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Liebig and Wöhler observed in 1832 in an investigation of benzoin resin (benzoic acid) that the compounds almond oil (benzaldehyde), "Benzoestoff" (benzyl alcohol), benzoyl chloride and benzamide all share a common CHO fragment and that these compounds could all be synthesized from almond oil by simple substitutions. The CHO fragment was considered a "radical of benzoic acid" and called benzoyl. Organic radicals were thus placed on the same level as the inorganic elements. Just like the inorganic elements (simple radicals) the organic radicals (compound radicals) were indivisible. The theory was developed thanks to improvements in elemental analysis by von Liebig. Laurent contributed to the theory by reporting the isolation of benzoyl itself in 1835, however the isolated chemical is today recognised at its dimer dibenzoyl. Raffaele Piria reported the salicyl radical as the base for salicylic acid. Liebig published a definition of a radical in 1838
Berzelius and Robert Bunsen investigated the radical cacodyl (reaction of cacodyl chloride with zinc) around 1841, now also known as a dimer species (CH)As—As(CH). Edward Frankland and Hermann Kolbe contributed to the radical theory by investigating the ethyl and the methyl radicals. Frankland first reported diethylzinc in 1848. Frankland and Kolbe together investigated the reaction of ethyl cyanide and zinc in 1849 reporting the isolation of not the ethyl radical but the methyl radical (CH) which in fact was ethane. Kolbe also investigated the electrolysis of potassium salts of some fatty acids. Acetic acid was regarded as the combination of the methyl radical and oxalic acid and electrolysis of the salt yielded as gas again ethane misidentified as the liberated methyl radical.
In 1850 Frankland investigated ethyl radicals. In the course of this work butane formed by reaction of ethyl iodide and zinc was mistakenly identified as the ethyl radical. | 0 | Theoretical and Fundamental Chemistry |
In blood vessels Endothelium-Derived Hyperpolarizing Factor or EDHF is proposed to be a substance and/or electrical signal that is generated or synthesized in and released from the endothelium; its action is to hyperpolarize vascular smooth muscle cells, causing these cells to relax, thus allowing the blood vessel to expand in diameter. | 1 | Applied and Interdisciplinary Chemistry |
How much gas is present could be specified by giving the mass instead of the chemical amount of gas. Therefore, an alternative form of the ideal gas law may be useful. The chemical amount, n (in moles), is equal to total mass of the gas (m) (in kilograms) divided by the molar mass, M (in kilograms per mole):
By replacing n with m/M and subsequently introducing density ρ = m/V, we get:
Defining the specific gas constant R as the ratio R/M,
This form of the ideal gas law is very useful because it links pressure, density, and temperature in a unique formula independent of the quantity of the considered gas. Alternatively, the law may be written in terms of the specific volume v, the reciprocal of density, as
It is common, especially in engineering and meteorological applications, to represent the specific gas constant by the symbol R. In such cases, the universal gas constant is usually given a different symbol such as or to distinguish it. In any case, the context and/or units of the gas constant should make it clear as to whether the universal or specific gas constant is being used. | 0 | Theoretical and Fundamental Chemistry |
The separating funnel relies on the concept of "like dissolves like", which describes the ability of polar solvents to dissolve polar solutes and non-polar solvents to dissolve non-polar solutes. When the separating funnel is agitated, each solute migrates to the solvent (also referred to as "phase") in which it is more soluble.
The solvents normally do not form a unified solution together because they are immiscible. When the funnel is kept stationary after agitation, the liquids form distinct physical layers - lower density liquids will stay above higher density liquids. A mixture of solutes is thus separated into two physically separate solutions, each enriched in different solutes.
The stopcock may be opened after the two phases separate to allow the bottom layer to escape the separator funnel. The top layer may be retained in the separating funnel for further extractions with additional batches of solvent or drained out into a separate vessel for other uses. If it is desired to retain the bottom layer in the separating funnel for further extractions, both layers are taken out separately, and then the former bottom layer is returned to the separating funnel.
Each independent solution can then be extracted again with additional batches of solvent, used for other physical or chemical processes. If the goal was to separate a soluble material from mixture, the solution containing that desired product can sometimes simply be evaporated to leave behind the purified solute. For this reason, it is a practical benefit to use volatile solvents for extracting the desired material from the mixture. | 0 | Theoretical and Fundamental Chemistry |
Other techniques for writing data in three-dimensions have also been examined, including:
Persistent spectral hole burning (PSHB), which also allows the possibility of spectral multiplexing to increase data density. However, PSHB media currently requires extremely low temperatures to be maintained in order to avoid data loss.
Void formation, where microscopic bubbles are introduced into a media by high intensity laser irradiation.
Chromophore poling, where the laser-induced reorientation of chromophores in the media structure leads to readable changes. | 0 | Theoretical and Fundamental Chemistry |
The original membership fee was very steep for the time: The first subscription fee was set at one guinea, which would be equivalent to nearly £400 today. Four grades of membership were agreed at the time: member, associate, student and honorary, with most appointments made on the basis of a review of their eligibility by the SCI council. Despite the high fee, by the time of the first official meeting of the Society of Chemical Industry in June 1881, it had attracted over 300 members. | 1 | Applied and Interdisciplinary Chemistry |
Ammonotelism is the excretion of ammonia and ammonium ions. Ammonia (NH) forms with the oxidation of amino groups.(-NH), which are removed from the proteins when they convert into carbohydrates. It is a very toxic substance to tissues and extremely soluble in water. Only one nitrogen atom is removed with it. A lot of water is needed for the excretion of ammonia, about 0.5 L of water is needed per 1 g of nitrogen to maintain ammonia levels in the excretory fluid below the level in body fluids to prevent toxicity. Thus, the marine organisms excrete ammonia directly into the water and are called ammonotelic. Ammonotelic animals include crustaceans, platyhelminths, cnidarians, poriferans, echinoderms, and other aquatic invertebrates. | 1 | Applied and Interdisciplinary Chemistry |
Microscopic simulation methods work directly with the equations of motion (classical or quantum) of the constituent molecules. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, a ketene is an organic compound of the form , where R and R' are two arbitrary monovalent chemical groups (or two separate substitution sites in the same molecule). The name may also refer to the specific compound ethenone , the simplest ketene.
Although they are highly useful, most ketenes are unstable. When used as reagents in a chemical procedure, they are typically generated when needed, and consumed as soon as (or while) they are produced. | 0 | Theoretical and Fundamental Chemistry |
At the beginning of the 20th century, the entire Russian industry was in a deep crisis, the consequences of which affected the factories of the Urals until 1909. In 1909, the Ural iron and steel plants smelted 34.7 million tons of iron, which is 30.9% less than in 1900. During the crisis years, the share of finished iron increased, new markets were searched for, syndicates and associations were created to fight the competition of factories in Southern Russia. To a lesser extent, the crisis affected the copper smelting industry, thanks to continued demand and an increase in customs duties on copper imports. In the first decade of the 20th century, small technically backward factories with worn-out equipment, which had become unprofitable, were closed. Of the 111 metallurgical plants operating in the Urals in 1900, 35 plants were shut down by 1913. In conditions of tough competition, factories were forced to modernize: blast furnaces with a lightweight casing were erected, hot blast was introduced everywhere, steam engines and ore preparation for smelting, furnaces and puddling furnaces were replaced by open-hearth furnaces, more powerful rolling mills were built, and factories received electricity. In the mountainous districts, the optimization and reorganization of capacities were carried out: the final processing was concentrated, as a rule, at the main plant of the district, the rest of the factories provided supplies of iron. During the Russo-Japanese War, the Izhevsk, Perm, and Zlatoust arms factories sharply increased the production of guns, rifles, and shells.
In 1908, the construction of the Porogi electrometallurgical plant for the production of ferroalloys, and one of the first hydroelectric power plants in Russia to provide the plant with electricity began. Until 1931, the plant was the only producer of ferroalloys in the country.
In 1910, an industrial boom began, which continued until the First World War. From 1910 to 1913, the production of iron increased to 55.3 million poods (by 29.9%), finished metal products - up to 40.8 million poods (by 9.6%). But the share of the Ural factories in the all-Russian iron smelting fell to 21.6%. Commercial banks actively invested in the development of the metallurgy of the Urals. The most important role in the Urals was played by the Azov-Don Commercial Bank, Saint Petersburg International Commercial Bank, and Russo-Asiatic Bank. The volume of investments at the turn of the 20th century was estimated at 10.8 million rubles. Modernization and reconstruction of mountain districts continued. In 1911, a new blast furnace with a volume of 150 m³ and an open-hearth furnace with a capacity of 25 tons were launched at the Nizhniy Tagil plant; two Bessemer converters and two new blast furnaces were installed at the Nizhnesaldinsky plant. The Votkinsk plant was reconstructed for the production of steam locomotives and river vessels. The factories that produced weapons were reconstructed and switched over to the production of civilian products. Also in the pre-war years, the concentration of production at large factories increased: in 1914, out of 49 Ural plants, 16 had the productivity of more than 1 million poods of iron per year and produced 65% of the total volume, including 5 factories with a capacity of more than 2 million poods of iron per year. Nadezhdinsky, Nizhnesaldinsky, Zlatoustovsky, Chusovskoy, and Votkinsky produced 36.1% of the total volume.
Copper smelters of the Urals at the beginning of the 20th century mastered pyrite smelting, which made it possible to process poor sulfur ores. In the pre-war years, the Nizhnekyshtymsky Copper Electrolytic Plant, the Karabashsky, and Kalatinsky plants were launched. Through syndicates formed, British companies owned 65.5% of the copper mined in the Urals. The gold-platinum mining industry underwent mechanization. The first Dutch dredges appeared in 1900 at the Neozhidany Mine on the Is River. By 1913, the number of dredges in the Urals reached 50, they ensured the extraction of 20% of gold and 50% of platinum. Until 1913, the average production of gold in the Urals was 550-650 poods per year, while the average production of platinum was 300-350 poods per year. | 1 | Applied and Interdisciplinary Chemistry |
Thermomechanical processing is a metallurgical process that combines mechanical or plastic deformation process like compression or forging, rolling, etc. with thermal processes like heat-treatment, water quenching, heating and cooling at various rates into a single process. | 1 | Applied and Interdisciplinary Chemistry |
A well dispersed colloidal suspension consists of individual, separated particles and is stabilized by repulsive inter-particle forces. When the repulsive forces weaken or become attractive through the addition of a coagulant, particles start to aggregate. Initially, particle doublets A will form from singlets A according to the scheme
In the early stage of the aggregation process, the suspension mainly contains individual particles. The rate of this phenomenon is characterized by the aggregation rate coefficient . Since doublet formation is a second order rate process, the units of this coefficients are ms since particle concentrations are expressed as particle number per unit volume (m). Since absolute aggregation rates are difficult to measure, one often refers to the dimensionless stability ratio , defined as where is the aggregation rate coefficient in the fast regime, and the coefficient at the conditions of interest. The stability ratio is close to unity in the fast regime, increases in the slow regime, and becomes very large when the suspension is stable.
Often, colloidal particles are suspended in water. In this case, they accumulate a surface charge and an electrical double layer forms around each particle. The overlap between the diffuse layers of two approaching particles results in a repulsive double layer interaction potential, which leads to particle stabilization. When salt is added to the suspension, the electrical double layer repulsion is screened, and van der Waals attraction become dominant and induce fast aggregation. The figure on the right shows the typical dependence of the stability ratio versus the electrolyte concentration, whereby the regimes of slow and fast aggregation are indicated.
The table below summarizes the critical coagulation concentration (CCC) ranges for different net charge of the counter ion.
The charge is expressed in units of elementary charge. This dependence reflects the Schulze–Hardy rule, which states that the CCC varies as the inverse sixth power of the counter ion charge. The CCC also depends on the type of ion somewhat, even if they carry the same charge. This dependence may reflect different particle properties or different ion affinities to the particle surface. Since particles are frequently negatively charged, multivalent metal cations thus represent highly effective coagulants.
Adsorption of oppositely charged species (e.g., protons, specifically adsorbing ions, surfactants, or polyelectrolytes) may destabilize a particle suspension by charge neutralization or stabilize it by buildup of charge, leading to a fast aggregation near the charge neutralization point, and slow aggregation away from it.
Quantitative interpretation of colloidal stability was first formulated within the DLVO theory. This theory confirms the existence slow and fast aggregation regimes, even though in the slow regime the dependence on the salt concentration is often predicted to be much stronger than observed experimentally. The Schulze–Hardy rule can be derived from DLVO theory as well.
Other mechanisms of colloid stabilization are equally possible, particularly, involving polymers. Adsorbed or grafted polymers may form a protective layer around the particles, induce steric repulsive forces, and lead to steric stabilization at it is the case with polycarboxylate ether (PCE), the last generation of chemically tailored superplasticizer specifically designed to increase the workability of concrete while reducing its water content to improve its properties and durability. When polymers chains adsorb to particles loosely, a polymer chain may bridge two particles, and induce bridging forces. This situation is referred to as bridging flocculation.
When particle aggregation is solely driven by diffusion, one refers to perikinetic aggregation. Aggregation can be enhanced through shear stress (e.g., stirring). The latter case is called orthokinetic aggregation. | 0 | Theoretical and Fundamental Chemistry |
NMR signals are usually detected inductively, but the low frequencies of the electromagnetic radiation emitted by samples in a ZULF experiment makes inductive detection impractical at low fields. Hence, the earliest approach for measuring zero-field NMR in solid samples was via field-cycling techniques. The field cycling involves three steps: preparation, evolution and detection. In the preparation stage, a field is applied in order to magnetize the nuclear spins. Then the field is suddenly switched to zero to initiate the evolution interval and the magnetization evolves under the zero-field Hamiltonian. After a time period, the field is again switched on and the signal is detected inductively at high field. In a single field cycle, the magnetization observed corresponds only to a single value of the zero-field evolution time. The time-varying magnetization can be detected by repeating the field cycle with incremented lengths of the zero-field interval, and hence the evolution and decay of the magnetization is measured point by point. The Fourier transform of this magnetization will result to the zero-field absorption spectrum.
The emergence of highly sensitive magnetometry techniques has allowed for the detection of zero-field NMR signals in situ. Examples include superconducting quantum interference devices (SQUIDs), magnetoresistive sensors, and SERF atomic magnetometers. SQUIDs have high sensitivity, but require cryogenic conditions to operate, which makes them practically somewhat difficult to employ for the detection of chemical or biological samples. Magnetoresistive sensors are less sensitive, but are much easier to handle and to bring close to the NMR sample which is advantageous since proximity improves sensitivity. The most common sensors employed in ZULF NMR experiments are optically-pumped magnetometers, which have high sensitivity and can be placed in close proximity to an NMR sample. | 0 | Theoretical and Fundamental Chemistry |
Members of the Hedgehog protein family act by binding to a transmembrane "Patched" receptor, which is bound to the "Smoothened" protein, by which the Hedgehog signal can be transduced. In the absence of Hedgehog, the Patched receptor inhibits Smoothened action. Inhibition of Smoothened causes the Cubitus interruptus (Ci), Fused, and Cos protein complex attached to microtubules to remain intact. In this conformation, the Ci protein is cleaved so that a portion of the protein is allowed to enter the nucleus and act as a transcriptional repressor. In the presence of Hedgehog, Patched no longer inhibits Smoothened. Then active Smoothened protein is able to inhibit PKA and Slimb, so that the Ci protein is not cleaved. This intact Ci protein can enter the nucleus, associate with CPB protein and act as a transcriptional activator, inducing the expression of Hedgehog-response genes. | 1 | Applied and Interdisciplinary Chemistry |
Type III restriction enzymes (e.g., EcoP15) recognize two separate non-palindromic sequences that are inversely oriented. They cut DNA about 20–30 base pairs after the recognition site. These enzymes contain more than one subunit and require AdoMet and ATP cofactors for their roles in DNA methylation and restriction digestion, respectively. They are components of prokaryotic DNA restriction-modification mechanisms that protect the organism against invading foreign DNA. Type III enzymes are hetero-oligomeric, multifunctional proteins composed of two subunits, Res () and Mod (). The Mod subunit recognises the DNA sequence specific for the system and is a modification methyltransferase; as such, it is functionally equivalent to the M and S subunits of type I restriction endonuclease. Res is required for restriction digestion, although it has no enzymatic activity on its own. Type III enzymes recognise short 5–6 bp-long asymmetric DNA sequences and cleave 25–27 bp downstream to leave short, single-stranded 5' protrusions. They require the presence of two inversely oriented unmethylated recognition sites for restriction digestion to occur. These enzymes methylate only one strand of the DNA, at the N-6 position of adenine residues, so newly replicated DNA will have only one strand methylated, which is sufficient to protect against restriction digestion. Type III enzymes belong to the beta-subfamily of N6 adenine methyltransferases, containing the nine motifs that characterise this family, including motif I, the AdoMet binding pocket (FXGXG), and motif IV, the catalytic region (S/D/N (PP) Y/F). | 1 | Applied and Interdisciplinary Chemistry |
Monatomic anions are named as the element modified with an -ide ending. The charge follows in brackets, (optional for 1) e.g.:
* Cl) or chloride
* S)
Some elements take their Latin name as the root e.g
*silver, Ag, argentide
*copper, Cu, cupride
*iron, Fe, ferride
*tin, Sn, stannide
Polyatomic anions of the same element are named as the element name preceded by di-, tri-, etc., e.g.:
* O) (or peroxide as an acceptable name)
* C) (or acetylide as an acceptable name)
* S)
or sometimes as an alternative derived from a substitutive name e.g.
* S</sup> disulfanediide
Polyatomic anions made up of different elements are named either substitutively or additively, the name endings are -ide and -ate respectively e.g. :
* GeH) (additive)
*TeH</sup> tellanuide substitutive where -uide specifies anion composed of additional hydride attached to parent hydride
* [PF]-phosphanuide (substitutive), or hexafluoridophosphate(1) (additive)
*SO) (additive), or sulfite (acceptable non-systematic name)
A full list of the alternative acceptable non-systematic names for cations and anions is in the recommendations.
Many anions have names derived from inorganic acids and these are dealt with later. | 0 | Theoretical and Fundamental Chemistry |
The use of synthetic oligonucleotides as specific probes for genetic sequence variations was pioneered by R. Bruce Wallace, working at the City of Hope National Medical Center in Duarte, California. In 1979 Wallace and his coworkers reported the use of ASO probes to detect variations in a single-stranded bacterial virus, and later applied the technique to cloned human genes. In 1983 and 1985 Wallace's lab reported the detection of the mutation for sickle cell anemia in samples of whole genomic DNA, although this application was hampered by the small amount of label that could be carried by the ASO.
Fortunately PCR, a method to greatly amplify a specific segment of DNA, was also reported in 1985. In less than a year PCR had been paired with ASO analysis. This combination solved the problem of ASO labeling, since the amount of target DNA could be amplified over a million-fold. Also, the specificity of the PCR process itself could be added to that of the ASO probes, greatly reducing the problem of spurious binding of the ASO to non-target sequences. The combination was specific enough that it could be used in a simple Dot blot, avoiding the laborious and inefficient Southern blot method. | 1 | Applied and Interdisciplinary Chemistry |
Rhodopin (1,2-dihydro-ψ,ψ-caroten-1-ol) is a carotenoid. It is a major carotenoid of phototropic bacteria such as Rhodomicrobium vannielii and Rhodopseudomonas acidophila strain 7050. | 1 | Applied and Interdisciplinary Chemistry |
Harmful algal bloom in coastal areas are also often referred to as "red tides". The term "red tide" is derived from blooms of any of several species of dinoflagellate, such as Karenia brevis. However, the term is misleading since algal blooms can widely vary in color, and growth of algae is unrelated to the tides. Not all red tides are produced by dinoflagellates. The mixotrophic ciliate Mesodinium rubrum produces non-toxic blooms coloured deep red by chloroplasts it obtains from the algae it eats.
As a technical term, it is being replaced in favor of more precise terminology, including the generic term "harmful algal bloom" for harmful species, and "algal bloom" for benign species. | 0 | Theoretical and Fundamental Chemistry |
A hormone response element (HRE) is a short sequence of DNA within the promoter of a gene, that is able to bind to a specific hormone receptor complex and therefore regulate transcription. The sequence is most commonly a pair of inverted repeats separated by three nucleotides, which also indicates that the receptor binds as a dimer. Specifically, HRE responds to steroid hormones, as the activated steroid receptor is the transcription factor binding HRE. This regulates the transcription of genes signalled by the steroid hormone.
A gene may have many different response elements, allowing complex control to be exerted over the level and rate of transcription.
HRE are used in transgenic animal cells as inducers of gene expression.
Examples of HREs include estrogen response elements and androgen response elements. | 1 | Applied and Interdisciplinary Chemistry |
*[http://www.pharmetrx.de/ PharMetrX: Pharmacometrics & Computational Disease Modelling] (annual call for applications, July - Sept 15th) | 1 | Applied and Interdisciplinary Chemistry |
To solve for the concentration of all components appearing in any general biochemical reaction as in (), the Michaelis–Menten kinetics for an enzymatic reaction are coupled with the Monod kinetics for biomass dynamics. The most general case is to assume that the enzyme concentration is proportional to the biomass concentration and that the reaction is not in quasi-steady state. These hypotheses lead to the following system of equations
with , and where is the concentration of the most limiting substrate in each reaction i, z is the enzyme yield coefficient, Y is the yield coefficient expressing the biomass gain per unit of released product and is the biomass mortality rate. | 0 | Theoretical and Fundamental Chemistry |
Photoionization is the physical process in which an incident photon ejects one or more electrons from an atom, ion or molecule. This is essentially the same process that occurs with the photoelectric effect with metals. In the case of a gas or single atoms, the term photoionization is more common.
The ejected electrons, known as photoelectrons, carry information about their pre-ionized states. For example, a single electron can have a kinetic energy equal to the energy of the incident photon minus the electron binding energy of the state it left. Photons with energies less than the electron binding energy may be absorbed or scattered but will not photoionize the atom or ion.
For example, to ionize hydrogen, photons need an energy greater than 13.6 electronvolts (the Rydberg energy), which corresponds to a wavelength of 91.2 nm. For photons with greater energy than this, the energy of the emitted photoelectron is given by:
where h is the Planck constant and ν is the frequency of the photon.
This formula defines the photoelectric effect.
Not every photon which encounters an atom or ion will photoionize it. The probability of photoionization is related to the photoionization cross-section, which depends on the energy of the photon and the target being considered. For photon energies below the ionization threshold, the photoionization cross-section is near zero. But with the development of pulsed lasers it has become possible to create extremely intense, coherent light where multi-photon ionization may occur. At even higher intensities (around 10 - 10 W/cm of infrared or visible light), non-perturbative phenomena such as barrier suppression ionization and rescattering ionization are observed. | 0 | Theoretical and Fundamental Chemistry |
Crassulacean acid metabolism, also known as CAM photosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions that allows a plant to photosynthesize during the day, but only exchange gases at night. In a plant using full CAM, the stomata in the leaves remain shut during the day to reduce evapotranspiration, but they open at night to collect carbon dioxide () and allow it to diffuse into the mesophyll cells. The is stored as four-carbon malic acid in vacuoles at night, and then in the daytime, the malate is transported to chloroplasts where it is converted back to , which is then used during photosynthesis. The pre-collected is concentrated around the enzyme RuBisCO, increasing photosynthetic efficiency. This mechanism of acid metabolism was first discovered in plants of the family Crassulaceae. | 0 | Theoretical and Fundamental Chemistry |
The US Government uses the Hazardous Materials Identification System (HMIS) standard for flammability ratings, as do many US regulatory agencies, and also the US National Fire Protection Association (NFPA).
The ratings are as follows: | 0 | Theoretical and Fundamental Chemistry |
In the typical porphyrin biosynthesis pathway, four molecules of porphobilinogen are concatenated by carbons 2 and 5 of the pyrrole ring (adjacent to the nitrogen atom) into hydroxymethyl bilane by the enzyme porphobilinogen deaminase, also known as hydroxymethylbilane synthase. | 1 | Applied and Interdisciplinary Chemistry |
Galactolysis refers to the catabolism of galactose.
In the liver, galactose is converted through the Leloir pathway to glucose 6-phosphate in the following reactions:
galacto- uridyl phosphogluco-
kinase transferase mutase
gal --------> gal 1 P ------------------> glc 1 P -----------> glc 6 P
/ v
UDP-glc UDP-gal
epimerase | 1 | Applied and Interdisciplinary Chemistry |
Ferroelectricity is a characteristic of certain materials that have a spontaneous electric polarization that can be reversed by the application of an external electric field. All ferroelectrics are also piezoelectric and pyroelectric, with the additional property that their natural electrical polarization is reversible. The term is used in analogy to ferromagnetism, in which a material exhibits a permanent magnetic moment. Ferromagnetism was already known when ferroelectricity was discovered in 1920 in Rochelle salt by Joseph Valasek. Thus, the prefix ferro, meaning iron, was used to describe the property despite the fact that most ferroelectric materials do not contain iron. Materials that are both ferroelectric and ferromagnetic are known as multiferroics. | 0 | Theoretical and Fundamental Chemistry |
The first version of SMPDB was released on January 1, 2010. This release contained more than 350 image-mapped pathways for small molecule pathways. The viewer interface was limited to scroll-bar image navigation with 3-step (small, medium, large) zooming. The pathways in this first version were limited to 1) human metabolic pathways; 2) human metabolic disease pathways; and 3) human metabolite signaling pathways. The second version of SMPDB was released in 2014. This version contained more than 620 small molecule pathways. The viewer interface was enhanced to include a Google-Map-like interface with click-n-drag image navigation and unlimited, interactive zooming. The pathways in this second version were expanded to include: 1) general human metabolic pathways; 2) human metabolic disease pathways; 3) human metabolite signaling pathways; 4) drug action pathways and 5) drug metabolism pathways. | 1 | Applied and Interdisciplinary Chemistry |
Modafinil was studied for the treatment of stimulant dependence, but the results are mixed and inconclusive. Modafinil is not a controlled substance in some countries, unlike other medications, such as bupropion, which is also used to treat depression and nicotine dependence. The clinical trials that have tested modafinil as a treatment for stimulant abuse have failed to demonstrate its efficacy and the optimal dose and duration of modafinil treatment remain unclear, and modafinil is not a recommended treatment for stimulant abuse. | 0 | Theoretical and Fundamental Chemistry |
In 1960, Atalla and Kahng fabricated the first MOSFET with a gate oxide thickness of 100 nm, along with a gate length of 20µm. In 1962, Atalla and Kahng fabricated a nanolayer-base metal–semiconductor junction (M–S junction) transistor. This device has a metallic layer with nanometric thickness sandwiched between two semiconducting layers, with the metal forming the base and the semiconductors forming the emitter and collector. With its low resistance and short transit times in the thin metallic nanolayer base, the device was capable of high operation frequency compared to bipolar transistors. Their pioneering work involved depositing metal layers (the base) on top of single crystal semiconductor substrates (the collector), with the emitter being a crystalline semiconductor piece with a top or a blunt corner pressed against the metallic layer (the point contact). They deposited gold (Au) thin films with a thickness of 10 nm on n-type germanium (n-Ge), while the point contact was n-type silicon (n-Si). Atalla resigned from BTL in 1962. | 0 | Theoretical and Fundamental Chemistry |
This reaction shows the oxidation of phenol by iron and peroxide. This combination of iron, which comes from iron oxide in the sediment, and the peroxide, commonly released by animals and plants into the environment, is known as the Fenton Reagent. This reagent is used to oxidize phenol groups by the use of a radical hydroxide group produced from the peroxide in the p-benzoquinone. This product of phenol's oxidation is now leached into the environment while other products include iron(II) and water. P-benzoquinone is listed as being a very toxic, acute environmental hazard. | 0 | Theoretical and Fundamental Chemistry |
Luminol is synthesized in a two-step process, beginning with 3-nitrophthalic acid. First, hydrazine (NH) is heated with the 3-nitrophthalic acid in a high-boiling solvent such as triethylene glycol and glycerol. An acyl substitution condensation reaction occurs, with loss of water, forming 3-nitrophthalhydrazide. Reduction of the nitro group to an amino group with sodium dithionite (NaSO), via a transient hydroxylamine intermediate, produces luminol.
The compound was first synthesized in Germany in 1902, but was not named "luminol" until 1934. | 0 | Theoretical and Fundamental Chemistry |
The process of translation is highly regulated in both eukaryotic and prokaryotic organisms. Regulation of translation can impact the global rate of protein synthesis which is closely coupled to the metabolic and proliferative state of a cell.
To delve deeper into this intricate process, scientists typically use a technique known as ribosome profiling. This method enables researchers to take a snapshot of the translatome, showing which parts of the mRNA are being translated into proteins by ribosomes at a given time. Ribosome profiling provides valuable insights into translation dynamics, revealing the complex interplay between gene sequence, mRNA structure, and translation regulation. For example, research utilizing this method has revealed that genetic differences and their subsequent expression as mRNAs can also impact translation rate in an RNA-specific manner.
Expanding on this concept, a more recent development is single-cell ribosome profiling, a technique that allows us to study the translation process at the resolution of individual cells. This is particularly significant as cells, even those of the same type, can exhibit considerable variability in their protein synthesis. Single-cell ribosome profiling has the potential to shed light on the heterogeneous nature of cells, leading to a more nuanced understanding of how translation regulation can impact cell behavior, metabolic state, and responsiveness to various stimuli or conditions. | 1 | Applied and Interdisciplinary Chemistry |
Momentum diffusion most commonly refers to the diffusion, or spread of momentum between particles (atoms or molecules) of matter, often in the fluid state.
This transport of momentum can occur in any direction of the fluid flow. Momentum diffusion can be attributed to either external pressure or shear stress or both. | 1 | Applied and Interdisciplinary Chemistry |
Geopolymerization forms aluminosilicate frameworks that are similar to those of rock-forming minerals. Yet, there are major differences. In 1994, Davidovits presented a theoretical structure for K-poly(sialate-siloxo) (K)-(Si-O-Al-O-Si-O) that was consistent with the NMR spectra. It does not show the presence of water in the structure because he only focused on the relationship between Si, Al, Na, K, atoms. Water is present only at temperatures below 150 °C – 200 °C, whereas numerous geopolymer industrial and commercial applications work at temperatures above 200 °C, up to 1400 °C, i.e. at temperatures above dehydroxylation. Nevertheless, scientists working on low temperature applications, such as cements and waste management, tried to pinpoint cation hydration and water molecules. This model shows an incompletely reacted geopolymer (left in the figure), which involves free Si-OH groups that will later with time or with temperature polycondense with opposed Al-O-K, into Si-O-Al-O sialate bonds. The water released by this reaction either remains in the pores, is associated with the framework similarly to zeolitic water, or can be released and removed. Several 3D-frameworks are described in the book Geopolymer Chemistry and Applications. After dehydroxylation (and dehydration), generally above 250 °C, geopolymers become more and more crystalline (right in the picture) and above 500-1000 °C (depending on the nature of the alkali cation present) crystallise and have X-ray diffraction patterns and framework structures identical to their geological analogues. | 0 | Theoretical and Fundamental Chemistry |
Mass-difference impurity scattering is given by:
where is a measure of the impurity scattering strength. Note that is dependent of the dispersion curves. | 0 | Theoretical and Fundamental Chemistry |
In 1947 after the Manhattan Project had been dismantled, Lathrop remained on staff at the lab as an associate biochemist as it was renamed Argonne National Laboratory. In 1954, tired of an exhausting commute, Lathrop left Argonne to pursue a career at the Argonne Cancer Research Hospital. It had opened in 1953 on the University of Chicago campus making it much closer to her home.
Lathrop was hired by the US Atomic Energy Commission facility as a research associate under the guidance of Paul Harper. Their goal was to find ways to manipulate radiation to allow for cancer detection and treatment. Their groundbreaking work on using the gamma camera to scan the body is a method still in practice to this day.
She published her last paper in 1999 and then retired in 2000. | 0 | Theoretical and Fundamental Chemistry |
The secondary structure of nucleic acid molecules can often be uniquely decomposed into stems and loops. The stem-loop structure (also often referred to as an "hairpin"), in which a base-paired helix ends in a short unpaired loop, is extremely common and is a building block for larger structural motifs such as cloverleaf structures, which are four-helix junctions such as those found in transfer RNA. Internal loops (a short series of unpaired bases in a longer paired helix) and bulges (regions in which one strand of a helix has "extra" inserted bases with no counterparts in the opposite strand) are also frequent.
There are many secondary structure elements of functional importance to biological RNAs; some famous examples are the Rho-independent terminator stem-loops and the tRNA cloverleaf. Active research is on-going to determine the secondary structure of RNA molecules, with approaches including both experimental and computational methods (see also the List of RNA structure prediction software). | 0 | Theoretical and Fundamental Chemistry |
*Quillin, M. L., Arduini, R. M., Olson, J. S., & Phillips Jr, G. N. (1993). High-resolution crystal structures of distal histidine mutants of sperm whale myoglobin. Journal of molecular biology, 234(1), 140–155.
*Springer, B. A., Sligar, S. G., Olson, J. S., & Phillips, G. N. J. (1994). Mechanisms of ligand recognition in myoglobin. Chemical Reviews, 94(3), 699–714.
*Eich, R. F., Li, T., Lemon, D. D., Doherty, D. H., Curry, S. R., Aitken, J. F., ... & Olson, J. S. (1996). Mechanism of NO-induced oxidation of myoglobin and hemoglobin. Biochemistry, 35(22), 6976–6983.
*Yang, F., Moss, L. G., & Phillips Jr, G. N. (1996). The molecular structure of green fluorescent protein. Nature biotechnology, 14(10), 1246–1251.
*Schotte, F., Lim, M., Jackson, T. A., Smirnov, A. V., Soman, J., Olson, J. S., ... & Anfinrud, P. A. (2003). Watching a protein as it functions with 150-ps time-resolved x-ray crystallography. Science, 300(5627), 1944–1947. | 1 | Applied and Interdisciplinary Chemistry |
Position-specific isotopes can be used to trace environmental pollutants through local and global environment. This is specifically useful as heavy isotopes are often used to synthesize chemicals and then will get incorporated into the natural environment through biodegradation. Thus, tracing position-specific isotopes in the environment can help trace the movement of these pollutants and chemical products. | 0 | Theoretical and Fundamental Chemistry |
Pure oxygen activated sludge aeration systems are sealed-tank reactor vessels with surface aerator type impellers mounted within the tanks at the oxygen carbon liquor surface interface. The amount of oxygen entrainment, or DO (Dissolved Oxygen), can be controlled by a weir adjusted level control, and a vent gas oxygen controlled oxygen feed valve. Oxygen is generated on site by cryogenic distillation of air, pressure swing adsorption, or other methods. These systems are used where wastewater plant space is at a premium and high sewage throughput is required as high energy costs are involved in purifying oxygen. | 1 | Applied and Interdisciplinary Chemistry |
To derive SUVA, first, UVC light (UV spectrum subtypes) at 254 nm or 280 nm, is measured in units of absorbance per meter of path length, often the sample must be diluted with ultrapure water because absorbance can be high. As increasing dissolved organic carbon concentration increases absorbance in the UV range, the UV light has to be normalized to the concentration of dissolved organic carbon in mg per L to ascertain differences in the aromatic quality of the water.
Aromatic character is used in the study of dissolved organic matter, from mineral soils, or organic soils, to use as an assay to whether or not dissolved organic carbon in the water is labile, a ready source of energy, or is from a relatively old source of carbon (recalcitrant). However, although a good indicator of aromaticity, caution must be used with determination of reactivity.
Measures of water purity often rely on measuring turbidity, not aromaticity. | 0 | Theoretical and Fundamental Chemistry |
The size and shape of the metal powder has a direct impact on the stability of the precursor as well as the resulting foam. For this purpose, powders that increase packing efficiency are most advantageous. The use of spherical particles may result in less contact of particles which consequently leads to larger secondary pores and a higher probability of pore collapse prior to complete sintering. This factor can be limited through different compaction techniques that decrease the degree of interstitial sites around the titanium particles. However, this method also has limitations; for example, the powders cannot be compacted to such a degree that would promote deformation of the spacer (unless anisotropic pore shape is desired). | 0 | Theoretical and Fundamental Chemistry |
In the US, the FDA can audit the files of local site investigators after they have finished participating in a study, to see if they were correctly following study procedures. This audit may be random, or for cause (because the investigator is suspected of fraudulent data). Avoiding an audit is an incentive for investigators to follow study procedures. A covered clinical study refers to a trial submitted to the FDA as part of a marketing application (for example, as part of an NDA or 510(k)), about which the FDA may require disclosure of financial interest of the clinical investigator in the outcome of the study. For example, the applicant must disclose whether an investigator owns equity in the sponsor, or owns proprietary interest in the product under investigation. The FDA defines a covered study as "...any study of a drug, biological product or device in humans submitted in a marketing application or reclassification petition that the applicant or FDA relies on to establish that the product is effective (including studies that show equivalence to an effective product) or any study in which a single investigator makes a significant contribution to the demonstration of safety."
Alternatively, many American pharmaceutical companies have moved some clinical trials overseas. Benefits of conducting trials abroad include lower costs (in some countries) and the ability to run larger trials in shorter timeframes, whereas a potential disadvantage exists in lower-quality trial management. Different countries have different regulatory requirements and enforcement abilities. An estimated 40% of all clinical trials now take place in Asia, Eastern Europe, and Central and South America. "There is no compulsory registration system for clinical trials in these countries and many do not follow European directives in their operations", says Jacob Sijtsma of the Netherlands-based WEMOS, an advocacy health organisation tracking clinical trials in developing countries.
Beginning in the 1980s, harmonization of clinical trial protocols was shown as feasible across countries of the European Union. At the same time, coordination between Europe, Japan and the United States led to a joint regulatory-industry initiative on international harmonization named after 1990 as the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH)
Currently, most clinical trial programs follow ICH guidelines, aimed at "ensuring that good quality, safe and effective medicines are developed and registered in the most efficient and cost-effective manner. These activities are pursued in the interest of the consumer and public health, to prevent unnecessary duplication of clinical trials in humans and to minimize the use of animal testing without compromising the regulatory obligations of safety and effectiveness." | 1 | Applied and Interdisciplinary Chemistry |
:V09CA01 Technetium (Tc) pentetic acid
:V09CA02 Technetium (Tc) succimer
:V09CA03 Technetium (Tc) mertiatide
:V09CA04 Technetium (Tc) gluceptate
:V09CA05 Technetium (Tc) gluconate
:V09CA06 Technetium (Tc) ethylenedicysteine | 1 | Applied and Interdisciplinary Chemistry |
Stainless steel is a material which is difficult to solder because of its stable, self-healing surface oxide layer and its low thermal conductivity. A solution of zinc chloride in hydrochloric acid is a common flux for stainless steels; it has however to be thoroughly removed afterwards as it would cause pitting corrosion. Another highly effective flux is phosphoric acid; its tendency to polymerize at higher temperatures however limits its applications. | 1 | Applied and Interdisciplinary Chemistry |
The Polycomb-group (PcG) regulatory complexes are known for their influence in the epigenetic regulation of stem cells,
especially in hematopoietic stem cells. The Polycomb Repressive Complex 1 (PRC 1) is directly involved in the process of hematopoiesis, and functions together with, for example, the PcG gene “Bmi1”. Studies in mice indicate that organisms with mutated “Bmi1” demonstrate deficient mitochondrial functioning, and also hindered the ability of hematopoietic cells to self-renew. Likewise, mutations in PRC2 genes were related to hematological conditions such as acute lymphoblastic leukemia (ALL), which is a form of leukemia. Hence, Polycomb-group genes and proteins are involved in the proper maintenance of hematopoiesis in the body. | 1 | Applied and Interdisciplinary Chemistry |
Because the molecule d-biotin has a much higher affinity to Strep-Tactin than Strep-tag, it can effectively compete for the binding site. Therefore, a MHC multimer based on the interaction of Strep-tag with Strep-Tactin is easily disrupted in the presence of relatively low concentrations of d-biotin. Without the Strep-Tactin backbone, the single MHC-Strep-tag fusion proteins spontaneously detach from the TCR of the T cell, because of weak binding affinities (monomeric MHC-epitope complexes cannot provide stable binding, see above). | 1 | Applied and Interdisciplinary Chemistry |
Sequential walking is a technique that can be used to solve various 2D NMR spectra. In a 2D experiment, cross peaks must be correlated to the correct nuclei. Using sequential walking, the correct nuclei can be assigned to their crosspeaks. The assigned crosspeaks can give valuable information such as spatial interactions between nuclei.
In a NOESY of DNA, for example, each nucleotide has a different chemical shift associated with it. In general, As are more downstream, Ts are more upstream, and Cs and Gs are intermediate. Each nucleotide has protons on the deoxyribose sugar, which can be assigned using sequential walking. To do this, the first nucleotide in the sequence must be detected. Knowing the DNA sequence helps, but in general the first nucleotide can be determined using the following rules.
1. 2 and 2" protons of a nucleotide will show up in its column, as well as in the column of the next nucleotide in the sequence. For example, in the sequence CATG, in the column for C, its own 2 and 2" protons will be seen, but none of the other nucleotides. For A, its own 2' and 2" protons will be seen, as well as those from C.
2. Methyl groups on the nucleotide are seen in the column for the nucleotide containing a methyl group, as well as for the nucleotide preceding it. For example, in CATG, the A and T will contain the methyl peak corresponding to the methyl group on T, but G will not.
Once the first nucleotide has been found, you determine which nucleotide is next to it because it should contain the 2' and 2" protons from the previous nucleotide. This is done by "walking" across the spectrum. This process is then repeated sequentially until all nucleotides have been assigned. | 0 | Theoretical and Fundamental Chemistry |
Mutations in the HNF4A gene have been linked to maturity onset diabetes of the young 1 (MODY1).
This seems to be caused by HNF4-a's [http://jme.endocrinology-journals.org/content/43/1/19.full.pdf] role in the synthesis of SHBG, which is known to be severely diminished in patients with insulin-resistance. | 1 | Applied and Interdisciplinary Chemistry |
Calculation of reactivity ratios generally involves carrying out several polymerizations at varying monomer ratios. The copolymer composition can be analysed with methods such as Proton nuclear magnetic resonance, Carbon-13 nuclear magnetic resonance, or Fourier transform infrared spectroscopy. The polymerizations are also carried out at low conversions, so monomer concentrations can be assumed to be constant. With all the other parameters in the copolymer equation known, and can be found. | 0 | Theoretical and Fundamental Chemistry |
Deoxyadenosine monophosphate (dAMP), also known as deoxyadenylic acid or deoxyadenylate in its conjugate acid and conjugate base forms, respectively, is a derivative of the common nucleic acid AMP, or adenosine monophosphate, in which the -OH (hydroxyl) group on the 2 carbon on the nucleotides pentose has been reduced to just a hydrogen atom (hence the "deoxy-" part of the name). Deoxyadenosine monophosphate is abbreviated dAMP. It is a monomer used in DNA. | 1 | Applied and Interdisciplinary Chemistry |
A mandrel is a steel rod or linked ball inserted into the tube while it is being bent to give the tube extra support to reduce wrinkling and breaking the tube during this process. The different types of mandrels are as follows.
* Plug mandrel: a solid rod used on normal bends
* Form mandrel: a solid rod with curved end used on bend when more support is needed
* Ball mandrel without cable: unlinked steel ball bearings inserted into tube, used on critical and precise bends
* Ball mandrel with cable: linked ball bearings inserted into tube, used on critical bend and precise bends
* Sand: sand packed into tube
In production of a product where the bend is not critical a plug mandrel can be used. A form type tapers the end of the mandrel to provide more support in the bend of the tube. When precise bending is needed a ball mandrel (or ball mandrel with steel cable) should be used. The conjoined ball-like disks are inserted into the tubing to allow for bending while maintaining the same diameter throughout. Other styles include using sand, cerrobend, or frozen water. These allow for a somewhat constant diameter while providing an inexpensive alternative to the aforementioned styles.
Performance automotive or motorcycle exhaust pipe is a common application for a mandrel. | 1 | Applied and Interdisciplinary Chemistry |
DLS is used to characterize the size of various particles including proteins, polymers, micelles, Protein cages and virus-like particles, vesicles, carbohydrates, nanoparticles, biological cells, and gels. If the system is not disperse in size, the mean effective diameter of the particles can be determined. This measurement depends on the size of the particle core, the size of surface structures, particle concentration, and the type of ions in the medium.
Since DLS essentially measures fluctuations in scattered light intensity due to diffusing particles, the diffusion coefficient of the particles can be determined. DLS software of commercial instruments typically displays the particle population at different diameters. If the system is monodisperse, there should only be one population, whereas a polydisperse system would show multiple particle populations. If there is more than one size population present in a sample then either the CONTIN analysis should be applied for photon correlation spectroscopy instruments, or the power spectrum method should be applied for Doppler shift instruments.
Stability studies can be done conveniently using DLS. Periodical DLS measurements of a sample can show whether the particles aggregate over time by seeing whether the hydrodynamic radius of the particle increases. If particles aggregate, there will be a larger population of particles with a larger radius. In some DLS machines, stability depending on temperature can be analyzed by controlling the temperature in situ. | 0 | Theoretical and Fundamental Chemistry |
The understanding of CHF phenomenon and an accurate prediction of the CHF condition are important for safe and economic design of many heat transfer units including nuclear reactors, fossil fuel boilers, fusion reactors, electronic chips, etc. Therefore, the phenomenon has been investigated extensively over the world since Nukiyama first characterized it. In 1950 Kutateladze suggested the hydrodynamical theory of the burnout crisis. Much of significant work has been done during the last decades with the development of water-cooled nuclear reactors. Now many aspects of the phenomenon are well understood and several reliable prediction models are available for conditions of common interests.
The use of the term critical heat flux (CHF) is inconsistent among authors. The United States Nuclear Regulatory Commission has suggested using the term “critical boiling transition” (CBT) to indicate the phenomenon associated with a significant reduction in two-phase heat transfer. For a single species, the liquid phase generally has considerably better heat transfer properties than the vapor phase, namely thermal conductivity. So in general CBT is the result of some degree of liquid deficiency to a local position along a heated surface. The two mechanisms that result in reaching CBT are: departure from nucleate boiling (DNB) and liquid film dryout.
Departure from nucleate boiling (DNB) occurs in sub-cooled flows and bubbly flow regimes. DNB happens when many bubbles near the heated surface coalesce and impede the ability of local liquid to reach the surface. The mass of vapor between the heated surface and local liquid may be referred to as a vapor blanket.
Dryout means the disappearance of liquid on the heat transfer surface which results in the CBT. Dryout of liquid film occurs in annular flow. Annular flow is characterized by a vapor core, liquid film on the wall, and liquid droplets entrained within the core. Shear at the liquid-vapor interface drives the flow of the liquid film along the heated surface. In general, the two-phase HTC increases as the liquid-film thickness decreases. The process has been shown to occur over many instances of dryout events, which span a finite duration and are local to a position. The CBT occurs when the fraction of time a local position is subjected to dryout becomes significant. A single dryout event, or even several dryout events, may be followed by periods of sustained contact between the liquid film and the previously dry region [https://mediaspace.wisc.edu/media/Dryout-rewet/1_7sn93wd2] . Many dryout events (hundreds or thousands) occurring in sequence are the mechanism for significant reduction in heat transfer-associated dryout CBT.
Post-CHF is used to denote the general heat transfer deterioration in flow boiling process, and liquid could be in the form of dispersed spray of droplets, continuous liquid core, or transition between the former two cases. Post-dryout can be specifically used to denote the heat transfer deterioration in the condition when liquid is only in the form of dispersed droplets, and denote the other cases by the term Post-DNB. | 0 | Theoretical and Fundamental Chemistry |
Sedimentation equilibrium experiments reports the molar mass of analytes and their chemical equilibrium constants. The rotor speed is adjusted such that a steady-state concentration profile c(r) of the sample in the cell is formed, where sedimentation and diffusion cancel out each other. | 1 | Applied and Interdisciplinary Chemistry |
The study of spinor condensates was initiated in 1998 by experimental groups at JILA
and MIT. These experiments utilised
Na and Rb atoms, respectively.
In contrast to most prior experiments on ultracold gases, these experiments utilised a purely
optical trap, which is spin-insensitive. Shortly thereafter, theoretical work appeared
which described the possible mean-field phases of spin-one spinor condensates. | 0 | Theoretical and Fundamental Chemistry |
An SADP is acquired under parallel electron illumination. In the case of convergent beam, a convergent beam electron diffraction (CBED) is achieved. The beam used in SAD is broad illuminating a wide sample area. In order to analyze only a specific sample area, the selected area aperture in the image plane is used. This is in contrast with nanodiffraction, where the site-selectivity is achieved using a beam condensed to a narrow probe. SAD is important in direct imaging for instance when orienting the sample for high resolution microscopy or setting up dark-field imaging conditions.
High-resolution electron microscope images can be transformed into an artificial diffraction pattern using Fourier transform. Then, they can be processed the same way as real diffractograms allowing to determine crystal orientation, measure interplanar angles and distances even with picometric precision.
SAD is similar to X-ray diffraction, but unique in that areas as small as several hundred nanometers in size can be examined, whereas X-ray diffraction typically samples areas much larger. | 0 | Theoretical and Fundamental Chemistry |
The physical manifestation of leaving group ability is the rate at which a reaction takes place. Good leaving groups give fast reactions. By transition state theory, this implies that reactions involving good leaving groups have low activation barriers leading to relatively stable transition states.
It is helpful to consider the concept of leaving group ability in the case of the first step of an S1/E1 reaction with an anionic leaving group (ionization), while keeping in mind that this concept can be generalized to all reactions that involve leaving groups. Because the leaving group bears a larger negative charge in the transition state (and products) than in the starting material, a good leaving group must be able to stabilize this negative charge, i.e. form stable anions. A good measure of anion stability is the pK of an anions conjugate acid (pK), and leaving group ability indeed generally follows this trend, with a lower pK' correlating well with better leaving group ability.
The correlation between pK and leaving group ability, however, is not perfect. Leaving group ability represents the difference in energy between starting materials and a transition state (ΔG) and differences in leaving group ability are reflected in changes in this quantity (ΔΔG). The pK, however, represents the difference in energy between starting materials and products (ΔG°) with differences in acidity reflected in changes in this quantity (ΔΔG°). The ability to correlate these energy differences is justified by the Hammond postulate and the Bell–Evans–Polanyi principle. Also, the starting materials in these cases are different. In the case of the acid dissociation constant, the "leaving group" is bound to a proton in the starting material, while in the case of leaving group ability, the leaving group is bound to (usually) carbon. It is with these important caveats in mind that one must consider pK to be reflective of leaving group ability. Nevertheless, one can generally examine acid dissociation constants to qualitatively predict or rationalize rate or reactivity trends relating to variation of the leaving group. Consistent with this picture, strong bases such as and tend to make poor leaving groups, due their inability to stabilize a negative charge.
What constitutes a reasonable leaving group is dependent on context. For S2 reactions, typical synthetically useful leaving groups include , , and . Substrates containing phosphate and carboxylate leaving groups are more likely to react by competitive addition-elimination, while sulfonium and ammonium salts generally form ylides or undergo E2 elimination when possible. With reference to the table above, phenoxides () constitute the lower limit for what is feasible as S2 leaving groups: very strong nucleophiles like or have been used to demethylate anisole derivatives through S2 displacement at the methyl group. Hydroxide, alkoxides, amides, hydride, and alkyl anions do not serve as leaving groups in S2 reactions.
On the other hand, when anionic or dianionic tetrahedral intermediates collapse, the high electron density of the neighboring heteroatom facilitates the expulsion of a leaving group. Thus, in the case of ester and amide hydrolysis under basic conditions, alkoxides and amides are commonly proposed as leaving groups. For the same reason, E1cb reactions involving hydroxide as a leaving group are not uncommon (e.g., in the aldol condensation). It is exceedingly rare for groups such as (hydrides), (alkyl anions, R = alkyl or H), or (aryl anions, Ar = aryl) to depart with a pair of electrons because of the high energy of these species. The Chichibabin reaction provides an example of hydride as a leaving group, while the Wolff-Kishner reaction and Haller-Bauer reaction feature unstabilized carbanion leaving groups. | 0 | Theoretical and Fundamental Chemistry |
Paste tailings is a modification to the conventional methods of disposal of tailings (pond storage). Conventional tailings slurries are composed of a low percent of solids and relatively high water content (normally ranging from 20% to 60% solids for most hard rock mining) and when deposited into the tailings pond the solids and liquids separate. In paste tailings the percent of solids in the tailings slurry is increased through the use of paste thickeners to produce a product where the minimal separation of water and solids occurs and the material is deposited into a storage area as a paste (with a consistency somewhat like toothpaste). Paste tailings has the advantage that more water is recycled in the processing plant and therefore the process is more water efficient than conventional tailings and there is a lower potential for seepage. However the cost of the thickening is generally higher than for conventional tailings and the pumping costs for the paste are also normally higher than for conventional tailings as positive displacement pumps are normally required to transport the tailings from the processing plant to the storage area. Paste tailings are used in several locations around the world including Sunrise Dam in Western Australia and Bulyanhulu Gold Mine in Tanzania. | 1 | Applied and Interdisciplinary Chemistry |
Compared to more commonly encountered states of matter, Bose–Einstein condensates are extremely fragile. The slightest interaction with the external environment can be enough to warm them past the condensation threshold, eliminating their interesting properties and forming a normal gas.
Nevertheless, they have proven useful in exploring a wide range of questions in fundamental physics, and the years since the initial discoveries by the JILA and MIT groups have seen an increase in experimental and theoretical activity. Examples include experiments that have demonstrated interference between condensates due to wave–particle duality, the study of superfluidity and quantized vortices, the creation of bright matter wave solitons from Bose condensates confined to one dimension, and the slowing of light pulses to very low speeds using electromagnetically induced transparency. Vortices in Bose–Einstein condensates are also currently the subject of analogue gravity research, studying the possibility of modeling black holes and their related phenomena in such environments in the laboratory. Experimenters have also realized "optical lattices", where the interference pattern from overlapping lasers provides a periodic potential. These have been used to explore the transition between a superfluid and a Mott insulator, and may be useful in studying Bose–Einstein condensation in fewer than three dimensions, for example the Tonks–Girardeau gas. Further, the sensitivity of the pinning transition of strongly interacting bosons confined in a shallow one-dimensional optical lattice originally observed by Haller has been explored via a tweaking of the primary optical lattice by a secondary weaker one. Thus for a resulting weak bichromatic optical lattice, it has been found that the pinning transition is robust against the
introduction of the weaker secondary optical lattice. Studies of vortices in nonuniform Bose–Einstein condensates as well as excitations of these systems by the application of moving repulsive or attractive obstacles, have also been undertaken. Within this context, the conditions for order and chaos in the dynamics of a trapped Bose–Einstein condensate have been explored by the application of moving blue and red-detuned laser beams (hitting frequencies slightly above and below the resonance frequency, respectively) via the time-dependent Gross-Pitaevskii equation.
Bose–Einstein condensates composed of a wide range of isotopes have been produced.
Cooling fermions to extremely low temperatures has created degenerate gases, subject to the Pauli exclusion principle. To exhibit Bose–Einstein condensation, the fermions must "pair up" to form bosonic compound particles (e.g. molecules or Cooper pairs). The first molecular condensates were created in November 2003 by the groups of Rudolf Grimm at the University of Innsbruck, Deborah S. Jin at the University of Colorado at Boulder and Wolfgang Ketterle at MIT. Jin quickly went on to create the first fermionic condensate, working with the same system but outside the molecular regime.
In 1999, Danish physicist Lene Hau led a team from Harvard University which slowed a beam of light to about 17 meters per second using a superfluid. Hau and her associates have since made a group of condensate atoms recoil from a light pulse such that they recorded the light's phase and amplitude, recovered by a second nearby condensate, in what they term "slow-light-mediated atomic matter-wave amplification" using Bose–Einstein condensates.
Another current research interest is the creation of Bose–Einstein condensates in microgravity in order to use its properties for high precision atom interferometry. The first demonstration of a BEC in weightlessness was achieved in 2008 at a drop tower in Bremen, Germany by a consortium of researchers led by Ernst M. Rasel from Leibniz University Hannover. The same team demonstrated in 2017 the first creation of a Bose–Einstein condensate in space and it is also the subject of two upcoming experiments on the International Space Station.
Researchers in the new field of atomtronics use the properties of Bose–Einstein condensates in the emerging quantum technology of matter-wave circuits.
In 1970, BECs were proposed by Emmanuel David Tannenbaum for anti-stealth technology.
In 2020, researchers reported the development of superconducting BEC and that there appears to be a "smooth transition between" BEC and Bardeen–Cooper–Shrieffer regimes. | 0 | Theoretical and Fundamental Chemistry |
John Ulric Nef (Johann Ulrich Nef; June 14, 1862 – August 13, 1915) was a Swiss-born American chemist and the discoverer of the Nef reaction and Nef synthesis. He was a member of the American Academy of Arts and Sciences and the National Academy of Sciences. | 0 | Theoretical and Fundamental Chemistry |
bonds adjacent to the carbonyl in ketones are more acidic pK ≈ 20) than the bonds in alkane (pK ≈ 50). This difference reflects resonance stabilization of the enolate ion that is formed upon deprotonation. The relative acidity of the α-hydrogen is important in the enolization reactions of ketones and other carbonyl compounds. The acidity of the α-hydrogen also allows ketones and other carbonyl compounds to react as nucleophiles at that position, with either stoichiometric and catalytic base. Using very strong bases like lithium diisopropylamide (LDA, pK of conjugate acid ~36) under non-equilibrating conditions (–78 °C, 1.1 equiv LDA in THF, ketone added to base), the less-substituted kinetic enolate is generated selectively, while conditions that allow for equilibration (higher temperature, base added to ketone, using weak or insoluble bases, e.g., sodium ethoxide| in ethanol|, or NaH) provides the more-substituted thermodynamic enolate.
Ketones are also weak bases, undergoing protonation on the carbonyl oxygen in the presence of Brønsted acids. Ketonium ions (i.e., protonated ketones) are strong acids, with pK values estimated to be somewhere between –5 and –7. Although acids encountered in organic chemistry are seldom strong enough to fully protonate ketones, the formation of equilibrium concentrations of protonated ketones is nevertheless an important step in the mechanisms of many common organic reactions, like the formation of an acetal, for example. Acids as weak as pyridinium cation (as found in pyridinium tosylate) with a pK of 5.2 are able to serve as catalysts in this context, despite the highly unfavorable equilibrium constant for protonation (K ). | 0 | Theoretical and Fundamental Chemistry |
Pyruvic acid (IUPAC name: 2-oxopropanoic acid, also called acetoic acid) (CHCOCOOH) is the simplest of the alpha-keto acids, with a carboxylic acid and a ketone functional group. Pyruvate, the conjugate base, CHCOCOO, is an intermediate in several metabolic pathways throughout the cell.
Pyruvic acid can be made from glucose through glycolysis, converted back to carbohydrates (such as glucose) via gluconeogenesis, or converted to fatty acids through a reaction with acetyl-CoA. It can also be used to construct the amino acid alanine and can be converted into ethanol or lactic acid via fermentation.
Pyruvic acid supplies energy to cells through the citric acid cycle (also known as the Krebs cycle) when oxygen is present (aerobic respiration), and alternatively ferments to produce lactate when oxygen is lacking. | 1 | Applied and Interdisciplinary Chemistry |
If the SAD is taken from one a or a few single crystals, the diffractogram depicts a regular pattern of bright spots. Since the diffraction pattern can be seen as a two-dimensional projection of reciprocal crystal lattice, the pattern can be used to measure lattice constants, specifically the distances and angles between crystallographic planes. The lattice parameters are typically distinctive for various materials and their phases which allows to identify the examined material or at least differentiate between possible candidates.
Even though the SAD-based analyses were not considered quantitative for a long time, computer tools brought accuracy and repeatability allowing to routinely perform accurate measurements of interplanar distances or angles on appropriately calibrated microscopes. Tools such as CrysTBox are capable of automated analysis achieving sub-pixel precision.
If the sample is tilted against the electron beam, diffraction conditions are satisfied for different set of crystallographic planes yielding different constellation of diffraction spots. This allows to determine the crystal orientation, which can be used for instance to set up the orientation needed for particular experiment, to determine misorientation between adjacent grains or crystal twins. Since different sample orientations provide different projections of the reciprocal lattice, they provide an opportunity to reconstruct the three-dimensional information lost in individual projections. A series of diffractograms varying in tilt can be acquired and processed with diffraction tomography analysis in order to reconstruct an unknown crystal structure.
SAD can also be used to analyze crystal defects such as stacking faults. | 0 | Theoretical and Fundamental Chemistry |
Secondary metabolites are often characterized as either qualitative or quantitative. Qualitative metabolites are defined as toxins that interfere with a herbivore's metabolism, often by blocking specific biochemical reactions. Qualitative chemicals are present in plants in relatively low concentrations (often less than 2% dry weight), and are not dosage dependent. They are usually small, water-soluble molecules, and therefore can be rapidly synthesized, transported and stored with relatively little energy cost to the plant. Qualitative allelochemicals are usually effective against non-adapted generalist herbivores.
Quantitative chemicals are those that are present in high concentration in plants (5 – 40% dry weight) and are equally effective against all specialists and generalist herbivores. Most quantitative metabolites are digestibility reducers that make plant cell walls indigestible to animals. The effects of quantitative metabolites are dosage dependent and the higher these chemicals proportion in the herbivores diet, the less nutrition the herbivore can gain from ingesting plant tissues. Because they are typically large molecules, these defenses are energetically expensive to produce and maintain, and often take longer to synthesize and transport.
The geranium, for example, produces the amino acid, quisqualic acid in its petals to defend itself from Japanese beetles. Within 30 minutes of ingestion the chemical paralyzes the herbivore. While the chemical usually wears off within a few hours, during this time the beetle is often consumed by its own predators. | 1 | Applied and Interdisciplinary Chemistry |
* 2023: Arthur C. Cope Scholar Award (American Chemical Society)
* 2018: University of California, Irvine Physical Science Outstanding Contributions to the Undergraduate Education
* 2017: Fellow of the AAAS
* 2013-2016: Humboldt Fellowship
* 2013: Japan Society for the Promotion of Science Fellowship
* 2008: NSF CAREER Award
* 2005-2006: National Institutes of Health Postdoctoral Fellow | 0 | Theoretical and Fundamental Chemistry |
In biology, quorum sensing or quorum signaling (QS) is the ability to detect and respond to cell population density by gene regulation. Quorum sensing is a type of cellular signaling, and more specifically can be considered a type of paracrine signaling. However, it also contains traits of both autocrine signaling: a cell produces both the autoinducer molecule and the receptor for the autoinducer. As one example, QS enables bacteria to restrict the expression of specific genes to the high cell densities at which the resulting phenotypes will be most beneficial, especially for phenotypes that would be ineffective at low cell densities and therefore too energetically costly to express. Many species of bacteria use quorum sensing to coordinate gene expression according to the density of their local population. In a similar fashion, some social insects use quorum sensing to determine where to nest. Quorum sensing in pathogenic bacteria activates host immune signaling and prolongs host survival, by limiting the bacterial intake of nutrients, such as tryptophan, which further is converted to serotonin. As such, quorum sensing allows a commensal interaction between host and pathogenic bacteria. Quorum sensing may also be useful for cancer cell communications.
In addition to its function in biological systems, quorum sensing has several useful applications for computing and robotics. In general, quorum sensing can function as a decision-making process in any decentralized system in which the components have: (a) a means of assessing the number of other components they interact with and (b) a standard response once a threshold number of components is detected. | 1 | Applied and Interdisciplinary Chemistry |
Inertial cavitation can also occur in the presence of an acoustic field. Microscopic gas bubbles that are generally present in a liquid will be forced to oscillate due to an applied acoustic field. If the acoustic intensity is sufficiently high, the bubbles will first grow in size and then rapidly collapse. Hence, inertial cavitation can occur even if the rarefaction in the liquid is insufficient for a Rayleigh-like void to occur.
Ultrasonic cavitation inception will occur when the acceleration of the ultrasound source is enough to produce the needed pressure drop. This pressure drop depends on the value of the acceleration and the size of the affected volume by the pressure wave. The dimensionless number that predicts ultrasonic cavitation is the Garcia-Atance number. High power ultrasonic horns produce accelerations high enough to create a cavitating region that can be used for homogenization, dispersion, deagglomeration, erosion, cleaning, milling, emulsification, extraction, disintegration, and sonochemistry. | 1 | Applied and Interdisciplinary Chemistry |
WDTC1 ("Adipose") is a gene associated with obesity.
WDTC1 is a gene that codes for a protein acting as a suppressor in lipid accumulation. WDTC1 protein consists of seven WD40 domains, three transient receptor potential channel protein-protein interaction domains, DDB1 binding elements, and a prenylated C-terminus. Reduced expression or disruption of WDTC1 gene is associated with obesity, increased triglyceride accumulation, and adipogenesis. WDTC1 is a factor in a complex composed of DDB1, CUL4, and ROC1 that restricts transcription in adipogenesis. | 1 | Applied and Interdisciplinary Chemistry |
4-Nitrophenol can be used as a pH indicator. A solution of 4-nitrophenol appears colorless below pH 5.4 and yellow above pH 7.5. This color-changing property makes this compound useful as a pH indicator.
The yellow color of the 4-nitrophenolate form (or 4-nitrophenoxide) is due to a maximum of absorbance at 405 nm (ε = 18.3 to 18.4 mM cm in strong alkali). In contrast, 4-nitrophenol has a weak absorbance at 405 nm (ε = 0.2 mM cm).
The isosbestic point for 4-nitrophenol/4-nitrophenoxide is at 348 nm, with ε = 5.4 mM cm. | 0 | Theoretical and Fundamental Chemistry |
The daughter of Morris and Etty Mizrahi, she was born in Harare, Zimbabwe and was educated there. Her family is a Sephardi Jewish family from the Greek island of Rhodes. | 1 | Applied and Interdisciplinary Chemistry |
The sievert has its origin in the röntgen equivalent man (rem) which was derived from CGS units. The International Commission on Radiation Units and Measurements (ICRU) promoted a switch to coherent SI units in the 1970s, and announced in 1976 that it planned to formulate a suitable unit for equivalent dose. The ICRP pre-empted the ICRU by introducing the sievert in 1977.
The sievert was adopted by the International Committee for Weights and Measures (CIPM) in 1980, five years after adopting the gray. The CIPM then issued an explanation in 1984, recommending when the sievert should be used as opposed to the gray. That explanation was updated in 2002 to bring it closer to the ICRP's definition of equivalent dose, which had changed in 1990. Specifically, the ICRP had introduced equivalent dose, renamed the quality factor (Q) to radiation weighting factor (W), and dropped another weighting factor "N" in 1990. In 2002, the CIPM similarly dropped the weighting factor "N" from their explanation but otherwise kept other old terminology and symbols. This explanation only appears in the appendix to the SI brochure and is not part of the definition of the sievert. | 0 | Theoretical and Fundamental Chemistry |
The mission of EPA is to protect human health and the environment.
EPA works to ensure that:
* Americans have clean air, land and water;
* National efforts to reduce environmental risks are based on the best available scientific information;
* Federal laws protecting human health and the environment are administered and enforced fairly, effectively and as Congress intended;
* Environmental stewardship is integral to U.S. policies concerning natural resources, human health, economic growth, energy, transportation, agriculture, industry, and international trade, and these factors are similarly considered in establishing environmental policy;
* All parts of society--communities, individuals, businesses, and state, local and tribal governments--have access to accurate information sufficient to effectively participate in managing human health and environmental risks;
* Contaminated lands and toxic sites are cleaned up by potentially responsible parties and revitalized; and
* Chemicals in the marketplace are reviewed for safety. | 0 | Theoretical and Fundamental Chemistry |
This is an actual reading obtained from such as an ambient dose gamma monitor, or a personal dosimeter. Such instruments are calibrated using radiation metrology techniques which will trace them to a national radiation standard, and thereby relate them to an operational quantity. The readings of instruments and dosimeters are used to prevent the uptake of excessive dose and to provide records of dose uptake to satisfy radiation safety legislation; such as in the UK, the Ionising Radiations Regulations 1999. | 0 | Theoretical and Fundamental Chemistry |
Despite the cancellation of funding by the DOE, the FutureGen Alliance continued to move forward with the project, opening an office in Mattoon and planning to buy the land for the plant in August 2008, in partnership with a local group.
During the 2008 U.S. presidential campaigns, Sen. Barack Obama pledged his support to clean coal technologies, with plans to develop five commercial-scale coal plants equipped with CCS technology.
In November 2008, Fred Palmer, senior vice president at Peabody Energy shared his outlook on FutureGen with the American Coalition for Clean Coal Electricity (ACCCE), saying that the FutureGen Alliance would "Make a concerted effort in the Obama administration to reinstate the project and get this built as originally planned."
On June 12, 2009, the DOE announced a restart of design work for the FutureGen project. "Following the completion of the detailed cost estimate and fundraising activities," the press release states, "the Department of Energy and the FutureGen Alliance will make a decision either to move forward or to discontinue the project early in 2010." | 1 | Applied and Interdisciplinary Chemistry |
The museum is also home to a large number of old tractors. Two D8 Caterpillars, a D9, a few large 1930s Caterpillars, some Best crawlers and many other examples of tracked tractors can be seen at the museum. The typical tractors such as Farmall, John Deere, Oliver, and Allis-Chalmers can be seen out at the museum, but there are more than a few rarer examples too. There is a 1924 Buffalo-Springfield road roller, a gigantic 1918 30-60 Aultman-Taylor gas tractor, a 1911 Fairbanks-Morse 15-25 kerosene tractor, a 1915 International Harvester Mogul 8-16, several Rumely Oil-Pulls, and many more. | 1 | Applied and Interdisciplinary Chemistry |
Downregulation refers to the decrease in the number of receptor molecules. This is usually the result of receptor endocytosis. In this process, the bound LCGR-hormone complex binds arrestin and concentrates in clathrin coated pits. Clathrin coated pits recruit dynamin and pinch off from the cell surface, becoming clathrin-coated vesicles. Clathrin-coated vesicles are processed into endosomes, some of which are recycled to the cell surface while others are targeted to lysosomes. Receptors targeted to lysosomes are degraded. Use of long-acting agonists will downregulate the receptor population by promoting their endocytosis. | 1 | Applied and Interdisciplinary Chemistry |
Its activities are focused on both fundamental objectives in analytical sciences and interactions with the socio-economic environment at local, national and international levels. The Institute has partnerships with international research centers (e.g. MIT, the École Polytechnique Fédérale de Lausanne, International Agency for Research on Cancer) and national academic partners (e.g. LabexIMUST, , ...) and industrial partners (BioMérieux, , Sanofi, Solvay, Total) and manufacturers (Agilent, Bruker, Waters ...).
The institute is involved in competitiveness clusters (Axelera, , Techtera, Plastipolis) and regional cluster (). Some scientists are experts in standardization committees at national and European levels. In addition, the Institute of Analytical Sciences plays a «Business incubator» role and hosts start-ups: ANAQUANT, metabolomics technical platform, etc. | 0 | Theoretical and Fundamental Chemistry |
Fucosylation is the process of adding fucose sugar units to a molecule. It is a type of glycosylation.
It is important clinically, and high levels of fucosylation have been reported in cancer. In cancer and inflammation there are significant changes in the expression of fucosylated molecules. Therefore, antibodies and lectins that are able to recognize cancer associated fucosylated oligosaccharides have been used as tumor markers in oncology.
It is performed by fucosyltransferase enzymes.
Fucosylation has been observed in vertebrates, invertebrates, plants, bacteria, and fungi. It has a role in cellular adhesion and immune regulation. Fucosylation inhibition applications are being explored for a range of clinical application including some associated with sickle cell disease, rheumatoid arthritis, tumor inhibition, and chemotherapy improvements. Recent studies on melanoma patient specimens indicated that melanoma fucosylation and fucosylated HLA-DRB1 are associated with anti-programmed cell death protein 1 (PD1) responder status, pointing to the potential use of melanoma fucosylation as a method for immunotherapy patient stratification. Moreover, it has been reported that fucosylation is an important regulator of anti-tumor immunity and -fucose can be used as a potent tool for increasing immunotherapy efficacy in melanoma.
Fucosylation can help with immune response when a foreign pathogen is introduced in the body. Rapid fucosylation can occur in the epithelial lining of the small intestine as a protective mechanism to support the body’s symbiotic gut bacteria. This may regulate the bacterial genes responsible for quorum sensing or virulence, thus resulting in an increased tolerance of the infection. | 0 | Theoretical and Fundamental Chemistry |
Kalpasutra mentions nine Ganas and 11 Ganadharas of Mahavira. Bhadrabahu is mentioned as prime Ganadhara of Mahavira. Bhadrabahu's disciple Godasa is mentioned to have founded Godasa Gana. | 1 | Applied and Interdisciplinary Chemistry |
Christian G. Hartinger (born 1974) is an Austrian-born New Zealand bioinorganic chemist known for his work in metal-based anticancer drugs. In 2022 he was elected a Fellow of the Royal Society Te Apārangi. | 0 | Theoretical and Fundamental Chemistry |
Bryan Research & Engineering, Inc. (BR&E) is a privately owned provider of software and engineering solutions to the oil, gas, refining and chemical industries. Since the company’s inception in 1974, BR&E has combined research and development in process simulation to provide clients with simulation tools. | 1 | Applied and Interdisciplinary Chemistry |
The reducing agents NADH, NADPH, and FADH, as well as metal ions, act as cofactors at various steps in anabolic pathways. NADH, NADPH, and FADH act as electron carriers, while charged metal ions within enzymes stabilize charged functional groups on substrates. | 1 | Applied and Interdisciplinary Chemistry |
Durrant has proposed an alternative definition of hypervalency, based on the analysis of atomic charge maps obtained from atoms in molecules theory. This approach defines a parameter called the valence electron equivalent, γ, as “the formal shared electron count at a given atom, obtained by any combination of valid ionic and covalent resonance forms that reproduces the observed charge distribution”. For any particular atom X, if the value of γ(X) is greater than 8, that atom is hypervalent. Using this alternative definition, many species such as PCl, , and XeF, that are hypervalent by Musher's definition, are reclassified as hypercoordinate but not hypervalent, due to strongly ionic bonding that draws electrons away from the central atom. On the other hand, some compounds that are normally written with ionic bonds in order to conform to the octet rule, such as ozone O, nitrous oxide NNO, and trimethylamine N-oxide , are found to be genuinely hypervalent. Examples of γ calculations for phosphate (γ(P) = 2.6, non-hypervalent) and orthonitrate (γ(N) = 8.5, hypervalent) are shown below. | 0 | Theoretical and Fundamental Chemistry |
In the 1989 Queen's Birthday Honours, Campbell was appointed an Officer of the Order of the British Empire, for services to science. | 0 | Theoretical and Fundamental Chemistry |
Pancreatic lipase is the most important lipolytic enzyme in the gastrointestinal tract and is essential for fat digestion.
Pancreatic lipase is secreted from acinar cells in the pancreas and its secretion, with the pancreatic juice to the small intestine, is stimulated by hormones. These hormones are induced in the stomach by hydrolysed products in gastric digestion.
The pancreatic lipase is secreted to the small intestine where it is most active, at pH 7-7,5.
Pancreatic lipase hydrolyses triglycerides and diglycerides by cleaving acyl chains at the sn-1 and sn-3 position
and releases free fatty acids and 2-monoglycerides.
The pancreatic lipase consists of 465 amino acids. Schematic picture of pancreatic lipase is shown in figure 2. Pancreatic and gastric lipases share little homology but have the same hydrophobic region at the active site, which is important for the lipolytic activity. The hydrophobic region has the hexapeptide sequence Val-Gly-His-Ser-Gln-Gly and is at Ser153 in pancreatic lipases but Ser152 in gastric lipases. | 1 | Applied and Interdisciplinary Chemistry |
Neutron emission usually happens from nuclei that are in an excited state, such as the excited O* produced from the beta decay of N. The neutron emission process itself is controlled by the nuclear force and therefore is extremely fast, sometimes referred to as "nearly instantaneous". This process allows unstable atoms to become more stable. The ejection of the neutron may be as a product of the movement of many nucleons, but it is ultimately mediated by the repulsive action of the nuclear force that exists at extremely short-range distances between nucleons. | 0 | Theoretical and Fundamental Chemistry |
The surface of any liquid is an interface between that liquid and some other medium. The top surface of a pond, for example, is an interface between the pond water and the air. Surface tension, then, is not a property of the liquid alone, but a property of the liquid's interface with another medium. If a liquid is in a container, then besides the liquid/air interface at its top surface, there is also an interface between the liquid and the walls of the container. The surface tension between the liquid and air is usually different (greater) than its surface tension with the walls of a container. And where the two surfaces meet, their geometry must be such that all forces balance.
Where the two surfaces meet, they form a contact angle, , which is the angle the tangent to the surface makes with the solid surface. Note that the angle is measured through the liquid, as shown in the diagrams above. The diagram to the right shows two examples. Tension forces are shown for the liquid–air interface, the liquid–solid interface, and the solid–air interface. The example on the left is where the difference between the liquid–solid and solid–air surface tension, , is less than the liquid–air surface tension, , but is nevertheless positive, that is
In the diagram, both the vertical and horizontal forces must cancel exactly at the contact point, known as equilibrium. The horizontal component of is canceled by the adhesive force, .
The more telling balance of forces, though, is in the vertical direction. The vertical component of must exactly cancel the difference of the forces along the solid surface, .
| rowspan="6" style="text-align:center;"|0°
| ethanol
| diethyl ether
| carbon tetrachloride
| glycerol
| acetic acid
| rowspan="2"|water
| paraffin wax
| style="text-align:center;"|107°
| silver
| style="text-align:center;"|90°
| rowspan="3"| methyl iodide
| soda-lime glass
| style="text-align:center;"|29°
| lead glass
| style="text-align:center;"|30°
| fused quartz
| style="text-align:center;"|33°
| mercury
| soda-lime glass
| style="text-align:center;"|140°
Since the forces are in direct proportion to their respective surface tensions, we also have:
where
* is the liquid–solid surface tension,
* is the liquid–air surface tension,
* is the solid–air surface tension,
* is the contact angle, where a concave meniscus has contact angle less than 90° and a convex meniscus has contact angle of greater than 90°.
This means that although the difference between the liquid–solid and solid–air surface tension, , is difficult to measure directly, it can be inferred from the liquid–air surface tension, , and the equilibrium contact angle, , which is a function of the easily measurable advancing and receding contact angles (see main article contact angle).
This same relationship exists in the diagram on the right. But in this case we see that because the contact angle is less than 90°, the liquid–solid/solid–air surface tension difference must be negative: | 0 | Theoretical and Fundamental Chemistry |
For species A:
For species B:
:Here the first (positive) term represents the formation of B by the first step , whose rate depends on the initial reactant A. The second (negative) term represents the consumption of B by the second step , whose rate depends on B as the reactant in that step.
For species C: | 0 | Theoretical and Fundamental Chemistry |
In combustion, flame stretch () is a quantity which measures the amount of stretch of the flame surface due to curvature and due to the outer velocity field strain. The early concept of flame stretch was introduced by Karlovitz in 1953, although the correct definition was introduced two decades later by Forman A. Williams in 1975.
George H. Markstein studied flame stretch by treating the flame surface as a hydrodynamic discontinuity (known as flame front). The flame stretch is also discussed by Bernard Lewis and Guenther von Elbe in their book. All these discussions treated flame stretch as an effect of flow velocity gradients. The stretch can be found even if there is no velocity gradient, but due to the flame curvature. So, the definition required a more general formulation and its precise definition was first introduced by Forman A. Williams in 1975 as the ratio of rate of change of flame surface area to the area itself
When , the flame is stretched, otherwise compressed. Sometimes the flame stretch is defined as non-dimensional quantity
where is the laminar flame thickness and is the laminar propagation speed of unstretched premixed flame. | 1 | Applied and Interdisciplinary Chemistry |
The sodium fusion extract is boiled with concentrated HNO followed by the addition of AgNO solution which yields a white (AgCl) or yellow (AgBr or AgI) precipitate if halogen is present.</blockquote> | 0 | Theoretical and Fundamental Chemistry |
Aerobic metabolism occurs in Bacteria, Archaea and Eucarya. Although most bacterial species are anaerobic, many are facultative or obligate aerobes. The majority of archaeal species live in extreme environments that are often highly anaerobic. There are, however, several cases of aerobic archaea such as Haiobacterium, Thermoplasma, Sulfolobus and Yymbaculum. Most of the known eukaryotes carry out aerobic metabolism within their mitochondria which is an organelle that had a symbiogenesis origin from prokarya . All aerobic organisms contain oxidases of the cytochrome oxidase super family, but some members of the Pseudomonadota (E. coli and Acetobacter) can also use an unrelated cytochrome bd complex as a respiratory terminal oxidase. | 1 | Applied and Interdisciplinary Chemistry |
Earlier mechanistic proposals for the EPOC phenomenon with solid electrolytes mainly emphasized tuning of the local work function of the surface of conductive catalysts by spilled-over species, which are in-situ generated during electrochemical polarization processes. It has been proposed that the spilled-over species can subsequently modulate the chemisorption strength between surface adsorbates (intermediates) and catalyst binding sites, thereby influencing the rate or selectivity of the target reactions significantly. Particularly in the case of oxygen-ion conducting electrolyte systems, for instance, the migrated anionic O species from the solid electrolyte to the metal-gas interface has been suggested as the origin of the corresponding EPOC effects along with the evidence that the migrated charged species on the surface can be identified via in-situ spectroscopic methods. On the other hand, the hypothesis of modification of the local work function to explain the origin of EPOC was recently criticized with a different view that heterogeneous catalysis needs to be explained by more recent concepts such as d-band center theory, rather than the surface work function, which might play a more trivial role in understanding of surface reactions. | 0 | Theoretical and Fundamental Chemistry |
The Swamee–Jain equation is used to solve directly for the Darcy–Weisbach friction factor f for a full-flowing circular pipe. It is an approximation of the implicit Colebrook–White equation. | 1 | Applied and Interdisciplinary Chemistry |
Theodore William Richards (January 31, 1868 – April 2, 1928) was an American physical chemist and the first American scientist to receive the Nobel Prize in Chemistry, earning the award "in recognition of his exact determinations of the atomic weights of a large number of the chemical elements." | 1 | Applied and Interdisciplinary Chemistry |
Launched in the 1940s by the Shirley Institute, the Shirley Togmeter is the standard apparatus for rating thermal resistance of textiles, commonly known as the Tog Test. This apparatus, described in BS 4745:2005, measures a sample of textile, either between two metal plates (for underclothing) or between a metal plate and free air (for outer layers). Each industry has its own specifications and methods for measuring thermal properties. | 0 | Theoretical and Fundamental Chemistry |
"Blue infrastructure" refers to urban infrastructure relating to water. Blue infrastructure is commonly associated with green infrastructure in urban environments and may be referred to as "blue-green infrastructure" when being viewed in combination. Rivers, streams, ponds, and lakes may exist as natural features within cities, or be added to an urban environment as an aspect of its design. Coastal urban developments may also utilize pre-existing features of the coastline specifically employed in their design. Harbours, quays, piers, and other extensions of the urban environment are also often added to capture benefits associated with the marine environment. Blue infrastructure can support unique aquatic biodiversity in urban areas, including aquatic insects, amphibians, and water birds. There may considerable co-benefits to the health and wellbeing of populations with access to blue spaces in the urban context. Accessible blue infrastructure in urban areas is also referred as to blue spaces. | 1 | Applied and Interdisciplinary Chemistry |
To neglect the influences by hydrodynamic instabilities such as Darrieus–Landau instability, Rayleigh–Taylor instability etc., the analysis usually neglects effects due to the thermal expansion of the gas mixture by assuming a constant density model. Such an approximation is referred to as diffusive-thermal approximation or thermo-diffusive approximation which was first introudced by Grigory Barenblatt, Yakov Zeldovich and A. G. Istratov in 1962. With a one-step chemistry model and assuming the perturbations to a steady planar flame in the form , where is the transverse coordinate system perpendicular to flame, is the time, is the perturbation wavevector and is the temporal growth rate of the disturbance, the dispersion relation for one-reactant flames is given implicitly by
where , , is the Lewis number of the fuel and is the Zeldovich number. This relation provides in general three roots for in which the one with maximum would determine the stability character. The stability margins are given by the following equations
describing two curves in the vs. plane. The first curve is associated with condition , whereas on the second curve The first curve separates the region of stable mode from the region corresponding to cellular instability, whereas the second condition indicates the presence of traveling and/or pulsating instability. | 1 | Applied and Interdisciplinary Chemistry |
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