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The screw axis appears in the dual quaternion formulation of a spatial displacement . The dual quaternion is constructed from the dual vector defining the screw axis and the dual angle , where φ is the rotation about and d the slide along this axis, which defines the displacement D to obtain,
A spatial displacement of points q represented as a vector quaternion can be defined using quaternions as the mapping
where d is translation vector quaternion and S is a unit quaternion, also called a versor, given by
that defines a rotation by 2θ around an axis S.
In the proper Euclidean group E(3) a rotation may be conjugated with a translation to move it to a parallel rotation axis. Such a conjugation, using quaternion homographies, produces the appropriate screw axis to express the given spatial displacement as a screw displacement, in accord with Chasles’ theorem. | 0 | Theoretical and Fundamental Chemistry |
Franz-Joseph Müller, Freiherr von Reichenstein or Franz-Joseph Müller von Reichenstein (1 July 1740 or 4 October 1742 – 12 October 1825 or 1826) was an Austrian mineralogist and mining engineer. Müller held several positions in the Habsburg monarchy administration of mines and coinage in the Banat, Transylvania, and Tyrol. During his time in Transylvania he discovered tellurium in 1782. In his later career he became a member of the imperial council in Vienna and was knighted and elevated to the rank Freiherr in 1820. | 1 | Applied and Interdisciplinary Chemistry |
Cordials were used to renew the natural heat, recreate and revive the spirits, and free the whole body from the malignity of diseases. Many cordials were also considered aphrodisiacs, a view which encouraged their consumption in a social as opposed to a medical context. Other early varieties of alcoholic cordials were flavoured with spices and herbal ingredients which were thought to settle the stomach after excessive eating. These cordials were called Surfeit Waters, which were specifically created for treating overindulgence.
Precious ingredients like gold, pearls and coral were sometimes added. These were believed to revive the spirit and to preclude disease. | 1 | Applied and Interdisciplinary Chemistry |
The power generated by a power station is measured in multiples of the watt, typically megawatts (10 watts) or gigawatts (10 watts). Power stations vary greatly in capacity depending on the type of power plant and on historical, geographical and economic factors. The following examples offer a sense of the scale.
Many of the largest operational onshore wind farms are located in China. As of 2022, the Roscoe Wind Farm is the largest onshore wind farm in the world, producing 8000 MW of power, followed by the Zhang Jiakou (3000 MW). As of January 2022, the Hornsea Wind Farm in United Kingdom is the largest offshore wind farm in the world at 1218 MW, followed by Walney Wind Farm in United Kingdom at 1026 MW.
In 2021, the worldwide installed capacity of power plants increased by 347 GW. Solar and wind power plant capacities rose by 80% in one year. , the largest photovoltaic (PV) power plants in the world are led by Bhadla Solar Park in India, rated at 2245 MW.
Solar thermal power stations in the U.S. have the following output:
:Ivanpah Solar Power Facility is the largest of the country with an output of 392 MW
Large coal-fired, nuclear, and hydroelectric power stations can generate hundreds of megawatts to multiple gigawatts. Some examples:
:The Koeberg Nuclear Power Station in South Africa has a rated capacity of 1860 megawatts.
:The coal-fired Ratcliffe-on-Soar Power Station in the UK has a rated capacity of 2 gigawatts.
:The Aswan Dam hydro-electric plant in Egypt has a capacity of 2.1 gigawatts.
:The Three Gorges Dam hydro-electric plant in China has a capacity of 22.5 gigawatts.
Gas turbine power plants can generate tens to hundreds of megawatts. Some examples:
:The Indian Queens simple-cycle, or open cycle gas turbine (OCGT), peaking power station in Cornwall UK, with a single gas turbine is rated 140 megawatts.
:The Medway Power Station, a combined-cycle gas turbine (CCGT) power station in Kent, UK, with two gas turbines and one steam turbine, is rated 700 megawatts.
The rated capacity of a power station is nearly the maximum electrical power that the power station can produce.
Some power plants are run at almost exactly their rated capacity all the time, as a non-load-following base load power plant, except at times of scheduled or unscheduled maintenance.
However, many power plants usually produce much less power than their rated capacity.
In some cases a power plant produces much less power than its rated capacity because it uses an intermittent energy source.
Operators try to pull maximum available power from such power plants, because their marginal cost is practically zero, but the available power varies widely—in particular, it may be zero during heavy storms at night.
In some cases operators deliberately produce less power for economic reasons.
The cost of fuel to run a load following power plant may be relatively high, and the cost of fuel to run a peaking power plant is even higher—they have relatively high marginal costs.
Operators keep power plants turned off ("operational reserve") or running at minimum fuel consumption ("spinning reserve") most of the time.
Operators feed more fuel into load following power plants only when the demand rises above what lower-cost plants (i.e., intermittent and base load plants) can produce, and then feed more fuel into peaking power plants only when the demand rises faster than the load following power plants can follow. | 1 | Applied and Interdisciplinary Chemistry |
The adsorption regeneration process is divided into three key elements which occur in different parts of the cell. All three occur continuously and simultaneously, with parameters such as charge passed, rate of effluent in/outflow and air inlet rate varied according to pollutant type and concentration. | 0 | Theoretical and Fundamental Chemistry |
When mutations occur in the genes responsible for the biological mechanisms that herbicides interfere with, these mutations may cause the herbicide mode of action to work less effectively. This is called target-site resistance. Specific mutations that have the most helpful effect for the plant have been shown to occur in separate instances and dominate throughout resistant weed populations. This is an example of convergent evolution. Some mutations conferring herbicide resistance may have fitness costs, reducing the plant's ability to survive in other ways, but over time, the least costly mutations tend to dominate in weed populations.
Recently, incidences of non-target site resistance have increasingly emerged, such as examples where plants are capable of producing enzymes that neutralize herbicides before they can enter the plant's cells – metabolic resistance. This form of resistance is particularly challenging, since plants can develop non-target-site resistance to herbicides their ancestors were never directly exposed to. | 1 | Applied and Interdisciplinary Chemistry |
Melted micrometeorites (cosmic spherules) were first collected from deep-sea sediments during the 1873 to 1876 expedition of HMS Challenger. In 1891, Murray and Renard found "two groups [of micrometeorites]: first, black magnetic spherules, with or without a metallic nucleus; second, brown-coloured spherules resembling chondr(ul)es, with a crystalline structure". In 1883, they suggested that these spherules were extraterrestrial because they were found far from terrestrial particle sources, they did not resemble magnetic spheres produced in furnaces of the time, and their nickel-iron (Fe-Ni) metal cores did not resemble metallic iron found in volcanic rocks. The spherules were most abundant in slowly accumulating sediments, particularly red clays deposited below the carbonate compensation depth, a finding that supported a meteoritic origin. In addition to those spheres with Fe-Ni metal cores, some spherules larger than 300 µm contain a core of elements from the platinum group.
Since the first collection of HMS Challenger, cosmic spherules have been recovered from ocean sediments using cores, box cores, clamshell grabbers, and magnetic sleds. Among these a magnetic sled, called the "Cosmic Muck Rake", retrieved thousands of cosmic spherules from the top 10 cm of red clays on the Pacific Ocean floor. | 0 | Theoretical and Fundamental Chemistry |
Ash content of coal is the non-combustible residue left after coal is burnt. It represents the bulk mineral matter after carbon, oxygen, sulfur and water (including from clays) has been driven off during combustion. Analysis is fairly straightforward, with the coal thoroughly burnt and the ash material expressed as a percentage of the original weight. It can also give an indication about the quality of coal.
Ash content may be determined as air dried basis and on oven dried basis. The main difference between the two is that the latter is determined after expelling the moisture content in the sample of coal. | 0 | Theoretical and Fundamental Chemistry |
A lot of emphasis has been given to RNA-Seq data after the Encyclopedia of DNA Elements (ENCODE) and The Cancer Genome Atlas (TCGA) projects have used this approach to characterize dozens of cell lines and thousands of primary tumor samples, respectively. ENCODE aimed to identify genome-wide regulatory regions in different cohort of cell lines and transcriptomic data are paramount to understand the downstream effect of those epigenetic and genetic regulatory layers. TCGA, instead, aimed to collect and analyze thousands of patient's samples from 30 different tumor types to understand the underlying mechanisms of malignant transformation and progression. In this context RNA-Seq data provide a unique snapshot of the transcriptomic status of the disease and look at an unbiased population of transcripts that allows the identification of novel transcripts, fusion transcripts and non-coding RNAs that could be undetected with different technologies. | 1 | Applied and Interdisciplinary Chemistry |
Nanog is a transcription factor that controls both self-renewal and pluripotency of embryonic stem cells. Similarly, the expression of Nanog family proteins is increased in many types of cancer and correlates with a worse prognosis. | 1 | Applied and Interdisciplinary Chemistry |
A large-scale application of carbenes is the industrial production of tetrafluoroethylene, the precursor to Teflon. Tetrafluoroethylene is generated via the intermediacy of difluorocarbene:
: CHClF → CF + HCl
:2 CF → FC=CF
The insertion of carbenes into C–H bonds has been exploited widely, e.g. the functionalization of polymeric materials and electro-curing of adhesives. Many applications rely on synthetic 3-aryl-3-trifluoromethyldiazirines (a carbene precursor that can be activated by heat, light, or voltage) but there is a whole family of carbene dyes. | 0 | Theoretical and Fundamental Chemistry |
Ceruloplasmin (or caeruloplasmin) is a ferroxidase enzyme that in humans is encoded by the CP gene.
Ceruloplasmin is the major copper-carrying protein in the blood, and in addition plays a role in iron metabolism. It was first described in 1948. Another protein, hephaestin, is noted for its homology to ceruloplasmin, and also participates in iron and probably copper metabolism. | 1 | Applied and Interdisciplinary Chemistry |
It is used to determine the ability of some organisms to produce a neutral end product, acetyl methyl carbinol (acetoin) from glucose fermentation. The production of acetoin, a neutral reacting end product produced by members such as Klebsiella, Enterobacter etc., is the chief end product of glucose metabolism and form less quantities of mixed acids. In the presence of atmospheric oxygen and 40% KOH, acetoin is converted to diacetyl and α-naphthol serves as catalyst to bring out red color complex. | 0 | Theoretical and Fundamental Chemistry |
As a system is formed from a solid surface and a drop of liquid, energy minima and maxima are produced by the free energy of the system. When the solid surface is rough or homogeneous, the system, which is made up of a solid, a liquid, and a fluid, could have multiple minima produced from the free energy at different minima points. One of these minima is called the global minimum. The global minimum has the lowest free energy within the system and is defined to be the stable equilibrium state. Furthermore, the other minima illustrate the metastable equilibrium states of the system. In between these minima are the energy barriers which hinder the motion of energy between the various metastable states in the system. The transition of energy between metastable states is also affected by the availability of external energy to the system, which is associated with the volume of the liquid drop on top of the solid surface. As such, the volume of the liquid may have an impact on the locations of the minima points, which could influence the contact angles created by the solid and the liquid. The contact angles are directly related to whether the solid surface is ideal, in other words, whether it is a smooth, heterogeneous surface.
In the captive bubble method, the bubble indicating the liquid drop forms an angle with the solid surface called the contact angle. The stability of the liquid phase on the solid is measured with an intrinsic contact angle. Theoretically, the contact angle equals the value of the local intrinsic contact angle, assuming line tension has a negligible effect. | 0 | Theoretical and Fundamental Chemistry |
- Unlike several other flow imaging techniques, PLIF may be combined with particle image velocimetry (PIV). This allows for the simultaneous measurement of a fluid velocity field and species concentration. | 1 | Applied and Interdisciplinary Chemistry |
Among his accolades, King was recognized by the ACS Awards in Pure Chemistry (1971) and in Inorganic Chemistry (1991). | 0 | Theoretical and Fundamental Chemistry |
Ballast tanks do not corrode uniformly throughout the tank. Each region behaves distinctively, according to it electrochemical loading. The differences can especially be seen in empty ballast tanks. The upper sections usually corrode but the lower sections will blister.
A ballast tank has three distinct sections: 1) upper, 2) mid or "boottop" area and, 3) the "double bottom" or lower wing sections. The upper regions are constantly affected by weather. This area experiences a high degree of thermal cycling and mechanical damage through vibration. This area tends to undergo anodic oxidation more rapidly than other sections and will weaken more rapidly. This ullage or headspace area contains more oxygen and thus speeds atmospheric corrosion, as evidenced by the appearance of rust scales.
In the midsection corrodes more slowly than upper or the bottom sections of the tank.
Double bottoms are prone to cathodic blistering. Temperatures in this area are much lower due to the cooling of the sea. If this extremely cathodic region is placed close to an anodic source (e.g. a corroding ballast pipe), cathodic blistering may occur especially where the epoxy coating is relatively new. Mud retained in ballast water can lead to microbial corrosion. | 1 | Applied and Interdisciplinary Chemistry |
For many workers in the field, a reactor is an item which is too expensive; instead, it is common to use a neutron source which uses a combination of an alpha emitter and beryllium. These sources tend to be much weaker than reactors. | 0 | Theoretical and Fundamental Chemistry |
Limans were built in order to fight desertification without depleting groundwater resources, which are becoming increasingly rare in arid ecosystems. Remaining soil humidity can be found in dry river beds (wadis) after rains occur, but these wadis are prone to flash floods. The result is massive soil erosion and the destruction of infrastructure. Also, the infiltration is insufficient because of the water's velocity, even though the runoff would be able to allow for the growth of trees in appropriate places. The aim of building limans is to stop flash floods and to increase water infiltration, thus sustaining the growth of drought-hardy tree species and vegetation underneath them. | 1 | Applied and Interdisciplinary Chemistry |
Cerimetry or cerimetric titration, also known as cerate oximetry, is a method of volumetric chemical analysis developed by Ion Atanasiu. It is a redox titration in which an iron(II)–1,10-phenanthroline complex (ferroin) color change indicates the end point. Ferroin can be reversibly discolored in its oxidized form upon titration with a Ce solution. The use of cerium(IV) salts as reagents for volumetric analysis was first proposed in the middle of 19th century, but systematic studies did not start until about 70 years later. Standard solutions can be prepared from different Ce salts, but often cerium sulfate is chosen.
Since cerimetry is linked to the Fe/Fe redox pair, it can be used for analyses of nonstoichiometric levels that either oxidize Fe or reduce Fe. For the case of oxidation, a precise excess of high-purity crystalline Mohr's salt is added upon the oxide digestion in aqueous hydrogen chloride (HCl), while for the case of reduction, an excess of 1 M iron trichloride (FeCl) is added. In both cases, Fe ions will be titrated subsequently. Because the Ce solution is prone to hydrolysis, the titration is done in a strongly HCl-acidic solution into which some phosphoric acid (HPO) is added to obtain a less colored phosphato complex of Fe.
According to tabulated values of standard potentials at pH 0 for the first-row transition metals, any nonstoichiometry below the following oxidation states will reduce 1 M FeCl solution whereas any nonstoichiometry above them will oxidize the Mohrs salt: Ti, V, Cr, Mn, Co, and Ni. In addition, any nonstoichiometry in the Fe(III)–Fe(II) range is titrated directly with no additives, any nonstoichiometry below Fe will reduce 1 M FeCl whereas any nonstoichiometry above Fe will oxidize Mohrs salt. In the second- and third-row transition metals, only the early elements would be suitable for the titration, and the limiting oxidation states are Zr, Nb, Mo, Hf, Ta, and W. Standard potentials involving rhenium ions are too close to E for Fe/Fe as well as to each other. Nonstoichiometry of oxides containing several elements in oxidation states suitable for cerimetry is determined in one titration. | 0 | Theoretical and Fundamental Chemistry |
Resonance is to be distinguished from isomerism. Isomers are molecules with the same chemical formula but are distinct chemical species with different arrangements of atomic nuclei in space. Resonance contributors of a molecule, on the other hand, can only differ in the way electrons are formally assigned to atoms in the Lewis structure depictions of the molecule. Specifically, when a molecular structure is said to be represented by a resonance hybrid, it does not mean that electrons of the molecule are "resonating" or shifting back and forth between several sets of positions, each one represented by a Lewis structure. Rather, it means that the set of contributing structures represents an intermediate structure (a weighted average of the contributors), with a single, well-defined geometry and distribution of electrons. It is incorrect to regard resonance hybrids as rapidly interconverting isomers, even though the term "resonance" might evoke such an image. (As described below, the term "resonance" originated as a classical physics analogy for a quantum mechanical phenomenon, so it should not be construed too literally.) Symbolically, the double headed arrow is used to indicate that A and B are contributing forms of a single chemical species (as opposed to an equilibrium arrow, e.g., ; see below for details on usage).
A non-chemical analogy is illustrative: one can describe the characteristics of a real animal, the narwhal, in terms of the characteristics of two mythical creatures: the unicorn, a creature with a single horn on its head, and the leviathan, a large, whale-like creature. The narwhal is not a creature that goes back and forth between being a unicorn and being a leviathan, nor do the unicorn and leviathan have any physical existence outside the collective human imagination. Nevertheless, describing the narwhal in terms of these imaginary creatures provides a reasonably good description of its physical characteristics.
Due to confusion with the physical meaning of the word resonance, as no entities actually physically "resonate", it has been suggested that the term resonance be abandoned in favor of delocalization and resonance energy abandoned in favor of delocalization energy. A resonance structure becomes a contributing structure and the resonance hybrid becomes the hybrid structure. The double headed arrows would be replaced by commas to illustrate a set of structures, as arrows of any type may suggest that a chemical change is taking place. | 0 | Theoretical and Fundamental Chemistry |
Partially digested food starts to arrive in the small intestine as semi-liquid chyme, one hour after it is eaten. The stomach is half empty after an average of 1.2 hours. After four or five hours the stomach has emptied.
In the small intestine, the pH becomes crucial; it needs to be finely balanced in order to activate digestive enzymes. The chyme is very acidic, with a low pH, having been released from the stomach and needs to be made much more alkaline. This is achieved in the duodenum by the addition of bile from the gall bladder combined with the bicarbonate secretions from the pancreatic duct and also from secretions of bicarbonate-rich mucus from duodenal glands known as Brunner's glands. The chyme arrives in the intestines having been released from the stomach through the opening of the pyloric sphincter. The resulting alkaline fluid mix neutralises the gastric acid which would damage the lining of the intestine. The mucus component lubricates the walls of the intestine.
When the digested food particles are reduced enough in size and composition, they can be absorbed by the intestinal wall and carried to the bloodstream. The first receptacle for this chyme is the duodenal bulb. From here it passes into the first of the three sections of the small intestine, the duodenum (the next section is the jejunum and the third is the ileum). The duodenum is the first and shortest section of the small intestine. It is a hollow, jointed C-shaped tube connecting the stomach to the jejunum. It starts at the duodenal bulb and ends at the suspensory muscle of duodenum. The attachment of the suspensory muscle to the diaphragm is thought to help the passage of food by making a wider angle at its attachment.
Most food digestion takes place in the small intestine. Segmentation contractions act to mix and move the chyme more slowly in the small intestine allowing more time for absorption (and these continue in the large intestine). In the duodenum, pancreatic lipase is secreted together with a co-enzyme, colipase to further digest the fat content of the chyme. From this breakdown, smaller particles of emulsified fats called chylomicrons are produced. There are also digestive cells called enterocytes lining the intestines (the majority being in the small intestine). They are unusual cells in that they have villi on their surface which in turn have innumerable microvilli on their surface. All these villi make for a greater surface area, not only for the absorption of chyme but also for its further digestion by large numbers of digestive enzymes present on the microvilli.
The chylomicrons are small enough to pass through the enterocyte villi and into their lymph capillaries called lacteals. A milky fluid called chyle, consisting mainly of the emulsified fats of the chylomicrons, results from the absorbed mix with the lymph in the lacteals. Chyle is then transported through the lymphatic system to the rest of the body.
The suspensory muscle marks the end of the duodenum and the division between the upper gastrointestinal tract and the lower GI tract. The digestive tract continues as the jejunum which continues as the ileum. The jejunum, the midsection of the small intestine contains circular folds, flaps of doubled mucosal membrane which partially encircle and sometimes completely encircle the lumen of the intestine. These folds together with villi serve to increase the surface area of the jejunum enabling an increased absorption of digested sugars, amino acids and fatty acids into the bloodstream. The circular folds also slow the passage of food giving more time for nutrients to be absorbed.
The last part of the small intestine is the ileum. This also contains villi and vitamin B12; bile acids and any residue nutrients are absorbed here. When the chyme is exhausted of its nutrients the remaining waste material changes into the semi-solids called feces, which pass to the large intestine, where bacteria in the gut flora further break down residual proteins and starches.
Transit time through the small intestine is an average of 4 hours. Half of the food residues of a meal have emptied from the small intestine by an average of 5.4 hours after ingestion. Emptying of the small intestine is complete after an average of 8.6 hours. | 1 | Applied and Interdisciplinary Chemistry |
The simplest way of measuring the contact angle of a sessile drop is with a contact angle goniometer, which allows the user to measure the contact angle visually. A droplet is deposited by a syringe which is positioned above the sample surface, and a high resolution camera captures the image from the profile or side view. The image can then be analyzed either by eye (with a protractor) or more often is measured using image analysis software. This type of measurement is referred to as a static contact angle measurement.
The contact angle is affected not only by the surface chemistry but also by the surface roughness. The Young equation, which is the basis for the contact angle, assumes a homogeneous surface with no surface roughness. In case surface roughness is present, the droplet can be in Wenzel state (homogeneous wetting), Cassie-Baxter state (heterogeneous wetting) or in an intermediary state. The surface roughness amplifies the wetting behavior caused by the surface chemistry.
In order to measure the contact angle hysteresis, the sessile droplet can be increased gradually in volume. The maximum possible contact angle is referred to as the advancing contact angle. The receding contact angle can be measured by removing volume from the drop until dewetting occurs. The minimum possible contact angle is referred to as the receding contact angle. The contact angle hysteresis is the difference between the advancing and receding contact angle. | 0 | Theoretical and Fundamental Chemistry |
In molecular biology, Pulmonary surfactant protein D (SP-D) is a protein domain predominantly found in lung surfactant. This protein plays a special role; its primary task is to act as a defence protein against any pathogens that may invade the lung. It also plays a role in lubricating the lung and preventing it from collapse. It has an interesting structure as it forms a triple-helical parallel coiled coil, helps the protein to fold into a trimer. | 0 | Theoretical and Fundamental Chemistry |
Flutamide, as a monotherapy, causes gynecomastia in 30 to 79% of men, and also produces breast tenderness. However, more than 90% of cases of gynecomastia with NSAAs including flutamide are mild to moderate. Tamoxifen, a selective estrogen receptor modulator (SERM) with predominantly antiestrogenic actions, can counteract flutamide-induced gynecomastia and breast pain in men. | 0 | Theoretical and Fundamental Chemistry |
Chromatofocusing is a protein-separation technique that allows resolution of single proteins and other ampholytes from a complex mixture according to differences in their isoelectric point. Chromatofocusing uses ion exchange resins and is typically performed on fast protein liquid chromatography (FPLC) or similar equipment capable of producing continuous buffer gradients, though this is not a requirement.
In contrast to typical ion exchange chromatography, where bound molecules are eluted from the resin by increasing the ionic strength of the buffer environment, chromatofocusing elutes bound species by altering the pH of the buffer. This changes the net surface charge of bound molecules, altering their avidity for the resin. As the changing pH of the buffer system traverses the pI of a given molecule, that molecule will elute from the resin as it will no longer possess a net surface charge (a requisite for molecular binding to ion exchange resins).
Chromatofocusing is a powerful purification technique with respect to proteins as it can resolve very similar species differing by less than 0.05 pH units that may not separate well, or at all, using traditional ion exchange strategies.
A major drawback to this technique is that some proteins will aggregate when they are present at relatively high concentrations and carry no net surface charge. This can cause blockage of the resin, which is highly problematic when using sealed columns of ion exchange resin on FPLC equipment, resulting in pressure buildup and possible equipment failure. Apparent aggregation issues can sometimes be overcome by limiting the sample concentration and use of buffer additives that deter aggregate formation. | 0 | Theoretical and Fundamental Chemistry |
Once the C-H bond of methane is activated by bonding to a transition metal complex, the net functionalization of the alkyl metal complex into another hydrocarbon containing a functional group is actually much harder to achieve. In general, alkanes of various lengths have typically been functionalized by a number of more commonly known reactions: electrophilic activation (Shilov system, see above), dehydrogenation, borylation, hydrogen-deuterium exchange, and carbene/nitrene/oxo insertion. The functionalization of methane in particular has been reported in four different methods that use homogeneous catalysts rather than heterogeneous catalysts. Heterogeneous systems, using copper- and iron exchanged Zeolite, are also investigated. In these systems, reactive oxygen species such as Alpha-Oxygen are generated which can perform a hydrogen atom abstraction. | 0 | Theoretical and Fundamental Chemistry |
The affinity concept was very closely linked to the visual representation of substances on a table. The first-ever affinity table, which was based on displacement reactions, was published in 1718 by the French chemist Étienne François Geoffroy. Geoffroys name is best known in connection with these tables of "affinities" (tables des rapports'), which were first presented to the French Academy of Sciences in 1718 and 1720.
During the 18th century many versions of the table were proposed with leading chemists like Torbern Bergman in Sweden and Joseph Black in Scotland adapting it to accommodate new chemical discoveries. All the tables were essentially lists, prepared by collating observations on the actions of substances one upon another, showing the varying degrees of affinity exhibited by analogous bodies for different reagents.
Crucially, the table was the central graphic tool used to teach chemistry to students and its visual arrangement was often combined with other kinds diagrams. Joseph Black, for example, used the table in combination with chiastic and circlet diagrams to visualise the core principles of chemical affinity. Affinity tables were used throughout Europe until the early 19th century when they were displaced by affinity concepts introduced by Claude Berthollet. | 0 | Theoretical and Fundamental Chemistry |
bHLH transcription factors have been shown to have a wide array of functions in developmental processes. More precisely, they have critical roles in the control of cellular differentiation, proliferation and regulation of oncogenesis. To date, 242 eukaryotic proteins belonging to the HLH superfamily have been reported. They have varied expression patterns in all eukaryotes from yeast to humans.
Structurally, bHLH proteins are characterised by a “highly conserved domain containing a stretch of basic amino acids adjacent to two amphipathic α-helices separated by a loop”.
These helices have important functional properties, forming part of the DNA binding and transcription activating domains. With respect to scleraxis, the bHLH region spans amino acid residues 78 to 131. A proline rich region is also predicted to lie between residues 161–170. A stretch of basic residues, which aids in DNA binding, is found closer to the N terminal end of scleraxis.
HLH proteins that lack this basic domain have been shown to negatively regulate the activities of bHLH proteins and are called inhibitors of differentiation (Id). Basic HLH proteins function normally as dimers and bind to a specific hexanucleotide DNA sequence (CAANTG) known as an E-box thus switching on the expression of various genes involved in cellular development and survival. | 1 | Applied and Interdisciplinary Chemistry |
Alkalimetry and acidimetry are types of volumetric analyses in which the fundamental reaction is a neutralization reaction. They involve the controlled addition of either an acid or a base (titrant) of known concentration to the solution of the unknown concentration (titrate) until the reaction reaches its stoichiometric equivalence point. At this point, the moles of acid and base are equal, resulting in a neutral solution:
:acid + base → salt + water
For example:
:HCl + NaOH → NaCl + HO
Acidimetry is the specialized analytical use of acid-base titration to determine the concentration of a basic (alkaline) substance using standard acid. This can be used for weak bases and strong bases. An example of an acidimetric titration involving a strong base is as follows:
:Ba(OH) + 2 H → Ba + 2 HO
In this case, the strong base (Ba(OH)) is neutralized by the acid until all of the base has reacted. This allows the viewer to calculate the concentration of the base from the volume of the standard acid that is used.
Alkalimetry follows uses same concept of specialized analytic acid-base titration, but to determine the concentration of an acidic substance using standard base. An example of an alkalimetric titration involving a strong acid is as follows:
:HSO + 2 OH → SO + 2 HO
In this case, the strong acid (HSO) is neutralized by the base until all of the acid has reacted. This allows the viewer to calculate the concentration of the acid from the volume of the standard base that is used.
The standard solution (titrant) is stored in the burette, while the solution of unknown concentration (analyte/titrate) is placed in the Erlenmeyer flask below it with an indicator. | 0 | Theoretical and Fundamental Chemistry |
Originally, the use of laser-induced shock waves on metals to achieve property or functional benefits was referred to as laser shock processing, a broader, more inclusive term. As it happened, laser peening was the first commercial aspect of laser shock processing. However, laser-induced shock waves have found uses in other industrial applications outside of surface enhancement technologies.
One application is for metal shaping or forming. By selectively laser shocking areas on the surface of metal sheets or plates, or smaller items such as airfoils, the associated compressive residual stresses cause the material to flex in a controllable manner. In this way a particular shape can be imparted to a component, or a distorted component might be brought back into the desired shape. Thus, this process is capable of bringing manufactured parts back into design tolerance limits and form shaping thin section parts.
Another variation is to use the shock wave for spallation testing of materials. This application is based on the behavior of shockwaves to reflect from the rear free surface of a work piece as a tensile wave. Depending on the material properties and the shock wave characteristics, the reflected tensile wave may be strong enough to form microcracks or voids near the back surface, or actually "blow-off" or spall material from the back surface. This approach has some value for testing ballistic materials.
Use of laser shocks to measure the bond strength of coatings on metals has been developed over a period of years in France called LASAT for Laser Adhesion Test. This application is also based on the behavior of shockwaves to reflect from the rear free surface of a work piece as a tensile wave. If the back surface is coated with an adherent coating, the tensile wave can be tailored to fracture the bond upon reflection from the surface. By controlling the characteristics of the shock wave, the bond strength of the coating can be measured, or alternatively, determined in a comparative sense.
Careful tailoring of the shockwave shape and intensity has also enabled the inspection of bonded composite structures via laser shocking. The technology, termed Laser Bond Inspection initiates a shockwave that reflects off the backside of a bonded structure and returns as a tensile wave. As the tensile wave passes back through the adhesive bond, depending on the strength of the bond and the peak tensile stress of the stress wave, the tensile wave will either pass through the bond or rupture it. By controlling the pressure of the tensile wave this procedure is capable of reliably locally testing adhesion strength between bonded joints. This technology is most often found in application to bonded fiber composite material structures but has also been shown to be successful in evaluating bonds between metal-composite material. Fundamental issues are also studied to characterize and quantify the effect of shock wave produced by laser inside these complex materials. | 1 | Applied and Interdisciplinary Chemistry |
A number of chemists in the early 1900s, including Staudinger and Pfenninger (1916), as well as Delepine (1920) studied episulfides. I 1934 Dachlauer and Jackel devised a general synthesis of episulfides from epoxides using alkali thiocyanates and thiourea. | 0 | Theoretical and Fundamental Chemistry |
All the reactions associated with synthesis of biomolecule converge into the following pathway, viz., glycolysis, the Krebs cycle and the electron transport chain, exist as an amphibolic pathway, meaning that they can function anabolically as well as catabolically.
Other important amphibolic pathways are the Embden-Meyerhof pathway, the pentose phosphate pathway and the Entner–Doudoroff pathway. | 1 | Applied and Interdisciplinary Chemistry |
A range of tripodal phosphines such as HC(CHPR), N(CHCHPPh) and P(CHCHPMe) have been reviewed. The tetra amine (tris(2-aminoethyl)amine) can be reacted with salicylaldehyde to form a ligand which can bind with three oxygens and three nitrogens to a metal. Trispyrazolylmethane (Tpm) is another class of scorpionate ligands, notable for having identical geometry and very similar coordination chemistry to Tp with only a difference in charge between them. Another variation is the Trisoxazolinylborate ligand.
Hydrotris(pyrazolyl)aluminate (Tpa) complexes have similar coordination geometries to Tp complexes, however Tpa ligands are more reactive due to the weaker Al-N and Al-H bonds, compared to B-N and B-H bonds of Tp ligands, which results in either Tpa ligand transfer, pyrazolate transfer, or hydride transfer with MX (M = Mg, Mn, Fe, Co, Ni, Cu, Zn; X = Cl, Br). | 0 | Theoretical and Fundamental Chemistry |
While nuclear pasta has not been observed in a neutron star, its phases are theorized to exist in the inner crust of neutron stars, forming a transition region between the conventional matter at the surface and the ultra-dense matter at the core. All phases are expected to be amorphous, with a heterogeneous charge distribution. Towards the top of this transition region, the pressure is great enough that conventional nuclei will be condensed into much more massive semi-spherical collections. These formations would be unstable outside the star, due to their high neutron content and size, which can vary between tens and hundreds of nucleons. This semispherical phase is known as the gnocchi phase.
When the gnocchi phase is compressed, as would be expected in deeper layers of the crust, the electric repulsion of the protons in the gnocchi is not fully sufficient to support the existence of the individual spheres, and they are crushed into long rods, which, depending on their length, can contain many thousands of nucleons. These rods are known as the spaghetti phase. Further compression causes the spaghetti phase rods to fuse and form sheets of nuclear matter called the lasagna phase. Further compression of the lasagna phase yields the uniform nuclear matter of the outer core. Progressing deeper into the inner crust, those holes in the nuclear pasta change from being cylindrical, called by some the bucatini phase or antispaghetti phase, into scattered spherical holes, which can be called the Swiss cheese phase. The nuclei disappear at the crust–core interface, transitioning into the liquid neutron core of the star.
The pasta phases also have interesting topological properties characterized by homology groups.
For a typical neutron star of 1.4 solar masses () and 12 km radius, the nuclear pasta layer in the crust can be about 100 m thick and have a mass of about 0.01 . In terms of mass, this is a significant portion of the crust of a neutron star. | 0 | Theoretical and Fundamental Chemistry |
Gene therapy approaches to replace a faulty gene with a healthy gene have been proposed and are being studied for treating some genetic diseases. As of 2017, 11.1% of gene therapy clinical trials targeted monogenic diseases.
Diseases such as sickle cell disease that are caused by autosomal recessive disorders for which a person's normal phenotype or cell function may be restored in cells that have the disease by a normal copy of the gene that is mutated, may be a good candidate for gene therapy treatment. The risks and benefits related to gene therapy for sickle cell disease are not known.
Gene therapy has been used in the eye. The eye is especially suitable for adeno-associated virus vectors. Luxturna is an approved gene therapy to treat Leber's hereditary optic neuropathy. Glybera, a treatment for pancreatitis caused by a genetic condition, and Zolgensma for the treatment of spinal muscular atrophy both use an adeno-associated virus vector. | 1 | Applied and Interdisciplinary Chemistry |
Modern biological research has revealed strong evidence that the enzymes of the mitochondrial respiratory chain assemble into larger, supramolecular structures called supercomplexes, instead of the traditional fluid model of discrete enzymes dispersed in the inner mitochondrial membrane. These supercomplexes are functionally active and necessary for forming stable respiratory complexes.
One supercomplex of complex I, III, and IV make up a unit known as a respirasome. Respirasomes have been found in a variety of species and tissues, including rat brain, liver, kidney, skeletal muscle, heart, bovine heart, human skin fibroblasts, fungi, plants, and C. elegans. | 1 | Applied and Interdisciplinary Chemistry |
The core of the basic cephalosporin molecule consists of a two ring system which includes a β-lactam ring condensed with dihydrothiazine ring. The core itself can also be referred to as 7-aminocephalosporanic acid which can be derived by hydrolysis from the natural compound cephalosporin C. Chemical compounds containing this core are relatively stable to acid hydrolysis and tolerance to β-lactamases. Cephalosporin C contains a side-chain which is derived from D-aminoadipic acid. Modification of side chains on the relevant positions has been used to create a whole new class of cephalosporin antibiotics. Modification of side-chains in position 7 of the lactam ring seems to affect the antibacterial activity while position 3 of the dihydrothiazine ring alters pharmacokinetic properties and receptor binding affinity. | 1 | Applied and Interdisciplinary Chemistry |
The Global Powder Metallurgy Database (GPMD) is an online searchable database that has been developed as the result of a joint project between leading regional powder metallurgy (PM) trade associations, the EPMA and its sister organisations in Japan (JPMA) and North America (MPIF).
This database was created in response to a worldwide recognition that the absence of a readily accessible source of design data was acting as a significant impediment to the wider application of PM products.
Primarily aimed at designers and engineers in the industries using PM products, it is designed to provide verified physical, mechanical and fatigue data for a range of commercially available PM materials.
This culminated in the initial launch of the database at the PM World Congress in Vienna in October 2004. The content of the database, at this launch, was restricted to data on low alloy ferrous and stainless steel PM structural part grades and bronze and iron-based PM bearing grades.
However, enhancement and extension of content and searching capability has been an ongoing process ever since. In January 2007, the content was expanded with the addition of data on non-ferrous PM structural part grades, followed, in March 2007, by the introduction of a new section covering data on Metal Injection Moulding (MIM) materials.
The latest extension to capability involves making full SN Fatigue Curve "pages" (comprising SN curves and details of individual test points) accessible to searchers. The initial content comprises over 130 SN Curve pages, covering a range of Fe-Cu-C grades and based on published information that has been analysed and collated by the group led by Professor Paul Beiss at the Technical University of Aachen. The collated SN curves cover a range of material processing conditions and density levels and a range of fatigue testing conditions (fatigue loading mode, mean stress level and notch factor).
In assembling the GPMD content, a broad range of mechanical, fatigue and physical property data has been collected from the associations’ memberships and rigorously evaluated by regional accreditation committees. However, the database's primary targets are designers and material specifiers in end-user industries who may have no prior knowledge of PM. Therefore, the bulk of the search structure has been designed to take such a searcher to the point where they can decide that they ought to contact a PM parts manufacturer to discuss a potential application in more detail. | 1 | Applied and Interdisciplinary Chemistry |
The method uses seasonal water balance components as input data. These are related to the surface hydrology (like rainfall, potential evaporation, irrigation, use of drain and well water for irrigation, runoff), and the aquifer hydrology (e.g., pumping from wells). The other water balance components (like actual evaporation, downward percolation, upward capillary rise, subsurface drainage, groundwater flow) are given as output.
The quantity of drainage water, as output, is determined by two drainage intensity factors for drainage above and below drain level respectively (to be given with the input data) and the height of the water table above the given drain level. This height results from the computed water balance Further, a drainage reduction factor can be applied to simulate a limited operation of the drainage system. Variation of the drainage intensity factors and the drainage reduction factor gives the opportunity to simulate the effect of different drainage options.
To obtain accuracy in the computations of the ground water flow (sect. 2.8), the actual evaporation and the capillary rise, the computer calculations are done on a daily basis. For this purpose, the seasonal hydrological data are divided by the number of days per season to obtain daily values. The daily values are added to yield seasonal values. | 0 | Theoretical and Fundamental Chemistry |
Unlike an electrical superconductor, color-superconducting quark matter comes in many varieties, each of which is a separate phase of matter. This is because quarks, unlike electrons, come in many species. There are three different colors (red, green, blue) and in the core of a compact star we expect three different flavors (up, down, strange), making nine species in all. Thus in forming the Cooper pairs there is a --> 9×9 color-flavor matrix of possible pairing patterns. The differences between these patterns are very physically significant: different patterns break different symmetries of the underlying theory, leading to different excitation spectra and different transport properties.
It is very hard to predict which pairing patterns will be favored in nature. In principle this question could be decided by a QCD calculation, since QCD is the theory that fully describes the strong interaction. In the limit of infinite density, where the strong interaction becomes weak because of asymptotic freedom, controlled calculations can be performed, and it is known that the favored phase in three-flavor quark matter is the color-flavor-locked phase. But at the densities that exist in nature these calculations are unreliable, and the only known alternative is the brute-force computational approach of lattice QCD, which unfortunately has a technical difficulty (the "sign problem") that renders it useless for calculations at high quark density and low temperature.
Physicists are currently pursuing the following lines of research on color superconductivity:
* Performing calculations in the infinite density limit, to get some idea of the behavior at one edge of the phase diagram.
* Performing calculations of the phase structure down to medium density using a highly simplified model of QCD, the Nambu–Jona-Lasinio (NJL) model, which is not a controlled approximation, but is expected to yield semi-quantitative insights.
* Writing down an effective theory for the excitations of a given phase, and using it to calculate the physical properties of that phase.
* Performing astrophysical calculations, using NJL models or effective theories, to see if there are observable signatures by which one could confirm or rule out the presence of specific color superconducting phases in nature (i.e. in compact stars: see next section). | 0 | Theoretical and Fundamental Chemistry |
The American Society for Biochemistry and Molecular Biology (ASBMB) is a learned society that was founded on December 26, 1906, at a meeting organized by John Jacob Abel (Johns Hopkins University). The roots of the society were in the American Physiological Society, which had been formed some 20 years earlier. ASBMB is the US member of the International Union of Biochemistry and Molecular Biology.
The ASBMB was originally called the American Society of Biological Chemists, before obtaining its current name in 1987. The society is based in Rockville, Maryland. ASBMB's mission is to advance the science of biochemistry and molecular biology through publication of scientific and educational journals, the organization of scientific meetings, advocacy for funding of basic research and education, support of science education at all levels, and by promoting the diversity of individuals entering the scientific workforce. The organization currently has over 12,000 members. | 1 | Applied and Interdisciplinary Chemistry |
While there will naturally have been some changes throughout the centuries, this section only tries to give a general overview of the situation that was recorded in detail in numerous 19th-century merchants' handbooks.
;Iberian Peninsula
On the Iberian Peninsula, apothecaries weights in the 19th century were relatively uniform, with 24 grains per scruple (576 grains per ounce), the standard in Romance countries. The weight of an apothecaries pound was 345.1 g in Spain and 344.2 g in Portugal. As in Italy, some of the additional subdivisions of the Roman system, such as the , were still in use there. It was standard to use the , defined as 8 ounces, instead of the pound.
;France
In 18th century France, there was a national weight standard, the of 8 ounces. The civil pound of 16 ounces was equivalent to 2 marks, and it was also used as the apothecaries' pound. With 30.6 g, the ounces were considerably heavier than other apothecaries ounces in Romance countries, but otherwise, the French system was not remarkable. Its history and connections to the English and Flemish standards are discussed below under Weight standards named after Troyes.
;Italy
Due in part to the political conditions in what would become a united Kingdom of Italy only in 1861, the variation of apothecaries' systems and standard weights in this region was enormous. (For background information, see History of Italy during foreign domination and the unification.) The (pound) generally consisted of the standard twelve ounces, however.
The civil weight systems were generally very similar to the apothecaries system, and since the (or the , where different systems were in use for light and heavy goods) generally had a suitable weight for an apothecaries pound it was often used for this purpose. Extreme cases were Rome and Genoa, where the same system was used for everything, including medicine. On the other hand, there were relatively large differences even between two cities in the same state. E.g. Bologna (in the Papal States) had an apothecaries pound that was less than the local civil pound, and 4% lighter than the pound used in Rome.
The weight of an apothecaries pound ranged generally between 300 g and 320 g, slightly less than that of a pound in the Roman Empire. An important exception to this rule is that the Kingdom of Lombardy–Venetia was under the rule of the Habsburg monarchy 1814–1859 and therefore had the extremely large Habsburg apothecaries pound of 420 g. (See below under Habsburg standard.) E.g. in the large city of Milan the apothecaries system based on a pound of 326.8 g was officially replaced by the metric system as early as 1803, because Milan was part of the Napoleonic Italian Republic. Since the successor of this little state, the Napoleonic Kingdom of Italy, fell to Habsburg in 1814 (at a time when even in France the had been introduced because the metric system was not accepted by the population), an apothecaries system was officially introduced again, but now based on the Habsburg apothecaries' pound, which weighed almost 30% more.
The apothecaries' pound in Venice had exactly the same subdivisions as those in the non-Romance countries, but its total weight of 301 g was at the bottom of the range. During the Habsburg reign of 1814–1859 an exception was made for Venice; as a result, the extreme weights of 301 g and 420 g coexisted within one state and in immediate proximity. The Venice standard was also used elsewhere, for example in Udine. In Dubrovnik (called "Ragusa" until 1909) its use was partially continued for a long time in spite of the official Habsburg weight reform.
The measure and weight systems for the large mainland part of the Kingdom of the Two Sicilies were unified in 1840. The area consisted of the southern half of the Italian Peninsula and included Naples and Salerno. The subdivision of apothecaries' weight in the unified system was essentially the same as that for gold, silver, coins, and silk. It was the most excentric variant in that the ounce was divided in 10 drachms, rather than the usual 8. The scruple, like in Venice but unlike in the rest of the Romance region, was divided into 20 grains. The existence of a unit called , the equivalent of , is interesting because 6 were 9 . In the original Salerno weight system an ounce was divided into 9 drachms, and so an would have been of an ounce. | 1 | Applied and Interdisciplinary Chemistry |
Optical rotation, also known as polarization rotation or circular birefringence, is the rotation of the orientation of the plane of polarization about the optical axis of linearly polarized light as it travels through certain materials. Circular birefringence and circular dichroism are the manifestations of optical activity. Optical activity occurs only in chiral materials, those lacking microscopic mirror symmetry. Unlike other sources of birefringence which alter a beam's state of polarization, optical activity can be observed in fluids. This can include gases or solutions of chiral molecules such as sugars, molecules with helical secondary structure such as some proteins, and also chiral liquid crystals. It can also be observed in chiral solids such as certain crystals with a rotation between adjacent crystal planes (such as quartz) or metamaterials.
When looking at the source of light, the rotation of the plane of polarization may be either to the right (dextrorotatory or dextrorotary — d-rotary, represented by (+), clockwise), or to the left (levorotatory or levorotary — l-rotary, represented by (−), counter-clockwise) depending on which stereoisomer is dominant. For instance, sucrose and camphor are d-rotary whereas cholesterol is l-rotary. For a given substance, the angle by which the polarization of light of a specified wavelength is rotated is proportional to the path length through the material and (for a solution) proportional to its concentration.
Optical activity is measured using a polarized source and polarimeter. This is a tool particularly used in the sugar industry to measure the sugar concentration of syrup, and generally in chemistry to measure the concentration or enantiomeric ratio of chiral molecules in solution. Modulation of a liquid crystal's optical activity, viewed between two sheet polarizers, is the principle of operation of liquid-crystal displays (used in most modern televisions and computer monitors). | 0 | Theoretical and Fundamental Chemistry |
Relative Surface Excess quantities are more useful than arbitrary surface excess quantities. The Relative surface excess relates the adsorption at the interface to a solvent in the bulk phase. An advantage of using the relative surface excess quantities is that they don't depend on the location of the dividing surface. The relative surface excess of species and solvent 1 is therefore: | 0 | Theoretical and Fundamental Chemistry |
Hellmut Fischmeister was elected as a foreign member of the Royal Swedish Academy of Engineering Sciences in 1975. In 1981, he was elected as a corresponding member of the Austrian Academy of Sciences and was a member of the Academia Europaea since 1989. In 1995, he became a full member of the mathematical-natural sciences class of the Austrian Academy of Sciences.
* 1969: Knight of the Royal Order of the North Star
* 1991: Honorary doctorate from the Royal Institute of Technology in Stockholm
* 1992: Honorary doctorate from Graz University of Technology
* 1997: Order of Merit of the Federal Republic of Germany, Cross of Merit 1st Class
* 2007: Honorary doctorate from the University of Leoben
* 2010: Austrian Cross of Honour for Science and Art, 1st class
* 2010: Honorary member of the German Materials Society (Deutsche Gesellschaft für Materialkunde) | 1 | Applied and Interdisciplinary Chemistry |
For atoms in the gas phase the principal effects are Doppler and pressure broadening. Lines are relatively sharp on the scale of measurement so that applications such as atomic absorption spectroscopy (AAS) and Inductively coupled plasma atomic emission spectroscopy (ICP) are used for elemental analysis. Atoms also have distinct x-ray spectra that are attributable to the excitation of inner shell electrons to excited states. The lines are relatively sharp because the inner electron energies are not very sensitive to the atom's environment. This is applied to X-ray fluorescence spectroscopy of solid materials. | 0 | Theoretical and Fundamental Chemistry |
Histones H2A, H2B, H3 and H4 form the core of a nucleosome and thus are called core histones. Processing of core histones is done differently because typical histone mRNA lacks several features of other eukaryotic mRNAs, such as poly(A) tail and introns. Thus, such mRNAs do not undergo splicing and their 3' processing is done independent of most cleavage and polyadenylation factors. Core histone mRNAs have a special stem-loop structure at 3-prime end that is recognized by a stem–loop binding protein and a downstream sequence, called histone downstream element (HDE) that recruits U7 snRNA. Cleavage and polyadenylation specificity factor 73 cuts mRNA between stem-loop and HDE
Histone variants, such as H2A.Z or H3.3, however, have introns and are processed as normal mRNAs including splicing and polyadenylation. | 1 | Applied and Interdisciplinary Chemistry |
William Christopher Zeise was born 15 October 1789 in Slagelse, the son of an apothecary, Frederick Zeise (1754–1836), who was an old friend of physicist Hans Christian Ørsteds father. Zeise attended Slagelse Latin school until he went to Copenhagen in 1805 to take up an apprenticeship under Gottfried Becker as a pharmacy assistant (Apoteksmedhjælper') at the Royal Court Pharmacy. Gottfried Becker, was an accomplished chemist who was employed as extraordinary Professor of Chemistry at the University. However Zeise felt dissatisfied there and returned home complaining of his health after having been there only a few months.
Around this time his interest in science (Natural Philosophy) began to develop. He familiarised himself with the new quantitative chemical theory of Antoine Lavosier; and read widely, including - Nicolai Tychsens "Apothekerkunst" (Theoretical and practical instructions for Pharmacists, 1804), Grens Chemistry, Adam Hauchs Principles of Natural Philosophy and Ørsteds papers in Scandinavian Literature and Letters (whose treatise on spontaneous combustion made an especially strong impression on him). At the same time he experimented with a home-made voltaic pile. At 17 years old, he rearranged his father's pharmacy in accordance with the new pharmacopoeia of 1805, which had imposed the antiphlogistic nomenclature. About the same time (summer of 1806) he mentioned in his diary "a most remarkable awakening within me for something higher, for scientific creative work in general, but for Science, chiefly Chemistry, deeply and in particular". How strong an impression this inner experience had made on him, can be established by the fact that he now wanted to return to Copenhagen, not to return to the Court apothecary, but to pursue a path studying chemistry. | 0 | Theoretical and Fundamental Chemistry |
When an electron beam is polarized, an unbalance between spin-up, , and spin-down electrons, , exists. The unbalance can be evaluated through the polarization defined as
It is known that, when an electron collides against a nucleus, the scattering event is governed by Coulomb interaction. This is the leading term in the Hamiltonian, but a correction due to spin-orbit coupling can be taken into account and the effect on the Hamiltonian can be evaluated with the perturbation theory. Spin orbit interaction can be evaluated, in the rest reference frame of the electron, as the result of the interaction of the spin magnetic moment of the electron
with the magnetic field that the electron sees, due to its orbital motion around the nucleus, whose expression in the non-relativistic limit is:
In these expressions is the spin angular-momentum, is the Bohr magneton, is the g-factor, is the reduced Planck constant, is the electron mass, is the elementary charge, is the speed of light, is the potential energy of the electron and is the angular momentum.
Due to spin orbit coupling, a new term will appear in the Hamiltonian, whose expression is
Due to this effect, electrons will be scattered with different probabilities at different angles. Since the spin-orbit coupling is enhanced when the involved nuclei possess a high atomic number Z, the target is usually made of heavy metals, such as mercury, gold and thorium. | 0 | Theoretical and Fundamental Chemistry |
The risks of isocyanates was brought to the world's attention with the 1984 Bhopal disaster, which caused the death of nearly 4000 people from the accidental release of methyl isocyanate. In 2008, the same chemical was involved in an explosion at a pesticide manufacturing plant in West Virginia.
LD50s for isocyanates are typically several hundred milligrams per kilogram. Despite this low acute toxicity, an extremely low short-term exposure limit (STEL) of 0.07 mg/m is the legal limit for all isocyanates (except methyl isocyanate: 0.02 mg/m) in the United Kingdom. These limits are set to protect workers from chronic health effects such as occupational asthma, contact dermatitis, or irritation of the respiratory tract.
Since they are used in spraying applications, the properties of their aerosols have attracted attention. In the U.S., OSHA conducted a National Emphasis Program on isocyanates starting in 2013 to make employers and workers more aware of the health risks.
Polyurethanes have variable curing times, and the presence of free isocyanates in foams vary accordingly.
Both the US National Toxicology Program (NTP) and International Agency for Research on Cancer (IARC) have evaluated TDI as a potential human carcinogen and Group 2B "possibly carcinogenic to humans". MDI appears to be relatively safer and is unlikely a human carcinogen. The IARC evaluates MDI as Group 3 "not classifiable as to its carcinogenicity in humans".
All major producers of MDI and TDI are members of the International Isocyanate Institute, which promotes the safe handling of MDI and TDI. | 0 | Theoretical and Fundamental Chemistry |
Since a sequence of single-stranded DNA needs to find its complementary strand to reform a double helix, common sequences renature more rapidly than rare sequences. Indeed, the rate at which a sequence will reassociate is proportional to the number of copies of that sequence in the DNA sample. A sample with a highly-repetitive sequence will renature rapidly, while complex sequences will renature slowly.
However, instead of simply measuring the percentage of double-stranded DNA versus time, the amount of renaturation is measured relative to a Ct value. The Ct value is the product of C (the initial concentration of DNA), t (time in seconds), and a constant that depends on the concentration of cations in the buffer. Repetitive DNA will renature at low Ct values, while complex and unique DNA sequences will renature at high Ct values. The fast renaturation of the repetitive DNA is because of the availability of numerous complementary sequences. | 1 | Applied and Interdisciplinary Chemistry |
The blood cells (erythrocytes, leukocytes and platelets) are produced by hematopoiesis.
The erythrocytes have as main function the O delivery to the tissues, and this transfer occurs by diffusion and is determined by the O tension (PO). The erythrocyte is able to feel the tissue need for O and cause a change in vascular caliber, through the pathway of ATP release, which requires an increase in cAMP, and are regulated by the phosphodiesterase (PDE). This pathway can be triggered via two mechanisms: physiological stimulus (like reduced O2 tension) and activation of the prostacyclin receptor (IPR). This pathway includes heterotrimeric G proteins, adenylyl cyclase (AC), protein kinase A (PKA), cystic fibrosis transmembrane conductance regulator (CFTR), and a final conduit that transport ATP to vascular lumen (pannexin 1 or voltage-dependent anion channel (VDAC)). The released ATP acts on purinergic receptors on endothelial cells, triggering the synthesis and release of several vasodilators, like nitric oxide (NO) and prostacyclin (PGI).
The current model of leukocyte adhesion cascade includes many steps mentioned in Table 1. The integrin-mediated adhesion of leukocytes to endothelial cells is related with morphological changes in both leukocytes and endothelial cells, which together support leukocyte migration through the venular walls. Rho and Ras small GTPases are involved in the principal leukocyte signaling pathways underlying chemokine-stimulated integrin-dependent adhesion, and have important roles in regulating cell shape, adhesion and motility.
After a vascular injury occurs, platelets are activated by locally exposed collagen (glycoprotein (GP) VI receptor), locally generated thrombin (PAR1 and PAR4 receptors), platelet-derived thromboxane A2 (TxA2) (TP receptor) and ADP (P2Y1 and P2Y12 receptors) that is either released from damaged cells or secreted from platelet dense granules. The von Willebrand factor (VWF) serves as an essential accessory molecule. In general terms, platelet activation initiated by agonist takes to a signaling cascade that leads to an increase of the cytosolic calcium concentration. Consequently, the integrin αβ is activated and the binding to fibrinogen allows the aggregation of platelets to each other. The increase of cytosolic calcium also leads to shape change and TxA2 synthesis, leading to signal amplification. | 0 | Theoretical and Fundamental Chemistry |
The following polyhedra are closo polyhedra, and are the basis for the 4n rules; each of these have triangular faces. The number of vertices in the cluster determines what polyhedron the structure is based on.
Using the electron count, the predicted structure can be found. n is the number of vertices in the cluster. The 4n rules are enumerated in the following table.
When counting electrons for each cluster, the number of valence electrons is enumerated. For each transition metal present, 10 electrons are subtracted from the total electron count. For example, in Rh(CO) the total number of electrons would be = = 26. Therefore, the cluster is a closo polyhedron because , with .
Other rules may be considered when predicting the structure of clusters:
# For clusters consisting mostly of transition metals, any main group elements present are often best counted as ligands or interstitial atoms, rather than vertices.
# Larger and more electropositive atoms tend to occupy vertices of high connectivity and smaller more electronegative atoms tend to occupy vertices of low connectivity.
# In the special case of boron hydride clusters, each boron atom connected to 3 or more vertices has one terminal hydride, while a boron atom connected to two other vertices has two terminal hydrogen atoms. If more hydrogen atoms are present, they are placed in open face positions to even out the coordination number of the vertices.
# For the special case of transition metal clusters, ligands are added to the metal centers to give the metals reasonable coordination numbers, and if any hydrogen atoms are present they are placed in bridging positions to even out the coordination numbers of the vertices.
In general, closo structures with n vertices are n-vertex polyhedra.
To predict the structure of a nido cluster, the closo cluster with n + 1 vertices is used as a starting point; if the cluster is composed of small atoms a high connectivity vertex is removed, while if the cluster is composed of large atoms a low connectivity vertex is removed.
To predict the structure of an arachno cluster, the closo polyhedron with n + 2 vertices is used as the starting point, and the n + 1 vertex nido complex is generated by following the rule above; a second vertex adjacent to the first is removed if the cluster is composed of mostly small atoms, a second vertex not adjacent to the first is removed if the cluster is composed mostly of large atoms.
Example:
:Electron count: 10 × Pb + 2 (for the negative charge) = 10 × 4 + 2 = 42 electrons.
:Since n = 10, 4n + 2 = 42, so the cluster is a closo bicapped square antiprism.
Example:
:Electron count: 4 × S – 2 (for the positive charge) = 4 × 6 – 2 = 22 electrons.
:Since n = 4, 4n + 6 = 22, so the cluster is arachno.
:Starting from an octahedron, a vertex of high connectivity is removed, and then a non-adjacent vertex is removed.
Example: Os(CO)
:Electron count: 6 × Os + 18 × CO – 60 (for 6 osmium atoms) = 6 × 8 + 18 × 2 – 60 = 24
:Since n = 6, 4n = 24, so the cluster is capped closo.
:Starting from a trigonal bipyramid, a face is capped. The carbonyls have been omitted for clarity.
Example:
:Electron count: 5 × B + 5 × H + 4 (for the negative charge) = 5 × 3 + 5 × 1 + 4 = 24
:Since n = 5, 4n + 4 = 24, so the cluster is nido.
:Starting from an octahedron, one of the vertices is removed.
The rules are useful in also predicting the structure of carboranes.
Example: CBH
:Electron count = 2 × C + 7 × B + 13 × H = 2 × 4 + 7 × 3 + 13 × 1 = 42
:Since n in this case is 9, 4n + 6 = 42, the cluster is arachno.
The bookkeeping for deltahedral clusters is sometimes carried out by counting skeletal electrons instead of the total number of electrons. The skeletal orbital (electron pair) and skeletal electron counts for the four types of deltahedral clusters are:
*n-vertex closo: n + 1 skeletal orbitals, 2n + 2 skeletal electrons
*n-vertex nido: n + 2 skeletal orbitals, 2n + 4 skeletal electrons
*n-vertex arachno: n + 3 skeletal orbitals, 2n + 6 skeletal electrons
*n-vertex hypho: n + 4 skeletal orbitals, 2n + 8 skeletal electrons
The skeletal electron counts are determined by summing the total of the following number of electrons:
*2 from each BH unit
*3 from each CH unit
*1 from each additional hydrogen atom (over and above the ones on the BH and CH units)
*the anionic charge electrons | 0 | Theoretical and Fundamental Chemistry |
Clozapine N-oxide (CNO) is a synthetic drug used mainly in biomedical research as a ligand to activate DREADD receptors. Although CNO was initially believed to be biologically inert. However, it has been shown not to enter the brain after administration and to reverse metabolise in peripheral tissues to form clozapine. Clozapine can bind to a number of different serotonergic, dopaminergic and adrenergic receptors within the brain. Therefore, behavioural data using the CNO-DREADD system in neuroscience experiments have to be interpreted with caution.
Alternatives to CNO with more affinity, more inert character, and faster kinetics include Compound 21 (C21) and deschloroclozapine (DCZ). | 1 | Applied and Interdisciplinary Chemistry |
Chemical messengers bind to metabotropic receptors to initiate a diversity of effects caused by biochemical signaling cascades. G protein-coupled receptors are all metabotropic receptors. When a ligand binds to a G protein-coupled receptor, a guanine nucleotide-binding protein, or G protein, activates a second messenger cascade which can alter gene transcription, regulate other proteins in the cell, release intracellular Ca, or directly affect ion channels on the membrane. These receptors can remain open from seconds to minutes and are associated with long-lasting effects, such as modifying synaptic strength and modulating short- and long-term synaptic plasticity.
Metabotropic receptors have a diversity of ligands, including but not limited to: small molecule transmitters, monoamines, peptides, hormones, and even gases. In comparison to fast-acting neurotransmitters, these ligands are not taken up again or degraded quickly. They can also enter the circulatory system to globalize a signal. Most metabotropic ligands have unique receptors. Some examples include: metabotropic glutamate receptors, muscarinic acetylcholine receptors, GABA receptors. | 1 | Applied and Interdisciplinary Chemistry |
When the two dental sealants are compared, there has always been a contradiction as to which materials is more effective in caries reduction. Therefore, there are claims against replacing resin-based sealants, the current gold standard, with glass ionomer. | 0 | Theoretical and Fundamental Chemistry |
Realizing the modest thermal conductivity enhancement in conventional nanofluids, a team of researchers at Indira Gandhi Centre for Atomic Research Centre, Kalpakkam developed a new class of magnetically polarizable nanofluids where the thermal conductivity enhancement up to 300% of basefluids is demonstrated. Fatty-acid-capped magnetite nanoparticles of different sizes (3-10 nm) have been synthesized for this purpose. It has been shown that both the thermal and rheological properties of such magnetic nanofluids are tunable by varying the magnetic field strength and orientation with respect to the direction of heat flow. Such response stimuli fluids are reversibly switchable and have applications in miniature devices such as micro- and nano-electromechanical systems.
In 2013, Azizian et al. considered the effect of an external magnetic field on the convective heat transfer coefficient of water-based magnetite nanofluid experimentally under laminar flow regime. Up to 300% enhancement obtained at Re=745 and magnetic field gradient of 32.5 mT/mm. The effect of the magnetic field on the pressure drop was not as significant. | 0 | Theoretical and Fundamental Chemistry |
Mathur's researches were focused on the organometallic chemistry of mixed metal cluster compounds and he has developed synthetic strategies for introducing chalcogen bridges. At IIT Mumbai, he handled projects related to the investigation of unusual metal mediated transformations and the interactions between the metal atoms and unsaturated organic species. He has published his researches by way of chapters contributed to books authored by others and over 180 peer-reviewed articles; ResearchGate and Google Scholar, two online repositories have listed several of them. He has also guided 22 doctoral scholars in their studies.
Mathur was a Fulbright scholar in 1995 and the Indian Academy of Sciences elected him as a fellow in 1996. The Council of Scientific and Industrial Research awarded him the Shanti Swarup Bhatnagar Prize, one of the highest Indian science awards, in 2000. He has also been honoured with an honorary D.Sc. degree by the University of Keele in the U.K. | 0 | Theoretical and Fundamental Chemistry |
The [http://hive.biochemistry.gwu.edu/ High-performance Integrated Virtual Environment] (HIVE) is a distributed computing environment used for healthcare-IT and biological research, including analysis of Next Generation Sequencing (NGS) data, preclinical, clinical and post market data, adverse events, metagenomic data, etc. Currently it is supported and continuously developed by US Food and Drug Administration (government domain), George Washington University (academic domain), and by DNA-HIVE, WHISE-Global and Embleema (commercial domain). HIVE currently operates fully functionally within the US FDA supporting wide variety (+60) of regulatory research and regulatory review projects as well as for supporting MDEpiNet medical device postmarket registries. Academic deployments of HIVE are used for research activities and publications in NGS analytics, cancer research, microbiome research and in educational programs for students at GWU. Commercial enterprises use HIVE for oncology, microbiology, vaccine manufacturing, gene editing, healthcare-IT, harmonization of real-world data, in preclinical research and clinical studies. | 1 | Applied and Interdisciplinary Chemistry |
Measuring cardiac biomarkers can be a step toward making a diagnosis for a condition. Whereas cardiac imaging often confirms a diagnosis, simpler and less expensive cardiac biomarker measurements can advise a physician whether more complicated or invasive procedures are warranted. In many cases medical societies advise doctors to make biomarker measurements an initial testing strategy especially for patients at low risk of cardiac death.
Many acute cardiac marker IVD products are targeted at nontraditional markets, e.g., the hospital ER instead of traditional hospital or clinical laboratory environments. Competition in the development of cardiac marker diagnostic products and their expansion into new markets is intense.
Recently, the intentional destruction of myocardium by alcohol septal ablation has led to the identification of additional potential markers. | 1 | Applied and Interdisciplinary Chemistry |
In 2008, Meibom was awarded with the Medal for Research Excellence by the European Mineralogical Union for his contributions in the field of cosmochemistry. From 2009 to 2012, he was appointed member of the Comité National Section 18 at the French National Centre for Scientific Research (CNRS), France. In 2009 and 2017, Meibom was awarded two advanced grants by the European Research Council for projects aiming to better understand biomineralization processes by marine organisms (Project BioCarb, 2009), as well as to better understand biocarbonate-based paleo-environmental records for the oceans (Project UltraPal, 2017). | 0 | Theoretical and Fundamental Chemistry |
Nanocrystalline materials show exceptional mechanical properties relative to their coarse-grained varieties. Because the volume fraction of grain boundaries in nanocrystalline materials can be as large as 30%, the mechanical properties of nanocrystalline materials are significantly influenced by this amorphous grain boundary phase. For example, the elastic modulus has been shown to decrease by 30% for nanocrystalline metals and more than 50% for nanocrystalline ionic materials. This is because the amorphous grain boundary regions are less dense than the crystalline grains, and thus have a larger volume per atom, . Assuming the interatomic potential, , is the same within the grain boundaries as in the bulk grains, the elastic modulus, , will be smaller in the grain boundary regions than in the bulk grains. Thus, via the rule of mixtures, a nanocrystalline material will have a lower elastic modulus than its bulk crystalline form. | 1 | Applied and Interdisciplinary Chemistry |
Aggregates may also form from colloids trapped on the surface of rising bubbles. For example, Kepkay et al. found that bubble coagulation leads to an increase in bacterial respiration since more food is available to them. | 0 | Theoretical and Fundamental Chemistry |
In coastal and environmental engineering, the closure of tidal inlets entails the deliberate prevention of the entry of seawater into inland areas through the use of fill material and the construction of barriers. The aim of such closures is usually to safeguard inland regions from flooding, thereby protecting ecological integrity and reducing potential harm to human settlements and agricultural areas.
The complexity of inlet closure varies significantly with the size of the estuary involved. For smaller estuaries, which may naturally dry out at low tide, the process can be relatively straightforward. However, the management of larger estuaries demands a sophisticated blend of technical expertise, encapsulating hydrodynamics, sediment transport, as well as mitigation of the potential ecological consequences of such interventions. The development of knowledge around such closures over time reflects a concerted effort to balance flood defence mechanisms with environmental stewardship, leading to the development of both traditional and technologically advanced solutions. | 1 | Applied and Interdisciplinary Chemistry |
Lessing rings are a type of random packing similar to the Raschig ring invented in the early 20th century by German-born British chemist Rudolf Lessing (1878-1964) of Mond Nickel Company. Originally wrapped from steel strips according to his 1919 patent, now they are made of ceramic. Lessing rings have partitions insides which increase the surface area and enhance mass transfer efficiency. Lessing rings have a high density and an excellent heat and acid resistance. Lessing rings withstand corrosion and are used in regenerative oxide systems and transfer systems. | 1 | Applied and Interdisciplinary Chemistry |
In coordination chemistry transition metal imido complexes feature the NR ligand. They are similar to oxo ligands in some respects. In some the M-N-C angle is 180º but often the angle is decidedly bent. The parent imide (NH) is an intermediate in nitrogen fixation by synthetic catalysts. | 0 | Theoretical and Fundamental Chemistry |
As powerful nucleophiles, enolates react readily with a variety of electrophiles. These reactions generate new C-C bonds and often new stereocenters. The stereoselectivity and regioselectivity is influenced by additives, solvent, counterions, etc. One important class of electrophiles are alkyl halides, and in this case a classic problem arises: O-alkylation vs C-alkylation. Controlling this selectivity has drawn much attention. The negative charge in enolates is concentrated on the oxygen, but that center is also highly solvated, which leads to C-alkylation.
Other important electrophiles are aldehydes/ketones and Michael acceptors. | 0 | Theoretical and Fundamental Chemistry |
G proteins contain an alpha-subunit that is critical to the functioning of receptors. These subunits can take a number of forms. There are four broad classes of form of G-protein: G, G, G, and G. Muscarinic receptors vary in the G protein to which they are bound, with some correlation according to receptor type. G proteins are also classified according to their susceptibility to cholera toxin (CTX) and pertussis toxin (PTX, whooping cough). G and some subtypes of G (G and G) are susceptible to CTX. Only G is susceptible to PTX, with the exception of one subtype of G (G) which is immune. Also, only when bound with an agonist, those G proteins normally sensitive to PTX also become susceptible to CTX.
The various G-protein subunits act differently upon secondary messengers, upregulating Phospholipases, downregulating cAMP, and so on.
Because of the strong correlations to muscarinic receptor type, CTX and PTX are useful experimental tools in investigating these receptors. | 1 | Applied and Interdisciplinary Chemistry |
Anthropogenic heat is heat generated by humans and human activity. The American Meteorological Society defines it as "Heat released to the atmosphere as a result of human activities, often involving combustion of fuels. Sources include industrial plants, space heating and cooling, human metabolism, and vehicle exhausts. In cities this source typically contributes 15–50 W/m to the local heat balance, and several hundred W/m in the center of large cities in cold climates and industrial areas." In 2020, the overall anthropogenic annual energy release was 168,000 terawatt-hours; given the 5.1×10 m surface area of Earth, this amounts to a global average anthropogenic heat release rate of 0.04 W/m. | 0 | Theoretical and Fundamental Chemistry |
The ductile iron used to manufacture the pipe is characterized by the spheroidal or nodular nature of the graphite within the iron. Typically, the pipe is manufactured using centrifugal casting in metal or resin lined moulds. Protective internal linings and external coatings are often applied to ductile iron pipes to inhibit corrosion: the standard internal lining is cement mortar and standard external coatings include bonded zinc, asphalt or water-based paint. In highly corrosive environments loose polyethylene sleeving (LPS) to encase the pipe may also be used.
Life expectancy of unprotected ductile iron pipes depends on the corrosiveness of soil present and tends to be shorter where soil is highly corrosive. However, a lifespan in excess of 100 years has been estimated for ductile iron pipelines installed using "evolved laying practices", including use of properly installed LPS (polyethylene encasement). Studies of ductile iron pipe's environmental impact have differing findings regarding emissions and energy consumed. Ductile iron pipe manufactured in the US has been certified as a sustainable product by the Institute for Market Transformation to Sustainability. | 1 | Applied and Interdisciplinary Chemistry |
Eyeglass frames made from titanium-containing SMAs are marketed under the trademarks Flexon and TITANflex. These frames are usually made out of shape-memory alloys that have their transition temperature set below the expected room temperature. This allows the frames to undergo large deformation under stress, yet regain their intended shape once the metal is unloaded again. The very large apparently elastic strains are due to the stress-induced martensitic effect, where the crystal structure can transform under loading, allowing the shape to change temporarily under load. This means that eyeglasses made of shape-memory alloys are more robust against being accidentally damaged. | 1 | Applied and Interdisciplinary Chemistry |
An economical semisynthesis of progesterone from the plant steroid diosgenin isolated from yams was developed by Russell Marker in 1940 for the Parke-Davis pharmaceutical company. This synthesis is known as the Marker degradation.
The 16-DPA intermediate is important to the synthesis of many other medically important steroids. A very similar approach can produce 16-DPA from solanine. | 0 | Theoretical and Fundamental Chemistry |
The ASARCO Amarillo copper refinery switched in 1991 from reverberatory furnace treatment of anode slimes to a BBOC to reduce the gold inventory. The original reverberatory furnace had a 15 t capacity. The production cycle of the reverberatory furnace was typically 7–10 days, with the final doré production being about 8 t per cycle.
A single 3 t capacity BBOC was installed, and it was found to increase rejection of selenium from the slimes, with a reduction in fluxing requirements of about 80%. | 1 | Applied and Interdisciplinary Chemistry |
Other systems involve liquid going through an orifice, expanding from a capillary, or sucked up from a surface into a column by a vacuum. A pressurized capillary rheometer can be used to design thermal treatments of fluid food. This instrumentation could help prevent over and under-processing of fluid food because extrapolation to high temperatures would not be necessary. | 1 | Applied and Interdisciplinary Chemistry |
The SUPERFAMILY annotation is based on a collection of hidden Markov models (HMM), which represent structural protein domains at the SCOP superfamily level.
A superfamily groups together domains which have an evolutionary relationship. The annotation is produced by scanning protein sequences from completely sequenced genomes against the hidden Markov models.
For each protein you can:
* Submit sequences for SCOP classification
* View domain organisation, sequence alignments and protein sequence details
For each genome you can:
* Examine superfamily assignments, phylogenetic trees, domain organisation lists and networks
* Check for over- and under-represented superfamilies within a genome
For each superfamily you can:
* Inspect SCOP classification, functional annotation, Gene Ontology annotation, InterPro abstract and genome assignments
* Explore taxonomic distribution of a superfamily across the tree of life
All annotation, models and the database dump are freely available for download to everyone. | 1 | Applied and Interdisciplinary Chemistry |
The water policy of the European Union is primarily codified in three directives:
*Directive on Urban Waste Water Treatment (91/271/EEC) of 21 May 1991 concerning discharges of municipal and some industrial wastewaters;
*The Drinking Water Directive (98/83/EC) of 3 November 1998 concerning potable water quality;
*Water Framework Directive (2000/60/EC) of 23 October 2000 concerning water resources management. | 0 | Theoretical and Fundamental Chemistry |
In physics, macrons are microscopic (dust-sized) particles, accelerated to high speeds. The term was first used in the late 1960s, when it was believed that macrons could be accelerated cheaply in small particle accelerators as a way of achieving low-cost fusion power. | 0 | Theoretical and Fundamental Chemistry |
In organosulfur chemistry, a Bunte salt is an archaic name for salts with the formula RSSONa. They are also called S-alkylthiosulfates or S-arylthiosulfates. These compounds are typically derived from alkylation on the pendant sulfur of sodium thiosulfate:
:RX + NaSO → Na[OSR] + NaX
They have been used as intermediates in the synthesis of thiols. They are also used to generate unsymmetrical disulfides:
:Na[OSR] + NaSR → RSSR + NaSO
According to X-ray crystallography, they adopt the expected structure with tetrahedral sulfur(VI) atom, a sulfur-sulfur single bond, and three equivalent sulfur-oxygen bonds. | 0 | Theoretical and Fundamental Chemistry |
Stephen T. Liddle FRSE FRSC is a British professor of inorganic chemistry at the University of Manchester. He is Head of Inorganic Chemistry and Co-Director of the Centre for Radiochemistry Research at the University of Manchester since 2015. | 0 | Theoretical and Fundamental Chemistry |
Although gas handling and processing are far more economical than converting coal into coke (not to mention the associated constraints, such as bulk handling, high sensitivity of coking plants to production fluctuations, environmental impact, etc.), replacing coke with natural gas only makes direct reduction attractive to steelmakers with cheap gas resources. This point is essential, as European steelmakers pointed out in 1998:This explains the development of certain reduction-melting processes which, because of the high temperatures involved, have a surplus of reducing gas. Reduction-melting processes such as the COREX, capable of feeding an ancillary Midrex direct reduction unit, or the Tecnored, are justified by their ability to produce CO-rich gas despite their higher investment cost. In addition, coke oven gas is an essential co-product in the energy strategy of a steel complex: the absence of a coke oven must therefore be compensated for by higher natural gas consumption for downstream tools, notably hot rolling and annealing furnaces.
The worldwide distribution of direct reduction plants is therefore directly correlated with the availability of natural gas and ore. In 2007, the breakdown was as follows:
* natural gas processes are concentrated in Latin America (where many have already been developed) and the Middle East;
* coal-fired processes are remarkably successful in India, maintaining the proportion of steel produced by direct reduction despite the strong development of the Chinese steel industry.
China, a country with gigantic needs and a deficit of scrap metal, and Europe, lacking competitive ore and fuels, have never invested massively in these processes, remaining faithful to the blast furnace route. The United States, meanwhile, has always had a few units, but since 2012, the exploitation of shale gas has given a new impetus to natural gas processes.
However, because direct reduction uses much more hydrogen as a reducing agent than blast furnaces (which is very clear for natural gas processes), it produces much less CO, a greenhouse gas. This advantage has motivated the development of ULCOS processes in developed countries, such as HISARNA, ULCORED, and others. The emergence of mature gas treatment technologies, such as pressure swing adsorption or amine gas treating, has also rekindled the interest of researchers. In addition to reducing CO emissions, pure hydrogen processes such as Hybrit are being actively studied with a view to decarbonizing the steel industry. | 1 | Applied and Interdisciplinary Chemistry |
In 1828 he wrote an anonymous review on Gall and Spurzheims work on phrenology, which was reprinted two years later, with comments by Spurzheim, in London. The Edinburgh Review and Foreign Quarterly Review' printed his various economic and cultural articles on France and England.
* 1802: [https://books.google.com/books?id=GidVnQEACAAJ Dramatic Poems: Leonora, a Tragedy; and Etha and Aidallo, a Dramatic Poem (Second Edition), London: W. Bulmer and Co.]
* 1812: [https://archive.org/details/twoplaysmantuan00chengoog Two Plays: Mantuan Revels, a Comedy, in Five Acts; Henry the Seventh, an Historical Tragedy, in Five Acts, J. Johnson & Co.]
* 1828: [https://archive.org/details/foreignquarterl48unkngoog "Gall and Spurzheim — Phrenology", The Foreign Quarterly Review, Vol.2, No.3, pp.1-59.]
* 1829: "On Mesmerism, Improperly Denominated Animal Magnetism", London Medical and Physical Journal, [https://archive.org/details/anappealtomedic02readgoog Vol.61], No.361, (March 1829), pp. 219–230; No.364, (June 1829), pp. 491–501; [https://archive.org/details/anappealtomedic00readgoog Vol.62], No.366, (August 1829), pp. 114–125; No.367, (September 1829), pp. 210–220; No.368, (October 1829), pp. 315–324.
* 1830: [https://archive.org/details/anessayuponnati03chengoog Phrenology Article of the Foreign Quarterly Review, by Rich. Chenevix, Esq., F.R.S., &c., With Notes from G. Spurzheim, M.D. of the Universities of Vienna and Paris, and Licentiate of the Royal College of Physicians of London, London; Treuttel, Würtz, and Richter.]
* 1832: [https://archive.org/details/anessayuponnati00chengoog An Essay Upon National Character: Being an Inquiry into Some of the Principal Causes Which Contribute to Form and Modify the Characters of Nations in the State of Civilisation, in Two Volumes: Vol.I, London: J. Johnson & Co.]
* 1832: [https://archive.org/details/anessayuponnati03chengoog An Essay Upon National Character: Being an Inquiry into Some of the Principal Causes Which Contribute to Form and Modify the Characters of Nations in the State of Civilisation, in Two Volumes: Vol.II, London: J. Johnson & Co.] | 1 | Applied and Interdisciplinary Chemistry |
Reaction dynamics is a field within physical chemistry, studying why chemical reactions occur, how to predict their behavior, and how to control them. It is closely related to chemical kinetics, but is concerned with individual chemical events on atomic length scales and over very brief time periods. It considers state-to-state kinetics between reactant and product molecules in specific quantum states, and how energy is distributed between translational, vibrational, rotational, and electronic modes.
Experimental methods of reaction dynamics probe the chemical physics associated with molecular collisions. They include crossed molecular beam and infrared chemiluminescence experiments, both recognized by the 1986 Nobel Prize in Chemistry awarded to Dudley Herschbach, Yuan T. Lee, and John C. Polanyi "for their contributions concerning the dynamics of chemical elementary processes", In the crossed beam method used by Herschbach and Lee, narrow beams of reactant molecules in selected quantum states are allowed to react in order to determine the reaction probability as a function of such variables as the translational, vibrational and rotational energy of the reactant molecules and their angle of approach. In contrast the method of Polanyi measures vibrational energy of the products by detecting the infrared chemiluminescence emitted by vibrationally excited molecules, in some cases for reactants in defined energy states.
Spectroscopic observation of reaction dynamics on the shortest time scales is known as femtochemistry, since the typical times studied are of the order of 1 femtosecond = 10 s. This subject has been recognized by the award of the 1999 Nobel Prize in Chemistry to Ahmed Zewail.
In addition, theoretical studies of reaction dynamics involve calculating the potential energy surface for a reaction as a function of nuclear positions, and then calculating the trajectory of a point on this surface representing the state of the system. A correction can be applied to include the effect of quantum tunnelling through the activation energy barrier, especially for the movement of hydrogen atoms. | 0 | Theoretical and Fundamental Chemistry |
Biosurfactant usually refers to surfactants of microbial origin. Most of the biosurfactants produced by microbes are synthesized extracellularly and many microbes are known to produce biosurfactants in large relative quantities. Some are of commercial interest. As a secondary metabolite of microorganisms, biosurfactants can be processed by the cultivation of biosurfactant producing microorganisms in the stationary phase on many sorts of low-priced substrates like biochar, plant oils, carbohydrates, wastes, etc. High-level production of biosurfactants can be controlled by regulation of environmental factors and growth circumstances. | 0 | Theoretical and Fundamental Chemistry |
*Heidt, L.J.; Koster, G.F.; Johnson, A.M. "Experimental and Crystal Field Study of the Absorption Spectrum at 2000 to 8000 A of to Manganous Perchlorate in Aqueous Perchloric Acid" J. Am. Chem. Soc. 1959, 80, 6471–6477.
*Rohde,J; In,J.; Lim, M.H.; Brennessel, W.W.; Bukowski, M.R.; Stubna, A.; Muonck, E.; Nam, W.; Que L. "Crystallographic and Spectroscopic Characterization of a Nonheme Fe(IV)O Complex" Science VOL 299 1037–1039.
*Decker, A.; Rohde,J.; Que, L.; Solomon, E.I. "Spectroscopic and Quantum Chemical Characterization of the Electronic Structure and Bonding in a Non-Heme FeO Complex" J. Am. Chem. Soc. 2004, 126, 5378–5379.
*Aliaga-Alcalde, N.; George, S.D.; Mienert, B.; Bill, E.; Wieghardt, K.; Neese, F. "The Geometric and Electronic Structure of [(cyclam-acetato)Fe(N)]: A Genuine Iron(V) Species with a Ground-State Spin S=1/2" Angew. Chem. Int. Ed. 2005, 44, 2908–2912. | 0 | Theoretical and Fundamental Chemistry |
In terms of representation theory, what has happened is that the two conjugate 2-dimensional spin representations of the spin group SU(2) = Spin(3) (as it sits inside the 3-dimensional Clifford algebra) have tensored to produce a 4-dimensional representation. The 4-dimensional representation descends to the usual orthogonal group SO(3) and so its objects are tensors, corresponding to the integrality of their spin. The 4-dimensional representation decomposes into the sum of a one-dimensional trivial representation (singlet, a scalar, spin zero) and a three-dimensional representation (triplet, spin 1) that is nothing more than the standard representation of SO(3) on . Thus the "three" in triplet can be identified with the three rotation axes of physical space. | 0 | Theoretical and Fundamental Chemistry |
Since TPD observes the mass of desorbed molecules, it shows what molecules are adsorbed on the surface. Moreover, TPD recognizes the different adsorption conditions of the same molecule from the differences between the desorption temperatures of molecules desorbing different sites at the surface, e.g. terraces vs. steps. TPD also obtains the amounts of adsorbed molecules on the surface from the intensity of the peaks of the TPD spectrum, and the total amount of adsorbed species is shown by the integral of the spectrum.
To measure TPD, one needs a mass spectrometer, such as a quadrupole mass spectrometer or a time-of-flight (TOF) mass spectrometer, under ultrahigh vacuum (UHV) conditions. The amount of adsorbed molecules is measured by increasing the temperature at a heating rate of typically 2 K/s to 10 K/s. Several masses may be simultaneously measured by the mass spectrometer, and the intensity of each mass as a function of temperature is obtained as a TDS spectrum.
The heating procedure is often controlled by the PID control algorithm, with the controller being either a computer or specialised equipment such as a Eurotherm.
Other methods of measuring desorption are Thermal Gravimetric Analysis (TGA) or using infrared detectors, thermal conductivity detectors etc. | 0 | Theoretical and Fundamental Chemistry |
Korea Foundation for the Science and Creativity, LG Chem, and Korea Dow Chemical Company supports the KChO. | 1 | Applied and Interdisciplinary Chemistry |
The bond length between two atoms in a molecule depends not only on the atoms but also on such factors as the orbital hybridization and the electronic and steric nature of the substituents. The carbon–carbon (C–C) bond length in diamond is 154 pm. It is generally considered the average length for a carbon–carbon single bond, but is also the largest bond length that exists for ordinary carbon covalent bonds. Since one atomic unit of length (i.e., a Bohr radius) is 52.9177 pm, the C–C bond length is 2.91 atomic units, or approximately three Bohr radii long.
Unusually long bond lengths do exist. Current record holder for the longest C-C bond with a length of 186.2 pm is 1,8-Bis(5-hydroxydibenzo[a,d]cycloheptatrien-5-yl)naphthalene, one of many molecules within a category of hexaaryl ethanes, which are derivatives based on hexaphenylethane skeleton. Bond is located between carbons C1 and C2 as depicted in a picture below.
Another notable compound with an extraordinary C-C bond length is tricyclobutabenzene, in which a bond length of 160 pm is reported. Longest C-C bond within the cyclobutabenzene category is 174 pm based on X-ray crystallography. In this type of compound the cyclobutane ring would force 90° angles on the carbon atoms connected to the benzene ring where they ordinarily have angles of 120°.
The existence of a very long C–C bond length of up to 290 pm is claimed in a dimer of two tetracyanoethylene dianions, although this concerns a 2-electron-4-center bond. This type of bonding has also been observed in neutral phenalenyl dimers. The bond lengths of these so-called "pancake bonds" are up to 305 pm.
Shorter than average C–C bond distances are also possible: alkenes and alkynes have bond lengths of respectively 133 and 120 pm due to increased s-character of the sigma bond. In benzene all bonds have the same length: 139 pm. Carbon–carbon single bonds increased s-character is also notable in the central bond of diacetylene (137 pm) and that of a certain tetrahedrane dimer (144 pm).
In propionitrile the cyano group withdraws electrons, also resulting in a reduced bond length (144 pm). Squeezing a C–C bond is also possible by application of strain. An unusual organic compound exists called In-methylcyclophane with a very short bond distance of 147 pm for the methyl group being squeezed between a triptycene and a phenyl group. In an in silico experiment a bond distance of 136 pm was estimated for neopentane locked up in fullerene. The smallest theoretical C–C single bond obtained in this study is 131 pm for a hypothetical tetrahedrane derivative.
The same study also estimated that stretching or squeezing the C–C bond in an ethane molecule by 5 pm required 2.8 or 3.5 kJ/mol, respectively. Stretching or squeezing the same bond by 15 pm required an estimated 21.9 or 37.7 kJ/mol. | 0 | Theoretical and Fundamental Chemistry |
Water quality is graded both on appearance, for example: clear, cloudy, full of algae, and chemistry. Determining the specific levels of enzymes, bacteria, metals, and minerals found in water is extremely important. Some contaminants, such as metals and certain organic wastes, can be lethal to individual creatures and could thereby ultimately lead to extinction of certain species. This could affect both aquatic and land ecosystems and cause disruption in other biomes and ecosystems. | 1 | Applied and Interdisciplinary Chemistry |
Particle radiation is the radiation of energy by means of fast-moving subatomic particles. Particle radiation is referred to as a particle beam if the particles are all moving in the same direction, similar to a light beam.
Due to the wave–particle duality, all moving particles also have wave character. Higher energy particles more easily exhibit particle characteristics, while lower energy particles more easily exhibit wave characteristics. | 0 | Theoretical and Fundamental Chemistry |
Hypothermia therapy for neonatal encephalopathy has been proven to improve outcomes for newborn infants affected by perinatal hypoxia-ischemia, hypoxic ischemic encephalopathy or birth asphyxia. A 2013 Cochrane review found that it is useful in full term babies with encephalopathy. Whole body or selective head cooling to , begun within six hours of birth and continued for 72 hours, reduces mortality and reduces cerebral palsy and neurological deficits in survivors. | 1 | Applied and Interdisciplinary Chemistry |
Neptunium silicide forms crystals of tetragonal crystal system, space group I4/amd, cell parameters: a = 0.396 nm, c = 1.367 nm, Z = 4.
Neptunium disilicide does not dissolve in water. | 0 | Theoretical and Fundamental Chemistry |
Splicing is catalyzed by the spliceosome, a large RNA-protein complex composed of five small nuclear ribonucleoproteins (snRNPs). Assembly and activity of the spliceosome occurs during transcription of the pre-mRNA. The RNA components of snRNPs interact with the intron and are involved in catalysis. Two types of spliceosomes have been identified (major and minor) which contain different snRNPs.
*The major spliceosome splices introns containing GU at the 5 splice site and AG at the 3 splice site. It is composed of the U1, U2, U4, U5, and U6 snRNPs and is active in the nucleus. In addition, a number of proteins including U2 small nuclear RNA auxiliary factor 1 (U2AF35), U2AF2 (U2AF65) and SF1 are required for the assembly of the spliceosome. The spliceosome forms different complexes during the splicing process:
:*Complex E
:**The U1 snRNP binds to the GU sequence at the 5' splice site of an intron;
:**Splicing factor 1 binds to the intron branch point sequence;
:**U2AF1 binds at the 3' splice site of the intron;
:**U2AF2 binds to the polypyrimidine tract;
:*Complex A (pre-spliceosome)
:**The U2 snRNP displaces SF1 and binds to the branch point sequence and ATP is hydrolyzed;
:*Complex B (pre-catalytic spliceosome)
:**The U5/U4/U6 snRNP trimer binds, and the U5 snRNP binds exons at the 5' site, with U6 binding to U2;
:*Complex B*
:**The U1 snRNP is released, U5 shifts from exon to intron, and the U6 binds at the 5' splice site;
:*Complex C (catalytic spliceosome)
:**U4 is released, U6/U2 catalyzes transesterification, making the 5-end of the intron ligate to the A on intron and form a lariat, U5 binds exon at 3 splice site, and the 5' site is cleaved, resulting in the formation of the lariat;
:*Complex C* (post-spliceosomal complex)
:**U2/U5/U6 remain bound to the lariat, and the 3' site is cleaved and exons are ligated using ATP hydrolysis. The spliced RNA is released, the lariat is released and degraded, and the snRNPs are recycled.
:This type of splicing is termed canonical splicing or termed the lariat pathway, which accounts for more than 99% of splicing. By contrast, when the intronic flanking sequences do not follow the GU-AG rule, noncanonical splicing is said to occur (see "minor spliceosome" below).
*The minor spliceosome is very similar to the major spliceosome, but instead it splices out rare introns with different splice site sequences. While the minor and major spliceosomes contain the same U5 snRNP, the minor spliceosome has different but functionally analogous snRNPs for U1, U2, U4, and U6, which are respectively called U11, U12, U4atac, and U6atac. | 1 | Applied and Interdisciplinary Chemistry |
Proteolysis is also used in research and diagnostic applications:
* Cleavage of fusion protein so that the fusion partner and protein tag used in protein expression and purification may be removed. The proteases used have high degree of specificity, such as thrombin, enterokinase, and TEV protease, so that only the targeted sequence may be cleaved.
* Complete inactivation of undesirable enzymatic activity or removal of unwanted proteins. For example, proteinase K, a broad-spectrum proteinase stable in urea and SDS, is often used in the preparation of nucleic acids to remove unwanted nuclease contaminants that may otherwise degrade the DNA or RNA.
* Partial inactivation, or changing the functionality, of specific protein. For example, treatment of DNA polymerase I with subtilisin yields the Klenow fragment, which retains its polymerase function but lacks 5'-exonuclease activity.
* Digestion of proteins in solution for proteome analysis by liquid chromatography-mass spectrometry (LC-MS). This may also be done by in-gel digestion of proteins after separation by gel electrophoresis for the identification by mass spectrometry.
* Analysis of the stability of folded domain under a wide range of conditions.
* Increasing success rate of crystallisation projects
* Production of digested protein used in growth media to culture bacteria and other organisms, e.g. tryptone in Lysogeny Broth. | 1 | Applied and Interdisciplinary Chemistry |
Before entering a tanning unit, the tanner usually applies indoor tanning lotion to the whole body and may use a separate facial-tanning lotion. These lotions are considerably more expensive than drugstore lotions. They contain no sunscreen, but instead moisturize the skin with ingredients such as aloe vera, hempseed oil and sunflower seed oil. They may also contain dihydroxyacetone, a sunless tanner. So-called "tingle" tanning lotions cause vasodilation, increasing blood circulation.
Goggles (eye protection) should be worn to avoid eye damage. In one 2004 study, tanners said they avoided goggles to prevent leaving pale skin around the eyes. In the US, CFR Title 21 requires that new tanning equipment come with eye protection and most states require that commercial tanning operators provide eye protection for their clients. Laws in other countries are similar. | 0 | Theoretical and Fundamental Chemistry |
Latvian Academy of Sciences named a biannual prize for advances in chemistry in Gustavs Vanags' name.
A commemorative plaque with bas-relief of G. Vanags is installed in the hall of Riga Technical University Faculty of Chemistry. A commemorative stone is erected at the place where his native house of "Rungas" once stood. | 0 | Theoretical and Fundamental Chemistry |
Officials used hydrometeorological data to create an image of what the potential nuclear fallout looked like after the Chernobyl disaster in 1986. Using this method, they were able to determine the distribution of radionuclides in the surrounding area, and discovered emissions from the nuclear reactor itself. These emissions included; fuel particles, radioactive gases, and aerosol particles. The fuel particles were due to the violent interaction between hot fuel and the cooling water in the reactor, and attached to these particles were Cerium, Zirconium, Lanthanum, and Strontium. All of these elements have low volatility, meaning they prefer to stay in a liquid or solid state rather than condensing into the atmosphere and existing as vapor.
* Cerium and Lanthanum can cause irreversible damage to marine life by deteriorating cell membranes, affecting reproductive capability, as well as crippling the nervous system.
* Strontium in its non-nuclear isotope is stable and harmless, however, when the radioactive isotope, Sr, is released into the atmosphere it can lead to anemia, cancers, and cause shortages in oxygen.
* The aerosol particles had traces of Tellurium, a toxic element which can create issues in developing fetuses, along with Caesium, which is an unstable, incredibly reactive, and toxic element.
* Also found in the aerosol particles was enriched Uranium-235.
* The most prevalent radioactive gas detected was Radon, a noble gas that has no odor, no color, and no taste, and can also travel into the atmosphere or bodies of water. Radon is also directly linked to lung cancer, and is the second leading cause of lung cancer in the populace.
All of these elements only deteriorate through radioactive decay, which is also known as a half-life. Half-lives of the nuclides previously discussed can range from mere hours, to decades. The shortest half-life for the previous elements is Zr, an isotope of zirconium which takes 1.4 hours to decay. The longest is Pu, which takes approximately 24,000 years to decay. While the initial release of these particles and elements was rather large, there were multiple low-level releases for at least a month after the initial incident at Chernobyl. | 0 | Theoretical and Fundamental Chemistry |
In analytical chemistry, glow discharges are usually operated in direct-current mode. For direct-current, the cathode (which is the sample in solids analysis) must be conductive. In contrast, analysis of a non conductive cathode requires the use of a high frequency alternating current.
The potential, pressure, and current are interrelated. Only two can be directly controlled at once, while the third must be allowed to vary. The pressure is most typically held constant, but other schemes may be used. The pressure and current may be held constant, while potential is allowed to vary. The pressure and voltage may be held constant while the current is allowed to vary. The power (product of voltage and current) may be held constant while the pressure is allowed to vary.
Glow discharges may also be operated in radio-frequency. The use of this frequency will establish a negative DC-bias voltage on the sample surface. The DC-bias is the result of an alternating current waveform that is centered about negative potential; as such it more or less represent the average potential residing on the sample surface. Radio-frequency has ability to appear to flow through insulators (non-conductive materials).
Both radio-frequency and direct-current glow discharges can be operated in pulsed mode, where the potential is turned on and off. This allows higher instantaneous powers to be applied without excessively heating the cathode. These higher instantaneous powers produce higher instantaneous signals, aiding detection. Combining time-resolved detection with pulsed powering results in additional benefits. In atomic emission, analyte atoms emit during different portions of the pulse than background atoms, allowing the two to be discriminated. Analogously, in mass spectrometry, sample and background ions are created at different times. | 0 | Theoretical and Fundamental Chemistry |
Libration (from the Latin verb librare "to balance, to sway"; cf. libra "scales") is a type of reciprocating motion in which an object with a nearly fixed orientation repeatedly rotates slightly back and forth. In physics and chemistry, a molecule (or other group of atoms) can undergo libration if it is subject to external forces or constraints that restrict its orientation.
For example, in liquid water, any given water molecule is attracted to neighboring molecules, so that it has a preferred orientation and cannot freely rotate. (Of course, over time, the neighboring molecules move around and the preferred orientation changes.) However, it can undergo librational motions, which are measureable in an infrared absorption spectrum and contribute to motional narrowing of other peaks, for instance the OH stretch.
Another example is a molecular crystal: Each molecular unit has a preferred orientation due to interactions with the nearby molecules, but they have librational modes corresponding to small rotations about this preferred orientation. | 0 | Theoretical and Fundamental Chemistry |
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