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A glycosidic bond or glycosidic linkage is a type of ether bond that joins a carbohydrate (sugar) molecule to another group, which may or may not be another carbohydrate.
A glycosidic bond is formed between the hemiacetal or hemiketal group of a saccharide (or a molecule derived from a saccharide) and the hydroxyl group of some compound such as an alcohol. A substance containing a glycosidic bond is a glycoside.
The term glycoside is now extended to also cover compounds with bonds formed between hemiacetal (or hemiketal) groups of sugars and several chemical groups other than hydroxyls, such as -SR (thioglycosides), -SeR (selenoglycosides), -NRR (N-glycosides), or even -CRRR (C-glycosides).
Particularly in naturally occurring glycosides, the compound ROH from which the carbohydrate residue has been removed is often termed the aglycone, and the carbohydrate residue itself is sometimes referred to as the glycone. | 0 | Theoretical and Fundamental Chemistry |
Although pneumatic cylinders will vary in appearance, size and function, they generally fall into one of the specific categories shown below. However, there are also numerous other types of pneumatic cylinder available, many of which are designed to fulfill specific and specialized functions. | 1 | Applied and Interdisciplinary Chemistry |
Cadmium sulfide has, like zinc sulfide, two crystal forms. The more stable hexagonal wurtzite structure (found in the mineral Greenockite) and the cubic zinc blende structure (found in the mineral Hawleyite). In both of these forms the cadmium and sulfur atoms are four coordinate. There is also a high pressure form with the NaCl rock salt structure.
Cadmium sulfide is a direct band gap semiconductor (gap 2.42 eV). The proximity of its band gap to visible light wavelengths gives it a coloured appearance.<br /> As well as this obvious property other properties result:
* the conductivity increases when irradiated, (leading to uses as a photoresistor)
* when combined with a p-type semiconductor it forms the core component of a photovoltaic (solar) cell and a CdS/CuS solar cell was one of the first efficient cells to be reported (1954)
* when doped with for example Cu ("activator") and Al ("coactivator") CdS luminesces under electron beam excitation (cathodoluminescence) and is used as phosphor
* both polymorphs are piezoelectric and the hexagonal is also pyroelectric
* electroluminescence
* CdS crystals can act as a gain medium in solid state laser
* In thin-film form, CdS can be combined with other layers for use in certain types of solar cells. CdS was also one of the first semiconductor materials to be used for thin-film transistors (TFTs). However interest in compound semiconductors for TFTs largely waned after the emergence of amorphous silicon technology in the late 1970s.
* Thin films of CdS can be piezoelectric and have been used as transducers which can operate at frequencies in the GHz region.
* Nanoribbons of CdS show a net cooling due annihilation of phonons, during anti-Stokes luminescence at ~510 nm. As a result, a maximum temperature drop of 40 and 15 K has been demonstrated when the nanoribbons are pumped with a 514 or 532 nm laser. | 0 | Theoretical and Fundamental Chemistry |
* Deutsche Akademie der Naturforscher Leopoldina
* Berlin-Brandenburgische Akademie der Wissenschaften
* American Academy of Arts and Sciences (Foreign Honorary Member)
* Real Academia de Ciencias Exactas, Físicas y Naturales (Spain, foreign member)
* US National Academy of Sciences (Foreign Associate) | 0 | Theoretical and Fundamental Chemistry |
Two types of OFM probes are currently available: Linear OFM probes for implantation into superficial tissues such as skin (dermal OFM, dOFM) and subcutaneous adipose tissue (adipose OFM, aOFM) as well as concentric probes for implantation into various regions of the brain (cerebral OFM, cOFM). | 1 | Applied and Interdisciplinary Chemistry |
In the 17th century, a renewed interest arose in Epicurean atomism and corpuscularianism as a hybrid or an alternative to Aristotelian physics. The main figures in the rebirth of atomism were Isaac Beeckman, René Descartes, Pierre Gassendi, and Robert Boyle, as well as other notable figures. | 1 | Applied and Interdisciplinary Chemistry |
The bound state of two solitons is known as a bion, or in systems where the bound state periodically oscillates, a breather. The interference-type forces between solitons could be used in making bions. However, these forces are very sensitive to their relative phases. Alternatively, the bound state of solitons could be formed by dressing atoms with highly excited Rydberg levels. The resulting self-generated potential profile features an inner attractive soft-core supporting the 3D self-trapped soliton, an intermediate repulsive shell (barrier) preventing solitons’ fusion, and an outer attractive layer (well) used for completing the bound state resulting in giant stable soliton molecules. In this scheme, the distance and size of the individual solitons in the molecule can be controlled dynamically with the laser adjustment.
In field theory bion usually refers to the solution of the Born–Infeld model. The name appears to have been coined by G. W. Gibbons in order to distinguish this solution from the conventional soliton, understood as a regular, finite-energy (and usually stable) solution of a differential equation describing some physical system. The word regular means a smooth solution carrying no sources at all. However, the solution of the Born–Infeld model still carries a source in the form of a Dirac-delta function at the origin. As a consequence it displays a singularity in this point (although the electric field is everywhere regular). In some physical contexts (for instance string theory) this feature can be important, which motivated the introduction of a special name for this class of solitons.
On the other hand, when gravity is added (i.e. when considering the coupling of the Born–Infeld model to general relativity) the corresponding solution is called EBIon, where "E" stands for Einstein. | 1 | Applied and Interdisciplinary Chemistry |
Ecological engineering uses ecology and engineering to predict, design, construct or restore, and manage ecosystems that integrate "human society with its natural environment for the benefit of both". | 1 | Applied and Interdisciplinary Chemistry |
The FSL Kode construct by nature of its composition in possessing both hydrophobic and hydrophilic regions are amphiphilic (or amphipathic). This characteristic determines the way in which the construct will interact with surfaces. When present in a solution they may form simple micelles or adopt more complex bilayer structures with two simplistic examples shown in Fig. 5a. More complex structures are expected. The actual nature of FSL micelles has not been determined. However, based on normal structural function of micelles, it is expected that it will be determined in part by the combination of functional group, spacer and lipid together with temperature, concentration, size and hydrophobicity/hydrophilicity for each FSL Kode construct type.
Surface coatings will occur via two theoretical mechanisms, the first being direct hydrophobic interaction of the lipid tail with a hydrophobic surface resulting in a monolayer of FSL at the surface (Fig. 5b). Hydrophobic binding of the FSL will be via its hydrophobic lipid tail interacting directly with the hydrophobic (lipophilic) surface. The second surface coating will be through the formation of bilayers as the lipid tail is unable to react with the hydrophilic surface. In this case the lipids will induce the formation of a bilayer, the surface of which will be hydrophilic. This hydrophilic membrane will then interact directly with the hydrophilic surface and will probably encapsulate fibres. This hydrophilic bilayer binding is the expected mechanism by which FSLs are able to bind to fibrous membranes such as paper and glass fibres (Fig. 5c) and (Fig. 9). | 1 | Applied and Interdisciplinary Chemistry |
The gold number is the minimum weight (in milligrams) of a protective colloid required to prevent the coagulation of 10 ml of a standard hydro gold sol when 1 ml of a 10% sodium chloride solution is added to it. It was first used by Richard Adolf Zsigmondy in 1901.
An electrical double layer is normally present on the gold sol particles, resulting in electrostatic repulsion between the particles. The sodium chloride ions disrupt this electrical double layer, causing coagulation to occur.
The coagulation of gold sol results in an increase in particle size, indicated by a colour change from red to blue or purple. The higher the gold number, the lower the protective power of the colloid, because a greater amount of colloid is required to prevent coagulation.
The gold number of some colloids are given below. | 0 | Theoretical and Fundamental Chemistry |
The evolution of ATP synthase is thought to have been modular whereby two functionally independent subunits became associated and gained new functionality. This association appears to have occurred early in evolutionary history, because essentially the same structure and activity of ATP synthase enzymes are present in all kingdoms of life. The F-ATP synthase displays high functional and mechanistic similarity to the V-ATPase. However, whereas the F-ATP synthase generates ATP by utilising a proton gradient, the V-ATPase generates a proton gradient at the expense of ATP, generating pH values of as low as 1.
The F region also shows significant similarity to hexameric DNA helicases (especially the Rho factor), and the entire enzyme region shows some similarity to -powered T3SS or flagellar motor complexes. The αβ hexamer of the F region shows significant structural similarity to hexameric DNA helicases; both form a ring with 3-fold rotational symmetry with a central pore. Both have roles dependent on the relative rotation of a macromolecule within the pore; the DNA helicases use the helical shape of DNA to drive their motion along the DNA molecule and to detect supercoiling, whereas the αβ hexamer uses the conformational changes through the rotation of the γ subunit to drive an enzymatic reaction.
The motor of the F particle shows great functional similarity to the motors that drive flagella. Both feature a ring of many small alpha-helical proteins that rotate relative to nearby stationary proteins, using a potential gradient as an energy source. This link is tenuous, however, as the overall structure of flagellar motors is far more complex than that of the F particle and the ring with about 30 rotating proteins is far larger than the 10, 11, or 14 helical proteins in the F complex. More recent structural data do however show that the ring and the stalk are structurally similar to the F particle.
The modular evolution theory for the origin of ATP synthase suggests that two subunits with independent function, a DNA helicase with ATPase activity and a motor, were able to bind, and the rotation of the motor drove the ATPase activity of the helicase in reverse. This complex then evolved greater efficiency and eventually developed into today's intricate ATP synthases. Alternatively, the DNA helicase/ motor complex may have had pump activity with the ATPase activity of the helicase driving the motor in reverse. This may have evolved to carry out the reverse reaction and act as an ATP synthase. | 0 | Theoretical and Fundamental Chemistry |
In September 2018, British physicist Jessica Wade created an article on the English Wikipedia about , but this was deleted on February 11, 2019. On April 12, The Washington Post published an op-ed about, in part, the English-language Wikipedias lack of coverage given to Phelps contribution to the discovery of element 117. The column, co-written by Wade, decried discussions among volunteer editors at the site that resulted in deletion of the article on Phelps. According to an article in the July 2019 Chemistry World, "her name didnt appear in the articles announcing tennessines discovery. She wasnt profiled by mainstream media. Most mentions of her work are on her employers website – a source that's not classed as independent by Wikipedia standards and therefore not admissible when it comes to establishing notability. The [Wikipedia] community consensus was that her biography had to go." The deletion was contested multiple times. By January 2020, there was a consensus to restore it, as by then new sources had become available. | 0 | Theoretical and Fundamental Chemistry |
Phosphatidylcholine molecules form ~85% of the lipid in surfactant and have saturated acyl chains. Phosphatidylglycerol (PG) forms about 11% of the lipids in the surfactant, it has unsaturated fatty acid chains that fluidize the lipid monolayer at the interface. Neutral lipids and cholesterol are also present. The components for these lipids diffuse from the blood into type II alveolar cells where they are assembled and packaged for secretion into secretory organelles called lamellar bodies. | 0 | Theoretical and Fundamental Chemistry |
* ATOMIC, MOLECULAR AND OPTICAL PHYSICS: NEW RESEARCH by L.T. Chen ; Nova Science Publishers, Inc. New York | 0 | Theoretical and Fundamental Chemistry |
A magnetohydrodynamic generator is an MHD converter that transforms the kinetic energy of an electrically conductive fluid, in motion with respect to a steady magnetic field, into electricity. MHD power generation has been tested extensively in the 1960s with liquid metals and plasmas as working fluids.
Basically, a plasma is hurtling down within a channel whose walls are fitted with electrodes. Electromagnets create a uniform transverse magnetic field within the cavity of the channel. The Lorentz force then acts upon the trajectory of the incoming electrons and positive ions, separating the opposite charge carriers according to their sign. As negative and positive charges are spatially separated within the chamber, an electric potential difference can be retrieved across the electrodes. While work is extracted from the kinetic energy of the incoming high-velocity plasma, the fluid slows down during the process. | 1 | Applied and Interdisciplinary Chemistry |
Researchers determined the crystal structure of the FI6 antibody when it was bound to H1 and H3 HA proteins. Sitting atop the HA spike is a globular head domain that binds to cellular receptors during viral entry and contains the major antigenic sites targeted by the immune system. Because of this selective pressure, the sequence in the head domain drifts enough to require an updated seasonal vaccine most years. A stalk domain connects the head to the viral membrane and is responsible for fusing viral and host membranes so that the pathogen can invade human cells. The immune system usually does not have a strong response to the partially hidden stalk domain, so portions of the stalk remain highly conserved across all influenza subtypes. The FI6 antibody makes extensive contacts with conserved parts of the stalk, thereby blocking HA from harpooning a sticky fusion peptide into the host membrane during viral entry.
The FI6 provides scientists with a broadly neutralizing antibody that recognizes all 16 HA subtypes, including emerging ones, such as H5N1. But, because the replication of the influenza virus is somewhat error-prone, the virus evolves as a quasispecies, and widespread use of antiviral drugs can lead to resistant strains. Such has been the case for oseltamivir and for the M2 ion channel blocker amantadine. Therefore, before considering FI6 as long-term prophylactic or therapeutic agent against seasonal influenza, we would first have to determine whether the influenza virus could quickly mutate the epitope targeted by FI6 and escape recognition by FI6 after exposure.
A more important clinical implication of this work is the identification of a universal neutralizing epitope in the HA stalk at the atomic level an important intellectual landmark for the development of a universal influenza vaccine. In the absence of the immunodominant head domain, isolated portions of the HA stalk that include the FI6 epitope and have already been shown to stimulate broad, but not universal, protective effects against H1N1 and H3N2 strains in vaccinated animals. Using protein engineering and adjuvants to focus the immune system on the FI6 epitope may be the critical next step along the path to a universal vaccine. | 1 | Applied and Interdisciplinary Chemistry |
Williams studied chemistry at Imperial College London, graduating with a Bachelor's degree in chemistry. She completed a PhD with Vernon C. Gibson and Nick Long. | 0 | Theoretical and Fundamental Chemistry |
Thylakoid proteins are targeted to their destination via signal peptides and prokaryotic-type secretory pathways inside the chloroplast. Most thylakoid proteins encoded by a plant's nuclear genome need two targeting signals for proper localization: An N-terminal chloroplast targeting peptide (shown in yellow in the figure), followed by a thylakoid targeting peptide (shown in blue). Proteins are imported through the translocon of the outer and inner membrane (Toc and Tic) complexes. After entering the chloroplast, the first targeting peptide is cleaved off by a protease processing imported proteins. This unmasks the second targeting signal and the protein is exported from the stroma into the thylakoid in a second targeting step. This second step requires the action of protein translocation components of the thylakoids and is energy-dependent. Proteins are inserted into the membrane via the SRP-dependent pathway (1), the Tat-dependent pathway (2), or spontaneously via their transmembrane domains (not shown in the figure). Lumenal proteins are exported across the thylakoid membrane into the lumen by either the Tat-dependent pathway (2) or the Sec-dependent pathway (3) and released by cleavage from the thylakoid targeting signal. The different pathways utilize different signals and energy sources. The Sec (secretory) pathway requires ATP as an energy source and consists of SecA, which binds to the imported protein and a Sec membrane complex to shuttle the protein across. Proteins with a twin arginine motif in their thylakoid signal peptide are shuttled through the Tat (twin arginine translocation) pathway, which requires a membrane-bound Tat complex and the pH gradient as an energy source. Some other proteins are inserted into the membrane via the SRP (signal recognition particle) pathway. The chloroplast SRP can interact with its target proteins either post-translationally or co-translationally, thus transporting imported proteins as well as those that are translated inside the chloroplast. The SRP pathway requires GTP and the pH gradient as energy sources. Some transmembrane proteins may also spontaneously insert into the membrane from the stromal side without energy requirement. | 0 | Theoretical and Fundamental Chemistry |
Nanoparticles were used by artisans since prehistory, albeit without knowledge of their nature. They were used by glassmakers and potters in Classical Antiquity, as exemplified by the Roman Lycurgus cup of dichroic glass (4th century CE) and the lusterware pottery of Mesopotamia (9th century CE). The latter is characterized by silver and copper nanoparticles dispersed in the glassy glaze. | 0 | Theoretical and Fundamental Chemistry |
Congo red was first synthesized in 1883 by Paul Böttiger, who had been employed at Friedrich Bayer Company in Elberfeld, Germany. He was looking for textile dyes that did not require a mordant step. The company which had a right of first refusal to his inventions was not interested in this bright red color, so he filed the patent under his own name and sold it to the AGFA company of Berlin. AGFA marketed the dye under the name "Congo red", a catchy name in Germany at the time of the 1884 Berlin West Africa Conference, an important event in the Colonisation of Africa. The dye was a major commercial success for AGFA. In the following years, for the same reason, other dyes were marketed using the "Congo" name: Congo rubine, Congo corinth, brilliant Congo, Congo orange, Congo brown, and Congo blue. Once of economic significance, Congo red has fallen into disuse as have all benzidine-derived dyes, owing to their carcinogenic activity.
It is prepared by azo coupling of the bis(diazonium) derivative of benzidine with naphthionic acid.
Congo blue, however, is in widespread international use, in gel sheet form, as a filter to place in front of theatrical, motion picture, television, church, and live event lighting instruments. It is sold under the item name "181 Congo Blue" by Lee Filters. It emits a deep rich saturated blue color with elements of red. Depending upon the color temperature of the source lamp, the light from a lighting instrument with a Congo Blue filter reflected from a white surface can vary from very saturated blue to purple or violet. The manufacturer reports that fluorescent light through a Congo Blue filter gives the appearance of black light. Congo Blue filters are frequently used at live music concerts at an angle from behind musicians to cross back-light with a "warm" color gel like yellow, straw, gold, orange, or magenta, from an opposing angle, for a very dramatic effect. Another use of Congo Blue filters by lighting technicians, is to cut a small strip from the gel sheet, which the technician looks through to make brightness adjustments to a video monitor displaying a standard color bar chart. The Congo Blue filter effectively removes the color from chart and shows the separate bars only in terms of their differing incremental brightness levels. This allows the technician to adjust the monitor to show a full and correct range of brightnesses. | 0 | Theoretical and Fundamental Chemistry |
Certain problems, such as the evolution of the shape of a bubble in a Stokes flow, are conducive to numerical solution by the boundary element method. This technique can be applied to both 2- and 3-dimensional flows. | 1 | Applied and Interdisciplinary Chemistry |
An applied example is a synthesis of sunitinib begins by mixing 5-fluoroisatin slowly into hydrazine hydrate. After 4 hours at 110 °C, the indole ring structure has been broken into (2-amino-5-fluoro-phenyl)-acetic acid hydrazide with reduction of the ketone at the 3-position. Subsequent annelation in strong acid creates the 1,3-dihydro-2-oxo indole structure required for the drug. | 0 | Theoretical and Fundamental Chemistry |
Copper thermite can be prepared using either copper(I) oxide (CuO, red) or copper(II) oxide (CuO, black). The burn rate tends to be very fast and the melting point of copper is relatively low, so the reaction produces a significant amount of molten copper in a very short time. Copper(II) thermite reactions can be so fast that it can be considered a type of flash powder. An explosion can occur, which sends a spray of copper drops to considerable distances.
Oxygen-balanced mixture has theoretical maximum density of 5.109 g/cm, adiabatic flame temperature 2843 K (phase transitions included) with the aluminium oxide being molten and copper in both liquid and gaseous form; 343 g of copper vapor per kg of this thermite are produced. The energy content is 974 cal/g.
Copper(I) thermite has industrial uses in e.g., welding of thick copper conductors (cadwelding). This kind of welding is being evaluated also for cable splicing on the US Navy fleet, for use in high-current systems, e.g., electric propulsion.
Oxygen balanced mixture has theoretical maximum density of 5.280 g/cm, adiabatic flame temperature 2843 K (phase transitions included) with the aluminium oxide being molten and copper in both liquid and gaseous form; 77.6 g of copper vapor per kg of this thermite are produced. The energy content is 575.5 cal/g. | 0 | Theoretical and Fundamental Chemistry |
Towing tests of warships had demonstrated that a below-water ram shape reduced resistance through the water before 1900. The bulbous bow concept is credited to David W. Taylor, a naval architect who served as Chief Constructor of the United States Navy during the First World War and who used the concept (known as a bulbous forefoot) in his design of the , which entered service in 1910. The bow design did not initially enjoy wide acceptance, although it was used in the to great success after the two ships of that class which survived the Washington Naval Treaty were converted to aircraft carriers. This lack of acceptance changed in the 1920s, with Germanys launching of and . They were referred to as Germanys North Atlantic greyhounds, two large commercial ocean liners that competed for the trans-Atlantic passenger trade. Both ships won the coveted Blue Riband, Bremen in 1929 with a crossing speed of , and Europa surpassing her in 1930 with a crossing speed of 27.91 knots.
The design began to be incorporated elsewhere, as seen in the U.S. built SS Malolo, SS President Hoover and SS President Coolidge passenger liners launched in the late 1920s and early 1930s. Still, the idea was viewed as experimental by many shipbuilders and owners.
In 1935 the French superliner was designed by Vladimir Yurkevich combining a bulbous forefoot with massive size and a redesigned hull shape. She was able to achieve speeds in excess of 30 knots (56 km/h). Normandie was famous for many things, including her clean entry into the water and markedly reduced bow wave. Normandies great rival, the British liner , achieved equivalent speeds using traditional stem and hull design. However, a crucial difference was that Normandie achieved these speeds with approximately thirty per cent less engine power than Queen Mary and a corresponding reduction in fuel use.
Bulbous bow designs were also developed and used by the Imperial Japanese Navy. A modest bulbous bow was used in a number of their ship designs, including the light cruiser and the carriers and . A far more radical bulbous bow design solution was incorporated into their massively large battleships, including , and the aircraft carrier . | 1 | Applied and Interdisciplinary Chemistry |
Tobermorite is a calcium silicate hydrate mineral with chemical formula:
CaSiO(OH)·4HO or
CaSi(O,OH)·5HO.
Two structural varieties are distinguished: tobermorite-11 Å and tobermorite-14 Å.
Tobermorite occurs in hydrated cement paste and can be found in nature as an alteration mineral in metamorphosed limestone and in skarn. It has been reported to occur in the Maqarin Area of north Jordan and in the Crestmore Quarry near Crestmore Heights, Riverside County, California.
Tobermorite was first described in 1880 for an occurrence in Scotland, on the Isle of Mull, around the locality of Tobermory. | 0 | Theoretical and Fundamental Chemistry |
Lithium oxalate is an organic compound with the chemical formula . It is a salt of lithium metal and oxalic acid. It consists of lithium cations and oxalate anions . Lithium oxalate is soluble in water and converts to lithium oxide when heated. | 0 | Theoretical and Fundamental Chemistry |
Arusi was born in Zawiya in 1961. He obtained a bachelor of science degree in chemical engineering from Tobruk University. In 1988, he received a master's degree from University of Manchester Institute of Science and Technology. He also holds a PhD from the same university in engineering and corrosion science, which he received in 1992. | 1 | Applied and Interdisciplinary Chemistry |
A method for detecting arsenious oxide, simple arsenic, in corpses was devised in 1773 by the Swedish chemist, Carl Wilhelm Scheele. His work was expanded upon, in 1806, by German chemist Valentin Ross, who learned to detect the poison in the walls of a victim's stomach.
James Marsh was the first to apply this new science to the art of forensics. He was called by the prosecution in a murder trial to give evidence as a chemist in 1832. The defendant, John Bodle, was accused of poisoning his grandfather with arsenic-laced coffee. Marsh performed the standard test by mixing a suspected sample with hydrogen sulfide and hydrochloric acid. While he was able to detect arsenic as yellow arsenic trisulfide, when it was shown to the jury it had deteriorated, allowing the suspect to be acquitted due to reasonable doubt.
Annoyed by that, Marsh developed a much better test. He combined a sample containing arsenic with sulfuric acid and arsenic-free zinc, resulting in arsine gas. The gas was ignited, and it decomposed to pure metallic arsenic, which, when passed to a cold surface, would appear as a silvery-black deposit. So sensitive was the test, known formally as the Marsh test, that it could detect as little as one-fiftieth of a milligram of arsenic. He first described this test in The Edinburgh Philosophical Journal in 1836. | 0 | Theoretical and Fundamental Chemistry |
The introduction of refrigeration and evolution of additional technologies drastically changed agriculture in the United States. During the beginning of the 20th century, farming was a common occupation and lifestyle for United States citizens, as most farmers actually lived on their farm. In 1935, there were 6.8 million farms in the United States and a population of 127 million. Yet, while the United States population has continued to climb, citizens pursuing agriculture continue to decline. Based on the 2007 US Census, less than one percent of a population of 310 million people claim farming as an occupation today. However, the increasing population has led to an increasing demand for agricultural products, which is met through a greater variety of crops, fertilizers, pesticides, and improved technology. Improved technology has decreased the risk and time involved for agricultural management and allows larger farms to increase their output per person to meet society's demand. | 0 | Theoretical and Fundamental Chemistry |
A perfectly immobile fluorescent moiety when exited with polarized light will emit light which is also polarized. However, if a molecule is moving, it will tend to "scramble" the polarization of the light by radiating at a different direction from the incident light. | 1 | Applied and Interdisciplinary Chemistry |
By rectifying the motion of individual swimming bacteria, microfluidic structures can be used to extract mechanical motion from a population of motile bacterial cells. This way, bacteria-powered rotors can be built. | 1 | Applied and Interdisciplinary Chemistry |
Colloidal particles can also serve as transport vector
of diverse contaminants in the surface water (sea water, lakes, rivers, fresh water bodies) and in underground water circulating in fissured rocks
(e.g. limestone, sandstone, granite). Radionuclides and heavy metals easily sorb onto colloids suspended in water. Various types of colloids are recognised: inorganic colloids (e.g. clay particles, silicates, iron oxy-hydroxides), organic colloids (humic and fulvic substances). When heavy metals or radionuclides form their own pure colloids, the term "eigencolloid" is used to designate pure phases, i.e., pure Tc(OH), U(OH), or Am(OH). Colloids have been suspected for the long-range transport of plutonium on the Nevada Nuclear Test Site. They have been the subject of detailed studies for many years. However, the mobility of inorganic colloids is very low in compacted bentonites and in deep clay formations
because of the process of ultrafiltration occurring in dense clay membrane.
The question is less clear for small organic colloids often mixed in porewater with truly dissolved organic molecules.
In soil science, the colloidal fraction in soils consists of tiny clay and humus particles that are less than 1μm in diameter and carry either positive and/or negative electrostatic charges that vary depending on the chemical conditions of the soil sample, i.e. soil pH. | 0 | Theoretical and Fundamental Chemistry |
It was once suggested that CO could be stored in the oceans by direct injection into the deep ocean and storing it there for some centuries. At the time, this proposal was called "ocean storage" but more precisely it was known as "direct deep-sea carbon dioxide injection". However, the interest in this avenue of carbon storage has much reduced since about 2001 because of concerns about the unknown impacts on marine lifeMarine life|, high costs and concerns about its stability or permanence. The "IPCC Special Report on Carbon Dioxide Capture and Storage" in 2005 did include this technology as an option.Marine life| However, the IPCC Fifth Assessment Report in 2014 no longer mentioned the term "ocean storage" in its report on climate change mitigation methods. The most recent IPCC Sixth Assessment Report in 2022 also no longer includes any mention of "ocean storage" in its "Carbon Dioxide Removal taxonomy". | 0 | Theoretical and Fundamental Chemistry |
Early biochips were based on the idea of a DNA microarray, e.g., the GeneChip DNAarray from Affymetrix, which is a piece of glass, plastic or silicon substrate, on which pieces of DNA (probes) are affixed in a microscopic array. Similar to a DNA microarray, a protein array is a miniature array where a multitude of different capture agents, most frequently monoclonal antibodies, are deposited on a chip surface; they are used to determine the presence and/or amount of proteins in biological samples, e.g., blood. A drawback of DNA and protein arrays is that they are neither reconfigurable nor scalable after manufacture. Digital microfluidics has been described as a means for carrying out Digital PCR. | 1 | Applied and Interdisciplinary Chemistry |
UPS has seen a considerable revival with the increasing availability of synchrotron light sources which provide a wide range of monochromatic photon energies. | 0 | Theoretical and Fundamental Chemistry |
The partial molar volume is broadly understood as the contribution that a component of a mixture makes to the overall volume of the solution. However, there is more to it than this:
When one mole of water is added to a large volume of water at 25 °C, the volume increases by 18 cm. The molar volume of pure water would thus be reported as 18 cm mol. However, addition of one mole of water to a large volume of pure ethanol results in an increase in volume of only 14 cm. The reason that the increase is different is that the volume occupied by a given number of water molecules depends upon the identity of the surrounding molecules. The value 14 cm is said to be the partial molar volume of water in ethanol.
In general, the partial molar volume of a substance X in a mixture is the change in volume per mole of X added to the mixture.
The partial molar volumes of the components of a mixture vary with the composition of the mixture, because the environment of the molecules in the mixture changes with the composition. It is the changing molecular environment (and the consequent alteration of the interactions between molecules) that results in the thermodynamic properties of a mixture changing as its composition is altered.
If, by , one denotes a generic extensive property of a mixture, it will always be true that it depends on the pressure (), temperature (), and the amount of each component of the mixture (measured in moles, n). For a mixture with q components, this is expressed as
Now if temperature T and pressure P are held constant, is a homogeneous function of degree 1, since doubling the quantities of each component in the mixture will double . More generally, for any :
By Euler's first theorem for homogeneous functions, this implies
where is the partial molar of component defined as:
By Euler's second theorem for homogeneous functions, is a homogeneous function of degree 0 (i.e., is an intensive property) which means that for any :
In particular, taking where , one has
where is the concentration expressed as the mole fraction of component .
Since the molar fractions satisfy the relation
the x are not independent, and the partial molar property is a function of only mole fractions:
The partial molar property is thus an intensive property - it does not depend on the size of the system.
The partial volume is not the partial molar volume. | 0 | Theoretical and Fundamental Chemistry |
In physics and chemistry, there are two main macroscopic consequences of the time-reversibility of microscopic dynamics: the principle of detailed balance and the Onsager reciprocal relations.
The statistical description of the macroscopic process as an ensemble of the elementary indivisible events (collisions) was invented by L. Boltzmann and formalised in the Boltzmann equation. He discovered that the time-reversibility of the Newtonian dynamics leads to the detailed balance for collision: in equilibrium collisions are equilibrated by their reverse collisions. This principle allowed Boltzmann to deduce simple and nice formula for entropy production and prove his famous H-theorem. In this way, microscopic reversibility was used to prove macroscopic irreversibility and convergence of ensembles of molecules to their thermodynamic equilibria.
Another macroscopic consequence of microscopic reversibility is the symmetry of kinetic coefficients, the so-called reciprocal relations. The reciprocal relations were discovered in the 19th century by Thomson and Helmholtz for some phenomena but the general theory was proposed by Lars Onsager in 1931. He found also the connection between the reciprocal relations and detailed balance. For the equations of the law of mass action the reciprocal relations appear in the linear approximation near equilibrium as a consequence of the detailed balance conditions. According to the reciprocal relations, the damped oscillations in homogeneous closed systems near thermodynamic equilibria are impossible because the spectrum of symmetric operators is real. Therefore, the relaxation to equilibrium in such a system is monotone if it is sufficiently close to the equilibrium. | 0 | Theoretical and Fundamental Chemistry |
Another classic but elusive family of targets are silylenes, analogues of carbenes. It was proposed that dechlorination of dimethyldichlorosilane generates dimethylsilylene:
:SiCl(CH) + 2 K → Si(CH) + 2 KCl
This inference is supported by conducting the dechlorination in the presence of trimethylsilane, the trapped product being pentamethyldisilane:
:Si(CH) + HSi(CH) → (CH)Si(H)-Si(CH)
Not that the trapping agent does not react with dimethyldichlorosilane or potassium metal. | 0 | Theoretical and Fundamental Chemistry |
*Reiner Salzer (Chair), TU Dresden, Dresden, Germany
*Pavel Drašar (Past-Chair), University of Chemistry and Technology, Prague, Czech Republic
*Ray Wallace (Secretary), Nottingham Trent University, Nottingham, UK
*a number of members | 1 | Applied and Interdisciplinary Chemistry |
The sessile drop technique has various applications for both materials engineering and straight characterization. In general, it is useful in determining the surface tension of liquids through the use of reference solids, with a similar technique being the Captive Bubble Method. There are various other specific applications which can be subdivided according to which of the above theories is most likely to be applicable to the circumstances:
The Zisman theory is mostly used for low energy surfaces and characterizes only the total surface energy. As such, it is probably most useful in cases that recall the conventional definition of surfaces, for example if a chemical engineer wants to know what the energy associated with fabricating a surface is. It may also be useful in cases where the surface energy has some effect on a spectroscopic technique being used on the solid in question.
The two component theories would most likely be applicable to materials engineering questions about the practical interactions of liquids and solids. The Fowkes theory, since it is more suited for higher energy solid surfaces, and since much of it is rooted in theories about adhesion, would likely be suited for the characterization of interactions where the solids and liquids have a high affinity for one another, such as, logically enough, adhesives and adhesive coatings. The Owens/Wendt theory, which deals in low energy solid surfaces, would be helpful in characterizing the interactions where the solids and liquids do not have a strong affinity for one another – for example, the effectiveness of waterproofing. Polyurethanes and PVC are good examples of waterproof plastics.
The Schultz theory is best used for the characterization of very high energy surfaces for which the other theories are ineffective, the most significant example being bare metals.
The van Oss theory is most suitable for cases in which acid/base interaction is an important consideration. Examples include pigments, pharmaceuticals, and paper. Specifically, notable examples include both paper used for the regular purpose of printing, and the more specialized case of litmus paper, which in itself is used to characterize acidity and basicity. | 0 | Theoretical and Fundamental Chemistry |
In 1950, a small amount of CoQ was isolated from the lining of a horses gut, a compound initially called substance SA, but later deemed to be quinone found in many animal tissues. In 1957, the same compound was isolated from mitochondrial membranes of beef heart, with research showing that it transported electrons within mitochondria. It was called Q-275 as a quinone. The Q-275/substance SA was later renamed ubiquinone as it was a ubiquitous quinone found in all animal tissues. In 1958, its full chemical structure was reported. Ubiquinone was later called either mitoquinone or coenzyme Q' due to its participation to the mitochondrial electron transport chain. In 1966, a study reported that reduced CoQ was an effective antioxidant in cells. | 1 | Applied and Interdisciplinary Chemistry |
* Spray painting
* High velocity oxygen fuel (HVOF)
* Plasma spraying
* Thermal spraying
* Kinetic metallization (KM)
* Plasma transferred wire arc thermal spraying
* The common forms of Powder coating | 1 | Applied and Interdisciplinary Chemistry |
There are three well-characterized families of opioid peptides produced by the body: enkephalins, β-endorphin, and dynorphins. The met-enkephalin peptide sequence is coded for by the enkephalin gene; the leu-enkephalin peptide sequence is coded for by both the enkephalin gene and the dynorphin gene. The proopiomelanocortin gene (POMC) also contains the met-enkephalin sequence on the N-terminus of beta-endorphin, but the endorphin peptide is not processed into enkephalin. | 1 | Applied and Interdisciplinary Chemistry |
Litmus can be found in different species of lichens. The dyes are extracted from such species as Roccella tinctoria (South American), Roccella fuciformis (Angola and Madagascar), Roccella pygmaea (Algeria), Roccella phycopsis, Lecanora tartarea (Norway, Sweden), Variolaria dealbata, Ochrolechia parella, Parmotrema tinctorum, and Parmelia. Currently, the main sources are Roccella montagnei (Mozambique) and Dendrographa leucophoea (California). | 0 | Theoretical and Fundamental Chemistry |
* Contributions to the synthetic and structural chemistry of acetals, especially cyclic acetals.
* Studies of hydrogels containing UV-absorbing agents. Correlating the concentration, absorptive properties and extractability of the agents.
* Interaction of polymers with IR laser radiation – demonstrating that the monomer release following the irradiation of IOL materials with surgical IR lasers is too low to cause deleterious effects in the eye.
* First investigation of interaction between poly(2-hydroxyethyl methacrylate) (PHEMA) and UV laser radiation. First use of X-ray photoelectron spectroscopy to investigate the process of ablation of ophthalmic hydrogels with excimer lasers. General studies on the interaction between high-energy laser radiation and polymers.
* Invention and development of melanin-containing synthetic hydrogels able to absorb UV and blue radiation and their application as IOL materials. First polymer-biopolymer combinations to be reported as interpenetrating polymer networks (IPNs).
* Invention and development of an artificial cornea. Initially known as "Chirila keratoprosthesis", this device has been commercially developed as AlphaCor and received approvals from FDA and other regulatory bodies and is used in human patients.
* Development of hydrogels with very high water content as potential substitutes for the vitreous body, including a methodology for their evaluation in vitro.
* Evaluation of porous hydrogel scaffolds for nerve repair.
* Development and study of polymer matrices for the sustained release of bioactive agents, including therapeutic oligonucleotides.
* Development of an orbital implant, currently commercialised as AlphaSphere.
* Contributions to the history of ophthalmology and biomaterials.
* Development of tissue-engineered corneal constructs for the restoration of ocular surface.
His research has resulted to date in 175 journal publications and 13 patents. He has contributed over 175 presentations at scientific meetings and he has been invited to present lectures in China, the United States, Japan, Romania, Italy, France, Switzerland, Korea, Germany and The Netherlands. | 0 | Theoretical and Fundamental Chemistry |
Ascorbic acid can also react with organic acids as an alcohol forming esters such as ascorbyl palmitate and ascorbyl stearate. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, a racemic mixture or racemate (), is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as racemates. | 0 | Theoretical and Fundamental Chemistry |
PUVA (psoralen and UVA) is an ultraviolet light therapy treatment for skin diseases: vitiligo, eczema, psoriasis, graft-versus-host disease, mycosis fungoides, large plaque parapsoriasis, and cutaneous T-cell lymphoma, using the sensitizing effects of the drug psoralen. The psoralen is applied or taken orally to sensitize the skin, then the skin is exposed to UVA.
Photodynamic therapy is the general use of nontoxic light-sensitive compounds that are exposed selectively to light, whereupon they become toxic to targeted malignant and other diseased cells. Still, PUVA therapy is often classified as a separate technique from photodynamic therapy. | 0 | Theoretical and Fundamental Chemistry |
Soluble fluorides are moderately toxic. For sodium fluoride, the lethal dose for adults is 5–10 g, which is equivalent to 32–64 mg of elemental fluoride per kilogram of body weight. The dose that may lead to adverse health effects is about one fifth of the lethal dose. Chronic excess fluoride consumption can lead to skeletal fluorosis, a disease of the bones that affects millions in Asia and Africa.
The fluoride ion is readily absorbed by the stomach and intestines. Ingested fluoride forms hydrofluoric acid in the stomach. In this form, fluoride crosses cell membranes and then binds with calcium and interferes with various enzymes. Fluoride is excreted through urine. Fluoride exposure limits are based on urine testing, which is used to determine the human body's capacity for ridding itself of fluoride.
Historically, most cases of fluoride poisoning have been caused by accidental ingestion of insecticides containing inorganic fluoride. Most calls to poison control centers for possible fluoride poisoning come from the ingestion of fluoride-containing toothpaste. Malfunction of water fluoridation equipment has occurred several times, including an Alaskan incident that sickened nearly 300 people and killed one. | 1 | Applied and Interdisciplinary Chemistry |
Where a compound has non standard bonding as compared to the parent hydride for example PCl the lambda convention is used. For example:
*PCl pentachloro-λ-phosphane
*SF hexafluoro-λ-sulfane | 0 | Theoretical and Fundamental Chemistry |
An Interest Group Macromolecules (EBF-IGM) was founded in 2008 to provide a platform for scientific exchange and harmonization of specific aspects for the bioanalysis of macromolecules: drugs and biomarkers as well as immunogenicity testing. | 0 | Theoretical and Fundamental Chemistry |
Retroposons are repetitive DNA fragments which are inserted into chromosomes after they had been reverse transcribed from any RNA molecule. | 1 | Applied and Interdisciplinary Chemistry |
* At high glucose levels, glycolysis takes place rapidly, thus increasing the amount of citrate produced from the citric acid cycle. This citrate is then exported to other organelles outside the mitochondria to be broken into acetyl-CoA and oxaloacetate by the enzyme ATP citrate lyase (ACL). This principal reaction is coupled with the hydrolysis of ATP.
* At low glucose levels:
** CoA is acetylated using acetate by acetyl-CoA synthetase (ACS), also coupled with ATP hydrolysis.
** Ethanol also serves as a carbon source for acetylation of CoA utilizing the enzyme alcohol dehydrogenase.
** Degradation of branched-chain ketogenic amino acids such as valine, leucine, and isoleucine occurs. These amino acids are converted to α-ketoacids by transamination and eventually to isovaleryl-CoA through oxidative decarboxylation by an α-ketoacid dehydrogenase complex. Isovaleryl-CoA undergoes dehydrogenation, carboxylation and hydration to form another CoA-derivative intermediate before it is cleaved into acetyl-CoA and acetoacetate. | 1 | Applied and Interdisciplinary Chemistry |
The vorticity equation can be expressed in tensor notation using Einstein's summation convention and the Levi-Civita symbol : | 1 | Applied and Interdisciplinary Chemistry |
The journal was established in 1983 and as submissions increased switched to a biomonthly schedule in 2006. The editor-in-chief is Chengshan Wang (Chinese Academy of Sciences). Baojun Liu (Division of Earth Sciences, Chinese Academy of Sciences) is honorary editor-in-chief. | 0 | Theoretical and Fundamental Chemistry |
Progesterone plays an important role in breast development in women. In conjunction with prolactin, it mediates lobuloalveolar maturation of the mammary glands during pregnancy to allow for milk production and thus lactation and breastfeeding of offspring following parturition (childbirth). Estrogen induces expression of the PR in breast tissue and hence progesterone is dependent on estrogen to mediate lobuloalveolar development. It has been found that is a critical downstream mediator of progesterone-induced lobuloalveolar maturation. RANKL knockout mice show an almost identical mammary phenotype to PR knockout mice, including normal mammary ductal development but complete failure of the development of lobuloalveolar structures. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, vinylogy is the transmission of electronic effects through a conjugated organic bonding system. The concept was introduced in 1926 by Ludwig Claisen to explain the acidic properties of formylacetone and related ketoaldehydes. Formylacetone, technically , only exists in the ionized form or . Its adjectival form, vinylogous, is used to describe functional groups in which the standard moieties of the group are separated by a carbon–carbon double bond.
For example, a carboxylic acid is defined as a carbonyl group () directly attached to a hydroxyl group (): O=C–OH. A vinylogous carboxylic acid has a vinyl unit (, vinylene) between the two groups that define the acid: O=C–C=C–OH. The usual resonance of a carboxylate can propagate through the alkene of a vinylogous carboxylate. Likewise, 3-dimethylaminoacrolein is the vinylogous-amide analog of dimethylformamide.
Due to the transmission of electronic information through conjugation, vinylogous functional groups often possess "analogous" reactivity or chemical properties compared to the parent functional group. Hence, vinylogy is a useful heuristic for the prediction of the behavior of systems that are structurally similar but contain intervening C=C bonds that are conjugated to the attached functional groups. For example, a key property of carboxylic acids is their Brønsted acidity. The simplest carboxylic acid, formic acid (), is a moderately strong organic acid with a pK of 3.7. We would expect vinylogous carboxylic acids to have similar acidity. Indeed, the vinylog of formic acid, 2-formyl-1-ethen-1-ol, has a substantial Brønsted acidity, with an estimated pK ~ 5–6. In particular, vinylogous carboxylic acids are substantially stronger acids than typical enols (pK ~ 12). Vitamin C (ascorbic acid, see below) is a biologically important example of a vinylogous carboxylic acid.
The insertion of a o- or p-phenylene (i.e., a benzene ring in the 1,2- or 1,4-orientation) also results in some similarities in reactivity (called "phenylogy"), although the effect is generally weaker, as conjugation through the aryl ring requires consideration of resonance forms or intermediates in which aromaticity is disrupted.
Vinylogous reactions are believed to occur when orbitals of the double bonds of the vinyl group and of an attached electron-withdrawing group (EWG; the π orbitals) are aligned and so can overlap and mix (i.e., are conjugated). Electron delocalization enables the EWG to receive electron density through participation of the conjugated system. | 0 | Theoretical and Fundamental Chemistry |
Millesimal fineness is a system of denoting the purity of platinum, gold and silver alloys by parts per thousand of pure metal by mass in the alloy. For example, an alloy containing 75% gold is denoted as "750". Many European countries use decimal hallmark stamps (i.e., "585", "750", etc.) rather than "14 k", "18 k", etc., which is used in the United Kingdom and United States.
It is an extension of the older karat system of denoting the purity of gold by fractions of 24, such as "18 karat" for an alloy with 75% (18 parts per 24) pure gold by mass.
The millesimal fineness is usually rounded to a three figure number, particularly where used as a hallmark, and the fineness may vary slightly from the traditional versions of purity.
Here are the most common millesimal finenesses used for precious metals and the most common terms associated with them. | 1 | Applied and Interdisciplinary Chemistry |
LAAM is indicated as a second-line treatment for the treatment and management of opioid dependence if patients fail to respond to drugs like methadone or buprenorphine.
LAAM is used as an oral solution of LAAM hydrochloride at a concentration of 10 mg/mL in bottles of 120 and 500 mL under the brand name Orlaam. The first dose of LAAM for patients who have not started treatment with methadone is 20–40 mg. The first dose for patients who have been receiving methadone will be a little higher than the amount of methadone that was being taken every day, but not more than 120 mg. Afterwards, the dosage may be adjusted as needed. Unlike methadone, which requires daily administration, LAAM is administered two to three times a week. | 0 | Theoretical and Fundamental Chemistry |
Electroporation is performed with electroporators, purpose-built appliances that create an electrostatic field in a cell solution. The cell suspension is pipetted into a glass or plastic cuvette which has two aluminium electrodes on its sides. For bacterial electroporation, typically a suspension of around 50 microliters is used. Prior to electroporation, this suspension of bacteria is mixed with the plasmid to be transformed. The mixture is pipetted into the cuvette, the voltage and capacitance are set, and the cuvette is inserted into the electroporator. The process requires direct contact between the electrodes and the suspension. Immediately after electroporation, one milliliter of liquid medium is added to the bacteria (in the cuvette or in an Eppendorf tube), and the tube is incubated at the bacteria's optimal temperature for an hour or more to allow recovery of the cells and expression of the plasmid, followed by bacterial culture on agar plates.
The success of the electroporation depends greatly on the purity of the plasmid solution, especially on its salt content. Solutions with high salt concentrations might cause an electrical discharge (known as arcing), which often reduces the viability of the bacteria. For a further detailed investigation of the process, more attention should be paid to the output impedance of the porator device and the input impedance of the cells suspension (e.g. salt content).
Since the cell membrane is not able to pass current (except in ion channels), it acts as an electrical capacitor. Subjecting membranes to a high-voltage electric field results in their temporary breakdown, resulting in pores that are large enough to allow macromolecules (such as DNA) to enter or leave the cell.
Additionally, electroporation can be used to increase permeability of cells during in Utero injections and surgeries. Particularly, the electroporation allows for a more efficient transfection of DNA, RNA, shRNA, and all nucleic acids into the cells of mice and rats. The success of in vivo electroporation depends greatly on voltage, repetition, pulses, and duration. Developing central nervous systems are most effective for in vivo electroporation due to the visibility of ventricles for injections of nucleic acids, as well as the increased permeability of dividing cells. Electroporation of injected in utero embryos is performed through the uterus wall, often with forceps-type electrodes to limit damage to the embryo. | 1 | Applied and Interdisciplinary Chemistry |
Stimuli that trigger vesicle fusion act by increasing intracellular Ca.
* Synaptic vesicles commit vesicle fusion by a nerve impulse reaching the synapse, activating voltage-dependent calcium channels that cause influx of Ca into the cell.
* In the endocrine system, many hormones are released by their releasing hormones binding to G protein coupled receptors coupled to the G alpha subunit, activating the IP3/DAG pathway to increase Ca. Examples of this mechanism include:
**Gonadotropin releasing hormone
**Thyrotropin releasing hormone
**Growth hormone releasing hormone (minor pathway - main one is cAMP dependent pathway) | 1 | Applied and Interdisciplinary Chemistry |
According to Ostwald's rule, usually less stable polymorphs crystallize before the stable form. The concept hinges on the idea that unstable polymorphs more closely resemble the state in solution, and thus are kinetically advantaged. The founding case of fibrous vs rhombic benzamide illustrates the case. Another example is provided by two polymorphs of titanium dioxide. Nevertheless, there are known systems, such as metacetamol, where only narrow cooling rate favors obtaining metastable form II.
Polymorphs have disparate stabilities. Some convert rapidly at room (or any) temperature. Most polymorphs of organic molecules only differ by a few kJ/mol in lattice energy. Approximately 50% of known polymorph pairs differ by less than 2 kJ/mol and stability differences of more than 10 kJ/mol are rare. Valuable to mention that polymorph stability may change upon temperature or pressure. Important to note that structural and thermodybnamic stability are different. Thermodynamic stability may be studied using experimental or computational methods.
Polymorphism is affected by the details of crystallisation. The solvent in all respects affects the nature of the polymorph, including concentration, other components of the solvent, i.e., species that inhibiting or promote certain growth patterns. A decisive factor is often the temperature of the solvent from which crystallisation is carried out.
Metastable polymorphs are not always reproducibly obtained, leading to cases of "disappearing polymorphs", with usually negative implications on law and business. | 0 | Theoretical and Fundamental Chemistry |
Chemical production and petroleum refineries will usually employ computers for logging and for limit testing the many temperatures associated with a process, typically numbering in the hundreds. For such cases, a number of thermocouple leads will be brought to a common reference block (a large block of copper) containing the second thermocouple of each circuit. The temperature of the block is in turn measured by a thermistor. Simple computations are used to determine the temperature at each measured location. | 1 | Applied and Interdisciplinary Chemistry |
One of the properties of polytorotaxanes involves the photoelectronic response when introducing photoactive or electrionic-active units into the mechanically interlocked structures.
For examples, the polyrotaxane structures are capable of enhancing the fluorescence quenching molecules that grafting on the rings and the other molecules at the ends. Amplification of a fluorescence chemosensory can be achieved by using polyrotaxane structure, which enhances the energy migration in the polymer. It was found that a rapid migration of the hole-electron pair to the rotaxanes sites is followed by a rapid combination which leads to the enhancement of the energy migration. In addition, the conductivity of these polyrotaxanes was lower than the parent components.
Also conductive polyrotaxanes can be obtained by employing metal binding in the polyrotaxanes structure. For example, a polyrotaxane containing a conjugated backbone can be synthesized through metal template and electropolymerization. The metal ion binding is reversible when another metal with stronger binding ability is employed to remove the previous ion, which results in the "scaffolding effect reversibility". The free coordination sites and the organic matrix are able to be maintained by the labile scaffolding. | 0 | Theoretical and Fundamental Chemistry |
*Kefir
**In Kefir, the lactose in milk is fermented by lactic acid bacteria to produce lactic acid, further breakdown to propionic acid is done by propionibacteria. Yeast in Kefir ferment to produce ethanol, which is consumed by other bacteria to make acids and aldehydes that contribute to flavor.
* Sake
** In the making of Sake, Koji molds are used to ferment rice producing free sugars that are then fermented by lactic acid bacteria and yeast, providing ethanol and flavor active compounds.
* Lambic Beer
** Wheat is fermented by yeast and LAB.
* Shochu
** Rice, wheat, and batata are fermented by mold, yeast, and LAB.
* Vinegar
** Rice is fermented by mold, yeast, LAB, and acetic acid bacteria.
* Soy Sauce
** Soy bean and wheat are fermented by mold, yeast, and LAB.
* Whiskey
** Barely, corn, and rye are fermented by yeast and LAB.
* Wine
** Grapes are fermented by yeast and LAB.
* Kombucha
** Tea and sucrose are fermented by yeast and acetic acid bacteria from a SCOBY. | 1 | Applied and Interdisciplinary Chemistry |
Metal fuels have the advantage of a much higher heat conductivity than oxide fuels but cannot survive equally high temperatures. Metal fuels have a long history of use, stretching from the Clementine reactor in 1946 to many test and research reactors. Metal fuels have the potential for the highest fissile atom density. Metal fuels are normally alloyed, but some metal fuels have been made with pure uranium metal. Uranium alloys that have been used include uranium aluminum, uranium zirconium, uranium silicon, uranium molybdenum, uranium zirconium hydride (UZrH) and uranium zirconium carbonitride. Any of the aforementioned fuels can be made with plutonium and other actinides as part of a closed nuclear fuel cycle. Metal fuels have been used in water reactors and liquid metal fast breeder reactors, such as EBR-II. | 0 | Theoretical and Fundamental Chemistry |
Group I and group II introns are found in genes encoding proteins (messenger RNA), transfer RNA and ribosomal RNA in a very wide range of living organisms. Following transcription into RNA, group I and group II introns also make extensive internal interactions that allow them to fold into a specific, complex three-dimensional architecture. These complex architectures allow some group I and group II introns to be self-splicing, that is, the intron-containing RNA molecule can rearrange its own covalent structure so as to precisely remove the intron and link the exons together in the correct order. In some cases, particular intron-binding proteins are involved in splicing, acting in such a way that they assist the intron in folding into the three-dimensional structure that is necessary for self-splicing activity. Group I and group II introns are distinguished by different sets of internal conserved sequences and folded structures, and by the fact that splicing of RNA molecules containing group II introns generates branched introns (like those of spliceosomal RNAs), while group I introns use a non-encoded guanosine nucleotide (typically GTP) to initiate splicing, adding it on to the 5'-end of the excised intron. | 1 | Applied and Interdisciplinary Chemistry |
The variations in oxygen and hydrogen isotope ratios have applications in hydrology since most samples lie between two extremes, ocean water and Arctic/Antarctic snow. Given a sample of water from an aquifer, and a sufficiently sensitive tool to measure the variation in the isotopic ratio of hydrogen in the sample, it is possible to infer the source, be it ocean water or precipitation seeping into the aquifer, and even to estimate the proportions from each source. Stable isotopologues of water are also used in partitioning water sources for plant transpiration and groundwater recharge.
Another application is in paleotemperature measurement for paleoclimatology. For example, one technique is based on the variation in isotopic fractionation of oxygen by biological systems with temperature. Species of Foraminifera incorporate oxygen as calcium carbonate in their shells. The ratio of the oxygen isotopes oxygen-16 and oxygen-18 incorporated into the calcium carbonate varies with temperature and the oxygen isotopic composition of the water. This oxygen remains "fixed" in the calcium carbonate when the foraminifera dies, falls to the sea bed, and its shell becomes part of the sediment. It is possible to select standard species of foraminifera from sections through the sediment column, and by mapping the variation in oxygen isotopic ratio, deduce the temperature that the Forminifera encountered during life if changes in the oxygen isotopic composition of the water can be constrained. Paleotemperature relationships have also enabled isotope ratios from calcium carbonate in barnacle shells to be used to infer the movement and home foraging areas of the sea turtles and whales on which some barnacles grow.
In ecology, carbon and nitrogen isotope ratios are widely used to determine the broad diets of many free-ranging animals. They have been used to determine the broad diets of seabirds, and to identify the geographical areas where individuals spend the breeding and non-breeding season in seabirds and passerines. Numerous ecological studies have also used isotope analyses to understand migration, food-web structure, diet, and resource use, such as hydrogen isotopes to measure how much energy from stream-side trees supports fish growth in aquatic habitats. Determining diets of aquatic animals using stable isotopes has been particularly common, as direct observations are difficult. They also enable researchers to measure how human interactions with wildlife, such as fishing, may alter natural diets.
In forensic science, research suggests that the variation in certain isotope ratios in drugs derived from plant sources (cannabis, cocaine) can be used to determine the drug's continent of origin.
In food science, stable isotope ratio analysis has been used to determine the composition of beer, shoyu sauce and dog food.
Stable isotope ratio analysis also has applications in doping control, to distinguish between endogenous and exogenous (synthetic) sources of hormones.
The accurate measurement of stable isotope ratios relies on proper procedures of analysis, sample preparation and storage.
Chondrite meteorites are classified using the oxygen isotope ratios. In addition, an unusual signature of carbon-13 confirms the non-terrestrial origin for organic compounds found in carbonaceous chondrites, as in the Murchison meteorite.
The uses of stable isotope ratios described above pertain to measurements of naturally occurring ratios. Scientific research also relies on the measurement of stable isotope ratios that have been artificially perturbed by the introduction of isotopically enriched material into the substance, process or system under study. Isotope dilution involves adding enriched stable isotope to a substance in order to quantify the amount of that substance by measuring the resulting isotope ratios. Isotope labeling uses enriched isotope to label a substance in order to trace its progress through, for example, a chemical reaction, metabolic pathway or biological system. Some applications of isotope labeling rely on the measurement of stable isotope ratios to accomplish this. | 0 | Theoretical and Fundamental Chemistry |
The jump method is difficult to execute mainly due to unaccounted vibrations entering the instrument. To overcome this, researchers developed the resonance method which measured surface forces at larger distances, 10 nm to 130 nm. In this case, the bottom cylinder is oscillated at a known frequency, while the frequency of the top cylinder is measured using a piezoelectric bimorph strain gauge. To minimize the dampening due to the surrounding substance, these measurements were originally done in a vacuum. | 0 | Theoretical and Fundamental Chemistry |
A related term "clarke of concentration" or "concentration clarke", synonym: "concentration factor (mineralogy)", is a measure to see how rich a particular ore is.
That is, the ratio between the concentrations of a chemical element in the ore, and its concentration in the whole Earth's crust (i.e. "clarke") .
If the concentration of a commodity in an ore X is , and the "clarke" of that commodity is ,
then "the clarke of concentration" of that commodity X is (dimensionless).
The value represents the degree to which the commodity is concentrated from crustal abundances to the ore by natural geochemical processes; a clue for whether the commodity could be mined economically. | 0 | Theoretical and Fundamental Chemistry |
Hormones that are glycoproteins include:
* Follicle-stimulating hormone
* Luteinizing hormone
* Thyroid-stimulating hormone
* Human chorionic gonadotropin
* Alpha-fetoprotein
* Erythropoietin (EPO) | 0 | Theoretical and Fundamental Chemistry |
Nuclei also have distinct energy states that are widely separated and lead to gamma ray spectra. Distinct nuclear spin states can have their energy separated by a magnetic field, and this allows for nuclear magnetic resonance spectroscopy. | 0 | Theoretical and Fundamental Chemistry |
Combination therapy with paricalcitol and trandolapril has been found to reduce fibrosis in obstructive uropathy. | 0 | Theoretical and Fundamental Chemistry |
*ATF1 NM_005171
*ATF2 NM_001880
*ATF4 Activating transcription factor 4 NM_001675
*ATF6 NM_007348
*ATF7 NM_001206682
*ATF7IP NM_018179
*BTF3 NM_001207 Homo sapiens basic transcription factor 3
*E2F4 Homo sapiens E2F transcription factor 4, p107/p130-binding (E2F4), mRNA
*ERH (gene) Enhancer of rudimentary homolog of drosophila (which in turn is the first enzymatic step in pyrimidine synthesis. Regulated by MITF)
*HMGB1 High mobility group box binds DNA
*ILF2 Homo sapiens interleukin enhancer binding factor 2, 45kDa (ILF2), mRNA
*IER2 formerly ETR101 Immediate Early Protein?
*JUND Homo sapiens jun D proto-oncogene (JUND), mRNA
*TCEB2 Elongin Matheo er rar | 1 | Applied and Interdisciplinary Chemistry |
The integrity of the systems are broken down into physical, hydraulic, and water quality.
The physical integrity includes concerns on the ability of the barriers to prevents contaminations from the external sources to get into water distribution systems. The deterioration can be caused by physical or chemical factors.
The hydraulic integrity is an ability to maintain adequate water pressure inside the pipes throughout distribution systems. It also includes the circulation and length of time that the water travels within a distribution system which has impacts on the effectiveness of the disinfectants.
The water quality integrity is a control of degradations as the water travels through distribution systems. The impacts of water quality can be caused by physical or hydraulic integrity factors. The water quality degradations can also take place within the distribution systems such as microorganism growth, nitrification, and internal corrosion of the pipes. | 1 | Applied and Interdisciplinary Chemistry |
In genetics, a regulator gene, regulator, or regulatory gene is a gene involved in controlling the expression of one or more other genes. Regulatory sequences, which encode regulatory genes, are often at the five prime end (5) to the start site of transcription of the gene they regulate. In addition, these sequences can also be found at the three prime end (3) to the transcription start site. In both cases, whether the regulatory sequence occurs before (5) or after (3) the gene it regulates, the sequence is often many kilobases away from the transcription start site. A regulator gene may encode a protein, or it may work at the level of RNA, as in the case of genes encoding microRNAs. An example of a regulator gene is a gene that codes for a repressor protein that inhibits the activity of an operator (a gene which binds repressor proteins thus inhibiting the translation of RNA to protein via RNA polymerase).
In prokaryotes, regulator genes often code for repressor proteins. Repressor proteins bind to operators or promoters, preventing RNA polymerase from transcribing RNA. They are usually constantly expressed so the cell always has a supply of repressor molecules on hand. Inducers cause repressor proteins to change shape or otherwise become unable to bind DNA, allowing RNA polymerase to continue transcription.
Regulator genes can be located within an operon, adjacent to it, or far away from it.
Other regulatory genes code for activator proteins. An activator binds to a site on the DNA molecule and causes an increase in transcription of a nearby gene. In prokaryotes, a well-known activator protein is the catabolite activator protein (CAP), involved in positive control of the lac operon.
In the regulation of gene expression, studied in evolutionary developmental biology (evo-devo), both activators and repressors play important roles.
Regulatory genes can also be described as positive or negative regulators, based on the environmental conditions that surround the cell. Positive regulators are regulatory elements that permit RNA polymerase binding to the promoter region, thus allowing transcription to occur. In terms of the lac operon, the positive regulator would be the CRP-cAMP complex that must be bound close to the site of the start of transcription of the lac genes. The binding of this positive regulator allows RNA polymerase to bind successfully to the promoter of the lac gene sequence which advances the transcription of lac genes; lac Z, lac Y, and lac A. Negative regulators are regulatory elements which obstruct the binding of RNA polymerase to the promoter region, thus repressing transcription. In terms of the lac operon, the negative regulator would be the lac repressor which binds to the promoter in the same site that RNA polymerase normally binds. The binding of the lac repressor to RNA polymerase's binding site inhibits the transcription of the lac genes. Only when a corepressor is bound to the lac repressor will the binding site be free for RNA polymerase to carry out transcription of the lac genes. | 1 | Applied and Interdisciplinary Chemistry |
Single-cell transcriptomics uses sequencing techniques similar to single cell genomics or direct detection using fluorescence in situ hybridization. The first step in quantifying the transcriptome is to convert RNA to cDNA using reverse transcriptase so that the contents of the cell can be sequenced using NGS methods as was done in genomics. Once converted, there is not enough cDNA to be sequenced so the same DNA amplification techniques discussed in single cell genomics are applied to the cDNA to make sequencing possible. Alternately, fluorescent compounds attached to RNA hybridization probes are used to identify specific sequences and sequential application of different RNA probes will build up a comprehensive transcriptome. | 1 | Applied and Interdisciplinary Chemistry |
In the carbon tetrachloride molecule, four chlorine atoms are positioned symmetrically as corners in a tetrahedral configuration joined to a central carbon atom by single covalent bonds. Because of this symmetric geometry, CCl is non-polar. Methane gas has the same structure, making carbon tetrachloride a halomethane. As a solvent, it is well suited to dissolving other non-polar compounds such as fats and oils. It can also dissolve iodine. It is volatile, giving off vapors with an odor characteristic of other chlorinated solvents, somewhat similar to the tetrachloroethylene odor reminiscent of dry cleaners' shops.
Solid tetrachloromethane has two polymorphs: crystalline II below −47.5 °C (225.6 K) and crystalline I above −47.5 °C. At −47.3 °C it has monoclinic crystal structure with space group C2/c and lattice constants a = 20.3, b = 11.6, c = 19.9 (.10 nm), β = 111°.
With a specific gravity greater than 1, carbon tetrachloride will be present as a dense nonaqueous phase liquid if sufficient quantities are spilt in the environment. | 1 | Applied and Interdisciplinary Chemistry |
When we have a set of possible events, coming from the distribution , we can encode them (with a lossless data compression) using entropy encoding. This compresses the data by replacing each fixed-length input symbol with a corresponding unique, variable-length, prefix-free code (e.g.: the events (A, B, C) with probabilities p = (1/2, 1/4, 1/4) can be encoded as the bits (0, 10, 11)). If we know the distribution in advance, we can devise an encoding that would be optimal (e.g.: using Huffman coding). Meaning the messages we encode will have the shortest length on average (assuming the encoded events are sampled from ), which will be equal to Shannon's Entropy of (denoted as ). However, if we use a different probability distribution () when creating the entropy encoding scheme, then a larger number of bits will be used (on average) to identify an event from a set of possibilities. This new (larger) number is measured by the cross entropy between and .
The cross entropy between two probability distributions ( and ) measures the average number of bits needed to identify an event from a set of possibilities, if a coding scheme is used based on a given probability distribution , rather than the "true" distribution . The cross entropy for two distributions and over the same probability space is thus defined as follows.
For explicit derivation of this, see the Motivation section above.
Under this scenario, relative entropies (kl-divergence) can be interpreted as the extra number of bits, on average, that are needed (beyond ) for encoding the events because of using for constructing the encoding scheme instead of . | 0 | Theoretical and Fundamental Chemistry |
In dynamic reaction mixtures, multiple products exist in equilibrium. Reversible assembly of molecular components generates products and semi-stable intermediates. Reactions can proceed along kinetic or thermodynamic pathways. Initial concentrations of kinetic intermediates are greater than thermodynamic products because the lower barrier of activation (ΔG‡), compared to the thermodynamic pathway, gives a faster rate of formation. A kinetic pathway is represented in figure 1 as a purple energy diagram. With time, the intermediates equilibrate towards the global minimum, corresponding to the lowest overall Gibbs free energy (ΔG°), shown in red on the reaction diagram in figure 1. The driving force for products to re-equilibrate towards the most stable products is referred to as thermodynamic control. The ratio of products to at any equilibrium state is determined by the relative magnitudes of free energy of the products. This relationship between population and relative energies is called the Maxwell-Boltzmann distribution. | 0 | Theoretical and Fundamental Chemistry |
Using conventional FT technology the process ranges in carbon efficiency from 25 to 50 percent and a thermal efficiency of about 50% for CTL facilities idealised at 60% with GTL facilities at about 60% efficiency idealised to 80% efficiency. | 0 | Theoretical and Fundamental Chemistry |
Aldehydes () take the suffix "-al". If other functional groups are present, the chain is numbered such that the aldehyde carbon is in the "1" position, unless functional groups of higher precedence are present.
If a prefix form is required, "oxo-" is used (as for ketones), with the position number indicating the end of a chain: is 3-oxopropanoic acid. If the carbon in the carbonyl group cannot be included in the attached chain (for instance in the case of cyclic aldehydes), the prefix "formyl-" or the suffix "-carbaldehyde" is used: is cyclohexanecarbaldehyde. If an aldehyde is attached to a benzene and is the main functional group, the suffix becomes benzaldehyde. | 0 | Theoretical and Fundamental Chemistry |
The effect is named after James Prescott Joule and William Thomson, 1st Baron Kelvin, who discovered it in 1852. It followed upon earlier work by Joule on Joule expansion, in which a gas undergoes free expansion in a vacuum and the temperature is unchanged, if the gas is ideal. | 0 | Theoretical and Fundamental Chemistry |
Just like the many uses of plasma, there are several means for its generation. However, one principle is common to all of them: there must be energy input to produce and sustain it. For this case, plasma is generated when an electric current is applied across a dielectric gas or fluid (an electrically non-conducting material) as can be seen in the adjacent image, which shows a discharge tube as a simple example (DC used for simplicity).
The potential difference and subsequent electric field pull the bound electrons (negative) toward the anode (positive electrode) while the cathode (negative electrode) pulls the nucleus. As the voltage increases, the current stresses the material (by electric polarization) beyond its dielectric limit (termed strength) into a stage of electrical breakdown, marked by an electric spark, where the material transforms from being an insulator into a conductor (as it becomes increasingly ionized). The underlying process is the Townsend avalanche, where collisions between electrons and neutral gas atoms create more ions and electrons (as can be seen in the figure on the right). The first impact of an electron on an atom results in one ion and two electrons. Therefore, the number of charged particles increases rapidly (in the millions) only "after about 20 successive sets of collisions", mainly due to a small mean free path (average distance travelled between collisions). | 0 | Theoretical and Fundamental Chemistry |
Research is being done into RCB and NCP, two non-catalytic thioredoxin-like proteins that activate chloroplast transcription. Knowing the exact mechanism can be useful to allow increasing photosynthesis (i.e. through genetic modification). | 0 | Theoretical and Fundamental Chemistry |
Methane has a limited atmospheric lifetime, about 10 years, due to substantial methane sinks. The primary methane sink is atmospheric oxidation, from hydroxyl radicals (~90% of the total sink) and chlorine radicals (0-5% of the total sink). The rest is consumed by methanotrophs and other methane-oxidizing bacteria and archaea in soils (~5%). | 1 | Applied and Interdisciplinary Chemistry |
A brochure produced by MMC and Countryside Properties, entitled Regeneration of Spodden Valley Community News Autumn 2005, and distributed to 50,000 households in the area, was determined by the Advertising Standards Authority (ASA) to have breached a code of honesty and truthfulness, and was misleading when it claimed:
* piles of crushed rubble at the site were "free" of asbestos
* a level of 0.01% asbestos was "safe"
The ASA advised MMC to "take greater care when producing marketing communications in future", and "to ensure that they held full substantation before making similar claims." | 1 | Applied and Interdisciplinary Chemistry |
Tissue opacity is thought to be the result of light scattering due to heterogeneous refractive indices. Tissue clearing methods chemically homogenize refractive indices, resulting in almost completely transparent tissue. | 1 | Applied and Interdisciplinary Chemistry |
Bound to the 5-untranslated region of messenger RNA (mRNA), Morpholinos can interfere with progression of the ribosomal initiation complex from the 5 cap to the start codon. This prevents translation of the coding region of the targeted transcript (called "knocking down" gene expression). This is useful experimentally when an investigator wishes to know the function of a particular protein; Morpholinos provide a convenient means of knocking down expression of the protein and learning how that knockdown changes the cells or organism. Some Morpholinos knock down expression so effectively that, after degradation of preexisting proteins, the targeted proteins become undetectable by Western blot.
In 2016 a synthetic peptide-conjugated PMO (PPMO) was found to inhibit the expression of New Delhi Metallo-beta-lactamase, an enzyme that many drug-resistant bacteria use to destroy carbapenems. | 1 | Applied and Interdisciplinary Chemistry |
Egap was born in Athens, Ohio, and went to school in New York City. She started her academic career at Stony Brook University as a philosophy major, but was inspired by her chemistry professor and switched to chemistry. She graduated from Stony Brook University in 2005. She completed her postgraduate studies in 2011 at the University of Washington under the supervision of Samson Jenekhe. Her doctoral work focused on the design and synthesis of organic macromolecules. She examined the structure–property relationships of these macromolecules in next generation electronic devices, including organic field-effect transistors, organic photovoltaics and light-emitting diodes. She investigated how charge carriers and excitons are confined in 0D and 1D nanostructures. This included benzobisthiazole-thiophene copolymers, which can be used for OFETs and OPVs. She worked on oligothiophene-functionalised naphthalene dimide nanowires that can form in solution. Whilst at the University of Washington she developed electron-transport materials for efficient blue phosphorescent OLEDs, using FIrpic and oligoquinolines.
Ahmed joined Massachusetts Institute of Technology as a postdoctoral fellow with Timothy M. Swager. She was a Martin Luther King Jr. Visiting Scholar between 2011 and 2013. She developed a platform that used polymer nanoparticles for in vivo imaging. She won the Gordon Research Conferences Carl Storm Award in 2013 and a graduate award at the MIT Polymer Day in 2014. | 0 | Theoretical and Fundamental Chemistry |
Heterolytic bond cleavage is a process where the electron pair that comprised a bond moves to one of the atoms that was formerly joined by a bond. The bond breaks, forming a negatively charged species (an anion) and a positively charged species (a cation). The anion is the species that retains the electrons from the bond while the cation is stripped of the electrons from the bond. The anion usually forms on the most electronegative atom, in this example atom A. This is because the most electronegative atom will naturally attract electrons towards itself more strongly, leading to its negative charge. | 0 | Theoretical and Fundamental Chemistry |
The word aldehyde was coined by Justus von Liebig as a contraction of the Latin (dehydrogenated alcohol). In the past, aldehydes were sometimes named after the corresponding alcohols, for example, vinous aldehyde for acetaldehyde. (Vinous is from Latin "wine", the traditional source of ethanol, cognate with vinyl.)
The term formyl group is derived from the Latin word "ant". This word can be recognized in the simplest aldehyde, formaldehyde, and in the simplest carboxylic acid, formic acid. | 0 | Theoretical and Fundamental Chemistry |
The International Fine Particle Research Institute (IFPRI) is a cooperative organisation concerned with advancing the fundamentals of fine particle technology. Its mission statement is "To define long-term research objectives in particle science and engineering aligned with the industrial agenda, providing the scientific foundations that will lead to the discovery of new and improved materials, and more efficient manufacturing process technology".
It was started in 1979 by 5 academics concerned with particle technology: Bob Pfeffer (City College of New York); Kurt Leschonski (Clausthal University of Technology); Koichi Iinoya (Kyoto University); Brian Scarlett (Loughborough University) ; and Frank Tiller (University of Houston), supported by 12 international companies.
As of 2017 it consists of a consortium of 23 industrial companies and some individual members who are engaged in particle research. The industrial members provide funding for research which is administered by IFPRI: the Institute is not institutionalized in a building. The research is published in the academic literature. In addition, IFPRI has produced over 500 research reports, giving the progress of projects which it has funded.
It provides networking for industry and academics in the area of particle technology via steering groups and through an annual meeting, and organizes workshops such as "Particle Technology Education in the Twenty-First Century Workshop" (April, Sheffield, UK). | 1 | Applied and Interdisciplinary Chemistry |
An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or "accepts"/"receives" an electron from a (called the , , or ). In other words, an oxidizer is any substance that oxidizes another substance. The oxidation state, which describes the degree of loss of electrons, of the oxidizer decreases while that of the reductant increases; this is expressed by saying that oxidizers "undergo reduction" and "are reduced" while reducers "undergo oxidation" and "are oxidized".
Common oxidizing agents are oxygen, hydrogen peroxide, and the halogens.
In one sense, an oxidizing agent is a chemical species that undergoes a chemical reaction in which it gains one or more electrons. In that sense, it is one component in an oxidation–reduction (redox) reaction. In the second sense, an oxidizing agent is a chemical species that transfers electronegative atoms, usually oxygen, to a substrate. Combustion, many explosives, and organic redox reactions involve atom-transfer reactions. | 0 | Theoretical and Fundamental Chemistry |
Several syntheses of oxoiron(IV) species have been reported. These compounds model biological complexes such as cytochrome P450, NO synthase, and isopenicillin N synthase. Two such reported compounds are thiolate-ligated oxoiron(IV) and cyclam-acetate oxoiron(IV).
Thiolate-ligated oxoiron(IV) is formed by the oxidation of a precursor, [Fe(TMCS)](PF) (TMCS = 1-mercaptoethyl-4,8,11-trimethyl-1,4,8,11-tetraza cyclotetradecane), and 3-5 equivalents of HO at -60 ˚C in methanol. The iron(IV) compound is deep blue in color and shows intense absorption features at 460 nm, 570 nm, 850 nm, and 1050 nm. This species Fe(=O)(TMCS)+ is stable at -60 ˚C, but decomposition is reported as temperature increases. Compound 2 was identified by Mössbauer spectroscopy, high resolution electrospray ionization mass spectrometry (ESI-MS), X-ray absorption spectroscopy, extended X-ray absorption fine structure (EXAFS), ultraviolet–visible spectroscopy (UV-vis), Fourier-transform infrared spectroscopy (FT-IR), and results were compared to density functional theory (DFT) calculations.
Tetramethylcyclam oxoiron(IV) is formed by the reaction of Fe(TMC)(OTf), TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane; OTf = CFSO, with iodosylbenzene (PhIO) in CHCN at -40 ˚C. A second method for formation of cyclam oxoiron(IV) is reported as the reaction of Fe(TMC)(OTf) with 3 equivalents of HO for 3 hours. This species is pale green in color and has an absorption maximum at 820 nm. It is reported to be stable for at least 1 month at -40 ˚C. It has been characterized by Mössbauer spectroscopy, ESI-MS, EXAFS, UV-vis, Raman spectroscopy, and FT-IR.
High-valent iron bispidine complexes can oxidize cyclohexane to cyclohexanol and cyclohexanone in 35% yield with an alcohol to ketone ratio up to 4. | 0 | Theoretical and Fundamental Chemistry |
Liquid is one of the four primary states of matter, with the others being solid, gas and plasma. A liquid is a fluid. Unlike a solid, the molecules in a liquid have a much greater freedom to move. The forces that bind the molecules together in a solid are only temporary in a liquid, allowing a liquid to flow while a solid remains rigid.
A liquid, like a gas, displays the properties of a fluid. A liquid can flow, assume the shape of a container, and, if placed in a sealed container, will distribute applied pressure evenly to every surface in the container. If liquid is placed in a bag, it can be squeezed into any shape. Unlike a gas, a liquid is nearly incompressible, meaning that it occupies nearly a constant volume over a wide range of pressures; it does not generally expand to fill available space in a container but forms its own surface, and it may not always mix readily with another liquid. These properties make a liquid suitable for applications such as hydraulics.
Liquid particles are bound firmly but not rigidly. They are able to move around one another freely, resulting in a limited degree of particle mobility. As the temperature increases, the increased vibrations of the molecules causes distances between the molecules to increase. When a liquid reaches its boiling point, the cohesive forces that bind the molecules closely together break, and the liquid changes to its gaseous state (unless superheating occurs). If the temperature is decreased, the distances between the molecules become smaller. When the liquid reaches its freezing point the molecules will usually lock into a very specific order, called crystallizing, and the bonds between them become more rigid, changing the liquid into its solid state (unless supercooling occurs). | 0 | Theoretical and Fundamental Chemistry |
Changeable optics filters are used in the colorimeter to select the wavelength which the solute absorbs the most, in order to maximize accuracy. The usual wavelength range is from 400 to 700 nm. If it is necessary to operate in the ultraviolet range then some modifications to the colorimeter are needed. In modern colorimeters the filament lamp and filters may be replaced by several (light-emitting diode) of different colors. | 0 | Theoretical and Fundamental Chemistry |
In Laser ablation electrospray ionization (LAESI) a laser is used to ablate the surface of the sample and the emitted molecules are ionized in the gas phase by charged droplets from electrospray. Similar to DESI the ionization happens in ambient conditions. Anderton et al. used this ionization technique coupled to a Fourier transform mass spectrometer to analyzed 200 single cells of Allium cepa (red onion) in high spatial resolution. | 1 | Applied and Interdisciplinary Chemistry |
Floral scent is often composed of hundreds of VOCs, in very variable proportions. The method used is a tradeoff between accurately detecting quantifying minor compounds and avoiding detector saturation by major compounds. For most analysis methods routinely used, the detection threshold of many VOCs is still higher than the perception threshold of insects, which reduces our capacity to understand plant-insect interactions mediated by floral scent.
Further, the chemical diversity in floral scent samples is challenging. The time of analysis is proportional to the range in molecular weight of VOCs present in the sample, hence a high diversity will increase analysis time. Floral scent may also be composed of very similar molecules, such as isomers and especially enantiomers, which tend to co-elute and then to be very hardly separated. Unambiguously detecting and quantifying them is of importance though, as enantiomers may trigger very different responses in pollinators. | 1 | Applied and Interdisciplinary Chemistry |
The Reynolds number is the ratio of inertial forces to viscous forces within a fluid that is subjected to relative internal movement due to different fluid velocities. A region where these forces change behavior is known as a boundary layer, such as the bounding surface in the interior of a pipe. A similar effect is created by the introduction of a stream of high-velocity fluid into a low-velocity fluid, such as the hot gases emitted from a flame in air. This relative movement generates fluid friction, which is a factor in developing turbulent flow. Counteracting this effect is the viscosity of the fluid, which tends to inhibit turbulence. The Reynolds number quantifies the relative importance of these two types of forces for given flow conditions and is a guide to when turbulent flow will occur in a particular situation.
This ability to predict the onset of turbulent flow is an important design tool for equipment such as piping systems or aircraft wings, but the Reynolds number is also used in scaling of fluid dynamics problems and is used to determine dynamic similitude between two different cases of fluid flow, such as between a model aircraft, and its full-size version. Such scaling is not linear and the application of Reynolds numbers to both situations allows scaling factors to be developed.
With respect to laminar and turbulent flow regimes:
* laminar flow occurs at low Reynolds numbers, where viscous forces are dominant, and is characterized by smooth, constant fluid motion;
* turbulent flow occurs at high Reynolds numbers and is dominated by inertial forces, which tend to produce chaotic eddies, vortices and other flow instabilities.
The Reynolds number is defined as
where:
* is the density of the fluid (SI units: kg/m)
* is the flow speed (m/s)
* is a characteristic length (m)
* is the dynamic viscosity of the fluid (Pa·s or N·s/m or kg/(m·s))
* is the kinematic viscosity of the fluid (m/s).
The Reynolds number can be defined for several different situations where a fluid is in relative motion to a surface. These definitions generally include the fluid properties of density and viscosity, plus a velocity and a characteristic length or characteristic dimension (L in the above equation). This dimension is a matter of convention – for example radius and diameter are equally valid to describe spheres or circles, but one is chosen by convention. For aircraft or ships, the length or width can be used. For flow in a pipe, or for a sphere moving in a fluid, the internal diameter is generally used today. Other shapes such as rectangular pipes or non-spherical objects have an equivalent diameter defined. For fluids of variable density such as compressible gases or fluids of variable viscosity such as non-Newtonian fluids, special rules apply. The velocity may also be a matter of convention in some circumstances, notably stirred vessels.
In practice, matching the Reynolds number is not on its own sufficient to guarantee similitude. Fluid flow is generally chaotic, and very small changes to shape and surface roughness of bounding surfaces can result in very different flows. Nevertheless, Reynolds numbers are a very important guide and are widely used. | 1 | Applied and Interdisciplinary Chemistry |
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