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During the synthesis of proteins, polypeptide chains, which are created by ribosomes translating mRNA, must be processed before assuming a mature conformation. The dephosphorylation of proteins is a mechanism for modifying behavior of a protein, often by activating or inactivating an enzyme. Components of the protein synthesis apparatus also undergo phosphorylation and dephosphorylation and thus regulate the rates of protein synthesis.
As part of posttranslational modifications, phosphate groups may be removed from serine, threonine, or tyrosine. As such, pathways of intracellular signal transduction depend on sequential phosphorylation and dephosphorylation of a wide variety of proteins. | 1 | Applied and Interdisciplinary Chemistry |
A biotransducer is the recognition-transduction component of a biosensor system. It consists of two intimately coupled parts; a bio-recognition layer and a physicochemical transducer, which acting together converts a biochemical signal to an electronic or optical signal. The bio-recognition layer typically contains an enzyme or another binding protein such as antibody. However, oligonucleotide sequences, sub-cellular fragments such as organelles (e.g. mitochondria) and receptor carrying fragments (e.g. cell wall), single whole cells, small numbers of cells on synthetic scaffolds, or thin slices of animal or plant tissues, may also comprise the bio-recognition layer. It gives the biosensor selectivity and specificity. The physicochemical transducer is typically in intimate and controlled contact with the recognition layer. As a result of the presence and biochemical action of the analyte (target of interest), a physico-chemical change is produced within the biorecognition layer that is measured by the physicochemical transducer producing a signal that is proportionate to the concentration of the analyte. The physicochemical transducer may be electrochemical, optical, electronic, gravimetric, pyroelectric or piezoelectric. Based on the type of biotransducer, biosensors can be classified as shown to the right. | 1 | Applied and Interdisciplinary Chemistry |
The original German publications described the mounds as having a lifespan of 5–6 years, after which they had to be rebuilt from scratch. | 1 | Applied and Interdisciplinary Chemistry |
R is the ratio of the hadronic cross section to the muon cross section in electron–positron collisions:
where the superscript (0) indicates that the cross section has been corrected for initial state radiation. R is an important input in the calculation of the anomalous magnetic dipole moment. Experimental values have been measured for center-of-mass energies from 400 MeV to 150 GeV.
R also provides experimental confirmation of the electric charge of quarks, in particular the charm quark and bottom quark, and the existence of three quark colors. A simplified calculation of R yields
where the sum is over all quark flavors with mass less than the beam energy. e is the electric charge of the quark, and the factor of 3 accounts for the three colors of the quarks. QCD corrections to this formula have been calculated.
Usually, the denominator in R is not the actual experimental μμ cross section, but the off-resonance theoretical QED cross-section: this makes resonances more visibly dramatic than normalization by the μμ cross section, which is also greatly enhanced at these resonances (hadronic states, and Z boson). | 0 | Theoretical and Fundamental Chemistry |
One of the original experiments performed by Winston and Holness was measuring the rate of oxidation in trans and cis substituted rings using a chromium catalyst. The large tert-butyl group used locks the conformation of each molecule, placing it equatorial (cis compound shown).
It was observed that the cis compound underwent oxidation at a much faster rate than the trans compound. The proposition was that the large hydroxyl group in the axial position was disfavored and formed the carbonyl more readily to relieve this strain. The trans compound had rates identical to those found in the monosubstituted cyclohexanol. | 0 | Theoretical and Fundamental Chemistry |
tert-Butyldimethylsilyl chloride is an organosilicon compound with the formula (MeC)MeSiCl (Me = CH). It is commonly abbreviated as TBSCl or TBDMSCl. It is a chlorosilane containing two methyl groups and a tert-butyl group. As such it is more bulky that trimethylsilyl chloride. It is a colorless or white solid that is soluble in many organic solvents but reacts with water and alcohols. The compound is used to protect alcohols in organic synthesis.
tert-Butyldimethylsilyl chloride reacts with alcohols in the presence of base to give tert-butyldimethylsilyl ethers:
:(MeC)MeSiCl + ROH → (MeC)MeSiOR + HCl
These silyl ethers hydrolyze much more slowly than the trimethylsilyl ethers.
It also can silylate terminal alkynes. | 0 | Theoretical and Fundamental Chemistry |
Terrestrial sediments also contain micrometeorites. These have been found in samples that:
*Have low sedimentation rates such as claystones and hardgrounds
*Are easily dissolved such as salt deposits and limestones
*Have been mass sorted such as heavy mineral concentrates found in deserts and beach sands.
The oldest MMs are totally altered iron spherules found in 140- to 180-million-year-old hardgrounds. | 0 | Theoretical and Fundamental Chemistry |
United States Navy researchers at the Space and Naval Warfare Systems Center (SPAWAR) in San Diego have been studying cold fusion since 1989. In 2002 they released a two-volume report, "Thermal and nuclear aspects of the Pd/DO system", with a plea for funding. This and other published papers prompted a 2004 Department of Energy (DOE) review. | 0 | Theoretical and Fundamental Chemistry |
A number of engineered genetic sequences must be incorporated into the host cell to perform two-hybrid analysis or one of its derivative techniques. The considerations and methods used in the construction and delivery of these sequences differ according to the needs of the assay and the organism chosen as the experimental background.
There are two broad categories of hybrid library: random libraries and cDNA-based libraries. A cDNA library is constituted by the cDNA produced through reverse transcription of mRNA collected from specific cells of types of cell. This library can be ligated into a construct so that it is attached to the BD or AD being used in the assay. A random library uses lengths of DNA of random sequence in place of these cDNA sections. A number of methods exist for the production of these random sequences, including cassette mutagenesis. Regardless of the source of the DNA library, it is ligated into the appropriate place in the relevant plasmid/phagemid using the appropriate restriction endonucleases. | 1 | Applied and Interdisciplinary Chemistry |
Research indicated that a substitution at the phthaloyl ring would increase TNF-α inhibition activity (Figure 5). An amino group substitution was tested at various locations on the phthaloyl ring (C4, C5, C6, C7) of thalidomide and EM-12 (previously described). Amino addition at the C4 location on both thalidomide and EM-12 resulted in much more potent inhibition of TNF-α. This also revealed that the amino group needed to be directly opposite the carbonyl group on the isoindolinone ring system for the most potent activity. These analogs do not inhibit PDE4 and therefore do not act by PDE4 inhibition. Other additions of longer and bigger groups at the C4 and C5 position of the phthaloyl ring system of thalidomide, some with an olefin functionality, have been tested with various results. Increased inhibitory effect, compared to thalidomide, was noticed with the groups that had an oxygen atom attached directly to the C5 or C4 olefin. Iodine and bromine addition at C4 or C5 resulted in equal or decreased activity compared to thalidomide. These groups were not compared with lenalidomide or pomalidomide. | 1 | Applied and Interdisciplinary Chemistry |
In medicine, the partial pressure of carbon dioxide in arterial blood is called or PaCO. Measurement of in the systemic circulation indicates the effectiveness of ventilation at the lungs' alveoli, given the diffusing capacity of the gas. It is a good indicator of respiratory function and the closely related factor of acid–base homeostasis, reflecting the amount of acid in the blood (without lactic acid). Normal values for humans are in the range 35–45 mmHg. Values less than this may indicate hyperventilation and (if blood pH is greater than 7.45) respiratory alkalosis. Values greater than 45 mmHg may indicate hypoventilation, and (if blood pH is less than 7.35) respiratory acidosis. | 0 | Theoretical and Fundamental Chemistry |
Seed treatments can achieve exceptionally high efficiencies, in terms of effective dose-transfer to a crop. Pesticides are applied to the seed prior to planting, in the form of a seed treatment, or coating, to protect against soil-borne risks to the plant; additionally, these coatings can provide supplemental chemicals and nutrients designed to encourage growth. A typical seed coating can include a nutrient layer—containing nitrogen, phosphorus, and potassium, a rhizobial layer—containing symbiotic bacteria and other beneficial microorganisms, and a fungicide (or other chemical) layer to make the seed less vulnerable to pests. | 1 | Applied and Interdisciplinary Chemistry |
The atomic mass of different isotopes affect their chemical kinetic behavior, leading to natural isotope separation processes. | 0 | Theoretical and Fundamental Chemistry |
Alloys that are not bronze and brass have had a limited representation in the literature for archaeometallurgy. This is mostly due to lack of interest or evidence in the archaeological record. Arsenical copper is one such limited research topic with some experimental work done by Pollard, Thomas, and Williams. Through several experimental smeltings of copper ores including arsenic, Pollard, Thomas, and Williams found that arsenic in copper is retained in higher levels when a lower smelting temperature is used, implying that arsenical copper may have been the result of early smelting technologies where temperatures were unable to pass a certain point.
Lead experimentation has been limited mostly because of its ease in production. Ore containing lead can be easily smelted, re-melted, and worked and as such there is not much difficulty in understanding how past societies may have produced lead. When lead experiments are conducted, they are done much in the same fashion as copper smelting experiments taking notes on quantitative elements such as completion time, airflow rates, fuel usage, and the resulting amount and composition of metal from the smelt. In addition, lead is a toxic element and special care has to take place in order to experiment with it, which makes limitations on the experiments. | 1 | Applied and Interdisciplinary Chemistry |
In n-pentane, the terminal methyl groups experience additional pentane interference.
Replacing hydrogen by fluorine in polytetrafluoroethylene changes the stereochemistry from the zigzag geometry to that of a helix due to electrostatic repulsion of the fluorine atoms in the 1,3 positions. Evidence for the helix structure in the crystalline state is derived from X-ray crystallography and from NMR spectroscopy and circular dichroism in solution. | 0 | Theoretical and Fundamental Chemistry |
Toxic algae blooms are thought to play a role in humans developing degenerative neurological disorders such as amyotrophic lateral sclerosis and Parkinson's disease.
Less than one percent of algal blooms produce hazardous toxins, such as microcystins. Although blue-green or other algae do not usually pose a direct threat to health, the toxins (poisons) which they produce are considered dangerous to humans, land animals, sea mammals, birds and fish when the toxins are ingested. The toxins are neurotoxins which destroy nerve tissue which can affect the nervous system, brain, and liver, and can lead to death. | 0 | Theoretical and Fundamental Chemistry |
Pharmacokinetic data of enalapril:
* Onset of action: about 1 hour
* Peak effect: 4–6 hours
* Duration: 12–24 hours
* Absorption: ~60%
* Metabolism: prodrug, undergoes biotransformation to enalaprilat | 0 | Theoretical and Fundamental Chemistry |
Immunoelectrophoresis is a general name for a number of biochemical methods for separation and characterization of proteins based on electrophoresis and reaction with antibodies. All variants of immunoelectrophoresis require immunoglobulins, also known as antibodies, reacting with the proteins to be separated or characterized. The methods were developed and used extensively during the second half of the 20th century. In somewhat chronological order: Immunoelectrophoretic analysis (one-dimensional immunoelectrophoresis ad modum Grabar), crossed immunoelectrophoresis (two-dimensional quantitative immunoelectrophoresis ad modum Clarke and Freeman or ad modum Laurell), rocket-immunoelectrophoresis (one-dimensional quantitative immunoelectrophoresis ad modum Laurell), fused rocket immunoelectrophoresis ad modum Svendsen and Harboe, affinity immunoelectrophoresis ad modum Bøg-Hansen. | 1 | Applied and Interdisciplinary Chemistry |
The Euglena photoreceptor was identified as a blue-light-activated adenylyl cyclase. Excitation of this receptor protein results in the formation of cyclic adenosine monophosphate (cAMP) as a second messenger. Chemical signal transduction ultimately triggers changes in flagellar beat patterns and cell movement.
The archaeal-type rhodopsins of Chlamydomonas contain an all-trans retinylidene chromatophore which undergoes photoisomerization to a 13-cis isomer. This activates a photoreceptor channel, leading to a change in membrane potential and cellular calcium ion concentration. Photoelectric signal transduction ultimately triggers changes in flagellar strokes and thus cell movement. | 1 | Applied and Interdisciplinary Chemistry |
Inhibition of PSII is caused by singlet oxygen produced either by weakly coupled chlorophyll molecules or by cytochromes or iron–sulfur centers. | 0 | Theoretical and Fundamental Chemistry |
The forces between the tip and the sample strongly depend on the geometry of the tip. Various studies were exploited in the past years to write the forces as a function of the tip parameters.
Among the different forces between the tip and the sample, the water meniscus forces are highly interesting, both in air and liquid environment. Other forces must be considered, like the Coulomb force, van der Waals forces, double layer interactions, solvation forces, hydration and hydrophobic forces. | 0 | Theoretical and Fundamental Chemistry |
*AkzoNobel Coil Coatings Europe, https://web.archive.org/web/20130528041259/http://www.akzonobel.com/CCE/coil_coatings/ourindustry/ecca/,
*ArcelorMittal, http://www.constructalia.com/francais/actualites/plus_dactus/plus_dactus100/magazine_ecca_2012_une_source_d_inspiration_pour_les_architectes,
*Shingels, https://web.archive.org/web/20140714204231/http://shingels.com/?page_id=657&lang=en,
*Precoat Metals, http://www.precoat.com/links.htm,
*Spooner Industries, http://www.spooner.co.uk/products/36/coil-coating ,
*Novacel, http://www.novacel.fr/fr/novacel/partenariat.html ,
*The Plan "Architecture and Technologies in details", https://web.archive.org/web/20140714212808/http://www.theplan.it/J/index.php?option=com_content&view=article&id=2366:alcoa&Itemid=1&lang=en,
*Union of International Associations, http://www.uia.be/s/or/en/1100007909,
*Tata Steel, http://www.tatasteel.com/,
*BASF, http://www.basf.com/ | 1 | Applied and Interdisciplinary Chemistry |
Pack cementation is a widely used CVD technique that consists of immersing the components to be coated in a metal powder mixture and ammonium halide activators and sealing them in a retort. The entire apparatus is placed inside a furnace and heated in a protective atmosphere to a lower than normal temperature that allows diffusion, due to the halide salts chemical reaction that causes a eutectic bond between the two metals. The surface alloy that is formed due to thermal-diffused ion migration has a metallurgical bond to the substrate and an intermetallic layer found in the gamma layer of the surface alloys.
The traditional pack consists of four components at temperatures below (750 °C):
* Substrate or parts
* Ferrous and non-ferrous powdered alloy: (Ti and/or Al, Si and/or Zn, B and/ or Cr)
* Halide salt activator: Ammonium halide salts
* Relatively inert filler powder (Al2O3, SiO2, or SiC)
This process includes:
* Aluminizing
* Chromizing
* Siliconizing
* Sherardizing
* Boronizing
* Titaniumizing
Pack cementation has reemerged when combined with other chemical processes to lower the temperatures of metal combinations and give intermetallic properties to different alloy combinations for surface treatments. | 1 | Applied and Interdisciplinary Chemistry |
In wire electrical discharge machining (WEDM), also known as wire-cut EDM and wire cutting, a thin single-strand metal wire, usually brass, is fed through the workpiece, submerged in a tank of dielectric fluid, typically deionized water. Wire-cut EDM is typically used to cut plates as thick as 300mm and to make punches, tools, and dies from hard metals that are difficult to machine with other methods.
The wire, which is constantly fed from a spool, is held between upper and lower diamond guides which is centered in a water nozzle head. The guides, usually CNC-controlled, move in the x–y plane. On most machines, the upper guide can also move independently in the z–u–v axis, giving rise to the ability to cut tapered and transitioning shapes (circle on the bottom, square at the top for example). The upper guide can control axis movements in the GCode standard, x–y–u–v–i–j–k–l–. This allows the wire-cut EDM to be programmed to cut very intricate and delicate shapes.
The upper and lower diamond guides are usually accurate to , and can have a cutting path or kerf as small as using Ø wire, though the average cutting kerf that achieves the best economic cost and machining time is using Ø brass wire. The reason that the cutting width is greater than the width of the wire is because sparking occurs from the sides of the wire to the work piece, causing erosion. This "overcut" is necessary, for many applications it is adequately predictable and therefore can be compensated for (for instance in micro-EDM this is not often the case). Spools of wire are long — an 8 kg spool of 0.25 mm wire is just over 19 kilometers in length. Wire diameter can be as small as and the geometry precision is not far from ± .
The wire-cut process uses water as its dielectric fluid, controlling its resistivity and other electrical properties with filters and PID controlled de-ionizer units. The water flushes the cut debris away from the cutting zone. Flushing is an important factor in determining the maximum feed rate for a given material thickness.
Along with tighter tolerances, multi axis EDM wire-cutting machining centers have added features such as multi heads for cutting two parts at the same time, controls for preventing wire breakage, automatic self-threading features in case of wire breakage, and programmable machining strategies to optimize the operation.
Wire-cutting EDM is commonly used when low residual stresses are desired, because it does not require high cutting forces for removal of material. If the energy per pulse is relatively low (as in finishing operations), little change in the mechanical properties of a material is expected due to these low residual stresses, although material that hasn't been stress-relieved can distort in the machining process.
The work piece may undergo a significant thermal cycle, its severity depending on the technological parameters used. Such thermal cycles may cause formation of a recast layer on the part and residual tensile stresses on the work piece. If machining takes place after heat treatment, dimensional accuracy will not be affected by heat treat distortion. | 1 | Applied and Interdisciplinary Chemistry |
The Herges compound (6 in the image below) was synthesized in several photochemical cycloaddition reactions from tetradehydrodianthracene 1 and the ladderane syn-tricyclooctadiene 2 as a substitute for cyclooctatetraene.
Intermediate 5 was a mixture of 2 isomers and the final product 6 a mixture of 5 isomers with different cis and trans configurations. One of them was found to have a C molecular symmetry corresponding to a Möbius aromatic and another Hückel isomer was found with C symmetry. Despite having 16 electrons in its pi system (making it a 4n antiaromatic compound) the Heilbronner prediction was borne out because according to Herges the Möbius compound was found to have aromatic properties. With bond lengths deduced from X-ray crystallography a HOMA value was obtained of 0.50 (for the polyene part alone) and 0.35 for the whole compound which qualifies it as a moderate aromat.
It was pointed out by Henry Rzepa that the conversion of intermediate 5 to 6 can proceed by either a Hückel or a Möbius transition state.
The difference was demonstrated in a hypothetical pericyclic ring opening reaction to cyclododecahexaene. The Hückel TS (left) involves 6 electrons (arrow pushing in red) with C molecular symmetry conserved throughout the reaction. The ring opening is disrotatory and suprafacial and both bond length alternation and NICS values indicate that the 6 membered ring is aromatic. The Möbius TS with 8 electrons on the other hand has lower computed activation energy and is characterized by C symmetry, a conrotatory and antarafacial ring opening and 8-membered ring aromaticity.
Another interesting system is the cyclononatetraenyl cation explored for over 30 years by Paul v. R. Schleyer et al. This reactive intermediate is implied in the solvolysis of the bicyclic chloride 9-deutero-9-chlorobicyclo[6.1.0]-nonatriene 1 to the indene dihydroindenol 4. The starting chloride is deuterated in only one position but in the final product deuterium is distributed at every available position. This observation is explained by invoking a twisted 8-electron cyclononatetraenyl cation 2 for which a NICS value of -13.4 (outsmarting benzene) is calculated. A more recent study, however, suggests that the stability of trans-CH is not much different in energy compared to a Hückel topology isomer. The same study suggested that for [13]annulenyl cation, the Möbius topology penta-trans'-CH is a global energy minimum and predicts that it may be directly observable.
In 2005 the same P. v. R. Schleyer questioned the 2003 Herges claim: he analyzed the same crystallographic data and concluded that there was indeed a large degree of bond length alternation resulting in a HOMA value of -0.02, a computed NICS value of -3.4 ppm also did not point towards aromaticity and (also inferred from a computer model) steric strain would prevent effective pi-orbital overlap.
A Hückel-Möbius aromaticity switch (2007) has been described based on a 28 pi-electron porphyrin system:
The phenylene rings in this molecule are free to rotate forming a set of conformers: one with a Möbius half-twist and another with a Hückel double-twist (a figure-eight configuration) of roughly equal energy.
In 2014, Zhu and Xia (with the help of Schleyer) synthesized a planar Möbius system that consisted of two pentene rings connected with an osmium atom. They formed derivatives where osmium had 16 and 18 electrons and determined that Craig–Möbius aromaticity is more important for the stabilization of the molecule than the metal's electron count. | 0 | Theoretical and Fundamental Chemistry |
Amylase also has medical applications in the use of pancreatic enzyme replacement therapy (PERT). It is one of the components in Sollpura (liprotamase) to help in the breakdown of saccharides into simple sugars. | 1 | Applied and Interdisciplinary Chemistry |
The interface between a liquid phase technique (HPLC) with a continuously flowing eluate, and a gas phase technique carried out in a vacuum was difficult for a long time. The advent of electrospray ionization changed this. Currently, the most common LC–MS interfaces are electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and atmospheric pressure photo-ionization (APPI). These are newer MS ion sources that facilitate the transition from a high pressure environment (HPLC) to high vacuum conditions needed at the MS analyzer. Although these interfaces are described individually, they can also be commercially available as dual ESI/APCI, ESI/APPI, or APCI/APPI ion sources. Various deposition and drying techniques were used in the past (e.g., moving belts) but the most common of these was the off-line MALDI deposition. A new approach still under development called direct-EI LC–MS interface, couples a nano HPLC system and an electron ionization equipped mass spectrometer. | 0 | Theoretical and Fundamental Chemistry |
NETA is marketed under a variety of brand names throughout the world including Primolut-Nor (major), Aygestin (), Gestakadin, Milligynon, Monogest, Norlutate (, ), Primolut N, SH-420 (), Sovel, and Styptin among others. | 1 | Applied and Interdisciplinary Chemistry |
The fugacity can be deduced from measurements of volume as a function of pressure at constant temperature. In that case,
This integral can also be calculated using an equation of state.
The integral can be recast in an alternative form using the compressibility factor
Then
This is useful because of the theorem of corresponding states: If the pressure and temperature at the critical point of the gas are and , we can define reduced properties and . Then, to a good approximation, most gases have the same value of for the same reduced temperature and pressure. However, in geochemical applications, this principle ceases to be accurate at pressures where metamorphism occurs.
For a gas obeying the van der Waals equation, the explicit formula for the fugacity coefficient is
This formula is based on the molar volume. Since the pressure and the molar volume are related through the equation of state; a typical procedure would be to choose a volume, calculate the corresponding pressure, and then evaluate the right-hand side of the equation. | 0 | Theoretical and Fundamental Chemistry |
The basic procedure for naming a complex is:
# When naming a complex ion, the ligands are named before the metal ion.
# The ligands' names are given in alphabetical order. Numerical prefixes do not affect the order.
#* Multiple occurring monodentate ligands receive a prefix according to the number of occurrences: di-, tri-, tetra-, penta-, or hexa-.
#* Multiple occurring polydentate ligands (e.g., ethylenediamine, oxalate) receive bis-, tris-, tetrakis-, etc.
#* Anions end in o. This replaces the final e when the anion ends with -ide, -ate or -ite, e.g. chloride becomes chlorido and sulfate becomes sulfato. Formerly, -ide was changed to -o (e.g. chloro and cyano), but this rule has been modified in the 2005 IUPAC recommendations and the correct forms for these ligands are now chlorido and cyanido.
#* Neutral ligands are given their usual name, with some exceptions: NH becomes ammine; HO becomes aqua or aquo; CO becomes carbonyl; NO becomes nitrosyl.
# Write the name of the central atom/ion. If the complex is an anion, the central atoms name will end in -ate', and its Latin name will be used if available (except for mercury).
# The oxidation state of the central atom is to be specified (when it is one of several possible, or zero), and should be written as a Roman numeral (or 0) enclosed in parentheses.
# Name of the cation should be preceded by the name of anion. (if applicable, as in last example)
Examples:
: [Cd(CN)(en)] → dicyanidobis(ethylenediamine)cadmium(II)
: [CoCl(NH)]SO → pentaamminechloridocobalt(III) sulfate
: [Cu(HO)] → hexaaquacopper(II) ion
: [CuClNH] → amminepentachloridocuprate(II) ion
: K[Fe(CN)] → potassium hexacyanidoferrate(II)
: [NiCl] → tetrachloridonickelate(II) ion (The use of chloro- was removed from IUPAC naming convention)
The coordination number of ligands attached to more than one metal (bridging ligands) is indicated by a subscript to the Greek symbol μ placed before the ligand name. Thus the dimer of aluminium trichloride is described by AlCl(μ-Cl).
Any anionic group can be electronically stabilized by any cation. An anionic complex can be stabilised by a hydrogen cation, becoming an acidic complex which can dissociate to release the cationic hydrogen. This kind of complex compound has a name with "ic" added after the central metal. For example, H[Pt(CN)] has the name tetracyanoplatinic (II) acid. | 0 | Theoretical and Fundamental Chemistry |
Theoretical oxygen demand (ThOD) is the calculated amount of oxygen required to oxidize a compound to its final oxidation products. However, there are some differences between standard methods that can influence the results obtained: for example, some calculations assume that nitrogen released from organic compounds is generated as ammonia, whereas others allow for ammonia oxidation to nitrate. Therefore, in expressing results, the calculation assumptions should always be stated.
In order to determine the ThOD for glycine (CH(NH)COOH) using the following assumptions:
#In the first step, the organic carbon and nitrogen are converted to carbon dioxide (CO) and ammonia (NH), respectively.
#In the second and third steps, the ammonia is oxidized sequentially to nitrite and nitrate.
#The ThOD is the sum of the oxygen required for all three steps.
We can calculate by following steps:
#Write balanced reaction for the carbonaceous oxygen demand.(NH)COOH + 1.5O → NH + 2CO + HO
#Write balanced reactions for the nitrogenous oxygen demand. + 1.5O → HNO + HO + 0.5O → HNO + 2O → HNO + HO
#Determine the ThOD./mol glycine/mol glycine × 32 g/mol O / 75 g/mol glycine/g glycine
The theoretical oxygen demand represents the worst-case scenario. The actual oxygen demand of any compound depends on the biodegradability of the compound and the specific organism metabolizing the compound. The actual oxygen demand can be measured experimentally and is called the biochemical oxygen demand (BOD). | 1 | Applied and Interdisciplinary Chemistry |
There have been proposals for automation to make rapid prediction of BOD so it could be used for on-line process monitoring and control. For example, the use of a computerised machine learning method to make rapid inferences about BOD using easy to measure water quality parameters. Ones such as flow rate, chemical oxygen demand, ammonia, nitrogen, pH and suspended solids can be obtained directly and reliably using on-line hardware sensors. In a test of this idea, measurements of these values along with BOD which had been made over three years was used to train and test a model for prediction. The technique could allow for some missing data. It indicated that this approach was possible but needed sufficient historic data to be available. | 0 | Theoretical and Fundamental Chemistry |
In 1903, Eichengrün co-developed the first soluble form of cellulose acetate with Theodore Becker. He developed processes for the manufacture of cellulose acetate materials and devoted the rest of his life to the technical and economic development of plastics, lacquers, enamels, and artificial fibers based on cellulose acetate. During World War I his relatively non-inflammable synthetic cellulose acetate lacquers were important in the aircraft industry. He also pioneered the influential technique of injection moulding. In 1904, he created and patented the first safety film with Becker, (cellulose diacetate) from a process they devised in 1901 for the direct acetylation of cellulose at a low temperature to prevent its degradation, which permitted the degree of acetylation to be controlled, thereby avoiding total conversion to its triacetate. Cellit was a stable, non-brittle cellulose acetate polymer that could be dissolved in acetone for further processing. It was used to manufacture cellulose diacetate cinematographic film, which Eastman Kodak and the Pathé Frères began to use in 1909. Cellulose acetate film became the standard in the 1950s, preferred over the highly flammable and unstable film stock produced from Nitrocellulose. | 0 | Theoretical and Fundamental Chemistry |
The impact of ultraviolet radiation on human health has implications for the risks and benefits of sun exposure and is also implicated in issues such as fluorescent lamps and health. Getting too much sun exposure can be harmful, but in moderation, sun exposure is beneficial. | 0 | Theoretical and Fundamental Chemistry |
The continuously mixed tank reactor is an open system with an influent stream of reactants and an effluent stream of products. A lake can be regarded as a tank reactor, and lakes with long turnover times (e.g. with low flux-to-volume ratios) can for many purposes be regarded as continuously stirred (e.g. homogeneous in all respects). The mass balance then becomes
where
* is the volumetric flow into the system;
* is the volumetric flow out of the system;
* is the concentration of A in the inflow;
* is the concentration of A in the outflow.
In an open system we can never reach a chemical equilibrium. We can, however, reach a steady state where all state variables (temperature, concentrations, etc.) remain constant (). | 1 | Applied and Interdisciplinary Chemistry |
Another solution is to build a CSO storage facility, such as a tunnel that can store flow from many sewer connections. Because a tunnel can share capacity among several outfalls, it can reduce the total volume of storage that must be provided for a specific number of outfalls. Storage tunnels store combined sewage but do not treat it. When the storm is over, the flows are pumped out of the tunnel and sent to a wastewater treatment plant. One of the main concerns with CSO storage is the length of time it is stored before it is released. Without careful management of this storage period, the water in the CSO storage facility runs the risk of going septic.
Washington, D.C., is building underground storage capacity as its primary strategy to address CSOs. In 2011, the city began construction on a system of four deep storage tunnels, adjacent to the Anacostia River, that will reduce overflows to the river by 98 percent, and 96 percent system-wide. The system will comprise over of tunnels with a storage capacity of . The first segment of the tunnel system, in length, went online in 2018. The remaining segments of the storage system are scheduled for completion in 2023. (The city's overall "Clean Rivers" project, projected to cost $2.6 billion, includes other components, such as reducing stormwater flows.) The South Boston CSO Storage Tunnel is a similar project, completed in 2011.
Indianapolis, Indiana, is building underground storage capacity in the form of a diameter deep rock tunnel system which will connect the two existing wastewater treatment plants, and provide collection of discharge water from the various CSO sites located along the White River, Eagle Creek, Fall Creek, Pogue's Run, and Pleasant Run. Citizens Energy Group is managing the efforts to construct the first phases of the work, which includes a deep Deep Rock Tunnel Connector between the Belmont Wastewater Treatment Plant and the Southport Wastewater Treatment Plant. Additional tunnels will branch under the existing watercourses located in Indianapolis. The planned cost for the project will total $1.9 billion.
Fort Wayne, Indiana, is constructing a , diameter, $180M tunnel under the 3RPORT (Three Rivers Protection and Overflow Reduction Tunnel) to address the myriad CSOs which outfall into the St. Mary's, St. Joseph, and Maumee Rivers. The 3RPORT is approximately below grade, and is anticipated to enter service in 2023. | 1 | Applied and Interdisciplinary Chemistry |
A grassed waterway is a to 48-metre-wide (157 ft) native grassland strip of green belt. It is generally installed in the thalweg, the deepest continuous line along a valley or watercourse, of a cultivated dry valley in order to control erosion. A study carried out on a grassed waterway during 8 years in Bavaria showed that it can lead to several other types of positive impacts, e.g. on biodiversity. | 1 | Applied and Interdisciplinary Chemistry |
Electrostatic coalescers use electrical fields to induce droplet coalescence in water-in-crude-oil emulsions to increase the droplet size. The squared dependence of droplet diameter in Stokes' law, increase the settling speed and destabilizes the emulsion. The effects on the water droplet arise from the very different dielectric properties of the conductive water droplets dispersed in the insulating oil. Water droplets have a permittivity that is much higher than the surrounding oil. Furthermore, water with dissolved salt is also a very good conductor. When an uncharged droplet is subjected to an AC electric field, the field will polarize the droplet, creating an electric field around the droplet to counteract the external field. As the water droplet is very conductive, the induced charges will reside on the surface. The droplet has no net charge but one positive and one negative side. Inside the droplet, the electric field is zero. When two droplets with induced dipoles get close to each other, they will experience a force pulling the droplets closer until they coalesce.
In oil production, co-produced water is mixed with the oil in choke valves and process equipment producing water-in-oil emulsions. The amount of water increases during the production life of the reservoir. The emulsions are destabilized using gravitational separators, and the settling rates are increased by applying heat, demulsifiers, and AC electric fields. The AC electric field gives rise to attractive forces between water droplets and increases the probability of coalescence at contact. According to Stokes' law, the settling rate increases proportionally with the square of the drop diameter. By promoting coalescence of small water droplets, the settling rate can be greatly increased. The water content is normally reduced to less than 0.5 vol% if this is the final treatment stage before the crude oil is exported.
Typical electrostatic coalescers are large settling tanks containing electrodes and operate under laminar-flow conditions with bare electrodes that may be vulnerable to short circuiting. An alternative to this type of coalescer is a flow through pre-coalescer that is installed upstream in a separator tank. In the Compact Electrostatic Coalescer, droplet coalescence is achieved by applying AC electric fields (50–60 Hz) to water-in-oil emulsions under turbulent-flow conditions. The turbulence increases the collision frequency between the water drops. The electrodes are insulated to prevent short circuiting, and permit water contents of up to 40% as well as water slugs. The equipment is a separate flow-through electrostatic treatment section installed upstream of a gravity separator to improve the performance. By keeping the treatment and settling sections separate, a compact electrostatic coalescer can be obtained that can also be retrofitted.
Liquid-liquid coalescers are also widely used in the oil refining industry to remove the last traces of contaminants like amine or caustic from intermediate products in oil refineries, and also for the last stage dewatering of final products like kerosene (jet fuel), LPG, gasoline and diesel to less than 15 mW free water in the hydrocarbon phase. These coalescers are often electrostatic type, in which a DC electrical field encourages the water droplets to coalesce, thus settling by gravity. | 0 | Theoretical and Fundamental Chemistry |
New mTOR-specific inhibitors came forth from screening and drug discovery efforts. These compounds block activity of both mTOR complexes and are called mTORC1/mTORC2 dual inhibitors. Compounds with this characteristics such as sapanisertib (codenamed INK128), AZD8055, and AZD2014 have entered clinical trials.
A series of these mTOR kinase inhibitors have been studied. Their structure is derived from morpholino pyrazolopyrimidine scaffold.
Improvements of this type of inhibitors have been made by exchanging the morpholines with bridged morpholines in pyrazolopyrimidine inhibitors and results showed increased selectivity to mTOR by 26000 fold. | 1 | Applied and Interdisciplinary Chemistry |
Emerging character of this interdisciplinary branch of science is reflected by a lack of established terminology. There are different terms and definitions used by different authors depending on the main approach used (chemical, physical, mechanical, vacuum science, etc.), specific gas emission mechanism (desorption, emanation, emission, etc.) and type of mechanical activation (friction, traction, etc.):<br />
:Mechanically stimulated outgassing (MSO)
:Tribodesorption
:Triboemission,
:Fractoemission
:Atomic and Molecular emission
:Outgassing stimulated by friction
:Outgassing stimulated by deformation
Desorption (tribodesorption, fractodesorption, etc.) refers to release of gases dissolved in the bulk and adsorbed on the surface. Therefore, desorption is only one of the contributing processes to MSGE. Outgassing is a technical term usually utilized in vacuum science. Thus, the term "gas emission" embraces various processes, reflects the physical nature of this complex phenomenon and is preferable for use in scientific publications. | 0 | Theoretical and Fundamental Chemistry |
High emissivity coatings that facilitate radiative cooling may be used in reusable thermal protection systems (RTPS) in spacecraft and hypersonic aircraft. In such heat shields a high emissivity material, such as molybdenum disilicide (MoSi) is applied on a thermally insulating ceramic substrate. In such heat shields high levels of total emissivity, typically in the range 0.8 - 0.9, need to be maintained across a range of high temperatures. Planck's law dictates that at higher temperatures the radiative emission peak shifts to lower wavelengths (higher frequencies), influencing material selection as a function of operating temperature. In addition to effective radiative cooling, radiative thermal protection systems should provide damage tolerance and may incorporate self-healing functions through the formation of a viscous glass at high temperatures. | 0 | Theoretical and Fundamental Chemistry |
Modified zeolite on which the external surface was partly covered with alkylsilane, called phase-boundary catalyst was prepared in two steps. First, titanium dioxide made from titanium isopropoxide was impregnated into NaY zeolite powder to give sample W-Ti-NaY. In the second step, alkysilane from n-octadecyltrichlorosilane (OTS) was impregnated into the W-Ti-NaY powder containing water. Due to the hydrophilicity of the w-Ti-NaY surface, addition of a small amount of water led to aggregation owing to the capillary force of water between particles. Under these conditions, it is expected that only the outer surface of aggregates, in contact with the organic phase can be modified with OTS, and indeed almost all of the particles were located at the phase boundary when added to an immiscible water–organic solvent (W/O) mixture. The partly modified sample is denoted w/o-Ti-NaY. Fully modified Ti-NaY (o-Ti-NaY), prepared without the addition of water in the above second step, is readily suspended in an organic solvent as expected. | 0 | Theoretical and Fundamental Chemistry |
The Zeisel determination or Zeisel test is a chemical test for the presence of esters or ethers in a chemical substance. It is named after the Czech chemist Simon Zeisel (1854–1933). In a qualitative test a sample is first reacted with a mixture of acetic acid and hydrogen iodide in a test tube. The ensuing reaction results in the cleavage of the ether or the ester into an alkyl iodide and respectively an alcohol or a carboxylic acid.
By heating this mixture, the gases are allowed to come into contact with a piece of paper higher up the test tube saturated with silver nitrate. Any alkyl iodide present will give a reaction with the silver compound to silver iodide which has a red or yellow color. By filtering and weighing this precipitate it is possible to quantitatively calculate the number of iodine atoms and hence alkoxy groups. For example, prior to the development of the more precise methods of NMR spectroscopy and mass spectrometry, the Zeisel test was widely used to determine the number of methoxy (-OCH) and ethoxy (-OCHCH) groups in carbohydrate and organophosphorus insecticides.
An alternative qualitative Zeisel test can be done with the use of mercury(II) nitrate instead of silver nitrate, leading to the formation of scarlet red mercury(II) iodide.
Synthetic applications: | 0 | Theoretical and Fundamental Chemistry |
In stereochemistry, a torsion angle is defined as a particular example of a dihedral angle, describing the geometric relation of two parts of a molecule joined by a chemical bond. Every set of three non-colinear atoms of a molecule defines a half-plane. As explained above, when two such half-planes intersect (i.e., a set of four consecutively-bonded atoms), the angle between them is a dihedral angle. Dihedral angles are used to specify the molecular conformation. Stereochemical arrangements corresponding to angles between 0° and ±90° are called syn (s), those corresponding to angles between ±90° and 180° anti (a). Similarly, arrangements corresponding to angles between 30° and 150° or between −30° and −150° are called clinal (c) and those between 0° and ±30° or ±150° and 180° are called periplanar (p).
The two types of terms can be combined so as to define four ranges of angle; 0° to ±30° synperiplanar (sp); 30° to 90° and −30° to −90° synclinal (sc); 90° to 150° and −90° to −150° anticlinal (ac); ±150° to 180° antiperiplanar (ap). The synperiplanar conformation is also known as the syn- or cis-conformation; antiperiplanar as anti or trans; and synclinal as gauche or skew.
For example, with n-butane two planes can be specified in terms of the two central carbon atoms and either of the methyl carbon atoms. The syn-conformation shown above, with a dihedral angle of 60° is less stable than the anti-conformation with a dihedral angle of 180°.
For macromolecular usage the symbols T, C, G, G, A and A are recommended (ap, sp, +sc, −sc, +ac and −ac respectively). | 0 | Theoretical and Fundamental Chemistry |
Dexmedetomidine can also be used for procedural sedation such as during colonoscopy. It can be used as an adjunct with other sedatives like benzodiazepines, opioids, and propofol to enhance sedation and help maintain hemodynamic stability by decreasing the requirement of other sedatives. Dexmedetomidine is also used for procedural sedation in children.
It can be used for sedation required for awake fibreoptic nasal intubation in patients with a difficult airway. | 0 | Theoretical and Fundamental Chemistry |
Russell Stephen Drago (November 5, 1928 – December 5, 1997) was an American professor of inorganic chemistry. He mentored more than 130 PhD students, authored over a dozen textbooks and four hundred research documents, which have been published in several languages. He filed 17 process patents. and established the Florida Catalysis Conference Foundation, Inc. | 0 | Theoretical and Fundamental Chemistry |
In many cases, the possible conditions in a system are limited by the stability region of water. In the Pourbaix diagram for uranium presented here above, the limits of stability of water are marked by the two dashed green lines, and the stability region for water falls between these two lines. It is also depicted here beside by the two dashed red lines in the simplified Pourbaix diagram restricted to the water stability region only.
Under highly reducing conditions (low E), water is reduced to hydrogen according to:
: (at low pH)
and,
: (at high pH)
Using the Nernst equation, setting E = 0 V as defined by convention for the standard hydrogen electrode (SHE, serving as reference in the reduction potentials series) and the hydrogen gas fugacity (corresponding to chemical activity for a gas) at 1, the equation for the lower stability line of water in the Pourbaix diagram at standard temperature and pressure is:
Below this line, water is reduced to hydrogen, and it will usually not be possible to pass beyond this line as long as there is still water present in the system to be reduced.
Correspondingly, under highly oxidizing conditions (high E) water is oxidized into oxygen gas according to:
: (at low pH)
and,
: (at high pH)
Using the Nernst equation as above, but with E = −ΔGO</sub>/2F = 1.229 V for water oxidation, gives an upper stability limit of water as a function of the pH value:
at standard temperature and pressure. Above this line, water is oxidized to form oxygen gas, and it will usually not be possible to pass beyond this line as long as there is still water present in the system to be oxidized.
The two upper and lower stability lines having the same negative slope (−59 mV/pH unit), they are parallel in a Pourbaix diagram and the reduction potential decreases with pH. | 0 | Theoretical and Fundamental Chemistry |
Salts containing fluoride are numerous and adopt myriad structures. Typically the fluoride anion is surrounded by four or six cations, as is typical for other halides. Sodium fluoride and sodium chloride adopt the same structure. For compounds containing more than one fluoride per cation, the structures often deviate from those of the chlorides, as illustrated by the main fluoride mineral fluorite (CaF) where the Ca ions are surrounded by eight F centers. In CaCl, each Ca ion is surrounded by six Cl centers. The difluorides of the transition metals often adopt the rutile structure whereas the dichlorides have cadmium chloride structures. | 1 | Applied and Interdisciplinary Chemistry |
It is likely that most externally fertilizing species (e.g. marine worms, sea urchins) coordinate their sexual behaviour (release of sperm and eggs) using pheromones. This coordination is very important because sperm are diluted easily, and are short-lived. Coordination therefore provides a selective advantage to both males and females: individuals that do not coordinate are unlikely to achieve fertilisation and hence to leave offspring.
The main selective advantage of outcrossing is that it promotes the masking of deleterious recessive alleles, while inbreeding promotes their harmful expression. | 1 | Applied and Interdisciplinary Chemistry |
There are two kinds of defects: Equilibrium defects, and Non-Equilibrium defects. Self-assembled structures contain defects. Dislocations caused during the assembling of nanomaterials can majorly affect the final structure and in general defects are never completely avoidable. Current research on defects is focused on controlling defect density.[23] In most cases, the thermodynamic driving force for self-assembly is provided by weak intermolecular interactions and is usually of the same order of magnitude as the entropy term. In order for a self-assembling system to reach the minimum free energy configuration, there has to be enough thermal energy to allow the mass transport of the self-assembling molecules. For defect formation, the free energy of single defect formation is given by:
The enthalpy term, does not necessarily reflect the intermolecular forces between the molecules, it is the energy cost associated with disrupting the pattern and may be thought of as a region where optimum arrangement does not occur and the reduction of enthalpy associated with ideal self-assembly did not occur. An example of this can be seen in a system of hexagonally packed cylinders where defect regions of lamellar structure exist.
If is negative, there will be a finite number of defects in the system and the concentration will be given by:
N is the number of defects in a matrix of N self-assembled particles or features and is the activation energy of defect formation. The activation energy, , should not be confused with . The activation energy represents the energy difference between the initial ideally arranges state and a transition state towards the defective structure. At low defect concentrations, defect formation is entropy driven until a critical concentration of defects allows the activation energy term to compensate for entropy. There is usually an equilibrium defect density indicated at the minimum free energy. The activation energy for defect formation increases this equilibrium defect density. | 0 | Theoretical and Fundamental Chemistry |
The use of N-terminal Fmoc protection allows for a milder deprotection scheme than used for Boc/Bzl SPPS, and this protection scheme is truly orthogonal under SPPS conditions. Fmoc deprotection utilizes a base, typically 20–50% piperidine in DMF. The exposed amine is therefore neutral, and consequently no neutralization of the peptide-resin is required, as in the case of the Boc/Bzl approach. The lack of electrostatic repulsion between the peptide chains can lead to increased risk of aggregation with Fmoc/tBu SPPS however. Because the liberated fluorenyl group is a chromophore, Fmoc deprotection can be monitored by UV absorbance of the reaction mixture, a strategy which is employed in automated peptide synthesizers.
The ability of the Fmoc group to be cleaved under relatively mild basic conditions while being stable to acid allows the use of side chain protecting groups such as Boc and tBu that can be removed in milder acidic final cleavage conditions (TFA) than those used for final cleavage in Boc/Bzl SPPS (HF). Scavengers such as water and triisopropylsilane (TIPS) are most commonly added during the final cleavage in order to prevent side reactions with reactive cationic species released as a result of side chain deprotection. Nevertheless, many other scavenger compounds could be used as well. The resulting crude peptide is obtained as a TFA salt, which is potentially more difficult to solubilize than the fluoride salts generated in Boc SPPS.
Fmoc/tBu SPPS is less atom-economical, as the fluorenyl group is much larger than the Boc group. Accordingly, prices for Fmoc amino acids were high until the large-scale piloting of one of the first synthesized peptide drugs, enfuvirtide, began in the 1990s, when market demand adjusted the relative prices of Fmoc- vs Boc- amino acids. | 1 | Applied and Interdisciplinary Chemistry |
Some applications of the electrodialysis are explained below.
* The desalination of whey is the largest area of use for this type of dialysis in the food industry. It is necessary to remove crude cheese whey containing calcium, phosphorus and other inorganic salts to produce different foods such as cake, bread, ice cream and baby foods. The limit of whey demineralisation is almost 90%.
* De-acidification of fruit juice such as grape, orange, apple and lemon are processes in which electrodialysis is applied. An anion-exchange membrane is employed in this technique implying that citrate ions from the juice are extracted and replaced by hydroxide ions.
* Desalting of soy sauce can be done by electrodialysis. The conventional values of salt in brewed soy sauce are about 16-18 %, which is a quite high content. Electrodialysis is used to reduce the amount of salt present in the soy sauce. Nowadays diets of low salt content are very present in the society.
* Electrodialysis allows the separation of amino acids into acidic, basic and neutral groups. Specifically, cytoplasmic leaf proteins are extracted from alfalfa leaves applying electrodialysis. When proteins are denatured, the solutions can be desalted (of K ions) and acidified with H ions. | 1 | Applied and Interdisciplinary Chemistry |
*Glow discharge plasmas: non-thermal plasmas generated by the application of DC or low frequency RF (<100 kHz) electric field to the gap between two metal electrodes. Probably the most common plasma; this is the type of plasma generated within fluorescent light tubes.
*Capacitively coupled plasma (CCP): similar to glow discharge plasmas, but generated with high frequency RF electric fields, typically 13.56 MHz. These differ from glow discharges in that the sheaths are much less intense. These are widely used in the microfabrication and integrated circuit manufacturing industries for plasma etching and plasma enhanced chemical vapor deposition.
*Cascaded arc plasma source: a device to produce low temperature (≈1eV) high density plasmas (HDP).
*Inductively coupled plasma (ICP): similar to a CCP and with similar applications but the electrode consists of a coil wrapped around the chamber where plasma is formed.
*Wave heated plasma: similar to CCP and ICP in that it is typically RF (or microwave). Examples include helicon discharge and electron cyclotron resonance (ECR). | 0 | Theoretical and Fundamental Chemistry |
Magnetic torque magnetometry can be even more sensitive than SQUID magnetometry. However, magnetic torque magnetometry doesnt measure magnetism directly as all the previously mentioned methods do. Magnetic torque magnetometry instead measures the torque τ acting on a samples magnetic moment μ as a result of a uniform magnetic field B, τ = μ × B. A torque is thus a measure of the samples magnetic or shape anisotropy. In some cases the samples magnetization can be extracted from the measured torque. In other cases, the magnetic torque measurement is used to detect magnetic phase transitions or quantum oscillations. The most common way to measure magnetic torque is to mount the sample on a cantilever and measure the displacement via capacitance measurement between the cantilever and nearby fixed object, or by measuring the piezoelectricity of the cantilever, or by optical interferometry off the surface of the cantilever. | 0 | Theoretical and Fundamental Chemistry |
Regenerative medicine has been studied by dentists to find ways that damaged teeth can be repaired and restored to obtain natural structure and function. Dental tissues are often damaged due to tooth decay, and are often deemed to be irreplaceable except by synthetic or metal dental fillings or crowns, which requires further damage to be done to the teeth by drilling into them to prevent the loss of an entire tooth.
Researchers from King's College London have created a drug called Tideglusib that claims to have the ability to regrow dentin, the second layer of the tooth beneath the enamel which encases and protects the pulp (often referred to as the nerve).
Animal studies conducted on mice in Japan in 2007 show great possibilities in regenerating an entire tooth. Some mice had a tooth extracted and the cells from bioengineered tooth germs were implanted into them and allowed to grow. The result were perfectly functioning and healthy teeth, complete with all three layers, as well as roots. These teeth also had the necessary ligaments to stay rooted in its socket and allow for natural shifting. They contrast with traditional dental implants, which are restricted to one spot as they are drilled into the jawbone.
A persons baby teeth are known to contain stem cells that can be used for regeneration of the dental pulp after a root canal treatment or injury. These cells can also be used to repair damage from periodontitis, an advanced form of gum disease that causes bone loss and severe gum recession. Research is still being done to see if these stem cells are viable enough to grow into completely new teeth. Some parents even opt to keep their childrens baby teeth in special storage with the thought that, when older, the children could use the stem cells within them to treat a condition. | 1 | Applied and Interdisciplinary Chemistry |
Certain lithium compounds, also known as lithium salts, are used as psychiatric medication, primarily for bipolar disorder and for major depressive disorder. In lower doses, other salts such as lithium citrate are known as nutritional lithium and have occasionally been used to treat ADHD. Lithium is taken orally (by mouth).
Common side effects include increased urination, shakiness of the hands, and increased thirst. Serious side effects include hypothyroidism, diabetes insipidus, and lithium toxicity. Blood level monitoring is recommended to decrease the risk of potential toxicity. If levels become too high, diarrhea, vomiting, poor coordination, sleepiness, and ringing in the ears may occur. Lithium is teratogenic at high doses, especially during the first trimester of pregnancy. The use of lithium while breastfeeding is controversial; however, many international health authorities advise against it, and the long-term outcomes of perinatal lithium exposure have not been studied. The American Academy of Pediatrics lists lithium as contraindicated for pregnancy and lactation. The United States Food and Drug Administration categorizes lithium as having positive evidence of risk for pregnancy and possible hazardous risk for lactation.
Lithium salts are classified as mood stabilizers. Lithium's mechanism of action is not known.
In the nineteenth century, lithium was used in people who had gout, epilepsy, and cancer. Its use in the treatment of mental disorders began with Carl Lange in Denmark and William Alexander Hammond in New York City, who used lithium to treat mania from the 1870s onwards, based on now-discredited theories involving its effect on uric acid. Use of lithium for mental disorders was re-established (on a different theoretical basis) in 1948 by John Cade in Australia. Lithium carbonate is on the World Health Organization's List of Essential Medicines, and is available as a generic medication. In 2020, it was the 197th most commonly prescribed medication in the United States, with more than 2million prescriptions. It appears to be under-utilised in older people, though the reason for that is unclear. | 1 | Applied and Interdisciplinary Chemistry |
Studies have shown that PFOS is a persistent, bioaccumulative, and toxic pollutant. It was added to Annex B of the Stockholm Convention on Persistent Organic Pollutants in May 2009. Regulations in the United States, Canada, European Union, Australia, and Japan have banned the new production of PFOS-based products, including firefighting foams. 3M phased out production of PFOS in 2002 due to toxicity concerns.
One study, published in 2015, found that firefighters were more likely to have fluorinated surfactants in their bloodstream. In 2016, the United States Air Force paid $4.3 million for a water treatment system for residents downstream of Peterson Air Force Base in Colorado.
In the United States, discharges of AFFF by vessels to surface waters are regulated by the United States Environmental Protection Agency (EPA) and Department of Defense, pursuant to the Clean Water Act.
In Australia, in 2015 a public safety announcement was issued by the New South Wales Environment Protection Authority following a water source contamination near RAAF Base Williamtown. Surface water, groundwater and fish were reported to contain chemicals from firefighting foams that had been released by the local Royal Australian Air Force base prior to training protocol changes in 2008. The residents of the area were advised to not consume any bore water, in addition to eggs and seafood from fauna exposed to the contaminated water. The discovery led to the banning of all forms of fishing in the waters of Fullerton Cove until the beginning of October 2016.
As of 2017, the Australian Department of Defence was dealing with two class action suits brought by those affected by contamination at Williamtown and at Army Aviation Centre Oakey. Along with many airports and fire services, the Department of Defence is investigating possible contamination at 18 military sites across Australia. At Williamtown, it is also conducting studies on the uptake and residual contamination in plants, chickens and eggs.
In December 2017, New Zealand's Minister for the Environment announced that higher than acceptable levels of PFOS and PFOA were found in groundwater at two Royal New Zealand Air Force bases, thought to be from historic use of firefighting foam containing the substances. Residents residing near the airbases were told to drink bottled water until more extensive testing could be carried out.
In 2020, state government agencies in the US are planning to dispose of firefighting foam, either by incineration or landfilling. Nearly of foam will be disposed by the US. The potential health risks of incinerating AFFF are still being investigated by EPA and state agencies. | 0 | Theoretical and Fundamental Chemistry |
Karl Barry Sharpless (born April 28, 1941) is an American stereochemist. He is a two-time Nobel laureate in Chemistry known for his work on stereoselective reactions and click chemistry.
Sharpless was awarded half of the 2001 Nobel Prize in Chemistry "for his work on chirally catalysed oxidation reactions", and one third of the 2022 prize, jointly with Carolyn R. Bertozzi and Morten P. Meldal, "for the development of click chemistry and bioorthogonal chemistry". Sharpless is the fifth person (in addition to two organizations), to have twice been awarded a Nobel prize, along with Marie Curie, John Bardeen, Linus Pauling and Frederick Sanger, and the third to have been awarded two prizes in the same discipline (after Bardeen and Sanger). | 0 | Theoretical and Fundamental Chemistry |
In the geometry of crystal nets, one can treat edges as line segments. For example, in a crystal net, it is presumed that edges do not “collide” in the sense that when treating them as line segments, they do not intersect. Several polyhedral constructions can be derived from crystal nets. For example, a vertex figure can be obtained by subdividing each edge (treated as a line segment) by the insertion of subdividing points, and then the vertex figure of a given vertex is the convex hull of the adjacent subdividing points (i.e., the convex polyhedron whose vertices are the adjacent subdividing points).
Another polyhedral construction is to determine the neighborhood of a vertex in the crystal net. One application is to define an energy function as a (possibly weighted) sum of squares of distances from vertices to their neighbors, and with respect to this energy function, the net is in equilibrium (with respect to this energy function) if each vertex is positioned at the centroid of its neighborhood, this is the basis of the crystal net identification program SYSTRE. (mathematicians
use the term ``harmonic realiaztions" instead of ``crystal nets in equilibrium positions" because the positions are characterized by the discrete Laplace equation; they also introduced the notion of standard realizations which are special harmonic realizations characterized by a certain minimal principle as well;see ). Some crystal nets are isomorphic to crystal nets in equilibrium positions, and since an equilibrium position is a normal form, the crystal net isomorphism problem (i.e., the query whether two given crystal nets are isomorphic as graphs; not to be confused with crystal isomorphism) is readily computed even though, as a subsumption of the graph isomorphism problem, it is apparently computationally difficult in general. | 0 | Theoretical and Fundamental Chemistry |
A nitronate (IUPAC: azinate) in organic chemistry is an anion with the general structure , containing the functional group, where R can be hydrogen, halogen, organyl group or other groups. It is the anion of nitronic acid (sometimes also called an aci-nitro compound, or an azinic acid), a tautomeric form of a nitro compound. Just as aldehydes and ketones can exist in equilibrium with their enol tautomer, nitro compounds exist in equilibrium with their nitronate tautomer under basic conditions. In practice they are formed by the deprotonation of the α-carbon, the pK of which is typically around 17.
Nitronates are formed as intermediates in the Henry reaction, Hass–Bender oxidation and Nef reaction, the latter of which also demonstrates the instability of the nitronic acid form. The nitronate has two different resonance structures, one with a negative charge on the α-carbon and a double bond between the nitrogen and one of the oxygens, and another resonance structure with a double bond between the nitrogen and the α-carbon, and single bonds between the nitrogen and the oxygens. | 0 | Theoretical and Fundamental Chemistry |
Modeling of the common representation of the Dalitz plot can be complicated due to its nontrivial shape. One can however introduce such kinematic variables so that Dalitz plot gets a rectangular (or squared) shape:
where is the invariant mass of particles 1 and 2 in a given decay event; and are its maximal and minimal kinematically allowed values, while is the angle between particles 1 and 3 in the rest frame of particles 1 and 2. This technique is commonly called "Square Dalitz plot" (SDP). | 0 | Theoretical and Fundamental Chemistry |
Corpuscularianism was associated by its leading proponents with the idea that some of the apparent properties of objects are artifacts of the perceiving mind, that is, "secondary" qualities as distinguished from "primary" qualities. Corpuscles were thought to be unobservable and having a very limited number of basic properties, such as size, shape, and motion. | 1 | Applied and Interdisciplinary Chemistry |
Metal substrates for use in SAMs can be produced through physical vapor deposition techniques, electrodeposition or electroless deposition. Thiol or selenium SAMs produced by adsorption from solution are typically made by immersing a substrate into a dilute solution of alkane thiol in ethanol, though many different solvents can be used besides use of pure liquids. While SAMs are often allowed to form over 12 to 72 hours at room temperature, SAMs of alkanethiolates form within minutes. Special attention is essential in some cases, such as that of dithiol SAMs to avoid problems due to oxidation or photoinduced processes, which can affect terminal groups and lead to disorder and multilayer formation. In this case appropriate choice of solvents, their degassing by inert gasses and preparation in the absence of light is crucial and allows formation of "standing up" SAMs with free –SH groups. Self-assembled monolayers can also be adsorbed from the vapor phase. In some cases when obtaining an ordered assembly is difficult or when different density phases need to be obtained substitutional self-assembly is used. Here one first forms the SAM of a given type of molecules, which give rise to ordered assembly and then a second assembly phase is performed (e.g. by immersion into a different solution). This method has also been used to give information on relative binding strengths of SAMs with different head groups and more generally on self-assembly characteristics. | 0 | Theoretical and Fundamental Chemistry |
The relative reducing and oxidizing natures of these photocatalysts can be understood by considering the ligands electronegativity and the catalyst complexs metal center. More electronegative metals and ligands can stabilize electrons better than their less electronegative counterparts. Therefore, complexes with more electronegative ligands are more oxidizing than less electronegative ligand complexes. For example, the ligands 2,2-bipyridine and 2,2-phenylpyridine are isoelectronic structures, containing the same number and arrangement of electrons. Phenylpyridine replaces one of the nitrogen atoms in bipyridine with a carbon atom. Carbon is less electronegative than nitrogen is, so it holds electrons less tightly. Since the remainder of the ligand molecule is identical and phenylpyridine holds electrons less tightly than bipyridine, it is more strongly electron-donating and less electronegative as a ligand. Hence, complexes with phenylpyridine ligands are more strongly reducing and less strongly oxidizing than equivalent complexes with bipyridine ligands.
Similarly, a fluorinated phenylpyridine ligand is more electronegative than phenylpyridine so complexes with fluorine-containing ligands are more strongly oxidizing and less strongly reducing than equivalent unsubstituted phenylpyridine complexes. The metal center's electronic influence on the complex is more complex than the ligand effect. According to the Pauling scale of electronegativity, both ruthenium and iridium have an electronegativity of 2.2. If this was the sole factor relevant to redox potentials, then complexes of ruthenium and iridium with the same ligands should be equally powerful photoredox catalysts. However, considering the Rehm-Weller equation, the spectroscopic properties of the metal play a role in determining the redox properties of the excited state. In particular, the parameter E is related to the emission wavelength of the complex and therefore, to the size of the Stokes shift - the difference in energy between the maximum absorption and emission of a molecule. Typically, ruthenium complexes have large Stokes shifts and hence, low energy emission wavelengths and small zero-zero excitation energies when compared to iridium complexes. In effect, while ground-state ruthenium complexes can be potent reductants, the excited-state complex is a far less potent reductant or oxidant than its equivalent iridium complex. This makes iridium preferred for the development of general organic transformations because the stronger redox potentials of the excited catalyst allows the use of weaker stoichiometric reductants and oxidants or the use of less reactive substrates.
It is often the case that these photocatalysts are balanced with a counter-ion, as is the case with the example complex tris-(2,2’-bipyridyl)ruthenium which is accompanied by two anions to balance the overall charge of the ion pair to zero. However, there are transition metal photoredox catalysts that exist without a counter-ion such as tris(2-phenylpyridine)iridium (often abbreviated Ir(ppy)). The significance of these counter-ions are dependent on the ion association between the photoredox catalyst and its counter-ion(s) and is dependent on the solvent used for the reaction. Although photophysical properties such as redox potential, excitation energy, and ligand electronegative have often been considered key parameters for the use and reactivity of these complexes, counter-ion identity has been shown to play a significant role in low-polarity solvents. Particularly, it has been shown that having a tightly associated counter-ion increases the rate of electron-transfer when reducing a substrate but significantly reduces the rate of electron-transfer when oxidizing a substrate. This is believed to occur because the counter-ion essentially "blocks" the electron-transfer into the photoredox complex by shielding the more positively charged region of the complex; whereas, having the tight counter-ion association pushes the electron density further from the photoredox catalyst's metal-center, making it easier to be transferred from the catalyst (of course this only applies to the case where the photoredox catalyst is a cation and the counter-ion is an anion). Counter-ion identity thus is an additional parameter to consider when developing new photoredox reactions. | 0 | Theoretical and Fundamental Chemistry |
Pigments offer great potential in modifying the application properties of a coating. Due to their fine particle size and inherently high surface energy, they often require a surface treatment in order to enhance their ease of dispersion in a liquid medium. A wide variety of surface treatments have been previously used, including the adsorption on the surface of a molecule in the presence of polar groups, monolayers of polymers, and layers of inorganic oxides on the surface of organic pigments.
New surfaces are constantly being created as larger pigment particles get broken down into smaller subparticles. These newly-formed surfaces consequently contribute to larger surface energies, whereby the resulting particles often become cemented together into aggregates. Because particles dispersed in liquid media are in constant thermal or Brownian motion, they exhibit a strong affinity for other pigment particles nearby as they move through the medium and collide. This natural attraction is largely attributed to the powerful short-range van der Waals forces, as an effect of their surface energies.
The chief purpose of pigment dispersion is to break down aggregates and form stable dispersions of optimally sized pigment particles. This process generally involves three distinct stages: wetting, deaggregation, and stabilization. A surface that is easy to wet is desirable when formulating a coating that requires good adhesion and appearance. This also minimizes the risks of surface tension related defects, such as crawling, cratering, and orange peel. This is an essential requirement for pigment dispersions; for wetting to be effective, the surface tension of the pigment's vehicle must be lower than the surface free energy of the pigment. This allows the vehicle to penetrate into the interstices of the pigment aggregates, thus ensuring complete wetting. Finally, the particles are subjected to a repulsive force in order to keep them separated from one another and lowers the likelihood of flocculation.
Dispersions may become stable through two different phenomena: charge repulsion and steric or entropic repulsion. In charge repulsion, particles that possess the same like electrostatic charges repel each other. Alternatively, steric or entropic repulsion is a phenomenon used to describe the repelling effect when adsorbed layers of material (such as polymer molecules swollen with solvent) are present on the surface of the pigment particles in dispersion. Only certain portions (anchors) of the polymer molecules are adsorbed, with their corresponding loops and tails extending out into the solution. As the particles approach each other their adsorbed layers become crowded; this provides an effective steric barrier that prevents flocculation. This crowding effect is accompanied by a decrease in entropy, whereby the number of conformations possible for the polymer molecules is reduced in the adsorbed layer. As a result, energy is increased and often gives rise to repulsive forces that aid in keeping the particles separated from each other. | 0 | Theoretical and Fundamental Chemistry |
During the 19th century, the demand for nitrates and ammonia for use as fertilizers and industrial feedstocks rapidly increased. The main source was mining niter deposits and guano from tropical islands. At the beginning of the 20th century these reserves were thought insufficient to satisfy future demands, and research into new potential sources of ammonia increased. Although atmospheric nitrogen (N) is abundant, comprising ~78% of the air, it is exceptionally stable and does not readily react with other chemicals.
Haber, with his assistant Robert Le Rossignol, developed the high-pressure devices and catalysts needed to demonstrate the Haber process at a laboratory scale. They demonstrated their process in the summer of 1909 by producing ammonia from the air, drop by drop, at the rate of about per hour. The process was purchased by the German chemical company BASF, which assigned Carl Bosch the task of scaling up Haber's tabletop machine to industrial scale. He succeeded in 1910. Haber and Bosch were later awarded Nobel Prizes, in 1918 and 1931 respectively, for their work in overcoming the chemical and engineering problems of large-scale, continuous-flow, high-pressure technology.
Ammonia was first manufactured using the Haber process on an industrial scale in 1913 in BASF's Oppau plant in Germany, reaching 20 tonnes/day in 1914. During World War I, the production of munitions required large amounts of nitrate. The Allies had access to large deposits of sodium nitrate in Chile (Chile saltpetre) controlled by British companies. India had large supplies too, but it was also controlled by the British. Germany had no such resources, so the Haber process proved essential to the German war effort. Synthetic ammonia from the Haber process was used for the production of nitric acid, a precursor to the nitrates used in explosives.
The original Haber–Bosch reaction chambers used osmium as the catalyst, but it was available in extremely small quantities. Haber noted uranium was almost as effective and easier to obtain than osmium. In 1909, BASF researcher Alwin Mittasch discovered a much less expensive iron-based catalyst that is still used. A major contributor to the elucidation of this catalysis was Gerhard Ertl. The most popular catalysts are based on iron promoted with KO, CaO, SiO, and AlO.
During the interwar years, alternative processes were developed, most notably the Casale process, Claude process, and the Mont-Cenis process developed by Friedrich Uhde Ingenieurbüro. Luigi Casale and Georges Claude proposed to increase the pressure of the synthesis loop to , thereby increasing the single-pass ammonia conversion and making nearly complete liquefaction at ambient temperature feasible. Claude proposed to have three or four converters with liquefaction steps in series, thereby avoiding recycling. Most plants continue to use the original Haber process ( and ), albeit with improved single-pass conversion and lower energy consumption due to process and catalyst optimization. | 0 | Theoretical and Fundamental Chemistry |
Iatrochemistry (; also known as chemiatria or chemical medicine) is an archaic pre-scientific school of thought that was supplanted by modern chemistry and medicine. Having its roots in alchemy, iatrochemistry sought to provide chemical solutions to diseases and medical ailments.
This area of science fell out of use in Europe since the rise of modern establishment medicine. Iatrochemistry was popular between 1525 and 1660, especially in the Low Countries. Its most notable leader was Paracelsus, an important Swiss alchemist of the 16th century. Iatrochemists believed that physical health was dependent on a specific balance of bodily fluids. Iatrochemical therapies and concepts are still in wide use in South Asia, East Asia and amongst their diasporic communities worldwide. | 1 | Applied and Interdisciplinary Chemistry |
Faraday force magnetometry uses the fact that a spatial magnetic field gradient produces force that acts on a magnetized object, F = (M⋅∇)B. In Faraday force magnetometry the force on the sample can be measured by a scale (hanging the sample from a sensitive balance), or by detecting the displacement against a spring. Commonly a capacitive load cell or cantilever is used because of its sensitivity, size, and lack of mechanical parts. Faraday force magnetometry is approximately one order of magnitude less sensitive than a SQUID. The biggest drawback to Faraday force magnetometry is that it requires some means of not only producing a magnetic field, but also producing a magnetic field gradient. While this can be accomplished by using a set of special pole faces, a much better result can be achieved by using set of gradient coils. A major advantage to Faraday force magnetometry is that it is small and reasonably tolerant to noise, and thus can be implemented in a wide range of environments, including a dilution refrigerator. Faraday force magnetometry can also be complicated by the presence of torque (see previous technique). This can be circumvented by varying the gradient field independently of the applied DC field so the torque and the Faraday force contribution can be separated, and/or by designing a Faraday force magnetometer that prevents the sample from being rotated. | 0 | Theoretical and Fundamental Chemistry |
Initially, analytes in a metabolomic sample comprise a highly complex mixture. This complex mixture can be simplified prior to detection by separating some analytes from others. Separation achieves various goals: analytes which cannot be resolved by the detector may be separated in this step; in MS analysis, ion suppression is reduced; the retention time of the analyte serves as information regarding its identity. This separation step is not mandatory and is often omitted in NMR and "shotgun" based approaches such as shotgun lipidomics.
Gas chromatography (GC), especially when interfaced with mass spectrometry (GC-MS), is a widely used separation technique for metabolomic analysis. GC offers very high chromatographic resolution, and can be used in conjunction with a flame ionization detector (GC/FID) or a mass spectrometer (GC-MS). The method is especially useful for identification and quantification of small and volatile molecules. However, a practical limitation of GC is the requirement of chemical derivatization for many biomolecules as only volatile chemicals can be analysed without derivatization. In cases where greater resolving power is required, two-dimensional chromatography (GCxGC) can be applied.
High performance liquid chromatography (HPLC) has emerged as the most common separation technique for metabolomic analysis. With the advent of electrospray ionization, HPLC was coupled to MS. In contrast with GC, HPLC has lower chromatographic resolution, but requires no derivatization for polar molecules, and separates molecules in the liquid phase. Additionally HPLC has the advantage that a much wider range of analytes can be measured with a higher sensitivity than GC methods.
Capillary electrophoresis (CE) has a higher theoretical separation efficiency than HPLC (although requiring much more time per separation), and is suitable for use with a wider range of metabolite classes than is GC. As for all electrophoretic techniques, it is most appropriate for charged analytes. | 1 | Applied and Interdisciplinary Chemistry |
A given substrate-liquid-vapor combination yields a continuous range of contact angle values in practice. The maximum contact angle is referred to as the advancing contact angle and the minimum contact angle is referred to as the receding contact angle. The advancing and receding contact angles are measured from dynamic experiments where droplets or liquid bridges are in movement. In contrast, the equilibrium contact angle described by the Young-Laplace equation is measured from a static state. Static measurements yield values in-between the advancing and receding contact angle depending on deposition parameters (e.g. velocity, angle, and drop size) and drop history (e.g. evaporation from time of deposition). Contact angle hysteresis is defined as although the term is also used to describe the expression . The static, advancing, or receding contact angle can be used in place of the equilibrium contact angle depending on the application. The overall effect can be seen as closely analogous to static friction, i.e., a minimal amount of work per unit distance is required to move the contact line.
The advancing contact angle can be described as a measure of the liquid-solid cohesion while the receding contact angle is a measure of liquid-solid adhesion. The advancing and receding contact angles can be measured directly using different methods and can also be calculated from other wetting measurements such as force tensiometry (aka Wilhemy-Plate method).
Advancing and receding contact angles can be measured directly from the same measurement if drops are moved linearly on a surface. For example, a drop of liquid will adopt a given contact angle when static, but when the surface is tilted the drop will initially deform so that the contact area between the drop and surface remains constant. The "downhill" side of the drop will adopt a higher contact angle while the "uphill" side of the drop will adopt a lower contact angle. As the tilt angle increases the contact angles will continue to change but the contact area between the drop and surface will remain constant. At a given surface tilt angle, the advancing and receding contact angles will be met and the drop will move on the surface. In practice, the measurement can be influenced by shear forces and momentum if the tilt velocity is high. The measurement method can also be challenging in practice for systems with high (>30 degrees) or low (<10 degrees) contact angle hysteresis.
Advancing and receding contact angle measurements can be carried out by adding and removing liquid from a drop deposited on a surface. If a sufficiently small volume of liquid is added to a drop, the contact line will still be pinned, and the contact angle will increase. Similarly, if a small amount of liquid is removed from a drop, the contact angle will decrease.
The Young's equation assumes a homogeneous surface and does not account for surface texture or outside forces such as gravity. Real surfaces are not atomically smooth or chemically homogeneous so a drop will assume contact angle hysteresis. The equilibrium contact angle () can be calculated from and as was shown theoretically by Tadmor and confirmed experimentally by Chibowski as,
where
On a surface that is rough or contaminated, there will also be contact angle hysteresis, but now the local equilibrium contact angle (the Young equation is now only locally valid) may vary from place to place on the surface. According to the Young–Dupré equation, this means that the adhesion energy varies locally – thus, the liquid has to overcome local energy barriers in order to wet the surface. One consequence of these barriers is contact angle hysteresis: the extent of wetting, and therefore the observed contact angle (averaged along the contact line), depends on whether the liquid is advancing or receding on the surface.
Because liquid advances over previously dry surface but recedes from previously wet surface, contact angle hysteresis can also arise if the solid has been altered due to its previous contact with the liquid (e.g., by a chemical reaction, or absorption). Such alterations, if slow, can also produce measurably time-dependent contact angles. | 0 | Theoretical and Fundamental Chemistry |
Some US cities have undertaken sewer separation projects — building a second piping system for all or part of the community. In many of these projects, cities have been able to separate only portions of their combined systems. High costs or physical limitations may preclude building a completely separate system. In 2011, Washington, D.C., separated its sewers in four small neighborhoods at a cost of $11 million. (The project cost also included improvements to the drinking water piping system.) | 1 | Applied and Interdisciplinary Chemistry |
In statistical copolymers the sequence of monomer residues follows a statistical rule. If the probability of finding a given type monomer residue at a particular point in the chain is equal to the mole fraction of that monomer residue in the chain, then the polymer may be referred to as a truly random copolymer (structure 3).
Statistical copolymers are dictated by the reaction kinetics of the two chemically distinct monomer reactants, and are commonly referred to interchangeably as "random" in the polymer literature. As with other types of copolymers, random copolymers can have interesting and commercially desirable properties that blend those of the individual homopolymers. Examples of commercially relevant random copolymers include rubbers made from styrene-butadiene copolymers and resins from styrene-acrylic or methacrylic acid derivatives. Copolymerization is particularly useful in tuning the glass transition temperature, which is important in the operating conditions of polymers; it is assumed that each monomer occupies the same amount of free volume whether it is in a copolymer or homopolymer, so the glass transition temperature (T) falls between the values for each homopolymer and is dictated by the mole or mass fraction of each component.
A number of parameters are relevant in the composition of the polymer product; namely, one must consider the reactivity ratio of each component. Reactivity ratios describe whether the monomer reacts preferentially with a segment of the same type or of the other type. For example, a reactivity ratio that is less than one for component 1 indicates that this component reacts with the other type of monomer more readily. Given this information, which is available for a multitude of monomer combinations in the "Wiley Database of Polymer Properties", the Mayo-Lewis equation can be used to predict the composition of the polymer product for all initial mole fractions of monomer. This equation is derived using the Markov model, which only considers the last segment added as affecting the kinetics of the next addition; the Penultimate Model considers the second-to-last segment as well, but is more complicated than is required for most systems. When both reactivity ratios are less than one, there is an azeotropic point in the Mayo-Lewis plot. At this point, the mole fraction of monomer equals the composition of the component in the polymer.
There are several ways to synthesize random copolymers. The most common synthesis method is free radical polymerization; this is especially useful when the desired properties rely on the composition of the copolymer rather than the molecular weight, since free radical polymerization produces relatively disperse polymer chains. Free radical polymerization is less expensive than other methods, and produces high-molecular weight polymer quickly. Several methods offer better control over dispersity. Anionic polymerization can be used to create random copolymers, but with several caveats: if carbanions of the two components do not have the same stability, only one of the species will add to the other. Additionally, anionic polymerization is expensive and requires very clean reaction conditions, and is therefore difficult to implement on a large scale. Less disperse random copolymers are also synthesized by ″living″ controlled radical polymerization methods, such as atom-transfer radical-polymerization (ATRP), nitroxide mediated radical polymerization (NMP), or reversible addition−fragmentation chain-transfer polymerization (RAFT). These methods are favored over anionic polymerization because they can be performed in conditions similar to free radical polymerization. The reactions require longer experimentation periods than free radical polymerization, but still achieve reasonable reaction rates. | 0 | Theoretical and Fundamental Chemistry |
Raman spectroscopy is similar to FTIR in using a focused laser on the glass phase of the melt inclusion or a vapor bubble that may be contained in the melt inclusion to identify wavelengths associated with the Raman vibrating bands of volatiles, such as HO and CO. Raman spectroscopy can also be used to determine the density of CO contained in a vapor bubble if present at a high enough concentration within a melt inclusion. | 0 | Theoretical and Fundamental Chemistry |
Nayak was named after Swami Vivekananda (born Narendra Nath Datta). He has stated that seeing his father's business premises being repossessed by the bank and his father buying a lottery ticket on the advice of an astrologer to pay off the loan with the total confidence that it would get the first prize made him turn to rationalism. He married Asha Nayak, a lawyer in Mangaluru in a non-religious ceremony. Nayak started out working as a lecturer in the Department of biochemistry in the Kasturba Medical College in Mangalore in 1978. In 1982, he met Basava Premanand, a notable rationalist from Kerala, and was influenced by him.
Karnataka State Police withdrew his security wherein Nayak was quoted to say that it was an open invitation by forces to finish him. | 1 | Applied and Interdisciplinary Chemistry |
A number of leading environmentalists are of the opinion that the project could be an ecological disaster. There would be a decrease in downstream flows resulting in reduction of fresh water inflows into the seas seriously jeopardizing aquatic life. | 1 | Applied and Interdisciplinary Chemistry |
In recent times, the construction of larger dams in the Netherlands has been driven by both the necessity to protect the hinterlands and the ambition to create new agricultural lands.
The formation of currents at the mouth of an inlet arises from the tidal actions of filling (high tide) and emptying (ebb tide) of the basin. The speed of these currents is influenced by the tidal range, the tidal curve, the volume of the tidal basin (also known as the storage area), and the size of the flow profile at that location. The tidal range varies along the Dutch coast, being minimal near Den Helder (about 1.5 metres) and maximal off the coast of Zeeland (2 to 3 metres), with the range expanding to 4 to 5 metres in the areas behind the Oosterschelde and Westerschelde.
In tidal basins with loosely packed seabeds, current channels emerge and may shift due to the constantly changing directions and speeds of currents. The strongest flows cause scour in the deepest channels, such as in the Oosterschelde where depths can reach up to 45 metres, while sandbanks form between these channels, occasionally becoming exposed at low tide.
The channel systems that naturally develop in tidal areas are generally in a state of approximate equilibrium, balancing flow velocity and the total flow profile. Conversely, when dike breaches are sealed, this equilibrium is often not yet achieved at the time of closure. For instance, rapid intervention in closing numerous breaches following the 1953 storm surge helped limit erosion. For the construction of a dam at the mouth of an inlet, activities are undertaken to reduce the flow profile, potentially leading to increased flow velocities and subsequent scouring unless pre-emptive measures are taken, such as reinforcing the beds and sides of channels with bottom protection. An exception occurs when the surface area of the tidal basin is preliminarily reduced by compartmentalisation dams.
The procedure for closing a tidal channel can generally be segmented into four phases:
# A preparatory phase with a slight reduction in the flow profile (to 80 to 90% of its original size), during which dam sections are constructed in shallow areas and soil protection is placed in the channels.
# A sill is then erected, serving as a foundation for the closing dike. This sill can help distribute the dike's pressure on the subsoil and/or act as a filter between the bottom protection and the closing structure. The closure gap at this stage must be wide enough to allow the ebb and flow currents to pass without damaging the sill and the protective measures.
# The actual closure, where the final gap is sealed.
# The final phase involves constructing the dike over and around the temporary dam.
Under specific circumstances, alternative construction methods may be applied; for instance, during a sand closure, dumping capacity is utilised in such a manner that more material is added per tide than can be removed by the current, typically negating the need for soil protection.
When the Zuiderzee was enclosed in 1932, it was still possible to manage the current with boulder clay, as the tidal difference there was only about 1 metre, preventing excessively high flow velocities in the closure gap that would require alternative materials. Numerous closure methods have been implemented in the Delta area, on both small and large scales, highly dependent on a variety of preconditions. These include hydraulic and soil mechanical prerequisites, as well as available resources such as materials, equipment, labour, finances, and expertise. Post-World War II, the experiences gained from dike repairs in Walcheren in 1945, the closure of the Brielse Maas in 1950, the Braakman in 1952, and the repair of the breaches after the 1953 storm surge significantly influenced the choice of closure methods for the first Delta dams.
Up until the completion of the Brouwersdam in 1971, the choice of closure method was almost entirely based on technical factors. However, environmental and fisheries considerations became equally vital in the selection of closure methods for the Markiezaatskade near Bergen op Zoom, the Philipsdam, Oesterdam, and the storm surge barrier in the Oosterschelde, taking into account factors like the timing of tidal organism mortality and salinity control during closures, which are critical for determining the initial conditions of the newly formed basin. | 1 | Applied and Interdisciplinary Chemistry |
In a non-polar solvent, it is the exposure of the hydrophilic head groups to the surrounding solvent that is energetically unfavourable, giving rise to a water-in-oil system. In this case, the hydrophilic groups are sequestered in the micelle core and the hydrophobic groups extend away from the center. These inverse micelles are proportionally less likely to form on increasing headgroup charge, since hydrophilic sequestration would create highly unfavorable electrostatic interactions.
It is well established that for many surfactant/solvent systems a small fraction of the inverse micelles spontaneously acquire a net charge of +q or -q. This charging takes place through a disproportionation/comproportionation mechanism rather than a dissociation/association mechanism and the equilibrium constant for this reaction is on the order of 10 to 10, which means about every 1 in 100 to 1 in 100 000 micelles will be charged. | 0 | Theoretical and Fundamental Chemistry |
The mechanistic study of the palladium-catalyzed meta-selective C–H bond activation with a nitrile-containing template was done by Yu, Wu, Houk and their co-workers. The DFT calculations suggest that the regioselectivity is achieved in the C–H activation step, which is the rate-determining step. It proceeds via a concerted metalation-deprotonation (CMD) pathway, which means that palladation and deprotonation of the C–H bond happen at the same time. Surprisingly, calculations reveal that the Pd–Ag heterodimeric transition state leads to meta-selectivity while the Pd monomeric transition state leads to ortho-selectivity.
The role of mono-N-protected amino acid is proposed as a dianionic ligand which participates in the CMD step assisting the deprotonation of the C–H bond in the rate- and regio-determining step. | 0 | Theoretical and Fundamental Chemistry |
Macroprolactin is the term used to describe complexed forms of the pituitary hormone prolactin which are found in blood. The most common complex found in blood consists of prolactin and immunoglobulin G (IgG). While the free prolactin hormone is active, prolactin in the macroprolactin complex does not have any biological activity in the body and is considered benign. However, macroprolactin is detected by all Laboratory tests that measure prolactin in blood. This leads to misdiagnosis of hyperprolactinaemia in many people, especially those with other symptoms, such as infertility or menstrual problems.
"Macroprolactin" is most commonly a complex of prolactin and IgG (typically IgG4), displaying a molecular weight of approximately 150 kDa (which is hence 6–7 fold higher that the native molecule). Polymeric aggregate of highly glycosylated prolactin monomers or prolactin-IgA complexes (i.e. non-IgG-type macroprolactin) act similarly and also count as "macroprolactin".
In patients with hyperprolactinemia, the serum pattern of prolactin isoforms usually encompasses 60%–90% monomeric prolactin, 15%–30% big-prolactin (40–60 kDa: usually prolactin dimers or big-big degradation products) and 0%–10% big-big prolactin (>100 kDa). The condition of macroprolactinaemia is hence defined as predominance (i.e. >30%–60%) of circulating prolactin isoforms with molecular weight >100 kDa.
There are certain chemicals, such as polyethylene glycol, that can be added to remove macroprolactin from a suspicious sample. The sample can then be re-analysed to see if the prolactin levels are still high. The gold standard test to diagnose macroprolactin is gel-filtration chromatography. | 1 | Applied and Interdisciplinary Chemistry |
Similar to how plant peroxisomal enzymes bind propionyl-CoA and isobutyryl-CoA, Gen5, an acetyltransferase in humans, binds to propionyl-CoA and butyryl-CoA. These specifically bind to the catalytic domain of Gen5L2. This conserved acetyltransferase is responsible for the regulation of transcription by lysine acetylation of the histone N-terminal tails. This function of acetylation has a much higher reaction rate than propionylation or butyrylation. Because of the structure of propionyl-CoA, Gen5 distinguishes between different acyl-CoA molecules. In fact, it was found that the propyl group of butyrl-CoA cannot bind due to lack of stereospecificity to the active binding site of Gen5 due to the unsaturated acyl chains. On the other hand, the third carbon of propionyl-CoA can fit into the active site of Gen5 with the correct orientation. | 1 | Applied and Interdisciplinary Chemistry |
Because one of the main purposes for biomedical engineering is to mimic body parts to sustain normal body functions, due to their biocompatible properties, biopolymers are used vastly for tissue engineering, medical devices and the pharmaceutical industry. Many biopolymers can be used for regenerative medicine, tissue engineering, drug delivery, and overall medical applications due to their mechanical properties. They provide characteristics like wound healing, and catalysis of bioactivity, and non-toxicity. Compared to synthetic polymers, which can present various disadvantages like immunogenic rejection and toxicity after degradation, many biopolymers are normally better with bodily integration as they also possess more complex structures, similar to the human body.
More specifically, polypeptides like collagen and silk, are biocompatible materials that are being used in ground-breaking research, as these are inexpensive and easily attainable materials. Gelatin polymer is often used on dressing wounds where it acts as an adhesive. Scaffolds and films with gelatin allow for the scaffolds to hold drugs and other nutrients that can be used to supply to a wound for healing.
As collagen is one of the more popular biopolymers used in biomedical science, here are some examples of their use:
Collagen based drug delivery systems: collagen films act like a barrier membrane and are used to treat tissue infections like infected corneal tissue or liver cancer. Collagen films have all been used for gene delivery carriers which can promote bone formation.
Collagen sponges: Collagen sponges are used as a dressing to treat burn victims and other serious wounds. Collagen based implants are used for cultured skin cells or drug carriers that are used for burn wounds and replacing skin.
Collagen as haemostat: When collagen interacts with platelets it causes a rapid coagulation of blood. This rapid coagulation produces a temporary framework so the fibrous stroma can be regenerated by host cells. Collagen based haemostat reduces blood loss in tissues and helps manage bleeding in organs such as the liver and spleen.
Chitosan is another popular biopolymer in biomedical research. Chitosan is derived from chitin, the main component in the exoskeleton of crustaceans and insects and the second most abundant biopolymer in the world. Chitosan has many excellent characteristics for biomedical science. Chitosan is biocompatible, it is highly bioactive, meaning it stimulates a beneficial response from the body, it can biodegrade which can eliminate a second surgery in implant applications, can form gels and films, and is selectively permeable. These properties allow for various biomedical applications of chitosan.
Chitosan as drug delivery: Chitosan is used mainly with drug targeting because it has potential to improve drug absorption and stability. In addition, chitosan conjugated with anticancer agents can also produce better anticancer effects by causing gradual release of free drug into cancerous tissue.
Chitosan as an anti-microbial agent: Chitosan is used to stop the growth of microorganisms. It performs antimicrobial functions in microorganisms like algae, fungi, bacteria, and gram-positive bacteria of different yeast species.
Chitosan composite for tissue engineering: Chitosan powder blended with alginate is used to form functional wound dressings. These dressings create a moist, biocompatible environment which aids in the healing process. This wound dressing is also biodegradable and has porous structures that allows cells to grow into the dressing. Furthermore, thiolated chitosans (see thiomers) are used for tissue engineering and wound healing, as these biopolymers are able to crosslink via disulfide bonds forming stable three-dimensional networks. | 1 | Applied and Interdisciplinary Chemistry |
Donor−acceptor (D−A) conjugated polymers have been investigated for the medicinal purposes. Nano-PCPDTBT CPs have two moieties: 2-ethylhexyl cyclopentadithiophene and 2,1,3-benzothiadiazole. When the PCPDTBT nanoparticle solution (0.115 mg/mL) was exposed to an 808 nm NIR laser (0.6 W/cm), the temperature could be increased by more than 30 °C. Wang et al. designed four NIR-absorbing D-A structured conjugated polymer dots (Pdots) containing diketopyrrolo-pyrrole (DPP) and thiophene units as effective photothermal materials with the PCE up to 65% for in vivo cancer therapy. Zhang et al. constructed PBIBDF-BT D-A CPs by using isoindigo derivative (BIBDF) and bithiophene (BT) as EA and ED respectively. PBIBDF-BT was further modified with poly(ethylene glycol)-block-poly(hexyl ethylene phosphate) (mPEG-b-PHEP) to obtain PBIBDF-BT@NP PPE with PCE of 46.7% and high stability in physiological environment. Yang’s group designed PBTPBF-BT CPs, in which the bis(5-oxothieno[3,2-b]pyrrole-6-ylidene)-benzodifurandione (BTPBF) and the 3,3′-didodecyl-2,2′-bithiophene (BT) units acting as EA and ED respectively. The D-A CPs have a maximum absorption peak at 1107 nm and a relative high photothermal conversion efficiency (66.4%). Pu et al. synthesized PC70BM-PCPDTBT D-A CPs via nanoprecipitation of EA (6,6)-phenyl-C71-butyric acid methyl ester (PC70BM) and ED PCPDTBT (SPs) for PA-guided PTT. Wang et al. developed D-A CPs TBDOPV-DT containing thiophene-fused benzodifurandione-based oligo(p-phenylenevinylene) (TBDOPV) as EA unit and 2,2′-bithio-phene (DT) as ED unit. TBDOPV-DT CPs have a strong absorption at 1093 nm and achieve highly efficient NIR-II photothermal conversion. | 0 | Theoretical and Fundamental Chemistry |
Examples of well-studied vdW molecules are Ar, H-Ar, HO-Ar, benzene-Ar, (HO), and (HF).
Others include the largest diatomic molecule He, and LiHe. | 0 | Theoretical and Fundamental Chemistry |
Thermodynamic diagrams usually show a net of five different lines:
* isobars = lines of constant pressure
* isotherms = lines of constant temperature
* dry adiabats = lines of constant potential temperature representing the temperature of a rising parcel of dry air
* saturated adiabats or pseudoadiabats = lines representing the temperature of a rising parcel saturated with water vapor
* mixing ratio = lines representing the dewpoint of a rising parcel
The lapse rate, dry adiabatic lapse rate (DALR) and moist adiabatic lapse rate (MALR), are obtained. With the help of these lines, parameters such as cloud condensation level, level of free convection, onset of cloud formation. etc. can be derived from the soundings. | 0 | Theoretical and Fundamental Chemistry |
This class allows the students to gain admission to a school of the Fédération Gay Lussac (19 schools) after two years. These 2 years consist of studying engineer's trades in the domain of chemistry.
There are 5 CPIs in France: Rennes, Clermont-Ferrand, Lille, Pau and Strasbourg at the ECPM
The last one was opened at the start of the 2011-12 school year in Strasbourg. The speciality of this school is that it welcomes a large number of international students, as well as that 20% of the courses are delivered in English and 10% are delivered in German (optional). There are 50 students in each year.
To gain admission to the CP2I:
* French students register on Admission Post-Bac and follow the steps.
Students are selected on the basis of their academic record and a 20-minute interview.
* International students submit their dossiers directly to the school.
International students are also selected on the basis of their academic record and an interview.
General presentation of CPI-CHEM.I.ST :
* A strong scientific program: a major part of chemistry, physics and maths during the 2 years with a total, for the first year, of around 700 hours of scientific lesson. We must add Lab Work of this scientific formation, with a total of 102 hours for the first year.
The CPI-CHEM.I.ST base of more practical work than in an intensive foundation degree, with high-quality laboratory. The program includes group work to develop the communication, the creativity around scientists projects. Moreover, in 2016, a "videxo" program was created. During, the "videxo" student solves a science problem on a board and in the same time someone films him to send the video to the teachers. The goal of this is to promote self-confidence, speaking, and the scientist reflexion which are important qualities for the future engineer.
* An international program in a multicultural environment: many students with different cultures and two foreign languages to learn. At the beginning of the formation, students can participate in an English language session for one week in order to learn the fundamentals of the scientific English. Insertions travels are organised at the end of the first year in Germany or in England. The students will participate in lectures and lab work in a foreign university. Most of the time the foreign students come from China. | 1 | Applied and Interdisciplinary Chemistry |
The state-of-the-art mechanism of today's sensor-based ore sorters is a pneumatic ejection. Here, a combination of high speed air valves and an array of nozzles perpendicular to the acceleration belt or chute allows precise application of air pulses to change the direction of flight of single particles. The nozzle pitch and diameter is adapted to the particle size. The air impulse must be precise enough to change the direction of flight of a single particle by applying the drag force to this single particle and directing it over the mechanical splitter plate. | 0 | Theoretical and Fundamental Chemistry |
Some organisms can oxidize methane, functionally reversing the process of methanogenesis, also referred to as the anaerobic oxidation of methane (AOM). Organisms performing AOM have been found in multiple marine and freshwater environments including methane seeps, hydrothermal vents, coastal sediments and sulfate-methane transition zones. These organisms may accomplish reverse methanogenesis using a nickel-containing protein similar to methyl-coenzyme M reductase used by methanogenic archaea. Reverse methanogenesis occurs according to the reaction:
: + CH → + HS + HO | 1 | Applied and Interdisciplinary Chemistry |
In addition to distinct physical mechanisms by which lichens break down raw stone, studies indicate lichens attack stone chemically, entering newly chelated minerals into the ecology. The substances exuded by lichens, known for their strong ability to bind and sequester metals, along with the common formation of new minerals, especially metal oxalates, and the traits of the substrates they alter, all highlight the important role lichens play in the process of chemical weathering. Over time, this activity creates new fertile soil from stone.
Lichens may be important in contributing nitrogen to soils in some deserts through being eaten, along with their rock substrate, by snails, which then defecate, putting the nitrogen into the soils. Lichens help bind and stabilize soil sand in dunes. In deserts and semi-arid areas, lichens are part of extensive, living biological soil crusts, essential for maintaining the soil structure. | 1 | Applied and Interdisciplinary Chemistry |
The coupling of a terminal alkyne and an aromatic ring is the pivotal reaction when talking about applications of the copper-promoted or copper-free Sonogashira reaction. The list of cases where the typical Sonogashira reaction using aryl halides has been employed is large, and choosing illustrative examples is difficult. A recent use of this methodology is shown below for the coupling of iodinated phenylalanine with a terminal alkyne derived from d-biotin using an in situ generated Pd species as catalyst, which allowed the preparation of alkyne-linked phenylalanine derivative for bioanalytical applications. There are also examples of the coupling partners both being attached to allyl resins, with the Pd catalyst effecting cleavage of the substrates and subsequent Sonogashira
coupling in solution. | 0 | Theoretical and Fundamental Chemistry |
The law was devised by French general Guillaume Piobert in 1839 to explain the behavior of gunpowder, but it has subsequently been applied to other solid propellants. Description of the reaction as burning may cause confusion with simple atmospheric combustion of solid materials where a similar reaction progression may be attributed to availability of the oxygen reactant only at the surface of the solid being consumed by the reaction. In the case of single-phase propellant grains, the progression is attributed to heat transfer from the surface of the solid of energy necessary to initiate the reaction. The heat transfer rate increases with pressure; and smokeless powder reaction rates vary with pressure as described by Paul Vieille in 1893. | 0 | Theoretical and Fundamental Chemistry |
Her publications include;
Her work was featured in the Journal of the American Chemical Society Young Investigators Issue in 2019. She serves on the editorial board of Inorganic Chemistry. | 0 | Theoretical and Fundamental Chemistry |
Quantum thermodynamics is the study of the relations between two independent physical theories: thermodynamics and quantum mechanics. The two independent theories address the physical phenomena of light and matter.
In 1905, Albert Einstein argued that the requirement of consistency between thermodynamics and electromagnetism leads to the conclusion that light is quantized, obtaining the relation . This paper is the dawn of quantum theory. In a few decades
quantum theory became established with an independent set of rules. Currently quantum thermodynamics addresses the emergence of thermodynamic laws from quantum mechanics.
It differs from quantum statistical mechanics in the emphasis on dynamical processes out of equilibrium.
In addition, there is a quest for the theory to be relevant for a single individual quantum system. | 0 | Theoretical and Fundamental Chemistry |
C-type lectins are a diverse superfamily of mainly Ca-dependent proteins that bind a variety of carbohydrates (including the glycan skeleton of peptidoglycan), and function as innate immune receptors. CLR proteins that bind to peptidoglycan include MBL (mannose binding lectin), ficolins, Reg3A (regeneration gene family protein 3A) and PTCLec1. In mammals, they initiate the lectin-pathway of the complement cascade. | 1 | Applied and Interdisciplinary Chemistry |
Pesticide application refers to the practical way in which pesticides (including herbicides, fungicides, insecticides, or nematode control agents) are delivered to their biological targets (e.g. pest organism, crop or other plant). Public concern about the use of pesticides has highlighted the need to make this process as efficient as possible, in order to minimise their release into the environment and human exposure (including operators, bystanders and consumers of produce). The practice of pest management by the rational application of pesticides is supremely multi-disciplinary, combining many aspects of biology and chemistry with: agronomy, engineering, meteorology, socio-economics and public health, together with newer disciplines such as biotechnology and information science. | 1 | Applied and Interdisciplinary Chemistry |
Lithium is readily absorbed from the gastrointestinal tract. It is distributed to the body with higher levels in the kidney, thyroid, and bone as compared to other tissues. Since lithium is almost exclusively excreted by the kidneys, people with preexisting chronic kidney disease are at high risk of developing lithium intoxication. The drug itself is also known to be nephrotoxic, opening up the possibility of spontaneous emergence of toxicity at doses that were previously well-tolerated. Lithium toxicity can be mistaken for other syndromes associated with antipsychotic use, such as serotonin syndrome because lithium increases serotonin metabolites in the cerebrospinal fluid.
There are several drug interactions with lithium. Interactions can occur from typical antipsychotics or atypical antipsychotics. In particular, certain drugs enhance lithium levels by increasing renal re-absorption at the proximal tubule. These drugs are angiotensin-converting enzyme inhibitors, non-steroidal anti-inflammatory drugs and thiazide diuretics. | 1 | Applied and Interdisciplinary Chemistry |
Insert size of up to 350 kb can be cloned in bacterial artificial chromosome (BAC). BACs are maintained in E. coli with a copy number of only 1 per cell. BACs are based on F plasmid, another artificial chromosome called the PAC is based on the P1 phage. | 1 | Applied and Interdisciplinary Chemistry |
Acid rain is rain or any other form of precipitation that is unusually acidic, meaning that it has elevated levels of hydrogen ions (low pH). Most water, including drinking water, has a neutral pH that exists between 6.5 and 8.5, but acid rain has a pH level lower than this and ranges from 4–5 on average. The more acidic the acid rain is, the lower its pH is. Acid rain can have harmful effects on plants, aquatic animals, and infrastructure. Acid rain is caused by emissions of sulfur dioxide and nitrogen oxide, which react with the water molecules in the atmosphere to produce acids.
Acid rain has been shown to have adverse impacts on forests, freshwaters, soils, microbes, insects and aquatic life-forms. In ecosystems, persistent acid rain reduces tree bark durability, leaving flora more susceptible to environmental stressors such as drought, heat/cold and pest infestation. Acid rain is also capable of detrimenting soil composition by stripping it of nutrients such as calcium and magnesium which play a role in plant growth and maintaining healthy soil. In terms of human infrastructure, acid rain also causes paint to peel, corrosion of steel structures such as bridges, and weathering of stone buildings and statues as well as having impacts on human health.
Some governments, including those in Europe and North America, have made efforts since the 1970s to reduce the release of sulfur dioxide and nitrogen oxide into the atmosphere through air pollution regulations. These efforts have had positive results due to the widespread research on acid rain starting in the 1960s and the publicized information on its harmful effects. The main source of sulfur and nitrogen compounds that result in acid rain are anthropogenic, but nitrogen oxides can also be produced naturally by lightning strikes and sulfur dioxide is produced by volcanic eruptions. | 1 | Applied and Interdisciplinary Chemistry |
John DeYoung provides a background history of the VLM in the NASA Langley workshop documentation SP-405.<br />
The VLM is the extension of Prandtl's lifting-line theory, where the wing of an aircraft is modeled as an infinite number of Horseshoe vortices. The name was coined by V.M. Falkner in his Aeronautical Research Council paper of 1946. The method has since then been developed and refined further by W.P. Jones, H. Schlichting, G.N. Ward and others.
Although the computations needed can be carried out by hand, the VLM benefited from the advent of computers for the large amounts of computations that are required.
Instead of only one horseshoe vortex per wing, as in the Lifting-line theory, the VLM utilizes a lattice of horseshoe vortices, as described by Falkner in his first paper on this subject in 1943. The number of vortices used vary with the required pressure distribution resolution, and with required accuracy in the computed aerodynamic coefficients. A typical number of vortices would be around 100 for an entire aircraft wing; an Aeronautical Research Council report by Falkner published in 1949 mentions the use of an "84-vortex lattice before the standardisation of the 126-lattice" (p. 4).
The method is comprehensibly described in all major aerodynamic textbooks, such as Katz & Plotkin, Anderson, Bertin & Smith Houghton & Carpenter or Drela, | 1 | Applied and Interdisciplinary Chemistry |
The chemical properties of fumaric acid can be anticipated from its component functional groups. This weak acid forms a diester, it undergoes bromination across the double bond, and it is a good dienophile. | 1 | Applied and Interdisciplinary Chemistry |
Transcription factories, in genetics describe the discrete sites where transcription occurs in the cell nucleus, and are an example of a biomolecular condensate. They were first discovered in 1993 and have been found to have structures analogous to replication factories, sites where replication also occurs in discrete sites. The factories contain an RNA polymerase (active or inactive) and the necessary transcription factors (activators and repressors) for transcription. Transcription factories containing RNA polymerase II are the most studied but factories can exist for RNA polymerase I and III; the nucleolus being seen as the prototype for transcription factories. It is possible to view them under both light and electron microscopy. The discovery of transcription factories has challenged the original view of how RNA polymerase interacts with the DNA polymer and it is thought that the presence of factories has important effects on gene regulation and nuclear structure. | 1 | Applied and Interdisciplinary Chemistry |
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