text stringlengths 105 4.57k | label int64 0 1 | label_text stringclasses 2
values |
|---|---|---|
Akkermansia is a genus in the phylum Verrucomicrobiota (Bacteria). The genus was first proposed by Derrien et al. (2004), with the type species Akkermansia muciniphila (gen. nov., sp. nov).
Until 2016 the genus contained a single known species, namely A. muciniphila. In 2016, Akkermansia glycaniphila was isolated in the feces of a reticulated python. | 1 | Applied and Interdisciplinary Chemistry |
*Parasiewicz, P. (2008): Application of MesoHABSIM and target fish community approaches for selecting restoration measures of the Quinebaug River, Connecticut and Massachusetts, USA. River Research and Application. 24: 459–471.
*Parasiewicz, P. (2007): The MesoHABSIM Model Revisited. River Research and Application 23 (8):893–903.
*Parasiewicz, P. (2007): Developing a reference habitat template and ecological management scenarios using the MesoHABSIM model. River Research and Application 23 (8): 924–932.
*Parasiewicz P. (2001): MesoHABSIM – a concept for application of instream flow models in river restoration planning. Fisheries 29 (9) p. 6–13.
*Parasiewicz, P., J. Nestler, N.L. Poff and A. Goodwin. (2008) Virtual Reference River: A Model for Scientific Discovery and Reconciliation. 2008. In: M. S. Alonso, I. M. Rubio (ed) Ecological Management: New Research, Nova Science Publishers, Inc. pp. –
*Parasiewicz, P., J. Rogers, J. Legros and M. Wirth. 2007. Assessment and restoration of instream habitat of the Eightmile River in Connecticut – Developing MesoHABSIM model. The National Park Service, Wild and Scenic River Study for the Eightmile River and the Eightmile River Wild and Scenic Study Committee. pp 62. https://web.archive.org/web/20080513142903/http://www.neihp.org/projects/eightmile/index.htm
*Parasiewicz, P. Ehmann, S. B. & P. Corp (2003). Fish habitat assessment on Stony Clove Creek, NY using MesoHABSIM. Report for New York City Department of Environmental Protection and Green County Soil and Water Conservation District and New York State Water Resources Institute. 410pp
*PARASIEWICZ, P. & S. EHMANN: MesoHABSIM application on the Quinebaug River, MA. Managing the flows for biodiversity – A conference on science, policy and conservation action. Colorado State University. Fort Collins, CO 7/30-8/2/2001
*Parasiewicz P. (2001): MesoHABSIM application on the Quinebaug River – the success story. 57th Northeast Fish and Wildlife Conference, Saratoga Springs, NY, 4/22-25/2001.
*PARASIEWICZ, P. & S. EHEMANN (2001): MesoHABSIM application on the Quinebaug River, MA. Managing the flows for biodiversity – A conference on science, policy and conservation action. Colorado State University. Fort Collins, CO 7/30-8/2/2001
*Parasiewicz P. & M. B. Bain (2000): MesoHABSIM or modeling of physical habitat at the scale relevant to river restoration planning. EISORS – Eight International Symposium on Regulated Rivers – Toulouse, France 8/17 – 21 August 2000.
*Parasiewicz P., E. Hammond, J. Xu & D. Ivanov (2006) MesoHABSIM Software | 1 | Applied and Interdisciplinary Chemistry |
RNA silencing is the mechanism that our cells (and cells from all kingdoms) use to fight RNA viruses and transposons (which originate from our own cells as well as from other vehicles). In the case of RNA viruses, these get destroyed immediately by the mechanism cited above. In the case of transposons, it's a little more indirect. Since transposons are located in different parts of the genome, the different transcriptions from the different promoters produce complementary mRNAs that can hybridize with each other. When this happens, the RNAi machinery goes into action, debilitating the mRNAs of the proteins that would be required to move the transposons themselves. | 1 | Applied and Interdisciplinary Chemistry |
Within the topic of gated drug delivery systems, utilizing magnetic forces generally goes hand in hand with temperature stimulus. The phenomenon of magnetic hyperthermia is when superparamagnetic nanoparticles reorient themselves after being exposed to heat generated by an alternating magnetic field (AMF). This concept has been utilized within the drug delivery field wherein gatekeepers are magnetically linked to the scaffolding and upon the application of heat, reorient and allow for the release of drug. This particular method has not been researched as heavily given the drawback that high energy is needed to produce the AMF and uncap the system. However, the Vallet-Regi lab based in Madrid, Spain decided to investigate the possibility of using magnetic gates bound to the scaffold using DNA. The lab generated oligonucleotide-modified superparamagnetic mesoporous silica nanoparticles. They capped the scaffolding using iron oxide nanoparticles that carried complementary DNA to the scaffold's oligonucleotide sequence. What the lab found was that they were able to cap their system due to the DNA coming together and creating a double strand. Upon heating the system using an AMF, the DNA bonds detached, the system became uncapped, and the drug was able to be released. Furthermore, the lab found that this linkage was reversible. As temperature was reduced, the DNA was able to re-link to its complementary half. This study was able to illustrate the possibility of having a drug delivery system that could be remotely triggered and exhibit an on-off switch. | 1 | Applied and Interdisciplinary Chemistry |
The total duration of a substance can be defined as the amount of time it takes for the effects of a substance to completely wear off into sobriety, starting from the moment the substance is first administered. | 1 | Applied and Interdisciplinary Chemistry |
Esters derived from carboxylic acids and alcohols are more polar than ethers but less polar than alcohols. They participate in hydrogen bonds as hydrogen-bond acceptors, but cannot act as hydrogen-bond donors, unlike their parent alcohols. This ability to participate in hydrogen bonding confers some water-solubility. Because of their lack of hydrogen-bond-donating ability, esters do not self-associate. Consequently, esters are more volatile than carboxylic acids of similar molecular weight. | 0 | Theoretical and Fundamental Chemistry |
The yeast mitochondrial code (translation table 3) is a genetic code used by the mitochondrial genome of yeasts, notably Saccharomyces cerevisiae, Candida glabrata, Hansenula saturnus, and Kluyveromyces thermotolerans. | 1 | Applied and Interdisciplinary Chemistry |
* A solution is a homogeneous mixture of two or more substances.
* The particles of solute in a solution cannot be seen by the naked eye. By contrast, particles may be visible in a suspension.
* A solution does not cause beams of light to scatter. By contrast, the particles in a suspension or colloid can cause Tyndall scattering or Rayleigh scattering.
* A solution is stable, and solutes will not precipitate unless added in excess of the mixture's solubility, at which point the excess would remain in its solid phase. A solution containing more dissolved solutes than at equilibrium is referred to as supersaturated.
* The solutes and solvents in a solution cannot be separated by filtration (or mechanically).
* It is composed of only one phase. | 0 | Theoretical and Fundamental Chemistry |
Increased intracellular levels of lactate can act as a signalling hormone, inducing changes in gene expression that will upregulate genes involved in lactate removal. These genes include MCT1, cytochrome c oxidase (COX), and other enzymes involved in the lactate oxidation complex. Additionally, lactate will increase levels of peroxisome proliferator activated receptor gamma coactivator 1-alpha (PGC1-α), suggesting that lactate stimulates mitochondrial biogenesis. | 1 | Applied and Interdisciplinary Chemistry |
A highly efficient gold and palladium combined methodology for the Sonogashira coupling of a wide array of electronically and structurally diverse aryl and heteroaryl halides has been reported.
The orthogonal reactivity of the two metals shows high selectivity and extreme functional group tolerance in Sonogashira coupling. A brief mechanistic study reveals that the gold-acetylide intermediate enters into palladium catalytic cycle at the transmetalation step. | 0 | Theoretical and Fundamental Chemistry |
Most class III adenylyl cyclases are transmembrane proteins with 12 transmembrane segments. The protein is organized with 6 transmembrane segments, then the C1 cytoplasmic domain, then another 6 membrane segments, and then a second cytoplasmic domain called C2. The important parts for function are the N-terminus and the C1 and C2 regions. The C1a and C2a subdomains are homologous and form an intramolecular dimer that forms the active site. In Mycobacterium tuberculosis and many other bacterial cases, the AC-III polypeptide is only half as long, comprising one 6-transmembrane domain followed by a cytoplasmic domain, but two of these form a functional homodimer that resembles the mammalian architecture with two active sites. In non-animal class III ACs, the catalytic cytoplasmic domain is seen associated with other (not necessarily transmembrane) domains.
Class III adenylyl cyclase domains can be further divided into four subfamilies, termed class IIIa through IIId. Animal membrane-bound ACs belong to class IIIa. | 1 | Applied and Interdisciplinary Chemistry |
Rooster tails are caused by constructive interference near and to the wake of objects within a flowing fluid. | 1 | Applied and Interdisciplinary Chemistry |
Among the first representatives of the organometallic bismuth chemistry are a series of iron cyclopentadienyl compounds synthesized by Cullen et al. Characteristic to these is a σ Fe-Bi bond, the iron center bound to 1 cyclopentadienyl and to carbon monoxide ligands only having 17 electron in its coordination sphere in the absence of the Bi bond.
Adding to this, Huttner et al. described the synthesis of mixed Mn-Bi compounds. Most of the synthetic routes use bismuth trichloride as the bismuth metal source. The first proposed route relied on manganese cyclopentadienyl tricarbonyl as the starting material. A better yielding route employed [Cp(CO)Mn(SiPh)] anionic species as the manganese metal source. The synthesized [{Cp(CO)Mn}BiCl] adduct dimerizes in the solid-state. | 0 | Theoretical and Fundamental Chemistry |
Chemically, oxidative stress is associated with increased production of oxidizing species or a significant decrease in the effectiveness of antioxidant defenses, such as glutathione. The effects of oxidative stress depend upon the size of these changes, with a cell being able to overcome small perturbations and regain its original state. However, more severe oxidative stress can cause cell death, and even moderate oxidation can trigger apoptosis, while more intense stresses may cause necrosis.
Production of reactive oxygen species is a particularly destructive aspect of oxidative stress. Such species include free radicals and peroxides. Some of the less reactive of these species (such as superoxide) can be converted by oxidoreduction reactions with transition metals or other redox cycling compounds (including quinones) into more aggressive radical species that can cause extensive cellular damage. Most long-term effects are caused by damage to DNA. DNA damage induced by ionizing radiation is similar to oxidative stress, and these lesions have been implicated in aging and cancer. Biological effects of single-base damage by radiation or oxidation, such as 8-oxoguanine and thymine glycol, have been extensively studied. Recently the focus has shifted to some of the more complex lesions. Tandem DNA lesions are formed at substantial frequency by ionizing radiation and metal-catalyzed HO reactions. Under anoxic conditions, the predominant double-base lesion is a species in which C8 of guanine is linked to the 5-methyl group of an adjacent 3'-thymine (G[8,5- Me]T). Most of these oxygen-derived species are produced by normal aerobic metabolism. Normal cellular defense mechanisms destroy most of these. Repair of oxidative damages to DNA is frequent and ongoing, largely keeping up with newly induced damages. In rat urine, about 74,000 oxidative DNA adducts per cell are excreted daily. There is also a steady state level of oxidative damages in the DNA of a cell. There are about 24,000 oxidative DNA adducts per cell in young rats and 66,000 adducts per cell in old rats. Likewise, any damage to cells is constantly repaired. However, under the severe levels of oxidative stress that cause necrosis, the damage causes ATP depletion, preventing controlled apoptotic death and causing the cell to simply fall apart.
Polyunsaturated fatty acids, particularly arachidonic acid and linoleic acid, are primary targets for free radical and singlet oxygen oxidations. For example, in tissues and cells, the free radical oxidation of linoleic acid produces racemic mixtures of 13-hydroxy-9Z,11E-octadecadienoic acid, 13-hydroxy-9E,11E-octadecadienoic acid, 9-hydroxy-10E,12-E-octadecadienoic acid (9-EE-HODE), and 11-hydroxy-9Z,12-Z-octadecadienoic acid as well as 4-Hydroxynonenal while singlet oxygen attacks linoleic acid to produce (presumed but not yet proven to be racemic mixtures of) 13-hydroxy-9Z,11E-octadecadienoic acid, 9-hydroxy-10E,12-Z-octadecadienoic acid, 10-hydroxy-8E,12Z-octadecadienoic acid, and 12-hydroxy-9Z-13-E-octadecadienoic (see 13-Hydroxyoctadecadienoic acid and 9-Hydroxyoctadecadienoic acid). Similar attacks on arachidonic acid produce a far larger set of products including various isoprostanes, hydroperoxy- and hydroxy- eicosatetraenoates, and 4-hydroxyalkenals. While many of these products are used as markers of oxidative stress, the products derived from linoleic acid appear far more predominant than arachidonic acid products and therefore easier to identify and quantify in, for example, atheromatous plaques. Certain linoleic acid products have also been proposed to be markers for specific types of oxidative stress. For example, the presence of racemic 9-HODE and 9-EE-HODE mixtures reflects free radical oxidation of linoleic acid whereas the presence of racemic 10-hydroxy-8E,12Z-octadecadienoic acid and 12-hydroxy-9Z-13-E-octadecadienoic acid reflects singlet oxygen attack on linoleic acid. In addition to serving as markers, the linoleic and arachidonic acid products can contribute to tissue and/or DNA damage but also act as signals to stimulate pathways which function to combat oxidative stress.
Table adapted from. | 1 | Applied and Interdisciplinary Chemistry |
Succinate is formed in E. coli in several steps.
Phosphoenolpyruvate (PEP), a glycolysis pathway intermediate, is carboxylated by the enzyme PEP carboxylase to form oxaloacetate.
This is followed by the conversion of oxaloacetate to malate by the enzyme malate dehydrogenase. Fumarate hydratase then catalyses the dehydration of malate to produce fumarate.
phosphoenolpyruvate + HCO → oxaloacetate + phosphate
oxaloacetate + NADH + H → malate + NAD
malate → fumarate + HO
The final reaction in the formation of succinate is the reduction of fumarate. It is catalysed by the enzyme fumarate reductase.
fumarate + NADH + H → succinate + NAD
This reduction is an anaerobic respiration reaction in E. coli, as it uses electrons associated with NADH dehydrogenase and the electron transport chain. ATP is generated by using an electrochemical gradient and ATP synthase. This is the only case in the mixed acid fermentation pathway where ATP is not produced via substrate-level phosphorylation.
Vitamin K, also known as menaquinone, is very important for electron transport to fumarate in E. coli. | 1 | Applied and Interdisciplinary Chemistry |
Simple rows or clusters of sharpened sticks (nowadays also known as punji sticks), and small caltrops have been used in anti-infantry warfare since antiquity. However, due to the difficulty of mass-producing them in the pre-modern age, they were rarely used except in the defense of limited areas or chokepoints, especially during sieges, where they were used to help seal breaches. Increasing ease of production still did not prevent these methods from slowly falling out of favor from the late Middle Ages onward.
Caltrops are still sometimes used in modern conflicts, such as during the Korean War, where Chinese troops, often wearing only light shoes, were particularly vulnerable. In modern times, special caltrops are also sometimes used against wheeled vehicles with pneumatic tires. Some South American urban guerrillas such as the Tupamaros and Montoneros, who called them "miguelitos," have used caltrops to avoid pursuit after ambushes. | 1 | Applied and Interdisciplinary Chemistry |
Ammonium can have toxic effort on aquatic organism. Nitrification also takes places in bodies of water, which leads to oxygen depletion. Furthermore, nitrate and ammonium are eutophying (fertilizing) nutrients that can impair water bodies. For these reasons, nitrification and, in many cases, nitrogen removal is necessary.
Two special steps are required for nitrogen removal:
a) Nitrification: Oxidation of ammonium nitrogen and organically bound nitrogen to nitrate. Nitrification is very sensitive to inhibitors and can lead to a pH value in poorly buffered water.
Nitrification takes places in following steps:
this results in:
Nitrification is associated with the production of acid (H+). This puts a strain on the buffering capacity of the water or a pH value shift may occur, which impairs the process.
b) Denitrification: Reduction of nitrate nitrogen to molecular nitrogen, which escapes from the wastewater into the atmosphere. This step can be carried out by microorganism commonly found in sewage treatment plants. However, these only use the nitrate as an electron acceptor if no dissolved oxygen is present.
In order for denitrification to take place in the activated sludge process, an electron source, a reductant, must therefore also be present that can reduce sufficient nitrate to N2. If there is too little substrate in the raw wastewater, this can be added artificially. In addition, denitrification corrects the change in H+ concentration (pH value shift) that occurs during nitrification. This is particularly important for poorly buffered water.
Nitrification and denitrification are in considerable contradiction with regard to the required environmental conditions. Nitrification requires oxygen and CO2. Denitrification only takes place in the absence of dissolved oxygen and with a sufficient supply of oxidizable substances. | 1 | Applied and Interdisciplinary Chemistry |
Inhibition of proton pumps significantly decreases the acidity of the gastrointestinal tract, reducing the symptoms of acid-related diseases. The resulting change in pH decreases survival of the bacteria H.pylori, a major cause of peptic ulcer disease. Once the proton pump inhibitor eradicates this bacteria within the gut, reversing erosive reflux.
Treating heart disease has improved with the use of drugs that inhibit AMPK via dephosphorylation.
In the treatment of diabetes, sulfonylurea drugs are able to stimulate dephosphorylation of the glucose transporter GLUT4, decreasing insulin resistance and increasing and glucose utilization. | 1 | Applied and Interdisciplinary Chemistry |
Examples of photochemical reactions are those between certain arenes and alkenes forming [2+2] and [2+4] cycloaddition adducts. | 0 | Theoretical and Fundamental Chemistry |
Mercury oxide is a highly toxic substance which can be absorbed into the body by inhalation of its aerosol, through the skin and by ingestion. The substance is irritating to the eyes, the skin and the respiratory tract and may have effects on the kidneys, resulting in kidney impairment. In the food chain important to humans, bioaccumulation takes place, specifically in aquatic organisms. The substance is banned as a pesticide in the EU.
Evaporation at 20 °C is negligible. HgO decomposes on exposure to light or on heating above 500 °C. Heating produces highly toxic mercury fumes and oxygen, which increases the fire hazard. Mercury(II) oxide reacts violently with reducing agents, chlorine, hydrogen peroxide, magnesium (when heated), disulfur dichloride and hydrogen trisulfide. Shock-sensitive compounds are formed with metals and elements such as sulfur and phosphorus. | 0 | Theoretical and Fundamental Chemistry |
), gives a system of four non-linear ordinary differential equations that define the rate of change of reactants with time
In this mechanism, the enzyme E is a catalyst, which only facilitates the reaction, so that its total concentration, free plus combined, is a constant (i.e. ). This conservation law can also be observed by adding the first and third equations above.--> | 0 | Theoretical and Fundamental Chemistry |
Temperature is a strong controlling factor on biochemical reaction rates and biological activity. Optimal temperature varies across aquatic organisms as some organisms are more cold-adapted while others prefer warmer habitats. There are rare cases of extreme thermal tolerance in hypersaline antarctic lakes (e.g. Don Juan Pond) or hot springs (e.g. Fly Geyser); however, most lake organisms on Earth reside in temperatures ranging from 0 to 40 °C. Metabolic rates typically scale exponentially with temperature, however, the activation energy for primary productivity and respiration often differ, with photosynthesis having a lower activation energy than aerobic respiration. These differences in activation energies could have implications for net metabolic balance within lake ecosystems as the climate warms. For example, Scharfenberger et al. (2019) show that increasing water temperature resulting from climate change could switch lakes from being net autotrophic to heterotrophic due to differences in activation energy, however, the temperature at which they switch depends on the amount of nutrients available. | 1 | Applied and Interdisciplinary Chemistry |
Glutamatergic means "related to glutamate". A glutamatergic agent (or drug) is a chemical that directly modulates the excitatory amino acid (glutamate/aspartate) system in the body or brain. Examples include excitatory amino acid receptor agonists, excitatory amino acid receptor antagonists, and excitatory amino acid reuptake inhibitors. | 1 | Applied and Interdisciplinary Chemistry |
Planar extension tests are carried out on thin specimens which are constrained from deforming in one direction. For planar extension in the directions with the direction constrained, the principal stretches are . From incompressibility . Hence .
Therefore,
The left Cauchy–Green deformation tensor can then be expressed as
If the directions of the principal stretches are oriented with the coordinate basis vectors, we have
The engineering strain is . The engineering stress is | 0 | Theoretical and Fundamental Chemistry |
The temperature dependent relationship is subtle ().
COO is a rare isotopologue (≈60 ppm [3]).
Therefore, to obtain adequate precision, this approach requires long analyses (≈2–3 hours) and very large and uncontaminated samples.
Clumped isotope analyses assume that measured Δ47 is composed of COO, the most common isotopologue of mass 47. Corrections to account for less common isotopologues of mass 47 (e.g. COO O) are not completely standardized between labs. | 0 | Theoretical and Fundamental Chemistry |
This method consists in exposing the cells to specific signaling pathways modulators and manipulating cell culture conditions (environmental or exogenous) to mimick the natural sequence of developmental decisions to produce a given cell type/tissue. A drawback of this approach is the necessity to have a good understanding of how the
cell type of interest is formed. | 1 | Applied and Interdisciplinary Chemistry |
In physics, a "coffee ring" is a pattern left by a puddle of particle-laden liquid after it evaporates. The phenomenon is named for the characteristic ring-like deposit along the perimeter of a spill of coffee. It is also commonly seen after spilling red wine. The mechanism behind the formation of these and similar rings is known as the coffee ring effect or in some instances, the coffee stain effect, or simply ring stain. | 0 | Theoretical and Fundamental Chemistry |
Around the 1960s, safety concerns began to limit the range of materials and experiments available in chemistry sets. In the United States, the Federal Hazardous Substances Labeling Act of 1960, the Toy Safety Act of 1969, the Consumer Product Safety Commission, established in 1972, and the Toxic Substances Control Act of 1976 all introduced new levels of regulation, which led to the decline of chemistry sets' popularity during the 1970s and 1980s. The A. C. Gilbert Company went out of business in 1967, and the Porter Chemical Company went out of business in 1984.
Modern chemistry sets, with a few exceptions, tend to include a more restricted range of chemicals and simplified instructions. Many chemistry kits are single use, containing only the types and amounts of chemicals for a specific application. Several authors note from the 1980s on, concerns about illegal drug production, terrorism, and legal liability have led to chemistry sets becoming increasingly bland and unexciting.
Nonetheless, a GCSE equipment set was produced, offering students better equipment, and there is a more up-market range of sets available from Thames & Kosmos such as the C3000 Kit. | 1 | Applied and Interdisciplinary Chemistry |
In 2011, the academy received a university status.
The successes of the university in education, research and innovation, the recognition of the scientific and pedagogical schools, its international status and worldwide fame are undoubtedly merit in the first professors, assistant professors, lecturers, and they have created in the walls of the university unique creative scientific and educational environment. Friendly and supportive atmosphere of the business and human interaction with the students and teachers together form the necessary conditions for the development of the individual, focused, motivated professional growth. | 1 | Applied and Interdisciplinary Chemistry |
Block or graft copolymers are commonly used as compatibilizing agents. The copolymer used is made of the two components in the immiscible blend. The respective portions of the copolymer are able to interact with the two phases of the blend to make the phase morphology more stable. The increased stability is caused by reducing the size of the phase-separated particles in the blend. The size reduction comes from the lower interfacial tension, due to accumulating block copolymers at the many interfaces between the two copolymers. This helps the immiscible blends break up into smaller particles in the melt phase. In turn, these phase separated particles will not be as inclined to consolidate and grow because the interfacial tension is now much lower. This stabilizes the polymer blend to a usable product.
An example of this are Ethylene/propylene copolymers. They are able to act as good compatibilizing agents for blends of polypropylene and low density polyethylene. In this specific application, longer ethylene sequences are preferred in the copolymer. This is because cocrystallization also factors into this case, and the longer ethylene sequences will retain some residual crystallinity. | 0 | Theoretical and Fundamental Chemistry |
Rivaroxaban, apixaban, edoxaban and betrixaban are already on the market. As of October 2016, several new direct Xa inhibitors have entered clinical trials. These are letaxaban from Takeda and eribaxaban from Pfizer. | 1 | Applied and Interdisciplinary Chemistry |
Bacteriophage Φ6, is a member of the Cystoviridae family. It infects Pseudomonas bacteria (typically plant-pathogenic P. syringae). It has a three-part, segmented, double-stranded RNA genome, totalling ~13.5 kb in length. Φ6 and its relatives have a lipid membrane around their nucleocapsid, a rare trait among bacteriophages. It is a lytic phage, though under certain circumstances has been observed to display a delay in lysis which may be described as a "carrier state". | 1 | Applied and Interdisciplinary Chemistry |
Nitrogen isotopes indicate the trophic level position of organisms (reflective of the time the tissue samples were taken). There is a larger enrichment component with δN because its retention is higher than that of N. This can be seen by analyzing the waste of organisms. Cattle urine has shown that there is a depletion of N relative to the diet. As organisms eat each other, the N isotopes are transferred to the predators. Thus, organisms higher in the trophic pyramid have accumulated higher levels of N ( and higher δN values) relative to their prey and others before them in the food web. Numerous studies on marine ecosystems have shown that on average there is a 3.2‰ enrichment of N vs. diet between different trophic level species in ecosystems. In the Baltic sea, Hansson et al. (1997) found that when analyzing a variety of creatures (such as particulate organic matter (phytoplankton), zooplankton, mysids, sprat, smelt and herring,) there was an apparent fractionation of 2.4‰ between consumers and their apparent prey.
In addition to trophic positioning of organisms, δN values have become commonly used in distinguishing between land derived and natural sources of nutrients. As water travels from septic tanks to aquifers, the nitrogen rich water is delivered into coastal areas. Waste-water nitrate has higher concentrations of N than the nitrate that is found in natural soils in near shore zones. For bacteria, it is more convenient for them to uptake N as opposed to N because it is a lighter element and easier to metabolize. Thus, due to bacteria's preference when performing biogeochemical processes such as denitrification and volatilization of ammonia, N is removed from the water at a faster rate than N, resulting in more N entering the aquifer. N is roughly 10-20‰ as opposed to the natural N values of 2-8‰. The inorganic nitrogen that is emitted from septic tanks and other human-derived sewage is usually in the form of . Once the nitrogen enters the estuaries via groundwater, it is thought that because there is more N entering, that there will also be more N in the inorganic nitrogen pool delivered and that it is picked up more by producers taking up N. Even though N is easier to take up, because there is much more N, there will still be higher amounts assimilated than normal. These levels of δN can be examined in creatures that live in the area and are non migratory (such as macrophytes, clams and even some fish). This method of identifying high levels of nitrogen input is becoming a more and more popular method in attempting to monitor nutrient input into estuaries and coastal ecosystems. Environmental managers have become more and more concerned about measuring anthropogenic nutrient inputs into estuaries because excess in nutrients can lead to eutrophication and hypoxic events, eliminating organisms from an area entirely. | 0 | Theoretical and Fundamental Chemistry |
In reptiles, amphibia and non-primate mammals pheromones are detected by regular olfactory membranes, and also by the vomeronasal organ (VNO), or Jacobson's organ, which lies at the base of the nasal septum between the nose and mouth and is the first stage of the accessory olfactory system. While the VNO is present in most amphibia, reptiles, and non-primate mammals, it is absent in birds, adult catarrhine monkeys (downward facing nostrils, as opposed to sideways), and apes. An active role for the human VNO in the detection of pheromones is disputed; while it is clearly present in the fetus it appears to be atrophied, shrunk or completely absent in adults. Three distinct families of vomeronasal receptors, putatively pheromone sensing, have been identified in the vomeronasal organ named V1Rs, V2Rs, and V3Rs. All are G protein-coupled receptors but are only distantly related to the receptors of the main olfactory system, highlighting their different role. | 1 | Applied and Interdisciplinary Chemistry |
12-Phosphotungstic acid, the compound James F. Keggin used to determine the structure, can be purchased commercially. Other compounds that contain the α-Keggin anion such as silicotungstic acid and phosphomolybdic acid are also commercially available at Aldrich Chemicals, Fisher Chemicals, Alfa Aesar, VWR Chemical, American Elements, and others. | 0 | Theoretical and Fundamental Chemistry |
Polanyis deliverance' (as he described it) from these rejections and criticism of his model occurred in 1930, when Fritz London proposed a new theory of cohesive forces founded on the theories of quantum mechanics on the polarization of electronic systems. Polanyi wrote to London asking,
After computational analysis, a joint publication was made between Polanyi and London claiming that the adsorptive forces behaved similarly to the model that Polanyi had proposed. | 0 | Theoretical and Fundamental Chemistry |
There are special rules for certain rare diseases ("orphan diseases") in several major drug regulatory territories. For example, diseases involving fewer than 200,000 patients in the United States, or larger populations in certain circumstances are subject to the Orphan Drug Act. Because medical research and development of drugs to treat such diseases is financially disadvantageous, companies that do so are rewarded with tax reductions, fee waivers, and market exclusivity on that drug for a limited time (seven years), regardless of whether the drug is protected by patents. | 1 | Applied and Interdisciplinary Chemistry |
The main improvements to immunofluorescence lie in the development of fluorophores and fluorescent microscopes. Fluorophores can be structurally modified to improve brightness and photostability, while preserving spectral properties and cell permeability.
Super-resolution fluorescence microscopy methods can produce images with a higher resolution than those microscopes imposed by the diffraction limit. This enables the determination of structural details within the cell. Super-resolution in fluorescence, more specifically, refers to the ability of a microscope to prevent the simultaneous fluorescence of adjacent spectrally identical fluorophores (spectral overlap). Some of the recently developed super-resolution fluorescent microscope methods include stimulated emission depletion (STED) microscopy, saturated structured-illumination microscopy (SSIM), fluorescence photoactivation localization microscopy (FPALM), and stochastic optical reconstruction microscopy (STORM). | 1 | Applied and Interdisciplinary Chemistry |
Pervious concrete was first used in the 1800s in Europe as pavement surfacing and load bearing walls. Cost efficiency was the main motive due to a decreased amount of cement. It became popular again in the 1920s for two storey homes in Scotland and England. It became increasingly viable in Europe after WWII due to the scarcity of cement. It did not become as popular in the US until the 1970s. In India it became popular in 2000. | 1 | Applied and Interdisciplinary Chemistry |
Gaseous scintillators consist of nitrogen and the noble gases helium, argon, krypton, and xenon, with helium and xenon receiving the most attention. The scintillation process is due to the de-excitation of single atoms excited by the passage of an incoming particle. This de-excitation is very rapid (~1 ns), so the detector response is quite fast. Coating the walls of the container with a wavelength shifter is generally necessary as those gases typically emit in the ultraviolet and PMTs respond better to the visible blue-green region. In nuclear physics, gaseous detectors have been used to detect fission fragments or heavy charged particles. | 0 | Theoretical and Fundamental Chemistry |
Prisms have higher dispersion in the UV region. Prism monochromators are favored in some instruments that are principally designed to work in the far UV region. Most monochromators use gratings, however. Some monochromators have several gratings that can be selected for use in different spectral regions. A double monochromator made by placing a prism and a grating monochromator in series typically does not need additional bandpass filters to isolate a single grating order. | 0 | Theoretical and Fundamental Chemistry |
N-Heterocyclic carbenes (NHCs) are particularly common carbene ligands. They are popular because they are more readily prepared than Schrock and Fischer carbenes. In fact, many NHCs are isolated as the free ligand, since they are persistent carbenes. Being strongly stabilized by π-donating substituents, NHCs are powerful σ-donors but π-bonding with the metal is weak. For this reason, the bond between the carbon and the metal center is often represented by a single dative bond, whereas Fischer and Schrock carbenes are usually depicted with double bonds to metal. Continuing with this analogy, NHCs are often compared with trialkylphosphine ligands. Like phosphines, NHCs serve as spectator ligands that influence catalysis through a combination of electronic and steric effects, but they do not directly bind substrates. | 0 | Theoretical and Fundamental Chemistry |
Activation of nucleoside and nucleotide reverse-transcriptase inhibitors is primarily dependent on cellular entry by passive diffusion or carrier-mediated transport. NRTIs are highly hydrophilic and have limited membrane permeability and therefore this step is very important.
NRTIs are analogues of endogenous 2´-deoxy-nucleoside and nucleotide. They are inactive in their parent forms and require successive phosphorylation.
Nucleosides must be triphosphorylated, while nucleotides, which possess one phosphonated group, must be diphosphorylated. This stepwise activation process occurs inside the cell and is mediated by a coordinated series of enzymes. The first, and often rate limiting, phosphorylation step (for nucleoside analogues) are most commonly catalyzed by deoxynucleoside kinases. Addition of the second phosphate group to nucleoside monophosphate analogues is completed by the nucleoside monophosphate kinases (NMP kinases). A variety of enzymes are able to catalyze the final phosphorylation step for NRTIs, including nucleoside diphosphate kinase (NDP kinase), phosphoglycerate kinase, pyruvate kinase and creatine kinase, resulting in formation of respective antivirally active triphosphate analogues.
In their respective triphosphate forms, NRTIs and the only NtRTI available compete with their corresponding endogenous deoxynucleotide triphosphate (dNTPs) for incorporation into the nascent DNA chain (see figure 1). Unlike dNTPs substrate, NRTIs lack a 3´-hydroxyl group on the deoxyribose moiety. Once incorporated into the DNA chain, the absence of a 3´-hydroxyl group, which normally forms the 5´- to 3´- phosphoester bond with the next nucleic acid, blocks further extension of the DNA by RT, and they act as chain terminators. | 1 | Applied and Interdisciplinary Chemistry |
Trap cropping uses alternative plants to attract pests away from a main crop. For example, nasturtium (Tropaeolum majus) is a food plant of some caterpillars which feed primarily on members of the cabbage family (brassicas); some gardeners claim that planting them around brassicas protects the food crops from damage, as eggs of the pests are preferentially laid on the nasturtium. However, while many trap crops divert pests from focal crops in small scale greenhouse, garden and field experiments, only a small portion of these plants reduce pest damage at larger commercial scales. | 1 | Applied and Interdisciplinary Chemistry |
Yuan Tseh Lee (; born 19 November 1936) is a Taiwanese chemist. He is a Professor Emeritus at the University of California, Berkeley. He was the first Taiwanese Nobel Prize laureate who, along with the Hungarian-Canadian John C. Polanyi and American Dudley R. Herschbach, won the Nobel Prize in Chemistry in 1986 "for their contributions to the dynamics of chemical elementary processes".
Lee's particular physical chemistry work was related to the use of advanced chemical kinetics techniques to investigate and manipulate the behavior of chemical reactions using crossed molecular beams. From 15 January 1994 to 19 October 2006, Lee served as the President of the Academia Sinica of Taiwan. In 2011, he was elected head of the International Council for Science. | 0 | Theoretical and Fundamental Chemistry |
In general, increased levels of fecal coliforms provide a warning of failure in water treatment, a break in the integrity of the distribution system, possible contamination with pathogens. When levels are high there may be an elevated risk of waterborne gastroenteritis. Tests for the bacteria are cheap, reliable and rapid (1-day incubation). | 0 | Theoretical and Fundamental Chemistry |
Consider the generic equation for beta decay
The value for this decay is
where is the mass of the nucleus of the atom, is the mass of the electron, and is the mass of the electron antineutrino. In other words, the total energy released is the mass energy of the initial nucleus, minus the mass energy of the final nucleus, electron, and antineutrino. The mass of the nucleus is related to the standard atomic mass by
That is, the total atomic mass is the mass of the nucleus, plus the mass of the electrons, minus the sum of all electron binding energies for the atom. This equation is rearranged to find , and is found similarly. Substituting these nuclear masses into the -value equation, while neglecting the nearly-zero antineutrino mass and the difference in electron binding energies, which is very small for high- atoms, we have
This energy is carried away as kinetic energy by the electron and antineutrino.
Because the reaction will proceed only when the value is positive, β decay can occur when the mass of atom is greater than the mass of atom . | 0 | Theoretical and Fundamental Chemistry |
Agmatine is present in small amounts in plant-, animal-, and fish-derived foodstuff and gut microbial production is an added source for agmatine. Oral agmatine is absorbed from the gastrointestinal tract and readily distributed throughout the body. Rapid elimination from non-brain organs of ingested (un-metabolized) agmatine by the kidneys has indicated a blood half life of about 2 hours. | 1 | Applied and Interdisciplinary Chemistry |
Jay Quade (born December 13, 1955) is an American geochemist and geologist. He is known for pioneering research applying geochemical isotopic methods for investigations of tectonics, global climate change, and the paleontology of Darwinian evolution. | 0 | Theoretical and Fundamental Chemistry |
The two ends of an actin filament differ in their dynamics of subunit addition and removal. They are thus referred to as the plus end (with faster dynamics, also called barbed end) and the minus end (with slower dynamics, also called pointed end). This difference results from the fact that subunit addition at the minus end requires a conformational change of the subunits. Note that each subunit is structurally polar and has to attach to the filament in a particular orientation. As a consequence, the actin filaments are also structurally polar.
Elongating the actin filament occurs when free-actin (G-actin) bound to ATP associates with the filament. Under physiological conditions, it is easier for G-actin to associate at the positive end of the filament, and harder at the negative end. However, it is possible to elongate the filament at either end. Association of G-actin into F-actin is regulated by the critical concentration outlined below. Actin polymerization can further be regulated by profilin and cofilin. Cofilin functions by binding to ADP-actin on the negative end of the filament, destabilizing it, and inducing depolymerization. Profilin induces ATP binding to G-actin so that it can be incorporated onto the positive end of the filament. | 1 | Applied and Interdisciplinary Chemistry |
Hassan Naim received his Ph.D. degree in biochemistry from the University of Bern, Switzerland. Following appointments at the Biochemistry Department, University of Lausanne (membrane transport in T cells) and the University Children’s Hospital Bern (structure and function of brush border membrane proteins) he moved in 1989 to the Biochemistry Department, University of Texas Southwestern Medical Center at Dallas, USA to continue his work on structure-function relationships of brush border proteins. In 1991 he was recruited as a group leader and Faculty member at the University of Düsseldorf, Germany. In 1997 he was appointed as a Professor and Chair of the Department of Biochemistry at the University of Veterinary Medicine in Hannover, Germany. | 1 | Applied and Interdisciplinary Chemistry |
Velocimetry is the measurement of the velocity of fluids. This is a task often taken for granted, and involves far more complex processes than one might expect. It is often used to solve fluid dynamics problems, study fluid networks, in industrial and process control applications, as well as in the creation of new kinds of fluid flow sensors. Methods of velocimetry include particle image velocimetry and particle tracking velocimetry, Molecular tagging velocimetry, laser-based interferometry, ultrasonic Doppler methods, Doppler sensors, and new signal processing methodologies.
In general, velocity measurements are made in the Lagrangian or Eulerian frames of reference (see Lagrangian and Eulerian coordinates). Lagrangian methods assign a velocity to a volume of fluid at a given time, whereas Eulerian methods assign a velocity to a volume of the measurement domain at a given time. A classic example of the distinction is particle tracking velocimetry, where the idea is to find the velocity of individual flow tracer particles (Lagrangian) and particle image velocimetry, where the objective is to find the average velocity within a sub-region of the field of view (Eulerian). | 1 | Applied and Interdisciplinary Chemistry |
Crystallinity refers to the degree of structural order in a solid. In a crystal, the atoms or molecules are arranged in a regular, periodic manner. The degree of crystallinity has a big influence on hardness, density, transparency and diffusion. In an ideal gas, the relative positions of the atoms or molecules are completely random. Amorphous materials, such as liquids and glasses, represent an intermediate case, having order over short distances (a few atomic or molecular spacings) but not over longer distances.
Many materials, such as glass-ceramics and some polymers, can be prepared in such a way as to produce a mixture of crystalline and amorphous regions. In such cases, crystallinity is usually specified as a percentage of the volume of the material that is crystalline. Even within materials that are completely crystalline, however, the degree of structural perfection can vary. For instance, most metallic alloys are crystalline, but they usually comprise many independent crystalline regions (grains or crystallites) in various orientations separated by grain boundaries; furthermore, they contain other crystallographic defects (notably dislocations) that reduce the degree of structural perfection. The most highly perfect crystals are silicon boules produced for semiconductor electronics; these are large single crystals (so they have no grain boundaries), are nearly free of dislocations, and have precisely controlled concentrations of defect atoms.
Crystallinity can be measured using x-ray crystallography, but calorimetric techniques are also commonly used. | 0 | Theoretical and Fundamental Chemistry |
Barring gear (or "turning gear") is the mechanism provided to rotate the turbine generator shaft at a very low speed after unit stoppages. Once the unit is "tripped" (i.e., the steam inlet valve is closed), the turbine coasts down towards standstill. When it stops completely, there is a tendency for the turbine shaft to deflect or bend if allowed to remain in one position too long. This is because the heat inside the turbine casing tends to concentrate in the top half of the casing, making the top half portion of the shaft hotter than the bottom half. The shaft therefore could warp or bend by millionths of inches.
This small shaft deflection, only detectable by eccentricity meters, would be enough to cause damaging vibrations to the entire steam turbine generator unit when it is restarted. The shaft is therefore automatically turned at low speed (about one percent rated speed) by the barring gear until it has cooled sufficiently to permit a complete stop. | 1 | Applied and Interdisciplinary Chemistry |
For many surface/adsorbate configurations, surface energy data and experimental observations are unavailable. As wetting interactions are of great importance in various applications, it is often desired to predict and compare the wetting behavior of various material surfaces with particular crystallographic orientations, with relation to water or other adsorbates. This can be done from an atomistic perspective with tools including molecular dynamics and density functional theory. In the theoretical prediction of wetting by ab initio approaches such as DFT, ice is commonly substituted for water. This is because DFT calculations are generally conducted assuming conditions of zero thermal movement of atoms, essentially meaning the simulation is conducted at absolute zero. This simplification nevertheless yields results that are relevant for the adsorption of water under realistic conditions and the use of ice for the theoretical simulation of wetting is commonplace. | 0 | Theoretical and Fundamental Chemistry |
The Sørensen formol titration(SFT) invented by S. P. L. Sørensen in 1907 is a titration of an amino acid with potassium hydroxide in the presence of formaldehyde. It is used in the determination of protein content in samples.
If instead of an amino acid an ammonium salt is used the reaction product with formaldehyde is hexamethylenetetramine:
The liberated hydrochloric acid is then titrated with the base and the amount of ammonium salt used can be determined.
With an amino acid the formaldehyde reacts with the amino group to form a methylene amino (R-N=CH) group. The remaining acidic carboxylic acid group can then again be titrated with base. | 1 | Applied and Interdisciplinary Chemistry |
As thiolated polymers exhibit biocompatibility, cellular mimicking properties and efficiently support proliferation and differentiation of various cell types, they are used as scaffolds for tissue engineering. Furthermore thiolated polymers such as thiolated hyaluronic acid and thiolated chitosan were shown to exhibit wound healing properties. | 0 | Theoretical and Fundamental Chemistry |
It is known from thermodynamics that conjugated quantities scale in a different manner. Two classes can be distinguished: intensive quantities as temperature T, pressure P and amount of substance N or extensive quantities as entropy S, volume V and chemical potential μ. Extensive quantities scale with system size, whereas the intensive quantities do not. The quantity pressure, for example, is defined as the (differential) quotient of two extensive variables: p=dE/dV (energy E and volume V) and therefore scale independent as the same scaling factors appearing in the nominator as well as the denominator cancel. In microsystems the problem rises that the extremely small volumes are difficult to be controlled. The reason is the predominance of surface effects as surface charges, van-der-Waals forces and entropic effects (e.g. dewetting due to rough surfaces: the restriction in degrees of freedom of molecules penetrating such a surface is entropically more expensive than staying in bulk). Furthermore, the microsystem has to be controlled from a macroscopic human scale. | 1 | Applied and Interdisciplinary Chemistry |
Some activists and scholars have, between 2002 and 2008, questioned the merits of Indian rivers inter-link projects, and questioned if appropriate study of benefits and risks to environment and ecology has been completed so far. Bandyopadhyay et al. claim there are knowledge gaps between the claimed benefits and potential threats from environment and ecological impact. They also question whether the inter-linking project will deliver the benefits of flood control. Vaidyanathan claimed, in 2003, that there are uncertainty and unknowns about operations, how much water will be shifted and when, whether this may cause water logging, salinity/alkalinity and the resulting desertification in the command areas of these projects. Other scholars have asked whether there are other technologies to address the cycle of droughts and flood havoc's, with less uncertainties about potential environmental and ecological impact. Rivers may change their courses every (approximately) 100 years, so the interlinking may not be useful after 100 years. Interlinking may also lead to deforestation and cause ecological imbalances, widely expected to alter fish communities. A study concluded that the project could reduce rainfall and change rainfall patterns in the region. | 1 | Applied and Interdisciplinary Chemistry |
Hans Max Jahn (4 July 1853 – 7 August 1906) was a German physical chemist who worked on thermochemistry and electrochemistry. As an experimental chemist he identified problems in the contemporary theory of electrolyte conductivity and examined the thermodynamic validity of the Gibbs-Helmholtz equation.
Jahn was born in Küstrin (now in Poland) and was educated at the Universities of Berlin and Heidelberg in chemistry and mathematics. His early influences included A. W. von Hofmann whom he assisted as a student, Robert Bunsen, G. Kirchhoff and the mathematician L. Kronecker. After receiving a doctorate in 1875 for work in organic chemistry he became an assistant to Anastassios Christomanos at Athens. In 1877 he moved to Vienna, working under Ernst Ludwig (1842–1915) and in 1884 he moved to Graz. From 1899 he taught at the agricultural school and university in Berlin. Jahn worked with Walther Nernst and one of his experimental result in 1900 was that there was an increased conductivity with increase in concentration of certain electrolytes. This went against the theory that Svante August Arrhenius has proposed and resulted in a major debate.
Jahn married Sophie von Sichrovsky in 1883. Jahn was a keen violinist but suffered from deteriorating hearing. He died in 1906 following complications after an appendictomy. | 0 | Theoretical and Fundamental Chemistry |
It is on the World Health Organization's List of Essential Medicines. It is available as a volatile liquid, at 30, 50, 200, and 250 ml per container but in many developed nations is not available having been displaced by newer agents.
It is the only inhalational anesthetic containing bromine, which makes it radiopaque. It is colorless and pleasant-smelling, but unstable in light. It is packaged in dark-colored bottles and contains 0.01% thymol as a stabilizing agent. | 0 | Theoretical and Fundamental Chemistry |
The split gene theory is a theory of the origin of introns, long non-coding sequences in eukaryotic genes between the exons. The theory holds that the randomness of primordial DNA sequences would only permit small (< 600bp) open reading frames (ORFs), and that important intron structures and regulatory sequences are derived from stop codons. In this introns-first framework, the spliceosomal machinery and the nucleus evolved due to the necessity to join these ORFs (now "exons") into larger proteins, and that intronless bacterial genes are less ancestral than the split eukaryotic genes. The theory originated with Periannan Senapathy.
The theory provides solutions to key questions concerning the split gene architecture, including split eukaryotic genes, exons, introns, splice junctions, and branch points, based on the origin of split genes from random genetic sequences. It also provides possible solutions to the origin of the spliceosomal machinery, the nuclear boundary and the eukaryotic cell.
This theory led to the Shapiro–Senapathy algorithm, which provides the methodology for detecting the splice sites, exons and split genes in eukaryotic DNA, and which is the main method for detecting splice site mutations in genes that cause hundreds of diseases.
Split gene theory requires a separate origin of all eukaryotic species. It also requires that the simpler prokaryotes evolved from eukaryotes. This completely contradicts the scientific consensus about the formation of eukaryotic cells by endosymbiosis of bacteria. In 1994, Senapathy wrote a book about this aspect of his theory - The Independent Birth of Organisms. It proposed that all eukaryotic genomes were formed separately in a primordial pool. Dutch biologist Gert Korthoff criticized the theory by posing various problems that cannot be explained by a theory of independent origins. He pointed out that various eukaryotes need nurturing and called this the boot problem, in that even the initial eukaryote needed parental care. Korthoff notes that a large fraction of eukaryotes are parasites. Senapathys theory would require a coincidence to explain their existence. Senapathys theory cannot explain the strong evidence for common descent (homology, universal genetic code, embryology, fossil record.) | 1 | Applied and Interdisciplinary Chemistry |
Glide reflections, denoted by G, where c is a point in the plane, v is a unit vector in R, and w is non-null a vector perpendicular to v are a combination of a reflection in the line described by c and v, followed by a translation along w. That is,
or in other words,
(It is also true that
that is, we obtain the same result if we do the translation and the reflection in the opposite order.)
Alternatively we multiply by an orthogonal matrix with determinant −1 (corresponding to a reflection in a line through the origin), followed by a translation. This is a glide reflection, except in the special case that the translation is perpendicular to the line of reflection, in which case the combination is itself just a reflection in a parallel line.
The identity isometry, defined by I(p) = p for all points p is a special case of a translation, and also a special case of a rotation. It is the only isometry which belongs to more than one of the types described above.
In all cases we multiply the position vector by an orthogonal matrix and add a vector; if the determinant is 1 we have a rotation, a translation, or the identity, and if it is −1 we have a glide reflection or a reflection.
A "random" isometry, like taking a sheet of paper from a table and randomly laying it back, "almost surely" is a rotation or a glide reflection (they have three degrees of freedom). This applies regardless of the details of the probability distribution, as long as θ and the direction of the added vector are independent and uniformly distributed and the length of the added vector has a continuous distribution. A pure translation and a pure reflection are special cases with only two degrees of freedom, while the identity is even more special, with no degrees of freedom. | 0 | Theoretical and Fundamental Chemistry |
Temocapril (also known as temocaprilum [Latin]; brand name Acecol) is an ACE inhibitor. It was not approved for use in the US.
It is administered as inactive prodrug, then converted to its active metabolite, temocaprilat.
It was patented in 1984 and approved for medical use in 1994. | 0 | Theoretical and Fundamental Chemistry |
Humans need a certain amount of certain metals to function normally. Most metals are used as cofactors or prosthetics in enzymes, catalyzing specific reactions and serving essential roles. The essential metals for humans are: Sodium, Potassium, Magnesium, Copper, Vanadium, Chromium, Manganese, Iron, Cobalt, Nickel, Zinc, Molybdenum, and Cadmium. Anemia symptoms are caused by lack of a certain essential metal. Anemia can be associated with malnourishment or faulty metabolic processes, usually caused by a genetic defect.
Examples of specific types of metal anemia include:
* Iron: common simple anemia (iron deficiency), results in the loss of functional heme proteins (hemoglobin, myoglobin, etc.), which are responsible for oxygen transport or utilization of oxygen. Pernicious anemia comes from a lack of vitamin B-12 (which contains a cobalt complex called cobalamin), which then in turn interferes with the function of red blood cells.
* Zinc: Zinc anemia is mostly due to diet can result in growth retardation.
* Copper: Copper anemia in infants results from infants with a poor diet and can cause heart disease. | 1 | Applied and Interdisciplinary Chemistry |
Atmospheric pressure (AP) matrix-assisted laser desorption/ionization (MALDI) is an ionization technique (ion source) that in contrast to vacuum MALDI operates at normal atmospheric environment. The main difference between vacuum MALDI and AP-MALDI is the pressure in which the ions are created. In vacuum MALDI, ions are typically produced at 10 mTorr or less while in AP-MALDI ions are formed in atmospheric pressure. In the past, the main disadvantage of the AP-MALDI technique compared to the conventional vacuum MALDI has been its limited sensitivity; however, ions can be transferred into the mass spectrometer with high efficiency and attomole detection limits have been reported. AP-MALDI is used in mass spectrometry (MS) in a variety of applications ranging from proteomics to drug discovery. Popular topics that are addressed by AP-MALDI mass spectrometry include: proteomics; mass analysis of DNA, RNA, PNA, lipids, oligosaccharides, phosphopeptides, bacteria, small molecules and synthetic polymers, similar applications as available also for vacuum MALDI instruments. The AP-MALDI ion source is easily coupled to an ion trap mass spectrometer or any other MS system equipped with electrospray ionization (ESI) or nanoESI source.
MALDI with ionization at reduced pressure is known to produce mainly singly-charged ions (see "Ionization mechanism" below). In contrast, ionization at atmopsheric pressure can generate highly-charged analytes as was first shown for infrared and later also for nitrogen lasers. Multiple charging of analytes is of great importance, because it allows to measure high-molecular-weight compounds like proteins in instruments, which provide only smaller m/z detection ranges such as quadrupoles. Besides the pressure, the composition of the matrix is important to achieve this effect. | 1 | Applied and Interdisciplinary Chemistry |
* The log-normal distribution is often used to approximate the particle size distribution of aerosols, aquatic particles and pulverized material.
* The Weibull distribution or Rosin–Rammler distribution is a useful distribution for representing particle size distributions generated by grinding, milling and crushing operations.
* The log-hyperbolic distribution was proposed by Bagnold and Barndorff-Nielsen to model the particle-size distribution of naturally occurring sediments. This model suffers from having non-unique solutions for a range of probability coefficients.
* The skew log-Laplace model was proposed by Fieller, Gilbertson and Olbricht as a simpler alternative to the log-hyperbolic distribution. | 0 | Theoretical and Fundamental Chemistry |
Experimental solid state heat engines, operating from the relatively small temperature differences in cold and hot water reservoirs, have been developed since the 1970s, including the Banks Engine, developed by Ridgway Banks. | 1 | Applied and Interdisciplinary Chemistry |
GaN transistors are suitable for high frequency, high voltage, high temperature and high efficiency applications. GaN is efficient at transferring current, and this ultimately means that less energy is lost to heat.
GaN High-electron-mobility transistor (HEMT)s have been offered commercially since 2006, and have found immediate use in various wireless infrastructure applications due to their high efficiency and high voltage operation. A second generation of devices with shorter gate lengths will address higher frequency telecom and aerospace applications.
GaN-based metal–oxide–semiconductor field-effect transistor (MOSFET) and metal–semiconductor field-effect transistor (MESFET) transistors also offer advantages including lower loss in high power electronics, especially in automotive and electric car applications. Since 2008 these can be formed on a silicon substrate. High-voltage (800 V) Schottky barrier diodes (SBDs) have also been made.
The higher efficiency and high power density of integrated GaN power ICs allows them to reduce the size, weight and component count of applications including mobile and laptop chargers, consumer electronics, computing equipment and electric vehicles.
GaN-based electronics (not pure GaN) have the potential to drastically cut energy consumption, not only in consumer applications but even for power transmission utilities.
Unlike silicon transistors which switch off due to power surges, GaN transistors are typically depletion mode devices (i.e. on / resistive when the gate-source voltage is zero). Several methods have been proposed to reach normally-off (or E-mode) operation, which is necessary for use in power electronics:
* the implantation of fluorine ions under the gate (the negative charge of the F-ions favors the depletion of the channel)
* the use of a MIS-type gate stack, with recess of the AlGaN
* the integration of a cascaded pair constituted by a normally-on GaN transistor and a low voltage silicon MOSFET
* the use of a p-type layer on top of the AlGaN/GaN heterojunction | 0 | Theoretical and Fundamental Chemistry |
In materials science, lamellar structures or microstructures are composed of fine, alternating layers of different materials in the form of lamellae. They are often observed in cases where a phase transition front moves quickly, leaving behind two solid products, as in rapid cooling of eutectic (such as solder) or eutectoid (such as pearlite) systems.
Such conditions force phases of different composition to form but allow little time for diffusion to produce those phases' equilibrium compositions. Fine lamellae solve this problem by shortening the diffusion distance between phases, but their high surface energy makes them unstable and prone to break up when annealing allows diffusion to progress. A deeper eutectic or more rapid cooling will result in finer lamellae; as the size of an individual lamellum approaches zero, the system will instead retain its high-temperature structure. Two common cases of this include cooling a liquid to form an amorphous solid, and cooling eutectoid austenite to form martensite.
In biology, normal adult bones possess a lamellar structure which may be disrupted by some diseases. | 0 | Theoretical and Fundamental Chemistry |
Phenol red exists as a red crystal that is stable in air. Its solubility is 0.77 grams per liter (g/L) in water and 2.9 g/L in ethanol. It is a weak acid with pK = 8.00 at .
A solution of phenol red is used as a pH indicator, often in cell culture. Its color exhibits a gradual transition from yellow (λ = 443 nm) to red (λ = 570 nm) over the pH range 6.8 to 8.2. Above pH 8.2, phenol red turns a bright pink (fuchsia) color.
In crystalline form, and in solution under very acidic conditions (low pH), the compound exists as a zwitterion as in the structure shown above, with the sulfate group negatively charged, and the ketone group carrying an additional proton. This form is sometimes symbolically written as and is orange-red. If the pH is increased (pK = 1.2), the proton from the ketone group is lost, resulting in the yellow, negatively charged ion denoted as HPS. At still higher pH (pK = 7.7), the phenol's hydroxy group loses its proton, resulting in the red ion denoted as PS.
In several sources, the structure of phenol red is shown with the sulfur atom being part of a cyclic group, similar to the structure of phenolphthalein. However, this cyclic structure could not be confirmed by X-ray crystallography.
Several indicators share a similar structure to phenol red, including bromothymol blue, thymol blue, bromocresol purple, thymolphthalein, and phenolphthalein. (A table of other common chemical indicators is available in the article on pH indicators.) | 0 | Theoretical and Fundamental Chemistry |
Gene targeting is relatively high efficiency in yeast, bacterial and moss (but is rare in higher eukaryotes). Hence gene targeting has been used in reverse genetics approaches to study gene function in these systems. | 1 | Applied and Interdisciplinary Chemistry |
G. E. Briggs and J. B. S. Haldane undertook an analysis that harmonized the approaches of Michaelis and Menten and of Van Slyke and Cullen, and is taken as the basic approach to enzyme kinetics today. They assumed that the concentration of the intermediate complex does not change on the time scale over which product formation is measured. This assumption means that . The resulting rate equation is as follows:
where
This is the generalized definition of the Michaelis constant. | 0 | Theoretical and Fundamental Chemistry |
The complement component 1, q subcomponent-like 1 (or C1QL1) is encoded by a gene located at chromosome 17q21.31. It is a secreted protein and is 258 amino acids in length.
The protein is widely expressed but its expression is highest in the brain and may also be involved in regulation of motor control.
The pre-mRNA of this protein is subject to RNA editing. | 1 | Applied and Interdisciplinary Chemistry |
Mercury oxide is sometimes used in the production of mercury as it decomposes quite easily. When it decomposes, oxygen gas is generated.
It is also used as a material for cathodes in mercury batteries. | 0 | Theoretical and Fundamental Chemistry |
Laboratory experiments are a very useful way of gaining information about a given flow without having to use more complex mathematical techniques. Sometimes physically seeing the change in the flow over time is just as useful as a numerical approach and any findings from these experiments can be related back to the underlying theory. Experimental analysis is also useful because it allows one to vary the governing parameters very easily and their effects will be visible.
When dealing with more complicated mathematical theories such as Bifurcation theory and Weakly nonlinear theory, numerically solving such problems becomes very difficult and time-consuming but with the help of computers this process becomes much easier and quicker. Since the 1980s computational analysis has become more and more useful, the improvement of algorithms which can solve the governing equations, such as the Navier–Stokes equation, means that they can be integrated more accurately for various types of flow. | 1 | Applied and Interdisciplinary Chemistry |
Aerobic digestion occurs much faster than anaerobic digestion. The process is usually run at ambient temperature and the process is much less complex and easier to manage than anaerobic digestion. | 1 | Applied and Interdisciplinary Chemistry |
The technical platforms to conduct ChIP-on-chip experiments are DNA microarrays, or "chips". They can be classified and distinguished according to various characteristics:
Probe type: DNA arrays can comprise either mechanically spotted cDNAs or PCR-products, mechanically spotted oligonucleotides, or oligonucleotides that are synthesized in situ. The early versions of microarrays were designed to detect RNAs from expressed genomic regions (open reading frames aka ORFs). Although such arrays are perfectly suited to study gene expression profiles, they have limited importance in ChIP experiments since most "interesting" proteins with respect to this technique bind in intergenic regions. Nowadays, even custom-made arrays can be designed and fine-tuned to match the requirements of an experiment. Also, any sequence of nucleotides can be synthesized to cover genic as well as intergenic regions.
Probe size: Early version of cDNA arrays had a probe length of about 200bp. Latest array versions use oligos as short as 70- (Microarrays, Inc.) to 25-mers (Affymetrix). (Feb 2007)
Probe composition: There are tiled and non-tiled DNA arrays. Non-tiled arrays use probes selected according to non-spatial criteria, i.e., the DNA sequences used as probes have no fixed distances in the genome. Tiled arrays, however, select a genomic region (or even a whole genome) and divide it into equal chunks. Such a region is called tiled path. The average distance between each pair of neighboring chunks (measured from the center of each chunk) gives the resolution of the tiled path. A path can be overlapping, end-to-end or spaced.
Array size: The first microarrays used for ChIP-on-Chip contained about 13,000 spotted DNA segments representing all ORFs and intergenic regions from the yeast genome. Nowadays, Affymetrix offers whole-genome tiled yeast arrays with a resolution of 5bp (all in all 3.2 million probes). Tiled arrays for the human genome become more and more powerful, too. Just to name one example, Affymetrix offers a set of seven arrays with about 90 million probes, spanning the complete non-repetitive part of the human genome with about 35bp spacing. (Feb 2007)
Besides the actual microarray, other hard- and software equipment is necessary to run ChIP-on-chip experiments. It is generally the case that one companys microarrays can not be analyzed by another companys processing hardware. Hence, buying an array requires also buying the associated workflow equipment. The most important elements are, among others, hybridization ovens, chip scanners, and software packages for subsequent numerical analysis of the raw data. | 1 | Applied and Interdisciplinary Chemistry |
Boyles great merit as a scientific investigator is that he carried out the principles which Francis Bacon espoused in the Novum Organum'. Yet he would not avow himself a follower of Bacon, or indeed of any other teacher.
On several occasions he mentions that to keep his judgment as unprepossessed as might be with any of the modern theories of philosophy, until he was "provided of experiments" to help him judge of them. He refrained from any study of the atomical and the Cartesian systems, and even of the Novum Organum itself, though he admits to "transiently consulting" them about a few particulars. Nothing was more alien to his mental temperament than the spinning of hypotheses. He regarded the acquisition of knowledge as an end in itself, and in consequence he gained a wider outlook on the aims of scientific inquiry than had been enjoyed by his predecessors for many centuries. This, however, did not mean that he paid no attention to the practical application of science nor that he despised knowledge which tended to use.
Robert Boyle was an alchemist; and believing the transmutation of metals to be a possibility, he carried out experiments in the hope of achieving it; and he was instrumental in obtaining the repeal, in 1689, of the statute of Henry IV against multiplying gold and silver. With all the important work he accomplished in physics – the enunciation of Boyles law, the discovery of the part taken by air in the propagation of sound, and investigations on the expansive force of freezing water, on specific gravities and refractive powers, on crystals, on electricity, on colour, on hydrostatics, etc. – chemistry was his peculiar and favourite study. His first book on the subject was The Sceptical Chymist', published in 1661, in which he criticised the "experiments whereby vulgar Spagyrists are wont to endeavour to evince their Salt, Sulphur and Mercury to be the true Principles of Things." For him chemistry was the science of the composition of substances, not merely an adjunct to the arts of the alchemist or the physician.
He endorsed the view of elements as the undecomposable constituents of material bodies; and made the distinction between mixtures and compounds. He made considerable progress in the technique of detecting their ingredients, a process which he designated by the term "analysis". He further supposed that the elements were ultimately composed of particles of various sorts and sizes, into which, however, they were not to be resolved in any known way. He studied the chemistry of combustion and of respiration, and conducted experiments in physiology, where, however, he was hampered by the "tenderness of his nature" which kept him from anatomical dissections, especially vivisections, though he knew them to be "most instructing". | 1 | Applied and Interdisciplinary Chemistry |
Variant genetic codes used by an organism can be inferred by identifying highly conserved genes encoded in that genome, and comparing its codon usage to the amino acids in homologous proteins of other organisms. For example, the program FACIL infers a genetic code by searching which amino acids in homologous protein domains are most often aligned to every codon. The resulting amino acid (or stop codon) probabilities for each codon are displayed in a genetic code logo.
As of January 2022, the most complete survey of genetic codes is done by Shulgina and Eddy, who screened 250,000 prokaryotic genomes using their Codetta tool. This tool uses a similar approach to FACIL with a larger Pfam database. Despite the NCBI already providing 27 translation tables, the authors were able to find new 5 genetic code variations (corroborated by tRNA mutations) and correct several misattributions. Codetta was later used to analyze genetic code change in ciliates. | 1 | Applied and Interdisciplinary Chemistry |
The property of photoconverted fluorescence Kaede protein was serendipitously discovered and first reported by Ando et al. in Proceedings of the United States National Academy of Sciences. An aliquot of Kaede protein was discovered to emit red fluorescence after being left on the bench and exposed to sunlight. Subsequent verification revealed that Kaede, which is originally green fluorescent, after exposure to UV light is photoconverted, becoming red fluorescent. It was then named Kaede. | 1 | Applied and Interdisciplinary Chemistry |
In single-phase heat transfer, convection is often the dominant mechanism of heat transfer. For adiabatic flow where the flow receives heat, the temperature of the coolant changes as it flows. An example of single-phase heat transfer is a gas-cooled reactor and molten-salt reactor.
The most convenient way for characterizing the single-phase heat transfer is based on an empirical approach, where the temperature difference between the wall and bulk flow can be obtained from the heat transfer coefficient. The heat transfer coefficient depends on several factors: mode of heat transfer (e.g., internal or external flow), type of fluid, geometry of the system, flow regime (e.g., laminar or turbulent flow), boundary condition, etc.
Examples of heat transfer correlations are Dittus-Boelter correlation (turbulent forced convection), Churchill & Chu (natural convection). | 0 | Theoretical and Fundamental Chemistry |
The Knudsen cell is used to measure the vapor pressures of a solid with very low vapor pressure. Such a solid forms a vapor at low pressure by sublimation. The vapor slowly effuses through the pinhole, and the loss of mass is proportional to the vapor pressure and can be used to determine this pressure. The heat of sublimation can also be determined by measuring the vapor pressure as a function of temperature, using the Clausius–Clapeyron relation. | 0 | Theoretical and Fundamental Chemistry |
In the Bodroux–Chichibabin aldehyde synthesis an ortho ester reacts with a Grignard reagent to form an aldehyde; this is an example of a formylation reaction. | 0 | Theoretical and Fundamental Chemistry |
Taq polymerase lacks a 3′ to 5′ exonuclease activity. Thus, Taq has no error-proof-reading activity, which consists of excision of any newly misincorporated nucleotide base from the nascent (i.e., extending) DNA strand that does not match with its opposite base in the complementary DNA strand. The lack in 3′ to 5′ proofreading of the Taq enzyme results in a high error rate (mutations per nucleotide per cycle) of approximately 1 in bases, which affects the fidelity of the PCR, especially if errors occur early in the PCR with low amounts of starting material, causing accumulation of a large proportion of amplified DNA with incorrect sequence in the final product.
Several "high-fidelity" DNA polymerases, having engineered 3′ to 5′ exonuclease activity, have become available that permit more accurate amplification for use in PCRs for sequencing or cloning of products. Examples of polymerases with 3′ to 5′ exonuclease activity include: KOD DNA polymerase, a recombinant form of Thermococcus kodakaraensis KOD1; Vent, which is extracted from Thermococcus litoralis; Pfu DNA polymerase, which is extracted from Pyrococcus furiosus; Pwo, which is extracted from Pyrococcus woesii; Q5 polymerase, with 280x higher fidelity amplification compared with Taq. | 1 | Applied and Interdisciplinary Chemistry |
Nyholm was associated with industry all of his life. One of his earliest positions was as a chemist at Eveready Batteries in Sydney. The application of science to useful products was of great importance to him, and he is purported to have admired the DuPont logo "Better things for better living through chemistry". He was an active consultant to a number of companies including ICI and Johnson Matthey in the UK and DuPont in the US. | 0 | Theoretical and Fundamental Chemistry |
One of Ted Ellis more famous works is an abstract depiction of Barack Obamas signature hope pose. Ellis painted the portrait in honor of Obamas 2008 Presidential inauguration. In Obama, the 44th President', Ellis uses red, blue, yellow, and green acrylic paint to portray Obama as someone who unites people across lines of color, ethnicity, and religion.
The piece was presented at a January 19, 2009, gala held by the National Black Chamber of Commerce and the National Newspaper Publishers Association Foundation at the Embassy of France in Washington, D.C. The proceeds from the autographed prints sold at the event supported NNPA Foundation and the Howard University School of Communications Building Fund (NNPA Media Wing). | 0 | Theoretical and Fundamental Chemistry |
Nonclassic antagonists lack the urea, thiourea, or amide groups typical of the classic TRPV1 ligands. Two major structural types of nonclassic antagonists have been discovered. First there are the imidazole derivatives. Starting from a 4,6-disubstituted benzimidazole lead structure, a series of 4,5-biarylimidazoles capable to block both capsaicin and acid-induced calcium influx in TRPV1-expressing Chinese hamster ovary cells. Imidazole (fig. 8a) was identified as a highly potent and orally bioavailable TRPV1. Another class are the diaryl ethers and amines. Compounds from a quinazoline series can be considered as conformationally restricted analogs of a biarylamide series. In terms of activity 5-isoquinoline was found the most active among and ranked in the order of 5-isoquinoline > 8-quinoline > 8-quinazoline > 8-isoquinoline ≥ cinnoline > phthalazine > quinoxaline > 5-quinoline e.g. AMG-517 (fig. 8b), although it lacks any recognizable carbonyl motif it still potently blocks capsaicin, proton, and heat activation of TRPV1 in vitro and shows a good tolerability profile. Also, the clinical candidates from Janssen, Abbott and Merck pharmaceuticals (fig. 8c) having a 5-aminoisoquinoline group as a common feature suggesting that there is a key interaction of this group at the receptor site for TRPV1 antagonist activity. | 1 | Applied and Interdisciplinary Chemistry |
The diffusion coefficient in solids at different temperatures is generally found to be well predicted by the Arrhenius equation:
where
*D is the diffusion coefficient (in m/s),
*D is the maximal diffusion coefficient (at infinite temperature; in m/s),
*E is the activation energy for diffusion (in J/mol),
*T is the absolute temperature (in K),
*R ≈ 8.31446J/(mol⋅K) is the universal gas constant.
Diffusion in crystalline solids, termed lattice diffusion, is commonly regarded to occur by two distinct mechanisms, interstitial and substitutional or vacancy diffusion. The former mechanism describes diffusion as the motion of the diffusing atoms between interstitial sites in the lattice of the solid it is diffusion into, the latter describes diffusion through a mechanism more analogue to that in liquids or gases: Any crystal at nonzero temperature will have a certain number of vacancy defects (i.e. empty sites on the lattice) due to the random vibrations of atoms on the lattice, an atom neighbouring a vacancy can spontaneously "jump" into the vacancy, such that the vacancy appears to move. By this process the atoms in the solid can move, and diffuse into each other. Of the two mechanisms, interstitial diffusion is typically more rapid. | 1 | Applied and Interdisciplinary Chemistry |
An ionotropic effect is the effect of a transmitter substance or hormone that activates or deactivates ionotropic receptors (ligand-gated ion channels). The effect can be either positive or negative, specifically a depolarization or a hyperpolarization respectively. This term is commonly confused with an inotropic effect, which refers to a change in the force of contraction (e.g. in heart muscle) produced by transmitter substances or hormones. | 1 | Applied and Interdisciplinary Chemistry |
To fix carbon dioxide into sugar molecules in the process of photosynthesis, chloroplasts use an enzyme called RuBisCO. RuBisCO has trouble distinguishing between carbon dioxide and oxygen, so at high oxygen concentrations, RuBisCO starts accidentally adding oxygen to sugar precursors. This has the result of ATP energy being wasted and being released, all with no sugar being produced. This is a big problem, since O is produced by the initial light reactions of photosynthesis, causing issues down the line in the Calvin cycle which uses RuBisCO.
plants evolved a way to solve this—by spatially separating the light reactions and the Calvin cycle. The light reactions, which store light energy in ATP and NADPH, are done in the mesophyll cells of a leaf. The Calvin cycle, which uses the stored energy to make sugar using RuBisCO, is done in the bundle sheath cells, a layer of cells surrounding a vein in a leaf.
As a result, chloroplasts in mesophyll cells and bundle sheath cells are specialized for each stage of photosynthesis. In mesophyll cells, chloroplasts are specialized for the light reactions, so they lack RuBisCO, and have normal grana and thylakoids, which they use to make ATP and NADPH, as well as oxygen. They store in a four-carbon compound, which is why the process is called photosynthesis. The four-carbon compound is then transported to the bundle sheath chloroplasts, where it drops off and returns to the mesophyll. Bundle sheath chloroplasts do not carry out the light reactions, preventing oxygen from building up in them and disrupting RuBisCO activity. Because of this, they lack thylakoids organized into grana stacks—though bundle sheath chloroplasts still have free-floating thylakoids in the stroma where they still carry out cyclic electron flow, a light-driven method of synthesizing ATP to power the Calvin cycle without generating oxygen. They lack photosystem II, and only have photosystem I—the only protein complex needed for cyclic electron flow. Because the job of bundle sheath chloroplasts is to carry out the Calvin cycle and make sugar, they often contain large starch grains.
Both types of chloroplast contain large amounts of chloroplast peripheral reticulum, which they use to get more surface area to transport stuff in and out of them. Mesophyll chloroplasts have a little more peripheral reticulum than bundle sheath chloroplasts. | 0 | Theoretical and Fundamental Chemistry |
When exposed to heat, barium chlorate alone will decompose to barium chloride and oxygen:
:Ba(ClO) → BaCl + 3 O | 0 | Theoretical and Fundamental Chemistry |
The einstein (symbol E) is an obsolete unit with two conflicting definitions. It was originally defined as the energy in one mole of photons ( photons). Because energy is inversely proportional to wavelength, the unit is frequency dependent. This unit is not part of the International System of Units (SI) and is redundant with the joule. If it were still in use, as of the 2019 redefinition of the SI base units, its value would be related to the frequency of the electromagnetic radiation by
: 1 einstein = 1 mol × = 1 mol × × × = × ,
where is the Avogadro constant, is the Planck constant, and is the frequency.
Sometime later, the unit was used differently in studies of photosynthesis to mean one mole of photons, rather than the energy in one mole of photons. As such, photosynthetically active radiation (PAR) was formerly often reported in microeinsteins per second per square meter (μE m s). This usage is also not part of the SI and when used this way it is redundant with the mole.
Since the unit does not have a standard definition and is not part of the SI system, it has long been considered obsolete. The same information about photosynthetically active radiation can be conveyed using the SI convention by stating something such as "The photon flux was 1500 μmol m s".
This unit was named after physicist Albert Einstein. | 0 | Theoretical and Fundamental Chemistry |
Mechanically created wounds in the plasma membrane have been observed as a result of sonoporation-produced shear forces. The nature of these wounds may vary based on the degree of acoustic cavitation leading to a spectrum of cell behavior, from membrane blebbing to instant cell lysis. Multiple studies examining membrane wounds note observing resealing behavior, a process dependent on recruitment of ATP and intracellular vesicles. | 1 | Applied and Interdisciplinary Chemistry |
Mingos undertook postdoctoral research at Northwestern University (Fulbright Fellow 1968–70) and at the University of Sussex (ICI Fellow 1970–71). From 1971 until 1976 he was a Lecturer at Queen Mary, University of London. He then moved to the University of Oxford as Fellow and Tutor at Keble College and University Lecturer. From 1977 until 1992 he was also Lecturer at Pembroke College, Oxford.
In 1978, Mingos, Stephen G. Davies and Malcolm Green compiled a set of rules that summarise where nucleophilic additions will occur on pi ligands.
Mingos 1984 paper on the polyhedral skeletal electron pair theory develops Wades electron counting rules for predicting the molecular geometry of cluster compounds.
In 1990 he was appointed Reader in Inorganic Chemistry and for the academic year 1991/92 he served as Assessor. From 1992 until 1999 he worked at Imperial College London as Sir Edward Frankland British Petroleum Professor of Inorganic Chemistry (1992–99) and Dean of the Royal College of Science (1996–99).
In 1999 Mingos was appointed Principal of St Edmund Hall, Oxford and at the same time he became a visiting professor at Imperial College London. In 2000 he received as a Title of Distinction the title of professor of inorganic chemistry at the University of Oxford. He was superseded as principal by Professor Keith Gull on 1 October 2009.
With David J. Wales he is the co-author of the textbook Introduction to Cluster Chemistry. | 0 | Theoretical and Fundamental Chemistry |
SPEARpesticides (Species At Risk) is a trait based biological indicator system for streams which quantitatively links pesticide contamination to the composition of invertebrate communities. The approach uses species traits that characterize the ecological requirements posed by pesticide contamination in running waters. Therefore, it is highly specific and only slightly influenced by other environmental factors. SPEARpesticides is linked to the quality classes of the EU Water Framework Directive (WFD) | 1 | Applied and Interdisciplinary Chemistry |
In Canada, one cycle of IVF treatment can cost between $7,750 to $12,250 CAD, and medications alone can cost between $2,500 to over $7,000 CAD. The funding mechanisms that influence accessibility in Canada vary by province and territory, with some provinces providing full, partial or no coverage.
New Brunswick provides partial funding through their Infertility Special Assistance Fund – a one time grant of up to $5,000. Patients may only claim up to 50% of treatment costs or $5,000 (whichever is less) occurred after April 2014. Eligible patients must be a full-time New Brunswick resident with a valid Medicare card and have an official medical infertility diagnosis by a physician.
In December 2015, the Ontario provincial government enacted the Ontario Fertility Program for patients with medical and non-medical infertility, regardless of sexual orientation, gender or family composition. Eligible patients for IVF treatment must be Ontario residents under the age of 43 and have a valid Ontario Health Insurance Plan card and have not already undergone any IVF cycles. Coverage is extensive, but not universal. Coverage extends to certain blood and urine tests, physician/nurse counselling and consultations, certain ultrasounds, up to two cycle monitorings, embryo thawing, freezing and culture, fertilisation and embryology services, single transfers of all embryos, and one surgical sperm retrieval using certain techniques only if necessary. Drugs and medications are not covered under this Program, along with psychologist or social worker counselling, storage and shipping of eggs, sperm or embryos, and the purchase of donor sperm or eggs. | 1 | Applied and Interdisciplinary Chemistry |
For condensed phases (solids and liquids), the pressure dependence of solubility is typically weak and usually neglected in practice. Assuming an ideal solution, the dependence can be quantified as:
where is the mole fraction of the -th component in the solution, is the pressure, is the absolute temperature, is the partial molar volume of the th component in the solution, is the partial molar volume of the th component in the dissolving solid, and is the universal gas constant.
The pressure dependence of solubility does occasionally have practical significance. For example, precipitation fouling of oil fields and wells by calcium sulfate (which decreases its solubility with decreasing pressure) can result in decreased productivity with time. | 0 | Theoretical and Fundamental Chemistry |
As a ship moves in the water, it creates standing waves that oppose its movement. This effect increases dramatically in full-formed hulls at a Froude number of about 0.35 (which corresponds to a speed/length ratio (see below for definition) of slightly less than 1.20 knot·ft) because of the rapid increase of resistance from the transverse wave train. When the Froude number grows to ~0.40 (speed/length ratio ~1.35), the wave-making resistance increases further from the divergent wave train. This trend of increase in wave-making resistance continues up to a Froude number of ~0.45 (speed/length ratio ~1.50), and peaks at a Froude number of ~0.50 (speed/length ratio ~1.70).
This very sharp rise in resistance at speed/length ratio around 1.3 to 1.5 probably seemed insurmountable in early sailing ships and so became an apparent barrier. This led to the concept of hull speed. | 1 | Applied and Interdisciplinary Chemistry |
Photocyclization can be carried out with ortho-, meta-, and para-substituted stilbene substrates.
ortho-Substituted substrates generally give 1-substituted phenanthrenes, unless the substituent
is a good leaving group, in which case elimination to form unsubstituted phenanthrene occurs. meta-
Substituted substrates give mixtures of 2- and 4-substituted products.
Substitution of the exocyclic double bond is well tolerated. Polycyclic aromatic compounds can be
synthesized using substrates containing multiple aromatic rings.
Stilbene derivatives containing fused aromatic systems may cyclize using either of two nonequivalent
ortho carbons. Which carbon reacts depends on both steric and electronic factors. Electronically, the
dihydrophenanthrene intermediate exhibiting greater aromatic stabilization is preferred. For instance, in
1-naphthyl-2-phenylethylene, electronic factors favor the formation of 1 over 2 in a ratio of 98.5:1.5.
ortho-Terphenyl substrates cyclize to the corresponding triphenylenes in the presence of an
oxidant, such as iodine. Oxygen is unsatisfactory because ring-opening to highly stabilized terphenyl is
faster than oxidation when oxygen is used.
Amides may cyclize to form lactams. Esters, which exist primarily in the trans conformation about the
C-O single bond, do not undergo this process efficiently.
Photocyclization can also form five-membered rings. In the vinyl naphthalene series, both oxidative and
non-oxidative processes are possible; although the latter requires a proton-transfer catalyst.
Cyclization of arylvinyl- or diarylamines provides indolines and carbazoles, respectively. In one
interesting example, the use of circularly polarized light provided 3 in slight enantiomeric excess.
In 2015, Li and Twieg reported a novel derivative of Mallory type photocyclizations and named it as photocyclodehydrofluorination (PCDHF). In the cyclization a stilbene (or ortho-terphenyl) with a pentafluorophenyl group, the fluorine atom can be used as a facile leaving group. | 0 | Theoretical and Fundamental Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.