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A delta ray is a secondary electron with enough energy to escape a significant distance away from the primary radiation beam and produce further ionization. The term is sometimes used to describe any recoil particle caused by secondary ionization. The term was coined by J. J. Thomson. | 0 | Theoretical and Fundamental Chemistry |
Lectin affinity chromatography is a form of affinity chromatography where lectins are used to separate components within the sample. Lectins, such as concanavalin A are proteins which can bind specific alpha-D-mannose and alpha-D-glucose carbohydrate molecules. Some common carbohydrate molecules that is used in lectin affinity chromatography are Con A-Sepharose and WGA-agarose. Another example of a lectin is wheat germ agglutinin which binds D-N-acetyl-glucosamine. The most common application is to separate glycoproteins from non-glycosylated proteins, or one glycoform from another glycoform. Although there are various ways to perform lectin affinity chromatography, the goal is extract a sugar ligand of the desired protein. | 0 | Theoretical and Fundamental Chemistry |
With the advent of asymmetric catalysis, it is necessary to consider the practicality of utilizing kinetic resolution for the preparation of enantiopure products. Even for a product which can be attained through an asymmetric catalytic or auxiliary-based route, the racemate may be significantly less expensive than the enantiopure material, resulting in heightened cost-effectiveness even with the inherent "loss" of 50% of the material. The following have been proposed as necessary conditions for a practical kinetic resolution:
* inexpensive racemate and catalyst
* no appropriate enantioselective, chiral pool, or classical resolution route is possible
* resolution proceeds selectively at low catalyst loadings
* separation of starting material and product is facile
To date, a number of catalysts for kinetic resolution have been developed that satisfy most, if not all of the above criteria, making them highly practical for use in organic synthesis. The following sections will discuss a number of key examples. | 0 | Theoretical and Fundamental Chemistry |
Atalla was awarded the Stuart Ballantine Medal (now the Benjamin Franklin Medal in physics) at the 1975 Franklin Institute Awards, for his important contributions to silicon semiconductor technology and his invention of the MOSFET. In 2003, Atalla received a Distinguished Alumnus doctorate from Purdue University.
In 2009, he was inducted into the National Inventors Hall of Fame for his important contributions to semiconductor technology as well as data security. He was referred to as one of the "Sultans of Silicon" along with several other semiconductor pioneers.
In 2014, the 1959 invention of the MOSFET was included on the list of IEEE milestones in electronics. In 2015, Atalla was inducted into the IT History Society's IT Honor Roll for his important contributions to information technology. | 0 | Theoretical and Fundamental Chemistry |
When anaerobic pathways are turned on, glycogen stores are depleted and accumulation of acidic waste products occurs. This is known as a Pasteur effect. A challenge hypoxia-tolerant fish face is how to produce ATP anaerobically without creating a significant Pasteur effect. Along with a reduction in metabolism, some fish have adapted traits to avoid accumulation of lactate. For example, the crucian carp, a highly hypoxia-tolerant fish, has evolved to survive months of anoxic waters. A key adaptation is the ability to convert lactate to ethanol in the muscle and excrete it out of their gills. Although this process is energetically costly is it crucial to their survival in hypoxic waters. | 0 | Theoretical and Fundamental Chemistry |
Deviations of the compressibility factor, Z, from unity are due to attractive and repulsive intermolecular forces. At a given temperature and pressure, repulsive forces tend to make the volume larger than for an ideal gas; when these forces dominate Z is greater than unity. When attractive forces dominate, Z is less than unity. The relative importance of attractive forces decreases as temperature increases (see effect on gases).
As seen above, the behavior of Z is qualitatively similar for all gases. Molecular nitrogen, N, is used here to further describe and understand that behavior. All data used in this section were obtained from the NIST Chemistry WebBook. It is useful to note that for N the normal boiling point of the liquid is 77.4 K and the critical point is at 126.2 K and 34.0 bar.
The figure on the right shows an overview covering a wide temperature range. At low temperature (100 K), the curve has a characteristic check-mark shape, the rising portion of the curve is very nearly directly proportional to pressure. At intermediate temperature (160 K), there is a smooth curve with a broad minimum; although the high pressure portion is again nearly linear, it is no longer directly proportional to pressure. Finally, at high temperature (400 K), Z is above unity at all pressures. For all curves, Z approaches the ideal gas value of unity at low pressure and exceeds that value at very high pressure.
To better understand these curves, a closer look at the behavior for low temperature and pressure is given in the second figure. All of the curves start out with Z equal to unity at zero pressure and Z initially decreases as pressure increases. N is a gas under these conditions, so the distance between molecules is large, but becomes smaller as pressure increases. This increases the attractive interactions between molecules, pulling the molecules closer together and causing the volume to be less than for an ideal gas at the same temperature and pressure. Higher temperature reduces the effect of the attractive interactions and the gas behaves in a more nearly ideal manner.
As the pressure increases, the gas eventually reaches the gas-liquid coexistence curve, shown by the dashed line in the figure. When that happens, the attractive interactions have become strong enough to overcome the tendency of thermal motion to cause the molecules to spread out; so the gas condenses to form a liquid. Points on the vertical portions of the curves correspond to N being partly gas and partly liquid. On the coexistence curve, there are then two possible values for Z, a larger one corresponding to the gas and a smaller value corresponding to the liquid. Once all the gas has been converted to liquid, the volume decreases only slightly with further increases in pressure; then Z is very nearly proportional to pressure.
As temperature and pressure increase along the coexistence curve, the gas becomes more like a liquid and the liquid becomes more like a gas. At the critical point, the two are the same. So for temperatures above the critical temperature (126.2 K), there is no phase transition; as pressure increases the gas gradually transforms into something more like a liquid. Just above the critical point there is a range of pressure for which Z drops quite rapidly (see the 130 K curve), but at higher temperatures the process is entirely gradual.
The final figures shows the behavior at temperatures well above the critical temperatures. The repulsive interactions are essentially unaffected by temperature, but the attractive interaction have less and less influence. Thus, at sufficiently high temperature, the repulsive interactions dominate at all pressures.
This can be seen in the graph showing the high temperature behavior. As temperature increases, the initial slope becomes less negative, the pressure at which Z is a minimum gets smaller, and the pressure at which repulsive interactions start to dominate, i.e. where Z goes from less than unity to greater than unity, gets smaller. At the Boyle temperature (327 K for N), the attractive and repulsive effects cancel each other at low pressure. Then Z remains at the ideal gas value of unity up to pressures of several tens of bar. Above the Boyle temperature, the compressibility factor is always greater than unity and increases slowly but steadily as pressure increases. | 0 | Theoretical and Fundamental Chemistry |
In Australia, over 97% of the population live in an area that bans expanded polystyrene. Between 2021-2023, the Australian Capital Territory, New South Wales, Queensland, South Australia, Victoria, and Western Australia enacted bans.
Nigeria's states of Lagos and Abia introduced bans in January 2024, with an initial transition period of three weeks. The state of Oyo introduced a ban in March 2024.
Municipal bans in the Philippines are in effect in Bailen, Boracay, Caloocan, Cordova, El Nido, Las Piñas, Makati, Mandaluyong City, Muntinlupa, Quezon City, and Tacloban.
In the United Arab Emirates, the municipal government of Dubai announced a ban affecting polystyrene in 2025, and all single-use plastic food containers in 2026. | 0 | Theoretical and Fundamental Chemistry |
Bracken fern increases the oncogenic risk in humans. Epidemiological survey revealed that bracken fern consumption was positively correlated with esophageal cancer and with gastric cancer in many geographical areas of the world. In 1989, Natori and co-workers showed that ptaquiloside had clastogenic effect and caused chromosomal aberration in mammalian cells. In 2003, Santos group reported significantly increased levels of chromosomal abnormalities, such as chromatid breaks in cultured peripheral lymphocytes. | 0 | Theoretical and Fundamental Chemistry |
Modeling by Dushek et al. proposes a possible mechanism for ultrasensitivity outside of the zero-order regime. For the case of membrane-bound enzymes acting on membrane-bound substrates with multiple enzymatic sites (such as tyrosine-phosphorylated receptors like the T-Cell receptor), ultrasensitive responses could be seen, crucially dependent on three factors:
1) limited diffusion in the membrane,
2) multiple binding sites on the substrate, and
3) brief enzymatic inactivation following catalysis.
Under these particular conditions, although the enzyme may be in excess of the substrate (first-order regime), the enzyme is effectively locally saturated with substrate due to the multiple binding sites, leading to switch-like responses. This mechanism of ultrasensitivity is independent of enzyme concentration, however the signal is significantly enhanced depending on the number of binding sites on the substrate. Both conditional factors (limited diffusion and inactivation) are physiologically plausible, but have yet to be experimentally confirmed. Dushek's modeling found increasing Hill cooperativity numbers with more substrate sites (phosphorylation sites), and with greater steric/diffusional hindrance between enzyme and substrate. This mechanism of ultrasensitivity based on local enzyme saturation arises partly from passive properties of slow membrane diffusion, and therefore may be generally applicable. | 1 | Applied and Interdisciplinary Chemistry |
When generating a time series of wind speeds for a set of points across a surface, coherence needs to be taken into account. That is, the instantaneous wind speed at some point, A, will bear some resemblance to the wind speed at some other point, B. Clearly, the resemblance is influenced by the separation of points A and B. That is, two points separated by a large distance will show less similarity to each other than two neighbouring points on the surface.
In addition, one would expect low frequency components of the wind speeds at points A and B to show more correlation than high frequency components. As such, many coherence functions have been proposed: Davenport, Solari, etc. The Solari coherence spectrum is provided as an example:
where is a constant, is the separation of points and on the surface, is the frequency, and and are the mean wind speeds at points and respectively. The indices and run from 1 to n, and the index covers the frequency range. From the coherence function stems the coherence matrix. To cover all relationships between all points, the coherence function must be an -by--by- matrix. Clearly, the coherence matrix is symmetric about the main diagonal if we are restricting ourselves to looking at the coherence function at a single frequency. This is because the spatial separation between points A and B is the same as the spatial separation between B and A. That is, for a n-by-n grid, only elements need to be calculated for each frequency.
It is worth noting at this point that whilst the coherence matrix is strictly a 3-dimensional matrix (i, j, and k), computer programmes which implement the Sandia method typically reduce the coherence matrix to a 2-dimensional matrix where the frequency dimension has been removed. This is to ease computational requirements. A 2-dimensional matrix is also required to perform some of the actions on the spectral matrix, such as a Cholesky decomposition, which is mentioned later. Of course, variation in frequency is still applied. However, the following process is carried out in full for one given frequency before proceeding to the next frequency. As such, in the following section, a power spectrum refers to the value of the power spectrum at a given frequency and not the full set of values across the frequency range being used. That is,
and
where an element of S, , would have given the strength of the spectrum at a particular frequency at a particular point in space. | 1 | Applied and Interdisciplinary Chemistry |
In industrial scale chemistry, many processes are catalysed by "solid acids". Solid acids do not dissolve in the reaction medium. Well known examples include these oxides, which function as Lewis acids: silico-aluminates (zeolites, alumina, silico-alumino-phosphate), sulfated zirconia, and many transition metal oxides (titania, zirconia, niobia, and more). Such acids are used in cracking. Many solid Brønsted acids are also employed industrially, including sulfonated polystyrene, sulfonated carbon, solid phosphoric acid, niobic acid, and heteropolyoxometallates.
A particularly large scale application is alkylation, e.g., the combination of benzene and ethylene to give ethylbenzene. Another major application is the rearrangement of cyclohexanone oxime to caprolactam. Many alkylamines are prepared by amination of alcohols, catalyzed by solid acids. In this role, the acid converts, OH, a poor leaving group, into a good one. Thus acids are used to convert alcohols into other classes of compounds, such as thiols and amines. | 0 | Theoretical and Fundamental Chemistry |
In 2000, Andreas Hirsch and coworkers in Erlangen, Germany, formulated a rule to determine when a fullerene would be aromatic. They found that if there were 2(n + 1) π-electrons, then the fullerene would display aromatic properties. This follows from the fact that an aromatic fullerene must have full icosahedral (or other appropriate) symmetry, so the molecular orbitals must be entirely filled. This is possible only if there are exactly 2(n + 1) electrons, where n is a nonnegative integer. In particular, for example, buckminsterfullerene, with 60 π-electrons, is non-aromatic, since 60 ÷ 2 = 30, which is not a perfect square.
In 2011, Jordi Poater and Miquel Solà expanded the rule to determine when a fullerene species would be aromatic. They found that if there were 2n + 2n + 1 π-electrons, then the fullerene would display aromatic properties. This follows from the fact that a spherical species having a same-spin half-filled last energy level with the whole inner levels being fully filled is also aromatic. | 0 | Theoretical and Fundamental Chemistry |
In a study, cyclamin was tested regarding its toxicity against several types of cancer cells: SK-BR-3, HT-29, HepG2/3A, NCI-H1299, BXPC-3, 22RV1 but also on its toxicity against human normal fibroblasts DMEM, which are not cancer cells. The results showed that cyclamin induced a significant increase of micronucleated cells after it was activated through metabolism. This means that heritable chromosome mutations could occur in these cells. This result was observed in all cell types that were analysed in this study, therefore including the fibroblasts. The toxicity was indicated by the IC50 value which gives the concentration of the compound at which it causes 50% of its inhibitory effect e.g. on enzymes in cells. The IC50 values of cyclamin were very similar across the different cell types, ranging from 0.32µM – 0.84µM, with the lowest IC50 value in the human normal fibroblasts DMEM cells, which indicates unspecific toxicity of cyclamin across different cell types (Table 1).
This indicates that cyclamin is more toxic to the human fibroblasts compared to its toxicity against cancer cell lines. Compared to the chemotherapeutic drug mitomycin C, which has IC50 values ranging from 0.45µM-20.20µM in the cancer cell lines, cyclamin was up to 50 times more toxic for certain cell types when comparing the IC50 values (Table 1).
The antioxidant activity of cyclamin was also determined. Cyclamin had an EC50 value of 0.96mM which indicates low antioxidant activity compared to reference compounds catechin (EC50 = 0.009 mM) and ascorbic acid (EC50 = 0.014 mM). The EC50 value represents the potency of a compound by stating the half-maximum concentration of the compound with regards to its concentration where it causes maximum response or effect. Furthermore, it seemed that cyclamin did not have an anticlastogenic effect in the tested cell lines.
Another study found that cyclamin was less toxic to human colorectal cancer cells, from that type HTC 166 and HT-29, compared to the chemotherapeutical drug paclitaxel. This could be concluded from the results that cyclamin had higher IC50 values compared to paclitaxel (Table 2).
To conclude, cyclamin shows broad toxicity against several cancer cell types, which would make it a promising drug to be used in that respect. However, its toxicity against normal human cells should be investigated further before using it as basis for chemotherapeutic drug to reduce unwanted side effects. For instance, cyclamin has been reported to selectively inhibit the proliferation of liver cancer cells. It is suspected to be related to molecular mechanisms increasing cell membrane permeabilization via targeting cholesterol. With this, it consequently targets the ligand-independent activation of Fas signalling pathway. Only after further investigation it can be decided if cyclamin is suitable for such a medical use. | 0 | Theoretical and Fundamental Chemistry |
The surfactant group of the taurates was developed by I.G. Farben in Germany (just like the isethionates) and produced under the trade name Igepon at the Hoechst plant. Taurates rapidly spread due to their lime resistance and their oil-removing effect in textile treatment, as detergent raw material and in cosmetics applications. They had a breakthrough in particular because they do not felt wool during washing (as opposed to soap). The production of taurates decreased after the outbreak of the World War II, since only poor quality fatty acids were available due to the fat management. | 0 | Theoretical and Fundamental Chemistry |
Weak links play a very important role in modern superconductivity. In most cases weak links are oxide barriers between two superconducting thin films, but it can also be a crystal boundary (in the case of high-Tc superconductors). A schematic representation is given in Fig. 4. Now consider the ring which is thick everywhere except for a small section where the ring is closed via a weak link (Fig. 3b). The velocity is zero except near the weak link. In these regions the velocity contribution to the total phase change in the loop is given by (with Eq. ())
The line integral is over the contact from one side to the other in such a way that the end points of the line are well inside the bulk of the superconductor where . So the value of the line integral is well-defined (e.g. independent of the choice of the end points). With Eqs. (), (), and ()
Without proof we state that the supercurrent through the weak link is given by the so-called DC Josephson relation
The voltage over the contact is given by the AC Josephson relation
The names of these relations (DC and AC relations) are misleading since they both hold in DC and AC situations. In the steady state (constant ) Eq. () shows that V=0 while a nonzero current flows through the junction. In the case of a constant applied voltage (voltage bias) Eq. () can be integrated easily and gives
Substitution in Eq. () gives
This is an AC current. The frequency
is called the Josephson frequency. One μV gives a frequency of about 500 MHz. By using Eq. () the flux quantum is determined with the high precision as given in Eq. ().
The energy difference of a Cooper pair, moving from one side of the contact to the other, is . With this expression Eq. () can be written as which is the relation for the energy of a photon with frequency ν.
:The AC Josephson relation (Eq. ()) can be easily understood in terms of Newtons law, (or from one of the London equations). We start with Newton's law
:Substituting the expression for the Lorentz force and using the general expression for the co-moving time derivative gives
:Eq. () gives so
:Take the line integral of this expression. In the end points the velocities are zero so the ∇v term gives no contribution. Using and Eq. (), with and , gives Eq. (). | 0 | Theoretical and Fundamental Chemistry |
The Schiff base rotates away from the extracellular side of the protein towards the cytoplasmic side, in preparation to accept a new proton. | 0 | Theoretical and Fundamental Chemistry |
Dielectrophoresis (DEP) is a phenomenon in which a force is exerted on a dielectric particle when it is subjected to a non-uniform electric field. This force does not require the particle to be charged. All particles exhibit dielectrophoretic activity in the presence of electric fields. However, the strength of the force depends strongly on the medium and particles electrical properties, on the particles shape and size, as well as on the frequency of the electric field. Consequently, fields of a particular frequency can manipulate particles with great selectivity. This has allowed, for example, the separation of cells or the orientation and manipulation of nanoparticles and nanowires. Furthermore, a study of the change in DEP force as a function of frequency can allow the electrical (or electrophysiological in the case of cells) properties of the particle to be elucidated. | 0 | Theoretical and Fundamental Chemistry |
Shortwave UV lamps are made using a fluorescent lamp tube with no phosphor coating, composed of fused quartz or vycor, since ordinary glass absorbs UV‑C. These lamps emit ultraviolet light with two peaks in the UV‑C band at 253.7 nm and 185 nm due to the mercury within the lamp, as well as some visible light. From 85% to 90% of the UV produced by these lamps is at 253.7 nm, whereas only 5–10% is at 185 nm. The fused quartz tube passes the 253.7 nm radiation but blocks the 185 nm wavelength. Such tubes have two or three times the UV‑C power of a regular fluorescent lamp tube. These low-pressure lamps have a typical efficiency of approximately 30–40%, meaning that for every 100 watts of electricity consumed by the lamp, they will produce approximately 30–40 watts of total UV output. They also emit bluish-white visible light, due to mercury's other spectral lines. These "germicidal" lamps are used extensively for disinfection of surfaces in laboratories and food-processing industries, and for disinfecting water supplies. | 0 | Theoretical and Fundamental Chemistry |
The water-repelling liquid is applied:
* To provide the surface of materials with excellent water resistance properties - the surface does not absorb water;
* To make the material frost- and corrosion resistant;
* To reduce the pollution of surface;
In addition, the treated surface does not change its appearance, maintains air permeability - material is not sweated and retains the ability to output pairs.
The water-repelling liquid is applied:
* To provide the surface of materials with excellent water resistance properties - the surface does not absorb water;
* To make the material frost- and corrosion resistant;
* To reduce the pollution of surface;
In addition, the treated surface does not change its appearance, maintains air permeability - material is not sweated and retains the ability to output pairs.
* The liquid is methyl hydride siloxane polymer with low viscosity of light-yellow color or colorless.
* It is readily dissoluble in aromatic and chlorinated hydrocarbons, and is undergone to gelation in the presence of amines, amino alcohols, strong acids and alkalis.
* No dissolution in lower alcohols and water.
The positive effects of the application of methyl hydride siloxane:
* Improved water resistance of various building materials - water remains on the surface in the form of droplets and does not penetrate the material;
* Increases frost resistance and improves thermal insulation materials;
* Does not prevent air exchange – the construction outputs pair outside and does not accumulate moisture;
* Prevents UV and infrared radiation;
* Preserves the appearance of the material;
* Extends the service life of materials;
* Prevents surface mosses and lichens.
Water emulsion of organo silicon the methyl hydride siloxane with additives of emulsifier, biocides and stabilizers
Solids content in the emulsion SE 50-94M is 50%. The color is from white to light gray.
Application:
The emulsion oligo methyl hydride siloxane has properties and characteristics similar with the methyl hydride siloxane. The emulsion is also used to provide various materials with water repellency properties.
However, as oligo methyl hydride siloxane is the water emulsion, it can be applied as an additive in the production of solutions and mixtures that is by the volumetric method.
* for concrete, asbestos, gypsum, ceramic, porcelain
* in the production of waterproof papers and leather;
* in the production of water-resistant fabrics;
* by volumetric method in the manufacture of paving tiles, slabs, curbs, fences of different silicate materials;
* as plasticizer in the preparation of plaster, lime and cement solutions;
* as an air involving admixture in the preparation of cement solution
Liquid is a mixture of tetra ethoxy silane and polyethoxy siloxanes.
Application
* Metal manufacture: binding agent in the manufacture of ceramic molds for precision core-mold casting; manufacture of rods exposed to high temperatures; manufacture of non-stick paints;
* Textile industry: feltproofing of woolen cloths; abatement of carpet shrinkage; antirot and antidust protection of carpets; impregnating compound for filter cloths;
* Construction engineering: hydrophobization of construction materials, treatment of coated surfaces; porosity decreasing impregnation of concrete; manufacture of acid-resistant cement;
* Glasswork and cerarnics: antireflection treatment of optical glass; application of light-diffusing coat to electric light bulbs; binding agent for ceramic mixtures, resistant to strongly corrosive mediums, with high manufacture of fireproof material standing temperatures of about 1750 °C and stress of above 127 kg/cm3;
* Coating industry: paint additives forming quick-drying, thermostable and water-resistant coats with constant gloss. | 0 | Theoretical and Fundamental Chemistry |
Lower-than-normal ceruloplasmin levels may indicate the following:
* Wilson disease (a rare [UK incidence 2/100,000] copper storage disease).
* Menkes disease (Menkes kinky hair syndrome) (rare – UK incidence 1/100,000)
* Copper deficiency
* Aceruloplasminemia
* Zinc toxicity | 1 | Applied and Interdisciplinary Chemistry |
Passage of hydrogen chloride through molten MsO yields MsCl.
Similar to MsCl, MsO can perform mesylation of alcohols to form sulfonates. Use of MsO avoids the alkyl chloride, which often appears as a side-product when MsCl is used. Unlike MsCl, MsO may not be suitable for mesylation of the unsaturated alcohols.
Examples of mesylation of alcohols with MsO:
* Octadecyl methanesulfonate was prepared from octadecanol in pyridine.
* Secondary alcohol at the anomeric carbon of 2,3,4,5-O-Benzyl-protected glucose reacted to form a glycosyl mesylate, which was found to be more stable than its triflate counterpart, in 2,4,6-collidine.
MsO also converts amines to sulfonamides. | 0 | Theoretical and Fundamental Chemistry |
Another commonly employed space-holder for titanium foams is urea, which yielded porosities from 20 to 75%. Wen et al. produced foams exhibiting a bimodal pore distribution with porosities ranging from 55 to 75%, Young's moduli between 3–6.4 GPa, and a plateau stress of 10–35 MPa. An inverse relationship between plateau stress and porosity was observed with increased porosity resulting in decreased plateau stress. Tuncer et al. utilized urea in combination with irregularly shaped titanium powders in an effort to increase green strength through increased packing efficiency (of particles). This also eliminated the need for the incorporation of a binder. | 0 | Theoretical and Fundamental Chemistry |
Exfoliation (or onion skin weathering) is the gradual removing of spall due to the cyclic increase and decrease in the temperature of the surface layers of the rock. Rocks do not conduct heat well, so when they are exposed to extreme heat, the outermost layer becomes much hotter than the rock underneath causing differential thermal expansion. This differential expansion causes sub-surface shear stress, in turn causing spalling. Extreme temperature change, such as forest fires, can also cause spalling of rock. This mechanism of weathering causes the outer surface of the rock to fall off in thin fragments, sheets or flakes, hence the name exfoliation or onion skin weathering. | 1 | Applied and Interdisciplinary Chemistry |
In order to simultaneously manipulate and image samples that exhibit fluorescence, optical tweezers can be built alongside a fluorescence microscope. Such instruments are particularly useful when it comes to studying single or small numbers of biological molecules that have been fluorescently labelled, or in applications in which fluorescence is used to track and visualize objects that are to be trapped.
This approach has been extended for simultaneous sensing and imaging of dynamic protein complexes using long and strong tethers generated by a highly efficient multi-step enzymatic approach and applied to investigations of disaggregation machines in action. | 1 | Applied and Interdisciplinary Chemistry |
Despite the fact that PPIs have revolutionized the treatment of GERD, there is still room for improvement in the speed of onset of acid suppression as well as mode of action that is independent of an acidic environment and also better inhibition of the proton pump. Therefore, a new class of PPIs, potassium-competitive acid blockers (P-CABs) or acid pump antagonists (APAs), have been under development the past years and will most likely be the next generation of drugs that suppress gastric activity. These new agents can in a reversible and competitive fashion inhibit the final step in the gastric acid secretion with respect to K binding to the parietal cell gastric H/K ATPase. That is, they block the action of the H/K ATPase by binding to or near the site of the K channel. Since the binding is competitive and reversible these agents have the potential to achieve faster inhibition of acid secretion and longer duration of action compared to PPIs, resulting in quicker symptom relief and healing. The imidazopyridine-based compound SCH28080 was the prototype of this class, and turned out to be hepatotoxic. Newer agents that are currently in development include CS-526, linaprazan, soraprazan and revaprazan in which the latter have reached clinical trials. Studies remain to determine whether these or other related compounds can become useful. In June 2006, Yuhan obtained approval from the Korean FDA for the use of revaprazan (brand name Revanex) in the treatment of gastritis. Vonoprazan is marketed in Japan. | 1 | Applied and Interdisciplinary Chemistry |
Nicotinamide adenine dinucleotide (NAD) is a coenzyme central to metabolism. Found in all living cells, NAD is called a dinucleotide because it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an adenine nucleobase and the other, nicotinamide. NAD exists in two forms: an oxidized and reduced form, abbreviated as NAD and NADH (H for hydrogen), respectively.
In cellular metabolism, NAD is involved in redox reactions, carrying electrons from one reaction to another, so it is found in two forms: NAD is an oxidizing agent, accepting electrons from other molecules and becoming reduced; with H, this reaction forms NADH, which can be used as a reducing agent to donate electrons. These electron transfer reactions are the main function of NAD. It is also used in other cellular processes, most notably as a substrate of enzymes in adding or removing chemical groups to or from proteins, in posttranslational modifications. Because of the importance of these functions, the enzymes involved in NAD metabolism are targets for drug discovery.
In organisms, NAD can be synthesized from simple building-blocks (de novo) from either tryptophan or aspartic acid, each a case of an amino acid. Alternatively, more complex components of the coenzymes are taken up from nutritive compounds such as niacin; similar compounds are produced by reactions that break down the structure of NAD, providing a salvage pathway that recycles them back into their respective active form.
Some NAD is converted into the coenzyme nicotinamide adenine dinucleotide phosphate (NADP), whose chemistry largely parallels that of NAD, though its predominant role is as a coenzyme in anabolic metabolism.
In the name NAD, the superscripted plus sign indicates the positive formal charge on one of its nitrogen atoms. | 0 | Theoretical and Fundamental Chemistry |
Toc75 is the most abundant protein on the outer chloroplast envelope. It is a transmembrane tube that forms most of the TOC pore itself. Toc75 is a β-barrel channel lined by 16 β-pleated sheets. The hole it forms is about 2.5 nanometers wide at the ends, and shrinks to about 1.4–1.6 nanometers in diameter at its narrowest point—wide enough to allow partially folded chloroplast preproteins to pass through.
Toc75 can also bind to chloroplast preproteins, but is a lot worse at this than Toc34 or Toc159.
Arabidopsis thaliana has multiple isoforms of Toc75 that are named by the chromosomal positions of the genes that code for them. AtToc75 III is the most abundant of these. | 0 | Theoretical and Fundamental Chemistry |
There are several methods for measuring particle size and particle size distribution. Some of them are based on light, other on ultrasound, or electric field, or gravity, or centrifugation. The use of sieves is a common measurement technique, however this process can be more susceptible to human error and is time consuming. Technology such as dynamic image analysis (DIA) can make particle size distribution analyses much easier. This approach can be seen in instruments like Retsch Technology's CAMSIZER or the Sympatec QICPIC series of instruments. They still lack the capability of inline measurements for real time monitoring in production environments. Therefore, inline imaging devices like the SOPAT system are most efficient.
Machine learning algorithms are used to increase the performance of particle size measurement. This line of research can yield low-cost and real time particle size analysis.
In all methods the size is an indirect measure, obtained by a model that transforms, in abstract way, the real particle shape into a simple and standardized shape, like a sphere (the most usual) or a cuboid (when minimum bounding box is used), where the size parameter (ex. diameter of sphere) makes sense. Exception is the mathematical morphology approach, where no shape hypothesis is necessary.
Definition of the particle size for an ensemble (collection) of particles presents another problem. Real systems are practically always polydisperse, which means that the particles in an ensemble have different sizes. The notion of particle size distribution reflects this polydispersity. There is often a need for a certain average particle size for the ensemble of particles. | 0 | Theoretical and Fundamental Chemistry |
Some reactions that are accomplished using M-Josiphos complexes as catalyst are listed below. Other reactions where Josiphos ligands can be used are: hydrogenation of C=N, C=C and C=O bonds, catalyzed allylic substitution, hydrocarboxylation, Michael addition, allylic alkylation, Heck-type reactions, oxabicycle ring-opening, and allylamine isomerization.
; Hydroboration of styrene
:Conducted at -78 °C, the above reaction has e.e.s up to 92% and TOF of 5-10 h. Hayashis Rh-binap complex gives better yield.
; Hydroformylation of Styrene
:This reaction scheme yields of up to 78% ee of the (R) product, but low TON and TOF of 10-210 and 1-14h (respectively).
;Reductive amination
:Above is the preparation of (S)-metolachlor. Good yields and a 100% conversion crucially require AcOH solvent.
;Hydrogenation of exocyclic methyl imine
:This key step to synthesize a HIV integrase inhibitor, Crixivan, is one of the few known homogeneous heteroarene hydrogenation reactions. Bulky R groups increase the catalyst's performance, with 97% e.e. and TON and TOF of 1k and 8 min, respectively.
;Asymmetric synthesis of chromanoylpyridine derivatives
:This reaction, for an intermediate in synthesis of an antihypertensive and anti-alopecic chromanoylpyridine derivative, exhibits high enantioselectivity, but low activity. | 0 | Theoretical and Fundamental Chemistry |
Bilins, bilanes or bile pigments are biological pigments formed in many organisms as a metabolic product of certain porphyrins. Bilin (also called bilichrome) was named as a bile pigment of mammals, but can also be found in lower vertebrates, invertebrates, as well as red algae, green plants and cyanobacteria. Bilins can range in color from red, orange, yellow or brown to blue or green.
In chemical terms, bilins are linear arrangements of four pyrrole rings (tetrapyrroles). In human metabolism, bilirubin is a breakdown product of heme. A modified bilane is an intermediate in the biosynthesis and uroporphyrinogen III from porphobilinogen.
Examples of bilins are found in animals (cardinal examples are bilirubin and biliverdin), and phycocyanobilin, the chromophore of the photosynthetic pigment phycocyanin, in algae and plants. In plants, bilins also serve as the photopigments of the photoreceptor protein phytochrome. An example of an invertebrate bilin is micromatabilin, which is responsible for the green color of the Green Huntsman Spider, Micrommata virescens. | 1 | Applied and Interdisciplinary Chemistry |
Methyl vinyl ketone, ethyl acetoacetate, and diethyl-methyl-(3-oxo-butyl)-ammonium iodide react to form a cyclic aldol product. Sodium methoxide is added to generate Hagemann's ester. | 0 | Theoretical and Fundamental Chemistry |
Born on 15 August 1946 in Ikwerre Local Government Area, Rivers State, Nigeria, Achinewhu had his primary education in his home town Aluu. He finished from County Grammar School, Ikwerre/Etche in 1963 with Grade One. He later proceeded to Government Secondary School, Owerri and got his Higher School Certificate in physics, chemistry, and zoology in 1965. In 1970, Achinewhu graduated from the University of Ibadan, B.Sc. second class honors, M.Sc. in 1972 and Ph.D. 1975 in food science and technology from University of Reading, UK. | 1 | Applied and Interdisciplinary Chemistry |
A15 phases are intermetallic alloys with an average coordination number (ACN) of 13.5 and eight AB stoichiometry atoms per unit cell where two B atoms are surrounded by CN12 polyhedral (icosahedra), and six A atoms are surrounded by CN14 polyhedral. NbGe is a superconductor with A15 structure. | 1 | Applied and Interdisciplinary Chemistry |
A cyclic compound or ring compound is a compound in which at least some its atoms are connected to form a ring. Rings vary in size from three to many tens or even hundreds of atoms. Examples of ring compounds readily include cases where:
* all the atoms are carbon (i.e., are carbocycles),
* none of the atoms are carbon (inorganic cyclic compounds), or where
* both carbon and non-carbon atoms are present (heterocyclic compounds with rings containing both carbon and non-carbon).
Common atoms can (as a result of their valences) form varying numbers of bonds, and many common atoms readily form rings. In addition, depending on the ring size, the bond order of the individual links between ring atoms, and their arrangements within the rings, cyclic compounds may be aromatic or non-aromatic; in the case of non-aromatic cyclic compounds, they may vary from being fully saturated to having varying numbers of multiple bonds. As a consequence of the constitutional variability that is thermodynamically possible in cyclic structures, the number of possible cyclic structures, even of small size (e.g., <17 atoms) numbers in the many billions.
Moreover, the closing of atoms into rings may lock particular functional group–substituted atoms into place, resulting in stereochemistry and chirality being associated with the compound, including some manifestations that are unique to rings (e.g., configurational isomers); As well, depending on ring size, the three-dimensional shapes of particular cyclic structures — typically rings of five atoms and larger — can vary and interconvert such that conformational isomerism is displayed. | 0 | Theoretical and Fundamental Chemistry |
Gibbs papers defined what Gibbs called the "thermodynamic surface," which expressed the relationship between the volume, entropy, and energy of a substance at different temperatures and pressures. However, Gibbs did not include any diagrams of this surface. After receiving reprints of Gibbs papers, Maxwell recognized the insight afforded by Gibbs new point of view and set about constructing physical three-dimensional models of the surface. This reflected Maxwells talent as a strong visual thinker and prefigured modern scientific visualization techniques.
Maxwell sculpted the original model in clay and made several plaster casts of the clay model, sending one to Gibbs as a gift, keeping two in his laboratory at Cambridge University. Maxwells copy is on display at the Cavendish Laboratory of Cambridge University, while Gibbs copy is on display at the Sloane Physics Laboratory of Yale University, where Gibbs held a professorship. Two copies reside at the National Museum of Scotland, one via Peter Tait and the other via George Chrystal. Another was sent to Thomas Andrews. A number of historic photographs were taken of these plaster casts during the middle of the twentieth century – including one by James Pickands II, published in 1942 – and these photographs exposed a wider range of people to Maxwell's visualization approach. | 0 | Theoretical and Fundamental Chemistry |
It has been hypothesized that blockage of the PI3K/AKT/mTOR pathway can lead to increased antitumor activity in TNBC. Preclinical data have shown that the combination of compounds targeting different cognate molecules in the PI3K/AKT/mTOR pathway leads to synergistic activity. On the basis of these findings, new compounds targeting different components of the PI3K/AKT/mTOR pathway simultaneously continue to be developed. For example, gedatolisib inhibits mutant forms of PI3K-α with elevated kinase activity at concentrations equivalent to the IC50 for wild-type PI3K-α. PI3K-β, -δ and -γ isoforms were inhibited by gedatolisib at concentrations approximately 10-fold higher than those observed for PI3K-α. Another advantage of simultaneously targeting PI3K and mTOR is the ensuing more robust inhibition of receptor tyrosine kinase-positive feedback loops seen with isolated PI3K inhibition. Gedatolisib is currently under development for the treatment of TNBC, in combination with PTK7 antibody–drug conjugate. Apitolisib (GDC-0980) is a PI3K inhibitor (subunits α, δ, and γ) that also targets mTORC | 1 | Applied and Interdisciplinary Chemistry |
The core of PSII consists of a pseudo-symmetric heterodimer of two homologous proteins D1 and D2. Unlike the reaction centers of all other photosystems in which the positive charge sitting on the chlorophyll dimer that undergoes the initial photoinduced charge separation is equally shared by the two monomers, in intact PSII the charge is mostly localized on one chlorophyll center (70−80%). Because of this, P680 is highly oxidizing and can take part in the splitting of water.
Photosystem II (of cyanobacteria and green plants) is composed of around 20 subunits (depending on the organism) as well as other accessory, light-harvesting proteins. Each photosystem II contains at least 99 cofactors: 35 chlorophyll a, 12 beta-carotene, two pheophytin, two plastoquinone, two heme, one bicarbonate, 20 lipids, the cluster (including two chloride ions), one non heme and two putative ions per monomer. There are several crystal structures of photosystem II. The PDB accession codes for this protein are , , (3BZ1 and 3BZ2 are monomeric structures of the Photosystem II dimer), , , , , , . | 0 | Theoretical and Fundamental Chemistry |
The first potentiometric titration was carried out in 1893 by Robert Behrend at Ostwald's Institute in Leipzig. He titrated mercurous solution with potassium chloride, potassium bromide, and potassium iodide. He used a mercury electrode along with a mercury/mercurous nitrate reference electrode. He found that in a cell composed of mercurous nitrate and mercurous nitrate/mercury, the initial voltage is 0. If potassium chloride is added to mercurous nitrate on one side, mercury (I) chloride is precipitated. This decreased the osmotic pressure of mercury (I) ions on the side and creates a potential difference. This potential difference increases slowly as additional potassium chloride is added, but then increases more rapidly. He found the greatest potential difference is achieved once all of the mercurous nitrate has been precipitated. This was used to discern end points of titrations.
Wilhelm Böttger then developed the tool of potentiometric titration while working at Ostwald's Institute. He used potentiometric titration to observe the differences in titration between strong and weak acids, as well as the behavior of polybasic acids. He introduced the idea of using potentiometric titrations for acids and bases that could not be titrated in conjunction with a colorimetric indicator
Potentiometric titrations were first used for redox titrations by Crotogino. He titrated halide ions with potassium permanganate using a shiny platinum electrode and a calomel electrode. He said that if an oxidizing agent is added to a reducing solution then the equilibrium between the reducing substance and reaction product will shift towards the reaction product. This changes the potential very slowly until the amount of reducing substance becomes very small. A large change in potential will occur then once a small addition of the titrating solution is added, as the final amounts of reducing agent are removed and the potential corresponds solely to the oxidizing agent. This large increase in potential difference signifies the endpoint of the reaction. | 0 | Theoretical and Fundamental Chemistry |
In 2003, Paterson and co-workers reported a strategy that relies heavily on substrate-derived stereocontrol. Instead of a reagent-controlled aldol reaction in Paterson first-generation synthesis, a dicyclohexylboron-mediated anti-aldol was used to connect C(5)-C(6), which leads to a significant increase in diastereoselectivity from 4:1 to 92:8. Notably, Still–Gennari modified Horner–Wadsworth–Emmons reaction was also used to construct the C(13)-C(14) trisubstituted olefin in early stage of this synthesis. The Paterson second-generation synthesis of (+)-discodermolide has an overall yield of 7.8% with a longest linear sequence of 24 steps and 35 total steps.
In 2004, Paterson and his co-workers disclosed the third-generation total synthesis of (+)-discodermolide. The stepwise method used in previous generations to incorporate the C(1)–C(8) subunit was replaced by a late-stage Still-Gennari olefination, which leads to a notable improvement in convergence. The Paterson third-generation synthesis of (+)-discodermolide has an overall yield of 11.1% (highest reported to date) with a longest linear sequence of 21 steps and 37 total steps. | 0 | Theoretical and Fundamental Chemistry |
In 1977, Edmonds et al. reported the identification, isolation, and synthesis of major arsenic-containing substance in sea organisms, the arsenobetaine. In 1999, NRC certified arsenobetaine in the dogfish muscle material DORM-2, which became the first matrix reference material certified for arsenobetaine. Before DORM-2, DORM-1 (issued in 1986) served as the reference material for which the concentration of arsenobetaine was widely reported in scientific literature. Besides arsenobetaine, NRC currently offers matrix reference materials certified for methylmercury (TORT-3), dibutyltin, and tributyltin (PACS-3).
* Biological tissues and sediments
** CARP, fish for dioxins, furans, and PCBs
** DOLT, dogfish liver for methylmercury
** DORM, fish protein for methylmercury
** TORT, lobster hepatopancreas for methylmercury and arsenobetaine
** PACS and SOPH, marine sediment for dibutyltin and tributyltin
** SELM, selenium-enriched yeast for methionine and selenomethionine | 1 | Applied and Interdisciplinary Chemistry |
Deane Judd was very interested the effect of light polarization and degree of diffusion on the appearance of objects. He made important contributions to the fields of colorimetry, color discrimination, color order, and color vision. Judd defined the scattering power for a sample as , where is the particle diameter. This is consistent with the belief that the scattering from a single particle is conceptually more important than the derived coefficients.
The above Kubelka–Munk equation can be resolved for the ratio in terms of . This led to a very early (perhaps the first) use of the term "remission" in place of "reflectance" when Judd defined a "remission function" as , where and are absorption and scattering coefficients, which replace and in the Kubelka–Munk equation above. Judd tabulated the remission function as a function of percent reflectance from an infinitely thick sample. This function, when used as a measure of absorption, was sometimes referred to as "pseudo-absorbance", a term which has been used later with other definitions as well. | 0 | Theoretical and Fundamental Chemistry |
One of the main competing models for cpDNA asserts that most cpDNA is linear and participates in homologous recombination and replication structures similar to bacteriophage T4. It has been established that some plants have linear cpDNA, such as maize, and that more still contain complex structures that scientists do not yet understand; however, the predominant view today is that most cpDNA is circular. When the original experiments on cpDNA were performed, scientists did notice linear structures; however, they attributed these linear forms to broken circles. If the branched and complex structures seen in cpDNA experiments are real and not artifacts of concatenated circular DNA or broken circles, then a D-loop mechanism of replication is insufficient to explain how those structures would replicate. At the same time, homologous recombination does not explain the multiple A → G gradients seen in plastomes. This shortcoming is one of the biggest for the linear structure theory. | 0 | Theoretical and Fundamental Chemistry |
Acute respiratory distress syndrome, respiratory syncytial virus infection, familial lung disease, and pneumocystis infection are examples of deficiencies in and issues with SP-B that are correlated with lung issues.
Because so many lung conditions are associated with issues around SP-B, synthetic replacements have been researched, created, and manufactured. It has been shown that 21 amino acid long peptides with positive charge and intermittent hydrophobic regions mimicking SP-B can minimize surface tension at the gas/fluid interface, and surfactant replacements for surfactant deficient patients has been used to save lives.
Once lung distress has occurred, SP-B has been shown to be effective as a biomarker in the blood stream. Higher levels of SP-B indicate some kind of lung distress, and can even indicate if the patient is currently a smoker. This may be useful in the future to predict atherosclerosis, a solidifying of vascular tissue that has negative effects on the heart. | 0 | Theoretical and Fundamental Chemistry |
Allelic exclusion is a process of gene expression when one allele is expressed and the other one kept silent. Two most studied cases of allelic exclusion are monoallelic expression of immunoglobulins in B and T cells and olfactory receptors in sensory neurons. Allelic exclusion is cell-type specific (as opposed to organism-wide XCI), which increases intercellular diversity, thus specificity towards certain antigens or odors.
Allele-biased expression is skewed expression level of one allele over the other, but both alleles are still expressed (in contrast to allelic exclusion). This phenomenon is often observed in cells of immune function | 1 | Applied and Interdisciplinary Chemistry |
Polar–π interactions involve molecules with permanent dipoles (such as water) interacting with the quadrupole moment of a π-system (such as that in benzene (see figure 5). While not as strong as a cation-π interaction, these interactions can be quite strong (~1-2 kcal/mol), and are commonly involved in protein folding and crystallinity of solids containing both hydrogen bonding and π-systems. In fact, any molecule with a hydrogen bond donor (hydrogen bound to a highly electronegative atom) will have favorable electrostatic interactions with the electron-rich π-system of a conjugated molecule. | 0 | Theoretical and Fundamental Chemistry |
The overdamped Langevin equationgives . The Boltzmann distribution is an equilibrium distribution, and assuming grows sufficiently rapidly (that is, the potential well is deep enough to confine the particle), the Boltzmann distribution is the unique equilibrium. | 1 | Applied and Interdisciplinary Chemistry |
* Azafullerenes are a class of heterofullerenes in which the element substituting for carbon is nitrogen. Examples include (biazafullerenyl), (diaza[60]fullerene), (triaza[60]fullerene) and . | 0 | Theoretical and Fundamental Chemistry |
For xDNA to be used as a substitute structure for information storage, it requires a reliable replication mechanism. Research into xDNA replication using a Klenow fragment from DNA polymerase I shows that a natural base partner is selectively added in instances of single-nucleotide insertion. However, DNA polymerase IV (Dpo4) has been able to successfully use xDNA for these types of insertions with high fidelity, making it a promising candidate for future research in extending replicates of xDNA. xDNA's mismatch sensitivity is similar to that of B-DNA. | 1 | Applied and Interdisciplinary Chemistry |
Oligosaprobes are organisms that inhabit clean water or water that is only slightly polluted by organic matter. Oxidation processes predominate in such waters owing to an excess of dissolved oxygen. Nitrates are among the nitrogen compounds present; there is little carbonic acid and no hydrogen sulfide. Oligosaprobic environments are aquatic environments rich in dissolved oxygen and (relatively) free from decayed organic matter. | 0 | Theoretical and Fundamental Chemistry |
Regarding biological membranes, the liquid ordered phase is a liquid crystalline phase of a lipid bilayer, and is of significant biological importance. It occurs in many lipid mixtures combining cholesterol with a phospholipid and/or sphingolipids e.g. sphingomyelin. This phase has been related to lipid rafts that may exist in plasma membranes. | 1 | Applied and Interdisciplinary Chemistry |
The simplest monoalkene is ethene. Many complexes of ethene are known, including Zeise's salt (see figure), RhCl(CH), Cp*Ti(CH), and the homoleptic Ni(CH). Substituted monoalkene include the cyclic cyclooctene, as found in chlorobis(cyclooctene)rhodium dimer. Alkenes with electron-withdrawing groups commonly bind strongly to low-valent metals. Examples of such ligands are TCNE, tetrafluoroethylene, maleic anhydride, and esters of fumaric acid. These acceptors form adducts with many zero-valent metals. | 0 | Theoretical and Fundamental Chemistry |
A monokine is a type of cytokine produced primarily by monocytes and macrophages.
Some monokines are:
* interleukin 1
* tumor necrosis factor-alpha
* alpha and beta interferon
* colony stimulating factors | 1 | Applied and Interdisciplinary Chemistry |
Glycogen was discovered by Claude Bernard. His experiments showed that the liver contained a substance that could give rise to reducing sugar by the action of a "ferment" in the liver. By 1857, he described the isolation of a substance he called "la matière glycogène", or "sugar-forming substance". Soon after the discovery of glycogen in the liver, A. Sanson found that muscular tissue also contains glycogen. The empirical formula for glycogen of () was established by Kekulé in 1858. | 1 | Applied and Interdisciplinary Chemistry |
As a hydrogen storage alloy, LaNi can absorb hydrogen to form the hydride LaNiH (x≈6) when the pressure is slightly high and the temperature is low, or when the pressure decreases or the temperature increases, hydrogen can be released to form repeated absorption and release of hydrogen. But for the dehydrogenation process, because it is an endothermic reaction, in order to enable the reaction to proceed, the necessary energy must be added, otherwise the reaction will stop due to the decrease in temperature. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, persulfide refers to the functional group R-S-S-H. Persulfides are intermediates in the biosynthesis of iron-sulfur proteins and are invoked as precursors to hydrogen sulfide, a signaling molecule. | 0 | Theoretical and Fundamental Chemistry |
Hammond's postulate is especially important when looking at the rate-limiting step of a reaction. However, one must be cautious when examining a multistep reaction or one with the possibility of rearrangements during an intermediate stage. In some cases, the final products appear in skewed ratios in favor of a more unstable product (called the kinetic product) rather than the more stable product (the thermodynamic product). In this case one must examine the rate-limiting step and the intermediates. Often, the rate-limiting step is the initial formation of an unstable species such as a carbocation. Then, once the carbocation is formed, subsequent rearrangements can occur. In these kinds of reactions, especially when run at lower temperatures, the reactants simply react before the rearrangements necessary to form a more stable intermediate have time to occur. At higher temperatures when microscopic reversal is easier, the more stable thermodynamic product is favored because these intermediates have time to rearrange. Whether run at high or low temperatures, the mixture of the kinetic and thermodynamic products eventually reach the same ratio, one in favor of the more stable thermodynamic product, when given time to equilibrate due to microreversal. | 0 | Theoretical and Fundamental Chemistry |
Chiral thin-layer chromatography is a variant of liquid chromatography that is employed for the separation of enantiomers. It is necessary to use either
* a chiral stationary phase or
* a chiral additive in the mobile phase.
The chiral stationary phase can be prepared by mixing chirally pure reagents such as L-amino acid, or brucine, or a chiral ligand exchange reagent with silica gel slurry, or by impregnation of the TLC plate in the solution of a chiral reagent.
The principle can also be applied to chemically modify the stationary phase before making the plate via bonding of the chiral moieties of interest to the reactive groups of the layer material. | 0 | Theoretical and Fundamental Chemistry |
Protic ionic liquids are formed via a proton transfer from an acid to a base. In contrast to other ionic liquids, which generally are formed through a sequence of synthesis steps, protic ionic liquids can be created more easily by simply mixing the acid and base.
Phosphonium cations (RP) are less common but offer some advantageous properties. Some examples of phosphonium cations are trihexyl(tetradecyl)phosphonium (P) and tributyl(tetradecyl)phosphonium (P). | 0 | Theoretical and Fundamental Chemistry |
Most, if not all, metals can be sintered. This applies especially to pure metals produced in vacuum which suffer no surface contamination. Sintering under atmospheric pressure requires the use of a protective gas, quite often endothermic gas. Sintering, with subsequent reworking, can produce a great range of material properties. Changes in density, alloying, and heat treatments can alter the physical characteristics of various products. For instance, the Youngs modulus E' of sintered iron powders remains somewhat insensitive to sintering time, alloying, or particle size in the original powder for lower sintering temperatures, but depends upon the density of the final product:
where D is the density, E is Youngs modulus and d' is the maximum density of iron.
Sintering is static when a metal powder under certain external conditions may exhibit coalescence, and yet reverts to its normal behavior when such conditions are removed. In most cases, the density of a collection of grains increases as material flows into voids, causing a decrease in overall volume. Mass movements that occur during sintering consist of the reduction of total porosity by repacking, followed by material transport due to evaporation and condensation from diffusion. In the final stages, metal atoms move along crystal boundaries to the walls of internal pores, redistributing mass from the internal bulk of the object and smoothing pore walls. Surface tension is the driving force for this movement.
A special form of sintering (which is still considered part of powder metallurgy) is liquid-state sintering in which at least one but not all elements are in a liquid state. Liquid-state sintering is required for making cemented carbide and tungsten carbide.
Sintered bronze in particular is frequently used as a material for bearings, since its porosity allows lubricants to flow through it or remain captured within it. Sintered copper may be used as a wicking structure in certain types of heat pipe construction, where the porosity allows a liquid agent to move through the porous material via capillary action. For materials that have high melting points such as molybdenum, tungsten, rhenium, tantalum, osmium and carbon, sintering is one of the few viable manufacturing processes. In these cases, very low porosity is desirable and can often be achieved.
Sintered metal powder is used to make frangible shotgun shells called breaching rounds, as used by military and SWAT teams to quickly force entry into a locked room. These shotgun shells are designed to destroy door deadbolts, locks and hinges without risking lives by ricocheting or by flying on at lethal speed through the door. They work by destroying the object they hit and then dispersing into a relatively harmless powder.
Sintered bronze and stainless steel are used as filter materials in applications requiring high temperature resistance while retaining the ability to regenerate the filter element. For example, sintered stainless steel elements are employed for filtering steam in food and pharmaceutical applications, and sintered bronze in aircraft hydraulic systems.
Sintering of powders containing precious metals such as silver and gold is used to make small jewelry items. Evaporative self-assembly of colloidal silver nanocubes into supercrystals has been shown to allow the sintering of electrical joints at temperatures lower than 200°C. | 1 | Applied and Interdisciplinary Chemistry |
Peripheral node addressin, often referred to as PNAd, are glycoprotein ligands. More formally, the term includes "lymph" to specify the node: peripheral lymph node addressin.
PNAd is a critical component of the immune system, enabling the targeted migration of lymphocytes to the lymph nodes and facilitating an effective immune response. PNAd's role in lymphocyte homing is essential for the proper functioning of the immune system, as it ensures that lymphocytes can efficiently enter the lymph nodes to encounter and respond to foreign antigens, such as viruses and bacteria.
PNAd is a type of cell adhesion molecule found on the surface of high endothelial venules (HEVs) in lymph nodes. It plays a crucial role in the immune system by facilitating the migration of lymphocytes, a type of white blood cell, from the bloodstream to the lymph nodes where they participate in immune responses.
The process of lymphocyte migration from the bloodstream to the lymph nodes is called lymphocyte homing. PNAd plays a key role in this process by interacting with L-selectin, which is present on the surface of lymphocytes. The adhesion molecule L-selectin binds to sulfated carbohydrate ligands on high endothelial venules (HEV). The binding between PNAd and L-selectin allows lymphocytes to slow down and roll along the inner surface of HEVs. This rolling action enables lymphocytes to come into close contact with other molecules called chemokines, which trigger the firm adhesion and subsequent transmigration of lymphocytes across the endothelial cells and into the lymph node. | 1 | Applied and Interdisciplinary Chemistry |
Inorganica Chimica Acta is a peer-reviewed scientific journal published since 1967 that covers original research and reviews of fundamental and applied aspects of inorganic chemistry. | 0 | Theoretical and Fundamental Chemistry |
Much of the Bay is shallow. At the point where the Susquehanna River flows into the Bay, the average depth is , although this soon diminishes to an average of southeast of the city of Havre de Grace, Maryland, to about just north of Annapolis. On average, the depth of the Bay is , including tributaries; over 24 percent of the Bay is less than deep.
Because the Bay is an estuary, it has fresh water, salt water and brackish water. Brackish water has three salinity zones: oligohaline, mesohaline, and polyhaline. The freshwater zone runs from the mouth of the Susquehanna River to north Baltimore. The oligohaline zone has very little salt. Salinity varies from 0.5 ppt (parts per thousand) to 10 ppt, and freshwater species can survive there. The north end of the oligohaline zone is north Baltimore and the south end is the Chesapeake Bay Bridge. The mesohaline zone has a medium amount of salt and runs from the Bay Bridge to the mouth of the Rappahannock River. Salinity there ranges from 1.07% to 1.8%. The polyhaline zone is the saltiest zone, and some of the water can be as salty as sea water. It runs from the mouth of the Rappahannock River to the mouth of the Bay. The salinity ranges from 1.87% to 3.6%. (3.6% is as salty as the ocean.)
The climate of the area surrounding the Bay is primarily humid subtropical, with hot, very humid summers and cold to mild winters. Only the area around the mouth of the Susquehanna River is continental in nature, and the mouth of the Susquehanna River and the Susquehanna flats often freeze in winter. It is rare for the surface of the Bay to freeze in winter, something that happened most recently in the winter of 1976–77.
The Chesapeake Bay is the end point of over 150 rivers and streams. The largest rivers flowing directly into the Bay, in order of discharge, are:
* Susquehanna River
* Potomac River
* James River
* Rappahannock River
* York River
* Patuxent River
* Choptank River
For more information on Chesapeake Bay rivers, see the List of Chesapeake Bay rivers. | 1 | Applied and Interdisciplinary Chemistry |
Chromatographic response function, often abbreviated to CRF, is a coefficient which measures the quality of the separation in the result of a chromatography.
The CRF concept have been created during the development of separation optimization, to compare the quality of many simulated or real chromatographic separations. Many CRFs have been proposed and discussed.
In high performance liquid chromatography the CRF is calculated from various parameters of the peaks of solutes (like width, retention time, symmetry etc.) are considered into the calculation. In TLC the CRFs are based on the placement of the spots, measured as RF values. | 0 | Theoretical and Fundamental Chemistry |
SPINA-GT is elevated in primary hyperthyroidism and reduced in both primary hypothyroidism and untreated autoimmune thyroiditis. It has been observed to correlate (with positive direction) to resting energy expenditure, resting heart rate, the colour Doppler ultrasound pattern and thyroid volume, and (with negative direction) to thyroid autoantibody titres, which reflect organ destruction due to autoimmunity. Elevated SPINA-GT in Graves' disease is reversible with antithyroid treatment. While SPINA-GT is significantly altered in primary thyroid disorders, it is insensitive to disorders of secondary nature (e.g. pure pituitary diseases). | 1 | Applied and Interdisciplinary Chemistry |
From the ideal gas law PV = nRT we get:
where P is pressure, V is volume, n is number of moles of a given substance, and T is temperature.
As pressure is defined as force per area of measurement, the gas equation can also be written as:
Area and volume are (length) and (length) respectively. Therefore:
Since force × length = work:
The physical significance of R is work per mole per degree. It may be expressed in any set of units representing work or energy (such as joules), units representing degrees of temperature on an absolute scale (such as kelvin or rankine), and any system of units designating a mole or a similar pure number that allows an equation of macroscopic mass and fundamental particle numbers in a system, such as an ideal gas (see Avogadro constant).
Instead of a mole the constant can be expressed by considering the normal cubic meter.
Otherwise, we can also say that:
Therefore, we can write R as:
And so, in terms of SI base units:
:R = . | 0 | Theoretical and Fundamental Chemistry |
Mitscherlich's law of isomorphism, or the law of isomorphism, is an approximate law suggesting that crystals composed of the same number of similar elements tend to demonstrate isomorphism.
Mitscherlich's law is named for German chemist Eilhard Mitscherlich, who formulated the law and published it between 1819 and 1823.
According to Ferenc Szabadváry, one of the clues that helped Berzelius determine the atomic weights of the elements was "the discovery of Mitscherlich that compounds which contain the same number of atoms and have similar structures, exhibit similar crystal forms (isomorphism)." | 0 | Theoretical and Fundamental Chemistry |
The chemical potential, , of a substance B in an ideal mixture of liquids or an ideal solution is given by
where μ is the chemical potential of a pure substance , and is the mole fraction of the substance in the mixture.
This is generalised to include non-ideal behavior by writing
when is the activity of the substance in the mixture,
where is the activity coefficient, which may itself depend on . As approaches 1, the substance behaves as if it were ideal. For instance, if ≈ 1, then Raoults law is accurate. For > 1 and < 1, substance B shows positive and negative deviation from Raoults law, respectively. A positive deviation implies that substance B is more volatile.
In many cases, as goes to zero, the activity coefficient of substance B approaches a constant; this relationship is Henry's law for the solvent. These relationships are related to each other through the Gibbs–Duhem equation.
Note that in general activity coefficients are dimensionless.
In detail: Raoult's law states that the partial pressure of component B is related to its vapor pressure (saturation pressure) and its mole fraction in the liquid phase,
with the convention
In other words: Pure liquids represent the ideal case.
At infinite dilution, the activity coefficient approaches its limiting value, . Comparison with Henry's law,
immediately gives
In other words: The compound shows nonideal behavior in the dilute case.
The above definition of the activity coefficient is impractical if the compound does not exist as a pure liquid. This is often the case for electrolytes or biochemical compounds. In such cases, a different definition is used that considers infinite dilution as the ideal state:
with
and
The symbol has been used here to distinguish between the two kinds of activity coefficients. Usually it is omitted, as it is clear from the context which kind is meant. But there are cases where both kinds of activity coefficients are needed and may even appear in the same equation, e.g., for solutions of salts in (water + alcohol) mixtures. This is sometimes a source of errors.
Modifying mole fractions or concentrations by activity coefficients gives the effective activities of the components, and hence allows expressions such as Raoult's law and equilibrium constants to be applied to both ideal and non-ideal mixtures.
Knowledge of activity coefficients is particularly important in the context of electrochemistry since the behaviour of electrolyte solutions is often far from ideal, due to the effects of the ionic atmosphere. Additionally, they are particularly important in the context of soil chemistry due to the low volumes of solvent and, consequently, the high concentration of electrolytes. | 0 | Theoretical and Fundamental Chemistry |
In the environmental context, reactive nitrogen compounds include the following classes:
*oxide gases: nitric oxide, nitrogen dioxide, nitrous oxide. Containing oxidized nitrogen, mainly the result of industrial processes and internal combustion engines.
*anions: nitrate, nitrite. Nitrate is a common component of fertilizers, e.g. ammonium nitrate.
*amine derivatives: ammonia and ammonium salts, urea. Containing reduced nitrogen, these compounds are components of fertilizers.
All of these compounds enter into the nitrogen cycle.
As a consequence, an excess of Nr can affect the environment relatively quickly. This also means that nitrogen-related problems need to be looked at in an integrated manner. | 1 | Applied and Interdisciplinary Chemistry |
The phomoxanthones are named after the fungus Phomopsis, from which they were first isolated, and after their xanthonoid structure, which means they have structures similar to the compound xanthone (pictured on the left). Chemically, the phomoxanthones are dimers of two tetrahydroxanthones, meaning that they consist of two subunits of xanthonoids that have four hydroxy groups each. The two subunits of the phomoxanthones are covalently linked to each other. PXA itself is a homodimer, meaning that it consists of two identical subunits. Both of these subunits are diacetylated tetrahydroxanthones, so two of their hydroxy groups have been replaced by acetyl groups. The position of the link between the two dimer subunits is the only structural difference between PXA and its less toxic isomers phomoxanthone B (PXB) and dicerandrol C: In PXA, the two xanthonoid monomers are symmetrically linked at the position C-4,4’, while in PXB, they are asymmetrically linked at C-2,4’, and in dicerandrol C, they are symmetrically linked at C-2,2’. Otherwise, these three compounds are structurally identical. The phomoxanthones are structurally closely related to the secalonic acids, another class of dimeric tetrahydroxanthone mycotoxins, with which they share several properties. Notably, both the phomoxanthones and the secalonic acids are unstable when dissolved in polar solvents such as DMSO, with the covalent bond between the two monomers shifting between 2,2′-, 2,4′-, and 4,4′-linkage. The two phomoxanthones PXA and PXB can thus slowly isomerise into each other as well as into the essentially non-toxic dicerandrol C, resulting in a loss of activity of PXA over time when dissolved in a polar solvent. | 1 | Applied and Interdisciplinary Chemistry |
Sucrose esters were first mentioned in 1880 by Herzfeld who described the preparation of sucrose octaacetate. The substance is still in use today as a food additive. In 1921, Hess and Messner synthesized sucrose octapalmitate and sucrose octastearate. Both are sucrose fatty acid esters.
Rosenthal, in 1924, synthesized highly substituted sucrose fatty acid esters using the classical condensation reaction between sucrose and the acid chloride of the drying oil fatty acid; pyridine was used as a solvent. Rheineck, Rabin, and Long followed the same procedure using alternative polyhydroxyl molecules such as mannitol. These condensation gave low yields, and the products, which were dark in color, needed extensive purification. Moreover, pyridine is a toxic solvent, so the synthesis was not commercially successful.
In 1939, Cantor, who patented a production route of sucrose fatty acid esters from starch factory by-products, claimed that the products could be used as emulsifying agents or fats. The classical esterification was used with a mixture of pyridine and either chloroform or carbontetrachloride as a solvent.
Later, the concept of synthesizing sucrose ester from sucrose and fatty acids was patented in 1952. The new synthesis pathway, which involved transesterification of triglycerides and sucrose in the new solvent dimethylformamide or DMF, was invented and seemed promising.
In 1950s, Foster Snell and his team conducted research on the production of several mono- and di-substituted sucrose esters. Many processes are still used in commercial production today. | 0 | Theoretical and Fundamental Chemistry |
Mao's other nanotechnology research has focused on seed-mediated crystallization for nanosensor scale up. Her early research examined the potential of designing nucleation seeds to induce shape change in molecular crystals. In her investigation of the impact of seed size and surface chemistry, her study illustrated the capability of nanoparticles to effectively change the ordering pattern of molecular crystals nucleated on the nanoparticle. Moreover, she examined the use of electrochemistry to deposit both the nanoparticle seeds and the molecular crystals on the seed to form a hybrid nanostructure. In 2020, her research group introduced a method for manufacturing nanowire sensors by electrochemically depositing charge-transfer salt nanowire crystals on sensor substrates, demonstrating their gas sensing capabilities for detecting ammonia concentrations in the range of 1–100 ppm through electrical impedance measurements. In 2023, Mao demonstrated the potential of electrochemistry for precise deposition and scale up of nanosensors. She applied atomic force microscopy and surface forces measurement techniques for the study of colloidal and biomolecular interfaces including liposomes, DNA nanoparticles, and viral particles. | 1 | Applied and Interdisciplinary Chemistry |
A blockbuster drug is a drug that generates more than $1 billion in revenue for a pharmaceutical company in a single year. Cimetidine was the first drug ever to reach more than $1 billion a year in sales, thus making it the first blockbuster drug. | 1 | Applied and Interdisciplinary Chemistry |
The New Jersey Zinc process is no longer used to produce primary zinc in the U.S., in Europe and Japan, but it still is used to treat secondary operations. This process peaked in 1960, when it accounted for 5% of world zinc production. A modified version of this process is still used at Huludao, China, which produced 65,000 metric tons per year.
This process begins by roasting concentrates that are mixed with coal and briquetted in two stages. The briquettes are then heated in an autogenous coker at and then charged into the retort. There are three reasons to briquette the calcine: to ensure free downward movement of the charge; to permit heat transfer across a practical size cross-section; to allow adequate porosity for the passage of reduced zinc vapour to the top of the retort. The reduced zinc vapour that is collected at the top of the retort is then condensed to a liquid.
Overpelt improved upon this design by using only one large condensation chamber, instead of many small ones, as it was originally designed. This allowed for the carbon monoxide to be recirculated into the furnaces for heating the retorts.
This process was licensed to the Imperial Smelting Corporation (ISC), based in Avonmouth, England, which had a large vertical retort (VR) plant in production for many years. It was used until the mid-1970s when it was superseded by the company's Imperial Smelting Furnace (ISF) plant. The VR plant was demolished in 1975. | 1 | Applied and Interdisciplinary Chemistry |
The feasibility of a "British Journal of Chemistry Education" was first discussed by the Royal Society of Chemistry in late 1962 (a similar journal, the Journal of Chemical Education had been in existence in the USA since 1924). Its launch was secured by the lobbying of Professor Ronald S. Nyholm who became the first Chair of the editorial board. The magazine was launched in 1963 under the editor Dr F. W. Gibbs with the first issue published in January 1964. Gibbs' first editorial, "Scientists and Teachers", set out the aims of the publication, "This journal has been launched with the avowed aim of improving the teaching and learning of chemistry at all levels." The journal was initially published quarterly.
Education in Chemistry celebrated 50 years since its launch in 2013 with an event attended by its current and former staff, contributors, editorial board and some special guests including Bill Bryson. | 1 | Applied and Interdisciplinary Chemistry |
Phosphonic esters are prepared using the Michaelis–Arbuzov reaction. For example, methyl iodide catalyses the conversion of trimethylphosphite to the phosphonate ester dimethyl methylphosphonate:
:P(OMe) → MePO(OMe)
These esters can be hydrolysed to the acid (Me = methyl):
:MePO(OMe) + HO → MePO(OH) + 2 MeOH
In the Michaelis–Becker reaction, a hydrogen phosphonate diester is first deprotonated and the resulting anion is alkylated. | 0 | Theoretical and Fundamental Chemistry |
Beginning in 1915, Bayer set up a number of shell corporations and subsidiaries in the United States, to hedge against the possibility of losing control of its American assets if the U.S. should enter the war and to allow Bayer to enter other markets (e.g., army uniforms). After the U.S. declared war on Germany in April 1917, alien property custodian A. Mitchell Palmer began investigating German-owned businesses, and soon turned his attention to Bayer. To avoid having to surrender all profits and assets to the government, Bayers management shifted the stock to a new company, nominally owned by Americans but controlled by the German-American Bayer leaders. Palmer, however, soon uncovered this scheme and seized all of Bayers American holdings. After the Trading with the Enemy Act was amended to allow sale of these holdings, the government auctioned off the Rensselaer plant and all Bayer's American patents and trademarks, including even the Bayer brand name and the Bayer cross logo. It was bought by a patent medicine company, Sterling Products, Inc. The rights to Bayer Aspirin and the U.S. rights to the Bayer name and trademarks were sold back to Bayer AG in 1994 for US$1 billion. | 1 | Applied and Interdisciplinary Chemistry |
Gallium palladide (GaPd or PdGa) is an intermetallic combination of gallium and palladium. It has the iron monosilicide crystal structure. The compound has been suggested as an improved catalyst for hydrogenation reactions. In principle, gallium palladide can be a more selective catalyst since unlike substituted compounds, the palladium atoms are spaced out in a regular crystal structure rather than randomly. | 1 | Applied and Interdisciplinary Chemistry |
By considering the arrangement of atoms relative to each other, their coordination numbers, interatomic distances, types of bonding, etc., it is possible to form a general view of the structures and alternative ways of visualizing them. | 0 | Theoretical and Fundamental Chemistry |
The Seebeck effect refers to the development of an electromotive force across two points of an electrically conducting material when there is a temperature difference between those two points.
Under open-circuit conditions where there is no internal current flow, the gradient of voltage () is directly proportional to the gradient in temperature ():
where is a temperature-dependent material property known as the Seebeck coefficient.
The standard measurement configuration shown in the figure shows four temperature regions and thus four voltage contributions:
# Change from to , in the lower copper wire.
# Change from to , in the alumel wire.
# Change from to , in the chromel wire.
# Change from to , in the upper copper wire.
The first and fourth contributions cancel out exactly, because these regions involve the same temperature change and an identical material.
As a result, does not influence the measured voltage.
The second and third contributions do not cancel, as they involve different materials.
The measured voltage turns out to be
where and are the Seebeck coefficients of the conductors attached to the positive and negative terminals of the voltmeter, respectively (chromel and alumel in the figure). | 1 | Applied and Interdisciplinary Chemistry |
The Krebs cycle, also known as the TCA cycle or Citric Acid cycle, is a biochemical pathway that facilitates the breakdown of glucose in a cell. Both citrate and malate involved in the citrate-malate shuttle are necessary intermediates of the Krebs cycle. Usually, oxaloacetate in the Krebs cycle is generated from the carboxylation of pyruvate in the mitochondrion; however, malate generated in the cytosol can also enter the mitochondrion through the transport protein located in the inner mitochondrial membrane to directly join the Krebs cycle.
The mitochondrial transport proteins are encoded by the SLC25 gene in humans and facilitate the transportation of various metabolites, including citrate and malate, in the Krebs cycle. These transport proteins control the flow of metabolites in and out of the inner mitochondrial membrane, which is impermeable to most molecules. They connect the carbohydrate metabolism of the Krebs cycle to fatty acid synthesis in lipogenesis by catalyzing the transportation of acetyl-CoA out of the mitochondrial matrix into the cytosol, which is done in the form of citrate export from the mitochondria to the cytosol. Cytosolic citrate, meaning citrate in the cytosol, is a key substrate for the generation of energy. It releases acetyl-CoA and provides NADPH for fatty acid synthesis, and, in subsequent pathways, generates NAD for glycolysis. Citrate also activates acetyl-CoA carboxylase, an enzyme that is essential in the fatty acid synthesis pathway.
Citrate-malate shuttle might partly or completely replace the function of the Krebs cycle in cancer cell metabolism. | 1 | Applied and Interdisciplinary Chemistry |
Condensation of SAMP or RAMP with an aldehyde or ketone affords the (E)-hydrazine. Deprotonation with lithium diisopropylamide and addition of an alkyl halide affords the alkylated product. The auxiliary can be removed by ozonolysis or hydrolysis.
<br /> | 0 | Theoretical and Fundamental Chemistry |
Modafinil is occasionally prescribed off-label for individuals with attention deficit hyperactivity disorder (ADHD). It has shown no efficacy in treating adult ADHD, especially when compared to other treatments such as lisdexamfetamine. In children, modafinil is efficient in treating ADHD symptoms.
Given its approved status in the US to treat narcolepsy, physicians can also prescribe modafinil for off-label uses, such as treating ADHD in both children and adults.
The Canadian Network for Mood and Anxiety Treatments (CANMAT) suggests modafinil as a second-line choice for ADHD, after the first-line choices such as bupropion are exhausted. | 0 | Theoretical and Fundamental Chemistry |
Dithiiranes are three membered rings containing two sulfur atoms and one carbon. One example was prepared by oxidation of a 1,3-dithietane. | 0 | Theoretical and Fundamental Chemistry |
During mitosis, mitotic spindle orientation is essential for determining the site of cleavage furrowing and position of daughter cells for subsequent cell fate determination. This orientation is achieved by polarizing cortical factors and rapid alignment of the spindle with the polarity axis. In fruit flies, three cortical factors have been found to regulate the position of the spindle: heterotrimeric G protein α subunit (Gαi), Partner of Inscuteable (Pins), and Mushroom body defect (Mud). Gαi localizes at apical cortex to recruit Pins. Upon binding to GDP-bound Gαi, Pins is activated and recruits Mud to achieve polarized distribution of cortical factors. N-terminal tetratricopeptide repeats (TPRs) in Pins is the binding region for Mud, but is autoinhibited by intrinsic C-terminal GoLoco domains (GLs) in the absence of Gαi. Activation of Pins by Gαi binding to GLs is highly ultrasensitive and is achieved through the following decoy mechanism: GLs 1 and 2 act as a decoy domains, competing with the regulatory domain, GL3, for Gαi inputs. This intramolecular decoy mechanism allows Pins to establish its threshold and steepness in response to distinct Gαi concentration. At low Gαi inputs, the decoy GLs 1 and 2 are preferentially bound. At intermediate Gαi concentration, the decoys are nearly saturated, and GL3 begins to be populated. At higher Gαi concentration, the decoys are fully saturated and Gαi binds to GL3, leading to Pins activation. Ultrasensitivity of Pins in response to Gαi ensures that Pins is activated only at the apical cortex where Gαi concentration is above the threshold, allowing for maximal Mud recruitment. | 1 | Applied and Interdisciplinary Chemistry |
The heat of neutralization of a fully dissociated acid with a fully dissociated base is approximately –56kJ/mol. The reaction is thus strongly exothermic, and is an excellent basis for a wide range of analysis in industry. An advantage for the industrial analyst is that the use of stronger titrants (1 to 2 mol/L) permits a reduction in the amount of sample preparation, and samples can often be directly and accurately dispensed into the titration vessel prior to titration. | 0 | Theoretical and Fundamental Chemistry |
The study of correlation functions is critical to the study of quantum optics as the Fourier transform of the correlation function is the energy spectral density. Thus the two-time correlation function is a useful tool in the calculation of the energy spectrum for a given system. We take the parameter to be the difference between the two times in which the function is calculated. While correlation functions can more easily be described using limits of the strength of the field and limits placed on the time of the system, they can be found more generally as well. For resonance fluorescence, the most important correlation functions are
where
Two-time correlation functions are generally shown to be independent of , and instead rely on as . These functions can be used to find the spectral density by computing the transform
where K is a constant. The spectral density can be viewed as the rate of photon emission of photons of frequency at the given time , which is useful in determining the power output of a system at a given time.
The correlation function associated with the spectral density of resonance fluorescence is reliant on the electric field. Thus once the constant K has been determined, the result is equivalent to
This is related to the intensity by
In the weak field limit when the power spectrum can be determined to be
In the strong field limit, the power spectrum is slight more complicated and found to be
From these two functions it is easy to see that in the weak field limit a single peak appears at in the spectral density due to the delta function, while in the strong field limit a Mollow triplet forms with sideband peaks at , and appropriate peak width of for the central peak and for the sideband peaks. | 0 | Theoretical and Fundamental Chemistry |
The operon consists of the promoter region fim S, the main constituent fim A, its gene product forming a rod like structure and fim H, coding for an adhesin at the tip, to name just a few important elements. The fim S region is flanked by 9bp repeats that are mirror images of each other. These mirror images serve as substrates for two ATP-dependent recombinases, fim B and fim E. These recombinases can invert the orientation of the fim S region and only one orientation allows for 3 to 5 transcription.
fim B "flips" the promoter region both ways, from the "on" position to the "off" position and vice versa, whereas fim E can only facilitate recombination from "on" to "off". This equilibrium, shifted towards maintaining the "off" position, due to higher fim E activity, serves as a mode of expressing pili only when adhesion is needed. Another level of transcriptional control in E. coli is mediated by the sensitivity of the recombinases to pH and osmolarity, further ensuring appropriate expression levels of type-I pili, given the stark differences in osmolarity inside and outside an animals body. Type-I pili are expressed by many species of Enterobacteriaceae. The transcriptional control can differ widely between species, in Salmonella typhimurium, for example much influence is exerted by a leucine-responsive regulatory protein and there is no fim' S element. | 1 | Applied and Interdisciplinary Chemistry |
A crucible and its lid are pre-weighed after thorough drying. The sample is added to the completely dry crucible and lid and together they are weighed to determine the mass of the sample by difference. The sample is placed in the hot furnace long enough so that complete combustion of the sample occurs. The crucible, lid and ash then are re-weighed. | 0 | Theoretical and Fundamental Chemistry |
A plasma, consisting of neutral particles, ions, and unbound electrons, responds to the oscillating electric field of incident electromagnetic radiation primarily through the motion of electrons (ions and neutral particles can often be regarded as stationary due to their larger mass). If the frequency of the incident radiation is sufficiently low and the plasma frequency is sufficiently high (corresponding to the Rayleigh scattering regime), the electrons will travel until the plasma object becomes polarized, counteracting the incident electric field and preventing further movement until the incident field reverses direction. If the frequency of the incident radiation is sufficiently high and the plasma frequency is sufficiently low (corresponding to the Thomson scattering regime), electrons will only travel a short distance before the electric field reverses direction, making collisions with other particles unlikely during a given oscillation.
If the frequency on the incident radiation is intermediate and a high density of neutral particles and ions is present, electrons will travel far enough to collide many times with other particles but not far enough to significantly polarize the plasma object. This characterizes the collisional scattering regime. The linear oscillation of unbound electrons in a relatively-small space gives rise to a short-dipole radiation pattern.
This is analogous to a spring-mass-damper system, where the polarization of the plasma object creates the restoring force and the drag due to collisions with other particles creates the damping force. The phase shift of the scattered wave is 90º in the Shneider-Miles regime due to the drag force being dominant.
Note that, in this context, Rayleigh scattering is regarded as volumetric small particle scattering rather than an even broader short-dipole approximation of the radiation. Otherwise, Thomson scattering would fall under the banner of "Rayleigh". Mie scattering experiences a similar ambiguity. | 0 | Theoretical and Fundamental Chemistry |
Deep sequencing of transcriptomes, also known as RNA-Seq, provides both the sequence and frequency of RNA molecules that are present at any particular time in a specific cell type, tissue or organ. Counting the number of mRNAs that are encoded by individual genes provides an indicator of protein-coding potential, a major contributor to phenotype. Improving methods for RNA sequencing is an active area of research both in terms of experimental and computational methods. | 1 | Applied and Interdisciplinary Chemistry |
Tissues can be analyzed to help determine a cause of death. The tissue samples that are most commonly analyzed are the liver, kidney, brain, and lungs. | 1 | Applied and Interdisciplinary Chemistry |
2,4,6-Trichlorobenzoyl chloride is prepared by reacting 2,4,6-trichloroaniline with N-butyllithium in a carbon dioxide atmosphere. This produces 2,4,6-trichlorobenzoic acid, which can then be refluxed in thionyl chloride to form 2,4,6-trichlorobenzoyl chloride.
Since 2,4,6-trichlorobenzoic acid is produced as a by product of the esterification process, it can be refluxed again to recreate 2,4,6-trichlorobenzoyl chloride. | 0 | Theoretical and Fundamental Chemistry |
GC–MS is increasingly used for detection of illegal narcotics, and may eventually supplant drug-sniffing dogs. A simple and selective GC–MS method for detecting marijuana usage was recently developed by the Robert Koch Institute in Germany. It involves identifying an acid metabolite of tetrahydrocannabinol (THC), the active ingredient in marijuana, in urine samples by employing derivatization in the sample preparation. GC–MS is also commonly used in forensic toxicology to find drugs and/or poisons in biological specimens of suspects, victims, or the deceased. In drug screening, GC–MS methods frequently utilize liquid-liquid extraction as a part of sample preparation, in which target compounds are extracted from blood plasma. | 0 | Theoretical and Fundamental Chemistry |
The linked-read sequencing is microfluidic-based, and only needs nanograms of input DNA. One nanogram of DNA can be distributed across more than 100,000 droplet partitions, where DNA fragments are barcoded and subjected to polymerase chain reactions (PCR). As a result, DNA fragments (or reads) that share the same barcode can be grouped as coming from one single long input DNA sequence. And, long range information can be assembled from short reads.
Steps of Linked-read sequencing:
# Sample Preparation: DNA is extracted from a sample (e.g., blood) and cut into fragments of 50 to 200 kilo base-pairs long.
# Barcode Sequencing: each DNA fragment is labelled with a unique barcode through a process known as "Gel Bead-In Emulsion" (GEM).
# Library Preparation: barcoded DNA fragments are amplified with PCR to generate sequencing libraries.
# Sequencing: with Illumina next-generation sequencing technology, generate millions to billions of short sequence reads that represent fragments of the original DNA molecules.
# Barcode Processing: group short reads to longer fragments based on barcodes.
# Downstream Analysis: processed reads are aligned to a reference genome, or used for de novo assembly of complex genomes, haplotype phasing, or identification of structural variations. | 1 | Applied and Interdisciplinary Chemistry |
In comparison to Proton exchange membrane electrolysis, the advantages of alkaline water electrolysis are mainly:
# Cheaper catalysts with respect to the platinum metal group based catalysts used for PEM water electrolysis.
# Higher durability due to an exchangeable electrolyte and lower dissolution of anodic catalyst.
# Higher gas purity due to lower gas diffusivity in alkaline electrolytes. | 0 | Theoretical and Fundamental Chemistry |
The flux control coefficient connectivity theorem is the easiest to understand. Starting with a simple two step pathway:
where and are fixed species so that the pathway can reach a steady-state. and are the reaction rates for the first and second steps.
We can write the flux connectivity theorem for this simple system as follows:
where is the elasticity of the first step with respect to the species and is the elasticity of the second step with respect to the species . It is easier to interpret the equation with a slight rearrangement to the following form:
The equation indicates that the ratio of the flux control coefficients is inversely proportional to the elasticities. That is, a high flux control coefficient on step one is associated with a low elasticity and vice versa. Likewise a high value for the flux control coefficient on step two is associated with a low elasticity .
This can be explained as follows: If is high (in absolute terms, since it is negative) then a change at will be resisted by the elasticity, hence the flux control coefficient on step one will be low. | 1 | Applied and Interdisciplinary Chemistry |
STAT3 has been shown to interact with:
* AR,
* ELP2,
* EP300,
* EGFR,
* HIF1A,
* JAK1,
* JUN
* KHDRBS1,
* mTOR,
* MYOD1,
* NDUFA13,
* NFKB1,
* NR3C1,
* NCOA1,
* PML,
* RAC1,
* RELA,
* RET,
* RPA2,
* STAT1,
* Stathmin,
* Src, and
* TRIP10.
* KPNA4.
Niclosamide seems to inhibit the STAT3 signalling pathway.
Nicotinamide (a type of vitamin B) naturally inhibits STAT3. However NAC (Acetylcysteine) inhibits STAT3 inhibitors. | 1 | Applied and Interdisciplinary Chemistry |
Over the last two centuries many environmental chemical observations have been made from a variety of ground-based, airborne, and orbital platforms and deposited in databases. Many of these databases are publicly available. All of the instruments mentioned in this article give online public access to their data. These observations are critical in developing our understanding of the Earth's atmosphere and issues such as climate change, ozone depletion and air quality. Some of the external links provide repositories of many of these datasets in one place. For example, the Cambridge Atmospheric Chemical Database, is a large database in a uniform ASCII format. Each observation is augmented with the meteorological conditions such as the temperature, potential temperature, geopotential height, and equivalent PV latitude. | 1 | Applied and Interdisciplinary Chemistry |
Tellurols are analogues of alcohols and phenols where tellurium replaces oxygen. Tellurols, selenols, and thiols have similar properties, but tellurols are the least stable. Although they are fundamental representatives of organotellurium compounds, tellurols are lightly studied because of their instability. Tellurol derivatives include telluroesters (RC(O)TeR') and tellurocyanates (RTeCN). | 0 | Theoretical and Fundamental Chemistry |
A FOCE system for studies of deep-sea benthic communities (designated dp-FOCE) was developed by Monterey Bay Aquarium Research Institute. The dpFOCE project, deployed at a depth of 900 m, was attached to the MARS cabled seafloor observatory in Monterey Bay, central California. The system used a flume concept for maintaining greater control over the experimental volume while still maintaining access to natural seafloor sediments and suspended particulate material. Time-delay wings attached to either end of the dpFOCE chamber allow for tidally driven changes in near-bottom currents, and provide sufficient time for full hydration of the injected CO enriched seawater before entering into the experiment chamber. Fans are integrated into the dpFOCE design to control flow rates through the experimental chamber and to simulate typical local-scale flow conditions. Multiple sensors (pH, CTD, ADV, and ADCP) used in conjunction with the fans and the enriched seawater injection system allow the control loop software to achieve the desired pH offset. dpFOCE connects to shore via the MARS cabled observatory, which provides power and data bandwidth. Enriched CO seawater is produced from liquid CO held in a small container near the dpFOCE chamber; seawater flowing slowly over the top of the liquid CO dissolves some of the liquid CO producing a CO-rich dissolution plume used for injection into the dpFOCE chamber. The dpFOCE system operated over 17 months and verified the effectiveness of the design hardware and software. | 0 | Theoretical and Fundamental Chemistry |
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