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Divergent evolution of active site residues is slow, due to strong chemical constraints. Nevertheless, some protease superfamilies have evolved from one nucleophile to another. This can be inferred when a superfamily (with the same fold) contains families that use different nucleophiles. Such nucleophile switches have occurred several times during evolutionary history, however the mechanisms by which this happen are still unclear.
Within protease superfamilies that contain a mixture of nucleophiles (e.g. the PA clan), families are designated by their catalytic nucleophile (C=cysteine proteases, S=serine proteases). | 1 | Applied and Interdisciplinary Chemistry |
Pyruvate, the result of glycolysis, can feed into both the TCA cycle and fermentation processes. Reactions beginning with either one or two molecules of pyruvate lead to the synthesis of alanine, valine, and leucine. Feedback inhibition of final products is the main method of inhibition, and, in E. coli, the ilvEDA operon also plays a part in this regulation. | 1 | Applied and Interdisciplinary Chemistry |
Several different types of events may take place as a result of the ion beam impinging on a target surface. Some of these events include electron or photon emission, electron transfer (both ion-surface and surface-ion), scattering, adsorption, and sputtering (i.e. ejection of atoms from the surface). For each system and each interaction there exists an interaction cross-section, and the study of these cross-sections is a field in its own right. As the name suggests, LEIS is primarily concerned with scattering phenomena. | 0 | Theoretical and Fundamental Chemistry |
The high sensitivity of DESI in the lipid range makes it a powerful technique for the detection and mapping of lipids abundances within tissue specimens. Recent developments in MALDI methods have enabled direct detection of lipids in-situ. Abundant lipid-related ions are produced from the direct analysis of thin tissue slices when sequential spectra are acquired across a tissue surface that has been coated with a MALDI matrix. Collisional activation of the molecular ions can be used to determine the lipid family and often structurally define the molecular species. These techniques enable detection of phospholipids, sphingolipids and glycerolipids in tissues such as heart, kidney and brain. Furthermore, distribution of many different lipid molecular species often define anatomical regions within these tissues. | 1 | Applied and Interdisciplinary Chemistry |
The C-terminal glucase enzymatic unit contains extra binding sites, which allows for it to bind to larger substrates for catalytic digestion. It was originally understood that maltase-glucoamylase's crystalline structure was inherently similar throughout the N and C-termini. Further studies have found that the C-terminus is composed of 21 more amino acid residues than the N-terminus, which account for its difference in function. Sucrase-Isomaltase –– located on chromosome 3q26–– has a similar crystalline structure to maltase-glucoamylase and work in tandem in the human small intestine. They have been derived from a common ancestor, as they both come from the same GH31 family. As a result of having similar properties, both of these enzymes work together in the small intestine in order to convert consumed starch into glucose for metabolic energy. The difference between these two enzymes is that maltase-glucoamylase has a specific activity at the 1-4 linkage of sugar, where at SI has a specific activity at the 1-6 linkage. | 1 | Applied and Interdisciplinary Chemistry |
When a salt is dissolved in a solvent, it always has the effect of raising the boiling point of that solvent – that is it decreases the volatility of the solvent. When the salt is readily soluble in one constituent of a mixture but not in another, the volatility of the constituent in which it is soluble is decreased and the other constituent is unaffected. In this way, for example, it is possible to break the water/ethanol azeotrope by dissolving potassium acetate in it and distilling the result. | 1 | Applied and Interdisciplinary Chemistry |
Trichloroethylene is a good analgesic at 0.35 to 0.5% concentrations. Trichloroethylene was used in the treatment of trigeminal neuralgia beginning in 1916.
From the 1940s through the 1980s, both in Europe and North America, trichloroethylene was used as a volatile anesthetic almost invariably administered with nitrous oxide. Marketed in the UK by Imperial Chemical Industries under the trade name Trilene it was coloured blue (with a dye called waxoline blue in 1:200,000 concentration) to avoid confusion with the similar-smelling chloroform. Trilene was stabilised with 0.01% thymol.
TCE replaced earlier anesthetics chloroform and ether in the 1940s due to its lower toxicity than chloroform and being relatively non-flammable (unlike ether which is extremely flammable), but was itself replaced in the 1960s in developed countries with the introduction of halothane, which allowed much faster induction and recovery times and was considerably easier to administer. Trilene was also used as an inhaled analgesic, mainly during childbirth, often self-applied by the patient. Trichloroethylene was introduced for obstetrical anaesthesia in 1943, and used until the 1980s. Its anaesthetic use was banned in the United States in 1977 but the anaesthetic use in the United Kingdom remained until the late 1980s.
TCE was used with halothane in the tri-service field anaesthetic apparatus used by the UK armed forces under field conditions. As of 2000, TCE was still in use as an anesthetic in Africa.
Trichloroethylene has been used in the production of halothane. | 1 | Applied and Interdisciplinary Chemistry |
According to the Vienna Convention on Road Traffic, which mostly covers Europe, if having a vehicle registered and legal to drive in one of the Convention countries, it is legal to drive it in any other of the countries, for visits and first year of residence after moving. This is regardless if it does not fulfil all rules of the visitor countries. This convention does not affect rules on usage or registration of local vehicles. | 0 | Theoretical and Fundamental Chemistry |
Next to the three major classes of organic superconductors (SCs) there are more organic systems becoming superconducting at low temperatures or under pressure. A few examples follow. | 0 | Theoretical and Fundamental Chemistry |
The matte, which is produced in the smelter, contains 30–70% copper (depending on the process used and the operating philosophy of the smelter), primarily as copper sulfide, as well as iron sulfide. The sulfur is removed at a high temperature as sulfur dioxide by blowing air through molten matte:
:2 CuS + 3 O → 2 CuO + 2 SO
:CuS + O → Cu + SO
In a parallel reaction the iron sulfide is converted to slag:
:2 FeS + 3 O → 2 FeO + 2 SO
:2 FeO + SiO → FeSiO
The purity of this product is 98%, it is known as blister because of the broken surface created by the escape of sulfur dioxide gas as blister copper pigs or ingots are cooled. By-products generated in the process are sulfur dioxide and slag. The sulfur dioxide is captured and converted to sulfuric acid and either sold on the open market or used in copper leaching processes. | 1 | Applied and Interdisciplinary Chemistry |
Fish do not synthesise vitamin D in a natural setting and rely on dietary sources. As with mammals, vitamin D is more bioavailable than vitamin D. Unlike mammals, both hydroxylation steps from vitamin D to the active form 1,25 hydroxyvitamin D occur in the liver, so plasma levels of 25 hydroxyvitamin D is not an accurate measure of vitamin D levels. | 1 | Applied and Interdisciplinary Chemistry |
Justus von Liebig and Friedrich Wöhler in Giessen, Germany, had investigated the purple product, murexide, obtained from snake excrement in the 1830s, but this was not an abundant raw material, and a method of using it as a dyestuff was not established at that time. In the 1850s, French colourists and dye-producers, such as Depoully in Paris, succeeded in making murexide from abundant South American guano and of applying it to natural fibres. It was then widely adopted in Britain, France and Germany. | 0 | Theoretical and Fundamental Chemistry |
A co-receptor is a cell surface receptor that binds a signalling molecule in addition to a primary receptor in order to facilitate ligand recognition and initiate biological processes, such as entry of a pathogen into a host cell. | 1 | Applied and Interdisciplinary Chemistry |
Science fiction has used cloning, most commonly and specifically human cloning, to raise the controversial questions of identity. A Number is a 2002 play by English playwright Caryl Churchill which addresses the subject of human cloning and identity, especially nature and nurture. The story, set in the near future, is structured around the conflict between a father (Salter) and his sons (Bernard 1, Bernard 2, and Michael Black) – two of whom are clones of the first one. A Number was adapted by Caryl Churchill for television, in a co-production between the BBC and HBO Films.
In 2012, a Japanese television series named "Bunshin" was created. The storys main character, Mariko, is a woman studying child welfare in Hokkaido. She grew up always doubtful about the love from her mother, who looked nothing like her and who died nine years before. One day, she finds some of her mothers belongings at a relative's house, and heads to Tokyo to seek out the truth behind her birth. She later discovered that she was a clone.
In the 2013 television series Orphan Black, cloning is used as a scientific study on the behavioral adaptation of the clones. In a similar vein, the book The Double by Nobel Prize winner José Saramago explores the emotional experience of a man who discovers that he is a clone. | 1 | Applied and Interdisciplinary Chemistry |
Levobupivacaine (rINN) is a local anaesthetic drug indicated for minor and major surgical anaesthesia and pain management. It is a long-acting amide-type local anaesthetic that blocks nerve impulses by inhibiting sodium ion influx into the nerve cells. Levobupivacaine is the S-enantiomer of racemic bupivacaine and therefore similar in pharmacological effects. The drug typically starts taking effect within 15 minutes and can last up to 16 hours depending on factors such as site of administration and dosage.
Levobupivacaine was designed, in the late 1970s, to be a safer and more effective alternative to bupivacaine, which had been associated with a higher risk of cardiotoxicity. Compared to bupivacaine, levobupivacaine is associated with less vasodilation and has a longer duration of action. It is approximately 13 per cent less potent (by molarity) than racemic bupivacaine and has a longer motor block onset time. Ropivacaine is, next to levobupivacaine, another less cardiotoxic alternative to bupivacaine.
Levobupivacaine hydrochloride is commonly marketed by AbbVie under the trade name Chirocaine. In Europe, Chirocaine is available – prescription only – in concentrations ranging from 0.625 mg/ml to 7.5 mg/mL. | 0 | Theoretical and Fundamental Chemistry |
* monitoring and assessing aquatic species (incl. plants, animals, and bacteria)
* monitoring the behavior of certain aquatic species and assessing any changes in species behavior
* analyzing the biochemical make-up of the waterbody, and its potential influence on the species that depend on it. | 1 | Applied and Interdisciplinary Chemistry |
Ogston studied potentiometric titration of amino acids in non-aqueous solvents. He was particularly interested in sinovial fluid, and fibrous proteins. More generally, he worked on the use of physico-chemical methods to study the size, weight and structure of molecules, such as ultracentrifugation, which he applied to insulin, for example, and electrophoresis. In this context he made many improvement to equipment used for studying the physical chemistry of proteins. For example, he devised a novel type of apparatus for measuring viscosity. He made many studies of enzymes such as peroxidase and creatine phosphotransferase. He contributed to the general field of enzyme kinetics by studying activation and inhibition.
He made a sceptical study of the suggestions of a repetitive structure of proteins made by Bergmann and Niemann and by Wrinch that were widely discussed in the 1940s. | 0 | Theoretical and Fundamental Chemistry |
Determining whether a potential biosignature is worth investigating is a fundamentally complicated process. Scientists must consider any and every possible alternate explanation before concluding that something is a true biosignature. Such consideration entails investigating the minute details that make other planets unique and understanding when there is a deviation from the expected non-biological processes present on a planet. In the case of a planet with life, these differences can be extremely small or not present at all, adding to the difficulties of discovering a biosignature. Years of scientific studies have culminated in three criteria that a potential biosignature must meet to be considered viable for further research: Reliability, survivability, and detectability. | 1 | Applied and Interdisciplinary Chemistry |
Dirichlet's problem is generalized by Bernhard Riemann in 1860 and by Norman R. Lebovitz in modern form in 1965. Let be the semi-axes of the ellipsoid, which varies with time. Since the ellipsoid is homogeneous, the constancy of mass requires the constancy of the volume of the ellipsoid,
same as the initial volume. Consider an inertial frame and a rotating frame , with being the linear transformation such that and it is clear that is orthogonal, i.e., . We can define an anti-symmetric matrix with this,
where we can write the dual of as (and ), where is nothing but the time-dependent rotation of the rotating frame with respect to the inertial frame.
Without loss of generality, let us assume that the inertial frame and the moving frame coincide initially, i.e., . By definition, Dirichlet's problem is looking for a solution which is a linear function of initial condition . Let us assume the following form,
and we define a diagonal matrix with diagonal elements being the semi-axes of the ellipsoid, then above equation can be written in matrix form as
where . It can shown then that the matrix transforms the vector linearly to the same vector at any later time , i.e., . From the definition of , we can realize the vector represents a unit normal on the surface of the ellipsoid (true only at the boundary) since a fluid element on the surface moves with the surface. Therefore, we see that transforms one unit vector on the boundary to another unit vector on the boundary, in other words, it is orthogonal, i.e., . In a similar manner as before, we can define another anti-symmetric matrix as
where its dual is defined as (and ). The problem is one of uniform vorticity with components given by
The pressure can take only quadratic form, can be seen from the momentum equation (and using the vanishing condition at the surface) given by
where is the central pressure, so that . Finally, the tensor momentum equation reduces to
where is the gravitational constant and is diagonal matrix, whose diagonal elements are given by
The tensor momentum equation and the conservation of mass equation, i.e., provides us with ten equations for the ten unknowns, | 1 | Applied and Interdisciplinary Chemistry |
A trap primer automatically injects water into a trap, maintaining a water seal to keep sewer gas out of buildings. It must be installed in an easily accessible place for adjustment, replacement, and repair. A trap primer, a specialized valve, is usually connected to a clean-water supply in addition to a DWV system. Because of the dual connection, it must be designed to resist the accidental backflow of contaminated water. | 1 | Applied and Interdisciplinary Chemistry |
The chiral switch concept is illustrated in the diagram. This chiral switch is from (±)-ibuprofen to (S)-(+)-ibuprofen (dexibuprofen). The nonsteroidal anti-inflammatory drug (NSAID) ibuprofen was the first chiral drug of the NSAID class to be switched to the single-enantiomer version in 1994. The switch was done based on the fact that the (S)-ibuprofen, the eutomer, was over 100-fold more potent as an inhibitor of cycloxygenase-1 (COX-1) enzyme than (R)-ibuprofen. Moreover, ibuprofen, when administered as the racemate, the active (R)-enantiomer undergoes partial unidirectional chiral inversion (approximately 60%) to the (S)-enantiomer. Therefore, the use of the single (S)-ibuprofen was expected to give faster onset of action at a lower dosage. Further, while choosing the chiral drug candidate for a chiral switch one should take a look at the chiral inversion tendency of the molecule. For instance, thalidomide, the sedative drug, undergoes bidirectional chiral inversion or racemization in biological systems. In such cases chiral switching efforts will be pointless. | 0 | Theoretical and Fundamental Chemistry |
Although the bond valence model is mostly used for validating newly determined structures, it is capable of predicting many of the properties of those chemical structures that can be described by localized bonds
In the bond valence model, the valence of an atom, V, is defined as the number of electrons the atom uses for bonding. This is equal to the number of electrons in its valence shell if all the valence shell electrons are used for bonding. If they are not, the remainder will form non-bonding electron pairs, usually known as lone pairs.
The valence of a bond, S, is defined as the number of electron pairs forming the bond. In general this is not an integral number. Since each of the terminal atoms contributes equal numbers of electrons to the bond, the bond valence is also equal to the number of valence electrons that each atom contributes. Further, since within each atom, the negatively charged valence shell is linked to the positively charged core by an electrostatic flux that is equal to the charge on the valence shell, it follows that the bond valence is also equal to the electrostatic flux that links the core to the electrons forming the bond. The bond valence is thus equal to three different quantities: the number of electrons each atom contributes to the bond, the number of electron pairs that form the bond, and the electrostatic flux linking each core to the bonding electron pair. | 0 | Theoretical and Fundamental Chemistry |
Some of the same properties that make nanoparticles efficient drug carriers also contribute to their toxicity. For example, gold nanoparticles are known to interact with proteins through surface adsorption, forming a protein corona, which can be utilized for cargo loading and immune shielding. However, this protein-adsorption property can also disrupt normal protein function that is essential for homeostasis, especially when the protein contains exposed sulfur groups. The photothermal effect, which can be induced to kill tumor cells, may also create reactive oxygen species that impose oxidative stress on surrounding healthy cells. Gold nanoparticles of sizes below 4-5 nm fit in DNA grooves which can interfere with transcription, gene regulation, replication, and other processes that rely on DNA-protein binding. Lack of biodegradability for some nanoparticle chemistries can lead to accumulation in certain tissues, thus interfering with a wide range of biological processes. Currently, there is no regulatory framework in the United States for testing nanoparticles for their general impact on health and on the environment. | 0 | Theoretical and Fundamental Chemistry |
The University of Sydney has typically performed well on the QS Chemistry Subject Ranking, where it was 30th in 2013, 42nd in 2014, 51-100th in 2015, 49th in 2016, 50th in 2017, 43rd in 2018, and 51-100th in 2019. The University of Sydney has been 151-200th in the Academic Ranking of World Universities in chemistry since its inception in 2017. In 2018, U.S. News & World Report ranked the School of Chemistry, University of Sydney 138th in the world and 6th in Australia. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, the inductive effect in a molecule is a local change in the electron density due to electron-withdrawing or electron-donating groups elsewhere in the molecule, resulting in a permanent dipole in a bond.
It is present in a σ (sigma) bond, unlike the electromeric effect which is present in a π (pi) bond.
The halogen atoms in an alkyl halide are electron withdrawing while the alkyl groups have electron donating tendencies. If the electronegative atom (missing an electron, thus having a positive charge) is then joined to a chain of atoms, usually carbon, the positive charge is relayed to the other atoms in the chain. This is the electron-withdrawing inductive effect, also known as the -I effect. In short, alkyl groups tend to donate electrons, leading to the +I effect. Its experimental basis is the ionization constant. It is distinct from and often opposite to the mesomeric effect. | 0 | Theoretical and Fundamental Chemistry |
The permanganate index is an assessment of water quality. It involves the detection of oxidation by potassium permanganate in an acid medium under hot conditions.
The method is to heat a sample in a boiling water-bath with a known amount of potassium permanganate and sulphuric acid for a fixed period time (10 min). Part of the permanganate will be reduced by oxidizable material in the sample. The consumed permanganate can be determined by addition of an excess of oxalate solution, followed by titration with permanganate. The method applies to waters having a chloride ion concentration of less than 300 mg/L. Samples having a permanganate index over 10 mg/L should be diluted before analysis. The lower limit of the optimum range of the test is 0.5 mg/L.
The permanganate index method is not recommended for waste water because some organic compounds are not oxidized or incompletely oxidized. | 0 | Theoretical and Fundamental Chemistry |
Thiopeptide biosynthesis involves particularly extensive modification of the core peptide scaffold. Indeed, due to the highly complex structures of thiopeptides, it was commonly thought that these natural products were nonribosomal peptides. Recognition of the ribosomal origin of these molecules came in 2009 with the independent discovery of the gene clusters for several thiopeptides.
The standard nomenclature for thiopeptide biosynthetic proteins follows that of the thiomuracin gene cluster. In addition to the precursor peptide, referred to as the A peptide, thiopeptide biosynthesis requires at least six genes. These include lanthipeptide-like dehydratases, designated the B and C proteins, which install dehydroalanine and dehydrobutyrine moieties by dehydrating Ser/Thr precursor residues. Azole and azoline synthesis is effected by the E protein, the dehydrogenase, and the G protein, the cyclodehydratase. The nitrogen-containing heterocycle is installed by the D protein cyclase via a putative [4+2] cycloaddition of dehydroalanine moieties to form the characteristic macrocycle. The F protein is responsible for binding of the leader peptide.
Thiopeptide biosynthesis is biochemically similar to that of cyanobactins, lanthipeptides, and linear azol(in)e-containing peptides (LAPs). As with cyanobactins and LAPs, azole and azoline synthesis occurs via the action of an ATP-dependent YcaO-domain cyclodehydratase. In contrast to LAPs, where cyclodehydration occurs via the action of two distinct proteins responsible for leader peptide binding and cyclodehydrative catalysis, these are fused into a single protein (G protein) in cyanobactin and thiopeptide biosynthesis. However, in thiopeptides, an additional protein, designated the Ocin-ThiF-like protein (F protein) is necessary for leader peptide recognition and potentially recruiting other biosynthetic enzymes. | 1 | Applied and Interdisciplinary Chemistry |
The transverse (or spin-spin) relaxation time T is the decay constant for the component of M perpendicular to B, designated M, M, or . For instance, initial xy magnetization at time zero will decay to zero (i.e. equilibrium) as follows:
i.e. the transverse magnetization vector drops to 37% of its original magnitude after one time constant T.
T relaxation is a complex phenomenon, but at its most fundamental level, it corresponds to a decoherence of the transverse nuclear spin magnetization. Random fluctuations of the local magnetic field lead to random variations in the instantaneous NMR precession frequency of different spins. As a result, the initial phase coherence of the nuclear spins is lost, until eventually the phases are disordered and there is no net xy magnetization. Because T relaxation involves only the phases of other nuclear spins it is often called "spin-spin" relaxation.
T values are generally much less dependent on field strength, B, than T values.
Hahn echo decay experiment can be used to measure the T time, as shown in the animation below. The size of the echo is recorded for different spacings of the two applied pulses. This reveals the decoherence which is not refocused by the 180° pulse. In simple cases, an exponential decay is measured which is described by the time. | 0 | Theoretical and Fundamental Chemistry |
Omics, especially genomics and proteomics, allow identifying and evaluating genes, proteins and enzymes involved in radionuclide bioremediation, apart from the structural and functional interactions that exist between them and other metabolites. Genome sequencing of various microorganisms has uncovered, for example, that Geobacter sulfurreducens possess more than 100 coding regions for c-type cytochromes involved in bioremediation radionuclide, or that NiCoT gene is significantly overexpressed in Rhodopseudomonas palustris and Novosphingobium aromaticivorans when grown in medium with radioactive cobalt.
From this information, different genetic engineering and recombinant DNA techniques are being developed to generate specific bacteria for bioremediation. Some constructs expressed in microbial species are phytochelatins, polyhistidines and other polypeptides by fusion-binding domains to outer-membrane-anchored proteins. Some of these genetically modified strains are derived from Deinococcus radiodurans, one of the most radiation-resistant organisms. D. radiodurans is capable to resist oxidative stress and DNA damage from radiation, and reduces technetium, uranium and chromium naturally as well. Besides, through insertion of genes from other species it has been achieved that it can also precipitates uranyl phosphates and degrades mercury by using toluene as an energy source to grow and stabilize other priority radionuclides.
Directed evolution of bacterial proteins related to bioremediation of radionuclides is also a field research. YieF enzyme, for example, naturally catalyzes the reduction of chromium with a very wide range of substrates. Following protein engineering, however, it has also been able to participate in uranyl ion reduction. | 1 | Applied and Interdisciplinary Chemistry |
TBS is isotonic and non-toxic. It can be used to dilute substances used in laboratory experiments. Additives can be used to add to a compound's functionality.
TBS is often used in immuno-blotting for both membrane washing and antibody dilution. | 1 | Applied and Interdisciplinary Chemistry |
One of the most prevalent features of iron chemistry is its redox chemistry. Iron has three oxidation states: metallic iron (Fe), ferrous iron (Fe), and ferric iron (Fe). Ferrous iron is the reduced form of iron, and ferric iron is the oxidized form of iron. In the presence of oxygen, ferrous iron is oxidized to ferric iron, thus ferric iron is the dominant redox state of iron at Earth's surface conditions. However, ferrous iron is the dominant redox state below the surface at depth. Because of this redox chemistry, iron can act as either an electron donor or receptor, making it a metabolically useful species.
Each form of iron has a specific distribution of electrons (i.e., electron configuration), tabulated below: | 0 | Theoretical and Fundamental Chemistry |
Ali Akbar Moosavi-Movahedi (born in Shiraz, Iran, February 1953) is an Iranian Biophysicist, and Biophysical Chemist at the Institute of Biochemistry and Biophysics, University of Tehran. He is the founder of the [http://isobc.com/ Iran Society of Biophysical Chemistry] . He is the fellow of The World Academy of Sciences (TWAS), fellow of Islamic World Academy of Sciences (IAS), and a member of the Islamic Republic of Iran Academy of Sciences. | 0 | Theoretical and Fundamental Chemistry |
Kerr frequency combs (also known as microresonator frequency combs) are optical frequency combs which are generated from a continuous wave pump laser by the Kerr nonlinearity. This coherent conversion of the pump laser to a frequency comb takes place inside an optical resonator which is typically of micrometer to millimeter in size and is therefore termed a microresonator. The coherent generation of the frequency comb from a continuous wave laser with the optical nonlinearity as a gain sets Kerr frequency combs apart from today's most common optical frequency combs. These frequency combs are generated by mode-locked lasers where the dominating gain stems from a conventional laser gain medium, which is pumped incoherently. Because Kerr frequency combs only rely on the nonlinear properties of the medium inside the microresonator and do not require a broadband laser gain medium, broad Kerr frequency combs can in principle be generated around any pump frequency.
While the principle of Kerr frequency combs is applicable to any type of optical resonator, the requirement for Kerr frequency comb generation is a pump laser field intensity above the parametric threshold of the nonlinear process. This requirement is easier to fulfill inside a microresonator because of the possible very low losses inside microresonators (and corresponding high quality factors) and because of the microresonators’ small mode volumes. These two features combined result in a large field enhancement of the pump laser inside the microresonator which allow the generation of broad Kerr frequency combs for reasonable powers of the pump laser.
One important property of Kerr frequency combs, which is a direct consequence of the small dimensions of the microresonators and their resulting large free spectral ranges (FSR), is the large mode spacing of typical Kerr frequency combs. For mode-locked lasers this mode spacing, which defines the distance in between adjacent teeth of the frequency comb, is typically in the range of 10 MHz to 1 GHz. For Kerr frequency combs the typical range is from around 10 GHz to 1 THz.
The coherent generation of an optical frequency comb from a continuous wave pump laser is not a unique property of Kerr frequency combs. Optical frequency combs generated with cascaded optical modulators also possess this property. For certain application this property can be advantageous. For example, to stabilize the offset frequency of the Kerr frequency comb one can directly apply feedback to the pump laser frequency. In principle it is also possible to generate a Kerr frequency comb around a particular continuous wave laser in order to use the bandwidth of the frequency comb to determine the exact frequency of the continuous wave laser.
Since their first demonstration in silica micro-toroid resonators, Kerr frequency combs have been demonstrated in a variety of microresonator platforms which notably also include crystalline microresonators and integrated photonics platforms such as waveguide resonators made from silicon nitride. More recent research has expanded the range of available platforms further which now includes diamond, aluminum nitride,
lithium niobate, and, for mid-infrared pump wavelengths, silicon.
Because both use the nonlinear effects of the propagation medium, the physics of Kerr frequency combs and of supercontinuum generation from pulsed lasers is very similar. In addition to the nonlinearity, the chromatic dispersion of the medium also plays a crucial role for these systems. As a result of the interplay of nonlinearity and dispersion, solitons can form. The most relevant type of solitons for Kerr frequency comb generation are bright dissipative cavity solitons, which are sometimes also called dissipative Kerr solitons (DKS). These bright solitons have helped to significantly advance the field of Kerr frequency combs as they provide a way to generate ultra-short pulses which in turn represent a coherent, broadband optical frequency comb, in a more reliable fashion than what was possible before.
In its simplest form with only the Kerr nonlinearity and second order dispersion the physics of Kerr frequency combs and dissipative solitons can be described well by the Lugiato–Lefever equation.
Other effects such as the Raman effect and higher order dispersion effects require additional terms in the equation. | 0 | Theoretical and Fundamental Chemistry |
A Fischer–Tropsch-type process has also been suggested to have produced a few of the building blocks of DNA and RNA within asteroids. Similarly, the hypothetical abiogenic petroleum formation requires some naturally occurring FT-like processes.
Biological Fischer-Tropsch-type chemistry can be carried out by the enzyme nitrogenase at ambient conditions. | 0 | Theoretical and Fundamental Chemistry |
The volume of a thermodynamic system typically refers to the volume of the working fluid, such as, for example, the fluid within a piston. Changes to this volume may be made through an application of work, or may be used to produce work. An isochoric process however operates at a constant-volume, thus no work can be produced. Many other thermodynamic processes will result in a change in volume. A polytropic process, in particular, causes changes to the system so that the quantity is constant (where is pressure, is volume, and is the polytropic index, a constant). Note that for specific polytropic indexes, a polytropic process will be equivalent to a constant-property process. For instance, for very large values of approaching infinity, the process becomes constant-volume.
Gases are compressible, thus their volumes (and specific volumes) may be subject to change during thermodynamic processes. Liquids, however, are nearly incompressible, thus their volumes can be often taken as constant. In general, compressibility is defined as the relative volume change of a fluid or solid as a response to a pressure, and may be determined for substances in any phase. Similarly, thermal expansion is the tendency of matter to change in volume in response to a change in temperature.
Many thermodynamic cycles are made up of varying processes, some which maintain a constant volume and some which do not. A vapor-compression refrigeration cycle, for example, follows a sequence where the refrigerant fluid transitions between the liquid and vapor states of matter.
Typical units for volume are (cubic meters), (liters), and (cubic feet). | 0 | Theoretical and Fundamental Chemistry |
Sodium amide, commonly called sodamide (systematic name sodium azanide), is the inorganic compound with the formula . It is a salt composed of the sodium cation and the azanide anion. This solid, which is dangerously reactive toward water, is white, but commercial samples are typically gray due to the presence of small quantities of metallic iron from the manufacturing process. Such impurities do not usually affect the utility of the reagent. conducts electricity in the fused state, its conductance being similar to that of NaOH in a similar state. has been widely employed as a strong base in organic synthesis. | 0 | Theoretical and Fundamental Chemistry |
The four most common methods of transition metal catalyzed methane activation are the Shilov system, sigma bond metathesis, oxidative addition, and 1,2 addition reactions.
The Shilov system involves platinum based complexes to produce metal alkyls. It was first discovered when a hydrogen-deuterium exchanged was observed in a deuterated solution with the platinum tetrachloride anion. Shilov et al. then was able to catalytically convert methane into methanol or methyl chloride when a Pt(IV) salt was used as a stoichiometric oxidant. The process is simplified down into three main steps: (1) C-H activation, (2) a redox reaction to form an octahedral intermediate, followed by (3) the formation of the carbon-oxygen bond to form methanol ().
Sigma bond metathesis involves the formation of new C-H and metal-carbon bonds, where the metals are typically in the d configuration. Starting with a metal alkyl, a C-H bond coordinates with the metal complex via sigma bonding. A four-member transition state is created, where a new metal-carbon bond is formed, and the former C-H linkage is broken ().
In oxidative addition, the metal center's oxidation state increases by 2 units during the process. First, the metal center coordinates with a sigma C-H bond to form an intermediate called a sigma-methane complex. The C-H linkage is then broken, as the metal becomes covalently bonded each to the carbon and the hydrogen ().
Similar to sigma bond metathesis is the 1,2 addition reaction, where a four-membered transition state is also formed. However, a polarized double or triple metal-ligand bond is required in order to favor the formation of the desired product (). | 0 | Theoretical and Fundamental Chemistry |
Twenty to fifty percent of hypothermia deaths are associated with paradoxical undressing. This typically occurs during moderate and severe hypothermia, as the person becomes disoriented, confused, and combative. They may begin discarding their clothing, which, in turn, increases the rate of heat loss.
Rescuers who are trained in mountain survival techniques are taught to expect this; however, people who die from hypothermia in urban environments who are found in an undressed state are sometimes incorrectly assumed to have been subjected to sexual assault.
One explanation for the effect is a cold-induced malfunction of the hypothalamus, the part of the brain that regulates body temperature. Another explanation is that the muscles contracting peripheral blood vessels become exhausted (known as a loss of vasomotor tone) and relax, leading to a sudden surge of blood (and heat) to the extremities, causing the person to feel overheated. | 1 | Applied and Interdisciplinary Chemistry |
* gamma-Decalactone intense peach flavor
* gamma-Nonalactone coconut odor, popular in suntan lotions
* delta-Octalactone creamy note
* Jasmine lactone powerful fatty-fruity peach and apricot
* Massoia lactone powerful creamy coconut
* Wine lactone sweet coconut odor
* Sotolon (maple syrup, curry, fenugreek) | 0 | Theoretical and Fundamental Chemistry |
Costs of IVF can be broken down into direct and indirect costs. Direct costs include the medical treatments themselves, including doctor consultations, medications, ultrasound scanning, laboratory tests, the actual IVF procedure, and any associated hospital charges and administrative costs. Indirect costs includes the cost of addressing any complications with treatments, compensation for the gestational surrogate, patients' travel costs, and lost hours of productivity. These costs can be exaggerated by the increasing age of the woman undergoing IVF treatment (particularly those over the age of 40), and the increase costs associated with multiple births. For instance, a pregnancy with twins can cost up to three times that of a singleton pregnancy. While some insurances cover one cycle of IVF, it takes multiple cycles of IVF to have a successful outcome. A study completed in Northern California reveals that the IVF procedure alone that results in a successful outcome costs $61,377, and this can be more costly with the use of a donor egg.
The cost of IVF rather reflects the costliness of the underlying healthcare system than the regulatory or funding environment, and ranges, on average for a standard IVF cycle and in 2006 United States dollars, between $12,500 in the United States to $4,000 in Japan. In Ireland, IVF costs around €4,000, with fertility drugs, if required, costing up to €3,000. The cost per live birth is highest in the United States ($41,000) and United Kingdom ($40,000) and lowest in Scandinavia and Japan (both around $24,500).
The high cost of IVF is also a barrier to access for disabled individuals, who typically have lower incomes, face higher health care costs, and seek health care services more often than non-disabled individuals.
Navigating insurance coverage for transgender expectant parents presents a unique challenge. Insurance plans are designed to cater towards a specific population, meaning that some plans can provide adequate coverage for gender-affirming care but fail to provide fertility services for transgender patients. Additionally, insurance coverage is constructed around a person's legally recognised sex and not their anatomy; thus, transgender people may not get coverage for the services they need, including transgender men for fertility services. | 1 | Applied and Interdisciplinary Chemistry |
The static pressure of air is the pressure in a free-flowing air stream and is depicted by isobars in weather maps. Differences in static pressure arise from global and microclimate thermal phenomena and create the air flow we call wind. Dynamic pressure is the pressure exerted when the wind comes into contact with an object such as a hill or a building and it is described by the following equation:
where (using SI units):
The impact of wind on a building affects the ventilation and infiltration rates through it and the associated heat losses or heat gains. Wind speed increases with height and is lower towards the ground due to frictional drag. In practical terms wind pressure will vary considerably creating complex air flows and turbulence by its interaction with elements of the natural environment (trees, hills) and urban context (buildings, structures). Vernacular and traditional buildings in different climatic regions rely heavily upon natural ventilation for maintaining thermal comfort conditions in the enclosed spaces. | 1 | Applied and Interdisciplinary Chemistry |
* Eliyahu-Behar, A.; Yahalom-Mack, N.; Ben-Shlomo, D. (2017). "[https://www.academia.edu/34274359/Excavation_and_Analysis_of_an_Early_Iron_Age_Lime_Kiln_Eliyahu-behar_et_al_IEJ_2017.pdf Excavation and Analysis of an Early Iron Age Lime Kiln]", Israel Exploration Journal 67, pp. 14–31 | 1 | Applied and Interdisciplinary Chemistry |
Imaging is a useful tool in visualization of the radioligand after injection, with Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT) being the most common types of imaging. PET scans are often utilized after radioligand administration because of the ease of use, image accuracy, and non-invasive nature. While PET and SPECT scans function similarly when imaging radioligands, the main difference lies in the type of radiation used, with PET Scans utilizing positrons and SPECT utilizing gamma rays. When comparing the two modalities, PET offers much better image quality and high diagnostic proficiency, however, the high cost limits the overall availability as well as the short half-lives of the positron-emitting isotopes. Alternatively, SPECT imaging is more dynamic because of the lower cost burden and longer half-lives of single-photon emitters. With advances in technology came hybrid imaging that can combine PET, SPECT, Computed Tomography (CT), and Magnetic Resonance Imaging (MRI). Some hybrid imaging modalities include: SPECT/CT, PET/CT and PET/MRI. Although combined imaging presents both cost and availability barriers, the technology is an extremely useful diagnostic tool. Often, the patient does not have to be moved for both imaging types to be completed and the clinicians are provided with rich, multi-dimensional imaging. | 1 | Applied and Interdisciplinary Chemistry |
Dioxiranes may either be prepared in advance or generated in situ for epoxidation reactions. In most cases, a two-phase system must be set up for in situ epoxidations, as KHSO is not soluble in organic solvents. Thus, substrates or products sensitive to hydrolysis will not survive in situ epoxidations. This section describes epoxidation conditions for alkenes with electron-donating or -withdrawing substituents, both of which may be epoxidized with dioxiranes in either the stoichiometric or catalytic mode.
Although dioxiranes are highly electrophilic, they epoxidize both electron-rich and electron-poor alkenes in good yield (although the latter react much more slowly). Electron-poor epoxide products also exhibit enhanced hydrolytic stability, meaning that they can often survive in situ conditions. Epoxidations of electron-rich double bonds have yielded intermediates of Rubottom oxidation. Upon hydrolysis, these siloxyepoxides yield α-hydroxyketones.
Electron-poor double bonds take much longer to epoxidize. Heating may be used to encourage oxidation, although the reaction temperature should never exceed 50 °C, to avoid decomposition of the dioxirane.
Alkenes bound to both electron-withdrawing and -donating groups tend to behave like the former, requiring long oxidation times and occasionally some heating. Like electron-poor epoxides, epoxide products from this class of substrates are often stable with respect to hydrolysis.
In substrates containing multiple double bonds, the most electron-rich double bond can usually be selectively epoxidized.
Epoxidations employing aqueous Oxone and a catalytic amount of ketone are convenient if a specialized dioxirane must be used (as in asymmetric applications) or if isolation of the dioxirane is inconvenient. Hydrolytic decomposition of the epoxidation product may be used to good advantage. | 0 | Theoretical and Fundamental Chemistry |
George Hermann Büchi (August 1, 1921 – August 28, 1998) was a Swiss organic chemist and professor at the Massachusetts Institute of Technology. "Paternòs reaction", known since the early twentieth century, was renamed to the "Paternò–Büchi reaction" based on enhancements made to it by Büchis research group.
Büchi died at the age of 77 of heart failure while hiking with his wife in Switzerland. | 0 | Theoretical and Fundamental Chemistry |
Charles Sibley and Jon Ahlquist, pioneers of the technique, used DNA–DNA hybridization to examine the phylogenetic relationships of avians (the Sibley–Ahlquist taxonomy) and primates. | 1 | Applied and Interdisciplinary Chemistry |
One of ATSDR’s primary responsibilities is conducting public health assessments and health consultations. The agency conducts public health assessments for all current or proposed sites on the National Priorities List (commonly known as Superfund sites). The purpose of public health assessments is to examine whether hazardous substances at a site pose a human health hazard and to issue recommendations about limiting or stopping exposure to those substances. ATSDR also conducts health consultations, often in response to requests from EPA and state and local agencies. Health consultations examine specific health questions, such as the health effects of exposure to a specific chemical at a site. Health consultations are more limited in scope than public health assessments. ATSDR also conducts public health assessments and health consultations in response to petitions from members of the public. To conduct public health assessments and health consultations, ATSDR relies on its own scientists or establishes cooperative agreements with states, providing technical assistance to state health departments. ATSDR issued more than 200 public health assessments in 2009 and provides about 1,000 health consultations each year.
When investigating sites, ATSDR examines environmental data, health data, and information from community members about how the site affects their quality of life. ATSDR normally does not collect its own environmental data; rather, it usually relies on partner organizations, such as EPA, to conduct testing and gather data. This environmental data provides information on the amount of contamination and possible ways humans could be exposed to the hazardous substances at the site. The health data provides information on rates of illness, disease, and death in the local community. Since ATSDR is an advisory agency, the conclusions in its public health assessments and health consultations are often in the form of recommendations to state and national environmental and health agencies, such as EPA, that have regulatory authority. Other agencies and the general public rely on ATSDR to provide trusted information on the health effects of hazardous substances at contaminated sites. | 1 | Applied and Interdisciplinary Chemistry |
Temperature gradient gel electrophoresis (TGGE) and denaturing gradient gel electrophoresis (DGGE) are forms of electrophoresis which use either a temperature or chemical gradient to denature the sample as it moves across an acrylamide gel. TGGE and DGGE can be applied to nucleic acids such as DNA and RNA, and (less commonly) proteins. TGGE relies on temperature dependent changes in structure to separate nucleic acids. DGGE separates genes of the same size based on their different denaturing ability which is determined by their base pair sequence. DGGE was the original technique, and TGGE a refinement of it. | 1 | Applied and Interdisciplinary Chemistry |
Melanie Jane Leng is a Professor of Isotope Geosciences at the University of Nottingham working on isotopes, palaeoclimate and geochemistry. She also serves as the Chief Scientist for Environmental Change Adaptation and Resilience at the British Geological Survey and Director of the Centre for Environmental Geochemistry, a collaboration between the University of Nottingham and the British Geological Survey. For many years (till 2019) she has been the UK convenor and representative of the UK geoscience community on the International Continental Scientific Drilling Program. | 0 | Theoretical and Fundamental Chemistry |
Cells are oval-shaped, non-motile and stain Gram-negative. Strictly anaerobic organism. Chemo-organotrophic. Mucolytic in pure culture. | 1 | Applied and Interdisciplinary Chemistry |
High-content screening (HCS) in cell-based systems uses living cells as tools in biological research to elucidate the workings of normal and diseased cells. HCS is also used to discover and optimize new drug candidates. High content screening is a combination of modern cell biology, with all its molecular tools, with automated high resolution microscopy and robotic handling. Cells are first exposed to chemicals or RNAi reagents. Changes in cell morphology are then detected using image analysis. Changes in the amounts of proteins synthesized by cells are measured using a variety of techniques such as the green fluorescent proteins fused to endogenous proteins, or by fluorescent antibodies.
The technology may be used to determine whether a potential drug is disease modifying. For example, in humans G-protein coupled receptors (GPCRs) are a large family of around 880 cell surface proteins that transduce extra-cellular changes in the environment into a cell response, like triggering an increase in blood pressure because of the release of a regulatory hormone into the blood stream. Activation of these GPCRs can involve their entry into cells and when this can be visualised it can be the basis of a systematic analysis of receptor function through chemical genetics, systematic genome wide screening or physiological manipulation.
At a cellular level, parallel acquisition of data on different cell properties, for example activity of signal transduction cascades and cytoskeleton integrity is the main advantage of this method in comparison to the faster but less detailed high throughput screening. While HCS is slower, the wealth of acquired data allows a more profound understanding of drug effects.
Automated image based screening permits the identification of small compounds altering cellular phenotypes and is of interest for the discovery of new pharmaceuticals and new cell biological tools for modifying cell function. The selection of molecules based on a cellular phenotype does not require a prior knowledge of the biochemical targets that are affected by compounds. However the identification of the biological target will make subsequent preclinical optimization and clinical development of the compound hit significantly easier. Given the increase in the use of phenotypic/visual screening as a cell biological tool, methods are required that permit systematic biochemical target identification if these molecules are to be of broad use. Target identification has been defined as the rate limiting step in chemical genetics/high-content screening. | 1 | Applied and Interdisciplinary Chemistry |
Meteorological conditions greatly influence fallout, particularly local fallout. Atmospheric winds are able to bring fallout over large areas. For example, as a result of a Castle Bravo surface burst of a 15 Mt thermonuclear device at Bikini Atoll on March 1, 1954, a roughly cigar-shaped area of the Pacific extending over 500 km downwind and varying in width to a maximum of 100 km was severely contaminated. There are three very different versions of the fallout pattern from this test, because the fallout was measured only on a small number of widely spaced Pacific Atolls. The two alternative versions both ascribe the high radiation levels at north Rongelap to a downwind hot spot caused by the large amount of radioactivity carried on fallout particles of about 50–100 micrometres size.
After Bravo, it was discovered that fallout landing on the ocean disperses in the top water layer (above the thermocline at 100 m depth), and the land equivalent dose rate can be calculated by multiplying the ocean dose rate at two days after burst by a factor of about 530. In other 1954 tests, including Yankee and Nectar, hot spots were mapped out by ships with submersible probes, and similar hot spots occurred in 1956 tests such as Zuni and Tewa.
However, the major U.S. "DELFIC" (Defence Land Fallout Interpretive Code) computer calculations use the natural size distributions of particles in soil instead of the afterwind sweep-up spectrum, and this results in more straightforward fallout patterns lacking the downwind hot spot.
Snow and rain, especially if they come from considerable heights, accelerate local fallout. Under special meteorological conditions, such as a local rain shower that originates above the radioactive cloud, limited areas of heavy contamination just downwind of a nuclear blast may be formed. | 0 | Theoretical and Fundamental Chemistry |
Enzymes are evolved to catalyse a particular reaction on a particular substrate with a high catalytic efficiency (k/K, cf. Michaelis–Menten kinetics). However, in addition to this main activity, they possess other activities that are generally several orders of magnitude lower, and that are not a result of evolutionary selection and therefore do not partake in the physiology of the organism.
This phenomenon allows new functions to be gained as the promiscuous activity could confer a fitness benefit under a new selective pressure leading to its duplication and selection as a new main activity. | 1 | Applied and Interdisciplinary Chemistry |
Liquid crystal (LC) is a state of matter whose properties are between those of conventional liquids and those of solid crystals. For example, a liquid crystal can flow like a liquid, but its molecules may be oriented in a common direction as in solid. There are many types of LC phases, which can be distinguished by their optical properties (such as textures). The contrasting textures arise due to molecules within one area of material ("domain") being oriented in the same direction but different areas having different orientations. An LC material may not always be in an LC state of matter (just as water may be ice or water vapor).
Liquid crystals can be divided into three main types: thermotropic, lyotropic, and metallotropic. Thermotropic and lyotropic liquid crystals consist mostly of organic molecules, although a few minerals are also known. Thermotropic LCs exhibit a phase transition into the LC phase as temperature changes. Lyotropic LCs exhibit phase transitions as a function of both temperature and concentration of molecules in a solvent (typically water). Metallotropic LCs are composed of both organic and inorganic molecules; their LC transition additionally depends on the inorganic-organic composition ratio.
Examples of LCs exist both in the natural world and in technological applications. Lyotropic LCs abound in living systems; many proteins and cell membranes are LCs, as well as the tobacco mosaic virus. LCs in the mineral world include solutions of soap and various related detergents, and some clays. Widespread liquid-crystal displays (LCD) use liquid crystals. | 0 | Theoretical and Fundamental Chemistry |
Enhancers as sites of extragenic transcription were initially discovered in genome-wide studies that identified enhancers as common regions of RNA polymerase II (RNA pol II) binding and non-coding RNA transcription. The level of RNA pol II–enhancer interaction and RNA transcript formation were found to be highly variable among these initial studies. Using explicit chromatin signature peaks, a significant proportion (~70%) of extragenic RNA Pol II transcription start sites were found to overlap enhancer sites in murine macrophages. Out of 12,000 neuronal enhancers in the mouse genome, almost 25% of the sites were found to bind RNA Pol II and generate transcripts. In parallel studies, 4,588 high confidence extragenic RNA Pol II binding sites were identified in murine macrophages stimulated with the inflammatory mediater lipopolysaccharide to induce transcription. These eRNAs, unlike messenger RNAs (mRNAs), lacked modification by polyadenylation, were generally short and non-coding, and were bidirectionally transcribed. Later studies revealed the transcription of another type of eRNAs, generated through unidirectional transcription, that were longer and contained a poly A tail. Furthermore, eRNA levels were correlated with mRNA levels of nearby genes, suggesting the potential regulatory and functional role of these non-coding enhancer RNA molecules. | 1 | Applied and Interdisciplinary Chemistry |
Bjerknes realized that the velocity field generated by an expanding particle in an incompressible fluid has the same geometrical structure as the electric field generated by a positively charged particle, and that the same applies for contracting particle and a negatively charged particle.
In the case of an oscillating motion, Bjerknes argued that two particles that oscillate in phase generate a velocity field that is geometrically equivalent to the electric field generated by two particles with the same charge, whereas two particles that oscillate in an opposite phase will generate a velocity field that is geometrically equivalent to the electric field generated by particles with an opposite sign.
Bjerknes then writes:This result is counter to our intuition, as it demonstrates that bodies oscillating in phase exert an attractive force on each other, despite creating a field akin to that of identically charged particles. This result was described by Bjerknes as "Astonishing". | 1 | Applied and Interdisciplinary Chemistry |
In 1975, Kono and Ito reported that Wilkinsons catalyst (Rh(PPh)Cl) can undergo oxidative addition with catecholborane (HBcat) or 4,4,6-trimethyl-1,3,2-dioxaborinane. These two borane compounds are otherwise slow to participate in hydroboration. In 1985, Männig and Nöth demonstrated for the first time that Wilkinsons catalyst indeed catalyzes hydroboration of alkenes with HBcat.
Whereas uncatalyzed hydroboration using HBcat leads to reduction of the carbonyl group, the catalyzed version is selective for the alkene.
As indicated by subsequent research, transition metal-catalyzed hydroboration proceeds with attractive functional group-, regio-, stereo-, and chemo- selectivity. | 0 | Theoretical and Fundamental Chemistry |
Materials with anisotropic structures, such as crystals (with less than cubic symmetry, for example martensitic phases) and many composites, will generally have different linear expansion coefficients in different directions. As a result, the total volumetric expansion is distributed unequally among the three axes. If the crystal symmetry is monoclinic or triclinic, even the angles between these axes are subject to thermal changes. In such cases it is necessary to treat the coefficient of thermal expansion as a tensor with up to six independent elements. A good way to determine the elements of the tensor is to study the expansion by x-ray powder diffraction. The thermal expansion coefficient tensor for the materials possessing cubic symmetry (for e.g. FCC, BCC) is isotropic. | 0 | Theoretical and Fundamental Chemistry |
When choosing primary standards in analytical chemistry, compounds with higher equivalent weights are generally more desirable because weighing errors are reduced. An example is the volumetric standardisation of a solution of sodium hydroxide which has been prepared to approximately 0.1 . It is necessary to calculate the mass of a solid acid which will react with about 20 cm of this solution (for a titration using a 25 cm burette): suitable solid acids include oxalic acid dihydrate, potassium hydrogen phthalate and potassium hydrogen iodate. The equivalent weights of the three acids 63.04 g, 204.23 g and 389.92 g respectively, and the masses required for the standardisation are 126.1 mg, 408.5 mg and 779.8 mg respectively. Given that the measurement uncertainty in the mass measured on a standard analytical balance is ±0.1 mg, the relative uncertainty in the mass of oxalic acid dihydrate would be about one part in a thousand, similar to the measurement uncertainty in the volume measurement in the titration. However the measurement uncertainty in the mass of potassium hydrogen iodate would be five times lower, because its equivalent weight is five times higher: such an uncertainty in the measured mass is negligible in comparison to the uncertainty in the volume measured during the titration (see example below).
As an example, assume that 22.45±0.03 cm of the sodium hydroxide solution reacts with 781.4±0.1 mg of potassium hydrogen iodate. As the equivalent weight of potassium hydrogen iodate is 389.92 g, the measured mass is 2.004 milliequivalents. The concentration of the sodium hydroxide solution is therefore 2.004 meq/0.02245 L = 89.3 meq/L. In analytical chemistry, a solution of any substance which contains one equivalent per litre is known as a normal solution (abbreviated N), so the example sodium hydroxide solution would be 0.0893 N. The relative uncertainty (u) in the measured concentration can be estimated by assuming a Gaussian distribution of the measurement uncertainties:
This sodium hydroxide solution can be used to measure the equivalent weight of an unknown acid. For example, if it takes 13.20±0.03 cm of the sodium hydroxide solution to neutralise 61.3±0.1 mg of an unknown acid, the equivalent weight of the acid is:
Because each mole of acid can only release an integer number of moles of hydrogen ions, the molar mass of the unknown acid must be an integer multiple of 52.0±0.1 g. | 0 | Theoretical and Fundamental Chemistry |
*Nuffield Commonwealth Fellow 1971–1972 (Cambridge)
*Fulbright Senior Scholar (California Institute of Technology, 1977, and Harvard University, 1986)
*H.G. Smith Memorial Medal 1981 (RACI)
*Member of the Australian Academy of Science 1983
*Flintoff Medal and Prize (RSC) 1990
*Fellow of the Royal Society of London 1990
*Hon. Fellow of the Royal Society of New Zealand 1991 (FRSNZ Hon)
*Made a Companion of the Order of Australia "for eminent service to science through pioneering contributions to organic chemistry in the field of plant growth hormones, to higher education as an academic, researcher and author, and to national and international scientific societies". | 0 | Theoretical and Fundamental Chemistry |
He completed his undergraduate studies at University of Gothenburg, earning a B.Sc. degree in chemistry in 1984. He then pursued a Licentiate in Physical Chemistry at the Institute of Chemistry and Chemical Engineering, Chalmers University of Technology in Göteborg, which he completed in 1986. Kubista obtained his Ph.D. in chemistry from Chalmers University of Technology. Following his doctoral studies, he conducted postdoctoral research at institutions such as La Trobe University in Melbourne, Australia, and Yale University in New Haven, US. Additionally, he has held visiting professor positions at various universities, including the University of Maryland in College Park, US, in June 2000, and the University of A Coruña in Spain, during September–November 2003 and July 2006 to June 2007. Since 2007, Kubista is serving as an adjunct professor at the Institute of Biotechnology, Czech Academy of Sciences. | 1 | Applied and Interdisciplinary Chemistry |
* WDS cannot determine elements below number 3 (lithium). This restricts WDS when analyzing geologically important elements such as H, Li, and Be.
* Despite the improved spectral resolution of elemental peaks, some peaks exhibit significant overlap that causes analytical challenges (e.g., VKα and TiKβ). WDS analyses are unable to distinguish the valence states of elements (e.g. Fe vs. Fe) which must be obtained by other techniques such as Mössbauer spectroscopy or electron energy loss spectroscopy.
* Element isotopes cannot be determined by WDS, but are most commonly obtained with a mass spectrometer. | 0 | Theoretical and Fundamental Chemistry |
In-situ leaching is also called "solution mining". This process initially involves drilling of holes into the ore deposit. Explosives or hydraulic fracturing are used to create open pathways within the deposit for solution to penetrate into. Leaching solution is pumped into the deposit where it makes contact with the ore. The solution is then collected and processed. The Beverley uranium deposit is an example of in-situ leaching. | 1 | Applied and Interdisciplinary Chemistry |
The bond coat adheres the thermal barrier to the substrate. Additionally, the bond coat provides oxidation protection and functions as a diffusion barrier against the motion of substrate atoms towards the environment. The five major types of bond coats are: the aluminides, the platinum-aluminides, MCrAlY, cobalt-cermets, and nickel-chromium. For aluminide bond coatings, the coatings final composition and structure depends on the substrate composition. Aluminides lack ductility below 750 °C, and exhibit limited thermomechanical fatigue strength. Pt-aluminides are similar to the aluminide bond coats except for a layer of Pt (5—10 μm) deposited on the blade. The Pt aids in oxide adhesion and contributes to hot corrosion, increasing blade lifespan. MCrAlY does not strongly interact with the substrate. Normally applied by plasma spraying, MCrAlY coatings from secondary aluminum oxides. This means that the coatings form an outer chromia layer and a secondary alumina layer underneath. These oxide formations occur at high temperatures in the range of those that superalloys usually encounter. The chromia provides oxidation and hot-corrosion resistance. The alumina controls oxidation mechanisms by limiting oxide growth by self-passivating. The yttrium enhances oxide adherence to the substrate, and limits the growth of grain boundaries (which can lead to coat flaking). Addition of rhenium and tantalum increases oxidation resistance. Cobalt-cermet-based coatings consisting of materials such as tungsten carbide/cobalt can be used due to excellent resistance to abrasion, corrosion, erosion, and heat. These cermet coatings perform well in situations where temperature and oxidation damage are significant concerns, such as boilers. One of cobalt cermets unique advantages is minimal loss of coating mass over time, due to the strength of carbides. Overall, cermet coatings are useful in situations where mechanical demands are equal to chemical demands. Nickel-chromium coatings are used most frequently in boilers fed by fossil fuels, electric furnaces, and waste incineration furnaces, where the danger of oxidizing agents and corrosive compounds in the vapor must be addressed. The specific method of spray-coating depends on the coating composition. Nickel-chromium coatings that also contain iron or aluminum provide better corrosion resistance when they are sprayed and laser glazed, while pure nickel-chromium coatings perform better when thermally sprayed exclusively. | 1 | Applied and Interdisciplinary Chemistry |
The importance of these untranslated regions of mRNA is just beginning to be understood. Various medical studies are being conducted that have found connections between mutations in untranslated regions and increased risk for developing a particular disease, such as cancer. For example, associations between polymorphisms in the HLA-G 3′UTR region and development of colorectal cancer have been discovered. Single Nucleotide Polymorphisms in the 3 UTR of another gene have also been associated with susceptibility to preterm birth. Mutations in the 3 UTR of the APP gene are related to development of cerebral amyloid angiopathy. | 1 | Applied and Interdisciplinary Chemistry |
At physiological pHs, hydrogen fluoride is usually fully ionised to fluoride. In biochemistry, fluoride and hydrogen fluoride are equivalent. Fluorine, in the form of fluoride, is considered to be a micronutrient for human health, necessary to prevent dental cavities, and to promote healthy bone growth. The tea plant (Camellia sinensis L.) is a known accumulator of fluorine compounds, released upon forming infusions such as the common beverage. The fluorine compounds decompose into products including fluoride ions. Fluoride is the most bioavailable form of fluorine, and as such, tea is potentially a vehicle for fluoride dosing. Approximately, 50% of absorbed fluoride is excreted renally with a twenty-four-hour period. The remainder can be retained in the oral cavity, and lower digestive tract. Fasting dramatically increases the rate of fluoride absorption to near 100%, from a 60% to 80% when taken with food. Per a 2013 study, it was found that consumption of one litre of tea a day, can potentially supply the daily recommended intake of 4 mg per day. Some lower quality brands can supply up to a 120% of this amount. Fasting can increase this to 150%. The study indicates that tea drinking communities are at an increased risk of dental and skeletal fluorosis, in the case where water fluoridation is in effect. Fluoride ion in low doses in the mouth reduces tooth decay. For this reason, it is used in toothpaste and water fluoridation. At much higher doses and frequent exposure, fluoride causes health complications and can be toxic. | 1 | Applied and Interdisciplinary Chemistry |
For more complex systems that are representative of water-surface interactions in nature, the Cassie-Baxter model is used. This model takes into consideration the fact that a water droplet may trap air between itself and the surface that it is on. The Cassie-Baxter model is described by the following equation:
= Contact angle of water predicted by Cassie-Baxter's model
= Liquid-air fraction, the fraction of the liquid droplet that is in contact with air | 0 | Theoretical and Fundamental Chemistry |
Senapathy addressed the origin of the spliceosomal machinery that edits out the introns from RNA transcripts. If the split genes had originated from random DNA, then the introns would have become an unnecessary but integral part of eukaryotic genes along with the splice junctions. The spliceosomal machinery would be required to remove them and to enable the short exons to be linearly spliced together as a contiguously coding mRNA that can be translated into a complete protein. Thus, the split gene theory argues that spliceosomal machinery exists to remove the unnecessary introns.
Blake states, “Work by Senapathy, when applied to RNA, comprehensively explains the origin of the segregated form of RNA into coding and noncoding regions. It also suggests why a splicing mechanism was developed at the start of primordial evolution.” | 1 | Applied and Interdisciplinary Chemistry |
Different biocatalytic approaches have been developed toward the synthesis of glycosides in the past decades, which using "glycosyltransferases" and "glycoside hydrolases" are among the most common catalysis. The former often needs expensive materials and the later often shows low yields, De Winter et al.
investigated use of cellobiose phosphorylase (CP) toward synthesis of alpha-glycosides in ionic liquids. The best condition for use of CP was found to be in the presence of IL AMMOENG 101 and ethyl acetate. | 0 | Theoretical and Fundamental Chemistry |
Beginning in about 3000 BC arsenic was mined and added to copper in the alloying of bronze, but the adverse health effects of working with arsenic led to it being abandoned when a viable alternative, tin, was discovered.
In addition to its presence as a poison, for centuries arsenic was used medicinally. It has been used for over 2,400 years as a part of traditional Chinese medicine. In the western world, arsenic compounds, such as salvarsan, were used extensively to treat syphilis before penicillin was introduced. It was eventually replaced as a therapeutic agent by sulfa drugs and then by other antibiotics. Arsenic was also an ingredient in many tonics (or "patent medicines").
In addition, during the Elizabethan era, some women used a mixture of vinegar, chalk, and arsenic applied topically to whiten their skin. This use of arsenic was intended to prevent aging and creasing of the skin, but some arsenic was inevitably absorbed into the blood stream.
During the Victorian era (late 19th century) in the United States, U.S. newspapers advertised "arsenic complexion wafers" that promised to remove facial blemishes such as moles and pimples.
Some pigments, most notably the popular Emerald Green (known also under several other names), were based on arsenic compounds. Overexposure to these pigments was a frequent cause of accidental poisoning of artists and craftsmen.
Arsenic became a favored method for murder of the Middle Ages and Renaissance, particularly among ruling classes in Italy allegedly. Because the symptoms are similar to those of cholera, which was common at the time, arsenic poisoning often went undetected. By the 19th century, it had acquired the nickname "inheritance powder," perhaps because impatient heirs were known or suspected to use it to ensure or accelerate their inheritances. It was also a common murder technique in the 19th century in domestic violence situations, such as the case of Rebecca Copin, who attempted to poison her husband by "putting arsenic in his coffee".
In post-WW1 Hungary, arsenic extracted by boiling fly paper was used in an estimated 300 murders by the Angel Makers of Nagyrév.
In imperial China, arsenic trioxide and sulfides were used in murder, as well as for capital punishment for members of the royal family or aristocracy. Forensic studies have determined that the Guangxu Emperor (d. 1908) was murdered by arsenic, most likely ordered by the Empress Dowager Cixi or Generalissimo Yuan Shikai. Likewise, in ancient Korea, and particularly in the Joseon Dynasty, arsenic-sulfur compounds had been used as a major ingredient of sayak (사약; 賜藥), which was a poison cocktail used in capital punishment of high-profile political figures and members of the royal family. Due to social and political prominence of the condemned, many of these events were well-documented, often in the Annals of Joseon Dynasty; they are sometimes portrayed in historical television miniseries because of their dramatic nature.
One of the worst incidents of arsenic poisoning via well water occurred in Bangladesh, which the World Health Organization called the "largest mass poisoning of a population in history" recognized as a major public health concern. The contamination in the Ganga-Brahmaputra fluvial plains in India and Padma-Meghna fluvial plains in Bangladesh demonstrated adverse impacts on human health.
Arsenic poisoning from exposure to groundwater is believed to be responsible for the illness experienced by those that witnessed the 2007 Carancas impact event in Peru, as local residents inhaled steam which was contaminated with arsenic, produced from groundwater which boiled from the intense heat and pressure produced by a chondrite meteorite impacting the ground. | 1 | Applied and Interdisciplinary Chemistry |
Hyperphosphatemia, or a high blood level of phosphates, is associated with elevated mortality in the general population. The most common cause of hyperphosphatemia in people, dogs, and cats is kidney failure. In cases of hyperphosphatemia, limiting consumption of phosphate-rich foods, such as some meats and dairy items and foods with a high phosphate-to-protein ratio, such as soft drinks, fast food, processed foods, condiments, and other products containing phosphate-salt additives is advised.
Phosphates induce vascular calcification, and a high concentration of phosphates in blood was found to be a predictor of cardiovascular events. | 0 | Theoretical and Fundamental Chemistry |
* Australian Capital Territory: Pepper spray is a "prohibited weapon", making it an offence to possess or use it.
* New South Wales: Possession of pepper spray by unauthorized persons is illegal, under schedule 1 of the Weapons Prohibition Act 1998, being classified as a "prohibited weapon".
* Northern Territory: Prescribed by regulation to be a prohibited weapon under the Weapons Control Act.
** This legislation makes it an offense for someone without a permit, normally anyone who is not an officer of Police/Correctional Services/Customs/Defence, to carry a prohibited weapon.
* Tasmania: Possession of pepper spray by unauthorized persons is illegal, under an amendment of the Police Offences Act 1935, being classified as an "offensive weapon". Likewise, possession of knives, batons, and any other instrument that may be considered, "Offensive Weapons" if they are possessed by an individual, in a Public Place, "Without lawful excuse", leading to confusion within the police force over what constitutes "lawful excuse". Self-defense as a lawful excuse to carry such items varies from one officer to the next.
** Pepper spray is commercially available without a license. Authority to possess and use Oleoresin Capsicum devices remains with Tasmania Police Officers (As part of general-issue operational equipment), and Tasmanian Justice Department (H.M. Prisons) Officers.
* South Australia: in South Australia, possession of pepper spray without lawful excuse is illegal.
* Western Australia: The possession of pepper spray by individuals for self-defense subject to a "reasonable excuse" test has been legal in Western Australia following the landmark Supreme Court decision in Hall v Collins [2003] WASCA 74 (4 April 2003).
* Victoria: Schedule 3 of the Control of Weapons Regulations 2011 designates "an article designed or adapted to discharge oleoresin capsicum spray" as a prohibited weapon.
* Queensland: in Queensland, pepper spray is considered an offensive weapon and can not be used for self-defence. | 1 | Applied and Interdisciplinary Chemistry |
The most common data interpretation is based on the Fresnel formulas, which treat the formed thin films as infinite, continuous dielectric layers. This interpretation may result in multiple possible refractive index and thickness values. Usually only one solution is within the reasonable data range. In multi-parametric surface plasmon resonance, two SPR curves are acquired by scanning a range of angles at two different wavelengths, which results in a unique solution for both thickness and refractive index.
Metal particle plasmons are usually modeled using the Mie scattering theory.
In many cases no detailed models are applied, but the sensors are calibrated for the specific application, and used with interpolation within the calibration curve. | 0 | Theoretical and Fundamental Chemistry |
Esketamine is the generic name of the drug and its and , while esketamine hydrochloride is its . It is also known as S(+)-ketamine, (S)-ketamine, or (–)-ketamine ((-)[+] ketamine), as well as by its developmental code name JNJ-54135419.
Esketamine is sold under the brand name Spravato for use as an antidepressant and the brand names Eskesia, Ketanest, Ketanest S, Ketanest-S, Keta-S for use as an anesthetic (veterinary), among others. | 0 | Theoretical and Fundamental Chemistry |
Eukaryotes have multiple types of nuclear RNAP, each responsible for synthesis of a distinct subset of RNA. All are structurally and mechanistically related to each other and to bacterial RNAP:
Eukaryotic chloroplasts contain an RNAP very highly similar to bacterial RNAP ("plastid-encoded polymerase, PEP"). They use sigma factors encoded in the nuclear genome.
Chloroplast also contain a second, structurally and mechanistically unrelated, single-subunit RNAP ("nucleus-encoded polymerase, NEP"). Eukaryotic mitochondria use POLRMT (human), a nucleus-encoded single-subunit RNAP. Such phage-like polymerases are referred to as RpoT in plants. | 1 | Applied and Interdisciplinary Chemistry |
Sharpless is a two-time Nobel Laureate. He is a recipient of the 2001 and 2022 Nobel Prize in Chemistry for his work on "chirally catalysed oxidation reactions", and "click chemistry", respectively.
In 2019, Sharpless was awarded the Priestley medal, the American Chemical Society's highest honor, for "the invention of catalytic, asymmetric oxidation methods, the concept of click chemistry and development of the copper-catalyzed version of the azide-acetylene cycloaddition reaction.". He received the Gold Medal of the American Institute of Chemists in 2023.
He is Distinguished University Professor at Kyushu University. He holds honorary degrees from the KTH Royal Institute of Technology (1995), Technical University of Munich (1995), Catholic University of Louvain (1996) and Wesleyan University (1999). | 0 | Theoretical and Fundamental Chemistry |
While earlier version of fiber-based laser traps exclusively used single mode beams, M. Kreysing and colleagues recently showed that the careful excitation of further optical modes in a short piece of optical fiber allows the realization of non-trivial trapping geometries. By this the researchers were able to orient various human cell types (individual cells and clusters) on a microscope. The main advantage of the so-called "optical cell rotator" technology over standard optical tweezers is the decoupling of trapping from imaging optics. This, its modular design, and the high compatibility of divergent laser traps with biological material indicates the great potential of this new generation of laser traps in medical research and life science. Recently, the optical cell rotator technology was implemented on the basis of adaptive optics, allowing to dynamically reconfigure the optical trap during operation and adapt it to the sample. | 1 | Applied and Interdisciplinary Chemistry |
A lixiviant is a chemical used in hydrometallurgy to extract elements from its ore. One of the most famous lixiviants is cyanide, which is used in extracting 90% of mined gold. The combination of cyanide and air converts gold particles into a soluble salt. Once separated from the bulk gangue, the solution is processed in a series of steps to give the metal. | 1 | Applied and Interdisciplinary Chemistry |
Chemists have demonstrated that many artificial supramolecular systems can be designed that exhibit molecular recognition. One of the earliest examples of such a system are crown ethers which are capable of selectively binding specific cations. However, a number of artificial systems have since been established. | 0 | Theoretical and Fundamental Chemistry |
Soil structure refers to the manner in which these individual soil particles are grouped together to form clusters of particles called aggregates. This is determined by the types of soil formation, parent material, and texture. Soil structure can be influenced by a wide variety of biota as well as management methods by humans. | 0 | Theoretical and Fundamental Chemistry |
Total carbon (TC) is an analytical parameter representing the concentration of carbon in a sample. TC includes carbon in any form, whether organic or inorganic, volatile or fixed, dissolved or suspended. In many application areas, rather than TC, a parameter representing of subset of TC is measured; examples include Total organic carbon (TOC), Particulate inorganic carbon (PIC), and Dissolved organic carbon (DOC). | 0 | Theoretical and Fundamental Chemistry |
The Journal of Trace Elements in Medicine and Biology is a bimonthly peer-reviewed medical journal covering the roles played by trace elements in medical and biological systems. It was established in 1987 as the Journal of Trace Elements and Electrolytes in Health and Disease, obtaining its current title in 1995. It is published by Elsevier on behalf of the Federation of European Societies on Trace Elements and Minerals (FESTEM), of which it is the official journal. The editor-in-chief is Dirk Schaumlöffel (Université de Pau et des Pays de lAdour/Centre national de la recherche scientifique). According to the Journal Citation Reports', the journal has a 2017 impact factor of 3.755. | 1 | Applied and Interdisciplinary Chemistry |
The examples above define a standard drink as 0.6 fluid ounces (14 g or 17.7 mL) of ethanol, whereas other definitions exist, for example 10 grams of ethanol. | 1 | Applied and Interdisciplinary Chemistry |
Lamb's general solution arises from the fact that the pressure satisfies the Laplace equation, and can be expanded in a series of solid spherical harmonics in spherical coordinates. As a result, the solution to the Stokes equations can be written:
where and are solid spherical harmonics of order :
and the are the associated Legendre polynomials. The Lamb's solution can be used to describe the motion of fluid either inside or outside a sphere. For example, it can be used to describe the motion of fluid around a spherical particle with prescribed surface flow, a so-called squirmer, or to describe the flow inside a spherical drop of fluid. For interior flows, the terms with are dropped, while for exterior flows the terms with are dropped (often the convention is assumed for exterior flows to avoid indexing by negative numbers). | 1 | Applied and Interdisciplinary Chemistry |
An enantiopure drug is a pharmaceutical that is available in one specific enantiomeric form. Most biological molecules (proteins, sugars, etc.) are present in only one of many chiral forms, so different enantiomers of a chiral drug molecule bind differently (or not at all) to target receptors. Chirality can be observed when the geometric properties of an object is not superimposable with its mirror image. Two forms of a molecule are formed (both mirror images) from a chiral carbon, these two forms are called enantiomers. One enantiomer of a drug may have a desired beneficial effect while the other may cause serious and undesired side effects, or sometimes even beneficial but entirely different effects. The desired enantiomer is known as an eutomer while the undesired enantiomer is known as the distomer. When equal amounts of both enantiomers are found in a mixture, the mixture is known as a racemic mixture. If a mixture for a drug does not have a 1:1 ratio of its enantiomers it is a candidate for an enantiopure drug. Advances in industrial chemical processes have made it economical for pharmaceutical manufacturers to take drugs that were originally marketed as a racemic mixture and market the individual enantiomers, either by specifically manufacturing the desired enantiomer or by resolving a racemic mixture. On a case-by-case basis, the U.S. Food and Drug Administration (FDA) has allowed single enantiomers of certain drugs to be marketed under a different name than the racemic mixture. Also case-by-case, the United States Patent Office has granted patents for single enantiomers of certain drugs. The regulatory review for marketing approval (safety and efficacy) and for patenting (proprietary rights) is independent, and differs country by country. | 0 | Theoretical and Fundamental Chemistry |
A crystal can be described as a lattice of atoms, which in turn this leads to the reciprocal lattice. With electrons, neutrons or x-rays there is diffraction by the atoms, and if there is an incident plane wave with a wavevector , there will be outgoing wavevectors and as shown in the diagram after the wave has been diffracted by the atoms.
The energy of the waves (electron, neutron or x-ray) depends upon the magnitude of the wavevector, so if there is no change in energy (elastic scattering) these have the same magnitude, that is they must all lie on the Ewald sphere. In the Figure the red dot is the origin for the wavevectors, the black spots are reciprocal lattice points (vectors) and shown in blue are three wavevectors. For the wavevector the corresponding reciprocal lattice point lies on the Ewald sphere, which is the condition for Bragg diffraction. For the corresponding reciprocal lattice point is off the Ewald sphere, so where is called the excitation error. The amplitude and also intensity of diffraction into the wavevector depends upon the Fourier transform of the shape of the sample, the excitation error , the structure factor for the relevant reciprocal lattice vector, and also whether the scattering is weak or strong. For neutrons and x-rays the scattering is generally weak so there is mainly Bragg diffraction, but it is much stronger for electron diffraction. | 0 | Theoretical and Fundamental Chemistry |
NaDMSO condenses with esters (1) to form β-ketosulfoxides (2), which can be useful intermediates. Reduction of β-ketosulfoxides with aluminium amalgam gives methyl ketones (3). Reaction with alkyl halides followed by elimination gives α,β-unsaturated ketones (4). β-ketosulfoxides can also be used in the Pummerer rearrangement to introduce nucleophiles alpha to a carbonyl (5). | 0 | Theoretical and Fundamental Chemistry |
*Glycolysis is the process of breaking down glucose into pyruvate, producing two molecules of ATP (per 1 molecule of glucose) in the process. When a cell has a higher concentration of ATP than ADP (i.e. has a high energy charge), the cell cannot undergo glycolysis, releasing energy from available glucose to perform biological work. Pyruvate is one product of glycolysis, and can be shuttled into other metabolic pathways (gluconeogenesis, etc.) as needed by the cell. Additionally, glycolysis produces reducing equivalents in the form of NADH (nicotinamide adenine dinucleotide), which will ultimately be used to donate electrons to the electron transport chain.
*Gluconeogenesis is the opposite of glycolysis; when the cell's energy charge is low (the concentration of ADP is higher than that of ATP), the cell must synthesize glucose from carbon- containing biomolecules such as proteins, amino acids, fats, pyruvate, etc. For example, proteins can be broken down into amino acids, and these simpler carbon skeletons are used to build/ synthesize glucose.
*The citric acid cycle is a process of cellular respiration in which acetyl coenzyme A, synthesized from pyruvate dehydrogenase, is first reacted with oxaloacetate to yield citrate. The remaining eight reactions produce other carbon-containing metabolites. These metabolites are successively oxidized, and the free energy of oxidation is conserved in the form of the reduced coenzymes FADH and NADH. These reduced electron carriers can then be re-oxidized when they transfer electrons to the electron transport chain.
*Ketosis is a metabolic process where the body prioritizes ketone bodies, produced from fat, as its primary fuel source instead of glucose. This shift often occurs when glucose levels are low: during prolonged fasting, strenuous exercise, or specialized diets like ketogenic plans, the body may also adopt ketosis as an efficient alternative for energy production. This metabolic adaptation allows the body to conserve precious glucose for organs that depend on it, like the brain, while utilizing readily available fat stores for fuel.
*Oxidative phosphorylation and the electron transport chain is the process where reducing equivalents such as NADPH, FADH and NADH can be used to donate electrons to a series of redox reactions that take place in electron transport chain complexes. These redox reactions take place in enzyme complexes situated within the mitochondrial membrane. These redox reactions transfer electrons "down" the electron transport chain, which is coupled to the proton motive force. This difference in proton concentration between the mitochondrial matrix and inner membrane space is used to drive ATP synthesis via ATP synthase.
*Photosynthesis, another major bioenergetic process, is the metabolic pathway used by plants in which solar energy is used to synthesize glucose from carbon dioxide and water. This reaction takes place in the chloroplast. After glucose is synthesized, the plant cell can undergo photophosphorylation to produce ATP. | 1 | Applied and Interdisciplinary Chemistry |
Storm water is typically channeled to a retention basin through a system of street and/or parking lot storm drains, and a network of drain channels or underground pipes. The basins are designed to allow relatively large flows of water to enter, but discharges to receiving waters are limited by outlet structures that function only during very large storm events.
Retention ponds are often landscaped with a variety of grasses, shrubs, and/or aquatic plants to provide bank stability and aesthetic benefits. Vegetation also provides water quality benefits by removing soluble nutrients through uptake. In some areas the ponds can attract nuisance types of wildlife like ducks or Canada geese, particularly where there is minimal landscaping and grasses are mowed. This reduces the ability of foxes, coyotes, and other predators to approach their prey unseen. Such predators tend to hide in the cattails and other tall, thick grass surrounding natural water features.
Proper depth of retention ponds is important for removal of pollutants and maintenance of fish populations. Urban fishing continues to be one of the fastest growing fishing segments as new suburban neighborhoods are built around these aquatic areas. | 1 | Applied and Interdisciplinary Chemistry |
Spt-Ada-Gcn5 acetyltransferase (SAGA) is a histone modifying transcriptional co-activator that is composed of 21 proteins and exhibits histone acetyltransferase (HAT) and deubiquitinating (DUB) activity. In yeast the SAGA complex serves to activate the transcription of approximately 10% of the genome, and this active gene/SAGA complex is then able to interact with the TREX-2 complex, a NPC-associated mRNA export complex. Numerous proteins involved in the formation of mRNA interact with the NPC, with the majority of these protein-protein interactions occurring between the SAGA complex and the TREX-2 complex at the NPC. Correct transcription and subsequent export of mRNA is largely dependent on this interaction. A common protein subunit of both the SAGA and TREX-2 complexes, Sus1, binds to the upstream activating sequence via SAGA, which then serves as the attachment point to the TREX-2 complex. The interacting surfaces between Sus1 and the TREX-2 complex are facilitated by the protein subunits Mex67 and Yra1 of the TREX-2 complex, as evidenced by co-immunoprecipitation experiments. The TREX-2 complex is bound to the NPC complex by the nucleoporin Nup1. All TREX-2 subunits are necessary for the successful formation and export of an mRNA transcript at the nuclear membrane for genes activated by the SAGA complex, and data suggest that SAGA and TREX-2 act in concert to recruit Sus1 to genes to be transcribed. Other investigations have shown that several SAGA subunits interact with the NPC protein Mlp1, providing another link between the NPC and the SAGA/active gene complex. | 1 | Applied and Interdisciplinary Chemistry |
Scrotal circumference is an indicator of a bull's fertility. A larger circumference is preferred and is an indicator for his sons to have a larger scrotal circumference and his daughters to reach puberty sooner and therefore have calves sooner.
Gestation length is an indicator of the probability of dystocia. The longer a calf is in utero the larger it will be at birth and the greater the chance of it having dystocia. It also gives the cow a larger postpartum interval between pregnancies. A shorter gestation length is usually preferred because of this.
Stayability is an indicator EPD of longevity of a bull's daughter in a cow herd. The higher the EPD value the greater chance a cow will stay in a herd over six years and continue producing quality offspring. | 1 | Applied and Interdisciplinary Chemistry |
Application of the [4+4] photocycloaddition is scarce because of competition with the [[2+2 Photocycloaddition|[2+2] cycloaddition]]. However, when accessible, this method can be used to build 8-membered ring with complex stereocenters and structures in one step, as is seen in proposed syntheses for Taxol and molecules of the fusicoccin family. Additionally, while this reaction first forms fused rings, subsequent cleavages can afford macrocycles.
In this partial synthesis of the BC rings of Taxol, the framework buildup utilized an intramolecule [4+4] photocycloaddition of a relatively linear and simple 2-pyridone derivative, folding it into the desired fused rings with correct stereochemistry at C3, C8, and C15 (compare with Taxol on the right) and two double bonds on the B ring ready to accept trans-addition. Consequent lactam-ring opening and functionalization were expected to give Taxol.
Similarly, molecules of the fusicoccin family, featuring 5-8-5 ring systems, could be constructed rapidly using this reaction. Although the high stereoselectivity of this reaction to form trans-isomers made it unsuitable for the specific target molecules, the general ease to create the four tertiary chiral centers is still noteworthy.
Use of [4+4] photocycloaddition need not be limited to the creation of 8-membered rings. By linking up a network of rings and then breaking the shared bonds, a single macrocycle with built-in stereocenters could be achieved. | 0 | Theoretical and Fundamental Chemistry |
Neuromelanin is directly biosynthesized from L-DOPA, precursor to dopamine, by tyrosine hydroxylase (TH) and aromatic acid decarboxylase (AADC). Alternatively, synaptic vesicles and endosomes accumulate cytosolic dopamine (via vesicular monoamine transporter 2 (VMAT2) and transport it to mitochondria where it is metabolized by monoamine oxidase. Excess dopamine and DOPA molecules are oxidized by iron catalysis into dopaquinones and semiquinones which are then phagocytosed and are stored as neuromelanin.
Neuromelanin biosynthesis is driven by excess cytosolic catecholamines not accumulated by synaptic vesicles. | 1 | Applied and Interdisciplinary Chemistry |
In economics, a similar concept also named after Le Chatelier was introduced by American economist Paul Samuelson in 1947. There the generalized Le Chatelier principle is for a maximum condition of economic equilibrium: Where all unknowns of a function are independently variable, auxiliary constraints—"just-binding" in leaving initial equilibrium unchanged—reduce the response to a parameter change. Thus, factor-demand and commodity-supply elasticities are hypothesized to be lower in the short run than in the long run because of the fixed-cost constraint in the short run.
Since the change of the value of an objective function in a neighbourhood of the maximum position is described by the envelope theorem, Le Chatelier's principle can be shown to be a corollary thereof. | 0 | Theoretical and Fundamental Chemistry |
The apparent (molal) volume of a solute can be expressed as a function of the molality b of that solute (and of the densities of the solution and solvent). The volume of solution per mole of solute is
Subtracting the volume of pure solvent per mole of solute gives the apparent molal volume:
For more solutes the above equality is modified with the mean molar mass of the solutes as if they were a single solute with molality b:
The sum of products molalities – apparent molar volumes of solutes in their binary solutions equals the product between the sum of molalities of solutes and apparent molar volume in ternary of multicomponent solution mentioned above. | 0 | Theoretical and Fundamental Chemistry |
Sunset yellow FCF is known as FD&C yellow No. 6 in the US and is approved for use in coloring food, drugs, and cosmetics with an acceptable daily intake of 3.75 mg/kg. | 0 | Theoretical and Fundamental Chemistry |
Two transport mechanisms are fundamental for nanoelectrochemistry: electron transfer and mass transport. The formulation of theoretical models allows to understand the role of the different species involved in the electrochemical reactions.
The electron transfer between the reactant and the nanoelectrode can be explained by the combination of various theories based on the Marcus theory.
Mass transport, that is the diffusion of the reactant molecules from the electrolyte bulk to the nanoelectrode, is influenced by the formation of a double electric layer at the electrode/electrolyte interface. At the nanoscale it is necessary to theorize a dynamic double electric layer which takes into account an overlap of the Stern layer and the diffuse layer.
Knowledge of the mechanisms involved allows to build computational models that combine the density functional theory with electron transfer theories and the dynamic double electric layer.
In the field of molecular modelling, accurate models could predict the behaviour of the system as reactants, electrolyte or electrode change. | 0 | Theoretical and Fundamental Chemistry |
The Convent of Sant’Anna is the first foundation of the Discalced Carmelites outside of Spain, established in 1584 under the impulse of father Nicolas of Jesus and Mary Doria, a descendant of the prominentDoria family. Returned from Spain twenty years after the reformation of the Carmelite Order operated by Saint Theresa of Avila and Saint John of the Cross, Father Doria established a monastery in his native city with the financial support of the noble families Doria, Cattaneo, Spinola e Pallavicini.
Soon after the foundation of the convent, the friars opened the pharmacy. At the end of the 16th century, one of the cloisters of the convent, presently known as the Cloister of the Roses, was used for the cultivation of curative herbs. Potatoes imported from the Americas were planted there for the very first time on Italian soil, after the founder Father Doria had seen them at the court of Philip II King of Spain. | 1 | Applied and Interdisciplinary Chemistry |
Restriction sites, or restriction recognition sites, are located on a DNA molecule containing specific (4-8 base pairs in length) sequences of nucleotides, which are recognized by restriction enzymes. These are generally palindromic sequences (because restriction enzymes usually bind as homodimers), and a particular restriction enzyme may cut the sequence between two nucleotides within its recognition site, or somewhere nearby. | 1 | Applied and Interdisciplinary Chemistry |
The relative vorticity is the vorticity relative to the Earth induced by the air velocity field. This air velocity field is often modeled as a two-dimensional flow parallel to the ground, so that the relative vorticity vector is generally scalar rotation quantity perpendicular to the ground. Vorticity is positive when – looking down onto the Earth's surface – the wind turns counterclockwise. In the northern hemisphere, positive vorticity is called cyclonic rotation, and negative vorticity is anticyclonic rotation; the nomenclature is reversed in the Southern Hemisphere.
The absolute vorticity is computed from the air velocity relative to an inertial frame, and therefore includes a term due to the Earth's rotation, the Coriolis parameter.
The potential vorticity is absolute vorticity divided by the vertical spacing between levels of constant (potential) temperature (or entropy). The absolute vorticity of an air mass will change if the air mass is stretched (or compressed) in the vertical direction, but the potential vorticity is conserved in an adiabatic flow. As adiabatic flow predominates in the atmosphere, the potential vorticity is useful as an approximate tracer of air masses in the atmosphere over the timescale of a few days, particularly when viewed on levels of constant entropy.
The barotropic vorticity equation is the simplest way for forecasting the movement of Rossby waves (that is, the troughs and ridges of 500 hPa geopotential height) over a limited amount of time (a few days). In the 1950s, the first successful programs for numerical weather forecasting utilized that equation.
In modern numerical weather forecasting models and general circulation models (GCMs), vorticity may be one of the predicted variables, in which case the corresponding time-dependent equation is a prognostic equation.
Related to the concept of vorticity is the helicity , defined as
where the integral is over a given volume . In atmospheric science, helicity of the air motion is important in forecasting supercells and the potential for tornadic activity. | 1 | Applied and Interdisciplinary Chemistry |
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