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"The single most important synthetic application of alkyl hydroperoxides is without doubt the metal-catalysed epoxidation of alkenes." In the Halcon process tert-butyl hydroperoxide (TBHP) is employed for the production of propylene oxide.
Of specialized interest, chiral epoxides are prepared using hydroperoxides as reagents in the Sharpless epoxidation. | 0 | Theoretical and Fundamental Chemistry |
In thermodynamics so-called "specific" quantities are quantities per unit mass (kg) and are denoted by lower-case characters. So h, u, and v are the specific enthalpy, specific internal energy, and specific volume (volume per unit mass, or reciprocal density), respectively. In a Joule–Thomson process the specific enthalpy h remains constant. To prove this, the first step is to compute the net work done when a mass m of the gas moves through the plug. This amount of gas has a volume of V = m v in the region at pressure P (region 1) and a volume V = m v when in the region at pressure P (region 2). Then in region 1, the "flow work" done on the amount of gas by the rest of the gas is: W = m Pv. In region 2, the work done by the amount of gas on the rest of the gas is: W = m Pv. So, the total work done on the mass m of gas is
The change in internal energy minus the total work done on the amount of gas is, by the first law of thermodynamics, the total heat supplied to the amount of gas.
In the Joule–Thomson process, the gas is insulated, so no heat is absorbed. This means that
where u and u denote the specific internal energies of the gas in regions 1 and 2, respectively. Using the definition of the specific enthalpy h = u + Pv, the above equation implies that
where h and h denote the specific enthalpies of the amount of gas in regions 1 and 2, respectively. | 0 | Theoretical and Fundamental Chemistry |
Problems in the digestion of phenylalanine (phe) to tyrosine (tyr) lead to the buildup of both phe and phenylpyruvate, in a disease called Phenylketonuria (PKU). These two compounds build up in the blood stream and cerebral spinal fluid, which can lead to mental retardation if left untreated. Treatment consists of a restricted diet of foods that contain phe or compounds that can breakdown into phe. Children in the US are routinely tested for this at birth. For more information see the Phenylketonuria page or the link below. | 1 | Applied and Interdisciplinary Chemistry |
The output from a colorimeter may be displayed by an analogue or digital meter and may be shown as transmittance (a linear scale from 0 to 100%) or as absorbance (a logarithmic scale from zero to infinity). The useful range of the absorbance scale is from 0 to 2 but it is desirable to keep within the range 0–1, because above 1 the results become unreliable due to scattering of light.
In addition, the output may be sent to a chart recorder, data logger, or computer. | 0 | Theoretical and Fundamental Chemistry |
The term "polymer" derives . The term was coined in 1833 by Jöns Jacob Berzelius, though with a definition distinct from the modern IUPAC definition. The modern concept of polymers as covalently bonded macromolecular structures was proposed in 1920 by Hermann Staudinger, who spent the next decade finding experimental evidence for this hypothesis. | 0 | Theoretical and Fundamental Chemistry |
Hash oil is produced by solvent extraction (maceration, infusion or percolation) of marijuana or hashish. After filtering and evaporating the solvent, a sticky resinous liquid with a strong herbal odor (remarkably different from the odor of hemp) remains.
Fresh, undried plant material is less suited for hash oil production, because much THC and CBD will be present in their carboxylic acid forms (THCA and CBDA), which may not be highly soluble in some solvents. The acids are decarboxylated during drying and heating (smoking).
A wide variety of solvents can be used for extraction, such as chloroform, dichloromethane, petroleum ether, naphtha, benzene, butane, methanol, ethanol, isopropanol, and olive oil. Currently, resinoids are often obtained by extraction with supercritical carbon dioxide. The alcohols extract undesirable water-soluble substances such as chlorophyll and sugars (which can be removed later by washing with water). Non-polar solvents such as benzene, chloroform and petroleum ether will not extract the water-soluble constituents of marijuana or hashish while still producing hash oil. In general, non-polar cannabis extracts taste much better than polar extracts. Alkali washing further improves the odor and taste.
The oil may be further refined by 1) alkali washing, or removing the heavy aromatic carboxylic acids with antibiotic properties, which may cause heartburn, gallbladder and pancreas irritation, and resistance to hemp antibiotics; 2) conversion of CBD to THC. Process 1) consists of dissolving the oil in a non-polar solvent such as petroleum ether, repeatedly washing (saponifying) with a base such as sodium carbonate solution until the yellow residue disappears from the watery phase, decanting, and washing with water to remove the base and the saponified components (and evaporating the solvents). This process reduces the oil yield, but the resulting oil is less acidic, more easily digestible and much more potent (almost pure THC). Process 2) consists of dissolving the oil in a suitable solvent such as absolute ethanol containing 0.05% hydrochloric acid, and boiling the mixture for 2 hours.
The majority of ready to consume extract products are produced via "Closed Loop Systems.". These systems typically entail: a vessel that holds the solvent, material columns to hold the plant material, a [https://www.aBHOutit.com flow meter] to measure the volume of solvent entering the plant material, a recovery vessel(where heat is applied via an external jacket) to convert the liquid solvent into a vapor and separate it from the THC, CBD, or other cannabinoids/byproducts, and some form of a heat exchanger to then convert the hydrocarbon vapors back into a liquid form prior to returning to the original vessel.
Ten grams of marijuana yields one to two grams of hash oil. The oil may retain considerable residual solvent: oil extracted with longer-chain volatile hydrocarbons (such as naphtha) is less viscous (thinner) than oil extracted with short-chain hydrocarbons (such as butane).
Colored impurities from the oil can be removed by adding activated charcoal to about one third to one half the weight or volume of the solvent containing the dissolved oil, mixing well, filtering, and evaporating the solvent. When decolorizing fatty oils, oil retention can be up to 50 wt % on bleaching earths and nearly 100 wt % on activated charcoal. The many different textures/types of hydrocarbon extracts include:
* shatter (solid, breaks easily, glass like oil)
* pull and snap (solid, bendable, but still breakable, taffy-like oil)
* diamonds/live resin (rock hard THCA isolated diamonds drenched in terpene sauce)
* crumble (solid oil that will break into small crumbs)
* budder/wax (soft, pliable, peanut butter-like consistency) | 0 | Theoretical and Fundamental Chemistry |
Phomoxanthone A was first identified in a screening for antimalarial compounds. It showed strong antibiotic activity against a multidrug-resistant strain of the main causative agent of malaria, the protozoan parasite Plasmodium falciparum. The same study also reported antibiotic activity of PXA against Mycobacterium tuberculosis and against three animal cell lines, two of which were derived from human cancer cells. These findings not only showed that PXA has antibiotic activity against very diverse organisms, but they also sparked further studies that investigated PXA as a potential antibiotic or anti-cancer drug. A later study also reported antibiotic activity for PXA against the alga Chlorella fusca, the fungus Ustilago violacea, and the bacterium Bacillus megaterium. This broad range of activity disqualified it as a specific antibiotic that could be used in the treatment of infectious diseases, however the hope that it could be used as an anti-cancer drug remained. Preliminary results from a study in human cancer cells and non-cancer cells suggested that PXA might be more toxic to the former than to the latter, although results from in vivo studies have not yet been presented.
Aside from a potential medical use, recent findings indicate that PXA might have an application as a research tool in the study of mitochondrial membrane dynamics, particularly non-canonical mitochondrial fission and remodelling of the mitochondrial matrix. | 1 | Applied and Interdisciplinary Chemistry |
Magnetometers based on atomic gasses can perform vector measurements of the magnetic field in the low field regime, where the decay of the atomic coherence becomes faster than the Larmor frequency. The physics of such magnetometers is based on the Hanle effect. Such zero-field optically pumped magnetometers have been tested in various configurations and with different atomic species, notably alkali (potassium, rubidium and cesium), helium and mercury. For the case of alkali, the coherence times were greatly limited due to spin-exchange relaxation. A major breakthrough happened at the beginning of the 2000 decade, Romalis group in Princeton demonstrated that in such a low field regime, alkali coherence times can be greatly enhanced if a high enough density can be reached by high temperature heating, this is the so-called SERF effect.
The main interest of optically-pumped magnetometers is to replace SQUID magnetometers in applications where cryogenic cooling is a drawback. This is notably the case of medical imaging where such cooling imposes a thick thermal insulation, strongly affecting the amplitude of the recorded biomagnetic signals. Several startup companies are currently developing optically pumped magnetometers for biomedical applications: those of TwinLeaf, quSpin and FieldLine being based on alkali vapors, and those of Mag4Health on metastable helium-4. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, Squires theorem states that of all the perturbations that may be applied to a shear flow (i.e. a velocity field of the form ), the perturbations which are least stable are two-dimensional, i.e. of the form , rather than the three-dimensional disturbances. This applies to incompressible flows which are governed by the Navier–Stokes equations. The theorem is named after Herbert Squire, who proved the theorem in 1933.
Squires theorem allows many simplifications to be made in stability theory. If we want to decide whether a flow is unstable or not, it suffices to look at two-dimensional perturbations. These are governed by the Orr–Sommerfeld equation for viscous flow, and by Rayleighs equation for inviscid flow. | 1 | Applied and Interdisciplinary Chemistry |
HSC Sim has been primarily developed for the use in the mining and mineral industry, though other use such as modelling of biochemical and organic chemistry processes is possible as well.
In mineral industry the simulator is used for process operator training as an OTS (operator training simulator). | 1 | Applied and Interdisciplinary Chemistry |
Bronze disease is an irreversible and nearly inexorable corrosion process that occurs when chlorides come into contact with bronze or other copper-bearing alloys. It can occur as both a dark green coating, or as a much lighter whitish fuzzy or furry green coating. It is not a bacterial infection, but the result of a chemical reaction with the chlorides that usually occurs due to contamination of the bronze object by saltwater or from burial in specific types of soil where chloride salts are present. If not treated, complete destruction of the affected artifact is possible. Treatment is very difficult, costly and not always effective. Transfer of chlorides from the contaminated artefact to other artefacts can spread the condition. | 1 | Applied and Interdisciplinary Chemistry |
Arthur Frost stated in his own original publication that there may be potential criticism for his Frost diagram. He predicts that “the slopes may not be as easily or accurately recognized as they are the direct numerical values of the oxidation potentials [of the Latimer diagram]”. Many inorganic chemists use both the Latimer and Frost diagrams in tandem, using the Latimer for quantitative data, and then converting those data into a Frost diagram for visualization. Frost suggested that the numerical values of standard potentials could be added next to the slopes to provide supplemental information.
In a paper published in the Journal of Chemical Education, Martinez de Ilarduya and Villafañe (1994) warn users of Frost diagrams to be aware of the definition of the free energy used to construct the diagrams. In acid-solution graphs, the standard nE° = −ΔG/F is universally used; therefore all sources’ acid-solution Frost diagrams will be identical. However, various textbooks show discrepancies in the Frost diagram of an element, in regards to the energy. Some textbooks use the reduction potential, E°(2 + 2 /H), defined in an acid-solution for a basic-solution. In the Phillips and Williams Inorganic Chemistry textbook, however, another reduction potential is used for the basic solutions given by the following formula: E°(OH) = E° − E°(2 HO + 2 /H + 2 OH) = E° + 0.828 V. This other way of presenting reduction potentials is used in some textbooks and not in others, but is not always explicitly indicated on the graph, creating confusion for the reader. So, users of the Frost diagram should be aware of the problem, and should always be clearly informed on which free-energy scale their diagrams are based. | 0 | Theoretical and Fundamental Chemistry |
The Flow waveform for the human respiratory system in lung ventilators, is the shape of air flow that is blown into the patient's airways. Computer technology allows the practitioner to select particular flow patterns, along with volume and pressure settings, in order to achieve the best patient outcomes and reduce complications experienced while on a mechanical ventilator. | 1 | Applied and Interdisciplinary Chemistry |
Alkane conformers arise from rotation around sp hybridised carbon–carbon sigma bonds. The smallest alkane with such a chemical bond, ethane, exists as an infinite number of conformations with respect to rotation around the C–C bond. Two of these are recognised as energy minimum (staggered conformation) and energy maximum (eclipsed conformation) forms. The existence of specific conformations is due to hindered rotation around sigma bonds, although a role for hyperconjugation is proposed by a competing theory.
The importance of energy minima and energy maxima is seen by extension of these concepts to more complex molecules for which stable conformations may be predicted as minimum-energy forms. The determination of stable conformations has also played a large role in the establishment of the concept of asymmetric induction and the ability to predict the stereochemistry of reactions controlled by steric effects.
In the example of staggered ethane in Newman projection, a hydrogen atom on one carbon atom has a 60° torsional angle or torsion angle with respect to the nearest hydrogen atom on the other carbon so that steric hindrance is minimised. The staggered conformation is more stable by 12.5 kJ/mol than the eclipsed conformation, which is the energy maximum for ethane. In the eclipsed conformation the torsional angle is minimised.
In butane, the two staggered conformations are no longer equivalent and represent two distinct conformers:the anti-conformation (left-most, below) and the gauche conformation (right-most, below).
Both conformations are free of torsional strain, but, in the gauche conformation, the two methyl groups are in closer proximity than the sum of their van der Waals radii. The interaction between the two methyl groups is repulsive (van der Waals strain), and an energy barrier results.
A measure of the potential energy stored in butane conformers with greater steric hindrance than the anti-conformer ground state is given by these values:
* Gauche, conformer – 3.8 kJ/mol
* Eclipsed H and CH – 16 kJ/mol
* Eclipsed CH and CH – 19 kJ/mol.
The eclipsed methyl groups exert a greater steric strain because of their greater electron density compared to lone hydrogen atoms.
The textbook explanation for the existence of the energy maximum for an eclipsed conformation in ethane is steric hindrance, but, with a C-C bond length of 154 pm and a Van der Waals radius for hydrogen of 120 pm, the hydrogen atoms in ethane are never in each other's way. The question of whether steric hindrance is responsible for the eclipsed energy maximum is a topic of debate to this day. One alternative to the steric hindrance explanation is based on hyperconjugation as analyzed within the Natural Bond Orbital framework. In the staggered conformation, one C-H sigma bonding orbital donates electron density to the antibonding orbital of the other C-H bond. The energetic stabilization of this effect is maximized when the two orbitals have maximal overlap, occurring in the staggered conformation. There is no overlap in the eclipsed conformation, leading to a disfavored energy maximum. On the other hand, an analysis within quantitative molecular orbital theory shows that 2-orbital-4-electron (steric) repulsions are dominant over hyperconjugation. A valence bond theory study also emphasizes the importance of steric effects. | 0 | Theoretical and Fundamental Chemistry |
Advocates of the non-classical nature of the stable 2-norbornyl cation typically depict the species using either resonance structures or a single structure with partial bonds (see Figure 2). This hypovalent interaction can be imagined as the net effect of i) a partial sigma bond between carbons 1 and 6, ii) a partial sigma bond between carbons 2 and 6, and iii) a partial pi bond between carbons 1 and 2. Each partial bond is represented as a full bond in one of the three resonance structures or as a dashed partial bond if the cation is depicted through a single structure.
There has been some debate over how much the pi-bonded resonance structure actually contributes to the delocalized electronic structure. Through H and C NMR spectroscopy, it has been confirmed that significant positive charge lies on methylene carbon 6. This is surprising as primary carbocations are much less stable than secondary carbocations. However, the 2-norbornyl cation can be formed from derivatives of β-(Δ-cyclopentenyl)-ethane, indicating that the pi-bonded resonance structure is significant.
The 2-norbornyl cation was one of the first examples of a non-classical ion. Non-classical ions can be defined as organic cations in which electron density of a filled bonding orbital is shared over three or more centers and contains some sigma-bond character. The 2-norbornyl cation is seen as the prototype for non-classical ions. Other simple cations such as protonated acetylene (ethynium, ), protonated ethylene (ethenium, ), and protonated ethane (ethanium, ) have been shown to be best described as non-classical through infrared spectroscopy.
The most frequently proposed molecular orbital depiction of the 2-norbornyl cation is shown in Figure 3. Two p-type orbitals, one on each of carbons 1 and 2, interact with a sp-hybridized orbital on carbon 6 to form the hypovalent bond. Extended Hückel Theory calculations for the 2-norbornyl cation suggest that the orbital on carbon 6 could instead be sp-hybridized, though this only affects the geometry of the geminal hydrogens. | 0 | Theoretical and Fundamental Chemistry |
Given that we saw that
If we make the previous assumptions of the fluid being ideal and the velocity being irrotational, then we have
Under these assumptions, our linearized sound equations become
Importantly, since is a constant, we have , and then the second equation tells us that
Or just that
Now, when we use this relation with the fact that , alongside cancelling and rearranging terms, we arrive at
We can write this in a familiar form as
This differential equation must be solved with the appropriate boundary conditions. Note that setting returns us the wave equation. Regardless, upon solving this equation for a moving medium, we then have | 1 | Applied and Interdisciplinary Chemistry |
Cibacron Blue F3GA, Procion Blue HB, or Reactive blue 2 is a purinergic receptor antagonist, such as P2Y purinoceptor, and also an ATP receptor channels antagonist. It has a formula of CHClNOS and a molecular weight of 774.2 g/mol. Cibacron blue is soluble in water and DMSO, however insoluble in ethanol. In water, saturated concentration is reached at 12.92 mM with the help of sonication. Cibacron Blue F3GA has a wide specificity for nucleotide-binding proteins or just a stereoselectivity electrostatic binding. It can be used to purify interferons, dehydrogenases, kinases, and serum albumin. For example, interferon purification from human gingival fibroblast extract using Cibacron Blue F3G-A on poly(2-hydroxyethyl methacrylate), the supporting matrix, in the form of cryogels. It has shown 97.6% purity of interferon. | 0 | Theoretical and Fundamental Chemistry |
The dissociation degree is the fraction of original solute molecules that have dissociated. It is usually indicated by the Greek symbol α. More accurately, degree of dissociation refers to the amount of solute dissociated into ions or radicals per mole. In case of very strong acids and bases, degree of dissociation will be close to 1. Less powerful acids and bases will have lesser degree of dissociation. There is a simple relationship between this parameter and the van 't Hoff factor . If the solute substance dissociates into ions, then
For instance, for the following dissociation
As , we would have that . | 0 | Theoretical and Fundamental Chemistry |
The ink is applied to the photocatalyst coating, usually using either a felt-tipped pen, air-brush, rubber stamp, paint brush, or a drawdown bar, and then exposed it to sunlight or an alternative, appropriate light source. The ink identifies the presence of the photocatalyst coating by changing colour upon irradiation of the latter at a rate (usually < 10 min) which provides a measure of the film's activity.
For example, it has been established that the rate of change in colour of an paii on commercial self-cleaning glass is directly related to the rate at which the glass is also able to photo-oxidatively mineralise, via reaction (1) the wax-like, natural fatty acid, stearic acid, found in finger prints. The rate of the rapid colour change associated with photocatalyst activity indicator inks has also been directly correlated with the photocatalytic oxidation of methylene blue and NO. It has also been shown that digital colour analysis of photographs monitoring the colour change of a paii can be used to extract apparent absorbance data which correlates well with UV-vis absorption data for the same sample, without the need for expensive spectrophotometric instrumentation.
By making the dyes in the ink increasing difficult to reduce chemically, for example by using: basic blue 66, resazurin, and acid violet 7, respectively, it is possible to make paiis which are effective on photocatalyst coatings which exhibit, respectively: low (most self-cleaning tiles), moderate (self-cleaning glass) or high (self-cleaning paints) activities. paiis based on the dyes 2,6-dichloroindophenol (DCIP) and methylene blue have also been reported. | 0 | Theoretical and Fundamental Chemistry |
Veins (sometimes referred to as nerves) constitute one of the most visible features of leaves. The veins in a leaf represent the vascular structure of the organ, extending into the leaf via the petiole and providing transportation of water and nutrients between leaf and stem, and play a crucial role in the maintenance of leaf water status and photosynthetic capacity. They also play a role in the mechanical support of the leaf. Within the lamina of the leaf, while some vascular plants possess only a single vein, in most this vasculature generally divides (ramifies) according to a variety of patterns (venation) and form cylindrical bundles, usually lying in the median plane of the mesophyll, between the two layers of epidermis. This pattern is often specific to taxa, and of which angiosperms possess two main types, parallel and reticulate (net like). In general, parallel venation is typical of monocots, while reticulate is more typical of eudicots and magnoliids ("dicots"), though there are many exceptions.
The vein or veins entering the leaf from the petiole are called primary or first-order veins. The veins branching from these are secondary or second-order veins. These primary and secondary veins are considered major veins or lower order veins, though some authors include third order. Each subsequent branching is sequentially numbered, and these are the higher order veins, each branching being associated with a narrower vein diameter.
In parallel veined leaves, the primary veins run parallel and equidistant to each other for most of the length of the leaf and then converge or fuse (anastomose) towards the apex. Usually, many smaller minor veins interconnect these primary veins, but may terminate with very fine vein endings in the mesophyll. Minor veins are more typical of angiosperms, which may have as many as four higher orders.
In contrast, leaves with reticulate venation have a single (sometimes more) primary vein in the centre of the leaf, referred to as the midrib or costa, which is continuous with the vasculature of the petiole. The secondary veins, also known as second order veins or lateral veins, branch off from the midrib and extend toward the leaf margins. These often terminate in a hydathode, a secretory organ, at the margin. In turn, smaller veins branch from the secondary veins, known as tertiary or third order (or higher order) veins, forming a dense reticulate pattern. The areas or islands of mesophyll lying between the higher order veins, are called areoles. Some of the smallest veins (veinlets) may have their endings in the areoles, a process known as areolation. These minor veins act as the sites of exchange between the mesophyll and the plant's vascular system. Thus, minor veins collect the products of photosynthesis (photosynthate) from the cells where it takes place, while major veins are responsible for its transport outside of the leaf. At the same time water is being transported in the opposite direction.
The number of vein endings is very variable, as is whether second order veins end at the margin, or link back to other veins. There are many elaborate variations on the patterns that the leaf veins form, and these have functional implications. Of these, angiosperms have the greatest diversity. Within these the major veins function as the support and distribution network for leaves and are correlated with leaf shape. For instance, the parallel venation found in most monocots correlates with their elongated leaf shape and wide leaf base, while reticulate venation is seen in simple entire leaves, while digitate leaves typically have venation in which three or more primary veins diverge radially from a single point.
In evolutionary terms, early emerging taxa tend to have dichotomous branching with reticulate systems emerging later. Veins appeared in the Permian period (299–252 mya), prior to the appearance of angiosperms in the Triassic (252–201 mya), during which vein hierarchy appeared enabling higher function, larger leaf size and adaption to a wider variety of climatic conditions. Although it is the more complex pattern, branching veins appear to be plesiomorphic and in some form were present in ancient seed plants as long as 250 million years ago. A pseudo-reticulate venation that is actually a highly modified penniparallel one is an autapomorphy of some Melanthiaceae, which are monocots; e.g., Paris quadrifolia (True-lover's Knot). In leaves with reticulate venation, veins form a scaffolding matrix imparting mechanical rigidity to leaves. | 0 | Theoretical and Fundamental Chemistry |
Gene regulation by miRNA is widespread across many genomes – by some estimates more than 60% of human protein-coding genes are likely to be regulated by miRNA, though the quality of experimental evidence for miRNA-target interactions is often weak. Because processing by microprocessor is a major determinant of miRNA abundance, microprocessor itself is then an important target of regulation.
Both Drosha and DGCR8 are subject to regulation by post-translational modifications modulating stability, intracellular localization, and activity levels. Activity against particular substrates may be regulated by additional protein cofactors interacting with the microprocessor complex. The loop region of the pri-miRNA stem-loop is also a recognition element for regulatory proteins, which may up- or down-regulate microprocessor processing of the specific miRNAs they target.
Microprocessor itself is auto-regulated by negative feedback through association with a pri-miRNA-like hairpin structure found in the DGCR8 mRNA, which when cleaved reduces DGCR8 expression. The structure in this case is located in an exon and is unlikely to itself function as miRNA in its own right. | 1 | Applied and Interdisciplinary Chemistry |
The enthalpy of sublimation has commonly been predicted using the equipartition theorem. If the lattice energy is assumed to be approximately half the packing energy, then the following thermodynamic corrections can be applied to predict the enthalpy of sublimation. Assuming a 1 molar ideal gas gives a correction for the thermodynamic environment (pressure and volume) in which pV = RT, hence a correction of 1RT. Additional corrections for the vibrations, rotations and translation then need to be applied. From the equipartition theorem gaseous rotation and translation contribute 1.5RT each to the final state, therefore a +3RT correction. Crystalline vibrations and rotations contribute 3RT each to the initial state, hence −6RT. Summing the RT corrections; −6RT + 3RT + RT = −2RT. This leads to the following approximate sublimation enthalpy. A similar approximation can be found for the entropy term if rigid bodies are assumed. | 0 | Theoretical and Fundamental Chemistry |
The common names for aldehydes do not strictly follow official guidelines, such as those recommended by IUPAC, but these rules are useful. IUPAC prescribes the following nomenclature for aldehydes:
# Acyclic aliphatic aldehydes are named as derivatives of the longest carbon chain containing the aldehyde group. Thus, HCHO is named as a derivative of methane, and is named as a derivative of butane. The name is formed by changing the suffix -e of the parent alkane to -al, so that HCHO is named methanal, and is named butanal.
# In other cases, such as when a group is attached to a ring, the suffix -carbaldehyde may be used. Thus, is known as cyclohexanecarbaldehyde. If the presence of another functional group demands the use of a suffix, the aldehyde group is named with the prefix formyl-. This prefix is preferred to methanoyl-.
# If the compound is a natural product or a carboxylic acid, the prefix oxo- may be used to indicate which carbon atom is part of the aldehyde group; for example, is named 2-oxoethanoic acid.
# If replacing the aldehyde group with a carboxyl group () would yield a carboxylic acid with a trivial name, the aldehyde may be named by replacing the suffix -ic acid or -oic acid in this trivial name by -aldehyde. | 0 | Theoretical and Fundamental Chemistry |
The line-operated vacuum tube receiver was invented in 1925 by Edward S. Rogers, Sr. The unit operated with 5 Rogers AC vacuum tubes and the Rogers Battery-Eliminator Power Unit (power supply). This unit was later marketed for $120 as "Type 120". He established the Toronto station CFRB (an abbreviation of Canadas First Rogers Batteryless') to promote sales of the product. Batteryless radios were not introduced into the United States until May 1926 and then into Europe in 1927.
Crystal radio receivers are a very simple kind of batteryless radio receiver. They do not need a battery or power source, except for the power that they receive from radio waves using their long outdoor wire antenna. Sharp Electronics first electrical product was a batteryless crystal radio introduced in 1925. It was Japans first -- and sold extremely well.
Thermoelectricity was widely used in the remote parts of the Soviet Union from the 1920s to power radios. The equipment comprised some bi-metal rods (thermocouples), one end of which could be inserted into the fireplace to get hot with the other end left out in the cold.
After the Second World War, kerosene radios were made in Moscow for use in rural areas. These all-wave radios were powered by the kerosene lamp hanging above them. A group of thermocouples was heated internally to by the flame. Fins cooled the outside to about . The temperature differential generated enough current to operate the low-drain receiver.
Foot-operated radio or pedal radio was once used in Australia. Other ways of achieving the same function are clockwork radio, hand crank radio and solar radio, especially for the Royal Flying Doctor Service and School of the Air.
As part of an energy harvesting electronics system, some batteryless radios render electricity to storage by means of storage capacitors. In this batteryless type of radio, the storage capacitors cache the electricity as static on layers of dielectric instead of chemical changes, providing energy like batteries do but batteryless. This can be quite effective. Storage capacitors recharge millions of times, they are relatively cheap, somewhat insensitive to temperature, and they never need replacing -- which is why they are usually soldered on. As part of an energy autarkic or energy harvesting batteryless radio, therefore, storage capacitors are an integral part, storing electricity like battery does for lean energy periods, but in a batteryless way which is more sustainable. About 15 billion batteries are consumed every year worldwide. | 0 | Theoretical and Fundamental Chemistry |
When any group is present at ortho position to an amide group (NH) in aniline then the basic character of that compound becomes weaker. For example, see the order of basicity of following substituted aniline:-
* p-Toluidine > m-Toluidine > Aniline > o-Toluidine
* Aniline > m-Nitroaniline > p-Nitroaniline > o-Nitroaniline
* Aniline > p-Haloaniline > m-Haloaniline > o-Haloaniline
* p-Aminophenol pKb=8.50 > o-Aminophenol pKb=9.28 > Aniline pKb=9.38 > m-Aminophenol pKb=9.80
The protonation of substituted aniline is inhibited by steric hindrance. When protonated, the nitrogen in the amino group changes its orbital hybridization from sp to sp, becoming non-planar. This leads to steric hindrance between the ortho-substituted group and the hydrogen atom of the amino group, reducing the stability of the conjugate acid and consequently decreasing the pH of substituted aniline. | 0 | Theoretical and Fundamental Chemistry |
Edward Roberts pursued his undergraduate studies in biochemistry with a minor in music at the University of Sussex, Brighton, England, earning a Bachelor of Science with Honors degree in 1979. He continued his academic journey with a Ph.D. in synthetic organic chemistry at the University of Newcastle-upon-Tyne, England, under Richard J Stoodley, completing his doctoral studies in 1982. | 0 | Theoretical and Fundamental Chemistry |
Depending on the kind of participants required, sponsors of clinical trials, or contract research organizations working on their behalf, try to find sites with qualified personnel as well as access to patients who could participate in the trial. Working with those sites, they may use various recruitment strategies, including patient databases, newspaper and radio advertisements, flyers, posters in places the patients might go (such as doctor's offices), and personal recruitment of patients by investigators.
Volunteers with specific conditions or diseases have additional online resources to help them locate clinical trials. For example, the Fox Trial Finder connects Parkinson's disease trials around the world to volunteers who have a specific set of criteria such as location, age, and symptoms. Other disease-specific services exist for volunteers to find trials related to their condition. Volunteers may search directly on ClinicalTrials.gov to locate trials using a registry run by the U.S. National Institutes of Health and National Library of Medicine. There also is software that allows clinicians to find trial options for an individual patient based on data such as genomic data. | 1 | Applied and Interdisciplinary Chemistry |
Many kinds of molecular-weight size markers exist, and each possess unique characteristics, lending to their involvement in a number of biological techniques. Selection of a molecular-weight size marker depends upon the marker type (DNA, RNA, or protein) and the length range it offers (e.g. 1kb). Before selecting a molecular-weight size marker, it is important to become familiar with these characteristics and properties. In a particular instance one type may be more appropriate than another. Although specific markers can vary between protocols for a given technique, this section will outline general markers and their roles. | 1 | Applied and Interdisciplinary Chemistry |
Phillips' research on heme proteins and ligand affinity has provided insights into engineering strategies for physiological functions. He explored the impact of His64 in sperm whale myoglobin on ligand affinity, shedding light on structural changes induced by ligand binding and mechanisms of ligand discrimination in myoglobin. By measuring CO binding properties in various mutants and comparing them to mutant myoglobins, he elucidated how mutations influence CO affinity. In his 1994 study, he delved into how heme proteins like myoglobin and hemoglobin differentiate between oxygen (O2) and carbon monoxide (CO) binding at the atomic level. He investigated the role of nitric oxide in physiological functions by examining the kinetics of NO-induced oxidation in myoglobins and hemoglobins revealing insights into protein engineering strategies aimed at mitigating hypertensive events. | 1 | Applied and Interdisciplinary Chemistry |
There have been several efforts to map eukaryotic interactomes through HTP methods. While no biological interactomes have been fully characterized, over 90% of proteins in Saccharomyces cerevisiae have been screened and their interactions characterized, making it the best-characterized interactome. Species whose interactomes have been studied in some detail include
* Schizosaccharomyces pombe
* Caenorhabditis elegans
* Drosophila melanogaster
* Homo sapiens
Recently, the pathogen-host interactomes of Hepatitis C Virus/Human (2008), Epstein Barr virus/Human (2008), Influenza virus/Human (2009) were delineated through HTP to identify essential molecular components for pathogens and for their host's immune system. | 1 | Applied and Interdisciplinary Chemistry |
Both Hahn and Meitner had been nominated for the chemistry and the physics Nobel Prizes many times even before the discovery of nuclear fission for their work on radioactive isotopes and protactinium. Several more nominations followed for the discovery of fission between 1940 and 1943. Nobel Prize nominations were vetted by committees of five, one for each award. Although both Hahn and Meitner received nominations for physics, radioactivity and radioactive elements had traditionally been seen as the domain of chemistry, and so the Nobel Committee for Chemistry evaluated the nominations in 1944.
The committee received reports from Theodor Svedberg in 1941 and in 1942. These chemists were impressed by Hahns work, but felt that the experimental work of Meitner and Frisch was not extraordinary. They did not understand why the physics community regarded their work as seminal. As for Strassmann, although his name was on the papers, there was a long-standing policy of conferring awards on the most senior scientist in a collaboration. In 1944 the Nobel Committee for Chemistry voted to recommend that Hahn alone be given the Nobel Prize in Chemistry for 1944. However, Germans had been forbidden to accept Nobel Prizes after the Nobel Peace Prize had been awarded to Carl von Ossietzky in 1936. The committees recommendation was rejected by the Royal Swedish Academy of Sciences, which decided to defer the award for one year.
The war was over when the academy reconsidered the award in September 1945. The Nobel Committee for Chemistry had now become more cautious, as it was apparent that much research had been undertaken by the Manhattan Project in the United States in secret, and it suggested deferring the 1944 Nobel Prize in Chemistry for another year. The academy was swayed by Göran Liljestrand, who argued that it was important for the academy to assert its independence from the Allies of World War II, and award the Nobel Prize in Chemistry to a German, as it had done after World War I when it had awarded it to Fritz Haber. Hahn therefore became the sole recipient of the 1944 Nobel Prize in Chemistry "for his discovery of the fission of heavy nuclei".
Meitner wrote in a letter to her friend Birgit Broomé-Aminoff on 20 November 1945:
In 1946, the Nobel Committee for Physics considered nominations for Meitner and Frisch received from Max von Laue, Niels Bohr, Oskar Klein, Egil Hylleraas and James Franck. Reports were written for the committee by Erik Hulthén, who held the chair of experimental physics at Stockholm University, in 1945 and 1946. Hulthén argued that theoretical physics should be considered award-worthy only if it inspired great experiments. The role of Meitner and Frisch in being the first to understand and explain fission was not understood. There may also have been personal factors: the chairman of the committee, Manne Siegbahn, disliked Meitner, and had a professional rivalry with Klein. Meitner and Frisch would continue to be nominated regularly for many years, but would never be awarded a Nobel Prize. | 0 | Theoretical and Fundamental Chemistry |
Gamma rays are the highest-energy form of electromagnetic radiation, being physically the same as all other forms (e.g., X-rays, visible light, infrared, radio) but having (in general) higher photon energy due to their shorter wavelength. Because of this, the energy of gamma-ray photons can be resolved individually, and a gamma-ray spectrometer can measure and display the energies of the gamma-ray photons detected.
Radioactive nuclei (radionuclides) commonly emit gamma rays in the energy range from a few keV to ~10 MeV, corresponding to the typical energy levels in nuclei with reasonably long lifetimes. Such sources typically produce gamma-ray "line spectra" (i.e., many photons emitted at discrete energies), whereas much higher energies (upwards of 1 TeV) may occur in the continuum spectra observed in astrophysics and elementary particle physics. The difference between gamma rays and X-rays is somewhat blurred. Gamma rays are always from nuclear energy level transitions of atoms and are mono energetic, whereas X-rays are electrically generated (X-ray tube, linear accelerator) and have a broad energy range. | 0 | Theoretical and Fundamental Chemistry |
The project is open source - all data and all software that is produced in the project can be freely accessed and used. | 1 | Applied and Interdisciplinary Chemistry |
* The ABCs of Islam
* Clarifying Concepts in Physics
In 2017, the posthumous book “The precise relativity of the point” was published , an extensive compilation of Bukele's thoughts gathered on his Twitter account and his program “Clarifying Concepts”. | 1 | Applied and Interdisciplinary Chemistry |
A metal salen complex is a coordination compound between a metal cation and a ligand derived from N,N′-bis(salicylidene)ethylenediamine, commonly called salen. The classical example is salcomine, the complex with divalent cobalt , usually denoted as Co(salen). These complexes are widely investigated as catalysts and enzyme mimics.
The metal-free salen compound (Hsalen or salenH) has two phenolic hydroxyl groups. The salen ligand is usually its conjugate base (salen), resulting from the loss of protons from those hydroxyl groups. The metal atom usually makes four coordination bonds to the oxygen and nitrogen atoms. | 0 | Theoretical and Fundamental Chemistry |
Changes in promoter sequences are critical in evolution as indicated by the relatively stable number of genes in many lineages. For instance, most vertebrates have roughly the same number of protein-coding genes (about 20,000) which are often highly conserved in sequence, hence much of evolutionary change must come from changes in gene expression. | 1 | Applied and Interdisciplinary Chemistry |
In forest plantations in British Columbia, an apparently abundant (not measured) meadow vole population was associated with a high rate of "not sufficient regeneration"; damage to tree seedlings was attributed to meadow voles and lemmings (Synaptomys sp.).
The cycle of meadow vole abundance is an important proximate factor affecting the life histories of its major predators. Meadow voles are usually the most abundant small mammals in northern prairie wetlands, often exceeding 40% of all individual small mammals present. Numbers of short-eared owls, northern harriers, rough-legged hawks (Buteo lagopus), coyotes (Canis latrans), and red foxes were directly related to large numbers of meadow voles in a field in Wisconsin. Predator numbers are positively associated with meadow vole abundance. | 1 | Applied and Interdisciplinary Chemistry |
Where primary energy is used to describe fossil fuels, the embodied energy of the fuel is available as thermal energy and around 70% is typically lost in conversion to electrical or mechanical energy. There are very much less significant conversion losses when hydroelectricity, wind and solar power produce electricity, but today's UN conventions on energy statistics counts the electricity made from hydroelectricity, wind and solar as the primary energy itself for these sources. One consequence of employing primary energy as an energy metric is that the contribution of hydro, wind and solar energy is under reported compared to fossil energy sources, and there is hence an international debate on how to count energy from non thermal renewables, with many estimates having them undercounted by a factor of about three. | 0 | Theoretical and Fundamental Chemistry |
If a gas is compressed adiabatically, i.e. without outflow of heat from the system, the temperature rises (due to the pressure increase) at a higher rate with respect to isothermal compression, where the performed work is dissipated as heat. The exponent, , with which the expansion of the gas can be calculated by the application of heat is called the isentropic – or adiabatic coefficient. Its value is determined by the Rüchardt experiment.
An adiabatic and reversible running state change is isentropic (entropy S remains the same as temperature T changes). The technique is usually an adiabatic change of state. For example, a steam turbine is not isentropic, as friction, choke and shock processes produce entropy. | 0 | Theoretical and Fundamental Chemistry |
In four dimensions, there are a geometrically chiral finite polytopes. One example is Roli's cube, a skew polytope on the skeleton of the 4-cube. | 0 | Theoretical and Fundamental Chemistry |
Plants produce a large number of secondary metabolites thanks to enzymes that, unlike those involved in primary metabolism, are less catalytically efficient but have a larger mechanistic elasticity (reaction types) and broader specificities. The liberal drift threshold (caused by the low selective pressure due to the small population size) allows the fitness gain endowed by one of the products to maintain the other activities even though they may be physiologically useless. | 1 | Applied and Interdisciplinary Chemistry |
When a plant is attacked, it emits GLVs into the environment through the air. How a plant responds depends on the type of damage involved. Plants respond differently to damage from a purely mechanical source and damage from herbivores. Mechanical damage tends to cause damage-associated molecular patterns (DAMPs) involving plant-derived substances and breakdown products. Herbivore-associated molecular patterns (HAMPs) involve characteristic molecules left by different types of herbivores when feeding. The oral secretions of herbivores appear to play an essential role in triggering the release of species-specific herbivore-induced plant volatiles. Wounds from herbivores, and mechanical wounds that have been treated with herbivore oral secretions, both trigger the release of higher quantities of plant volatiles than mechanical damage.
Volatile blends are proposed to convey a variety of information to insects and plants. "Each plant species and even each plant genotype releases its own specific blend, and the quantities and ratios in which they are released also vary with the arthropod that is feeding on a plant and may even provide information on the time of day that feeding occurs." In addition to GLVs, herbivore induced plant volatiles (HIPVs) include terpenes, ethylene, methyl salicylate and other VOCs.
GLVs activate the expression of genes related to the plants' defense mechanisms.
Different antagonists trigger different expression of genes and the biosynthesis of signaling peptides which mediate systemic defense responses. | 1 | Applied and Interdisciplinary Chemistry |
Band emission, is the fraction of the total emission from a blackbody that is in a certain wavelength interval or band. For a prescribed temperature T and spectral interval from 0 to λ, it is the ratio of the total emissive power of a black body from 0 to λ to the total emissive power over the entire spectrum. | 0 | Theoretical and Fundamental Chemistry |
Other methods mapping and profiling the methylome have been effective but are not without their limitations that can affect resolution, level of throughput, or experimental variations. For instance, RLGS is limited by the number of restriction sites in genome that can be targets for the restriction enzyme; typically, a maximum of ~4100 landmarks can be assessed. Bisulfite sequencing-based methods, despite possible single-nucleotide resolution, have a drawback: the conversion of unmethylated cytosine to uracil can be unstable. In addition, when bisulfite conversion is coupled with DNA microarrays to detect bisulfite converted sites, the reduced sequence complexity of DNA is a problem. Microarrays capable of comprehensively profiling the whole-genome become difficult to design as fewer unique probes are available. | 1 | Applied and Interdisciplinary Chemistry |
The properties of a photocured material, such as flexibility, adhesion, and chemical resistance, are provided by the functionalized oligomers present in the photocurable composite. Oligomers are typically epoxides, urethanes, polyethers, or polyesters, each of which provide specific properties to the resulting material. Each of these oligomers are typically functionalized by an acrylate. An example shown below is an epoxy oligomer that has been functionalized by acrylic acid. Acrylated epoxies are useful as coatings on metallic substrates and result in glossy hard coatings. Acrylated urethane oligomers are typically abrasion resistant, tough, and flexible, making ideal coatings for floors, paper, printing plates, and packaging materials. Acrylated polyethers and polyesters result in very hard solvent resistant films, however, polyethers are prone to UV degradation and therefore are rarely used in UV curable material. Often formulations are composed of several types of oligomers to achieve the desirable properties for a material.
The monomers used in radiation curable systems help control the speed of cure, crosslink density, final surface properties of the film, and viscosity of the resin. Examples of monomers include styrene, N-Vinylpyrrolidone, and acrylates. Styrene is a low cost monomer and provides a fast cure, N-vinylpyrrolidone results in a material that is highly flexible when cured and has low toxicity, and acrylates are highly reactive, allowing for rapid cure rates, and are highly versatile with monomer functionality ranging from monofunctional to tetrafunctional. Like oligomers, several types of monomers can be employed to achieve the desired properties of the final material. | 0 | Theoretical and Fundamental Chemistry |
An uncommon class of esters are the orthoesters. One of them are the esters of orthocarboxylic acids. Those esters have the formula , where R stands for any group (organic or inorganic) and R stands for organyl group. For example, triethyl orthoformate () is derived, in terms of its name (but not its synthesis) from esterification of orthoformic acid () with ethanol. | 0 | Theoretical and Fundamental Chemistry |
* Isaac Asimovs short story "Whats in a Name?" (1956) introduced the Beilstein Handbook of Organic Chemistry as an important plot element. | 0 | Theoretical and Fundamental Chemistry |
In mammals, the eIF4E•G•A trimeric complex can be directly purified from cells, while only the two subunit eIF4E•G can be purified from yeast cells. eIF4E binds the mG 5 cap and the eIF4G scaffold, connecting the mRNA 5 terminus to a hub of other initiation factors and mRNA. The interaction of eIF4G•A is thought to guide the formation of a single-stranded RNA landing pad for the 43S preinitiation complex (43S PIC) via eIF4A's RNA helicase activity.
The eIF4F proteins interact with a number of different binding partners, and there are multiple genetic isoforms of eIF4A, eIF4E, and eIF4G in the human genome. In mammals, eIF4F is bridged to the 40S ribosomal subunit by eIF3 via eIF4G, while budding yeast lacks this connection. Interactions between eIF4G and PABP are thought to mediate the circularization of mRNA particles.
Approximate molecular weight for human proteins.
In addition to the major proteins encompassing the eIF4F trimer, the eIF4F complex functionally interacts with proteins including eIF4B and eIF4H. The unusual isoform of eIF4G, eIF4G2 or DAP5, also appears to perform a non-canonical translation function. | 1 | Applied and Interdisciplinary Chemistry |
Clore played a pivotal role in the development of three- and four-dimensional NMR spectroscopy, the use of residual dipolar couplings for structure determination, the development of simulated annealing and restrained molecular dynamics for three-dimensional protein and nucleic acid structure determination, the solution NMR structure determination of large protein complexes, the development of the combined use of NMR and small-angle X-ray scattering in solution structure determination, and the analysis and characterization of protein dynamics by NMR. Clore's work on complexes of all the cytoplasmic components of the bacterial phosphotransferase system (PTS) led to significant insights into how signal transduction proteins recognize multiple, structurally dissimilar partners by generating similar binding surfaces from completely different structural elements and exploiting side chain conformational plasticity. Clore is also one of the main authors of the very widely used XPLOR-NIH NMR structure determination program | 0 | Theoretical and Fundamental Chemistry |
Smeltmills were water-powered mills used to smelt lead or other metals.
The older method of smelting lead on wind-blown bole hills began to be superseded by artificially-blown smelters. The first such furnace was built by Burchard Kranich at Makeney, Derbyshire in 1554, but produced less good lead than the older bole hill. William Humfrey (the Queen's assay master), and a leading shareholder in the Company of Mineral and Battery Works introduced the ore hearth from the Mendips about 1577. This was initially blown by a foot-blast, but was soon developed into a water-powered smelt mill at Beauchief (now a suburb of Sheffield).
A typical smelt mill had an orehearth and a slaghearth, the latter being used to reprocess slags from the orehearth in order to recover further lead from the slag | 1 | Applied and Interdisciplinary Chemistry |
Abergel began her independent career at Berkeley Lab in 2009. She joined the Nuclear Engineering Department of UC Berkeley in 2018 and became the Heavy Element Chemistry Group Leader and Glenn T. Seaborg Center Director at Berkeley Lab that same year. In 2023, she joined the UC Berkeley Chemistry Department and became Associate Dean of the College of Engineering. | 0 | Theoretical and Fundamental Chemistry |
PET can also be used in image guided surgery for the treatment of intracranial tumors, arteriovenous malformations and other surgically treatable conditions. | 1 | Applied and Interdisciplinary Chemistry |
Simultaneously theoretical and computational approaches provided data necessary for identification of new spectra and interpretation of observed line intensities. New laboratory and theoretical data become very useful for spectral observation in space. It was a real upheaval of works on MIA in USA, England, France, Italy, Israel, Sweden, Russia and other countries
A new page in the spectroscopy of MIA may be dated as 1986 with development of EBIT (Levine and Marrs, LLNL) due to a favorable composition of modern high technologies such as cryogenics, ultra-high vacuum, superconducting magnets, powerful electron beams and semiconductor detectors. Very quickly EBIT sources were created in many countries (see NIST summary for many details as well as reviews.)
A wide field of spectroscopic research with EBIT is enabled including achievement of highest grades of ionization (U), wavelength measurement, hyperfine structure of energy levels, quantum electrodynamic studies, ionization cross-sections (CS) measurements, electron-impact excitation CS, X-ray polarization, relative line intensities, dielectronic recombination CS, magnetic octupole decay, lifetimes of forbidden transitions, charge-exchange recombination, etc. | 0 | Theoretical and Fundamental Chemistry |
A potential role for pharmacogenomics is to reduce the occurrence of polypharmacy: it is theorized that with tailored drug treatments, patients will not need to take several medications to treat the same condition. Thus they could potentially reduce the occurrence of adverse drug reactions, improve treatment outcomes, and save costs by avoiding purchase of some medications. For example, maybe due to inappropriate prescribing, psychiatric patients tend to receive more medications than age-matched non-psychiatric patients.
The need for pharmacogenomically tailored drug therapies may be most evident in a survey conducted by the Slone Epidemiology Center at Boston University from February 1998 to April 2007. The study elucidated that an average of 82% of adults in the United States are taking at least one medication (prescription or nonprescription drug, vitamin/mineral, herbal/natural supplement), and 29% are taking five or more. The study suggested that those aged 65 years or older continue to be the biggest consumers of medications, with 17-19% in this age group taking at least ten medications in a given week. Polypharmacy has also shown to have increased since 2000 from 23% to 29%. | 1 | Applied and Interdisciplinary Chemistry |
The principal manuscripts are:
* The Lucca MS, Lucca, Biblioteca Capitolare Feliniana, Codex 490, the oldest witness, c. 800.
* The Sélestat MS, Sélestat, Bibliothèque Humaniste, MS 17. A very full yet old witness, early ninth century.
* The Codex Matritensis (Madrid codex), Madrid, Biblioteca Nacional, MS A.16 (Was: MS A.19), c. 1130.
* The Phillipps-Corning Manuscript, Corning Museum of Glass, MS 5, late twelfth century.
These are simply among the fullest witnesses - there are dozens more that preserve extracts. | 1 | Applied and Interdisciplinary Chemistry |
The Science and Technology Council (STC) coordinates the scientific and technical activities of the IIR. The Science and Technology Council includes five distinct Sections that are in turn divided into ten Commissions. The Science and Technology Council includes:
* one President
* six Vice-presidents
* ten Commission Presidents
* one congress liaison contact person. | 0 | Theoretical and Fundamental Chemistry |
An amidinate salt has the general structure M[RNRCNR] and can be accessed by reaction of a carbodiimide with an organometallic compound such as methyl lithium. They are used widely as ligands in organometallic complexes. | 0 | Theoretical and Fundamental Chemistry |
Notable people with mitochondrial disease include:
* Mattie Stepanek, a poet, peace advocate, and motivational speaker who had dysautonomic mitochondrial myopathy, and who died at age 13.
* Rocco Baldelli, a coach and former center fielder in Major League Baseball who had to retire from active play at age 29 due to mitochondrial channelopathy.
* Charlie Gard, a British boy who had mitochondrial DNA depletion syndrome; decisions about his care were taken to various law courts.
* Charles Darwin, a nineteenth century naturalist who suffered from a disabling illness, is speculated to have MELAS syndrome. | 1 | Applied and Interdisciplinary Chemistry |
While the bays salinity is ideal for oysters and the oyster fishery was at one time the bays most commercially viable, the population has in the last fifty years been devastated. Maryland once had roughly of oyster reefs. In 2008 there were about . It has been estimated that in pre-colonial times, oysters could filter the entirety of the bay in about 3.3 days; by 1988 this time had increased to 325 days. The harvest's gross value decreased 88% from 1982 to 2007. One report suggested the bay had fewer oysters in 2008 than 25 years earlier.
The primary problem is overharvesting. Lax government regulations allow anyone with a license to remove oysters from state-owned beds, and although limits are set, they are not strongly enforced. The overharvesting of oysters has made it difficult for them to reproduce, which requires close proximity to one another. A second cause for the oyster depletion is that the drastic increase in human population caused a sharp increase in pollution flowing into the bay. The bay's oyster industry has also suffered from two diseases: MSX and Dermo.
The depletion of oysters has had a particularly harmful effect on the quality of the bay. Oysters serve as natural water filters, and their decline has further reduced the water quality of the bay. Water that was once clear for meters is now so turbid that a wader may lose sight of his feet while his knees are still dry. | 1 | Applied and Interdisciplinary Chemistry |
Singly substituted isotopologues may be used for nuclear magnetic resonance experiments, where deuterated solvents such as deuterated chloroform (CDCl) do not interfere with the solutes' H signals, and in investigations of the kinetic isotope effect. | 0 | Theoretical and Fundamental Chemistry |
Ram compression jet engines are airbreathing engines similar to gas turbine engines in so far as they both use the Brayton cycle. Gas turbine and ram compression engines differ, however, in how they compress the incoming airflow. Whereas gas turbine engines use axial or centrifugal compressors to compress incoming air, ram engines rely only on air compressed in the inlet or diffuser. A ram engine thus requires a substantial initial forward airspeed before it can function. Ramjets are considered the simplest type of air breathing jet engine because they have no moving parts in the engine proper, only in the accessories.
Scramjets differ mainly in the fact that the air does not slow to subsonic speeds. Rather, they use supersonic combustion. They are efficient at even higher speed. Very few have been built or flown. | 1 | Applied and Interdisciplinary Chemistry |
Among the early (group 4 and 5) transition metal elements, few examples of arsenic activation has been reported to date. Carbon monoxide complexes of zirconium with derivatized cyclopentadienyl ligands were shown to react with yellow arsenic in boiling xylene to release CO and bind the As moiety in η-fashion. Trace amounts of a zirconium dimer bridged by a (μ,η-As)-moiety were also reported in this study, which described the complexes as possible reagents for As transfer. In group 5, arsenic activation has been more widely explored, with complexes of both niobium and tantalum known. Investigation of the electron density topology in a phosphorus/arsenic/niobium-containing system demonstrated the unique η-bonding configuration in these complexes, in which an arsenic-phosphorus double bond binds side-on to a niobium center. | 0 | Theoretical and Fundamental Chemistry |
There have been reported cases of blood alcohol content higher than 1%:
* In 1982, a 24-year-old woman was admitted to the UCLA emergency room with a serum alcohol content of 1.51%, corresponding to a blood alcohol content of 1.33%. She was alert and oriented to person and place and survived. Serum alcohol concentration is not equal to nor calculated in the same way as blood alcohol content.
* In 1984, a 30-year-old man survived a blood alcohol concentration of 1.5% after vigorous medical intervention that included dialysis and intravenous therapy with fructose.
* In 1995, a man from Wrocław, Poland, caused a car accident near his hometown. He had a blood alcohol content of 1.48%; he was tested five times, with each test returning the same reading. He died a few days later of injuries from the accident.
* In 2004, an unidentified Taiwanese woman died of alcohol intoxication after immersion for twelve hours in a bathtub filled with 40% ethanol. Her blood alcohol content was 1.35%. It was believed that she had immersed herself as a response to the SARS epidemic.
* In South Africa, a man driving a Mercedes-Benz Vito light van containing 15 sheep allegedly stolen from nearby farms was arrested on December 22, 2010, near Queenstown in Eastern Cape. His blood had an alcohol content of 1.6%. Also in the vehicle were five boys and a woman, who were also arrested.
* On 26 October 2012, a man from Gmina Olszewo-Borki, Poland, who died in a car accident, recorded a blood alcohol content of 2.23%; however, the blood sample was collected from a wound and thus possibly contaminated.
* On 26 July 2013 a 30-year-old man from Alfredówka, Poland, was found by Municipal Police Patrol from Nowa Dęba lying in the ditch along the road in Tarnowska Wola. At the hospital, it was recorded that the man had a blood alcohol content of 1.374%. The man survived. | 1 | Applied and Interdisciplinary Chemistry |
IVF is expensive in China and not generally accessible to unmarried women. In August 2022, China's National Health Authority announced that it will take steps to make assisted reproductive technology more accessible, including by guiding local governments to include such technology in its national medical system.
Croatia
No egg or sperm donations take place in Croatia, however using donated sperm or egg in ART and IUI is allowed. With donated eggs, sperm or embryo, a heterosexual couple and single women have legal access to IVF. Male or female couples do not have access to ART as a form of reproduction. The minimum age for males and females to access ART in Croatia is 18 there is no maximum age. Donor anonymity applies, but the born child can be given access to the donor's identity at a certain age | 1 | Applied and Interdisciplinary Chemistry |
References to silicon carbide heating elements exist from the early 20th century when they were produced by Acheson's Carborundum Co. in the U.S. and EKL in Berlin. Silicon carbide offered increased operating temperatures compared with metallic heaters. Silicon carbide elements are used today in the melting of glass and non-ferrous metal, heat treatment of metals, float glass production, production of ceramics and electronics components, igniters in pilot lights for gas heaters, etc. | 1 | Applied and Interdisciplinary Chemistry |
The Control of Nature is a 1989 nonfiction book by John McPhee that chronicles three attempts to control natural processes that had varying success. The book combines three long essays previously published in The New Yorker: "Atchafalaya", "Cooling the Lava", and "Los Angeles Against the Mountains". These respectively describe the Old River Control Structure regulating inflow to the Atchafalaya River; the Eldfell volcanic eruption of 1973; and debris flow from the San Gabriel Mountains. | 1 | Applied and Interdisciplinary Chemistry |
The formula for decay correcting is:
where is the original activity count at time zero, is the activity at time "t", "λ" is the decay constant, and "t" is the elapsed time.
The decay constant is where "" is the half-life of the radioactive material of interest. | 0 | Theoretical and Fundamental Chemistry |
The composition of sea foam is generally a mixture of decomposed organic materials, including zooplankton, phytoplankton, algae (including diatoms), bacteria, fungi, protozoans, and vascular plant detritus, though each occurrence of sea foam varies in its specific contents. In some areas, sea foam is found to be made up of primarily protein, dominant in both fresh and old foam, as well as lipids and carbohydrates. The high protein and low carbohydrate concentration suggest that sugars originally present in the surrounding mucilage created by algae or plant matter has been quickly consumed by bacteria. Additional research has shown that a small fraction of the dry weight in sea foam is organic carbon, which contains phenolics, sugars, amino sugars, and amino acids. In the Bay of Fundy, high mortality rates of an abundant tube-dwelling amphipod (Corophium volutator) by natural die-offs as well as predation by migrating seabirds contributed to amino sugars released in the surrounding environment and thus, in sea foam.
The organic matter in sea foam has been found to increase dramatically during phytoplankton blooms in the area. Some research has shown very high concentrations of microplankton in sea foam, with significantly higher numbers of autotrophic phytoplankton than heterotrophs Some foams are particularly rich in their diatom population which can make up the majority of the microalgal biomass in some cases. A diversity of bacteria is also present in sea foam; old foam tends to have a higher density of bacteria. One study found that 95% of sea foam bacteria were rod-shaped, while the surrounding surface water contained mostly coccoid-form bacteria and only 5% - 10% rod-shaped bacteria. There is also seasonal variability of sea foam composition; in some regions there is a seasonal occurrence of pollen in sea foam which can alter its chemistry. Though foam is not inherently toxic, it may contain high concentrations of contaminants. Foam bubbles can be coated with or contain these materials which can include petroleum compounds, pesticides, and herbicides. | 0 | Theoretical and Fundamental Chemistry |
Mo can be obtained by the neutron activation (n,γ reaction) of Mo in a high-neutron-flux reactor. However, the most frequently used method is through fission of uranium-235 in a nuclear reactor. While most reactors currently engaged in Mo production use highly enriched uranium-235 targets, proliferation concerns have prompted some producers to transition to low-enriched uranium targets. The target is irradiated with neutrons to form Mo as a fission product (with 6.1% yield). Molybdenum-99 is then separated from unreacted uranium and other fission products in a hot cell. | 0 | Theoretical and Fundamental Chemistry |
The extent of nephrotoxicity for vancomycin remains controversial. In 1980s, vancomycin with a purity > 90% was available, and kidney toxicity defined by an increase in serum creatinine of at least 0.5 mg/dl, occurred in only about 5% of patients. However, dosing guidelines from the 1980s until 2008 recommended vancomycin trough concentrations between 5 and 15 μg/ml. Concern for treatment failures prompted recommendations for higher dosing (troughs 15 to 20 μg/ml) for serious infection, and acute kidney injury (AKI) rates attributable to the vancomycin increased.
Importantly, the risk of AKI increases with co-administration of other known nephrotoxins, in particular, aminoglycosides. Furthmore, the sort of infections treated with vancomycin may also cause AKI and sepsis is the most common cause of AKI in critically ill patients. Finally, studies in humans are mainly associations studies where the cause of AKI is usually multifacotorial.
Animal studies have demonstrated that higher doses and longer duration of vancomycin exposure correlates with increased histopathologic damage and elevations in urinary biomarkers of AKI.37-38 Damage is most prevalent at the proximal tubule, which is further supported by urinary biomarkers, such as kidney injury molecule-1 (KIM-1), clusterin, and osteopontin (OPN),
and in humans, insulin-like growth factor binding protein 7 (IGFBP7) as part of the nephrocheck test.
The mechanisms that underlie the pathogenesis of vancomycin nephrotoxicity are multifactorial but include interstitial nephritis, tubular injury due to oxidative stress, and cast formation.
Therapeutic drug monitoring can be used during vancomycin therapy to minimize the risk of nephrotoxicity associated with excessive drug exposure. Immunoassays are commonly utilized for measuring vancomycin levels.
In children, the concomitant administration of vancomycin and piperacillin/tazobactam has been associated with an elevated incidence of AKI, relative to other antibiotic regimens. | 0 | Theoretical and Fundamental Chemistry |
A carbazone is a partially oxidized carbazide with the general formula R=NNH(C=O)NH-NHR. The sulfur analog is called a thiocarbazone, of which dithizone is an example. | 0 | Theoretical and Fundamental Chemistry |
Selenols are important in certain biological processes. Three enzymes found in mammals contain selenols at their active sites: glutathione peroxidase, iodothyronine deiodinase, and thioredoxin reductase. The selenols in these proteins are part of the essential amino acid selenocysteine. The selenols function as reducing agents to give selenenic acid derivative (), which in turn are re-reduced by thiol-containing enzymes. Methaneselenol (commonly named "methylselenol") (), which can be produced in vitro by incubating selenomethionine with a bacterial methionine gamma-lyase (METase) enzyme, by biological methylation of selenide ion or in vivo by reduction of methaneseleninic acid (), has been invoked to explain the anticancer activity of certain organoselenium compounds. Precursors of methaneselenol are under active investigation in cancer prevention and therapy. In these studies, methaneselenol is found to be more biologically active than ethaneselenol () or 2-propaneselenol (). | 0 | Theoretical and Fundamental Chemistry |
HABs from cyanobacteria (blue-green algae) can appear as a foam, scum, or mat on or just below the surface of water and can take on various colors depending on their pigments. Cyanobacteria blooms in freshwater lakes or rivers may appear bright green, often with surface streaks that look like floating paint. Cyanobacterial blooms are a global problem.
Most blooms occur in warm waters with excessive nutrients. The harmful effects from such blooms are due to the toxins they produce or from using up oxygen in the water which can lead to fish die-offs. Not all algal blooms produce toxins, however, with some only discoloring water, producing a smelly odor, or adding a bad taste to the water. Unfortunately, it is not possible to tell if a bloom is harmful from just appearances, since sampling and microscopic examination is required. In many cases microscopy is not sufficient to tell the difference between toxic and non-toxic populations. In these cases, tools can be employed to measure the toxin level or to determine if the toxin-production genes are present. | 0 | Theoretical and Fundamental Chemistry |
A disintegrin and metalloprotease 17 (ADAM17), also called TACE (tumor necrosis factor-α-converting enzyme), is a 70-kDa enzyme that belongs to the ADAM protein family of disintegrins and metalloproteases, activated by substrate presentation. | 1 | Applied and Interdisciplinary Chemistry |
* Electronics
* Bandgap voltage reference
* Condensed matter physics
* Direct and indirect bandgaps
* Electrical conduction
* Electron hole
* Field-effect transistor
* Light-emitting diode
* Photodiode
* Photoresistor
* Photovoltaics
* Solar cell
* Solid state physics
* Semiconductor
* Semiconductor devices
* Strongly correlated material
* Valence band | 0 | Theoretical and Fundamental Chemistry |
One of the easiest methods of forming azomethine ylides is by condensation of an aldehyde with an amine. If the amine contains an electron-withdrawing group on the alpha carbon, such as an ester, the deprotonation occurs readily. A possible disadvantage of using this method is that the ester ends up in the cycloaddition product. An alternative is to use a carboxylic acid, which can easily be removed during the cycloaddition process by decarboxylation. | 0 | Theoretical and Fundamental Chemistry |
Unlike in vivo MRS which is intensively used in clinical settings, fMRS is used primarily as a research tool, both in a clinical context, for example, to study metabolite dynamics in patients with epilepsy, migraine and dyslexia, and to study healthy brains.
fMRS can be used to study metabolism dynamics also in other parts of the body, for example, in muscles and heart; however, brain studies have been far more popular.
The main goals of fMRS studies are to contribute to the understanding of energy metabolism in the brain, and to test and improve data acquisition and quantification techniques to ensure and enhance validity and reliability of fMRS studies. | 0 | Theoretical and Fundamental Chemistry |
In addition, the cost of CO emissions avoided through Ca-looping is lower than the cost of emissions avoided via an oxyfuel combustion process (~US$23.8/t). This can be explained by the fact that, despite the capital costs incurred in constructing the carbonator for Ca-looping, CO will not only be captured from the oxy-fired combustion, but also from the main combustor (before the carbonator). The oxygen required in the calciners is only 1/3 that required for an oxyfuel process, lowering air separation unit capital costs and operating costs.
Sensitivity Analysis: Figure 3 shows how varying 8 separate parameters affects the cost/metric ton of CO captured through Ca-looping. It is evident that the dominant variables that affect cost are related to sorbent use, the Ca/C ratio and the CaO deactivation ratio. This is because the large sorbent quantities required dominate the economics of the capture process.
These variables should therefore be taken into account to achieve further cost reductions in the Ca-looping process. The cost of limestone is largely driven by market forces, and is outside the control of the plant. Currently, carbonators require a Ca/C ratio of 4 for effective CO capture. However, if the Ca/C ratio or CaO deactivation is reduced (i.e. the sorbent can be made to work more efficiently), the reduction in material consumption and waste can lower feedstock demand and operating costs. | 1 | Applied and Interdisciplinary Chemistry |
Following is a table of the approximate values of the two relaxation time constants for hydrogen nuclear spins in nonpathological human tissues.
Following is a table of the approximate values of the two relaxation time constants for chemicals that commonly show up in human brain magnetic resonance spectroscopy (MRS) studies, physiologically or pathologically. | 0 | Theoretical and Fundamental Chemistry |
The terms "base" and "alkali" are often used interchangeably, particularly outside the context of chemistry and chemical engineering.
There are various, more specific definitions for the concept of an alkali. Alkalis are usually defined as a subset of the bases. One of two subsets is commonly chosen.
* A basic salt of an alkali metal or alkaline earth metal (this includes Mg(OH) (magnesium hydroxide) but excludes NH (ammonia)).
* Any base that is soluble in water and forms hydroxide ions or the solution of a base in water. (This includes both Mg(OH) and NH, which forms NHOH.)
The second subset of bases is also called an "Arrhenius base". | 0 | Theoretical and Fundamental Chemistry |
DNA molecules are unique in that they are long, charged polymers which when in a separation medium, such as agarose gel, can exhibit highly non-linear velocity profiles in response to an electric field. As such, DNA is easily separated from other molecules that are not both charged and strongly non-linear, using SCODA | 1 | Applied and Interdisciplinary Chemistry |
This demonstration of the triplet nature of the genetic code, although carried out with bacteriophage, later proved to be universally applicable to all forms of life.
The results of this experiment inspired many to begin decoding the triplet code discovered by Brenner and Crick et al. Once this paper was published in 1961, researchers knew that there are 64 possible triplet codons, since there are four nitrogenous bases (4 x 4 x 4 = 64). Today, scientists have decoded what all 64 codons encode for, and the assignments have proven to be nearly universal. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, sulfonic acid (or sulphonic acid) refers to a member of the class of organosulfur compounds with the general formula , where R is an organic alkyl or aryl group and the group a sulfonyl hydroxide. As a substituent, it is known as a sulfo group. A sulfonic acid can be thought of as sulfuric acid with one hydroxyl group replaced by an organic substituent. The parent compound (with the organic substituent replaced by hydrogen) is the parent sulfonic acid, , a tautomer of sulfurous acid, . Salts or esters of sulfonic acids are called sulfonates. | 0 | Theoretical and Fundamental Chemistry |
The chemical composition of the Earth and other bodies is determined by two opposing processes: differentiation and mixing. In the Earth's mantle, differentiation occurs at mid-ocean ridges through partial melting, with more refractory materials remaining at the base of the lithosphere while the remainder rises to form basalt. After an oceanic plate descends into the mantle, convection eventually mixes the two parts together. Erosion differentiates granite, separating it into clay on the ocean floor, sandstone on the edge of the continent, and dissolved minerals in ocean waters. Metamorphism and anatexis (partial melting of crustal rocks) can mix these elements together again. In the ocean, biological organisms can cause chemical differentiation, while dissolution of the organisms and their wastes can mix the materials again. | 0 | Theoretical and Fundamental Chemistry |
The White catalyst is a transition metal coordination complex named after the chemist by whom it was first synthesized, M. Christina White, a professor at the University of Illinois. The catalyst has been used in a variety of allylic C-H functionalization reactions of α-olefins. In addition, it has been shown to catalyze oxidative Heck reactions. | 0 | Theoretical and Fundamental Chemistry |
The Gastruloid model system draws its origins from work by Marikawa et al.. In that study, small numbers of mouse P19 embryonal carcinoma (EC) cells, were aggregated as embryoid bodies (EBs) and used to model and investigate the processes involved in anteroposterior polarity and the formation of a primitive streak region. In this work, the EBs were able to organise themselves into structures with polarised gene expression, axial elongation/organisation and up-regulation of posterior mesodermal markers. This was in stark contrast to work using EBs from mouse ESCs, which had shown some polarisation of gene expression in a small number of cases but no further development of the multicellular system.
Following this study, the [http://amapress.gen.cam.ac.uk Martinez Arias] laboratory in the Department of Genetics at the University of Cambridge demonstrated how aggregates of mouse embryonic stem cells (ESCs) were able to generate structures that exhibited collective behaviours with striking similarity to those during early development such as symmetry-breaking (in terms of gene expression), axial elongation and germ-layer specification. To quote from the original paper: "Altogether, these observations further emphasize the similarity between the processes that we have uncovered here and the events in the embryo. The movements are related to those of cells in gastrulating embryos and for this reason we term these aggregates ‘gastruloids’". As noted by the authors of this protocol, a crucial difference between this culture method and previous work with mouse EBs was the use of small numbers of cells which may be important for generating the correct length scale for patterning, and the use of culture conditions derived from directed differentiation of ESCs in adherent culture
Brachyury (T/Bra), a gene which marks the primitive streak and the site of gastrulation, is up-regulated in the Gastruloids following a pulse of the Wnt/β-Catenin agonist CHIR99021 (Chi; other factors have also been tested) and becomes regionalised to the elongating tip of the Gastruloid. From or near the region expressing T/Bra, cells expressing the mesodermal marker tbx6 are extruded from the similar to cells in the gastrulating embryo; it is for this reason that these structures are called Gastruloids.
Further studies revealed that the events that specify T/Bra expression in gastruloids mimic those in the embryo. After seven days gastruloids exhibit an organization very similar to a midgestation embryo with spatially organized primordia for all mesodermal (axial, paraxial, intermediate, cardiac, cranial and hematopoietic) and endodermal derivatives as well as the spinal cord. They also implement Hox gene expression with the spatiotemporal coordinates as the embryo. Gastruloids lack brain as well as extraembryonic tissues but characterisation of the cellular complexity of gastruloids at the level of single cell and spatial transcriptomics, reveals that they contain representatives of the three germ layers including neural crest, Primordial Germ cells and placodal primordia.
A feature of gastruloids is a disconnect between the transcriptional programs and outlines and the morphogenesis. However, changes in the culture conditions can elicit morphogenesis, most significantly gastruloids have been shown to form somites and early cardiac structures. In addition, interactions between gastruloids and extraembryonic tissues promote an anterior, brain-like polarised tissue.
Gastruloids have recently been obtained from human ESCs, which gives developmental biologists the ability to study early human development without needing human embryos. Importantly though, the human gastruloid model is not able to form a human embryo, meaning that is a non-intact, non-viable and non-equivalent to in vivo human embryos.
The term Gastruloid has been expanded to include self-organised human embryonic stem cell arrangements on patterned (micro patterns) that mimic early patterning events in development; these arrangements should be referred to as 2D gastruloids. | 1 | Applied and Interdisciplinary Chemistry |
He graduated with high honors in chemistry from Yale in 1892, and went on to study analytical methods of inorganic chemistry and rare earth elements for two years in Germany at Ludwig-Maxamillian University of Munich. Afterwards, he returned to Yale and earned a PhD in 1897 and became an instructor in the Sheffield Scientific School there from 1896-1900. His teaching and research work at Yale focused on physical chemistry, despite it being a relatively new field. Lacking resources in English for teaching the subject, he translated two books from German, Alexander Classen, "Quantitative Analysis by Electrolysis," and the other by Charles Van Deventer, "Physical Chemistry for Beginners." He was particularly handy in the lab, often improving upon methods and devices. For example, he developed a low melting point wax that found use in labs across the country and was called, "Boltwax".
From 1900-1906, he had a private lab in New Haven, Connecticut. He worked as a consulting chemist, analyzing ore samples for miners. This experience brought him into contact with the rare earth metals he had studied as well as uranium and thorium, elements that would become the crux of his greatest scientific contributions. | 0 | Theoretical and Fundamental Chemistry |
Sulfur dioxide is a convenient and widely used source of the sulfonyl functional group. Specifically, Sulfur dioxide participates in cycloaddition reactions with dienes.
The industrially useful solvent sulfolane is prepared by addition of sulfur dioxide to buta-1,3-diene followed by hydrogenation of the resulting sulfolene. | 0 | Theoretical and Fundamental Chemistry |
This substance is produced with a wide range of compositions and has many different applications. It is encountered as an additive E 554 in food where it acts as an anticaking (free flow) agent. As it is manufactured with a range of compositions it is not strictly a chemical compound with a fixed stoichiometry. One supplier quotes a typical analysis for one of their products as 14SiO·AlO·NaO·3HO,(NaAlSiO·3HO).
The US FDA has as of April 1, 2012 approved sodium aluminosilicate (sodium silicoaluminate) for direct contact with consumable items under 21 CFR 182.2727. Sodium aluminosilicate is used as molecular sieve in medicinal containers to keep contents dry.
Sodium aluminosilicate may also be listed as:
* aluminium sodium salt
* sodium silicoaluminate
* aluminosilicic acid, sodium salt
* sodium aluminium silicate
* aluminum sodium silicate
* sodium silico aluminate
* sasil | 0 | Theoretical and Fundamental Chemistry |
Resonance has a deeper significance in the mathematical formalism of valence bond theory (VB). Quantum mechanics requires that the wavefunction of a molecule obey its observed symmetry. If a single contributing structure does not achieve this, resonance is invoked.
For example, in benzene, valence bond theory begins with the two Kekulé structures which do not individually possess the sixfold symmetry of the real molecule. The theory constructs the actual wave function as a linear superposition of the wave functions representing the two structures. As both Kekulé structures have equal energy, they are equal contributors to the overall structure – the superposition is an equally weighted average, or a 1:1 linear combination of the two in the case of benzene. The symmetric combination gives the ground state, while the antisymmetric combination gives the first excited state, as shown.
In general, the superposition is written with undetermined coefficients, which are then variationally optimized to find the lowest possible energy for the given set of basis wave functions. When more contributing structures are included, the molecular wave function becomes more accurate and more excited states can be derived from different combinations of the contributing structures. | 0 | Theoretical and Fundamental Chemistry |
Besides having adequate dentinal moisture, agitation of the primers during application of two-step etch-and-rinse adhesives may be critical for optimal penetration into the demineralized collagen fibres. It also may aid the evaporation of residual water in the adhesive and hybrid layers, thus preventing nano leakage.
In a clinical trial comparing the performance of Prime & Bond NT using no rubbing action, slight rubbing action and vigorous rubbing action in the restoration of NCCLs, 92.5% of restorations in vigorous rubbing action group were found to retain after 24 months of clinical service. For the other two groups, the retention rates of the restoration were slightly lower, at 82.5%. | 0 | Theoretical and Fundamental Chemistry |
Inversions and translocations are relatively easy to detect by an invalid pair of sequenced-end. For instance, a translocation can be detected if the paired-ends are mapped onto different chromosomes on the reference genome. Inversion can be detected by divergent orientation of the reads, where the insert will have two plus-end or two minus-end. | 1 | Applied and Interdisciplinary Chemistry |
For example, for a macroscopic scalar field and a macroscopic vector field the definition becomes:
In the scalar case is simply the gradient of a scalar, while is the covariant derivative of the macroscopic vector (which can also be thought of as the Jacobian matrix of as a function of ).
In particular for a scalar field in a three-dimensional Cartesian coordinate system , the components of the velocity are , and the convective term is then: | 1 | Applied and Interdisciplinary Chemistry |
It was found that the stability of the complex of copper(II) with the macrocyclic ligand cyclam (1,4,8,11-tetraazacyclotetradecane) was much greater than expected in comparison to the stability of the complex with the corresponding open-chain amine.
This phenomenon was named the macrocyclic effect and it was also interpreted as an entropy effect. However, later studies suggested that both enthalpy and entropy factors were involved.
An important difference between macrocyclic ligands and open-chain (chelating) ligands is that they have selectivity for metal ions, based on the size of the cavity into which the metal ion is inserted when a complex is formed. For example, the crown ether 18-crown-6 forms much stronger complexes with the potassium ion, K than with the smaller sodium ion, Na.
In hemoglobin an iron(II) ion is complexed by a macrocyclic porphyrin ring. The article hemoglobin incorrectly states that oxyhemoglogin contains iron(III). It is now known that the iron(II) in hemoglobin is a low-spin complex, whereas in oxyhemoglobin it is a high-spin complex. The low-spin Fe ion fits snugly into the cavity of the porphyrin ring, but high-spin iron(II) is significantly larger and the iron atom is forced out of the plane of the macrocyclic ligand. This effect contributes the ability of hemoglobin to bind oxygen reversibly under biological conditions. In Vitamin B12 a cobalt(II) ion is held in a corrin ring. Chlorophyll is a macrocyclic complex of magnesium(II). | 0 | Theoretical and Fundamental Chemistry |
A photocathode is a surface engineered to convert light (photons) into electrons using the photoelectric effect. Photocathodes are important in accelerator physics where they are utilised in a photoinjector to generate high brightness electron beams. Electron beams generated with photocathodes are commonly used for free electron lasers and for ultrafast electron diffraction. Photocathodes are also commonly used as the negatively charged electrode in a light detection device such as a photomultiplier, phototube and image intensifier. | 0 | Theoretical and Fundamental Chemistry |
In susceptible persons, beryllium exposure can lead to a cell-mediated immune response. The T-cells become sensitized to beryllium. Each subsequent exposure leads to an immune response involving CD4+ helper T-lymphocytes and macrophages accumulating in the lungs. As this response continues macrophages, CD+4 T-lymphocytes and plasma cells aggregate together to form the noncaseating granulomas. When beryllium is phagocytized by macrophages, the beryllium triggers macrophage apoptosis, thereby reducing beryllium clearance from the lungs and eventually resulting in secondary necrosis and lysis. Eventually, the outcome is fibrosis of the lung.
Several studies have shown that there is a genetic component to beryllium sensitivity. Specifically, those beryllium-exposed workers with a mutation at the HLA-DPB1 Glu position have increased prevalence of beryllium sensitization and chronic beryllium disease. The HLA-DPB1 gene is important for MHC class II molecule function on antigen presenting cells. A study of the immune response to beryllium in individuals who express the HLA-DP2 allele found that CD4 T-cells do not detect the Be+ cation itself, but instead detect surface changes in the HLA-DP2/peptide complex in which Be+ is embedded. Those researchers concluded that chronic beryllium disease is a predisposition that lies between "allergic hypersensitivity and autoimmunity."
According to the International Agency for Research on Cancer, beryllium and beryllium compounds are Category 1 carcinogens; they are carcinogenic to both animals and humans. | 1 | Applied and Interdisciplinary Chemistry |
The VSEPR theory also predicts that substitution of a ligand at a central atom by a lone pair of valence electrons leaves the general form of the electron arrangement unchanged with the lone pair now occupying one position. For molecules with five pairs of valence electrons including both bonding pairs and lone pairs, the electron pairs are still arranged in a trigonal bipyramid but one or more equatorial positions is not attached to a ligand atom so that the molecular geometry (for the nuclei only) is different.
The seesaw molecular geometry is found in sulfur tetrafluoride (SF) with a central sulfur atom surrounded by four fluorine atoms occupying two axial and two equatorial positions, as well as one equatorial lone pair, corresponding to an AXE molecule in the AXE notation. A T-shaped molecular geometry is found in chlorine trifluoride (ClF), an AXE molecule with fluorine atoms in two axial and one equatorial position, as well as two equatorial lone pairs. Finally, the triiodide ion () is also based upon a trigonal bipyramid, but the actual molecular geometry is linear with terminal iodine atoms in the two axial positions only and the three equatorial positions occupied by lone pairs of electrons (AXE); another example of this geometry is provided by xenon difluoride, XeF. | 0 | Theoretical and Fundamental Chemistry |
Sit studied detoxification, namely the process of conjugation by which metabolic by-products are made soluble prior to excretion. She also studied metabolism within cancer cells and found aerobic respiration within mitochondria in cancer cells, which contradicts the Warburg hypothesis. | 1 | Applied and Interdisciplinary Chemistry |
Ohmic metal-semiconductor contacts are made to both the n-type and p-type sides of the solar cell, and the electrodes connected to an external load. Electrons that are created on the n-type side, or created on the p-type side, "collected" by the junction and swept onto the n-type side, may travel through the wire, power the load, and continue through the wire until they reach the p-type semiconductor-metal contact. Here, they recombine with a hole that was either created as an electron-hole pair on the p-type side of the solar cell, or a hole that was swept across the junction from the n-type side after being created there.
The voltage measured is equal to the difference in the quasi Fermi levels of the majority carriers (electrons in the n-type portion and holes in the p-type portion) at the two terminals. | 0 | Theoretical and Fundamental Chemistry |
Costs for HDS systems depend on site-specific conditions such as land characteristics, amount of runoff to be treated, system depth and performance requirements. Be aware that not all HDS systems are alike in treatment performance, and basing a decision solely on the installation and operating cost of a system may compromise system performance and the environment. Long-term maintenance costs should also be considered with overall costs when purchasing or selecting a stormwater BMP as initial installation and operating costs may not reflect the long-term investment needed to maintain the system. | 1 | Applied and Interdisciplinary Chemistry |
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