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Since evaporation causes oceanic and terrestrial waters to have a different ratio of O to O, the Dole effect will reflect the relevant importances of land-based and marine photosynthesis. The complete removal of land-based productivity would result .
The stability (to within 0.5‰) of the atmospheric O to O ratio with respect to sea surface waters since the last interglacial (the last 130 000 years), as derived from ice cores, suggests that terrestrial and marine productivity have varied together during this time period.
Millennial variations of the Dole effect were found to be related to abrupt climate change events in the North Atlantic region during the last 60 kyr (1kyr=1000years). High correlations of the Dole effect to speleothem δO, an indicator for monsoon precipitation, suggest that it is subject to changes in low-latitude terrestrial productivity. Orbital scale variations of the Dole effect, characterized by periods of 20-100 kyr, respond strongly to Earth's orbital eccentricity and precession, but not obliquity.
The Dole effect can also be applied as a tracer in sea water, with slight variations in chemistry being used to track a discrete "parcel" of water and determine its age. | 0 | Theoretical and Fundamental Chemistry |
All physical and chemical systems in the universe follow the second law of thermodynamics and proceed in a downhill, i.e., exergonic, direction. Thus, left to itself, any physical or chemical system will proceed, according to the second law of thermodynamics, in a direction that tends to lower the free energy of the system, and thus to expend energy in the form of work. These reactions occur spontaneously.
A chemical reaction is endergonic when non spontaneous. Thus in this type of reaction the Gibbs free energy increases. The entropy is included in any change of the Gibbs free energy. This differs from an endothermic reaction where the entropy is not included. The Gibbs free energy is calculated with the Gibbs–Helmholtz equation:
where:
: = temperature in kelvins (K)
: = change in the Gibbs free energy
: = change in entropy (at 298 K) as
: = change in enthalpy (at 298 K) as
A chemical reaction progresses non spontaneously when the Gibbs free energy increases, in that case the is positive. In exergonic reactions the is negative and in endergonic reactions the is positive:
: exergonic
: endergonic
where equals the change in the Gibbs free energy after completion of a chemical reaction. | 0 | Theoretical and Fundamental Chemistry |
Despite the experimental support mentioned above, Clars rule suffers from some limitations. In the first place, Clars rule is formulated only for species with hexagonal rings, and thus it cannot be applied to species having rings different from the benzene moiety, even though an extension of the rule to molecules with rings of any dimension has been provided by Glidewell and Lloyd. Secondly, if more than one Clar structure exist for a given species, Clars rule does not allow to determine the relative importance of each of them in the determination of the physicochemical properties. Finally, it is important to mention that exceptions to the Clars rule exist, such as in the case of triangulenes. | 0 | Theoretical and Fundamental Chemistry |
In organosulfur chemistry, sulfenamides (also spelled sulphenamides) are a class of organosulfur compounds characterized by the general formula , where the R groups are hydrogen, alkyl, or aryl. Sulfenamides have been used extensively in the vulcanization of rubber using sulfur. They are related to the oxidized compounds known as sulfinamides () and sulfonamides (). | 0 | Theoretical and Fundamental Chemistry |
The drug is composed of three monoclonal antibodies (mAbs), initially harvested from mice exposed to Ebola virus proteins, that have been chimerized with human constant regions. The components are chimeric monoclonal antibody c13C6 from a previously existing antibody cocktail called "MB-003" and two chimeric mAbs from a different antibody cocktail called ZMab, c2G4, and c4G7. ZMapp is manufactured in the tobacco plant Nicotiana benthamiana in the bioproduction process known as "pharming" by Kentucky BioProcessing, a subsidiary of Reynolds American. | 1 | Applied and Interdisciplinary Chemistry |
The endogenous cannabinoids, or endocannabinoids, are endogenous lipids that activate cannabinoid receptors. The first such lipid to be isolated was anandamide which is the arachidonoyl amide of ethanolamine. Anandamide is formed via enzymatic release from N-arachidonoyl phosphatidylethanolamine by the N-acyl phosphatidylethanolamine phospholipase D (NAPE-PLD). Anandamide activates both the CB1 receptor, found primarily in the central nervous system, and the CB2 receptor which is found primarily in lymphocytes and the periphery. It is found at very low levels (nM) in most tissues and is inactivated by the fatty acid amide hydrolase. Subsequently, another endocannabinoid was isolated, 2-arachidonoylglycerol, which is produced when phospholipase C releases diacylglycerol which is then converted to 2-AG by diacylglycerol lipase. 2-AG can also activate both cannabinoid receptors and is inactivated by monoacylglycerol lipase. It is present at approximately 100-times the concentration of anandamide in most tissues. Elevations in either of these lipids causes analgesia and anti-inflammation and tissue protection during states of ischemia, but the precise roles played by these various endocannabinoids are still not totally known and intensive research into their function, metabolism, and regulation is ongoing. One saturated lipid from this class, often called an endocannabinoid, but with no relevant affinity for the CB1 and CB 2 receptor is palmitoylethanolamide. This signaling lipid has great affinity for the GRP55 receptor and the PPAR alpha receptor. It has been identified as an anti-inflammatory compound already in 1957, and as an analgesic compound in 1975. Rita Levi-Montalcini first identified one of its biological mechanisms of action, the inhibition of activated mast cells. Palmitoylethanolamide is the only endocannabinoid available on the market for treatment, as a food supplement. | 1 | Applied and Interdisciplinary Chemistry |
Microfluidics refers to a system that manipulates a small amount of fluids (10 to 10 liters) using small channels with sizes ten to hundreds micrometres. It is a multidisciplinary field that involves molecular analysis, molecular biology, and microelectronics. It has practical applications in the design of systems that process low volumes of fluids to achieve multiplexing, automation, and high-throughput screening. Microfluidics emerged in the beginning of the 1980s and is used in the development of inkjet printheads, DNA chips, lab-on-a-chip technology, micro-propulsion, and micro-thermal technologies.
Typically, micro means one of the following features:
* Small volumes (μL, nL, pL, fL)
* Small size
* Low energy consumption
* Microdomain effects
Typically microfluidic systems transport, mix, separate, or otherwise process fluids. Various applications rely on passive fluid control using capillary forces, in the form of capillary flow modifying elements, akin to flow resistors and flow accelerators. In some applications, external actuation means are additionally used for a directed transport of the media. Examples are rotary drives applying centrifugal forces for the fluid transport on the passive chips. Active microfluidics refers to the defined manipulation of the working fluid by active (micro) components such as micropumps or microvalves. Micropumps supply fluids in a continuous manner or are used for dosing. Microvalves determine the flow direction or the mode of movement of pumped liquids. Often, processes normally carried out in a lab are miniaturised on a single chip, which enhances efficiency and mobility, and reduces sample and reagent volumes. | 1 | Applied and Interdisciplinary Chemistry |
The spin-echo effect was discovered by Erwin Hahn when he applied two successive 90° pulses separated by short time period, but detected a signal, the echo, when no pulse was applied. This phenomenon of spin echo was explained by Erwin Hahn in his 1950 paper, and further developed by Carr and Purcell who pointed out the advantages of using a 180° refocusing pulse for the second pulse. The pulse sequence may be better understood by breaking it down into the following steps:
Several simplifications are used in this sequence: no decoherence is included and each spin experiences perfect pulses during which the environment provides no spreading. Six spins are shown above and these are not given the chance to dephase significantly. The spin-echo technique is more useful when the spins have dephased more significantly such as in the animation below: | 0 | Theoretical and Fundamental Chemistry |
Pol I requires no TATA box in the promoter, instead relying on an upstream control element (UCE) located between −200 and −107, and a core element located between −45 and +20.
#The dimeric eukaryotic upstream binding factor (UBF) binds the UCE and the core element.
#UBF recruits and binds a protein complex called SL1 in humans (or TIF-IB in mouse), composed of the TATA-binding protein (TBP) and three TBP-associated factors (TAFs).
#The UBF dimer contains several high-mobility-group boxes (HMG-boxes) that introduce loops into the upstream region, allowing the UCE and the core elements to come into contact.
#RRN3/TIF-IA is phosphorylated and binds Pol I.
#Pol I binds to the UBF/SL1 complex via RRN3/TIF-IA, and transcription starts.
Note that this process is variable in different organisms. | 1 | Applied and Interdisciplinary Chemistry |
To be a useful fuel for nuclear fission chain reactions, the material must:
* Be in the region of the binding energy curve where a fission chain reaction is possible (i.e., above radium)
* Have a high probability of fission on neutron capture
* Release more than one neutron on average per neutron capture. (Enough of them on each fission, to compensate for non-fissions and absorptions in non-fuel material)
* Have a reasonably long half-life
* Be available in suitable quantities
Fissile nuclides in nuclear fuels include:
* Uranium-233, bred from thorium-232 by neutron capture with intermediate decays steps omitted.
* Uranium-235, which occurs in natural uranium and enriched uranium
* Plutonium-239, bred from uranium-238 by neutron capture with intermediate decays steps omitted.
* Plutonium-241, bred from plutonium-240 directly by neutron capture.
Fissile nuclides do not have a 100% chance of undergoing fission on absorption of a neutron. The chance is dependent on the nuclide as well as neutron energy. For low and medium-energy neutrons, the neutron capture cross sections for fission (σ), the cross section for neutron capture with emission of a gamma ray (σ), and the percentage of non-fissions are in the table at right.
Fertile nuclides in nuclear fuels include:
* Thorium-232, which breeds uranium-233 by neutron capture with intermediate decays steps omitted.
* Uranium-238, which breeds plutonium-239 by neutron capture with intermediate decays steps omitted.
* Plutonium-240, bred from plutonium-239 directly by neutron capture. | 0 | Theoretical and Fundamental Chemistry |
The debate over the nature and classification of hypervalent molecules goes back to Gilbert N. Lewis and Irving Langmuir and the debate over the nature of the chemical bond in the 1920s. Lewis maintained the importance of the two-center two-electron (2c-2e) bond in describing hypervalence, thus using expanded octets to account for such molecules. Using the language of orbital hybridization, the bonds of molecules like PF and SF were said to be constructed from spd orbitals on the central atom. Langmuir, on the other hand, upheld the dominance of the octet rule and preferred the use of ionic bonds to account for hypervalence without violating the rule (e.g. " 2F" for SF).
In the late 1920s and 1930s, Sugden argued for the existence of a two-center one-electron (2c-1e) bond and thus rationalized bonding in hypervalent molecules without the need for expanded octets or ionic bond character; this was poorly accepted at the time. In the 1940s and 1950s, Rundle and Pimentel popularized the idea of the three-center four-electron bond, which is essentially the same concept which Sugden attempted to advance decades earlier; the three-center four-electron bond can be alternatively viewed as consisting of two collinear two-center one-electron bonds, with the remaining two nonbonding electrons localized to the ligands.
The attempt to actually prepare hypervalent organic molecules began with Hermann Staudinger and Georg Wittig in the first half of the twentieth century, who sought to challenge the extant valence theory and successfully prepare nitrogen and phosphorus-centered hypervalent molecules. The theoretical basis for hypervalency was not delineated until J.I. Musher's work in 1969.
In 1990, Magnusson published a seminal work definitively excluding the significance of d-orbital hybridization in the bonding of hypervalent compounds of second-row elements. This had long been a point of contention and confusion in describing these molecules using molecular orbital theory. Part of the confusion here originates from the fact that one must include d-functions in the basis sets used to describe these compounds (or else unreasonably high energies and distorted geometries result), and the contribution of the d-function to the molecular wavefunction is large. These facts were historically interpreted to mean that d-orbitals must be involved in bonding. However, Magnusson concludes in his work that d-orbital involvement is not implicated in hypervalency.
Nevertheless, a 2013 study showed that although the Pimentel ionic model best accounts for the bonding of hypervalent species, the energetic contribution of an expanded octet structure is also not null. In this modern valence bond theory study of the bonding of xenon difluoride, it was found that ionic structures account for about 81% of the overall wavefunction, of which 70% arises from ionic structures employing only the p orbital on xenon while 11% arises from ionic structures employing an hybrid on xenon. The contribution of a formally hypervalent structure employing an orbital of spd hybridization on xenon accounts for 11% of the wavefunction, with a diradical contribution making up the remaining 8%. The 11% spd contribution results in a net stabilization of the molecule by mol, a minor but significant fraction of the total energy of the total bond energy ( mol). Other studies have similarly found minor but non-negligible energetic contributions from expanded octet structures in SF (17%) and XeF (14%).
Despite the lack of chemical realism, the IUPAC recommends the drawing of expanded octet structures for functional groups like sulfones and phosphoranes, in order to avoid the drawing of a large number of formal charges or partial single bonds. | 0 | Theoretical and Fundamental Chemistry |
Because of the equivalences between many properties and derivatives within thermodynamics (e.g., see Maxwell Relations), there are many formulations of the thermal pressure coefficient, which are equally valid, leading to distinct yet correct interpretations of its meaning.
Some formulations for the thermal pressure coefficient include:
Where is the volume thermal expansion, the isothermal bulk modulus, the Grüneisen parameter, the compressibility and the constant-volume heat capacity.
Details of the calculation: | 0 | Theoretical and Fundamental Chemistry |
The critical heat flux is an important point on the boiling curve and it may be desirable to operate a boiling process near this point. However, one could become cautious of dissipating heat in excess of this amount. Zuber, through a hydrodynamic stability analysis of the problem has developed an expression to approximate this point.
Units: critical flux: kW/m; h: kJ/kg; σ: N/m; ρ: kg/m; g: m/s.
It is independent of the surface material and is weakly dependent upon the heated surface geometry described by the constant C. For large horizontal cylinders, spheres and large finite heated surfaces, the value of the Zuber constant . For large horizontal plates, a value of is more suitable.
The critical heat flux depends strongly on pressure. At low pressures (including atmospheric pressure), the pressure dependence is mainly through the change in vapor density leading to an increase in the critical heat flux with pressure. However, as pressures approach the critical pressure, both the surface tension and the heat of vaporization converge to zero, making them the dominant sources of pressure dependency.
For water at 1atm, the above equation calculates a critical heat flux of approximately 1000 kW/m. | 0 | Theoretical and Fundamental Chemistry |
Plastocyanin was the first of the blue copper proteins to be characterised by X-ray crystallography. It features an eight-stranded antiparallel β-barrel containing one copper center.
Structures of the protein from poplar, algae, parsley, spinach, and French bean plants have been characterized crystallographically. In all cases the binding site is generally conserved. Bound to the copper center are four ligands: the imidazole groups of two histidine residues (His37 and His87), the thiolate of Cys84 and the thioether of Met92. The geometry of the copper binding site is described as a ‘distorted trigonal pyramidal’. The Cu-S (cys) contact is much shorter (207 picometers) than Cu-S (met) (282 pm) bond. The elongated Cu-thioether bond appears to destabilise the Cu state thereby enhancing its oxidizing power. The blue colour (597 nm peak absorption) is assigned to a charge transfer transition from S to Cu-y</sub>.
In the reduced form of plastocyanin, His-87 becomes protonated.
While the molecular surface of the protein near the copper binding site varies slightly, all plastocyanins have a hydrophobic surface surrounding the exposed histidine of the copper binding site. In plant plastocyanins, acidic residues are located on either side of the highly conserved tyrosine-83. Algal plastocyanins, and those from vascular plants in the family Apiaceae, contain similar acidic residues but are shaped differently from those of plant plastocyanins—they lack residues 57 and 58. In cyanobacteria, the distribution of charged residues on the surface is different from eukaryotic plastocyanins and variations among different bacterial species is large. Many cyanobacterial plastocyanins have 107 amino acids. Although the acidic patches are not conserved in bacteria, the hydrophobic patch is always present. These hydrophobic and acidic patches are believed to be the recognition/binding sites for the other proteins involved in electron transfer. | 0 | Theoretical and Fundamental Chemistry |
On 17 November 2020, a buoy moored in of water on Amphitrite Bank in the Pacific Ocean off Ucluelet, Vancouver Island, British Columbia, Canada, at recorded a lone tall wave among surrounding waves about in height. The wave exceeded the surrounding significant wave heights by a factor of 2.93. When the wave's detection was revealed to the public in February 2022, one scientific paper and many news outlets christened the event as "the most extreme rogue wave event ever recorded" and a "once-in-a-millennium" event, claiming that at about three times the height of the waves around it, the Ucluelet wave set a record as the most extreme rogue wave ever recorded at the time in terms of its height in proportion to surrounding waves, and that a wave three times the height of those around it was estimated to occur on average only once every 1,300 years worldwide.
The Ucluelet event generated controversy. Analysis of scientific papers dealing with rogue wave events since 2005 revealed the claims for the record-setting nature and rarity of the wave to be incorrect. The paper Oceanic rogue waves by Dysthe, Krogstad and Muller reports on an event in the Black Sea in 2004 which was far more extreme than the Ucluelet wave, where the Datawell Waverider buoy reported a wave that was 3.91 times the significant wave height, as detailed in the paper. Thorough inspection of the buoy after the recording revealed no malfunction. The authors of the paper that reported the Black Sea event assessed the wave as "anomalous" and suggested several theories on how such an extreme wave may have arisen. What sets the Black Sea event apart is that it, like the Ucluelet wave, was recorded with a high-precision instrument. The Oceanic rogue waves paper also reports even more extreme waves from a different source, but these were possibly overestimated, as assessed by the datas own authors. Furthermore, a paper by I. Nikolkina and I. Didenkulova also reveals waves more extreme than the Ucluelet wave. From the paper, they infer that in 2006 a wave appeared in a sea with a significant wave height of . The factor difference is 5.38, almost twice that of the Ucluelet wave. The paper also reveals the MV Pont-Aven incident as marginally more extreme than the Ucluelet event. The paper also assesses a report of an wave in a significant wave height of , but casts doubt on that claim. Finally, perhaps the most extreme rogue wave event ever recorded (but not by a high-precision instrument), is revealed by Craig B. Smiths paper. The incident saw a wall of water arise in "calm seas." Such "extreme" rogue waves are rare but could pose a danger to any ship in the oceans. | 1 | Applied and Interdisciplinary Chemistry |
In May 2005 the Save Spodden Valley group claimed that it had uncovered internal MMC correspondence which identified numerous sites where asbestos fibres had been found in September 2004, predating the planning application. The document stated: "The audit undertaken was visual and no samples have been sent away for analysis. I enclose a site map where the asbestos has been located: Top section of road near hair pin bend, asbestos sheets and asbestos fibre found in tree stumps. Road leading to Healey Dell, asbestos cloth." The developers responded that they had been aware of contamination in the northern portion of the site, but their testing report submitted to the council did not include this area as there had been no intention to develop there. Instead they had confined their testing only to those areas where they intended to develop and that there had been "some misunderstanding of our intentions and the test result." | 1 | Applied and Interdisciplinary Chemistry |
To derive the theoretical equations for a moving shock, one may start by denoting the region in front of the shock as subscript 1, with the subscript 2 defining the region behind the shock. This is shown in the figure, with the shock wave propagating to the right.
The velocity of the gas is denoted by u, pressure by p, and the local speed of sound by a.
The speed of the shock wave relative to the gas is W, making the total velocity equal to u + W.
Next, suppose a reference frame is then fixed to the shock so it appears stationary as the gas in regions 1 and 2 move with a velocity relative to it. Redefining region 1 as x and region 2 as y leads to the following shock-relative velocities:
With these shock-relative velocities, the properties of the regions before and after the shock can be defined below introducing the temperature as T, the density as ρ, and the Mach number as M:
Introducing the heat capacity ratio as γ, the speed of sound, density, and pressure ratios can be derived:
One must keep in mind that the above equations are for a shock wave moving towards the right. For a shock moving towards the left, the x and y subscripts must be switched and: | 1 | Applied and Interdisciplinary Chemistry |
In TEM, the electron beam passes through a thin film of the material as illustrated in Figure 10. Before and after the sample the beam is manipulated by the electron optics including magnetic lenses, deflectors and apertures; these act on the electrons similar to how glass lenses focus and control light. Optical elements above the sample are used to control the incident beam which can range from a wide and parallel beam to one which is a converging cone and can be smaller than an atom, 0.1 nm. As it interacts with the sample, part of the beam is diffracted and part is transmitted without changing its direction. This occurs simultaneously as electrons are everywhere until they are detected (wavefunction collapse) according to the Copenhagen interpretation.
Below the sample, the beam is controlled by another set of magnetic lneses and apertures. Each set of initially parallel rays (a plane wave) is focused by the first lens (objective) to a point in the back focal plane of this lens, forming a spot on a detector; a map of these directions, often an array of spots, is the diffraction pattern. Alternatively the lenses can form a magnified image of the sample. Herein the focus is on collecting a diffraction pattern; for other information see the pages on TEM and scanning transmission electron microscopy. | 0 | Theoretical and Fundamental Chemistry |
The 2-norbornyl cation can also be formed via rearrangements of similar ions, such as the 1-norbornyl and 7-norbornyl cations, though these are generally not as well understood. Carbon-14 radioactive isotope labeling experiments have shown that complex scrambling in norbornyl cation systems allow C to be present at all seven positions of the norbornyl system. By cycling between low and high temperatures during the hydrolyses of 1- and 7-choloronorbornanes, a large amount of 2-norbornanol was observed in addition to the expected 1- and 7-norbornanols, respectively. Thus the 1- and 7-norbornyl cations have some mechanism by which they can rearrange to the more stable 2-norbornyl cation on the timescale of solvolysis reactions. | 0 | Theoretical and Fundamental Chemistry |
Size-exclusion chromatography, also known as molecular sieve chromatography, is a chromatographic method in which molecules in solution are separated by their size, and in some cases molecular weight. It is usually applied to large molecules or macromolecular complexes such as proteins and industrial polymers. Typically, when an aqueous solution is used to transport the sample through the column, the technique is known as gel-filtration chromatography, versus the name gel permeation chromatography, which is used when an organic solvent is used as a mobile phase. The chromatography column is packed with fine, porous beads which are commonly composed of dextran, agarose, or polyacrylamide polymers. The pore sizes of these beads are used to estimate the dimensions of macromolecules. SEC is a widely used polymer characterization method because of its ability to provide good molar mass distribution (Mw) results for polymers.
Size exclusion chromatography (SEC) is fundamentally different from all other chromatographic techniques in that separation is based on a simple procedure of classifying molecule sizes rather than any type of interaction. | 1 | Applied and Interdisciplinary Chemistry |
Macrostructure refers to the overall geometric properties that will influence the force at failure, stiffness, bending, stress distribution, and the weight of the material. It requires little to no magnification to reveal the macrostructure of a material. Observing the macrostructure reveals properties such as cavities, porosity, gas bubbles, stratification, and fissures. The material's strength and elastic modulus are both independent of the macrostructure. | 1 | Applied and Interdisciplinary Chemistry |
While new production of these refrigerants has been banned, large volumes still exist in older systems and have been said to pose an immediate threat to our environment. Preventing the release of these harmful refrigerants has been ranked as one of the single most effective actions we can take to mitigate catastrophic climate change. | 1 | Applied and Interdisciplinary Chemistry |
In the early 2000s, a link between bisphosphonate use and impaired bone physiology was noted. The strong inhibition of osteoclast function precipitated by bisphosphonate therapy can lead to inhibition of normal bone turnover, leading to impaired wound healing following trauma (such as dental surgery) or even spontaneous non-healing bone exposure. Because bisphosphonates are preferentially deposited in bone with high turnover rates, it is possible that the levels of bisphosphonate within the jaw bones are selectively elevated.
With the advent of implant dentistry, more dental patients are undergoing therapies in the oral cavity that involve bone healing, such as surgical implant placement and bone grafting procedures. In order to evaluate the risk of osteonecrosis for a patient taking bisphosphonates, use of the CTX biomarker was introduced in 2000 by Rosen. | 1 | Applied and Interdisciplinary Chemistry |
In 1812, Davy was knighted and gave up his lecturing position at the Royal Institution. He was given the title of Honorary Professor of Chemistry. He gave a farewell lecture to the Institution, and married a wealthy widow, Jane Apreece. (While Davy was generally acknowledged as being faithful to his wife, their relationship was stormy, and in later years he travelled to continental Europe alone.)
Davy then published his Elements of Chemical Philosophy, part 1, volume 1, though other parts of this title were never completed. He made notes for a second edition, but it was never required.
In October 1813, he and his wife, accompanied by Michael Faraday as his scientific assistant (also treated as a valet), travelled to France to collect the second edition of the prix du Galvanisme, a medal that Napoleon Bonaparte had awarded Davy for his electro-chemical work. Faraday noted "Tis indeed a strange venture at this time, to trust ourselves in a foreign and hostile country, where so little regard is had to protestations of honour, that the slightest suspicion would be sufficient to separate us for ever from England, and perhaps from life". Davy's party sailed from Plymouth to Morlaix by cartel, where they were searched.
Upon reaching Paris, Davy was a guest of honour at a meeting of the First Class of the and met with André-Marie Ampère and other French chemists. It was later reported that Davy's wife had thrown the medal onto the sea, near her Cornish home, "as it raised bad memories". The Royal Society of Chemistry has offered over £1,800 for the recovery of the medal.
While in Paris, Davy attended lectures at the Ecole Polytechnique, including those by Joseph Louis Gay-Lussac on a mysterious substance isolated by Bernard Courtois. Davy wrote a paper for the Royal Society on the element, which is now called iodine. This led to a dispute between Davy and Gay-Lussac on who had the priority on the research.
Davys party did not meet Napoleon in person, but they did visit the Empress Joséphine de Beauharnais at the Château de Malmaison. The party left Paris in December 1813, travelling south to Italy. They sojourned in Florence, where using the burning glass of the Grand Duke of Tuscany in a series of experiments conducted with Faradays assistance, Davy succeeded in using the sun's rays to ignite diamond, proving it is composed of pure carbon.
Davy's party continued to Rome, where he undertook experiments on iodine and chlorine and on the colours used in ancient paintings. This was the first chemical research on the pigments used by artists.
He also visited Naples and Mount Vesuvius, where he collected samples of crystals. By June 1814, they were in Milan, where they met Alessandro Volta, and then continued north to Geneva. They returned to Italy via Munich and Innsbruck, and when their plans to travel to Greece and Istanbul were abandoned after Napoleon's escape from Elba, they returned to England.
After the Battle of Waterloo, Davy wrote to Lord Liverpool urging that the French be treated with severity: | 1 | Applied and Interdisciplinary Chemistry |
Calcareous sediments are typically deposited in shallow water closer to land, as marine organisms that precipitate calcium carbonate primarily reside within shallow water ecosystems due to an inability to precipitate calcium carbonate at depth (see carbonate compensation depth). Generally speaking, the farther from land sediments fall, the less calcareous they are, and deviations from this expectation arise if (a) the ocean floor is shallower than the CCD or (b) storms/ocean currents transport calcareous sediments away from their origin point, leading to the interbedding of calcareous sediments in alternative locations.
An additional form of calcareous marine sediment consists of calcareous ooze, which is a form of calcium carbonate sediment that consists of >30% biogenous material predominantly consisting of organisms such as coccolithophores and foraminifera. These oozes form slowly under low-energy environments, and necessitate higher seawater saturation states or a deeper CCD (see supersaturation and precipitation vs. undersaturation and dissolution). Therefore, in shallow CCD conditions (i.e., undersaturation of calcium carbonate at depth), stable, non-calcareous sediments such as siliceous ooze or pelagic red clay will prevail in marine sediment records. | 0 | Theoretical and Fundamental Chemistry |
Typical nitrones sources are hydroxylamine oxidation or condensation with carbonyl compounds. Secondary hydroxylamines oxidize to nitrones in air over a timescale of several weeks, a process cupric salts accelerate. The most general reagent used for the oxidation of hydroxylamines is aqueous mercury(II) oxide:
However, a hydroxylamine with two α hydrogens may unsaturate on either side. Carbonyl condensation avoids this ambiguity...
...but is inhibited if both ketone substituents are bulky.
In principle, N-alkylation could produce nitrones from oximes, but in practice electrophiles typically perform a mixture of N- and O-attack. | 0 | Theoretical and Fundamental Chemistry |
In chemistry the descriptor vicinal (from Latin vicinus = neighbor), abbreviated vic, is a descriptor that identifies two functional groups as bonded to two adjacent carbon atoms (i.e., in a 1,2-relationship). It may arise from vicinal difunctionalization. | 0 | Theoretical and Fundamental Chemistry |
Water-splitting photoelectrochemical (PEC) cells use light energy to decompose water into hydrogen and oxygen within a two-electrode cell. In theory, three arrangements of photo-electrodes in the assembly of PECs exist:
* photo-anode made of a n-type semiconductor and a metal cathode
* photo-anode made of a n-type semiconductor and a photo-cathode made of a p-type semiconductor
* photo-cathode made of a p-type semiconductor and a metal anode
There are several requirements for photoelectrode materials in PEC production:
* light absorbance: determined by band gap and appropriate for solar irradiation spectrum
* charge transport: photoelectrodes must be conductive (or semi-conductive) to minimize resistive losses
* suitable band structure: large enough band gap to split water (1.23V) and appropriate positions relative to redox potentials for and
* catalytic activity: high catalytic activity increases efficiency of the water-splitting reaction
* stability: materials must be stable to prevent decomposition and loss of function
In addition to these requirements, materials must be low-cost and earth abundant for the widespread adoption of PEC water splitting to be feasible.
While the listed requirements can be applied generally, photoanodes and photocathodes have slightly different needs. A good photocathode will have early onset of the oxygen evolution reaction (low overpotential), a large photocurrent at saturation, and rapid growth of photocurrent upon onset. Good photoanodes, on the other hand, will have early onset of the hydrogen evolution reaction in addition to high current and rapid photocurrent growth. To maximize current, anode and cathode materials need to be matched together; the best anode for one cathode material may not be the best for another. | 0 | Theoretical and Fundamental Chemistry |
A general double group transfer reaction which is synchronous can be represented as an interaction between a component with p π electrons and a component with q π electrons as shown.
Then the selection rules are the same as for the generalized cycloaddition reactions. That is
* For supra/supra or antara/antara double group transfers, if p + q = 4n + 2 it is thermally allowed, and if p + q = 4n it is photochemically allowed
* For supra/antara double group transfers, if p + q = 4n it is thermally allowed, and if p + q = 4n + 2 it is photochemically allowed
This is summarized in the following table:
The case of q = 0 corresponds to the thermal elimination of the "transferred" R groups. There is evidence that the pyrolytic eliminations of dihydrogen and ethane from 1,4-cyclohexadiene and 3,3,6,6-tetramethyl-1,4-cyclohexadiene, respectively, represent examples of this type of pericyclic process.
The ene reaction is often classified as a type of group transfer process, even though it does not involve the transfer of two σ-bonded groups. Rather, only one σ-bond is transferred while a second σ-bond is formed from a broken π-bond. As an all suprafacial process involving 6 electrons, it is symmetry-allowed under thermal conditions. The Woodward-Hoffmann symbol for the ene reaction is [2 + 2 + 2] (see below). | 0 | Theoretical and Fundamental Chemistry |
Agmatine sulfate injection can increase food intake with carbohydrate preference in satiated, but not hungry, rats and this effect may be mediated by neuropeptide Y. However, supplementation in rat drinking water results in slight reductions in water intake, body weight, and blood pressure. In addition, force feeding with agmatine leads to a reduction in body weight gain during rat development. It is also found that many fermented foods contain agmatine. | 1 | Applied and Interdisciplinary Chemistry |
A number of places and objects are associated with the name and achievements of the scientist.
In Saint Petersburg his name was given to D. I. Mendeleev Institute for Metrology, the National Metrology Institute, dealing with establishing and supporting national and worldwide standards for precise measurements. Next to it there is a monument to him that consists of his sitting statue and a depiction of his periodic table on the wall of the establishment.
In the Twelve Collegia building, now being the centre of Saint Petersburg State University and in Mendeleevs time – Head Pedagogical Institute – there is Dmitry Mendeleevs Memorial Museum Apartment with his archives. The street in front of these is named after him as Mendeleevskaya liniya (Mendeleev Line).
In Moscow, there is the D. Mendeleyev University of Chemical Technology of Russia.
Mendelevium, which is a synthetic chemical element with the symbol Md (formerly Mv) and the atomic number 101, was named after Mendeleev. It is a metallic radioactive transuranic element in the actinide series, usually synthesized by bombarding einsteinium with alpha particles.
The mineral mendeleevite-Ce, , was named in Mendeleev's honor in 2010. The related species mendeleevite-Nd, , was described in 2015.
A large lunar impact crater Mendeleev, that is located on the far side of the Moon, also bears the name of the scientist.
The Russian Academy of Sciences has occasionally awarded a Mendeleev Golden Medal since 1965.
On 8 February 2016, Google celebrated Dmitri Mendeleev's 182nd Birthday with a doodle. | 0 | Theoretical and Fundamental Chemistry |
Baloola was born on April 14, 1981, in Abu Dhabi, United Arab Emirates.
Baloola received a Bachelor of Science in biomedical engineering from Ajman University of Science and Technology in September 2009. Then he joined Ajman University as a teaching assistant in the Faculty of Engineering. He won many awards during his studies and after graduating. | 0 | Theoretical and Fundamental Chemistry |
Sulfonic acids can be converted to esters. This class of organic compounds has the general formula R−SO−OR. Sulfonic esters such as methyl triflate are considered good alkylating agents in organic synthesis. Such sulfonate esters are often prepared by alcoholysis of the sulfonyl chlorides:
:RSOCl + R′OH → RSOOR′ + HCl | 0 | Theoretical and Fundamental Chemistry |
Bernard Lucas Feringa (, born 18 May 1951) is a Dutch synthetic organic chemist, specializing in molecular nanotechnology and homogeneous catalysis. He is the Jacobus van 't Hoff Distinguished Professor of Molecular Sciences, at the Stratingh Institute for Chemistry, University of Groningen, Netherlands, and an Academy Professor of the Royal Netherlands Academy of Arts and Sciences. He was awarded the 2016 Nobel Prize in Chemistry, together with Sir J. Fraser Stoddart and Jean-Pierre Sauvage, "for the design and synthesis of molecular machines". | 0 | Theoretical and Fundamental Chemistry |
Due to the COVID-19 pandemic, IChO 2020, 2021 and 2022 were organized remotely without a laboratory exam in order to keep the Olympic spirit of collaboration and peace even in harsh times. | 1 | Applied and Interdisciplinary Chemistry |
Orthopaedic implants help alleviate issues with the bones and joints of the body. They are used to treat bone fractures, osteoarthritis, scoliosis, spinal stenosis, and chronic pain. Examples include a wide variety of pins, rods, screws, and plates used to anchor fractured bones while they heal.
Metallic glasses based on magnesium with zinc and calcium addition are tested as the potential metallic biomaterials for biodegradable medical implants.
Patients with orthopaedic implants sometimes need to be put under magnetic resonance imaging (MRI) machine for detailed musculoskeletal study. Therefore, concerns have been raised regarding the loosening and migration of implant, heating of the implant metal which could cause thermal damage to surrounding tissues, and distortion of the MRI scan that affects the imaging results. A study of orthopaedic implants in 2005 has shown that majority of the orthopaedic implants does not react with magnetic fields under the 1.0 Tesla MRI scanning machine with the exception of external fixator clamps. However, at 7.0 Tesla, several orthopaedic implants would show significant interaction with the MRI magnetic fields, such as heel and fibular implant. | 1 | Applied and Interdisciplinary Chemistry |
Enzymatic synthesis of HMOs through transgalactosylation is an efficient way for production. Various donors, including p-nitrophenyl-β-galactopyranoside, uridine diphosphate galactose and lactose, can be used in transgalactosylation. In particular, lactose may act as either a donor or an acceptor in a variety of enzymatic reactions and is available in large quantities from the whey produced as a co-processing product from cheese production. There is a lack of published data, however, describing the large-scale production of such galacto-oligosaccharides. | 0 | Theoretical and Fundamental Chemistry |
Starting point are the linearized one-dimensional Saint-Venant equations for an open channel with a rectangular cross section (vertical side walls). These equations describe the evolution of a wave with free surface elevation and horizontal flow velocity with the horizontal coordinate along the channel axis and the time:
where is the gravity of Earth (taken as a constant), is the mean water depth, is the channel width and and are denoting partial derivatives with respect to space and time. The slow variation of width and depth with distance along the channel axis is brought into account by denoting them as and where is a small parameter: The above two equations can be combined into one wave equation for the surface elevation:
In the Liouville–Green method, the approach is to convert the above wave equation with non-homogeneous coefficients into a homogeneous one (neglecting some small remainders in terms of ). | 1 | Applied and Interdisciplinary Chemistry |
Metal–inorganic frameworks (MIFs) are a class of compounds consisting of metal ions or clusters coordinated to inorganic ligands to form one-, two-, or three-dimensional structures. They are a subclass of coordination polymers, with the special feature that they are often porous. They are inorganic counterpart of Metal–organic frameworks.
__TOC__ | 0 | Theoretical and Fundamental Chemistry |
When an ecosystem experiences an increase in nutrients, primary producers reap the benefits first. In aquatic ecosystems, species such as algae experience a population increase (called an algal bloom). Algal blooms limit the sunlight available to bottom-dwelling organisms and cause wide swings in the amount of dissolved oxygen in the water. Oxygen is required by all aerobically respiring plants and animals and it is replenished in daylight by photosynthesizing plants and algae. Under eutrophic conditions, dissolved oxygen greatly increases during the day, but is greatly reduced after dark by the respiring algae and by microorganisms that feed on the increasing mass of dead algae. When dissolved oxygen levels decline to hypoxic levels, fish and other marine animals suffocate. As a result, creatures such as fish, shrimp, and especially immobile bottom dwellers die off. In extreme cases, anaerobic conditions ensue, promoting growth of bacteria. Zones where this occurs are known as dead zones. | 1 | Applied and Interdisciplinary Chemistry |
In molecular biology and genetics, the sense of a nucleic acid molecule, particularly of a strand of DNA or RNA, refers to the nature of the roles of the strand and its complement in specifying a sequence of amino acids. Depending on the context, sense may have slightly different meanings. For example, the negative-sense strand of DNA is equivalent to the template strand, whereas the positive-sense strand is the non-template strand whose nucleotide sequence is equivalent to the sequence of the mRNA transcript. | 1 | Applied and Interdisciplinary Chemistry |
NHCs are often strongly basic (the pKa value of the conjugate acid of an imidazol-2-ylidene was measured at ca. 24) and react with oxygen. Clearly these reactions are performed using air-free techniques, avoiding compounds of even moderate acidity. Although imidazolium salts are stable to nucleophilic addition, other non-aromatic salts are not (i.e. formamidinium salts).
In these cases, strong unhindered nucleophiles are avoided whether they are generated in situ or are present as an impurity in other reagents (such as LiOH in BuLi).
Several approaches have been developed in order to prepare stable carbenes, these are outlined below. | 0 | Theoretical and Fundamental Chemistry |
A black light lamp emits long-wave UV‑A radiation and little visible light. Fluorescent black light lamps work similarly to other fluorescent lamps, but use a phosphor on the inner tube surface which emits UV‑A radiation instead of visible light. Some lamps use a deep-bluish-purple Woods glass optical filter that blocks almost all visible light with wavelengths longer than 400 nanometers. The purple glow given off by these tubes is not the ultraviolet itself, but visible purple light from mercurys 404 nm spectral line which escapes being filtered out by the coating. Other black lights use plain glass instead of the more expensive Wood's glass, so they appear light-blue to the eye when operating.
Incandescent black lights are also produced, using a filter coating on the envelope of an incandescent bulb that absorbs visible light (see section below). These are cheaper but very inefficient, emitting only a small fraction of a percent of their power as UV. Mercury-vapor black lights in ratings up to 1 kW with UV-emitting phosphor and an envelope of Wood's glass are used for theatrical and concert displays.
Black lights are used in applications in which extraneous visible light must be minimized; mainly to observe fluorescence, the colored glow that many substances give off when exposed to UV light. UV‑A / UV‑B emitting bulbs are also sold for other special purposes, such as tanning lamps and reptile-husbandry. | 0 | Theoretical and Fundamental Chemistry |
Significant radiation doses are not frequently encountered in everyday life. The following examples can help illustrate relative magnitudes; these are meant to be examples only, not a comprehensive list of possible radiation doses. An "acute dose" is one that occurs over a short and finite period of time, while a "chronic dose" is a dose that continues for an extended period of time so that it is better described by a dose rate. | 0 | Theoretical and Fundamental Chemistry |
In case (d), the rotational coupling between and is much stronger than the electrostatic coupling of to the internuclear axis. Thus we form by coupling and and the form by coupling and .
The good quantum numbers in case (d) are , , , , and . Because is a good quantum number, the rotational energy is simply . | 0 | Theoretical and Fundamental Chemistry |
Her awards and honors include;
* 2019 AAAS IF/THEN Ambassador
* 2019 Young Observer Award at the 50th IUPAC General Assembly and 47th World Chemistry Congress in Paris, France
* 2020 American Chemical Society Grady-Stack award for her public engagement excellence
*BBC Science Focus named her one of six women changing chemistry in February 2021
*2023 Research Corporation for Science Advancement’s Robert Holland Jr. Award for Research Excellence and Contributions to Diversity, Equity, and Inclusion | 0 | Theoretical and Fundamental Chemistry |
The Knudsen layer thickness can be approximated by , given by
where is Boltzmann's constant, is the temperature, is the molecular diameter and is the pressure. | 1 | Applied and Interdisciplinary Chemistry |
Radical elimination can be viewed as the reverse of radical addition. In radical elimination, an unstable radical compound breaks down into a spin-paired molecule and a new radical compound. Shown below is an example of a radical elimination reaction, where a benzoyloxy radical breaks down into a phenyl radical and a carbon dioxide molecule. | 1 | Applied and Interdisciplinary Chemistry |
Most self-healing hydrogels rely on electrostatic attraction to spontaneously create new bonds. The electrostatic attraction can be masked using protonation of the polar functional groups. When the pH is raised the polar functional groups become deprotonated, freeing the polar functional group to react.
Since the hydrogels rely on electrostatic attraction for self-healing, the process can be affected by electrostatic screening. The effects of a change in salinity can be modeled using the Gouy-Chapman-Stern theory Double Layer .
* : Zeta Potential
*: Salinity of solution
*: Distance between molecules, if the polar functional group is one molecule and an ion in solution is the other.
To calculate the Gouy-Chapmanm potential, the salinity factor must be calculated. The expression given for the salinity factor is as follows:
*: Charge of ion
*: 1.6 * 10^{-19} C
*: Number of ions per cubic meter
*: Dielectric constant of solvent
*: 8.85 * 10^{-12} C^2/(J*m), the permittivity of free space
*: 1.38 * 10^{-23} m^2 kg/(s^2), Boltzmann Constant
*: Temperature in kelvins
These effects become important when considering the application of self-healing hydrogels to the medical field. They will be affected by the pH and salinity of blood.
These effects also come into play during synthesis when trying to add large hydrophobes to a hydrophilic polymer backbone. A research group from the Istanbul Technical University has shown that large hydrophobes can be added by adding an electrolyte in a sufficient amount. During synthesis, the hydrophobes were held in micelles before attaching to the polymer backbone. By increasing the salinity of the solution, the micelles were able to grow and encompass more hydrophobes. If there are more hydrophobes in a micelle, then the solubility of the hydrophobe increases. The increase in the solubility lead to an increase in the formation of hydrogels with large hydrophobes. | 0 | Theoretical and Fundamental Chemistry |
The width of the diffraction peaks are found to broaden at higher Bragg angles. This angular dependency was originally represented by
where , , and are the half-width parameters and may be refined during the fit. | 0 | Theoretical and Fundamental Chemistry |
The Schilling test has multiple stages. As noted below, it can be done at any time after vitamin B supplementation and body store replacement, and some clinicians recommend that in severe deficiency cases, at least several weeks of vitamin repletion be done before the test (more than one B shot, and also oral folic acid), in order to ensure that impaired absorption of B (with or without intrinsic factor) is not occurring due to damage to the intestinal mucosa from the B and folate deficiency themselves. | 1 | Applied and Interdisciplinary Chemistry |
Benedetto Castelli, and Evangelista Torricelli, two of the disciples of Galileo, applied the discoveries of their master to the science of hydrodynamics. In 1628 Castelli published a small work, Della misura dell acque correnti, in which he satisfactorily explained several phenomena in the motion of fluids in rivers and canals; but he committed a great paralogism in supposing the velocity of the water proportional to the depth of the orifice below the surface of the vessel. Torricelli, observing that in a jet where the water rushed through a small ajutage it rose to nearly the same height with the reservoir from which it was supplied, imagined that it ought to move with the same velocity as if it had fallen through that height by the force of gravity, and hence he deduced the proposition that the velocities of liquids are as the square root of the head, apart from the resistance of the air and the friction of the orifice. This theorem was published in 1643, at the end of his treatise De motu gravium projectorum', and it was confirmed by the experiments of Raffaello Magiotti on the quantities of water discharged from different ajutages under different pressures (1648). | 1 | Applied and Interdisciplinary Chemistry |
Southern Research's Energy & Environment division focuses on technology for clean energy, clean air, and clean water. Southern Research develops and tests air and water emissions control technologies for leading utilities, industrial manufacturers, municipal water utilities, and related trade organizations. The division has also historically partnered with private sector firms and government agencies to develop new technologies that transform energy generation, chemical synthesis, and air and water purification. | 1 | Applied and Interdisciplinary Chemistry |
The Society for Mining, Metallurgy & Exploration publishes the monthly magazine Mining Engineering since 1949. | 1 | Applied and Interdisciplinary Chemistry |
Herbicide use generally has negative impacts on many aspects of the environment. Insects, non-targeted plants, animals, and aquatic systems subject to serious damage from herbicides. Impacts are highly variable. | 1 | Applied and Interdisciplinary Chemistry |
15% of the world's production of vanillin is produced from lignosulfonates, a byproduct from the manufacture of cellulose via the sulfite process. The sole producer of wood-based vanillin is the company Borregaard located in Sarpsborg, Norway.
Wood-based vanillin is produced by copper-catalyzed oxidation of the lignin structures in lignosulfonates under alkaline conditions and is claimed by the manufacturing company to be preferred by their customers due to, among other reasons, its much lower carbon footprint than petrochemically synthesized vanillin. | 0 | Theoretical and Fundamental Chemistry |
Red mud is the waste product that is produced in the digestion of bauxite with sodium hydroxide. It has high calcium and sodium hydroxide content with a complex chemical composition, and accordingly is very caustic and a potential source of pollution. The amount of red mud produced is considerable, and this has led scientists and refiners to seek uses for it. It has received attention as a possible source of vanadium. Due to the low extraction yield much of the gallium ends up in the aluminium oxide as an impurity and in the red mud.
One use of red mud is in ceramic production. Red mud dries into a fine powder that contains iron, aluminium, calcium and sodium. It becomes a health risk when some plants use the waste to produce aluminium oxides.
In the United States, the waste is disposed in large impoundments, a sort of reservoir created by a dam. The impoundments are typically lined with clay or synthetic liners. The US does not approve of the use of the waste due to the danger it poses to the environment. The EPA identified high levels of arsenic and chromium in some red mud samples. | 1 | Applied and Interdisciplinary Chemistry |
The first catalysts for the dehydrogenation of ABs were derived from reduction of Rh(I) complexes to form the active colloidal heterogeneous catalyst. As in the case with the metal carbonyl catalysts, bulky secondary amine-boranes form monomeric aminoboranes. For RhL- and Rh(H)L-derived catalysts, the active species is a homogeneous catalyst, with the phosphine ligands interacting directly with the dehydrocoupling process. Changing the phosphine ligands from PPr to PBu significantly increases the turnover rate of the catalyst. Unlike other Rh(I) catalysts, the rhodium analogue of Wilkinson's catalyst RhCl(PHCy) (Cy=cyclohexyl) behaves like the RhL and Rh(H)L catalysts as a homogeneous species.
In comparison to RhCl(PHCy), the iridium analogue has reduced catalytic activity on the dehydrogenation of non sterically hindered amine-boranes, and increased activity on more sterically hindered substrates. Dehydrocoupling of primary diborazanes NHR—BH—NHR—BH can be catalyzed by via conversion to the metal-bound species MeNH—BH and subsequent polymerization/oligomerization. This same reaction has been found to occur in the absence of the iridium metal, upon heating of the reaction mixture. Dehydrogenation of ammonia-borane with Brookhart's catalyst results in quantitative formation of the cyclic pentamer [NHBH] rather than the typically seen cyclic dimers from other amine-borane dehydrogenations. When catalyzing ammonia-borane dehydrogenation, the catalyst acts homogeneously at a 0.5 mol% catalyst loading. Rather than the typical high temperatures needed for this dehydrogenation, the reaction proceeds cleanly at room temperature, with complete substrate conversion in 14min. | 0 | Theoretical and Fundamental Chemistry |
Elsholz et al. (2012), showed that McsB and YwlE are a protein arginine kinase and phosphatase, rather than a tyrosine kinase and phosphatase because they observed only an McsB/YwlE-dependent detection of protein arginine phosphorylation or dephosphorylation in vivo. Specifically, they suggested that YwIE acts as a PAP in vivo.
McsB and YwlE were thought to be tyrosine kinases and phosphatases. However, in 2012, Elsholz et al. detected 121 arginine phosphorylation sites in 87 proteins in living Bacillus Subtilis (B.subtillis), a gram-positive bacterium present in soil and human gastrointestinal tract. Their observations led them to believe that protein arginine phosphorylation exists in vivo as a posttranslational modification in bacteria. The arginine-phosphorylated proteins they detected were distributed among "distinct physiological classes of proteins" such as regulators, metabolic enzymes, stress, and ribosomal proteins. This result suggested that YwlE acts as a protein arginine phosphatase that explicitly dephosphorylates arginine residues both in vitro and in vivo
Secondly, Elsholz et al. (2012) were only able to detect protein arginine phosphorylation in a YwIE mutant gene and not the wild-type strain. But protein phosphorylates on either serine, threonine, or tyrosine were detected in both wild-type and a YwIE mutant strain in equal amounts. Therefore, they thought that YwIE might solely act as a protein arginine phosphatase. That is, the detection of protein arginine phosphorylation depended on the presence of YwIE. They confirmed this hypothesis after failing to detect protein arginine phosphorylation after (1) analyzing a mutant extract treated in vitro with purified YwIE protein before conducting mass spectroscopy analysis; and (2) overexpressing the YwIE in trans in a YwIE mutant in-vivo. The close interaction of the arginine phosphorylated proteins with YwIE suggested that the stability of the modifications was indeed influenced by the YwIE protein. | 1 | Applied and Interdisciplinary Chemistry |
A spouted bed is used in drying and coating. It involves spraying a liquid into a bed packed with the solid to be coated. A fluidizing gas fed from the bottom of the bed causes a spout, which causes the solids to circle linearly around the liquid. Work has been undertaken to model the minimum velocity of gas required for spouting in a spouted bed, including the use of artificial neural networks. Testing with such models found that Archimedes number is a parameter that has a very large effect on the minimum spouting velocity. | 1 | Applied and Interdisciplinary Chemistry |
When a photon hits a piece of semiconductor, one of three things can happen:
# The photon can pass straight through the semiconductor — this (generally) happens for lower energy photons.
# The photon can reflect off the surface.
# The photon can be absorbed by the semiconductor if the photon energy is higher than the band gap value. This generates an electron-hole pair and sometimes heat depending on the band structure.
When a photon is absorbed, its energy is given to an electron in the crystal lattice. Usually this electron is in the valence band. The energy given to the electron by the photon "excites" it into the conduction band where it is free to move around within the semiconductor. The network of covalent bonds that the electron was previously a part of now has one fewer electron. This is known as a hole, and it has positive charge. The presence of a missing covalent bond allows the bonded electrons of neighboring atoms to move into the "hole", leaving another hole behind, thus propagating holes throughout the lattice in the opposite direction to the movement of the negatively electrons. It can be said that photons absorbed in the semiconductor create electron-hole pairs.
A photon only needs to have energy greater than that of the band gap in order to excite an electron from the valence band into the conduction band. However, the solar frequency spectrum approximates a black body spectrum at about 5,800 K, and as such, much of the solar radiation reaching the Earth is composed of photons with energies greater than the band gap of silicon (1.12eV), which is near to the ideal value for a terrestrial solar cell (1.4eV). These higher energy photons will be absorbed by a silicon solar cell, but the difference in energy between these photons and the silicon band gap is converted into heat (via lattice vibrations — called phonons) rather than into usable electrical energy. | 0 | Theoretical and Fundamental Chemistry |
The following genes encode the polypeptide components for various acid phosphatase isoenzymes:
*ACP1
*ACP2
*ACPP (ACP3), prostatic acid phosphatase
*ACP5, tartrate-resistant acid phosphatase
*ACP6
*ACPT, testicular acid phosphatase
*Tissue acid phosphatase, or lysosomal acid phosphatase | 1 | Applied and Interdisciplinary Chemistry |
[RhH(CO)(PPh)] was first prepared by the reduction of [RhCl(CO)(PPh)], e.g. with sodium tetrahydroborate, or triethylamine and hydrogen, in ethanol in the presence of excess triphenylphosphine:
:[RhCl(CO)(PPh)] + NaBH + PPh → [RhH(CO)(PPh)] + NaCl + BH
It can also be prepared from an aldehyde, rhodium trichloride and triphenylphosphine in basic alcoholic media. | 0 | Theoretical and Fundamental Chemistry |
Solid-state NMR spectroscopy serves as an effective analytical tool in biological, organic, and inorganic chemistry due to its close resemblance to liquid-state spectra while providing additional insights into anisotropic interactions.
It is used to characterize chemical composition, supramolecular structure, local motions, kinetics, and thermodynamics, with the special ability to assign the observed behavior to specific sites in a molecule. It is also crucial in the area of surface and interfacial chemistry. | 0 | Theoretical and Fundamental Chemistry |
The idea of creating "a library of reference and a chemical museum" in the United States can be found in the Proceedings of the first meeting of the American Chemical Society (ACS) in 1876.
The idea of a Science History Institute dates to 1976, when the nations bicentennial and the ACS centennial stimulated interest in history and chemistry. As part of the ACS centennial activities, John H. Wotiz of its history-of-chemistry division organized a session on the history of chemistry; he was a strong proponent of a national center for historical chemistry. | 1 | Applied and Interdisciplinary Chemistry |
The density of aluminium granules ranges from 1.0 to 1.8 g/cm and is much higher compared to aluminium powder. | 1 | Applied and Interdisciplinary Chemistry |
E–Z configuration, or the E–Z convention, is the IUPAC preferred method of describing the absolute stereochemistry of double bonds in organic chemistry. It is an extension of cis–trans isomer notation (which only describes relative stereochemistry) that can be used to describe double bonds having two, three or four substituents. E and Z notation are only used when a compound doesn't have two identical substituents.
Following the Cahn–Ingold–Prelog priority rules (CIP rules), each substituent on a double bond is assigned a priority, then positions of the higher of the two substituents on each carbon are compared to each other. If the two groups of higher priority are on opposite sides of the double bond (trans to each other), the bond is assigned the configuration E (from entgegen, , the German word for "opposite"). If the two groups of higher priority are on the same side of the double bond (cis to each other), the bond is assigned the configuration Z (from zusammen, , the German word for "together").
The letters E and Z are conventionally printed in italic type, within parentheses, and separated from the rest of the name with a hyphen. They are always printed as full capitals (not in lowercase or small capitals), but do not constitute the first letter of the name for English capitalization rules (as in the example above).
Another example: The CIP rules assign a higher priority to bromine than to chlorine, and a higher priority to chlorine than to hydrogen, hence the following (possibly counterintuitive) nomenclature.
For organic molecules with multiple double bonds, it is sometimes necessary to indicate the alkene location for each E or Z symbol. For example, the chemical name of alitretinoin is (2E,4E,6Z,8E)-3,7-dimethyl-9-(2,6,6-trimethyl-1-cyclohexenyl)nona-2,4,6,8-tetraenoic acid, indicating that the alkenes starting at positions 2, 4, and 8 are E while the one starting at position 6 is Z. | 0 | Theoretical and Fundamental Chemistry |
A solution describes a homogeneous mixture where the dispersed particles will not settle if the solution is left undisturbed for a prolonged period of time.
A colloid is a heterogeneous mixture where the dispersed particles have at least in one direction a dimension roughly between 1 nm and 1 µm or that in a system discontinuities are found at distances of that order.
A suspension is a heterogeneous dispersion of larger particles in a medium. Unlike solutions and colloids, if left undisturbed for a prolonged period of time, the suspended particles will settle out of the mixture.
Although suspensions are relatively simple to distinguish from solutions and colloids, it may be difficult to distinguish solutions from colloids since the particles dispersed in the medium may be too small to distinguish by the human eye. Instead, the Tyndall effect is used to distinguish solutions and colloids. Due to the various reported definitions of solutions, colloids, and suspensions provided in the literature, it is difficult to label each classification with a specific particle size range. The International Union of Pure and Applied Chemistry attempts to provide a standard nomenclature for colloids as particles in a size range having a dimension roughly between 1 nm and 1 µm.
In addition to the classification by particle size, dispersions can also be labeled by the combination of the dispersed phase and the medium phase that the particles are suspended in. Aerosols are liquids dispersed in a gas, sols are solids in liquids, emulsions are liquids dispersed in liquids (more specifically a dispersion of two immiscible liquids), and gels are liquids dispersed in solids. | 0 | Theoretical and Fundamental Chemistry |
Phred uses a four-phase procedure as outlined by Ewing et al. to determine a sequence of base calls from the processed DNA sequence tracing:
# Predicted peak locations are determined, based on the assumption that fragments are relatively evenly spaced, on average, in most regions of the gel, to determine the correct number of bases and their idealized evenly spaced locations in regions where the peaks are not well resolved, noisy, or displaced (as in compressions)
# Observed peaks are identified in the trace
# Observed peaks are matched to the predicted peak locations, omitting some peaks and splitting others; as each observed peak comes from a specific array and is thus associated with 1 of the 4 bases (A, G, T, or C), the ordered list of matched observed peaks determines a base sequence for the trace.
# The unmatched observed peaks are checked for any peak that appears to represent a base but could not be assigned to a predicted peak in the third phase and if found, the corresponding base is inserted into the read sequence.
The entire procedure is rapid, usually taking less than half a second per trace. The results can be output as a PHD file, which contains base data as triples consisting of the base call, quality, and position. | 1 | Applied and Interdisciplinary Chemistry |
When dissolved in water, the dye has a blue-violet colour with an absorbance maximum at 590 nm and an extinction coefficient of 87,000 M cm. The colour of the dye depends on the acidity of the solution. At a pH of +1.0, the dye is green with absorption maxima at 420 nm and 620 nm, while in a strongly acidic solution (pH −1.0), the dye is yellow with an absorption maximum at 420 nm.
The different colours are a result of the different charged states of the dye molecule. In the yellow form, all three nitrogen atoms carry a positive charge, of which two are protonated, while the green colour corresponds to a form of the dye with two of the nitrogen atoms positively charged. At neutral pH, both extra protons are lost to the solution, leaving only one of the nitrogen atoms positive charged. The pK for the loss of the two protons are approximately 1.15 and 1.8.
In alkaline solutions, nucleophilic hydroxyl ions attack the electrophilic central carbon to produce the colourless triphenylmethanol or carbinol form of the dye. Some triphenylmethanol is also formed under very acidic conditions when the positive charges on the nitrogen atoms lead to an enhancement of the electrophilic character of the central carbon, which allows the nucleophilic attack by water molecules. This effect produces a slight fading of the yellow colour. | 0 | Theoretical and Fundamental Chemistry |
This method uses a rod which is lowered into a test liquid. The rod is then pulled out of the liquid and the force required to pull the rod is precisely measured. The method isn't standardized but is sometimes used. The Du Noüy-Padday rod pull tensiometer will take measurements quickly and will work with liquids with a wide range of viscosities. Interfacial tensions cannot be measured. | 0 | Theoretical and Fundamental Chemistry |
Elections for membership are held annually with candidates for membership being nominated and elected exclusively by existing EMBO members, membership cannot be applied for directly. Three types of membership exist:
# EMBO Member, for scientists living (or who have lived) in a European Molecular Biology Conference (EMBC) Member State
# EMBO Associate Member, for scientists living outside of the EMBC Member States
# EMBO Young Investigator | 1 | Applied and Interdisciplinary Chemistry |
A biomolecular complex, also called a biomacromolecular complex, is any biological complex made of more than one biopolymer (protein, RNA, DNA,
carbohydrate) or large non-polymeric biomolecules (lipid). The interactions between these biomolecules are non-covalent.
Examples:
* Protein complexes, some of which are multienzyme complexes: proteasome, DNA polymerase III holoenzyme, RNA polymerase II holoenzyme, symmetric viral capsids, chaperonin complex GroEL-GroES, photosystem I, ATP synthase, ferritin.
* RNA-protein complexes: ribosome, spliceosome, vault, SnRNP. Such complexes in cell nucleus are called ribonucleoproteins (RNPs).
* DNA-protein complexes: nucleosome.
* Protein-lipid complexes: lipoprotein.
The biomacromolecular complexes are studied structurally by X-ray crystallography, NMR spectroscopy of proteins, cryo-electron microscopy and successive single particle analysis, and electron tomography.
The atomic structure models obtained by X-ray crystallography and biomolecular NMR spectroscopy can be docked into the much larger structures of biomolecular complexes obtained by lower resolution techniques like electron microscopy, electron tomography, and small-angle X-ray scattering.
Complexes of macromolecules occur ubiquitously in nature, where they are involved in the construction of viruses and all living cells. In addition, they play fundamental roles in all basic life processes (protein translation, cell division, vesicle trafficking, intra- and inter-cellular exchange of material between compartments, etc.). In each of these roles, complex mixtures of become organized in specific structural and spatial ways. While the individual macromolecules are held together by a combination of covalent bonds and intramolecular non-covalent forces (i.e., associations between parts within each molecule, via charge-charge interactions, van der Waals forces, and dipole–dipole interactions such as hydrogen bonds), by definition MAs themselves are held together solely via the noncovalent forces, except now exerted between molecules (i.e., intermolecular interactions). | 1 | Applied and Interdisciplinary Chemistry |
Sulfimides (also called a sulfilimines) are sulfur–nitrogen compounds of structure RS=NR′, the nitrogen analog of sulfoxides. They are of interest in part due to their pharmacological properties. When two different R groups are attached to sulfur, sulfimides are chiral. Sulfimides form stable α-carbanions.
Sulfoximides (also called sulfoximines) are tetracoordinate sulfur–nitrogen compounds, isoelectronic with sulfones, in which one oxygen atom of the sulfone is replaced by a substituted nitrogen atom, e.g., RS(O)=NR′. When two different R groups are attached to sulfur, sulfoximides are chiral. Much of the interest in this class of compounds is derived from the discovery that methionine sulfoximide (methionine sulfoximine) is an inhibitor of glutamine synthetase.
Sulfonediimines (also called sulfodiimines, sulfodiimides or sulfonediimides) are tetracoordinate sulfur–nitrogen compounds, isoelectronic with sulfones, in which both oxygen atoms of the sulfone are replaced by a substituted nitrogen atom, e.g., RS(=NR′). They are of interest because of their biological activity and as building blocks for heterocycle synthesis. | 0 | Theoretical and Fundamental Chemistry |
Fluorene, the repeat unit in polyfluorene derivatives, was isolated from coal tar and discovered by Marcellin Berthelot prior to 1883.
Its name originates from its interesting fluorescence (and not to fluorine, which is not one of its elements).
Fluorene became the subject of chemical-structure related color variation (visible rather than luminescent), among other things, throughout the early to mid-20th century. Since it was an interesting chromophore researchers wanted to understand which parts of the molecule were chemically reactive, and how substituting these sites influenced the color. For instance, by adding various electron donating or electron accepting moieties to fluorene, and by reacting with bases, researchers were able to change the color of the molecule.
The physical properties of the fluorene molecule were recognizably desirable for polymers; as early as the 1970s researchers began incorporating this moiety into polymers. For instance, because of fluorene’s rigid, planar shape a polymer containing fluorene was shown to exhibit enhanced thermo-mechanical stability.
However, more promising was integrating the optoelectronic properties of fluorene into a polymer. Reports of the oxidative polymerization of fluorene (into a fully conjugated form) exist from at least 1972. However, it was not until after the highly publicized high conductivity of doped polyacetylene, presented in 1977 by Heeger, MacDiarmid and Shirakawa, that substantial interest in the electronic properties of conjugated polymers took off.
As interest in conducting plastics grew, fluorene again found application. The aromatic nature of fluorene makes it an excellent candidate component of a conducting polymer because it can stabilize and conduct a charge; in the early 1980s fluorene was electropolymerized into conjugated polymer films with conductivities of 10 S cm.
The optical properties (such as variable luminescence and visible light spectrum absorption) that accompany the extended conjugation in polymers of fluorene have become increasingly attractive for device applications. Throughout the 1990s and into the 2000s, many devices such as organic light-emitting diodes (OLEDs), organic solar cells., organic thin film transistors, and biosensors have all taken advantage of the luminescent, electronic and absorptive properties of polyfluorenes. | 0 | Theoretical and Fundamental Chemistry |
Soundproofing is any means of impeding sound propagation. There are several basic ways to reduce sound: increasing the distance between source and receiver, decoupling, using noise barriers to reflect or absorb the energy of the sound waves, using damping structures such as sound baffles for absorption, or using active antinoise sound generators.
Acoustic quieting and noise control can be used to limit unwanted noise. Soundproofing can reduce the transmission of unwanted direct sound waves from the source to an involuntary listener through the use of distance and intervening objects in the sound path (see sound transmission class and sound reduction index).
Soundproofing can suppress unwanted indirect sound waves such as reflections that cause echoes and resonances that cause reverberation. | 1 | Applied and Interdisciplinary Chemistry |
The covalent pair-wise interaction between boronic acids and hydroxy groups as found in alcohols and acids is rapid and reversible in aqueous solutions. The equilibrium established between boronic acids and the hydroxyl groups present on saccharides has been successfully employed to develop a range of sensors for saccharides. One of the key advantages with this dynamic covalent strategy lies in the ability of boronic acids to overcome the challenge of binding neutral species in aqueous media. If arranged correctly, the introduction of a tertiary amine within these supramolecular systems will permit binding to occur at physiological pH and allow signalling mechanisms such as photoinduced electron transfer mediated fluorescence emission to report the binding event.
Potential applications for this research include blood glucose monitoring systems to help manage diabetes mellitus. As the sensors employ an optical response, monitoring could be achieved using minimally invasive methods, one such example is the investigation of a contact lens that contains a boronic acid based sensor molecule to detect glucose levels within ocular fluids. | 0 | Theoretical and Fundamental Chemistry |
Mitochondria and plastids evolved from free-living prokaryotes into current cytoplasmic organelles through endosymbiotic evolution. Mitochondria are thought to be necessary for eukaryotic life to exist. They are known as the cell's powerhouses because they provide the majority of the energy or ATP required by the cell. The mitochondrial genome (mtDNA) is replicated separately from the host genome. Human mtDNA codes for 13 proteins, most of which are involved in oxidative phosphorylation (OXPHOS). The nuclear genome encodes the remaining mitochondrial proteins, which are then transported into the mitochondria. The genomes of these organelles have become far smaller than those of their free-living predecessors. This is mostly due to the widespread transfer of genes from prokaryote progenitors to the nuclear genome, followed by their elimination from organelle genomes. In evolutionary timescales, the continuous entry of organelle DNA into the nucleus has provided novel nuclear genes. Furthermore, Mitochondria depend on nuclear genes for essential protein production as they cannot generate all necessary proteins independently. | 1 | Applied and Interdisciplinary Chemistry |
A cubane-type cluster is an arrangement of atoms in a molecular structure that forms a cube. In the idealized case, the eight vertices are symmetry equivalent and the species has O symmetry. Such a structure is illustrated by the hydrocarbon cubane. With chemical formula , cubane has carbon atoms at the corners of a cube and covalent bonds forming the edges. Most cubanes have more complicated structures, usually with nonequivalent vertices. They may be simple covalent compounds or macromolecular or supramolecular cluster compounds. | 0 | Theoretical and Fundamental Chemistry |
Work is progressing on bypassing the conventional route of atomising wrought feedstock or sponge and the inherent cost associated with the traditional Kroll process. Several of these processes, such as the FFC, MER Corporation, OS, Ginatta and BHP Billiton processes rely on the electrolytic reduction of TiO (a cheap and abundant material) to form Ti metal. So far, no material from these processes has been sold commercially on the open market, and cost models have yet to be published, but they offer the possibility of inexpensive titanium powder in the near future. The countries that have such facilities to generate Titanium Sponge are Saudi Arabia, China, Japan, Russia, Kazakhstan, the USA, Ukraine and India. The Titanium Sponge Plant in India is the only one in the world that can undertake all the different activities of manufacturing aerospace grade titanium sponge under one roof. | 1 | Applied and Interdisciplinary Chemistry |
Atmospheric pollutant concentrations expressed as mass per unit volume of atmospheric air (e.g., mg/m, µg/m, etc.) at sea level will decrease with increasing altitude because the atmospheric pressure decreases with increasing altitude.
The change of atmospheric pressure with altitude can be obtained from this equation:
Given an atmospheric pollutant concentration at an atmospheric pressure of 1 atmosphere (i.e., at sea level altitude), the concentration at other altitudes can be obtained from this equation:
As an example, given a concentration of 260 mg/m at sea level, calculate the equivalent concentration at an altitude of 1,800 meters:
C = 260 × 0.9877 = 208 mg/m at 1,800 meters altitude | 1 | Applied and Interdisciplinary Chemistry |
Another common system uses Greek letter prefixes as locants, which is useful in identifying the relative location of carbon atoms as well as hydrogen atoms to other functional groups.
The α-carbon (alpha-carbon) refers to the first carbon atom that attaches to a functional group, such as a carbonyl. The second carbon atom is called the β-carbon (beta-carbon), the third is the γ-carbon (gamma-carbon), and the naming system continues in alphabetical order.
The nomenclature can also be applied to the hydrogen atoms attached to the carbon atoms. A hydrogen atom attached to an α-carbon is called an α-hydrogen, a hydrogen atom on the β-carbon is a β-hydrogen, and so on.
Organic molecules with more than one functional group can be a source of confusion. Generally the functional group responsible for the name or type of the molecule is the reference group for purposes of carbon-atom naming. For example, the molecules nitrostyrene and phenethylamine are quite similar; the former can even be reduced into the latter. However, nitrostyrene's α-carbon atom is adjacent to the phenyl group; in phenethylamine this same carbon atom is the β-carbon atom, as phenethylamine (being an amine rather than a styrene) counts its atoms from the opposite "end" of the molecule. | 0 | Theoretical and Fundamental Chemistry |
* 1971 – M.L. Lieberman reports growth of three different graphitic like filaments; tubular, twisted, and balloon like. TEM images and diffraction data shows that the hollow tubes are multi-walled carbon nanotubes (MWCNT).
* 1976 – A. Oberlin, Morinobu Endo, and T. Koyama reported CVD (Chemical Vapor Deposition) growth of nanometer-scale carbon fibers, and they also reported the discovery of carbon nanofibers, including that some were shaped as hollow tubes.
* 1979 – Arthur C. Clarkes science fiction novel The Fountains of Paradise popularizes the idea of a space elevator using "a continuous pseudo-one dimensional diamond crystal'". | 1 | Applied and Interdisciplinary Chemistry |
Zinc is an essential trace element for humans and other animals, for plants and for microorganisms. Zinc is required for the function of over 300 enzymes and 1000 transcription factors, and is stored and transferred in metallothioneins. It is the second most abundant trace metal in humans after iron and it is the only metal which appears in all enzyme classes.
In proteins, zinc ions are often coordinated to the amino acid side chains of aspartic acid, glutamic acid, cysteine and histidine. The theoretical and computational description of this zinc binding in proteins (as well as that of other transition metals) is difficult.
Roughly grams of zinc are distributed throughout the human body. Most zinc is in the brain, muscle, bones, kidney, and liver, with the highest concentrations in the prostate and parts of the eye. Semen is particularly rich in zinc, a key factor in prostate gland function and reproductive organ growth.
Zinc homeostasis of the body is mainly controlled by the intestine. Here, ZIP4 and especially TRPM7 were linked to intestinal zinc uptake essential for postnatal survival.
In humans, the biological roles of zinc are ubiquitous. It interacts with "a wide range of organic ligands", and has roles in the metabolism of RNA and DNA, signal transduction, and gene expression. It also regulates apoptosis. A review from 2015 indicated that about 10% of human proteins (~3000) bind zinc, in addition to hundreds more that transport and traffic zinc; a similar in silico study in the plant Arabidopsis thaliana found 2367 zinc-related proteins.
In the brain, zinc is stored in specific synaptic vesicles by glutamatergic neurons and can modulate neuronal excitability. It plays a key role in synaptic plasticity and so in learning. Zinc homeostasis also plays a critical role in the functional regulation of the central nervous system. Dysregulation of zinc homeostasis in the central nervous system that results in excessive synaptic zinc concentrations is believed to induce neurotoxicity through mitochondrial oxidative stress (e.g., by disrupting certain enzymes involved in the electron transport chain, including complex I, complex III, and α-ketoglutarate dehydrogenase), the dysregulation of calcium homeostasis, glutamatergic neuronal excitotoxicity, and interference with intraneuronal signal transduction. L- and D-histidine facilitate brain zinc uptake. SLC30A3 is the primary zinc transporter involved in cerebral zinc homeostasis. | 1 | Applied and Interdisciplinary Chemistry |
Butyric acid (pK 4.82) is fully ionized at physiological pH, so its anion is the material that is mainly relevant in biological systems.
It is one of two primary endogenous agonists of human hydroxycarboxylic acid receptor 2 (, also known as GPR109A), a G protein-coupled receptor (GPCR),
Like other short-chain fatty acids (SCFAs), butyrate is an agonist at the free fatty acid receptors FFAR2 and FFAR3, which function as nutrient sensors that facilitate the homeostatic control of energy balance; however, among the group of SCFAs, only butyrate is an agonist of HCA. It is also an HDAC inhibitor (specifically, HDAC1, HDAC2, HDAC3, and HDAC8), a drug that inhibits the function of histone deacetylase enzymes, thereby favoring an acetylated state of histones in cells. Histone acetylation loosens the structure of chromatin by reducing the electrostatic attraction between histones and DNA. In general, it is thought that transcription factors will be unable to access regions where histones are tightly associated with DNA (i.e., non-acetylated, e.g., heterochromatin). Therefore, butyric acid is thought to enhance the transcriptional activity at promoters, which are typically silenced or downregulated due to histone deacetylase activity. | 1 | Applied and Interdisciplinary Chemistry |
Chloroplasts alone make almost all of a plant cell's amino acids in their stroma except the sulfur-containing ones like cysteine and methionine. Cysteine is made in the chloroplast (the proplastid too) but it is also synthesized in the cytosol and mitochondria, probably because it has trouble crossing membranes to get to where it is needed. The chloroplast is known to make the precursors to methionine but it is unclear whether the organelle carries out the last leg of the pathway or if it happens in the cytosol. | 0 | Theoretical and Fundamental Chemistry |
Types of living soil biota can be divided into categories of plants (flora), animals (fauna), and microorganisms. Plants play a role in soil chemistry by exchanging nutrients with microorganisms and absorbing nutrients, creating concentration gradients of cations and anions. In addition to this, the differences in water potential created by plants influence water movement in soil, which affects the form and transportation of various particles. Vegetative cover on the soil surface greatly reduces erosion, which in turn prevents compaction and helps to maintain aeration in the soil pore space, providing oxygen and carbon to the biota and cation exchange sites that depend on it (Peri et al., 2022).
Animals are essential to soil chemistry, as they regulate the cycling of nutrients and energy into different forms. This is primarily done through food webs. Some types of soil animals can be found below.
* Detritivores
** Examples include millipedes, woodlice, and dung beetles
* Decomposers
** Examples include fungi, earthworms, and bacteria
* Protozoans
** Examples include amoeba, euglena, and paramecium
Soil microbes play a major role in a multitude of biological and chemical activities that take place in soil. These microorganisms are said to make up around 1,000–10,000 kg of biomass per hectare in some soils (García-Sánchez, 2016). They are mostly recognized for their association with plants. The most well-known example of this is mycorrhizae, which exchange carbon for nitrogen with plant roots in a symbiotic relationship. Additionally, microbes are responsible for the majority of respiration that takes place in the soil, which has implications for the release of gases like methane and nitrous oxide from soil (giving it significance in discussion of climate change) (Frouz et al., 2020). Given the significance of the effects of microbes on their environment, the conservation and promotion of microbial life is often desired by many plant growers, conservationists, and ecologists. | 0 | Theoretical and Fundamental Chemistry |
Typically, metallacycles are cyclic compounds with two metal carbon bonds.
Many compounds containing metals in rings are known, for example chelate rings. Usually, such compounds are not classified as metallacycles, but the naming conventions are not rigidly followed. Within the area of coordination chemistry and supramolecular chemistry, examples include metallacrowns, metallacryptands, metallahelices, and molecular wheels. | 0 | Theoretical and Fundamental Chemistry |
One study that was done by Royal College of Surgeons (RCS) in rat model shows that a recessive mutation in a receptor tyrosine kinase gene, mertk results in a premature stop codon and impaired phagocytosis function by RPE cells. This mutation causes the accumulation of outer segment debris in the subretinal space, which causes photoreceptor cell death. The model organism with this disease received a subretinal injection of AAV serotype 2 carrying a mouse Mertk cDNA under the control of either the CMV or RPE65 promoters. This treatment was found to prolong photoreceptor cell survival for several months and also the number of photoreceptor was 2.5 fold higher in AAV-Mertk- treated eyes compared with controls 9 weeks after injection, also they found decreased amount of debris in the subretinal space.
The protein RPE65 is used in the retinoid cycle where the all-trans-retinol within the rod outer segment is isomerized to its 11-cis form and oxidized to 11-cis retinal before it goes back to the photoreceptor and joins with opsin molecule to form functional rhodopsin. In animal knockout model (RPE65-/-), gene transfer experiment shows that early intraocular delivery of human RPE65 vector on embryonic day 14 shows efficient transduction of retinal pigment epithelium in the RPE65-/- knockout mice and rescues visual functions. This shows successful gene therapy can be attributed to early intraocular deliver to the diseased animal. | 1 | Applied and Interdisciplinary Chemistry |
The Australian Synroc (synthetic rock) is a more sophisticated way to immobilize such waste, and this process may eventually come into commercial use for civil wastes (it is currently being developed for U.S. military wastes). Synroc was invented by Ted Ringwood, a geochemist at the Australian National University. The Synroc contains pyrochlore and cryptomelane type minerals. The original form of Synroc (Synroc C) was designed for the liquid high-level waste (PUREX raffinate) from a light-water reactor. The main minerals in this Synroc are hollandite (BaAlTiO), zirconolite (CaZrTiO) and perovskite (CaTiO). The zirconolite and perovskite are hosts for the actinides. The strontium and barium will be fixed in the perovskite. The caesium will be fixed in the hollandite. A Synroc waste treatment facility began construction in 2018 at ANSTO. | 0 | Theoretical and Fundamental Chemistry |
The process may be likened to how yeast ferments sugars to produce ethanol for wine, beer, or fuel, but the organisms that carry out the ABE fermentation are strictly anaerobic (obligate anaerobes). The ABE fermentation produces solvents in a ratio of 3 parts acetone, 6 parts butanol to 1 part ethanol. It usually uses a strain of bacteria from the Class Clostridia (Family Clostridiaceae). Clostridium acetobutylicum is the most well-studied and widely used. Although less effective, Clostridium beijerinckii and Clostridium saccharobutylicum bacterial strains have shown good results as well.
The ABE fermentation pathway generally proceeds in two phases. In the initial acidogenesis phase, the cells grow exponentially and accumulate acetate and butyrate. The low pH along with other factors then trigger a metabolic shift to the solventogenesis phase, in which acetate and butyrate are used to produce the solvents.
For gas stripping, the most common gases used are the off-gases from the fermentation itself, a mixture of carbon dioxide and hydrogen gas. | 1 | Applied and Interdisciplinary Chemistry |
Under thermal effect, the end of polymer chain departs, and forms low free radical which has low activity. Then according to the chain reaction mechanism, the polymer loses the monomer one by one. However, the molecular chain doesn't change a lot in a short time. The reaction is shown below. This process is common for polymethymethacrylate (perspex).
CH-C(CH)COOCH-CH-C*(CH)COOCH→CH-C*(CH)COOCH + CH=C(CH)COOCH | 0 | Theoretical and Fundamental Chemistry |
Judd–Ofelt theory is a theory in physical chemistry describing the intensity of electron transitions within the 4f shell of rare-earth ions in solids and solutions.
The theory was introduced independently in 1962 by Brian R. Judd of the University of California, Berkeley, and PhD candidate George S. Ofelt at Johns Hopkins University. Their work was published in Physical Review and the Journal of Chemical Physics, respectively.
Judd and Ofelt did not meet until 2003 at a workshop in Lądek-Zdrój, Poland.
Judd and Ofelts work was cited approximately 2000 times between 1962 and 2004. Brian M. Walsh of NASA Langley places Judd and Ofelts theory at the "forefront" of a 1960s revolution in spectroscopic research on rare-earth ions. | 0 | Theoretical and Fundamental Chemistry |
Microcystinase is a protease that selectively degrades Microcystin, an extremely potent cyanotoxin that results in marine pollution and human and animal food chain poisoning. The enzyme is naturally produced by a number of bacteria isolated in Japan and New Zealand. As of 2012, the chemical structure of this enzyme has not been scientifically determined. The enzyme degrades the cyclic peptide toxin microcystin into a linear peptide, which is 160 times less toxic. Other bacteria then further degrade the linear peptide. | 1 | Applied and Interdisciplinary Chemistry |
Fatty acid metabolism consists of various metabolic processes involving or closely related to fatty acids, a family of molecules classified within the lipid macronutrient category. These processes can mainly be divided into (1) catabolic processes that generate energy and (2) anabolic processes where they serve as building blocks for other compounds.
In catabolism, fatty acids are metabolized to produce energy, mainly in the form of adenosine triphosphate (ATP). When compared to other macronutrient classes (carbohydrates and protein), fatty acids yield the most ATP on an energy per gram basis, when they are completely oxidized to CO and water by beta oxidation and the citric acid cycle. Fatty acids (mainly in the form of triglycerides) are therefore the foremost storage form of fuel in most animals, and to a lesser extent in plants.
In anabolism, intact fatty acids are important precursors to triglycerides, phospholipids, second messengers, hormones and ketone bodies. For example, phospholipids form the phospholipid bilayers out of which all the membranes of the cell are constructed from fatty acids. Phospholipids comprise the plasma membrane and other membranes that enclose all the organelles within the cells, such as the nucleus, the mitochondria, endoplasmic reticulum, and the Golgi apparatus. In another type of anabolism, fatty acids are modified to form other compounds such as second messengers and local hormones. The prostaglandins made from arachidonic acid stored in the cell membrane are probably the best-known of these local hormones. | 1 | Applied and Interdisciplinary Chemistry |
At constant pressure and temperature, the root-mean-square speed and therefore the effusion rate are inversely proportional to the square root of the molecular weight. Gases with a lower molecular weight effuse more rapidly than gases with a higher molecular weight, so that the number of lighter molecules passing through the hole per unit time is greater. | 0 | Theoretical and Fundamental Chemistry |
In biochemistry, glycoside hydrolases (also called glycosidases or glycosyl hydrolases) are a class of enzymes which catalyze the hydrolysis of glycosidic bonds in complex sugars. They are extremely common enzymes, with roles in nature including degradation of biomass such as cellulose (cellulase), hemicellulose, and starch (amylase), in anti-bacterial defense strategies (e.g., lysozyme), in pathogenesis mechanisms (e.g., viral neuraminidases) and in normal cellular function (e.g., trimming mannosidases involved in N-linked glycoprotein biosynthesis). Together with glycosyltransferases, glycosidases form the major catalytic machinery for the synthesis and breakage of glycosidic bonds. | 0 | Theoretical and Fundamental Chemistry |
Eddy permitting and eddy resolving models are used to examine the effect of eddy saturation and eddy compensation in the ACC. In these models resolution is of great importance. Ocean observations do not have a high enough resolution to fully estimate the degree of eddy saturation and eddy compensation. Idealized studies show that the MOC response is more sensitive to model resolution than the ACC transport. A general conclusion in such numerical models is that southward eddy transport in combination with enhanced westerlies results in an increase in EKE. | 1 | Applied and Interdisciplinary Chemistry |
The catalytic cracking process involves the presence of solid acid catalysts, usually silica-alumina and zeolites. The catalysts promote the formation of carbocations, which undergo processes of rearrangement and scission of C-C bonds. Relative to thermal cracking, cat cracking proceeds at milder temperatures, which saves energy. Furthermore, by operating at lower temperatures, the yield of alkenes is diminished. Alkenes cause instability of hydrocarbon fuels.
Fluid catalytic cracking is a commonly used process, and a modern oil refinery will typically include a cat cracker, particularly at refineries in the US, due to the high demand for gasoline. The process was first used around 1942 and employs a powdered catalyst. During WWII, the Allied Forces had plentiful supplies of the materials in contrast to the Axis Forces, which suffered severe shortages of gasoline and artificial rubber. Initial process implementations were based on low activity alumina catalyst and a reactor where the catalyst particles were suspended in a rising flow of feed hydrocarbons in a fluidized bed.
In newer designs, cracking takes place using a very active zeolite-based catalyst in a short-contact time vertical or upward-sloped pipe called the "riser". Pre-heated feed is sprayed into the base of the riser via feed nozzles where it contacts extremely hot fluidized catalyst at . The hot catalyst vaporizes the feed and catalyzes the cracking reactions that break down the high-molecular weight oil into lighter components including LPG, gasoline, and diesel. The catalyst-hydrocarbon mixture flows upward through the riser for a few seconds, and then the mixture is separated via cyclones. The catalyst-free hydrocarbons are routed to a main fractionator for separation into fuel gas, LPG, gasoline, naphtha, light cycle oils used in diesel and jet fuel, and heavy fuel oil.
During the trip up the riser, the cracking catalyst is "spent" by reactions which deposit coke on the catalyst and greatly reduce activity and selectivity. The "spent" catalyst is disengaged from the cracked hydrocarbon vapors and sent to a stripper where it contacts steam to remove hydrocarbons remaining in the catalyst pores. The "spent" catalyst then flows into a fluidized-bed regenerator where air (or in some cases air plus oxygen) is used to burn off the coke to restore catalyst activity and also provide the necessary heat for the next reaction cycle, cracking being an endothermic reaction. The "regenerated" catalyst then flows to the base of the riser, repeating the cycle.
The gasoline produced in the FCC unit has an elevated octane rating but is less chemically stable compared to other gasoline components due to its olefinic profile. Olefins in gasoline are responsible for the formation of polymeric deposits in storage tanks, fuel ducts and injectors. The FCC LPG is an important source of C-C olefins and isobutane that are essential feeds for the alkylation process and the production of polymers such as polypropylene. | 0 | Theoretical and Fundamental Chemistry |
Monoaminergic cell groups refers to collections of neurons in the central nervous system that have been demonstrated by histochemical fluorescence to contain one of the neurotransmitters serotonin, dopamine, norepinephrine or epinephrine. Thus, it represents the combination of catecholaminergic cell groups and serotonergic cell groups. | 1 | Applied and Interdisciplinary Chemistry |
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