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RFLP stands for restriction fragment length polymorphism and, in terms of DNA analysis, describes a DNA testing method which utilizes restriction enzymes to "cut" the DNA at short and specific sequences throughout the sample. To start off processing in the laboratory, the sample has to first go through an extraction protocol, which may vary depending on the sample type or laboratory SOPs (Standard Operating Procedures). Once the DNA has been "extracted" from the cells within the sample and separated away from extraneous cellular materials and any nucleases that would degrade the DNA, the sample can then be introduced to the desired restriction enzymes to be cut up into discernable fragments. Following the enzyme digestion, a Southern Blot is performed. Southern Blots are a size-based separation method that are performed on a gel with either radioactive or chemiluminescent probes. RFLP could be conducted with single-locus or multi-locus probes (probes which target either one location on the DNA or multiple locations on the DNA). Incorporating the multi-locus probes allowed for higher discrimination power for the analysis, however completion of this process could take several days to a week for one sample due to the extreme amount of time required by each step required for visualization of the probes. | 1 | Biochemistry |
Aluminium-based nanogalvanic alloys refer to a class of nanostructured metal powders that spontaneously and rapidly produce hydrogen gas upon contact with water or any liquid containing water as a result of their galvanic metal microstructure. It serves as a method of hydrogen production that can take place at a rapid pace at room temperature without the assistance of chemicals, catalysts, or externally supplied power. | 2 | Environmental Chemistry |
The use of plasmids as a technique in molecular biology is supported by bioinformatics software. These programs record the DNA sequence of plasmid vectors, help to predict cut sites of restriction enzymes, and to plan manipulations. Examples of software packages that handle plasmid maps are ApE, Clone Manager, GeneConstructionKit, Geneious, Genome Compiler, LabGenius, Lasergene, MacVector, pDraw32, Serial Cloner, VectorFriends, Vector NTI, and WebDSV. These pieces of software help conduct entire experiments in silico before doing wet experiments. | 1 | Biochemistry |
A sublimatory or sublimation apparatus is equipment, commonly laboratory glassware, for purification of compounds by selective sublimation. In principle, the operation resembles purification by distillation, except that the products do not pass through a liquid phase. | 3 | Analytical Chemistry |
A typical vapor phase osmometer consists of: (1) two thermistors, one with a polymer-solvent solution droplet adhered to it and another with a pure solvent droplet adhered to it; (2) a thermostatted chamber with an interior saturated with solvent vapor; (3) a liquid solvent vessel in the chamber; and (4) an electric circuit to measure the bridge output imbalance difference between the two thermistors. The voltage difference is an accurate way of measuring the temperature difference between the two thermistors, which is a consequence of solvent vapor condensing on the solution droplet (the solution droplet has a lower vapor pressure than the solvent). | 7 | Physical Chemistry |
Most trace fossils are known from marine deposits. Essentially, there are two types of traces, either exogenic ones, which are made on the surface of the sediment (such as tracks) or endogenic ones, which are made within the layers of sediment (such as burrows).
Surface trails on sediment in shallow marine environments stand less chance of fossilization because they are subjected to wave and current action. Conditions in quiet, deep-water environments tend to be more favorable for preserving fine trace structures.
Most trace fossils are usually readily identified by reference to similar phenomena in modern environments. However, the structures made by organisms in recent sediment have only been studied in a limited range of environments, mostly in coastal areas, including tidal flats. | 2 | Environmental Chemistry |
Experimental solid state heat engines, operating from the relatively small temperature differences in cold and hot water reservoirs, have been developed since the 1970s, including the Banks Engine, developed by Ridgway Banks. | 8 | Metallurgy |
N terminus - N-acetylhexosamine 1-dehydrogenase - N-acylmannosamine 1-dehydrogenase - N-formylmethionylaminoacyl-tRNA deformylase - N-isopropylammelide isopropylaminohydrolase - Na+-transporting two-sector ATPase - NADH:ubiquinone reductase (Na+-transporting) - native gel - nematode Her-1 - neolactotetraosylceramide alpha-2,3-sialyltransferase - nested PCR - neurofibromatosis - NH41 - nick (DNA) - nick translation - NIDDM1 - Niemann-Pick disease, type C - nitrate-transporting ATPase - non-coding DNA - non-coding strand - non-directiveness - nonconservative substitution - nonpolar-amino-acid-transporting ATPase - nonsense codon - nonsense mutation - nontranslated RNA - Northern blot - NT - nuclear run-on - nuclease - nuclease protection assay - nucleoplasmin ATPase - nucleoside - nucleoside-triphosphate diphosphatase - nucleotide - Nucleotide universal IDentifier - nucleus - | 1 | Biochemistry |
The Castner process for production of sodium metal was introduced in 1888 by Hamilton Castner. At that time (prior to the introduction in the same year of the Hall-Héroult process) the primary use for sodium metal was as a reducing agent to produce aluminium from its purified ores. The Castner process reduced the cost of producing sodium in comparison to the old method of reducing sodium carbonate at high temperature using carbon. This in turn reduced the cost of producing aluminium, although the reduction-by-sodium method still could not compete with Hall-Héroult. The Castner process continued nevertheless due to Castner's finding new markets for sodium. In 1926, the Downs cell replaced the Castner process. | 8 | Metallurgy |
As they are inert, perfluoroalkanes have essentially no chemical uses, but their physical properties have led to their use in many diverse applications. These include:
*Perfluorocarbon tracer
*Liquid dielectric
*Chemical vapor deposition
*Organic Rankine cycle
*Fluorous biphasic catalysis
*Cosmetics
*Ski waxes
As well as several medical uses:
*Contrast-enhanced ultrasound
*Oxygen Therapeutics
*Blood substitute
*Liquid breathing
*Eye surgery
*Tattoo removal | 2 | Environmental Chemistry |
Sand particles range in size (about 0.05–2 mm). Sand is the most coarse of the particle groups. Sand has the largest pores and soil particles of the particle groups. It also drains the most easily. These particles become more involved in chemical reactions when coated with clay. | 9 | Geochemistry |
In the laboratory, for ICSI treatments, the identified eggs are stripped of surrounding cells (also known as cumulus cells) and prepared for fertilisation. An oocyte selection may be performed prior to fertilisation to select eggs that can be fertilised, as it is required they are in metaphase II. There are cases in which if oocytes are in the metaphase I stage, they can be kept being cultured so as to undergo a posterior sperm injection. In the meantime, semen is prepared for fertilisation by removing inactive cells and seminal fluid in a process called sperm washing. If semen is being provided by a sperm donor, it will usually have been prepared for treatment before being frozen and quarantined, and it will be thawed ready for use. | 1 | Biochemistry |
The human trace amines include:
While not trace amines themselves, the classical monoamines norepinephrine, serotonin, and histamine are all partial agonists at the human TAAR1 receptor; dopamine is a high-affinity agonist at human TAAR1. and are endogenous amines in humans, however, their human TAAR1 binding has not been determined | 1 | Biochemistry |
The number of reported harmful algal blooms (cyanobacterial) has been increasing throughout the world. It is unclear whether the apparent increase in frequency and severity of HABs in various parts of the world is in fact a real increase or is due to increased observation effort and advances in species identification technology.
In 2008, the U.S. government prepared a report on the problem, "Harmful Algal Bloom Management and Response: Assessment and Plan". The report recognized the seriousness of the problem:
Researchers have reported the growth of HABs in Europe, Africa and Australia. Those have included blooms on some of the African Great Lakes, such as Lake Victoria, the second largest freshwater lake in the world. India has been reporting an increase in the number of blooms each year. In 1977 Hong Kong reported its first coastal HAB. By 1987 they were getting an average of 35 per year. Additionally, there have been reports of harmful algal blooms throughout popular Canadian lakes such as Beaver Lake and Quamichan Lake. These blooms were responsible for the deaths of a few animals and led to swimming advisories.
Global warming and pollution is causing algal blooms to form in places previously considered "impossible" or rare for them to exist, such as under the ice sheets in the Arctic, in Antarctica, the Himalayan Mountains, the Rocky Mountains, and in the Sierra Nevada Mountains.
In the U.S., every coastal state has had harmful algal blooms over the last decade and new species have emerged in new locations that were not previously known to have caused problems. Inland, major rivers have seen an increase in their size and frequency. In 2015 the Ohio River had a bloom which stretched an "unprecedented" into adjoining states and tested positive for toxins, which created drinking water and recreation problems. A portion of Utah's Jordan River was closed due to toxic algal bloom in 2016.
Off the west coast of South Africa, HABs caused by Alexandrium catanella occur every spring. These blooms of organisms cause severe disruptions in fisheries of these waters as the toxins in the phytoplankton cause filter-feeding shellfish in affected waters to become poisonous for human consumption. | 3 | Analytical Chemistry |
In an electrolyte or a colloidal suspension, the Debye length for a monovalent electrolyte is usually denoted with symbol κ
where
* I is the ionic strength of the electrolyte in number/m units,
* ε is the permittivity of free space,
* ε is the dielectric constant,
* k is the Boltzmann constant,
* T is the absolute temperature in kelvins,
* is the elementary charge,
or, for a symmetric monovalent electrolyte,
where
* R is the gas constant,
* F is the Faraday constant,
* C is the electrolyte concentration in molar units (M or mol/L).
Alternatively,
where is the Bjerrum length of the medium in nm,
and the factor derives from transforming unit volume from cubic dm to cubic nm.
For deionized water at room temperature, at pH=7, λ ≈ 1μm.
At room temperature (), one can consider in water the relation:
where
* κ is expressed in nanometres (nm)
* I is the ionic strength expressed in molar (M or mol/L)
There is a method of estimating an approximate value of the Debye length in liquids using conductivity, which is described in ISO Standard, and the book. | 7 | Physical Chemistry |
The Trolox equivalent antioxidant capacity (TEAC) assay measures the antioxidant capacity of a given substance, as compared to the standard, Trolox. Most commonly, antioxidant capacity is measured using the ABTS Decolorization Assay. Other antioxidant capacity assays which use Trolox as a standard include the diphenylpicrylhydrazyl (DPPH), oxygen radical absorbance capacity (ORAC) and ferric reducing ability of plasma (FRAP) assays. The TEAC assay is often used to measure the antioxidant capacity of foods, beverages and nutritional supplements. | 1 | Biochemistry |
In 1984 Kocienski received the Hickinbottom Fellowship of the Royal Society of Chemistry. He was elected a Fellow of the Royal Society (FRS) in 1997. He won the Marie Curie Medal in 1997. Since 2000 he has been a foreign member of Polish Academy of Sciences. | 0 | Organic Chemistry |
Sulfones are typically prepared by organic oxidation of thioethers, often referred to as sulfides. Sulfoxides are intermediates in this route. For example, dimethyl sulfide oxidizes to dimethyl sulfoxide and then to dimethyl sulfone. | 0 | Organic Chemistry |
Negishi died in Indianapolis, Indiana, on June 6, 2021. He was 85 years old. No funeral services took place in the United States, but his family planned to lay him to rest in Japan in 2022. | 0 | Organic Chemistry |
* In acids: violet
* At equivalence point (pH 5.2): grey
* In bases: green
Methylene blue functions to change the red-yellow shift of methyl red to a more distinct violet-green shift. | 3 | Analytical Chemistry |
The essential components of a spectroradiometric system are as follows:
*Input optics that gather the electromagnetic radiation from the source (Diffusers, Lenses, Fiber optic light guides)
*An entrance slit, determines how much light will enter the spectrometer. A smaller slit with have greater resolution, but less overall sensitivity
*Order sorting filters for reduction of second-order effects
*Collimator directs the light to the Grating or prism
*A grating or prism for dispersion of the light
*Focusing optics to align the light onto the Detector
*A detector, CMOS sensor or CCD array
*A control and logging system to define data and store it. | 7 | Physical Chemistry |
Whether or not the principle of maximum power efficiency can be considered the fourth law of thermodynamics and the fourth principle of energetics is moot. Nevertheless, H.T. Odum also proposed a corollary of maximum power as the organisational principle of evolution, describing the evolution of microbiological systems, economic systems, planetary systems, and astrophysical systems. He called this corollary the maximum empower principle. This was suggested because, as S.E. Jorgensen, M.T. Brown, H.T. Odum (2004) note,
C. Giannantoni may have confused matters when he wrote "The "Maximum Em-Power Principle" (Lotka–Odum) is generally considered the "Fourth Thermodynamic Principle" (mainly) because of its practical validity for a very wide class of physical and biological systems" (C. Giannantoni 2002, § 13, p. 155). Nevertheless, Giannantoni has proposed the Maximum Em-Power Principle as the fourth principle of thermodynamics (Giannantoni 2006).
The preceding discussion is incomplete. The "maximum power" was discovered several times independently, in physics and engineering, see: Novikov (1957), El-Wakil (1962), and Curzon and Ahlborn (1975). The incorrectness of this analysis and design evolution conclusions was demonstrated by Gyftopoulos (2002). | 7 | Physical Chemistry |
In general, no good evidence supports the commonly held belief that vitamin D supplements can help prevent osteoporosis. Its general use for prevention of this disease in those without vitamin D deficiency is thus likely not needed. For older people with osteoporosis, taking vitamin D with calcium may help prevent hip fractures, but it also slightly increases the risk of stomach and kidney problems. A study found that supplementation with 800 IU or more daily, in those older than 65 years was "somewhat favorable in the prevention of hip fracture and non-vertebral fracture". The effect is small or none for people living independently. Low serum vitamin D levels have been associated with falls, and low bone mineral density. Taking extra vitamin D, however, does not appear to change the risk.
Athletes who are vitamin D deficient are at an increased risk of stress fractures and/or major breaks, particularly those engaging in contact sports. The greatest benefit with supplementation is seen in athletes who are deficient (25(OH)D serum levels <30ng/mL), or severely deficient (25(OH)D serum levels <25ng/mL). Incremental decreases in risks are observed with rising serum 25(OH)D concentrations plateauing at 50ng/mL with no additional benefits seen in levels beyond this point.
A 2020 Cochrane systematic review has found limited evidence that vitamin D plus calcium, but not independently can improve healing in children with nutritional rickets, but the evidence was not conclusive for reducing fractures.
The US Food and Drug Administration (FDA) has required manufacturers to declare the amount of vitamin D on nutrition facts labels, as "nutrients of public health significance", since May 2016. By a proposed deadline extension, some manufacturers had until 1 July 2021, to comply. | 1 | Biochemistry |
According to a more specific definition presented by Trasatti, the absolute electrode potential is the difference in electronic energy between a point inside the metal (Fermi level) of an electrode and a point outside the electrolyte in which the electrode is submerged (an electron at rest in vacuum).
This potential is difficult to determine accurately. For this reason, a standard hydrogen electrode is typically used for reference potential. The absolute potential of the SHE is 4.44 ± 0.02 V at 25 °C. Therefore, for any electrode at 25 °C:
where:
: is electrode potential
:V is the unit volt
:M denotes the electrode made of metal M
:(abs) denotes the absolute potential
:(SHE) denotes the electrode potential relative to the standard hydrogen electrode.
A different definition for the absolute electrode potential (also known as absolute half-cell potential and single electrode potential) has also been discussed in the literature. In this approach, one first defines an isothermal absolute single-electrode process (or absolute half-cell process.) For example, in the case of a generic metal being oxidized to form a solution-phase ion, the process would be
:M → M +
For the hydrogen electrode, the absolute half-cell process would be
:H → H +
Other types of absolute electrode reactions would be defined analogously.
In this approach, all three species taking part in the reaction, including the electron, must be placed in thermodynamically well-defined states. All species, including the electron, are at the same temperature, and appropriate standard states for all species, including the electron, must be fully defined. The absolute electrode potential is then defined as the Gibbs free energy for the absolute electrode process. To express this in volts one divides the Gibbs free energy by the negative of Faraday's constant.
Rockwood's approach to absolute-electrode thermodynamics is easily expendable to other thermodynamic functions. For example, the absolute half-cell entropy has been defined as the entropy of the absolute half-cell process defined above. An alternative definition of the absolute half-cell entropy has recently been published by Fang et al. who define it as the entropy of the following reaction (using the hydrogen electrode as an example):
:H → H +
This approach differs from the approach described by Rockwood in the treatment of the electron, i.e. whether it is placed in the gas phase or the metal. The electron can also be in another state, that of a solvated electron in solution, as studied by Alexander Frumkin and B. Damaskin and others. | 7 | Physical Chemistry |
Transcription factor II F (TFF) is one of several general transcription factors that make up the RNA polymerase II preinitiation complex.
TFF is encoded by the , , and genes.
TFF binds to RNA polymerase II when the enzyme is already unbound to any other transcription factor, thus preventing it from contacting DNA outside the promoter. Furthermore, TFF stabilizes the RNA polymerase II while it's contacting TBP and TFB. | 1 | Biochemistry |
Cyclopropyl cyanide is an organic compound consisting of a nitrile group as a substituent on a cyclopropane ring. It is the smallest cyclic compound containing a nitrile. | 7 | Physical Chemistry |
Proteomics permits the quantitative analysis and detection of changes to proteins or protein biomarkers. Protein biomarkers detect a variety of biological changes, such as protein-protein interactions, post-translational modifications and immunological responses. | 1 | Biochemistry |
Cementation is a type of precipitation, a heterogeneous process in which ions are reduced to zero valence at a solid metallic interface. The process is often used to refine leach solutions.
Cementation of copper is a common example. Copper ions in solution, often from an ore leaching process, are precipitated out of solution in the presence of solid iron. The iron oxidizes, and the copper ions are reduced through the transfer of electrons. The reaction is spontaneous because copper is higher on the galvanic series than iron.
: Cu(aq) + Fe(s) → Cu(s) + Fe(aq)
This was a historically useful process for the production of copper, where the precipitated solid copper metal was recovered as flakes or powder on the surface of scrap iron.
Cementation is used industrially to recover a variety of heavy metals including cadmium, and the cementation of gold by zinc in the Merrill-Crowe process accounts for a substantial fraction of world gold production. | 8 | Metallurgy |
Janet Gretchen Osteryoung (March 1, 1939 – September 21, 2021) was an American chemist who was the director of the Chemistry Division of the National Science Foundation from 1994 to 2001. Her research furthered the development of electroanalysis and especially that of square wave voltammetry. She was elected a Fellow of the American Association for the Advancement of Science in 1984 and awarded the Garvan–Olin Medal in 1987. | 3 | Analytical Chemistry |
In the original paper Ginzburg and Landau observed the existence of two types of superconductors depending
on the energy of the interface between the normal and superconducting states. The Meissner state breaks down when the applied magnetic field is too large. Superconductors can be divided into two classes according to how this breakdown occurs. In Type I superconductors, superconductivity is abruptly destroyed when the strength of the applied field rises above a critical value H. Depending on the geometry of the sample, one may obtain an intermediate state consisting of a baroque pattern of regions of normal material carrying a magnetic field mixed with regions of superconducting material containing no field. In Type II superconductors, raising the applied field past a critical value H leads to a mixed state (also known as the vortex state) in which an increasing amount of magnetic flux penetrates the material, but there remains no resistance to the flow of electric current as long as the current is not too large. At a second critical field strength H, superconductivity is destroyed. The mixed state is actually caused by vortices in the electronic superfluid, sometimes called fluxons because the flux carried by these vortices is quantized. Most pure elemental superconductors, except niobium and carbon nanotubes, are Type I, while almost all impure and compound superconductors are Type II.
The most important finding from Ginzburg–Landau theory was made by Alexei Abrikosov in 1957.
He used Ginzburg–Landau theory to explain experiments on superconducting alloys and thin films. He found that in a type-II superconductor in a high magnetic field, the field penetrates in a triangular lattice of quantized tubes of flux vortices. For this and related work, he was awarded the Nobel Prize in 2003 with Ginzburg and Leggett. | 7 | Physical Chemistry |
Few episodes of euxinia are evident in the sedimentary record during the Cenozoic. Since the end of the Cretaceous OAEs, it is most likely that the oceanic bottom waters have stayed oxic. | 9 | Geochemistry |
Translational glycobiology or applied glycobiology is the branch of glycobiology and glycochemistry that focuses on developing new pharmaceuticals through glycomics and glycoengineering. Although research in this field presents many difficulties, translational glycobiology presents applications with therapeutic glycoconjugates, with treating various bone diseases, and developing therapeutic cancer vaccines and other targeted therapies. Some mechanisms of action include using the glycan for drug targeting, engineering protein glycosylation for better efficacy, and glycans as drugs themselves. | 1 | Biochemistry |
There are currently very few ova banks in existence.
Generally, the main purpose of storing ova, at present, is to overcome infertility which may arise at a later age, or due to a disease. The ova are generally collected between 31 and 35 years of age.
The procedure of collecting ova may or may not include ovarian hyperstimulation.
It can be expected however that ova collection will become more important in the future, i.e. for third party reproduction, and/or for producing stem cells, i.e. from unfertilized eggs (oocytes). | 1 | Biochemistry |
The SSA can be simply calculated from a particle size distribution, making some assumption about the particle shape. This method, however, fails to account for surface associated with the surface texture of the particles. | 7 | Physical Chemistry |
Bamboos and the related rice have an improved C3 efficiency. This improvement might be due to its ability to recapture CO produced during photorespiration, a behavior termed "carbon refixation". These plants achieve refixation by growing chloroplast extensions called "stromules" around the stroma in mesophyll cells, so that any photorespired CO from the mitochondria has to pass through the RuBisCO-filled chloroplast.
Refixation is also performed by a wide variety of plants. The common approach involving growing a bigger bundle sheath leads down to C2 photosynthesis. | 5 | Photochemistry |
*[http://www.prepaintedmetal.eu prepaintedmetal.eu]
*[http://www.prepaintedmetalacademy.eu prepaintedmetalacademy.eu]
*[http://www.creativebuilding.eu creativebuilding.eu]
*[http://www.creativeroofing.eu creativeroofing.eu] | 8 | Metallurgy |
Silicon carbide is used as a raw ingredient in some glazes applied to ceramics. At high temperatures it can reduce metal oxides forming silica and carbon dioxide. This can be used to make the glaze foam and crater due to the evolved carbon dioxide gas, or to reduce the colorant oxides and achieve colors such as copper reds otherwise only possible in a fuel powered reduction firing in an electric kiln. | 8 | Metallurgy |
In this example we will use the five liquids in the Table 2 (Liquid Data) to find the critical wetting surface tension needed to effectively wet PC (polycarbonate) using the Zisman Plot.
The data of the liquids given from the table above is then graphed on the Zisman Plot (Figure 2) with the independent variable as the surface tension of the liquid in dynes/cm and the dependent variable as 1-cos(θ). There also are different variations of the Zisman plot since the Y-axis is unitless as seen in Table 1 and as mentioned above.
Liquids 1 and 2 fully wet the surface as shown by their low contact angles, so they should be neglected when first drawing the line of best fit to find the critical liquid surface tension needed to effectively wet the PC surface, γ, which is simply the x-intercept of the best fit line for the Zisman Plot. To find the best fit line a least squares regression is recommended by using a computer program such as Microsoft Excel, Minitab, Matlab, or it can also be done using a modern graphing calculator such as a TI-84. This was done with the data from Table 1 and the fit data for liquids 3,4, and 5 can be seen on Figure 3.
The x-intercept lands at 39.5 dynes per centimeter (This can be calculated by setting y equal to zero and solving for x) which is less than that of liquid 2, 42.9 dynes per centimeter; therefore, a more accurate measurement of the critical liquid surface tension needed to effectively wet the surface of PC can be obtained by including liquid 2 when making the line of best fit, as seen in Figure 4.
The x-intercept here lands at 42.1 dynes per centimeter (This can be calculated by setting y equal to zero and solving for x), indicating the critical liquid surface tension for PC. | 7 | Physical Chemistry |
where is specific enthalpy, is dissipation function and is temperature. And where
i.e. internal energy per unit volume equals mass density times the sum of: proper energy per unit mass, kinetic energy per unit mass, and gravitational potential energy per unit mass.
i.e. change in heat per unit volume (negative divergence of heat flow) equals the divergence of heat conductivity times the gradient of the temperature.
i.e. divergence of work done against stress equals flow of material times divergence of stress plus stress times divergence of material flow.
i.e. stress times divergence of material flow equals deviatoric stress tensor times divergence of material flow minus pressure times material flow.
i.e. enthalpy per unit mass equals proper energy per unit mass plus pressure times volume per unit mass (reciprocal of mass density). | 7 | Physical Chemistry |
UIT enables life extension of steel bridges. This technique has been employed in numerous US states as well as other nations. The result is a greatly reduced cost of infrastructure. UIT has been certified for this use by AASHTO.
The use of UIT on draglines and other heavy equipment in the mining industry has resulted in increased production and has decreased downtime and maintenance costs.
UIT is employed on drive shafts and crank shafts in a number of industries. Results show that UIT increases shaft life by over a factor of 3.
The US Navy uses UIT to address cracked areas in certain aluminum decks. Without UIT, crack repairs resulted in almost immediate re-cracking. With UIT, repairs have shown to last over eight months without cracks. | 8 | Metallurgy |
Research efforts have been focused on determining how thalidomide causes birth defects and its other activities in the human body, efforts to develop safer analogs, and efforts to find further uses for thalidomide. | 4 | Stereochemistry |
Golgi enzymes play a key role in determining the synthesis of the various types of glycans. The order of action of the enzymes is reflected in their position in the Golgi stack: | 0 | Organic Chemistry |
The Müllerian strategy is usually contrasted with Batesian mimicry, in which one harmless species adopts the appearance of an unprofitable species to gain the advantage of predators avoidance; Batesian mimicry is thus in a sense parasitic on the models defences, whereas Müllerian is to mutual benefit. However, because comimics may have differing degrees of protection, the distinction between Müllerian and Batesian mimicry is not absolute, and there can be said to be a spectrum between the two forms.
Viceroy butterflies and monarchs (types of admiral butterfly) are both poisonous Müllerian mimics, though they were long thought to be Batesian. Mitochondrial DNA analysis of admiral butterflies shows that the viceroy is the basal lineage of two western sister species in North America. The variation in wing patterns appears to have preceded the evolution of toxicity, while other species remain non-toxic, refuting the hypothesis that the toxicity of these butterflies is a conserved characteristic from a common ancestor. | 1 | Biochemistry |
The Martian atmosphere contains high abundances of photochemically produced CO and H, which are reducing molecules. Mars' atmosphere is otherwise mostly oxidizing, leading to a source of untapped energy that life could exploit if it used by a metabolism compatible with one or both of these reducing molecules. Because these molecules can be observed, scientists use this as evidence for an antibiosignature. Scientists have used this concept as an argument against life on Mars. | 2 | Environmental Chemistry |
Carbon-neutral fuel is fuel which produces no net-greenhouse gas emissions or carbon footprint. In practice, this usually means fuels that are made using carbon dioxide (CO) as a feedstock. Proposed carbon-neutral fuels can broadly be grouped into synthetic fuels, which are made by chemically hydrogenating carbon dioxide, and biofuels, which are produced using natural CO-consuming processes like photosynthesis.
The carbon dioxide used to make synthetic fuels may be directly captured from the air, recycled from power plant flue exhaust gas or derived from carbonic acid in seawater. Common examples of synthetic fuels include ammonia and methane, although more complex hydrocarbons such as gasoline and jet fuel have also been successfully synthesized artificially. In addition to being carbon neutral, such renewable fuels can alleviate the costs and dependency issues of imported fossil fuels without requiring either electrification of the vehicle fleet or conversion to hydrogen or other fuels, enabling continued compatible and affordable vehicles. In order to be truly carbon-neutral, any energy required for the process must be itself be carbon-neutral or emissions-free, like renewable energy or nuclear energy.
If the combustion of carbon-neutral fuels is subject to carbon capture at the flue, they result in net-negative carbon dioxide emission and may thus constitute a form of greenhouse gas remediation. Negative emissions are widely considered an indispensable component of efforts to limit global warming, although negative emissions technologies are currently not economically viable for private sector companies. Carbon credits are likely to play an important role for carbon-negative fuels. | 0 | Organic Chemistry |
The cosmetic industry claims that the UV filter acts as an "artificial melanin". But those artificial substances used in sunscreens do not efficiently dissipate the energy of the UV photon as heat. Instead these substances have a very long excited state lifetime. In fact, the substances used in sunscreens are often used as photosensitizers in chemical reactions. (see Benzophenone).
Oxybenzone, titanium oxide and octyl methoxycinnamate are photoprotective agents used in many sunscreens, providing broad-spectrum UV coverage, including UVB and short-wave UVA rays. | 5 | Photochemistry |
In the 1960s and 70s various studies showed that the D–L test was not specific to cannabis, although some flawed studies claimed to show the opposite. A 1969 UK government scientist reported twenty-five plant substances giving a D–L test result very similar to that of cannabis and warned that the D–L test "should never be relied upon as the only positive evidence." Another 1969 study found false positives from "a variety of vegetable extracts".
The study most cited in favour of the specificity of the D–L test is Thornton and Nakamura (1972). The authors themselves reported that the D–L test gave false positives, but declared the D–L test confirmatory when combined with the presence of cystolithic hairs, which marijuana plants possess. However, many plant species have such hairs, and the study only confirmed that 82 of them did not give D–L test false positives.
A 2000 study by the US NIST examined 12 chemical spot tests, and concluded that all the tests examined "may indicate a specific drug or class of drugs is in the sample, but the tests are not always specific for a single drug or [class]", and noted that "mace, nutmeg and tea reacted with the modified Duquenois–Levine [test]".
A 2012 Brazilian study tested 40 vegetal drugs with Duquenóis-Levine test and obtained false-positive results to Chilean boldo (Peumus boldus Molina), pot marigold (Calendula officinalis L.), leather hat (Echinodorus grandiflorus (Cham. & Schltdl.) Micheli.), cecropia (Cecropia hololeuca Miq.), lemon balm (Melissa officinalis), anise (Pimpinella anisum L.), guaraná (Paulinia cupana Kunth.), jaborandi (Pilocarpus jaborandi Holmes.) and laurel (Laurus nobilis L.). | 3 | Analytical Chemistry |
In organic chemistry, a phosphite ester or organophosphite usually refers to an organophosphorous compound with the formula P(OR). They can be considered as esters of an unobserved tautomer phosphorous acid, HPO, with the simplest example being trimethylphosphite, P(OCH). Some phosphites can be considered esters of the dominant tautomer of phosphorous acid (HP(O)(OH)). The simplest representative is dimethylphosphite with the formula HP(O)(OCH). Both classes of phosphites are usually colorless liquids. | 0 | Organic Chemistry |
By combining topographic image formation with tomographic image reconstruction, distributions of defects can be resolved in three dimensions. Unlike "classical" computed tomography (CT), image contrast is not based on differences in absorption (absorption contrast), but on the usual contrast mechanisms of topography (diffraction contrast). In this way, three-dimensional distributions of dislocations in crystals have been imaged.
Literature: | 3 | Analytical Chemistry |
Z2 spin liquid obtained using slave-particle approach may be the first theoretical example of string-net liquid. | 7 | Physical Chemistry |
In equation , stands for the rate constant of t-BuCl reaction in 80% aqueous Ethanol, which is chosen as the reference. The variable stands for the rate constant of the same reaction in a different solvent system, such as ethanol-water, methanol-water, and acetic acid-formic acid. Thus, Y reflects the ionizing power of different nucleophile solvents. | 7 | Physical Chemistry |
In organic chemistry, an ynone is an organic compound containing a ketone () functional group and a triple bond. Many ynones are α,β-ynones, where the carbonyl and alkyne groups are conjugated. Capillin is a naturally occurring example. Some ynones are not conjugated. | 0 | Organic Chemistry |
In chemistry, folding is the process by which a molecule assumes its shape or conformation. The process can also be described as intramolecular self-assembly, a type of molecular self-assembly, where the molecule is directed to form a specific shape through noncovalent interactions, such as hydrogen bonding, metal coordination, hydrophobic forces, van der Waals forces, pi-pi interactions, and electrostatic effects.
The most active area of interest in the folding of molecules is the process of protein folding, which analyses the specific sequences of amino acids in a protein. The shape of the folded protein can be used to understand its function and design drugs to influence the processes that it is involved in.
There is also a great deal of interest in the construction of artificial folding molecules or foldamers. They are studied as models of biological molecules and for potential application to the development of new functional materials. | 6 | Supramolecular Chemistry |
In basic medium, OH ions and water are added to balance each half-reaction. For example, in a reaction between potassium permanganate and sodium sulfite:
:Unbalanced reaction: KMnO + NaSO + HO → MnO + NaSO + KOH
:Reduction: 3 e + 2 HO + → MnO + 4 OH
:Oxidation: 2 OH + → + HO + 2 e
Here, spectator ions (K, Na) were omitted from the half-reactions. By multiplying the stoichiometric coefficients so the numbers of electrons in both half reaction match:
:6 e + 4 HO + 2 → 2 MnO + 8 OH
:6 OH + 3 → 3 + 3 HO + 6 e
the balanced overall reaction is obtained:
:2 KMnO + 3 NaSO + HO → 2 MnO + 3 NaSO + 2 KOH | 7 | Physical Chemistry |
Evidence showing neurturin’s role in neuron survival and management has made it a popular candidate for the potential treatment or reversal of neurodegeneration. In addition, mice models have shown the dying neurons exposed to trophic factors can be rescued. Neurturin is an example of a trophic factor that is difficult to utilize clinically because of its inability to cross the blood-brain barrier of the CNS (central nervous system). Ceregene sponsored a double-blind phase II clinical trial of CERE-120, a viral vector mediated gene transfer drug that allows for the continuous delivery of neurturin to the nigrostratial system. The hope was to reverse damaged and diseased tissue in Parkinson's patients and overall slow the progression of the disease. However, results were inconclusive and showed that while the drug appears to be relatively safe, there was no statistically significant data supporting the improvement of motor function or neuronal health. Neurturin’s therapeutic potential is unknown and future studies aim to improve delivery of the drug. | 1 | Biochemistry |
In polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained from the copolymerization of two monomer species are sometimes called bipolymers. Those obtained from three and four monomers are called terpolymers and quaterpolymers, respectively. Copolymers can be characterized by a variety of techniques such as NMR spectroscopy and size-exclusion chromatography to determine the molecular size, weight, properties, and composition of the material.
Commercial copolymers include acrylonitrile butadiene styrene (ABS), styrene/butadiene co-polymer (SBR), nitrile rubber, styrene-acrylonitrile, styrene-isoprene-styrene (SIS) and ethylene-vinyl acetate, all of which are formed by chain-growth polymerization. Another production mechanism is step-growth polymerization, which is used to produce the nylon-12/6/66 copolymer of nylon 12, nylon 6 and nylon 66, as well as the copolyester family. Copolymers can be used to develop commercial goods or drug delivery vehicles.
Since a copolymer consists of at least two types of constituent units (also structural units), copolymers can be classified based on how these units are arranged along the chain. Linear copolymers consist of a single main chain and include alternating copolymers, statistical copolymers, and block copolymers. Branched copolymers consist of a single main chain with one or more polymeric side chains, and can be grafted, star shaped, or have other architectures. | 7 | Physical Chemistry |
The phenomenon of macromolecular crowding alters the properties of molecules in a solution when high concentrations of macromolecules such as proteins are present. Such conditions occur routinely in living cells; for instance, the cytosol of Escherichia coli contains about 300– of macromolecules. Crowding occurs since these high concentrations of macromolecules reduce the volume of solvent available for other molecules in the solution, which has the result of increasing their effective concentrations. Crowding can promote formation of a biomolecular condensate by colloidal phase separation.
This crowding effect can make molecules in cells behave in radically different ways than in test-tube assays. Consequently, measurements of the properties of enzymes or processes in metabolism that are made in the laboratory (in vitro) in dilute solutions may be different by many orders of magnitude from the true values seen in living cells (in vivo). The study of biochemical processes under realistically crowded conditions is very important, since these conditions are a ubiquitous property of all cells and crowding may be essential for the efficient operation of metabolism. Indeed, in vitro studies have shown that crowding greatly influences binding stability of proteins to DNA. | 7 | Physical Chemistry |
Scintillation counters are usually not ideal for the detection of heavy ions for three reasons:
# the very high ionizing power of heavy ions induces quenching effects which result in a reduced light output (e.g. for equal energies, a proton will produce 1/4 to 1/2 the light of an electron, while alphas will produce only about 1/10 the light);
# the high stopping power of the particles also results in a reduction of the fast component relative to the slow component, increasing detector dead-time;
# strong non-linearities are observed in the detector response especially at lower energies.
The reduction in light output is stronger for organics than for inorganic crystals. Therefore, where needed, inorganic crystals, e.g. , (typically used in thin sheets as α-particle monitors), , should be preferred to organic materials. Typical applications are α-survey instruments, dosimetry instruments, and heavy ion dE/dx detectors. Gaseous scintillators have also been used in nuclear physics experiments. | 5 | Photochemistry |
In Molecular biology, an insert is a piece of DNA that is inserted into a larger DNA vector by a recombinant DNA technique, such as ligation or recombination. This allows it to be multiplied, selected, further manipulated or expressed in a host organism.
Inserts can range from physical nucleotide additions using a technique system or the addition of artificial structures on a molecule via mutagenic chemicals, such as ethidium bromide or crystals.
Inserts into the genome of an organism normally occur due to natural causes. These causes include environmental conditions and intracellular processes. Environmental inserts range from exposure to radioactive radiation such as Ultraviolet, mutagenic chemicals, or DNA viruses. Intracellular inserts can occur through heritable changes in parent cells or errors in DNA replication or DNA repair.
Gene insertion techniques can be used for characteristic mutations in an organism for a desired phenotypic gene expression. A gene insert change can be expressed in a large variety of ends. These variants can range from the loss, or gain, of protein function to changes in physical structure i.e., hair, or eye, color. The goal of changes in expression are focused on a gain of function in proteins for regulation or to termination of cellular function for prevention of disease. The results of the variations are dependent on the place in the genome the addition, or mutation is located. The aim is to learn, understand, and possibly predict the expression of genetic material in organisms using physical and chemical analysis. To see the results of genetic mutations, or inserts, techniques such as DNA sequencing, gel electrophoresis, immunoassay, or microscopy can observe mutation. | 1 | Biochemistry |
Sour crude oil has high natural sulphur content (at least 0.5%). Extra treatment is required in the refining process; impurities are removed to refine the crude into gasoline. Due to the greater cost associated, it is more commonly refined into fuel oil and diesel - less valuable outputs than products of sweet crude oil. | 9 | Geochemistry |
Communication between neurons happens primarily through chemical neurotransmission at the synapse. Neurotransmitters are packaged into synaptic vesicles for release from the presynaptic cell into the synapse, from where they diffuse and can bind to postsynaptic receptors. While most presynaptic cells are historically thought to release one vesicle at a time per active site, more recent research has pointed towards the possibility of multiple vesicles being released from the same active site (multivesicular release; MVR) in response to an action potential. | 1 | Biochemistry |
In the United States, immediate release (IR) formulations of dextroamphetamine sulfate are available generically as 5 mg and 10 mg tablets, marketed by Barr (Teva Pharmaceutical Industries), Mallinckrodt Pharmaceuticals, Wilshire Pharmaceuticals, Aurobindo Pharmaceutical USA and CorePharma. Previous IR tablets sold under the brand names Dexedrine and Dextrostat have been discontinued but in 2015, IR tablets became available by the brand name Zenzedi, offered as 2.5 mg, 5 mg, 7.5 mg, 10 mg, 15 mg, 20 mg and 30 mg tablets. Dextroamphetamine sulfate is also available as a controlled-release (CR) capsule preparation in strengths of 5 mg, 10 mg, and 15 mg under the brand name Dexedrine Spansule, with generic versions marketed by Barr and Mallinckrodt. A bubblegum flavored oral solution is available under the brand name ProCentra, manufactured by FSC Pediatrics, which is designed to be an easier method of administration in children who have difficulty swallowing tablets, each 5 mL contains 5 mg dextroamphetamine. The conversion rate between dextroamphetamine sulfate to amphetamine free base is .728.
In Australia, dexamfetamine is available in bottles of 100 instant release 5 mg tablets as a generic drug or slow release dextroamphetamine preparations may be compounded by individual chemists. In the United Kingdom, it is available in 5 mg instant release sulfate tablets under the generic name dexamfetamine sulfate as well as 10 mg and 20 mg strength tablets under the brand name Amfexa. It is also available in generic dexamfetamine sulfate 5 mg/ml oral sugar-free syrup. The brand name Dexedrine was available in the United Kingdom prior to UCB Pharma disinvesting the product to another pharmaceutical company (Auden Mckenzie). | 4 | Stereochemistry |
Sawdust is flammable and accumulations provide a ready source of fuel. Airborne sawdust can be ignited by sparks or even heat accumulation and result in dust fire or explosions. | 2 | Environmental Chemistry |
Potassium dichromate is a strong oxidizing agent under acidic conditions. Acidity is usually achieved by the addition of sulfuric acid. The reaction of potassium dichromate with organic compounds is given by:
where . Most commonly, a 0.25 N solution of potassium dichromate is used for COD determination, although for samples with COD below 50 mg/L, a lower concentration of potassium dichromate is preferred.
In the process of oxidizing the organic substances found in the water sample, potassium dichromate is reduced (since in all redox reactions, one reagent is oxidized and the other is reduced), forming Cr. The amount of Cr is determined after oxidization is complete, and is used as an indirect measure of the organic contents of the water sample. | 9 | Geochemistry |
Transposable elements represent one of several types of mobile genetic elements. TEs are assigned to one of two classes according to their mechanism of transposition, which can be described as either copy and paste (Class I TEs) or cut and paste (Class II TEs). | 1 | Biochemistry |
Furthermore, one can assess whether the folding proceeds according to a two-state unfolding as described above. This can be done with differential scanning calorimetry by comparing the calorimetric enthalpy of denaturation i.e. the area under the peak, to the van 't Hoff enthalpy described as follows:
at the can be described as:
When a two-state unfolding is observed the . The is the height of the heat capacity peak. | 7 | Physical Chemistry |
GABA degradation pathways exists in almost all eukaryotic organisms and takes place by the action of similar enzymes. Although, GABA in E.coli is predominantly used as an alternative source of energy through GABA degradation pathways, GABA in higher eukaryotic organisms acts as an inhibitory neurotransmitter and also as regulator of muscle tone. GABA degradation pathways in eukaryotes are responsible for the inactivation of GABA. | 1 | Biochemistry |
Trimethyl orthoformate (TMOF) is the organic compound with the formula HC(OCH). A colorless liquid, it is the simplest orthoester. It is a reagent used in organic synthesis for the formation of methyl ethers. The product of reaction of an aldehyde with trimethyl orthoformate is an acetal. In general cases, these acetals can be deprotected back to the aldehyde by using hydrochloric acid. | 0 | Organic Chemistry |
Typically the presence of an amine functional group is deduced by a combination of techniques, including mass spectrometry as well as NMR and IR spectroscopies. H NMR signals for amines disappear upon treatment of the sample with DO. In their infrared spectrum primary amines exhibit two N-H bands, whereas secondary amines exhibit only one. In their IR spectra, primary and secondary amines exhibit distinctive N-H stretching bands near 3300 cm. Somewhat less distinctive are the bands appearing below 1600 cm, which are weaker and overlap with C-C and C-H modes. For the case of propyl amine, the H-N-H scissor mode appears near 1600 cm, the C-N stretch near 1000 cm, and the RN-H bend near 810 cm. | 0 | Organic Chemistry |
To begin to generate an isolobal fragment, the molecule needs to follow certain criteria. Molecules based around main group elements should satisfy the octet rule when all bonding and nonbonding molecular orbitals (MOs) are filled and all antibonding MOs are empty. For example, methane is a simple molecule from which to form a main group fragment. The removal of a hydrogen atom from methane generates a methyl radical. The molecule retains its molecular geometry as the frontier orbital points in the direction of the missing hydrogen atom. Further removal of hydrogen results in the formation of a second frontier orbital. This process can be repeated until only one bond remains to the molecule's central atom.
The isolobal fragments of octahedral complexes, such as type ML, can be created in a similar fashion. Transition metal complexes should initially satisfy the eighteen electron rule, have no net charge, and their ligands should be two electron donors (Lewis bases). Consequently, the metal center for the ML starting point must be d. Removal of a ligand is analogous to the removal of hydrogen of methane in the previous example resulting in a frontier orbital, which points toward the removed ligand. Cleaving the bond between the metal center and one ligand results in a radical complex. In order to satisfy the zero-charge criteria the metal center must be changed. For example, a MoL complex is d and neutral. However, removing a ligand to form the first frontier orbital would result in a complex because Mo has obtained an additional electron making it d. To remedy this, Mo can be exchanged for Mn, which would form a neutral d complex in this case, as shown in Figure 3. This trend can continue until only one ligand is left coordinated to the metal center. | 0 | Organic Chemistry |
If the hydration energy is greater than the lattice energy, then the enthalpy of solution is negative (heat is released), otherwise it is positive (heat is absorbed).
The hydration energy should not be confused with solvation energy, which is the change in Gibb's free energy (not enthalpy) as solute in the gaseous state is dissolved. If the solvation energy is positive, then the solvation process is endergonic; otherwise, it is exergonic.
For instance, water warms when treated with CaCl (anhydrous calcium chloride) as a consequence of the large heat of hydration. However, the hexahydrate, CaCl·6HO cools the water upon dissolution. The latter happens because the hydration energy does not completely overcome the lattice energy, and the remainder has to be taken from the water in order to compensate the energy loss.
The hydration energies of the gaseous Li, Na, and Cs are respectively 520, 405, and 265 kJ/mol. | 7 | Physical Chemistry |
Larive began her career as a professor in the chemistry department at the University of Kansas, and later joined the faculty of the University of California, Riverside, in 2005. Since 2004 she has served as the editor-in-chief of the Analytical Sciences Digital Library.
In February 2017, Larive was appointed interim provost and executive vice chancellor for University of California, Riverside, and the appointment was made permanent in October.
On May 16, 2019, Larive was announced as the new chancellor of University of California, Santa Cruz, succeeding George Blumenthal effective July 1. | 3 | Analytical Chemistry |
An estimated 550,000 people live in the triangle of death. The annual death rate per 100,000 inhabitants from liver cancer is approximately 38.4 for men and 20.8 for women in this area, as compared to the national average of 14. The death rate for bladder cancer and cancer of the central nervous system was also higher than the national average. The high death rates from cancers pointed towards the presence of illegal and improper hazardous waste disposal by various organized crime groups including the Camorra. The 2004 Lancet Oncology article noted, "Today, the difference between lawful management of waste and illegal manipulation with regard to their compliance with health regulations is very narrow, and the health risks are rising... The 5000 illegal or uncontrolled landfill sites in Italy drew particular criticism; Italy has already been warned twice for flouting the Hazardous Waste Directive and the Landfill Directive, and the EU has now referred Italy to the European Court of Justice for further action."
The report was met with criticism by the National Research Council, dismissing the methods used by Senior and Mazza as biased. Despite this, it sparked the first interest and concern into this matter, and has become the most cited source of evidence throughout the crisis.
Though some media outlets report France and Germany as waste sources, the EU has remained silent as to the sources of the waste in its criticism and demands of Italy. | 2 | Environmental Chemistry |
The mutual information,
is the relative entropy of the joint probability distribution from the product of the two marginal probability distributions — i.e. the expected number of extra bits that must be transmitted to identify and if they are coded using only their marginal distributions instead of the joint distribution. Equivalently, if the joint probability is known, it is the expected number of extra bits that must on average be sent to identify if the value of is not already known to the receiver. | 7 | Physical Chemistry |
After a genomic library is constructed with a viral vector, such as lambda phage, the titer of the library can be determined. Calculating the titer allows researchers to approximate how many infectious viral particles were successfully created in the library. To do this, dilutions of the library are used to transform cultures of E. coli of known concentrations. The cultures are then plated on agar plates and incubated overnight. The number of viral plaques are counted and can be used to calculate the total number of infectious viral particles in the library. Most viral vectors also carry a marker that allows clones containing an insert to be distinguished from those that do not have an insert. This allows researchers to also determine the percentage of infectious viral particles actually carrying a fragment of the library.
A similar method can be used to titer genomic libraries made with non-viral vectors, such as plasmids and BACs. A test ligation of the library can be used to transform E. coli. The transformation is then spread on agar plates and incubated overnight. The titer of the transformation is determined by counting the number of colonies present on the plates. These vectors generally have a selectable marker allowing the differentiation of clones containing an insert from those that do not. By doing this test, researchers can also determine the efficiency of the ligation and make adjustments as needed to ensure they get the desired number of clones for the library. | 1 | Biochemistry |
Addition reactions occur when nucleophiles react with carbonyls. When a nucleophile adds to a simple aldehyde or ketone, the result is a 1,2-addition. When a nucleophile adds to a conjugated carbonyl system, the result is a 1,4-addition. The designations 1,2 and 1,4 are derived from numbering the atoms of the starting compound where the oxygen is labeled “1” and each atom adjacent to the oxygen are sequentially numbered out to the site of nucleophilic addition. A 1,2-addition occurs with nucleophilic addition to position 2 while a 1,4-addition occurs with nucleophilic addition to position 4. | 0 | Organic Chemistry |
Small Tim proteins are synthesised lacking a cleavable presequence, but instead containing internal targeting information and need to be imported to the intermembrane space. The intermembrane space import and assembly machinery (MIA) is believed to mediate transport of the small Tim precursors into the intermembrane space subcompartment. MIA is composed of two main essential cysteine-rich proteins; Mia40 and Erv1. Mia40 is also referred to as Tim40 in yeast and deficiency of Mia40 has been reported to affect import of the small Tims. Mia40 is anchored to the mitochondrial inner membrane via an N-terminal hydrophobic segment, exposing a large domain to the intermembrane space. It contains 6 conserved cysteine residues, which allow the binding of incoming Tim precursor proteins. Following import of small Tim proteins into the intermembrane space Mia40 interacts with small Tim proteins via disulfide bonds. Following isomerisation of the disulfide bridge, the polypeptide is released. Mia40 which is now in reduced state, is then oxidised by Erv1. This oxidation step is vital to facilitate further rounds of precursor protein import. Without Erv1 activity, reduced Mia40 accumulates and is in inactive conformation. Interaction between the incoming precursor proteins, Mia40 and Erv1, is maintained as a result of a flow of electrons that are transferred from the incoming protein to Mia40 and from reduced Mia40 to oxidised Erv1. Precursors are then released in oxidised state and form disulfide bridges which prevents their escape out of the intermembrane space. Small Tim proteins are then maintained in active conformation within the intermembrane space by Hot13 (helper of Tims). It is possible that Hot13 may have reducing effects on small Tim proteins as they counterbalance the harmful effects that oxidative agents exhibit. | 1 | Biochemistry |
2-Iodophenol (o-iodophenol) is an aromatic organic compound with the formula ICHOH. It is a pale yellow solid that melts near room temperature. It undergoes a variety of coupling reactions in which the iodine substituent is replaced by a new carbon group ortho to the hydroxy group of the phenol, which can be followed by cyclization to form heterocycles.
It can be prepared by treatment of 2-chloromercuriphenol with iodine:
Direct reaction of phenol with iodine gives a mixture of 2- and 4-iodo derivatives. | 0 | Organic Chemistry |
The correct structure of heme C was published in mid 20th century by the Swedish biochemist K.-G. Paul. This work confirmed the structure first inferred by the great Swedish biochemist Hugo Theorell. The structure of heme C, based upon NMR and IR experiments of the reduced Fe(II) form of the heme, was confirmed in 1975. The structure of heme C including the absolute stereochemical configuration about the thioether bonds was first presented for the vertebrate protein, cytochrome c and is now extended to many other heme C containing proteins. | 1 | Biochemistry |
When studying or discussing explosive safety, or the safety of systems containing explosives, the terms deflagration, detonation and deflagration-to-detonation transition (commonly referred to as DDT) must be understood and used appropriately to convey relevant information. As explained above, a deflagration is a subsonic reaction, whereas a detonation is a supersonic (greater than the [https://www.nde-ed.org/Physics/Sound/vibration.xhtml sound speed of the material]) reaction. Distinguishing between a deflagration or a detonation can be difficult to impossible to the casual observer. Rather, confidently differentiating between the two requires instrumentation and diagnostics to ascertain reaction speed in the affected material. Therefore, when an unexpected event or an accident occurs with an explosive material or an explosive-containing system it is usually impossible to know whether the explosive deflagrated or detonated as both can appear as very violent, energetic reactions. Therefore, the energetic materials community coined the term "high explosive violent reaction" or "HEVR" to describe a violent reaction that, because it lacked diagnostics to measure sound-speed, could have been either a deflagration or a detonation. | 7 | Physical Chemistry |
Meropenem is administered intravenously as an aqueous solution. Meropenem is stored in vials as white crystalline powder (containing meropenem as the trihydrate blended with anhydrous sodium carbonate). For intravenous administration, the powder is dissolved in 5% monobasic potassium phosphate solution, since meropenem is soluble in 5% monobasic potassium phosphate solution and only sparingly soluble in water (). For intravenous bolus administration, injection vials are reconstituted with sterile water for injection.
Reconstituted (dissolved) meropenem degrades over time. The degradation may be associated with color change of the solution, typical for a hydrolysis of the amide bond of the β-lactam ring as seen with most β-lactam antibiotics, while particularly for merapenem the color is changing from colorless or pale yellow to vivid yellowish. Upon reconstitution, the merapenem infusion solution, prepared with 0.9% sodium chloride, exhibits both chemical and physical stability for a duration of 3 hours at a temperature up to °C. If refrigerated (°C), the stability extends to 24 hours. However, when the product is reconstituted in a 5% dextrose solution, it is used immediately to ensure its efficacy. The degradation of meropenem in a water-based solution is affected by factors such as pH, temperature, initial concentration, and the specific type of infusion solution used. Meropenem solutions should not be frozen.
Meropenem is administered every 8 hours.
Dosing must be adjusted for altered kidney function and for haemofiltration.
Studies recomment application of meropenem therapeutic drug monitoring for optimal application.
As with other β-lactams antibiotics, the effectiveness of treatment depends on the amount of time during the dosing interval that the meropenem concentration is above the minimum inhibitory concentration for the bacteria causing the infection. For β-lactams, including meropenem, prolonged intravenous administration is associated with lower mortality than bolus intravenous infusion in persons with whose infections are severe, or caused by bacteria that are less sensitive to meropenem, such as Pseudomonas aeruginosa.
Meropenem exhibit poor permeability across the gut and low oral bioavailability because of its hydrophilic properties, which inhibit its passive diffusion across the intestinal epithelium. The challenges related to research of oral delivery of meropenem are related to high susceptibility of meropenem to degradation through hydrolysis of the amide bond in the β-lactam ring, even at relatively low temperatures and humidity. This instability can result in the loss of meropenems antibacterial activity. Besides that, neropenem is unstable in the acidic environment of the stomach, leading to extensive degradation and loss of the drug after oral administration. In addition, intestinal efflux (secretory) transport can pump the drug back into the gut: efflux transporters, particularly P-glycoprotein (P-gp), present in the gastrointestinal tract can actively pump meropenem back into the gut lumen, limiting its absorption and reducing oral bioavailability; in the attempts of oral administration bacteria can develop resistance to meropenem by enhancing the active efflux of the antibiotic through efflux transporters, such as the MexAB-OprM tripartite efflux system in Pseudomonas aeruginosa. Thats why meropenem is administered intravenously.
There is insufficient data regarding the administration of meropenem during breastfeeding. However, it has been observed that, in general, the concentration of this beta-lactam antibiotic in breast milk is relatively low, therefore, beta-lactam antibiotics are not anticipated to induce detrimental effects in infants who are breastfed. Nonetheless, there have been sporadic reports of disturbances in the gastrointestinal flora of the infant, manifesting as diarrhea or oral candidiasis (thrush), associated with the use of beta-lactam antibiotics, however, these potential side effects have not been thoroughly investigated specifically in the context of meropenem use, therefore, the safety profile of meropenem in breastfeeding mothers and their infants is unknown. | 4 | Stereochemistry |
Myristoylation plays a vital role in membrane targeting and signal transduction in plant responses to environmental stress. In addition, in signal transduction via G protein, palmitoylation of the α subunit, prenylation of the γ subunit, and myristoylation is involved in tethering the G protein to the inner surface of the plasma membrane so that the G protein can interact with its receptor. | 1 | Biochemistry |
Chinese mythology generally reflects a time when metallurgy had long been practiced. According to the Romanian anthropologist, orientalist, and philosopher Mircea Eliade, the Iron Age produced a large number of rites, myths and symbols; the blacksmith was the main agent of diffusion of mythology, rites and metallurgical mysteries. The secret knowledge of metallurgists and their powers made them founders of the human world and masters of the spirit world. This metallurgical model was reinterpreted again by Taoist alchemists.
Some metalworkers illustrate the close relationship between Chinese mystical and sovereign power and the mining and metallurgy industries. Although the name Huangdi is absent from Shang or Zhou inscriptions, it appears in the Spring and Autumn periods Guoyu and Zuo zhuan'. According to Mitarai (1984), Huangdi may have lived in early antiquity and led a regional ethnic group who worshiped him as a deity; "The Yellow Emperor fought Chiyou at Mount Kunwu whose summit was covered with a large quantity of red copper".
"The seventy-two brothers of Chiyou had copper heads and iron fronts; they ate iron and stones [...] In the province of Ji where Chiyou is believed to have lived (Chiyou shen), when we dig the earth and we find skulls that seem to be made of copper and iron, they are identified as the bones of Chiyou." Chiyou was the leader of the indigenous Sanmiao (or Jiuli) tribes who defeated Xuanyuan, the future Yellow Emperor. Chiyou, a rival of the Yellow Emperor, belonged to a clan of blacksmiths. The advancement of weaponry is sometimes attributed to the Yellow Emperor and Chiyou, and Chiyou reportedly discovered the process of casting. Kunwu is associated with a people, a royal blacksmith, a mountain which produces metals, and a sword. Kui, a master of music and dance cited by Shun, was succeeded by Yu the Great. Yu the Great, reported founder of the Xia dynasty (China's first), spent many years working on flood control and is credited with casting the Nine Tripod Cauldrons. Helped by dragons descended from heaven, he died on Mount Xianglu in Zhejiang. In these myths and legends, mines and forges are associated with leadership. | 8 | Metallurgy |
Adding a monolayer to the surface reduces the surface tension, and the surface pressure, is given by the following equation:
where is equal to the surface tension of the water and is the surface tension due to the monolayer. But the concentration-dependence of surface tension (similar to Langmuir isotherm) is as follows:
Thus,
or
The last equation indicates a relationship similar to ideal gas law. However, the concentration-dependence of surface tension is valid only when the solutions are dilute and concentrations are low. Hence, at very low concentrations of the surfactant, the molecules behave like ideal gas molecules.
Experimentally, the surface pressure is usually measured using the Wilhelmy plate. A pressure sensor/electrobalance arrangement detects the pressure exerted by the monolayer. Also monitored is the area to the side of the barrier which the monolayer resides.
A simple force balance on the plate leads to the following equation for the surface pressure:
only when . Here, and are the dimensions of the plate, and is the difference in forces. The Wilhelmy plate measurements give pressure – area isotherms that show phase transition-like behaviour of the LM films, as mentioned before (see figure below). In the gaseous phase, there is minimal pressure increase for a decrease in area. This continues until the first transition occurs and there is a proportional increase in pressure with decreasing area. Moving into the solid region is accompanied by another sharp transition to a more severe area dependent pressure. This trend continues up to a point where the molecules are relatively close packed and have very little room to move. Applying an increasing pressure at this point causes the monolayer to become unstable and destroy the monolayer forming polylayer structures towards the air phase. The surface pressure during the monolayer collapse may remain approximately constant (in a process near the equilibrium) or may decay abruptly (out of equilibrium - when the surface pressure was over-increased because lateral compression was too fast for monomolecular rearrangements). | 7 | Physical Chemistry |
Epoxidation of alkenes is a common reaction because epoxides can be derivatized in a number of useful ways. Classically, laboratory epoxidation is carried out with mCPBA or other peracids. Oxaziridines have been found to be useful for the formation of highly acid sensitive epoxides. (−)-Chaetominine was synthesized via oxaziridine epoxidation as a late stage transformation as seen below.
Another transformation of high synthetic utility is asymmetric epoxidation. A number of asymmetric epoxidations exist: the Sharpless epoxidation, the Jacobsen-Katsuki epoxidation, and the Juliá-Colonna epoxidation. These methods require specific functionality in order to achieve selectivity. The Sharpless epoxidation is specific to allylic alcohols, the Jacobsen epoxidation requires cis-disubstituted aryl alkenes, and the Juliá epoxidation requires α-β unsaturated ketones. Chiral oxaziridines act stereospecifically on many unfunctionalized alkenes. It has even possible to effect stereospecific epoxidation catalytically in the oxaziridine chiral unit. Further investigation into these reactions may be required before levels of enantiometic excess become practical for large scale synthesis. Lusinichi et al. have investigated asymmetric epoxidation with a chiral oxaziridinium salt using oxone as the stoichiometric oxidant seen below. | 0 | Organic Chemistry |
ArcB consists of 778 amino acids. It is a multipass transmembrane protein that passes through the inner membrane twice. The majority of the secondary structure of ArcB is alpha helices; five alpha helices and one beta sheet. The two transmembrane portions of the protein are 20 amino acid long alpha helices that are both rich in hydrophobic amino acids. Amino acids 79-778 are cytoplasmic, 93% of the protein is cytoplasmic. Both the sensory and regulator regions of ArcB are present in this cytoplasmic domain.
ArcA consists of 238 amino acids. This is an oligomeric protein with two identical subunits; each subunit composed of 119 amino acids, five alpha helices, and six beta sheets. Amino acids 134-234 have the DNA binding domain which can activate or suppress gene expression. There are 76 DNA binding sites in the E. coli genome, however, ArcA directly regulates approximately 30 different operons. | 1 | Biochemistry |
In November 1949, with the seminal paper, "Sickle Cell Anemia, a Molecular Disease", in Science magazine, Linus Pauling, Harvey Itano and their collaborators laid the groundwork for establishing the field of molecular medicine. In 1956, Roger J. Williams wrote Biochemical Individuality, a prescient book about genetics, prevention and treatment of disease on a molecular basis, and nutrition which is now variously referred to as individualized medicine and orthomolecular medicine. Another paper in Science by Pauling in 1968, introduced and defined this view of molecular medicine that focuses on natural and nutritional substances used for treatment and prevention.
Published research and progress was slow until the 1970s' "biological revolution" that introduced many new techniques and commercial applications. | 1 | Biochemistry |
Oxacillin is a penicillinase-resistant β-lactam. It is similar to methicillin, and has replaced methicillin in clinical use. Other related compounds are nafcillin, cloxacillin, dicloxacillin, and flucloxacillin. Since it is resistant to penicillinase enzymes, such as that produced by Staphylococcus aureus, it is widely used clinically in the US to treat penicillin-resistant Staphylococcus aureus. However, with the introduction and widespread use of both oxacillin and methicillin, antibiotic-resistant strains called methicillin-resistant and oxacillin-resistant Staphylococcus aureus (MRSA/ORSA) have become increasingly prevalent worldwide. MRSA/ORSA can be treated with vancomycin or other new antibiotics. | 4 | Stereochemistry |
The dynamic behavior of compressible flows is governed by the dimensionless thermodynamic quantity , which is known as the fundamental derivative of gasdynamics and is defined as
where
* is the speed of sound [m/s];
* is the specific entropy per unit mass [J/(kg K)].
From a mathematical point of view, the fundamental derivative is a non-dimensional measure of the curvature of isentropes in the pressure-volume thermodynamic plane. From a physical point of view, the definition of tells that the speed of sound increases with pressure in isentropic transformations for values of , while, by contrast, it decreases with pressure for .
Based on the value of , three gasdynamic regimes can be defined:
* ideal gasdynamic regime for ;
* non-ideal classical gasdynamic regime for ;
* non-classical gasdynamic regime for . | 7 | Physical Chemistry |
Flooding occurs when a watercourse is unable to convey the quantity of runoff flowing downstream. The frequency with which this occurs is described by a return period. Flooding is a natural process, which maintains ecosystem composition and processes, but it can also be altered by land use changes such as river engineering. Floods can be both beneficial to societies or cause damage. Agriculture along the Nile floodplain took advantage of the seasonal flooding that deposited nutrients beneficial for crops. However, as the number and susceptibility of settlements increase, flooding increasingly becomes a natural hazard. In urban areas, surface runoff is the primary cause of urban flooding, known for its repetitive and costly impact on communities. Adverse impacts span loss of life, property damage, contamination of water supplies, loss of crops, and social dislocation and temporary homelessness. Floods are among the most devastating of natural disasters. The use of supplemental irrigation is also recognized as a significant way in which crops such as maize can retain nitrogen fertilizers in soil, resulting in improvement of crop water availability. | 2 | Environmental Chemistry |
RajanBabu received his B. Sc (Special) from Kerala University in 1969 and M. Sc. degree from The Indian Institute of Technology (IIT, Madras) in 1971. He obtained his Ph. D. from The Ohio State University in 1979 working with Professor Harold Shechter, and was a postdoctoral fellow at Harvard University with Professor R. B. Woodward from 1978 to 1979. Notable work during his postdoctoral career includes the total synthesis of erythromycin. RajanBabu was a Member of Research Staff and Research Fellow at DuPont Central Research from 1980 to 1994 until joining the Ohio State University faculty as a Professor of Chemistry in 1995. | 0 | Organic Chemistry |
In many pairs of liquids, there is no uniformity of attractive forces, i.e., the adhesive (between dissimilar molecules) and cohesive forces (between similar molecules) are not uniform between the two liquids. Therefore, they deviate from Raoult's law, which applies only to ideal solutions. | 7 | Physical Chemistry |
Several numerical studies of small lattice systems appear to tentatively confirm the predictions of the eigenstate thermalization hypothesis in interacting systems which would be expected to thermalize. Likewise, systems which are integrable tend not to obey the eigenstate thermalization hypothesis.
Some analytical results can also be obtained if one makes certain assumptions about the nature of highly excited energy eigenstates. The original 1994 paper on the ETH by Mark Srednicki studied, in particular, the example of a quantum hard sphere gas in an insulated box. This is a system which is known to exhibit chaos classically. For states of sufficiently high energy, Berrys conjecture states that energy eigenfunctions in this many-body system of hard sphere particles will appear to behave as superpositions of plane waves, with the plane waves entering the superposition with random' phases and Gaussian-distributed amplitudes (the precise notion of this random superposition is clarified in the paper). Under this assumption, one can show that, up to corrections which are negligibly small in the thermodynamic limit, the momentum distribution function for each individual, distinguishable particle is equal to the Maxwell–Boltzmann distribution
where is the particle's momentum, m is the mass of the particles, k is the Boltzmann constant, and the "temperature" is related to the energy of the eigenstate according to the usual equation of state for an ideal gas,
where N is the number of particles in the gas. This result is a specific manifestation of the ETH, in that it results in a prediction for the value of an observable in one energy eigenstate which is in agreement with the prediction derived from a microcanonical (or canonical) ensemble. Note that no averaging over initial states whatsoever has been performed, nor has anything resembling the H-theorem been invoked. Additionally, one can also derive the appropriate Bose–Einstein or Fermi–Dirac distributions, if one imposes the appropriate commutation relations for the particles comprising the gas.
Currently, it is not well understood how high the energy of an eigenstate of the hard sphere gas must be in order for it to obey the ETH. A rough criterion is that the average thermal wavelength of each particle be sufficiently smaller than the radius of the hard sphere particles, so that the system can probe the features which result in chaos classically (namely, the fact that the particles have a finite size ). However, it is conceivable that this condition may be able to be relaxed, and perhaps in the thermodynamic limit, energy eigenstates of arbitrarily low energies will satisfy the ETH (aside from the ground state itself, which is required to have certain special properties, for example, the lack of any nodes ). | 7 | Physical Chemistry |
Normality is defined as the molar concentration divided by an equivalence factor . Since the definition of the equivalence factor depends on context (which reaction is being studied), the International Union of Pure and Applied Chemistry and National Institute of Standards and Technology discourage the use of normality. | 3 | Analytical Chemistry |
Fumonisin B2 is a fumonisin mycotoxin produced by the fungi Fusarium verticillioides (formerly Fusarium moniliforme) and Aspergillus niger.
It is a structural analog of fumonisin B3, while it is lacking one hydroxy group compared to fumonisin B1.
Fumonisin B2 is more cytotoxic than fumonisin B1. Fumonisin B2 inhibits sphingosine acyltransferase.
Fumonisin B2 and other fumonisins frequently contaminate maize and other crops, while recently it has been shown using LC–MS/MS that FB2 can contaminate coffee beans as well. | 1 | Biochemistry |
A synomone is an interspecific semiochemical that is beneficial to both interacting organisms, the emitter and receiver, e.g. floral synomone of certain Bulbophyllum species (Orchidaceae) attracts fruit fly males (Tephritidae: Diptera) as pollinators, so can be classed as an attractant. In this true mutualistic inter-relationship, both organisms gain benefits in their respective sexual reproductive systems – i.e. orchid flowers are pollinated and the Dacini fruit fly males are rewarded with a sex pheromone precursor or booster. The floral synomone, also acts as a reward to pollinators, is either in the form of a phenylpropanoid (e.g. methyl eugenol) or a phenylbutanoid (e.g. raspberry ketone and zingerone). | 1 | Biochemistry |
The DNA sequencing methods used in the 1970s and 1980s were manual; for example, Maxam–Gilbert sequencing and Sanger sequencing. Several whole bacteriophage and animal viral genomes were sequenced by these techniques, but the shift to more rapid, automated sequencing methods in the 1990s facilitated the sequencing of the larger bacterial and eukaryotic genomes.
The first virus to have its complete genome sequenced was the Bacteriophage MS2 by 1976. In 1992, yeast chromosome III was the first chromosome of any organism to be fully sequenced. The first organism whose entire genome was fully sequenced was Haemophilus influenzae in 1995. After it, the genomes of other bacteria and some archaea were first sequenced, largely due to their small genome size. H. influenzae has a genome of 1,830,140 base pairs of DNA. In contrast, eukaryotes, both unicellular and multicellular such as Amoeba dubia and humans (Homo sapiens) respectively, have much larger genomes (see C-value paradox). Amoeba dubia has a genome of 700 billion nucleotide pairs spread across thousands of chromosomes. Humans contain fewer nucleotide pairs (about 3.2 billion in each germ cell – note the exact size of the human genome is still being revised) than A. dubia, however, their genome size far outweighs the genome size of individual bacteria.
The first bacterial and archaeal genomes, including that of H. influenzae, were sequenced by Shotgun sequencing. In 1996 the first eukaryotic genome (Saccharomyces cerevisiae) was sequenced. S. cerevisiae, a model organism in biology has a genome of only around 12 million nucleotide pairs, and was the first unicellular eukaryote to have its whole genome sequenced. The first multicellular eukaryote, and animal, to have its whole genome sequenced was the nematode worm: Caenorhabditis elegans in 1998. Eukaryotic genomes are sequenced by several methods including Shotgun sequencing of short DNA fragments and sequencing of larger DNA clones from DNA libraries such as bacterial artificial chromosomes (BACs) and yeast artificial chromosomes (YACs).
In 1999, the entire DNA sequence of human chromosome 22, the second shortest human autosome, was published. By the year 2000, the second animal and second invertebrate (yet first insect) genome was sequenced – that of the fruit fly Drosophila melanogaster – a popular choice of model organism in experimental research. The first plant genome – that of the model organism Arabidopsis thaliana – was also fully sequenced by 2000. By 2001, a draft of the entire human genome sequence was published. The genome of the laboratory mouse Mus musculus was completed in 2002.
In 2004, the Human Genome Project published an incomplete version of the human genome. In 2008, a group from Leiden, the Netherlands, reported the sequencing of the first female human genome (Marjolein Kriek).
Currently thousands of genomes have been wholly or partially sequenced. | 1 | Biochemistry |
Concretes are produced from natural plant materials—mainly flowers. Some of the most popular natural flowers used are rose, lavender, jasmine, tuberose, jonquil, and ylang-ylang. | 7 | Physical Chemistry |
Phosphites, sometimes called phosphite esters, have the general structure P(OR) with oxidation state +3. Such species arise from the alcoholysis of phosphorus trichloride:
:PCl + 3 ROH → P(OR) + 3 HCl
The reaction is general, thus a vast number of such species are known. Phosphites are employed in the Perkow reaction and the Michaelis–Arbuzov reaction. They also serve as ligands in organometallic chemistry.
Intermediate between phosphites and phosphines are phosphonites (P(OR)R) and phosphinite (P(OR)R). Such species arise via alcoholysis reactions of the corresponding phosphonous and phosphinous chlorides ((PClR) and (PClR) , respectively). The latter are produced by reaction of a phosphorus trichloride with a poor metal-alkyl complex, e.g. organomercury, organolead, or a mixed lithium-organoaluminum compound. | 0 | Organic Chemistry |
Fractoluminescence is often used as a synonym for triboluminescence. It is the emission of light from the fracture (rather than rubbing) of a crystal, but fracturing often occurs with rubbing. Depending upon the atomic and molecular composition of the crystal, when the crystal fractures, a charge separation can occur, making one side of the fractured crystal positively charged and the other side negatively charged. Like in triboluminescence, if the charge separation results in a large enough electric potential, a discharge across the gap and through the bath gas between the interfaces can occur. The potential at which this occurs depends upon the dielectric properties of the bath gas. | 5 | Photochemistry |
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