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* 1945–1946 – Nikolay Bogoliubov develops a general method for a microscopic derivation of kinetic equations for classical statistical systems using BBGKY hierarchy
* 1947 – Nikolay Bogoliubov and Kirill Gurov extend this method for a microscopic derivation of kinetic equations for quantum statistical systems
* 1948 – Claude Elwood Shannon establishes information theory
* 1957 – Aleksandr Solomonovich Kompaneets derives his Compton scattering Fokker–Planck equation
* 1957 – Ryogo Kubo derives the first of the Green-Kubo relations for linear transport coefficients
* 1957 – Edwin T. Jaynes publishes two papers detailing the MaxEnt interpretation of thermodynamics from information theory
* 1960–1965 – Dmitry Zubarev develops the method of non-equilibrium statistical operator, which becomes a classical tool in the statistical theory of non-equilibrium processes
* 1972 – Jacob Bekenstein suggests that black holes have an entropy proportional to their surface area
* 1974 – Stephen Hawking predicts that black holes will radiate particles with a black-body spectrum which can cause black hole evaporation
*1977 – Ilya Prigogine wins the Nobel prize for his work on dissipative structures in thermodynamic systems far from equilibrium. The importation and dissipation of energy could reverse the 2nd law of thermodynamics | 0 | Theoretical and Fundamental Chemistry |
The Oligomer Restriction technique was developed as a variation of the Restriction Fragment Length Polymorphism (RFLP) assay method, with the hope of avoiding the laborious Southern blotting step used in RFLP analysis. OR was conceived by Randall Saiki and Henry Erlich in the early 1980s, working at Cetus Corporation in Emeryville, California. It was patented in 1984 and published in 1985, having been applied to the genomic mutation responsible for Sickle Cell Anemia. OR was soon replaced by the more general technique of Allele Specific Oligonucleotide (ASO) probes. | 1 | Applied and Interdisciplinary Chemistry |
Liu Yunbin () (1925 – 21 November 1967) was a Chinese nuclear chemist and the son of former President of the People's Republic of China Liu Shaoqi. | 0 | Theoretical and Fundamental Chemistry |
Testosterone sulfate is an endogenous, naturally occurring steroid and minor urinary metabolite of testosterone. | 1 | Applied and Interdisciplinary Chemistry |
At birth, infants don't develop enough ability to conjugate bilirubin. Up to 8% to 11% neonates will develop hyperbilirubinemia in the first week of their lives. | 1 | Applied and Interdisciplinary Chemistry |
Butyric acid was first observed in an impure form in 1814 by the French chemist Michel Eugène Chevreul. By 1818, he had purified it sufficiently to characterize it. However, Chevreul did not publish his early research on butyric acid; instead, he deposited his findings in manuscript form with the secretary of the Academy of Sciences in Paris, France. Henri Braconnot, a French chemist, was also researching the composition of butter and was publishing his findings and this led to disputes about priority. As early as 1815, Chevreul claimed that he had found the substance responsible for the smell of butter. By 1817, he published some of his findings regarding the properties of butyric acid and named it. However, it was not until 1823 that he presented the properties of butyric acid in detail. The name butyric acid comes from , meaning "butter", the substance in which it was first found. The Latin name butyrum (or buturum) is similar. | 1 | Applied and Interdisciplinary Chemistry |
Jelly-falls are primarily made up of the decaying corpses of Cnidaria and Thaliacea (Pyrosomida, Doliolida, and Salpida). Several circumstances can trigger the death of gelatinous organisms which would cause them to sink. These include high levels of primary production that can clog the feeding apparatuses of the organisms, a sudden temperature change, when an old bloom runs out of food, when predators damage the bodies of the jellies, and parasitism. In general, however, jelly-falls are linked to jelly-blooms and primary production, with over 75% of the jelly falls in subpolar and temperate regions occurring after spring blooms, and over 25% of the jelly-falls in the tropics occurring after upwelling events.
With global climates shifting towards creating warmer and more acidic oceans, conditions not favored by non-resilient species, jellies are likely to grow in population sizes. Eutrophic areas and dead zones can become jelly hot spots with substantial blooms. As the climate changes and ocean waters warm, jelly blooms become more prolific and the transport of jelly-carbon to the lower ocean increases. With a possible slowing of the classic biological pump, the transport of carbon and nutrients to the deep sea through jelly-falls may become more and more important to deep ocean. | 0 | Theoretical and Fundamental Chemistry |
The rivers inter-linking feasibility reports completed by 2013, suggest the following investment needs and potential economic impact:
The cost conversion in US $ is at latest conversion price on the historical cost estimates in Indian rupees | 1 | Applied and Interdisciplinary Chemistry |
Carbon isotopes aid us in determining the primary production source responsible for the energy flow in an ecosystem. The transfer of C through trophic levels remains relatively the same, except for a small increase (an enrichment C between animals indicate that they have different food sources or that their food webs are based on different primary producers (i.e. different species of phytoplankton, marsh grasses.) Because δC indicates the original source of primary producers, the isotopes can also help us determine shifts in diets, both short term, long term or permanent. These shifts may even correlate to seasonal changes, reflecting phytoplankton abundance. Scientists have found that there can be wide ranges of δC values in phytoplankton populations over a geographic region. While it is not quite certain as to why this may be, there are several hypotheses for this occurrence. These include isotopes within dissolved inorganic carbon pools (DIC) may vary with temperature and location and that growth rates of phytoplankton may affect their uptake of the isotopes. δC has been used in determining migration of juvenile animals from sheltered inshore areas to offshore locations by examining the changes in their diets. A study by Fry (1983) studied the isotopic compositions in juvenile shrimp of south Texas grass flats. Fry found that at the beginning of the study the shrimp had isotopic values of δC = -11 to -14‰ and 6-8‰ for δN and δS. As the shrimp matured and migrated offshore, the isotopic values changed to those resembling offshore organisms (δC= -15‰ and δN = 11.5‰ and δS = 16‰). | 0 | Theoretical and Fundamental Chemistry |
Lineatin was first isolated in 1977 by MacConnell. The absolute configuration of the biologically active form was later determined as (+)-(1R,4S,5R,7R)-3,3,7-trimethyl-2,9- dioxatricyclo[3.3.1.0]nonane, whereas other enatinomers process no biological attraction activity. | 0 | Theoretical and Fundamental Chemistry |
As more electrons are added to a 5n cluster, the number of electrons per vertex approaches 6. Instead of adopting structures based on 4n or 5n rules, the clusters tend to have structures governed by the 6n rules, which are based on rings. The rules for the 6n structures are as follows.
Example: S
:Electron count = 8 × S = 8 × 6 = 48 electrons.
:Since n = 8, 6n = 48, so the cluster is an 8-membered ring.
Hexane (CH)
:Electron count = 6 × C + 14 × H = 6 × 4 + 14 × 1 = 38
:Since n = 6, 6n = 36 and 6n + 2 = 38, so the cluster is a 6-membered chain. | 0 | Theoretical and Fundamental Chemistry |
Besides imaging, AFM can be used for force spectroscopy, the direct measurement of tip-sample interaction forces as a function of the gap between the tip and sample. The result of this measurement is called a force-distance curve. For this method, the AFM tip is extended towards and retracted from the surface as the deflection of the cantilever is monitored as a function of piezoelectric displacement. These measurements have been used to measure nanoscale contacts, atomic bonding, Van der Waals forces, and Casimir forces, dissolution forces in liquids and single molecule stretching and rupture forces. AFM has also been used to measure, in an aqueous environment, the dispersion force due to polymer adsorbed on the substrate. Forces of the order of a few piconewtons can now be routinely measured with a vertical distance resolution of better than 0.1 nanometers. Force spectroscopy can be performed with either static or dynamic modes. In dynamic modes, information about the cantilever vibration is monitored in addition to the static deflection.
Problems with the technique include no direct measurement of the tip-sample separation and the common need for low-stiffness cantilevers, which tend to "snap" to the surface. These problems are not insurmountable. An AFM that directly measures the tip-sample separation has been developed. The snap-in can be reduced by measuring in liquids or by using stiffer cantilevers, but in the latter case a more sensitive deflection sensor is needed. By applying a small dither to the tip, the stiffness (force gradient) of the bond can be measured as well. | 0 | Theoretical and Fundamental Chemistry |
Upon job specification, the material may be chosen. Material range from nickel-plated brass to aluminum, and even steel and stainless steel. Depending on the level of loads, humidity, temperature, and stroke lengths specified, the appropriate material may be selected. | 1 | Applied and Interdisciplinary Chemistry |
A mill test report (MTR) and often also called a certified mill test report, certified material test report, mill test certificate (MTC), inspection certificate, certificate of test, or a host of other names, is a quality assurance document used in the metals industry that certifies a material's chemical and physical properties and states a product made of metal (steel, aluminum, brass or other alloys) complies with an international standards organization (such as ANSI, ASME, etc.) specific standards.
Mill here refers to an industry which manufactures and processes raw materials. | 1 | Applied and Interdisciplinary Chemistry |
In surface science, selective adsorption is the effect when minima associated with bound-state resonances occur in specular intensity in atom-surface scattering.
In crystal growth, selective adsorption refers to the phenomenon where adsorbing molecules attach preferentially to certain crystal faces.
An example of selective adsorption can be demonstrated in the growth of Rochelle salt crystals. If copper ions are added to solution during the growth process, some crystal faces will slow down as copper apparently becomes a barrier to adsorption. However, by then adding sodium hydroxide to the solution, the preferred crystal faces will change once again. | 0 | Theoretical and Fundamental Chemistry |
At a temperature below the boiling point, any matter in liquid form will evaporate until reaching equilibrium with the reverse process of condensation of its vapor. At this point the vapor will condense at the same rate as the liquid evaporates. Thus, a liquid cannot exist permanently if the evaporated liquid is continually removed. A liquid at or above its boiling point will normally boil, though superheating can prevent this in certain circumstances.
At a temperature below the freezing point, a liquid will tend to crystallize, changing to its solid form. Unlike the transition to gas, there is no equilibrium at this transition under constant pressure, so unless supercooling occurs, the liquid will eventually completely crystallize. However, this is only true under constant pressure, so that (for example) water and ice in a closed, strong container might reach an equilibrium where both phases coexist. For the opposite transition from solid to liquid, see melting. | 0 | Theoretical and Fundamental Chemistry |
Directing a synthesis toward a desirable intermediate can greatly narrow the focus of analysis. This allows bidirectional search techniques. | 0 | Theoretical and Fundamental Chemistry |
He was born in Durban, South Africa, although his parents returned to England soon afterwards. He was educated at Thetford Grammar School and Ipswich School and went on to study chemistry at Lincoln College, Oxford, gaining a doctorate at the university's Engineering Laboratory. | 0 | Theoretical and Fundamental Chemistry |
The velocity potential of a point source or sink of strength ( for source and for sink) in spherical polar coordinates is given by
where in fact is the volume flux across a closed surface enclosing the source or sink. The velocity field in spherical polar coordinates are | 1 | Applied and Interdisciplinary Chemistry |
The equivalence of the two formulations can also be seen by a simple parity argument without appeal to case analysis.
Proposition. The following formulations of the Woodward–Hoffmann rules are equivalent:
(A) For a pericyclic reaction, if the sum of the number of suprafacial 4q + 2 components and antarafacial 4r components is odd then it is thermally allowed; otherwise the reaction is thermally forbidden.
(B) For a pericyclic reaction, if the total number of antarafacial components of a (4n + 2)-electron reaction is even or the total number of antarafacial components of a 4n-electron reaction is odd then it is thermally allowed; otherwise the reaction is thermally forbidden.
Proof of equivalence: Index the components of a k-component pericyclic reaction and assign component i with Woodward-Hoffmann symbol N the electron count and topology parity symbol according to the following rules:<blockquote><math>n_i = \begin{cases} 0, & N\equiv 0\ (\mathrm{mod}\ 4)\\ 1, & N\equiv 2\ (\mathrm{mod}\ 4) \end{cases}\quad\mathrm{and}\quad
p_i = \begin{cases} 0, & i\text{ is supra}\\ 1, & i\text{ is antara} \end{cases}.We have a mathematically equivalent restatement of (A):
(A) A collection of symbols is thermally allowed if and only if the number of symbols with the property is odd.'
Since the total electron count is 4n + 2 or 4n precisely when (the number of (4q + 2)-electron components) is odd or even, respectively, while gives the number of antarafacial components, we can also restate (B):
(B) A collection of symbols is thermally allowed if and only if exactly one of or is odd.'
It suffices to show that (A) and (B) are equivalent. Exactly one of or is odd if and only if is odd. If , holds; hence, omission of symbols with the property from a collection will not change the parity of . On the other hand, when , we have , but simply enumerates the number of components with the property . Therefore, <blockquote><math>\sum_i n_i+p_i\equiv\sum_{n_i\neq p_i} n_i+p_i=
\sum_{n_i\neq p_i} 1=\#\{(n_i,p_i,i)\ |\ n_i\neq p_i\}\
(\mathrm{mod}\ 2)Thus, and the number of symbols in a collection with the property have the same parity. Since formulations (A) and (B) are equivalent, so are (A) and (B), as claimed.
To give a concrete example, a hypothetical reaction with the descriptor [6 + 4 + 2] would be assigned the collection {(1, 0, 1), (0, 1, 2), (1, 1, 3)} in the scheme above. There are two components, (1, 0, 1) and (0, 1, 2), with the property , so the reaction is not allowed by (A). Likewise, and are both even, so (B) yields the same conclusion (as it must): the reaction is not allowed. | 0 | Theoretical and Fundamental Chemistry |
Vanillin is most prominent as the principal flavor and aroma compound in vanilla. Cured vanilla pods contain about 2% by dry weight vanillin. On cured pods of high quality, relatively pure vanillin may be visible as a white dust or "frost" on the exterior of the pod.
It is also found in Leptotes bicolor, a species of orchid native to Paraguay and southern Brazil, and the Southern Chinese red pine.
At lower concentrations, vanillin contributes to the flavor and aroma profiles of foodstuffs as diverse as olive oil, butter, raspberry, and lychee fruits.
Aging in oak barrels imparts vanillin to some wines, vinegar, and spirits.
In other foods, heat treatment generates vanillin from other compounds. In this way, vanillin contributes to the flavor and aroma of coffee, maple syrup, and whole-grain products, including corn tortillas and oatmeal. | 0 | Theoretical and Fundamental Chemistry |
The following is a list of humans genes that encode components of complex I:
* NADH dehydrogenase (ubiquinone) 1 alpha subcomplex
** NDUFA1 – NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 1, 7.5kDa
** NDUFA2 – NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 2, 8kDa
** NDUFA3 – NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 3, 9kDa
** NDUFA4 – NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 4, 9kDa - recently described to be part of complex IV
** NDUFA4L – NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 4-like
** NDUFA4L2 – NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 4-like 2
** NDUFA5 – NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 5, 13kDa
** NDUFA6 – NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 6, 14kDa
** NDUFA7 – NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 7, 14.5kDa
** NDUFA8 – NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 8, 19kDa
** NDUFA9 – NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 9, 39kDa
** NDUFA10 – NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 10, 42kDa
** NDUFA11 – NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 11, 14.7kDa
** NDUFA12 – NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 12
** NDUFA13 – NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 13
** NDUFAB1 – NADH dehydrogenase (ubiquinone) 1, alpha/beta subcomplex, 1, 8kDa
** NDUFAF1 – NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, assembly factor 1
** NDUFAF2 – NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, assembly factor 2
** NDUFAF3 – NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, assembly factor 3
** NDUFAF4 – NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, assembly factor 4
* NADH dehydrogenase (ubiquinone) 1 beta subcomplex
** NDUFB1 – NADH dehydrogenase (ubiquinone) 1 beta subcomplex, 1, 7kDa
** NDUFB2 – NADH dehydrogenase (ubiquinone) 1 beta subcomplex, 2, 8kDa
** NDUFB3 – NADH dehydrogenase (ubiquinone) 1 beta subcomplex, 3, 12kDa
** NDUFB4 – NADH dehydrogenase (ubiquinone) 1 beta subcomplex, 4, 15kDa
** NDUFB5 – NADH dehydrogenase (ubiquinone) 1 beta subcomplex, 5, 16kDa
** NDUFB6 – NADH dehydrogenase (ubiquinone) 1 beta subcomplex, 6, 17kDa
** NDUFB7 – NADH dehydrogenase (ubiquinone) 1 beta subcomplex, 7, 18kDa
** NDUFB8 – NADH dehydrogenase (ubiquinone) 1 beta subcomplex, 8, 19kDa
** NDUFB9 – NADH dehydrogenase (ubiquinone) 1 beta subcomplex, 9, 22kDa
** NDUFB10 – NADH dehydrogenase (ubiquinone) 1 beta subcomplex, 10, 22kDa
** NDUFB11 – NADH dehydrogenase (ubiquinone) 1 beta subcomplex, 11, 17.3kDa
* NADH dehydrogenase (ubiquinone) 1, subcomplex unknown
** NDUFC1 – NADH dehydrogenase (ubiquinone) 1, subcomplex unknown, 1, 6kDa
** NDUFC2 – NADH dehydrogenase (ubiquinone) 1, subcomplex unknown, 2, 14.5kDa
* NADH dehydrogenase (ubiquinone) Fe-S protein
** NDUFS1 – NADH dehydrogenase (ubiquinone) Fe-S protein 1, 75kDa (NADH-coenzyme Q reductase)
** NDUFS2 – NADH dehydrogenase (ubiquinone) Fe-S protein 2, 49kDa (NADH-coenzyme Q reductase)
** NDUFS3 – NADH dehydrogenase (ubiquinone) Fe-S protein 3, 30kDa (NADH-coenzyme Q reductase)
** NDUFS4 – NADH dehydrogenase (ubiquinone) Fe-S protein 4, 18kDa (NADH-coenzyme Q reductase)
** NDUFS5 – NADH dehydrogenase (ubiquinone) Fe-S protein 5, 15kDa (NADH-coenzyme Q reductase)
** NDUFS6 – NADH dehydrogenase (ubiquinone) Fe-S protein 6, 13kDa (NADH-coenzyme Q reductase)
** NDUFS7 – NADH dehydrogenase (ubiquinone) Fe-S protein 7, 20kDa (NADH-coenzyme Q reductase)
** NDUFS8 – NADH dehydrogenase (ubiquinone) Fe-S protein 8, 23kDa (NADH-coenzyme Q reductase)
* NADH dehydrogenase (ubiquinone) flavoprotein 1
** NDUFV1 – NADH dehydrogenase (ubiquinone) flavoprotein 1, 51kDa
** NDUFV2 – NADH dehydrogenase (ubiquinone) flavoprotein 2, 24kDa
** NDUFV3 – NADH dehydrogenase (ubiquinone) flavoprotein 3, 10kDa
* mitochondrially encoded NADH dehydrogenase subunit
** MT-ND1 - mitochondrially encoded NADH dehydrogenase subunit 1
** MT-ND2 - mitochondrially encoded NADH dehydrogenase subunit 2
** MT-ND3 - mitochondrially encoded NADH dehydrogenase subunit 3
** MT-ND4 - mitochondrially encoded NADH dehydrogenase subunit 4
** MT-ND4L - mitochondrially encoded NADH dehydrogenase subunit 4L
** MT-ND5 - mitochondrially encoded NADH dehydrogenase subunit 5
** MT-ND6 - mitochondrially encoded NADH dehydrogenase subunit 6 | 1 | Applied and Interdisciplinary Chemistry |
Eukaryotic promoters are diverse and can be difficult to characterize, however, recent studies show that they are divided in more than 10 classes.
Gene promoters are typically located upstream of the gene and can have regulatory elements several kilobases away from the transcriptional start site (enhancers). In eukaryotes, the transcriptional complex can cause the DNA to bend back on itself, which allows for placement of regulatory sequences far from the actual site of transcription. Eukaryotic RNA-polymerase-II-dependent promoters can contain a TATA box (consensus sequence TATAAA), which is recognized by the general transcription factor TATA-binding protein (TBP); and a B recognition element (BRE), which is recognized by the general transcription factor TFIIB. The TATA element and BRE typically are located close to the transcriptional start site (typically within 30 to 40 base pairs).
Eukaryotic promoter regulatory sequences typically bind proteins called transcription factors that are involved in the formation of the transcriptional complex. An example is the E-box (sequence CACGTG), which binds transcription factors in the basic helix-loop-helix (bHLH) family (e.g. BMAL1-Clock, cMyc). Some promoters that are targeted by multiple transcription factors might achieve a hyperactive state, leading to increased transcriptional activity.
* Core promoter – the minimal portion of the promoter required to properly initiate transcription
** Includes the transcription start site (TSS) and elements directly upstream
** A binding site for RNA polymerase
*** RNA polymerase I: transcribes genes encoding 18S, 5.8S and 28S ribosomal RNAs
*** RNA polymerase II: transcribes genes encoding messenger RNA and certain small nuclear RNAs and microRNA
*** RNA polymerase III: transcribes genes encoding transfer RNA, 5s ribosomal RNAs and other small RNAs
** General transcription factor binding sites, e.g. TATA box, B recognition element.
** Many other elements/motifs may be present. There is no such thing as a set of "universal elements" found in every core promoter.
* Proximal promoter – the proximal sequence upstream of the gene that tends to contain primary regulatory elements
** Approximately 250 base pairs upstream of the start site
** Specific transcription factor binding sites
* Distal promoter – the distal sequence upstream of the gene that may contain additional regulatory elements, often with a weaker influence than the proximal promoter
** Anything further upstream (but not an enhancer or other regulatory region whose influence is positional/orientation independent)
** Specific transcription factor binding sites | 1 | Applied and Interdisciplinary Chemistry |
Nanocomposite hydrogels incorporated with polymeric nanoparticles are tailored for drug delivery and tissue engineering. The addition of polymeric nanoparticles gives these hydrogels a reinforced polymeric network that is more stiff and has the ability to enclose hydrophilic and hydrophobic drugs along with genes and proteins. The high stress-absorbing property makes them a potential candidate for cartilage tissue engineering. | 0 | Theoretical and Fundamental Chemistry |
Glide-reflection symmetry with respect to two parallel lines with the same translation implies that there is also translational symmetry in the direction perpendicular to these lines, with a translation distance which is twice the distance between glide reflection lines. This corresponds to wallpaper group pg; with additional symmetry it occurs also in pmg, pgg and p4g.
If there are also true reflection lines in the same direction then they are evenly spaced between the glide reflection lines. A glide reflection line parallel to a true reflection line already implies this situation. This corresponds to wallpaper group cm. The translational symmetry is given by oblique translation vectors from one point on a true reflection line to two points on the next, supporting a rhombus with the true reflection line as one of the diagonals. With additional symmetry it occurs also in cmm, p3m1, p31m, p4m and p6m.
In the Euclidean plane 3 of 17 wallpaper groups require glide reflection generators. p2gg has orthogonal glide reflections and 2-fold rotations. cm has parallel mirrors and glides, and pg has parallel glides. (Glide reflections are shown below as dashed lines) | 0 | Theoretical and Fundamental Chemistry |
A simple case of diffusion with time in one dimension (taken as the -axis) from a boundary located at position , where the concentration is maintained at a value is
where is the complementary error function. This is the case when corrosive gases diffuse through the oxidative layer towards the metal surface (if we assume that concentration of gases in the environment is constant and the diffusion space – that is, the corrosion product layer – is semi-infinite, starting at 0 at the surface and spreading infinitely deep in the material). If, in its turn, the diffusion space is infinite (lasting both through the layer with , and that with , ), then the solution is amended only with coefficient in front of (as the diffusion now occurs in both directions). This case is valid when some solution with concentration is put in contact with a layer of pure solvent. (Bokstein, 2005) The length is called the diffusion length and provides a measure of how far the concentration has propagated in the -direction by diffusion in time (Bird, 1976).
As a quick approximation of the error function, the first two terms of the Taylor series can be used:
If is time-dependent, the diffusion length becomes
This idea is useful for estimating a diffusion length over a heating and cooling cycle, where varies with temperature. | 0 | Theoretical and Fundamental Chemistry |
National Pipe Thread series have the same 60° included angle as Sellers thread. On the other hand, for sealing capability, tapered (pressure-tight) threads have crest and root shapes that differ from Sellers. For example, the NPT has a crest width of 0.038 to 0.062 pitch, which is sharper than the 0.125 pitch of Sellers. | 1 | Applied and Interdisciplinary Chemistry |
The societys annual meeting is held in the first week of September as well as regular special interest group meetings (Lipidomics, MALDI & Imaging, Ambient Ionisation, Environmental & Food Analysis) through the year, in locations throughout the United Kingdom. Locations of the societys annual meetings beginning in 1965: | 1 | Applied and Interdisciplinary Chemistry |
After Saigon fell on 30 April 1975, ending the Vietnam War, the military purpose of Project 523 subsided. Researchers could not publish their findings but could share their works within the working groups. The first publication in English (and thus circulated outside China) was in the December 1979 issue of the Chinese Medical Journal, authored simply by the Qinghaosu Antimalaria Coordinating Research Group. This attracted collaboration with the Special Programme for Research and Training in Tropical Diseases (TDR), sponsored by the United Nations Children's Fund, the United Nations Development Programme, the World Bank, and WHO, but the research remained closed to non-Chinese scientists. By the early 1980s, research had practically stopped, and the project was officially terminated in 1981. The TDR took this opportunity to organise the first international conference in Beijing on artemisinin and its variants in 1981. Supported by WHO, the Chinese Ministry of Health established the National Chinese Steering Committee for Development of Qinghaosu and its Derivatives to continue the important achievements of Project 523.
The first international collaboration was between Keith Arnold at the Roche Far East Research Foundation, Hong Kong, and Chinese researchers Jing-Bo Jiang, Xing-Bo Guo, Guo-Qiao Li, and Yun Cheung Kong. They made their first international publication in 1982 in The Lancet, in which they reported the comparative efficacy of artemisinin and mefloquine on chloroquine-resistant Plasmodium falciparum. Arnold was among those who developed mefloquine in 1979 and was planning to test the new drug in China. He and his wife Moui became the most important people in translating the historical account of the Project 523 and bringing it to international recognition. The Division of Experimental Therapeutics at the Walter Reed Army Institute of Research, under the United States Army, was the first to produce artemisinin and its derivatives outside China. Their production paved the way for commercial success. | 1 | Applied and Interdisciplinary Chemistry |
NMR experiments require creating a transient non-stationary state of the spin system. In conventional high-field experiments, radio frequency pulses tilt the magnetization from along the main magnetic field direction to the transverse plan. Once in the transverse plan, the magnetization is no longer in a stationary state (or eigenstate) and so it begins to precess about the main magnetic field creating a detectable oscillating magnetic field.
In ZULF experiments, constant magnetic field pulses are used to induce non-stationary states of the spin system. The two main strategies consist of (1) switching of the magnetic field from pseudo-high field to zero (or ultra-low) field, or (2) of ramping down the magnetic field experienced by the spins to zero field in order to convert the Zeeman populations into zero-field eigenstates adiabatically and subsequently in applying a constant magnetic field pulse to induce a coherence between the zero-field eigenstates. In the simple case of a heteronuclear pair of J-coupled spins, both these excitation schemes induce a transition between the singlet and triplet-0 states, which generates a detectable oscillatory magnetic field.
More sophisticated pulse sequences have been reported including selective pulses, two-dimensional experiments and decoupling schemes. | 0 | Theoretical and Fundamental Chemistry |
Diphosphagermylenes are a class of compounds containing a divalent germanium atom bound to two phosphorus atoms. While these compounds resemble diamidocarbenes, such as N-heterocyclic carbenes (NHC), diphosphagermylenes display bonding characteristics distinct from those of diamidocarbenes. In contrast to NHC compounds, in which there is effective N-C p(π)-p(π) overlap between the lone pairs of planar nitrogens and an empty p-orbital of a carbene, systems containing P-Ge p(π)-p(π) overlap are rare. Until 2014, the geometry of phosphorus atoms in all previously reported diphosphatetrylenes are pyramidal, with minimal P-Ge p(π)-p(π) interaction. It has been suggested that the lack of p(π)-p(π) in Ge-P bonds is due to the high energetic barrier associated with achieving a planar configuration at phosphorus, which would allow for efficient p(π)-p(π) overlap between the phosphorus lone pair and the empty P orbital of Ge. The resulting lack of π stabilization contributes to the difficulty associated with isolating diphosphagermylene and the Ge-P double bonds. However, utilization of sterically encumbering phosphorus centers has allowed for the isolation of diphosphagermylenes with a planar phosphorus center with a significant P-Ge p(π)-p(π) interaction. | 0 | Theoretical and Fundamental Chemistry |
Fluorescent moieties emit photons several nanoseconds after absorption following an exponential decay curve, which differs between dyes and depends on the surrounding solvent. When the dye is attached to a macromolecules the decay curve becomes multiexponential. Conjugated dyes generally have a lifetime between 1–10 ns, a small amount of longer lived exceptions exist, notably pyrene with a lifetime of 400ns in degassed solvents or 100ns in lipids and coronene with 200ns. On a different category of fluorphores are the fluorescent organometals (lanthanides and transition metal-ligand complexes) which have been previously described, which have much longer lifetimes due to the restricted states: lanthanides have lifetimes of 0.5 to 3 ms, while transition metal-ligand complexes have lifetimes of 10 ns to 10 µs. Note that fluorescent lifetime should not be confused with the photodestruction lifetime or the "shelf-life" of a dye. | 1 | Applied and Interdisciplinary Chemistry |
The first known variant of the AnMBR was developed by Dorr-Oliver in 1980, specifically to treat wastewater with high organic loads, specifically, dairy wastewater. Due to the high cost of membranes, the technology was never applied on a larger commercial scale, only going through laboratory and pilot scale trials.
There are three main configurations of the AnMBR, each with a different location of the membrane unit. The variants all have their own advantages and disadvantages both in terms of cost and operability. | 1 | Applied and Interdisciplinary Chemistry |
The channelosome (not to be confused with "channelome") is the collection of (usually) signalling proteins associated with an ion channel. The channelosome is frequently clustered within a lipid microdomain or caveolae. This collection of proteins may be involved with anchoring, phosphorylation or some other modulatory or support function. An example is neural KCNQ/M (Kv7) potassium channelosome (see Delmas & Brown, 2005). | 1 | Applied and Interdisciplinary Chemistry |
The CCR family of receptors are a group of g-protein coupled receptors (GPCRs) that normally operate as chemokine receptors. They are primarily found on immunological cells, especially T-cells. CCR receptors are also expressed on neuronal cells, such as dendrites and microglia. Perhaps the most famous and well-studied of the CCR family is CCR5 (and its near-homologue CXCR4) which acts as the primary co-receptor for HIV viral infection. The HIV envelope glycoprotein GP120 binds to CD4 as its primary receptor, CCR5 then forms a complex with CD4 and HIV, allowing viral entry into the cell. CCR5 is not the only member of the CCR family that allows for HIV infection. Due to the commonality of structures found throughout the family, CCR2b, CCR3, and CCR8 can be utilized by some HIV strains as co-receptors to facilitate infection. CXCR4 is very similar to CCR5 in structure. While only some HIV strains can utilize CCR2b, CCR3 and CCR8, all HIV strains can infect through CCR5 and CXCR4.
CCR5 is known to have an affinity for macrophage inflammatory protein (MIP) and is thought to play a role in inflammatory immunological responses. The primary role of this receptor is less understood than its role in HIV infection, as inflammation responses remain a poorly understood facet of the immune system. CCR5's affinity for MIP makes it of great interest for practical applications such as tissue engineering, where attempts are being made to control host inflammatory and immunological responses at a cellular signalling level. The affinity for MIP has been utilized in-vitro to prevent HIV infection through ligand competition; however, these entry-inhibitors have failed in-vivo due to the highly adaptive nature of HIV and toxicity concerns. | 1 | Applied and Interdisciplinary Chemistry |
The lithosphere is 46.6% oxygen by volume, present mainly as silica minerals (SiO) and other oxide minerals. | 0 | Theoretical and Fundamental Chemistry |
Fluoroalkanes are generally inert and non-toxic.
Fluoroalkanes are not ozone depleting, as they contain no chlorine or bromine atoms, and they are sometimes used as replacements for ozone-depleting chemicals.
The term fluorocarbon is used rather loosely to include any chemical containing fluorine and carbon, including chlorofluorocarbons, which are ozone depleting. Fluoroalkanes are sometimes confused with fluorosurfactants, which significantly bioaccumulate.
Perfluoroalkanes do not bioaccumulate; those used in medical procedures are rapidly excreted from the body, primarily via expiration with the rate of excretion as a function of the vapour pressure; the half-life for octafluoropropane is less than 2 minutes, compared to about a week for perfluorodecalin.
Low-boiling perfluoroalkanes are potent greenhouse gases, in part due to their very long atmospheric lifetime, and their use is covered by the Kyoto Protocol. The global warming potential (compared to that of carbon dioxide) of many gases can be found in the IPCC 5th assessment report, with an extract below for a few perfluoroalkanes.
The aluminium smelting industry has been a major source of atmospheric perfluorocarbons (tetrafluoromethane and hexafluoroethane especially), produced as by-product of the electrolysis process. However, the industry has been actively involved in reducing emissions in recent years. | 1 | Applied and Interdisciplinary Chemistry |
The crystallization process of polymers does not always obey simple chemical rate equations. Polymers can crystallize through a variety of different regimes and unlike simple molecules, the polymer crystal lamellae have two very different surfaces. The two most prominent theories in polymer crystallization kinetics are the Avrami equation and Lauritzen–Hoffman growth theory. | 0 | Theoretical and Fundamental Chemistry |
Mechanical work performed on a working fluid causes a change in the mechanical constraints of the system; in other words, for work to occur, the volume must be altered. Hence, volume is an important parameter in characterizing many thermodynamic processes where an exchange of energy in the form of work is involved.
Volume is one of a pair of conjugate variables, the other being pressure. As with all conjugate pairs, the product is a form of energy. The product is the energy lost to a system due to mechanical work. This product is one term which makes up enthalpy :
where is the internal energy of the system.
The second law of thermodynamics describes constraints on the amount of useful work which can be extracted from a thermodynamic system. In thermodynamic systems where the temperature and volume are held constant, the measure of "useful" work attainable is the Helmholtz free energy; and in systems where the volume is not held constant, the measure of useful work attainable is the Gibbs free energy.
Similarly, the appropriate value of heat capacity to use in a given process depends on whether the process produces a change in volume. The heat capacity is a function of the amount of heat added to a system. In the case of a constant-volume process, all the heat affects the internal energy of the system (i.e., there is no pV-work, and all the heat affects the temperature). However, in a process without a constant volume, the heat addition affects both the internal energy and the work (i.e., the enthalpy); thus the temperature changes by a different amount than in the constant-volume case and a different heat capacity value is required. | 0 | Theoretical and Fundamental Chemistry |
The earliest estimated use of bitumen dates back 40,000 years to the paleolithic age in which Bitumen was used to adhere handles onto primitive stone tools.
A re-examination of artifacts uncovered in 1908 at Le Moustier rock shelters in France has identified Mousterian stone tools that were attached to grips made of ochre and bitumen. The grips were formulated with 55% ground goethite ochre and 45% cooked liquid bitumen to create a moldable putty that hardened into handles. Earlier excavations at Le Moustier prevent conclusive identification of the archaeological culture and age, but the European Mousterian style of these tools suggests they are associated with Neanderthals during the late Middle Paleolithic, between 60,000 and 35,000 years before present. It is the earliest evidence of compound adhesive use in Europe. | 0 | Theoretical and Fundamental Chemistry |
Conserved cycles in a biochemical network can be identified by examination of the stoichiometry matrix, The stoichiometry matrix for a simple cycle with species A and AP is given by:
The rates of change of A and AP can be written using the equation:
Expanding the expression leads to:
Note that . This means that , where is the total mass of moiety .
Given an arbitrary system:
elementary row operations can be applied to both sides such that the stoichiometric matrix is reduced to its echelon form, giving:
The elementary operations are captured in the matrix. We can partition to match the echelon matrix where the zero rows begin such that:
By multiplying out the lower partition, we obtain:
The matrix will contain entries corresponding to the conserved cycle participants. | 1 | Applied and Interdisciplinary Chemistry |
A limitation of FRET performed with fluorophore donors is the requirement for external illumination to initiate the fluorescence transfer, which can lead to background noise in the results from direct excitation of the acceptor or to photobleaching. To avoid this drawback, bioluminescence resonance energy transfer (or BRET) has been developed. This technique uses a bioluminescent luciferase (typically the luciferase from Renilla reniformis) rather than CFP to produce an initial photon emission compatible with YFP.
BRET has also been implemented using a different luciferase enzyme, engineered from the deep-sea shrimp Oplophorus gracilirostris. This luciferase is smaller (19 kD) and brighter than the more commonly used luciferase from Renilla reniformis, and has been named NanoLuc or NanoKAZ. Promega has developed a patented substrate for NanoLuc called furimazine, though other valuables coelenterazine substrates for NanoLuc have also been published. A split-protein version of NanoLuc developed by Promega has also been used as a BRET donor in experiments measuring protein-protein interactions. | 1 | Applied and Interdisciplinary Chemistry |
Joule performed his experiment with air at room temperature which was expanded from a pressure of about 22 bar. Air, under these conditions, is almost an ideal gas, but not quite. As a result the real temperature change will not be exactly zero. With our present knowledge of the thermodynamic properties of air we can calculate that the temperature of the air should drop by about 3 degrees Celsius when the volume is doubled under adiabatic conditions. However, due to the low heat capacity of the air and the high heat capacity of the strong copper containers and the water of the calorimeter, the observed temperature drop is much smaller, so Joule found that the temperature change was zero within his measuring accuracy. | 0 | Theoretical and Fundamental Chemistry |
An application of HSAB theory is the so-called Kornblum's rule (after Nathan Kornblum) which states that in reactions with ambident nucleophiles (nucleophiles that can attack from two or more places), the more electronegative atom reacts when the reaction mechanism is S1 and the less electronegative one in a S2 reaction. This rule (established in 1954) predates HSAB theory but in HSAB terms its explanation is that in a S1 reaction the carbocation (a hard acid) reacts with a hard base (high electronegativity) and that in a S2 reaction tetravalent carbon (a soft acid) reacts with soft bases.
According to findings, electrophilic alkylations at free CN occur preferentially at carbon, regardless of whether the S1 or S2 mechanism is involved and whether hard or soft electrophiles are employed. Preferred N attack, as postulated for hard electrophiles by the HSAB principle, could not be observed with any alkylating agent. Isocyano compounds are only formed with highly reactive electrophiles that react without an activation barrier because the diffusion limit is approached. It is claimed that the knowledge of absolute rate constants and not of the hardness of the reaction partners is needed to predict the outcome of alkylations of the cyanide ion. | 0 | Theoretical and Fundamental Chemistry |
In the Earths atmosphere, the chief factor affecting the speed of sound is the temperature. For a given ideal gas with constant heat capacity and composition, the speed of sound is dependent solely upon temperature; see ' below. In such an ideal case, the effects of decreased density and decreased pressure of altitude cancel each other out, save for the residual effect of temperature.
Since temperature (and thus the speed of sound) decreases with increasing altitude up to , sound is refracted upward, away from listeners on the ground, creating an acoustic shadow at some distance from the source. The decrease of the speed of sound with height is referred to as a negative sound speed gradient.
However, there are variations in this trend above . In particular, in the stratosphere above about , the speed of sound increases with height, due to an increase in temperature from heating within the ozone layer. This produces a positive speed of sound gradient in this region. Still another region of positive gradient occurs at very high altitudes, in the thermosphere above . | 1 | Applied and Interdisciplinary Chemistry |
Live vaccines, such as oral polio vaccine, can be stabilized by deuterium, either alone or in combination with other stabilizers such as MgCl. | 0 | Theoretical and Fundamental Chemistry |
Masking is the process of applying the maskant material to the surface to ensure that only desired areas are etched. Liquid maskants may be applied via dip-masking, in which the part is dipped into an open tank of maskant and then the maskant dried. Maskant may also be applied by flow coating: liquid maskant is flowed over the surface of the part. Certain conductive maskants may also be applied by electrostatic deposition, where electrical charges are applied to particles of maskant as it is sprayed onto the surface of the material. The charge causes the particles of maskant to adhere to the surface. | 1 | Applied and Interdisciplinary Chemistry |
Neuromuscular-blocking drugs, or Neuromuscular blocking agents (NMBAs), block transmission at the neuromuscular junction, causing paralysis of the affected skeletal muscles. This is accomplished via their action on the post-synaptic acetylcholine (Nm) receptors.
In clinical use, neuromuscular block is used adjunctively to anesthesia to produce paralysis, firstly to paralyze the vocal cords, and permit endotracheal intubation, and secondly to optimize the surgical field by inhibiting spontaneous ventilation, and causing relaxation of skeletal muscles. Because the appropriate dose of neuromuscular-blocking drug may paralyze muscles required for breathing (i.e., the diaphragm), mechanical ventilation should be available to maintain adequate respiration.
This class of medications helps to reduce patient movement, breathing, or ventilator dyssynchrony and allows lower insufflation pressures during laparoscopy. It has several indications for use in the intense care unit. It can help reduce hoarseness in voice as well as injury to the vocal cord during intubation. In addition, it plays an important role in facilitating mechanical ventilation in patients with poor lung function.
Patients are still aware of pain even after full conduction block has occurred; hence, general anesthetics and/or analgesics must also be given to prevent anesthesia awareness. | 1 | Applied and Interdisciplinary Chemistry |
Antifoaming agents are also sold commercially to relieve bloating. A familiar example is the drug simethicone, which is the active ingredient in drugs such as Gas-X. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, specific rotation ([α]) is a property of a chiral chemical compound. It is defined as the change in orientation of monochromatic plane-polarized light, per unit distance–concentration product, as the light passes through a sample of a compound in solution. Compounds which rotate the plane of polarization of a beam of plane polarized light clockwise are said to be dextrorotary, and correspond with positive specific rotation values, while compounds which rotate the plane of polarization of plane polarized light counterclockwise are said to be levorotary, and correspond with negative values. If a compound is able to rotate the plane of polarization of plane-polarized light, it is said to be “optically active”.
Specific rotation is an intensive property, distinguishing it from the more general phenomenon of optical rotation. As such, the observed rotation (α) of a sample of a compound can be used to quantify the enantiomeric excess of that compound, provided that the specific rotation ([α]) for the enantiopure compound is known. The variance of specific rotation with wavelength—a phenomenon known as optical rotatory dispersion—can be used to find the absolute configuration of a molecule. The concentration of bulk sugar solutions is sometimes determined by comparison of the observed optical rotation with the known specific rotation. | 0 | Theoretical and Fundamental Chemistry |
In May 1990, the GFP reached an agreement with the Société chimique de France, becoming its Division of "Polymeric materials and elastomers". In 2001 this agreement was modified to create a "Polymer and Materials Chemistry" Division that was common to the two societies. In 2002, a similar agreement with the Société française de physique created a common "Polymer" Division between the two organizations. The GFP is a founding member of the Fédération française des matériaux (French Materials Federation), and a member of the European Polymer Federation, whose first conference was organized by the GFP in Lyon in 1986. In 2020, the GFP signed a Memorandum of Understanding with the Society of Polymer Science Japan. | 1 | Applied and Interdisciplinary Chemistry |
The process of binding is central in determining the "strength" of promoters, that is the relative estimation of how "well" a promoter perform the expression of a gene under specific circumstances. Brewster et al., using a simple thermodynamical model based on the postulate that transcriptional activity is proportional to the probability of finding the RNA polymerase bound at the promoter, obtained predictions of the scaling of the RNA polymerase binding energy. This models support the relationship between the probability of binding and the output of gene expression | 1 | Applied and Interdisciplinary Chemistry |
The principle of microscopic reversibility in physics and chemistry is twofold:
* First, it states that the microscopic detailed dynamics of particles and fields is time-reversible because the microscopic equations of motion are symmetric with respect to inversion in time (T-symmetry);
* Second, it relates to the statistical description of the kinetics of macroscopic or mesoscopic systems as an ensemble of elementary processes: collisions, elementary transitions or reactions. For these processes, the consequence of the microscopic T-symmetry is: | 0 | Theoretical and Fundamental Chemistry |
After the hazards of strontium-90 became evident, the next step was to focus on impact and damage per detonation. Smith's tests focused primarily on how many atomic weapons could potentially be detonated before radioactive contamination of air, water and soil became a long-term effect on crops, animals and humans worldwide. In 1949, Smith estimated that it would take 3,000 Hiroshima-sized detonations in a single growing season to see if it have an effect on people who ate crops in affected areas. In 1951, Smith repeated this study with new information from the previous two detonations. With the new information, he then calculated that 10,000 Hiroshima-sized detonations would be needed before the long-term hazards became serious.
The testing was done with bones, urine and tissue samples collected worldwide. These samples were all tested for nuclear fallout, yet were falsely studied under the guise of nutritional importance and naturally occurring radon. It was determined that Sr-90 is a "bone-seeker," depositing in bones and marrow after ingestion. Civilian prisoners were considered for certain radiation testing, mainly Utah State prison inmates. One document revealed tests done on the bones of a stillborn baby showed that strontium-90 levels were 36% higher than the average 55% of other stillborn. | 0 | Theoretical and Fundamental Chemistry |
Most antibodies have the similar structure except the hypervariable region which is called the antigen binding site. This region is constituted by the combination of various amino acids. When the antigen is a kind of carbohydrate (Polysaccharide), the binding could be regarded as a protein-carbohydrate interaction. | 0 | Theoretical and Fundamental Chemistry |
Consider a two-point velocity correlation tensor for homogeneous turbulence
For isotropic turbulence, this correlation tensor can be expressed in terms of two scalar functions, using the invariant theory of full rotation group, first derived by Howard P. Robertson in 1940,
where is the root mean square turbulent velocity and are turbulent velocity in all three directions. Here, is the longitudinal correlation and is the lateral correlation of velocity at two different points. From continuity equation, we have
Thus uniquely determines the two-point correlation function. Theodore von Kármán and Leslie Howarth derived the evolution equation for from Navier–Stokes equation as
where uniquely determines the triple correlation tensor | 1 | Applied and Interdisciplinary Chemistry |
C/EBPβ has been found to have a role in the development of osteoporosis. The full-length isoform of the C/EBPβ protein (LAP) activates the MafB gene, whereas the short isoform (LIP) suppresses it. MafB gene activation suppresses the formation of osteoclasts. Thus, upregulation of LAP diminishes the number of osteoclasts, and this weakens the osteoporotic process, whereas upregulation of LIP does the opposite, increasing loss of bone mass.
The LAP/LIP balance is determined by the mTOR protein. Inhibition of the expression of mTOR can stop osteoclast activity. | 1 | Applied and Interdisciplinary Chemistry |
The eudysmic ratio (also spelled eudismic ratio) represents the difference in pharmacologic activity between the two enantiomers of a drug. In most cases where a chiral compound is biologically active, one enantiomer is more active than the other. The eudysmic ratio is the ratio of activity between the two. A eudysmic ratio significantly differing from 1 means that they are statistically different in activity. Eudisimic ratio (ER) reflects the degree of enantioselectivity of the biological systems. For example, (S)-propranolol (ER = 130) meaning that (S)-propranolol is 130 times more active than its (R)-enantiomer. | 0 | Theoretical and Fundamental Chemistry |
The experimental determination of pK values is commonly performed by means of titrations, in a medium of high ionic strength and at constant temperature. A typical procedure would be as follows. A solution of the compound in the medium is acidified with a strong acid to the point where the compound is fully protonated. The solution is then titrated with a strong base until all the protons have been removed. At each point in the titration pH is measured using a glass electrode and a pH meter. The equilibrium constants are found by fitting calculated pH values to the observed values, using the method of least squares.
The total volume of added strong base should be small compared to the initial volume of titrand solution in order to keep the ionic strength nearly constant. This will ensure that pK remains invariant during the titration.
A calculated titration curve for oxalic acid is shown at the right. Oxalic acid has pK values of 1.27 and 4.27. Therefore, the buffer regions will be centered at about pH 1.3 and pH 4.3. The buffer regions carry the information necessary to get the pK values as the concentrations of acid and conjugate base change along a buffer region.
Between the two buffer regions there is an end-point, or equivalence point, at about pH 3. This end-point is not sharp and is typical of a diprotic acid whose buffer regions overlap by a small amount: pK − pK is about three in this example. (If the difference in pK values were about two or less, the end-point would not be noticeable.) The second end-point begins at about pH 6.3 and is sharp. This indicates that all the protons have been removed. When this is so, the solution is not buffered and the pH rises steeply on addition of a small amount of strong base. However, the pH does not continue to rise indefinitely. A new buffer region begins at about pH 11 (pK − 3), which is where self-ionization of water becomes important.
It is very difficult to measure pH values of less than two in aqueous solution with a glass electrode, because the Nernst equation breaks down at such low pH values. To determine pK values of less than about 2 or more than about 11 spectrophotometric or NMR measurements may be used instead of, or combined with, pH measurements.
When the glass electrode cannot be employed, as with non-aqueous solutions, spectrophotometric methods are frequently used. These may involve absorbance or fluorescence measurements. In both cases the measured quantity is assumed to be proportional to the sum of contributions from each photo-active species; with absorbance measurements the Beer–Lambert law is assumed to apply.
Isothermal titration calorimetry (ITC) may be used to determine both a pK value and the corresponding standard enthalpy for acid dissociation. Software to perform the calculations is supplied by the instrument manufacturers for simple systems.
Aqueous solutions with normal water cannot be used for H NMR measurements but heavy water, , must be used instead. C NMR data, however, can be used with normal water and H NMR spectra can be used with non-aqueous media. The quantities measured with NMR are time-averaged chemical shifts, as proton exchange is fast on the NMR time-scale. Other chemical shifts, such as those of P can be measured. | 0 | Theoretical and Fundamental Chemistry |
Digital PCR has many applications in basic research, clinical diagnostics and environmental testing. Its uses include pathogen detection and digestive health analysis; liquid biopsy for cancer monitoring, organ transplant rejection monitoring and non-invasive prenatal testing for serious genetic abnormalities; copy number variation analysis, single gene expression analysis, rare sequence detection, gene expression profiling and single-cell analysis; the detection of DNA contaminants in bioprocessing, the validation of gene edits and detection of specific methylation changes in DNA as biomarkers of cancer. dPCR is also frequently used as an orthogonal method to confirm rare mutations detected through next-generation sequencing (NGS) and to validate NGS libraries. | 1 | Applied and Interdisciplinary Chemistry |
"Lucas' reagent" is a solution of anhydrous zinc chloride in concentrated hydrochloric acid. This solution is used to classify alcohols of low molecular weight. The reaction is a substitution in which the chloride replaces a hydroxyl group. A positive test is indicated by a change from clear and colourless to turbid, signalling formation of a chloroalkane. Also, the best results for this test are observed in tertiary alcohols, as they form the respective alkyl halides fastest due to higher stability of the intermediate tertiary carbocation. The test was reported in 1930 and became a standard method in qualitative organic chemistry. The test has since become somewhat obsolete with the availability of various spectroscopic and chromatographic methods of analysis. It was named after Howard Lucas (1885–1963). | 0 | Theoretical and Fundamental Chemistry |
To illustrate the processes, consider the case of dissolving a weak acid, HA, in water. The pH can be calculated using an ICE table. Note that in this example, we are assuming that the acid is not very weak, and that the concentration is not very dilute, so that the concentration of [OH] ions can be neglected. This is equivalent to the assumption that the final pH will be below about 6 or so. See pH calculations for more details.
First write down the equilibrium expression.
The columns of the table correspond to the three species in equilibrium.
The first row shows the reaction, which some authors label R and some leave blank.
The second row, labeled I, has the initial conditions: the nominal concentration of acid is C and it is initially undissociated, so the concentrations of A and H are zero.
The third row, labeled C, specifies the change that occurs during the reaction. When the acid dissociates, its concentration changes by an amount , and the concentrations of A and H both change by an amount . This follows from consideration of mass balance (the total number of each atom/molecule must remain the same) and charge balance (the sum of the electric charges before and after the reaction must be zero).
Note that the coefficients in front of the "x" correlate to the mole ratios of the reactants to the product. For example, if the reaction equation had 2 H ions in the product, then the "change" for that cell would be "2x"
The fourth row, labeled E, is the sum of the first two rows and shows the final concentrations of each species at equilibrium.
It can be seen from the table that, at equilibrium, [H] = x.
To find x, the acid dissociation constant (that is, the equilibrium constant for acid-base dissociation) must be specified.
Substitute the concentrations with the values found in the last row of the ICE table.
With specific values for C and K this quadratic equation can be solved for x. Assuming that pH = −log[H] the pH can be calculated as pH = −logx.
If the degree of dissociation is quite small, C ≫ x and the expression simplifies to
and pH = (pK − log C). This approximate expression is good for pK values larger than about 2 and concentrations high enough. | 0 | Theoretical and Fundamental Chemistry |
Al-Kindis ninth century AD book, De Gradibus and Ibn Sina (Avicenna)s The Canon of Medicine, covers a range of drugs known to the practice of medicine in the medieval Islamic world.
Medieval medicine of Western Europe saw advances in surgery compared to previously, but few truly effective drugs existed, beyond opium (found in such extremely popular drugs as the "Great Rest" of the Antidotarium Nicolai at the time) and quinine. Folklore cures and potentially poisonous metal-based compounds were popular treatments. Theodoric Borgognoni, (1205–1296), one of the most significant surgeons of the medieval period, responsible for introducing and promoting important surgical advances including basic antiseptic practice and the use of anaesthetics. Garcia de Orta described some herbal treatments that were used. | 1 | Applied and Interdisciplinary Chemistry |
Astrobiological exploration is founded upon the premise that biosignatures encountered in space will be recognizable as extraterrestrial life. The usefulness of a biosignature is determined not only by the probability of life creating it but also by the improbability of non-biological (abiotic) processes producing it. Concluding that evidence of an extraterrestrial life form (past or present) has been discovered requires proving that a possible biosignature was produced by the activities or remains of life. As with most scientific discoveries, discovery of a biosignature will require evidence building up until no other explanation exists.
Possible examples of a biosignature include complex organic molecules or structures whose formation is virtually unachievable in the absence of life:
# Cellular and extracellular morphologies
# Biomolecules in rocks
# Bio-organic molecular structures
# Chirality
# Biogenic minerals
# Biogenic isotope patterns in minerals and organic compounds
# Atmospheric gases
# Photosynthetic pigments | 1 | Applied and Interdisciplinary Chemistry |
Born at Montpellier, France, on 30 September 1802, he started as an apothecary, but taking up teaching he acted as chemical assistant at the faculty of sciences of his native town, and then became professor of chemistry at the royal college and school of pharmacy and at the faculty of sciences. In 1826 he discovered in seawater a substance which he recognized as a previously unknown element and named it bromine. It had been independently prepared by Carl Jacob Löwig the previous year and the two are both regarded as having discovered the element.
This achievement brought him the reputation that secured his election as successor to Louis Jacques Thénard in the chair of chemistry at the faculty of sciences in Paris, and in 1851 he was appointed professor of chemistry at the College de France, where he had Marcellin Berthelot first as pupil, then as assistant and finally as colleague. Balard also had Louis Pasteur as a pupil when Pasteur was only 26 years old. It was in Balard's laboratory that Pasteur discovered the difference between "right-handed" and "left-handed" crystals while he was working with tartaric acid. Balard died in Paris on 30 April 1876.
While the discovery of bromine and the preparation of many of its compounds was his most conspicuous piece of work, Balard was an industrious chemist on both the pure and applied sides. In his researches on the bleaching compounds of chlorine he was the first to advance the view that bleaching-powder is a double compound of calcium chloride and hypochlorite; and he devoted much time to the problem of economically obtaining soda and potash from seawater, though here his efforts were nullified by the discovery of the much richer sources of supply afforded by the Stassfurt deposits. In organic chemistry he published papers on the decomposition of ammonium oxalate, with formation of oxamic acid, on amyl alcohol, on the cyanides, and on the difference in constitution between ethyl nitrate and ethyl sulfate. He also helped Louis Pasteur devise the experiment that would prove spontaneous generation to be false. | 1 | Applied and Interdisciplinary Chemistry |
Starch granules are very common in chloroplasts, typically taking up 15% of the organelle's volume, though in some other plastids like amyloplasts, they can be big enough to distort the shape of the organelle. Starch granules are simply accumulations of starch in the stroma, and are not bounded by a membrane.
Starch granules appear and grow throughout the day, as the chloroplast synthesizes sugars, and are consumed at night to fuel respiration and continue sugar export into the phloem, though in mature chloroplasts, it is rare for a starch granule to be completely consumed or for a new granule to accumulate.
Starch granules vary in composition and location across different chloroplast lineages. In red algae, starch granules are found in the cytoplasm rather than in the chloroplast. In plants, mesophyll chloroplasts, which do not synthesize sugars, lack starch granules. | 0 | Theoretical and Fundamental Chemistry |
*Firewater control
*Pipeline safety systems
*Residential plumbing systems (both water and gas)
*Nuclear reactors
*Oil and gas wells
*Chemical plant
*Oil production plant
*Power plant | 1 | Applied and Interdisciplinary Chemistry |
For MLL, two isomers are possible - a facial isomer (fac) in which each set of three identical ligands occupies one face of the octahedron surrounding the metal atom, so that any two of these three ligands are mutually cis, and a meridional isomer (mer) in which each set of three identical ligands occupies a plane passing through the metal atom. | 0 | Theoretical and Fundamental Chemistry |
From the perspective of solid state physics, Brillouin scattering is an interaction between an electromagnetic wave and one of the three above-mentioned crystalline lattice waves (e.g. electrostriction and magnetostriction). The scattering is inelastic i.e. the photon may lose energy (Stokes process) and in the process create one of the three quasiparticle types (phonon, polariton, magnon) or it may gain energy (anti-Stokes process) by absorbing one of those quasiparticle types. Such a shift in photon energy, corresponding to a Brillouin shift in frequency, is equal to the energy of the released or absorbed quasiparticle. Thus, Brillouin scattering can be used to measure the energies, wavelengths and frequencies of various atomic chain oscillation types (quasiparticles). To measure a Brillouin shift a commonly employed device called the Brillouin spectrometer is used, the design of which is derived from a Fabry–Pérot interferometer. Alternatively, high-speed photodiodes, such as those recovered from inexpensive 25-gigabit Ethernet optical transceivers, may be used in combination with a software-defined radio or RF spectrum analyzer. | 0 | Theoretical and Fundamental Chemistry |
Another example is [Co(HO)]. Note that the ligand is the same as the last example. Here the cobalt ion has the oxidation state of +2, and it is a d ion. From the high-spin (left) side of the d Tanabe–Sugano diagram, the ground state is T(F), and the spin multiplicity is a quartet. The diagram shows that there are three quartet excited states: T, A, and T(P). From the diagram one can predict that there are three spin-allowed transitions. However, the spectrum of [Co(HO)] does not show three distinct peaks that correspond to the three predicted excited states. Instead, the spectrum has a broad peak (spectrum shown below). Based on the T–S diagram, the lowest energy transition is T to T, which is seen in the near IR and is not observed in the visible spectrum. The main peak is the energy transition T(F) to T(P), and the slightly higher energy transition (the shoulder) is predicted to be T to A. The small energy difference leads to the overlap of the two peaks, which explains the broad peak observed in the visible spectrum. | 0 | Theoretical and Fundamental Chemistry |
According to the work of the corrosion electrochemist Shoesmith the nanoparticles of Mo-Tc-Ru-Pd have a strong effect on the corrosion of uranium dioxide fuel. For instance his work suggests that when the hydrogen (H) concentration is high (due to the anaerobic corrosion of the steel waste can) the oxidation of hydrogen at the nanoparticles will exert a protective effect on the uranium dioxide. This effect can be thought of as an example of protection by a sacrificial anode where instead of a metal anode reacting and dissolving it is the hydrogen gas which is consumed. | 0 | Theoretical and Fundamental Chemistry |
SDS is mainly used in detergents for laundry with many cleaning applications. It is a highly effective surfactant and is used in any task requiring the removal of oily stains and residues. For example, it is found in higher concentrations with industrial products including engine degreasers, floor cleaners, and car exterior cleaners.
It is a component in hand soap, toothpastes, shampoos, shaving creams, and bubble bath formulations, for its ability to create a foam (lather), for its surfactant properties, and in part for its thickening effect. | 1 | Applied and Interdisciplinary Chemistry |
* Christopher Longuet-Higgins (Founding Editor)
* Joan van der Waals (Founding Editor)
* John Shipley Rowlinson
* A. David Buckingham
* Lawrence D. Barron
* Martin Quack
* Dominic Tildesley
* Henry F. Schaefer III
* Nicholas C. Handy
* Ruth Lynden-Bell
* Jean-Pierre Hansen
* Timothy Softley
* Martin Head-Gordon
* Trygve Helgaker | 0 | Theoretical and Fundamental Chemistry |
Aurin (C.I. 43800), sometimes named rosolic acid or corallin is an organic compound, forming yellowish or deep-red crystals with greenish metallic luster. It is practically insoluble in water, freely soluble in alcohol. It is soluble in strong acids to form yellow solution, or in aqueous alkalis to form carmine red solutions. Due to this behaviour it can be used as pH indicator with pH transition range 5.0 - 6.8. It is used as an intermediate in manufacturing of dyes. | 0 | Theoretical and Fundamental Chemistry |
Circulation within local systems, such as bays, estuaries, and groundwater, may be examined with radium isotopes. Ra has a half-life of 11 days and can occur naturally at specific locations in rivers and groundwater sources. The isotopic ratio of radium will then decrease as the water from the source river enters a bay or estuary. By measuring the amount of Ra at a number of different locations, a circulation pattern can be deciphered. This same exact process can also be used to study the movement and discharge of groundwater.
Various isotopes of lead can be used to study circulation on a global scale. Different oceans (i.e. the Atlantic, Pacific, Indian, etc.) have different isotopic signatures. This results from differences in isotopic ratios of sediments and rocks within the different oceans. Because the different isotopes of lead have half-lives of 50–200 years, there is not enough time for the isotopic ratios to be homogenized throughout the whole ocean. Therefore, precise analysis of Pb isotopic ratios can be used to study the circulation of the different oceans. | 0 | Theoretical and Fundamental Chemistry |
The method of slipping is one which exploits the thermodynamic stability of the rotaxane. If the end groups of the dumbbell are an appropriate size it will be able to reversibly thread through the macrocycle at higher temperatures. By cooling the dynamic complex, it becomes kinetically trapped as a rotaxane at the lower temperature. | 0 | Theoretical and Fundamental Chemistry |
Neoglycorandomization is a chemoselective glycodiversification method inspired by the alkoxyamine-based ‘neoglycosylation’ reaction first described Peri and Dumy. This reaction proceeds via an oxy-iminium intermediate to ultimately provide the more thermodynamically-favored closed ring neoglycoside. The neoglycosylation reaction is compatible with a wide range of saccharide and aglycon functionality where neoglycoside anomeric stereospecificity is a thermodynamically-driven. Importantly, structural and functional studies reveal neoglycosides to serve as good mimics of their O-glycosidic comparators. The first neoglycorandomization proof of concept focused upon digitoxin where the rapid generation and cancer cell line cytotoxicity screening of 78 digitoxigenin neoglycosides revealed unique analogs with improved anticancer activity and reduced potential for cardiotoxicity. This platform has since been automated and used as an effective medicinal chemistry tool to modulate the properties of a range of natural products and pharmaceutical drugs. | 0 | Theoretical and Fundamental Chemistry |
In physics and engineering, mass flow rate is the mass of a substance which passes per unit of time. Its unit is kilogram per second in SI units, and slug per second or pound per second in US customary units. The common symbol is (ṁ, pronounced "m-dot"), although sometimes μ (Greek lowercase mu) is used.
Sometimes, mass flow rate is termed mass flux or mass current, see for example Schaums Outline of Fluid Mechanics'. In this article, the (more intuitive) definition is used.
Mass flow rate is defined by the limit:
i.e., the flow of mass through a surface per unit time .
The overdot on the is Newtons notation for a time derivative. Since mass is a scalar quantity, the mass flow rate (the time derivative of mass) is also a scalar quantity. The change in mass is the amount that flows after' crossing the boundary for some time duration, not the initial amount of mass at the boundary minus the final amount at the boundary, since the change in mass flowing through the area would be zero for steady flow. | 1 | Applied and Interdisciplinary Chemistry |
John Robert Huizenga (April 21, 1921 – January 25, 2014) was an American physicist who helped build the first atomic bomb and who also debunked University of Utah scientists' claim of achieving cold fusion. | 0 | Theoretical and Fundamental Chemistry |
In general, many questions exist about the health and environmental effects of many herbicides because of the large number of herbicides and the myriad potential targets, mostly unintended. For example, a 1995 panel of 13 scientists reviewing studies on the carcinogenicity of 2,4-D had divided opinions on the likelihood 2,4-D causes cancer in humans. , studies on phenoxy herbicides were too few to accurately assess the risk of many types of cancer from these herbicides, even although evidence was stronger that exposure to these herbicides is associated with increased risk of soft tissue sarcoma and non-Hodgkin lymphoma.
Herbicides have widely variable toxicity in addition to acute toxicity arising from ingestion of a significant quantity rapidly, and chronic toxicity arising from environmental and occupational exposure over long periods. Much public suspicion of herbicides revolves around a confusion between valid statements of acute toxicity as opposed to equally valid statements of lack of chronic toxicity at the recommended levels of usage. For instance, while glyphosate formulations with tallowamine adjuvants are acutely toxic, their use was found to be uncorrelated with any health issues like cancer in a massive US Department of Health study on 90,000 members of farmer families for over a period of 23 years. That is, the study shows lack of chronic toxicity, but cannot question the herbicide's acute toxicity.
Some herbicides cause a range of health effects ranging from skin rashes to death. The pathway of attack can arise from intentional or unintentional direct consumption, improper application resulting in the herbicide coming into direct contact with people or wildlife, inhalation of aerial sprays, or food consumption prior to the labelled preharvest interval. Under some conditions, certain herbicides can be transported via leaching or surface runoff to contaminate groundwater or distant surface water sources. Generally, the conditions that promote herbicide transport include intense storm events (particularly shortly after application) and soils with limited capacity to adsorb or retain the herbicides. Herbicide properties that increase likelihood of transport include persistence (resistance to degradation) and high water solubility.
Cases have been reported where Phenoxy herbicides are contaminated with dioxins such as TCDD; research has suggested such contamination results in a small rise in cancer risk after occupational exposure to these herbicides. Triazine exposure has been implicated in a likely relationship to increased risk of breast cancer, although a causal relationship remains unclear.
Herbicide manufacturers have at times made false or misleading claims about the safety of their products. Chemical manufacturer Monsanto Company agreed to change its advertising after pressure from New York attorney general Dennis Vacco; Vacco complained about misleading claims that its spray-on glyphosate-based herbicides, including Roundup, were safer than table salt and "practically non-toxic" to mammals, birds, and fish (though proof that this was ever said is hard to find). Roundup is toxic and has resulted in death after being ingested in quantities ranging from 85 to 200 ml, although it has also been ingested in quantities as large as 500 ml with only mild or moderate symptoms. The manufacturer of Tordon 101 (Dow AgroSciences, owned by the Dow Chemical Company) has claimed Tordon 101 has no effects on animals and insects, in spite of evidence of strong carcinogenic activity of the active ingredient, picloram, in studies on rats. | 1 | Applied and Interdisciplinary Chemistry |
Chain shuttling polymerization is a dual-catalyst method for producing block copolymers with alternating or variable tacticity. The desired effect of this method is to generate hybrid polymers that bear the properties of both polymer chains, such as a high melting point accompanied by high elasticity. It is a relatively new method, the first instance of its use being reported by Arriola et al. in May 2006. | 0 | Theoretical and Fundamental Chemistry |
Cyclohexene derivatives, such as imines, epoxides, and halonium ions, react with nucleophiles in a stereoselective fashion, affording trans-diaxial addition products. The term “Trans-diaxial addition” describes the mechanism of the addition, however the products are likely to equilibrate by ring flip to the lower energy conformer, placing the new substituents in the equatorial position. | 0 | Theoretical and Fundamental Chemistry |
In superconducting materials, the characteristics of superconductivity appear when the temperature T is lowered below a critical temperature T. The value of this critical temperature varies from material to material. Conventional superconductors usually have critical temperatures ranging from around 20 K to less than 1 K. Solid mercury, for example, has a critical temperature of 4.2 K. As of 2015, the highest critical temperature found for a conventional superconductor is 203 K for HS, although high pressures of approximately 90 gigapascals were required. Cuprate superconductors can have much higher critical temperatures: YBaCuO, one of the first cuprate superconductors to be discovered, has a critical temperature above 90 K, and mercury-based cuprates have been found with critical temperatures in excess of 130 K. The basic physical mechanism responsible for the high critical temperature is not yet clear. However, it is clear that a two-electron pairing is involved, although the nature of the pairing ( wave vs. wave) remains controversial.
Similarly, at a fixed temperature below the critical temperature, superconducting materials cease to superconduct when an external magnetic field is applied which is greater than the critical magnetic field. This is because the Gibbs free energy of the superconducting phase increases quadratically with the magnetic field while the free energy of the normal phase is roughly independent of the magnetic field. If the material superconducts in the absence of a field, then the superconducting phase free energy is lower than that of the normal phase and so for some finite value of the magnetic field (proportional to the square root of the difference of the free energies at zero magnetic field) the two free energies will be equal and a phase transition to the normal phase will occur. More generally, a higher temperature and a stronger magnetic field lead to a smaller fraction of electrons that are superconducting and consequently to a longer London penetration depth of external magnetic fields and currents. The penetration depth becomes infinite at the phase transition.
The onset of superconductivity is accompanied by abrupt changes in various physical properties, which is the hallmark of a phase transition. For example, the electronic heat capacity is proportional to the temperature in the normal (non-superconducting) regime. At the superconducting transition, it suffers a discontinuous jump and thereafter ceases to be linear. At low temperatures, it varies instead as e for some constant, α. This exponential behavior is one of the pieces of evidence for the existence of the energy gap.
The order of the superconducting phase transition was long a matter of debate. Experiments indicate that the transition is second-order, meaning there is no latent heat. However, in the presence of an external magnetic field there is latent heat, because the superconducting phase has a lower entropy below the critical temperature than the normal phase. It has been experimentally demonstrated that, as a consequence, when the magnetic field is increased beyond the critical field, the resulting phase transition leads to a decrease in the temperature of the superconducting material.
Calculations in the 1970s suggested that it may actually be weakly first-order due to the effect of long-range fluctuations in the electromagnetic field. In the 1980s it was shown theoretically with the help of a disorder field theory, in which the vortex lines of the superconductor play a major role, that the transition is of second order within the type II regime and of first order (i.e., latent heat) within the type I regime, and that the two regions are separated by a tricritical point. The results were strongly supported by Monte Carlo computer simulations. | 0 | Theoretical and Fundamental Chemistry |
A promoter is defined in RegulonDB as the nucleotide sequence 60 bases upstream and 20 downstream from the precise initiation of transcription or +1. Terminators are regions where transcription ends, and RNA Polymerase unbinds from DNA. | 1 | Applied and Interdisciplinary Chemistry |
Racemic drugs are not drug combinations in the accepted sense of two or more co-formulated therapeutic agents, but combinations of isomeric substances whose pharmacological activity may reside predominantly in one specific enantiomeric form. In case of stereoselectivity in action only one of the components in the racemic mixture is truly active. The other isomer, the distomer, should be regarded as impurity or isomeric ballast, a term coined by Ariëns, not contributing to the effects aimed at. In contrast to the pharmacokinetic properties of an enantiomeric pair, differences in pharmacodynamic activity tend to be more obvious. There is a wide spectrum of possibilities of distomer actions, many of which are confirmed experimentally. Selected examples of the distomer actions (viz. equipotent, less active, inactive, antagonistic, chiral inversion) are presented in the table below. | 0 | Theoretical and Fundamental Chemistry |
Modafinil has been studied in the treatment of major depressive disorder. In a 2021 systematic review and meta-analysis of randomized controlled trials of psychostimulants for depression, modafinil and other stimulants such as methylphenidate and amphetamines improved depression in traditional meta-analysis. However, when subjected to network meta-analysis, modafinil and most other stimulants did not significantly improve depression, with only methylphenidate remaining effective. Modafinil and other stimulants likewise did not improve quality of life in the meta-analysis, although there was evidence for reduced fatigue and sleepiness with modafinil and other stimulants. While significant effectiveness of modafinil for depression has been reported by particular trials, reviews and meta-analyses note that the effectiveness of modafinil for depression is limited, the quality of available evidence is low, and the results are inconclusive. | 0 | Theoretical and Fundamental Chemistry |
He received his second Ph.D. degree at Duke University where he was a Fulbright Scholar from 1964 to 1968. He worked in the laboratory of Charles Tanford, Department of Biochemistry in the protein folding area focussing his career on the folding thermodynamics and
kinetics, properties of the native and the unfolded proteins. His early collaborative work in uncovering residual native protein structure, following treatment with heat, acid (low pH) experimentally in a number of model proteins in his lab was published in 1967. He actually performed equilibrium unfolding studies on ribonuclease protein in guanidine hydrochloride, the findings of which were acceptable for the aforementioned Ph.D. degree in biochemistry by Duke University (1968).
Salahuddin returned to AMU Aligarh and joined the Department of Biochemistry, Faculty of Medicine, J.N. Medical College in 1968 as a reader. Salahuddin was present at the foundation ceremony of the new IBU Building on 15 January 1986. The event was inaugurated by Abdus Salam. He performed a critical role toward the establishment of the Interdisciplinary Biotechnology Institute for Modern Biological and Biotechnological Education at Aligarh along with the AMU administration in 1984. | 1 | Applied and Interdisciplinary Chemistry |
pH in rivers is affected by the geology of the water source, atmospheric inputs and a range of other chemical contaminants. pH is only likely to become an issue on very poorly buffered upland rivers where atmospheric sulphur and nitrogen oxides may very significantly depress the pH as low as pH4 or in eutrophic alkaline rivers where photosynthetic bi-carbonate ion production in photosynthesis may drive the pH up above pH10. | 1 | Applied and Interdisciplinary Chemistry |
Boron is used in pyrotechnics to prevent the amide-forming reaction between aluminium and nitrates. A small amount of boric acid is added to the composition to neutralize alkaline amides that can react with the aluminium.
Boric acid can be used as a colorant to make fire green. For example, when dissolved in methanol it is popularly used by fire jugglers and fire spinners to create a deep green flame much stronger than copper sulfate. | 0 | Theoretical and Fundamental Chemistry |
Ernest Rutherford, 1st Baron Rutherford of Nelson, (30 August 1871 – 19 October 1937) was a New Zealand physicist who was a pioneering researcher in both atomic and nuclear physics. Rutherford has been described as "the father of nuclear physics", and "the greatest experimentalist since Michael Faraday". In 1908, he was awarded the Nobel Prize in Chemistry "for his investigations into the disintegration of the elements, and the chemistry of radioactive substances." He was the first Oceanian Nobel laureate, and the first to perform the awarded work in Canada.
Rutherford's discoveries include the concept of radioactive half-life, the radioactive element radon, and the differentiation and naming of alpha and beta radiation. Together with Thomas Royds, Rutherford is credited with proving that alpha radiation is composed of helium nuclei. In 1911, he theorized that atoms have their charge concentrated in a very small nucleus. This was done through his discovery and interpretation of Rutherford scattering during the gold foil experiment performed by Hans Geiger and Ernest Marsden, resulting in his conception of the Rutherford model of the atom. In 1917, he performed the first artificially-induced nuclear reaction by conducting experiments where nitrogen nuclei were bombarded with alpha particles. As a result, he discovered the emission of a subatomic particle which he initially called the "hydrogen atom", but later (more accurately) named the proton. He is also credited with developing the atomic numbering system alongside Henry Moseley. His other achievements include advancing the fields of radio communications and ultrasound technology.
Rutherford became Director of the Cavendish Laboratory at the University of Cambridge in 1919. Under his leadership, the neutron was discovered by James Chadwick in 1932. In the same year, the first controlled experiment to split the nucleus was performed by John Cockcroft and Ernest Walton, working under his direction. In honour of his scientific advancements, Rutherford was recognised as a Baron in the peerages of New Zealand and Britain. After his death in 1937, he was buried in Westminster Abbey near Charles Darwin and Isaac Newton. The chemical element rutherfordium (Rf) was named after him in 1997. | 1 | Applied and Interdisciplinary Chemistry |
Oxocarbenium ions have been utilized in total synthesis on several occasions. A major subunit of (+)-clavosolide was synthesized with a reduction of a six-membered oxocarbenium ring. All the large substituents were found in an equatorial position, and the transformation went through the chair transition state, as predicted.
A second example is seen in the key step of the synthesis of (−)-neopeltolide, which uses another six-membered oxocarbenium ring reduction for a diastereoselective hydride addition. | 0 | Theoretical and Fundamental Chemistry |
Whereas a four-spin AA′BB′ (or AA′XX′) system may have the requisite symmetry and coupling properties, its signals may show more or less complexity and, as with other coupling phenomena, the appearance of a signal from magnetically inequivalent nuclei will also depend on the instrumental field strength. A large number of such systems show less complexity, with fewer lines than is possible, particularly when the instrumental resolution is low, whence nearby peaks appear to coalesce, when J ≈ J, when J ≈ −J, when J ≈ J or when J ≈ 0. The apparent complexity is also diminished in AA′XX′ systems when ν−ν >> J. This kind of simplication is enhanced as the instrumental magnetic field is increased, since the field-independent differences between coupling constants or between a coupling constant and zero appear proportionately smaller on the δ (ppm) scale, and since the field-dependent quantity (ν−ν)/J is magnified.
In molecules of uncertain or otherwise unproven structure, the definitive appearance of complexity in a pair of signals, beyond what can be explained by first-order analysis of HC-CH pairs or HC-CH fragments, can be taken to signify the presence of magnetic inequivalence and, therefore, of an element of symmetry aggregating them. Thus, the appearance of such complexity in the aromatic region of the H-NMR spectrum of the bis-(acetylacetonato)ruthenium complex of o-benzoquinonediimine served to prove its C-symmetrical nature. | 0 | Theoretical and Fundamental Chemistry |
Diffusers are generally referred to as either:
# Fine Bubble/Fine Pore
# Coarse Bubble
Other diffused aeration devices include: jet aerators, aspirators, and U tubes. | 1 | Applied and Interdisciplinary Chemistry |
MSO is phosphorylated by glutamine synthetase. The resulting product acts as a transition state analog that is unable to diffuse from the active site, thereby inhibiting the enzyme. | 1 | Applied and Interdisciplinary Chemistry |
is the latinized form of Greek (), from sárx (, "flesh") and kólla (, "glue"). It is variously known in Arabic as or , as Persian gum (), and as Kerman gum () and in Persian as , as or , and as . The medieval Latin name of the product was from corruption of the Andalusian Arabic form of or , probably via Old Spanish. | 1 | Applied and Interdisciplinary Chemistry |
Cumulative fission yields give the amounts of nuclides produced either directly in the fission or by decay of other nuclides. | 0 | Theoretical and Fundamental Chemistry |
Ashe joined the University of Minnesota Medical School in 1992 as an assistant professor of neurology. She has also worked with the Minneapolis Veterans Affairs Health Care System. She was the founding director of the N. Bud Grossman Center for Memory Research and Care. As of 2022, she has received over $28million in grants from the U.S. National Institutes of Health.
The Minneapolis Star Tribune described Ashe as a "distinguished professor considered by many to be on the short list for a Nobel Prize for her work". | 1 | Applied and Interdisciplinary Chemistry |
Despite its major advantages, RT-PCR is not without drawbacks. The exponential growth of the reverse transcribed complementary DNA (cDNA) during the multiple cycles of PCR produces inaccurate end point quantification due to the difficulty in maintaining linearity. In order to provide accurate detection and quantification of RNA content in a sample, qRT-PCR was developed using fluorescence-based modification to monitor the amplification products during each cycle of PCR. The extreme sensitivity of the technique can be a double edged sword since even the slightest DNA contamination can lead to undesirable results. A simple method for elimination of false positive results is to include anchors, or tags, to the 5' region of a gene specific primer. Additionally, planning and design of quantification studies can be technically challenging due to the existence of numerous sources of variation including template concentration and amplification efficiency. Spiking in a known quantity of RNA into a sample, adding a series of RNA dilutions generating a standard curve, and adding in a no template copy sample (no cDNA) may used as controls. | 1 | Applied and Interdisciplinary Chemistry |
The entries in BTO are updated bi-annually as part of the major update of BRENDA. It is available via the BRENDA website in the category “[https://www.brenda-enzymes.org/ontology.php Ontology Explorer]”. The enzyme source terms can be searched via the BTO query form. As a result, the user receives a list of EC numbers which are directly connected to the enzyme information of BRENDA. It is also possible to search via the BRENDA “Source Tissue” search form (“Classic View”). The result page displays all enzymes which are isolated or detected in the searched tissue term, directly linked to BTO.
BTO and BRENDA are freely accessible for academic users. It can be freely downloaded via the “[https://www.brenda-enzymes.info/ontology/tissue/tree/update/update_files/BrendaTissueOBO Ontology Explorer]” of the BRENDA website or in the OBO format from “[http://www.obofoundry.org/ontology/bto.html Obofoundry]”. | 1 | Applied and Interdisciplinary Chemistry |
, translated as external alchemy<nowiki/> or external elixir<nowiki/>, is the early branch of Chinese alchemy that focuses upon compounding elixirs of immortality by heating minerals, metals, and other natural substances in a luted crucible. The later branch of esoteric neidan inner alchemy, which borrowed doctrines and vocabulary from exoteric , is based on allegorically producing elixirs within the endocrine or hormonal system of the practitioner's body, through Daoist meditation, diet, and physiological practices. The practice of external alchemy originated in the early Han dynasty (206 BCE–220 CE), grew in popularity until the Tang (618–907), when began and several emperors died from alchemical elixir poisoning, and gradually declined until the Ming dynasty (1368–1644). | 1 | Applied and Interdisciplinary Chemistry |
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