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CCL7 is expressed in many types of cells, including stromal cells, keratinocytes, airway smooth muscle cells, parenchymal cells, fibroblasts and leukocytes and also in tumor cells.
CCL7 mainly acts as a chemoattractant for several leukocytes, including monocytes, eosinophils, basophils, dendritic cells (DCs), neutrophils, NK cells and activated T lymphocytes. Thus, chemotactic factor CCL7 recruits leukocytes to infected tissues to mediate the immune response. Furthermore, CCL7 has an influence to diapedesis and extravasation of leukocytes. The positive effect of CCL7 is mainly observed in monocyte mobilization from bone marrow to blood circulation and in the recruitment of monocytes to sites of inflammation. It was also reported, that CCL7 can also induce neutrophil migration to the inflammatory site by increasing intracellular Ca2+ flux, which is more typical for the CXC chemokine family members.
The speed of immune responses varies depending on the type of the cells. In epithelial cells, fibroblasts, and endothelial cells the response is immediate after the stimulation by proinflammatory cytokines as IL-1β and TNFα. In T lymphocytes the expression of CCL7 occurs after 3–5 days after the stimulation.
CCL7 has been shown to interact with MMP2 by binding CCR2 receptor. | 1 | Applied and Interdisciplinary Chemistry |
Gecko feet are hydrophobic, but that is not the only property that assists in their self-cleaning nature. Estrada and Lin created polypropylene, polyethylene, and polycaprolactone nanofibers using a porous template. These nanofiber geometries were shown to be self-cleaning in fiber dimensions of 5, 0.6, and 0.2 microns. However, a hydrophobic surface alone does not explain the perpetually clean toe pad of the gecko, even in dry environments, where water is not available for self-cleaning. This resulting fouling is a common problem for reversible adhesives modeled after the gecko toe pad. Digital hyperextension, or a movement of the toe with each gecko step, contributes to the self-cleaning. A surface or system that mimics this dynamic self-cleaning process has yet to be developed. | 0 | Theoretical and Fundamental Chemistry |
Athena Pashko was born on 10 October 1931 in the village of Bystrytsia, Drohobych district, Lwów Voivodeship, an administrative unit of interwar Poland. She graduated from Ukrainian National Forestry University.
Since the mid-1960s, she was persecuted and banned from publishing her works for defending repressed Ukrainian cultural figures. A reprimand was announced at her place of work, and searches were conducted in her apartment. In 1970, she signed an appeal to the Supreme Court of the Ukrainian Soviet Socialist Republic with a demand to overturn the sentence of Veronica Morozova, for which she was fired. Pashko was constantly under KGB surveillance. In December 1991, the founding congress of the Ukrainian Womens Union took place in Kyiv, and Pashko was elected chair of the Union. She later held the title of, Honorary Chair of the Union of Ukrainian Women. After the tragic death of her husband, Viacheslav Chornovil, on 25 March 1999 in a car accident, Pashko continued her political mission, and was even called the guardian of the Peoples Movement of Ukraine. She died in Kyiv on 20 March 2012, and was buried in Kyiv at the Baikove Cemetery, next to her husband. | 1 | Applied and Interdisciplinary Chemistry |
The type of growth factor signaling can effect whether or not NSCs differentiate into motor neurons or not. Priming a media with FGF2 lowers the activity of the PI3K/AKT pathway, which activates GSK3β. This increases expression of HB9. Directly inhibiting PI3K in NSCs leads to a population of cells that are purely HB9+ and differentiate at an elevated efficiency into motor neurons. Grafting these cells into different parts of rats generates motor neurons regardless of the transplanted cells' microenvironment. Following injury, neural stem cells enter a repair phase and express high levels of PI3K to enhance proliferation. This is better for survival of the neurons as a whole but is at the expense of generating motor neurons. Therefore, it can be difficult for injured motor neurons to recover their ability. It is the purpose of modern research to generate neural stem cells that can proliferate but still differentiate into motor neurons. Lowering the effect of the PI3K pathway and increasing the effect of GSK3β and HB9 in NSCs is a potential way of generating these cells. | 1 | Applied and Interdisciplinary Chemistry |
These effects have been supposed to exist since the time of Michael Faraday.
There have also been observations on the existence of Hall effect in electrolytes. Until these observations, magnetoelectrochemistry was an esoteric curiosity, though
this field has had a rapid development in the past years and is now an active area of research. Other scientific fields which contributed to the development of magnetoelectrochemistry are magnetohydrodynamics and convective diffusion theory. | 0 | Theoretical and Fundamental Chemistry |
Photocatalyst radical generation species allow for the degradation of organic pollutants into non-toxic compounds at a high efficiency. Use of CuO nanosheets to breakdown azo bonds in food dyes is one such example, with 96.99% degradation after only 6 minutes. Degradation of organic matter is a highly applicable property, particularly in waste processing.
The use of photocatalyst TiO as a support system for filtration membranes shows promise in improving membrane bioreactors in the treatment of wastewater. Polymer-based membranes have shown reduced fouling and self-cleaning properties in both blended and coated TiO membranes. Photocatalyst-coated membranes show the most promise, as the increased surface exposure of the photocatalyst increases its organic degradation activity.
Photocatalysts are also highly effective reducers of toxic heavy metals like hexavalent chromium from water systems. Under visible light the reduction of Cr(VI) by a Ce-ZrO sol-gel on a silicon carbide was 97% effective at reducing the heavy metal to trivalent chromium. | 0 | Theoretical and Fundamental Chemistry |
Initially, EZM was developed for modelling the transport and chemical transformation of pollutants in selected European regions in the frame of the EUROTRAC sub-project EUMAC and therefore it was formerly called the EUMAC Zooming Model (EUROTRAC, 1992). EZM has evolved to be one of the most frequently applied mesoscale air pollution model systems in Europe. It has already been successfully applied for various European airsheds including the Upper Rhine valley and the areas of Basel, Graz, Barcelona, Lisbon, Madrid, Milano, London, Cologne, Lyon, The Hague, Athens (Moussiopoulos, 1994; Moussiopoulos, 1995) and Thessaloniki. More details are to be found elsewhere (Moussiopoulos 1989), (Flassak 1990), (Moussiopoulos et al. 1993). | 1 | Applied and Interdisciplinary Chemistry |
After the deprotonation, the hydrazone turns into an azaenolate with lithium cation chelating both the nitrogen and oxygen. There are two possible options for lithium chelation. One is that lithium is antiperiplanar to the C=C bond (blue colored), leading to the conformation of Z; the other one is that lithium and the C=C bond are at the same side of the C-N bond (red colored), leading to the E conformer. There are also two available orientations for the chelating nitrogen and R group, being either E or Z. This leads to four possible azaenolate intermediates (A, B, C and D) for the Enders' SAMP/RAMP hydrazone alkylation reaction.
Experiments and calculations show that one specific stereoisomer of the azaenolate is favored over the other three possible candidates. Therefore, although four isomers are possible for the azaenolate, only the one (azaenolate A) with the stereochemistry of its C=C double bonds being E and that of its C-N bond being Z stereochemistry is dominant (EZ) for both cyclic and acyclic ketones. | 0 | Theoretical and Fundamental Chemistry |
With the advent of high resolution imaging, researchers have started to obtain experimental data which have led them to question the assumptions of the Cassie–Baxter equation when calculating the apparent contact angle. These groups believe the apparent contact angle is largely dependent on the triple line. The triple line, which is in contact with the heterogeneous surface, cannot rest on the heterogeneous surface like the rest of the drop. In theory, it should follow the surface imperfection. This bending in the triple line is unfavorable and is not seen in real-world situations. A theory that preserves the Cassie–Baxter equation while at the same time explaining the presence of the minimized energy state of the triple line hinges on the idea of a precursor film. This film of submicrometer thickness advances ahead of the motion of the droplet and is found around the triple line. Furthermore, this precursor film allows the triple line to bend and take different conformations that were originally considered unfavorable. This precursor fluid has been observed using environmental scanning electron microscopy (ESEM) in surfaces with pores formed in the bulk. With the introduction of the precursor film concept, the triple line can follow energetically feasible conformations, thereby correctly explaining the Cassie–Baxter model. | 0 | Theoretical and Fundamental Chemistry |
The non-random two-liquid model (abbreviated NRTL model) is an activity coefficient model introduced by Renon
and Prausnitz in 1968 that correlates the activity coefficients of a compound with its mole fractions in the liquid phase concerned. It is frequently applied in the field of chemical engineering to calculate phase equilibria. The concept of NRTL is based on the hypothesis of Wilson, who stated that the local concentration around a molecule in most mixtures is different from the bulk concentration. This difference is due to a difference between the interaction energy of the central molecule with the molecules of its own kind and that with the molecules of the other kind . The energy difference also introduces a non-randomness at the local molecular level. The NRTL model belongs to the so-called local-composition models. Other models of this type are the Wilson model, the UNIQUAC model, and the group contribution model UNIFAC. These local-composition models are not thermodynamically consistent for a one-fluid model for a real mixture due to the assumption that the local composition around molecule i is independent of the local composition around molecule j. This assumption is not true, as was shown by Flemr in 1976. However, they are consistent if a hypothetical two-liquid model is used. Models, which have consistency between bulk and the local molecular concentrations around different types of molecules are COSMO-RS, and COSMOSPACE. | 0 | Theoretical and Fundamental Chemistry |
AMTEC requires energy input at modest elevated temperatures and thus is easily adapted to any heat source, including radioisotope, concentrated solar power, external combustion, or a nuclear reactor. A solar thermal power conversion system based on an AMTEC could have advantages over other technologies for some applications including (thermal energy storage with phase-change material) and power conversion in a compact unit. The overall system could achieve as high as 14 W/kg with present collector technology and future AMTEC conversion efficiencies. The energy storage system has the potential to batteries, and the temperatures at which the system operates allows long life and reduced radiator size (heat-reject temperature of 600 K).
NASA investigated AMTEC conversion as a next-generation radioisotope power source for deep-space applications, but the technology was not selected for the next-generation systems.
While space power systems are of intrinsic interest, terrestrial applications could offer large-scale applications for AMTEC systems. At the 25% efficiency projected for the device and projected costs of 350 USD/kW, AMTEC could prove useful for a very wide variety of distributed generation applications including self-powered fans for high-efficiency furnaces and water heaters and recreational vehicle power supplies. | 0 | Theoretical and Fundamental Chemistry |
A prototypical spatio-spectral scanning system, introduced in June 2014, consists of a basic slit spectroscope (slit + dispersive element) at some suitable, non-zero distance before a camera. (If the effective camera distance is zero, the system is applicable to spatial scanning). The imaging process is based on spectrally-decoded camera obscura projections: A series of projections from a continuous array of pinholes (= the slit) is projected onto the dispersive element, each projection contributing a rainbow-colored strip to the recorded two-dimensional image. The field of view in the wavelength-coded spatial dimension asymptotically approaches the dispersion angle of the dispersive element as the camera distance from the dispersive element approaches infinity.
Scanning is achieved by moving the camera transverse to the slit (stationary platform), or by moving the entire system transverse to the slit (mobile platform). | 0 | Theoretical and Fundamental Chemistry |
In astrophysics, the Emden–Chandrasekhar equation is a dimensionless form of the Poisson equation for the density distribution of a spherically symmetric isothermal gas sphere subjected to its own gravitational force, named after Robert Emden and Subrahmanyan Chandrasekhar. The equation was first introduced by Robert Emden in 1907. The equation readswhere is the dimensionless radius and is the related to the density of the gas sphere as , where is the density of the gas at the centre. The equation has no known explicit solution. If a polytropic fluid is used instead of an isothermal fluid, one obtains the Lane–Emden equation. The isothermal assumption is usually modeled to describe the core of a star. The equation is solved with the initial conditions,
The equation appears in other branches of physics as well, for example the same equation appears in the Frank-Kamenetskii explosion theory for a spherical vessel. The relativistic version of this spherically symmetric isothermal model was studied by Subrahmanyan Chandrasekhar in 1972. | 1 | Applied and Interdisciplinary Chemistry |
In naphtha cracking process, C4R4 refers to C4 residual obtained after separation of 1,3-butadiene, isobutylene, 1-butene, and cis- or trans-2-butene from C4 raffinate stream which mainly consists of n-butane. Normally C4R4 is a side product in tert-butyl alcohol plant if C4R3 is used for feed. | 0 | Theoretical and Fundamental Chemistry |
Sildenafil has been shown to significantly improve neurovascular coupling without affecting overall cerebral blood flow by increasing brain levels of cGMP, evoking neurogenesis and reducing neurological deficits in rats 2 or 24 hours after stroke. These experimental data suggest that PDE5 inhibitors may have a role in promoting recovery from stroke. However, studies in humans remain inconclusive. | 1 | Applied and Interdisciplinary Chemistry |
The heat transfer dynamics in two-phase two component flow systems are governed by the dynamic behavior of droplets/bubbles that are injected into the circulating coolant stream. The injected bubbles/droplets are typically of a lower density than the coolant and thus experience an upward buoyancy force. They enhance the thermal performance of cooling systems because as they float upwards in heated pipes the coolant is forced to flow around the bubbles/droplets. The secondary flow around the droplets modifies the coolant flow creating a quasi-mixing effect in the bulk fluid that increases the heat transfer from the pipe walls to the coolant. Current two-component, two-phase cooling systems such as nuclear reactors, control the cooling rate by optimizing solely the coolant type, flow rate, and bubble/droplet injection rate. This approach modifies only bulk flow settings and does not provide engineers the option of control of directly modulating the mechanisms that govern the heat transfer dynamics. Inducing oscillations in the bubbles/droplets is a promising approach to improving convective cooling because creates secondary and tertiary flow patterns that could improve heat transfer without introducing significant heat to the system.
Electrodynamic droplet deformation also of particular interest in crude oil processing as a method to improve the separation rate of water and salts from the bulk. In its unprocessed form, crude oil cannot be used directly in industrial processes because the presence of salts can corrode heat exchangers and distillation equipment. To avoid fouling due to these impurities it is necessary to first remove the salt, which is concentrated in suspended water droplets. Exposing batches of crude oil to both DC and AC high-voltage electric fields induces droplet deformation that ultimately causes the water droplets to coalesce into larger droplets. Droplet coalescence improves the separation rate of water from crude oil because the upward velocity of a sphere is proportional to the square of the sphere’s radius. This can be easily shown by considering gravitational force, buoyancy, and Stokes flow drag. It has been reported that increasing both the amplitude and frequency of the applied electric fields can significantly increases water separation up to 90%. | 1 | Applied and Interdisciplinary Chemistry |
Free induction decay (FID) is the magnetic resonance due to Larmor precession that results from the stimulation of nuclei by means of either a pulsed dc magnetic field or a pulsed resonant frequency (rf) magnetic field, somewhat analogous respectively to the effects of plucking or bowing a stringed instrument. Whereas a pulsed rf field is usual in conventional (high field) NMR spectrometers, the pulsed dc polarising field method of stimulating FID is usual in EFNMR spectrometers and PPMs.
EFNMR equipment typically incorporates several coils, for stimulating the samples and for sensing the resulting NMR signals. Signal levels are very low, and specialised electronic amplifiers are required to amplify the EFNMR signals to usable levels. The stronger the polarising magnetic field, the stronger the EFNMR signals and the better the signal-to-noise ratios. The main trade-offs are performance versus portability and cost.
Since the FID resonant frequencies of NMR active nuclei are directly proportional to the magnetic field affecting those nuclei, we can use widely available NMR spectroscopy data to analyse suitable substances in the Earth's magnetic field.
An important feature of EFNMR compared with high-field NMR is that some aspects of molecular structure can be observed more clearly at low fields and low frequencies, whereas other features observable at high fields may not be observable at low fields. This is because:
* Electron-mediated heteronuclear J-couplings (spin-spin couplings) are field independent, producing clusters of two or more frequencies separated by several Hz, which are more easily observed in a fundamental resonance of about 2 kHz. "Indeed it appears that enhanced resolution is possible due to the long spin relaxation times and high field homogeneity which prevail in EFNMR."
* Chemical shifts of several parts per million (ppm) are clearly separated in high field NMR spectra, but have separations of only a few millihertz at proton EFNMR frequencies, and so are undetectable in an experiment that takes place on a timescale of tenths of a second.
For more context and explanation of NMR principles, please refer to the main articles on NMR and NMR spectroscopy. For more detail see proton NMR and carbon-13 NMR. | 0 | Theoretical and Fundamental Chemistry |
Protein electrophoresis is a method for analysing the proteins in a fluid or an extract. The electrophoresis may be performed with a small volume of sample in a number of alternative ways with or without a supporting medium, namely agarose or polyacrylamide. Variants of gel electrophoresis include SDS-PAGE, free-flow electrophoresis, electrofocusing, isotachophoresis, affinity electrophoresis, immunoelectrophoresis, counterelectrophoresis, and capillary electrophoresis. Each variant has many subtypes with individual advantages and limitations. Gel electrophoresis is often performed in combination with electroblotting or immunoblotting to give additional information about a specific protein. | 1 | Applied and Interdisciplinary Chemistry |
In 1986, convincing evidence was provided that selenocysteine (Sec) was incorporated co-translationally. Moreover, the codon partially directing its incorporation in the polypeptide chain was identified as UGA also known as the opal termination codon. Different mechanisms for overriding the termination function of this codon have been identified in prokaryotes and in eukaryotes. A particular difference between these kingdoms is that cis elements seem restricted to the neighborhood of the UAG codon in prokaryotes while in eukaryotes this restriction is not present. Instead such locations seem disfavored albeit not prohibited.
In 2003, a landmark paper described the identification of all known selenoproteins in humans: 25 in total. Similar analyses have been run for other organisms.
The UAG codon can translate into pyrrolysine (Pyl) in a similar manner. | 1 | Applied and Interdisciplinary Chemistry |
Carbon nanotubes have also been used to create surfaces similar to rice leaves. Similar to the lotus leaf, a hierarchical structure provides the hydrophobicity of rice leaf. Unlike the lotus leaf, rice leaves have an anisotropic structure. When CNT’s are made to mimic rice leaf papillae patterns, the contact angle to differ along the CNT direction or perpendicular. Sun et al. observed anisotropic dewetting of this CNT film. They then hypothesized and tested a three-dimensional anisotropic CNT array, which in fact exhibited anisotropic dewetting depending on the CNT spacing. | 0 | Theoretical and Fundamental Chemistry |
The fourth generation cephalosporins have greater activity against gram-negative bacteria than the second and third generation. This difference is attributed to them being dipolar ionic zwitterion compounds. The C-7 side chain is similar to third generation cephalosporins usually containing iminomethoxy-aminothiazole group or in the case of cefclidin an aminothiadiazole. Because of the positively charged quaternary nitrogen in the C-3 side chain fourth generation cephalosporins can diffuse through the gram-negative bacterial membrane more readily than earlier cephalosporins. It is thought that the positive charge orients the drug molecule to the entrance of the porin channel. | 1 | Applied and Interdisciplinary Chemistry |
The term stem is not used consistently in linguistics. It has been defined as a form to which affixes (of any type) can be attached. Under a different and apparently more common view, this is the definition of a root, while a stem consists of the root plus optional derivational affixes, meaning that it is the part of a word to which inflectional affixes are added. INN stems employ the first definition, while under the more common alternative they would be described as roots. | 1 | Applied and Interdisciplinary Chemistry |
The photostationary state of a reversible photochemical reaction is the equilibrium chemical composition under a specific kind of electromagnetic irradiation (usually a single wavelength of visible or UV radiation).
It is a property of particular importance in photochromic compounds, often used as a measure of their practical efficiency and usually quoted as a ratio or percentage.
The position of the photostationary state is primarily a function of the irradiation parameters, the absorbance spectra of the chemical species, and the quantum yields of the reactions. The photostationary state can be very different from the composition of a mixture at thermodynamic equilibrium. As a consequence, photochemistry can be used to produce compositions that are "contra-thermodynamic".
For instance, although cis-stilbene is "uphill" from trans-stilbene in a thermodynamic sense, irradiation of trans-stilbene results in a mixture that is predominantly the cis isomer. As an extreme example, irradiation of benzene at 237 to 254 nm results in formation of benzvalene, an isomer of benzene that is 71 kcal/mol higher in energy than benzene itself. | 0 | Theoretical and Fundamental Chemistry |
From 2008 Kuipers is supervisor, coach and coordinator of the iGEM student team Groningen. iGEM is a worldwide competition in the field of synthetic biology between teams of students from all over the world. The team from Groningen won in the annual in Boston (United States) organized international competition several gold medals (2008 to 2016). In 2012, when the team from Groningen became world champion, the research concerned a study of an alternative method to determine whether food is spoiled: the Food warden . This method makes use of genetic engineered bacteria responsive to the volatiles of the decomposing meat. A pigment makes the decomposition visible. | 0 | Theoretical and Fundamental Chemistry |
In 1993 Philex Mining Corporation, a Philippines mining company, replaced the mechanical cleaner circuit with Cells at its Benguet copper concentrator. Following their successful operation, Philex replaced the mechanical cells in its cleaner-scavenger circuit in 1994 and began the phased introduction of Cell rougher and scavenger lines that was completed in early 1996. This was the first operation in which the external recycle mechanism system was applied. By the time the last Jameson Cell was installed, the entire flotation circuit was composed of Jameson Cells.
The motivation for installing Jameson Cells was, in part, to take advantage of their space-saving capabilities and to improve copper recovery at a minimum cost. The Cell circuit occupied 60% less floor area and achieved equivalent results to the mechanical banks with 40% of their residence time. They provided a power saving of 18%.
In addition to these benefits, the use of the Jameson Cells in the rougher and rougher–scavenger section of the plant resulted in a 3.3% increase in copper recovery and a 4.5% increase in gold recovery. When combined with the other Cells in the cleaner, recleaner and cleaner–scavenger section, there was a 2.6% increase in final copper concentrate grade and a 3.5% increase in plant copper recovery, with a 2.6% increase in plant gold recovery. | 1 | Applied and Interdisciplinary Chemistry |
A benzene solution of 1 eq of diethylaluminum chloride was added dropwise at 0° to a solution of 1 eq of lithium 2,2,6,6-tetramethylpiperidide prepared in the usual fashion in benzene. The resulting slurry was stirred for 30 minutes and used immediately.
To a stirred mixture of 0.004 mol of diethylaluminum 2,2,6,6-tetramethylpiperidide in 10 mL of benzene at 0 °C was added dropwise over 5 minutes a solution of 0.18 g (0.001 mol) of epoxide in 3 mL of benzene. The mixture was stirred at 0 °C until analysis indicated the absence of starting material. The reaction was quenched by the addition of ice-cold 1 N hydrochloric acid. The organic layer was separated, and the aqueous layer was extracted with ether. The organic layers were combined, washed with brine, dried, and concentrated. The residue was purified by preparative TLC (R 0.22 in 1:2 ether–hexane) to give 99% of (E)-2-cyclododecenol: IR (neat) 3330–3370, 1465, 1450, 970 cm; NMR (CCl) δ 3.73–4.20 (1, m), 4.97–5.82 (2, m); mass spectrum (m/z) 182 (16), 164 (13), 139 (32), 125 (46), and 98 (100). | 0 | Theoretical and Fundamental Chemistry |
Four versions of Ficks law for binary gas mixtures are given below. These assume: thermal diffusion is negligible; the body force per unit mass is the same on both species; and either pressure is constant or both species have the same molar mass. Under these conditions, Ref. shows in detail how the diffusion equation from the kinetic theory of gases reduces to this version of Ficks law:
where is the diffusion velocity of species . In terms of species flux this is
If, additionally, , this reduces to the most common form of Fick's law,
If (instead of or in addition to ) both species have the same molar mass, Fick's law becomes
where is the mole fraction of species . | 0 | Theoretical and Fundamental Chemistry |
The fungal component of a lichen is called the mycobiont. The mycobiont may be an Ascomycete or Basidiomycete. The associated lichens are called either ascolichens or basidiolichens, respectively. Living as a symbiont in a lichen appears to be a successful way for a fungus to derive essential nutrients, since about 20% of all fungal species have acquired this mode of life.
Thalli produced by a given fungal symbiont with its differing partners may be similar, and the secondary metabolites identical, indicating that the fungus has the dominant role in determining the morphology of the lichen. But the same mycobiont with different photobionts may also produce very different growth forms. Lichens are known in which there is one fungus associated with two or even three algal species.
Although each lichen thallus generally appears homogeneous, some evidence seems to suggest that the fungal component may consist of more than one genetic individual of that species.
Two or more fungal species can interact to form the same lichen.
The following table lists the orders and families of fungi that include lichen-forming species. | 1 | Applied and Interdisciplinary Chemistry |
Biological hydrogels are derived from preexisting components of body tissues such as collagen, hyaluronic acid (HA), or fibrin. Collagen, HA, and fibrin are components that occur naturally in the extracellular matrix of mammals. Collagen is the main structural component in tissues and it already contains cell-signaling domains that can promote cell growth. In order to mechanically enhance collagen into a hydrogel, it must be chemically crosslinked, crosslinked using UV light or temperature, or mixed with other polymers. Collagen hydrogels would be nontoxic and biocompatible. | 0 | Theoretical and Fundamental Chemistry |
Lipid signaling, broadly defined, refers to any biological cell signaling event involving a lipid messenger that binds a protein target, such as a receptor, kinase or phosphatase, which in turn mediate the effects of these lipids on specific cellular responses. Lipid signaling is thought to be qualitatively different from other classical signaling paradigms (such as monoamine neurotransmission) because lipids can freely diffuse through membranes (see osmosis). One consequence of this is that lipid messengers cannot be stored in vesicles prior to release and so are often biosynthesized "on demand" at their intended site of action. As such, many lipid signaling molecules cannot circulate freely in solution but, rather, exist bound to special carrier proteins in serum. | 1 | Applied and Interdisciplinary Chemistry |
Etching has applications in the printed circuit board and semiconductor fabrication industries. It is also used in the aerospace industry to remove shallow layers of material from large aircraft components, missile skin panels, and extruded parts for airframes. Etching is used widely to manufacture integrated circuits and Microelectromechanical systems. In addition to the standard, liquid-based techniques, the semiconductor industry commonly uses plasma etching. | 1 | Applied and Interdisciplinary Chemistry |
An analytical ultracentrifuge has a light source and optical detectors. To allow the light to pass through the analyte during the ultracentrifuge run, specialized cells are required which have to meet high optical standards as well as to resist the centrifugal forces. Each cell consists of a housing, two windows made from optically pure quartz glass, and a centrepiece with one or two sectors and filling holes for the sector(s), closed with a screw plug in the housing. These cell are placed into a rotor cavity with a continuous bore, with a collar at the bottom to retain the cell. | 1 | Applied and Interdisciplinary Chemistry |
Seliwanoff’s test is a chemical test which distinguishes between aldose and ketose sugars. If the sugar contains a ketone group, it is a ketose. If a sugar contains an aldehyde group, it is an aldose. This test relies on the principle that, when heated, ketoses are more rapidly dehydrated than aldoses. It is named after Theodor Seliwanoff, the chemist who devised the test. When added to a solution containing ketoses, a red color is formed rapidly indicating a positive test. When added to a solution containing aldoses, a slower forming light pink is observed instead.
The reagents consist of resorcinol and concentrated hydrochloric acid:
* The acid hydrolysis of polysaccharide and oligosaccharide ketoses yields simpler sugars followed by furfural.
* The dehydrated ketose then reacts with two equivalents of resorcinol in a series of condensation reactions to produce a molecule with a deep cherry red color.
* Aldoses may react slightly to produce a faint pink color.
Fructose and sucrose are two common sugars which give a positive test. Sucrose gives a positive test as it is a disaccharide consisting of fructose and glucose.
Generally, 6M HCl is used to run this test. Ketoses are dehydrated faster and give stronger colors. Aldoses react very slowly and give faint colors. | 0 | Theoretical and Fundamental Chemistry |
The reaction mechanism consists of two nucleophilic substitutions: the amine is the first nucleophile displacing the bromine atom which then acts as the second nucleophile. In following the mechanism is described using trimethylamine as example:
First, the trimethylamine reacts with the cyanogen bromide to form a quaternary ammonium salt, which in the next step reacts by splitting off bromomethane to give the dimethylcyanamide. This is a second-order nucleophilic substitution (S2). | 0 | Theoretical and Fundamental Chemistry |
*Bacteriorhodopsin-like proteins including rhodopsin (see also opsin)
*Bacterial photosynthetic reaction centres and photosystems I and II
*Light harvesting complexes from bacteria and chloroplasts | 1 | Applied and Interdisciplinary Chemistry |
Replication, in metallography, is the use of thin plastic films to nondestructively duplicate the microstructure of a component. The film is then examined at high magnifications.
Replication is a method of copying the topography of a surface by casting or impressing material onto the surface. It is the commonly used technique to duplicate surfaces that are inaccessible in metrology to other forms of nondestructive testing. Replicas can be used in biology as well:
The replicas may be imaged in the light microscope or coated with heavy metals, the replicating film melted away, and the heavy metal replica imaged in a Transmission Electron Microscope (TEM).
The same materials, cellulose acetate films, are used for creating replicas of biological materials such as bacteria.
Field Metallurgical Replication (FMR), in field metallography, is the use of metallurgical preparation on surfaces in the field, by polishing to a mirror image, along with application of acetate or other thin plastic films designed to nondestructively duplicate the microstructure of a part or structure in-situ. The FMR replica is then transferred to a glass slide for examination by optical microscopy, electron microscopy, and other methods. | 1 | Applied and Interdisciplinary Chemistry |
Gene gating is a phenomenon by which transcriptionally active genes are brought next to nuclear pore complexes (NPCs) so that nascent transcripts can quickly form mature mRNA associated with export factors. Gene gating was first hypothesised by Günter Blobel in 1985. It has been shown to occur in Saccharomyces cerevisiae, Caenorhabditis elegans, Drosophila melanogaster as well as mammalian model systems.
The proteins that constitute the NPCs, known as nucleoporins, have been shown to play a role in DNA binding and mRNA transport, making gene gating possible. In addition, gene gating is orchestrated by two protein complexes, Spt-Ada-Gcn5-acetyltransferase (SAGA) and transcription–export complex 2 (TREX-2 complex). SAGA is a chromatin remodeling complex responsible for activating the transcription of certain inducible genes. The SAGA complex binds to gene promoters and also interacts with the TREX-2 complex. In turn, the TREX-2 complex interacts with the NPC, thus favouring the relocation of actively transcribed genes to the periphery of the cell nucleus. In contrast, the rest of the periphery, i.e. those parts not associated with NPCs, is transcriptionally silent heterochromatin. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, a molecular knot is a mechanically interlocked molecular architecture that is analogous to a macroscopic knot. Naturally-forming molecular knots are found in organic molecules like DNA, RNA, and proteins. It is not certain that naturally occurring knots are evolutionarily advantageous to nucleic acids or proteins, though knotting is thought to play a role in the structure, stability, and function of knotted biological molecules. The mechanism by which knots naturally form in molecules, and the mechanism by which a molecule is stabilized or improved by knotting, is ambiguous. The study of molecular knots involves the formation and applications of both naturally occurring and chemically synthesized molecular knots. Applying chemical topology and knot theory to molecular knots allows biologists to better understand the structures and synthesis of knotted organic molecules.
The term knotane was coined by Vögtle et al. in 2000 to describe molecular knots by analogy with rotaxanes and catenanes, which are other mechanically interlocked molecular architectures. The term has not been broadly adopted by chemists and has not been adopted by IUPAC. | 0 | Theoretical and Fundamental Chemistry |
The overlap extension polymerase chain reaction (or OE-PCR) is a variant of PCR. It is also referred to as Splicing by overlap extension / Splicing by overhang extension (SOE) PCR. It is used assemble multiple smaller double stranded DNA fragments into a larger DNA sequence. OE-PCR is widely used to insert mutations at specific points in a sequence or to assemble custom DNA sequence from smaller DNA fragments into a larger polynucleotide. | 1 | Applied and Interdisciplinary Chemistry |
In the context of rheumatoid arthritis (RA), CRP is one of the acute phase reactants, whose assessment is defined as part of the joint 2010 ACR/EULAR classification criteria for RA with abnormal levels accounting for a single point within the criteria Higher levels of CRP are associated with more severe disease and a higher likelihood of radiographic progression. Rheumatoid arthritis associated antibodies together with 14-3-3η YWHAH have been reported to complement CRP in predicting clinical and radiographic outcomes in patients with recent onset inflammatory polyarthritis. Elevated levels of CRP appear to be associated with common comorbidities including cardiovascular disease, metabolic syndrome, diabetes and interstitial lung (pulmonary) disease. Mechanistically, CRP also appears to influence osteoclast activity leading to bone resorption and also stimulates RANKL expression in peripheral blood monocytes.
It has previously been speculated that single-nucleotide polymorphisms in the CRP gene may affect clinical decision-making based on CRP in rheumatoid arthritis, e.g. DAS28 (Disease Activity Score 28 joints). A recent study showed that CRP genotype and haplotype were only marginally associated with serum CRP levels and without any association to the DAS28 score. Thus, that DAS28, which is the core parameter for inflammatory activity in RA, can be used for clinical decision-making without adjustment for CRP gene variants. | 1 | Applied and Interdisciplinary Chemistry |
A stream of airborne microorganisms, including marine viruses, bacteria and protists, circles the planet above weather systems but below commercial air lanes. Some peripatetic microorganisms are swept up from terrestrial dust storms, but most originate from marine microorganisms in sea spray. In 2018, scientists reported that hundreds of millions of these viruses and tens of millions of bacteria are deposited daily on every square meter around the planet.
Compared to the sub-surface waters, the sea surface microlayer contains elevated concentration of bacteria and viruses, as well as toxic metals and organic pollutants. These materials can be transferred from the sea-surface to the atmosphere in the form of wind-generated aqueous aerosols due to their high vapor tension and a process known as volatilisation. When airborne, these microbes can be transported long distances to coastal regions. If they hit land they can have detrimental effects on animals, vegetation and human health. Marine aerosols that contain viruses can travel hundreds of kilometers from their source and remain in liquid form as long as the humidity is high enough (over 70%). These aerosols are able to remain suspended in the atmosphere for about 31 days. Evidence suggests that bacteria can remain viable after being transported inland through aerosols. Some reached as far as 200 meters at 30 meters above sea level. It was also noted that the process which transfers this material to the atmosphere causes further enrichment in both bacteria and viruses in comparison to either the SML or sub-surface waters (up to three orders of magnitude in some locations). | 0 | Theoretical and Fundamental Chemistry |
When the pre-mRNA has been transcribed from the DNA, it includes several introns and exons. (In nematodes, the mean is 4–5 exons and introns; in the fruit fly Drosophila there can be more than 100 introns and exons in one transcribed pre-mRNA.) The exons to be retained in the mRNA are determined during the splicing process. The regulation and selection of splice sites are done by trans-acting splicing activator and splicing repressor proteins as well as cis-acting elements within the pre-mRNA itself such as exonic splicing enhancers and exonic splicing silencers.
The typical eukaryotic nuclear intron has consensus sequences defining important regions. Each intron has the sequence GU at its 5 end. Near the 3 end there is a branch site. The nucleotide at the branchpoint is always an A; the consensus around this sequence varies somewhat. In humans the branch site consensus sequence is yUnAy. The branch site is followed by a series of pyrimidines – the polypyrimidine tract – then by AG at the 3' end.
Splicing of mRNA is performed by an RNA and protein complex known as the spliceosome, containing snRNPs designated U1, U2, U4, U5, and U6 (U3 is not involved in mRNA splicing). U1 binds to the 5' GU and U2, with the assistance of the U2AF protein factors, binds to the branchpoint A within the branch site. The complex at this stage is known as the spliceosome A complex. Formation of the A complex is usually the key step in determining the ends of the intron to be spliced out, and defining the ends of the exon to be retained. (The U nomenclature derives from their high uridine content).
The U4,U5,U6 complex binds, and U6 replaces the U1 position. U1 and U4 leave. The remaining complex then performs two transesterification reactions. In the first transesterification, 5 end of the intron is cleaved from the upstream exon and joined to the branch site A by a 2,5-phosphodiester linkage. In the second transesterification, the 3 end of the intron is cleaved from the downstream exon, and the two exons are joined by a phosphodiester bond. The intron is then released in lariat form and degraded. | 1 | Applied and Interdisciplinary Chemistry |
Among the superconducting graphite intercalation compounds, exhibits the highest critical temperature T = 11.5 K, which further increases under applied pressure (15.1 K at 8 GPa). Superconductivity in these compounds is thought to be related to the role of an interlayer state, a free electron like band lying roughly above the Fermi level; superconductivity only occurs if the interlayer state is occupied. Analysis of pure using a high quality ultraviolet light revealed to conduct angle-resolved photoemission spectroscopy measurements. The opening of a superconducting gap in the π* band revealed a substantial contribution to the total electron–phonon-coupling strength from the π*-interlayer interband interaction. | 0 | Theoretical and Fundamental Chemistry |
In 2013, the Fujita group rediscovered that the molecular structure of liquids can be elucidated by X-ray crystallography in the presence of [(ZnI)(TPT)] crystalline sponges. The guest compounds, such as cyclohexanone, cinnamaldehyde were dropped onto the pre-made single crystal of crystalline sponges. The liquid samples would penetrate into the crystalline sponges, and occupy the sponges’ cavities. As crystalline sponges provide a well-organized structure, the guests in sponges’ cavities would also have organized distribution in the space. As a result, the structure of guest can be characterized by X-ray crystallography .
Some of the structures of liquid natural products which are difficult to differentiate by NMR spectroscopy can be easily characterized by crystalline sponges techniques. Elatenyne is a liquid molecule isolated from Laurencia elata, marine red algae. Due to its pseudo-C symmetry, the difference of NMR spectrum between elatenyne and its stereoisomer is hard to differentiate. However, with the crystalline sponges, the Fujita group easily elucidated the chirality in the elatenyne.
Cycloelatanene A and B are a pair of diastereomers isolated from Laurencia elata. Both compounds are liquid, so the traditional X-ray diffraction analysis cannot elucidate their absolute chirality. After the crystalline sponges assisted X-ray crystallography, the Fujita group revised the chirality of C4 position reported by precedent NMR analysis. | 0 | Theoretical and Fundamental Chemistry |
In contrast to most fresh-water sources, iron levels in surface sea-water are extremely low (1 nM to 1 μM in the upper 200 m) and much lower than those of V, Cr, Co, Ni, Cu and Zn. Virtually all this iron is in the iron(III) state and complexed to organic ligands. These low levels of iron limit the primary production of phytoplankton and have led to the Iron Hypothesis where it was proposed that an influx of iron would promote phytoplankton growth and thereby reduce atmospheric CO. This hypothesis has been tested on more than 10 different occasions and in all cases, massive blooms resulted. However, the blooms persisted for variable periods of time. An interesting observation made in some of these studies was that the concentration of the organic ligands increased over a short time span in order to match the concentration of added iron, thus implying biological origin and in view of their affinity for iron possibly being of a siderophore or siderophore-like nature. Significantly, heterotrophic bacteria were also found to markedly increase in number in the iron-induced blooms. Thus there is the element of synergism between phytoplankton and heterotrophic bacteria. Phytoplankton require iron (provided by bacterial siderophores), and heterotrophic bacteria require non-CO carbon sources (provided by phytoplankton).
The dilute nature of the pelagic marine environment promotes large diffusive losses and renders the efficiency of the normal siderophore-based iron uptake strategies problematic. However, many heterotrophic marine bacteria do produce siderophores, albeit with properties different from those produced by terrestrial organisms. Many marine siderophores are surface-active and tend to form molecular aggregates, for example aquachelins. The presence of the fatty acyl chain renders the molecules with a high surface activity and an ability to form micelles. Thus, when secreted, these molecules bind to surfaces and to each other, thereby slowing the rate of diffusion away from the secreting organism and maintaining a relatively high local siderophore concentration. Phytoplankton have high iron requirements and yet the majority (and possibly all) do not produce siderophores. Phytoplankton can, however, obtain iron from siderophore complexes by the aid of membrane-bound reductases and certainly from iron(II) generated via photochemical decomposition of iron(III) siderophores. Thus a large proportion of iron (possibly all iron) absorbed by phytoplankton is dependent on bacterial siderophore production. | 1 | Applied and Interdisciplinary Chemistry |
The Dische test, or Dische reaction, is used to distinguish DNA from RNA. It was invented by Zacharias Dische. | 0 | Theoretical and Fundamental Chemistry |
Small activating Ribonucleic acids (saRNAs) are small double-stranded RNAs (dsRNAs) that target gene promoters to induce transcriptional gene activation in a process known as RNA activation (RNAa).
Small dsRNAs, such as small interfering RNAs (siRNAs) and microRNAs (miRNAs), are known to be the trigger of an evolutionarily conserved mechanism known as RNA interference (RNAi). RNAi invariably leads to gene silencing via remodeling of chromatin to thereby suppress transcription, degrading complementary mRNA, or blocking protein translation. Later it was found that dsRNAs can also act to activate transcription and was thus designated saRNA. By targeting selected sequences in gene promoters, saRNAs induce target gene expression at the transcriptional/epigenetic level.
saRNAs are typically 21 nucleotides in length with a 2 nucleotide overhang at the 3 end of each strand, the same structure as a typical siRNA. To identify an saRNA that can activate a gene of interest, several saRNAs need to be designed within a 1- to 2-kb promoter region by following a set of rules and tested in cultured cells. In some reports, saRNAs are designed in such a way to target non-coding transcripts that overlap the promoter sequence of a protein coding gene. Both chemically synthesized saRNAs and saRNAs expressed as short hairpin RNA (shRNA) have been used in in vitro and in vivo' experiments.
An online resource for saRNAs has been developed ([https://bioinfo.imtech.res.in/manojk/sarna/ https://bioinfo.imtech.res.in/manojk/sarna/]) and published.
Therapeutic use of saRNAs have been suggested. They have been tested in animal models to treat bladder tumors,
liver carcinogenesis,
pancreatic cancer,
and erectile dysfunction.
In 2016, a phase I clinical trial involving advanced liver cancer patients was launched for the saRNA drug MTL-CEBPA. It aimed to complete in 2021. | 1 | Applied and Interdisciplinary Chemistry |
The bulk of the radioactivity in nuclear accident fallout is more long-lived than that in weapons fallout. A good table of the nuclides, such as that provided by the Korean Atomic Energy Research Institute, includes the fission yields of the different nuclides. From this data it is possible to calculate the isotopic mixture in the fallout (due to fission products in bomb fallout). | 0 | Theoretical and Fundamental Chemistry |
When working on the global annual average isotopic composition of oxygen-18 and deuterium (H) in meteoric water, geochemist Harmon Craig observed a correlation between these two isotopes, and subsequently developed and defined the equation for GMWL:
Where δO and δH (also known as δD) are the ratio of heavy to light isotopes (e.g. O/O, H/H).
The relationship of δO and δH in meteoric water is caused by mass dependent fractionation of oxygen and hydrogen isotopes between evaporation from ocean seawater and condensation from vapor. As oxygen isotopes (O and O) and hydrogen isotopes (H and H) have different masses, they behave differently in the evaporation and condensation processes, and thus result in the fractionation between O and O as well as H and H. Equilibrium fractionation causes the isotope ratios of δO and δH to vary between localities within the area. The fractionation processes can be influenced by a number of factors including: temperature, latitude, continentality, and most importantly, humidity. | 0 | Theoretical and Fundamental Chemistry |
Cyclohexenone is a widely used building block in organic synthesis chemistry, as it offers many different ways to extend molecular frameworks.
As an enone, cyclohexenone is easily adapted to Michael addition with nucleophiles (such as enolates or silyl enol ethers) or, it could be employed by a Diels-Alder reaction with electron-rich dienes. Furthermore, this compound reacts with organocopper compounds from 1,4-addition (Michael addition), or with Grignard reagents 1,2-addition, i.e., with attack of the nucleophile at the carbonyl carbon atom. Cyclohexenone is also used in multi-step synthesis in the construction of polycyclic natural products. It is prochiral.
With strong bases, the positions 4 and 6 (the two CH-groups of the carbonyl group and the C-C double bond adjacent) are deprotonated.
Cyclohexenone is an in-vitro catalyst for a relatively mild decarboxylation of alpha amino acids. | 0 | Theoretical and Fundamental Chemistry |
* Water: detergents, fertilizer, raw sewage, prescription medication, pesticides, herbicides, heavy metals, PCBs
* Soil: heavy metals, herbicides, pesticides, PCBs
* Air: particulate matter, carbon monoxide, sulfur dioxide, nitrogen dioxide, asbestos, ground-level ozone, lead (from aircraft fuel, mining, and industrial processes)
The EPA maintains a list of priority pollutants for testing and regulation. | 1 | Applied and Interdisciplinary Chemistry |
Anaerobic membrane bioreactors (sometimes abbreviated AnMBR) were introduced in the 1980s in South Africa. However, anaerobic processes are normally used when a low-cost treatment is required that enables energy recovery but does not achieve advanced treatment (low carbon removal, no nutrients removal). In contrast, membrane-based technologies enable advanced treatment (disinfection), but at a high energy cost. Therefore, the combination of both can only be economically viable if a compact process for energy recovery is desired, or when disinfection is required after anaerobic treatment (cases of water reuse with nutrients). If maximal energy recovery is desired, a single anaerobic process will always be superior to a combination with a membrane process.
Recently, anaerobic membrane bioreactors have seen successful full-scale application to the treatment of some types of industrial wastewaters—typically high-strength wastes. Example applications include the treatment of alcohol stillage wastewater in Japan and the treatment of salad dressing/barbecue sauce wastewater in the United States. | 1 | Applied and Interdisciplinary Chemistry |
For a two-dimensional Cartesian grid, the equation can be expanded to
On a staggered grid, the x-momentum equation is
and the y-momentum equation is
The goal at this point is to determine expressions for the face-values for u, v, and P and to approximate the derivatives using finite difference approximations. For this example we will use backward difference for the time derivative and central difference for the spatial derivatives. For both momentum equations, the time derivative becomes
where n is the current time index and Δt is the time-step. As an example for the spatial derivatives, derivative in the west-face diffusion term in the x-momentum equation becomes
where I and J are the indices of the x-momentum cell of interest. | 1 | Applied and Interdisciplinary Chemistry |
The variable region rearrangements happen in an orderly sequence in the bone marrow. Usually, the assortment of these gene segments occurs at B cell maturation. | 1 | Applied and Interdisciplinary Chemistry |
Autoacceleration of the overall rate of a free-radical polymerization system has been noted in many bulk polymerization systems. The polymerization of methyl methacrylate, for example, deviates strongly from classical mechanism behavior around 20% conversion; in this region the conversion and molecular mass of the polymer produced increases rapidly. This increase of polymerization is usually accompanied by a large rise in temperature if heat dissipation is not adequate. Without proper precautions, autoacceleration of polymerization systems could cause metallurgic failure of the reaction vessel or, worse, explosion.
To avoid the occurrence of thermal runaway due to autoacceleration, suspension polymerization techniques are employed to make polymers such as polystyrene. The droplets dispersed in the water are small reaction vessels, but the heat capacity of the water lowers the temperature rise, thus moderating the reaction. | 0 | Theoretical and Fundamental Chemistry |
A thermocouple can be used as a vacuum gauge over the range of approximately 0.001 to 1 torr absolute pressure. In this pressure range, the mean free path of the gas is comparable to the dimensions of the vacuum chamber, and the flow regime is neither purely viscous nor purely molecular. In this configuration, the thermocouple junction is attached to the centre of a short heating wire, which is usually energised by a constant current of about 5 mA, and the heat is removed at a rate related to the thermal conductivity of the gas.
The temperature detected at the thermocouple junction depends on the thermal conductivity of the surrounding gas, which depends on the pressure of the gas. The potential difference measured by a thermocouple is proportional to the square of pressure over the low- to medium-vacuum range. At higher (viscous flow) and lower (molecular flow) pressures, the thermal conductivity of air or any other gas is essentially independent of pressure. The thermocouple was first used as a vacuum gauge by Voege in 1906. The mathematical model for the thermocouple as a vacuum gauge is quite complicated, as explained in detail by Van Atta, but can be simplified to:
where P is the gas pressure, B is a constant that depends on the thermocouple temperature, the gas composition and the vacuum-chamber geometry, V is the thermocouple voltage at zero pressure (absolute), and V is the voltage indicated by the thermocouple.
The alternative is the Pirani gauge, which operates in a similar way, over approximately the same pressure range, but is only a 2-terminal device, sensing the change in resistance with temperature of a thin electrically heated wire, rather than using a thermocouple. | 1 | Applied and Interdisciplinary Chemistry |
A blue roof is a roof of a building that is designed explicitly to provide initial temporary water storage and then gradual release of stored water, typically rainfall. Blue roofs are constructed on flat or low sloped roofs in urban communities where flooding is a risk due to a lack of permeable surfaces for water to infiltrate, or seep back into the ground.
Water is stored in blue roof systems until it either evaporates or is released downstream after the storm event has passed. Blue roofs that are used for temporary rooftop storage can be classified as "active" or "passive" depending on the types of control devices used to regulate drainage of water from the roof. Blue roofs can provide a number of benefits depending on design. These benefits include temporary storage of rainfall to mitigate runoff impacts, storage for reuse such as irrigation or cooling water makeup, or recreational opportunities. | 1 | Applied and Interdisciplinary Chemistry |
Dynamic allele-specific hybridization (DASH) genotyping takes advantage of the differences in the melting temperature in DNA that results from the instability of mismatched base pairs. The process can be vastly automated and encompasses a few simple principles.
In the first step, a genomic segment is amplified and attached to a bead through a PCR reaction with a biotinylated primer. In the second step, the amplified product is attached to a streptavidin column and washed with NaOH to remove the unbiotinylated strand. An allele-specific oligonucleotide is then added in the presence of a molecule that fluoresces when bound to double-stranded DNA. The intensity is then measured as temperature is increased until the melting temperature (Tm) can be determined. A SNP will result in a lower than expected Tm.
Because DASH genotyping is measuring a quantifiable change in Tm, it is capable of measuring all types of mutations, not just SNPs. Other benefits of DASH include its ability to work with label free probes and its simple design and performance conditions. | 1 | Applied and Interdisciplinary Chemistry |
* In cardiac physiology: the cardiac output
* In hydrology: discharge
** List of rivers by discharge
** List of waterfalls by flow rate
** Weir § Flow measurement
* In dust collection systems: the air-to-cloth ratio | 1 | Applied and Interdisciplinary Chemistry |
Positron annihilation spectroscopy (PAS) or sometimes specifically referred to as positron annihilation lifetime spectroscopy (PALS) is a non-destructive spectroscopy technique to study voids and defects in solids. | 0 | Theoretical and Fundamental Chemistry |
The reagent is prepared by dissolving 0.5–2.0 g of p–dimethylaminobenzaldehyde (DMAB) in 50 mL of 95% ethanol and 50 mL of concentrated hydrochloric acid and is best used when fresh. Other alcohols, such as 1-propanol, can also be used as well.
The Ehrlich reagent is similar to a number of other indole tests:
* The van Urk reagent, which uses 0.125 g of p-DMAB, 0.2 mL of ferric chloride solution (25 mg/mL) in 100 mL of 65% sulfuric acid. This is sometimes referred to as the Hofmann reagent or p-DMAB-TS (Test Solution) and gives slightly different colours with different indoles.
* The Renz and Loew reagent, which uses p-dimethylaminocinnamaldehyde and may also be used for the detection of flavonoids.
* The "improved hallucinogen reagent", which uses a 1:1 solution of 5% DMAB in concentrated phosphoric acid (specific gravity 1.45) to methanol. | 0 | Theoretical and Fundamental Chemistry |
Nuclear matter is an idealized system of interacting nucleons (protons and neutrons) that exists in several phases of exotic matter that, as of yet, are not fully established. It is not matter in an atomic nucleus, but a hypothetical substance consisting of a huge number of protons and neutrons held together by only nuclear forces and no Coulomb forces. Volume and the number of particles are infinite, but the ratio is finite. Infinite volume implies no surface effects and translational invariance (only differences in position matter, not absolute positions).
A common idealization is symmetric nuclear matter, which consists of equal numbers of protons and neutrons, with no electrons.
When nuclear matter is compressed to sufficiently high density, it is expected, on the basis of the asymptotic freedom of quantum chromodynamics, that it will become quark matter, which is a degenerate Fermi gas of quarks.
Some authors use "nuclear matter" in a broader sense, and refer to the model described above as "infinite nuclear matter", and consider it as a "toy model", a testing ground for analytical techniques. However, the composition of a neutron star, which requires more than neutrons and protons, is not necessarily locally charge neutral, and does not exhibit translation invariance, often is differently referred to, for example, as neutron star matter or stellar matter and is considered distinct from nuclear matter. In a neutron star, pressure rises from zero (at the surface) to an unknown large value in the center.
Methods capable of treating finite regions have been applied to stars and to atomic nuclei. One such model for finite nuclei is the liquid drop model, which includes surface effects and Coulomb interactions. | 0 | Theoretical and Fundamental Chemistry |
Members of the enediyne family all share a unique enediyne core that is the cause of their potent cytotoxicity. The enediyne cores are derived from linear, probably polyketide, precursors that consist of seven or eight head-to-tail coupled acetate units. Enediyne assembly involves a highly conserved, iterative type I polyketide synthase (PKS) pathway Sequencing of enediyne gene clusters has confirmed the polyketide origin of the enediyne core, and elucidated the biosynthetic pathways and mechanisms of enediynes.
Differences in the biosynthetic pathways of enediynes are due to the different origins of the -yne carbons as well as differences in isotope incorporation patterns. More differentiation comes from the attachment of various functional groups at different positions to the enediyne warheads during their maturation stage. These moieties can be either aromatic or sugars and define sequence specificity of DNA binding as well as the physical properties of the enediyne chromophores.
Due to the cytotoxicity of the enediyne chromophores, their biosynthesis is tightly regulated, although the regulatory mechanisms are still largely unclear. Organisms that produce enediynes have been shown to protect themselves with a self-resistance mechanism that uses a self-sacrificing protein. Notably, some microbes use CalC to sequester calicheamicin so that the reactive diradical abstracts hydrogens from a glycine inside of the protein instead of from DNA. | 0 | Theoretical and Fundamental Chemistry |
To collect bioaerosols falling within a specific size range, impactors can be stacked to capture the variation of particulate matter (PM). For example, a PM filter lets smaller sizes pass through. This is similar to the size of a human hair. Particulates are deposited onto the slides, agar plates, or tape at the base of the impactor. The Hirst spore trap samples at 10 liters/minute (LPM) and has a wind vane to always sample in the direction of wind flow. Collected particles are impacted onto a vertical glass slide greased with petroleum.
Variations such as the 7-day recording volumetric spore trap have been designed for continuous sampling using a slowly rotating drum that deposits impacted material onto a coated plastic tape. The airborne bacteria sampler can sample at rates up to 700 LPM, allowing for large samples to be collected in a short sampling time. Biological material is impacted and deposited onto an agar lined Petri dish, allowing cultures to develop. | 0 | Theoretical and Fundamental Chemistry |
Entropy also plays a role in a substituent's preference for the equatorial position. The entropic component is determined by the following formula:
Where σ is equal to the number of microstates available for each conformation.
Due to the larger number of possible conformations of ethyl cyclohexane, the A value is reduced from what would be predicted based purely on enthalpic terms. Due to these favorable entropic conditions, the steric relevance of an ethyl group is similar to that of a methyl substituent. | 0 | Theoretical and Fundamental Chemistry |
As SPR biosensors facilitate measurements at different temperatures, thermodynamic analysis can be performed
to obtain a better understanding of the studied interaction. By performing measurements at different temperatures,
typically between 4 and 40 °C, it is possible to relate association and dissociation rate constants with activation
energy and thereby obtain thermodynamic parameters including binding enthalpy, binding entropy,
Gibbs free energy and heat capacity. | 0 | Theoretical and Fundamental Chemistry |
A fundamental criterion that must be established while developing any device with a semi-permeable membrane is to adjust the permeability of the device in terms of entry and exit of molecules. It is essential that the cell microcapsule is designed with uniform thickness and should have a control over both the rate of molecules entering the capsule necessary for cell viability and the rate of therapeutic products and waste material exiting the capsule membrane. Immunoprotection of the loaded cell is the key issue that must be kept in mind while working on the permeability of the encapsulation membrane as not only immune cells but also antibodies and cytokines should be prevented entry into the microcapsule which in fact depends on the pore size of the biomembrane.
It has been shown that since different cell types have different metabolic requirements, thus depending on the cell type encapsulated in the membrane the permeability of the membrane has to be optimized. Several groups have been dedicated towards the study of membrane permeability of cell microcapsules and although the role of permeability of certain essential elements like oxygen has been demonstrated, the permeability requirements of each cell type are yet to be determined.
Sodium Citrate is used for degradation of alginate beads after encapsulation of cells. In order to determine viability of the cells or for further experimentation. Concentrations of approximately 25mM are used to dissolve the alginate spheres and the solution is spun down using a centrifuge so the sodium citrate can be removed and the cells can be collected. | 1 | Applied and Interdisciplinary Chemistry |
# To make plain crude kilju, the must weight must be zero: A fermentation lock should indicate less than a bubble per minute. Then the sugar reserve is measured with a must weight refractometer/hygrometer. If there's sugar left, then more yeast should be added to consume it, and this measurement process should be repeated. A solution with sugar is not fermented water, but fermented syrup.
# Clarification: The solution is clarified, typically with a fining agent like bentonite.
# Alcohol by volume: Only when the must weight is zero, and when the solution has been clarified, an alcoholic hydrometer, or an ethanol-type refractometer, will display accurate alcohol volume. A leftover sugar reserve will give false values. | 1 | Applied and Interdisciplinary Chemistry |
The relevance of Brownian motors to the requirement of directed motion in nanorobotics has become increasingly apparent to researchers from both academia and industry.
Artificial replication of Brownian motors are informed by and differ from nature, and one specific type is the photomotor, wherein the motor switches states due to pulses of light and generates directed motion. These photomotors, in contrast to their natural counterpartsˇ, are inorganic and possess greater efficiency and average velocity, and are thus better suited to human use than existing alternatives, such as organic protein motors.
Currently, one of the six current "Grand Challenges" of the University of Sydney Nano Institute is to develop nanorobotics for health, a key aspect of which is a “nanoscale parts foundry” that can produce nanoscale Brownian motors for “active transport around the body”. The Institute predicts that among the implications of this research is a "paradigm shift" in healthcare "away from the "break-fix" model to a focus on prevention and early intervention," such as in the case with heart disease:
Professor Paul Bannon, an adult cardiothoracic surgeon of international standing and leading medical researcher, summarises the benefits of nanorobotics in health. | 0 | Theoretical and Fundamental Chemistry |
The ability to deliver pieces of DNA to the required parts of a cell includes many challenges. Current research is being performed to find ways to use dendrimers to traffic genes into cells without damaging or deactivating the DNA. To maintain the activity of DNA during dehydration, the dendrimer/DNA complexes were encapsulated in a water-soluble polymer, and then deposited on or sandwiched in functional polymer films with a fast degradation rate to mediate gene transfection. Based on this method, PAMAM dendrimer/DNA complexes were used to encapsulate functional biodegradable polymer films for substrate mediated gene delivery. Research has shown that the fast-degrading functional polymer has great potential for localized transfection. | 0 | Theoretical and Fundamental Chemistry |
Some caveats should be considered with the above.
1. Like all statistical mechanical results according to the MaxEnt school, this increase in thermodynamic entropy is only a prediction. It assumes in particular that the initial macroscopic description contains all of the information relevant to predicting the later macroscopic state. This may not be the case, for example if the initial description fails to reflect some aspect of the preparation of the system which later becomes relevant. In that case the "failure" of a MaxEnt prediction tells us that there is something more which is relevant that we may have overlooked in the physics of the system.
It is also sometimes suggested that quantum measurement, especially in the decoherence interpretation, may give an apparently unexpected reduction in entropy per this argument, as it appears to involve macroscopic information becoming available which was previously inaccessible. (However, the entropy accounting of quantum measurement is tricky, because to get full decoherence one may be assuming an infinite environment, with an infinite entropy).
2. The argument so far has glossed over the question of fluctuations. It has also implicitly assumed that the uncertainty predicted at time t for the variables at time t will be much smaller than the measurement error. But if the measurements do meaningfully update our knowledge of the system, our uncertainty as to its state is reduced, giving a new S which is less than S. (Note that if we allow ourselves the abilities of Laplaces demon, the consequences of this new information can also be mapped backwards, so our uncertainty about the dynamical state at time t is now also reduced from S to S').
We know that S > S; but we can now no longer be certain that it is greater than S = S. This then leaves open the possibility for fluctuations in S. The thermodynamic entropy may go "down" as well as up. A more sophisticated analysis is given by the entropy Fluctuation Theorem, which can be established as a consequence of the time-dependent MaxEnt picture.
3. As just indicated, the MaxEnt inference runs equally well in reverse. So given a particular final state, we can ask, what can we "retrodict" to improve our knowledge about earlier states? However the Second Law argument above also runs in reverse: given macroscopic information at time t, we should expect it too to become less useful. The two procedures are time-symmetric. But now the information will become less and less useful at earlier and earlier times. (Compare with Loschmidt's paradox.) The MaxEnt inference would predict that the most probable origin of a currently low-entropy state would be as a spontaneous fluctuation from an earlier high entropy state. But this conflicts with what we know to have happened, namely that entropy has been increasing steadily, even back in the past.
The MaxEnt proponents' response to this would be that such a systematic failing in the prediction of a MaxEnt inference is a "good" thing. It means that there is thus clear evidence that some important physical information has been missed in the specification the problem. If it is correct that the dynamics "are" time-symmetric, it appears that we need to put in by hand a prior probability that initial configurations with a low thermodynamic entropy are more likely than initial configurations with a high thermodynamic entropy. This cannot be explained by the immediate dynamics. Quite possibly, it arises as a reflection of the evident time-asymmetric evolution of the universe on a cosmological scale (see arrow of time). | 0 | Theoretical and Fundamental Chemistry |
Similar principles guide the lowest energy conformations of larger ring systems. Along with the acyclic stereocontrol principles outlined below, subtle interactions between remote substituents in large rings, analogous to those observed for 8-10 membered rings, can influence the conformational preferences of a molecule. In conjunction with remote substituent effects, local acyclic interactions can also play an important role in determining the outcome of macrocyclic reactions. The conformational flexibility of larger rings potentially allows for a combination of acyclic and macrocyclic stereocontrol to direct reactions. | 0 | Theoretical and Fundamental Chemistry |
Conventional SNP typing methods are typically time-consuming and expensive, requiring several probe based assays to be multiplexed together or the use of DNA microarrays. HRM is more cost-effective and reduces the need to design multiple pairs of primers and the need to purchase expensive probes. The HRM method has been successfully used to detect a single G to A substitution in the gene Vssc (Voltage Sensitive Sodium Channel) which confers resistance to the acaricide permethrin in Scabies mite. This mutation results in a coding change in the protein (G1535D). The analysis of scabies mites collected from suspected permethrin susceptible and tolerant populations by HRM showed distinct melting profiles. The amplicons from the sensitive mites were observed to have a higher melting temperature relative to the tolerant mites, as expected from the higher thermostability of the GC base pair
In a field more relevant to clinical diagnostics, HRM has been shown to be suitable in principle for the detection of mutations in the breast cancer susceptibility genes BRCA1 and BRCA2. More than 400 mutations have been identified in these genes.<br />The sequencing of genes is the gold standard for identifying mutations. Sequencing is time-consuming and labour-intensive and is often preceded by techniques used to identify heteroduplex DNA, which then further amplify these issues. HRM offers a faster and more convenient closed-tube method of assessing the presence of mutations and gives a result which can be further investigated if it is of interest. In a study carried out by Scott et al. in 2006, 3 cell lines harbouring different BRCA mutations were used to assess the HRM methodology. It was found that the melting profiles of the resulting PCR products could be used to distinguish the presence or absence of a mutation in the amplicon. Similarly in 2007 Krypuy et al. showed that the careful design of HRM assays (with regards to primer placement) could be successfully employed to detect mutations in the TP53 gene, which encodes the tumour suppressor protein p53 in clinical samples of breast and ovarian cancer. Both these studies highlighted the fact that changes in the melting profile can be in the form of a shift in the melting temperature or an obvious difference in the shape of the melt curve. Both of these parameters are a function of the amplicon sequence.
The consensus is that HRM is a cost efficient method that can be employed as an initial screen for samples suspected of harbouring polymorphisms or mutations. This would reduce the number of samples which need to be investigated further using more conventional methods. | 1 | Applied and Interdisciplinary Chemistry |
The commercial semisynthesis (by Bristol-Myers Squibb) of paclitaxel starting from 10-deacetylbaccatin III (isolated from the European yew) is based on tail addition of the so-called Ojima lactam to its free hydroxyl group:
Another commercial semisynthesis (by the company Natural Pharmaceuticals) relies on the isolation of a group of paclitaxel derivatives isolated from primary ornamental taxanes. These derivatives have the same skeleton as paclitaxel except for the organic residue R of the terminal tail amide group which can be phenyl, or propyl or pentyl (among others) whereas in paclitaxel it is an explicit phenyl group. The semisynthesis consists of conversion of the amide group to an amine with Schwartz's reagent through an imine followed by acidic workup and a benzoylation.
In the production process Michigan grown yews which mature in 8 years are periodically topped and dried. This material is shipped to Mexico for a first extraction step (10% paclitaxel content) and then to Canada for further purification to 95% purity. The semisynthesis to final product takes place in China. | 0 | Theoretical and Fundamental Chemistry |
* Studied and identified chromophores and a variety of dyes commonly used as biomolecule labels like: tryptophan, DAPI, fluorescein, thiazole orange, and BEBO.
* Explained DNA strand exchange in homologous recombination.
* Applying Widlund experiment, identified specific nucleosome positioning sequences.
* Uncovered mechanism of oncogene activation involving the formation of internal G-quadruplexes.
* Designed a probe that exhibit luminescence upon binding to specific nucleic acids.
* Techniques for gene expression at the level of individual cells and subcellular compartments.
* The occurrence of horizontal transfer of mitochondria within living organisms. | 1 | Applied and Interdisciplinary Chemistry |
After the RNase cleavage of the last six nucleotides, the next step is phosphorylation of the 5'-end via Kinase. Then the next cycle of ligation can be repeated. | 1 | Applied and Interdisciplinary Chemistry |
* 1929–34: Personal assistant (preparateur) to Marie Curie, Institut du Radium.
* 1934–46: Radiochemist, Institut du Radium.
* 1946–49: Maitre de Recherches, Centre National de la Recherche Scientifique (CNRS), Institut du Radium.
* 1949: Professeur titulaire de la Chaire de Chimie Nucleaire, Universite de Strasbourg.
* 1950–63: Member of the Atomic Weights Commission | 1 | Applied and Interdisciplinary Chemistry |
Functional genomics includes function-related aspects of the genome itself such as mutation and polymorphism (such as single nucleotide polymorphism (SNP) analysis), as well as the measurement of molecular activities. The latter comprise a number of "-omics" such as transcriptomics (gene expression), proteomics (protein production), and metabolomics. Functional genomics uses mostly multiplex techniques to measure the abundance of many or all gene products such as mRNAs or proteins within a biological sample. A more focused functional genomics approach might test the function of all variants of one gene and quantify the effects of mutants by using sequencing as a readout of activity. Together these measurement modalities endeavor to quantitate the various biological processes and improve our understanding of gene and protein functions and interactions. | 1 | Applied and Interdisciplinary Chemistry |
The Overman synthesis (1993) took a chiral cyclopentene compound as starting material obtained by enzymatic hydrolysis of cis-1,4-diacetoxycyclopent-2-ene. This starting material was converted in several steps to trialkylstannane 2 which was then coupled with an aryl iodide 1 in a Stille reaction in presence of carbon monoxide (tris(dibenzylideneacetone)dipalladium(0), triphenylarsine). The internal double in 3 was converted to an epoxide using tert-Butyl hydroperoxide, the carbonyl group was then converted to an alkene in a Wittig reaction using PhP=CH and the TIPS group was hydrolyzed (TBAF) and replaced by a trifluoroacetamide group (NHCOCF, NaH) in 4. Cyclization (NaH) took place next, opening the epoxide ring and the trifluoroacetyl group was removed using KOH affording azabicyclooctane 5.
The key step was an aza-Cope-Mannich reaction initiated by an amine-carbonyl condensation using formaldehyde and forming 6 in a quantitative yield:
In the final sequence strychnine was obtained through the Wieland-Gumlich aldehyde (10):
Intermediate 6 was acylated using methyl cyanoformate and two protective groups (tert-butyl and ) were removed using HCl / MeOH in 7. The C8C13 double bond was reduced with zinc (MeOH/H) to saturated ester 8 (mixture). Epimerization at C13 with sodium methoxide in MeOH produced beta-ester 9 which was reduced with diisobutylaluminium hydride to Wieland-Gumlich aldehyde 10. Conversion of this compound with malonic acid to (−)-strychnine 11 was already known as a procedure. | 0 | Theoretical and Fundamental Chemistry |
Philip Hauge Abelson (April 27, 1913 – August 1, 2004) was an American physicist, scientific editor and science writer. Trained as a nuclear physicist, he co-discovered the element neptunium, worked on isotope separation in the Manhattan Project, and wrote the first study of nuclear marine propulsion for submarines. He later worked on a broad range of scientific topics and related public policy, including organic geochemistry, paleobiology and energy policy.
Abelson served as editor-in-chief of the journal Science from 1962–84, president of the Carnegie Institution of Washington from 1971–78, and president of the American Geophysical Union from 1972-74. His frequent editorials in Science, both during and after his term as editor, became known for their strident and thought-provoking views. A collection of 100 of his editorials was published as a book, entitled Enough of Pessimism. He may have been the original source of the phrase extraordinary claims require extraordinary evidence. | 1 | Applied and Interdisciplinary Chemistry |
In a SRAS measurement, as in most laser ultrasound techniques, two lasers are used, one for the generation of acoustic waves and one for the subsequent detection of these waves. Considering first the generation of acoustic waves, an optical amplitude grating, illuminated by the a short pulse pump laser (typically ~1ns), is imaged onto the sample surface. The incident light is thermoelastically absorbed, creating surface acoustic waves, such as Rayleigh waves. As the laser pulse contains a broad range of frequencies, only the frequencies which match the grating spacing and acoustic velocity of that sample point will be generated. Using a second, continuous wave, laser these surface acoustic waves can then be measured through a number of interferometry techniques. Detection is usually achieved by optical beam deflection.
As Rayleigh waves are non-dispersive the phase velocity of the acoustic wave can be found by
where is the distance between the grating fringes imaged onto the sample surface and is the dominant frequency of the wave packet, found by fast Fourier transform.
As the measurement probes the frequency of the wave packet, which does not change along the propagation length, the measured SAW velocity is determined by only the properties of the specimen at the area where the grating pattern is imaged, unlike more traditional time of flight measurements that are influenced by the sample properties along the propagation length. This makes SRAS robust and immune to the aberrating and scattering effects of the microstructure. | 0 | Theoretical and Fundamental Chemistry |
Hydrogen–deuterium exchange of fast-exchanging species (e.g. hydroxyl groups) can be measured at atomic resolution quantitatively by neutron crystallography, and in real time if exchange is conducted during the diffraction experiment.
High intensity neutron beams are generally generated by spallation at linac particle accelerators such as the Spallation Neutron Source. Neutrons diffract crystals similarly to X-rays and can be used for structural determination. Hydrogen atoms, with between one and zero electrons in a biological setting, diffract X-rays poorly and are effectively invisible under normal experimental conditions. Neutrons scatter from atomic nuclei, and are therefore capable of detecting hydrogen and deuterium atoms.
Hydrogen atoms are routinely replaced with deuterium, which introduce a strong and positive scattering factor. It is often sufficient to replace only the solvent and labile hydrogen atoms in a protein crystal by vapor diffusion. In such a structure the occupancy of an exchangeable deuterium atom in a crystal will refine from 0-100%, directly quantifying the amount of exchange. | 0 | Theoretical and Fundamental Chemistry |
Organic matter plays an important role in drinking water and wastewater treatment and recycling, natural aquatic ecosystems, aquaculture, and environmental rehabilitation. It is therefore important to have reliable methods of detection and characterisation, for both short- and long-term monitoring. A variety of analytical detection methods for organic matter have existed for up to decades, to describe and characterise organic matter. These include, but are not limited to: total and dissolved organic carbon, mass spectrometry, nuclear magnetic resonance (NMR) spectroscopy, infrared (IR) spectroscopy, UV-Visible spectroscopy, and fluorescence spectroscopy. Each of these methods has its own advantages and limitations. | 0 | Theoretical and Fundamental Chemistry |
Phenethylamine is produced by a wide range of species throughout the plant and animal kingdoms, including humans; it is also produced by certain fungi and bacteria (genera: Lactobacillus, Clostridium, Pseudomonas and the family Enterobacteriaceae) and acts as a potent antimicrobial against certain pathogenic strains of Escherichia coli (e.g., the O157:H7 strain) at sufficient concentrations. | 1 | Applied and Interdisciplinary Chemistry |
He won the bronze medal in the hammer throw at the 1924 Summer Olympics. Four years later he finished eleventh in the 1928 Olympic hammer throw competition. In 1923 he beat the British hammer throw record, but did so in a demonstration rather than a competition, so his throw did not count for record purposes.
He won the gold medal for England in the 1930 British Empire Games in the hammer throw contest and finished fifth in the discus throw event. At the 1934 British Empire Games he won again the gold medal in the hammer throw competition.
Nokes was the Amateur Athletic Association (AAA) Champion from 1923 to 1926 and placed second in 1921–22 and 1927–28. He was chairman of the AAA's Coaching Committee, and also a member of the Achilles Club.
He was a graduate of Magdalen College, Oxford, where he studied chemistry and wrote a thesis on metaphenetidine. Nokes served in the Great War in the Royal Artillery in the trenches and then as an observer in the Royal Flying Corps. He was awarded a Military Cross for his service, becoming MC Nokes MC. In the Second World War he served as an officer in the Royal Air Force Volunteer Reserve (Training Branch) while a schoolmaster.
He taught chemistry at Malvern College and later at Harrow School, where he was appointed Head of Science; he had come to the attention of Harrow when two schools colocated during the Second World War, although they did not merge. His practical demonstrations of the reaction of sodium with water were popular and famous among his pupils. These often entailed an explosion as MC Nokes put more than the recommended quantity of sodium into the water, and as the smoke cleared and noise subsided, MC Nokes would say "Note the small report." He was a member of the Science Masters' Association. Later he worked at Harwell and then was Head of Laboratories at CENTO Institute of Nuclear & Applied Science in Tehran. In retirement he lived in Honiton, Devon, and then in Alton, Hampshire. His nicknames included "Nokey", "Glaxo" and "Stally."
The chronology of his career was:
* 1909—16 schoolboy at Bishop's Stortford College (School House A)
* 1916—18 Royal Garrison Artillery (RGA) & Royal Flying Corps (RFC), served on the Western Front. (August 1917 awarded MC)
* 1918—19 Royal Air Force, served on the Western Front
* 1921 Completed the shortened course in Chemistry at Oxford University, Magdalen College, with a distinction
* 1923 Awarded BSc. Chemistry, Oxford University, Magdalen College
* 1922—46 Malvern College, science teacher & head of department. (Housemaster 1932–40)
* 1946—57 Harrow School
* 1957—59 Atomic Energy Research Establishment, Harwell (Isotope Division)
* 1959—66 CENTO Institute of Nuclear Science, Tehran, with status of Third Secretary in the British Embassy, Tehran
* 1966—69 Tehran University Institute of Nuclear Science
During his time at Harrow, he served as a councillor in what is now Harrow London Borough Council, being elected as a Conservative for the ward of Harrow-on-the-Hill & Greenhill. During his service as a borough councillor, he proposed and was instrumental in bringing into service one of the first electric dust carts to be used in England, as part of the modernization of public health services in Harrow.
MC Nokes was one of eight children of Walter Nokes. His brothers included Gerald Dacre Nokes, a barrister and Indian judge, and George Augustus Nokes. | 0 | Theoretical and Fundamental Chemistry |
When carbon dioxide is held above its critical pressure (73.773 bar) and temperature (30.9780 °C), it can behave both as a gas and as a liquid, that is it expands to fill entirely its container like a gas but has a density similar to that of a liquid.
Supercritical CO is chemically stable, very cheap, and non-flammable, making it suitable as a working fluid for transcritical cycles. For example, it is employed in domestic water heat pumps, which can reach high efficiencies.
Moreover, when used in power generation plants that employ Brayton and Rankine cycles, it can improve efficiency and power output. Its high density enables a strong reduction in turbomachines dimensions, still ensuring the high efficiency of these components. Simpler designs can therefore be adopted, while steam turbines require multiple turbine stages, which necessarily yield larger dimensions and costs.
By contrast, mechanical components within sCO Brayton cycles, especially turbomachinery and heat exchangers, suffer from corrosion. | 0 | Theoretical and Fundamental Chemistry |
*factitious air (Davy)
*dephlogisticated nitrous air
*protoxide of nitrogen
*hypo-nitrous oxide
*gaseous oxide of azote | 1 | Applied and Interdisciplinary Chemistry |
In practice, the osmotic pressure produced by an ideally dilute solution would be too small to be accurately measured. For accurate measurements, solutions are not ideally dilute and a virial equation is used to account for deviations from ideal behavior and allow the calculation of . The virial equation takes a form similar to van ‘t Hoff's law of osmotic pressure, but contains additional constants to account for non-ideal behavior:
where are constants and is still the concentration of polymer 1. This virial equation may be represented in different additional forms:
where and are constants and . | 0 | Theoretical and Fundamental Chemistry |
Many physical processes over ocean surface can generate sea salt aerosols. One common cause is the bursting of air bubbles, which are entrained by the wind stress during the whitecap formation. Another is tearing of drops from wave tops. Wind speed is the key factor to determine the production rate in both mechanisms. Sea salt particle number concentration can reach 50 cm or more with high winds (>10 m s), compared to ~10 cm or less under moderate wind regimes. Due to the dependence on wind speed, it could be expected that sea-salt particle production and its impacts on climate may vary with climate change. | 0 | Theoretical and Fundamental Chemistry |
For fluid power, a working fluid is a gas or liquid that primarily transfers force, motion, or mechanical energy. In hydraulics, water or hydraulic fluid transfers force between hydraulic components such as hydraulic pumps, hydraulic cylinders, and hydraulic motors that are assembled into hydraulic machinery, hydraulic drive systems, etc. In pneumatics, the working fluid is air or another gas which transfers force between pneumatic components such as compressors, vacuum pumps, pneumatic cylinders, and pneumatic motors. In pneumatic systems, the working gas also stores energy because it is compressible. (Gases also heat up as they are compressed and cool as they expand; this incidental heat pump is rarely exploited.) (Some gases also condense into liquids as they are compressed and boil as pressure is reduced.)
For passive heat transfer, a working fluid is a gas or liquid, usually called a coolant or heat transfer fluid, that primarily transfers heat into or out of a region of interest by conduction, convection, and/or forced convection (pumped liquid cooling, air cooling, etc.).
The working fluid of a heat engine or heat pump is a gas or liquid, usually called a refrigerant, coolant, or working gas, that primarily converts thermal energy (temperature change) into mechanical energy (or vice versa) by phase change and/or heat of compression and expansion. Examples using phase change include water↔steam in steam engines, and refrigerants in vapor-compression refrigeration and air conditioning systems. Examples without phase change include air or hydrogen in hot air engines such as the Stirling engine, air or gases in gas-cycle heat pumps, etc. (Some heat pumps and heat engines use "working solids", such as rubber bands, for elastocaloric refrigeration or thermoelastic cooling and nickel titanium in a prototype heat engine.)
Working fluids other than air or water are necessarily recirculated in a loop. Some hydraulic and passive heat-transfer systems are open to the water supply and/or atmosphere, sometimes through breather filters. Heat engines, heat pumps, and systems using volatile liquids or special gases are usually sealed behind relief valves. | 0 | Theoretical and Fundamental Chemistry |
Clusters can be found in all classes of chemical compounds. According to the commonly accepted definition, a cluster consists minimally of a triangular set of atoms that are directly bonded to each other. But metal-metal bonded dimetallic complexes are highly relevant to the area. Clusters occur in "pure" inorganic systems, organometallic chemistry, main group chemistry, and bioinorganic chemistry. The distinction between very large clusters and bulk solids is increasingly blurred. This interface is the chemical basis of nanoscience or nanotechnology and specifically arise from the study of quantum size effects in cadmium selenide clusters. Thus, large clusters can be described as an array of bound atoms intermediate in character between a molecule and a solid.
* Examples: Fe(CO), BH, [[Molybdenum(II) chloride|[MoCl]]], 4Fe-4S | 0 | Theoretical and Fundamental Chemistry |
A major application of photochlorination is the production of chloroparaffins. Mixtures of complex composition consisting of several chlorinated paraffins are formed. Chlorinated paraffins have the general sum formula CHCl and are categorized into three groups: Low molecular weight chlorinated paraffins are short chain chloroparaffins (SCCP) with 10 to 13 carbon atoms, followed by medium chain chloroparaffins (MCCP) with carbon chain lengths of 14 to 17 carbon atoms and long chain chlorinated paraffins (LCCP), owing a carbon chainwith more than 17 carbon atoms. Approximately 70% of the chloroparaffins produced are MCCPs with a degree of chlorination from 45 to 52%. The remaining 30% are divided equally between SCCP and LCCP. Short chain chloroparaffins have high toxicity and easily accumulate in the environment. The European Union has classified SCCP as a category III carcinogen and restricted its use.
In 1985 the world production was 300,000 tonnes; since then the production volumes are falling in Europe and North America. In China, on the other hand, production rose sharply. China produced more than 600,000 tonnes of chlorinated paraffins in 2007, while in 2004 it was less than 100,000 tonnes.
The quantum yield for the photochlorination of n-heptane is about 7000, for example. In photochlorination plants, the quantum yield is about 100. In contrast to the thermal chlorination, which can utilize the formed reaction energy, the energy required to maintain the photochemical reaction must be constantly delivered.
The presence of inhibitors, such as oxygen or nitrogen oxides, must be avoided. Too high chlorine concentrations lead to high absorption near the light source and have a disadvantageous effect. | 0 | Theoretical and Fundamental Chemistry |
An einzel lens is an electrostatic lens that focuses without changing the energy of the beam. It consists of three or more sets of cylindrical or rectangular tubes in series along an axis. | 0 | Theoretical and Fundamental Chemistry |
The conventional units for the solubility parameter are (calories per cm), or cal cm. The SI units are J m, equivalent to the pascal. 1 calorie is equal to 4.184 J.
1 cal cm = (523/125 J) (10 m) = (4.184 J) (0.01 m) = 2.045483 10 J m = 2.045483 (10 J/m)= 2.045483 MPa.
Given the non-exact nature of the use of δ, it is often sufficient to say that the number in MPa is about twice the number in cal cm.
Where the units are not given, for example, in older books, it is usually safe to assume the non-SI unit. | 0 | Theoretical and Fundamental Chemistry |
7-Chlorokynurenic acid (7-CKA) is a tool compound that acts as a potent and selective competitive antagonist of the glycine site of the NMDA receptor. It produces ketamine-like rapid antidepressant effects in animal models of depression. However, 7-CKA is unable to cross the blood-brain-barrier, and for this reason, is unsuitable for clinical use. As a result, a centrally-penetrant prodrug of 7-CKA, 4-chlorokynurenine (AV-101), has been developed for use in humans, and is being studied in clinical trials as a potential treatment for major depressive disorder, and anti-nociception. In addition to antagonizing the NMDA receptor, 7-CKA also acts as a potent inhibitor of the reuptake of glutamate into synaptic vesicles (or as a vesicular glutamate reuptake inhibitor), an action that it mediates via competitive blockade of vesicular glutamate transporters (K = 0.59 mM). | 1 | Applied and Interdisciplinary Chemistry |
Fellutanine A, B, C and D are bio-active diketopiperazine alkaloids isolated from the cultures of Penicillium fellutanum, that belongs to a class of naturally occurring 2,5-diketopiperazines. Originally they were thought to be based on the "trans" cyclic dipetide cyclo(L-Trp-D-Trp) but were later shown to be based on the "cis" cyclic dipetide cyclo(L-Trp-L-Trp). This was also confirmed when fellutanine A, B and C were isolated from Penicillium simplicissimum. The fellutanines A−C, are non-annulated analogues of cyclo(L-Trp-L-Trp), but unlike their diannulated analogue fellutanine D are not cytotoxic. | 0 | Theoretical and Fundamental Chemistry |
He can also be hyperpolarized using metastability exchange optical pumping (MEOP). This process is able to polarize He nuclei in the ground state with optically pumped He nuclei in the metastable state. MEOP only involves He nuclei at room temperature and at low pressure (≈a few mbars). The process of MEOP is very efficient (high polarization rate), however, compression of the gas up to atmospheric pressure is needed. | 0 | Theoretical and Fundamental Chemistry |
Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile.
Biological hydrolysis is the cleavage of biomolecules where a water molecule is consumed to effect the separation of a larger molecule into component parts. When a carbohydrate is broken into its component sugar molecules by hydrolysis (e.g., sucrose being broken down into glucose and fructose), this is recognized as saccharification.
Hydrolysis reactions can be the reverse of a condensation reaction in which two molecules join into a larger one and eject a water molecule. Thus hydrolysis adds water to break down, whereas condensation builds up by removing water. | 0 | Theoretical and Fundamental Chemistry |
DNA synthesis begins at specific sites called origins of replication. These are regions of the genome where the DNA replication machinery is assembled and the DNA is unwound to begin DNA synthesis. In most cases, replication proceeds in both directions from the replication origin.
The main features of replication origins are sequences where specific initiation proteins are bound. A typical replication origin covers about 100-200 base pairs of DNA. Prokaryotes have one origin of replication per chromosome or plasmid but there are usually multiple origins in eukaryotic chromosomes. The human genome contains about 100,000 origins of replication representing about 0.3% of the genome. | 1 | Applied and Interdisciplinary Chemistry |
It is often useful to alter the copolymer equation by expressing concentrations in terms of mole fractions. Mole fractions of monomers and in the feed are defined as and where
Similarly, represents the mole fraction of each monomer in the copolymer:
These equations can be combined with the Mayo–Lewis equation to give
This equation gives the composition of copolymer formed at each instant. However the feed and copolymer compositions can change as polymerization proceeds. | 0 | Theoretical and Fundamental Chemistry |
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