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The replacement of dihydropyran ring with a benzene ring increases the lipophilicity of a drug and makes the drug much more stable and more synthetically accessible. Based on the interaction of DANA and NA, the benzoic derivatives were synthesized. They have shown similar or better inhibitory activity compared to Neu5Ac. | 1 | Applied and Interdisciplinary Chemistry |
Manufactured foods fortified with vitamin D include some fruit juices and fruit juice drinks, meal replacement energy bars, soy protein-based beverages, certain cheese and cheese products, flour products, infant formulas, many breakfast cereals, and milk.
In 2016 in the United States, the Food and Drug Administration (FDA) amended food additive regulations for milk fortification, stating that vitamin D levels not exceed 42IU vitamin D per 100g (400IU per US quart) of dairy milk, 84IU of vitamin D per 100g (800IU per quart) of plant milks, and 89IU per 100g (800IU per quart) in plant-based yogurts or in soy beverage products. Plant milks are defined as beverages made from soy, almond, rice, among other plant sources intended as alternatives to dairy milk.
While some studies have found that vitamin D raises 25(OH)D blood levels faster and remains active in the body longer, others contend that vitamin D sources are equally bioavailable and effective as D for raising and sustaining 25(OH)D. | 1 | Applied and Interdisciplinary Chemistry |
Multispectral imaging captures image data within specific wavelength ranges across the electromagnetic spectrum. The wavelengths may be separated by filters or detected with the use of instruments that are sensitive to particular wavelengths, including light from frequencies beyond the visible light range, i.e. infrared and ultra-violet. It can allow extraction of additional information the human eye fails to capture with its visible receptors for red, green and blue. It was originally developed for military target identification and reconnaissance. Early space-based imaging platforms incorporated multispectral imaging technology to map details of the Earth related to coastal boundaries, vegetation, and landforms. Multispectral imaging has also found use in document and painting analysis.
Multispectral imaging measures light in a small number (typically 3 to 15) of spectral bands. Hyperspectral imaging is a special case of spectral imaging where often hundreds of contiguous spectral bands are available. | 0 | Theoretical and Fundamental Chemistry |
If half of the tetrahedral sites of the parent HCP lattice are filled by ions of opposite charge, the structure formed is the wurtzite crystal structure. If all the octahedral sites of the anion HCP lattice are filled by cations, the structure formed is the nickel arsenide structure. | 0 | Theoretical and Fundamental Chemistry |
Zintl phases are intermetallic compounds that have a pronounced ionic bonding character. They are made up of a polyanionic substructure and group 1 or 2 counter ions, and their structure can be understood by a formal electron transfer from the electropositive element to the more electronegative element in their composition. Thus, the valence electron concentration (VEC) of the anionic element is increased, and it formally moves to the right in its row of the periodic table. Generally the anion does not reach an octet, so to reach that closed shell configuration, bonds are formed. The structure can be explained by the 8-N rule (replacing the number of valence electrons, N, by VEC), making it comparable to an isovalent element. The formed polyanionic substructures can be chains (two-dimensional), rings, and other two-or three-dimensional networks or molecule-like entities.
The Zintl line is a hypothetical boundary drawn between groups 13 and 14. It separates the columns based on the tendency for group 13 elements to form metals when reacted with electropositive group 1 or 2 elements and for group 14 and above to form ionic solids. The typical salts formed in these reactions become more metallic as the main group element becomes heavier. | 0 | Theoretical and Fundamental Chemistry |
In humans, fatty acids are formed from carbohydrates predominantly in the liver and adipose tissue, as well as in the mammary glands during lactation.
The pyruvate produced by glycolysis is an important intermediary in the conversion of carbohydrates into fatty acids and cholesterol. This occurs via the conversion of pyruvate into acetyl-CoA in the mitochondrion. However, this acetyl CoA needs to be transported into cytosol where the synthesis of fatty acids and cholesterol occurs. This cannot occur directly. To obtain cytosolic acetyl-CoA, citrate (produced by the condensation of acetyl CoA with oxaloacetate) is removed from the citric acid cycle and carried across the inner mitochondrial membrane into the cytosol. There it is cleaved by ATP citrate lyase into acetyl-CoA and oxaloacetate. The oxaloacetate can be used for gluconeogenesis (in the liver), or it can be returned into mitochondrion as malate. The cytosolic acetyl-CoA is carboxylated by acetyl CoA carboxylase into malonyl CoA, the first committed step in the synthesis of fatty acids. | 1 | Applied and Interdisciplinary Chemistry |
The overall aim of treating sewage is to produce an effluent that can be discharged to the environment while causing as little water pollution as possible, or to produce an effluent that can be reused in a useful manner. This is achieved by removing contaminants from the sewage. It is a form of waste management.
With regards to biological treatment of sewage, the treatment objectives can include various degrees of the following: to transform or remove organic matter, nutrients (nitrogen and phosphorus), pathogenic organisms, and specific trace organic constituents (micropollutants).
Some types of sewage treatment produce sewage sludge which can be treated before safe disposal or reuse. Under certain circumstances, the treated sewage sludge might be termed biosolids and can be used as a fertilizer. | 1 | Applied and Interdisciplinary Chemistry |
RNA-dependent RNA polymerase (RdRp) or RNA replicase is an enzyme that catalyzes the replication of RNA from an RNA template. Specifically, it catalyzes synthesis of the RNA strand complementary to a given RNA template. This is in contrast to typical DNA-dependent RNA polymerases, which all organisms use to catalyze the transcription of RNA from a DNA template.
RdRp is an essential protein encoded in the genomes of most RNA-containing viruses with no DNA stage including SARS-CoV-2. Some eukaryotes also contain RdRps, which are involved in RNA interference and differ structurally from viral RdRps. | 1 | Applied and Interdisciplinary Chemistry |
In the early 17th century, ironworkers in Western Europe had developed the cementation process for carburizing wrought iron. Wrought iron bars and charcoal were packed into stone boxes, then sealed with clay to be held at a red heat continually tended in an oxygen-free state immersed in nearly pure carbon (charcoal) for up to a week. During this time, carbon diffused into the surface layers of the iron, producing cement steel or blister steel—also known as case hardened, where the portions wrapped in iron (the pick or axe blade) became harder, than say an axe hammer-head or shaft socket which might be insulated by clay to keep them from the carbon source. The earliest place where this process was used in England was at Coalbrookdale from 1619, where Sir Basil Brooke had two cementation furnaces (recently excavated in 2001–2005). For a time in the 1610s, he owned a patent on the process, but had to surrender this in 1619. He probably used Forest of Dean iron as his raw material, but it was soon found that oregrounds iron was more suitable. The quality of the steel could be improved by faggoting, producing the so-called shear steel. | 1 | Applied and Interdisciplinary Chemistry |
The biosynthesis of longifolene begins with farnesyl diphosphate (1) (also called farnesyl pyrophosphate) by means of a cationic polycyclization cascade. Loss of the pyrophosphate group and cyclization by the distal alkene gives intermediate 3, which by means of a 1,3-hydride shift gives intermediate 4. After two additional cyclizations, intermediate 6 produces longifolene by a 1,2-alkyl migration. | 0 | Theoretical and Fundamental Chemistry |
In 2004, Malcolm Grant became provost of UCL. He commissioned external reports on the reorganisation of the college. The distinguished vice-president of the University of Manchester, Richard Alan North FRS, was asked to assess several options for the reorganisation of the Faculty of Life Sciences. One was to create large Research Departments, including one of Neuroscience, Physiology and Pharmacology, from the existing academic Departments. Professor North's only comment on the options was that the proposed "research departments in Life Sciences were too big". Grant accepted the conclusions except for the part about the size of departments.
On 24 May 2007 Grant persuaded the Academic Board to authorise him to act on its behalf and on 13 June 2007 the Department of Pharmacology was disestablished, after a century of distinction and innovation.
The academic staff at the time had three main concerns about the proposals. (a) The separation of teaching from research is bad, especially for teaching: the fact that a degree is offered in, for example, Pharmacology without a Pharmacology department to support it, means that there is no guarantee that there will be staff qualified or fully motivated to teach it. Moreover, the collegiality that comes from designing and providing a first-rate degree course is lost. (b) The size of the merged department of Neurosciences, Physiology and Pharmacology means less interaction between staff, and less collegiate spirit. (c) The changes created two extra levels of administration, so that now five levels existed between academics and the provost.
Staff were told at the time that the new organisation would be rolled out to other Faculties across UCL, though this has not happened. David Colquhoun has kept a personal diary of the process on his blog: In Memoriam Department of Pharmacology, UCL 1905 – 2007. On the positive side, UCL's current provost, Michael Arthur, has put much emphasis on the quality of teaching, and maintaining its connections with research.
As of 2019, UCL still offers pharmacology degrees, though within the now merged Neuroscience, Physiology and Pharmacology department. | 1 | Applied and Interdisciplinary Chemistry |
Methane clathrate, also known commonly as methane hydrate, is a form of water ice that contains a large amount of methane within its crystal structure. Potentially large deposits of methane clathrate have been found under sediments on the ocean floors of the Earth, although the estimates of total resource size given by various experts differ by many orders of magnitude, leaving doubt as to the size of methane clathrate deposits (particularly in the viability of extracting them as a fuel resource). Indeed, cores of greater than 10 centimeters' contiguous depth had only been found in three sites as of 2000, and some resource reserve size estimates for specific deposits/locations have been based primarily on seismology. The sudden release of large amounts of natural gas from methane clathrate deposits in runaway climate change could be a cause of past, future, and present climate changes.
In the Arctic ocean, clathrates can exist in shallower water stabilized by lower temperatures rather than higher pressures; these may potentially be marginally stable much closer to the surface of the sea-bed, stabilized by a frozen lid of permafrost preventing methane escape. The so-called self-preservation phenomenon has been studied by Russian geologists starting in the late 1980s. This metastable clathrate state can be a basis for release events of methane excursions, such as during the interval of the Last Glacial Maximum. A study from 2010 concluded with the possibility for a trigger of abrupt climate warming based on metastable methane clathrates in the East Siberian Arctic Shelf (ESAS) region. | 0 | Theoretical and Fundamental Chemistry |
Supercritical fluids generally have properties between those of a gas and a liquid. In Table 1, the critical properties are shown for some substances that are commonly used as supercritical fluids.
Table 2 shows density, diffusivity and viscosity for typical liquids, gases and supercritical fluids.
Also, there is no surface tension in a supercritical fluid, as there is no liquid/gas phase boundary. By changing the pressure and temperature of the fluid, the properties can be "tuned" to be more liquid-like or more gas-like. One of the most important properties is the solubility of material in the fluid. Solubility in a supercritical fluid tends to increase with density of the fluid (at constant temperature). Since density increases with pressure, solubility tends to increase with pressure. The relationship with temperature is a little more complicated. At constant density, solubility will increase with temperature. However, close to the critical point, the density can drop sharply with a slight increase in temperature. Therefore, close to the critical temperature, solubility often drops with increasing temperature, then rises again. | 0 | Theoretical and Fundamental Chemistry |
The "official" version of Lavoisiers Easter Memoir appeared in 1778. In the intervening period, Lavoisier had ample time to repeat some of Priestleys latest experiments and perform some new ones of his own. In addition to studying Priestley's dephlogisticated air, he studied more thoroughly the residual air after metals had been calcined. He showed that this residual air supported neither combustion nor respiration and that approximately five volumes of this air added to one volume of the dephlogisticated air gave common atmospheric air. Common air was then a mixture of two distinct chemical species with quite different properties. Thus when the revised version of the Easter Memoir was published in 1778, Lavoisier no longer stated that the principle which combined with metals on calcination was just common air but "nothing else than the healthiest and purest part of the air" or the "eminently respirable part of the air". The same year he coined the name oxygen for this constituent of the air, from the Greek words meaning "acid former". He was struck by the fact that the combustion products of such nonmetals as sulfur, phosphorus, charcoal, and nitrogen were acidic. He held that all acids contained oxygen and that oxygen was therefore the acidifying principle. | 1 | Applied and Interdisciplinary Chemistry |
Iron is a popular research target for many catalytic processes, owing largely to its low cost and low toxicity relative to other transition metals. Asymmetric hydrogenation methods using iron have been realized, although in terms of rates and selectivity, they are inferior to catalysts based on precious metals. In some cases, structurally ill-defined nanoparticles have proven to be the active species in situ and the modest selectivity observed may result from their uncontrolled geometries. | 0 | Theoretical and Fundamental Chemistry |
CKLF like MARVEL transmembrane domain-containing 6 (i.e. CMTM6), previously termed chemokine-like factor superfamily 6 (i.e. CKLFSF6), is a transmembrane protein encoded in humans by the CMTM6 gene (also termed the CKLFSF6, PRO2219, ayoube, or gourari gene). This gene is located in band 22.3 on the short (or "p") arm of chromosome 3. CMTM6 protein belongs to the CKLF-like MARVEL transmembrane domain-containing family of proteins. This family consist of 9 member proteins: CKLF and CMTM1 through CMTM8. The CMTM family proteins are involved in autoimmune diseases, cardiovascular diseases, the male reproductive system, haematopoiesis, and cancer development. CMTM6 protein regulates immune responses to normal and abnormal (particularly cancerous) cells. | 1 | Applied and Interdisciplinary Chemistry |
*TXN2 NM_012473
*TXNDC11 NM_015914
*TXNDC12 NM_015913
*TXNDC15 NM_024715
*TXNDC17 NM_032731
*TXNDC9 NM_005783
*TXNL1 NM_004786
*TXNL4A NM_006701
*TXNL4B NM_017853
*TXNRD1 NM_003330 | 1 | Applied and Interdisciplinary Chemistry |
There are several surface measurement (including flasks and continuous in situ) networks including NOAA/ERSL, WDCGG, and RAMCES. The NOAA/ESRL Baseline Observatory Network, and the Scripps Institution of Oceanography Network data are hosted at the CDIAC at ORNL. The World Data Centre for Greenhouse Gases (WDCGG), part of GAW, data are hosted by the JMA. The Reseau Atmospherique de Mesure des Composes an Effet de Serre database (RAMCES) is part of IPSL.
From these measurements, further products are made which integrate data from the various sources. These products also address issues such as data discontinuity and sparseness. GLOBALVIEW- is one of these products.
Ongoing ground-based total column measurements began more recently. Column measurements typically refer to an averaged column amount denoted X, rather than a surface only measurement. These measurements are made by the TCCON. These data are also hosted on the CDIAC, and made publicly available according to the data use policy. | 1 | Applied and Interdisciplinary Chemistry |
Anthocyanins (), also called anthocyans, are water-soluble vacuolar pigments that, depending on their pH, may appear red, purple, blue, or black. In 1835, the German pharmacist Ludwig Clamor Marquart named a chemical compound that gives flowers a blue color, Anthokyan, in his treatise "Die Farben der Blüthen". Food plants rich in anthocyanins include the blueberry, raspberry, black rice, and black soybean, among many others that are red, blue, purple, or black. Some of the colors of autumn leaves are derived from anthocyanins.
Anthocyanins belong to a parent class of molecules called flavonoids synthesized via the phenylpropanoid pathway. They can occur in all tissues of higher plants, including leaves, stems, roots, flowers, and fruits. Anthocyanins are derived from anthocyanidins by adding sugars. They are odorless and moderately astringent.
Although approved as food and beverage colorant in the European Union, anthocyanins are not approved for use as a food additive because they have not been verified as safe when used as food or supplement ingredients. There is no conclusive evidence that anthocyanins have any effect on human biology or diseases. | 0 | Theoretical and Fundamental Chemistry |
In materials science, effective medium approximations (EMA) or effective medium theory (EMT) pertain to analytical or theoretical modeling that describes the macroscopic properties of composite materials. EMAs or EMTs are developed from averaging the multiple values of the constituents that directly make up the composite material. At the constituent level, the values of the materials vary and are inhomogeneous. Precise calculation of the many constituent values is nearly impossible. However, theories have been developed that can produce acceptable approximations which in turn describe useful parameters including the effective permittivity and permeability of the materials as a whole. In this sense, effective medium approximations are descriptions of a medium (composite material) based on the properties and the relative fractions of its components and are derived from calculations, and effective medium theory. There are two widely used formulae.
Effective permittivity and permeability are averaged dielectric and magnetic characteristics of a microinhomogeneous medium. They both were derived in quasi-static approximation when the electric field inside a mixture particle may be considered as homogeneous. So, these formulae can not describe the particle size effect. Many attempts were undertaken to improve these formulae. | 0 | Theoretical and Fundamental Chemistry |
Even before the first selective COX-2 inhibitor was marketed, specialists began to suspect that there might be a cardiovascular risk associated with this class of medicines. In the VIGOR study (Vioxx Gastrointestinal Outcomes Research), rofecoxib (Vioxx) was compared to naproxen. After a short time, it became evident that there was a fivefold higher risk of myocardial infarction in the rofecoxib group compared to the group that received naproxen. The authors suggested that the difference was due to the cardioprotective effects of naproxen. The APPROVe (Adenomatous Poly Prevention on Vioxx) study was a multicentre, randomized, placebo-controlled, double blind trial aimed to assess the effect of three-year treatment with rofecoxib on recurrence of neoplastic polyps in individuals with a history of colorectal adenomas. In 2000 and 2001, 2587 patients with a history of colorectal adenomas were recruited and followed. The trial was stopped early (2 months before expected completion) on recommendations of its data safety and monitoring board because of concerns about cardiovascular toxicity. When looking at the results of the study, it showed a statistically significant increase in cardiovascular risk when taking rofecoxib compared to placebo beginning after 18 months of treatment. Then on 30 September Merck gave out a news release announcing their voluntary worldwide withdrawal of Vioxx.
Some studies of other coxibs have also shown increase in the risk of cardiovascular events, while others have not. For instance, the Adenoma Prevention with Celecoxib study (APC) showed a dose-related increase in risk of cardiovascular death, myocardial infarction, stroke, or heart failure when taking celecoxib compared to placebo; and the Successive Celecoxib Efficacy and Safety Study I (SUCCESS-I) showed increased risk of myocardial infarction when taking 100 mg twice a day of celecoxib compared to diclofenac and naproxen; but taking 200 mg twice a day had lower incidence of myocardial infarction compared to diclofenac and naproxen. Nussmeier et al. (2005) showed in a study increase in incidence of cardiovascular events when taking parecoxib and valdecoxib (compared to placebo) after coronary artery bypass surgery. | 1 | Applied and Interdisciplinary Chemistry |
For educational purposes the European Federation for Medicinal Chemistry and Chemical Biology (EFMC) shared a series of webinars including Best Practices for Hit Finding as well as Hit Generation Case Studies. | 1 | Applied and Interdisciplinary Chemistry |
Thorium fuels have fueled several different reactor types, including light water reactors, heavy water reactors, high temperature gas reactors, sodium-cooled fast reactors, and molten salt reactors. | 0 | Theoretical and Fundamental Chemistry |
Measurements of the EMF are obtained using an E-field sensor or H-field sensor which can be isotropic or mono-axial, active or passive.
A mono-axial, omnidirectional probe is a device which senses the Electric (short dipole) or Magnetic field linearly polarized in a given direction.
Using a mono-axial probe implies the need for three measurements taken with the sensor axis set up along three mutually orthogonal directions, in a X, Y, Z configuration.
As an example, it can be used as a probe which senses the Electric field component parallel to the direction of its axis of symmetry. In these conditions, where E is the amplitude of incident electric field, and θ is the amplitude of the angle between sensor axis and direction of electric field E, the signal detected is proportional to |E|cos θ (right). This allows obtainment of the correct total amplitude of the field in the form of
or, in case of the magnetic field
An isotropic (tri-axial) probe simplifies the measurement procedure because the total field value is determined with three measures taken without changing sensor position: this results from the geometry of the device which is made by three independent broadband sensing elements placed orthogonal to each other. In practice, each element's output is measured in three consecutive time intervals supposing field components being time stationary . | 1 | Applied and Interdisciplinary Chemistry |
The chemical traffic light is a color-changing redox reaction that is related to the blue bottle experiment. One of the early formulas consists of glucose, sodium hydroxide, indigo carmine (dye), and water. Another formula consists of indigo carmine, ascorbic acid (Vitamin C), sodium bicarbonate, sodium chloride, copper(II) sulfate, sodium hydroxide and water. By doing so, chemical waste and the level of corrosive chemicals is reduced. The amount of solid chemicals dissolved in the experiment could be reduced from 60 grams to 6 grams. And the pH could be lowered from 13 to 3 which is easier to neutralize the pH to 7 by adding baking soda before disposal. Also, it is safer and the reactions also occur faster and are easier to perform.
At first, all chemicals are added together and the color appears yellow. After shaking, the color turns green and then changes to red after it is left untouched. When further observed, the color turns back to yellow, which is why the solution is called the chemical traffic light. This reaction can be repeated many times, but it needs additional oxygen or indigo carmine.
This reaction occurs by oxidation and reduction of the solution where alkaline glucose solution is acting as a reducing agent. The glucose solution is added to the solution containing indicator (dye indigo carmine) the color changes occur. This reaction is also known as chemical clock experiment because concentrations of the products and reactants changed over the specific period. When the solution is shaken, oxygen dissolves in the solution and oxidizes indigo carmine. Solution becomes red if a small amount of oxygen is dissolved, and green if all of indigo carmine is oxidized. The solution will turn back to original yellow color when the concentration of oxygen level drops. | 1 | Applied and Interdisciplinary Chemistry |
The word hydrolysis is applied to chemical reactions in which a substance reacts with water. In organic chemistry, the products of the reaction are usually molecular, being formed by combination with H and OH groups (e.g., hydrolysis of an ester to an alcohol and a carboxylic acid). In inorganic chemistry, the word most often applies to cations forming soluble hydroxide or oxide complexes with, in some cases, the formation of hydroxide and oxide precipitates. | 0 | Theoretical and Fundamental Chemistry |
As part of Chemfluence14, the final day of the symposium was reserved for EECON14 - the first National Conference on Energy & Environment. Being the first ever symposium to be organised in the university by the student fraternity, the conference begun with the EECON'14 souvenir release and a keynote address by Dr. G. Sekaran, Chief Scientist, CLRI on handling wastes in the tanning sector at the Colin Mckenzie Auditorium. Subsequently, six paper presentation sessions and a poster presentation session were held on a plethora of topics such as Solid Waste Management, Air Pollution Control and Modeling of Environmentally benign processes. Chairpersons for the sessions were personalities high on caliber including Dr. T. Renganathan, Assistant Professor, IIT- Madras, Dr. S. Kanmani, Director, CTDT, Anna University and Dr. M. K. Gowthaman, CLRI amongst many others. | 1 | Applied and Interdisciplinary Chemistry |
Stop codon suppression or translational readthrough occurs when in translation a stop codon is interpreted as a sense codon, that is, when a (standard) amino acid is encoded by the stop codon. Mutated tRNAs can be the cause of readthrough, but also certain nucleotide motifs close to the stop codon. Translational readthrough is very common in viruses and bacteria, and has also been found as a gene regulatory principle in humans, yeasts, bacteria and drosophila. This kind of endogenous translational readthrough constitutes a variation of the genetic code, because a stop codon codes for an amino acid. In the case of human malate dehydrogenase, the stop codon is read through with a frequency of about 4%. The amino acid inserted at the stop codon depends on the identity of the stop codon itself: Gln, Tyr, and Lys have been found for the UAA and UAG codons, while Cys, Trp, and Arg for the UGA codon have been identified by mass spectrometry. Extent of readthrough in mammals have widely variable extents, and can broadly diversify the proteome and affect cancer progression. | 1 | Applied and Interdisciplinary Chemistry |
Hammonds postulate is useful for understanding the relationship between the rate of a reaction and the stability of the products. While the rate of a reaction depends just on the activation energy (often represented in organic chemistry as ΔG “delta G double dagger”), the final ratios of products in chemical equilibrium depends only on the standard free-energy change ΔG (“delta G'”). The ratio of the final products at equilibrium corresponds directly with the stability of those products.
Hammond's postulate connects the rate of a reaction process with the structural features of those states that form part of it, by saying that the molecular reorganizations have to be small in those steps that involve two states that are very close in energy. This gave birth to the structural comparison between the starting materials, products, and the possible "stable intermediates" that led to the understanding that the most stable product is not always the one that is favored in a reaction process. | 0 | Theoretical and Fundamental Chemistry |
Chelating resins operate similarly to ordinary ion-exchange resins.
Most chelating resins are polymers (copolymers to be precise) with reactive functional groups that chelate to metal ions. The variation in chelating resins arises from the nature of the chelating agents pendant from the polymer backbone. Dowex chelating resin A-1, also known as Chelex 100, is based on iminodiacetic acid in a styrene-divinylbenzene matrix. Dowex A-1 is available commercially and is widely used to determine general properties of chelating resins such as rate determining step and pH dependence, etc. Dowex A-1 is produced from chloromethylated styrene-divinylbenzene copolymer via amination with aminodiacetic acid.
Poly metal chelating resin has almost negligible affinity to both alkali and alkaline earth metals; small quantities of resin can be utilized to concentrate trace metals in natural water systems or biological fluids, in which there are three or four orders of magnitude greater alkali and alkaline earth metal concentration than the trace metal concentrations.
Other functional groups bound to chelating resins are aminophosphonic acids, thiourea, and 2-picolylamine. | 0 | Theoretical and Fundamental Chemistry |
Ultraviolet photoelectron spectroscopy (UPS) refers to the measurement of kinetic energy spectra of photoelectrons emitted by molecules which have absorbed ultraviolet photons, in order to determine molecular orbital energies in the valence region. | 0 | Theoretical and Fundamental Chemistry |
Muon-catalyzed fusion (abbreviated as μCF or MCF) is a process allowing nuclear fusion to take place at temperatures significantly lower than the temperatures required for thermonuclear fusion, even at room temperature or lower. It is one of the few known ways of catalyzing nuclear fusion reactions.
Muons are unstable subatomic particles which are similar to electrons but 207 times more massive. If a muon replaces one of the electrons in a hydrogen molecule, the nuclei are consequently drawn 186 times closer than in a normal molecule, due to the reduced mass being 186 times the mass of an electron. When the nuclei move closer together, the fusion probability increases, to the point where a significant number of fusion events can happen at room temperature.
Methods for obtaining muons, however, require far more energy than can be produced by the resulting fusion reactions. Muons have a mean lifetime of , much longer than many other subatomic particles but nevertheless far too brief to allow their useful storage.
To create useful room-temperature muon-catalyzed fusion, reactors would need a cheap, efficient muon source and/or a way for each individual muon to catalyze many more fusion reactions. | 0 | Theoretical and Fundamental Chemistry |
The image of the sewer recurs in European culture as they were often used as hiding places or routes of escape by the scorned or the hunted, including partisans and resistance fighters in World War II. Fighting erupted in the sewers during the Battle of Stalingrad. The only survivors from the Warsaw Uprising and Warsaw Ghetto made their final escape through city sewers. Some have commented that the engravings of imaginary prisons by Piranesi were inspired by the Cloaca Maxima, one of the world's earliest sewers. | 1 | Applied and Interdisciplinary Chemistry |
The dynamic reciprocity theory states that a cell’s fate depends on the exchange of chemical signals between the extracellular matrix and the nucleus of the cell. Focussing on connections between laminin-111 and other proteins involved in cell-to-cell communication could spark further research that may help to further our current understanding of cancer and how to slow down or stop its process.
Actin plays a role in nuclear activity which is an important process with regard to cell signalling influencing cell differentiation and replication. It has been suggested that actin interactions directly influence gene transcription as it interacts with chromatin remodeling complexes as well as RNA polymerases I, II and III. However, the exact role that actin plays in transcription has not yet been determined. | 0 | Theoretical and Fundamental Chemistry |
Many maritime accidents have been caused by corrosion, and this has led to stringent regulations concerning protective coatings for ballast tanks. The Coating Performance Standard for Ballast Tank Coatings (PSPC), became effective in 2008. It specifies how protective coatings should be applied during vessel construction with the intention of giving a coating a 15-year service life. Additional regulations, such as those established by The International Convention for the Control and Management of Ships Ballast Water & Sediments (SBWS) sought to avoid introducing invasive species throughout the world through ship's ballast tanks. The methods used to avoid having these invasive species surviving in ballast tanks however greatly increased the rate of corrosion. Therefore ongoing research attempts to find water treatment systems that kill invasive species, while not having a destructive effect on the ballast tank coatings. As double-hulled tankers were introduced it meant that there was more ballast tank area had to be coated and therefore a greater capital investment for ship owners. With the onset of the OPA 90 and later the amendments to MARPOL annex 1, single hull tankers (without alternative method) have basically phased out.
Modern double hull tankers, with their fully "segregated ballast tanks" propose another problem. Empty tanks act as insulation from the cold sea and allow the warm cargo areas to retain their heat longer. Corrosion rates increase with differences in temperature. Consequently, the cargo side of the ballast tank corrodes more quickly than it did with single hull tankers. | 1 | Applied and Interdisciplinary Chemistry |
Positional scanning was introduced independently by Furka et al. and Pinilla et al. The method is based on the synthesis and testing of series of sublibraries. in which a certain sequence position is occupied by the same amino acid. The figure shows the nine sublibraries (B1-D3) of a full peptide trimer library (A) made from three amino acids. In sublibraries there is a position which is occupied by the same amino acid in all components. In the synthesis of a sublibrary the support is not divided and only one amino acid is coupled to the whole sample. As a result, one position is really occupied by the same amino acid in all components. For example, in the B2 sublibrary position 2 is occupied by the "yellow" amino acid in all the nine components. If in a screening test this sublibrary gives positive answer it means that position 2 in the active peptide is also occupied by the "yellow" amino acid. The amino acid sequence can be determined by testing all the nine (or sometime less) sublibraries. | 1 | Applied and Interdisciplinary Chemistry |
Researchers have invented a nanofluid-based ultrasensitive optical sensor that changes its colour on exposure to extremely low concentrations of toxic cations. The sensor is useful in detecting minute traces of cations in industrial and environmental samples. Existing techniques for monitoring cations levels in industrial and environmental samples are expensive, complex and time-consuming. The sensor is designed with a magnetic nanofluid that consists of nano-droplets with magnetic grains suspended in water. At a fixed magnetic field, a light source illuminates the nanofluid where the colour of the nanofluid changes depending on the cation concentration. This color change occurs within a second after exposure to cations, much faster than other existing cation sensing methods.
Such response stimulus nanofluids are also used to detect and image defects in ferromagnetic components. The photonic eye, as it has been called, is based on a magnetically polarizable nano-emulsion that changes colour when it comes into contact with a defective region in a sample. The device might be used to monitor structures such as rail tracks and pipelines. | 0 | Theoretical and Fundamental Chemistry |
CeCoIn is a member of a rich family of heavy-fermion compounds. CeIn is heavy-fermion metal with cubic crystal structure that orders antiferromagnetically below 10K. With applying external pressure, antiferromagnetism in CeIn is continuously suppressed, and a superconducting dome emerges in the phase diagram near the antiferromagnetic quantum critical point. CeCoIn has a tetragonal crystal structure, and the unit cell of CeCoIn can be considered as CeIn with an additional CoIn layer per unit cell.
Closely related to CeCoIn is the heavy-fermion material CeRhIn, which has the same crystal structure and which orders antiferromagnetically below 4K, but does not become superconducting at ambient pressure. At high pressure CeRhIn becomes superconducting with a maximum T slightly above 2 K at a pressure around 2 GPa, and at the same pressure the Fermi surface of CeRhIn changes suggesting so-called local quantum criticality.
Also the compound PuCoGa, which is a superconductor with T approximately 18.5 K and which can be considered an intermediate between heavy-fermion and cuprate superconductors, has the same crystal structure.
Growth of single-crystalline CeCoIn has been very successful soon after the discovery of the material, and large single crystals of CeCoIn, such as required for inelastic neutron scattering, have been prepared. (In contrast to some other heavy-fermion compounds where single-crystal growth is more challenging.) | 1 | Applied and Interdisciplinary Chemistry |
In classical mechanics, the state of an ideal gas of energy U, volume V and with N particles, each particle having mass m, is represented by specifying the momentum vector p and the position vector x for each particle. This can be thought of as specifying a point in a 6N-dimensional phase space, where each of the axes corresponds to one of the momentum or position coordinates of one of the particles. The set of points in phase space that the gas could occupy is specified by the constraint that the gas will have a particular energy:
and be contained inside of the volume V (lets say V is a cube of side X' so that ):
for and
The first constraint defines the surface of a 3N-dimensional hypersphere of radius (2mU) and the second is a 3N-dimensional hypercube of volume V. These combine to form a 6N-dimensional hypercylinder. Just as the area of the wall of a cylinder is the circumference of the base times the height, so the area φ of the wall of this hypercylinder is:
The entropy is proportional to the logarithm of the number of states that the gas could have while satisfying these constraints. In classical physics, the number of states is infinitely large, but according to quantum mechanics it is finite. Before the advent of quantum mechanics, this infinity was regularized by making phase space discrete. Phase space was divided up in blocks of volume h. The constant h thus appeared as a result of a mathematical trick and thought to have no physical significance. However, using quantum mechanics one recovers the same formalism in the semi-classical limit, but now with h being the Planck constant. One can qualitatively see this from Heisenbergs uncertainty principle; a volume in N phase space smaller than h (h' is the Planck constant) cannot be specified.
To compute the number of states we must compute the volume in phase space in which the system can be found and divide that by h. This leads us to another problem: The volume seems to approach zero, as the region in phase space in which the system can be is an area of zero thickness. This problem is an artifact of having specified the energy U with infinite accuracy. In a generic system without symmetries, a full quantum treatment would yield a discrete non-degenerate set of energy eigenstates. An exact specification of the energy would then fix the precise state the system is in, so the number of states available to the system would be one, the entropy would thus be zero.
When we specify the internal energy to be U, what we really mean is that the total energy of the gas lies somewhere in an interval of length around U. Here is taken to be very small, it turns out that the entropy doesnt depend strongly on the choice of for large N. This means that the above "area" φ' must be extended to a shell of a thickness equal to an uncertainty in momentum , so the entropy is given by:
where the constant of proportionality is k, the Boltzmann constant. Using Stirlings approximation for the Gamma function which omits terms of less than order N, the entropy for large N' becomes:
This quantity is not extensive as can be seen by considering two identical volumes with the same particle number and the same energy. Suppose the two volumes are separated by a barrier in the beginning. Removing or reinserting the wall is reversible, but the entropy increases when the barrier is removed by the amount
which is in contradiction to thermodynamics if you re-insert the barrier. This is the Gibbs paradox.
The paradox is resolved by postulating that the gas particles are in fact indistinguishable. This means that all states that differ only by a permutation of particles should be considered as the same state. For example, if we have a 2-particle gas and we specify AB as a state of the gas where the first particle (A) has momentum p and the second particle (B) has momentum p, then this state as well as the BA state where the B particle has momentum p and the A particle has momentum p should be counted as the same state.
For an N-particle gas, there are N! states which are identical in this sense, if one assumes that each particle is in a different single particle state. One can safely make this assumption provided the gas isnt at an extremely high density. Under normal conditions, one can thus calculate the volume of phase space occupied by the gas, by dividing Equation 1 by N!. Using the Stirling approximation again for large N, ln(N!) ≈ N ln(N) − N, the entropy for large N' is:
which can be easily shown to be extensive. This is the Sackur–Tetrode equation. | 0 | Theoretical and Fundamental Chemistry |
In South Africa, modafinil is Schedule V substance, which means that it is legal to use modafinil in South Africa, but only with a valid prescription from a licensed medical practitioner. | 0 | Theoretical and Fundamental Chemistry |
Methanation is an important step in the creation of synthetic or substitute natural gas (SNG). Coal or wood undergo gasification which creates a producer gas that must undergo methanation in order to produce a usable gas that just needs to undergo a final purification step.
The first commercial synthetic gas plant opened in 1984 and is the Great Plains Synfuel plant in Beulah, North Dakota. It is still operational and produces 1500 MW worth of SNG using coal as the carbon source. In the years since its opening, other commercial facilities have been opened using other carbon sources such as wood chips.
In France, the AFUL Chantrerie, located in Nantes, started in November 2017 the demonstrator MINERVE. This methanation unit of 14 Nm3/day was carried out by Top Industrie, with the support of Leaf. This installation is used to feed a CNG station and to inject methane into the natural gas boiler. | 0 | Theoretical and Fundamental Chemistry |
The potential for corrosion, leading to pipe failure, is significantly impacted by the corrosivity of soil. Unprotected pipes in highly corrosive soil tend to have shorter lifespans. The lifespan of ductile iron pipe installed in an aggressive environment without appropriate protection may be between 21 and 40 years. The introduction of corrosion mitigation methods for ductile pipe, including the use of polyethylene sleeving, can reduce corrosion by controlling the effect of corrosive soil on piping.
In the United States, the American National Standards Institute and American Water Works Association have standardized the use of polyethylene sleeving to protect ductile iron pipe from the effects of corrosion. A 2003 report by researchers from the National Research Council of Canada noted that "both good and poor performances" of polyethylene sleeving had been reported. However, a study in the Ductile Iron Pipe Research Association's Florida test site found that, compared with uncoated pipes exposed to a corrosive environment, pipes encased in loose polyethylene sleeving were "in excellent condition".
Based on a 2005 meta analysis of 1,379 pipe specimens, loose polyethylene sleeving was found to be highly effective at mitigating corrosion. The only environment for which the analysis found the polyethylene sleeving did not provide effective corrosion control was for "uniquely severe" environments, a classification of a rare but extremely corrosive environment. The analysis found that a lifespan of 37 years could be expected in these "uniquely severe" environments.
Pipes manufactured under International Organization for Standardization (ISO) standards are typically coated with zinc, to provide protection against corrosion. In instances of more aggressive soils, polyethylene sleeving is installed over the zinc coated pipe to provide added protection.
Cathodic protection may also be used to prevent corrosion and tends to be advocated by corrosion engineers for pipes in corrosive soils as an addition to external dielectric coatings.
Engineers and water authorities in the United States are divided on the use of different coatings or cathodic protection. Mixed results have been found for all methods of protection. However, this may be due to the impact of variations in local soil corrosiveness and temperature or by damage occurring during installation, which can impact effectiveness of protective coatings. | 1 | Applied and Interdisciplinary Chemistry |
Several yttrium oxalate double salts are known containing additional cations. Also a mixed-anion compound with carbonate is known. | 0 | Theoretical and Fundamental Chemistry |
The Trost ligand is a diphosphine used in the palladium-catalyzed Trost asymmetric allylic alkylation. Other C-symmetric ligands derived from trans-1,2-diaminocyclohexane (DACH) have been developed, such as the (R,R)-DACH-naphthyl ligand derived from 2-diphenylphosphino-1-naphthalenecarboxylic acid. Related bidentate phosphine-containing ligands derived from other chiral diamines and 2-diphenylphosphinobenzoic acid have also been developed for applications in asymmetric synthesis. | 0 | Theoretical and Fundamental Chemistry |
Trichloroethylene is an effective solvent for a variety of organic materials. It is mainly used for cleaning. Trichloroethylene is an ingredient in various printing ink, varnishes and industrial paint formulations, as an active ingredient. Other uses include dyeing and finishing operations, adhesive formulations, the rubber industry, adhesives, lacquers, and paint strippers. It is applied before plating, anodizing, and painting.
When trichloroethylene was first widely produced in the 1920s, its major use was to extract vegetable oils from plant materials such as soy, coconut, and palm. Other uses in the food industry included coffee decaffeination (removal of caffeine) and the preparation of flavoring extracts from hops and spices. TCE was used a freezing point depressant in carbon tetrachloride fire extinguishers.
Dehydrochlorination of trichloroethylene with potassium hydride gives dichloroacetylene. Trichloroethylene is also a chain terminator for polyvinyl chloride. Chlorination gives pentachloroethane. | 1 | Applied and Interdisciplinary Chemistry |
Molecular medicine is a new scientific discipline in European universities. Combining contemporary medical studies with the field of biochemistry, it offers a bridge between the two subjects. At present only a handful of universities offer the course to undergraduates. With a degree in this discipline, the graduate is able to pursue a career in medical sciences, scientific research, laboratory work, and postgraduate medical degrees. | 1 | Applied and Interdisciplinary Chemistry |
The CC chemokine (or β-chemokine) proteins have two adjacent cysteines (amino acids), near their amino terminus.
There have been at least 27 distinct members of this subgroup reported for mammals, called CC chemokine ligands (CCL)-1 to -28; CCL10 is the same as CCL9. Chemokines of this subfamily usually contain four cysteines (C4-CC chemokines), but a small number of CC chemokines possess six cysteines (C6-CC chemokines). C6-CC chemokines include CCL1, CCL15, CCL21, CCL23 and CCL28. CC chemokines induce the migration of monocytes and other cell types such as NK cells and dendritic cells.
Examples of CC chemokine include monocyte chemoattractant protein-1 (MCP-1 or CCL2) which induces monocytes to leave the bloodstream and enter the surrounding tissue to become tissue macrophages.
CCL5 (or RANTES) attracts cells such as T cells, eosinophils and basophils that express the receptor CCR5.
Increased CCL11 levels in blood plasma are associated with aging (and reduced neurogenesis) in mice and humans. | 1 | Applied and Interdisciplinary Chemistry |
Strontium-90 is classified as high-level waste. Its 29-year half-life means that it can take hundreds of years to decay to negligible levels. Exposure from contaminated water and food may increase the risk of leukemia and bone cancer. Reportedly, thousands of capsules of radioactive strontium containing millions of curies are stored at Hanford Site's Waste Encapsulation and Storage Facility. | 0 | Theoretical and Fundamental Chemistry |
Fused quartz is produced by fusing (melting) high-purity silica sand, which consists of quartz crystals. There are four basic types of commercial silica glass:
* Type I is produced by induction melting natural quartz in a vacuum or an inert atmosphere.
* Type II is produced by fusing quartz crystal powder in a high-temperature flame.
* Type III is produced by burning SiCl in a hydrogen-oxygen flame.
* Type IV is produced by burning SiCl in a water vapor-free plasma flame.
Quartz contains only silicon and oxygen, although commercial quartz glass often contains impurities. Two dominant impurities are aluminium and titanium which affect the optical transmission at ultraviolet wavelengths. If water is present in the manufacturing process, hydroxyl (OH) groups may become embedded which reduces transmission in the infrared. | 1 | Applied and Interdisciplinary Chemistry |
A recent development in calorimetry, however, is that of constant flux cooling/heating jackets. These use variable geometry cooling jackets and can operate with cooling jackets at substantially constant temperature. These reaction calorimeters tend to be much simpler to use and are much more tolerant of changes in the process conditions (which would affect calibration in heat flow or power compensation calorimeters).
A key part of reaction calorimetry is the ability to control temperature in the face of extreme thermal events. Once the temperature is able to be controlled, measurement of a variety of parameters can allow an understanding of how much heat is being released of absorbed by a reaction.
In essence, constant flux calorimetry is a highly developed temperature control mechanism which can be used to generate highly accurate calorimetry. It works by controlling the jacket area of a controlled lab reactor, while keeping the inlet temperature of the thermal fluid constant. This allows the temperature to be precisely controlled even under strongly exothermic or endothermic events as additional cooling is always available by simply increasing the area over which the heat is being exchanged.
This system is generally more accurate than heat balance calorimetry (on which it is based), as changes in the delta temperature (T - T) are magnified by keeping the fluid flow as low as possible.
One of the main advantages of constant flux calorimetry is the ability to dynamically measure heat transfer coefficient (U). We know from the heat balance equation that:
:Q = m.Cp.T - T
We also know that from the heat flow equation that
:Q = U.A.LMTD
We can therefore rearrange this such that
:U = m.Cp.T - T /A.LMTD
This will allow us therefore to monitor U as a function of time. | 1 | Applied and Interdisciplinary Chemistry |
*4.D.1 The Putative Vectorial Glycosyl Polymerization (VGP) Family
*4.D.2 The Glycosyl Transferase 2 (GT2) Family
*4.D.3 The Glycan Glucosyl Transferase (OpgH) Family | 1 | Applied and Interdisciplinary Chemistry |
Brenna was a member of the Dietary Guidelines Advisory Committee advising on the 2015 U.S. Dietary Guidelines for Americans. He was one of four members of the Food Sustainability and Safety subcommittee whose work on sustainability was excluded from consideration by an act of Congress. | 0 | Theoretical and Fundamental Chemistry |
The electrochemical window (EW) of a substance is the electrode electric potential range between which the substance is neither oxidized nor reduced. The EW is one of the most important characteristics to be identified for solvents and electrolytes used in electrochemical applications. The EW is a term that is commonly used to indicate the potential range and the potential difference. It is calculated by subtracting the reduction potential (cathodic limit) from the oxidation potential (anodic limit).
When the substance of interest is water, it is often referred to as the water window.
This range is important for the efficiency of an electrode. Out of this range, the electrodes will react with the electrolyte, instead of driving the electrochemical reaction.
In principle, ammonia has an extremely small electrochemical window, but thermodynamically-favored reactions less than 1 V outside the window are very slow. Consequently, the electrochemical window for many practical reactions is much larger, comparable to water. Ionic liquids famously have a very large electrochemical window, about 4–5 V. | 0 | Theoretical and Fundamental Chemistry |
In the kinetic theory, heat is explained in terms of the microscopic motions and interactions of constituent particles, such as electrons, atoms, and molecules. The immediate meaning of the kinetic energy of the constituent particles is not as heat. It is as a component of internal energy.
In microscopic terms, heat is a transfer quantity, and is described by a transport theory, not as steadily localized kinetic energy of particles. Heat transfer arises from temperature gradients or differences, through the diffuse exchange of microscopic kinetic and potential particle energy, by particle collisions and other interactions. An early and vague expression of this was made by Francis Bacon. Precise and detailed versions of it were developed in the nineteenth century.
In statistical mechanics, for a closed system (no transfer of matter), heat is the energy transfer associated with a disordered, microscopic action on the system, associated with jumps in occupation numbers of the energy levels of the system, without change in the values of the energy levels themselves. It is possible for macroscopic thermodynamic work to alter the occupation numbers without change in the values of the system energy levels themselves, but what distinguishes transfer as heat is that the transfer is entirely due to disordered, microscopic action, including radiative transfer. A mathematical definition can be formulated for small increments of quasi-static adiabatic work in terms of the statistical distribution of an ensemble of microstates. | 0 | Theoretical and Fundamental Chemistry |
In the liver, bilirubin is conjugated with glucuronic acid by the enzyme glucuronyltransferase, first to bilirubin glucuronide and then to bilirubin diglucuronide, making it soluble in water: the conjugated version is the main form of bilirubin present in the "direct" bilirubin fraction. Much of it goes into the bile and thus out into the small intestine. Though most bile acid is reabsorbed in the terminal ileum to participate in enterohepatic circulation, conjugated bilirubin is not absorbed and instead passes into the colon.
There, colonic bacteria deconjugate and metabolize the bilirubin into colorless urobilinogen, which can be oxidized to form urobilin and stercobilin. Urobilin is excreted by the kidneys to give urine its yellow color and stercobilin is excreted in the feces giving stool its characteristic brown color. A trace (~1%) of the urobilinogen is reabsorbed into the enterohepatic circulation to be re-excreted in the bile.
Conjugated bilirubin's half-life is shorter than delta bilirubin. | 1 | Applied and Interdisciplinary Chemistry |
Vasdev has introduced new radiochemical methods and radiopharmaceuticals for imaging the living human brain. The Vasdev Lab is exploring new ways to image neuroinflammation and tau protein. He is the co-inventor of the method patent for the first and only FDA-approved tau-PET radiopharmaceutical Tauvid that has been employed worldwide to image patients with Alzheimer's disease (AD) and related dementias, as well as patients with symptomatic traumatic brain injuries, including professional athletes and military veterans. The Vasdev Lab is partnering with Concussion Legacy Foundation Canada and the Canadian Military to work on the Project Enlist to study whether some military training exercises could be negatively impacting long-term brain health. “We are getting very close to advancing new radio tracers in humans to image the tau that is more prevalent in C.T.E.”. | 0 | Theoretical and Fundamental Chemistry |
Bronze statuettes were also made in every period of antiquity for votive use, and at least in Hellenistic and Roman times for domestic ornaments and furniture of household shrines. But the art of bronze statuary hardly existed before the introduction of hollow casting, about the middle of the 6th century BC. The most primitive votive statuettes are oxen and other animals, which evidently represent victims offered to the gods. They have been found abundantly on many temple sites. But classical art preferred the human subject, votaries holding gifts or in their ordinary guise, or gods themselves in human form. Such figures are frequently inscribed with formulas of dedication. Gods and goddesses posed conformably with their traditional characters and bearing their distinctive attributes are the most numerously represented class of later statuettes. They are a religious genre, appearing first in 4th-century sculpture and particularly favoured by Hellenistic sentiment and Roman pedantry. Many of them were doubtless votive figures, others were images in domestic shrines, and some were certainly ornaments. Among the cult-idols are the dancing Lares, who carry cornucopias and libation-bowls. The little Heracles that Lysippus made for Alexander was a table-ornament (epitrapezios): he was reclining on the lion's skin, his club in one hand, a wine-cup in the other. | 1 | Applied and Interdisciplinary Chemistry |
Numerous natural processes are capable of fractionating sulfur isotopes. Microbes are capable of a wide variety of sulfur metabolisms, including the oxidation, reduction, and disproportionation (or simultaneous oxidation and reduction) of sulfur compounds. The effect of these metabolisms on sulfur isotopic composition of the reactants and products is also highly variable, depending on the rate of relevant reactions, availability of nutrients, diagenesis, and other biological, physical and environmental parameters. As an example, the microbial reduction of sulfate to sulfide generally results in a S-depleted product, but the strength of this fractionation has been shown to range from 0 to 65.6‰ VCDT.
Many abiotic processes also fractionate sulfur isotopes. Small fractionations with ε values from 0–5‰ have been observed in the formation of the mineral gypsum, an evaporite mineral produced through the evaporation of seawater. Some sulfide minerals, including pyrite and galena, can form through thermochemical sulfate reduction, a process in which seawater sulfate trapped in seafloor rock is reduced to sulfide by geological heat as the rock is buried; this process generally fractionates sulfur more strongly than gypsum formation.
Prior to the rise of oxygen in Earth's atmosphere (referred to as the Great Oxidation Event), additional sulfur-fractionating processes referred to as mass-anomalous or mass-independent fractionation uniquely affected the abundance of S and S in the rock record. Mass-anomalous fractionations are rare, but they can occur through certain photochemical reactions of gases in the atmosphere. Studies have shown that photochemical reactions of atmospheric sulfur dioxide can cause substantial mass-anomalous fractionation of sulfur isotopes. | 0 | Theoretical and Fundamental Chemistry |
Cryptophanes were discovered by André Collet and Jacqueline Gabard in 1981 when these researchers created, using template-directed synthesis, the first cryptophane, now known as cryptophane-A. | 0 | Theoretical and Fundamental Chemistry |
The geologic component of the carbon cycle operates slowly in comparison to the other parts of the global carbon cycle. It is one of the most important determinants of the amount of carbon in the atmosphere, and thus of global temperatures.
As the biological pump plays an important role in the Earths carbon cycle, significant effort is spent quantifying its strength. However, because they occur as a result of poorly constrained ecological interactions usually at depth, the processes that form the biological pump are difficult to measure. A common method is to estimate primary production fuelled by nitrate and ammonium as these nutrients have different sources that are related to the remineralisation of sinking material. From these it is possible to derive the so-called f-ratio, a proxy for the local strength of the biological pump. Applying the results of local studies to the global scale is complicated by the role the oceans circulation plays in different ocean regions. | 0 | Theoretical and Fundamental Chemistry |
In this example, a cnoidal wave according to the Korteweg–de Vries (KdV) equation is considered. The following parameters of the wave are given:
* mean water depth h = ,
* wave height H = ,
* wave period τ = 7 s, and
* gravitational acceleration g = 9.81 m/s (32 ft/s).
Instead of the period τ, in other cases the wavelength λ may occur as a quantity known beforehand.
First, the dimensionless period is computed:
which is larger than seven, so long enough for cnoidal theory to be valid. The main unknown is the elliptic parameter m. This has to be determined in such a way that the wave period τ, as computed from cnoidal wave theory for the KdV equation:
: and
is consistent with the given value of τ; here λ is the wavelength and c is the phase speed of the wave. Further, K(m) and E(m) are complete elliptic integrals of the first and second kind, respectively. Searching for the elliptic parameter m can be done by trial and error, or by use of a numerical root-finding algorithm. In this case, starting from an initial guess m = 0.99, by trial and error the answer
is found. Within the process, the wavelength λ and phase speed c have been computed:
* wavelength λ = , and
* phase speed c = .
The phase speed c can be compared with its value according to the shallow water equations:
showing a 3.8% increase due to the effect of nonlinear amplitude dispersion, which wins in this case from the reduction of phase speed by frequency dispersion.
Now the wavelength is known, the Ursell number can be computed as well:
which is not small, so linear wave theory is not applicable, but cnoidal wave theory is. Finally, the ratio of wavelength to depth is λ / h = 10.2 > 7, again indicating this wave is long enough to be considered as a cnoidal wave. | 1 | Applied and Interdisciplinary Chemistry |
Craig observed that δO and δH isotopic composition of cold meteoric water from sea ice in the Arctic and Antarctica are much more negative than that in warm meteoric water from the tropic. A correlation between temperature (T) and δO was proposed later in the 1970s. Such correlation is then applied to study surface temperature change over time. The δO composition in ancient meteoric water, preserved in ice cores, can also be collected and applied to reconstruct paleoclimate.
A meteoric water line can be calculated for a given area, named as local meteoric water line (LMWL), and used as a baseline within that area. Local meteoric water line can differ from the global meteoric water line in slope and intercept. Such deviated slope and intercept is a result largely from humidity. In 1964, the concept of deuterium excess d (d=δH - 8δO) was proposed. Later, a parameter of deuterium excess as a function of humidity has been established, as such the isotopic composition in local meteoric water can be applied to trace local relative humidity, study local climate and used as a tracer of climate change.
In hydrogeology, the δO and δH composition in groundwater are often used to study the origin of groundwater and groundwater recharge.
Recently it has been shown that, even taking into account the standard deviation related to instrumental errors and the natural variability of the amount-weighted precipitations, the LMWL calculated with the EIV (error in variable regression) method has no differences on the slope compared to classic OLSR (ordinary least square regression) or other regression methods. However, for certain purposes such as the evaluation of the shifts from the line of the geothermal waters, it would be more appropriate to calculate the so-called "prediction interval" or "error wings" related to LMWL. | 0 | Theoretical and Fundamental Chemistry |
Histone modification is a well-studied mechanism to transiently adjust chromatin density. Pioneer factors can play a role in this by binding specific enhancers and flagging histone modification enzymes to that specific gene. Repressive pioneer factors can inhibit transcription by recruiting factors that modify histones that further tighten the chromatin. This is important to limit gene expression to specific cell types and has to be removed only when cell differentiation begins. FoxD3 has been associated as a repressor of both B-cell and melanocytic cell differentiation pathways, maintaining repressive histone modifications where bound, that have to be overcome to start differentiation. Pioneer factors can also be associated with recruiting transcription-activating histone modifications. Enzymes that modify H3K4 with mono and di-methylation are associated with increasing transcription and have been shown to bind pioneer factors. In B cell differentiation PU.1 is necessary to signal specific histones for activating H3K4me1 modifications that differentiate hematopoietic stem cells into either the B-cell or macrophage lineage. FoxA1 binding induces HSK4me2 during neuronal differentiation of pluripotent stem cells as well as the loss of DNA methylation. SOX9 recruits histone modification enzymes MLL3 and MLL4 to deposit H3K4me1 prior to the opening of enhancers in developing hair follicle and basal cell carcinoma. | 1 | Applied and Interdisciplinary Chemistry |
Biochemical research in Australia began in the 1920s in the Australian national science agency Council for Scientific and Industrial Research (now the CSIRO). The first university biochemistry department then started at the University of Adelaide under Thorburn Brailsford Robertson. There was initially a joint biochemistry and physiology section within the Australian and New Zealand Association for the Advancement of Science.
The society began in 1955 as the Australian Biochemical Society, with Rudi Lemberg as its founding president. It was based on Lembergs experience with the British Biochemical Society and Hugh Ennors meetings with the International Union of Biochemistry and relevant university department heads in Australia. Additional key initial members included Frederick Collins as treasurer and Victor Trikojus in a recruitment role. | 1 | Applied and Interdisciplinary Chemistry |
An alternating magnetic field is applied at the atomizer (graphite furnace) to split the absorption line into three components, the π component, which remains at the same position as the original absorption line, and two σ components, which are moved to higher and lower wavelengths, respectively. Total absorption is measured without magnetic field and background absorption with the magnetic field on. The π component has to be removed in this case, e.g. using a polarizer, and the σ components do not overlap with the emission profile of the lamp, so that only the background absorption is measured. The advantages of this technique are that total and background absorption are measured with the same emission profile of the same lamp, so that any kind of background, including background with fine structure can be corrected accurately, unless the molecule responsible for the background is also affected by the magnetic field and using a chopper as a polariser reduces the signal to noise ratio. While the disadvantages are the increased complexity of the spectrometer and power supply needed for running the powerful magnet needed to split the absorption line. | 0 | Theoretical and Fundamental Chemistry |
The following table shows radiation quantities in SI and non-SI units:
The measure of the ionizing effect of gamma and X-rays in dry air is called the exposure, for which a legacy unit, the röntgen, was used from 1928. This has been replaced by kerma, now mainly used for instrument calibration purposes but not for received dose effect. The effect of gamma and other ionizing radiation on living tissue is more closely related to the amount of energy deposited in tissue rather than the ionisation of air, and replacement radiometric units and quantities for radiation protection have been defined and developed from 1953 onwards. These are:
*The gray (Gy), is the SI unit of absorbed dose, which is the amount of radiation energy deposited in the irradiated material. For gamma radiation this is numerically equivalent to equivalent dose measured by the sievert, which indicates the stochastic biological effect of low levels of radiation on human tissue. The radiation weighting conversion factor from absorbed dose to equivalent dose is 1 for gamma, whereas alpha particles have a factor of 20, reflecting their greater ionising effect on tissue.
*The rad is the deprecated CGS unit for absorbed dose and the rem is the deprecated CGS unit of equivalent dose, used mainly in the USA. | 0 | Theoretical and Fundamental Chemistry |
The Kramatorsk radiological accident happened in 1989 when a small capsule 8x4 mm in size of caesium-137 was found inside the concrete wall of an apartment building in Kramatorsk, Ukrainian SSR. It is believed that the capsule, originally a part of a measurement device, was lost in the late 1970s and ended up mixed with gravel used to construct the building in 1980. Over 9 years, two families had lived in the apartment. By the time the capsule was discovered, 6 residents of the building had died, 4 from leukemia and 17 more receiving varying doses of radiation. | 0 | Theoretical and Fundamental Chemistry |
People who survive an intoxication episode may develop persistent health problems. This group of persistent health symptoms are called syndrome of irreversible lithium-effectuated neurotoxicity (SILENT). The syndrome presents with irreversible neurological and neuro-psychiatric effects. The neurological signs are cerebellar dysfunction, extrapyramidal symptoms, and brainstem dysfunction. The neuro-psychiatric findings present with memory deficits, cognitive deficits, and sub-cortical dementia. For a diagnosis, the syndrome requires the absence of prior symptoms and persistence of symptoms for greater than 2 months after cessation of lithium. | 1 | Applied and Interdisciplinary Chemistry |
The hazards which accompany harmful algal blooms have hindered visitors' enjoyment of beaches and lakes in places in the U.S. such as Florida, California, Vermont, and Utah. Persons hoping to enjoy their vacations or days off have been kept away to the detriment of local economies. Lakes and rivers in North Dakota, Minnesota, Utah, California and Ohio have had signs posted warning about the potential of health risk.
Similar blooms have become more common in Europe, with France among the countries reporting them. In the summer of 2009, beaches in northern Brittany became covered by tonnes of potentially lethal rotting green algae. A horse being ridden along the beach collapsed and died from fumes given off by the rotting algae.
The economic damage resulting from lost business has become a serious concern. According to one report in 2016, the four main economic impacts from harmful algal blooms come from damage to human health, fisheries, tourism and recreation, and the cost of monitoring and management of area where blooms appear. EPA estimates that algal blooms impact 65 percent of the country's major estuaries, with an annual cost of $2.2 billion. In the U.S. there are an estimated 166 coastal dead zones. Because data collection has been more difficult and limited from sources outside the U.S., most of the estimates as of 2016 have been primarily for the U.S.
In port cities in the Shandong Province of eastern China, residents are no longer surprised when massive algal blooms arrive each year and inundate beaches. Prior to the Beijing Olympics in 2008, over 10,000 people worked to clear 20,000 tons of dead algae from beaches. In 2013 another bloom in China, thought to be its largest ever, covered an area of 7,500 square miles, and was followed by another in 2015 which blanketed an even greater 13,500 square miles. The blooms in China are thought to be caused by pollution from untreated agricultural and industrial discharges into rivers leading to the ocean. | 0 | Theoretical and Fundamental Chemistry |
There are two main advantages to CRDS over other absorption methods:
First, it is not affected by fluctuations in the laser intensity. In most absorption measurements, the light source must be assumed to remain steady between blank (no analyte), standard (known amount of analyte), and sample (unknown amount of analyte). Any drift (change in the light source) between measurements will introduce errors. In CRDS, the ringdown time does not depend on the intensity of the laser, so fluctuations of this type are not a problem. Independency from laser intensity makes CRDS needless to any calibration and comparison with standards.
Second, it is very sensitive due to its long pathlength. In absorption measurements, the smallest amount that can be detected is proportional to the length that the light travels through a sample. Since the light reflects many times between the mirrors, it ends up traveling long distances. For example, a laser pulse making 500 round trips through a 1-meter cavity will effectively have traveled through 1 kilometer of sample.
Thus, the advantages include:
*High sensitivity due to the multipass nature (i.e. long pathlength) of the detection cell.
*Immunity to shot variations in laser intensity due to the measurement of a rate constant.
*Wide range of use for a given set of mirrors; typically, ±5% of the center wavelength.
*High throughput, individual ring down events occur on the millisecond time scale.
*No need for a fluorophore, which makes it more attractive than laser-induced fluorescence (LIF) or resonance-enhanced multiphoton ionization (REMPI) for some (e.g. rapidly predissociating) systems.
*Commercial systems available. | 0 | Theoretical and Fundamental Chemistry |
Knowledge of bioaerosols has shaped our understanding of microorganisms and the differentiation between microbes, including airborne pathogens. In the 1970s, a breakthrough occurred in atmospheric physics and microbiology when ice nucleating bacteria were identified.
The highest concentration of bioaerosols is near the Earth’s surface in the PBL. Here wind turbulence causes vertical mixing, bringing particles from the ground into the atmosphere. Bioaerosols introduced to the atmosphere can form clouds, which are then blown to other geographic locations and precipitate out as rain, hail, or snow. Increased levels of bioaerosols have been observed in rain forests during and after rain events. Bacteria and phytoplankton from marine environments have been linked to cloud formation.
However, for this same reason, bioaerosols cannot be transported long distances in the PBL since the clouds will eventually precipitate them out. Furthermore, it would take additional turbulence or convection at the upper limits of the PBL to inject bioaerosols into the troposphere where they may transported larger distances as part of tropospheric flow. This limits the concentration of bioaerosols at these altitudes.
Cloud droplets, ice crystals, and precipitation use bioaerosols as a nucleus where water or crystals can form or hold onto their surface. These interactions show that air particles can change the hydrological cycle, weather conditions, and weathering around the world. Those changes can lead to effects such as desertification which is magnified by climate shifts. Bioaerosols also intermix when pristine air and smog meet, changing visibility and/or air quality. | 0 | Theoretical and Fundamental Chemistry |
The van der Waals radius, r, of an atom is the radius of an imaginary hard sphere representing the distance of closest approach for another atom.
It is named after Johannes Diderik van der Waals, winner of the 1910 Nobel Prize in Physics, as he was the first to recognise that atoms were not simply points and to demonstrate the physical consequences of their size through the van der Waals equation of state. | 0 | Theoretical and Fundamental Chemistry |
Memory transfer was a biological process proposed by James V. McConnell and others in the 1960s. Memory transfer proposes a chemical basis for memory termed memory RNA which can be passed down through flesh instead of an intact nervous system. Since RNA encodes information living cells produce and modify RNA in reaction to external events, it might also be used in neurons to record stimuli. This explained the results of McConnells experiments in which planarians retained memory of acquired information after regeneration. Memory transfer through memory RNA is not currently a well-accepted explanation and McConnells experiments proved to be largely irreproducible.
In McConnells experiments, he classically conditioned planarians to contract their bodies upon exposure to light by pairing it with an electric shock. The planarians retained this acquired information after being sliced and regenerated, even after multiple slicings to produce a planarian where none of the original trained planarian was present. The same held true after the planarians were ground up and fed untrained cannibalistic planarians, usually Dugesia dorotocephala'. As the nervous system was fragmented but the nucleic acids were not, this seemed to indicate the existence of memory RNA but it was later suggested that only sensitization was transferred, or that no transfer occurred and the effect was due to stress hormones in the donor or pheromone trails left on dirty lab glass. However, other experiments seem to support the original findings in that some memories may be stored outside the brain. | 1 | Applied and Interdisciplinary Chemistry |
These are turbulence models in which the Reynolds stresses, as obtained from a Reynolds averaging of the Navier–Stokes equations, are modelled by a linear constitutive relationship with the mean flow straining field, as:
where
:* is the coefficient termed turbulence "viscosity" (also called the eddy viscosity)
:* is the mean turbulent kinetic energy
:* is the mean strain rate
: Note that that inclusion of in the linear constitutive relation is required by tensorial algebra purposes when solving for two-equation turbulence models (or any other turbulence model that solves a transport equation for . | 1 | Applied and Interdisciplinary Chemistry |
The second part contains 8 free response questions. Complete written explanations and calculations are required for full credit on a question, and partial credit is awarded. More thorough knowledge of basic theories is required, and often there are questions on less-emphasized portions of normal high school chemistry curricula, such as organic chemistry and coordination chemistry. One hour and 45 minutes (105 minutes) are allowed for this section. | 1 | Applied and Interdisciplinary Chemistry |
The branching ratio of a polymer relates to the number of branch units in a randomly branched polymer and the number of arms in star-branched polymers and was defined by Zimm and Stockmayer as
Where is the mean square radius of branched and linear macromolecules with identical molar masses. By utilizing MALS in conjunction with a concentration detector as described above, one create a log-log plot of the root-mean-square radius vs molar mass. The slope of this plot yields the branching ratio, g.
In addition to branching, the log-log plot of size vs. molar mass indicates the shape or conformation of a macromolecule. An increase in the slope of the plot indicates a variation in conformation of a polymer from spherical to random coil to linear. Combining the mean-square radius from MALS with the hydrodynamic radius attained from DLS measurements yields the shape factor ρ = , for each macromolecular size fraction. | 0 | Theoretical and Fundamental Chemistry |
This is a different class of inhibitors that was identified with HTS. Aromatic heterocyclic-based DPP-4 inhibitors have gained increased attention recently. The first patents describing xanthines (Figure 10) as DPP-4 inhibitors came from Boehringer-Ingelheim(BI) and Novo Nordisk.
When xanthine based DPP-4 inhibitors are compared with sitagliptin and vildagliptin it has shown a superior profile. Xanthines are believed to have higher potency, longer-lasting inhibition and longer-lasting improvement of glucose tolerance. | 1 | Applied and Interdisciplinary Chemistry |
In nuclear magnetic resonance spectroscopy, the highly abundant C isotope does not produce any signal whereas the comparably rare C isotope is easily detected. As a result, carbon isotopomers of a compound can be studied by carbon-13 NMR to learn about the different carbon atoms in the structure. Each individual structure that contains a single C isotope provides data about the structure in its immediate vicinity. A large sample of a chemical contains a mixture of all such isotopomers, so a single spectrum of the sample contains data about all carbons in it. Nearly all of the carbon in normal samples of carbon-based chemicals is C, with only about 1% abundance of C, so there is only about a 1% abundance of the total of the singly-substituted isotopologues, and exponentially smaller amounts of structures having two or more C in them. The rare case where two adjacent carbon atoms in a single structure are both C causes a detectable coupling effect between them as well as signals for each one itself. The INADEQUATE correlation experiment uses this effect to provide evidence for which carbon atoms in a structure are attached to each other, which can be useful for determining the actual structure of an unknown chemical. | 0 | Theoretical and Fundamental Chemistry |
Most of the reactivity of thioacetic acid arises from the conjugate base, thioacetate. Salts of this anion, e.g. potassium thioacetate, are used to generate thioacetate esters. Thioacetate esters undergo hydrolysis to give thiols. A typical method for preparing a thiol from an alkyl halide using thioacetic acid proceeds in four discrete steps, some of which can be conducted sequentially in the same flask:
:, where X = Cl, Br, I
In an application that illustrates the use of its radical behavior, thioacetic acid is used with AIBN in a free radical mediated nucleophilic addition to an exocyclic alkene forming a thioester: | 0 | Theoretical and Fundamental Chemistry |
At equivalent molecular weights, RNA will migrate faster than DNA. However, both RNA and DNA have a negative linear slope between their migration distance and logarithmic molecular weight. That is, samples of less weight are able to migrate a greater distance. This relationship is a consideration when choosing RNA or DNA markers as a standard.
When running RNA markers and RNA samples on a gel, it is important to prevent nuclease contamination, as RNA is very sensitive to ribonuclease (RNase) degradation through catalysis. Thus, all materials to be used in the procedure must be taken into consideration. Any glassware that is to come into contact with RNA should be pretreated with diethylpyrocarbonate (DEPC) and plastic materials should be disposable. | 1 | Applied and Interdisciplinary Chemistry |
There are different types of drug delivery vehicles, such as polymeric micelles, liposomes, lipoprotein-based drug carriers, nano-particle drug carriers, dendrimers, etc. An ideal drug delivery vehicle must be non-toxic, biocompatible, non-immunogenic, biodegradable, and must avoid recognition by the host's defense mechanisms. | 1 | Applied and Interdisciplinary Chemistry |
Emission microspectroscopy is a sensitive technique with excitation and emission ranging from the ultraviolet, visible and NIR regions. As such, it has numerous biomedical, biotechnological and agricultural applications. There are several powerful, highly specific and sensitive fluorescence techniques that are currently in use, or still being developed; among the former are FLIM, FRAP, FRET and FLIM-FRET; among the latter are NIR fluorescence and probe-sensitivity enhanced NIR fluorescence microspectroscopy and nanospectroscopy techniques (see "Further reading" section). Fluorescence emission microspectroscopy and imaging are also commonly used to locate protein crystals in solution, for the characterization of metamaterials and biotechnology devices. | 0 | Theoretical and Fundamental Chemistry |
Cyanobacteria are photosynthetic prokaryotes with highly differentiated membrane systems. Cyanobacteria have an internal system of thylakoid membranes where the fully functional electron transfer chains of photosynthesis and respiration reside. The presence of different membrane systems lends these cells a unique complexity among bacteria. Cyanobacteria must be able to reorganize the membranes, synthesize new membrane lipids, and properly target proteins to the correct membrane system. The outer membrane, plasma membrane, and thylakoid membranes each have specialized roles in the cyanobacterial cell. Understanding the organization, functionality, protein composition, and dynamics of the membrane systems remains a great challenge in cyanobacterial cell biology.
In contrast to the thylakoid network of higher plants, which is differentiated into grana and stroma lamellae, the thylakoids in cyanobacteria are organized into multiple concentric shells that split and fuse to parallel layers forming a highly connected network. This results in a continuous network that encloses a single lumen (as in higher‐plant chloroplasts) and allows water‐soluble and lipid‐soluble molecules to diffuse through the entire membrane network. Moreover, perforations are often observed within the parallel thylakoid sheets. These gaps in the membrane allow for the traffic of particles of different sizes throughout the cell, including ribosomes, glycogen granules, and lipid bodies. The relatively large distance between the thylakoids provides space for the external light-harvesting antennae, the phycobilisomes. This macrostructure, as in the case of higher plants, shows some flexibility during changes in the physicochemical environment. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, functionality is the presence of functional groups in a molecule. A monofunctional molecule possesses one functional group, a bifunctional (or difunctional) two, a trifunctional three, and so forth. In organic chemistry (and other fields of chemistry), a molecule's functionality has a decisive influence on its reactivity.
In polymer chemistry, the functionality of a monomer refers to its number of polymerizable groups, and affects the formation and the degree of crosslinking of polymers. | 0 | Theoretical and Fundamental Chemistry |
Plastic pipes under water or other fluids experience hydrodynamic forces that can result in fatigue. The pipes reach failure sooner as temperatures and exposure to aggressive substances increase. For static fatigue tests, rotating machines apply weight on the material under study causing it to bend in different directions, which weakens the material overtime. | 1 | Applied and Interdisciplinary Chemistry |
The theory of electron capture was first discussed by Gian-Carlo Wick in a 1934 paper, and then developed by Hideki Yukawa and others. K-electron capture was first observed by Luis Alvarez, in vanadium, , which he reported in 1937. Alvarez went on to study electron capture in gallium () and other nuclides. | 0 | Theoretical and Fundamental Chemistry |
Power plants that can be dispatched (scheduled) to provide energy to a system include:
* Base load power plants run nearly continually to provide that component of system load that does not vary during a day or week. Baseload plants can be highly optimized for low fuel cost, but may not start or stop quickly during changes in system load. Examples of base-load plants would include large modern coal-fired and nuclear generating stations, or hydro plants with a predictable supply of water.
* Peaking power plants meet the daily peak load, which may only be for one or two hours each day. While their incremental operating cost is always higher than base load plants, they are required to ensure security of the system during load peaks. Peaking plants include simple cycle gas turbines and reciprocating internal combustion engines, which can be started up rapidly when system peaks are predicted. Hydroelectric plants may also be designed for peaking use.
* Load following power plants can economically follow the variations in the daily and weekly load, at lower cost than peaking plants and with more flexibility than baseload plants.
Non-dispatchable plants include such sources as wind and solar energy; while their long-term contribution to system energy supply is predictable, on a short-term (daily or hourly) base their energy must be used as available since generation cannot be deferred. Contractual arrangements ("take or pay") with independent power producers or system interconnections to other networks may be effectively non-dispatchable. | 1 | Applied and Interdisciplinary Chemistry |
We now turn to calculating the effect of CO on radiation, using a one-layer model, i.e. we treat the whole troposphere as a single layer:
Looking at a particular wavelength λ up to λ+dλ, the whole atmosphere has an optical depth OD, while the tropopause has an optical depth 0.12*OD; the troposphere has an optical depth of 0.88*OD.
Thus,
of the radiation from below the tropopause is transmitted out, but this includes of the radiation that originates from the ground.
Thus, the weight of the troposphere in determining the radiation that is emitted to outer space is:
A relative increase in the CO concentration means an equal relative increase in the total CO content of the atmosphere, dN/N where N is the number of CO molecules.
Adding a minute number of such molecules dN will increase the troposphere's weight in determining the radiation for the relevant wavelengths, approximately by the relative amount dN/N, and thus by:
Since CO hardly influences sunlight absorption by Earth, the radiative forcing due to an increase in CO content is equal to the difference in the flux radiated by Earth due to such an increase. To calculate this, one must multiply the above by the difference in radiation due to the difference in temperature. According to Planck's law, this is:
The ground is at temperature T = 288 K, and for the troposphere we will take a typical temperature, the one at the average height of molecules, 6.3 km, where the temperature is T247 K.
Therefore, dI, the change in Earth's emitted radiation is, in a rough approximation, is:
Since dN/N = d(ln N), this can be written as:
The function is maximal for x = 2.41, with a maximal value of 0.66, and it drops to half this value at x=0.5 and x = 9.2. Thus we look at wavelengths for which the OD is between 0.5 and 9.2: This gives a wavelength band at the width of approximately 1 micron around 17 microns, and less than 1 micron around 13.5 microns. We therefore take:
:λ = 13.5 microns and again 17 microns (summing contributions from both)
:dλ = 0.5 micron for the 13.5 microns band, and 1 micron for the 17 microns band.
Which gives -2.3 W/m for the 13.5 microns band, and -2.7 W/m for the 17 microns band, for a total of 5 W/m.
A 2-fold increase in CO content changes the wavelengths ranges only slightly, and so this derivative is approximately constant along such an increase. Thus, a 2-fold increase in CO content will reduce the radiation emitted by Earth by approximately:
:ln(2)*5 W/m = 3.4 W/m.
More generally, an increase by a factor c/c gives:
:ln(c/c)*5 W/m
These results are close to the approximation of a more elaborate yet simplified model giving
:ln(c/c)*5.35 W/m, and the radiative forcing due to CO doubling with much more complicated models giving 3.1 W/m. | 1 | Applied and Interdisciplinary Chemistry |
In 2018, the Iowa Department of Natural Resources found microcystins at levels of 0.3 µg/L, or micrograms per liter (ppb), in the raw water supplies of 15 out of 26 public water systems tested. | 1 | Applied and Interdisciplinary Chemistry |
In their study, Fuhrmann et al. (2009), performed a biochemical and structural analysis of the bacterial transcriptional regulators CtsR/McsB stress response. They sort to clarify and outline the exact function of CtsR and McsB in bacterial stress response. So, they screened proteins from various gram-negative bacteria for recombinant production and succeeded in reconstituting the Bacillus stearothermophilus CtsR/McsB system in vitro. Subsequently, they identified McsB as a protein kinase that targets arginine. | 1 | Applied and Interdisciplinary Chemistry |
Nitric acid can be used to convert metals to oxidized forms, such as converting copper metal to cupric nitrate. It can also be used in combination with hydrochloric acid as aqua regia to dissolve noble metals such as gold (as chloroauric acid). These salts can be used to purify gold and other metals beyond 99.9% purity by processes of recrystallization and selective precipitation. Its ability to dissolve certain metals selectively or be a solvent for many metal salts makes it useful in gold parting processes. | 0 | Theoretical and Fundamental Chemistry |
Specific areas of the 16S rRNA in the Enterobacteriaceae genus are bound by oligonucleotide probes, which aids in monitoring the quality of drinking water. Specifically, E. coli is labelled with a soybean peroxidase-labeled peptide nucleic acid (PNA) probes that bind to a specific sequence in their 16S rRNA. When used in conjunction with a chemiluminescent substrate, light is produced where each colony of E. coli is located, indicating that they are present in the sample. | 0 | Theoretical and Fundamental Chemistry |
In a mineral, nearly all elements distribute unevenly between the solid and liquid phase. This phenomenon known as chemical fractionation and can be described by an equilibrium constant, which sets a fixed distribution of an element between any two phases at equilibrium. A distribution constant is used to define the relationship between the solid and liquid phase of a reaction. This value is essentially a ratio of the concentration of an element between two phases, typically between the solid and liquid phase in this context. This constant is often referred to as when dealing with trace elements, where
for trace elements
The equilibrium constant is an empirically determined value. These values depend on temperature, pressure, and composition of the mineral melt. values differ considerably between major elements and trace elements. By definition, incompatible trace elements have an equilibrium constant value of less than one because trace elements have higher concentrations in the melt than solids. This means that compatible elements have a value of . Thus, incompatible elements are concentrated in the melt, whereas compatible elements tend to be concentrated in the solid. Compatible elements with are strongly fractionated and have very low concentrations in the liquid phase. | 0 | Theoretical and Fundamental Chemistry |
Enantiomer self-disproportionation is a process in stereochemistry describing the separation of a non-racemic mixture of enantiomers in an enantioenriched fraction and a more racemic fraction as a result of the formation of heterochiral or homochiral aggregates. This process is known to occur in achiral column chromatography.
The phenomenon was first reported in 1983 in the separation of an excess of
carbon-14 labeled (S)-(−)-nicotine enantiomer and its isomer. Two fractions were recorded, one containing racemic nicotine and the other pure (S) enantiomer.
In 2006, Vadim A. Soloshonok introduced the term Enantiomer self-disproportionation or self-disproportionation of enantiomers. He investigated achiral separations of several trifluoromethyl compounds.
By column chromatography on regular silica gel with a hexane / ethyl acetate eluent (5:1), a 66.6% ee sample of a trifluoromethyl substrate is separated into several fractions ranging from 8.1% ee for the first fraction collected to > 99.9% ee for the last fraction collected. A presence of a strong electronegative group in the substrate such as the trifluoromethyl group is a prerequisite. The effect disappears when a more polar eluent is selected. A possible explanation is offered. Compounds with large electronegative groups such as trifluoromethyl can form supramolecular associations or aggregates or clusters in which these groups are separated from each other as much as possible with minimized electrostatic repulsions. When these associations are stacks of alternating (R) and (S) molecules (as in syndiotactic polymers) this can be accomplished very efficiently. This association will form a racemic fraction of relatively high molecular weight eluting more slowly than the non-associating enantiopure fraction. | 0 | Theoretical and Fundamental Chemistry |
Since corepressors participate and regulate a vast range of gene expression, it is not surprising that aberrant corepressor activities can cause diseases.
Acute myeloid leukemia (AML) is a highly lethal blood cancer characterized by uncontrolled myeloid cell growth. Two homologous corepressor genes, BCOR (BCL6 corepressor) and BCORL1, are recurrently mutated in AML patients. BCOR works with multiple transcription factors and is known to play vital regulatory roles in embryonic development. Clinical results detected BCOR somatic mutations in ~4% of an unselected group of AML patients, and ~17% in a subset of patients who lack known AML-causing mutations. Similarly, BCORL1 is a corepressor that regulates cellular processes, and was found to be mutated in ~6% of tested AML patients. These studies point out a strong association between corepressor mutations and AML. Further corepressor research may reveal potential therapeutic targets for AML and other diseases. | 1 | Applied and Interdisciplinary Chemistry |
Lithium carbonate () is the most commonly used form of lithium, although lithium citrate () and other salts, including lithium sulfate, lithium chloride, and lithium orotate are also used. Nanoparticles and microemulsions have also been invented as drug delivery mechanisms. As of 2020, there is a lack of evidence that alternate formulations or salts of lithium would reduce the need for monitoring serum lithium levels or to lower systemic toxicity.
As of 2017 lithium was marketed under many brand names worldwide, including Cade, Calith, Camcolit, Carbolim, Carbolit, Carbolith, Carbolithium, Carbolitium, Carbonato de Litio, Carboron, Ceglution, Contemnol, D-Gluconsäure, Lithiumsalz, Efadermin (Lithium and Zinc Sulfate), Efalith (Lithium and Zinc Sulfate), Elcab, Eskalit, Eskalith, Frimania, Hypnorex, Kalitium, Karlit, Lalithium, Li-Liquid, Licarb, Licarbium, Lidin, Ligilin, Lilipin, Lilitin, Limas, Limed, Liskonum, Litarex, Lithane, Litheum, Lithicarb, Lithii carbonas, Lithii citras, Lithioderm, Lithiofor, Lithionit, Lithium, Lithium aceticum, Lithium asparagicum, Lithium Carbonate, Lithium Carbonicum, Lithium Citrate, Lithium DL-asparaginat-1-Wasser, Lithium gluconicum, Lithium-D-gluconat, Lithiumcarbonaat, Lithiumcarbonat, Lithiumcitrat, Lithiun, Lithobid, Lithocent, Lithotabs, Lithuril, Litiam, Liticarb, Litijum, Litio, Litiomal, Lito, Litocarb, Litocip, Maniprex, Milithin, Neurolepsin, Plenur, Priadel, Prianil, Prolix, Psicolit, Quilonium, Quilonorm, Quilonum, Téralithe, and Theralite. | 1 | Applied and Interdisciplinary Chemistry |
Applying standard diffraction techniques to crystal powders or polycrystals is tantamount to collapsing the 3D reciprocal space, as obtained via single-crystal diffraction, onto a 1D axis. The resulting partial-to-total overlap of symmetry-independent reflections renders the structure determination process more difficult, if not impossible.
Powder diffraction data can be plotted as diffracted intensity (I) versus reciprocal lattice spacing (1/d). Reflection positions and intensities of known crystal phases, mostly from X-ray diffraction data, are stored, as d-I data pairs, in the Powder Diffraction File (PDF) database. The list of d-I data pairs is highly characteristic of a crystal phase and, thus, suitable for the identification, also called ‘fingerprinting’, of crystal phases.
Search-match algorithms compare selected test reflections of an unknown crystal phase with entries in the database. Intensity-driven algorithms utilize the three most intense lines (so-called ‘Hanawalt search’), while d-spacing-driven algorithms are based on the eight to ten largest d-spacings (so-called ‘Fink search’).
X-ray powder diffraction fingerprinting has become the standard tool for the identification of single or multiple crystal phases and is widely used in such fields as metallurgy, mineralogy, forensic science, archeology, condensed matter physics, and the biological and pharmaceutical sciences. | 0 | Theoretical and Fundamental Chemistry |
8-Hydroxyguanosine is an RNA nucleoside which is an oxidative derivative of guanosine. Measurement of the levels of 8-hydroxyguanosine is used as a biomarker of oxidative stress causing RNA damage. | 1 | Applied and Interdisciplinary Chemistry |
The concentration of HCFC-142b in the atmosphere grew to over 20 parts per trillion by year 2010. It has an ozone depletion potential (ODP) of 0.07. This is low compared to the ODP=1 of trichlorofluoromethane (CFC-11, R-11), which also grew about ten times more abundant in the atmosphere by year 1985 (prior to introduction of HFC-142b and the Montreal Protocol).
HFC-142b is also a minor but potent greenhouse gas. It has an estimated lifetime of about 17 years and a 100-year global warming potential ranging 2300 to 5000. This compares to the GWP=1 of carbon dioxide, which had a much greater atmospheric concentration near 400 parts per million in year 2020. | 1 | Applied and Interdisciplinary Chemistry |
Carbohydrate deficient transferrin increases in the blood with heavy ethanol consumption and can be monitored through laboratory testing.
Transferrin is an acute phase protein and is seen to decrease in inflammation, cancers, and certain diseases (in contrast to other acute phase proteins, e.g., C-reactive protein, which increase in case of acute inflammation). | 1 | Applied and Interdisciplinary Chemistry |
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