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*Nitinol can be used to replace conventional actuators (solenoids, servo motors, etc.), such as in the Stiquito, a simple hexapod robot.
*Nitinol springs are used in thermal valves for fluidics, where the material both acts as a temperature sensor and an actuator.
*It is used as autofocus actuator in action cameras and as an optical image stabilizer in mobile phones.
*It is used in pneumatic valves for comfort seating and has become an industry standard.
*The 2014 Chevrolet Corvette incorporates nitinol actuators, which replaced heavier motorized actuators to open and close the hatch vent that releases air from the trunk, making it easier to close. | 8 | Metallurgy |
The aforementioned hydrodynamic and hydrostatic instruments may be employed in a variety of ways, or modes of operation, in order to address the particular separation needs of the scientist. Many modes of operation have been devised to take advantage of the strengths and potentialities of the countercurrent chromatography technique. Generally, the following modes may be performed with commercially available instruments. | 3 | Analytical Chemistry |
In chemistry, dialysis is the process of separating molecules in solution by the difference in their rates of diffusion through a semipermeable membrane, such as dialysis tubing.
Dialysis is a common laboratory technique that operates on the same principle as medical dialysis. In the context of life science research, the most common application of dialysis is for the removal of unwanted small molecules such as salts, reducing agents, or dyes from larger macromolecules such as proteins, DNA, or polysaccharides. Dialysis is also commonly used for buffer exchange and drug binding studies.
The concept of dialysis was introduced in 1861 by the Scottish chemist Thomas Graham. He used this technique to separate sucrose (small molecule) and gum Arabic solutes (large molecule) in aqueous solution. He called the diffusible solutes crystalloids and those that would not pass the membrane colloids.
From this concept dialysis can be defined as a spontaneous separation process of suspended colloidal particles from dissolved ions or molecules of small dimensions through a semi permeable membrane. Most common dialysis membrane are made of cellulose, modified cellulose or synthetic polymer (cellulose acetate or nitrocellulose). | 1 | Biochemistry |
Gas phase coating is carried out at higher temperatures, about 1080 °C. The coating material is usually loaded onto trays without physical contact with the parts to be coated. The coating mixture contains active coating material and activator, but usually not thermal ballast. As in the pack cementation process, gaseous aluminium chloride (or fluoride) is transferred to the surface of the part. However, in this case the diffusion is outwards. This kind of coating also requires diffusion heat treatment. | 8 | Metallurgy |
The aim of the soft chemistry is to synthesize materials, drawing capacity of living beings - more or less basic - such as diatoms capable of producing glass from silicates dissolved. It is a new branch of materials science that differs from conventional solid-state chemistry and its application to the intense energy to explore the chemical inventiveness of the living world. This specialty emerged in the 1980s around the label of "chimie douce", which was first published by the French chemist, Jacques Livage in Le Monde, 26 October 1977. French hits, the term soft chemistry is employed as such in the early twenty-first century in scientific publications, English and others. His mode of synthesis is similar generally for reactions involved in the polymerizations based on organic and the establishment of solutions reactive energy intake without essential polycondensation. The fundamental interest of this kind of polymerization mineral obtained at room temperature is to preserve organic molecules or microorganisms that wishes to fit. The products obtained by means of the so-called soft chemistry sol-gel can be stored in several types:
* mineral structures of various qualities (smoothness, uniformity, etc.)
* mixed structures combining inorganic and organic molecules on mineral structures
* wrapper complex molecules and even microorganisms maintaining or optimizing their beneficial characteristics.
The early results have included the creation of glasses and ceramic with new properties. These different structures are more or less composite mobilized a wide range of applications ranging from health to the needs of the conquest of space. Beyond its mode of synthesis, a compound with the label soft chemistry combines the advantages of the mineral (resistance, transparency, repetition patterns, etc.) and now exploring the potential of the biochemistry and organic chemistry (interface with the organic world, reactivity, synthesis capability, etc.). According to its practitioners, "soft chemistry" is only in its early success and opens up vast prospects. | 1 | Biochemistry |
On a crushing and screening plant, punch plates or perforated plates are mostly used on scalper vibrating screens, after raw products pass on grizzly bars. Most likely installed on a tensioned deck, punch plates offer excellent wear life for high-impact and high material flow applications. | 8 | Metallurgy |
In their 1959 publication, Yukawa and Tsuno attributed observed deviations from Hammett Plot linearity in electrophilic reactions to additional resonance effects occurring through the pi bonds of substituent groups in their compounds. This implied that the inductive component of the Hammett substituent constant remains constant in such reactions, while the resonance component, , does not. From this assumption, the two scientists defined a new resonance substituent constant, , that is mathematically represented as follows:
for a reaction in which positive charge is built up at the reactive center in the transition state. In order to quantify the extent of the observed enhanced resonance effects, Yukawa and Tsuno introduced an enhanced resonance parameter, , that quantifies the "demand for resonance" at the reactive center. Thus, the resultant Yukawa–Tsuno effective substituent constant is given by:
and the Yukawa–Tsuno equation (modified Hammett equation) takes the form:
Values of have been determined and catalogued for a number of substituents for quick application of the Yukawa–Tsuno equation. | 7 | Physical Chemistry |
Methylcyclopentadiene is any of three isomeric cyclic dialkenes with the formula CMeH (Me = CH). These isomers are the organic precursor to the methylcyclopentadienyl ligand (CHMe, often denoted as Cp′), commonly found in organometallic chemistry.
As with cyclopentadiene, methylcyclopentadiene is prepared by thermal cracking of its Diels–Alder dimer, followed by distillation for removal of cyclopentadiene, a common impurity. | 0 | Organic Chemistry |
The endogenous cannabinoids, or endocannabinoids, are endogenous lipids that activate cannabinoid receptors. The first such lipid to be isolated was anandamide which is the arachidonoyl amide of ethanolamine. Anandamide is formed via enzymatic release from N-arachidonoyl phosphatidylethanolamine by the N-acyl phosphatidylethanolamine phospholipase D (NAPE-PLD). Anandamide activates both the CB1 receptor, found primarily in the central nervous system, and the CB2 receptor which is found primarily in lymphocytes and the periphery. It is found at very low levels (nM) in most tissues and is inactivated by the fatty acid amide hydrolase. Subsequently, another endocannabinoid was isolated, 2-arachidonoylglycerol, which is produced when phospholipase C releases diacylglycerol which is then converted to 2-AG by diacylglycerol lipase. 2-AG can also activate both cannabinoid receptors and is inactivated by monoacylglycerol lipase. It is present at approximately 100-times the concentration of anandamide in most tissues. Elevations in either of these lipids causes analgesia and anti-inflammation and tissue protection during states of ischemia, but the precise roles played by these various endocannabinoids are still not totally known and intensive research into their function, metabolism, and regulation is ongoing. One saturated lipid from this class, often called an endocannabinoid, but with no relevant affinity for the CB1 and CB 2 receptor is palmitoylethanolamide. This signaling lipid has great affinity for the GRP55 receptor and the PPAR alpha receptor. It has been identified as an anti-inflammatory compound already in 1957, and as an analgesic compound in 1975. Rita Levi-Montalcini first identified one of its biological mechanisms of action, the inhibition of activated mast cells. Palmitoylethanolamide is the only endocannabinoid available on the market for treatment, as a food supplement. | 1 | Biochemistry |
Dimethyldioxirane (DMDO) is the organic compound with the formula . It is the dioxirane derived from acetone and can be considered as a monomer of acetone peroxide. It is a powerful selective oxidizing agent that finds some use in organic synthesis. It is known only in the form of a dilute solution, usually in acetone, and hence the properties of the pure material are largely unknown. | 0 | Organic Chemistry |
Molecular physics is the study of the physical properties of molecules and molecular dynamics. The field overlaps significantly with physical chemistry, chemical physics, and quantum chemistry. It is often considered as a sub-field of atomic, molecular, and optical physics. Research groups studying molecular physics are typically designated as one of these other fields. Molecular physics addresses phenomena due to both molecular structure and individual atomic processes within molecules. Like atomic physics, it relies on a combination of classical and quantum mechanics to describe interactions between electromagnetic radiation and matter. Experiments in the field often rely heavily on techniques borrowed from atomic physics, such as spectroscopy and scattering. | 7 | Physical Chemistry |
Whiting event clouds consist of calcium carbonate polymorphs; aragonite tends to be the dominant precipitate, but some studies in oligotrophic and mesotrophic lakes show calcite is favored. Whiting events have been observed in tropical and temperate waters, and they can potentially cover hundreds of meters. They tend to occur more often in summer months, as warmer waters promote calcium carbonate precipitation, and in hard waters. Whitings are typically characterized by cloudy, white patches of water, but they can also be tanner in hue in very shallow waters (less than 5m deep). In some cases, the whiting might be cryptic (not visible at the surface), but still generate calcium carbonate. These shallow water whiting events also tend to last less than a day in comparison to deeper water events that can last for several days up to several months. Regardless of the event's lifespan, the clouds it produces increase turbidity and hamper light penetration. | 9 | Geochemistry |
The colloidal gold protein assay is a highly sensitive biochemical assay for determining the total concentration of protein in a solution (~0.1 ng/µL to 200 ng/µL). It was first described in 1987 by two groups who used commercially available "Aurodye" colloidal gold solutions. Notably, the formulation of Aurodye changed between 1987 and 1990 such that it became incompatible with protein assays, however vendors such as Bio-Rad & Diversified Biotech starting offering colloidal gold formulations that were suitable for protein assays. These products have since been discontinued and there are no vendors that currently explicitly sell colloidal gold for the assay, however detailed synthetic procedures were published to produce the ~17-40 nm gold nanoparticles that are suitable for the assay, along with modifications to increase the shelf stability of the colloidal gold & adapt the assay to microplate format & increase its sensitivity. Gold nanoparticles in the ~17-40 nm size range that are presumably compatible with the assay are currently commercially available. | 1 | Biochemistry |
The substitution reaction of tert-Butyl chloride was chosen as reference reaction. The first step, ionizing step, is the rate determining step, SO stands for the nucleophilic solvent. The reference solvent is 80% Ethanol and 20% water by volume. Both of them can carry out the nucleophilic attack on the carbocation.
The S1 reaction is performed through a stable carbocation intermediate, the more nucleophilic solvent can stabilize the carbocation better, thus the rate constant of the reaction could be larger. Since there’s no sharp line between the S1 and S2 reaction, a reaction that goes through S1 mechanism more is preferred to achieve a better linear relationship, hence t-BuCl was chosen. | 7 | Physical Chemistry |
Salinosporamide A was discovered by William Fenical and Paul Jensen from Scripps Institution of Oceanography in La Jolla, CA. In preliminary screening, a high percentage of the organic extracts of cultured Salinispora strains possessed antibiotic and anticancer activities, which suggests that these bacteria are an excellent resource for drug discovery. Salinispora strain CNB-392 was isolated from a heat-treated marine sediment sample and cytotoxicity-guided fractionation of the crude extract led to the isolation of salinosporamide A. Although salinosporamide A shares an identical bicyclic ring structure with omuralide, it is uniquely functionalized. Salinosporamide A displayed potent in vitro cytotoxicity against HCT-116 human colon carcinoma with an IC50 value of 11 ng mL-1. This compound also displayed potent and highly selective activity in the NCI's 60-cell-line panel with a mean GI50 value (the concentration required to achieve 50% growth inhibition) of less than 10 nM and a greater than 4 log LC50 differential between resistant and susceptible cell lines. The greatest potency was observed against NCI-H226 non-small cell lung cancer, SF-539 brain tumor, SK-MEL-28 melanoma, and MDA-MB-435 melanoma (formerly misclassified as breast cancer), all with LC50 values less than 10 nM. Salinosporamide A was tested for its effects on proteasome function because of its structural relationship to omuralide. When tested against purified 20S proteasome, salinosporamide A inhibited proteasomal chymotrypsin-like proteolytic activity with an IC50 value of 1.3 nM. This compound is approximately 35 times more potent than omuralide which was tested as a positive control in the same assay. Thus, the unique functionalization of the core bicyclic ring structure of salinosporamide A appears to have resulted in a molecule that is a significantly more potent proteasome inhibitor than omuralide. | 0 | Organic Chemistry |
;Total phosphorus and phosphate,
Phosphates enter surface waters through both nonpoint sources and point sources. Nonpoint source (NPS) pollution refers to water pollution from diffuse sources. Nonpoint source pollution can be contrasted with point source pollution, where discharges occur to a body of water at a single location. The nonpoint sources of phosphates include natural decomposition of rocks and minerals, stormwater runoff, agricultural pollution, erosion and sedimentation, atmospheric deposition, and direct input by animals/wildlife. Point sources of phosphorus may include municipal sewage treatment plants and industrial dischargers. In general, the nonpoint source pollution typically is significantly higher than the point sources of pollution. Therefore, the key to sound management is to limit the input from both point and nonpoint sources of phosphate. High concentration of phosphate in water bodies is an indication of pollution and largely responsible for eutrophication.
Phosphates are not toxic to people or animals unless they are present in very high levels. Digestive problems could occur from extremely high levels of phosphate.
The following criteria for total phosphorus were recommended by the U.S. Environmental Protection Agency.
# No more than 0.1 mg/L for streams which do not empty into reservoirs,
# No more than 0.05 mg/L for streams discharging into reservoirs, and
# No more than 0.025 mg/L for reservoirs.
Phosphorus is normally low (< 1 mg/L) in clean potable water sources and usually not regulated; | 3 | Analytical Chemistry |
Amine-borane dehydrogenation can be coupled with hydride transfer to unsaturated functional groups, usually olefins in an anti-Markovnikov fashion. Hydroboration of the olefin and release of H from the amine-borane occur in parallel reactions, reducing the percent of olefin reduced. | 0 | Organic Chemistry |
Ruthenium(II) complexes of amine ligands are known for engaging in the outer-sphere mechanism, during which the imine/iminium substrate does not bind to the metal center directly. Instead, substrate receives the elements of H by interaction with Ru-H and N-H sites. This process is utilized by the Shvo catalyst and many ruthenium amine complexes. One such complex is Baratta's catalyst RuCl(PPh)(ampy) (ampy = 2-picolylamine) for transfer hydrogenation. | 0 | Organic Chemistry |
T cell - T-cell antigen receptors - tachykinin - tachykinin receptor - talin protein - tandem repeat sequence - taste bud - TATA box - tax gene product - taxonomy - telophase - tertiary structure - tetrodotoxin - thermochemistry - thermometer - thiamin - thioredoxin - threonine - thrombin - thrombin receptor - thrombomodulin - thromboxane receptor - thylakoid - thyroid hormone receptor - thyrotropin - thyrotropin receptor - thyrotropin-releasing hormone receptor - thyroxine - timeline of biology and organic chemistry - titration - tobacco mosaic virus - topoisomerase - toxin - trans-activator - transcription factor - transcription factor AP-1 - transducin - transformation - transforming growth factor - transforming growth factor alpha - transforming growth factor beta - transforming growth factor beta receptor - transient receptor potential - translation (biology) - transmembrane ATPase - transmembrane helix - transmembrane protein - transmembrane receptor - transport protein - transport vesicle - triiodothyronine - trinucleotide repeat - triose - tropomyosin - troponin - tryptophan - tubulin - tumor necrosis factors - tumor necrosis factor receptor - tyrosine - tyrosine 3-monooxygenase | 1 | Biochemistry |
Point groups can be classified into chiral (or purely rotational) groups and achiral groups.
The chiral groups are subgroups of the special orthogonal group SO(d): they contain only orientation-preserving orthogonal transformations, i.e., those of determinant +1. The achiral groups contain also transformations of determinant −1. In an achiral group, the orientation-preserving transformations form a (chiral) subgroup of index 2.
Finite Coxeter groups or reflection groups are those point groups that are generated purely by a set of reflectional mirrors passing through the same point. A rank n Coxeter group has n mirrors and is represented by a Coxeter–Dynkin diagram. Coxeter notation offers a bracketed notation equivalent to the Coxeter diagram, with markup symbols for rotational and other subsymmetry point groups. Reflection groups are necessarily achiral (except for the trivial group containing only the identity element). | 4 | Stereochemistry |
Equilibria are defined for specific crystal phases. Therefore, the solubility product is expected to be different depending on the phase of the solid. For example, aragonite and calcite will have different solubility products even though they have both the same chemical identity (calcium carbonate). Under any given conditions one phase will be thermodynamically more stable than the other; therefore, this phase will form when thermodynamic equilibrium is established. However, kinetic factors may favor the formation the unfavorable precipitate (e.g. aragonite), which is then said to be in a metastable state.
In pharmacology, the metastable state is sometimes referred to as amorphous state. Amorphous drugs have higher solubility than their crystalline counterparts due to the absence of long-distance interactions inherent in crystal lattice. Thus, it takes less energy to solvate the molecules in amorphous phase. The effect of amorphous phase on solubility is widely used to make drugs more soluble. | 7 | Physical Chemistry |
* Diabetic neuropathy
* Antidepressant
* Postherpetic neuralgia
* Premature ejaculation
* Adjunct to local anesthesia | 4 | Stereochemistry |
Mitogen-activated protein kinase 1 (MAPK1) is also known as extracellular signal-regulated kinase 2 (ERK2). Two similar protein kinases with 85% sequence identity were originally called ERK1 and ERK2. They were found during a search for protein kinases that are rapidly phosphorylated after activation of cell surface tyrosine kinases such as the epidermal growth factor receptor. Phosphorylation of ERKs leads to the activation of their kinase activity.
The molecular events linking cell surface receptors to activation of ERKs are complex. It was found that Ras GTP-binding proteins are involved in the activation of ERKs. Another protein kinase, Raf-1, was shown to phosphorylate a "MAP kinase-kinase", thus qualifying as a "MAP kinase kinase kinase". The MAP kinase-kinase, which activates ERK, was named "MAPK/ERK kinase" (MEK).
Receptor-linked tyrosine kinases, Ras, Raf, MEK, and MAPK could be fitted into a signaling cascade linking an extracellular signal to MAPK activation. See: MAPK/ERK pathway.
Transgenic gene knockout mice lacking MAPK1 have major defects in early development. Conditional deletion of Mapk1 in B cells showed a role for MAPK1 in T-cell-dependent antibody production. A dominant gain-of-function mutant of Mapk1 in transgenic mice showed a role for MAPK1 in T-cell development. Conditional inactivation of Mapk1 in neural progenitor cells of the developing cortex lead to a reduction of cortical thickness and reduced proliferation in neural progenitor cells. | 1 | Biochemistry |
Electron transfer flavoprotein-ubiquinone oxidoreductase (ETF-Q oxidoreductase), also known as electron transferring-flavoprotein dehydrogenase, is a third entry point to the electron transport chain. It is an enzyme that accepts electrons from electron-transferring flavoprotein in the mitochondrial matrix, and uses these electrons to reduce ubiquinone. This enzyme contains a flavin and a [4Fe–4S] cluster, but, unlike the other respiratory complexes, it attaches to the surface of the membrane and does not cross the lipid bilayer.
In mammals, this metabolic pathway is important in beta oxidation of fatty acids and catabolism of amino acids and choline, as it accepts electrons from multiple acetyl-CoA dehydrogenases. In plants, ETF-Q oxidoreductase is also important in the metabolic responses that allow survival in extended periods of darkness. | 1 | Biochemistry |
Many medical devices and products come into contact with the internal surfaces of the body, such as surgical tools and implants. When a non-native material enters the body, the first step of the immune response takes place and host extracellular matrix and plasma proteins aggregate to the material in attempts to contain, neutralize, or wall-off the injurious agent. These proteins can facilitate the attachment of various cell types such as osteoblasts and fibroblasts that can encourage tissue repair. Taking this a step further, implantable devices can be coated with a bioactive material to encourage adsorption of specific proteins, fibrous capsule formation, and wound healing. This would reduce the risk of implant rejection and accelerate recovery by selecting for the necessary proteins and cells necessary for endothelialization. After the formation of the endothelium, the body will no longer be exposed to the foreign material, and will stop the immune response.
Proteins such as collagen or fibrin often serve as scaffolds for cell adhesion and cell growth. This is an integral part to the structural integrity of cell sheets and their differentiation into more complex tissue and organ structures. The adhesion properties of proteins to non-biological surfaces greatly influences whether or not cells can indirectly attach to them via scaffolds. An implant like a hip-stem replacement necessitates integration with the host tissues, and protein adsorption facilitates this integration.
Surgical tools can be designed to be sterilized more easily so that proteins do not remain adsorbed to a surface, risking cross-contamination. Some diseases such as Creutzfeldt–Jakob disease and kuru (both related to mad cow disease) are caused by the transmission of prions, which are errant or improperly folded forms of a normally native protein. Surgical tools contaminated with prions require a special method of sterilization to completely eradicate all trace elements of the misfolded protein, as they are resistant to many of the normally used cleansing methods.
However, in some cases, protein adsorption to biomaterials can be an extremely unfavorable event. The adhesion of clotting factors may induce thrombosis, which may lead to stroke or other blockages. Some devices are intended to interact with the internal body environment such as sensors or drug-delivery vehicles, and protein adsorption would hinder their effectiveness. | 1 | Biochemistry |
Failure of safety-critical polymer components can cause serious accidents, such as fire in the case of cracked and degraded polymer fuel lines. Chlorine-induced cracking of acetal resin plumbing joints and polybutylene pipes has caused many serious floods in domestic properties, especially in the US in the 1990s. Traces of chlorine in the water supply attacked polymers present in the plumbing, a problem which occurs faster if any of the parts have been poorly extruded or injection molded. Attack of the acetal joint occurred because of faulty molding, leading to cracking along the threads of the fitting where there is stress concentration.
Polymer oxidation has caused accidents involving medical devices. One of the oldest known failure modes is ozone cracking caused by chain scission when ozone gas attacks susceptible elastomers, such as natural rubber and nitrile rubber. They possess double bonds in their repeat units which are cleaved during ozonolysis. Cracks in fuel lines can penetrate the bore of the tube and cause fuel leakage. If cracking occurs in the engine compartment, electric sparks can ignite the gasoline and can cause a serious fire. In medical use degradation of polymers can lead to changes of physical and chemical characteristics of implantable devices.
Nylon 66 is susceptible to acid hydrolysis, and in one accident, a fractured fuel line led to a spillage of diesel into the road. If diesel fuel leaks onto the road, accidents to following cars can be caused by the slippery nature of the deposit, which is like black ice. Furthermore, the asphalt concrete road surface will suffer damage as a result of the diesel fuel dissolving the asphaltenes from the composite material, this resulting in the degradation of the asphalt surface and structural integrity of the road. | 7 | Physical Chemistry |
Protein–carbohydrate interactions play an important role in biological function.
* Cell adhesion
* Signal Transduction
* Host-Pathogen Recognition
* Inflammation
* Stabilization of protein structure | 0 | Organic Chemistry |
Vanillin can trigger migraine headaches in a small fraction of the people who experience migraines.
Some people have allergic reactions to vanilla. They may be allergic to synthetically produced vanilla but not to natural vanilla, or the other way around, or to both.
Vanilla orchid plants can trigger contact dermatitis, especially among people working in the vanilla trade if they come into contact with the plant's sap. An allergic contact dermatitis called vanillism produces swelling and redness, and sometimes other symptoms. The sap of most species of vanilla orchid which exudes from cut stems or where beans are harvested can cause moderate to severe dermatitis if it comes in contact with bare skin. The sap of vanilla orchids contains calcium oxalate crystals, which are thought to be the main causative agent of contact dermatitis in vanilla plantation workers.
A pseudophytodermatitis called vanilla lichen can be caused by tiny mites. | 0 | Organic Chemistry |
Antiquarian interest in the gold artefacts of prehistory emerged in the British Isles during the Early Modern period. In 1696, the Ashmolean Museum in Oxford, southern England obtained the Ballyshannon Disk, the first such artefact of its type in their collection, although in ensuing centuries they would gain a number of other items to accompany it. The British Museum in London would follow suit almost a century later, gaining its first Bronze Age gold artefact, a disk from Kirk Andrews on the Isle of Man, in 1782. | 8 | Metallurgy |
A number of materials contract on heating within certain temperature ranges; this is usually called negative thermal expansion, rather than "thermal contraction". For example, the coefficient of thermal expansion of water drops to zero as it is cooled to 3.983 °C and then becomes negative below this temperature; this means that water has a maximum density at this temperature, and this leads to bodies of water maintaining this temperature at their lower depths during extended periods of sub-zero weather.
Other materials are also known to exhibit negative thermal expansion. Fairly pure silicon has a negative coefficient of thermal expansion for temperatures between about 18 and 120 kelvin. ALLVAR Alloy 30, a titanium alloy, exhibits anisotropic negative thermal expansion across a wide range of temperatures. | 7 | Physical Chemistry |
Sodium bisulfite (or sodium bisulphite, sodium hydrogen sulfite) is a chemical mixture with the approximate chemical formula NaHSO. Sodium bisulfite in fact is not a real compound, but a mixture of salts that dissolve in water to give solutions composed of sodium and bisulfite ions. It appears in form of white or yellowish-white crystals with an odor of sulfur dioxide. Regardless of its ill-defined nature, sodium bisulfite is used in many different industries such as a food additive with E number E222 in the food industry, a reducing agent in the cosmetic industry, and a decomposer of residual hypochlorite used in the bleaching industry. | 0 | Organic Chemistry |
Each reaction rate coefficient has a temperature dependency, which is usually given by the Arrhenius equation:
where
* is the activation energy;
* is the gas constant;
* is the exponential function.
Since at temperature the molecules have energies given by a Boltzmann distribution, one can expect the number of collisions with energy greater than to be proportional to The coefficient, , is the pre-exponential factor or frequency factor.
The values for and are dependent on the reaction. There are also more complex equations possible, which describe the temperature dependence of other rate constants that do not follow this pattern.
Temperature is a measure of the average kinetic energy of the reactants. As temperature increases, the kinetic energy of the reactants increases. That is, the particles move faster. With the reactants moving faster this allows more collisions to take place at a greater speed, so the chance of reactants forming into products increases, which in turn results in the rate of reaction increasing. A rise of ten degrees Celsius results in approximately twice the reaction rate.
The minimum kinetic energy required for a reaction to occur is called the activation energy and is denoted by or . The transition state or activated complex shown on the diagram is the energy barrier that must be overcome when changing reactants into products. The molecules with an energy greater than this barrier have enough energy to react.
For a successful collision to take place, the collision geometry must be right, meaning the reactant molecules must face the right way so the activated complex can be formed.
A chemical reaction takes place only when the reacting particles collide. However, not all collisions are effective in causing the reaction. Products are formed only when the colliding particles possess a certain minimum energy called threshold energy. As a rule of thumb, reaction rates for many reactions double for every ten degrees Celsius increase in temperature. For a given reaction, the ratio of its rate constant at a higher temperature to its rate constant at a lower temperature is known as its temperature coefficient, (). Q is commonly used as the ratio of rate constants that are ten degrees Celsius apart. | 7 | Physical Chemistry |
The first measurements of photoinhibition were published in 1956 by Bessel Kok. Even in the very first studies, it was obvious that plants have a repair mechanism that continuously repairs photoinhibitory damage. In 1966, Jones and Kok measured the action spectrum of photoinhibition and found that ultraviolet light is highly photoinhibitory. The visible-light part of the action spectrum was found to have a peak in the red-light region, suggesting that chlorophylls act as photoreceptors of photoinhibition. In the 1980s, photoinhibition became a popular topic in photosynthesis research, and the concept of a damaging reaction counteracted by a repair process was re-invented. Research was stimulated by a paper by Kyle, Ohad and Arntzen in 1984, showing that photoinhibition is accompanied by selective loss of a 32-kDa protein, later identified as the PSII reaction center protein D1. The photosensitivity of PSII from which the oxygen evolving complex had been inactivated with chemical treatment was studied in the 1980s and early 1990s. A paper by Imre Vass and colleagues in 1992 described the acceptor-side mechanism of photoinhibition. Measurements of production of singlet oxygen by photoinhibited PSII provided further evidence for an acceptor-side-type mechanism. The concept of a repair cycle that continuously repairs photoinhibitory damage, evolved and was reviewed by Aro et al. in 1993. Many details of the repair cycle, including the finding that the FtsH protease plays an important role in the degradation of the D1 protein, have been discovered since. In 1996, a paper by Tyystjärvi and Aro showed that the rate constant of photoinhibition is directly proportional to light intensity, a result that opposed the former assumption that photoinhibition is caused by the fraction of light energy that exceeds the maximum capability of photosynthesis. The following year, laser pulse photoinhibition experiments done by Itzhak Ohad's group led to the suggestion that charge recombination reactions may be damaging because they can lead to production of singlet oxygen. The molecular mechanism(s) of photoinhibition are constantly under discussion. The newest candidate is the manganese mechanism suggested 2005 by the group of Esa Tyystjärvi. A similar mechanism was suggested by the group of Norio Murata, also in 2005. | 5 | Photochemistry |
A Python library [http://hitran.org/hapi HAPI] (HITRAN Application Programming Interface) has been developed which serves as a tool for absorption and transmission calculations as well as comparisons of spectroscopic data sets. HAPI extends the functionality of the main site, in particular, for the calculation of spectra using several types of line shape calculations, including the flexible HT (Hartmann-Tran) profile. This HT line shape can also be reduced to a number of conventional line profiles such as Gaussian (Doppler), Lorentzian, Voigt, Rautian, Speed-Dependent Voigt and Speed-Dependent Rautian. In addition to accounting for pressure, temperature and optical path length, the user can include a number of instrumental functions to simulate experimental spectra. HAPI is able to account for broadening of lines due to mixtures of gases as well as make use of all broadening parameters supplied by HITRAN. This includes the traditional broadeners (air, self) as well as additional parameters for CO, HO, H and He broadening. The following spectral functions can be calculated in the current version #1 of HAPI:
* absorption coefficient
* absorption spectrum
* transmittance spectrum
* radiance spectrum
HAPIEST (an acronym for HITRAN Application Programming Interface and Efficient Spectroscopic Tools) is a graphical user interface allowing users to access some of the functionality provided by HAPI without any knowledge of Python programming, including downloading data from HITRAN, and plotting of spectra and cross-sections. The source code for HAPIEST is available on GitHub [https://github.com/hitranonline/hapiest (HAPIEST)], along with binary distributions for Mac and PC. | 7 | Physical Chemistry |
There are two functionally different classes of disaccharides:
*Reducing disaccharides, in which one monosaccharide, the reducing sugar of the pair, still has a free hemiacetal unit that can perform as a reducing aldehyde group; lactose, maltose and cellobiose are examples of reducing disaccharides, each with one hemiacetal unit, the other occupied by the glycosidic bond, which prevents it from acting as a reducing agent. They can easily be detected by the Woehlk test or Fearon's test on methylamine.
*Non-reducing disaccharides, in which the component monosaccharides bond through an acetal linkage between their anomeric centers. This results in neither monosaccharide being left with a hemiacetal unit that is free to act as a reducing agent. Sucrose and trehalose are examples of non-reducing disaccharides because their glycosidic bond is between their respective hemiacetal carbon atoms. The reduced chemical reactivity of the non-reducing sugars, in comparison to reducing sugars, may be an advantage where stability in storage is important. | 0 | Organic Chemistry |
The stack effect in industrial flue gas stacks is similar to that in buildings, except that it involves hot flue gases having large temperature differences with the ambient outside air. Furthermore, an industrial flue gas stack typically provides little obstruction for the flue gas along its length and is, in fact, normally optimized to enhance the stack effect to reduce fan energy requirements.
Large temperature differences between the outside air and the flue gases can create a strong stack effect in chimneys for buildings using a fireplace for heating.
Before the development of large volume fans, mines were ventilated using the stack effect. A downcast shaft allowed air into the mine. At the foot of the upcast shaft a furnace was kept continuously burning. The shaft (commonly several hundred yards deep) behaved like a chimney and air rose through it drawing fresh air down the downcast stack and around the mine. | 7 | Physical Chemistry |
Denitrification generally proceeds through some combination of the following half reactions, with the enzyme catalyzing the reaction in parentheses:
* NO + 2 H + 2 e → + HO (Nitrate reductase)
* + 2 H + e → NO + HO (Nitrite reductase)
* 2 NO + 2 H + 2 e → + HO (Nitric-oxide reductase)
* + 2 H + 2 e → + HO (Nitrous-oxide reductase)
The complete process can be expressed as a net balanced redox reaction, where nitrate (NO) gets fully reduced to dinitrogen (N):
* 2 NO + 10 e + 12 H → N + 6 HO | 1 | Biochemistry |
Buffers in gel electrophoresis are used to provide ions that carry a current and to maintain the pH at a relatively constant value.
These buffers have plenty of ions in them, which is necessary for the passage of electricity through them. Something like distilled water or benzene contains few ions, which is not ideal for the use in electrophoresis. There are a number of buffers used for electrophoresis. The most common being, for nucleic acids Tris/Acetate/EDTA (TAE), Tris/Borate/EDTA (TBE). Many other buffers have been proposed, e.g. lithium borate, which is rarely used, based on Pubmed citations (LB), isoelectric histidine, pK matched goods buffers, etc.; in most cases the purported rationale is lower current (less heat) matched ion mobilities, which leads to longer buffer life. Borate is problematic; Borate can polymerize, or interact with cis diols such as those found in RNA. TAE has the lowest buffering capacity but provides the best resolution for larger DNA. This means a lower voltage and more time, but a better product. LB is relatively new and is ineffective in resolving fragments larger than 5 kbp; However, with its low conductivity, a much higher voltage could be used (up to 35 V/cm), which means a shorter analysis time for routine electrophoresis. As low as one base pair size difference could be resolved in 3% agarose gel with an extremely low conductivity medium (1 mM Lithium borate).
Most SDS-PAGE protein separations are performed using a "discontinuous" (or DISC) buffer system that significantly enhances the sharpness of the bands within the gel. During electrophoresis in a discontinuous gel system, an ion gradient is formed in the early stage of electrophoresis that causes all of the proteins to focus on a single sharp band in a process called isotachophoresis. Separation of the proteins by size is achieved in the lower, "resolving" region of the gel. The resolving gel typically has a much smaller pore size, which leads to a sieving effect that now determines the electrophoretic mobility of the proteins. | 1 | Biochemistry |
Coning and quartering is a method used by analytical chemists to reduce the sample size of a powder without creating a systematic bias. The technique involves pouring the sample so that it takes on a conical shape, and then flattening it out into a cake. The cake is then divided into quarters; the two quarters which sit opposite one another are discarded, while the other two are combined and constitute the reduced sample. The same process is continued until an appropriate sample size remains. Analyses are made with respect to the sample left behind. | 3 | Analytical Chemistry |
Type S (90%Pt/10%Rh–Pt, by weight) thermocouples, similar to type R, are used up to 1600 °C. Before the introduction of the International Temperature Scale of 1990 (ITS-90), precision type-S thermocouples were used as the practical standard thermometers for the range of 630 °C to 1064 °C, based on an interpolation between the freezing points of antimony, silver, and gold. Starting with ITS-90, platinum resistance thermometers have taken over this range as standard thermometers. | 8 | Metallurgy |
Smith has focused his research on mineral processing technology along with engineering education by facilitating faculty and graduate student professional growth, exploring the role of cooperation in learning and design, addressing problem formulation, modeling, and knowledge engineering, and managing projects and knowledge. | 8 | Metallurgy |
Carboxylic acids are polar. Because they are both hydrogen-bond acceptors (the carbonyl ) and hydrogen-bond donors (the hydroxyl ), they also participate in hydrogen bonding. Together, the hydroxyl and carbonyl group form the functional group carboxyl. Carboxylic acids usually exist as dimers in nonpolar media due to their tendency to "self-associate". Smaller carboxylic acids (1 to 5 carbons) are soluble in water, whereas bigger carboxylic acids have limited solubility due to the increasing hydrophobic nature of the alkyl chain. These longer chain acids tend to be soluble in less-polar solvents such as ethers and alcohols. Aqueous sodium hydroxide and carboxylic acids, even hydrophobic ones, react to yield water-soluble sodium salts. For example, enanthic acid has a low solubility in water (0.2 g/L), but its sodium salt is very soluble in water. | 0 | Organic Chemistry |
Native silver is a rare element. Although it exists as such, it is usually found in nature combined with other metals, or in minerals that contain silver compounds, generally in the form of sulfides such as galena (lead sulfide) or cerussite (lead carbonate). So the primary production of silver requires the smelting and then cupellation of argentiferous lead ores.
Lead melts at 327 °C, lead oxide at 888 °C, and silver melts at 960 °C. To separate the silver, the alloy is melted again at the high temperature of 960 °C to 1000 °C in an oxidizing environment. The lead oxidises to lead monoxide, then known as litharge, which captures the oxygen from the other metals present. The liquid lead oxide is removed or absorbed by capillary action into the hearth linings. This chemical reaction may be viewed as
: (s) + 2 (s) + (g) → 2 (absorbed) + Ag(l)
The base of the hearth was dug in the form of a saucepan and covered with an inert and porous material rich in calcium or magnesium such as shells, lime, or bone ash. The lining had to be calcareous because lead reacts with silica (clay compounds) to form viscous lead silicate that prevents the needed absorption of litharge, whereas calcareous materials do not react with lead. Some of the litharge evaporates, and the rest is absorbed by the porous earth lining to form "litharge cakes".
Litharge cakes are usually circular or concavo-convex, about 15 cm in diameter. They are the most common archaeological evidence of cupellation in the Early Bronze Age. By analyzing their chemical composition, archaeologists can discern what kind of ore was treated, its main components, and the chemical conditions used in the process. This permits insights about production process, trade, social needs or economic situations. | 8 | Metallurgy |
where M is the molecular weight.
The method uses a two-parameter equation to describe the temperature dependency of the dynamic viscosity. The authors state that the parameters are valid from the melting temperature up to 0.7 of the critical temperature (T < 0.7). | 7 | Physical Chemistry |
The enzyme cytochrome c oxidase or Complex IV, (was , now reclassified as a translocase [https://www.enzyme-database.org/query.php?name=EC+7.1.1.9&search=search_all&display=show_all&order=ec_num&nr=50 EC 7.1.1.9]) is a large transmembrane protein complex found in bacteria, archaea, and the mitochondria of eukaryotes.
It is the last enzyme in the respiratory electron transport chain of cells located in the membrane. It receives an electron from each of four cytochrome c molecules and transfers them to one oxygen molecule and four protons, producing two molecules of water. In addition to binding the four protons from the inner aqueous phase, it transports another four protons across the membrane, increasing the transmembrane difference of proton electrochemical potential, which the ATP synthase then uses to synthesize ATP. | 1 | Biochemistry |
At sawmills, unless reprocessed into particleboard, burned in a sawdust burner, or used to make heat for other milling operations, sawdust may collect in piles and add harmful leachates into local water systems, creating an environmental hazard. This has placed small sawyers and environmental agencies in a deadlock.
Questions about the science behind the determination of sawdust being an environmental hazard remain for sawmill operators (though this is mainly with finer particles), who compare wood residuals to dead trees in a forest. Technical advisors have reviewed some of the environmental studies, but say most lack standardized methodology or evidence of a direct impact on wildlife. They do not take into account large drainage areas, so the amount of material that is getting into the water from the site in relation to the total drainage area is minuscule.
Other scientists have a different view, saying the "dilution is the solution to pollution" argument is no longer accepted in environmental science. The decomposition of a tree in a forest is similar to the impact of sawdust, but the difference is of scale. Sawmills may be storing thousands of cubic metres of wood residues in one place, so the issue becomes one of concentration.
Of larger concern are substances such as lignins and fatty acids that protect trees from predators while they are alive, but can leach into water and poison wildlife. Those types of things remain in the tree and, as the tree decays, they slowly are broken down. But when sawyers are processing a large volume of wood and large concentrations of these materials permeate into the runoff, the toxicity they cause is harmful to a broad range of organisms. | 2 | Environmental Chemistry |
Ibuprofen was derived from propionic acid by the research arm of Boots Group during the 1960s. The name is derived from the 3 functional groups: isobutyl (ibu) propionic acid (pro) phenyl (fen). Its discovery was the result of research during the 1950s and 1960s to find a safer alternative to aspirin. The molecule was discovered and synthesized by a team led by Stewart Adams, with a patent application filed in 1961. Adams initially tested the drug as treatment for his hangover. In 1985, Boots' worldwide patent for ibuprofen expired and generic products were launched.
The medication was launched as a treatment for rheumatoid arthritis in the United Kingdom in 1969, and in the United States in 1974. Later, in 1983 and 1984, it became the first NSAID (other than aspirin) to be available over the counter (OTC) in these two countries. Boots was awarded the Queen's Award for Technical Achievement in 1985 for the development of the drug.
In November 2013, work on ibuprofen was recognized by the erection of a Royal Society of Chemistry blue plaque at Boots' Beeston Factory site in Nottingham, which reads:
and another at BioCity Nottingham, the site of the original laboratory, which reads: | 4 | Stereochemistry |
Increased RNA levels of Alu, which requires L1 proteins, are associated with a form of age-related macular degeneration, a neurological disorder of the eyes.
The naturally occurring mouse retinal degeneration model rd7 is caused by an L1 insertion in the Nr2e3 gene. | 1 | Biochemistry |
EQCM is broadly used to study the deposition/dissolution process on electrode surface, such as the oscillation of electrode potential during Cu/CuO layered nanostructure electrodeposition, deposition growth process of cobalt and nickel hexacyanoferrate in calcium nitrate and barium nitrate electrolyte solution, and the Mg electrode electrochemical behaviour in various polar aprotic electrolyte solutions. EQCM can be used as a powerful tool for corrosion and corrosion protection study, which is usually combined with other characterization technologies. A previous work used EQCM and XPS studied Fe-17Cr-33Mo/ Fe-25Cr alloy electrodes mass changes during the potential sweep and potential step experiments in the passive potential region in an acidic and a basic electrolyte. Another previous work used EQCM and SEM to study the influence of purine (PU) on Cu electrode corrosion and spontaneous dissolution in NaCl electrolyte solution. | 7 | Physical Chemistry |
HPTLC finds extensive application in various fields, including pharmaceutical industries, clinical chemistry, forensic chemistry, biochemistry, cosmetology, food and drug analysis, environmental analysis, and more, owing to its numerous advantages. It distinguishes itself by being the only chromatographic method capable of presenting results as images and offers simplicity, cost-effectiveness, parallel analysis of samples, high sample capacity, rapid results, and the option for multiple detection methods.
Le Roux's research team assessed HPTLC for determining salbutamol serum levels in clinical trials and concluded that it is a suitable method for analyzing serum samples.
HPTLC has also been used successfully in the separation of various lipid subclasses, with reproducible and promising results obtained for 20 different lipid subclasses. Numerous reports related to clinical medicine studies have been published in various journals. As a result, HPTLC is now strongly recommended for drug analysis in serum and other tissues. | 3 | Analytical Chemistry |
Mixed potential theory is a theory used in electrochemistry that relates the potentials and currents from differing constituents into a weighted potential at zero net current. In other words, it is an electrode potential resulting from a simultaneous action of more than a single redox couple, while the net electrode current is zero. | 7 | Physical Chemistry |
The term was coined by Joseph Marius DallaValle in his book Micromeritics: The Technology of Fine Particles (1948). It was derived from the Greek words meaning "small" and meaning "part". The size range which he covered in the book was from 10 to 10 micrometers. Anything smaller than this but bigger than a molecule was referred to at the time as a colloid but is now often referred to as a nanoparticle. Applications included soil physics, mineral physics, chemical engineering, geology, and hydrology. Characteristics discussed included particle size and shape, packing, electrical, optical, chemical and surface science. | 7 | Physical Chemistry |
Electrochemical energy conversion is a field of energy technology concerned with electrochemical methods of energy conversion including fuel cells and photoelectrochemical. This field of technology also includes electrical storage devices like batteries and supercapacitors. It is increasingly important in context of automotive propulsion systems. There has been the creation of more powerful, longer running batteries allowing longer run times for electric vehicles. These systems would include the energy conversion fuel cells and photoelectrochemical mentioned above. | 7 | Physical Chemistry |
During his years working as a physician Michaelis a friend (Peter Rona) built a compact lab, in the hospital, and over the course of five years – Michaelis successfully became published over 100 times. During his research in the hospital, he was the first to view the different types of inhibition; specifically using fructose and glucose as inhibitors of maltase activity. Maltase breaks maltose into two units of glucose. Findings from that experiment allowed for the divergence of non-competitive and competitive inhibition. Non-competitive inhibition affects the k value (but not the K) on any given graph; this inhibitor binds to a site that has specificity for the certain molecule. Michaelis determined that when the inhibitor is bound, the enzyme would become inactivated.
Like many other scientists of their time, Leonor Michaelis and Maud Menten worked on a reaction that was used to change the composition of sucrose and make it lyse into two products – fructose and glucose. The enzyme involved in this reaction is called invertase, and it is the enzyme the kinetics of which have been supported by Michaelis and Menten to be revolutionary for the kinetics of other enzymes. While expressing the rate of the reaction studied, they derived an equation that described the rate in a way which suggested that it is mostly dependent on the enzyme concentration, as well as on presence of the substrate, but only to a certain extent.
Adrian Brown and Victor Henri laid the groundwork for the discoveries in enzyme kinetics that Michaelis and Menten are known for. Brown theoretically envisioned the mechanism now accepted for enzyme kinetics, but did not have the quantitative data to make a claim. Victor Henri made significant contributions to enzyme kinetics during his doctoral thesis, however he lacked noting the importance of hydrogen ion concentration and mutarotation of glucose. The goal of Henris thesis was to compare his knowledge of enzyme-catalysed reactions to the recognized laws of physical chemistry. Henri is credited with being the first to write the equation that is now known as the Michaelis-Menten equation. Using glucose and fructose in the catalytic reactions controlled by maltase and invertase, Leonor Michaelis was the first scientist to distinguish the different types of inhibition by using the pH scale which did not exist in Henris time.
Particularly during their work on describing the rate of this reaction they also tested and extrapolated on the idea of another scientist, Victor Henri, that enzyme they were using had some affinity for both products of this reaction – fructose and glucose. Using Henris methods, Michaelis and Menten nearly perfected this concept of initial-rate method for steady-state experiments. They were studying inhibition when they found that non-competitive (mixed) inhibition is characterized by its effect on k (catalyst rate) while competitive is characterized by its effect on velocity (V). In the Michaelis and Menten experiments they heavily focused on pH effects of invertase using hydrogen ions. Invertase is an enzyme found in extracellular yeast and catalyzed reactions by hydrolysis or inverting a sucrose (mixture of sucrose and fructose) to “invert sugar.” The main reason for using invertase was that it could be easily assayed and experiments could be done in quicker manner. Sucrose rotates in polarimeter as dextroratatory-D whereas invert sugar is levorotatory-L. This made tracking the inversion of sugar relatively simple. They also found that α-D-glucose is released in reactions catalyzed by invertase which is very unstable and spontaneously changes to β-D-glucose. Although, these are both in the dextrorotatory form, this is where they noted that glucose can change spontaneously, also known as mutarotation. Failing to take this into consideration was one of the main reasons Henris experiments fell short. Using invertase to catalyze sucrose inversion, they could see how fast the enzyme was reacting by polarimetry; therefore, non-competitive inhibition was found to occur in the reaction where sucrose was inverted with invertase. | 1 | Biochemistry |
Concentration depends on the variation of the volume of the solution with temperature, due mainly to thermal expansion. | 3 | Analytical Chemistry |
The first stereographic projection defined in the preceding section sends the "south pole" (0, 0, −1) of the unit sphere to (0, 0), the equator to the unit circle, the southern hemisphere to the region inside the circle, and the northern hemisphere to the region outside the circle.
The projection is not defined at the projection point = (0, 0, 1). Small neighborhoods of this point are sent to subsets of the plane far away from (0, 0). The closer is to (0, 0, 1), the more distant its image is from (0, 0) in the plane. For this reason it is common to speak of (0, 0, 1) as mapping to "infinity" in the plane, and of the sphere as completing the plane by adding a point at infinity. This notion finds utility in projective geometry and complex analysis. On a merely topological level, it illustrates how the sphere is homeomorphic to the one-point compactification of the plane.
In Cartesian coordinates a point on the sphere and its image on the plane either both are rational points or none of them:
Stereographic projection is conformal, meaning that it preserves the angles at which curves cross each other (see figures). On the other hand, stereographic projection does not preserve area; in general, the area of a region of the sphere does not equal the area of its projection onto the plane. The area element is given in coordinates by
Along the unit circle, where , there is no inflation of area in the limit, giving a scale factor of 1. Near (0, 0) areas are inflated by a factor of 4, and near infinity areas are inflated by arbitrarily small factors.
The metric is given in coordinates by
and is the unique formula found in Bernhard Riemanns Habilitationsschrift on the foundations of geometry, delivered at Göttingen in 1854, and entitled Über die Hypothesen welche der Geometrie zu Grunde liegen'.
No map from the sphere to the plane can be both conformal and area-preserving. If it were, then it would be a local isometry and would preserve Gaussian curvature. The sphere and the plane have different Gaussian curvatures, so this is impossible.
Circles on the sphere that do not pass through the point of projection are projected to circles on the plane. Circles on the sphere that do pass through the point of projection are projected to straight lines on the plane. These lines are sometimes thought of as circles through the point at infinity, or circles of infinite radius. These properties can be verified by using the expressions of in terms of given in : using these expressions for a substitution in the equation of the plane containing a circle on the sphere, and clearing denominators, one gets the equation of a circle, that is, a second-degree equation with as its quadratic part. The equation becomes linear if that is, if the plane passes through the point of projection.
All lines in the plane, when transformed to circles on the sphere by the inverse of stereographic projection, meet at the projection point. Parallel lines, which do not intersect in the plane, are transformed to circles tangent at projection point. Intersecting lines are transformed to circles that intersect transversally at two points in the sphere, one of which is the projection point. (Similar remarks hold about the real projective plane, but the intersection relationships are different there.)
The loxodromes of the sphere map to curves on the plane of the form
where the parameter measures the "tightness" of the loxodrome. Thus loxodromes correspond to logarithmic spirals. These spirals intersect radial lines in the plane at equal angles, just as the loxodromes intersect meridians on the sphere at equal angles.
The stereographic projection relates to the plane inversion in a simple way. Let and be two points on the sphere with projections and on the plane. Then and are inversive images of each other in the image of the equatorial circle if and only if and are reflections of each other in the equatorial plane.
In other words, if:
* is a point on the sphere, but not a north pole and not its antipode, the south pole ,
* is the image of in a stereographic projection with the projection point and
* is the image of in a stereographic projection with the projection point ,
then and are inversive images of each other in the unit circle. | 3 | Analytical Chemistry |
Shape-memory coupling is a system for connecting pipes using shape-memory alloys. In its typical form the technique uses an internally ribbed sleeve of alloy such as Tinel(see Nitinol) that is slightly smaller in diameter than the pipes it is to connect. The sleeve is cooled in liquid nitrogen then, in this low-temperature state, mechanically expanded with a mandrel to fit easily over the two pipe ends to be joined. After fitting, it is allowed to rewarm, when the memory effect causes the sleeve to shrink back to its original smaller size, creating a tight joint.
It was first produced in the late 1960s or early 1970s by the Raychem Corporation under the trade name CryoFit. Manufacture of these couplings for aerospace hydraulic connections was later transferred to AMCI (Advanced Metal Components Inc.) and then later to [http://www.aerofit.com Aerofit Products Inc.] Additional products using the same shape-memory alloy technology are produced under Cryolive and CryoFlare trade names. | 8 | Metallurgy |
The functional mammalian sAC consist of two heterologous catalytic domains (C1 and C2), forming the 50 kDa amino terminus of the protein. The additional ~140 kDa C terminus of the enzyme includes an autoinhibitory region, canonical P-loop, potential heme-binding domain, and leucine zipper-like sequence, which are a form of putative regulatory domains.
A truncated form of the enzyme only includes the C1 and C2 domains and it is refers to as the minimal functional sAC variant. This sAC-truncated form has cAMP-forming activity much higher than its full-length type. These sAC variants are stimulated by HCO3- and respond to all known selective sAC inhibitors. Crystal structures of this sAC variant comprising only the catalytic core, in apo form and in as complex with various substrate analogs, products, and regulators, reveal a generic Class III AC architecture with sAC-specific features. The structurally related domains C1 and C2 form the typical pseudo-heterodimer, with one active site. The pseudo-symmetric site accommodates the sAC-specific activator HCO3−, which activates by triggering a rearrangement of Arg176, a residue connecting both sites. The anionic sAC inhibitor 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS) acts as a blocker for the entrance to active site and bicarbonate binding pocket. | 1 | Biochemistry |
The variety of electron-deficient sigma aromatic clusters formed by bismuth gives rise to a wide range of spectroscopic behaviors. Of particular interest are the systems capable of low-energy electronic transitions, as these have demonstrated potential as near-infrared light emitters. It is the tendency of electron-deficient bismuth to form sigma-delocalized clusters with small HOMO/LUMO gaps that gives rise to the near-infrared emissions. This property makes these species potentially valuable to the field of near-infrared optical tomography, which exploits the near-infrared window in biological tissue. | 7 | Physical Chemistry |
The problem of landslides in spoil tips was first brought to public attention in October 1966 in English speaking world when a spoil tip at Aberfan in Wales gave way, killing 144 people, 116 of them children. The tip was built over a spring, increasing its instability, and its height exceeded guidelines. Water from heavy rainfall had built up inside the tip, weakening the structure, until it suddenly collapsed onto a school below.
The wider issue of stability had been known about prior to the Aberfan disaster; for example, it was discussed in a paper by Professor George Knox in 1927, but received little serious consideration by professional engineers and geologists — even to those directly concerned with mining. Also Aberfan disaster was not the first landslide with casualties: for example, in 1955 two successive landslides killed 73 people in Sasebo, Nagasaki in Japan.[ja]
In February 2013, a spoil tip landslip caused the temporary closure of the Scunthorpe to Doncaster railway line in England.
Landslides are rare in spoil tips after settling and vegetation growth act to stabilise the spoil. However, when heavy rain falls on spoil tips that are undergoing combustion, infiltrated water changes to steam; increasing pressure that may lead to a landslide. In Herstal, Belgium, a landslide on the Petite Bacnure spoil tip in April 1999 closed off a street for many years. | 8 | Metallurgy |
Hydroxylamine and its salts are commonly used as reducing agents in myriad organic and inorganic reactions. They can also act as antioxidants for fatty acids.
High concentrations of hydroxylamine are used by biologists to introduce mutations by acting as a DNA nucleobase amine-hydroxylating agent. In is thought to mainly act via hydroxylation of cytidine to hydroxyaminocytidine, which is misread as thymidine, thereby inducing C:G to T:A transition mutations. But high concentrations or over-reaction of hydroxylamine in vitro are seemingly able to modify other regions of the DNA & lead to other types of mutations. This may be due to the ability of hydroxylamine to undergo uncontrolled free radical chemistry in the presence of trace metals and oxygen, in fact in the absence of its free radical affects Ernst Freese noted hydroxylamine was unable to induce reversion mutations of its C:G to T:A transition effect & even considered hydroxylamine to be the most specific mutagen known. Practically, it has been largely surpassed by more potent mutagens such as EMS, ENU, or nitrosoguanidine, but being a very small mutagenic compound with high specificity, it found some specialized uses such as mutation of DNA packed within bacteriophage capsids, & mutation of purified DNA in vitro.
An alternative industrial synthesis of paracetamol developed by Hoechst–Celanese involves the conversion of ketone to a ketoxime with hydroxylamine.
Some non-chemical uses include removal of hair from animal hides and photographic developing solutions. In the semiconductor industry, hydroxylamine is often a component in the "resist stripper", which removes photoresist after lithography.
Hydroxylamine can also be used to better characterize the nature of a post-translational modification onto proteins. For example, poly(ADP-Ribose) chains are sensitive to hydroxylamine when attached to glutamic or aspartic acids but not sensitive when attached to serines. Similarly, Ubiquitin molecules bound to serines or threonines residues are sensitive to hydroxylamine, but those bound to lysine (isopeptide bond) are resistant. | 0 | Organic Chemistry |
Few transition metals can achieve the +6 oxidation state in an oxide, so oxides with the stoichiometry MO are rare. | 7 | Physical Chemistry |
The naturally occurring polysaccharide form the basis for an important group of columns designed for chiral separation. The main polysaccharides are cellulose, amylose, chitosan, dextran, xylan, curdlan, and inulin. Polysaccharide-based stationary phase have a high loading capacity, many chiral centers and complicated stereochemistry, and can be used for the separation of a wide range of compounds.
Polysaccharide-based chiral stationary phases have a wide application due to their high separation efficiency, selectivity, sensitivity and reproducibility under normal and reversed-phase conditions, as well as their broad applicability for structurally diversified compounds. The mechanism of chiral interaction on the polysaccharide-based chiral stationary phase has not yet been elucidated. However, the following interactions are believed to play a role in the retention:
(i) Hydrogen bonding interactions of the polar chiral analyte with carbamate groups on the CSP;
(ii) π-π interactions between phenyl groups on the CSP and aromatic groups of the solute;
(i) Dipole-dipole interactions
(ii) Steric interactions due to the helical structure of the CSP.
These effects on the retention process originate also from the functionality of the derivatives of the polysaccharide, its average molecular weight, and size distribution, the solvent used to immobilize it on the macroporous silica support, and the nature of the macroporous silica support itself. | 4 | Stereochemistry |
The 5′ untranslated region (also known as 5′ UTR, leader sequence, transcript leader, or leader RNA) is the region of a messenger RNA (mRNA) that is directly upstream from the initiation codon. This region is important for the regulation of translation of a transcript by differing mechanisms in viruses, prokaryotes and eukaryotes. While called untranslated, the 5′ UTR or a portion of it is sometimes translated into a protein product. This product can then regulate the translation of the main coding sequence of the mRNA. In many organisms, however, the 5′ UTR is completely untranslated, instead forming a complex secondary structure to regulate translation.
The 5′ UTR has been found to interact with proteins relating to metabolism, and within the 5′ UTR. In addition, this region has been involved in transcription regulation, such as the sex-lethal gene in Drosophila. Regulatory elements within 5′ UTRs have also been linked to mRNA export. | 1 | Biochemistry |
Most MAPKs have a number of shared characteristics, such as the activation dependent on two phosphorylation events, a three-tiered pathway architecture and similar substrate recognition sites. These are the "classical" MAP kinases. But there are also some ancient outliers from the group as sketched above, that do not have dual phosphorylation sites, only form two-tiered pathways, and lack the features required by other MAPKs for substrate binding. These are usually referred to as "atypical" MAPKs. It is yet unclear if the atypical MAPKs form a single group as opposed to the classical ones.
The mammalian MAPK family of kinases includes three subfamilies:
# Extracellular signal-regulated kinases (ERKs)
# c-Jun N-terminal kinases (JNKs)
# p38 mitogen-activated protein kinases (p38s)
Generally, ERKs are activated by growth factors and mitogens, whereas cellular stresses and inflammatory cytokines activate JNKs and p38s. | 1 | Biochemistry |
Lactoperoxidase-catalysed reactions yield short-lived intermediary oxidation products of SCN, providing antibacterial activity.
The major intermediary oxidation product is hypothiocyanite OSCN, which is produced in an amount of about 1 mole per mole of hydrogen peroxide. At the pH optimum of 5.3, the OSCN is in equilibrium with HOSCN. The uncharged HOSCN is considered to be the greater bactericidal of the two forms. At pH 7, it was evaluated that HOSCN represents 2% compare to OSCN 98%.
The action of OSCN against bacteria is reported to be caused by sulfhydryl (SH) oxidation.
The oxidation of -SH groups in the bacterial cytoplasmic membrane results in loss of the ability to transport glucose and also in leaking of potassium ions, amino acids and peptide.
OSCN has also been identified as an antimicrobial agent in milk, saliva, tears, and mucus.
OSCN is considered as a safe product as it is not mutagenic. | 1 | Biochemistry |
* Chapter: Molecular Spectroscopy 2.
* Chapter 4: Fundamentals of Fluorescence and Fluorescence Microscopy | 7 | Physical Chemistry |
For air at standard conditions for temperature and pressure (STP), the voltage needed to arc a 1-metre gap is about 3.4 MV. The intensity of the electric field for this gap is therefore 3.4 MV/m.
The electric field needed to arc across the minimal-voltage gap is much greater than what is necessary to arc a gap of one metre. At large gaps (or large pd) Paschen's Law is known to fail. The Meek Criteria for breakdown is usually used for large gaps.
It takes into account non-uniformity in the electric field and formation of streamers due to the build up of charge within the gap that can occur over long distances. For a 7.5 μm gap the arc voltage is 327 V, which is 43 MV/m. This is about 14 times greater than the field strength for the 1.5-metre gap. The phenomenon is well verified experimentally and is referred to as the Paschen minimum.
The equation loses accuracy for gaps under about 10 μm in air at one atmosphere
and incorrectly predicts an infinite arc voltage at a gap of about 2.7 micrometres. Breakdown voltage can also differ from the Paschen curve prediction for very small electrode gaps, when field emission from the cathode surface becomes important. | 7 | Physical Chemistry |
A simple modification to atom transfer radical polymerization (ATRP) was introduced in 2007 to kinetically control the polymerization by increasing the ratio of inactive copper(II) catalyst to active copper(I) catalyst. The modification to this strategy is termed deactivation enhanced ATRP, whereby different ratios of copper(II)/copper(I) are added. Alternatively a copper(II) catalyst may be used in the presence of small amounts of a reducing agent such as ascorbic acid to produce low percentages of copper(I) in situ and to control the ratio of copper (II)/copper (I). Deactivation enhanced ATRP features the decrease of the instantaneous kinetic chain length ν as defined by:,
<br />
meaning an average number of monomer units are added to a propagating chain end during each activation/deactivation cycle, The resulting chain growth rate is slowed down to allow sufficient control over the reaction thus greatly increasing the percentage of multi-vinyl monomers in the reaction system (even up to 100 percent (homopolymerization)). | 7 | Physical Chemistry |
* 24 February 2009 - Orbiting Carbon Observatory was launched on a Taurus XL rocket but failed to achieve orbit when the fairing failed to separate from the satellite.
* 1 February 2010 - The 2010 President's budget included funding for development and re-flight of an OCO replacement.
* October 2010 - The Orbiting Carbon Observatory-2 project went into implementation phase.
* 2 July 2014 - OCO-2 was successfully launched from Vandenberg Air Force Base with a Delta II rocket.
* 2015 - Funding for the OCO-3 project cancelled.
* 22 December 2015 - OCO-3 project authorized to proceed. Funding was included in the 2016 spending bill.
* 16 March 2017 - OCO-3 was not included in the proposed FY2018 presidential budget.
* 23 March 2018 - Funding for the OCO-3 project was restored.
* May 2018 - Instrument underwent TVAC testing.
* 4 May 2019 - Launched using a Falcon 9 rocket from Cape Canaveral Air Force Station. The delivery was part of SpaceX CRS-17, which also included delivery of STP-H6 and a cargo resupply.
* After arrival - Robotic installation onto Exposed Facility Unit 3 (EFU 3) on the JEM-EF. | 2 | Environmental Chemistry |
* IMP dehydrogenase (IMPDH) converts IMP into XMP
* GMP synthase converts XMP into GMP
* GMP reductase converts GMP back into IMP | 1 | Biochemistry |
Benzene, as well as most other annulenes (cyclodecapentaene excepted) with the formula CH where n is an even number, such as cyclotetradecaheptaene. | 7 | Physical Chemistry |
Currently the most important application is due to the special magnetic properties of some ferromagnetic metallic glasses. The low magnetization loss is used in high efficiency transformers (amorphous metal transformer) at line frequency and some higher frequency transformers. Amorphous steel is a very brittle material which makes it difficult to punch into motor laminations. Also electronic article surveillance (such as theft control passive ID tags,) often uses metallic glasses because of these magnetic properties.
A commercial amorphous alloy, Vitreloy 1 (41.2% Zr, 13.8% Ti, 12.5% Cu, 10% Ni, and 22.5% Be), was developed at Caltech, as a part of Department of Energy and NASA research of new aerospace materials.
Ti-based metallic glass, when made into thin pipes, have a high tensile strength of , elastic elongation of 2% and high corrosion resistance. Using these properties, a Ti–Zr–Cu–Ni–Sn metallic glass was used to improve the sensitivity of a Coriolis flow meter. This flow meter is about 28-53 times more sensitive than conventional meters, which can be applied in fossil-fuel, chemical, environmental, semiconductor and medical science industry.
Zr-Al-Ni-Cu based metallic glass can be shaped into pressure sensors for automobile and other industries, and these sensors are smaller, more sensitive, and possess greater pressure endurance compared to conventional stainless steel made from cold working. Additionally, this alloy was used to make the world's smallest geared motor with diameter to be produced and sold at the time. | 8 | Metallurgy |
Optical sequencing is a single molecule DNA sequencing technique that follows sequence-by-synthesis and uses optical mapping technology. Similar to other single molecular sequencing approaches such as SMRT sequencing, this technique analyzes a single DNA molecule, rather than amplify the initial sample and sequence multiple copies of the DNA. During synthesis, fluorochrome-labeled nucleotides are incorporated through the use of DNA polymerases and tracked by fluorescence microscopy. This technique was originally proposed by David C. Schwartz and Arvind Ramanathan in 2003. | 1 | Biochemistry |
Such as trace minerals, micronutrients, human-induced cycles for synthetic compounds such as polychlorinated biphenyl (PCB). | 9 | Geochemistry |
The adhesion of gas or liquid molecules to the surface is known as adsorption. This can be due to either chemisorption or physisorption, and the strength of molecular adsorption to a catalyst surface is critically important to the catalyst's performance (see Sabatier principle). However, it is difficult to study these phenomena in real catalyst particles, which have complex structures. Instead, well-defined single crystal surfaces of catalytically active materials such as platinum are often used as model catalysts. Multi-component materials systems are used to study interactions between catalytically active metal particles and supporting oxides; these are produced by growing ultra-thin films or particles on a single crystal surface.
Relationships between the composition, structure, and chemical behavior of these surfaces are studied using ultra-high vacuum techniques, including adsorption and temperature-programmed desorption of molecules, scanning tunneling microscopy, low energy electron diffraction, and Auger electron spectroscopy. Results can be fed into chemical models or used toward the rational design of new catalysts. Reaction mechanisms can also be clarified due to the atomic-scale precision of surface science measurements. | 7 | Physical Chemistry |
Once the gel has set, the comb is removed, leaving wells where DNA samples can be loaded. Loading buffer is mixed with the DNA sample before the mixture is loaded into the wells. The loading buffer contains a dense compound, which may be glycerol, sucrose, or Ficoll, that raises the density of the sample so that the DNA sample may sink to the bottom of the well. If the DNA sample contains residual ethanol after its preparation, it may float out of the well. The loading buffer also includes colored dyes such as xylene cyanol and bromophenol blue used to monitor the progress of the electrophoresis. The DNA samples are loaded using a pipette. | 1 | Biochemistry |
Greenhouse gas monitoring involves the direct measurement of atmospheric concentrations and direct and indirect measurement of greenhouse gas emissions. Indirect methods calculate emissions of greenhouse gases based on related metrics such as fossil fuel extraction.
There are several different methods of measuring carbon dioxide concentrations in the atmosphere, including infrared analyzing and manometry. Methane and nitrous oxide are measured by other instruments, such as the range-resolved infrared differential absorption lidar (DIAL). Greenhouse gases are measured from space such as by the Orbiting Carbon Observatory and through networks of ground stations such as the Integrated Carbon Observation System.
The Annual Greenhouse Gas Index (AGGI) is defined by atmospheric scientists at NOAA as the ratio of total direct radiative forcing due to long-lived and well-mixed greenhouse gases for any year for which adequate global measurements exist, to that present in year 1990. These radiative forcing levels are relative to those present in year 1750 (i.e. prior to the start of the industrial era). 1990 is chosen because it is the baseline year for the Kyoto Protocol, and is the publication year of the first IPCC Scientific Assessment of Climate Change. As such, NOAA states that the AGGI "measures the commitment that (global) society has already made to living in a changing climate. It is based on the highest quality atmospheric observations from sites around the world. Its uncertainty is very low." | 2 | Environmental Chemistry |
The Wu theory (after Souheng Wu) is also essentially similar to the Owens/Wendt and Fowkes theories, in that it divides surface energy into a polar and a dispersive component. The primary difference is that Wu uses the harmonic means rather than the geometric means of the known surface tensions, and subsequently the use of more rigorous mathematics is employed. | 7 | Physical Chemistry |
The bright blue hues produced by the microorganisms during nights of very little moonlight or new moon attracts tourists to the bio bay. It is one of the three bio bays in Puerto Rico; the other two are Laguna Grande in Fajardo and La Parguera in Lajas. The bay and its surrounding mangrove forest are protected by the Vieques Bioluminescent Bay Natural Reserve and no swimming is allowed. Guided tours allow visitors to kayak in the bay and observe the bioluminescence. The bio bay is located near the beach community of Esperanza, between the barrios of Puerto Ferro and Puerto Real in Vieques, Puerto Rico. | 1 | Biochemistry |
The Kröhnke pyridine synthesis is reaction in organic synthesis between α-pyridinium methyl ketone salts and α, β-unsaturated carbonyl compounds used to generate highly functionalized pyridines. Pyridines occur widely in natural and synthetic products, so there is wide interest in routes for their synthesis. The method is named after Fritz Kröhnke. | 0 | Organic Chemistry |
Cloning has been used in fiction as a way of recreating historical figures. In the 1976 Ira Levin novel The Boys from Brazil and its 1978 film adaptation, Josef Mengele uses cloning to create copies of Adolf Hitler.
In Michael Crichtons 1990 novel Jurassic Park, which spawned a series of Jurassic Park' feature films, the bioengineering company InGen develops a technique to resurrect extinct species of dinosaurs by creating cloned creatures using DNA extracted from fossils. The cloned dinosaurs are used to populate the Jurassic Park wildlife park for the entertainment of visitors. The scheme goes disastrously wrong when the dinosaurs escape their enclosures. Despite being selectively cloned as females to prevent them from breeding, the dinosaurs develop the ability to reproduce through parthenogenesis. | 1 | Biochemistry |
In 1978, basic tests were being conducted on squid giant axons in order to find evidence of ephaptic events. It was shown that an action potential of one axon could be propagated to a neighboring axon. The level of transmission varied, from subthreshold changes to initiation of an action potential in a neighboring cell, but in all cases, it was apparent that there are implications of ephaptic coupling that are of physiological importance. | 1 | Biochemistry |
Frequency modulated Doppler-broadened signals can be modeled basically as ordinary fm-signals, although an extended description has to be used if the transition is optically saturated. Wavelength modulated Doppler broadened can be modeled by applying the conventional theory for wavelength modulation on the fm-signals.
Since the electrical field in NICE-OHMS consists of three modes, a carrier and two sidebands, which propagate in positive and negative directions in the cavity, up to nine sub-Doppler signals can appear; four appearing at the absorption and five at the dispersion phase. Each of these signals can, in turn, originate from interactions between several groups of molecules with various pairs of modes (e.g. carrier-carrier, sideband-carrier, sideband-sideband in various combinations). In addition, since sub-Doppler signals necessarily involve optical saturation, each of these interactions has to be modeled by a more extensive description. This implies that the situation can be complex. In fact, there are still some types of sub-Doppler signals for which there so far are no adequate theoretical description. | 7 | Physical Chemistry |
*SDHA NM_004168 Succinate Dehydrogenase subunit A
*SDHAF2 NM_017841
*SDHB NM_002973 Iron-sulfur protein (IP) subunit of succinate dehydrogenase (SDH) that is involved in complex II of the mitochondrial electron transport chain and is responsible for transferring electrons from succinate to ubiquinone (coenzyme Q)
*SDHC NM_003000 Membrane-anchoring subunit of succinate dehydrogenase (SDH) that is involved in complex II of the mitochondrial electron transport chain and is responsible for transferring electrons from succinate to ubiquinone (coenzyme Q).
*SDHD NM_003001 | 1 | Biochemistry |
The full 3D representation of crystallographic texture is given by the orientation distribution function (ODF) which can be achieved through evaluation of a set of pole figures or diffraction patterns. Subsequently, all pole figures can be derived from the ODF.
The ODF is defined as the volume fraction of grains with a certain orientation .
The orientation is normally identified using three Euler angles. The Euler angles then describe the transition from the sample’s reference frame into the crystallographic reference frame of each individual grain of the polycrystal. One thus ends up with a large set of different Euler angles, the distribution of which is described by the ODF.
The orientation distribution function, ODF, cannot be measured directly by any technique. Traditionally both X-ray diffraction and EBSD may collect pole figures. Different methodologies exist to obtain the ODF from the pole figures or data in general. They can be classified based on how they represent the ODF. Some represent the ODF as a function, sum of functions or expand it in a series of harmonic functions. Others, known as discrete methods, divide the ODF space in cells and focus on determining the value of the ODF in each cell. | 8 | Metallurgy |
Fluorides include compounds that contain ionic fluoride and those in which fluoride does not dissociate. The nomenclature does not distinguish these situations. For example, sulfur hexafluoride and carbon tetrafluoride are not sources of fluoride ions under ordinary conditions.
The systematic name fluoride, the valid IUPAC name, is determined according to the additive nomenclature. However, the name fluoride is also used in compositional IUPAC nomenclature which does not take the nature of bonding involved into account.
Fluoride is also used non-systematically, to describe compounds which release fluoride upon dissolving. Hydrogen fluoride is itself an example of a non-systematic name of this nature. However, it is also a trivial name, and the preferred IUPAC name for fluorane. | 1 | Biochemistry |
In H-NMR spectroscopy, the coupling of two hydrogen atoms on adjacent carbon atoms is called vicinal coupling. The coupling constant J represents coupling of vicinal hydrogen atoms because they couple through three bonds. Depending on the other substituents, the vicinal coupling constant is typically a value between 0 and +20 Hz. The dependence of the vicinal coupling constant on the dihedral angle is described by the Karplus relation. | 4 | Stereochemistry |
This idea consists of introducing a modified version of the forcing term: (or equilibrium distribution) into the LBM as a stress divergence force. This force is considered space-time dependent and contains solid properties
where denotes the Cauchy stress tensor. and are respectively the gravity vector and solid matter density.
The stress tensor is usually computed across the lattice aiming finite difference schemes. | 7 | Physical Chemistry |
The Raman shift chemical imaging spectral range spans from approximately 50 to 4,000 cm; the actual spectral range over which a particular Raman measurement is made is a function of the laser excitation frequency. The basic principle behind Raman spectroscopy differs from the MIR and NIR in that the x-axis of the Raman spectrum is measured as a function of energy shift (in cm) relative to the frequency of the laser used as the source of radiation. Briefly, the Raman spectrum arises from inelastic scattering of incident photons, which requires a change in polarizability with vibration, as opposed to infrared absorption, which requires a change in dipole moment with vibration. The end result is spectral information that is similar and in many cases complementary to the MIR. The Raman effect is weak - only about one in 10 photons incident to the sample undergoes Raman scattering. Both organic and inorganic materials possess a Raman spectrum; they generally produce sharp bands that are chemically specific. Fluorescence is a competing phenomenon and, depending on the sample, can overwhelm the Raman signal, for both bulk spectroscopy and imaging implementations.
Raman chemical imaging requires little or no sample preparation. However, physical sample sectioning may be used to expose the surface of interest, with care taken to obtain a surface that is as flat as possible. The conditions required for a particular measurement dictate the level of invasiveness of the technique, and samples that are sensitive to high power laser radiation may be damaged during analysis. It is relatively insensitive to the presence of water in the sample and is therefore useful for imaging samples that contain water such as biological material. | 7 | Physical Chemistry |
A DNA machine is a molecular machine constructed from DNA. Research into DNA machines was pioneered in the late 1980s by Nadrian Seeman and co-workers from New York University. DNA is used because of the numerous biological tools already found in nature that can affect DNA, and the immense knowledge of how DNA works previously researched by biochemists.
DNA machines can be logically designed since DNA assembly of the double helix is based on strict rules of base pairing that allow portions of the strand to be predictably connected based on their sequence. This "selective stickiness" is a key advantage in the construction of DNA machines.
An example of a DNA machine was reported by Bernard Yurke and co-workers at Lucent Technologies in the year 2000, who constructed molecular tweezers out of DNA.
The DNA tweezers contain three strands: A, B and C. Strand A latches onto half of strand B and half of strand C, and so it joins them all together. Strand A acts as a hinge so that the two "arms" — AB and AC — can move. The structure floats with its arms open wide. They can be pulled shut by adding a fourth strand of DNA (D) "programmed" to stick to both of the dangling, unpaired sections of strands B and C. The closing of the tweezers was proven by tagging strand A at either end with light-emitting molecules that do not emit light when they are close together. To re-open the tweezers add a further strand (E) with the right sequence to pair up with strand D. Once paired up, they have no connection to the machine BAC, so float away. The DNA machine can be opened and closed repeatedly by cycling between strands D and E. These tweezers can be used for removing drugs from inside fullerenes as well as from a self assembled DNA tetrahedron. The state of the device can be determined by measuring the separation between donor and acceptor fluorophores using FRET.
DNA walkers are another type of DNA machine. | 6 | Supramolecular Chemistry |
Solvents can affect rates through equilibrium-solvent effects that can be explained on the basis of the transition state theory. In essence, the reaction rates are influenced by differential solvation of the starting material and transition state by the solvent. When the reactant molecules proceed to the transition state, the solvent molecules orient themselves to stabilize the transition state. If the transition state is stabilized to a greater extent than the starting material then the reaction proceeds faster. If the starting material is stabilized to a greater extent than the transition state then the reaction proceeds slower. However, such differential solvation requires rapid reorientational relaxation of the solvent (from the transition state orientation back to the ground-state orientation). Thus, equilibrium-solvent effects are observed in reactions that tend to have sharp barriers and weakly dipolar, rapidly relaxing solvents. | 7 | Physical Chemistry |
Two drops of gastric juice are mixed with two drops of Gunzberg's reagent in an evaporating dish. The mixture is evaporated and if red is seen, free hydrochloric acid is present. | 3 | Analytical Chemistry |
*Davis, Mackenzie Leo, and David A. Cornwell. Introduction to Environmental Engineering. Dubuque, IA: McGraw-Hill Companies, 2008. Print.
*Gray, N. F. Biology of Wastewater Treatment. London: Imperial College, 2004. Print.
*Davis, Mackenzie Leo, and David A. Cornwell. Introduction to Environmental Engineering. Boston, MA: WCB McGraw-Hill, 1998. Print.
*http://www.cee.mtu.edu/~nurban/classes/CE3502/spring12/modelreports/MLSSreport.pdf
*http://ragsdaleassociates.com/WastewaterSystemOperatorsManual/Chapter%208%20-%20Activated%20Sludge.pdf | 3 | Analytical Chemistry |
A Chromatography column is a device used in chromatography for the separation of chemical compounds. A chromatography column contains the stationary phase, allowing the mobile phase to pass through it. Chromatography columns of different types are used in both gas and liquid chromatography. | 3 | Analytical Chemistry |
Alizarine Yellow R is a yellow colored azo dye made by the diazo coupling reaction. It is usually commercially available as a sodium salt. In its pure form, it is a rust-colored solid. It is mainly used as a pH indicator. | 3 | Analytical Chemistry |
Sufficiently dense matter containing protons experiences proton degeneracy pressure, in a manner similar to the electron degeneracy pressure in electron-degenerate matter: protons confined to a sufficiently small volume have a large uncertainty in their momentum due to the Heisenberg uncertainty principle. However, because protons are much more massive than electrons, the same momentum represents a much smaller velocity for protons than for electrons. As a result, in matter with approximately equal numbers of protons and electrons, proton degeneracy pressure is much smaller than electron degeneracy pressure, and proton degeneracy is usually modelled as a correction to the equations of state of electron-degenerate matter. | 7 | Physical Chemistry |
For organic chemistry, a carbonyl group is a functional group with the formula , composed of a carbon atom double-bonded to an oxygen atom, and it is divalent at the C atom. It is common to several classes of organic compounds (such as aldehydes, ketones and carboxylic acids), as part of many larger functional groups. A compound containing a carbonyl group is often referred to as a carbonyl compound.
The term carbonyl can also refer to carbon monoxide as a ligand in an inorganic or organometallic complex (a metal carbonyl, e.g. nickel carbonyl).
The remainder of this article concerns itself with the organic chemistry definition of carbonyl, such that carbon and oxygen share a double bond. | 0 | Organic Chemistry |
AMGs may influence gene expression by modulating the activity of transcription factors, which control the rate at which specific genes are transcribed into mRNA, thereby impacting the levels of corresponding proteins involved in metabolic pathways. | 1 | Biochemistry |
The asialoglycoprotein receptor was first characterized in 1968 by [https://www.sciencedirect.com/science/article/pii/S0021925818993373?via%3Dihub Morell et al.] and was the first mammalian lectin identified. The researchers transferred radioactively-labeled ceruloplasmin that had undergone a reaction via the enzyme neuraminidase to remove the protein's terminal sialic acid, generating an asialoglycoprotein. Upon injection of the radioactive protein into rabbits, the radioactivity of the entire asialoglycoprotein (rather than a portion of the protein) quickly moved from the blood into the liver. This rapid movement from the blood into the liver only occurred if the sialic acid of the protein was removed; i.e., if the protein had an exposed galactose residue (that would normally be covered by the sialic acid). Thus, it was concluded that a receptor is capable of recognizing asialoglycoproteins (i.e., proteins that have lost their terminal sialic acids) and removing them from circulation by transporting them to the liver. | 1 | Biochemistry |
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