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Radioactive elements (Ra and RaD) were used by V. G. Khlopin and B. A. Nikitin as indicators in determining the nature of a new kind of mixed Gramm crystals. These studies showed a fundamental difference between true mixed crystals in the spirit of Eilhard Mitscherlich, when the substitution of one component for another is expressed in the form of ion for ion, or atom for atom, molecule for molecule, and mixed crystals of a new kind, in which such a simple substitution is impossible, and proceeds by means of very small sizes of the ready sections of the crystal lattice of each component. Scientists have shown that mixed crystals of a new kind fundamentally differ from true mixed crystals by the presence of a low miscibility limit - they are not formed at low concentration of one of the components at all. In this case, they are similar to anomalous mixed crystals (as shown experimentally by V. G. Khlopin and M. A. Tolstaya), and relate to the latter approximately as a colloidal solution with suspension. These works (on the structure and properties of mixed crystals of a new kind and anomalous mixed crystals) led V. G. Khlopin to the idea of the need to classify isomorphic bodies not by considering the structure of isomorphic mixtures in static equilibrium (as it was done, for example, by V. G. Goldschmidt and his school), but according to the methods of substitution of components - taking into account the dynamics of the formation of an isomorphic mixture. In this case, all isomorphic bodies are strictly divided into two groups according to the method of substitution:
(a) Isomorphic compounds in the spirit of E. Mitscherlich, truly isomorphic. Substitution in the formation of mixed crystals by such compounds occurs according to the first principle: ion on ion, etc. The above distribution laws apply to such crystals. Such compounds have similar chemical composition and molecular structure.
(b) All other isomorphic compounds, when the formation of mixed crystals is conditioned by the second principle: substitution of sites from the unit cell or close to them (mixed crystals of a new kind or isomorphic of the 2nd kind according to W.G. Goldschmidt), up to microscopic - anomalous mixed crystals such as FeCl — NHCl, Ba(NO), Pb(NO), methylene blue KSO - Ponsorot, etc., showing heterogeneity).
3.Thanks to the works discussed in the previous two paragraphs, V. G. Khlopin was able to present in a new form the law of E. Mitscherlich, which makes it possible to judge the composition and molecular structure of unknown compounds on the basis of their formation of isomorphous mixtures with compounds whose composition and molecular structure are known. V.G. Khlopin proposed the method of isomorphous co-crystallization from solutions for fixation of weightless and unstable chemical compounds and determination of their composition. The method made it possible to discover and determine the composition of individual compounds of divalent and hexavalent polonium (V. G. Khlopin and A. G. Samartseva).
4. Studying adsorption of isomorphous ions on the surface of crystalline precipitates, V. G. Khlopin showed that adsorption equilibrium is established in 20–30 minutes; adsorption of isomorphous ions does not depend on the charge of the adsorber surface when its solubility does not change. Correctly reproducible results of adsorption study and full reversibility of this process are achieved only if the adsorber surface remains unchanged throughout the experiment - if the adsorber solubility remains unchanged; in case of changes in the liquid phase composition or under other additional conditions, when the adsorber solubility changes, adsorption acquires a more complex character, which is accompanied by co-crystallization distorting the results. Studying the adsorption kinetics, a similar phenomenon was encountered by L. Imre. V. G. Khlopin gave a formula for determining the surface of crystalline precipitates by adsorption of an isomorphic ion on them and experimentally confirmed its applicability (V. G. Khlopin, M. S. Merkulova). | 0 | Theoretical and Fundamental Chemistry |
* The mineral components of the soil are derived from the parental rocks or regolith. The minerals present about 90% of the total weight of the soil. Some important elements, which are found in compound state, are oxygen, iron, silicon, aluminium, nitrogen, phosphorus, potassium, calcium, magnesium, carbon, hydrogen, etc.
* The formation of primary and secondary minerals can better define what minerals are in the rock composition | 0 | Theoretical and Fundamental Chemistry |
*The wallpaper group of a pattern is invariant under isometries and uniform scaling (similarity transformations).
*Translational symmetry is preserved under arbitrary bijective affine transformations.
*Rotational symmetry of order two ditto; this means also that 4- and 6-fold rotation centres at least keep 2-fold rotational symmetry.
*Reflection in a line and glide reflection are preserved on expansion/contraction along, or perpendicular to, the axis of reflection and glide reflection. It changes p6m, p4g, and p3m1 into cmm, p3m1 into cm, and p4m, depending on direction of expansion/contraction, into pmm or cmm. A pattern of symmetrically staggered rows of points is special in that it can convert by expansion/contraction from p6m to p4m.
Note that when a transformation decreases symmetry, a transformation of the same kind (the inverse) obviously for some patterns increases the symmetry. Such a special property of a pattern (e.g. expansion in one direction produces a pattern with 4-fold symmetry) is not counted as a form of extra symmetry.
Change of colors does not affect the wallpaper group if any two points that have the same color before the change, also have the same color after the change, and any two points that have different colors before the change, also have different colors after the change.
If the former applies, but not the latter, such as when converting a color image to one in black and white, then symmetries are preserved, but they may increase, so that the wallpaper group can change. | 0 | Theoretical and Fundamental Chemistry |
The phenolic metabolic pathways and enzymes may be studied by mean of transgenesis of genes. The Arabidopsis regulatory gene in the production of anthocyanin pigment 1 (AtPAP1) may be expressed in other plant species. | 0 | Theoretical and Fundamental Chemistry |
Oximes can be synthesized by condensation of an aldehyde or a ketone with hydroxylamine. The condensation of aldehydes with hydroxylamine gives aldoximes, and ketoximes are produced from ketones and hydroxylamine. In general, oximes exist as colorless crystals or as thick liquids and are poorly soluble in water. Therefore, oxime formation can be used for the identification of ketone or aldehyde functional groups.
Oximes can also be obtained from reaction of nitrites such as isoamyl nitrite with compounds containing an acidic hydrogen atom. Examples are the reaction of ethyl acetoacetate and sodium nitrite in acetic acid, the reaction of methyl ethyl ketone with ethyl nitrite in hydrochloric acid. and a similar reaction with propiophenone, the reaction of phenacyl chloride, the reaction of malononitrile with sodium nitrite in acetic acid
A conceptually related reaction is the Japp–Klingemann reaction. | 0 | Theoretical and Fundamental Chemistry |
The number of two-component systems present in a bacterial genome is highly correlated with genome size as well as ecological niche; bacteria that occupy niches with frequent environmental fluctuations possess more histidine kinases and response regulators. New two-component systems may arise by gene duplication or by lateral gene transfer, and the relative rates of each process vary dramatically across bacterial species. In most cases, response regulator genes are located in the same operon as their cognate histidine kinase; lateral gene transfers are more likely to preserve operon structure than gene duplications. | 1 | Applied and Interdisciplinary Chemistry |
In non-scanning, a single 2-D sensor output contains all spatial (x, y) and spectral (λ) data. HSI devices for non-scanning yield the full datacube at once, without any scanning. Figuratively speaking, a single snapshot represents a perspective projection of the datacube, from which its three-dimensional structure can be reconstructed. The most prominent benefits of these snapshot hyperspectral imaging systems are the snapshot advantage (higher light throughput) and shorter acquisition time. A number of systems have been designed, including computed tomographic imaging spectrometry (CTIS), fiber-reformatting imaging spectrometry (FRIS), integral field spectroscopy with lenslet arrays (IFS-L), multi-aperture integral field spectrometer (Hyperpixel Array), integral field spectroscopy with image slicing mirrors (IFS-S), image-replicating imaging spectrometry (IRIS), filter stack spectral decomposition (FSSD), coded aperture snapshot spectral imaging (CASSI), image mapping spectrometry (IMS), and multispectral Sagnac interferometry (MSI). However, computational effort and manufacturing costs are high. In an effort to reduce the computational demands and potentially the high cost of non-scanning hyperspectral instrumentation, prototype devices based on Multivariate Optical Computing have been demonstrated. These devices have been based on the Multivariate Optical Element spectral calculation engine or the Spatial Light Modulator spectral calculation engine. In these platforms, chemical information is calculated in the optical domain prior to imaging such that the chemical image relies on conventional camera systems with no further computing. As a disadvantage of these systems, no spectral information is ever acquired, i.e. only the chemical information, such that post processing or reanalysis is not possible. | 0 | Theoretical and Fundamental Chemistry |
Yulia Sister was born in 1936 in Chișinău (Russian: Kishinev), at the time in the Kingdom of Romania, a city which later became the capital of the Moldavian SSR and since 1991 is the capital of Moldova. Her parents and paternal grandparents were also born in this city. The grandparents were there and survived the pogrom of 1903.
David Iosifovich, Yulias father, was a doctor educated in Prague at Charles University. He used to tell his daughter about his student years, the Bessarabian association of fellow-countrymen in Prague and his meetings with famous people. Yulias mother Yevgenia (Bathsheba) Moiseevna copied for her by hand children's verses and Yulia learned to read quite early. Among the first poems was "What Is Good and What Is Bad" by Mayakovsky.
Yulia's grandparents stuck to traditions and spoke Yiddish, and grandfather Yosef (Iosif) even wrote Yiddish poetry. But Yulia could hardly remember them. Her grandfather Moshe (Moisei) died before she was born; her parental grandparents lost their lives in the Kishinev Ghetto in the Holocaust and her grandmother Sarah died during the World War II in evacuation.
During the 2nd World War Bessarabia was reclaimed and then occupied by the Soviet Union in June 1940. A year later in July 1941 it was reconquered by Germany and Romania, and in August 1944 reoccupied by the Soviet Union. In her memoirs Yulia recalled the day when the Red Army entered Kishinev. She also remembered the German bombing of the city and the air raids on the roads, by which her family escaped to the East from the Nazis.
At the beginning of the war David Sister and his family was evacuated to the left bank of the Volga River where he was appointed chief physician at the district hospital and a consultant of the nearby military hospital. The hospital was located in the open steppe between two villages and on the other side of Volga there was Stalingrad. The family lived there a few years. There were no other children in the neighborhood and Yulia had no friends to play with. But she was fascinated by the local nature and made observations of plants and animals. The inhabitants of the hospital could hear the cannonade from the other bank, and during the battle of Stalingrad it became particularly strong.
In 1944 Yulias family moved to Kirovograd where she, after a years delay, was enrolled in the first grade of primary education. A year later the family came back to the native city of Kishinev. Despite severe post-war shortages and difficulties, the Sister's family succeeded to restore their home, which included a huge library. Among the family friends and guests were writers, actors, musicians and scientists, and Yulia grew up in an atmosphere of thirst for knowledge.
Between the years of 1945 and 1954 Yulia Sister studied at the School for Girls Number 2 in Kishinev. Chemistry was taught very passionately by a teacher that loved the subject and was able to convey her enthusiasm to the students. On the advice of her teacher Sister participated in the chemistry enrichment program for school children that was carried out by Professor at the University of Kishinev. | 0 | Theoretical and Fundamental Chemistry |
The reaction proceeds via a cascade of four subsequent pericyclic reactions (Scheme 3). Heating a cyclobutenone above 80 °C initiates a four-electron electrocyclic cleavage generating a vinyl ketene which reacts with an acetylene in a regiospecific [2+2] cycloaddition (Scheme 4). Reversible electrocyclic cleavage of the 2-vinylcyclobutenone yields a dienylketene. The dienylketene then undergoes a six-electron electrocyclization to give a hexadienone intermediate which rapidly tautomerizes to yield a highly substituted phenol or naphthol structures.
In the case of the modified benzannulation reaction (Scheme 5); irradiation of the diazoketones induces the Wolff rearrangement yielding the vinyl ketene intermediate which reacts with the acetylene in a [2+2] cycloaddition then a four-electron cleavage of the resulting 4-substituted cyclobutenone produces a dienylketene which then undergoes a six-electron electrocyclization to give the 2,4-cyclohexanedione which tautomerizes to the final aromatic product. | 0 | Theoretical and Fundamental Chemistry |
Classical pharmacology traditionally has been the basis for the discovery of new drugs. Compounds are screened in cellular or animal models of disease to identify compounds that cause a desirable change in phenotype. Only after the compounds have been discovered, an effort is made to determine the biological target of the compounds through target validation experiments often involving chemoproteomics. More recently it has become popular to develop a hypothesis that a certain biological target is disease modifying and screen for compounds that modulate the activity of this purified target. Afterwards, these compounds are tested in animals to see if they have the desired effect. This approach is known as "reverse pharmacology" or "target based drug discovery" (TDD). However, recent statistical analysis reveals that a disproportionate number of first-in-class drugs with novel mechanisms of action come from phenotypic screening, which has led to a resurgence of interest in this method. | 1 | Applied and Interdisciplinary Chemistry |
Anodizing can be performed in combination with chromate conversion coating. Each process provides corrosion resistance, with anodizing offering a significant advantage when it comes to ruggedness or physical wear resistance. The reason for combining the processes can vary, however, the significant difference between anodizing and chromate conversion coating is the electrical conductivity of the films produced. Although both stable compounds, chromate conversion coating has a greatly increased electrical conductivity. Applications where this may be useful are varied, however the issue of grounding components as part of a larger system is an obvious one.
The dual finishing process uses the best each process has to offer, anodizing with its hard wear resistance and chromate conversion coating with its electrical conductivity.
The process steps can typically involve chromate conversion coating the entire component, followed by a masking of the surface in areas where the chromate coating must remain intact. Beyond that, the chromate coating is then dissolved in unmasked areas. The component can then be anodized, with anodizing taking to the unmasked areas. The exact process will vary dependent on service provider, component geometry and required outcome. It helps to protect aluminium article. | 1 | Applied and Interdisciplinary Chemistry |
The Molecularium Project is an informal science education project of Rensselaer Polytechnic Institute. The project introduces young audiences to the world of atoms and molecules using character driven stories, animations, games and activities, and molecular visualizations. Rensselaers three principal scientist and educators behind the project are Linda Schadler, Richard W. Siegel, and Shekhar Garde. The Molecularium Project began as an outreach project of Rensselaers Nanoscale Science and Engineering Center. To realize the productions, the scientists collaborated with Nanotoon Entertainment, led by writer and director V. Owen Bush, and writer/producer Kurt Przybilla. The Molecularium Project is funded by Rensselaer, the National Science Foundation, and New York State. | 1 | Applied and Interdisciplinary Chemistry |
As the group 2 elements (also referred to as the alkaline earth metals) contain two valence electrons, their chemistries have similarities group 12 organometallic compounds. Both readily assume a +2 oxidation states with higher and lower states being rare, and are less electronegative than carbon. However, as the group two elements (with the exception of beryllium) have considerably low electronegativity the resulting C-M bonds are more highly polarized and ionic-like, if not entirely ionic for the heavier barium compounds. The lighter organoberyllium and organomagnesium compounds are often considered covalent, but with some ionic bond characteristics owing to the attached carbon bearing a negative dipole moment. This higher ionic character and bond polarization tends to produce high coordination numbers and many compounds (particularly dialklys) are polymeric in solid or liquid states with highly complex structures in solution, though in the gaseous state they are often monomeric.
Metallocene compounds with group 2 elements are rare, but some do exist. Bis(cyclopentadienyl)beryllium or beryllocene (CpBe), with a molecular dipole moment of 2.2 D, is so-called slipped η/η sandwich. While magnesocene (CpMg) is a regular metallocene, bis(pentamethylcyclopentadienyl)calcium (Cp)Ca is bent with an angle of 147°. | 0 | Theoretical and Fundamental Chemistry |
SPE is in fact a method of chromatography, in the sense of having a mobile phase, carrying mixtures through a stationary phase, packed inside a column. The chromatographic process is harnessed to create a solid-liquid extractive technique—allowing separation of a mixture of components by taking advantage of large differences between the solid and liquid phase K, or equilibrium constant, for each component in the mixture. The chemical considerations for the selection of stationary and mobile phases are similar to those for liquid column chromatography and many of the adsorbents/materials used are the same. The theory, procedures, and aims are different, however, and as an extractive technique it has a unique niche in modern chemical science. | 0 | Theoretical and Fundamental Chemistry |
The formation of an enantiopure drug results from the separation of the enantiomers of a chiral drug. This separation was prompted when it was found that each enantiomer of a molecule can have different effects when used in drugs. This is because the body is very chiral selective reacting to each enantiomer differently and therefore producing different pharmaceutical effects. The use of a drug with a single enantiomer makes the drug more effective. Before a drug of a pure enantiomer can be formed, the two enantiomers must first be separated and tested. Three main techniques are used for this separation: capillary gas chromatography, high performance liquid chromatography, and capillary electrophoresis. Other technique such as chiral crystallization, enzyme-based kinetic separation, and enantioselective synthesis are also used. | 0 | Theoretical and Fundamental Chemistry |
In 1669 his health, never very strong, began to fail seriously and he gradually withdrew from his public engagements, ceasing his communications to the Royal Society, and advertising his desire to be excused from receiving guests, "unless upon occasions very extraordinary", on Tuesday and Friday forenoon, and Wednesday and Saturday afternoon. In the leisure thus gained he wished to "recruit his spirits, range his papers", and prepare some important chemical investigations which he proposed to leave "as a kind of Hermetic legacy to the studious disciples of that art", but of which he did not make known the nature. His health became still worse in 1691, and he died on 31 December that year, just a week after the death of his sister, Katherine, in whose home he had lived and with whom he had shared scientific pursuits for more than twenty years. Boyle died from paralysis. He was buried in the churchyard of St Martin-in-the-Fields, his funeral sermon being preached by his friend, Bishop Gilbert Burnet. In his will, Boyle endowed a series of lectures that came to be known as the Boyle Lectures. | 1 | Applied and Interdisciplinary Chemistry |
The salt is prepared by the addition of elemental sulfur to potassium sulfide. An idealized equation is shown for potassium hydrosulfide:
The structure consists of zigzag chains of paired with ions. | 0 | Theoretical and Fundamental Chemistry |
In 1962, Harvard professor Edward O. Wilson published one of the first concrete studies constructing the groundwork for the notion of trail pheromones. Claiming an odor trail is deposited by the sting apparatus of the hymenopteran Solenopsis saevissima which results in a pathway from the colony to a food source, this study encouraged further investigation of how this chemical is laid, how it affects communication between species within and outside of its own, the evolution of the semiochemical, etc. | 1 | Applied and Interdisciplinary Chemistry |
Carbenes add to double bonds to form cyclopropanes, and, in the presence of a copper catalyst, to alkynes to give cyclopropenes. Addition reactions are commonly very fast and exothermic, and carbene generation limits reaction rate.
In Simmons-Smith cyclopropanation, the iodomethylzinc iodide typically complexes to any allylic hydroxy groups such that addition is syn to the hydroxy group. | 0 | Theoretical and Fundamental Chemistry |
Fretting damage in steel can be identified by the presence of a pitted surface and fine red iron oxide dust resembling cocoa powder. Strictly this debris is not rust as its production requires no water. The particles are much harder than the steel surfaces in contact, so abrasive wear is inevitable; however, particulates are not required to initiate fret. | 1 | Applied and Interdisciplinary Chemistry |
Bjerknes forces are translational forces on bubbles in a sound wave. The phenomenon is a type of acoustic radiation force. Primary Bjerknes forces are caused by an external sound field; secondary Bjerknes forces are attractive or repulsive forces between pairs of bubbles in the same sound field caused by the pressure field generated by each bubble volumes oscillations. They were first described by Vilhelm Bjerknes in his 1906 Fields of Force'. | 1 | Applied and Interdisciplinary Chemistry |
For a Bragg peak , the observed integrated intensity, , as determined from numerical integration is
where is the total number of data points in the range of the Bragg peak. The integrated intensity depends on multiple factors, and can be expressed as the following product:
where:
* : scale factor
* : multiplicity factor, which accounts for symmetrically equivalent points in the reciprocal lattice
* : Lorentz multiplier, defined by diffraction geometry
* : polarization factor
* : absorption multiplier
* : preferred orientation factor
* : extinction factor (often neglected as it is usually insignificant in powders)
* : structure factor as determined by the crystal structure of the material | 0 | Theoretical and Fundamental Chemistry |
The COLUMBUS PROGRAMS were started in 1980 in the Department of Chemistry of Ohio State University by Isaiah Shavitt, Hans Lischka and Ron Shepard. The programs pioneered the Graphical Unitary Group Approach (GUGA) for configuration interaction calculations, which is now available in many other program suites. The programs are named after Columbus, OH. | 0 | Theoretical and Fundamental Chemistry |
is built up of double layers of hydroxyl groups with aluminium ions occupying two-thirds of the octahedral holes between the two layers. Four polymorphs are recognized. All feature layers of octahedral aluminium hydroxide units, with hydrogen bonds between the layers. The polymorphs differ in terms of the stacking of the layers. All forms of crystals are hexagonal :
* gibbsite is also known as γ- or α-
* bayerite is also known as α- or β-alumina trihydrate
* nordstrandite is also known as
* doyleite
Hydrargillite, once thought to be aluminium hydroxide, is an aluminium phosphate. Nonetheless, both gibbsite and hydrargillite refer to the same polymorphism of aluminium hydroxide, with gibbsite used most commonly in the United States and hydrargillite used more often in Europe. Hydrargillite is named after the Greek words for water () and clay (). | 0 | Theoretical and Fundamental Chemistry |
In case (e), we first form and then form by coupling and . This case is rare but has been observed. Rydberg states which converge to ionic states with spin–orbit coupling (such as Π) are best described as case (e).
The good quantum numbers in case (e) are , , and . Because is once again a good quantum number, the rotational energy is . | 0 | Theoretical and Fundamental Chemistry |
Initiation of translation usually involves the interaction of certain key proteins, the initiation factors, with a special tag bound to the 5-end of an mRNA molecule, the 5 cap, as well as with the 5' UTR. These proteins bind the small (40S) ribosomal subunit and hold the mRNA in place.
eIF3 is associated with the 40S ribosomal subunit and plays a role in keeping the large (60S) ribosomal subunit from prematurely binding. eIF3 also interacts with the eIF4F complex, which consists of three other initiation factors: eIF4A, eIF4E, and eIF4G. eIF4G is a scaffolding protein that directly associates with both eIF3 and the other two components. eIF4E is the cap-binding protein. Binding of the cap by eIF4E is often considered the rate-limiting step of cap-dependent initiation, and the concentration of eIF4E is a regulatory nexus of translational control. Certain viruses cleave a portion of eIF4G that binds eIF4E, thus preventing cap-dependent translation to hijack the host machinery in favor of the viral (cap-independent) messages. eIF4A is an ATP-dependent RNA helicase that aids the ribosome by resolving certain secondary structures formed along the mRNA transcript. The poly(A)-binding protein (PABP) also associates with the eIF4F complex via eIF4G, and binds the poly-A tail of most eukaryotic mRNA molecules. This protein has been implicated in playing a role in circularization of the mRNA during translation.
This 43S preinitiation complex (43S PIC) accompanied by the protein factors moves along the mRNA chain toward its 3-end, in a process known as scanning', to reach the start codon (typically AUG). In eukaryotes and archaea, the amino acid encoded by the start codon is methionine. The Met-charged initiator tRNA (Met-tRNA) is brought to the P-site of the small ribosomal subunit by eukaryotic initiation factor 2 (eIF2). It hydrolyzes GTP, and signals for the dissociation of several factors from the small ribosomal subunit, eventually leading to the association of the large subunit (or the 60S subunit). The complete ribosome (80S) then commences translation elongation.
Regulation of protein synthesis is partly influenced by phosphorylation of eIF2 (via the α subunit), which is a part of the eIF2-GTP-Met-tRNA ternary complex (eIF2-TC). When large numbers of eIF2 are phosphorylated, protein synthesis is inhibited. This occurs under amino acid starvation or after viral infection. However, a small fraction of this initiation factor is naturally phosphorylated. Another regulator is 4EBP, which binds to the initiation factor eIF4E and inhibits its interactions with eIF4G, thus preventing cap-dependent initiation. To oppose the effects of 4EBP, growth factors phosphorylate 4EBP, reducing its affinity for eIF4E and permitting protein synthesis.
While protein synthesis is globally regulated by modulating the expression of key initiation factors as well as the number of ribosomes, individual mRNAs can have different translation rates due to the presence of regulatory sequence elements. This has been shown to be important in a variety of settings including yeast meiosis and ethylene response in plants. In addition, recent work in yeast and humans suggest that evolutionary divergence in cis-regulatory sequences can impact translation regulation. Additionally, RNA helicases such as DHX29 and Ded1/DDX3 may participate in the process of translation initiation, especially for mRNAs with structured 5'UTRs. | 1 | Applied and Interdisciplinary Chemistry |
Thiolate-protected gold clusters are a type of ligand-protected metal cluster, synthesized from gold ions and thin layer compounds that play a special role in cluster physics because of their unique stability and electronic properties. They are considered to be stable compounds.
These clusters can range in size up to hundreds of gold atoms, above which they are classified as passivated gold nanoparticles. | 0 | Theoretical and Fundamental Chemistry |
Bilirubin glucuronide is a water-soluble reaction intermediate over the process of conjugation of indirect bilirubin. Bilirubin glucuronide itself belongs to the category of conjugated bilirubin along with bilirubin di-glucuronide. However, only the latter one is primarily excreted into the bile in the normal setting.
Upon macrophages spot and phagocytize the effete Red Blood Corpuscles containing hemoglobin, unconjugated bilirubin is discharged from macrophages into the blood plasma. Most often, the free and water-insoluble unconjugated bilirubin which has an internal hydrodren bonding will bind to albumin and, to a much lesser extent, high density lipoprotein in order to decrease its hydrophobicity and to limit the probability of unnecessary contact with other tissues and keep bilirubin in the vascular space from traversing to extravascular space including brain, and from ending up increasing glomerular filtration. Nevertheless, there is still a little portion of indirect bilirubins stays free-of-bound. Free unconjugated bilirubin can poison the cerebrum.
Finally, albumin leads the indirect bilirubin to the liver. In the liver sinusoid, albumin disassociates with the indirect bilirubin and returns to the circulation while the hepatocyte transfers the indirect bilirubin to ligandin and glucuronide conjugates the indirect bilirubin in the endoplasmic reticulum by disrupting unconjugated bilirubin's internal hydrogen bonding, which is the thing that makes indirect bilirubin having the property of eternal half-elimination life and insoluble in water, and by attaching two molecules of glucuronic acid to it in a two step process. The reaction is a transfer of two glucuronic acid groups including UDP glucuronic acid sequentially to the propionic acid groups of the bilirubin, primarily catalyzed by UGT1A1. In greater detail about this reaction, a glucuronosyl moiety is conjugated to one of the propionic acid side chains, located on the C8 and C12 carbons of the two central pyrrole rings of bilirubin.
When the first step is completely done, the substrate bilirubin glucuronide (also known as mono-glucuronide) is born at this stage and is water-soluble and readily excreted in bile. Thereafter, so long as the second step of attachment of the other glucuronic acid to it succeeds (officially called "re-glucuronidated"), the substrate bilirubin glucuronide will turn into bilirubin di-glucuronide (8,12-diglucuronide) and be excreted into bile canaliculi by way of C-MOAT and MRP2 as normal human bile along with a little amount of unconjugated bilirubin as much as only 1 to 4 percent of total pigments in normal bile. That means up to 96%-99% of bilirubin in the bile are conjugated.
Normally, there is just a little conjugated bilirubin escapes into the general circulation. Nonetheless, in the setting of severe liver disease, a significantly greater number of conjugated bilirubin will leak into circulation and then dissolve into the blood and thereby filtered by the kidney, and only a part of the leaked conjugated bilirubin will be re-absorbed in the renal tubules, the remainder will be present in the urine making it dark-colored. | 1 | Applied and Interdisciplinary Chemistry |
Many water managers treat USS by directly addressing the symptoms, most commonly through channel reconfiguration that includes reshaping rock to address altered hydrology and sediment regimes. In spite of having ecological objectives, this approach has been criticized for addressing physical failures in the system without improving ecological conditions. | 1 | Applied and Interdisciplinary Chemistry |
In an experiment in 1995, display of Glutathione S-transferase was attempted on both pVII and pIX and failed. However, phage display of this protein was completed successfully after the addition of a periplasmic signal sequence (pelB or ompA) on the N-terminus. In a recent study, it has been shown that AviTag, FLAG and His could be displayed on pVII without the need of a signal sequence. Then the expression of single chain Fv's (scFv), and single chain T cell receptors (scTCR) were expressed both with and without the signal sequence.
PelB (an amino acid signal sequence that targets the protein to the periplasm where a signal peptidase then cleaves off PelB) improved the phage display level when compared to pVII and pIX fusions without the signal sequence. However, this led to the incorporation of more helper phage genomes rather than phagemid genomes. In all cases, phage display levels were lower than using pIII fusion. However, lower display might be more favorable for the selection of binders due to lower display being closer to true monovalent display. In five out of six occasions, pVII and pIX fusions without pelB was more efficient than pIII fusions in affinity selection assays. The paper even goes on to state that pVII and pIX display platforms may outperform pIII in the long run.
The use of pVII and pIX instead of pIII might also be an advantage because virion rescue may be undertaken without breaking the virion-antigen bond if the pIII used is wild type. Instead, one could cleave in a section between the bead and the antigen to elute. Since the pIII is intact it does not matter whether the antigen remains bound to the phage. | 1 | Applied and Interdisciplinary Chemistry |
* (2007): Death of a dissident: The Poisoning of Alexander Litvinenko and the Return of the KGB. The Free Press. | 1 | Applied and Interdisciplinary Chemistry |
Neutron scattering measurements of cesium chlorocuprate CsCuCl, a spin-1/2 antiferromagnet on a triangular lattice, displayed diffuse scattering. This was attributed to spinons arising from a 2D RVB state. Later theoretical work challenged this picture, arguing that all experimental results were instead consequences of 1D spinons confined to individual chains.
Afterwards, it was observed in an organic Mott insulator (κ-(BEDT-TTF)Cu(CN)) by Kanoda's group in 2003. It may correspond to a gapless spin liquid with spinon Fermi surface (the so-called uniform RVB state). The peculiar phase diagram of this organic quantum spin liquid compound was first thoroughly mapped using muon spin spectroscopy. | 0 | Theoretical and Fundamental Chemistry |
Cyanobactin biosynthesis requires proteolytic cleavage of both N-terminal and C-terminal portions of the precursor peptide. The defining proteins are thus an N-terminal protease, referred to as the A protein, and a C-terminal protease, referred to as the G protein. The G protein is also responsible for macrocyclization.
For cyanobactins, the precursor peptide is referred to as the E peptide. Minimally, the E peptide requires a leader peptide region, a core (structural) region, and both N-terminal and C-terminal protease recognition sequences. In contrast to most RiPPs, for which a single precursor peptide encodes a single natural product via a lone core peptide, cyanobactin E peptides can contain multiple core regions; multiple E peptides can even be present in a single gene cluster.
Many cyanobactins also undergo heterocyclization by a heterocyclase (referred to as the D protein), installing oxazoline or thiazoline moieties from Ser/Thr/Cys residues prior to the action of the A and G proteases. The heterocyclase is an ATP-dependent YcaO homologue that behaves biochemically in the same manner as YcaO-domain cyclodehydratases in thiopeptide and linear azol(in)e-containing peptide (LAP) biosynthesis (described above).
A common modification is prenylation of hydroxyl groups by an F protein prenyltransferase. Oxidation of azoline heterocycles to azoles can also be accomplished by an oxidase domain located on the G protein. Unusual for ribosomal peptides, cyanobactins can include D-amino acids; these can occur adjacent to azole or azoline residues. The functions of some proteins found commonly in cyanobactin biosynthetic gene clusters, the B and C proteins, are unknown. | 1 | Applied and Interdisciplinary Chemistry |
In 1980, Staden wrote: In order to make it easier to talk about our data gained by the shotgun method of sequencing we have invented the word "contig". A contig is a set of gel readings that are related to one another by overlap of their sequences. All gel readings belong to one and only one contig, and each contig contains at least one gel reading. The gel readings in a contig can be summed to form a contiguous consensus sequence and the length of this sequence is the length of the contig. | 1 | Applied and Interdisciplinary Chemistry |
One application area that has seen significant academic effort and some commercial effort is in the area of particle detection in fluids. Particle detection of small fluid-borne particles down to about 1 μm in diameter is typically done using a Coulter counter, in which electrical signals are generated when a weakly-conducting fluid such as in saline water is passed through a small (~100 μm diameter) pore, so that an electrical signal is generated that is directly proportional to the ratio of the particle volume to the pore volume. The physics behind this is relatively simple, described in a classic paper by DeBlois and Bean, and the implementation first described in Coulter's original patent. This is the method used to e.g. size and count erythrocytes (red blood cells [wiki]) as well as leukocytes (white blood cells) for standard blood analysis. The generic term for this method is resistive pulse sensing (RPS); Coulter counting is a trademark term. However, the RPS method does not work well for particles below 1 μm diameter, as the signal-to-noise ratio falls below the reliably detectable limit, set mostly by the size of the pore in which the analyte passes and the input noise of the first-stage amplifier.
The limit on the pore size in traditional RPS Coulter counters is set by the method used to make the pores, which while a trade secret, most likely uses traditional mechanical methods. This is where microfluidics can have an impact: The lithography-based production of microfluidic devices, or more likely the production of reusable molds for making microfluidic devices using a molding process, is limited to sizes much smaller than traditional machining. Critical dimensions down to 1 μm are easily fabricated, and with a bit more effort and expense, feature sizes below 100 nm can be patterned reliably as well. This enables the inexpensive production of pores integrated in a microfluidic circuit where the pore diameters can reach sizes of order 100 nm, with a concomitant reduction in the minimum particle diameters by several orders of magnitude.
As a result, there has been some university-based development of microfluidic particle counting and sizing with the accompanying commercialization of this technology. This method has been termed microfluidic resistive pulse sensing (MRPS). | 1 | Applied and Interdisciplinary Chemistry |
Stokes flow (named after George Gabriel Stokes), also named creeping flow or creeping motion, is a type of fluid flow where advective inertial forces are small compared with viscous forces. The Reynolds number is low, i.e. . This is a typical situation in flows where the fluid velocities are very slow, the viscosities are very large, or the length-scales of the flow are very small. Creeping flow was first studied to understand lubrication. In nature, this type of flow occurs in the swimming of microorganisms and sperm. In technology, it occurs in paint, MEMS devices, and in the flow of viscous polymers generally.
The equations of motion for Stokes flow, called the Stokes equations, are a linearization of the Navier–Stokes equations, and thus can be solved by a number of well-known methods for linear differential equations. The primary Green's function of Stokes flow is the Stokeslet, which is associated with a singular point force embedded in a Stokes flow. From its derivatives, other fundamental solutions can be obtained. The Stokeslet was first derived by Oseen in 1927, although it was not named as such until 1953 by Hancock. The closed-form fundamental solutions for the generalized unsteady Stokes and Oseen flows associated with arbitrary time-dependent translational and rotational motions have been derived for the Newtonian and micropolar fluids. | 1 | Applied and Interdisciplinary Chemistry |
Gunpowder may have been used during the Mongol invasions of Europe. "Fire catapults", "pao", and "naphtha-shooters" are mentioned in some sources. However, according to Timothy May, "there is no concrete evidence that the Mongols used gunpowder weapons on a regular basis outside of China."
Shortly after the Mongol invasions of Japan (1274–1281), the Japanese produced a scroll painting depicting a bomb. Called tetsuhau in Japanese, the bomb is speculated to have been the Chinese thunder crash bomb. Archaeological findings by the Kyushu Okinawa Society for Underwater Archaeology confirmed the existence of bombs in the Yuan invasions arsenal. Multiple bomb shells were discovered in an underwater shipwreck off the shore of Japan and X-rays of the excavated shells show that they contained gunpowder and were also packed with scrap iron. Japanese descriptions of the invasions also talk of iron and bamboo pao causing "light and fire" and emitting 2–3,000 iron bullets. The Nihon Kokujokushi, written around 1300, mentions huo tong (fire tubes) at the Battle of Tsushima in 1274 and the second coastal assault led by Holdon in 1281. The Hachiman Gudoukun of 1360 mentions iron pao "which caused a flash of light and a loud noise when fired." The Taiheki of 1370 mentions "iron pao' shaped like a bell." | 1 | Applied and Interdisciplinary Chemistry |
In 1805, Thomas Young defined the contact angle θ by analyzing the forces acting on a fluid droplet resting on a solid surface surrounded by a gas.
where
: = Interfacial tension between the solid and gas
: = Interfacial tension between the solid and liquid
: = Interfacial tension between the liquid and gas
θ can be measured using a contact angle goniometer.
Wenzel determined that when the liquid is in intimate contact with a microstructured surface, θ will change to θ
where r is the ratio of the actual area to the projected area. Wenzel's equation shows that microstructuring a surface amplifies the natural tendency of the surface. A hydrophobic surface (one that has an original contact angle greater than 90°) becomes more hydrophobic when microstructured – its new contact angle becomes greater than the original. However, a hydrophilic surface (one that has an original contact angle less than 90°) becomes more hydrophilic when microstructured – its new contact angle becomes less than the original.
Cassie and Baxter found that if the liquid is suspended on the tops of microstructures, θ will change to θ:
where φ is the area fraction of the solid that touches the liquid. Liquid in the Cassie–Baxter state is more mobile than in the Wenzel state.
We can predict whether the Wenzel or Cassie–Baxter state should exist by calculating the new contact angle with both equations. By a minimization of free energy argument, the relation that predicted the smaller new contact angle is the state most likely to exist. Stated in mathematical terms, for the Cassie–Baxter state to exist, the following inequality must be true.
A recent alternative criterion for the Cassie–Baxter state asserts that the Cassie–Baxter state exists when the following 2 criteria are met:1) Contact line forces overcome body forces of unsupported droplet weight and 2) The microstructures are tall enough to prevent the liquid that bridges microstructures from touching the base of the microstructures.
A new criterion for the switch between Wenzel and Cassie-Baxter states has been developed recently based on surface roughness and surface energy. The criterion focuses on the air-trapping capability under liquid droplets on rough surfaces, which could tell whether Wenzels model or Cassie-Baxters model should be used for certain combination of surface roughness and energy.
Contact angle is a measure of static hydrophobicity, and contact angle hysteresis and slide angle are dynamic measures. Contact angle hysteresis is a phenomenon that characterizes surface heterogeneity. When a pipette injects a liquid onto a solid, the liquid will form some contact angle. As the pipette injects more liquid, the droplet will increase in volume, the contact angle will increase, but its three-phase boundary will remain stationary until it suddenly advances outward. The contact angle the droplet had immediately before advancing outward is termed the advancing contact angle. The receding contact angle is now measured by pumping the liquid back out of the droplet. The droplet will decrease in volume, the contact angle will decrease, but its three-phase boundary will remain stationary until it suddenly recedes inward. The contact angle the droplet had immediately before receding inward is termed the receding contact angle. The difference between advancing and receding contact angles is termed contact angle hysteresis and can be used to characterize surface heterogeneity, roughness, and mobility. Surfaces that are not homogeneous will have domains that impede motion of the contact line. The slide angle is another dynamic measure of hydrophobicity and is measured by depositing a droplet on a surface and tilting the surface until the droplet begins to slide. In general, liquids in the Cassie–Baxter state exhibit lower slide angles and contact angle hysteresis than those in the Wenzel state. | 0 | Theoretical and Fundamental Chemistry |
PRR3, PRR5, PRR7 and PRR9 participate in the repressilator of a negative autoregulatory feedback loop that synchronizes to environmental inputs. The repressilator has a morning, evening, and night loop that are regulated in part by the pseudo-response regulator proteins' interactions with CCA1 and LHY. CCA1 and LHY exhibit peak binding to PRR9, PRR7, and PRR5 in the morning, evening, and night, respectively. | 1 | Applied and Interdisciplinary Chemistry |
Huntley has pointed out that a dimensional analysis can become more powerful by discovering new independent dimensions in the quantities under consideration, thus increasing the rank of the dimensional matrix.
He introduced two approaches:
* The magnitudes of the components of a vector are to be considered dimensionally independent. For example, rather than an undifferentiated length dimension L, we may have L represent dimension in the x-direction, and so forth. This requirement stems ultimately from the requirement that each component of a physically meaningful equation (scalar, vector, or tensor) must be dimensionally consistent.
* Mass as a measure of the quantity of matter is to be considered dimensionally independent from mass as a measure of inertia. | 1 | Applied and Interdisciplinary Chemistry |
"Nanoscale" is usually understood to be the range from 1 to 100 nm because the novel properties that differentiate particles from the bulk material typically develop at that range of sizes.
For some properties, like transparency or turbidity, ultrafiltration, stable dispersion, etc., substantial changes characteristic of nanoparticles are observed for particles as large as 500 nm. Therefore, the term is sometimes extended to that size range. | 0 | Theoretical and Fundamental Chemistry |
Disulfide bonds can be formed under oxidising conditions and play an important role in the folding and stability of some proteins, usually proteins secreted to the extracellular medium. Since most cellular compartments are reducing environments, in general, disulfide bonds are unstable in the cytosol, with some exceptions as noted below, unless a sulfhydryl oxidase is present.
Disulfide bonds in proteins are formed between the thiol groups of cysteine residues by the process of oxidative folding. The other sulfur-containing amino acid, methionine, cannot form disulfide bonds. A disulfide bond is typically denoted by hyphenating the abbreviations for cysteine, e.g., when referring to ribonuclease A the "Cys26–Cys84 disulfide bond", or the "26–84 disulfide bond", or most simply as "C26–C84" where the disulfide bond is understood and does not need to be mentioned. The prototype of a protein disulfide bond is the two-amino-acid peptide cystine, which is composed of two cysteine amino acids joined by a disulfide bond. The structure of a disulfide bond can be described by its χ dihedral angle between the C−S−S−C atoms, which is usually close to ±90°.
The disulfide bond stabilizes the folded form of a protein in several ways:
#It holds two portions of the protein together, biasing the protein towards the folded topology. That is, the disulfide bond destabilizes the unfolded form of the protein by lowering its entropy.
#The disulfide bond may form the nucleus of a hydrophobic core of the folded protein, i.e., local hydrophobic residues may condense around the disulfide bond and onto each other through hydrophobic interactions.
#Related to 1 and 2, the disulfide bond links two segments of the protein chain, increases the effective local concentration of protein residues, and lowers the effective local concentration of water molecules. Since water molecules attack amide-amide hydrogen bonds and break up secondary structure, a disulfide bond stabilizes secondary structure in its vicinity. For example, researchers have identified several pairs of peptides that are unstructured in isolation, but adopt stable secondary and tertiary structure upon formation of a disulfide bond between them.
A disulfide species is a particular pairing of cysteines in a disulfide-bonded protein and is usually depicted by listing the disulfide bonds in parentheses, e.g., the "(26–84, 58–110) disulfide species". A disulfide ensemble is a grouping of all disulfide species with the same number of disulfide bonds, and is usually denoted as the 1S ensemble, the 2S ensemble, etc. for disulfide species having one, two, etc. disulfide bonds. Thus, the (26–84) disulfide species belongs to the 1S ensemble, whereas the (26–84, 58–110) species belongs to the 2S ensemble. The single species with no disulfide bonds is usually denoted as R for "fully reduced". Under typical conditions, disulfide reshuffling is much faster than the formation of new disulfide bonds or their reduction; hence, the disulfide species within an ensemble equilibrate more quickly than between ensembles.
The native form of a protein is usually a single disulfide species, although some proteins may cycle between a few disulfide states as part of their function, e.g., thioredoxin. In proteins with more than two cysteines, non-native disulfide species may be formed, which are almost always misfolded. As the number of cysteines increases, the number of nonnative species increases factorially. | 0 | Theoretical and Fundamental Chemistry |
In metabolism research, tritium and C-labeled glucose are commonly used in glucose clamps to measure rates of glucose uptake, fatty acid synthesis, and other metabolic processes. While radioactive tracers are sometimes still used in human studies, stable isotope tracers such as C are more commonly used in current human clamp studies. Radioactive tracers are also used to study lipoprotein metabolism in humans and experimental animals.
In medicine, tracers are applied in a number of tests, such as Tc in autoradiography and nuclear medicine, including single-photon emission computed tomography (SPECT), positron emission tomography (PET) and scintigraphy. The urea breath test for helicobacter pylori commonly used a dose of C labeled urea to detect h. pylori infection. If the labeled urea was metabolized by h. pylori in the stomach, the patient's breath would contain labeled carbon dioxide. In recent years, the use of substances enriched in the non-radioactive isotope C has become the preferred method, avoiding patient exposure to radioactivity.
In hydraulic fracturing, radioactive tracer isotopes are injected with hydraulic fracturing fluid to determine the injection profile and location of created fractures. Tracers with different half-lives are used for each stage of hydraulic fracturing. In the United States amounts per injection of radionuclide are listed in the US Nuclear Regulatory Commission (NRC) guidelines. According to the NRC, some of the most commonly used tracers include antimony-124, bromine-82, iodine-125, iodine-131, iridium-192, and scandium-46. A 2003 publication by the International Atomic Energy Agency confirms the frequent use of most of the tracers above, and says that manganese-56, sodium-24, technetium-99m, silver-110m, argon-41, and xenon-133 are also used extensively because they are easily identified and measured. | 0 | Theoretical and Fundamental Chemistry |
The fraction of absorbed photosynthetically active radiation (FAPAR, sometimes also noted fAPAR or fPAR) is the fraction of the incoming solar radiation in the photosynthetically active radiation spectral region that is absorbed by a photosynthetic organism, typically describing the light absorption across an integrated plant canopy.
This biophysical variable is directly related to the primary productivity of photosynthesis and some models use it to estimate the assimilation of carbon dioxide in vegetation in conjunction with the leaf area index. FAPAR can also be used as an indicator of the state and evolution of the vegetation cover; with this function, it advantageously replaces the Normalized Difference Vegetation Index (NDVI), provided it is itself properly estimated.
FAPAR can be directly measured on the ground, by putting a spectrometer above and below canopy cover. On a larger scale, however, it is estimated from space measurements in the solar spectral range and a number of state of the art algorithms have been proposed to derive this important environmental variable. Currently, there are some remote sensing products of FAPAR, such as AVHRR and MODIS.
FAPAR is one of the 50 Essential Climate Variables recognized by the UN Global Climate Observing System (GCOS) as necessary to characterize the climate of the Earth. GCOS has issued specific recommendations to monitor this variable systematically, both through a reanalysis of existing databases and in the future with current and forthcoming instruments. | 0 | Theoretical and Fundamental Chemistry |
EPANETs computational engine is available for download as a separate dynamic link library for incorporation into other applications. The source code for EPANET 2 is available on the EPAs EPANET website.
In 2012 the EPANET toolkit, written in C, was rewritten in Java in a more object-oriented style. The code in Java is available on GitHub: https://github.com/Baseform/Baseform-Epanet-Java-Library. | 1 | Applied and Interdisciplinary Chemistry |
Over the last 50 or so years, pan evaporation has been carefully monitored. For decades, pan evaporation measurements were not analyzed critically for long term trends. But in the 1990s scientists reported that the rate of evaporation was falling. According to data, the downward trend had been observed all over the world except in a few places where it has increased.
It is currently theorized that, all other things being equal, as the global climate warms evaporation would increase proportionately and as a result, the hydrological cycle in its most general sense is bound to accelerate. The downward trend of pan evaporation has since also been linked to a phenomenon called global dimming. In 2005 Wild et al. and Pinker et al. found that the "dimming" trend had reversed since about 1990.
Other theories suggest that measurements have not taken the local environment into account. Since the local moisture level has increased in the local terrain, less water evaporates from the pan. This leads to false measurements and must be compensated for in the data analysis. Models accounting for additional local terrain moisture match global estimates.
In a different view, an analysis of pan trends in records from 154 instruments shows no coherency and pattern of statistically significant trends, with 38% decreasing, 42% no change and 20% increasing. Changes in the local environment are implicated, in which increasing tree density near the pans elevating surface friction and slowing local wind runs, reducing pan evaporation. The evaporation paradox is a result of ongoing changes in the nearby environments. | 1 | Applied and Interdisciplinary Chemistry |
* Ertl, P. [https://books.google.com/books?id=wEsxCtyUJUEC&pg=PA111 Polar Surface Area], in Molecular Drug Properties, R. Mannhold (ed), Wiley-VCH, pp. 111–126, 2007 | 1 | Applied and Interdisciplinary Chemistry |
In biochemistry, the oxygen effect refers to a tendency for increased radiosensitivity of free living cells and organisms in the presence of oxygen than in anoxic or hypoxic conditions, where the oxygen tension is less than 1% of atmospheric pressure (i.e., <1% of 101.3 kPa, 760 mmHg or 760 torr). | 1 | Applied and Interdisciplinary Chemistry |
Alaska had fewer than 4,000 gallons of dispersants available at the time of the Exxon Valdez oil spill, and no aircraft with which to dispense them. The dispersants introduced were relatively ineffective due to insufficient wave action to mix the oil and water, and their use was shortly abandoned.
A report by David Kirby for TakePart found that the main component of the Corexit 9527 formulation used during Exxon Valdez cleanup, 2-butoxyethanol, was identified as "one of the agents that caused liver, kidney, lung, nervous system, and blood disorders among cleanup crews in Alaska following the 1989 Exxon Valdez spill." | 1 | Applied and Interdisciplinary Chemistry |
Shamoo was born and raised in Baghdad, Iraq. He is an ethnic Iraqi. He attended the University of Baghdad and graduated with a degree in physics in 1962. In 1966, he earned a Master's of Science in physics from the University of Louisville. Four years later, in 1970, he finished his Ph.D. in the program in Biology at the City University of New York. | 1 | Applied and Interdisciplinary Chemistry |
Staphylococcus aureus is a type of pathogen that causes infection to the skin and soft tissue and can lead to a variety of more severe diseases such as osteomyelitis, pneumonia, and endocarditis. Staphylococcus aureus uses biofilms in order to increase its chances of survival by becoming resistant to antibiotics. Biofilms help Staphylococcus aureus become up to 1500 times more resistant to antibiofilm agents which try to break down biofilms formed by Staphylococcus aureus. | 1 | Applied and Interdisciplinary Chemistry |
* ~40% dipalmitoylphosphatidylcholine (DPPC);
* ~40% other phospholipids (PC);
* ~10% surfactant proteins (SP-A, SP-B, SP-C and SP-D);
* ~10% neutral lipids (Cholesterol);
* Traces of other substances. | 0 | Theoretical and Fundamental Chemistry |
The Descriptions of Plant Viruses (DPVs) were first published by the Association of Applied Biologists in 1970 as a series of leaflets, each one written by an expert describing a particular plant virus. In 1998 all of the 354 DPVs published in paper were scanned, and converted into an electronic format in a database and distributed on CDROM. In 2001 the descriptions were made available on the new DPVweb site, providing open access to the now 400+ DPVs (currently 415) as well as taxonomic and sequence data on all plant viruses. | 1 | Applied and Interdisciplinary Chemistry |
Joseph Joshua Weiss (30 August 1905 – 9 April 1972) was a Jewish-Austrian chemist and Professor at the Newcastle University. He was a pioneer in the field of radiation chemistry and photochemistry. | 0 | Theoretical and Fundamental Chemistry |
Second group of TI antigens consists mainly of highly repetitive surface structures (epitopes) of encapsulated bacteria. They do not have an intrinsic B-cell activating activity. The activation of B lymphocytes is caused by cross-linking of a critical number of B cell receptors, which leads to accumulation of BCRs and cross activation of these receptors. It results in proliferation and differentiation of B lymphocytes and production of antibodies. TI-2 antigens can activate only mature B lymphocytes. Immature B cells are anergized, so they do not elicit any immune response. That may explain why children up to 5 years are not capable of producing effective antibodies against polysaccharide antigens, as the majority of their B cell population is immature.
Even though the response on TI antigens is not dependent on T lymphocytes, there are some cytokines, produced mainly by T lymphocytes and natural killer (NK) cells, necessary for eliciting reaction against these antigens. The most necessary are interleukin 2 (IL-2), interleukin 3 (IL-3) and interferon γ (IFN-γ). Moreover, additional stimulation by dendritic cells (DC) and macrophages is required. | 1 | Applied and Interdisciplinary Chemistry |
The Thyroid Feedback Quantile-based Index (TFQI) is a calculated parameter for thyrotropic pituitary function. It was defined to be more robust to distorted data than established markers including Jostel's TSH index (JTI) and the thyrotroph thyroid hormone sensitivity index (TTSI). | 1 | Applied and Interdisciplinary Chemistry |
According to Gordon Pusch, a physicist at Argonne National Laboratory, various breakeven calculations on muon-catalyzed fusion omit the heat energy the muon beam itself deposits in the target. By taking this factor into account, muon-catalyzed fusion can already exceed breakeven; however, the recirculated power is usually very large compared to power out to the electrical grid (about 3–5 times as large, according to estimates). Despite this rather high recirculated power, the overall cycle efficiency is comparable to conventional fission reactors; however the need for 4–6 MW electrical generating capacity for each megawatt out to the grid probably represents an unacceptably large capital investment. Pusch suggested using Bogdan Maglich's "migma" self-colliding beam concept to significantly increase the muon production efficiency, by eliminating target losses, and using tritium nuclei as the driver beam, to optimize the number of negative muons.
In 2021, Kelly, Hart and Rose produced a μCF model whereby the ratio, Q, of thermal energy produced to the kinetic energy of the accelerated deuterons used to create negative pions (and thus negative muons through pion decay) was optimized. In this model, the heat energy of the incoming deuterons as well as that of the particles produced due to the deuteron beam impacting a tungsten target was recaptured to the extent possible, as suggested by Gordon Pusch in the previous paragraph. Additionally, heat energy due to tritium breeding in a lithium-lead shell was recaptured, as suggested by Jändel, Danos and Rafelski in 1988. The best Q value was found to be about 130% assuming that 50% of the muons produced were actually utilized for fusion catalysis. Furthermore, assuming that the accelerator was 18% efficient at transforming electrical energy into deuteron kinetic energy and conversion efficiency of heat energy into electrical energy of 60%, they estimate that, currently, the amount of electrical energy that could be produced by a μCF reactor would be 14% of the electrical energy consumed. In order for this to improve, they suggest that some combination of a) increasing accelerator efficiency and b) increasing the number of fusion reactions per negative muon above the assumed level of 150 would be needed. | 0 | Theoretical and Fundamental Chemistry |
LaAlO doped with neodymium gave laser emission at 1080 nm. Mixed methylammonium lead halide () cells fashioned into optically pumped vertical-cavity surface-emitting lasers (VCSELs) convert visible pump light to near-IR laser light with a 70% efficiency. | 0 | Theoretical and Fundamental Chemistry |
Another class of INIs could be IN binding inhibitors (INBIs) such as V-165. V-165 is a compound shown to inhibit integration but without obvious effect on viral DNA synthesis. When the mechanism of action was studied it showed that V-165 interferes with viral DNA-IN complex formation. Due to its interfering action it is classified as an IN binding inhibitor. Other compounds, such as styrylquinolines share similar mechanism by competing with the LTR substrate for IN binding. | 1 | Applied and Interdisciplinary Chemistry |
Clonal derivation exists in nature in some animal species and is referred to as parthenogenesis (reproduction of an organism by itself without a mate). This is an asexual form of reproduction that is only found in females of some insects, crustaceans, nematodes, fish (for example the hammerhead shark), Cape honeybees, and lizards including the Komodo dragon and several whiptails. The growth and development occurs without fertilization by a male. In plants, parthenogenesis means the development of an embryo from an unfertilized egg cell, and is a component process of apomixis. In species that use the XY sex-determination system, the offspring will always be female. An example is the little fire ant (Wasmannia auropunctata), which is native to Central and South America but has spread throughout many tropical environments. | 1 | Applied and Interdisciplinary Chemistry |
Biliproteins found in plants and algae serve as a system of pigments whose purpose is to detect and absorb light needed for photosynthesis. The absorption spectra of biliproteins complements that of other photosynthetic pigments such as chlorophyll or carotene. The pigments detect and absorb energy from sunlight; the energy later being transferred to chlorophyll via internal energy transfer. According to a 2002 article written by Takashi Hirata et al., the chromophores of certain phycobiliproteins are responsible for antioxidant activities in these biliproteins, and phycocyanin also possesses anti-inflammatory qualities due to its inhibitory apoprotein. When induced by both collagen and adenosine triphosphate (ADP), the chromophore phycocyanobilin suppresses platelet aggregation in phycocyanin, its corresponding phycobiliprotein. | 1 | Applied and Interdisciplinary Chemistry |
Antoine Lavoisier considered that radiation of heat was concerned with the condition of the surface of a physical body rather than the material of which it was composed. Lavoisier described a poor radiator to be a substance with a polished or smooth surface as it possessed its molecules lying in a plane closely bound together thus creating a surface layer of caloric fluid which insulated the release of the rest within. He described a great radiator to be a substance with a rough surface as only a small amount of molecules held caloric in within a given plane allowing for greater escape from within. Count Rumford would later cite this explanation of caloric movement as insufficient to explain the radiation of cold becoming a point of contention for the theory as a whole.
In his first memoir, Augustin-Jean Fresnel responded to a view he extracted from a French translation of Isaac Newtons Optics'. He says that Newton imagined particles of light traversing space uninhibited by the caloric medium filling it, and refutes this view (never actually held by Newton) by saying that a body under illumination would increase indefinitely in heat.
In Marc-Auguste Pictet's famous experiment of 1790, it was reported that a thermometer detected a lower temperature when a set of mirror were used to focus "frigorific rays" from a cold object.
In 1791, Pierre Prevost a colleague of Pictet, introduced the concept of radiative equilibrium, wherein all objects both radiates and absorb heat. When an object is cooler than its surroundings, it absorbs more heat than it emits, causing its temperature to increase until it reaches equilibrium. Even at equilibrium, it continues to radiate heat, balancing absorption and emission.
The discovery of infrared radiation is ascribed to astronomer William Herschel. Herschel published his results in 1800 before the Royal Society of London. Herschel used a prism to refract light from the sun and detected the calorific rays, beyond the red part of the spectrum, as an increase in the temperature recorded on a thermometer in that region. | 0 | Theoretical and Fundamental Chemistry |
For a mixture of two materials with permittivities and with corresponding volume fractions and , D.A.G. Bruggeman proposed a formula of the following form:
Here the positive sign before the square root must be altered to a negative sign in some cases in order to get the correct imaginary part of effective complex permittivity which is related with electromagnetic wave attenuation. The formula is symmetric with respect to swapping the d and m roles. This formula is based on the equality
where is the jump of electric displacement flux all over the integration surface, is the component of microscopic electric field normal to the integration surface, is the local relative complex permittivity which takes the value inside the picked metal particle, the value inside the picked dielectric particle and the value outside the picked particle, is the normal component of the macroscopic electric field. Formula (4) comes out of Maxwells equality . Thus only one picked particle is considered in Bruggemans approach. The interaction with all the other particles is taken into account only in a mean field approximation described by . Formula (3) gives a reasonable resonant curve for plasmon excitations in metal nanoparticles if their size is 10 nm or smaller. However, it is unable to describe the size dependence for the resonant frequency of plasmon excitations that are observed in experiments | 0 | Theoretical and Fundamental Chemistry |
Seventy percent of the worlds supply of ascorbic acid is produced in China. Ascorbic acid is prepared in industry from glucose in a method based on the historical Reichstein process. In the first of a five-step process, glucose is catalytically hydrogenated to sorbitol, which is then oxidized by the microorganism Acetobacter suboxydans' to sorbose. Only one of the six hydroxy groups is oxidized by this enzymatic reaction. From this point, two routes are available. Treatment of the product with acetone in the presence of an acid catalyst converts four of the remaining hydroxyl groups to acetals. The unprotected hydroxyl group is oxidized to the carboxylic acid by reaction with the catalytic oxidant TEMPO (regenerated by sodium hypochlorite bleaching solution). Historically, industrial preparation via the Reichstein process used potassium permanganate as the bleaching solution. Acid-catalyzed hydrolysis of this product performs the dual function of removing the two acetal groups and ring-closing lactonization. This step yields ascorbic acid. Each of the five steps has a yield larger than 90%.
A more biotechnological process, first developed in China in the 1960s, but further developed in the 1990s, bypasses the use of acetone-protecting groups. A second genetically modified microbe species, such as mutant Erwinia, among others, oxidises sorbose into 2-ketogluconic acid (2-KGA), which can then undergo ring-closing lactonization via dehydration. This method is used in the predominant process used by the ascorbic acid industry in China, which supplies 70% of world's ascorbic acid. Researchers are exploring means for one-step fermentation. | 1 | Applied and Interdisciplinary Chemistry |
Leaves are normally extensively vascularized and typically have networks of vascular bundles containing xylem, which supplies water for photosynthesis, and phloem, which transports the sugars produced by photosynthesis. Many leaves are covered in trichomes (small hairs) which have diverse structures and functions. | 0 | Theoretical and Fundamental Chemistry |
Elemental fluorine is highly toxic. Above a concentration of 25 ppm, it causes significant irritation while attacking the eyes, airways and lungs and affecting the liver and kidneys. At a concentration of 100 ppm, human eyes and noses are seriously damaged. People can be exposed to fluorine in the workplace by breathing it in, skin contact, or eye contact. The Occupational Safety and Health Administration (OSHA) has set the legal limit (Permissible exposure limit) for fluorine exposure in the workplace as 0.1 ppm (0.2 mg/m) over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of 0.1 ppm (0.2 mg/m) over an 8-hour workday. At levels of 25 ppm, fluorine is immediately dangerous to life and health. | 1 | Applied and Interdisciplinary Chemistry |
A transversely isotropic material is one with physical properties that are symmetric about an axis that is normal to a plane of isotropy. This transverse plane has infinite planes of symmetry and thus, within this plane, the material properties are the same in all directions. Hence, such materials are also known as "polar anisotropic" materials. In geophysics, vertically transverse isotropy (VTI) is also known as radial anisotropy.
This type of material exhibits hexagonal symmetry (though technically this ceases to be true for tensors of rank 6 and higher), so the number of independent constants in the (fourth-rank) elasticity tensor are reduced to 5 (from a total of 21 independent constants in the case of a fully anisotropic solid). The (second-rank) tensors of electrical resistivity, permeability, etc. have two independent constants. | 0 | Theoretical and Fundamental Chemistry |
In October 2006, the X Prize Foundation, working in collaboration with the J. Craig Venter Science Foundation, established the Archon X Prize for Genomics, intending to award $10 million to "the first team that can build a device and use it to sequence 100 human genomes within 10 days or less, with an accuracy of no more than one error in every 1,000,000 bases sequenced, with sequences accurately covering at least 98% of the genome, and at a recurring cost of no more than $1,000 per genome". The Archon X Prize for Genomics was cancelled in 2013, before its official start date. | 1 | Applied and Interdisciplinary Chemistry |
A disproportionation reaction is one in which a single substance is both oxidized and reduced. For example, thiosulfate ion with sulfur in oxidation state +2 can react in the presence of acid to form elemental sulfur (oxidation state 0) and sulfur dioxide (oxidation state +4).
Thus one sulfur atom is reduced from +2 to 0, while the other is oxidized from +2 to +4. | 0 | Theoretical and Fundamental Chemistry |
Deuterium-depleted water has a lower concentration of deuterium (H) than occurs in nature at sea level. Deuterium is a naturally-occurring, stable (non-radioactive) isotope of hydrogen with a nucleus consisting of one proton and one neutron. The nucleus of ordinary hydrogen (protium) consists of one proton only, and no neutron. Deuterium atoms have about twice the atomic mass of normal hydrogen atoms as a result. Heavy water consists of water molecules with two deuterium atoms instead of the two normal hydrogen atoms. The hydrogen in normal water consists of about 99.98% (by weight) of normal hydrogen (H).
The production of heavy water involves isolating and removing deuterium-containing isotopologues within natural water. The by-product of this process is deuterium-depleted water.
Due to the heterogeneity of hydrological conditions, the isotopic composition of natural water varies around the Earth. Distance from the ocean and the equator and the height above sea level have a positive correlation with water deuterium depletion.
In Vienna Standard Mean Ocean Water (VSMOW) that defines the isotopic composition of the ocean water, deuterium occurs at a concentration of 155.76 ppm. For the SLAP (Standard Light Antarctic Precipitation) standard that determines the isotopic composition of natural water from the Antarctic, the concentration of deuterium is 89.02 ppm.
Snow water, especially from glacial mountain meltwater, is significantly lighter than ocean water. Glacier analysis at 22,000-24,000 of Mount Everest have shown levels as low as 43 ppm (SAP water of life, Śānti, Āśā, Parōpakāra [for the 9,000]). The weight quantities of isotopologues in natural water are calculated on the basis of the data collected using molecular spectroscopy:
According to the table above, the weight concentration of heavy isotopologues in natural water can reach 2.97 g/kg, which is mostly due to HO, i.e. water with light hydrogen and heavy oxygen. Furthermore, there are about 300 milligrams of deuterium-containing isotopologues in each liter of water. This presents a significant value comparable, for example, with the content of mineral salts. | 0 | Theoretical and Fundamental Chemistry |
This semiregular tiling is a member of a sequence of snubbed polyhedra and tilings with vertex figure (3.3.3.3.n) and Coxeter–Dynkin diagram . These figures and their duals have (n32) rotational symmetry, being in the Euclidean plane for n=6, and hyperbolic plane for any higher n. The series can be considered to begin with n=2, with one set of faces degenerated into digons.
From a Wythoff construction there are eight hyperbolic uniform tilings that can be based from the regular heptagonal tiling.
Drawing the tiles colored as red on the original faces, yellow at the original vertices, and blue along the original edges, there are 8 forms. | 0 | Theoretical and Fundamental Chemistry |
Functional MRI (fMRI) has been the modality of choice to visualize brain activity, and takes advantages of a range of techniques that can be used to interpret it. However, the signal that fMRI is acquiring is BOLD signal, which does not directly correlate with blood flow. Cerebral blood flow on the other hand does, allowing for cardiovascular disease (CVD) and inflammatory risk factor analysis, and disorders (such as schizophrenia and bipolar disorder) that have comorbid effects with CVD. ASL imaging can be a useful tool to complement fMRI and vice versa. | 0 | Theoretical and Fundamental Chemistry |
Electrothermal AAS (ET AAS) using graphite tube atomizers was pioneered by Boris V. L’vov at the Saint Petersburg Polytechnical Institute, Russia, since the late 1950s, and investigated in parallel by Hans Massmann at the Institute of Spectrochemistry and Applied Spectroscopy (ISAS) in Dortmund, Germany.
Although a wide variety of graphite tube designs have been used over the years, the dimensions nowadays are typically 20–25 mm in length and 5–6 mm inner diameter. With this technique liquid/dissolved, solid and gaseous samples may be analyzed directly. A measured volume (typically 10–50 μL) or a weighed mass (typically around 1 mg) of a solid sample are introduced into the graphite tube and subject to a temperature program. This typically consists of stages, such as drying – the solvent is evaporated; pyrolysis – the majority of the matrix constituents are removed; atomization – the analyte element is released to the gaseous phase; and cleaning – eventual residues in the graphite tube are removed at high temperature.
The graphite tubes are heated via their ohmic resistance using a low-voltage high-current power supply; the temperature in the individual stages can be controlled very closely, and temperature ramps between the individual stages facilitate separation of sample components. Tubes may be heated transversely or longitudinally, where the former ones have the advantage of a more homogeneous temperature distribution over their length. The so-called stabilized temperature platform furnace (STPF) concept, proposed by Walter Slavin, based on research of Boris L’vov, makes ET AAS essentially free from interference. The major components of this concept are atomization of the sample from a graphite platform inserted into the graphite tube (L’vov platform) instead of from the tube wall in order to delay atomization until the gas phase in the atomizer has reached a stable temperature; use of a chemical modifier in order to stabilize the analyte to a pyrolysis temperature that is sufficient to remove the majority of the matrix components; and integration of the absorbance over the time of the transient absorption signal instead of using peak height absorbance for quantification.
In ET AAS a transient signal is generated, the area of which is directly proportional to the mass of analyte (not its concentration) introduced into the graphite tube. This technique has the advantage that any kind of sample, solid, liquid or gaseous, can be analyzed directly. Its sensitivity is 2–3 orders of magnitude higher than that of flame AAS, so that determinations in the low μg L range (for a typical sample volume of 20 μL) and ng g range (for a typical sample mass of 1 mg) can be carried out. It shows a very high degree of freedom from interferences, so that ET AAS might be considered the most robust technique available nowadays for the determination of trace elements in complex matrices. | 0 | Theoretical and Fundamental Chemistry |
It is easy to verify that for an ideal gas defined by suitable microscopic postulates that αT = 1, so the temperature change of such an ideal gas at a Joule–Thomson expansion is zero.
For such an ideal gas, this theoretical result implies that:
:The internal energy of a fixed mass of an ideal gas depends only on its temperature (not pressure or volume).
This rule was originally found by Joule experimentally for real gases and is known as Joule's second law. More refined experiments found important deviations from it. | 0 | Theoretical and Fundamental Chemistry |
Hexafluoroethane's solid phase has two polymorphs. In the scientific literature, different phase transition temperatures have been stated. The latest works assign it at 103 K (−170 °C). Below 103 K it has a slightly disordered structure, and over the transition point, it has a body centered cubic structure. The critical point is at 19.89 °C (293.04 K) and 30.39 bar.
Table of densities:
Vapor density is 4.823 (air = 1), specific gravity at 21 °C is 4.773 (air = 1) and specific volume at 21 °C is 0.1748 m/kg. | 1 | Applied and Interdisciplinary Chemistry |
The most common adverse effects of Captopril, skin rash and loss of taste, are the same as caused by mercapto-containing penicillamine. Therefore, a group of researchers aimed at finding potent, selective ACE inhibitors that would not contain a mercapto (SH) function and would have a weaker chelating function. They returned to work with carboxyl compounds and started working with substituted N-carboxymethyl-dipeptides as a general structure (R-CHCOOH-A-A). According to previous research they assumed that cyclic imino acids would result in good potency if substituted on the carboxyl terminus of the dipeptide. Therefore, substituting A with proline gave good results. They also noted that according to the enzymes specificity imino acids in the position next to the carboxyl terminus would not give a potent compound. By substituting R and A groups with hydrophobic and basic residues would give a potent compound. By substituting –NH in the general structure resulted in loss of potency which is consistent to the enzymes need for a –NH in corresponding position on the substrates. The results were 2 active inhibitors: Enalaprilat and Lisinopril. These compounds both have phenylalanine in R position which occupies the S groove in the enzyme. The result was thus these two new, potent tripeptide analogues with zinc-coordinating carboxyl group: Enalaprilat and Lisinopril. | 1 | Applied and Interdisciplinary Chemistry |
Eilaf Egap (née Ahmed) is an adjunct assistant professor of Materials Science at Rice University. She works on imaging techniques and biomaterials for early diagnostics and drug delivery. She was a Massachusetts Institute of Technology MLK Visiting Scholar in 2011. | 0 | Theoretical and Fundamental Chemistry |
Missions after 2010 requiring RTGs will instead use the multi-mission radioisotope thermoelectric generator (MMRTG) containing lead telluride (PbTe) thermocouples and Pu-238 dioxide for spacecraft power applications. | 0 | Theoretical and Fundamental Chemistry |
A few advantages of ATM over other related microspectroscopy techniques include the orientation of the THz electric field at the sample and the ability to readily measure materials that are sensitive to environmental conditions like hydration, cryo-cooling, and evacuation. | 0 | Theoretical and Fundamental Chemistry |
Kurt Wüthrich (born 4 October 1938 in Aarberg, Canton of Bern) is a Swiss chemist/biophysicist and Nobel Chemistry laureate, known for developing nuclear magnetic resonance (NMR) methods for studying biological macromolecules. | 0 | Theoretical and Fundamental Chemistry |
Oligosaccharides that participate in O-linked glycosylation are attached to threonine or serine on the hydroxyl group of the side chain. O-linked glycosylation occurs in the Golgi apparatus, where monosaccharide units are added to a complete polypeptide chain. Cell surface proteins and extracellular proteins are O-glycosylated. Glycosylation sites in O-linked oligosaccharides are determined by the secondary and tertiary structures of the polypeptide, which dictate where glycosyltransferases will add sugars. | 0 | Theoretical and Fundamental Chemistry |
Returning to his native Korea, he began studies of the staple Korean diet and its effects on metabolism as a research assistant at Kyŏngsŏng Medical College in February 1928. He was appointed an instructor of physiology in the department of biochemistry of Severance Union Medical College (now Yonsei University College of Medicine) and an adjunct instructor of dietetics at Ewha Womans University College of Medicine.
In 1932, Suksin Lee was the first Korean to earn a Ph.D. in biochemistry for his thesis, A Study on the Eating Habits of Koreans, presented to Kyoto Imperial University on the nutrition and metabolism of prisoners in Korea. Among his advisers at the time was Professor Sato of Keijo Imperial University.
He was then appointed full-time professor of biochemistry in 1933 at Severance Union Medical College, the first Korean to hold such a position. He continued to lead the department, later serving as Severance's Dean of Student Affairs, until his death aged approximately 47 of a cerebral hemorrhage on 12 December 1944. | 1 | Applied and Interdisciplinary Chemistry |
pH is defined in terms of the activity of the hydrogen ion
:pH = −log {H}
In the approximation of ideal behaviour, activity is replaced by concentration. pH is measured by means of a glass electrode, a mixed equilibrium constant, also known as a Brønsted constant, may result.
:HL L + H;
It all depends on whether the electrode is calibrated by reference to solutions of known activity or known concentration. In the latter case the equilibrium constant would be a concentration quotient. If the electrode is calibrated in terms of known hydrogen ion concentrations it would be better to write p[H] rather than pH, but this suggestion is not generally adopted. | 0 | Theoretical and Fundamental Chemistry |
*Significant improvement of resolution in data collection
*Reduced or eliminated radiation damage in crystals | 0 | Theoretical and Fundamental Chemistry |
The standard established for carbon-13 work was the Pee Dee Belemnite (PDB) and was based on a Cretaceous marine fossil, Belemnitella americana, which was from the Peedee Formation in South Carolina. This material had an anomalously high C:C ratio (0.0112372), and was established as δC value of zero. Since the original PDB specimen is no longer available, its C:C ratio can be back-calculated from a widely measured carbonate standard NBS-19, which has a δC value of +1.95‰. The C:C ratio of NBS-19 was reported as . Therefore, one could calculate the C:C ratio of PDB derived from NBS-19 as . Note that this value differs from the widely used PDB C:C ratio of 0.0112372 used in isotope forensics and environmental scientists; this discrepancy was previously attributed by a wikipedia author to a sign error in the interconversion between standards, but no citation was provided. Use of the PDB standard gives most natural material a negative δC. A material with a ratio of 0.010743 for example would have a δC value of −44‰ from . The standards are used for verifying the accuracy of mass spectroscopy; as isotope studies became more common, the demand for the standard exhausted the supply. Other standards calibrated to the same ratio, including one known as VPDB (for "Vienna PDB"), have replaced the original.
The C:C ratio for VPDB, which the International Atomic Energy Agency (IAEA) defines as δC value of zero is 0.01123720. | 0 | Theoretical and Fundamental Chemistry |
Frank Erhart Emmanuel Germann (December 6, 1887 – February 27, 1974) was an American physicist, physical chemist, and university professor. He was a founding member of the modern chemistry department of the University of Colorado. | 0 | Theoretical and Fundamental Chemistry |
Nonclassical describes those carbonyl complexes where ν is higher than that for free carbon monoxide. In nonclassical CO complexes, the C-O distance is shorter than free CO (113.7 pm). The structure of [Fe(CO)], with d = 112.9 pm, illustrates this effect. These complexes are usually cationic, sometimes dicationic. | 0 | Theoretical and Fundamental Chemistry |
The Flettner rotor inspired Sigurd Johannes Savonius to invent a spinning ventilation device after a collaboration between the two inventors. Anton Flettners company Flettner Ventilator Limited acquired Savonius patent and still sells them in the United Kingdom. The devices are often referred to as "Flettner ventilators" even though the mechanism more closely resembles a Savonius wind turbine, which was a 1924 invention that resulted from the same collaboration. | 1 | Applied and Interdisciplinary Chemistry |
Before a PSD can be determined, it is vital that a representative sample is obtained. In the case where the material to be analysed is flowing, the sample must be withdrawn from the stream in such a way that the sample has the same proportions of particle sizes as the stream. The best way to do this is to take many samples of the whole stream over a period, instead of taking a portion of the stream for the whole time. In the case where the material is in a heap, scoop or thief sampling needs to be done, which is inaccurate: the sample should ideally have been taken while the powder was flowing towards the heap. After sampling, the sample volume typically needs to be reduced. The material to be analysed must be carefully blended, and the sample withdrawn using techniques that avoid size segregation, for example using a rotary divider. Particular attention must be paid to avoidance of loss of fines during manipulation of the sample. | 0 | Theoretical and Fundamental Chemistry |
A known result of cytosine methylation is the increase of C-to-T transition mutations through the process of deamination. Cytosine deamination can alter the genome's many regulatory functions; previously silenced transposable elements (TEs) may become transcriptionally active due to the loss of CPG sites. TEs have been proposed to accelerate the mechanism of enhancer creation by providing extra DNA that is compatible with the host transcription factors that eventually have an impact on C-to-T mutations. | 1 | Applied and Interdisciplinary Chemistry |
To fully understand the interaction of an incident beam of nuclei with a crystalline structure, it is necessary to comprehend two more key concepts: blocking and channeling.
When a beam of ions with parallel trajectories is incident on a target atom, scattering off that atom will prevent collisions in a cone-shaped region "behind" the target relative to the beam. This occurs because the repulsive potential of the target atom bends close ion trajectories away from their original path, and is referred to as blocking. The radius of this blocked region, at a distance L from the original atom, is given by
When an ion is scattered from deep inside a sample, it can then re-scatter off a second atom, creating a second blocked cone in the direction of the scattered trajectory. This can be detected by carefully varying the detection angle relative to the incident angle.
Channeling is observed when the incident beam is aligned with a major symmetry axis of the crystal. Incident nuclei which avoid collisions with surface atoms are excluded from collisions with all atoms deeper in the sample, due to blocking by the first layer of atoms. When the interatomic distance is large compared to the radius of the blocked cone, the incident ions can penetrate many times the interatomic distance without being backscattered. This can result in a drastic reduction of the observed backscattered signal when the incident beam is oriented along one of the symmetry directions, allowing determination of a sample's regular crystal structure. Channeling works best for very small blocking radii, i.e. for high-energy, low-atomic-number incident ions such as He.
The tolerance for the deviation of the ion beam angle of incidence relative to the symmetry direction depends on the blocking radius, making the allowable deviation angle proportional to
While the intensity of an RBS peak is observed to decrease across most of its width when the beam is channeled, a narrow peak at the high-energy end of larger peak will often be observed, representing surface scattering from the first layer of atoms. The presence of this peak opens the possibility of surface sensitivity for RBS measurements. | 0 | Theoretical and Fundamental Chemistry |
An aerosol is a suspension of fine solid particles or liquid droplets in air or another gas. Aerosols can be generated from natural or human causes. The term aerosol commonly refers to the mixture of particulates in air, and not to the particulate matter alone. Examples of natural aerosols are fog, mist or dust. Examples of human caused aerosols include particulate air pollutants, mist from the discharge at hydroelectric dams, irrigation mist, perfume from atomizers, smoke, dust, sprayed pesticides, and medical treatments for respiratory illnesses.
The liquid or solid particles in an aerosol have diameters typically less than 1 μm. Larger particles with a significant settling speed make the mixture a suspension, but the distinction is not clear. In everyday language, aerosol often refers to a dispensing system that delivers a consumer product from a spray can.
Diseases can spread by means of small droplets in the breath, sometimes called bioaerosols. | 0 | Theoretical and Fundamental Chemistry |
Thermal mass is ideally placed within the building and situated where it still can be exposed to low-angle winter sunlight (via windows) but insulated from heat loss. In summer the same thermal mass should be obscured from higher-angle summer sunlight in order to prevent overheating of the structure.
The thermal mass is warmed passively by the sun or additionally by internal heating systems during the day. Thermal energy stored in the mass is then released back into the interior during the night. It is essential that it be used in conjunction with the standard principles of passive solar design.
Any form of thermal mass can be used. A concrete slab foundation either left exposed or covered with conductive materials, e.g. tiles, is one easy solution. Another novel method is to place the masonry facade of a timber-framed house on the inside (reverse-brick veneer). Thermal mass in this situation is best applied over a large area rather than in large volumes or thicknesses. 7.5–10 cm (3″–4″) is often adequate.
Since the most important source of thermal energy is the Sun, the ratio of glazing to thermal mass is an important factor to consider. Various formulas have been devised to determine this. As a general rule, additional solar-exposed thermal mass needs to be applied in a ratio from 6:1 to 8:1 for any area of sun-facing (north-facing in Southern Hemisphere or south-facing in Northern Hemisphere) glazing above 7% of the total floor area. For example, a 200 m house with 20 m of sun-facing glazing has 10% of glazing by total floor area; 6 m of that glazing will require additional thermal mass. Therefore, using the 6:1 to 8:1 ratio above, an additional 36–48 m of solar-exposed thermal mass is required. The exact requirements vary from climate to climate. | 0 | Theoretical and Fundamental Chemistry |
Globo H's biosynthetic pathway is involved in the synthesis pathways of other globo-series glycosphingolipid antigens that are also specific to cancer cells, including stage-specific embryonic antigen-3 (SSEA3) and stage-specific embryonic antigen-4 (SSEA4). The biosynthetic pathway of these antigens includes the enzyme β 1,3-galactosyltransferase V (β3GalT5). β3GalT5 catalyzes the galactosylation of globoside-4 (Gb4) to SSEA3. SSEA3 can then be converted to SSEA4 by sialyltransferase adding a sialic acid group to its end, or it can be converted to Globo H by fucosyltransferase adding a fucose ring to its end. Playing a part in the formation of three different cancer-specific antigens, β3GalT5 is of particular interest in its relevance to cancer treatment, and it has been shown to be critical for cancer cell survival. | 1 | Applied and Interdisciplinary Chemistry |
The effect of UCP2 and UCP3 on ATP concentrations varies depending on cell type. For example, pancreatic beta cells experience a decrease in ATP concentration with increased activity of UCP2. This is associated with cell degeneration, decreased insulin secretion, and type II diabetes. Conversely, UCP2 in hippocampus cells and UCP3 in muscle cells stimulate production of mitochondria. The larger number of mitochondria increases the combined concentration of ADP and ATP, actually resulting in a net increase in ATP concentration when these uncoupling proteins become coupled (i.e. the mechanism to allow proton leaking is inhibited). | 1 | Applied and Interdisciplinary Chemistry |
In nickel-based superalloys, regions of NiAl (called γ' phase) precipitate out of the nickel-rich matrix (called γ phase) to give high strength and creep resistance. Many alloy formulations are available and they usually include other elements, such as chromium, molybdenum, and iron, in order to improve various properties. | 1 | Applied and Interdisciplinary Chemistry |
The mass number (symbol A, from the German word: Atomgewicht, "atomic weight"), also called atomic mass number or nucleon number, is the total number of protons and neutrons (together known as nucleons) in an atomic nucleus. It is approximately equal to the atomic (also known as isotopic) mass of the atom expressed in atomic mass units. Since protons and neutrons are both baryons, the mass number A is identical with the baryon number B of the nucleus (and also of the whole atom or ion). The mass number is different for each isotope of a given chemical element, and the difference between the mass number and the atomic number Z gives the number of neutrons (N) in the nucleus: .
The mass number is written either after the element name or as a superscript to the left of an elements symbol. For example, the most common isotope of carbon is carbon-12, or , which has 6 protons and 6 neutrons. The full isotope symbol would also have the atomic number (Z') as a subscript to the left of the element symbol directly below the mass number: . | 0 | Theoretical and Fundamental Chemistry |
A point mutation is a genetic mutation where a single nucleotide base is changed, inserted or deleted from a DNA or RNA sequence of an organism's genome. Point mutations have a variety of effects on the downstream protein product—consequences that are moderately predictable based upon the specifics of the mutation. These consequences can range from no effect (e.g. synonymous mutations) to deleterious effects (e.g. frameshift mutations), with regard to protein production, composition, and function. | 1 | Applied and Interdisciplinary Chemistry |
Autopharmacology relates to the scientific study of the regulation of body functions by the activity of its naturally existent (or endogenous) chemical factors of the tissues. A more restricted definition would consider substances that were first identified as external agents which had a documented action on physiological functions, but later were discovered as existing as endogenous factors. The best example is the class of endorphins, which, as its name implies, were discovered to exist in the brain and have specific receptors in it, by investigations on the mechanism of action of opioids, such as morphine.
Historically, the first approach to the concept of autopharmacology began with British physiologist and pharmacologist Henry Dale in the 1910s, discovered the role of acetylcholine in synaptic transmission, and later proved by Austrian physiologist Otto Loewi, to be the neurotransmitter involved in the proximal synapses of the autonomic nervous system (initially named Vagusstoff by Loewi, and later identified as acetylcholine). The same happened to another autonomic neurotransmitter, noradrenaline (Akzeleransstoff by Loewi), which later proved to be chemically similar to a long used pharmacological agent, adrenaline, a hormone secreted by the adrenal glands. Both scientists were awarded the 1936 Nobel Prize for Physiology or Medicine for their pioneering and important contributions.
A research area where autopharmacology principles assumed great importance was that of pain and inflammation, due to the great number of endogenous messengers, transmitters and modulators involved in their complex response at molecular and cellular level. The control and regulation mechanisms of the circulatory system and renal functions and their interactions (such as the renin/angiotensin system) are also greatly influenced by autopharmacological agents; One of the autopharmacology pioneers was Professor Mauricio Rocha e Silva, leader of the team of Brazilian researchers who discovered bradykinin in 1948, an endogenous substance involved in hypotension in circulatory shock. Of course, all these systems are of extreme importance for clinical practice and for the discovery of new therapeutic drugs.
Endogenous substances that could fall under the concept of autopharmacology are:
* Endorphins
* Dynorphin
* Bradykinin
* Prostaglandins
* Angiotensin
* Secretin
* Gastrin
* Cholecystokinin
* Histamine
* Cannabinoids
* Substance P
The main scientific criterion for an autopharmacological agent is the discovery of specific membrane receptors for it and, hopefully, its transduction and cell signaling mechanisms.
The term was never much of a mainstream concept, and has fallen into disuse, as research on basic mechanisms has advanced. In a [https://www.ncbi.nlm.nih.gov/pubmed?term=autopharmacology recent literature search] on PubMed, only six titles refer to the term autopharmacology. | 1 | Applied and Interdisciplinary Chemistry |
The histone tail extensions constitute up to 30% by mass of histones, but are not visible in the crystal structures of nucleosomes due to their high intrinsic flexibility, and have been thought to be largely unstructured. The N-terminal tails of histones H3 and H2B pass through a channel formed by the minor grooves of the two DNA strands, protruding from the DNA every 20 bp. The N-terminal tail of histone H4, on the other hand, has a region of highly basic amino acids (16-25), which, in the crystal structure, forms an interaction with the highly acidic surface region of a H2A-H2B dimer of another nucleosome, being potentially relevant for the higher-order structure of nucleosomes. This interaction is thought to occur under physiological conditions also, and suggests that acetylation of the H4 tail distorts the higher-order structure of chromatin. | 1 | Applied and Interdisciplinary Chemistry |
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