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Diamines form a wide range of coordination complexes. They typically form 5- and 6-membered chelate rings. Examples of the former include ethylenediamine and 2,2′-bipyridine. Six-membered chelate rings are formed by 1,3-diaminopropane. The bite angle in such complexes is usually near 90°. Longer chain diamines, which are "floppy", tend not to form chelate rings. | 0 | Theoretical and Fundamental Chemistry |
In organometallic species, metal complexes with the formulae LMCRR' are often described as carbene complexes. Such species do not however react like free carbenes and are rarely generated from carbene precursors, except for the persistent carbenes. The transition metal carbene complexes can be classified according to their reactivity, with the first two classes being the most clearly defined:
*Fischer carbenes, in which the carbene is bonded to a metal that bears an electron-withdrawing group (usually a carbonyl). In such cases the carbenoid carbon is mildly electrophilic.
*Schrock carbenes, in which the carbene is bonded to a metal that bears an electron-donating group. In such cases the carbenoid carbon is nucleophilic and resembles a Wittig reagent (which are not considered carbene derivatives).
*Carbene radicals, in which the carbene is bonded to an open-shell metal with the carbene carbon possessing a radical character. Carbene radicals have features of both Fischer and Schrock carbenes, but are typically long-lived reaction intermediates.
*N-Heterocyclic (NHC), Arduengo or Wanzlick carbenes are C-deprotonated imidazolium or dihydroimidazolium salts. They often are deployed as ancillary ligands in organometallic chemistry. Such carbenes are usually very strong σ-donor spectator ligands, similar to phosphines. | 0 | Theoretical and Fundamental Chemistry |
Understanding and measuring the absorption of electromagnetic radiation has a variety of applications.
* In radio propagation, it is represented in non-line-of-sight propagation. For example, see computation of radio wave attenuation in the atmosphere used in satellite link design.
* In meteorology and climatology, global and local temperatures depend in part on the absorption of radiation by atmospheric gases (such as in the greenhouse effect) and land and ocean surfaces (see albedo).
* In medicine, X-rays are absorbed to different extents by different tissues (bone in particular), which is the basis for X-ray imaging.
* In chemistry and materials science, different materials and molecules absorb radiation to different extents at different frequencies, which allows for material identification.
* In optics, sunglasses, colored filters, dyes, and other such materials are designed specifically with respect to which visible wavelengths they absorb, and in what proportions they are in.
* In biology, photosynthetic organisms require that light of the appropriate wavelengths be absorbed within the active area of chloroplasts, so that the light energy can be converted into chemical energy within sugars and other molecules.
* In physics, the D-region of Earth's ionosphere is known to significantly absorb radio signals that fall within the high-frequency electromagnetic spectrum.
* In nuclear physics, absorption of nuclear radiations can be used for measuring the fluid levels, densitometry or thickness measurements.
In scientific literature is known a system of mirrors and lenses that with a laser "can enable any material to absorb all light from a wide range of angles." | 0 | Theoretical and Fundamental Chemistry |
At terminal (or settling) velocity, the excess force due to the difference between the weight and buoyancy of the sphere (both caused by gravity) is given by:
where (in SI units):
* is the mass density of the sphere [kg/m]
* is the mass density of the fluid [kg/m]
* is the gravitational acceleration [m/s]
Requiring the force balance and solving for the velocity gives the terminal velocity . Note that since the excess force increases as and Stokes' drag increases as , the terminal velocity increases as and thus varies greatly with particle size as shown below. If a particle only experiences its own weight while falling in a viscous fluid, then a terminal velocity is reached when the sum of the frictional and the buoyant forces on the particle due to the fluid exactly balances the gravitational force. This velocity [m/s] is given by:
where (in SI units):
* is the gravitational field strength [m/s]
* is the radius of the spherical particle [m]
* is the mass density of the particle [kg/m]
* is the mass density of the fluid [kg/m]
* is the dynamic viscosity [kg/(m•s)]. | 1 | Applied and Interdisciplinary Chemistry |
Although there are many nonlinear optical phenomena, only multiphoton absorption is capable of injecting into the media the significant energy required to electronically excite molecular species and cause chemical reactions. Two-photon absorption is the strongest multiphoton absorbance by far, but still it is a very weak phenomenon, leading to low media sensitivity. Therefore, much research has been directed at providing chromophores with high two-photon absorption cross-sections.
Writing by two-photon absorption can be achieved by focusing the writing laser on the point where the photochemical writing process is required. The wavelength of the writing laser is chosen such that it is not linearly absorbed by the medium, and therefore it does not interact with the medium except at the focal point. At the focal point two-photon absorption becomes significant, because it is a nonlinear process dependent on the square of the laser fluence.
Writing by two-photon absorption can also be achieved by the action of two lasers in coincidence. This method is typically used to achieve the parallel writing of information at once. One laser passes through the media, defining a line or plane. The second laser is then directed at the points on that line or plane that writing is desired. The coincidence of the lasers at these points excited two-photon absorption, leading to writing photochemistry. | 0 | Theoretical and Fundamental Chemistry |
If is a vector field and is a vector representing the differential length of a small element of a defined curve, the contribution of that differential length to circulation is :
Here, is the angle between the vectors and .
The circulation of a vector field around a closed curve is the line integral:
In a conservative vector field this integral evaluates to zero for every closed curve. That means that a line integral between any two points in the field is independent of the path taken. It also implies that the vector field can be expressed as the gradient of a scalar function, which is called a potential. | 1 | Applied and Interdisciplinary Chemistry |
Ivar Karl Ugi (9 September 1930 in Saaremaa, Estonia – 29 September 2005 in Munich) was an Estonian-born German chemist who made major contributions to organic chemistry. He is known for the research on multicomponent reactions, yielding the Ugi reaction. | 0 | Theoretical and Fundamental Chemistry |
Vitamin D overdose causes hypercalcemia, which is a strong indication of vitamin D toxicity – this can be noted with an increase in urination and thirst. If hypercalcemia is not treated, it results in excess deposits of calcium in soft tissues and organs such as the kidneys, liver, and heart, resulting in pain and organ damage.
The main symptoms of vitamin D overdose are hypercalcemia including anorexia, nausea, and vomiting. These may be followed by polyuria, polydipsia, weakness, insomnia, nervousness, pruritus and ultimately kidney failure. Furthermore, proteinuria, urinary casts, azotemia, and metastatic calcification (especially in the kidneys) may develop. Other symptoms of vitamin D toxicity include intellectual disability in young children, abnormal bone growth and formation, diarrhea, irritability, weight loss, and severe depression.
Vitamin D toxicity is treated by discontinuing vitamin D supplementation and restricting calcium intake. Kidney damage may be irreversible. Exposure to sunlight for extended periods of time does not normally cause vitamin D toxicity. The concentrations of vitamin D precursors produced in the skin reach an equilibrium, and any further vitamin D produced is degraded. | 1 | Applied and Interdisciplinary Chemistry |
Pesticides may exhibit toxic effects on humans and other non-target species, the severity of which depends on the frequency and magnitude of exposure. Toxicity also depends on the rate of absorption, distribution within the body, metabolism, and elimination of compounds from the body. Commonly used pesticides like organophosphates and carbamates act by inhibiting acetylcholinesterase activity, which prevents the breakdown of acetylcholine at the neural synapse. Excess acetylcholine can lead to symptoms like muscle cramps or tremors, confusion, dizziness and nausea. Studies show that farm workers in Ethiopia, Kenya, and Zimbabwe have decreased concentrations of plasma acetylcholinesterase, the enzyme responsible for breaking down acetylcholine acting on synapses throughout the nervous system. Other studies in Ethiopia have observed reduced respiratory function among farm workers who spray crops with pesticides. Numerous exposure pathways for farm workers increase the risk of pesticide poisoning, including dermal absorption walking through fields and applying products, as well as inhalation exposure. | 1 | Applied and Interdisciplinary Chemistry |
Photosensitizers absorb light (hν) and transfer the energy from the incident light into another nearby molecule either directly or by a chemical reaction. Upon absorbing photons of radiation from incident light, photosensitizers transform into an excited singlet state. The single electron in the excited singlet state then flips in its intrinsic spin state via Intersystem crossing to become an excited triplet state. Triplet states typically have longer lifetimes than excited singlets. The prolonged lifetime increases the probability of interacting with other molecules nearby. Photosensitizers experience varying levels of efficiency for intersystem crossing at different wavelengths of light based on the internal electronic structure of the molecule. | 0 | Theoretical and Fundamental Chemistry |
This is a table of surface tension values for some interfaces at the indicated temperatures. Note that the SI units millinewtons per meter (mN·m) are equivalent to the cgs units dynes per centimetre (dyn·cm). | 0 | Theoretical and Fundamental Chemistry |
Baculovirus-infected insect cells (Sf9, Sf21, High Five strains) or mammalian cells (HeLa, HEK 293) allow production of glycosylated or membrane proteins that cannot be produced using fungal or bacterial systems. It is useful for production of proteins in high quantity. Genes are not expressed continuously because infected host cells eventually lyse and die during each infection cycle. | 1 | Applied and Interdisciplinary Chemistry |
It can be shown that the radial distribution function is related to the two-particle potential of mean force by:
In the dilute limit, the potential of mean force is the exact pair potential under which the equilibrium point configuration has a given . | 0 | Theoretical and Fundamental Chemistry |
* Culliford, Bryan J., The Examination and Typing of Bloodstains in the Crime Laboratory, Washington, D.C.: U.S. Government Printing Office, 1971.
* Gaensslen, Robert E., Sourcebook in Forensic Serology, Immunology, and Biochemistry, Washington, D.C.: U.S. Government Printing Office, 1983.
* Kirk, Paul L., Crime Investigation, John Wiley and Son, 1974.
* Metropolitan Police Forensic Science Laboratory, Biology Methods Manual, 1978.
* Ponce, Ana Castelló; Pascual, Fernando A. Verdú, [http://projects.nfstc.org/workshops/resources/literature/Screening/10_Critical%20Revision%20of%20Presumptive%20Tests%20for%20Bloodstains.pdf "Critical Revision of Presumptive Tests for Bloodstains,"] Forensic Science Communications, vol. 1, No. 2, July 1999, pages 1–15.
* Saferstein, Richard, Forensic Science Handbook, Prentice Hall, Inc., 1982. | 0 | Theoretical and Fundamental Chemistry |
The elasticities for a reversible uni-uni enzyme catalyzed reaction was previously given by:
An interesting result can be obtained by evaluating the sum . This can be shown to equal:
Two extremes can be considered. At high saturation (), the right-hand term tends to zero so that:
That is the absolute magnitudes of the substrate and product elasticities tends to equal each other. However, it is unlikely that a given enzyme will have both substrate and product concentrations much greater than their respective Kms. A more plausible scenario is when the enzyme is working under sub-saturating conditions (). Under these conditions we obtain the simpler result:
Expressed in a different way we can state:
That is, the absolute value for the substrate elasticity will be greater than the absolute value for the product elasticity. This means that a substrate will have a great influence over the forward reaction rate than the corresponding product.
This result has important implications for the distribution of flux control in a pathway with sub-saturated reaction steps. In general, a perturbation near the start of a pathway will have more influence over the steady state flux than steps downstream. This is because a perturbation that travels downstream is determined by all the substrate elasticities, whereas a perturbation downstream that has to travel upstream if determined by the product elasticities. Since we have seen that the substrate elasticities tends to be larger than the product elasticities, it means that perturbations traveling downstream will be less attenuated than perturbations traveling upstream. The net effect is that flux control tends to be more concentrated at upstream steps compared to downstream steps.
The table below summarizes the extreme values for the elasticities given a reversible Michaelis-Menten rate law. Following Westerhoff et al. the table is split into four cases that include one reversible type, and three irreversible types. | 0 | Theoretical and Fundamental Chemistry |
For free atoms, electron configurations have been determined by atomic spectroscopy. Lists of atomic energy levels and their electron configurations have been published by the National Institute of Standards and Technology (NIST) for both neutral and ionized atoms.
For neutral atoms of all elements, the ground-state electron configurations are listed in general chemistry and inorganic chemistry textbooks. The ground-state configurations are often explained using two principles: the Aufbau principle that subshells are filled in order of increasing energy, and the Madelung rule that this order corresponds to the order of increasing values of (n + ) where n is the principal quantum number and is the azimuthal quantum number. This rule predicts for example that the 4s orbital (n = 4, = 0, n + = 4) is filled before the 3d orbital (n = 3, = 2, n + = 5), as in titanium with configuration [Ar]4s3d.
There are a few exceptions with only one electron (or zero for palladium) in the ns orbital in favor of completing a half or a whole d shell. The usual explanation in chemistry textbooks is that half-filled or completely filled subshells are particularly stable arrangements of electrons. An example is chromium whose electron configuration is [Ar]4s3d with a d electron count of 5 for a half-filled d subshell, although Madelung's rule predicts [Ar]4s3d. Similarly copper is [Ar]4s3d with a full d subshell, and not [Ar]4s3d. The configuration of palladium is [Kr]4d with zero 5s electrons. However this trend is not consistent: tungsten, a group VI element like Cr and Mo has a Madelung-following [Xe]6s4f5d, and niobium has a [Kr]5s4d as opposed to the Madelung rule predicted [Kr]5s4d which creates two partially-filled subshells.
When a transition metal atom loses one or more electrons to form a positive ion, overall electron repulsion is reduced and the n d orbital energy is lowered more than the (n+1) s orbital energy. The ion is formed by removal of the outer s electrons and tends to have a d configuration, even though the s subshell is added to neutral atoms before the d subshell. For example, the Ti ion has the ground-state configuration [Ar]3d with a d electron count of 2, even though the total number of electrons is the same as the neutral calcium atom which is [Ar]4s.
In coordination complexes between an electropositive transition metal atom and an electronegative ligand, the transition metal is approximately in an ionic state as assumed in crystal field theory, so that the electron configuration and d electron count are those of the transition metal ion rather than the neutral atom. | 0 | Theoretical and Fundamental Chemistry |
A biosignature must be able to dominate over all other processes that may produce similar physical, spectral, and chemical features. When investigating a potential biosignature, scientists must carefully consider all other possible origins of the biosignature in question. Many forms of life are known to mimic geochemical reactions. One of the theories on the origin of life involves molecules developing the ability to catalyse geochemical reactions to exploit the energy being released by them. These are some of the earliest known metabolisms (see methanogenesis). In such case, scientists might search for a disequilibrium in the geochemical cycle, which would point to a reaction happening more or less often than it should. A disequilibrium such as this could be interpreted as an indication of life. | 1 | Applied and Interdisciplinary Chemistry |
In general, cells are cultivated in unlabeled or stable (non-radioactive) isotope labeled media. For example, the medium can contain glucose labeled with six carbon-13 atoms (C) instead of the normal carbon-12 (C). Cells growing in this medium, will, depending on model organism, incorporate the heavy glucose into all of their RNA molecules. Thereafter, all nucleotides are 5 Da heavier than their unlabeled isotopologues due to a complete carbon labeling of the ribose. After cultivation and appropriate labeling of the cells, they are generally harvested using phenol/chloroform/guanidinium isothiocyanate. Other extraction methods are possible and sometimes needed (e.g. for yeast). RNA is then isolated by Phenol-Chloroform extraction and iso-Propanol precipitation. Further purification of specific RNA species (e.g. rRNA, tRNA) is usually done by size-exclusion chromatography (SEC) but other approaches are available as well. For most applications the final product needs to be enzymatically digested to nucleosides before analysis by LC-MS. Therefore, digestion enzymes such as benzonase, NP1 and CIP are used. Typically, a triple quadrupole in MRM mode is used for the measurements. | 0 | Theoretical and Fundamental Chemistry |
Coupled substitution is the geological process by which two elements simultaneous substitute into a crystal in order to maintain overall electrical neutrality and keep the charge constant. In forming a solid solution series, ionic size is more important than ionic charge, as this can be compensated for elsewhere in the structure. | 0 | Theoretical and Fundamental Chemistry |
Typically, the rearrangement is carried out just after the formation of the divinylcyclopropane, in the same pot. Heating is sometimes necessary, particularly for trans substrates, which must undergo epimerization prior to rearrangement. With enough energy to surmount activation barriers, however, the isomerization is usually very efficient. | 0 | Theoretical and Fundamental Chemistry |
Although an attenuation mechanism that involves translation while transcription is ongoing, like to the mechanism for the trp operon (and some other amino acid biosynthetic operons), would not work in eukaryotes, there is evidence for attenuation in Eukaryotes. Research conducted on microRNA processing provides evidence of eukaryotic attenuation; after co-transcriptional endonucleolitical cleavage by Drosha 5->3 exonuclease XRN2 may terminate further transcription by torpedo mechanism. | 1 | Applied and Interdisciplinary Chemistry |
Lichens may be long-lived, with some considered to be among the oldest living organisms. Lifespan is difficult to measure because what defines the "same" individual lichen is not precise. Lichens grow by vegetatively breaking off a piece, which may or may not be defined as the "same" lichen, and two lichens can merge, then becoming the "same" lichen. One specimen of Rhizocarpon geographicum on East Baffin Island has an estimated age of 9500 years. Thalli of Rhizocarpon geographicum and Rhizocarpon eupetraeoides/inarense in the central Brooks Range of northern Alaska have been given a maximum possible age of 10,000–11,500 years. | 1 | Applied and Interdisciplinary Chemistry |
The World Uranium Hearing was held in Salzburg, Austria in September 1992.Anti-nuclear speakers from all continents, including indigenous speakers and scientists, testified to the health and environmental problems of uranium mining and processing, nuclear power, nuclear weapons, nuclear tests, and radioactive waste disposal.
People who spoke at the 1992 Hearing include: Thomas Banyacya, Katsumi Furitsu, Manuel Pino and Floyd Red Crow Westerman. They said they were deeply dismayed by the atomic bombings of Hiroshima and Nagasaki and highlighted what they called the inherently destructive nature of all phases of the nuclear supply chain. They recalled the disastrous impact of nuclear weapons testing in places such as the Nevada Test Site, Bikini Atoll and Eniwetok, Tahiti, Maralinga, and Central Asia. They highlighted the threat of radioactive contamination to all peoples, especially indigenous communities and said that their survival requires self-determination and emphasis on spiritual and cultural values. Increased renewable energy commercialization was advocated.
The proceedings were published as a book, Poison fire, sacred earth testimonies, lectures, conclusions. The outcome document, the Declaration of Salzburg was accepted by the United Nations Working Group on Indigenous Populations. | 0 | Theoretical and Fundamental Chemistry |
The health effects of radon are harmful, and include an increased chance of lung cancer. Radon is a radioactive, colorless, odorless, tasteless noble gas, which has been studied by a number of scientific and medical bodies for its effects on health. A naturally-occurring gas formed as a decay product of radium, radon is one of the densest substances that remains a gas under normal conditions, and is considered to be a health hazard due to its radioactivity. Its most stable isotope, radon-222, has a half-life of 3.8 days. Due to its high radioactivity, it has been less well studied by chemists, but a few compounds are known.
Radon-222 is formed as part of the uranium series i.e. the normal radioactive decay chain of uranium-238 that terminates in lead-206. Uranium has been present since the Earth was formed, and its most common isotope has a very long half-life (4.5 billion years), which is the time required for one-half of uranium to break down. Thus, uranium and radon will continue to occur for millions of years at about the same concentrations as they do now.
Radon is responsible for the majority of public exposure to ionizing radiation. It is often the single largest contributor to an individual's background radiation dose, and is the most variable from location to location. Radon gas from natural sources can accumulate in buildings, especially in confined areas such as attics and basements. It can also be found in some spring waters and hot springs.
According to a 2003 report EPAs Assessment of Risks from Radon in Homes' from the United States Environmental Protection Agency, epidemiological evidence shows a clear link between lung cancer and high concentrations of radon, with 21,000 radon-induced U.S. lung cancer deaths per year—second only to cigarette smoking. Thus in geographic areas where radon is present in heightened concentrations, radon is considered a significant indoor air contaminant. | 1 | Applied and Interdisciplinary Chemistry |
In organometallic chemistry, a transition metal indenyl complex is a coordination compound that contains one or more indenyl ligands. The indenyl ligand is formally the anion derived from deprotonation of indene. The η-indenyl ligand is related to the ηcyclopentadienyl anion (Cp), thus indenyl analogues of many cyclopentadienyl complexes are known. Indenyl ligands lack the 5-fold symmetry of Cp, so they exhibit more complicated geometries. Furthermore, some indenyl complexes also exist with only η-bonding mode. The η- and η-bonding modes sometimes interconvert. | 0 | Theoretical and Fundamental Chemistry |
Investigations of planktonic foraminiferal population indicate that tropical species attain their largest test sizes in tropical waters, and polar species reach maximum sizes in polar waters. Species living in subtropical and subpolar waters decrease in test size with both increasing and decreasing temperature.
The proloculus (the first chamber) sizes of benthic forams are affected by sea water temperature and their mean has been used as proxy for paleoclimatic investigations.
Mean test diameters of the planktonic foraminifer Orbulina universa have been used to interpret sea surface temperature history in Somali Basin. R-mode factor and Q-mode cluster analyses define five significant factor assemblages and five clusters reflecting different environmental characteristics, including increased oxygenation, high surface productivity. | 0 | Theoretical and Fundamental Chemistry |
Reducing the species and its related precursors with sodium or potassium have given dimeric magnesium(I) compounds such as [{(Priso)Mg}] and other compounds with substituted versions of β-diketiminato. These compounds, with a general formula of [{(ArNacnac)Mg}]. However, as the size of the substituent on Nacnac decreased, the difficulty to isolate a magnesium(I) dimer increased. This can be shown by phenol, where only a Mg(II) dimer was gained, given by [(PhNacnac)Mg]. For a bulkier analogue such as [{(Nacnac)Mg}] a different synthesis route was carried out. Dibutyl magnesium and iodine were chosen since the free β -diketimine, tBuNacnacH has a different reactivity.This is due to tBuNacnacH not reacting with the Grignard reagent shown above. Instead, it can be heated with dibutylmagnesium and become deprotonated.
For the reactant, the was stabilized by utilizing a bulkier, or more sterically demanding, N-ligand. This reaction is carried out through potassium reduction of the α-diimine, DAB and Mg(II) chloride in tetrahydrofuran (THF). It can be noted that DAB can be shown by the chemical formula as [(DipNCMe)]). The shown Mg(I) complexes are all thermally stable. Some can even tolerate temperatures up to 300 °C. They also range in colors from colorless to orange. As these compounds are investigated further, the dimers have been found to be kinetically stabilized by multiple β-diketiminate derivatives, a guanidinate, a diiminophosphinate, an enediamide, and several diimine-enolates. | 0 | Theoretical and Fundamental Chemistry |
More generally, in a non-isotropic Newtonian fluid, the coefficient that relates internal friction stresses to the spatial derivatives of the velocity field is replaced by a nine-element viscous stress tensor .
There is general formula for friction force in a liquid: The vector differential of friction force is equal the viscosity tensor increased on vector product differential of the area vector of adjoining a liquid layers and rotor of velocity:
where is the viscosity tensor. The diagonal components of viscosity tensor is molecular viscosity of a liquid, and not diagonal components – turbulence eddy viscosity. | 1 | Applied and Interdisciplinary Chemistry |
The addition of hydrogen and an amino group (NR) using reagents other than the amine HNR is known as a "formal hydroamination" reaction. Although the advantages of atom economy and/or ready available of the nitrogen source are diminished as a result, the greater thermodynamic driving force, as well as ability to tune the aminating reagent are potentially useful. In place of the amine, hydroxylamine esters and nitroarenes have been reported as nitrogen sources. | 0 | Theoretical and Fundamental Chemistry |
Photosynthesis is the primary process by which carbon moves from the atmosphere into living things. In photosynthetic pathways is absorbed slightly more easily than , which in turn is more easily absorbed than . The differential uptake of the three carbon isotopes leads to / and / ratios in plants that differ from the ratios in the atmosphere. This effect is known as isotopic fractionation.
To determine the degree of fractionation that takes place in a given plant, the amounts of both and isotopes are measured, and the resulting / ratio is then compared to a standard ratio known as PDB. The / ratio is used instead of / because the former is much easier to measure, and the latter can be easily derived: the depletion of relative to is proportional to the difference in the atomic masses of the two isotopes, so the depletion for is twice the depletion of . The fractionation of , known as , is calculated as follows:
where the ‰ sign indicates parts per thousand. Because the PDB standard contains an unusually high proportion of , most measured values are negative.
For marine organisms, the details of the photosynthesis reactions are less well understood, and the values for marine photosynthetic organisms are dependent on temperature. At higher temperatures, has poor solubility in water, which means there is less available for the photosynthetic reactions. Under these conditions, fractionation is reduced, and at temperatures above the values are correspondingly higher, while at lower temperatures, becomes more soluble and hence more available to marine organisms.
The value for animals depends on their diet. An animal that eats food with high values will have a higher than one that eats food with lower values. The animals own biochemical processes can also impact the results: for example, both bone minerals and bone collagen typically have a higher concentration of than is found in the animals diet, though for different biochemical reasons. The enrichment of bone also implies that excreted material is depleted in relative to the diet.
Since makes up about 1% of the carbon in a sample, the / ratio can be accurately measured by mass spectrometry. Typical values of have been found by experiment for many plants, as well as for different parts of animals such as bone collagen, but when dating a given sample it is better to determine the value for that sample directly than to rely on the published values.
The carbon exchange between atmospheric and carbonate at the ocean surface is also subject to fractionation, with in the atmosphere more likely than to dissolve in the ocean. The result is an overall increase in the / ratio in the ocean of 1.5%, relative to the / ratio in the atmosphere. This increase in concentration almost exactly cancels out the decrease caused by the upwelling of water (containing old, and hence -depleted, carbon) from the deep ocean, so that direct measurements of radiation are similar to measurements for the rest of the biosphere. Correcting for isotopic fractionation, as is done for all radiocarbon dates to allow comparison between results from different parts of the biosphere, gives an apparent age of about 400 years for ocean surface water. | 0 | Theoretical and Fundamental Chemistry |
Like many organolithium reagents, lithium bis(trimethylsilyl)amide can form aggregates in solution. The extent of aggregation depends on the solvent. In coordinating solvents, such as ethers and amines, the monomer and dimer are prevalent. In the monomeric and dimeric state, one or two solvent molecules bind to lithium centers. With ammonia as donor base lithium bis(trimethylsilyl)amide forms a trisolvated monomer that is stabilized by intermolecular hydrogen bonds. In noncoordinating solvents, such as aromatics or pentane, the complex oligomers predominate, including the trimer. In the solid state structure is trimeric. | 0 | Theoretical and Fundamental Chemistry |
A body of icy or rocky material in outer space may, if it can build and retain sufficient heat, develop a differentiated interior and alter its surface through volcanic or tectonic activity. The length of time through which a planetary body can maintain surface-altering activity depends on how well it retains heat, and this is governed by its surface area-to-volume ratio. For Vesta (r=263 km), the ratio is so high that astronomers were surprised to find that it did differentiate and have brief volcanic activity. The moon, Mercury and Mars have radii in the low thousands of kilometers; all three retained heat well enough to be thoroughly differentiated although after a billion years or so they became too cool to show anything more than very localized and infrequent volcanic activity. As of April 2019, however, NASA has announced the detection of a "marsquake" measured on April 6, 2019, by NASA's InSight lander. Venus and Earth (r>6,000 km) have sufficiently low surface area-to-volume ratios (roughly half that of Mars and much lower than all other known rocky bodies) so that their heat loss is minimal. | 0 | Theoretical and Fundamental Chemistry |
Although usually the anion of the mineralizer is most active in dissolving the nutrient material, the cation also exerts an influence in some cases. The mineralizer can interact with impurities on the surface of the crystal and increase the growth rate. For example, the growth rate for sapphire (AlO) and zincite (ZnO) in potassium-containing solution (KOH, KCO) is higher in comparison to that in sodium-containing solution (NaOH, NaCO). This difference is not readily understood, but are attributed the interaction between potassium and an impurity absorbed on the surface. | 0 | Theoretical and Fundamental Chemistry |
Purple bacteria is a type of photosynthetic organism with a light harvesting complex consisting of two pigment protein complexes referred to as LH1 and LH2. Within the photosynthetic membrane, these two complexes differ in terms of their arrangement. The LH1 complexes surrounds the reaction centre, while the LH2 complexes are arranged around the LH1 complexes and the reaction centre in a peripheral fashion. Purple bacteria use bacteriochlorophyll and carotenoids to gather light energy. These proteins are arranged in a ring-like fashion creating a cylinder that spans the membrane. | 0 | Theoretical and Fundamental Chemistry |
NANOG is a transcription factor in embryonic stem cells (ESCs) and is thought to be a key factor in maintaining pluripotency. NANOG is thought to function in concert with other factors such as POU5F1 (Oct-4) and SOX2 to establish ESC identity. These cells offer an important area of study because of their ability to maintain pluripotency. In other words, these cells have the ability to become virtually any cell of any of the three germ layers (endoderm, ectoderm, mesoderm). It is for this reason that understanding the mechanisms that maintain a cell's pluripotency is critical for researchers to understand how stem cells work, and may lead to future advances in treating degenerative diseases.
NANOG has been described to be expressed in the posterior side of the epiblast at the onset of gastrulation. There, NANOG has been implicated in inhibiting embryonic hematopoiesis by repressing the expression of the transcription factor Tal1. In this embryonic stage, NANOG represses Pou3f1, a transcription factor crucial for the anterior-posterior axis formation.
Analysis of arrested embryos demonstrated that embryos express pluripotency marker genes such as POU5F1, NANOG and Rex1. Derived human ESC lines also expressed specific pluripotency markers:
*TRA-1-60
*TRA-1-81
*SSEA4
*alkaline phosphatase
*TERT
*Rex1
These markers allowed for the differentiation in vitro and in vivo conditions into derivatives of all three germ layers.
POU5F1, TDGF1 (CRIPTO), SALL4, LECT1, and BUB1 are also related genes all responsible for self-renewal and pluripotent differentiation.
The NANOG protein has been found to be a transcriptional activator for the Rex1 promoter, playing a key role in sustaining Rex1 expression. Knockdown of NANOG in embryonic stem cells results in a reduction of Rex1 expression, while forced expression of NANOG stimulates Rex1 expression.
Besides the effects of NANOG in the embryonic stages of life, ectopic expression of NANOG in the adult stem cells can restore the proliferation and differentiation potential that is lost due to organismal aging or cellular senescence. | 1 | Applied and Interdisciplinary Chemistry |
Schuster was recruited to New York University by Kurt Mislow, who was also interested in photochemistry, and joined the faculty there in late 1961 in what was at the time the University Heights, Bronx campus. He remained at NYU for his entire academic career. Schuster received tenure in 1968 and spent the 1968–69 academic year on sabbatical in London in the laboratory of George Porter. In 1974 NYU closed its Bronx campus, requiring Schuster to move his laboratory to the Manhattan campus near Washington Square Park. Among Schuster's influential advisees are structural biologist Dinshaw Patel and synthetic organic chemist Phil Baran, who worked in the laboratory as an NYU undergraduate. Schuster closed his laboratory and retired, assuming professor emeritus status, in 2010.
Schuster was elected a fellow of the American Association for the Advancement of Science in 1992 and received the Arthur C. Cope Scholar Award, given by the American Chemical Society, in 2012. | 0 | Theoretical and Fundamental Chemistry |
Layering graphene on top of gold has been shown to improve SPR sensor performance. Its high electrical conductivity increases the sensitivity of detection. The large surface area of graphene also facilitates the immobilization of biomolecules while its low refractive index minimizes its interference. Enhancing SPR sensitivity by incorporating graphene with other materials expands the potential of SPR sensors, making them practical in a broader range of applications. For instance, the enhanced sensitivity of graphene can be used in conjunction with a silver SPR sensor, providing a cost-effective alternative for measuring glucose levels in urine.
Graphene has also been shown to improve the resistance of SPR sensors to high-temperature annealing up to 500 °C. | 0 | Theoretical and Fundamental Chemistry |
The water molecule is an asymmetric top, that is, it has three independent moments of inertia. Rotation about the 2-fold symmetry axis is illustrated at the left. Because of the low symmetry of the molecule, a large number of transitions can be observed in the far infrared region of the spectrum. Measurements of microwave spectra have provided a very precise value for the O−H bond length, 95.84 ± 0.05 pm and H−O−H bond angle, 104.5 ± 0.3°. | 0 | Theoretical and Fundamental Chemistry |
Soil that is well aggregated has a range of pore sizes. Each pore size plays a role in soil's physical functioning. Large pores drain rapidly and are needed for good air exchange during wet periods, preventing oxygen deficiency that can drown plants and increase pest problems. Oxygen-deficient wet soils increase denitrification – conversion of nitrogen to gaseous forms. In degraded soil large pores are compressed into small ones.
Small pores are critical for water retention and help a crop endure dry periods with minimal yield loss. | 0 | Theoretical and Fundamental Chemistry |
As early as 1913, James was involved in searching for element 61, the last of the rare earth elements. At least seven times, investigators believed that they had identified element 61. Charles James and B. Smith Hopkins from the University of Illinois both sought it. In 1926, himself close to publishing on the subject, James was asked to review a paper from Hopkins for the Journal of the American Chemical Society. James subsequently sent his own paper on element 61 to the lesser-known Proceedings of the National Academy of Sciences to avoid any possible conflict of interest. As a result it received less attention than might have been expected. It is likely that neither chemist was aware of the others work before James reviewed Hopkins paper. James also reviewed Hopkinsʼs book Chemistry of the Rarer Elements, saying he recommended it.
Eventually it was determined that promethium, a radioactive element, does not form stable isotopes. As a result, it is extremely rare and unlikely to occur in nature, but can be formed in a nuclear reactor. | 1 | Applied and Interdisciplinary Chemistry |
: For Newton number, see also Kissing number in the sphere packing problem.
The power number N (also known as Newton number) is a commonly used dimensionless number relating the resistance force to the inertia force.
The power-number has different specifications according to the field of application. E.g., for stirrers the power number is defined as:
with
*P: power
*ρ: fluid density
*n: rotational speed in revolutions per second
*D: diameter of stirrer | 1 | Applied and Interdisciplinary Chemistry |
In the study of heat transfer, critical heat flux (CHF) is the heat flux at which boiling ceases to be an effective form of transferring heat from a solid surface to a liquid. | 0 | Theoretical and Fundamental Chemistry |
The journal is abstracted and indexed in BIOSIS, Chemical Abstracts, Current Contents/Life Sciences, EMBASE, MEDLINE, and Scopus. | 1 | Applied and Interdisciplinary Chemistry |
If alkali builds up due to ion exchange, and remains on the surface of the glass, the decay process will accelerate. The presence of sodium or potassium ions in the alkali build up will increase the pH on the surface of the glass, causing it to become basic. This will dissolve silica from the glass as well as releasing more alkali ions.
The haziness seen on the glass may not disappear entirely when washed and dried. When examined closely at an angle with a low light, fine cracks like tiny silvery lines or shimmering rays, may be visible. A microscope can confirm the presence of cracks. The cracks are caused by the loss of alkali, which leaves microscopic gaps in the structure of the glass. | 0 | Theoretical and Fundamental Chemistry |
A recently growing way to analyze T-RFLP profiles is use multivariate statistical methods to interpret the T-RFLP data. Usually the methods applied are those commonly used in ecology and especially in the study of biodiversity. Among them ordinations and cluster analysis are the most widely used.
In order to perform multivariate statistical analysis on T-RFLP data, the data must first be converted to table known as a “sample by species table“ which depicts the different samples (T-RFLP profiles) versus the species (T-RFS) with the height or area of the peaks as values. | 1 | Applied and Interdisciplinary Chemistry |
The types of anomalous diffusion given above allows one to measure the type, but how does anomalous diffusion arise? There are many possible ways to mathematically define a stochastic process which then has the right kind of power law. Some models are given here.
These are long range correlations between the signals continuous-time random walks (CTRW) and fractional Brownian motion (fBm), and diffusion in disordered media. Currently the most studied types of anomalous diffusion processes are those involving the following
* Generalizations of Brownian motion, such as the fractional Brownian motion and scaled Brownian motion
* Diffusion in fractals and percolation in porous media
* Continuous time random walks
These processes have growing interest in cell biophysics where the mechanism behind anomalous diffusion has direct physiological importance. Of particular interest, works by the groups of Eli Barkai, Maria Garcia Parajo, Joseph Klafter, Diego Krapf, and Ralf Metzler have shown that the motion of molecules in live cells often show a type of anomalous diffusion that breaks the ergodic hypothesis. This type of motion require novel formalisms for the underlying statistical physics because approaches using microcanonical ensemble and Wiener–Khinchin theorem break down. | 0 | Theoretical and Fundamental Chemistry |
Measuring the size of a protein molecule is useful as an overall quality indicator, since misfolding, unfolding, oligomerization, aggregation or degradation can all affect size.
The literature specifically demonstrates the use of MDS in sizing protein-nanobody complexes, monitoring the formation of α-synuclein amyloid fibrils. and in observing protein assembly into oligomers
MDS can also be used to size membrane proteins, as the use of a protein specific labelling and detection system allows other species present in the solution (such as free lipid micelles or detergents) to be ignored. | 1 | Applied and Interdisciplinary Chemistry |
There are several consequences the formation of a transcription factory has on nuclear and genomic structures. It has been proposed that the factories are responsible for nuclear organisation; they have been suggested to promote chromatin loop formation by two potential mechanisms:
The first mechanism suggests that loops form because 2 genes on the same chromosome require the same transcription machinery that would be found in a specific transcription factory. This requirement will attract the gene loci to the factory thus creating a loop.
Transcription factories are also suggested to be responsible for gene clustering, this is because related genes would require the same transcriptional machinery and if a factory satisfies these needs the genes would be attracted to the factory
. While the clustering of genes can be beneficial for transcriptional efficiency, there could be negative consequences to this. Gene translocation events occur when genes are in close proximity to one another; which will occur more often when a transcriptional factory is present. Gene translocation events, like point mutations, generally are detrimental to the organism and so therefore could lead to the possibility of disease. However, on the other hand recent research has suggested that there is no correlation between inter-gene interactions and translocation frequencies. | 1 | Applied and Interdisciplinary Chemistry |
FuseNet is the umbrella organization and single voice for the training and education of the next generation fusion engineers and scientists. FuseNet is recognized as such by the European Commission. | 0 | Theoretical and Fundamental Chemistry |
Peptides are ancient signaling systems that are found in almost all animals on Earth. Genome sequencing reveals evidence of neuropeptide genes in Cnidaria, Ctenophora, and Placozoa, some of oldest living animals with nervous systems or neural-like tissues. Recent studies also show genomic evidence of neuropeptide processing machinery in metazoans and choanoflagellates, suggesting that neuropeptide signaling may predate the development of nervous tissues. Additionally, Ctenophore and Placozoa neural signaling is entirely peptidergic and lacks the major amine neurotransmitters such as acetylcholine, dopamine, and serotonin. This also suggests that neuropeptide signaling developed before amine neurotransmitters. | 1 | Applied and Interdisciplinary Chemistry |
M13 phage - m7G(5')pppN diphosphatase - malformation - maltose-transporting ATPase - manganese-transporting ATPase - mannose-6-phosphate 6-reductase - mapping - marker - melanoma - melting - menaquinol oxidase (H+-transporting) - Johann Mendel - Mendelian inheritance - message - messenger RNA - metaphase - methylphenyltetrahydropyridine N-monooxygenase - methylsterol monooxygenase - methyltetrahydroprotoberberine 14-monooxygenase - microarray technology - microsatellite - MIMT1 - minusheet perfusion culture system - Mir-188 microRNA precursor family - Mir-615 microRNA precursor family - Mir-675 microRNA precursor family - missense mutation - mitochondrial DNA - mobility shift - molecular weight size marker - monoclonal antibody - monosaccharide-transporting ATPase - monosomy - morphine 6-dehydrogenase - mouse model - mRNA - multicistronic message - multicopy plasmid - multiple cloning site - multiple endocrine neoplasia, type 1 - mutation - myristoyl-CoA 11-(E) desaturase - myristoyl-CoA 11-(Z) desaturase - | 1 | Applied and Interdisciplinary Chemistry |
In the United States, the Corning Museum of Glass in New York is the preeminent institute for glass research through the conservation department and library. The conservation department advises on the best practices of displaying, mounting, lighting, storing, and handling glass objects. Additionally, the museum regularly holds courses on the principles and practice of historical and archaeological glass cleaning, care, conservation and restoration for conservators. | 0 | Theoretical and Fundamental Chemistry |
An under-expanded jet is one that manifests when the pressure at downstream conditions (at the end of a nozzle or orifice) is greater that the pressure of the environment where the gas is being released in. It is said to be under-expanded since the gas will expand, trying to reach the same pressure of its surroundings. When under-expanded, the jet will have characteristics of a compressible flow, a condition in which pressure variations are significant enough to have a strong effect on the velocity (where it can exceed the speed of sound of the gas), density and temperature. It is important to note that as the jet expands and incorporates gases from the surrounding medium, the jet will behave more and more like an incompressible fluid, allowing for a general definition of the structure of a jet to be the following:
*Nearfield zone: this zone is composed of a core layer that is isolated from the surrounding medium, with its behavior being mostly dominated by compressible effects, and an outer layer that is in contact with the surrounding medium fluid. Due to turbulent effects, the outer layer, nominated as mixing layer, permits gas entrainment as it is facilitated, diluting the jet. In this shearing zone, a subsonic and supersonic section may be distinguished, where temperature, density and pressure vary wildly in a few centimeters of distance from the source. This zone has the characteristics of a compressible fluid.
*Transition zone: the beginning of this zone represents the ending of the nearfield zone, where variations (longitudinally and radially to the axis of the jet) are small compared to the previous one. Density and temperature variations are mostly because of mixing with the surrounding fluid.
*Farfield zone: this final zone is one of a fully expanded and incompressible jet. Longitudinal velocity and temperature are now inversely proportional to the distance from the source and radial evolution can be described by a gaussian dispersion model. It is important to note that this zone can be further split into inertial (dominated by initial acceleration), buoyant (dominated by internal buoyancy forces) and turbulent zones (dominated by ambient turbulence). | 1 | Applied and Interdisciplinary Chemistry |
Mass concentration depends on the variation of the volume of the solution due mainly to thermal expansion. On small intervals of temperature the dependence is :
where is the mass concentration at a reference temperature, is the thermal expansion coefficient of the mixture. | 0 | Theoretical and Fundamental Chemistry |
Chlorine and bromine reversibly intercalate into graphite. Iodine does not. Fluorine reacts irreversibly. In the case of bromine, the following stoichiometries are known: for n = 8, 12, 14, 16, 20, and 28.
Because it forms irreversibly, carbon monofluoride is often not classified as an intercalation compound. It has the formula . It is prepared by reaction of gaseous fluorine with graphitic carbon at 215–230 °C. The color is greyish, white, or yellow. The bond between the carbon and fluorine atoms is covalent. Tetracarbon monofluoride () is prepared by treating graphite with a mixture of fluorine and hydrogen fluoride at room temperature. The compound has a blackish-blue color. Carbon monofluoride is not electrically conductive. It has been studied as a cathode material in one type of primary (non-rechargeable) lithium batteries.
Graphite oxide is an unstable yellow solid. | 0 | Theoretical and Fundamental Chemistry |
The lysophosphatidic acid receptors (LPARs) are a group of G protein-coupled receptors for lysophosphatidic acid (LPA) that include:
* Lysophosphatidic acid receptor 1 (LPAR1; formerly known as EDG2, GPR26)
* Lysophosphatidic acid receptor 2 (LPAR2; formerly known as EDG4)
* Lysophosphatidic acid receptor 3 (LPAR3; formerly known as EDG7)
* Lysophosphatidic acid receptor 4 (LPAR4; formerly known as GPR23, P2RY9)
* Lysophosphatidic acid receptor 5 (LPAR5; formerly known as GPR92)
* Lysophosphatidic acid receptor 6 (LPAR6; formerly known as GPR87, P2RY5) | 1 | Applied and Interdisciplinary Chemistry |
The most commonly studied system to date is the system, consisting of a proton bound with a ion. The system was first observed in 2000 by a group at the University of Waterloo in Canada.
The formation of the ion can be understood classically; as the single electron in a hydrogen atom cannot fully shield the positively charged nucleus, another electron brought into close proximity will feel an attractive force. While this classical description is nice for getting a feel for the interactions involved, it is an oversimplification; many other atoms have a greater electron affinity than hydrogen. In general the process of forming a negative ion is driven by the filling of atomic electron shells to form a lower energy configuration.
Only a small number of molecules have been used to produce heavy Rydberg systems although in principle any atom with a positive electron affinity can bind with a positive ion. Species used include , and . Fluorine and oxygen are particularly favoured due to their high electron affinity, high ionisation energy and consequently high electronegativity. | 0 | Theoretical and Fundamental Chemistry |
In eukaryotic cells the structure of the chromatin complex of DNA is folded in a way that functionally mimics the supercoiled state characteristic of prokaryotic DNA, so although the enhancer DNA may be far from the gene in a linear way, it is spatially close to the promoter and gene. This allows it to interact with the general transcription factors and RNA polymerase II. The same mechanism holds true for silencers in the eukaryotic genome. Silencers are antagonists of enhancers that, when bound to its proper transcription factors called repressors, repress the transcription of the gene. Silencers and enhancers may be in close proximity to each other or may even be in the same region only differentiated by the transcription factor the region binds to.
An enhancer may be located upstream or downstream of the gene it regulates. Furthermore, an enhancer does not need to be located near the transcription initiation site to affect transcription, as some have been found located several hundred thousand base pairs upstream or downstream of the start site. Enhancers do not act on the promoter region itself, but are bound by activator proteins. These activator proteins interact with the mediator complex, which recruits polymerase II and the general transcription factors which then begin transcribing the genes. Enhancers can also be found within introns. An enhancer's orientation may even be reversed without affecting its function; additionally, an enhancer may be excised and inserted elsewhere in the chromosome, and still affect gene transcription. That is one reason that introns polymorphisms may have effects although they are not translated. Enhancers can also be found at the exonic region of an unrelated gene and they may act on genes on another chromosome.
Enhancers are bound by p300-CBP and their location can be predicted by ChIP-seq against this family of coactivators. | 1 | Applied and Interdisciplinary Chemistry |
The thylakoid lumen is a continuous aqueous phase enclosed by the thylakoid membrane. It plays an important role for photophosphorylation during photosynthesis. During the light-dependent reaction, protons are pumped across the thylakoid membrane into the lumen making it acidic down to pH 4. | 0 | Theoretical and Fundamental Chemistry |
Space groups in 2 dimensions are the 17 wallpaper groups which have been known for several centuries, though the proof that the list was complete was only given in 1891, after the much more difficult classification of space groups had largely been completed.
In 1879 the German mathematician Leonhard Sohncke listed the 65 space groups (called Sohncke groups) whose elements preserve the chirality. More accurately, he listed 66 groups, but both the Russian mathematician and crystallographer Evgraf Fedorov and the German mathematician Arthur Moritz Schoenflies noticed that two of them were really the same. The space groups in three dimensions were first enumerated in 1891 by Fedorov (whose list had two omissions (I3d and Fdd2) and one duplication (Fmm2)), and shortly afterwards in 1891 were independently enumerated by Schönflies (whose list had four omissions (I3d, Pc, Cc, ?) and one duplication (P2m)). The correct list of 230 space groups was found by 1892 during correspondence between Fedorov and Schönflies. later enumerated the groups with a different method, but omitted four groups (Fdd2, I2d, P2d, and P2c) even though he already had the correct list of 230 groups from Fedorov and Schönflies; the common claim that Barlow was unaware of their work is incorrect. describes the history of the discovery of the space groups in detail. | 0 | Theoretical and Fundamental Chemistry |
The amount of negative charge from deprotonation of clay hydroxy groups or organic matter depends on the pH of the surrounding solution. Increasing the pH (i.e. decreasing the concentration of H cations) increases this variable charge, and therefore also increases the cation-exchange capacity. | 0 | Theoretical and Fundamental Chemistry |
Cannabinoidergic, or cannabinergic, means "working on the endocannabinoid neurotransmitters". As with terms such as dopaminergic and serotonergic, related proteins and cellular components involved endocannabinoid signaling, such as the cannabinoid (CB) receptor, as well as exogenous compounds, such as phytocannabinoids or other cannabinoids which modulate the activity of endocannabinoid system, can be described as cannabinoidergic. | 1 | Applied and Interdisciplinary Chemistry |
On 14 November 1889 Demarçay married Jeanne Berard (1865–1933) at the Temple du St. Esprit, Paris, in a Protestant wedding. His granddaughter, Joseph de Carayon Talpayrac, was alive in Paris in 2003.
Eugène-Anatole Demarçay died 5 March 1903, at his home at 80 Boulevard Malesherbes, Paris. His brother Jean became executor of his estate, and offered the state of the art equipment from his laboratory to Pierre Curie. Curie eventually arranged for it to be given to rare earths researcher Georges Urbain. | 1 | Applied and Interdisciplinary Chemistry |
Restriction endonucleases, also known as restriction enzymes are enzymes that cleave the sugar-phosphate backbone of the DNA at specific nucleotides sequences that are usually four to six nucleotides long. Studies performed by Horton and colleagues have shown that the mechanism by which these enzymes cleave the DNA involves base flipping as well as bending the DNA and the expansion of the minor groove. In 2006, Horton and colleagues, x-ray crystallography evidence was presented showing that the restriction endonuclease HinP1I utilizes base flipping in order to recognize its target sequence. This enzyme is known to cleave the DNA at the palindromic tetranucleotide sequence G↓CGC. | 1 | Applied and Interdisciplinary Chemistry |
Sodium is a metal where humans have discovered a great deal of its total roles in the body as well as being one of the only two alkali metals that play a major role in the bodily functions. It plays an important role in maintenance of the cell membrane potential and the electrochemical gradient in the body via the sodium-potassium pump and sodium-glucose transport proteins. Sodium also serves a purpose in the nervous system and cell communication as they flood into axons during an action potential to preserve the strength of the signal. It has also been shown that sodium affects immune response both in efficiency and speed. Macrophages have increased proliferation rates at high-salt concentrations and the body uses high-sodium concentrations in isolated regions to generate an heightened immune response which fades after the infection has been dealt with. | 1 | Applied and Interdisciplinary Chemistry |
Boric acid reacts with alcohols to form borate esters, where R is alkyl or aryl. The reaction is typically driven by a dehydrating agent, such as concentrated sulfuric acid:
: + 3 ROH → + 3 | 0 | Theoretical and Fundamental Chemistry |
The EFI's primary deliverable is development and dissemination of an integrated sequence/structure strategy for functional assignment. The EFI now offers access to two high-throughput docking tools, a web tool for comparing protein sequences within entire protein families, and a web tool for composing a genome context inventory based on a protein sequence similarity network. Additionally, as the strategy is developed, data and clones generated by the EFI are made freely available via several online resources. | 1 | Applied and Interdisciplinary Chemistry |
* 1982 Ledlie Prize, Harvard University
* 1988 Wallace P. Rowe Award, National Institute of Allergy and Infectious Diseases
* 1990 Louisa Gross Horwitz Prize (with Don Wiley and Michael Rossmann), Columbia University
* 1990 Harvey Lecturer, The Harvey Society, New York
* 1995 George Ledlie Prize, Harvard University
* 1997 ICN International Prize in Virology
* 2001 Paul Ehrlich and Ludwig Darmstaedter Prize (with Michael Rossmann)
* 2005 Bristol-Myers Squibb Award for Distinguished Achievement in Infectious Diseases Research
* 2006 Gregori Aminoff Prize in Crystallography (with David Stuart)
* 2007 UCSD/Merck Life Sciences Achievement Award
* 2011 William Silen Lifetime Achievement in Mentoring Award, Harvard Medical School
* 2012 Pauling Lectureship, Stanford University
* 2014 Elected as a Foreign Member of the Royal Society of London.
* 2015 The Welch Award in Chemistry
* 2015 Honorary Doctorate in Medicine, University of Milan
* 2018 48th Rosenstiel Award for research on proteins and viruses. | 1 | Applied and Interdisciplinary Chemistry |
The conventional source of "electrophilic fluorine", i.e. the equivalent to the superelectrophile F, is gaseous fluorine, which requires specialised equipment for manipulation. Selectfluor reagent is a salt, the use of which requires only routine procedures. Like F, the salt delivers the equivalent of F. It is mainly used in the synthesis of organofluorine compounds: | 0 | Theoretical and Fundamental Chemistry |
Planetary scientists often classify volatiles with exceptionally low melting points, such as hydrogen and helium, as gases, whereas those volatiles with melting points above about 100 K (–173 °C, –280 °F) are referred to as ices. The terms "gas" and "ice" in this context can apply to compounds that may be solids, liquids or gases. Thus, Jupiter and Saturn are gas giants, and Uranus and Neptune are ice giants, even though the vast majority of the "gas" and "ice" in their interiors is a hot, highly dense fluid that gets denser as the center of the planet is approached. Inside of Jupiter's orbit, cometary activity is driven by the sublimation of water ice. Supervolatiles such as CO and CO have generated cometary activity as far out as . | 0 | Theoretical and Fundamental Chemistry |
As an abstract graph, the Laves graph can be constructed as the maximal abelian covering graph of the complete graph . Being an abelian covering graph of means that the vertices of the Laves graph can be four-colored such that each vertex has neighbors of the other three colors and so that there are color-preserving symmetries taking any vertex to any other vertex with the same color. For the Laves graph in its geometric form with integer coordinates, these symmetries are translations that add even numbers to each coordinate (additionally, the offsets of all three coordinates must be congruent modulo four). When applying two such translations in succession, the net translation is irrespective of their order: they commute with each other, forming an abelian group. The translation vectors of this group form a three-dimensional lattice. Finally, being a maximal abelian covering graph means that there is no other covering graph of involving a higher-dimensional lattice. This construction justifies an alternative name of the Laves graph, the crystal.
A maximal abelian covering graph can be constructed from any finite graph ; applied to , the construction produces the (abstract) Laves graph, but does not give it the same geometric layout. Choose a spanning tree of , let be the number of edges that are not in the spanning tree (in this case, three non-tree edges), and choose a distinct unit vector in for each of these non-tree edges. Then, fix the set of vertices of the covering graph to be the ordered pairs where is a vertex of and is a vector in . For each such pair, and each edge adjacent to in , make an edge from to where is the zero vector if belongs to the spanning tree, and is otherwise the basis vector associated with , and where the plus or minus sign is chosen according to the direction the edge is traversed. The resulting graph is independent of the chosen spanning tree, and the same construction can also be interpreted more abstractly using homology.
Using the same construction, the hexagonal tiling of the plane is the maximal abelian covering graph of the three-edge dipole graph, and the diamond cubic is the maximal abelian covering graph of the four-edge dipole. The -dimensional integer lattice (as a graph with unit-length edges) is the maximal abelian covering graph of a graph with one vertex and self-loops. | 0 | Theoretical and Fundamental Chemistry |
It has been shown that the fundamental thermodynamic relation together with the following three postulates
is sufficient to build the theory of statistical mechanics without the equal a priori probability postulate.
For example, in order to derive the Boltzmann distribution, we assume the probability density of microstate satisfies . The normalization factor (partition function) is therefore
The entropy is therefore given by
If we change the temperature by while keeping the volume of the system constant, the change of entropy satisfies
where
Considering that
we have
From the fundamental thermodynamic relation, we have
Since we kept constant when perturbing , we have . Combining the equations above, we have
Physics laws should be universal, i.e., the above equation must hold for arbitrary systems, and the only way for this to happen is
That is
It has been shown that the third postulate in the above formalism can be replaced by the following:
However, the mathematical derivation will be much more complicated. | 0 | Theoretical and Fundamental Chemistry |
The computation of pair-wise interactions between atoms, which is a prerequisite for the operation of many virtual screening programs, scales by , N is the number of atoms in the system. Due to the quadratic scaling, the computational costs increase quickly. | 1 | Applied and Interdisciplinary Chemistry |
Microcystins—or cyanoginosins—are a class of toxins produced by certain freshwater cyanobacteria, commonly known as blue-green algae. Over 250 different microcystins have been discovered so far, of which microcystin-LR is the most common. Chemically they are cyclic heptapeptides produced through nonribosomal peptide synthases.
Cyanobacteria can produce microcystins in large quantities during algal blooms which then pose a major threat to drinking and irrigation water supplies, and the environment at large. | 1 | Applied and Interdisciplinary Chemistry |
* Translated into Chinese and Japanese.
* Translated into Chinese.
* Translated into Chinese.
* Translated into Chinese | 0 | Theoretical and Fundamental Chemistry |
Cancer is not just one disease but a group of diseases involving abnormal cell growth and metastasis of such cells to other body parts. There are also several types of cancers, each with its own distinctive characteristics and stages that may require different treatment or targeted drug delivery approaches. Yet, even these treatments have their own advantages and disadvantages. Thus, since the discovery of cancer, researchers have constantly been developing new and innovative cancer treatments, including chemotactic drug delivery. For example, and as mentioned earlier in this article, researchers have sought to use microdroplets, protocells, and biological and bio-hybrid drug carriers to deliver drugs to cancer cells in a more effective manner, while reducing unwanted side effects. In fact, the justification for using such systems, guided by chemotaxis, is that the environment inside a tumor has a higher resting temperature, higher peroxide concentration, lower pH, and a lower oxygen concentration than its surrounding tissue. With these unique conditions, researchers can exploit chemotactic drug delivery to target tumor cells directly, avoiding healthy tissues, reducing toxicity, improving drug efficacy, and decreasing drug dosage. | 1 | Applied and Interdisciplinary Chemistry |
Alternative splicing was first observed in 1977. The adenovirus produces five primary transcripts early in its infectious cycle, prior to viral DNA replication, and an additional one later, after DNA replication begins. The early primary transcripts continue to be produced after DNA replication begins. The additional primary transcript produced late in infection is large and comes from 5/6 of the 32kb adenovirus genome. This is much larger than any of the individual adenovirus mRNAs present in infected cells. Researchers found that the primary RNA transcript produced by adenovirus type 2 in the late phase was spliced in many different ways, resulting in mRNAs encoding different viral proteins. In addition, the primary transcript contained multiple polyadenylation sites, giving different 3’ ends for the processed mRNAs.
In 1981, the first example of alternative splicing in a transcript from a normal, endogenous gene was characterized. The gene encoding the thyroid hormone calcitonin was found to be alternatively spliced in mammalian cells. The primary transcript from this gene contains 6 exons; the calcitonin mRNA contains exons 1–4, and terminates after a polyadenylation site in exon 4. Another mRNA is produced from this pre-mRNA by skipping exon 4, and includes exons 1–3, 5, and 6. It encodes a protein known as CGRP (calcitonin gene related peptide). Examples of alternative splicing in immunoglobin gene transcripts in mammals were also observed in the early 1980s.
Since then, many other examples of biologically relevant alternative splicing have been found in eukaryotes. The "record-holder" for alternative splicing is a D. melanogaster gene called Dscam, which could potentially have 38,016 splice variants.
In 2021, it was discovered that the genome of adenovirus type 2, the adenovirus in which alternative splicing was first identified, was able to produce a much greater variety of mRNA than previously thought. By using next generation sequencing technology, researchers were able to update the human adenovirus type 2 transcriptome, and present a mind-boggling 904 unique mRNA, produced by the virus through a complex pattern of alternative splicing. Very few of these splice variants have been shown to be functional, a point that the authors raise in their paper.
::"An outstanding question is what roles the menagerie of novel RNAs play or whether they are spurious molecules generated by an overloaded splicing machinery." | 1 | Applied and Interdisciplinary Chemistry |
This reaction accounts for around half of the transformation of wustite FeO into iron, and removes 30% of the total oxygen supplied, mainly in the form of iron oxide FeO. This mode of wustite reduction is highly endothermic, whereas the reduction of iron oxides by CO is slightly exothermic (+155.15 kJ/mol vs. -17.45 kJ/mol), so it is essential to keep it to a minimum.
This reaction concerns all the iron oxides present in a blast furnace, but also manganese(II) oxides (Mno), silica (SiO), chromium, vanadium and titanium, which are partially reduced in blast furnaces. These chemical reactions are described below:
MnO + C → Mn + CO consuming 282,4 kJ/mol à 1 400 °C (begins above 1,000°C and involves half of the manganese present in the charge)
SiO + 2 C → Si + 2 CO consuming 655,5 kJ/mol (begins above 1 500 °C)
Chromium and vanadium behave like manganese, titanium like silicon. As for the other iron oxides, their direct reduction is of negligible importance. This can be written as:
3 FeO + C → 2 FeO + CO consuming 118,821 kJ/mol
FeO + C → 3 FeO + CO consuming 209,256 kJ/mol
In non-steel blast furnaces, dedicated to the production of ferroalloys, direct reduction is fundamental. For example, for ferronickel production, both direct reduction reactions are used:
NiO + C → Ni + CO above 445 °C
FeO + C → Fe + CO above 800 °C
So, although nickel reduces slightly more easily than iron, it cannot be reduced and cast independently of iron. | 1 | Applied and Interdisciplinary Chemistry |
1,1'-Carbonyldiimidazole (CDI) is an organic compound with the molecular formula (CHN)CO. It is a white crystalline solid. It is often used for the coupling of amino acids for peptide synthesis and as a reagent in organic synthesis. | 0 | Theoretical and Fundamental Chemistry |
Until recently, clinical uses for aquasomes were primarily for targeted drug delivery of general treatment drugs. Additional applications have been since explored, including delivery of antigen, insulin, hemoglobin, and vaccines. | 0 | Theoretical and Fundamental Chemistry |
In mixtures of substances, the bubble point is the saturated liquid temperature, whereas the saturated vapor temperature is called the dew point. Because the bubble and dew lines of a zeotropic mixture's temperature-composition diagram do not intersect, a zeotropic mixture in its liquid phase has a different fraction of a component than the gas phase of the mixture. On a temperature-composition diagram, after a mixture in its liquid phase is heated to the temperature at the bubble (boiling) curve, the fraction of a component in the mixture changes along an isothermal line connecting the dew curve to the boiling curve as the mixture boils. At any given temperature, the composition of the liquid is the composition at the bubble point, whereas the composition of the vapor is the composition at the dew point. Unlike azeotropic mixtures, there is no azeotropic point at any temperature on the diagram where the bubble line and dew lines would intersect. Thus, the composition of the mixture will always change between the bubble and dew point component fractions upon boiling from a liquid to a gas until the mass fraction of a component reaches 1 (i.e. the zeotropic mixture is completely separated into its pure components). As shown in Figure 1, the mole fraction of component 1 decreases from 0.4 to around 0.15 as the liquid mixture boils to the gas phase. | 1 | Applied and Interdisciplinary Chemistry |
Metabolic wastes or excrements are substances left over from metabolic processes (such as cellular respiration) which cannot be used by the organism (they are surplus or toxic), and must therefore be excreted. This includes nitrogen compounds, water, CO, phosphates, sulphates, etc. Animals treat these compounds as excretes. Plants have metabolic pathways which transforms some of them (primarily the oxygen compounds) into useful substances.
All the metabolic wastes are excreted in a form of water solutes through the excretory organs (nephridia, Malpighian tubules, kidneys), with the exception of CO, which is excreted together with the water vapor throughout the lungs. The elimination of these compounds enables the chemical homeostasis of the organism. | 1 | Applied and Interdisciplinary Chemistry |
Amoxicillin is used in the treatment of a number of infections, including acute otitis media, streptococcal pharyngitis, pneumonia, skin infections, urinary tract infections, Salmonella infections, Lyme disease, and chlamydia infections. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, mesoionic carbenes (MICs) are a type of reactive intermediate that are related to N-heterocyclic carbenes (NHCs); thus, MICs are also referred to as abnormal N-heterocyclic carbenes (aNHCs) or remote N-heterocyclic carbenes (rNHCs). Unlike simple NHCs, the canonical resonance structures of these carbenes are mesoionic: an MIC cannot be drawn without adding additional charges to some of the atoms.
A variety of free carbenes can be isolated and are stable at room temperature. Other free carbenes are not stable and are susceptible to intermolecular decomposition pathways. MICs do not dimerize according to Wanzlick equilibrium as do normal NHCs. This results in relaxed steric requirements for mesoionic carbenes as compared to NHCs.
There are several mesoionic carbenes that cannot be generated as free compounds, but can be synthesized as a ligand in a transition metal complex. Most MIC transition metal complexes are less sensitive to air and moisture than phosphine or normal NHC complexes. They are also resistant to oxidation. The robust nature of MIC complexes is due to the ligand’s strong σ-donating ability. They are stronger σ-donors than phosphines, as well as normal N-heterocyclic carbenes due to decreased heteroatom stabilization. The strength of carbene ligands is attributed to the electropositive carbon center that forms strong bonds of a covalent nature with the metal. They have been shown to lower the frequency of CO stretching vibrations in metal complexes and exhibit large trans effects. | 0 | Theoretical and Fundamental Chemistry |
Anaerobic wastewater treatment processes (for example UASB, EGSB) are also widely applied in the treatment of industrial wastewaters and biological sludge. | 1 | Applied and Interdisciplinary Chemistry |
Dehydrogenation of amine-boranes or dehydrocoupling of amine-boranes is a chemical process in main group and organometallic chemistry wherein dihydrogen is released by the coupling of two or more amine-borane adducts. This process is of due to the potential of using amine-boranes for hydrogen storage. | 0 | Theoretical and Fundamental Chemistry |
The theory of Daniel Bernoulli was opposed also by Jean le Rond dAlembert. When generalizing the theory of pendulums of Jacob Bernoulli he discovered a principle of dynamics so simple and general that it reduced the laws of the motions of bodies to that of their equilibrium. He applied this principle to the motion of fluids, and gave a specimen of its application at the end of his Dynamics in 1743. It was more fully developed in his Traité des fluides, published in 1744, in which he gave simple and elegant solutions of problems relating to the equilibrium and motion of fluids. He made use of the same suppositions as Daniel Bernoulli, though his calculus was established in a very different manner. He considered, at every instant, the actual motion of a stratum as composed of a motion which it had in the preceding instant and of a motion which it had lost; and the laws of equilibrium between the motions lost furnished him with equations representing the motion of the fluid. It remained a desideratum to express by equations the motion of a particle of the fluid in any assigned direction. These equations were found by dAlembert from two principles – that a rectangular canal, taken in a mass of fluid in equilibrium, is itself in equilibrium, and that a portion of the fluid, in passing from one place to another, preserves the same volume when the fluid is incompressible, or dilates itself according to a given law when the fluid is elastic. His ingenious method, published in 1752, in his Essai sur la résistance des fluides, was brought to perfection in his Opuscules mathématiques, and was adopted by Leonhard Euler. | 1 | Applied and Interdisciplinary Chemistry |
Some fisheye lenses use a stereographic projection to capture a wide-angle view. Compared to more traditional fisheye lenses which use an equal-area projection, areas close to the edge retain their shape, and straight lines are less curved. However, stereographic fisheye lenses are typically more expensive to manufacture. Image remapping software, such as Panotools, allows the automatic remapping of photos from an equal-area fisheye to a stereographic projection.
The stereographic projection has been used to map spherical panoramas, starting with Horace Bénédict de Saussures in 1779. This results in effects known as a little planet (when the center of projection is the nadir) and a tube' (when the center of projection is the zenith).
The popularity of using stereographic projections to map panoramas over other azimuthal projections is attributed to the shape preservation that results from the conformality of the projection. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, the desulfonation reaction is the hydrolysis of sulfonic acids:
:RCHSOH + HO → RCH + HSO
The reaction applied to aryl and naphthylsulfonic acids. It is the reverse of sulfonation. The temperature of desulfonation correlates with the ease of the sulfonation. | 0 | Theoretical and Fundamental Chemistry |
The Elizabeth River estuary is used for commercial and military use and is one of the most commonly used ports on the East Coast of the USA. From 2015-2019, 11 different conditions were measured in various areas of the Elizabeth River. Throughout the river, there were consistently high levels of nitrogen and phosphorus, along with high levels of other contaminants contributing to the poor quality of life for bottom feeders along the river. The main cause of the pollution to the Elizabeth river has been the military and industrial activities through the 1990s. In 1993, the Elizabeth River Project was started in attempt to do a restoration project on the river. Adopting one of the fish whose species had been largely impacted by the pollution, the Fundulus heteroclitus (Mummichog), the group was able to gain traction and carry out multiple projects and has removed thousands of tons of contaminated sediment. In 2006, Maersk-APM, a major shipping company, wanted to build a new port on the Elizabeth River. As part of the environmental mitigation they worked with the Elizabeth River Project to create the Money Point Project, which was an effort to restore Money Point, which had been deemed biologically depleted due to a black tar like substance called creosote laying at the bottom. Maersk-APM gave $5 million to help get the project up and running. By 2012, they were able to restore over 7 acres of tidal marsh, 3 acres of oyster reef and created a new shoreline. In 2019, the Money Point Project received the "Best Restored Shore" award from the American Shore and Beach Preservation Association. | 0 | Theoretical and Fundamental Chemistry |
According to the United States Environmental Protection Agency, mixed waste (MW) is a waste type defined as follows; "MW contains both hazardous waste (as defined by RCRA and its amendments) and radioactive waste (as defined by AEA and its amendments). It is jointly regulated by NRC or NRCs Agreement States and EPA or EPAs RCRA Authorized States. The fundamental and most comprehensive statutory definition is found in the Federal Facilities Compliance Act (FFCA) where Section 1004(41) was added to RCRA: "The term mixed waste means waste that contains both hazardous waste and source, special nuclear, or byproduct material subject to the Atomic Energy Act of 1954."
Mixed waste is much more expensive to manage and dispose of than waste that is solely radioactive. Waste generators can avoid higher charge back costs by eliminating or minimizing the volume of mixed waste generated. | 0 | Theoretical and Fundamental Chemistry |
One common pair fluorophores for biological use is a cyan fluorescent protein (CFP) – yellow fluorescent protein (YFP) pair. Both are color variants of green fluorescent protein (GFP). Labeling with organic fluorescent dyes requires purification, chemical modification, and intracellular injection of a host protein. GFP variants can be attached to a host protein by genetic engineering which can be more convenient. Additionally, a fusion of CFP and YFP ("tandem-dimer") linked by a protease cleavage sequence can be used as a cleavage assay. | 1 | Applied and Interdisciplinary Chemistry |
In fluid and molecular dynamics, the Batchelor scale, determined by George Batchelor (1959), describes the size of a droplet of fluid that will diffuse in the same time it takes the energy in an eddy of size to dissipate. The Batchelor scale can be determined by:
where:
* is the Kolmogorov length scale.
* is the Schmidt number.
* is the kinematic viscosity.
* is the mass diffusivity.
* is the rate of dissipation of turbulence kinetic energy per unit mass.
Similar to the Kolmogorov microscales – which describe the smallest scales of turbulence before viscosity dominates – the Batchelor scale describes the smallest length scales of fluctuations in scalar concentration that can exist before being dominated by molecular diffusion. It is important to note that for , which is common in many liquid flows, the Batchelor scale is small when compared to the Kolmogorov microscales. This means that scalar transport occurs at scales smaller than the smallest eddy size. | 1 | Applied and Interdisciplinary Chemistry |
Enzymes and receptors are often activated or inhibited by endogenous protein, but can be also inhibited by endogenous or exogenous small molecule inhibitors or activators, which can bind to the active site or on the allosteric site.
An example is the teratogen and carcinogen phorbol 12-myristate 13-acetate, which is a plant terpene that activates protein kinase C, which promotes cancer, making it a useful investigative tool. There is also interest in creating small molecule artificial transcription factors to regulate gene expression, examples include wrenchnolol (a wrench shaped molecule).
Binding of ligand can be characterised using a variety of analytical techniques such as surface plasmon resonance, microscale thermophoresis or dual polarisation interferometry to quantify the reaction affinities and kinetic properties and also any induced conformational changes. | 1 | Applied and Interdisciplinary Chemistry |
In this assay the genome is digested by DpnI, which cuts only methylated GATCs. Double-stranded adapters with a known sequence are then ligated to the ends generated by DpnI. Ligation products are then digested by DpnII. This enzyme cuts non-methylated GATCs, ensuring that only fragments flanked by consecutive methylated GATCs are amplified in the subsequent PCR. A PCR with primers matching the adaptors is then carried out, leading to the specific amplification of genomic fragments flanked by methylated GATCs. | 1 | Applied and Interdisciplinary Chemistry |
The Kharasch addition is an organic reaction and a metal-catalysed free radical addition of CXCl compounds (X = Cl, Br, H) to alkenes. The reaction is used to append trichloromethyl or dichloromethyl groups to terminal alkenes. The method has attracted considerable interest, but it is of limited value because of narrow substrate scope and demanding conditions.
The basic reaction proceeds through the CXCl free radical. Examples of organohalides are carbon tetrachloride and chloroform. Radicals are often generated by abstraction of a halide radical by a metal ion. The addition is an anti-Markovnikov addition. Early work linked the addition to olefin polymerization and is therefore considered a first step into what was to become atom transfer radical polymerization.
An example of Kharasch addition is the synthesis of 1,1,3-trichloro-n-nonane from 1-octene and chloroform using an iron-based catalyst. | 0 | Theoretical and Fundamental Chemistry |
P (systematically araBp) is a promoter found in bacteria and especially as part of plasmids used in laboratory studies. The promoter is a part of the arabinose operon whose name derives from the genes it regulates transcription of: araB, araA, and araD. In E. coli, the P promoter is adjacent to the P promoter (systematically araCp), which transcribes the araC gene in the opposite direction. araC encodes the AraC protein, which regulates activity of both the P and P promoters. The cyclic AMP receptor protein CAP binds between the P and P promoters, stimulating transcription of both when bound by cAMP. | 1 | Applied and Interdisciplinary Chemistry |
There are four commonly used types of applications for nitinol:
; Free recovery
: Nitinol is deformed at a low temperature, remains deformed, and then is heated to recover its original shape through the shape memory effect.
; Constrained recovery
: Similar to free recovery, except that recovery is rigidly prevented and thus a stress is generated.
; Work production
: The alloy is allowed to recover, but to do so it must act against a force (thus doing work).
; Superelasticity
: Nitinol acts as a super spring through the superelastic effect.
Superelastic materials undergo stress-induced transformation and are commonly recognized for their "shape-memory" property. Due to its superelasticity, NiTi wires exhibit "elastocaloric" effect, which is stress-triggered heating/cooling. NiTi wires are currently under research as the most promising material for the technology. The process begins with tensile loading on the wire, which causes fluid (within the wire) to flow to HHEX (hot heat exchanger). Simultaneously, heat will be expelled, which can be used to heat the surrounding. In the reverse process, tensile unloading of the wire leads to fluid flowing to CHEX (cold heat exchanger), causing the NiTi wire to absorb heat from the surrounding. Therefore, the temperature of the surrounding can be decreased (cooled).
Elastocaloric devices are often compared with magnetocaloric devices as new methods of efficient heating/cooling. Elastocaloric device made with NiTi wires has an advantage over magnetocaloric device made with gadolinium due to its specific cooling power (at 2 Hz), which is 70X better (7 kWh/kg vs. 0.1 kWh/kg). However, elastocaloric device made with NiTi wires also have limitations, such as its short fatigue life and dependency on large tensile forces (energy consuming).
In 1989 a survey was conducted in the United States and Canada that involved seven organizations. The survey focused on predicting the future technology, market, and applications of SMAs. The companies predicted the following uses of nitinol in a decreasing order of importance: (1) Couplings, (2) Biomedical and medical, (3) Toys, demonstration, novelty items, (4) Actuators, (5) Heat Engines, (6) Sensors, (7) Cryogenically activated die and bubble memory sockets, and finally (8) lifting devices. | 1 | Applied and Interdisciplinary Chemistry |
There have been some reports of algae operating a biochemical CCM: shuttling metabolites within single cells to concentrate in one area. This process is not fully understood. | 0 | Theoretical and Fundamental Chemistry |
This spot test may be performed by wetting the thallus with K followed immediately by C. The initial application of K breaks down (via hydrolysis) ester bonds in depsides and depsidones. If a phenolic hydroxyl group is released that is meta to another hydroxyl, then a red to orange colour is produced as C is applied. Alectoronic acid and physodic acid produce this colour, while a violet colour results when picrolichenic acid is present. The CK test is a less commonly used variation that reverses the order of the application of chemicals. It is used in special cases when testing for orange colour produced by barbatic acid or diffractaic acid, such as is present in Cladonia floerkeana. Lugol's iodine is another reagent that may be useful in identifying certain species.
Hypogymnia tubulosa is a lichen that is KC+ (orange-pink) because of the depsidone physodic acid; Cetrelia olivetorum is KC+ (pink-red) due to the depsidone alectoronic acid. | 0 | Theoretical and Fundamental Chemistry |
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