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Chemotactic drug delivery systems are an emerging field of drug delivery that aims to apply the natural phenomenon of chemotaxis in guiding and delivering a drug to a specific tissue or cell within the body. Thus, similar to how organisms use chemotaxis, researchers have designed drug delivery systems to detect, maneuver, and react to chemical molecules released by a desired cell or its surrounding area. | 1 | Biochemistry |
An example of a plumbide is CeRhPb. The lead atom has a coordination number of 12 in the crystal structure of this compound. It is bound to four rhodiums, six ceriums, and two other lead atoms in the crystal structure of the chemical.
Several other plumbides are the MPdPb plumbides, where M is a rare-earth element, and the intermetallic additionally contains a palladium. These plumbides tend to exhibit antiferromagnetism, and all of them are conductors.
A third plumbide is TiPb. Like the above plumbides, it is an intermetallic, but it only contains titanium as the other metal, and not any rare earths.
Plumbides can also be Zintl phase compounds, such as [K(18-crown-6)]KPb·(en). This is not a simple Zintl compound, but rather contains the organic molecules 18-crown-6 and ethylenediamine (en) in order to stabilize the crystal structure. | 7 | Physical Chemistry |
The rate of cell growth is directly dependent on the rate of protein synthesis, which is itself intricately linked to ribosome synthesis and rRNA transcription. Thus, intracellular signals must coordinate the synthesis of rRNA with that of other components of protein translation. Myc is known to bind to human ribosomal DNA in order to stimulate rRNA transcription by RNA polymerase I. Two specific mechanisms have been identified, ensuring proper control of rRNA synthesis and Pol I-mediated transcription.
Given the large numbers of rDNA genes (several hundreds) available for transcription, the first mechanism involves adjustments in the number of genes being transcribed at a specific time. In mammalian cells, the number of active rDNA genes varies between cell types and level of differentiation. In general, as a cell becomes more differentiated, it requires less growth and, therefore, will have a decrease in rRNA synthesis and a decrease in rDNA genes being transcribed. When rRNA synthesis is stimulated, SL1 (selectivity factor 1) will bind to the promoters of rDNA genes that were previously silent, and recruit a pre-initiation complex to which Pol I will bind and start transcription of rRNA.
Changes in rRNA transcription can also occur via changes in the rate of transcription. While the exact mechanism through which Pol I increases its rate of transcription is as yet unknown, evidence has shown that rRNA synthesis can increase or decrease without changes in the number of actively transcribed rDNA. | 1 | Biochemistry |
Compared to the other major proton-pumping subunits of the electron transport chain, the number of subunits found can be small, as small as three polypeptide chains. This number does increase, and eleven subunits are found in higher animals. Three subunits have prosthetic groups. The cytochrome b subunit has two b-type hemes (b and b), the cytochrome c subunit has one c-type heme (c), and the Rieske Iron Sulfur Protein subunit (ISP) has a two iron, two sulfur iron-sulfur cluster (2Fe•2S).
Structures of complex III: , | 1 | Biochemistry |
The method is currently being developed and was applied to investigate translation dynamics in live yeast cells and is extending, rather than simply combining, the capabilities of the previous techniques. The only other transcriptome-wide method for mapping ribosome positions over mRNA with nucleotide precision is ribosome (translation) profiling. However, it captures positions of only elongating ribosomes, and most dynamic and functionally important intermediates of translation at the initiation stage are not detected.
TCP-seq was designed to specifically target these blind spots. It can essentially provide the same level of details for elongation phase as ribosome (translation) profiling, but also includes recording of initiation, termination and recycling intermediates (and basically any other possible translation complexes as long as the ribosome or its subunits are contacting and protecting the mRNA) of protein synthesis that previously remained out of the reach. Therefore, TCP-seq provides a single approach for a complete insight into the translation process of a biological sample. This particular aspect of the method can be expected to be developed further as the dynamics of ribosomal scanning on mRNA during translation initiation is generally unknown for the most of life. Current dataset containing TCP-seq data for translation initiation is available for yeast Saccharomyces cerevisiae, and likely to be extended for other organisms in the future. | 1 | Biochemistry |
Nitrogen is present in the environment in a wide variety of chemical forms including organic nitrogen, ammonium (), nitrite (), nitrate (), nitrous oxide (), nitric oxide (NO) or inorganic nitrogen gas (). Organic nitrogen may be in the form of a living organism, humus or in the intermediate products of organic matter decomposition. The processes in the nitrogen cycle is to transform nitrogen from one form to another. Many of those processes are carried out by microbes, either in their effort to harvest energy or to accumulate nitrogen in a form needed for their growth. For example, the nitrogenous wastes in animal urine are broken down by nitrifying bacteria in the soil to be used by plants. The diagram alongside shows how these processes fit together to form the nitrogen cycle. | 1 | Biochemistry |
Differential refractometers are often used for the analysis of polymer samples in size exclusion chromatography. | 3 | Analytical Chemistry |
Arash Ghorbani-Choghamarani (born 23 September 1979) is an Iranian chemist and Professor of Chemistry at Bu-Ali Sina University. He is also Deputy of Research and Technology at this university since November 2021.
Ghorbani-Choghamarani is among the most-cited Iranian researchers and is known for his works on organic chemistry, nanochemistry, heterogeneous catalysis, heterocyclic compounds and organic synthesis.
Previously He was professor and Deputy of Education at Ilam University.
Ghorbani-Choghamarani is a winner of Ilam Province Book of the Year for his book Drug Delivery Systems and Their Effectiveness Through Nanotechnology. | 0 | Organic Chemistry |
ATP can be generated by substrate-level phosphorylation in mitochondria in a pathway that is independent from the proton motive force. In the matrix there are three reactions capable of substrate-level phosphorylation, utilizing either phosphoenolpyruvate carboxykinase or succinate-CoA ligase, or monofunctional C1-tetrahydrofolate synthase. | 1 | Biochemistry |
Light production may first be triggered by nerve impulses which stimulate the photocyte to release the enzyme luciferase into a "reaction chamber" of luciferin substrate. In some species the release occurs continually without the precursor impulse via osmotic diffusion. Molecular oxygen is then actively gated through surrounding tracheal cells which otherwise limit the natural diffusion of oxygen from blood vessels; the resulting reaction with the luciferase and luciferin produces light energy and a by-product (usually carbon dioxide). The reaction occurs in the peroxisome of the cell.
Researchers once postulated that ATP was the source of reaction energy for photocytes, but since ATP only produces a fraction the energy of the luciferase reaction, any resulting light wave-energy would be too small for detection by a human eye. The wavelengths produced by most photocytes fall close to 490 nm; although light as energetic as 250 nm is reportedly possible.
The variations of color seen in different photocytes are usually the result of color filters that alter the wavelength of the light prior to exiting the endoderm, thanks to the other parts of the photophore. The range of colors vary between bioluminescent species.
The exact combinations of luciferase and luciferin types found among photocytes are specific to the species to which they belong. This would seem to be the result of consistent evolutionary divergence. | 1 | Biochemistry |
There is an important shortcoming for DLTS: it cannot be used for insulating materials. (Note: an insulator can be considered as a very large bandgap semiconductor.) For insulating materials it is difficult or impossible to produce a device having a space region for which width could be changed by the external voltage bias and thus the capacitance measurement-based DLTS methods cannot be applied for the defect analysis. Basing on experiences of the thermally stimulated current (TSC) spectroscopy, the current transients are analyzed with the DLTS methods (I-DLTS), where the light pulses are used for the defect occupancy disturbance. This method in the literature is sometimes called the Photoinduced Transient Spectroscopy (PITS). I-DLTS or PITS are also used for studying defects in the i-region of a p-i-n diode. | 7 | Physical Chemistry |
Levoamphetamine{{#tag:ref|Synonyms and alternate spellings include: (IUPAC name), levamfetamine (International Nonproprietary Name [INN]), , , , and is a central nervous system (CNS) stimulant known to increase wakefulness and concentration in association with decreased appetite and fatigue. Pharmaceuticals that contain levoamphetamine are currently indicated and prescribed for the treatment of attention deficit hyperactivity disorder (ADHD), obesity, and narcolepsy in some countries.
Levoamphetamine is the levorotatory stereoisomer of the amphetamine molecule. While pharmaceutical formulations containing enantiopure levoamphetamine are no longer manufactured, levomethamphetamine (levmetamfetamine) is still marketed and sold over-the-counter as a nasal decongestant. | 4 | Stereochemistry |
The oxide crystal structure is based on a close-pack array of oxygen anions, with metal cations occupying interstitial sites. The close-packed arrays, such as face-centered-cubic (fcc) and hexagonal-close packed (hcp), have both octahedral and tetrahedral interstices. | 7 | Physical Chemistry |
Eukaryotic transcription repressors share some of the mechanisms used by their prokaryotic counterparts. For example, by binding to a site on DNA that overlaps with the binding site of an activator, a repressor can inhibit binding of the activator. But more frequently, eukaryotic repressors inhibit the function of an activator by masking its activating domain, preventing its nuclear localization, promoting its degradation, or inactivating it through chemical modifications. Repressors can directly inhibit transcription initiation by binding to a site upstream of a promoter and interacting with the transcriptional machinery. Repressors can indirectly repress transcription by recruiting histone modifiers (deacetylases and methylases) or nucleosome remodeling enzymes that affect the accessibility of the DNA. Repressing histone and DNA modifications are also the basis of transcriptional silencing that can spread along the chromatin and switch off multiple genes. | 1 | Biochemistry |
The word catabolism is from Neo-Latin, which got the roots from Greek: κάτω kato, "downward" and βάλλειν ballein, "to throw". | 1 | Biochemistry |
Immunomodulation and immunoregulation were a particular focus of early myokine research, as, according to Dr. Bente Klarlund Pedersen and her colleagues, "the interactions between exercise and the immune system provided a unique opportunity to evaluate the role of underlying endocrine and cytokine mechanisms."
Muscle has an impact on the trafficking and inflammation of lymphocytes and neutrophils. During exercise, both neutrophils and NK cells and other lymphocytes enter the blood. Long-duration, high-intensity exercise leads to a decrease in the number of lymphocytes, while the concentration of neutrophils increases through mechanisms including adrenaline and cortisol.Interleukin-6 has been shown to mediate the increase in Cortisol: IL-6 stimulates the production of cortisol and therefore induces leukocytosis and lymphocytopenia. | 1 | Biochemistry |
The molecular organization of the nodes corresponds to their specialized function in impulse propagation. The level of sodium channels in the node versus the internode suggests that the number IMPs corresponds to sodium channels. Potassium channels are essentially absent in the nodal axolemma, whereas they are highly concentrated in the paranodal axolemma and Schwann cell membranes at the node. The exact function of potassium channels have not quite been revealed, but it is known that they may contribute to the rapid repolarization of the action potentials or play a vital role in buffering the potassium ions at the nodes. This highly asymmetric distribution of voltage-gated sodium and potassium channels is in striking contrast to their diffuse distribution in unmyelinated fibers.
The filamentous network subjacent to the nodal membrane contains cytoskeletal proteins called spectrin and ankyrin. The high density of ankyrin at the nodes may be functionally significant because several of the proteins that are populated at the nodes share the ability to bind to ankyrin with extremely high affinity. All of these proteins, including ankyrin, are enriched in the initial segment of axons which suggests a functional relationship. Now the relationship of these molecular components to the clustering of sodium channels at the nodes is still not known. Although some cell-adhesion molecules have been reported to be present at the nodes inconsistently; however, a variety of other molecules are known to be highly populated at the glial membranes of the paranodal regions where they contribute to its organization and structural integrity. | 1 | Biochemistry |
Several techniques of re-utilising the spoil tips exist, usually including either geotechnics or recycling. Most commonly, old spoil tips are partially revegetated to provide valuable green spaces since they are inappropriate for building purposes. At Nœux-les-Mines, an artificial ski slope has been constructed on the tip. If spoil tips are considered to contain sufficient amounts of residual material, various methods are employed to remove the spoil from the site for subsequent processing.
The oldest coal-based spoil tips may still contain enough coal to begin spontaneous slow combustion. This results in a form of vitrification of the shale, which then acquires sufficient mechanical strength to be of use in road construction. Some can therefore have a new life in being thus exploited; for example, the flattened pile of residue from the 11/19 site of Loos-en-Gohelle. Conversely, others are painstakingly preserved on account of their ecological wealth. With the passage of time, they become colonised with a variety of flora and fauna, sometimes foreign to the region. This diversity follows the mining exploitation. In South Wales some spoil tips are protected as Sites of Special Scientific Interest because they provide a unique habitat for 57 species of Lichen, several of which are at risk due to their limited environment being developed and by vegetation development.
For example, because the miners threw their apple or pear cores into the wagons, the spoil tips became colonised with fruit trees. One can even observe the proliferation of buckler-leaved sorrel (French sorrel – Rumex scutatus), the seeds of which have been carried within the cracks in the pine timber used in the mines. Furthermore, on account of its dark colour, the south face of the spoil tip is significantly warmer than its surroundings, which contributes to the diverse ecology of the area. In this way, the spoil tip of Pinchonvalles, at Avion, hosts 522 different varieties of higher plants. Some sixty species of birds nest there.
Some are used to cultivate vines, as in the case of Spoil Tip No. 7 of the coal-mining region of Mariemont-Bascoup near Chapelle-lez-Herlaimont (province of Hainaut). It produces some 3,000 litres of wine each year from a vineyard on its slopes.
Some spoil tips are used for various sporting activities. The slopes of the spoil tips of 11/19 at Loos-en-Gohelle, or again, at Nœux-les-Mines, are used for winter sports, for example ski and luge. A piste was built on the flank of the heap. In Belgium, a long distance footpath along the spoil tips (GR-412, Sentier des terrils) was opened in 2005. It leads from Bernissart in western Hainaut to Blegny in the province of Liège.
In the United States, coal mining companies have not been allowed to leave behind abandoned piles since the Surface Mining Control and Reclamation Act was passed in 1977. The Virginia City Hybrid Energy Center uses coal gob as a fuel source for energy production. | 8 | Metallurgy |
Polymer molecules within a brush are stretched away from the attachment surface as a result of the fact that they repel each other (steric repulsion or osmotic pressure). More precisely, they are more elongated near the attachment point and unstretched at the free end, as depicted on the drawing.
More precisely, within the approximation derived by Milner, Witten, Cates, the average density of all monomers in a given chain is always the same up to a prefactor:
where is the altitude of the end monomer and the number of monomers per chain.
The averaged density profile of the end monomers of all attached chains, convoluted with the above density profile for one chain, determines the density profile of the brush as a whole:
A dry brush has a uniform monomer density up to some altitude . One can show that the corresponding end monomer density profile is given by:
where is the monomer size.
The above monomer density profile for one single chain minimizes the total elastic energy of the brush,
regardless of the end monomer density profile , as shown in. | 7 | Physical Chemistry |
In organic chemistry, a hemiacetal or a hemiketal has the general formula , where is hydrogen or an organic substituent. They generally result from the addition of an alcohol (a compound with at least one group) to an aldehyde () or a ketone (), although the latter are sometimes called hemiketals. Most sugars are hemiacetals. | 0 | Organic Chemistry |
Flutamide has been found to be effective in the treatment of acne and seborrhea in women in a number of studies. In a long-term study of 230 women with acne, 211 of whom also had seborrhea, very-low-dose flutamide alone or in combination with an oral contraceptive caused a marked decrease in acne and seborrhea after 6 months of treatment, with maximal effect by 1 year of treatment and benefits maintained in the years thereafter. In the study, 97% of the women reported satisfaction with the control of their acne with flutamide. In another study, flutamide decreased acne and seborrhea scores by 80% in only 3 months. In contrast, spironolactone decreased symptoms by only 40% in the same time period, suggesting superior effectiveness for flutamide for these indications. Flutamide has, in general, been found to reduce symptoms of acne by as much as 90% even at low doses, with several studies showing complete acne clearance. | 4 | Stereochemistry |
Production and use of Rieke metals often involves the handling of highly pyrophoric materials, requiring the use of air-free techniques. | 0 | Organic Chemistry |
The localization of ADAM17 is speculated to be an important determinant of shedding activity. TNF-α processing has classically been understood to occur in the trans-Golgi network, and be closely connected to transport of soluble TNF-α to the cell surface. Shedding is also associated with clustering of ADAM17 with its substrate, membrane bound TNF, in lipid rafts. The overall process is called substrate presentation and regulated by cholesterol. Research also suggests that the majority of mature, endogenous ADAM17 may be localized to a perinuclear compartment, with only a small amount of TACE being present on the cell surface. The localization of mature ADAM17 to a perinuclear compartment, therefore, raises the possibility that ADAM17-mediated ectodomain shedding may also occur in the intracellular environment, in contrast with the conventional model.
Functional ADAM17 has been documented to be ubiquitously expressed in the human colon, with increased activity in the colonic mucosa of patients with ulcerative colitis, a main form of inflammatory bowel disease. Other experiments have also suggested that expression of ADAM17 may be inhibited by ethanol. | 1 | Biochemistry |
Terpenoids facilitate communication between plants and insects, mammals, fungi, microorganisms, and other plants. Terpenoids may act as both attractants and repellants for various insects. For example, pine shoot beetles (Tomicus piniperda) are attracted to certain monoterpenes ( (+/-)-a-pinene, (+)-3-carene and terpinolene) produced by Scots pines (Pinus sylvestris), while being repelled by others (such as verbenone).
Terpenoids are a large family of biological molecules with over 22,000 compounds. Terpenoids are similar to terpenes in their carbon skeleton but unlike terpenes contain functional groups. The structure of terpenoids is described by the biogenetic isoprene rule which states that terpenoids can be thought of being made of isoprenoid subunits, arranged either regularly or irregularly. The biosynthesis of terpenoids occurs via the methylerythritol phosphate (MEP) and mevalonic acid(MVA) pathways both of which include isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) as key components. The MEP pathway produces hemiterpenes, monoterpenes, diterpenes, and volatile carotenoid derivatives while the MVA pathway produces sesquiterpenes. | 1 | Biochemistry |
Fluorine is relatively rare in the universe compared to other elements of nearby atomic weight. On Earth, fluorine is essentially found only in mineral compounds because of its reactivity. The main commercial source, fluorite, is a common mineral. | 9 | Geochemistry |
A body-centered cubic unit cell has six octahedral voids located at the center of each face of the unit cell, and twelve further ones located at the midpoint of each edge of the same cell, for a total of six net octahedral voids. Additionally, there are 24 tetrahedral voids located in a square spacing around each octahedral void, for a total of twelve net tetrahedral voids. These tetrahedral voids are not local maxima and are not technically voids, but they do occasionally appear in multi-atom unit cells. | 3 | Analytical Chemistry |
Various diphosphates are used as emulsifiers, stabilisers, acidity regulators, raising agents, sequestrants, and water retention agents in food processing. They are classified in the E number scheme under E450:
*E450(a): disodium dihydrogen diphosphate; trisodium diphosphate; tetrasodium diphosphate (TSPP); tetrapotassium diphosphate
*E450(b): pentasodium and pentapotassium triphosphate
*E450(c): sodium and potassium polyphosphates
In particular, various formulations of diphosphates are used to stabilize whipped cream. | 1 | Biochemistry |
Multiple Michael/aldol reaction (or domino Michael/aldol reaction) is a consecutive series of reactions composed of either Michael addition reactions or aldol reactions. More than two steps of reaction are usually involved. This reaction has been used for synthesis of large macrocyclic or polycyclic ring structures.
Gary Posner and co-workers were the first to report using multiple Michael/aldol reactions to construct macrolide structures. Their method utilized a Michael-Michael-Michael-ring closure (MIMI-MIRC) or a Michael-Michael-aldol-ring closure annulation sequences to assemble acrylates and/or aldehydes together to form substituted 9-, 10-, and 11-membered macrolide structures. Besides synthesis of complex ring structures, multiple Michael/aldol reaction can also be used for rapid production of complex compound libraries.
Aldolases have been used to mediate multiple aldol reactions. Chi-Huey Wong and co-workers had shown that 2-deoxyribose-5-phosphate aldolase and fructose-1, 6-diphosphate aldolase could be used together in a one-pot reaction to connect two aldehydes and one ketone together through sequential aldol reactions. This reaction could be used to generate a variety of carbohydrate derivatives. | 0 | Organic Chemistry |
Lithium-associated hyperparathyroidism is the leading cause of hypercalcemia in lithium-treated patients. Lithium may lead to exacerbation of pre-existing primary hyperparathyroidism or cause an increased set-point of calcium for parathyroid hormone suppression, leading to parathyroid hyperplasia. | 1 | Biochemistry |
The hexol cation exists as two optical isomers that are mirror images of each other, depending on the arrangement of the bonds between the central cobalt atom and the three bidentate peripheral units [Co(NH)(HO)]. It belongs to the D point group. The nature of chirality can be compared to that of the ferrioxalate anion .
In a historic set of experiments, a salt of hexol with an optically active anion — specifically, its -(+)-bromocamphorsulfonate – was resolved into separate salts of the two cation isomers by fractional crystallisation. A more efficient resolution involves the bis(tartrato)diantimonate(III) anion. The hexol hexacation has a high specific rotation of 2640°. | 4 | Stereochemistry |
Dislocations require proper lattice ordering to move through a material. At grain boundaries, there is a lattice mismatch, and every atom that lies on the boundary is uncoordinated. This stops dislocations that encounter the boundary from moving. | 8 | Metallurgy |
Coelenteramine is a metabolic product of the bioluminescent reactions in organisms that utilize coelenterazine. It was first isolated from Aequorea victoria along with coelenteramide after coelenterates were stimulated to emit light. | 1 | Biochemistry |
Traditionally the level of multiplexing in SILAC was limited due to the number of SILAC isotopes available. Recently, a new technique called NeuCode (neutron encoding) SILAC, has augmented the level of multiplexing achievable with metabolic labeling (up to 4). The NeuCode amino acid method is similar to SILAC but differs in that the labeling only utilizes heavy amino acids. The use of only heavy amino acids eliminates the need for 100% incorporation of amino acids needed for SILAC. The increased multiplexing capability of NeuCode amino acids is from the use of mass defects from extra neutrons in the stable isotopes. These small mass differences however need to be resolved on high-resolution mass spectrometers. | 1 | Biochemistry |
Hydrogen peroxide can be detected with high sensitivity by the luminescence of lanthanide probes—however only at relatively high pH values. A lanthanide-based analytical procedure was proposed in 2002 based on the finding that the europium complex with various tetracyclines binds hydrogen peroxide forming a luminescent complex. | 1 | Biochemistry |
The osmolarity of a solution, given in osmoles per liter (osmol/L) is calculated from the following expression:
where
* is the osmotic coefficient, which accounts for the degree of non-ideality of the solution. In the simplest case it is the degree of dissociation of the solute. Then, is between 0 and 1 where 1 indicates 100% dissociation. However, can also be larger than 1 (e.g. for sucrose). For salts, electrostatic effects cause to be smaller than 1 even if 100% dissociation occurs (see Debye–Hückel equation);
* is the number of particles (e.g. ions) into which a molecule dissociates. For example: glucose has of 1, while NaCl has of 2;
* is the molar concentration of the solute;
* the index represents the identity of a particular solute.
Osmolarity can be measured using an osmometer which measures colligative properties, such as Freezing-point depression, Vapor pressure, or Boiling-point elevation. | 3 | Analytical Chemistry |
Two molecules (including polyatomic ions) A and B have the same structure if each atom of A can be paired with an atom of B of the same element, in a one-to-one way, so that for every bond in A there is a bond in B, of the same type, between corresponding atoms; and vice versa. This requirement applies also complex bonds that involve three or more atoms, such as the delocalized bonding in the benzene molecule and other aromatic compounds.
Depending on the context, one may require that each atom be paired with an atom of the same isotope, not just of the same element.
Two molecules then can be said to be structural isomers (or, if isotopes matter, structural isotopomers) if they have the same molecular formula but do not have the same structure. | 4 | Stereochemistry |
* G. Reginald Bashforth, The manufacture of iron and steel, vol. 2: Steel production, London, Chapman & Hall Ltd, 1951, 461 p.
* Thomas Turner (dir.), The metallurgy of iron: By Thomas Turner...: Being one of a series of treatises on metallurgy written by associates of the Royal school of mines, C. Griffin & company, limited, coll. "Griffin's metallurgical series", 1908, 3rd ed., 463 p.
* Walter MacFarlane, The principles and practice of iron and steel manufacture, Longmans, Green, and Co, 1917, 5th ed.
* R.W. Burnie, Memoir and letters of Sidney Gilchrist Thomas, Inventor, John Murray, 1891
* William Tulloch Jeans, The Creators of the Age of Steel, 1884, 356 p.
* Hermann Wedding (translated from German by: William B. Phillips, Ph.D. & Ernst Prochaska), Weddings basic Bessemer process' ["Basische Bessemer - oder Thomas-Process"], New York Scientific Publishing Company, 1891, 224 p.
* Jean Duflot, Encyclopædia Universalis, "Sidérurgie" | 8 | Metallurgy |
In these processes, iron ore is brought into contact with reducing gases produced and heated by a separate plant in a closed enclosure. As a result, these processes are naturally suited to the use of natural gas. | 8 | Metallurgy |
Common uses of episulfides in both academic and industrial settings most often involve their use as monomers in polymerization reactions.
Episulfides have an innate ring strain due to the nature of three-membered rings. Therefore, most reactions of episulfides involve ring-opening. Most commonly, nucleophiles are employed for the ring-opening process. For terminal episulfide, nucleophiles attack the primary carbon. Nucleophiles include hydrides, thiolates, alkoxides, amines, and carbanions. | 0 | Organic Chemistry |
QCD is one part of the modern theory of particle physics called the Standard Model. Other parts of this theory deal with electroweak interactions and neutrinos. The theory of electrodynamics has been tested and found correct to a few parts in a billion. The theory of weak interactions has been tested and found correct to a few parts in a thousand. Perturbative forms of QCD have been tested to a few percent. Perturbative models assume relatively small changes from the ground state, i.e. relatively low temperatures and densities, which simplifies calculations at the cost of generality. In contrast, non-perturbative forms of QCD have barely been tested. The study of the QGP, which has both a high temperature and density, is part of this effort to consolidate the grand theory of particle physics.
The study of the QGP is also a testing ground for finite temperature field theory, a branch of theoretical physics which seeks to understand particle physics under conditions of high temperature. Such studies are important to understand the early evolution of our universe: the first hundred microseconds or so. It is crucial to the physics goals of a new generation of observations of the universe (WMAP and its successors). It is also of relevance to Grand Unification Theories which seek to unify the three fundamental forces of nature (excluding gravity). | 7 | Physical Chemistry |
Statistics Canada administers the Canadian Health Measures Survey, which includes biomonitoring for environmental chemicals. Health Canada administers a program called Mother-Infant Research on Environmental Chemicals, which focuses on 2,000 pregnant women and their infants. | 2 | Environmental Chemistry |
Although the presence of carbon in the Earths core is well-constrained, recent studies suggest large inventories of carbon could be stored in this region. Shear (S) waves moving through the inner core travel at about fifty percent of the velocity expected for most iron-rich alloys. Considering the cores composition is widely believed to be an alloy of crystalline iron with a small amount of nickel, this seismographic anomaly points to another substances existence within the region. One theory postulates that such a phenomenon is the result of various light elements, including carbon, in the core. In fact, studies have utilised diamond anvil cells to replicate the conditions in the Earths core, the results of which indicate that iron carbide (FeC) matches the inner cores sound and density velocities considering its temperature and pressure profile. Hence, the iron carbide model could serve as evidence that the core holds as much as 67% of the Earths carbon. Furthermore, another study found that carbon dissolved in iron and formed a stable phase with the same FeC composition—albeit with a different structure than the one previously mentioned. Hence, although the amount of carbon potentially stored in the Earth's core is not known, recent research indicates that the presence of iron carbides could be consistent with geophysical observations. | 9 | Geochemistry |
Flash photolysis is a pump-probe laboratory technique, in which a sample is first excited by a strong pulse of light from a pulsed laser of nanosecond, picosecond, or femtosecond pulse width or by another short-pulse light source such as a flash lamp. This first strong pulse is called the pump pulse and starts a chemical reaction or leads to an increased population for energy levels other than the ground state within a sample of atoms or molecules. Typically the absorption of light by the sample is recorded within short time intervals (by a so-called test or probe pulses) to monitor relaxation or reaction processes initiated by the pump pulse.
Flash photolysis was developed shortly after World War II as an outgrowth of attempts by military scientists to build cameras fast enough to photograph missiles in flight. The technique was developed in 1949 by Manfred Eigen, Ronald George Wreyford Norrish and George Porter, who won the 1967 Nobel Prize in Chemistry for this invention. Over the next 40 years the technique became more powerful and sophisticated due to developments in optics and lasers. Interest in this method grew considerably as its practical applications expanded from chemistry to areas such as biology, materials science, and environmental sciences. Today, flash photolysis facilities are extensively used by researchers to study light-induced processes in organic molecules, polymers, nanoparticles, semiconductors, photosynthesis in plants, signaling, and light-induced conformational changes in biological systems. | 7 | Physical Chemistry |
In neuroscience, repolarization refers to the change in membrane potential that returns it to a negative value just after the depolarization phase of an action potential which has changed the membrane potential to a positive value. The repolarization phase usually returns the membrane potential back to the resting membrane potential. The efflux of potassium (K) ions results in the falling phase of an action potential. The ions pass through the selectivity filter of the K channel pore.
Repolarization typically results from the movement of positively charged K ions out of the cell. The repolarization phase of an action potential initially results in hyperpolarization, attainment of a membrane potential, termed the afterhyperpolarization, that is more negative than the resting potential. Repolarization usually takes several milliseconds.
Repolarization is a stage of an action potential in which the cell experiences a decrease of voltage due to the efflux of potassium (K) ions along its electrochemical gradient. This phase occurs after the cell reaches its highest voltage from depolarization. After repolarization, the cell hyperpolarizes as it reaches resting membrane potential (−70 mV in neuron). Sodium (Na) and potassium ions inside and outside the cell are moved by a sodium potassium pump, ensuring that electrochemical equilibrium remains unreached to allow the cell to maintain a state of resting membrane potential. In the graph of an action potential, the hyper-polarization section looks like a downward dip that goes lower than the line of resting membrane potential. In this afterhyperpolarization (the downward dip), the cell sits at more negative potential than rest (about −80 mV) due to the slow inactivation of voltage gated K delayed rectifier channels, which are the primary K channels associated with repolarization. At these low voltages, all of the voltage gated K channels close, and the cell returns to resting potential within a few milliseconds. A cell which is experiencing repolarization is said to be in its absolute refractory period. Other voltage gated K channels which contribute to repolarization include A-type channels and Ca-activated K channels. Protein transport molecules are responsible for Na out of the cell and K into the cell to restore the original resting ion concentrations. | 7 | Physical Chemistry |
The Polyarc reactor needs hydrogen and air, which are both gases used in any existing FID setup. Software for capturing and analyzing FID signals remains applicable, and no extra software is necessary for the device. Gas flows to the device are controlled using an external control box that must be calibrated manually for the desired flows of air and hydrogen. The detector's overall response can be analyzed either by an external or an internal standard method.
In the external standard method, the FID signal is correlated to the concentration of carbon separately from the analysis. In practice, this entails the injection of any carbon species at varying amounts to create a plot of signal (i.e., peak area) versus injected carbon amount (e.g., moles of carbon). The user should take care to account for any sample splitting, adsorption, inlet discrimination, and leaks. The data should form a line with a slope, m, and an intercept, b. The inverse of this line can be used to determine the amount of carbon in any subsequent injection from any compound.
This is different from a typical FID calibration where this procedure would need to be completed for each compound to account for the relative response differences. The calibration should be examined periodically to account for catalyst deactivation and other sources of detector drift.
In the internal standard method, the sample is doped with a known amount of some organic molecule and the amount of all other species can be derived from their relative response to the internal standard (IS). The IS can be any organic molecule and should be chosen for ease of use and compatibility with the compounds in the mixture. For example, one could add 0.01 g of methanol as the IS to 0.9 g of gasoline. The 1 wt% mixture of methanol/gasoline is then injected and the concentration of all other species can be determined from their relative response to methanol on a carbon basis,
The effects of injection-to-injection variability resulting from different injection volumes, varying split ratios and leaks are eliminated with the internal standard method. However, inlet discrimination caused by adsorption, reaction, or preferential vaporization in the inlet can lead to accuracy issues when the internal standard is influenced differently than the analyte.
Any non-carbon species that would not be detected in a traditional FID setup (e.g. water, nitrogen, ammonia) will not be detected with Polyarc/FID. This detector can be paired with other detectors that give complementary information such as the mass spectrometer or thermal conductivity detector. | 3 | Analytical Chemistry |
Carbonate esters have planar OC(OC) cores, which confers rigidity. The unique O=C bond is short (1.173 Å in the depicted example), while the C-O bonds are more ether-like (the bond distances of 1.326 Å for the example depicted).
Carbonate esters can be divided into three structural classes: acyclic, cyclic, and polymeric. The first and general case is the acyclic carbonate group. Organic substituents can be identical or not. Both aliphatic or aromatic substituents are known, they are called dialkyl or diaryl carbonates, respectively. The simplest members of these classes are dimethyl carbonate and diphenyl carbonate.
Alternatively, the carbonate groups can be linked by a 2- or 3-carbon bridge, forming cyclic compounds such as ethylene carbonate and trimethylene carbonate. The bridging compound can also have substituents, e.g. CH for propylene carbonate. Instead of terminal alkyl or aryl groups, two carbonate groups can be linked by an aliphatic or aromatic bifunctional group.
A third family of carbonates are the polymers, such as poly(propylene carbonate) and poly(bisphenol A carbonate) (e.g. Makrolon or Lexan). | 0 | Organic Chemistry |
Removal of a halogen atom from an organohalide generates a radical. Such reactions are difficult to achieve and, when they can be achieved, these processes often lead to complicated mixtures. When a pair of halides are mutually adjacent (vicinal), their removal is favored. Such reactions give alkenes in the case of vicinal alkyl dihalides:
Most desirable from the perspective of remediation are dehalogenations by hydrogenolysis, i.e. the replacement of a bond by a bond. Such reactions are amenable to catalysis:
The rate of dehalogenation depends on the strength of the bond between the carbon and halogen atom. The bond dissociation energies of carbon-halogen bonds are described as: (234 kJ/mol), (293 kJ/mol), (351 kJ/mol), and (452 kJ/mol). Thus, for the same structures the bond dissociation rate for dehalogenation will be: . Additionally, the rate of dehalogenation for alkyl halide also varies with steric environment and follows this trend: halides. | 0 | Organic Chemistry |
Each part of the digestive system is subject to a wide range of disorders many of which can be congenital. Mouth diseases can also be caused by pathogenic bacteria, viruses, fungi and as a side effect of some medications. Mouth diseases include tongue diseases and salivary gland diseases. A common gum disease in the mouth is gingivitis which is caused by bacteria in plaque. The most common viral infection of the mouth is gingivostomatitis caused by herpes simplex. A common fungal infection is candidiasis commonly known as thrush which affects the mucous membranes of the mouth.
There are a number of esophageal diseases such as the development of Schatzki rings that can restrict the passageway, causing difficulties in swallowing. They can also completely block the esophagus.
Stomach diseases are often chronic conditions and include gastroparesis, gastritis, and peptic ulcers.
A number of problems including malnutrition and anemia can arise from malabsorption, the abnormal absorption of nutrients in the GI tract. Malabsorption can have many causes ranging from infection, to enzyme deficiencies such as exocrine pancreatic insufficiency. It can also arise as a result of other gastrointestinal diseases such as coeliac disease. Coeliac disease is an autoimmune disorder of the small intestine. This can cause vitamin deficiencies due to the improper absorption of nutrients in the small intestine. The small intestine can also be obstructed by a volvulus, a loop of intestine that becomes twisted enclosing its attached mesentery. This can cause mesenteric ischemia if severe enough.
A common disorder of the bowel is diverticulitis. Diverticula are small pouches that can form inside the bowel wall, which can become inflamed to give diverticulitis. This disease can have complications if an inflamed diverticulum bursts and infection sets in. Any infection can spread further to the lining of the abdomen (peritoneum) and cause potentially fatal peritonitis.
Crohn's disease is a common chronic inflammatory bowel disease (IBD), which can affect any part of the GI tract, but it mostly starts in the terminal ileum.
Ulcerative colitis an ulcerative form of colitis, is the other major inflammatory bowel disease which is restricted to the colon and rectum. Both of these IBDs can give an increased risk of the development of colorectal cancer. Ulcerative colitis is the most common of the IBDs
Irritable bowel syndrome (IBS) is the most common of the functional gastrointestinal disorders. These are idiopathic disorders that the Rome process has helped to define.
Giardiasis is a disease of the small intestine caused by a protist parasite Giardia lamblia. This does not spread but remains confined to the lumen of the small intestine. It can often be asymptomatic, but as often can be indicated by a variety of symptoms. Giardiasis is the most common pathogenic parasitic infection in humans.
There are diagnostic tools mostly involving the ingestion of barium sulphate to investigate disorders of the GI tract. These are known as upper gastrointestinal series that enable imaging of the pharynx, larynx, oesophagus, stomach and small intestine and lower gastrointestinal series for imaging of the colon. | 1 | Biochemistry |
Somatic cells of different types can be fused to obtain hybrid cells. Hybrid cells are useful in a variety of ways, e.g.,
:(i) to study the control of cell division and gene expression,
:(ii) to investigate malignant transformations,
:(iii) to obtain viral replication,
:(iv) for gene or chromosome mapping and for
:(v) production of monoclonal antibodies by producing hybridoma (hybrid cells between an immortalised cell and an antibody producing lymphocyte), etc.
Chromosome mapping through somatic cell hybridization is essentially based on fusion of human and mouse somatic cells. Generally, human fibrocytes or leucocytes are fused with mouse continuous cell lines.
When human and mouse cells (or cells of any two mammalian species or of the same species) are mixed, spontaneous cell fusion occurs at a very low rate (10-6). Cell fusion is enhanced 100 to 1000 times by the addition of ultraviolet inactivated Sendai (parainfluenza) virus or polyethylene glycol (PEG).
These agents adhere to the plasma membranes of cells and alter their properties in such a way that facilitates their fusion. Fusion of two cells produces a heterokaryon, i.e., a single hybrid cell with two nuclei, one from each of the cells entering fusion. Subsequently, the two nuclei also fuse to yield a hybrid cell with a single nucleus.
A generalized scheme for somatic cell hybridization may be described as follows. Appropriate human and mouse cells are selected and mixed together in the presence of inactivated Sendai virus or PEG to promote cell fusion. After a period of time, the cells (a mixture of man, mouse and hybrid cells) are plated on a selective medium, e.g., HAT medium, which allows the multiplication of hybrid cells only.
Several clones (each derived from a single hybrid cell) of the hybrid cells are thus isolated and subjected to both cytogenetic and appropriate biochemical analyses for the detection of enzyme/ protein/trait under investigation. An attempt is now made to correlate the presence and absence of the trait with the presence and absence of a human chromosome in the hybrid clones.
If there is a perfect correlation between the presence and absence of a human chromosome and that of a trait in the hybrid clones, the gene governing the trait is taken to be located in the concerned chromosome.
The HAT medium is one of the several selective media used for the selection of hybrid cells. This medium is supplemented with hypoxanthine, aminopterin and thymidine, hence the name HAT medium. Antimetabolite aminopterin blocks the cellular biosynthesis of purines and pyrimidines from simple sugars and amino acids.
However, normal human and mouse cells can still multiply as they can utilize hypoxanthine and thymidine present in the medium through a salvage pathway, which ordinarily recycles the purines and pyrimidines produced from degradation of nucleic acids.
Hypoxanthine is converted into guanine by the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT), while thymidine is phosphorylated by thymidine kinase (TK); both HGPRT and TK are enzymes of the salvage pathway.
On a HAT medium, only those cells that have active HGPRT (HGPRT+) and TK (TK+) enzymes can proliferate, while those deficient in these enzymes (HGPRr- and/or TK-) can not divide (since they cannot produce purines and pyrimidines due to the aminopterin present in the HAT medium).
For using HAT medium as a selective agent, human cells used for fusion must be deficient for either the enzyme HGPRT or TK, while mouse cells must be deficient for the other enzyme of this pair. Thus, one may fuse HGPRT deficient human cells (designated as TK+ HGPRr-) with TK deficient mouse cells (denoted as TK- HGPRT+).
Their fusion products (hybrid cells) will be TK+ (due to the human gene) and HGPRT+ (due to the mouse gene) and will multiply on the HAT medium, while the man and mouse cells will fail to do so. Experiments with other selective media can be planned in a similar fashion. | 1 | Biochemistry |
Because digitized 2D periodic images are in the information theoretical approach just data organized in 2D arrays of pixels, core features of Crystallographic Image Processing can be utilized independent of the type of microscope with which the images/data were recorded. The CIP technique has, accordingly been applied (on the basis of the 2dx program) to atomic resolution Z-contrast images of Si-clathrates, as recorded in an aberration-corrected scanning transmission electron microscope. Images of 2D periodic arrays of flat lying molecules on a substrate as recorded with scanning tunneling microscopes were also crystallographic processed utilizing the program CRISP. | 3 | Analytical Chemistry |
Humidity and cloud coverage significantly weaken PDRC effectiveness. A study by Huang et al. noted that "vertical variations of both vapor concentration and temperature in the atmosphere" can have a considerable impact on radiative coolers. The authors put forth that aerosol and cloud coverage can also weaken the effectiveness of radiators and thus concluded that adaptable "design strategies of radiative coolers" are needed to maximize effectiveness under these climatic conditions. Regions with high humidity and cloud cover have less global cooling potential than areas with low humidity and cloud cover. | 7 | Physical Chemistry |
RdRps are highly conserved throughout viruses and are even related to telomerase, though the reason for this is an ongoing question as of 2009. The similarity has led to speculation that viral RdRps are ancestral to human telomerase.
The most famous example of RdRp is that of the polio virus. The viral genome is composed of RNA, which enters the cell through receptor-mediated endocytosis. From there, the RNA is able to act as a template for complementary RNA synthesis, immediately. The complementary strand is then, itself, able to act as a template for the production of new viral genomes that are further packaged and released from the cell ready to infect more host cells. The advantage of this method of replication is that there is no DNA stage; replication is quick and easy. The disadvantage is that there is no back-up DNA copy.
Many RdRps are associated tightly with membranes and are, therefore, difficult to study. The best-known RdRps are polioviral 3Dpol, vesicular stomatitis virus L, and hepatitis C virus NS5B protein.
Many eukaryotes also have RdRps and these are involved in RNA interference: these amplify microRNAs and small temporal RNAs and produce double-stranded RNA using small interfering RNAs as primers. In fact these same RdRps that are used in the defense mechanisms can be usurped by RNA viruses for their benefit. Their evolutionary history has been reviewed. | 1 | Biochemistry |
In inorganic chemistry, a Nowotny chimney ladder phase (NCL phase) is a particular intermetallic crystal structure found with certain binary compounds. NLC phases are generally tetragonal and are composed of two separate sublattices. The first is a tetragonal array of transition metal atoms, generally from group 4 through group 9 of the periodic table. Contained within this array of transition metal atoms is a second network of main group atoms, typically from group 13 (boron group) or group 14 (carbon group). The transition metal atoms form a chimney with helical zigzag chain. The main-group elements form a ladder spiraling inside the transition metal helix.
The phase is named after one of the early investigators H. Nowotny. Examples are RuGa, MnSi, RuGe, IrGa, IrGe VGe, CrGe, MnSi, MnSi, MoGe, MoGe, RhGa, and RhGe.
In RuGa the ruthenium atoms in the chimney are separated by 329 pm. The gallium atoms spiral around the Ru chimney with a Ga–Ga intrahelix distance of 257 pm. The view perpendicular to the chimney axis is that of a hexagonal lattice with gallium atoms occupying the vertices and ruthenium atoms occupying the center. Each gallium atom bonds to 5 other gallium atoms forming a distorted trigonal bipyramid. The gallium atoms carry a positive charge and the ruthenium atoms have a formal charge of −2 (filled 4d shell).
In RuSn the ruthenium atoms spiral around the tin inner helix. In two dimension the Ru atoms form a tetragonal lattice with the tin atoms appearing as triangular units in the Ru channels.
The occurrence of a LCP phase can be predicted by the so-called 14 electron rule. In it the total number of valence electrons per transition metal atom is 14. | 8 | Metallurgy |
Hyperthecosis, or ovarian hyperthecosis, is hyperplasia of the theca interna of the ovary. Hyperthecosis occurs when an area of luteinization occurs along with stromal hyperplasia. The luteinized cells produce androgens, which may lead to hirsutism and virilization (or masculinization) in affected women.
The term hyperthecosis refers to the presence of nests of luteinized theca cells in the ovarian stroma due to differentiation of the ovarian interstitial cells into steroidogenically active luteinized stromal cells. These nests or islands of luteinized theca cells are scattered throughout the stroma of the ovary, rather than being confined to areas around cystic follicles as in polycystic ovary syndrome (PCOS). These luteinized theca cells result in greater production of androgens.
Seen as a severe form of PCOS, the clinical features of hyperthecosis are similar to those of PCOS. Women with hyperthecosis often have more markedly elevated testosterone, more hirsutism, and are much more likely to be virilized. While elevated androgens in postmenopausal women is rare, hyperthecosis can present in both premenopausal or postmenopausal women. Women with hyperthecosis may or may not have always had underlying PCOS. | 1 | Biochemistry |
Vancomycin is one of the few antibiotics used in plant tissue culture to eliminate Gram-positive bacterial infection. It has relatively low toxicity to plants. | 0 | Organic Chemistry |
Faraday's laws of electrolysis are quantitative relationships based on the electrochemical research published by Michael Faraday in 1833. | 7 | Physical Chemistry |
R-22 is often used as an alternative to the highly ozone-depleting CFC-11 and CFC-12, because of its relatively low ozone depletion potential of 0.055, among the lowest for chlorine-containing haloalkanes. However, even this lower ozone depletion potential is no longer considered acceptable.
As an additional environmental concern, R-22 is a powerful greenhouse gas with a GWP equal to 1810 (which indicates 1810 times as powerful as carbon dioxide). Hydrofluorocarbons (HFCs) are often substituted for R-22 because of their lower ozone depletion potential, but these refrigerants often have a higher GWP. R-410A, for example, is often substituted, but has a GWP of 2088. Another substitute is R-404A with a GWP of 3900. Other substitute refrigerants are available with low GWP. Ammonia (R-717), with a GWP of <1, remains a popular substitute on fishing vessels and large industrial applications. Ammonia's toxicity in high concentrations limit its application in small-scale refrigeration applications.
Propane (R-290) is another example, and has a GWP of 3. Propane was the de facto refrigerant in systems smaller than industrial scale before the introduction of CFCs. The reputation of propane refrigerators as a fire hazard kept delivered ice and the ice box the overwhelming consumer choice despite its inconvenience and higher cost until safe CFC systems overcame the negative perceptions of refrigerators. Illegal to use as a refrigerant in the US for decades, propane is now permitted for use in limited mass suitable for small refrigerators. It is not lawful to use in air conditioners or larger refrigerators because of its flammability and potential for explosion. | 2 | Environmental Chemistry |
Fluorescence spectroscopy aka fluorometry or spectrofluorometry, is a type of electromagnetic spectroscopy which analyzes fluorescence from a sample. It involves using a beam of light, usually ultraviolet light, that excites the electrons in molecules of certain compounds and causes them to emit light of a lower energy, typically, but not necessarily, visible light. A complementary technique is absorption spectroscopy.
Devices that measure fluorescence are called fluorometers or fluorimeters. | 7 | Physical Chemistry |
Chemical synapses are biological junctions through which neurons' signals can be sent to each other and to non-neuronal cells such as those in muscles or glands. Chemical synapses allow neurons to form circuits within the central nervous system. They are crucial to the biological computations that underlie perception and thought. They allow the nervous system to connect to and control other systems of the body.
At a chemical synapse, one neuron releases neurotransmitter molecules into a small space (the synaptic cleft) that is adjacent to another neuron. The neurotransmitters are contained within small sacs called synaptic vesicles, and are released into the synaptic cleft by exocytosis. These molecules then bind to neurotransmitter receptors on the postsynaptic cell. Finally, the neurotransmitters are cleared from the synapse through one of several potential mechanisms including enzymatic degradation or re-uptake by specific transporters either on the presynaptic cell or on some other neuroglia to terminate the action of the neurotransmitter.
The adult human brain is estimated to contain from 10 to 5 × 10 (100–500 trillion) synapses. Every cubic millimeter of cerebral cortex contains roughly a billion (short scale, i.e. 10) of them. The number of synapses in the human cerebral cortex has separately been estimated at 0.15 quadrillion (150 trillion)
The word "synapse" was introduced by Sir Charles Scott Sherrington in 1897. Chemical synapses are not the only type of biological synapse: electrical and immunological synapses also exist. Without a qualifier, however, "synapse" commonly refers to chemical synapses. | 1 | Biochemistry |
Spectroelectrochemistry (SEC) is a set of multi-response analytical techniques in which complementary chemical information (electrochemical and spectroscopic) is obtained in a single experiment. Spectroelectrochemistry provides a whole vision of the phenomena that take place in the electrode process. The first spectroelectrochemical experiment was carried out by Theodore Kuwana, PhD, in 1964.
The main objective of spectroelectrochemical experiments is to obtain simultaneous, time-resolved and in-situ electrochemical and spectroscopic information on reactions taking place on the electrode surface. The base of the technique consist in studying the interaction of a beam of electromagnetic radiation with the compounds involved in these reactions. The changes of the optical and electrical signal allow us to understand the evolution of the electrode process.
The techniques on which the spectroelectrochemistry is based are:
*Electrochemistry, which studies the interaction between electrical energy and chemical changes. This technique allows us to analyse reactions that involve electron transfer processes (redox reactions).
*Spectroscopy, which studies the interaction between electromagnetic radiation and matter (absorption, dispersion or emission).
Spectroelectrochemistry provides molecular, thermodynamic and kinetic information of reagents, products and/or intermediates involved in the electron transfer process. | 7 | Physical Chemistry |
A common form for the rate equation is a power law:
The constant is called the rate constant. The exponents, which can be fractional, are called partial orders of reaction and their sum is the overall order of reaction.
In a dilute solution, an elementary reaction (one having a single step with a single transition state) is empirically found to obey the law of mass action. This predicts that the rate depends only on the concentrations of the reactants, raised to the powers of their stoichiometric coefficients.
The differential rate equation for an elementary reaction using product notation is:
Where:
* is the rate of change of reactant concentration with respect to time.
*k is the rate constant of the reaction.
* represents the concentrations of the reactants, raised to the powers of their stoichiometric coefficients and multiplied together. | 7 | Physical Chemistry |
In organic chemistry, functionality is often used as a synonym for functional group. For example, a hydroxyl group can also be called a HO-function.
Functionalisation means the introduction of functional groups, for example
* the functionalisation of a surface (e.g. silanization for the specific modification of the adhesion of a surface)
* the functionalization of nanoparticles of a metal or metal oxide to stabilize such nanoparticles or
* the so-called C-H functionalization, which means the substitution of a C-H bond by a functional group, bonded at the same carbon atom | 0 | Organic Chemistry |
Many viruses undergo frequent mutations that result in changes in amino acid composition of their important proteins. Epitopes located on the protein may also undergo alterations in the process. Such an altered epitope binds less strongly with the antibodies specific to the unaltered epitope that would have stimulated the immune system. This is unfortunate because somatic hypermutation does give rise to clones capable of producing soluble antibodies that would have bound the altered epitope avidly enough to neutralize it. But these clones would consist of naive cells which are not allowed to proliferate by the weakly binding antibodies produced by the priorly stimulated clone. This doctrine is known as the original antigenic sin. This phenomenon comes into play particularly in immune responses against influenza, dengue and HIV viruses. This limitation, however, is not imposed by the phenomenon of polyclonal response, but rather, against it by an immune response that is biased in favor of experienced memory cells against the "novice" naive cells. | 1 | Biochemistry |
Acylsilanes are a group of chemical compounds sharing a common functional group with the general structure RC(O)-SiR. | 0 | Organic Chemistry |
At the beginning of the twentieth century, as steel production became more dependent on the use of electric arc furnace technology in mini-mill environments, the convenient transportation of scrap metal became a competitive advantage of manufacturers, so the availability of geographical resources was no longer the most significant driving force for iron-and-steel production growth. The Birmingham area began to invest in building the earliest mini-mills, and continued to have a strong foundry emphasis, attracting many large cast-iron pipe producers, such as American Cast Iron Pipe Company. Headquartered in Birmingham in 1905, American Cast Iron Pipe Company, with its 2,100 acre site and 2,400 employees at its operations, became the worlds largest iron pipe casting plant. With advanced expertise and the latest technological innovations, Birmingham furnaces produced millions of tons of pig iron from 1990s to 1970s. A half of the produced pig iron was used for steel production, and the other half was sold as foundry iron. This trend reflected that the regions iron ore was of poor quality, so manufacturers had difficulties in extracting it. This is a geological factor that limited the further development of Alabama's iron and steel industry, despite the help of advanced technology and innovative smelting practices. | 8 | Metallurgy |
The Nernst–Planck equation is a conservation of mass equation used to describe the motion of a charged chemical species in a fluid medium. It extends Fick's law of diffusion for the case where the diffusing particles are also moved with respect to the fluid by electrostatic forces. It is named after Walther Nernst and Max Planck. | 7 | Physical Chemistry |
Methane (CH) in the Earth's atmosphere is a powerful greenhouse gas with a global warming potential (GWP) 84 times greater than CO over a 20-year time frame. Methane is not as persistent as CO, and tails off to about 28 times greater than CO over a 100-year time frame.
Radiative or climate forcing is the scientific concept used to measure the human impact on the environment in watts per square meter (W/m). It refers to the "difference between solar irradiance absorbed by the Earth and energy radiated back to space" The direct radiative greenhouse gas forcing effect of methane relative to the year 1750 was estimated at 0.5 W/m in the 2007 IPCC "Climate Change Synthesis Report 2007".
In their May 21, 2021 173-page "Global Methane Assessment", the UNEP and CCAP said that their "understanding of methane's effect on radiative forcing" improved with research by teams led by M. Etminan in 2016, and William Collins in 2018, which resulted in an "upward revision" since the 2014 IPCC Fifth Assessment Report (AR5). The "improved understanding" says that prior estimates of the "overall societal impact of methane emissions" were likely underestimated.
Etminan et al. published their new calculations for methane's radiative forcing (RF) in a 2016 Geophysical Research Letters journal article which incorporated the shortwave bands of CH in measuring forcing, not used in previous, simpler IPCC methods. Their new RF calculations which significantly revised those cited in earlier, successive IPCC reports for well mixed greenhouse gases (WMGHG) forcings by including the shortwave forcing component due to CH, resulted in estimates that were approximately 20–25% higher. Collins et al. said that CH mitigation that reduces atmospheric methane by the end of the century, could "make a substantial difference to the feasibility of achieving the Paris climate targets", and would provide us with more "allowable carbon emissions to 2100".
In addition to the direct heating effect and the normal feedbacks, the methane breaks down to carbon dioxide and water. This water is often above the tropopause, where little water usually reaches. Ramanathan (1998) notes that both water and ice clouds, when formed at cold lower stratospheric temperatures, are extremely efficient in enhancing the atmospheric greenhouse effect. He also notes that there is a distinct possibility that large increases in methane in future may lead to a surface warming that increases nonlinearly with the methane concentration.
Mitigation efforts to reduce short-lived climate pollutants like methane and black carbon would help combat "near-term climate change" and would support Sustainable Development Goals. | 2 | Environmental Chemistry |
Biopolymers are polymers produced by living organisms. Cellulose and starch, proteins and peptides, and DNA and RNA are all examples of biopolymers, in which the monomeric units, respectively, are sugars, amino acids, and nucleotides. Cellulose is both the most common biopolymer and the most common organic compound on Earth. About 33% of all plant matter is cellulose. On a similar manner, silk (proteinaceous biopolymer) has garnered tremendous research interest in a myriad of domains including tissue engineering and regenerative medicine, microfluidics, drug delivery. | 1 | Biochemistry |
Serinolamide A is a cannabinoid structurally related to endocannabinoids found in cyanobacteria such as Lyngbya majuscula and other species in the Oscillatoria family. | 1 | Biochemistry |
Recently it has been shown that a Michaelian signaling pathway can be converted to an ultrasensitive signaling pathway by the introduction of two positive feedback loops. In this synthetic biology approach, Palani and Sarkar began with a linear, graded response pathway, a pathway that showed a proportional increase in signal output relative to the amount of signal input, over a certain range of inputs. This simple pathway was composed of a membrane receptor, a kinase and a transcription factor. Upon activation the membrane receptor phosphorylates the kinase, which moves into the nucleus and phosphorylates the transcription factor, which turns on gene expression. To transform this graded response system into an ultrasensitive, or switch-like signaling pathway, the investigators created two positive feedback loops. In the engineered system, activation of the membrane receptor resulted in increased expression of both the receptor itself and the transcription factor. This was accomplished by placing a promoter specific for this transcription factor upstream of both genes. The authors were able to demonstrate that the synthetic pathway displayed high ultrasensitivity and bistability.
Recent computational analysis of the effects of a signaling proteins concentration on the presence of an ultrasensitive response has come to complementary conclusions about the influence of a signaling proteins concentration on the conversion of a graded response to an ultrasensitive one. Rather than focus on the generation of signaling proteins through positive feedback, however, the study instead focused on how the dynamics of a signaling proteins exit from the system influences the response. Soyer, Kuwahara, and Csika´sz-Nagy devised a signaling pathway composed of a protein (P) that possesses two possible states (unmodified P or modified P*) and can be modified by an incoming stimulus E. Furthermore, while the unmodified form, P, is permitted to enter or leave the system, P* is only allowed to leave (i.e. it is not generated elsewhere). After varying the parameters of this system, the researchers discovered that the modification of P to P* can shift between a graded response and an ultrasensitive response via the modification of the exit rates of P and P* relative to each other. The transition from an ultrasensitive response to E and a graded response to E was generated when the two rates went from highly similar to highly dissimilar, irrespective of the kinetics of the conversion from P to P* itself. This finding suggests at least two things: 1) the simplifying assumption that the levels of signaling molecules stay constant in a system can severely limit the understanding of ultrasensitivitys complexity; and 2) it may be possible to induce or inhibit ultrasensitivity artificially by regulating the rates of the entry and exit of signaling molecules occupying a system of interest. | 1 | Biochemistry |
Due to the lack of long-range order, standard crystallographic techniques are often inadequate in determining the structure of amorphous solids. A variety of electron, X-ray, and computation-based techniques have been used to characterize amorphous materials. Multi-modal analysis is very common for amorphous materials. | 7 | Physical Chemistry |
DNA condensation can be induced in vitro either by applying external force to bring the double helices together, or by inducing attractive interactions between the DNA segments. The former can be achieved e.g. with the help of the osmotic pressure exerted by crowding neutral polymers in the presence of monovalent salts. In this case, the forces pushing the double helices together are coming from entropic random collisions with the crowding polymers surrounding DNA condensates, and salt is required to neutralize DNA charges and decrease DNA-DNA repulsion. The second possibility can be realized by inducing attractive interactions between the DNA segments by multivalent cationic charged ligands (multivalent metal ions, inorganic cations, polyamines, protamines, peptides, lipids, liposomes and proteins). | 1 | Biochemistry |
There are many types of coupled transition such as are observed in vibration–rotation spectra. The excited-state wave function is the product of two wave functions such as vibrational and rotational. The general principle is that the symmetry of the excited state is obtained as the direct product of the symmetries of the component wave functions. In rovibronic transitions, the excited states involve three wave functions.
The infrared spectrum of hydrogen chloride gas shows rotational fine structure superimposed on the vibrational spectrum. This is typical of the infrared spectra of heteronuclear diatomic molecules. It shows the so-called P and R branches. The Q branch, located at the vibration frequency, is absent. Symmetric top molecules display the Q branch. This follows from the application of selection rules.
Resonance Raman spectroscopy involves a kind of vibronic coupling. It results in much-increased intensity of fundamental and overtone transitions as the vibrations "steal" intensity from an allowed electronic transition. In spite of appearances, the selection rules are the same as in Raman spectroscopy. | 7 | Physical Chemistry |
Katsonis was born in Vienna. She grew up in Orsay, in Paris Region. She is half French and half Greek. She studied chemical engineering at the Chimie ParisTech, before moving to Ecole Normal Superieure for her graduate studies with Ludovic Jullien. Katsonis earned her doctoral degree at the Pierre and Marie Curie University. She worked on nanoscale probes of two dimensional molecular self-assemblies with Denis Fichou. She joined the research group of Ben Feringa at the University of Groningen, where she worked on self-assembly of motors and switches. Whilst at Groningen Katsonis developed scanning probe microscopy for the determination of molecular chirality. | 0 | Organic Chemistry |
Nikolai Timofeevich Beliaev or Nicholas Timothy Belaiew (26 June 1878 – 5 November 1955) was a Russian metallurgist. He was famous for his studies on Damascus steel and the idea of crystallization in metals and the production of Widmanstatten structures. He also wrote on the history of steel making.
Beliaev was born in St. Petersburg to General T. M. Beliaev and Maria Nikolayevna Septjurina. He was educated at Mikhailovskaya Artilleriiskaya Academy and was trained under Dmitry Konstantinovich Chernov and Henry Le Chatelier. He became a professor of metallurgy in 1909. During World War I he was wounded and he was sent to England in 1915. He received a Bessemer Gold Medal in 1937 from the British Institute of Steel and Iron in London. A major contribution was on the studies of crystal structure in steels both man-made and of meteoric origin and examined their mechanical properties. He also took an interest in Icelandic research. | 8 | Metallurgy |
Dr. Chris Ballentine is the chair of geochemistry and head of the Department of Earth Sciences at the University of Oxford, in the United Kingdom. He uses properties of the noble gases to understand the origin and evolution of Earth's atmosphere and mantle. | 9 | Geochemistry |
In 2010, the International Fragrance Association published a list of 3,059 chemicals used in 2011 based on a voluntary survey of its members, identifying about 90% of the world's production volume of fragrances. | 0 | Organic Chemistry |
The N-terminal domain of restriction endonuclease EcoRII; the C-terminal domain of restriction endonuclease BfiI possess a similar DNA-binding pseudobarrel protein fold. | 1 | Biochemistry |
Trabectedin, sold under the brand name Yondelis, is an antitumor chemotherapy medication for the treatment of advanced soft-tissue sarcoma and ovarian cancer.
The most common adverse reactions include nausea, fatigue, vomiting, constipation, decreased appetite, diarrhea, peripheral edema, dyspnea, and headache.
It is sold by Pharma Mar S.A. and Johnson and Johnson. It is approved for use in the European Union, Russia, South Korea and the United States. The European Commission and the U.S. Food and Drug Administration (FDA) granted orphan drug status to trabectedin for soft-tissue sarcomas and ovarian cancer. | 0 | Organic Chemistry |
The experiment itself involves having a radioactive positron source (often Na) situated near the analyte. Positrons are emitted near-simultaneously with gamma rays. These gamma rays are detected by a nearby scintillator. | 7 | Physical Chemistry |
The concentration of Zn in bulk silicate Earth is ~55 ppm, while its average concentration in fresh mid-oceanic ridge basalt (MORB) glass is ~87 ppm. Like Cu, Zn commonly associates with Fe to form a variety of zinc sulfide minerals such as sphalerite. Additionally, Zn associates with carbonates and hydroxides to form numerous diverse minerals (e.g., smithsonite, sweetite, etc.). In mafic and ultramafic rocks, Zn tends to concentrate in oxides such as spinel and magnetite. In freshwater, Zn predominantly complexes with water to form an octahedrally coordinated aqua ion . In seawater, Cl ions replace up to four water molecules in the Zn aqua ion, forming , and . | 9 | Geochemistry |
Foot-and-mouth disease virus (FMDV) is a member of the Aphthovirus genus in the Picornaviridae family and is the cause of foot-and-mouth disease in pigs, cattle, sheep and goats. It is a non-enveloped, positive strand, RNA virus. FMDV is a highly contagious virus. It enters the body through inhalation. | 1 | Biochemistry |
There has been evidence that the nonsense-mediated mRNA decay pathway participates in X chromosome dosage compensation in mammals. In higher eukaryotes with dimorphic sex chromosomes, such as humans and fruit flies, males have one X chromosome, whereas females have two. These organisms have evolved a mechanism that compensates not only for the different number of sex chromosomes between the two sexes, but also for the differing X/autosome ratios. In this genome-wide survey, the scientists found that autosomal genes are more likely to undergo nonsense-mediated decay than X-linked genes. This is because NMD fine tunes X chromosomes and it was demonstrated by inhibiting the pathway. The results were that balanced gene expression between X and autosomes gene expression was decreased by 10–15% no matter the method of inhibition. The NMD pathway is skewed towards depressing expression of larger population or autosomal genes than x-linked ones. In conclusion, the data supports the view that the coupling of alternative splicing and NMD is a pervasive means of gene expression regulation. | 1 | Biochemistry |
* Killick, D. 2004. Review Essay: "What Do We Know About African Iron Working?" Journal of African Archaeology. Vol 2 (1) pp. 135–152
* Bocoum, H. (ed.), 2004, The origins of iron metallurgy in Africa – New lights on its antiquity, H. Bocoum (ed.), UNESCO publishing
* Schmidt, P.R., Mapunda, B.B., 1996. "Ideology and the Archaeological Record in Africa: Interpreting Symbolism in Iron Smelting Technology". Journal of Anthropological Archaeology. Vol 16, pp. 73–102
* Rehren, T., Charlton, M., Shadrek, C., Humphris, J., Ige, A., Veldhuijen, H.A. "Decisions set in slag: the human factor in African iron smelting". La Niece, S., Hook, D., and Craddock, P., (eds). Metals and mines : studies in archaeometallurgy. 2007, pp. 211–218.
* Okafor, E.E., 1993. "New Evidence on Early Iron-Smelting from Southeastern Nigeria". Shaw, T., Sinclair, P., Bassey, A., Okpoko, A (eds). The Archaeology of Africa Food, Metals and Towns. London, Routledge, pp. 432–448
* Kense, F.J., and Okora, J.A., 1993. "Changing Perspectives on Traditional Iron Production in West Africa". Shaw, T., Sinclair, P., Bassey, A., Okpoko, A (eds). The Archaeology of Africa Food, Metals and Towns. London, Routledge, pp. 449– 458
* Muhammed, I.M., 1993. "Iron Technology in the Middle Sahel/Savanna: With Emphasis on Central Darfur". Shaw, T., Sinclair, P., Bassey, A., Okpoko, A (eds). The Archaeology of Africa Food, Metals and Towns. London, Routledge, pp. 459–467
* Buleli, NS., 1993. Iron-Making Techniques in the Kivu Region of Zaire: Some of the Differences Between the South Maniema Region and North Kivu. Shaw, T., Sinclair, P., Bassey, A., Okpoko, A (eds). The Archaeology of Africa Food, Metals and Towns'. London, Routledge, pp. 468–477
* Radimilahy, C., 1993 "Ancient Iron-Working in Madagascar". Shaw, T., Sinclair, P., Bassey, A., Okpoko, A (eds). The Archaeology of Africa Food, Metals and Towns. London, Routledge, pp. 478–473
* Kiriama, H.O., 1993. "The Iron Using Communities in Kenya". Shaw, T., Sinclair, P., Bassey, A., Okpoko, A (eds). The Archaeology of Africa Food, Metals and Towns. London, Routledge, pp. 484–498
* Martinelli, B., 1993, "Fonderies ouest-africaines. Classement comparatif et tendances", in Atouts et outils de lethnologie des techniques – Sens et tendance en technologie comparée, Revue Techniques et culture', n 21 : 195–221.
* Martinelli, B., 2004, "On the Threshold of Intensive Metallurgy – The choice of Slow Combustion in the Niger River Bend (Burkina Faso and Mali)" in The origins of iron metallurgy in Africa – New lights on its antiquity, H. Bocoum (ed.), UNESCO publishing : pp. 216–247
* Collet, D.P., 1993. "Metaphors and Representations Associated with Precolonial Iron-Smelting in Eastern and Southern Africa". Shaw, T., Sinclair, P., Bassey, A., Okpoko, A (eds). The Archaeology of Africa Food, Metals and Towns. London, Routledge, pp. 499–511 | 8 | Metallurgy |
Unlike other ACE inhibitors that are primarily excreted by the kidneys, fosinopril is eliminated from the body by both renal and hepatic pathways. This characteristic of fosinopril makes the drug a safer choice than other ACE inhibitors for heart failure patients with impaired kidney function resulting from poor perfusion as fosinopril can still be eliminated by the liver, preventing accumulation of the drug in the body.
Fosinopril is de-esterified by the liver or gastrointestinal mucosa and is converted to its active form, fosinoprilat. Fosinoprilat competitively binds to ACE, preventing ACE from binding to and converting angiotensin I to angiotensin II. Inhibiting the production of AII lowers peripheral vascular resistance, decreases afterload, and decreases blood pressure, thus helping to alleviate the negative effects of AII on cardiac performance. | 4 | Stereochemistry |
The term neuston describes the organisms in the SML and was first suggested by Naumann in 1917. As in other marine ecosystems, bacterioneuston communities have important roles in SML functioning. Bacterioneuston community composition of the SML has been analysed and compared to the underlying water in different habitats with varying results, and has primarily focused on coastal waters and shelf seas, with limited study of the open ocean . In the North Sea, a distinct bacterial community was found in the SML with Vibrio spp. and Pseudoalteromonas spp. dominating the bacterioneuston. During an artificially induced phytoplankton bloom in a fjord mesocosm experiment, the most dominant denaturing gradient gel electrophoresis (DGGE) bands of the bacterioneuston consisted of two bacterial families: Flavobacteriaceae and Alteromonadaceae. Other studies have however, found little or no differences in the bacterial community composition of the SML and the ULW. Difficulties in direct comparisons between studies can arise because of the different methods used to sample the SML, which result in varied sampling depths.
Even less is known about the community control mechanisms in the SML and how the bacterial community assembles at the air-sea interface. The bacterioneuston community could be altered by differing wind conditions and radiation levels, with high wind speeds inhibiting the formation of a distinct bacterioneuston community. Wind speed and radiation levels refer to external controls, however, bacterioneuston community composition might also be influenced by internal factors such as nutrient availability and organic matter (OM) produced either in the SML or in the ULW.
One of the principal OM components consistently enriched in the SML are transparent exopolymer particles (TEP), which are rich in carbohydrates and form by the aggregation of dissolved precursors excreted by phytoplankton in the euphotic zone. Higher TEP formation rates in the SML, facilitated through wind shear and dilation of the surface water, have been proposed as one explanation for the observed enrichment in TEP. Also, due to their natural positive buoyancy, when not ballasted by other particles sticking to them, TEP ascend through the water column and ultimately end up at the SML . A second possible pathway of TEP from the water column to the SML is by bubble scavenging.
Next to rising bubbles, another potential transport mechanism for bacteria from the ULW to the SML could be ascending particles or more specifically TEP. Bacteria readily attach to TEP in the water column. TEP can serve as microbial hotspots and can be used directly as a substrate for bacterial degradation, and as grazing protection for attached bacteria, e.g., by acting as an alternate food source for zooplankton. TEP have also been suggested to serve as light protection for microorganisms in environments with high irradiation. | 7 | Physical Chemistry |
This is the smallest piece, which was moved to Mandu during Dilawar Khan's reign. Its length is according to both Coussen and Roessler. It is mostly of an octagonal cross-section, except one circular part at the end. Roessler estimated its weight at .
This piece was brought back from Mandu to Dhar sometime between 1844 and 1893. In 1893, A. A. Führer of ASI noticed it in the garden of the Dhar Maharaja's guest house. In February 1902, this piece was fixed in a masonry basement at Lal Bagh public gardens near the Anand High School. Henry Cousens of ASI later had it removed from the basement to measure it. The piece was then moved to the Anand High School museum. From there, it was moved to Lat Masjid, similar to the second piece. | 8 | Metallurgy |
In 1910, Goldberg married Ullman. In 1923, they moved back to Geneva when Ullman accepted a faculty position at Geneva University.
Her exact death date is not known, but her name does appear at the top of a list of people signing a memorial notice in a Geneva newspaper for her deceased husband, Fritz Ullmann in 1939. | 0 | Organic Chemistry |
A frequency comb allows a direct link from radio frequency standards to optical frequencies. Current frequency standards such as atomic clocks operate in the microwave region of the spectrum, and the frequency comb brings the accuracy of such clocks into the optical part of the electromagnetic spectrum. A simple electronic feedback loop can lock the repetition rate to a frequency standard.
There are two distinct applications of this technique. One is the optical clock, where an optical frequency is overlapped with a single tooth of the comb on a photodiode, and a radio frequency is compared to the beat signal, the repetition rate, and the CEO-frequency (carrier–envelope offset). Applications for the frequency-comb technique include optical metrology, frequency-chain generation, optical atomic clocks, high-precision spectroscopy, and more precise GPS technology.
The other is doing experiments with few-cycle pulses, like above-threshold ionization, attosecond pulses, highly efficient nonlinear optics or high-harmonics generation. These can be single pulses, so that no comb exists, and therefore it is not possible to define a carrier–envelope offset frequency, rather the carrier–envelope offset phase is important. A second photodiode can be added to the setup to gather phase and amplitude in a single shot, or difference-frequency generation can be used to even lock the offset on a single-shot basis, albeit with low power efficiency.
Without an actual comb one can look at the phase vs frequency. Without a carrier–envelope offset all frequencies are cosines. This means that all frequencies have the phase zero. The time origin is arbitrary. If a pulse comes at later times, the phase increases linearly with frequency, but still the zero-frequency phase is zero. This phase at zero frequency is the carrier–envelope offset. The second harmonic not only has twice the frequency, but also twice the phase. Thus for a pulse with zero offset the second harmonic of the low-frequency tail is in phase with the fundamental of the high-frequency tail, and otherwise it is not. Spectral phase interferometry for direct electric-field reconstruction (SPIDER) measures how the phase increases with frequency, but it cannot determine the offset, so the name “electric field reconstruction” is a bit misleading.
In recent years, the frequency comb has been garnering interest for astro-comb applications, extending the use of the technique as a spectrographic observational tool in astronomy.
There are other applications that do not need to lock the carrier–envelope offset frequency to a radio-frequency signal. These include, among others, optical communications, the synthesis of optical arbitrary waveforms, spectroscopy (especially dual-comb spectroscopy) or radio-frequency photonics.
On the other hand, optical frequency combs have found new applications in remote sensing. Ranging lidars based on dual comb spectroscopy have been developed, enabling high-resolution range measurements at fast update rates. Optical frequency combs can also be utilized to measure greenhouse gas emissions with great precision. For instance, in 2019, scientists at NIST employed spectroscopy to quantify methane emissions from oil and gas fields . More recently, a greenhouse gas lidar based on electro-optic combs has been successfully demonstrated. | 7 | Physical Chemistry |
Biosurveys are used by government agencies responsible for management of public lands, environmental planning and/or environmental regulation to assess ecological resources, such as rivers, streams, lakes and wetlands. They involve collection and analysis of animal and/or plant samples which serve as bioindicators. The studies may be conducted by professional scientists or volunteer organizations. They are conducted according to published procedures to ensure consistency in data collection and analysis, and to compare findings to established metrics.
Biosurveys typically use metrics such as species composition and richness (e.g. number of species, extent of pollution-tolerant species), and ecological factors (number of individuals, proportion of predators, presence of disease). Biosurveys may identify pollution problems that are difficult or expensive to detect using chemical testing procedures.
A biosurvey may be used to generate an index of biological integrity (IBI), a scoring system for an ecological resource. | 2 | Environmental Chemistry |
In March 2013, NASA reported Curiosity found evidence that geochemical conditions in Gale Crater were once suitable for microbial life after analyzing the first drilled sample of Martian rock, "John Klein" rock at Yellowknife Bay in Gale Crater. The rover detected water, carbon dioxide, oxygen, sulfur dioxide and hydrogen sulfide. Chloromethane and dichloromethane were also detected. Related tests found results consistent with the presence of smectite clay minerals. | 9 | Geochemistry |
Hagemann's ester has been used as a key building block in many syntheses. For example, a key intermediate for the fungal hormone trisporic acid was made by its alkylation and it has been used to make sterols. Other authors have used it in inverse-electron-demand Diels–Alder reactions leading to sesquiterpene dimers or in reactions forming simple derivatives. | 0 | Organic Chemistry |
In igneous petrology, an intermediate composition refers to the chemical composition of a rock that has 51.563 wt% SiO being an intermediate between felsic and mafic compositions. Typical intermediate rocks include andesite and trachyandesite among volcanic rocks and diorite and granodiorite among plutonic rocks. | 9 | Geochemistry |
Secondary sulfides—those formed by supergene secondary enrichment—are resistant (refractory) to sulfuric leaching. Secondary copper sulfides are dominated by the mineral chalcocite; a mineral formed from primary sulfides, like chalcopyrite, that undergo chemical processes such as oxidation or reduction. Typically, secondary sulfide ores are concentrated using froth flotation. Other extraction processes like leaching are effectively used for the extraction of secondary copper sulfides, but as demand for copper rises, extraction processes tailored for low-grade ores are required, due to the depletion of copper resources. Processes including in situ, dump, and heap leaching are cost-effective methods that are suitable for extracting copper from low-grade ores.
Extraction processes for secondary copper sulfides and low-grade ores includes the process of heap bioleaching. Heap bioleaching presents a cost efficient extraction method that requires a less intensive energy input resulting in a higher profit. This extraction process can be applied to large quantities of low-grade ores, at a lower capital cost with minimal environmental impact.
Generally, direct froth flotation is not used to concentrate copper oxide ores, as a result of the largely ionic and hydrophilic structure of the copper oxide mineral surface. Copper oxide ores are typically treated via chelating-reagent flotation and fatty-acid flotation, which use organic reagents to ensure adsorption onto the mineral surface through the formation of hydrophobic compounds on the mineral surface.
Some supergene sulfide deposits can be leached using a bacterial oxidation heap leach process to oxidize the sulfides to sulfuric acid, which also allows for simultaneous leaching with sulfuric acid to produce a copper sulfate solution. For oxide ores, solvent extraction and electrowinning technologies are used to recover the copper from the pregnant leach solution. To ensure the best recovery of copper, it is important to acknowledge the effect copper dissolution, acid consumption, and gangue mineral composition has on the efficacy of extraction.
Supergene sulfide ores rich in native copper are refractory to treatment with sulfuric acid leaching on all practicable time scales, and the dense metal particles do not react with froth flotation media. Typically, if native copper is a minor part of a supergene profile it will not be recovered and will report to the tailings. When rich enough, native copper ore bodies may be treated to recover the contained copper by gravity separation. Often, the nature of the gangue is important, as clay-rich native copper ores prove difficult to liberate. This is because clay minerals interact with flotation reagents used in extraction processes, that are then consumed, which results in minimal recovery of a high grade copper concentrate. | 8 | Metallurgy |
The majority of the computer models available for water and solute transport in the soil (e.g. Swatre, DrainMod ) are based on Richard's differential equation for the movement of water in unsaturated soil in combination with a differential salinity dispersion equation. The models require input of soil characteristics like the relation between unsaturated soil moisture content, water tension, hydraulic conductivity and dispersivity.
These relations vary to a great extent from place to place and are not easy to measure. The models use short time steps and need at least a daily data base of hydrological phenomena. Altogether this makes model application to a fairly large project the job of a team of specialists with ample facilities. | 9 | Geochemistry |
A sensor-based sorting equipment supplier with large installed base in the industries mining, recycling and food. Tomras sensor-based sorting equipment and services for the precious metals and base metals segment are marketed through a cooperation agreement with Outotec from Finland, which brings the extensive comminution, processing and application experience of Outotec together with Tomras sensor-based ore sorting technology and application expertise. | 3 | Analytical Chemistry |
Adhesion GPCRs appear capable to follow standard GPCR signaling modes and signal through Gαs, Gαq, Gαi, and Gα12/13. As of today, many of the adhesion GPCRs are still orphan receptors and their signalling pathways have not been identified. Research groups are working to elucidate the downstream signaling molecules utilizing several methods, including chemical screens and analysis of second messenger levels in over-expressed cells. Adding drugs in vitro, while the cells are over-expressing an adhesion GPCR, has allowed the identification of the molecules activating the GPCR and the second messengers being utilized.
GPR133 signals through Gαs to activate adenylyl cyclase. It has been shown that overexpressing GPCRs in vitro can result in receptor activation in the absence of a ligand or agonist. By over expressing GPR133 in vitro, an elevation in reporter genes and cAMP was observed. Signaling of the overexpressed GPR133 did not require an N-terminus or GPS cleavage. Missense mutations in the 7TM region resulted in loss of signalling.
The latrophilin homolog LPHN1 was shown in C. elegans to require a GPS for signaling, but cleavage at the GPS site was not necessary. Furthermore, having a shortened 7 transmembrane domain, but with an intact GPS domain, resulted in a loss of signaling. This suggests that having both the GPS and 7 transmembrane domain intact is involved in signaling and that the GPS site could act as or be a necessary part of an endogenous ligand.
GPR56 has been shown to be cleaved at the GPS site and then remain associated with the 7TM domain. In a study where the N-terminus was removed up to N342 (the start of the GPS), the receptor became constitutively active and an up regulation of Gα12/13 was seen. When receptors are active, they are ubiquitinated and GPR56 lacking an N-terminus was highly ubiquitinated. | 1 | Biochemistry |
Due to the regulatory role during transcription of epigenetic modifications in genes, it is not surprising that changes in epigenetic markers, such as acetylation, can contribute to cancer development. HDACs expression and activity in tumor cells is very different from normal cells. The overexpression and increased activity of HDACs has been shown to be characteristic of tumorigenesis and metastasis, suggesting an important regulatory role of histone deacetylation on the expression of tumor suppressor genes. One of the examples is the regulation role of histone acetylation/deacetylation in P300 and CBP, both of which contribute to oncogenesis.
Approved in 2006 by the U.S. Food and Drug Administration (FDA), Vorinostat represents a new category for anticancer drugs that are in development. Vorinostat targets histone acetylation mechanisms and can effectively inhibit abnormal chromatin remodeling in cancerous cells. Targets of Vorinostat includes HDAC1, HDAC2, HDAC3 and HDAC6.
Carbon source availability is reflected in histone acetylation in cancer. Glucose and glutamine are the major carbon sources of most mammalian cells, and glucose metabolism is closely related to histone acetylation and deacetylation. Glucose availability affects the intracellular pool of acetyl-CoA, a central metabolic intermediate that is also the acetyl donor in histone acetylation. Glucose is converted to acetyl-CoA by the pyruvate dehydrogenase complex (PDC), which produces acetyl-CoA from glucose-derived pyruvate; and by adenosine triphosphate-citrate lyase (ACLY), which generates acetyl-CoA from glucose-derived citrate. PDC and ACLY activity depend on glucose availability, which thereby influences histone acetylation and consequently modulates gene expression and cell cycle progression. Dysregulation of ACLY and PDC contributes to metabolic reprogramming and promotes the development of multiple cancers. At the same time, glucose metabolism maintains the NAD+/NADH ratio, and NAD+ participates in SIRT-mediated histone deacetylation. SIRT enzyme activity is altered in various malignancies, and inhibiting SIRT6, a histone deacetylase that acts on acetylated H3K9 and H3K56, promotes tumorigenesis. SIRT7, which deacetylates H3K18 and thereby represses transcription of target genes, is activated in cancer to stabilize cells in the transformed state. Nutrients appear to modulate SIRT activity. For example, long-chain fatty acids activate the deacetylase function of SIRT6, and this may affect histone acetylation. | 0 | Organic Chemistry |
The organometallic chemistry of titanium typically starts from . An important reaction involves sodium cyclopentadienyl to give titanocene dichloride, . This compound and many of its derivatives are precursors to Ziegler–Natta catalysts. Tebbe's reagent, useful in organic chemistry, is an aluminium-containing derivative of titanocene that arises from the reaction of titanocene dichloride with trimethylaluminium. It is used for the "olefination" reactions.
Arenes, such as react to give the piano-stool complexes (R = H, ; see figure above). This reaction illustrates the high Lewis acidity of the entity, which is generated by abstraction of chloride from by aluminium trichloride|. | 0 | Organic Chemistry |
* [http://www.anilaggrawal.com/ij/indexpapers.html Anil Aggrawal's Internet Journal of Forensic Medicine and Toxicology] .
* Forensic Magazine – [http://www.forensicmag.com Forensicmag.com].
* [https://web.archive.org/web/20110222013558/http://www2.fbi.gov/hq/lab/fsc/current/index.htm Forensic Science Communications], an open access journal of the FBI.
* [http://www.elsevier.com/wps/find/journaldescription.cws_home/505512/description#description Forensic sciences international] – An international journal dedicated to the applications of medicine and science in the administration of justice – – Elsevier
* [https://www.pbs.org/wgbh/pages/frontline/real-csi/ "The Real CSI"], PBS Frontline documentary, 17 April 2012.
* Baden, Michael; Roach, Marion. Dead Reckoning: The New Science of Catching Killers, Simon & Schuster, 2001. .
* Bartos, Leah, [https://www.propublica.org/article/no-forensic-background-no-problem "No Forensic Background? No Problem"], ProPublica, 17 April 2012.
* Guatelli-Steinberg, Debbie; Mitchell, John C. [http://www.struers.com/default.asp?doc_id=404 Structure Magazine no. 40, "RepliSet: High Resolution Impressions of the Teeth of Human Ancestors"].
* Holt, Cynthia. [https://web.archive.org/web/20061031175558/https://lu.com/showbook.cfm?isbn=9781591582212 Guide to Information Sources in the Forensic Sciences] Libraries Unlimited, 2006. .
* Jamieson, Allan; Moenssens, Andre (eds). [http://ca.wiley.com/WileyCDA/WileyTitle/productCd-0470018267,descCd-description.html Wiley Encyclopedia of Forensic Science] John Wiley & Sons Ltd, 2009. . [https://archive.today/20121211065812/http://mrw.interscience.wiley.com/emrw/9780470061589/home/ Online version].
* Kind, Stuart; Overman, Michael. Science Against Crime Doubleday, 1972. .
* Lewis, Peter Rhys; Gagg Colin; Reynolds, Ken. Forensic Materials Engineering: Case Studies CRC Press, 2004.
* Nickell, Joe; Fischer, John F. Crime Science: Methods of Forensic Detection, University Press of Kentucky, 1999. .
* Owen, D. (2000). Hidden Evidence: The Story of Forensic Science and how it Helped to Solve 40 of the Worlds Toughest Crimes' Quintet Publishing, London. .
* Quinche, Nicolas, and Margot, Pierre, "Coulier, Paul-Jean (1824–1890): A precursor in the history of fingermark detection and their potential use for identifying their source (1863)", Journal of forensic identification (Californie), 60 (2), March–April 2010, pp. 129–134.
* Silverman, Mike; Thompson, Tony. Written in Blood: A History of Forensic Science. 2014. | 3 | Analytical Chemistry |
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