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Dallol is a unique, terrestrial hydrothermal system around a cinder cone volcano in the Danakil Depression, northeast of the Erta Ale Range in Ethiopia. It is known for its unearthly colors and mineral patterns, and the very acidic fluids that discharge from its hydrothermal springs. | 0 | Theoretical and Fundamental Chemistry |
Disarming sugars can also be accomplished by adding 1,3-dioxane and 1,3-dioxolane protecting groups onto sugars. These protecting groups “lock” the sugars into a rigid chair conformation. When the sugar forms the necessary oxocarbenium ion, it flattens at the anomeric position. This change in configuration is a high-energy transformation when cyclic protecting groups are present, and leads to the sugar being “disarmed”. These groups can be easily removed following glycosylation, effectively “arming” the sugar, and allowing for control of the glycosylation.
Further work has shown that the effect of 1,3-dioxanes and 1,3-dioxolanes on disarming sugars can be attributed to the electronics of the systems as well as torsional strain. When a 1,3-dioxane is formed between O-4 and O-6, the oxygens adapt an anti-periplanar geometry with O-5. This orientation allows for hyperconjugation of O-5 to O-4 and O-6, removing electron density from O-5. The loss of electron density at O-5 results in a destabilization of the oxocarbenium ion, slowing its formation, and “disarming” the sugar. Experiments were conducted by altering the configuration of the O-6 and examining the rate of hydrolysis of these compounds. The gauche-gauche orientation seen in the second example has a higher rate of hydrolysis due to its longer bond length. The hydrogen at C-5 is able to hyperconjugate with O-6, effectively lengthening the bond. This increase in bond length decreases the inductive electron withdrawing ability of O-6, causing a higher rate of hydrolysis than the other two conformations. The effect of anti-periplanar orientation is also visible in comparing glucopyranose and galactopyranose hydrolysis. Glucopyranose has an anti-perplanar orientation between O-4 and O-5, while galactopyranose does not and shows the appropriate increase in reactivity. | 0 | Theoretical and Fundamental Chemistry |
Compared to other biomedical fields, lipidology was long-neglected as the handling of oils, smears, and greases was unappealing to scientists and lipid separation was difficult. It was not until 2002 that lipidomics, the study of lipid networks and their interaction with other molecules, appeared in the scientific literature. Attention to the field was bolstered by the introduction of chromatography, spectrometry, and various forms of spectroscopy to the field, allowing lipids to be isolated and analyzed. The field was further popularized following the cytologic application of the electron microscope, which led scientists to find that many metabolic pathways take place within, along, and through the cell membrane - the properties of which are strongly influenced by lipid composition. | 1 | Applied and Interdisciplinary Chemistry |
This snail has been studied in relation to human pathology and the epidemiology of schistosomiasis. S. masoni is known to change its host’s (B. glabrata's) behavior via the upregulation/downregulation of neuropeptides such as schistosomin and NPY, and some studies have reported that FMRFamide is aminergic, and may be implicated in the secretion of molecules to respond to infection with parasites.
The ganglionic central nervous system (CNS) of B. glabrata consists of paired cerebral, pedal, pleural, parietal, and buccal ganglia, and one unpaired visceral ganglion. FMRFamide is concentrated in the concentrated in the cerebral and visceral ganglia, although evidence from current research suggests that FMRFamide moves downward of the head-foot region of the snail as embryonic development proceeds.
The exact role of FMRFamide during early development of the embryonic central nervous system is not well studied. Detection of this neuropeptide is important because its expression lays down the foundation of the CNS in the early stages of development in invertebrates. In recent years, neuromodulatory actions of FMRFamide in invertebrates have become more apparent. This is in part due to the extensive studies done on the Planorbidae and Lymnaeidae families of pond snails.
FMRFamide expression in B. glabrata can be detected as early 72 hours, post-cleavage. Studies have shown its expression pattern in the posterior of the ganglionic nervous system, as the first FMRFamide immunoreactive cell appears at 25-28% of development and is located at the extreme posterior of the embryo. The cell sends a single process on each side and each process follows the body curvature.
As these processes elongate, two lateral FMRFamide-expressing cells are apparent on either side of the body wall. Some studies have suggested that FMRFamide these structures may innervate muscles that originate in trochopore larvae and expand during development. This neuromodulator helps to regulate cardiac activity. Several FMRFamid related peptides are known, regulating various cellular functions and possessing pharmacological actions, such as anti-opiate effects. FMRFamide may also play a role in osmoregulation and developmental patterning. This neuropeoptide has multiple functions and controls many processes that allow the embryo to mature into an adult snail. | 1 | Applied and Interdisciplinary Chemistry |
Throughout his career, Oladipo has held various positions, including Head of Division, Environmental and Earth Sciences, CERD, OAU, and membership on the Academic Board, CERD, OAU. | 0 | Theoretical and Fundamental Chemistry |
He was awarded the CNRS silver medal in 1998. He is a member of the French Academy of Technology (2000), the Academia Europaea (2002), the European Academy of Sciences (2003), the French Academy of Sciences (2004) and the American Association for Advancement of Sciences (2006). He was recently awarded the Sir Ronald Nyholm Medal from the SRC (2009), the Grand Prix Le Bel from the French Chemical Society (2010), the ACS Prize in Inorganic Chemistry (2014), the Sir Geoffrey Wilkinson Prize from the SRC (2016) and the Sacconi Medal from the Italian Chemical Society (2017). He is one of the associate editors of Chemical Reviews and a member of the editorial boards of several journals.
He is Chevalier of the Légion d'Honneur. | 0 | Theoretical and Fundamental Chemistry |
Arsenic is a ubiquitous naturally occurring chemical element, and the 20th most common element on Earth. Arsenic levels in the groundwater vary from around 0.5 parts per billion to 5000 parts per billion, depending on an area's geologic features, and possible presence on industrial waste. The highest groundwater arsenic levels have been recorded in Brazil, Cambodia, Afghanistan, Australia, and Bangladesh.
Arsenic is a ubiquitous element present in American drinking water. In the US, the U.S. Geological Survey estimates that the median groundwater concentration is 1 μg/L or less, although some groundwater aquifers, particularly in the western United States, can contain much higher levels. For example, median levels in Nevada were about 8 μg/L but levels of naturally occurring arsenic as high as 1000 μg/L have been measured in the United States in drinking water. Groundwater associated with volcanics in California contain As at concentrations ranging up to 48,000 μg/L, with As-bearing sulfide minerals as the main source. Geothermal waters on Dominica in the Lesser Antilles also contain concentrations of As >50 μg/L. In Wisconsin, As concentrations of water in sandstone and dolomite aquifers were as high as 100 μg/L. Oxidation of pyrite hosted by these formations was the likely source of the As. In the Piedmont of Pennsylvania and New Jersey, groundwater in Mesozoic age aquifers contains elevated levels of As—domestic well waters from Pennsylvania contained up to 65 μg/L, whereas in New Jersey the highest concentration measured recently was 215 μg/L.
Organic arsenic is less harmful than inorganic arsenic. Seafood is a common source of the less toxic organic arsenic in the form of arsenobetaine. Because of its high toxicity, arsenic is seldom used in the Western world, although in Asia it is still a popular pesticide. Arsenic is mainly encountered occupationally in the smelting of zinc and copper ores.
In the United States, Schoof et al. estimated an average adult intake of 3.2 μg/day, with a range of 1–20 μg/day. Estimates for children were similar. Food also contains many organic arsenic compounds. The key organic arsenic compounds that can be routinely found in food (depending on food type) include monomethylarsonic acid (MMAsV), dimethylarsinic acid (DMAsV), arsenobetaine, arsenocholine, arsenosugars, and arsenolipids. DMAsV or MMAsV can be found in various types of fin fish, crabs, and mollusks, but often at very low levels.
Arsenobetaine is the major form of arsenic in marine animals, and is considered nontoxic. Arsenocholine, which is mainly found in shrimp, is chemically similar to arsenobetaine, and is considered to be "essentially nontoxic". Although arsenobetaine is little studied, available information indicates it is not mutagenic, immunotoxic, or embryotoxic. Arsenosugars and arsenolipids have recently been identified. Exposure to these compounds and toxicological implications are currently being studied. Arsenosugars are detected mainly in seaweed but are also found to a lesser extent in marine mollusks. Studies addressing arsenosugar toxicity, however, have largely been limited to in vitro studies, which show that arsenosugars are significantly less toxic than both inorganic arsenic and trivalent methylated arsenic metabolites.
It has been found that rice is particularly susceptible to accumulation of arsenic from soil. Rice grown in the United States has an average 260 ppb of arsenic, according to a study; but U.S. arsenic intake remains far below World Health Organization-recommended limits. China has set a standard for arsenic limits in food (150 ppb), as levels in rice exceed those in water.
The European Commission (2000) reports that levels of arsenic in air range 0–1 ng/m in remote areas, 0.2–1.5 ng/m in rural areas, 0.5–3 ng/m in urban areas, and up to about 50 ng/m in the vicinity of industrial sites. Based on these data, the European Commission (2000) estimated that in relation to food, cigarette smoking, water, and soil, air contributes less than 1% of total arsenic exposure. | 1 | Applied and Interdisciplinary Chemistry |
The decline in coal consumption in the U.S. has been notable, decreasing by nearly 15% compared to the previous year. This decrease is largely attributed to the reduced use of coal in electricity generation, as more cost-effective and environmentally friendly alternatives have become available. | 1 | Applied and Interdisciplinary Chemistry |
Aza enolates (also known as imine anions, enamides, metallated Schiff bases, and metalloenamines) are nitrogen analogous to enolates. When imines get treated with strong bases such as LDA, highly nucleophilic aza enolates are generated.
The major benefit of using aza enolates is that they don't undergo self-condensation (i.e. aldol reaction for aldehydes) in a basic or neutral solution, but rather they favor alkylation on the alpha-carbon. This is mainly because imines contain carbon-nitrogen double bonds unlike aldehydes, which contain oxygen-carbon double bonds. Since oxygen is more electronegative than nitrogen, it withdraws more electron density from the carbonyl carbon, inducing a greater partially positive charge on the carbon. Therefore, with more electrophilic carbon, aldehydes allow for better nucleophilic addition to the carbon on the carbon-oxygen double bond.
On the other hand, imine has less electronegative nitrogen which induces a weaker partially positive charge on the carbonyl-carbon. As a result, while imines can still react with organolithiums, they don't react with other nucleophiles (including aza enolates) to undergo nucleophilic additions.
Instead, aza enolates react similarly to enolates, forming SN2 alkylated products. Through nitrogen lone pair conjugation, β-carbon becomes a nucleophilic site, permitting aza enolates to undergo alkylation reactions. Thus, aza enolates can react with numerous electrophiles like epoxides and alkyl halides to form a new carbon-carbon bond on β-carbon.
Two potential reaction mechanisms are shown below:
Since epoxide is a three-membered ring molecule, it has a high degree of ring strain. Although the carbons in the ring system are tetrahedral, preferring 109.5 degrees between each atom, epoxide strains the ring angles into 60 degrees. To counter this effect, the nucleophilic aza enolates easily react with epoxides to reduce their ring strains.
Besides reacting with epoxides, aza enolates can also react with alkyl halides (or allyl halides as depicted above) to form a new carbon-carbon sigma bond. This reaction is one of the key steps in the synthesis of the male aggression pheromone, Oulema melanopus. Aza enolate is generated by LDA reacting with pivaldehyde, which then reacts with an alkyl halide to form an Oulema melanopus intermediate.
Aza enolates can also be formed with Grignard reagents and react with other soft electrophiles, including Michael receptors. | 0 | Theoretical and Fundamental Chemistry |
Salinosporamide A inhibits proteasome activity by covalently modifying the active site threonine residues of the 20S proteasome. | 0 | Theoretical and Fundamental Chemistry |
Monosaccharides are the simplest form of carbohydrates with only one simple sugar. They essentially contain an aldehyde or ketone group in their structure. The presence of an aldehyde group in a monosaccharide is indicated by the prefix aldo-. Similarly, a ketone group is denoted by the prefix keto-. Examples of monosaccharides are the hexoses, glucose, fructose, Trioses, Tetroses, Heptoses, galactose, pentoses, ribose, and deoxyribose. Consumed fructose and glucose have different rates of gastric emptying, are differentially absorbed and have different metabolic fates, providing multiple opportunities for two different saccharides to differentially affect food intake. Most saccharides eventually provide fuel for cellular respiration.
Disaccharides are formed when two monosaccharides, or two single simple sugars, form a bond with removal of water. They can be hydrolyzed to yield their saccharin building blocks by boiling with dilute acid or reacting them with appropriate enzymes. Examples of disaccharides include sucrose, maltose, and lactose.
Polysaccharides are polymerized monosaccharides, or complex carbohydrates. They have multiple simple sugars. Examples are starch, cellulose, and glycogen. They are generally large and often have a complex branched connectivity. Because of their size, polysaccharides are not water-soluble, but their many hydroxy groups become hydrated individually when exposed to water, and some polysaccharides form thick colloidal dispersions when heated in water. Shorter polysaccharides, with 3 to 10 monomers, are called oligosaccharides.
A fluorescent indicator-displacement molecular imprinting sensor was developed for discriminating saccharides. It successfully discriminated three brands of orange juice beverage. The change in fluorescence intensity of the sensing films resulting is directly related to the saccharide concentration. | 0 | Theoretical and Fundamental Chemistry |
Different sigma factors are utilized under different environmental conditions. These specialized sigma factors bind the promoters of genes appropriate to the environmental conditions, increasing the transcription of those genes.
Sigma factors in E. coli:
*σ(RpoD) – σ – the "housekeeping" sigma factor or also called as primary sigma factor (Group 1), transcribes most genes in growing cells. Every cell has a "housekeeping" sigma factor that keeps essential genes and pathways operating. In the case of E. coli and other gram-negative rod-shaped bacteria, the "housekeeping" sigma factor is σ. Genes recognized by σ all contain similar promoter consensus sequences consisting of two parts. Relative to the DNA base corresponding to the start of the RNA transcript, the consensus promoter sequences are characteristically centered at 10 and 35 nucleotides before the start of transcription (−10 and −35).
*σ (FecI) – the ferric citrate sigma factor, regulates the fec gene for iron transport and metabolism
*σ (RpoE) – extreme heat stress response and the extracellular proteins sigma factor
*σ (RpoF/FliA) – the flagellar synthesis and chemotaxis sigma factor
*σ (RpoH) – the heat shock sigma factor, it is turned on when the bacteria are exposed to heat. Due to the higher expression, the factor will bind with a high probability to the polymerase-core-enzyme. Doing so, other heatshock proteins are expressed, which enable the cell to survive higher temperatures. Some of the enzymes that are expressed upon activation of σ are chaperones, proteases and DNA-repair enzymes.
*σ (RpoS) – the starvation/stationary phase sigma factor
*σ (RpoN) – the nitrogen-limitation sigma factor
There are also anti-sigma factors that inhibit the function of sigma factors and anti-anti-sigma factors that restore sigma factor function. | 1 | Applied and Interdisciplinary Chemistry |
In combustion, the Williams spray equation, also known as the Williams–Boltzmann equation, describes the statistical evolution of sprays contained in another fluid, analogous to the Boltzmann equation for the molecules, named after Forman A. Williams, who derived the equation in 1958. | 1 | Applied and Interdisciplinary Chemistry |
The society makes a number of merit awards, four annually and others either biennially or triennially, to acknowledge excellence and achievement in both specific and general fields of science. The annual awards comprise the Morton Lecture, the Colworth Medal, the Centenary Award and the Novartis Medal and Prize. | 1 | Applied and Interdisciplinary Chemistry |
An ion-exchange membrane is generally made of organic or inorganic polymer with charged (ionic) side groups, such as ion-exchange resins. Anion-exchange membranes contain fixed cationic groups with predominantly mobile anions; because anions are the majority species, most of the conductivity is due to anion transport. The reverse holds for cation-exchange membranes.
The so-called heterogeneous ion-exchange membranes have low cost and a thicker composition with higher resistance and a rough surface that can be subject to fouling. Homogeneous membranes are more expensive, but have a thinner composition with lower resistance and a smooth surface, less susceptible to fouling. Homogeneous membrane surfaces can be modified to alter the membrane permselectivity to protons, monovalent ions, and divalent ions. | 0 | Theoretical and Fundamental Chemistry |
Marine snow is made up of a variety of mostly organic matter, including dead or dying animals and phytoplankton, protists, fecal matter, sand, and other inorganic dust. Most trapped particles are more vulnerable to grazers than they would be as free-floating individuals. Aggregates can form through abiotic processes (i.e. extrapolymeric substances). These are natural polymers exuded as waste products mostly by phytoplankton and bacteria. Mucus secreted by zooplankton (mostly salps, appendicularians, and pteropods) also contribute to the constituents of marine snow aggregates. These aggregates grow over time and may reach several centimeters in diameter, traveling for weeks before reaching the ocean floor.
Marine snow often forms during algal blooms. As phytoplankton accumulate, they aggregate or get captured in other aggregates, both of which accelerate the sinking rate. Aggregation and sinking is actually thought to be a large component of sources for algae loss from surface water. Most organic components of marine snow are consumed by microbes, zooplankton and other filter-feeding animals within the first 1,000 metres of their journey. In this way marine snow may be considered the foundation of deep-sea mesopelagic and benthic ecosystems: As sunlight cannot reach them, deep-sea organisms rely heavily on marine snow as an energy source. The small percentage of material not consumed in shallower waters becomes incorporated into the muddy "ooze" blanketing the ocean floor, where it is further decomposed through biological activity.
Marine snow aggregates exhibit characteristics that fit Goldman's "aggregate spinning wheel hypothesis". This hypothesis states that phytoplankton, microorganisms and bacteria live attached to aggregate surfaces and are involved in rapid nutrient recycling. Phytoplankton have been shown to be able to take up nutrients from small local concentrations of organic material (e.g. fecal matter from an individual zooplankton cell, regenerated nutrients from organic decomposition by bacteria). As the aggregates slowly sink to the bottom of the ocean, the many microorganisms residing on them are constantly respiring and contribute greatly to the microbial loop. | 0 | Theoretical and Fundamental Chemistry |
After a sufficiently large time frame to allow hybridization, the array is illuminated with fluorescent light. Those probes on the array that are hybridized to one of the labeled fragments emit a light signal that is captured by a camera. This image contains all raw data for the remaining part of the workflow.
This raw data, encoded as false-color image, needs to be converted to numerical values before the actual analysis can be done. The analysis and information extraction of the raw data often remains the most challenging part for ChIP-on-chip experiments. Problems arise throughout this portion of the workflow, ranging from the initial chip read-out, to suitable methods to subtract background noise, and finally to appropriate algorithms that normalize the data and make it available for subsequent statistical analysis, which then hopefully lead to a better understanding of the biological question that the experiment seeks to address. Furthermore, due to the different array platforms and lack of standardization between them, data storage and exchange is a huge problem. Generally speaking, the data analysis can be divided into three major steps:
During the first step, the captured fluorescence signals from the array are normalized, using control signals derived from the same or a second chip. Such control signals tell which probes on the array were hybridized correctly and which bound nonspecifically.
In the second step, numerical and statistical tests are applied to control data and IP fraction data to identify POI-enriched regions along the genome. The following three methods are used widely: median percentile rank, single-array error, and sliding-window. These methods generally differ in how low-intensity signals are handled, how much background noise is accepted, and which trait for the data is emphasized during the computation. In the recent past, the sliding-window approach seems to be favored and is often described as most powerful.
In the third step, these regions are analyzed further. If, for example, the POI was a transcription factor, such regions would represent its binding sites. Subsequent analysis then may want to infer nucleotide motifs and other patterns to allow functional annotation of the genome. | 1 | Applied and Interdisciplinary Chemistry |
Villy Sundström (born February 6, 1949) is a Swedish physical chemist known for his work in ultrafast science and molecular photochemistry using time-resolved laser and X-ray spectroscopy techniques. | 0 | Theoretical and Fundamental Chemistry |
Several monoclonal antibody technologies have been developed recently, such as phage display, single B cell culture, single cell amplification from various B cell populations and single plasma cell interrogation technologies. Different from traditional hybridoma technology, the newer technologies use molecular biology techniques to amplify the heavy and light chains of the antibody genes by PCR and produce in either bacterial or mammalian systems with recombinant technology. One of the advantages of the new technologies is applicable to multiple animals, such as rabbit, llama, chicken and other common experimental animals in the laboratory. | 1 | Applied and Interdisciplinary Chemistry |
Sepro Mineral Systems Corp. is a Canadian company founded in 1987 and headquartered in British Columbia, Canada. The outcome of the acquisition of Sepro Mineral Processing International by Falcon Concentrators in 2008, the company's key focus is the production of mineral processing equipment for the mining and aggregate industries. Sepro Mineral Systems Corp. also provides engineering and process design services. Products sold by Sepro include grinding mills, ore scrubbers, vibrating screens, centrifugal gravity concentrators, agglomeration drums, and dense media separators. The company is also a supplier of single source modular pre-designed and custom designed plants and circuits.
Today, Sepro Mineral Systems Corp. is represented by global agents in over 15 countries and has equipment operating in over 31 countries around the world. | 1 | Applied and Interdisciplinary Chemistry |
Cavitand cages are formed by linking bowl-shaped organic molecules called cavitands. The two "bowls" are linked with organometallic complexes.
In order for a cavitand cage to efficiently self-assemble, the following requirements must be met: The cavitand scaffold must be rigid, the incoming metal complex must impose cis geometry, and there must be enough preorganization in the structure such that the entropic barrier to create the cage can be overcome. The complexes used to assemble cavitand cages are square planar with one η2 ligand; this helps enforce the final geometry. Without cis geometry, only small oligomers will form. Self-assembly also requires a ligand exchange; weakly bound ions such as BF- and PF- promote assembly because they leave the complex so it can bind with the nitriles on the rest of the structure. | 0 | Theoretical and Fundamental Chemistry |
A nuclear gene is a gene that has its DNA nucleotide sequence physically situated within the cell nucleus of a eukaryotic organism. This term is employed to differentiate nuclear genes, which are located in the cell nucleus, from genes that are found in mitochondria or chloroplasts. The vast majority of genes in eukaryotes are nuclear. | 1 | Applied and Interdisciplinary Chemistry |
I is a beta and gamma emitter. It is used both to destroy thyroid and thyroid cancer tissues (via beta radiation, which is short-range), and also other neuroendocrine tissues when used in MIBG. It can also be seen by a gamma camera, and can serve as a diagnostic imaging tracer, when treatment is also being attempted at the same time. However iodine-123 is usually preferred when only imaging is desired. | 0 | Theoretical and Fundamental Chemistry |
In order of decreasing economic efficiency, the common processes for recovery of the solubilized gold from solution are (certain processes may be precluded from use by technical factors):
* Carbon in pulp
* Electrowinning
* Merrill–Crowe process | 1 | Applied and Interdisciplinary Chemistry |
In clinical terms, a potentiator is a reagent that enhances sensitization of an antigen. Potentiators are used in the clinical laboratory for performing blood banking procedures that require enhancement of agglutination to detect the presence of antibodies or antigens in a patient's blood sample. Examples of potentiators include albumin, LISS (low ionic-strength saline) and PEG (polyethylene glycol). Potentiators are also known as enhancement reagents.
Albumin acts as a potentiator by reducing the zeta potential around the suspended red blood cells, thus dispersing the repulsive negative charges and enhancing agglutination. Low ionic strength saline (LISS) is a potentiator that acts by not only reducing the zeta potential, but also by increasing the amount of antibody taken up by the red blood cell during sensitization. LISS is a solution of glycine and albumin. Polyethylene glycol (PEG) in a LISS solution removes water from the system and thus concentrates the antibodies present. PEG can cause non-specific aggregation of cells, thus eliminating the necessity for centrifugation after incubation. PEG is not appropriate for use in samples from patients with increased plasma protein, such as patients with multiple myeloma. False-positive results may occur more frequently with the use of polyethylene glycol due to its strong agglutination capabilities. | 0 | Theoretical and Fundamental Chemistry |
In the harmonic approximation the potential energy is a quadratic function of the normal coordinates. Solving the Schrödinger wave equation, the energy states for each normal coordinate are given by
where n is a quantum number that can take values of 0, 1, 2 ... In molecular spectroscopy where several types of molecular energy are studied and several quantum numbers are used, this vibrational quantum number is often designated as v.
The difference in energy when n (or v) changes by 1 is therefore equal to , the product of the Planck constant and the vibration frequency derived using classical mechanics. For a transition from level n to level n+1 due to absorption of a photon, the frequency of the photon is equal to the classical vibration frequency (in the harmonic oscillator approximation).
See quantum harmonic oscillator for graphs of the first 5 wave functions, which allow certain selection rules to be formulated. For example, for a harmonic oscillator transitions are allowed only when the quantum number n changes by one,
but this does not apply to an anharmonic oscillator; the observation of overtones is only possible because vibrations are anharmonic. Another consequence of anharmonicity is that transitions such as between states n=2 and n=1 have slightly less energy than transitions between the ground state and first excited state. Such a transition gives rise to a hot band. To describe vibrational levels of an anharmonic oscillator, Dunham expansion is used. | 0 | Theoretical and Fundamental Chemistry |
Energy and charge are transferred between projectile and target. Some examples of this kind of reactions are:
* (p,n)
* (He,t) | 0 | Theoretical and Fundamental Chemistry |
Amines can be classified according to the nature and number of substituents on nitrogen. Aliphatic amines contain only H and alkyl substituents. Aromatic amines have the nitrogen atom connected to an aromatic ring.
Amines, alkyl and aryl alike, are organized into three subcategories based on the number of carbon atoms adjacent to the nitrogen (how many hydrogen atoms of the ammonia molecule are replaced by hydrocarbon groups):
*Primary (1°) amines—Primary amines arise when one of three hydrogen atoms in ammonia is replaced by an alkyl or aromatic group. Important primary alkyl amines include methylamine, most amino acids, and the buffering agent tris, while primary aromatic amines include aniline.
*Secondary (2°) amines—Secondary amines have two organic substituents (alkyl, aryl or both) bound to the nitrogen together with one hydrogen. Important representatives include dimethylamine, while an example of an aromatic amine would be diphenylamine.
*Tertiary (3°) amines—In tertiary amines, nitrogen has three organic substituents. Examples include trimethylamine, which has a distinctively fishy smell, and EDTA.
A fourth subcategory is determined by the connectivity of the substituents attached to the nitrogen:
*Cyclic amines—Cyclic amines are either secondary or tertiary amines. Examples of cyclic amines include the 3-membered ring aziridine and the six-membered ring piperidine. N-methylpiperidine and N-phenylpiperidine are examples of cyclic tertiary amines.
It is also possible to have four organic substituents on the nitrogen. These species are not amines but are quaternary ammonium cations and have a charged nitrogen center. Quaternary ammonium salts exist with many kinds of anions. | 0 | Theoretical and Fundamental Chemistry |
Nearly all cell membranes in animals, plants and fungi maintain a voltage difference between the exterior and interior of the cell, called the membrane potential. A typical voltage across an animal cell membrane is −70 mV. This means that the interior of the cell has a negative voltage relative to the exterior. In most types of cells, the membrane potential usually stays fairly constant. Some types of cells, however, are electrically active in the sense that their voltages fluctuate over time. In some types of electrically active cells, including neurons and muscle cells, the voltage fluctuations frequently take the form of a rapid upward (positive) spike followed by a rapid fall. These up-and-down cycles are known as action potentials. In some types of neurons, the entire up-and-down cycle takes place in a few thousandths of a second. In muscle cells, a typical action potential lasts about a fifth of a second. In plant cells, an action potential may last three seconds or more.
The electrical properties of a cell are determined by the structure of its membrane. A cell membrane consists of a lipid bilayer of molecules in which larger protein molecules are embedded. The lipid bilayer is highly resistant to movement of electrically charged ions, so it functions as an insulator. The large membrane-embedded proteins, in contrast, provide channels through which ions can pass across the membrane. Action potentials are driven by channel proteins whose configuration switches between closed and open states as a function of the voltage difference between the interior and exterior of the cell. These voltage-sensitive proteins are known as voltage-gated ion channels. | 0 | Theoretical and Fundamental Chemistry |
Acylureas (also called N-acylureas or ureides) are a class of chemical compounds formally derived from the acylation of urea. | 0 | Theoretical and Fundamental Chemistry |
The propagation of radiation in a medium that is assumed to be homogeneous, isotropic, and at rest takes place in straight lines and has the same velocity in all directions. Unless if propagating through a vacuum, thermal radiation does decay over time as energy is scattered.
Scattering occurs due to the presence of discontinuities in every medium that arise from their atomic structure. An example of scattering is when thermal radiation from the sun scatters after entering the earth's atmosphere. On a clear day at noon, only about two-thirds of this radiation actually reaches the surface. The rest is intercepted by particles in the air and changed into heat in the process. Scattering is noticeably larger for rays of shorter wave length; hence the blue color of skylight. | 0 | Theoretical and Fundamental Chemistry |
On the contrary to Stokes paradox, there exists the unsteady-state solution of the same problem which models a fluid flow moving around a circular cylinder with Reynolds number being small. This solution can be given by explicit formula in terms of vorticity of the flows vector field. | 1 | Applied and Interdisciplinary Chemistry |
The National Chemical Emergency Centre (NCEC) is a former UK government agency, now privately owned as part of Ricardo plc, providing information related to chemical accidents (spillages and fires) to emergency services in the United Kingdom and other countries.
The NCEC is headquartered on the Harwell Science and Innovation Campus in the Vale of White Horse in Oxfordshire. | 1 | Applied and Interdisciplinary Chemistry |
Ligand field theory (LFT) describes the bonding, orbital arrangement, and other characteristics of coordination complexes. It represents an application of molecular orbital theory to transition metal complexes. A transition metal ion has nine valence atomic orbitals - consisting of five nd, one (n+1)s, and three (n+1)p orbitals. These orbitals have the appropriate energy to form bonding interactions with ligands. The LFT analysis is highly dependent on the geometry of the complex, but most explanations begin by describing octahedral complexes, where six ligands coordinate with the metal. Other complexes can be described with reference to crystal field theory. Inverted ligand field theory (ILFT) elaborates on LFT by breaking assumptions made about relative metal and ligand orbital energies. | 0 | Theoretical and Fundamental Chemistry |
Haloalkanes can be produced from virtually all organic precursors. From the perspective of industry, the most important ones are alkanes and alkenes. | 0 | Theoretical and Fundamental Chemistry |
A sulfonium ion is a positively charged ion featuring three organic substituents attached to sulfur, with the formula [RS]. Together with their negatively charged counterpart, the anion, the compounds are called sulfonium salts. An oxosulfonium ion is a positively charged ion featuring three organic substituents and an oxygen attached to sulfur, with the formula [RS=O]. Together with their negatively charged counterpart, the anion, the compounds are called oxosulfonium salts. Related species include alkoxysulfonium and chlorosulfonium ions, [RSOR] and [RSCl], respectively. | 0 | Theoretical and Fundamental Chemistry |
This fitting differs from a standard cross in that two ports have curved inlets. Although it has been used in the past for connecting the drains of back-to-back fixtures (such as back-to-back sinks), some current codes—including the 2006 Uniform Plumbing Code in the United States—prohibit the use of this fitting for that purpose and require a double-fixture fitting (double combination wye) to minimize wastewater from one side flowing into the other. | 1 | Applied and Interdisciplinary Chemistry |
For applications in materials science dealing with phase changes between different solid structures, pressure is often imagined to be constant (for example at one atmosphere), and is ignored as a degree of freedom, so the formula becomes:
This is sometimes incorrectly called the "condensed phase rule", but it is not applicable to condensed systems which are subject to high pressures (for example, in geology), since the effects of these pressures are important. | 0 | Theoretical and Fundamental Chemistry |
Lecithinase is a type of phospholipase that acts upon lecithin.
It can be produced by Clostridium perfringens, Staphylococcus aureus, Pseudomonas aeruginosa or Listeria monocytogenes. C. perfringens alpha toxin (lecithinase) causes myonecrosis and hemolysis. The lecithinase of S. aureus is used in detection of coagulase-positive strains, because of high link between lecithinase activity and coagulase activity. | 1 | Applied and Interdisciplinary Chemistry |
The great majority of contemporary spectrometers use a mixture of commercially available and bespoke components which users integrate according to their particular needs. Instruments can be broadly categorised according to their general operating principles. Although rotational transitions can be found across a very broad region of the electromagnetic spectrum, fundamental physical constraints exist on the operational bandwidth of instrument components. It is often impractical and costly to switch to measurements within an entirely different frequency region. The instruments and operating principals described below are generally appropriate to microwave spectroscopy experiments conducted at frequencies between 6 and 24 GHz. | 0 | Theoretical and Fundamental Chemistry |
Ectopic is a word used with a prefix ecto-, meaning “out of”, and the suffix -topic, meaning "place." Ectopic expression is an abnormal gene expression in a cell type, tissue type, or developmental stage in which the gene is not usually expressed. The term ectopic expression is predominantly used in studies using metazoans, especially in Drosophila melanogaster for research purposes. | 1 | Applied and Interdisciplinary Chemistry |
High-carbon steel has approximately 0.6 to 1.0% carbon content. It is very strong, used for springs, edged tools, and high-strength wires. | 1 | Applied and Interdisciplinary Chemistry |
The ions or molecules surrounding the central atom are called ligands. Ligands are classified as L or X (or a combination thereof), depending on how many electrons they provide for the bond between ligand and central atom. L ligands provide two electrons from a lone electron pair, resulting in a coordinate covalent bond. X ligands provide one electron, with the central atom providing the other electron, thus forming a regular covalent bond. The ligands are said to be coordinated to the atom. For alkenes, the pi bonds can coordinate to metal atoms. An example is ethylene in the complex (Zeise's salt). | 0 | Theoretical and Fundamental Chemistry |
In a typical PL experiment, a semiconductor is excited with a light-source that provides photons with an energy larger than the bandgap energy.
The incoming light excites a polarization that can be described with the semiconductor Bloch equations. Once the photons are absorbed, electrons and holes are formed with finite momenta in the conduction and valence bands, respectively. The excitations then undergo energy and momentum relaxation towards the band-gap minimum. Typical mechanisms are Coulomb scattering and the interaction with phonons. Finally, the electrons recombine with holes under emission of photons.
Ideal, defect-free semiconductors are many-body systems where the interactions of charge-carriers and lattice vibrations have to be considered in addition to the light-matter coupling. In general, the PL properties are also extremely sensitive to internal electric fields and to the dielectric environment (such as in photonic crystals) which impose further degrees of complexity. A precise microscopic description is provided by the semiconductor luminescence equations. | 0 | Theoretical and Fundamental Chemistry |
Air pollution emission plume – flow of pollutant in the form of vapor or smoke released into the air. Plumes are of considerable importance in the atmospheric dispersion modelling of air pollution. There are three primary types of air pollution emission plumes:
* Buoyant plumes – Plumes which are lighter than air because they are at a higher temperature and lower density than the ambient air which surrounds them, or because they are at about the same temperature as the ambient air but have a lower molecular weight and hence lower density than the ambient air. For example, the emissions from the flue gas stacks of industrial furnaces are buoyant because they are considerably warmer and less dense than the ambient air. As another example, an emission plume of methane gas at ambient air temperatures is buoyant because methane has a lower molecular weight than the ambient air.
* Dense gas plumes – Plumes which are heavier than air because they have a higher density than the surrounding ambient air. A plume may have a higher density than air because it has a higher molecular weight than air (for example, a plume of carbon dioxide). A plume may also have a higher density than air if the plume is at a much lower temperature than the air. For example, a plume of evaporated gaseous methane from an accidental release of liquefied natural gas (LNG) may be as cold as .
* Passive or neutral plumes – Plumes which are neither lighter or heavier than air. | 1 | Applied and Interdisciplinary Chemistry |
The term Dallol was coined by the Afar people and means dissolution or disintegration, describing a landscape of green acid ponds and geysers (pH-values less than 1) and iron oxide, sulfur and salt desert plains. | 0 | Theoretical and Fundamental Chemistry |
To operate in this cycle, the desiccant is required to absorb moisture from air coming off of the coil that is colder and about 98% RH and to desorb moisture to air that is warmer and at a lower RH. The desiccant is regenerated by the vapor pressure differential inherent in the RH differences rather than heat or temperature difference. Desiccants that have a moisture sorption isotherm of the type shown in Figure 3 (Type III) are common, such as many formulations of silica gel. Type III desiccants absorb little moisture below 70% RH but many will take up more than their own weight in water from the air when presented with over 90% RH. The absorption isotherm is very steep between 90 and 100% RH. Desiccants of Type III have plenty of potential for the cycling of moisture from the air off of the coil, around 98% RH, over to the return air stream, typically around 50% RH. | 0 | Theoretical and Fundamental Chemistry |
Indicator bacteria are types of bacteria used to detect and estimate the level of fecal contamination of water. They are not dangerous to human health but are used to indicate the presence of a health risk.
Each gram of human feces contains approximately ~100 billion () bacteria. These bacteria may include species of pathogenic bacteria, such as Salmonella or Campylobacter, associated with gastroenteritis. In addition, feces may contain pathogenic viruses, protozoa and parasites. Fecal material can enter the environment from many sources including waste water treatment plants, livestock or poultry manure, sanitary landfills, septic systems, sewage sludge, pets and wildlife. If sufficient quantities are ingested, fecal pathogens can cause disease. The variety and often low concentrations of pathogens in environmental waters makes them difficult to test for individually. Public agencies therefore use the presence of other more abundant and more easily detected fecal bacteria as indicators of the presence of fecal contamination. Aside from bacteria being found in fecal matter, it can also be found in oral and gut contents. | 0 | Theoretical and Fundamental Chemistry |
* AM404 – an active metabolite of paracetamol.
* AM1172
* LY-2183240
* O-2093
* OMDM-2
* UCM-707
* VDM-11
* Guineensine
*WOBE437 and RX-055 | 1 | Applied and Interdisciplinary Chemistry |
The derivation of the method proceeds as follows. First we introduce rank-one (separable)
approximation to the potential
The integral equation for the rank-one part of potential is easily soluble. The full solution of the original problem can therefore be expressed as
in terms of new function . This function is solution of modified Lippmann–Schwinger equation
with
The remainder potential term is transparent for incoming wave
i. e. it is weaker operator than the original one.
The new problem thus obtained for is of the same form as the original one and we can repeat the procedure.
This leads to recurrent relations
It is possible to show that the T-matrix of the original problem can be expressed in the form of chain fraction
where we defined
In practical calculation the infinite chain fraction is replaced by finite one assuming that
This is equivalent to assuming that the remainder solution
is negligible. This is plausible assumption, since the remainder potential has all vectors
in its null space and it can be shown that this potential converges to zero and the chain fraction converges to the exact T-matrix. | 0 | Theoretical and Fundamental Chemistry |
Romen Efimovich Sova () (5 November 1938 - 22 December 2001), was a Soviet and Ukrainian toxicologist. Corresponding Member of the Ukrainian Ecological Academy of Sciences, Doctor of Medical Sciences. | 0 | Theoretical and Fundamental Chemistry |
At least three DNA conformations are believed to be found in nature, A-DNA, B-DNA, and Z-DNA. The B form described by James Watson and Francis Crick is believed to predominate in cells. It is 23.7 Å wide and extends 34 Å per 10 bp of sequence. The double helix makes one complete turn about its axis every 10.4–10.5 base pairs in solution. This frequency of twist (termed the helical pitch) depends largely on stacking forces that each base exerts on its neighbours in the chain. The absolute configuration of the bases determines the direction of the helical curve for a given conformation.
A-DNA and Z-DNA differ significantly in their geometry and dimensions to B-DNA, although still form helical structures. It was long thought that the A form only occurs in dehydrated samples of DNA in the laboratory, such as those used in crystallographic experiments, and in hybrid pairings of DNA and RNA strands, but DNA dehydration does occur in vivo, and A-DNA is now known to have biological functions. Segments of DNA that cells have methylated for regulatory purposes may adopt the Z geometry, in which the strands turn about the helical axis the opposite way to A-DNA and B-DNA. There is also evidence of protein-DNA complexes forming Z-DNA structures.
Other conformations are possible; A-DNA, B-DNA, C-DNA, E-DNA, -DNA (the enantiomeric form of -DNA), P-DNA, S-DNA, Z-DNA, etc. have been described so far. In fact, only the letters F, Q, U, V, and Y are available to describe any new DNA structure that may appear in the future. However, most of these forms have been created synthetically and have not been observed in naturally occurring biological systems. There are also triple-stranded DNA forms and quadruplex forms such as the G-quadruplex and the i-motif. | 0 | Theoretical and Fundamental Chemistry |
Pisum sativum (garden pea) plants communicate stress cues via their roots to allow neighboring unstressed plants to anticipate an abiotic stressor. Pea plants are commonly grown in temperate regions throughout the world. However, this adaptation allows plants to anticipate abiotic stresses such as drought. In 2011, Falik et al. tested the ability of unstressed pea plants to sense and respond to stress cues by inducing osmotic stress on a neighboring plant. Falik et al. subjected the root of an externally-induced plant to mannitol in order to inflict osmotic stress and drought-like conditions. Five unstressed plants neighbored both sides of this stressed plant. On one side, the unstressed plants shared their root system with their neighbors to allow for root communication. On the other side, the unstressed plants did not share root systems with their neighbors.
Falik et al. found that unstressed plants demonstrated the ability to sense and respond to stress cues emitted from the roots of the osmotically stressed plant. Furthermore, the unstressed plants were able to send additional stress cues to other neighboring unstressed plants in order to relay the signal. A cascade effect of stomatal closure was observed in neighboring unstressed plants that shared their rooting system but was not observed in the unstressed plants that did not share their rooting system. Therefore, neighboring plants demonstrate the ability to sense, integrate, and respond to stress cues transmitted through roots. Although Falik et al. did not identify the chemical responsible for perceiving stress cues, research conducted in 2016 by Delory et al. suggests several possibilities. They found that plant roots synthesize and release a wide array of organic compounds including solutes and volatiles (i.e. terpenes). They cited additional research demonstrating that root-emitted molecules have the potential to induce physiological responses in neighboring plants either directly or indirectly by modifying the soil chemistry. Moreover, Kegge et al. demonstrated that plants perceive the presence of neighbors through changes in water/nutrient availability, root exudates, and soil microorganisms.
Although the underlying mechanism behind stress cues emitted by roots remains largely unknown, Falik et al. suggested that the plant hormone abscisic acid (ABA) may be responsible for integrating the observed phenotypic response (stomatal closure). Further research is needed to identify a well-defined mechanism and the potential adaptive implications for priming neighbors in preparation for forthcoming abiotic stresses; however, a literature review by Robbins et al. published in 2014 characterized the root endodermis as a signaling control center in response to abiotic environmental stresses including drought. They found that the plant hormone ABA regulates the root endodermal response under certain environmental conditions. In 2016 Rowe et al. experimentally validated this claim by showing that ABA regulated root growth under osmotic stress conditions. Additionally, changes in cytosolic calcium concentrations act as signals to close stomata in response to drought stress cues. Therefore, the flux of solutes, volatiles, hormones, and ions are likely involved in the integration of the response to stress cues emitted by roots. | 1 | Applied and Interdisciplinary Chemistry |
The major breakthroughs occurred during the Second World War as the result of research conducted independently in the United Kingdom and the United States into the potential use of herbicides in war. The compound 2,4-D was first synthesized by W. G. Templeman at Imperial Chemical Industries. In 1940, his work with indoleacetic acid and naphthaleneacetic acid indicated that "growth substances applied appropriately would kill certain broad-leaved weeds in cereals without harming the crops," though these substances were too expensive and too short-lived in soil due to degradation by microorganisms to be of practical agricultural use; by 1941, his team succeeded in synthesizing a wide range of chemicals to achieve the same effect at lower cost and better efficacy, including 2,4-D. In the same year, R. Pokorny in the US achieved this as well. Independently, a team under Juda Hirsch Quastel, working at the Rothamsted Experimental Station made the same discovery. Quastel was tasked by the Agricultural Research Council (ARC) to discover methods for improving crop yield. By analyzing soil as a dynamic system, rather than an inert substance, he was able to apply techniques such as perfusion. Quastel was able to quantify the influence of various plant hormones, inhibitors, and other chemicals on the activity of microorganisms in the soil and assess their direct impact on plant growth. While the full work of the unit remained secret, certain discoveries were developed for commercial use after the war, including the 2,4-D compound.
When 2,4-D was commercially released in 1946, it became the first successful selective herbicide, triggering a worldwide revolution in agricultural output. It allowed for greatly enhanced weed control in wheat, maize (corn), rice, and similar cereal grass crops, because it kills dicots (broadleaf plants), but not most monocots (grasses). The low cost of 2,4-D has led to continued usage today, and it remains one of the most commonly used herbicides in the world. Like other acid herbicides, current formulations use either an amine salt (often trimethylamine) or one of many esters of the parent compound. | 1 | Applied and Interdisciplinary Chemistry |
The starting point for the collection of the substituent constants is a chemical equilibrium for which the substituent constant is arbitrarily set to 0 and the reaction constant is set to 1: the deprotonation of benzoic acid or benzene carboxylic acid (R and R' both H) in water at 25 °C.
Having obtained a value for K, a series of equilibrium constants (K) are now determined based on the same process, but now with variation of the para substituent—for instance, or . These values, combined in the Hammett equation with K and remembering that ρ = 1, give the para substituent constants compiled in table 1 for amine, methoxy, ethoxy, dimethylamino, methyl, fluorine, bromine, chlorine, iodine, nitro and cyano substituents. Repeating the process with meta-substituents afford the meta substituent constants. This treatment does not include ortho-substituents, which would introduce steric effects.
The σ values displayed in the Table above reveal certain substituent effects. With ρ = 1, the group of substituents with increasing positive values—notably cyano and nitro—cause the equilibrium constant to increase compared to the hydrogen reference, meaning that the acidity of the carboxylic acid (depicted on the left of the equation) has increased. These substituents stabilize the negative charge on the carboxylate oxygen atom by an electron-withdrawing inductive effect (-I) and also by a negative mesomeric effect (-M).
The next set of substituents are the halogens, for which the substituent effect is still positive but much more modest. The reason for this is that while the inductive effect is still negative, the mesomeric effect is positive, causing partial cancellation. The data also show that for these substituents, the meta effect is much larger than the para effect, due to the fact that the mesomeric effect is greatly reduced in a meta substituent. With meta substituents a carbon atom bearing the negative charge is further away from the carboxylic acid group (structure 2b).
This effect is depicted in scheme 3, where, in a para substituted arene 1a, one resonance structure 1b is a quinoid with positive charge on the X substituent, releasing electrons and thus destabilizing the Y substituent. This destabilizing effect is not possible when X has a meta orientation.
Other substituents, like methoxy and ethoxy, can even have opposite signs for the substituent constant as a result of opposing inductive and mesomeric effect. Only alkyl and aryl substituents like methyl are electron-releasing in both respects.
Of course, when the sign for the reaction constant is negative (next section), only substituents with a likewise negative substituent constant will increase equilibrium constants. | 0 | Theoretical and Fundamental Chemistry |
The quinhydrone electrode provides an alternative to the most commonly used glass electrode. however, it is not reliable above pH 8 (at 298 K) and cannot be used with solutions that contain a strong oxidizing or reducing agent. | 0 | Theoretical and Fundamental Chemistry |
Consider a cylindrical duct with axis along direction with radius through which fuel is fed from the bottom and the tube mouth is located at . Oxidizer is fed along the same axis, but in the concentric tube of radius outside the fuel tube. Let the mass fraction in the fuel tube be and the mass fraction of the oxygen in the outside duct be . Fuel and oxygen mixing occurs in the region . The following assumptions were made in the analysis:
* The average velocity is parallel to axis ( direction) of the ducts,
*The mass flux in the axial direction is constant,
*Axial diffusion is negligible compared to the transverse/radial diffusion
* The flame occurs infinitely fast (Burke–Schumann limit), therefore flame appears as a reaction sheet across which properties of flow changes
* Effects of gravity has been neglected
Consider a one-step irreversible Arrhenius law, , where is the mass of oxygen required to burn unit mass of fuel and is the amount of heat released per unit mass of fuel burned. If is the mass of fuel burned per unit volume per unit time and introducing the non-dimensional fuel and mass fraction and the Stoichiometry parameter,
the governing equations for fuel and oxidizer mass fraction reduce to
where Lewis number of both species is assumed to be unity and is assumed to be constant, where is the thermal diffusivity. The boundary conditions for the problem are
The equation can be linearly combined to eliminate the non-linear reaction term and solve for the new variable
where is known as the mixture fraction. The mixture fraction takes the value of unity in the fuel stream and zero in the oxidizer stream and it is a scalar field which is not affected by the reaction. The equation satisfied by is
(If the Lewis numbers of fuel and oxidizer are not equal to unity, then the equation satisfied by is nonlinear as follows from Shvab–Zeldovich–Liñán formulation). Introducing the following coordinate transformation
reduces the equation to
The corresponding boundary conditions become
The equation can be solved by separation of variables
where and are the Bessel function of the first kind and is the nth root of Solution can also be obtained for the planar ducts instead of the axisymmetric ducts discussed here. | 1 | Applied and Interdisciplinary Chemistry |
Hammond's 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 |
Ketenes are highly electrophilic at the carbon atom bonded with the heteroatom, due to its sp character. Ketene can be formed with different heteroatom bonded to the sp carbon atom, such as O, S or Se, respectively named ketene, thioketene and selenoketene.
Ethenone, the simplest ketene, has different experimental lengths for each of the double bonds; the C=O bond is 1,160Å and the C=C bond is 1,314Å. The angle between the two H atoms is 121.5°, similar to the theoretically ideal angle formed in alkenes between sp carbon atom and H substituents.
Ketenes are unstable and cannot be stored. In the absence of nucleophiles with which to react, ethenone dimerises to give β-lactone, a cyclic ester. If the ketene is disubstituted, the dimerisation product is a substituted cyclobutadione. For monosubstituted ketenes, the dimerisation could afford either the ester or the diketone product. | 0 | Theoretical and Fundamental Chemistry |
Some examples of biologically important molecular motors:
* Cytoskeletal motors
** Myosins are responsible for muscle contraction, intracellular cargo transport, and producing cellular tension.
** Kinesin moves cargo inside cells away from the nucleus along microtubules, in anterograde transport.
** Dynein produces the axonemal beating of cilia and flagella and also transports cargo along microtubules towards the cell nucleus, in retrograde transport.
* Polymerisation motors
** Actin polymerization generates forces and can be used for propulsion. ATP is used.
** Microtubule polymerization using GTP.
** Dynamin is responsible for the separation of clathrin buds from the plasma membrane. GTP is used.
*Rotary motors:
**FF-ATP synthase family of proteins convert the chemical energy in ATP to the electrochemical potential energy of a proton gradient across a membrane or the other way around. The catalysis of the chemical reaction and the movement of protons are coupled to each other via the mechanical rotation of parts of the complex. This is involved in ATP synthesis in the mitochondria and chloroplasts as well as in pumping of protons across the vacuolar membrane.
** The bacterial flagellum responsible for the swimming and tumbling of E. coli and other bacteria acts as a rigid propeller that is powered by a rotary motor. This motor is driven by the flow of protons across a membrane, possibly using a similar mechanism to that found in the F motor in ATP synthase.
* Nucleic acid motors:
** RNA polymerase transcribes RNA from a DNA template.
** DNA polymerase turns single-stranded DNA into double-stranded DNA.
** Helicases separate double strands of nucleic acids prior to transcription or replication. ATP is used.
** Topoisomerases reduce supercoiling of DNA in the cell. ATP is used.
** RSC and SWI/SNF complexes remodel chromatin in eukaryotic cells. ATP is used.
** SMC proteins responsible for chromosome condensation in eukaryotic cells.
** Viral DNA packaging motors inject viral genomic DNA into capsids as part of their replication cycle, packing it very tightly. Several models have been put forward to explain how the protein generates the force required to drive the DNA into the capsid. An alternative proposal is that, in contrast with all other biological motors, the force is not generated directly by the protein, but by the DNA itself. In this model, ATP hydrolysis is used to drive protein conformational changes that alternatively dehydrate and rehydrate the DNA, cyclically driving it from B-DNA to A-DNA and back again. A-DNA is 23% shorter than B-DNA, and the DNA shrink/expand cycle is coupled to a protein-DNA grip/release cycle to generate the forward motion that propels DNA into the capsid.
* Enzymatic motors: The enzymes below have been shown to diffuse faster in the presence of their catalytic substrates, known as enhanced diffusion. They also have been shown to move directionally in a gradient of their substrates, known as chemotaxis. Their mechanisms of diffusion and chemotaxis are still debated. Possible mechanisms include solutal buoyancy, phoresis or conformational changes leading to change in effective diffusivity and kinetic asymmetry.
**Catalase
**Urease
**Aldolase
**Hexokinase
**Phosphoglucose isomerase
**Phosphofructokinase
**Glucose Oxidase
A recent study has also shown that certain enzymes, such as Hexokinase and Glucose Oxidase, are aggregating or fragmenting during catalysis. This changes their hydrodynamic size that can affect enhanced diffusion measurements.
*Synthetic molecular motors have been created by chemists that yield rotation, possibly generating torque. | 0 | Theoretical and Fundamental Chemistry |
Zinc can be present in six different forms in soil namely; water soluble zinc, exchangeable zinc, organically bound zinc, carbonate bound zinc, aluminium and manganese oxide bound zinc and residual fractions of zinc.
In toxic conditions, species of Calluna, Erica and Vaccinium can grow in zinc-metalliferous soils, because translocation of toxic ions is prevented by the action of ericoid mycorrhizal fungi. | 1 | Applied and Interdisciplinary Chemistry |
LH is released from the pituitary gland along with FSH in response to GnRH release into the hypophyseal portal system. Pulsatile GnRH release causes pulsatile LH and FSH release to occur, which modulates and maintains appropriate levels of bioavailable gonadal hormone: testosterone in males and estradiol in females subject to the requirements of a superior feedback loop. In females the levels of LH is typically 1–20 IU/L during the reproductive period and is estimated to be 1.8–8.6 IU/L in males over 18 years of age. | 1 | Applied and Interdisciplinary Chemistry |
Full article: Ocean acidification
The pH of the oceans is declining due to uptake of atmospheric CO. The rise in dissolved carbon dioxide reduces the availability of the carbonate ion, reducing CaCO saturation state, thus making it thermodynamically harder to make CaCO shell. Carbonate ions preferentially bind to hydrogen ions to form bicarbonate, thus a reduction in carbonate ion availability increases the amount of unbound hydrogen ions, and decreases the amount of bicarbonate formed (Equations 1–3). pH is a measurement of hydrogen ion concentration, where a low pH means there are more unbound hydrogen ions. pH is therefore an indicator of carbonate speciation (the format of carbon present) in the oceans and can be used to assess how healthy the ocean is.
The list of organisms that may struggle due to ocean acidification include coccolithophores and foraminifera (the base of the marine food chain in many areas), human food sources such as oysters and mussels, and perhaps the most conspicuous, a structure built by organisms – the coral reefs. Most surface water will remain supersaturated with respect to CaCO (both calcite and aragonite) for some time on current emissions trajectories, but the organisms that require carbonate will likely be replaced in many areas. Coral reefs are under pressure from overfishing, nitrate pollution, and warming waters; ocean acidification will add additional stress on these important structures. | 0 | Theoretical and Fundamental Chemistry |
In 1932, organisms were discovered that could convert hydrogen gas and carbon dioxide into acetic acid. The first acetogenic bacterium species, Clostridium aceticum, was discovered in 1936 by Klaas Tammo Wieringa. A second species, Moorella thermoacetica, attracted wide interest because of its ability, reported in 1942, to convert glucose into three moles of acetic acid. | 1 | Applied and Interdisciplinary Chemistry |
In species of algae that contain a single chloroplast, regulation of chloroplast division is extremely important to ensure that each daughter cell receives a chloroplast—chloroplasts can't be made from scratch. In organisms like plants, whose cells contain multiple chloroplasts, coordination is looser and less important. It is likely that chloroplast and cell division are somewhat synchronized, though the mechanisms for it are mostly unknown.
Light has been shown to be a requirement for chloroplast division. Chloroplasts can grow and progress through some of the constriction stages under poor quality green light, but are slow to complete division—they require exposure to bright white light to complete division. Spinach leaves grown under green light have been observed to contain many large dumbbell-shaped chloroplasts. Exposure to white light can stimulate these chloroplasts to divide and reduce the population of dumbbell-shaped chloroplasts. | 0 | Theoretical and Fundamental Chemistry |
Crayfish have also been hypothesized as being suitable bioindicators, under the appropriate conditions. One example of use is an examination of accumulation of microplastics in the digestive tract of red swamp crayfish (Procambarus clarkii) being used as a bioindicator of wider microplastics pollution. | 1 | Applied and Interdisciplinary Chemistry |
Chemical process modeling is a computer modeling technique used in chemical engineering process design. It typically involves using purpose-built software to define a system of interconnected components, which are then solved so that the steady-state or dynamic behavior of the system can be predicted. The system components and connections are represented as a process flow diagram. Simulations can be as simple as the mixing of two substances in a tank, or as complex as an entire alumina refinery.
Chemical process modeling requires a knowledge of the properties of the chemicals involved in the simulation, as well as the physical properties and characteristics of the components of the system, such as tanks, pumps, pipes, pressure vessels, and so on. | 1 | Applied and Interdisciplinary Chemistry |
The cation-exchange capacity of a soil is determined by its constituent materials, which can vary greatly in their individual CEC values. CEC is therefore dependent on parent materials from which the soil developed, and the conditions under which it developed. These factors are also important for determining soil pH, which has a major influence on CEC. | 0 | Theoretical and Fundamental Chemistry |
The borax method of gold extraction has been used by artisanal gold miners in the Benguet area north of Manila in the Philippines for more than 30 years. Some believe it was in practice as early as the 1900s. The method is increasingly being seen as a safe alternative to the widespread use of toxic mercury in artisanal gold mining today. About 30% of the world's mercury emissions comes from small scale mining. Efforts are being made to revive the method and spread its use. As of 2012, around 15,000 artisanal gold miners in a small area of Luzon, the main island in the northern portion of the Philippines, use this method exclusively. The mineral is inexpensive and easily available, and the miners have reportedly found that more gold is recovered through its use. | 1 | Applied and Interdisciplinary Chemistry |
Here are some GeneRIFs taken from Entrez Gene for GeneID 7157, the human gene TP53.
The PubMed document identifiers have been omitted from the examples. Note the wide variability with respect to the presence or absence of punctuation and of sentence-initial capital letters.
* p53 and c-erbB-2 may have independent role in carcinogenesis of gall bladder cancer
* Degradation of endogenous HIPK2 depends on the presence of a functional p53 protein.
* p53 codon 72 alleles influence the response to anticancer drugs in cells from aged people by regulating the cell cycle inhibitor p21WAF1
* Logistic regression analysis showed p53 and COX-2 as dependent predictors in pancreatic carcinogenesis, and a reciprocal relationship to neoplastic progression between p53 and COX-2.
GeneRIFs are an unusual type of textual genre, and they have recently been the subject of a number of articles from the natural language processing community. | 1 | Applied and Interdisciplinary Chemistry |
An ionic compound is named by its cation followed by its anion. See polyatomic ion for a list of possible ions.
For cations that take on multiple charges, the charge is written using Roman numerals in parentheses immediately following the element name. For example, Cu(NO) is copper(II) nitrate, because the charge of two nitrate ions () is 2 × −1 = −2, and since the net charge of the ionic compound must be zero, the Cu ion has a 2+ charge. This compound is therefore copper(II) nitrate. In the case of cations with a +4 oxidation state, the only acceptable format for the Roman numeral 4 is IV and not IIII.
The Roman numerals in fact show the oxidation number, but in simple ionic compounds (i.e., not metal complexes) this will always equal the ionic charge on the metal. For a simple overview see [http://www.cofc.edu/~deavorj/101/nomenclature.html] , for more details see [http://www2.potsdam.edu/walkerma/inorg_naming.pdf selected pages from IUPAC rules for naming inorganic compounds] . | 0 | Theoretical and Fundamental Chemistry |
Enediynes are organic compounds containing two triple bonds and one double bond.
Enediynes are most notable for their limited use as antitumor antibiotics (known as enediyne anticancer antibiotics). They are efficient at inducing apoptosis in cells, but cannot differentiate cancerous cells from healthy cells. Consequently, research is being conducted to increase the specificity of enediyne toxicity. | 0 | Theoretical and Fundamental Chemistry |
Vargulin (with the associated luciferase) has applications in biotechnology:
* in a variety of assays, to report gene or gene expression after luciferase have been genetically introduced in cells,
* to detect ATP, that is used in the vargulin/luciferase reaction (cell viability assays).
Although less stable, the Cypridina system is useful because can be used in multiplex assays with other (red-emitting) luciferin assays. | 1 | Applied and Interdisciplinary Chemistry |
Dissociation of pyrophosphoric acid generates four anions, , where the charge k ranges from 1 to 4. The last one is pyrophosphate . The pyrophosphates are mostly water-soluble.
Likewise, tripolyphosphoric acid yields at least five anions , where k ranges from 1 to 5, including tripolyphosphate . Tetrapolyphosphoric acid yields at least six anions, including tetrapolyphosphate , and so on. Note that each extra phosphoric unit adds one extra P atom, three extra O atoms, and either one extra hydrogen atom or an extra negative charge.
Branched polyphosphoric acids give similarly branched polyphosphate anions. The simplest example of this is triphosphono phosphate and its partially dissociated versions.
The general formula for such (non-cyclic) polyphosphate anions, linear or branched, is , where the charge k may vary from 1 to . Generally in an aqueous solution, the degree or percentage of dissociation depends on the pH of the solution. | 0 | Theoretical and Fundamental Chemistry |
There are not many drugs that can effectively treat or reverse obesity. Obesity can increase ones risk of diseases primarily linked to health problems such as diabetes, hypertension, cardiovascular disease and even certain types of cancers. A study revolving around treatment and prevention of obesity using transgenic mice to experiment on reports positive feedback that proposes miR-378 may sure be a promising agent for preventing and treating obesity in humans. The study findings demonstrate that activation of the pyruvate-PEP futile cycle in skeletal muscle through miR-378 is the primary cause of elevated lipolysis in adipose tissues of miR-378 transgenic mice, and it helps orchestrate the crosstalk between muscle and fat to control energy homeostasis in mice.
Our general understanding of futile cycle is a substrate cycle, occurring when two overlapping metabolic pathways run in opposite directions, that when left without regulation will continue to go on uncontrolled without any actual production until all the cells energy is depleted. However, the idea behind the study indicates miR-378-activated pyruvate-phosphoenolpyruvate futile cycle plays a regulatory benefit. Not only does miR-378 result in lower body fat mass due to enhanced lipolysis it is also speculated that futile cycles regulate metabolism to maintain energy homeostasis. miR-378 has a unique function in regulating metabolic communication between the muscle and adipose tissues to control energy homeostasis at whole-body levels. | 1 | Applied and Interdisciplinary Chemistry |
ILs are potential heat transfer and storage media in solar thermal energy systems. Concentrating solar thermal facilities such as parabolic troughs and solar power towers focus the sun's energy onto a receiver, which can generate temperatures of around . This heat can then generate electricity in a steam or other cycle. For buffering during cloudy periods or to enable generation overnight, energy can be stored by heating an intermediate fluid. Although nitrate salts have been the medium of choice since the early 1980s, they freeze at and thus require heating to prevent solidification. Ionic liquids such as [Cmim][] have more favorable liquid-phase temperature ranges (-75 to 459 °C) and could therefore be excellent liquid thermal storage media and heat transfer fluids. | 0 | Theoretical and Fundamental Chemistry |
* The Bay, a 2012 found footage-style eco-horror movie about a pandemic due to deadly pollution from chicken factory farm run-off and mutant isopods and aquatic parasites able to infect humans.
* Expedition Chesapeake, A Journey of Discovery, a 2019 film starring Jeff Corwin created by The Whitaker Center for Science and the Arts. | 1 | Applied and Interdisciplinary Chemistry |
When placed into solution, salts begin to dissolve and form ions. This is not always in equal proportion, due to the preference of an ion to be dissolved in a given solution. The ability of an ion to preferentially dissolve (as a result of unequal activities) over its counterion is classified as the potential determining ion. The properties of this ion are strongly related to the surface potential present on a corresponding solid.
This unequal property between corresponding ions results in a net surface charge. In some cases this arises because one of the ions freely leaves a corresponding solid and the other does not or it is bound to the solid by some other means. Adsorption of an ion to the solid may result in the solid acting as an electrode. (e.g., H and OH on the surfaces of clays).
In a colloidal dispersed system, ion dissolution arises, where the dispersed particles exist in equilibrium with their saturated counterpart, for example:
:NaCl Na + Cl
The behavior of this system is characterised by the components activity coefficients and solubility product:
:a
In clay-aqueous systems the potential of the surface is determined by the activity of ions which react with the mineral surface. Frequently this is the hydrogen ion H in which case the important activity is determined by pH.
The simultaneous adsorption of protons and hydroxyls as well as other potential determining cations and anions, leads to the concept of point of zero charge or PZC, where the total charge from the cations and anions at the surface is equal to zero.
The charge must be zero, and this does not necessarily mean the number of cations versus anions in the solution are equal. For clay minerals the potential determining ions are H and OH and complex ions formed by bonding with H and OH. | 0 | Theoretical and Fundamental Chemistry |
Carbon-fiber reinforced composite materials can improve efficiency in engineered systems (for example, airframes) by reducing structural weight for given strength and stiffness requirements, but present challenges with manufacturing and certification. High-performance composite components employ many continuous fibers that span the shape of a component, and are embedded in a resin matrix. Such parts typically require custom tooling, pressurization for consolidation and heated curing. Joining such parts adds complexity and structural vulnerabilities.
RCCM eliminate the need for custom tooling because parts can be incrementally added/removed. Their construction, modification, repair and re-use can all employ the same reversible linking process. Heterogeneous elements can be incorporated in structures with functions determined by their relative placement. Exact assembly of discrete cellular composites offers new properties and performance not available with the analog alternatives of continuously depositing or removing material. | 0 | Theoretical and Fundamental Chemistry |
Sediment that has piled up at the top of the continental slope, particularly at the heads of submarine canyons can create turbidity current due to overloading, thus consequent slumping and sliding. | 1 | Applied and Interdisciplinary Chemistry |
There are causes for deficiency other than low dietary intake of vitamin A as retinol or carotenes. Adequate dietary protein and caloric energy are needed for a normal rate of synthesis of RBP, without which, retinol cannot be mobilized to leave the liver. Systemic infections can cause transient decreases in RBP synthesis even if protein-calorie malnutrition is absent. Chronic alcohol consumption reduces liver vitamin A storage. Non-alcoholic fatty liver disease (NAFLD), characterized by the accumulation of fat in the liver, is the hepatic manifestation of metabolic syndrome. Liver damage from NAFLD reduces liver storage capacity for retinol and reduces the ability to mobilize liver stores to maintain normal circulating concentration.
Vitamin A appears is involved in the pathogenesis of anemia by diverse biological mechanisms, such as the enhancement of growth and differentiation of erythrocyte progenitor cells, potentiation of immunity to infection , and mobilization of iron stores from tissues. | 1 | Applied and Interdisciplinary Chemistry |
Chemical Engineering Science is a peer-reviewed scientific journal covering all aspects of chemical engineering. It is published by Elsevier and was established in 1951. The editor-in-chief is A.P.J. Middelberg (University of Queensland). | 1 | Applied and Interdisciplinary Chemistry |
In these cells the electrolyte between the electrodes is a water solution of some salt or hydrophylic compound. An essential property of these compounds is that they must be able to undergo redox reactions in order to shuttle electrons from one electrode to the other during the cell operation. | 0 | Theoretical and Fundamental Chemistry |
Different grains and their orientations can be observed using scanning electron microscope (SEM) techniques such as electron backscatter diffraction (EBSD) or polarized optical microscopy (POM). Samples are initially cold- or hot-rolled to introduce a high degree of dislocation density, and then deformed at different strain rates so that dynamic recrystallization occurs. The deformation may be in the form of compression, tension, or torsion. The grains elongate in the direction of applied stress and the misorientation angle of subgrain boundaries increases. | 1 | Applied and Interdisciplinary Chemistry |
One of the few known cases of a functional system in which ephaptic coupling is responsible for an observable physiological event is in the Purkinje cells of the rat cerebellum. It was demonstrated in this study that the basket cells which encapsulate some regions of Purkinje fibers can cause inhibitory effects on the Purkinje cells. The firing of these basket cells, which occurs more rapidly than in the Purkinje cells, draws current across the Purkinje cell and generates a passive hyperpolarizing potential which inhibits the activity of the Purkinje cell. Although the exact functional role of this inhibition is still unclear, it may well have a synchronizing effect in the Purkinje cells as the ephaptic effect will limit the firing time.
A similar ephaptic effect has been studied in the Mauthner cells of teleosts. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, a sterically induced reduction happens when an oxidized metal behaves as, and exhibits similar reducing properties to, the more reduced form of the metal. This effect is mainly caused by the surrounding ligands that are complexed to the metal and it is the ligands that are involved in the reduction chemistry instead of the metal due to electronic destabilization by being significantly distanced from the metal. Sterically induced reductions commonly involve metals found in the lanthanoid and actinoid series. | 0 | Theoretical and Fundamental Chemistry |
The processes just above have assumed that the boundaries are also impermeable to particles. Otherwise, we may assume boundaries that are rigid, but are permeable to one or more types of particle. Similar considerations then hold for the chemical potential–particle number conjugate pair, which is concerned with the transfer of energy via this transfer of particles.
* In a constant chemical potential process the system is particle-transfer connected, by a particle-permeable boundary, to a constant-µ reservoir.
* The conjugate here is a constant particle number process. These are the processes outlined just above. There is no energy added or subtracted from the system by particle transfer. The system is particle-transfer-insulated from its environment by a boundary that is impermeable to particles, but permissive of transfers of energy as work or heat. These processes are the ones by which thermodynamic work and heat are defined, and for them, the system is said to be closed. | 0 | Theoretical and Fundamental Chemistry |
At that time the French Academy of Sciences was organizing a major scientific expedition to Quito, in present-day Ecuador, in order to measure the length of a degree of meridian arc (i.e., latitude) at the equator. This was part of an effort to determine in the precise figure of the Earth in order to settle the scientific debate between the defenders of René Descartes's physics and those who advocated the newer Newtonian mechanics. In 1735, Ulloa and another young naval officer, Jorge Juan, were appointed by the Spanish Crown to accompany the French Geodesic Mission to Quito. This was a sensitive assignment, both politically and scientifically.
The early work of the French Geodesic Mission, led by Charles Marie de La Condamine, was delayed and hindered by lack of cooperation from the local Spanish authorities. Indeed, in 1737 the personal dispute between Ulloa and the president of the Real Audiencia de Quito, Joseph de Araujo y Río, reached such a pitch that Araujo ordered the arrest of Ulloa and Juan, announcing his intention to have them killed. Juan and Ulloa took refuge in a church and Ulloa then escaped through the cordon of Araujos men, reaching Lima and obtaining the protection of the Viceroy of Peru, the Marquis of Villagarcía. When war between Spain and Great Britain broke out in 1739 (see War of Jenkins Ear), Juan and Ulloa, as naval officers, actively participated in the defense of Peru.
Ulloa traveled throughout the territories of the Viceroyalty of Peru from 1736 to 1744, making many astronomic, natural, and social observations. In one of his reports he described, for the first time in the European scientific literature, some of the properties of a metal that he called platina ("little silver") and which he encountered during his inspection the gold panning operations in the Chocó region of what is now Colombia. This metal would later be identified as a new chemical element, now known as platinum. Ulloa is therefore often credited as the discoverer of platinum.
The final results of French Geodesic Mission, published by La Condamine in 1745, combined with the measurements of meridian arc near the Arctic Circle that had been published in 1738 by Pierre Louis Maupertuis following the French Geodesic Mission to Lapland, decisively vindicated the predictions first made by Isaac Newton in Book III of his Principia Mathematica of 1687. These results greatly contributed to the triumph of Newtonianism over Cartesianism among Continental European savants. | 1 | Applied and Interdisciplinary Chemistry |
Vitamin D supplementation is not associated with a reduced risk of stroke, cerebrovascular disease, myocardial infarction, or ischemic heart disease. Supplementation does not lower blood pressure in the general population. | 1 | Applied and Interdisciplinary Chemistry |
In eukaryotic cells the pyruvate decarboxylation occurs inside the mitochondrial matrix, after transport of the substrate, pyruvate, from the cytosol. The transport of pyruvate into the mitochondria is via the transport protein pyruvate translocase. Pyruvate translocase transports pyruvate in a symport fashion with a proton (across the inner mitochondrial membrane), which may be considered to be a form of secondary active transport, but further confirmation/support may be needed for the usage of "secondary active transport" desciptor here (Note: the pyruvate transportation method via the pyruvate translocase appears to be coupled to a proton gradient according to S. Papa et al., 1971, seemingly matching secondary active transport in definition).
Alternative sources say "transport of pyruvate across the outer mitochondrial membrane appears to be easily accomplished via large non-selective channels such as voltage-dependent anion channels, which enable passive diffusion" and transport across inner mitochondrial membrane is mediated by mitochondrial pyruvate carrier 1 (MPC1) and mitochondrial pyruvate carrier 2 (MPC2).
Upon entry into the mitochondrial matrix, the pyruvate is decarboxylated, producing acetyl-CoA (and carbon dioxide and NADH). This irreversible reaction traps the acetyl-CoA within the mitochondria (the acetyl-CoA can only be transported out of the mitochondrial matrix under conditions of high oxaloacetate via the citrate shuttle, a TCA intermediate that is normally sparse). The carbon dioxide produced by this reaction is nonpolar and small, and can diffuse out of the mitochondria and out of the cell.
In prokaryotes, which have no mitochondria, this reaction is either carried out in the cytosol, or not at all. | 1 | Applied and Interdisciplinary Chemistry |
If ferritin is high, there is iron in excess or else there is an acute inflammatory reaction in which ferritin is mobilized without iron excess. For example, ferritins may be high in infection without signaling body iron overload.
Ferritin is also used as a marker for iron overload disorders, such as hemochromatosis or hemosiderosis. Adult-onset Still's disease, some porphyrias, and hemophagocytic lymphohistiocytosis/macrophage activation syndrome are diseases in which the ferritin level may be abnormally raised.
As ferritin is also an acute-phase reactant, it is often elevated in the course of disease. A normal C-reactive protein can be used to exclude elevated ferritin caused by acute phase reactions.
Ferritin has been shown to be elevated in some cases of COVID-19 and may correlate with worse clinical outcome.
Ferritin and IL-6 are considered to be possible immunological biomarkers for severe and fatal cases of COVID-19. Ferritin and C-reactive protein may be possible screening tools for early diagnosis of systemic inflammatory response syndrome in cases of COVID-19.
According to a study of anorexia nervosa patients, ferritin can be elevated during periods of acute malnourishment, perhaps due to iron going into storage as intravascular volume and thus the number of red blood cells falls.
Another study suggests that due to the catabolic nature of anorexia nervosa, isoferritins may be released. Furthermore, ferritin has significant non-storage roles within the body, such as protection from oxidative damage. The rise of these isoferritins may contribute to an overall increase in ferritin concentration. The measurement of ferritin through immunoassay or immunoturbidimeteric methods may also be picking up these isoferritins thus not a true reflection of iron storage status.
Studies reveal that a transferrin saturation (serum iron concentration ÷ total iron binding capacity) over 60 percent in men and over 50 percent in women identified the presence of an abnormality in iron metabolism (hereditary hemochromatosis, heterozygotes, and homozygotes) with approximately 95 percent accuracy. This finding helps in the early diagnosis of hereditary hemochromatosis, especially while serum ferritin still remains low. The retained iron in hereditary hemochromatosis is primarily deposited in parenchymal cells, with reticuloendothelial cell accumulation occurring very late in the disease. This is in contrast to transfusional iron overload in which iron deposition occurs first in the reticuloendothelial cells and then in parenchymal cells. This explains why ferritin levels remain relative low in hereditary hemochromatosis, while transferrin saturation is high. | 1 | Applied and Interdisciplinary Chemistry |
Aluminium granules have been found safer and economical compared to atomized aluminium powder. Aluminium granules have lower explosion risk in production and in use of the product itself. | 1 | Applied and Interdisciplinary Chemistry |
Numerous policies have been put in place since the 1975 oil crisis in order to promote the use of Renewable Fuels in the United States, Canada and Europe. In Canada, these included the implementation of excise taxes exempting propane and natural gas which was extended to ethanol made from biomass and methanol in 1992. The federal government also announced their renewable fuels strategy in 2006 which proposed four components: increasing availability of renewable fuels through regulation, supporting the expansion of Canadian production of renewable fuels, assisting farmers to seize new opportunities in this sector and accelerating the commercialization of new technologies. These mandates were quickly followed by the Canadian provinces:
BC introduced a 5% ethanol and 5% renewable diesel requirement which was effective by January 2010. It also introduced a low carbon fuel requirement for 2012 to 2020.
Alberta introduced a 5% ethanol and 2% renewable diesel requirement implemented April 2011. The province also introduced a minimum 25% GHG emission reduction requirement for qualifying renewable fuels.
Saskatchewan implemented a 2% renewable diesel requirement in 2009.
Additionally, in 2006, the Canadian Federal Government announced its commitment to using its purchasing power to encourage the biofuel industry. Section three of the 2006 alternative fuels act stated that when it is economically feasible to do so-75% per cent of all federal bodies and crown corporation will be motor vehicles. | 1 | Applied and Interdisciplinary Chemistry |
The following topics make up a typical curriculum in environmental engineering:
#Mass and Energy transfer
#Environmental chemistry
##Inorganic chemistry
##Organic Chemistry
##Nuclear Chemistry
#Growth models
##Resource consumption
##Population growth
##Economic growth
#Risk assessment
##Hazard identification
##Dose-response Assessment
##Exposure assessment
## Risk characterization
## Comparative risk analysis
#Water pollution
##Water resources and pollutants
##Oxygen demand
## Pollutant transport
##Water and waste water treatment
#Air pollution
## Industry, transportation, commercial and residential emissions
## Criteria and toxic air pollutants
## Pollution modelling (e.g. Atmospheric dispersion modeling)
##Pollution control
## Air pollution and meteorology
#Global change
##Greenhouse effect and global temperature
##Carbon, nitrogen, and oxygen cycle
##IPCC emissions scenarios
## Oceanic changes (ocean acidification, other effects of global warming on oceans) and changes in the stratosphere (see Physical impacts of climate change)
#Solid waste management and resource recovery
##Life cycle assessment
##Source reduction
##Collection and transfer operations
##Recycling
##Waste-to-energy conversion
##Landfill | 1 | Applied and Interdisciplinary Chemistry |
The rhodophyte, or red algae chloroplast group is another large and diverse chloroplast lineage. Rhodophyte chloroplasts are also called rhodoplasts, literally "red chloroplasts".
Rhodoplasts have a double membrane with an intermembrane space and phycobilin pigments organized into phycobilisomes on the thylakoid membranes, preventing their thylakoids from stacking. Some contain pyrenoids. Rhodoplasts have chlorophyll a and phycobilins for photosynthetic pigments; the phycobilin phycoerythrin is responsible for giving many red algae their distinctive red color. However, since they also contain the blue-green chlorophyll a and other pigments, many are reddish to purple from the combination. The red phycoerytherin pigment is an adaptation to help red algae catch more sunlight in deep water—as such, some red algae that live in shallow water have less phycoerythrin in their rhodoplasts, and can appear more greenish. Rhodoplasts synthesize a form of starch called floridean starch, which collects into granules outside the rhodoplast, in the cytoplasm of the red alga. | 0 | Theoretical and Fundamental Chemistry |
Since the oceanic intake of carbon dioxide is limited, CO influx can also be described by the Revelle factor. The Revelle Factor is a ratio of the change of carbon dioxide to the change in dissolved inorganic carbon, which serves as an indicator of carbon dioxide dissolution in the mixed layer considering the solubility pump. The Revelle Factor is an expression to characterize the thermodynamic efficiency of the DIC pool to absorb CO into bicarbonate. The lower the Revelle factor, the higher the capacity for ocean water to take in carbon dioxide. While Revelle calculated a factor of around 10 in his day, in a 2004 study data showed a Revelle factor ranging from approximately 9 in low-latitude tropical regions to 15 in the southern ocean near Antarctica. | 0 | Theoretical and Fundamental Chemistry |
A chromatography detector is a device that detects and quantifies separated compounds as they elute from the chromatographic column. These detectors are integral to various chromatographic techniques, such as gas chromatography, liquid chromatography, and high-performance liquid chromatography, and supercritical fluid chromatography among others. The main function of a chromatography detector is to translate the physical or chemical properties of the analyte molecules into measurable signal, typically electrical signal, that can be displayed as a function of time in a graphical presentation, called a chromatograms. Chromatograms can provide valuable information about the composition and concentration of the components in the sample.
Detectors operate based on specific principles, including optical, electrochemical, thermal conductivity, fluorescence, mass spectrometry, and more. Each type of detector has its unique capabilities and is suitable for specific applications, depending on the nature of the analytes and the sensitivity and selectivity required for the analysis.
There are two general types of detectors: destructive and non-destructive. The destructive detectors perform continuous transformation of the column effluent (burning, evaporation or mixing with reagents) with subsequent measurement of some physical property of the resulting material (plasma, aerosol or reaction mixture). The non-destructive detectors are directly measuring some property of the column eluent (for example, ultraviolet absorption) and thus affords greater analyte recovery. | 0 | Theoretical and Fundamental Chemistry |
A blocking antibody is an antibody that does not have a reaction when combined with an antigen, but prevents other antibodies from combining with that antigen. This function of blocking antibodies has had a variety of clinical and experimental uses.
The term can also be used for inhibiting antibody, prozone phenomenon and, agglutination reaction.
Blocking antibodies have been described as a mechanism for HSV-1 to evade the immune system. | 1 | Applied and Interdisciplinary Chemistry |
Sensitizers (denoted "Sens") are compounds, such as fluorescein dyes, methylene blue, and polycyclic aromatic hydrocarbons, which are able to absorb electromagnetic radiation (usually in the visible range of the spectrum) and eventually transfer that energy to molecular oxygen or the substrate of photooxygenation process. Many sensitizers, both naturally occurring and synthetic, rely on extensive aromatic systems to absorb light in the visible spectrum. When sensitizers are excited by light, they reach a singlet state, Sens*. This singlet is then converted into a triplet state (which is more stable), Sens*, via intersystem crossing. The Sens* is what reacts with either the substrate or O in the three types of photooxygenation reactions. | 0 | Theoretical and Fundamental Chemistry |
Controversy has swirled around the provenance of the copper oxhide ingots. Lead isotope analysis (LIA) suggests that the late LBA ingots (that is, after 1250 BC) are composed of Cypriot copper, specifically copper from the Apilki mine and its surrounding area. The Gelidonya ingots' ratios are consistent with Cypriot ores while the Uluburun ingots fall on the periphery of the Cypriot isotopic field. On the other hand, Late Minoan I ingots found on Crete have Paleozoic lead isotope ratios and are more consistent with ore sources in Afghanistan, Iran, or Central Asia. The controversy settles on the validity of LIA. Paul Budd argues that LBA copper is the product of such extensive mixing and recycling that LIA, which works best for metals from a single ore deposit, is unfeasible.
Some scholars worry that the 1250 BC date is too limiting. They note that Cyprus was smelting copper on a large scale in the early LBA and had the potential to export the metal to Crete and other places at this time. Furthermore, copper ore is more plentiful on Cyprus than on Sardinia and far more plentiful than on Crete. Archaeologists have discovered numerous Cypriot exports to Sardinia including metalworking tools and prestige metal objects.
Due to the heavy corrosion of tin oxhide ingots and the limited data for lead isotopic studies of tin, the provenance of the tin ingots has been uncertain. The fact that scholars have been unable to pinpoint Bronze Age tin ore deposits compounds this problem. | 1 | Applied and Interdisciplinary Chemistry |
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