text stringlengths 105 4.57k | label int64 0 1 | label_text stringclasses 2
values |
|---|---|---|
Microfluidics is the study and design of the control or transport of small volumes of fluid flow through porous material or narrow channels for a variety of applications (e.g. mixing, separations). Capillary pressure is one of many geometry-related characteristics that can be altered in a microfluidic device to optimize a certain process. For instance, as the capillary pressure increases, a wettable surface in a channel will pull the liquid through the conduit. This eliminates the need for a pump in the system, and can make the desired process completely autonomous. Capillary pressure can also be utilized to block fluid flow in a microfluidic device.
The capillary pressure in a microchannel can be described as:
where:
: is the surface tension of the liquid
: is the contact angle at the bottom
: is the contact angle at the top
: is the contact angle at the left side of the channel
: is the contact angles at the right side of the channel
: is the depth
: is the width
Thus, the capillary pressure can be altered by changing the surface tension of the fluid, contact angles of the fluid, or the depth and width of the device channels. To change the surface tension, one can apply a surfactant to the capillary walls. The contact angles vary by sudden expansion or contraction within the device channels. A positive capillary pressure represents a valve on the fluid flow while a negative pressure represents the fluid being pulled into the microchannel. | 1 | Applied and Interdisciplinary Chemistry |
In the presence of air and various cofactors and enzymes, fatty acids are converted to acetyl-CoA. The pathway is called beta-oxidation. Each cycle of beta-oxidation shortens the fatty acid chain by two carbon atoms and produces one equivalent each of acetyl-CoA, NADH, and FADH. The acetyl-CoA is metabolized by the citric acid cycle to generate ATP, while the NADH and FADH are used by oxidative phosphorylation to generate ATP. Dozens of ATP equivalents are generated by the beta-oxidation of a single long acyl chain. | 1 | Applied and Interdisciplinary Chemistry |
Perilipin is an important regulator of lipid storage. Both an overexpression or deficiency of the protein, caused by a mutation, lead to severe health issues. | 1 | Applied and Interdisciplinary Chemistry |
Presence of VMAT1 in cells has been shown to protect them from the damaging effects of cooling and rewarming associated with hypothermia. Experiments were carried out on aortic and kidney cells and tissues. Evidence was found that an accumulation of serotonin using VMAT1 and TPH1 allowed for the subsequent release of serotonin when exposed to cold temperatures. This allows cystathionine beta synthase (CBS) mediated generation of HS. The protection against the damage caused by hypothermia is due to a reduction in the generation of reactive oxygen species (ROS), which can induce apoptosis, due to the presence of HS. | 1 | Applied and Interdisciplinary Chemistry |
In order to study trace metal stable isotope biogeochemistry, it is necessary to compare the relative abundances of isotopes of trace metals in a given biological, geological, or chemical pool to a standard (discussed individually for each isotope system below) and monitor how those relative abundances change as a result of various biogeochemical processes. Conventional notations used to mathematically describe isotope abundances, as exemplified here for Fe, include the isotope ratio (R), fractional abundance (F) and delta notation (δFe). Furthermore, as different biogeochemical processes vary the relative abundances of the isotopes of a given trace metal, different reaction pools or substances will become enriched or depleted in specific isotopes. This partial separation of isotopes between different pools is termed isotope fractionation, and is mathematically described by fractionation factors α or ε (which express the difference in isotope ratio between two pools), or by "cap delta" (Δ; the difference between two δ values). For a more complete description of these notations, see the isotope notation section in Hydrogen isotope biogeochemistry. | 0 | Theoretical and Fundamental Chemistry |
The conventional method of preparation of sodium tetrachloroaurate involves the addition of tetrachloroauric acid solution to sodium chloride or sodium carbonate to form a mixture. The mixture is stirred at 100 °C, and then subjected to evaporation, cooling, crystallization, and drying to obtain the orange crystals of sodium tetrachloroaurate.
However, more efficient preparation methods have been discovered recently. These are the addition of gold with sodium oxy-halogen salts and hydrochloric acid. | 0 | Theoretical and Fundamental Chemistry |
Basic oxygen steelmaking (BOS, BOP, BOF, or OSM), also known as Linz-Donawitz steelmaking or the oxygen converter process, is a method of primary steelmaking in which carbon-rich molten pig iron is made into steel. Blowing oxygen through molten pig iron lowers the carbon content of the alloy and changes it into low-carbon steel. The process is known as basic because fluxes of burnt lime or dolomite, which are chemical bases, are added to promote the removal of impurities and protect the lining of the converter.
The process was invented in 1948 by Swiss engineer Robert Durrer and commercialized in 1952–1953 by the Austrian steelmaking company VOEST and ÖAMG. The LD converter, named after the Austrian towns Linz and Donawitz (a district of Leoben) is a refined version of the Bessemer converter where blowing of air is replaced with blowing oxygen. It reduced capital cost of the plants and smelting time, and increased labor productivity. Between 1920 and 2000, labor requirements in the industry decreased by a factor of 1,000, from more than 3 man-hours per metric ton to just 0.003. The majority of steel manufactured in the world is produced using the basic oxygen furnace. In 2000, it accounted for 60% of global steel output.
Modern furnaces will take a charge of iron of up to 400 tons and convert it into steel in less than 40 minutes, compared to 10–12 hours in an open hearth furnace. | 1 | Applied and Interdisciplinary Chemistry |
In the cell nucleus, it seems that promoters are distributed preferentially at the edge of the chromosomal territories, likely for the co-expression of genes on different chromosomes. Furthermore, in humans, promoters show certain structural features characteristic for each chromosome. | 1 | Applied and Interdisciplinary Chemistry |
Gene trapping is based on random insertion of a cassette, while gene targeting manipulates a specific gene. Cassettes can be used for many different things while the flanking homology regions of gene targeting cassettes need to be adapted for each gene. This makes gene trapping more easily amenable for large scale projects than targeting. On the other hand, gene targeting can be used for genes with low transcriptions that would go undetected in a trap screen. The probability of trapping increases with intron size, while for gene targeting, small genes are just as easily altered. | 1 | Applied and Interdisciplinary Chemistry |
Aside from measuring the concentration of protein in meat, calculating bioavailability is another way in determining the total amount of component and quality. The calculation is done when food molecules are digested in various steps. Since human digestion is very complicated, a wide range of analytical techniques are used to obtain the data, including foodomics protocol and an in vitro static simulation of digestion.
The procedure is divided into 3 stages as the samples are collected from oral, gastric and duodenal digestion in order to study protein digestibility closely and thoroughly. A meat based food, Bresaola, is evaluated because beef muscles are still intact, which can be used to indicate nutritional value.
The consequences of oral step can be observed at the beginning of the gastric digestion, the first stage. As there is no enzymatic proteolytic activity at this stage, the level of H-NMR, a spectrum used to determine the structure, is still constant because there is no change going on. However, when pepsin takes action, TD-NMR, a special technique used for measuring mobile water population with macromolecular solutes, reveals that progressive unbundling of meat fibers helps pepsin activity to digest. TD-NMR data proves that bolus structure changes considerably during the first part of digestion and water molecules, consequently, leave the spaces inside the myofibrils and fiber bundles. This results in a low level of water that can be detected in duodenal stage. Since digestion is in progress, protein molecules become smaller and molecular weight gets lower, in other words, there is an increase in the spectra total area. | 1 | Applied and Interdisciplinary Chemistry |
Because they have many applications and are easily prepared, halomethanes have been of intense commercial interest. | 1 | Applied and Interdisciplinary Chemistry |
Le Bel-vant Hoff rule states that for a structure with n asymmetric carbon atoms, there is a maximum of 2 different stereoisomers possible. As an example, -glucose is an aldohexose and has the formula CHO. Four of its six carbon atoms are stereogenic, which means -glucose is one of 2=16 possible stereoisomers. | 0 | Theoretical and Fundamental Chemistry |
Inverse photoemission spectroscopy (IPES) is a surface science technique used to study the unoccupied electronic structure of surfaces, thin films, and adsorbates. A well-collimated beam of electrons of a well defined energy (< 20 eV) is directed at the sample. These electrons couple to high-lying unoccupied electronic states and decay to low-lying unoccupied states, with a subset of these transitions being radiative. The photons emitted in the decay process are detected and an energy spectrum, photon counts vs. incident electron energy, is generated. Due to the low energy of the incident electrons, their penetration depth is only a few atomic layers, making inverse photoemission a particularly surface sensitive technique. As inverse photoemission probes the electronic states above the Fermi level of the system, it is a complementary technique to photoemission spectroscopy. | 0 | Theoretical and Fundamental Chemistry |
In a redox reaction an electron donor D must diffuse to the acceptor A, forming a precursor complex, which is labile but allows electron transfer to give successor complex. The pair then dissociates. For a one electron transfer the reaction is
(D and A may already carry charges). Here k, k and k are diffusion constants, k and k are rate constants of activated reactions. The total reaction may be diffusion controlled (the electron transfer step is faster than diffusion, every encounter leads to reaction) or activation controlled (the "equilibrium of association" is reached, the electron transfer step is slow, the separation of the successor complex is fast). The ligand shells around A and D are retained. This process is called outer sphere electron transfer. Outer sphere ET is the main focus of traditional Marcus Theory. The other kind or redox reactions is inner sphere where A and D are covalently linked by a bridging ligand. Rates for such ET reactions depend on ligand exchange rates. | 0 | Theoretical and Fundamental Chemistry |
Electromechanical Film (EMFI, EMFIT, trademarks of Emfit Ltd) is a thin, flexible film that can function as a sensor or actuator. It is composed of a charged polymer coated with two conductive layers, making it an electret. It was invented and first made by Finnish inventor Kari Kirjavainen. Its voided internal structure and high resistivity allow it to hold a high electric charge and make the film very sensitive to force. Changes in the films thickness create an electric charge and make it operate as a sensor, or when an electric voltage is applied, it can function as an actuator. This gives the film applications in different fields of technology, including, but not limited to, mechanical vibration and ultrasound sensors, microphones, loudspeaker panels, keyboards, and physiological touch sensors. Other than being cheap, its main advantage is its versatility; it can be cut, reshaped, and resized depending on its surface of application. | 1 | Applied and Interdisciplinary Chemistry |
The British Mass Spectrometry Society is a registered charity founded in 1964 that encourages participation in every aspect of mass spectrometry. It aims to encourage participation in all aspects of mass spectrometry on the widest basis, to promote knowledge and advancement in the field and to provide a forum for the exchange of views and information. It is committed to ensuring equal opportunities and reflecting the diversity of the society as a whole. The first foundations of the BMSS were laid in 1949 with the establishment of the Mass Spectrometry Panel by the Hydrocarbon Research Group. | 1 | Applied and Interdisciplinary Chemistry |
Substitution reactions involve the replacement of the halogen with another molecule—thus leaving saturated hydrocarbons, as well as the halogenated product. Haloalkanes behave as the R synthon, and readily react with nucleophiles.
Hydrolysis, a reaction in which water breaks a bond, is a good example of the nucleophilic nature of haloalkanes. The polar bond attracts a hydroxide ion, OH (NaOH being a common source of this ion). This OH is a nucleophile with a clearly negative charge, as it has excess electrons it donates them to the carbon, which results in a covalent bond between the two. Thus C–X is broken by heterolytic fission resulting in a halide ion, X. As can be seen, the OH is now attached to the alkyl group, creating an alcohol. (Hydrolysis of bromoethane, for example, yields ethanol). Reactions with ammonia give primary amines.
Chloro- and bromoalkanes are readily substituted by iodide in the Finkelstein reaction. The iodoalkanes produced easily undergo further reaction. Sodium iodide is used as a catalyst.
Haloalkanes react with ionic nucleophiles (e.g. cyanide, thiocyanate, azide); the halogen is replaced by the respective group. This is of great synthetic utility: chloroalkanes are often inexpensively available. For example, after undergoing substitution reactions, cyanoalkanes may be hydrolyzed to carboxylic acids, or reduced to primary amines using lithium aluminium hydride. Azoalkanes may be reduced to primary amines by Staudinger reduction or lithium aluminium hydride. Amines may also be prepared from alkyl halides in amine alkylation, Gabriel synthesis and Delepine reaction, by undergoing nucleophilic substitution with potassium phthalimide or hexamine respectively, followed by hydrolysis.
In the presence of a base, haloalkanes alkylate alcohols, amines, and thiols to obtain ethers, N-substituted amines, and thioethers respectively. They are substituted by Grignard reagent to give magnesium salts and an extended alkyl compound. | 0 | Theoretical and Fundamental Chemistry |
Kinesins are a superfamily of related motor proteins that use a microtubule track in anterograde movement. They are vital to spindle formation in mitotic and meiotic chromosome separation during cell division and are also responsible for shuttling mitochondria, Golgi bodies, and vesicles within eukaryotic cells. Kinesins have two heavy chains and two light chains per active motor. The two globular head motor domains in heavy chains can convert the chemical energy of ATP hydrolysis into mechanical work to move along microtubules. The direction in which cargo is transported can be towards the plus-end or the minus-end, depending on the type of kinesin. In general, kinesins with N-terminal motor domains move their cargo towards the plus ends of microtubules located at the cell periphery, while kinesins with C-terminal motor domains move cargo towards the minus ends of microtubules located at the nucleus. Fourteen distinct kinesin families are known, with some additional kinesin-like proteins that cannot be classified into these families.
Genomic representation of kinesin motors:
* Fungi (yeast): 6
* Plants (Arabidopsis thaliana): 61
* Insects (Drosophila melanogaster): 25
* Mammals (human): 45 | 0 | Theoretical and Fundamental Chemistry |
A chiral auxiliary is an organic compound which couples to the starting material to form a new compound which can then undergo diastereoselective reactions via intramolecular asymmetric induction. At the end of the reaction the auxiliary is removed, under conditions that will not cause racemization of the product. It is typically then recovered for future use.
Chiral auxiliaries must be used in stoichiometric amounts to be effective and require additional synthetic steps to append and remove the auxiliary. However, in some cases the only available stereoselective methodology relies on chiral auxiliaries and these reactions tend to be versatile and very well-studied, allowing the most time-efficient access to enantiomerically pure products. Additionally, the products of auxiliary-directed reactions are diastereomers, which enables their facile separation by methods such as column chromatography or crystallization. | 0 | Theoretical and Fundamental Chemistry |
Specific cavitands form the basis of rigid templates onto which de novo proteins can be chemically linked. This template assembled synthetic protein (TASP) structure provides a platform for the study of protein structure.
Silicon surfaces functionalized with tetraphosphonate cavitands have been used to singularly detect sarcosine in water and urine solutions. | 0 | Theoretical and Fundamental Chemistry |
After graduating from St. Petersburg University, V. G. Khlopin was left at the department of Professor L. A. Chugaev, but while still a student, in 1911 he conducted a workshop on the chemical methods of sanitary analyzes with doctors at the St. Petersburg Clinical Institute, and continued this course of practical training in 1912 and 1913.
From 1917 to 1924, V. G. Khlopin served as an assistant in the department of general chemistry at the university, and from 1924, as an assistant professor, he began teaching a special course on radioactivity and the chemistry of radioelements - the first in the USSR; since brief and incomplete data and summaries existed only in foreign literature, this course was completely developed by V. G. Khlopin, who taught it until 1930, and resumed in 1934 as a professor, teaching it until 1935. In the spring of 1945, the scientist organized and headed the department of radiochemistry at Leningrad University.
Developed by V. G. Khlopin in collaboration with B. A. Nikitin and A. P. Ratner, a course of lectures on radiochemistry formed the basis of an extensive monograph on the chemistry of radioactive substances.
V. G. Khlopin took an active part in the work of the Russian Physical-Chemical Society, and after the latter was transformed into the All-Union Chemical Society, he was a member of the Council of the Leningrad branch of the organization, and later was its chairman.
At the Academy of Sciences, V. G. Khlopin was a member of the Analytical Commission, the Commission on Isotopes, and the Commission for the Development of the Scientific Heritage of D. I. Mendeleev. From 1941 to 1945, V. G. Khlopin, as Deputy Academician-Secretary, did a lot of work in the Department of Chemical Sciences of the USSR Academy of Sciences. During the Eastern Front (World War II), V. G. Khlopin served as deputy chairman of the Commission for the Mobilization of Resources of the Volga and Kama Region and chairman of its chemical section.
For many years he was a member of the Editorial Council of the Chemical-Technical Publishing House (Khimteoret). The scientist was the executive editor of the journal Uspekhi Khimii and was on the editorial boards of the journals: “Reports of the USSR Academy of Sciences”, “Izvestia of the USSR Academy of Sciences (Department of Chemical Sciences)”, “Journal of General Chemistry” and “Journal of Physical Chemistry”.
Vitaly Grigorievich Khlopin trained students in all the most important areas of scientific activity, many of whom became not only independent scientific researchers, but also the creators of their own scientific directions and schools. | 0 | Theoretical and Fundamental Chemistry |
Lower alkyl tin compounds are often highly toxic and have penetrating odors. Tributyltin azide causes skin rashes, itching or blisters. | 0 | Theoretical and Fundamental Chemistry |
The most important benefit of CAM to the plant is the ability to leave most leaf stomata closed during the day. Plants employing CAM are most common in arid environments, where water is scarce. Being able to keep stomata closed during the hottest and driest part of the day reduces the loss of water through evapotranspiration, allowing such plants to grow in environments that would otherwise be far too dry. Plants using only carbon fixation, for example, lose 97% of the water they take up through the roots to transpiration - a high cost avoided by plants able to employ CAM. | 0 | Theoretical and Fundamental Chemistry |
The concentration of naturally produced HMB has been measured in several human body fluids using nuclear magnetic resonance spectroscopy, liquid chromatography–mass spectrometry, and gas chromatography–mass spectrometry methods. In the blood plasma and cerebrospinal fluid (CSF) of healthy adults, the average molar concentration of HMB has been measured at 4.0 micromolar (μM). The average concentration of HMB in the intramuscular fluid of healthy men of ages has been measured at 7.0 μM. In the urine of healthy individuals of any age, the excreted urinary concentration of HMB has been measured in a range of micromoles per millimole (μmol/mmol) of creatinine. In the breast milk of healthy lactating women, HMB and have been measured in ranges of μg/L and mg/L. In comparison, HMB has been detected and measured in the milk of healthy cows at a concentration of μg/L. This concentration is far too low to be an adequate dietary source of HMB for obtaining pharmacologically active concentrations of the compound in blood plasma.
In a study where participants consumed 2.42 grams of pure while fasting, the average plasma HMB concentration increased from a basal level of 5.1 to 408 μM after 30 minutes. At 150 minutes post-ingestion, the average plasma HMB concentration among participants was 275 μM.
Abnormal HMB concentrations in urine and blood plasma have been noted in several disease states where it may serve as a diagnostic biomarker, particularly in the case of metabolic disorders. The following table lists some of these disorders along with the associated HMB concentrations detected in urine or blood plasma. | 1 | Applied and Interdisciplinary Chemistry |
A sensitizer in chemiluminescence is a chemical compound, capable of light emission after it has received energy from a molecule, which became excited previously in the chemical reaction. A good example is this:
When an alkaline solution of sodium hypochlorite and a concentrated solution of hydrogen peroxide are mixed, a reaction occurs:
:ClO(aq) + HO(aq) → O*(g) + H(aq) + Cl(aq) + OH(aq)
O*is excited oxygen – meaning, one or more electrons in the O molecule have been promoted to higher-energy molecular orbitals. Hence, oxygen produced by this chemical reaction somehow absorbed the energy released by the reaction and became excited. This energy state is unstable, therefore it will return to the ground state by lowering its energy. It can do that in more than one way:
*it can react further, without any light emission
*it can lose energy without emission, for example, giving off heat to the surroundings or transferring energy to another molecule
*it can emit light
The intensity, duration and color of emitted light depend on quantum and kinetical factors. However, excited molecules are frequently less capable of light emission in terms of brightness and duration when compared to sensitizers. This is because sensitizers can store energy (that is, be excited) for longer periods of time than other excited molecules. The energy is stored through means of quantum vibration, so sensitizers are usually compounds which either include systems of aromatic rings or many conjugated double and triple bonds in their structure. Hence, if an excited molecule transfers its energy to a sensitizer thus exciting it, longer and easier to quantify light emission is often observed.
The color (that is, the wavelength), brightness and duration of emission depend upon the sensitizer used. Usually, for a certain chemical reaction, many different sensitizers can be used. | 0 | Theoretical and Fundamental Chemistry |
Carbonic acid gas was an ancient term to specify the gaseous state of carbonic acid (synonymous with carbonic acid). It is listed as an alternative name for carbon dioxide in PubChem. In 1796 externally applied carbonic acid gas to the epidermis was reported to treat breast cancer; and inhalation treated tuberculosis and other indications. | 1 | Applied and Interdisciplinary Chemistry |
Removal of monomers and solvents from Latex and suspensions, for example in the production of synthetic rubber, are usually done via stirred vessels. | 1 | Applied and Interdisciplinary Chemistry |
Mefloquine is metabolized primarily through the liver. Its elimination in persons with impaired liver function may be prolonged, resulting in higher plasma levels and an increased risk of adverse reactions. The mean elimination plasma half-life of mefloquine is between two and four weeks. Total clearance is through the liver, and the primary means of excretion is through the bile and feces, as opposed to only 4% to 9% excreted through the urine. During long-term use, the plasma half-life remains unchanged.
Liver function tests should be performed during long-term administration of mefloquine. Alcohol use should be avoided during treatment with mefloquine. | 0 | Theoretical and Fundamental Chemistry |
Taylor–von Neumann–Sedov blast wave (or sometimes referred to as Sedov–von Neumann–Taylor blast wave) refers to a blast wave induced by a strong explosion. The blast wave was described by a self-similar solution independently by G. I. Taylor, John von Neumann and Leonid Sedov during World War II. | 1 | Applied and Interdisciplinary Chemistry |
Bioswales are useful low-impact development work to decrease the velocity of stormwater runoff while removing pollutants from the discharge. They are extremely beneficial in protecting surface water and local waterways from excessive pollution from stormwater runoff. The longer the runoff stays within the bioswale, the better the pollutant removal outcome. It is also beneficial in removing standing ponds that could potentially attract mosquitos. Bioswales can also be designed to be aesthetically pleasing and attract animals and create habitats. Bioswales can also be beneficial for groundwater recharge. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, brosyl (or para-bromophenylsulfonyl) group is a functional group with the chemical formula BrCHSO. This group is usually introduced using the compound brosyl chloride, BrCHSOCl, which forms sulfonyl esters and amides of p-bromophenylsulfonic acid. The term brosylate refers to the anion of p-bromophenylsulfonic acid (BrCHSO). | 0 | Theoretical and Fundamental Chemistry |
One stable N-heterocyclic carbene has a structure analogous to borazine with one boron atom replaced by a methylene group. This results in a planar six-electron compound. | 0 | Theoretical and Fundamental Chemistry |
Spectrophotometry is a branch of electromagnetic spectroscopy concerned with the quantitative measurement of the reflection or transmission properties of a material as a function of wavelength. Spectrophotometry uses photometers, known as spectrophotometers, that can measure the intensity of a light beam at different wavelengths. Although spectrophotometry is most commonly applied to ultraviolet, visible, and infrared radiation, modern spectrophotometers can interrogate wide swaths of the electromagnetic spectrum, including x-ray, ultraviolet, visible, infrared, and/or microwave wavelengths. | 0 | Theoretical and Fundamental Chemistry |
Elementary mode analysis closely matches the approach used by extreme pathways. Similar to extreme pathways, there is always a unique set of elementary modes available for a particular metabolic network. These are the smallest sub-networks that allow a metabolic reconstruction network to function in steady state. According to Stelling (2002), elementary modes can be used to understand cellular objectives for the overall metabolic network. Furthermore, elementary mode analysis takes into account stoichiometrics and thermodynamics when evaluating whether a particular metabolic route or network is feasible and likely for a set of proteins/enzymes. | 1 | Applied and Interdisciplinary Chemistry |
The Langmuir–McLean equation for segregation, when using the regular solution model for a binary system, is valid for surface segregation (although sometimes the equation will be written replacing with ). The free energy of surface segregation is . The enthalpy is given by
where and are matrix surface energies without and with solute, is their heat of mixing, Z and are the coordination numbers in the matrix and at the surface, and is the coordination number for surface atoms to the layer below. The last term in this equation is the elastic strain energy , given above, and is governed by the mismatch between the solute and the matrix atoms. For solid metals, the surface energies scale with the melting points. The surface segregation enrichment ratio increases when the solute atom size is larger than the matrix atom size and when the melting point of the solute is lower than that of the matrix.
A chemisorbed gaseous species on the surface can also have an effect on the surface composition of a binary alloy. In the presence of a coverage of a chemisorbed species theta, it is proposed that the Langmuir-McLean model is valid with the free energy of surface segregation given by , where
and are the chemisorption energies of the gas on solute A and matrix B and is the fractional coverage. At high temperatures, evaporation from the surface can take place, causing a deviation from the McLean equation. At lower temperatures, both grain boundary and surface segregation can be limited by the diffusion of atoms from the bulk to the surface or interface. | 0 | Theoretical and Fundamental Chemistry |
Johan Gadolin (5 June 176015 August 1852) was a Finnish chemist, physicist and mineralogist. Gadolin discovered a "new earth" containing the first rare-earth compound yttrium, which was later determined to be a chemical element. He is also considered the founder of Finnish chemistry research, as the second holder of the Chair of Chemistry at the Royal Academy of Turku (or Åbo Kungliga Akademi). Gadolin was ennobled for his achievements and awarded the Order of Saint Vladimir and the Order of Saint Anna. | 1 | Applied and Interdisciplinary Chemistry |
Cryoprotectants are also used to preserve foods. These compounds are typically sugars that are inexpensive and do not pose any toxicity concerns. For example, many (raw) frozen chicken products contain a sucrose and sodium phosphates solution in water. | 1 | Applied and Interdisciplinary Chemistry |
One consequence of this difference is that the color charge is too large for perturbative computations which are the mainstay of QED. As a result, the main theoretical tools to explore the theory of the QGP is lattice gauge theory. The transition temperature (approximately ) was first predicted by lattice gauge theory. Since then lattice gauge theory has been used to predict many other properties of this kind of matter. The AdS/CFT correspondence conjecture may provide insights in QGP, moreover the ultimate goal of the fluid/gravity correspondence is to understand QGP. The QGP is believed to be a phase of QCD which is completely locally thermalized and thus suitable for an effective fluid dynamic description. | 0 | Theoretical and Fundamental Chemistry |
The efficiency of conversion of ingested food to unit of body substance (ECI, also termed "growth efficiency") is an index measure of food fuel efficiency in animals. The ECI is a rough scale of how much of the food ingested is converted into growth in the animal's mass. It can be used to compare the growth efficiency as measured by the weight gain of different animals from consuming a given quantity of food relative to its size.
The ECI effectively represents efficiencies of both digestion (approximate digestibility or AD) and metabolic efficiency, or how well digested food is converted to mass (efficiency of conversion of digested food or ECD). The formula for the efficiency of food fuel is thus:
These concepts are also very closely related to the feed conversion ratio (FCR) and feed efficiency. | 1 | Applied and Interdisciplinary Chemistry |
Primary and secondary consumers in lakes require organic matter (either from plants or animals) to maintain organismal function. Organic matter including tree leaves, dissolved organic matter, and algae provide essential resources to these consumers and in the process increase lake ecosystem respiration rates in the conversion of organic matter to cellular growth and organismal maintenance. Some sources of organic matter may impact the availability of other constituents. For example, dissolved organic matter often darkens lake water which reduces the amount of light available in the lake, thus reducing primary production. However, increases in organic matter loading to a lake can also increase nutrients that are associated with the organic matter, which can stimulate primary production and respiration. Increased dissolved organic matter loading can create tradeoffs between increasing light limitation and release from nutrient limitation. This tradeoff can create non-linear relationships between lake primary production and dissolved organic matter loading based on how much nutrients are associated with the organic matter and how quickly the dissolved organic matter blocks out light in the water column. This is because at low dissolved organic matter concentrations as dissolved organic matter concentration increases, increased associated nutrients enhances GPP. But as dissolved organic matter continues to increase, the reduction in light from the darkening of the lake water suppresses GPP as light becomes the limiting resource for primary productivity. Differences in the magnitude and location of maximum GPP in response to increased DOC load are hypothesized to arise based on the ratio of DOC to nutrients coming into the lake as well as the effect of DOC on lake light climate. The darkening of the lake water can also change thermal regimes within the lake as darker waters typically mean that warmer waters remain at the top of the lake while cooler waters are at the bottom. This change in heat energy distribution can impact the rates of pelagic and benthic productivity (see Temperature above), and change water column stability, with impacts on vertical distribution of nutrients, therefore having effects on vertical distribution of metabolic rates. | 1 | Applied and Interdisciplinary Chemistry |
The Society of Chemical Industry (SCI) is a learned society set up in 1881 "to further the application of chemistry and related sciences for the public benefit". | 1 | Applied and Interdisciplinary Chemistry |
Armando Bukele Kattán (16 December 1944 – 30 November 2015) was a Salvadoran businessman and Muslim religious leader and father of current Salvadoran President Nayib Bukele. | 1 | Applied and Interdisciplinary Chemistry |
Here, the aglycone is coumarin or a derivative. An example is apterin which is reported to dilate the coronary arteries as well as block calcium channels. Other coumarin glycosides are obtained from dried leaves of Psoralea corylifolia. | 0 | Theoretical and Fundamental Chemistry |
Agents that increase surface tension are "surface active" in the literal sense but are not called surfactants as their effect is opposite to the common meaning. A common example of surface tension increase is salting out: adding an inorganic salt to an aqueous solution of a weakly polar substance will cause the substance to precipitate. The substance may itself be a surfactant, which is one of the reasons why many surfactants are ineffective in sea water. | 0 | Theoretical and Fundamental Chemistry |
An important functional feature of genes is the phenotype caused by mutations. Mutants can be produced by random mutations or by directed mutagenesis, including site-directed mutagenesis, deleting complete genes, or other techniques. | 1 | Applied and Interdisciplinary Chemistry |
Orally consumed retinoic acid (RA), as all-trans-tretinoin or 13-cis-isotretinoin has been shown to improve facial skin health by switching on genes and differentiating keratinocytes (immature skin cells) into mature epidermal cells. RA reduces the size and secretion of the sebaceous glands, and by doing so reduces bacterial numbers in both the ducts and skin surface. It reduces inflammation via inhibition of chemotactic responses of monocytes and neutrophils. In the US, isotretinoin was released to the market in 1982 as a revolutionary treatment for severe and refractory acne vulgaris. It was shown that a dose of 0.5‑1.0 mg/kg body weight/day is enough to produce a reduction in sebum excretion by 90% within a month or two, but the recommended treatment duration is 4 to 6 months. Isotretinoin is a known teratogen, with an estimated 20‑35% risk of physical birth defects to infants that are exposed to isotretinoin in utero, including numerous congenital defects such as craniofacial defects, cardiovascular and neurological malformations or thymic disorders. Neurocognitive impairments in the absence of any physical defects has been established to be 30‑60%. For these reasons, physician- and patient-education programs were initiated, recommending that for women of child-bearing age, contraception be initiated a month before starting oral (or topical) isotretinoin, and continue for a month after treatment ended.
In addition to the approved use for treating acne vulgaris, researchers have investigated off-label applications for dermatological conditions, such as rosacea, psoriasis, and other conditions. Rosacea was reported as responding favorably to doses lower than used for acne. Isotretinoin in combination with ultraviolet light was shown affective for treating psoriasis. Isotretinoin in combination with injected interferon-alpha showed some potential for treating genital warts. Isotretinoin in combination with topical fluorouracil or injected interferon-alpha showed some potential for treating precancerous skin lesions and skin cancer. | 1 | Applied and Interdisciplinary Chemistry |
In most cases, splicing removes introns as single units from precursor mRNA transcripts. However, in some cases, especially in mRNAs with very long introns, splicing happens in steps, with part of an intron removed and then the remaining intron is spliced out in a following step. This has been found first in the Ultrabithorax (Ubx) gene of the fruit fly, Drosophila melanogaster, and a few other Drosophila genes, but cases in humans have been reported as well. | 1 | Applied and Interdisciplinary Chemistry |
Reverberatory furnaces are long furnaces that can treat wet, dry, or roasted concentrate. Most of the reverberatory furnaces used in the latter years treated roasted concentrate because putting dry feed materials into the reverberatory furnace is more energy efficient, and because the elimination of some of the sulfur in the roaster results in higher matte grades.
The reverberatory furnace feed is added to the furnace through feed holes along the sides of the furnace, and the solid charge is melted. Additional silica is normally added to help form the slag. The furnace is fired with burners using pulverized coal, fuel oil or natural gas
Reverberatory furnaces can additionally be fed with molten slag from the later converting stage to recover the contained copper and other materials with a high copper content.
Because the reverberatory furnace bath is quiescent, very little oxidation of the feed occurs (and thus very little sulfur is eliminated from the concentrate). It is essentially a melting process. Consequently, wet-charged reverberatory furnaces have less copper in their matte product than calcine-charged furnaces, and they also have lower copper losses to slag. Gill quotes a copper in slag value of 0.23% for a wet-charged reverberatory furnace vs 0.37% for a calcine-charged furnace.
In the case of calcine-charged furnaces, a significant portion of the sulfur has been eliminated during the roasting stage, and the calcine consists of a mixture of copper and iron oxides and sulfides. The reverberatory furnace acts to allow these species to approach chemical equilibrium at the furnace operating temperature (approximately 1600 °C at the burner end of the furnace and about 1200 °C at the flue end; the matte is about 1100 °C and the slag is about 1195 °C). In this equilibration process, oxygen associated with copper compounds exchanges with sulfur associated with iron compounds, increasing the iron oxide content of the furnace, and the iron oxides interact with silica and other oxide materials to form the slag.
The main equilibration reaction is:
:CuO + FeS → CuS + FeO
The slag and the matte form distinct layers that can be removed from the furnace as separate streams. The slag layer is periodically allowed to flow through a hole in the wall of the furnace above the height of the matte layer. The matte is removed by draining it through a hole into ladles for it to be carried by crane to the converters. This draining process is known as tapping the furnace. The matte taphole is normally a hole through a water-cooled copper block that prevents erosion of the refractory bricks lining the furnace. When the removal of the matte or slag is complete, the hole is normally plugged with clay, which is removed when the furnace is ready to be tapped again.
Reverberatory furnaces were often used to treat molten converter slag to recover contained copper. This would be poured into the furnaces from ladles carried by cranes. However, the converter slag is high in magnetite and some of this magnetite would precipitate from the converter slag (due to its higher melting point), forming an accretion on the hearth of the reverberatory furnace and necessitating shut downs of the furnace to remove the accretion. This accretion formation limits the quantity of converter slag that can be treated in a reverberatory furnace.
While reverberatory furnaces have very low copper losses to slag, they are not very energy-efficient and the low concentrations of sulfur dioxide in their off-gases make its capture uneconomic. Consequently, smelter operators devoted a lot of money in the 1970s and 1980s to developing new, more efficient copper smelting processes. In addition, flash smelting technologies had been developed in earlier years and began to replace reverberatory furnaces. By 2002, 20 of the 30 reverberatory furnaces still operating in 1994 had been shut down. | 1 | Applied and Interdisciplinary Chemistry |
NEM is a Michael acceptor in the Michael reaction, which means that it adds nucleophiles such as thiols. The resulting thioether features a strong C-S bond and the reaction is virtually irreversible. Reaction with thiols occur in the pH range 6.5–7.5, NEM may react with amines or undergo hydrolysis at a more alkaline pH. NEM has been widely used to probe the functional role of thiol groups in enzymology. NEM is an irreversible inhibitor of all cysteine peptidases, with alkylation occurring at the active site thiol group (see schematic). | 1 | Applied and Interdisciplinary Chemistry |
Copperas works are manufactories where copperas (iron(II) sulfate) is produced from pyrite, often obtained as a byproduct during coal mining, and iron. The history of producing green vitriol, as it was known, goes back hundreds of years in Scotland. In 1814 the wool-producing city of Steubenville, Ohio had seven copperas-producing manufacturers.
Pyrite has been used since classical times to manufacture copperas. Iron pyrite was heaped up and allowed to weather (an example of an early form of heap leaching). The acidic runoff from the heap was then boiled with iron to produce iron sulfate.
Containment of leachate is important due to its toxicity; a fish kill that occurred in the 1890s in the Kanawha River was attributed to copperas solution release from the mines in Cannelton, West Virginia.
The "vitriolic waters of Fahlun" (Falun, Sweden), according to Murray (1844), annually produced "about 600 quintals of green vitriol" (sulfate of iron), as well as a "small quantity of blue vitriol" (sulfate of copper). These may have been obtained through evaporation of the groundwater associated with mines in order to yield the crystalline form of copperas. | 1 | Applied and Interdisciplinary Chemistry |
Researchers conjugated the thermo-responsive polymer poly(N-isopropylacrylamide) (pNIPAm) with the biotin-recognizing protein streptavidin close to its recognition site. At temperatures above the lower critical solution temperature (LCST), the polymer collapses and blocks the binding site, thus reversibly preventing biotin from binding to streptavidin. By copolymerization with two different thermosensitive polymers poly(sulfobetaine methacrylamide) (pSBAm) and pNIPAm together, researchers can control enzyme activity in a small temperature window. | 1 | Applied and Interdisciplinary Chemistry |
The synthesis of NanoPutian’s lower body begins with nitroaniline as a starting material. Addition of Br in acetic acid places two equivalents of bromine on the benzene ring. NH is an electron donating group, and NO is an electron withdrawing group, which both direct bromination to the meta position relative to the NO substituent. Addition of NaNO, HSO, and EtOH removes the NH substituent. The Lewis acid SnCl, a reducing agent in THF/EtOH solvent, replaces NO with NH, which is subsequently replaced by iodine upon the addition of NaNO, HSO, and KI to yield 3,5-dibromoiodobenzene. In this step, the Sandmeyer reaction converts the primary amino group (NH) to a diazonium leaving group (N), which is subsequently replaced by iodine. Iodine serves as an excellent coupling partner for the attachment of the stomach, which is executed through Sonogashira coupling with trimethylsilylacetylene to yield 3,5-dibromo(trimethylsilylethynyl)benzene. Attachment of the legs replaces the Br substituents with 1-pentyne through another Sonogashira coupling to produce 3,5-(1′-Pentynyl)-1-(trimethylsilylethynyl) benzene. To complete the synthesis of the lower body, the TMS protecting group is removed by selective deprotection through the addition of KCO, MeOH, and CHCl to yield 3,5-(1′-Pentynyl)-1-ethynylbenzene. | 1 | Applied and Interdisciplinary Chemistry |
The concept of microstructure is observable in macrostructural features in commonplace objects. Galvanized steel, such as the casing of a lamp post or road divider, exhibits a non-uniformly colored patchwork of interlocking polygons of different shades of grey or silver. Each polygon is a single crystal of zinc adhering to the surface of the steel beneath. Zinc and lead are two common metals which form large crystals (grains) visible to the naked eye. The atoms in each grain are organized into one of seven 3d stacking arrangements or crystal lattices (cubic, tetrahedral, hexagonal, monoclinic, triclinic, rhombohedral and orthorhombic). The direction of alignment of the matrices differ between adjacent crystals, leading to variance in the reflectivity of each presented face of the interlocked grains on the galvanized surface. The average grain size can be controlled by processing conditions and composition, and most alloys consist of much smaller grains not visible to the naked eye. This is to increase the strength of the material (see Hall-Petch Strengthening). | 1 | Applied and Interdisciplinary Chemistry |
Cellulose bioplastics are mainly the cellulose esters (including cellulose acetate and nitrocellulose) and their derivatives, including celluloid.
Cellulose can become thermoplastic when extensively modified. An example of this is cellulose acetate, which is expensive and therefore rarely used for packaging. However, cellulosic fibers added to starches can improve mechanical properties, permeability to gas, and water resistance due to being less hydrophilic than starch.
A group at Shanghai University was able to construct a novel green plastic based on cellulose through a method called hot pressing. | 0 | Theoretical and Fundamental Chemistry |
The rate of hypothyroidism is around six times higher in people who take lithium. Low thyroid hormone levels in turn increase the likelihood of developing depression. People taking lithium thus should routinely be assessed for hypothyroidism and treated with synthetic thyroxine if necessary.
Because lithium competes with the antidiuretic hormone in the kidney, it increases water output into the urine, a condition called nephrogenic diabetes insipidus. Clearance of lithium by the kidneys is usually successful with certain diuretic medications, including amiloride and triamterene. It increases the appetite and thirst ("polydypsia") and reduces the activity of thyroid hormone (hypothyroidism). The latter can be corrected by treatment with thyroxine and does not require the lithium dose to be adjusted. Lithium is also believed to permanently affect renal function, although this does not appear to be common. | 1 | Applied and Interdisciplinary Chemistry |
Another direction for transparent wood applications is as a high optical transmittance for optoelectronic devices as substrates in photovoltaic solar cells. Li and her colleagues at the KTH Royal Institute of Technology studied the high optical transmittance that makes transparent wood a candidate for substrate in perovskite solar cells. They concluded that transparent wood has high optical transmittance of 86% and long term stability with fracture of toughness 3.2 MPa⋅m compared to glass substrate fracture of toughness 0.7–0.85 MPa⋅m, which meets the substrates requirements for solar cells. These are relevant information for transparent woods possible application because it is a suitable and sustainable solution to the substrate for solar cell assembly with potential in energy-efficient building applications, as well as replacements for glass and lowering the carbon footprint for the devices.
Transparent wood could transform the material sciences and building industries by enabling new applications such as load-bearing windows. These components could also generate improvements in energy savings and efficiency over glass or other traditional materials. A lot of work and research is needed to understand the interaction between light and the wood structure further, to tune the optical and mechanical properties, and to take advantage of advanced transparent wood composite applications | 0 | Theoretical and Fundamental Chemistry |
Moscow State University of Fine Chemical Technologies named after M.V. Lomonosov (traditional abbreviation "MITHT") is one of the oldest universities in the country that offer training in a wide range of specialties in the field of chemical technology.
Currently, there are more than 4,500 students in nine areas of undergraduate, 28 master's programs and 23 scientific specialties for training of candidates and doctors of science. In MITHT there are eight dissertation councils for doctoral and PhD theses.
Research and teaching activities are performed by more than 400 professors and 158 scientists, including more than 120 doctors of science and professors. Located in Moscow at Vernadsky Avenue, Building 86 (new building complex) and Malaya Pirogovskaya, Building 1 (historic building). | 1 | Applied and Interdisciplinary Chemistry |
The quantum number J refers to the total angular momentum, as before. Since there are three independent moments of inertia, there are two other independent quantum numbers to consider, but the term values for an asymmetric rotor cannot be derived in closed form. They are obtained by individual matrix diagonalization for each J value. Formulae are available for molecules whose shape approximates to that of a symmetric top.
The water molecule is an important example of an asymmetric top. It has an intense pure rotation spectrum in the far infrared region, below about 200 cm. For this reason far infrared spectrometers have to be freed of atmospheric water vapour either by purging with a dry gas or by evacuation. The spectrum has been analyzed in detail. | 0 | Theoretical and Fundamental Chemistry |
Stratified waters, in combination with slow vertical mixing, are essential to maintaining euxinic conditions. Stratification occurs when two or more water masses with different densities occupy the same basin. While the less dense surface water can exchange gas with the oxygen-rich atmosphere, the denser bottom waters maintain low oxygen content. In the modern oceans, thermohaline circulation and upwelling prevent the oceans from maintaining anoxic bottom waters. In a silled basin, the stable stratified layers only allow surface water to flow out of the basin while the deep water remains anoxic and relatively unmixed. During an intrusion of dense saltwater however, the nutrient-rich bottom water upwells, causing increased productivity in the surface, further enhancing the nutrient trap due to biological pumping. Rising sea level can exacerbate this process by increasing the amount of deep water entering a silled basin and enhancing estuarine circulation. | 0 | Theoretical and Fundamental Chemistry |
Chlorotrifluoromethane, R-13, CFC-13, or Freon 13, is a non-flammable, non-corrosive, nontoxic chlorofluorocarbon (CFC) and also a mixed halomethane. It is a man-made substance used primarily as a refrigerant. When released into the environment, CFC-13 has a high ozone depletion potential, and long atmospheric lifetime. Only a few other greenhouse gases surpass CFC-13 in global warming potential (GWP). The IPCC AR5 reported that CFC-13's atmospheric lifetime was 640 years. | 1 | Applied and Interdisciplinary Chemistry |
The interaction between bases on different strands depends somewhat on the neighboring bases. Instead of treating a DNA helix as a string of interactions between base pairs, the nearest-neighbor model treats a DNA helix as a string of interactions between neighboring base pairs. So, for example, the DNA shown below has nearest-neighbor interactions indicated by the arrows.
The free energy of forming this DNA from the individual strands, ΔG°, is represented (at 37 °C) as
ΔG°(predicted) = ΔG°(C/G initiation) + ΔG°(CG/GC) + ΔG°(GT/CA) + ΔG°(TT/AA) + ΔG°(TG/AC) + ΔG°(GA/CT) + ΔG°(A/T initiation)
Except for the C/G initiation term, the first term represents the free energy of the first base pair, CG, in the absence of a nearest neighbor. The second term includes both the free energy of formation of the second base pair, GC, and stacking interaction between this base pair and the previous base pair. The remaining terms are similarly defined. In general, the free energy of forming a nucleic acid duplex is
where represents the free energy associated with one of the ten possible the nearest-neighbor nucleotide pairs, and represents its count in the sequence.
Each ΔG° term has enthalpic, ΔH°, and entropic, ΔS°, parameters, so the change in free energy is also given by
Values of ΔH° and ΔS° have been determined for the ten possible pairs of interactions. These are given in Table 1, along with the value of ΔG° calculated at 37 °C. Using these values, the value of ΔG° for the DNA duplex shown above is calculated to be −22.4 kJ/mol. The experimental value is −21.8 kJ/mol.
The parameters associated with the ten groups of neighbors shown in table 1 are determined from melting points of short oligonucleotide duplexes. It works out that only eight of the ten groups are independent.
The nearest-neighbor model can be extended beyond the Watson-Crick pairs to include parameters for interactions between mismatches and neighboring base pairs. This allows the estimation of the thermodynamic parameters of sequences containing isolated mismatches, like e.g. (arrows indicating mismatch)
These parameters have been fitted from melting experiments and an extension of Table 1 which includes mismatches can be found in literature.
A more realistic way of modeling the behavior of nucleic acids would seem to be to have parameters that depend on the neighboring groups on both sides of a nucleotide, giving a table with entries like "TCG/AGC". However, this would involve around 32 groups for Watson-Crick pairing and even more for sequences containing mismatches; the number of DNA melting experiments needed to get reliable data for so many groups would be inconveniently high. However, other means exist to access thermodynamic parameters of nucleic acids: microarray technology allows hybridization monitoring of tens of thousands sequences in parallel. This data, in combination with molecular adsorption theory allows the determination of many thermodynamic parameters in a single experiment and to go beyond the nearest neighbor model. In general the predictions from the nearest neighbor method agree reasonably well with experimental results, but some unexpected outlying sequences, calling for further insights, do exist. Finally, we should also mention the increased accuracy provided by single molecule unzipping assays which provide a wealth of new insight into the thermodynamics of DNA hybridization and the validity of the nearest-neighbour model as well. | 1 | Applied and Interdisciplinary Chemistry |
The GFP publishes a newsletter "Actualités du GFP", 2-3 times per year. Additionally, its Education Commission periodically releases books on different aspects of polymers and their applications. In 2004, the GFP joined forces with the International Union for Pure and Applied Chemistry to promote education in polymer science in French-speaking countries. | 1 | Applied and Interdisciplinary Chemistry |
Compounds containing fluorine-18, a radioactive isotope that emits positrons, are often used in positron emission tomography (PET) scanning, because the isotopes half-life of about 110 minutes is usefully long by positron-emitter standards. One such radiopharmaceutical is 2-deoxy-2-(F)fluoro-D-glucose (generically referred to as fludeoxyglucose), commonly abbreviated as F-FDG, or simply FDG. In PET imaging, FDG can be used for assessing glucose metabolism in the brain and for imaging cancer tumors. After injection into the blood, FDG is taken up by "FDG-avid" tissues with a high need for glucose, such as the brain and most types of malignant tumors. Tomography, often assisted by a computer to form a PET/CT (CT stands for "computer tomography") machine, can then be used to diagnose or monitor treatment of cancers, especially Hodgkins lymphoma, lung cancer, and breast cancer.
Natural fluorine is monoisotopic, consisting solely of fluorine-19. Fluorine compounds are highly amenable to nuclear magnetic resonance (NMR), because fluorine-19 has a nuclear spin of , a high nuclear magnetic moment, and a high magnetogyric ratio. Fluorine compounds typically have a fast NMR relaxation, which enables the use of fast averaging to obtain a signal-to-noise ratio similar to hydrogen-1 NMR spectra. Fluorine-19 is commonly used in NMR study of metabolism, protein structures and conformational changes. In addition, inert fluorinated gases have the potential to be a cheap and efficient tool for imaging lung ventilation. | 1 | Applied and Interdisciplinary Chemistry |
Most MAPKs have a number of shared characteristics, such as the activation dependent on two phosphorylation events, a three-tiered pathway architecture and similar substrate recognition sites. These are the "classical" MAP kinases. But there are also some ancient outliers from the group as sketched above, that do not have dual phosphorylation sites, only form two-tiered pathways, and lack the features required by other MAPKs for substrate binding. These are usually referred to as "atypical" MAPKs. It is yet unclear if the atypical MAPKs form a single group as opposed to the classical ones.
The mammalian MAPK family of kinases includes three subfamilies:
# Extracellular signal-regulated kinases (ERKs)
# c-Jun N-terminal kinases (JNKs)
# p38 mitogen-activated protein kinases (p38s)
Generally, ERKs are activated by growth factors and mitogens, whereas cellular stresses and inflammatory cytokines activate JNKs and p38s. | 1 | Applied and Interdisciplinary Chemistry |
The need for fluorescently tracking RNA rose as its roles in complex cellular functions has grown to not only include mRNA, rRNA, and tRNA, but also RNAi, siRNA, snoRNA, and lncRNA, among others. Spinach is a synthetically derived RNA aptamer born out of the need for a way of studying the role of RNAs at the cellular level. This aptamer was created using Systematic Evolution for Ligands by EXponential enrichment, or SELEX, which is also known as in vitro evolution. The aptamer was designed to be an RNA mimic of green fluorescent protein (GFP); similar to GFP for proteins, Spinach can be used for the fluorescently labeling RNA and tracking it in vivo. A method for inserting the Spinach sequence after an RNA sequence of interest is readily available.
GFP’s fluorophore is made up of three cyclized amino acids within the beta-barrel structure: Serine65-Tyrosine66-Glycine67. This structure, 4-hydroxybenzylidene imidazolinone (HBI) was the basis for the synthetic analogue used in the SELEX studies. Many derivatives of this structure were screened using SELEX, but the chosen fluorophore, 3,5-difluoro-4-hydroxybenzylidene imidazolinone (DFHBI), showed the best selective fluorescence with high quantum yield (0.72) when bound to the RNA sequence 24-2, deemed Spinach.
It was determined that DFHBI only binds Spinach in the phenolate form. At pH < 6.0, both the phenolic and phenolate forms are detected. At pH = 6.0, only the phenolate peak is detected. DFHBI is also incredibly robust and resists photobleaching over a long period of time as compared to HBI and EGFP. It is believed that the free exchange of bound and unbound ligand allows for this persistence. As the fluorophore of GFP and its derivatives are covalently bound to/a part of the protein, free exchange cannot happen and thus photobleaching results.
Spinach is an 84-nucleotide-long structure with two helical strands and an internal bulge with a G-quadruplex motif. It is at this G-quadruplex that the fluorophore binds. Based on crystallographic data, massive rearrangement of the adjacent bases occurs once the fluorophore binds to accommodate the molecule. This binding is favorable, however, as it promotes base-stacking in a normally unstable region, i.e. the internal bulge. Similar to GFP, the DFHBI is also dehydrated, which would help with its high quantum yield.
Spinach has also been adapted for sensing proteins or molecules in vivo. An adapted structure, which includes two binding sites, limits fluorescence of the aptamer to (1) the fluorophore and (2) the protein or small molecule. | 1 | Applied and Interdisciplinary Chemistry |
The parent metallacyclobutane has the formula LM(CH) where L is a ligand attached to M. A stable example is (PPh)Pt(CH). The first example was prepared by oxidative addition of cyclopropane to platinum.
Metallacyclobutane intermediates are involved in the alkene metathesis and in the oligomerization and dimerization of ethylene. In alkene metathesis, the Chauvin mechanism invokes the attack of an alkene at an electrophilic metal carbene catalyst. This work helped to validate the Chauvin mechanism for olefin metathesis. | 0 | Theoretical and Fundamental Chemistry |
Plants have been engineered for scientific research, to display new flower colors, deliver vaccines, and to create enhanced crops. Many plants are pluripotent, meaning that a single cell from a mature plant can be harvested and under the right conditions can develop into a new plant. This ability can be taken advantage of by genetic engineers; by selecting for cells that have been successfully transformed in an adult plant a new plant can then be grown that contains the transgene in every cell through a process known as tissue culture.
Much of the advances in the field of genetic engineering has come from experimentation with tobacco. Major advances in tissue culture and plant cellular mechanisms for a wide range of plants has originated from systems developed in tobacco. It was the first plant to be altered using genetic engineering and is considered a model organism for not only genetic engineering, but a range of other fields. As such the transgenic tools and procedures are well established making tobacco one of the easiest plants to transform. Another major model organism relevant to genetic engineering is Arabidopsis thaliana. Its small genome and short life cycle makes it easy to manipulate and it contains many homologs to important crop species. It was the first plant sequenced, has a host of online resources available and can be transformed by simply dipping a flower in a transformed Agrobacterium solution.
In research, plants are engineered to help discover the functions of certain genes. The simplest way to do this is to remove the gene and see what phenotype develops compared to the wild type form. Any differences are possibly the result of the missing gene. Unlike mutagenisis, genetic engineering allows targeted removal without disrupting other genes in the organism. Some genes are only expressed in certain tissues, so reporter genes, like GUS, can be attached to the gene of interest allowing visualization of the location. Other ways to test a gene is to alter it slightly and then return it to the plant and see if it still has the same effect on phenotype. Other strategies include attaching the gene to a strong promoter and see what happens when it is overexpressed, forcing a gene to be expressed in a different location or at different developmental stages.
Some genetically modified plants are purely ornamental. They are modified for flower color, fragrance, flower shape and plant architecture. The first genetically modified ornamentals commercialized altered color. Carnations were released in 1997, with the most popular genetically modified organism, a blue rose (actually lavender or mauve) created in 2004. The roses are sold in Japan, the United States, and Canada. Other genetically modified ornamentals include Chrysanthemum and Petunia. As well as increasing aesthetic value there are plans to develop ornamentals that use less water or are resistant to the cold, which would allow them to be grown outside their natural environments.
It has been proposed to genetically modify some plant species threatened by extinction to be resistant to invasive plants and diseases, such as the emerald ash borer in North American and the fungal disease, Ceratocystis platani, in European plane trees. The papaya ringspot virus devastated papaya trees in Hawaii in the twentieth century until transgenic papaya plants were given pathogen-derived resistance. However, genetic modification for conservation in plants remains mainly speculative. A unique concern is that a transgenic species may no longer bear enough resemblance to the original species to truly claim that the original species is being conserved. Instead, the transgenic species may be genetically different enough to be considered a new species, thus diminishing the conservation worth of genetic modification. | 1 | Applied and Interdisciplinary Chemistry |
Antibody Solutions was founded in 1995 by current president, John Kenney, PhD, Judith Lynch-Kenney, and Dennis and Bette Gould. Dr. Kenney previously managed the monoclonal antibody (MAb) development laboratory for Syntex Research (Roche) in Palo Alto, while Gould managed the MAb production facility for Syva Diagnostics. Gould left Antibody Solutions in 1997, eventually becoming a vice president for Sepragen Corporation. Kenney and Gould were assisted in the startup of the company by Barry Bredt, who had the foresight to acquire the domain name, [https://www.antibody.com www.antibody.com], for the company. Bredt later became director of the University of California at San Francisco’s General Clinical Research Center, and was a pioneer of the HIV/AIDS Diagnostics EasyCD4; he died on April 8, 2007.
Antibody Solutions was incorporated in 1998 with Dr. Kenney as president and Judith Lynch-Kenney as chief financial officer. One of the first independent antibody discovery companies, the firm focused on custom antibody discovery for therapeutics, diagnostics and critical reagents. The company pioneered the use of bioreactors in antibody research by becoming the first CRO to produce antibodies in CELLine flasks in 2000.
From 2004 to 2011, Antibody Solutions was headquartered in Mountain View, a short distance from Shoreline Park, Moffett Field and the Googleplex. In 2011, the company moved to new facilities in Sunnyvale. It moved to its current 33,300-square-foot location at 3033 Scott Blvd. in Santa Clara near the San Tomas Expressway in mid-2019. A grand opening for the Scott Blvd. facility was held on January 30, 2020, to coincide with the company's Silver Anniversary. | 1 | Applied and Interdisciplinary Chemistry |
The BRENDA tissue ontology (BTO) represents a comprehensive structured encyclopedia. It provides terms, classifications, and definitions of tissues, organs, anatomical structures, plant parts, cell cultures, cell types, and cell lines of organisms from all taxonomic groups (animals, plants, fungi, protozoon) as enzyme sources. The information is connected to the functional data in the BRENDA ("BRaunschweig ENzyme DAtabase“) enzyme information system.
BTO is one of the first tissue-specific ontologies in life sciences, not restricted to a specific organism or a specific organism group providing a user-friendly access to the wide range of tissue and cell-type information. Databases, such as Ontology Lookup Service or ses, such as MIRIAM Registry or of the EBI-EMBL, the TissueDistributionDB, including the Tissue Synonym Library of the German Cancer Research Center (DKFZ) in Heidelberg or the Bioportal platform of the National Center for Biomedical Ontology in Stanford, USA rely on BTO and implement the encyclopedia as an essential repository of information into their respective platform.
BTO enables users from medical research and pharmaceutical sciences to search for the occurrence and histological detection of disease-related enzymes in tissues, which play an important role in diagnosis, therapies, and drug development. In biochemistry and biotechnology the organism-specific tissue terms linked to enzyme functional data are an important resource for the understanding of the metabolism and regulation in life sciences. Ontologies represent classification systems that provide controlled and structured vocabularies. They are important tools to illustrate and to link evolutionary correlations.
Development of BTO started in 2003, aimed to connect the biochemical and molecular biological enzyme data of BRENDA with a hierarchical and standardized collection of tissue-specific terms. The functional enzyme data and information in BRENDA have been manually annotated and structured by experts from biochemistry, biology, and chemistry. By October 2022, the BTO contained over 6,527 terms, linked to 6,065 synonyms and 5,474 definitions. The terms are classified under generic categories, rules, and formats of the Gene Ontology Consortium (GO,), organized as a directed acyclic graph (DAG) created using the open-source OBO-Edit. All terms from each level are directly connected the enzyme data in BRENDA. BTO is a suitable tool to distinguish between different enzymes which are expressed in a tissue-specific manner. | 1 | Applied and Interdisciplinary Chemistry |
Ying Ge is a Chinese-American chemist who is a Professor of Cell and Regenerative Biology at the University of Wisconsin–Madison. Her research considers the molecular mechanisms that underpin cardiac disease. She has previously served on the board of directors of the American Society for Mass Spectrometry. In 2020 Ge was named on the Analytical Scientist Power List. | 1 | Applied and Interdisciplinary Chemistry |
Self-complementarity refers to the fact that a sequence of DNA or RNA may fold back on itself, creating a double-strand like structure. Depending on how close together the parts of the sequence are that are self-complementary, the strand may form hairpin loops, junctions, bulges or internal loops. RNA is more likely to form these kinds of structures due to base pair binding not seen in DNA, such as guanine binding with uracil. | 1 | Applied and Interdisciplinary Chemistry |
Alkenes undergo "hydroesterification" in the presence of metal carbonyl catalysts. Esters of propanoic acid are produced commercially by this method:
A preparation of methyl propionate is one illustrative example.
The carbonylation of methanol yields methyl formate, which is the main commercial source of formic acid. The reaction is catalyzed by sodium methoxide: | 0 | Theoretical and Fundamental Chemistry |
Traffic waves, also called stop waves, ghost jams, traffic snakes or traffic shocks, are traveling disturbances in the distribution of cars on a highway. Traffic waves travel backwards relative to the cars themselves. Relative to a fixed spot on the road the wave can move with, or against the traffic, or even be stationary (when the wave moves away from the traffic with exactly the same speed as the traffic). Traffic waves are a type of traffic jam. A deeper understanding of traffic waves is a goal of the physical study of traffic flow, in which traffic itself can often be seen using techniques similar to those used in fluid dynamics. It is related to the accordion effect. | 1 | Applied and Interdisciplinary Chemistry |
The electron affinity of molecules is a complicated function of their electronic structure.
For instance the electron affinity for benzene is negative, as is that of naphthalene, while those of anthracene, phenanthrene and pyrene are positive. In silico experiments show that the electron affinity of hexacyanobenzene surpasses that of fullerene. | 0 | Theoretical and Fundamental Chemistry |
A two-dimensional polymer (2DP) is a sheet-like monomolecular macromolecule consisting of laterally connected repeat units with end groups along all edges. This recent definition of 2DP is based on Hermann Staudinger's polymer concept from the 1920s. According to this, covalent long chain molecules ("Makromoleküle") do exist and are composed of a sequence of linearly connected repeat units and end groups at both termini.
Moving from one dimension to two offers access to surface morphologies such as increased surface area, porous membranes, and possibly in-plane pi orbital-conjugation for enhanced electronic properties. They are distinct from other families of polymers because 2D polymers can be isolated as multilayer crystals or as individual sheets.
The term 2D polymer has also been used more broadly to include linear polymerizations performed at interfaces, layered non-covalent assemblies, or to irregularly cross-linked polymers confined to surfaces or layered films. 2D polymers can be organized based on these methods of linking (monomer interaction): covalently linked monomers, coordination polymers and supramolecular polymers. 2D polymers containing pores are also known as porous polymers.
Topologically, 2DPs may thus be understood as structures made up from regularly tessellated regular polygons (the repeat units). Figure 1 displays the key features of a linear and a 2DP according to this definition. For usage of the term "2D polymer" in a wider sense, see "History". | 0 | Theoretical and Fundamental Chemistry |
To obtain the reduction potential as a function of the measured concentrations of the redox-active species in solution, it is necessary to express the activities as a function of the concentrations.
Given that the chemical activity denoted here by { } is the product of the activity coefficient γ by the concentration denoted by [ ]: a = γ·C, here expressed as {X} = γ [X] and {X} = (γ) [X] and replacing the logarithm of a product by the sum of the logarithms (i.e., log (a·b) = log a + log b), the log of the reaction quotient () (without {H} already isolated apart in the last term as h pH) expressed here above with activities { } becomes:
It allows to reorganize the Nernst equation as:
Where is the formal standard potential independent of pH including the activity coefficients.
Combining directly with the last term depending on pH gives:
For a pH = 7:
So,
It is therefore important to know to what exact definition does refer the value of a reduction potential for a given biochemical redox process reported at pH = 7, and to correctly understand the relationship used.
Is it simply:
* calculated at pH 7 (with or without corrections for the activity coefficients),
* , a formal standard reduction potential including the activity coefficients but no pH calculations, or, is it,
* , an apparent formal standard reduction potential at pH 7 in given conditions and also depending on the ratio .
This requires thus to dispose of a clear definition of the considered reduction potential, and of a sufficiently detailed description of the conditions in which it is valid, along with a complete expression of the corresponding Nernst equation. Were also the reported values only derived from thermodynamic calculations, or determined from experimental measurements and under what specific conditions? Without being able to correctly answering these questions, mixing data from different sources without appropriate conversion can lead to errors and confusion. | 1 | Applied and Interdisciplinary Chemistry |
Polyether polyols have numerous uses. As an example, polyurethane foam is a big user of polyether polyols.
Polyester polyols can be used to produce rigid foam. They are available in both aromatic and aliphatic versions. They are also available in mixed aliphatic-aromatic versions often made from recycled raw materials, typically polyethylene terephthalate (PET).
Acrylic polyols are generally used in higher performance applications where stability to ultraviolet light is required and also lower VOC coatings. Other uses include direct to metal coatings. As they are used where good UV resistance is required, such as automotive coatings, the isocyanate component also tends to be UV resistant and hence isocyanate oligomers or prepolymers based on Isophorone diisocyanate are generally used.
Caprolactone-based polyols produce polyurethanes with enhanced hydrolysis resistance.
Polycarbonate polyols are more expensive than other polyols and are thus used in more demanding applications. They have been used to make an isophorone diisocyanate based prepolymer which is then used in glass coatings. They may be used in reactive hotmelt adhesives.
All polyols may be used to produce polyurethane prepolymers. These then find use in coatings, adhesives, sealants and elastomers. | 0 | Theoretical and Fundamental Chemistry |
Usually, transition metal NHC complexes are prepared less directly. A popular method entails transmetallation of silver-NHC complexes. Such reagents are generated by the reaction of silver(I) oxide with the imidazolium salt. | 0 | Theoretical and Fundamental Chemistry |
The problem of landslides in spoil tips was first brought to public attention in October 1966 in English speaking world when a spoil tip at Aberfan in Wales gave way, killing 144 people, 116 of them children. The tip was built over a spring, increasing its instability, and its height exceeded guidelines. Water from heavy rainfall had built up inside the tip, weakening the structure, until it suddenly collapsed onto a school below.
The wider issue of stability had been known about prior to the Aberfan disaster; for example, it was discussed in a paper by Professor George Knox in 1927, but received little serious consideration by professional engineers and geologists — even to those directly concerned with mining. Also Aberfan disaster was not the first landslide with casualties: for example, in 1955 two successive landslides killed 73 people in Sasebo, Nagasaki in Japan.[ja]
In February 2013, a spoil tip landslip caused the temporary closure of the Scunthorpe to Doncaster railway line in England.
Landslides are rare in spoil tips after settling and vegetation growth act to stabilise the spoil. However, when heavy rain falls on spoil tips that are undergoing combustion, infiltrated water changes to steam; increasing pressure that may lead to a landslide. In Herstal, Belgium, a landslide on the Petite Bacnure spoil tip in April 1999 closed off a street for many years. | 1 | Applied and Interdisciplinary Chemistry |
DNA and RNA are broken down into mononucleotides by the nucleases deoxyribonuclease and ribonuclease (DNase and RNase) from the pancreas. | 1 | Applied and Interdisciplinary Chemistry |
Large-scale industrial/municipal systems recover typically 75% to 80% of the feed water, or as high as 90%, because they can generate the required higher pressure. | 0 | Theoretical and Fundamental Chemistry |
The half life of tritium is listed by the National Institute of Standards and Technology as () – an annualized rate of approximately 5.5% per year. Tritium decays into helium-3 by beta-minus decay as shown in this nuclear equation:
releasing 18.6 keV of energy in the process. The electron's kinetic energy varies, with an average of 5.7 keV, while the remaining energy is carried off by the nearly undetectable electron antineutrino. Beta particles from tritium can penetrate only about of air, and they are incapable of passing through the dead outermost layer of human skin. Because of their low energy compared to other beta particles, the amount of bremsstrahlung generated is also lower. The unusually low energy released in the tritium beta decay makes the decay (along with that of rhenium-187) useful for absolute neutrino mass measurements in the laboratory.
The low energy of tritium's radiation makes it difficult to detect tritium-labeled compounds except by using liquid scintillation counting. | 0 | Theoretical and Fundamental Chemistry |
Rogue waves (also known as freak waves, monster waves, episodic waves, killer waves, extreme waves, and abnormal waves) are unusually large and unpredictable surface waves that can be extremely dangerous to ships and isolated structures such as lighthouses. They are distinct from tsunamis, which are often almost unnoticeable in deep waters and are caused by the displacement of water due to other phenomena (such as earthquakes). A rogue wave at the shore is sometimes called a sneaker wave.
In oceanography, rogue waves are more precisely defined as waves whose height is more than twice the significant wave height (H or SWH), itself defined as the mean of the largest third of waves in a wave record. Rogue waves do not appear to have a single distinct cause but occur where physical factors such as high winds and strong currents cause waves to merge to create a single exceptionally large wave. A study based on AI prediction methods suggested a different possible cause, the authors identifying “linear superposition” as the main contributing factor.
Among other causes, studies of nonlinear waves such as the Peregrine soliton, and waves modeled by the nonlinear Schrödinger equation (NLS), suggest that modulational instability can create an unusual sea state where a "normal" wave begins to draw energy from other nearby waves, and briefly becomes very large. Such phenomena are not limited to water and are also studied in liquid helium, nonlinear optics, and microwave cavities. A 2012 study reported that in addition to the Peregrine soliton reaching up to about three times the height of the surrounding sea, a hierarchy of higher order wave solutions could also exist having progressively larger sizes and demonstrated the creation of a "super rogue wave" (a breather around five times higher than surrounding waves) in a water-wave tank.
A 2012 study supported the existence of oceanic rogue holes, the inverse of rogue waves, where the depth of the hole can reach more than twice the significant wave height. Rogue holes have been replicated in experiments using water-wave tanks but have not been confirmed in the real world. | 1 | Applied and Interdisciplinary Chemistry |
The rate of reductive elimination is greatly influenced by the geometry of the metal complex. In octahedral complexes, reductive elimination can be very slow from the coordinatively saturated center, and often, reductive elimination only proceeds via a dissociative mechanism, where a ligand must initially dissociate to make a five-coordinate complex. This complex adopts a Y-type distorted trigonal bipyramidal structure where a π-donor ligand is at the basal position and the two groups to be eliminated are brought very close together. After elimination, a T-shaped three-coordinate complex is formed, which will associate with a ligand to form the square planar four-coordinate complex. | 0 | Theoretical and Fundamental Chemistry |
Flow boiling is boiling at a flowing fluid. Compared with pool boiling, flow boiling heat transfer depends on many factors including flow pressure, mass flow rate, fluid type, upstream condition, wall materials, system geometry, and applied heat flux. Characterization of flow boiling requires comprehensive consideration of operating condition. In 2021 a prototype electric vehicle charging cable using flow boiling was able to remove 24.22 kW of heat, allowing the charging current to reach 2,400 amps, far higher than state of the art charging cables that top out at 520 amps. | 0 | Theoretical and Fundamental Chemistry |
Iron ore in the form of siderite, commonly known as iron stone or historically as mine, occurs in patches or bands in the Cretaceous clays of the Weald. Differing qualities of ore were extracted and mixed by experienced smelters to give the best results. Sites of opencast quarries survive from the pre-Roman and Roman eras, but medieval ore extraction was mainly done by digging a series of minepits about five metres in diameter and up to twelve metres deep with material being winched up in baskets suspended from a wooden tripod. This was less destructive of the land as spoil from one pit was used to backfill the previous pit allowing continued land use.
The fuel for smelting was charcoal, which needed to be produced as close as possible to the smelting sites because it would crumble to dust if transported far by cart over rough tracks. Wood was also needed for pre-roasting the ore on open fires, a process which broke down the lumps or nodules and converted the carbonate into oxide. Large areas of woodland were available in the Weald and coppicing woodlands could provide a sustainable source of wood. Sustainable charcoal production for a post-medieval blast furnace required the timber production from a radius of a furnace in a landscape that was a quarter to a third wooded. Forging and finishing of the iron from bloomeries and blast furnaces also required large quantities of charcoal and was usually carried out at a separate site.
Water power became important with the introduction of blast furnaces and finery forges in the late medieval period. Blast furnaces needed to operate continuously for as long as possible and a series of ponds were often created in a valley to give a sustainable flow for the waterwheel. A campaign, as the production run was known, usually ran from October through to late spring when streams began to dry up, although Lamberhurst Furnace driven by the River Teise ran continuously for more than three years in the 1740s. Finery forges with three or four waterwheels to drive bellows and hammers needed more water than a furnace at times, although continuity was not as important. They tended to be sited downstream from a furnace if they were in the same valley. Ponds were created by building a dam known as a pond bay, which often served as a road, across one of the many valleys in the undulating Wealden landscape. In 1754 one furnace was so drought-stricken that its manager considered hiring workmen to turn the wheel as a treadmill. This need for continuous water power was an incentive in the development of the water-returning engine, a waterwheel driven by water raised by a steam engine pump. | 1 | Applied and Interdisciplinary Chemistry |
Inside a magnet the wires are subjected to high Lorentz forces as well as thermal stresses during cooling. Any strain in the niobium tin causes a decrease in the superconducting performance of the material, and can cause the brittle material to fracture. Because of this, the wires need to be as stiff as possible. The Young's modulus of niobium tin is around 140 GPa at room temperature. However, the stiffness drops down to as low as 50 GPa when the material is cooled below . Engineers must therefore find ways of improving the strength of the material. Strengthening fibers are often incorporated in the composite niobium tin wires to increase their stiffness. Common strengthening materials include Inconel, stainless steel, molybdenum, and tantalum because of their high stiffness at cryogenic temperatures. Since the thermal expansion coefficients of the matrix, fiber, and niobium tin are all different, significant amounts of strain can be generated after the wire is annealed and cooled all the way down to operating temperatures. This strain is referred to as the pre-strain in the wire. Since any strain in the niobium tin generally decreases the superconducting performance of the material, a proper combination of materials must be used to minimize this value. The pre-strain in a composite wire can be calculated by the formula
where ε is the pre-strain, ΔL/L and ΔL/L are changes in length due to thermal expansion of the niobium tin conduit and strengthening fiber respectively; V, V, V, and V are the volume fractions of conduit, fiber, copper, and bronze; σ, and σ are the yield stresses of copper and bronze; and E, and E are the Young's modulus of the conduit and the fiber. Since the copper and bronze matrix deforms plastically during cooldown, they apply a constant stress equal to their yield stress. The conduit and fiber, however, deform elastically by design. Commercial superconductors manufactured by the bronze process generally have a pre-strain value around 0.2% to 0.4%. The so-called strain effect causes a reduction in the superconducting properties of many materials including niobium tin. The critical strain, the maximum allowable strain over which superconductivity is lost, is given by the formula
where ε is the critical strain, ε is a material dependent parameter equal to 1.5% in tension (−1.8% in compression) for niobium tin, B is the applied magnetic field, and B is the maximum upper critical field of the material. Strain in the niobium tin causes tetragonal distortions in the crystal lattice, which changes the electron-phonon interaction spectrum. This is equivalent to an increase in disorder in the A15 crystal structure. At high enough strain, around 1%, the niobium tin conduit will develop fractures and the current carrying capability of the wire will be irreversibly damaged. In most circumstances, except for high field conditions, the niobium tin conduit will fracture before the critical strain is reached. | 1 | Applied and Interdisciplinary Chemistry |
Silicon carbide fibers are used to measure gas temperatures in an optical technique called thin-filament pyrometry. It involves the placement of a thin filament in a hot gas stream. Radiative emissions from the filament can be correlated with filament temperature. Filaments are SiC fibers with a diameter of 15 micrometers, about one fifth that of a human hair. Because the fibers are so thin, they do little to disturb the flame and their temperature remains close to that of the local gas. Temperatures of about 800–2500 K can be measured. | 1 | Applied and Interdisciplinary Chemistry |
Through photosynthesis, plants use CO from the atmosphere, water from the ground, and energy from the sun to create sugars used for growth and fuel. While using these sugars as fuel releases carbon back into the atmosphere (photorespiration), growth stores carbon in the physical structures of the plant (i.e. leaves, wood, or non-woody stems). With about 19 percent of Earth's carbon stored in plants, plant growth plays an important role in storing carbon on the ground rather than in the atmosphere. In the context of carbon storage, growth of plants is often referred to as biomass productivity. This term is used because researchers compare the growth of different plant communities by their biomass, amount of carbon they contain.
Increased biomass productivity directly increases the amount of carbon stored in plants. And because researchers are interested in carbon storage, they are interested in where most of the biomass is found in individual plants or in an ecosystem. Plants will first use their available resources for survival and support the growth and maintenance of the most important tissues like leaves and fine roots which have short lives. With more resources available plants can grow more permanent, but less necessary tissues like wood.
If the air surrounding plants has a higher concentration of carbon dioxide, they may be able to grow better and store more carbon and also store carbon in more permanent structures like wood. Evidence has shown this occurring for a few different reasons. First, plants that were otherwise limited by carbon or light availability benefit from a higher concentration of carbon. Another reason is that plants are able use water more efficiently because of reduced stomatal conductance. Plants experiencing higher CO concentrations may benefit from a greater ability to gain nutrients from mycorrhizal fungi in the sugar-for-nutrients transaction. The same interaction can may also increase the amount of carbon stored in the soil by mycorrhizal fungi. | 1 | Applied and Interdisciplinary Chemistry |
In spite of the usefulness in cell tracking and cell visualization of Kaede, there are some limitations.
Although Kaede will shift to red upon the exposure of UV or violet light and display a 2,000-fold increase in red-to-green fluorescence ratio, using both the red and green fluorescence bands can cause problems in multilabel experiments. The tetramerization of Kaede may disturb the localization and trafficking of fusion proteins. This limits the usefulness of Kaede as a fusion protein tag. | 1 | Applied and Interdisciplinary Chemistry |
Tissue reactions have a threshold of irradiation under which they do not appear and above which they typically appear. Fractionation of dose, dose rate, the application of antioxidants and other factors may affect the precise threshold at which a tissue reaction occurs. Tissue reactions include skin reactions (epilation, erythema, moist desquamation), cataracts, circulatory disease, and other conditions. Seven proteins were discovered in a systematic review, which correlated with radiosensitivity in normal tissues: γH2AX, TP53BP1, VEGFA, CASP3, CDKN2A, IL6, and IL1B. | 0 | Theoretical and Fundamental Chemistry |
Because the system must address different depths in the medium, and at different depths the spherical aberration induced in the wavefront is different, a method is required to dynamically account for these differences. Many possible methods exist that include optical elements that swap in and out of the optical path, moving elements, adaptive optics, and immersion lenses. | 0 | Theoretical and Fundamental Chemistry |
An allele-specific oligonucleotide (ASO) is a short piece of synthetic DNA complementary to the sequence of a variable target DNA. It acts as a probe for the presence of the target in a Southern blot assay or, more commonly, in the simpler dot blot assay. It is a common tool used in genetic testing, forensics, and molecular biology research.
An ASO is typically an oligonucleotide of 15–21 nucleotide bases in length. It is designed (and used) in a way that makes it specific for only one version, or allele, of the DNA being tested. The length of the ASO, which strand it is chosen from, and the conditions by which it is bound to (and washed from) the target DNA all play a role in its specificity. These probes can usually be designed to detect a difference of as little as 1 base in the target's genetic sequence, a basic ability in the assay of single-nucleotide polymorphisms (SNPs), important in genotype analysis and the Human Genome Project. To be detected after it has bound to its target, the ASO must be labeled with a radioactive, enzymatic, or fluorescent tag. The Illumina Methylation Assay technology takes advantage of ASO to detect one base pair difference (cytosine versus thymine) to measure methylation at a specific CpG site. | 1 | Applied and Interdisciplinary Chemistry |
Methylene blue is used in aquaculture and by tropical fish hobbyists as a treatment for fungal infections. It can also be effective in treating fish infected with ich although a combination of malachite green and formaldehyde is far more effective against the parasitic protozoa Ichthyophthirius multifiliis. It is usually used to protect newly laid fish eggs from being infected by fungus or bacteria. This is useful when the hobbyist wants to artificially hatch the fish eggs.
Methylene blue is also very effective when used as part of a "medicated fish bath" for treatment of ammonia, nitrite, and cyanide poisoning as well as for topical and internal treatment of injured or sick fish as a "first response". | 0 | Theoretical and Fundamental Chemistry |
Through competitive fellowship stipends, ECS supports students and young professionals as they pursue new ideas and forge connections with professionals both within and outside the field. | 0 | Theoretical and Fundamental Chemistry |
Antoine Jérôme Balard met John Stuart Mill while Mill was studying at the Montpellier Faculty of Sciences in the Winter of 1820.
In Mill's journal of the period he writes of visiting Balard at his home, being shown his herbarium and receiving from him a selection of his plants from the Montpellier area, in addition to other accounts of the two embarking on daytrips around the city of Montpellier and to the sea to look for coastal plants. In a later letter to Auguste Comte, Mill describes Balard as his first real friend. A ‘friend of my own choice as opposed to those given to me by family ties’.
A portion of John Stuart Mill's Herbarium, believed to be in the vicinity of 4000 specimens, is housed at the National Herbarium of Victoria (MEL) and within the Mill Herbarium are contained these Balard collections, mainly from the area of Montpellier. | 1 | Applied and Interdisciplinary Chemistry |
The American Society for Biochemistry and Molecular Biology publishes three research journals and a monthly magazine covering society news and activity updates. ASBMB journals are peer-reviewed and cover research in the fields of microbiology, molecular genetics, RNA-related research, proteomics, genomics, transcription, peptides, cell signaling, lipidomics, and systems biology. All articles are published online as "Papers in Press" upon acceptance. As of January 2021, all three ASBMB journals are fully open access.
* The Journal of Biological Chemistry publishes research in any area of biochemistry or molecular biology in one online-only issue per week.
* Molecular & Cellular Proteomics is a monthly online only publication. Articles appearing in MCP "...describe the structural and functional properties of proteins and their expression, particularly with respect to the developmental time courses of the organism of which they are a part." The journal also publishes other content such as "HUPO views" (reports from the Human Proteome Organization), proceedings from HUPO meetings, and the proceedings of the International Symposium On Mass Spectrometry In The Life Sciences.
* The Journal of Lipid Research covers "...the science of lipids in health and disease. The Journal emphasizes lipid function and the biochemical and genetic regulation of lipid metabolism. In addition, JLR publishes manuscripts on patient-oriented and epidemiological research relating to altered lipid metabolism, including modification of dietary lipids."
* ASBMB Today is the societys monthly news magazine. It contains extensive coverage of awards, meetings, research highlights, job placement advertising and human interest articles. All ASBMB members receive a complimentary subscription to ASBMB Today'. The online version of the magazine features daily publishing. | 1 | Applied and Interdisciplinary Chemistry |
A magneto-optical trap (MOT) is commonly used for cooling and trapping a substance by Doppler cooling. In the process of Doppler cooling, the red detuned light would be absorbed by atoms from one certain direction and re-emitted in a random direction. The electrons of the atoms would decay to an alternative ground states if the atoms have more than one hyperfine ground level. There is the case of all the atoms in the other ground states rather than the ground states of Doppler cooling, then system cannot cool the atoms further.
In order to solve this problem, the other re-pumping light would be incident on the system to repopulate the atoms to restart the Doppler cooling process. This would induce higher amounts of fluorescence being emitted from the atoms which can be absorbed by other atoms, acting as a repulsive force. Due to this problem, the Doppler limit would increase and is easy to meet. When there is a dark spot or lines on the shape of the re-pumping light, the atoms in the middle of the atomic gas would not be excited by the re-pumping light which can decrease the repulsion force from the previous cases.
This can help to cool the atoms to a lower temperature than the typical Doppler cooling limit. This is called a dark magneto-optical trap (DMOT). | 0 | Theoretical and Fundamental Chemistry |
Phosgene is a planar molecule as predicted by VSEPR theory. The C=O distance is 1.18 Å, the C−Cl distance is 1.74 Å and the Cl−C−Cl angle is 111.8°. Phosgene is a carbon oxohalide and it can be considered one of the simplest acyl chlorides, being formally derived from carbonic acid. | 0 | Theoretical and Fundamental Chemistry |
Jiří Hálas textbook states that soils vary greatly in their ability to bind radioisotopes, the clay particles and humic acids can alter the distribution of the isotopes between the soil water and the soil. The distribution coefficient K is the ratio of the soils radioactivity (Bq g) to that of the soil water (Bq ml). If the radioactivity is tightly bonded to by the minerals in the soil then less radioactivity can be absorbed by crops and grass growing in the soil.
* Cs-137 K = 1000
* Pu-239 K = 10000 to 100000
* Sr-90 K = 80 to 150
* I-131 K = 0.007 to 50 | 0 | Theoretical and Fundamental Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.