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This system is also used by most bacteria for chromosome segregation.
Type I partition systems are composed of an ATPase which contains Walker motifs and a CBP which is structurally distinct in type Ia and Ib. ATPases and CBP from type Ia are longer than the ones from type Ib, but both CBPs contain an arginine finger in their N-terminal part.
ParA proteins from different plasmids and bacterial species show 25 to 30% of sequence identity to the protein ParA of the plasmid P1.
The partition of type I system uses a "diffusion-ratchet" mechanism. This mechanism works as follows:
# Dimers of ParA-ATP dynamically bind to nucleoid DNA
# ParA in its ATP-bound state interacts with ParB bound to parS
# ParB bound to parS stimulates the release of ParA from the nucleoid region surrounding the plasmid
# The plasmid then chases the resulting ParA gradient on the perimeter of the ParA depleted region of the nucleoid
# The ParA that was released from the nucleoid behind the plasmid's movement redistributes to other regions of the nucleoid after a delay
# After plasmid replication, the sister copies segregate to opposite cell halves as they chase ParA on the nucleoid in opposite directions
There are likely to be differences in the details of type I mechanisms.
Type 1 partition has been mathematically modelled with variations in the mechanism described above. | 1 | Applied and Interdisciplinary Chemistry |
In 1922, de Hevesy co-discovered (with Dirk Coster) the element hafnium (Hf) (Latin Hafnia for "Copenhagen", the home town of Niels Bohr). Mendeleevs 1869 periodic table arranged the chemical elements into a logical system, but a chemical element with 72 protons was missing. Hevesy determined to look for that element on the basis of Bohrs atomic model. The mineralogical museum of Norway and Greenland in Copenhagen furnished the material for the research. Characteristic X-ray spectra recordings made of the sample indicated that a new element was present. The accepted account has been disputed by Mansel Davies and Eric Scerri who attribute the prediction that element 72 would be a transition element to the chemist Charles Bury.
Supported financially by the Rockefeller Foundation, Hevesy had a very productive year. He developed the X-ray fluorescence analytical method, and discovered the samarium alpha-ray. It was here he began the use of radioactive isotopes in studying the metabolic processes of plants and animals, by tracing chemicals in the body by replacing part of stable isotopes with small quantities of the radioactive isotopes. In 1923, Hevesy published the first study on the use of the naturally radioactive Pb as radioactive tracer to follow the absorption and translocation in the roots, stems and leaves of Vicia faba, also known as the broad bean. Later, in 1943, the work on radioactive tracing would earn Hevesy the Nobel Prize in Chemistry.
In 1924, Hevesy returned to Freiburg as Professor of Physical Chemistry. In 1930, he went to Cornell University, Ithaca as Baker Lecturer. In 1934, after the Nazis came to power in Germany, he returned to Niels Bohr's Institute at the University of Copenhagen. In 1936, he invented Neutron Activation Analysis. In 1943 he fled to Stockholm (Sweden being neutral during the war), where he an associate of the Institute of Research in Organic Chemistry. In 1949 he was elected Franqui Professor in the University of Ghent. In his retirement, he remained an active scientific associate of the University of Stockholm. | 1 | Applied and Interdisciplinary Chemistry |
Spontaneous fission (SF) is a form of radioactive decay in which a heavy atomic nucleus splits into two or more lighter nuclei. In contrast to induced fission, there is no inciting particle to trigger the decay; it is a purely probabilistic process.
Spontaneous fission is a dominant decay mode for superheavy elements, with nuclear stability generally falling as nuclear mass increases. It thus forms a practical limit to heavy element nucleon number. Heavier nuclides may be created instantaneously by physical processes, both natural (via the r-process) and artificial, though rapidly decay to more stable nuclides. As such, apart from minor decay branches in primordial radionuclides, spontaneous fission is not observed in nature.
Observed fission half-lives range from 4.1 microseconds () to greater than the current age of the universe (). | 0 | Theoretical and Fundamental Chemistry |
Four companies initially a part of the FutureGen Industrial Alliance have since dropped out of the project. | 1 | Applied and Interdisciplinary Chemistry |
These three metals generally form in a certain type of granite, via a similar mechanism to intrusive-related gold and copper. They are considered together because the process of forming these deposits is essentially the same. Skarn type mineralisation related to these granites is a very important type of tin, tungsten, and molybdenum deposit. Skarn deposits form by reaction of mineralised fluids from the granite reacting with wall rocks such as limestone. Skarn mineralisation is also important in lead, zinc, copper, gold, and occasionally uranium mineralisation.
Greisen granite is another related tin-molybdenum and topaz mineralisation style. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, lubrication theory describes the flow of fluids (liquids or gases) in a geometry in which one dimension is significantly smaller than the others. An example is the flow above air hockey tables, where the thickness of the air layer beneath the puck is much smaller than the dimensions of the puck itself.
Internal flows are those where the fluid is fully bounded. Internal flow lubrication theory has many industrial applications because of its role in the design of fluid bearings. Here a key goal of lubrication theory is to determine the pressure distribution in the fluid volume, and hence the forces on the bearing components. The working fluid in this case is often termed a lubricant.
Free film lubrication theory is concerned with the case in which one of the surfaces containing the fluid is a free surface. In that case, the position of the free surface is itself unknown, and one goal of lubrication theory is then to determine this. Examples include the flow of a viscous fluid over an inclined plane or over topography. Surface tension may be significant, or even dominant. Issues of wetting and dewetting then arise. For very thin films (thickness less than one micrometre), additional intermolecular forces, such as Van der Waals forces or disjoining forces, may become significant. | 1 | Applied and Interdisciplinary Chemistry |
A very popular Russian story credits Mendeleev with setting the 40% standard strength of vodka. For example, Russian Standard vodka advertises: "In 1894, Dmitri Mendeleev, the greatest scientist in all Russia, received the decree to set the Imperial quality standard for Russian vodka and the Russian Standard was born" Others cite "the highest quality of Russian vodka approved by the royal government commission headed by Mendeleev in 1894".
In fact, the 40% standard was already introduced by the Russian government in 1843, when Mendeleev was nine years old. It is true that Mendeleev in 1892 became head of the Archive of Weights and Measures in Saint Petersburg, and evolved it into a government bureau the following year, but that institution was charged with standardising Russian trade weights and measuring instruments, not setting any production quality standards. Also, Mendeleev's 1865 doctoral dissertation was entitled "A Discourse on the combination of alcohol and water", but it only discussed medical-strength alcohol concentrations over 70%, and he never wrote anything about vodka. | 0 | Theoretical and Fundamental Chemistry |
A dead zone exists in the Lower St. Lawrence River area from east the Saguenay River to east of Baie Comeau, greatest at depths over and noticed since the 1930s. The main concern for Canadian scientists is the impact on fish found in the area. | 0 | Theoretical and Fundamental Chemistry |
Diffusion process can also be calculated with Arrhenius equation:
where D is the diffusion coefficient and E is diffusion activation energy.
All three processes strongly depend on surface morphology at a certain time. For example, atoms tend to lend at the edges of a group of connected atoms, the so-called island, rather than on a flat surface, this reduces the total energy. When atoms diffuse and connect to an island, each atom tends to diffuse no further, because activation energy to detach itself out of the island is much higher. Moreover, if an atom landed on top of an island, it would not diffuse fast enough, and the atom would tend to move down the steps and enlarge it. | 0 | Theoretical and Fundamental Chemistry |
He enrolled at Glasgow University in 1785, but did not take a degree; however, he did graduate A.B. from the University of Dublin. | 1 | Applied and Interdisciplinary Chemistry |
Water and zirconium can react violently at 1200 °C, at the same temperature the zircaloy cladding can react with uranium dioxide to form zirconium oxide and a uranium/zirconium alloy melt. | 0 | Theoretical and Fundamental Chemistry |
Polymerase chain reaction itself is the process used to amplify DNA samples, via a temperature-mediated DNA polymerase. The products can be used for sequencing or analysis, and this process is a key part of many genetics research laboratories, along with uses in DNA fingerprinting for forensics and other human genetic cases. Conventional PCR requires primers complementary to the termini of the target DNA. The amount of product from the PCR increases with the number of temperature cycles that the reaction is subjected to. A commonly occurring problem is primers binding to incorrect regions of the DNA, giving unexpected products. This problem becomes more likely with an increased number of cycles of PCR. | 1 | Applied and Interdisciplinary Chemistry |
Because filtration and growth of biomass leads to an accumulation of matter in the filtering media, this type of fixed-film process is subject to bioclogging and flow channeling. Depending on the type of application and on the media used for microbial growth, bioclogging can be controlled using physical and/or chemical methods. Backwash steps can be implemented using air and/or water to disrupt the biomat and recover flow whenever possible. Chemicals such as oxidizing (peroxide, ozone) or biocide agents can also be used.
Biofiltration can require a large area for some treatment techniques (suspended growth and attached growth processes) as well as long hydraulic retention times (anaerobic lagoon and anaerobic baffled reactor). | 1 | Applied and Interdisciplinary Chemistry |
The first and most important of the complementary organizations to link with Fulmer was Yarsley, whose expertise was particularly strong in plastics and polymers and their applications. The Yarsley organization was founded by Dr Victor Yarsley a pioneer expert in plastics and an entrepreneur. Before the Second World War he had been a consultant in this new field and, starting in 1941 he had built a series of laboratories, mostly by converting and extending domestic premises, just as in the case of Fulmer. By 1970 his group consisted of Yarsley Research Laboratories (YRL) at Chessington, Surrey and Yarsley Testing Laboratories (YTL) at Ashtead, Surrey. A collaboration agreement was signed in 1970 and in 1973 Fulmer purchased Yarsley. By early 1974, most of the Chessington activities had been moved to another new building on the Stoke Poges site and the others to Ashtead.
Also in 1973 Fulmer purchased the engineering activities of Aeon Laboratories, Englefield Green, Surrey. Aeon's engineering work focussed on the manufacture of ancillary equipment for electron microscopes and for computers.
In 1975 Fulmer strengthened Yarsleys plastics processing capability by acquiring IPEC (Independent Plastics Engineering Centre) of Newhaven, Sussex. The Newhaven activities were combined with Yarsleys own plastics processing operation to form a new company: Yarsley Polymer Engineering Centre (YPEC).
In 1977 a new site was acquired at Redhill, Surrey to accommodate YPEC and the Yarsley research and testing facilities. This involved progressively transferring all the staff and equipment from Newhaven and Ashtead and the polymer facilities from Stoke Poges. A new company Yarsley Technical Centre Limited (YTEC) was set up to embrace all the activities carried out by YRL, YTL and YPEC.
In 1982 Fulmer established Fulmer Research & Development (Singapore) Pte Ltd, a joint venture with the Singapore-based company Chemical Laboratories Pte Ltd. The joint venture offered metallurgical and polymer-based technical services.
A second overseas company Fulmer Research (SA) Pty Ltd was set up in Johannesburg, South Africa in 1985. This was not successful and was closed after a few years. | 1 | Applied and Interdisciplinary Chemistry |
Survivin has been shown to interact with:
* Aurora B kinase,
* CDCA8,
* Caspase 3,
* Caspase 7,
* Diablo homolog and
* INCENP. | 1 | Applied and Interdisciplinary Chemistry |
An important implication of encapsulation is that the guest behaves differently from the way it would when in solution. The guest molecule tends to be unreactive and often has distinctive spectroscopic signatures. Compounds normally highly unstable in solution, such as arynes or cycloheptatetraene, have been isolated at room temperature when molecularly encapsulated. | 0 | Theoretical and Fundamental Chemistry |
The central theme of hydrology is that water circulates throughout the Earth through different pathways and at different rates. The most vivid image of this is in the evaporation of water from the ocean, which forms clouds. These clouds drift over the land and produce rain. The rainwater flows into lakes, rivers, or aquifers. The water in lakes, rivers, and aquifers then either evaporates back to the atmosphere or eventually flows back to the ocean, completing a cycle. Water changes its state of being several times throughout this cycle.
The areas of research within hydrology concern the movement of water between its various states, or within a given state, or simply quantifying the amounts in these states in a given region. Parts of hydrology concern developing methods for directly measuring these flows or amounts of water, while others concern modeling these processes either for scientific knowledge or for making a prediction in practical applications. | 1 | Applied and Interdisciplinary Chemistry |
The dominant use for sulfuric acid is in the "wet method" for the production of phosphoric acid, used for manufacture of phosphate fertilizers. In this method, phosphate rock is used, and more than 100 million tonnes are processed annually. This raw material is shown below as fluorapatite, though the exact composition may vary. This is treated with 93% sulfuric acid to produce calcium sulfate, hydrogen fluoride (HF) and phosphoric acid. The HF is removed as hydrofluoric acid. The overall process can be represented as:
Ammonium sulfate, an important nitrogen fertilizer, is most commonly produced as a byproduct from coking plants supplying the iron and steel making plants. Reacting the ammonia produced in the thermal decomposition of coal with waste sulfuric acid allows the ammonia to be crystallized out as a salt (often brown because of iron contamination) and sold into the agro-chemicals industry.
Sulfuric acid is also important in the manufacture of dyestuffs solutions. | 0 | Theoretical and Fundamental Chemistry |
Calcineurin is linked to receptors for several brain chemicals including glutamate, dopamine and GABA. An experiment with genetically-altered mice that could not produce calcineurin showed similar symptoms as in humans with schizophrenia: impairment in working memory, attention deficits, aberrant social behavior, and several other abnormalities characteristic of schizophrenia. | 1 | Applied and Interdisciplinary Chemistry |
Paludiculture practices include cultivating Sphagnum and cattail. One of the largest research projects was carried out between 2006 and 2012 by researchers from Université Laval in Quebec, trialling Sphagnum farming in eastern Canada. Their bog site, on the Acadian Peninsula, was previously used for block-cutting peat for fuel and so consisted of ditches of Sphagnum and raised areas of other vegetation. They found that Sphagnum farming could be practiced large-scale in the ditches, although they recommend active irrigation management for more consistent harvests. | 1 | Applied and Interdisciplinary Chemistry |
Electrofusion is a method of joining MDPE, HDPE and other plastic pipes using special fittings that have built-in electric heating elements which are used to weld the joint together.
The pipes to be joined are cleaned, inserted into the electrofusion fitting (with a temporary clamp if required) and a voltage (typically 40V) is applied for a fixed time depending on the fitting in use. The built in heater coils then melt the inside of the fitting and the outside of the pipe wall, which weld together producing a very strong homogeneous joint. The assembly is then left to cool for a specified time.
Electrofusion welding is beneficial because it does not require the operator to use dangerous or sophisticated equipment. After some preparation, the electrofusion welder will guide the operator through the steps to take. Welding heat and time is dependent on the type and size of the fitting. All electrofusion fittings are not created equal – precise positioning of the energising coils of wire in each fitting ensures uniform melting for a strong joint and the minimisation of welding and cooling time.
The operator must be qualified according to the local and national laws. In Australia, an electrofusion course can be done within 8 hours. Electrofusion welding training focuses on the importance of accurately fusing EF fittings. Both manual and automatic methods of calculating electrofusion time gives operators the skills they need in the field. There is much to learn about the importance of preparation, timing, pressure, temperature, cool down time and handling, etc.
Training and certification are very important in this field of welding, as the product can become dangerous under certain circumstances. There has been cases of major harm and death, including when molten polyethylene spurts out of the edge of a mis-aligned weld, causing skin burns. Another case was due to a tapping saddle being incorrectly installed on a gas line, causing the death of the two welders in the trench due to gas inhalation. There are many critical parts to electrofusion welding that can cause weld failures, most of which can be greatly reduced by using welding clamps, and correct scraping equipment.
To keep their qualification current, a trained operator can get their fitting tested, which involves cutting open the fitting and examining the integrity of the weld. | 1 | Applied and Interdisciplinary Chemistry |
Hydrocarbon mixtures are a group of various volatile, highly flammable, mixtures used chiefly as nonpolar solvents. | 0 | Theoretical and Fundamental Chemistry |
Seeds from crosses are sown out and harvested separately for a growing season or two until enough seeds are available. | 1 | Applied and Interdisciplinary Chemistry |
The Langelier saturation index (sometimes Langelier stability index) is a calculated number used to predict the calcium carbonate stability of water. It indicates whether the water will precipitate, dissolve, or be in equilibrium with calcium carbonate. In 1936, Wilfred Langelier developed a method for predicting the pH at which water is saturated in calcium carbonate (called pH). The LSI is expressed as the difference between the actual system pH and the saturation pH:
:LSI = pH (measured) − pH
* For LSI > 0, water is supersaturated and tends to precipitate a scale layer of CaCO.
* For LSI = 0, water is saturated (in equilibrium) with CaCO. A scale layer of CaCO is neither precipitated nor dissolved.
* For LSI .
If the actual pH of the water is below the calculated saturation pH, the LSI is negative and the water has a very limited scaling potential. If the actual pH exceeds pHs, the LSI is positive, and being supersaturated with CaCO, the water tends to form scale. At increasing positive index values, the scaling potential increases.
In practice, water with an LSI between −0.5 and +0.5 will not display enhanced mineral dissolving or scale-forming properties. Water with an LSI below −0.5 tends to exhibit noticeably increased dissolving abilities while water with an LSI above +0.5 tends to exhibit noticeably increased scale-forming properties.
The LSI is temperature-sensitive. The LSI becomes more positive as the water temperature increases. This has particular implications in situations where well water is used. The temperature of the water when it first exits the well is often significantly lower than the temperature inside the building served by the well or at the laboratory where the LSI measurement is made. This increase in temperature can cause scaling, especially in cases such as water heaters. Conversely, systems that reduce water temperature will have less scaling.
: Water analysis:
:: pH = 7.5
:: TDS = 320 mg/L
:: Calcium = 150 mg/L (or ppm) as CaCO
:: Alkalinity = 34 mg/L (or ppm) as CaCO
: LSI formula:
:: LSI = pH − pH
:: pH = (9.3 + A + B) − (C + D) where:
:: A = = 0.15
:: B = −13.12 × log(°C + 273) + 34.55 = 2.09 at 25 °C and 1.09 at 82 °C
:: C = log[Ca as CaCO] - 0.4 = 1.78
::: (Ca as CaCO is also called calcium hardness, and is calculated as 2.5[Ca])
:: D = log[alkalinity as CaCO] = 1.53 | 0 | Theoretical and Fundamental Chemistry |
Zelinsky created a large scientific school and its scientists made fundamental contributions to various fields of chemistry. Among his students werw Academicians of the Academy of Sciences of the USSR A. A. Balandin, L. F. Vereshchagin, B. A. Kazansky, K. A. Kocheshkov, S. S. Nametkin, A. N. Nesmeyanov; Corresponding Members of the Academy of Sciences of the USSR N. A. Izgaryshev, K. P. Lavrovsky, Yu. G. Mamedaliev, B. M. Mikhailov, A. V. Rakovsky, V. V. Chelintsev, N. I. Shuikin; professors V. V. Longinov, A. E. Uspensky, L. A. Chugaev, N. A. Shilov, V. A. Nekrasova-Popova and others.
N. D. Zelinsky - one of the organizers of the All-Union Chemical Society named after D. I. Mendeleev; since 1941 he was its honorary member. Since 1921 - an honorary member of the Moscow Society of Naturalists, since 1935 he was its president. | 0 | Theoretical and Fundamental Chemistry |
Lithium has been associated with several forms of kidney injury. It is estimated that impaired urinary concentrating ability is present in at least half of individuals on chronic lithium therapy, a condition called lithium-induced nephrogenic diabetes insipidus. Continued use of lithium can lead to more serious kidney damage in an aggravated form of diabetes insipidus. Chronic kidney disease caused by lithium has not been proven with various contradicting results presented by a 2018 review. In rare cases, some forms of lithium-caused kidney damage may be progressive and lead to end-stage kidney failure with a reported incidence of 0.2% to 0.7%. | 1 | Applied and Interdisciplinary Chemistry |
Ortho effect is an organic chemistry phenomenon where the presence of an chemical group at the at ortho position or the 1 and 2 position of a phenyl ring, relative to the carboxylic compound changes the chemical properties of the compound. This is caused by steric effects and bonding interactions along with polar effects caused by the various substituents which are in a given molecule, resulting in changes in its chemical and physical properties. The ortho effect is associated with substituted benzene compounds.
There are three main ortho effects in substituted benzene compounds:
* Steric hindrance forces cause substitution of a chemical group in the ortho position of benzoic acids become stronger acids.
* Steric Inhibition of Protonation caused by substitution of anilines to become weaker bases, compared to substitution of isomers in the meta and para position.
* Electrophilic aromatic substitution of disubstituted benzene compounds causes steric effects which determines the regioselectivity of an incoming electrophile in disubstituted benzene compounds | 0 | Theoretical and Fundamental Chemistry |
Taking (the Planck constant divided by ), (the speed of light), and (the electromagnetic coupling constant i.e. a measure of the strength of the electromagnetic force (where is the absolute value of the electronic charge and is the vacuum permittivity)) we can form a dimensionless quantity called the fine-structure constant:
The fine-structure constant is the coupling constant of quantum electrodynamics (QED) determining the strength of the interaction between electrons and photons. It turns out that the fine-structure constant is not really a constant at all owing to the zero-point energy fluctuations of the electron-positron field. The quantum fluctuations caused by zero-point energy have the effect of screening electric charges: owing to (virtual) electron-positron pair production, the charge of the particle measured far from the particle is far smaller than the charge measured when close to it.
The Heisenberg inequality where , and , are the standard deviations of position and momentum states that:
It means that a short distance implies large momentum and therefore high energy i.e. particles of high energy must be used to explore short distances. QED concludes that the fine-structure constant is an increasing function of energy. It has been shown that at energies of the order of the Z boson rest energy, 90 GeV, that:
rather than the low-energy . The renormalization procedure of eliminating zero-point energy infinities allows the choice of an arbitrary energy (or distance) scale for defining . All in all, depends on the energy scale characteristic of the process under study, and also on details of the renormalization procedure. The energy dependence of has been observed for several years now in precision experiment in high-energy physics. | 0 | Theoretical and Fundamental Chemistry |
The genetic code is the set of rules used by living cells to translate information encoded within genetic material (DNA or RNA sequences of nucleotide triplets, or codons) into proteins. Translation is accomplished by the ribosome, which links proteinogenic amino acids in an order specified by messenger RNA (mRNA), using transfer RNA (tRNA) molecules to carry amino acids and to read the mRNA three nucleotides at a time. The genetic code is highly similar among all organisms and can be expressed in a simple table with 64 entries.
The codons specify which amino acid will be added next during protein biosynthesis. With some exceptions, a three-nucleotide codon in a nucleic acid sequence specifies a single amino acid. The vast majority of genes are encoded with a single scheme (see the RNA codon table). That scheme is often referred to as the canonical or standard genetic code, or simply the genetic code, though variant codes (such as in mitochondria) exist. | 1 | Applied and Interdisciplinary Chemistry |
Consider a spherically converging shock wave that was initiated by some means at a radial location and directed towards the center. As the shock wave travels towards the origin, its strength increases since the shock wave compresses lesser and lesser amount of mass as it propagates. The shock wave location thus varies with time. The self-similar solution to be described corresponds to the region , that is to say, the shock wave has travelled enough to forget about the initial condition.
Since the shock wave in the self-similar region is strong, the pressure behind the wave is very large in comparison with the pressure ahead of the wave . According to Rankine–Hugoniot conditions, for strong waves, although , , where represents gas density; in other words, the density jump across the shock wave is finite. For the analysis, one can thus assume and , which in turn removes the velocity scale by setting since .
At this point, it is worth noting that the analogous problem in which a strong shock wave propagating outwards is known to be described by the Taylor–von Neumann–Sedov blast wave. The description for Taylor–von Neumann–Sedov blast wave utilizes and the total energy content of the flow to develop a self-similar solution. Unlike this problem, the imploding shock wave is not self-similar throughout the entire region (the flow field near depends on the manner in which the shock wave is generated) and thus the Guderley–Landau–Stanyukovich problem attempts to describe in a self-similar manner, the flow field only for ; in this self-similar region, energy is not constant and in fact, will be shown to decrease with time (the total energy of the entire region is still constant). Since the self-similar region is small in comparison with the initial size of the shock wave region, only a small fraction of the total energy is accumulated in the self-similar region. The problem thus contains no length scale to use dimensional arguments to find out the self-similar description i.e., the dependence of on cannot be determined by dimensional arguments alone. The problems of these kind are described by the self-similar solution of the second kind.
For convenience, measure the time such that the converging shock wave reaches the origin at time . For , the converging shock approaches the origin and for , the reflected shock wave emerges from the origin. The location of shock wave is assumed to be described by the function
where is the similarity index and is a constant. The reflected shock emerges with the same similarity index. The value of is determined from the condition that a self-similar solution exists, whereas the constant cannot be described from the self-similar analysis; the constant contains information from the region and therefore can be determined only when the entire region of the flow is solved. The dimension of will be found only after solving for . For Taylor–von Neumann–Sedov blast wave, dimensional arguments can be used to obtain
The shock-wave velocity is given by
According to Rankine–Hugoniot conditions the gas velocity , pressure and density immediately behind the strong shock front, for an ideal gas are given by
These will serve as the boundary conditions for the flow behind the shock front. | 1 | Applied and Interdisciplinary Chemistry |
The purification process utilizes the cementation process to further purify the zinc. It uses zinc dust and steam to remove copper, cadmium, cobalt, and nickel, which would interfere with the electrolysis process. After purification, concentrations of these impurities are limited to less than 0.05 milligram per liter (4×10 pound per U.S. gallon). Purification is usually conducted in large agitated tanks. The process takes place at temperatures ranging from , and pressures ranging from atmospheric to (absolute scale). The by-products are sold for further refining.
The zinc sulfate solution must be very pure for electrowinning to be at all efficient. Impurities can change the decomposition voltage enough to where the electrolysis cell produces largely hydrogen gas rather than zinc metal. | 1 | Applied and Interdisciplinary Chemistry |
Many drugs are hindered when providing treatment when crossing the blood-brain barrier yielding poor uptake into areas of the brain. Transferrin glycoproteins are able to bypass the blood-brain barrier via receptor-mediated transport for specific transferrin receptors found in the brain capillary endothelial cells. Due to this functionality, it is theorized that nanoparticles acting as drug carriers bound to transferrin glycoproteins can penetrate the blood-brain barrier allowing these substances to reach the diseased cells in the brain. Advances with transferrin conjugated nanoparticles can lead to non-invasive drug distribution in the brain with potential therapeutic consequences of central nervous system (CNS) targeted diseases (e.g. Alzheimers or Parkinsons disease). | 1 | Applied and Interdisciplinary Chemistry |
Ouabain is a cardiac glycoside that acts by non-selectively inhibiting the -ATPase sodium–potassium ion pump. Once ouabain binds to this enzyme, the enzyme ceases to function, leading to an increase of intracellular sodium. This increase in intracellular sodium reduces the activity of the sodium–calcium exchanger (NCX), which pumps one calcium ion out of the cell and three sodium ions into the cell down their concentration gradient. Therefore, the decrease in the concentration gradient of sodium into the cell which occurs when the Na/K-ATPase is inhibited reduces the ability of the NCX to function. This in turn elevates intracellular calcium. This results in higher cardiac contractility and an increase in cardiac vagal tone. The change in ionic gradients caused by ouabain can also affect the membrane voltage of the cell and result in cardiac arrhythmias. | 0 | Theoretical and Fundamental Chemistry |
Exometabolomics, or "metabolic footprinting", is the study of extracellular metabolites. It uses many techniques from other subfields of metabolomics, and has applications in biofuel development, bioprocessing, determining drugs' mechanism of action, and studying intercellular interactions. | 1 | Applied and Interdisciplinary Chemistry |
For spherical vessel, there is no known explicit solution, so Frank-Kamenetskii used numerical methods to find the critical value. Here , then
If the transformations and , where is the maximum temperature which occurs at due to symmetry, are introduced
The above equation is nothing but Emden–Chandrasekhar equation, which appears in astrophysics describing isothermal gas sphere. Unlike planar and cylindrical case, the spherical vessel has infinitely many solutions for oscillating about the point , instead of just two solutions, which was shown by Israel Gelfand. The lowest branch will be chosen to explain explosive behavior.
From numerical solution, it is found that the critical Frank-Kamenetskii parameter is . The system has no steady state( or explodes) for and for , the system goes to a steady state with very slow reaction. The maximum temperature occurs at and maximum critical temperature is . | 1 | Applied and Interdisciplinary Chemistry |
Due to early issues with biofilm reactors, like hydraulic instability and uneven biofilm distribution, moving bed biofilm technology was developed. The MBBR system consists of an aeration tank (similar to an activated sludge tank) with special plastic carriers that provide a surface where a biofilm can grow. There is a wide variety of plastic carriers used in these systems. These carriers vary in surface area and in shape, each offering different advantages and disadvantages. Surface area plays a very important role in biofilm formation. Free-floating carriers allow biofilms to form on the surface, therefore a large internal surface area is crucial for contact with water, air, bacteria, and nutrients. The carriers will be mixed in the tank by the aeration system and thus will have good contact between the substrate in the influent wastewater and the biomass on the carriers. The most preferable material is currently high density polyethylene (HDPE) due to its plasticity, density, and durability.
To achieve higher concentration of biomass in the bioreactors, hybrid MBBR systems have been used where suspended and attached biomass co-exist contributing both to biological processes. Additionally, there are anaerobic MBBRs that have been mainly used for industrial wastewater treatment. A 2019 article described a combination of anaerobic (methanogenic) MBBR with aerobic MBBR that was applied in a municipal wastewater treatment laboratory, with simultaneous production of biogas. | 1 | Applied and Interdisciplinary Chemistry |
Shape-memory alloys have different shape-memory effects. The two common effects are one-way SMA and two-way SMA. A schematic of the effects is shown below.
The procedures are very similar: starting from martensite, adding a deformation, heating the sample and cooling it again. | 1 | Applied and Interdisciplinary Chemistry |
An aroma compound, also known as an odorant, aroma, fragrance or flavoring, is a chemical compound that has a smell or odor. For an individual chemical or class of chemical compounds to impart a smell or fragrance, it must be sufficiently volatile for transmission via the air to the olfactory system in the upper part of the nose. As examples, various fragrant fruits have diverse aroma compounds, particularly strawberries which are commercially cultivated to have appealing aromas, and contain several hundred aroma compounds.
Generally, molecules meeting this specification have molecular weights of less than 310. Flavors affect both the sense of taste and smell, whereas fragrances affect only smell. Flavors tend to be naturally occurring, and the term fragrances may also apply to synthetic compounds, such as those used in cosmetics.
Aroma compounds can naturally be found in various foods, such as fruits and their peels, wine, spices, floral scent, perfumes, fragrance oils, and essential oils. For example, many form biochemically during the ripening of fruits and other crops. Wines have more than 100 aromas that form as byproducts of fermentation. Also, many of the aroma compounds play a significant role in the production of compounds used in the food service industry to flavor, improve, and generally increase the appeal of their products.
An odorizer may add a detectable odor to a dangerous odorless substance, like propane, natural gas, or hydrogen, as a safety measure. | 0 | Theoretical and Fundamental Chemistry |
The most fundamental operation in DNA computing and molecular programming is the strand displacement mechanism. Currently, there are two ways to perform strand displacement:
* Toehold mediated strand displacement (TMSD)
* Polymerase-based strand displacement (PSD) | 1 | Applied and Interdisciplinary Chemistry |
The concepts of Hesss law can be expanded to include changes in entropy and in Gibbs free energy, since these are also state functions. The Bordwell thermodynamic cycle is an example of such an extension that takes advantage of easily measured equilibria and redox potentials to determine experimentally inaccessible Gibbs free energy values. Combining ΔG</sup> values found with Hesss law can be helpful in determining entropy values that have not been measured directly and therefore need to be calculated through alternative paths.
For the free energy:
For entropy, the situation is a little different. Because entropy can be measured as an absolute value, not relative to those of the elements in their reference states (as with ΔH</sup>), there is no need to use the entropy of formation; one simply uses the absolute entropies for products and reactants: | 0 | Theoretical and Fundamental Chemistry |
A further phenomenon of importance is whether a plume has laminar flow or turbulent flow. Usually, there is a transition from laminar to turbulent as the plume moves away from its source. This phenomenon can be clearly seen in the rising column of smoke from a cigarette. When high accuracy is required, computational fluid dynamics (CFD) can be employed to simulate plumes, but the results can be sensitive to the turbulence model chosen. CFD is often undertaken for rocket plumes, where condensed phase constituents can be present in addition to gaseous constituents. These types of simulations can become quite complex, including afterburning and thermal radiation, and (for example) ballistic missile launches are often detected by sensing hot rocket plumes.
Spacecraft designers are sometimes concerned with impingement of attitude control system thruster plumes onto sensitive subsystems like solar arrays and star trackers, or with the impingement of rocket engine plumes onto moon or planetary surfaces where they can cause local damage or even mid-term disturbances to planetary atmospheres.
Another phenomenon which can also be seen clearly in the flow of smoke from a cigarette is that the leading-edge of the flow, or the starting-plume, is quite often approximately in the shape of a ring-vortex (smoke ring). | 1 | Applied and Interdisciplinary Chemistry |
For ordinary alkenes, [2+2] cycloadditions only observed under photochemical activation.
The rationale for the non-observation of thermal [2+2] cycloadditions begins with the analysis of the four possible stereochemical consequences for the [2+2] cycloaddition: [2 + 2], [2 + 2], [2 + 2], [2 + 2]. The geometrically most plausible [2 + 2] mode is forbidden under thermal conditions, while the [2 + 2], [2 + 2] approaches are allowed from the point of view of symmetry but are rare due to an unfavorable strain and steric profile.
Considering the [2 + 2] cycloaddition. This mechanism leads to a retention of stereochemistry in the product, as illustrated to the right. Two symmetry elements are present in the starting materials, transition state, and product: σ and σ. σ is the mirror plane between the components perpendicular to the p-orbitals; σ splits the molecules in half perpendicular to the σ-bonds. These are both local-symmetry elements in the case that the components are not identical.
To determine symmetry and asymmetry with respect to σ and σ, the starting material molecular orbitals must be considered in tandem. The figure to the right shows the molecular orbital correlation diagram for the [2 + 2] cycloaddition. The two π and π molecular orbitals of the starting materials are characterized by their symmetry with respect to first σ and then σ. Similarly, the σ and σ molecular orbitals of the product are characterized by their symmetry. In the correlation diagram, molecular orbitals transformations over the course of the reaction must conserve the symmetry of the molecular orbitals. Thus π correlates with σ, π correlates with σ, π correlates with σ, and finally π correlates with σ. Due to conservation of orbital symmetry, the bonding orbital π is forced to correlate with the antibonding orbital σ. Thus a high barrier is predicted.
This is made precise in the state correlation diagram below. The ground state in the starting materials is the electronic state where π and π are both doubly populated – i.e. the state (SS)(AS). As such, this state attempts to correlate with the electronic state in the product where both σ and σ are doubly populated – i.e. the state (SS)(AS). However, this state is neither the ground state (SS)(SA) of cyclobutane, nor the first excited state ES-1=(SS)(SA)(AS), where an electron is promoted from the HOMO to the LUMO.(AS).
Similarly, the ground state of the product cyclobutane, as can be seen in the molecular orbital diagram above, is the electronic state where both σ and σ are doubly populated – i.e. the state (SS)(SA). This attempts to correlate with the state where π and π are both doubly populated – i.e. a second excited state ES-2=(SS)(SA).
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Finally, the first excited state of the starting materials is the electronic configuration where π is doubly populated, and π and π are both singly occupied – i.e. the state (SS)(AS)(SA). The first excited state of the product is also the state (SS)(SA)(AS) as σ is doubly populated, and σ and σ are both singly occupied. Thus these two excited states correlate. | 0 | Theoretical and Fundamental Chemistry |
There has been a long debate over the question of whether zero-point fluctuations of quantized vacuum fields are "real" i.e. do they have physical effects that cannot be interpreted by an equally valid alternative theory? Schwinger, in particular, attempted to formulate QED without reference to zero-point fluctuations via his "source theory". From such an approach it is possible to derive the Casimir Effect without reference to a fluctuating field. Such a derivation was first given by Schwinger (1975) for a scalar field, and then generalized to the electromagnetic case by Schwinger, DeRaad, and Milton (1978). in which they state "the vacuum is regarded as truly a state with all physical properties equal to zero". More recently Jaffe (2005) has highlighted a similar approach in deriving the Casimir effect stating "the concept of zero-point fluctuations is a heuristic and calculational aid in the description of the Casimir effect, but not a necessity in QED."
Nevertheless, as Jaffe himself notes in his paper, "no one has shown that source theory or another S-matrix based approach can provide a complete description of QED to all orders." Furthermore, Milonni has shown the necessity of the vacuum field for the formal consistency of QED. In QCD, color confinement has led physicists to abandon the source theory or S-matrix based approach for the strong interactions. The Higgs mechanism, Hawking Radiation and the Unruh effect are also theorized to be dependent on zero-point vacuum fluctuations, the field contribution being an inseparable parts of these theories. Jaffe continues "Even if one could argue away zero-point contributions to the quantum vacuum energy, the problem of spontaneous symmetry breaking remains: condensates [ground state vacua] that carry energy appear at many energy scales in the Standard Model. So there is good reason to be skeptical of attempts to avoid the standard formulation of quantum field theory and the zero-point energies it brings with it." It is difficult to judge the physical reality of infinite zero-point energies that are inherent in field theories, but modern physics does not know any better way to construct gauge-invariant, renormalizable theories than with zero-point energy and they would seem to be a necessity for any attempt at a unified theory. | 0 | Theoretical and Fundamental Chemistry |
The International Institute of Welding Technology IIW published the Guideline "Recommendations for the HFMI Treatment" in October 2016. An overview of higher frequency hammers (HFMI) is presented, and recommendations for the correct application of the method and quantitative measurements for quality assurance the guideline provides the basis for measurements of HFMI improved welded joints on the basis of all known stress calculation concepts.
In numerous experiments at various institutes and universities an 80 to 100 percent increase of fatigue strength and a 5 – to 15-fold increase in weld-life could be demonstrated. The most extensive research project was from 2006 to 2009 "REFRESH – life extension of existing and new welded steel structures (P702). In this research project, the HiFIT device was developed and made ready for production. This report is available in book form at the FOSTA (Forschungsvereinigung Stahlanwendung e.V.) and can be ordered under the number . The book contains detailed scientific verifications and validations. | 1 | Applied and Interdisciplinary Chemistry |
Chemicals and their metabolites can be detected in a variety of biological substances such as blood, urine, exhaled air, hair, nails, feces, semen, breast milk, or saliva. Blood and urine are the most commonly used in occupational safety and health.
Breast milk is a favored matrix (substance) to measure lipophilic (fat-loving) persistent, bioaccumulative, and toxic (PBT) compounds during lactation; this exposure route is dominant for breastfeeding children. A lipophilic compound might also be detected in blood, while a hydrophilic (water-loving) compound might be detected in urine.
Analytical methods used by the CDC include isotope dilution mass spectrometry, inductively coupled plasma mass spectrometry, or graphite furnace atomic absorption spectrometry. Others include gas chromatography or high-performance liquid chromatography coupled with various detectors such as ultraviolet, electron capture, flame ionization, atomic emission, or mass spectrometric detectors. Ligand-binding assays and immunoassays are also used.
As biomonitoring necessarily involves working with human subjects and specimens, biosafety procedures are necessary to prevent the transmission of pathogens. | 1 | Applied and Interdisciplinary Chemistry |
The Mount Polley mineralization is classified as an alkalic porphyry copper-gold deposit. The deposits are located in the Quesnel trough, a Mesozoic volcanic arc in the Canadian segment of the North American Cordillera. Precious metal mineralization in the two Mount Polley deposits occur the felsic stock occurred during the Jurassic-Triassic period. The copper-gold mineralization occurs within crackle and inclusion breccias. | 1 | Applied and Interdisciplinary Chemistry |
For an exothermic reaction, heat is released, making the net enthalpy change negative. Thus, according to the definition of the slope:
For an exothermic reaction , so
Thus, for an exothermic reaction, the Van 't Hoff plot should always have a positive slope. | 0 | Theoretical and Fundamental Chemistry |
Fajans worked with Henry G. Moseley at the laboratory of Ernest Rutherford researching properties of the radioactive rows of the periodic table. He identified the half-lives of the uranium-actinium row and thorium nuclides.
He discovered the phenomenon of the electrochemical branching of the radioactive rows. Afterwards Fajans worked on the electrochemical properties of elements as a result of the radioactive changes, and he formulated the law of the radioactive shifts which was later named the radioactive displacement law of Fajans and Soddy (Frederick Soddy received the Nobel Prize in chemistry in 1921 for his isotopic research). In 1913, together with Oswald Helmuth Göhring, he discovered the first radionuclide of a new element, which was later named protactinium. Fajans and Otto Hahn discovered the formula that defined the conditions of precipitation and absorption of radioactive substances. It is very significant for separation and purification of radioactive substances found in the smallest number.
In 1919, Fajans began researching the structure of crystals by thermochemical and refractometric methods. The co-relation of Born, Fajans and Haber is a basic thermochemical rule. On the basis of his research data Fajans formulated the essential relationships concerning chemical bond strength and deformation of ions and particles, such as heat of ion hydration, refractive index and the heat of sublimation. In 1923 he formulated Fajans' rules of inorganic chemistry, which are used to predict whether a chemical bond will be covalent or ionic.
In the United States he researched nuclear reactions using a cyclotron and discovered a radioactive lead isotope with Voigt, and a new rhenium isotope with Sullivan. He developed the quantum theory which explained chemical bonding through electrostatic impacts between quanta and nuclear cores. He was a member of the Polish Institute of Arts and Sciences in America and of many societies and academies. | 1 | Applied and Interdisciplinary Chemistry |
Action potentials are most commonly initiated by excitatory postsynaptic potentials from a presynaptic neuron. Typically, neurotransmitter molecules are released by the presynaptic neuron. These neurotransmitters then bind to receptors on the postsynaptic cell. This binding opens various types of ion channels. This opening has the further effect of changing the local permeability of the cell membrane and, thus, the membrane potential. If the binding increases the voltage (depolarizes the membrane), the synapse is excitatory. If, however, the binding decreases the voltage (hyperpolarizes the membrane), it is inhibitory. Whether the voltage is increased or decreased, the change propagates passively to nearby regions of the membrane (as described by the cable equation and its refinements). Typically, the voltage stimulus decays exponentially with the distance from the synapse and with time from the binding of the neurotransmitter. Some fraction of an excitatory voltage may reach the axon hillock and may (in rare cases) depolarize the membrane enough to provoke a new action potential. More typically, the excitatory potentials from several synapses must work together at nearly the same time to provoke a new action potential. Their joint efforts can be thwarted, however, by the counteracting inhibitory postsynaptic potentials.
Neurotransmission can also occur through electrical synapses. Due to the direct connection between excitable cells in the form of gap junctions, an action potential can be transmitted directly from one cell to the next in either direction. The free flow of ions between cells enables rapid non-chemical-mediated transmission. Rectifying channels ensure that action potentials move only in one direction through an electrical synapse. Electrical synapses are found in all nervous systems, including the human brain, although they are a distinct minority. | 0 | Theoretical and Fundamental Chemistry |
Wu Yangjie (; born 1 January 1928) is a Chinese organic chemist and a professor at Zhengzhou University. He is an academician of the Chinese Academy of Sciences. | 0 | Theoretical and Fundamental Chemistry |
Stokes's law of sound attenuation applies to sound propagation in an isotropic and homogeneous Newtonian medium. Consider a plane sinusoidal pressure wave that has amplitude at some point. After traveling a distance from that point, its amplitude will be
The parameter is a kind of attenuation constant, dimensionally the reciprocal of length.
In the International System of Units (SI), it is expressed in neper per meter or simply reciprocal of meter (m). That is, if = 1 m, the wave's amplitude decreases by a factor of for each meter traveled. | 1 | Applied and Interdisciplinary Chemistry |
Some fluorescent chemicals exhibit significant fluorescent quenching when exposed to increasing temperatures. This effect has been used to measure and examine the thermogenic properties of mitochondria. This involves placing mitochondria-targeting thermosensitive fluorophores inside cells, which naturally localise inside the mitochondria due to the inner mitochondrial membrane matrix-faces negative charge (as the fluorophores are cationic). The temperature of these fluorophores is inversely proportional to their fluorescence emission, and thus by measuring the fluorescent output, the temperature of actively-respiring mitochondria can be deduced. The fluorophores used are typically lipophilic cations derived from Rhodamine-B, such as ThermoFishers MitoTracker probes. This technique has contributed significantly to the general scientific consensus that mitochondria are physiologically maintained at close to 50 ˚C, more than 10˚C above the rest of the cell.
The inverse relationship between fluorescence and temperature can be explained by the change in the number of atomic collisions in the fluorophore's environment, depending on the kinetic energy. Collisions promote radiationless decay and loss of extra energy as heat, so more collisions or more forceful collisions will promote radiationless decay and reduce fluorescence emission.
This temperature-measurement technique is, however, limited. These cationic fluorophores are heavily influenced by the charge of the inner mitochondrial membrane matrix-face, dependent on the cell type. For example, the thermosensitive fluorophore MTY (MitoTracker Yellow) shows a sudden and drastic drop in fluorescence after the addition of oligomycin (an ATP synthase inhibitor) to the mitochondria of human primary fibroblasts. This would suggest a sharp increase in mitochondrial temperature but is, in reality, explained by the hyperpolarisation of the mitochondrial inner membrane by oligomycin - leading to the breakdown of the positively-charged MTY fluorophore. | 1 | Applied and Interdisciplinary Chemistry |
In industrial process plants, using the fact that the mass entering and leaving any portion of a process plant must balance, data validation and reconciliation algorithms may be employed to correct measured flows, provided that enough redundancy of flow measurements exist to permit statistical reconciliation and exclusion of detectably erroneous measurements. Since all real world measured values contain inherent error, the reconciled measurements provide a better basis than the measured values do for financial reporting, optimization, and regulatory reporting. Software packages exist to make this commercially feasible on a daily basis. | 1 | Applied and Interdisciplinary Chemistry |
Monochromators are used in many optical measuring instruments and in other applications where tunable monochromatic light is wanted. Sometimes the monochromatic light is directed at a sample and the reflected or transmitted light is measured. Sometimes white light is directed at a sample and the monochromator is used to analyze the reflected or transmitted light. Two monochromators are used in many fluorometers; one monochromator is used to select the excitation wavelength and a second monochromator is used to analyze the emitted light.
An automatic scanning spectrometer includes a mechanism to change the wavelength selected by the monochromator and to record the resulting changes in the measured quantity as a function of the wavelength.
If an imaging device replaces the exit slit, the result is the basic configuration of a spectrograph. This configuration allows the simultaneous analysis of the intensities of a wide band of colors. Photographic film or an array of photodetectors can be used, for instance to collect the light. Such an instrument can record a spectral function without mechanical scanning, although there may be tradeoffs in terms of resolution or sensitivity for instance.
An absorption spectrophotometer measures the absorption of light by a sample as a function of wavelength. Sometimes the result is expressed as percent transmission and sometimes it is expressed as the inverse logarithm of the transmission. The Beer–Lambert law relates the absorption of light to the concentration of the light-absorbing material, the optical path length, and an intrinsic property of the material called molar absorptivity. According to this relation the decrease in intensity is exponential in concentration and path length. The decrease is linear in these quantities when the inverse logarithm of transmission is used. The old nomenclature for this value was optical density (OD), current nomenclature is absorbance units (AU). One AU is a tenfold reduction in light intensity. Six AU is a millionfold reduction.
Absorption spectrophotometers often contain a monochromator to supply light to the sample. Some absorption spectrophotometers have automatic spectral analysis capabilities.
Absorption spectrophotometers have many everyday uses in chemistry, biochemistry, and biology. For example, they are used to measure the concentration or change in concentration of many substances that absorb light. Critical characteristics of many biological materials, many enzymes for instance, are measured by starting a chemical reaction that produces a color change that depends on the presence or activity of the material being studied. Optical thermometers have been created by calibrating the change in absorbance of a material against temperature. There are many other examples.
Spectrophotometers are used to measure the specular reflectance of mirrors and the diffuse reflectance of colored objects. They are used to characterize the performance of sunglasses, laser protective glasses, and other optical filters. There are many other examples.
In the UV, visible and near IR, absorbance and reflectance spectrophotometers usually illuminate the sample with monochromatic light. In the corresponding IR instruments, the monochromator is usually used to analyze the light coming from the sample.
Monochromators are also used in optical instruments that measure other phenomena besides simple absorption or reflection, wherever the color of the light is a significant variable. Circular dichroism spectrometers contain a monochromator, for example.
Lasers produce light which is much more monochromatic than the optical monochromators discussed here, but only some lasers are easily tunable, and these lasers are not as simple to use.
Monochromatic light allows for the measurement of the quantum efficiency (QE) of an imaging device (e.g. CCD or CMOS imager). Light from the exit slit is passed either through diffusers or an integrating sphere on to the imaging device while a calibrated detector simultaneously measures the light. Coordination of the imager, calibrated detector, and monochromator allows one to calculate the carriers (electrons or holes) generated for a photon of a given wavelength, QE. | 0 | Theoretical and Fundamental Chemistry |
Canuel was named a Leopold fellow in 2011. She was elected a fellow of the Geochemical Society and the European Association of Geochemistry in 2016, and was named a sustaining fellow of the Association for the Sciences of Limnology and Oceanography in 2019. | 0 | Theoretical and Fundamental Chemistry |
is a traditional Japanese chemical compound used in the niiro process for artificially inducing patination in decorative non-ferrous metals, especially several copper alloys, with the results being metals of the irogane class. These "colour metals," virtually unknown outside Japan until the late 19th century, have achieved some popularity in craft circles in other parts of the world since then. | 1 | Applied and Interdisciplinary Chemistry |
As shown in Scheme 2, the next phase involved addition of the carbon atoms required for the formation of the C ring. Ketone 7 was treated with magnesium bromide diisopropylamide and underwent an aldol reaction with 4-pentanal (8) to give β-hydroxyketone 9. The hydroxyl group was protected as the asymmetric carbonate ester (10). Oxidation of the enolate of ketone 10 with (-)-camphorsulfonyl oxaziridine (11) gave α-hydroxyketone 12. Reduction of the ketone group with 20 equivalents of sodium bis(2-methoxyethoxy)aluminumhydride (Red-Al) gave triol 13, which was immediately converted to carbonate 14 by treatment with phosgene. Swern oxidation of alcohol 14 gave ketone 15. The next step set the final carbon-carbon bond between the B and C rings. This was achieved through a Chan rearrangement of 15 using lithium tetramethylpiperidide to give α-hydroxylactone 16 in 90% yield. The hydroxyl group was reductively removed using samarium(II) iodide to give an enol, and chromatography of this enol on silica gel gave the separable diastereomers cis 17c (77%) and trans 17t (15%), which could be recycled to 17c through treatment with potassium tert-butoxide. Treatment of pure 17c with lithium tetramethylpiperidide and (±)-camphorsulfonyl oxaziridine gave separable α-hydroxyketones 18c (88%) and 18t (8%) in addition to some recovered starting material (3%). Reduction of pure ketone 18c using Red-Al followed by basic work-up resulted in epimerization to give the required trans-fused diol 19 in 88% yield. | 0 | Theoretical and Fundamental Chemistry |
Vancomycin was isolated in 1953 and used clinically by 1958, while teicoplanin was discovered in 1978 and became clinically-available in 1984. Telavancin is a semi-synthetic lipoglycopeptide derivative of vancomycin approved by FDA in 2009.
Teicoplanin has historically been more widely-marketed - and thus more used - in Europe compared to the U.S. It has more fatty acid chains than vancomycin and is considered to be 50 to 100 times more lipophilic. Teicoplanin also has an increased half-life compared to vancomycin, as well as having better tissue penetration. It can be two to four times more active than vancomycin, but it does depend upon the organism. Teicoplanin is more acidic, forming water-soluble salts, so it can be given intramuscularly. Teicoplanin is much better at penetrating into leukocytes and phagocytes than vancomycin.
Since 2002, isolates of vancomycin-resistant Staphylococcus aureus (VRSA) have been found in the USA and other countries.
Glycopeptides have typically been considered the last effective line of defense for cases of MRSA, however several newer classes of antibiotics have proven to have activity against MRSA- including, in 2000, linezolid of the oxazolidinone class, and in 2003 daptomycin of the lipopeptide class. | 0 | Theoretical and Fundamental Chemistry |
The sigma-2 receptor is expressed in brain and retinal cells where it regulates key pathways involved in age-related diseases such as Alzheimers disease and synucleinopathies such as Parkinsons disease and dementia with Lewy bodies, as well as dry age-related macular degeneration (dry AMD). The normal activity of processes regulated by sigma-2, such as protein trafficking and autophagy, is impaired by cellular stresses such as oxidative stress and the build-up of amyloid-β and α-synuclein oligomers. Studies support that sigma-2 modulators can rescue biological processes that are impaired in neurodegenerative diseases.
In vitro studies of experimental sigma-2 receptor modulators demonstrated an ability to prevent the binding of amyloid-β oligomers to neurons and also to displace bound amyloid-β oligomers from neuronal receptors. In addition, transgenic mice treated sigma-2 receptor modulators performed significantly better in the Morris water maze task than did vehicle-treated mice. Taken together, these studies suggest that sigma-2 receptor modulation may be a viable approach for treating certain neurodegenerative diseases of the CNS and retina. | 1 | Applied and Interdisciplinary Chemistry |
In molecular biology, a histone octamer is the eight-protein complex found at the center of a nucleosome core particle. It consists of two copies of each of the four core histone proteins (H2A, H2B, H3, and H4). The octamer assembles when a tetramer, containing two copies of H3 and two of H4, complexes with two H2A/H2B dimers. Each histone has both an N-terminal tail and a C-terminal histone-fold. Each of these key components interacts with DNA in its own way through a series of weak interactions, including hydrogen bonds and salt bridges. These interactions keep the DNA and the histone octamer loosely associated, and ultimately allow the two to re-position or to separate entirely. | 1 | Applied and Interdisciplinary Chemistry |
The database was pulled from the internet by the Trump administration in December 2019. The NLM said in a statement that much of the information remained available from the original sources, and that thus the database could be removed; critics, such as the Environmental Data & Governance Initiative, suggested it was part of a larger effort on the part of the administration to obfuscate the detrimental results of the rollback of Obama-era environmental regulations.
The data underlying TOXMAP remains accessible through their original resources: Government of Canada National Pollutant Release Inventory (NPRI), U.S. Census Bureau, U.S. EPA Clean Air Markets Program, U.S. EPA Geospatial Applications, U.S. EPA Facilities Registry System (FRS), U.S. EPA Superfund Program, U.S. EPA Toxics Release Program (TRI), U.S. NIH NCI Surveillance, Epidemiology, and End Results Program (SEER), U.S. Nuclear Regulatory Commission (NRC). | 1 | Applied and Interdisciplinary Chemistry |
A conductometric titration method can also be used for the determination of the base number of petroleum products. A conductivity sensor is used to measure the conductivity of the analyte which allows the endpoint to be detected. It is suitable for both new and used products having base numbers from 1 mg to 40 mg KOH/g. A sample is dissolved in a solvent mixture of Toluene/ Propan-2-ol with 0.5% deionised water. A conductivity cell is placed in the titration vessel. The sample solution is titrated with alcoholic hydrochloric acid. | 0 | Theoretical and Fundamental Chemistry |
The most common supercomplexes observed are Complex I/III, Complex I/III/IV, and Complex III/IV. Most of Complex II is found in a free-floating form in both plant and animal mitochondria. Complex V can be found co-migrating as a dimer with other supercomplexes, but scarcely as part of the supercomplex unit.
Supercomplex assembly appears to be dynamic and respiratory enzymes are able to alternate between participating in large respirasomes and existing in a free state. It is not known what triggers changes in complex assembly, but research has revealed that the formation of supercomplexes is heavily dependent upon the lipid composition of the mitochondrial membrane, and in particular requires the presence of cardiolipin, a unique mitochondrial lipid. In yeast mitochondria lacking cardiolipin, the number of enzymes forming respiratory supercomplexes was significantly reduced. According to Wenz et al. (2009), cardiolipin stabilizes the supercomplex formation by neutralizing the charges of lysine residues in the interaction domain of Complex III with Complex IV. In 2012, Bazan et al. was able to reconstitute trimer and tetramer Complex III/IV supercomplexes from purified complexes isolated from Saccharomyces cerevisiae and exogenous cardiolipin liposomes.
Another hypothesis for respirasome formation is that membrane potential may initiate changes in the electrostatic/hydrophobic interactions mediating the assembly/disassembly of supercomplexes. | 1 | Applied and Interdisciplinary Chemistry |
Surfactin has non-specific cytotoxicity, causing lysis through disruption to the phospholipid bilayer present in all cells. When injected into humans as an intravascular antibiotic at concentrations at or above the of 40-60 μM, surfactin has hemolytic effects. | 0 | Theoretical and Fundamental Chemistry |
A transcript is an RNA molecule that is copied or transcribed from a DNA template. A transcript can be further processed by alternative splicing, which is the retention of different combinations of exons. These unique combinations of exons are termed RNA transcript isoforms. The transcriptome is a set of all RNA, including rRNA, mRNA, tRNA, and non-coding RNA. Specifically mRNA transcripts can be used to investigate differences in gene expression patterns. Transcriptome profiling is determining the composition of transcripts and their relative expression levels in a given reference set of cells. This analysis involves characterization of all functional genomic elements, coding and non-coding.
The current RNA capture methods involve sorting cells in suspension from acutely dissociated tissue, and thus can lose information about cell morphology and microenvironment. Transcript abundance and isoforms are significantly different across tissues and are continually changing throughout an individual’s life. Gene expression is highly tissue specific, therefore with traditional RNA capture methods one must be cautious in the interpretation of gene expression patterns, as they often reflect expression of a heterogeneous mix of cell populations. Even in the same cell type, tissue measurements, where a population of cells is obtained, mask both low-level mRNA expression in single cells and variation in expression between cells. The photoactivatable TIVA tag is engineered to capture the mRNA of a single cell in complex tissues. | 1 | Applied and Interdisciplinary Chemistry |
Photoredox catalysis is a branch of photochemistry that uses single-electron transfer. Photoredox catalysts are generally drawn from three classes of materials: transition-metal complexes, organic dyes, and semiconductors. While organic photoredox catalysts were dominant throughout the 1990s and early 2000s, soluble transition-metal complexes are more commonly used today. | 0 | Theoretical and Fundamental Chemistry |
The characteristics of pool boiling are different for zeotropic mixtures than that of pure mixtures. For example, the minimum superheating needed to achieve this boiling is greater for zeotropic mixtures than for pure liquids because of the different proportions of individual substances in the liquid versus gas phases of the zeotropic mixture. Zeotropic mixtures and pure liquids also have different critical heat fluxes. In addition, the heat transfer coefficients of zeotropic mixtures are less than the ideal values predicted using the coefficients of pure liquids. This decrease in heat transfer is due to the fact that the heat transfer coefficients of zeotropic mixtures do not increase proportionately with the mass fractions of the mixture's components. | 1 | Applied and Interdisciplinary Chemistry |
The Strouhal number has significant importance in analyzing the flight of animals since it is based on the streamlines and the animal's velocity as it travels through the fluid. Its significance is demonstrated through the motion of alcids as it passes through different mediums (air to water). The assessment of alcids determined the peculiarity of being able to fly under the efficient Strouhal number range in air and water despite a high mass relative to their wing area. The alcid’s efficient dual-medium motion developed through natural selection where the environment played a role in the evolution of animals over time to fall under a certain efficient range. The dual-medium motion demonstrates how alcids had two different flight patterns based on the stroke velocities as it moved through each fluid. However, as the bird travels through a different medium, it has to face the influence of the fluid’s density and viscosity. Furthermore, the alcid also has to resist the upward-acting buoyancy as it moves horizontally. | 1 | Applied and Interdisciplinary Chemistry |
Quantification of VOCs is based on the peak area measured on the chromatogram and compared to the peak area of a chemical standard:
* Internal calibration: a known quantity of a specific chemical standard is injected together with the VOCs, the measured area on the chromatogram is proportional to the injected quantity. Because the chemical properties of VOCs alter their affinity to the solid phase (the chromatographic column) and subsequently the peak area on the chromatogram, it is best to use several standards that reflect the best chemical diversity of the floral scent sample. This method allows a more robust comparison among samples.
* External calibration: calibration curves (quantity vs. peak area) are established independently by the injection of a range of quantities of chemical standard. This method is best when the relative and absolute amount of VOCs in floral scent samples varies from sample to sample and from VOC to VOC and when the chemical diversity of VOCs in the sample is high. However, it is more time-consuming and may be a source of errors (e.g. matrix effects due to solvent or very abundant VOCs compared to trace VOCs). | 1 | Applied and Interdisciplinary Chemistry |
Porous asphalt is produced and placed using the same methods as conventional asphalt concrete; it differs in that fine (small) aggregates are omitted from the asphalt mixture. The remaining large, single-sized aggregate particles leave open voids that give the material its porosity and permeability. To ensure pavement strength, fiber may be added to the mix or a polymer-modified asphalt binder may be used. Generally, porous asphalt pavements are designed with a subsurface reservoir that holds water that passes through the pavement, allowing it to evaporate and/or percolate slowly into the surround soils.
Open-graded friction courses (OGFC) are a porous asphalt surface course used on highways to improve driving safety by removing water from the surface. These use an open-graded mix design for the top layer of asphalt. Unlike a full-depth porous asphalt pavement, OGFCs do not drain water to the base of a pavement. Instead, they allow water to infiltrate the top 3/4 to 1.5 inch of the pavement and then drain out to the side of the roadway. This can improve the friction characteristics of the road and reduce road spray. | 1 | Applied and Interdisciplinary Chemistry |
Yeast artificial chromosomes (YACs) are genetically engineered chromosomes derived from the DNA of the yeast, Saccharomyces cerevisiae [https://www.genome.gov/genetics-glossary/Yeast-Artificial-Chromosome], which is then ligated into a bacterial plasmid. By inserting large fragments of DNA, from 100–1000 kb, the inserted sequences can be cloned and physically mapped using a process called chromosome walking. This is the process that was initially used for the Human Genome Project, however due to stability issues, YACs were abandoned for the use of bacterial artificial chromosome [https://www.genome.gov/genetics-glossary/Bacterial-Artificial-Chromosome]
The bakers yeast S. cerevisiae' is one of the most important experimental organisms for studying eukaryotic molecular genetics.
Beginning with the initial research of the Rankin et al., Strul et al., and Hsaio et al., the inherently fragile chromosome was stabilized by discovering the necessary autonomously replicating sequence (ARS); a refined YAC utilizing this data was described in 1983 by Murray et al.
The primary components of a YAC are the ARS, centromere [https://www.nature.com/articles/nrm.2015.5], and telomeres [https://www.nature.com/articles/350569a0] from S. cerevisiae. Additionally, selectable marker genes, such as antibiotic resistance and a visible marker, are utilized to select transformed yeast cells. Without these sequences, the chromosome will not be stable during extracellular replication, and would not be distinguishable from colonies without the vector. | 1 | Applied and Interdisciplinary Chemistry |
Recent evidence suggests that similar chemical cycles to Earth's occur on a lesser scale on Mars, facilitated by the thin atmosphere, including carbon dioxide (and possibly carbon), water, sulphur, methane, oxygen, ozone, and nitrogen cycles. Many studies point to significantly more active chemical cycles on Mars in the past, however the faint young Sun paradox has proved problematic in determining chemical cycles involved in early climate models of the planet. | 0 | Theoretical and Fundamental Chemistry |
A high-resolution imaging (HRI) black-and-white, or panchromatic, camera is mounted adjacent to the HSI camera to enable both cameras to capture the same reflected light. The HRI camera uses a pushbroom approach just like the HSI camera with a similar lens and slit arrangement to limit the incoming light to a thin, wide beam. However, the HRI camera does not have a diffraction grating to disperse the incoming reflected light. Instead, the light is directed to a wider CCD to capture more image data. Because it captures a single line of the ground image per frame, it is called a line scan camera. The HRI CCD is 6,144 pixels wide and one pixel high. It operates at a frame rate of 720 Hz. At ARCHER search speed and altitude (100 knots over the ground at 2,500 ft AGL) each pixel in the black-and-white image represents a 3 inch by 3 inch area of the ground. This high resolution adds the capability to identify some objects. | 0 | Theoretical and Fundamental Chemistry |
The definition of the dalton was not affected by the 2019 redefinition of SI base units, that is, 1 Da in the SI is still of the mass of a carbon-12 atom, a quantity that must be determined experimentally in terms of SI units. However, the definition of a mole was changed to be the amount of substance consisting of exactly entities and the definition of the kilogram was changed as well. As a consequence, the molar mass constant remains close to but no longer exactly 1 g/mol, meaning that the mass in grams of one mole of any substance remains nearly but no longer exactly numerically equal to its average molecular mass in daltons, although the relative standard uncertainty of at the time of the redefinition is insignificant for all practical purposes. | 0 | Theoretical and Fundamental Chemistry |
Methylmercury is formed from inorganic mercury by the action of microbes that live in aquatic systems including lakes, rivers, wetlands, sediments, soils and the open ocean. This methylmercury production has been primarily attributed to anaerobic bacteria in the sediment. Significant concentrations of methylmercury in ocean water columns are strongly associated with nutrients and organic matter remineralization, which indicate that remineralization may contribute to methylmercury production. Direct measurements of methylmercury production using stable mercury isotopes have also been observed in marine waters, but the microbes involved are still unknown. Increased methylmercury concentrations in water and fish have been detected after flooding of soils associated with reservoir creation (e.g. for hydroelectric power generation) and in thermokarst wetlands that form after permafrost thaw.
There are various sources of inorganic mercury that may indirectly contribute to the production of methylmercury from microbes in the environment. Natural sources of mercury released to the atmosphere include volcanoes, forest fires, volatilization from the ocean and weathering of mercury-bearing rocks. Anthropogenic sources of mercury include the burning of wastes containing inorganic mercury and from the burning of fossil fuels, particularly coal. Although inorganic mercury is only a trace constituent of such fuels, their large scale combustion in utility and commercial/industrial boilers in the United States alone results in release of some 80.2 tons (73 metric tons) of elemental mercury to the atmosphere each year, out of total anthropogenic mercury emissions in the United States of 158 tons (144 metric tons)/year.
In the past, methylmercury was produced directly and indirectly as part of several industrial processes such as the manufacture of acetaldehyde. However, currently there are few direct anthropogenic sources of methylmercury pollution in the United States.
Whole-lake ecosystem experiments at IISD-ELA in Ontario, Canada, showed that mercury falling directly on a lake had the fastest impacts on aquatic ecosystems as opposed to mercury falling on the surrounding land. This inorganic mercury is converted to methylmercury by bacteria. Different stable isotopes of mercury were added to lakes, wetlands, and uplands, simulating rain, and then mercury concentrations in fish were analyzed to find their source. The mercury applied to lakes was found in young-of-the-year yellow perch within two months, whereas the mercury applied to wetlands and uplands had a slower but longer influx.
Acute methylmercury poisoning can occur either directly from the release of methylmercury into the environment or indirectly from the release of inorganic mercury that is subsequently methylated in the environment. For example, methylmercury poisoning occurred at Grassy Narrows in Ontario, Canada (see Ontario Minamata disease), as a result of mercury released from the mercury-cell Chloralkali process, which uses liquid mercury as an electrode in a process that entails electrolytic decomposition of brine, followed by mercury methylation in the aquatic environment. An acute methylmercury poisoning tragedy occurred also in Minamata, Japan, following release of methylmercury into Minamata Bay and its tributaries (see Minamata disease). In the Ontario case, inorganic mercury discharged into the environment was methylated in the environment; whereas, in Minamata, Japan, there was direct industrial discharge of methylmercury. | 0 | Theoretical and Fundamental Chemistry |
This is related to the sampling rate of the analyser and the FFT rate. It is also important for the realtime spectrum analyzer to give good level accuracy.
Example: for an analyser with of realtime bandwidth (the maximum RF span that can be processed in realtime) approximately (complex) are needed. If the spectrum analyzer produces an FFT calculation is produced every For a FFT a full spectrum is produced approximately every This also gives us our overlap rate of 80% (20 μs − 4 μs) / 20 μs = 80%. | 0 | Theoretical and Fundamental Chemistry |
The isotopic ratios of a molecule can also be determined by isotope ratio mass spectrometry (IRMS), sample quantity for IRMS is much lower than for NMR, and there is the possibility of coupling the mass spectrometer to a chromatographic system to enable on-line purification or analyses of several components of a complex mixture. However the sample is burnt after a physical transformation such as combustion or pyrolysis. Therefore, it gives a mean value of the concentration of the isotope studied between all sites of the molecule. IRMS is the official AOAC technique used for the average ratio C/C (or δC) of sugars or ethanol, and the official CEN and OIV method for the 18O/16O in water.
The SNIF-NMR method (Site-Specific Natural Isotope Fractionation studied by Nuclear Magnetic Resonance) is able to determine, to a high level of accuracy, the isotopic ratios for each of the sites of the molecule, which enables a better discrimination. For example, for ethanol (CHCHOH), the three ratios ((D/H)CH, (D/H)CH and (D/H)) can be obtained. | 0 | Theoretical and Fundamental Chemistry |
At the time of discovery, it was the only homoleptic trimetallic non-carbonyl cluster featuring hydrocarbon ligands. An isolobal analogy can be made with the related Fe(CO) (μ-CO) cluster first prepared by Jones and Dewar.
Alternatively, the compound could be compared to ferrocene. In this interpretation, each iron fragment bears an η allyl and η pentadienyl ligand as depicted. Under Green and Parkin's covalent bond classification method, this would yield LX and LX respectively. Then additionally, the iron centers donate a pair of electrons into an adjacent empty iron orbital as an adduct (donor-acceptor pairs L and Z type), to overall yield MLX (18 electrons). In fact, the bond orders in ferrocene and Fe3(COT)3 are reported to be very similar.
In fact, Fe(CO) and the group 5 analogues, Ru(CO) and Os(CO) are also known to feature highly fluxional CO ligands in solution (and even in the solid state).
Hypoelectronic derivatives (M=Ti, Cr, V, Mn) of Fe(CH) would be predicted to have metal multiple bonds. Some somewhat related compounds, notably, Ti(CH) and Cr(CH) have been experimentally isolated. | 0 | Theoretical and Fundamental Chemistry |
Russian biochemist Aleksander Oparin and British biologist J.B.S. Haldane independently hypothesized in the 1920s that the first cells in early Earths oceans could be, in essence, coacervate droplets. Haldane used the term primordial soup to refer to the dilute mixture of organic molecules that could have built up as a result of reactions between inorganic building blocks such as ammonia, carbon dioxide and water, in presence of UV light as an energy source. Oparin proposed that simple building blocks with increasing complexity could organize locally, or self-assemble, to form protocells with living properties. He performed experiments based on Bungenberg de Jongs colloidal aggregates (coacervates) to encapsulate proteinoids and enzymes within protocells. Further work by chemists Sidney Fox, Kaoru Harada, Stanley Miller and Harold Urey further strengthened the theory that inorganic building blocks could increase in complexity and give rise to cell-like structures.
The Oparin-Haldane hypothesis established the foundations of research on the chemistry of abiogenesis, but the lipid-world and RNA-world scenarios have gained more attention since the 1980s with the work of Morowitz, Luisi and Szostak. However, recently, there has been a rising interest in coacervates as protocells, resonating with current findings that reactions too slow or unlikely in aqueous solutions can be significantly favored in such membraneless compartments. | 0 | Theoretical and Fundamental Chemistry |
Green roofs have been increasing in popularity in Australia over the past 10 years. Some of the early examples include the Freshwater Place residential tower in Melbourne (2002) with its Level 10 rooftop Half Acre Garden, CH2 building housing the Melbourne City Council (2006) – Australia's first 6-star Green Star Design commercial office building as certified by the Green Building Council of Australia, and Condor Tower (2005) with a lawn on the 4th floor.
Since 2008, city councils and influential business groups in Australia have become active promoting the benefits of green roofs. "The Blueprint to Green Roof Melbourne" is one program being run by the Committee for Melbourne. In 2010, the largest Australian green roof project was announced. The Victorian Desalination Project will have a "living tapestry" of 98,000 Australian indigenous plants over a roof area spanning more than . The roof will form part of the desalination plant's sophisticated roof system, designed to blend the building into the landscape, and provide acoustic protection, corrosion resistance, thermal control, and reduced maintenance.
In June 2014 ecological artist Lloyd Godman, with structural engineer Stuart Jones and environmental scientist Grant Harris collaborated to install an experiment using Tillandsia plants in extreme outdoor conditions at levels 92, 91, 65 and 56 on Eureka Tower in Melbourne, Australia. The selected air plants are extremely light, and are able to grow with no soil or watering system, and the plants have been checked at regular intervals since their installation and are still growing and flowering. One species; Tillandsia bergeri, has grown from a single shoot to several thriving colonies.
The project is now titled Tillandsia SWARM and has been expanded to include many other buildings across Australia, including Federation Square, National Gallery of Victoria and Essendon Airport. Godman has also experimented with Tillandsia plant screens that can be moved across skylights to create shade in summer and to allow in sun during winter. Temperature readings taken on a 40°C day in summer revealed that the surface temperature on the roof had reached 84°C, while the shadows cast by the plants had reduced the surface temperature on the roof to 51°C. | 1 | Applied and Interdisciplinary Chemistry |
To the left is the NFPA diamond as determined by the Safety Data Sheet, or SDS, by Fisher Scientific. There is minimal risk in handling the chemical. | 0 | Theoretical and Fundamental Chemistry |
Robert Howard Crabtree (born 17 April 1948) is a British-American chemist. He is serving as Conkey P. Whitehead Professor Emeritus of Chemistry at Yale University in the United States. He is a naturalized citizen of the United States. Crabtree is particularly known for his work on "Crabtree's catalyst" for hydrogenations, and his textbook on organometallic chemistry. | 0 | Theoretical and Fundamental Chemistry |
Life and particulate organic matter in the ocean have fundamentally shaped the planet. On the most basic level, particulate organic matter can be defined as both living and non-living matter of biological origin with a size of ≥0.2 μm in diameter, including anything from a small bacterium (0.2 μm in size) to blue whales (20 m in size). Organic matter plays a crucial role in regulating global marine biogeochemical cycles and events, from the Great Oxidation Event in Earth's early history to the sequestration of atmospheric carbon dioxide in the deep ocean. Understanding the distribution, characteristics, dynamics, and changes over time of particulate matter in the ocean is hence fundamental in understanding and predicting the marine ecosystem, from food web dynamics to global biogeochemical cycles. | 0 | Theoretical and Fundamental Chemistry |
Transuranic waste (TRU) is stated by U.S. regulations, and independent of state or origin, to be waste which has been contaminated with alpha emitting transuranic radionuclides possessing half-lives greater than 20 years and in concentrations greater than 100 nCi/g (3.7 MBq/kg).
Elements having atomic numbers greater than that of uranium are called transuranic. Elements within TRU are typically man-made and are known to contain americium-241 and several isotopes of plutonium. Because of the elements' longer half-lives, TRU is disposed of more cautiously than low level waste and intermediate level waste. In the U.S. it is a byproduct of weapons production, nuclear research and power production, and consists of protective gear, tools, residue, debris and other items contaminated with small amounts of radioactive elements (mainly plutonium).
Under U.S. law, TRU is further categorized into "contact-handled" (CH) and "remote-handled" (RH) on the basis of the radiation field measured on the waste container's surface. CH TRU has a surface dose rate not greater than 2 mSv per hour (200 mrem/h), whereas RH TRU has rates of 2 mSv/h or higher. CH TRU has neither the high radioactivity of high level waste, nor its high heat generation. In contrast, RH TRU can be highly radioactive, with surface dose rates up to 10 Sv/h (1000 rem/h).
The United States currently permanently disposes of TRU generated from defense nuclear activities at the Waste Isolation Pilot Plant, a deep geologic repository.
Other countries do not include this category, favoring variations of High, Medium/Intermediate, and Low Level waste. | 0 | Theoretical and Fundamental Chemistry |
A Flettner rotor mounted beneath the waterline of a ship's hull and emerging laterally will act to stabilize the ship in heavy seas. By controlling the direction and speed of rotation, strong lift or downforce can be generated. The largest deployment of the system to date is in the motor yacht Eclipse. | 1 | Applied and Interdisciplinary Chemistry |
The sample is dissolved in water, or a mixture of water and ethanol, and a few drops of neutral ferric chloride (FeCl) solution, which is prepared by adding de-ionised water. Add sodium hydroxide to the mixture until a permanent brown precipitate is formed. The formation of a red, blue, green, or purple coloration indicates the presence of phenols. Where the sample is insoluble in water, it may be dissolved in dichloromethane with a small amount of pyridine. | 0 | Theoretical and Fundamental Chemistry |
SIN3A has been shown to interact with:
* CABIN1
* HBP1,
* HDAC1,
* HDAC9,
* Histone deacetylase 2,
* Host cell factor C1,
* IKZF1,
* ING1,
* KLF11,
* MNT,
* MXD1,
* Methyl-CpG-binding domain protein 2,
* Nuclear receptor co-repressor 2,
* OGT,
* PHF12,
* Promyelocytic leukemia protein,
* RBBP4,
* RBBP7,
* SAP130,
* SAP30,
* SMARCA2,
* SMARCA4,
* SMARCC1,
* SUDS3,
* TAL1, and
* Zinc finger and BTB domain-containing protein 16. | 1 | Applied and Interdisciplinary Chemistry |
Armodafinil (trade name Nuvigil) is the enantiopure compound of the eugeroic modafinil (Provigil). It consists of only the (R)-(−)-enantiomer of the racemic modafinil. Armodafinil is produced by the pharmaceutical company Cephalon Inc. and was approved by the U.S. Food and Drug Administration (FDA) in June 2007. In 2016, the FDA granted Mylan rights for the first generic version of Cephalon's Nuvigil to be marketed in the U.S.
Because armodafinil has a longer half-life than modafinil does, it may be more effective at improving wakefulness in patients with excessive daytime sleepiness. | 0 | Theoretical and Fundamental Chemistry |
Stream restoration or river restoration, also sometimes referred to as river reclamation, is work conducted to improve the environmental health of a river or stream, in support of biodiversity, recreation, flood management and/or landscape development.
Stream restoration approaches can be divided into two broad categories: form-based restoration, which relies on physical interventions in a stream to improve its conditions; and process-based restoration, which advocates the restoration of hydrological and geomorphological processes (such as sediment transport or connectivity between the channel and the floodplain) to ensure a streams resilience and ecological health. Form-based restoration techniques include deflectors; cross-vanes; weirs, step-pools and other grade-control structures; engineered log jams; bank stabilization methods and other channel-reconfiguration efforts. These induce immediate change in a stream, but sometimes fail to achieve the desired effects if degradation originates at a wider scale. Process-based restoration includes restoring lateral or longitudinal connectivity of water and sediment fluxes and limiting interventions within a corridor defined based on the streams hydrology and geomorphology. The beneficial effects of process-based restoration projects may sometimes take time to be felt since changes in the stream will occur at a pace that depends on the stream dynamics.
Despite the significant number of stream-restoration projects worldwide, the effectiveness of stream restoration remains poorly quantified, partly due to insufficient monitoring. However, in response to growing environmental awareness, stream-restoration requirements are increasingly adopted in legislation in different parts of the world. | 1 | Applied and Interdisciplinary Chemistry |
In many kinds of breast cancer, aberrations in the PI3K/AKT/mTOR pathway are the most common genomic abnormalities. The most common known aberrations include the PIK3CA gene mutation and the loss-of-function mutations or epigenetic silencing of PTEN. The phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathway is activated in approximately 30–40% of BC cases. In triple-negative breast cancer (TNBC), oncogenic activation of the PI3K/AKT/mTOR pathway can happen as a function of overexpression of upstream regulators like EGFR, activating mutations of PIK3CA, loss of function or expression of phosphatase and tensin homolog (PTEN), and the proline-rich inositol polyphosphatase, which are downregulators of PI3K. It is consistent with the hypothesis that PI3K inhibitors can overcome resistance to endocrine therapy when it is acquired | 1 | Applied and Interdisciplinary Chemistry |
Sulfuric acid is non-flammable.
The main occupational risks posed by this acid are skin contact leading to burns (see above) and the inhalation of aerosols. Exposure to aerosols at high concentrations leads to immediate and severe irritation of the eyes, respiratory tract and mucous membranes: this ceases rapidly after exposure, although there is a risk of subsequent pulmonary edema if tissue damage has been more severe. At lower concentrations, the most commonly reported symptom of chronic exposure to sulfuric acid aerosols is erosion of the teeth, found in virtually all studies: indications of possible chronic damage to the respiratory tract are inconclusive as of 1997. Repeated occupational exposure to sulfuric acid mists may increase the chance of lung cancer by up to 64 percent. In the United States, the permissible exposure limit (PEL) for sulfuric acid is fixed at 1 mg/m: limits in other countries are similar. There have been reports of sulfuric acid ingestion leading to vitamin B12 deficiency with subacute combined degeneration. The spinal cord is most often affected in such cases, but the optic nerves may show demyelination, loss of axons and gliosis. | 0 | Theoretical and Fundamental Chemistry |
Oxazolidinones can be prepared from amino acids or readily available amino alcohols. A large number of oxazolidinones are commercially available, including the four below.
Acylation of the oxazolidinone is achieved by deprotonation with n-butyllithium and quench with an acyl chloride. | 0 | Theoretical and Fundamental Chemistry |
Many woody plants produce resins and antimicrobial chemicals to limit the spread of pathogens after an injury. | 1 | Applied and Interdisciplinary Chemistry |
In 1929, the conversion of oleic acid to stearic acid in the presence of hydrazine was observed. The short-lived intermediate diimide was not implicated in this reductive process until the 1960s. Since that time, several methods of generating transient amounts of diimide have been developed. In the presence of unpolarized alkenes, alkynes or allenes, diimide is converted into dinitrogen with reduction (net addition of dihydrogen) of the unsaturated functionality. Diimide formation is the rate-limiting step of the process, and a concerted mechanism involving cis-diimide has been proposed. This reduction represents a metal-free alternative to catalytic hydrogenation reductions, and does not lead to the cleavage of sensitive O–O and N–O bonds. | 0 | Theoretical and Fundamental Chemistry |
Alkylation is a chemical reaction that entails transfer of an alkyl group. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effecting alkylation. Alkyl groups can also be removed in a process known as dealkylation. Alkylating agents are often classified according to their nucleophilic or electrophilic character. In oil refining contexts, alkylation refers to a particular alkylation of isobutane with olefins. For upgrading of petroleum, alkylation produces a premium blending stock for gasoline. In medicine, alkylation of DNA is used in chemotherapy to damage the DNA of cancer cells. Alkylation is accomplished with the class of drugs called alkylating antineoplastic agents. | 0 | Theoretical and Fundamental Chemistry |
The alleles that cause heritable changes in the alleles they come into contact which are called paramutagenic, and the alleles modified by them are paramutable. Alleles that do not take part in this interaction are called neutral. When present together in an organism, the paramutable allele is converted to the paramutagenic allele, and retains its paramutagenicity in subsequent generations. No change in DNA sequence accompanies this transformation, but instead epigenetic modifications (e.g. DNA methylation) differentiate the paramutagenic from paramutable alleles. In most cases, it is the paramutable allele that is highly transcribed and the paramutagenic allele that undergoes little to no transcription.
The first described and most extensively researched example is the r1 locus in maize. The gene at this locus, when actively transcribed, codes for a transcription factor that promotes anthocyanin production, resulting in kernels with a purple color. One allele at this locus, referred to as B’, is capable of causing methylation at the other allele, B-I. This methylation results in reduced transcription and, as a result, decreased anthocyanin production. These alleles do not differ in DNA sequence, but they do differ in their degree of DNA methylation. As with other examples of paramutation, this change of the B-I allele to the B’ allele is stable and heritable. Other, similar examples of paramutation exist at other maize loci, as well as in other plants such as the model system Arabidopsis thaliana and transgenic petunias.
Paramutation has also been documented in animals such as fruit flies, C. elegans, and mice. | 1 | Applied and Interdisciplinary Chemistry |
Much experimentation has been done using solitons in fiber optics applications. Solitons in a fiber optic system are described by the Manakov equations.
Solitons' inherent stability make long-distance transmission possible without the use of repeaters, and could potentially double transmission capacity as well. | 1 | Applied and Interdisciplinary Chemistry |
Identifying the biological origin of a disease, and the potential targets for intervention, is the first step in the discovery of a medicine using the reverse pharmacology approach. Potential drug targets are not necessarily disease causing but must by definition be disease modifying. An alternative means of identifying new drug targets is forward pharmacology based on phenotypic screening to identify "orphan" ligands whose targets are subsequently identified through target deconvolution. | 1 | Applied and Interdisciplinary Chemistry |
Covalent organic frameworks (COFs) are a class of porous polymers that form two- or three-dimensional structures through reactions between organic precursors resulting in strong, covalent bonds to afford porous, stable, and crystalline materials. COFs emerged as a field from the overarching domain of organic materials as researchers optimized both synthetic control and precursor selection. These improvements to coordination chemistry enabled non-porous and amorphous organic materials such as organic polymers to advance into the construction of porous, crystalline materials with rigid structures that granted exceptional material stability in a wide range of solvents and conditions. Through the development of reticular chemistry, precise synthetic control was achieved and resulted in ordered, nano-porous structures with highly preferential structural orientation and properties which could be synergistically enhanced and amplified. With judicious selection of COF secondary building units (SBUs), or precursors, the final structure could be predetermined, and modified with exceptional control enabling fine-tuning of emergent properties. This level of control facilitates the COF material to be designed, synthesized, and utilized in various applications, many times with metrics on scale or surpassing that of the current state-of-the-art approaches. | 0 | Theoretical and Fundamental Chemistry |
The third most abundant trace metal in the human body.
It is found in cytochrome c oxidase, a protein necessary for the electron transport chain in mitochondria. | 0 | Theoretical and Fundamental Chemistry |
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