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Queen's Metal, an alloy of nine parts tin and one each of antimony, lead, and bismuth, is intermediate in hardness between pewter and britannia metal. It was developed by English pewtersmiths in the 16th century; the recipe was initially a secret and was reserved for pieces made for the English royal family. | 1 | Applied and Interdisciplinary Chemistry |
Lawessons reagent (LR) is a chemical compound used in organic synthesis as a thiation agent. Lawessons reagent was first made popular by Sven-Olov Lawesson, who did not, however, invent it. Lawesson's reagent was first made in 1956 during a systematic study of the reactions of arenes with PS. | 0 | Theoretical and Fundamental Chemistry |
The mean daily BSi rate strongly depends on the region:
* Coastal upwelling: 46 mmol.m.d
* Sub-arctic Pacific: 18 mmol.m.d
* Southern Ocean: 3–38 mmol.m.d
* mid-ocean gyres: 0.2–1.6 mmol.m.d
Likewise, the integrated annual BSi production strongly depends on the region:
* Coastal upwelling: 3 × 10 mol.yr
* Subarctic Pacific: 8 × 10 mol.yr
* Southern Ocean: 17–37 × 10 mol.yr
* mid-ocean gyres: 26 × 10 mol.yr
BSi production is controlled by:
* Dissolved silica availability, however, half saturation constant Kμ for silicon-limited growth is lower than Ks for silicon uptake.
* Light availability: There is no direct light requirement; silicon uptake at 2x depth of photosynthesis; silicon uptake continues at night but cells must be actively growing.
* Micronutrient availability. | 1 | Applied and Interdisciplinary Chemistry |
. The coordinate system has been chosen to move with the shock so that the particle velocities outside the shock are zero. The shock front does not change with time in a stationary shock.
Comment:
The graphs contain rarefaction shock wave (density behind the wave is less than that ahead of the jump); for normal gas (for example, for perfect gas) this contradicts the second law of thermodynamics (Zemplén theorem).
The Rankine–Hugoniot conditions, also referred to as Rankine–Hugoniot jump conditions or Rankine–Hugoniot relations, describe the relationship between the states on both sides of a shock wave or a combustion wave (deflagration or detonation) in a one-dimensional flow in fluids or a one-dimensional deformation in solids. They are named in recognition of the work carried out by Scottish engineer and physicist William John Macquorn Rankine and French engineer Pierre Henri Hugoniot.
The basic idea of the jump conditions is to consider what happens to a fluid when it undergoes a rapid change. Consider, for example, driving a piston into a tube filled with non-reacting gas. A disturbance is propagated through the fluid somewhat faster than the speed of sound. Because the disturbance propagates supersonically, it is a shock wave, and the fluid downstream of the shock has no advance information of it. In a frame of reference moving with the wave, atoms or molecules in front of the wave slam into the wave supersonically. On a microscopic level, they undergo collisions on the scale of the mean free path length until they come to rest in the post-shock flow (but moving in the frame of reference of the wave or of the tube). The bulk transfer of kinetic energy heats the post-shock flow. Because the mean free path length is assumed to be negligible in comparison to all other length scales in a hydrodynamic treatment, the shock front is essentially a hydrodynamic discontinuity. The jump conditions then establish the transition between the pre- and post-shock flow, based solely upon the conservation of mass, momentum, and energy. The conditions are correct even though the shock actually has a positive thickness. This non-reacting example of a shock wave also generalizes to reacting flows, where a combustion front (either a detonation or a deflagration) can be modeled as a discontinuity in a first approximation. | 1 | Applied and Interdisciplinary Chemistry |
Chemical additives are small chemical compounds that are added to the crystallization process to increase the yield of crystals. The role of small molecules in protein crystallization had not been well thought of in the early days since they were thought of as contaminants in most case. Smaller molecules crystallize better than macromolecules such as proteins, therefore, the use of chemical additives had been limited prior to the study by McPherson. However, this is a powerful aspect of the experimental parameters for crystallization that is important for biochemists and crystallographers to further investigate and apply. | 0 | Theoretical and Fundamental Chemistry |
Tollens reagent (chemical formula ) is a chemical reagent used to distinguish between aldehydes and ketones along with some alpha-hydroxy ketones which can tautomerize into aldehydes. The reagent consists of a solution of silver nitrate, ammonium hydroxide and some sodium hydroxide (to maintain a basic pH of the reagent solution). It was named after its discoverer, the German chemist Bernhard Tollens. A positive test with Tollens reagent is indicated by the precipitation of elemental silver, often producing a characteristic "silver mirror" on the inner surface of the reaction vessel. | 0 | Theoretical and Fundamental Chemistry |
MIKE 21C is a computer program that simulates the development in the river bed and channel plan form in two dimensions. MIKE 21C was developed by DHI. MIKE 21C uses curvilinear finite difference grids.
Simulated processes with MIKE 21C include bank erosion, scouring and shoaling brought about by activities such as construction and dredging, seasonal fluctuations in flow, etc. | 1 | Applied and Interdisciplinary Chemistry |
Evangelista Torricellis original derivation can be found in the second book De motu aquarum of his Opera Geometrica (see ): He starts a tube AB (Figure (a)) filled up with water to the level A. Then a narrow opening is drilled at the level of B and connected to a second vertical tube BC. Due to the hydrostatic principle of communicating vessels the water lifts up to the same filling level AC in both tubes (Figure (b)). When finally the tube BC is removed (Figure (c)) the water should again lift up to this height, which is named AD in Figure (c). The reason for that behavior is the fact that a droplets falling velocity from a height A to B is equal to the initial velocity that is needed to lift up a droplet from B to A.
When performing such an experiment only the height C (instead of D in figure (c)) will be reached which contradicts the proposed theory. Torricelli attributes this defect to the air resistance and to the fact that the descending drops collide with ascending drops.
Torricelli's argumentation is, as a matter of fact, wrong because the pressure in free jet is the surrounding atmospheric pressure, while the pressure in a communicating vessel is the hydrostatic pressure. At that time the concept of pressure was unknown. | 1 | Applied and Interdisciplinary Chemistry |
Orotidine 5'-monophosphate (OMP), also known as orotidylic acid, is a pyrimidine nucleotide which is the last intermediate in the biosynthesis of uridine monophosphate. OMP is formed from orotate and phosphoribosyl pyrophosphate by the enzyme orotate phosphoribosyltransferase.
In humans, the enzyme UMP synthase converts OMP into uridine 5'- monophosphate. If UMP synthase is defective, orotic aciduria can result. | 1 | Applied and Interdisciplinary Chemistry |
The apparent molar volume of salt is usually less than the molar volume of the solid salt. For instance, solid NaCl has a volume of 27 cm per mole, but the apparent molar volume at low concentrations is only 16.6 cc/mole. In fact, some aqueous electrolytes have negative apparent molar volumes: NaOH −6.7, LiOH −6.0, and NaCO −6.7 cm/mole. This means that their solutions in a given amount of water have a smaller volume than the same amount of pure water. (The effect is small, however.) The physical reason is that nearby water molecules are strongly attracted to the ions so that they occupy less space. | 0 | Theoretical and Fundamental Chemistry |
Triazenes derived from primary amines engage in tautomerism. In the case of symmetric triazenes, the tautomers are identical.
Triazenes can be converted to diazonium salts.
Triazenes decompose in the presence of protonating or alkylating agents into quaternary amines and diazonium salts; as such triazenes have been used as an in situ source of diazonium that reacted with sodium sulfide to give the corresponding thiophenols. A strategy for the protection and deprotection of sensitive secondary amines is based on this principle.
Polymeric triazenes are applied as conductive and absorbent materials. Triazenes have been used in the synthesis of cinnoline, functionalized lactams, and coumarins. | 0 | Theoretical and Fundamental Chemistry |
Consider a spherically outgoing Chapman–Jouguet detonation wave propagating with a constant velocity . By definition, immediately behind the detonation wave, the gas velocity is equal to the local sound speed with respect to the wave. Let be the radial velocity of the gas behind the wave, in a fixed frame. The detonation is ignited at at . For , the gas velocity must be zero at the center and should take the value at the detonation location . The fluid motion is governed by the inviscid Euler equations
where is the density, is the pressure and is the entropy. The last equation implies that the flow is isentropic and hence we can write .
Since there are no length or time scales involved in the problem, one may look for a self-similar solution of the form , where . The first two equations then become
where prime denotes differentiation with respect to . We can eliminate between the two equations to obtain an equation that contains only and . Because of the isentropic condition, we can express , that is to say, we can replace with . This leads to
For polytropic gases with constant specific heats, we have . The above set of equations cannot be solved analytically, but has to be integrated numerically. The solution has to be found for the range subjected to the condition at
The function is found to monotonically decrease from its value to zero at a finite value of , where a weak discontinuity (that is a function is continuous, but its derivatives may not) exists. The region between the detonation front and the trailing weak discontinuity is the rarefaction (or expansion) flow. Interior to the weak discontinuity everywhere. | 1 | Applied and Interdisciplinary Chemistry |
A contig (from contiguous) is a set of overlapping DNA segments that together represent a consensus region of DNA.
In bottom-up sequencing projects, a contig refers to overlapping sequence data (reads); in top-down sequencing projects, contig refers to the overlapping clones that form a physical map of the genome that is used to guide sequencing and assembly. Contigs can thus refer both to overlapping DNA sequences and to overlapping physical segments (fragments) contained in clones depending on the context. | 1 | Applied and Interdisciplinary Chemistry |
In nature, carbon fixation is done by green plants using the enzyme RuBisCO as a part of the Calvin cycle. RuBisCO is a rather slow catalyst compared to the vast majority of other enzymes, incorporating only a few molecules of carbon dioxide into ribulose-1,5-bisphosphate per minute, but does so at atmospheric pressure and in mild, biological conditions. The resulting product is further reduced and eventually used in the synthesis of glucose, which in turn is a precursor to more complex carbohydrates, such as cellulose and starch. The process consumes energy in the form of ATP and NADPH.
Artificial CO reduction for fuel production aims mostly at producing reduced carbon compounds from atmospheric CO. Some transition metal polyphosphine complexes have been developed for this end; however, they usually require previous concentration of CO before use, and carriers (molecules that would fixate CO) that are both stable in aerobic conditions and able to concentrate CO at atmospheric concentrations haven't been yet developed. The simplest product from CO reduction is carbon monoxide (CO), but for fuel development, further reduction is needed (for example, to multi-carbon products), and a key step also needing further development is the transfer of hydride anions to CO. | 0 | Theoretical and Fundamental Chemistry |
After studying in Berlin with Carl Liebermann, he received his Ph.D at the University of Göttingen. Giesel worked at the Chininfabrik Braunschweig. Besides his work in the factory, Giesel's focus was on radiochemistry. Shortly after publication of the discovery of polonium in the summer of 1898, he started to isolate the new element from the waste of uranium production in the chemical plant E. de Haën in Hanover. By March 1899 he could present the first radium to the chemical society of Braunschweig and by mid-1899 he published his results on radium. Giesel improved the separation of radium from barium by using the bromides instead of the chlorides for the fractional crystallization. He produced large quantities of pure radium and polonium for commercial applications from uranium ore. Even William Ramsay and Frederick Soddy were buying radium from the factory of Giesel.
The use of Sidots blende (zinc sulfide) instead of barium platinocyanide as a luminescence material to make the radioactive rays visible was a commonly accepted improvement. He did several self-experiments with radioactive substances and was able to affirm the damaging effects of radioactive radiation on skin. Because of prolonged contact with radioactive material, fingers of his right hand had to be amputated and he suffered from lung cancer. He died of lung cancer in 1927. His name was included on the Monument to the X-ray and Radium Martyrs of All Nations' erected in Hamburg, Germany in 1936. | 1 | Applied and Interdisciplinary Chemistry |
The ketone carbon is often described as sp hybridized, a description that includes both their electronic and molecular structure. Ketones are trigonal planar around the ketonic carbon, with C–C–O and C–C–C bond angles of approximately 120°. Ketones differ from aldehydes in that the carbonyl group (C=O) is bonded to two carbons within a carbon skeleton. In aldehydes, the carbonyl is bonded to one carbon and one hydrogen and are located at the ends of carbon chains. Ketones are also distinct from other carbonyl-containing functional groups, such as carboxylic acids, esters and amides.
The carbonyl group is polar because the electronegativity of the oxygen is greater than that for carbon. Thus, ketones are nucleophilic at oxygen and electrophilic at carbon. Because the carbonyl group interacts with water by hydrogen bonding, ketones are typically more soluble in water than the related methylene compounds. Ketones are hydrogen-bond acceptors. Ketones are not usually hydrogen-bond donors and cannot hydrogen-bond to themselves. Because of their inability to serve both as hydrogen-bond donors and acceptors, ketones tend not to "self-associate" and are more volatile than alcohols and carboxylic acids of comparable molecular weights. These factors relate to the pervasiveness of ketones in perfumery and as solvents. | 0 | Theoretical and Fundamental Chemistry |
Analysis is usually made up of three steps
* Solving heat and material balances
* Sizing and costing the equipment and
* Evaluating the economic worth, safety, operability etc. of the chosen flow sheet | 1 | Applied and Interdisciplinary Chemistry |
Adhesion GPCRs appear capable to follow standard GPCR signaling modes and signal through Gαs, Gαq, Gαi, and Gα12/13. As of today, many of the adhesion GPCRs are still orphan receptors and their signalling pathways have not been identified. Research groups are working to elucidate the downstream signaling molecules utilizing several methods, including chemical screens and analysis of second messenger levels in over-expressed cells. Adding drugs in vitro, while the cells are over-expressing an adhesion GPCR, has allowed the identification of the molecules activating the GPCR and the second messengers being utilized.
GPR133 signals through Gαs to activate adenylyl cyclase. It has been shown that overexpressing GPCRs in vitro can result in receptor activation in the absence of a ligand or agonist. By over expressing GPR133 in vitro, an elevation in reporter genes and cAMP was observed. Signaling of the overexpressed GPR133 did not require an N-terminus or GPS cleavage. Missense mutations in the 7TM region resulted in loss of signalling.
The latrophilin homolog LPHN1 was shown in C. elegans to require a GPS for signaling, but cleavage at the GPS site was not necessary. Furthermore, having a shortened 7 transmembrane domain, but with an intact GPS domain, resulted in a loss of signaling. This suggests that having both the GPS and 7 transmembrane domain intact is involved in signaling and that the GPS site could act as or be a necessary part of an endogenous ligand.
GPR56 has been shown to be cleaved at the GPS site and then remain associated with the 7TM domain. In a study where the N-terminus was removed up to N342 (the start of the GPS), the receptor became constitutively active and an up regulation of Gα12/13 was seen. When receptors are active, they are ubiquitinated and GPR56 lacking an N-terminus was highly ubiquitinated. | 1 | Applied and Interdisciplinary Chemistry |
There may be a general misconception between the term corrosion inspection and corrosion monitoring, but inspection means frequent checkpoints to check for changes or deviations from predicted results, while corrosion monitoring is a continuous check to control and act quickly against change. In inspection, the purpose is to evaluate or estimate the corrosion time in order to replace or correct the corrosion, while in corrosion monitoring, the purpose is to take care of the change in order to prevent corrosion and to improve the ways of prevention. | 1 | Applied and Interdisciplinary Chemistry |
The ratio of H, also known as deuterium, to H has been studied in both plant and animal tissue. Hydrogen isotopes in plant tissue are correlated with local water values but vary based on fractionation during photosynthesis, transpiration, and other processes in the formation of cellulose. A study on the isotope ratios of tissues from plants growing within a small area in Texas found tissues from CAM plants were enriched in deuterium relative to C4 plants. Hydrogen isotope ratios in animal tissue reflect diet, including drinking water, and have been used to study bird migration and aquatic food webs. | 0 | Theoretical and Fundamental Chemistry |
Trifluoromethylsulfur pentafluoride, CFSF, is a rarely used industrial greenhouse gas. It was first identified in the atmosphere in 2000. Trifluoromethylsulfur pentafluoride is considered to be one of the several "super-greenhouse gases". | 1 | Applied and Interdisciplinary Chemistry |
Hydride generation techniques are specialized in solutions of specific elements. The technique provides a means of introducing samples containing arsenic, antimony, selenium, bismuth, and lead into an atomizer in the gas phase. With these elements, hydride atomization enhances detection limits by a factor of 10 to 100 compared to alternative methods. Hydride generation occurs by adding an acidified aqueous solution of the sample to a 1% aqueous solution of sodium borohydride, all of which is contained in a glass vessel. The volatile hydride generated by the reaction that occurs is swept into the atomization chamber by an inert gas, where it undergoes decomposition. This process forms an atomized form of the analyte, which can then be measured by absorption or emission spectrometry. | 0 | Theoretical and Fundamental Chemistry |
The dynamic behavior of Min proteins has been reconstituted in vitro using artificial lipid bilayers, with varying lipid composition and different confinement geometry as mimics for the cell membrane. The first pattern to be reconstituted were spiraling waves of MinD chased by MinE, followed by the reconstitution of waves of all three proteins, MinD, MinE and MinC. Importantly, MinD and MinE can self-organize into a wide variety of patterns depending on the reaction conditions.
Additional study is required to elucidate the extent of temporal and spatial signaling permissible by this biological function. These in vitro systems offered unprecedented access to features such as residence times and molecular motility. | 1 | Applied and Interdisciplinary Chemistry |
Silver-thiosulfate complexes are produced by common photographic fixers. By dissolving silver halides the fixer stabilises the image. The dissolution process entails reactions involving the formation of 1:2 and 1:3 complexes (X = halide): Fixation involves these chemical reactions (X = halide, typically ):
Sodium aurothiosulfate dihydrate, , has been widely discussed in the context of the extraction of gold from its ores. Presently cyanide salts are used on a large scale for that
purpose with obvious risks. | 0 | Theoretical and Fundamental Chemistry |
Alain-Edgard Berton (1912–1979) was a French chemical engineer who specialized in toxicology and in the analysis of air components in industrial environments. In the late 1950s he invented the "Osmopile", a measuring device, dubbed "the first artificial nose," which initiated, through the use of highly sensitive galvanic cells, the electrochemical analysis of air to detect dangerous components. | 0 | Theoretical and Fundamental Chemistry |
The highest flux of solar neutrinos come directly from the proton–proton interaction, and have a low energy, up to 400 keV. There are also several other significant production mechanisms, with energies up to 18 MeV. From the Earth, the amount of neutrino flux at Earth is around 7·10 particles·cm·s . The number of neutrinos can be predicted with great confidence by the standard solar model, but the number of neutrinos detected on Earth versus the number of neutrinos predicted are different by a factor of a third, which is the solar neutrino problem.
Solar models additionally predict the location within the Sun's core where solar neutrinos should originate, depending on the nuclear fusion reaction which leads to their production. Future neutrino detectors will be able to detect the incoming direction of these neutrinos with enough precision to measure this effect.
The energy spectrum of solar neutrinos is also predicted by solar models. It is essential to know this energy spectrum because different neutrino detection experiments are sensitive to different neutrino energy ranges. The Homestake experiment used chlorine and was most sensitive to solar neutrinos produced by the decay of the beryllium isotope Be. The Sudbury Neutrino Observatory is most sensitive to solar neutrinos produced by B. The detectors that use gallium are most sensitive to the solar neutrinos produced by the proton–proton chain reaction process, however they were not able to observe this contribution separately. The observation of the neutrinos from the basic reaction of this chain, proton–proton fusion in deuterium, was achieved for the first time by Borexino in 2014. In 2012 the same collaboration reported detecting low-energy neutrinos for the proton–electron–proton (pep reaction) that produces 1 in 400 deuterium nuclei in the Sun. The detector contained 100 metric tons of liquid and saw on average 3 events each day (due to C production) from this relatively uncommon thermonuclear reaction.
In 2014, Borexino reported a successful direct detection of neutrinos from the pp-reaction at a rate of 144±33/day, consistent with the predicted rate of 131±2/day that was expected based on the standard solar model prediction that the pp-reaction generates 99% of the Suns luminosity and their analysis of the detectors efficiency.
And in 2020, Borexino reported the first detection of CNO cycle neutrinos from deep within the solar core.
Note that Borexino measured neutrinos of several energies; in this manner they have demonstrated experimentally, for the first time, the pattern of solar neutrino oscillations predicted by the theory. Neutrinos can trigger nuclear reactions. By looking at ancient ores of various ages that have been exposed to solar neutrinos over geologic time, it may be possible to interrogate the luminosity of the Sun over time, which, according to the standard solar model, has changed over the eons as the (presently) inert byproduct helium has accumulated in its core. | 0 | Theoretical and Fundamental Chemistry |
* First position – primary direction – z direction, assigned to the higher-order axis.
* Second position – symmetrically equivalent secondary directions, which are perpendicular to the z-axis. These can be 2, m, or
* Third position – symmetrically equivalent tertiary directions, passing between secondary directions. These can be 2, m, or
These are the crystallographic groups 3, 32, 3m, , and (trigonal crystal system), 4, 422, 4mm, , 2m, , and (tetragonal), and 6, 622, 6mm, , m2, , and (hexagonal). Analogously, symbols of non-crystallographic groups (with axes of order 5, 7, 8, 9, ...) can be constructed. These groups can be arranged in the following table
It can be noticed that in groups with odd-order axes n and the third position in symbol is always absent, because all n directions, perpendicular to higher-order axis, are symmetrically equivalent. For example, in the picture of a triangle all three mirror planes (S, S, S) are equivalent – all of them pass through one vertex and the center of the opposite side.
For even-order axes n and there are secondary directions and tertiary directions. For example, in the picture of a regular hexagon one can distinguish two sets of mirror planes – three planes go through two opposite vertexes, and three other planes go through the centers of opposite sides. In this case any of two sets can be chosen as secondary directions, the rest set will be tertiary directions. Hence groups 2m, 2m, 2m, ... can be written as m2, m2, m2, ... . For symbols of point groups this order usually doesnt matter; however, it will be important for Hermann–Mauguin symbols of corresponding space groups, where secondary directions are directions of symmetry elements along unit cell translations b and c, while the tertiary directions correspond to the direction between unit cell translations b and c. For example, symbols Pm2 and P2m denote two different space groups. This also applies to symbols of space groups with odd-order axes 3 and . The perpendicular symmetry elements can go along unit cell translations b and c' or between them. Space groups P321 and P312 are examples of the former and the latter cases, respectively.
The symbol of point group may be confusing; the corresponding Schoenflies symbol is D, which means that the group consists of 3-fold axis, three perpendicular 2-fold axes, and 3 vertical diagonal planes passing between these 2-fold axes, so it seems that the group can be denoted as 32m or 3m2. However, one should remember that, unlike Schoenflies notation, the direction of a plane in a Hermann–Mauguin symbol is defined as the direction perpendicular to the plane, and in the D group all mirror planes are perpendicular to 2-fold axes, so they should be written in the same position as . Second, these complexes generate an inversion center, which combining with the 3-fold rotation axis generates a rotoinversion axis.
Groups with n = ∞ are called limit groups or Curie groups. | 0 | Theoretical and Fundamental Chemistry |
Since the Trinity test and excluding combat use, countries with nuclear weapons have detonated roughly 1,700 nuclear explosions, all but six as tests. Of these, six were peaceful nuclear explosions. Nuclear tests are experiments carried out to determine the effectiveness, yield and explosive capability of nuclear weapons. Throughout the 20th century, most nations that have developed nuclear weapons had a staged test of them. Testing nuclear weapons can yield information about how the weapons work, as well as how the weapons behave under various conditions and how structures behave when subjected to a nuclear explosion. Additionally, nuclear testing has often been used as an indicator of scientific and military strength, and many tests have been overtly political in their intention; most nuclear weapons states publicly declared their nuclear status by means of a nuclear test. Nuclear tests have taken place at more than 60 locations across the world; some in secluded areas and others more densely populated. Detonation of nuclear weapons (in a test or during war) releases radioactive fallout that concerned the public in the 1950s. This led to the Limited Test Ban Treaty of 1963 signed by the United States, Great Britain, and the Soviet Union. This treaty banned nuclear weapons testing in the atmosphere, outer space, and under water. | 0 | Theoretical and Fundamental Chemistry |
Glass containing two or more phases with different refractive indices shows coloring based on the Tyndall effect and explained by the Mie theory, if the dimensions of the phases are similar or larger than the wavelength of visible light. The scattered light is blue and violet as seen in the image, while the transmitted light is yellow and red. | 0 | Theoretical and Fundamental Chemistry |
Protocol databases correlate results from bioassays to their metadata about experimental conditions and protocol designs. | 1 | Applied and Interdisciplinary Chemistry |
Very analogous to ketones and aldehydes, primary imines are susceptible to attack by carbanion equivalents. The method allow for the synthesis of secondary amines:
:RC=NR + R"Li → RR"CN(Li)R
:RR"CN(Li)R + HO → RR"CNHR + LiOH | 0 | Theoretical and Fundamental Chemistry |
Gustav Robert Kirchhoff, “IV. Ueber das Verhältniß zwischen dem Emissionsvermögen und dem Absorptionsvermögen der Körper für Wärme und Licht,” Annalen der Physik 185(2), 275-301 (1860). (coinage of term “blackbody”) [On the relationship between the emissivity and the absorptivity of bodies for heat and light] | 1 | Applied and Interdisciplinary Chemistry |
Bacterial populations interact in a similar manner to cells in tissue. They communicate through physical interactions and signaling molecules such as homoserine lactones and peptides as a means to control metabolism and regulate growth . A common example and one of the most studied forms of bacterial cell interactions is biofilm. Biofilm is a cell aggregate that can be attached to biological or abiotic surfaces. Bacteria form biofilms to adapt to various environments such as changes in substrate availability. For example, the formation of biofilm increases a bacterial cell's resistance to antibiotics compared to cells which are not part of the aggregate. | 1 | Applied and Interdisciplinary Chemistry |
The Sommerfeld Number is typically defined by the following equation:
where:
: S is the Sommerfeld Number or bearing characteristic number
: r is the shaft radius
: c is the radial clearance
: µ is the absolute viscosity of the lubricant
: N is the speed of the rotating shaft in rev/s
: P is the load per unit of projected bearing area
The second part of the equation is seen to be the Hersey number. However, an alternative definition for S is used in some texts based on angular velocity:
where:
: is angular velocity of the shaft in rad/s.
: W is the applied load
: L is the bearing length
: D is the bearing diameter
It is therefore necessary to check which definition is being used when referring to design data or textbooks, since the value of S will differ by a factor of 2π. | 1 | Applied and Interdisciplinary Chemistry |
Mice can distinguish close relatives from more distantly related individuals on the basis of scent signals, which enables them to avoid mating with close relatives and minimizes deleterious inbreeding.
In addition to mice, two species of bumblebee, in particular Bombus bifarius and Bombus frigidus, have been observed to use pheromones as a means of kin recognition to avoid inbreeding. For example, B. bifarius males display "patrolling" behavior in which they mark specific paths outside their nests with pheromones and subsequently "patrol" these paths. Unrelated reproductive females are attracted to the pheromones deposited by males on these paths, and males that encounter these females while patrolling can mate with them. Other bees of the Bombus species are found to emit pheromones as precopulatory signals, such as Bombus lapidarius. | 1 | Applied and Interdisciplinary Chemistry |
Some substances that appear to be solid, can be shown to instead be extremely viscous liquids, because they form drops and display droplet behavior. In the famous pitch drop experiments, pitch – a substance somewhat like solid bitumen – is shown to be a liquid in this way. Pitch in a funnel slowly forms droplets, each droplet taking about 10 years to form and break off. | 1 | Applied and Interdisciplinary Chemistry |
Carbon catabolite repression, or simply catabolite repression, is an important part of global control system of various bacteria and other microorganisms. Catabolite repression allows microorganisms to adapt quickly to a preferred (rapidly metabolizable) carbon and energy source first. This is usually achieved through inhibition of synthesis of enzymes involved in catabolism of carbon sources other than the preferred one. The catabolite repression was first shown to be initiated by glucose and therefore sometimes referred to as the glucose effect. However, the term "glucose effect" is actually a misnomer since other carbon sources are known to induce catabolite repression. | 1 | Applied and Interdisciplinary Chemistry |
On 24 April 1939, Paul Harteck and his assistant, Wilhelm Groth, had written to Reich Ministry of War, alerting it to the possibility of the development of an atomic bomb. In response, the Army Weapons Branch (HWA) had established a physics section under nuclear physicist Kurt Diebner. After World War II broke out on 1 September 1939, the HWA moved to control the German nuclear weapons program. From then on, Hahn participated in a ceaseless series of meetings related to the project. After the Director of the Kaiser Wilhelm Institute for Physics, Peter Debye, left for the United States in 1940 and never returned, Diebner was installed as its director. Hahn reported to the HWA on the progress of his research. Together with his assistants, Hans-Joachim Born, Siegfried Flügge, Hans Götte, Walter Seelmann-Eggebert and Strassmann, he catalogued about one hundred fission product isotopes. They also investigated means of isotope separation; the chemistry of element 93; and methods for purifying uranium oxides and salts.
On the night of 15 February 1944, the Kaiser Wilhelm Institute for Chemistry building was struck by a bomb. Hahn's office was destroyed, along with his correspondence with Rutherford and other researchers, and many of his personal possessions. The office was the intended target of the raid, which had been ordered by Brigadier General Leslie Groves, the director of the Manhattan Project, in the hope of disrupting the German uranium project. Albert Speer, the Reich Minister of Armaments and War Production, arranged for the institute to move to Tailfingen in southern Germany. All work in Berlin ceased by July. Hahn and his family moved to the house of a textile manufacturer there.
Life became precarious for those married to Jewish women. One was Philipp Hoernes, a chemist working for Auergesellschaft, the firm that mined the uranium ore used by the project. After the firm let him go in 1944, Hoernes faced being conscripted for forced labour. At the age of 60, it was doubtful that he would survive. Hahn and Nikolaus Riehl arranged for Hoernes to work at the Kaiser Wilhelm Institute for Chemistry, claiming that his work was essential to the uranium project and that uranium was highly toxic, making it hard to find people to work with it. Hahn was aware that uranium ore was fairly safe in the laboratory, although not so much for the 2,000 female slave labourers from Sachsenhausen concentration camp who mined it in Oranienburg. Another physicist with a Jewish wife was . Hahn certified that his work was important to the war effort, and that his wife Maria, who had a doctorate in physics, was required as his assistant. After he died on 19 September 1944, Maria faced being sent to a concentration camp. Hahn mounted a lobbying campaign to get her released, but to no avail, and she was sent to the Theresienstadt Ghetto in January 1945. She survived the war, and was reunited with her daughters in England after the war. | 0 | Theoretical and Fundamental Chemistry |
In situ, controlled perturbation experiments, often conducted over weeks to months, can provide inference concerning the response of natural communities to ocean acidification that is difficult or impossible to derive from laboratory experiments. Studies conducted in situ can include the effects of potentially important factors such as natural variation in planktonic food resources, larval abundance, changes in predators or competitors, as well as oceanographic conditions (e.g. changes in upwelling intensity). Drawing on the experience of Free Air CO Enrichment (FACE) experiments used to investigate the response of terrestrial plant communities to rising atmospheric CO levels, the scientific community has developed an analogous approach, Free Ocean CO Enrichment (FOCE) experiments, for studying marine communities, and to complement a range of experimental methods and technologies for ocean acidification studies research. FOCE was first proposed and implemented by researchers at the Monterey Bay Aquarium Research Institute (MBARI). | 0 | Theoretical and Fundamental Chemistry |
The fossil record for lichens is poor. The extreme habitats that lichens dominate, such as tundra, mountains, and deserts, are not ordinarily conducive to producing fossils. There are fossilized lichens embedded in amber. The fossilized Anzia is found in pieces of amber in northern Europe and dates back approximately 40 million years. Lichen fragments are also found in fossil leaf beds, such as Lobaria from Trinity County in northern California, US, dating back to the early to middle Miocene.
The oldest fossil lichen in which both symbiotic partners have been recovered is Winfrenatia, an early zygomycetous (Glomeromycotan) lichen symbiosis that may have involved controlled parasitism, is permineralized in the Rhynie Chert of Scotland, dating from early Early Devonian, about 400 million years ago. The slightly older fossil Spongiophyton has also been interpreted as a lichen on morphological and isotopic grounds, although the isotopic basis is decidedly shaky. It has been demonstrated that Silurian-Devonian fossils Nematothallus and Prototaxites were lichenized. Thus lichenized Ascomycota and Basidiomycota were a component of Early Silurian-Devonian terrestrial ecosystems. Newer research suggests that lichen evolved after the evolution of land plants.
The ancestral ecological state of both Ascomycota and Basidiomycota was probably saprobism, and independent lichenization events may have occurred multiple times. In 1995, Gargas and colleagues proposed that there were at least five independent origins of lichenization; three in the basidiomycetes and at least two in the Ascomycetes. Lutzoni et al. (2001) suggest lichenization probably evolved earlier and was followed by multiple independent losses. Some non-lichen-forming fungi may have secondarily lost the ability to form a lichen association. As a result, lichenization has been viewed as a highly successful nutritional strategy.
Lichenized Glomeromycota may extend well back into the Precambrian. Lichen-like fossils consisting of coccoid cells (cyanobacteria?) and thin filaments (mucoromycotinan Glomeromycota?) are permineralized in marine phosphorite of the Doushantuo Formation in southern China. These fossils are thought to be 551 to 635 million years old or Ediacaran. Ediacaran acritarchs also have many similarities with Glomeromycotan vesicles and spores. It has also been claimed that Ediacaran fossils including Dickinsonia, were lichens, although this claim is controversial. Endosymbiotic Glomeromycota comparable with living Geosiphon may extend back into the Proterozoic in the form of 1500 million year old Horodyskia and 2200 million year old Diskagma. Discovery of these fossils suggest that fungi developed symbiotic partnerships with photoautotrophs long before the evolution of vascular plants, though the Ediacaran lichen hypothesis is largely rejected due to an inappropriate definition of lichens based on taphonomy and substrate ecology. However, a 2019 study by the same scientist who rejected the Ediacaran lichen hypothesis, Nelsen, used new time-calibrated phylogenies to conclude that there is no evidence of lichen before the existence of vascular plants.
Lecanoromycetes, one of the most common classes of lichen-forming fungi, diverged from its ancestor, which may have also been lichen forming, around 258 million years ago, during the late Paleozoic period. However, the closely related clade Euritiomycetes appears to have become lichen-forming only 52 million years ago, during the early Cenozoic period. | 1 | Applied and Interdisciplinary Chemistry |
EVB has been successfully applied to calculating reaction free energies of enzymes. More recently it has been looked at as a tool to study enzyme evolution and to assist in enzyme design. | 0 | Theoretical and Fundamental Chemistry |
Research has indicated that MFGM, or components thereof, may potentially play roles in brain development and cognitive function, immunity and gut health, and cardiovascular health.
MFGM has a set of proteins and lipids unique to breast milk: lactoferrin, Immunoglobulin G, sialic acid, cholesterol, phospholipids, sphingolipids, gangliosides and choline. All components of the MFGM are important for child development. Phospholipids and gangliosides influence the formation and folding of the cerebral cortex. These structures translate directly into neuronal development and cognitive abilities. The use of MFGM in Geo-Poland [https://laktowit.pl/mfgm/ infant formula] is essential to mimic breast milk. A not insignificant proportion of studies investigating the health effects of formula supplementation with MFGM on infant health were (co-)funded by the cow's milk and formula industry. | 1 | Applied and Interdisciplinary Chemistry |
Any of the thermodynamic potentials may be held constant during a process. For example:
* An isenthalpic process introduces no change in enthalpy in the system. | 0 | Theoretical and Fundamental Chemistry |
Block copolymers are a well-studied and versatile class of self-assembling materials characterized by
chemically distinct polymer blocks that are covalently bonded. This molecular architecture of the
covalent bond enhancement is what causes block copolymers to spontaneously form nanoscale
patterns. In block copolymers, covalent bonds frustrate the natural tendency of each individual polymer to remain separate (in general, different polymers, do not like to mix), so the material assembles into a nano-pattern instead. These copolymers offer the ability to self-assemble into uniform, nanosized micelles and accumulate in tumors via the enhanced permeability and retention effect. Polymer composition can be chosen to control the micelle size and compatibility with the drug of choice. The challenges of this application are the difficulty of reproducing or controlling the size of self-assembly nano micelle, preparing predictable size-distribution, and the stability of the micelle with high drug load content. | 0 | Theoretical and Fundamental Chemistry |
Ambergris is relatively nonreactive to acid. White crystals of a terpenoid known as ambrein, discovered by Leopold Ružička and Fernand Lardon in 1946, can be separated from ambergris by heating raw ambergris in alcohol, then allowing the resulting solution to cool. Breakdown of the relatively scentless ambrein through oxidation produces ambroxide and ambrinol, the main odor components of ambergris.
Ambroxide is now produced synthetically and used extensively in the perfume industry. | 1 | Applied and Interdisciplinary Chemistry |
Myristamine oxide is an amine oxide based zwitterionic surfactant with a C (tetradecyl) alkyl tail. It is used as a foam stabilizer and hair conditioning agent in some shampoos and conditioners. Like other amine oxide based surfactants it is antimicrobial, being slightly more effective than lauryldimethylamine oxide against the common bacteria S. aureus and E. coli. | 0 | Theoretical and Fundamental Chemistry |
Lasers are used to couple each ion's internal and external motional degrees of freedom. The Coulomb interaction between the two ions couples their motion. This allows the internal state of one ion to be transferred to the other. An auxiliary "logic ion" provides cooling, state preparation, and state detection for the co-trapped "spectroscopy ion," which has an electronic transition of interest. The logic ion is used to sense and control the internal and external state of the spectroscopy ion.
The logic ion is selected to have a simple energy level structure that can be directly laser cooled, often an alkaline earth ion. The laser cooled logic ion provides sympathetic cooling to the spectroscopy ion, which lacks an efficient laser cooling scheme. Cooling the spectroscopy ion reduces the number of rotational and vibrational states that it can occupy. The remaining states are then accessed by driving stimulated Raman spectroscopy transitions with a laser. The light used for driving these transitions is far off-resonant from any electronic transitions. This enables control over the spectroscopy ion's rotational and vibrational state.
Thus far, QLS is limited to diatomic molecules with a mass within 1 AMU of the laser cooled "logic" ion. This is largely due to poorer coupling of the motional states of the occupants of the ion trap as the mass mismatch becomes larger. Other techniques more tolerant of large mass mismatches are better suited to cases where the ultimate resolution of QLS is not needed, but single-molecule sensitivity is still desired. | 0 | Theoretical and Fundamental Chemistry |
There are two main non-correlation alternatives to FCS that are widely used to study the dynamics of fluorescent species. | 0 | Theoretical and Fundamental Chemistry |
C (peak levels) occurs approximately 2 to 3 hours after modafinil administration. Food slows absorption of modafanil, but does not affect the total AUC. In vitro measurements indicate that 60% of modafinil is bound to plasma proteins at clinical concentrations of the drug. This percentage changes very little when the concentration of modafinil is varied.
Renal excretion of unchanged modafinil usually accounts for less than 10% of an oral dose. This means that when modafinil is taken by mouth, less than 10% of the drug is eliminated from the body through the urine without being metabolized by the liver or other organs. The rest of the drug is either metabolized or excreted through other routes, such as feces or bile.
The two major circulating metabolites of modafinil are modafinil acid (CRL-40467) and modafinil sulfone (CRL-41056). Both of these metabolites have been described as inactive, and neither appears to contribute to the wakefulness-promoting effects of modafinil. However, modafinil sulfone does appear to possess anticonvulsant effects, a property that it shares with modafinil.
Elimination half-life is in the range of 10 to 12 hours, subject to differences in sex, in cytochrome P450 genotypes, liver function and renal function. Modafinil is metabolized mainly in the liver, and its inactive metabolites are excreted in the urine. Urinary excretion of the unchanged drug is usually less than 10%, but can range from 0% to as high as 18.7%, depending on the factors mentioned.
Modafinil exhibits sex-specific pharmacokinetic differences. It demonstrates higher bioavailability in women compared to men. The mean C is higher in women than in men, vs. (p < 0.05), following a single oral dose of modafinil. This difference persists even after adjusting for body weight ( vs. ). The clearance of modafinil is 30% higher in men than in women, and plasma concentrations after a single dose are significantly higher in women than in men. These sex-specific pharmacokinetic differences may have implications for the efficacy and safety of modafinil. | 0 | Theoretical and Fundamental Chemistry |
Gag/pol translational readthrough site (or Retroviral readthrough element) is a cis-regulatory element found in retroviruses. The readthrough site facilitates the mechanism of translation readthrough of the stop codon at the gag-pol junction producing the gag and pol fusion protein in certain retroviruses.
Retroviruses whose gag and pol genes are in the same reading frame often depend upon approximately 5% read-through of the gag UAG termination codon to form the gag-pol polyprotein. This readthrough is usually dependent on a pseudoknot located eight nucleotides downstream of the stop codon (UAG). Sequence conservation is found in the second pseudoknot loop. | 1 | Applied and Interdisciplinary Chemistry |
The first method to detect A-to-I RNA modifications, developed in 1997, was inosine-specific cleavage. RNA samples are treated with glyoxal and borate to specifically modify all G bases, and subsequently enzymatically digested to by RNase T1, which cleaves after I sites. The amplification of these fragments then allows analysis of cleavage sites and inference of A-to-I modification.
. It was used to prove the position of inosine at specific sites rather than identify novel sites or transcriptome-wide profiles. | 1 | Applied and Interdisciplinary Chemistry |
A bioassay is an analytical method to determine the potency or effect of a substance by its effect on living animals or plants (in vivo), or on living cells or tissues (in vitro). A bioassay can be either quantal or quantitative, direct or indirect. If the measured response is binary, the assay is quantal; if not, it is quantitative.
A bioassay may be used to detect biological hazards or to give an assessment of the quality of a mixture. A bioassay is often used to monitor water quality as well as wastewater discharges and its impact on the surroundings. It is also used to assess the environmental impact and safety of new technologies and facilities.
Bioassays are essential in pharmaceutical, medical and agricultural sciences for development and launching of new drugs, vitamins, etc. | 1 | Applied and Interdisciplinary Chemistry |
Tissue clearing refers to a group of chemical techniques used to turn tissues transparent. This allows deep insight into these tissues, while preserving spatial resolution. Many tissue clearing methods exist, each with different strengths and weaknesses. Some are generally applicable, while others are designed for specific applications. Tissue clearing is usually combined with one or more labeling techniques and subsequently imaged, most often by optical sectioning microscopy techniques. Tissue clearing has been applied to many areas in biological research. | 1 | Applied and Interdisciplinary Chemistry |
Camphorsultam, or Oppolzer's sultam, is a classic chiral auxiliary.
In the total synthesis of manzacidin B, Ohfune group utilized camphorsultam to construct the core oxazoline ring asymmetrically. Comparing with oxazolidinone as the chiral auxiliary, camphorsultam had a significant (2S,3R)-selectivity.
Camphorsultam also acts as a chiral auxiliary in Michael addition. Lithium base promoted stereoselective Michael addition of thiols to N-mcthacryloylcamphorsultam produced the corresponding addition products in high diastereoselectivity.
Camphorsultam was used as a chiral auxiliary for the asymmetric Claisen rearrangement. In the presence of butylated hydroxytoluene (BHT) used as a radical scavenger, a toluene solution of the adduct between geraniol and camphorsultam was heated in a sealed tube at 140 °C, to provide mainly the (2R,3S)-isomer as the major rearrangement product in 72% yield, securing the two contiguous stereocenters including the quaternary carbon. | 0 | Theoretical and Fundamental Chemistry |
Along with anti-siphon valves, anti-siphoning devices also exist. The two are unrelated in application. Siphoning can be used to remove fuel from tanks. With the cost of fuel increasing, it has been linked in several countries to the rise in fuel theft. Trucks, with their large fuel tanks, are most vulnerable. The anti-siphon device prevents thieves from inserting a tube into the fuel tank. | 1 | Applied and Interdisciplinary Chemistry |
Sour crude oil has high natural sulphur content (at least 0.5%). Extra treatment is required in the refining process; impurities are removed to refine the crude into gasoline. Due to the greater cost associated, it is more commonly refined into fuel oil and diesel - less valuable outputs than products of sweet crude oil. | 0 | Theoretical and Fundamental Chemistry |
The force of viscosity on a small sphere moving through a viscous fluid is given by:
where (in SI units):
* is the frictional force – known as Stokes' drag – acting on the interface between the fluid and the particle (newtons, kg m s);
* (some authors use the symbol ) is the dynamic viscosity (Pascal-seconds, kg m s);
* is the radius of the spherical object (meters);
* is the flow velocity relative to the object (meters per second).
Stokes' law makes the following assumptions for the behavior of a particle in a fluid:
*Laminar flow
*No inertial effects (zero Reynolds number)
*Spherical particles
*Homogeneous (uniform in composition) material
*Smooth surfaces
*Particles do not interfere with each other.
Depending on desired accuracy, the failure to meet these assumptions may or may not require the use of a more complicated model. To 10% error, for instance, velocities need be limited to those giving Re < 1.
For molecules Stokes' law is used to define their Stokes radius and diameter.
The CGS unit of kinematic viscosity was named "stokes" after his work. | 1 | Applied and Interdisciplinary Chemistry |
The use of an ideal high quality biomaterial with the inherent properties of biocompatibility is the most crucial factor that governs the long term efficiency of this technology. An ideal biomaterial for cell encapsulation should be one that is totally biocompatible, does not trigger an immune response in the host and does not interfere with cell homeostasis so as to ensure high cell viability. However, one major limitation has been the inability to reproduce the different biomaterials and the requirements to obtain a better understanding of the chemistry and biofunctionality of the biomaterials and the microencapsulation system. Several studies demonstrate that surface modification of these cell containing microparticles allows control over the growth and cellular differentiation. of the encapsulated cells.
One study proposed the use of zeta potential which measures the electric charge of the microcapsule as a means to predict the interfacial reaction between microcapsule and the surrounding tissue and in turn the biocompatibility of the delivery system. | 1 | Applied and Interdisciplinary Chemistry |
Sieve tray towers use a similar process to packed towers, but instead of packed materials being evenly distributed, the materials are separated into several trays with holes that allow water to drip through them. An electric air compressor is typically positioned at the bottom of the system where the air from the fans travels through the holes and becomes exposed to the water. A natural draft can also be used as an air source to separate contaminants from the water. A natural draft is used for removing more volatile substances such as hydrogen sulfide, radon, or vinyl chloride. On the other hand, mechanical air compressors are used to remove less volatile substances. | 1 | Applied and Interdisciplinary Chemistry |
Despite having been integrated into genomes of vertebrates for millions of years, ERVs represent an intermediate stage between exogenous viruses and the host genome; it is suggested that immunological tolerance to HERV-derived proteins and peptides is imperfect due to the epigenetic silencing of HERV in the thymus and bone marrow, which prevents deletion of all HERV-specific T and B cells. As evidence of this, immunization of non-human primates with ERV-derived antigens mounted robust polyfunctional cytotoxic T cell response as well as high antibody titers. According to phylogenetic studies, among 30 HERV families existing in the human genome, HERV-K (HML-2) elements which integrated most recently are the most intact and biologically active forms. HERV-K env and HERV-H env, considered to be a new class of tumor-associated antigens, have been found to promote strong cytotoxic T-cell responses in patients with various types of cancers.
On a level of the innate immune sensing of nucleic acids, single-stranded RNA (ssRNA) and double-stranded RNA (dsRNA) derived from endogenous retroviruses are recognized by pattern recognition receptors (PRRs).
SsRNAs can be sensed by Toll-like receptors TLR-7 and TLR-8, resulting in secretion of IFN-α by stimulated dendritic cells (DCs) and macrophages, which was observed for ssRNAs derived from HIV-1.
DsRNAs might be one of the most immunogenic nucleic acid pathogen-associated molecular patterns (PAMPs), since they are not found in cells in a normal state. HERV-derived dsRNA can be recognized by TLR-3, RIG-I and MDA5; RIG-I and MDA5 are known to induce a type I IFN response.
When retrotranscribed into DNA, retroviruses can be sensed by cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway, leading to the activation of nuclear factor-kappa B (NF-kB) and IFN regulatory factor 3 (IRF3), which in turn trigger a type I IFN response. DsDNA could also be sensed by DNA-dependent activator of IFN-regulatory factors (DAI); DNA:RNA hybrids could be recognized by TLR-9
The recognition of nucleic acids through PRRs provides a very efficient strategy to fight against viral infections, at the same time imposing the host to a risk due to the possibility of recognizing self-nucleic acids and promotion of autoimmunity. Not surprisingly, HERVs have been found to be associated with different autoimmune and inflammatory diseases, such as multiple sclerosis, amyotrophic lateral sclerosis (ALS), systemic lupus erythematosus (SLE), rheumathoid arthritis (RA), Sjögren syndrome (SS).
On a protein level, a direct interaction between TLRs and certain HERV proteins has been shown. For example, the surface unit of HERV-W Env (also known as Multiple sclerosis-associated retroviral element (MSRV) env) was found to bind to TLR4 and CD14, stimulating the production of pro-inflammatory cytokines including IL-1β, IL-6, and TNFα. HERV-W Env can trigger a maturation process in human dendritic cells, endowing them with the capacity to support a Th1-like type of Th cell differentiation.
Immunological studies have shown some evidence for T cell immune responses against HERVs in HIV-infected individuals. The hypothesis that HIV induces HERV expression in HIV-infected cells led to the proposal that a vaccine targeting HERV antigens could specifically eliminate HIV-infected cells. The potential advantage of this novel approach is that, by using HERV antigens as surrogate markers of HIV-infected cells, it could circumvent the difficulty inherent in directly targeting notoriously diverse and fast-mutating HIV antigens. | 1 | Applied and Interdisciplinary Chemistry |
Biofiltration was first introduced in England in 1893 as a trickling filter for wastewater treatment and has since been successfully used for the treatment of different types of water. Biological treatment has been used in Europe to filter surface water for drinking purposes since the early 1900s and is now receiving more interest worldwide. Biofiltration is also common in wastewater treatment, aquaculture and greywater recycling, as a way to minimize water replacement while increasing water quality. | 1 | Applied and Interdisciplinary Chemistry |
Leachate treatment plants are used to treat leachate from landfills. Treatment options include: biological treatment, mechanical treatment by ultrafiltration, treatment with active carbon filters, electrochemical treatment including electrocoagulation by various proprietary technologies and reverse osmosis membrane filtration using disc tube module technology. | 1 | Applied and Interdisciplinary Chemistry |
* Thermal desorption: the adsorbent material is flash-heated so that all adsorbed VOCs are carried away from the adsorbent and injected into the separation system. This is how work injectors in gas chromatography machines, which literally volatilize introduced samples. For VOCs adsorbed on bigger amount of adsorbent material such as cartridges, thermal desorption may require the use of a specific machine, a thermal desorber, connected to the separation system.
* Desorption by solvent: VOCs adsorbed on the adsorbent material are carried away by a small quantity of solvent which is volatilized and injected in the separation system. Most commonly used solvents are very volatile molecules, such as methanol, to avoid co-elution with slightly heavier VOCs | 1 | Applied and Interdisciplinary Chemistry |
Following his retirement, he pursued his interest in the history of chemistry. He wrote a history of the chemistry department at Victoria University, first published in 2012, with later editions in 2014 and 2018, and a collection of short biographies of notable chemists from Lancashire, published in 2015 as A legacy of Lancashire: its chemists, biochemists and industrialists. He also wrote an autobiography, From Coronation Street to a consummate chemist, published in 2011.
Halton died in Wellington on 23 February 2019. | 0 | Theoretical and Fundamental Chemistry |
A biofilter is a bed of media on which microorganisms attach and grow to form a biological layer called biofilm. Biofiltration is thus usually referred to as a fixed–film process. Generally, the biofilm is formed by a community of different microorganisms (bacteria, fungi, yeast, etc.), macro-organisms (protozoa, worms, insect's larvae, etc.) and extracellular polymeric substances (EPS) (Flemming and Wingender, 2010). Air or water flows through a media bed and any suspended compounds are transferred into a surface biofilm where microorganisms are held to degrade pollutants. The aspect of the biofilm is usually slimy and muddy.
Water to be treated can be applied intermittently or continuously over the media, via upflow or downflow. Typically, a biofilter has two or three phases, depending on the feeding strategy (percolating or submerged biofilter):
* a solid phase (media);
* a liquid phase (water);
* a gaseous phase (air).
Organic matter and other water components diffuse into the biofilm where the treatment occurs, mostly by biodegradation. Biofiltration processes are usually aerobic, which means that microorganisms require oxygen for their metabolism. Oxygen can be supplied to the biofilm, either concurrently or countercurrently with water flow. Aeration occurs passively by the natural flow of air through the process (three phase biofilter) or by forced air supplied by blowers.
Microorganisms' activity is a key-factor of the process performance. The main influencing factors are the water composition, the biofilter hydraulic loading, the type of media, the feeding strategy (percolation or submerged media), the age of the biofilm, temperature, aeration, etc.
The mechanisms by which certain microorganisms can attach and colonize on the surface of filter media of a biofilter can be via transportation, initial adhesion, firm attachment, and colonization [Van Loosdrecht et al., 1990]. The transportation of microorganisms to the surface of the filter media is further controlled by four main processes of diffusion (Brownian motion), convection, sedimentation, and active mobility of the microorganisms. The overall filtration process consists of microorganism attachment, substrate utilization which causes biomass growth, to biomass detachment. | 1 | Applied and Interdisciplinary Chemistry |
The key terms involved in redox can be confusing. For example, a reagent that is oxidized loses electrons; however, that reagent is referred to as the reducing agent. Likewise, a reagent that is reduced gains electrons and is referred to as the oxidizing agent. These mnemonics are commonly used by students to help memorise the terminology:
* "OIL RIG" — oxidation is loss of electrons, reduction is gain of electrons
* "LEO the lion says GER [grr]" — loss of electrons is oxidation, gain of electrons is reduction
* "LEORA says GEROA" — the loss of electrons is called oxidation (reducing agent); the gain of electrons is called reduction (oxidizing agent).
* "RED CAT" and "AN OX", or "AnOx RedCat" ("an ox-red cat") — reduction occurs at the cathode and the anode is for oxidation
* "RED CAT gains what AN OX loses" – reduction at the cathode gains (electrons) what anode oxidation loses (electrons)
* "PANIC" – Positive Anode and Negative is Cathode. This applies to electrolytic cells which release stored electricity, and can be recharged with electricity. PANIC does not apply to cells that can be recharged with redox materials. These galvanic or voltaic cells, such as fuel cells, produce electricity from internal redox reactions. Here, the positive electrode is the cathode and the negative is the anode. | 0 | Theoretical and Fundamental Chemistry |
* (Paris: Chez Durand, Didot, Esprit, 1774). ([https://archive.org/details/opusculesphysiq00goog Second edition, 1801])
* Lart de fabriquer le salin et la potasse, publié par ordre du Roi, par les régisseurs-généraux des Poudres & Salpêtres' (Paris, 1779).
* Instruction sur les moyens de suppléer à la disette des fourrages, et daugmenter la subsistence des bestiaux, Supplément à linstruction sur les moyens de pourvoir à la disette des fourrages, publiée par ordre du Roi le 31 mai 1785 (Instruction on the means of compensating for the food shortage with fodder, and of increasing the subsistence of cattle, Supplement to the instruction on the means of providing for the food shortage with fodder, published by order of King on 31 May 1785).
* (with Guyton de Morveau, Claude-Louis Berthollet, Antoine Fourcroy) [https://web.archive.org/web/20110721021630/http://imgbase-scd-ulp.u-strasbg.fr/displayimage.php?album=692&pos=3 Méthode de nomenclature chimique] (Paris: Chez Cuchet, 1787)
* (with Fourcroy, Morveau, Cadet, Baumé, dArcet, and Sage) [https://books.google.com/books?id=-bM5AAAAcAAJ Nomenclature chimique, ou synonymie ancienne et moderne, pour servir à lintelligence des auteurs.] (Paris: Chez Cuchet, 1789)
* [http://isnature.org/Files/Lavoisier1789-Traite_elementaire_de_chimie.htm Traité élémentaire de chimie, présenté dans un ordre nouveau et daprès les découvertes modernes]' (Paris: Chez Cuchet, 1789; Bruxelles: Cultures et Civilisations, 1965) (lit. Elementary Treatise on Chemistry, presented in a new order and alongside modern discoveries) also [https://web.archive.org/web/20100109164241/http://www.lavoisier.cnrs.fr/ice/ice_book_detail-fr-text-lavosier-Lavoisier-89-6.html here]
* (with Pierre-Simon Laplace) "[http://www.lavoisier.cnrs.fr/ice/ice_page_detail.php?lang=fr&type=text&bdd=lavosier&table=Lavoisier&typeofbookDes=Memoires&bookId=38&pageChapter=M%E9moire%20sur%20la%20chaleur&pageOrder=1&facsimile=off&search=no&num=&nav=1 Mémoire sur la chaleur]," Mémoires de lAcadémie des sciences' (1780), pp. 355–408.
* [http://www.lavoisier.cnrs.fr/ice/ice_page_detail.php?lang=fr&type=text&bdd=lavosier&table=Lavoisier&typeofbookDes=Memoires&bookId=65&pageChapter=Premier%20m%E9moire%20contenant%20les%20exp%E9riences%20faites%20sur%20la%20chaleur,%20pendant%20l%27hiver%20de%201783%20%E0%201784,%20par%20P.S.%20de%20Laplace%20et%20A.L.%20%20Lavoisier&pageOrder=1&facsimile=off&search=no&num=&nav=1 Mémoire contenant les expériences faites sur la chaleur, pendant lhiver de 1783 à 1784, par P.S. de Laplace & A. K. Lavoisier]' (1792)
* Mémoires de Physique et de Chimie, de la Société dArcueil' (1805: posthumous) | 1 | Applied and Interdisciplinary Chemistry |
The flow velocity of a fluid effectively describes everything about the motion of a fluid. Many physical properties of a fluid can be expressed mathematically in terms of the flow velocity. Some common examples follow: | 1 | Applied and Interdisciplinary Chemistry |
There are several options of introducing an acetoxy functionality in a molecule from an alcohol (in effect protecting the alcohol by acetylation):
* Acetyl halide, such as acetyl chloride in the presence of a base like triethylamine
* Activated ester form of acetic acid, such as a N-hydroxysuccinimide ester, although this is not advisable due to higher costs and difficulties.
* Acetic anhydride in the presence of base with a catalyst such as pyridine with a bit of DMAP added.
An alcohol is not a particularly strong nucleophile and, when present, more powerful nucleophiles like amines will react with the above-mentioned reagents in preference to the alcohol. | 0 | Theoretical and Fundamental Chemistry |
Marc Julia (23 October 1922 – 29 June 2010) was a French chemist and the winner of the 1990 CNRS Gold Medal in chemistry. He discovered the Julia olefination reaction in 1973. | 0 | Theoretical and Fundamental Chemistry |
Recombinant DNA is widely used in biotechnology, medicine and research. Today, recombinant proteins and other products that result from the use of DNA technology are found in essentially every western pharmacy, physician or veterinarian office, medical testing laboratory, and biological research laboratory. In addition, organisms that have been manipulated using recombinant DNA technology, as well as products derived from those organisms, have found their way into many farms, supermarkets, home medicine cabinets, and even pet shops, such as those that sell GloFish and other genetically modified animals.
The most common application of recombinant DNA is in basic research, in which the technology is important to most current work in the biological and biomedical sciences. Recombinant DNA is used to identify, map and sequence genes, and to determine their function. rDNA probes are employed in analyzing gene expression within individual cells, and throughout the tissues of whole organisms. Recombinant proteins are widely used as reagents in laboratory experiments and to generate antibody probes for examining protein synthesis within cells and organisms.
Many additional practical applications of recombinant DNA are found in industry, food production, human and veterinary medicine, agriculture, and bioengineering. Some specific examples are identified below. | 1 | Applied and Interdisciplinary Chemistry |
The program may run with fixed input data for the number of years determined by the user. This option can be used to predict future developments based on long-term average input values, e.g. rainfall, as it will be difficult to assess the future values of the input data year by year.
The program also offers the possibility to follow historic records with annually changing input values (e.g. rainfall, irrigation, agricultural practices), the calculations must be made year by year. If this possibility is chosen, the program creates transfer files by which the final conditions of the previous year (e.g. water table and salinity) are automatically used as the initial conditions for the subsequent period. This facility makes it possible to use various generated rainfall sequences drawn randomly from a known rainfall probability distribution and obtain a stochastic prediction of the resulting output parameters.
If the computations are made with annual changes, not all input parameters can be changed, notably the thickness of the soil reservoirs and their total porosities as these would cause illogical shifts in the water and salt balances. | 0 | Theoretical and Fundamental Chemistry |
Wein filter. In Wien filter mass separation is done with crossed homogeneous electric and magnetic fields perpendicular to ionized cluster beam. The net force on a charged cluster with mass M, charge Q, and velocity v vanishes if E = Bv/c. The cluster ions are accelerated by a voltage V to an energy QV. Passing through the filter, clusters with M/Q = 2V/(Ec/B) are un-deflected. The un-deflected cluster ions are selected with appropriately positioned collimators.
Quadrupole mass filter. The quadrupole mass filter operates on the principle that ion trajectories in a two-dimensional quadrupole field are stable if the field has an AC component superimposed on a DC component with appropriate amplitudes and frequencies. It is responsible for filtering sample ions based on their mass-to-charge ratio.
Time of flight mass spectroscopy. Time-of-flight spectroscopy consists of an ion gun, a field-free drift space and an ion cluster source. The neutral clusters are ionized, typically using pulsed laser or an electron beam. The ion gun accelerates the ions that pass through the field-free drift space (flight tube) and ultimately impinge on an ion detector. Usually an oscilloscope records the arrival time of the ions. The mass is calculated from the measured time of flight.
Molecular beam chromatography. In this method, cluster ions produced in a laser vaporized cluster source are mass selected and introduced in a long inert-gas-filled drift tube with an entrance and exit aperture. Since cluster mobility depends upon the collision rate with the inert gas, they are sensitive to the cluster shape and size. | 0 | Theoretical and Fundamental Chemistry |
Walter was one of the youngest students of the Jagiellonian University in Kraków, where he studied history and chemistry in 1825–28. Subsequently, he studied at Berlin University, receiving a Ph.D. with his dissertation On Combination of Oxalic Acid and Alkali. Simultaneously he served as assistant to Professor Eilhard Mitscherlich.
On the outbreak of the November 1830 Uprising, he went to Warsaw and joined the Polish Army. He served as adjutant to Colonel Samuel Różycki, commander of the 7th infantry regiment. In 1831, aged 21, he was named professor of chemistry at the Jagiellonian University, but he left to Paris where he worked with Jean-Baptiste Dumas at the École Centrale des Arts et Manufactures. Here Walter began to teach analytical chemistry. He examined plant extracts and along with Pierre Joseph Pelletier he extracted toluene by distillation of pine resin in 1838. In 1840 they extracted octene (CH) from naphtha. Walter was able to demonstrate the substitution of carbon by sulphur in camphor in 1842. His achievements won him recognition from the French Academy. In sum, he isolated and studied 24 new chemical compounds, including toluene, biphenyl, nitrotoluene, cedrene, potassium hydroxide dihydrate, chromyl chloride, cumene, benzyl chloride, benzyl bromide, and menthene.
In 1847 he was decorated with the cross of the Legion of Honour. | 0 | Theoretical and Fundamental Chemistry |
Capacitance sensors (or Dielectric sensors) use capacitance to measure the dielectric permittivity of a surrounding medium.
The configuration is like the neutron probe where an access tube made of PVC is installed in the soil; probes can also be modular (comb-like) and connected to a logger. The sensing head consists of an oscillator circuit, the frequency is determined by an annular electrode, fringe-effect capacitor, and the dielectric constant of the soil.
Each capacitor sensor consists of two metal rings mounted on the circuit board at some distance from the top of the access tube. These rings are a pair of electrodes, which form the plates of the capacitor with the soil acting as the dielectric in between. The plates are connected to an oscillator, consisting of an inductor and a capacitor. The oscillating electrical field is generated between the two rings and extends into the soil medium through the wall of the access tube. The capacitor and the oscillator form a circuit, and changes in dielectric constant of surrounding media are detected by changes in the operating frequency. The capacitance sensors are designed to oscillate in excess of 100 MHz inside the access tube in free air. The output of the sensor is the frequency response of the soil’s capacitance due to its soil moisture level. | 0 | Theoretical and Fundamental Chemistry |
* In the "Liquid Solar Fuel Production demonstration Project" in 2020 the large-scale production of renewable methanol with sun power with a 10 MW electrolyzer was demonstrated.
* More than 20 000 taxis are operated in China with methanol (as of 2020)
* End of 2021 in Henan province the world's largest plant for production of methanol from CO with a capacity of 110 000 t/a shall be commissioned in "Shunli CO-To-Methanol Plant" with assistance of Carbon Recycling International.
* Several major Chinese automakers such as FAW Group, Shanghai Huapu (Shanghai Maple), Geely Group, Chang’an and SAIC prepare for mass production of methanol capable vehicles and fleets of taxis and buses.
* In Shanxi province there exist more than 1000 petrol stations that sell M15 and further 40 M85-M100 refueling points. Until 2025 the government of Shanxi wants to convert more than 2000 refueling stations for methanol fuel as well as 200 000 vehicles for operation with methanol. | 1 | Applied and Interdisciplinary Chemistry |
In physical chemistry, Henrys law is a gas law that states that the amount of dissolved gas in a liquid is directly proportional to its partial pressure above the liquid. The proportionality factor is called Henrys law constant. It was formulated by the English chemist William Henry, who studied the topic in the early 19th century.
In simple words, we can say that the partial pressure of a gas in vapour phase is directly proportional to the mole fraction of a gas in solution.
An example where Henrys law is at play is the depth-dependent dissolution of oxygen and nitrogen in the blood of underwater divers that changes during decompression, going to decompression sickness. An everyday example is given by ones experience with carbonated soft drinks, which contain dissolved carbon dioxide. Before opening, the gas above the drink in its container is almost pure carbon dioxide, at a pressure higher than atmospheric pressure. After the bottle is opened, this gas escapes, moving the partial pressure of carbon dioxide above the liquid to be much lower, resulting in degassing as the dissolved carbon dioxide comes out of the solution. | 0 | Theoretical and Fundamental Chemistry |
Alkyl groups have a low to zero value for F but sensible values for R. This is most commonly explained by hyperconjugation, meaning little to no inductive effects but partial resonance effects.
CF has a much higher R/F ratio than other substituents with high degrees of conjugation. This was studied in greater detail by Swain but is still explained best by fluoride hyperconjugation.
Positively charged substituents (i.e., and ) have larger positive F values due to a positive charge that is saturated near the carbon framework in question. Negatively charged substituents (i.e., CO and SO) have much lower F values because of their ability to resonate electron density amongst the oxygen atoms and stabilize it through hydrogen-bonding with solvents.
Linear free energy relationships are still useful, despite their disadvantages when pushed to the limits. New techniques to solve for Swain–Lupton substituent parameters involve studying chemical shifts through nuclear magnetic resonance spectroscopy. Recently, N NMR chemical shifts and substituent effects of 1,2,3,4,5,6,7,8-octahydroacridine and derivatives were studied. Values for R and F were found for the group, which could not be found previously using known methods. | 0 | Theoretical and Fundamental Chemistry |
In surface science, surface energy (also interfacial free energy or surface free energy) quantifies the disruption of intermolecular bonds that occurs when a surface is created. In solid-state physics, surfaces must be intrinsically less energetically favorable than the bulk of the material (that is, the atoms on the surface must have more energy than the atoms in the bulk), otherwise there would be a driving force for surfaces to be created, removing the bulk of the material (see sublimation). The surface energy may therefore be defined as the excess energy at the surface of a material compared to the bulk, or it is the work required to build an area of a particular surface. Another way to view the surface energy is to relate it to the work required to cut a bulk sample, creating two surfaces. There is "excess energy" as a result of the now-incomplete, unrealized bonding between the two created surfaces.
Cutting a solid body into pieces disrupts its bonds and increases the surface area, and therefore increases surface energy. If the cutting is done reversibly, then conservation of energy means that the energy consumed by the cutting process will be equal to the energy inherent in the two new surfaces created. The unit surface energy of a material would therefore be half of its energy of cohesion, all other things being equal; in practice, this is true only for a surface freshly prepared in vacuum. Surfaces often change their form away from the simple "cleaved bond" model just implied above. They are found to be highly dynamic regions, which readily rearrange or react, so that energy is often reduced by such processes as passivation or adsorption. | 0 | Theoretical and Fundamental Chemistry |
Maintenance of pipelines includes checking cathodic protection levels for the proper range, surveillance for construction, erosion, or leaks by foot, land vehicle, boat, or air, and running cleaning pigs, when there is anything carried in the pipeline that is corrosive.
US pipeline maintenance rules are covered in Code of Federal Regulations(CFR) sections, 49 CFR 192 for natural gas pipelines, and 49 CFR 195 for petroleum liquid pipelines. | 1 | Applied and Interdisciplinary Chemistry |
The IChemE is licensed by the Engineering Council UK to assess candidates for inclusion on ECUK's Register of professional Engineers, giving the status of Chartered Engineer, Incorporated Engineer and Engineering Technician. It is licensed by the Science Council to grant the status of Chartered Scientist and Registered Science Technician. It is licensed by the Society for the Environment to grant the status of Chartered Environmentalist. It is a member of the European Federation of Chemical Engineering. It accredits chemical engineering degree courses in 25 countries worldwide. | 1 | Applied and Interdisciplinary Chemistry |
William M. Williams (25 February 1927 – 28 January 2011) was a Welsh-born metallurgical engineer and Birks professor of metallurgy at McGill University. | 1 | Applied and Interdisciplinary Chemistry |
Sealed sources are categorised by the IAEA according to their activity in relation to a minimum dangerous source (where a dangerous source is one that could cause significant injury to humans). The ratio used is A/D, where A is the activity of the source and D is the minimum dangerous activity.
Note that sources with sufficiently low radioactive output (such as those used in Smoke detectors) as to not cause harm to humans are not categorised. | 0 | Theoretical and Fundamental Chemistry |
Most electrofusion welding power supplies are constant voltage machines. Constant current machines would provide more consistent energy input due to the smaller fluctuations in current applied to the coils during welding. However, this additional consistency is generally not worth the higher cost of these machines. When a constant voltage machine is used, the value of the applied current slowly decreases throughout the welding process. This effect is due to the increasing resistance of the coils as energy is applied. As heat is generated in the coils, their temperature increases, leading to a higher electrical resistance in the coils. This increased electrical resistance causes a smaller current to be generated from the same voltage level as the process progresses. The extent of the current decrease is determined by the material used for the coil. The energy input per unit area can be calculated and used to monitor the process. Typical values for this range from 2–13 J/mm, with a value of 3.9 J/mm having been found to produce the strongest joints. | 0 | Theoretical and Fundamental Chemistry |
Biodegradable biomaterials refers to materials that are degradable through natural enzymatic reactions. The application of biodegradable synthetic polymers began in the later 1960s. Biodegradable materials have an advantage over other materials, as they have lower risk of harmful effects long term. In addition to ethical advancements using biodegradable materials, they also improve biocompatibility for materials used for implantation. Several properties including biocompatibility are important when considering different biodegradable biomaterials. Biodegradable biomaterials can be synthetic or natural depending on their source and type of extracellular matrix (ECM). | 1 | Applied and Interdisciplinary Chemistry |
ATP is the phosphorylated version of adenosine diphosphate (ADP), which stores energy in a cell and powers most cellular activities. ATP is the energized form, while ADP is the (partially) depleted form. NADP is an electron carrier which ferries high energy electrons. In the light reactions, it gets reduced, meaning it picks up electrons, becoming NADPH. | 0 | Theoretical and Fundamental Chemistry |
Thyroids secretory capacity (G, also referred to as thyroids incretory capacity, maximum thyroid hormone output, T4 output or, if calculated from serum levels of thyrotropin and thyroxine, as SPINA-GT) is the maximum stimulated amount of thyroxine that the thyroid can produce in a given time-unit (e.g. one second). | 1 | Applied and Interdisciplinary Chemistry |
A SPARROW model is a SPAtially-Referenced Regression on Watershed attributes, which helps integrate water quality data with landscape information. More specifically the USGS used this model to display long-term changes within watersheds to further explain in-stream water measurement in relation to upstream sources, water quality, and watershed properties. These models predict data for various spatial scales and integrate streamflow data with water quality at numerous locations across the US. A SPARROW model used by the USGS focused on the nutrients in the Nation's major rivers and estuaries; this model helped create a better understanding of where nutrients come from, where they are transported to while in the water bodies, and where they end up (reservoirs, other estuaries, etc.). | 0 | Theoretical and Fundamental Chemistry |
Reduction of with aluminium results in one-electron reduction. The trichloride (Titanium(III) chloride|) and tetrachloride have contrasting properties: the trichloride is a colored solid, being a coordination polymer, and is paramagnetic. When the reduction is conducted in THF solution, the Ti(III) product converts to the light-blue adduct . | 0 | Theoretical and Fundamental Chemistry |
Apart from the end replication problem, in vitro studies have shown that telomeres accumulate damage due to oxidative stress and that oxidative stress-mediated DNA damage has a major influence on telomere shortening in vivo. There is a multitude of ways in which oxidative stress, mediated by reactive oxygen species (ROS), can lead to DNA damage; however, it is yet unclear whether the elevated rate in telomeres is brought about by their inherent susceptibility or a diminished activity of DNA repair systems in these regions. Despite widespread agreement of the findings, widespread flaws regarding measurement and sampling have been pointed out; for example, a suspected species and tissue dependency of oxidative damage to telomeres is said to be insufficiently accounted for. Population-based studies have indicated an interaction between anti-oxidant intake and telomere length. In the Long Island Breast Cancer Study Project (LIBCSP), authors found a moderate increase in breast cancer risk among women with the shortest telomeres and lower dietary intake of beta carotene, vitamin C or E. These results suggest that cancer risk due to telomere shortening may interact with other mechanisms of DNA damage, specifically oxidative stress. | 1 | Applied and Interdisciplinary Chemistry |
Oswald Helmuth Göhring, also known as Otto Göhring, (1889) was a German chemist who, with his teacher Kasimir Fajans, co-discovered the chemical element protactinium in 1913. | 1 | Applied and Interdisciplinary Chemistry |
The purpose of single cell metabolomics is to gain a better understanding at the molecular level of major biological topics such as: cancer, stem cells, aging, as well as the development of drug resistance. In general the focus of metabolomics is mostly on understanding how cells deal with environmental stresses at the molecular level, and to give a more dynamic understanding of cellular functions. | 1 | Applied and Interdisciplinary Chemistry |
In ancient alchemy, a protoscience that contributed to the development of modern chemistry and medicine, alchemists developed a structure of basic laboratory techniques, theory, terminology, and experimental methods. Sublimation was used to refer to the process in which a substance is heated to a vapor, then immediately collects as sediment on the upper portion and neck of the heating medium (typically a retort or alembic), but can also be used to describe other similar non-laboratory transitions. It was mentioned by alchemical authors such as Basil Valentine and George Ripley, and in the Rosarium philosophorum, as a process necessary for the completion of the magnum opus. Here, the word sublimation was used to describe an exchange of "bodies" and "spirits" similar to laboratory phase transition between solids and gases. Valentine, in his Le char triomphal de lantimoine' (Triumphal Chariot of Antimony, published 1646) made a comparison to spagyrics in which a vegetable sublimation can be used to separate the spirits in wine and beer. Ripley used language more indicative of the mystical implications of sublimation, indicating that the process has a double aspect in the spiritualization of the body and the corporalizing of the spirit. He writes:
<blockquote><poem>
And Sublimations we make for three causes,
The first cause is to make the body spiritual.
The second is that the spirit may be corporeal,
And become fixed with it and consubstantial.
The third cause is that from its filthy original.
It may be cleansed, and its saltiness sulphurious
May be diminished in it, which is infectious. | 0 | Theoretical and Fundamental Chemistry |
Gas porosity is the formation of bubbles within the casting after it has cooled. This occurs because most liquid materials can hold a large amount of dissolved gas, but the solid form of the same material cannot, so the gas forms bubbles within the material as it cools. Gas porosity may present itself on the surface of the casting as porosity or the pore may be trapped inside the metal, which reduces strength in that vicinity. Nitrogen, oxygen and hydrogen are the most encountered gases in cases of gas porosity. In aluminium castings, hydrogen is the only gas that dissolves in significant quantity, which can result in hydrogen gas porosity. For casting that are a few kilograms in weight the pores are usually in size. In larger casting, they can be up to a millimetre (0.040 in) in diameter.
To prevent gas porosity the material may be melted in a vacuum, in an environment of low-solubility gases, such as argon or carbon dioxide, or under a flux that prevents contact with the air. To minimize gas solubility the superheat temperatures can be kept low. Turbulence from pouring the liquid metal into the mould can introduce gases, so the moulds are often streamlined to minimize such turbulence. Other methods include vacuum degassing, gas flushing, or precipitation. Precipitation involves reacting the gas with another element to form a compound that will form a dross that floats to the top. For instance, oxygen can be removed from copper by adding phosphorus; aluminium or silicon can be added to steel to remove oxygen. A third source consists of reactions of the molten metal with grease or other residues in the mould.
Hydrogen is produced by the reaction of the metal with humidity or residual moisture in the mould. Drying the mould can eliminate this source of hydrogen formation.
Gas porosity can sometimes be difficult to distinguish from micro shrinkage because microshrinkage cavities can contain gases as well. In general, microporosities will form if the casting is not properly risered or if a material with a wide solidification range is cast. If neither of these are the case then most likely the porosity is due to gas formation.
Tiny gas bubbles are called porosities, but larger gas bubbles are called blowholes or blisters. Such defects can be caused by air entrained in the melt, steam or smoke from the casting sand, or other gasses from the melt or mould. (Vacuum holes caused by metal shrinkage (see above) may also be loosely referred to as blowholes). Proper foundry practices, including melt preparation and mould design, can reduce the occurrence of these defects. Because they are often surrounded by a skin of sound metal, blowholes may be difficult to detect, requiring harmonic, ultrasonic, magnetic, or X-ray (e.g., industrial CT scanning) analysis. | 1 | Applied and Interdisciplinary Chemistry |
Aminosulfuranes are highly selective for the replacement of hydroxyl groups with fluoride, but in the absence of alcohol functionality, they have the ability to transform a wide array of substrates into the corresponding fluorides or acyl fluorides. For example, ketones are converted to geminal difluorides. However, unlike sulfur tetrafluoride, aminosulfuranes do not convert carboxylic acids into trifluoromethyl groups; the reaction halts at the acyl fluoride stage. Silyl ethers are converted to organofluorides in the presence of DAST.
Aldehydes and ketones react with DAST to form the corresponding geminal difluorides. Fluorination of enolizable ketones gives a mixture of the difluoroalkane and vinyl fluoride. In glyme with fuming sulfuric acid, the vinyl fluoride product predominates. Electron-rich carbonyl compounds, such as esters and amides, do not react with DAST or other aminosulfuranes.
Epoxides may yield a variety of products depending on their structure. Generally, the products that form in highest yield are vicinal difluorides and bis(α-fluoroalkyl)ethers. However, this reaction results in low yields and is not synthetically useful.
The polar mechanism of fluorination by DAST implies that certain substrates may suffer Wagner-Meerwein rearrangements. This process has been observed in the fluorination of pivalaldehyde, which affords a mixture of 1,2-difluoro-1,2-dimethylpropane, 1,1-difluoro-2,2-dimethylpropane, and 1-fluoro-2,2-dimethylethylene.
Diols can undergo pinacol rearrangement under fluorination conditions.
When sulfoxides are treated with DAST, an interesting Pummerer-type rearrangement occurs to afford α-fluoro sulfides. | 0 | Theoretical and Fundamental Chemistry |
The hinges form the technological heart of the sea defence system. They constrain the gates to the housing structures, allow them to move and connect the gates to the operating plant.
The steel gates consist of a male element ( high and weighing ) connected to the gate, a female element ( high and weighing ) fastened to the housing structure and an attachment assembly to connect the male and female elements.
A total of 156 hinges (two for each gate) will be fabricated, together with a number of reserve elements. | 1 | Applied and Interdisciplinary Chemistry |
Resulting from either naturally occurring isotopes or artificial isotopic labeling, isotopologues can be used in various mass spectrometry applications. | 0 | Theoretical and Fundamental Chemistry |
Yttrium oxalate is an inorganic compound, a salt of yttrium and oxalic acid with the chemical formula Y(CO). The compound does not dissolve in water and forms crystalline hydrates—colorless crystals. | 0 | Theoretical and Fundamental Chemistry |
A fermentation crock, also known as a gärtopf crock or Harsch crock, is a crock for fermentation. It has a gutter in the rim which is then filled with water so that when the top is put on an airlock is created, which prevents the food within from spoiling due to the development of surface molds. Ceramic weights may also be used to keep the fermenting food inside submerged. | 1 | Applied and Interdisciplinary Chemistry |
Compared with vertebrates, insects and crustaceans possess a number of structurally unusual hormones such as the juvenile hormone, a sesquiterpenoid. | 1 | Applied and Interdisciplinary Chemistry |
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