the charge of the cations. The full cell consists of two half-cells, usually connected by a semi-permeable membrane or by a salt bridge that prevents the ions of the more noble metal from plating out at the other electrode.
A specific example is the Daniell cell (see figure), with a zinc (Zn) half-cell containing a solution of ZnSO (zinc sulfate) and a copper (Cu) half-cell containing a solution of CuSO (copper sulfate). A salt bridge is used here to complete the electric circuit.
If an external electrical conductor connects the copper and zinc electrodes, zinc from the zinc electrode dissolves into the solution as Zn ions (oxidation), releasing electrons that enter the external conductor. To compensate for the increased zinc ion concentration, via the salt bridge zinc ions leave and anions enter the zinc half-cell. In the copper half-cell, the copper ions plate onto the copper electrode (reduction), taking up electrons that leave the external conductor. Since the Cu ions (cations) plate onto the copper electrode, the latter is called the cathode. Correspondingly the zinc electrode is the anode. The electrochemical reaction is
This is the same reaction as given in the previous example. In addition, electrons flow through the external conductor, which is the primary application of the galvanic cell.
As discussed under cell voltage, the electromotive force of the cell is the difference of the half-cell potentials, a measure of the relative ease of dissolution of the two electrodes into the electrolyte. The emf depends on both the electrodes and on the electrolyte, an indication that the emf is chemical in nature. | 1 | Applied and Interdisciplinary Chemistry |
The formula of S53P4 was first developed in the early 1990s in Turku, Finland, at Åbo Akademi University and University of Turku. It has received the product claim for use in bone cavity filling in the treatment of chronic osteomyelitis in 2011. S53P4 is among the most studied bioactive glasses on the market with over 150 publications.
When S53P4 bioactive glass is placed into the bone cavity, it reacts with body fluids to activate the glass. During this activation period, the bioactive glass goes through a series of chemical reactions, creating the ideal conditions for the bone to rebuild through osteoconduction.
* Na, Si, Ca, and P ions are released.
* A silica gel layer forms on the bioactive glass surface.
* CaP crystallizes, forming a layer of hydroxyapatite on the surface of the bioactive glass.
Once the hydroxyapatite layer is formed, the bioactive glass interacts with biological entities, i.e., blood proteins, growth factors and collagen. Following this interaction, the osteoconductive and osteostimulative processes help the new bone grow onto and between the bioactive glass structures.
* Bioactive glass bonds to bone –facilitating new bone formation.
* Osteostimulation begins by stimulating osteogenic cells to increase the remodeling rate of bone.
* Radio-dense quality of bioactive glass allows for post-operative evaluation.
In the final transformative phase, the process of bone regeneration and remodeling continues. Over time the bone fully regenerates, restoring the patient's natural anatomy.
* Bone consolidation occurs.
* S53P4 bioactive glass continues to remodel into bone over a period of years.
Bioactive glass S53P4 is currently the only bioactive glass on the market which has been proven to inhibit bacterial growth effectively. The bacterial growth inhibiting properties of S53P4 derive from two simultaneous chemical and physical processes, which occurrs once the bioactive glass reacts with body fluids. Sodium (Na) is released from the surface of the bioactive glass and induces an increase in pH (alkaline environment), which is not favorable for the bacteria, thus inhibiting their growth. The released Na, Ca, Si and P ions give rise to an increase in osmotic pressure due to an elevation in salt concentration, i.e., an environment where bacteria cannot grow. | 0 | Theoretical and Fundamental Chemistry |
In spite of the apparent complexity of the flow transition, application of simple analytic tools to a two dimensional analysis is effective in providing analytic results which closely parallel both field and laboratory results. Analysis shows:
* Height of the jump: the relationship between the depths before and after the jump as a function of flow rate
* Energy loss in the jump
* Location of the jump on a natural or an engineered structure
* Character of the jump: undular or abrupt | 1 | Applied and Interdisciplinary Chemistry |
Neisseria meningitidis has multiple type II restriction endonuclease systems that are employed in natural genetic transformation. Natural genetic transformation is a process by which a recipient bacterial cell can take up DNA from a neighboring donor bacterial cell and integrate this DNA into its genome by recombination. Although early work on restriction modification systems focused on the benefit to bacteria of protecting themselves against invading bacteriophage DNA or other foreign DNA, it is now known that these systems can also be used to restrict DNA introduced by natural transformation from other members of the same, or related species.
In the pathogenic bacterium Neisseria meningitidis (meningococci), competence for transformation is a highly evolved and complex process where multiple proteins at the bacterial surface, in the membranes and in the cytoplasm interact with the incoming transforming DNA. Restriction-modification systems are abundant in the genus Neisseria. N. meningitidis has multiple type II restriction endonuclease systems. The restriction modification systems in N. meningitidis vary in specificity between different clades. This specificity provides an efficient barrier against DNA exchange between clades. Luria, on page 99 of his autobiography, referred to such a restriction behavior as "an extreme instance of unfriendliness." Restriction-modification appears to be a major driver of sexual isolation and speciation in the meningococci. Caugant and Maiden suggested that restriction-modification systems in meningococci may act to allow genetic exchange among very close relatives while reducing (but not completely preventing) genetic exchange among meningococci belonging to different clonal complexes and related species.
RM systems can also act as selfish genetic elements, forcing their maintenance on the cell through postsegregational cell killing.
Some viruses have evolved ways of subverting the restriction modification system, usually by modifying their own DNA, by adding methyl or glycosyl groups to it, thus blocking the restriction enzymes. Other viruses, such as bacteriophages T3 and T7, encode proteins that inhibit the restriction enzymes.
To counteract these viruses, some bacteria have evolved restriction systems which only recognize and cleave modified DNA, but do not act upon the host's unmodified DNA. Some prokaryotes have developed multiple types of restriction modification systems.
R-M systems are more abundant in promiscuous species, wherein they establish preferential paths of genetic exchange within and between lineages with cognate R-M systems. Because the repertoire and/or specificity of R-M systems in bacterial lineages vary quickly, the preferential fluxes of genetic transfer within species are expected to constantly change, producing time-dependent networks of gene transfer. | 1 | Applied and Interdisciplinary Chemistry |
Scaffolds localize the signaling reaction to a specific area in the cell, a process that could be important for the local production of signaling intermediates. A particular example of this process is the scaffold, A-kinase anchor proteins (AKAPs), which target cyclic AMP-dependent protein kinase (PKA) to various sites in the cell. This localization is able to locally regulate PKA and results in the local phosphorylation by PKA of its substrates. | 1 | Applied and Interdisciplinary Chemistry |
The ventilation rate, for commercial, industrial, and institutional (CII) buildings, is normally expressed by the volumetric flow rate of outdoor air, introduced to the building. The typical units used are cubic feet per minute (CFM) in the imperial system, or liters per second (L/s) in the metric system (even though cubic meter per second is the preferred unit for volumetric flow rate in the SI system of units). The ventilation rate can also be expressed on a per person or per unit floor area basis, such as CFM/p or CFM/ft², or as air changes per hour (ACH). | 1 | Applied and Interdisciplinary Chemistry |
Fusion of Armstrong's acid in NaOH gives the disodium salt of 1,5-dihydroxynaphthalene, which can be acidified to give the diol. The intermediate in this hydrolysis, 1-hydroxynaphthalene-5-sulfonic acid, is also useful. Nitration gives nitrodisulfonic acids, which are precursors to amino derivatives.
The disodium salt is sometimes used as a divalent counterion for forming salts of basic drug compounds, as an alternative to the related mesylate or tosylate salts. When used in this way such a salt is called a naphthalenedisulfonate salt, as seen with the most common salt form of the stimulant drug CFT. The disodium salt is also used as an electrolyte in certain kinds of chromatography. | 0 | Theoretical and Fundamental Chemistry |
A powerful research technique is to simultaneously measure chlorophyll fluorescence and gas exchange to obtain a full picture of the response of plants to their environment. One technique is to simultaneously measure CO fixation and PSII photochemistry at different light intensities, in non-photorespiratory conditions. A plot of CO fixation and PSII photochemistry indicates the electron requirement per molecule CO fixed. From this estimation, the extent of photorespiration may be estimated. This has been used to explore the significance of photorespiration as a photoprotective mechanism during drought.
Fluorescence analysis can also be applied to understanding the effects of low and high temperatures.
* Sobrado (2008) investigated gas exchange and chlorophyll a fluorescence responses to high intensity light, of pioneer species and forest species. Midday leaf gas exchange was measured using a photosynthesis system, which measured net photosynthetic rate, gs, and intercellular CO concentration (). In the same leaves used for gas exchange measurements, chlorophyll a fluorescence parameters (initial, ; maximum, ; and variable, ) were measured using a fluorometer. The results showed that despite pioneer species and forest species occupying different habitats, both showed similar vulnerability to midday photoinhibition in sun-exposed leaves. | 0 | Theoretical and Fundamental Chemistry |
I, with a half-life of 8 days, is a hazard from nuclear fallout because iodine concentrates in the thyroid gland. See also Radiation effects from Fukushima Daiichi nuclear disaster#Iodine-131 and
Downwinders#Nevada.
In common with Sr, I is used for the treatment of cancer. A small dose of I can be used in a thyroid function test while a large dose can be used to destroy the thyroid cancer. This treatment will also normally seek out and destroy any secondary tumor which arose from a thyroid cancer. Much of the energy from the beta emission from the I will be absorbed in the thyroid, while the gamma rays are likely to be able to escape from the thyroid to irradiate other parts of the body.
Large amounts of I was released during an experiment named the Green Run in which fuel which had only been allowed to cool for a short time after irradiation was reprocessed in a plant which had no iodine scrubber in operation.
I, with a half-life almost a billion times as long, is a long-lived fission product. It is among the most troublesome because it accumulates in a relatively small organ (the thyroid) where even its comparatively low radiation dose can cause great damage as it has a long biological half life. For this reason, Iodine is often considered for transmutation despite the presence of stable in spent fuel. In the thermal neutron spectrum, more Iodine-129 is destroyed than newly created since Iodine-128 is short lived and the isotope ratio is in favor of . Depending on the design of the transmutation apparatus, care must be taken as Xenon, the product of Iodine's beta decay, is both a strong neutron poison and a gas that is nigh impossible to chemically "fix" in solid compounds, so it will either escape to the outside air or put pressure on the vessel containing the transmutation target.
I is stable, the only one of the isotopes of iodine that is nonradioactive. It makes up only about of the iodine in spent fuel, with I-129 about . | 0 | Theoretical and Fundamental Chemistry |
The nanoDSF technology was used to confirm on-target binding of BI-3231 to HSD17B13 and to elucidate its uncompetitive mode of inhibition with regards to NAD. | 1 | Applied and Interdisciplinary Chemistry |
Bullous keratopathy that is characterized by corneal stromal edema related to cell loss and endothelial decompensation as well as subepithelial fibrosis and corneal vascularization in further cases, results vision problems due to loss of corneal transparency. Fibrin glue is used as a sutureless method onto the corneal surface to fix amniotic membrane that is cryopreserved. Complete re-epithelialization on the ocular surface with no symptom is achieved in 3 weeks. Results show that fibrin glue fixation is easy, reliable and efficient with the corneal surface. | 1 | Applied and Interdisciplinary Chemistry |
* 1988 Alexander von Humboldt fellowship of Germany: Research with Jürgen Martens at the University of Oldenburg and Hans Brückner University of Giessen.
* 1992 European Economic Community Fellowship: Research with Peter Shewry University of Bristol
* 1993 Fellow of the Royal Society of Chemistry
* 2001 Fellow of the National Academy of Sciences India | 0 | Theoretical and Fundamental Chemistry |
The presence of a vapor bubble adds an additional component for analysis given that the vapor bubble could contain a significant proportion of the HO and CO originally in the melt sampled by the melt inclusion. If the vapor bubble is composed primarily of CO, Raman spectroscopy can be used to determine the density of CO present. | 0 | Theoretical and Fundamental Chemistry |
The mappae clavicula is a medieval Latin text containing manufacturing recipes for crafts materials, including for metals, glass, mosaics, and dyes and tints for materials. The information and style in the recipes is very terse. Each recipe consists of the names of the ingredients and typically about two sentences on combining the ingredients together. A small minority of the recipes go to about six sentences. The text comes with a short preamble, and other than that it is just recipes. The number of recipes was expanded over the course of the medieval centuries, and some medieval copies have deletions as well as additions, so it is better thought of as a family of texts with a largely common core, not a single text. Most of the Mappae Clavicula recipes are also in medieval Latin in a text known as the Compositiones ad Tingenda (English: "Recipes for Coloring (or Tingeing)"). | 1 | Applied and Interdisciplinary Chemistry |
Based on their band structure, materials are characterised with a direct band gap or indirect band gap. In the free-electron model, k is the momentum of a free electron and assumes unique values within the Brillouin zone that outlines the periodicity of the crystal lattice. If the momentum of the lowest energy state in the conduction band and the highest energy state of the valence band of a material have the same value, then the material has a direct bandgap. If they are not the same, then the material has an indirect band gap and the electronic transition must undergo momentum transfer to satisfy conservation. Such indirect "forbidden" transitions still occur, however at very low probabilities and weaker energy. For materials with a direct band gap, valence electrons can be directly excited into the conduction band by a photon whose energy is larger than the bandgap. In contrast, for materials with an indirect band gap, a photon and phonon must both be involved in a transition from the valence band top to the conduction band bottom, involving a momentum change. Therefore, direct bandgap materials tend to have stronger light emission and absorption properties and tend to be better suited for photovoltaics (PVs), light-emitting diodes (LEDs), and laser diodes; however, indirect bandgap materials are frequently used in PVs and LEDs when the materials have other favorable properties. | 0 | Theoretical and Fundamental Chemistry |
Pressure drop (often abbreviated as "dP" or "ΔP") is defined as the difference in total pressure between two points of a fluid carrying network. A pressure drop occurs when frictional forces, caused by the resistance to flow, act on a fluid as it flows through a conduit (such as a channel, pipe, or tube). This friction converts some of the fluid’s hydraulic energy to thermal energy (i.e., internal energy). Since the thermal energy cannot be converted back to hydraulic energy, the fluid experiences a drop in pressure, as is required by conservation of energy.
The main determinants of resistance to fluid flow are fluid velocity through the pipe and fluid viscosity. Pressure drop increases proportionally to the frictional shear forces within the piping network. A piping network containing a high relative roughness rating as well as many pipe fittings and joints, tube convergence, divergence, turns, surface roughness, and other physical properties will affect the pressure drop. High flow velocities or high fluid viscosities result in a larger pressure drop across a pipe section, valve, or elbow joint. Low velocity will result in less (or no) pressure drop. The fluid may also be biphasic as in pneumatic conveying with a gas and a solid; in this case, the friction of the solid must also be taken into consideration for calculating the pressure drop. | 1 | Applied and Interdisciplinary Chemistry |
In general, enols are less stable than their keto equivalents because of the favorability of the C=O double bond over C=C double bond. However, enols can be stabilized kinetically or thermodynamically.
Some enols are sufficiently stabilized kinetically so that they can be characterized.
Delocalization can stabilize the enol tautomer. Thus, very stable enols are phenols. Another stabilizing factor in 1,3-dicarbonyls is intramolecular hydrogen bonding. Both of these factors influence the enol-dione equilibrium in acetylacetone. | 0 | Theoretical and Fundamental Chemistry |
Masri founded and manages the first Palestinian equity fund, a 90 million investment initiative known as "Siraj Fund" in 2003, and the companys first fun "Siraj Palestine Fund I" was launched in February 2011, the company was founded for the sole purpose of managing investment funds in Palestine. The company focuses on promising startups and capital investments in small and medium-sized enterprises in the sectors of information and communication technology services, energy, agriculture, clean technology, healthcare, logistics, education, manufacturing, transportation, construction and financial services. Sirajs investments in these companies range between $250,000 and $12 million, and plans on expanding in the MENA region in the future. | 1 | Applied and Interdisciplinary Chemistry |
The first publication of the structure of wheel shaped cluster anion, first determined for the nitrosyl derivative by Achim Müller et al. was announced in New Scientist as "Big Wheel rolls back the molecular frontier". Further work by the same group then refined the initial findings and determined the structure of the wheel produced in molybdate solutions as [MoOH(HO)]. The Mo-type cluster was then shown to be the basic structural type of molybdenum blue compounds obtained under slightly different conditions.
The structure of the big wheel is constructed from units containing 11 Mo atoms ({Mo}-type units), 14 of which are linked together to form the {Mo}-type cluster that has an external diameter of 3.4 nm. (12 {Mo}-type units are also involved in the construction of higher symmetrical spherical systems called Keplerates) These units consist of a central MoO bipyramid sharing edges with 5 MoO octahedra (an illustration of this is on page 155 of the review ). With 5 more linking MoO octahedra the repeating {Mo}-type unit is built up. | 0 | Theoretical and Fundamental Chemistry |
SP-B is encoded by SFTPB, a single, 11425 nucleotide long gene on chromosome 2. Mutations in this gene are the basis for several of the lung conditions mentioned above. Both frameshift mutations and several single nucleotide polymorphisms (SNPs) have been found correlated to a variety of lung conditions. A frame shift mutation responsible for congenital alveolar proteinosis (CAP) was identified by Kattan et al. Many SNP's have been identified in relation to lung conditions. They have been correlated to severe influenza, neonatal respiratory distress syndrome, mechanical ventilation necessity, and more. | 0 | Theoretical and Fundamental Chemistry |
Kinetic relations have been observed in many systems and, since their conception, have gone by many terms, among which are the Meyer-Neldel effect or rule, the Barclay-Butler rule, the theta rule, and the Smith-Topley effect. Generally, chemists will talk about the isokinetic relation (IKR), from the importance of the isokinetic (or isoequilibrium) temperature, condensed matter physicists and material scientists use the Meyer-Neldel rule, and biologists will use the compensation effect or rule.
An interesting homework problem appears following Chapter 7: Structure-Reactivity Relationships in Kenneth Connorss textbook Chemical Kinetics: The Study of Reaction Rates':
:From the last four digits of the office telephone numbers of the faculty in your department, systematically construct pairs of "rate constants" as two-digit numbers times 10 s at temperatures 300 K and 315 K (obviously the larger rate constant of each pair to be associated with the higher temperature). Make a two-point Arrhenius plot for each faculty member, evaluating and . Examine the plot of against for evidence of an isokinetic relationship.
The existence of any real compensation effect has been widely derided in recent years and attributed to the analysis of interdependent factors and chance. Because the physical roots remain to be fully understood, it has been called into question whether compensation is a truly physical phenomenon or a coincidence due to trivial mathematical connections between parameters. The compensation effect has been criticized in other respects, namely for being the result of random experimental and systematic errors producing the appearance of compensation. The principal complaint lodged states that compensation is an artifact of data from a limited temperature range or from a limited range for the free energies.
In response to the criticisms, investigators have stressed that compensatory phenomena are real, but appropriate and in-depth data analysis is always needed. The F-test has been used to such an aim, and it minimizes the deviations of points constrained to pass through an isokinetic temperature to the deviation of the points from the unconstrained line is achieved by comparing the mean deviations of points. Appropriate statistical tests should be performed as well. W. Linert wrote in a 1983 paper:
:There are few topics in chemistry in which so many misunderstandings and controversies have arisen as in connection with the so-called isokinetic relationship (IKR) or compensation law. Up to date, a great many chemists appear to be inclined to dismiss the IKR as being accidental. The crucial problem is that the activation parameters are mutually dependent because of their determination from the experimental data. Therefore, it has been stressed repeatedly, the isokinetic plot (i.e., against ) is unfit in principle to substantiate a claim of an isokinetic relationship. At the same time, however, it is a fatal error to dismiss the IKR because of that fallacy.
Common among all defenders is the agreement that stringent criteria for the assignment of true compensation effects must be adhered to. | 0 | Theoretical and Fundamental Chemistry |
Proton transfer reaction mass spectrometry has traditionally used drift tubes as ion traps. However, radio frequency ion funnels offer an attractive alternative, as they improve compound specific sensitivity significantly. This is due to increasing the effective reaction time and focusing the ions. The same pressure ranges are required for ion funnels and drift tubes, so the technology is not difficult to implement. Ion funnels have been shown to favor transmission of ions with high m/z. | 0 | Theoretical and Fundamental Chemistry |
Depending on their location around the world, gyres can be regions of high biological productivity or low productivity. Each gyre has a unique ecological profile but can be grouped by region due to dominating characteristics. Generally, productivity is greater for cyclonic gyres (e.g., subpolar gyres) that drive upwelling through Ekman suction and lesser for anticyclonic gyres (e.g., subtropical gyres) that drive downwelling through Ekman pumping, but this can differ between seasons and regions.
Subtropical gyres are sometimes described as "ocean deserts" or "biological deserts", in reference to arid land deserts where little life exists. Due to their oligotrophic characteristics, warm subtropical gyres have some of the least productive waters per unit surface area in the ocean. The downwelling of water that occurs in subtropical gyres takes nutrients deeper in the ocean, removing them from surface waters. Organic particles can also be removed from surface waters through gravitational sinking, where the particle is too heavy to remain suspended in the water column. However, since subtropical gyres cover 60% of the ocean surface, their relatively low production per unit area is made up for by covering massive areas of the Earth. This means that, despite being areas of relatively low productivity and low nutrients, they play a large role in contributing to the overall amount of ocean production.
In contrast to subtropical gyres, subpolar gyres can have a lot of biological activity due to Ekman suction upwelling driven by wind stress curl. Subpolar gyres in the North Atlantic have a "bloom and crash" pattern following seasonal and storm patterns. The highest productivity in the North Atlantic occurs in boreal spring when there are long days and high levels of nutrients. This is different to the subpolar North Pacific, where almost no phytoplankton bloom occurs and patterns of respiration are more consistent through time than in the North Atlantic. | 1 | Applied and Interdisciplinary Chemistry |
The second analysis, taking into account the measured Faraday efficiency, yielded an actual excess heat of 0.13% +/- 0.48%. In other words, when the actual Faraday efficiency was measured and taken into account, the energy balance of the cells was zero, with no excess heat. | 0 | Theoretical and Fundamental Chemistry |
Modern concept of polymers credited to Hermann Staudinger, who substantiated the existence of covalently linked ultralong molecules in 1920, which he called as macromolecules. The preamble of the field of supramolecular polymers can be considered dye-aggregates and host-guest complexes. In early 19th century, scientists working in the field of pigments have noticed certain dye aggregates that may formed via "a special kind of polymerization", however no theory was proposed. After the establishment of the field of supramolecular chemistry and after the award of the Nobel Prize in chemistry in 1987 to Donald J. Cram, Jean-Marie Lehn, and Charles J. Pedersen, chemists started to design and study larger assembled structures from small molecules. In 1988, Takuzo Aida, a Japanese polymer chemist, reported the concept of cofacial assembly wherein the amphiphilic porphyrin monomers are connected via van der Waals interaction forming one-dimensional architectures in solution, which can be considered as a prototype of supramolecular polymers. In the same year 1988, James D. Wuest introduced one-dimensional aggregates based on hydrogen bonding interaction in the crystalline state. With a different strategyusing hydrogen bonds, Jean M. J. Fréchet showed in 1989 that mesogenic molecules with carboxylic acid and pyridyl motifs, upon mixing in bulk, heterotropically dimerize to form a stable liquid crystalline structure. In 1990, Jean-Marie Lehn showed that this strategy can be expanded to form a new category of polymers, which he called "liquid crystalline supramolecular polymer" using complementary triple hydrogen bonding motifs in bulk. In 1993, M. Reza Ghadiri reported a nanotubular supramolecular polymer where a b-sheet-forming macrocyclic peptide monomer assembled together via multiple hydrogen bonding between adjacent macrocycles. In 1994, Anselm. C. Griffin showed an amorphous supramolecular material using a single hydrogen bond between a homotropic molecules having carboxylic acid and pyridine termini. The idea to make mechanically strong polymeric materials by 1D supramolecular association of small molecules requires a high association constant between the repeating building blocks. In 1997, E.W. "Bert" Meijer reported a telechelic monomer with ureidopyrimidinone termini as a "self-complementary" quadruple hydrogen bonding motif and demonstrated that the resulting supramolecular polymer in chloroform shows a temperature-dependent viscoelastic property in solution. This is the first demonstration that supramolecular polymers, when sufficiently mechanically robust, are physically entangled in solution. | 0 | Theoretical and Fundamental Chemistry |
Researchers at the University of North Carolina published an article in Clinical Biochemistry which found Baby wash products could cause false drug test results. Newborn drug screening has a significant implications in both the healthcare and legal domains, on occasion resulting in involvement by social services or false child abuse allegations. The accuracy of the screening results is therefore essential. This research highlights reasons why false positive cannabinoid (THC) screening results may have occurred. Researchers identified commonly used soap and wash products used for newborn and infant care as potential causes of false positive THC screening results. | 1 | Applied and Interdisciplinary Chemistry |
In polymer chemistry, condensation polymers are any kind of polymers whose process of polymerization involves a condensation reaction (i.e. a small molecule, such as water or methanol, is produced as a byproduct). Natural proteins as well as some common plastics such as nylon and PETE are formed in this way. Condensation polymers are formed by polycondensation, when the polymer is formed by condensation reactions between species of all degrees of polymerization, or by condensative chain polymerization, when the polymer is formed by sequential addition of monomers to an active site in a chain reaction. The main alternative forms of polymerization are chain polymerization and polyaddition, both of which give addition polymers.
Condensation polymerization is a form of step-growth polymerization. Linear polymers are produced from bifunctional monomers, i.e. compounds with two reactive end-groups. Common condensation polymers include polyesters, polyamides such as nylon, polyacetals, and proteins. | 0 | Theoretical and Fundamental Chemistry |
Measurement consists of packing the powder into a cylindrical "bed" having a known porosity (i.e. volume of air-space between particles divided by total bed volume). A pressure drop is set up along the length of the bed cylinder. The resulting flow-rate of air through the bed yields the specific surface by the Kozeny–Carman equation:
where:
:S is specific surface, m·kg
:d is the cylinder diameter, m
:ρ is the sample particle density, kg·m
:ε is the volume porosity of the bed (dimensionless)
:δP is the pressure drop across the bed, Pa
:l is the cylinder length, m
:η is the air dynamic viscosity, Pa·s
:Q is the flowrate, m·s
It can be seen that the specific surface is proportional to the square root of the ratio of pressure to flow. Various standard methods have been proposed:
* Maintain a constant flowrate, and measure the pressure drop
* Maintain a constant pressure drop, and measure the flowrate
* Allow both to vary, deriving the ratio from the characteristics of the apparatus. | 1 | Applied and Interdisciplinary Chemistry |
Cavitation can occur in control valves. If the actual pressure drop across the valve as defined by the upstream and downstream pressures in the system is greater than the sizing calculations allow, pressure drop flashing or cavitation may occur. The change from a liquid state to a vapor state results from the increase in flow velocity at or just downstream of the greatest flow restriction which is normally the valve port. To maintain a steady flow of liquid through a valve the flow velocity must be greatest at the vena contracta or the point where the cross sectional area is the smallest. This increase in flow velocity is accompanied by a substantial decrease in the fluid pressure which is partially recovered downstream as the area increases and flow velocity decreases. This pressure recovery is never completely to the level of the upstream pressure. If the pressure at the vena contracta drops below the vapor pressure of the fluid bubbles will form in the flow stream. If the pressure recovers after the valve to a pressure that is once again above the vapor pressure, then the vapor bubbles will collapse and cavitation will occur. | 1 | Applied and Interdisciplinary Chemistry |
Hydroamination has been examined with a variety of amines, unsaturated substrates, and vastly different catalysts. Amines that have been investigated span a wide scope including primary, secondary, cyclic, acyclic, and anilines with diverse steric and electronic substituents. The unsaturated substrates that have been investigated include alkenes, dienes, alkynes, and allenes. For intramolecular hydroamination, various aminoalkenes have been examined. | 0 | Theoretical and Fundamental Chemistry |
Phenotypic threshold effect is when there is a certain amount of wild-type mtDNA present in the mitochondrion which is able to balance out the number of mutated mtDNA. As a result, the phenotype is normal. However, if the number of wild-type mtDNA decreases and the number of mutant mtDNA increases, resulting in an imbalance between the two, the threshold level has been altered which causes complications. This occurs because the wild-type mtDNA present are able to keep the electron transport chain and ATP synthesis functioning despite there being a few number of them present. They are able to counterbalance the mutated mtDNA, however, when the number drops below threshold level the mutant mtDNA take over. | 1 | Applied and Interdisciplinary Chemistry |
Amino acid metabolism in plants has been deemed a controversial topic, due to the lack of concrete evidence for any particular pathway. However, it has been suggested that enzymes related to the production and use of propionyl-CoA are involved. Associated with this is the metabolism of isobutyryl-CoA. These two molecules are deemed to be intermediates in valine metabolism. As propionate consists in the form of propionyl-CoA, it was discovered that propionyl-CoA is converted to β-hydroxypropionate through a peroxisomal enzymatic β-oxidation pathway. Nevertheless, in the plant Arabidopsis, key enzymes in the conversion of valine to propionyl-CoA were not observed. Through different experiments performed by Lucas et al., it has been suggested that in plants, through peroxisomal enzymes, propionyl-CoA (and isobutyryl-CoA) are involved in the metabolism of many different substrates (currently being evaluated for identity), and not just valine. | 1 | Applied and Interdisciplinary Chemistry |
Paul Sydney Braterman (born August 1938) is Emeritus Professor of chemistry at the University of North Texas and honorary senior Research Fellow in Chemistry at the University of Glasgow. Braterman is also a science writer and education campaigner. The author of "From Stars to Stalagmites", and over 120 technical publications, Braterman is a board member of the British Centre for Science Education, and the Scottish Secular Society. Braterman has campaigned successfully against creationism in the classroom in both England and Scotland. | 0 | Theoretical and Fundamental Chemistry |
Lithium-containing NASICON-type crystals are described by the general formula , in which M stands for a metal or a metalloid (Ti, Zr, Hf, Sn, Ge), and display a complex three-dimensional network of corner-sharing octahedra and phosphate tetrahedra. Lithium ions are hosted in voids in between, which can be subdivided into three kinds of sites:
* Li(1) 6-fold coordinated sites at Wyckoff 6b position;
* Li(2) sites at Wyckoff 18e position;
* Li(3) sites at Wyckoff 36f position.
In order to promote lithium conductivity at sufficiently high rates, Li(1) sites should be fully occupied and Li(2) sites should be fully empty. Li(3) sites are located between Li(1) and Li(2) sites and are occupied only when large tetravalent cations are present in the structure, such as Zr, Hf, and Sn. If some Ge cations in the (LGP) structure are partially replaced by Al cations, the LAGP material is obtained with the general formula . The single-phase NASICON structure is stable with x between 0.1 and 0.6; when this limit is exceeded, a solid solution is no more possible and secondary phases tend to be formed. Although Ge and Al cations have very similar ionic radii (0.53 Å for Ge vs. 0.535 Å for Al), cationic substitution leads to compositional disorder and promotes the incorporation of a larger amount of lithium ions to achieve electrical neutrality. Additional lithium ions can be incorporated in either Li(2) or Li(3) empty sites.
In the available scientific literature, there is not a unique description of the sites available for lithium ions and of their atomic coordination, as well as of the sites directly involved during the conduction mechanism. For example, only two available sites, namely Li(1) and Li(2), are mentioned in some cases, while the Li(3) site is neither occupied nor involved in the conduction process. This results in the lack of unambiguous description of LAGP local crystal structure, especially concerning the arrangement of lithium ions and site occupancy when germanium is partially replaced by aluminium.
LAGP displays a rhombohedral unit cell with a space group Rc. | 0 | Theoretical and Fundamental Chemistry |
The compound crystallizes from a heated solution of mercuric iodide, potassium iodide, and precisely 2% water in acetone. Attempted synthesis in concentrated aqueous solution will give the pale orange monohydrate instead. | 0 | Theoretical and Fundamental Chemistry |
Ninhydrin reacts with amino acids and amines to form a colored compound "Ruhemann's purple" (RP). Spraying with a zinc chloride solution forms a 1:1 complex RP:, which is more readily detected as it fluoresces more intensely than RP. | 0 | Theoretical and Fundamental Chemistry |
As an approach to calculation of the impact, activity-based costing (ABC) will be used for calculations of environmental costs. Emblemssvåg and Bras worked and analyzed the ABC as a method for environmental analyses. The method substitutes the cost for the production in money with an environmental emission, e.g. CO emissions. The emissions are measured and calculated from the energy and resources used. Then the emissions are allocated to the different products produced using the resources in the model.
The problems with ABC is that it requires a lot of data for a qualitative and accurate allocation of the cost from the resources. This is why the method fits well into a DES model. During a run In a DES environment it is easy to grab lot of detailed results needed for accurate allocation. The problem is that DES require a lot of initial effort to build the model. The approach to analyze environmental impact in a DES model is only beneficial if there is requirements for detailed analyzes and “what-if” scenarios is needed. | 1 | Applied and Interdisciplinary Chemistry |
Trioxidane readily decomposes into water and singlet oxygen, with a half-life of about 16 minutes in organic solvents at room temperature, but only milliseconds in water. It reacts with organic sulfides to form sulfoxides, but little else is known of its reactivity.
Recent research found that trioxidane is the active ingredient responsible for the antimicrobial properties of the well known ozone/hydrogen peroxide mix. Because these two compounds are present in biological systems as well it is argued that an antibody in the human body can generate trioxidane as a powerful oxidant against invading bacteria. The source of the compound in biological systems is the reaction between singlet oxygen and water (which proceeds in either direction, of course, according to concentrations), with the singlet oxygen being produced by immune cells.
Computational chemistry predicts that more oxygen chain molecules or hydrogen polyoxides exist and that even indefinitely long oxygen chains can exist in a low-temperature gas. With this spectroscopic evidence a search for these type of molecules can start in interstellar space. A 2022 publication suggested the possibility of the presence of detectable concentrations of polyoxides in the atmosphere. | 0 | Theoretical and Fundamental Chemistry |
Some sulfate-reducing bacteria produce hydrogen sulfide, which can cause sulfide stress cracking. Acidithiobacillus bacteria produce sulfuric acid; Acidothiobacillus thiooxidans frequently damages sewer pipes. Ferrobacillus ferrooxidans directly oxidizes iron to iron oxides and iron hydroxides; the rusticles forming on the RMS Titanic wreck are caused by bacterial activity. Other bacteria produce various acids, both organic and mineral, or ammonia.
In presence of oxygen, aerobic bacteria like Acidithiobacillus thiooxidans, Thiobacillus thioparus, and Thiobacillus concretivorus, all three widely present in the environment, are the common corrosion-causing factors resulting in biogenic sulfide corrosion.
Without presence of oxygen, anaerobic bacteria, especially Desulfovibrio and Desulfotomaculum, are common. Desulfovibrio salixigens requires at least 2.5% concentration of sodium chloride, but D. vulgaris and D. desulfuricans can grow in both fresh and salt water. D. africanus is another common corrosion-causing microorganism. The genus Desulfotomaculum comprises sulfate-reducing spore-forming bacteria; Dtm. orientis and Dtm. nigrificans are involved in corrosion processes. Sulfate-reducers require a reducing environment; an electrode potential lower than -100 mV is required for them to thrive. However, even a small amount of produced hydrogen sulfide can achieve this shift, so the growth, once started, tends to accelerate.
Layers of anaerobic bacteria can exist in the inner parts of the corrosion deposits, while the outer parts are inhabited by aerobic bacteria.
Some bacteria are able to utilize hydrogen formed during cathodic corrosion processes.
Bacterial colonies and deposits can form concentration cells, causing and enhancing galvanic corrosion. [https://web.archive.org/web/20060504072637/http://httd.njuct.edu.cn/MatWeb/corrosie/c_bio.htm].
Bacterial corrosion may appear in form of pitting corrosion, for example in pipelines of the oil and gas industry. Anaerobic corrosion is evident as layers of metal sulfides and hydrogen sulfide smell. On cast iron, a graphitic corrosion selective leaching may be the result, with iron being consumed by the bacteria, leaving graphite matrix with low mechanical strength in place.
Various corrosion inhibitors can be used to combat microbial corrosion. Formulae based on benzalkonium chloride are common in oilfield industry.
Microbial corrosion can also apply to plastics, concrete, and many other materials. Two examples are Nylon-eating bacteria and Plastic-eating bacteria. | 1 | Applied and Interdisciplinary Chemistry |
Seeded supersonic nozzle Seeded supersonic nozzles are mostly used to create clusters of low-boiling-point metal. In this source method metal is vaporized in a hot oven. The metal vapor is mixed with (seeded in) inert carrier gas. The vapor mixture is ejected into a vacuum chamber via a small hole, producing a supersonic molecular beam. The expansion into vacuum proceeds adiabatically cooling the vapor. The cooled metal vapor becomes supersaturated, condensing in cluster form.
Gas aggregation Gas aggregation is mostly used to synthesize large clusters of nanoparticles. Metal is vaporized and introduced in a flow of cold inert gas, which causes the vapor to become highly supersaturated. Due to the low temperature of the inert gas, cluster production proceeds primarily by successive single-atom addition.
Laser vaporization Laser vaporization source can be used to create clusters of various size and polarity. Pulse laser is used to vaporize the target metal rod and the rod is moved in a spiral so that a fresh area can be evaporated every time. The evaporated metal vapor is cooled by using cold helium gas, which causes the cluster formation.
Pulsed arc cluster ion This is similar to laser vaporization, but an intense electric discharge is used to evaporate the target metal.
Ion sputtering Ion sputtering source produces an intense continuous beam of small singly ionized cluster of metals. Cluster ion beams are produced by bombarding the surface with high energetic inert gas (krypton and xenon) ions. The cluster production process is still not fully understood.
Liquid-metal ion In liquid-metal ion source a needle is wetted with the metal to be investigated. The metal is heated above the melting point and a potential difference is applied. A very high electric field at the tip of the needle causes a spray of small droplets to be emitted from the tip. Initially very hot and often multiply ionized droplets undergo evaporative cooling and fission to smaller clusters. | 0 | Theoretical and Fundamental Chemistry |
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