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Percoll is a tool for efficient density separation in Cell biology that was first formulated by Pertoft and colleagues. It is used for the isolation of cells, organelles, and/or viruses by density centrifugation. Percoll consists of colloidal silica particles of 15–30 nm diameter (23% w/w in water) which have been coated with polyvinylpyrrolidone (PVP).
Percoll is well suited for density gradient experiments because it possesses a low viscosity compared to alternatives, a low osmolarity, and no toxicity towards cells and their constituents.
Percoll is a registered trademark of GE Healthcare. | 1 | Applied and Interdisciplinary Chemistry |
About 8,100 plant species use carbon fixation, which represents about 3% of all terrestrial species of plants. All these 8,100 species are angiosperms. carbon fixation is more common in monocots compared with dicots, with 40% of monocots using the pathway, compared with only 4.5% of dicots. Despite this, only three families of monocots use carbon fixation compared to 15 dicot families. Of the monocot clades containing plants, the grass (Poaceae) species use the photosynthetic pathway most. 46% of grasses are and together account for 61% of species. has arisen independently in the grass family some twenty or more times, in various subfamilies, tribes, and genera, including the Andropogoneae tribe which contains the food crops maize, sugar cane, and sorghum. Various kinds of millet are also . Of the dicot clades containing species, the order Caryophyllales contains the most species. Of the families in the Caryophyllales, the Chenopodiaceae use carbon fixation the most, with 550 out of 1,400 species using it. About 250 of the 1,000 species of the related Amaranthaceae also use .
Members of the sedge family Cyperaceae, and members of numerous families of eudicots – including Asteraceae (the daisy family), Brassicaceae (the cabbage family), and Euphorbiaceae (the spurge family) – also use .
No large trees (above 15 m in height) use , however a number of small trees or shrubs smaller than 10 m exist which do: six species of Euphorbiaceae all native to Hawaii and two species of Amaranthaceae growing in deserts of the Middle-East and Asia. | 0 | Theoretical and Fundamental Chemistry |
Zinc deficiency appears to be the most common micronutrient deficiency in crop plants; it is particularly common in high-pH soils. Zinc-deficient soil is cultivated in the cropland of about half of Turkey and India, a third of China, and most of Western Australia. Substantial responses to zinc fertilization have been reported in these areas. Plants that grow in soils that are zinc-deficient are more susceptible to disease. Zinc is added to the soil primarily through the weathering of rocks, but humans have added zinc through fossil fuel combustion, mine waste, phosphate fertilizers, pesticide (zinc phosphide), limestone, manure, sewage sludge, and particles from galvanized surfaces. Excess zinc is toxic to plants, although zinc toxicity is far less widespread. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, the mass concentration (or ) is defined as the mass of a constituent divided by the volume of the mixture .
For a pure chemical the mass concentration equals its density (mass divided by volume); thus the mass concentration of a component in a mixture can be called the density of a component in a mixture. This explains the usage of (the lower case Greek letter rho), the symbol most often used for density. | 0 | Theoretical and Fundamental Chemistry |
Most experimentally determined values of the thermal contact resistance fall between
0.000005 and 0.0005 m K/W (the corresponding range of thermal contact
conductance is 200,000 to 2000 W/m K). To know whether the thermal contact resistance is significant or not, magnitudes of the thermal resistances of the layers are compared with typical values of thermal contact resistance. Thermal contact resistance is significant and may dominate for good heat conductors such as metals but can be neglected for poor heat conductors such as insulators.
Thermal contact conductance is an important factor in a variety of applications, largely because many physical systems contain a mechanical combination of two materials. Some of the fields where contact conductance is of importance are:
* Electronics
** Electronic packaging
** Heat sinks
** Brackets
* Industry
** Nuclear reactor cooling
** Gas turbine cooling
** Internal combustion engines
** Heat exchangers
** Thermal insulation
** Press hardening of automotive steels
* Flight
** Hypersonic flight vehicles
** Thermal supervision for space vehicles
* Residential/building science
** Performance of building envelopes | 0 | Theoretical and Fundamental Chemistry |
The overall movement of a bacterium is the result of alternating tumble and swim phases, called run-and-tumble motion. As a result, the trajectory of a bacterium swimming in a uniform environment will form a random walk with relatively straight swims interrupted by random tumbles that reorient the bacterium. Bacteria such as E. coli are unable to choose the direction in which they swim, and are unable to swim in a straight line for more than a few seconds due to rotational diffusion; in other words, bacteria "forget" the direction in which they are going. By repeatedly evaluating their course, and adjusting if they are moving in the wrong direction, bacteria can direct their random walk motion toward favorable locations.
In the presence of a chemical gradient bacteria will chemotax, or direct their overall motion based on the gradient. If the bacterium senses that it is moving in the correct direction (toward attractant/away from repellent), it will keep swimming in a straight line for a longer time before tumbling; however, if it is moving in the wrong direction, it will tumble sooner. Bacteria like E. coli use temporal sensing to decide whether their situation is improving or not, and in this way, find the location with the highest concentration of attractant, detecting even small differences in concentration.
This biased random walk is a result of simply choosing between two methods of random movement; namely tumbling and straight swimming. The helical nature of the individual flagellar filament is critical for this movement to occur. The protein structure that makes up the flagellar filament, flagellin, is conserved among all flagellated bacteria. Vertebrates seem to have taken advantage of this fact by possessing an immune receptor (TLR5) designed to recognize this conserved protein.
As in many instances in biology, there are bacteria that do not follow this rule. Many bacteria, such as Vibrio, are monoflagellated and have a single flagellum at one pole of the cell. Their method of chemotaxis is different. Others possess a single flagellum that is kept inside the cell wall. These bacteria move by spinning the whole cell, which is shaped like a corkscrew. | 1 | Applied and Interdisciplinary Chemistry |
The main use of -ascorbic acid and its salts is as food additives, mostly to combat oxidation. It is approved for this purpose in the EU with E number E300, the US, Australia, and New Zealand. | 1 | Applied and Interdisciplinary Chemistry |
In fluid dynamics, Landau–Levich flow or the Landau–Levich problem describes the flow created by a moving plate which is pulled out of a liquid surface. Landau–Levich flow finds many applications in thin film coating. The solution to the problem was described by Lev Landau and Veniamin Levich in 1942. The problem assumes that the plate is dragged out of the liquid slowly, so that the three major forces which are in balance are viscous force, the force due to gravity, and the force due to surface tension. | 1 | Applied and Interdisciplinary Chemistry |
In 1969, two separate labs simultaneously identified antigens in the sera of SLE and SS patients. Clark et al. referred to the antigen as Ro – named after the patient from which the antibodies were extracted, while Alspaugh & Tanand used the term SSA. It was later found that the labs described the same antigen, hence the compound term for the antibody, Anti-SSA/Ro, Anti-Ro/SSA. | 1 | Applied and Interdisciplinary Chemistry |
In 1799, the first volume of the West-Country Collections was issued. Half consisted of Davys essays On Heat, Light, and the Combinations of Light, On Phos-oxygen and its Combinations, and on the Theory of Respiration'. On 22 February 1799 Davy, wrote to Davies Giddy, "I am now as much convinced of the non-existence of caloric as I am of the existence of light." | 1 | Applied and Interdisciplinary Chemistry |
The normal halide of boron is boron trifluoride|. Boron forms many subhalides: several , including diboron tetrafluoride|; also BF. Aluminium forms a variety of subhalides. For gallium, adducts of are known. Phosphorus subhalides include diphosphorus tetraiodide|, , and (structurally related to ). For bismuth, the compound originally described as bismuth monochloride was later shown to consist of clusters and chloride anions. There are many tellurium subhalides, including tritellurium dichloride|, ditellurium bromide| (X = Cl, Br, I), and two forms of TeI. | 0 | Theoretical and Fundamental Chemistry |
In this microbiological procedure, theoretically, the antibacterial or anti-fungal activity of the volatile oils from a chosen plant may be tested against a selection of gram-positive and gram-negative bacteria or a species of fungus. The growth of the bacteria or fungi are then monitored on a timely basis to measure the bacteriostatic or anti-fungal activity of the volatile oils. In some cases, a complete inhibition of growth for the bacteria tested can be observed. | 1 | Applied and Interdisciplinary Chemistry |
In the presence of a magnetic field, the likelihood of an avalanche discharge occurring under high vacuum conditions can be increased through a phenomenon known as Penning discharge. This occurs when electrons can become trapped within a potential minimum, thereby extending the mean free path of the electrons [Fränkle 2014]. | 0 | Theoretical and Fundamental Chemistry |
4-(γ-Glutamylamino)butanoic acid is molecule that consists of -glutamate conjugated to γ-aminobutyric acid (GABA). It is the substrate of the enzyme γ-glutamyl-γ-aminobutyrate hydrolase, which is involved in the biosynthesis of polyamines. | 1 | Applied and Interdisciplinary Chemistry |
A stormwater detention vault is an underground structure designed to manage excess stormwater runoff on a developed site, often in an urban setting. This type of best management practice may be selected when there is insufficient space on the site to infiltrate the runoff or build a surface facility such as a detention basin or retention basin.
Detention vaults manage stormwater quantity flowing to nearby surface waters. They help prevent flooding and can reduce erosion in rivers and streams. They do not provide treatment to improve water quality, though some are attached to a media filter bank to remove pollutants. | 1 | Applied and Interdisciplinary Chemistry |
A liquid-impregnated surface consists of two distinct layers. The first is a highly textured or porous substrate with features spaced sufficiently close to stably contain the second layer which is an impregnating liquid that fills in the spaces between the features. The liquid must have a surface energy well-matched to the substrate in order to form a stable film. These surfaces bioimitate the carnivorous Venezuelan pitcher plant, which uses microscale hairs to create a water slide that causes ants to slip to their death. Slippery surfaces are finding applications in commercial products, anti-fouling surfaces, anti-icing and biofilm-resistant medical devices. | 0 | Theoretical and Fundamental Chemistry |
The first modern definition of acids and bases in molecular terms was devised by Svante Arrhenius. A hydrogen theory of acids, it followed from his 1884 work with Friedrich Wilhelm Ostwald in establishing the presence of ions in aqueous solution and led to Arrhenius receiving the Nobel Prize in Chemistry in 1903.
As defined by Arrhenius:
* An Arrhenius acid is a substance that ionises in water to form hydrogen ions (); that is, an acid increases the concentration of H ions in an aqueous solution.
This causes the protonation of water, or the creation of the hydronium () ion. Thus, in modern times, the symbol is interpreted as a shorthand for , because it is now known that a bare proton does not exist as a free species in aqueous solution. This is the species which is measured by pH indicators to measure the acidity or basicity of a solution.
* An Arrhenius base is a substance that dissociates in water to form hydroxide () ions; that is, a base increases the concentration of ions in an aqueous solution.
The Arrhenius definitions of acidity and alkalinity are restricted to aqueous solutions and are not valid for most non-aqueous solutions, and refer to the concentration of the solvent ions. Under this definition, pure and HCl dissolved in toluene are not acidic, and molten NaOH and solutions of calcium amide in liquid ammonia are not alkaline. This led to the development of the Brønsted–Lowry theory and subsequent Lewis theory to account for these non-aqueous exceptions.
The reaction of an acid with a base is called a neutralization reaction. The products of this reaction are a salt and water.
In this traditional representation an acid–base neutralization reaction is formulated as a double-replacement reaction. For example, the reaction of hydrochloric acid (HCl) with sodium hydroxide (NaOH) solutions produces a solution of sodium chloride (NaCl) and some additional water molecules.
The modifier (aq) in this equation was implied by Arrhenius, rather than included explicitly. It indicates that the substances are dissolved in water. Though all three substances, HCl, NaOH and NaCl are capable of existing as pure compounds, in aqueous solutions they are fully dissociated into the aquated ions and . | 0 | Theoretical and Fundamental Chemistry |
There are more than thirty treatises attributed to al-Kindi in the field of medicine, in which he was chiefly influenced by the ideas of Galen. His most important work in this field is probably De Gradibus, in which he demonstrates the application of mathematics to medicine, particularly in the field of pharmacology. For example, he developed a mathematical scale to quantify the strength of a drug, and a system (based on the phases of the moon) that would allow a doctor to determine in advance the most critical days of a patient's illness. According to Plinio Prioreschi, this was the first attempt at serious quantification in medicine. | 1 | Applied and Interdisciplinary Chemistry |
By the process of silylation, polar functional groups such as alcohols and amines readily undergo reaction with trimethylsilyl chloride, giving trimethylsilyl ethers and trimethylsilyl amines. These new groups "protect" the original functional group by removing the labile protons and decreasing the basicity of the heteroatom. The lability of the and groups allow them to be easily removed afterwards ("deprotected"). Trimethylsilylation can also be used to increase the volatility of a compound, enabling gas chromatography of normally nonvolatile substances such as glucose.
Trimethylsilyl chloride also reacts with carbanions to give trimethylsilyl derivatives. Lithium acetylides react to give trimethylsilylalkynes such as bis(trimethylsilyl)acetylene. Such derivatives are useful protected forms of alkynes.
In the presence of triethylamine and lithium diisopropylamide, enolisable aldehydes, ketones and esters are converted to trimethylsilyl enol ethers. Despite their hydrolytic instability, these compounds have found wide application in organic chemistry; oxidation of the double bond by epoxidation or dihydroxylation can be used to return the original carbonyl group with an alcohol group at the alpha carbon. The trimethylsilyl enol ethers can also be used as masked enolate equivalents in the Mukaiyama aldol addition. | 0 | Theoretical and Fundamental Chemistry |
Pollutants released to the ground can work their way down into the groundwater, leading to groundwater pollution. The resulting body of polluted water within an aquifer is called a plume, with its migrating edges called plume fronts. Plumes are used to locate, map, and measure water pollution within the aquifers total body of water, and plume fronts to determine directions and speed of the contaminations spreading in it.
Plumes are of considerable importance in the atmospheric dispersion modelling of air pollution. A classic work on the subject of air pollution plumes is that by Gary Briggs.
A thermal plume is one which is generated by gas rising above a heat source. The gas rises because thermal expansion makes warm gas less dense than the surrounding cooler gas. | 1 | Applied and Interdisciplinary Chemistry |
The size and strength of the induced vortices around a conducting particle have direct relationship with the applied electric filed and also the size of the conducted surface. This phenomenon is experimentally and numerically proven by several studies. The vortices grow as the external electric field increases and generate "sinkhole" at the center of the each vortex while circulates the fluid faster. It is demonstrated that increasing the size of the conducting surface forms bigger induced vortices to the point that geometry does not limits this grows. | 0 | Theoretical and Fundamental Chemistry |
The calcium salt of atorvastatin is marketed under the trade name Lipitor for the lowering of blood cholesterol. The first enantioselective medicinal chemistry route to atorvastatin relied on a diastereoselective aldol reaction with a chiral ester to set one of the two alcohol stereocenters. In the commercial route to atorvastatin, this stereocenter is carried forward from the readily available food additive isoascorbic acid. | 0 | Theoretical and Fundamental Chemistry |
Computational and experimental techniques have been imperative for the study of inverted ligand fields, especially when used in cooperatively. | 0 | Theoretical and Fundamental Chemistry |
Sir John Warcup Cornforth Jr., (7 September 1917 – 8 December 2013) was an AustralianBritish chemist who won the Nobel Prize in Chemistry in 1975 for his work on the stereochemistry of enzyme-catalysed reactions, becoming the only Nobel laureate born in New South Wales.
Cornforth investigated enzymes that catalyse changes in organic compounds, the substrates, by taking the place of hydrogen atoms in a substrate's chains and rings. In his syntheses and descriptions of the structure of various terpenes, olefins, and steroids, Cornforth determined specifically which cluster of hydrogen atoms in a substrate were replaced by an enzyme to effect a given change in the substrate, allowing him to detail the biosynthesis of cholesterol. For this work, he won a share of the Nobel Prize in Chemistry in 1975, alongside co-recipient Vladimir Prelog, and was knighted in 1977. | 0 | Theoretical and Fundamental Chemistry |
Loss-of-function mutations in females can lead to infertility. In 46, XY individuals severe inactivation can cause male pseudohermaphroditism, as fetal Leydig cells during may not respond and thus interfere with masculinization. Less severe inactivation can result in hypospadias or a micropenis. | 1 | Applied and Interdisciplinary Chemistry |
A 2018 study found that Icaridin, is highly toxic to salamander larvae, in what the authors described as conservative exposure doses. The LC50 standard was additionally found to be completely inadequate in the context of finding this result.
Permethrin is highly toxic to cats but not to dogs or humans. | 1 | Applied and Interdisciplinary Chemistry |
The design of polymeric properties requires great control over the structure of the polymer. For instance, low band gap polymers require regularly alternating electron donating and electron accepting monomers.
More recently, many popular cross-coupling chemistries have been applied to polyfluorenes and have enabled controlled polymerization; Palladium-catalyzed coupling reactions such as Suzuki coupling, Heck coupling, etc., as well as nickel catalyzed Yamamoto and Grignard coupling reactions have been applied to polymerization of fluorene derivatives. Such routes have enabled excellent control over the properties of polyfluorenes; the fluorene-thiophene-benzothiadiazole copolymer shown above, with a band gap of 1.78 eV when the side chains are alkoxy, appears blue because it is absorbing in the red wavelengths. | 0 | Theoretical and Fundamental Chemistry |
The LD50 (median lethal dose) for THC (Delta 9 Tetrahydrocannabinol) is not precisely known, as there have been no recorded fatalities. Hash oil can contain up to 80% THC, though up to 99% is possible with other methods of extraction. While health issues of the lungs may be exacerbated by use of hash oil, it is not known to cause side effects not already found in other preparations of cannabis. | 0 | Theoretical and Fundamental Chemistry |
The forces between the atoms in a solid can take a variety of forms. For example, a crystal of sodium chloride (common salt) is made up of ionic sodium and chlorine, which are held together by ionic bonds. In diamond or silicon, the atoms share electrons and form covalent bonds. In metals, electrons are shared in metallic bonding. Some solids, particularly most organic compounds, are held together with van der Waals forces resulting from the polarization of the electronic charge cloud on each molecule. The dissimilarities between the types of solid result from the differences between their bonding. | 0 | Theoretical and Fundamental Chemistry |
Kilju () is the Finnish word for home made alcoholic beverage typically made of sugar, yeast, and water.
The ABV is around 15–17%, and since it does not contain a sweet reserve it is completely dry. Crude fermented water may be distilled to moonshine. Kilju for consumption is clarified to avoid wine fault, it is a flax-colored liquid with no discernible taste other than that of ethanol; an alcoholic beverage used as an ethanol base for drink mixers. | 1 | Applied and Interdisciplinary Chemistry |
In the energy balance of groundwater flow a hydraulic equivalent of Joule's law is used:
where:
* = loss of hydraulic energy () due to friction of flow in -direction per unit of time (m/day), comparable to
* = flow velocity in -direction (m/day), comparable to
* = hydraulic conductivity of the soil (m/day), the hydraulic conductivity is inversely proportional to the hydraulic resistance which compares to | 0 | Theoretical and Fundamental Chemistry |
The quantification of dynamic PET studies to measure Ki requires the measurement of the skeletal time-activity curves (TAC) from the region of interest (ROI) and the arterial input function (AIF), which can be measured in various different ways. However, the most common is to correct the image-based blood time-activity curves using several venous blood samples taken at discrete time points while the patient is scanned. The calculation of rate constants or K requires three steps:
* Measurement of the arterial input function (AIF), which acts as the first input to the mathematical model of tracer distribution.
* Measurement of the time-activity curve (TAC) within the skeletal region of interest, which acts as the second input to the mathematical model of tracer distribution.
* Kinetic modelling of AIF and TAC using mathematical modelling to obtain net plasma clearance (K) to the bone mineral. | 1 | Applied and Interdisciplinary Chemistry |
A more sophisticated system involving the use of mechanical equipment to circulate the air was developed in the mid-19th century. A basic system of bellows was put in place to ventilate Newgate Prison and outlying buildings, by the engineer Stephen Hales in the mid-1700s. The problem with these early devices was that they required constant human labor to operate. David Boswell Reid was called to testify before a Parliamentary committee on proposed architectural designs for the new House of Commons, after the old one burned down in a fire in 1834. In January 1840 Reid was appointed by the committee for the House of Lords dealing with the construction of the replacement for the Houses of Parliament. The post was in the capacity of ventilation engineer, in effect; and with its creation there began a long series of quarrels between Reid and Charles Barry, the architect.
Reid advocated the installation of a very advanced ventilation system in the new House. His design had air being drawn into an underground chamber, where it would undergo either heating or cooling. It would then ascend into the chamber through thousands of small holes drilled into the floor, and would be extracted through the ceiling by a special ventilation fire within a great stack.
Reids reputation was made by his work in Westminster. He was commissioned for an air quality survey in 1837 by the Leeds and Selby Railway in their tunnel. The steam vessels built for the Niger expedition of 1841 were fitted with ventilation systems based on Reids Westminster model. Air was dried, filtered and passed over charcoal. Reids ventilation method was also applied more fully to St. Georges Hall, Liverpool, where the architect, Harvey Lonsdale Elmes, requested that Reid should be involved in ventilation design. Reid considered this the only building in which his system was completely carried out. | 1 | Applied and Interdisciplinary Chemistry |
The phrase "spectral lines", when not qualified, usually refers to lines having wavelengths in the visible band of the full electromagnetic spectrum. Many spectral lines occur at wavelengths outside this range. At shorter wavelengths, which correspond to higher energies, ultraviolet spectral lines include the Lyman series of hydrogen. At the much shorter wavelengths of X-rays, the lines are known as characteristic X-rays because they remain largely unchanged for a given chemical element, independent of their chemical environment. Longer wavelengths correspond to lower energies, where the infrared spectral lines include the Paschen series of hydrogen. At even longer wavelengths, the radio spectrum includes the 21-cm line used to detect neutral hydrogen throughout the cosmos. | 0 | Theoretical and Fundamental Chemistry |
It is common practice in laboratories to make a solution directly from its constituent ingredients. There are three cases in practical calculation:
* Case 1: amount of solvent volume is given.
* Case 2: amount of solute mass is given.
* Case 3: amount of final solution volume is given.
In the following equations, A is solvent, B is solute, and C is concentration. Solute volume contribution is considered through the ideal solution model.
* Case 1: amount (mL) of solvent volume V is given. Solute mass m = C V d /(100-C/d)
* Case 2: amount of solute mass m is given. Solvent volume V = m (100/C-1/ d )
* Case 3: amount (mL) of final solution volume Vt is given. Solute mass m = C Vt /100; Solvent volume V=(100/C-1/ d) m
* Case 2: solute mass is known, V = m 100/C
* Case 3: total solution volume is known, same equation as case 1. V=Vt; m = C V /100
Example: Make 2 g/100mL of NaCl solution with 1 L water. The density of the resulting solution is considered to be equal to that of water, statement holding especially for dilute solutions, so the density information is not required.
:m = C V = ( 2 / 100 ) g/mL × 1000 mL = 20 g
Chemists often make concentrated stock solutions that may then be diluted as needed for laboratory applications. Standard solutions are those where concentrations of solutes are accurately and precisely known. | 0 | Theoretical and Fundamental Chemistry |
Suspension Peroxide Oxidation Combined Acidity and Sulfur (SPOCAS) method is a suite of tests used to determine the net acidity via the measurement of: Titratable Peroxide Acidity (TPA) (as a measure of PSA); Titratable Actual Acidity (TAA); Excess Acid Neutralising Capacity (ANC); and Residual Acid Soluble Sulfur (S) or Net Acid-Soluble Sulfur (S) (as measures of retained acidity).
As SPOCAS is effectively a self-contained ABA test, it is very useful and popular. However, the use of peroxide digestion for TPA may overestimate PSA where organic matter is present (see discussion on S). Therefore, it is recommended to measure S for at least one sample per batch of samples to determine if there is a substantial discrepancy between PSA measured via S and TPA. Additionally, note that S does not reliably measure the concentration of jarosite or schwertmannite (the typical sources of retained acidity); and S typically only accounts for 50-60% of jarosite. Consequently, S should be doubled to obtain a more accurate measure of Retained Acidity where jarosite is likely the principal source of Retained Acidity (which is the usual case). This calculation may or may not be performed by commercial labs before they present the ABA results to the client.
Retained Acidity is a very recalcitrant pool of acidity in that it is slow to release and not easily neutralised. Therefore, soils with high amounts of Retained Acidity may require special management considerations to mitigate gradual acidification over tens to hundreds of years. | 0 | Theoretical and Fundamental Chemistry |
As described in the article Nociception, nociception is the sensory nervous system's response to harmful stimuli, such as a toxic chemical applied to a tissue. In nociception, chemical stimulation of sensory nerve cells called nociceptors produces a signal that travels along a chain of nerve fibers via the spinal cord to the brain. Nociception triggers a variety of physiological and behavioral responses and usually results in a subjective experience, or perception, of pain.
Work by Pan et al. first showed that TET1 and TET3 proteins are normally present in the spinal cords of mice. They used a pain inducing model of intra plantar injection of 5% formalin into the dorsal surface of the mouse hindpaw and measured time of licking of the hindpaw as a measure of induced pain. Protein expression of TET1 and TET3 increased by 152% and 160%, respectively, by 2 hours after formalin injection. Forced reduction of expression of TET1 or TET3 by spinal injection of Tet1-siRNA or Tet3-siRNA for three consecutive days before formalin injection alleviated the mouse perception of pain. On the other hand, forced overexpression of TET1 or TET3 for 2 consecutive days significantly produced pain-like behavior as evidenced by a decrease in the mouse of the thermal pain threshold.
They further showed that the nociceptive pain effects occurred through TET mediated conversion of 5-methylcytosine to 5-hydroxymethylcytosine in the promoter of a microRNA designated miR-365-3p, thus increasing its expression. This microRNA, in turn, ordinarily targets (decreases expression of) the messenger RNA of Kcnh2, that codes for a protein known as K11.1 or KCNH2. KCNH2 is the alpha subunit of a potassium ion channel in the central nervous system. Forced decrease in expression of TET1 or TET3 through pre-injection of siRNA reversed the decrease of KCNH2 protein in formalin-treated mice. | 1 | Applied and Interdisciplinary Chemistry |
A major source of differentiation is fractionation, an unequal distribution of elements and isotopes. This can be the result of chemical reactions, phase changes, kinetic effects, or radioactivity.
On the largest scale, planetary differentiation is a physical and chemical separation of a planet into chemically distinct regions. For example, the terrestrial planets formed iron-rich cores and silicate-rich mantles and crusts. In the Earths mantle, the primary source of chemical differentiation is partial melting, particularly near mid-ocean ridges. This can occur when the solid is heterogeneous or a solid solution, and part of the melt is separated from the solid. The process is known as equilibrium or batch melting if the solid and melt remain in equilibrium until the moment that the melt is removed, and fractional or Rayleigh' melting if it is removed continuously.
Isotopic fractionation can have mass-dependent and mass-independent forms. Molecules with heavier isotopes have lower ground state energies and are therefore more stable. As a result, chemical reactions show a small isotope dependence, with heavier isotopes preferring species or compounds with a higher oxidation state; and in phase changes, heavier isotopes tend to concentrate in the heavier phases. Mass-dependent fractionation is largest in light elements because the difference in masses is a larger fraction of the total mass.
Ratios between isotopes are generally compared to a standard. For example, sulfur has four stable isotopes, of which the two most common are S and S. The ratio of their concentrations, , is reported as
where is the same ratio for a standard. Because the differences are small, the ratio is multiplied by 1000 to make it parts per thousand (referred to as parts per mil). This is represented by the symbol . | 0 | Theoretical and Fundamental Chemistry |
Al-Tughrai was an 11th–12th century Persian physician. whose work the Masabih al-hikma wa-mafatih al-rahma (The Lanterns of Wisdom and the Keys of Mercy) is one of the earliest works of material sciences. | 1 | Applied and Interdisciplinary Chemistry |
Of the hundreds of facet arrangements that have been used, the most famous is probably the round brilliant cut, used for diamond and many colored gemstones. This first early version of what would become the modern Brilliant Cut is said to have been devised by an Italian named Peruzzi, sometime in the late 17th century. Later on, the first angles for an "ideal" cut diamond were calculated by Marcel Tolkowsky in 1919. Slight modifications have been made since then, but angles for "ideal" cut diamonds are still similar to Tolkowskys formula. Round brilliants cut before the advent of "ideal" angles are often referred to as "Early round brilliant cut" or "Old European brilliant cut" and are considered poorly cut by todays standards, though there is still interest in them from collectors. Other historic diamond cuts include the "Old Mine Cut" which is similar to early versions of the round brilliant, but has a rectangular outline, and the "Rose Cut" which is a simple cut consisting of a flat, polished back, and varying numbers of angled facets on the crown, producing a faceted dome. Sometimes a 58th facet, called a culet is cut on the bottom of the stone to help prevent chipping of the pavilion point. Earlier brilliant cuts often have very large culets, while modern brilliant cut diamonds generally lack the culet facet, or it may be present in minute size. | 0 | Theoretical and Fundamental Chemistry |
Multi-state modeling of biomolecules refers to a series of techniques used to represent and compute the behaviour of biological molecules or complexes that can adopt a large number of possible functional states.
Biological signaling systems often rely on complexes of biological macromolecules that can undergo several functionally significant modifications that are mutually compatible. Thus, they can exist in a very large number of functionally different states. Modeling such multi-state systems poses two problems: The problem of how to describe and specify a multi-state system (the "specification problem") and the problem of how to use a computer to simulate the progress of the system over time (the "computation problem"). To address the specification problem, modelers have in recent years moved away from explicit specification of all possible states, and towards rule-based modeling that allow for implicit model specification, including the κ-calculus, BioNetGen, the Allosteric Network Compiler and others. To tackle the computation problem, they have turned to particle-based methods that have in many cases proved more computationally efficient than population-based methods based on ordinary differential equations, partial differential equations, or the Gillespie stochastic simulation algorithm. Given current computing technology, particle-based methods are sometimes the only possible option. Particle-based simulators further fall into two categories: Non-spatial simulators such as StochSim, DYNSTOC, RuleMonkey, and NFSim
and spatial simulators, including Meredys, SRSim and MCell. Modelers can thus choose from a variety of tools; the best choice depending on the particular problem. Development of faster and more powerful methods is ongoing, promising the ability to simulate ever more complex signaling processes in the future. | 1 | Applied and Interdisciplinary Chemistry |
Ge was born in China. She attended Peking University for her undergraduate studies, where she studied chemistry. After graduating in 1997 Ge moved to the United States, where she joined Cornell University as a doctoral student. Here she started to work on mass spectrometry, using electron-capture dissociation to study proteins. She worked under the supervision of Tadhg Begley and Fred McLafferty. After completing her doctorate, Ge worked as a research scientist at Wyeth. | 1 | Applied and Interdisciplinary Chemistry |
Alkaline sulfur liquid battery (SLIQ) is a liquid battery which consists of only one rechargeable liquid and a technology which can be used for grid storage. | 1 | Applied and Interdisciplinary Chemistry |
In water solution, orthophosphoric acid and its three derived anions coexist according to the dissociation and recombination equilibria below
Values are at 25°C and 0 ionic strength.
The pK values are the pH values where the concentration of each species is equal to that of its conjugate bases. At pH 1 or lower, the phosphoric acid is practically undissociated. Around pH 4.7 (mid-way between the first two pK values) the dihydrogen phosphate ion, , is practically the only species present. Around pH 9.8 (mid-way between the second and third pK values) the monohydrogen phosphate ion, , is the only species present. At pH 13 or higher, the acid is completely dissociated as the phosphate ion, .
This means that salts of the mono- and di-phosphate ions can be selectively crystallised from aqueous solution by setting the pH value to either 4.7 or 9.8.
In effect, , and behave as separate weak acids because the successive pK differ by more than 4.
Phosphate can form many polymeric ions such as pyrophosphate, , and triphosphate, . The various metaphosphate ions (which are usually long linear polymers) have an empirical formula of and are found in many compounds. | 0 | Theoretical and Fundamental Chemistry |
Mollapour holds a BSc (Hons) in Microbiology and Biochemistry from the University of East London, MSc in Applied Molecular Biology of Infectious Diseases and Diploma in Tropical Medicine & Infectious Diseases from the London School of Hygiene & Tropical Medicine. In 2001 he received his PhD in [https://www.ucl.ac.uk/biosciences/departments/structural-and-molecular-biology%29 Biochemistry] from the University College London. | 1 | Applied and Interdisciplinary Chemistry |
Vacuum metallurgy is the field of materials technology that deals with making, shaping, or treating metals in a controlled atmosphere, at pressures significantly less than normal atmospheric pressure. The purpose of vacuum metallurgy is to prevent contamination of metal by gases in the atmosphere. Alternatively, in some processes, a reactive gas may be introduced into the process to become part of the resultant product. Examples of vacuum metallurgy include vacuum degassing of molten steel in steelmaking operations, vacuum deposition of thin metal layers in manufacture of optics and semiconductors, vacuum casting, vacuum arc remelting of alloys, and vacuum induction melting. | 1 | Applied and Interdisciplinary Chemistry |
The basic principle consists of a continuous phase fluid (focusing or sheath fluid) flanking or surrounding the dispersed phase (focused or core fluid), so as to give rise to droplet or bubble break-off in the vicinity of an orifice through which both fluids are extruded. The principle may be extended to two or more coaxial fluids; gases and liquids may be combined; and, depending on the geometry of the feed tube and orifices, the flow pattern may be cylindrical or planar. Both cylindrical and planar flow focusing have led to a variety of developments (see also the works of Peter Walzal).
A flow focusing device consists of a pressure chamber pressurized with a continuous focusing fluid supply. Inside, one or more focused fluids are injected through a capillary feed tube whose extremity opens up in front of a small orifice, linking the pressure chamber with the exterior ambient. The focusing fluid stream moulds the fluid meniscus into a cusp giving rise to a steady micro or nano-jet exiting the chamber through the orifice; the jet size is much smaller than the exit orifice, thus precluding any contact (which may lead to unwanted deposition or reaction). Capillary instability breaks up the steady jet into homogeneous droplets or bubbles.
The feed tube may be composed of two or more concentric needles and different immiscible liquids or gases to be injected, leading to compound drops. On being suitably cured, such drops may lead to multilayer microcapsules with multiple shells of controllable thickness. Flow focusing ensures an extremely fast as well as controlled production of up to millions of droplets per second as the jet breaks up.
The role of the tangential viscous stress is essential in establishing a steady meniscus shape in flow focusing, as illustrated in the case of a simple liquid jet surrounded by a gas. In the absence of a sufficiently strong tangential stress, a round-apex meniscus is obtained. Both the inner liquid and the external gas flows would exhibit stagnation regions around the round apex. The surface tension stress σ/D would be simply balanced by an appropriate pressure jump across the interface. If one slowly pushes a liquid flow rate Q, the system would spit intermittently the excess of liquid to recover the round-apex equilibrium shape. However, when the tangential stress is sufficiently vigorous compared to σ /D, the surface can be deformed into a steady tapering shape, which allows the continuous and smooth acceleration of the liquid under the combined actions of the pressure drop ΔP and the tangential viscous stress τs on the liquid surface. | 1 | Applied and Interdisciplinary Chemistry |
Neutron stars form as remnants of massive stars after a supernova event. Unlike their progenitor star, neutron stars do not consist of a gaseous plasma. Rather, the intense gravitational attraction of the compact mass overcomes the electron degeneracy pressure and causes electron capture to occur within the star. The result is a compact ball of nearly pure neutron matter with sparse protons and electrons interspersed, filling a space several thousand times smaller than the progenitor star.
At the surface, the pressure is low enough that conventional nuclei, such as helium and iron, can exist independently of one another and are not crushed together due to the mutual Coulomb repulsion of their nuclei. At the core, the pressure is so great that this Coulomb repulsion cannot support individual nuclei, and some form of ultra-dense matter, such as the theorized quark–gluon plasma, should exist.
The presence of a small population of protons is essential to the formation of nuclear pasta. The nuclear attraction between protons and neutrons is greater than the nuclear attraction of two protons or two neutrons. Similar to how neutrons act to stabilize heavy nuclei of conventional atoms against the electric repulsion of the protons, the protons act to stabilize the pasta phases. The competition between the electric repulsion of the protons, the attractive force between nuclei, and the pressure at different depths in the star lead to the formation of nuclear pasta. | 0 | Theoretical and Fundamental Chemistry |
Sustainable materials are key elements of green buildings. Some benefits of sustainable materials include durability, long life, recyclability, and energy and thermal efficiency. Copper ranks highly in all of these categories.
Copper is one of natures most efficient thermal and electrical conductors, which helps to conserve energy. Because of its high thermal conductivity, it is used extensively in building heating systems, direct exchange heat pumps, and solar power and hot water equipment. Its high electrical conductivity increases the efficiency of lighting, electrical motors, fans, and appliances, making a buildings operation more cost effective with less energy and environmental impact.
Because copper has a better thermal conductivity rating than usual façade and roofing materials, it is well-suited to solar thermal façade systems. The first commercial application of a fully integrated solar thermal copper façade system was installed at the Pori Public Swimming Complex in Finland. The installation is an urban example of sustainability and carbon emissions reduction. The solar façade works in conjunction with roof collectors and is supplemented by roof-mounted photovoltaics that provide 120,000 kWh of heat, an amount of energy equivalent to that used annually by six average family houses in cold-climate Finland.
One standard in the United States Green Building Council (USGBC)'s Leadership in Energy and Environmental Design rating system (LEED) requires that newly constructed buildings include materials containing pre- and post-consumer recycled content. Most copper products used in construction (except electrical materials that require highly refined virgin copper) contain a large percentage of recycled content. See: Copper in architecture#Recycling. | 1 | Applied and Interdisciplinary Chemistry |
Alexander Nikolayevich's work on the chemistry of organoelement compounds brought him fame and recognition not only in the Soviet Union, but also in the world. He was elected an honorary member of several dozen foreign national academies and scientific societies. | 0 | Theoretical and Fundamental Chemistry |
Standpipes are not fail-safe systems and there have been many instances where fire operations have been compromised by standpipe systems which were damaged or otherwise not working properly. Firefighters must take precautions to flush the standpipe before use to clear out debris and ensure that water is available. | 1 | Applied and Interdisciplinary Chemistry |
Annulenes are monocyclic hydrocarbons that contain the maximum number of non-cumulated or conjugated double bonds (mancude). They have the general formula CH (when n is an even number) or CH (when n is an odd number). The IUPAC accepts the use of annulene nomenclature in naming carbocyclic ring systems with 7 or more carbon atoms, using the name [n]annulene for the mancude hydrocarbon with n carbon atoms in its ring, though in certain contexts (e.g., discussions of aromaticity for different ring sizes), smaller rings (n = 3 to 6) can also be informally referred to as annulenes. Using this form of nomenclature 1,3,5,7-cyclooctatetraene is [8]annulene and benzene is [6]annulene (and occasionally referred to as just annulene).
The discovery that [18]annulene possesses a number of key properties associated with other aromatic molecules was an important development in the understanding of aromaticity as a chemical concept.
In the related annulynes, one double bond is replaced by a triple bond. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, 1-propenyl (or simply propenyl) has the formula CH=CHCH and 2-propenyl (isopropenyl) has the formula CH=C-CH. These groups are found in many compounds. Propenyl compounds are isomeric with allyl compounds, which have the formula CH-CH=CH. | 0 | Theoretical and Fundamental Chemistry |
Phosphinous acids are usually organophosphorus compounds with the formula RPOH. They are pyramidal in structure. Phosphorus is in the oxidation state III. Most phosphinous acids rapidly convert to the corresponding phosphine oxide, which are tetrahedral and are assigned oxidation state V. | 0 | Theoretical and Fundamental Chemistry |
Iminium cations are obtained by protonation and alkylation of imines:
They also are generated by the condensation of secondary amines with ketones or aldehydes:
This rapid, reversible reaction is one step in "iminium catalysis".
More exotic routes to iminium cations are known, e.g. from ring-opening reactions of pyridine. | 0 | Theoretical and Fundamental Chemistry |
Currently, the stability of most ionic liquids under practical electrochemical conditions is unknown, and the fundamental choice of ionic fluid is still empirical as there is almost no data on metal ion thermodynamics to feed into solubility and speciation models. Also, there are no Pourbaix diagrams available, no standard redox potentials, and bare knowledge of speciation or pH-values. It must be noticed that most processes reported in the literature involving ionic fluids have a Technology Readiness Level (TRL) 3 (experimental proof-of-concept) or 4 (technology validated in the lab), which is a disadvantage for short-term implementation. However, ionometallurgy has the potential to effectively recover metals in a more selective and sustainable way, as it considers environmentally benign solvents, reduction of greenhouse gas emissions and avoidance of corrosive and harmful reagents. | 1 | Applied and Interdisciplinary Chemistry |
For example, consider the following two rounds of shotgun reads:
In this extremely simplified example, none of the reads cover the full length of the original sequence, but the four reads can be assembled into the original sequence using the overlap of their ends to align and order them. In reality, this process uses enormous amounts of information that are rife with ambiguities and sequencing errors. Assembly of complex genomes is additionally complicated by the great abundance of repetitive sequences, meaning similar short reads could come from completely different parts of the sequence.
Many overlapping reads for each segment of the original DNA are necessary to overcome these difficulties and accurately assemble the sequence. For example, to complete the Human Genome Project, most of the human genome was sequenced at 12X or greater coverage; that is, each base in the final sequence was present on average in 12 different reads. Even so, current methods have failed to isolate or assemble reliable sequence for approximately 1% of the (euchromatic) human genome, as of 2004. | 1 | Applied and Interdisciplinary Chemistry |
Ligands are molecules responsible for binding to receptors in the cellular targeting process. Surface-coupled ligands offer a greater degree of freedom to move on the liposome membrane for optimal interactions. Ligands are typically monoclonal antibodies (mAbs) or antibody fragments, but can also include other molecules such as ARPG, proteins, peptides, vitamins, carbohydrates, and glycoproteins. The choice of ligand can significantly influence the behavioral and functional properties of a ligand-targeted liposome. Antibody fragments have lower immunogenicity and improved pharmacokinetics. mAbs are unique and can be used for inhibition of DNA repair, terminating the cell cycle, and triggering apoptosis, all of which factor into applications for anticancer drugs. Peptides are relatively easy and affordable to prepare with low antigenicity and lower opsonization which are more resistant to enzymatic degradation. Proteins can target the transferrin receptor membrane glycoprotein. Sugars and vitamins are recognized by cellular transport receptors. Ligand choice is based on receptor expression, ligand internalization, binding affinity, and type of ligand. Ligands alone are not able to carry an efficient payload for therapeutic levels but can carry more of the agent when combined with liposomes. | 1 | Applied and Interdisciplinary Chemistry |
Oxygen and carbon dioxide are removed from the feed water by deaeration. Deaeration can be accomplished by using deaerator heaters, vacuum deaerators, mechanical pumps, and steam-jet ejectors. In deaerating heaters, steam sprays incoming feed water and carries away the dissolved gases. The deaerators also store hot feed water which is ready to be used in the boiler. This means of mechanical deaeration is used with chemical oxygen scavenging agents to increase efficiency. (Sendelbach, p. 129) Deaerating heaters can be classified in two groups: spray types and tray types. With tray type heaters the incoming water is sprayed into steam atmosphere to reach saturation temperature. When the saturation temperature is reached most of the oxygen and non-condensable gases are released. There are seals that prevent the recontamination of the water in the spray section. The water then falls to the storage tank below. The non-condensables and oxygen are then vented to the atmosphere. The components of the tray type deaerating heater are a shell, spray nozzles, a direct contact vent condenser, tray stacks, and protective interchamber walls. The spray type deaerator is similar to the tray type deaerator. The water is sprayed into a steam atmosphere and most of the oxygen and non-condensables are released to the steam. The water then falls to the steam scrubber where the slight pressure loss causes the water to flash a little bit which also aids the removal of oxygen and non-condensables. The water then overflows to the storage tank. The gases are then vented to the atmosphere. With vacuum deaeration a vacuum is applied to the system and water is then brought to its saturation temperature. The water is sprayed into the tank like the spray and tray deaerators. The oxygen and non-condensables are vented to the atmosphere. (Sendelbach, p. 130) | 1 | Applied and Interdisciplinary Chemistry |
The density of aptamer packing on the electrode surface is an important parameter to optimize signal. Depending on the size and nature of target molecule, different aptamer packing densities favor signal gain. Studies have shown that small target molecules enable a greater signal gain for low density aptamer packing, while larger proteins as a target generate the greatest signal at intermediate probe packing densities. Signal gain decreases as packing density increase above the range of optimal signal gain due to steric hindrance. When the probe surface neighboring an aptamer is blocked by an adjacent aptamer, the redox tag on the target-bound aptamer will not have room to come into contact with the electrode, therefore failing to report target binding. The concentration of aptamer in solution that incubates a clean probe is found to be proportional to the density of aptamers that are immobilized on the probe. Studies have reported suggesting that small targets such as cocaine E-AB sensors generate the most signal with the lowest probe packing density. Conversely, larger protein targets such as the protein Thrombin generate the most signal at intermediate probe packing densities. | 0 | Theoretical and Fundamental Chemistry |
The Ostwald–Freundlich equation governs boundaries between two phases; specifically, it relates the surface tension of the boundary to its curvature, the ambient temperature, and the vapor pressure or chemical potential in the two phases.
The Ostwald–Freundlich equation for a droplet or particle with radius is:
: = atomic volume
: = Boltzmann constant
: = surface tension (J m)
: = equilibrium partial pressure (or chemical potential or concentration)
: = partial pressure (or chemical potential or concentration)
: = absolute temperature
One consequence of this relation is that small liquid droplets (i.e., particles with a high surface curvature) exhibit a higher effective vapor pressure, since the surface is larger in comparison to the volume.
Another notable example of this relation is Ostwald ripening, in which surface tension causes small precipitates to dissolve and larger ones to grow. Ostwald ripening is thought to occur in the formation of orthoclase megacrysts in granites as a consequence of subsolidus growth. See rock microstructure for more. | 0 | Theoretical and Fundamental Chemistry |
Probably the most well-known receptors of peptidoglycan are the NOD-like receptors (NLRs), mainly NOD1 and NOD2. The NOD1 receptor is activated after iE-DAP (γ-d-glutamyl-meso-diaminopimelic acid) binding, while NOD2 recognizes MDP (muramyl dipeptide), by their LRR domains. Activation leads to self-oligomerization, resulting in activation of two signalling cascades. One triggers activation of NF-κB (through RIP2, TAK1 and IKK), second leads to MAPK signalling cascade. Activation of these pathways induces production of inflammatory cytokines and chemokines.
NOD1 is expressed by diverse cell types, including myeloid phagocytes, epithelial cells and neurons. NOD2 is expressed in monocytes and macrophages, epithelial intestinal cells, Paneth cells, dendritic cells, osteoblasts, keratinocytes and other epithelial cell types. As cytosolic sensors, NOD1 and NOD2 must either detect bacteria that enter the cytosol, or peptidoglycan must be degraded to generate fragments that must be transported into the cytosol for these sensors to function.
Recently, it was demonstrated that NLRP3 is activated by peptidoglycan, through a mechanism that is independent of NOD1 and NOD2. In macrophages, N-acetylglucosamine generated by peptidoglycan degradation was found to inhibit hexokinase activity and induce its release from the mitochondrial membrane. It promotes NLRP3 inflammasome activation through a mechanism triggered by increased mitochondrial membrane permeability.
NLRP1 is also considered as a cytoplasmic sensor of peptidoglycan. It can sense MDP and promote IL-1 secretion through binding NOD2. | 1 | Applied and Interdisciplinary Chemistry |
The Sepro Leach Reactor is a high concentration leach reactor developed to treat the gold concentrate produced by the Falcon Concentrator. The unit consists of a concentrate holding tank and a leach tank and impeller which are linked by a Sepro vertical bowl pump. The SLR uses either peroxide or oxygen gas to achieve elevated levels of dissolved oxygen required to accelerate the leaching process with no reagents required. The pregnant leach solution produced can be directly electrowon. With the addition of an electrowinning unit the final product becomes a gold plated carbon that can be directly refined to produce gold bullion. Extensive test work of the SLR on site has shown over 99% of the target mineral is recovered through a simple, fully automated process that is easily incorporated into recovery operations. Sepro Mineral Systems Corp. supplies SLR units with capacities ranging from . | 1 | Applied and Interdisciplinary Chemistry |
The liquid junction potential interferes with the exact measurement of the electromotive force of a chemical cell, so its effect should be minimized as much as possible for accurate measurement. The most common method of eliminating the liquid junction potential is to place a salt bridge consisting of a saturated solution of potassium chloride (KCl) and ammonium nitrate (NHNO) with lithium acetate (CHCOOLi) between the two solutions constituting the junction. When such a bridge is used, the ions in the bridge are present in large excess at the junction and they carry almost the whole of the current across the boundary. The efficiency of KCl/NHNO is connected with the fact that in these salts, the transport numbers of anions and cations are the same. | 0 | Theoretical and Fundamental Chemistry |
In thermodynamics, the quantity of work done by a closed system on its surroundings is defined by factors strictly confined to the interface of the surroundings with the system and to the surroundings of the system, for example, an extended gravitational field in which the system sits, that is to say, to things external to the system.
A main concern of thermodynamics is the properties of materials. Thermodynamic work is defined for the purposes of thermodynamic calculations about bodies of material, known as thermodynamic systems. Consequently, thermodynamic work is defined in terms of quantities that describe the states of materials, which appear as the usual thermodynamic state variables, such as volume, pressure, temperature, chemical composition, and electric polarization. For example, to measure the pressure inside a system from outside it, the observer needs the system to have a wall that can move by a measurable amount in response to pressure differences between the interior of the system and the surroundings. In this sense, part of the definition of a thermodynamic system is the nature of the walls that confine it.
Several kinds of thermodynamic work are especially important. One simple example is pressure–volume work. The pressure of concern is that exerted by the surroundings on the surface of the system, and the volume of interest is the negative of the increment of volume gained by the system from the surroundings. It is usually arranged that the pressure exerted by the surroundings on the surface of the system is well defined and equal to the pressure exerted by the system on the surroundings. This arrangement for transfer of energy as work can be varied in a particular way that depends on the strictly mechanical nature of pressure–volume work. The variation consists in letting the coupling between the system and surroundings be through a rigid rod that links pistons of different areas for the system and surroundings. Then for a given amount of work transferred, the exchange of volumes involves different pressures, inversely with the piston areas, for mechanical equilibrium. This cannot be done for the transfer of energy as heat because of its non-mechanical nature.
Another important kind of work is isochoric work, i.e., work that involves no eventual overall change of volume of the system between the initial and the final states of the process. Examples are friction on the surface of the system as in Rumfords experiment; shaft work such as in Joules experiments; stirring of the system by a magnetic paddle inside it, driven by a moving magnetic field from the surroundings; and vibrational action on the system that leaves its eventual volume unchanged, but involves friction within the system. Isochoric mechanical work for a body in its own state of internal thermodynamic equilibrium is done only by the surroundings on the body, not by the body on the surroundings, so that the sign of isochoric mechanical work with the physics sign convention is always negative.
When work, for example pressure–volume work, is done on its surroundings by a closed system that cannot pass heat in or out because it is confined by an adiabatic wall, the work is said to be adiabatic for the system as well as for the surroundings. When mechanical work is done on such an adiabatically enclosed system by the surroundings, it can happen that friction in the surroundings is negligible, for example in the Joule experiment with the falling weight driving paddles that stir the system. Such work is adiabatic for the surroundings, even though it is associated with friction within the system. Such work may or may not be isochoric for the system, depending on the system and its confining walls. If it happens to be isochoric for the system (and does not eventually change other system state variables such as magnetization), it appears as a heat transfer to the system, and does not appear to be adiabatic for the system. | 0 | Theoretical and Fundamental Chemistry |
RopB regulation speB is a key determinant in the expression of the speB proteinase which is a primary virulence factor and the most abundant extracellular protein in Streptococcal secretions. SpeB cleaves host serum proteins that make up the human extracellular matrix and bacterial proteins including other secreted Streptococcal proteins. As previously mentioned, it is responsible for the dissemination of a host of infectious diseases including but not limited to pharyngitis, impetigo, streptococcal toxic shock syndrome, necrotizing fasciitis, and scarlet fever. Therefore, study of the inactivation of speB's many functional pathways and regulators are of critical importance in developing potential novel therapeutics. | 1 | Applied and Interdisciplinary Chemistry |
Phosphate is used in fertilisers. Immense quantities of phosphate rock or phosphorite occur in sedimentary shelf deposits, ranging in age from the Proterozoic to currently forming environments. Phosphate deposits are thought to be sourced from the skeletons of dead sea creatures which accumulated on the seafloor. Similar to iron ore deposits and oil, particular conditions in the ocean and environment are thought to have contributed to these deposits within the geological past.
Phosphate deposits are also formed from alkaline igneous rocks such as nepheline syenites, carbonatites, and associated rock types. The phosphate is, in this case, contained within magmatic apatite, monazite, or other rare-earth phosphates. | 0 | Theoretical and Fundamental Chemistry |
According to Lucretius, the unpredictable swerve occurs "at no fixed place or time":
This swerving, according to Lucretius, provides the "free will which living things throughout the world have". Lucretius never gives the primary cause of the deflections. | 1 | Applied and Interdisciplinary Chemistry |
Liquid chromatography–mass spectrometry (LC–MS) is an analytical chemistry technique that combines the physical separation capabilities of liquid chromatography (or HPLC) with the mass analysis capabilities of mass spectrometry (MS). Coupled chromatography – MS systems are popular in chemical analysis because the individual capabilities of each technique are enhanced synergistically. While liquid chromatography separates mixtures with multiple components, mass spectrometry provides spectral information that may help to identify (or confirm the suspected identity of) each separated component. MS is not only sensitive, but provides selective detection, relieving the need for complete chromatographic separation. LC–MS is also appropriate for metabolomics because of its good coverage of a wide range of chemicals. This tandem technique can be used to analyze biochemical, organic, and inorganic compounds commonly found in complex samples of environmental and biological origin. Therefore, LC–MS may be applied in a wide range of sectors including biotechnology, environment monitoring, food processing, and pharmaceutical, agrochemical, and cosmetic industries. Since the early 2000s, LC–MS (or more specifically LC–MS–MS) has also begun to be used in clinical applications.
In addition to the liquid chromatography and mass spectrometry devices, an LC–MS system contains an interface that efficiently transfers the separated components from the LC column into the MS ion source. The interface is necessary because the LC and MS devices are fundamentally incompatible. While the mobile phase in a LC system is a pressurized liquid, the MS analyzers commonly operate under high vacuum. Thus, it is not possible to directly pump the eluate from the LC column into the MS source. Overall, the interface is a mechanically simple part of the LC–MS system that transfers the maximum amount of analyte, removes a significant portion of the mobile phase used in LC and preserves the chemical identity of the chromatography products (chemically inert). As a requirement, the interface should not interfere with the ionizing efficiency and vacuum conditions of the MS system. Nowadays, most extensively applied LC–MS interfaces are based on atmospheric pressure ionization (API) strategies like electrospray ionization (ESI), atmospheric-pressure chemical ionization (APCI), and atmospheric pressure photoionization (APPI). These interfaces became available in the 1990s after a two decade long research and development process. | 0 | Theoretical and Fundamental Chemistry |
The Muslim world acquired the gunpowder formula some time after 1240, but before 1280, by which time Hasan al-Rammah had written, in Arabic, recipes for gunpowder, instructions for the purification of saltpeter, and descriptions of gunpowder incendiaries. Early Muslim sources suggest that knowledge of gunpowder was acquired from China and may have been introduced by invading Mongols. This is implied by al-Rammahs usage of "terms that suggested he derived his knowledge from Chinese sources." Early Arab texts on gunpowder refer to saltpeter as "Chinese snow" ( ), fireworks as "Chinese flowers" and rockets as "Chinese arrows" (sahm al-Khitai'). Similarly, the Persians called saltpeter "Chinese salt" or "salt from Chinese salt marshes" ( ). Fireworks listed by al-Rammah include "wheels of China" and "flowers of China".
The gunpowder formula of al-Rammah has a saltpeter content of 68% to 75%, which is more explosive than is necessary for rockets, however no explosives are mentioned. Al-Rammahs text, The Book of Military Horsemanship and Ingenious War Devices (Kitab al-Furusiya wal-Munasab al-Harbiya), does however mention fuses, incendiary bombs, naphtha pots, fire lances, and an illustration and description of the earliest torpedo. The torpedo was called the "egg which moves itself and burns." Two iron sheets were fastened together and tightened using felt. The flattened pear shaped vessel was filled with gunpowder, metal filings, "good mixtures," two rods, and a large rocket for propulsion. Judging by the illustration, it was evidently supposed to glide across the water.
Hasan al-Rammah was the first Muslim to describe the purification of saltpeter using the chemical processes of solution and crystallization. This was the first clear method for the purification of saltpeter.
According to Joseph Needham, fire lances were used in battles between the Muslims and Mongols in 1299 and 1303.
The earliest surviving documentary evidence for cannons in the Islamic world is from an Arabic manuscript dated to the early 14th century. The authors name is uncertain but may have been Shams al-Din Muhammad, who died in 1350. Dating from around 1320–1350, the illustrations show gunpowder weapons such as gunpowder arrows, bombs, fire tubes, and fire lances or proto-guns. The manuscript describes a type of gunpowder weapon called a midfa which uses gunpowder to shoot projectiles out of a tube at the end of a stock. Some consider this to be a cannon while others do not. The problem with identifying cannons in early 14th century Arabic texts is the term midfa, which appears from 1342 to 1352 but cannot be proven to be true hand-guns or bombards. Contemporary accounts of a metal-barrel cannon in the Islamic world do not occur until 1365. Needham believes that in its original form the term midfa' refers to the tube or cylinder of a naphtha projector (flamethrower), then after the invention of gunpowder it meant the tube of fire lances, and eventually it applied to the cylinder of hand-gun and cannon.
According to Paul E. J. Hammer, the Mamluks certainly used cannons by 1342. According to J. Lavin, cannons were used by Moors at the siege of Algeciras in 1343. A metal cannon firing an iron ball was described by Shihab al-Din Abu al-Abbas al-Qalqashandi between 1365 and 1376. | 1 | Applied and Interdisciplinary Chemistry |
Group 2 organometallic chemistry refers to the chemistry of compounds containing carbon bonded to any group 2 element. By far the most common group 2 organometallic compounds are the magnesium-containing Grignard reagents which are widely used in organic chemistry. Other organometallic group 2 compounds are rare and are typically limited to academic interests. | 0 | Theoretical and Fundamental Chemistry |
Such is the case in building applications where artificial light can be replaced by sunlight through a light transmittance design. Based on research and simulation performed by Joseph Arehart at the University of Colorado Boulder, transparent wood as a glass glazing system replacement could reduce the space conditioning energy consumption by 24.6% to 33.3% in medium (climate zone 3C, San Francisco, CA) and large office spaces (climate zone 4C, Seattle, Washington) respectably. These are relevant insights in transparent wood's potential functionality because it shows lower thermal conductivity and better impact strength compared to popular glass glazing systems. | 0 | Theoretical and Fundamental Chemistry |
The Hiyama coupling can be applied to the formation of C-C (e.g. aryl–aryl) bonds as well as C-C (e.g. aryl–alkyl) bonds. Good synthetic yields are obtained with couplings of aryl halides, vinyl halides, and allylic halides and organo­iodides afford the best yields.
The scope of this reaction was expanded to include closure of medium-sized rings by Scott E. Denmark.
The coupling of alkyl halides with organo­halo­silanes as alternative organo­silanes has also been performed. Organo­chloro­silanes allow couplings with aryl chlorides, which are abundant and generally more eco­nomical than aryl iodides. A nickel catalyst allows for access to new reactivity of organo­trifluoro­silanes as reported by GC Fu et al. Secondary alkyl halides are coupled with aryl silanes with good yields using this reaction. | 0 | Theoretical and Fundamental Chemistry |
The metabolism of HMB is catalyzed by an uncharacterized enzyme which converts it to (). HMB-CoA is metabolized by either enoyl-CoA hydratase or another uncharacterized enzyme, producing β-methylcrotonyl-CoA () or hydroxymethylglutaryl-CoA () respectively. is then converted by the enzyme methylcrotonyl-CoA carboxylase to methylglutaconyl-CoA (), which is subsequently converted to by methylglutaconyl-CoA hydratase. is then cleaved into and acetoacetate by lyase or used in the production of cholesterol via the mevalonate pathway. | 1 | Applied and Interdisciplinary Chemistry |
The 11 September 2001 collapse of the World Trade Center buildings in New York City resulted in the release of chemicals from the destruction of construction and electrical material and long-term chemical fires. This collapse caused the release of several toxic chemicals, including fluorinated surfactants used as soil- and stain-resistant coatings on various materials. First responders to this incident were exposed to PFOA, PFNA, and PFHxS through inhalation of dust and smoke released during and after the collapse of the World Trade Center.
Fire responders who were working at or near ground zero were assessed for respiratory and other health effects from exposure to emissions at the World Trade Center. Early clinical testing showed a high prevalence of respiratory health effects. Early symptoms of exposure often presented with persistent coughing and wheezing. PFOA and PFHxS levels were present in both smoke and dust exposure, but first responders exposed to smoke had higher concentrations of PFOA and PFHxS than those exposed to dust. | 0 | Theoretical and Fundamental Chemistry |
For typical three-dimensional metals, the temperature-dependence of the electrical resistivity ρ(T) due to the scattering of electrons by acoustic phonons changes from a high-temperature regime in which ρ ∝ T to a low-temperature regime in which ρ ∝ T at a characteristic temperature known as the Debye temperature. For low density electron systems, however, the Fermi surface can be substantially smaller than the size of the Brillouin zone, and only a small fraction of acoustic phonons can scatter off electrons. This results in a new characteristic temperature known as the Bloch–Grüneisen temperature that is lower than the Debye temperature. The Bloch–Grüneisen temperature is defined as 2ħvk/k, where ħ is the Planck constant, v is the velocity of sound, ħk is the Fermi momentum, and k is the Boltzmann constant.
When the temperature is lower than the Bloch–Grüneisen temperature, the most energetic thermal phonons have a typical momentum of kT/v which is smaller than ħk, the momentum of the conducting electrons at the Fermi surface. This means that the electrons will only scatter in small angles when they absorb or emit a phonon. In contrast when the temperature is higher than the Bloch–Grüneisen temperature, there are thermal phonons of all momenta and in this case electrons will also experience large angle scattering events when they absorb or emit a phonon. In many cases, the Bloch–Grüneisen temperature is approximately equal to the Debye temperature (usually written ), which is used in modeling specific heat capacity. However, in particular circumstances these temperatures can be quite different.
The theory was initially put forward by Felix Bloch and Eduard Grüneisen. The Bloch–Grüneisen temperature has been observed experimentally in a two-dimensional electron gas and in graphene.
Mathematically, the Bloch–Grüneisen model produces a resistivity given by:
Here, is a characteristic temperature (typically matching well with the Debye temperature). Under Bloch's original assumptions for simple metals, . For , this can be approximated as dependence. In contrast, the so called Bloch–Wilson limit, where works better for s-d inter-band scattering, such as with transition metals. The second limit gives at low temperatures. In practice, which model is more applicable depends on the particular material. | 0 | Theoretical and Fundamental Chemistry |
Electron-withdrawing groups are the opposite effect of electron-donating groups (EDGs). Both describe functional groups, however, electron-withdrawing groups pull electron density away from a molecule, whereas EDGs push electron density onto a substituent. | 0 | Theoretical and Fundamental Chemistry |
The emission of blue light is often attributed to Cherenkov radiation.
Cherenkov radiation is produced by charged particles which are traveling through a dielectric substance at a speed greater than the speed of light in that medium. Despite the production of similarity-colored light and an association with high-energy particles, Cherenkov radiation is generated by a fundamentally different mechanism. | 0 | Theoretical and Fundamental Chemistry |
On heating a haloalkane and concentrated ammonia in a sealed tube with ethanol, a series of amines are formed along with their salts. The tertiary amine is usually the major product.
This is known as Hoffmann's ammonolysis. | 1 | Applied and Interdisciplinary Chemistry |
The reaction catalyzed is:
ATP + AMP ⇔ 2 ADP
The equilibrium constant varies with condition, but it is close to 1. Thus, ΔG for this reaction is close to zero. In muscle from a variety of species of vertebrates and invertebrates, the concentration of ATP is typically 7-10 times that of ADP, and usually greater than 100 times that of AMP. The rate of oxidative phosphorylation is controlled by the availability of ADP. Thus, the mitochondrion attempts to keep ATP levels high due to the combined action of adenylate kinase and the controls on oxidative phosphorylation. | 1 | Applied and Interdisciplinary Chemistry |
If with , , as integers represents the reciprocal lattice for a crystal lattice (defined by ) in real space, we know that with an integer due to the known orthogonality between primitive vectors for the reciprocal lattice and those for the crystal lattice. (We use the physical, not crystallographers, definition for reciprocal lattice vectors which gives the factor of .) But notice that this is nothing but the Laue equations. Hence we identify , means that allowed scattering vectors are those equal to reciprocal lattice vectors for a crystal in diffraction, and this is the meaning of the Laue equations. This fact is sometimes called the Laue condition. In this sense, diffraction patterns are a way to experimentally measure the reciprocal lattice for a crystal lattice.'
The Laue condition can be rewritten as the following.
Applying the elastic scattering condition (In other words, the incoming and diffracted waves are at the same (temporal) frequency. We can also say that the energy per photon does not change.)
To the above equation, we obtain
The second equation is obtained from the first equation by using .
The result (also ) is an equation for a plane (as the set of all points indicated by satisfying this equation) as its equivalent equation is a plane equation in geometry. Another equivalent equation, that may be easier to understand, is (also ). This indicates the plane that is perpendicular to the straight line between the reciprocal lattice origin and and located at the middle of the line. Such a plane is called Bragg plane. This plane can be understood since for scattering to occur. (It is the Laue condition, equivalent to the Laue equations.) And, the elastic scattering has been assumed so , , and form a rhombus. Each is by definition the wavevector of a plane wave in the Fourier series of a spatial function which periodicity follows the crystal lattice (e.g., the function representing the electronic density of the crystal), wavefronts of each plane wave in the Fourier series is perpendicular to the plane waves wavevector , and these wavefronts are coincident with parallel crystal lattice planes. This means that X-rays are seemingly "reflected" off parallel crystal lattice planes perpendicular at the same angle as their angle of approach to the crystal with respect to the lattice planes; in the elastic light (typically X-ray)-crystal scattering, parallel crystal lattice planes perpendicular to a reciprocal lattice vector for the crystal lattice play as parallel mirrors for light which, together with , incoming (to the crystal) and outgoing (from the crystal by scattering) wavevectors forms a rhombus.'
Since the angle between and is , (Due to the mirror-like scattering, the angle between and is also .) . Recall, with as the light (typically X-ray) wavelength, and with as the distance between adjacent parallel crystal lattice planes and as an integer. With these, we now derive Bragg's law that is equivalent to the Laue equations (also called the Laue condition): | 0 | Theoretical and Fundamental Chemistry |
The Riemschneider thiocarbamate synthesis for aromatic compounds does not work efficiently for ortho-substituted compounds such as ortho-carboxy, ortho-methoxy or ortho-nitro derivative compounds. The reaction is also not as efficient for compounds that are sensitive to concentrated acid, such as thiocyanophenols. The reaction works well for other compounds. Various thiocyanate compounds underwent the Riemschneider synthesis to form thiocarbamates, and all had melting points similar to the predicted value. | 0 | Theoretical and Fundamental Chemistry |
Hiyama is best known for developing:
*The Nozaki-Hiyama-Kishi reaction (NHK reaction) is a nickel/chromium mediated cross-coupling reaction between an allyl, vinyl or aryl halide and an aldehyde to form an alcohol upon aqueous workup.
It was originally discovered in 1977, where Hiyama and Nozaki reported a chemospecific synthesis of homoallyl alcohols from an aldehyde and allyl halide using chromium(II) chloride.
In 1983, Hiyama and Nozaki published another paper extending the scope of the reaction to include aryl and vinyl halides.
In 1986, Nozaki and Kishi independently discovered that the reaction depended on the nickel impurities in the chromium(II) chloride salt. Since then, nickel(II) chloride has been used as a co-catalyst.
The NHK reaction demonstrates high chemoselectivity towards aldehydes, as it tolerates a range of functional groups, and has been used on the process scale.
*The Hiyama coupling is a palladium-catalyzed cross-coupling reaction between aryl, alkenyl or alkyl halides and an organosilicon compound to form a C-C bond.
:* : Aryl, Alkenyl or Alkynyl
:* : Aryl, Alkenyl, Alkynyl or Alkyl
:* : Cl, F or Alkyl
:* : Cl, Br, I or OTf
Hiyama developed this reaction in 1988. He says he developed this method in order to overcome the shortcomings of Grignard reagents. While Grignard reagents are powerful, Hiyama says, they can be hard to use in total synthesis as they are not as tolerant of other functional groups. | 0 | Theoretical and Fundamental Chemistry |
The coffee ring effect is utilized in convective deposition by researchers wanting to order particles on a substrate using capillary-driven assembly, replacing a stationary droplet with an advancing meniscus drawn across the substrate. This process differs from dip-coating in that evaporation drives flow along the substrate as opposed to gravity.
Convective deposition can control particle orientation, resulting in the formation of crystalline monolayer films from nonspherical particles such as hemispherical, dimer, and dumbbell shaped particles. Orientation is afforded by the system trying to reach a state of maximum packing of the particles in the thin meniscus layer over which evaporation occurs. They showed that tuning the volume fraction of particles in solution will control the specific location along the varying meniscus thickness at which assembly occurs. Particles will align with their long axis in- or out-of-plane depending on whether or not their longer dimension of the particle was equal to the thickness of the wetting layer at the meniscus location. Such thickness transitions were established with spherical particles as well. It was later shown that convective assembly could control particle orientation in assembling multi-layers, resulting in long-range 3D colloidal crystals from dumbbell shaped particles. These finds were attractive for the self-assembled of colloidal crystal films for applications such as photonics. Recent advances have increased the application of coffee-ring assembly from colloidal particles to organized patterns of inorganic crystals. | 0 | Theoretical and Fundamental Chemistry |
Measuring the speed of second sound in He-He mixtures can be
used as a thermometer in the range 0.01-0.7 K.
Oscillating superleak transducers (OST) use second sound to locate defects in superconducting accelerator cavities. | 0 | Theoretical and Fundamental Chemistry |
The history of chromatography spans from the mid-19th century to the 21st. Chromatography, literally "color writing", was used—and named— in the first decade of the 20th century, primarily for the separation of plant pigments such as chlorophyll (which is green) and carotenoids (which are orange and yellow). New forms of chromatography developed in the 1930s and 1940s made the technique useful for a wide range of separation processes and chemical analysis tasks, especially in biochemistry. | 1 | Applied and Interdisciplinary Chemistry |
Although turbulence leads to unpredictable results in the time domain, it can, to some extent, be characterized in the frequency domain. Turbulent fluctuations are dominated by low frequency components, with higher frequency components having less influence. For further information, see Kolmogorov's theory on turbulence.
Several models of frequency domain representations of point wind speeds have been developed: the von Kármán wind turbulence model and Dryden Wind Turbulence Model are examples of such. | 1 | Applied and Interdisciplinary Chemistry |
Workers in various occupations may be at a greater level of risk for several types of toxicity, including neurotoxicity. The expression "Mad as a hatter" and the "Mad Hatter" of the book Alice in Wonderland derive from the known occupational toxicity of hatters who used a toxic chemical for controlling the shape of hats. Exposure to chemicals in the workplace environment may be required for evaluation by industrial hygiene professionals. | 1 | Applied and Interdisciplinary Chemistry |
An example of a prototype for a synthetic chemically driven rotary molecular motor was reported by Kelly and co-workers in 1999. Their system is made up from a three-bladed triptycene rotor and a helicene, and is capable of performing a unidirectional 120° rotation.
This rotation takes place in five steps. The amine group present on the triptycene moiety is converted to an isocyanate group by condensation with phosgene (a). Thermal or spontaneous rotation around the central bond then brings the isocyanate group in proximity of the hydroxyl group located on the helicene moiety (b), thereby allowing these two groups to react with each other (c). This reaction irreversibly traps the system as a strained cyclic urethane that is higher in energy and thus energetically closer to the rotational energy barrier than the original state. Further rotation of the triptycene moiety therefore requires only a relatively small amount of thermal activation in order to overcome this barrier, thereby releasing the strain (d). Finally, cleavage of the urethane group restores the amine and alcohol functionalities of the molecule (e).
The result of this sequence of events is a unidirectional 120° rotation of the triptycene moiety with respect to the helicene moiety. Additional forward or backward rotation of the triptycene rotor is inhibited by the helicene moiety, which serves a function similar to that of the pawl of a ratchet. The unidirectionality of the system is a result from both the asymmetric skew of the helicene moiety as well as the strain of the cyclic urethane which is formed in c. This strain can be only be lowered by the clockwise rotation of the triptycene rotor in d, as both counterclockwise rotation as well as the inverse process of d are energetically unfavorable. In this respect the preference for the rotation direction is determined by both the positions of the functional groups and the shape of the helicene and is thus built into the design of the molecule instead of dictated by external factors.
The motor by Kelly and co-workers is an elegant example of how chemical energy can be used to induce controlled, unidirectional rotational motion, a process which resembles the consumption of ATP in organisms in order to fuel numerous processes. However, it does suffer from a serious drawback: the sequence of events that leads to 120° rotation is not repeatable. Kelly and co-workers have therefore searched for ways to extend the system so that this sequence can be carried out repeatedly. Unfortunately, their attempts to accomplish this objective have not been successful and currently the project has been abandoned. In 2016 David Leigh's group invented the first autonomous chemically-fuelled synthetic molecular motor.
Some other examples of synthetic chemically driven rotary molecular motors that all operate by sequential addition of reagents have been reported, including the use of the stereoselective ring opening of a racemic biaryl lactone by the use of chiral reagents, which results in a directed 90° rotation of one aryl with respect to the other aryl. Branchaud and co-workers have reported that this approach, followed by an additional ring closing step, can be used to accomplish a non-repeatable 180° rotation.
Feringa and co-workers used this approach in their design of a molecule that can repeatably perform 360° rotation. The full rotation of this molecular motor takes place in four stages. In stages A and C rotation of the aryl moiety is restricted, although helix inversion is possible. In stages B and D the aryl can rotate with respect to the naphthalene with steric interactions preventing the aryl from passing the naphthalene. The rotary cycle consists of four chemically induced steps which realize the conversion of one stage into the next. Steps 1 and 3 are asymmetric ring opening reactions which make use of a chiral reagent in order to control the direction of the rotation of the aryl. Steps 2 and 4 consist of the deprotection of the phenol, followed by regioselective ring formation. | 0 | Theoretical and Fundamental Chemistry |
Megaphone is a cytotoxic neolignan obtained from Aniba megaphylla, a flowering plant of Laurel family which gave the compound its name. Megaphone has also been prepared synthetically.
Studies carried out in the 1960s demonstrated that an alcoholic extract of the ground root of Aniba megaphylla inhibited, in vitro, growth of cells derived from human carcinoma of the nasopharynx. In 1978, the active components of the extract were isolated using silica gel chromatography, characterized and named as megaphone (CHO, solid), megaphone acetate (CHO, oily liquid) and megaphyllone acetate (CHO, oily liquid). For comparison, megaphone acetate was also produced synthetically by reacting megaphone with acetic anhydride at 50 °C for 6 hours. Stirring an alcoholic solution of megaphone (megaphone acetate), with added palladium catalyst, in hydrogen atmosphere, followed by evaporation of the solvent yields tetrahydromegaphone (tetrahydromegaphone acetate) as an oil. Millimeter-sized crystals of megaphone can be grown from an ether-chloroform solution. They have monoclinic symmetry with space group P2, lattice constants a = 0.8757 nm, b = 1.1942 nm and c = 1.0177 nm and two formula units per unit cell. Megaphone and megaphone acetate molecules are chiral and the reported extraction and synthesis procedures yielded their racemic mixtures. Megaphone acetate was also isolated from the root of Endlicheria dysodantha, another plant of Laurel family, using chromatography of ethanolic solution. It showed inhibitory activity against cells of crown gall tumor and human lung, breast and colon carcinomas. | 0 | Theoretical and Fundamental Chemistry |
*McGannon, Harold E. editor (1971). The Making, Shaping and Treating of Steel: Ninth Edition. Pittsburgh, Pennsylvania: United States Steel Corporation.
*Smil, Vaclav (2006). [https://books.google.com/books?id=tl23A0mCPLUC Transforming the twentieth century: technical innovations and their consequences, Volume 2]. Oxford University Press US. .
*Brock, James W.; Elzinga, Kenneth G. (1991). [https://books.google.com/books?id=2Xj1qt1daHAC Antitrust, the market, and the state: the contributions of Walter Adams]. M. E. Sharpe. .
*Tweraser, Kurt (2000). The Marshall Plan and the Reconstruction of the Austrian Steel Industry 1945–1953. in: Bischof, Gunther et al. (2000). [https://books.google.com/books?id=pKlWyYA26GMC The Marshall Plan in Austria]. Transaction Publishers. . pp. 290–322. | 1 | Applied and Interdisciplinary Chemistry |
On 1 August 2009 it was announced that the decision by Corby Borough Council regarding whether or not to appeal the ruling would be taken on 18 August 2009, the day before the deadline for appeal decisions to be submitted to Mr Justice Akenhead. Unusually, the authority decided that openness and public opinion were required at the extraordinary full council sitting after which councillors will vote on whether to appeal or instead pay the compensation to 16 children who were born with birth defects.
Chief Executive Chris Mallender stated: "The council is doing the right thing by reaching the decision in public. We will be starting the meeting at 6pm so we can give the opportunity for [the public] to speak," a move he said would make sure councillors' decisions reflected public opinion.
The council, which has an annual budget of £12m, has already spent £1.9m fighting the case and has now received a bill for £4.7m from the families' solicitor.
At the meeting the council voted to appeal against the ruling but said that they would follow a "twin track" approach, preferring to attend independent mediation sessions to come to an out-of-court settlement with the families. They also stated that any mediation would include the cases of the two youngest claimants despite these not being covered by the ruling. The chief executive gave a statement that if a causal link between the toxins and the limb deformities was ever proven he would "offer an unreserved apology", however he believed "that the judgement is unsound and will be found wanting on appeal." | 1 | Applied and Interdisciplinary Chemistry |
Currently, CO capture uses mostly amine-based absorption technologies, which are energy intensive and solvent intensive. Volatile organic compounds alone in chemical processes represent a multibillion-dollar industry. Therefore, ionic liquids offer an alternative that prove attractive should their other deficiencies be addressed.
During the capture process, the anion and cation play a crucial role in the dissolution of CO. Spectroscopic results suggest a favorable interaction between the anion and CO, wherein CO molecules preferentially attach to the anion. Furthermore, intermolecular forces, such as hydrogen bonds, van der Waals bonds, and electrostatic attraction, contributes to the solubility of CO in ionic liquids. This makes ionic liquids promising candidates for CO capture because the solubility of CO can be modeled accurately by the regular solubility theory (RST), which reduces operational costs in developing more sophisticated model to monitor the capture process. | 0 | Theoretical and Fundamental Chemistry |
Chlorophyll plays a crucial role in photosynthesis. It contains a magnesium enclosed in a chlorin ring. However, the magnesium ion is not directly involved in the photosynthetic function and can be replaced by other divalent ions with little loss of activity. Rather, the photon is absorbed by the chlorin ring, whose electronic structure is well-adapted for this purpose.
Initially, the absorption of a photon causes an electron to be excited into a singlet state of the Q band. The excited state undergoes an intersystem crossing from the singlet state to a triplet state in which there are two electrons with parallel spin. This species is, in effect, a free radical, and is very reactive and allows an electron to be transferred to acceptors that are adjacent to the chlorophyll in the chloroplast. In the process chlorophyll is oxidized. Later in the photosynthetic cycle, chlorophyll is reduced back again. This reduction ultimately draws electrons from water, yielding molecular oxygen as a final oxidation product. | 1 | Applied and Interdisciplinary Chemistry |
Actinism () is the property of solar radiation that leads to the production of photochemical and photobiological effects. Actinism is derived from the Ancient Greek ἀκτίς, ἀκτῖνος ("ray, beam"). The word actinism is found, for example, in the terminology of imaging technology (esp. photography), medicine (concerning sunburn), and chemistry (concerning containers that protect from photo-degradation), and the concept of actinism is applied, for example, in chemical photography and X-ray imaging.
Actinic () chemicals include silver salts used in photography and other light sensitive chemicals. | 0 | Theoretical and Fundamental Chemistry |
Only with the Incas would metals really come into practical use. At Machu Picchu and other sites, metal was used for bolas, plumb bobs, chisels, gravers, pry bars, tweezers, needles, plates, fish hooks, spatulas, ladles, knives (tumi), bells, breastplates, lime spoons, mace heads, ear spools, bowls, cloak pins (tupus), axes, and foot plow adzes.
Nonetheless, they remained materials through which to display wealth and status. The characteristic importance placed on colour, which had led to some of the earlier developments, was still present (sun/moon association with gold/silver). Metals other than gold also had an intrinsic value, with axe pieces being of particular note in this regard. With the spread of metal tools by the Incas, it is thought possible that a more Old World use of metals would have become more common. In any case, as Bruhns notes, "[b]ronze can be seen as an expensive substitute for the equally efficient stone". However, sediment research in Bolivia has revealed that metals such as silver were smelted on a very large scale, thousands of tons, from late Tiwanaku to Inca times (1000–1530 CE), which suggests that the paucity of metal (particularly precious metal) at Inca sites is more likely caused by Spanish acquisition and export than by limited pre-colonial use.
It has been claimed that the Inca Empire expanded into Diaguita lands in what is now north-central Chile because of its mineral wealth, but that view is rejected by some scholars.
Further, an additional possibility is that the Incas invaded the relatively well-populated Eastern Diaguita valleys (present-day Argentina) to obtain labor to send to Chilean mining districts. The Incas influenced Diaguitas, who adopted Incan metalworking techniques.
Farther south in Chile, Mapuche tribes within or near the Incan Empire paid tributes in gold. Incan yanakuna are believed by archaeologists Tom Dillehay and Américo Gordon to have extracted gold south of the Incan frontier in free Mapuche territory. Following that thought, the main motive for Incan expansion into Mapuche territory would have been to access gold mines.
Among the Mapuche people of central and south-central Chile, gold had an important cultural significance that predates Inca contact.
At the time of the Spanish conquest of Chile, Mapuches are reported by various chroniclers to use gold ornaments. According to historian Osvaldo Silva gold ornaments of the Mapuche of the Concepción area evidence some kind of interaction between the Mapuche and the Inca that may have been trade, gifts, or spoils of war taken from a defeated Inca army.
Pre-Hispanic Mapuche tools are known to have been relatively simple and made of wood and stone, but a few of them were actually made of copper and bronze. | 1 | Applied and Interdisciplinary Chemistry |
Dialkylphosphinic acids have the formula RPOH, where R is an alkyl or aryl group. The phosphorus(V) center has tetrahedral molecular geometry. Under the brand names Aerophine and Cyanex, dialkylphosphinic acids are used in extraction and separation of metals as one of the techniques of hydrometallurgy Characteristically the organic substituents are branched to confer solubility and preclude crystallization.
Formaldehyde and HPO react to give (HOCH)POH. | 0 | Theoretical and Fundamental Chemistry |
It is possible to introduce an artificial electron acceptor into the light reaction, such as a dye that changes color when it is reduced. These are known as Hill reagents. These dyes permitted the finding of electron transport chains during photosynthesis. Dichlorophenolindophenol (DCPIP), an example of these dyes, is widely used by experimenters. DCPIP is a dark blue solution that becomes lighter as it is reduced. It provides experimenters with a simple visual test and easily observable light reaction.
In another approach to studying photosynthesis, light-absorbing pigments such as chlorophyll can be extracted from chloroplasts. Like so many important biological systems in the cell, the photosynthetic system is ordered and compartmentalized in a system of membranes. | 0 | Theoretical and Fundamental Chemistry |
Discussion of cloning in the popular media often presents the subject negatively. In an article in the 8 November 1993 article of Time, cloning was portrayed in a negative way, modifying Michelangelos Creation of Adam to depict Adam with five identical hands. Newsweek' 10 March 1997 issue also critiqued the ethics of human cloning, and included a graphic depicting identical babies in beakers.
The concept of cloning, particularly human cloning, has featured a wide variety of science fiction works. An early fictional depiction of cloning is Bokanovskys Process which features in Aldous Huxleys 1931 dystopian novel Brave New World. The process is applied to fertilized human eggs in vitro, causing them to split into identical genetic copies of the original. Following renewed interest in cloning in the 1950s, the subject was explored further in works such as Poul Andersons 1953 story UN-Man, which describes a technology called "exogenesis", and Gordon Rattray Taylors book The Biological Time Bomb, which popularised the term "cloning" in 1963.
Cloning is a recurring theme in a number of contemporary science fiction films, ranging from action films such as Anna to the Infinite Power, The Boys from Brazil, Jurassic Park (1993), Alien Resurrection (1997), The 6th Day (2000), Resident Evil (2002), Star Wars: Episode II – Attack of the Clones (2002), The Island (2005) and Moon (2009) to comedies such as Woody Allens 1973 film Sleeper'.
The process of cloning is represented variously in fiction. Many works depict the artificial creation of humans by a method of growing cells from a tissue or DNA sample; the replication may be instantaneous, or take place through slow growth of human embryos in artificial wombs. In the long-running British television series Doctor Who, the Fourth Doctor and his companion Leela were cloned in a matter of seconds from DNA samples ("The Invisible Enemy", 1977) and then – in an apparent homage to the 1966 film Fantastic Voyage – shrunk to microscopic size to enter the Doctors body to combat an alien virus. The clones in this story are short-lived, and can only survive a matter of minutes before they expire. Science fiction films such as The Matrix and Star Wars: Episode II – Attack of the Clones' have featured scenes of human foetuses being cultured on an industrial scale in mechanical tanks.
Cloning humans from body parts is also a common theme in science fiction. Cloning features strongly among the science fiction conventions parodied in Woody Allens Sleeper, the plot of which centres around an attempt to clone an assassinated dictator from his disembodied nose. In the 2008 Doctor Who story "Journeys End", a duplicate version of the Tenth Doctor spontaneously grows from his severed hand, which had been cut off in a sword fight during an earlier episode.
After the death of her beloved 14-year-old Coton de Tulear named Samantha in late 2017, Barbra Streisand announced that she had cloned the dog, and was now "waiting for [the two cloned pups] to get older so [she] can see if they have [Samantha's] brown eyes and her seriousness". The operation cost $50,000 through the pet cloning company ViaGen. | 1 | Applied and Interdisciplinary Chemistry |
The Compendium of Macromolecular Nomenclature, by the International Union of Pure and Applied Chemistry (IUPAC), provides definition of polymer related terms and rules of nomenclature of polymers. It is referred to as the Purple Book. It was published in 1991 () by Blackwell Science. The author of this book is W.V. Metanomski.
The expansion of this book named Compendium of Polymer Terminology and Nomenclature: IUPAC Recommendations, 2008 was published by the Royal Society of Chemistry in 2009 ().
The rules and definitions were set up by the IUPAC Commission on Macromolecular Nomenclature. The work was carried on by the Subcommittee on Polymer Terminology (IUPAC Division IV) after the Commission on Macromolecular Nomenclature was terminated. | 0 | Theoretical and Fundamental Chemistry |
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