text
stringlengths 105
4.44k
| label
int64 0
9
| label_text
stringclasses 10
values |
|---|---|---|
There are several methods of directly measuring and quantifying igneous differentiation processes;
* Whole rock geochemistry of representative samples, to track changes and evolution of the magma systems
** Using the above, calculating normative mineralogy and investigating trends
* Trace element geochemistry
* Isotope geochemistry
** Investigating the contamination of magma systems by wall rock assimilation using radiogenic isotopes
In all cases, the primary and most valuable method for identifying magma differentiation processes is mapping the exposed rocks, tracking mineralogical changes within the igneous rocks and describing field relationships and textural evidence for magma differentiation. Clinopyroxene thermobarometry can be used to determine pressures and temperatures of magma differentiation. | 9 | Geochemistry |
Photoexcitation is the production of an excited state of a quantum system by photon absorption. The excited state originates from the interaction between a photon and the quantum system. Photons carry energy that is determined by the wavelengths of the light that carries the photons. Objects that emit light with longer wavelengths, emit photons carrying less energy. In contrast to that, light with shorter wavelengths emit photons with more energy. When the photon interacts with a quantum system, it is therefore important to know what wavelength one is dealing with. A shorter wavelength will transfer more energy to the quantum system than longer wavelengths.
On the atomic and molecular scale photoexcitation is the photoelectrochemical process of electron excitation by photon absorption, when the energy of the photon is too low to cause photoionization. The absorption of the photon takes place in accordance with Planck's quantum theory.
Photoexcitation plays a role in photoisomerization and is exploited in different techniques:
*Dye-sensitized solar cells makes use of photoexcitation by exploiting it in cheaper inexpensive mass production solar cells. The solar cells rely on a large surface area in order to catch and absorb as many high energy photons as possible. Shorter wavelengths are more efficient for the energy conversion compared to longer wavelengths, since shorter wavelengths carry photons that are more energy rich. Light containing shorter wavelengths therefore cause a longer and less efficient conversion of energy in dye-sensitized solar cells.
*Photochemistry
*Luminescence
*Optically pumped lasers use photoexcitation in a way that the excited atoms in the lasers get an enormous direct-gap gain needed for the lasers. The density that is needed for the population inversion in the compound Ge, a material often used in lasers, must become 10 cm, and this is acquired via photoexcitation. The photoexcitation causes the electrons in atoms to go to an excited state. The moment the amount of atoms in the excited state is higher than the amount in the normal ground state, the population inversion occurs. The inversion, like the one caused with germanium, makes it possible for materials to act as lasers.
*Photochromic applications. Photochromism causes a transformation of two forms of a molecule by absorbing a photon. For example, the BIPS molecule(2H-l-benzopyran-2,2-indolines) can convert from trans to cis and back by absorbing a photon. The different forms are associated with different absorption bands. In a cis-form of BIPS, the transient absorption band has a value of 21050 cm, in contrast to the band from the trans-form, that has a value of 16950 cm. The results were optically visible, where the BIPS in gels turned from a colorless appearance to a brown or pink color after repeatedly being exposed to a high energy UV pump beam. High energy photons cause a transformation in the BIPS molecule making the molecule change its structure.
On the nuclear scale photoexcitation includes the production of nucleon and delta baryon resonances in nuclei. | 7 | Physical Chemistry |
The LIFT fast repetition rate (FRR) fluorescence technique is a method for measuring plant fluorescence. It uses a series of short bursts of blue light pulses from a LED to excite photosystem II in the plant. When the quinone acceptor A (Q) reaches its capacity for binding electrons, the system becomes saturated and consequently red fluorescence is emitted. This is regulated by a precise excitation protocol, which consists of a saturation sequence (SQA) and a relaxation sequence (RQA) with a set of short excitation flashes (1 μs).
The fluorescence can then be measured with FRR fluorometry. For that purpose, the LIFT instrument has a built-in optical interference filter to separate the red chlorophyll fluorescence from reflected light, with a wavelength of 685 ± 10 nm.
The fluorescence transient resulting from this excitation protocol shows the kinetics of the reduction of Q and its subsequent re-oxidation, and can be used to calculate various photosynthetic indicators. These indicators provide information on the level of photosynthetic activity, such as the efficiency of light utilization, the quantum yield of photochemical conversion, and the rate of electron transport. | 5 | Photochemistry |
Sphere packing on the corners of a hypercube (with the spheres defined by Hamming distance) corresponds to designing error-correcting codes: if the spheres have radius t, then their centers are codewords of a (2t + 1)-error-correcting code. Lattice packings correspond to linear codes. There are other, subtler relationships between Euclidean sphere packing and error-correcting codes. For example, the binary Golay code is closely related to the 24-dimensional Leech lattice.
For further details on these connections, see the book Sphere Packings, Lattices and Groups by Conway and Sloane. | 3 | Analytical Chemistry |
To compare gas volume between two conditions of different temperature or pressure (1 and 2), assuming nR are the same, the following equation uses humidity exclusion in addition to the ideal gas law:
Where, in addition to terms used in the ideal gas law:
* p is the partial pressure of gaseous water during condition 1 and 2, respectively
For example, calculating how much 1 liter of air (a) at 0 °C, 100 kPa, p = 0 kPa (known as STPD, see below) would fill when breathed into the lungs where it is mixed with water vapor (l), where it quickly becomes , 100 kPa, p = 6.2 kPa (BTPS): | 7 | Physical Chemistry |
The word is an Algonquian word referring to a village at a big river. It is the seventh-oldest surviving English placename in the United States, first applied as Chesepiook by explorers heading north from the Roanoke Colony into a Chesapeake tributary in 1585 or 1586. The name may also refer to the Chesapeake people or the Chesepian, a Native American tribe who inhabited the area now known as South Hampton Roads in the U.S. state of Virginia. They occupied an area that is now the Norfolk, Portsmouth, Chesapeake, and Virginia Beach areas. In 2005, Algonquian linguist Blair Rudes "helped to dispel one of the areas most widely held beliefs: that Chesapeake means something like great shellfish bay. It does not, Rudes said. The name might have actually meant something like great water, or it might have just referred to a village location at the Bays mouth." | 2 | Environmental Chemistry |
Guliye trained many other scientists. From 1951 to 1960 he was the Chair of Organic Chemistry in Baku State University. From 1960 to 1974, he chaired the department. In 1958, Guliyev was elected a correspondent member of Azerbaijan, and in 1959, academician of AS of Azerbaijan. | 0 | Organic Chemistry |
This definition is not however standardized, and MWCOs can also be defined as the molecular weight at which 80% of the analytes (or solutes) are prohibited from membrane diffusion.
Commercially available microdialysis probes typically have molecular weight cutoffs that range from 1,000 to 300,000 Da, and larger thresholds of filtration are measured in µm. Microdialysis may also be used to separate nanoparticles from the solutions in which they were formed. In such a separation, the eluate will consist of non-complexed reactants and components.
Ultrafiltration membrane manufacturers commonly produce and offer MWCO's of 2k, 5k, 10k, 30k, 50k, 100k, and 1,000k. Devices offered range from laboratory focused centrifugal devices (100ul to 100ml) to laboratory and bioprocessing relevant tangential flow filtration (TFF) devices (50ml to hundreds of litres). | 7 | Physical Chemistry |
Control of flux through a metabolic pathway requires that
*The degree to which metabolic steps determine the metabolic flux varies based on the organisms' metabolic needs.
*The change in flux that occurs due to the above requirement being communicated to the rest of the metabolic pathway in order to maintain a steady-state.
Control of flux in a metabolic pathways:
*The control of flux is a systemic property, that is it depends, to varying degrees, on all interactions in the system.
*The control of flux is measured by the flux control coefficient
*In a linear chain of reactions, the flux control coefficient will have values between zero and one.
*A step with a flux control coefficient of zero means that, that particular step, has no influence over the steady-state flux.
*A step in a linear chain with a flux control coefficient of one means that that particular step has complete control over the steady-state flux.
*A flux control coefficient can only be measured in the intact system and cannot for example be determined by inspection of an isolated enzyme in vitro. | 1 | Biochemistry |
One of the principal sources of elevated concentrations of organic chemical constituents is from treated sewage.
Dissolved organic material is most commonly measured using either the Biochemical oxygen demand (BOD) test or the Chemical oxygen demand (COD) test. Organic constituents are significant in river chemistry for the effect that they have on dissolved oxygen concentration and for the impact that individual organic species may have directly on aquatic biota.
Any organic and degradable material consumes oxygen as it decomposes. Where organic concentrations are significantly elevated the effects on oxygen concentrations can be significant and as conditions get extreme the river bed may become anoxic.
Some organic constituents such as synthetic hormones, pesticides, phthalates have direct metabolic effects on aquatic biota and even on humans drinking water taken from the river. Understanding such constituents and how they can be identified and quantified is becoming of increasing importance in the understanding of freshwater chemistry. | 2 | Environmental Chemistry |
The Butler–Volmer equation is:
or in a more compact form:
where:
* : electrode current density, A/m (defined as j = I/S)
*: exchange current density, A/m
* : electrode potential, V
* : equilibrium potential, V
* : absolute temperature, K
* : number of electrons involved in the electrode reaction
* : Faraday constant
* : universal gas constant
*: so-called cathodic charge transfer coefficient, dimensionless
*: so-called anodic charge transfer coefficient, dimensionless
* : activation overpotential (defined as ).
The right hand figure shows plots valid for . | 7 | Physical Chemistry |
Water vapor plays a key role in lightning production in the atmosphere. From cloud physics, usually clouds are the real generators of static charge as found in Earth's atmosphere. The ability of clouds to hold massive amounts of electrical energy is directly related to the amount of water vapor present in the local system.
The amount of water vapor directly controls the permittivity of the air. During times of low humidity, static discharge is quick and easy. During times of higher humidity, fewer static discharges occur. Permittivity and capacitance work hand in hand to produce the megawatt outputs of lightning.
After a cloud, for instance, has started its way to becoming a lightning generator, atmospheric water vapor acts as a substance (or insulator) that decreases the ability of the cloud to discharge its electrical energy. Over a certain amount of time, if the cloud continues to generate and store more static electricity, the barrier that was created by the atmospheric water vapor will ultimately break down from the stored electrical potential energy. This energy will be released to a local oppositely charged region, in the form of lightning. The strength of each discharge is directly related to the atmospheric permittivity, capacitance, and the source's charge generating ability. | 2 | Environmental Chemistry |
Plasma ignition in the definition of Townsend (Townsend discharge) is a self-sustaining discharge, independent of an external source of free electrons. This means that electrons from the cathode can reach the anode in the distance and ionize at least one atom on their way. So according to the definition of this relation must be fulfilled:
If is used instead of () one gets for the breakdown voltage | 7 | Physical Chemistry |
Technically, Hammonds postulate only describes the geometric structure of a chemical reaction. However, Hammonds postulate indirectly gives information about the rate, kinetics, and activation energy of reactions. Hence, it gives a theoretical basis for the understanding the Bell-Evans-Polanyi principle, which describes the experimental observation that the enthalpy change and rate of similar reactions were usually correlated.
The relationship between Hammond's postulate and the BEP principle can be understood by considering a S1 reaction. Although two transition states occur during a S1 reaction (dissociation of the leaving group and then attack by the nucleophile), the dissociation of the leaving group is almost always the rate-determining step. Hence, the activation energy and therefore rate of the reaction will depend only upon the dissociation step.
First, consider the reaction at secondary and tertiary carbons. As the BEP principle notes, experimentally S1 reactions at tertiary carbons are faster than at secondary carbons. Therefore, by definition, the transition state for tertiary reactions will be at a lower energy than for secondary reactions. However, the BEP principle cannot justify why the energy is lower.
Using Hammond's postulate, the lower energy of the tertiary transition state means that its structure is relatively closer to its reactants R(tertiary)-X than to the carbocation "product" when compared to the secondary case. Thus, the tertiary transition state will be more geometrically similar to the R(tertiary)-X reactants than the secondary transition state is to its R(secondary)-X reactants. Hence, if the tertiary transition state is close in structure to the (low energy) reactants, then it will also be lower in energy because structure determines energy. Likewise, if the secondary transition state is more similar to the (high energy) carbocation "product," then it will be higher in energy. | 7 | Physical Chemistry |
*Metallurgical and Materials Transactions A – [https://link.springer.com/search?query=&search-within=Journal&facet-journal-id=11661&package=openaccessarticles open access articles]
*Metallurgical and Materials Transactions B – [https://link.springer.com/search?query=&search-within=Journal&facet-journal-id=11663&package=openaccessarticles open access articles]
*Advanced Engineering Materials – [http://www.aem-journal.de articles]
*Metals – [https://www.mdpi.com/journal/metals open access articles]
*Journal of Alloys and Compounds – [http://www.sciencedirect.com/science/journal/09258388/ open access articles]
*Acta Materialia – [http://www.sciencedirect.com/science/journal/13596454/open-access open access articles]
*International Journal of Materials Research – [https://www.degruyter.com/journal/key/ijmr/html articles] | 8 | Metallurgy |
The MAPK/ERK pathway (also known as the Ras-Raf-MEK-ERK pathway) is a chain of proteins in the cell that communicates a signal from a receptor on the surface of the cell to the DNA in the nucleus of the cell.
The signal starts when a signaling molecule binds to the receptor on the cell surface and ends when the DNA in the nucleus expresses a protein and produces some change in the cell, such as cell division. The pathway includes many proteins, such as mitogen-activated protein kinases (MAPKs), originally called extracellular signal-regulated kinases (ERKs), which communicate by adding phosphate groups to a neighboring protein (phosphorylating it), thereby acting as an "on" or "off" switch.
When one of the proteins in the pathway is mutated, it can become stuck in the "on" or "off" position, a necessary step in the development of many cancers. In fact, components of the MAPK/ERK pathway were first discovered in cancer cells, and drugs that reverse the "on" or "off" switch are being investigated as cancer treatments. | 1 | Biochemistry |
The product of the process, sodium hypochlorite, provides 0.7% to 1% chlorine. Anything below the concentration of 1% chlorine is considered a non-hazardous chemical although still a very effective disinfectant. The sodium hypochlorite produced is in the range of pH 6-7.5, relatively neutral in regards to acidity or baseness. At that pH range, the sodium hypochlorite is relatively stable. | 7 | Physical Chemistry |
Polymer chemistry is a sub-discipline of chemistry that focuses on the structures of chemicals, chemical synthesis, and chemical and physical properties of polymers and macromolecules. The principles and methods used within polymer chemistry are also applicable through a wide range of other chemistry sub-disciplines like organic chemistry, analytical chemistry, and physical chemistry. Many materials have polymeric structures, from fully inorganic metals and ceramics to DNA and other biological molecules. However, polymer chemistry is typically related to synthetic and organic compositions. Synthetic polymers are ubiquitous in commercial materials and products in everyday use, such as plastics, and rubbers, and are major components of composite materials. Polymer chemistry can also be included in the broader fields of polymer science or even nanotechnology, both of which can be described as encompassing polymer physics and polymer engineering. | 7 | Physical Chemistry |
In these processes, the ore is fed into a tank, where it remains until it is completely reduced. The vessel is then emptied of its pre-reduced ore, and filled with another charge of untreated ore. These processes can therefore be easily extrapolated from laboratory experiments. What's more, their principle, based on batch production, facilitates process control. | 8 | Metallurgy |
Three molecular stages are required for actively, enzymatically reprogramming the DNA methylome. Stage 1: Recruitment. The enzymes needed for reprogramming are recruited to genome sites that require demethylation or methylation. Stage 2: Implementation. The initial enzymatic reactions take place. In the case of methylation, this is a short step that results in the methylation of cytosine to 5-methylcytosine. Stage 3: Base excision DNA repair. The intermediate products of demethylation are catalysed by specific enzymes of the base excision DNA repair pathway that finally restore cystosine in the DNA sequence. | 1 | Biochemistry |
A semi sacrificial coating known as a safety shield acts as a penetrating sealer on the wall or surface protecting the surface pores. If the surface is vandalized the coating can be partially removed using a combination of graffiti removal solvent and high-pressure washer. The anti graffiti safety shield is generally reapplied every second attack. While it is possible to use only pressure to remove coating, this will cause additional surface erosion. | 7 | Physical Chemistry |
William Michael Gelbart (born June 12, 1946) is Distinguished Professor of Chemistry and Biochemistry at the University of California, Los Angeles, and a member of the California NanoSystems Institute and the UCLA Molecular Biology Institute. He obtained his Bachelor of Science degree from Harvard University in 1967, his Master's (1968) and PhD (1970) degrees from the University of Chicago, and did postdoctoral work at the University of Paris (1971) and the University of California, Berkeley (1972). After 30 years of research in theoretical physical chemistry, contributing notably to the fields of gas-phase photophysics, optical properties of simple liquids, and the statistical physics of complex fluids, he started a biophysics laboratory with Charles Knobler in 2002 to investigate the physical aspects of viral infectivity. | 7 | Physical Chemistry |
The strength and range of the electric force and the good conductivity of plasmas usually ensure that the densities of positive and negative charges in any sizeable region are equal ("quasineutrality"). A plasma with a significant excess of charge density, or, in the extreme case, is composed of a single species, is called a non-neutral plasma. In such a plasma, electric fields play a dominant role. Examples are charged particle beams, an electron cloud in a Penning trap and positron plasmas. | 7 | Physical Chemistry |
The formation of the link between the glycan and the protein is key element of the synthesis of glycoproteins. The most common method of glycosylation of N-linked glycoproteins is through the reaction between a protected glycan and a protected Asparagine. Similarly, an O-linked glycoprotein can be formed through the addition of a glycosyl donor with a protected Serine or Threonine. These two methods are examples of natural linkage. However, there are also methods of unnatural linkages. Some methods include ligation and a reaction between a serine-derived sulfamidate and thiohexoses in water. Once this linkage is complete, the amino acid sequence can be expanded upon using solid-phase peptide synthesis. | 0 | Organic Chemistry |
The efficiency of a heat engine is ultimately dependent on the temperature difference between heat source and sink (Carnot cycle). To improve efficiency of power stations the operating temperature must be raised. Using water as the working fluid, this takes it into supercritical conditions. Efficiencies can be raised from about 39% for subcritical operation to about 45% using current technology. Supercritical water reactors (SCWRs) are promising advanced nuclear systems that offer similar thermal efficiency gains. Carbon dioxide can also be used in supercritical cycle nuclear power plants, with similar efficiency gains. Many coal-fired supercritical steam generators are operational all over the world, and have enhanced the efficiency of traditional steam-power plants. Supercritical carbon dioxide is also proposed as a working fluid, which would have the advantage of lower critical pressure than water, but issues with corrosion are not yet fully solved. One proposed application is the Allam cycle. Both carbon dioxide and water are neutron moderators, but they have a lower density as supercritical fluids than liquid water does. This allows nuclear reactors with those supercritical fluids as a primary coolant to run in a reduced moderation mode ("semi-fast" or "epithermal") but not usually as a fast neutron reactor. On the other hand, some extra moderation would have to be provided for a fully thermal neutron spectrum. | 7 | Physical Chemistry |
*Ar for any aromatic substituent (Ar is also the symbol for the element argon. However, argon is inert under all usual conditions encountered in organic chemistry, so the use of Ar to represent an aryl substituent never causes confusion.)
*Het for any heteroaromatic substituent
*Bn or Bzl for the benzyl group (not to be confused with Bz for benzoyl group; However, old literature may use Bz for benzyl group.)
*Dipp for the 2,6-diisopropylphenyl group
*Mes for the mesityl group
*Ph, Φ, or φ for the phenyl group (the use of phi for phenyl has been in decline)
*Tol for the tolyl group, usually the para isomer
*Is or Tipp for the 2,4,6-triisopropylphenyl group (the former symbol is derived from the synonym isityl)
*An for the anisyl group, usually the para isomer (An is also the symbol for a generic actinoid element. However, since the anisyl group is monovalent, while the actinides are usually divalent, trivalent, or even higher valency, ambiguity rarely, if ever, arises in practice.)
*Cp for the cyclopentadienyl group (Cp was the symbol for cassiopeium, a former name for lutetium)
*Cp* for the pentamethylcyclopentadienyl group
*Vi for the vinyl group (uncommon) | 0 | Organic Chemistry |
In 1999 Cédric Boissière and his team developed a two-step process whereby the hydrolysis at low pH (1 – 4) is completed before the condensation reaction is initiated by the addition of sodium fluoride (NaF). The two-step procedure includes the addition of a nonionic surfactant template to ultimately produce mesoporous silica particles. The main advantage of sequencing the hydrolysis and condensation reactions is the ability to ensure complete homogeneity of the surfactant and the precursor TEOS mixture. Consequently, the diameter and shape of the product particles as well as the pore size are determined solely by the reaction kinetics and the quantity of sodium fluoride introduced; higher relative fluoride levels produces a greater number of nucleation sites and hence smaller particles. Decoupling the hydrolysis and condensation process affords a level of product control that is substantially superior to that afforded by the one-step Stöber process, with particle size controlled nearly completely by the sodium fluoride-to-TEOS ratio.
The two-step Stöber process begins with a mixture of TEOS, water, alcohol, and a nonionic surfactant, to which hydrochloric acid is added to produce a microemulsion. This solution is allowed to stand until hydrolysis is complete, much like in the one-step Stöber process but with the hydrochloric acid replacing the ammonia as catalyst. Sodium fluoride is added to the resulting homogeneous solution, initiating the condensation reaction by acting as nucleation seed. The silica particles are collected by filtration and calcined to remove the nonionic surfactant template by combustion, resulting in the mesoporous silica product.
The selection of conditions for the process allows for control of pore sizes, particle diameter, and their distributions, as in the case of the one-step approach. Porosity in the modified process is controllable through the introduction of a swelling agent, the choice of temperature, and the quantity of sodium fluoride catalyst added. A swelling agent (such as mesitylene) causes increases in volume and hence in pore size, often by solvent absorption, but is limited by the solubility of the agent in the system. Pore size varies directly with temperature, bound by the lower out of the surfactant cloud point and the boiling point of water. Sodium fluoride concentration produces direct but non-linear changes in porosity, with the effect decreasing as the added fluoride concentration tends to an upper limit. | 7 | Physical Chemistry |
Interfacial rheology is a branch of rheology that studies the flow of matter at the interface between a gas and a liquid or at the interface between two immiscible liquids. The measurement is done while having surfactants, nanoparticles or other surface active compounds present at the interface. Unlike in bulk rheology, the deformation of the bulk phase is not of interest in interfacial rheology and its effect is aimed to be minimized. Instead, the flow of the surface active compounds is of interest..
The deformation of the interface can be done either by changing the size or shape of the interface. Therefore interfacial rheological methods can be divided into two categories: dilational and shear rheology methods. | 7 | Physical Chemistry |
Hydrophobic concrete has been produced since the mid-20th century.
Active recent research on superhydrophobic materials might eventually lead to more industrial applications.
A simple routine of coating cotton fabric with silica or titania particles by sol-gel technique has been reported, which protects the fabric from UV light and makes it superhydrophobic.
An efficient routine has been reported for making polyethylene superhydrophobic and thus self-cleaning. 99% of dirt on such a surface is easily washed away.
Patterned superhydrophobic surfaces also have promise for lab-on-a-chip microfluidic devices and can drastically improve surface-based bioanalysis.
In pharmaceuticals, hydrophobicity of pharmaceutical blends affects important quality attributes of final products, such as drug dissolution and hardness. Methods have been developed to measure the hydrophobicity of pharmaceutical materials.
The development of hydrophobic passive daytime radiative cooling (PDRC) surfaces, whose effectiveness at solar reflectance and thermal emittance is predicated on their cleanliness, has improved the "self-cleaning" of these surfaces. Scalable and sustainable hydrophobic PDRCs that avoid VOCs have further been developed. | 6 | Supramolecular Chemistry |
MALDI mass spectrometry is a laser-based soft-ionization method often used for analysis of large proteins, but has been used successfully for lipids. The lipid is mixed with a matrix, such as 2,5-dihydroxybenzoic acid, and applied to a sample holder as a small spot. A laser is fired at the spot, and the matrix absorbs the energy, which is then transferred to the analyte, resulting in ionization of the molecule. MALDI-Time-of-flight (MALDI-TOF) MS has become a very promising approach for lipidomics studies, particularly for the imaging of lipids from tissue slides. | 1 | Biochemistry |
With the experiments onboard of the EXPOSE facilities, various aspects of astrobiology were investigated that could not be sufficiently approached by use of laboratory facilities on ground. The chemical set of experiments is designed to reach a better understanding of the role of interstellar, cometary and planetary chemistry in the origin of life. Comets and meteorites are interpreted as exogenous sources of prebiotic molecules on the early Earth. All data achieved from the astrobiological experiments on both EXPOSE missions will add to the understanding of the origin and evolution of life on Earth and on the possibility of its distribution in space or origin elsewhere.
Data obtained from the studies on complex organics of cometary interest will support the interpretation of in-situ data obtained from the Rosetta mission after landing on Comet 67P/Churyumov–Gerasimenko in 2014, and samples analyzed by the Curiosity and ExoMars rovers on Mars. Finally the chemical experiments will contribute to the understanding of the chemical processes on Saturn's moon Titan and possible analogies to the prebiotic chemistry on the early Earth.
The biology experiments used the full extraterrestrial spectrum of solar UV radiation and suitable cut-off filters to study both, the role of the ozone layer in protecting our biosphere and the likelihood of resistant terrestrial microorganisms (extremophiles) to survive in outer space. The latter studies will provide experimental data to the lithopanspermia hypothesis, and they will provide basic data to planetary protection issues. To get better insight into the habitability of Mars, one set of samples was exposed to simulated Martian conditions (UV-radiation climate, pressure, atmosphere), with and without a protective cover of simulated Martian soil. The biological test samples selected are hardy representatives of various branches of life. | 1 | Biochemistry |
Only precious metal watch cases must be hallmarked in Switzerland. Swiss hallmarking for other articles such as jewelry and cutlery is optional. In addition to the Swiss hallmark, all precious metal goods may be stamped with the Common Control Mark of the Vienna Convention. Switzerland recognizes platinum, gold, silver and palladium as precious metals which may be hallmarked and thus are subject to assay. | 3 | Analytical Chemistry |
DLVO theory is the combined effect of van der Waals and double layer force. For the derivation, different conditions must be taken into account and different equations can be obtained. But some useful assumptions can effectively simplify the process, which are suitable for ordinary conditions. The simplified way to derive it is to add the two parts together. | 7 | Physical Chemistry |
Edward W Davis of the University of Minnesota is credited for devising the process of pelletizing iron ore.
Pelletizing iron ore is undertaken due to the excellent physical and metallurgical properties of iron ore pellets. Iron ore pellets are spheres of typically to be used as raw material for blast furnaces. They typically contain 64–72% Fe and various additional material adjusting the chemical composition and the metallurgic properties of the pellets. Typically limestone, dolomite and olivine is added and Bentonite is used as binder.
The process of pelletizing combines mixing of the raw material, forming the pellet and a thermal treatment baking the soft raw pellet to hard spheres. The raw material is rolled into a ball, then fired in a kiln or in travelling grate to sinter the particles into a hard sphere.
The configuration of iron ore pellets as packed spheres in the blast furnace allows air to flow between the pellets, decreasing the resistance to the air that flows up through the layers of material during the smelting. The configuration of iron ore powder in a blast furnace is more tightly-packed and restricts the air flow. This is the reason that iron ore is preferred in the form of pellets rather than in the form of finer particles. The quality of the iron ore pellets depends on different factors, which include feed particle size, amount of water used, disc rotating speed, inclination angle of the disc bottom, residence time in the disc as well as the quality and quantity of the binder(s) used. | 8 | Metallurgy |
A co-receptor is a cell surface receptor that binds a signalling molecule in addition to a primary receptor in order to facilitate ligand recognition and initiate biological processes, such as entry of a pathogen into a host cell. | 1 | Biochemistry |
Phenol red exists as a red crystal that is stable in air. Its solubility is 0.77 grams per liter (g/L) in water and 2.9 g/L in ethanol. It is a weak acid with pK = 8.00 at .
A solution of phenol red is used as a pH indicator, often in cell culture. Its color exhibits a gradual transition from yellow (λ = 443 nm) to red (λ = 570 nm) over the pH range 6.8 to 8.2. Above pH 8.2, phenol red turns a bright pink (fuchsia) color.
In crystalline form, and in solution under very acidic conditions (low pH), the compound exists as a zwitterion as in the structure shown above, with the sulfate group negatively charged, and the ketone group carrying an additional proton. This form is sometimes symbolically written as and is orange-red. If the pH is increased (pK = 1.2), the proton from the ketone group is lost, resulting in the yellow, negatively charged ion denoted as HPS. At still higher pH (pK = 7.7), the phenol's hydroxy group loses its proton, resulting in the red ion denoted as PS.
In several sources, the structure of phenol red is shown with the sulfur atom being part of a cyclic group, similar to the structure of phenolphthalein. However, this cyclic structure could not be confirmed by X-ray crystallography.
Several indicators share a similar structure to phenol red, including bromothymol blue, thymol blue, bromocresol purple, thymolphthalein, and phenolphthalein. (A table of other common chemical indicators is available in the article on pH indicators.) | 3 | Analytical Chemistry |
The initiation of the transcription is a multistep sequential process that involves several mechanisms: promoter location, initial reversible binding of RNA polymerase, conformational changes in RNA polymerase, conformational changes in DNA, binding of nucleoside triphosphate (NTP) to the functional RNA polymerase-promoter complex, and nonproductive and productive initiation of RNA synthesis.
The promoter binding process is crucial in the understanding of the process of gene expression. Tuning synthetic genetic systems relies on precisely engineered synthetic promoters with known levels of transcription rates. | 1 | Biochemistry |
The fim switch in Escherichia coli is the mechanism by which the fim gene cluster, encoding Type I Pili, is transcriptionally controlled.
These pili are virulence factors involved in adhesion, especially important in uropathogenic Escherichia coli. The gene undergoes phase variation mediated via two recombinases and is a model example of site specific inversion. | 1 | Biochemistry |
Phenanthroline may be prepared by two successive Skraup reactions of glycerol with o-phenylenediamine, catalyzed by sulfuric acid, and an oxidizing agent, traditionally aqueous arsenic acid or nitrobenzene. Dehydration of glycerol gives acrolein which condenses with the amine followed by a cyclization. | 3 | Analytical Chemistry |
HMB is eliminated via the kidneys, with roughly of an ingested dose being excreted unchanged in urine. The remaining of the dose is retained in tissues or excreted as HMB metabolites. The fraction of a given dose of HMB that is excreted unchanged in urine increases with the dose. | 1 | Biochemistry |
The Sepro Blackhawk 100 Cone Crusher is a modern, hydraulically operated cone crusher designed to be simple, rugged and effective for heavy duty mining and aggregate applications. The combination of the speed and eccentric throw of the crusher provides fine crushing capability and high capacity in a very compact design. The Blackhawk is capable of being applied as a secondary or tertiary crusher as well as a pebble crusher. The Blackhawk 100 is driven directly via a flexible coupling to the electric drive motor. This arrangement eliminates the need for sheaves and v-belts, allowing for simplified operation and maintenance. A variable speed drive package is included to optimize the speed of the machine to the given liner profile, feed and production conditions. | 8 | Metallurgy |
LDA is commonly formed by treating a cooled (0 to −78 °C) mixture of tetrahydrofuran and diisopropylamine with n-butyllithium.
When dissociated, the diisopropylamide anion can become protonated to form diisopropylamine. Diisopropylamine has a pK value of 36. Therefore, its conjugate base is suitable for the deprotonation of compounds with greater acidity, importantly, such weakly acidic compounds (carbon acids) of the type , where Z = C(O)R, C(O)OR or CN. Conventional protic functional groups such as alcohols and carboxylic acids are readily deprotonated.
Like most organolithium reagents, LDA is not a salt, but is highly polar. It forms aggregates in solution, with the extent of aggregation depending on the nature of the solvent. In THF its structure is primarily that of a solvated dimer. In nonpolar solvents such as toluene, it forms a temperature-dependent oligomer equilibrium. At room temperature trimers and tetramers are the most likely structures. With decreasing temperature the aggregation extends to pentameric and higher oligomeric structures.
Solid LDA is pyrophoric, but its solutions are generally not. As such it is commercially available as a solution in polar aprotic solvents such as THF and ether; however, for small scale use (less than 50 mmol), it is common and more cost effective to prepare LDA in situ. | 0 | Organic Chemistry |
In addition to their main use in agriculture, pesticides have a number of other applications. Pesticides are used to control organisms that are considered to be harmful, or pernicious to their surroundings. For example, they are used to kill mosquitoes that can transmit potentially deadly diseases like West Nile virus, yellow fever, and malaria. They can also kill bees, wasps or ants that can cause allergic reactions. Insecticides can protect animals from illnesses that can be caused by parasites such as fleas. Pesticides can prevent sickness in humans that could be caused by moldy food or diseased produce. Herbicides can be used to clear roadside weeds, trees, and brush. They can also kill invasive weeds that may cause environmental damage. Herbicides are commonly applied in ponds and lakes to control algae and plants such as water grasses that can interfere with activities like swimming and fishing and cause the water to look or smell unpleasant. Uncontrolled pests such as termites and mold can damage structures such as houses. Pesticides are used in grocery stores and food storage facilities to manage rodents and insects that infest food such as grain. Pesticides are used on lawns and golf courses, partly for cosmetic reasons.
Integrated pest management, the use of multiple approaches to control pests, is becoming widespread and has been used with success in countries such as Indonesia, China, Bangladesh, the U.S., Australia, and Mexico. IPM attempts to recognize the more widespread impacts of an action on an ecosystem, so that natural balances are not upset.
Each use of a pesticide carries some associated risk. Proper pesticide use decreases these associated risks to a level deemed acceptable by pesticide regulatory agencies such as the United States Environmental Protection Agency (EPA) and the Pest Management Regulatory Agency (PMRA) of Canada.
DDT, sprayed on the walls of houses, is an organochlorine that has been used to fight malaria vectors (mosquitos) since the 1940s. The World Health Organization recommend this approach. It and other organochlorine pesticides have been banned in most countries worldwide because of their persistence in the environment and human toxicity. DDT has become less effective, as resistance was identified in Africa as early as 1955, and by 1972 nineteen species of mosquito worldwide were resistant to DDT. | 2 | Environmental Chemistry |
The Skimwing ("Tsurak" in Navi) is a large Flying Fish like creature. They are primarily ridden by the Metkayina Clan in place of Banshee into battle. They do not form long-term bonds like the Mountain Banshee. They are first introduced in Avatar: The Way of Water', where Jake Sully tames one for battle. | 1 | Biochemistry |
In chemistry, π backbonding is a π-bonding interaction between a filled (or half filled) orbital of a transition metal atom and a vacant orbital on an adjacent ion or molecule. In this type of interaction, electrons from the metal are used to bond to the ligand, which dissipates excess negative charge and stabilizes the metal. It is common in transition metals with low oxidation states that have ligands such as carbon monoxide, olefins, or phosphines. The ligands involved in π backbonding can be broken into three groups: carbonyls and nitrogen analogs, alkenes and alkynes, and phosphines. Compounds where π backbonding is prominent include Ni(CO), Zeise's salt, and molybdenym and iron dinitrogen complexes. | 0 | Organic Chemistry |
Lineatin is a monoterprene with unique tricyclic acetal structure. Most of the studies regarding lineatin were focused on the total synthesis; little attentions were put on its biosynthesis. It is suggested that lineatin is derived through oxidation and cyclization of a monoterponid precursor, but no experimental has been done on proving this route. Based on its partial structure similarity to iridoid class of terprenoids, here, a possible biosynthesis pathway was proposed and outlined in figure 2. | 0 | Organic Chemistry |
Luciferins are a class of small-molecule substrates that react with oxygen in the presence of a luciferase (an enzyme) to release energy in the form of light. It is not known just how many types of luciferins there are, but some of the better-studied compounds are listed below.
Because of the chemical diversity of luciferins, there is no clear unifying mechanism of action, except that all require molecular oxygen, The variety of luciferins and luciferases, their diverse reaction mechanisms and the scattered phylogenetic distribution indicate that many of them have arisen independently in the course of evolution. | 1 | Biochemistry |
A lunar terrane is a major geological province on the Moon. Three terranes have been identified on the Moon: the Procellarum KREEP Terrane, the Feldspathic Highlands Terrane, and the South Pole–Aitken Terrane. Each terrane has a unique origin, composition, and thermal evolution. | 9 | Geochemistry |
Nitrification is a process of nitrogen compound oxidation (effectively, loss of electrons from the nitrogen atom to the oxygen atoms), and is catalyzed step-wise by a series of enzymes.
: (Nitrosomonas, Comammox)
: (Nitrobacter, Nitrospira, Comammox)
OR
In Nitrosomonas europaea, the first step of oxidation (ammonia to hydroxylamine) is carried out by the enzyme ammonia monooxygenase (AMO).
The second step (hydroxylamine to nitrite) is catalyzed by two enzymes. Hydroxylamine oxidoreductase (HAO), converts hydroxylamine to nitric oxide.
Another currently unknown enzyme converts nitric oxide to nitrite.
The third step (nitrite to nitrate) is completed in a distinct organism. | 1 | Biochemistry |
The anode is the oxidising electrode and as a result has a lower localised pH during electrolysis which also promotes desorption of some organic pollutants. Regeneration efficiencies of activated carbon in the anodic compartment are lower than that achievable in the cathodic compartment by between 5-20% for the same regeneration times and currents, however there is no observed residual organic due to the strong oxidising nature of the anode. | 7 | Physical Chemistry |
Mitochondria and other membranous organelles are normally enriched in the PNP region of peripheral myelinated axons, especially those large caliber axons. The actual physiological role of this accumulation and factors that regulate it are not understood; however, it is known that mitochondria are usually present in areas of the cell that expresses a high energy demand. In these same regions, they are also understood to contain growth cones, synaptic terminals, and sites of action potential initiation and regeneration, such as the nodes of Ranvier. In the synaptic terminals, mitochondria produce the ATP needed to mobilize vesicles for neurotransmission. In the nodes of Ranvier, mitochondria serve as an important role in impulse conduction by producing the ATP that is essential to maintain the activity of energy-demanding ion pumps. Supporting this fact, about five times more mitochondria are present in the PNP axoplasm of large peripheral axons than in the corresponding internodal regions of these fibers. | 1 | Biochemistry |
The citrate-malate shuttle allows the cell to produce fatty acid with excess acetyl-CoA for storage. The principle is similar to that of insulin, which turns excess glucose in the body into glycogen for storage in the liver cells and skeletal muscles, so that when there is a lack of energy intake, the body could still provide itself with glucose by breaking down glycogen. The citrate-malate shuttle enables more compact storage of chemical energy in the body in the form of fatty acid by transporting acetyl-CoA into the cytosol for fatty acid and cholesterol synthesis. The lipids produced can then be stored so that they can be used in the future.
Acetyl-CoA is generated in the mitochondrial matrix from two sources: pyruvate decarboxylation in glycolysis and the breakdown of fatty acids through β-oxidation, which are both essential pathways of energy production in humans. Pyruvate decarboxylation is the step that connects glycolysis and the Krebs cycle and is regulated by the pyruvate dehydrogenase complex when blood glucose levels are high. Otherwise, fatty acid β-oxidation occurs, and acetyl-CoA is required to generate ATP through the Krebs cycle. In a subject with defective citrate-malate shuttle, acetyl-CoA in mitochondria cannot exit into the cytosol. Fatty acid synthesis is hence hindered, and the body would not be able to store excess energy as efficiently as a normal subject.
In addition, improper functioning of the citrate-malate shuttle can result in disruption of the Krebs cycle. | 1 | Biochemistry |
The use of oxacillin is contraindicated in individuals that have experienced a hypersensitivity reaction to any medication in the penicillin family of antibiotics. Cross-allergenicity has been documented in individuals taking oxacillin that experienced a previous hypersensitivity reaction when given cephalosporins and cephamycins. | 4 | Stereochemistry |
In spatial scanning, each two-dimensional (2-D) sensor output represents a full slit spectrum (x, λ). Hyperspectral imaging (HSI) devices for spatial scanning obtain slit spectra by projecting a strip of the scene onto a slit and dispersing the slit image with a prism or a grating. These systems have the drawback of having the image analyzed per lines (with a push broom scanner) and also having some mechanical parts integrated into the optical train. With these line-scan cameras, the spatial dimension is collected through platform movement or scanning. This requires stabilized mounts or accurate pointing information to reconstruct the image. Nonetheless, line-scan systems are particularly common in remote sensing, where it is sensible to use mobile platforms. Line-scan systems are also used to scan materials moving by on a conveyor belt. A special case of line scanning is point scanning (with a whisk broom scanner), where a point-like aperture is used instead of a slit, and the sensor is essentially one-dimensional instead of 2-D. | 7 | Physical Chemistry |
Diimide is most effective at reducing unpolarized carbon-carbon double or triple bonds. In reactions with other unsaturated systems, disproportionation of diimide to nitrogen gas and hydrazine is a competing process that significantly degrades the reducing agent. Many groups that are ordinarily sensitive to reductive conditions, including peroxides, are not affected by the conditions of diimide reductions.
Diimide will selectively reduce less substituted double bonds under some conditions. Discrimination between terminal and disubstituted double bonds is often low, however.
Allenes are reduced to the more highly substituted alkene in the presence of diimide, although yields are low.
Iodoalkynes represent an exception to the rule that alkenes cannot be obtained from alkynes. After diimide reduction of iodoalkynes, cis-iodoalkenes may be isolated in good yield.
Recently, diimide has been generated catalytically through the oxidation of hydrazine by a flavin-based organocatalyst. This system selectively reduces terminal double bonds.
In general, diimide does not efficiently reduce polarized double bonds; however, a limited number of examples do exist in the literature. Aromatic aldehydes are reduced by diimide generated through the decarboxylation of potassium azodicarboxylate. | 0 | Organic Chemistry |
Vancomycin is a branched tricyclic glycosylated nonribosomal peptide produced by the Actinomycetota species Amycolatopsis orientalis (formerly designated Nocardia orientalis).
Vancomycin exhibits atropisomerism—it has multiple chemically distinct rotamers owing to the rotational restriction of some of the bonds. The form present in the drug is the thermodynamically more stable conformer. | 0 | Organic Chemistry |
Filamentous fungi, especially Aspergillus and Trichoderma, have long been used to produce diverse industrial enzymes from their own genomes ("native", "homologous") and from recombinant DNA ("heterologous").
More recently, Myceliophthora thermophila C1 has been developed into an expression platform for screening and production of native and heterologous proteins.The expression system C1 shows a low viscosity morphology in submerged culture, enabling the use of complex growth and production media. C1 also does not "hyperglycosylate" heterologous proteins, as Aspergillus and Trichoderma tend to do. | 1 | Biochemistry |
Desorption, specifically thermal desorption, can be applied as an environmental remediation technique. This physical process is designed to remove contaminants at relatively low temperatures, ranging from 90 to 560 °C, from the solid matrix. The contaminated media is heated to volatilize water and organic contaminants, followed by treatment in a gas treatment system in which after removal, the contaminants are collected or thermally destroyed. They are transported using a carrier gas or vacuum to a vapor treatment system for removal/transformation into less toxic compounds.
Thermal desorption systems operate at a lower design temperature, which is sufficiently high to achieve adequate volatilization of organic contaminants. Temperatures and residence times are designed to volatilize selected contaminants but typically will not oxidize them. It is applicable at sites where high direct waste burial is present, and a short timeframe is necessary to allow for continued use or redevelopment of the site. | 7 | Physical Chemistry |
JES is the flagship journal of The Electrochemical Society. Published continuously from 1902 to the present, JES is one of the most highly-cited journals in electrochemistry and solid-state science and technology. | 7 | Physical Chemistry |
The American biochemist George Wald and others had outlined the visual cycle by 1958. For his work, Wald won a share of the 1967 Nobel Prize in Physiology or Medicine with Haldan Keffer Hartline and Ragnar Granit. | 1 | Biochemistry |
Degradation can be detected before serious cracks are seen in a product using infrared spectroscopy. In particular, peroxy-species and carbonyl groups formed by photo-oxidation have distinct absorption bands. | 7 | Physical Chemistry |
Heterocyclic analogs of cyclohexane are pervasive in sugars, piperidines, dioxanes, etc. They exist generally follow the trends seen for cyclohexane, i.e. the chair conformer being most stable. The axial–equatorial equilibria (A values) are however strongly affected by the replacement of a methylene by O or NH. Illustrative are the conformations of the glucosides. 1,2,4,5-Tetrathiane ((SCH)) lacks the unfavorable 1,3-diaxial interactions of cyclohexane. Consequently its twist-boat conformation is populated; in the corresponding tetramethyl structure, 3,3,6,6-tetramethyl-1,2,4,5-tetrathiane, the twist-boat conformation dominates. | 4 | Stereochemistry |
Milk fat globule membrane (MFGM) is a complex and unique structure composed primarily of lipids and proteins that surrounds milk fat globule secreted from the milk producing cells of humans and other mammals. It is a source of multiple bioactive compounds, including phospholipids, glycolipids, glycoproteins, and carbohydrates that have important functional roles within the brain and gut.
Preclinical studies have demonstrated effects of MFGM-derived bioactive components on brain structure and function, intestinal development, and immune defense. Similarly, pediatric clinical trials have reported beneficial effects on cognitive and immune outcomes. In populations ranging from premature infants to preschool-age children, dietary supplementation with MFGM or its components has been associated with improvements in cognition and behavior, gut and oral bacterial composition, fever incidence, and infectious outcomes including diarrhea and otitis media.
MFGM may also play a role in supporting cardiovascular health by modulating cholesterol and fat uptake. Clinical trials in adult populations have shown that MFGM could positively affect markers associated with cardiovascular disease including lowering serum cholesterol and triacylglycerol levels as well as blood pressure. | 1 | Biochemistry |
Chrysocolla (gold-solder, Greek ; Latin chrȳsocolla, oerugo, santerna; Syriac "tankar" (Bar Bahlul), alchemical symbol 🜸), also known as "goldsmith's solder" and "solder of Macedonia" (Pseudo-Democritus), denotes:
* The soldering of gold.
* The materials used for soldering gold, as well as certain gold alloys, still used by goldsmiths. Martin Ruland (Lexicon alchemiae) explains chrysocolla as molybdochalkos, a copper-lead alloy. In Leyden papyrus X recipe 31 chrysocolla is an alloy composed of 4 parts copper, 2 parts asem (a kind of tin-copper alloy) and 1 part gold. Argyrochrysocolla appears to designate an alloy of gold and silver.
* A mix of copper and iron salts, produced by the dissolution of a metallic vein by water, either spontaneously or by introducing water into a mine from winter to summer, and letting the mass dry during summer, which results in a yellow product.
* Malachite (green carbonate of copper), and other alkaline copper salts of green colour. Azurite, the blue congener of malachite, was known as armenion, as it was mined in Armenia. On heating, malachite decomposes to carbon dioxide and copper, the latter inducing the soldering effect. According to an older opinion, chrysocolla was borax, which had been found in ancient gold foundries and is still used for soldering gold. Aristoteles (De mirabilibus) mentions that the Chalcedonian island Demonesus has a mine of cyan () and chrysocolla. Theophrastus (De lapidibus) describes chrysocolla as a kind of "false emerald" found in gold and copper mines, used for soldering gold. Pliny (Historia Naturalis) and Celsus mention that chrysocolla is extracted along with gold, and is used as a pigment and medicament. Dioscorides (De materia medica) describes the purification of the ore and its use in healing wounds, also noting its poisonous effect.
* Greenish copper salts obtained by boiling infants urine and natron in copper vessels. The resulting copper salts were scraped off and used for soldering gold. Infants urine (Greek , Latin ) appears in many ancient recipes (Dioscorides, Pliny, Celsus, etc.) as a source of phosphates and ammonia.
* A particular copper hydrosilicate is named chrysocolla by modern mineralogists. | 8 | Metallurgy |
The chute-type machine has a lower footprint and fewer moving parts which results in lower investment and operating costs. In general, it is more applicable to well liberated material and surface detection, because a double sided scanning is possible on a more reliable on the system. The applicable top size of the chute-type machine is bigger, as material handling of particles up to is only technically viable on this setup.
The cost for most average farmers and industry workers is around $500 for the study and ergonomic design of the sensor. The sensor itself is still a prototype not yet built but looking to be approved by FDA around 2003 | 3 | Analytical Chemistry |
The Falcon semi batch centrifugal concentrator is primarily used for the recovery of free (liberated) precious metals such as gold, silver and platinum. The machine generates forces up to 200 times the force of gravity (200 Gs) and makes use of a two-stage rotating bowl for mineral separation. The smooth-walled lower portion is for particle stratification and then a fluidized upper portion is used for the collection of the heavier particles. The machine is stopped periodically to rinse and collect the valuable concentrate from the bowl. The Falcon SB concentrator is used for gold recovery at many mines around the world, including Quadra FNX Minings Robinson mine in the United States, Newcrest's Telfer Gold Mine in Australia and the Sadiola Gold Mine (owned principally by AngloGold Ashanti and Iamgold) in Mali. | 8 | Metallurgy |
Membrane fusion is a key biophysical process that is essential for the functioning of life itself. It is defined as the event where two lipid bilayers approach each other and then merge to form a single continuous structure. In living beings, cells are made of an outer coat made of lipid bilayers; which then cause fusion to take place in events such as fertilization, embryogenesis and even infections by various types of bacteria and viruses. It is therefore an extremely important event to study. From an evolutionary angle, fusion is an extremely controlled phenomenon. Random fusion can result in severe problems to the normal functioning of the human body. Fusion of biological membranes is mediated by proteins. Regardless of the complexity of the system, fusion essentially occurs due to the interplay of various interfacial forces, namely hydration repulsion, hydrophobic attraction and van der Waals forces. | 6 | Supramolecular Chemistry |
A cumomer is a set of isotopomer sharing similar properties and is a concept that relates to metabolic flux analysis. The concept was developed in 1999. In a metabolic cascade, many molecules will contain the same pattern of isotope labelling. In order to simplify the analysis of such cascades, molecules with identically labelled atoms are aggregated into a virtual molecular called a cumomer (a conflation of cumulative and isotopomer). | 4 | Stereochemistry |
The Protein Information Resource (PIR), located at Georgetown University Medical Center, is an integrated public bioinformatics resource to support genomic and proteomic research, and scientific studies. It contains protein sequences databases | 1 | Biochemistry |
After separation, an additional separation method may then be used, such as isoelectric focusing or SDS-PAGE. The gel will then be physically cut, and the protein complexes extracted from each portion separately. Each extract may then be analysed, such as by peptide mass fingerprinting or de novo peptide sequencing after in-gel digestion. This can provide a great deal of information about the identities of the proteins in a complex. | 1 | Biochemistry |
These forms of AC have been reported in specific bacteria (Prevotella ruminicola and Rhizobium etli , respectively) and have not been extensively characterized. There are a few extra members (~400 in Pfam) known to be in class VI. Class VI enzymes possess a catalytic core similar to the one in Class III. | 1 | Biochemistry |
Latest generation transmissometer technology makes use of a co-located forward scatter visibility sensor on the transmitter unit to allow for higher accuracies over an Extended Meteorological Optical Range or EMOR. After 10,000 meters the accuracy of transmissometer technology diminishes, and at higher visibilities forward scatter visibility sensor technology is more accurate. The co-location of the two sensors allows for the most accurate technology to be used when reporting current visibility. The forward scatter sensor also enables auto-alignment and auto-calibration of the transmissometer device. Hence it is very useful for oceanography and water optics study. | 7 | Physical Chemistry |
Reineke earned her bachelors degree at University of Wisconsin–Eau Claire. She moved to Arizona State University for her graduate studies and earned a masters degree in 1998. Reineke was a PhD student at the University of Michigan, where she was supervised by Michael O'Keeffe and Omar M. Yaghi. She was awarded the Wirt and Mary Cornell Prize for Outstanding Graduate Research. Reineke joined the California Institute of Technology as an National Institutes of Health postdoctoral fellow in 2000. | 1 | Biochemistry |
Siderophile (from sideron, "iron", and phileo, "love") elements are the transition metals which tend to sink into the core because they dissolve readily in iron either as solid solutions or in the molten state, although some sources include elements which are not transition metals in their list of siderophiles, such as germanium. Other sources may also differ in their list based on the temperature being discussed – niobium, vanadium, chromium, and manganese may be considered siderophiles or not, depending on the assumed temperature and pressure. Also confusing the issue is that some elements, such as the aforementioned manganese, as well as molybdenum, form strong bonds with oxygen, but in the free state (as they existed on the primitive Earth when free oxygen did not exist) can mix so easily with iron that they do not concentrate in the siliceous crust, as do true lithophile elements. Iron, meanwhile, is simply everywhere.
The siderophile elements include the highly siderophilic ruthenium, rhodium, palladium, rhenium, osmium, iridium, platinum, and gold, the moderately siderophilic cobalt and nickel, in addition to the "disputed" elements mentioned earlier – some sources even include tungsten and silver.
Most siderophile elements have practically no affinity whatsoever for oxygen: indeed oxides of gold are thermodynamically unstable with respect to the elements. They form stronger bonds with carbon or sulfur, but even these are not strong enough to separate out with the chalcophile elements. Thus, siderophile elements are bound through metallic bonds with iron in the dense layer of the Earths core, where pressures may be high enough to keep the iron solid. Manganese, iron, and molybdenum do form strong bonds with oxygen, but in the free state (as they existed on the primitive Earth when free oxygen did not exist) can mix so easily with iron that they do not concentrate in the siliceous crust, as do true lithophile elements. However, ores of manganese are found in much the same sites as are those of aluminium and titanium, owing to manganeses great reactivity towards oxygen.
Because they are so concentrated in the dense core, siderophile elements are known for their rarity in the Earths crust. Most of them have always been known as precious metals because of this. Iridium is the rarest transition metal occurring within the Earths crust, with an abundance by mass of less than one part per billion. Mineable deposits of precious metals usually form as a result of the erosion of ultramafic rocks, but are not highly concentrated even compared to their crustal abundances, which are typically several orders of magnitude below their solar abundances. However, because they are concentrated in the Earth's mantle and core, siderophile elements are believed to be present in the Earth as a whole (including the core) in something approaching their solar abundances. | 9 | Geochemistry |
The atomic beam is formed through a supersonic expansion, which is a standard technique used in helium atom scattering. The centreline of the gas is selected by a skimmer to form an atom beam with a narrow velocity distribution. The gas is then further collimated by a pinhole to form a narrow beam, which is typically between 1–10 μm. The use of a focusing element (such as a zone plate) allows beam spot sizes below 1 μm to be achieved, but currently still comes with low signal intensity.
The gas then scatters from the surface and is collected into a detector. In order to measure the flux of the neutral helium atoms, they must first be ionised. The inertness of helium that makes it a gentle probe means that it is difficult to ionise and therefore reasonably aggressive electron bombardment is typically used to create the ions. A mass spectrometer setup is then used to select only the helium ions for detection.
Once the flux from a specific part of the surface is collected, the sample is moved underneath the beam to generate an image. By obtaining the value of the scattered flux across a grid of positions, then values can then be converted to an image.
The observed contrast in helium images has typically been dominated by the variation in topography of the sample. Typically, since the wavelength of the atom beam is small, surfaces appear extremely rough to the incoming atom beam. Therefore, the atoms are diffusely scattered and roughly follow Knudsens Law [citation?] (the atom equivalent of Lamberts cosine law in optics). However, more recently work has begun to see divergence from diffuse scattering due to effects such as diffraction and chemical contrast effects. However, the exact mechanisms for forming contrast in a helium microscope is an active field of research. Most cases have some complex combination of several contrast mechanisms making it difficult to disentangle the different contributions.
Combinations of images from multiple perspectives allows stereophotogrammetry to produce partial three dimensional images, especially valuable for biological samples subject to degradation in electron microscopes. | 7 | Physical Chemistry |
Anti-Scl-70 antibodies are linked to scleroderma. The sensitivity of the antibodies for scleroderma is approximately 34%, but is higher for cases with diffuse cutaneous involvement (40%), and lower for limited cutaneous involvement (10%). The specificity of the antibodies is 98% and 99.6% in other rheumatic diseases and normal individuals, respectively. In addition to scleroderma, these antibodies are found in approximately 5% of individuals with SLE. The antigenic target of anti-Scl-70 antibodies is topoisomerase I. | 1 | Biochemistry |
1-cyclohexyl-(2-morpholinoethyl)carbodiimide metho-p-toluene sulfonate is a carbodiimide developed for the chemical probing of RNA structure in biochemistry. | 0 | Organic Chemistry |
Tic214 is another TIC core complex protein, named because it weighs just under 214 kilodaltons. It is 1786 amino acids long and is thought to have six transmembrane domains on its N-terminal end. Tic214 is notable for being coded for by chloroplast DNA, more specifically the first open reading frame ycf1. Tic214 and Tic20 together probably make up the part of the one million dalton TIC complex that spans the entire membrane. Tic20 is buried inside the complex while Tic214 is exposed on both sides of the inner chloroplast membrane. | 5 | Photochemistry |
In the last two decades, optical forces are combined with thermophoretic forces to enable trapping at reduced laser powers, thus resulting in minimized photon damage. By introducing light-absorbing elements (either particles or substrates), microscale temperature gradients are created, resulting in thermophoresis. Typically, particles (including biological objects such as cells, bacteria, DNA/RNA) drift towards the cold - resulting in particle repulsion using optical tweezers. Overcoming this limitation, different techniques such as beam shaping and solution modification with electrolytes and surfactants were used to successfully trap the objects. Laser cooling was also achieved with Ytterbium-doped yttrium lithium fluoride crystals to generate cold spots using lasers to achieve trapping with reduced photobleaching. The sample temperature has also been reduced to achieve optical trapping for a significantly increased selection of particles using optothermal tweezers for drug delivery applications. | 1 | Biochemistry |
In 1783, Carl Wilhelm Scheele discovered that gold dissolved in aqueous solutions of cyanide. Through the work of Bagration (1844), Elsner (1846), and Faraday (1847), it was determined that each atom of gold required two cyanide ions, i.e. the stoichiometry of the soluble compound. | 8 | Metallurgy |
This book describes separating silver from copper or iron. This is achieved by adding large amounts of lead at a temperature just above the melting point of lead. The lead will liquate out with the silver. This process will need to be repeated several times. The lead and silver can be separated by cupellation. | 8 | Metallurgy |
Low temperature heat contains very little capacity to do work (Exergy), so the heat is qualified as waste heat and rejected to the environment. Economically most convenient is the rejection of such heat to water from a sea, lake or river. If sufficient cooling water is not available, the plant can be equipped with a cooling tower or air cooler to reject the waste heat into the atmosphere. In some cases it is possible to use waste heat, for instance in district heating systems. | 7 | Physical Chemistry |
In molecular biology, two nucleotides on opposite complementary DNA or RNA strands that are connected via hydrogen bonds are called a base pair (often abbreviated bp). In the canonical Watson-Crick base pairing, adenine (A) forms a base pair with thymine (T) and guanine (G) forms one with cytosine (C) in DNA. In RNA, thymine is replaced by uracil (U). Alternate hydrogen bonding patterns, such as the wobble base pair and Hoogsteen base pair, also occur—particularly in RNA—giving rise to complex and functional tertiary structures. Importantly, pairing is the mechanism by which codons on messenger RNA molecules are recognized by anticodons on transfer RNA during protein translation. Some DNA- or RNA-binding enzymes can recognize specific base pairing patterns that identify particular regulatory regions of genes.
Hydrogen bonding is the chemical mechanism that underlies the base-pairing rules described above. Appropriate geometrical correspondence of hydrogen bond donors and acceptors allows only the "right" pairs to form stably. DNA with high GC-content is more stable than DNA with low GC-content, but contrary to popular belief, the hydrogen bonds do not stabilize the DNA significantly and stabilization is mainly due to stacking interactions.
The larger nucleobases, adenine and guanine, are members of a class of doubly ringed chemical structures called purines; the smaller nucleobases, cytosine and thymine (and uracil), are members of a class of singly ringed chemical structures called pyrimidines. Purines are only complementary with pyrimidines: pyrimidine-pyrimidine pairings are energetically unfavorable because the molecules are too far apart for hydrogen bonding to be established; purine-purine pairings are energetically unfavorable because the molecules are too close, leading to overlap repulsion. The only other possible pairings are GT and AC; these pairings are mismatches because the pattern of hydrogen donors and acceptors do not correspond. The GU wobble base pair, with two hydrogen bonds, does occur fairly often in RNA. | 4 | Stereochemistry |
*Demonstration model heat engines have been built which use nitinol wire to produce mechanical energy from hot and cold heat sources. A prototype commercial engine developed in the 1970s by engineer Ridgway Banks at Lawrence Berkeley National Laboratory, was named the Banks Engine.
*Nitinol is also popular in extremely resilient glasses frames. It is also used in some mechanical watch springs.
*Boeing engineers successfully flight-tested SMA-actuated morphing chevrons on the Boeing 777-300ER Quiet Technology Demonstrator 2.
*The Ford Motor Company has registered a US patent for what it calls a "bicycle derailleur apparatus for controlling bicycle speed". Filed on 22 April 2019, the patent depicts a front derailleur for a bicycle, devoid of cables, instead using two nitinol wires to provide the movement needed to shift gears.
*It can be used as a temperature control system; as it changes shape, it can activate a switch or a variable resistor to control the temperature.
*It has been used in cell-phone technology as a retractable antenna, or microphone boom, due to its highly flexible and mechanical memory nature.
*It is used to make certain surgical implants, such as the SmartToe.
*It is used in some novelty products, such as self-bending spoons which can be used by amateur and stage magicians to demonstrate "psychic" powers or as a practical joke, as the spoon will bend itself when used to stir tea, coffee, or any other warm liquid.
*It can also be used as wires which are used to locate and mark breast tumours so that the following surgery can be more exact.
*Due to the high damping capacity of superelastic nitinol, it is also used as a golf club insert.
*Nickel titanium can be used to make the underwires for underwire bras.
*It is used in the neckbands of several headphones due to its superelasticity and durability.
*It is being increasingly used for wire stemmed fishing floats due to its superelasticity. | 8 | Metallurgy |
Ternary (where there is an alkali or alkaline earth metal, a transition metal as well as tin e.g. LiRhSn and MgRuSn) have been investigated. | 7 | Physical Chemistry |
In 1843, Louis Pasteur discovered optical activity in paratartaric, or racemic, acid found in grape wine. He was able to separate two enantiomer crystals that rotated polarized light in opposite directions. | 4 | Stereochemistry |
Schymanski is married to Stan Schymanski, an ecohydrologist. and he has shared insight about dual career couples and their path to positions in Luxembourg. They are the first dual career couple to both receive the FNR ATTRACT award. | 0 | Organic Chemistry |
Herbert Morawetz (October 16, 1915-Oct. 29, 2017) was a Czechoslovakian-American chemical engineer. He was a professor of chemistry at Polytechnic Institute of Brooklyn; now New York University. His work focused on polymer chemistry and macromolecules. He published two books: Macromolecules in Solution and Polymers and The Origins and Growth of a Science both Wiley). | 7 | Physical Chemistry |
Quantum mechanics uses the word degenerate in two ways: degenerate energy levels and as the low temperature ground state limit for states of matter. The electron degeneracy pressure occurs in the ground state systems which are non-degenerate in energy levels. The term "degeneracy" derives from work on the specific heat of gases that pre-dates the use of the term in quantum mechanics.
In 1914 Walther Nernst described the reduction of the specific heat of gases at very low temperature as "degeneration"; he attributed this to quantum effects. In subsequent work in various papers on quantum thermodynamics by Albert Einstein, by Max Planck, and by Erwin Schrödinger, the effect at low temperatures came to be called "gas degeneracy". A fully degenerate gas has no volume dependence on pressure when temperature approaches absolute zero.
Early in 1927 Enrico Fermi and separately Llewellyn Thomas developed a semi-classical model for electrons in a metal. The model treated the electrons as a gas. Later in 1927, Arnold Sommerfeld applied the Pauli principle via Fermi-Dirac statistics to this electron gas model, computing the specific heat of metals; the result became Fermi gas model for metals. Sommerfeld called the low temperature region with quantum effects a "wholly degenerate gas".
Also in 1927 Ralph H. Fowler applied Fermi's model to the puzzle of the stability of white dwarf stars. This approach was extended to relativistic models by later studies and with the work of Subrahmanyan Chandrasekhar became the accepted model for star stability. | 7 | Physical Chemistry |
In the 1950s, shipping costs made up 33 percent of the price of oil transported from the Persian Gulf to the United States, but due to the development of supertankers in the 1970s, the cost of shipping dropped to only 5 percent of the price of Persian oil in the US. Due to the increase in the value of crude oil during the last 30 years, the share of the shipping cost on the final cost of the delivered commodity was less than 3% in 2010. | 7 | Physical Chemistry |
R-M systems are major players in the co-evolutionary interaction between mobile genetic elements (MGEs) and their hosts. Genes encoding R-M systems have been reported to move between prokaryotic genomes within MGEs such as plasmids, prophages, insertion sequences/transposons, integrative conjugative elements (ICEs) and integrons. However, it was recently found that there are relatively few R-M systems in plasmids, some in prophages, and practically none in phages. On the other hand, all these MGEs encode a large number of solitary R-M genes, notably MTases. In light of this, it is likely that R-M mobility may be less dependent on MGEs and more dependent, for example, on the existence of small genomic integration hotspots. It is also possible that R-M systems frequently exploit other mechanisms such as natural transformation, vesicles, nanotubes, gene transfer agents or generalized transduction in order to move between genomes. | 1 | Biochemistry |
Dexmedetomidine may enhance the effects of other sedatives and anesthetics when co-administered. Similarly, drugs that lower blood pressure and heart rate, such as beta blockers, may also have enhanced effects when co-administered with dexmedetomidine. | 4 | Stereochemistry |
Biofuels that are produced through hydrothermal liquefaction are carbon neutral, meaning that there are no net carbon emissions produced when burning the biofuel. The plant materials used to produce bio-oils use photosynthesis to grow, and as such consume carbon dioxide from the atmosphere. The burning of the biofuels produced releases carbon dioxide into the atmosphere, but is nearly completely offset by the carbon dioxide consumed from growing the plants, resulting in a release of only 15-18 g of CO per kWh of energy produced. This is substantially lower than the releases rate of fossil fuel technologies, which can range from releases of 955 g/kWh (coal), 813 g/kWh (oil), and 446 g/kWh (natural gas). Recently, Steeper Energy announced that the carbon intensity (CI) of its Hydrofaction™ oil is 15 COeq/MJ according to [http://www.ghgenius.ca/ GHGenius model] (version 4.03a), while diesel fuel is 93.55 COeq/MJ.
Hydrothermal liquefaction is a clean process that doesn't produce harmful compounds, such as ammonia, NO, or SO. Instead the heteroatoms, including nitrogen, sulfur, and chlorine, are converted into harmless byproducts such as N and inorganic acids that can be neutralized with bases. | 0 | Organic Chemistry |
In the research laboratory, due to safety concerns phosgene nowadays finds limited use in organic synthesis. A variety of substitutes have been developed, notably trichloromethyl chloroformate ("diphosgene"), a liquid at room temperature, and bis(trichloromethyl) carbonate ("triphosgene"), a crystalline substance. | 0 | Organic Chemistry |
MLSS (g/L) = SV [mL/L]/SVI [mL/g] or SVI [mL/g] = SV30 [mL/L]/MLSS (g/L)
Where:<br />
SVI = sludge volume index (mL/g)<br />
SV30 = Volume of settled solids per 1 litre after 30 minutes
In fact SVI is a calculation from two analyses : SV30 and MLSS.
0=(Q+Q)(X)-(QX+QX')
Where: <br />
Q = wastewater flow rate (m/d)<br />
Q = return sludge flow rate (m/d)<br />
X' = MLSS (kg/m)<br />
X' = return sludge concentration (kg/m)<br />
Q = sludge surplus (or excess) flow rate (m/d)<br />
This equilibrium formula for settling tanks is mostly calculated for the initial flows in m3/h.
This formula describes that the incoming amount of MLSS in a settler should be equivalent to the outcoming amount of MLSS via the return sludge flow. This equilibrium is only valid if the effluent water contains a low concentration in suspended solids. In normal conditions the excess amount is very low in comparison to the return amount, and for that reason many times the excess amount is neglected.
In that case the formula will be : (Q+Q)(X) = (QX) | 3 | Analytical Chemistry |
The form of the Kelvin equation here is not the form in which it appeared in Lord Kelvins article of 1871. The derivation of the form that appears in this article from Kelvins original equation was presented by Robert von Helmholtz (son of German physicist Hermann von Helmholtz) in his dissertation of 1885. In 2020, researchers found that the equation was accurate down to the 1nm scale. | 7 | Physical Chemistry |
Adina Paytan is a research professor at the Institute of Marine Sciences at the University of California, Santa Cruz. known for research into biogeochemical cycling in the present and the past. She has over 270 scientific publications in journals such as Science, Nature, Proceedings of the National Academy of Sciences, and Geophysical Research Letters. | 9 | Geochemistry |
The diffusive theory of bainite's transformation process is based on the assumption that a bainitic ferrite plate grows with a similar mechanism as Widmanstätten ferrite at higher temperatures. Its growth rate thus depends on how rapidly carbon can diffuse from the growing ferrite into the austenite. A common misconception is that this mechanism excludes the possibility of coherent interfaces and a surface relief. In fact it is accepted by some that formation of Widmanstätten ferrite is controlled by carbon diffusion and do show a similar surface relief. | 8 | Metallurgy |
2,6-Di-tert-butylpyridine is an organic compound with the formula (MeC)CHN. This colourless, oily liquid is derived from pyridine by replacement of the two H atoms with tert-butyl groups. It is a hindered base. For example, it can be protonated, but it does not form an adduct with boron trifluoride. | 0 | Organic Chemistry |
a cells produce a-factor, a mating pheromone which signals the presence of an a cell to neighbouring α cells. a cells respond to α-factor, the α cell mating pheromone, by growing a projection (known as a shmoo, due to its distinctive shape resembling the Al Capp cartoon character Shmoo) towards the source of α-factor. Similarly, α cells produce α-factor, and respond to a-factor by growing a projection towards the source of the pheromone. The response of haploid cells only to the mating pheromones of the opposite mating type allows mating between a and α cells, but not between cells of the same mating type.
These phenotypic differences between a and α cells are due to a different set of genes being actively transcribed and repressed in cells of the two mating types. a cells activate genes which produce a-factor and produce a cell surface receptor (Ste2) which binds to α-factor and triggers signaling within the cell. a cells also repress the genes associated with being an α cell. Similarly, α cells activate genes which produce α-factor and produce a cell surface receptor (Ste3) which binds and responds to a-factor, and α cells repress the genes associated with being an a cell. | 1 | Biochemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.