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The chair conformation is the most stable conformer. At , 99.99% of all molecules in a cyclohexane solution adopt this conformation.
The symmetry group is D. All carbon centers are equivalent. Six hydrogen centers are poised in axial positions, roughly parallel with the C3 axis, and six hydrogen atoms are parallel with the equator of the molecule.
Each carbon bears one "up" and one "down" hydrogen. The C–H bonds in successive carbons are thus staggered so that there is little torsional strain. The chair geometry is often preserved when the hydrogen atoms are replaced by halogens or other simple groups. However, when these hydrogens are substituted for a larger group, strain is imposed upon the molecule due to diaxial interactions. This is an interaction (that is usually repulsive) between two substituents in the axial position on a cyclohexane ring.
If one thinks of a carbon atom as a point with four half-bonds sticking out towards the vertices of a tetrahedron, they can imagine them standing on a surface with one half-bond pointing straight up. Looking from right above, the other three would appear to go outwards towards the vertices of an equilateral triangle, so the bonds would appear to have an angle of 120° between them. Now consider six such atoms standing on the surface so that their non-vertical half-bonds meet up and form a perfect hexagon. If three of the atoms are then reflected to be below the surface, the result will be something very similar to chair-conformation cyclohexane. In this model, the six vertical half-bonds are exactly vertical, and the ends of the six non-vertical half-bonds that stick out from the ring are exactly on the equator (that is, on the surface). Since C–H bonds are actually longer than half a C–C bond, the "equatorial" hydrogen atoms of chair cyclohexane will actually be below the equator when attached to a carbon that is above the equator, and vice versa. This is also true of other substituents. The dihedral angle for a series of four carbon atoms going around the ring in this model alternates between exactly +60° and −60° (called gauche).
The chair conformation cannot deform without changing the bond angles or lengths. We can think of it as two chains, mirror images one of the other, containing atoms (1,2,3,4) and (1,6,5,4), with opposite dihedral angles. The distance from atom 1 to atom 4 depends on the absolute value of the dihedral angle. If these two dihedral angles change (still being opposite one of the other), it is not possible to maintain the correct bond angle at both carbon 1 and carbon 4. | 0 | Theoretical and Fundamental Chemistry |
N-linked glycosylation, is the attachment of an oligosaccharide, a carbohydrate consisting of several sugar molecules, sometimes also referred to as glycan, to a nitrogen atom (the amide nitrogen of an asparagine (Asn) residue of a protein), in a process called N-glycosylation, studied in biochemistry. The resulting protein is called an N-linked glycan, or simply an N-glycan.
This type of linkage is important for both the structure and function of many eukaryotic proteins. The N-linked glycosylation process occurs in eukaryotes and widely in archaea, but very rarely in bacteria. The nature of N-linked glycans attached to a glycoprotein is determined by the protein and the cell in which it is expressed. It also varies across species. Different species synthesize different types of N-linked glycan. | 0 | Theoretical and Fundamental Chemistry |
Some animals, including birds, reptiles, and insects such as bees, can see near-ultraviolet wavelengths. Many fruits, flowers, and seeds stand out more strongly from the background in ultraviolet wavelengths as compared to human color vision. Scorpions glow or take on a yellow to green color under UV illumination, thus assisting in the control of these arachnids. Many birds have patterns in their plumage that are invisible at usual wavelengths but observable in ultraviolet, and the urine and other secretions of some animals, including dogs, cats, and human beings, are much easier to spot with ultraviolet. Urine trails of rodents can be detected by pest control technicians for proper treatment of infested dwellings.
Butterflies use ultraviolet as a communication system for sex recognition and mating behavior. For example, in the Colias eurytheme butterfly, males rely on visual cues to locate and identify females. Instead of using chemical stimuli to find mates, males are attracted to the ultraviolet-reflecting color of female hind wings. In Pieris napi butterflies it was shown that females in northern Finland with less UV-radiation present in the environment possessed stronger UV signals to attract their males than those occurring further south. This suggested that it was evolutionarily more difficult to increase the UV-sensitivity of the eyes of the males than to increase the UV-signals emitted by the females.
Many insects use the ultraviolet wavelength emissions from celestial objects as references for flight navigation. A local ultraviolet emitter will normally disrupt the navigation process and will eventually attract the flying insect.
The green fluorescent protein (GFP) is often used in genetics as a marker. Many substances, such as proteins, have significant light absorption bands in the ultraviolet that are of interest in biochemistry and related fields. UV-capable spectrophotometers are common in such laboratories.
Ultraviolet traps called bug zappers are used to eliminate various small flying insects. They are attracted to the UV and are killed using an electric shock, or trapped once they come into contact with the device. Different designs of ultraviolet radiation traps are also used by entomologists for collecting nocturnal insects during faunistic survey studies. | 0 | Theoretical and Fundamental Chemistry |
Shortly before the war, Hans von Halban and Lew Kowarski moved their research on neutron moderation from France to Britain, smuggling the entire global supply of heavy water (which had been made in Norway) across in twenty-six steel drums.
During World War II, Nazi Germany was known to be conducting experiments using heavy water as moderator for a nuclear reactor design. Such experiments were a source of concern because they might allow them to produce plutonium for an atomic bomb. Ultimately it led to the Allied operation called the "Norwegian heavy water sabotage", the purpose of which was to destroy the Vemork deuterium production/enrichment facility in Norway. At the time this was considered important to the potential progress of the war.
After World War II ended, the Allies discovered that Germany was not putting as much serious effort into the program as had been previously thought. The Germans had completed only a small, partly built experimental reactor (which had been hidden away) and had been unable to sustain a chain reaction. By the end of the war, the Germans did not even have a fifth of the amount of heavy water needed to run the reactor, partially due to the Norwegian heavy water sabotage operation. However, even if the Germans had succeeded in getting a reactor operational (as the U.S. did with Chicago Pile-1 in late 1942), they would still have been at least several years away from the development of an atomic bomb. The engineering process, even with maximal effort and funding, required about two and a half years (from first critical reactor to bomb) in both the U.S. and U.S.S.R., for example. | 0 | Theoretical and Fundamental Chemistry |
In biochemistry, intercalation is the insertion of molecules between the bases of DNA. This process is used as a method for analyzing DNA and it is also the basis of certain kinds of poisoning.
Clathrates are chemical substances consisting of a lattice that traps or contains molecules. Usually, clathrate compounds are polymeric and completely envelop the guest molecule. Inclusion compounds are often molecules, whereas clathrates are typically polymeric. Intercalation compounds are not 3-dimensional, unlike clathrate compounds. According to IUPAC, clathrates are "Inclusion compounds in which the guest molecule is in a cage formed by the host molecule or by a lattice of host molecules." | 0 | Theoretical and Fundamental Chemistry |
A case study by Beale et al. involved preparation of iron phosphates and bismuth molybdate catalysts from an amorphous precursor gel. The study found that there were no intermediate phases in the reaction, and helped to determine kinetic and structural information. The article uses the dated term in-situ, but the experiment uses, in essence, an operando method. Although x-ray diffraction does not count as a spectroscopy method, it is often being used as an operando method in various fields, including catalysis. | 0 | Theoretical and Fundamental Chemistry |
Epinephrine and glucagon affect the activity of protein kinase A by changing the levels of cAMP in a cell via the G-protein mechanism, using adenylate cyclase. Protein kinase A acts to phosphorylate many enzymes important in metabolism. For example, protein kinase A phosphorylates acetyl-CoA carboxylase and pyruvate dehydrogenase. Such covalent modification has an inhibitory effect on these enzymes, thus inhibiting lipogenesis and promoting net gluconeogenesis. Insulin, on the other hand, decreases the level of phosphorylation of these enzymes, which instead promotes lipogenesis. Recall that gluconeogenesis does not occur in myocytes. | 1 | Applied and Interdisciplinary Chemistry |
In late February and early March 2003, a large amount of media attention circulated around the globe regarding largely unknown and unpublished documents, evidently written by Isaac Newton, indicating that he believed the world would end no earlier than 2060. The story garnered vast amounts of public interest and found its way onto the front page of several widely distributed newspapers, including the UKs Daily Telegraph, Canadas National Post, Israels Maariv and Yediot Aharonot, and was also featured in an article in the scientific journal Canadian Journal of History. Television and internet stories in the following weeks heightened the exposure and ultimately would include the production of several documentary films focused upon the topic of the 2060 prediction and some of Newtons lesser known beliefs and practices.
The two documents detailing this prediction are currently housed within the Jewish National and University Library in Jerusalem. Both were believed to be written toward the end of Newtons life, circa 1705, a time frame most notably established by the use of the full title of Sir' Isaac Newton within portions of the documents.
These documents do not appear to have been written with the intention of publication and Newton expressed a strong personal dislike for individuals who provided specific dates for the Apocalypse purely for sensational value. Furthermore, he at no time provides a specific date for the end of the world in either of these documents.
To understand the reasoning behind the 2060 prediction, an understanding of Newtons theological beliefs should be taken into account, particularly his apparent antitrinitarian beliefs and his Protestant views on the Papacy. Both of these lay essential to his calculations, which ultimately would provide the 2060 time frame. See Isaac Newtons religious views for more details.
The first document, part of the Yahuda collection, is a small letter slip, on the back of which is written haphazardly in Newton's hand:
The second reference to the 2060 prediction can be found in a folio, in which Newton writes:
Clearly Newton's mathematical prediction of the end of the world is one derived from his interpretation of not only scripture, but also one based upon his theological viewpoint regarding specific chronological dates and events as he saw them.
Newton may not have been referring to the post 2060 event as a destructive act resulting in the annihilation of the globe and its inhabitants, but rather one in which he believed the world, as he saw it, was to be replaced with a new one based upon a transition to an era of divinely inspired peace. In Christian and Islamic theology this concept is often referred to as The Second Coming of Jesus Christ and the establishment of The Kingdom of God on Earth. In a separate manuscript, Isaac Newton paraphrases Revelation 21 and 22 and relates the post 2060 events by writing: | 1 | Applied and Interdisciplinary Chemistry |
Interfering RNA are a class of short, noncoding RNA that act to translationally or post-translationally repress gene expression. Their discovery and subsequent identification as key effectors of post-transcriptional gene regulation have made small interfering RNA (siRNA) and micro RNA (miRNA) potential therapeutics for systemic diseases. The RNAi system was originally discovered in 1990 by Jorgensen et al., who were doing research involving the introduction of coloration genes into petunias, and it is thought that this system originally developed as a means of innate immunity against double-stranded RNA viruses. | 1 | Applied and Interdisciplinary Chemistry |
In 1835, Charles Wheatstone reported that different metals could be easily distinguished by the different bright lines in the emission spectra of their sparks, thereby introducing an alternative mechanism to flame spectroscopy. In 1849, J. B. L. Foucault experimentally demonstrated that absorption and emission lines appearing at the same wavelength are both due to the same material, with the difference between the two originating from the temperature of the light source. In 1853, the Swedish physicist Anders Jonas Ångström presented observations and theories about gas spectra in his work Optiska Undersökningar (Optical investigations) to the [[Royal Swedish Academy of Sciences. Ångström postulated that an incandescent gas emits luminous rays of the same wavelength as those it can absorb. Ångström was unaware of Foucalt's experimental results. At the same time George Stokes and William Thomson (Kelvin) were discussing similar postulates. Ångström also measured the emission spectrum from hydrogen later labeled the Balmer lines. In 1854 and 1855, David Alter published observations on the spectra of metals and gases, including an independent observation of the Balmer lines of hydrogen.
The systematic attribution of spectra to chemical elements began in the 1860s with the work of German physicists Robert Bunsen and Gustav Kirchhoff, who found that Fraunhofer lines correspond to emission spectral lines observed in laboratory light sources. This laid way for spectrochemical analysis in laboratory and astrophysical science. Bunsen and Kirchhoff applied the optical techniques of Fraunhofer, Bunsens improved flame source and a highly systematic experimental procedure to a detailed examination of the spectra of chemical compounds. They established the linkage between chemical elements and their unique spectral patterns. In the process, they established the technique of analytical spectroscopy. In 1860, they published their findings on the spectra of eight elements and identified these elements presence in several natural compounds. They demonstrated that spectroscopy could be used for trace chemical analysis and several of the chemical elements they discovered were previously unknown. Kirchhoff and Bunsen also definitively established the link between absorption and emission lines, including attributing solar absorption lines to particular elements based on their corresponding spectra. Kirchhoff went on to contribute fundamental research on the nature of spectral absorption and emission, including what is now known as Kirchhoffs law of thermal radiation. Kirchhoffs applications of this law to spectroscopy are captured in three laws of spectroscopy:
#An incandescent solid, liquid or gas under high pressure emits a continuous spectrum.
#A hot gas under low pressure emits a "bright-line" or emission-line spectrum.
#A continuous spectrum source viewed through a cool, low-density gas produces an absorption-line spectrum.
In the 1860s the husband-and-wife team of William and Margaret Huggins used spectroscopy to determine that the stars were composed of the same elements as found on earth. They also used the non-relativistic Doppler shift (redshift) equation on the spectrum of the star Sirius in 1868 to determine its axial speed. They were the first to take a spectrum of a planetary nebula when the Cat's Eye Nebula (NGC 6543) was analyzed. Using spectral techniques, they were able to distinguish nebulae from stars.
August Beer observed a relationship between light absorption and concentration and created the color comparator which was later replaced by a more accurate device called the spectrophotometer. | 0 | Theoretical and Fundamental Chemistry |
Transmutation of transuranium elements (i.e. actinides minus actinium to uranium) such as the isotopes of plutonium (about 1wt% in the light water reactors used nuclear fuel or the minor actinides (MAs, i.e. neptunium, americium, and curium), about 0.1wt% each in light water reactors used nuclear fuel) has the potential to help solve some problems posed by the management of radioactive waste by reducing the proportion of long-lived isotopes it contains. (This does not rule out the need for a deep geological repository for high level radioactive waste.) When irradiated with fast neutrons in a nuclear reactor, these isotopes can undergo nuclear fission, destroying the original actinide isotope and producing a spectrum of radioactive and nonradioactive fission products.
Ceramic targets containing actinides can be bombarded with neutrons to induce transmutation reactions to remove the most difficult long-lived species. These can consist of actinide-containing solid solutions such as , , , , or just actinide phases such as , , , mixed with some inert phases such as , , , and . The role of non-radioactive inert phases is mainly to provide stable mechanical behaviour to the target under neutron irradiation.
There are issues with this P&T (partitioning and transmutation) strategy however:
* it is limited by the costly and cumbersome need to separate long-lived fission product isotopes before they can undergo transmutation.
* some long-lived fission products, including the nuclear waste product caesium-137, are unable to capture enough neutrons for effective transmutation to occur due to their small neutron cross-section and resultingly low capture rate.
The new study led by Satoshi Chiba at Tokyo Tech (called "Method to Reduce Long-lived Fission Products by Nuclear Transmutations with Fast Spectrum Reactors") shows that effective transmutation of long-lived fission products can be achieved in fast spectrum reactors without the need for isotope separation. This can be achieved by adding a yttrium deuteride moderator. | 0 | Theoretical and Fundamental Chemistry |
Among the faculty members who have worked at the Graduate Institute of Ferrous Technology, several Professors are distinguished world-widely:
** Sir Professor Harshad_Bhadeshia
** Professor Frédéric Barlat
** Professor Nack Joon KIM
** Professor Bruno De Cooman
** Prof. Yasushi Sasaki
** Prof. Hae-Geon Lee
** Prof. Chong Soo Lee | 1 | Applied and Interdisciplinary Chemistry |
Smolková-Keulemansová suffered from dysentery, jaundice, typhus and tuberculosis after liberation. She could not give an address to anyone she knew in Prague, so the International Red Cross did not allow her to return to her country of origin. To receive medical treatment, she was selected to go to Sweden for a six-month recovery stay with 6,000 other prisoners. | 0 | Theoretical and Fundamental Chemistry |
Anthocyanins fluoresce, enabling a tool for plant cell research to allow live cell imaging without a requirement for other fluorophores. Anthocyanin production may be engineered into genetically modified materials to enable their identification visually. | 0 | Theoretical and Fundamental Chemistry |
Although NBS is easier and safer to handle than bromine, precautions should be taken to avoid inhalation. NBS should be stored in a refrigerator. NBS will decompose over time giving off bromine. Pure NBS is white, but it is often found to be off-white or brown colored by bromine.
In general, reactions involving NBS are exothermic. Therefore, extra precautions should be taken when using on a large scale. | 0 | Theoretical and Fundamental Chemistry |
In the United States, an all-out effort for making atomic weapons was begun in late 1942. This work was taken over by the U.S. Army Corps of Engineers in 1943, and known as the Manhattan Engineer District. The top-secret Manhattan Project, as it was colloquially known, was led by General Leslie R. Groves. Among the project's dozens of sites were: Hanford Site in Washington, which had the first industrial-scale nuclear reactors and produced plutonium; Oak Ridge, Tennessee, which was primarily concerned with uranium enrichment; and Los Alamos, in New Mexico, which was the scientific hub for research on bomb development and design. Other sites, notably the Berkeley Radiation Laboratory and the Metallurgical Laboratory at the University of Chicago, played important contributing roles. Overall scientific direction of the project was managed by the physicist J. Robert Oppenheimer.
In July 1945, the first atomic explosive device, dubbed "The Gadget", was detonated in the New Mexico desert in the Trinity test. It was fueled by plutonium created at Hanford. In August 1945, two more atomic devices – "Little Boy", a uranium-235 bomb, and "Fat Man", a plutonium bomb – were used against the Japanese cities of Hiroshima and Nagasaki. | 0 | Theoretical and Fundamental Chemistry |
The temperature-entropy conjugate pair is concerned with the transfer of energy, especially for a closed system.
* An isothermal process occurs at a constant temperature. An example would be a closed system immersed in and thermally connected with a large constant-temperature bath. Energy gained by the system, through work done on it, is lost to the bath, so that its temperature remains constant.
* An adiabatic process is a process in which there is no matter or heat transfer, because a thermally insulating wall separates the system from its surroundings. For the process to be natural, either (a) work must be done on the system at a finite rate, so that the internal energy of the system increases; the entropy of the system increases even though it is thermally insulated; or (b) the system must do work on the surroundings, which then suffer increase of entropy, as well as gaining energy from the system.
* An isentropic process is customarily defined as an idealized quasi-static reversible adiabatic process, of transfer of energy as work. Otherwise, for a constant-entropy process, if work is done irreversibly, heat transfer is necessary, so that the process is not adiabatic, and an accurate artificial control mechanism is necessary; such is therefore not an ordinary natural thermodynamic process. | 0 | Theoretical and Fundamental Chemistry |
The applications of synthetic nucleotides vary widely and include disease diagnosis, treatment, or precision medicine.
# Antiviral or Antiretroviral agents: several nucleotide derivatives have been used in the treatment against infection with Hepatitis and HIV. Examples of direct nucleoside analog reverse-transcriptase inhibitors (NRTIs) include Tenofovir disoproxil, Tenofovir alafenamide, and Sofosbuvir. On the other hand, agents such as Mericitabine, Lamivudine, Entecavir and Telbivudine must first undergo metabolization via phosphorylation to become activated.
# Antisense oligonucleotides (ASO): synthetic oligonucleotides have been used in the treatment of rare heritable diseases since they can bind specific RNA transcripts and ultimately modulate protein expression. Spinal muscular atrophy, amyotrophic lateral sclerosis, homozygous familial hypercholesterolemia, and primary hyperoxaluria type 1 are all amenable to ASO-based therapy. The application of oligonucleotides is a new frontier in precision medicine and management of conditions which are untreatable.
# Synthetic guide RNA (gRNA): synthetic nucleotides can be used to design gRNA which are essential for the proper function of gene-editing technologies such as CRISPR-Cas9. | 1 | Applied and Interdisciplinary Chemistry |
Consider a nonconductive charged body rotating about an axis of symmetry. According to the laws of classical physics, it has both a magnetic dipole moment due to the movement of charge and an angular momentum due to the movement of mass arising from its rotation. It can be shown that as long as its charge and mass density and flow are distributed identically and rotationally symmetric, its gyromagnetic ratio is
where is its charge and is its mass.
The derivation of this relation is as follows. It suffices to demonstrate this for an infinitesimally narrow circular ring within the body, as the general result then follows from an integration. Suppose the ring has radius , area , mass , charge , and angular momentum . Then the magnitude of the magnetic dipole moment is | 0 | Theoretical and Fundamental Chemistry |
Dioxiranes may be produced through the action of KHSO on carbonyl compounds. Because of their low-lying σ* orbital, they are highly electrophilic oxidants and react with unsaturated functional groups, Y-H bonds (yielding oxygen insertion products), and heteroatoms. The most common dioxiranes employed for organic synthesis are dimethyldioxirane (DMD) and trifluoromethyl-methyldioxirane (TFD). The latter is effective for chemoselective oxidations of C-H and Si-H bonds. Although this class of reagents is most famous for the epoxidation of alkenes, dioxiranes have been used extensively for other kinds of oxidations as well. | 0 | Theoretical and Fundamental Chemistry |
A stink bomb, sometimes called a stinkpot, is a device designed to create an unpleasant smell. They range in effectiveness from being used as simple pranks to military grade malodorants or riot control chemical agents. | 1 | Applied and Interdisciplinary Chemistry |
In polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained from the copolymerization of two monomer species are sometimes called bipolymers. Those obtained from three and four monomers are called terpolymers and quaterpolymers, respectively. Copolymers can be characterized by a variety of techniques such as NMR spectroscopy and size-exclusion chromatography to determine the molecular size, weight, properties, and composition of the material.
Commercial copolymers include acrylonitrile butadiene styrene (ABS), styrene/butadiene co-polymer (SBR), nitrile rubber, styrene-acrylonitrile, styrene-isoprene-styrene (SIS) and ethylene-vinyl acetate, all of which are formed by chain-growth polymerization. Another production mechanism is step-growth polymerization, which is used to produce the nylon-12/6/66 copolymer of nylon 12, nylon 6 and nylon 66, as well as the copolyester family. Copolymers can be used to develop commercial goods or drug delivery vehicles.
Since a copolymer consists of at least two types of constituent units (also structural units), copolymers can be classified based on how these units are arranged along the chain. Linear copolymers consist of a single main chain and include alternating copolymers, statistical copolymers, and block copolymers. Branched copolymers consist of a single main chain with one or more polymeric side chains, and can be grafted, star shaped, or have other architectures. | 0 | Theoretical and Fundamental Chemistry |
Benzeneselenol was first reported in 1888 by the reaction of benzene with selenium tetrachloride () in the presence of aluminium trichloride (). | 0 | Theoretical and Fundamental Chemistry |
A standing wave is a continuous form of normal mode. In a standing wave, all the space elements (i.e. (x, y, z) coordinates) are oscillating in the same frequency and in phase (reaching the equilibrium point together), but each has a different amplitude.
The general form of a standing wave is:
where ƒ(x, y, z) represents the dependence of amplitude on location and the cosine\sine are the oscillations in time.
Physically, standing waves are formed by the interference (superposition) of waves and their reflections (although one may also say the opposite; that a moving wave is a superposition of standing waves). The geometric shape of the medium determines what would be the interference pattern, thus determines the ƒ(x, y, z) form of the standing wave. This space-dependence is called a normal mode.
Usually, for problems with continuous dependence on (x, y, z) there is no single or finite number of normal modes, but there are infinitely many normal modes. If the problem is bounded (i.e. it is defined on a finite section of space) there are countably many normal modes (usually numbered n = 1, 2, 3, ...). If the problem is not bounded, there is a continuous spectrum of normal modes. | 0 | Theoretical and Fundamental Chemistry |
Xylenes are an important petrochemical produced by catalytic reforming and also by coal carbonisation in the manufacture of coke fuel. They also occur in crude oil in concentrations of about 0.5–1%, depending on the source. Small quantities occur in gasoline and aircraft fuels.
Xylenes are produced mainly as part of the BTX aromatics (benzene, toluene, and xylenes) extracted from the product of catalytic reforming known as reformate.
Several million tons are produced annually. In 2011, a global consortium began construction of one of the world's largest xylene plants in Singapore. | 1 | Applied and Interdisciplinary Chemistry |
Initiation of metastasis requires invasion, which is enabled by EMT. Carcinoma cells in a primary tumor lose cell-cell adhesion mediated by E-cadherin repression and break through the basement membrane with increased invasive properties, and enter the bloodstream through intravasation. Later, when these circulating tumor cells (CTCs) exit the bloodstream to form micro-metastases, they undergo MET for clonal outgrowth at these metastatic sites. Thus, EMT and MET form the initiation and completion of the invasion-metastasis cascade. At this new metastatic site, the tumor may undergo other processes to optimize growth. For example, EMT has been associated with PD-L1 expression, particularly in lung cancer. Increased levels of PD-L1 suppresses the immune system which allows the cancer to spread more easily.
EMT confers resistance to oncogene-induced premature senescence. Twist1 and Twist2, as well as ZEB1 protects human cells and mouse embryonic fibroblasts from senescence. Similarly, TGF-β can promote tumor invasion and evasion of immune surveillance at advanced stages. When TGF-β acts on activated Ras-expressing mammary epithelial cells, EMT is favored and apoptosis is inhibited. This effect can be reversed by inducers of epithelial differentiation, such as GATA-3.
EMT has been shown to be induced by androgen deprivation therapy in metastatic prostate cancer. Activation of EMT programs via inhibition of the androgen axis provides a mechanism by which tumor cells can adapt to promote disease recurrence and progression. Brachyury, Axl, MEK, and Aurora kinase A are molecular drivers of these programs, and inhibitors are currently in clinical trials to determine therapeutic applications. Oncogenic PKC-iota can promote melanoma cell invasion by activating Vimentin during EMT. PKC-iota inhibition or knockdown resulted an increase E-cadherin and RhoA levels while decreasing total Vimentin, phosphorylated Vimentin (S39) and Par6 in metastatic melanoma cells. These results suggested that PKC-ι is involved in signaling pathways which upregulate EMT in melanoma.
EMT has been indicated to be involved in acquiring drug resistance. Gain of EMT markers was found to be associated with the resistance of ovarian carcinoma epithelial cell lines to paclitaxel. Similarly, SNAIL also confers resistance to paclitaxel, adriamycin and radiotherapy by inhibiting p53-mediated apoptosis. Furthermore, inflammation, that has been associated with the progression of cancer and fibrosis, was recently shown to be related to cancer through inflammation-induced EMT. Consequently, EMT enables cells to gain a migratory phenotype, as well as induce multiple immunosuppression, drug resistance, evasion of apoptosis mechanisms.
Some evidence suggests that cells that undergo EMT gain stem cell-like properties, thus giving rise to Cancer Stem Cells (CSCs). Upon transfection by activated Ras, a subpopulation of cells exhibiting the putative stem cell markers CD44high/CD24low increases with the concomitant induction of EMT. Also, ZEB1 is capable of conferring stem cell-like properties, thus strengthening the relationship between EMT and stemness. Thus, EMT may present increased danger to cancer patients, as EMT not only enables the carcinoma cells to enter the bloodstream, but also endows them with properties of stemness which increases tumorigenic and proliferative potential.
However, recent studies have further shifted the primary effects of EMT away from invasion and metastasis, toward resistance to chemotherapeutic agents. Research on breast cancer and pancreatic cancer both demonstrated no difference in cells' metastatic potential upon acquisition of EMT. These are in agreement with another study showing that the EMT transcription factor TWIST actually requires intact adherens junctions in order to mediate local invasion in breast cancer. The effects of EMT and its relationship to invasion and metastasis may therefore be highly context specific.
In urothelial carcinoma cell lines overexpression of HDAC5 inhibits long-term proliferation but can promote epithelial-to-mesenchymal transition (EMT). | 1 | Applied and Interdisciplinary Chemistry |
The nucleate boiling regime is important to engineers because of the high heat fluxes possible with moderate temperature differences. The data can be correlated by an equation of the form
Where is the Nusselt number, defined as:
where:
* is the total heat flux,
* is the maximum bubble diameter as it leaves the surface,
* is the excess temperature,
* is the thermal conductivity of the liquid,
* is the Prandtl number of the liquid,
* is the bubble Reynolds number, where:
** is the average mass velocity of the vapor leaving the surface
** is the liquid viscosity.
Rohsenow has developed the first and most widely used correlation for nucleate boiling,
where:
* is the specific heat of the liquid,
* is the surface fluid combination and vary for various combinations of fluid and surface,
* is the surface tension of the liquid-vapor interface.
The variable depends on the surface fluid combination and typically has a value of 1.0 or 1.7. For example, water and nickel have a of 0.006 and of 1.0. | 1 | Applied and Interdisciplinary Chemistry |
Convenient generation of a directing group on the nitrogen of indoles is possible through treatment with an organolithium reagent and carbon dioxide. A similar method can be applied for lateral lithiations of ortho-tolyl anilines.
Oxazoles containing two methyl groups exhibit interesting selectivity patterns. In the absence of a directing substituent, the methyl group closer to the more electronegative oxygen atom is selectively metalated. However, in the presence of a directing substituent, the director fully controls the site of lithiation. | 0 | Theoretical and Fundamental Chemistry |
Molecular biology is a branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including biomolecular synthesis, modification, mechanisms, and interactions.
Molecular biology was first described as an approach focused on the underpinnings of biological phenomena—uncovering the structures of biological molecules as well as their interactions, and how these interactions explain observations of classical biology.
The term molecular biology was first used in 1945 by physicist William Astbury. In 1953 Francis Crick, James Watson, Rosalind Franklin, and colleagues working at the Medical Research Council Unit, Cavendish Laboratory, created the double helix model of DNA. They proposed the DNA structure based on previous research done by Franklin, which was conveyed to them by Maurice Wilkins and Max Perutz. This led to the discovery of DNA material in other microorganisms, plants, and animals.
The field of molecular biology includes techniques which enable scientists to learn about molecular processes. These techniques are used to efficiently target new drugs, diagnose disease, and better understand cell physiology. Some clinical research and medical therapies arising from molecular biology are covered under gene therapy whereas the use of molecular biology or molecular cell biology in medicine is now referred to as molecular medicine. | 1 | Applied and Interdisciplinary Chemistry |
In the process industry dispersing agents are added to process liquids to prevent unwanted deposits by keeping them finely dispersed. They function in both aqueous and nonaqueous media. | 0 | Theoretical and Fundamental Chemistry |
The geology that underlies a river or lake has a major impact on its chemistry. A river flowing across very ancient precambrian schists is likely to have dissolved very little from the rocks and maybe similar to de-ionised water at least in the headwaters. Conversely a river flowing through chalk hills, and especially if its source is in the chalk, will have a high concentration of carbonates and bicarbonates of Calcium and possibly Magnesium.
As a river progresses along its course it may pass through a variety of geological types and it may have inputs from aquifers that do not appear on the surface anywhere in the locality. | 1 | Applied and Interdisciplinary Chemistry |
Charles law appears to imply that the volume of a gas will descend to zero at a certain temperature (−266.66 °C according to Gay-Lussacs figures) or −273.15 °C. Gay-Lussac was clear in his description that the law was not applicable at low temperatures:
At absolute zero temperature, the gas possesses zero energy and hence the molecules restrict motion.
Gay-Lussac had no experience of liquid air (first prepared in 1877), although he appears to have believed (as did Dalton) that the "permanent gases" such as air and hydrogen could be liquified. Gay-Lussac had also worked with the vapours of volatile liquids in demonstrating Charles' law, and was aware that the law does not apply just above the boiling point of the liquid:
The first mention of a temperature at which the volume of a gas might descend to zero was by William Thomson (later known as Lord Kelvin) in 1848:
However, the "absolute zero" on the Kelvin temperature scale was originally defined in terms of the second law of thermodynamics, which Thomson himself described in 1852. Thomson did not assume that this was equal to the "zero-volume point" of Charles law, merely said that Charles law provided the minimum temperature which could be attained. The two can be shown to be equivalent by Ludwig Boltzmann's statistical view of entropy (1870).
However, Charles also stated:
:The volume of a fixed mass of dry gas increases or decreases by times the volume at 0 °C for every 1 °C rise or fall in temperature. Thus:
:where is the volume of gas at temperature , is the volume at 0 °C. | 0 | Theoretical and Fundamental Chemistry |
Nomenclature generally follows the conventions of human nomenclature. Gene symbols generally are italicised, with all letters in uppercase (e.g., NLGN1, for neuroligin1). Protein designations are the same as the gene symbol, but are not italicised; all letters are in uppercase (NLGN1). mRNAs and cDNAs use the same formatting conventions as the gene symbol. | 1 | Applied and Interdisciplinary Chemistry |
Consider gas in a one-dimensional container (e.g., a long thin tube). Assume that the fluid is inviscid (i.e., it shows no viscosity effects as for example friction with the tube walls). Furthermore, assume that there is no heat transfer by conduction or radiation and that gravitational acceleration can be neglected. Such a system can be described by the following system of conservation laws, known as the 1D Euler equations, that in conservation form is:
where
* fluid mass density,
* fluid velocity,
* specific internal energy of the fluid,
* fluid pressure, and
* is the total energy density of the fluid, [J/m], while e is its specific internal energy
Assume further that the gas is calorically ideal and that therefore a polytropic equation-of-state of the simple form
is valid, where is the constant ratio of specific heats . This quantity also appears as the polytropic exponent of the polytropic process described by
For an extensive list of compressible flow equations, etc., refer to NACA Report 1135 (1953).
Note: For a calorically ideal gas is a constant and for a thermally ideal gas is a function of temperature. In the latter case, the dependence of pressure on mass density and internal energy might differ from that given by equation (). | 1 | Applied and Interdisciplinary Chemistry |
The pillar carries a number of inscriptions of different dates, some of which have not been studied systematically despite the pillar's prominent location and easy access. | 1 | Applied and Interdisciplinary Chemistry |
It was originally hypothesized that salinosporamide B was a biosynthetic precursor to salinosporamide A due to their structural similarities.
It was thought that the halogenation of the unactivated methyl group was catalyzed by a non-heme iron halogenase. Recent work using C-labeled feeding experiments reveal distinct biosynthetic origins of salinosporamide A and B.
While they share the biosynthetic precursors acetate and presumed β-hydroxycyclohex-2'-enylalanine (3), they differ in the origin of the four-carbon building block that gives rise to their structural differences involving the halogen atom. A hybrid polyketide synthase-nonribosomal peptide synthetase (PKS-NRPS) pathway is most likely the biosynthetic mechanism in which acetyl-CoA and butyrate-derived ethylmalonyl-CoA condense to yield the β-ketothioester (4), which then reacts with (3) to generate the linear precursor (5). | 0 | Theoretical and Fundamental Chemistry |
Levofloxacin is not approved in most countries for the treatment of children except in unique and life-threatening infections because it is associated with an elevated risk of musculoskeletal injury in this population, a property it shares with other fluoroquinolones.
In the United States levofloxacin is approved for the treatment of anthrax and plague in children over six months of age.
Levofloxacin is recommended by the Pediatric Infectious Disease Society and the Infectious Disease Society of America as a first-line treatment for pediatric pneumonia caused by penicillin-resistant Streptococcus pneumoniae, and as a second-line agent for the treatment of penicillin-sensitive cases.
In one study, 1534 juvenile patients (age 6 months to 16 years) treated with levofloxacin as part of three efficacy trials were followed up to assess all musculoskeletal events occurring up to 12 months post-treatment. At 12 months follow-up the cumulative incidence of musculoskeletal adverse events was 3.4%, compared to 1.8% among 893 patients treated with other antibiotics. In the levafloxacin-treated group, approximately two-thirds of these musculoskeletal adverse events occurred in the first 60 days, 86% were mild, 17% were moderate, and all resolved without long-term sequelae. | 0 | Theoretical and Fundamental Chemistry |
Hundreds of such cycles have been proposed and investigated. This task has been eased by the availability of computers, allowing a systematic screening of chemical reactions sequences based on thermodynamic databases. Only the main "families" will be described in this article. | 0 | Theoretical and Fundamental Chemistry |
Phenolics can also be found in non-vascular land plants (bryophytes). Dihydrostilbenoids and bis(dibenzyls) can be found in liverworts (Marchantiophyta), for instance, the macrocycles cavicularin and riccardin C. Though lignin is absent in mosses (Bryophyta) and hornworts (Anthocerotophyta), some phenolics can be found in those two taxa. For instance, rosmarinic acid and a rosmarinic acid 3-O-β-D-glucoside can be found in the hornwort Anthoceros agrestis'. | 0 | Theoretical and Fundamental Chemistry |
The concept of reflection can be extended to three-dimensional objects, including the inside parts, even if they are not transparent. The term then relates to structural as well as visual aspects. A three-dimensional object is reversed in the direction perpendicular to the mirror surface. In physics, mirror images are investigated in the subject called geometrical optics. More fundamentally in geometry and mathematics they form the principal objects of Coxeter group theory and reflection groups.
In chemistry, two versions (isomers) of a molecule, one a "mirror image" of the other, are called enantiomers if they are not "superposable" (the correct technical term, though the term "superimposable" is also used) on each other. That is an example of chirality. In general, an object and its mirror image are called enantiomorphs.
If a point of an object has coordinates (x, y, z) then the image of this point (as reflected by a mirror in the y, z plane) has coordinates (−x, y, z). Thus reflection is a reversal of the coordinate axis perpendicular (normal) to the mirrors surface. Although a plane mirror reverses an object only in the direction normal to the mirror surface, this turns the entire three-dimensional image seen in the mirror inside-out, so there is a perception' of a left-right reversal. Hence, the reversal is somewhat misleadingly called a "lateral inversion". The perception of a left-right reversal is geometrically explained by the fact that a three-dimensional object seen in a mirror is an inside-out version of the actual object, like a glove stripped off the left hand and turned into a right-hand glove, but there is still some confusion about the explanation amongst psychologists. The psychology of the perceived left-right reversal is discussed in "Much ado about mirrors" by Professor Michael Corballis (see "external links", below).
Reflection in a mirror does result in a change in chirality, more specifically from a right-handed to a left-handed coordinate system (or vice versa). If one looks in a mirror two axes (up-down and left-right) coincide with those in the mirror, but the third axis (front-back) is reversed.
If a person stands side-on to a mirror, left and right hands will be reversed directly by the mirror, because the persons left-right axis is then normal to the mirror plane. However, it is important to understand that there are always' only two enantiomorphs, the object and its inside-out image. Therefore, no matter how the object is oriented towards the mirror, all the resulting images are fundamentally identical (as Corballis explains in his paper "Much ado about mirrors", mentioned above).
In the picture of the mountain reflected in the lake (photograph top right), the reversal normal to the reflecting surface is obvious. Notice that there is no obvious front-back or left-right of the mountain. In the example of the urn and mirror (photograph to right), the urn is fairly symmetrical front-back (and left-right). Thus, no obvious reversal of any sort can be seen in the mirror image of the urn.
A mirror image appears more obviously three-dimensional if the observer moves, or if the image is viewed using binocular vision. This is because the relative position of objects changes as the observer's perspective changes, or is differently viewed with each eye.
Looking through a mirror from different positions (but necessarily with the point of observation restricted to the halfspace on one side of the mirror) is like looking at the 3D mirror image of space; without further mirrors only the mirror image of the halfspace before the mirror is relevant; if there is another mirror, the mirror image of the other halfspace is too. | 0 | Theoretical and Fundamental Chemistry |
Schoell has made many contributions to geochemistry with emphasis on the applications of stable isotope analysis. The results of Schoells work have included identifying the pathways of formation that distinguish methane of biogenic origin from that of thermogenic origin using stable isotope analysis. In the paper, "Biogenic methane formation in marine and freshwater environments: CO reduction VS. acetate fermentation-Isotope evidence", Schoell et al. identify that the two primary methods for aquatic and marine methane production are carbon dioxide reduction and acetate fermentation, respectively. By recognizing the difference in δC and δD fractionation of the water environments and observing the differences in δC and δD fractionations of the methane product, Schoell et al. concluded that the dominant pathway of methane in marine environments is via acetate fermentation, while methane in freshwater environments arises from CO reduction. By analyzing the CH and HO fractionation, Schoell, et al.' offer a technique for identifying the original environment in which methane was produced.
Schoell continued his work with methane origin studies expanding his research to consider how stable isotopes can provide insight regarding the temperature of the environment for both thermogenic and biogenic methane production. Specifically, Schoell collaborated on the paper "Formation temperatures of thermogenic and biogenic methane" authored by D. Stolper, which used "clustered isotope" techniques to determine the temperature at which methane was produced. This approach has become useful for identifying the thermal conditions of methane formation for both the high temperatures of thermogenic methane production and the relatively lower temperatures of microbial methane production as well as characterizing the contribution of both producers to a mixed sample.
While the majority of Schoell's work has revolved around identifying the origins and pathways of methane production, he has also done work using stable isotope analysis to address how environmental factors affect preservable products of biological activity. Schoell addresses this topic in the paper, "Sensitivity of biomarker properties to depositional environment and/or source input in the Lower Toarcian of SW-Germany". In addition to this, his career has included the research of how stable isotope analysis can be used to identify the mixing and composition of natural gasses, as discussed in "Use of Gas Isotope Analyses for Reservoir Management". | 0 | Theoretical and Fundamental Chemistry |
Espín died in Havana at 4:14 p.m. EDT on 18 June 2007, following a long illness. An official mourning-period was declared from 8 p.m. on 18 June until 10 p.m. on 19 June. A funeral ceremony was held at the Karl Marx Theatre in Havana the day after her death. Thousands of Cubans paid their respects in a receiving line at the Plaza of the Revolution in Havana. Raúl Castro was in the receiving line, but Fidel Castro was not present. The Cuban government released a statement praising her as "one of the most relevant fighters for women's emancipation in our country and in the world." Her body was cremated, and her remains rest in the Frank País Mausoleum, Municipio II Frente in the province of Santiago de Cuba, Cuba. The Vilma Espín elementary school was opened in Havana in April 2013. Espin founded the Frente Continental de Mujeres Contra la Intervención (Continental Women’s Front Against Intervention, FCMCI) and the Regional Center of the International Democratic Federation of Women for the Americas and Caribbean. | 1 | Applied and Interdisciplinary Chemistry |
The ideal gas law follows from the van der Waals equation whenever is sufficiently large (or correspondingly whenever the molar density, , is sufficiently small), Specifically
* when , then is numerically indistinguishable from ,
* and when , then is numerically indistinguishable from .
Putting these two approximations into the van der Waals equation when is large enough that both inequalities are satisfied reduces it to
which is the ideal gas law. This is not surprising since the van der Waals equation was constructed from the ideal gas equation in order to obtain an equation valid beyond the limit of ideal gas behavior.
What is truly remarkable is the extent to which van der Waals succeeded. Indeed, Epstein in his classic thermodynamics textbook began his discussion of the van der Waals equation by writing: "In spite of its simplicity, it comprehends both the gaseous and the liquid state and brings out, in a most remarkable way, all the phenomena pertaining to the continuity of these two states". Also in Volume 5 of his Lectures on Theoretical Physics Sommerfeld, in addition to noting that "Boltzmann described van der Waals as the Newton of real gases", also wrote "It is very remarkable that the theory due to van der Waals is in a position to predict, at least qualitatively, the unstable [referring to superheated liquid, and subcooled vapor now called metastable] states" that are associated with the phase change process. | 0 | Theoretical and Fundamental Chemistry |
From 1941 to 1951, Vinograd worked for the Shell Development Company in Emeryville, California. During this period, his wife Sherna gave birth to their two daughters, Julia and Deborah. In 1951 he became a senior research fellow at the California Institute of Technology, in Pasadena, California, where he remained for the rest of his career. In 1956 he became a research associate, and in 1965 he was promoted to professor of chemistry and biology. He pioneered the use of ultracentrifugation for the analysis of complex molecules, in particular DNA. | 0 | Theoretical and Fundamental Chemistry |
In humans, DNA methylation occurs at the 5′ position of the pyrimidine ring of the cytosine residues within CpG sites to form 5-methylcytosines. The presence of multiple methylated CpG sites in CpG islands of promoters causes stable inhibition (silencing) of genes. Silencing of transcription of a gene may be initiated by other mechanisms, but this is often followed by methylation of CpG sites in the promoter CpG island to cause the stable silencing of the gene. | 1 | Applied and Interdisciplinary Chemistry |
KaiC is a gene belonging to the KaiABC gene cluster (with KaiA, and KaiB) that, together, regulate bacterial circadian rhythms, specifically in cyanobacteria. KaiC encodes for the KaiC protein, which interacts with the KaiA and KaiB proteins in a post-translational oscillator (PTO). The PTO is cyanobacteria master clock that is controlled by sequences of phosphorylation of KaiC protein. Regulation of KaiABC expression and KaiABC phosphorylation is essential for cyanobacteria circadian rhythmicity, and is particularly important for regulating cyanobacteria processes such as nitrogen fixation, photosynthesis, and cell division. Studies have shown similarities to Drosophila, Neurospora, and mammalian clock models in that the kaiABC regulation of the cyanobacteria slave circadian clock is also based on a transcription translation feedback loop (TTFL). KaiC protein has both auto-kinase and auto-phosphatase activity and functions as the circadian regulator in both the PTO and the TTFL. KaiC has been found to not only suppress kaiBC when overexpressed, but also suppress circadian expression of all genes in the cyanobacterial genome. | 1 | Applied and Interdisciplinary Chemistry |
Consider a parallel shear flow in the direction, which varies only in the cross-flow direction The stability of the flow is studied by adding small perturbations to the flow velocity and in the and directions, respectively. The flow is described using the incompressible Euler equations, which become after linearization – using velocity components and
with the partial derivative operator with respect to time, and similarly and with respect to and The pressure fluctuations ensure that the continuity equation is fulfilled. The fluid density is denoted as and is a constant in the present analysis. The prime denotes differentiation of with respect to its argument
The flow oscillations and are described using a streamfunction ensuring that the continuity equation is satisfied:
Taking the - and -derivatives of the - and -momentum equation, and thereafter subtracting the two equations, the pressure can be eliminated:
which is essentially the vorticity transport equation, being (minus) the vorticity.
Next, sinusoidal fluctuations are considered:
with the complex-valued amplitude of the streamfunction oscillations, while is the imaginary unit () and denotes the real part of the expression between the brackets. Using this in the vorticity transport equation, Rayleigh's equation is obtained.
The boundary conditions for flat impermeable walls follow from the fact that the streamfunction is a constant at them. So at impermeable walls the streamfunction oscillations are zero, i.e. For unbounded flows the common boundary conditions are that | 1 | Applied and Interdisciplinary Chemistry |
Two types of sulfate-induced hot corrosion are generally distinguished: Type I takes place above the melting point of sodium sulfate, whereas Type II occurs below the melting point of sodium sulfate but in the presence of small amounts of SO.
In Type I, the protective oxide scale is dissolved by the molten salt. Sulfur is released from the salt and diffuses into the metal substrate, forming grey- or blue-colored aluminum or chromium sulfides. With the aluminum or chromium sequestered, after the salt layer has been removed, the steel cannot rebuild a new protective oxide layer. Alkali sulfates are formed from sulfur trioxide and sodium-containing compounds. As the formation of vanadates is preferred, sulfates are formed only if the amount of alkali metals is higher than the corresponding amount of vanadium.
The same kind of attack has been observed for potassium sulfate and magnesium sulfate. | 1 | Applied and Interdisciplinary Chemistry |
*Bisulfite sequencing
*DNA sequencing
*Expression cloning
*Fluorescence in situ hybridization
*Lab-on-a-chip
*Comparison of nucleic acid simulation software
*Northern blot
*Nuclear run-on assay
*Radioactivity in the life sciences
*Southern blot
*Differential centrifugation (sucrose gradient)
*Toeprinting assay
*Several bioinformatics methods, as seen in list of RNA structure prediction software | 1 | Applied and Interdisciplinary Chemistry |
Different assembly tools have been developed to handle jumping library data. One example is DELLY. DELLY was developed to discover genomic structural variants and "integrates short insert paired-ends, long-range mate-pairs and split-read alignments" to detect rearrangements at sequence level.
An example of joint development of new experimental design and algorithm development is demonstrated by the ALLPATHS-LG assembler. | 1 | Applied and Interdisciplinary Chemistry |
The purpose of studying the proteome is to better understand the activity of cells at the single cells level. Since proteins are responsible for determining how the cell acts, understanding the proteome of single cell gives the best understanding of how a cell operates, and how gene expression changes in a cell due to different environmental stimuli. Although transcriptomics has the same purpose as proteomics it is not as accurate at determining gene expression in cells as it does not take into account post-transcriptional regulation. Transcriptomics is still important as studying the difference between RNA levels and protein levels could give insight on which genes are post-transcriptionally regulated. | 1 | Applied and Interdisciplinary Chemistry |
Perfluorohexane (), or tetradecafluorohexane, is a fluorocarbon. It is a derivative of hexane in which all the hydrogen atoms are replaced by fluorine atoms. It is used in one formulation of the electronic cooling liquid/insulator Fluorinert for low-temperature applications due to its low boiling point of 56 °C and freezing point of −90 °C. It is odorless and colorless. Unlike typical hydrocarbons, the structure features a helical carbon backbone. | 1 | Applied and Interdisciplinary Chemistry |
In partnership with Sunfire, Audi produces E-diesel in small scale with two steps, the second one being FT. | 0 | Theoretical and Fundamental Chemistry |
Bene Meat Technologies a.s. was founded in 2020 by Mgr. Roman Kříž, who is the project leader. The main biologist of the scientific team is Jiří Janoušek and one of the external scientists involved in the ongoing research is the immunologist Prof. RNDr. Jan Černý, Ph.D. In 2022, the BMT research team consisted of 70 scientists | 1 | Applied and Interdisciplinary Chemistry |
Cooperativity is not only a phenomenon of ligand binding, but also applies anytime energetic interactions make it easier or more difficult for something to happen involving multiple units as opposed to with single units. (That is, easier or more difficult compared with what is expected when only accounting for the addition of multiple units). For example, unwinding of DNA involves cooperativity: Portions of DNA must unwind in order for DNA to carry out replication, transcription and recombination. Positive cooperativity among adjacent DNA nucleotides makes it easier to unwind a whole group of adjacent nucleotides than it is to unwind the same number of nucleotides spread out along the DNA chain. The cooperative unit size is the number of adjacent bases that tend to unwind as a single unit due to the effects of positive cooperativity. This phenomenon applies to other types of chain molecules as well, such as the folding and unfolding of proteins and in the "melting" of phospholipid chains that make up the membranes of cells. Subunit cooperativity is measured on the relative scale known as Hill's Constant. | 1 | Applied and Interdisciplinary Chemistry |
In Chemistry, a kryptoracemic compound or kryptoracemate (sometimes false conglomerate) is a racemic compound crystallizing in a Sohncke space group.
In most of the cases, racemic compounds crystallize in centrosymmetric crystal structures. In a kryptoracemic compound the chemical composition of the crystal is racemic although the crystal belongs to space groups in which all enantiomerically pure molecules have to crystallize.
Crystallographically, in kryptoracemic compounds, the number of independent molecules in the asymmetric unit (Z′) is necessarily greater than 1 and should take an even value (to respect the racemic composition). By extension, the scalemic compounds (or unbalanced compounds), i.e. crystal with non-stoichiometric ratio of enantiomer, crystallizing in Sohncke space group are sometimes included in kryptoracemic compounds although they are not strito-sensu kryptoracemic. | 0 | Theoretical and Fundamental Chemistry |
Because channels underlie the nerve impulse and because "transmitter-activated" channels mediate conduction across the synapses, channels are especially prominent components of the nervous system. Indeed, numerous toxins that organisms have evolved for shutting down the nervous systems of predators and prey (e.g., the venoms produced by spiders, scorpions, snakes, fish, bees, sea snails, and others) work by modulating ion channel conductance and/or kinetics. In addition, ion channels are key components in a wide variety of biological processes that involve rapid changes in cells, such as cardiac, skeletal, and smooth muscle contraction, epithelial transport of nutrients and ions, T-cell activation, and pancreatic beta-cell insulin release. In the search for new drugs, ion channels are a frequent target. | 1 | Applied and Interdisciplinary Chemistry |
The rule can be used to understand the stability of completely conjugated monocyclic hydrocarbons (known as annulenes) as well as their cations and anions.
The best-known example is benzene (CH) with a conjugated system of six π electrons, which equals 4n + 2 for n = 1. The molecule undergoes substitution reactions which preserve the six π electron system rather than addition reactions which would destroy it. The stability of this π electron system is referred to as aromaticity. Still, in most cases, catalysts are necessary for substitution reactions to occur.
The cyclopentadienyl anion () with six π electrons is planar and readily generated from the unusually acidic cyclopentadiene (pK 16), while the corresponding cation with four π electrons is destabilized, being harder to generate than a typical acyclic pentadienyl cations and is thought to be antiaromatic. Similarly, the tropylium cation (), also with six π electrons, is so stable compared to a typical carbocation that its salts can be crystallized from ethanol. On the other hand, in contrast to cyclopentadiene, cycloheptatriene is not particularly acidic (pK 37) and the anion is considered nonaromatic. The cyclopropenyl cation () and the triboracyclopropenyl dianion () are considered examples of a two π electron system, which are stabilized relative to the open system, despite the angle strain imposed by the 60° bond angles.
Planar ring molecules with 4n π electrons do not obey Hückels rule, and theory predicts that they are less stable and have triplet ground states with two unpaired electrons. In practice such molecules distort from planar regular polygons. Cyclobutadiene (CH) with four π electrons is stable only at temperatures below 35 K and is rectangular rather than square. Cyclooctatetraene (CH) with eight π electrons has a nonplanar "tub" structure. However the dianion (cyclooctatetraenide anion), with ten π electrons obeys the 4n + 2 rule for n = 2 and is planar, while the 1,4-dimethyl derivative of the dication, with six π electrons, is also believed to be planar and aromatic. The Cyclononatetraenide anion () is the largest all-cis monocyclic annulene/annulenyl system that is planar and aromatic. These bond angles (140°) differ significantly from the ideal angles of 120°. Larger rings possess trans bonds to avoid the increased angle strain. However, 10 to 14-membered systems all experience considerable transannular strain. Thus, these systems are either nonaromatic or experience modest aromaticity. This changes when we get to [[Cyclooctadecanonaene|[18]annulene]], with (4×4) + 2 = 18 π electrons, which is large enough to accommodate six interior hydrogen atoms in a planar configuration (3 cis double bonds and 6 trans' double bonds). Thermodynamic stabilization, NMR chemical shifts, and nearly equal bond lengths all point to considerable aromaticity for [18]annulene.
The (4n+2) rule is a consequence of the degeneracy of the π orbitals in cyclic conjugated hydrocarbon molecules. As predicted by Hückel molecular orbital theory, the lowest π orbital in such molecules is non-degenerate and the higher orbitals form degenerate pairs. For benzene the lowest π orbital is non-degenerate and can hold 2 electrons, and the next 2 π orbitals form a degenerate pair which can hold 4 electrons. The 6 π electrons in benzene therefore form a stable closed shell in a regular hexagonal molecule.
However for cyclobutadiene or cyclooctatrene with regular geometries, the highest molecular orbital pair is occupied by only 2 π electrons forming a less stable open shell. The molecules therefore stabilize by geometrical distortions which separate the degenerate orbital energies so that the last two electrons occupy the same orbital, but the molecule as a whole is less stable in the presence of such a distortion. | 0 | Theoretical and Fundamental Chemistry |
The term “Brownian motor” was originally invented by Swiss theoretical physicist Peter Hänggi in 1995. The Brownian motor, like the phenomenon of Brownian motion that underpinned its underlying theory, was also named after 19th century Scottish botanist Robert Brown, who, while looking through a microscope at pollen of the plant Clarkia pulchella immersed in water, famously described the random motion of pollen particles in water in 1827. In 1905, almost eighty years later, theoretical physicist Albert Einstein published a paper where he modeled the motion of the pollen as being moved by individual water molecules, and this was verified experimentally by Jean Perrin in 1908, who was awarded the Nobel Prize in Physics in 1926 "for his work on the discontinuous structure of matter". These developments helped to create the fundamentals of the present theories of the nanoscale world.
Nanoscience has traditionally long remained at the intersection of the physical sciences of physics and chemistry, but more recent developments in research increasingly position it beyond the scope of either of these two traditional fields. | 0 | Theoretical and Fundamental Chemistry |
When phosphorylated by an unknown kinase, PRR5 and PRR3 proteins demonstrate increased binding to TIMING OF CAB2 EXPRESSION 1 ( TOC1). This interaction stabilizes both TOC1 and PRR5 and prevents their degradation by the F-box protein ZEITLUPE (ZTL). Through this mechanism, PRR5 is indirectly activated by light, as ZTL is inhibited by light. Additionally, PRR5 contributes to the transcriptional repression of the genes encoding the single MYB transcription factors CCA1 and LHY. | 1 | Applied and Interdisciplinary Chemistry |
Paiis can be used as quality control and marketing tools in commerce and as a quick and easy way to assess and/or map the activities of new photocatalytic materials in research. In addition, it has also been demonstrated that such inks can be used on highly coloured and black surfaces, provided the oxidised and/or reduced form of the redox dye is luminescent, and that they can be effectively used to demonstrate the activity of visible light photocatalysts. In light of the need for in situ testing of commercial photocatalyst materials, paii labels have been developed that can be applied simply in the field on any surface to be tested, in both a non-reusable and reusable form. One noteworthy application of paiis is where a uniform film has been applied to a photocatalytic surface, and the variation in the rate of colour change across the surface has been monitored and used to generate a surface map of the photoactivity. By this method the uniformity of the surface activity may be investigated, and any "hotspots" of photoactivity identified. By varying the composition of a semiconductor photocatalyst surface across the surface itself, a paii photoactivity surface map may be used to determine the optimal composition which yields the greatest photocatalytic response.
The rapid colour change of paiis makes them suitable for such applications as:
* Quality control (in laboratory, factory and on site);
* Marketing;
* Counterfeit identification;
* Research material assessment. | 0 | Theoretical and Fundamental Chemistry |
The term "push-pull" was established in 1987 as an approach for integrated pest management (IPM). This strategy uses a mixture of behavior-modifying stimuli to manipulate the distribution and abundance of insects. "Push" means the insects are repelled or deterred away from whatever resource is being protected. "Pull" means that certain stimuli (semiochemical stimuli, pheromones, food additives, visual stimuli, genetically altered plants, etc.) are used to attract pests to trap crops where they will be killed. There are numerous different components involved in order to implement a Push-Pull Strategy in IPM.
Many case studies testing the effectiveness of the push-pull approach have been done across the world. The most successful push-pull strategy was developed in Africa for subsistence farming. Another successful case study was performed on the control of Helicoverpa in cotton crops in Australia. In Europe, the Middle East, and the United States, push-pull strategies were successfully used in the controlling of Sitona lineatus in bean fields.
Some advantages of using the push-pull method are less use of chemical or biological materials and better protection against insect habituation to this control method. Some disadvantages of the push-pull strategy are that if there is a lack of appropriate knowledge of the behavioral and chemical ecology of the host-pest interactions then this method becomes unreliable. Furthermore, because the push-pull method is not a very popular method of IPM operational and registration costs are higher. | 1 | Applied and Interdisciplinary Chemistry |
In the theory of magnetohydrodynamics, the magnetic Reynolds number can be derived from the induction equation:
where
* is the magnetic field,
* is the fluid velocity,
* is the magnetic diffusivity.
The first term on the right hand side accounts for effects from magnetic induction in the plasma and the second term accounts for effects from magnetic diffusion. The relative importance of these two terms can be found by taking their ratio, the magnetic Reynolds number . If it is assumed that both terms share the scale length such that and the scale velocity such that , the induction term can be written as
and the diffusion term as
The ratio of the two terms is therefore | 1 | Applied and Interdisciplinary Chemistry |
Although some host-guest interactions are not strong, increasing the amount of the host-guest interaction can improve the mechanical properties of the materials. As an example, threading the host molecules onto the polymer is one of the commonly used strategies for increasing the mechanical properties of the polymer. It takes time for the host molecules to de-thread from the polymer, which can be a way of energy dissipation. Another method is to use the slow exchange host-guest interaction. Though the slow exchange improves the mechanical properties, simultaneously, self-healing properties will be sacrificed. | 0 | Theoretical and Fundamental Chemistry |
Corrosion Science is a peer-reviewed scientific journal published by Elsevier in 16 issues per year. Established in 1961, it covers a wide range of topics in the study of pure/applied corrosion and corrosion engineering, including but not limited to oxidation, biochemical corrosion, stress corrosion cracking, and corrosion control methods, as well as surface science and engineering. The editors-in-chief are J.M.C. Mol (Delft University of Technology) and O.R. Mattos (Federal University of Rio de Janeiro). | 1 | Applied and Interdisciplinary Chemistry |
The source for APCI is similar to ESI except that ions are formed by the interaction of the heated analyte solvent with a corona discharge needle set at a high electrical potential. Primary ions are formed immediately surrounding the needle, and these interact with the solvent to form secondary ions that ultimately ionize the sample. APCI is particularly useful for the analysis of nonpolar lipids such as triacylglycerols, sterols, and fatty acid esters. | 1 | Applied and Interdisciplinary Chemistry |
Both short- and long-acting β-agonists are used to treat chronic obstructive pulmonary disease. COPD causes airflow limitations in the lungs because of inflammation. Smoking is the main risk factor but inhalation of toxic and harmful particles and gases can also cause the disease. The symptoms are abnormal mucus production, inflation in the lungs that causes airflow limitation, abnormal gas exchange and pulmonary hypertension. COPD is most common in people over fifty who have a long history of smoking. The symptoms are at first mild but worsen over time. | 1 | Applied and Interdisciplinary Chemistry |
Acid flux types (not used in electronics) may contain hydrochloric acid, zinc chloride or ammonium chloride, which are harmful to humans. Therefore, flux should be handled with gloves and goggles, and used with adequate ventilation.
Prolonged exposure to rosin fumes released during soldering can cause occupational asthma (formerly called colophony disease in this context) in sensitive individuals, although it is not known which component of the fumes causes the problem.
While molten solder has low tendency to adhere to organic materials, molten fluxes, especially of the resin/rosin type, adhere well to fingers. A mass of hot sticky flux can transfer more heat to skin and cause more serious burns than a comparable particle of non-adhering molten metal, which can be quickly shaken off. In this regard, molten flux is similar to molten hot glue. | 1 | Applied and Interdisciplinary Chemistry |
Scientific studies have been carried out at the River Dee in Wales in the United Kingdom, the Garonne and Sélune in France, the Daly River in Australia, and the Qiantang River estuary in China. The force of the tidal bore flow often poses a challenge to scientific measurements, as evidenced by a number of field work incidents in the River Dee, Rio Mearim, Daly River, and Sélune River. | 1 | Applied and Interdisciplinary Chemistry |
An important parameter in wet scrubbing systems is the rate of liquid flow. It is common in wet scrubber terminology to express the liquid flow as a function of the gas flow rate that is being treated. This is commonly called the liquid-to-gas ratio (L/G ratio) and uses the units of gallons per 1,000 actual cubic feet or litres per cubic metre (L/m).
Expressing the amount of liquid used as a ratio enables systems of different sizes to be readily compared.
For particulate removal, the liquid-to-gas ratio is a function of the mechanical design of the system; while for gas absorption this ratio gives an indication of the difficulty of removing a pollutant. Most wet scrubbers used for particulate control operate with liquid-to-gas ratios in the range of 4 to 20 gallons per 1,000 actual cubic foot (0.5 to 3 litres per actual cubic metre).
Depending on scrubber design, a minimum volume of liquid is required to "wet" the scrubber internals and create sufficient collection targets. After a certain optimum point, adding excess liquid to a particulate wet scrubber does not increase efficiency and in fact, could be counter-productive by causing excessive pressure loss. Liquid-to-gas ratios for gas absorption are often higher, in the range of 20 to 40 gallons per 1,000 actual cubic foot (3 to 6 litres per actual cubic metre).
L/G ratio illustrates a number of points about the choice of wet scrubbers used for gas absorption. For example, because flue-gas desulfurization systems must deal with heavy particulate loadings, open, simple designs (such as venturi, spray chamber and moving bed) are used.
Also, the liquid-to-gas ratio for the absorption process is higher than for particle removal and gas velocities are kept low to enhance the absorption process.
Solubility is a very important factor affecting the amount of a pollutant that can be absorbed. Solubility governs the amount of liquid required (liquid-to-gas ratio) and the necessary contact time. More soluble gases require less liquid. Also, more soluble gases will be absorbed faster. | 0 | Theoretical and Fundamental Chemistry |
The mechanism of its actions is thought to be related to the selective inhibition of viral RNA-dependent RNA polymerase. Favipiravir is a prodrug that is metabolized to its active form, favipiravir-ribofuranosyl-5'-triphosphate (favipiravir-RTP), available in both oral and intravenous formulations. In 2014, favipiravir was approved in Japan for stockpiling against influenza pandemics. However, favipiravir has not been shown to be effective in primary human airway cells, casting doubt on its efficacy in influenza treatment.
Favipiravir-RTP is a nucleoside analogue. It mimics both guanosine and adenosine for the viral RdRP. Incorporating two such bases in a row stops primer extension, although it is unclear how as of 2013. | 0 | Theoretical and Fundamental Chemistry |
Several technologies are related to soil vapor extraction. As noted above, various soil-heating remediation technologies (e.g., electrical resistive heating, in situ vitrification) require a soil gas collection component, which may take the form of SVE and/or a surface barrier (i.e., hood). Bioventing is a related technology, the goal of which is to introduce additional oxygen (or possibly other reactive gases) into the subsurface to stimulate biological degradation of the contamination. In situ air sparging is a remediation technology for treating contamination in groundwater. Air is injected and "sparged" through the groundwater and then collected via soil vapor extraction wells. | 1 | Applied and Interdisciplinary Chemistry |
One way that enzymatic catalysis proceeds is by stabilizing the transition state through electrostatics. By lowering the energy of the transition state, it allows a greater population of the starting material to attain the energy needed to overcome the transition energy and proceed to product. | 0 | Theoretical and Fundamental Chemistry |
Abnormally high or low levels of dietary selenium can have an adverse effect on sperm quality, with a consequent lowering of fertility. | 1 | Applied and Interdisciplinary Chemistry |
Benzylpenicillin is produced by fermentation of Penicillium chrysogenum. The production of benzylpenicillin involves fermentation, recovery and purification of the penicillin.
The fermentation process of the production of benzylpenicillin creates the product. The presence of the product in solution inhibits the reaction and reduces the product rate and yield. Thus, in order to obtain the most product and increase the rate of reaction, it is continuously extracted. This is done by mixing the mold with either glucose, sucrose, lactose, starch, or dextrin, nitrate, ammonium salt, corn steep liquor, peptone, meat or yeast extract, and small amounts of inorganic salts.
The recovery of the benzylpenicillin is the most important part of the production process because it affects the later purification steps if done incorrectly. There are several techniques used to recover benzylpenicillin: aqueous two-phase extraction, liquid membrane extraction, microfiltration, and solvent extraction. Extraction is more commonly used in the recovery process.
In the purification step, the benzylpenicillin is separated from the extraction solution. This is normally done by using a separation column. | 0 | Theoretical and Fundamental Chemistry |
Albert Ernest Alexander was born on 5 January 1914 in Ringwood, Hampshire, the sixth of seven children of William Albert Alexander, a master builder, and Beatrice (née Daw), formerly a teacher. He attended Brockenhurst County School, from where he gained a place in 1931 at the University of Reading. He graduated in 1934 with First Class Honours in Chemistry and an Open Scholarship to King's College, Cambridge. He was awarded a First Class in the Tripos Examination.
With the benefit of a King's College Senior Scholarship, a DSIR grant for research, and a Ramsay Memorial Fellowship, Alexander joined the Department of Colloid Science to work under Professor E K Rideal (later Sir Eric Keightley Rideal, MBE, FRS). He began with work on the orientation in films of long-chain esters and continued by examining porphyrins, chlorophylls and other molecules, with and without metals.
Alexander was awarded his PhD in 1938, and then went hitch-hiking in Scandinavia with his friend from Cambridge F S Dainton. During their holiday they visited Theodor Svedberg's laboratory in Uppsala in August 1938, after which Alexander decided he would like to spend as much time as he could working with Torsten Teorell in Uppsala. He started at the Institute of Medical Chemistry in December 1938, but had to return to England at the outbreak of war in September 1939. His work in that nine-month period was published that year.
He returned to Cambridge, where he was elected a Fellow of King's College. In the Department of Colloid Science work continued on a wide range of topics including the role of hydrogen bonding in condensed monomolecular films and the effects of soaps and synthetic wetting agents on the biological activities of phenols. Fourteen publications appeared in the war years.
In 1944 Alexander became one of two Assistant Directors of Research in the Colloid Science Department; Gordon Sutherland was the other. On 6 February 1947 he delivered the Tilden Lecture in recognition of the prize he had been awarded by the Chemical Society of London.
In October 1947 the Société de Chimie Physique and the Faraday Society held a joint discussion meeting at Bordeaux on Surface Chemistry, at which Alexander and colleagues gave five papers. In 1949 Alexander and Johnson published Colloid Science which an anonymous reviewer praised as a broad, modern, and authoritative treatment of the subject of colloid physics and chemistry from the fundamental rather than from the phenomenological viewpoint.
In Australia, the government of New South Wales created an Institute of Technology as part of its plan to expand its technical education system at the tertiary level. They advertised for applications for a Chair in Applied Chemistry, to which Alexander was appointed. On 1 October 1949 he and his family sailed from London to Sydney on the RMS Maloja. They lived at 178 Raglan Street, Mosman, a suburb of Sydney, and only a short drive from the Sydney Technical College. During Alexander's seven years there he authored or co-authored some 40 papers. Many involved systems of practical importance, such as efforts to reduce evaporation from dams, and the cattle tick problem in NSW.
But, disillusioned with the lack of progress with the status of the Technical College to an autonomous university, Alexander moved to the University of Sydney in 1956. Work was quickly restarted on topics that may be catalogued under four headings: (a) monolayer studies, (b) micellar solutions, (c) the roles of surfactants in heterogeneous polymerisations, and (d) the effects of polyelectrolytes on the crystallisations of sparingly soluble salts. Fifty or more papers appeared from Alexander and his group. Their work is described in detail in Le Fèvre’s memoir. | 0 | Theoretical and Fundamental Chemistry |
Claude Schwob (1910–2000) was an American nuclear chemist who worked on the Manhattan Project. After the end of World War II, he was employed at the Naval Radiological Defense Laboratory. Schwob, who was gay, was open about his sexuality throughout his life. | 0 | Theoretical and Fundamental Chemistry |
Significant developments in belt press filter technology include: cloth developments, using three belts and, the V-fold belt. Cloth developments include the double weave which incorporates different yarn types to combine the specific advantages of each. A double weave woven wire belt is also available which has a better life span and durability than a conventional wire belt.
A belt press filter using three belts can achieve independent speeds and have different belt types for the pressure and gravity zones. This allows the filter system to accommodate higher hydraulic loadings occurring with dilute feed sludge (feed solid concentration below 1.5%). The three belt system is more efficient with both a higher production rate and cake solid concentration at the expense of mechanical complexity.
The V-fold belt is similar to the belt filter press with the main difference being that only a single belt, folded along the centreline is used. The technology has not been widely proven. A final dry weight solids content of 9-13% can usually be achieved; this is smaller than competing technologies. Currently this technology is suited to small-scale applications (up to approximately 3000 L of slurry per hour as the maximum belt size is 0.75 m). V-fold belts have a small footprint, low energy and wash water consumption and low capital and operating costs. They are self-tracking and can process sludge of varying composition, reducing operator involvement. | 1 | Applied and Interdisciplinary Chemistry |
Turkevich was born on July 23, 1916, in Manhattan, New York, at the bishops house attached to Saint Nicholas Russian Orthodox Cathedral. His father, Leonid Turkevich, was dean at the time, and later became the Metropolitan of the Orthodox Church in North America. He had two brothers. Turkevich studied at Dartmouth College and obtained his bachelors degree in chemistry in 1937. He completed his Ph.D. at Princeton University on the structure of small molecules in 1940. | 0 | Theoretical and Fundamental Chemistry |
* Nano- and bio-organic materials: production, synthesis, structure and properties, diagnostic methods using X-ray and synchrotron radiation, electrons, neutrons and atomic force microscopy
* Fundamental aspects of the formation of crystalline materials and nanosystems, their real structure and properties
* Creation and study of new crystalline and functional materials | 0 | Theoretical and Fundamental Chemistry |
The baculovirus-insect cell expression system has the ability to express a variety of recombinant proteins at high levels and provide significant eukaryotic protein processing capabilities, including phosphorylation, glycosylation, myristoylation and palmitoylation. Similar to mammalian cells, proteins expressed are mostly soluble, accurately folded, and biologically active. However, it has slower growth rate and requires higher cost of growth medium than bacteria and yeast, and confers toxicological risks. A notable feature is the existence of elements of control that allow for the expression of secreted and membrane-bound proteins in Baculovirus-insect cells.
Licensed recombinant subunit vaccines that utilises baculovirus-insect cells include Cervarix (papillomavirus C-terminal truncated major capsid protein L1 types 16 and 18) and Flublok Quadrivalent (hemagglutinin (HA) proteins from four strains of influenza viruses). | 1 | Applied and Interdisciplinary Chemistry |
*Albert Hewett Coons (1912-1978), physician, pathologist and immunologist.
*Cornelia Mitchell Downs (1892–1987), microbiologist and journalist | 1 | Applied and Interdisciplinary Chemistry |
Inversion recovery is an MRI sequence that provides high contrast between tissue and lesion. It can be used to provide high T1 weighted image, high T2 weighted image, and to suppress the signals from fat, blood, or cerebrospinal fluid (CSF). | 0 | Theoretical and Fundamental Chemistry |
The Deborah number is particularly useful in conceptualizing the time–temperature superposition principle. Time-temperature superposition has to do with altering experimental time scales using reference temperatures to extrapolate temperature-dependent mechanical properties of polymers. A material at low temperature with a long experimental or relaxation time behaves like the same material at high temperature and short experimental or relaxation time if the Deborah number remains the same. This can be particularly useful when working with materials which relax on a long time scale under a certain temperature. The practical application of this idea arises in the Williams–Landel–Ferry equation. Time-temperature superposition avoids the inefficiency of measuring a polymer's behavior over long periods of time at a specified temperature by utilizing the Deborah number. | 1 | Applied and Interdisciplinary Chemistry |
Temperature usually has a major effect on the rate of a chemical reaction. Molecules at a higher temperature have more thermal energy. Although collision frequency is greater at higher temperatures, this alone contributes only a very small proportion to the increase in rate of reaction. Much more important is the fact that the proportion of reactant molecules with sufficient energy to react (energy greater than activation energy: E > E) is significantly higher and is explained in detail by the Maxwell–Boltzmann distribution of molecular energies.
The effect of temperature on the reaction rate constant usually obeys the Arrhenius equation , where A is the pre-exponential factor or A-factor, E is the activation energy, R is the molar gas constant and T is the absolute temperature.
At a given temperature, the chemical rate of a reaction depends on the value of the A-factor, the magnitude of the activation energy, and the concentrations of the reactants. Usually, rapid reactions require relatively small activation energies.
The rule of thumb that the rate of chemical reactions doubles for every 10 °C temperature rise is a common misconception. This may have been generalized from the special case of biological systems, where the α (temperature coefficient) is often between 1.5 and 2.5.
The kinetics of rapid reactions can be studied with the temperature jump method. This involves using a sharp rise in temperature and observing the relaxation time of the return to equilibrium. A particularly useful form of temperature jump apparatus is a shock tube, which can rapidly increase a gas's temperature by more than 1000 degrees. | 0 | Theoretical and Fundamental Chemistry |
Albert Rakoto Ratsimamanga was born on 28 December 1907, in Antananarivo, Madagascar, to Razanadrakoto Ratsimamanga and Lala Ralisoa. He was the grandson of Prince Ratsimamanga, uncle and advisor to Queen Ranavalona III, who was executed in 1897 at the beginning of the French colonisation of Madagascar. When Albert was only eleven years old, his father died in 1918 from heavy drinking.
He received his early education at the Faculty of Medicine, University of Antananarivo, until he became a doctor of Indigenous Medicine in 1924. Ratsimamanga was a member of the Malagasy delegation to the 1930 Colonial Exhibition in Paris, during which he decided to join the University of Paris to become a Doctor of Science (MS) and a Doctor of Medicine (MD). He also graduated from the Institute of Exotic Medicine and the Pasteur Institut, and founded the association of Malagasy Students in France. | 1 | Applied and Interdisciplinary Chemistry |
In 1849, the French chemists Jean-François Persoz and Bloch, and the German chemist Peter Kremers (1827-?), independently first synthesized thionyl chloride by reacting phosphorus pentachloride with sulfur dioxide. However, their products were impure: both Persoz and Kremers claimed that thionyl chloride contained phosphorus, and Kremers recorded its boiling point as 100 °C (instead of 74.6 °C). In 1857, the German-Italian chemist Hugo Schiff subjected crude thionyl chloride to repeated fractional distillations and obtained a liquid which boiled at 82 °C and which he called Thionylchlorid. In 1859, the German chemist Georg Ludwig Carius noted that thionyl chloride could be used to make acid anhydrides and acyl chlorides from carboxylic acids and to make alkyl chlorides from alcohols. | 0 | Theoretical and Fundamental Chemistry |
The structural components of plants are formed primarily from cellulose. Wood is largely cellulose and lignin, while paper and cotton are nearly pure cellulose. Cellulose is a polymer made with repeated glucose units bonded together by beta-linkages. Humans and many animals lack an enzyme to break the beta-linkages, so they do not digest cellulose. Certain animals, such as termites can digest cellulose, because bacteria possessing the enzyme are present in their gut. Cellulose is insoluble in water. It does not change color when mixed with iodine. On hydrolysis, it yields glucose. It is the most abundant carbohydrate in nature. | 0 | Theoretical and Fundamental Chemistry |
tRNA (also tRNA-like) splicing is another rare form of splicing that usually occurs in tRNA. The splicing reaction involves a different biochemistry than the spliceosomal and self-splicing pathways.
In the yeast Saccharomyces cerevisiae, a yeast tRNA splicing endonuclease heterotetramer, composed of TSEN54, TSEN2, TSEN34, and TSEN15, cleaves pre-tRNA at two sites in the acceptor loop to form a 5-half tRNA, terminating at a 2,3-cyclic phosphodiester group, and a 3-half tRNA, terminating at a 5-hydroxyl group, along with a discarded intron. Yeast tRNA kinase then phosphorylates the 5-hydroxyl group using adenosine triphosphate. Yeast tRNA cyclic phosphodiesterase cleaves the cyclic phosphodiester group to form a 2-phosphorylated 3 end. Yeast tRNA ligase adds an adenosine monophosphate group to the 5 end of the 3-half and joins the two halves together. NAD-dependent 2-phosphotransferase then removes the 2-phosphate group. | 1 | Applied and Interdisciplinary Chemistry |
Damages can occur during the casting and de-shuttering processes. For instance, the corners of beams can be damaged during the removal of shuttering because they are less effectively compacted by means of vibration (improved by using form-vibrators). Other physical damages can be caused by the use of steel shuttering without base plates. The steel shuttering pinches the top surface of a concrete slab due to the weight of the next slab being constructed.
Concrete slabs, block walls and pipelines are susceptible to cracking during ground settlement, seismic tremors or other sources of vibration, and also from expansion and contraction during adverse temperature changes. | 1 | Applied and Interdisciplinary Chemistry |
Anti-Ro and anti-La antibodies, also known as SS-A and SS-B, respectively, are commonly found in primary Sjögrens syndrome, an autoimmune disorder that affects the exocrine glands. The presence of both antibodies is found in 30–60% of Sjögrens syndrome, anti-Ro antibodies alone are found in 50–70% of Sjögrens syndrome and 30% of SLE with cutaneous involvement, and anti-La antibodies are rarely found in isolation. Anti-La antibodies are also found in SLE; however, Sjögrens syndrome is normally also present. Anti-Ro antibodies are also found less frequently in other disorders including autoimmune liver diseases, coeliac disease, autoimmune rheumatic diseases, cardiac neonatal lupus erythematosus and polymyositis. During pregnancy, anti-Ro antibodies can cross the placenta and cause heart block and neonatal lupus in babies. In Sjögren's syndrome, anti-Ro and anti-La antibodies correlate with early onset, increased disease duration, parotid gland enlargement, disease outside the glands and infiltration of glands by lymphocytes. Anti-Ro antibodies are specific to components of the Ro-RNP complex, comprising 45kDa, 52kDa, 54kDa and 60kDa proteins and RNA. The 60kDa DNA/RNA binding protein and 52kDa T-cell regulatory protein are the best characterised antigens of anti-Ro antibodies. Collectively, these proteins are part of a ribonucleoprotein (RNP) complex that associate with the human Y RNAs, hY1-hY5. The La antigen is a 48kDa transcription termination factor of RNA polymerase III, which associates with the Ro-RNP complex.
The mechanism of antibody production in Sjögrens syndrome is not fully understood, but apoptosis (programmed cell death) and molecular mimicry may play a role. The Ro and La antigens are expressed on the surface of cells undergoing apoptosis and may cause the inflammation within the salivary gland by interaction with cells of the immune system. The antibodies may also be produced through molecular mimicry, where cross reactive antibodies bind to both virus and human proteins. This may occur with one of the antigens, Ro or La, and may subsequently produce antibodies to other proteins through a process known as epitope spreading. The retroviral gag protein shows similarity to the La protein and is proposed as a possible example for molecular mimicry in Sjögrens syndrome. | 1 | Applied and Interdisciplinary Chemistry |
*Steric effects strain – Increasing the steric strain of the chelate backbone in square planar complexes pushes the carbonyl and methyl groups closer together, increasing the reactivity of insertion reactions.
*Oxidation state – Oxidation of the metal tends to increase insertion reaction rates. The main rate-limiting step in the mechanism is the migration of the methyl group onto a carbonyl ligand, oxidizing the metal by imparting a greater partial positive charge on the acetyl carbon, and thus increasing the rate of reaction.
*Lewis acids – Lewis acids also increase the reaction rates, for reasons similar to metal oxidation increasing the positive charge on the carbon. Lewis acids bind to the CO oxygen and remove charge, increasing the electrophilicity of the carbon. This can increase the reaction rate by a factor of up to 10, and the complex formed is stable enough that the reaction proceeds even without additional CO to bind to the metal.
*Electronegativity of the leaving group - Increasing the electronegativity of the leaving alkyl group stabilizes the metal-carbon bond interaction and thus increases the activation energy required for migration, decreasing the reaction rate.
*Trans-effect – Ligands in an octahedral or square planar complex are known to influence the reactivity of the group to which they are trans. This ligand influence is often referred to as the trans-influence, and it varies in intensity between ligands. A partial list of trans-influencing ligands is as follows, from highest trans-effect to lowest: aryl, alkyl > NR > PR > AsR > CO > Cl. Ligands with a greater trans-influence impart greater electrophilicity to the active site. Increasing the electrophilicity of the CO group has been shown experimentally to greatly increase the reaction rate, while decreasing the electrophilicity of the methyl group slightly increases the reaction rate. This can be demonstrated by reacting a square planar [(PN)M(CO)(CH)] complex with CO, where PN is a bidentate phosphorus- or nitrogen-bound ligand. This reaction proceeds in much greater yield when the methyl group is trans-P and the CO trans-N, owing to the higher trans-influence of the more electronegative nitrogen. | 0 | Theoretical and Fundamental Chemistry |
Cohen worked at a holiday camp in Massachusetts while he was a student at Tufts. While waiting tables, he courted Pearl Silverman, a bookish woman from New York. The biochemist and author, Isaac Asimov, also vacationed there and became friends with Cohen. Observing the romance, Asimov wrote songs about it for the camp show, "Poor Teds in bed. Hes lonely but well read"; the couple were later married and went on to have two children, Bret and Rima.
He died of chronic lymphocytic leukemia. | 0 | Theoretical and Fundamental Chemistry |
* Water is essential for organisms within the soil profile, and it partially fills up the macropores in an ideal soil.
* Leaching of the soil occurs as water carries along with it ions deeper into the lower soil horizons, causing the soil to become more oxidized in other soil horizons.
* Water also will go from a higher water potential to a lower water potential, this can result in capillarity activity and gravitational force occurring with the water due to adhesion of the water to the soil surface and cohesion amongst the water molecules. | 0 | Theoretical and Fundamental Chemistry |
Resiniferatoxin has a score of 16 billion Scoville heat units, making pure resiniferatoxin about 500 to 1000 times hotter than pure capsaicin. Resiniferatoxin activates transient vanilloid receptor 1 (TRPV1) in a subpopulation of primary afferent sensory neurons involved in nociception, the transmission of physiological pain. TRPV1 is an ion channel in the plasma membrane of sensory neurons and stimulation by resiniferatoxin causes this ion channel to become permeable to cations, especially calcium. The influx of cations causes the neuron to depolarize, transmitting signals similar to those that would be transmitted if the innervated tissue were being burned or damaged. This stimulation is followed by desensitization and analgesia, in part because the nerve endings die from calcium overload. | 0 | Theoretical and Fundamental Chemistry |
Several anti-infective medications have been derived from fungi including penicillin and the cephalosporins (antibacterial drugs from Penicillium rubens and Cephalosporium acremonium, respectively) and griseofulvin (an antifungal drug from Penicillium griseofulvum). Other medicinally useful fungal metabolites include lovastatin (from Pleurotus ostreatus), which became a lead for a series of drugs that lower cholesterol levels, cyclosporin (from Tolypocladium inflatum), which is used to suppress the immune response after organ transplant operations, and ergometrine (from Claviceps spp.), which acts as a vasoconstrictor, and is used to prevent bleeding after childbirth. Asperlicin (from Aspergillus alliaceus) is another example. Asperlicin is a novel antagonist of cholecystokinin, a neurotransmitter thought to be involved in panic attacks, and could potentially be used to treat anxiety. | 1 | Applied and Interdisciplinary Chemistry |
Ultrasound attenuation spectroscopy is a method for characterizing properties of fluids and dispersed particles. It is also known as acoustic spectroscopy.
There is an international standard for this method.
Measurement of attenuation coefficient versus ultrasound frequency yields raw data for further calculation of various system properties. Such raw data are often used in the calculation of the particle size distribution in heterogeneous systems such as emulsions and colloids. In the case of acoustic rheometers, the raw data are converted into extensional viscosity or volume viscosity.
Instruments that employ ultrasound attenuation spectroscopy are referred to as Acoustic spectrometers. | 0 | Theoretical and Fundamental Chemistry |
The Society for Cryobiology is an international scientific society that was founded in 1964. Its objectives are to promote research in low temperature biology, to improve scientific understanding in this field, and to disseminate and aid in the application of this knowledge. The Society also publishes a journal called Cryobiology.
The society has hosted 60 annual meetings to date, with the 2024 annual meeting being held in Washington. The three-day event will host over 350 delegates from more than 35 countries. | 1 | Applied and Interdisciplinary Chemistry |
The mnemonics BrINClHOF, pronounced "Brinklehof", HONClBrIF, pronounced "Honkelbrif", “HOBrFINCl”, pronounced “Hoberfinkel”, and HOFBrINCl, pronounced "Hofbrinkle", have been coined to aid recall of the list of diatomic elements. Another method, for English-speakers, is the sentence: "Never Have Fear of Ice Cold Beer" as a representation of Nitrogen, Hydrogen, Fluorine, Oxygen, Iodine, Chlorine, Bromine. | 0 | Theoretical and Fundamental Chemistry |
SMRT (silencing mediator of retinoic acid and thyroid hormone receptor), also known as NCoR2, is an alternatively spliced SRC-1(steroid receptor coactivator-1). It is negatively and positively affected by MAPKKK (mitogen activated protein kinase kinase kinase) and casein kinase 2 phosphorylation, respectively. SMRT has two major mechanisms: first, similar to NCoR, SMRT also recruits class I histone deacetylases through SIN3 and directly binds to class II histone deacetylases. Second, it binds and sequesters components of the general transcriptional machinery, such as transcription factor II B. | 1 | Applied and Interdisciplinary Chemistry |
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