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Application of this discharge are usually seen where production of filter cakes that blind the filter media thoroughly and processes that have low solid concentration slurry. Pre coat discharge is used if slurry with very low solid concentration slurry is used that resulted in difficult cake formation or if the slurry is difficult to filter to produce cake . | 3 | Analytical Chemistry |
A seasonal dead zone exists in the central part of Lake Erie from east of Point Pelee to Long Point and stretches to shores in Canada and the United States. Between the months of July and October the dead zone has the ability to grow to the size of 10,000 square kilometers. Lake Erie has an excess of phosphorus due to agricultural runoff that quickens the growth of algae which then contributes to hypoxic conditions. The superabundance of phosphorus in the lake has been linked to nonpoint source pollution such as urban and agricultural runoff as well as point source pollution that includes sewage and wastewater treatment plants. The zone was first noticed in the 1960s amid the peak of eutrophication occurring in the lake. After public concern increased, Canada and the US launched efforts to reduce runoff pollution into the lake in the 1970s as means to reverse the dead zone growth. Scientists in 2018 stated that phosphorus runoff would have to further decrease by 40% to avoid the emergence of the dead zones in the area. The commercial and recreational fishing industry have been significantly impacted by the hypoxic zone. In 2021, the low-oxygenated waters caused a mass-kill event of freshwater drum fish species (also known as sheepshead fish). Water from the lake is also used for human drinking. Water from the lake has been said to acquire a pervasive odor and discoloration when the dead zone is active in the late summer months. | 9 | Geochemistry |
In thermodynamics and chemical engineering, the vapor–liquid equilibrium (VLE) describes the distribution of a chemical species between the vapor phase and a liquid phase.
The concentration of a vapor in contact with its liquid, especially at equilibrium, is often expressed in terms of vapor pressure, which will be a partial pressure (a part of the total gas pressure) if any other gas(es) are present with the vapor. The equilibrium vapor pressure of a liquid is in general strongly dependent on temperature. At vapor–liquid equilibrium, a liquid with individual components in certain concentrations will have an equilibrium vapor in which the concentrations or partial pressures of the vapor components have certain values depending on all of the liquid component concentrations and the temperature. The converse is also true: if a vapor with components at certain concentrations or partial pressures is in vapor–liquid equilibrium with its liquid, then the component concentrations in the liquid will be determined dependent on the vapor concentrations and on the temperature. The equilibrium concentration of each component in the liquid phase is often different from its concentration (or vapor pressure) in the vapor phase, but there is a relationship. The VLE concentration data can be determined experimentally or approximated with the help of theories such as Raoults law, Daltons law, and Henry's law.
Such vapor–liquid equilibrium information is useful in designing columns for distillation, especially fractional distillation, which is a particular specialty of chemical engineers. Distillation is a process used to separate or partially separate components in a mixture by boiling (vaporization) followed by condensation. Distillation takes advantage of differences in concentrations of components in the liquid and vapor phases.
In mixtures containing two or more components, the concentrations of each component are often expressed as mole fractions. The mole fraction of a given component of a mixture in a particular phase (either the vapor or the liquid phase) is the number of moles of that component in that phase divided by the total number of moles of all components in that phase.
Binary mixtures are those having two components. Three-component mixtures are called ternary mixtures. There can be VLE data for mixtures with even more components, but such data is often hard to show graphically. VLE data is a function of the total pressure, such as 1 atm or at the pressure the process is conducted at.
When a temperature is reached such that the sum of the equilibrium vapor pressures of the liquid components becomes equal to the total pressure of the system (it is otherwise smaller), then vapor bubbles generated from the liquid begin to displace the gas that was maintaining the overall pressure, and the mixture is said to boil. This temperature is called the boiling point of the liquid mixture at the given pressure. (It is assumed that the total pressure is held steady by adjusting the total volume of the system to accommodate the specific volume changes that accompany boiling.) The boiling point at an overall pressure of 1 atm is called the normal boiling point of the liquid mixture. | 7 | Physical Chemistry |
The first benchtop detector was introduced in 2014 with detection capabilities between 120 - 240 nm. This portion of the ultraviolet spectrum had historically been restricted to bright source synchrotron facilities due to significant background absorption challenges inherent to working within the wavelength range. Further detector platform development has extended the wavelength detection range out from 120 - 430 nm. | 7 | Physical Chemistry |
The research in his laboratory focuses on cardiovascular and systemic metabolism and particularly on signaling mechanisms that link cardiac stress in diabetes, sepsis and ischemia with altered myocardial fatty acid metabolism. His published work focuses on the transcriptional regulation of proteins that underlie lipoprotein metabolism, cardiac and systemic fatty acid metabolism, and mitochondrial function. His work has identified the role of Krüppel-like factor 5 (KLF5) in the regulation of cardiac fatty acid metabolism in diabetes and ischemic heart failure, as well as how cardiac lipotoxicity leads to cardiac dysfunction, and the importance of cardiac fatty acid oxidation and mitochondrial integrity for the treatment of cardiac dysfunction in sepsis. | 1 | Biochemistry |
Because pump–probe microscopy does not rely on fluorescent targets, the modality takes advantage of multiple different types of multiphoton absorption. | 7 | Physical Chemistry |
Chromatography is a method chemists use to separate compounds. This type of filter paper has specific water flow rate and absorption speed to maximize the result of paper chromatography. The absorption speed of this type of filter paper is from 6 cm to 18 cm and the thickness is from 0.17 mm from 0.93 mm. | 3 | Analytical Chemistry |
Folchs clinical training at university included a period as an intern in the surgical clinic of Dr. Antoni Trias and as the sole physician in Almedret, a small Catalan village of 800 people. By contrast, the basic sciences consisted mainly of lectures with little opportunity for hands-on laboratory experience. Folch was fortunate to have the opportunity to study at the Institute of Physiology in Barcelona, which was founded by his uncle August Pi Sunyer and Jesus Maria Bellido and was dedicated to carrying out basic research using contemporary methods and ideas. He worked as an assistant to his cousin Cesar Pi Sunyer and by the time he received his M.D. degree, they had jointly published four papers on glycogen synthesis in three different languages (German, French, and Spanish). Folch also studied blood glucose and lactic acid metabolism under the direction of the man he considered his scientific mentor, Professor Rosend Carrasco Formiguera. He was the person who particularly encouraged the young Folch in his research. Folchs experiences at the Institute of Physiology intensified his interest in physiology and in clinical questions, particularly as they related to metabolic problems. Thanks to Carrasco's contacts, Francisco Duran Reynals, a biochemist at the Rockefeller Institute in New York, became interested in Folch and arranged for him to come to that institution as a volunteer.
In 1936, just before the Spanish Civil War broke out, he was accepted as a research fellow at the Rockefeller Institute in New York, and he took the post. At the insistence of his family (who had fought for the defeated Republican side—his brother Albert and sister Nuria had to exile into Mexico and his other brother Frederic spent a few months in prison after returning from exile in France), he decided to stay in the United States after the Civil War ended. | 1 | Biochemistry |
The complex changes that the Schwann cell undergoes during the process of myelination of peripheral nerve fibers have been observed and studied by many. The initial envelopment of the axon occurs without interruption along the entire extent of the Schwann cell. This process is sequenced by the in-folding of the Schwann cell surface so that a double membrane of the opposing faces of the in-folded Schwann cell surface is formed. This membrane stretches and spirally wraps itself over and over as the in-folding of the Schwann cell surface continues. As a result, the increase in the thickness of the extension of the myelin sheath in its cross-sectional diameter is easily ascertained. It is also evident that each of the consecutive turns of the spiral increases in size along the length of the axon as the number of turns increase. However, it is not clear whether or not the increase in length of the myelin sheath can be accounted solely by the increase in length of axon covered by each successive turn of the spiral, as previously explained.
At the junction of two Schwann cells along an axon, the directions of the lamellar overhang of the myelin endings are of opposite sense. This junction, adjacent of the Schwann cells, constitutes the region designated as the node of Ranvier. | 1 | Biochemistry |
The variable parameter of greatest interest in reaction progress kinetic analysis is the excess (e) of one substrate over another, given in units of molarity. The initial concentrations of two species in a reaction may be defined by:
:[B] = [A] + e
and, assuming a one-to-one reaction stoichiometry, that excess of one substrate over the other is quantitatively preserved over the course of the entire reaction such that:
:[B] = [A] + e
A similar set can be constructed for reactions with higher order stoichiometry in which case the excess varies predictably over the course of the reaction. While e may be any value (positive, negative, or zero) generally positive or negative values smaller in magnitude than one equivalent of substrate are used in reaction progress kinetic analysis. (One might note that pseudo-zero-order kinetics uses excess values much much greater in magnitude than the one equivalent of substrate).
Defining the parameter of excess (e) allows for the construction of same-excess experiments in which two or more runs of a kinetic experiment with different initial concentrations, but the same-excess allow one to artificially enter the reaction at any point. These experiments are critical for RPKA of catalytic reactions, as they enable one to probe a number of mechanistic possibilities including catalyst activation (induction periods), catalyst deactivation, and product inhibition described in further detail below. | 7 | Physical Chemistry |
In chemistry, intramolecular describes a process or characteristic limited within the structure of a single molecule, a property or phenomenon limited to the extent of a single molecule. | 0 | Organic Chemistry |
An expression vector has features that any vector may have, such as an origin of replication, a selectable marker, and a suitable site for the insertion of a gene like the multiple cloning site. The cloned gene may be transferred from a specialized cloning vector to an expression vector, although it is possible to clone directly into an expression vector. The cloning process is normally performed in Escherichia coli. Vectors used for protein production in organisms other than E.coli may have, in addition to a suitable origin of replication for its propagation in E. coli, elements that allow them to be maintained in another organism, and these vectors are called shuttle vectors. | 1 | Biochemistry |
The first generation carcerands are based on calixarene hemicarcerands with 4 alkyl substituents on the upper rim and 4 reactive substituents on the lower rim. The coupling of both hemicarcerands takes place through a spacer group. In the original 1985 publication two different hemicarcerands react, one with chloromethylene reactive groups and one with thiomethylene reactive groups in a nucleophilic displacement and the resulting spacer group is a dimethylsulfide (CHSCH). In this experiment the guests were the molecules already present in the reaction medium such as argon and dimethylformamide.
In another configuration the 4 lower rim functional groups are aldehydes which condense with O-Phenylenediamine to the corresponding di-imines. The 4 spacer groups connecting the two spheres are now much longer and consequently the internal cavity is much larger. Compounds trapped in the cavity are said to be held there by constrictive binding. They can be introduced by simply heating in neat solvent like hexachlorobutadiene (a fungicide). The half-life of the reverse process is 3.2 hours at 25 °C in CDCl by NMR analysis. Ferrocene can be introduced by heating with the hemicarcerand in a large bulky solvent such as tripiperidylphosphine oxide. The half-life for ferrocene liberation is 19.6 hours at 112 °C. | 6 | Supramolecular Chemistry |
Compounds that contain C-O bonds each possess differing reactivity based upon the location and hybridization of the C-O bond, owing to the electron-withdrawing effect of sp-hybridized oxygen (carbonyl groups) and the donating effects of sp-hybridized oxygen (alcohol groups). | 0 | Organic Chemistry |
Various effects of heat on the freezing of water were described by ancient scientists, including Aristotle: "The fact that the water has previously been warmed contributes to its freezing quickly: for so it cools sooner. Hence many people, when they want to cool water quickly, begin by putting it in the sun." Aristotles explanation involved antiperistasis': "...the supposed increase in the intensity of a quality as a result of being surrounded by its contrary quality."
Francis Bacon noted that "slightly tepid water freezes more easily than that which is utterly cold." René Descartes wrote in his Discourse on the Method, relating the phenomenon to his vortex theory: "One can see by experience that water that has been kept on a fire for a long time freezes faster than other, the reason being that those of its particles that are least able to stop bending evaporate while the water is being heated."
Scottish scientist Joseph Black investigated a special case of the phenomenon by comparing previously boiled with unboiled water; he found that the previously boiled water froze more quickly. Evaporation was controlled for. He discussed the influence of stirring on the results of the experiment, noting that stirring the unboiled water led to it freezing at the same time as the previously boiled water, and also noted that stirring the very-cold unboiled water led to immediate freezing. Joseph Black then discussed Daniel Gabriel Fahrenheit's description of supercooling of water, arguing that the previously boiled water could not be as readily supercooled. | 7 | Physical Chemistry |
Liden applied the HBV model to estimate the riverine transport of three different substances, nitrogen, phosphorus and suspended sediment in four different countries: Sweden, Estonia, Bolivia and Zimbabwe. The relation between internal hydrological model variables and nutrient transport was assessed. A model for nitrogen sources was developed and analysed in comparison with a statistical method. A model for suspended sediment transport in tropical and semi-arid regions was developed and tested. It was shown that riverine total nitrogen could be well simulated in the Nordic climate and riverine suspended sediment load could be estimated fairly well in tropical and semi-arid climates. The HBV model for material transport generally estimated material transport loads well. The main conclusion of the study was that the HBV model can be used to predict material transport on the scale of the drainage basin during stationary conditions, but cannot be easily generalised to areas not specifically calibrated. In a different work, Castanedo et al. applied an evolutionary algorithm to automated watershed model calibration.
The United States EPA developed the DSSAM Model to analyze water quality impacts from land use and wastewater management decisions in the Truckee River basin, an area which include the cities of Reno and Sparks, Nevada as well as the Lake Tahoe basin. The model satisfactorily predicted nutrient, sediment and dissolved oxygen parameters in the river. It is based on a pollutant loading metric called "Total Maximum Daily Load" (TMDL). The success of this model contributed to the EPAs commitment to the use of the underlying TMDL protocol in EPAs national policy for management of many river systems in the United States.
The DSSAM Model is constructed to allow dynamic decay of most pollutants; for example, total nitrogen and phosphorus are allowed to be consumed by benthic algae in each time step, and the algal communities are given a separate population dynamic in each river reach (e.g. based upon river temperature). Regarding stormwater runoff in Washoe County, the specific elements within a new xeriscape ordinance were analyzed for efficacy using the model. For the varied agricultural uses in the watershed, the model was run to understand the principal sources of impact, and management practices were developed to reduce in-river pollution. Use of the model has specifically been conducted to analyze survival of two endangered species found in the Truckee River and Pyramid Lake: the Cui-ui sucker fish (endangered 1967) and the Lahontan cutthroat trout (threatened 1970). | 2 | Environmental Chemistry |
Soil gases (soil atmosphere) are the gases found in the air space between soil components. The spaces between the solid soil particles, if they do not contain water, are filled with air. The primary soil gases are nitrogen, carbon dioxide and oxygen. Oxygen is critical because it allows for respiration of both plant roots and soil organisms. Other natural soil gases include nitric oxide, nitrous oxide, methane, and ammonia. Some environmental contaminants below ground produce gas which diffuses through the soil such as from landfill wastes, mining activities, and contamination by petroleum hydrocarbons which produce volatile organic compounds.
Gases fill soil pores in the soil structure as water drains or is removed from a soil pore by evaporation or root absorption. The network of pores within the soil aerates, or ventilates, the soil. This aeration network becomes blocked when water enters soil pores. Not only are both soil air and soil water very dynamic parts of soil, but both are often inversely related. | 9 | Geochemistry |
TI-1 antigens have an intrinsic B cell activating activity, that can directly cause proliferation and differentiation of B lymphocytes without T cell stimulation and independently of their BCR specificity. TI-1 antigens activate B-cells via Toll like receptors, which are expressed in humans on the surface of B lymphocytes after BCR stimulation. TI-1 antigens are classified as B-cell mitogens, because they induce numerous cell divisions. In higher concentrations, TI-1 antigens bind to BCR and TLR of various clones of B lymphocytes, which leads to production of multiclonal antibodies. But when the concentration of TI-1 is lower, it can activate only B lymphocytes with specific binding of TI-1 on their BCR, and leads to production of monoclonal antibodies.
This part of immune response may be important in some early stages of infection by extracellular pathogens, because it is rapidly activated and does not require T cell help or clonal maturation and expansion. An example of TI-1 antigen is lipopolysaccharide (LPS) or bacterial DNA. | 1 | Biochemistry |
This annex contains a list of elements by atomic number, giving the names and standard symbols of the chemical elements from atomic number 1 (hydrogen, H) to 109 (unnilennium, Une).
The list given in ISO 31-8:1992 was quoted from the 1998 IUPAC "Green Book" Quantities, Units and Symbols in Physical Chemistry and adds in some cases in parentheses the Latin name for information, where the standard symbol has no relation to the English name of the element. Since the 1992 edition of the standard was published, some elements with atomic number above 103 have been discovered and renamed. | 7 | Physical Chemistry |
It is believed that the enhanced concentration of hydroxyl present in irradiated water in the inner coolant loops of a light-water reactor must be taken into account when designing nuclear power plants, to prevent coolant loss resulting from corrosion. | 5 | Photochemistry |
Multiple-pass or long path absorption cells are commonly used in spectroscopy to measure low-concentration components or to observe weak spectra in gases or liquids. Several important advances were made in this area beginning in the 1930s, and research into a wide range of applications continues to the present day. | 7 | Physical Chemistry |
Levosulpiride, sold under the brand name SULPEPTA , is a potent prokinetic agent of the benzamide class. It is a selective antagonist of the dopamine D receptors and 5HT4 Agonism on both central and peripheral nervous systems. Levosulpiride is claimed to have mood elevating properties.
Chemically, it is the (S)-(−)-enantiomer of sulpiride. | 4 | Stereochemistry |
Indirect photocatalysis may occur via the production of a reactive species which then participates in another reaction. For example, photodegradation of certain compounds has been observed in the presence of kaolinite and montmorillonite, and this may proceed via the formation of reactive oxygen species at the surface of these clay minerals. Indeed, reactive oxygen species have been observed when soil surfaces are exposed to sunlight. The ability of irradiated soil to generate singlet oxygen was found to be independent of the organic matter content, and both the mineral and organic components of soil appear to contribute to this process. Indirect photolysis in soil has been observed to occur at depths of up to 2 mm due to migration of reactive species; in contrast, direct photolysis (in which the degraded compound itself absorbs light) was restricted to a "photic depth" of 0.2 to 0.4 mm. Like certain minerals, organic matter in solution, as well as particulate organic matter, may act as an indirect catalyst via formation of singlet oxygen which then reacts with other compounds. | 5 | Photochemistry |
MLSS is responsible for removing the biochemical oxygen demand make-up of a large portion of the solids that are retained in the activated sludge process within the water treatment process. They are the "active" part of the activated sludge process. Mixed liquor suspended solids are the solids under aeration. MLSS is measured by filtering a known volume of the mixed liquor sample, which is the same way that suspended solids are measured in wastewater. Some of the MLSS may be an inorganic material. Sometimes this may represent a large percentage of the solids present in the wastewater.
Environmental engineering focuses on the particles suspended in water and the suitable operation of water treatment plants. Therefore, it is important to measure the total mass of suspended solids, which is the MLSS, as well as the mass of organic matter suspended in the activated sludge unit. These measurements allow engineers to adjust the flow rate of return sludge from the secondary clarifier into the secondary treatment reactor. This ensures that influent organic matter will be treated with a correct concentration of microorganisms. | 3 | Analytical Chemistry |
The effects of a particular signal transduction pathway can be very different among distinct cell types. For example, the same signal transduction pathway may promote the survival of one cell type but the maturation of another. This depends both on the nature of a cell but also on its particular state which may change over the course of its lifetime. Identifying cell types where a signal transduction pathway is operational is a first step to uncovering potentially new properties of this pathway.
The STAT3-Ser/Hes3 signaling axis has been shown to operate on various cell types. So far, research has mostly focused on stem cells and cancerous tissue and, more recently, in the function of the endocrine pancreas:
:* Fetal and adult mouse and rat neural stem cells.
:* Adult monkey (rhesus macaque) neural stem cells.
:* Human cancer stem cells from glioblastoma multiforme.
:* In a human prostate cancer cell line, STAT3-Ser was shown to promote tumorigenesis independently of STAT3-Tyr.
:* Chromaffin progenitor cells of the bovine adrenal medulla.
:* Mouse insulinoma cells (MIN6 cell line) and mouse pancreatic islet cells.
:* Mouse embryonic fibroblasts (MEF) during reprogramming to the induced pluripotent stem cell state.
:* Human embryonic stem cells
:* Mouse neural stem cells derived from induced pluripotent stem cells. | 1 | Biochemistry |
Polymer solutions are used in producing fibers, films, glues, lacquers, paints, and other items made of polymer materials. Thin layers of polymer solution can be used to produce light-emitting devices. Guar polymer solution gels can be used in hydraulic fracturing ("fracking"). | 7 | Physical Chemistry |
The phenotypic features of the skeletal muscle in a patient with this disorder are muscle glycogen depletion, mitochondrial proliferation, and a marked predominance of slow-twitch, oxidative muscle fibres. The mutations in the glycogenin-1 gene GYG1 are also a cause of cardiomyopathy and arrhythmia. | 1 | Biochemistry |
Information from the British Drinking Water Inspectorate shows that drinking water in England is generally considered to be very hard, with most areas of England, particularly east of a line between the Severn and Tees estuaries, exhibiting above 200 ppm for the calcium carbonate equivalent. Water in London, for example, is mostly obtained from the River Thames and River Lea both of which derive a significant proportion of their dry weather flow from springs in limestone and chalk aquifers. Wales, Devon, Cornwall and parts of northwest England are softer water areas and range from 0 to 200 ppm. In the brewing industry in England and Wales, water is often deliberately hardened with gypsum in the process of Burtonisation.
Generally, water is mostly hard in urban areas of England where soft water sources are unavailable. Several cities built water supply sources in the 18th century as the industrial revolution and urban population burgeoned. Manchester was a notable such city in North West England and its wealthy corporation built several reservoirs at Thirlmere and Haweswater in the Lake District to the north. There is no exposure to limestone or chalk in their headwaters and consequently the water in Manchester is rated as very soft. Similarly, tap water in Birmingham is also soft as it is sourced from the Elan Valley Reservoirs in Wales, even though groundwater in the area is hard. | 3 | Analytical Chemistry |
The term "remineralization" is used in several contexts across different disciplines. The term is most commonly used in the medicinal and physiological fields, where it describes the development or redevelopment of mineralized structures in organisms such as teeth or bone. In the field of biogeochemistry, however, remineralization is used to describe a link in the chain of elemental cycling within a specific ecosystem. In particular, remineralization represents the point where organic material constructed by living organisms is broken down into basal inorganic components that are not obviously identifiable as having come from an organic source. This differs from the process of decomposition which is a more general descriptor of larger structures degrading to smaller structures.
Biogeochemists study this process across all ecosystems for a variety of reasons. This is done primarily to investigate the flow of material and energy in a given system, which is key to understanding the productivity of that ecosystem along with how it recycles material versus how much is entering the system. Understanding the rates and dynamics of organic matter remineralization in a given system can help in determining how or why some ecosystems might be more productive than others. | 9 | Geochemistry |
The fundamental difference between traditional cells and nanogap cells is their electric potential distribution. This is the premise of the "virtual breakdown" effect.
For electrochemical reactions with high-concentration electrolyte in the macrosystem, the Debye-length is quite small. Due to the screening effect almost all of the potential drop is confined within the small Debye-length region (or double layer region). The potential in bulk solution (far from the electrodes) does not change too much, meaning that there is nearly zero electric field inside the bulk solution. However, when the counter electrode is within the Debye-length region (i.e., nanogap electrochemical cells), two double layers from anode and cathode overlap with each other. The electrostatic potential inside the entire gap changes dramatically, meaning that the huge electric field is uniformly distributed across the entire gap. | 7 | Physical Chemistry |
Solid solution strengthening increases yield strength of the material by increasing the shear stress, , to move dislocations:
where c is the concentration of the solute atoms, G is the shear modulus, b is the magnitude of the Burger's vector, and is the lattice strain due to the solute. This is composed of two terms, one describing lattice distortion and the other local modulus change.
Here, the term that captures the local modulus change, a constant dependent on the solute atoms and is the lattice distortion term.
The lattice distortion term can be described as:
, where a is the lattice parameter of the material.
Meanwhile, the local modulus change is captured in the following expression:
, where G is shear modulus of the solute material. | 8 | Metallurgy |
The synthesis of ionic carbonyl complexes is possible by oxidation or reduction of the neutral complexes. Anionic metal carbonylates can be obtained for example by reduction of dinuclear complexes with sodium. A familiar example is the sodium salt of iron tetracarbonylate (NaFe(CO), Collmans reagent'), which is used in organic synthesis.
The cationic hexacarbonyl salts of manganese, technetium and rhenium can be prepared from the carbonyl halides under carbon monoxide pressure by reaction with a Lewis acid.
:Mn(CO)Cl + AlCl + CO → [][]
The use of strong acids succeeded in preparing gold carbonyl cations such as [Au(CO)], which is used as a catalyst for the carbonylation of alkenes. The cationic platinum carbonyl complex [Pt(CO)] can be prepared by working in so-called superacids such as antimony pentafluoride. Although CO is considered generally as a ligand for low-valent metal ions, the tetravalent iron complex [Cp*Fe] (16-valence electron complex) quantitatively binds CO to give the diamagnetic Fe(IV)-carbonyl [Cp*FeCO] (18-valence electron complex). | 0 | Organic Chemistry |
Lithium is recommended for the treatment of schizophrenic disorders only after other antipsychotics have failed; it has limited effectiveness when used alone. The results of different clinical studies of the efficacy of combining lithium with antipsychotic therapy for treating schizophrenic disorders have varied. | 1 | Biochemistry |
18-Crown-6 binds to a variety of small cations, using all six oxygens as donor atoms. Crown ethers can be used in the laboratory as phase transfer catalysts. Salts which are normally insoluble in organic solvents are made soluble by crown ether. For example, potassium permanganate dissolves in benzene in the presence of 18-crown-6, giving the so-called "purple benzene", which can be used to oxidize diverse organic compounds.
Various substitution reactions are also accelerated in the presence of 18-crown-6, which suppresses ion-pairing. The anions thereby become naked nucleophiles. For example, using 18-crown-6, potassium acetate is a more powerful nucleophile in organic solvents:
:[K(18-crown-6)]OAc + CHCHCl → CHCHOAc + [K(18-crown-6)]Cl
The first electride salt to be examined with X-ray crystallography, [Cs(18-crown-6)]·e, was synthesized in 1983. This highly air- and moisture-sensitive solid has a sandwich molecular structure, where the electron is trapped within nearly spherical lattice cavities. However, the shortest electron-electron distance is too long (8.68 Å) to make this material a conductor of electricity. | 6 | Supramolecular Chemistry |
Those who use lithium should receive regular serum level tests and should monitor thyroid and kidney function for abnormalities, as it interferes with the regulation of sodium and water levels in the body, and can cause dehydration. Dehydration, which is compounded by heat, can result in increasing lithium levels. The dehydration is due to lithium inhibition of the action of antidiuretic hormone, which normally enables the kidney to reabsorb water from urine. This causes an inability to concentrate urine, leading to consequent loss of body water and thirst.
Lithium concentrations in whole blood, plasma, serum or urine may be measured using instrumental techniques as a guide to therapy, to confirm the diagnosis in potential poisoning victims or to assist in the forensic investigation in a case of fatal overdosage. Serum lithium concentrations are usually in the range of 0.5–1.3 mmol/L (0.5–1.3 mEq/L) in well-controlled people, but may increase to 1.8–2.5 mmol/L in those who accumulate the drug over time and to 3–10 mmol/L in acute overdose.
Lithium salts have a narrow therapeutic/toxic ratio, so should not be prescribed unless facilities for monitoring plasma concentrations are available. Doses are adjusted to achieve plasma concentrations of 0.4 to 1.2 mmol /L on samples taken 12 hours after the preceding dose.
Given the rates of thyroid dysfunction, thyroid parameters should be checked before lithium is instituted and monitored after 3–6 months and then every 6–12 months.
Given the risks of kidney malfunction, serum creatinine and eGFR should be checked before lithium is instituted and monitored after 3–6 months at regular interval. Patients who have a rise in creatinine on three or more occasions, even if their eGFR is > 60 ml/min/
1.73m2 require further evaluation, including a urinalysis for haematuria, proteinuria, a review of their medical history with attention paid to cardiovascular, urological and medication history, and blood pressure control and management. Overt proteinuria should be further quantified with a urine protein to creatinine ratio. | 1 | Biochemistry |
There are four typically Organic field-effect transistor architectures: Top-gate, bottom-contacts; bottom-gate, top-contacts; bottom-gate, bottom-contacts; top-gate, top-contact.
In order to create the accumulation charge layer, a positive/negative direct current voltage is applied to the gate of the organic field-effect transistor (positive for the P type transistor, negative for the N type transistor). In order to modulate the charge, an AC voltage is given between the gate and source. It is important to notice that only mobile charge can follow the modulation and that the modulation frequency given to lock-in amplifier has to be synchronous. | 7 | Physical Chemistry |
The permanganate index is an assessment of water quality. It involves the detection of oxidation by potassium permanganate in an acid medium under hot conditions.
The method is to heat a sample in a boiling water-bath with a known amount of potassium permanganate and sulphuric acid for a fixed period time (10 min). Part of the permanganate will be reduced by oxidizable material in the sample. The consumed permanganate can be determined by addition of an excess of oxalate solution, followed by titration with permanganate. The method applies to waters having a chloride ion concentration of less than 300 mg/L. Samples having a permanganate index over 10 mg/L should be diluted before analysis. The lower limit of the optimum range of the test is 0.5 mg/L.
The permanganate index method is not recommended for waste water because some organic compounds are not oxidized or incompletely oxidized. | 3 | Analytical Chemistry |
Using a light microscope, it is just barely possible to see tiny green granules—which were named grana. With electron microscopy, it became possible to see the thylakoid system in more detail, revealing it to consist of stacks of flat thylakoids which made up the grana, and long interconnecting stromal thylakoids which linked different grana.
In the transmission electron microscope, thylakoid membranes appear as alternating light-and-dark bands, 8.5 nanometers thick.
The three-dimensional structure of the thylakoid membrane system haz been disputed. Many models have been proposed, the most prevalent being the helical model, in which granum stacks of thylakoids are wrapped by helical stromal thylakoids. Another model known as the bifurcation model, which was based on the first electron tomography study of plant thylakoid membranes, depicts the stromal membranes as wide lamellar sheets perpendicular to the grana columns which bifurcates into multiple parallel discs forming the granum-stroma assembly. The helical model was supported by several additional works, but ultimately it was determined in 2019 that features from both the helical and bifurcation models are consolidated by newly discovered left-handed helical membrane junctions. Likely for ease, the thylakoid system is still commonly depicted by older "hub and spoke" models where the grana are connected to each other by tubes of stromal thylakoids.
Grana consist of a stacks of flattened circular granal thylakoids that resemble pancakes. Each granum can contain anywhere from two to a hundred thylakoids, though grana with 10–20 thylakoids are most common. Wrapped around the grana are multiple parallel right-handed helical stromal thylakoids, also known as frets or lamellar thylakoids. The helices ascend at an angle of ~20°, connecting to each granal thylakoid at a bridge-like slit junction.
The stroma lamellae extend as large sheets perpendicular to the grana columns. These sheets are connected to the right-handed helices either directly or through bifurcations that form left-handed helical membrane surfaces. The left-handed helical surfaces have a similar tilt angle to the right-handed helices (~20°), but ¼ the pitch. Approximately 4 left-handed helical junctions are present per granum, resulting in a pitch-balanced array of right- and left-handed helical membrane surfaces of different radii and pitch that consolidate the network with minimal surface and bending energies. While different parts of the thylakoid system contain different membrane proteins, the thylakoid membranes are continuous and the thylakoid space they enclose form a single continuous labyrinth. | 5 | Photochemistry |
It was found that the stability of the complex of copper(II) with the macrocyclic ligand cyclam (1,4,8,11-tetraazacyclotetradecane) was much greater than expected in comparison to the stability of the complex with the corresponding open-chain amine.
This phenomenon was named the macrocyclic effect and it was also interpreted as an entropy effect. However, later studies suggested that both enthalpy and entropy factors were involved.
An important difference between macrocyclic ligands and open-chain (chelating) ligands is that they have selectivity for metal ions, based on the size of the cavity into which the metal ion is inserted when a complex is formed. For example, the crown ether 18-crown-6 forms much stronger complexes with the potassium ion, K than with the smaller sodium ion, Na.
In hemoglobin an iron(II) ion is complexed by a macrocyclic porphyrin ring. The article hemoglobin incorrectly states that oxyhemoglogin contains iron(III). It is now known that the iron(II) in hemoglobin is a low-spin complex, whereas in oxyhemoglobin it is a high-spin complex. The low-spin Fe ion fits snugly into the cavity of the porphyrin ring, but high-spin iron(II) is significantly larger and the iron atom is forced out of the plane of the macrocyclic ligand. This effect contributes the ability of hemoglobin to bind oxygen reversibly under biological conditions. In Vitamin B12 a cobalt(II) ion is held in a corrin ring. Chlorophyll is a macrocyclic complex of magnesium(II). | 7 | Physical Chemistry |
* Any non-racemic chiral substance is called scalemic. Scalemic materials can be enantiopure or enantioenriched.
* A chiral substance is enantiopure when only one of two possible enantiomers is present so that all molecules within a sample have the same chirality sense. Use of homochiral as a synonym is strongly discouraged.
* A chiral substance is enantioenriched or heterochiral when its enantiomeric ratio is greater than 50:50 but less than 100:0.
* Enantiomeric excess or e.e. is the difference between how much of one enantiomer is present compared to the other. For example, a sample with 40% e.e. of R contains 70% R and 30% S (70% − 30% = 40%). | 4 | Stereochemistry |
Before 1918, many professionals and scientists using the metric system of units defined the standard reference conditions of temperature and pressure for expressing gas volumes as being and . During those same years, the most commonly used standard reference conditions for people using the imperial or U.S. customary systems was and 14.696 psi (1 atm) because it was almost universally used by the oil and gas industries worldwide. The above definitions are no longer the most commonly used in either system of units. | 7 | Physical Chemistry |
Polymers with an all-carbon backbone, such as polyolefins, are usually resistant to hydrolysis. Condensation polymers like polyesters, polyamides, polyurethanes and polycarbonates can be degraded by hydrolysis of their carbonyl groups, to give lower molecular weight molecules. Such reactions are exceedingly slow at ambient temperatures, however, they remain a significant source of degradation for these materials, particularly in the marine environment. Swelling caused by the absorption of minute amounts of water can also cause environmental stress cracking, which accelerates degradation. | 7 | Physical Chemistry |
HEPPS (EPPS) is a buffering agent used in biology and biochemistry. The pKa of HEPPS is 8.00. It is ones of Good's buffers.
Research on mice with Alzheimers disease-like amyloid beta plaques has shown that HEPPS can cause the plaques to break up, reversing some of the symptoms in the mice. HEPPS was reported to dissociate amyloid beta oligomers in patients plasma samples enabling blood diagnosis of Alzheimer's disease. | 1 | Biochemistry |
Laser power beaming was envisioned by some at NASA as a stepping stone to further industrialization of space. In the 1980s, researchers at NASA worked on the potential use of lasers for space-to-space power beaming, focusing primarily on the development of a solar-powered laser. In 1989, it was suggested that power could also be usefully beamed by laser from Earth to space. In 1991, the SELENE project (SpacE Laser ENErgy) had begun, which included the study of laser power beaming for supplying power to a lunar base. The SELENE program was a two-year research effort, but the cost of taking the concept to operational status was too high, and the official project ended in 1993 before reaching a space-based demonstration. | 7 | Physical Chemistry |
A simple lipid is a fatty acid ester of different alcohols and carries no other substance. These lipids belong to a heterogeneous class of predominantly nonpolar compounds, mostly insoluble in water, but soluble in nonpolar organic solvents such as chloroform and benzene.
"Simple lipid" can refer to many different types of lipid depending on the classification system used, but the most basic definitions usually classify simple lipids as those that do not contain acyl groups. The simple lipids are then divided further into glycerides, cholesteryl esters, and waxes. The term was first used by in 1947 to separate "simple" greases and waxes from "mixed" triglycerides found in animal fats. | 1 | Biochemistry |
The Lauritzen–Hoffman growth theory breaks the kinetics of polymer crystallization into ultimately two rates. The model breaks down into the addition of monomers onto a growing surface. This initial step is generally associated with the nucleation of the polymer. From there, the kinetics become the rate which the polymer grows on the surface, or the lateral growth rate, in comparison with the growth rate onto the polymer extending the chain, the secondary nucleation rate. These two rates can result in three situations. | 7 | Physical Chemistry |
Willauer attended Berry College in Georgia, graduating with a bachelor's degree in chemistry in 1996. In mid-1999 she participated in the 11th International Conference on Partitioning in Aqueous Two-Phase Systems, held in Gulf Shores, Alabama. In 2002, she earned a doctorate in analytical chemistry from the University of Alabama, writing her thesis on "Fundamentals of phase behavior and solute partitioning in ABS and applications to the paper industry," the "ABS" an abbreviation for "aqueous biphasic systems". She began working with the NRL as an associate, then in 2004 she advanced to the position of research chemist. | 3 | Analytical Chemistry |
In acid catalysis and base catalysis, a chemical reaction is catalyzed by an acid or a base. By Brønsted–Lowry acid–base theory, the acid is the proton (hydrogen ion, H) donor and the base is the proton acceptor. Typical reactions catalyzed by proton transfer are esterifications and aldol reactions. In these reactions, the conjugate acid of the carbonyl group is a better electrophile than the neutral carbonyl group itself. Depending on the chemical species that act as the acid or base, catalytic mechanisms can be classified as either specific catalysis and general catalysis. Many enzymes operate by general catalysis. | 7 | Physical Chemistry |
Sulfides are typically prepared by alkylation of thiols. Alkylating agents include not only alkyl halides, but also epoxides, aziridines, and Michael acceptors.
Such reactions are usually conducted in the presence of a base, which converts the thiol into the more nucleophilic thiolate. Analogously, the reaction of disulfides with organolithium reagents produces thioethers:
Analogous reactions are known starting with Grignard reagents.
Alternatively, sulfides can be synthesized by the addition of a thiol to an alkene in the thiol-ene reaction:
This reaction is often catalysed by free radicals produced from a photoinitiator.
Sulfides can also be prepared by many other methods, such as the Pummerer rearrangement. Trialkysulfonium salts react with nucleophiles with a dialkyl sulfide as a leaving group:
This reaction is exploited in biological systems as a means of transferring an alkyl group. For example, S-adenosylmethionine acts as a methylating agent in biological S2 reactions.
An unusual but well tested method for the synthesis of thioethers involves addition of alkenes, especially ethylene across the S-Cl bond of sulfur dichloride. This method has been used in the production of bis(2-chloroethyl)sulfide, a mustard gas: | 0 | Organic Chemistry |
Fluxes have several serious drawbacks:
* Corrosivity, which is mostly due to the aggressive compounds of the activators; hygroscopic properties of the flux residues may aggravate the effects
* Interference with test equipment, which is due to the insulating residues deposited on the test contacts on electronic circuit boards
* Interference with machine vision systems when the layer of flux or its remains is too thick or improperly located
* Contamination of sensitive parts, e.g. facets of laser diodes, contacts of connectors and mechanical switches, and MEMS assemblies
* Deterioration of electrical properties of printed circuit boards, as soldering temperatures are above the glass transition temperature of the board material and flux components (e.g. glycols, or chloride and bromide ions) can diffuse into its matrix; e.g. water-soluble fluxes containing polyethylene glycol were demonstrated to have such impact
* Deterioration of high-frequency circuit performance by flux residues
* Deterioration of surface insulation resistance, which tends to be as much as three orders of magnitude lower than the bulk resistance of the material
* Electromigration and growth of whiskers between nearby traces, aided by ionic residues, surface moisture and a bias voltage
* The fumes liberated during soldering have adverse health effects, and volatile organic compounds can be outgassed during processing
* The solvents required for post-soldering cleaning of the boards are expensive and may have adverse environmental impact
In special cases the drawbacks are sufficiently serious to warrant using fluxless techniques. | 8 | Metallurgy |
As a society, there are certain steps we can take to ensure the minimization of eutrophication, thereby reducing its harmful effects on humans and other living organisms in order to sustain a healthy norm of living, some of which are as follows: | 2 | Environmental Chemistry |
Although the biosynthetic pathway of callystatin A has not been explicitly described, its polyketide structure indicates that the pathway must involve the polyketide synthase (PKS) enzyme complex. In general, in a modular fashion, an acetate starting unit in the loading module is extended by two carbons each time by the ketosynthase (KS) domain. The acyl groups are loaded onto the acyl carrier protein (ACP) with the help of the acyltransferase (AT) domain. Each module contains different combinations of the ketoreductase (KR), dehydratase (DH), and enoyl reductase (ER) domains that can modify and tailor the two-carbon subunits to form the resulting fatty acid chain. The final module contains a thioesterase (TE) domain that hydrolyzes the thioester bond to release the fatty acid chain and coenzyme A.
In the same manner, callystatin A biosynthesis starts with an acetate unit and elongates by either the malonate or the methyl malonate extender units, depending on the specific module. An exception to this is in module 7 where an ethyl malonate molecule replaces the other two options as the extender unit. It is assumed that the stereochemistry results from the activity of the domains and the absolute configuration is specified by the overall PKS complex. After being released from the thioesterase domain as a long fatty acid chain, the characteristic α,β-unsaturated lactone moiety is formed through a lactonization step to result in the final structure. | 0 | Organic Chemistry |
Biomethylation is the pathway for converting some heavy elements into more mobile or more lethal derivatives that can enter the food chain. The biomethylation of arsenic compounds starts with the formation of methanearsonates. Thus, trivalent inorganic arsenic compounds are methylated to give methanearsonate. S-adenosylmethionine is the methyl donor. The methanearsonates are the precursors to dimethylarsonates, again by the cycle of reduction (to methylarsonous acid) followed by a second methylation. Related pathways are found in the microbial methylation of mercury to methylmercury. | 0 | Organic Chemistry |
There are several differences in the regulation of metabolic control in eukaryotes and in prokaryotes. Prokaryotes vary the numbers of specific enzymes made in their cells in order to regulate gene expression, which is slow metabolic control, and also regulate enzymatic pathways through mechanisms such as feedback inhibition and allosteric regulation, which is rapid metabolic control. The genes of prokaryotes are grouped together based on similar functions into units called operons which consist of a promoter and an operator. The operator is the binding site for the repressor and thus has a function equivalent to the silencer region in Eukaryotic DNA. When a repressor protein is bound to the operator, RNA polymerase cannot bind to the promoter to initiate the transcription of the operon. | 1 | Biochemistry |
The nuclear protein in testis gene (i.e. NUTM1 gene) encodes (i.e. directs the synthesis of) a 1,132-amino acid protein termed NUT that is expressed almost exclusively in the testes, ovaries, and ciliary ganglion (i.e. a parasympathetic ganglion of nerve cells located just behind the eye). NUT protein facilitates the acetylation of chromatin (i.e. DNA-protein bundles) by histone acetyltransferase EP300 in testicular spermatids (cells that mature into sperms). This acetylation is a form of chromatin remodeling which compacts spermatid chromatin, a critical step required for the normal conduct of spermatogenesis, i.e. the maturation of spermatids into sperm. Male mice that lacked the mouse Nutm1 gene using a gene knockout method had abnormally small testes, lacked sperm in their cauda epididymis (i.e. tail of the epididymis which contains sperm in fertile male mice), and were completely sterile. These findings indicate that Nutm1 gene is essential for the development of normal fertility in male mice and suggest that the NUTM1 gene may play a similar role in men.
The NUTM1 gene is located in band 14 on the long (or "q") arm of chromosome 15. In the early 1990s, this gene was implicated in the development of certain epithelial cell cancers that: a) occurred in the midline structures of young people, b) were rapidly fatal, and c) consisted of poorly differentiated (i.e. not resembling any particular cell type), immature-appearing cells containing a BRD4-NUTM1 fusion gene. BRD4 is the bromodomain-containing protein 4 gene. A fusion gene is an abnormal gene consisting of parts from two different genes that form as a result of a large scale gene mutation such as a chromosomal translocation, interstitial deletion, or inversion. The BRD4-NUTM1 fusion gene is a translocation that encodes a fusion protein that has merged most of the protein coding region of the NUTM1 gene with a large part of the BRD4 gene located in band 13 on the short (i.e. "q") arm of chromosome 19. This translocation is notated as t(15;19)(q13, p13.1).
BRD4 protein recognizes acetylated lysine residues on proteins and by doing so participates in the regulation of DNA replication, DNA transcription, and thereby key cellular processes involved in the development of neoplasms (i.e. malignant or benign tissue growths). The product of the BRD4-NUTM1 fusion gene, BRD4-NUT protein, stimulates the expression of at least 4 relevant genes, MYC, TP63, SOX2, and MYB in cultured cells. All four of these genes are oncogenes, i.e., genes that when overexpressed and/or overly active promote the development of certain types of cancers. Overexpression of the MYC and SOX2 genes can also act to maintain cells in an undifferentiated stem cell-like state similar to the cells in the neoplasms driven by the BRD4-NUTM1 fusion gene. It is generally accepted that the BRD4-NUT protein promotes these neoplasms by maintaining their neoplastic cells in a perpetually undifferentiated, proliferative state. Further studies are needed to confirm and expand these views and to determine if any of the overexpressed gene products of the BRD4-NUT protein contribute to the development and/or progression, or can serve as targets for the treatment, of the neoplasms associated with the BRD4-NUTM1 fusion gene. These questions also apply to a wide range of neoplasms that have more recently been associated with the NUTM1 gene fused to other genes. | 1 | Biochemistry |
An EOSFET or electrolyte–oxide–semiconductor field-effect transistor is a FET, like a MOSFET, but with an electrolyte solution replacing the metal for the detection of neuronal activity. Many EOSFETs are integrated in a neurochip. | 7 | Physical Chemistry |
The IIR holds international conferences and congresses on key themes which include:
* natural refrigerants
* the cold chain
* magnetic refrigeration
* cryogenics
* compressors
* phase-change materials and slurries
* thermophysical properties and transfer processes of refrigerants
* new technologies | 7 | Physical Chemistry |
Hydroformylation of prochiral alkenes creates new stereocenters. Using chiral phosphine ligands, the hydroformylation can be tailored to favor one enantiomer. Thus, for example, dexibuprofen, the (+)−(S)-enantiomer of ibuprofen, can be produced by enantioselective hydroformylation followed by oxidation. | 0 | Organic Chemistry |
8-Hydroxyguanosine is an RNA nucleoside which is an oxidative derivative of guanosine. Measurement of the levels of 8-hydroxyguanosine is used as a biomarker of oxidative stress causing RNA damage. | 1 | Biochemistry |
The mold cavity of a casting does not reflect the exact dimensions of the finished part due to a number of reasons. These modifications to the mold cavity are known as allowances and account for patternmaker's shrinkage, draft, machining, and distortion. In non-expendable processes, these allowances are imparted directly into the permanent mold, but in expendable mold processes they are imparted into the patterns, which later form the mold cavity. Note that for non-expendable molds an allowance is required for the dimensional change of the mold due to heating to operating temperatures.
For surfaces of the casting that are perpendicular to the parting line of the mold a draft must be included. This is so that the casting can be released in non-expendable processes or the pattern can be released from the mold without destroying the mold in expendable processes. The required draft angle depends on the size and shape of the feature, the depth of the mold cavity, how the part or pattern is being removed from the mold, the pattern or part material, the mold material, and the process type. Usually the draft is not less than 1%.
The machining allowance varies drastically from one process to another. Sand castings generally have a rough surface finish, therefore need a greater machining allowance, whereas die casting has a very fine surface finish, which may not need any machining tolerance. Also, the draft may provide enough of a machining allowance to begin with.
The distortion allowance is only necessary for certain geometries. For instance, U-shaped castings will tend to distort with the legs splaying outward, because the base of the shape can contract while the legs are constrained by the mold. This can be overcome by designing the mold cavity to slope the leg inward to begin with. Also, long horizontal sections tend to sag in the middle if ribs are not incorporated, so a distortion allowance may be required.
Cores may be used in expendable mold processes to produce internal features. The core can be of metal but it is usually done in sand. | 8 | Metallurgy |
Carbon-carbon bond activation refers to the breaking of carbon-carbon bonds in organic molecules. This process is an important tool in organic synthesis, as it allows for the formation of new carbon-carbon bonds and the construction of complex organic molecules. However, C–C bond activation is challenging mainly for the following reasons: (1) C-H bond activation is a competitive process of C-C activation, which is both energetically and kinetically more favorable; (2) the accessibility of the transition metal center to C–C bonds is generally difficult due to its hidden nature; (3) relatively high stability of the C–C bond (90 kcal/mol). As a result, in the early stage, most examples of C-C activation are of stringed ring systems, which makes C-C activation more favorable by increasing the energy of the starting material. However, C-C activation of unstrained C-C bonds has remained challenging until the recent two decades. | 0 | Organic Chemistry |
The process involves transesterification of sucrose and triglycerides under a basic condition at 90 °C. DMF was used as a solvent at first, but was later substituted with dimethyl sulfoxide or DMSO, which is less hazardous and cheaper. This process produces a mixture of sucrose monoesters and more substituted esters at about a 5:1 ratio.
The other method involves transesterification of sucrose and fatty acid methyl ester using sodium methoxide as a basic catalyst. The by-product methanol can be removed via distillation to drive the equilibrium to favor sucrose esters.
The process does not work for food industry because DMF is poisonous and may not be used in food production. | 0 | Organic Chemistry |
Pseudogenes are mostly former genes that have become non-functional due to mutation but the term also refers to inactive DNA sequences that are derived from RNAs produced by functional genes (processed pseudogenes). Pseudogenes are only a small fraction of noncoding DNA in prokaryotic genomes because they are eliminated by negative selection. In some eukaryotes, however, pseudogenes can accumulate because selection is not powerful enough to eliminate them (see Nearly neutral theory of molecular evolution).
The human genome contains about 15,000 pseudogenes derived from protein-coding genes and an unknown number derived from noncoding genes. They may cover a substantial fraction of the genome (~5%) since many of them contain former intron sequences.
Pseudogenes are junk DNA by definition and they evolve at the neutral rate as expected for junk DNA. Some former pseudogenes have secondarily acquired a function and this leads some scientists to speculate that most pseudogenes are not junk because they have a yet-to-be-discovered function. | 1 | Biochemistry |
Polysome profiling is a technique in molecular biology that is used to study the association of mRNAs with ribosomes. It is important to note that this technique is different from ribosome profiling. Both techniques have been reviewed and both are used in analysis of the translatome, but the data they generate are at very different levels of specificity. When employed by experts, the technique is remarkably reproducible: the 3 profiles in the first image are from 3 different experiments. | 1 | Biochemistry |
There are also many other descriptive terms, often with very specialized usage and confined to specific taxonomic groups. The conspicuousness of veins depends on a number of features. These include the width of the veins, their prominence in relation to the lamina surface and the degree of opacity of the surface, which may hide finer veins. In this regard, veins are called obscure and the order of veins that are obscured and whether upper, lower or both surfaces, further specified.
Terms that describe vein prominence include bullate, channelled, flat, guttered, impressed, prominent and recessed (Fig. 6.1 Hawthorne & Lawrence 2013). Veins may show different types of prominence in different areas of the leaf. For instance Pimenta racemosa has a channelled midrib on the upper surface, but this is prominent on the lower surface.
Describing vein prominence:
;Bullate: Surface of leaf raised in a series of domes between the veins on the upper surface, and therefore also with marked depressions. e.g. Rytigynia pauciflora, Vitis vinifera
;Channelled (canalicululate): Veins sunken below the surface, resulting in a rounded channel. Sometimes confused with "guttered" because the channels may function as gutters for rain to run off and allow drying, as in many Melastomataceae. e.g. (see) Pimenta racemosa (Myrtaceae), Clidemia hirta (Melastomataceae).
;Guttered: Veins partly prominent, the crest above the leaf lamina surface, but with channels running along each side, like gutters
;Impressed: Vein forming raised line or ridge which lies below the plane of the surface which bears it, as if pressed into it, and are often exposed on the lower surface. Tissue near the veins often appears to pucker, giving them a sunken or embossed appearance
;Obscure: Veins not visible, or not at all clear; if unspecified, then not visible with the naked eye. e.g. Berberis gagnepainii. In this Berberis, the veins are only obscure on the undersurface.
;Prominent: Vein raised above surrounding surface so to be easily felt when stroked with finger. e.g. (see) Pimenta racemosa, Spathiphyllum cannifolium
;Recessed: Vein is sunk below the surface, more prominent than surrounding tissues but more sunken in channel than with impressed veins. e.g. Viburnum plicatum.
Describing other features:
;Plinervy (plinerved): More than one main vein (nerve) at the base. Lateral secondary veins branching from a point above the base of the leaf. Usually expressed as a suffix, as in 3-plinerved or triplinerved leaf. In a 3-plinerved (triplinerved) leaf three main veins branch above the base of the lamina (two secondary veins and the main vein) and run essentially parallel subsequently, as in Ceanothus and in Celtis. Similarly, a quintuplinerve (five-veined) leaf has four secondary veins and a main vein. A pattern with 3–7 veins is especially conspicuous in Melastomataceae. The term has also been used in Vaccinieae. The term has been used as synonymous with acrodromous, palmate-acrodromous or suprabasal acrodromous, and is thought to be too broadly defined.
;Scalariform: Veins arranged like the rungs of a ladder, particularly higher order veins
;Submarginal: Veins running close to leaf margin
;Trinerved: 2 major basal nerves besides the midrib | 5 | Photochemistry |
Initially, the presence of chlororespiration as a legitimate respiratory process in plants was heavily doubted. However, experimentation on Chlamydomonas reinhardtii, discovered Plastoquinone (PQ) to be a redox carrier. The role of this redox carrier is to transport electrons from the NAD(P)H enzyme to oxygen molecules on the thylakoid membrane. Using this cyclic electron chain around photosystem one (PS I), chlororespiration compensates for the lack of light. This cyclic pathway also allows electrons to re-enter the PQ pool through NAD(P)H enzyme activity and production, which is then used to supply ATP molecules (energy) to plant cells.
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In the year 2002, the discovery of the molecules; plastid terminal oxidase (PTOX) and NDH complexes have revolutionised the concept of chlororespiration. Using evidence from experimentation on the plant species Rosa Meillandina, this latest model observes the role of PTOX to be an enzyme that prevents the PQ pool from over-reducing, by stimulating its reoxidation. Whereas, the NDH complexes are responsible for providing a gateway for electrons to form an ETC. The presence of such molecules are apparent in the non-appressed thylakoid membranes of higher order plants like Rosa Meillandina. | 1 | Biochemistry |
* Protein NMR Spectroscopy : Principles and Practice (1995) John Cavanagh, Wayne J. Fairbrother, Arthur G. Palmer III, Nicholas J. Skelton, Academic Press | 7 | Physical Chemistry |
The PageRank algorithm has several applications in biochemistry. ("PageRank" is an algorithm used in Google Search for ranking websites in their results, but it has been adopted for other purposes also. According to Google, PageRank works by "counting the number and quality of links to a page to determine a rough estimate of how important the website is," the underlying assumption being that more important websites are likely to receive more links from other websites.) | 1 | Biochemistry |
A benzene solution of 1 eq of diethylaluminum chloride was added dropwise at 0° to a solution of 1 eq of lithium 2,2,6,6-tetramethylpiperidide prepared in the usual fashion in benzene. The resulting slurry was stirred for 30 minutes and used immediately.
To a stirred mixture of 0.004 mol of diethylaluminum 2,2,6,6-tetramethylpiperidide in 10 mL of benzene at 0 °C was added dropwise over 5 minutes a solution of 0.18 g (0.001 mol) of epoxide in 3 mL of benzene. The mixture was stirred at 0 °C until analysis indicated the absence of starting material. The reaction was quenched by the addition of ice-cold 1 N hydrochloric acid. The organic layer was separated, and the aqueous layer was extracted with ether. The organic layers were combined, washed with brine, dried, and concentrated. The residue was purified by preparative TLC (R 0.22 in 1:2 ether–hexane) to give 99% of (E)-2-cyclododecenol: IR (neat) 3330–3370, 1465, 1450, 970 cm; NMR (CCl) δ 3.73–4.20 (1, m), 4.97–5.82 (2, m); mass spectrum (m/z) 182 (16), 164 (13), 139 (32), 125 (46), and 98 (100). | 0 | Organic Chemistry |
Drug repurposing and chiral switches are part of the secondary pharmaceuticals strategy. The COVID-19 pandemic has increased drug repurposing and this approach suggests combining the two strategies for better results. This combination strategy is not new, but has not been intentional until now. The combination strategy may improve pharmacology, patents, reduce costs, speed up approval times, and increase regulatory exclusivities. The benefits of the combination strategy include superior pharmacology, stronger patents, shorter approval times, and more exclusivity. Patenting this combination strategy is not considered evergreening, product hopping, or me-too. This perspective calls for a comprehensive search for worldwide-approved racemic drugs to be repurposed and combined with chiral switches. | 4 | Stereochemistry |
α- and β-amylases are important in brewing beer and liquor made from sugars derived from starch. In fermentation, yeast ingests sugars and excretes ethanol. In beer and some liquors, the sugars present at the beginning of fermentation have been produced by "mashing" grains or other starch sources (such as potatoes). In traditional beer brewing, malted barley is mixed with hot water to create a "mash", which is held at a given temperature to allow the amylases in the malted grain to convert the barley's starch into sugars. Different temperatures optimize the activity of alpha or beta amylase, resulting in different mixtures of fermentable and unfermentable sugars. In selecting mash temperature and grain-to-water ratio, a brewer can change the alcohol content, mouthfeel, aroma, and flavor of the finished beer.
In some historic methods of producing alcoholic beverages, the conversion of starch to sugar starts with the brewer chewing grain to mix it with saliva. This practice continues to be practiced in home production of some traditional drinks, such as chhaang in the Himalayas, chicha in the Andes and kasiri in Brazil and Suriname. | 1 | Biochemistry |
In 1909, parents sent Alexander to P. N. Strakhovs private Moscow gymnasium, which he graduated with honors. In 1917, he entered the natural department of the Faculty of Physics and Mathematics at Moscow University. There were no entrance exams due to the passage of the revolution. Studying in this difficult time required great self-sacrifice and fanatical dedication. They studied in unheated rooms and there was not enough laboratory equipment. Transport was bad, and sometimes Alexander had to walk on foot to the university from Sokolniki. In 1920, classes at Moscow State University were frozen due to problems with heating, and Nesmeyanov entered the Military Pedagogical Academy on Bolshaya Gruzinskaya Street. At the same time, he worked in the laboratories of the Shanyavsky Moscow City Peoples University. By the end of 1920, Alexander Nikolayevich returned to studies at the academy and at Moscow University, where heating had already been restored. He meets the "future scientific mentor", Professor N. D. Zelinsky. While he was working as a night watchman at the faculty, Nesmeyanov lived in the laboratory of N. D. Zelinsky and devoting all his time to scientific experiments. | 0 | Organic Chemistry |
There are several magazines and publications that cover topics directly related to the Chesapeake Bay and life and tourism within the Bay region:
*The Bay Journal provides environmental news for the Chesapeake Bay watershed region.
*Bay Weekly is the Chesapeake Bay region's independent newspaper.
*The Capital, a newspaper based in Annapolis, reports about news pertaining to the Western Shore of Maryland and the Annapolis area.
*Chesapeake Bay Magazine and PropTalk focus on powerboating in the Bay, and SpinSheet focuses on sailing.
*Whats Up' Magazine is a free monthly publication with special issues focused on Annapolis and the Eastern Shore. | 2 | Environmental Chemistry |
PGC-1α is thought to be a master integrator of external signals. It is known to be activated by a host of factors, including:
# Reactive oxygen species and reactive nitrogen species, both formed endogenously in the cell as by-products of metabolism but upregulated during times of cellular stress.
#Fasting can also increase gluconeogenic gene expression, including hepatic PGC-1α.
# It is strongly induced by cold exposure, linking this environmental stimulus to adaptive thermogenesis.
# It is induced by endurance exercise and recent research has shown that PGC-1α determines lactate metabolism, thus preventing high lactate levels in endurance athletes and making lactate as an energy source more efficient.
# cAMP response element-binding (CREB) proteins, activated by an increase in cAMP following external cellular signals.
# Protein kinase B (Akt) is thought to downregulate PGC-1α, but upregulate its downstream effectors, NRF1 and NRF2. Akt itself is activated by PIP, often upregulated by PI3K after G protein signals. The Akt family is also known to activate pro-survival signals as well as metabolic activation.
# SIRT1 binds and activates PGC-1α through deacetylation inducing gluconeogenesis without affecting mitochondrial biogenesis.
PGC-1α has been shown to exert positive feedback circuits on some of its upstream regulators:
# PGC-1α increases Akt (PKB) and Phospho-Akt (Ser 473 and Thr 308) levels in muscle.
# PGC-1α leads to calcineurin activation.
Akt and calcineurin are both activators of NF-kappa-B (p65). Through their activation, PGC-1α seems to activate NF-kappa-B. Increased activity of NF-kappa-B in muscle has recently been demonstrated following induction of PGC-1α. The finding seems to be controversial. Other groups found that PGC-1s inhibit NF-kappa-B activity. The effect was demonstrated for PGC-1 alpha and beta.
PGC-1α has also been shown to drive NAD biosynthesis to play a large role in renal protection in acute kidney injury. | 1 | Biochemistry |
*BAT1 aka DDX39B which is involved in RNA splicing
*BSG Basigin Immunoglobulin Superfamily, extracellular metalloproteinase
*MIF macrophage migration inhibitory factor
*TAPBP | 1 | Biochemistry |
Pulvermacher patented the chain battery in the US in 1853. This was soon followed by the wearable chain battery belt, or electric belt. Electric belts became enormously popular in the US, far more so than in Europe. This led to the company headquarters being moved to Cincinnati by the 1880s as the Pulvermacher Galvanic Company, but still calling themselves Pulvermacher's of London for the prestige of a European connection. Early models had to be soaked in vinegar before use as in England, but later on models that worked purely by galvanic action with body sweat were introduced. Since the device was being sold essentially as a quack cure it was only necessary to generate enough electricity that the wearer could feel it, no matter how slightly, and know that it was working.
Electric belts were made for every conceivable part of the human anatomy: limbs, abdomen, chest, neck – sometimes all worn at the same time. Pulvermacher even had a model designed to attach to the male genitals in a special sac which was claimed to cure impotence and erectile dysfunction. Pulvermacher promoted a theory that loss of "male vigour" in later life was a consequence of masturbation in early life and that a limited supply of semen, which provided the vigour, would run out before time if wasted. Pulvermacher's device was meant to address this shortcoming.
Competition was very intense for this lucrative market and the claimed benefits became ever more extravagant. Amongst Pulvermachers many competitors in the US were the German Electric Belt Company (actually New York based), Dr Crystals, Dr. Horns, Addisons, Edsons, Edisons, Owens and Heidelbergs. Edisons was founded by Thomas Edison Junior, whose father was the famous Thomas Edison. Owens was originally New York based but expanded across the country until they were put out of business due to fraud. In Europe too, there were competitors. The Medical Battery Company of England made a popular belt. They attempted (unsuccessfully) to sue the Electrical Review when that paper accused them of quackery in 1892. The Iona Company, an Oregon-based company founded by Henry Gaylord Wilshire was still selling belts in 1926 and making large profits: $36,000 ($ inflation adjusted) net from 2,445 belts in five months. By the end of the 1920s the electric belts popularity had severely declined (but not the publics appetite for other quack electric cures) and the scientific market had long since moved on to better electrical generation technology than chain batteries. | 7 | Physical Chemistry |
Incongruent transition, in chemistry, is a mass transition between two phases which involves a change in chemical composition. This is contrasted with congruent transition, for which the composition remains the same.
The transition may be that of melting, vaporization or allotropism. The concept is also often extended to related phenomena, for example, incongruent dissolution of a solid by a liquid solvent, which is often encountered in geology.
The term "phase decomposition" is sometimes used to describe incongruent transition. However, it has to be kept in mind that incongruent transition is described by an equilibrium.
For an example, see incongruent melting. | 7 | Physical Chemistry |
In chiral column chromatography the stationary phase is made chiral with similar resolving agents as described above. | 4 | Stereochemistry |
Signal transducer and activator of transcription 1 (STAT1) is a transcription factor which in humans is encoded by the STAT1 gene. It is a member of the STAT protein family. | 1 | Biochemistry |
The most commonly applied methods are MS and HPLC, in which the glycan part is cleaved either enzymatically or chemically from the target and subjected to analysis. In case of glycolipids, they can be analyzed directly without separation of the lipid component.
N-glycans from glycoproteins are analyzed routinely by high-performance-liquid-chromatography (reversed phase, normal phase and ion exchange HPLC) after tagging the reducing end of the sugars with a fluorescent compound (reductive labeling).
A large variety of different labels were introduced in the recent years, where 2-aminobenzamide (AB), anthranilic acid (AA), 2-aminopyridin (PA), 2-aminoacridone (AMAC) and 3-(acetylamino)-6-aminoacridine (AA-Ac) are just a few of them.
O-glycans are usually analysed without any tags, due to the chemical release conditions preventing them to be labeled.
Fractionated glycans from high-performance liquid chromatography (HPLC) instruments can be further analyzed by MALDI-TOF-MS(MS) to get further information about structure and purity. Sometimes glycan pools are analyzed directly by mass spectrometry without prefractionation, although a discrimination between isobaric glycan structures is more challenging or even not always possible. Anyway, direct MALDI-TOF-MS analysis can lead to a fast and straightforward illustration of the glycan pool.
In recent years, high performance liquid chromatography online coupled to mass spectrometry became very popular. By choosing porous graphitic carbon as a stationary phase for liquid chromatography, even non derivatized glycans can be analyzed. Electrospray ionisation (ESI) is frequently used for this application. | 0 | Organic Chemistry |
Fic-1 is the only Fic protein present in the genetic code of C. elegans. It is primarily found in the ER nuclear envelope of adult germline cells and embryotic cells, but small amounts may be found within the cytoplasm. This extra-ER pool of FICD-1s is credited with AMPylation of core histones and eEF1-A type translation factors within the nematode.
Though varying AMPylation levels did not create any noticeable effects within the nematodes behaviour or physiology, Fic-1 knockout worms were more susceptible to infection by Pseudomonas aeruginosa' compared to the counterparts with active Fic-1 domains, implying a link between AMPylation of cellular targets and immune responses within nematodes. | 1 | Biochemistry |
Oxhide ingots are heavy (20–30 kg) metal slabs, usually of copper but sometimes of tin, produced and widely distributed during the Mediterranean Late Bronze Age (LBA). Their shape resembles the hide of an ox with a protruding handle in each of the ingot’s four corners. Early thought was that each ingot was equivalent to the value of one ox. However, the similarity in shape is simply a coincidence. The ingots' producers probably designed these protrusions to make the ingots easily transportable overland on the backs of pack animals. Complete or partial oxhide ingots have been discovered in Sardinia, Crete, Peloponnese, Cyprus, Cannatello in Sicily, Boğazköy in Turkey (ancient Hattusa, the Hittite capital), Qantir in Egypt (ancient Pi-Ramesses), and Sozopol in Bulgaria. Archaeologists have recovered many oxhide ingots from two shipwrecks off the coast of Turkey (one off Uluburun and one in Cape Gelidonya). | 8 | Metallurgy |
All materials, even those not usually classified as adhesives, experience an attraction to other materials simply due to dispersion forces. In many situations, these attractions are trivial; however, dispersive adhesion plays a dominant role in various adhesive systems, especially when multiple forms of intermolecular attractions are present. It has been shown by experimental methods that the dispersive mechanism of adhesion plays a large role in the overall adhesion of polymeric systems in particular. | 6 | Supramolecular Chemistry |
In Arabidopsis, the protein DWF1 plays an enzymatic role in the biosynthesis of brassinosteroids, steroid hormones in plants that are required for growth. An interaction occurs between CaM and DWF1, and DWF1 being unable to bind CaM is unable to produce a regular growth phenotype in plants. Hence, CaM is essential for the DWF1 function in plant growth.
CaM binding proteins are also known to regulate reproductive development in plants. For instance, the CaM-binding protein kinase in tobacco acts as a negative regulator of flowering. However, these CaM-binding protein kinase are also present in the shoot apical meristem of tobacco and a high concentration of these kinases in the meristem causes a delayed transition to flowering in the plant.
S-locus receptor kinase (SRK) is another protein kinase that interacts with CaM. SRK is involved in the self-incompatibility responses involved in pollen-pistil interactions in Brassica.
CaM targets in Arabidopsis are also involved in pollen development and fertilization. Ca transporters are essential for pollen tube growth. Hence, a constant Ca gradient is maintained at the apex of pollen tube for elongation during the process of fertilization. Similarly, CaM is also essential at the pollen tube apex, where its primarily role involves the guidance of the pollen tube growth. | 1 | Biochemistry |
Acid rain has been shown to have adverse impacts on forests, freshwaters and soils, killing insect and aquatic life-forms as well as causing damage to buildings and having impacts on human health. | 2 | Environmental Chemistry |
Species community assemblages and changes therein can help researchers to infer changes in the health of an ecosystem. In typical unpolluted temperate streams of Europe and North America, certain insect taxa predominate. Mayflies (Ephemeroptera), caddisflies (Trichoptera), and stoneflies (Plecoptera) are the most common insects in these undisturbed streams. In contrast, in rivers disturbed by urbanization, agriculture, forestry, and other perturbations, flies (Diptera), and especially midges (family Chironomidae) predominate. | 2 | Environmental Chemistry |
Methylmercury (sometimes methyl mercury) is an organometallic cation with the formula . It is the simplest organomercury compound. Methylmercury is extremely toxic, and its derivatives are the major source of organic mercury for humans. It is a bioaccumulative environmental toxicant with a 50-day half-life. | 0 | Organic Chemistry |
In the United Kingdom, the Hallmarking Act 1973 makes it an offence to describe as platinum, gold or silver an item which is not hallmarked as appropriate or exempt from hallmarking. In July 2009, following a proposal by the British Hallmarking Council, an amendment to the Act also brought palladium under the hallmarking regime.
The first UK assay office was Goldsmiths Hall, founded around 1300, and where the term "hallmarking" originates, meaning "marked in Goldsmiths Hall". Since then, there have been ten assay offices in the UK.
There are four remaining assay offices in the UK: | 3 | Analytical Chemistry |
Metallurgy in pre-Columbian America is the extraction, purification and alloying of metals and metal crafting by Indigenous peoples of the Americas prior to European contact in the late 15th century. Indigenous Americans had been using native metals from ancient times, with recent finds of gold artifacts in the Andean region dated to 2155–1936 BCE,
and North American copper finds being dated to approximately 5000 BCE.
The metal would have been found in nature without the need for smelting, and shaped into the desired form using hot and cold hammering without chemical alteration or alloying. To date "no one has found evidence that points to the use of melting, smelting and casting in prehistoric eastern North America."
In South America the case is quite different. Indigenous South Americans had full metallurgy with smelting and various metals being purposely alloyed. Metallurgy in Mesoamerica and western Mexico may have developed following contact with South America through Ecuadorian marine traders. | 8 | Metallurgy |
Cram described the interior of the container compound as the inner phase in which radically different reactivity was observed. He used a hemicarcerand to isolate highly unstable, antiaromatic cyclobutadiene at room temperature. The hemicarcerand stabilizes guests within its cavity by preventing their reaction with other molecules. | 6 | Supramolecular Chemistry |
Alkenes undergo "hydroesterification" in the presence of metal carbonyl catalysts. Esters of propanoic acid are produced commercially by this method:
A preparation of methyl propionate is one illustrative example.
The carbonylation of methanol yields methyl formate, which is the main commercial source of formic acid. The reaction is catalyzed by sodium methoxide: | 0 | Organic Chemistry |
Hassan Naim is a Lebanese-Swiss biochemist. He currently holds the position of Director of the "Institut für Physiologische Chemie" (Institute for Physiological Chemistry/Biochemistry) at the University of Veterinary Medicine Hanover, while collaborating regularly with the University of Hannover. | 1 | Biochemistry |
*3.A.1 ABC transporters including BtuCD, molybdate uptake transporter, Cystic fibrosis transmembrane conductance regulator and others
*3.A.2 The H- or Na-translocating F-type ATPase, V-type ATPase and A-type ATPase superfamily
*3.A.3 The P-type ATPase Superfamily
*3.A.4 The Arsenite-Antimonite efflux family
*3.A.5 General secretory pathway (Sec) translocon (preprotein translocase SecY)
*3.A.6 The Type III (Virulence-related) Secretory Pathway (IIISP) Family
*3.A.7 The Type IV (Conjugal DNA-Protein Transfer or VirB) Secretory Pathway (IVSP) Family
*3.A.8 The Mitochondrial Protein Translocase (MPT) Family
*3.A.9 The Chloroplast Envelope Protein Translocase (CEPT or Tic-Toc) Family
*3.A.10 H, Na-translocating Pyrophosphatase family
*3.A.11 The Bacterial Competence-related DNA Transformation Transporter (DNA-T) Family
*3.A.12 The Septal DNA Translocator (S-DNA-T) Family
*3.A.13 The Filamentous Phage Exporter (FPhE) Family
*3.A.14 The Fimbrilin/Protein Exporter (FPE) Family
*3.A.15 The Outer Membrane Protein Secreting Main Terminal Branch (MTB) Family
*3.A.16 The Endoplasmic Reticular Retrotranslocon (ER-RT) Family
*3.A.17 The Phage T7 Injectisome (T7 Injectisome) Family
*3.A.18 The Nuclear mRNA Exporter (mRNA-E) Family
*3.A.19 The TMS Recognition/Insertion Complex (TRC) Family
*3.A.20 The Peroxisomal Protein Importer (PPI) Family
*3.A.21 The C-terminal Tail-Anchored Membrane Protein Biogenesis/ Insertion Complex (TAMP-B) Family
*3.A.22 The Transcription-coupled TREX/TAP Nuclear mRNA Export Complex (TREX) Family
*3.A.23 The Type VI Symbiosis/Virulence Secretory Pathway (VISP) Family
*3.A.24 Type VII or ESX Protein Secretion System (T7SS) Family
*3.A.25 The Symbiont-specific ERAD-like Machinery (SELMA) Family
*3.A.26 The Plasmodium Translocon of Exported proteins (PTEX) Family | 1 | Biochemistry |
During manufacture, hydrogen can be dissolved into the component by processes such as phosphating, pickling, electroplating, casting, carbonizing, surface cleaning, electrochemical machining, welding, hot roll forming, and heat treatments.
During service use, hydrogen can be dissolved into the metal from wet corrosion or through misapplication of protection measures such as cathodic protection. In one case of failure during construction of the San Francisco–Oakland Bay Bridge galvanized (i.e. zinc-plated) rods were left wet for 5 years before being tensioned. The reaction of the zinc with water introduced hydrogen into the steel.
A common case of embrittlement during manufacture is poor arc welding practice, in which hydrogen is released from moisture, such as in the coating of welding electrodes or from damp welding rods. To avoid atomic hydrogen formation in the high temperature plasma of the arc, welding rods have to be perfectly dried in an oven at the appropriate temperature and duration before use. Another way to minimize the formation of hydrogen is to use special low-hydrogen electrodes for welding high-strength steels.
Apart from arc welding, the most common problems are from chemical or electrochemical processes which, by reduction of hydrogen ions or water, generate hydrogen atoms at the surface, which rapidly dissolve in the metal. One of these chemical reactions involves hydrogen sulfide () in sulfide stress cracking (SSC), a significant problem for the oil and gas industries.
After a manufacturing process or treatment which may cause hydrogen ingress, the component should be baked to remove or immobilize the hydrogen. | 7 | Physical Chemistry |
Meprin A (, endopeptidase-2, meprin-a, meprin, N-benzoyl-L-tyrosyl-p-aminobenzoic acid hydrolase, PABA-peptide hydrolase, PPH) is an enzyme that cleaves protein and peptide substrates preferentially on carboxyl side of hydrophobic residues. This metalloprotease can be associated with inflammatory responses. It can be found in the extracellular space where it can also form complex structures by joining its monomers together.
Meprin A is a dimer composed of the products transcribed from the following two genes: | 1 | Biochemistry |
In about 50 BCE, the Roman philosopher Lucretius proposed that apparently static macroscopic bodies were composed on a small scale of rapidly moving atoms all bouncing off each other. This Epicurean atomistic point of view was rarely considered in the subsequent centuries, when Aristotlean ideas were dominant.
In 1738 Daniel Bernoulli published Hydrodynamica, which laid the basis for the kinetic theory of gases. In this work, Bernoulli posited the argument, that gases consist of great numbers of molecules moving in all directions, that their impact on a surface causes the pressure of the gas, and that their average kinetic energy determines the temperature of the gas. The theory was not immediately accepted, in part because conservation of energy had not yet been established, and it was not obvious to physicists how the collisions between molecules could be perfectly elastic.
Other pioneers of the kinetic theory, whose work was also largely neglected by their contemporaries, were Mikhail Lomonosov (1747), Georges-Louis Le Sage (ca. 1780, published 1818), John Herapath (1816) and John James Waterston (1843), which connected their research with the development of mechanical explanations of gravitation. In 1856 August Krönig created a simple gas-kinetic model, which only considered the translational motion of the particles.
In 1857 Rudolf Clausius developed a similar, but more sophisticated version of the theory, which included translational and, contrary to Krönig, also rotational and vibrational molecular motions. In this same work he introduced the concept of mean free path of a particle. In 1859, after reading a paper about the diffusion of molecules by Clausius, Scottish physicist James Clerk Maxwell formulated the Maxwell distribution of molecular velocities, which gave the proportion of molecules having a certain velocity in a specific range. This was the first-ever statistical law in physics. Maxwell also gave the first mechanical argument that molecular collisions entail an equalization of temperatures and hence a tendency towards equilibrium. In his 1873 thirteen page article Molecules, Maxwell states: "we are told that an atom is a material point, invested and surrounded by potential forces and that when flying molecules strike against a solid body in constant succession it causes what is called pressure of air and other gases."
In 1871, Ludwig Boltzmann generalized Maxwell's achievement and formulated the Maxwell–Boltzmann distribution. The logarithmic connection between entropy and probability was also first stated by Boltzmann.
At the beginning of the 20th century, atoms were considered by many physicists to be purely hypothetical constructs, rather than real objects. An important turning point was Albert Einsteins (1905) and Marian Smoluchowskis (1906) papers on Brownian motion, which succeeded in making certain accurate quantitative predictions based on the kinetic theory.
Following the development of the Boltzmann equation, a framework for its use in developing transport equations was developed independently by David Enskog and Sydney Chapman in 1917 and 1916. The framework provided a route to prediction of the transport properties of dilute gases, and became known as Chapman–Enskog theory. The framework was gradually expanded throughout the following century, eventually becoming a route to prediction of transport properties in real, dense gases. | 7 | Physical Chemistry |
Research at the University of California Irvine showed the ability of vanadium nitrogenase to convert carbon monoxide into trace amounts of propane, ethylene, and ethane in the absence of nitrogen through the reduction of carbon monoxide by dithionite and ATP hydrolysis . The process of forming these hydrocarbons is carried out through proton and electron transfer in which short carbon chains are formed and may ultimately allow the production of hydrocarbon fuel from CO at an industrial scale. | 0 | Organic Chemistry |
1968 – Ralph E. Grim<br />
1969 – C. S. Ross<br />
1970 – Paul F. Kerr<br />
1971 – Walter D. Keller<br />
1972 – G. W. Brindley<br />
1975 – William F. Bradley<br />
1975 – Sturges W. Bailey<br />
1975 – Jose J. Fripiat<br />
1977 – M. L. Jackson<br />
1979 – Toshio Sudo<br />
1980 – Haydn H. Murray<br />
1984 – C. Edmund Marshall<br />
1985 – Charles E. Weaver<br />
1988 – Max M. Mortland<br />
1989 – R. C. Reynolds, Jr.<br />
1990 – Joe L. White<br />
1990 – John Hower<br />
1991 – Joe B. Dixon<br />
1992 – Philip F. Low<br />
1993 – Thomas J. Pinnavaia<br />
1995 – W. D. Johns<br />
1996 – Victor A. Drits<br />
1997 – Udo Schwertmann<br />
1998 – Brij L. Sawhney<br />
2000 – Boris B. Zvyagin<br />
2001 – Keith Norrish<br />
2002 – Gerhard Lagaly<br />
2004 – Benny K. G. Theng<br />
2005 – M. Jeff Wilson<br />
2006 – Frederick J. Wicks<br />
2007 – no award made<br />
2008 – Norbert Clauer<br />
2009 – Joseph W Stucki<br />
2010 – J. M. Serratosa<br />
2011 – Sridhar Komarneni<br />
2012 – Akihiko Yamagishi<br />
2013 – Stephen Guggenheim<br />
2014 – no award made<br />
2015 – James Kirkpatrick<br />
2016 – Lisa Heller-Kallai<br />
2018 – Gordon "Jock" Churchman<br />
2019 – Dennis D. Eberl<br />
2020 – Eduardo Ruiz-Hitzky<br/>
2021 – David L. Bish<br/> | 9 | Geochemistry |
The optical band gap (see below) determines what portion of the solar spectrum a photovoltaic cell absorbs. Strictly, a semiconductor will not absorb photons of energy less than the band gap; whereas most of the photons with energies exceeding the band gap will generate heat. Neither of them contribute to the efficiency of a solar cell. One way to circumvent this problem is based on the so-called photon management concept, in which case the solar spectrum is modified to match the absorption profile of the solar cell. | 7 | Physical Chemistry |
In chemistry, bifunctionality or difunctionality is the presence of two functional groups in a molecule. A bifunctional species has the properties of each of the two types of functional groups, such as an alcohol (), amide (), aldehyde (), nitrile () or carboxylic acid (). Many bifunctional species are used to produce complex materials. They participate in condensation polymerization like polyester and polyamide.
Polyfunctional species have more than two functional groups. Most biological compounds are polyfunctional. | 0 | Organic Chemistry |
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