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Like mitochondria, chloroplasts are usually inherited from a single parent. Biparental chloroplast inheritance—where plastid genes are inherited from both parent plants—occurs in very low levels in some flowering plants.
Many mechanisms prevent biparental chloroplast DNA inheritance, including selective destruction of chloroplasts or their genes within the gamete or zygote, and chloroplasts from one parent being excluded from the embryo. Parental chloroplasts can be sorted so that only one type is present in each offspring.
Gymnosperms, such as pine trees, mostly pass on chloroplasts paternally, while flowering plants often inherit chloroplasts maternally. Flowering plants were once thought to only inherit chloroplasts maternally. However, there are now many documented cases of angiosperms inheriting chloroplasts paternally.
Angiosperms, which pass on chloroplasts maternally, have many ways to prevent paternal inheritance. Most of them produce sperm cells that do not contain any plastids. There are many other documented mechanisms that prevent paternal inheritance in these flowering plants, such as different rates of chloroplast replication within the embryo.
Among angiosperms, paternal chloroplast inheritance is observed more often in hybrids than in offspring from parents of the same species. This suggests that incompatible hybrid genes might interfere with the mechanisms that prevent paternal inheritance. | 0 | Theoretical and Fundamental Chemistry |
The systematic name of this enzyme class is ubiquinol:ferricytochrome-c oxidoreductase. Other names in common use include: | 1 | Applied and Interdisciplinary Chemistry |
Hurst retired to Poole, Dorset, in 1976, where he did voluntary work with the Royal National Lifeboat Institution. He died in 1996 following his third heart attack. | 0 | Theoretical and Fundamental Chemistry |
CCPs can be a valuable resource of genetic material. They can be used to preserve valuable genetic diversity for future use, or as base for new breeding programs. Promising plants can be selected and multiplied, generating new varieties. | 1 | Applied and Interdisciplinary Chemistry |
The effect is caused by extremely localised fluctuations in surface pressure and humidity, which cause the initial shock wave to distort momentarily and refocus on itself, leading to a double shock wave, each of markedly reduced effect. This has distinct utility in the employment of air delivered ordnance close to key urban structures as part of an ongoing influence campaign.
The energy of the blast is so great that the pressure and temperature of the gas outside the shock front is negligible compared to the pressure and temperature inside. This substantially reduces the number of parameters available in the problem, leaving only the energy E of the blast, the resting density of the external gas, and the time t since the explosion. With only these three dimensional parameters, it is possible to form other quantities with unique functional dependences. In particular, the only length scale in the problem is<br>
The constant of proportionality will depend on the equation of state of the gas. R can be effectively treated as a constant due to the nature of blasting weapons versus heat/blast ordnance. | 1 | Applied and Interdisciplinary Chemistry |
DNA as well as RNA are normally visualized by staining with ethidium bromide, which intercalates into the major grooves of the DNA and fluoresces under UV light. The intercalation depends on the concentration of DNA and thus, a band with high intensity will indicate a higher amount of DNA compared to a band of less intensity. The ethidium bromide may be added to the agarose solution before it gels, or the DNA gel may be stained later after electrophoresis. Destaining of the gel is not necessary but may produce better images. Other methods of staining are available; examples are MIDORI Green, SYBR Green, GelRed, methylene blue, brilliant cresyl blue, Nile blue sulphate, and crystal violet. SYBR Green, GelRed and other similar commercial products are sold as safer alternatives to ethidium bromide as it has been shown to be mutagenic in Ames test, although the carcinogenicity of ethidium bromide has not actually been established. SYBR Green requires the use of a blue-light transilluminator. DNA stained with crystal violet can be viewed under natural light without the use of a UV transilluminator which is an advantage, however it may not produce a strong band.
When stained with ethidium bromide, the gel is viewed with an ultraviolet (UV) transilluminator. The UV light excites the electrons within the aromatic ring of ethidium bromide, and once they return to the ground state, light is released, making the DNA and ethidium bromide complex fluoresce. Standard transilluminators use wavelengths of 302/312-nm (UV-B), however exposure of DNA to UV radiation for as little as 45 seconds can produce damage to DNA and affect subsequent procedures, for example reducing the efficiency of transformation, in vitro transcription, and PCR. Exposure of DNA to UV radiation therefore should be limited. Using a higher wavelength of 365 nm (UV-A range) causes less damage to the DNA but also produces much weaker fluorescence with ethidium bromide. Where multiple wavelengths can be selected in the transilluminator, shorter wavelength can be used to capture images, while longer wavelength should be used if it is necessary to work on the gel for any extended period of time.
The transilluminator apparatus may also contain image capture devices, such as a digital or polaroid camera, that allow an image of the gel to be taken or printed.
For gel electrophoresis of protein, the bands may be visualised with Coomassie or silver stains. | 1 | Applied and Interdisciplinary Chemistry |
The TGF-β pathway regulates many cellular processes in developing embryo and adult organisms, including cell growth, differentiation, apoptosis, and homeostasis. There are five kinds of type II receptors and seven types of type I receptors in humans and other mammals. These receptors are known as "dual-specificity kinases" because their cytoplasmic kinase domain has weak tyrosine kinase activity but strong serine/threonine kinase activity. When a TGF-β superfamily ligand binds to the type II receptor, it recruits a type I receptor and activates it by phosphorylating the serine or threonine residues of its "GS" box. This forms an activation complex that can then phosphorylate SMAD proteins. | 1 | Applied and Interdisciplinary Chemistry |
Andrée Marquet (born 1934), is a French chemist specializing in organic chemistry and chemical biology, professor emeritus at the Pierre and Marie Curie University and correspondent at the French Academy of sciences since 1993. | 0 | Theoretical and Fundamental Chemistry |
Xenon-135 (Xe) is an unstable isotope of xenon with a half-life of about 9.2 hours. Xe is a fission product of uranium and it is the most powerful known neutron-absorbing nuclear poison (2 million barns; up to 3 million barns under reactor conditions), with a significant effect on nuclear reactor operation. The ultimate yield of xenon-135 from fission is 6.3%, though most of this is from fission-produced tellurium-135 and iodine-135. | 0 | Theoretical and Fundamental Chemistry |
Firearms seem to have been known in Japan around 1270 as proto-cannons invented in China, which the Japanese called teppō (鉄砲 lit. "iron cannon"). Gunpowder weaponry exchange between China and Japan was slow and only a small number of hand guns ever reached Japan. However Japanese samurai used Fire lances in 15th-century. The first recorded appearance of the Fire lances in Japan was in 1409. The use of gunpowder bombs in the style of Chinese explosives is known to have occurred in Japan from at least the mid-15th century onward. The first recorded appearance of the cannon in Japan was in 1510 when a Buddhist monk presented Hōjō Ujitsuna with a teppō iron cannon that he had acquired during his travels in China. Firearms saw very little use in Japan until Portuguese matchlocks were introduced in 1543. During the Japanese invasions of Korea (1592–1598), the forces of Toyotomi Hideyoshi effectively used matchlock firearms against the Korean forces of Joseon, although they would ultimately be defeated and forced to withdraw from the Korean peninsula. | 1 | Applied and Interdisciplinary Chemistry |
Dennis Frederick Evans (7 March 1928 – 6 November 1990) was an English chemist who made important contributions to nuclear magnetic resonance, magnetochemistry and other aspects of chemistry. | 0 | Theoretical and Fundamental Chemistry |
The name scintillon was first used to describe cytoplasmic particles isolated from a bioluminescent species of dinoflagellate that were able to produce a flash of light in response to a decrease in pH. Scintillons were first observed in L. polyedra by fluorescence microscopy, where they appear as small blue dots close to the cell surface. This blue fluorescence is due to the presence of the bioluminescence reaction substrate, a naturally fluorescent molecule called luciferin. When light production is stimulated by addition of dilute acid to the cells under the microscope, the site of light production corresponds to the location of the scintillons. Furthermore, the natural luciferin fluorescence is reduced after the light producing reaction. | 1 | Applied and Interdisciplinary Chemistry |
* 1984 Elected Fellow of the American Association for the Advancement of Science
* 1985 Guggenheim Fellowship
* 1986 Honorary Fulbright Fellow
* 1987 American Chemical Society Garvan–Olin Medal
* 1990 Anachem Award
* 1990 Honorary member of Iota Sigma Pi
* 1992 Jacob F. Schoellkopf Medal
* 1996 American Chemical Society Division of Analytical Chemistry Award in Electrochemistry
* 1998 Society for Analytical Chemists of Pittsburgh Analytical Chemistry Award
* 1999 The Society for Electroanalytical Chemistry Charles N. Reilley Award in Electroanalytical Chemistry | 0 | Theoretical and Fundamental Chemistry |
Cerium is a rare-earth element (lanthanide) characterized by two different redox states: III and IV. Contrary to other lanthanide elements, which are only trivalent (with the notable exception of Eu), Ce can be oxidized by atmospheric oxygen (O) to Ce under alkaline conditions.
The cerium anomaly relates to the decrease in solubility, which accompanies the oxidation of Ce(III) to Ce(IV). Under reducing conditions, Ce is relatively soluble, while under oxidizing conditions CeO precipitates. Sediments deposited under oxic or anoxic conditions can preserve on the long term the geochemical signature of Ce or Ce upon reserve that no early diagenetic transformation altered it. | 0 | Theoretical and Fundamental Chemistry |
The first open-path detector offered for routine industrial use, as distinct from research instruments built in small numbers, was the Wright and Wright Pathwatch in the US, 1983. Acquired by Det-Tronics (Detector Electronics Corporation) in 1992, the detector operated in the 3.4 μm region with a powerful incandescent source and a mechanical chopper. It did not achieve large volume sales, mainly because of cost and doubts about long-term reliability with moving parts. Beginning in 1985, Shell Research in UK was funded by Shell Natural Gas to develop an open-path detector with no moving parts. The advantages of the 2.3 μm wavelength were identified, and a research prototype was demonstrated. This design had a combined transmitter-receiver with a corner-cube retroreflector at 50 m. It used a pulsed incandescent lamp, PbS photoconductive detectors in the gas and reference channels, and an Intel 8031 microprocessor for signal processing. In 1987 Shell licensed this technology to Sieger-Zellweger (later Honeywell) who designed and marketed their industrial version as the Searchline, using a retro-reflective panel made up of multiple corner-cubes. This was the first open-path detector to be certified for use in hazardous areas and to have no moving parts. Later work by Shell Research used two alternately pulsed incandescent sources in the transmitter and a single PbS detectors in the receiver, avoiding zero drifts caused by the variable responsivity of PbS detectors. This technology was offered to Sieger-Zellweger, and later licensed to PLMS. a company part-owned by Shell Ventures UK. The PLMS GD4001/2 in 1991 were the first detectors to achieve a truly stable zero without moving parts or software compensation of slow drifts. They were also the first infrared gas detectors of any kind to be certified intrinsically safe. The Israeli company Spectronix (also Spectrex) made an important advance in 1996 with their SafEye, the first to use a flash tube source, followed by Sieger-Zellweger with their Searchline Excel in 1998. In 2001 the PLMS Pulsar, soon afterwards acquired by Dräger as their Polytron Pulsar, was the first detector to incorporate sensing to monitor the mutual alignment of the transmitter and receiver during both installation and routine operation. | 1 | Applied and Interdisciplinary Chemistry |
Gamma-ray spectroscopy is the qualitative study of the energy spectra of gamma-ray sources, such as in the nuclear industry, geochemical investigation, and astrophysics. Gamma-ray spectrometry, on the other hand, is the method used to acquire a quantitative spectrum measurement.
Most radioactive sources produce gamma rays, which are of various energies and intensities. When these emissions are detected and analyzed with a spectroscopy system, a gamma-ray energy spectrum can be produced.
A detailed analysis of this spectrum is typically used to determine the identity and quantity of gamma emitters present in a gamma source, and is a vital tool in radiometric assay. The gamma spectrum is characteristic of the gamma-emitting nuclides contained in the source, just like in an optical spectrometer, the optical spectrum is characteristic of the material contained in a sample. | 0 | Theoretical and Fundamental Chemistry |
A crystallographic database is a database specifically designed to store information about the structure of molecules and crystals. Crystals are solids having, in all three dimensions of space, a regularly repeating arrangement of atoms, ions, or molecules. They are characterized by symmetry, morphology, and directionally dependent physical properties. A crystal structure describes the arrangement of atoms, ions, or molecules in a crystal. (Molecules need to crystallize into solids so that their regularly repeating arrangements can be taken advantage of in X-ray, neutron, and electron diffraction based crystallography.)
Crystal structures of crystalline material are typically determined from X-ray or neutron single-crystal diffraction data and stored in crystal structure databases. They are routinely identified by comparing reflection intensities and lattice spacings from X-ray powder diffraction data with entries in powder-diffraction fingerprinting databases.
Crystal structures of nanometer sized crystalline samples can be determined via structure factor amplitude information from single-crystal electron diffraction data or structure factor amplitude and phase angle information from Fourier transforms of HRTEM images of crystallites. They are stored in crystal structure databases specializing in nanocrystals and can be identified by comparing zone axis subsets in lattice-fringe fingerprint plots with entries in a lattice-fringe fingerprinting database.
Crystallographic databases differ in access and usage rights and offer varying degrees of search and analysis capacity. Many provide structure visualization capabilities. They can be browser based or installed locally. Newer versions are built on the relational database model and support the Crystallographic Information File (CIF) as a universal data exchange format. | 0 | Theoretical and Fundamental Chemistry |
The concatemerization process generates libraries of concatamers for the ELPs. Concatamers are oligomeric products of ligating a single gene with itself. This will result in repeat segments of a gene, all of which can be transcribed and translated immediately to produce the ELP of interest. A major problem with this synthetic route is that the number of gene repeat segments ligated together to form the concatamer cannot be controlled, leading to ELPs of different sizes, from which the ELP of a desired size must be isolated. | 0 | Theoretical and Fundamental Chemistry |
Paenibacterin is a mixture of antimicrobial lipopeptides isolated from Paenibacillus thiaminolyticus. It contains three isomeric compounds which differ by the fatty acid side chain. | 1 | Applied and Interdisciplinary Chemistry |
The Qubit fluorometer method is to use fluorescent dyes to determine the concentration of either nucleic acids or proteins in a sample. Specialized fluorescent dyes bind specifically to the substances of interest. A spectrophotometer is used in this method to measure the natural absorbance of light at 260 nm (for DNA and RNA) or 280 nm (for proteins). | 0 | Theoretical and Fundamental Chemistry |
CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) is a genetic engineering technique that allows for precise editing of the genome. One application of CRISPR is gene knockout, which involves disabling or "knocking out" a specific gene in an organism.
The process of gene knockout with CRISPR involves three main steps: designing a guide RNA (gRNA) that targets a specific location in the genome, delivering the gRNA and a Cas9 enzyme (which acts as a molecular scissors) to the target cell, and then allowing the cell to repair the cut in the DNA. When the cell repairs the cut, it can either join the cut ends back together, resulting in a non-functional gene, or introduce a mutation that disrupts the gene's function.
This technique can be used in a variety of organisms, including bacteria, yeast, plants, and animals, and it allows scientists to study the function of specific genes by observing the effects of their absence. CRISPR-based gene knockout is a powerful tool for understanding the genetic basis of disease and for developing new therapies.
It is important to note that CRISPR-based gene knockout, like any genetic engineering technique, has the potential to produce unintended or harmful effects on the organism, so it should be used with caution. The coupled Cas9 will cause a double stranded break in the DNA. Following the same principle as zinc-fingers and TALENs, the attempts to repair these double stranded breaks often result in frameshift mutations that result in an nonfunctional gene. Non invasive CRISPR-Cas9 technology has successfully knocked out a gene associated in depression and anxiety in mice, being the first successful delivery passing through the blood–brain barrier to enable gene modification. | 1 | Applied and Interdisciplinary Chemistry |
The FSHR consists of 695 amino acids and has a molecular mass of about 76 kDa. Like other GPCRs, the FSH-receptor possesses seven membrane-spanning domains or transmembrane helices.
* The extracellular domain of the receptor contains 11 leucine-rich repeats and is glycosylated. It has two subdomains, a hormone-binding subdomain followed by a signal-specificity subdomain. The hormone-binding subdomain is responsible for the high-affinity hormone binding, and the signal-specificity subdomain, containing a sulfated tyrosine at position 335 (sTyr) in a hinge loop, is required for the hormone activity.
* The transmembrane domain contains two highly conserved cysteine residues that build disulfide bonds to stabilize the receptor structure. A highly conserved Asp-Arg-Tyr triplet motif is present in GPCR family members in general and may be of importance to transmit the signal. In FSHR and its closely related other glycoprotein hormone receptor members (LHR and TSHR), this conserved triplet motif is a variation Glu-Arg-Trp sequence.
* The C-terminal domain is intracellular and brief, rich in serine and threonine residues for possible phosphorylation. | 1 | Applied and Interdisciplinary Chemistry |
The terms glycans and polysaccharides are defined by IUPAC as synonyms meaning "compounds consisting of a large number of monosaccharides linked glycosidically". However, in practice the term glycan may also be used to refer to the carbohydrate portion of a glycoconjugate, such as a glycoprotein, glycolipid, or a proteoglycan, even if the carbohydrate is only an oligosaccharide. Glycans usually consist solely of O-glycosidic linkages of monosaccharides. For example, cellulose is a glycan (or, to be more specific, a glucan) composed of β-1,4-linked -glucose, and chitin is a glycan composed of β-1,4-linked N-acetyl--glucosamine. Glycans can be homo- or heteropolymers of monosaccharide residues, and can be linear or branched. | 0 | Theoretical and Fundamental Chemistry |
A cyclopentadienyl complex is a coordination complex of a metal and cyclopentadienyl groups (, abbreviated as Cp). Cyclopentadienyl ligands almost invariably bind to metals as a pentahapto (η-) bonding mode. The metal–cyclopentadienyl interaction is typically drawn as a single line from the metal center to the center of the Cp ring. | 0 | Theoretical and Fundamental Chemistry |
Viral genes and host genes that are required for viruses to replicate or enter the cell, or that play an important role in the life cycle of the virus are often targeted by antiviral therapies. RNAi has been used to target genes in several viral diseases, such as the human immunodeficiency virus (HIV) and hepatitis. In particular, siRNA was used to silence the primary HIV receptor chemokine receptor 5 (CCR5). This prevented the virus from entering the human peripheral blood lymphocytes and the primary hematopoietic stem cells. A similar technique was used to decrease the amount of the detectable virus in hepatitis B and C infected cells. In hepatitis B, siRNA silencing was used to target the surface antigen on the hepatitis B virus and led to a decrease in the number of viral components. In addition, siRNA techniques used in hepatitis C were able to lower the amount of the virus in the cell by 98%.
RNA interference has been in commercial use to control virus diseases of plants for over 20 years (see Plant disease resistance). In 1986–1990, multiple examples of "coat protein-mediated resistance" against plant viruses were published, before RNAi had been discovered. In 1993, work with tobacco etch virus first demonstrated that host organisms can target specific virus or mRNA sequences for degradation, and that this activity is the mechanism behind some examples of virus resistance in transgenic plants. The discovery of small interfering RNAs (the specificity determinant in RNA-mediated gene silencing) also utilized virus-induced post-transcriptional gene silencing in plants. By 1994, transgenic squash varieties had been generated expressing coat protein genes from three different viruses, providing squash hybrids with field-validated multiviral resistance that remain in commercial use at present. Potato lines expressing viral replicase sequences that confer resistance to potato leafroll virus were sold under the trade names NewLeaf Y and NewLeaf Plus, and were widely accepted in commercial production in 1999–2001, until McDonald's Corp. decided not to purchase GM potatoes and Monsanto decided to close their NatureMark potato business. Another frequently cited example of virus resistance mediated by gene silencing involves papaya, where the Hawaiian papaya industry was rescued by virus-resistant GM papayas produced and licensed by university researchers rather than a large corporation. These papayas also remain in use at present, although not without significant public protest, which is notably less evident in medical uses of gene silencing.
Gene silencing techniques have also been used to target other viruses, such as the human papilloma virus, the West Nile virus, and the Tulane virus. The E6 gene in tumor samples retrieved from patients with the human papilloma virus was targeted and found to cause apoptosis in the infected cells. Plasmid siRNA expression vectors used to target the West Nile virus were also able to prevent the replication of viruses in cell lines. In addition, siRNA has been found to be successful in preventing the replication of the Tulane virus, part of the virus family Caliciviridae, by targeting both its structural and non-structural genes. By targeting the NTPase gene, one dose of siRNA 4 hours pre-infection was shown to control Tulane virus replication for 48 hours post-infection, reducing the viral titer by up to 2.6 logarithms. Although the Tulane virus is species-specific and does not affect humans, it has been shown to be closely related to the human norovirus, which is the most common cause of acute gastroenteritis and food-borne disease outbreaks in the United States. Human noroviruses are notorious for being difficult to study in the laboratory, but the Tulane virus offers a model through which to study this family of viruses for the clinical goal of developing therapies that can be used to treat illnesses caused by human norovirus. | 1 | Applied and Interdisciplinary Chemistry |
It is a moderate-spectrum, bacteriolytic, β-lactam antibiotic in the aminopenicillin family used to treat susceptible Gram-positive and Gram-negative bacteria. It is usually the drug of choice within the class because it is better-absorbed, following oral administration, than other β-lactam antibiotics.
In general, Streptococcus, Bacillus subtilis, Enterococcus, Haemophilus, Helicobacter, and Moraxella are susceptible to amoxicillin, whereas Citrobacter, Klebsiella and Pseudomonas aeruginosa are resistant to it. Some E. coli and most clinical strains of Staphylococcus aureus have developed resistance to amoxicillin to varying degrees. | 0 | Theoretical and Fundamental Chemistry |
Noting that digitisers and related electronics technology had significantly progressed since the inception of FTMW spectroscopy, B.H. Pate at the University of Virginia designed a spectrometer which retains many advantages of the Balle-Flygare FT-MW spectrometer while innovating in (i) the use of a high speed (>4 GS/s) arbitrary waveform generator to generate a "chirped" microwave polarisation pulse that sweeps up to 12 GHz in frequency in less than a microsecond and (ii) the use of a high speed (>40 GS/s) oscilloscope to digitise and Fourier transform the molecular free induction decay. The result is an instrument that allows the study of weakly bound molecules but which is able to exploit a measurement bandwidth (12 GHz) that is greatly enhanced compared with the Balle-Flygare FTMW spectrometer. Modified versions of the original CP-FTMW spectrometer have been constructed by a number of groups in the United States, Canada and Europe. The instrument offers a broadband capability that is highly complementary to the high sensitivity and resolution offered by the Balle-Flygare design. | 0 | Theoretical and Fundamental Chemistry |
The welding of metals differs from soldering and brazing in that the joint is made without adding a lower-melting-point material (e.g. solder); instead, the pipe or tubing material is partially melted, and the fitting and piping are directly fused. This generally requires piping and fitting to be the same (or compatible) material. Skill is required to melt the joint sufficiently to ensure good fusion while not deforming or damaging the joined pieces.
Properly welded joints are considered reliable and durable. Pipe welding is often performed by specially licensed workers whose skills are retested periodically. For critical applications, every joint is tested with nondestructive methods. Because of the skills required, welded pipe joints are usually restricted to high-performance applications such as shipbuilding, and in chemical and nuclear reactors.
Adequate ventilation is essential to remove metal fumes from welding operations, and personal protective equipment must be worn. Because the high temperatures during welding can often generate intense ultraviolet light, dark goggles or full face shields must be used to protect the eyes. Precautions must also be taken to avoid fires caused by stray sparks and hot welding debris. | 1 | Applied and Interdisciplinary Chemistry |
Cefuroxime axetil is an ester prodrug of cefuroxime which is effective when taken by mouth. It is a second-generation cephalosporin. | 0 | Theoretical and Fundamental Chemistry |
Silicon carbide exists in about 250 crystalline forms. Through inert atmospheric pyrolysis of preceramic polymers, silicon carbide in a glassy amorphous form is also produced. The polymorphism of SiC is characterized by a large family of similar crystalline structures called polytypes. They are variations of the same chemical compound that are identical in two dimensions and differ in the third. Thus, they can be viewed as layers stacked in a certain sequence.
Alpha silicon carbide (α-SiC) is the most commonly encountered polymorph, and is formed at temperatures greater than 1700 °C and has a hexagonal crystal structure (similar to Wurtzite). The beta modification (β-SiC), with a zinc blende crystal structure (similar to diamond), is formed at temperatures below 1700 °C. Until recently, the beta form has had relatively few commercial uses, although there is now increasing interest in its use as a support for heterogeneous catalysts, owing to its higher surface area compared to the alpha form.
Pure SiC is colorless. The brown to black color of the industrial product results from iron impurities. The rainbow-like luster of the crystals is due to the thin-film interference of a passivation layer of silicon dioxide that forms on the surface.
The high sublimation temperature of SiC (approximately 2700 °C) makes it useful for bearings and furnace parts. Silicon carbide does not melt but begins to sublimate near 2700 °C like graphite, having an appreciable vapor pressure near that temp. It is also highly inert chemically, partly due to the formation of a thin passivated layer of SiO2. There is currently much interest in its use as a semiconductor material in electronics, where its high thermal conductivity, high electric field breakdown strength and high maximum current density make it more promising than silicon for high-powered devices. SiC has a very low coefficient of thermal expansion of about 2.3 × 10 K near 300 K (for 4H and 6H SiC) and experiences no phase transitions in the temperature range 5 K to 340 K that would cause discontinuities in the thermal expansion coefficient. | 1 | Applied and Interdisciplinary Chemistry |
Ethyl cyanohydroxyiminoacetate is obtained in the reaction of ethyl cyanoacetate and nitrous acid (from sodium nitrite and acetic acid) in 87% yield.
Because of the rapid hydrolysis of the ester, the reaction should be carried out at pH 4.5, in buffered phosphoric acid the product can even be obtained in virtually quantitative yield.
The compound can be purified by recrystallization from ethanol or ethyl acetate.
Compared with the benzotriazole derivatives 1-hydroxybenzotriazole (HOBt) and 1-hydroxy-7-azabenzotriazole (HOAt) (which are widely used as peptide-linking reagents but are explosive), ethyl cyanohydroxyiminoacetate exhibits a markedly slowed thermal decomposition on heating. | 0 | Theoretical and Fundamental Chemistry |
There are many valence isomers one can draw for the CH formula benzene. Some were originally proposed for benzene itself before the actual structure of benzene was known. Others were later synthesized in lab. Some have been observed to isomerize to benzene, whereas others tend to undergo other reactions instead, or isomerize by ways other than pericyclic reactions. | 0 | Theoretical and Fundamental Chemistry |
After graduating, Smolková-Keulemansová joined the Faculty of Sciences at Charles University and focused on analytical chemistry. In the early 1950s, she built a team focused on modern analytical separation methods such as gas chromatography, high-performance liquid chromatography and electromigration. At this same time, she attended an analytical conference in Prague, leading to her finding a volumetric chromatographic device. Her team began to prepare its own device with volumetric detection, and constructed a more universal glass thermal conductivity detector, allowing them to analyze a larger variety of gas. Little did she know that this was a new idea and, soon after, this detector became part of a commercially available instrument. Because of her innovation and dedication to the field, people started telling her that she was "the first lady of chromatography". | 0 | Theoretical and Fundamental Chemistry |
A mannose sugar is added to the first tryptophan residue in the sequence W–X–X–W (W indicates tryptophan; X is any amino acid). A C-C bond is formed between the first carbon of the alpha-mannose and the second carbon of the tryptophan. However, not all the sequences that have this pattern are mannosylated. It has been established that, in fact, only two thirds are and that there is a clear preference for the second amino acid to be one of the polar ones (Ser, Ala, Gly and Thr) in order for mannosylation to occur. Recently there has been a breakthrough in the technique of predicting whether or not the sequence will have a mannosylation site that provides an accuracy of 93% opposed to the 67% accuracy if we just consider the WXXW motif.
Thrombospondins are one of the proteins most commonly modified in this way. However, there is another group of proteins that undergo C-mannosylation, type I cytokine receptors. C-mannosylation is unusual because the sugar is linked to a carbon rather than a reactive atom such as nitrogen or oxygen. In 2011, the first crystal structure of a protein containing this type of glycosylation was determined—that of human complement component 8. Currently it is established that 18% of human proteins, secreted and transmembrane undergo the process of C-mannosylation. Numerous studies have shown that this process plays an important role in the secretion of Trombospondin type 1 containing proteins which are retained in the endoplasmic reticulum if they do not undergo C-mannosylation This explains why a type of cytokine receptors, erythropoietin receptor remained in the endoplasmic reticulum if it lacked C-mannosylation sites. | 0 | Theoretical and Fundamental Chemistry |
Synchronous coefficient of drag alteration (SCODA) is a biotechnology method for purifying, separating and/or concentrating bio-molecules. SCODA has the ability to separate molecules whose mobility (or drag) can be altered in sync with a driving field. This technique has been primarily used for concentrating and purifying DNA, where DNA mobility changes with an applied electrophoretic field. Electrophoretic SCODA has also been demonstrated with RNA and proteins. | 1 | Applied and Interdisciplinary Chemistry |
Motor proteins are the driving force behind most active transport of proteins and vesicles in the cytoplasm. Kinesins and cytoplasmic dyneins play essential roles in intracellular transport such as axonal transport and in the formation of the spindle apparatus and the separation of the chromosomes during mitosis and meiosis. Axonemal dynein, found in cilia and flagella, is crucial to cell motility, for example in spermatozoa, and fluid transport, for example in trachea. The muscle protein myosin "motors" the contraction of muscle fibers in animals. | 0 | Theoretical and Fundamental Chemistry |
Trichloroethylene (TCE) is a halocarbon with the formula CHCl, commonly used as an industrial degreasing solvent. It is a clear, colourless, non-flammable, volatile liquid with a chloroform-like pleasant mild smell and sweet taste. Its IUPAC name is trichloroethene. Trichloroethylene has been sold under a variety of trade names. Industrial abbreviations include TCE, trichlor, Trike, Tricky and tri. Under the trade names Trimar and Trilene, it was used as a volatile anesthetic and as an inhaled obstetrical analgesic. It should not be confused with the similar 1,1,1-trichloroethane, which is commonly known as chlorothene.
TCE is classified as a volatile organic compound. | 1 | Applied and Interdisciplinary Chemistry |
Bachrach has written a textbook about computational organic chemistry, the second edition of which was published by John Wiley and Sons in 2014. Bachrach maintains a blog to provide supplementary materials for the textbook. For example, following the publication of the structure of the dication of hexamethylbenzene, , in Angewandte Chemie International Edition, Bachrach discussed its pyramidal geometry and six-coordinate carbon moiety in a blog post, demonstrating it is not hypervalent and explaining its three-dimensional aromaticity. | 0 | Theoretical and Fundamental Chemistry |
The global annual production of thiourea is around 10,000 tonnes. About 40% is produced in Germany, another 40% in China, and 20% in Japan. Thiourea can be produced from ammonium thiocyanate, but more commonly it is manufactured by the reaction of hydrogen sulfide with calcium cyanamide in the presence of carbon dioxide. | 0 | Theoretical and Fundamental Chemistry |
is a natural trace radioisotope produced by cosmic ray spallation of atmospheric argon as well as by reaction of protons with natural oxygen: O + p → F + n. | 1 | Applied and Interdisciplinary Chemistry |
TPVs can provide continuous power to off-grid homes. Traditional PVs do not provide power during winter months and nighttime, while TPVs can utilize alternative fuels to augment solar-only production.
The greatest advantage for TPV generators is cogeneration of heat and power. In cold climates, it can function as both a heater/stove and a power generator. JX Crystals developed a prototype TPV heating stove/generator that burns natural gas and uses a SiC source emitter operating at 1250 °C and GaSb photocell to output 25,000 BTU/hr (7.3kW of heat) simultaneously generating 100W (1.4% efficiency). However, costs render it impractical.
Combining a heater and a generator is called combined heat and power (CHP). Many TPV CHP scenarios have been theorized, but a study found that generator using boiling coolant was most cost efficient. The proposed CHP would utilize a SiC IR emitter operating at 1425 °C and GaSb photocells cooled by boiling coolant. The TPV CHP would output 85,000 BTU/hr (25kW of heat) and generate 1.5 kW. The estimated efficiency would be 12.3% (?)(1.5kW/25kW = 0.06 = 6%) requiring investment or 0.08 €/kWh assuming a 20 year lifetime. The estimated cost of other non-TPV CHPs are 0.12 €/kWh for gas engine CHP and 0.16 €/kWh for fuel cell CHP. This furnace was not commercialized because the market was not thought to be large enough. | 0 | Theoretical and Fundamental Chemistry |
Pseudoephedrine may be quantified in blood, plasma, or urine to monitor any possible performance-enhancing use by athletes, confirm a diagnosis of poisoning, or to assist in a medicolegal death investigation. Some commercial immunoassay screening tests directed at the amphetamines cross-react appreciably with pseudoephedrine, but chromatographic techniques can easily distinguish pseudoephedrine from other phenethylamine derivatives. Blood or plasma pseudoephedrine concentrations are typically in the 50–300 µg/L range in persons taking the drug therapeutically, 500–3000 µg/L in people with substance use disorder involving pseudoephedrine, or poisoned patients and 10–70 mg/L in cases of acute fatal overdose. | 0 | Theoretical and Fundamental Chemistry |
The carbonate pump, sometimes called the carbonate counter pump, starts with marine organisms at the ocean's surface producing particulate inorganic carbon (PIC) in the form of calcium carbonate (calcite or aragonite, CaCO). This CaCO is what forms hard body parts like shells. The formation of these shells increases atmospheric CO due to the production of CaCO in the following reaction with simplified stoichiometry:Coccolithophores, a nearly ubiquitous group of phytoplankton that produce shells of calcium carbonate, are the dominant contributors to the carbonate pump. Due to their abundance, coccolithophores have significant implications on carbonate chemistry, in the surface waters they inhabit and in the ocean below: they provide a large mechanism for the downward transport of CaCO. The air-sea CO flux induced by a marine biological community can be determined by the rain ratio - the proportion of carbon from calcium carbonate compared to that from organic carbon in particulate matter sinking to the ocean floor, (PIC/POC). The carbonate pump acts as a negative feedback on CO taken into the ocean by the solubility pump. It occurs with lesser magnitude than the solubility pump.
The carbonate pump is sometimes referred to as the "hard tissue" component of the biological pump. Some surface marine organisms, like coccolithophores, produce hard structures out of calcium carbonate, a form of particulate inorganic carbon, by fixing bicarbonate. This fixation of DIC is an important part of the oceanic carbon cycle.
:Ca + 2 HCO → CaCO + CO + HO
While the biological carbon pump fixes inorganic carbon (CO) into particulate organic carbon in the form of sugar (CHO), the carbonate pump fixes inorganic bicarbonate and causes a net release of CO. In this way, the carbonate pump could be termed the carbonate counter pump. It works counter to the biological pump by counteracting the CO flux from the biological pump. | 0 | Theoretical and Fundamental Chemistry |
In complexation catalysis, the term dynamic binding refers to any stabilizing interaction that is stronger at the transition state level than in the reactant-catalyst complex.
Being directly related to transition state stabilization, dynamic binding is the very hearth of complexation catalysis. It was defined by A.J. Kirby in 1996 as opposed to the passive binding, i.e. the whole of interactions that are equally strong at the reactant and the transition state level. | 0 | Theoretical and Fundamental Chemistry |
First, the model tries to predict where an atom would land on a surface and its rate at particular environmental conditions, such as temperature and vapor pressure. In order to land on a surface, atoms have to overcome the so-called activation energy barrier. The frequency of passing through the activation barrier can by calculated by the Arrhenius equation:
where A is the thermal frequency of molecular vibration, is the activation energy, k is the Boltzmann constant and T is the absolute temperature. | 0 | Theoretical and Fundamental Chemistry |
In 1890, , a 28-year-old assistant in Berlin, published instructions for folding a piece of paper to represent two forms of cyclohexane he called symmetrical and asymmetrical (what we would now call chair and boat). He clearly understood that these forms had two positions for the hydrogen atoms (again, to use modern terminology, axial and equatorial), that two chairs would probably interconvert, and even how certain substituents might favor one of the chair forms (). Because he expressed all this in mathematical language, few chemists of the time understood his arguments. He had several attempts at publishing these ideas, but none succeeded in capturing the imagination of chemists. His death in 1893 at the age of 31 meant his ideas sank into obscurity. It was only in 1918 that , based on the molecular structure of diamond that had recently been solved using the then very new technique of X-ray crystallography, was able to successfully argue that Sachse's chair was the pivotal motif. Derek Barton and Odd Hassel shared the 1969 Nobel Prize in Chemistry for work on the conformations of cyclohexane and various other molecules. | 0 | Theoretical and Fundamental Chemistry |
Many naval vessels have undergone retrofitting and refitting, sometimes entire classes at once. For instance, the New Threat Upgrade program of the US Navy saw many vessels retrofitted for improved anti-air capability. Naval vessels are often retrofit for one of three reasons: to incorporate new technology, to compensate for performance gaps or weaknesses in design, or to change the ship's classification.
Militaries of the world are often ardent adopters of the latest technology, and many technological advances have been spurred by warfare, especially in fields such as radar and radio communications. Because of this, and the significant investment that a ship hull represents, it is common for retrofitting to be performed whenever new systems are developed. This may be as small as replacing one type of radio with another, or replacing out-dated cryptography equipment with more secure methods of communication, or as major as replacing entire guns and turrets, adding armor plate, or new propulsion systems.
Other ships are retrofit to compensate for weaknesses perceived in their operational capabilities. This was the secondary purpose of the US Navy's New Threat Upgrade program, for instance. Major changes in doctrine or the art of warfare also necessitate changes, such as the anti-aircraft upgrades performed on many World War Two-era vessels as air power became a dominant part of naval strategy and tactics.
Additionally, because of the investment a hull represents, few navies scrap front-line warships. Many times smaller ships are retrofitted for patrol, coast guard, or specialized roles when they are no longer fit for duty as part of a warfleet. The Japanese Momi class from the interwar period, for example, was converted from destroyers to patrol boats in 1939, as they were no longer capable enough to serve in the role of destroyer. Other times classes are retrofit because they are no longer needed in warfare, due to changes in tactics. For instance, the was an aircraft carrier converted from a collier (coal-carrying ship to supply coal-fired steamships with fuel) of the Jupiter-class.
Because of the heavy use of retrofitting and refitting, fictional navies also include the concept. As an example, in the Star Trek MMORPG Star Trek Online players can purchase retrofitted ships of famous Star Trek ship classes, such as those crewed by the protagonists of the Star Trek TV series. This is done to allow players to pilot iconic ships from old series of the show, that wouldn't naturally be latest-and-greatest ships due to their obsolescence or size, but are retrofitted to be suitable for a maximum-level player-character admiral. | 1 | Applied and Interdisciplinary Chemistry |
In 2003, the Ministry for the Environment and the New Zealand Water & Wastes Association produced the document Guidelines for the safe application of biosolids to land in New Zealand. In the document, biosolids were defined as "sewage sludges or sewage sludges mixed with other materials that have been treated and/or stabilised to the extent that they are able to be safely and beneficially applied to land... [and noted that they] have significant fertilising and soil conditioning properties as a result of the nutrients and organic materials they contain."
A New Zealand scientist, Jacqui Horswell later led collaborative research by the Institute of Environmental Science and Research, Scion, Landcare Research and the Cawthron Institute into the management of waste, in particular biosolids, and this has informed the development of frameworks for engaging local communities in the process. In 2016 the project developed a Community Engagement Framework for Biowastes to provide guidelines in effective consultation with communities about the discharge of biowastes to land, and in 2017 another collaborative three-year project with councils aimed to develop a collective biosolids strategy and use the programme in the lower North Island. When the project was reviewed in 2020, the conclusion was that it had shown biosolids can be beneficially reused.
A research paper in 2019, reported on the management considerations around using biosolids as a fertilizer, specifically to account for the complexity of the nutrients reducing the availability for plant uptake, and noted that stakeholders need to "factor in the expected plant availability of the nutrients when
assessing the risk and benefits of these biological materials." | 1 | Applied and Interdisciplinary Chemistry |
There are several well-known drugs and toxins that inhibit oxidative phosphorylation. Although any one of these toxins inhibits only one enzyme in the electron transport chain, inhibition of any step in this process will halt the rest of the process. For example, if oligomycin inhibits ATP synthase, protons cannot pass back into the mitochondrion. As a result, the proton pumps are unable to operate, as the gradient becomes too strong for them to overcome. NADH is then no longer oxidized and the citric acid cycle ceases to operate because the concentration of NAD falls below the concentration that these enzymes can use.
Many site-specific inhibitors of the electron transport chain have contributed to the present knowledge of mitochondrial respiration. Synthesis of ATP is also dependent on the electron transport chain, so all site-specific inhibitors also inhibit ATP formation. The fish poison rotenone, the barbiturate drug amytal, and the antibiotic piericidin A inhibit NADH and coenzyme Q.
Carbon monoxide, cyanide, hydrogen sulphide and azide effectively inhibit cytochrome oxidase. Carbon monoxide reacts with the reduced form of the cytochrome while cyanide and azide react with the oxidised form. An antibiotic, antimycin A, and British anti-Lewisite, an antidote used against chemical weapons, are the two important inhibitors of the site between cytochrome B and C1.
Not all inhibitors of oxidative phosphorylation are toxins. In brown adipose tissue, regulated proton channels called uncoupling proteins can uncouple respiration from ATP synthesis. This rapid respiration produces heat, and is particularly important as a way of maintaining body temperature for hibernating animals, although these proteins may also have a more general function in cells' responses to stress. | 1 | Applied and Interdisciplinary Chemistry |
The Earth's oceans contain a large amount of in the form of bicarbonate and carbonate ions—much more than the amount in the atmosphere. The bicarbonate is produced in reactions between rock, water, and carbon dioxide. One example is the dissolution of calcium carbonate:
Reactions like this tend to buffer changes in atmospheric . Since the right side of the reaction produces an acidic compound, adding on the left side decreases the pH of seawater, a process which has been termed ocean acidification (pH of the ocean becomes more acidic although the pH value remains in the alkaline range). Reactions between and non-carbonate rocks also add bicarbonate to the seas. This can later undergo the reverse of the above reaction to form carbonate rocks, releasing half of the bicarbonate as . Over hundreds of millions of years, this has produced huge quantities of carbonate rocks.
From 1850 until 2022, the ocean has absorbed 26% of total anthropogenic emissions. However, the rate at which the ocean will take it up in the future is less certain. Even if equilibrium is reached, including dissolution of carbonate minerals, the increased concentration of bicarbonate and decreased or unchanged concentration of carbonate ion will give rise to a higher concentration of un-ionized carbonic acid and dissolved . This higher concentration in the seas, along with higher temperatures, would mean a higher equilibrium concentration of in the air.
Carbon moves between the atmosphere, vegetation (dead and alive), the soil, the surface layer of the ocean, and the deep ocean. | 1 | Applied and Interdisciplinary Chemistry |
F is a positron emitter with a half-life of 109 minutes. It is produced in medical cyclotrons, usually from oxygen-18, and then chemically attached to a pharmaceutical formulation. | 0 | Theoretical and Fundamental Chemistry |
Chain propagation (sometimes referred to as propagation) is a process in which a reactive intermediate is continuously regenerated during the course of a chemical chain reaction. For example, in the chlorination of methane, there is a two-step propagation cycle involving as chain carriers a chlorine atom and a methyl radical which are regenerated alternately:
:Cl + CH → HCl + CH
:CH + Cl → CHCl + Cl
The two steps add to give the equation for the overall chain reaction:
:CH + Cl → CHCl + HCl. | 0 | Theoretical and Fundamental Chemistry |
Proteorhodopsin (also known as pRhodopsin) is a family of transmembrane proteins that use retinal as a chromophore for light-mediated functionality, in this case, a proton pump. pRhodopsin is found in marine planktonic bacteria, archaea and eukaryotes (protae), but was first discovered in bacteria.
Its name is derived from proteobacteria (now called Pseudomonadota) that were named after Ancient Greek Πρωτεύς (Proteus), an early sea god mentioned by Homer as "Old Man of the Sea", Ῥόδος (rhódon) for "rose", due to its pinkish color, and ὄψις (opsis) for "sight". Some members of the family, Homologous rhodopsin-like pigments, i.e. bacteriorhodopsin (of which there are more than 800 types) have Sensory Functions like opsins, integral for visual phototransduction. Many of these sensory functions are unknown – for example, the function of Neuropsin in the human retina. Members are known to have different absorption spectra including green and blue visible light. | 0 | Theoretical and Fundamental Chemistry |
Going from the bottom to the top of the table the metals:
* increase in reactivity;
* lose electrons (oxidize) more readily to form positive ions;
* corrode or tarnish more readily;
* require more energy (and different methods) to be isolated from their compounds;
* become stronger reducing agents (electron donors). | 0 | Theoretical and Fundamental Chemistry |
From a hydraulic perspective, vertical closures are preferable due to their reduced turbulence and consequent minimisation of soil erosion issues. However, their implementation is more complex. For parts of the dam submerged underwater, stone dumpers (either bottom or side dumpers) can be employed. Yet, this becomes impractical for the final segments due to insufficient navigational depth. Two alternatives exist: the construction of an auxiliary bridge or the use of a cable car. | 1 | Applied and Interdisciplinary Chemistry |
An organism's demand for oxygen is dependent on its metabolic rate. Metabolic rates can be affected by external factors such as the temperature of the water, and internal factors such as the species, life stage, size, and activity level of the organism. The body temperature of ectotherms (such as fishes and invertebrates) fluctuates with the temperature of the water. As the external temperature increases, ectotherm metabolisms increase as well, increasing their demand for oxygen. Different species have different basal metabolic rates and therefore different oxygen demands.
Life stages of organisms also have different metabolic demands. In general, younger stages tend to grow in size and advance in developmental complexity quickly. As the organism reaches maturity, metabolic demands switch from growth and development to maintenance, which requires far fewer resources. Smaller organisms have higher metabolisms per unit of mass, so smaller organisms will require more oxygen per unit mass, while larger organisms generally require more total oxygen. Higher activity levels also require more oxygen.
This is why bioavailability is important in deoxygenated systems: an oxygen quantity which is dangerously low for one species might be more than enough for another species. | 0 | Theoretical and Fundamental Chemistry |
Sleeping pills, including eszopiclone, have been associated with an increased risk of death.
Hypersensitivity to eszopiclone is a contraindication to its use. The presence of liver impairment, lactation and activities requiring mental alertness (e.g., driving) may be considered when determining frequency and dosage.
* unpleasant taste
* headache
* peripheral edema
* chest pain
* abnormal thinking
* behavior changes
* depression
* hallucinations
* sleep driving and sleepwalking
* dry mouth
* rash
* altered sleep patterns
* impaired coordination
* dizziness
* daytime drowsiness
* itching
* painful or frequent urination
* back pain
* aggressive behavior
* confusion
* agitation
* suicidal thoughts
* depersonalization
* amnesia
A 2009 meta-analysis found a 44% higher rate of mild infections, such as pharyngitis or sinusitis, in people taking eszopiclone or other hypnotic drugs compared to those taking a placebo. | 0 | Theoretical and Fundamental Chemistry |
Presently known "super" states of matter are superconductors, superfluid liquids and gases, and supersolids. Egor Babaev predicted that if hydrogen and deuterium have liquid metallic states, they might have quantum ordered states that cannot be classified as superconducting or superfluid in the usual sense. Instead, they might represent two possible novel types of quantum fluids: superconducting superfluids and metallic superfluids. Such fluids were predicted to have highly unusual reactions to external magnetic fields and rotations, which might provide a means for experimental verification of Babaev's predictions. It has also been suggested that, under the influence of a magnetic field, hydrogen might exhibit phase transitions from superconductivity to superfluidity and vice versa. | 0 | Theoretical and Fundamental Chemistry |
Reactions with neutrons are important in nuclear reactors and nuclear weapons. While the best-known neutron reactions are neutron scattering, neutron capture, and nuclear fission, for some light nuclei (especially odd-odd nuclei) the most probable reaction with a thermal neutron is a transfer reaction:
Some reactions are only possible with fast neutrons:
*(n,2n) reactions produce small amounts of protactinium-231 and uranium-232 in the thorium cycle which is otherwise relatively free of highly radioactive actinide products.
*Be + n → 2α + 2n can contribute some additional neutrons in the beryllium neutron reflector of a nuclear weapon.
*Li + n → T + α + n unexpectedly contributed additional yield in the Bravo, Romeo and Yankee shots of Operation Castle, the three highest-yield nuclear tests conducted by the U.S. | 0 | Theoretical and Fundamental Chemistry |
The last formula in the Colebrook equation section of this article is for free surface flow. The approximations elsewhere in this article are not applicable for this type of flow. | 1 | Applied and Interdisciplinary Chemistry |
Everhardus Ariëns grew up as the sixth of ten children in Wijk bij Duurstede. After a temporary boarding school experience, in 1935 he was admitted to Wageningen, the general university. Then he took a degree in chemistry at the University of Utrecht in which he completed in 1942, although his preference was actually the biology. Another study was interrupted by the Second World War. After his refusal to sign a declaration of loyalty to the German Reich and an escape from the Germany occupied Netherlands via Switzerland, France and England, he found asylum with the U.S. Army. He completed the unfinished part of his studies medicine after the Second World War. | 0 | Theoretical and Fundamental Chemistry |
Reactive transport modeling requires input from numerous fields, including hydrology, geochemistry and biogeochemistry, microbiology, soil physics, and fluid dynamics. The numerical formulation and solution of reactive transport problems can be especially difficult due to errors arising in the coupling process, beyond those inherent to the individual processes. Valocchi and Malmstead (1992), for example, reported on the potential errors arising from the operator splitting technique.
Even in the absence of numerical difficulties, the general lack of knowledge available to practitioners creates uncertainty. Field sites are typically heterogeneous, both physically and chemically, and sampling is often sparse. The prevailing assumption of Fickian dispersion is often inadequate. Equilibrium constants and kinetic rate laws for relevant reactions are often poorly known. The complexity of many processes requires expertise in one or more of the aforementioned fields. Many processes, such as long-term nuclear waste storage, cannot be experimentally verified; reactive transport problems can only attempt to predict such long-term behavior. The current descriptions of multi-phase flow and mechanical deformation processes are still being developed. | 0 | Theoretical and Fundamental Chemistry |
Electrophilic additions of allylsilanes generally occur via an anti S2 process. Allylsilanes react through a conformation in which the smallest substituent on the carbon attached to silicon is essentially eclipsing the double bond. The silyl moiety forces electrophilic attack on the face opposite the silyl group for steric and electronic reasons, although the effects are not large. This model predicts that when the double bond is 1,2-disubstituted, the Z isomer should exhibit greater selectivity than the E' isomer, and this has been observed
Vinylsilane additions proceed with retention of double bond configuration, and follow a similar principle. After addition of the electrophile to the top or bottom face of the double bond, the silyl moiety rotates to become parallel to the adjacent empty 2p orbital. The principle of least motion provides that the electrophile moves into a position close to that formerly occupied by the silyl group. Thus, the configuration of the double bond is retained after loss of the silyl group. | 0 | Theoretical and Fundamental Chemistry |
Defined by a cycle of transfers into and out of a system, a cyclic process is described by the quantities transferred in the several stages of the cycle. The descriptions of the staged states of the system may be of little or even no interest. A cycle is a sequence of a small number of thermodynamic processes that indefinitely often, repeatedly returns the system to its original state. For this, the staged states themselves are not necessarily described, because it is the transfers that are of interest. It is reasoned that if the cycle can be repeated indefinitely often, then it can be assumed that the states are recurrently unchanged. The condition of the system during the several staged processes may be of even less interest than is the precise nature of the recurrent states. If, however, the several staged processes are idealized and quasi-static, then the cycle is described by a path through a continuous progression of equilibrium states. | 0 | Theoretical and Fundamental Chemistry |
PA is a vital cell lipid that acts as a biosynthetic precursor for the formation (directly or indirectly) of all acylglycerol lipids in the cell.
In mammalian and yeast cells, two different pathways are known for the de novo synthesis of PA, the glycerol 3-phosphate pathway or the dihydroxyacetone phosphate pathway. In bacteria, only the former pathway is present, and mutations that block this pathway are lethal, demonstrating the importance of PA. In mammalian and yeast cells, where the enzymes in these pathways are redundant, mutation of any one enzyme is not lethal. However, it is worth noting that in vitro, the various acyltransferases exhibit different substrate specificities with respect to the acyl-CoAs that are incorporated into PA. Different acyltransferases also have different intracellular distributions, such as the endoplasmic reticulum (ER), the mitochondria or peroxisomes, and local concentrations of activated fatty acids. This suggests that the various acyltransferases present in mammalian and yeast cells may be responsible for producing different pools of PA.
The conversion of PA into diacylglycerol (DAG) by LPPs is the commitment step for the production of phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylserine (PS). In addition, DAG is also converted into CDP-DAG, which is a precursor for phosphatidylglycerol (PG), phosphatidylinositol (PI) and phosphoinositides (PIP, PIP, PIP).
PA concentrations are maintained at extremely low levels in the cell by the activity of potent LPPs. These convert PA into DAG very rapidly and, because DAG is the precursor for so many other lipids, it too is soon metabolised into other membrane lipids. This means that any upregulation in PA production can be matched, over time, with a corresponding upregulation in LPPs and in DAG metabolising enzymes.
PA is, therefore, essential for lipid synthesis and cell survival, yet, under normal conditions, is maintained at very low levels in the cell. | 1 | Applied and Interdisciplinary Chemistry |
If the solvent is a gas, only gases (non-condensable) or vapors (condensable) are dissolved under a given set of conditions. An example of a gaseous solution is air (oxygen and other gases dissolved in nitrogen). Since interactions between gaseous molecules play almost no role, non-condensable gases form rather trivial solutions. In the literature, they are not even classified as solutions, but simply addressed as homogeneous mixtures of gases. The Brownian motion and the permanent molecular agitation of gas molecules guarantee the homogeneity of the gaseous systems. Non-condensable gaseous mixtures (e.g., air/CO, or air/xenon) do not spontaneously demix, nor sediment, as distinctly stratified and separate gas layers as a function of their relative density. Diffusion forces efficiently counteract gravitation forces under normal conditions prevailing on Earth. The case of condensable vapors is different: once the saturation vapor pressure at a given temperature is reached, vapor excess condenses into the liquid state. | 0 | Theoretical and Fundamental Chemistry |
After the expression of the gene product, it may be necessary to purify the expressed protein; however, separating the protein of interest from the great majority of proteins of the host cell can be a protracted process. To make this purification process easier, a purification tag may be added to the cloned gene. This tag could be histidine (His) tag, other marker peptides, or a fusion partners such as glutathione S-transferase or maltose-binding protein. Some of these fusion partners may also help to increase the solubility of some expressed proteins. Other fusion proteins such as green fluorescent protein may act as a reporter gene for the identification of successful cloned genes, or they may be used to study protein expression in cellular imaging. | 1 | Applied and Interdisciplinary Chemistry |
While magnetometers can be used to help map basin shape at a regional scale, they are more commonly used to map hazards to coal mining, such as basaltic intrusions (dykes, sills, and volcanic plug) that destroy resources and are dangerous to longwall mining equipment. Magnetometers can also locate zones ignited by lightning and map siderite (an impurity in coal).
The best survey results are achieved on the ground in high-resolution surveys (with approximately 10 m line spacing and 0.5 m station spacing). Bore-hole magnetometers using a Ferretcan also assist when coal seams are deep, by using multiple sills or looking beneath surface basalt flows.
Modern surveys generally use magnetometers with GPS technology to automatically record the magnetic field and their location. The data set is then corrected with data from a second magnetometer (the base station) that is left stationary and records the change in the Earth's magnetic field during the survey. | 0 | Theoretical and Fundamental Chemistry |
Site-directed mutagenesis is used to mutate specific bases (and thus amino acids). This is critical to investigate the function of specific amino acids in a protein, e.g. in the active site of an enzyme. | 1 | Applied and Interdisciplinary Chemistry |
As the internal energy is a convex function of entropy and volume, the stability condition requires that the second derivative of internal energy with entropy or volume to be positive. It is commonly expressed as . Since the maximum principle of entropy is equivalent to minimum principle of internal energy, the combined criteria for stability or thermodynamic equilibrium is expressed as and for parameters, entropy and volume. This is analogous to and condition for entropy at equilibrium. The same concept can be applied to the various thermodynamic potentials by identifying if they are convex or concave of respective their variables.
and
Where Helmholtz energy is a concave function of temperature and convex function of volume.
and
Where enthalpy is a concave function of pressure and convex function of entropy.
and
Where Gibbs potential is a concave function of both pressure and temperature.
In general the thermodynamic potentials (the internal energy and its Legendre transforms), are convex functions of their extrinsic variables and concave functions of intrinsic variables. The stability conditions impose that isothermal compressibility is positive and that for non-negative temperature, . | 0 | Theoretical and Fundamental Chemistry |
For abrasions and wounds, nanochemistry has demonstrated applications in improving the healing process. Electrospinning is a polymerization method used biologically in tissue engineering but can also be used for wound dressing and drug delivery. This produces nanofibers that encourage cell proliferation, antibacterial properties, in controlled environment. These properties appear macroscopically, however, nanoscale versions may show improved efficiency due to nanotopographical features. Targeted interfaces between nanofibers and wounds have higher surface area interactions and are advantageous in vivo. There is evidence that certain nanoparticles of silver are useful to inhibit some viruses and bacteria. | 0 | Theoretical and Fundamental Chemistry |
Bacteria biooxidation is an oxidation process caused by microbes where the valuable metal remains (but becomes enriched) in the solid phase. In this process, the metal remains in the solid phase and the liquid can be discarded.
Bacterial oxidation is a biohydrometallurgical process developed for pre-cyanidation treatment of refractory gold ores or concentrates. The bacterial culture is a mixed culture of Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans. The bacterial oxidation process comprises contacting refractory sulfide ROM ore or concentrate with a strain of the bacterial culture for a suitable treatment period under an optimum operating environment. The bacteria oxidise the sulfide minerals, thus liberating the occluded gold for subsequent recovery via cyanidation.
The BIOX® process is a proprietary technology owned by Biomin South Africa and used under licence by a number of operating mines. The BIOX® process involves bacterial oxidation in agitated tanks for pre-treatment of refractory ores and concentrates ahead of conventional cyanide leach for gold recovery.
Under controlled continuous plant conditions, the number of bacterial cells and their activity is optimised to attain the highest rate of sulfide oxidation. The bacteria require a very acidic environment (pH 1.0 to 4.0), a temperature of between 30 and 45 °C, and a steady supply of oxygen and carbon dioxide for optimum growth and activity. The unusual operating conditions for the bacteria are not favourable for the growth of most other microbes, thus eliminating the need for sterility during the bacterial oxidation process. Because organic substances are toxic to the bacteria, they are non-pathogenic and incapable of causing disease. The bacteria employed in the process do not, therefore, pose a health risk to humans or any animals.
The bacterial oxidation of iron sulfide minerals produces iron(III) sulfate and sulfuric acid, and in the case of arsenopyrite, arsenic acid is also produced. The arsenic is removed from the liquor by coprecipitation with the iron and sulfate in a two-stage neutralisation process. This produces a solid neutralisation precipitate containing largely calcium sulfate, basic iron(III) arsenate and iron(III) hydroxide. The iron(III) arsenate is sufficiently insoluble and stable to allow the neutralisation product to be safely disposed of on a slimes dam. The neutralisation liquor, purified to contain an acceptable level of arsenic, can be re-used in the milling, flotation or bacterial oxidation circuits. | 0 | Theoretical and Fundamental Chemistry |
A number of independent studies examine the efficacy of the DrugWipe, particularly for its lack of sensitivity for detecting Cannabis (delta-9-thc) which the Australian National Health Survey 2009 listed as the most frequently used illicit drug at 10.4% with 36% smoking at least once a week or more in 2016. Independent field testing of the DrugWipe in Finland recorded a high rate of false negatives, particularly for Cannabis, this is where a person tests negative however had recently used 14.4%. including the sensitivity of less than 50%. According to statistics by the National Institute for Health and Welfare in Finland, of positive results for cannabis, cocaine, and opioids, two-thirds were false compared to blood samples. As positive test results have been used as sufficient grounds for a ban on driving, the Finnish Parliamentary Ombudsman issued a statement condemning the practice.
THC in the saliva is said to be an index of recent cannabis smoking and closely linked to the effects of intoxication however in another study, volunteers were recruited to consume cannabis and subsequent levels of THC taken from saliva. The amounts detected were only above the level of the DrugWipe at 10 ng/ml for 70 minutes, with volunteers reporting feeling intoxicated for a further 2 hours.
As this 1999 DEA Bulletin shows, Drugwipe is still effective when testing black cocaine even when chemical tests fail to detect it.
"At three checkpoints organized by the Swiss police in Bern, 61 drivers were tested for the presence of drugs of abuse using the Drugwipe 5 device. In parallel, oral fluid was collected with the Intercept DOA Oral Specimen Collection device and tested by gas chromatography-mass spectrometry (GC-MS) after methylation of THC (limit of quantitation 1 ng/mL)
The Drugwipe device identified 1 exposed driver, but with GC-MS, 18 drivers tested positive. THC concentrations in the Intercept buffer ranged from 2.1 to 205.1 ng/mL. These concentrations represent about 1/2 to 1/3 the authentic THC concentrations in oral fluid because of the dilution by the blue liquid of the device. Two main limitations of oral fluid were 1. the amount of matrix collected is smaller when compared to urine, and 2. the levels of drugs in urine are higher than in oral fluid. A current limitation of the use of this specimen for roadside testing is the absence of a suitable immunoassay that detects the parent compound in sufficiently low concentrations."
"The three tested on-site screening devices, Mavand RapidSTAT®, Securetec Drugwipe-5+® and Dräger DrugTest 5000® were able to detect about 70% of all cocaine and cannabis users in a roadside setting. Amphetamine/MDMA users were detected more easily, with a sensitivity higher than 92%. The sensitivity of oral fluid screening tests for THC is increasing as manufacturers are still trying to lower the cut-off of their devices. First results using the new DrugTest 5000 test cassette® demonstrate that a sensitivity of 93% is possible."
"During a 11-month period, 1.212 drivers were tested. Both OF and on-site urine tests were compared to serum results. The following sensitivities were obtained by the oral fluid devices: THC 71% (DrugWipe(®)), 87% (Dräger), 91% (RapidSTAT); opiates 95% (Dräger), 100% (DrugWipe(®), RapidSTAT(®)); amphetamine 84% (DrugTest(®) 5000), 90% (RapidSTAT(®)), 100% (DrugTest(®) 5000); methamphetamine 50% (DrugTest(®) 5000), 100% (RapidSTAT(®)); cocaine 76% (DrugTest(®) 5000), 100% (DrugWipe(®), RapidSTAT(®)); methadone 33-63%, and benzodiazepines 0-33% (both with a low number of positives). THC specificity was especially low (29% [DrugWipe(®)] and 47% [DrugTest(®) 5000]) due to low cut-off concentrations. These data were similar to those obtained from the literature (e.g., DRUID project)."
Drugwipe tests from saliva used by Finnish police have been found to be unreliable. According to statistics by the National Institute for Health and Welfare in Finland, of positive results for cannabis, cocaine and opioids, two-thirds were false compared to a blood test. As positive test results have been used as sufficient grounds for a ban on driving, the Finnish Parliamentary Ombudsman issued a statement condemning the practice. | 0 | Theoretical and Fundamental Chemistry |
Chelate complexes of gadolinium are often used as contrast agents in MRI scans, although iron particle and manganese chelate complexes have also been explored. Bifunctional chelate complexes of zirconium, gallium, fluorine, copper, yttrium, bromine, or iodine are often used for conjugation to monoclonal antibodies for use in antibody-based PET imaging. These chelate complexes often employ the usage of hexadentate ligands such as desferrioxamine B (DFO), according to Meijs et al., and the gadolinium complexes often employ the usage of octadentate ligands such as DTPA, according to Desreux et al. Auranofin, a chelate complex of gold, is used in the treatment of rheumatoid arthritis, and penicillamine, which forms chelate complexes of copper, is used in the treatment of Wilson's disease and cystinuria, as well as refractory rheumatoid arthritis. | 0 | Theoretical and Fundamental Chemistry |
Columnar structures have also been studied intensively in the context of nanotubes. Their physical or chemical properties can be altered by trapping identical particles inside them. These are usually done by self-assembling fullerenes such as C60, C70, or C78 into carbon nanotubes, but also boron nitride nanotubes
Such structures also assemble when particles are coated on the surface of a spherocylinder as in the context of pharmaceutical research. Lazáro et al. examined the morphologies of virus capsid proteins self-assembled around metal nanorods. Drug particles were coated as densely as possible on a spherocylinder to provide the best medical treatment.
Wu et al. built rods of the size of several microns. These microrods are created by densely packing silica colloidal particles inside cylindrical pores. By solidifying the assembled structures the microrods were imaged and examined using scanning electron microscopy (SEM).
Columnar arrangements are also investigated as a possible candidate of optical metamaterials (i.e. materials with a negative refractive index) which find applications in super lenses or optical cloaking. Tanjeem et al. are constructing such a resonator by self-assembling nanospheres on the surface of the cylinder. The nanospheres are suspended in an SDS solution together with a cylinder of diameter , much larger than the diameter of the nanospheres (). The nanospheres then stick to the surface of the cylinders by a depletion force. | 0 | Theoretical and Fundamental Chemistry |
It was not until after the observations of certain molecular phenomena that stereochemical principles were developed. In 1815, Jean-Baptiste Biots observation of optical activity marked the beginning of organic stereochemistry history. He observed that organic molecules were able to rotate the plane of polarized light in a solution or in the gaseous phase. Despite Biots discoveries, Louis Pasteur is commonly described as the first stereochemist, having observed in 1842 that salts of tartaric acid collected from wine production vessels could rotate the plane of polarized light, but that salts from other sources did not. This property, the only physical property in which the two types of tartrate salts differed, is due to optical isomerism. In 1874, Jacobus Henricus van t Hoff and Joseph Le Bel explained optical activity in terms of the tetrahedral arrangement of the atoms bound to carbon. Kekulé used tetrahedral models earlier in 1862 but never published these; Emanuele Paternò probably knew of these but was the first to draw and discuss three dimensional structures, such as of 1,2-dibromoethane in the Giornale di Scienze Naturali ed Economiche' in 1869. The term "chiral" was introduced by Lord Kelvin in 1904. Arthur Robertson Cushny, Scottish Pharmacologist, in 1908, first offered a definite example of a bioactivity difference between enantiomers of a chiral molecule viz. (-)-Adrenaline is two times more potent than the (±)- form as a vasoconstrictor and in 1926 laid the foundation for chiral pharmacology/stereo-pharmacology (biological relations of optically isomeric substances). Later in 1966, the Cahn-Ingold-Prelog nomenclature or Sequence rule was devised to assign absolute configuration to stereogenic/chiral center (R- and S- notation) and extended to be applied across olefinic bonds (E- and Z- notation). | 0 | Theoretical and Fundamental Chemistry |
All igneous magmas contain dissolved gases (water, carbonic acid, hydrogen sulfide, chlorine, fluorine, boric acid, etc.). Of these water is the principal, and was formerly believed to have percolated downwards from the Earth's surface to the heated rocks below, but is now generally admitted to be an integral part of the magma. Many peculiarities of the structure of the plutonic rocks as contrasted with the lavas may reasonably be accounted for by the operation of these gases, which were unable to escape as the deep-seated masses slowly cooled, while they were promptly given up by the superficial effusions. The acid plutonic or intrusive rocks have never been reproduced by laboratory experiments, and the only successful attempts to obtain their minerals artificially have been those in which special provision was made for the retention of the "mineralizing" gases in the crucibles or sealed tubes employed. These gases often do not enter into the composition of the rock-forming minerals, for most of these are free from water, carbonic acid, etc. Hence as crystallization goes on the residual melt must contain an ever-increasing proportion of volatile constituents. It is conceivable that in the final stages the still uncrystallized part of the magma has more resemblance to a solution of mineral matter in superheated steam than to a dry igneous fusion. Quartz, for example, is the last mineral to form in a granite. It bears much of the stamp of the quartz which we know has been deposited from aqueous solution in veins, etc. It is at the same time the most infusible of all the common minerals of rocks. Its late formation shows that in this case it arose at comparatively low temperatures and points clearly to the special importance of the gases of the magma as determining the sequence of crystallization.
When solidification is nearly complete the gases can no longer be retained in the rock and make their escape through fissures towards the surface. They are powerful agents in attacking the minerals of the rocks which they traverse, and instances of their operation are found in the kaolinization of granites, tourmalinization and formation of greisen, deposition of quartz veins, and the group of changes known as propylitization. These "pneumatolytic" processes are of the first importance in the genesis of many ore deposits. They are a real part of the history of the magma itself and constitute the terminal phases of the volcanic sequence. | 0 | Theoretical and Fundamental Chemistry |
In the 1960s, a light driven proton pump was discovered in Halobacterium salinarum, and called Bacteriorhodopsin. Over the following years, there were various studies of the membrane of H. salinarum to determine the mechanism of these light-driven proton pumps.
In 1988, another Manabu Yoshidas group at Osaka University reported a novel light-sensitive proton pump from a strain of Halobacterium' which they termed Archaerhodopsin. A year later, the same group reported isolating the gene that encodes Archaerhodopsin. | 0 | Theoretical and Fundamental Chemistry |
Wetting theory: Wetting is the oldest and most prevalent theory of adhesion. The adhesive components in a liquid solution anchor themselves in irregularities on the substrate and eventually harden, providing sites on which to adhere. Surface tension effects restrict the movement of the adhesive along the surface of the substrate, and is related to the thermodynamic work of adhesion by Dupre's Equation. Measuring the affinity of the adhesive for the substrate is performed by determining the contact angle. Contact angles closer to zero indicate a more wettable interaction, and those interactions have a greater spreadability.
Adsorption theory: Adsorption is another widely accepted theory, where adhesion between the substrate and adhesive is due to primary and secondary bonding. The primary bonds are due to chemisorption, and result in comparatively long lasting covalent and non-covalent bonds. Among covalent bonds disulfide bonds are likely most important. Thiolated polymers – designated thiomers – are mucoadhesive polymers that can form disulfide bonds with cysteine-rich subdomains of mucus glycoproteins. Recently several new classes of polymers have been developed that are capable of forming covalent bonds with mucosal surfaces similarly to thiomers. These polymers have acryloyl, methacryloyl, maleimide, boronate and N‐hydroxy (sulfo) succinimide ester groups in their structure. Among non-covalent bonds likely ionic interactions such as interactions of mucoadhesive chitosans with the anionically charged mucus and Hydrogen bonding are most important. The secondary bonds include weak Van Der Waals forces, and interactions between hydrophobic substructure.
Diffusion theory: The mechanism for diffusion involves polymer and mucin chains from the adhesive penetrating the matrix of the substrate and forming a semipermanent bond. As the similarities between the adhesive and the substrate increase, so does the degree of mucoadhesion. The bond strength increases with the degree of penetration, increasing the adhesion strength. The penetration rate is determined by the diffusion coefficient, the degree of flexibility of the adsorbate chains, mobility and contact time. The diffusion mechanism itself is affected by the length of the molecular chains being implanted and cross-linking density, and is driven by a concentration gradient.
Electrostatic theory: is an electrostatic process involving the transfer of electrons across the interface between the substrate and adhesive. The net result is the formation of a double layer of charges that are attracted to each other due to balancing of the Fermi layers, and therefore cause adhesion. This theory only works given the assumption that the substrate and adhesive have different electrostatic surface characteristics.
Fracture theory: Fracture theory is the major mechanism by which to determine the mechanical strength of a particular mucoadhesive, and describes the force necessary to separate the two materials after mucoadhesion has occurred. Ultimate tensile strength is determined by the separating force and the total surface area of the adhesion, and failure generally occurs in one of the surfaces rather than at the interface. Since the fracture theory only deals with the separation force, the diffusion and penetration of polymers is not accounted for in this mechanism. | 1 | Applied and Interdisciplinary Chemistry |
Primordial fluctuations, density variations in the early universe, are quantified by a power spectrum which gives the power of the variations as a function of spatial scale. | 0 | Theoretical and Fundamental Chemistry |
Globally, seagrass has been declining rapidly. It is estimated that 21% of the 71 known seagrass species have decreasing population trends and 11% of those species have been designated as threatened on the ICUN Red List. Hypoxia that leads to eutrophication caused form ocean deoxygenation is one of the main underlying factors of these die-offs. Eutrophication causes enhanced nutrient enrichment which can result in seagrass productivity, but with continual nutrient enrichment in seagrass meadows, it can cause excessive growth of microalgae, epiphytes and phytoplankton resulting in hypoxic conditions.
Seagrass is both a source and a sink for oxygen in the surrounding water column and sediments. At night, the inner part of seagrass oxygen pressure is linearly related to the oxygen concentration in the water column, so low water column oxygen concentrations often result in hypoxic seagrass tissues, which can eventually kill off the seagrass. Normally, seagrass sediments must supply oxygen to the below-ground tissue through either photosynthesis or by diffusing oxygen from the water column through leaves to rhizomes and roots. However, with the change in seagrass oxygen balances, it can often result in hypoxic seagrass tissues. Seagrass exposed to this hypoxic water column show increased respiration, reduced rates of photosynthesis, smaller leaves, and reduced number of leaves per shoot. This causes insufficient supply of oxygen to the belowground tissues for aerobic respiration, so seagrass must rely on the less-efficient anaerobic respiration. Seagrass die-offs create a positive feedback loop in which the mortality events cause more death as higher oxygen demands are created when dead plant material decomposes.
Because hypoxia increases the invasion of sulfides in seagrass, this negatively affects seagrass through photosynthesis, metabolism and growth. Generally, seagrass is able to combat the sulfides by supplying enough oxygen to the roots. However, deoxygenation causes the seagrass to be unable to supply this oxygen, thus killing it off.
Deoxygenation reduces the diversity of organisms inhabiting seagrass beds by eliminating species that cannot tolerate the low oxygen conditions. Indirectly, the loss and degradation of seagrass threatens numerous species that rely on seagrass for either shelter or food. The loss of seagrass also effects the physical characteristics and resilience of seagrass ecosystems. Seagrass beds provide nursery grounds and habitat to many harvested commercial, recreational, and subsistence fish and shellfish. In many tropical regions, local people are dependent on seagrass associated fisheries as a source of food and income.
Seagrass also provides many ecosystem services including water purification, coastal protection, erosion control, sequestration and delivery of trophic subsidies to adjacent marine and terrestrial habitats. Continued deoxygenation causes the effects of hypoxia to be compounded by climate change which will increase the decline in seagrass populations. | 0 | Theoretical and Fundamental Chemistry |
According to the U.S. Environmental Protection Agency (EPA), “Using structural BMPs that can be placed underground and are design to withstand site specific soil, groundwater and traffic loading conditions provide valuable savings in land area compared to conventional volume-based stormwater treatment practices such as ponds, wetlands, and swales.” HDS systems may be ideal for areas where land is not readily available and/or tight retrofits are needed as they are installed underground. | 1 | Applied and Interdisciplinary Chemistry |
Biofilm processes in general require less space than activated sludge systems because the biomass is more concentrated, and the efficiency of the system is less dependent on the final sludge separation.
MBBR systems do not need a recycling of the sludge, which is the case with activated sludge systems.
The MBBR system is often installed as a retrofit of existing activated sludge tanks to increase the capacity of the existing system. The degree of filling of carriers can be adapted to the specific situation and the desired capacity. Thus an existing treatment plant can increase its capacity without increasing the footprint by constructing new tanks.
Some other advantages are:
* Increased performance and volumetric treatment capacity
* Higher effective sludge retention time (SRT) which is favorable for nitrification
* Responds to load fluctuations without operator intervention
* Lower sludge production
* Less area required
* Resilient to toxic shock
* Process performance independent of secondary clarifier (due to the fact that there is no sludge return line). | 1 | Applied and Interdisciplinary Chemistry |
Admission to the School of Chemistry's research programs is competitive. Generally, admission to the School of Chemistry Honours program requires a SCIWAM of at least 65 or equivalent. Each faculty member is limited to 2.5 full-time equivalent (FTE) Honours students to ensure adequate supervision where co-supervised projects count as 0.5 FTE for each faculty. As a result, admission for some projects is significantly more competitive than others.
The School of Chemistry offer postgraduate research degrees in the Doctor of Philosophy, Master of Philosophy, and Graduate Diploma in Science where admission is by application to the University of Sydney. Applications for funding and scholarships is a separate application but also to the University of Sydney, this is a competitive process and a successful candidate is typically offered a stipend and a scholarship to cover living expenses and tuition fees, respectively. | 1 | Applied and Interdisciplinary Chemistry |
While lipolysis is triglyceride hydrolysis (the process by which triglycerides are broken down), esterification is the process by which triglycerides are formed. Esterification and lipolysis are, in essence, reversals of one another. | 1 | Applied and Interdisciplinary Chemistry |
The Influenza Antiviral Drug Search was a distributed computing project that was running on the BOINC platform. It is a project of the University of Texas Medical Branch. | 1 | Applied and Interdisciplinary Chemistry |
A number of enzymatic dynamic kinetic resolutions have been reported. A prime example using PSL effectively resolves racemic acyloins in the presence of triethylamine and vinyl acetate as the acylating agent. As shown below, the product was isolated in 75% yield and 97% ee. Without the presence of the base, regular kinetic resolution occurred, resulting in 45% yield of >99% ee acylated product and 53% of the starting material in 92% ee.
Another excellent, though not high-yielding, example is the kinetic resolution of (±)-8-amino-5,6,7,8-tetrahydroquinoline. When exposed to Candida antarctica lipase B (CALB) in toluene and ethyl acetate for 3–24 hours, normal kinetic resolution occurs, resulting in 45% yield of 97% ee of starting material and 45% yield of >97% ee acylated amine product. However, when the reaction is allowed to stir for 40–48 hours, racemic starting material and >60% of >95% ee acylated product are recovered.
Here, the unreacted starting material racemizes in situ via a dimeric enamine, resulting in a recovery of greater than 50% yield of the enantiopure acylated amine product. | 0 | Theoretical and Fundamental Chemistry |
A standard black oxide is magnetite (FeO), which is more mechanically stable on the surface and provides better corrosion protection than red oxide (rust) FeO. Modern industrial approaches to forming black oxide include the hot and mid-temperature processes described below. Traditional methods are described in the article on bluing. They are of interest historically, and are also useful for hobbyists to form black oxide safely with little equipment and without toxic chemicals.
Low temperature oxide, also described below, is not a conversion coating—the low-temperature process does not oxidize the iron, but deposits a copper selenium compound. | 0 | Theoretical and Fundamental Chemistry |
M30 Apoptosense® ELISA is an enzyme-linked immunosorbent assay developed for the detection of soluble caspase-cleaved keratin 18 (ccK18, K18-Asp396, formerly cytokeratin 18, ccCK18 or CK18-Asp396). | 1 | Applied and Interdisciplinary Chemistry |
A living organism is a thermodynamic system of an active type (in which energy transformations occur), striving for a stable nonequilibrium thermodynamic state. The nonequilibrium thermodynamic state in plants is achieved by continuous alternation of phases of solar energy consumption as a result of photosynthesis and subsequent biochemical reactions, as a result of which adenosine triphosphate (ATP) is synthesized in the daytime, and the subsequent release of energy during the splitting of ATP mainly in the dark. Thus, one of the conditions for the existence of life on Earth is the alternation of light and dark time of day.
In animals, the processes of alternating cycles of biochemical reactions of ATP synthesis and cleavage occur automatically. Moreover, the processes of alternating cycles of biochemical reactions at the levels of organs, systems and the whole organism, for example, respiration, heart contractions and others occur with different periods and externally manifest themselves in the form of biorhythms. At the same time, the stability of the nonequilibrium thermodynamic state, optimal under certain conditions of vital activity, is provided by feedback systems through the regulation of biochemical reactions in accordance with the Lyapunov stability theory. This principle of vital activity was formulated by B. Dobroborsky in the form of the 2nd law of thermodynamics of biological systems in the following wording:
The stability of the nonequilibrium thermodynamic state of biological systems is ensured by the continuous alternation of phases of energy consumption and release through controlled reactions of synthesis and cleavage of ATP.
The following consequences follow from this law:
1. In living organisms, no process can occur continuously, but must alternate with the opposite direction: inhalation with exhalation, work with rest, wakefulness with sleep, synthesis with cleavage, etc.
2. The state of a living organism is never static, and all its physiological and energy parameters are always in a state of continuous fluctuations relative to the average values both in frequency and amplitude.
This principle of functioning of living organisms provides them with the properties of phenotypic adaptation and a number of others. | 0 | Theoretical and Fundamental Chemistry |
The more assumptions that are made, the more uncertain estimates of risk related to pathogens will be. However, even with considerable uncertainty, QMRAs are a good way to compare different risk scenarios. In a study comparing estimated health risks from exposures to recreational waters impacted by human and non-human sources of fecal contamination, QMRA determined that the risk of gastrointestinal illness from exposure to waters impacted by cattle were similar to those impacted by human waste, and these were higher than for waters impacted by gull, chicken, or pig faeces. Such studies could be useful to risk managers for determining how best to focus their limited resources, however, risk managers must be aware of the limitations of data used in these calculations. For example, this study used data describing concentrations of Salmonella in chicken feces published in 1969. Methods for quantifying bacteria, changes in animal housing practices and sanitation, and many other factors may have changed the prevalence of Salmonella since that time. Also, such an approach often ignores the complicated fate and transport processes that determine bacteria concentrations from the source to the point of exposure. | 0 | Theoretical and Fundamental Chemistry |
Choline is an essential nutrient. The cholines are a family of water-soluble quaternary ammonium compounds. Choline is the parent compound of the cholines class, consisting of ethanolamine having three methyl substituents attached to the amino function. Healthy humans fed artificially composed diets that are deficient in choline develop fatty liver, liver damage, and muscle damage. Choline was not initially classified as essential because the human body can produce choline in small amounts through phosphatidylcholine metabolism. | 0 | Theoretical and Fundamental Chemistry |
* [http://www.adigosstemcells.com/regenerative-medicines.php Regenerative Medicine], gives more details about Regenerative Stem Cells.
* Kevin Strange and Viravuth Yin, "A Shot at Regeneration: A once abandoned drug compound shows an ability to rebuild organs damaged by illness and injury", Scientific American, vol. 320, no. 4 (April 2019), pp. 56–61. | 1 | Applied and Interdisciplinary Chemistry |
Denitrification is a microbially facilitated process where nitrate (NO) is reduced and ultimately produces molecular nitrogen (N) through a series of intermediate gaseous nitrogen oxide products. Facultative anaerobic bacteria perform denitrification as a type of respiration that reduces oxidized forms of nitrogen in response to the oxidation of an electron donor such as organic matter. The preferred nitrogen electron acceptors in order of most to least thermodynamically favorable include nitrate (NO), nitrite (NO), nitric oxide (NO), nitrous oxide (NO) finally resulting in the production of dinitrogen (N) completing the nitrogen cycle. Denitrifying microbes require a very low oxygen concentration of less than 10%, as well as organic C for energy. Since denitrification can remove NO, reducing its leaching to groundwater, it can be strategically used to treat sewage or animal residues of high nitrogen content. Denitrification can leak NO, which is an ozone-depleting substance and a greenhouse gas that can have a considerable influence on global warming.
The process is performed primarily by heterotrophic bacteria (such as Paracoccus denitrificans and various pseudomonads), although autotrophic denitrifiers have also been identified (e.g., Thiobacillus denitrificans). Denitrifiers are represented in all main phylogenetic groups. Generally several species of bacteria are involved in the complete reduction of nitrate to N, and more than one enzymatic pathway has been identified in the reduction process. The denitrification process does not only provide energy to the organism performing nitrate reduction to dinitrogen gas, but also some anaerobic ciliates can use denitrifying endosymbionts to gain energy similar to the use of mitochondria in oxygen respiring organisms.
Direct reduction from nitrate to ammonium, a process known as dissimilatory nitrate reduction to ammonium or DNRA, is also possible for organisms that have the nrf-gene. This is less common than denitrification in most ecosystems as a means of nitrate reduction. Other genes known in microorganisms which denitrify include nir (nitrite reductase) and nos (nitrous oxide reductase) among others; organisms identified as having these genes include Alcaligenes faecalis, Alcaligenes xylosoxidans, many in the genus Pseudomonas, Bradyrhizobium japonicum, and Blastobacter denitrificans. | 1 | Applied and Interdisciplinary Chemistry |
Oceanographers generally study particles that measure 0.2 micrometres and larger, which means a lot of nanoscale particles are not examined, particularly with respect to formation mechanisms. | 0 | Theoretical and Fundamental Chemistry |
Sequanium was the proposed name for a new element that Romanian physicist Horia Hulubei reported he had discovered in 1939. The name derived from the Latin word Sequana for the river Seine running through Paris where Hulubei worked at that time.
Hulubei thought he had discovered element 93 in a tantalite sample from the French region Haute-Vienne. Element 93 was synthesised in 1940 and named neptunium. It does in fact occur in nature in trace amounts, but it is not commonly believed that Hulubei actually discovered it. | 1 | Applied and Interdisciplinary Chemistry |
In a column published in Images Magazine, Ted Ellis calls on the younger generations of black artists to recognize the hardship faced by and the effort put in by the previous generation of black artists in order to pave the way for the newer generation to be able to succeed, and to do so with far less difficulty.
He says African-American are still not within the mainstream, and despite being the most financially minded black artists yet, that the current generation still earns less than it should. Ellis further assigns partial responsibility on an academic world that he sees as not paying sufficient attention to the genre.
He believes strongly that African-Americans should value their art on their terms, looking past aesthetics, and that only thus will the genre grow and be better appreciated. | 0 | Theoretical and Fundamental Chemistry |
Alpine lakes located in the Central Pyrenees region of northeast Spain are unaffected by anthropogenic factors making these oligotrophic lakes ideal indicators for sediment input and environmental change. Dissolved organic matter and nutrients from dust transport can aid bacteria with growth and production in low nutrient waters. Within the collected samples of one study, a high diversity of airborne microorganisms were detected and had strong similarities to Mauritian soils despite Saharan dust storms occurring at the time of detection. | 0 | Theoretical and Fundamental Chemistry |
In magnetohydrodynamics, the magnetic Reynolds number (R) is a dimensionless quantity that estimates the relative effects of advection or induction of a magnetic field by the motion of a conducting medium to the magnetic diffusion. It is the magnetic analogue of the Reynolds number in fluid mechanics and is typically defined by:
where
* is a typical velocity scale of the flow,
* is a typical length scale of the flow,
* is the magnetic diffusivity.
The mechanism by which the motion of a conducting fluid generates a magnetic field is the subject of dynamo theory. When the magnetic Reynolds number is very large, however, diffusion and the dynamo are less of a concern, and in this case
focus instead often rests on the influence of the magnetic field on the flow. | 1 | Applied and Interdisciplinary Chemistry |
The modern era of CCC began with the development of the planetary centrifuge by Dr. Yoichiro Ito which was first introduced in 1966 as a closed helical tube which was rotated on a "planetary" axis as is turned on a "sun" axis. A flow-through model was subsequently developed and the new technique was called countercurrent chromatography in 1970. The technique was further developed by employing test mixtures of DNP amino acids in a chloroform:glacial acetic acid:0.1 M aqueous hydrochloric acid (2:2:1 v/v) solvent system. Much development was needed to engineer the instrument so that required planetary motion could be sustained while the phases were being pumped through the coil(s). Parameters such as the relative rotation of the two axes (synchronous or non-synchronous), the direction of flow through the coil, and the rotor angles were investigated. | 0 | Theoretical and Fundamental Chemistry |
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