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Aromaticity They are extracted from complex mixtures obtained by the refining of oil or by distillation of coal tar, and are used to produce a range of important chemicals and polymers, including styrene, phenol, aniline, polyester and nylon. The overwhelming majority of aromatic compounds are compounds of carbon, but ... | https://en.wikipedia.org/wiki?curid=239836 |
Aromaticity The lone pair on the nitrogen is not part of the aromatic π system. Pyrrole and imidazole are both five membered aromatic rings that contain heteroatoms. In pyrrole, each of the four sp-hybridized carbons contributes one π-electron, and the nitrogen atom is also sp-hybridized and contributes two π-electrons... | https://en.wikipedia.org/wiki?curid=239836 |
Aromaticity Ions that satisfy Huckel's rule of 4"n" + 2 π-electrons in a planar, cyclic, conjugated molecule are considered to be aromatic ions. For example, the cyclopentadienyl anion and the cycloheptatrienylium cation are both considered to be aromatic ions, and the azulene molecule can be approximated as a combinat... | https://en.wikipedia.org/wiki?curid=239836 |
Aromaticity Homoaromaticity is the state of systems where conjugation is interrupted by a single sp hybridized carbon atom. Y-aromaticity is used to describe a Y-shaped, planar (flat) molecule with resonance bonds. The concept was developed to explain the extraordinary stability and high basicity of the guanidinium cat... | https://en.wikipedia.org/wiki?curid=239836 |
Aromaticity But as of 2012, no Möbius aromatic molecules had been synthesized. Aromatics with two half-twists corresponding to the paradromic topologies were first suggested by Johann Listing. In one form of carbo-benzene, the ring is expanded and contains alkyne and allene groups. Spherical aromaticity is aromaticity ... | https://en.wikipedia.org/wiki?curid=239836 |
Tap water ("running water", "city water", "town water", "municipal water", "sink water", etc.) is water supplied to a tap (valve). Its uses include drinking, washing, cooking, and the flushing of toilets. Indoor tap water is distributed through "indoor plumbing", which has existed since antiquity but was available to v... | https://en.wikipedia.org/wiki?curid=239918 |
Tap water Water-borne diseases are vastly reduced by proper sewage and fresh water availability. Providing tap water to large urban or suburban populations requires a complex and carefully designed system of collection, storage, treatment and distribution, and is commonly the responsibility of a government agency, ofte... | https://en.wikipedia.org/wiki?curid=239918 |
Tap water Domestic water systems have been evolving since people first located their homes near a running water supply, such as a stream or river. The water flow also allowed sending waste water away from the residences. Modern indoor plumbing delivers clean, safe, potable water to each service point in the distributio... | https://en.wikipedia.org/wiki?curid=239918 |
Tap water As the consumption points above perform their function, most produce waste/sewage components that will require removal by the waste/sewage side of the system. The minimum is an air gap. See cross connection control & backflow prevention for an overview of backflow prevention methods and devices currently in u... | https://en.wikipedia.org/wiki?curid=239918 |
Tap water Remnants of pipes in some languages are the names of the experts involved in the execution, reparation, maintenance, and installation of water supply systems, which have been formed from the Latin word 'lead', English word 'plumber', French word, 'plombier'. Before a water supply system is constructed or modi... | https://en.wikipedia.org/wiki?curid=239918 |
Tap water In the developed world, levels of contaminants found in tap water vary for every household and plumbing system but tend to be low. Two general conceptions with popular appeal are: Both lack scientific support. In reality, both tap water and bottled water are usually safe, although in both cases exceptions can... | https://en.wikipedia.org/wiki?curid=239918 |
Tap water However, the bottled water industry was quick to dispute the claim, saying bottled water is one of the most highly regulated food products under the FDA regulatory authority and that the FDA system worked extremely well when coupled with the International Bottled Water Association's Model Code and unannounced... | https://en.wikipedia.org/wiki?curid=239918 |
Tap water "Bottled water is often tap water put through another filter and not held to the same quality regulations as public utility water is." Chlorine is a disinfectant which is added to tap water in the United States. Chlorine can leave organic material like trihalomethanes and haloacetic acids in the water. The le... | https://en.wikipedia.org/wiki?curid=239918 |
Water treatment is any process that improves the quality of water to make it more acceptable for a specific end-use. The end use may be drinking, industrial water supply, irrigation, river flow maintenance, water recreation or many other uses, including being safely returned to the environment. removes contaminants and... | https://en.wikipedia.org/wiki?curid=239926 |
Water treatment Measures taken to ensure water quality not only relate to the treatment of the water, but to its conveyance and distribution after treatment. It is therefore common practice to keep residual disinfectants in the treated water to kill bacteriological contamination during distribution. Water supplied to d... | https://en.wikipedia.org/wiki?curid=239926 |
Water treatment End use of the treated water dictates the necessary quality monitoring technologies, and locally available skills typically dictate the level of automation adopted. Saline water can be treated to yield fresh water. Two main processes are used, reverse osmosis or distillation. Both methods require more e... | https://en.wikipedia.org/wiki?curid=239926 |
Water treatment Where drinking water quality standards do exist, most are expressed as guidelines or targets rather than requirements, and very few water standards have any legal basis or, are subject to enforcement. Two exceptions are the European Drinking Water Directive and the Safe Drinking Water Act in the United ... | https://en.wikipedia.org/wiki?curid=239926 |
Water treatment Boiler water treatment is a type of industrial water treatment focused on removal or chemical modification of substances potentially damaging to the boiler. Varying types of treatment are used at different locations to avoid scale, corrosion, or foaming. External treatment of raw water supplies intended... | https://en.wikipedia.org/wiki?curid=239926 |
Water treatment Chemical additives to reduce these disadvantages may introduce toxicity to wastewater. Water cooling is commonly used for cooling automobile internal combustion engines and large industrial facilities such as nuclear and steam electric power plants, hydroelectric generators, petroleum refineries and che... | https://en.wikipedia.org/wiki?curid=239926 |
Water treatment This can ensure the efficiency of such programs after the departure of the research team, as monitoring is difficult because of the remoteness of many locations. Energy Consumption: plants can be significant consumers of energy. In California, more than 4% of the state's electricity consumption goes tow... | https://en.wikipedia.org/wiki?curid=239926 |
Water treatment The "Contaminant Candidate List" is published every five years, and EPA is required to decide whether to regulate at least five or more listed contaminants. Local drinking water utilities may apply for low interest loans, to make facility improvements, through the Drinking Water State Revolving Fund. | https://en.wikipedia.org/wiki?curid=239926 |
Regulatory sequence A regulatory sequence is a segment of a nucleic acid molecule which is capable of increasing or decreasing the expression of specific genes within an organism. Regulation of gene expression is an essential feature of all living organisms and viruses. In DNA, regulation of gene expression normally ha... | https://en.wikipedia.org/wiki?curid=240060 |
Regulatory sequence Research to find all regulatory regions in the genomes of all sorts of organisms is under way. Conserved non-coding sequences often contain regulatory regions, and so they are often the subject of these analyses. Regulatory sequences for the insulin gene are: | https://en.wikipedia.org/wiki?curid=240060 |
Room temperature Colloquially, room temperature is the range of air temperatures that most people prefer for indoor settings, which feel comfortable when wearing typical indoor clothing. Human comfort can extend beyond this range depending on humidity, air circulation and other factors. In certain fields, like science ... | https://en.wikipedia.org/wiki?curid=240105 |
Room temperature For those with respiratory problems or allergies, they recommend no less than , and for the sick, disabled, very old or very young, a minimum of . Temperature ranges are defined as "room temperature" for certain products and processes in industry, science, and consumer goods. For instance, for the ship... | https://en.wikipedia.org/wiki?curid=240105 |
Plasticity (physics) In physics and materials science, plasticity, also known as plastic deformation, is the ability of a solid material to undergo permanent deformation, a non-reversible change of shape in response to applied forces. For example, a solid piece of metal being bent or pounded into a new shape displays p... | https://en.wikipedia.org/wiki?curid=240123 |
Plasticity (physics) However, once the load exceeds a threshold – the yield strength – the extension increases more rapidly than in the elastic region; now when the load is removed, some degree of extension will remain. Elastic deformation, however, is an approximation and its quality depends on the time frame consider... | https://en.wikipedia.org/wiki?curid=240123 |
Plasticity (physics) Lead shows sufficient plasticity at room temperature, while cast iron does not possess sufficient plasticity for any forging operation even when hot. This property is of importance in forming, shaping and extruding operations on metals. Most metals are rendered plastic by heating and hence shaped h... | https://en.wikipedia.org/wiki?curid=240123 |
Plasticity (physics) Since amorphous materials, like polymers, are not well-ordered, they contain a large amount of free volume, or wasted space. Pulling these materials in tension opens up these regions and can give materials a hazy appearance. This haziness is the result of "crazing", where fibrils are formed within ... | https://en.wikipedia.org/wiki?curid=240123 |
Plasticity (physics) Inelastic deformations of rocks and concrete are primarily caused by the formation of microcracks and sliding motions relative to these cracks. At high temperatures and pressures, plastic behavior can also be affected by the motion of dislocations in individual grains in the microstructure. There a... | https://en.wikipedia.org/wiki?curid=240123 |
Plasticity (physics) If the stress exceeds a critical value, as was mentioned above, the material will undergo plastic, or irreversible, deformation. This critical stress can be tensile or compressive. The Tresca and the von Mises criteria are commonly used to determine whether a material has yielded. However, these cr... | https://en.wikipedia.org/wiki?curid=240123 |
Plasticity (physics) Von Mises solves for an effective stress under uniaxial loading, subtracting out hydrostatic stresses, and states that all effective stresses greater than that which causes material failure in uniaxial loading will result in plastic deformation. Again, a visual representation of the yield surface m... | https://en.wikipedia.org/wiki?curid=240123 |
Standard state In chemistry, the standard state of a material (pure substance, mixture or solution) is a reference point used to calculate its properties under different conditions. A superscript circle is used to designate a thermodynamic quantity in the standard state, such as change in enthalpy (ΔH°), change in entr... | https://en.wikipedia.org/wiki?curid=240224 |
Standard state The standard enthalpy change of formation for an element in its standard state is zero, and this convention allows a wide range of other thermodynamic quantities to be calculated and tabulated. The standard state of a substance does not have to exist in nature: for example, it is possible to calculate va... | https://en.wikipedia.org/wiki?curid=240224 |
Standard state For most elements, the reference point of Δ"H" = 0 is defined for the most stable allotrope of the element, such as graphite in the case of carbon, and the β-phase (white tin) in the case of tin. An exception is white phosphorus, the most common allotrope of phosphorus, which is defined as the standard s... | https://en.wikipedia.org/wiki?curid=240224 |
Standard state A range of similar symbols are used in the literature: a stroked lowercase letter O (), a superscript zero () or a circle with a horizontal bar either where the bar extends beyond the boundaries of the circle () or is enclosed by the circle, dividing the circle in half (). When compared to the plimsoll s... | https://en.wikipedia.org/wiki?curid=240224 |
Biological pump The biological pump, in its simplest form, is the ocean's biologically driven sequestration of carbon from the atmosphere to the ocean interior and seafloor sediments. It is the part of the oceanic carbon cycle responsible for the cycling of organic matter formed mainly by phytoplankton during photosynt... | https://en.wikipedia.org/wiki?curid=240228 |
Biological pump It is this aggregation that gives particles a better chance of escaping predation and decomposition in the water column and eventually make it to the sea floor. The fixed carbon that is either decomposed by bacteria on the way down or once on the sea floor then enters the final phase of the pump and is ... | https://en.wikipedia.org/wiki?curid=240228 |
Biological pump Oceanic primary production accounts for about half of the carbon fixation carried out on Earth. Approximately 50–60 Pg of carbon are fixed by marine phytoplankton each year despite the fact that they comprise less than 1% of the total photosynthetic biomass on Earth. The majority of this carbon fixation... | https://en.wikipedia.org/wiki?curid=240228 |
Biological pump In addition, the sequestration of CaCO serves to lower overall oceanic alkalinity and again raise atmospheric levels. The vast majority of carbon incorporated in organic and inorganic biological matter is formed at the sea surface and then must sink to the ocean floor. A single phytoplankton cell has a ... | https://en.wikipedia.org/wiki?curid=240228 |
Biological pump The portion of carbon that makes it to the sea floor becomes part of the geologic record and in the case of the calcium carbonate, may form large deposits and resurface through tectonic motion as in the case with the White Cliffs of Dover in Southern England. These cliffs are made almost entirely of the... | https://en.wikipedia.org/wiki?curid=240228 |
Biological pump Changes in land use, the combustion of fossil fuels, and the production of cement have led to an increase in CO concentration in the atmosphere. At present, about one third (approximately 2 Pg C y = 2 × 10 grams of carbon per year) of anthropogenic emissions of CO are believed to be entering the ocean. ... | https://en.wikipedia.org/wiki?curid=240228 |
Biological pump In 2019, a study indicated that at current rates of seawater acidification, we could see Antarctic phytoplanktons smaller and less effective at storing carbon before the end of the century. | https://en.wikipedia.org/wiki?curid=240228 |
Carbonated water (also known as soda water, sparkling water, fizzy water, water with gas or, especially in the U.S., seltzer or seltzer water) is water containing dissolved carbon dioxide gas, either artificially injected under pressure or occurring due to natural geological processes. Carbonation causes small bubbles ... | https://en.wikipedia.org/wiki?curid=240561 |
Carbonated water Priestley's apparatus, which featured a bladder between the generator and the absorption tank to regulate the flow of carbon dioxide, was soon joined by a wide range of others. However, it wasn't until 1781 that carbonated water began being produced on a large scale with the establishment of companies ... | https://en.wikipedia.org/wiki?curid=240561 |
Carbonated water such as club soda or sparkling water is defined in US law as a food of minimal nutritional value, even if minerals, vitamins, or artificial sweeteners have been added to it. may increase irritable bowel syndrome symptoms of bloating and gas due to the release of carbon dioxide in the digestive tract. I... | https://en.wikipedia.org/wiki?curid=240561 |
Carbonated water A 2017 study by the American Dental Association showed that, although seltzer water is more erosive than tap water, it would take over 100 years of daily drinking to cause damage to human teeth. However, if there is added sugar or artificial flavorings, this does not apply. Natural flavoring, on the ot... | https://en.wikipedia.org/wiki?curid=240561 |
Carbonated water Many alcoholic drinks, such as beer, champagne, cider, and spritzer, were naturally carbonated through the fermentation process for centuries. In 1662 Christopher Merret was creating 'sparkling wine'. William Brownrigg was apparently the first to produce artificial carbonated water, in the early 1740s,... | https://en.wikipedia.org/wiki?curid=240561 |
Carbonated water In 1772, Priestley published a paper titled "Impregnating Water with Fixed Air" in which he describes dripping "oil of vitriol" (sulfuric acid) onto chalk to produce carbon dioxide gas, and encouraging the gas to dissolve into an agitated bowl of water. Priestley referred to his invention of this treat... | https://en.wikipedia.org/wiki?curid=240561 |
Carbonated water The article says that in the hot summer of 1777 in London "aerated waters" (that is, carbonated) were selling well but there was as yet no mention of "soda water", though the first effervescent drinks were probably made using "soda powders" containing bicarbonate of soda and tartaric acid. The name sod... | https://en.wikipedia.org/wiki?curid=240561 |
Carbonated water Naturally carbonated water, "Selters", has been commercially bottled and shipped from this town since the 18th century or earlier. Generally, "seltzer water" has no added sodium salts, while "club soda" still retains some of the sodium salts that once were used. The term "Seltzer water" is virtually un... | https://en.wikipedia.org/wiki?curid=240561 |
Carbonated water The bulb is pressed into the valve assembly at the top of the siphon, the gas injected, then the bulb withdrawn. Soda water made in this way tends not to be as carbonated as commercial soda water because water from the refrigerator is not chilled as much as possible, and the pressure of carbon dioxide ... | https://en.wikipedia.org/wiki?curid=240561 |
Carbonated water Soon after its introduction, the bottle became extremely popular with the soft drink and brewing industries mainly in Europe, Asia and Australasia, though some alcohol drinkers disdained the use of the bottle. One etymology of the term "codswallop" originates from beer sold in Codd bottles, though this... | https://en.wikipedia.org/wiki?curid=240561 |
Carbonated water The process of dissolving carbon dioxide in water is called carbonation. Commercial soda water in siphons is made by chilling filtered plain water to or below, optionally adding a sodium or potassium based alkaline compound such as sodium bicarbonate to reduce acidity, and then pressurizing the water w... | https://en.wikipedia.org/wiki?curid=240561 |
Carbonated water is a diluent mixed with alcoholic beverages where it is used to top-off the drink and provide a degree of 'fizz'. Adding soda water to 'short' drinks such as spirits dilutes them and makes them 'long' not to be confused with long drinks such as those made with vermouth. also works well in short drinks ... | https://en.wikipedia.org/wiki?curid=240561 |
Gene silencing is the regulation of gene expression in a cell to prevent the expression of a certain gene. can occur during either transcription or translation and is often used in research. In particular, methods used to silence genes are being increasingly used to produce therapeutics to combat cancer and other disea... | https://en.wikipedia.org/wiki?curid=240850 |
Gene silencing The antisense oligonucleotides can affect gene expression in two ways: by using an RNase H-dependent mechanism or by using a steric blocking mechanism. RNase H-dependent oligonucleotides cause the target mRNA molecules to be degraded, while steric-blocker oligonucleotides prevent translation of the mRNA ... | https://en.wikipedia.org/wiki?curid=240850 |
Gene silencing The last ribozyme motif, the RNase P ribozyme, is found in "Escherichia coli" and is known for its ability to cleave the phosphodiester bonds of several tRNA precursors when joined to a protein cofactor. The general catalytic mechanism used by ribozymes is similar to the mechanism used by protein ribonuc... | https://en.wikipedia.org/wiki?curid=240850 |
Gene silencing The fragments integrate into a multi-subunit protein called the RNA-induced silencing complex, which contains Argonaute proteins that are essential components of the RNAi pathway. One strand of the molecule, called the "guide" strand, binds to RISC, while the other strand, known as the "passenger" strand... | https://en.wikipedia.org/wiki?curid=240850 |
Gene silencing By binding to specific sites within the 3'-UTR, a large number of specific miRNAs decrease gene expression of their particular target mRNAs by either inhibiting translation or directly causing degradation of the transcript, using a mechanism similar to RNA interference (see MicroRNA). The 3'-UTR also may... | https://en.wikipedia.org/wiki?curid=240850 |
Gene silencing The effects of miRNA dysregulation of gene expression seem to be important in cancer. For instance, in gastrointestinal cancers, nine miRNAs have been identified as epigenetically altered and effective in down regulating DNA repair enzymes. The effects of miRNA dysregulation of gene expression also seem ... | https://en.wikipedia.org/wiki?curid=240850 |
Gene silencing Receptors involved in mitogenic pathways that lead to the increased production of cancer cells there have also been targeted by siRNA molecules. The chemokine receptor chemokine receptor 4 (CXCR4), associated with the proliferation of breast cancer, was cleaved by siRNA molecules that reduced the number ... | https://en.wikipedia.org/wiki?curid=240850 |
Gene silencing This prevented the virus from entering the human peripheral blood lymphocytes and the primary hematopoietic stem cells. A similar technique was used to decrease the amount of the detectable virus in hepatitis B and C infected cells. In hepatitis B, siRNA silencing was used to target the surface antigen o... | https://en.wikipedia.org/wiki?curid=240850 |
Gene silencing Potato lines expressing viral replicase sequences that confer resistance to potato leafroll virus were sold under the trade names NewLeaf Y and NewLeaf Plus, and were widely accepted in commercial production in 1999–2001, until McDonald's Corp. decided not to purchase GM potatoes and Monsanto decided to ... | https://en.wikipedia.org/wiki?curid=240850 |
Gene silencing By targeting the NTPase gene, one dose of siRNA 4 hours pre-infection was shown to control Tulane virus replication for 48 hours post-infection, reducing the viral titer by up to 2.6 logarithms. Although the Tulane virus is species-specific and does not affect humans, it has been shown to be closely rela... | https://en.wikipedia.org/wiki?curid=240850 |
Gene silencing In addition, siRNA was used to prevent the bacteria, "Psueomonas aeruginosa", from invading murine lung epithelial cells by knocking down the caveolin-2 (CAV2) gene. Thus, though bacteria cannot be directly targeted by siRNA mechanisms, they can still be affected by siRNA when the components involved in ... | https://en.wikipedia.org/wiki?curid=240850 |
Gene silencing Researchers have been looking to gene silencing as a potential therapeutic for HD. can be used to treat HD by targeting the mutant huntingtin protein. The mutant huntingtin protein has been targeted through gene silencing that is allele specific using allele specific oligonucleotides. In this method, the... | https://en.wikipedia.org/wiki?curid=240850 |
Gene silencing The disease causes motor neurons to degenerate, which eventually leads to neuron death and muscular degeneration. Hundreds of mutations in the Cu/Zn superoxide dismutase (SOD1) gene have been found to cause ALS. has been used to knock down the SOD1 mutant that is characteristic of ALS. In specific, siRNA... | https://en.wikipedia.org/wiki?curid=240850 |
Gene silencing Thus, researchers are searching for more efficient methods to deliver and develop specific gene silencing therapeutics that are still safe and effective. Arctic Apples are a suite of trademarked apples that contain a nonbrowning trait created by using gene silencing to reduce the expression of polyphenol... | https://en.wikipedia.org/wiki?curid=240850 |
SN1 reaction The S1 reaction is a substitution reaction in organic chemistry. "S" stands for "nucleophilic substitution", and the "1" says that the rate-determining step is unimolecular. Thus, the rate equation is often shown as having first-order dependence on electrophile and zero-order dependence on nucleophile. Thi... | https://en.wikipedia.org/wiki?curid=240935 |
SN1 reaction An example of a reaction taking place with an S1 reaction mechanism is the hydrolysis of tert-butyl bromide forming "tert"-butanol: This S1 reaction takes place in three steps: The S1 mechanism tends to dominate when the central carbon atom is surrounded by bulky groups because such groups sterically hinde... | https://en.wikipedia.org/wiki?curid=240935 |
SN1 reaction This is illustrated below in the S1 reaction of S-3-chloro-3-methylhexane with an iodide ion, which yields a racemic mixture of 3-iodo-3-methylhexane: However, an excess of one stereoisomer can be observed, as the leaving group can remain in proximity to the carbocation intermediate for a short time and bl... | https://en.wikipedia.org/wiki?curid=240935 |
SN1 reaction Since the S1 reaction involves formation of an unstable carbocation intermediate in the rate-determining step, anything that can facilitate this will speed up the reaction. The normal solvents of choice are both "polar" (to stabilize ionic intermediates in general) and "protic solvents" (to solvate the lea... | https://en.wikipedia.org/wiki?curid=240935 |
Markovnikov's rule In organic chemistry, or Markownikoff's rule describes the outcome of some addition reactions. The rule was formulated by Russian chemist Vladimir Markovnikov in 1870. The rule states that with the addition of a protic acid HX to an asymmetric alkene, the acid hydrogen (H) gets attached to the carbon... | https://en.wikipedia.org/wiki?curid=240949 |
Markovnikov's rule Therefore, the major product of the addition of HX (where X is some atom more electronegative than H) to an alkene has the hydrogen atom in the less substituted position and X in the more substituted position Mechanisms that do not involve a carbocation intermediate may react through other mechanisms... | https://en.wikipedia.org/wiki?curid=240949 |
Markovnikov's rule In this case, the terminal carbon is a reactant that produces a primary addition product instead of a secondary addition product, in the case of propene. A new method of anti-Markovnikov addition has been described by Hamilton and Nicewicz, who utilize aromatic molecules and light energy from a low-e... | https://en.wikipedia.org/wiki?curid=240949 |
Markovnikov's rule Another notable example of anti-Markovnikov addition is hydroboration. | https://en.wikipedia.org/wiki?curid=240949 |
Hydration reaction In chemistry, a hydration reaction is a chemical reaction in which a substance combines with water. In organic chemistry, water is added to an unsaturated substrate, which is usually an alkene or an alkyne. This type of reaction is employed industrially to produce ethanol, isopropanol, and 2-butanol.... | https://en.wikipedia.org/wiki?curid=240960 |
Hydration reaction In the case of ethanol production, this step can be written: Subsequently, this sulphate ester is hydrolyzed to regenerate sulphuric acid and release ethanol: This two step route is called the "indirect process". In the "direct process," the acid protonates the alkene, and water reacts with this inci... | https://en.wikipedia.org/wiki?curid=240960 |
Hydration reaction Conceptually similar reactions include hydroamination and hydroalkoxylation, which involve adding amines and alcohols to alkenes. Hydration is an important process in many other applications; one example is the production of Portland cement by the crosslinking of calcium oxides and silicates that is ... | https://en.wikipedia.org/wiki?curid=240960 |
Carbon tetrachloride Carbon tetrachloride, also known by many other names (such as tetrachloromethane, also recognised by the IUPAC, carbon tet in the cleaning industry, Halon-104 in firefighting, and Refrigerant-10 in HVACR) is an organic compound with the chemical formula CCl. It is a colourless liquid with a "sweet"... | https://en.wikipedia.org/wiki?curid=241047 |
Carbon tetrachloride In the carbon tetrachloride molecule, four chlorine atoms are positioned symmetrically as corners in a tetrahedral configuration joined to a central carbon atom by single covalent bonds. Because of this symmetric geometry, CCl is non-polar. Methane gas has the same structure, making carbon tetrachl... | https://en.wikipedia.org/wiki?curid=241047 |
Carbon tetrachloride was widely used as a dry cleaning solvent, as a refrigerant, and in lava lamps. In case of the latter, carbon tetrachloride is a key ingredient that adds weight to the otherwise buoyant wax. It once was a popular solvent in organic chemistry, but, because of its adverse health effects, it is rarely... | https://en.wikipedia.org/wiki?curid=241047 |
Carbon tetrachloride In 1911, Pyrene patented a small, portable extinguisher that used the chemical. The extinguisher consisted of a brass bottle with an integrated handpump that was used to expel a jet of liquid toward the fire. As the container was unpressurized, it could easily be refilled after use. was suitable fo... | https://en.wikipedia.org/wiki?curid=241047 |
Carbon tetrachloride is still used to manufacture less destructive refrigerants. made from heavy chlorine-37 has been used in the detection of neutrinos. is one of the most potent hepatotoxins (toxic to the liver), so much so that it is widely used in scientific research to evaluate hepatoprotective agents. Exposure to... | https://en.wikipedia.org/wiki?curid=241047 |
DNA–DNA hybridization generally refers to a molecular biology technique that measures the degree of genetic similarity between pools of DNA sequences. It is usually used to determine the genetic distance between two organisms. This has been used extensively in phylogeny and taxonomy. The DNA of one organism is labelled... | https://en.wikipedia.org/wiki?curid=241191 |
DNA–DNA hybridization These samples would have to be separated in their own lanes inside the membranes and then the membrane would have to be rotated to a different angle where it would result in simultaneous hybridization with many different DNA probes. When several species are compared, similarity values allow organi... | https://en.wikipedia.org/wiki?curid=241191 |
DNA–DNA hybridization Critics argue that the technique is inaccurate for comparison of closely related species, as any attempt to measure differences between orthologous sequences between organisms is overwhelmed by the hybridization of paralogous sequences within an organism's genome. DNA sequencing and computational ... | https://en.wikipedia.org/wiki?curid=241191 |
Poisson's ratio formula_1 (nu) is a measure of the Poisson effect, that describes the expansion or contraction of a material in directions perpendicular to the direction of loading. The value of is the negative of the ratio of transverse strain to axial strain. For small values of these changes, formula_1 is the amount... | https://en.wikipedia.org/wiki?curid=241223 |
Poisson's ratio A perfectly incompressible isotropic material deformed elastically at small strains would have a of exactly 0.5. Most steels and rigid polymers when used within their design limits (before yield) exhibit values of about 0.3, increasing to 0.5 for post-yield deformation which occurs largely at constant v... | https://en.wikipedia.org/wiki?curid=241223 |
Poisson's ratio Assuming that the material is stretched or compressed along the axial direction (the "x" axis in the diagram below): where For a cube stretched in the "x"-direction (see Figure 1) with a length increase of formula_7 in the "x" direction, and a length decrease of formula_8 in the "y" and "z" directions, ... | https://en.wikipedia.org/wiki?curid=241223 |
Poisson's ratio However, the symmetry of the stress and strain tensors implies that not all the six Poisson's ratios in the equation are independent. There are only nine independent material properties: three elastic moduli, three shear moduli, and three Poisson's ratios. The remaining three Poisson's ratios can be obt... | https://en.wikipedia.org/wiki?curid=241223 |
Poisson's ratio When subjected to positive strain in a longitudinal axis, the transverse strain in the material will actually be positive (i.e. it would increase the cross sectional area). For these materials, it is usually due to uniquely oriented, hinged molecular bonds. In order for these bonds to stretch in the lon... | https://en.wikipedia.org/wiki?curid=241223 |
Poisson's ratio At finite strains, the relationship between the transverse and axial strains formula_57 and formula_58 is typically not well described by the Poisson's ratio. In fact, the is often considered a function of the applied strain in the large strain regime. In such instances, the is replaced by the Poisson f... | https://en.wikipedia.org/wiki?curid=241223 |
Poisson's ratio This rock will expand or contract in the vertical direction as a direct result of the applied stress, and it will also deform in the horizontal direction as a result of Poisson's effect. This change in strain in the horizontal direction can affect or form joints and dormant stresses in the rock. Althoug... | https://en.wikipedia.org/wiki?curid=241223 |
Leaving group In chemistry, a leaving group is a molecular fragment that departs with a pair of electrons in heterolytic bond cleavage. Leaving groups can be anions, cations or neutral molecules, but in either case it is crucial that the leaving group be able to stabilize the additional electron density that results fr... | https://en.wikipedia.org/wiki?curid=241440 |
Leaving group A good measure of anion stability is the pKa of an anion's conjugate acid, and leaving group ability indeed generally follows this trend, with a lower pKH being associated with better leaving group ability. The correlation between pKH and leaving group ability, however, is not perfect. ability represents ... | https://en.wikipedia.org/wiki?curid=241440 |
Leaving group The ability of a group to leave is contextual. For example, in SAr reactions, the rate is generally increased when the leaving group is fluoride relative to the other halogens. This effect is due to the fact that the highest energy transition state for this two step addition-elimination process occurs in ... | https://en.wikipedia.org/wiki?curid=241440 |
Leaving group This situation is broadly defined as leaving group activation There can still exist contextual differences in leaving group ability in the purest form, that is when the actual group that leaves is not affected by the reaction conditions (by protonation or Lewis acid complexation) "and" the departure of th... | https://en.wikipedia.org/wiki?curid=241440 |
Leaving group The requirement for a good leaving group is relaxed in conjugate base elimination reactions. These reactions include loss of a leaving group in the β position of an enolate as well as the regeneration of a carbonyl group from the tetrahedral intermediate in nucleophilic acyl substitution. Under forcing co... | https://en.wikipedia.org/wiki?curid=241440 |
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