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Fick's second law is a special case of the convection–diffusion equation in which there is no advective flux and no net volumetric source. It can be derived from the continuity equation:
where is the total flux and is a net volumetric source for . The only source of flux in this situation is assumed to be diffusive flux:
Plugging the definition of diffusive flux to the continuity equation and assuming there is no source (), we arrive at Fick's second law:
If flux were the result of both diffusive flux and advective flux, the convection–diffusion equation is the result. | 0 | Theoretical and Fundamental Chemistry |
At the same temperature, a column of dry air will be denser or heavier than a column of air containing any water vapor, the molar mass of diatomic nitrogen and diatomic oxygen both being greater than the molar mass of water. Thus, any volume of dry air will sink if placed in a larger volume of moist air. Also, a volume of moist air will rise or be buoyant if placed in a larger region of dry air. As the temperature rises the proportion of water vapor in the air increases, and its buoyancy will increase. The increase in buoyancy can have a significant atmospheric impact, giving rise to powerful, moisture rich, upward air currents when the air temperature and sea temperature reaches 25 °C or above. This phenomenon provides a significant driving force for cyclonic and anticyclonic weather systems (typhoons and hurricanes). | 1 | Applied and Interdisciplinary Chemistry |
Most chloroplasts in a photosynthetic cell do not develop directly from proplastids or etioplasts. In fact, a typical shoot meristematic plant cell contains only 7–20 proplastids. These proplastids differentiate into chloroplasts, which divide to create the 30–70 chloroplasts found in a mature photosynthetic plant cell. If the cell divides, chloroplast division provides the additional chloroplasts to partition between the two daughter cells.
In single-celled algae, chloroplast division is the only way new chloroplasts are formed. There is no proplastid differentiation—when an algal cell divides, its chloroplast divides along with it, and each daughter cell receives a mature chloroplast.
Almost all chloroplasts in a cell divide, rather than a small group of rapidly dividing chloroplasts. Chloroplasts have no definite S-phase—their DNA replication is not synchronized or limited to that of their host cells.
Much of what we know about chloroplast division comes from studying organisms like Arabidopsis and the red alga Cyanidioschyzon merolæ.
The division process starts when the proteins FtsZ1 and FtsZ2 assemble into filaments, and with the help of a protein ARC6, form a structure called a Z-ring within the chloroplast's stroma. The Min system manages the placement of the Z-ring, ensuring that the chloroplast is cleaved more or less evenly. The protein MinD prevents FtsZ from linking up and forming filaments. Another protein ARC3 may also be involved, but it is not very well understood. These proteins are active at the poles of the chloroplast, preventing Z-ring formation there, but near the center of the chloroplast, MinE inhibits them, allowing the Z-ring to form.
Next, the two plastid-dividing rings, or PD rings form. The inner plastid-dividing ring is located in the inner side of the chloroplasts inner membrane, and is formed first. The outer plastid-dividing ring is found wrapped around the outer chloroplast membrane. It consists of filaments about 5 nanometers across, arranged in rows 6.4 nanometers apart, and shrinks to squeeze the chloroplast. This is when chloroplast constriction begins. <br />In a few species like Cyanidioschyzon merolæ, chloroplasts have a third plastid-dividing ring located in the chloroplasts intermembrane space.
Late into the constriction phase, dynamin proteins assemble around the outer plastid-dividing ring, helping provide force to squeeze the chloroplast. Meanwhile, the Z-ring and the inner plastid-dividing ring break down. During this stage, the many chloroplast DNA plasmids floating around in the stroma are partitioned and distributed to the two forming daughter chloroplasts.
Later, the dynamins migrate under the outer plastid dividing ring, into direct contact with the chloroplast's outer membrane, to cleave the chloroplast in two daughter chloroplasts.
A remnant of the outer plastid dividing ring remains floating between the two daughter chloroplasts, and a remnant of the dynamin ring remains attached to one of the daughter chloroplasts.
Of the five or six rings involved in chloroplast division, only the outer plastid-dividing ring is present for the entire constriction and division phase—while the Z-ring forms first, constriction does not begin until the outer plastid-dividing ring forms. | 0 | Theoretical and Fundamental Chemistry |
Fusion Nuclear Science Facility (FNSF) is a low cost, low aspect ratio compact tokamak reactor design, aiming for a 9 Tesla field at the plasma centre.
It is considered a step after ITER on the path to a fusion power plant.
Because of the high neutron irradiation damage expected, non-insulating superconducting coils are being considered for it. | 0 | Theoretical and Fundamental Chemistry |
Exome sequencing can be used to diagnose the genetic cause of disease in a patient. Identification of the underlying disease gene mutation(s) can have major implications for diagnostic and therapeutic approaches, can guide prediction of disease natural history, and makes it possible to test at-risk family members. There are many factors that make exome sequencing superior to single gene analysis including the ability to identify mutations in genes that were not tested due to an atypical clinical presentation or the ability to identify clinical cases where mutations from different genes contribute to the different phenotypes in the same patient.
Having diagnosed a genetic cause of a disease, this information may guide the selection of appropriate treatment. The first time this strategy was performed successfully in the clinic was in the treatment of an infant with inflammatory bowel disease. A number of conventional diagnostics had previously been used, but the results could not explain the infants symptoms. Analysis of exome sequencing data identified a mutation in the XIAP gene. Knowledge of this genes function guided the infant's treatment, leading to a bone marrow transplantation which cured the child of disease.
Researchers have used exome sequencing to identify the underlying mutation for a patient with Bartter Syndrome and congenital chloride diarrhea. Bilgular's group also used exome sequencing and identified the underlying mutation for a patient with severe brain malformations, stating "[These findings] highlight the use of whole exome sequencing to identify disease loci in settings in which traditional methods have proved challenging... Our results demonstrate that this technology will be particularly valuable for gene discovery in those conditions in which mapping has been confounded by locus heterogeneity and uncertainty about the boundaries of diagnostic classification, pointing to a bright future for its broad application to medicine".
Researchers at University of Cape Town, South Africa used exome sequencing to discover the genetic mutation of CDH2 as the underlying cause of a genetic disorder known as arrhythmogenic right ventricle cardiomyopathy (ARVC)‚ which increases the risk of heart disease and cardiac arrest. [https://www.news.uct.ac.za/article/-2017-03-10-uct-researchers-discover-heart-attack-gene] | 1 | Applied and Interdisciplinary Chemistry |
Donetsk Metallurgical Plant also called Donetsk Iron and Steel Works is an enterprise of Donetsk, Ukraine. It is a ferrous metallurgy enterprise that is located in the Leninskyi district of Donetsk. | 1 | Applied and Interdisciplinary Chemistry |
A DNase footprinting assay is a DNA footprinting technique from molecular biology/biochemistry that detects DNA-protein interaction using the fact that a protein bound to DNA will often protect that DNA from enzymatic cleavage. This makes it possible to locate a protein binding site on a particular DNA molecule. The method uses an enzyme, deoxyribonuclease (DNase, for short), to cut the radioactively end-labeled DNA, followed by gel electrophoresis to detect the resulting cleavage pattern.
For example, the DNA fragment of interest may be PCR amplified using a P 5' labeled primer, with the result being many DNA molecules with a radioactive label on one end of one strand of each double stranded molecule. Cleavage by DNase will produce fragments. The fragments which are smaller with respect to the P-labelled end will appear further on the gel than the longer fragments. The gel is then used to expose a special photographic film.
The cleavage pattern of the DNA in the absence of a DNA binding protein, typically referred to as free DNA, is compared to the cleavage pattern of DNA in the presence of a DNA binding protein. If the protein binds DNA, the binding site is protected from enzymatic cleavage. This protection will result in a clear area on the gel which is referred to as the "footprint".
By varying the concentration of the DNA-binding protein, the binding affinity of the protein can be estimated according to the minimum concentration of protein at which a footprint is observed.
This technique was developed by David J. Galas and Albert Schmitz at Geneva in 1977 | 1 | Applied and Interdisciplinary Chemistry |
In hydrology, studies of water quality concern organic and inorganic compounds, and both dissolved and sediment material. In addition, water quality is affected by the interaction of dissolved oxygen with organic material and various chemical transformations that may take place. Measurements of water quality may involve either in-situ methods, in which analyses take place on-site, often automatically, and laboratory-based analyses and may include microbiological analysis. | 1 | Applied and Interdisciplinary Chemistry |
Green death is a solution used to test the resistance of metals and alloys to corrosion. It consists of a mixture of sulfuric acid, hydrochloric acid, iron(III) chloride and copper(II) chloride and its boiling point is at approximately 103 °C. Its typical chemical composition is given in the table hereafter:
The chemical composition of the green death solution allows it to achieve a particularly aggressive oxidizing chloride solution. Indeed, among the four reagents, all are oxidizing species (, , ) except hydrochloric acid (HCl) in which the chlorine atom is present in its lowest oxidation state as anion. The chloride anions, also added to the solution as counter-ions of iron(III) and copper(II) species, are very aggressive for the localized corrosion of metals and alloys as they induce severe pitting corrosion problems. The green death solution is also used to determine the critical pitting temperature (CPT) and the critical crevice temperature (CCT) of metals and alloys. | 1 | Applied and Interdisciplinary Chemistry |
Some necessary apparatus include:
* crucible (or similar porcelain or metal dishes)
* muffled furnace
* hot plate
* the sample | 0 | Theoretical and Fundamental Chemistry |
He has been involved in many editorial boards of scientific journals. He was member of the editorial board of the Journal of Applied Electrochemistry (1988-2010), [http://www.scielo.cl/scielo.php?script=sci_serial&pid=0717-9707&lng=es&nrm=iso Journal of the Chilean Chemical Society] (1984-2007) and Electrocatalysis (2010-2015) and is presently member of the Editorial Board of several international publications: [https://link.springer.com/journal/10008 Journal of Solid State Electrochemistry] (Springer), [http://www.hindawi.com/journals/ijelc/ International Journal of Electrochemistry] (Hindawi), [http://www.journals.elsevier.com/electrochemistry-communications/ Electrochemistry Communications] (Elsevier), [https://web.archive.org/web/20141003071519/http://www.shd.org.rs/JSCS/ Journal of the Serbian Chemical Society], [http://www.degruyter.com/view/j/eetech Electrochemical Energy Technology] (De Goutyer) and [http://www.scielo.br/revistas/qn/iedboard.htm Chimica Nova] and Frontiers in Chemistry. He has been a Guest Editor for the Journal of Applied Electrochemistry, Current Opinion in Electrochemistry and for the International Journal of Electrochemistry. | 0 | Theoretical and Fundamental Chemistry |
The Boltzmann constant ( or ) is the proportionality factor that relates the average relative thermal energy of particles in a gas with the thermodynamic temperature of the gas. It occurs in the definitions of the kelvin and the gas constant, and in Plancks law of black-body radiation and Boltzmanns entropy formula, and is used in calculating thermal noise in resistors. The Boltzmann constant has dimensions of energy divided by temperature, the same as entropy. It is named after the Austrian scientist Ludwig Boltzmann.
As part of the 2019 redefinition of SI base units, the Boltzmann constant is one of the seven "defining constants" that have been given exact definitions. They are used in various combinations to define the seven SI base units. The Boltzmann constant is defined to be exactly . | 0 | Theoretical and Fundamental Chemistry |
The streaming vibration current was experimentally observed in 1948 by Williams. A theoretical model was developed some 30 years later by Dukhin and others. This effect opens another possibility for characterizing the electric properties of the surfaces in porous bodies. A similar effect can be observed at a non-porous surface, when sound is bounced off at an oblique angle. The incident and reflected waves superimpose to cause oscillatory fluid motion in the plane of the interface, thereby generating an AC streaming current at the frequency of the sound waves. | 0 | Theoretical and Fundamental Chemistry |
Constant head is important in simplifying constraint when measuring the movement of water in soil. Several measurement techniques employ the Mariottes bottle to provide constant head. The Guelph Permeameter measures unsaturated hydraulic conductivity in the field and uses this principle to create a constant head. Single and double ring infiltrometers can also use the Marriottes bottle.
Another application is a similar arrangement in some fuel tanks used in control line model airplanes, where it is called a "uniflow" tank, where the tank venting tubing goes to the end of the prismatic tank, close to the fuel pick-up tube that feeds the engine; thus, when fuel is consumed, the uniflow tank supplies approximately the same pressure, regardless of the quantity of fuel that remains in the tank for the rest of the flight, which keeps the same carburetor calibration and air-fuel ratio. | 1 | Applied and Interdisciplinary Chemistry |
The Cassie–Baxter wetting regime also explains the water repellent features of the pennae (feathers) of a bird. The feather consists of a topography network of barbs and barbules and a droplet that is deposited on a these resides in a solid-liquid-air non-wetting composite state, where tiny air pockets are trapped within. | 0 | Theoretical and Fundamental Chemistry |
After postdoctoral stints in Minnesota and California, he moved to UiT – The Arctic University of Norway in 1996, where he has remained ever since. He has had several secondary positions/affiliations: Senior Fellow of the San Diego Supercomputer Center at the University of California San Diego (1997–2004), Outstanding Younger Researcher awardee of the Research Council of Norway (2004–2010), a co-principal investigator at the national center of excellence Centre for Theoretical and Computational Chemistry (2007–2017), and a visiting professor at the University of Auckland, New Zealand, on many occasions (2006–2016). He edited two books, The Smallest Biomolecules: Diatomics and their Interactions with Heme Proteins (Elsevier, 2008), a monograph on the subject, and Letters to a Young Chemist (Wiley, 2011), a popular science book on careers in chemistry research. In 2014, he coauthored Arrow Pushing in Inorganic Chemistry: A Logical Approach to the Chemistry of the Main Group Elements (Wiley) with Steffen Berg, which won the 2015 Prose Award for best textbook in the Physical Sciences and Mathematics. He has served on the editorial advisory board of the Journal of Biological Inorganic Chemistry (1999–2001, 2005–2007) and currently serves on the editorial boards of the Journal of Porphyrins and Phthalocyanines (2000–) and Journal of Inorganic Biochemistry (2007–present). He has authored/coauthored over 250 scientific papers, which have been cited over 12,000 times with an h-index of 64 (according to Google Scholar). In 2022, he received the Hans Fischer Career Award for lifetime contributions to porphyrin science. He is a member of several national and international academies including the European Academy of Sciences and the Academia Europaea. | 0 | Theoretical and Fundamental Chemistry |
One of the effects of transannular strain is the difficulty of synthesizing medium-sized rings. Illuminati et al. have studied the kinetics of intramolecular ring closing using the simple nucleophilic substitution reaction of ortho-bromoalkoxyphenoxides. Specifically, they studied the ring closing of 5 to 10 carbon cyclic ethers. They found that as the number of carbons increased, so did the enthalpy of activation for the reaction. This indicates that strain within the cyclic transition states is higher if there are more carbons in the ring. Since transannular strain is the largest source of strain in rings this size, the larger enthalpies of activation result in much slower cyclizations due to transannular interactions in the cyclic ethers. | 0 | Theoretical and Fundamental Chemistry |
There are five main methodologies to create coordination cages. In directional bonding, also called edge-directed self-assembly, polyhedra are designed using a stoichiometric ratio of ligand to metal precursor. The symmetry interaction method involves combining naked metal ions with multibranched chelating ligands. This results in highly symmetric cages. The molecular paneling method, also called the face-directed method, was the method developed by Fujita.
Here, rigid ligands act as panels and coordination complexes join them together to create the shape. In the figure at left, the yellow triangles represent panel ligands, and the blue dots are metal complexes. The ligands of the complex itself helps enforce the final geometry.
In the weak link method, a hemilabile ligand is used: a weak metal-heteroatom bond is the weak link. The formation of the complexes is driven by favorable π-π interactions between the spacers and the ligands, as well as the chelation of the metal. The metals used in the assembly must be available to perform further in the final structure, without compromising the cage structure. The initial structure is referred to as condensed. In the condensed structure, the weak M-X bond can be selectively replaced by introducing an ancillary ligand with a higher binding affinity, leading to an open cage structure. In the figure to the right, the M is the metal, the orange ellipses are ligands, and the A is the ancillary ligand. For the dimetallic building block method, two pieces are needed: the metal dimer and its nonlinking ligands, and linking ligands. The nonlinking ligands need to be relatively nonlabile, and not too bulky; amidinates, for instance, work well. The linking ligands are either equatorial or axial: equatorial ligands are small polycarboxylato anions, and axial linkers are usually rigid aromatic structures. Axial and equatorial ligands may be used separately or in combination, depending on the desired cage structure. | 0 | Theoretical and Fundamental Chemistry |
Phenolphthalein's common use is as an indicator in acid-base titrations. It also serves as a component of universal indicator, together with methyl red, bromothymol blue, and thymol blue.
Phenolphthalein adopts different forms in aqueous solution depending on the pH of the solution. Inconsistency exists in the literature about hydrated forms of the compounds and the color of sulfuric acid. Wittke reported in 1983 that it exists in protonated form (HIn) under strongly acidic conditions, providing an orange coloration. However, a later paper suggested that this color is due to sulfonation to phenolsulfonphthalein.
The lactone form (HIn) is colorless between strongly acidic and slightly basic conditions. The doubly deprotonated (In) phenolate form (the anion form of phenol) gives the familiar pink color. In strongly basic solutions, phenolphthalein is converted to its In(OH) form, and its pink color undergoes a rather slow fading reaction and becomes completely colorless when pH is greater than 13.
The pK values of phenolphthalein were found to be 9.05, 9.50 and 12 while those of phenolsulfonphthalein are 1.2 and 7.70. | 0 | Theoretical and Fundamental Chemistry |
The sun bombards the earth with billions of charged nanoparticles with an immense amount of energy stored in them. This energy can be used for water heating, space heating, space cooling and process heat generation. Many steam generation systems have adapted to using sunlight as a primary source for heating feed water, a development that has greatly increased the overall efficiency of boilers and many other types of waste heat recovery systems. Solar cookers use sunlight for cooking, drying and pasteurization. Solar distillation is used for water treatment processes to create potable drinking water, which has been an extremely powerful player in providing countries in need with relief efforts through the use of advancing technology. | 0 | Theoretical and Fundamental Chemistry |
In economic geology, the term humate refers to geological materials, such as weathered coal beds (leonardite), mudrock, or pore material in sandstones, that are rich in humic acids. Humate has been mined from the Fruitland Formation of New Mexico for use as a soil amendment since the 1970s, with nearly 60,000 metric tons produced by 2016. Humate deposits may also play an important role in the genesis of uranium ore bodies. | 0 | Theoretical and Fundamental Chemistry |
Waste from nuclear weapons decommissioning is unlikely to contain much beta or gamma activity other than tritium and americium. It is more likely to contain alpha-emitting actinides such as Pu-239 which is a fissile material used in bombs, plus some material with much higher specific activities, such as Pu-238 or Po.
In the past the neutron trigger for an atomic bomb tended to be beryllium and a high activity alpha emitter such as polonium; an alternative to polonium is Pu-238. For reasons of national security, details of the design of modern bombs are normally not released to the open literature.
Some designs might contain a radioisotope thermoelectric generator using Pu-238 to provide a long-lasting source of electrical power for the electronics in the device.
It is likely that the fissile material of an old bomb which is due for refitting will contain decay products of the plutonium isotopes used in it, these are likely to include U-236 from Pu-240 impurities, plus some U-235 from decay of the Pu-239; due to the relatively long half-life of these Pu isotopes, these wastes from radioactive decay of bomb core material would be very small, and in any case, far less dangerous (even in terms of simple radioactivity) than the Pu-239 itself.
The beta decay of Pu-241 forms Am-241; the in-growth of americium is likely to be a greater problem than the decay of Pu-239 and Pu-240 as the americium is a gamma emitter (increasing external-exposure to workers) and is an alpha emitter which can cause the generation of heat. The plutonium could be separated from the americium by several different processes; these would include pyrochemical processes and aqueous/organic solvent extraction. A truncated PUREX type extraction process would be one possible method of making the separation. Naturally occurring uranium is not fissile because it contains 99.3% of U-238 and only 0.7% of U-235. | 0 | Theoretical and Fundamental Chemistry |
microRNA mediated repression occurs in two ways, either by translational repression or stimulating mRNA decay. miRNA recruit the RISC complex to the mRNA to which they are bound. The link to P-bodies comes by the fact that many, if not most, of the proteins necessary for miRNA gene silencing are localized to P-bodies, as reviewed by Kulkarni et al. (2010). These proteins include, but are not limited to, the scaffold protein GW182, Argonaute (Ago), decapping enzymes and RNA helicases.
The current evidence points toward P-bodies as being scaffolding centers of miRNA function, especially due to the evidence that a knock down of GW182 disrupts P-body formation. However, there remain many unanswered questions about P-bodies and their relationship to miRNA activity. Specifically, it is unknown whether there is a context dependent (stress state versus normal) specificity to the P-body's mechanism of action. Based on the evidence that P-bodies sometimes are the site of mRNA decay and sometimes the mRNA can exit the P-bodies and re-initiate translation, the question remains of what controls this switch. Another ambiguous point to be addressed is whether the proteins that localize to P-bodies are actively functioning in the miRNA gene silencing process or whether they are merely on standby. | 1 | Applied and Interdisciplinary Chemistry |
The acylurea functional group is also found in some pharmaceutical drugs such as the anticonvulsants phenacemide, pheneturide, chlorphenacemide, and acetylpheneturide (which are phenylureides), and the sedatives acecarbromal, bromisoval, and carbromal (which are bromoureides). Others include apronal (apronalide), capuride, and ectylurea. Barbiturates (a class of cyclic ureas) are structurally and mechanistically related to them. The phenylureides are also closely related to the hydantoins, such as phenytoin, and may be considered ring-opened analogues of them. | 0 | Theoretical and Fundamental Chemistry |
Karrers early research concerned complex metal compounds but his most important work has concerned plant pigments, particularly the yellow carotenoids. He elucidated their chemical structure and showed that some of these substances are transformed in the body into vitamin A. His work led to the establishment of the correct constitutional formula for beta-carotene, the chief precursor of vitamin A; the first time that the structure of a vitamin or provitamin had been established. George Wald worked briefly in Karrers lab while studying the role of vitamin A in the retina. Later, Karrer confirmed the structure of ascorbic acid (vitamin C) and extended his researches into the vitamin B and E. His important contributions to the chemistry of the flavins led to identification of lactoflavin as part of the complex originally thought to be vitamin B.
Karrer published many papers, and received many honours and awards, including the Nobel Prize in 1937. His textbook Lehrbuch der Organischen Chemie (Textbook of Organic Chemistry) was published in 1927, went through thirteen editions, and was published in seven languages. | 0 | Theoretical and Fundamental Chemistry |
Poolman has received numerous awards, including the Biochemistry Award (1989) of the Dutch Biochemistry and Molecular Biology Organisation (NVBMB), a Royal Netherlands Academy of Arts and Sciences fellowship (1989), a Human Frontiers Science Program Organization award (1992), the SON ‘Jonge Chemici’ award (1997), the Federation European Biochemical Society Lecturer Award (2014), and the Joel Mandelstam Memorial Lecture award (2016).
He obtained four TOP program grants from the Netherlands Organisation for Scientific Research (NWO)(2001, 2007, 2010, 2014)., two program grants from the Netherlands Proteomics Centre (2005 en 2008), and coordinated three large European networks (1996, 1999 and 2012). In 2015 he received an ERC Advanced Grant and in 2019 an ERC Proof-of-Concept Grant, and in 2017 the BaSyC consortium (with Poolman as one of the lead principal investigators) was awarded a multimillion Dutch Gravitation grant. | 0 | Theoretical and Fundamental Chemistry |
Methenamine silver stains are used for staining in histology, including the following types:
*Grocott's methenamine silver stain, used widely as a screen for fungal organisms.
*Jones' stain, a methenamine silver-Periodic acid-Schiff that stains for basement membrane, availing to view the "spiked" Glomerular basement membrane associated with membranous glomerulonephritis. | 0 | Theoretical and Fundamental Chemistry |
Most photosynthetic organisms are photoautotrophs, which means that they are able to synthesize food directly from carbon dioxide and water using energy from light. However, not all organisms use carbon dioxide as a source of carbon atoms to carry out photosynthesis; photoheterotrophs use organic compounds, rather than carbon dioxide, as a source of carbon.
In plants, algae, and cyanobacteria, photosynthesis releases oxygen. This oxygenic photosynthesis is by far the most common type of photosynthesis used by living organisms. Some shade-loving plants (sciophytes) produce such low levels of oxygen during photosynthesis that they use all of it themselves instead of releasing it to the atmosphere.
Although there are some differences between oxygenic photosynthesis in plants, algae, and cyanobacteria, the overall process is quite similar in these organisms. There are also many varieties of anoxygenic photosynthesis, used mostly by bacteria, which consume carbon dioxide but do not release oxygen.
Carbon dioxide is converted into sugars in a process called carbon fixation; photosynthesis captures energy from sunlight to convert carbon dioxide into carbohydrates. Carbon fixation is an endothermic redox reaction. In general outline, photosynthesis is the opposite of cellular respiration: while photosynthesis is a process of reduction of carbon dioxide to carbohydrates, cellular respiration is the oxidation of carbohydrates or other nutrients to carbon dioxide. Nutrients used in cellular respiration include carbohydrates, amino acids and fatty acids. These nutrients are oxidized to produce carbon dioxide and water, and to release chemical energy to drive the organism's metabolism.
Photosynthesis and cellular respiration are distinct processes, as they take place through different sequences of chemical reactions and in different cellular compartments.
The general equation for photosynthesis as first proposed by Cornelis van Niel is:
Since water is used as the electron donor in oxygenic photosynthesis, the equation for this process is:
This equation emphasizes that water is both a reactant in the light-dependent reaction and a product of the light-independent reaction, but canceling n water molecules from each side gives the net equation:
Other processes substitute other compounds (such as arsenite) for water in the electron-supply role; for example some microbes use sunlight to oxidize arsenite to arsenate: The equation for this reaction is:
: + + → + (used to build other compounds in subsequent reactions)
Photosynthesis occurs in two stages. In the first stage, light-dependent reactions or light reactions capture the energy of light and use it to make the hydrogen carrier NADPH and the energy-storage molecule ATP. During the second stage, the light-independent reactions use these products to capture and reduce carbon dioxide.
Most organisms that use oxygenic photosynthesis use visible light for the light-dependent reactions, although at least three use shortwave infrared or, more specifically, far-red radiation.
Some organisms employ even more radical variants of photosynthesis. Some archaea use a simpler method that employs a pigment similar to those used for vision in animals. The bacteriorhodopsin changes its configuration in response to sunlight, acting as a proton pump. This produces a proton gradient more directly, which is then converted to chemical energy. The process does not involve carbon dioxide fixation and does not release oxygen, and seems to have evolved separately from the more common types of photosynthesis. | 0 | Theoretical and Fundamental Chemistry |
SEOP has successfully been used and is fairly well developed for He, Xe, and Kr for biomedical applications. Additionally, several improvements are under way to get enhanced and interpretable imaging of cancer cells in biomedical science. Studies involving hyperpolarization of Xe are underway, piquing the interest of physicists. There are also improvements being made to allow not only rubidium to be utilized in the spin transfer, but also cesium. In principle, any alkali metal can be used for SEOP, but rubidium is usually preferred due to its high vapor pressure, allowing experiments to be carried out at relatively low temperatures (80 °C-130 °C), decreasing the chance of damaging the glass cell. Additionally, laser technology for the alkali metal of choice has to exist and be developed enough get substantial polarization. Previously, the lasers available to excite the D cesium transition were not well-developed, but they are now becoming more powerful and less expensive. Preliminary studies even show that cesium may provide better results than rubidium, even though rubidium has been the go-to alkali metal of choice for SEOP.
The hyperpolarization method called spin-exchange optical pumping (SEOP) is being used to hyperpolarize noble gases such as Xenon-129 and Helium-3. When an inhaled hyperpolarized gas like 3He or 129Xe is imaged, there is a higher magnetization density of NMR-active molecules in the lung compared to traditional 1H imaging, which improves the MRI images that can be obtained. Unlike proton MRI which reports on anatomical features of lung tissues, XenonMRI reports lung function including gas ventilation, diffusion, and perfusion. | 0 | Theoretical and Fundamental Chemistry |
In colloidal chemistry, the critical micelle concentration (CMC) of a surfactant is one of the parameters in the Gibbs free energy of micellization. The concentration at which the monomeric surfactants self-assemble into thermodynamically stable aggregates is the CMC. The Krafft temperature of a surfactant is the lowest temperature required for micellization to take place. There are many parameters that affect the CMC. The interaction between the hydrophilic heads and the hydrophobic tails play a part, as well as the concentration of salt within the solution and surfactants. | 0 | Theoretical and Fundamental Chemistry |
On September 11, 2007, Sepracor signed a marketing deal with British pharmaceutical company GlaxoSmithKline for the rights to sell eszopiclone (under the name Lunivia rather than Lunesta) in Europe. Sepracor was expected to receive approximately $155 million if the deal went through. In 2008 Sepracor submitted an application to the EMA (the European Unions equivalent to the U.S. FDA) for authorization to market the drug in the EU, and initially received a favorable response. However, Sepracor withdrew its authorization application in 2009 after the EMA stated it would not be granting eszopiclone new active substance status, as it was essentially pharmacologically and therapeutically too similar to zopiclone to be considered a new patentable product. Since the patent on zopiclone has expired, this ruling would have allowed rival companies to also legally produce cheaper generic versions of eszopiclone for the European market. , Sepracor has not resubmitted its authorization application and eszopiclone is not available in Europe. The deal with GSK fell through, and GSK instead launched a $3.3 billion deal to market Actelions almorexant sleeping tablet, which entered phase 3 medical trials before development was abandoned due to side effects. | 0 | Theoretical and Fundamental Chemistry |
DEAD is an orange-red liquid which weakens its color to yellow or colorless upon dilution or chemical reaction. This color change is conventionally used for visual monitoring of the synthesis. DEAD dissolves in most common organic solvents, such as toluene, chloroform, ethanol, tetrahydrofuran and dichloromethane but has low solubility in water or carbon tetrachloride; the solubility in water is higher for the related azo compound dimethyl azodicarboxylate.
DEAD is a strong electron acceptor and easily oxidizes a solution of sodium iodide in glacial acetic acid. It also reacts vigorously with hydrazine hydrate producing diethyl hydrazodicarboxylate and evolving nitrogen. Linear combination of atomic orbitals molecular orbital method (LCAO-MO) calculations suggest that the molecule of DEAD is unusual in having a high-lying vacant bonding orbital, and therefore tends to withdraw hydrogen atoms from various hydrogen donors. Photoassisted removal of hydrogen by DEAD was demonstrated for isopropyl alcohol, resulting in pinacol and tetraethyl tetrazanetetracarboxylate, and for acetaldehyde yielding diacetyl and diethyl hydrazodicarboxylate. Similarly, reacting DEAD with ethanol and cyclohexanol abstracts hydrogen producing acetaldehyde and cyclohexanone. Those reactions also proceed without light, although at much lower yields.
Thus, in general DEAD is an aza-dienophile and dehydrogenating agent, converting alcohols to aldehydes, thiols to disulfides and hydrazo groups to azo groups. It also undergoes pericyclic reactions with alkenes and dienes via ene and Diels–Alder mechanisms. | 0 | Theoretical and Fundamental Chemistry |
Cells require a full and functional cellular machinery to live. When they belong to complex multicellular organisms, they need to communicate among themselves and work for symbiosis in order to give life to the organism. These communications between cells triggers intracellular signaling cascades, termed signal transduction pathways, that regulate specific cellular functions. Each signal transduction occurs with a primary extracellular messenger that binds to a transmembrane or nuclear receptor, initiating intracellular signals. The complex formed produces or releases second messengers that integrate and adapt the signal, amplifying it, by activating molecular targets, which in turn trigger effectors that will lead to the desired cellular response. | 0 | Theoretical and Fundamental Chemistry |
The primary sources of mold exposure are from the indoor air in buildings with substantial mold growth and the ingestion of food with mold growths. | 1 | Applied and Interdisciplinary Chemistry |
Figure 9 depicts a heat-conduction experiment between two temperatures T and T connected by a tube filled with He-II. When heat is applied to the hot end a pressure builds up at the hot end according to Eq.. This pressure drives the normal component from the hot end to the cold end according to
Here η is the viscosity of the normal component, Z some geometrical factor, and the volume flow. The normal flow is balanced by a flow of the superfluid component from the cold to the hot end. At the end sections a normal to superfluid conversion takes place and vice versa. So heat is transported, not by heat conduction, but by convection. This kind of heat transport is very effective, so the thermal conductivity of He-II is very much better than the best materials. The situation is comparable with heat pipes where heat is transported via gas–liquid conversion. The high thermal conductivity of He-II is applied for stabilizing superconducting magnets such as in the Large Hadron Collider at CERN. | 1 | Applied and Interdisciplinary Chemistry |
The product is manufactured by hydrogenation of methylene diphenyl diisocyanate. It may also be manufactured by phosgenation of 4,4-Diaminodicyclohexylmethane. | 0 | Theoretical and Fundamental Chemistry |
In genetics, a silencer is a DNA sequence capable of binding transcription regulation factors, called repressors. DNA contains genes and provides the template to produce messenger RNA (mRNA). That mRNA is then translated into proteins. When a repressor protein binds to the silencer region of DNA, RNA polymerase is prevented from transcribing the DNA sequence into RNA. With transcription blocked, the translation of RNA into proteins is impossible. Thus, silencers prevent genes from being expressed as proteins.
RNA polymerase, a DNA-dependent enzyme, transcribes the DNA sequences, called nucleotides, in the 3 to 5 direction while the complementary RNA is synthesized in the 5 to 3 direction. RNA is similar to DNA, except that RNA contains uracil, instead of thymine, which forms a base pair with adenine. An important region for the activity of gene repression and expression found in RNA is the 3 untranslated region. This is a region on the 3 terminus of RNA that will not be translated to protein but includes many regulatory regions.
Not much is yet known about silencers but scientists continue to study in hopes to classify more types, locations in the genome, and diseases associated with silencers. | 1 | Applied and Interdisciplinary Chemistry |
* Maryland Chemist of the Year Award (American Chemical Society Maryland Section), 2011
* F. Albert Cotton Award in Synthetic Inorganic Chemistry, 2009
* 2009 Sierra Nevada Distinguished Chemist Award
* Appointed to Ira Remsen Chair in Chemistry, Johns Hopkins University, May 1999.
* Elected Chair, 1998 Metals in Biology Gordon Research Conference
* "MERIT" Award, 1993–2003, National Institute of General Medical Sciences (NIH)
* Fellow, American Association for the Advancement of Science (AAAS) – elected October, 1992
* 1991 Buck-Whitney Award (ACS Eastern New York Section Research Award)
* University "Excellence in Research" Award, SUNY at Albany, 1988
* General Electric Visiting Faculty Research Fellow, GE R&D Center, Schenectady, NY, 1986–87 | 0 | Theoretical and Fundamental Chemistry |
Lanthanum acetate is an inorganic compound, a salt of lanthanum with acetic acid with the chemical formula . | 0 | Theoretical and Fundamental Chemistry |
In general, biosignatures can be grouped into ten broad categories:
#Isotope patterns: Isotopic evidence or patterns that require biological processes.
#Chemistry: Chemical features that require biological activity.
#Organic matter: Organics formed by biological processes.
#Minerals: Minerals or biomineral-phases whose composition and/or morphology indicate biological activity (e.g., biomagnetite).
#Microscopic structures and textures: Biologically formed cements, microtextures, microfossils, and films.
#Macroscopic physical structures and textures: Structures that indicate microbial ecosystems, biofilms (e.g., stromatolites), or fossils of larger organisms.
#Temporal variability: Variations in time of atmospheric gases, reflectivity, or macroscopic appearance that indicates life's presence.
#Surface reflectance features: Large-scale reflectance features due to biological pigments could be detected remotely.
#Atmospheric gases: Gases formed by metabolic and/or aqueous processes, which may be present on a planet-wide scale.
#Technosignatures: Signatures that indicate a technologically advanced civilization. | 1 | Applied and Interdisciplinary Chemistry |
Roberts was made a fellow of the American Association for the Advancement of Science, and a chemistry professorship at Wellesley now bears her name. | 0 | Theoretical and Fundamental Chemistry |
Crystallographic directions are lines linking nodes (atoms, ions or molecules) of a crystal. Similarly, crystallographic planes are planes linking nodes. Some directions and planes have a higher density of nodes; these dense planes have an influence on the behavior of the crystal:
*optical properties: in condensed matter, light "jumps" from one atom to the other with the Rayleigh scattering; the velocity of light thus varies according to the directions, whether the atoms are close or far; this gives the birefringence
*adsorption and reactivity: adsorption and chemical reactions can occur at atoms or molecules on crystal surfaces, these phenomena are thus sensitive to the density of nodes;
*surface tension: the condensation of a material means that the atoms, ions or molecules are more stable if they are surrounded by other similar species; the surface tension of an interface thus varies according to the density on the surface
** Pores and crystallites tend to have straight grain boundaries following dense planes
**cleavage
*dislocations (plastic deformation)
**the dislocation core tends to spread on dense planes (the elastic perturbation is "diluted"); this reduces the friction (Peierls–Nabarro force), the sliding occurs more frequently on dense planes;
**the perturbation carried by the dislocation (Burgers vector) is along a dense direction: the shift of one node in a dense direction is a lesser distortion;
**the dislocation line tends to follow a dense direction, the dislocation line is often a straight line, a dislocation loop is often a polygon.
For all these reasons, it is important to determine the planes and thus to have a notation system. | 0 | Theoretical and Fundamental Chemistry |
Fecal Sludge is often processed through a series of treatment steps to first separate the liquids from the solids, and then treat both the liquid and solid trains while recovering as much of the energy or nutritive value as possible. Common processes at fecal sludge treatment plants include:
* Fecal sludge reception – where the truck interfaces with the treatment plant and sludge is unloaded.
* Preliminary treatment – to remove garbage, sand, grit, and FOG (fats, oil and grease)
* Primary treatment – simple separation of liquid and solids by physical means (dewatering and thickening), e.g. with drying beds
* Liquids treatment – for example by using constructed wetlands, waste stabilization ponds, anaerobic digesters
* Solids processing – using the solids resulting from fecal sludge treatment for beneficial use where possible.
Constructed wetlands are gaining attention as a low-cost treatment technology that can be constructed in many instances using local materials and labor. For sites with enough land and a ready supply of gravel and sand, this technology offers low cost, scalability, and simple operation. | 1 | Applied and Interdisciplinary Chemistry |
The first magnesium transporter isolated in any multicellular organism, AtMHX shows no similarity to any previously isolated Mg transport protein. The gene was initially identified in the A. thaliana genomic DNA sequence database, by its similarity to the SLC8 family of Na+/Ca exchanger genes in humans.
The cDNA sequence of 1990 bp is predicted to produce a 539-amino acid protein. AtMHX is quite closely related to the SLC8 family at the amino acid level and shares a topology with eleven predicted TM domains (Figure A10.5). There is one major difference in the sequence, in that the long non-membranal loop (see Figure A10.5) is 148 amino acids in the AtMHX protein but 500 amino acids in the SLC8 proteins. However, this loop is not well conserved and is not required for transport function in the SLC8 family.
The AtMHX gene is expressed throughout the plant but most strongly in the vascular tissue. The authors suggest that the physiological role of the protein is to store Mg in these tissues for later release when needed. The protein localisation to the vacuolar membrane supports this suggestion (see also Chapter 1.5).
The protein transports Mg into the vacuolar space and H out, as demonstrated by electrophysiological techniques. The transport is driven by the ΔpH maintained between the vacuolar space (pH 4.5 – 5.9) and the cytoplasm (pH 7.3 – 7.6) by an H-ATPase. How the transport of Mg by the protein is regulated was not determined. Currents were observed to pass through the protein in both directions, but the Mg out current required a ‘cytoplasmic’ pH of 5.5, a condition not found in plant cells under normal circumstances. In addition to the transport of Mg, Shaul et al. (1999) also showed that the protein could transport Zn and Fe, but did not report on the capacity of the protein to transport other divalent cations (e.g. Co and Ni) or its susceptibility to inhibition by cobalt (III) hexaammine.
The detailed kinetics of Mg transport have not been determined for AtMHX. However, physiological effects have been demonstrated. When A. thaliana plants were transformed with overexpression constructs of the AtMHX gene driven by the CaMV 35S promoter, the plants over-accumulated the protein and showed a phenotype of necrotic lesions in the leaves, which the authors suggest is caused by a disruption in the normal function of the vacuole, given their observation that the total Mg (or Zn) content of the plants was not altered in the transgenic plants.
The image has been adapted from Shaul et al. (1999) and Quednau et al. (2004), and combined with an analysis using HMMTOP, this figure shows the computer predicted membrane topology of the AtMHX protein in Arabidopsis thaliana. At this time the topology shown should be considered a tentative hypothesis. The TM domains are shown in light blue, the orientation in the membrane and the positions of the N- and C-termini are indicated, and the figure is not drawn to scale. The α1 and α2 domains, shown in green, are both quite hydrophobic and may both be inserted into the membrane. | 1 | Applied and Interdisciplinary Chemistry |
The relative permittivity is an essential piece of information when designing capacitors, and in other circumstances where a material might be expected to introduce capacitance into a circuit. If a material with a high relative permittivity is placed in an electric field, the magnitude of that field will be measurably reduced within the volume of the dielectric. This fact is commonly used to increase the capacitance of a particular capacitor design. The layers beneath etched conductors in printed circuit boards (PCBs) also act as dielectrics. | 0 | Theoretical and Fundamental Chemistry |
Escitalopram is the (S)-enantiomer (left-handed version) of the racemate citalopram, which is responsible for its name: escitalopram. | 0 | Theoretical and Fundamental Chemistry |
In liquid scintillation counting, a small aliquot, filter or swab is added to scintillation fluid and the plate or vial is placed in a scintillation counter to measure the radioactive emissions. Manufacturers have incorporated solid scintillants into multi-well plates to eliminate the need for scintillation fluid and make this into a high-throughput technique.
A gamma counter is similar in format to scintillation counting but it detects gamma emissions directly and does not require a scintillant.
A Geiger counter is a quick and rough approximation of activity. Lower energy emitters such as tritium can not be detected. | 0 | Theoretical and Fundamental Chemistry |
In World War II Eshelby began working for the Admiralty on the degaussing of ships, but on 4 May 1940 he joined the Technical Branch of the Royal Air Force. His work from February 1941 to June 1942 was for the Coastal Command Development Unit conducting performance trials of Air-to-Surface Vessel radar and other operational devices in all types of aircraft. He was then involved in radar work, from August 1942 to February 1943 with 76 signals wing and from February 1943 to September 1944 at the radar establishment at Malvern. He was then transferred to disarmament work and then to the Air Historical branch in September 1945. He left the RAF as a squadron leader on 4 October 1946.
After the war Eshelby returned to Bristol University to study for a PhD and taught himself the theory of elasticity for his thesis on "Stationary and moving dislocations". He obtained his PhD in 1950 under Nevill Mott. In 1951 he moved to the University of Illinois Urbana-Champaign as a Research Associate, where he stayed until 1953 when he was appointed a lecturer at the University of Birmingham, where he taught from 1953 to 1964 at the Department of Metallurgy. During this time, he worked on point defects and dislocations, developing the method of transformation strains and studying the Eshelby inclusion problems for the first time, as well as the study of forces on elastic singularities.
In 1964 he moved to the Cavendish Laboratory at Cambridge University at the behest of Neville Mott, and was a Fellow of Churchill College from 1965 to 1966. He was then appointed Reader in the Faculty of Materials (Theory of Materials) at the University of Sheffield, where he became Professor in 1971. | 1 | Applied and Interdisciplinary Chemistry |
Andrei Nikolaevich Khlobystov was born in Soviet Russia in 1974. He obtained a Master of Science degree in chemistry from Moscow State University in 1997, and received a PhD in 2002 from the University of Nottingham under the supervision of Martin Schröder and Neil Champness. | 0 | Theoretical and Fundamental Chemistry |
There are several design considerations and mitigation techniques that can be used to reduce the susceptibility to CAF. Certain material selection (i.e. laminate) and design rules (i.e. via spacing) can help reduce CAF risk. Poor adhesion between the resin and glass fibers in the PCB can create a path for CAF to occur. This may depend on parameters of the silane finish applied to the glass fibers, which is used to promote adhesion to the resin. There are also testing standards that can be performed to assess CAF risk. IPC TM-650 2.6.25 provides a test method to assess CAF susceptibility. Additionally, IPC TM-650 2.6.16 provides a pressure vessel test method to rapidly evaluate glass epoxy laminate integrity. This is helpful but it may often be better to use design rules and proper material selection to proactively mitigate the issue. | 0 | Theoretical and Fundamental Chemistry |
Members of the family include blood serotransferrin (or siderophilin, usually simply called transferrin); lactotransferrin (lactoferrin); milk transferrin; egg white ovotransferrin (conalbumin); and membrane-associated melanotransferrin. | 1 | Applied and Interdisciplinary Chemistry |
The origins of dimensional analysis have been disputed by historians. The first written application of dimensional analysis has been credited to François Daviet, a student of Lagrange, in a 1799 article at the Turin Academy of Science.
This led to the conclusion that meaningful laws must be homogeneous equations in their various units of measurement, a result which was eventually later formalized in the Buckingham π theorem.
Simeon Poisson also treated the same problem of the parallelogram law by Daviet, in his treatise of 1811 and 1833 (vol I, p. 39). In the second edition of 1833, Poisson explicitly introduces the term dimension instead of the Daviet homogeneity.
In 1822, the important Napoleonic scientist Joseph Fourier made the first credited important contributions based on the idea that physical laws like Newton's second law| should be independent of the units employed to measure the physical variables.
James Clerk Maxwell played a major role in establishing modern use of dimensional analysis by distinguishing mass, length, and time as fundamental units, while referring to other units as derived. Although Maxwell defined length, time and mass to be "the three fundamental units", he also noted that gravitational mass can be derived from length and time by assuming a form of Newtons law of universal gravitation in which the gravitational constant is taken as unity, thereby defining . By assuming a form of Coulombs law in which the Coulomb constant k is taken as unity, Maxwell then determined that the dimensions of an electrostatic unit of charge were , which, after substituting his equation for mass, results in charge having the same dimensions as mass, viz. .
Dimensional analysis is also used to derive relationships between the physical quantities that are involved in a particular phenomenon that one wishes to understand and characterize. It was used for the first time in this way in 1872 by Lord Rayleigh, who was trying to understand why the sky is blue. Rayleigh first published the technique in his 1877 book The Theory of Sound.
The original meaning of the word dimension, in Fouriers Theorie de la Chaleur', was the numerical value of the exponents of the base units. For example, acceleration was considered to have the dimension 1 with respect to the unit of length, and the dimension −2 with respect to the unit of time. This was slightly changed by Maxwell, who said the dimensions of acceleration are TL, instead of just the exponents. | 1 | Applied and Interdisciplinary Chemistry |
The angle between the C-C bonds in each carbon atom is 108°, which is the angle between adjacent sides of a regular pentagon. That value is quite close to the 109.5° central angle of a regular tetrahedron—the ideal angle between the bonds on an atom that has sp hybridisation. As a result, there is minimal angle strain. However, the molecule has significant levels of torsional strain as a result of the eclipsed conformation along each edge of the structure.
The molecule has perfect icosahedral (I) symmetry, as evidenced by its proton NMR spectrum in which all hydrogen atoms appear at a single chemical shift of 3.38 ppm. Unlike buckminsterfullerene, dodecahedrane has no delocalized electrons and hence has no aromaticity. | 0 | Theoretical and Fundamental Chemistry |
Solvents also have an effect on allylic strain. When used in conjunction with knowledge of the effects of polarity on allylic strain, solvents can be very useful in directing the conformation of a product that contains an allylic structure in its transition state. When a bulky and polar solvent is able to interact with one of the substituents in the allylic group, the complex of the solvent can energetically force the bulky complex out of the allylic strain in favor of a smaller group. | 0 | Theoretical and Fundamental Chemistry |
Photoelectrolysis of water, also known as photoelectrochemical water splitting, occurs in a photoelectrochemical cell when light is used as the energy source for the electrolysis of water, producing dihydrogen which can be used as a fuel. This process is one route to a "hydrogen economy", in which hydrogen fuel is produced efficiently and inexpensively from natural sources without using fossil fuels. In contrast, steam reforming usually or always uses a fossil fuel to obtain hydrogen. Photoelectrolysis is sometimes known colloquially as the hydrogen holy grail for its potential to yield a viable alternative to petroleum as a source of energy; such an energy source would supposedly come without the sociopolitically undesirable effects of extracting and using petroleum.
Some researchers have practiced photoelectrolysis by means of a nanoscale process. Nanoscale photoelectrolysis of water could someday reach greater efficiency than that of "traditional" photoelectrolysis. Semiconductors with bandgaps smaller than 1.7 eV would ostensibly be required for efficient nanoscale photoelectrolysis using light from the Sun.
Devices based on hydrogenase have also been investigated. | 0 | Theoretical and Fundamental Chemistry |
The esophagus, commonly known as the foodpipe or gullet, consists of a muscular tube through which food passes from the pharynx to the stomach. The esophagus is continuous with the laryngopharynx. It passes through the posterior mediastinum in the thorax and enters the stomach through a hole in the thoracic diaphragm—the esophageal hiatus, at the level of the tenth thoracic vertebra (T10). Its length averages 25 cm, varying with an individual's height. It is divided into cervical, thoracic and abdominal parts. The pharynx joins the esophagus at the esophageal inlet which is behind the cricoid cartilage.
At rest the esophagus is closed at both ends, by the upper and lower esophageal sphincters. The opening of the upper sphincter is triggered by the swallowing reflex so that food is allowed through. The sphincter also serves to prevent back flow from the esophagus into the pharynx. The esophagus has a mucous membrane and the epithelium which has a protective function is continuously replaced due to the volume of food that passes inside the esophagus. During swallowing, food passes from the mouth through the pharynx into the esophagus. The epiglottis folds down to a more horizontal position to direct the food into the esophagus, and away from the trachea.
Once in the esophagus, the bolus travels down to the stomach via rhythmic contraction and relaxation of muscles known as peristalsis. The lower esophageal sphincter is a muscular sphincter surrounding the lower part of the esophagus. The gastroesophageal junction between the esophagus and the stomach is controlled by the lower esophageal sphincter, which remains constricted at all times other than during swallowing and vomiting to prevent the contents of the stomach from entering the esophagus. As the esophagus does not have the same protection from acid as the stomach, any failure of this sphincter can lead to heartburn. | 1 | Applied and Interdisciplinary Chemistry |
The RFamide peptide family, or the RFamide-related peptides (RFRPs), are a family of neuropeptides. They are characterized by the possession of an Arg-Phe-NH motif at their C-terminal extremities.
Members of the family include:
* Neuropeptide FF group
** Neuropeptide AF
** Neuropeptide FF
** Neuropeptide SF (RFRP-1)
** Neuropeptide VF (RFRP-3) (GnIH - avian species)
* Prolactin-releasing peptide (PrRP)
* Pyroglutamylated RFamide peptide (QRFP)
* Kisspeptin (disputed) | 1 | Applied and Interdisciplinary Chemistry |
Many major physiological processes depend on regulation of proteolytic enzyme activity and there can be dramatic consequences when equilibrium between an enzyme and its substrates is disturbed. In this prospective, the discovery of small-molecule ligands, like protease inhibitors, that can modulate catalytic activities has an enormous therapeutic effect. Hence, inhibition of the HIV protease is one of the most important approaches for the therapeutic intervention in HIV infection and their development is regarded as major success of structure-based drug design. They are highly effective against HIV and have, since the 1990s, been a key component of anti-retroviral therapies for HIV/AIDS. | 1 | Applied and Interdisciplinary Chemistry |
The compound is prepared by adding hexafluoropropene to a solution of diethylamine in ether at 0 °C and distilling the product in vacuo. The amount of enamine in the product depends on temperature control during the reaction – the higher the temperature the more enamine. | 0 | Theoretical and Fundamental Chemistry |
The protein complex nitrogenase is responsible for catalyzing the reduction of nitrogen gas (N) to ammonia (NH). In cyanobacteria, this enzyme system is housed in a specialized cell called the heterocyst. The production of the nitrogenase complex is genetically regulated, and the activity of the protein complex is dependent on ambient oxygen concentrations, and intra- and extracellular concentrations of ammonia and oxidized nitrogen species (nitrate and nitrite). Additionally, the combined concentrations of both ammonium and nitrate are thought to inhibit N, specifically when intracellular concentrations of 2-oxoglutarate (2-OG) exceed a critical threshold. The specialized heterocyst cell is necessary for the performance of nitrogenase as a result of its sensitivity to ambient oxygen.
Nitrogenase consist of two proteins, a catalytic iron-dependent protein, commonly referred to as MoFe protein and a reducing iron-only protein (Fe protein). There are three different iron dependent proteins, molybdenum-dependent, vanadium-dependent, and iron-only, with all three nitrogenase protein variations containing an iron protein component. Molybdenum-dependent nitrogenase is the most commonly present nitrogenase. The different types of nitrogenase can be determined by the specific iron protein component. Nitrogenase is highly conserved. Gene expression through DNA sequencing can distinguish which protein complex is present in the microorganism and potentially being expressed. Most frequently, the nifH gene is used to identify the presence of molybdenum-dependent nitrogenase, followed by closely related nitrogenase reductases (component II) vnfH and anfH representing vanadium-dependent and iron-only nitrogenase, respectively. In studying the ecology and evolution of nitrogen-fixing bacteria, the nifH gene is the biomarker most widely used. nifH has two similar genes anfH and vnfH that also encode for the nitrogenase reductase component of the nitrogenase complex. | 1 | Applied and Interdisciplinary Chemistry |
Müllerian mimicry was discovered and has mainly been researched in insects. However, there is no reason why the mechanisms evolutionary advantages should not be exploited in other groups. There is some evidence that birds in the New Guinea genus Pitohui are Müllerian mimics. Pitohui dichrous and Pitohui kirhocephalus' "share a nearly identical colour pattern" where their geographic ranges overlap, but differ elsewhere; they are conspicuous; and they are chemically defended by a powerful neurotoxic alkaloid, batrachotoxin, in their feathers and skin. This combination of facts implies that the populations in these zones of overlap have converged to share honest warning signals.
Many species of flowers resemble each other but actual mimicry has not been demonstrated. It has been proposed that spiny plants such as Cactaceae and Agave in the Americas, Aloe, Euphorbia, white-thorned Acacia in Africa and spiny Asteraceae of the Mediterranean may form Müllerian mimicry rings, as they are strongly defended, are generally agreed to be aposematic, have similar conspicuous patterns and coloration, and are found in overlapping territories.
Aposematic mammals in the families Mustelidae, Viverridae, and Herpestidae have independently evolved conspicuous black-and-white coloration, suggesting that Müllerian mimicry may be involved. | 1 | Applied and Interdisciplinary Chemistry |
Because so many chloroplast genes have been moved to the nucleus, many proteins that would originally have been translated in the chloroplast are now synthesized in the cytoplasm of the plant cell. These proteins must be directed back to the chloroplast, and imported through at least two chloroplast membranes.
Curiously, around half of the protein products of transferred genes arent even targeted back to the chloroplast. Many became exaptations, taking on new functions like participating in cell division, protein routing, and even disease resistance. A few chloroplast genes found new homes in the mitochondrial genome—most became nonfunctional pseudogenes, though a few tRNA genes still work in the mitochondrion. Some transferred chloroplast DNA protein products get directed to the secretory pathway, though many secondary plastids are bounded by an outermost membrane derived from the hosts cell membrane, and therefore topologically outside of the cell because to reach the chloroplast from the cytosol, the cell membrane must be crossed, which signifies entrance into the extracellular space. In those cases, chloroplast-targeted proteins do initially travel along the secretory pathway.
Because the cell acquiring a chloroplast already had mitochondria (and peroxisomes, and a cell membrane for secretion), the new chloroplast host had to develop a unique protein targeting system to avoid having chloroplast proteins being sent to the wrong organelle.
In most, but not all cases, nuclear-encoded chloroplast proteins are translated with a cleavable transit peptide that's added to the N-terminus of the protein precursor. Sometimes the transit sequence is found on the C-terminus of the protein, or within the functional part of the protein. | 0 | Theoretical and Fundamental Chemistry |
Isoaspartyl formation reactions have been conjectured to be one of the factors that limit the useful lifetime of proteins.
Isoaspartyl formation proceeds much more quickly if the asparagine is followed by a small, flexible residue (such as Gly) that leaves the peptide group open for attack. These reactions also proceed much more quickly at elevated pH (>10) and temperatures. | 1 | Applied and Interdisciplinary Chemistry |
Despite the growing use of nuclear medicine, the potential expansion of nuclear power plants, and worries about protection against nuclear threats and the management of the nuclear waste generated in past decades, the number of students opting to specialize in nuclear and radiochemistry has decreased significantly over the past few decades. Now, with many experts in these fields approaching retirement age, action is needed to avoid a workforce gap in these critical fields, for example by building student interest in these careers, expanding the educational capacity of universities and colleges, and providing more specific on-the-job training.
Nuclear and Radiochemistry (NRC) is mostly being taught at university level, usually first at the Master- and PhD-degree level. In Europe, as substantial effort is being done to harmonize and prepare the NRC education for the industrys and societys future needs. This effort is being coordinated in a project funded by the Coordinated Action supported by the European Atomic Energy Community's 7th Framework Program. Although NucWik is primarily aimed at teachers, anyone interested in nuclear and radiochemistry is welcome and can find a lot of information and material explaining topics related to NRC. | 0 | Theoretical and Fundamental Chemistry |
Copper electrocatalysts produce multicarbon compounds from CO. These include C products (ethylene, ethanol, acetate, etc.) and even C products (propanol, acetone, etc.) These products are more valuable than C1 products, but the current efficiencies are low. | 1 | Applied and Interdisciplinary Chemistry |
In 1939, Martin Kamen and Samuel Ruben of the Radiation Laboratory at Berkeley began experiments to determine if any of the elements common in organic matter had isotopes with half-lives long enough to be of value in biomedical research. They synthesized using the laboratorys cyclotron accelerator and soon discovered that the atoms half-life was far longer than had been previously thought. This was followed by a prediction by Serge A. Korff, then employed at the Franklin Institute in Philadelphia, that the interaction of thermal neutrons with in the upper atmosphere would create . It had previously been thought that would be more likely to be created by deuterons interacting with . At some time during World War II, Willard Libby, who was then at Berkeley, learned of Korff's research and conceived the idea that it might be possible to use radiocarbon for dating.
In 1945, Libby moved to the University of Chicago, where he began his work on radiocarbon dating. He published a paper in 1946 in which he proposed that the carbon in living matter might include as well as non-radioactive carbon. Libby and several collaborators proceeded to experiment with methane collected from sewage works in Baltimore, and after isotopically enriching their samples they were able to demonstrate that they contained . By contrast, methane created from petroleum showed no radiocarbon activity because of its age. The results were summarized in a paper in Science in 1947, in which the authors commented that their results implied it would be possible to date materials containing carbon of organic origin.
Libby and James Arnold proceeded to test the radiocarbon dating theory by analyzing samples with known ages. For example, two samples taken from the tombs of two Egyptian kings, Zoser and Sneferu, independently dated to 2625 BC plus or minus 75 years, were dated by radiocarbon measurement to an average of 2800 BC plus or minus 250 years. These results were published in Science in December 1949. Within 11 years of their announcement, more than 20 radiocarbon dating laboratories had been set up worldwide. In 1960, Libby was awarded the Nobel Prize in Chemistry for this work. | 0 | Theoretical and Fundamental Chemistry |
The PHLPP isoforms (PH domain and Leucine rich repeat Protein Phosphatases) are a pair of protein phosphatases, PHLPP1 and PHLPP2, that are important regulators of Akt serine-threonine kinases (Akt1, Akt2, Akt3) and conventional/novel protein kinase C (PKC) isoforms. PHLPP may act as a tumor suppressor in several types of cancer due to its ability to block growth factor-induced signaling in cancer cells.
PHLPP dephosphorylates Ser-473 (the hydrophobic motif) in Akt, thus partially inactivating the kinase.
In addition, PHLPP dephosphorylates conventional and novel members of the protein kinase C family at their hydrophobic motifs, corresponding to Ser-660 in PKCβII. | 1 | Applied and Interdisciplinary Chemistry |
Given the advantages provided by the working mechanism of thermogalvanic cells, their main application is electricity production under conditions where there is an excess of heat available. In particular thermogalvanic cells are being used to produce electricity in the following areas. | 0 | Theoretical and Fundamental Chemistry |
As well as using 3D structure and family precedence, it is possible to estimate druggability using other properties of a protein such as features derived from the amino-acid sequence (feature-based druggability) which is applicable to assessing small-molecule based druggability or biotherapeutic-based druggability or the properties of ligands or compounds known to bind the protein (Ligand-based druggability). | 1 | Applied and Interdisciplinary Chemistry |
Nucleophilic epoxidation is the formation of epoxides from electron-deficient double bonds through the action of nucleophilic oxidants. Nucleophilic epoxidation methods represent a viable alternative to electrophilic methods, many of which do not epoxidize electron-poor double bonds efficiently.
Although the most commonly used asymmetric epoxidation methods (the Sharpless-Katsuki, and Jacobsen epoxidations) rely on the catalytic reactivity of electrophilic oxidants, nucleophilic oxygen sources substituted with a suitable leaving group can also act as epoxidation reagents. The classic example, the Weitz-Scheffer reaction employs hydrogen peroxide under basic conditions (Z = OH below). Other notable examples have employed hypochlorites (Z = Cl) and chiral peroxides (Z = OR*).
Asymmetric versions of the above reaction have taken advantage of a number of strategies for achieving asymmetric induction. The highest yielding and most enantioselective methods include:
* Use of stoichiometric chiral oxidant
* Use of stoichiometric metal peroxides substituted with chiral ligands
* Use of stoichiometric chiral base
* Use of polypeptides
Although the mechanisms of each of these reactions differ somewhat, in each case the chiral catalyst or reagent must be involved in the [https://en.wiktionary.org/wiki/enantio- enantio] determining conjugate addition step. Cis-epoxides are difficult to access using nucleophilic epoxidation methods. Nearly all nucleophilic epoxidations of cis olefins afford trans epoxides. | 0 | Theoretical and Fundamental Chemistry |
Almost any biological sample containing a full copy of the DNA—even a very small amount of DNA or ancient DNA—can provide the genetic material necessary for full genome sequencing. Such samples may include saliva, epithelial cells, bone marrow, hair (as long as the hair contains a hair follicle), seeds, plant leaves, or anything else that has DNA-containing cells.
The genome sequence of a single cell selected from a mixed population of cells can be determined using techniques of single cell genome sequencing. This has important advantages in environmental microbiology in cases where a single cell of a particular microorganism species can be isolated from a mixed population by microscopy on the basis of its morphological or other distinguishing characteristics. In such cases the normally necessary steps of isolation and growth of the organism in culture may be omitted, thus allowing the sequencing of a much greater spectrum of organism genomes.
Single cell genome sequencing is being tested as a method of preimplantation genetic diagnosis, wherein a cell from the embryo created by in vitro fertilization is taken and analyzed before embryo transfer into the uterus. After implantation, cell-free fetal DNA can be taken by simple venipuncture from the mother and used for whole genome sequencing of the fetus. | 1 | Applied and Interdisciplinary Chemistry |
The precipitation method is the one used for the determination of the amount of calcium in water. Using this method, an excess of oxalic acid, HCO, is added to a measured, known volume of water. By adding a reagent, here ammonium oxalate, the calcium will precipitate as calcium oxalate. The proper reagent, when added to aqueous solution, will produce highly insoluble precipitates from the positive and negative ions that would otherwise be soluble with their counterparts (equation 1).
The reaction is:
Formation of calcium oxalate:
Ca + CO → CaCO
The precipitate is collected, dried and ignited to high (red) heat which converts it entirely to calcium oxide.
The reaction is pure calcium oxide formed
CaCO → CaO + CO+ CO
The pure precipitate is cooled, then measured by weighing, and the difference in weights before and after reveals the mass of analyte lost, in this case calcium oxide. That number can then be used to calculate the amount, or the percent concentration, of it in the original mix. | 0 | Theoretical and Fundamental Chemistry |
Good single crystal X-ray diffraction experiments in diamond anvil cells require sample stage to rotate on the vertical axis, omega. Most diamond anvil cells do not feature a large opening that would allow the cell to be rotated to high angles, a 60 degrees opening is considered sufficient for most crystals but larger angles are possible. The first cell to be used for single crystal experiments was designed by a graduate student at the University of Rochester, Leo Merrill. The cell was triangular with beryllium seats that the diamonds were mounted on; the cell was pressurized with screws and guide pins holding everything in place. | 0 | Theoretical and Fundamental Chemistry |
A number of companies have commercialized mercury detection via CVAFS and produced transportable analysers capable of measuring mercury in ambient air. These devices can measure levels in the low parts per quadrillion range (10). | 0 | Theoretical and Fundamental Chemistry |
In engineering, physics, and chemistry, the study of transport phenomena concerns the exchange of mass, energy, charge, momentum and angular momentum between observed and studied systems. While it draws from fields as diverse as continuum mechanics and thermodynamics, it places a heavy emphasis on the commonalities between the topics covered. Mass, momentum, and heat transport all share a very similar mathematical framework, and the parallels between them are exploited in the study of transport phenomena to draw deep mathematical connections that often provide very useful tools in the analysis of one field that are directly derived from the others.
The fundamental analysis in all three subfields of mass, heat, and momentum transfer are often grounded in the simple principle that the total sum of the quantities being studied must be conserved by the system and its environment. Thus, the different phenomena that lead to transport are each considered individually with the knowledge that the sum of their contributions must equal zero. This principle is useful for calculating many relevant quantities. For example, in fluid mechanics, a common use of transport analysis is to determine the velocity profile of a fluid flowing through a rigid volume.
Transport phenomena are ubiquitous throughout the engineering disciplines. Some of the most common examples of transport analysis in engineering are seen in the fields of process, chemical, biological, and mechanical engineering, but the subject is a fundamental component of the curriculum in all disciplines involved in any way with fluid mechanics, heat transfer, and mass transfer. It is now considered to be a part of the engineering discipline as much as thermodynamics, mechanics, and electromagnetism.
Transport phenomena encompass all agents of physical change in the universe. Moreover, they are considered to be fundamental building blocks which developed the universe, and which is responsible for the success of all life on earth. However, the scope here is limited to the relationship of transport phenomena to artificial engineered systems. | 1 | Applied and Interdisciplinary Chemistry |
Level 2 vectors have two inverted BpiI sites from the insertion of level 1 modules. The upstream fusion site is compatible to a gene cloned in level 1 vector while the downstream fusion site has a universal sequence. Each cloning allows 2-6 genes to be inserted in the same vector.
Adding more genes in one cloning step is not recommended, for this would result in incorrect constructs. On one hand, this can induce more restriction sites in the construct, where this open construct allows additional genes be added. On the other hand, this can also eliminate restriction sites, where this close construct stop the further addition of genes.
Therefore, constructs of more than six genes need successive cloning steps, which requires end-linkers containing BsaI or BsmBI internal restriction sites and blue or purple markers. Each cloning step needs to alternate the restriction site and the marker. Furthermore, two restriction enzymes are needed, where BpiI is used for releasing level 1 modules from level 1 constructs and BsaI/BsmBI is for digesting and opening the recipient level 2-n plasmid. When screening, the correct colonies should alternate from blue to purple every cloning step, but if a "closed" end-linker is used, the colonies will be white. | 1 | Applied and Interdisciplinary Chemistry |
Once transported, the translated protein is 396 residues in length, with an N-terminus located at amino acids 1-25, a C-terminus at 155-396 (note that the spectrin homology located at 228-380 within the C-terminal), and a putative coiled coil domain at amino acids 26-154. Additionally, the protein has binding sites for endophilin 3 and dynamin 2 at amino acids 89-100 and 195-214, respectively. While Arc mRNA is subject to degradation by NMD, the translated protein contains a PEST sequence at amino acids 351-392, indicating proteasome-dependent degradation. The translated protein can be visualized with an immunoblot as a band at 55 kDa. The ARC protein can form virus-like capsids that package mRNA and can traffic between cells.
Synaptically localized Arc protein interacts with dynamin and endophilin, proteins involved in clathrin-mediated endocytosis, and facilitates the removal of AMPA receptors from the plasma membrane. Consistent with this, increased Arc levels reduce AMPA currents, while Arc KOs display increases in surface AMPA expression. | 1 | Applied and Interdisciplinary Chemistry |
The dioxane molecule is centrosymmetric, meaning that it adopts a chair conformation, typical of relatives of cyclohexane. However, the molecule is conformationally flexible, and the boat conformation is easily adopted, e.g. in the chelation of metal cations.
Dioxane resembles a smaller crown ether with only two ethyleneoxyl units. | 0 | Theoretical and Fundamental Chemistry |
The Berry mechanism in square pyramidal molecules (such as IF) is somewhat like the inverse of the mechanism in bipyramidal molecules. Starting at the "transition phase" of bipyramidal pseudorotation, one pair of fluorines scissors back and forth with a third fluorine, causing the molecule to vibrate. Unlike with pseudorotation in bipyramidal molecules, the atoms and ligands which are not actively vibrating in the "scissor" motion are still participating in the process of pseudorotation; they make general adjustment based on the movement of the actively vibrating atoms and ligands. However, this geometry requires a significant amount of energy to occur of about 26.7 kcal/mol. | 0 | Theoretical and Fundamental Chemistry |
Cell differentiation involves a transition from a proliferative mode toward differentiation mode. Directed differentiation consists in mimicking developmental (embryo's development) decisions in vitro using the stem cells as source material. For this purpose, pluripotent stem cells (PSCs) are cultured in controlled conditions involving specific substrate or extracellular matrices promoting cell adhesion and differentiation, and define culture media compositions. A limited number of signaling factors such as growth factors or small molecules, controlling cell differentiation, is applied sequentially or in a combinatorial manner, at varying dosage and exposure time. Proper differentiation of the cell type of interest is verified by analyzing cell type specific markers, gene expression profile, and functional assays. | 1 | Applied and Interdisciplinary Chemistry |
Whales and other marine mammals also enhance primary productivity in their feeding areas by concentrating nitrogen near the surface through the release of flocculent fecal plumes. For example, whales and seals may be responsible for replenishing more nitrogen in the Gulf of Maine's euphotic zone than the input of all rivers combined. This upward whale pump played a much larger role before industrial fishing devastated marine mammal stocks, when recycling of nitrogen was likely more than three times the atmospheric nitrogen input.
The biological pump mediates the removal of carbon and nitrogen from the euphotic zone through the downward flux of aggregates, feces, and vertical migration of invertebrates and fish. Copepods and other zooplankton produce sinking fecal pellets and contribute to downward transport of dissolved and particulate organic matter by respiring and excreting at depth during migration cycles, thus playing an important role in the export of nutrients (N, P, and Fe) from surface waters.
Zooplankton feed in the euphotic zone and export nutrients via sinking fecal pellets, and vertical migration. Fish typically release nutrients at the same depth at which they feed. Excretion for marine mammals, tethered to the surface for respiration, is expected to be shallower in the water column than where they feed.
Marine mammals provide important ecosystem services. On a global scale, they can influence climate, through fertilization events and the export of carbon from surface waters to the deep sea through sinking whale carcasses. In coastal areas, whales retain nutrients locally, increasing ecosystem productivity and perhaps raising the carrying capacity for other marine consumers, including commercial fish species. It has been estimated that, in terms of carbon sequestration, one whale is equivalent to thousands of trees. | 0 | Theoretical and Fundamental Chemistry |
Young received her B.S. and M.S. from Wake Forest University, working with Prof. Huw Davies. She was co-author on an early application of Davies' rhodium(II) carbenoid insertion - Cope rearrangement chemistry, leading to the total synthesis of three small tropane natural products. Young received her Ph.D. from Princeton in 1993, working with Edward C. Taylor on heterocycles derived from natural pigments, one of which ultimately became pemetrexed (Alimta), an oncology treatment. In her postdoctoral fellowship with Samuel Danishefsky, Young was among one of a handful of groups in the mid-1990s to synthesize paclitaxel (Taxol), a highly-oxygenated terpenoid natural product used to treat cancer. | 1 | Applied and Interdisciplinary Chemistry |
The superfluid phase of neutron matter exists in neutron stars.
The superfluidity is described by the BCS model with a realistic nucleon-nucleon interaction potential.
By increasing the density of nuclear matter above the saturation density, quark matter is formed. It is expected that dense quark matter at low
temperatures is a color superconductor.
In the case of the SU(3) color group, a Bose–Einstein condensate of the quark Cooper pairs carries an open color. To meet the requirement of confinement,
a Bose–Einstein condensate of colorless 6-quark states is considered, or the projected BCS theory is used. | 0 | Theoretical and Fundamental Chemistry |
The largest "classic" pinch device was the ZETA, which started operation in the UK in 1957. Its name is a take-off on small experimental fission reactors that often had "zero energy" in their name, such as ZEEP.
In early 1958, John Cockcroft announced that fusion had been achieved in the ZETA, an announcement that made headlines around the world. He dismissed US physicists' concerns. US experiments soon produced similar neutrons, although temperature measurements suggested these could not be from fusion. The ZETA neutrons were later demonstrated to be from different versions of the instability processes that had plagued earlier machines. Cockcroft was forced to retract his fusion claims, tainting the entire field for years. ZETA ended in 1968. | 0 | Theoretical and Fundamental Chemistry |
The effects of friction and viscosity in diminishing the velocity of running water were noticed in the Principia of Sir Isaac Newton, who threw much light upon several branches of hydromechanics. At a time when the Cartesian system of vortices universally prevailed, he found it necessary to investigate that hypothesis, and in the course of his investigations he showed that the velocity of any stratum of the vortex is an arithmetical mean between the velocities of the strata which enclose it; and from this it evidently follows that the velocity of a filament of water moving in a pipe is an arithmetical mean between the velocities of the filaments which surround it. Taking advantage of these results, French engineer Henri Pitot afterwards showed that the retardations arising from friction are inversely as the diameters of the pipes in which the fluid moves. | 1 | Applied and Interdisciplinary Chemistry |
Chemical and electrical synapses are two ways of synaptic transmission.
* In a chemical synapse, electrical activity in the presynaptic neuron is converted (via the activation of voltage-gated calcium channels) into the release of a chemical called a neurotransmitter that binds to receptors located in the plasma membrane of the postsynaptic cell. The neurotransmitter may initiate an electrical response or a secondary messenger pathway that may either excite or inhibit the postsynaptic neuron. Chemical synapses can be classified according to the neurotransmitter released: glutamatergic (often excitatory), GABAergic (often inhibitory), cholinergic (e.g. vertebrate neuromuscular junction), and adrenergic (releasing norepinephrine). Because of the complexity of receptor signal transduction, chemical synapses can have complex effects on the postsynaptic cell.
* In an electrical synapse, the presynaptic and postsynaptic cell membranes are connected by special channels called gap junctions that are capable of passing an electric current, causing voltage changes in the presynaptic cell to induce voltage changes in the postsynaptic cell. In fact, gap junctions facilitate the direct flow of electrical current without the need for neurotransmitters, as well as small molecules like calcium. Thus, the main advantage of an electrical synapse is the rapid transfer of signals from one cell to the next.
* Mixed chemical electrical synapses are synaptic sites that feature both a gap junction and neurotransmitter release. This combination allows a signal to have both a fast component (electrical) and a slow component (chemical).
The formation of neural circuits in nervous systems, appears to heavily depend on the crucial interactions between chemical and electrical synapses. Thus, these interactions govern the generation of synaptic transmission. Synaptic communication is distinct from an ephaptic coupling, in which communication between neurons occurs via indirect electric fields. An autapse is a chemical or electrical synapse that forms when the axon of one neuron synapses onto dendrites of the same neuron. | 1 | Applied and Interdisciplinary Chemistry |
An estimated 4,100,000,000 kg of chloromethane are produced annually by natural sources. The oceans are estimated to release 1 to 2 million tons of bromomethane annually. | 0 | Theoretical and Fundamental Chemistry |
The coding region of a gene, also known as the coding sequence (CDS), is the portion of a gene's DNA or RNA that codes for a protein. Studying the length, composition, regulation, splicing, structures, and functions of coding regions compared to non-coding regions over different species and time periods can provide a significant amount of important information regarding gene organization and evolution of prokaryotes and eukaryotes. This can further assist in mapping the human genome and developing gene therapy. | 1 | Applied and Interdisciplinary Chemistry |
Thermal perturbations are the most common type of external stimulus used to induce SCO. One example is [Fe(tmphen)][Co(CN)] trigonal bipyramid (TBP), with the Fe centers in the equatorial positions. The HS Fe remains under 20% i the range of 4.2 K to 50 K, but at room temperature about two-thirds of the Fe ions in the sample are HS, as shown by the absorption band at 2.1 mm/s, while the other third of the ions remain in the LS state. The thermally induced spin transition is an entropy driven process. Around 25% of the total entropy gain from the LS to HS transition originates from the increase in spin multiplicity according to the relationship:
and the larger contribution arises from vibrational effects, since the metal-ligand bond distances are larger in the HS state. | 0 | Theoretical and Fundamental Chemistry |
Simple twinned crystals may be contact twins or penetration twins. Contact twins meet on a single composition plane, often appearing as mirror images across the boundary. Plagioclase, quartz, gypsum, and spinel often exhibit contact twinning. Merohedral twinning occurs when the lattices of the contact twins superimpose in three dimensions, such as by relative rotation of one twin from the other. An example is metazeunerite. Contact twinning characteristically creates reentrant faces where faces of the crystal segments meet on the contact plane at an angle greater than 180°.
A type of twinning involving 180° relationships is called hemitropism or hemitropy.
In penetration twins the individual crystals have the appearance of passing through each other in a symmetrical manner. Orthoclase, staurolite, pyrite, and fluorite often show penetration twinning. The composition surface in penetration twins is usually irregular and extends to the center of the crystal.
Contact twinning can arise from either reflection or rotation, whereas penetration twinning is usually produced by rotation.
If several twin crystal parts are aligned by the same twin law they are referred to as multiple or repeated twins. If these multiple twins are aligned in parallel they are called polysynthetic twins. When the multiple twins are not parallel they are cyclic twins. Albite, calcite, and pyrite often show polysynthetic twinning. Closely spaced polysynthetic twinning is often observed as striations or fine parallel lines on the crystal face. Rutile, aragonite, cerussite, and chrysoberyl often exhibit cyclic twinning, typically in a radiating pattern.
For rotational twinning the relationship between the twin axis and twin plane falls into one of three types:
:#parallel twinning, when the twin axis and compositional plane lie parallel to each other,
:#normal twinning, when the twin plane and compositional plane lie normally, and
:#complex twinning, a combination of parallel twinning and normal twinning on one compositional plane. | 0 | Theoretical and Fundamental Chemistry |
María Vallet-Regí (born 19 April 1946) is a Spanish inorganic chemist. As of 2012, she heads the Smart Biomaterials group at the Universidad Complutense de Madrid. | 0 | Theoretical and Fundamental Chemistry |
This fitting (also known as a "bungalow fitting" or a "cottage fitting") is a sanitary tee that allows two trap arms to be connected at the same level. A toilet is the main connection, with the option of a right or left-hand outlet to the 3" inlet with a choice of 1-1/2" or 2" in size. It is used to keep stack-vented fixtures high to the joist space and thus conserves the headroom in a basement. As the water closet must be the lowest fixture, the smaller side outlet (usually used to connect the bathtub trap arm) enters slightly above the larger connection. | 1 | Applied and Interdisciplinary Chemistry |
A monochromator's adjustment range might cover the visible spectrum and some part of both or either of the nearby ultraviolet (UV) and infrared (IR) spectra, although monochromators are built for a great variety of optical ranges, and to a great many designs. | 0 | Theoretical and Fundamental Chemistry |
The light reactions take place on the thylakoid membranes. They take light energy and store it in NADPH, a form of NADP, and ATP to fuel the dark reactions. | 0 | Theoretical and Fundamental Chemistry |
Brkić and Praks show one approximation of the Colebrook equation based on the Wright -function, a cognate of the Lambert W-function
:, , , and
The equation was found to match the Colebrook–White equation within 0.0497%. | 1 | Applied and Interdisciplinary Chemistry |
Larry Paul Kelley established ICT (International Crystal Technology) in 1970 with Craig Hardy and Tom VanBergen. Kelley had worked for Dow Chemical in Ludington and at a factory in Ann Arbor that produced laser crystals. The facility was sited in Shelby because the town had a new industrial park. By 2015, Kelley was ICT's sole owner.
The Shelby Gem Factory initially produced only synthetic ruby, with ruby lasers being the principal application, primarily sold to firms in California. However, laser technology was in its infancy, and the far greater profit potential of converting ruby rods into a variety of artificial gemstones of various colors led to a change in the factorys focus. Larry Kelley built on Soviet research into cubic zirconia and became its first commercial producer, having solved issues of temperature control that had impeded its production. For a time, cubic zirconia was a lucrative product line; Shelby opened factories outside the United States to keep up with demand. However, the value of cubic zirconia soon declined to the point that it was used as fill when the factory was expanded. In 1983, ICT opened a faceting factory in southern China to create gemstones for jewelry use from the crystals produced in Shelby; this closed in 1991, and separate companies in China and South Korea were contracted to continue faceting. The South Korean market represented up to 40 percent of the factorys sales until a precipitous decline caused by the 1997 Asian financial crisis. In 1994, the factory entered the business of recrystallizing rubies, buying low-grade gems from Myanmar to be melted down in the process.
A 50-seat theater ran a presentation for visitors, and jewelry was sold on site.
The factory closed in 2019 after Kelley was diagnosed in 2017 with Alzheimer's disease. Other issues that contributed to the closing were worldwide competition and online markets. Larry Kelley died on October 24, 2020. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, a water cluster is a discrete hydrogen bonded assembly or cluster of molecules of water. Many such clusters have been predicted by theoretical models (in silico), and some have been detected experimentally in various contexts such as ice, bulk liquid water, in the gas phase, in dilute mixtures with non-polar solvents, and as water of hydration in crystal lattices. The simplest example is the water dimer (HO).
Water clusters have been proposed as an explanation for some anomalous properties of liquid water, such as its unusual variation of density with temperature. Water clusters are also implicated in the stabilization of certain supramolecular structures. They are expected to play a role also in the hydration of molecules and ions dissolved in water. | 0 | Theoretical and Fundamental Chemistry |
Considerable evidence indicate that HERVs can be reactivated by viral infections, such as:
1) retroviruses – human immunodeficiency virus type-1 (HIV-1), human T-lymphotropic virus 1 (HTLV-1);
2) RNA viruses – influenza A virus, hepatitis C virus (HCV), severe acute respiratory syndrome coronavirus-2 (SARSCoV-2);
3) DNA viruses – herpes simplex virus type-1 (HSV-1), Epstein-Barr virus (EBV), human cytomegalovirus (CMV), Kaposi’s sarcoma-associated herpesvirus (KSHV)
Several studies have shown that EBV is able to transactivate the expression of the normally inactive HERV-K18 Env protein, e.g., interacting with resting B cells via CD21 receptor. Further studies revealed that the mechanism of transactivation depends on the expression of the major EBV late gene transactivator, EBNA-2. In-depth analysis completed the picture identifying the EBV latent membrane protein LMP-2A as a strong candidate for the HERV-K18 transactivation. HERV-K18 has also been reported to have superantigen activity (i.e. polyclonal T and B cell activation regardless of the specificity of their antigen receptor).
It has also been shown that in vitro binding of the EBV gp350 protein caused activation of MSRVenv and syncytin-1 in B-cells, monocytes, macrophages and in astrocytes - cells that are involved in pathogenesis of multiple sclerosis. Monocytes, especially after their differentiation into macrophages, appeared to be the most responsive to EBVgp350, expressing even higher levels of HERV-Wenv than B cells. This finding is concordant with another study, which demonstrated that during infectious mononucleosis EBV promoted the strongest activation of HERV-W/MSRV expression in monocytes compared to other blood cell types. | 1 | Applied and Interdisciplinary Chemistry |
The Open Pharmacological Space created by the consortium intended to support open innovation and in-house non-public drug discovery research by removing bottlenecks in drug development. Resources from the project are publicly available on GitHub.
To reduce the barriers to drug discovery in industry, academia and for small businesses, the Open PHACTS consortium built the Open PHACTS Discovery Platform. This platform was freely available, integrating pharmacological data from a variety of information resources and providing tools and services to question this integrated data to support pharmacological research. | 1 | Applied and Interdisciplinary Chemistry |
In naphtha cracking process, C4R1 refers to C4 residual obtained after separation of 1,3-butadiene from C4 raffinate stream and which, mainly consists of isobutylene 40~50 wt% and cis- or trans-2-butene 30~35 wt%. Normally C4R1 is a side product in 1,3-butadiene plant and feed to tert-butyl alcohol plant. | 0 | Theoretical and Fundamental Chemistry |
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