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Carbohydrate NMR spectroscopy is the application of nuclear magnetic resonance (NMR) spectroscopy to structural and conformational analysis of carbohydrates. This method allows the scientists to elucidate structure of monosaccharides, oligosaccharides, polysaccharides, glycoconjugates and other carbohydrate derivatives from synthetic and natural sources. Among structural properties that could be determined by NMR are primary structure (including stereochemistry), saccharide conformation, stoichiometry of substituents, and ratio of individual saccharides in a mixture. Modern high field NMR instruments used for carbohydrate samples, typically 500 MHz or higher, are able to run a suite of 1D, 2D, and 3D experiments to determine a structure of carbohydrate compounds. | 0 | Theoretical and Fundamental Chemistry |
Transforming C-H bonds into C-B bonds through borylation has been thoroughly investigated due to their utility in synthesis (i.e. for cross-coupling reactions). John F. Hartwig reported a highly regioselective arene and alkane borylation catalyzed by a rhodium complex. In the case of alkanes, exclusive terminal functionalization was observed.
Later, ruthenium catalysts were discovered to have higher activity and functional group compatibility.
Other borylation catalysts have also been developed, including iridium-based catalysts, which successfully activate C-H bonds with high compatibility.
For more information, consult borylation. | 0 | Theoretical and Fundamental Chemistry |
Some research groups initially reported that they had replicated the Fleischmann and Pons results but later retracted their reports and offered an alternative explanation for their original positive results. A group at Georgia Tech found problems with their neutron detector, and Texas A&M discovered bad wiring in their thermometers. These retractions, combined with negative results from some famous laboratories, led most scientists to conclude, as early as 1989, that no positive result should be attributed to cold fusion. | 0 | Theoretical and Fundamental Chemistry |
Like any ferroic material, a multiferroic system is fragmented into domains. A domain is a spatially extended region with a constant direction and phase of its order parameters. Neighbouring domains are separated by transition regions called domain walls. | 0 | Theoretical and Fundamental Chemistry |
As mentioned above, agonists have the potential to bind in different locations and in different ways depending on the type of agonist and the type of receptor. The process of binding is unique to the receptor-agonist relationship, but binding induces a conformational change and activates the receptor. This conformational change is often the result of small changes in charge or changes in protein folding when the agonist is bound. Two examples that demonstrate this process are the muscarinic acetylcholine receptor and NMDA receptor and their respective agonists.
For the muscarinic acetylcholine receptor, which is a G protein-coupled receptor(GPCR), the endogenous agonist is acetylcholine. The binding of this neurotransmitter causes the conformational changes that propagate a signal into the cell. The conformational changes are the primary effect of the agonist, and are related to the agonist's binding affinity and agonist efficacy. Other agonists that bind to this receptor will fall under one of the different categories of agonist mentioned above based on their specific binding affinity and efficacy.
The NMDA receptor is an example of an alternate mechanism of action, as the NMDA receptor requires co-agonists for activation. Rather than simply requiring a single specific agonist, the NMDA receptor requires both the endogenous agonists, N-methyl-D-aspartate (NMDA) and glycine. These co-agonists are both required to induce the conformational change needed for the NMDA receptor to allow flow through the ion channel, in this case calcium. An aspect demonstrated by the NMDA receptor is that the mechanism or response of agonists can be blocked by a variety of chemical and biological factors. NMDA receptors specifically are blocked by a magnesium ion unless the cell is also experiencing depolarization.
These differences show that agonists have unique mechanisms of action depending on the receptor activated and the response needed. The goal and process remains generally consistent however, with the primary mechanism of action requiring the binding of the agonist and the subsequent changes in conformation to cause the desired response at the receptor. This response as discussed above can vary from allowing flow of ions to activating a GPCR and transmitting a signal into the cell. | 1 | Applied and Interdisciplinary Chemistry |
Functional models are simpler than structural models, focusing only on dissipating energy at a rate that is physically correct. These are based on an artificial eddy viscosity approach, where the effects of turbulence are lumped into a turbulent viscosity. The approach treats dissipation of kinetic energy at sub-grid scales as analogous to molecular diffusion. In this case, the deviatoric part of is modeled as:
where is the turbulent eddy viscosity and is the rate-of-strain tensor.
Based on dimensional analysis, the eddy viscosity must have units of . Most eddy viscosity SGS models model the eddy viscosity as the product of a characteristic length scale and a characteristic velocity scale. | 1 | Applied and Interdisciplinary Chemistry |
Sodium iodide, as well as potassium iodide, is commonly used to treat and prevent iodine deficiency. Iodized table salt contains 10 ppm iodide. | 0 | Theoretical and Fundamental Chemistry |
Initially, the laser light induces coherent polarization in the sample, i.e., the transitions between electron and hole states oscillate with the laser frequency and a fixed phase. The polarization dephases typically on a sub-100 fs time-scale in case of nonresonant excitation due to ultra-fast Coulomb- and phonon-scattering.
The dephasing of the polarization leads to creation of populations of electrons and holes in the conduction and the valence bands, respectively. The lifetime of the carrier populations is rather long, limited by radiative and non-radiative recombination such as Auger recombination. During this lifetime a fraction of electrons and holes may form excitons, this topic is still controversially discussed in the literature. The formation rate depends on the experimental conditions such as lattice temperature, excitation density, as well as on the general material parameters, e.g., the strength of the Coulomb-interaction or the exciton binding energy.
The characteristic time-scales are in the range of hundreds of picoseconds in GaAs; they appear to be much shorter in wide-gap semiconductors.
Directly after the excitation with short (femtosecond) pulses and the quasi-instantaneous decay of the polarization, the carrier distribution is mainly determined by the spectral width of the excitation, e.g., a laser pulse. The distribution is thus highly non-thermal and resembles a Gaussian distribution, centered at a finite momentum. In the first hundreds of femtoseconds, the carriers are scattered by phonons, or at elevated carrier densities via Coulomb-interaction. The carrier system successively relaxes to the Fermi–Dirac distribution typically within the first picosecond. Finally, the carrier system cools down under the emission of phonons. This can take up to several nanoseconds, depending on the material system, the lattice temperature, and the excitation conditions such as the surplus energy.
Initially, the carrier temperature decreases fast via emission of optical phonons. This is quite efficient due to the comparatively large energy associated with optical phonons, (36meV or 420K in GaAs) and their rather flat dispersion, allowing for a wide range of scattering processes under conservation of energy and momentum. Once the carrier temperature decreases below the value corresponding to the optical phonon energy, acoustic phonons dominate the relaxation. Here, cooling is less efficient due their dispersion and small energies and the temperature decreases much slower beyond the first tens of picoseconds. At elevated excitation densities, the carrier cooling is further inhibited by the so-called hot-phonon effect. The relaxation of a large number of hot carriers leads to a high generation rate of optical phonons which exceeds the decay rate into acoustic phonons. This creates a non-equilibrium "over-population" of optical phonons and thus causes their increased reabsorption by the charge-carriers significantly suppressing any cooling. Thus, a system cools slower, the higher the carrier density is. | 0 | Theoretical and Fundamental Chemistry |
Despite flucloxacillin being insensitive to beta-lactamases, some organisms have developed resistance to it and other narrow-spectrum β-lactam antibiotics including methicillin. Such organisms include methicillin-resistant Staphylococcus aureus, which has developed resistance to flucloxacillin and other penicillins by having an altered penicillin-binding protein. | 0 | Theoretical and Fundamental Chemistry |
Lanthanum(III) iodide can be synthesised by the reaction of lanthanum metal with mercury(II) iodide:
:2 La + 3 HgI → 2 LaI + 3 Hg
It can also be prepared from the elements, that is by the reaction of metallic lanthanum with iodine:
:2 La + 3 I → 2 LaI
While lanthanum(III) iodide solutions can be generated by dissolving lanthanum oxide in hydroiodic acid, the product will hydrolyse and form polymeric hydroxy species:
:LaO + 6 HI → 2 LaI + 3 HO → further reactions | 0 | Theoretical and Fundamental Chemistry |
Urey created the names protium, deuterium, and tritium in an article published in 1934. The name is based in part on advice from Gilbert N. Lewis who had proposed the name "deutium". The name comes from Greek deuteros second, and the nucleus was to be called a "deuteron" or "deuton". Isotopes and new elements were traditionally given the name that their discoverer decided. Some British scientists, such as Ernest Rutherford, wanted to call the isotope "diplogen", from Greek diploos double, and the nucleus to be called "diplon".
The amount inferred for normal abundance of deuterium was so small (only about 1 atom in 6400 hydrogen atoms in seawater [156 parts per million]) that it had not noticeably affected previous measurements of (average) hydrogen atomic mass. This explained why it hadnt been suspected before. Urey was able to concentrate water to show partial enrichment of deuterium. Lewis, Ureys graduate advisor at Berkeley, had prepared and characterized the first samples of pure heavy water in 1933. The discovery of deuterium, coming before the discovery of the neutron in 1932, was an experimental shock to theory; but when the neutron was reported, making deuteriums existence more explicable, Urey was awarded the Nobel Prize in Chemistry only three years after the isotopes isolation. Lewis was deeply disappointed by the Nobel Committee's decision in 1934 and several high-ranking administrators at Berkeley believed this disappointment played a central role in his suicide a decade later. | 0 | Theoretical and Fundamental Chemistry |
The basic working principle of diffraction topography is as follows:
An incident, spatially extended beam (mostly of X-rays, or neutrons) impinges on a sample.
The beam may be either monochromatic, i.e. consist one single wavelength of X-rays or neutrons, or polychromatic, i.e. be composed of a mixture of wavelengths ("white beam" topography). Furthermore, the incident beam may be either parallel, consisting only of "rays" propagating all along nearly the same direction, or divergent/convergent, containing several more strongly different directions of propagation.
When the beam hits the crystalline sample, Bragg diffraction occurs, i.e. the incident wave is reflected by the atoms on certain lattice planes of the sample, if it hits those planes at the right Bragg angle.
Diffraction from sample can take place either in reflection geometry (Bragg case), with the beam entering and leaving through the same surface, or in transmission geometry (Laue case).
Diffraction gives rise to a diffracted beam, which will leave the sample and propagate along a direction differing from the incident direction by the scattering angle .
The cross section of the diffracted beam may or may not be identical to the one of the incident beam. In the case of strongly asymmetric reflections, the beam size (in the diffraction plane) is considerably expanded or compressed, with expansion occurring if the incidence angle is much smaller than the exit angle, and vice versa. Independently of this beam expansion, the relation of sample size to image size is given by the exit angle alone: The apparent lateral size of sample features parallel to the exit surface is downscaled in the image by the projection effect of the exit angle.
A homogeneous sample (with a regular crystal lattice) would yield a homogeneous intensity distribution in the topograph (a "flat" image with no contrast). Intensity modulations (topographic contrast) arise from irregularities in the crystal lattice, originating from various kinds of defects such as
* voids and inclusions in the crystal
* phase boundaries (regions of different crystallographic phase, polytype, ...)
* defective areas, non-crystalline (amorphous) areas / inclusions
* cracks, surface scratches
* stacking faults
* dislocations, dislocation bundles
* grain boundaries, domain walls
* growth striations
* point defects or defect clusters
* crystal deformation
* strain fields
In many cases of defects such as dislocations, topography is not directly sensitive to the defects themselves (atomic structure of the dislocation core), but predominantly to the strain field surrounding the defect region. | 0 | Theoretical and Fundamental Chemistry |
Currently there are only two drugs in this category, ceftobiprole and ceftaroline. These new drugs are also the only β-lactam antibiotics that are effective against methicillin-resistant-Staphylococcus-aureus (MRSA). Ceftobiprole is a pyrrolidinone-3-ylidenemethyl cephem. The C-3 side chain was specifically designed to have a strong binding affinity to PBP2a and PBP2x. PBP2a is known to give staphylococci resistance to other β-lactam drugs and PBPx does the same for pneumococci. Ceftobiprole also has an aminothiazoyl-hydroxyimino side chain at the C-7 position which is known to give good resistance to β-lactamase from S. aureus. Together these active groups make ceftobiprole bactericidal to MRSA. Ceftobiprole has poor water solubility and is therefore administered intravenously as an ester prodrug called ceftobiprole medocaril. It is rapidly broken down into active ceftobiprole by plasma esterases.
Ceftaroline was developed from the fourth generation cephalosporin cefozopran. It retains the alkoxyimino group at position C-7 from earlier generations so it is fairly stable in the presence of many β-lactamases. Since MRSA and penicillin-resistant Streptococcus pneumoniae have resistance dedicated to new types of PBP, PBP2a and PBP2x respectively, both ceftaroline and ceftobiprole have C-3 side chains specially engineered to bind these new PBP. In the case of ceftaroline this side chain contains a 2-thioazolythio spacer linkage optimised for its anti-MRSA activity. Ceftaroline has low water solubility but this problem was overcome by attaching a N-phosphonoamino group to the molecule making the intravenous prodrug ceftaroline fosamil. The prodrug is dephosphorylated in plasma to form active ceftaroline. | 1 | Applied and Interdisciplinary Chemistry |
A germanium-68/gallium-68 generator is a device used to extract the positron-emitting isotope Ga of gallium from a source of decaying germanium-68. The parent isotope Ge has a half-life of 271 days and can be easily utilized for in-hospital production of generator produced Ga. Its decay product gallium-68 (with a half-life of only 68 minutes, inconvenient for transport) is extracted and used for certain positron emission tomography nuclear medicine diagnostic procedures, where the radioisotope's relatively short half-life and emission of positrons for creation of 3-dimensional PET scans, are useful. | 0 | Theoretical and Fundamental Chemistry |
Solomon is well known for several of his research achievements. In particular his work on free radical polymerization revolutionized the field through the development of the first living free-radical polymerization technique; Nitroxide Mediated Polymerization (NMP). He also led the team, and was principal inventor of the world's first polymer banknote. | 0 | Theoretical and Fundamental Chemistry |
Manganese like magnesium plays a crucial role as a co-factor in various enzymes though its concentration is noticeably lower than the other. Enzymes that use manganese as a co-factor are known as "manganoproteins." These proteins include enzymes, like oxidoreductases, transferases and hydrolases, which are necessary for metabolic functions and antioxidant responses. Manganese plays a significant role in host defense, blood clotting, reproduction, digestion and various other functions in the body. In particular, when concerning host defense, manganese acts as a preventative measure for oxidative stress by destroying free radicals which are ions that have an unpaired electron in their outer shells. | 1 | Applied and Interdisciplinary Chemistry |
Folch was born in Barcelona, Spain. His father Rafel Folch was a lawyer and a Catalan poet, and his mother Maria Pi a teacher. His mother spoke French, Folch went to high school at the Lycée Français of Barcelona, from which he graduated in 1927. He then undertook Medicine studies and received an M.D. degree from the University of Barcelona Medical school in 1932. | 1 | Applied and Interdisciplinary Chemistry |
Elaidinization of oleic acid, a common component of vegetable oils, yields its trans-isomer elaidic acid. | 0 | Theoretical and Fundamental Chemistry |
The Taiwan Typhoon and Flood Research Institute was inaugurated in 2011 in the city of Taichung. Lee Cheng-shang was the inaugural Director.
TTFRI is a coordinator of research into quantitative precipitation forecasting.
TTFRI has worked with the Central Weather Bureau to develop a radar assimilation system which has increased the accuracy of the six hour rainfall forecast by twenty percent.
In 2018 TTFRI began a project to improve the flood management of Cayo District in Belize in partnership with the Belizean Government which is one of Taiwan's few remaining official diplomatic allies. | 1 | Applied and Interdisciplinary Chemistry |
The anti-Markovnikov addition selectivity to aldehyde can be achieved through exploiting inherent stereoelectronics of the substrate. Placement of directing group at homo-allylic (i.e. Figure 3, A) and allylic position (i.e. Figure 3, B) to the terminal olefin favors the anti-Markovnikov aldehyde product, which suggests that in the catalytic cycle the directing group chelates to the palladium complex such that water attacks at the anti-Markovnikov carbon to generate the more thermodynamically stable palladacycle. Anti-Markovnikov selectivity is also observed in styrenyl substrates (i.e. Figure 3, C), presumably via η-palladium-styrene complex after water attacks anti-Markovnikov. More examples of substrate-controlled, anti-Markovnikov Tsuji-Wacker Oxidation of olefins are given in reviews by Namboothiri, Feringa, and Muzart.
Grubbs and co-workers paved way for anti-Markovnikov oxidation of stereoelectronically unbiased terminal olefins, through the use of palladium-nitrite system (Figure 2, D). In his system, the terminal olefin was oxidized to the aldehyde with high selectivity through a catalyst-control pathway. The mechanism is under investigation, however evidence suggests it goes through a nitrite radical adds into the terminal carbon to generate the more thermodynamically stable, secondary radical. Grubbs expanded this methodology to more complex, unbiased olefins. | 0 | Theoretical and Fundamental Chemistry |
Field-flow fractionation (FFF) can be considered as an alternative to GPC, especially when particles or high molar mass polymers cause clogging of the column, shear degradation is an issue or agglomeration takes place but cannot be made visible. FFF is separation in an open flow channel without having a static phase involved so no interactions occur. With one field-flow fractionation version, thermal field-flow fractionation, separation of polymers having the same size but different chemical compositions is possible. | 0 | Theoretical and Fundamental Chemistry |
PELP1 functions as a coactivator of several NRs and regulates genes involved in proliferation and cancer progression. PELP1 enhances transcription functions of ESR1, ESR2, AR, GR, E2F and STAT3. PELP1 participates in activation of ESR1 extra-nuclear actions by coupling ESR1 with Src kinase PI3K STAT3 ILK1 and mTOR PELP1 participates in E2-mediated cell proliferation and is a substrate of CDK4/cyclin D1, CDK2/cyclin E and CDK2/cyclin A complexes. Studies using TG mice model suggested the existence of an autocrine loop involving the CDK–cyclin D1–PELP1 axis in promoting mammary tumorigenesis
PELP1 has a histone binding domain; functions as a reader of histone modifications, interacts with epigenetic modifiers such as HDAC2, KDM1, PRMT6, CARM1; and facilitates activation of genes involved in proliferation and cancer progression. PELP1 modulates the expression of miRs, PELP1-mediated epigenetic changes play important role in the regulation miR expression and many of PELP1 mediated miRS are involved in promoting metastasis. PELP1 is needed for optimal DNA damage response, is phosphorylated by DDR kinases and is important for p53 coactivation function. PELP1 also interacts with MTp53, regulates its recruitment, and alters MTp53 target gene expression. PELP1 depletion contributes to increased stability of E2F1. PELP1 binds RNA, and participates in RNA splicing. The PELP1-regulated genome includes several uniquely spliced isoforms. Mechanistic studies showed that PELP1 interaction with the arginine methyltransferase PRMT6 plays a role in RNA splicing.
PELP1 plays critical roles in 60S ribosomal subunit synthesis and ribosomal RNA transcription. The SENP3-associated complex comprising PELP1, TEX10 and WDR18 is involved in maturation and nucleolar release of the large ribosomal subunit. SUMO conjugation/deconjugation of PELP1 controls its dynamic association with the AAA ATPase MDN1, a key factor of pre-60S remodeling. Modification of PELP1 promotes the recruitment of MDN1 to pre-60S particles, while deSUMOylation is needed to release both MDN1 and PELP1 from pre-ribosomes.
PELP1 is widely expressed in many regions of brain, including the hippocampus, hypothalamus, and cerebral cortex. PELP1 interacts with ESR1, Src, PI3K and GSK3β in the brain. It is essential for E2-mediated extra-nuclear signaling following global cerebral ischemic. PELP1 plays an essential role in E2-mediated rapid extranuclear signaling, neuroprotection, and cognitive function in the brain. Ability of E2 to exert anti-inflammatory effects was lost in PELP1 forebrain-specific knockout mice, indicating a key role for PELP1 in E2 anti-inflammatory signaling.
PELP1 is a proto-oncogene that provides cancer cells with a distinct growth and survival advantage. PELP1 interacts with various enzymes that modulate the cytoskeleton, cell
migration, and metastasis. PELP1 deregulation in vivo promotes development of mammary gland hyperplasia and carcinoma PELP1 is implicated in progression of breast, endometrial, ovarian, salivary prostate, lung, pancreas, and colon neoplasms.
PELP1 signaling contributes to hormonal therapy resistance. Altered localization of PLP1 contributes to tamoxifen resistance via excessive activation of the AKT pathway and cytoplasmic PELP1 induces signaling pathways that converge on ERRγ to promote cell survival in the presence of tamoxifen. AR, PELP1 and Src form constitutive complexes in prostate neoplasms model cells that exhibit androgen independence. Cytoplasmic localization of PELP1 upregulates pro-tumorigenic IKKε and secrete inflammatory signals, which through paracrine macrophage activation, regulate the migratory phenotype associated with breast cancer initiation. | 1 | Applied and Interdisciplinary Chemistry |
If the chromatographic separation can be modified to prevent coelution of suppressing species then other approaches need not be considered. The effect of chromatographic modification may be evaluated using the detector response monitoring under constant infusion approach described previously. | 0 | Theoretical and Fundamental Chemistry |
In the 1870s, the French industrialist Pierre Manhès began his first attempts with a small, ordinary Bessemer converter of 50 kg in his factory in Vedène, then in factories in Éguilles, near Avignon. He sought to refine a matte with 25 to 30% copper previously melted in a crucible. But like Hollway, he did not succeed in completely refining the matte. The oxidation of undesirable elements occurred as expected, but the operation was quickly disrupted by the appearance of metallic copper. The matte, which was an ionic compound, was immiscible with the slag, but also with the molten metal. The latter, which is denser (ρ ≈ 9), went to the bottom of the converter and clogged the tuyeres.
Pierre Manhès then patented the use of additives whose oxidation would release enough heat to avoid getting stuck. In the end, it was the Frenchman Paul David, then an engineer in his factory in 1880, who suggested the solution. He proposed horizontal tuyeres placed at a sufficient distance from the bottom of the converter so that the copper could gather below them and the air blow constantly in the matte. By 1881, their converter was both technically operational and cost-effective.
In the autumn of 1884, the process was adopted in the United States by the Parrot Silver and Copper Company in Butte, Montana. The two types became larger and larger, increasing from a capacity of one ton to eight tons in 1912, and even fifteen tons for cylindrical converters in 1920. | 1 | Applied and Interdisciplinary Chemistry |
Although they are classically thought of working only together, GPCRs may signal through G-protein-independent mechanisms, and heterotrimeric G-proteins may play functional roles independent of GPCRs. GPCRs may signal independently through many proteins already mentioned for their roles in G-protein-dependent signaling such as β-arrs, GRKs, and Srcs. Such signaling has been shown to be physiologically relevant, for example, β-arrestin signaling mediated by the chemokine receptor CXCR3 was necessary for full efficacy chemotaxis of activated T cells. In addition, further scaffolding proteins involved in subcellular localization of GPCRs (e.g., PDZ-domain-containing proteins) may also act as signal transducers. Most often the effector is a member of the MAPK family. | 1 | Applied and Interdisciplinary Chemistry |
The main metabolic challenge for methylotrophs is the assimilation of single carbon units into biomass. Through de novo synthesis, methylotrophs must form carbon-carbon bonds between 1-Carbon () molecules. This is an energy intensive process, which facultative methylotrophs avoid by using a range of larger organic compounds. However, obligate methylotrophs must assimilate molecules. There are four distinct assimilation pathways with the common theme of generating one molecule. Bacteria use three of these pathways while Fungi use one. All four pathways incorporate 3 molecules into multi-carbon intermediates, then cleave one intermediate into a new molecule. The remaining intermediates are rearranged to regenerate the original multi-carbon intermediates. | 0 | Theoretical and Fundamental Chemistry |
* Methyl esters are often susceptible to decarboxylation in the Krapcho decarboxylation.
* Phenyl esters react to hydroxyarylketones in the Fries rearrangement.
* Specific esters are functionalized with an α-hydroxyl group in the Chan rearrangement.
* Esters with β-hydrogen atoms can be converted to alkenes in ester pyrolysis.
*A direct conversion of esters to nitriles.
* Pairs of esters are coupled to give α-hydroxyketones in the acyloin condensation | 0 | Theoretical and Fundamental Chemistry |
LINE elements propagate by a so-called target primed reverse transcription mechanism (TPRT), which was first described for the R2 element from the silkworm Bombyx mori.
ORF2 (and ORF1 when present) proteins primarily associate in cis with their encoding mRNA, forming a ribonucleoprotein (RNP) complex, likely composed of two ORF2s and an unknown number of ORF1 trimers. The complex is transported back into the nucleus, where the ORF2 endonuclease domain opens the DNA (at TTAAAA hexanucleotide motifs in mammals). Thus, a 3'OH group is freed for the reverse transcriptase to prime reverse transcription of the LINE RNA transcript. Following the reverse transcription the target strand is cleaved and the newly created cDNA is integrated
New insertions create short target site duplications (TSDs), and the majority of new inserts are severely 5’-truncated (average insert size of 900bp in humans) and often inverted (Szak et al., 2002). Because they lack their 5’UTR, most of new inserts are non functional. | 1 | Applied and Interdisciplinary Chemistry |
Any real measuring instrument has a limited range over which it can accurately measure absorbance. An instrument must be calibrated and checked against known standards if the readings are to be trusted. Many instruments will become non-linear (fail to follow the Beer–Lambert law) starting at approximately 2 AU (~1% transmission). It is also difficult to accurately measure very small absorbance values (below ) with commercially available instruments for chemical analysis. In such cases, laser-based absorption techniques can be used, since they have demonstrated detection limits that supersede those obtained by conventional non-laser-based instruments by many orders of magnitude (detection has been demonstrated all the way down to ). The theoretical best accuracy for most commercially available non-laser-based instruments is attained in the range near 1 AU. The path length or concentration should then, when possible, be adjusted to achieve readings near this range. | 0 | Theoretical and Fundamental Chemistry |
Corriu and coworkers performed early work characterizing reactions thought to proceed through a hypervalent transition state. Measurements of the reaction rates of hydrolysis of tetravalent chlorosilanes incubated with catalytic amounts of water returned a rate that is first order in chlorosilane and second order in water. This indicated that two water molecules interacted with the silane during hydrolysis and from this a binucleophilic reaction mechanism was proposed. Corriu and coworkers then measured the rates of hydrolysis in the presence of nucleophilic catalyst HMPT, DMSO or DMF. It was shown that the rate of hydrolysis was again first order in chlorosilane, first order in catalyst and now first order in water. Appropriately, the rates of hydrolysis also exhibited a dependence on the magnitude of charge on the oxygen of the nucleophile.
Taken together this led the group to propose a reaction mechanism in which there is a pre-rate determining nucleophilic attack of the tetracoordinated silane by the nucleophile (or water) in which a hypervalent pentacoordinated silane is formed. This is followed by a nucleophilic attack of the intermediate by water in a rate determining step leading to hexacoordinated species that quickly decomposes giving the hydroxysilane.
Silane hydrolysis was further investigated by Holmes and coworkers in which tetracoordinated (Mes = mesityl) and pentacoordinated were reacted with two equivalents of water. Following twenty-four hours, almost no hydrolysis of the tetracoordinated silane was observed, while the pentacoordinated silane was completely hydrolyzed after fifteen minutes. Additionally, X-ray diffraction data collected for the tetraethylammonium salts of the fluorosilanes showed the formation of hydrogen bisilonate lattice supporting a hexacoordinated intermediate from which is quickly displaced leading to the hydroxylated product. This reaction and crystallographic data support the mechanism proposed by Corriu et al..
The apparent increased reactivity of hypervalent molecules, contrasted with tetravalent analogues, has also been observed for Grignard reactions. The Corriu group measured Grignard reaction half-times by NMR for related 18-crown-6 potassium salts of a variety of tetra- and pentacoordinated fluorosilanes in the presence of catalytic amounts of nucleophile.
Though the half reaction method is imprecise, the magnitudinal differences in reactions rates allowed for a proposed reaction scheme wherein, a pre-rate determining attack of the tetravalent silane by the nucleophile results in an equilibrium between the neutral tetracoordinated species and the anionic pentavalent compound. This is followed by nucleophilic coordination by two Grignard reagents as normally seen, forming a hexacoordinated transition state and yielding the expected product.
The mechanistic implications of this are extended to a hexacoordinated silicon species that is thought to be active as a transition state in some reactions. The reaction of allyl- or crotyl-trifluorosilanes with aldehydes and ketones only precedes with fluoride activation to give a pentacoordinated silicon. This intermediate then acts as a Lewis acid to coordinate with the carbonyl oxygen atom. The further weakening of the silicon–carbon bond as the silicon becomes hexacoordinate helps drive this reaction. | 0 | Theoretical and Fundamental Chemistry |
Archaeological evidence shows that bloomeries appeared in China around 800 BC. Originally it was thought that the Chinese started casting iron right from the beginning, but this theory has since been debunked by the discovery of more than ten iron digging implements found in the tomb of Duke Jing of Qin (d. 537 BC), whose tomb is located in Fengxiang County, Shaanxi (a museum exists on the site today). There is however no evidence of the bloomery in China after the appearance of the blast furnace and cast iron. In China, blast furnaces produced cast iron, which was then either converted into finished implements in a cupola furnace, or turned into wrought iron in a fining hearth.
Although cast iron farm tools and weapons were widespread in China by the 5th century BC, employing workforces of over 200 men in iron smelters from the 3rd century onward, the earliest blast furnaces constructed were attributed to the Han dynasty in the 1st century AD. These early furnaces had clay walls and used phosphorus-containing minerals as a flux. Chinese blast furnaces ranged from around two to ten meters in height, depending on the region. The largest ones were found in modern Sichuan and Guangdong, while the 'dwarf" blast furnaces were found in Dabieshan. In construction, they are both around the same level of technological sophistication.
The effectiveness of the Chinese human and horse powered blast furnaces was enhanced during this period by the engineer Du Shi (c. AD 31), who applied the power of waterwheels to piston-bellows in forging cast iron. Early water-driven reciprocators for operating blast furnaces were built according to the structure of horse powered reciprocators that already existed. That is, the circular motion of the wheel, be it horse driven or water driven, was transferred by the combination of a belt drive, a crank-and-connecting-rod, other connecting rods, and various shafts, into the reciprocal motion necessary to operate a push bellow. Donald Wagner suggests that early blast furnace and cast iron production evolved from furnaces used to melt bronze. Certainly, though, iron was essential to military success by the time the State of Qin had unified China (221 BC). Usage of the blast and cupola furnace remained widespread during the Song and Tang dynasties. By the 11th century, the Song dynasty Chinese iron industry made a switch of resources from charcoal to coke in casting iron and steel, sparing thousands of acres of woodland from felling. This may have happened as early as the 4th century AD.
The primary advantage of the early blast furnace was in large scale production and making iron implements more readily available to peasants. Cast iron is more brittle than wrought iron or steel, which required additional fining and then cementation or co-fusion to produce, but for menial activities such as farming it sufficed. By using the blast furnace, it was possible to produce larger quantities of tools such as ploughshares more efficiently than the bloomery. In areas where quality was important, such as warfare, wrought iron and steel were preferred. Nearly all Han period weapons are made of wrought iron or steel, with the exception of axe-heads, of which many are made of cast iron.
Blast furnaces were also later used to produce gunpowder weapons such as cast iron bomb shells and cast iron cannons during the Song dynasty. | 1 | Applied and Interdisciplinary Chemistry |
The dominant epoxides industrially are ethylene oxide and propylene oxide, which are produced respectively on the scales of approximately 15 and 3 million tonnes/year. | 0 | Theoretical and Fundamental Chemistry |
Cryoimmunotherapy, also referred to as cryoimmunology, is an oncological treatment for various cancers that combines cryoablation of tumor with immunotherapy treatment. In-vivo cryoablation of a tumor, alone, can induce an immunostimulatory, systemic anti-tumor response, resulting in a cancer vaccine—the abscopal effect. Thus, cryoablation of tumors is a way of achieving autologous, in-vivo tumor lysate vaccine and treat metastatic disease. However, cryoablation alone may produce an insufficient immune response, depending on various factors, such as high freeze rate. Combining cryotherapy with immunotherapy enhances the immunostimulating response and has synergistic effects for cancer treatment.
Although, cryoblation and immunotherapy has been used successfully in oncological clinical practice for over 100 years, and can treat metastatic disease with curative intent, it has been ignored in modern practice. Only recently has cryoimmunotherapy been resurrected to become the gold standard in cancer treatment of all stages of disease. | 1 | Applied and Interdisciplinary Chemistry |
TRIM24 has been shown to interact with Mineralocorticoid receptor, TRIM33, Estrogen receptor alpha and Retinoid X receptor alpha. | 1 | Applied and Interdisciplinary Chemistry |
This precatalyst was uncovered in attempts to use tris(triphenylphosphine)rhodium chloride as a hydroformylation catalyst. It was found that the complex would quickly carbonylate and that the catalytic activity of the resulting material was enhanced by a variety of additives but inhibited by halides. This inhibition did not occur in the presence of base, suggesting that the hydrido-complex represented the catalytic form of the complex. | 0 | Theoretical and Fundamental Chemistry |
Organic selenocyanates can be reduced to the selenol, which readily oxidize to the diselenide:
:RSeCN + 2e → RSe + CN
:RSe + H → RSeH
:2 RSeH + 0.5O → RSeSeR + HO
Oxidation of selenocyanates gives the seleninic acids. | 0 | Theoretical and Fundamental Chemistry |
There are two main sources of new research projects, namely ideas originating from the researchers themselves ("supply push") and those coming from customers ("demand pull"). Ideas for new processes typically originate from researchers, ideas for new products from customers, respectively customer contacts. Particularly in custom manufacturing, "demand pull" prevails industrial reality. The "new product committee" is the body of choice for evaluating new and monitoring ongoing research activities. It has the assignment to evaluate all new product ideas. It decides whether a new product idea should be taken up in research, reassesses a project at regular intervals and, last but not least decides also about the abandonment of a project, once it becomes evident that the objectives cannot be reached. In a typical project the overall responsibility for the economic and technical success lies with the project champion. He is assisted by the project manager, who is responsible for the technical success. In custom manufacturing, a typical project starts with the acceptance of the product idea, which originates mainly from business development, by the new product committee, followed by the preparation of a laboratory process, and ends with the successful completion of demonstration runs on industrial scale and the signature of a multiyear supply contract, respectively. The input from the customer is contained in the "technology package". Its main constituents are (1) reaction scheme, (2) target of project & deliverables (product, quantity, required dates, specifications), (3) list of analytical methods, (4) process development opportunities (stepwise assessment), (5) list of required reports, (6) Safety, Health and Environment (SHE) issues, (7) materials to be supplied by customer and (8) packaging & shipping information The technical part of a project usually determines its duration. Depending on the quality of the information contained in the "technology package" received from the customer and the complexity of the project as such, particularly the number of steps that have to be performed; it can be any time between 12 and 24 months. Depending on the number of researches involved, the total budget easily amounts to several million US dollars. | 0 | Theoretical and Fundamental Chemistry |
In the sugarcane industry, the organic waste is usually burned in the power cogeneration process. When contaminated by chloride, this waste burns, releasing methyl chloride in the atmosphere. | 1 | Applied and Interdisciplinary Chemistry |
Four potential processes exist for a chemical interacting with an animal: absorption, distribution, metabolism and excretion (ADME). Absorption describes the entrance of the chemical into the body, and can occur through the air, water, food, or soil. Once a chemical is inside a body, it can be distributed to other areas of the body through diffusion or other biological processes. At this point, the chemical may undergo metabolism and be biotransformed into other chemicals (metabolites). These metabolites can be less or more toxic than the parent compound. After this potential biotransformation occurs, the metabolites may leave the body, be transformed into other compounds, or continue to be stored in the body compartments.
A well designed toxicokinetic study may involve several different strategies and depends on the scientific question to be answered. Controlled acute and repeated toxicokinetic animal studies are useful to identify a chemical's biological persistence, tissue and whole body half-life, and its potential to bioaccumulate. Toxicokinetic profiles can change with increasing exposure duration or dose. Real world environmental exposures generally occur as low level mixtures, such as from air, water, food, or tobacco products. Mixture effects may differ from individual chemical toxicokinetic profiles because of chemical interactions, synergistic, or competitive processes. For other reasons, it is equally important to characterize the toxicokinetics of individual chemicals constituents found in mixtures as information on behavior or fate of the individual chemical can help explain environmental, human, and wildlife biomonitoring studies. | 1 | Applied and Interdisciplinary Chemistry |
There is a fairly large variation in the types of inorganic substrates that these microorganisms can use to produce energy. Sulfur is one of many inorganic substrates that can be used in different reduced forms depending on the specific biochemical process that a lithotroph uses. The chemolithotrophs that are best documented are aerobic respirers, meaning that they use oxygen in their metabolic process. The list of these microorganisms that employ anaerobic respiration though is growing. At the heart of this metabolic process is an electron transport system that is similar to that of chemoorganotrophs. The major difference between these two microorganisms is that chemolithotrophs directly provide electrons to the electron transport chain, while chemoorganotrophs must generate their own cellular reducing power by oxidizing reduced organic compounds. Chemolithotrophs bypass this by obtaining their reducing power directly from the inorganic substrate or by the reverse electron transport reaction. Certain specialized chemolithotrophic bacteria use different derivatives of the Sox system; a central pathway specific to sulfur oxidation. This ancient and unique pathway illustrates the power that chemolithotrophs have evolved to use from inorganic substrates, such as sulfur.
In chemolithotrophs, the compounds - the electron donors - are oxidized in the cell, and the electrons are channeled into respiratory chains, ultimately producing ATP. The electron acceptor can be oxygen (in aerobic bacteria), but a variety of other electron acceptors, organic and inorganic, are also used by various species. Aerobic bacteria such as the nitrifying bacteria, Nitrobacter, use oxygen to oxidize nitrite to nitrate. Some lithotrophs produce organic compounds from carbon dioxide in a process called chemosynthesis, much as plants do in photosynthesis. Plants use energy from sunlight to drive carbon dioxide fixation, but chemosynthesis can take place in the absence of sunlight (e.g., around a hydrothermal vent). Ecosystems establish in and around hydrothermal vents as the abundance of inorganic substances, namely hydrogen, are constantly being supplied via magma in pockets below the sea floor. Other lithotrophs are able to directly use inorganic substances, e.g., ferrous iron, hydrogen sulfide, elemental sulfur, thiosulfate, or ammonia, for some or all of their energy needs.
Here are a few examples of chemolithotrophic pathways, any of which may use oxygen or nitrate as electron acceptors: | 1 | Applied and Interdisciplinary Chemistry |
Most tests employ a monoclonal antibody, which is specific to the β-subunit of hCG (β-hCG). This procedure is employed to ensure that tests do not make false positives by confusing hCG with LH and FSH. (The latter two are always present at varying levels in the body, whereas the presence of hCG almost always indicates pregnancy.)
Many hCG immunoassays are based on the sandwich principle, which uses antibodies to hCG labeled with an enzyme or a conventional or luminescent dye.
Pregnancy urine dipstick tests are based on the lateral flow technique.
* The urine test may be a chromatographic immunoassay or any of several other test formats, home-, physician's office-, or laboratory-based. Published detection thresholds range from 20 to 100 mIU/mL, depending on the brand of test. Early in pregnancy, more accurate results may be obtained by using the first urine of the morning (when urine is most concentrated). When the urine is dilute (specific gravity less than 1.015), the hCG concentration may not be representative of the blood concentration, and the test may be falsely negative.
* The serum test, using 2-4 mL of venous blood, is typically a chemiluminescent or fluorimetric immunoassay that can detect βhCG levels as low as 5 mIU/mL and allows quantification of the βhCG concentration. | 1 | Applied and Interdisciplinary Chemistry |
In colloidal mixtures quintuple and sixtuple points have been described in violation of Gibbs phase rule but it is argued that in these systems the rule can be generalized to where accounts for additional parameters of interaction among the components like the diameter of one type of particle in relation to the diameter of the other particles in the solution. | 0 | Theoretical and Fundamental Chemistry |
Ram Charan Mehrotra (16 February 1922 – 11 July 2004) was an Indian analytical and organometallic chemist, academic, educationist and the vice chancellor of the Universities of Delhi and Allahabad. He was known for his studies on the chemical theory of indicators, alkoxides and carboxylates of many elements. He was an elected fellow of the Indian National Science Academy, Indian Chemical Society, Chemical Society of London, Royal Institute of Chemistry, National Academy of Sciences, India and Indian Academy of Sciences. The Council of Scientific and Industrial Research, the apex agency of the Government of India for scientific research, awarded him the Shanti Swarup Bhatnagar Prize for Science and Technology, one of the highest Indian science awards, in 1965, for his contributions to chemical sciences. | 0 | Theoretical and Fundamental Chemistry |
In chiral column chromatography the stationary phase is made chiral with similar resolving agents as described above. | 0 | Theoretical and Fundamental Chemistry |
In genetic epidemiology, endophenotype (or intermediate phenotype) is a term used to separate behavioral symptoms into more stable phenotypes with a clear genetic connection. By seeing the EP notion as a special case of a larger collection of multivariate genetic models, which may be fitted using currently accessible methodology, it is possible to maximize its valuable potential lessons for etiological study in psychiatric disorders.
The concept was coined by Bernard John and Kenneth R. Lewis in a 1966 paper attempting to explain the geographic distribution of grasshoppers. They claimed that the particular geographic distribution could not be explained by the obvious and external "exophenotype" of the grasshoppers, but instead must be explained by their microscopic and internal "endophenotype". The endophenotype idea represents the influence of two important conceptual currents in biology and psychology research. An adequate technology would be required to perceive the endophenotype, which represents an unobservable latent entity that cannot be directly observed with the unaided naked eye. In the investigation of anxiety and affective disorders, the endophenotype idea has gained popularity.
The next major use of the term was in psychiatric genetics, to bridge the gap between high-level symptom presentation and low-level genetic variability, such as single nucleotide polymorphisms. It is therefore more applicable to more heritable disorders, such as bipolar disorder and schizophrenia. Through their impact on the growth and operation of the vital components of the nervous system, such as neurons, transmitter systems, and neural networks, genes have an impact on complex behavior. Therefore, heritable differences in mental abilities may be caused by changes in the code describing the shape and operation of the underlying neural network. One significant expression of this idea is believed to be the many cognitive deficiencies seen in ADHD, making them ideal candidates for an endophenotype approach. Since then, the concept has expanded to many other fields, such as the study of ADHD, addiction, Alzheimer's disease, obesity and cystic fibrosis. Some other terms which have a similar meaning but do not stress the genetic connection as highly are "intermediate phenotype", "biological marker", "subclinical trait", "vulnerability marker", and "cognitive marker". The strength of an endophenotype is its ability to differentiate between potential diagnoses that present with similar symptoms. | 1 | Applied and Interdisciplinary Chemistry |
Denaturation can also be caused by changes in the pH which can affect the chemistry of the amino acids and their residues. The ionizable groups in amino acids are able to become ionized when changes in pH occur. A pH change to more acidic or more basic conditions can induce unfolding. Acid-induced unfolding often occurs between pH 2 and 5, base-induced unfolding usually requires pH 10 or higher. | 1 | Applied and Interdisciplinary Chemistry |
Chemotaxis refers to the directional migration of cells in response to chemical gradients; several variations of chemical-induced migration exist as listed below.
* Chemokinesis refers to an increase in cellular motility in response to chemicals in the surrounding environment. Unlike chemotaxis, the migration stimulated by chemokinesis lacks directionality, and instead increases environmental scanning behaviors.
* In haptotaxis the gradient of the chemoattractant is expressed or bound on a surface, in contrast to the classical model of chemotaxis, in which the gradient develops in a soluble fluid. The most common biologically active haptotactic surface is the extracellular matrix (ECM); the presence of bound ligands is responsible for induction of transendothelial migration and angiogenesis.
* Necrotaxis embodies a special type of chemotaxis when the chemoattractant molecules are released from necrotic or apoptotic cells. Depending on the chemical character of released substances, necrotaxis can accumulate or repel cells, which underlines the pathophysiological significance of this phenomenon. | 1 | Applied and Interdisciplinary Chemistry |
The size of the task requires a parallel computing infrastructure, such as a cluster of Linux systems, running a batch queue processor to handle the work, such as Sun Grid Engine or Torque PBS.
A means of handling the input from large compound libraries is needed. This requires a form of compound database that can be queried by the parallel cluster, delivering compounds in parallel to the various compute nodes. Commercial database engines may be too ponderous, and a high speed indexing engine, such as Berkeley DB, may be a better choice. Furthermore, it may not be efficient to run one comparison per job, because the ramp up time of the cluster nodes could easily outstrip the amount of useful work. To work around this, it is necessary to process batches of compounds in each cluster job, aggregating the results into some kind of log file. A secondary process, to mine the log files and extract high scoring candidates, can then be run after the whole experiment has been run. | 1 | Applied and Interdisciplinary Chemistry |
For a simple cubic packing, the number of atoms per unit cell is one. The side of the unit cell is of length 2r, where r is the radius of the atom. | 0 | Theoretical and Fundamental Chemistry |
The Ludwieg tube was invented by Hubert Ludwieg (1912-2000) in 1955 in response to a competition for a transonic or supersonic wind tunnel design that would be capable of producing high Reynolds number at low operating cost. Professor Ludwieg was also responsible for the experimental demonstration and explanation of the large effect of sweep on the drag of transonic wings (his dissertation in 1937). | 1 | Applied and Interdisciplinary Chemistry |
The Richardson number (Ri) is named after Lewis Fry Richardson (1881–1953). It is the dimensionless number that expresses the ratio of the buoyancy term to the flow shear term:
where is gravity, is density, is a representative flow speed, and is depth.
The Richardson number, or one of several variants, is of practical importance in weather forecasting and in investigating density and turbidity currents in oceans, lakes, and reservoirs.
When considering flows in which density differences are small (the
Boussinesq approximation), it is common to use the reduced gravity
g ' and the relevant parameter is the densimetric Richardson number
which is used frequently when considering atmospheric or oceanic flows.
If the Richardson number is much less than unity, buoyancy is unimportant
in the flow. If it is much greater than unity, buoyancy is dominant (in
the sense that there is insufficient kinetic energy to homogenize the fluids).
If the Richardson number is of order unity, then the flow is likely to
be buoyancy-driven: the energy of the flow derives from the potential energy in the system originally. | 1 | Applied and Interdisciplinary Chemistry |
Simplified sewerage, also called small-bore sewerage, is a sewer system that collects all household wastewater (blackwater and greywater) in small-diameter pipes laid at fairly flat gradients. Simplified sewers are laid in the front yard or under the pavement (sidewalk) or - if feasible - inside the back yard, rather than in the centre of the road as with conventional sewerage. It is suitable for existing unplanned low-income areas, as well as new housing estates with a regular layout. It allows for a more flexible design. With simplified sewerage it is crucial to have management arrangements in place to remove blockages, which are more frequent than with conventional sewers. It has been estimated that simplified sewerage reduces investment costs by up to 50% compared to conventional sewerage.
Simplified sewerage is sometimes also referred to as conventional sewerage with appropriate standards, implying that most conventional sewers are overdesigned.
The concept of simplified sewerage emerged in parallel in Natal, Brazil and Karachi, Pakistan in the early 1980s without any interaction or communication.
In both cases particular emphasis was given to community mobilization, an essential element for the success of simplified sewerage. In Latin America, and particularly in Brazil, simplified sewerage is also known as condominial sewerage, a term that underscores the importance of community participation in planning and maintenance at the level of a housing block (known as condominio in the Spanish and Portuguese use of the term). | 1 | Applied and Interdisciplinary Chemistry |
Mixed oxides of nitrogen (MON) are solutions of nitric oxide (NO) in dinitrogen tetroxide/nitrogen dioxide (NO and NO). It may be used as an oxidizing agent in rocket propulsion systems. A broad range of compositions is available, and can be denoted as MONi, where i represents the percentage of nitric oxide in the mixture (e.g. MON3 contains 3% nitric oxide, MON25 25% nitric oxide). An upper limit is MON40 (40% by weight). In Europe MON 1.3 is mostly used for rocket propulsion systems, while NASA seems to prefer MON 3. A higher percentage of NO decreases the corrosiveness and oxidation potential of the liquid, but increases costs.
The addition of nitric oxide also reduces the freezing point to a more desirable temperature. The freezing point of pure nitrogen tetroxide is , while MON3 is and MON25 is . | 0 | Theoretical and Fundamental Chemistry |
A wide variety of sampling configurations are used for thermal desorption, depending on the application. The most popular are listed below. | 0 | Theoretical and Fundamental Chemistry |
The cinnamyl alcohol glycosides rosin, rosavin and rosarin occur in the context of rhodiola species, only in Rhodiola rosea. | 0 | Theoretical and Fundamental Chemistry |
Studies of phenotype of mice showed that having a loss of an allele resulted in obesity and poor metabolic profiles. Transgenic expression of the WDTC1 gene in mice showed the opposite effect with mice having less adipose. | 1 | Applied and Interdisciplinary Chemistry |
*DNA extraction
*Phenol–chloroform extraction
*Minicolumn purification
*RNA extraction
*Boom method
*Synchronous coefficient of drag alteration (SCODA) DNA purification | 1 | Applied and Interdisciplinary Chemistry |
The mining and mineral processing industry uses screening for a variety of processing applications. For example, after mining the minerals, the material is transported to a primary crusher. Before crushing large boulder are scalped on a shaker with thick shielding screening. Further down stream after crushing the material can pass through screens with openings or slots that continue to become smaller. Finally, screening is used to make a final separation to produce saleable products based on a grade or a size range. | 1 | Applied and Interdisciplinary Chemistry |
*C.H. Giles and S.D. Forrester, "The origins of the surface film balance: Studies in the early history of surface chemistry, part 3", Chemistry and Industry, pp. 43–53 (9 January 1971). (Note: This article contains one of the most detailed stories on Agnes Pockels, including photos of her and her family.)
*Charles Tanford, Ben Franklin stilled the waves: An informal history of pouring oil on water with reflections on the ups and downs of scientific life in general, Oxford University Press, 2004.
*M. Elizabeth Derrick, "[https://www.scribd.com/document/368170781/Agnes-Pocket Agnes Pockels, 1862-1935]", Journal of Chemical Education, vol. 59, no. 12, pp. 1030–1031 (Dec. 1982).
*Andrea Kruse and Sonja M. Schwarzl. "Zum Beispiel Agnes Pockels." In: Nachrichten aus der Chemie, 06, 2002. | 0 | Theoretical and Fundamental Chemistry |
Levomethorphan (LVM) (INN, BAN) is an opioid analgesic of the morphinan family that has never been marketed. It is the -stereoisomer of racemethorphan (methorphan). The effects of the two isomers of racemethorphan are quite different, with dextromethorphan (DXM) being an antitussive at low doses and a dissociative hallucinogen at much higher doses. Levomethorphan is about five times stronger than morphine.
Levomethorphan is a prodrug to levorphanol, analogously to DXM acting as a prodrug to dextrorphan or codeine behaving as a prodrug to morphine. As such, levomethorphan has similar effects to levorphanol but is less potent as it must be demethylated to the active form by liver enzymes before being able to produce its effects. As a prodrug of levorphanol, levomethorphan functions as a potent agonist of all three of the opioid receptors, μ, κ (κ and κ but notably not κ), and δ, as an NMDA receptor antagonist, and as a serotonin-norepinephrine reuptake inhibitor. Via activation of the κ-opioid receptor, levomethorphan can produce dysphoria and psychotomimetic effects such as dissociation and hallucinations.
Levomethorphan is listed under the Single Convention on Narcotic Drugs 1961 and is regulated like morphine in most countries. In the United States it is a Schedule II Narcotic controlled substance with a DEA ACSCN of 9210 and a 2014 annual aggregate manufacturing quota of 195 grams, up from 6 grams the year before. The salts in use are the tartrate (free base conversion ratio 0.644) and hydrobromide (0.958). At the current time, no levomethorphan pharmaceuticals are marketed in the United States. | 0 | Theoretical and Fundamental Chemistry |
Possible adverse effects in the central nervous system caused by levobupivacaine usage are light-headedness, tinnitus, tongue numbness and convulsions, which may be due to the blockade of sodium, potassium and calcium channels in tissues that were not intended as targets. Cardiotoxicity may be a result of indirect effects of the drug, such as the blockade of myocardial sympathetic nerves, thus leading to contractile delay, or by direct effects, such as the blockade of potassium channels.
Effects of this nature lead to lowered contractile function and arrhythmogenic effects, which can potentially cause cardiovascular collapse and death. It is to note that the drug also has vasoconstrictive activity, thereby increasing the duration of sensory blockage with a relatively low risk of central nervous system toxicity on one hand, and on the other, it can have the same effect on uteroplacental blood flow, which can harm the foetus. Ultimately, levobupivacaine has been shown to have a lower risk of cardiovascular and central nervous system toxicity compared to bupivacaine in animal studies, not at the expense of potency and efficacy, and should be therefore considered as an alternative. | 0 | Theoretical and Fundamental Chemistry |
KAP1 facilitates the establishment of viral latency in certain cell types for Human Cytomegalovirus (HCMV) and other endogenous retroviruses
. KAP1 acts as a transcriptional corepressor of the viral genome. The protein binds to the histones of the viral chromatin and then recruits Mi2α and SETB1. SETB1 is a histone methyltransferase that recruits HP1, thus inducing heterochromatin formation. This heterochromatin formation prevents the transcription of the viral genome. mTOR has been implicated in the phosphorylation of KAP1 resulting in a switch from latency to the lytic cycle. | 1 | Applied and Interdisciplinary Chemistry |
Detrimental secondary phases can also form because of thermal treatments or during the material production. Excessively high sintering/annealing temperatures or long dwelling times will result in the loss of volatile species (especially LiO) and in the decomposition of LAGP main phase into AlPO and GeO. LAGP bulk samples and thin films are typically stable up to 700-750 °C; if this temperature is exceeded, volatile lithium is lost and the impurity phase GeO forms. If the temperature is further increased beyond 950 °C, also AlPO appears.
Raman spectroscopy and in situ X-ray diffraction (XRD) are useful techniques that can be employed to recognise the phase purity of LAGP samples during and after the heat treatments. | 0 | Theoretical and Fundamental Chemistry |
By symmetry of second derivatives, for any "well-behaved" (non-pathological) function , we have
Hence, in a simply-connected region R of the xy-plane, where are independent, a differential form
is an exact differential if and only if the equation
holds. If it is an exact differential so and , then is a differentiable (smoothly continuous) function along and , so . If holds, then and are differentiable (again, smoothly continuous) functions along and respectively, and is only the case.
For three dimensions, in a simply-connected region R of the xyz-coordinate system, by a similar reason, a differential
is an exact differential if and only if between the functions A, B and C there exist the relations
These conditions are equivalent to the following sentence: If G is the graph of this vector valued function then for all tangent vectors X,Y of the surface G then s(X, Y) = 0 with s the symplectic form.
These conditions, which are easy to generalize, arise from the independence of the order of differentiations in the calculation of the second derivatives. So, in order for a differential dQ, that is a function of four variables, to be an exact differential, there are six conditions (the combination ) to satisfy. | 0 | Theoretical and Fundamental Chemistry |
With such table top laboratory equipment it is now also possible to produce films, fibers and test samples (rods, rings, tablets) from mixtures as small as 5 ml in less than 10 min. By the small footprint less lab space is needed than for a parallel twin screw extruder. Because of these benefits screening of optimum formulations in R&D is really feasible and affordable.
In pharmaceutical and biomedical R&D, where sample costs are a key issue, an easy to clean, 2 to 5 ml GMP compliant pharma micro-extruder was developed. This equipment is used for testing the improvement of bioavailability of poorly soluble drugs or realizing sustained release of dispersed or dissolved APIs. As pharmaceutical formulations are usually difficult to feed because of fluffy, static powders, this pharma micro-extruder has special options to easily fill and easily clean, which further speeds up the R&D process. | 0 | Theoretical and Fundamental Chemistry |
One method for synthesizing ynones is the acyl substitution reaction of an alkynyldimethylaluminum with an acyl chloride. An alkynyldimethylaluminum compound is the reaction product of trimethylaluminum and a terminal alkyne.
An alternative is the direct coupling of an acyl chloride with a terminal alkyne, using a copper-based nanocatalyst:
Other methods utilize an oxidative cleavage of an aldehyde, followed by reaction with a hypervalent alkynyl iodide, using a gold catalyst.
An alternative but longer synthetic method involves the reaction of an alkynyllithium compound with an aldehyde. The reaction produces a secondary alcohol that then can be oxidized via the Swern oxidation. | 0 | Theoretical and Fundamental Chemistry |
Robert Bowie Owens (October 29, 1870 – November 3, 1940) was a U.S. electrical engineer. He was the director of the Maryland Academy of Science. He was secretary of Franklin Institute from 1910 to 1924. He is credited as a discoverer of the alpha ray. | 1 | Applied and Interdisciplinary Chemistry |
Chemurgy is a branch of applied chemistry concerned with preparing industrial products from agricultural raw materials. The concept developed by the early years of the 20th century. For example, products such as brushes and motion picture film were made from cellulose. Beginning in the 1920s, William J. Hale, agricultural journalist Wheeler McMillen, and other Americans began advocating a greater link between farmers and industry. The word "chemurgy" was coined by chemist William J. Hale and first publicized in his 1934 book The Farm Chemurgic. | 1 | Applied and Interdisciplinary Chemistry |
Apamin is a polypeptide possessing an amino acid sequence of H-Cys-Asn-Cys-Lys-Ala-Pro-Glu-Thr-Ala-Leu-Cys-Ala-Arg-Arg-Cys-Gln-Gln-His-NH (one-letter sequence CNCKAPETALCARRCQQH-NH, with disulfide bonds between Cys-Cys and Cys-Cys). Apamin is very rigid because of the two disulfide bridges and seven hydrogen bonds. The three-dimensional structure of apamin has been studied with several spectroscopical techniques: HNMR, Circular Dichroism, Raman spectroscopy, FT-IR. The structure is presumed to consist of an alpha-helix and beta-turns, but the exact structure is still unknown.
By local alterations it is possible to find the amino acids that are involved in toxicity of apamin. It was found by Vincent et al. that guanidination of the ε-amino group of lysine does not decrease toxicity. When the ε-amino group of lysine and the α-amino group of cysteine are acetylated or treated with fluorescamine, toxicity decreases with a factor of respectively 2.5 and 2.8. This is only a small decrease, which indicates that neither the ε-amino group of lysine nor the α-amino group of cysteine is essential for the toxicity of apamin. Glutamine was altered by formation of an amide bond with glycine ethyl ester, this resulted in a decrease in toxicity of a factor 2.0. Glutamine also doesn't appear to be essential for toxicity. When histidine is altered by carbethoxylation, toxicity decreases only by a factor 2.6. But when histidine, the ε-amino group of lysine and the α-amino group of cysteine all are carbethoxylated and acetylated toxicity decreases drastically. This means that these three amino acids are not essential for toxicity on their own, but the three of them combined are. Chemical alteration of arginine and arginine by treatment of 1,2-cyclohexanedione and cleavage by trypsin decreases toxicity by a factor greater than 10. The amino acids that cause toxicity of apamin are cysteine, lysine, arginine, arginine and histidine. | 1 | Applied and Interdisciplinary Chemistry |
During the 1940s and 1950s, chemists had trouble explaining why even slight changes in the reactants caused significant differences in the rate and product distributions of a reaction. In 1955 George Hammond, a young professor at Iowa State University, postulated that transition-state theory could be used to qualitatively explain the observed structure-reactivity relationships. Notably, John E. Leffler of Florida State University proposed a similar idea in 1953. However, Hammonds version has received more attention since its qualitative nature was easier to understand and employ than Lefflers complex mathematical equations. Hammond's postulate is sometimes called the Hammond–Leffler postulate to give credit to both scientists. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, a ring is an ambiguous term referring either to a simple cycle of atoms and bonds in a molecule or to a connected set of atoms and bonds in which every atom and bond is a member of a cycle (also called a ring system). A ring system that is a simple cycle is called a monocycle or simple ring, and one that is not a simple cycle is called a polycycle or polycyclic ring system. A simple ring contains the same number of sigma bonds as atoms, and a polycyclic ring system contains more sigma bonds than atoms.
A molecule containing one or more rings is called a cyclic compound, and a molecule containing two or more rings (either in the same or different ring systems) is termed a polycyclic compound. A molecule containing no rings is called an acyclic or open-chain compound. | 0 | Theoretical and Fundamental Chemistry |
In a separate research, the micro-atmosphere method was used to investigate the anti-fungal efficacy of the essential oils from the cinnamon, a plant belonging to the genus Cinnamomum.
The procedure was employed to ensure that the active films, the material containing the active compound, does not come into direct contact to the tested fungal suspension.
The micro-atmosphere method was performed, in order to evaluate the indirect effects of active films against P. digitatum. Addition of 0.5% cinnamon essential oil, led to 12% inhibition of fungal growth. Higher anti-fungal effects were obtained by adding higher amounts of the essential oil. An inhibition of fungal growth between 28% and 50% were observed for the films incorporated with 1.5% and 3% essential oil, respectively.
In this particular research, the potential anti-fungal agent was subjected to both disk diffusion test and the micro-atmosphere method for comparison and to get an idea of how the active compound may be utilized. The active compound exhibited higher anti-fungal effects in the disc diffusion test compared to the micro-atmosphere assays. This could be attributed to the fact that in the disc diffusion test, both direct contact and migration of active compounds from the film to the outside induced the observed antimicrobial effects. On the other hand, only the migration of the volatile compounds to the headspace, may cause the anti-fungal effect in the micro-atmosphere method. | 1 | Applied and Interdisciplinary Chemistry |
Naturally occurring iron has four stable isotopes, Fe, Fe, Fe, and Fe.
Stable iron isotopes are described as the relative abundance of each of the stable isotopes with respect to Fe. The standard for iron is elemental iron, IRMM-014, and it is distributed by the Institute for Reference Materials and Measurement. The delta value is compared to this standard, and is defined as:
Delta values are often reported as per mil values (‰), or part-per-thousand differences from the standard. Iron isotopic fractionation is also commonly described in units of per mil per atomic mass unit.
In many cases, the δFe value can be related to the δFe and δFe values through mass-dependent fractionation: | 0 | Theoretical and Fundamental Chemistry |
Soil E is also largely a function of hydrological conditions. In the event of a flood, saturated soils can shift from oxic to anoxic, creating a reducing environment as anaerobic microbial processes dominate. Moreover, small anoxic hotspots may develop within soil pore spaces, creating reducing conditions. With time, the starting E of a soil can be restored as water drains and the soil dries out. Soils with redox gradients formed by ascending groundwater are classified as gleysols, while soils with gradients formed by stagnant water are classified as stagnosols and planosols.
Soil E generally ranges from −300 to +900 mV. The table below summarizes typical E values for various soil conditions:
Generally accepted E limits that are tolerable by plants are +300 mV ) is also closely tied to pH, and both have significant influence on the function of soil-plant-microorganism systems. The main source of electrons in soil is organic matter. Organic matter consumes oxygen as it decomposes, resulting in reducing soil conditions and lower E. | 0 | Theoretical and Fundamental Chemistry |
Anti-DFS70 antibodies generate a dense fine speckled pattern in indirect immunofluorescence and are found in normals and in various conditions, but are not associated with a systemic autoimmune pathology. Therefore, they can be used to help to rule out such conditions in ANA positive individuals. A significant number of patients are diagnosed as systemic lupus erythematosus or undifferentiated connective tissue disease largely based on a positive ANA. In case no defined autoantibody can be detected (e.g. anti-ENA antibodies), the testing of anti-DFS70 antibodies is recommended to verify the diagnosis. Anti-DFS70 antibody tests are available as CE-marked tests. Until now, no FDA cleared assay is available. | 1 | Applied and Interdisciplinary Chemistry |
Amine oxides are common metabolites of medication and psychoactive drugs. Examples include nicotine, Zolmitriptan, and morphine.
Amine oxides of anti-cancer drugs have been developed as prodrugs that are metabolized in the oxygen-deficient cancer tissue to the active drug. | 0 | Theoretical and Fundamental Chemistry |
The decay rate, or activity, of a radioactive substance is characterized by the following time-independent parameters:
* The half-life, , is the time taken for the activity of a given amount of a radioactive substance to decay to half of its initial value.
* The decay constant, "lambda", the reciprocal of the mean lifetime (in ), sometimes referred to as simply decay rate.
* The mean lifetime, "tau", the average lifetime (1/e life) of a radioactive particle before decay.
Although these are constants, they are associated with the statistical behavior of populations of atoms. In consequence, predictions using these constants are less accurate for minuscule samples of atoms.
In principle a half-life, a third-life, or even a (1/√2)-life, can be used in exactly the same way as half-life; but the mean life and half-life have been adopted as standard times associated with exponential decay.
Those parameters can be related to the following time-dependent parameters:
* Total activity (or just activity), , is the number of decays per unit time of a radioactive sample.
* Number of particles, , in the sample.
* Specific activity, , is the number of decays per unit time per amount of substance of the sample at time set to zero (). "Amount of substance" can be the mass, volume or moles of the initial sample.
These are related as follows:
where N is the initial amount of active substance — substance that has the same percentage of unstable particles as when the substance was formed. | 0 | Theoretical and Fundamental Chemistry |
To obtain a degree in natural resource engineering, a solid engineering background is required, as well as specific technical knowledge specific to natural resources and their role in our environment. Most degree programs within this specific discipline are partnered within larger disciplines of engineering such as environmental engineering, biological engineering, or agricultural engineering. | 1 | Applied and Interdisciplinary Chemistry |
Lanthanum oxalate is an inorganic compound, a salt of lanthanum metal and oxalic acid with the chemical formula .
__TOC__ | 0 | Theoretical and Fundamental Chemistry |
Fermentative/hydrolytic microorganisms hydrolyze complex organic polymers to monomers which are further converted to a mixture of lower-molecular-weight organic acids and alcohols by obligatory producing acidogenic bacteria.
Utilization of wastewater as a potential substrate for biohydrogen production has been drawing considerable interest in recent years especially in the dark fermentation process. Industrial wastewater as a fermentative substrate for H production addresses most of the criteria required for substrate selection viz., availability, cost and biodegradability. Chemical wastewater (Venkata Mohan, et al., 2007a,b), cattle wastewater (Tang, et al., 2008), dairy process wastewater (Venkata Mohan, et al. 2007c, Rai et al. 2012), starch hydrolysate wastewater (Chen, et al., 2008) and designed synthetic wastewater (Venkata Mohan, et al., 2007a, 2008b) have been reported to produce biohydrogen apart from wastewater treatment from dark fermentation processes using selectively enriched mixed cultures under acidophilic conditions. Various wastewaters viz., paper mill wastewater (Idania, et al., 2005), starch effluent (Zhang, et al., 2003), food processing wastewater (Shin et al., 2004, van Ginkel, et al., 2005), domestic wastewater (Shin, et al., 2004, 2008e), rice winery wastewater (Yu et al., 2002), distillery and molasses based wastewater (Ren, et al., 2007, Venkata Mohan, et al., 2008a), wheat straw wastes (Fan, et al., 2006) and palm oil mill wastewater (Vijayaraghavan and Ahmed, 2006) have been studied as fermentable substrates for H production along with wastewater treatment. Using wastewater as a fermentable substrate facilitates both wastewater treatment apart from H production. The efficiency of the dark fermentative H production process was found to depend on pre-treatment of the mixed consortia used as a biocatalyst, operating pH, and organic loading rate apart from wastewater characteristics (Venkata Mohan, et al., 2007d, 2008c, d, Vijaya Bhaskar, et al., 2008d).
In spite of its advantages, the main challenge observed with fermentative H production processes is the relatively low energy conversion efficiency from the organic source. Typical H yields range from 1 to 2 mol of H/mol of glucose, which results in 80-90% of the initial COD remaining in the wastewater in the form of various volatile organic acids (VFAs) and solvents, such as acetic acid, propionic acid, butyric acid, and ethanol. Even under optimal conditions about 60-70% of the original organic matter remains in solution. Bioaugmentation with selectively enriched acidogenic consortia to enhance H production was also reported (Venkata Mohan, et al., 2007b). Generation and accumulation of soluble acid metabolites causes a sharp drop in the system pH and inhibits the H production process. Usage of unutilized carbon sources present in acidogenic process for additional biogas production sustains the practical applicability of the process. One way to utilize/recover the remaining organic matter in a usable form is to produce additional H by terminal integration of photo-fermentative processes of H production (Venkata Mohan, et al. 2008e, Rai et al. 2012) and methane by integrating acidogenic processes to terminal methanogenic processes. | 1 | Applied and Interdisciplinary Chemistry |
Undervirilization can occur if a genetic male cannot produce enough androgen or the body tissues cannot respond to it. Extreme undervirilization occurs when no significant androgen hormones can be produced or the body is completely insensitive to androgens. Both result in a female body. Partial undervirilization produces ambiguous genitalia part-way between male and female. Examples of undervirilization are androgen insensitivity syndrome, 5 alpha reductase deficiency, and some forms of congenital adrenal hyperplasia. | 1 | Applied and Interdisciplinary Chemistry |
The term metabolism is derived from the Greek – for change, or overthrow. The history of the scientific study of metabolism spans 800 years. The earliest of all metabolic studies began during the early thirteenth century (1213–1288) by a Muslim scholar from Damascus named Ibn al-Nafis. al-Nafis stated in his most well-known work Theologus Autodidactus that "that body and all its parts are in a continuous state of dissolution and nourishment, so they are inevitably undergoing permanent change." Although al-Nafis was the first documented physician to have an interest in biochemical concepts, the first controlled experiments in human metabolism were published by Santorio Santorio in 1614 in his book . This book describes how he weighed himself before and after eating, sleeping, working, sex, fasting, drinking, and excreting. He found that most of the food he took in was lost through what he called "insensible perspiration". | 1 | Applied and Interdisciplinary Chemistry |
Damage repair is the conversion of a damaged metabolite back to its original state via one or more enzymatic reactions; the concept is similar to DNA repair and protein repair. For example, the promiscuous activity of malate dehydrogenase causes reduction of alpha-ketoglutarate to L-2-hydroxyglutarate. This compound is a dead-end metabolite and is not a substrate for any other enzyme in central metabolism, and its accumulation in humans causes L-2-Hydroxyglutaric aciduria. The repair enzyme L-2-hydroxyglutarate dehydrogenase oxidizes L-2-hydroxyglutarate back to alpha-ketoglutarate, thus repairing this metabolite. In humans, L-2-hydroxyglutarate dehydrogenase uses FAD as the cofactor, while the E. coli enzyme reduces molecular oxygen. | 1 | Applied and Interdisciplinary Chemistry |
Balls exist in any dimension and are generically called n-balls or hyperballs, where n is the number of dimensions.
The same reasoning can be generalized to n-balls using the general equations for volume and surface area, which are:
So the ratio equals . Thus, the same linear relationship between area and volume holds for any number of dimensions (see figure): doubling the radius always halves the ratio. | 0 | Theoretical and Fundamental Chemistry |
Several synthetic molecular knots have been reported. Knot types that have been successfully synthesized in molecules are and 8 knots. Though the and knots have been found to naturally occur in knotted molecules, they have not been successfully synthesized. Small-molecule composite knots have also not yet been synthesized.
Artificial DNA, RNA, and protein knots have been successfully synthesized. DNA is a particularly useful model of synthetic knot synthesis, as the structure naturally forms interlocked structures and can be easily manipulated into forming knots control precisely the raveling necessary to form knots. Molecular knots are often synthesized with the help of crucial metal ion ligands. | 0 | Theoretical and Fundamental Chemistry |
The third class of PTPs contains three cell cycle regulators, CDC25A, CDC25B and CDC25C, which dephosphorylate CDKs at their N-terminal, a reaction required to drive progression of the cell cycle. They are themselves regulated by phosphorylation and are degraded in response to DNA damage to prevent chromosomal abnormalities. | 1 | Applied and Interdisciplinary Chemistry |
As the functional group of the amino acid cysteine, the thiol group plays a very important role in biology. When the thiol groups of two cysteine residues (as in monomers or constituent units) are brought near each other in the course of protein folding, an oxidation reaction can generate a cystine unit with a disulfide bond (−S−S−). Disulfide bonds can contribute to a protein's tertiary structure if the cysteines are part of the same peptide chain, or contribute to the quaternary structure of multi-unit proteins by forming fairly strong covalent bonds between different peptide chains. A physical manifestation of cysteine-cystine equilibrium is provided by hair straightening technologies.
Sulfhydryl groups in the active site of an enzyme can form noncovalent bonds with the enzyme's substrate as well, contributing to covalent catalytic activity in catalytic triads. Active site cysteine residues are the functional unit in cysteine protease catalytic triads. Cysteine residues may also react with heavy metal ions (Zn, Cd, Pb, Hg, Ag) because of the high affinity between the soft sulfide and the soft metal (see hard and soft acids and bases). This can deform and inactivate the protein, and is one mechanism of heavy metal poisoning.
Drugs containing thiol group
6-Mercaptopurine (anticancer)
Captopril (antihypertensive)
D-penicillamine (antiarthritic)
Sodium aurothiolate (antiarthritic) | 0 | Theoretical and Fundamental Chemistry |
In the main isotopes of light elements, such as carbon, nitrogen and oxygen, the most stable combination of neutrons and of protons occurs when the numbers are equal (this continues to element 20, calcium). However, in heavier nuclei, the disruptive energy of protons increases, since they are confined to a tiny volume and repel each other. The energy of the strong force holding the nucleus together also increases, but at a slower rate, as if inside the nucleus, only nucleons close to each other are tightly bound, not ones more widely separated.
The net binding energy of a nucleus is that of the nuclear attraction, minus the disruptive energy of the electric force. As nuclei get heavier than helium, their net binding energy per nucleon (deduced from the difference in mass between the nucleus and the sum of masses of component nucleons) grows more and more slowly, reaching its peak at iron. As nucleons are added, the total nuclear binding energy always increases—but the total disruptive energy of electric forces (positive protons repelling other protons) also increases, and past iron, the second increase outweighs the first. Iron-56 (Fe) is the most efficiently bound nucleus meaning that it has the least average mass per nucleon. However, nickel-62 is the most tightly bound nucleus in terms of binding energy per nucleon. (Nickel-62s higher binding energy does not translate to a larger mean mass loss than Fe, because Ni has a slightly higher ratio of neutrons/protons than does iron-56, and the presence of the heavier neutrons increases nickel-62s average mass per nucleon).
To reduce the disruptive energy, the weak interaction allows the number of neutrons to exceed that of protons—for instance, the main isotope of iron has 26 protons and 30 neutrons. Isotopes also exist where the number of neutrons differs from the most stable number for that number of nucleons. If changing one proton into a neutron or one neutron into a proton increases the stability (lowering the mass), then this will happen through beta decay, meaning the nuclide will be radioactive.
The two methods for this conversion are mediated by the weak force, and involve types of beta decay. In the simplest beta decay, neutrons are converted to protons by emitting a negative electron and an antineutrino. This is always possible outside a nucleus because neutrons are more massive than protons by an equivalent of about 2.5 electrons. In the opposite process, which only happens within a nucleus, and not to free particles, a proton may become a neutron by ejecting a positron and an electron neutrino. This is permitted if enough energy is available between parent and daughter nuclides to do this (the required energy difference is equal to 1.022 MeV, which is the mass of 2 electrons). If the mass difference between parent and daughter is less than this, a proton-rich nucleus may still convert protons to neutrons by the process of electron capture, in which a proton simply electron captures one of the atom's K orbital electrons, emits a neutrino, and becomes a neutron.
Among the heaviest nuclei, starting with tellurium nuclei (element 52) containing 104 or more nucleons, electric forces may be so destabilizing that entire chunks of the nucleus may be ejected, usually as alpha particles, which consist of two protons and two neutrons (alpha particles are fast helium nuclei). (Beryllium-8 also decays, very quickly, into two alpha particles.) This type of decay becomes more and more probable as elements rise in atomic weight past 104.
The curve of binding energy is a graph that plots the binding energy per nucleon against atomic mass. This curve has its main peak at iron and nickel and then slowly decreases again, and also a narrow isolated peak at helium, which is more stable than other low-mass nuclides. The heaviest nuclei in more than trace quantities in nature, uranium U, are unstable, but having a half-life of 4.5 billion years, close to the age of the Earth, they are still relatively abundant; they (and other nuclei heavier than helium) have formed in stellar evolution events like supernova explosions preceding the formation of the Solar System. The most common isotope of thorium, Th, also undergoes alpha particle emission, and its half-life (time over which half a number of atoms decays) is even longer, by several times. In each of these, radioactive decay produces daughter isotopes that are also unstable, starting a chain of decays that ends in some stable isotope of lead. | 0 | Theoretical and Fundamental Chemistry |
The FCC and HCP packings are the densest known packings of equal spheres with the highest symmetry (smallest repeat units).
Denser sphere packings are known, but they involve unequal sphere packing.
A packing density of 1, filling space completely, requires non-spherical shapes, such as honeycombs.
Replacing each contact point between two spheres with an edge connecting the centers of the touching spheres produces tetrahedrons and octahedrons of equal edge lengths.
The FCC arrangement produces the tetrahedral-octahedral honeycomb.
The HCP arrangement produces the gyrated tetrahedral-octahedral honeycomb.
If, instead, every sphere is augmented with the points in space that are closer to it than to any other sphere, the duals of these honeycombs are produced: the rhombic dodecahedral honeycomb for FCC, and the trapezo-rhombic dodecahedral honeycomb for HCP.
Spherical bubbles appear in soapy water in a FCC or HCP arrangement when the water in the gaps between the bubbles drains out. This pattern also approaches the rhombic dodecahedral honeycomb or trapezo-rhombic dodecahedral honeycomb. However, such FCC or HCP foams of very small liquid content are unstable, as they do not satisfy Plateau's laws. The Kelvin foam and the Weaire–Phelan foam are more stable, having smaller interfacial energy in the limit of a very small liquid content.
There are two types of interstitial holes left by hcp and fcc conformations; tetrahedral and octahedral void. Four spheres surround the tetrahedral hole with three spheres being in one layer and one sphere from the next layer. Six spheres surround an octahedral voids with three spheres coming from one layer and three spheres coming from the next layer. Structures of many simple chemical compounds, for instance, are often described in terms of small atoms occupying tetrahedral or octahedral holes in closed-packed systems that are formed from larger atoms.
Layered structures are formed by alternating empty and filled octahedral planes. Two octahedral layers usually allow for four structural arrangements that can either be filled by an hpc of fcc packing systems. In filling tetrahedral holes a complete filling leads to fcc field array. In unit cells, hole filling can sometimes lead to polyhedral arrays with a mix of hcp and fcc layering. | 0 | Theoretical and Fundamental Chemistry |
Detergents and surfactants are molecules that combine highly nonpolar and highly polar groups. Traditionally, soaps are the popular surfactants, being derived from fatty acids. Since the mid-20th century, the usage of sulfonic acids has surpassed soap in advanced societies. For example, an estimated 2 billion kilograms of alkylbenzenesulfonates are produced annually for diverse purposes. Lignin sulfonates, produced by sulfonation of lignin are components of drilling fluids and additives in certain kinds of concrete. | 0 | Theoretical and Fundamental Chemistry |
A recent advance in the production of nucleosome core particles with enhanced stability involves site-specific disulfide crosslinks. Two different crosslinks can be introduced into the nucleosome core particle. A first one crosslinks the two copies of H2A via an introduced cysteine (N38C) resulting in histone octamer which is stable against H2A/H2B dimer loss during nucleosome reconstitution. A second crosslink can be introduced between the H3 N-terminal histone tail and the nucleosome DNA ends via an incorporated convertible nucleotide. The DNA-histone octamer crosslink stabilizes the nucleosome core particle against DNA dissociation at very low particle concentrations and at elevated salt concentrations. | 1 | Applied and Interdisciplinary Chemistry |
Enalapril, sold under the brand name Vasotec among others, is an ACE inhibitor medication used to treat high blood pressure, diabetic kidney disease, and heart failure. For heart failure, it is generally used with a diuretic, such as furosemide. It is given by mouth or by injection into a vein. Onset of effects are typically within an hour when taken by mouth and last for up to a day.
Common side effects include headache, tiredness, feeling lightheaded with standing, and cough. Serious side effects include angioedema and low blood pressure. Use during pregnancy is believed to result in harm to the baby. It is in the angiotensin-converting-enzyme (ACE) inhibitor family of medications.
Enalapril was patented in 1978, and came into medical use in 1984. It is on the World Health Organization's List of Essential Medicines. In 2021, it was the 278th most commonly prescribed medication in the United States, with more than 800,000 prescriptions. It is available as a generic medicine. | 0 | Theoretical and Fundamental Chemistry |
TCE has also been used as a dry cleaning solvent, although mostly replaced by tetrachloroethylene (also known as perchloroethylene), except for spot cleaning where it is still used under the trade name Picrin.
Perhaps the greatest use of TCE is as a degreaser for metal parts. It has been widely used in degreasing and cleaning since the 1920s because of its low cost, low flammability, low toxicity and high effectivity as a solvent. The demand for TCE as a degreaser began to decline in the 1950s in favor of the less toxic 1,1,1-trichloroethane. However, 1,1,1-trichloroethane production has been phased out in most of the world under the terms of the Montreal Protocol due to its effect of ozone depletion. As a result, trichloroethylene has experienced some resurgence in use as a degreaser.
Trichloroethylene is used to remove grease and lanolin from wool before weaving.
TCE has also been used in the United States to clean kerosene-fueled rocket engines (TCE was not used to clean hydrogen-fueled engines such as the Space Shuttle Main Engine). During static firing, the RP-1 fuel would leave hydrocarbon deposits and vapors in the engine. These deposits had to be flushed from the engine to avoid the possibility of explosion during engine handling and future firing. TCE was used to flush the engines fuel system immediately before and after each test firing. The flushing procedure involved pumping TCE through the engines fuel system and letting the solvent overflow for a period ranging from several seconds to 30–35 minutes, depending upon the engine. For some engines, the engine's gas generator and liquid oxygen (LOX) dome were also flushed with TCE before test firing. The F-1 rocket engine had its LOX dome, gas generator, and thrust chamber fuel jacket flushed with TCE during launch preparations. | 1 | Applied and Interdisciplinary Chemistry |
The use of different fuels in nuclear reactors results in different spent nuclear fuel (SNF) composition, with varying activity curves. The most abundant material being U-238 with other uranium isotopes, other actinides, fission products and activation products.
Long-lived radioactive waste from the back end of the fuel cycle is especially relevant when designing a complete waste management plan for SNF. When looking at long-term radioactive decay, the actinides in the SNF have a significant influence due to their characteristically long half-lives. Depending on what a nuclear reactor is fueled with, the actinide composition in the SNF will be different.
An example of this effect is the use of nuclear fuels with thorium. Th-232 is a fertile material that can undergo a neutron capture reaction and two beta minus decays, resulting in the production of fissile U-233. The SNF of a cycle with thorium will contain U-233. Its radioactive decay will strongly influence the long-term activity curve of the SNF around a million years. A comparison of the activity associated to U-233 for three different SNF types can be seen in the figure on the top right. The burnt fuels are thorium with reactor-grade plutonium (RGPu), thorium with weapons-grade plutonium (WGPu), and Mixed oxide fuel (MOX, no thorium). For RGPu and WGPu, the initial amount of U-233 and its decay around a million years can be seen. This has an effect on the total activity curve of the three fuel types. The initial absence of U-233 and its daughter products in the MOX fuel results in a lower activity in region 3 of the figure on the bottom right, whereas for RGPu and WGPu the curve is maintained higher due to the presence of U-233 that has not fully decayed. Nuclear reprocessing can remove the actinides from the spent fuel so they can be used or destroyed (see ). | 0 | Theoretical and Fundamental Chemistry |
Depletion forces have been observed and measured using a variety of instrumentation including atomic force microscopy, optical tweezers, and hydrodynamic force balance machines. | 0 | Theoretical and Fundamental Chemistry |
Lipinskis rule of five, also known as Pfizers rule of five or simply the rule of five (RO5), is a rule of thumb to evaluate druglikeness or determine if a chemical compound with a certain pharmacological or biological activity has chemical properties and physical properties that would likely make it an orally active drug in humans. The rule was formulated by Christopher A. Lipinski in 1997, based on the observation that most orally administered drugs are relatively small and moderately lipophilic molecules.
The rule describes molecular properties important for a drug's pharmacokinetics in the human body, including their absorption, distribution, metabolism, and excretion ("ADME"). However, the rule does not predict if a compound is pharmacologically active.
The rule is important to keep in mind during drug discovery when a pharmacologically active lead structure is optimized step-wise to increase the activity and selectivity of the compound as well as to ensure drug-like physicochemical properties are maintained as described by Lipinski's rule. Candidate drugs that conform to the RO5 tend to have lower attrition rates during clinical trials and hence have an increased chance of reaching the market.
Some authors have criticized the rule of five for the implicit assumption that passive diffusion is the only important mechanism for the entry of drugs into cells, ignoring the role of transporters. For example, O'Hagan and co-authors wrote as follows:
Studies have also demonstrated that some natural products break the chemical rules used in Lipinski filters such as macrolides and peptides. | 1 | Applied and Interdisciplinary Chemistry |
*Thermal wheel, or rotary heat exchanger (including enthalpy wheel and desiccant wheel)
*Recuperator, or cross plate heat exchanger
*Heat pipe | 0 | Theoretical and Fundamental Chemistry |
The first use of diazonium salts was to produce water-fast dyed fabrics by immersing the fabric in an aqueous solution of the diazonium compound, followed by immersion in a solution of the coupler (the electron-rich ring that undergoes electrophilic substitution). The major applications of diazonium compounds remains in the dye and pigment industry.
The most widely practiced reaction of diazonium salts remains azo coupling, which is exploited in the production of azo dyes. In this process, the diazonium compound is attacked by, i.e., coupled to, electron-rich substrates. When the coupling partners are arenes such as anilines and phenols, the process is an example of electrophilic aromatic substitution:
Another commercially important class of coupling partners are acetoacetic amides, as illustrated by the preparation of Pigment Yellow 12, a diarylide pigment.
The resulting azo compounds are often useful dyes and in fact are called azo dyes. The deep colors of the dyes reflects their extended conjugation. For example, the dye called aniline yellow is produced by mixing aniline and cold solution of diazonium salt and then shaking it vigorously. Aniline yellow is obtained as a yellow solid. Similarly, a cold basic solution of Naphthalen-2-ol (beta-naphthol) give the intensely orange-red precipitate. Methyl orange is an example of an azo dye that is used in the laboratory as a pH indicator. | 0 | Theoretical and Fundamental Chemistry |
The photodegradation of pharmaceuticals is of interest because they are found in many water supplies. They have deleterious effects on aquatic organisms including toxicity, endocrine disruption, genetic damage. But also in the primary packaging material the photodegradation of pharmaceuticals has to be prevented. For this, amber glasses like Fiolax amber and Corning 51-L are commonly used to protect the pharmaceutical from UV radiations. Iodine (in the form of Lugol's solution) and colloidal silver are universally used in packaging that lets through very little UV light so as to avoid degradation. | 0 | Theoretical and Fundamental Chemistry |
Bioceramics have been proposed as a possible treatment for cancer. Two methods of treatment have been proposed: hyperthermia and radiotherapy. Hyperthermia treatment involves implanting a bioceramic material that contains a ferrite or other magnetic material. The area is then exposed to an alternating magnetic field, which causes the implant and surrounding area to heat up. Alternatively, the bioceramic materials can be doped with β-emitting materials and implanted into the cancerous area.
Other trends include engineering bioceramics for specific tasks. Ongoing research involves the chemistry, composition, and micro- and nanostructures of the materials to improve their biocompatibility. | 0 | Theoretical and Fundamental Chemistry |
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