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The structures that soap films make can not just be enclosed as spheres, but virtually any shape, for example in wire frames. Therefore, many different minimal surfaces can be designed. It is actually sometimes easier to physically make them than to compute them by mathematical modelling. This is why the soap films can be considered as analog computers which can outperform conventional computers, depending on the complexity of the system. | 1 | Applied and Interdisciplinary Chemistry |
Rather than directly measuring concentrations of carbon dioxide in the atmosphere, OCO-2 records how much of the sunlight reflected off the Earth is absorbed by molecules in an air column. OCO-2 makes measurements in three different spectral bands over four to eight different footprints of approximately each. About 24 soundings are collected per second while in sunlight and over 10% of these are sufficiently cloud free for further analysis. One spectral band is used for column measurements of oxygen (A-band 0.765 microns), and two are used for column measurements of carbon dioxide (weak band 1.61 microns, strong band 2.06 microns).
In the retrieval algorithm measurements from the three bands are combined to yield column-averaged dry-air mole fractions of carbon dioxide. Because these are dry-air mole fractions, these measurements do not change with water content or surface pressure. Because the molecular oxygen content of the atmosphere (i.e. excluding the oxygen in water vapour) is well known to be 20.95%, oxygen is used as a measure of the total dry air column. To ensure these measurements are traceable to the World Meteorological Organization, OCO-2 measurements are carefully compared with measurements by the Total Carbon Column Observing Network (TCCON). | 1 | Applied and Interdisciplinary Chemistry |
The biological pump (or ocean carbon biological pump or marine biological carbon pump) is the ocean's biologically driven sequestration of carbon from the atmosphere and land runoff to the ocean interior and seafloor sediments. In other words, it is a biologically mediated process which results in the sequestering of carbon in the deep ocean away from the atmosphere and the land. The biological pump is the biological component of the "marine carbon pump" which contains both a physical and biological component. It is the part of the broader oceanic carbon cycle responsible for the cycling of organic matter formed mainly by phytoplankton during photosynthesis (soft-tissue pump), as well as the cycling of calcium carbonate (CaCO) formed into shells by certain organisms such as plankton and mollusks (carbonate pump).
Budget calculations of the biological carbon pump are based on the ratio between sedimentation (carbon export to the ocean floor) and remineralization (release of carbon to the atmosphere).
The biological pump is not so much the result of a single process, but rather the sum of a number of processes each of which can influence biological pumping. Overall, the pump transfers about 10.2 gigatonnes of carbon every year into the ocean's interior and a total of 1300 gigatonnes carbon over an average 127 years. This takes carbon out of contact with the atmosphere for several thousand years or longer. An ocean without a biological pump would result in atmospheric carbon dioxide levels about 400 ppm higher than the present day. | 0 | Theoretical and Fundamental Chemistry |
Levetiracetam is a Schedule 4 substance in Australia under the Poisons Standard (February 2020). A Schedule 4 substance is classified as "Prescription Only Medicine, or Prescription Animal Remedy – Substances, the use or supply of which should be by or on the order of persons permitted by State or Territory legislation to prescribe and should be available from a pharmacist on prescription." | 0 | Theoretical and Fundamental Chemistry |
The International Thermonuclear Experimental Reactor (ITER) coalition forms, involving EURATOM, Japan, the Soviet Union and United States and kicks off the conceptual design process. | 0 | Theoretical and Fundamental Chemistry |
Acid guanidinium thiocyanate-phenol-chloroform extraction (abbreviated AGPC) is a liquid–liquid extraction technique in biochemistry. It is widely used in molecular biology for isolating RNA (as well as DNA and protein in some cases). This method may take longer than a column-based system such as the silica-based purification, but has higher purity and the advantage of high recovery of RNA: an RNA column is typically unsuitable for purification of short (<200 nucleotides) RNA species, such as siRNA, miRNA, gRNA and tRNA.
It was originally devised by Piotr Chomczynski and Nicoletta Sacchi, who published their protocol in 1987. The reagent is sold by Sigma-Aldrich by the name TRI Reagent; by Invitrogen under the name TRIzol; by Bioline as Trisure; and by Tel-Test as STAT-60. | 1 | Applied and Interdisciplinary Chemistry |
Heparin was discovered by Jay McLean and William Henry Howell in 1916, it was first isolated from a canine liver, which in Greek translates to hepar. Heparin targets multiple factors in the blood coagulation cascade, one of them being FXa. At first, it had many side effects but for the next twenty years, investigators worked on heparin to make it better and safer. It entered clinical trials in 1935 and the first drug was launched in 1936. Chains of natural heparin can vary from 5.000 to 40.000 daltons. In the 1980s Low molecular weight heparin (LMWH) were developed and they only contain chains with an average molecular weight of less than 8.000 Da. | 1 | Applied and Interdisciplinary Chemistry |
Due to the high activity of the enzyme, expression of untethered Dam results in methylation of all regions of accessible chromatin. This approach can be used as an alternative to ATAC-seq or DNAse-seq. When combined with cell-type specific DamID methods, expression of untethered Dam can be used to identify cell-type specific promoter or enhancer regions. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, the von Baeyer nomenclature is a system for describing polycyclic (i.e. multi-ringed) hydrocarbons. The system was originally developed in 1900 by German chemist Adolf von Baeyer for bicyclic systems and in 1913 expanded by Eduard Buchner and Wilhelm Weigand for tricyclic systems. The system has been adopted and extended by the IUPAC as part of its nomenclature for organic chemistry. The modern version has been extended to cover more cases of compounds including an arbitrary number of cycles, heterocyclic compounds and unsaturated compounds. | 0 | Theoretical and Fundamental Chemistry |
Kristi Lynn Kiick is the Blue and Gold Distinguished Professor of Materials Science and Engineering at the University of Delaware. She studies polymers, biomaterials and hydrogels for drug delivery and regenerative medicine. She is a Fellow of the American Chemical Society, the American Institute for Medical and Biological Engineering, and of the National Academy of Inventors. She served for nearly eight years as the deputy dean of the college of engineering at the University of Delaware. | 0 | Theoretical and Fundamental Chemistry |
* When solute particles associate in solution, is less than 1. For example, carboxylic acids such as acetic acid (ethanoic acid) or benzoic acid form dimers in benzene, so that the number of solute particles is half the number of acid molecules.
* When solute particles dissociate in solution, is greater than 1 (e.g. sodium chloride in water, potassium chloride in water, magnesium chloride in water).
* When solute particles neither dissociate nor associate in solution, equals 1 (e.g. glucose in water).
The value of is the actual number of particles in solution after dissociation divided by the number of formula units initially dissolved in solution and means the number of particles per formula unit of the solute when a solution is dilute. | 0 | Theoretical and Fundamental Chemistry |
* Albidiferax (Betaproteobacteria)
* Shewanella (Gammaproteobacteria)
* Geobacter (Deltaproteobacteria)
* Geothrix fermentans (Acidobacteria)
* Deferribacter (Deferribacteres)
* Thermoanaerobacter (Firmicutes) | 1 | Applied and Interdisciplinary Chemistry |
This refrigeration method cools a contained area by melting ice, or by sublimating dry ice. Perhaps the simplest example of this is a portable cooler, where items are put in it, then ice is poured over the top. Regular ice can maintain temperatures near, but not below the freezing point, unless salt is used to cool the ice down further (as in a traditional ice-cream maker). Dry ice can reliably bring the temperature well below water freezing point. | 0 | Theoretical and Fundamental Chemistry |
Photoinhibition can also be induced with short flashes of light using either a pulsed laser or a xenon flash lamp. When very short flashes are used, the photoinhibitory efficiency of the flashes depends on the time difference between the flashes. This dependence has been interpreted to indicate that the flashes cause photoinhibition by inducing recombination reactions in PSII, with subsequent production of singlet oxygen. The interpretation has been criticized by noting that the photoinhibitory efficiency of xenon flashes depends on the energy of the flashes even if such strong flashes are used that they would saturate the formation of the substrate of the recombination reactions. | 0 | Theoretical and Fundamental Chemistry |
Carboxylic acids tend to have higher boiling points than water, because of their greater surface areas and their tendency to form stabilized dimers through hydrogen bonds. For boiling to occur, either the dimer bonds must be broken or the entire dimer arrangement must be vaporized, increasing the enthalpy of vaporization requirements significantly. | 0 | Theoretical and Fundamental Chemistry |
Singlet oxygen luminesces concomitant with its decay to the triplet ground state. This phenomenon was first observed in the thermal degradation of the endo peroxide of rubrene. | 0 | Theoretical and Fundamental Chemistry |
Clinker is a generic name given to waste from industrial processes, particularly those that involve smelting metals, welding, burning fossil fuels and use of a blacksmith's forge, which commonly causes a large buildup of clinker around the tuyere. Clinker often forms a loose, dark deposit consisting of waste materials such as coke, coal, slag, charcoal, and grit. Clinker often has a glassy look to it, usually because of the formation of molten silica compounds during processing. Clinker generally is much denser than coke, and, unlike coke, generally contains too little carbon to be of any value as fuel. It is also applied to the byproduct of combustion and heating by those who use anthracite or lignite coal-fired boilers.
Clinkers can occur naturally, for example in underground deposits of coal that has been altered by heat from nearby molten magma; volcanic clinkers are jagged pieces of lava that look similar to industrial clinker. | 1 | Applied and Interdisciplinary Chemistry |
Thermal hydrolysis is a process used for treating industrial waste, municipal solid waste and sewage sludge. | 0 | Theoretical and Fundamental Chemistry |
The major industrial synthesis involves the reaction of sulfur trioxide and sulfur dichloride: This synthesis can be adapted to the laboratory by heating oleum to slowly distill the sulfur trioxide into a cooled flask of sulfur dichloride.
Other methods include syntheses from:
*Phosphorus pentachloride:
*Chlorine and sulfur dichloride:
*Phosgene:
The second of the above four reactions also affords phosphorus oxychloride (phosphoryl chloride), which resembles thionyl chloride in many of its reactions. | 0 | Theoretical and Fundamental Chemistry |
In 1999, Smith and his co-workers reported the first gram-scale synthesis of (+)-discodermolide, which make the development of (+)-discodermolide as a potential chemotherapeutic agent possible. This synthetic route was licensed to Novartis Pharmaceuticals. One of the major improvements was that no purification was required in the first four steps of the five-step sequence towards the common precursor as the intermediate, aldol adduct, is a crystalline solid. A chelation-controlled Mukaiyama-aldol reaction was used to set the stereogenicity at C(5) of the lactone fragment.
Two years later, Smith and his co-workers publish a third-generation synthesis in which the bulky TBS ether protecting group at C(11) of the precursor iodide was replaced by a less sterically encumbering group, MOM. This modification favors the formation of the desired phosphonium salt. The Smith third-generation synthesis of (+)-discodermolide has an overall yield of 6.0% with a longest linear sequence of 21 steps and 35 total steps. | 0 | Theoretical and Fundamental Chemistry |
The number of molecules capable of eliciting chemotactic responses is relatively high, and we can distinguish primary and secondary chemotactic molecules. The main groups of the primary ligands are as follows:
* Formyl peptides are di-, tri-, tetrapeptides of bacterial origin, formylated on the N-terminus of the peptide. They are released from bacteria in vivo or after decomposition of the cell[ a typical member of this group is the N-formylmethionyl-leucyl-phenylalanine (abbreviated fMLF or fMLP). Bacterial fMLF is a key component of inflammation has characteristic chemoattractant effects in neutrophil granulocytes and monocytes. The chemotactic factor ligands and receptors related to formyl peptides are summarized in the related article, Formyl peptide receptors.
* Complement 3a (C3a) and complement 5a (C5a) are intermediate products of the complement cascade. Their synthesis is joined to the three alternative pathways (classical, lectin-dependent, and alternative) of complement activation by a convertase enzyme. The main target cells of these derivatives are neutrophil granulocytes and monocytes as well.
* Chemokines belong to a special class of cytokines; not only do their groups (C, CC, CXC, CXC chemokines) represent structurally related molecules with a special arrangement of disulfide bridges but also their target cell specificity is diverse. CC chemokines act on monocytes (e.g., RANTES), and CXC chemokines are neutrophil granulocyte-specific (e.g., IL-8). Investigations of the three-dimensional structures of chemokines provided evidence that a characteristic composition of beta-sheets and an alpha helix provides expression of sequences required for interaction with the chemokine receptors. Formation of dimers and their increased biological activity was demonstrated by crystallography of several chemokines, e.g. IL-8.
*Metabolites of polyunsaturated fatty acids
** Leukotrienes are eicosanoid lipid mediators made by the metabolism of arachidonic acid by ALOX5 (also termed 5-lipoxygenase). Their most prominent member with chemotactic factor activity is leukotriene B4, which elicits adhesion, chemotaxis, and aggregation of leukocytes. The chemoattractant action of LTB4 is induced via either of two G protein–coupled receptors, BLT1 and BLT2, which are highly expressed in cells involved in inflammation and allergy.
** The family of 5-Hydroxyicosatetraenoic acid eicosanoids are arachidonic acid metabolites also formed by ALOX5. Three members of the family form naturally and have prominent chemotactic activity. These, listed in order of decreasing potency, are: 5-oxo-eicosatetraenoic acid, 5-oxo-15-hydroxy-eicosatetraenoic acid, and 5-Hydroxyeicosatetraenoic acid. This family of agonists stimulates chemotactic responses in human eosinophils, neutrophils, and monocytes by binding to the Oxoeicosanoid receptor 1, which like the receptors for leukotriene B4, is a G protein-coupled receptor. Aside from the skin, neutrophils are the body's first line of defense against bacterial infections. After leaving nearby blood vessels, these cells recognize chemicals produced by bacteria in a cut or scratch and migrate "toward the smell".
**5-hydroxyeicosatrienoic acid and 5-oxoeicosatrienoic acid are metabolites of Mead acid (5Z,8Z,11Z-eicosatrirenoid acid); they stimulate leukocyte chemotaxis through the oxoeicosanoid receptor 1 with 5-oxoeicosatrienoic acid being as potent as its arachidonic acid-derived analog, 5-oxo-eicosatetraenoic acid, in stimulating human blood eosinophil and neutrophil chemotaxis.
**12-Hydroxyeicosatetraenoic acid is an eicosanoid metabolite of arachidonic acid made by ALOX12 which stimulates leukocyte chemotaxis through the leukotriene B4 receptor, BLT2.
**Prostaglandin D2 is an eicosanoid metabolite of arachidononic acid made by cyclooxygenase 1 or cyclooxygenase 2 that stimulates chemotaxis through the Prostaglandin DP2 receptor. It elicits chemotactic responses in eosinophils, basophils, and T helper cells of the Th2 subtype.
**12-Hydroxyheptadecatrienoic acid is a non-eicosanoid metabolite of arachidonic acid made by cyclooxygenase 1 or cyclooxygenase 2 that stimulates leukocyte chemotaxis though the leukotriene B4 receptor, BLT2.
**15-oxo-eicosatetraenoic acid is an eicosanoid metabolite of arachidonic acid made my ALOX15; it has weak chemotactic activity for human monocytes (sees 15-Hydroxyeicosatetraenoic acid#15-oxo-ETE). The receptor or other mechanism by which this metabolite stimulates chemotaxis has not been elucidated. | 1 | Applied and Interdisciplinary Chemistry |
Auto Ejection Melt Spinning (AEMS) describes a type of melt spinning where ejection of the melt occurs as soon as it has liquefied, eliminating the need for a technician to manually control the flow rate, temperature, and/or release timing of the melt stream.
This modification allows for a much higher ribbon consistency between runs, and a greater level of automation in the process. | 1 | Applied and Interdisciplinary Chemistry |
In Complex II (succinate dehydrogenase or succinate-CoQ reductase; ) additional electrons are delivered into the quinone pool (Q) originating from succinate and transferred (via flavin adenine dinucleotide (FAD)) to Q. Complex II consists of four protein subunits: succinate dehydrogenase (SDHA); succinate dehydrogenase [ubiquinone] iron–sulfur subunit mitochondrial (SDHB); succinate dehydrogenase complex subunit C (SDHC); and succinate dehydrogenase complex subunit D (SDHD). Other electron donors (e.g., fatty acids and glycerol 3-phosphate) also direct electrons into Q (via FAD). Complex II is a parallel electron transport pathway to Complex I, but unlike Complex I, no protons are transported to the intermembrane space in this pathway. Therefore, the pathway through Complex II contributes less energy to the overall electron transport chain process. | 1 | Applied and Interdisciplinary Chemistry |
It is used to determine the ability of an organism to produce mixed acids by fermentation of glucose and to overcome the buffering capacity of the medium. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, decomplexation refers to the removal of a ligand from a coordination complex. Decomplexation is of particular interest when the ligand has been synthesized within the coordination sphere of the metal, as is often the case in organometallic chemistry. | 0 | Theoretical and Fundamental Chemistry |
Several different morphologies of the block copolymer used to create the polymersome have been used. The most frequently used are the linear diblock or triblock copolymers. In these cases, the block copolymer has one block that is hydrophobic; the other block or blocks are hydrophilic. Other morphologies used include comb copolymers, where the backbone block is hydrophilic and the comb branches are hydrophobic, and dendronized block copolymers, where the dendrimer portion is hydrophilic.
In the case of diblock, comb and dendronized copolymers the polymersome membrane has the same bilayer morphology of a liposome, with the hydrophobic blocks of the two layers facing each other in the interior of the membrane. In the case of triblock copolymers the membrane is a monolayer that mimics a bilayer, the central block filling the role of the two facing hydrophobic blocks of a bilayer.
In general they can be prepared by the methods used in the preparation of liposomes. Film rehydration, direct injection method or dissolution method. | 1 | Applied and Interdisciplinary Chemistry |
Odum et al. viewed the maximum power theorem as a principle of power-efficiency reciprocity selection with wider application than just electronics. For example, Odum saw it in open systems operating on solar energy, like both photovoltaics and photosynthesis (1963, p. 438). Like the maximum power theorem, Odums statement of the maximum power principle relies on the notion of matching, such that high-quality energy maximizes power by matching and amplifying energy (1994, pp. 262, 541): "in surviving designs a matching of high-quality energy with larger amounts of low-quality energy is likely to occur" (1994, p. 260). As with electronic circuits, the resultant rate of energy transformation will be at a maximum at an intermediate power efficiency. In 2006, T.T. Cai, C.L. Montague and J.S. Davis said that, "The maximum power principle is a potential guide to understanding the patterns and processes of ecosystem development and sustainability. The principle predicts the selective persistence of ecosystem designs that capture a previously untapped energy source." (2006, p. 317). In several texts H.T. Odum gave the Atwood machine as a practical example of the principle' of maximum power. | 0 | Theoretical and Fundamental Chemistry |
The cantilever sensor is made out of single crystal SOI-silicon with a specially developed dry-etching process that leads to a highly stable and robust component; this is why the sensor is practically totally immune to temperature and humidity variations. In addition, the sensor does not suffer from wearing. The sensor and readout can be isolated in terms of temperature allowing heated gas cell which enables applications that require gas analysis at elevated temperatures such as chemical emissions monitoring and process control. | 0 | Theoretical and Fundamental Chemistry |
Water treatment plants have evolved their technology over the years to tackle health threats due to water contamination eg cholera, typhoid, and dysentery. Treatment plants began to implement chlorination. Chlorination virtually wiped out both the spread and initial contamination of these diseases, and did so in a way that earned it the title of "probably the most significant public health advance of the millennium" from Life Magazine.
Electrochlorination is the next step in the evolution of this process. It chlorinates drinking water without producing environmental toxins. Unlike other chlorination techniques, electrochlorination generates no sludge or by-products other than hydrogen which must be managed safely. It is safer for the operators of the chlorinators as there is no handling of chlorine gas, which is highly toxic and corrosive. A risk assessment is required as the hydrogen released is flammable and explosive. | 0 | Theoretical and Fundamental Chemistry |
Commercial nuclear fission reactors are operated in the otherwise self-extinguishing prompt subcritical state. Certain fission products decay over seconds to minutes, producing additional delayed neutrons crucial to sustaining criticality. An example is bromine-87 with a half-life of about a minute. Operating in this delayed critical state, power changes slowly enough to permit human and automatic control. Analogous to fire dampers varying the movement of wood embers towards new fuel, control rods are moved as the nuclear fuel burns up over time.
In a nuclear power reactor, the main sources of radioactivity are fission products along with actinides and activation products. Fission products are most of the radioactivity for the first several hundred years, while actinides dominate roughly 10 to 10 years after fuel use.
Most fission products are retained near their points of production. They are important to reactor operation not only because some contribute delayed neutrons useful for reactor control, but some are neutron poisons that inhibit the nuclear reaction. Buildup of neutron poisons is a key to how long a given fuel element can be kept in the reactor. Fission product decay also generates heat that continues even after the reactor has been shut down and fission stopped. This decay heat requires removal after shutdown; loss of this cooling damaged the reactors at Three Mile Island and Fukushima.
If the fuel cladding around the fuel develops holes, fission products can leak into the primary coolant. Depending on the chemistry, they may settle within the reactor core or travel through the coolant system and chemistry control systems are provided to remove them. In a well-designed power reactor running under normal conditions, coolant radioactivity is very low.
The isotope responsible for most of the gamma exposure in fuel reprocessing plants (and the Chernobyl site in 2005) is caesium-137. Iodine-129 is a major radioactive isotope released from reprocessing plants. In nuclear reactors both caesium-137 and strontium-90 are found in locations away from the fuel because they're formed by the beta decay of noble gases (xenon-137, with a 3.8-minute half-life, and krypton-90, with a 32-second half-life) which enable them to be deposited away from the fuel, e.g. on control rods. | 0 | Theoretical and Fundamental Chemistry |
In some cases proteins are attracted to surfaces by an excessive surface charge. When a surface in a fluid has a net charge, ions in the fluid will adsorb to the surface. Proteins also have charged surfaces due to charge amino acid residues on the surface of the protein. The surface and the protein are then attracted by Coulombic forces.
The attraction a protein feels from a charged surface () depends exponentially on the surface's charge, as described by the following formula:
Where
* is the potential felt by the protein
* is the actual potential of the surface
* is the distance from the protein to the surface, and
* is the Debye length.
A proteins surfaces potential is given by the number of charged amino acids it has and its isoelectric point, pI. | 1 | Applied and Interdisciplinary Chemistry |
Drospirenone, also known as 1,2-dihydrospirorenone or as 17β-hydroxy-6β,7β:15β,16β-dimethylene-3-oxo-17α-pregn-4-ene-21-carboxylic acid, γ-lactone, is a synthetic steroidal 17α-spirolactone, or more simply a spirolactone. It is an analogue of other spirolactones like spironolactone, canrenone, and spirorenone. Drospirenone differs structurally from spironolactone only in that the C7α acetyl thio substitution of spironolactone has been removed and two methylene groups have been substituted in at the C6β–7β and C15β–16β positions.
Spirolactones like drospirenone and spironolactone are derivatives of progesterone, which likewise has progestogenic and antimineralocorticoid activity. The loss of the C7α acetylthio group of spironolactone, a compound with negligible progestogenic activity, appears to be involved in the restoration of progestogenic activity in drospirenone, as SC-5233, the analogue of spironolactone without a C7α substitution, has potent progestogenic activity similarly to drospirenone. | 0 | Theoretical and Fundamental Chemistry |
The categories comprise:
* Slag-based geopolymer cement;
* Rock-based geopolymer cement;
* Fly ash-based geopolymer cement:
** type 1: alkali-activated fly ash geopolymer,
** type 2: slag/fly ash-based geopolymer cement.
* Ferro-sialate-based geopolymer cement.
The first geopolymer cement developed in the 1980s was of the type (K,Na,Ca)-poly(sialate) (or slag-based geopolymer cement) and resulted from the research developments carried out by Joseph Davidovits and J.L. Sawyer at Lone Star Industries, USA and yielded the invention of Pyrament® cement. The American patent application was filed in 1984 and the patent US 4,509,985 was granted on April 9, 1985 with the title Early high-strength mineral polymer.
In the 1990s, building on the works conducted on geopolymeric cements and on the synthesis of zeolites from fly ashes on the other hand, Wastiels et al. , Silverstrim et al. and van Jaarsveld and van Deventer developed geopolymeric fly ash-based cements.
Presently two types based on siliceous (EN 197) or class F (ASTM C618) fly ashes:
* : alkali-activated fly ash geopolymer:
: In many cases requires heat curing at 60-80°C; not manufactured separately as a cement, but rather produced directly as a fly-ash based concrete. NaOH (user-hostile) + fly ash: partially-reacted fly ash particles embedded in an alumino-silicate gel with Si:Al= 1 to 2, zeolitic type (chabazite-Na and sodalite) structures.
* : slag/fly ash-based geopolymer cement:
: Room-temperature cement hardening. User-friendly silicate solution + blast furnace slag + fly ash: fly ash particles embedded in a geopolymeric matrix with Si:Al ~ 2. | 0 | Theoretical and Fundamental Chemistry |
P1 artificial chromosomes (PACs) have features of both P1 vectors and Bacterial Artificial Chromosomes (BACs). Similar to P1 vectors, they contain a plasmid and a lytic replicon as described above. Unlike P1 vectors, they do not need to be packaged into bacteriophage particles for transduction. Instead they are introduced into E. coli as circular DNA molecules through electroporation just as BACs are. Also similar to BACs, these are relatively harder to prepare due to a single origin of replication. | 1 | Applied and Interdisciplinary Chemistry |
The calcite compensation depth (CCD) occurs at the depth that the rate of calcite to the sediments is balanced with the dissolution flux, the depth at which the CaCO content are values 2–10%. Hence, the lysocline and CCD are not equivalent. The lysocline and compensation depth occur at greater depths in the Atlantic (5000–6000 m) than in the Pacific (4000–5000 m), and at greater depths in equatorial regions than in polar regions.
The depth of the CCD varies as a function of the chemical composition of the seawater and its temperature. Specifically, it is the deep waters that are undersaturated with calcium carbonate primarily because its solubility increases strongly with increasing pressure and salinity and decreasing temperature. As the atmospheric concentration of carbon dioxide continues to increase, the CCD can be expected to decrease in depth, as the ocean's acidity rises. | 0 | Theoretical and Fundamental Chemistry |
Volume percent is the concentration of a certain solute, measured by volume, in a solution. It has as a denominator the volume of the mixture itself, as usual for expressions of concentration, rather than the total of all the individual components’ volumes prior to mixing:
Volume percent is usually used when the solution is made by mixing two fluids, such as liquids or gases. However, percentages are only additive for ideal gases.
The percentage by volume (vol%) is one way of expressing the composition of a mixture with a dimensionless quantity; mass fraction (percentage by weight, wt%) and mole fraction (percentage by moles, mol%) are others.
In the case of a mixture of ethanol and water, which are miscible in all proportions, the designation of solvent and solute is arbitrary. The volume of such a mixture is slightly less than the sum of the volumes of the components. Thus, by the above definition, the term "40% alcohol by volume" refers to a mixture of 40 volume units of ethanol with enough water to make a final volume of 100 units, rather than a mixture of 40 units of ethanol with 60 units of water. The "enough water" is actually slightly more than 60 volume units, since water-ethanol mixture loses volume due to intermolecular attraction. | 0 | Theoretical and Fundamental Chemistry |
In 1987 Gelbart was elected a Fellow of the American Physical Society "for his many contributions to the light scattering and phase transition properties of simple fluids, liquid crystals, and surfactant solutions". He received the 1991 Lennard-Jones Prize of the British Royal Society of Chemistry, a 1998 Guggenheim Fellowship, the 2001 Liquids Prize of the American Chemical Society, election to the American Academy of Arts and Sciences in 2009, and endowed lectureships over the past 25 years at the Curie Institute (Paris), the University of Leeds (England), Case Western Reserve University, Cornell University, Carnegie Mellon University, the University of Pittsburgh, and the University of Texas at Austin. At UCLA he won the 1996 University Distinguished Teaching Award, served as Chair of the Department of Chemistry and Biochemistry (2000-2004), and was awarded the Glenn T. Seaborg Medal in 2017. In 2016, his 70th birthday was honored by an international symposium on "Self Assembly, from Atoms to Life" at the Meso-American Center for Theoretical Physics, and by a "festschrift" issue of the Journal of Physical Chemistry B. | 0 | Theoretical and Fundamental Chemistry |
The Goldman–Hodgkin–Katz voltage equation, sometimes called the Goldman equation, is used in cell membrane physiology to determine the Resting potential across a cell's membrane, taking into account all of the ions that are permeant through that membrane.
The discoverers of this are David E. Goldman of Columbia University, and the Medicine Nobel laureates Alan Lloyd Hodgkin and Bernard Katz. | 0 | Theoretical and Fundamental Chemistry |
A more commonly used parameter is the half-life . Given a sample of a particular radionuclide, the half-life is the time taken for half the radionuclide's atoms to decay. For the case of one-decay nuclear reactions:
the half-life is related to the decay constant as follows: set and = to obtain
This relationship between the half-life and the decay constant shows that highly radioactive substances are quickly spent, while those that radiate weakly endure longer. Half-lives of known radionuclides vary by almost 54 orders of magnitude, from more than years ( sec) for the very nearly stable nuclide Te, to seconds for the highly unstable nuclide H.
The factor of in the above relations results from the fact that the concept of "half-life" is merely a way of selecting a different base other than the natural base for the lifetime expression. The time constant is the -life, the time until only 1/e remains, about 36.8%, rather than the 50% in the half-life of a radionuclide. Thus, is longer than . The following equation can be shown to be valid:
Since radioactive decay is exponential with a constant probability, each process could as easily be described with a different constant time period that (for example) gave its "(1/3)-life" (how long until only 1/3 is left) or "(1/10)-life" (a time period until only 10% is left), and so on. Thus, the choice of and for marker-times, are only for convenience, and from convention. They reflect a fundamental principle only in so much as they show that the same proportion of a given radioactive substance will decay, during any time-period that one chooses.
Mathematically, the life for the above situation would be found in the same way as aboveby setting , and substituting into the decay solution to obtain | 0 | Theoretical and Fundamental Chemistry |
While small-scale columns range from inner diameters of 0.5 cm and withstand pressures of up to 130 MPa, industrial large scale columns reach diameters of up to 2 m and operate at considerable lower pressures (below 1 MPa). While it is favorable to view the packed bed of a column large scale columns are manufactured from steel due to its superior resilience.
Chromatography columns can be used as stand-alone devices or in combination with manual or automated chromatography systems. Medium to large columns are almost exclusively operated together with automated systems to decrease the risk of process failure and loss of product. | 0 | Theoretical and Fundamental Chemistry |
Acoustic droplet ejection uses a pulse of ultrasound to move low volumes of fluids (typically nanoliters or picoliters) without any physical contact. This technology focuses acoustic energy into a fluid sample to eject droplets as small as a millionth of a millionth of a litre (picoliter = 10 litre). ADE technology is a very gentle process, and it can be used to transfer proteins, high molecular weight DNA and live cells without damage or loss of viability. This feature makes the technology suitable for a wide variety of applications including proteomics and cell-based assays. | 1 | Applied and Interdisciplinary Chemistry |
Complex metal hydrides are salts wherein the anions contain hydrides. In older chemical literature and even in contemporary materials science textbooks, a "metal hydride" is assumed to be nonmolecular, i.e. three-dimensional lattices of atomic ions. In such systems, hydrides are often interstitial and nonstoichiometric, and the bonding between the metal and hydrogen atoms is significantly ionic. In contrast, complex metal hydrides typically contain more than one type of metal or metalloid and may be soluble but invariably react with water. They exhibit ionic bonding between a positive metal ion with molecular anions containing the hydride. In such materials the hydrogen is bonded with significant covalent character to the second metal or metalloid atoms. | 0 | Theoretical and Fundamental Chemistry |
This method was developed by German physicist Johann Wilhelm Hittorf in 1853., and is based on observations of the changes in concentration of an electrolyte solution in the vicinity of the electrodes. In the Hittorf method, electrolysis is carried out in a cell with three compartments: anode, central, and cathode. Measurement of the concentration changes in the anode and cathode compartments determines the transport numbers. The exact relationship depends on the nature of the reactions at the two electrodes. For the electrolysis of aqueous copper(II) sulfate () as an example, with and ions, the cathode reaction is the reduction and the anode reaction is the corresponding oxidation of Cu to . At the cathode, the passage of coulombs of electricity leads to the reduction of moles of , where is the Faraday constant. Since the ions carry a fraction of the current, the quantity of flowing into the cathode compartment is moles, so there is a net decrease of in the cathode compartment equal to . This decrease may be measured by chemical analysis in order to evaluate the transport numbers. Analysis of the anode compartment gives a second pair of values as a check, while there should be no change of concentrations in the central compartment unless diffusion of solutes has led to significant mixing during the time of the experiment and invalidated the results. | 0 | Theoretical and Fundamental Chemistry |
Ketene is produced on a commercial scale by thermal dehydration of acetic acid. Substituted ketenes can be prepared from acyl chlorides by an elimination reaction in which HCl is lost:
In this reaction, a base, usually triethylamine, removes the acidic proton alpha to the carbonyl group, inducing the formation of the carbon-carbon double bond and the loss of a chloride ion:
Ketenes can also be formed from α-diazoketones by the Wolff rearrangement.
Another way to generate ketenes is through flash vacuum thermolysis (FVT) with 2-pyridylamines. Plüg and Wentrup developed a method in 1997 that improved on FVT reactions to produce ketenes with a stable FVT that is moisture insensitive, using mild conditions (480 °C). The N-pyridylamines are prepared via a condensation with R-malonates with N-amino(pyridene) and DCC as the solvent.
A more robust method for preparing ketenes is the carbonylation of metal-carbenes, and in situ reaction of the thus produced highly reactive ketenes with suitable reagents such as imines, amines, or alcohols. This method is an efficient one‐pot tandem protocol of the carbonylation of α‐diazocarbonyl compounds and a variety of N‐tosylhydrazones catalysed by Co(II)–porphyrin metalloradicals leading to the formation of ketenes, which subsequently react with a variety of nucleophiles and imines to form esters, amides and β‐lactams. This system has a broad substrate scope and can be applied to various combinations of carbene precursors, nucleophiles and imines. | 0 | Theoretical and Fundamental Chemistry |
Since gases fill the entirety of the container which they occupy, the volumetric thermal expansion coefficient at constant pressure, , is the only one of interest.
For an ideal gas, a formula can be readily obtained by differentiation of the ideal gas law, . This yields
where is the pressure, is the molar volume (, with the total number of moles of gas), is the absolute temperature and is equal to the gas constant.
For an isobaric thermal expansion, , so that and the isobaric thermal expansion coefficient is:
which is a strong function of temperature; doubling the temperature will halve the thermal expansion coefficient. | 0 | Theoretical and Fundamental Chemistry |
In meteorology and physical oceanography, advection often refers to the horizontal transport of some property of the atmosphere or ocean, such as heat, humidity or salinity, and convection generally refers to vertical transport (vertical advection). Advection is important for the formation of orographic clouds (terrain-forced convection) and the precipitation of water from clouds, as part of the hydrological cycle. | 1 | Applied and Interdisciplinary Chemistry |
The mycotoxin phomoxanthone B, or PXB for short, is a toxic natural product. It is a less toxic isomer of phomoxanthone A and one of the two founding members of the class of phomoxanthone compounds. The phomoxanthones are named after the fungus Phomopsis, from which they were first isolated, and after their xanthonoid structure. Chemically, they are dimers of two tetrahydroxanthones that are covalently linked to each other. PXB itself is a homodimer of two identical diacetylated tetrahydroxanthones. The position of the link between the two tetrahydroxanthones is the only structural difference between PXB and its isomers PXA and dicerandrol C: In PXA, the two xanthonoid monomers are symmetrically linked at C-4,4’, while in PXB, they are asymmetrically linked at C-2,4’, and in dicerandrol C, they are symmetrically linked at C-2,2’. | 1 | Applied and Interdisciplinary Chemistry |
In 1808, English physicist John Dalton (1766–1844) assimilated the known experimental work of many people to summarize the empirical evidence on the composition of matter. He noticed that distilled water everywhere analyzed to the same elements, hydrogen and oxygen. Similarly, other purified substances decomposed to the same elements in the same proportions by weight.
:Therefore we may conclude that the ultimate particles of all homogeneous bodies are perfectly alike in weight, figure, etc. In other words, every particle of water is like every other particle of water; every particle of hydrogen is like every other particle of hydrogen, etc.
Furthermore, he concluded that there was a unique atom for each element, using Lavoisier's definition of an element as a substance that could not be analyzed into something simpler. Thus, Dalton concluded the following.
:Chemical analysis and synthesis go no farther than to the separation of particles one from another, and to their reunion. No new creation or destruction of matter is within the reach of chemical agency. We might as well attempt to introduce a new planet into the solar system, or to annihilate one already in existence, as to create or destroy a particle of hydrogen. All the changes we can produce, consist in separating particles that are in a state of cohesion or combination, and joining those that were previously at a distance.
And then he proceeded to give a list of relative weights in the compositions of several common compounds, summarizing:
:1st. That water is a binary compound of hydrogen and oxygen, and the relative weights of the two elementary atoms are as 1:7, nearly;
:2nd. That ammonia is a binary compound of hydrogen and azote nitrogen, and the relative weights of the two atoms are as 1:5, nearly...
Dalton concluded that the fixed proportions of elements by weight suggested that the atoms of one element combined with only a limited number of atoms of the other elements to form the substances that he listed. | 1 | Applied and Interdisciplinary Chemistry |
Apothecary () is an archaic English term for a medical professional who formulates and dispenses materia medica (medicine) to physicians, surgeons and patients. The modern terms pharmacist and chemist (British English) have taken over this role.
In some languages and regions, "apothecary" is not archaic and has become those languages' term for "pharmacy" or a pharmacist who owns one.
Apothecaries' investigation of herbal and chemical ingredients was a precursor to the modern sciences of chemistry and pharmacology.
In addition to dispensing herbs and medicine, apothecaries offered general medical advice and a range of services that are now performed by other specialist practitioners, such as surgeons and obstetricians. Apothecary shops sold ingredients and the medicines they prepared wholesale to other medical practitioners, as well as dispensing them to patients. In 17th-century England, they also controlled the trade in tobacco which was imported as a medicine. | 1 | Applied and Interdisciplinary Chemistry |
Cyanobacteria contain both PSI and PSII. Their light-harvesting system is different from that found in plants (they use phycobilins, rather than chlorophylls, as antenna pigments), but their electron transport chain
→ PSII → plastoquinol → bf → cytochrome c → PSI → ferredoxin → NADPH
bf ← plastoquinol
is, in essence, the same as the electron transport chain in chloroplasts. The mobile water-soluble electron carrier is cytochrome c in cyanobacteria, having been replaced by plastocyanin in plants.
Cyanobacteria can also synthesize ATP by oxidative phosphorylation, in the manner of other bacteria. The electron transport chain is
NADH dehydrogenase → plastoquinol → bf → cyt c → cyt aa →
where the mobile electron carriers are plastoquinol and cytochrome c, while the proton pumps are NADH dehydrogenase, cyt bf and cytochrome aa (member of the COX3 family).
Cyanobacteria are the only bacteria that produce oxygen during photosynthesis. Earth's primordial atmosphere was anoxic. Organisms like cyanobacteria produced our present-day oxygen-containing atmosphere.
The other two major groups of photosynthetic bacteria, purple bacteria and green sulfur bacteria, contain only a single photosystem and do not produce oxygen. | 0 | Theoretical and Fundamental Chemistry |
In biocatalysis, many reactions are sought that are absent in nature. To do this, enzymes with a small promiscuous activity towards the required reaction are identified and evolved via directed evolution or rational design.
An example of a commonly evolved enzyme is ω-transaminase which can replace a ketone with a chiral amine and consequently libraries of different homologues are commercially available for rapid biomining (eg. Codexis).
Another example is the possibility of using the promiscuous activities of cysteine synthase (cysM) towards nucleophiles to produce non-proteinogenic amino acids. | 1 | Applied and Interdisciplinary Chemistry |
Pulsatile insulin secretion from individual beta cells is driven by oscillation of the calcium concentration in the cells. In beta cells lacking contact (i.e. outside islet of Lagerhans), the periodicity of these oscillations is rather variable (2-10 min). However, within an islet of Langerhans, the oscillations become synchronized by electrical coupling between closely located beta cells that are connected by gap junctions, and the periodicity is more uniform (3-6 min). In addition to gap junctions, pulse coordination is managed by ATP signaling. α and δ cells in the pancreas also share secrete factors in a similar pulsatile manner. | 1 | Applied and Interdisciplinary Chemistry |
The Fluid Dynamics Prize has been awarded to:
* 2022: Elisabeth Charlaix
* 2020: Katepalli Sreenivasan
* 2019: Alexander Smits
* 2018: Keith Moffatt
* 2017: Detlef Lohse
* 2016: Howard A. Stone
* 2015: Morteza Gharib
* 2014: Geneviève Comte-Bellot
* 2013: Elaine Surick Oran
* 2012: John F. Brady
* 2011: Tony Maxworthy
* 2010: E. John Hinch
* 2009: Stephen B. Pope
* 2006: Thomas S. Lundgren
* 2005: Ronald J. Adrian
* 2002: Gary Leal
* 2001: Howard Brenner
* 1999: Daniel D. Joseph
* 1998: Fazle Hussain
* 1997: Louis Norberg Howard
* 1996: Parviz Moin
* 1995: Harry L Swinney
* 1994: Stephen H. Davis
* 1993: Theodore Yao-tsu Wu
* 1992: William R. Sears
* 1991: Andreas Acrivos
* 1990: John L. Lumley
* 1987: Anatol Roshko
* 1986: Robert T. Jones
* 1985: Chia-Shun Yih
* 1984: George Carrier
* 1983: Stanley Corrsin
* 1982: Howard W. Emmons
* 1980: Hans Wolfgang Liepmann
* 1979: Chia Chiao Lin | 1 | Applied and Interdisciplinary Chemistry |
The basic principle of displacement chromatography is: there are only a finite number of binding sites for solutes on the matrix (the stationary phase), and if a site is occupied by one molecule, it is unavailable to others. As in any chromatography, equilibrium is established between molecules of a given kind bound to the matrix and those of the same kind free in solution. Because the number of binding sites is finite, when the concentration of molecules free in solution is large relative to the dissociation constant for the sites, those sites will mostly be filled. This results in a downward-curvature in the plot of bound vs free solute, in the simplest case giving a Langmuir isotherm. A molecule with a high affinity for the matrix (the displacer) will compete more effectively for binding sites, leaving the mobile phase enriched in the lower-affinity solute. Flow of mobile phase through the column preferentially carries off the lower-affinity solute and thus at high concentration the higher-affinity solute will eventually displace all molecules with lesser affinities. | 0 | Theoretical and Fundamental Chemistry |
Let represent the surface pressure coefficient for an impermeable cylinder:
where is the surface pressure of the impermeable cylinder. Now let be the internal pressure coefficient inside the cylinder, then a slight normal velocity due to the slight porousness is given by
but the zero net flux condition
requires that . Therefore,
Then the solution to the first-order approximation is | 1 | Applied and Interdisciplinary Chemistry |
Ronald James Gillespie, (August 21, 1924 – February 26, 2021) was a British chemist specializing in the field of molecular geometry, who arrived in Canada after accepting an offer that included his own laboratory with new equipment, which post-World War II Britain could not provide. He was responsible for establishing inorganic chemistry education in Canada.
He was educated at the University of London obtaining a B.Sc. in 1945, a Ph.D. in 1949 and a D.Sc. in 1957. He was assistant lecturer and then lecturer in the Department of Chemistry at University College London in England from 1950 to 1958.
He moved to McMaster University, Hamilton, Ontario, Canada, in 1958, dying on February 26, 2021, at the age of ninety-six in the nearby town of Dundas, Ontario. He was elected as a Fellow of the Royal Society of Canada in 1965, a Fellow of the Royal Society of London in 1977, and made a member of the Order of Canada in 2007.
Gillespie did extensive work on expanding the idea of the Valence Shell Electron Pair Repulsion (VSEPR) model of Molecular Geometry, which he developed with Ronald Nyholm (and thus is also known as the Gillespie-Nyholm theory), and setting the rules for assigning numbers. He has written several books on this VSEPR topic in chemistry. With other workers he developed LCP theory, (ligand close packing theory), which for some molecules allows geometry to be predicted on the basis of ligand-ligand repulsions. Gillespie has also done extensive work on interpreting the covalent radius of fluorine. The covalent radius of most atoms is found by taking half the length of a single bond between two similar atoms in a neutral molecule. Calculating the covalent radius for fluorine is more difficult because of its high electronegativity compared to its small atomic radius size. Gillespie's work on the bond length of fluorine focuses on theoretically determining the covalent radius of fluorine by examining its covalent radius when it is attached to several different atoms. | 0 | Theoretical and Fundamental Chemistry |
* Zharkova, Olga Nicholaevna (b. 11 January 1979, Moscow) – Russian curler, member of two Olympic Games (2002 and 2006), European champion in 2006. | 1 | Applied and Interdisciplinary Chemistry |
Hydrogenated starch hydrolysates (HSHs), also known as polyglycitol syrup (INS 964), are mixtures of several sugar alcohols (a type of sugar substitute). Hydrogenated starch hydrolysates were developed by the Swedish company Lyckeby Starch in the 1960s. The HSH family of polyols is an approved food ingredient in Canada, Japan, and Australia. HSH sweeteners provide 40 to 90% sweetness relative to table sugar.
Hydrogenated starch hydrolysates are produced by the partial hydrolysis of starch – most often corn starch, but also potato starch or wheat starch. This creates dextrins (glucose and short glucose chains). The hydrolyzed starch (dextrin) then undergoes hydrogenation to convert the dextrins to sugar alcohols.
Hydrogenated starch hydrolysates are similar to sorbitol: if the starch is completely hydrolyzed so that only single glucose molecules remain, then after hydrogenation the result is sorbitol. Because in HSHs the starch is not completely hydrolyzed, a mixture of sorbitol, maltitol, and longer chain hydrogenated saccharides (such as maltotriitol) is produced. When no single polyol is dominant in the mix, the generic name hydrogenated starch hydrolysates is used. However, if 50% or more of the polyols in the mixture are of one type, it can be labeled as "sorbitol syrup", or "maltitol syrup", etc. | 0 | Theoretical and Fundamental Chemistry |
The cDNA molecules generated by RACE can be sequenced using high-throughput sequencing technologies (also called, RACE-seq). High-throughput sequencing characterization of RACE fragments is highly time-efficient, more sensitive, less costly and technically feasible compared to traditional characterization of RACE fragments with molecular cloning followed by Sanger sequencing of a few clones. | 1 | Applied and Interdisciplinary Chemistry |
Because of the diffraction limit in the resolution of conventional lens-based microscopes, namely D = 0.61λ/nsinθ, the maximum resolution obtainable with an optical microscope is ~200 nm. A new type of lens using multiple scattering of light allowed to improve the resolution to about 100 nm. Several new microscopy techniques with a sub-nanometer resolution have been developed in the last several decades, such as electron microscopy (SEM and TEM) and scanning probe microscopy (NSOM, STM and AFM). SPM differs from other techniques in that the excitation and signal collection are very close (less than diffraction limit distance) to the sample. Instead of using a conventional lens to obtain magnified images of samples, an SPM scans across the sample with a very sharp probe. Whereas SEM and TEM usually require vacuum and an extensive sample preparation, SPM measurements can be performed in atmospheric or liquid conditions.
Despite the achievable resolution of atomic scale for AFM and NSOM techniques, it does not provide chemical information of the sample. The infrared part of the electromagnetic spectrum covers molecular vibrations which can characterize chemical bonding within the sample.
By combining SPM and vibrational spectroscopy, AFM/IR-NSOM and AFM-IR have emerged as useful characterization tools that integrate the high spatial resolution abilities of AFM with IR spectroscopy. This new technique can be referred to as AFM-FTIR, AFM-IR and NSOM/FTIR. AFM and NSOM can be used to detect the response when a modulated infrared radiation generated by an FTIR spectrometer is absorbed by a material. In the AFM-IR technique the absorption of the radiation by sample will cause a rapid thermal expansion wave which will be transferred to the vibrational modes of the AFM cantilever. Specifically, thermal expansion wave induces a vertical displacement of the ATM tip (Figure 6). A local IR absorption spectrum then can be obtained through the measurement of the amplitude of the cantilever, which is a function of the IR source wavelength. For example, when the radiation laser wavelength is tuned at the resonance frequency with the vibrational absorption frequency of the sample, the displacement intensity of the cantilever will increase until the laser wavelength reaches the maximum of sample absorption. The displacement of the cantilever will then be reduced as the laser wavelength is tuned past the absorption maximum. This approach can map chemical composition beyond the diffraction-limit resolution and can also provide three-dimensional topographic, thermal and mechanical information at the nanoscale. Overall, it overcomes the resolution limit of traditional IR spectroscopy and adds chemical and mechanical mapping to the AFM and NSOM. | 0 | Theoretical and Fundamental Chemistry |
Lower pH and lower applied redox potential facilitate the evolution and the enrichment of hydrogen during the process of SCC, thus increasing the SCC intensity.
* Certain austenitic stainless steels and aluminium alloys crack in the presence of chlorides. This limits the usefulness of austenitic stainless steel for containing water with higher than a few parts per million content of chlorides at temperatures above ;
* mild steel cracks in the presence of alkali (e.g. boiler cracking and caustic stress corrosion cracking) and nitrates;
* copper alloys crack in ammoniacal solutions (season cracking);
* high-tensile steels have been known to crack in an unexpectedly brittle manner in a whole variety of aqueous environments, especially when chlorides are present.
With the possible exception of the latter, which is a special example of hydrogen cracking, all the others display the phenomenon of subcritical crack growth, i.e. small surface flaws propagate (usually smoothly) under conditions where fracture mechanics predicts that failure should not occur. That is, in the presence of a corrodent, cracks develop and propagate well below critical stress intensity factor (). The subcritical value of the stress intensity, designated as , may be less than 1% of . | 1 | Applied and Interdisciplinary Chemistry |
The most common side effects (more than 10% of patients) are hot flashes and sweating, which are typical of estrogen deficiency as caused by exemestane, and also insomnia, headache, and joint pain. Nausea and fatigue are mainly observed in patients with advanced breast cancer.
An occasional decrease in lymphocytes has been observed in approximately 20% of patients receiving Aromasin, particularly in patients with pre-existing lymphopenia.
Exemestane has androgenic properties similarly to formestane and can produce androgenic side effects such as acne and weight gain, although these are generally associated with supratherapeutic dosages of the drug. | 0 | Theoretical and Fundamental Chemistry |
In the case of the hyperbolic conservation law (), we have seen that the shock speed can be obtained by simple division. However, for the 1D Euler equations (), () and (), we have the vector state variable and the jump conditions become
Equations (), () and () are known as the Rankine–Hugoniot conditions for the Euler equations and are derived by enforcing the conservation laws in integral form over a control volume that includes the shock. For this situation cannot be obtained by simple division. However, it can be shown by transforming the problem to a moving co-ordinate system
(setting , , to remove ) and some algebraic manipulation (involving the elimination of from the transformed equation () using the transformed equation ()), that the shock speed is given by
where is the speed of sound in the fluid at upstream conditions. | 1 | Applied and Interdisciplinary Chemistry |
After its heyday in the Tang dynasty Daoist alchemy continued to flourish during the Song dynasty (960–1279) period. However, since six Tang emperors and many court officials died from elixir poisoning, Song alchemists exercised more caution, not only in the composition of the elixirs themselves, but also in attempts to find pharmaceutical methods of counteracting the toxic effects. The number of ingredients used in elixir formulas was reduced and there was a tendency to return to the ancient and difficult terminology of the Cantongqi, perhaps to conceal the processes from rash and ignorant operators. Psycho-physiological neidan alchemy became steadily more popular than laboratory waidan alchemy.
During the Song dynasty, the practice of consuming metallic elixirs was not confined to the imperial court and expanded to anyone wealthy enough to pay. The author and official Ye Mengde (1077–1148) described how two of his friends had died from elixirs of immortality in one decade. First, Lin Yanzhen, who boasted about his health and muscular strength, took an elixir for three years, "Whereupon ulcers developed in his chest, first near the hairs as large as rice-grains, then after a couple of days his neck swelled up so that chin and chest seemed continuous." Lin died after ten months of suffering, and his doctors discovered cinnabar powder had accumulated in his pus and blood. Second, whenever Xie Renbo "heard of anyone who had some cinnabar subdued by fire he went after it, caring nothing about the distance, and his only fear was that he would not have enough." He also developed ulcers on the chest. Although his friends noticed changes in his appearance and behavior, Xie did not recognize that he had been poisoned, "till suddenly it came upon him like a storm of wind and rain, and he died in a single night".
The scientist and statesman Shen Kuos 1088 Dream Pool Essays' suggested that mercury compounds might be medicinally valuable and needed further study—foreshadowing the use of metallic compounds in modern medicine, such as mercury in salvarsan for syphilis or antimony for visceral leishmaniasis. Shen says his cousin once transformed cinnabar into an elixir, but one of his students mistakenly ate a leftover piece, became delirious, and died the next day.
Su Shi (1037–1101), the Song dynasty scholar and pharmacologist, was familiar with the life-prolonging claims of alchemists, but wrote in a letter that, "I have recently received some cinnabar (elixir) which shows a most remarkable colour, but I cannot summon up enough courage to try it".
The forensic medical expert Song Ci was familiar with the effects of metal poisoning, and his c. 1235 Collected Cases of Injustice Rectified handbook for coroners gives a test for mercury poisoning: plunge a piece of gold into the intestine or tissues and see if a superficial amalgam forms. He also describes the colic, cramps, and discharge of blood from arsenic poisoning, and gives several antidotes including emetics. | 1 | Applied and Interdisciplinary Chemistry |
The semiconductor is a collective term for a series of devices. It mainly includes three categories：two-terminal devices, three-terminal devices, and four-terminal devices. The combination of the semiconductors is called an integrated circuit.
The relationship between Ficks law and semiconductors: the principle of the semiconductor is transferring chemicals or dopants from a layer to a layer. Ficks law can be used to control and predict the diffusion by knowing how much the concentration of the dopants or chemicals move per meter and second through mathematics.
Therefore, different types and levels of semiconductors can be fabricated.
Integrated circuit fabrication technologies, model processes like CVD, thermal oxidation, wet oxidation, doping, etc. use diffusion equations obtained from Fick's law. | 0 | Theoretical and Fundamental Chemistry |
As metabolite analyses are being conducted at the individual patient level, pharmacometabolomics may be considered a form of personalized medicine. This field is currently being employed in a predictive manner to determine the potential responses of therapeutic compounds in individual patients, allowing for more customized treatment regimens. It is anticipated that such pharmacometabolomics approaches will lead to the improved ability to predict an individuals response to a compound, the efficacy and metabolism of it as well as adverse or off-target effects that may take place in the body. The metabolism of certain drugs varies from patient to patient as the copy number of the genes which code for common drug metabolizing enzymes varies within the population, and leads to differences in the ability of an individual to metabolize different compounds. Other important personal factors contributing to an individuals metabolic profile, such as patient nutritional status, commensal bacteria, age, and pre-existing medical conditions, are also reflected in metabolite assessment., Overall, pharmacometabolomic analyses combined with such approaches as pharmacogenetics, can function to identify the metabolic processes and particular genetic alterations that may compromise the anticipated efficacy of a drug in a particular patient. The results of such analyses can then allow modification of treatment regimens for an optimal outcome. | 1 | Applied and Interdisciplinary Chemistry |
Since the 1980s, new methods of marketing for prescription drugs to consumers have become important. Direct-to-consumer media advertising was legalised in the FDA Guidance for Industry on Consumer-Directed Broadcast Advertisements. | 1 | Applied and Interdisciplinary Chemistry |
The SIP peptide binding pocket is the docking station of the eight amino acid leaderless peptide signal, speB-inducing peptide (SIP). The binding pocket is a tripartite construction of the C-terminals α12 helix which is a capping helix, TPR3s α6 helix that has a hydrophobic interplay with SIP sidechains, and TPR 4's α8 helix which electrostatically stabilizes SIP. Variations in pH level altered strength of adherence between SIP and the SIP binding pocket with acidic pH levels between 5.5 and 6.5 enhancing adherence and pH levels between 7 and 9 reducing adherence. | 1 | Applied and Interdisciplinary Chemistry |
Interfacial rheology is a branch of rheology that studies the flow of matter at the interface between a gas and a liquid or at the interface between two immiscible liquids. The measurement is done while having surfactants, nanoparticles or other surface active compounds present at the interface. Unlike in bulk rheology, the deformation of the bulk phase is not of interest in interfacial rheology and its effect is aimed to be minimized. Instead, the flow of the surface active compounds is of interest..
The deformation of the interface can be done either by changing the size or shape of the interface. Therefore interfacial rheological methods can be divided into two categories: dilational and shear rheology methods. | 0 | Theoretical and Fundamental Chemistry |
An open-label clinical study for infantile neuroaxonal dystrophy evaluating long-term evaluation of efficacy, safety, tolerability, and pharmacokinetics of RT001, which, when taken with food, can protect the neuronal cells from degeneration, started in the Summer 2018. | 1 | Applied and Interdisciplinary Chemistry |
MCP-RHEED is a system in which an electron beam is amplified by a micro-channel plate (MCP). This system consists of an electron gun and an MCP equipped with a fluorescent screen opposite to the electron gun. Because of the amplification, the intensity of the electron beam can be decreased by several orders of magnitude and the damage to the samples is diminished. This method is used to observe the growth of insulator crystals such as organic films and alkali halide films, which are easily damaged by electron beams. | 0 | Theoretical and Fundamental Chemistry |
Porphyrins have been evaluated in the context of photodynamic therapy (PDT) since they strongly absorb light, which is then converted to heat in the illuminated areas. This technique has been applied in macular degeneration using verteporfin.
PDT is considered a noninvasive cancer treatment, involving the interaction between light of a determined frequency, a photo-sensitizer, and oxygen. This interaction produces the formation of a highly reactive oxygen species (ROS), usually singlet oxygen, as well as superoxide anion, free hydroxyl radical, or hydrogen peroxide. These high reactive oxygen species react with susceptible cellular organic biomolecules such as; lipids, aromatic amino acids, and nucleic acid heterocyclic bases, to produce oxidative radicals that damage the cell, possibly inducing apoptosis or even necrosis. | 1 | Applied and Interdisciplinary Chemistry |
The asialoglycoprotein receptor was first characterized in 1968 by [https://www.sciencedirect.com/science/article/pii/S0021925818993373?via%3Dihub Morell et al.] and was the first mammalian lectin identified. The researchers transferred radioactively-labeled ceruloplasmin that had undergone a reaction via the enzyme neuraminidase to remove the protein's terminal sialic acid, generating an asialoglycoprotein. Upon injection of the radioactive protein into rabbits, the radioactivity of the entire asialoglycoprotein (rather than a portion of the protein) quickly moved from the blood into the liver. This rapid movement from the blood into the liver only occurred if the sialic acid of the protein was removed; i.e., if the protein had an exposed galactose residue (that would normally be covered by the sialic acid). Thus, it was concluded that a receptor is capable of recognizing asialoglycoproteins (i.e., proteins that have lost their terminal sialic acids) and removing them from circulation by transporting them to the liver. | 1 | Applied and Interdisciplinary Chemistry |
The ions undergoing fusion in many systems will essentially never occur alone but will be mixed with electrons that in aggregate neutralize the ions' bulk electrical charge and form a plasma. The electrons will generally have a temperature comparable to or greater than that of the ions, so they will collide with the ions and emit x-ray radiation of 10–30 keV energy, a process known as Bremsstrahlung.
The huge size of the Sun and stars means that the x-rays produced in this process will not escape and will deposit their energy back into the plasma. They are said to be opaque to x-rays. But any terrestrial fusion reactor will be optically thin for x-rays of this energy range. X-rays are difficult to reflect but they are effectively absorbed (and converted into heat) in less than mm thickness of stainless steel (which is part of a reactor's shield). This means the bremsstrahlung process is carrying energy out of the plasma, cooling it.
The ratio of fusion power produced to x-ray radiation lost to walls is an important figure of merit. This ratio is generally maximized at a much higher temperature than that which maximizes the power density (see the previous subsection). The following table shows estimates of the optimum temperature and the power ratio at that temperature for several reactions:
The actual ratios of fusion to Bremsstrahlung power will likely be significantly lower for several reasons. For one, the calculation assumes that the energy of the fusion products is transmitted completely to the fuel ions, which then lose energy to the electrons by collisions, which in turn lose energy by Bremsstrahlung. However, because the fusion products move much faster than the fuel ions, they will give up a significant fraction of their energy directly to the electrons. Secondly, the ions in the plasma are assumed to be purely fuel ions. In practice, there will be a significant proportion of impurity ions, which will then lower the ratio. In particular, the fusion products themselves must remain in the plasma until they have given up their energy, and will remain for some time after that in any proposed confinement scheme. Finally, all channels of energy loss other than Bremsstrahlung have been neglected. The last two factors are related. On theoretical and experimental grounds, particle and energy confinement seem to be closely related. In a confinement scheme that does a good job of retaining energy, fusion products will build up. If the fusion products are efficiently ejected, then energy confinement will be poor, too.
The temperatures maximizing the fusion power compared to the Bremsstrahlung are in every case higher than the temperature that maximizes the power density and minimizes the required value of the fusion triple product. This will not change the optimum operating point for – very much because the Bremsstrahlung fraction is low, but it will push the other fuels into regimes where the power density relative to – is even lower and the required confinement even more difficult to achieve. For – and –, Bremsstrahlung losses will be a serious, possibly prohibitive problem. For –, p– and p– the Bremsstrahlung losses appear to make a fusion reactor using these fuels with a quasineutral, isotropic plasma impossible. Some ways out of this dilemma have been considered but rejected. This limitation does not apply to non-neutral and anisotropic plasmas; however, these have their own challenges to contend with. | 0 | Theoretical and Fundamental Chemistry |
Different transition metals have been used to catalyze carboamination reactions, including palladium, copper, and rhodium etc. The reaction mechanism varies with different transition metals. For palladium-catalyzed carboamination reactions, Pd(0)/Pd(II) and Pd(II)/Pd(IV) catalytic cycles are the most common mechanisms that have been proposed.
The reaction mode for the key aminopalladation step is different in these two cases. In Wolfe’s chemistry, which is known as the Pd(0)/Pd(II) catalytic system, syn-aminopalladation is observed. While in the Pd(II)/Pd(IV) catalytic system, which was developed by Forrest Michael, anti-aminopalladation was observed. It is believed that the pH of the reaction will affect the existing form of the amine nucleophile, which will determine whether the nitrogen coordinates with palladium center or not during the aminopalladation step. For the C–H activation step in Pd(II)/Pd(IV) chemistry, since there is no directing effect on the aromatic ring, large excess of arenes are required.
In 2015, Rovis and coworkers reported a rhodium-catalyzed intermolecular carboamination. In this reaction, enoxyphthalimide was used to serve as both the nitrogen and carbon source. The reaction mechanism is proposed in the paper (vide infra).
In 2017, Liu and coworkers reported a copper-catalyzed three component carboamination reaction of styrenes. In the meantime, Engle and coworkers published a palladium-catalyzed three component carboamination reaction using directing group strategy. These two works are the very rare examples of three component carboamination reactions. | 0 | Theoretical and Fundamental Chemistry |
Prior to the invention of the theodolite, the goniometer was used in surveying. The application of triangulation to geodesy was described in the second (1533) edition of Cosmograficus liber by Petri Appiani as a 16-page appendix by Frisius entitled Libellus de locorum describendorum ratione. | 0 | Theoretical and Fundamental Chemistry |
Inert anodes are non-carbon based alternatives to traditional anodes used during aluminum reduction. These anodes do not chemically react with the electrolyte, and are therefore not consumed during the reduction process. Because the anode does not contain carbon, carbon dioxide is not produced. Through a review of literature, Haradlsson et al. found that inert anodes reduced the green house gas emissions of the aluminum smelting process by approximately 2 tonnes CO2eq/ tonne Al. | 1 | Applied and Interdisciplinary Chemistry |
* Member of the American Academy of Arts and Sciences (1956).
* Member of the United States National Academy of Sciences (1978).
* Honorary professorship by the Faculty of Medicine of the University of Barcelona (Spain).
* Honorary degree by the University of Montpelier (France).
* Honorary degree by the University of Chile, Santiago (Chile).
* Medal as honorary councilor of CSIC (Supreme National Council for Scientific Research, Spain). | 1 | Applied and Interdisciplinary Chemistry |
Crawfords book "Experimental Enquiry into the Effects of Tonics and Other Medicinal Substances on the Cohesion of Animal Fibre", written near the end of his life, offers a very readable presentation of his way of doing chemistry. Heres an example: | 1 | Applied and Interdisciplinary Chemistry |
Similarly to surface waves, internal waves change as they approach the shore. As the ratio of wave amplitude to water depth becomes such that the wave “feels the bottom,” water at the base of the wave slows down due to friction with the sea floor. This causes the wave to become asymmetrical and the face of the wave to steepen, and finally the wave will break, propagating forward as an internal bore. Internal waves are often formed as tides pass over a shelf break. The largest of these waves are generated during springtides and those of sufficient magnitude break and progress across the shelf as bores. These bores are evidenced by rapid, step-like changes in temperature and salinity with depth, the abrupt onset of upslope flows near the bottom and packets of high frequency internal waves following the fronts of the bores.
The arrival of cool, formerly deep water associated with internal bores into warm, shallower waters corresponds with drastic increases in phytoplankton and zooplankton concentrations and changes in plankter species abundances. Additionally, while both surface waters and those at depth tend to have relatively low primary productivity, thermoclines are often associated with a chlorophyll maximum layer. These layers in turn attract large aggregations of mobile zooplankton that internal bores subsequently push inshore. Many taxa can be almost absent in warm surface waters, yet plentiful in these internal bores. | 1 | Applied and Interdisciplinary Chemistry |
Dentin bonding refers to process of bonding a resin to conditioned dentin, where mineral component is replaced with resin monomers to form a biocomposite comprising dentin collagen and cured resin. The adhesive-dentin interface forms a tight and permanent bond between dentin and composite resins.
It can be accomplished by either etch-and-rinse (total etch) or self-etch adhesives. In etch-and rinse, acid will dissolve the minerals to a certain depth and leaves the highly porous dentinal collagen network suspended in water. Then, the collagen network is infiltrated with resin monomers. After chemical polymerization of these monomers happen, activated by light cure, it will result in a polymer-collagen biocomposite, commonly known as the hybrid layer:
The mechanism of action is explained below:
a) Application of acid to dentin will result in partial/total removal of smear layer and demineralization of the dentin.
b) Acid will demineralize the intertubular and peritubular dentin, and then open the dentinal tubules while exposing the collagen fibres, hence increasing the microporosity of intertubular dentin.
c) Dentin will be demineralized by up to approximately 7.5 µmeter, depending on the type of acid used, time of application and concentration.
d) Primer system is designed to increase critical surface tension of dentin, which gets decreased after etching of acid.
e) Bonding mechanism is when:
# When primer and bonding resin are applied to etched dentin, they penetrate the intertubular dentin, forming hybrid layer.
# They also penetrate and polymerize in open dentinal tubules, forming resin tags.
Moist bonding technique has been shown repeatedly to enhance bond strengths of etch-and-rinse adhesives because water preserves the porosity of collagen network for monomer interdiffusion. | 0 | Theoretical and Fundamental Chemistry |
Molecular interactions can occur between molecules belonging to different biochemical families (proteins, nucleic acids, lipids, carbohydrates, etc.) and also within a given family. Whenever such molecules are connected by physical interactions, they form molecular interaction networks that are generally classified by the nature of the compounds involved. Most commonly, interactome refers to protein–protein interaction (PPI) network (PIN) or subsets thereof. For instance, the Sirt-1 protein interactome and Sirt family second order interactome is the network involving Sirt-1 and its directly interacting proteins where as second order interactome illustrates interactions up to second order of neighbors (Neighbors of neighbors). Another extensively studied type of interactome is the protein–DNA interactome, also called a gene-regulatory network, a network formed by transcription factors, chromatin regulatory proteins, and their target genes. Even metabolic networks can be considered as molecular interaction networks: metabolites, i.e. chemical compounds in a cell, are converted into each other by enzymes, which have to bind their substrates physically.
In fact, all interactome types are interconnected. For instance, protein interactomes contain many enzymes which in turn form biochemical networks. Similarly, gene regulatory networks overlap substantially with protein interaction networks and signaling networks. | 1 | Applied and Interdisciplinary Chemistry |
Experimentally Pierre Louis Dulong and Alexis Thérèse Petit had found in 1819 that the heat capacity per weight (the mass-specific heat capacity) for 13 measured elements was close to a constant value, after it had been multiplied by a number representing the presumed relative atomic weight of the element. These atomic weights had shortly before been suggested by John Dalton and modified by Jacob Berzelius.
Dulong and Petit were unaware of the relationship with R, since this constant had not yet been defined from the later kinetic theory of gases. The value of 3R is about 25 joules per kelvin, and Dulong and Petit essentially found that this was the heat capacity of certain solid elements per mole of atoms they contained.
The Kopp's law developed in 1865 by Hermann Franz Moritz Kopp extended the Dulong–Petit law to chemical compounds from further experimental data.
Amedeo Avogadro remarked in 1833 that the law did not fit the experimental data of carbon samples. In 1876, Heinrich Friedrich Weber, noticed that the specific heat of diamond was sensible to temperature.
In 1877, Ludwig Boltzmann showed that the constant value of Dulong–Petit law could be explained in terms of independent classical harmonic oscillators. With the advent of quantum mechanics, this assumption was refined by Weber's student, Albert Einstein in 1907, employing quantum harmonic oscillators to explain the experimentally observed decrease of the heat capacity at low temperatures in diamond.
Peter Debye followed in 1912 with a new model based on Max Plancks photon gas, where the vibrations are not to individual oscillators but as vibrational modes of the ionic lattice. Debyes model allowed to predict the behavior of the ionic heat capacity at temperature close to 0 kelvin, and as the Einstein solid, both recover the Dulong–Petit law at high temperature.
The electronic heat capacity was overestimated by the 1900 Drude-Lorentz model to be half of the value predicted by Dulong–Petit. With the development of the quantum mechanical free electron model in 1927 by Arnold Sommerfeld the electronic contribution was found to be orders of magnitude smaller. This model explained why conductors and insulators have roughly the same heat capacity at large temperatures as it depends mostly on the lattice and not on the electronic properties. | 0 | Theoretical and Fundamental Chemistry |
The introduction of the three-centered two-electron delocalized bond invoked in the non-classical picture of the 2-norbornyl cation allowed chemists to explore a whole new realm of chemical bonds. Chemists were eager to apply the characteristics of hypovalent electronic states to new and old systems alike (though several got too carried away). One of the most fundamentally important concepts that emerged from the intense research focused around non-classical ions was the idea that electrons already involved in sigma bonds could be involved with reactivity. Though filled pi orbitals were known to be electron donors, chemists had doubted that sigma orbitals could function in the same capacity. The non-classical description of the 2-norbornyl cation can be seen as the donation of an electron pair from a carbon-carbon sigma bond into an empty p-orbital of carbon 2. Thus this carbocation showed that sigma-bond electron donation is as plausible as pi-bond electron donation.
The intense debate that followed Brown’s challenge to non-classical ion proponents also had a large impact on the field of chemistry. In order to prove or disprove the non-classical nature of the 2-norbornyl cation, chemists on both sides of the debate zealously sought out new techniques for chemical characterization and more innovative interpretations of existing data. One spectroscopic technique that was further developed to investigate the 2-norbornyl cation was nuclear magnetic resonance spectroscopy of compounds in highly acidic media. Comparisons of the 2-norbornyl cation to unstable transition states with delocalized electronic states were often made when trying to elucidate whether the norbornyl system was stable or not. These efforts motivated closer investigations of transition states and vastly increased the scientific community’s understanding of their electronic structure. In short, vigorous competition between scientific groups led to an extensive research and a better understanding of the underlying chemical concepts. | 0 | Theoretical and Fundamental Chemistry |
Host recognition of bacteriophages occur via bacteria-binding proteins that have strong binding affinities to specific protein or carbohydrate structures on the surface of the bacterial host. Bacteria-binding proteins derived from bacteriophage coating paramagnetic beads will bind to specific cell components present on the surface of host thus capturing the cells and facilitate the concentration of these bead-attached cells. The concentration process is created by a magnet placed on the side of the test tube bringing the beads to it. Due to the phage-ligand technology, AMS is superior to the antibody based immunomagnetic separation (IMS) on sorting bacterial cells. | 1 | Applied and Interdisciplinary Chemistry |
The Department of Energy ordered suspension of FutureGen 2.0 in February, 2015. The funds, appropriated by the American Recovery and Reinvestment Act of 2009, needed to be committed by July 1 and spent by Sept 30, 2015. The government also cited the Alliance's inability to raise the requisite amount of private funding. Energy Secretary Ernest Moniz explained at a press conference “If you look between now and July 1, without them having closed their financing, and try as we might, we just don’t see how it gets over the finish line.” At the time of suspension the power plant part of the project had spent $116.5 million and the sequestration part had spent $86 million. | 1 | Applied and Interdisciplinary Chemistry |
A Bpin (pinacolatoboron) group, of use in Suzuki-Miyaura cross coupling reactions, can be installed by reaction of a diazonium salt with bis(pinacolato)diboron in the presence of benzoyl peroxide (2 mol %) as an initiator:. Alternatively similar borylation can be achieved using transition metal carbonyl complexes including dimanganese decacarbonyl. | 0 | Theoretical and Fundamental Chemistry |
The second solar spectrum is an electromagnetic spectrum of the Sun that shows the degree of linear polarization. The term was coined by V. V. Ivanov in 1991. The polarization is at a maximum close to the limb (edge) of the Sun, thus the best place to observe such a spectrum is from just inside the limb. It is also possible to get polarized light from outside the limb, but since this is much dimmer compared to the disk of the Sun, it is very easily polluted by scattered light.
The second solar spectrum differs significantly from the solar spectrum determined by the intensity of light.
Large effects come around the Ca II K and H line. These have broad effects 200 Å wide and show a sign reversal at their centers. Molecular lines with stronger polarization than the background due to MgH and C are common. Rare-earth elements stand out far more than expected from the intensity spectrum.
Other odd lines include Li I at 6708 Å which has 0.005% more polarization at its peak, but is almost unobservable in the intensity spectrum. The Ba II 4554 Å appears as a triplet in the second solar spectrum. This is due to differing isotopes and hyperfine structure.
Two lines at 5896 Å 4934 Å being the D lines of sodium and barium were predicted not to be polarized, but nevertheless are present in this spectrum. | 0 | Theoretical and Fundamental Chemistry |
Expression of genes in mammals can be upregulated when signals are transmitted to the promoters associated with the genes. Cis-regulatory DNA sequences that are located in DNA regions distant from the promoters of genes can have very large effects on gene expression, with some genes undergoing up to 100-fold increased expression due to such a cis-regulatory sequence. These cis-regulatory sequences include enhancers, silencers, insulators and tethering elements. Among this constellation of sequences, enhancers and their associated transcription factor proteins have a leading role in the regulation of gene expression.
Enhancers are sequences of the genome that are major gene-regulatory elements. Enhancers control cell-type-specific gene expression programs, most often by looping through long distances to come in physical proximity with the promoters of their target genes. In a study of brain cortical neurons, 24,937 loops were found, bringing enhancers to promoters. Multiple enhancers, each often at tens or hundred of thousands of nucleotides distant from their target genes, loop to their target gene promoters and coordinate with each other to control expression of their common target gene.
The schematic illustration in this section shows an enhancer looping around to come into close physical proximity with the promoter of a target gene. The loop is stabilized by a dimer of a connector protein (e.g. dimer of CTCF or YY1), with one member of the dimer anchored to its binding motif on the enhancer and the other member anchored to its binding motif on the promoter (represented by the red zigzags in the illustration). Several cell function specific transcription factor proteins (in 2018 Lambert et al. indicated there were about 1,600 transcription factors in a human cell) generally bind to specific motifs on an enhancer and a small combination of these enhancer-bound transcription factors, when brought close to a promoter by a DNA loop, govern the level of transcription of the target gene. Mediator (coactivator) (a complex usually consisting of about 26 proteins in an interacting structure) communicates regulatory signals from enhancer DNA-bound transcription factors directly to the RNA polymerase II (RNAP II) enzyme bound to the promoter.
Enhancers, when active, are generally transcribed from both strands of DNA with RNA polymerases acting in two different directions, producing two eRNAs as illustrated in the Figure. An inactive enhancer may be bound by an inactive transcription factor. Phosphorylation of the transcription factor may activate it and that activated transcription factor may then activate the enhancer to which it is bound (see small red star representing phosphorylation of a transcription factor bound to an enhancer in the illustration). An activated enhancer begins transcription of its RNA before activating a promoter to initiate transcription of messenger RNA from its target gene. | 1 | Applied and Interdisciplinary Chemistry |
TOXMAP helped users create nationwide, regional, or local area maps showing where TRI chemicals are released on-site into the air, water, ground, and by underground injection, as reported by industrial facilities in the United States. It also identified the releasing facilities, color-codes release amounts for a single year or year range, and provides multi-year aggregate chemical release data and trends over time, starting with 1988. Maps also can show locations of Superfund sites on the Agency for Toxic Substances and Disease Registry National Priorities List (NPL), which lists all chemical contaminants present at these sites. TOXMAP is a useful environmental health tool that makes epidemiological and environmental information available to the public.
There were two versions of TOXMAP available from its home page: the classic version of TOXMAP released in 2004 and, a newer version released in 2014 that is based on Adobe Flash/Apache Flex technology. In addition to many of the features of TOXMAP classic, the new version provides an improved map appearance and interactive capabilities as well as a more current GIS look-and-feel. This included seamless panning, immediate update of search results when zooming to a location, two collapsible side panels to maximize map size, and automatic size adjustment after a window resize. The new TOXMAP also improved U.S. Census layers and availability by Census Tract (2000 and 2010), Canadian National Pollutant Release Inventory (NPRI) data, U.S. commercial nuclear power plants, as well as improved and updated congressional district boundaries.
TOXMAP classic users may search the system by location (such as city, state, or ZIP code), chemical name, chemical name fragment, release medium, release amount, facility name and ID, and can filter results to those residing within a pre-defined or custom geographic region.
Search results may be brought up in Google Maps or Google Earth, or saved for use in other tools. TOXMAP also overlays map data such as U.S. Census population information, income figures from the Bureau of Economic Analysis, and health data from the National Cancer Institute and the National Center for Health Statistics.
The data shown in TOXMAP comes from the following sources:
* EPA Toxics Release Inventory (TRI)
* EPA Superfund Program (National Priorities List/NPL)
* Environment Canada
* National Institute of Environmental Health Sciences (NIEHS) Superfund Research Program
* Hazardous Substances Data Bank
* [https://www.nlm.nih.gov/pubs/factsheets/toxlinfs.html NLM TOXLINE (Toxicology Bibliographic Information)]
* Agency for Toxic Substances and Disease Registry
* National Atlas of the United States
* Surveillance, Epidemiology, and End Results database
* National Center for Health Statistics
* Nuclear Regulatory Commission
* Esri | 1 | Applied and Interdisciplinary Chemistry |
Synthesis of morphine-like alkaloids in chemistry describes the total synthesis of the natural morphinan class of alkaloids that includes codeine, morphine, oripavine, and thebaine and the closely related semisynthetic analogs methorphan, buprenorphine, hydromorphone, hydrocodone, isocodeine, naltrexone, nalbuphine, oxymorphone, oxycodone, and naloxone.
The structure of morphine is not particularly complex, however the electrostatic polarization of adjacent bonded atoms does not alternate uniformly throughout the structure. This "dissonant connectivity" makes bond formation more difficult and therefore significantly complicates any synthetic strategy that is applied to this family of molecules.
The first morphine total synthesis, devised by Marshall D. Gates, Jr. in 1952 remains a widely used example of total synthesis. This synthesis took a total of 31 steps and proceeded in 0.06% overall yield. The hydrocodone synthesis of Kenner C. Rice is one of the most efficient and proceeds in 30% overall yield in 14 steps. At 9 steps, the Barriault route is the shortest to date, but contains a number of low-yielding steps and is racemic.
Several other syntheses were reported, notably by the research groups of Evans, Fuchs, Parker, Overman, Mulzer-Trauner, White, Taber, Trost, Fukuyama, Guillou, Stork, Magnus, Smith, and Barriault. | 0 | Theoretical and Fundamental Chemistry |
One of the metabolic pathways that a tetrose is involved in is the Pentose Phosphate Pathway. In the Pentose Phosphate Pathway, there is an oxidative stage and a non-oxidative stage. A tetrose sugar, D-erythrose, is utilized in the non-oxidative stage, where D-ribulose 5-phosphate is generated into a 6 carbon sugar (fructose 6-phosphate) and a 3 carbon sugar (glyceraldehyde 3-phosphate). Both of these molecules can be used elsewhere in the body.
D-erythrose 4-phosphate is generated as a product of a reaction called transaldolation. In the Pentose Phosphate Pathway, a transaldolase removes the first 3 carbon molecules of sedoheptulose 7-phosphate and places them onto a glyceraldehyde 3-phosphate. The transaldolase utilizes a Schiff base to perform a reverse aldol reaction and a forward aldol reaction in its mechanism, generating an erythrose 4-phosphate and fructose 6-phosphate. The erythrose 4-phosphate is an important intermediate in the Pentose Phosphate Pathway because it is then used in the final non-oxidative step of the pathway.
The final non-oxidative step of the pathway is a transketolase reaction. A transketolase utilizes a thiamine pyrophosphate, or TPP cofactor, to break the unfavorable bond between the carbon in a carbonyl and the alpha carbon. TPP attacks a xylulose 5-phosphate molecule and facilitates the cleavage of the bond between the C2 (carbonyl carbon) and the C3 (alpha carbon), where glyceraldehyde 3-phosphate is released. Then, C2 can attack erythrose 4-phosphate, which forms fructose 6-phosphate. Both of the products of this reaction can enter the gluconeogenesis pathway to regenerate glucose. | 1 | Applied and Interdisciplinary Chemistry |
The building of the laboratory began in 1913 and was finished in 1916 to the designs of Paul Waterhouse, the contractors being Armitage and Hodgson of Leeds. Funding came in part from C. W. Dyson Perrins of Queen's College. In 1920–22 an eastern wing was added as contemplated in the original design, this was followed in 1934 by an extension for medical students and in 1940–41 a new brick wing to the north was built.
Research in organic chemistry at Oxford is now conducted across South Parks Road at the University's state-of-the-art Chemistry Research Laboratory. The majority of the building has been handed over to the Oxford University Geography Department for the establishment of the Oxford University Centre for the Environment (OUCE). | 1 | Applied and Interdisciplinary Chemistry |
Singlet fission is a spin-allowed process, unique to molecular photophysics, whereby one singlet excited state is converted into two triplet states. The phenomenon has been observed in molecular crystals, aggregates, disordered thin films, and covalently-linked dimers, where the chromophores are oriented such that the electronic coupling between singlet and the double triplet states is large. Being spin allowed, the process can occur very rapidly (on a picosecond or femtosecond timescale) and out-compete radiative decay (that generally occurs on a nanosecond timescale) thereby producing two triplets with very high efficiency. The process is distinct from intersystem crossing, in that singlet fission does not involve a spin flip, but is mediated by two triplets coupled into an overall singlet. It has been proposed that singlet fission in organic photovoltaic devices could improve the photoconversion efficiencies. | 0 | Theoretical and Fundamental Chemistry |
A "black body" is a body which has the property of allowing all incident rays to enter without surface reflection and not allowing them to leave again.
Blackbodies are idealized surfaces that act as the perfect absorber and emitter. They serve as the standard against which real surfaces are compared when characterizing thermal radiation. A blackbody is defined by three characteristics:
# A blackbody absorbs all incident radiation, regardless of wavelength and direction.
# No surface can emit more energy than a blackbody for a given temperature and wavelength.
# A blackbody is a diffuse emitter. | 0 | Theoretical and Fundamental Chemistry |
The ionizing or excitation effects of beta particles on matter are the fundamental processes by which radiometric detection instruments detect and measure beta radiation. The ionization of gas is used in ion chambers and Geiger–Müller counters, and the excitation of scintillators is used in scintillation counters.
The following table shows radiation quantities in SI and non-SI units:
* The gray (Gy), is the SI unit of absorbed dose, which is the amount of radiation energy deposited in the irradiated material. For beta radiation this is numerically equal to the equivalent dose measured by the sievert, which indicates the stochastic biological effect of low levels of radiation on human tissue. The radiation weighting conversion factor from absorbed dose to equivalent dose is 1 for beta, whereas alpha particles have a factor of 20, reflecting their greater ionising effect on tissue.
* The rad is the deprecated CGS unit for absorbed dose and the rem is the deprecated CGS unit of equivalent dose, used mainly in the USA. | 0 | Theoretical and Fundamental Chemistry |
Norrish and Smith, Trommsdorff, and later, Schultz and Harborth, concluded that autoacceleration must be caused by a totally different polymerization mechanism. They rationalized through experiment that a decrease in the termination rate was the basis of the phenomenon. This decrease in termination rate, k, is caused by the raised viscosity of the polymerization region when the concentration of previously formed polymer molecules increases. Before autoacceleration, chain termination by combination of two free-radical chains is a very rapid reaction that occurs at very high frequency (about one in 10 collisions). However, when the growing polymer molecules – with active free-radical ends – are surrounded in the highly viscous mixture consisting of a growing concentration of "dead" polymer, the rate of termination becomes limited by diffusion. The Brownian motion of the larger molecules in the polymer "soup" is restricted, therefore limiting the frequency of their effective (termination) collisions. | 0 | Theoretical and Fundamental Chemistry |
For a continuous stirred-tank reactor (CSTR), the following relationship applies:
where:
* is the reactor volume
* is the molar flow rate per unit time of the entering reactant A
* is the conversion of reactant A
* is the rate of disappearance of reactant A per unit volume per unit time
For a plug flow reactor (PFR), the following relationship applies:
If is plotted as a function of , the required volume to achieve a specific conversion can be determined given an entering molar flow rate.
The volume of a CSTR necessary to achieve a certain conversion at a given flow rate is equal to the area of the rectangle with height equal to and width equal to .
The volume of a PFR necessary to achieve a certain conversion at a given flow rate is equal to the area under the curve of plotted against . | 1 | Applied and Interdisciplinary Chemistry |
The isotopic ratio of the product can be used to define the instantaneous isotopic ratio
and the time-dependent fractionation factor | 0 | Theoretical and Fundamental Chemistry |
The journal invites letters, articles, features, and perspectives (reviews) that address challenges of sustainability in the chemical enterprise and advance principles of green chemistry and green engineering. | 1 | Applied and Interdisciplinary Chemistry |
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