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Hydroperoxides are intermediates in the production of many organic compounds in industry. For example, the cobalt catalyzed oxidation of cyclohexane to cyclohexanone:
Drying oils, as found in many paints and varnishes, function via the formation of hydroperoxides. | 0 | Theoretical and Fundamental Chemistry |
The concept of a reversible reaction was introduced by Claude Louis Berthollet in 1803, after he had observed the formation of sodium carbonate crystals at the edge of a salt lake (one of the natron lakes in Egypt, in limestone):
:2NaCl + CaCO → NaCO + CaCl
He recognized this as the reverse of the familiar reaction
: NaCO + CaCl→ 2NaCl + CaCO
Until then, chemical reactions were thought to always proceed in one direction. Berthollet reasoned that the excess of salt in the lake helped push the "reverse" reaction towards the formation of sodium carbonate.
In 1864, Peter Waage and Cato Maximilian Guldberg formulated their law of mass action which quantified Berthollets observation. Between 1884 and 1888, Le Chatelier and Braun formulated Le Chateliers principle, which extended the same idea to a more general statement on the effects of factors other than concentration on the position of the equilibrium. | 0 | Theoretical and Fundamental Chemistry |
As discussed previously, biomaterials are used in medical devices to treat, assist, or replace a function within the human body. The application of a specific biomaterial must combine the necessary composition, material properties, structure, and desired in vivo reaction in order to perform the desired function. Categorizations of different desired properties are defined in order to maximize functional results. | 1 | Applied and Interdisciplinary Chemistry |
* In Iceland the company Carbon Recycling International operates a plant for production of e-Methanol of CO from a geothermal plant with a methanol manufacturing capacity of more than 4000 t/a. The plant was named after George Olah.
* BioMCN from Netherlands has a production capacity of more than 60 000 t/a for production of renewable methanol (biomethanol and e-Methanol)
* BASF produces methanol of renewable resources named EU-REDcert methanol using waste based biomass.
* In May 2019 a demonstration plant was started in Germany in Niederaußem with a daily production capacity of one ton as part of the project MefCO. The methanol was used for denitrification in a waste water treatment facility.
* In Germany there is a project called Carbon2Chem of Thyssenkrupp to produce methanol from smelter gases.
* Within the scope of the consortium Power to Methanol Antwerp BV consisting of ENGIE, Fluxys, Indaver, INOVYN, Oiltanking, PMV and Port of Antwerp a plant for production of 8000 t/a renewable methanol shall be built. The CO for the production of the e-methanol shall be separated by Carbon Capture and Utilisation (CCU) from emissions.
* Wacker Chemie AG from Germany plans as part of a submitted funding project (RHYME) to build a plant for production of green hydrogen and renewable methanol (as of April 2021). For synthesis of methanol of green hydrogen the CO shall be originated from production processes of the chemical site and perhaps of other industrial processes (e.g. CO from cement plants). 15 000 t/a of renewable methanol shall be produced which shall be used for company internal production processes (e.g. synthesis of silicones) as well as for selling as a fuel.
* At site Örnsköldsvik in Sweden the consortium Liquid Wind together with Worley plan a plant with a production capacity of 50 000 t/a for renewable e-Methanol (as of May 2021). The CO shall be originated from a biomass plant. Until 2050 Liquid Wind wants to build 500 similar plants. Members of the consortium are Alfa Laval, Haldor Topsoe, Carbon Clean and Siemens Energy.
* Total Energies (the largest methanol producer in Europe with production capacity of 700 000 t/a) starts the project e-CO2Met for production of renewable methanol in Leuna, Germany (as of June 2021). Hereby a 1 MW high temperature electrolyzer shall be used. The CO for the methanol production shall be originated from production processes of a refinery. | 1 | Applied and Interdisciplinary Chemistry |
Pancratistatin (PST) is a natural compound initially extracted from spider lily, a Hawaiian native plant of the family Amaryllidaceae (AMD). | 0 | Theoretical and Fundamental Chemistry |
At temperatures above −35.9 °C, xenon tetroxide is very prone to explosion, decomposing into xenon and oxygen gases with ΔH = −643 kJ/mol:
:XeO → Xe + 2 O
Xenon tetroxide dissolves in water to form perxenic acid and in alkalis to form perxenate salts:
:XeO + 2 HO → HXeO
:XeO + 4 NaOH → NaXeO + 2 HO
Xenon tetroxide can also react with xenon hexafluoride to give xenon oxyfluorides:
:XeO + XeF → XeOF + XeOF
:XeO + 2XeF → XeOF + 2 XeOF | 0 | Theoretical and Fundamental Chemistry |
The Swedish International Development Cooperation Agency (Sida) funded the "SanRes R&D programme" during 1993 to 2001 which lay the foundation for the subsequent "EcoSanRes programme" carried out by Stockholm Environment Institute (2002–2011). A publication by Sida called "Ecological sanitation" in 1998 compiled the knowledge generated to date about ecosan in a popular book which was published as a second edition in 2004. The book has also been translated into Chinese, French and Spanish.
The German government enterprise GIZ also had a large "ecosan program" from 2001 to 2012. Whilst the term "ecosan" was preferred in the initial stages of this program, it was from 2007 onwards more and more replaced by the broader term "sustainable sanitation". In fact, the Sustainable Sanitation Alliance was founded in 2007 in an attempt to broaden the ecosan concept and to bring together various actors under one umbrella.
Research into how to make reuse of urine and feces safe in agriculture was carried out by Swedish researchers, for example Hakan Jönsson and his team, whose publication on "Guidelines on the Use of Urine and feces in Crop Production" was a milestone which was later incorporated into the WHO "Guidelines on Safe Reuse of Wastewater, Excreta and Greywater" from 2006. The multiple barrier concept to reuse, which is the key cornerstone of this publication, has led to a clear understanding on how excreta reuse can be done safely. | 1 | Applied and Interdisciplinary Chemistry |
Trefonas joined MEMC Electronic Materials in late 1984. In 1986, he and others co-founded Aspect Systems Inc., utilizing photolithography technology acquired from MEMC. Trefonas worked at Aspect from 1986-1989. Then, through a succession of company acquisitions, he moved to Shipley Company (1990-2000), Rohm and Haas (1997-2008), to The Dow Chemical Company (2008-2019), and finally to DuPont (2019-current).
Trefonas has published at least 132 journal articles and technical publications. He has received 107 American patents, and has more than 15 active patent applications pending. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, a wake may either be:
* the region of recirculating flow immediately behind a moving or stationary blunt body, caused by viscosity, which may be accompanied by flow separation and turbulence, or
* the wave pattern on the water surface downstream of an object in a flow, or produced by a moving object (e.g. a ship), caused by density differences of the fluids above and below the free surface and gravity (or surface tension). | 1 | Applied and Interdisciplinary Chemistry |
In geometry, the trihexagonal tiling is one of 11 uniform tilings of the Euclidean plane by regular polygons. It consists of equilateral triangles and regular hexagons, arranged so that each hexagon is surrounded by triangles and vice versa. The name derives from the fact that it combines a regular hexagonal tiling and a regular triangular tiling. Two hexagons and two triangles alternate around each vertex, and its edges form an infinite arrangement of lines. Its dual is the rhombille tiling.
This pattern, and its place in the classification of uniform tilings, was already known to Johannes Kepler in his 1619 book Harmonices Mundi. The pattern has long been used in Japanese basketry, where it is called kagome. The Japanese term for this pattern has been taken up in physics, where it is called a kagome lattice. It occurs also in the crystal structures of certain minerals. Conway calls it a hexadeltille, combining alternate elements from a hexagonal tiling (hextille) and triangular tiling (deltille). | 0 | Theoretical and Fundamental Chemistry |
Tribocorrosion is a material degradation process due to the combined effect of corrosion and wear. The name tribocorrosion expresses the underlying disciplines of tribology and corrosion. Tribology is concerned with the study of friction, lubrication and wear (its name comes from the Greek "tribo" meaning to rub) and corrosion is concerned with the chemical and electrochemical interactions between a material, normally a metal, and its environment. As a field of research tribocorrosion is relatively new, but tribocorrosion phenomena have been around ever since machines and installations are being used.
Wear is a mechanical material degradation process occurring on rubbing or impacting surfaces, while corrosion involves chemical or electrochemical reactions of the material. Corrosion may accelerate wear and wear may accelerate corrosion. One then speaks of corrosion accelerated wear or wear accelerated corrosion. Both these phenomena, as well as fretting corrosion (which results from small amplitude oscillations between contacting surfaces) fall into the broader category of tribocorrosion. Erosion-corrosion is another tribocorrosion phenomenon involving mechanical and chemical effects: impacting particles or fluids erode a solid surface by abrasion, chipping or fatigue while simultaneously the surface corrodes. | 1 | Applied and Interdisciplinary Chemistry |
The context of a photogeochemical reaction is implicitly the surface of Earth, since that is where sunlight is available (although other sources of light such as chemiluminescence would not be strictly excluded from photogeochemical study). Reactions may occur among components of land such as rocks, soil and detritus; components of surface water such as sediment and dissolved organic matter; and components of the atmospheric boundary layer directly influenced by contact with land or water, such as mineral aerosols and gases. Visible and medium- to long-wave ultraviolet radiation is the main source of energy for photogeochemical reactions; wavelengths of light shorter than about 290 nm are completely absorbed by the present atmosphere, and are therefore practically irrelevant, except in consideration of atmospheres different from that of Earth today.
Photogeochemical reactions are limited to chemical reactions not facilitated by living organisms. The reactions comprising photosynthesis in plants and other organisms, for example, are not considered photogeochemistry, since the physiochemical context for these reactions is installed by the organism, and must be maintained in order for these reactions to continue (i.e. the reactions cease if the organism dies). In contrast, if a certain compound is produced by an organism, and the organism dies but the compound remains, this compound may still participate independently in a photogeochemical reaction even though its origin is biological (e.g. biogenic mineral precipitates or organic compounds released from plants into water).
The study of photogeochemistry is primarily concerned with naturally occurring materials, but may extend to include other materials, inasmuch as they are representative of, or bear some relation to, those found on Earth. For example, many inorganic compounds have been synthesized in the laboratory to study photocatalytic reactions. Although these studies are usually not undertaken in the context of environmental or Earth sciences, the study of such reactions is relevant to photogeochemistry if there is a geochemical implication (i.e. similar reactants or reaction mechanisms occur naturally). Similarly, photogeochemistry may also include photochemical reactions of naturally occurring materials that are not touched by sunlight, if there is the possibility that these materials may become exposed (e.g. deep soil layers uncovered by mining).
Except for several isolated instances, studies that fit the definition of photogeochemistry have not been explicitly specified as such, but have been traditionally categorized as photochemistry, especially at the time when photochemistry was an emerging field or new facets of photochemistry were being explored. Photogeochemical research, however, may be set apart in light of its specific context and implications, thereby bringing more exposure to this "poorly explored area of experimental geochemistry". Past studies that fit the definition of photogeochemistry may be designated retroactively as such. | 0 | Theoretical and Fundamental Chemistry |
Corpuscularianism remained a dominant theory for centuries and was blended with alchemy by early scientists such as Robert Boyle and Isaac Newton in the 17th century. In his work The Sceptical Chymist (1661), Boyle abandoned the Aristotelian ideas of the classical elements—earth, water, air, and fire—in favor of corpuscularianism. In his later work, The Origin of Forms and Qualities (1666), Boyle used corpuscularianism to explain all of the major Aristotelian concepts, marking a departure from traditional Aristotelianism. | 1 | Applied and Interdisciplinary Chemistry |
In 1970, Wanzlick's group generated imidazol-2-ylidene carbenes by the deprotonation of an imidazolium salt. Wanzlick as well as Roald Hoffmann, proposed that these imidazole-based carbenes should be more stable than their 4,5-dihydro analogues, due to Hückel-type aromaticity. Wanzlick did not however isolate imidazol-2-ylidenes, but instead their coordination compounds with mercury and isothiocyanate:
In 1988, Guy Bertrand and others isolated a phosphinocarbene. These species can be represented as either a λ-phosphinocarbene or λ-phosphaacetylene:
These compounds were called "push-pull carbenes" in reference to the contrasting electron affinities of the phosphorus and silicon atoms. They exhibit both carbenic and alkynic reactivity. An X-ray structure of this molecule has not been obtained and at the time of publication some doubt remained as to their exact carbenic nature.
In 1991, Arduengo and coworkers crystallized a diaminocarbene by deprotonation of an imidazolium cation:
This carbene, the forerunner of a large family of carbenes with the imidazol-2-ylidene core, is indefinitely stable at room temperature in the absence of oxygen and moisture. It melts at 240–241 °C without decomposition. The C NMR spectrum shows a signal at 211 ppm for the carbenic atom. The X-ray structure revealed longer N–C bond lengths in the ring of the carbene than in the parent imidazolium compound, indicating that there was very little double bond character to these bonds.
The first air-stable ylidic carbene, a chlorinated member of the imidazol-2-ylidene family, was obtained in 1997.
In 2000, Bertrand obtained additional carbenes of the phosphanyl type, including (phosphanyl)(trifluoromethyl)carbene, stable in solution at -30 °C and a moderately stable (amino)(aryl)carbene with only one heteroatom adjacent to the carbenic atom. | 0 | Theoretical and Fundamental Chemistry |
In rainbow trout as well as a variety of other teleosts, increased RBC pH stems from the activation of B-andrenergic exchange protein (BNHE) on the RBC membrane via circulating catelcholamines. This process causes the internal pH of the RBC to increase through the outwards movement of and inwards movement of . The net consequence of alkalizing the RBC is an increase in Hb-O affinity via the Bohr effect. The net influx of ions and the compensatory activation of -ATPase to maintain ionic equilibrium within the RBC results in a steady decline in cellular ATP, also serving to increase Hb-O affinity. As a further result of inward movement, the osmolarity of the RBC increases causing osmotic influx of water and cell swelling. The dilution of the cell contents causes further spatial separation of hemoglobin from the inorganic phosphates and again serves to increase Hb-O affinity.
Intertidal hypoxia-tolerant triplefin fish (Family Tripterygiidae) species seem to take advantage of intracellular acidosis and appears to "bypasse" the traditional oxidative phosphorylation and directly drives mitochondrial ATP synthesis using the cytosolic pool of protons that likely accumulates in hypoxia (via lactic acidosis and ATP hydrolysis). | 0 | Theoretical and Fundamental Chemistry |
Second sound is a quantum mechanical phenomenon in which heat transfer occurs by wave-like motion, rather than by the more usual mechanism of diffusion. Heat takes the place of pressure in normal sound waves. This leads to a very high thermal conductivity. It is known as "second sound" because the wave motion of heat is similar to the propagation of sound in air. | 1 | Applied and Interdisciplinary Chemistry |
* [Si]
* [Si]
* [Si]
* [Si]
* [Ge]
* [Ge]
* [Ge]
* [Sn]
* [Sn]
* [Pb]
* [Pb]
* [P]
* [P]
* [P]
* [As]
* [As]
* [Sb]
* [Sb]
* [Bi]
* [Bi]
* [Bi] | 0 | Theoretical and Fundamental Chemistry |
In the gas phase at ultralow pressures, single-molecule experiments have been around for decades, but in the condensed phase only since 1989 with the work by W. E. Moerner and Lothar Kador. One year later, Michel Orrit and Jacky Bernard were able to show also the detection of the absorption of single molecules by their fluorescence.
Many techniques have the ability to observe one molecule at a time, most notably mass spectrometry, where single ions are detected. In addition, one of the earliest means of detecting single molecules, came about in the field of ion channels with the development of the patch clamp technique by Erwin Neher and Bert Sakmann (who later went on to win the Nobel prize for their seminal contributions). However, the idea of measuring conductance to look at single molecules placed a serious limitation on the kind of systems which could be observed.
Fluorescence is a convenient means of observing one molecule at a time, mostly due to the sensitivity of commercial optical detectors, capable of counting single photons. However, spectroscopically, the observation of one molecule requires that the molecule is in an isolated environment and that it emits photons upon excitation, which owing to the technology to detect single photons by use of photomultiplier tubes (PMT) or avalanche photodiodes (APD), enables one to record photon emission events with great sensitivity and time resolution.
More recently, single-molecule fluorescence is the subject of intense interest for biological imaging, through the labeling of biomolecules such as proteins and nucleotides to study enzymatic function which cannot easily be studied on the bulk scale, due to subtle time-dependent movements in catalysis and structural reorganization. The most studied protein has been the class of myosin/actin enzymes found in muscle tissues. Through single-molecule techniques the step mechanism has been observed and characterized in many of these proteins.
In 1997, single-molecule detection was demonstrated with surface-enhanced Raman spectroscopy (SERS) by Katrin Kneipp, H. Kneipp, Y. Wang, L.T. Perelman and others at MIT and independently by S. Nie and S. R. Emory at Indiana University. The MIT team used non-resonance Raman excitation and surface enhancement with silver nanoclusters to detect single cresyl violet molecules, while the team at Indiana University used resonance Raman excitation and surface enhancement with silver nanoparticles to detect single rhodamine 6G molecules.
Nanomanipulators such as the atomic force microscope are also suited to single-molecule experiments of biological significance, since they work on the same length scale of most biological polymers. Besides, atomic force microscopy (AFM) is appropriate for the studies of synthetic polymer molecules. AFM provides a unique possibility of 3D visualization of polymer chains. For instance, AFM tapping mode is gentle enough for the recording of adsorbed polyelectrolyte molecules (for example, 0.4 nm thick chains of poly(2-vinylpyridine)) under liquid medium. The location of two-chain-superposition correspond in these experiments to twice the thickness of single chain (0.8 nm in the case of the mentioned example). At the application of proper scanning parameters, conformation of such molecules remain unchanged for hours that allows the performance of experiments under liquid media having various properties. Furthermore, by controlling the force between the tip and the sample high resolution images can be obtained. Optical tweezers have also been used to study and quantify DNA-protein interactions. | 0 | Theoretical and Fundamental Chemistry |
The Nyāya metaphysics recognizes sixteen padarthas or categories and includes all six (or seven) categories of the Vaisheshika in the second one of them, called prameya.
These sixteen categories are:
#pramāṇa (valid means of knowledge or knowledge sources),
#prameya (objects of valid knowledge),
#saṁśaya (doubt),
#prayojana (aim),
#dṛṣṭānta (example),
#siddhānta (conclusion or accepted position),
#avayava (members of syllogism or inferential components),
#tarka (hypothetical/suppositional reasoning),
#nirṇaya (settlement or certainty),
#vāda (discussion or debate for truth),
#jalpa (wrangling or disputation),
#vitaṇḍā (cavilling or destructive debate),
#hetvābhāsa (fallacy or pseudo-proovers),
#chala (quibbling or equivocation),
#jāti (sophisticated refutation or misleading/futile objections) and
#nigrahasthāna (point of defeat or clinchers).
According to Matthew Dasti and Stephen Phillips, it may be useful to interpret the word jnana as cognition rather than knowledge when studying the Nyāya system. | 1 | Applied and Interdisciplinary Chemistry |
Applied spectroscopy is the application of various spectroscopic methods for the detection and identification of different elements or compounds to solve problems in fields like forensics, medicine, the oil industry, atmospheric chemistry, and pharmacology. | 0 | Theoretical and Fundamental Chemistry |
Many kinds of paints and inks—e.g., plastisols used in silkscreen textile printing—exhibit thixotropic qualities. In many cases it is desirable for the fluid to flow sufficiently to form a uniform layer, then to resist further flow, thereby preventing sagging on a vertical surface. Some other inks, such as those used in CMYK-type process printing, are designed to regain viscosity even faster, once they are applied, in order to protect the structure of the dots for accurate color reproduction.
Thixotropic ink (along with a gas pressurized cartridge and special shearing ball design) is a key feature of the Fisher Space Pen, used for writing during zero gravity space flights by the US and Russian space programs.
Solder pastes used in electronics manufacturing printing processes are thixotropic.
Thread-locking fluid is a thixotropic adhesive that cures anaerobically.
Thixotropy has been proposed as a scientific explanation of blood liquefaction miracles such as that of Saint Januarius in Naples.
Semi-solid casting processes such as thixomoulding use the thixotropic property of some alloys (mostly light metals like magnesium). Within certain temperature ranges and with appropriate preparation, an alloy can be put into a semi-solid state, which can be injected with less shrinkage and better overall properties than by normal injection molding.
Fumed silica is commonly used as a rheology agent to make otherwise low-viscous fluids thixotropic. Examples range from foods to epoxy resin in structural bonding applications like fillet joints. | 1 | Applied and Interdisciplinary Chemistry |
Sizing of a UV system is affected by three variables: flow rate, lamp power, and UV transmittance in the water. Manufacturers typically developed sophisticated computational fluid dynamics (CFD) models validated with bioassay testing. This involves testing the UV reactor's disinfection performance with either MS2 or T1 bacteriophages at various flow rates, UV transmittance, and power levels in order to develop a regression model for system sizing. For example, this is a requirement for all public water systems in the United States per the EPA UV manual.
The flow profile is produced from the chamber geometry, flow rate, and particular turbulence model selected. The radiation profile is developed from inputs such as water quality, lamp type (power, germicidal efficiency, spectral output, arc length), and the transmittance and dimension of the quartz sleeve. Proprietary CFD software simulates both the flow and radiation profiles. Once the 3D model of the chamber is built, it is populated with a grid or mesh that comprises thousands of small cubes.
Points of interest—such as at a bend, on the quartz sleeve surface, or around the wiper mechanism—use a higher resolution mesh, whilst other areas within the reactor use a coarse mesh. Once the mesh is produced, hundreds of thousands of virtual particles are "fired" through the chamber. Each particle has several variables of interest associated with it, and the particles are "harvested" after the reactor. Discrete phase modeling produces delivered dose, head loss, and other chamber-specific parameters. | 0 | Theoretical and Fundamental Chemistry |
The United States Radium Corporation was a company, most notorious for its operations between the years 1917 to 1926 in Orange, New Jersey, in the United States that led to stronger worker protection laws. After initial success in developing a glow-in-the-dark radioactive paint, the company was subject to several lawsuits in the late 1920s in the wake of severe illnesses and deaths of workers (the Radium Girls) who had ingested radioactive material. The workers had been told that the paint was harmless. During World War I and World War II, the company produced luminous watches and gauges for the United States Army for use by soldiers.
U.S. Radium workers, especially women who painted the dials of watches and other instruments with luminous paint, suffered serious radioactive contamination. Lawyer Edward Markley was in charge of defending the company in these cases. | 0 | Theoretical and Fundamental Chemistry |
The Association of Public Analysts (APA) is a UK professional association for public analysts. It was founded in 1954, although an earlier body, the Society of Public Analysts, was founded in 1874, became the Society for Analytical Chemistry, and was one of the bodies which merged to form the Royal Society of Chemistry in 1980.
Through its activities it seeks to serve the public by using analytical chemistry to addressing a wide range of issues including not only the adulteration and contamination of food, drugs and other commercial products but also to adi in their accurrate description. the APA president is Jane White.
It publishes the Journal of the Association of Public Analysts (JAPA), which appeared in print from 1963 to 1997, volumes 1-33 (), and was then relaunched as an online journal from volume 34, 2006 (). | 1 | Applied and Interdisciplinary Chemistry |
A scintillation detector or scintillation counter is obtained when a scintillator is coupled to an electronic light sensor such as a photomultiplier tube (PMT), photodiode, or silicon photomultiplier. PMTs absorb the light emitted by the scintillator and re-emit it in the form of electrons via the photoelectric effect. The subsequent multiplication of those electrons (sometimes called photo-electrons) results in an electrical pulse which can then be analyzed and yield meaningful information about the particle that originally struck the scintillator. Vacuum photodiodes are similar but do not amplify the signal while silicon photodiodes, on the other hand, detect incoming photons by the excitation of charge carriers directly in the silicon. Silicon photomultipliers consist of an array of photodiodes which are reverse-biased with sufficient voltage to operate in avalanche mode, enabling each pixel of the array to be sensitive to single photons. | 0 | Theoretical and Fundamental Chemistry |
The liquid droplet radiator (LDR) system consists of a droplet generator, a collector, a heat exchanger, a recirculating pump, and a bellows-type pressure regulator (accumulator).
While undergoing a reduction in pressure the saturated liquid is sprayed into space as coherent streams of tiny, discrete droplets.
The droplet stream can be a column or a sheet of liquid droplets moving through space from the droplet generator to the collector.
The droplets carry the waste heat generated by a space power system and radiate this waste heat directly to space during their flight by transient radiative heat transfer.
The liquid droplets are collected at a lower temperature, reheated, and pumped to the droplet generator and reused to continue to remove waste heat from the thermodynamic power cycle.
The pressure at which liquid droplets are formed can vary widely in different applications, but it was found that once the droplet flow has been established, substantially lower pressures are needed to maintain the flow of droplet streams. | 0 | Theoretical and Fundamental Chemistry |
The location of spliceosomal activity for the minor class spliceosome is regarded by most experts to be in the nucleus. However, a single paper has claimed that the minor spliceosome is active in the cytosol. The data presented within this paper are not fully accepted within the field and directly contradict numerous other papers. | 1 | Applied and Interdisciplinary Chemistry |
Despite the many honours that Meitner received in her lifetime, she did not receive the Nobel Prize while it was awarded to Otto Hahn for the discovery of nuclear fission. She was nominated 49 times for Physics and Chemistry Nobel Prizes but never won. On 15 November 1945, the Royal Swedish Academy of Sciences announced that Hahn had been awarded the 1944 Nobel Prize in Chemistry for "his discovery of the fission of heavy atomic nuclei". Meitner was the one who told Hahn and Strassman to test their radium in more detail, and it was she who told Hahn that it was possible for the nucleus of uranium to disintegrate. Without these contributions of Meitner, Hahn would not have found that the uranium nucleus can split in half.
In 1945 the Nobel Committee for Chemistry in Sweden that selected the Nobel Prize in Chemistry decided to award that prize solely to Hahn: Hahn only found out from a newspaper while interned in Farm Hall Cambridgeshire England. In the 1990s, the long-sealed records of the Nobel Committees proceedings became public, and the comprehensive biography of Meitner published in 1996 by Ruth Lewin Sime took advantage of this unsealing to reconsider Meitners exclusion. In a 1997 article in the American Physical Society journal Physics Today, Sime and her colleagues Elisabeth Crawford and Mark Walker wrote:
The five-member physics committee included Manne Siegbahn, his former student Erik Hulthén, the professor of experimental physics at Uppsala University, and Axel Lindh, who eventually succeeded Hulthén. All three were part of the Siegbahn school of x-ray spectroscopy. The poor relationship between Siegbahn and Meitner was a factor here, as was the bias towards experimental rather than theoretical physics. In his report on the work of Meitner and Frisch, Hulthén relied on pre-war papers. He did not think that their work was groundbreaking, and argued that the prize for physics was given for experimental rather than theoretical work, which had not been the case for many years.
At the time Meitner herself wrote in a letter, "Surely Hahn fully deserved the Nobel Prize for chemistry. There is really no doubt about it. But I believe that Frisch and I contributed something not insignificant to the clarification of the process of uranium fission—how it originates and that it produces so much energy and that was something very remote to Hahn." Hahn's receipt of a Nobel Prize was long expected. Both he and Meitner had been nominated for both the chemistry and the physics prizes several times even before the discovery of nuclear fission. According to the Nobel Prize archive, she was nominated 19 times for Nobel Prize in Chemistry between 1924 and 1948, and 30 times for Nobel Prize in Physics between 1937 and 1967. Her nominators included Arthur Compton, Dirk Coster, Kasimir Fajans, James Franck, Otto Hahn, Oscar Klein, Niels Bohr, Max Planck and Max Born. Despite not having been awarded the Nobel Prize, Meitner was invited to attend the Lindau Nobel Laureate Meeting in 1962.
Max Perutz, the 1962 Nobel prizewinner in chemistry, reached a similar conclusion: "Having been locked up in the Nobel Committees files these fifty years, the documents leading to this unjust award now reveal that the protracted deliberations by the Nobel jury were hampered by lack of appreciation both of the joint work that had preceded the discovery and of Meitners written and verbal contributions after her flight from Berlin." | 1 | Applied and Interdisciplinary Chemistry |
Equilibrium constants are determined in order to quantify chemical equilibria. When an equilibrium constant is expressed as a concentration quotient,
it is implied that the activity quotient is constant. For this assumption to be valid, equilibrium constants must be determined in a medium of relatively high ionic strength. Where this is not possible, consideration should be given to possible activity variation.
The equilibrium expression above is a function of the concentrations [A], [B] etc. of the chemical species in equilibrium. The equilibrium constant value can be determined if any one of these concentrations can be measured. The general procedure is that the concentration in question is measured for a series of solutions with known analytical concentrations of the reactants. Typically, a titration is performed with one or more reactants in the titration vessel and one or more reactants in the burette. Knowing the analytical concentrations of reactants initially in the reaction vessel and in the burette, all analytical concentrations can be derived as a function of the volume (or mass) of titrant added.
The equilibrium constants may be derived by best-fitting of the experimental data with a chemical model of the equilibrium system. | 0 | Theoretical and Fundamental Chemistry |
The tetranucleotide hypothesis of Phoebus Levene proposed that DNA was composed of repeating sequences of four nucleotides. It was very influential for three decades, and was developed by Levene at least into the 1910, and the diagram at the right illustrates the view of Levene and Tipson. In 1940, at the time of Levene's death, Bass wrote in his obituary
In that form there is an implication that the four bases are present in equal amounts in DNA, and small variations in the experimental values were assumed to be the result of experimental error.
However, Erwin Chargaff showed that the four frequencies were not equal, with variations consistent between different studies. Specifically, according to his rules the correct relationship is G = C ≠ A = T. The equalities G = C and A = T suggested that these bases were paired, this pairing being the basis of the DNA structure that is now known to be correct. Conversely the inequalities G ≠ A etc. meant that DNA could not have a systematic repetition of a fundamental unit, as required by the tetranucleotide hypothesis. Thus there was no reason why the sequence could not store information.
In later years some authorities considered the tetranucleotide hypothesis to have been harmful to the development of molecular biology. Bentley Glass, for example, called it a "scientific catastrophe". More recently, Hargittai saw it in a more positive light, and Frixione and Ruiz-Zamarripa wrote as follows: | 1 | Applied and Interdisciplinary Chemistry |
In order to create a coherent pattern, a material surface should exert a sustained and consistent action on nearby trajectories throughout the time interval . Examples of such action are attraction, repulsion, or shear. In principle, any well-defined mathematical property qualifies that creates coherent patterns out of randomly selected nearby initial conditions.
Most such properties can be expressed by strict inequalities. For instance, we call a material surface attracting over the interval if all small enough initial perturbations to are carried by the flow into even smaller final perturbations to . In classical dynamical systems theory, invariant manifolds satisfying such an attraction property over infinite times are called attractors. They are not only special, but even locally unique in the phase space: no continuous family of attractors may exist.
In contrast, in dynamical systems defined over a finite time interval , strict inequalities do not define exceptional (i.e., locally unique) material surfaces. This follows from the continuity of the flow map over . For instance, if a material surface attracts all nearby trajectories over the time interval , then so will any sufficiently close other material surface.
Thus, attracting, repelling and shearing material surfaces are necessarily stacked on each other, i.e., occur in continuous families. This leads to the idea of seeking LCSs in finite-time dynamical systems as exceptional material surfaces that exhibit a coherence-inducing property more strongly than any of the neighboring material surfaces. Such LCSs, defined as extrema (or more generally, stationary surfaces) for a finite-time coherence property, will indeed serve as observed centerpieces of trajectory patterns. Examples of attracting, repelling and shearing LCSs are in a direct numerical simulation of 2D turbulence are shown in Fig.2a. | 1 | Applied and Interdisciplinary Chemistry |
In contrast to catabolic pathways, anabolic pathways require an energy input to construct macromolecules such as polypeptides, nucleic acids, proteins, polysaccharides, and lipids. The isolated reaction of anabolism is unfavorable in a cell due to a positive Gibbs Free Energy (+ΔG). Thus, an input of chemical energy through a coupling with an exergonic reaction is necessary. The coupled reaction of the catabolic pathway affects the thermodynamics of the reaction by lowering the overall activation energy of an anabolic pathway and allowing the reaction to take place. Otherwise, an endergonic reaction is non-spontaneous.
An anabolic pathway is a biosynthetic pathway, meaning that it combines smaller molecules to form larger and more complex ones. An example is the reversed pathway of glycolysis, otherwise known as gluconeogenesis, which occurs in the liver and sometimes in the kidney to maintain proper glucose concentration in the blood and supply the brain and muscle tissues with adequate amount of glucose. Although gluconeogenesis is similar to the reverse pathway of glycolysis, it contains four distinct enzymes(pyruvate carboxylase, phosphoenolpyruvate carboxykinase, fructose 1,6-bisphosphatase, glucose 6-phosphatase) from glycolysis that allow the pathway to occur spontaneously. | 1 | Applied and Interdisciplinary Chemistry |
Beyond arranging lipids in a way that reduces surface tension, SP-B actually directly interferes with attractive forces between water molecules. This disruption in the cohesion of water minimizes further the surface tension at the gas/fluid interface. | 0 | Theoretical and Fundamental Chemistry |
In 1625, Sala pursued his research interests in conjunction with his service as the personal physician. His research and discoveries led to a better understanding of chemical reactions and the realisation that some substances are composed of chemical combinations of other substances.
Sala's discovery of light-sensitivity of silver was advanced by other chemists before photography was finally achieved in the 1830s.
Sala was above all a practitioner. In his view, demonstrations could be carried out only through manual operations (inventionibus manualibus), that is to say, only with the aid of experimental examples, which he clearly distinguished from argumentation. For him, chemistry was still a handcraft (ars).
The Carl von Ossietzky University Oldenburg annually awards students of northern German schools with the Angelus Sala Prize for the "Day of Chemistry", for those in the 10th class who have achieved outstanding academic achievements in chemistry. | 1 | Applied and Interdisciplinary Chemistry |
*Volcanic eruptions release large amounts of sulphuric acid, hydrogen sulfide and hydrochloric acid into the atmosphere. These gases represent aerosols and eventually return to earth as acid rain, having a number of adverse effects on the environment and human life.
*Aerosols interact with the Earth's energy budget in two ways, directly and indirectly.
::E.g., a direct effect is that aerosols scatter and absorb incoming solar radiation. This will mainly lead to a cooling of the surface (solar radiation is scattered back to space) but may also contribute to a warming of the surface (caused by the absorption of incoming solar energy). This will be an additional element to the greenhouse effect and therefore contributing to the global climate change.
::The indirect effects refer to the aerosol interfering with formations that interact directly with radiation. For example, they are able to modify the size of the cloud particles in the lower atmosphere, thereby changing the way clouds reflect and absorb light and therefore modifying the Earth's energy budget.
:There is evidence to suggest that anthropogenic aerosols actually offset the effects of greenhouse gases in some areas, which is why the Northern Hemisphere shows slower surface warming than the Southern Hemisphere, although that just means that the Northern Hemisphere will absorb the heat later through ocean currents bringing warmer waters from the South. On a global scale however, aerosol cooling decreases greenhouse-gases-induced heating without offsetting it completely.
*When aerosols absorb pollutants, it facilitates the deposition of pollutants to the surface of the earth as well as to bodies of water. This has the potential to be damaging to both the environment and human health.
*Aerosols in the 20 μm range show a particularly long persistence time in air conditioned rooms due to their "jet rider" behaviour (move with air jets, gravitationally fall out in slowly moving air); as this aerosol size is most effectively adsorbed in the human nose, the primordial infection site in COVID-19, such aerosols may contribute to the pandemic.
*Aerosol particles with an effective diameter smaller than 10 μm can enter the bronchi, while the ones with an effective diameter smaller than 2.5 μm can enter as far as the gas exchange region in the lungs, which can be hazardous to human health. | 0 | Theoretical and Fundamental Chemistry |
In benzo-homologated purines (xA and xG), the benzene ring is bound to the nitrogenous base through nitrogen-carbon (N-C) bonds. Benzo-homologated pyrimidines are formed through carbon-carbon (C-C) bonds between the base and the benzene. Thus far, x-nucleobases have been added to strands of DNA using phosphoramidite derivatives, as traditional polymerases have been unsuccessful in synthesizing strands of xDNA. X-nucleotides are poor candidates as substrates for B-DNA polymerases as their size interferes with binding at the catalytic domain. Attempts at using template-independent enzymes have been successful as they have a reduced geometric constraint for substrates. Terminal deoxynucleotidyl transferase (TdT) has been used previously to synthesize strands of bases which have been bound to fluorophores. Using TdT, up to 30 monomers can be combined to form a double-helix of xDNA, however this oligomeric xDNA appears to inhibit its own extension beyond this length due to the overwhelming hydrogen bonding. In order to minimize inhibition, xDNA can be hybridized into a regular helix. | 1 | Applied and Interdisciplinary Chemistry |
Gurgling is a characteristic sound made by unstable two-phase fluid flow, for example, as liquid is poured from a bottle, or during gargling. | 1 | Applied and Interdisciplinary Chemistry |
β-Hydride elimination is a reaction in which an alkyl group bonded to a metal centre is converted into the corresponding metal-bonded hydride and an alkene. The alkyl must have hydrogens on the β-carbon. For instance butyl groups can undergo this reaction but methyl groups cannot. The metal complex must have an empty (or vacant) site cis to the alkyl group for this reaction to occur. Moreover, for facile cleavage of the C–H bond, a d electron pair is needed for donation into the σ* orbital of the C–H bond. Thus, d metals alkyls are generally more stable to β-hydride elimination than d and higher metal alkyls and may form isolable agostic complexes, even if an empty coordination site is available.
The β-hydride elimination can either be a vital step in a reaction or an unproductive side reaction. The Shell higher olefin process relies on β-hydride elimination to produce α-olefins which are used to produce detergents. Illustrative of a sometimes undesirable β-hydride elimination, β-hydride elimination in Ziegler–Natta polymerization results in polymers of decreased molecular weight. In the case of nickel- and palladium-catalyzed couplings of aryl halides with alkyl Grignard reagents, the β-hydride elimination can lower the yield. The production of branched polymers from ethylene relies on chain walking, a key step of which is β-hydride elimination.
In some cases, β-hydride elimination is the first in a series of steps. For instance in the synthesis of RuHCl(CO)(PPh) from ruthenium trichloride, triphenylphosphine and 2-methoxyethanol, an intermediate alkoxide complex undergoes a β-hydride elimination to form the hydride ligand and the pi-bonded aldehyde which then is later converted into the carbonyl (carbon monoxide) ligand. | 0 | Theoretical and Fundamental Chemistry |
As SPR allows real-time monitoring, individual steps in sequential binding events can be thoroughly assessed when investigating the suitability between antibodies in a sandwich configuration. Additionally, it allows the mapping of epitopes as antibodies of overlapping epitopes will be associated with an attenuated signal compared to those capable of interacting simultaneously. | 0 | Theoretical and Fundamental Chemistry |
Britannia metal was first produced in 1769 or 1770. James Vickers created it after purchasing the formula from a dying friend. It was originally known as "Vickers White Metal" when made under contract by the Sheffield manufacturers Ebenezer Hancock and Richard Jessop. In 1776 James Vickers took over the manufacturing himself and remained as owner until his death in 1809, when the company passed to his son John and son-in-law Elijah West. In 1836 the company was sold to John Vickers's nephew Ebenezer Stacey (the son of Hannah Vickers and John Stacey).
After the development of electroplating with silver in 1846, Britannia metal was widely used as the base metal for silver-plated household goods and cutlery. The abbreviation EPBM on such items denotes "electroplated Britannia metal". Britannia metal was generally used as a cheaper alternative to electroplated nickel silver (EPNS) which is more durable.
Until 2016, britannium was used to make the solid core of the Oscar statuettes. The 8½ lb (4 kg) statuettes were Britannia metal plated with gold. The awards have since changed to a bronze core.
In his essay "A Nice Cup of Tea", writer George Orwell asserts that "britanniaware" teapots "produce inferior tea" when compared to chinaware. | 1 | Applied and Interdisciplinary Chemistry |
A DNA transcription unit encoding for a protein may contain both a coding sequence, which will be translated into the protein, and regulatory sequences, which direct and regulate the synthesis of that protein. The regulatory sequence before (upstream from) the coding sequence is called the five prime untranslated regions (5UTR); the sequence after (downstream from) the coding sequence is called the three prime untranslated regions (3UTR).
As opposed to DNA replication, transcription results in an RNA complement that includes the nucleotide uracil (U) in all instances where thymine (T) would have occurred in a DNA complement.
Only one of the two DNA strands serves as a template for transcription. The antisense strand of DNA is read by RNA polymerase from the 3 end to the 5 end during transcription (3 → 5). The complementary RNA is created in the opposite direction, in the 5 → 3 direction, matching the sequence of the sense strand except switching uracil for thymine. This directionality is because RNA polymerase can only add nucleotides to the 3 end of the growing mRNA chain. This use of only the 3 → 5' DNA strand eliminates the need for the Okazaki fragments that are seen in DNA replication. This also removes the need for an RNA primer to initiate RNA synthesis, as is the case in DNA replication.
The non-template (sense) strand of DNA is called the coding strand, because its sequence is the same as the newly created RNA transcript (except for the substitution of uracil for thymine). This is the strand that is used by convention when presenting a DNA sequence.
Transcription has some proofreading mechanisms, but they are fewer and less effective than the controls for copying DNA. As a result, transcription has a lower copying fidelity than DNA replication. | 1 | Applied and Interdisciplinary Chemistry |
A central concept in NMR is the precession of the spin magnetization around the magnetic field at the nucleus, with the angular frequency where relates to the oscillation frequency and B is the magnitude of the field. This means that the spin magnetization, which is proportional to the sum of the spin vectors of nuclei in magnetically equivalent sites (the expectation value of the spin vector in quantum mechanics), moves on a cone around the B field. This is analogous to the precessional motion of the axis of a tilted spinning top around the gravitational field. In quantum mechanics, is the Bohr frequency of the and expectation values. Precession of non-equilibrium magnetization in the applied magnetic field B occurs with the Larmor frequency without change in the populations of the energy levels because energy is constant (time-independent Hamiltonian). | 0 | Theoretical and Fundamental Chemistry |
The original theory from 1927 of nucleation in nanoparticle formation was Classical Nucleation Theory (CNT). It was believed that the changes in particle size could be described by burst nucleation alone. In 1950, Viktor LaMer used CNT as the nucleation basis for his model of nanoparticle growth. There are three portions to the LaMer model: 1. Rapid increase in the concentration of free monomers in solution, 2. fast nucleation of the monomer characterized by explosive growth of particles, 3. Growth of particles controlled by diffusion of the monomer. This model describes that the growth on the nucleus is spontaneous but limited by diffusion of the precursor to the nuclei surface. The LaMer model has not been able to explain the kinetics of nucleation in any modern system. | 0 | Theoretical and Fundamental Chemistry |
Polyfunctional ligands can attach to metals in many ways and thus can bridge metals in diverse ways, including sharing of one atom or using several atoms. Examples of such polyatomic ligands are the oxoanions and the related carboxylates, , and the polyoxometalates. Several organophosphorus ligands have been developed that bridge pairs of metals, a well-known example being . | 0 | Theoretical and Fundamental Chemistry |
In a stationary vortex, the typical streamline (a line that is everywhere tangent to the flow velocity vector) is a closed loop surrounding the axis; and each vortex line (a line that is everywhere tangent to the vorticity vector) is roughly parallel to the axis. A surface that is everywhere tangent to both flow velocity and vorticity is called a vortex tube. In general, vortex tubes are nested around the axis of rotation. The axis itself is one of the vortex lines, a limiting case of a vortex tube with zero diameter.
According to Helmholtz's theorems, a vortex line cannot start or end in the fluid – except momentarily, in non-steady flow, while the vortex is forming or dissipating. In general, vortex lines (in particular, the axis line) are either closed loops or end at the boundary of the fluid. A whirlpool is an example of the latter, namely a vortex in a body of water whose axis ends at the free surface. A vortex tube whose vortex lines are all closed will be a closed torus-like surface.
A newly created vortex will promptly extend and bend so as to eliminate any open-ended vortex lines. For example, when an airplane engine is started, a vortex usually forms ahead of each propeller, or the turbofan of each jet engine. One end of the vortex line is attached to the engine, while the other end usually stretches out and bends until it reaches the ground.
When vortices are made visible by smoke or ink trails, they may seem to have spiral pathlines or streamlines. However, this appearance is often an illusion and the fluid particles are moving in closed paths. The spiral streaks that are taken to be streamlines are in fact clouds of the marker fluid that originally spanned several vortex tubes and were stretched into spiral shapes by the non-uniform flow velocity distribution. | 1 | Applied and Interdisciplinary Chemistry |
Non-coding DNA (ncDNA) sequences are components of an organism's DNA that do not encode protein sequences. Some non-coding DNA is transcribed into functional non-coding RNA molecules (e.g. transfer RNA, microRNA, piRNA, ribosomal RNA, and regulatory RNAs). Other functional regions of the non-coding DNA fraction include regulatory sequences that control gene expression; scaffold attachment regions; origins of DNA replication; centromeres; and telomeres. Some non-coding regions appear to be mostly nonfunctional, such as introns, pseudogenes, intergenic DNA, and fragments of transposons and viruses. Regions that are completely nonfunctional are called junk DNA. | 1 | Applied and Interdisciplinary Chemistry |
Prostaglandins are formed through oxidation of arachidonic acid by cyclooxygenases and other prostaglandin synthases. There are currently nine known G-protein coupled receptors (eicosanoid receptors) that largely mediate prostaglandin physiology (although some prostaglandins activate nuclear receptors, see below). | 1 | Applied and Interdisciplinary Chemistry |
Metal ions can be described as consisting of series of two concentric coordination spheres, the first and second. More distant from the second coordination sphere, the solvent molecules behave more like "bulk solvent." Simulation of the second coordination sphere is of interest in computational chemistry. The second coordination sphere can consist of ions (especially in charged complexes), molecules (especially those that hydrogen bond to ligands in the first coordination sphere) and portions of a ligand backbone. Compared to the first coordination sphere, the second coordination sphere has a less direct influence on the reactivity and chemical properties of the metal complex. Nonetheless the second coordination sphere is relevant to understanding reactions of the metal complex, including the mechanisms of ligand exchange and catalysis. | 0 | Theoretical and Fundamental Chemistry |
Black oxide for copper, sometimes known by the trade name Ebonol C, converts the copper surface to cupric oxide. For the process to work the surface has to have at least 65% copper; for copper surfaces that have less than 90% copper it must first be pretreated with an activating treatment. The finished coating is chemically stable and very adherent. It is stable up to ; above this temperature the coating degrades due to oxidation of the base copper. To increase corrosion resistance, the surface may be oiled, lacquered, or waxed. It is also used as a pre-treatment for painting or enamelling. The surface finish is usually satin, but it can be turned glossy by coating in a clear high-gloss enamel.
On a microscopic scale dendrites form on the surface finish, which trap light and increase absorptivity. Because of this property the coating is used in aerospace, microscopy and other optical applications to minimise light reflection.
In printed circuit boards (PCBs), the use of black oxide provides better adhesion for the fiberglass laminate layers. The PCB is dipped in a bath containing hydroxide, hypochlorite, and cuprate, which becomes depleted in all three components. This indicates that the black copper oxide comes partially from the cuprate and partially from the PCB copper circuitry. Under microscopic examination, there is no copper(I) oxide layer.
An applicable U.S. military specification is MIL-F-495E. | 0 | Theoretical and Fundamental Chemistry |
Phenylalanine, tyrosine, and tryptophan, the aromatic amino acids, arise from chorismate. The first step, condensation of 3-deoxy-D-arabino-heptulosonic acid 7-phosphate (DAHP) from PEP/E4P, uses three isoenzymes AroF, AroG, and AroH. Each one of these has its synthesis regulated from tyrosine, phenylalanine, and tryptophan, respectively. The rest of the enzymes in the common pathway (conversion of DAHP to chorismate) appear to be synthesized constitutively, except for shikimate kinase, which can be inhibited by shikimate through linear mixed-type inhibition.
Tyrosine and phenylalanine are biosynthesized from prephenate, which is converted to an amino acid-specific intermediate. This process is mediated by a phenylalanine (PheA) or tyrosine (TyrA) specific chorismate mutase-prephenate dehydrogenase. PheA uses a simple dehydrogenase to convert prephenate to phenylpyruvate, while TyrA uses a NAD-dependent dehydrogenase to make 4-hydroxylphenylpyruvate. Both PheA and TyrA are feedback inhibited by their respective amino acids. Tyrosine can also be inhibited at the transcriptional level by the TyrR repressor. TyrR binds to the TyrR boxes on the operon near the promoter of the gene that it wants to repress.
Tryptophan biosynthesis involves conversion of chorismate to anthranilate using anthranilate synthase. This enzyme requires either glutamine as the amino group donor or ammonia itself. Anthranilate synthase is regulated by the gene products of trpE and trpG. trpE encodes the first subunit, which binds to chorismate and moves the amino group from the donor to chorismate. trpG encodes the second subunit, which facilitates the transfer of the amino group from glutamine. Anthranilate synthase is also regulated by feedback inhibition: tryptophan is a co-repressor to the TrpR repressor. | 1 | Applied and Interdisciplinary Chemistry |
The plate count method relies on bacteria growing a colony on a nutrient medium so that the colony becomes visible to the naked eye and the number of colonies on a plate can be counted. To be effective, the dilution of the original sample must be arranged so that on average between 30 and 300 colonies of the target bacterium are grown. Fewer than 30 colonies makes the interpretation statistically unsound whilst greater than 300 colonies often results in overlapping colonies and imprecision in the count. To ensure that an appropriate number of colonies will be generated several dilutions are normally cultured. This approach is widely utilised for the evaluation of the effectiveness of water treatment by the inactivation of representative microbial contaminants such as E. coli following ASTM D5465.
The laboratory procedure involves making serial dilutions of the sample (1:10, 1:100, 1:1000, etc.) in sterile water and cultivating these on nutrient agar in a dish that is sealed and incubated. Typical media include plate count agar for a general count or MacConkey agar to count Gram-negative bacteria such as E. coli. Typically one set of plates is incubated at 22 °C and for 24 hours and a second set at 37 °C for 24 hours. The composition of the nutrient usually includes reagents that resist the growth of non-target organisms and make the target organism easily identified, often by a colour change in the medium. Some recent methods include a fluorescent agent so that counting of the colonies can be automated. At the end of the incubation period the colonies are counted by eye, a procedure that takes a few moments and does not require a microscope as the colonies are typically a few millimetres across. | 0 | Theoretical and Fundamental Chemistry |
Enantioselective carbonyl allylations are frequently applied to the synthesis of polyketide natural products. In 1978, Hoffmann reported the first asymmetric carbonyl allylation using a chiral allylmetal reagent, an allylborane derived from camphor. Subsequently, other chiral allylmetal reagents were developed by Kumada, Roush, Brown, Leighton, and others. These methods utilize preformed allyl metal reagents and generate stoichiometric quantities of metal byproducts.
In 1991, Yamamoto disclosed the first catalytic enantioselective method for carbonyl allylation, which employed a chiral boron Lewis acid-catalyst in combination with allyltrimethylsilane. Numerous catalytic enantioselective methods for carbonyl allylation followed, including work by Umani-Ronchi and Keck. While these methods had a significant impact, they do not circumvent the use of preformed allylmetal reagents. Catalytic variants of the Nozaki-Hiyama-Kishi reaction represent an alternative method for asymmetric carbonyl allylation, but stoichiometric metallic reductants are required.
Whereas the allylmetal reagents used in these first-generation technologies are often difficult to prepare and handle, the Krische allylation exploits highly tractable allylic acetates. Additionally, the Krische allylation avoids the use of preformed allyl metal reagents or metallic reductants and chiral auxiliaries, significantly reducing waste generation. | 0 | Theoretical and Fundamental Chemistry |
Receptor desensitization is mediated through a combination phosphorylation, β-arr binding, and endocytosis as described above. Downregulation occurs when endocytosed receptor is embedded in an endosome that is trafficked to merge with an organelle called a lysosome. Because lysosomal membranes are rich in proton pumps, their interiors have low pH (≈4.8 vs. the pH≈7.2 cytosol), which acts to denature the GPCRs. In addition, lysosomes contain many degradative enzymes, including proteases, which can function only at such low pH, and so the peptide bonds joining the residues of the GPCR together may be cleaved. Whether or not a given receptor is trafficked to a lysosome, detained in endosomes, or trafficked back to the plasma membrane depends on a variety of factors, including receptor type and magnitude of the signal.
GPCR regulation is additionally mediated by gene transcription factors. These factors can increase or decrease gene transcription and thus increase or decrease the generation of new receptors (up- or down-regulation) that travel to the cell membrane. | 1 | Applied and Interdisciplinary Chemistry |
According to X-ray crystallography the linkage is linear in typical diazonium salts. The bond distance in benzenediazonium tetrafluoroborate is 1.083(3) Å, which is almost identical to that for dinitrogen molecule (N≡N).
The linear free energy constants σ and σ indicate that the diazonium group is strongly electron-withdrawing. Thus, the diazonio-substituted phenols and benzoic acids have greatly reduced pK values compared to their unsubstituted counterparts. The pK of phenolic proton of 4-hydroxybenzenediazonium is 3.4, versus 9.9 for phenol itself. In other words, the diazonium group lowers the pK (enhances the acidity) by a million-fold.
The stability of arenediazonium salts is highly sensitive to the counterion. Phenyldiazonium chloride is dangerously explosive, but benzenediazonium tetrafluoroborate is easily handled on the bench.
S1 and S2 reactions do not occur.
Arenediazonium salts are versatile reagents as described in the next sections After electrophilic aromatic substitution, diazonium chemistry is the most frequently applied strategy to prepare aromatic compounds. | 0 | Theoretical and Fundamental Chemistry |
Klaus Schmiegel (born June 28, 1939), is a German chemist best known for his work in organic chemistry, which led to the invention of Prozac, a widely used antidepressant. | 0 | Theoretical and Fundamental Chemistry |
The rocks on the plains of Gusev are a type of basalt. They contain the minerals olivine, pyroxene, plagioclase, and magnetite, and they look like volcanic basalt as they are fine-grained with irregular holes (geologists would say they have vesicles and vugs).
Much of the soil on the plains came from the breakdown of the local rocks. Fairly high levels of nickel were found in some soils; probably from meteorites.
Analysis shows that the rocks have been slightly altered by tiny amounts of water. Outside coatings and cracks inside the rocks suggest water deposited minerals, maybe bromine compounds. All the rocks contain a fine coating of dust and one or more harder rinds of material. One type can be brushed off, while another needed to be ground off by the Rock Abrasion Tool (RAT).
There are a variety of rocks in the Columbia Hills (Mars), some of which have been altered by water, but not by very much water.
The dust in Gusev Crater is the same as dust all around the planet. All the dust was found to be magnetic. Moreover, Spirit found the magnetism was caused by the mineral magnetite, especially magnetite that contained the element titanium. One magnet was able to completely divert all dust hence all Martian dust is thought to be magnetic. The spectra of the dust was similar to spectra of bright, low thermal inertia regions like Tharsis and Arabia that have been detected by orbiting satellites. A thin layer of dust, maybe less than one millimeter thick covers all surfaces. Something in it contains a small amount of chemically bound water. | 0 | Theoretical and Fundamental Chemistry |
Firefly luciferin (also known as beetle luciferin) is the luciferin, or light-emitting compound, used for the firefly (Lampyridae), railroad worm (Phengodidae), starworm (Rhagophthalmidae), and click-beetle (Pyrophorini) bioluminescent systems. It is the substrate of luciferase (EC 1.13.12.7), which is responsible for the characteristic yellow light emission from many firefly species.
As with all other luciferins, oxygen is required to elicit light; however, it has also been found adenosine triphosphate (ATP) and magnesium are required for light emission. | 1 | Applied and Interdisciplinary Chemistry |
*Metallurgical and Materials Transactions A – [https://link.springer.com/search?query=&search-within=Journal&facet-journal-id=11661&package=openaccessarticles open access articles]
*Metallurgical and Materials Transactions B – [https://link.springer.com/search?query=&search-within=Journal&facet-journal-id=11663&package=openaccessarticles open access articles]
*Advanced Engineering Materials – [http://www.aem-journal.de articles]
*Metals – [https://www.mdpi.com/journal/metals open access articles]
*Journal of Alloys and Compounds – [http://www.sciencedirect.com/science/journal/09258388/ open access articles]
*Acta Materialia – [http://www.sciencedirect.com/science/journal/13596454/open-access open access articles]
*International Journal of Materials Research – [https://www.degruyter.com/journal/key/ijmr/html articles] | 1 | Applied and Interdisciplinary Chemistry |
Using truncated BET theory (the gas adsorption theory developed by Brunauer, Emmett, and Teller), Seah and Hondros write the solid-state analogue as:
where
is the solid solubility, which is known for many elements (and can be found in metallurgical handbooks). In the dilute limit, a slightly soluble substance has , so the above equation reduces to that found with the Langmuir-McLean theory. This equation is only valid for . If there is an excess of solute such that a second phase appears, the solute content is limited to and the equation becomes
This theory for grain boundary segregation, derived from truncated BET theory, provides excellent agreement with experimental data obtained by Auger electron spectroscopy and other techniques. | 0 | Theoretical and Fundamental Chemistry |
The HEC-Meeting dates back to an initiative in the year 1998 of Manfred Weiss and Rolf Hilgenfeld, who were researchers at the Institute for Molecular Biotechnology (IMB) in Jena and intended to establish a meeting format similar to the [http://regiomeeting.eu/ Rhine-Knee Regional Meeting on Structural Biology] in the New Länder. Both conferences are regional meetings of German scientists together with scientific research groups of the neighbouring countries. Nine groups from Germany (the new states and West-Berlin), Poland and Czech Republic participated in the first HEC-Meeting from 8 to 10 October 1998. Later also groups from Austria and the Old Federal States participated. Due to the Covid-19 pandemic, no meeting was organized in 2020 and HEC-23 took place as an online meeting.
Former HEC-Meetings: | 1 | Applied and Interdisciplinary Chemistry |
The Mpemba effect is the name given to the observation that a liquid (typically water) which is initially hot can freeze faster than the same liquid which begins cold, under otherwise similar conditions. There is disagreement about its theoretical basis and the parameters required to produce the effect.
The Mpemba effect is named after Tanzanian scientist Erasto Bartholomeo Mpemba, who described it in 1963 as a secondary school student. The initial discovery and observations of the effect originate in ancient times; Aristotle said that it was common knowledge. | 0 | Theoretical and Fundamental Chemistry |
Fulmer benefited from the immediate post-war climate which was favourable to Research and Development. The UK Government and its agencies continued to spend heavily on R&D. This was despite the fact that Britain was essentially bankrupt and hugely indebted to the United States and Canada. The technological advances which had been made on both sides of the conflict had been impressive: radar, the jet engine, the V-2 rocket and the atomic bomb are just a few examples. The Cold War soon added urgency to further military development and there was enthusiasm for developing peaceful uses of atomic energy. | 1 | Applied and Interdisciplinary Chemistry |
Expanded polyethylene (aka EPE foam) refers to foams made from polyethylene. Typically it is made from expanded pellets (EPE bead) made with use of a blowing agent, followed by expansion into a mold in a steam chest - the process is similar to that used to make expanded polystyrene foam. | 0 | Theoretical and Fundamental Chemistry |
Glass ionomer cement is primarily used in the prevention of dental caries. This dental material has good adhesive bond properties to tooth structure, allowing it to form a tight seal between the internal structures of the tooth and the surrounding environment. Dental caries are caused by bacterial production of acid during their metabolic actions. The acid produced from this metabolism results in the breakdown of tooth enamel and subsequent inner structures of the tooth, if the disease is not intervened by a dental professional, or if the carious lesion does not arrest and/or the enamel re-mineralises by itself. Glass ionomer cements act as sealants when pits and fissures in the tooth occur and release fluoride to prevent further enamel demineralisation and promote remineralisation. Fluoride can also hinder bacterial growth, by inhibiting their metabolism of ingested sugars in the diet. It does this by inhibiting various metabolic enzymes within the bacteria. This leads to a reduction in the acid produced during the bacteria's digestion of food, preventing a further drop in pH and therefore preventing caries.
There is evidence that when using sealants, only 6% of people develop tooth decay over a 2-year period, in comparison to 40% of people when not using a sealant. However, it is recommended that the use of fluoride varnish alongside glass ionomer sealants should be applied in practice to further reduce the risk of secondary dental caries. | 0 | Theoretical and Fundamental Chemistry |
*2000: L'Oréal-UNESCO Awards for Women in Science
*2007: Order of Mapungubwe - Silver
*2013: Christophe Mérieux Prize
*2018: Harry Oppenheimer Fellowship Award | 1 | Applied and Interdisciplinary Chemistry |
The material may be solid, liquid, gas, a material of some intermediate characteristics such as gel or sputum, tissue, organism, or a combination of these. Even if a material sample is not countable as individual items, the quantity of the sample may still be describable in terms of its volume, mass, size, or other such dimensions. A solid sample can come in one or a few discrete pieces, or it can be fragmented, granular, or powdered. A section of a rod, wire, cord, sheeting, or tubing may be considered a sample. Samples which are not a solid piece are commonly kept in a container of some sort.
Where goods are sold or supplied by reference to a sample, relevant sale of goods legislation may dictate the supplier's legal obligations in ensuring that the bulk of the goods corresponds with the goods comprising the sample, for example in the UK, the Sale of Goods Act 1979, section 15, the Supply of Goods and Services Act 1982, section 5, and the Consumer Rights Act 2015, section 13. | 0 | Theoretical and Fundamental Chemistry |
The only chemical elements that are stable diatomic homonuclear molecular gases at STP are hydrogen (H), nitrogen (N), oxygen (O), and two halogens: fluorine (F) and chlorine (Cl). When grouped with the monatomic noble gases – helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn) – these gases are referred to as "elemental gases". | 0 | Theoretical and Fundamental Chemistry |
The many examples of implant failure include rupture of silicone breast implants, hip replacement joints, and artificial heart valves, such as the Bjork–Shiley valve, all of which have caused FDA intervention. The consequences of implant failure depend on the nature of the implant and its position in the body. Thus, heart valve failure is likely to threaten the life of the individual, while breast implant or hip joint failure is less likely to be life-threatening.
Devices implanted directly in the grey matter of the brain produce the highest quality signals, but are prone to scar-tissue build-up, causing the signal to become weaker, or even non-existent, as the body reacts to a foreign object in the brain.
In 2018, Implant files, an investigation made by ICIJ revealed that medical devices that are unsafe and have not been adequately tested were implanted in patients' bodies. In United Kingdom, Prof Derek Alderson, president of the Royal College of Surgeons, concludes: "All implantable devices should be registered and tracked to monitor efficacy and patient safety in the long-term." | 1 | Applied and Interdisciplinary Chemistry |
Upon introducing surfactants (or any surface active materials) into a system, they will initially partition into the interface, reducing the system free energy by:
# lowering the energy of the interface (calculated as area times surface tension), and
# removing the hydrophobic parts of the surfactant from contact with water.
Subsequently, when the surface coverage by the surfactants increases, the surface free energy (surface tension) decreases and the surfactants start aggregating into micelles, thus again decreasing the system's free energy by decreasing the contact area of hydrophobic parts of the surfactant with water. Upon reaching CMC, any further addition of surfactants will just increase the number of micelles (in the ideal case).
According to one well-known definition, CMC is the total concentration of surfactants under the conditions:
:if C = CMC, (d/dC) = 0
: = A[C] + B[C]; i.e., in words C = [single surfactant ion] , C = [micelles] and A and B are proportionality constants
:C = C + NC; i.e., N = represents the number of detergent ions per micelle | 0 | Theoretical and Fundamental Chemistry |
In dehydrohalogenation reactions, the halogen and an adjacent proton are removed from halocarbons, thus forming an alkene. For example, with bromoethane and sodium hydroxide (NaOH) in ethanol, the hydroxide ion HO abstracts a hydrogen atom. A Bromide ion is then lost, resulting in ethene, HO and NaBr. Thus, haloalkanes can be converted to alkenes. Similarly, dihaloalkanes can be converted to alkynes.
In related reactions, 1,2-dibromocompounds are debrominated by zinc dust to give alkenes and geminal dihalides can react with strong bases to give carbenes. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, the triflyl group (systematic name: trifluoromethanesulfonyl group) is a functional group with the formula and structure . The triflyl group is often represented by –Tf.
The related triflate group (trifluoromethanesulfonate) has the formula , and is represented by –OTf. | 0 | Theoretical and Fundamental Chemistry |
IChemE has two main types of membership, qualified and non-qualified, with the technician member grade being available in both categories.
Qualified membership grades.
Fellow – A chemical engineering professional in a very senior position in industry and/or academia. Entitling the holder to the post-nominal FIChemE and is a chartered grade encompassing all the privileges of Chartered Member grade.
Chartered Member – Internationally recognised level of professional and academic competence requiring at least 4 years of field experience and a bachelors degree with honours. Entitles the holder to the post-nominal MIChemE and registration as one or a combination of; Chartered Engineer (CEng), Chartered Scientist (CSci) and Chartered Environmentalist (CEnv). This also entitles the individual to register as a European Engineer with the pre-nominal Eur Ing.
Associate Member – This grade is for young professionals who are qualified in chemical & process engineering to bachelors with honours level or a higher. Typically this is the grade held by those working towards Chartered Member level or those graduates working other fields. This grade entitles the holder to the post-nominal AMIChemE. This grade can also lead to the grade of Incorporated Engineer (IEng) for those with some field experience but which falls short of the level required for Chartered Member grade.
Technician Member – Uses practical understanding to solve engineering problems and could have a qualification, an apprenticeship or years of experience. This grade can lead to the Eng Tech TIChemE post-nominal and now in conjunction with the Nuclear Institute the post-nominal Eng Tech TIChemE TNucI.
Non-qualified membership grades.
Associate Fellow – Senior professionals trained in other fields of a level comparable to Fellow in other professional bodies.
Affiliate – For people working in, with or with a general interest in the sector.
Student – For undergraduate chemical & process engineering students. | 1 | Applied and Interdisciplinary Chemistry |
eIF2 activity is regulated by a mechanism involving both guanine nucleotide exchange and phosphorylation. Phosphorylation takes place at the α-subunit, which is a target for a number of serine kinases that phosphorylate serine 51. Those kinases act as a result of stress such as amino acid deprivation (GCN2), ER stress (PERK), the presence of dsRNA (PKR) heme deficiency (HRI), or interferon. Once phosphorylated, eIF2 shows increased affinity for eIF2B, its GEF. However, eIF2B is able to exchange GDP for GTP only if eIF2 is in its unphosphorylated state. Phosphorylated eIF2, however, due to its stronger binding, acts as an inhibitor of its own GEF (eIF2B). Since the cellular concentration of eIF2B is much lower than that of eIF2, even a small amount of phosphorylated eIF2 can completely abolish eIF2B activity by sequestration. Without the GEF, eIF2 can no longer be returned to its active (GTP-bound) state. As a consequence, translation comes to a halt since initiation is no longer possible without any available ternary complex. Furthermore, low concentration of ternary complex allows the expression of GCN4 (starved condition), which, in turn, results in increased activation of amino acid synthesis genes | 1 | Applied and Interdisciplinary Chemistry |
Case A – Antipsychotic adverse reaction
Patient A has schizophrenia. Their treatment included a combination of ziprasidone, olanzapine, trazodone and benztropine. The patient experienced dizziness and sedation, so they were tapered off ziprasidone and olanzapine, and transitioned to quetiapine. Trazodone was discontinued. The patient then experienced excessive sweating, tachycardia and neck pain, gained considerable weight and had hallucinations. Five months later, quetiapine was tapered and discontinued, with ziprasidone re-introduced into their treatment, due to the excessive weight gain. Although the patient lost the excessive weight they had gained, they then developed muscle stiffness, cogwheeling, tremors and night sweats. When benztropine was added they experienced blurry vision. After an additional five months, the patient was switched from ziprasidone to aripiprazole. Over the course of 8 months, patient A gradually experienced more weight gain and sedation, and developed difficulty with their gait, stiffness, cogwheeling and dyskinetic ocular movements. A pharmacogenomics test later proved the patient had a CYP2D6 *1/*41, which has a predicted phenotype of IM and CYP2C19 *1/*2 with a predicted phenotype of IM as well.
Case B – Pain Management
Patient B is a woman who gave birth by caesarian section. Her physician prescribed codeine for post-caesarian pain. She took the standard prescribed dose, but she experienced nausea and dizziness while she was taking codeine. She also noticed that her breastfed infant was lethargic and feeding poorly. When the patient mentioned these symptoms to her physician, they recommended that she discontinue codeine use. Within a few days, both the patients and her infants symptoms were no longer present. It is assumed that if the patient had undergone a pharmacogenomic test, it would have revealed she may have had a duplication of the gene CYP2D6, placing her in the Ultra-rapid metabolizer (UM) category, explaining her reactions to codeine use.
Case C – FDA Warning on Codeine Overdose for Infants
On February 20, 2013, the FDA released a statement addressing a serious concern regarding the connection between children who are known as CYP2D6 UM, and fatal reactions to codeine following tonsillectomy and/or adenoidectomy (surgery to remove the tonsils and/or adenoids). They released their strongest Boxed Warning to elucidate the dangers of CYP2D6 UMs consuming codeine. Codeine is converted to morphine by CYP2D6, and those who have UM phenotypes are in danger of producing large amounts of morphine due to the increased function of the gene. The morphine can elevate to life-threatening or fatal amounts, as became evident with the death of three children in August 2012. | 1 | Applied and Interdisciplinary Chemistry |
In addition, some carbamates are used in human pharmacotherapy, for example, the acetylcholinesterase inhibitors neostigmine and rivastigmine, whose chemical structure is based on the natural alkaloid physostigmine. Other examples are meprobamate and its derivatives like carisoprodol, felbamate, mebutamate, phenprobamate, and tybamate, a class of anxiolytic and muscle relaxant drugs widely used in the 1960s before the rise of benzodiazepines, and still used nowadays in some cases. Carbachol is primarily used for various ophthalmic purposes.
The protease inhibitor darunavir for HIV treatment also contains a carbamate functional group.
Ephedroxane, an aminorex analogue used as a stimulant, also falls into the carbamate category. | 0 | Theoretical and Fundamental Chemistry |
Scaffold materials are designed to enhance tissue formation through control of the local and surrounding environments. Scaffolds are critical in regulating cellular growth and provide a volume in which vascularization and stem cell differentiation can occur. Scaffold geometry significantly affects tissue differentiation through physical growth ques. Predicting tissue formation computationally requires theories that link physical growth ques to cell differentiation. Current models rely on mechano-regulation theory, widely shaped by Prendergast et al. for predicting cell growth. Thus a quantitative analysis of geometry and materials commonly used in tissue scaffolds is capable.
Such materials include:
* Porous ceramic and demineralized bone matrix supports
* Coralline cylinders
* Biodegradable material such as poly(α-hydroxy esters)
* Decellularized tissue matrices
* Injectable biomaterials or hydrogels are typically composed of polysaccharides, proteins/peptide mimetics, or synthetic polymers such as (poly(ethylene glycol)).
* Peptide amphiphile (PA) systems are self assembling and can form solid bioactive scaffolds after injection within the body.
* Inert systems have been proven to be adequate for tissue formation. Cartilage formation has occurred by injecting an inert agarose gel beneath the periosteum in a rabbit model, vascularization was restricted.
* fibrin
* Sponges made from collagen | 1 | Applied and Interdisciplinary Chemistry |
A tire (in American English and Canadian English) or tyre (in British English, New Zealand English, Australian English and others) is a ring-shaped covering that fits around a wheel rim to protect it and enable better vehicle performance by providing a flexible cushion that absorbs shock while keeping the wheel in close contact with the ground. The word itself may be derived from the word "tie," which refers to the outer steel ring part of a wooden cart wheel that ties the wood segments together (see Etymology below).
The fundamental materials of modern tires are synthetic rubber, natural rubber, fabric and wire, along with other compound chemicals. They consist of a tread and a body. The tread provides traction while the body ensures support. Before rubber was invented, the first versions of tires were simply bands of metal that fitted around wooden wheels in order to prevent wear and tear. Today, the vast majority of tires are pneumatic inflatable structures, comprising a doughnut-shaped body of cords and wires encased in rubber and generally filled with compressed air to form an inflatable cushion. Pneumatic tires are used on many types of vehicles, such as bicycles, motorcycles, cars, trucks, earthmovers, and aircraft. | 1 | Applied and Interdisciplinary Chemistry |
The simplest model for describing an inhomogeneous structure is a double layer arrangement, where each layer is characterized by its permittivity and its conductivity . The relaxation time for such an arrangement is given by
Importantly, since the materials' conductivities are in general frequency dependent, this shows that the double layer composite generally has a frequency dependent relaxation time even if the individual layers are characterized by frequency independent permittivities.
A more sophisticated model for treating interfacial polarization was developed by Maxwell , and later generalized by Wagner and Sillars. Maxwell considered a spherical particle with a dielectric permittivity and radius suspended in an infinite medium characterized by . Certain European text books will represent the constant with the Greek letter ω (Omega), sometimes referred to as Doyles constant. | 0 | Theoretical and Fundamental Chemistry |
In chemistry and materials science, molecular self-assembly is the process by which molecules adopt a defined arrangement without guidance or management from an outside source. There are two types of self-assembly: intermolecular and intramolecular. Commonly, the term molecular self-assembly refers to the former, while the latter is more commonly called folding. | 0 | Theoretical and Fundamental Chemistry |
IL-20 - induces cheratin proliferation and Stat-3 signal transduction pathway; is expressed in the CNS, myeloid cells, and keratinocytes. When IL-20 is inhibited in the CNS can stop such inflammations as acute ischemic brain injury. | 1 | Applied and Interdisciplinary Chemistry |
The psychedelic drug (or entheogen) lysergic acid diethylamide (LSD) was first synthesized on November 16, 1938, by the Swiss chemist Albert Hofmann in the Sandoz laboratories in Basel, Switzerland. It was not until five years later on April 19, 1943, that the psychedelic properties were found. Today, the discovery of LSD is celebrated worldwide during the annual Bicycle Day holiday, serving also as the day celebrating the psychedelic revolution in general.[https://www.forbes.com/sites/rebeccacoffey/2021/04/19/bicycle-day-and-the-1962-harvard-experiment-that-showed-psilocybin-can-create-lasting-positive-spiritual-change/?sh=52bb0962713c] | 1 | Applied and Interdisciplinary Chemistry |
Electrowinning, also called electroextraction, is the electrodeposition of metals from their ores that have been put in solution via a process commonly referred to as leaching. Electrorefining uses a similar process to remove impurities from a metal. Both processes use electroplating on a large scale and are important techniques for the economical and straightforward purification of non-ferrous metals. The resulting metals are said to be electrowon.
In electrowinning, an electrical current is passed from an inert anode through a leach solution containing the dissolved metal ions so that the metal is recovered as it is reduced and deposited in an electroplating process onto the cathode. In electrorefining, the anode consists of the impure metal (e.g., copper) to be refined. The impure metallic anode is oxidized and the metal dissolves into solution. The metal ions migrate through the electrolyte towards the cathode where the pure metal is deposited. Insoluble solid impurities sedimenting below the anode often contain valuable rare elements such as gold, silver and selenium. | 1 | Applied and Interdisciplinary Chemistry |
As it is known that survivin is over-expressed in most cancers, which may be contributing to the cancer cells' resistance to apoptotic stimuli from the environment. The use of antisense survivin therapy hopes to render cancer cells susceptible to apoptosis by eliminating survivin expression in the cancer cells.
Olie et al. developed different 20-mer phosphorothioate antisense oligonucleotides that target different regions in the mRNA of the survivin gene. The antisense function of the oligonucleotides allows binding to surviving mRNA and, depending on the region on which it binds, might inhibit surviving mRNA from being translated into a functional protein. Real-time PCR was used to assess the levels of mRNA present in a lung adenocarcinoma cell line A549 that overexpresses survivin. The best antisense oligonucleotide was identified that effectively down-regulated survivin mRNA levels and resulted in apoptosis of the cells. Survivin's role in cancer development in the context of a signaling pathway is its ability to inhibit activation of downstream caspase-3 and -7 from apoptosis inducing stimuli. The overexpression of survivin in tumors may serve to increase the tumors resistance to apoptosis and, thus, contribute to cell immortality even in the presence of death stimuli. In this experiment, the oligonucleotide 4003 that targets nucleotides 232-251 of survivin mRNA was found to be the most effective at down-regulating the levels of survivin mRNA in the A549 tumour line. The 4003 oligonucleotides were introduced into the tumour cells by transfection. Further experiments were then conducted on 4003. One of the additional experiments involved determining the dose-dependent effect of 4003 on the down-regulation of survivin mRNA levels. It was found that a concentration of 400 nM resulted in a maximum down-regulation of 70% of the initial survivin mRNA present. Another experiment on 4003 involved assessing any biological or cytotoxic effect 4003 down-regulation of survivin mRNA has on A549 cells using the MTT assay. The numbers of A549 cells transfected with 4003 significantly decreased with increasing concentration of 4003 compared to cells transfected either with a mismatch form of the 4003 or lipofectin control. Many physical observations that confirmed the induction of apoptosis by 4003 were made. For example, lysates of the 4003-treated cells showed increased levels of caspase-3-like protease activity; nuclei were observed to be condensed and chromatin was fragmented. | 1 | Applied and Interdisciplinary Chemistry |
Historically Hansen solubility parameters (HSP) have been used in industries such as paints and coatings where understanding and controlling solvent–polymer interactions was vital. Over the years their use has been extended widely to applications such as:
* Environmental stress cracking of polymers
* Controlled dispersion of pigments, such as carbon black
* Understanding of solubility/dispersion properties of carbon nanotubes, Buckyballs, and quantum dots
* Adhesion to polymers
* Permeation of solvents and chemicals through plastics to understand issues such as glove safety, food packaging barrier properties and skin permeation
* Diffusion of solvents into polymers via understanding of surface concentration based on RED number
* Cytotoxicity via interaction with DNA
* Artificial noses (where response depends on polymer solubility of the test odor)
* Safer, cheaper, and faster solvent blends where an undesirable solvent can be rationally replaced by a mix of more desirable solvents whose combined HSP equals the HSP of the original solvent. | 0 | Theoretical and Fundamental Chemistry |
Sulfuric acid is a very important commodity chemical, and indeed, a nation's sulfuric acid production is a good indicator of its industrial strength. World production in the year 2004 was about 180 million tonnes, with the following geographic distribution: Asia 35%, North America (including Mexico) 24%, Africa 11%, Western Europe 10%, Eastern Europe and Russia 10%, Australia and Oceania 7%, South America 7%. Most of this amount (≈60%) is consumed for fertilizers, particularly superphosphates, ammonium phosphate and ammonium sulfates. About 20% is used in chemical industry for production of detergents, synthetic resins, dyestuffs, pharmaceuticals, petroleum catalysts, insecticides and antifreeze, as well as in various processes such as oil well acidicizing, aluminium reduction, paper sizing, and water treatment. About 6% of uses are related to pigments and include paints, enamels, printing inks, coated fabrics and paper, while the rest is dispersed into a multitude of applications such as production of explosives, cellophane, acetate and viscose textiles, lubricants, non-ferrous metals, and batteries. | 0 | Theoretical and Fundamental Chemistry |
About 164,000,000 tons were produced in 2019. It is obtained as the "heavy" (i.e., difficult to distill) fraction. Material with a boiling point greater than around 500 °C is considered asphalt. Vacuum distillation separates it from the other components in crude oil (such as naphtha, gasoline and diesel). The resulting material is typically further treated to extract small but valuable amounts of lubricants and to adjust the properties of the material to suit applications. In a de-asphalting unit, the crude bitumen is treated with either propane or butane in a supercritical phase to extract the lighter molecules, which are then separated. Further processing is possible by "blowing" the product: namely reacting it with oxygen. This step makes the product harder and more viscous.
Bitumen is typically stored and transported at temperatures around . Sometimes diesel oil or kerosene are mixed in before shipping to retain liquidity; upon delivery, these lighter materials are separated out of the mixture. This mixture is often called "bitumen feedstock", or BFS. Some dump trucks route the hot engine exhaust through pipes in the dump body to keep the material warm. The backs of tippers carrying asphalt, as well as some handling equipment, are also commonly sprayed with a releasing agent before filling to aid release. Diesel oil is no longer used as a release agent due to environmental concerns. | 0 | Theoretical and Fundamental Chemistry |
Food: Biopolymers are being used in the food industry for things like packaging, edible encapsulation films and coating foods. Polylactic acid (PLA) is very common in the food industry due to is clear color and resistance to water. However, most polymers have a hydrophilic nature and start deteriorating when exposed to moisture. Biopolymers are also being used as edible films that encapsulate foods. These films can carry things like antioxidants, enzymes, probiotics, minerals, and vitamins. The food consumed encapsulated with the biopolymer film can supply these things to the body.
Packaging: The most common biopolymers used in packaging are polyhydroxyalkanoates (PHAs), polylactic acid (PLA), and starch. Starch and PLA are commercially available and biodegradable, making them a common choice for packaging. However, their barrier properties (either moisture-barrier or gas-barrier properties) and thermal properties are not ideal. Hydrophilic polymers are not water resistant and allow water to get through the packaging which can affect the contents of the package. Polyglycolic acid (PGA) is a biopolymer that has great barrier characteristics and is now being used to correct the barrier obstacles from PLA and starch.
Water purification: Chitosan has been used for water purification. It is used as a flocculant that only takes a few weeks or months rather than years to degrade in the environment. Chitosan purifies water by chelation. This is the process in which binding sites along the polymer chain bind with the metal ions in the water forming chelates. Chitosan has been shown to be an excellent candidate for use in storm and wastewater treatment. | 1 | Applied and Interdisciplinary Chemistry |
Thomas Shirley Hele, OBE, MD, FRCP (b Carlisle 24 October 1881 – d Cambridge 23 January 1953) was an academic in the 20th century.
Hele was educated at Carlisle Grammar School ; Sedbergh School; Emmanuel College, Cambridge (Fellow, 1911); and Barts. He was University Lecturer in Biochemistry from 1921; Tutor at Emmanuel from 1922 to 1935; its Master from 1935 to 1951; and Vice-Chancellor of the University of Cambridge from 1943 to 1945. | 1 | Applied and Interdisciplinary Chemistry |
The pharmacokinetic properties of sitagliptin and vildagliptin appear unaffected by age, sex or BMI. Clinical researches have shown that sitagliptin and vildagliptin do not have the side effects that tend to follow type 2 diabetes treatment, e.g. weight gain and hyperglycemia, but however, other side effects have been observed, including upper respiratory tract infections, sore throat and diarrhea. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, peroxydicarbonate (sometimes peroxodicarbonate) is a divalent anion with the chemical formula . It is one of the oxocarbon anions, which consist solely of carbon and oxygen. Its molecular structure can be viewed as two carbonate anions joined so as to form a peroxide bridge –O–O–.
The anion is formed, together with peroxocarbonate , at the negative electrode during electrolysis of molten lithium carbonate. The anion can also be obtained by electrolysis of a saturated solution of rubidium carbonate in water.
In addition, the peroxodicarbonate anion can be obtained by electrosynthesis on boron doped diamond (BDD) during water oxidation. The formal oxidation of two carbonate ions takes place at the anode. Due to the high oxidation potential of the peroxodicarbonate anion, a high anodic overpotential is necessary. This is even more important if hydroxyl radicals are involved in the formation process. Recent publications show that a concentration of 282 mmol/L of peroxodicarbonate can be reached in an undivided cell with sodium carbonate as starting material at current densities of 720 mA/cm. The described process is suitable for the pilot scale production of sodium peroxodicarbonate.
Potassium peroxydicarbonate KCO was obtained by Constam and von Hansen in 1895; its crystal structure was determined only in 2002. It too can be obtained by electrolysis of a saturated potassium carbonate solution at −20 °C. It is a light blue crystalline solid that decomposes at 141 °C, releasing oxygen and carbon dioxide, and decomposes slowly at lower temperatures.
Rubidium peroxodicarbonate is a light blue crystalline solid that decomposes at . Its structure was published in 2003. In both salts, each of the two carbonate units is planar. In the rubidium salt the whole molecule is planar, whereas in the potassium salt the two units lie on different and nearly perpendicular planes, both of which contain the O–O bond. | 0 | Theoretical and Fundamental Chemistry |
Reverse electrodialysis is a technology based on membranes which gets electricity from a mixing of two water streams with different salinities. It commonly uses anion exchange membranes (AEM) and cation exchange membranes (CEM). AEMs are used to allow the pass of anions and obstruct the pass of cations and CEMs are used to do the opposite. The cations and anions in the high salinity water moves to the low salinity water, cations passing through the CEMs and anions through the AEMs. This phenomenon can be converted to electricity. | 1 | Applied and Interdisciplinary Chemistry |
The Kantrowitz limit has many applications in gas dynamics of inlet flow, including jet engines and rockets operating at high-subsonic and supersonic velocities, and high-speed transportation systems such as the Hyperloop. | 1 | Applied and Interdisciplinary Chemistry |
Transuranic waste (TRUW) as defined by U.S. regulations is, without regard to form or origin, waste that is contaminated with alpha-emitting transuranic radionuclides with half-lives greater than 20 years and concentrations greater than 100 nCi/g (3.7 MBq/kg), excluding high-level waste. Elements that have an atomic number greater than uranium are called transuranic ("beyond uranium"). Because of their long half-lives, TRUW is disposed of more cautiously than either low- or intermediate-level waste. In the United States, it arises mainly from nuclear weapons production, and consists of clothing, tools, rags, residues, debris, and other items contaminated with small amounts of radioactive elements (mainly plutonium).
Under U.S. law, transuranic waste is further categorized into "contact-handled" (CH) and "remote-handled" (RH) on the basis of the radiation dose rate measured at the surface of the waste container. CH TRUW has a surface dose rate not greater than 200 mrem per hour (2 mSv/h), whereas RH TRUW has a surface dose rate of 200 mrem/h (2 mSv/h) or greater. CH TRUW does not have the very high radioactivity of high-level waste, nor its high heat generation, but RH TRUW can be highly radioactive, with surface dose rates up to 1,000,000 mrem/h (10,000 mSv/h). The United States currently disposes of TRUW generated from military facilities at the Waste Isolation Pilot Plant (WIPP) in a deep salt formation in New Mexico. | 0 | Theoretical and Fundamental Chemistry |
Firesetting is the process of exposing a rock face to high temperatures to induce cracking, spalling, and an overall increase to the brittleness of the rock in order to make it more susceptible to mining processes. Understanding the process of firesetting has been a crucial element to the development of an archaeological history of mining and as such has been the subject of several experiments to reproduce the technique. Typically firesetting experiments are conducted by setting a fire next to a predetermined rock face while taking measurements on the amount of and type of fuel used, temperatures of the fire and rock face, the amount of spalling before and after excavation, as well as the amount of time required for the different procedures. This examination allows for several possible inferences to be made about the mining process including the total amount of fuel a mining site may have needed to complete and its effects on the surrounding environment as well as how mining labor could have been organized. One outcome of firesetting experimentation is the realization that the quenching, or dousing the rock face with water after heating, is not necessary to making the rock face easier to excavate. The quenching process had been a standard step in most experiments with firesetting, but now more research is necessary to answer the new question of why quenching was used if it was not effective. | 1 | Applied and Interdisciplinary Chemistry |
Ghosh has contributed to many areas of porphyrin-related research. His early contributions include the use of X-ray photoelectron spectroscopy (XPS) to study short-strong hydrogen bonds in porphyrin-type molecules and also some of the first large-scale ab initio calculations applied to porphyrins and other bioinorganic systems. He has had an abiding interest in the phenomenon of ligand noninnocence and has contributed substantially to studying the phenomenon in transition metal nitrosyl and corrole derivatives. In recent years, he has developed the field of heavy element corrole derivatives, which are unusual size-mismatched metal-ligand assemblies that incorporate a large 4d or 5d transition metal ion within the sterically compressed central cavity of a corrole. In this area he has reported some of the first examples of Tc, rhenium, osmium, platinum, and gold corroles. Despite their size-mismatched character, many of these complexes have proved rugged and found applications as near-IR phosphorescent photosensitizers in oxygen sensing and photodynamic therapy as well as in dye-sensitized solar cells. Ghosh's work on 4d and 5d elements has also led to new insights into metal-metal bonds (quadruple bonds) and relativistic effects.
In 2017, Ghosh and coworkers reported the first example of a stable cis tautomer of a free-base porphyrin in the form of a termolecular hydrogen-bonded complex. Subsequently, they found additional examples of porphyrin cis tautomers, proving that they can be reliably obtained from virtually any strongly saddled porphyrin co-crystallized with two molecules of a hydrogen donor (typically water or an alcohol). | 0 | Theoretical and Fundamental Chemistry |
Hash oil or cannabis oil is an oleoresin obtained by the extraction of cannabis or hashish. It is a cannabis concentrate containing many of its resins and terpenes – in particular, tetrahydrocannabinol (THC), cannabidiol (CBD), and other cannabinoids. Hash oil is usually consumed by smoking, vaporizing or eating. Preparations of hash oil may be solid or semi-liquid colloids depending on both production method and temperature and are usually identified by their appearance or characteristics. Color most commonly ranges from transparent golden or light brown, to tan or black. There are various extraction methods, most involving a solvent, such as butane or ethanol.
Hash oil is an extracted cannabis product that may use any part of the plant, with minimal or no residual solvent. It is generally thought to be indistinct from traditional hashish, at-least according to the 1961 UN Single Convention on Narcotic Drugs that defines these products as "the separated resin, whether crude or purified, obtained from the cannabis plant".
Hash oil may be sold in cartridges used with pen vaporizers. Cannabis retailers in California have reported about 40% of their sales are from smokeable cannabis oils. | 0 | Theoretical and Fundamental Chemistry |
α,β-Unsaturated thioesters are intermediates in several enzymatic processes. Two prominent examples are coumaroyl-coenzyme A and crotonyl-coenzyme A. They arise by the action of acyl-CoA dehydrogenases. Flavin adenine dinucleotide (FAD) is a required co-factor. | 0 | Theoretical and Fundamental Chemistry |
Anders Gustav Ekeberg was a Swedish scientist, mathematician and expert in Greek literature.
His father, Joseph Erik Ekeberg, was a shipbuilder. His uncle was Carl Gustaf Ekeberg.
Anders Gustav Ekeberg attended school at Kalmar, Söderåkra, Vestervik, and Karlskrona.
He was a gifted student and enrolled at Uppsala University in 1784, graduating in 1788. His thesis addressed the extraction of oils from seeds. In 1789 and 1790, he traveled and studied in Germany, hearing Martin Heinrich Klaproth lecture in Berlin as well as Christian Ehrenfried Weigel in Greifswald. | 1 | Applied and Interdisciplinary Chemistry |
Solder bumping technology (the process of joining a chip to a substrate without shorting using solder) was first conceived and implemented by IBM in the early 1960s. Three versions of this type of solder joining were developed. The first was to embed copper balls in the solder bumps to provide a positive stand-off. The second solution, developed by Delco Electronics (General Motors) in the late 1960s, was similar to embedding copper balls except that the design employed a rigid silver bump. The bump provided a positive stand-off and was attached to the substrate by means of solder that was screen-printed onto the substrate. The third solution was to use a screened glass dam near the electrode tips to act as a ‘‘stop-off’’ to prevent the ball solder from flowing down the electrode. By then the Ball Limiting Metallurgy (BLM) with a high-lead (Pb) solder system and a copper ball had proven to work well. Therefore, the ball was simply removed and the solder evaporation process extended to form pure solder bumps that were approximately 125μm high. This system became known as the controlled collapse chip connection (C3 or C4).
Until the mid-1990s, this type of flip-chip assembly was practiced almost exclusively by IBM and Delco. Around this time, Delco sought to commercialize its technology and formed Flip Chip Technologies with Kulicke & Soffa Industries as a partner. At the same time, MCNC (which had developed a plated version of IBM’s C4 process) received funding from DARPA to commercialize its technology. These two organizations, along with APTOS (Advanced Plating Technologies on Silicon), formed the nascent out-sourcing market.
During this same time, companies began to look at reducing or streamlining their packaging, from the earlier multi-chip-on-ceramic packages that IBM had originally developed C4 to support, to what were referred to as Chip Scale Packages (CSP). There were a number of companies developing products in this area. These products could usually be put into one of two camps: either they were scaled down versions of the multi-chip on ceramic package (of which the Tessera package would be one example); or they were the streamlined versions developed by Unitive Electronics, et al. (where the package wiring had been transferred to the chip, and after bumping, they were ready to be placed).
One of the issues with the CSP type of package (which was intended to be soldered directly to an FR4 or flex circuit) was that for high-density interconnects, the soft solder bump provided less of a stand-off as the solder bump diameter and pitch were decreased. Different solutions were employed including one developed by Focus Interconnect Technology (former APTOS engineers), which used a high aspect ratio plated copper post to provide a larger fixed standoff than was possible for a soft solder collapse joint.
Today, flip chip is a well established technology and collapsed soft solder connections are used in the vast majority of assemblies. The copper post stand-off developed for the CSP market has found a home in high-density interconnects for advanced micro-processors and is used today by IBM for its CPU packaging. | 0 | Theoretical and Fundamental Chemistry |
The first consumer commercial application was a shape-memory coupling for piping, e.g. oil pipe lines, for industrial applications, water pipes and similar types of piping for consumer/commercial applications. | 1 | Applied and Interdisciplinary Chemistry |
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