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Bilirubin glucuronide is a water-soluble reaction intermediate over the process of conjugation of indirect bilirubin. Bilirubin glucuronide itself belongs to the category of conjugated bilirubin along with bilirubin di-glucuronide. However, only the latter one is primarily excreted into the bile in the normal setting.
Upon macrophages spot and phagocytize the effete Red Blood Corpuscles containing hemoglobin, unconjugated bilirubin is discharged from macrophages into the blood plasma. Most often, the free and water-insoluble unconjugated bilirubin which has an internal hydrodren bonding will bind to albumin and, to a much lesser extent, high density lipoprotein in order to decrease its hydrophobicity and to limit the probability of unnecessary contact with other tissues and keep bilirubin in the vascular space from traversing to extravascular space including brain, and from ending up increasing glomerular filtration. Nevertheless, there is still a little portion of indirect bilirubins stays free-of-bound. Free unconjugated bilirubin can poison the cerebrum.
Finally, albumin leads the indirect bilirubin to the liver. In the liver sinusoid, albumin disassociates with the indirect bilirubin and returns to the circulation while the hepatocyte transfers the indirect bilirubin to ligandin and glucuronide conjugates the indirect bilirubin in the endoplasmic reticulum by disrupting unconjugated bilirubin's internal hydrogen bonding, which is the thing that makes indirect bilirubin having the property of eternal half-elimination life and insoluble in water, and by attaching two molecules of glucuronic acid to it in a two step process. The reaction is a transfer of two glucuronic acid groups including UDP glucuronic acid sequentially to the propionic acid groups of the bilirubin, primarily catalyzed by UGT1A1. In greater detail about this reaction, a glucuronosyl moiety is conjugated to one of the propionic acid side chains, located on the C8 and C12 carbons of the two central pyrrole rings of bilirubin.
When the first step is completely done, the substrate bilirubin glucuronide (also known as mono-glucuronide) is born at this stage and is water-soluble and readily excreted in bile. Thereafter, so long as the second step of attachment of the other glucuronic acid to it succeeds (officially called "re-glucuronidated"), the substrate bilirubin glucuronide will turn into bilirubin di-glucuronide (8,12-diglucuronide) and be excreted into bile canaliculi by way of C-MOAT and MRP2 as normal human bile along with a little amount of unconjugated bilirubin as much as only 1 to 4 percent of total pigments in normal bile. That means up to 96%-99% of bilirubin in the bile are conjugated.
Normally, there is just a little conjugated bilirubin escapes into the general circulation. Nonetheless, in the setting of severe liver disease, a significantly greater number of conjugated bilirubin will leak into circulation and then dissolve into the blood and thereby filtered by the kidney, and only a part of the leaked conjugated bilirubin will be re-absorbed in the renal tubules, the remainder will be present in the urine making it dark-colored. | 1 | Biochemistry |
In carbohydrate chemistry, the Lobry de Bruyn–Van Ekenstein transformation also known as the Lobry de Bruyn–Alberda van Ekenstein transformation is the base or acid catalyzed transformation of an aldose into the ketose isomer or vice versa, with a tautomeric enediol as reaction intermediate. Ketoses may be transformed into 3-ketoses, etcetera. The enediol is also an intermediate for the epimerization of an aldose or ketose.
The reactions are usually base catalyzed, but can also take place under acid or neutral conditions. A typical rearrangement reaction is that between the aldose glyceraldehyde and the ketose dihydroxyacetone in a chemical equilibrium.
The Lobry de Bruyn–Van Ekenstein transformation is relevant for the industrial production of certain ketoses and was discovered in 1885 by Cornelis Adriaan Lobry van Troostenburg de Bruyn and Willem Alberda van Ekenstein. | 0 | Organic Chemistry |
As in many other systems, vortices can exist in BECs.
Vortices can be created, for example, by "stirring" the condensate with lasers,
rotating the confining trap,
or by rapid cooling across the phase transition.
The vortex created will be a quantum vortex with core shape determined by the interactions. Fluid circulation around any point is quantized due to the single-valued nature of the order BEC order parameter or wavefunction, that can be written in the form where and are as in the cylindrical coordinate system, and is the angular quantum number (a.k.a. the "charge" of the vortex). Since the energy of a vortex is proportional to the square of its angular momentum, in trivial topology only vortices can exist in the steady state; Higher-charge vortices will have a tendency to split into vortices, if allowed by the topology of the geometry.
An axially symmetric (for instance, harmonic) confining potential is commonly used for the study of vortices in BEC. To determine , the energy of must be minimized, according to the constraint . This is usually done computationally, however, in a uniform medium, the following analytic form demonstrates the correct behavior, and is a good approximation:
Here, is the density far from the vortex and , where is the healing length of the condensate.
A singly charged vortex () is in the ground state, with its energy given by
where is the farthest distance from the vortices considered.(To obtain an energy which is well defined it is necessary to include this boundary .)
For multiply charged vortices () the energy is approximated by
which is greater than that of singly charged vortices, indicating that these multiply charged vortices are unstable to decay. Research has, however, indicated they are metastable states, so may have relatively long lifetimes.
Closely related to the creation of vortices in BECs is the generation of so-called dark solitons in one-dimensional BECs. These topological objects feature a phase gradient across their nodal plane, which stabilizes their shape even in propagation and interaction. Although solitons carry no charge and are thus prone to decay, relatively long-lived dark solitons have been produced and studied extensively. | 7 | Physical Chemistry |
The final section of the guidelines involves information on how the analysis of the qPCR data was done. The essential parts of that include the program and program version used for the analysis, the method for how the Cq was determined, figuring out the outlier points in the data and how they are used or excluded and why, what results were found for the controls with no template genetic material, an explanation for why the reference genes used were chosen and why the number of them was chosen, the method used to normalize the data, how many technical replicates were included, how repeatable was the data within the assays, what methods were used to determine significance of the results, and what software was used for this part of the qualitative analysis.
It is also desired to include information on the number of biological replicates and whether they matched the results from the technical replicates, the reproducibility data for the concentration variants, data on the power analysis, and lastly for the researchers to submit the raw data in the RDML file format. | 1 | Biochemistry |
Catecholaminergic cell groups refers to collections of neurons in the central nervous system that have been demonstrated by histochemical fluorescence to contain one of the neurotransmitters dopamine or norepinephrine. Thus, it represents the combination of dopaminergic cell groups and noradrenergic cell groups. Some authors include in this category putative adrenergic cell groups, collections of neurons that stain for PNMT, the enzyme that converts norepinephrine to epinephrine (adrenaline).
Catecholaminergic cell groups and Parkinsons disease have an interactive relationship. Catecholaminergic neurons containing neuromelanin are more susceptible to Parkinsons related cell death than nonmelanized catecholaminergic neurons. Neuromelanin is an autoxidation byproduct of catecholamines, and it has been suggested that catecholaminergic neurons surrounded by a low density of glutathione peroxidase cells are more susceptible to degeneration in Parkinsons disease than those protected against oxidative stress. Hyperoxidation may be responsible for the selective degeneration of catecholaminergic neurons, specifically in the substantia nigra'. | 1 | Biochemistry |
The difference between the current that is actually obtained, at any particular value of the potential of the indicator or working electrode, for the reduction or oxidation of an ionic electroactive substance and the current that would be obtained, at the same potential, if there were no transport of that substance due to the electric field between the electrodes. The sign convention regarding current is such that the migration current is negative for the reduction of a cation or for the oxidation of an anion, and positive for the oxidation of a cation or the reduction of an anion. Hence the migration current may tend to either increase or decrease the total current observed. In any event the migration current approaches zero as the transport number of the electroactive substance is decreased by increasing the concentration of the supporting electrolyte, and hence the conductivity. | 7 | Physical Chemistry |
Iodic acid is used as a strong acid in analytical chemistry. It may be used to standardize solutions of both weak and strong bases, using methyl red or methyl orange as the indicator. | 3 | Analytical Chemistry |
Monochromators are used in many optical measuring instruments and in other applications where tunable monochromatic light is wanted. Sometimes the monochromatic light is directed at a sample and the reflected or transmitted light is measured. Sometimes white light is directed at a sample and the monochromator is used to analyze the reflected or transmitted light. Two monochromators are used in many fluorometers; one monochromator is used to select the excitation wavelength and a second monochromator is used to analyze the emitted light.
An automatic scanning spectrometer includes a mechanism to change the wavelength selected by the monochromator and to record the resulting changes in the measured quantity as a function of the wavelength.
If an imaging device replaces the exit slit, the result is the basic configuration of a spectrograph. This configuration allows the simultaneous analysis of the intensities of a wide band of colors. Photographic film or an array of photodetectors can be used, for instance to collect the light. Such an instrument can record a spectral function without mechanical scanning, although there may be tradeoffs in terms of resolution or sensitivity for instance.
An absorption spectrophotometer measures the absorption of light by a sample as a function of wavelength. Sometimes the result is expressed as percent transmission and sometimes it is expressed as the inverse logarithm of the transmission. The Beer–Lambert law relates the absorption of light to the concentration of the light-absorbing material, the optical path length, and an intrinsic property of the material called molar absorptivity. According to this relation the decrease in intensity is exponential in concentration and path length. The decrease is linear in these quantities when the inverse logarithm of transmission is used. The old nomenclature for this value was optical density (OD), current nomenclature is absorbance units (AU). One AU is a tenfold reduction in light intensity. Six AU is a millionfold reduction.
Absorption spectrophotometers often contain a monochromator to supply light to the sample. Some absorption spectrophotometers have automatic spectral analysis capabilities.
Absorption spectrophotometers have many everyday uses in chemistry, biochemistry, and biology. For example, they are used to measure the concentration or change in concentration of many substances that absorb light. Critical characteristics of many biological materials, many enzymes for instance, are measured by starting a chemical reaction that produces a color change that depends on the presence or activity of the material being studied. Optical thermometers have been created by calibrating the change in absorbance of a material against temperature. There are many other examples.
Spectrophotometers are used to measure the specular reflectance of mirrors and the diffuse reflectance of colored objects. They are used to characterize the performance of sunglasses, laser protective glasses, and other optical filters. There are many other examples.
In the UV, visible and near IR, absorbance and reflectance spectrophotometers usually illuminate the sample with monochromatic light. In the corresponding IR instruments, the monochromator is usually used to analyze the light coming from the sample.
Monochromators are also used in optical instruments that measure other phenomena besides simple absorption or reflection, wherever the color of the light is a significant variable. Circular dichroism spectrometers contain a monochromator, for example.
Lasers produce light which is much more monochromatic than the optical monochromators discussed here, but only some lasers are easily tunable, and these lasers are not as simple to use.
Monochromatic light allows for the measurement of the quantum efficiency (QE) of an imaging device (e.g. CCD or CMOS imager). Light from the exit slit is passed either through diffusers or an integrating sphere on to the imaging device while a calibrated detector simultaneously measures the light. Coordination of the imager, calibrated detector, and monochromator allows one to calculate the carriers (electrons or holes) generated for a photon of a given wavelength, QE. | 7 | Physical Chemistry |
For a Van der Waals gas, the coefficient iswith inversion temperature .
For the Dieterici gas, the reduced inversion temperature is , and the relation between reduced pressure and reduced inversion temperature is . This is plotted on the right. The critical point falls inside the region where the gas cools on expansion. The outside region is where the gas warms on expansion. | 7 | Physical Chemistry |
Polyether polyols have numerous uses. As an example, polyurethane foam is a big user of polyether polyols.
Polyester polyols can be used to produce rigid foam. They are available in both aromatic and aliphatic versions. They are also available in mixed aliphatic-aromatic versions often made from recycled raw materials, typically polyethylene terephthalate (PET).
Acrylic polyols are generally used in higher performance applications where stability to ultraviolet light is required and also lower VOC coatings. Other uses include direct to metal coatings. As they are used where good UV resistance is required, such as automotive coatings, the isocyanate component also tends to be UV resistant and hence isocyanate oligomers or prepolymers based on Isophorone diisocyanate are generally used.
Caprolactone-based polyols produce polyurethanes with enhanced hydrolysis resistance.
Polycarbonate polyols are more expensive than other polyols and are thus used in more demanding applications. They have been used to make an isophorone diisocyanate based prepolymer which is then used in glass coatings. They may be used in reactive hotmelt adhesives.
All polyols may be used to produce polyurethane prepolymers. These then find use in coatings, adhesives, sealants and elastomers. | 7 | Physical Chemistry |
In organosulfur chemistry, a sulfonate is a salt, anion or ester of a sulfonic acid. Its formula is , containing the functional group , where R is typically an organyl group, amino group or a halogen atom. Sulfonates are the conjugate bases of sulfonic acids. Sulfonates are generally stable in water, non-oxidizing, and colorless. Many useful compounds and even some biochemicals feature sulfonates. | 0 | Organic Chemistry |
Zone axis, a term sometimes used to refer to "high-symmetry" orientations in a crystal, most generally refers to any direction referenced to the direct lattice (as distinct from the reciprocal lattice) of a crystal in three dimensions. It is therefore indexed with direct lattice indices, instead of with Miller indices.
High-symmetry zone axes through a crystal lattice, in particular, often lie in the direction of tunnels through the crystal between planes of atoms. This is because, as we see below, such zone axis directions generally lie within more than one plane of atoms in the crystal. | 3 | Analytical Chemistry |
The INHIBIT logic gate incorporates a Tb ion in a chelate complex. This two-input logic gate is the first of its kind and displays non-commutative behavior with chemical inputs and a phosphorescence output. Whenever dioxygen (input “1”) is present, the system is quenched and no phosphorescence is observed (output “0”). The second input, H, must also be present for an output “1” to be observed. This is understood from a two-input INHIBIT truth table as included in Table 2. | 6 | Supramolecular Chemistry |
The Regional Scale Nodes (RSN) is a component of the National Science Foundations (NSFs) Ocean Observatories Initiative (OOI). The NSF's OOI is managed and coordinated by the OOI Project Office at the [http://www.oceanleadership.org Consortium for Ocean Leadership] (COL) in Washington, D.C. The UW, located in Seattle, Washington, is the RSN Implementing Organization for the COL.
The [http://www.interactiveoceans.washington.edu/story/Mission_and_Vision vision] behind RSN is to launch a new era of scientific discovery and understanding of the oceans.
The RSN consists of two infrastructures: primary and secondary. The primary infrastructure network, which was designed, qualified, manufactured, and installed in 2012 by [http://www.l-3mps.com/maripro/index.aspx L-3 Maripro], consists of a shore facility located in Pacific City, Oregon; two fiber-optic cable lines covering a distance of 800 kilometers, and seven primary science nodes.
The RSN system delivers 200 kilowatts of power and 240Gbit/s of TCP/IP Internet data communications to the seven primary science nodes. RSN is designed to last for 25 years and is capable of significant expansion to serve future science needs. | 9 | Geochemistry |
* Worldwide: alcohol (beer, wine), vinegar, olives, yogurt, bread, cheese
* Asia
** East and Southeast Asia: amazake, atchara, belacan, burong mangga, com ruou, doenjang, douchi, fish sauce, lah pet, lambanog, kimchi, kombucha, leppet-so, narezushi, miso, nata de coco, nattō, ngapi, oncom, padaek, pla ra, prahok, ruou nep, sake, shrimp paste, soju, soy sauce, stinky tofu, tape, tempeh, zha cai
** Central Asia: kumis, kefir, shubat, qatiq (yogurt)
** South Asia: achar, appam, dosa, dhokla, dahi (yogurt), idli, mixed pickle, ngari, sinki, tongba, paneer
* Africa: garri, injera, laxoox, mageu, ogi, ogiri, iru
* Americas: chicha, chocolate, vanilla, hot sauce, tibicos, pulque, muktuk, kiviak , parakari
* Middle East: torshi, boza
* Europe: sourdough bread, elderberry wine, kombucha, pickling, rakfisk, sauerkraut, pickled cucumber, surströmming, mead, kvass, salami, sucuk, prosciutto, cultured milk products such as quark, kefir, filmjölk, crème fraîche, smetana, skyr, rakı, tupí, żur.
* Oceania: poi, kānga pirau | 1 | Biochemistry |
Even though quark-gluon plasma can only occur under quite extreme conditions of temperature and/or pressure, it is being actively studied at particle colliders, such as the Large Hadron Collider LHC at CERN and the Relativistic Heavy Ion Collider RHIC at Brookhaven National Laboratory.
In these collisions, the plasma only occurs for a very short time before it spontaneously disintegrates. The plasma's physical characteristics are studied by detecting the debris emanating from the collision region with large particle detectors
Heavy-ion collisions at very high energies can produce small short-lived regions of space whose energy density is comparable to that of the 20-micro-second-old universe. This has been achieved by colliding heavy nuclei such as lead nuclei at high speeds, and a first time claim of formation of quark–gluon plasma came from the SPS accelerator at CERN in February 2000.
This work has been continued at more powerful accelerators, such as RHIC in the US, and as of 2010 at the European LHC at CERN located in the border area of Switzerland and France. There is good evidence that the quark–gluon plasma has also been produced at RHIC. | 7 | Physical Chemistry |
Validation of analytical procedures is imperative in demonstrating that a drug substance is suitable for a particular purpose. Common validation characteristics include: accuracy, precision (repeatability and intermediate precision), specificity, detection limit, quantitation limit, linearity, range, and robustness. In cases such as changes in synthesis of the drug substance, changes in composition of the finished product, and changes in the analytical procedure, revalidation is necessary to ensure quality control.
All analytical procedures should be validated. Identification tests are conducted to ensure the identity of an analyte in a sample through comparison of the sample to a reference standard through methods such as spectrum, chromatographic behavior, and chemical reactivity. Impurity testing can either be a quantitative test or a limit test. Both tests should accurately measure the purity of the sample. Quantitative tests of either the active moiety or other components of a sample can be conducted through assay procedures. Other analytical procedures such as dissolution testing or particle size determination may also need to be validated and are equally important. | 2 | Environmental Chemistry |
The resting potential of photocytes was found to exist in a range between 50 and 65 millivolts. It is generally accepted that the emission of light was found to occur after depolarization of the photocyte membrane although some have argued that the depolarization follows the emission of light. The depolarization of the membrane results in an increase of the rate of diffusion of ions across it. The depolarization of the photocyte was found to occur 0.5 seconds following nervous impulse culminating at one second with the maximum degree of depolarization observed. A higher frequency of nervous stimulation was associated with a smaller depolarization event. Exposure to neurotransmitters including epinephrine, norepinephrine, and synephrine, results in the emission of light but without any corresponding depolarization of the photocyte membrane. | 1 | Biochemistry |
The 1st group of anions consist of CO, HCO, CHCOO, S, SO, Thiosulfate| and NO. The reagent for Group 1 anions is dilute hydrochloric acid (HCl) or dilute sulfuric acid (HSO).
* Carbonates give a brisk effervescence with dilute HSO due to the release of CO, a colorless gas which turns limewater milky due to formation of CaCO (carbonatation). The milkiness disappears on passing an excess of the gas through the lime water, due to formation of Ca(HCO).
* Acetates give the vinegar-like smell of CHCOOH when treated with dilute HSO and heated. A blood red colouration is produced upon addition of yellow FeCl, due to formation of iron(III) acetate.
* Sulfides give the rotten egg smell of HS when treated with dilute HSO. The presence of sulfide is confirmed by adding lead(II) acetate paper, which turns black due to the formation of PbS. Sulfides also turn solutions of red sodium nitroprusside purple.
* Sulfites produce SO gas, which smells of burning sulfur, when treated with dilute acid. They turn acidified KCrO from orange to green.
* Thiosulfates produce SO gas when treated with dilute acid. In addition, they form a cloudy precipitate of sulfur.
* Nitrites give reddish-brown fumes of NO when treated with dilute HSO. These fumes cause a solution of potassium iodide (KI) and starch to turn blue. | 3 | Analytical Chemistry |
Because of the unique shapes, reactivities, properties, and bioactivities that they engender, cyclic compounds are the largest majority of all molecules involved in the biochemistry, structure, and function of living organisms, and in the man-made molecules (e.g., drugs, herbicides, etc.) through which man attempts to exert control over nature and biological systems. | 4 | Stereochemistry |
*Group 2 elements form [[Alkaline earth octacarbonyl complex|[M(CO)]]] (M = Ca, Sr, Ba), characterized in gas phase by mass spectrometry and vibrational spectroscopy.
*Group 3 elements form [Sc(CO)] and [Y(CO)] in gas phase.
*Group 7 elements as monocations resemble neutral group 6 derivative [M(CO)] (M = Mn, Tc, Re).
*Group 8 elements as dications also resemble neutral group 6 derivatives [M(CO)] (M = Fe, Ru, Os). | 0 | Organic Chemistry |
A biosignature must be detectable with the current technology to be relevant in scientific investigation. This seems to be an obvious statement, however, there are many scenarios in which life may be present on a planet yet remain undetectable because of human-caused limitations. | 2 | Environmental Chemistry |
Biodistribution is a method of tracking where compounds of interest travel in an experimental animal or human subject. For example, in the development of new compounds for PET (positron emission tomography) scanning, a radioactive isotope is chemically joined with a peptide (subunit of a protein). This particular class of isotopes emits positrons (which are antimatter particles, equal in mass to the electron, but with a positive charge). When ejected from the nucleus, positrons encounter an electron, and undergo annihilation which produces two gamma rays travelling in opposite directions. These gamma rays can be measured, and when compared to a standard, quantified. | 1 | Biochemistry |
Epoxidation of allyl- and vinylsilanes can be easily accomplished with peracids. Silyl epoxides can be converted into ketones, aldehydes, or alkenes after selective epoxide opening and elimination. When allylsilanes are combined with peracids, the intermediate epoxides are usually converted to allylic alcohols before isolation.
Halogen electrophiles, primarily X, react with vinyl- and allylsilanes to give a number of halogenated products. Further reaction of the initial adducts is common, and may lead, for instance, to conjugated dienes. Dienes may react further with X under the reaction conditions or undergo [4+2] cycloadditions in the presence of dienophiles.
A few metal electrophiles react with allylsilanes to give interesting products. Reactions of allylsilanes with thallium tris (trifluoroacetate) form electrophilic allylthallium(II) compounds. Palladation of allylsilanes provides π-allylpalladium compounds. | 0 | Organic Chemistry |
There are a variety of specialized reactions whose use is solely the formation of rings, and these will be discussed below. In addition to those, there are a wide variety of general organic reactions that historically have been crucial in the development, first, of understanding the concepts of ring chemistry, and second, of reliable procedures for preparing ring structures in high yield, and with defined orientation of ring substituents (i.e., defined stereochemistry). These general reactions include:
* Acyloin condensation;
* Anodic oxidations; and
* the Dieckmann condensation as applied to ring formation. | 4 | Stereochemistry |
Among hindered dialkylboranes is disiamylborane, abbreviated SiaBH. It also is a dimer. Owing to its steric bulk, it selectively hydroborates less hindered, usually terminal alkenes in the presence of more substituted alkenes. Disiamylborane must be freshly prepared as its solutions can only be stored at 0 °C for a few hours. Dicyclohexylborane ChxBH exhibits improved thermal stability than SiaBH. | 0 | Organic Chemistry |
Sorption is a physical and chemical process by which one substance becomes attached to another. Specific cases of sorption are treated in the following articles:
; Absorption: "the incorporation of a substance in one state into another of a different state" (e.g., liquids being absorbed by a solid or gases being absorbed by a liquid);
; Adsorption: The physical adherence or bonding of ions and molecules onto the surface of another phase (e.g., reagents adsorbed to a solid catalyst surface);
; Ion exchange: An exchange of ions between two electrolytes or between an electrolyte solution and a complex.
The reverse of sorption is desorption. | 7 | Physical Chemistry |
A noble metal is ordinarily regarded as a metallic chemical element that is generally resistant to corrosion and is usually found in nature in its raw form. Gold, platinum, and the other platinum group metals (ruthenium, rhodium, palladium, osmium, iridium) are most often so classified. Silver, copper, and mercury are sometimes included as noble metals, but each of these usually occurs in nature combined with sulfur.
In more specialized fields of study and applications the number of elements counted as noble metals can be smaller or larger. In physics, there are only three noble metals: copper, silver, and gold. In dentistry, silver is not always considered a noble metal because it is subject to corrosion when present in the mouth. In chemistry, the term noble metal is sometimes applied more broadly to any metallic or semimetallic element that does not react with a weak acid and give off hydrogen gas in the process. This broader set includes copper, mercury, technetium, rhenium, arsenic, antimony, bismuth, polonium, gold, the six platinum group metals, and silver.
__TOC__ | 8 | Metallurgy |
*2011 – Elected Fellow, Royal Society of Canada
*2012 – Elected Fellow, Mineralogical Society of America
*2013 – Island Arc Award, the Geological Society of Japan
*2022 – Takeo Kato Gold Medal, the Society of Resource Geology
*2022 – International Exchange Lecturer, Society of Economic Geologists
*2023 – Distinguished University Professor, University of Ottawa | 9 | Geochemistry |
Parvoviruses are linear, non-segmented single-stranded DNA viruses, with an average genome size of 5000 nucleotides. They are classified as group II viruses in Baltimore classification of viruses. Parvoviruses are among the smallest viruses (hence the name, from Latin parvus meaning small) and are 18–28 nm in diameter.
Parvoviruses can cause disease in some animals, including starfish and humans. Because the viruses require actively dividing cells to replicate, the type of tissue infected varies with the age of the animal. The gastrointestinal tract and lymphatic system can be affected at any age, leading to vomiting, diarrhea and immunosuppression but cerebellar hypoplasia is only seen in cats that were infected in the womb or at less than two weeks of age, and disease of the myocardium is seen in puppies infected between the ages of three and eight weeks. | 1 | Biochemistry |
Harmonized standards for the accuracy and precision of laser diffraction measurements have been defined both by ISO, in standard ISO 13320:2020, and by the United States Pharmacopoeia, in chapter USP <429>. | 7 | Physical Chemistry |
The compound's band structure exhibits a double Dirac cone, enabling Dirac fermions. A 30 meV gap separates the cones, which indicates the quantum Hall effect and massive Dirac fermions. Close measurement of the Fermi surface via the de Haas-van Alphen effect suggests that the massive fermions also exhibit Kane-Mele-type spin-orbit coupling.
FeSn can also host magnetic skyrmions, but these typically require high magnetic fields to nucleate. For samples with a small (but nonzero) thickness gradient, only a small-amplitude (5-10 mT), direction-variant magnetic field suffices to nucleate the quasiparticles. | 8 | Metallurgy |
In molecular biology, a primosome is a protein complex responsible for creating RNA primers on single stranded DNA during DNA replication.
The primosome consists of seven proteins: DnaG primase, DnaB helicase, DnaC helicase assistant, DnaT, PriA, Pri B, and PriC. At each replication fork, the primosome is utilized once on the leading strand of DNA and repeatedly, initiating each Okazaki fragment, on the lagging DNA strand. Initially the complex formed by PriA, PriB, and PriC binds to DNA. Then the DnaB-DnaC helicase complex attaches along with DnaT. This structure is referred to as the pre-primosome. Finally, DnaG will bind to the pre-primosome forming a complete primosome. The primosome attaches 1-10 RNA nucleotides to the single stranded DNA creating a DNA-RNA hybrid. This sequence of RNA is used as a primer to initiate DNA polymerase III. The RNA bases are ultimately replaced with DNA bases by RNase H nuclease (eukaryotes) or DNA polymerase I nuclease (prokaryotes). DNA Ligase then acts to join the two ends together.
Assembly of the Escherichia coli primosome requires six proteins, PriA, PriB, PriC, DnaB, DnaC, and DnaT, acting at a primosome assembly site (pas) on an SSBcoated single-stranded (8s) DNA. Assembly is initiated by interactions of PriA and PriB with ssDNA and the pas. PriC, DnaB, DnaC, and DnaT then act on the PriAPriB- DNA complex to yield the primosome.
Primosomes are nucleoproteins assemblies that activate DNA replication forks. Their primary role is to recruit the replicative helicase onto single-stranded DNA. The "replication restart" primosome, defined in Escherichia coli, is involved in the reactivation of arrested replication forks. Binding of the PriA protein to forked DNA triggers its assembly. PriA is conserved in bacteria, but its primosomal partners are not. In Bacillus subtilis, genetic analysis has revealed three primosomal proteins, DnaB, DnaD, and DnaI, that have no obvious homologues in E. coli. They are involved in primosome function both at arrested replication forks and at the chromosomal origin. Our biochemical analysis of the DnaB and DnaD proteins unravels their role in primosome assembly. They are both multimeric and bind individually to DNA. Furthermore, DnaD stimulates DnaB binding activities. DnaD alone and the DnaD/DnaB pair interact specifically with PriA of B. subtilis on several DNA substrates. This suggests that the nucleoprotein assembly is sequential in the PriA, DnaD, DnaB order. The preferred DNA substrate mimics an arrested DNA replication fork with unreplicated lagging strand, structurally identical to a product of recombinational repair of a stalled replication fork. | 1 | Biochemistry |
Historically Hansen solubility parameters (HSP) have been used in industries such as paints and coatings where understanding and controlling solvent–polymer interactions was vital. Over the years their use has been extended widely to applications such as:
* Environmental stress cracking of polymers
* Controlled dispersion of pigments, such as carbon black
* Understanding of solubility/dispersion properties of carbon nanotubes, Buckyballs, and quantum dots
* Adhesion to polymers
* Permeation of solvents and chemicals through plastics to understand issues such as glove safety, food packaging barrier properties and skin permeation
* Diffusion of solvents into polymers via understanding of surface concentration based on RED number
* Cytotoxicity via interaction with DNA
* Artificial noses (where response depends on polymer solubility of the test odor)
* Safer, cheaper, and faster solvent blends where an undesirable solvent can be rationally replaced by a mix of more desirable solvents whose combined HSP equals the HSP of the original solvent. | 7 | Physical Chemistry |
PCL consists in introducing a somatic adult or senescent cell nucleus or entire cell with enlarged membrane pores in an (activated) oocyte and to withdraw this treated cell before its de-differentiation and first cell division occurs. Thus, the progressive rejuvenation capability of the oocyte is used only temporarily in order to obtain a partial natural rejuvenation. PCL permits to envisage a chosen degree of partial rejuvenation in changing the duration of the introduction of the treated cell in the oocyte. Using PCL cell de-differentiation and its age reprogramming might be, at least partially, separable. Thus the existence of an isolated ageing clock would be confirmed at least during a certain part of the cellular evolution and involution. | 1 | Biochemistry |
The Payne rearrangement occurs with inversion of stereochemistry at C-2. Substrates containing multiple adjacent hydroxyl groups may undergo "cascade" epoxide migrations with inversion at each site of nucleophilic attack. In one example, inversion of three contiguous stereocenters results after two epoxide migrations, opening of the epoxide by carboxylate, and hydrolysis of the resulting lactone. | 0 | Organic Chemistry |
Carboxylation is a chemical reaction in which a carboxylic acid is produced by treating a substrate with carbon dioxide. The opposite reaction is decarboxylation. In chemistry, the term carbonation is sometimes used synonymously with carboxylation, especially when applied to the reaction of carbanionic reagents with CO. More generally, carbonation usually describes the production of carbonates. | 0 | Organic Chemistry |
The basic ideas behind transition state theory are as follows:
#Rates of reaction can be studied by examining activated complexes near the saddle point of a potential energy surface. The details of how these complexes are formed are not important. The saddle point itself is called the transition state.
#The activated complexes are in a special equilibrium (quasi-equilibrium) with the reactant molecules.
#The activated complexes can convert into products, and kinetic theory can be used to calculate the rate of this conversion. | 7 | Physical Chemistry |
Pre-B-cell leukemia homeobox (PBX) refers to a family of transcription factors.
Types include:
* PBX1
* PBX2
* PBX3
* PBX4 | 1 | Biochemistry |
The Molecular Kink Paradigm envisions a representative network chain as a series of vectors that follow the chain contour within its tube. Each vector represents the equilibrium end-to-end distance of a kink. The actual 3-dimensional path of the chain is not pertinent, since all elastic forces are assumed to operate along the chain contour. In addition to the chain's contour length, the only other important parameter is its tortuosity, the ratio of its contour length to its end-to-end distance. As the chain is extended, in response to an applied strain, the induced elastic force is assumed to propagate uniformly along its contour. Consider a network chain whose end points (network nodes) are more or less aligned with the tensile strain axis. As the initial strain is applied to the rubber sample, the network nodes at the ends of the chain begin to move apart and all of the kink vectors along the contour are stretched simultaneously. Physically, the applied strain forces the kinks to stretch beyond their thermal equilibrium end-to-end distances, causing a decrease in their entropy. The increase in free energy associated with this change in entropy, gives rise to a (linear) elastic force that opposes the strain. The force constant for the low strain regime can be estimated by sampling molecular dynamics (MD) trajectories of a kink, i.e. short chains, composed of 2–3 isoprene units, at relevant temperatures, e.g. 300K. By taking many samples of the coordinates over the course of the simulations, the probability distributions of end-to-end distance for a kink can be obtained. Since these distributions (which turn out to be approximately Gaussian) are directly related to the number of states, we may associate them with the entropy of the kink at any end-to-end distance. By numerically differentiating the probability distribution, the change in entropy, and hence free energy, with respect to the kink end-to-end distance can be found. The force model for this regime is found to be linear and proportional to the temperature divided by the chain tortuosity. | 7 | Physical Chemistry |
The Circe effect is a phenomenon proposed by William Jencks seen in chemistry and biochemistry where in order to speed up a reaction, the ground state of the substrate is destabilized by an enzyme. | 1 | Biochemistry |
Ribozymes, antisense oligonucleotides, and more recently RNAi have been used to target mRNA molecules involved in asthma. These experiments have suggested that siRNA may be used to combat other respiratory diseases, such as chronic obstructive pulmonary disease (COPD) and cystic fibrosis. COPD is characterized by goblet cell hyperplasia and mucus hypersecretion. Mucus secretion was found to be reduced when the transforming growth factor (TGF)-α was targeted by siRNA in NCI-H292 human airway epithelial cells. In addition to mucus hypersecretion, chronic inflammation and damaged lung tissue are characteristic of COPD and asthma. The transforming growth factor TGF-β is thought to play a role in these manifestations. As a result, when interferon (IFN)-γ was used to knock down TGF-β, fibrosis of the lungs, caused by damage and scarring to lung tissue, was improved. | 1 | Biochemistry |
Anomerization is the process of conversion of one anomer to the other. For reducing sugars, anomerization is referred to as mutarotation and occurs readily in solution and is catalyzed by acid and base. This reversible process typically leads to an anomeric mixture in which eventually an equilibrium is reached between the two single anomers.
The ratio of the two anomers is specific for the regarding sugar. For example, regardless of the configuration of the starting -glucose, a solution will gradually move towards being a mixture of approximately 64% β--glucopyranoside and 36% of α--glucopyranose. As the ratio changes, the optical rotation of the mixture changes; this phenomenon is called mutarotation. | 4 | Stereochemistry |
Liquid fluorocarbons have a very high capacity for holding gas in solution. They can hold more oxygen or carbon dioxide than blood does. For that reason, they have attracted ongoing interest related to the possibility of artificial blood or of liquid breathing.
Blood substitutes are the subject of research because the demand for blood transfusions grows faster than donations. In some scenarios, artificial blood may be more convenient or safe. Because fluorocarbons do not normally mix with water, they must be mixed into emulsions (small droplets of perfluorocarbon suspended in water) in order to be used as blood. One such product, Oxycyte, has been through initial clinical trials.
Possible medical uses of liquid breathing (which uses pure perfluorocarbon liquid, not a water emulsion) involve assistance for premature babies or for burn patients (if normal lung function is compromised). Both partial and complete filling of the lungs have been considered, although only the former has undergone any significant tests in humans. Several animal tests have been performed and there have been some human partial liquid ventilation trials. One effort, by Alliance Pharmaceuticals, reached clinical trials but was abandoned because of insufficient advantage compared to other therapies.
Nanocrystals represent a possible method of delivering water- or fat-soluble drugs within a perfluorochemical fluid. The use of these particles is being developed to help treat babies with damaged lungs.
Perfluorocarbons are banned from sports, where they may be used to increase oxygen use for endurance athletes. One cyclist, Mauro Gianetti, was investigated after a near-fatality where PFC use was suspected. Other posited applications include deep-sea diving and space travel, applications that both require total, not partial, liquid ventilation. The 1989 film The Abyss depicted a fictional use of perfluorocarbon for human diving but also filmed a real rat surviving while cooled and immersed in perfluorocarbon. (See also list of fictional treatments of perfluorocarbon breathing.) | 1 | Biochemistry |
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 | Biochemistry |
Propionyl-CoA is also a substrate for post-translational modification of proteins by reacting with lysine residues on proteins, a reaction called protein propionylation. Due to structural similarities of Acetyl-CoA and Propionyl-CoA, propionylation reaction are thought to use many of the same enzymes used for protein acetylation. Although functional consequences of protein propionylation are currently not completely understood, in vitro propionylation of the Propionyl-CoA Synthetase enzyme controls its activity. | 1 | Biochemistry |
The method produces genome-wide mappings of in vivo nucleosome occupancy to detect the tissue-of-origin of cfDNA molecules. The method uses reads' endpoint position aligned which are expected to be close to nucleosome core particle (NCP) sites. Windowed Protection Score (WPS) is proposed to quantify the cfDNA density close to NCPs using the frequency of cfDNA particles that cover 120 base pairs centred at a given location minus the frequency of fragments with an endpoint at the same interval. Then, the peaks are called heuristically for WPS to identify footprints. The cells contributing to cfDNA are then predicted from the footprints. These footprints can be used for identifying non-malignant epigenetic or genetic sites like transcription factor binding sites, and detection of malignancy-related biomarkers based on the extent of tissue damage and cell deaths. | 1 | Biochemistry |
Dextrose equivalent (DE) is a measure of the amount of reducing sugars present in a sugar product, expressed as a percentage on a dry basis relative to dextrose. The dextrose equivalent gives an indication of the average degree of polymerisation (DP) for starch sugars. As a rule of thumb, DE × DP = 120.
In all glucose polymers, from the native starch to glucose syrup, the molecular chain begins with a reducing sugar, containing a free aldehyde. As the starch is hydrolysed, the molecules become shorter and more reducing sugars are present. Therefore, the dextrose equivalent describes the degree of conversion of starch to dextrose. The standard method of determining the dextrose equivalent is the Lane-Eynon titration, based on the reduction of copper(II) sulfate in an alkaline tartrate solution, an application of Fehling's test.
Examples:
*A maltodextrin with a DE of 10 would have 10% of the reducing power of dextrose which has a DE of 100.
*Maltose, a disaccharide made of two glucose (dextrose) molecules, has a DE of 52, correcting for the water loss in molecular weight when the two molecules are combined. Glucose (dextrose) has a molecular mass of 180, while water has a molecular mass of 18. For each 2 glucose monomers binding, a water molecule is removed.
Therefore, the molecular mass of a glucose polymer can be calculated by using the formula (180*n - 18*(n-1)) with n the DP (degree of polymerisation) of the glucose polymer. The DE can be calculated as 100*(180 / Molecular mass( glucose polymer)). In this example the DE is calculated as 100*(180/(180*2-18*1)) = 52.
*Sucrose actually has a DE of zero even though it is a disaccharide, because both reducing groups of the monosaccharides that make it are connected, so there are no remaining reducing groups.
Because different reducing sugars (e.g. fructose and glucose) have different sweetness, it is incorrect to assume that there is any direct relationship between dextrose equivalent and sweetness. | 3 | Analytical Chemistry |
Peak oil is a term applied to the projection that future petroleum production, whether for individual oil wells, entire oil fields, whole countries, or worldwide production, will eventually peak and then decline at a similar rate to the rate of increase before the peak as these reserves are exhausted. The peak of oil discoveries was in 1965, and oil production per year has surpassed oil discoveries every year since 1980. However, this does not mean that potential oil production has surpassed oil demand.
It is difficult to predict the oil peak in any given region, due to the lack of knowledge and/or transparency in the accounting of global oil reserves. Based on available production data, proponents have previously predicted the peak for the world to be in the years 1989, 1995, or 1995–2000. Some of these predictions date from before the recession of the early 1980s, and the consequent lowering in global consumption, the effect of which was to delay the date of any peak by several years. Just as the 1971 U.S. peak in oil production was only clearly recognized after the fact, a peak in world production will be difficult to discern until production clearly drops off.
In 2020, according to BP's Energy Outlook 2020, peak oil had been reached, due to the changing energy landscape coupled with the economic toll of the COVID-19 pandemic.
While there has been much focus historically on peak oil supply, the focus is increasingly shifting to peak demand as more countries seek to transition to renewable energy. The GeGaLo index of geopolitical gains and losses assesses how the geopolitical position of 156 countries may change if the world fully transitions to renewable energy resources. Former oil exporters are expected to lose power, while the positions of former oil importers and countries rich in renewable energy resources is expected to strengthen. | 7 | Physical Chemistry |
If any method is ever successful, a suggestion has been made to introduce the hybrids to a wildlife reserve in Siberia called the Pleistocene Park, but some biologists question the ethics of such recreation attempts. In addition to the technical problems, not much habitat is left that would be suitable for mammoth–elephant hybrids. Because both species are [were] social and gregarious, creating a few specimens would not be ideal. The time and resources required would be enormous, and the scientific benefits would be unclear, suggesting these resources should instead be used to preserve extant elephant species which are endangered. The ethics of using elephants as surrogate mothers in hybridisation attempts has also been questioned, as most embryos would not survive, and knowing the exact needs of a hybrid mammoth–elephant calf would be impossible. | 1 | Biochemistry |
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. | 7 | Physical Chemistry |
If a magnetic field is oriented along the defect axis it leads to Zeeman splitting separating the m = +1 from the m = -1 states. This technique is used to lift the degeneracy and use only two of the spin states (usually the ground states with m = -1 and m = 0) as a qubit. Population can then be transferred between them using a microwave field. In the specific instance that the magnetic field reaches 1027 G (or 508 G) then the m = –1 and m = 0 states in the ground (or excited) state become equal in energy (Ground/Excited State Level Anticrossing). The following strong interaction results in so-called spin polarization, which strongly affects the intensity of optical absorption and luminescence transitions involving those states.
Importantly, this splitting can be modulated by applying an external electric field, in a similar fashion to the magnetic field mechanism outlined above, though the physics of the splitting is somewhat more complex. Nevertheless, an important practical outcome is that the intensity and position of the luminescence lines is modulated. Strain has a similar effect on the NV center as electric fields.
There is an additional splitting of the m = ±1 energy levels, which originates from the hyperfine interaction between surrounding nuclear spins and the NV center. These nuclear spins create magnetic and electric fields of their own leading to further distortions of the NV spectrum (see nuclear Zeeman and quadrupole interaction). Also the NV center's own spin–orbit interaction and orbital degeneracy leads to additional level splitting in the excited E state.
Temperature and pressure directly influence the zero-field term of the NV center leading to a shift between the ground and excited state levels.
The Hamiltonian, a quantum mechanical equation describing the dynamics of a system, which shows the influence of different factors on the NV center can be found below.
Although it can be challenging, all of these effects are measurable, making the NV center a perfect candidate for a quantum sensor. | 7 | Physical Chemistry |
Rayleigh scattering, too, can be considered to be due to fluctuations in the density, composition and orientation of molecules within the transmitting medium, and hence of its refraction index, in small volumes of matter (particularly in gases or liquids). The difference is that Rayleigh scattering involves only the random and incoherent thermal fluctuations, in contrast with the correlated, periodic fluctuations (phonons) that cause Brillouin scattering. Moreover, Rayleigh scattering is elastic in that no energy is lost or gained. | 7 | Physical Chemistry |
Certain species of plants are considered indicators of high selenium content of the soil, since they require high levels of selenium to thrive. The main selenium indicator plants are Astragalus species (including some locoweeds), princes plume (Stanleya sp.), woody asters (Xylorhiza sp.), and false goldenweed (Oonopsis' sp.) | 1 | Biochemistry |
In the 1879 paper the assumption that reaction rate was proportional to the product of concentrations was justified microscopically in terms of the frequency of independent collisions, as had been developed for gas kinetics by Boltzmann in 1872 (Boltzmann equation). It was also proposed that the original theory of the equilibrium condition could be generalised to apply to any arbitrary chemical equilibrium.
The exponents α, β etc. are explicitly identified for the first time as the stoichiometric coefficients for the reaction. | 7 | Physical Chemistry |
Supramolecular chemistry has found many applications, in particular molecular self-assembly processes have been applied to the development of new materials. Large structures can be readily accessed using bottom-up synthesis as they are composed of small molecules requiring fewer steps to synthesize. Thus most of the bottom-up approaches to nanotechnology are based on supramolecular chemistry. Many smart materials are based on molecular recognition. | 6 | Supramolecular Chemistry |
Type M (82%Ni/18%Mo–99.2%Ni/0.8%Co, by weight) are used in vacuum furnaces for the same reasons as with type C (described below). Upper temperature is limited to 1400 °C. It is less commonly used than other types. | 8 | Metallurgy |
The Uptake of Hexose Phosphates (Uhp) is a protein system found in bacteria. It is a type of two-component sensory transduction pathway which helps bacteria react to their environment. | 1 | Biochemistry |
The psychrometric chart depicts the changes of the cycle to the standard air conditioning cycle. First, the end state point 4 for air from the wheel represents a latent ratio increase (moisture removal) to about 45%, as opposed to the 25% of the typical coil shown. Secondly, the air quality delivered by the cycle is much dryer, about 55% RH (state point 4), rather than 98% with the standard coil (state point 4). Third, this is accomplished with a higher average evaporator temperature. Compare the midpoint of the evaporators temperature, line 1 to 4’, to the midpoint of the Cromer cycles evaporators temperature, line 2 to 3. These lines represent the work done by the coil on the air stream (its change in enthalpy). This is significant because, given a constant condenser temperature and equivalent change in enthalpy, the higher the evaporator coil temperature, the more efficient is the Carnot refrigeration cycle and the greater the energy efficiency a particular system can deliver.
Common dehumidification strategies include: reheating (electric or hot-gas bypass), where sensible heat is added to the air leaving the equipment; recuperative heat (run-around coils or heat pipes), where sensible heat is transferred from the return air to the supply air; or the Cromer cycle, where the latent heat of moisture sorption and evaporation is transferred from the return air to the supply air. These various strategies were compared in an ASHRAE Journal article that found that "the Cromer cycle produces similar enhanced dehumidification performance as is obtained with recuperative configurations." | 7 | Physical Chemistry |
Thermal radiation plays a crucial role in human comfort, influencing perceived temperature sensation. Various technologies have been developed to enhance thermal comfort, including personal heating and cooling devices.
The mean radiant temperature is a metric used to quantify the exchange of radiant heat between a human and their surrounding environment. | 7 | Physical Chemistry |
A glycosyl acceptor is any suitable nucleophile-containing molecule that will react with a glycosyl donor to form a new glycosidic bond. By convention, the acceptor is the member of this pair which did not contain the resulting anomeric carbon of the new glycosidic bond. Since the nucleophilic atom of the acceptor is typically an oxygen atom, this can be remembered using the mnemonic of the acceptor is the alcohol. A glycosyl acceptor can be a mono- or oligosaccharide that contains an available nucleophile, such as an unprotected hydroxyl. | 0 | Organic Chemistry |
Another advantage of duplex sequencing is that it can be used in combination with the majority of NGS platforms without making significant changes to the standard protocols. | 1 | Biochemistry |
Culminating in the 1930s, the British chemists Christopher Ingold and Robert Robinson among others had investigated the mechanisms of organic reactions, and had come up with empirical rules which could predict reactivity of organic molecules. Woodward was perhaps the first synthetic organic chemist who used these ideas as a predictive framework in synthesis. Woodward's style was the inspiration for the work of hundreds of successive synthetic chemists who synthesized medicinally important and structurally complex natural products. | 4 | Stereochemistry |
Countries in the Caspian region, particularly Azerbaijan, Kazakhstan and Turkmenistan, have high-value natural-resource-based economies, where the oil and gas compose more than 10 percent of their GDP and 40 percent of their exports. All the Caspian region economies are highly dependent on this type of mineral wealth. The world energy markets were influenced by Azerbaijan and Kazakhstan, as they became strategically crucial in this sphere, thus attracting the largest share of foreign direct investment (FDI).
All of the countries are rich in solar energy and harnessing potential, with the highest rainfall much less than the mountains of central Europe in the mountains of the west, which are also rich in hydroelectricity sources.
Iran has high fossil fuel energy potential. It has reserves of 137.5 billion barrels of crude oil, the fourth largest in the world, producing around four million barrels a day. Iran has an estimated 988.4 trillion cubic feet of natural gas, around 16 percent of world reserves, thus key to current paradigms in global energy security.
Russias economy ranks as the twelfth largest by nominal GDP and sixth largest by purchasing power parity in 2015. Russias extensive mineral and energy resources are the largest such reserves in the world, making it the second leading producer of oil and natural gas globally.
Caspian littoral states join efforts to develop infrastructure, tourism and trade in the region. The first Caspian Economic Forum was convened on August 12, 2019, in Turkmenistan and brought together representatives of Kazakhstan, Russia, Azerbaijan, Iran and that state. It hosted several meetings of their ministers of economy and transport.
The Caspian countries develop robust cooperation in the tech and digital field as part of the Caspian Digital Hub. The project helps expand data transmission capabilities in Kazakhstan as well as data transit capabilities between Asia and Europe. The project generated interest from investors from all over the world, including the UK. | 2 | Environmental Chemistry |
Thymolphthalein is a phthalein dye used as an acid–base (pH) indicator. Its transition range is around pH 9.3–10.5. Below this pH, it is colorless; above, it is blue. The molar extinction coefficient for the blue thymolphthalein dianion is 38,000 M cm at 595 nm.
Thymolphthalein is also known to have use as a laxative and for disappearing ink. | 3 | Analytical Chemistry |
Dates indicate publication years in which someone was credited as a lead editor or co-editor of a journal volume. The planning process for a volume begins well before the volume appears, so appointment to the position of lead editor generally occurred prior to the first year shown here. An editor who has retired or died may be credited as a lead editor of a volume that they helped to plan, even if it is published after their retirement or death.
* Gerhard Krohn Rollefson (1950–1955)
* Henry Eyring (1956–1976)
* Benton Seymour Rabinovitch (1977–1985)
* Herbert L. Strauss (1986–2001)
* Stephen Leone (2002–2011; retired 2011; credited 2012–2013)
* Mark A. Johnson (appointed 2012; credited 2014–2023)) and Todd Martínez (co-editors) (appointed 2012; credited 2014–present)
* Todd J. Martínez and Anne McCoy (appointed 2023) | 7 | Physical Chemistry |
Poly(p-phenylene) (PPP) is made of repeating p-phenylene units, which act as the precursor to a conducting polymer of the rigid-rod polymer family. The synthesis of PPP has proven challenging, but has been accomplished through excess polycondensation with the Suzuki coupling method.
Early efforts typically produced black, insoluble powders that were difficult to characterize. For example, a 1962 paper reports "The solid glowed red-hot in a Bunsen flame, with no evidence of flame formation, and disappeared only slowly." (J. Polym. Sci. (1960), 47, 45) Initially, the chemical and thermal stability of the material drove interest in its synthesis. It was used in rocket nozzles and some fabrics requiring high thermal stability.
Oxidation or the use of dopants is used to convert the non-conductive form to a semiconductor. | 7 | Physical Chemistry |
G.V. Pigulevsky was born on December 10, 1888 (November 28, old style) in Kovno (nowadays Kaunas, Lithuania) in the family of a lawyer Vasily Ivanovich Pigulevsky. There were two other sons in the family - Boris and Vladimir. In 1906, after graduating from the Vilna Gymnasium, he entered the Faculty of Physics and Mathematics of the Saint Petersburg Imperial University. After graduation in 1911, he stayed at the Department of Chemistry at the suggestion of Professor L.A. Chugaev. Since 1912 he simultaneously became a laboratory assistant in the Agricultural Scientific Committee of the Ministry of Agriculture, in 1914-23 he worked as a scientific specialist of the same committee. At the same time, he lectured at the Psychoneurological Institute (1914-1918). In 1919, he taught analytical chemistry at the Women's Medical Institute.
In 1920 Pigulevsky became a lecturer (since 1929 - associate professor) at Petrograd University (later - Leningrad State University). In 1924-1928, he worked as the head of the laboratory of labor protection of the People's Commissariat for Labour of the North-Western Region. In 1929, Pigulevsky was elected as a professor of the Institute of Chemical Technology. In the same year, he headed the Department of fats and oils of this Institute (1929-1930). In 1931-1934 while continuing to teach at Leningrad State University, Pigulevsky headed the Department of Organic Chemistry at the Arkhangelsk Forestry Engineering Institute. In 1934, he became a professor of organic chemistry at Leningrad State University. At the same time, he headed the laboratory of bioproducts of this University. In 1935, he obtained Doctor of Science in chemistry degree without thesis defense.
In 1941-1942, as a part of a group of chemists Pigulevsky organized the production of medicines (streptocide, phenamine, glucose, sulfidine and sulfazol) in besieged Leningrad. In the summer of 1942, he was evacuated to Kazan. In 1942-1943, he served as a senior researcher at the I.P. Pavlov Physiological Institute of the Academy of Sciences of the USSR. In 1943, Pigulevsky accepted an invitation to head the biochemical laboratory of the V.L. Komarov Botanical Institute and led it until the end of his life. In 1944, Pigulevsky returned to Leningrad.
After coming back to Leningrad, he again headed the laboratory of bioproducts at Leningrad State University. In 1957, this laboratory was reorganized as the problematic laboratory of natural compounds of the Faculty of Chemistry of the Leningrad State University. Pigulevsky headed it until the end of his life. He died in 1964 in Leningrad. | 0 | Organic Chemistry |
Chain propagation (sometimes referred to as propagation) is a process in which a reactive intermediate is continuously regenerated during the course of a chemical chain reaction. For example, in the chlorination of methane, there is a two-step propagation cycle involving as chain carriers a chlorine atom and a methyl radical which are regenerated alternately:
:Cl + CH → HCl + CH
:CH + Cl → CHCl + Cl
The two steps add to give the equation for the overall chain reaction:
:CH + Cl → CHCl + HCl. | 7 | Physical Chemistry |
An alternative to the ensemble-based method described above is the voltage-clamp experiment. In a voltage-clamp experiment, two compartments of electrolyte are divided by an aperture, usually between 5-250 micrometres in diameter. A lipid bilayer is painted across this aperture, thus electrically separating the compartments; the molecular nature can be ascertained by measuring its capacitance.
Upon the addition of an (ideal) ion channel, a defined path between the two compartments is formed. Through this pore, ions flow down the potential and electrochemical gradient rapidly (>10/second), the maximum flux limited by the geometry and dimensions of the pore. At some later instant the pore may close or collapse, whereupon the current returns to zero. This open-state current, originating and amplified from a single-molecule event, is typically on the order of pA to nA, with time-resolution of approx. millisecond. Ideal or close-to-ideal events is termed "square-tops" in the literature, and have been considered as signature for a channel-based mechanism.
It is notable that the events observed at this scale are truly stochastic - that is, they are the result of random molecular collision and conformation changes. As the membrane area is much larger than that of a pore, multiple copies may open and close independently of one another, giving rise to the staircase like appearance (Panel C in figure); these ideal events are often modelled as Markov processes.
By using the activity grid notation, synthetic ion channels studied with the voltage-clamp method during the period 1982-2010 have been critically reviewed. While the ideal traces are most frequently analyzed and reported in the literature, many records are decidedly non-ideal, with a subset was shown to be fractal. Developing methods for analyzing these non-ideal traces and clarifying their relationship to transport mechanism is an area of contemporary research. | 6 | Supramolecular Chemistry |
When a salt is distributed between two phases, the Galvani potential difference is called the distribution potential and is obtained from the respective Nernst equations for the cation C and the anion A to read
where γ represents the activity coefficient. | 7 | Physical Chemistry |
In contrast, in Gram-positive bacteria (e.g. Bacillus stearothermophilus) and eukaryotes the central PDC core contains 60 E2 molecules arranged into an icosahedron. This E2 subunit “core” coordinates to 30 subunits of E1 and 12 copies of E3.
Eukaryotes also contain 12 copies of an additional core protein, E3 binding protein (E3BP) which bind the E3 subunits to the E2 core. The exact location of E3BP is not completely clear. Cryo-electron microscopy has established that E3BP binds to each of the icosahedral faces in yeast. However, it has been suggested that it replaces an equivalent number of E2 molecules in the bovine PDC core.
Up to 60 E1 or E3 molecules can associate with the E2 core from Gram-positive bacteria - binding is mutually exclusive. In eukaryotes E1 is specifically bound by E2, while E3 associates with E3BP. It is thought that up to 30 E1 and 6 E3 enzymes are present, although the exact number of molecules can vary in vivo and often reflects the metabolic requirements of the tissue in question. | 1 | Biochemistry |
Physicists overwhelmingly reject any possibility that the zero-point energy field can be exploited to obtain useful energy (work) or uncompensated momentum; such efforts are seen as tantamount to perpetual motion machines.
Nevertheless, the allure of free energy has motivated such research, usually falling in the category of fringe science. As long ago as 1889 (before quantum theory or discovery of the zero point energy) Nikola Tesla proposed that useful energy could be obtained from free space, or what was assumed at that time to be an all-pervasive aether. Others have since claimed to exploit zero-point or vacuum energy with a large amount of pseudoscientific literature causing ridicule around the subject. Despite rejection by the scientific community, harnessing zero-point energy remains an interest of research, particularly in the US where it has attracted the attention of major aerospace/defence contractors and the U.S. Department of Defense as well as in China, Germany, Russia and Brazil. | 7 | Physical Chemistry |
Laura Frances Robinson, born November 1976, is a British scientist who is Professor of Geochemistry at the University of Bristol. She makes use of geochemistry to study the processes that govern the climate. In particular, Robinson studies radioactive elements, as these can be analysed in geological materials. She was awarded the 2010 President's Award of the Geological Society of London. | 9 | Geochemistry |
Colorless fluorescent dyes that emit blue light under UV are added as optical brighteners to paper and fabrics. The blue light emitted by these agents counteracts yellow tints that may be present and causes the colors and whites to appear whiter or more brightly colored.
UV fluorescent dyes that glow in the primary colors are used in paints, papers, and textiles either to enhance color under daylight illumination or to provide special effects when lit with UV lamps. Blacklight paints that contain dyes that glow under UV are used in a number of art and aesthetic applications.
Amusement parks often use UV lighting to fluoresce ride artwork and backdrops. This often has the side effect of causing rider's white clothing to glow light-purple.
To help prevent counterfeiting of currency, or forgery of important documents such as driver's licenses and passports, the paper may include a UV watermark or fluorescent multicolor fibers that are visible under ultraviolet light. Postage stamps are tagged with a phosphor that glows under UV rays to permit automatic detection of the stamp and facing of the letter.
UV fluorescent dyes are used in many applications (for example, biochemistry and forensics). Some brands of pepper spray will leave an invisible chemical (UV dye) that is not easily washed off on a pepper-sprayed attacker, which would help police identify the attacker later.
In some types of nondestructive testing UV stimulates fluorescent dyes to highlight defects in a broad range of materials. These dyes may be carried into surface-breaking defects by capillary action (liquid penetrant inspection) or they may be bound to ferrite particles caught in magnetic leakage fields in ferrous materials (magnetic particle inspection). | 5 | Photochemistry |
Normal metabolism of nucleotide sugars is very important. Any malfunction in any contributing enzyme will lead to a certain disease for example:
#Inclusion body myopathy: is a congenital disease resulted from altered function of UDP-GlcNAc epimerase .
#Macular corneal dystrophy: is a congenital disease resulted from malfunction of GlcNAc-6-sulfotransferase.
#Congenital disorder in α-1,3 mannosyl transferase will result in a variety of clinical symptoms, e.g. hypotonia, psychomotor retardation, liver fibrosis and various feeding problems. | 0 | Organic Chemistry |
Commonly fluorophores (such as rhodamine or fluorescein) are linked to the ring linked to the sugar (in para) via a flexible arm, presumably extruding from the major groove of the helix. Due to low processivity of the nucleotides linked to bulky adducts such as florophores by [Taq polymerase]s, the sequence is typically copied using a nucleotide with an arm and later coupled with a reactive fluorophore (indirect labelling):
* Amine reactive: aminoallyl nucleotides contain a primary amine group on a linker that reacts with the amino-reactive dye such as cyanine or Alexa Fluor dyes, which contain a reactive leaving group like succinimidyl ester (NHS). Base-pairing amino groups are not affected.
* Thiol reactive: thiol-containing nucleotides react with the fluorophore linked to a reactive leaving group like maleimide.
* Biotin-linked nucleotides rely on the same indirect labelling principle (and fluorescent streptavidin) and are used in Affymetrix DNAchips.
Fluorophores find a variety of uses in medicine and biochemistry. | 1 | Biochemistry |
A Maucha diagram, or Maucha symbol, is a graphical representation of the major cations and anions in a chemical sample. R. Maucha published the symbol in 1932.
It is mainly used by biologists and chemists for quickly recognising samples by their chemical composition. The symbol is similar in concept to the Stiff diagram. It conveys similar ionic information to the Piper diagram, though in a more compact format that is suitable as a map symbol or for showing changes with time. The Maucha diagram is a special case of the Radar chart and overcomes some of the limitations of the Pie chart by having equal angles for all variables and consistently showing each variable in the same position.
The star shape comprises eight kite-shaped polygons, the area of each of which is proportional to the concentration of an ion in milliequivalents per litre. The anions carbonate, bicarbonate, chloride and sulphate are on the left, while the cations potassium, sodium, calcium and magnesium are on the right. The total ionic concentration adds up to the area of the background circle, the total anion concentration adds up to the left semicircle and the total cation concentration adds up to the right semicircle. A method for drawing the diagram in R is available on GitHub.
Broch and Yake modified Maucha's original fixed-size diagram by scaling for concentration.
Further scaling using the logarithm of the ionic concentration enables the plotting of a wide range of concentrations on a single map. | 3 | Analytical Chemistry |
Directing a synthesis toward a desirable intermediate can greatly narrow the focus of analysis. This allows bidirectional search techniques. | 0 | Organic Chemistry |
On June 20, 2017, the United States Postal Service released the first application of thermochromic ink to postage stamps in its Total Eclipse of the Sun Forever stamp to commemorate the solar eclipse of August 21, 2017. When pressed with a finger, body heat turns the black circle in the center of the stamp into an image of the full moon. The stamp image is a photo of a total solar eclipse seen in Jalu, Libya, on March 29, 2006. The photo was taken by retired NASA astrophysicist Fred Espenak, aka "Mr. Eclipse". | 7 | Physical Chemistry |
There are two simple regular lattices that achieve this highest average density. They are called face-centered cubic (FCC) (also called cubic close packed) and hexagonal close-packed (HCP), based on their symmetry. Both are based upon sheets of spheres arranged at the vertices of a triangular tiling; they differ in how the sheets are stacked upon one another. The FCC lattice is also known to mathematicians as that generated by the A root system. | 3 | Analytical Chemistry |
Human satellite II is an exceptionally high-copy but unexplored sequence of the human genome thought of as junk DNA has a surprising ability to impact master regulators of our genome, and it goes awry in 50 percent of tumors.
Because HSAT-II DNA is normally methylated (a form of gene regulation), it remains dormant in healthy cells. For this reason, the HSAT-II hasn't been extensively studied and has not been thought to have a function. Due to its similarities to Human Satellite 3, the primary sequence component of the traditional human satellite fraction II (also known as Human Satellite 2 or HSat2) is sometimes incorrectly marked by RepeatMasker. In RepeatMasker annotations, both repeats frequently appear as a mixed pattern of "HSATII" and "(CATTC)n simple repeats." Based on this problem, Oxford Nanopore Technologies researcher used their own characterization of these sequences inside the CHM13 genome To further classify each HSat2 array into its previously identified subfamilies.
In fact, standard genomic experiments intentionally screen HSAT-II out of the results. Both herpes viruses and cancer manipulate this same pathway causing genetic instability and disease. | 1 | Biochemistry |
The dye-tuning capabilities cucurbiturils possess have been explored by researchers in recent years. In general, it has been found that the confined, low-polarity environment provided by the cucurbiturils leads to enhanced brightness, increased photostability, increased fluorescence lifetimes, and solvatochromism consistent with moving to an environment of lower polarity. | 6 | Supramolecular Chemistry |
In some cases where stereogenic centers are formed, the configuration must be specified. Without the presence of a non-covalent interaction, a compound is achiral. Some professionals have proposed a new rule to account for this. This rule states that "non-covalent interactions have a fictitious number between 0 and 1" when assigning priority. Compounds in which this occurs are referred to as coordination compounds. | 4 | Stereochemistry |
In his presentation at a 2019 chemometrics conference in France, Steven Brown called Kowalski the "father" of the following areas of chemometrics: NAS methods (with K. Booksh), multiway methods (with E. Sanchez), heuristics in chemistry (with C. Bender), multi-algorithms in chemistry for “big data” ( > 16 kb).
Responding to a question posed during a 1988 interview, Kowalski felt that his most impactful paper to date was the one he wrote with C. Bender, published in the Journal of the American Chemical Society in 1972, "Pattern recognition. A Powerful approach to interpreting chemical data". Wold categorized this publication as a "seminal" paper in pattern recognition in chemistry.
Kowalski's areas of interest outside of chemometrics were analytical instrumentation, remote sensing, process modeling, and chemical sensors in process analysis and control. | 3 | Analytical Chemistry |
In chemistry, phosphorus oxoacid (or phosphorus acid) is a generic name for any acid whose molecule consists of atoms of phosphorus, oxygen, and hydrogen. There is a potentially infinite number of such compounds. Some of them are unstable and have not been isolated, but the derived anions and organic groups are present in stable salts and esters. The most important ones—in biology, geology, industry, and chemical research—are the phosphoric acids, whose esters and salts are the phosphates.
In general, any hydrogen atom bonded to an oxygen atom is acidic, meaning that the –OH group can lose a proton leaving a negatively charged – group and thus turning the acid into a phosphorus oxoanion. Each additional proton lost has an associated acid dissociation constant K, K K, ..., often expressed by its cologarithm (pK, pK, pK, ...). Hydrogen atoms bonded directly to phosphorus are generally not acidic. | 0 | Organic Chemistry |
Recent progress in the field of microfluidics has led to the development of microdroplets, a new drug-delivery system that uses uniform droplets to deliver drugs to specific locations within the body. These microdroplets allow researchers to load drugs during the polymerization step of their formation and provide variations in porosity, which can control the time it takes to release a therapeutic payload. Thus, by using the natural process of chemotaxis, researchers aim to guide these tiny droplets by using chemical gradients released by a specific cell, tissue, or organ within the body. In fact, a few examples of microdroplet systems that use chemotaxis are self-propelling, ionic liquid-based, and synthetic base. These microdroplet-based drug delivery systems offer several advantages over traditional drug delivery methods, which are talked about later in the advantage and limitations subsection of this article. Overall, the development of microdroplet-based drug delivery systems using the phenomenon of chemotaxis is just one of may avenues to potentially revolutionize the field of medicine and targeted drug delivery. | 1 | Biochemistry |
When two metals touch each other and water is present, electrolysis occurs. One well known example is the reaction between zinc (Zn) and iron (Fe). Zinc atoms will lose electrons in preference to the iron as they are more electropositive and therefore zinc is oxidized and corrodes.
Zn(s)→(aq) +2e (oxidation) | 7 | Physical Chemistry |
Coagulation, the formation of a blood clot or thrombus, occurs when the proteins of the coagulation cascade are activated, either by contact with a damaged blood vessel wall and exposure to collagen in the tissue space (intrinsic pathway) or by activation of factor VII by tissue activating factors (extrinsic pathway). Both pathways lead to the generation of thrombin, an enzyme that turns the soluble blood protein fibrinogen into fibrin, which aggregates into protofibrils. Another thrombin-generated enzyme, factor XIII, then crosslinks the fibrin protofibrils at the D fragment site, leading to the formation of an insoluble gel that serves as a scaffold for blood clot formation.
The circulating enzyme plasmin, the main enzyme of fibrinolysis, cleaves the fibrin gel in a number of places. The resultant fragments, "high molecular weight polymers", are digested several times more by plasmin to lead to intermediate and then to small polymers (fibrin degradation products or FDPs). The cross-link between two D fragments remains intact, however, and these are exposed on the surface when the fibrin fragments are sufficiently digested. The structure of D-dimer is either a 180 kDa or 195 kDa molecule of two D domains, or a 340 kDa molecule of two D domains and one E domain of the original fibrinogen molecule. The half-life of D-dimer in blood is approximately 6 to 8 hours.
D-dimers are not normally present in human blood plasma, except when the coagulation system has been activated, for instance, because of the presence of thrombosis or disseminated intravascular coagulation. The D-dimer assay depends on the binding of a monoclonal antibody to a particular epitope on the D-dimer fragment. Several detection kits are commercially available; all of them rely on a different monoclonal antibody against D-dimer. For some of these, the area of the D-dimer to which the antibody binds is known. The binding of the antibody is then measured quantitatively by one of various laboratory methods. | 1 | Biochemistry |
STAT5 has been found to be constitutively phosphorylated in cancer cells, implying that the protein is always present in its active form. This constant activation is brought about either by mutations or by aberrant expressions of cell signalling, resulting in poor regulation, or complete lack of control, of the activation of transcription for genes influenced by STAT5. This leads to constant and increased expression of these genes. For example, mutations may lead to increased expression of anti-apoptotic genes, the products of which actively prevent cell death. The constant presence of these products preserves the cell in spite of it having become cancerous, causing the cell to eventually become malignant. | 1 | Biochemistry |
Typical domestic exposures are of around 100Bq/m indoors, but specifics of construction and ventilation strongly affect levels of accumulation; a further complication for risk assessment is that concentrations in a single location may differ by a factor of two over an hour, and concentrations can vary greatly even between two adjoining rooms in the same structure.
The distribution of radon concentrations is highly skewed: the larger concentrations have a disproportionately greater weight. Indoor radon concentration is usually assumed to follow a lognormal distribution on a given territory. Thus, the geometric mean is generally used to estimate the "average" radon concentration in an area.
The mean concentration ranges from less than 10 Bq/m to over 100 Bq/m in some European countries. Typical geometric standard deviations found in studies range between 2 and 3, meaning (given the 68–95–99.7 rule) that the radon concentration is expected to be more than a hundred times the mean concentration for 2 to 3% of the cases.
The so-called "Watras incident" in 1984 is named for American construction engineer Stanley Watras, an employee at the Limerick nuclear power plant in the United States, who triggered radiation monitors while leaving work over several days—even though the plant had not yet been fueled, and despite Watras being decontaminated and sent home "clean" each evening. This pointed to a source of contamination outside the power plant, which turned out to be radon levels of 100,000 Bq/m (2.7 nCi/L) in the basement of his home. He was told that living in the home was the equivalent of smoking 135 packs of cigarettes a day, and he and his family had increased their risk of developing lung cancer by 13 or 14 percent. The incident dramatized the fact that radon levels in particular dwellings can occasionally be orders of magnitude higher than typical. Radon soon became a standard homeowner concern, though typical domestic exposures are two to three orders of magnitude lower (100 Bq/m, or 2.5 pCi/L), making individual testing essential to assessment of radon risk in any particular dwelling.
Radon exists in every U.S. state, and about 6% of American houses have elevated levels. The highest average radon concentrations in the United States are found in Iowa and in the Appalachian Mountain areas in southeastern Pennsylvania. Some of the highest readings have been recorded in Mallow, County Cork, Ireland. Iowa has the highest average radon concentrations in the United States due to significant glaciation that ground the granitic rocks from the Canadian Shield and deposited it as soils making up the rich Iowa farmland. Many cities within the state, such as Iowa City, have passed requirements for radon-resistant construction in new homes. In a few locations, uranium tailings have been used for landfills and were subsequently built on, resulting in possible increased exposure to radon. | 2 | Environmental Chemistry |
We will assume that the Hamiltonian may be written as
where is the free Hamiltonian (or more generally, a Hamiltonian with known eigenvectors). For example, in nonrelativistic quantum mechanics may be
Intuitively is the interaction energy of the system. Let there be an eigenstate of :
Now if we add the interaction into the mix, the Schrödinger equation reads
Now consider the Hellmann–Feynman theorem, which requires the energy eigenvalues of the Hamiltonian to change continuously with continuous changes in the Hamiltonian. Therefore, we wish that as . A naive solution to this equation would be
where the notation denotes the inverse of . However is singular since is an eigenvalue of . As is described below, this singularity is eliminated in two distinct ways by making the denominator slightly complex:
By insertion of a complete set of free particle states,
the Schrödinger equation is turned into an integral equation. The "in" and "out" states are assumed to form bases too, in the distant past and distant future respectively having the appearance of free particle states, but being eigenfunctions of the complete Hamiltonian. Thus endowing them with an index, the equation becomes | 7 | Physical Chemistry |
Natural products containing acid anhydrides have been isolated from animals, bacteria and fungi. Examples include cantharidin from species of blister beetle, including the Spanish fly, Lytta vesicatoria, and tautomycin, from the bacterium Streptomyces spiroverticillatus. The maleidride family of fungal secondary metabolites, which possess a wide range of antibiotic and antifungal activity, are alicyclic compounds with maleic anhydride functional groups.
A number of proteins in prokaryotes and eukaryotes undergo spontaneous cleavage between the amino acid residues aspartic acid and proline via an acid anhydride intermediate. In some cases, the anhydride may then react with nucleophiles of other cellular components, such as at the surface of the bacterium Neisseria meningitidis or on proteins localized nearby. | 0 | Organic Chemistry |
Alkali metal alkoxides are often oligomeric or polymeric compounds, especially when the R group is small (Me, Et). The alkoxide anion is a good bridging ligand, thus many alkoxides feature or linkages. In solution, the alkali metal derivatives exhibit strong ion-pairing, as expected for the alkali metal derivative of a strongly basic anion. | 0 | Organic Chemistry |
An attractant is any chemical that attracts an organism, e.g. i) synthetic lures; ii) aggregation and sex pheromones (intraspecific interactions); and iii) synomone (interspecific interactions) | 1 | Biochemistry |
No truly smooth surfaces really exist, and surface imperfections are visible under a microscope. As a result, when two bodies are pressed together, contact is only performed in a finite number of points, separated by relatively large gaps, as can be shown in Fig. 2. Since the actual contact area is reduced, another resistance for heat flow exists. The gases/fluids filling these gaps may largely influence the total heat flow across the interface. The thermal conductivity of the interstitial material and its pressure, examined through reference to the Knudsen number, are the two properties governing its influence on contact conductance, and thermal transport in heterogeneous materials in general.
In the absence of interstitial materials, as in a vacuum, the contact resistance will be much larger, since flow through the intimate contact points is dominant. | 7 | Physical Chemistry |
To apply the strategy, a high-molecular-weight DNA strand is sheared into random fragments, size-selected (usually 2, 10, 50, and 150 kb), and cloned into an appropriate vector. The clones are then sequenced from both ends using the chain termination method yielding two short sequences. Each sequence is called an end-read or read 1 and read 2 and two reads from the same clone are referred to as mate pairs. Since the chain termination method usually can only produce reads between 500 and 1000 bases long, in all but the smallest clones, mate pairs will rarely overlap. | 1 | Biochemistry |
Specifically, an SMB system has two or more identical columns, which are connected to the mobile phase pump, and each other, by a multi-port valve. The plumbing is configured in such a way that:
:a) all columns will be connected in series, forming a single continuous loop;
:b) typically, between each column there will be provisions for four process streams: incoming feed mixture, exiting purified fast component, exiting purified slow component, and incoming solvent or eluent;
and
:c) each process stream (two inlets and two outlets) will proceed in the same direction after a set time (the steptime). | 3 | Analytical Chemistry |
M13 phage - m7G(5')pppN diphosphatase - malformation - maltose-transporting ATPase - manganese-transporting ATPase - mannose-6-phosphate 6-reductase - mapping - marker - melanoma - melting - menaquinol oxidase (H+-transporting) - Johann Mendel - Mendelian inheritance - message - messenger RNA - metaphase - methylphenyltetrahydropyridine N-monooxygenase - methylsterol monooxygenase - methyltetrahydroprotoberberine 14-monooxygenase - microarray technology - microsatellite - MIMT1 - minusheet perfusion culture system - Mir-188 microRNA precursor family - Mir-615 microRNA precursor family - Mir-675 microRNA precursor family - missense mutation - mitochondrial DNA - mobility shift - molecular weight size marker - monoclonal antibody - monosaccharide-transporting ATPase - monosomy - morphine 6-dehydrogenase - mouse model - mRNA - multicistronic message - multicopy plasmid - multiple cloning site - multiple endocrine neoplasia, type 1 - mutation - myristoyl-CoA 11-(E) desaturase - myristoyl-CoA 11-(Z) desaturase - | 1 | Biochemistry |
Ultraviolet (UV) LD is typically employed in the analysis of biological molecules, especially large, flexible, long molecules that prove difficult to structurally determine by such methods as NMR and X-ray diffraction. | 7 | Physical Chemistry |
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