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Very similar equations may be applied to the growth and melting of crystals in the confined geometry of porous systems. However the geometry term for the crystal-liquid interface may be different, and there may be additional surface energy terms to consider, which can be written as a wetting angle term . The angle is usually considered to be near 180°. In cylindrical pores there is some evidence that the freezing interface may be spherical, while the melting interface may be cylindrical, based on preliminary measurements for the measured ratio for in cylindrical pores.
Thus for a spherical interface between a non-wetting crystal and its own liquid, in an infinite cylindrical pore of diameter , the structural melting point depression
is given by: | 0 | Theoretical and Fundamental Chemistry |
cDNA is created from a mature mRNA from a eukaryotic cell with the use of reverse transcriptase. In eukaryotes, a poly-(A) tail (consisting of a long sequence of adenine nucleotides) distinguishes mRNA from tRNA and rRNA and can therefore be used as a primer site for reverse transcription. This has the problem that not all transcripts, such as those for the histone, encode a poly-A tail. | 1 | Applied and Interdisciplinary Chemistry |
The International Association of Geochemistry and Cosmochemistry (IAGC) was formally founded on 8 May 1967. Prior to that time the organization of international geochemical affairs was largely carried out through the Inorganic Chemistry section of the International Union of Pure and Applied Chemistry (IUPAC) starting in 1960. It was at the twenty-first International Geological Congress (IGC) at Copenhagen in 1960 when the International Union of Geological Sciences (IUGS) was formally established and geochemists formed a close bond with the world geological community. Earl Ingerson, as Chairman or Secretary to three of the then existing international geochemical organizations, coordinated a meeting of members of the committees on geochemistry of the IGC, IUGG and IUPAC in New Delhi in 1964, but was himself unable to attend. This meeting, chaired by Ken Sugawara, drew up draft statutes and nominated temporary officers, with the result that in November 1965, Earl Ingerson called a meeting in Paris to name the association, complete the statutes, elect temporary officers and apply to IUGS for immediate affiliation. The first Council meeting was held on 8 May 1967 at UNESCO headquarters in Paris, presided over by Earl Ingerson.
Until 2000, the Association's governing body was the General Assembly which met during each IGC. The main internal financial support was provided by National Members who voted at the General Assembly. Some outside funding also came from UNESCO and IUGS Day-to-day operations between each General Assembly were carried out by a Council of five officers and eight Council members.
During its existence, IAGC has, through its various working groups and members, sponsored or co-sponsored more than 40 international meetings, which represent its main financial expenditure. Many of these meetings result from close cooperation with other associations affiliated with IUGS and IUGG, as well as various international, national, provincial and academic organizations. Proceedings of these meetings are usually published. In 1986 the IAGC launched its official journal, Applied Geochemistry.
At the General Assembly of the IAGC in Rio de Janeiro, National Memberships were terminated as it was widely felt that the IAGC was sufficiently mature and financially stable that the control and support of individual countries on the IAGC, through designated representatives (who may not have been geochemists), was redundant and potentially counter-productive. Thus, the IAGC evolved into a self-supported organization whose activities were controlled by its members, through an elected Executive and Council.
Recently, the Statutes of the IAGC have undergone important revisions to be more applicable to current plans and operations. Also, as described on the IAGC homepage, there has been a name change to reflect the applied geochemical nature of the IAGC (now the International Association of GeoChemistry). | 0 | Theoretical and Fundamental Chemistry |
Conditional constants, also known as apparent constants, are concentration quotients which are not true equilibrium constants but can be derived from them. A very common instance is where pH is fixed at a particular value. For example, in the case of iron(III) interacting with EDTA, a conditional constant could be defined by
This conditional constant will vary with pH. It has a maximum at a certain pH. That is the pH where the ligand sequesters the metal most effectively.
In biochemistry equilibrium constants are often measured at a pH fixed by means of a buffer solution. Such constants are, by definition, conditional and different values may be obtained when using different buffers. | 0 | Theoretical and Fundamental Chemistry |
In solid-state physics, an orientational glass is a molecular solid in which crystalline long-range order coexists with quenched disorder in some rotational degree of freedom.
An orientational glass is either obtained by quenching a plastic crystal, (e.g. cyclohexane, levoglucosan), or it is a mixed crystal in which positional disorder causes additional disorder of molecular orientations, e.g. CN orientations in KCN:KBr. | 0 | Theoretical and Fundamental Chemistry |
Pierre Curie's grandfather, Paul Curie (1799–1853), a doctor of medicine, was a committed Malthusian humanist and married Augustine Hofer, daughter of Jean Hofer and great-granddaughter of Jean-Henri Dollfus, great industrialists from Mulhouse in the second half of the 18th century and the first part of the 19th century.
Through this paternal grandmother, Pierre Curie is also a direct descendant of the Basel scientist and mathematician Jean Bernoulli (1667–1748), as is Pierre-Gilles de Gennes, winner of the 1991 Nobel Prize in Physics.
Pierre and Marie Curies daughter, Irène, and their son-in-law, Frédéric Joliot-Curie, were also physicists involved in the study of radioactivity, and each also received Nobel prizes for their work. The Curies other daughter, Ève, wrote a noted biography of her mother. She was the only member of the Curie family to not become a physicist. Ève married Henry Richardson Labouisse Jr., who received a Nobel Peace Prize on behalf of Unicef in 1965. Pierre and Marie Curie's granddaughter, Hélène Langevin-Joliot, is a professor of nuclear physics at the University of Paris, and their grandson, Pierre Joliot, who was named after Pierre Curie, is a noted biochemist. | 1 | Applied and Interdisciplinary Chemistry |
[Co(NH)] is diamagnetic, with a low-spin 3d octahedral Co(III) center. The cation obeys the 18-electron rule and is considered to be a classic example of an exchange inert metal complex. As a manifestation of its inertness, [Co(NH)]Cl can be recrystallized unchanged from concentrated hydrochloric acid: the NH is so tightly bound to the Co(III) centers that it does not dissociate to allow its protonation. In contrast, labile metal ammine complexes, such as [Ni(NH)]Cl, react rapidly with acids, reflecting the lability of the Ni(II)–NH bonds. Upon heating, hexamminecobalt(III) begins to lose some of its ammine ligands, eventually producing a stronger oxidant.
)] is a moderately strong Bronsted acid.
The chloride ions in [Co(NH)]Cl can be exchanged with a variety of other anions such as nitrate, bromide, iodide, sulfamate to afford the corresponding [Co(NH)]X derivative. Such salts are orange or bright yellow and display varying degrees of water solubility. The chloride ion can be also exchanged with more complex anions such as the hexathiocyanatochromate(III), yielding a pink compound with formula [Co(NH)] [Cr(SCN)], or the ferricyanide ion. | 0 | Theoretical and Fundamental Chemistry |
Carbonato complexes are prepared by salt metathesis reactions using alkali metal carbonate salts as precursors. In some cases, bicarbonate intermediates are implicated since carbonate does not exist in appreciable concentrations near neutral pH. The other chief route to metal carbonato complexes involves addition of to metal oxides. Such reactions may be catalyzed by water since the carbonation of metal hydroxides is particularly well established. Isotope labeling studies show that these reactions can proceed (and perhaps usually proceed) without scission of the M-OH bond (L = generic ligand):
Many esoteric routes have been demonstrated. For example, the deoxygenation of peroxycarbonate by tertiary phosphines:
: (Ph = CH)
Carbon dioxide undergoes disproportionation upon reaction with low-valence metals. | 0 | Theoretical and Fundamental Chemistry |
A cumulative or overall constant, given the symbol β, is the constant for the formation of a complex from reagents. For example, the cumulative constant for the formation of ML is given by
The stepwise constants, K and K refer to the formation of the complexes one step at a time.
It follows that
A cumulative constant can always be expressed as the product of stepwise constants. Conversely, any stepwise constant can be expressed as a quotient of two or more overall constants. There is no agreed notation for stepwise constants, though a symbol such as K is sometimes found in the literature. It is good practice to specify each stability constant explicitly, as illustrated above. | 0 | Theoretical and Fundamental Chemistry |
Low-impact development (also referred to as green stormwater infrastructure) are systems and practices that use or mimic natural processes that result in the infiltration, evapotranspiration or use of stormwater in order to protect water quality and associated aquatic habitat. LID practices aim to preserve, restore and create green space using soils, vegetation, and rainwater harvest techniques. It is an approach to land development (or re-development) that works with nature to manage stormwater as close to its source as possible. Many low impact development tools integrate vegetation or the existing soil to reduce runoff and let rainfall enter the natural water cycle. | 1 | Applied and Interdisciplinary Chemistry |
The mathematical treatments of absorption spectroscopy for scattering materials were originally largely borrowed from other fields. The most successful treatments use the concept of dividing a sample into layers, called plane parallel layers. They are generally those consistent with a two-flux or two-stream approximation. Some of the treatments require all the scattered light, both remitted and transmitted light, to be measured. Others apply only to remitted light, with the assumption that the sample is "infinitely thick" and transmits no light. These are special cases of the more general treatments.
There are several general treatments, all of which are compatible with each other, related to the mathematics of plane parallel layers. They are the Stokes formulas, equations of Benford, Hecht finite difference formula, and the Dahm equation. For the special case of infinitesimal layers, the Kubelka–Munk and Schuster–Kortüm treatments also give compatible results. Treatments which involve different assumptions and which yield incompatible results are the Giovanelli exact solutions, and the particle theories of Melamed and Simmons. | 0 | Theoretical and Fundamental Chemistry |
Tubes are essential components in heat exchange systems to assist with cooling down motors and other instruments. Industrial applications use pressure-resistant tubes to safely contain gases and liquids under pressure without leading to air leakage or malfunction. Moreover, devices powered by ultrasound often employ special types of thin-walled tubes that can generate vibration when exposed to an electric field. Finally, tube components provide efficient energy conservation in housing insulation materials such as silicon rubber foam insulation and polyethylene foam insulation. | 1 | Applied and Interdisciplinary Chemistry |
The growth rates of calthemite stalactite straws, stalagmites and flowstone etc., is very much dependent on the supply rate and continuity of the saturated leachate solution to the location of CaCO deposition. The concentration of atmospheric CO in contact with the leachate, also has a large influence on how quickly the CaCO can precipitate from the leachate. Evaporation of the leachate solution and ambient atmospheric temperature appears to have very minimal influence on the CaCO deposition rate.
Calthemite straw stalactites precipitated (deposited) from hyperalkaline leachate have the potential to grow up to ≈200 times faster than normal cave speleothems precipitated from near neutral pH solution. One calthemite soda straw has been recorded as growing 2 mm per day over several consecutive days, when the leachate drip rate was a constant 11 minutes between drips. When the drip rate is more frequent than one drop per minute, there is no discernible deposition of CaCO at the tip of the stalactite (hence no growth) and the leachate solution falls to the ground where the CaCO is deposited to create a calthemite stalagmite. If the leachate supply to the stalactite straw's tip reduces to a level where the drip rate is greater than approximately 25 to 30 minutes between drops, there is a chance that the straw tip will calcify over and block up. New straw stalactites can often form next to a previously active, but now dry (dormant) straw, because the leachate has simply found an easier path through the micro cracks and voids in the concrete structure.
Despite both being composed of Calcium Carbonate, Calthemite straws are on average just 40% the mass per unit length of speleothem straws of equivalent external diameter. This is due to the different chemistry involved in creating the straws. The calthemite straws have a thin wall thickness and a less-dense calcium carbonate structure compared to speleothem straws.
Calthemite straws can vary in outside diameter as they grow in length. Changes in diameter can take a matter of days or weeks and are due to changes in drip rate over time. A slow dripping calthemite straw tends to be slightly larger in diameter than a fast-dripping straw. | 1 | Applied and Interdisciplinary Chemistry |
Potassium pentasulfide is the inorganic compound with the formula . It is a red-orange solid that dissolves in water. The salt decomposes rapidly in air.
It is one of several polysulfide salts with the general formula , where M = Li, Na, K and n = 2, 3, 4, 5, 6. The polysulfide salts of potassium and sodium are similar. | 0 | Theoretical and Fundamental Chemistry |
Townsend avalanche discharges are fundamental to the operation of gaseous ionisation detectors such as the Geiger–Müller tube and the proportional counter in either detecting ionising radiation or measuring its energy. The incident radiation will ionise atoms or molecules in the gaseous medium to produce ion pairs, but different use is made by each detector type of the resultant avalanche effects.
In the case of a GM tube the high electric field strength is sufficient to cause complete ionisation of the fill gas surrounding the anode from the initial creation of just one ion pair. The GM tube output carries information that the event has occurred, but no information about the energy of the incident radiation.
In the case of proportional counters, multiple creation of ion pairs occurs in the "ion drift" region near the cathode. The electric field and chamber geometries are selected so that an "avalanche region" is created in the immediate proximity of the anode. A negative ion drifting towards the anode enters this region and creates a localised avalanche that is independent of those from other ion pairs, but which can still provide a multiplication effect. In this way spectroscopic information on the energy of the incident radiation is available by the magnitude of the output pulse from each initiating event.
The accompanying plot shows the variation of ionisation current for a co-axial cylinder system. In the ion chamber region, there are no avalanches and the applied voltage only serves to move the ions towards the electrodes to prevent re-combination.
In the proportional region, localised avalanches occur in the gas space immediately round the anode which are numerically proportional to the number of original ionising events. Increasing the voltage further increases the number of avalanches until the Geiger region is reached where the full volume of the fill gas around the anodes ionised, and all proportional energy information is lost. Beyond the Geiger region the gas is in continuous discharge owing to the high electric field strength. | 0 | Theoretical and Fundamental Chemistry |
The sol-gel technique enables the production of LAGP particles at lower processing temperatures compared to sintering or glass crystallization. The typical precursor is a germanium organic compound, like germanium ethoxide , which is dissolved in an aqueous solution with stoichiometric amounts of the sources of lithium, phosphorus, and aluminium. The mixture is then heated and stirred. The sol-gel process starts after the addition of a gelation agent and the final material is obtained after subsequent heating steps aimed at eliminating water and at promoting the pyrolysis reaction, followed by calcination.
The sol-gel process requires the use of germanium organic precursors, which are more expensive compared to GeO. | 0 | Theoretical and Fundamental Chemistry |
The ion transport is accomplished by cyclical conformational changes of the enzyme between its two main reaction states, E1 and E2. The cytoplasmic-open E1 and luminal-open E2 states have high affinity for H and K. The expulsion of the proton at 160 mM (pH 0.8) concentration results from movement of lysine 791 into the ion binding site in the E2P configuration. | 1 | Applied and Interdisciplinary Chemistry |
Solar energy conversion describes technologies devoted to the transformation of solar energy to other (useful) forms of energy, including electricity, fuel, and heat. It covers light-harvesting technologies including traditional semiconductor photovoltaic devices (PVs), emerging photovoltaics, solar fuel generation via electrolysis, artificial photosynthesis, and related forms of photocatalysis directed at the generation of energy rich molecules.
Fundamental electro-optical aspects in several emerging solar energy conversion technologies for generation of both electricity (photovoltaics) and solar fuels constitute an active area of current research. | 0 | Theoretical and Fundamental Chemistry |
The Arctic ocean covers an area of 14,056,000 square kilometers, and supports a diverse and important socioeconomic food web of organisms, despite its average water temperature being 32 degrees Fahrenheit. Over the last three decades, the Arctic Ocean has experienced drastic changes due to climate change. One of the changes is in the acidity levels of the ocean, which have been consistently increasing at twice the rate of the Pacific and Atlantic oceans. Arctic Ocean acidification is a result of feedback from climate system mechanisms, and is having negative impacts on Arctic Ocean ecosystems and the organisms that live within them. | 0 | Theoretical and Fundamental Chemistry |
This method is limited to the measurement of the oxygen consumption due only to carbonaceous oxidation. Ammonia oxidation is inhibited.
The sample is kept in a sealed container fitted with a pressure sensor. A substance that absorbs carbon dioxide (typically lithium hydroxide) is added in the container above the sample level. The sample is stored in conditions identical to the dilution method. Oxygen is consumed and, as ammonia oxidation is inhibited, carbon dioxide is released. The total amount of gas, and thus the pressure, decreases because carbon dioxide is absorbed. From the drop of pressure, the sensor electronics computes and displays the consumed quantity of oxygen.
The main advantages of this method compared to the dilution method are:
* simplicity: no dilution of sample required, no seeding, no blank sample.
* direct reading of BOD value.
* continuous display of BOD value at the current incubation time. | 0 | Theoretical and Fundamental Chemistry |
The flow due to the presence of a solid surface at in planar stagnation-point flow was described first by Karl Hiemenz in 1911, whose numerical computations for the solutions were improved later by Leslie Howarth. A familiar example where Hiemenz flow is applicable is the forward stagnation line that occurs in the flow over a circular cylinder.
The solid surface lies on the . According to potential flow theory, the fluid motion described in terms of the stream function and the velocity components are given by
The stagnation line for this flow is . The velocity component is non-zero on the solid surface indicating that the above velocity field do not satisfy no-slip boundary condition on the wall. To find the velocity components that satisfy the no-slip boundary condition, one assumes the following form
where is the Kinematic viscosity and is the characteristic thickness where viscous effects are significant. The existence of constant value for the viscous effects thickness is due to the competing balance between the fluid convection that is directed towards the solid surface and viscous diffusion that is directed away from the surface. Thus the vorticity produced at the solid surface is able to diffuse only to distances of order ; analogous situations that resembles this behavior occurs in asymptotic suction profile and von Kármán swirling flow. The velocity components, pressure and Navier–Stokes equations then become
The requirements that at and that as translate to
The condition for as cannot be prescribed and is obtained as a part of the solution. The problem formulated here is a special case of Falkner-Skan boundary layer. The solution can be obtained from numerical integrations and is shown in the figure. The asymptotic behaviors for large are
where is the displacement thickness. | 1 | Applied and Interdisciplinary Chemistry |
Apoptotic DNA fragmentation is a natural fragmentation that cells perform in apoptosis (programmed cell death). DNA fragmentation is a biochemical hallmark of apoptosis. In dying cells, DNA is cleaved by an endonuclease that fragments the chromatin into nucleosomal units, which are multiples of about 180-bp oligomers and appear as a DNA ladder when run on an agarose gel. The enzyme responsible for apoptotic DNA fragmentation is the Caspase-activated DNase. CAD is normally inhibited by another protein, the Inhibitor of Caspase Activated DNase (ICAD). During apoptosis, the apoptotic effector caspase, caspase 3, cleaves ICAD and thus causes CAD to become activated.
CAD cleaves the DNA at the internucleosomal linker sites between the nucleosomes, protein-containing structures that occur in chromatin at ~180-bp intervals. This is because the DNA is normally tightly wrapped around histones, the core proteins of the nucleosomes. The linker sites are the only parts of the DNA strand that are exposed and thus accessible to CAD.
Men with sperm motility defects often have high levels of sperm DNA fragmentation.
The degree of DNA fragmentation in sperm cells can predict outcomes for in vitro fertilization (IVF) and its expansion intracytoplasmic sperm injection (ICSI). The sperm chromatin dispersion test (SCD) and TUNEL assay are both effective in detecting sperm DNA damage. Using bright-field microscopy, the SCD test appears to be more sensitive than the TUNEL assay. | 1 | Applied and Interdisciplinary Chemistry |
The earliest habitation at the site dates back to the Chalcolithic period.
Arslantepe (VII) became important in this region in the Late Chalcolithic. A monumental area with a huge mudbrick building stood on top of a mound. This large building had wall decorations; its function is uncertain. | 1 | Applied and Interdisciplinary Chemistry |
MIKE BASIN can be used for providing solutions and alternatives to water allocation and water shortage problems, improving and optimizing reservoir and hydropower operations, exploring conjunctive use of groundwater and surface water, evaluating and improving irrigation performance, solving multi-criteria optimization problems, establishing cost-effective measures for water quality compliance. | 1 | Applied and Interdisciplinary Chemistry |
Reductive elimination is often seen in higher oxidation states, and can involve a two-electron change at a single metal center (mononuclear) or a one-electron change at each of two metal centers (binuclear, dinuclear, or bimetallic).
For mononuclear reductive elimination, the oxidation state of the metal decreases by two, while the d-electron count of the metal increases by two. This pathway is common for d metals Ni(II), Pd(II), and Au(III) and d metals Pt(IV), Pd(IV), Ir(III), and Rh(III). Additionally, mononuclear reductive elimination requires that the groups being eliminated must be cis to one another on the metal center.
For binuclear reductive elimination, the oxidation state of each metal decreases by one, while the d-electron count of each metal increases by one. This type of reactivity is generally seen with first row metals, which prefer a one-unit change in oxidation state, but has been observed in both second and third row metals. | 0 | Theoretical and Fundamental Chemistry |
This is closer in spirit to the proof sketch given by Purcell. The key result is to show that a swimmer in a Stokes fluid does not depend on time. That is, a one cannot detect if a movie of a swimmer motion is slowed down, sped up, or reversed. The other results then are simple corollaries.
The stress tensor of the fluid is .
Let be a nonzero real constant. Suppose we have a swimming motion, then we can do the following scaling:and obtain another solution to the Stokes equation. That is, if we scale hydrostatic pressure, flow-velocity, and stress tensor all by , we still obtain a solution to the Stokes equation.
Since the motion is in the low Reynolds number regime, inertial forces are negligible, and the instantaneous total force and torque on the swimmer must both balance to zero. Since the instantaneous total force and torque on the swimmer is computed by integrating the stress tensor over its surface, the instantaneous total force and torque increase by as well, which are still zero.
Thus, scaling both the swimmer's motion and the motion of the surrounding fluid scales by the same factor, we still obtain a motion that respects the Stokes equation. | 1 | Applied and Interdisciplinary Chemistry |
Ferrocene-containing dendrimers are dendrimers that contain ferrocene substituents. Some ferrocene-containing dendrimers feature ferrocene cores and others do not. All feature with peripheral ferrocene groups. | 0 | Theoretical and Fundamental Chemistry |
Levofloxacin, sold under the brand name Levaquin among others, is an antibiotic medication. It is used to treat a number of bacterial infections including acute bacterial sinusitis, pneumonia, H. pylori (in combination with other medications), urinary tract infections, chronic prostatitis, and some types of gastroenteritis. Along with other antibiotics it may be used to treat tuberculosis, meningitis, or pelvic inflammatory disease. Use is generally recommended only when other options are not available. It is available by mouth, intravenously, and in eye drop form.
Common side effects include nausea, diarrhea, and trouble sleeping. Serious side effects may include tendon rupture, tendon inflammation, seizures, psychosis, and potentially permanent peripheral nerve damage. Tendon damage may appear months after treatment is completed. People may also sunburn more easily. In people with myasthenia gravis, muscle weakness and breathing problems may worsen. While use during pregnancy is not recommended, risk appears to be low. The use of other medications in this class appear to be safe while breastfeeding; however, the safety of levofloxacin is unclear. Levofloxacin is a broad-spectrum antibiotic of the fluoroquinolone drug class. It usually results in death of the bacteria. It is the left-handed isomer of the medication ofloxacin.
Levofloxacin was patented in 1985 and approved for medical use in the United States in 1996. It is on the World Health Organization's List of Essential Medicines. It is available as a generic medication. In 2021, it was the 223rd most commonly prescribed medication in the United States, with more than 1million prescriptions. | 0 | Theoretical and Fundamental Chemistry |
A minigene is a minimal gene fragment that includes an exon and the control regions necessary for the gene to express itself in the same way as a wild type gene fragment. This is a minigene in its most basic sense. More complex minigenes can be constructed containing multiple exons and intron(s). Minigenes provide a valuable tool for researchers evaluating splicing patterns both in vivo and in vitro biochemically assessed experiments. Specifically, minigenes are used as splice reporter vectors (also called exon-trapping vectors) and act as a probe to determine which factors are important in splicing outcomes. They can be constructed to test the way both cis-regulatory elements (RNA effects) and trans-regulatory elements (associated proteins/splicing factors) affect gene expression. | 1 | Applied and Interdisciplinary Chemistry |
For heterogeneous surfaces (consisting of two or more different types of material), the contact angle of a drop of liquid at each point along the three phase contact line with a solid surface is a result of the surface tension of the surface at that point. For example, if the heterogeneous regions of the surface form very large domains, and the drop exists entirely within a homogeneous domain, then it will have a contact angle corresponding to the surface tension of that homogeneous region. Likewise, a drop that straddles two domains of differing surface tensions will have different contact angles along the three phase contact line corresponding to the different surface tensions at each point. However, with sufficiently small domains (such as in those of a block copolymer), the observed surface energy of the surface approaches the weighted average of the surface energies of each of the constituents of the surface:
where:
: is the overall surface energy of the polymer
: is the fraction of the component of the polymer's surface
: is the surface energy of the component
This occurs because as the size of the homogeneous domains become very small compared to the size of the drop, the differences in contact angles along different homogeneous regions becomes indistinguishable from the average of the contact angles.
The observed contact angle is given by the following formula:
where:
:is the fraction of component
: is the contact angle component
If the polymer is made out of only two different monomers, it is possible use the above equation to determine the composition of the polymer simply by measuring the contact angle of a drop of liquid placed on it:
where:
: is the observed contact angle
: is the area fraction of one component, and the area fraction of the other.
: and are the contact angles of the first and second components of the polymer. | 0 | Theoretical and Fundamental Chemistry |
The advances in bisulfite sequencing have led to the possibility of applying them at a genome-wide scale, where, previously, global measure of DNA methylation was feasible only using other techniques, such as Restriction landmark genomic scanning. The mapping of the human epigenome is seen by many scientists as the logical follow-up to the completion of the Human Genome Project. This epigenomic information will be important in understanding how the function of the genetic sequence is implemented and regulated. Since the epigenome is less stable than the genome, it is thought to be important in gene-environment interactions.
Epigenomic mapping is inherently more complex than genome sequencing, however, since the epigenome is much more variable than the genome. One's epigenome varies with age, differs between tissues, is altered by environmental factors, and shows aberrations in diseases. Such rich epigenomic mapping, however, representing different ages, tissue types, and disease states, would yield valuable information on the normal function of epigenetic marks as well as the mechanisms leading to aging and disease.
Direct benefits of epigenomic mapping include probable advances in cloning technology. It is believed that failures to produce cloned animals with normal viability and lifespan result from inappropriate patterns of epigenetic marks. Also, aberrant methylation patterns are well characterized in many cancers. Global hypomethylation results in decreased genomic stability, while local hypermethylation of tumour suppressor gene promoters often accounts for their loss of function. Specific patterns of methylation are indicative of specific cancer types, have prognostic value, and can help to guide the best course of treatment.
Large-scale epigenome mapping efforts are under way around the world and have been organized under the Human Epigenome Project. This is based on a multi-tiered strategy, whereby bisulfite sequencing is used to obtain high-resolution methylation profiles for a limited number of reference epigenomes, while less thorough analysis is performed on a wider spectrum of samples. This approach is intended to maximize the insight gained from a given amount of resources, as high-resolution genome-wide mapping remains a costly undertaking.
Gene-set analysis (for example using tools like DAVID and GoSeq) has been shown to be severely biased when applied to high-throughput methylation data (e.g. genome-wide bisulfite sequencing); it has been suggested that this can be corrected using sample label permutations or using a statistical model to control for differences in the numberes of CpG probes / CpG sites that target each gene. | 1 | Applied and Interdisciplinary Chemistry |
Problems with mRNA stability have been identified in viral genomes, cancer cells, and various diseases. Research shows that many of these problems arise because of faulty ARE function. Some of these problems have been listed below:
* The c-fos gene produces a transcription factor that is activated in several cancers, and it lacks the ARE elements.
* c-myc gene, also responsible for producing transcription factors found in several cancers, has also been reported to lack the ARE elements.
* The Cox-2 gene catalyses the production of prostaglandins—it overexpresses in several cancers, and is stabilized by the binding of CUGBP2 RNA-binding protein to ARE | 1 | Applied and Interdisciplinary Chemistry |
Using ethenolysis, higher molecular weight internal alkenes can be converted to more valuable terminal alkenes. The Shell higher olefin process (SHOP process) uses ethenolysis on an industrial scale. The SHOP α-olefin mixtures are separated by distillation, the higher molecular weight fractions are isomerized by alkaline alumina catalysts in the liquid phase. The resulting internal olefins are reacted with ethylene to regenerate α-olefins. The large excess of ethylene moves the reaction equilibrium to the terminal α-olefins. Catalysts are often prepared from Rhenium(VII) oxide () supported on alumina.
In one application, neohexene, a precursor to perfumes, is prepared by ethenolysis of diisobutene:
α,ω-Dienes, i.e., diolefins of the formula , are prepared industrially by ethenolysis of cyclic alkenes. For example, 1,5-hexadiene, a useful crosslinking agent and synthetic intermediate, is produced from 1,5-cyclooctadiene:
The catalyst is derived from rhenium(VII) oxide supported on alumina. 1,9-Decadiene, a related species, is produced similarly from cyclooctene.
In an application directed at using renewable feedstocks, methyl oleate, derived from natural seed oils, can be converted to 1-decene and methyl 9-decenoate: | 0 | Theoretical and Fundamental Chemistry |
Kacser and Burns introduced an additional coefficient that described how a biochemical pathway would respond the external environment. They termed this coefficient the response coefficient and designated it using the symbol R. The response coefficient is an important metric because it can be used to assess how much a nutrient or perhaps more important, how a drug can influence a pathway. This coefficient is therefore highly relevant to the pharmaceutical industry.
The response coefficient is related to the core of metabolic control analysis via the response coefficient theorem, which is stated as follows:
where is a chosen observable such as a flux or metabolite concentration, is the step that the external factor targets, is the control coefficient of the target steps, and is the elasticity of the target step with respect to the external factor .
The key observation of this theorem is that an external factor such as a therapeutic drug, acts on the organism's phenotype via two influences: 1) How well the drug can affect the target itself through effective binding of the drug to the target protein and its effect on the protein activity. This effectiveness is described by the elasticity and 2) How well do modifications of the target influence the phenotype by transmission of the perturbation to the rest of the network. This is indicated by the control coefficient .
A drug action, or any external factor, is most effective when both these factors are strong. For example, a drug might be very effective at changing the activity of its target protein, however if that perturbation in protein activity is unable to be transmitted to the final phenotype then the effectiveness of the drug is greatly diminished.
If a drug or external factor, , targets multiple sites of action, for example sites, then the overall response in a phenotypic factor , is the sum of the individual responses: | 1 | Applied and Interdisciplinary Chemistry |
Photosystem II is the photosystem that generates the two electrons that will eventually reduce NADP in ferredoxin-NADP-reductase. Photosystem II is present on the thylakoid membranes inside chloroplasts, the site of photosynthesis in green plants. The structure of Photosystem II is remarkably similar to the bacterial reaction center, and it is theorized that they share a common ancestor.
The core of Photosystem II consists of two subunits referred to as D1 and D2. These two subunits are similar to the L and M subunits present in the bacterial reaction center. Photosystem II differs from the bacterial reaction center in that it has many additional subunits that bind additional chlorophylls to increase efficiency. The overall reaction catalyzed by Photosystem II is:
:2Q + 2HO + hν → O + 2QH
Q represents the oxidized form of plastoquinone while QH represents its reduced form. This process of reducing quinone is comparable to that which takes place in the bacterial reaction center. Photosystem II obtains electrons by oxidizing water in a process called photolysis. Molecular oxygen is a byproduct of this process, and it is this reaction that supplies the atmosphere with oxygen. The fact that the oxygen from green plants originated from water was first deduced by the Canadian-born American biochemist Martin David Kamen. He used a stable isotope of oxygen, O, to trace the path of the oxygen from water to gaseous molecular oxygen. This reaction is catalyzed by a reactive center in Photosystem II containing four manganese ions.
The reaction begins with the excitation of a pair of chlorophyll molecules similar to those in the bacterial reaction center. Due to the presence of chlorophyll a, as opposed to bacteriochlorophyll, Photosystem II absorbs light at a shorter wavelength. The pair of chlorophyll molecules at the reaction center are often referred to as P680. When the photon has been absorbed, the resulting high-energy electron is transferred to a nearby pheophytin molecule. This is above and to the right of the pair on the diagram and is coloured grey. The electron travels from the pheophytin molecule through two plastoquinone molecules, the first tightly bound, the second loosely bound. The tightly bound molecule is shown above the pheophytin molecule and is colored red. The loosely bound molecule is to the left of this and is also colored red. This flow of electrons is similar to that of the bacterial reaction center. Two electrons are required to fully reduce the loosely bound plastoquinone molecule to QH as well as the uptake of two protons.
The difference between Photosystem II and the bacterial reaction center is the source of the electron that neutralizes the pair of chlorophyll a molecules. In the bacterial reaction center, the electron is obtained from a reduced compound haem group in a cytochrome subunit or from a water-soluble cytochrome-c protein.
Every time the P680 absorbs a photon, it gives off an electron to pheophytin, gaining a positive charge. After this photoinduced charge separation, P680 is a very strong oxidant of high energy. It passes its energy to water molecules that are bound at the manganese center directly below the pair and extracts an electron from them. This center, below and to the left of the pair in the diagram, contains four manganese ions, a calcium ion, a chloride ion, and a tyrosine residue. Manganese is adept at these reactions because it is capable of existing in four oxidation states: Mn, Mn, Mn and Mn. Manganese also forms strong bonds with oxygen-containing molecules such as water. The process of oxidizing two molecules of water to form an oxygen molecule requires four electrons. The water molecules that are oxidized in the manganese center are the source of the electrons that reduce the two molecules of Q to QH. To date, this water splitting catalytic center has not been reproduced by any man-made catalyst. | 0 | Theoretical and Fundamental Chemistry |
Sandra Pizzarello's research over the last forty years involved the analysis of organic compounds in several carbonaceous chondrites, particularly molecular, chiral, and isotopic characterization of amino acids. Because the formation of these organic-rich meteorites pre-date the origin of life, they had been under investigation as potential sites of primal organic compounds which could shed light on abiogenesis, specifically the origin of biological homochirality. Such studies, however, had been inconclusive until 1997 when Cronin and Pizzarello detected 7-9% L-enantiomeric excesses of three abiological amino acids while analyzing the Murchison meteorite.
Given Earths history of meteoric impacts and the observation that meteors contain an excess of the biologically relevant L-stereoisomer of certain amino acids, Pizzarello studied the effect of meteoritic amino acids in enantiomeric excess on the formation of other biological molecules. In one study, Pizzarello found that nonracemic solutions of abiological isovaline and proteinogenic alanine can direct the condensation of glycolaldehyde to produce nonracemic solutions of threose and erythrose via an aldol reaction concluding that amino acids can act as asymmetric catalysts in carbohydrate synthesis. These findings support the origin of life hypothesis that homochirality originated prior to life and from extraterrestrial origins. However, Pizzarellos theoretical inquiries into cosmochemical evolution remain debated based on suspect analytical evidence of meteoritic enantiomeric excesses. | 1 | Applied and Interdisciplinary Chemistry |
According to the jargon in polymer chemistry, telomerization requires a telogen to react with at least one unsaturated taxogen molecule. Fluorotelomers are an example. | 0 | Theoretical and Fundamental Chemistry |
A handful of studies utilized tissue engineering of heart valves in vivo in animal models and humans. In 2000, Matheny conducted a study in which he used a pig's small intestinal submucosa to replace one pulmonary valve leaflet. Limited studies have also been conducted in a clinical setting. For instance in 2001, Elkins implanted SynerGraft treated decellularized human pulmonary valves in patients. Simon similarly used SynerGraft decellularized pig valves for implantation in children; however, these valves widely failed as there were no host cells but rather high amounts of inflammatory cells found at the scaffold site instead. Studies led by Dohmen, Konertz, and colleagues in Berlin, Germany involved the implantation of a biological pig valve in 50 patients who underwent the Ross operation from 2002 to 2004. Using a decellularized porcine xenograft valve, also called Matrix P, in adults with a median age of 46 years, the aim of the study was to offer a proposal for pulmonary valve replacement. While some patients died postoperatively and had to undergo reoperation, the short-term results appear to be going well as the valve is behaving similarly to a native, healthy valve. One animal trial combined the transcatheter aortic valve replacement (TAVR) procedure with tissue engineered heart valves (TEHVs). A TAVR stent integrated with human cell-derived extracellular matrix was implanted and examined in sheep, in which the valve upheld structural integrity and cell infiltration, allowing the potential clinical application to extend TAVR to younger patients. | 1 | Applied and Interdisciplinary Chemistry |
Sealing is the final step in the anodizing process. Acidic anodizing solutions produce pores in the anodized coating. These pores can absorb dyes and retain lubricants but are also an avenue for corrosion. When lubrication properties are not critical, they are usually sealed after dyeing to increase corrosion resistance and dye retention. There are three most common types of sealing.
# Long immersion in boiling-hot——deionized water or steam is the simplest sealing process, although it is not completely effective and reduces abrasion resistance by 20%. The oxide is converted into its hydrated form and the resulting swelling reduces the porosity of the surface.
# Mid-temperature sealing process which works at in solutions containing organic additives and metal salts. However, this process will likely leach the colors.
# Cold sealing process, where the pores are closed by impregnation of a sealant in a room-temperature bath, is more popular due to energy savings. Coatings sealed in this method are not suitable for adhesive bonding. Teflon, nickel acetate, cobalt acetate, and hot sodium or potassium dichromate seals are commonly used. MIL-A-8625 requires sealing for thin coatings (Types I and II) and allows it as an option for thick ones (Type III). | 1 | Applied and Interdisciplinary Chemistry |
Many alkoxides are prepared by salt-forming reactions from a metal chlorides and sodium alkoxide:
Such reactions are favored by the lattice energy of the NaCl, and purification of the product alkoxide is simplified by the fact that NaCl is insoluble in common organic solvents.
For electrophilic metal halides, conversion to the alkoxide requires no or mild base. Titanium tetrachloride reacts with alcohols to give the corresponding tetraalkoxides, concomitant with the evolution of hydrogen chloride:
The reaction can be accelerated by the addition of a base, such as a tertiary amine. Other electrophilic metal halides can be used instead of titanium, for example . | 0 | Theoretical and Fundamental Chemistry |
* Post-doctorate fellowship senior scholar Fulbright Fellowship (1985), where he was a visiting Fulbright fellow.
* Post-doctorate fellow Association of Commonwealth Universities (1984-1985), where he was a visiting Commonwealth fellow | 1 | Applied and Interdisciplinary Chemistry |
Trans-spanning ligands are bidentate ligands that can span coordination positions on opposite sides of a coordination complex. | 0 | Theoretical and Fundamental Chemistry |
A kairomone is a semiochemical, emitted by an organism, which mediates interspecific interactions in a way that benefits an individual of another species which receives it, without benefitting the emitter. Two main ecological cues are provided by kairomones; they generally either indicate a food source for the receiver, or give warning of the presence of a predator. Often a pheromone may be utilized as a kairomone by a predator or parasitoid to locate the emitting organism. | 1 | Applied and Interdisciplinary Chemistry |
Indirectly, it has been deduced that the origin of KREEP is contained in the origin of the Moon. This is now commonly thought to be the result of a rocky object the size of Mars that struck the Earth about 4.5 billion (4.5×10) years ago. This collision threw a large amount of broken rock into orbit around the Earth. This ultimately gathered together to form the Moon.
Given the high energy such a collision would involve, it has been deduced that a large portion of the Moon would have been liquified, and this
formed a lunar magma ocean. As the crystallization of this liquid rock proceeded, minerals such as olivine and pyroxene precipitated and sank to the bottom to form the lunar mantle.
After the solidification was about 75% complete, the material anorthositic plagioclase began to crystallize, and because of its low density, it floated, forming a solid crust. Hence, elements that are usually incompatible (i.e., those that usually partition in the liquid phase) would have been progressively concentrated into the magma. Thus a KREEP-rich magma was formed that was sandwiched at first between the crust and mantle. The evidence for these processes comes from the highly anorthositic composition of the crust of the lunar highlands, as well as the presence of the rocks rich in KREEP. | 0 | Theoretical and Fundamental Chemistry |
Suzuki has not obtained a patent on Suzuki reaction technology because he thinks that the research was supported by government funds, therefore coupling technology has become widespread, and many products using this technology have been put into practical use. To date, there are more than 6,000 papers and patents related to Suzuki reaction. | 0 | Theoretical and Fundamental Chemistry |
Colliding beam fusion (CBF), or colliding beam fusion reactor (CBFR), is a class of fusion power concepts that are based on two or more intersecting beams of fusion fuel ions that are independently accelerated to fusion energies using a variety of particle accelerator designs or other means. One of the beams may be replaced by a static target, in which case the approach is termed accelerator based fusion or beam-target fusion, but the physics is the same as colliding beams.
CBFRs face several problems that have limited their ability to be seriously considered as candidates for fusion power. When two ions collide, they are more likely to scatter than to fuse. Magnetic confinement fusion reactors overcome this problem using a bulk plasma and confining it for some time so that the ions have many thousands of chances to collide. Two beams colliding give ions little time to interact before the beams fly apart. This limits how much fusion power a beam-beam machine can make.
CBFR offers more efficient ways to provide the activation energy for fusion, by directly accelerating individual particles rather than heating a bulk fuel. The CBFR reactants are naturally non-thermal which gives them advantages, especially that they can directly carry enough energy to overcome the Coulomb barrier of aneutronic fusion fuels. Several designs have sought to address the shortcomings of earlier CBFRs, including Migma, MARBLE, MIX, and other beam-based concepts. These attempt to overcome the fundamental challenges of CBFR by applying radio waves, bunching beams together, increasing recirculation, or applying some quantum effects. None of these approaches have succeeded yet. | 0 | Theoretical and Fundamental Chemistry |
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 | Applied and Interdisciplinary Chemistry |
Selenium is an essential micronutrient in mammals, but is also recognized as toxic in excess. Selenium exerts its biological functions through selenoproteins, which contain the amino acid selenocysteine. Twenty-five selenoproteins are encoded in the human genome. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water.
Hydrophobic molecules tend to be nonpolar and, thus, prefer other neutral molecules and nonpolar solvents. Because water molecules are polar, hydrophobes do not dissolve well among them. Hydrophobic molecules in water often cluster together, forming micelles. Water on hydrophobic surfaces will exhibit a high contact angle.
Examples of hydrophobic molecules include the alkanes, oils, fats, and greasy substances in general. Hydrophobic materials are used for oil removal from water, the management of oil spills, and chemical separation processes to remove non-polar substances from polar compounds.
Hydrophobic is often used interchangeably with lipophilic, "fat-loving". However, the two terms are not synonymous. While hydrophobic substances are usually lipophilic, there are exceptions, such as the silicones and fluorocarbons.
The term hydrophobe comes from the Ancient Greek (), "having a fear of water", constructed . | 0 | Theoretical and Fundamental Chemistry |
The Deal–Grove model works very well for single-crystal silicon under most conditions. However, experimental data shows that very thin oxides (less than about 25 nanometres) grow much more quickly in than the model predicts. In silicon nanostructures (e.g., silicon nanowires) this rapid growth is generally followed by diminishing oxidation kinetics in a process known as self-limiting oxidation, necessitating a modification of the Deal–Grove model.
If the oxide grown in a particular oxidation step greatly exceeds 25 nm, a simple adjustment accounts for the aberrant growth rate. The model yields accurate results for thick oxides if, instead of assuming zero initial thickness (or any initial thickness less than 25 nm), we assume that 25 nm of oxide exists before oxidation begins. However, for oxides near to or thinner than this threshold, more sophisticated models must be used.
In the 1980s, it became obvious that an update to the Deal-Grove model is necessary to model the aforementioned thin oxides (self-limiting cases). One such approach that more accurately models thin oxides is the Massoud model from 1985 [2]. The Massoud model is analytical and based on parallel oxidation mechanisms. It changes the parameters of the Deal-Grove model to better model the initial oxide growth with the addition of rate-enhancement terms.
The Deal-Grove model also fails for polycrystalline silicon ("poly-silicon"). First, the random orientation of the crystal grains makes it difficult to choose a value for the linear rate constant. Second, oxidant molecules diffuse rapidly along grain boundaries, so that poly-silicon oxidizes more rapidly than single-crystal silicon.
Dopant atoms strain the silicon lattice, and make it easier for silicon atoms to bond with incoming oxygen. This effect may be neglected in many cases, but heavily doped silicon oxidizes significantly faster. The pressure of the ambient gas also affects oxidation rate. | 1 | Applied and Interdisciplinary Chemistry |
In the study of diffusion flame, Liñán's equation is a second-order nonlinear ordinary differential equation which describes the inner structure of the diffusion flame, first derived by Amable Liñán in 1974. The equation reads as
subjected to the boundary conditions
where is the reduced or rescaled Damköhler number and is the ratio of excess heat conducted to one side of the reaction sheet to the total heat generated in the reaction zone. If , more heat is transported to the oxidizer side, thereby reducing the reaction rate on the oxidizer side (since reaction rate depends on the temperature) and consequently greater amount of fuel will be leaked into the oxidizer side. Whereas, if , more heat is transported to the fuel side of the diffusion flame, thereby reducing the reaction rate on the fuel side of the flame and increasing the oxidizer leakage into the fuel side. When , all the heat is transported to the oxidizer (fuel) side and therefore the flame sustains extremely large amount of fuel (oxidizer) leakage.
The equation is, in some aspects, universal (also called as the canonical equation of the diffusion flame) since although Liñán derived the equation for stagnation point flow, assuming unity Lewis numbers for the reactants, the same equation is found to represent the inner structure for general laminar flamelets, having arbitrary Lewis numbers. | 1 | Applied and Interdisciplinary Chemistry |
As in the case of single molecule fluorescence spectroscopy, the technique known as single channel recording can be used to obtain specific kinetic information—in this case about ion channel function—that is not available when ensemble recording, such as whole-cell recording, is performed. Specifically, ion channels alternate between conducting and non-conducting classes, which differ in conformation. Therefore, the functional state of ion channels can be directly measured with sufficiently sensitive electronics, provided that proper precautions are taken to minimize noise. In turn, each of these classes may be divided into one or more kinetic states with direct bearing on the underlying function of the ion channel. Performing these types of single molecule studies under systematically varying conditions (e.g. agonist concentration and structure, permeant ion and/or channel blocker, mutations in the ion channel amino acids), can provide information regarding the interconversion of various kinetic states of the ion channel. In a minimal model for an ion channel, there are two states: open and closed. However, other states are often needed in order to accurately represent the data, including multiple closed states as well as inactive and/or desensitized states, which are non-conducting states that can occur even in the presence of stimulus. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, a ring flip (also known as a ring inversion or ring reversal) is the interconversion of cyclic conformers that have equivalent ring shapes (e.g., from a chair conformer to another chair conformer) that results in the exchange of nonequivalent substituent positions. The overall process generally takes place over several steps, involving coupled rotations about several of the molecule's single bonds, in conjunction with minor deformations of bond angles. Most commonly, the term is used to refer to the interconversion of the two chair conformers of cyclohexane derivatives, which is specifically referred to as a chair flip, although other cycloalkanes and inorganic rings undergo similar processes. | 0 | Theoretical and Fundamental Chemistry |
Due to the binding capabilities of antipsychotic drugs and various neurotransmitters associated with mood, the sigma-2 receptor is a viable target for therapies related to neuropsychiatric disorders and modulation of emotional response. It is thought to be involved in the pathophysiology of schizophrenia, and sigma-2 receptors have been shown to be less abundant in schizophrenic patients. Additionally, PCP, which is an NMDA antagonist, can induce schizophrenia, while sigma-2 receptor activation has been shown to antagonize effects of PCP, implying antipsychotic capabilities. Sigma receptors are a potential target for treatment of dystonia, given high densities in affected regions of the brain. Anti-ischemics ifenprodil and eliprodil, the binding of which increases blood flow, have also shown affinity to sigma receptors.
In experimental trials in mice and rats, the sigma-2 receptor ligand siramesine caused reduced anxiety and displayed antidepressant capabilities, while other studies have shown inhibition of selective sigma receptor radioligands by antidepressants, in the mouse and rat brain. | 1 | Applied and Interdisciplinary Chemistry |
The Haber–Weiss reaction generates •OH (hydroxyl radicals) from HO (hydrogen peroxide) and superoxide (•O) catalyzed by iron ions. It was first proposed by Fritz Haber and his student Joseph Joshua Weiss in 1932.
This reaction has long been studied and revived in different contexts, including organic chemistry, free radicals, radiochemistry, and water radiolysis. In the 1970, with the emerging interest for the effect of free radicals onto the ageing mechanisms of living cells due to oxygen (O), it was proposed that the Haber–Weiss reaction was a source of radicals responsible for cellular oxidative stress. However, this hypothesis was later disproved by several research works. The oxidative stress toxicity is not caused by the Haber–Weiss reaction as a whole, but by the Fenton reaction, which is one specific part of it.
The reaction is kinetically slow, but is catalyzed by dissolved iron ions. The first step of the catalytic cycle involves the reduction of the ferric (Fe) ion into the ferrous (Fe) ion:
:Fe + •O → Fe + O
The second step is the Fenton reaction:
:Fe + HO → Fe + OH + •OH
Net reaction:
:•O + HO → •OH + OH + O | 1 | Applied and Interdisciplinary Chemistry |
Following transcription, Arc mRNA is transported out of the nucleus and localized to neuronal dendrites and activated synapses, a process dependent on the 3 UTR, polymerization of actin, and ERK phosphorylation. The mRNA (and aggregate protein) is carried along microtubules radiating out from the nucleus by kinesin (specifically KIF5) and likely translocated into dendritic spines by the actin-based motor protein myosin-Va. Arc has been shown to be associated with polyribosomes at synaptic sites, and is translated in isolated synaptoneurosomal fractions in vitro indicating that the protein is likely locally translated in vivo'. | 1 | Applied and Interdisciplinary Chemistry |
In organic synthesis, aminochlorination is a reaction that installs both a chlorine atom and an amino (or amido) group to give an 2-aminoalkyl chloride. The reaction typically is effected by combining alkene substrates with chloramines. An alternative implementation involves Pd(II)-induced nucleophilic attack of the amine on the alkene followed by oxidation by a cupric chloride. | 0 | Theoretical and Fundamental Chemistry |
The newly formed primordial germ cells (PGC) in the implanted embryo devolve from the somatic cells. At this point the PGCs have high levels of methylation. These cells migrate from the epiblast toward the gonadal ridge. As reviewed by Messerschmidt et al., the majority of PGCs are arrested in the G2 phase of the cell cycle, while they migrate toward the hindgut during embryo days 7.5 to 8.5. Then demethylation of the PGCs takes place in two waves. At day 9.5 the primordial germ cells begin to rapidly replicate going from about 200 PGCs at embryo day 9.5 to about 10,000 PGCs at day 12.5. During days 9.5 to 12.5 DNMT3a and DNMT3b are repressed and DNMT1 is present in the nucleus at a high level. But DNMT1 is unable to methylate cytosines during days 9.5 to 12.5 because the UHRF1 gene (also known as NP95) is repressed and UHRF1 is an essential protein needed to recruit DNMT1 to replication foci where maintenance DNA methylation takes place. This is a passive, dilution form of demethylation.
In addition, from embryo day 9.5 to 13.5 there is an active form of demethylation. As indicated below in "Molecular stages of active reprogramming," two enzymes are central to active demethylation. These are a ten-eleven translocation methylcytosine dioxygenase (TET) and thymine-DNA glycosylase (TDG). One particular TET enzyme, TET1, and TDG are present at high levels from embryo day 9.5 to 13.5, and are employed in active demethylation during gametogenesis. PGC genomes display the lowest levels of DNA methylation of any cells in the entire life cycle of the mouse at embryonic day 13.5. | 1 | Applied and Interdisciplinary Chemistry |
Attempting a separable solution of the form reduces the problem to
with boundary conditions
The solution is
Therefore, the velocity field is
Pressure can be obtained through integration of the momentum equation
which gives, | 1 | Applied and Interdisciplinary Chemistry |
A spinthariscope () is a device for observing individual nuclear disintegrations caused by the interaction of ionizing radiation with a phosphor (see radioluminescence) or scintillator. | 0 | Theoretical and Fundamental Chemistry |
The use of cold for pain relief and as an anti-inflammatory has been known since the time of Hippocrates (460–377 BC). Since then there have been numerous accounts of ice used for pain relief including from the Ancient Egyptians and Avicenna of Persia (982–1070 AD). In 1812 Napoleon's Surgeon General noted that half-frozen soldiers from the Moscow battle were able to tolerate amputations with reduced pain and in 1851, ice and salt mixtures were promoted by Arnott for the treatment of nerve pain. Campbell White, in 1899, was the first to use refrigerants medically, and Allington, in 1950, was the first to use liquid nitrogen for medical treatments. In 1961, Cooper et al. created an early cryoprobe that reached −190 °C using liquid nitrogen. Shortly thereafter, in 1967, an ophthalmic surgeon named Amoils used carbon dioxide and nitrous oxide to create a cryoprobe that reached −70 °C. | 1 | Applied and Interdisciplinary Chemistry |
Collision-induced absorption was first reported in compressed oxygen gas in 1949
by Harry Welsch and associates at frequencies of the fundamental band of the
O molecule. (Note that an unperturbed O molecule, like all other diatomic homonuclear molecules, is infrared inactive on account of the inversion symmetry and does thus not possess a "dipole allowed" rotovibrational spectrum at any frequency). | 0 | Theoretical and Fundamental Chemistry |
CPA-1 and CPA-2 (and, it is presumed, all other CPAs) employ a zinc ion within the protein for hydrolysis of the peptide bond at the C-terminal end of an amino acid residue. Loss of the zinc leads to loss of activity, which can be replaced easily by zinc, and also by some other divalent metals (cobalt, nickel). Carboxypeptidase A is produced in the pancreas and is crucial to many processes in the human body to include digestion, post-translational modification of proteins, blood clotting, and reproduction. | 1 | Applied and Interdisciplinary Chemistry |
In cell biology, diffusion is a main form of transport for necessary materials such as amino acids within cells. Diffusion of solvents, such as water, through a semipermeable membrane is classified as osmosis.
Metabolism and respiration rely in part upon diffusion in addition to bulk or active processes. For example, in the alveoli of mammalian lungs, due to differences in partial pressures across the alveolar-capillary membrane, oxygen diffuses into the blood and carbon dioxide diffuses out. Lungs contain a large surface area to facilitate this gas exchange process. | 1 | Applied and Interdisciplinary Chemistry |
Algae can be converted into various types of fuels, depending on the production technologies and the part of the cells used. The lipid, or oily part of the algae biomass can be extracted and converted into biodiesel through a process similar to that used for any other vegetable oil, or converted in a refinery into "drop-in" replacements for petroleum-based fuels. Alternatively or following lipid extraction, the carbohydrate content of algae can be fermented into bioethanol or butanol fuel. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, a dithiol is a type of organosulfur compound with two thiol () functional groups. Their properties are generally similar to those of monothiols in terms of solubility, odor, and volatility. They can be classified according to the relative location of the two thiol groups on the organic backbone. | 0 | Theoretical and Fundamental Chemistry |
Usually, a thin intermembrane space about 10–20 nanometers thick exists between the outer and inner chloroplast membranes.
Glaucophyte algal chloroplasts have a peptidoglycan layer between the chloroplast membranes. It corresponds to the peptidoglycan cell wall of their cyanobacterial ancestors, which is located between their two cell membranes. These chloroplasts are called muroplasts (from Latin "mura", meaning "wall"). Other chloroplasts were assumed to have lost the cyanobacterial wall, leaving an intermembrane space between the two chloroplast envelope membranes, but has since been found also in moss, lycophytes and ferns. | 0 | Theoretical and Fundamental Chemistry |
A different technique to simulate the metabolic network is to perform flux balance analysis. This method uses linear programming, but in contrast to elementary mode analysis and extreme pathways, only a single solution results in the end. Linear programming is usually used to obtain the maximum potential of the objective function that you are looking at, and therefore, when using flux balance analysis, a single solution is found to the optimization problem. In a flux balance analysis approach, exchange fluxes are assigned to those metabolites that enter or leave the particular network only. Those metabolites that are consumed within the network are not assigned any exchange flux value. Also, the exchange fluxes along with the enzymes can have constraints ranging from a negative to positive value (ex: -10 to 10).
Furthermore, this particular approach can accurately define if the reaction stoichiometry is in line with predictions by providing fluxes for the balanced reactions. Also, flux balance analysis can highlight the most effective and efficient pathway through the network in order to achieve a particular objective function. In addition, gene knockout studies can be performed using flux balance analysis. The enzyme that correlates to the gene that needs to be removed is given a constraint value of 0. Then, the reaction that the particular enzyme catalyzes is completely removed from the analysis. | 1 | Applied and Interdisciplinary Chemistry |
The high cost of radon remediation in the 1980s led to detractors arguing that the issue is a financial boondoggle reminiscent of the swine flu scare of 1976. They further argued that the results of mitigation are inconsistent with lowered cancer risk, especially when indoor radon levels are in the lower range of the actionable exposure level. | 1 | Applied and Interdisciplinary Chemistry |
An induction period in chemical kinetics is an initial slow stage of a chemical reaction; after the induction period, the reaction accelerates. Ignoring induction periods can lead to runaway reactions.
In some catalytic reactions, a pre-catalyst needs to undergo a transformation to form the active catalyst, before the catalyst can take effect. Time is required for this transformation, hence the induction period. For example, with Wilkinson's catalyst, one triphenylphosphine ligand must dissociate to give the coordinatively unsaturated 14-electron species which can participate in the catalytic cycle:
Similarly, for an autocatalytic reaction, where one of the reaction products catalyzes the reaction itself, the rate of reaction is low initially until sufficient products have formed to catalyze the reaction.
Reactions generally accelerate when heat is applied. Where a reaction is exothermic, the rate of the reaction may initially be low. As the reaction proceeds, heat is generated, and the rate of reaction increases. This type of reaction often exhibits an induction period as well.
The reactions to form Grignard reagents are notorious for having induction periods. This is usually due to two reasons: Firstly, the thin film of oxide on the magnesium reagent must be removed before the bulk magnesium can react. Secondly, Grignard reactions, while exothermic, are typically conducted at low temperature for better selectivity. For these two reasons, Grignard reactions often can have a long induction period, followed by a thermal runaway, even causing the reaction solvent to boil-off. | 0 | Theoretical and Fundamental Chemistry |
Cyclic compounds can be partly or completely conjugated. Annulenes, completely conjugated monocyclic hydrocarbons, may be aromatic, nonaromatic or antiaromatic. | 0 | Theoretical and Fundamental Chemistry |
To date, few in-depth studies on the in vivo behavior of PAMAM dendrimers have been carried out. This could be in part due to the diverse behavior of PAMAMs depending on surface modification (see below), which make characterization of their in vivo properties largely case-dependent. Nonetheless, the fate and transport of unmodified PAMAM dendrimers is an important case study as any biological applications could involve unmodified PAMAM as a metabolic byproduct. In the only major systematic study of in vivo PAMAM behavior, injections of high levels of bare PAMAMs over extended periods of time in mice showed no evidence of toxicity up through G5 PAMAM, and for G3-G7 PAMAM, low immunogenicity was observed. These systemic-level observations seem to align with the observation that PAMAM dendrimers are not extremely cytotoxic overall; however, more in-depth studies of the pharmacokinetics and biodistribution of PAMAM are required before a move toward in vivo applications can be made. | 0 | Theoretical and Fundamental Chemistry |
In biology, methylene blue is used as a dye for a number of different staining procedures, such as Wrights stain and Jenners stain. Since it is a temporary staining technique, methylene blue can also be used to examine RNA or DNA under the microscope or in a gel: as an example, a solution of methylene blue can be used to stain RNA on hybridization membranes in northern blotting to verify the amount of nucleic acid present. While methylene blue is not as sensitive as ethidium bromide, it is less toxic and it does not intercalate in nucleic acid chains, thus avoiding interference with nucleic acid retention on hybridization membranes or with the hybridization process itself.
It can also be used as an indicator to determine whether eukaryotic cells such as yeast are alive or dead. The methylene blue is reduced in viable cells, leaving them unstained. However dead cells are unable to reduce the oxidized methylene blue and the cells are stained blue. Methylene blue can interfere with the respiration of the yeast as it picks up hydrogen ions made during the process. | 0 | Theoretical and Fundamental Chemistry |
Many polymerization reactions are initiated by radicals. Polymerization involves an initial radical adding to non-radical (usually an alkene) to give new radicals. This process is the basis of the radical chain reaction. The art of polymerization entails the method by which the initiating radical is introduced. For example, methyl methacrylate (MMA) can be polymerized to produce Poly(methyl methacrylate) (PMMA – Plexiglas or Perspex) via a repeating series of radical addition steps:
Newer radical polymerization methods are known as living radical polymerization. Variants include reversible addition-fragmentation chain transfer (RAFT) and atom transfer radical polymerization (ATRP).
Being a prevalent radical, O reacts with many organic compounds to generate radicals together with the hydroperoxide radical. Drying oils and alkyd paints harden due to radical crosslinking initiated by oxygen from the atmosphere. | 1 | Applied and Interdisciplinary Chemistry |
This modification involves the addition of a methyl group (-CH3) group to the 6th nitrogen on the adenine base in an mRNA molecule. This was among the first mRNA modifications to be discovered in 1974. This modification is common in viral mRNA transcripts and is found in nearly 25% of them. The distribution of the modification not uniform with some transcripts containing more than 10. mA modifications are a dynamic process with many applications ranging from viral interactions with cellular machinery and structural adjustments to viral life cycle control. Studies have shown different regulatory patterns for different viruses depending on the context. For single stranded RNA viruses, the effects of the modifications appear to differ on the basis of the viral family. In the HIV-1 genome, the single stranded positive sense RNA contains mA modifications at multiple sites in both the untranslated and coding regions. The presence of this modifications in the viral transcript is enough to increase corresponding modifications in host cell mRNA through binding interactions between the HIV-1 gp 120 envelope protein, and the CD4 receptor in T lymphocytes without causing a corresponding increase in. For HIV-1 and other RNA viral families like chikungunya, enteroviruses and influenza, studies show both a positive and negative role for mA modifications on viral life replication and infection. For other families, the role effects are clearer. For the flaviridae family, the modification had a negative role and hindered viral replication. The modification in respiratory syncytial virus families showed a positive role and enhanced viral replication and infection. The causes of these apparently different roles from different responses within the same family of viruses and why the viral families like flaviridae conserve mA modifications when they negatively impact their cycles are currently unknown and under investigation.
Most of the RNA viruses carry out their cycles in the cytoplasm, away from the required machinery for writing and erasing mA modifications which are housed in the nucleus. For DNA viruses, that cycle in the nucleus with direct access to said machinery, no clear general positive or negative regulatory role can be attributed to mA modifications. In the simian virus and hepatitis B viruses, different mA reading complexes were shown to have different roles in regulation with some having a conserved positive role and others having a neutral or negative effect on replication. | 1 | Applied and Interdisciplinary Chemistry |
kT (also written as kT) is the product of the Boltzmann constant, k (or k), and the temperature, T. This product is used in physics as a scale factor for energy values in molecular-scale systems (sometimes it is used as a unit of energy), as the rates and frequencies of many processes and phenomena depend not on their energy alone, but on the ratio of that energy and kT, that is, on (see Arrhenius equation, Boltzmann factor). For a system in equilibrium in canonical ensemble, the probability of the system being in state with energy E is proportional to .
More fundamentally, kT is the amount of heat required to increase the thermodynamic entropy of a system by k.
In physical chemistry, as kT often appears in the denominator of fractions (usually because of Boltzmann distribution), sometimes β = 1/kT is used instead of kT, turning into . | 0 | Theoretical and Fundamental Chemistry |
The International Committee of the Red Cross (ICRC) uses forensic science for humanitarian purposes to clarify the fate of missing persons after armed conflict, disasters or migration, and is one of the services related to Restoring Family Links and Missing Persons. Knowing what has happened to a missing relative can often make it easier to proceed with the grieving process and move on with life for families of missing persons.
Forensic science is used by various other organizations to clarify the fate and whereabouts of persons who have gone missing. Examples include the NGO Argentine Forensic Anthropology Team, working to clarify the fate of people who disappeared during the period of the 1976–1983 military dictatorship. The International Commission on Missing Persons (ICMP) used forensic science to find missing persons, for example after the conflicts in the Balkans.
Recognising the role of forensic science for humanitarian purposes, as well as the importance of forensic investigations in fulfilling the state's responsibilities to investigate human rights violations, a group of experts in the late-1980s devised a UN Manual on the Prevention and Investigation of Extra-Legal, Arbitrary and Summary Executions, which became known as the Minnesota Protocol. This document was revised and re-published by the Office of the High Commissioner for Human Rights in 2016. | 0 | Theoretical and Fundamental Chemistry |
Edman degradation, developed by Pehr Edman, is a method of sequencing amino acids in a peptide. In this method, the amino-terminal residue is labeled and cleaved from the peptide without disrupting the peptide bonds between other amino acid residues. | 0 | Theoretical and Fundamental Chemistry |
* The main advantage is that the equation can be solved very efficiently with an iterative method that avoids the need of matrix factorization and consequently has a minimal requirement for storage; this makes it very attractive for low pressure networks with a large number of pipes.
* Fast convergence which is less sensitive to the initial conditions. | 1 | Applied and Interdisciplinary Chemistry |
To find the solution to the linearized equation, a stream function was introduced by Lord Rayleigh for the perturbations of the flow velocity:
These new definitions of the stream function are used to rewrite the linearized barotropic vorticity equation.
Here, is the second derivative of with respect to . To solve this equation for the stream function, a wave-like solution was proposed by Rayleigh which reads . The amplitude may be complex number, is the wave number which is a real number and is the phase velocity which may be complex as well. Inserting this proposed solution leads us to the equation which is known as Rayleigh's equation.
To get to this equation, in the last step it was used that cant be zero and neither can the exponential. This means that the terms in the square brackets needs to be zero. The symbol denotes the second derivative of the amplitude of the stream function, with respect to . This last equation that was derived, is known as Rayleigh's equation which is a linear ordinary differential equation. It is very difficult to explicitly solve this equation. It is therefore that Hsiao-Lan Kuo came up with a stability criterion for this problem without actually solving it. | 1 | Applied and Interdisciplinary Chemistry |
An enzyme modulator is a type of drug which modulates enzymes. They include enzyme inhibitors and enzyme inducers. In an homogeneous assay, "an enzyme modulator ... is covalently linked to the ligand which competes with free ligand from the test sample for the available antibodies." | 1 | Applied and Interdisciplinary Chemistry |
The mTORC2 signaling pathway is less defined than the mTORC1 signaling pathway. The functions of the components of the mTORC complexes have been studied using knockdowns and knockouts and were found to produce the following phenotypes:
* NIP7: Knockdown reduced mTORC2 activity that is indicated by decreased phosphorylation of mTORC2 substrates.
* RICTOR: Overexpression leads to metastasis and knockdown inhibits growth factor-induced PKC-phosphorylation. Constitutive deletion of Rictor in mice leads to embryonic lethality, while tissue specific deletion leads to a variety of phenotypes; a common phenotype of Rictor deletion in liver, white adipose tissue, and pancreatic beta cells is systemic glucose intolerance and insulin resistance in one or more tissues. Decreased Rictor expression in mice decreases male, but not female, lifespan.
* mTOR: Inhibition of mTORC1 and mTORC2 by PP242 [2-(4-Amino-1-isopropyl-1H-pyrazolo[3,4-d]pyrimidin-3-yl)-1H-indol-5-ol] leads to autophagy or apoptosis; inhibition of mTORC2 alone by PP242 prevents phosphorylation of Ser-473 site on AKT and arrests the cells in G1 phase of the cell cycle. Genetic reduction of mTOR expression in mice significantly increases lifespan.
* PDK1: Knockout is lethal; hypomorphic allele results in smaller organ volume and organism size but normal AKT activation.
* AKT: Knockout mice experience spontaneous apoptosis (AKT1), severe diabetes (AKT2), small brains (AKT3), and growth deficiency (AKT1/AKT2). Mice heterozygous for AKT1 have increased lifespan.
* TOR1, the S. cerevisiae orthologue of mTORC1, is a regulator of both carbon and nitrogen metabolism; TOR1 KO strains regulate response to nitrogen as well as carbon availability, indicating that it is a key nutritional transducer in yeast. | 1 | Applied and Interdisciplinary Chemistry |
The principle of detailed balance can be used in kinetic systems which are decomposed into elementary processes (collisions, or steps, or elementary reactions). It states that at equilibrium, each elementary process is in equilibrium with its reverse process. | 0 | Theoretical and Fundamental Chemistry |
Flue-gas desulfurization (FGD) is a set of technologies used to remove sulfur dioxide () from exhaust flue gases of fossil-fuel power plants, and from the emissions of other sulfur oxide emitting processes such as waste incineration, petroleum refineries, cement and lime kilns. | 1 | Applied and Interdisciplinary Chemistry |
In contrast to the paucity of evidence for , the corresponding arsenic ion, ortho-arsenite, is known. An example is AgAsO as well as the polymeric meta-arsenite . The iso-electronic sulfite ion, is known from its salts. | 0 | Theoretical and Fundamental Chemistry |
Intrachromosomal homologous recombination in Arabidopsis thaliana plants was found to occur in all organs examined from the seed stage to the flowering stage of somatic plant development. Recombination frequencies were typically in the range of 10 to 10 events per genome. A. thaliana mutants selected for hypersensitivity to X-irradiation also proved to be simultaneously hypersensitive to the DNA damaging agents mitomycin C and/or methyl methanesulfonate. The mutants were also deficient in somatic homologous recombination. These findings suggest that repair of some types of DNA damage requires a recombinational process that was defective in the mutants studied. In nature, plants are continuously exposed to UV-B (280-320 nm) radiation, a component of sunlight that damages the DNA of somatic cells. Cyclobutane pyrimidine dimers (CPD) are a type of damage induced by UV-B. In A. thaliana, homologous recombination appears to be directly involved in repairing CPD damage. | 1 | Applied and Interdisciplinary Chemistry |
Some people maintain that belief kills (e.g., voodoo death: Cannon in 1942 describes a number of instances from a variety of different cultures) and belief heals (e.g., faith healing). A self-willed death (due to voodoo hex, evil eye, pointing the bone procedure, etc.) is an extreme form of a culture-specific syndrome or mass psychogenic illness that produces a particular form of psychosomatic or psychophysiological disorder which results in a psychogenic death. Rubel in 1964 spoke of "culture bound" syndromes, which were those "from which members of a particular group claim to suffer and for which their culture provides an etiology, diagnosis, preventive measures, and regimens of healing".
Certain anthropologists, such as Robert Hahn and Arthur Kleinman, have extended the placebo/nocebo distinction into this realm in order to allow a distinction to be made between rituals, like faith healing, that are performed in order to heal, cure, or bring benefit (placebo rituals) and others, like "pointing the bone", that are performed in order to kill, injure or bring harm (nocebo rituals). As the meaning of the two inter-related and opposing terms has extended, we now find anthropologists speaking, in various contexts, of nocebo or placebo (harmful or helpful) rituals:
* that might entail nocebo or placebo (unpleasant or pleasant) procedures;
* about which subjects might have nocebo or placebo (harmful or beneficial) beliefs;
* that are delivered by operators that might have nocebo or placebo (pathogenic, disease-generating or salutogenic, health-promoting) expectations;
* that are delivered to subjects that might have nocebo or placebo (negative, fearful, despairing or positive, hopeful, confident) expectations about the ritual;
* which are delivered by operators who might have nocebo or placebo (malevolent or benevolent) intentions, in the hope that the rituals will generate nocebo or placebo (lethal, injurious, harmful or restorative, curative, healthy) outcomes; and, that all of this depends upon the operator's overall beliefs in the harmful nature of the nocebo ritual or the beneficial nature of the placebo ritual.
Yet it may become even more terminologically complex, for as Hahn and Kleinman indicate, there can also be cases where there are paradoxical nocebo outcomes from placebo rituals, as well as paradoxical placebo outcomes from nocebo rituals (see also unintended consequences). Writing from his extensive experience of treating cancer (including more than 1,000 melanoma cases) at Sydney Hospital, Milton in 1973 warned of the impact of the delivery of a prognosis, and how many of his patients, upon receiving their prognosis, simply turned their face to the wall and died a premature death: "there is a small group of patients in whom the realization of impending death is a blow so terrible that they are quite unable to adjust to it, and they die rapidly before the malignancy seems to have developed enough to cause death. This problem of self-willed death is in some ways analogous to the death produced in primitive peoples by witchcraft (pointing the bone)". | 1 | Applied and Interdisciplinary Chemistry |
Caspases are an important group of proteases involved in apoptosis or programmed cell death. The precursors of caspase, procaspase, may be activated by proteolysis through its association with a protein complex that forms apoptosome, or by granzyme B, or via the death receptor pathways. | 1 | Applied and Interdisciplinary Chemistry |
Minor losses in pipe flow are a major part in calculating the flow, pressure, or energy reduction in piping systems. Liquid moving through pipes carries momentum and energy due to the forces acting upon it such as pressure and gravity. Just as certain aspects of the system can increase the fluids energy, there are components of the system that act against the fluid and reduce its energy, velocity, or momentum. Friction and minor losses in pipes are major contributing factors. | 1 | Applied and Interdisciplinary Chemistry |
Decomposition products of dead plant materials form intimate associations with minerals, making it difficult to isolate and characterize soil organic constituents. 18th century soil chemists successfully used alkaline extraction to isolate a portion of the organic constituents in soil. This led to the theory that a humification process created humic substances; most commonly humic acid, fulvic acid, and humin. However, these humic substances have not been observed in soil. Although humification theory is unsupported by evidence, "the underlying theory persists in the contemporary literature, including current textbooks." Attempts to redefine humic substances in valid terms have resulted in a proliferation of incompatible definitions, "with far-reaching implications beyond our ability to communicate scientifically accurate soil processes and properties." | 0 | Theoretical and Fundamental Chemistry |
Ring A was synthesised starting from geraniol 1 and involved acylation (acetic anhydride, DMAP, EtN) to 2, epoxidation (N-bromosuccinimide, tBuOH/HO then triethylamine) to 3, radical cyclisation (titanocene dichloride, manganese, triethylborane, 2,6-lutidine) to 4, alcohol protection (ethyl vinyl ether, camphorsulfonic acid) to 5, alcohol deprotection (NaOH, MeOH/THF/HO) to alcohol 6, Parikh-Doering oxidation to aldehyde 7, isomerization (DBU) to enone 8, organic reduction (sodium borohydride) to alcohol 9, alcohol protection (TBSCl, EtN) to TBS ether 10, hydrazone formation (HNNHTs) to 11 and finally vinyl bromide formation (tBuLi, 1,2-Dibromoethane) in 12. | 0 | Theoretical and Fundamental Chemistry |
As of 2022, the editorial committee consists of the two co-editors and the following members:
* Ravi S. Kane
* Linda J. Broadbelt
* Kookheon Char
* Wilfred Chen
* Lydia Contreras
* Christopher W. Jones
* Sanat K. Kumar
* Joseph B. Powell
* Irina Smirnova
* Levi T. Thompson | 1 | Applied and Interdisciplinary Chemistry |
Croccos theorem is an aerodynamic theorem relating the flow velocity, vorticity, and stagnation pressure (or entropy) of a potential flow. Croccos theorem gives the relation between the thermodynamics and fluid kinematics. The theorem was first enunciated by Alexander Friedmann for the particular case of a perfect gas and published in 1922:
However, usually this theorem is connected with the name of Italian scientist Luigi Crocco, a son of Gaetano Crocco.
Consider an element of fluid in the flow field subjected to translational and rotational motion: because stagnation pressure loss and entropy generation can be viewed as essentially the same thing, there are three popular forms for writing Crocco's theorem:
# Stagnation pressure:
# Entropy (the following form holds for plane steady flows):
# Momentum:
In the above equations, is the flow velocity vector, is the vorticity, is the specific volume, is the stagnation pressure, is temperature, is specific entropy, is specific enthalpy, is specific body force, and is the direction normal to the streamlines. All quantities considered (entropy, enthalpy, and body force) are specific, in the sense of "per unit mass". | 1 | Applied and Interdisciplinary Chemistry |
Automaker Henry Ford began to test farm crops for their industrial potential around 1930, and soon settled on hemp and the soybean as particularly promising (the famous Hemp Body or Soybean Car). The Ford Motor Company used soybeans in such parts as gearshift knobs and horn buttons, and hemp for the body of the car. The automobile was designed to run on hemp diesel. Ford Motor Company accessed these innovations via the discovery and ingenuity of George Washington Carver, Tuskegee Scientist and Father of Chemurgy.
In 1935, the Farm Chemurgic Council (later renamed the National Farm Chemurgic Council) was formed to encourage greater use of renewable raw materials in industry. In its early years, the Council received substantial publicity. It was perceived by the Roosevelt Administration as a political threat, since Council leaders questioned U.S. Department of Agriculture policies. First placing much of its emphasis on demonstrating the benefits of Agrol (a line of blended motor fuels that included ethanol), the Council drew strong opposition from the petroleum industry. The Agrol pilot plant, which also experienced management and financial difficulties, shut down in 1938. Wheeler McMillen, who had become president of the Council the previous year, decided to distance the chemurgy movement from ethanol, mend fences with the petroleum industry, and place the Council on a more cautious course.
The Council’s cause received an unexpected boost when Theodore G. Bilbo, a U.S. senator from Mississippi, sought a means to promote new uses for his region’s surplus cotton. To make his goal more politically attractive, he supported a broader research program. In the end, four regional U.S. Department of Agriculture laboratories, dedicated to finding new uses for farm crops, were authorized under the Agricultural Adjustment Act of 1938. The labs were established in Wyndmoor, Pennsylvania; New Orleans, Louisiana; Peoria, Illinois; and Albany, California. Over time, their research agendas expanded, and they became less focused on chemurgy. Nevertheless, their involvement in that field was symbolic of the chemurgy movement’s transformation from a cause associated with Roosevelt Administration critics to one with clear support from that administration. | 1 | Applied and Interdisciplinary Chemistry |
*ALDOA
*B3GALT6 NM_080605
*B4GALT3 NM_003779 Homo sapiens UDP-Gal:betaGlcNAc beta 1,4- galactosyltransferase, polypeptide 3
*B4GALT5 NM_004776
*B4GALT7 NM_007255
*GSK3A
*GSK3B
*TPI1
*PGK1 Phosphoglycerate kinase
*PGAM5
*ENOPH1 Enolase phosphatase
*LDHA Lactate dehydrogenase
*TALDO1 Transaldolase in pentose shunt
*TSTA3 Mannose metabolism | 1 | Applied and Interdisciplinary Chemistry |
NHCs are widely used as ancillary ligand in organometallic chemistry. One practical application is the ruthenium-based Grubbs' catalyst and NHC-Palladium Complexes for cross-coupling reactions. NHC-metal complexes, specifically Ag(I)-NHC complexes have been widely tested for their biological applications. | 0 | Theoretical and Fundamental Chemistry |
If is such that and and , then we have a traveling-wave solution (with a constant speed ) given by
This solution describes the variation of pressure across a weak shock wave. When and to
with . | 1 | Applied and Interdisciplinary Chemistry |
The eluent (mobile phase) should be the appropriate solvent to dissolve the polymer, should not interfere with the response of the polymer analyzed, and should wet the packing surface and make it inert to interactions with the polymers. The most common eluents for polymers that dissolve at room temperature GPC are tetrahydrofuran (THF), o-dichlorobenzene and trichlorobenzene at 130–150 °C for crystalline polyalkynes and hexafluoroisopropanol (HFIP) for crystalline condensation polymers such as polyamides and polyesters. | 0 | Theoretical and Fundamental Chemistry |
For two-dimensional potential flow, the continuity equation and the Euler equations (in fact, the compressible Bernoulli's equation due to irrotationality) in Cartesian coordinates involving the variables fluid velocity , specific enthalpy and density are
with the equation of state acting as third equation. Here is the stagnation enthalpy, is the magnitude of the velocity vector and is the entropy. For isentropic flow, density can be expressed as a function only of enthalpy , which in turn using Bernoulli's equation can be written as .
Since the flow is irrotational, a velocity potential exists and its differential is simply . Instead of treating and as dependent variables, we use a coordinate transform such that and become new dependent variables. Similarly the velocity potential is replaced by a new function (Legendre transformation)
such then its differential is , therefore
Introducing another coordinate transformation for the independent variables from to according to the relation and , where is the magnitude of the velocity vector and is the angle that the velocity vector makes with the -axis, the dependent variables become
The continuity equation in the new coordinates become
For isentropic flow, , where is the speed of sound. Using the Bernoulli's equation we find
where . Hence, we have | 1 | Applied and Interdisciplinary Chemistry |
Plasma level monitoring of vancomycin is necessary due to the drug's biexponential distribution, intermediate hydrophilicity, and potential for ototoxicity and nephrotoxicity, especially in populations with poor renal function and/or increased propensity to bacterial infection. Vancomycin activity is considered to be time-dependent; that is, antimicrobial activity depends on the duration that the serum drug concentration exceeds the minimum inhibitory concentration of the target organism. Thus, peak serum levels have not been shown to correlate with efficacy or toxicity; indeed, concentration monitoring is unnecessary in most cases. Circumstances in which therapeutic drug monitoring is warranted include: patients receiving concomitant aminoglycoside therapy, patients with (potentially) altered pharmacokinetic parameters, patients on haemodialysis, patients administered high-dose or prolonged treatment, and patients with impaired renal function. In such cases, trough concentrations are measured.
Therapeutic drug monitoring is also used for dose optimization of vancomycin in treating children.
Target ranges for serum vancomycin concentrations have changed over the years. Early authors suggested peak levels of 30 to 40 mg/L and trough levels of 5 to 10 mg/L,
but current recommendations are that peak levels need not be measured and that trough levels of 10 to 15 mg/L or 15 to 20 mg/L, depending on the nature of the infection and the specific needs of the patient, may be appropriate. Using measured vancomycin concentrations to calculate doses optimizes therapy in patients with augmented renal clearance. | 0 | Theoretical and Fundamental Chemistry |
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