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This process was developed by the St. Joseph Mineral Company in 1930, and is the only pyrometallurgical process still used in the US to smelt zinc. The advantage of this system is that it is able to smelt a wide variety of zinc-bearing materials, including electric arc furnace dust. The disadvantage of this process is that it is less efficient than the electrolysis process.
The process begins with a downdraft sintering operation. The sinter, which is a mixture of roaster calcine and EAF (electric arc furnace) calcine, is loaded onto a gate type conveyor and then combustions gases are pumped through the sinter. The carbon in the combustion gases react with some impurities, such as lead, cadmium, and halides. These impurities are driven off into filtration bags. The sinter after this process, called product sinter, usually has a composition of 48% zinc, 8% iron, 5% aluminium, 4% silicon, 2.5% calcium, and smaller quantities of magnesium, lead, and other metals. The sinter product is then charged with coke into an electric retort furnace. A pair of graphite electrodes from the top and bottom of the furnace produce current flow through the mixture. The coke provides electrical resistance to the mixture in order to heat the mixture to and produce carbon monoxide. These conditions allow for the following chemical reaction to occur:
The zinc vapour and carbon dioxide pass to a vacuum condenser, where zinc is recovered by bubbling through a molten zinc bath. Over 95% of the zinc vapour leaving the retort is condensed to liquid zinc. The carbon dioxide is regenerated with carbon, and the carbon monoxide is recycled back to the retort furnace. | 1 | Applied and Interdisciplinary Chemistry |
The Jameson Cell is used to recover the organic solvent in solvent extraction – electrowinning plants from both the electrolyte and raffinate streams.
Contamination of the electrolyte increases operating costs and reduces the quality of the copper product. Any solvent remaining in the raffinate stream represents a loss of solvent and hence an increase in operating costs.
Major users of the Cell in SX–EW plants include Freeport McMoRan at its Morenci operations, BHP Billiton at its Olympic Dam operations and Grupo México at its Cananea and La Caridad operations. In all, Xstrata Technology reports 41 SX–EW applications.
Recent developments in the Cell design for SX–EW applications include large, flat-bottomed cell design to allow it to sit on the ground and large (500 mm diameter) downcomers that can have multiple liquor (there being no slurry in SX–EW applications) lenses fitted to each downcomer.
The biggest operating Cell is at the Olympic Dam operations, treating 3000 m/h of raffinate. | 1 | Applied and Interdisciplinary Chemistry |
Stereochemistry also plays a role assigning faces to trigonal molecules such as ketones. A nucleophile in a nucleophilic addition can approach the carbonyl group from two opposite sides or faces. When an achiral nucleophile attacks acetone, both faces are identical and there is only one reaction product. When the nucleophile attacks butanone, the faces are not identical (enantiotopic) and a racemic product results. When the nucleophile is a chiral molecule diastereoisomers are formed. When one face of a molecule is shielded by substituents or geometric constraints compared to the other face the faces are called diastereotopic. The same rules that determine the stereochemistry of a stereocenter (R or S) also apply when assigning the face of a molecular group. The faces are then called the Re-face and Si-face. In the example displayed on the right, the compound acetophenone is viewed from the Re-face. Hydride addition as in a reduction process from this side will form the (S)-enantiomer and attack from the opposite Si-face will give the (R)-enantiomer. However, one should note that adding a chemical group to the prochiral center from the Re-face will not always lead to an (S)-stereocenter, as the priority of the chemical group has to be taken into account. That is, the absolute stereochemistry of the product is determined on its own and not by considering which face it was attacked from. In the above-mentioned example, if chloride (Z = 17) were added to the prochiral center from the Re-face, this would result in an (R)-enantiomer. | 0 | Theoretical and Fundamental Chemistry |
Imidazol-2-ylidenes, triazol-5-ylidenes (and less so, diaminocarbenes) have been shown to coordinate to a plethora of elements, from alkali metals, main group elements, transition metals and even lanthanides and actinides. A periodic table of elements gives some idea of the complexes which have been prepared, and in many cases these have been identified by single crystal X-ray crystallography.
Stable carbenes are believed to behave in a similar fashion to organophosphines in their coordination properties to metals. These ligands are said to be good σ-donors through the carbenic lone pair, but poor π-acceptors due to internal ligand back-donation from the nitrogen atoms adjacent to the carbene centre, and so are able to coordinate to even relatively electron deficient metals. Enders and Hermann have shown that these carbenes are suitable replacements for phosphine ligands in several catalytic cycles. Whilst they have found that these ligands do not activate the metal catalyst as much as phosphine ligands they often result in more robust catalysts. Several catalytic systems have been looked into by Hermann and Enders, using catalysts containing imidazole and triazole carbene ligands, with moderate success. Grubbs has reported replacing a phosphine ligand (PCy) with an imidazol-2-ylidene in the olefin metathesis catalyst RuCl(PCy)CHPh, and noted increased ring closing metathesis as well as exhibiting "a remarkable air and water stability". Molecules containing two and three carbene moieties have been prepared as potential bidentate and tridentate carbene ligands. | 0 | Theoretical and Fundamental Chemistry |
Bioreactor landfills being a novel technology are still in the development phase and are being studied in the laboratory-scale. Pilot projects for bioreactor landfills are showing promise and more are being experimented with in different parts of the world. Despite the potential benefits of bioreactor landfills there are no standardised and approved designs with guidelines and operational procedures. Following is a list of bioreactor landfill projects which are being used to collect data for forming these needed guidelines and procedures: | 1 | Applied and Interdisciplinary Chemistry |
In the time-independent formalism of quantum scattering, the initial wave function (before scattering) is taken to be a plane wave with definite momentum :
where and are the relative coordinates between the projectile and the target. The arrow indicates that this only describes the asymptotic behavior of the wave function when the projectile and target are too far apart for the interaction to have any effect.
After scattering takes place it is expected that the wave function takes on the following asymptotic form:
where is some function of the angular coordinates known as the scattering amplitude. This general form is valid for any short-ranged, energy-conserving interaction. It is not true for long-ranged interactions, so there are additional complications when dealing with electromagnetic interactions.
The full wave function of the system behaves asymptotically as the sum
The differential cross section is related to the scattering amplitude:
This has the simple interpretation as the probability density for finding the scattered projectile at a given angle.
A cross section is therefore a measure of the effective surface area seen by the impinging particles, and as such is expressed in units of area. The cross section of two particles (i.e. observed when the two particles are colliding with each other) is a measure of the interaction event between the two particles. The cross section is proportional to the probability that an interaction will occur; for example in a simple scattering experiment the number of particles scattered per unit of time (current of scattered particles ) depends only on the number of incident particles per unit of time (current of incident particles ), the characteristics of target (for example the number of particles per unit of surface ), and the type of interaction. For we have | 0 | Theoretical and Fundamental Chemistry |
The Tsuji–Trost reaction (also called the Trost allylic alkylation or allylic alkylation) is a palladium-catalysed substitution reaction involving a substrate that contains a leaving group in an allylic position. The palladium catalyst first coordinates with the allyl group and then undergoes oxidative addition, forming the -allyl complex. This allyl complex can then be attacked by a nucleophile, resulting in the substituted product.
This work was first pioneered by Jirō Tsuji in 1965 and, later, adapted by Barry Trost in 1973 with the introduction of phosphine ligands.
The scope of this reaction has been expanded to many different carbon, nitrogen, and oxygen-based nucleophiles, many different leaving groups, many different phosphorus, nitrogen, and sulfur-based ligands, and many different metals (although palladium is still preferred).
The introduction of phosphine ligands led to improved reactivity and numerous asymmetric allylic alkylation strategies. Many of these strategies are driven by the advent of chiral ligands, which are often able to provide high enantioselectivity and high diastereoselectivity under mild conditions. This modification greatly expands the utility of this reaction for many different synthetic applications. The ability to form carbon-carbon, carbon-nitrogen, and carbon-oxygen bonds under these conditions, makes this reaction very appealing to the fields of both medicinal chemistry and natural product synthesis. | 0 | Theoretical and Fundamental Chemistry |
A Kurie plot (also known as a Fermi–Kurie plot) is a graph used in studying beta decay developed by Franz N. D. Kurie, in which the square root of the number of beta particles whose momenta (or energy) lie within a certain narrow range, divided by the Fermi function, is plotted against beta-particle energy. It is a straight line for allowed transitions and some forbidden transitions, in accord with the Fermi beta-decay theory. The energy-axis (x-axis) intercept of a Kurie plot corresponds to the maximum energy imparted to the electron/positron (the decay's value). With a Kurie plot one can find the limit on the effective mass of a neutrino. | 0 | Theoretical and Fundamental Chemistry |
Plastid types in algae and protists include:
* Chloroplasts: found in green algae (plants) and other organisms that derived their genomes from green algae.
* Muroplasts: also known as cyanoplasts or cyanelles, the plastids of glaucophyte algae are similar to plant chloroplasts, excepting they have a peptidoglycan cell wall that is similar to that of bacteria.
* Rhodoplasts: the red plastids found in red algae, which allows them to photosynthesize down to marine depths of 268 m. The chloroplasts of plants differ from rhodoplasts in their ability to synthesize starch, which is stored in the form of granules within the plastids. In red algae, floridean starch is synthesized and stored outside the plastids in the cytosol.
* Secondary and tertiary plastids: from endosymbiosis of green algae and red algae.
* Leucoplast: in algae, the term is used for all unpigmented plastids. Their function differs from the leucoplasts of plants.
* Apicoplast: the non-photosynthetic plastids of Apicomplexa derived from secondary endosymbiosis.
The plastid of photosynthetic Paulinella species is often referred to as the cyanelle or chromatophore, and is used in photosynthesis. It had a much more recent endosymbiotic event, in the range of 140–90 million years ago, which is the only other known primary endosymbiosis event of cyanobacteria.
Etioplasts, amyloplasts and chromoplasts are plant-specific and do not occur in algae. Plastids in algae and hornworts may also differ from plant plastids in that they contain pyrenoids. | 0 | Theoretical and Fundamental Chemistry |
Multi-parametric surface plasmon resonance, a special configuration of SPR, can be used to characterize layers and stacks of layers. Besides binding kinetics, MP-SPR can also provide information on structural changes in terms of layer true thickness and refractive index. MP-SPR has been applied successfully in measurements of lipid targeting and rupture, CVD-deposited single monolayer of graphene (3.7Å) as well as micrometer thick polymers. | 0 | Theoretical and Fundamental Chemistry |
The opportunity provided by the use of glass in concrete is a potential solution that uses circular economy principles to unlock value and create new business opportunities: first, by finding a use for glass of higher value than landfill, and second by decreasing the negative externalities of the construction sector. By using glass in concrete, it would be possible to:
*Re-utilize the 8 million tons of post-consumer glass that is landfilled each year.
*Reduce the 90-million-ton annual demand for cement, whose production leads to 90 million tons of emissions (equivalent to nearly 20 million cars).
*Minimize exposure to heavy metals and other potentially toxic components in concrete – especially during the renovation and demolition of buildings. | 0 | Theoretical and Fundamental Chemistry |
The pyrolysis (thermal decomposition) of acetaldehyde, CHCHO (g) → CH (g) + CO (g), proceeds via the Rice-Herzfeld mechanism:
*Initiation (formation of free radicals):
: CHCHO (g) → •CH (g) + •CHO (g) k
The methyl and CHO groups are free radicals.
*Propagation (two steps):
: •CH (g) + CHCHO (g) → CH (g) + •CHCO (g) k
This reaction step provides methane, which is one of the two main products.
: •CHCO (g) → CO (g) + •CH (g) k
The product •CHCO (g) of the previous step gives rise to carbon monoxide (CO), which is the second main product.
The sum of the two propagation steps corresponds to the overall reaction CHCHO (g) → CH (g) + CO (g), catalyzed by a methyl radical •CH.
*Termination:
: •CH (g) + •CH (g) → CH (g) k
This reaction is the only source of ethane (minor product) and it is concluded to be the main chain ending step.
Although this mechanism explains the principal products, there are others that are formed in a minor degree, such as acetone (CHCOCH) and propanal (CHCHCHO).
Applying the Steady State Approximation for the intermediate species CH(g) and CHCO(g), the rate law for the formation of methane and the order of reaction are found:
The rate of formation of the product methane is
For the intermediates
and
Adding (2) and (3), we obtain
so that
Using (4) in (1) gives the rate law , which is order 3/2 in the reactant CHCHO. | 0 | Theoretical and Fundamental Chemistry |
The specific study of the ferrous compounds (those including iron, Fe) used in the past. Iron metal was first encountered in meteorites, and was later extracted from iron ores to create wrought iron which was never fully molten, and later, cast iron. Iron combined with carbon formed steel, allowing people to develop superior tools and weapons from the Iron Age to the industrial revolution. | 1 | Applied and Interdisciplinary Chemistry |
Steroid 5α-reductase is a membrane-associated enzyme in an oxidoreductase family and has an important role in biological actions towards steroid metabolism. If the steroid 5α-reductase is overexpressed it causes overproduction of DHT that can lead to androgenic disorders in humans.
The 5α-reductase isozymes possess a similar steroidal catalytic site. The only available information about the 5α-reductase isozymes is their primary sequence estimated from c-DNAs and that affects the design of the novel inhibitors. The crystal structure of the 5α-reductase isozymes is not known because the nature of the 5α-reductase enzyme is so unstable during purification. The first 5-ARIs were designed by modifying the structure of natural substrates, including the substitution of one carbon atom of the rings of the steroids by a heteroatom such as nitrogen thereby forming azasteroids. The receptor is known to consist of two hydrogen bond donors, where the C3 and 17β-side chain of the ligands connect, as well as three hydrophobic groups distributed over the steroidal structure. The best receptor inhibitors comply with these factors. Azasteroids are a type of steroid derivatives which have nitrogen atoms replaced at various positions for one of the carbon atoms in the steroid ring system. Two 4-azasteroids, finasteride and dutasteride are marketed as 5-ARIs. Finasteride (Proscar or Propecia) was the first steroidal 5α-reductase inhibitor approved by the U.S. Food and Drug Administration (USFDA). It inhibits the function of two of the isoenzymes (type II and III). In human it decreases the prostatic DHT level by 70–90% and reduces the prostatic size.
Dutasteride (Avodart) was the second steroidal 5α-reductase approved after finasteride. It is a competitive inhibitor of all three 5α-reductase isoenzymes and it inhibits types 1 and 2 better than finasteride, leading to it causing further reduction in DHT, with >90% recuded DHT levels following 1 year of oral administration.
Epristeride is the third marketed steroidal 5-ARI. It is a noncompetitive, specific inhibitor. It potency is not as significant as finasteride or dutasteride and thus it is only marketed in China. | 1 | Applied and Interdisciplinary Chemistry |
Major places where cavitation occurs are in pumps, on propellers, or at restrictions in a flowing liquid.
As an impellers (in a pump) or propellers (as in the case of a ship or submarine) blades move through a fluid, low-pressure areas are formed as the fluid accelerates around and moves past the blades. The faster the blade moves, the lower the pressure can become around it. As it reaches vapor pressure, the fluid vaporizes and forms small bubbles of gas. This is cavitation. When the bubbles collapse later, they typically cause very strong local shock waves in the fluid, which may be audible and may even damage the blades.
Cavitation in pumps may occur in two different forms: | 1 | Applied and Interdisciplinary Chemistry |
* Acid value
* Bromine number
* Amine value
* Epoxy value
* Iodine value
* Peroxide value
* Saponification value | 0 | Theoretical and Fundamental Chemistry |
Translational control is critical for the development and survival of cancer. Cancer cells must frequently regulate the translation phase of gene expression, though it is not fully understood why translation is targeted over steps like transcription. While cancer cells often have genetically altered translation factors, it is much more common for cancer cells to modify the levels of existing translation factors. Several major oncogenic signaling pathways, including the RAS–MAPK, PI3K/AKT/mTOR, MYC, and WNT–β-catenin pathways, ultimately reprogram the genome via translation. Cancer cells also control translation to adapt to cellular stress. During stress, the cell translates mRNAs that can mitigate the stress and promote survival. An example of this is the expression of AMPK in various cancers; its activation triggers a cascade that can ultimately allow the cancer to escape apoptosis (programmed cell death) triggered by nutrition deprivation. Future cancer therapies may involve disrupting the translation machinery of the cell to counter the downstream effects of cancer. | 1 | Applied and Interdisciplinary Chemistry |
Taken over all species and experiments, high light does not affect the organic nitrogen concentration, but decreases the concentration of chlorophyll and minerals. It increases the concentration of starch and sugars, soluble phenolics, and also the xanthophyll/chlorophyll ratio and the chlorophyll a/b ratio. | 0 | Theoretical and Fundamental Chemistry |
Charles James (27 April 1880 – 10 December 1928) was a chemist of British origin working in the United States. He became a professor and head of the chemistry department at the New Hampshire College of Agriculture and the Mechanic Arts (now the University of New Hampshire) in Durham, New Hampshire, US.
James developed the James method for the separation and identification of rare-earth elements by fractional precipitation and crystallization, and provided extracted elements to researchers worldwide. James was one of the first scientists to identify element 71, later named lutetium, and believed that he had found the final rare earth element 61, later named promethium.
In 1999 the American Chemical Society recognized Charles James's work in chemical separations as a National Historic Chemical Landmark. | 1 | Applied and Interdisciplinary Chemistry |
GenGIS merges geographic, ecological and phylogenetic biodiversity data in a single interactive visualization and analysis environment. A key feature of GenGIS is the testing of geographic axes that can correspond to routes of migration or gradients that influence community similarity. Data can also be explored using graphical summaries of data on a site-by-site basis, as 3D geophylogenies, or custom visualizations developed using a plugin framework. Standard statistical test such as linear regression and Mantel are provided, and the R statistical language can be accessed directly within GenGIS. Since its release, GenGIS has been used to investigate the phylogeography of viruses and bacteriophages, bacteria, and eukaryotes. | 1 | Applied and Interdisciplinary Chemistry |
Chemical-based transfection can be divided into several kinds: cyclodextrin, polymers, liposomes, or nanoparticles (with or without chemical or viral functionalization. See below).
*One of the cheapest methods uses calcium phosphate, originally discovered by F. L. Graham and A. J. van der Eb in 1973 (see also). HEPES-buffered saline solution (HeBS) containing phosphate ions is combined with a calcium chloride solution containing the DNA to be transfected. When the two are combined, a fine precipitate of the positively charged calcium and the negatively charged phosphate will form, binding the DNA to be transfected on its surface. The suspension of the precipitate is then added to the cells to be transfected (usually a cell culture grown in a monolayer). By a process not entirely understood, the cells take up some of the precipitate, and with it, the DNA. This process has been a preferred method of identifying many oncogenes.
*Another method is the use of cationic polymers such as DEAE-dextran or polyethylenimine (PEI). The negatively charged DNA binds to the polycation and the complex is taken up by the cell via endocytosis.
*Lipofection (or liposome transfection) is a technique used to inject genetic material into a cell by means of liposomes, which are vesicles that can easily merge with the cell membrane since they are both made of a phospholipid bilayer. Lipofection generally uses a positively charged (cationic) lipid (cationic liposomes or mixtures) to form an aggregate with the negatively charged (anionic) genetic material. This transfection technology performs the same tasks as other biochemical procedures utilizing polymers, DEAE-dextran, calcium phosphate, and electroporation. The efficiency of lipofection can be improved by treating transfected cells with a mild heat shock.
* Fugene is a series of widely used proprietary non-liposomal transfection reagents capable of directly transfecting a wide variety of cells with high efficiency and low toxicity.
*Dendrimer is a class of highly branched molecules based on various building blocks and synthesized through a convergent or a divergent method. These dendrimers bind the nucleic acids to form dendriplexes that then penetrate the cells. | 1 | Applied and Interdisciplinary Chemistry |
Bis(trimethylsilyl)amine is synthesized by treatment of trimethylsilyl chloride with ammonia:
:2 (CH)SiCl + 3 NH → [(CH)Si]NH + 2 NHCl
Ammonium nitrate together with triethylamine can be used instead. This method is also useful for N isotopic enrichment of HMDS.
Alkali metal bis(trimethylsilyl)amides result from the deprotonation of bis(trimethylsilyl)amine. For example, lithium bis(trimethylsilyl)amide (LiHMDS) is prepared using n-butyllithium:
:[(CH)Si]NH + BuLi → [(CH)Si]NLi + BuH
LiHMDS and other similar derivatives: sodium bis(trimethylsilyl)amide (NaHMDS) and potassium bis(trimethylsilyl)amide (KHMDS) are used as a non-nucleophilic bases in synthetic organic chemistry. | 0 | Theoretical and Fundamental Chemistry |
Anthropogenic changes to the natural greenhouse effect are sometimes referred to as the enhanced greenhouse effect.
This table shows the most important contributions to the overall greenhouse effect, without which the average temperature of Earths surface would be about , instead of around . This table also specifies tropospheric' ozone, because this gas has a cooling effect in the stratosphere, but a warming influence comparable to nitrous oxide and CFCs in the troposphere. | 1 | Applied and Interdisciplinary Chemistry |
The Warburg–Christian method is an ultraviolet spectroscopic protein and nucleic acid assay method based on the absorbance of UV light at 260 nm and 280 nm wavelengths. Proteins generally absorb light at 280 nanometers due to the presence of tryptophan and tyrosine. Nucleic acids absorb more at 260 nm, primarily due to purine and pyrimidine bases. The Warburg–Christian method combines measurements at these wavelengths to estimate the amounts of protein and nucleic acid present. Original description of the method appeared in 1941.
The method is named for its creators, the German cancer researcher Otto Heinrich Warburg, Nobel Prize winner, and his employee Walter Christian of the Kaiser Wilhelm Institute for Biology in Berlin. | 0 | Theoretical and Fundamental Chemistry |
Nitrogen, unlike its neighbor carbon, is much less likely to form chains that are stable at room temperature. Some examples of which are solid nitrogen, triazane, azide anion and triazoles. Even longer series with eight nitrogen atoms or more, such as 1,1'-Azobis-1,2,3-triazole, have been synthesized. These compounds have potential use as a convenient way to store large amount of energy. | 0 | Theoretical and Fundamental Chemistry |
Exome sequencing, also known as whole exome sequencing (WES), is a genomic technique for sequencing all of the protein-coding regions of genes in a genome (known as the exome). It consists of two steps: the first step is to select only the subset of DNA that encodes proteins. These regions are known as exons—humans have about 180,000 exons, constituting about 1% of the human genome, or approximately 30 million base pairs. The second step is to sequence the exonic DNA using any high-throughput DNA sequencing technology.
The goal of this approach is to identify genetic variants that alter protein sequences, and to do this at a much lower cost than whole-genome sequencing. Since these variants can be responsible for both Mendelian and common polygenic diseases, such as Alzheimer's disease, whole exome sequencing has been applied both in academic research and as a clinical diagnostic. | 1 | Applied and Interdisciplinary Chemistry |
Source:
* Kern Prize of the ETH Zurich (1949)
* Werner Prize of the Swiss Chemical Society (1956)
* Ruzicka Prize of the ETH Zurich (1958)
* Ernest Guenther Award (1966)
* Austrian Cross of Honour for Science and Art (1974)
* Welch Award (1974)
* Kirkwood Medal, Yale University (1976)
* Davy Medal (1978)
* Tetrahedron Prize for Creativity in Organic Chemistry (1981)
* Arthur C. Cope Award (1984)
* Wolf Prize in Chemistry of the Wolf Foundation, Tel Aviv, Israel (1986)
* Cothenius Medal (1991)
* Nakanishi Prize (1998)
* Oparin Medal (2002)
* Frank H. Westheimer Medal (Harvard University (2004)
* F.A. Cotton Medal for Excellence in Chemical Research of the American Chemical Society (2004)
* Paul Karrer Gold Medal (University of Zurich, 2008)
* Benjamin Franklin Medal in Chemistry from the Franklin Institute in Philadelphia, Pennsylvania (2008) | 0 | Theoretical and Fundamental Chemistry |
A very convenient way to get a quantitative understanding of the throttling process is by using diagrams such as h-T diagrams, h-P diagrams, and others. Commonly used are the so-called T-s diagrams. Figure 2 shows the T-s diagram of nitrogen as an example. Various points are indicated as follows:
As shown before, throttling keeps h constant. E.g. throttling from 200 bar and 300K (point a in fig. 2) follows the isenthalpic (line of constant specific enthalpy) of 430kJ/kg. At 1 bar it results in point b which has a temperature of 270K. So throttling from 200 bar to 1 bar gives a cooling from room temperature to below the freezing point of water. Throttling from 200 bar and an initial temperature of 133K (point c in fig. 2) to 1 bar results in point d, which is in the two-phase region of nitrogen at a temperature of 77.2K. Since the enthalpy is an extensive parameter the enthalpy in d (h) is equal to the enthalpy in e (h) multiplied with the mass fraction of the liquid in d (x) plus the enthalpy in f (h) multiplied with the mass fraction of the gas in d (1 − x). So
With numbers: 150 = x 28 + (1 − x) 230 so x is about 0.40. This means that the mass fraction of the liquid in the liquid–gas mixture leaving the throttling valve is 40%. | 0 | Theoretical and Fundamental Chemistry |
Condition three relates to the non-decomposability of an elementary mode and is partly what makes elementary modes interesting. The two other important features as indicated before are pathway uniqueness and thermodynamic plausibility. Decomposition implies that it is possible to represent a mode as a combination of two or more other modes. For example, a mode might be composed from two other modes, and :
If a mode can be decomposed, does it mean that the mode is not an elementary mode? Condition three provides a rule to determine whether a decomposition means that a given mode is an elementary mode or not. If it is only possible to decompose a given mode by introducing enzymes that are not used in the mode, then the mode is elementary. That is, is there more than one way to generate a pathway (i.e., something that can sustain a steady state) with the enzymes currently used in the mode? If so, then the mode is not elementary. To illustrate this subtle condition, consider the pathway shown in below.
This pathway represents a stylized rendition of glycolysis. Step three and six are reversible and correspond to triose phosphate isomerase and glycerol 3-phosphate dehydrogenase, respectively.
The network has four elementary flux modes, which are shown in the figure below.
The elementary flux mode vectors are shown below:
Note that it is possible to have negative entries in the set of elementary modes because they will correspond to the reversible steps. Of interest is the observation that the fourth vector, (where represents the transpose) can be formed from the sum of the first and second vectors. This suggests that the fourth vector is not an elementary mode.
However, this decomposition only works because we have introduced a new enzyme, (triose phosphate isomerase) which is not used in . It is, in fact impossible to decompose into pathways that can sustain a steady state with only the five steps, , used in the elementary mode. We conclude therefore that is an elementary mode. | 1 | Applied and Interdisciplinary Chemistry |
Microspheres are hollow, micron-sized carriers often formed via self-assembly of polymeric compounds which are most often used to encapsulate the active drug for delivery. Drug release is often achieved by diffusion through pores in the microsphere structure or by degradation of the microsphere shell. Some of the research currently being done uses advanced assembly techniques, such as precision particle fabrication (PPF), to create microspheres capable of sustained control over drug release. | 1 | Applied and Interdisciplinary Chemistry |
The activity coefficient of component i is found by differentiation of the excess Gibbs energy towards x.
This yields, when applied only to the first term and using the Gibbs–Duhem equation,:
In here A and A are constants which are equal to the logarithm of the limiting activity coefficients: and respectively.
When , which implies molecules of same molecular size but different polarity, the equations reduce to the one-parameter Margules activity model:
In that case the activity coefficients cross at x=0.5 and the limiting activity coefficients are equal. When A=0 the model reduces to the ideal solution, i.e. the activity of a compound is equal to its concentration (mole fraction). | 0 | Theoretical and Fundamental Chemistry |
Carbon monoxide bonds to transition metals using "synergistic pi* back-bonding". The M-C bonding has three components, giving rise to a partial triple bond. A sigma (σ) bond arises from overlap of the nonbonding (or weakly anti-bonding) sp-hybridized electron pair on carbon with a blend of d-, s-, and p-orbitals on the metal. A pair of pi (π) bonds arises from overlap of filled d-orbitals on the metal with a pair of π*-antibonding orbitals projecting from the carbon atom of the CO. The latter kind of binding requires that the metal have d-electrons, and that the metal is in a relatively low oxidation state (0 or +1) which makes the back-donation of electron density favorable. As electrons from the metal fill the π-antibonding orbital of CO, they weaken the carbon–oxygen bond compared with free carbon monoxide, while the metal–carbon bond is strengthened. Because of the multiple bond character of the M–CO linkage, the distance between the metal and carbon atom is relatively short, often less than 1.8 Å, about 0.2 Å shorter than a metal–alkyl bond. The M-CO and MC-O distance are sensitive to other ligands on the metal. Illustrative of these effects are the following data for Mo-C and C-O distances in Mo(CO) and Mo(CO)(4-methylpyridine): 2.06 vs 1.90 and 1.11 vs 1.18 Å.
Infrared spectroscopy is a sensitive probe for the presence of bridging carbonyl ligands. For compounds with doubly bridging CO ligands, denoted μ-CO or often just μ-CO, the bond stretching frequency ν is usually shifted by 100–200 cm to lower energy compared to the signatures of terminal CO, which are in the region 1800 cm. Bands for face capping (μ) CO ligands appear at even lower energies. In addition to symmetrical bridging modes, CO can be found to bridge asymmetrically or through donation from a metal d orbital to the π* orbital of CO. The increased π-bonding due to back-donation from multiple metal centers results in further weakening of the C–O bond. | 0 | Theoretical and Fundamental Chemistry |
Acinetobacter anitratus, Acinetobacter calcoaceticus, Actinomyces odontolyticus, Aeromonas hydrophila, Bacteroides distasonis, Bacteroides uniformis, and Clostridium perfringens are generally susceptible to imipenem, while Acinetobacter baumannii, some Acinetobacter spp., Bacteroides fragilis, and Enterococcus faecalis have developed resistance to imipenem to varying degrees. Not many species are resistant to imipenem except Pseudomonas aeruginosa (Oman) and Stenotrophomonas maltophilia. | 0 | Theoretical and Fundamental Chemistry |
The liquid in the outer jacket is heated until no more air escapes from the side tube. Then, a graduated tube filled with water is inverted over the side tube dipping in a trough filled with water. A small quantity of substance is weighed exactly in a small stoppered bottle and is dropped in the Victor Meyer's tube and sealed immediately. The bottle falls on the asbestos pad and its contents suddenly change into vapour, blows out the stopper and displaces an equal volume of air in graduated tube. The volume of air displaced is measured by taking the graduated tube out, closing its mouth with thumb and dipping in a jar filled with water. When water levels inside and outside the tube is equal, the volume of air displaced is noted. The atmospheric pressure and laboratory temperature are noted. | 0 | Theoretical and Fundamental Chemistry |
FCS almost always refers to the single point, single channel, temporal autocorrelation measurement, although the term "fluorescence correlation spectroscopy" out of its historical scientific context implies no such restriction. FCS has been extended in a number of variations by different researchers, with each extension generating another name (usually an acronym). | 0 | Theoretical and Fundamental Chemistry |
Plants produce chemicals at the injury site that signal the presence of damage and may help to reduce further damage. The chemicals involved depend to some extent on the plant species, though several of them are shared among species; and the signals given depend on the cause of the injury. Plants injured by spider mites release volatile chemicals that attract predatory mites, serving to reduce the attack on the plants. As another example, maize plants damaged by the caterpillars of noctuid moths release a mixture of terpenoid substances which attract the parasitoid wasp Cotesia marginiventris, which kills caterpillars. Many plants give off such herbivory-induced signals. | 1 | Applied and Interdisciplinary Chemistry |
A complete description of hypervalent molecules arises from consideration of molecular orbital theory through quantum mechanical methods. An LCAO in, for example, sulfur hexafluoride, taking a basis set of the one sulfur 3s-orbital, the three sulfur 3p-orbitals, and six octahedral geometry symmetry-adapted linear combinations (SALCs) of fluorine orbitals, a total of ten molecular orbitals are obtained (four fully occupied bonding MOs of the lowest energy, two fully occupied intermediate energy non-bonding MOs and four vacant antibonding MOs with the highest energy) providing room for all 12 valence electrons. This is a stable configuration only for SX molecules containing electronegative ligand atoms like fluorine, which explains why SH is not a stable molecule. In the bonding model, the two non-bonding MOs (1e) are localized equally on all six fluorine atoms. | 0 | Theoretical and Fundamental Chemistry |
The BASF-oxo process starts mostly with higher olefins and relies on cobalt carbonyl-based catalyst. By conducting the reaction at low temperatures, one observes increased selectivity favoring the linear product. The process is carried out at a pressure of about 30 MPa and in a temperature range of 150 to 170 °C. The cobalt is recovered from the liquid product by oxidation to water-soluble Co, followed by the addition of aqueous formic or acetic acids. This process gives an aqueous phase of cobalt, which can then be recycled. Losses are compensated by the addition of cobalt salts. | 0 | Theoretical and Fundamental Chemistry |
Dimercaprol and dimercaptosuccinic acid are chelating agents that sequester the arsenic away from blood proteins and are used in treating acute arsenic poisoning. The most important side effect is hypertension. Dimercaprol is considerably more toxic than succimer. Dimercaptosuccinic acid monoesters, e.g. MiADMSA, are promising antidotes for arsenic poisoning. | 1 | Applied and Interdisciplinary Chemistry |
Over the years, the utility of molecular logic gates has been explored in a wide range of fields such as chemical and biological detection, the pharmaceutical and food industries, and the emerging fields of nanomaterials and chemical computing. | 0 | Theoretical and Fundamental Chemistry |
Depending on the dosage form and route of administration, mucoadhesives may be used for either local or systemic drug delivery. An overview on the mucoadhesive properties of mucoadhesives is provided by Vjera Grabovac and Andreas Bernkop-Schnürch. The bioavailability of such drugs is affected by many factors unique to each route of application. In general, mucoadhesives work to increase the contact time at these sites, prolonging the residence time and maintaining an effective release rate. These polymeric coatings may be applied to a wide variety of liquid and solid dosages, each specially suited for the route of administration. | 1 | Applied and Interdisciplinary Chemistry |
Asemota conducted PhD research at the University of Benin and Frankfurt University, where she studied the molecular genetics and metabolism of the browning of yam tubers in storage.
Upon moving to Jamaica, prompted by ongoing problems with production and storage in the Jamaican yam industry, Asemota continued researching yams, founding the multidisciplinary UWI Yam Biotechnology Project. Initially, Asemota investigated the biochemical effects of removing yam heads at harvest, a common farming practice in Jamaica. Over the ensuing decades, Asemota's research team has investigated many aspects of yam biochemistry and physiology, from DNA fingerprinting studies of Jamaican yam varieties to the carbohydrate metabolism of yam tubers in storage.
In addition to her work on yam production and storage, Asemota has studied the metabolic effects of yams and yam-derived products on animal models of diseases such as diabetes. More recently, the Yam Biotechnology Project has moved towards a farm to finished products strategy, with the goal of producing yam-based food, medical, and biofuel products to benefit the Jamaican economy. She has also applied similar research techniques to other types of tropical crop.
Asemota has served as Principal Investigator for the National Institute of Health (NIH) and National Science Foundation (NSF) grants. She has lectured undergraduates, postgraduates and postdoctoral levels worldwide, and has supervised or advised at least 30 postgraduate students in Biochemistry or Biotechnology. She has over 250 publications, and owns four patents from her research. | 1 | Applied and Interdisciplinary Chemistry |
(sorted alphabetically)
* Burapha University
** Department of Chemical Engineering
* Chiang Mai University
** [https://web.archive.org/web/20060221195845/http://www.science.cmu.ac.th/department/ic/ Department of Industrial Chemistry]
* Chulalongkorn University
** [https://web.archive.org/web/20060619212238/http://www.chem.eng.chula.ac.th/ Department of Chemical Engineering]
** [http://www.chemtech.sc.chula.ac.th/ Department of Chemical Technology]
** [http://www.ppc.chula.ac.th/ The Petroleum and Petrochemical College]
* Kasetsart University
** [http://www.che.eng.ku.ac.th/ Department of Chemical Engineering]
* Khon Kaen University
** [https://web.archive.org/web/20070330150329/http://www.en.kku.ac.th/dept/che/ Department of Chemical Engineering]
* King Mongkut's Institute of Technology Ladkrabang
** [https://web.archive.org/web/20060604013609/http://www.kmitl.ac.th/che/ Department of Chemical Engineering]
* King Mongkut's University of Technology North Bangkok
** [http://www.che.kmutnb.ac.th/ Department of Chemical Engineering]
** [https://web.archive.org/web/20090221000826/http://www.ic.kmutnb.ac.th/ Department of Industrial Chemistry]
* King Mongkut's University of Technology Thonburi
** [https://web.archive.org/web/20060623130130/http://www.che.eng.kmutt.ac.th/ Department of Chemical Engineering]
* Mahanakorn University of Technology
** [https://web.archive.org/web/20060716195522/http://www.eng.mut.ac.th/Chemical/ Department of Chemical Engineering]
* Mahidol University
** [https://web.archive.org/web/20060623124931/http://www.eg.mahidol.ac.th/dept/egche/pages/?page=1&lang=en Department of Chemical Engineering]
* Prince of Songkla University
** [https://web.archive.org/web/20051227231948/http://homepage.eng.psu.ac.th/chem/index.html Department of Chemical Engineering]
* Rajamangala University of Technology Thanyaburi (Klong 6)
** [https://web.archive.org/web/20060603050345/http://www.en.rmut.ac.th/che/ Department of Chemical Engineering]
* Rangsit University
** [http://www.rsu.ac.th/engineer/che/index.htm Department of Chemical and Material Engineering]
* Silpakorn University
** [https://web.archive.org/web/20060515114818/http://www.eng.su.ac.th/che/viewtopic.php?id=main Department of Chemical Engineering]
* Srinakharinwirot University
** [https://web.archive.org/web/20060516172852/http://eng.swu.ac.th/department/che_dept.html Department of Chemical Engineering]
* Suranaree University of Technology
** [http://www.sut.ac.th/engineering/Chem/ School of Chemical Engineering]
* Thammasat University
** [http://www.che.engr.tu.ac.th/ Department of Chemical Engineering]
* Ubon Ratchathani University
** [https://web.archive.org/web/20050312022533/http://web.eng.ubu.ac.th/%7Echemical/indexthai.htm Department of Chemical Engineering] | 1 | Applied and Interdisciplinary Chemistry |
Petroleum, also known as crude oil or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name petroleum covers both naturally occurring unprocessed crude oil and petroleum products that consist of refined crude oil.
Petroleum is primarily recovered by oil drilling. Drilling is carried out after studies of structural geology, sedimentary basin analysis, and reservoir characterisation. Unconventional reserves such as oil sands and oil shale exist.
Once extracted, oil is refined and separated, most easily by distillation, into innumerable products for direct use or use in manufacturing. Products include fuels such as petrol (gasoline), diesel, kerosene and jet fuel; asphalt and lubricants; chemical reagents used to make plastics; solvents, textiles, refrigerants, paint, synthetic rubber, fertilizers, pesticides, pharmaceuticals, and thousands of others. Petroleum is used in manufacturing a vast variety of materials essential for modern life, and it is estimated that the world consumes about each day. Petroleum production can be extremely profitable and was critical to global economic development in the 20th century, with some countries, so-called "oil states", gaining significant economic and international power because of their control of oil production.
Petroleum exploitation can be damaging to the environment and human health. Extraction, refining and burning of petroleum fuels all release large quantities of greenhouse gases, so petroleum is one of the major contributors to climate change. Other negative environmental effects include direct releases, such as oil spills, and as well as air and water pollution at almost all stages of use. These environmental effects have direct and indirect health consequences for humans. Oil has also been a source of internal and inter-state conflict, leading to both state-led wars and other resource conflicts. Production of petroleum is estimated to reach peak oil before 2035 as global economies lower dependencies on petroleum as part of climate change mitigation and a transition towards renewable energy and electrification. Oil has played a key role in industrialization and economic development. | 0 | Theoretical and Fundamental Chemistry |
Chowdhury was born on 1 August 1930 to Abdul Aziz Chowdhury, an educationist and Afifa Khatun of Kunja Sreepur village, in Comilla District, Bengal Presidency. | 0 | Theoretical and Fundamental Chemistry |
Small nuclear ribonucleoproteins (snRNPs) assemble in a tightly orchestrated and regulated process that involves both the cell nucleus and cytoplasm. | 1 | Applied and Interdisciplinary Chemistry |
In condensed matter physics, a time crystal is a quantum system of particles whose lowest-energy state is one in which the particles are in repetitive motion. The system cannot lose energy to the environment and come to rest because it is already in its quantum ground state. Time crystals were first proposed theoretically by Frank Wilczek in 2012 as a time-based analogue to common crystals – whereas the atoms in crystals are arranged periodically in space, the atoms in a time crystal are arranged periodically in both space and time. Several different groups have demonstrated matter with stable periodic evolution in systems that are periodically driven. In terms of practical use, time crystals may one day be used as quantum computer memory.
The existence of crystals in nature is a manifestation of spontaneous symmetry breaking, which occurs when the lowest-energy state of a system is less symmetrical than the equations governing the system. In the crystal ground state, the continuous translational symmetry in space is broken and replaced by the lower discrete symmetry of the periodic crystal. As the laws of physics are symmetrical under continuous translations in time as well as space, the question arose in 2012 as to whether it is possible to break symmetry temporally, and thus create a "time crystal" that is resistant to entropy.
If a discrete time-translation symmetry is broken (which may be realized in periodically driven systems), then the system is referred to as a discrete time crystal. A discrete time crystal never reaches thermal equilibrium, as it is a type (or phase) of non-equilibrium matter. Breaking of time symmetry can only occur in non-equilibrium systems. Discrete time crystals have in fact been observed in physics laboratories as early as 2016 (published in 2017). One example of a time crystal, which demonstrates non-equilibrium, broken time symmetry is a constantly rotating ring of charged ions in an otherwise lowest-energy state. | 0 | Theoretical and Fundamental Chemistry |
# The critical temperature of the fluid should be well above the highest temperature existing in the proposed cycle. Evaporation of the working fluid — and thus the significant addition of heat — can then ensue at the maximum temperature of the cycle. This results in a relatively high cycle efficiency.
# The slope ds/dT of the saturated vapour line in T–s diagram (see Chapter Classification of pure (single-component) working fluids) should be nearly zero in the applied pressure ratio of the expander. This prevents significant moisture (liquid droplet) formation or excessive superheat occurring during the expansion. It also ensures that all the heat rejection in the condenser occurs at the minimum cycle temperature, which increases the thermal efficiency.
# A low value for the specific heat of the liquid or, alternatively, a low ratio of number of atoms per molecule divided by the molecular weight and a high ratio of the latent heat of vaporisation to the liquids specific heat should appertain. This reduces the amount of the heat required to raise the temperature of the subcooled liquid of the working fluid to the saturation temperature corresponding to the pressure in the Rankinecycles evaporator. So most of the heat is added at the maximum cycle temperature, and the Rankine cycle can approach more closely the Carnot cycle. | 0 | Theoretical and Fundamental Chemistry |
The direhorse (Pali in Navi ) is a bioluminescent, hexapodal, superficially equine animal. It is scientifically known as Equidirus hoplites. The Navi use the direhorse to hunt. The direhorse was conceived and designed by Cameron and Stan Winston Studios. The direhorse is grey with blue stripes and stands tall, long. The Navi "break" a direhorse by connecting the fleshy tip of their hair to the animals antennae. Xenobiologists call this a neural whip. Once intertwined, the Navi rider can communicate motor commands instantly through the neural interface; however, this connection does not lead to a lifelong, exclusive bond, as it does with the mountain banshee. Cameron described the creature as a "six-legged alien Clydesdale with moth-like antennae". The direhorse uses its long tongue to eat the sap out of pitcher plants. | 1 | Applied and Interdisciplinary Chemistry |
When a neurotransmitter is released at a synapse, it reaches its highest concentration inside the narrow space of the synaptic cleft, but some of it is certain to diffuse away before being reabsorbed or broken down. If it diffuses away, it has the potential to activate receptors that are located either at other synapses or on the membrane away from any synapse. The extrasynaptic activity of a neurotransmitter is known as volume transmission. It is well established that such effects occur to some degree, but their functional importance has long been a matter of controversy.
Recent work indicates that volume transmission may be the predominant mode of interaction for some special types of neurons. In the mammalian cerebral cortex, a class of neurons called neurogliaform cells can inhibit other nearby cortical neurons by releasing the neurotransmitter GABA into the extracellular space. Along the same vein, GABA released from neurogliaform cells into the extracellular space also acts on surrounding astrocytes, assigning a role for volume transmission in the control of ionic and neurotransmitter homeostasis. Approximately 78% of neurogliaform cell boutons do not form classical synapses. This may be the first definitive example of neurons communicating chemically where classical synapses are not present. | 1 | Applied and Interdisciplinary Chemistry |
Some materials, such as certain silicate minerals, absorb little or no solar radiation, but may still participate in light-driven reactions by mechanisms other than direct transfer of energy to reactants. | 0 | Theoretical and Fundamental Chemistry |
In the United States, the National Weather Service has standardized its measurements on the Class A evaporation pan, a cylinder with a diameter of 47.5 in (120.7 cm) that has a depth of 10 in (25 cm). The pan rests on a carefully leveled, wooden base and is often enclosed by a chain link fence to prevent animals drinking from it. Evaporation is measured daily as the depth of water (in inches) evaporates from the pan. The measurement day begins with the pan filled to exactly two inches (5 cm) from the pan top. At the end of 24 hours, the amount of water to refill the pan to exactly two inches from its top is measured.
If precipitation occurs in the 24-hour period, it is taken into account in calculating the evaporation. Sometimes precipitation is greater than evaporation, and measured increments of water must be dipped from the pan. Evaporation cannot be measured in a Class A pan when the pan's water surface is frozen.
The Class A Evaporation Pan is of limited use on days with rainfall events of >30mm (203mm rain gauge) unless it is emptied more than once per 24hours. Analysis of the daily rainfall and evaporation readings in areas with regular heavy rainfall events shows that almost without fail, on days with rainfall in excess of 30mm (203mm Rain Gauge) the daily evaporation is spuriously higher than other days in the same month where conditions more receptive to evaporation prevailed.
The most common and obvious error is in daily rainfall events of >55mm (203mm rain gauge) where the Class A Evaporation pan will likely overflow.
The less obvious, and therefore more concerning, is the influence of heavy or intense rainfall causing spuriously high daily evaporation totals without obvious overflow. | 1 | Applied and Interdisciplinary Chemistry |
To understand and predict the behavior of the MR fluid it is necessary to model the fluid mathematically, a task slightly complicated by the varying material properties (such as yield stress).
As mentioned above, smart fluids are such that they have a low viscosity in the absence of an applied magnetic field, but become quasi-solid with the application of such a field. In the case of MR fluids (and ER), the fluid actually assumes properties comparable to a solid when in the activated ("on") state, up until a point of yield (the shear stress above which shearing occurs). This yield stress (commonly referred to as apparent yield stress) is dependent on the magnetic field applied to the fluid, but will reach a maximum point after which increases in magnetic flux density have no further effect, as the fluid is then magnetically saturated. The behavior of a MR fluid can thus be considered similar to a Bingham plastic, a material model which has been well-investigated.
However, MR fluid does not exactly follow the characteristics of a Bingham plastic. For example, below the yield stress (in the activated or "on" state), the fluid behaves as a viscoelastic material, with a complex modulus that is also known to be dependent on the magnetic field intensity. MR fluids are also known to be subject to shear thinning, whereby the viscosity above yield decreases with increased shear rate. Furthermore, the behavior of MR fluids when in the "off" state is also non-Newtonian and temperature dependent, however it deviates little enough for the fluid to be ultimately considered as a Bingham plastic for a simple analysis.
Thus our model of MR fluid behavior in the shear mode becomes:
Where = shear stress; = yield stress; = Magnetic field intensity = Newtonian viscosity; is the velocity gradient in the z-direction. | 1 | Applied and Interdisciplinary Chemistry |
The Kantrowitz limit is a fundamental concept in the Hyperloop, a proposed high-speed transportation system. The Hyperloop moves passengers in sealed pods through a partial-vacuum tube at high-subsonic speeds. As the air in the tube moves into and around the smaller cross-sectional area between the pod and tube, the air flow must speed up due to the continuity principle. If the pod is travelling through the tube fast enough, the air flow around the pod will reach the speed of sound, and the flow will become choked, resulting in large air resistance on the pod. The condition that determines if the flow around the pod chokes is the Kantrowitz limit. The Kantrowitz limit therefore acts a "speed limit" - for a given ratio of tube area and pod area, there is a maximum speed that the pod can travel before flow around the pod chokes and air resistance sharply increases.
In order to break through the speed limit set by the Kantrowitz limit, there are two possible approaches. The first would increase the diameter of the tube in order to provide more bypass area for the air around the pod, preventing the flow from choking. This solution is not very practical in practice however, as the tube would have to be built very large, and logistical costs of such a large tube are impractical.
As an alternative, it has been found during the main study of the Swissmetro project (1993 -1998) that a turbine can be installed on board of the vehicle to push the displaced air across the vehicle body (TurboSwissMetro) and hence to reduce far field impacts. This would avoid the continuous increase of the vehicle drag due to the choking of the flow at the cost of the power required to drive the turbine and hence enable larger speeds. The computer program NUMSTA has been developed in this context; it allows to simulate the dynamical interaction of several high speed vehicles in complex tunnel networks including the choking effect.
This idea has also been proposed by Elon Musk in his 2013 Hyperloop Alpha paper where a compressor is placed at the front of the pod. The compressor actively draws in air from the front of the pod and transfers it to the rear, bypassing the gap between pod and tube while diverting a fraction of the flow to power a low-friction air-bearing suspension system. The inclusion of a compressor in the Hyperloop pod circumvents the Kantrowitz limit, allowing the pod to travel at speeds over 700 mph (about 1126 km/h) in a relatively narrow tube.
For a pod travelling through a tube, the Kantrowitz limit is given as the ratio of tube area to bypass area both around the outside of the pod and through any air-bypass compressor: | 1 | Applied and Interdisciplinary Chemistry |
He was one of the founding members of a Pakistani militant organisation called Ummah Tameer-e-Nau. He was accused of travelling through Afghanistan without notifying the Government of Pakistan. Along with fellow nuclear scientist Sultan Bashiruddin Mahmood, he was arrested in October 2001 in Islamabad by a joint-operation of the Inter-Services Intelligence and the Federal Investigation Agency, because of their connections to the Taliban.
In the hope of securing a quick release from the intelligence agencies and returning to his research at the PAEC, he readily confessed. The FIA and ISIs joint-Intelligence report, which was given to the Parliaments Committee on National Security and Defence Affairs, stated that Majeed admitted that Osama bin Laden had asked them to build either a radiological or a biological weapon. He was subsequently designated by the Al-Qaida and Taliban Sanctions Committee of the Security Council in December 2001.
American CIA intelligence officials said that the first interrogation of the two Pakistani scientists concluded that Mahmood and Majeed did not know enough to help build a nuclear weapon. "These two guys were nuclear scientists who didnt know how to build one themselves," the American official said. "If you had to have guys go bad, these are the guys youd want. They didn't know much." | 0 | Theoretical and Fundamental Chemistry |
The RNA world hypothesis, if true, has important implications for the definition of life and the origin of life. For most of the time that followed Franklin, Watson and Crick's elucidation of DNA structure in 1953, life was largely defined in terms of DNA and proteins: DNA and proteins seemed the dominant macromolecules in the living cell, with RNA only aiding in creating proteins from the DNA blueprint.
The RNA world hypothesis places RNA at center-stage when life originated. The RNA world hypothesis is supported by the observations that ribosomes are ribozymes: the catalytic site is composed of RNA, and proteins hold no major structural role and are of peripheral functional importance. This was confirmed with the deciphering of the 3-dimensional structure of the ribosome in 2001. Specifically, peptide bond formation, the reaction that binds amino acids together into proteins, is now known to be catalyzed by an adenine residue in the rRNA.
RNAs are known to play roles in other cellular catalytic processes, specifically in the targeting of enzymes to specific RNA sequences. In eukaryotes, the processing of pre-mRNA and RNA editing take place at sites determined by the base pairing between the target RNA and RNA constituents of small nuclear ribonucleoproteins (snRNPs). Such enzyme targeting is also responsible for gene down regulation through RNA interference (RNAi), where an enzyme-associated guide RNA targets specific mRNA for selective destruction. Likewise, in eukaryotes the maintenance of telomeres involves copying of an RNA template that is a constituent part of the telomerase ribonucleoprotein enzyme. Another cellular organelle, the vault, includes a ribonucleoprotein component, although the function of this organelle remains to be elucidated. | 0 | Theoretical and Fundamental Chemistry |
A number of lactose derivatives or analogs have been described that are useful for work with the lac operon. These compounds are mainly substituted galactosides, where the glucose moiety of lactose is replaced by another chemical group.
* Isopropyl-β-D-thiogalactopyranoside (IPTG) is frequently used as an inducer of the lac operon for physiological work. IPTG binds to repressor and inactivates it, but is not a substrate for β-galactosidase. One advantage of IPTG for in vivo studies is that since it cannot be metabolized by E. coli. Its concentration remains constant and the rate of expression of lac p/o-controlled genes is not a variable in the experiment. IPTG intake is dependent on the action of lactose permease in P. fluorescens, but not in E. coli.
* Phenyl-β-D-galactose (phenyl-Gal) is a substrate for β-galactosidase, but does not inactivate repressor and so is not an inducer. Since wild type cells produce very little β-galactosidase, they cannot grow on phenyl-Gal as a carbon and energy source. Mutants lacking repressor are able to grow on phenyl-Gal. Thus, minimal medium containing only phenyl-Gal as a source of carbon and energy is selective for repressor mutants and operator mutants. If 10 cells of a wild type strain are plated on agar plates containing phenyl-Gal, the rare colonies which grow are mainly spontaneous mutants affecting the repressor. The relative distribution of repressor and operator mutants is affected by the target size. Since the lacI gene encoding repressor is about 50 times larger than the operator, repressor mutants predominate in the selection.
* Thiomethyl galactoside [TMG] is another lactose analog. These inhibit the lacI repressor. At low inducer concentrations, both TMG and IPTG can enter the cell through the lactose permease. However at high inducer concentrations, both analogs can enter the cell independently. TMG can reduce growth rates at high extracellular concentrations.
* Other compounds serve as colorful indicators of β-galactosidase activity.
** ONPG is cleaved to produce the intensely yellow compound, orthonitrophenol and galactose, and is commonly used as a substrate for assay of β-galactosidase in vitro.
** Colonies that produce β-galactosidase are turned blue by X-gal (5-bromo-4-chloro-3-indolyl-β-D-galactoside) which is an artificial substrate for B-galactosidase whose cleavage results in galactose and 4-Cl,3-Br indigo thus producing a deep blue color.
* Allolactose is an isomer of lactose and is the inducer of the lac operon. Lactose is galactose-β(1→4)-glucose, whereas allolactose is galactose-β(1→6)-glucose. Lactose is converted to allolactose by β-galactosidase in an alternative reaction to the hydrolytic one. A physiological experiment which demonstrates the role of LacZ in production of the "true" inducer in E. coli cells is the observation that a null mutant of lacZ can still produce LacY permease when grown with IPTG, a non-hydrolyzable analog of allolactose, but not when grown with lactose. The explanation is that processing of lactose to allolactose (catalyzed by β-galactosidase) is needed to produce the inducer inside the cell. | 1 | Applied and Interdisciplinary Chemistry |
Wilkinson was married to Lise Schou, a Danish plant physiologist whom he had met at Berkeley. They had two daughters, Anne and Pernille. | 0 | Theoretical and Fundamental Chemistry |
Trifluoromethanesulfonic acid was first synthesized in 1954 by Robert Haszeldine and Kidd by the following reaction: | 0 | Theoretical and Fundamental Chemistry |
In all of the above examples, the initial nuclide decays into just one product. Consider the case of one initial nuclide that can decay into either of two products, that is and in parallel. For example, in a sample of potassium-40, 89.3% of the nuclei decay to calcium-40 and 10.7% to argon-40. We have for all time :
which is constant, since the total number of nuclides remains constant. Differentiating with respect to time:
defining the total decay constant in terms of the sum of partial decay constants and :
Solving this equation for :
where is the initial number of nuclide A. When measuring the production of one nuclide, one can only observe the total decay constant . The decay constants and determine the probability for the decay to result in products or as follows:
because the fraction of nuclei decay into while the fraction of nuclei decay into . | 0 | Theoretical and Fundamental Chemistry |
A strong base deprotonates the dicarbonyl α-carbon. This carbon is preferred over the methyl carbon because the formed enolate is conjugated and thus resonance stabilized. The carbon then undergoes nucleophilic substitution. When heated with aqueous acid, the newly alkylated ester is hydrolyzed to a β-keto acid, which is decarboxylated to form a methyl ketone. | 0 | Theoretical and Fundamental Chemistry |
Formic acid is produced as a primary product from CORR over diverse catalysts.
Catalysts that promote Formic Acid production from CO operate by strongly binding to both oxygen atoms of CO, allowing protons to attack the central carbon. After attacking the central carbon, one proton attaching to an oxygen results in the creation of formate. Indium catalysts promote formate production because the Indium-Oxygen binding energy is stronger than the Indium-Carbon binding energy. This promotes the production of formate instead of Carbon Monoxide. | 1 | Applied and Interdisciplinary Chemistry |
To begin to generate an isolobal fragment, the molecule needs to follow certain criteria. Molecules based around main group elements should satisfy the octet rule when all bonding and nonbonding molecular orbitals (MOs) are filled and all antibonding MOs are empty. For example, methane is a simple molecule from which to form a main group fragment. The removal of a hydrogen atom from methane generates a methyl radical. The molecule retains its molecular geometry as the frontier orbital points in the direction of the missing hydrogen atom. Further removal of hydrogen results in the formation of a second frontier orbital. This process can be repeated until only one bond remains to the molecule's central atom.
The isolobal fragments of octahedral complexes, such as type ML, can be created in a similar fashion. Transition metal complexes should initially satisfy the eighteen electron rule, have no net charge, and their ligands should be two electron donors (Lewis bases). Consequently, the metal center for the ML starting point must be d. Removal of a ligand is analogous to the removal of hydrogen of methane in the previous example resulting in a frontier orbital, which points toward the removed ligand. Cleaving the bond between the metal center and one ligand results in a radical complex. In order to satisfy the zero-charge criteria the metal center must be changed. For example, a MoL complex is d and neutral. However, removing a ligand to form the first frontier orbital would result in a complex because Mo has obtained an additional electron making it d. To remedy this, Mo can be exchanged for Mn, which would form a neutral d complex in this case, as shown in Figure 3. This trend can continue until only one ligand is left coordinated to the metal center. | 0 | Theoretical and Fundamental Chemistry |
[https://gallica.bnf.fr/ark:/12148/bpt6k56745752/f70 G. Piobert, Mémoire sur les poudres de guerre, des différents procédés de frabrication (1844)] | 0 | Theoretical and Fundamental Chemistry |
To observe one-to-one binding between a single host (H) and guest (G) using UV/Vis absorbance, the Benesi–Hildebrand method can be employed. The basis behind this method is that the acquired absorbance should be a mixture of the host, guest, and the host–guest complex.
With the assumption that the initial concentration of the guest (G) is much larger than the initial concentration of the host (H), then the absorbance from H should be negligible.
The absorbance can be collected before and following the formation of the HG complex. This change in absorbance (ΔA) is what is experimentally acquired, with A being the initial absorbance before the interaction of HG and A being the absorbance taken at any point of the reaction.
Using the Beer–Lambert law, the equation can be rewritten with the absorption coefficients and concentrations of each component.
Due to the previous assumption that , one can expect that [G] = [G]. Δε represents the change in value between ε and ε.
A binding isotherm can be described as "the theoretical change in the concentration of one component as a function of the concentration of another component at constant temperature." This can be described by the following equation:
By substituting the binding isotherm equation into the previous equation, the equilibrium constant K can now be correlated to the change in absorbance due to the formation of the HG complex.
Further modifications results in an equation where a double reciprocal plot can be made with 1/ΔA as a function of 1/[G]. Δε can be derived from the intercept while K can be calculated from the slope. | 0 | Theoretical and Fundamental Chemistry |
Lucium was the proposed name for an alleged new element found by chemist Prosper Barrière in 1896 in the mineral monazite. Later, William Crookes confirmed that the new element was actually an impure sample of yttrium. | 1 | Applied and Interdisciplinary Chemistry |
Chromatography is a common technique used in the field of Forensic Science. Chromatography is a method of separating the components of a mixture from a mobile phase. Chromatography is an essential tool used in forensic science, helping analysts identify and compare trace amounts of samples including ignitable liquids, drugs, and biological samples. Many laboratories utilize gas chromatography/mass spectrometry (GC/MS) to examine these kinds of samples; this analysis provides rapid and reliant data to identify samples in question. | 0 | Theoretical and Fundamental Chemistry |
Children may be at greater risk for adverse reactions to repellents, in part, because their exposure may be greater.
Children can be at greater risk of accidental eye contact or ingestion.
As with chemical exposures in general, pregnant women should take care to avoid exposures to repellents when practical, as the fetus may be vulnerable.
Some experts also recommend against applying chemicals such as DEET and sunscreen simultaneously since that would increase DEET penetration. Canadian researcher, Xiaochen Gu, a professor at the University of Manitoba's faculty of Pharmacy who led a study about mosquitos, advises that DEET should be applied 30 or more minutes later. Gu also recommends insect repellent sprays instead of lotions which are rubbed into the skin "forcing molecules into the skin".
Regardless of which repellent product used, it is recommended to read the label before use and carefully follow directions. Usage instructions for repellents vary from country to country. Some insect repellents are not recommended for use on younger children.
In the DEET Reregistration Eligibility Decision (RED) the United States Environmental Protection Agency (EPA) reported 14 to 46 cases of potential DEET associated seizures, including 4 deaths. The EPA states: "... it does appear that some cases are likely related to DEET toxicity," but observed that with 30% of the US population using DEET, the likely seizure rate is only about one per 100 million users.
The Pesticide Information Project of Cooperative Extension Offices of Cornell University states that, "Everglades National Park employees having extensive DEET exposure were more likely to have insomnia, mood disturbances and impaired cognitive function than were lesser exposed co-workers".
The EPA states that citronella oil shows little or no toxicity and has been used as a topical insect repellent for 60 years. However, the EPA also states that citronella may irritate skin and cause dermatitis in certain individuals. Canadian regulatory authorities concern with citronella based repellents is primarily based on data-gaps in toxicology, not on incidents.
Within countries of the European Union, implementation of Regulation 98/8/EC, commonly referred to as the Biocidal Products Directive, has severely limited the number and type of insect repellents available to European consumers. Only a small number of active ingredients have been supported by manufacturers in submitting dossiers to the EU Authorities.
In general, only formulations containing DEET, icaridin (sold under the trade name Saltidin and formerly known as Bayrepel or KBR3023), IR3535 and citriodiol (p-menthane-3,8-diol) are available. Most "natural" insect repellents such as citronella, neem oil, and herbal extracts are no longer permitted for sale as insect repellents in the EU due to their lack of effectiveness; this does not preclude them from being sold for other purposes, as long as the label does not indicate they are a biocide (insect repellent). | 1 | Applied and Interdisciplinary Chemistry |
Current association studies have focused on common variation across the genome, as these are the easiest to identify with our current assays. However, disease-causing variants of large effect have been found to lie within exomes in candidate gene studies, and because of negative selection, are found in much lower allele frequencies and may remain untyped in current standard genotyping assays. Whole genome sequencing is a potential method to assay novel variant across the genome. However, in complex disorders (such as autism), a large number of genes are thought to be associated with disease risk. This heterogeneity of underlying risk means that very large sample sizes are required for gene discovery, and thus whole genome sequencing is not particularly cost-effective. This sample size issue is alleviated by the development of novel advanced analytic methods, which effectively map disease genes despite the genetic mutations are rare at variant level. In addition, variants in coding regions have been much more extensively studied and their functional implications are much easier to derive, making the practical applications of variants within the targeted exome region more immediately accessible.
Exome sequencing in rare variant gene discovery remains a very active and ongoing area of research, and there is growing evidence that a significant burden of risk is observed across sets of genes. The exome sequencing has been reported rare variants in KRT82 gene in the autoimmune disorder Alopecia Areata. | 1 | Applied and Interdisciplinary Chemistry |
A typical humic substance is a mixture of many molecules, some of which are based on a motif of aromatic nuclei with phenolic and carboxylic substituents, linked together; the illustration shows a typical structure.
The functional groups that contribute most to surface charge and reactivity of humic substances are phenolic and carboxylic groups. Humic acids behave as mixtures of dibasic acids, with a pK value around 4 for protonation of carboxyl groups and around 8 for protonation of phenolate groups. There is considerable overall similarity among individual humic acids. For this reason, measured pK values for a given sample are average values relating to the constituent species. The other important characteristic is charge density. The molecules may form a supramolecular structure held together by non-covalent forces, such as van der Waals force, π-π, and CH-π bonds.
The presence of carboxylate and phenolate groups gives the humic acids the ability to form complexes with ions such as Mg, Ca, Fe, and Fe. Many humic acids have two or more of these groups arranged so as to enable the formation of chelate complexes. The formation of (chelate) complexes is an important aspect of the biological role of humic acids in regulating bioavailability of metal ions. | 0 | Theoretical and Fundamental Chemistry |
Fructosephosphates are sugar phosphates based upon fructose, and are common in the biochemistry of cells.
Fructosephosphates play integral roles in many metabolic pathways, particularly glycolysis, gluconeogenesis and the pentose phosphate pathway.
The major biologically active fructosephosphates are:
*Fructose 1-phosphate
*Fructose 2-phosphate
*Fructose 3-phosphate
*Fructose 6-phosphate
*Fructose 1,6-bisphosphate
*Fructose 2,6-bisphosphate | 1 | Applied and Interdisciplinary Chemistry |
After graduation Hussein joined Kuwait National Petroleum Company in February 1972 and worked there until April 1980. Then he began to work at Shuaiba refinery (1972-1974). Then he joined planning department in 1977 and his tenure at the department lasted until 1977. From 1977 to 1980 he worked at international marketing department. He served as the board chairman and managing director of the Petrochemical Industries Company (PIC) from 1990 to 1995.
He held different posts at the Kuwait Petroleum Corporation (KPC) including managing director for oil refining and local marketing and managing director for marketing. From 1998 to 2004 he was also board chairman and managing director of Kuwait National Petroleum Company (KNPC). Hussein was made chief executive officer of the KPC in 2004 and he replaced Nader Sultan in the post. Hussein resigned from office in April 2007. In June 2007, then Prime Minister Nasser Al-Mohammad Al-Sabah appointed Hussein as his chief petroleum advisor.
Hussein was appointed oil minister to the cabinet led by Prime Minister Jaber Al Sabah on 24 February 2012, replacing Mohammad Busairi in the post. In a December 2012 cabinet reshuffle Hussein was reappointed to the post. However, he resigned from office on 26 May 2013 due to tensions with members of the Kuwaiti parliament. Finance Minister Mustafa Al Shamali was appointed as acting oil minister to succeed him, and on 4 August Shamali was appointed to full portfolio in a cabinet reshuffle. | 1 | Applied and Interdisciplinary Chemistry |
The intracellular degradation of protein may be achieved in two ways—proteolysis in lysosome, or a ubiquitin-dependent process that targets unwanted proteins to proteasome. The autophagy-lysosomal pathway is normally a non-selective process, but it may become selective upon starvation whereby proteins with peptide sequence KFERQ or similar are selectively broken down. The lysosome contains a large number of proteases such as cathepsins.
The ubiquitin-mediated process is selective. Proteins marked for degradation are covalently linked to ubiquitin. Many molecules of ubiquitin may be linked in tandem to a protein destined for degradation. The polyubiquinated protein is targeted to an ATP-dependent protease complex, the proteasome. The ubiquitin is released and reused, while the targeted protein is degraded. | 1 | Applied and Interdisciplinary Chemistry |
Abiotic foldamers are again organic molecules designed to exhibit dynamic folding. They exploit a few known key intermolecular interactions, as optimized by their design. One example is oligopyrroles that organize upon binding anions like chloride through hydrogen bonding (see figure). Folding is induced in the presence of an anion: the polypyrrole groups have little conformational restriction otherwise. | 0 | Theoretical and Fundamental Chemistry |
An autoluminograph is a photograph produced by placing a light emitting object directly on a piece of film. A famous example is an autoluminograph published in Science magazine in 1986 of a glowing transgenic tobacco plant bearing the luciferase gene of fireflies placed on Kodak Ektachrome 200 film. | 1 | Applied and Interdisciplinary Chemistry |
An increase in certain hormones such as oestrogen, progesterone, human placental lactogen, human placental growth hormone and cortisol during the second and third trimester of pregnancy cause an increase in insulin resistance. This increase in insulin resistance and following increase in insulin secretion ensures that the foetus develops a normal glucose tolerance. Gestational Diabetes Mellitus (GDM) arises when beta cells do not secrete enough insulin to adopt to the insulin resistance triggered by pregnancy, which leads to mild hyperglycaemia.
Although the mechanisms are still largely unknown, foetus exposure to GDM and maternal diabetes has been shown to lead to lifelong metabolic complications because of metabolic imprinting. The risk of Type II diabetes developing in offspring is significantly higher in offspring where the mother was diagnosed with Type II diabetes before pregnancy rather than after. In addition, the age at which offspring are diagnosed with Type 2 diabetes is significantly younger in offspring exposed to maternal diabetes/GDM than those who are not. It is suggested that this is a result of DNA methylation during foetal development. | 1 | Applied and Interdisciplinary Chemistry |
The process is named for its inventor Anson Gardner Betts who filed several patents for this method starting in 1901. | 1 | Applied and Interdisciplinary Chemistry |
Mononuclear complexes feature terminal nitride ligands, typically with short M-N distances consistent with metal ligand multiple bonds. For example, in the anion in PPh[MoNCl], the Mo-N distance is 163.7 pm. The occurrence of terminal nitrido ligands follow the patterns seen for oxo complexes: they are more common for early and heavier metals. Many bi- and polynuclear complexes are known with bridging nitrido ligands. More exotic metal nitrido complexes are also possible, such as a recently reported compound containing a terminal uranium nitride (-U≡N) bond. | 0 | Theoretical and Fundamental Chemistry |
Improvised nuclear devices (INDs) and nuclear weapons are weapons of mass destruction. They are difficult to acquire, manufacture, refurbish, and handle. While INDs can be constructed to emit only low amounts of radiation making them difficult to detect with RPMs, all INDs emit some amounts of gamma and neutron radiation. | 0 | Theoretical and Fundamental Chemistry |
A volatile corrosion inhibitor (VCI) is a material that protects metals from corrosion. Corrosion inhibitors are chemical compounds that can decrease the corrosion rate of a material, typically a metal or an alloy. NACE International Standard TM0208 defines volatile corrosion inhibitor (VCI) as a chemical substance that acts to reduce corrosion by a combination of volatilization from a VCI material, vapor transport in the atmosphere of an enclosed environment, and condensation onto surface in the space, including absorption, dissolution, and hydrophobic effects on metal surfaces, where the rate of corrosion of metal surfaces is thereby inhibited. They also called vapor-phase inhibitors, vapor-phase corrosion inhibitors, and vapor-transported corrosion inhibitors.
VCIs come in various formulations that are dependent on the type of system they will be used in; for example, films, oils, coatings, cleaners, etc. There are also variety of formulations that provide protection in ferrous, nonferrous, or multi-metal applications. Other variables include the amount of vapor phase compared to contact phase inhibitors. Because they are volatile at ambient temperature, VCI compounds can reach inaccessible crevices in metallic structures.
V.VCI is also called Vacuum VCI meaning they have special properties of performance in vacuum as well as corrosion protection properties. | 1 | Applied and Interdisciplinary Chemistry |
In Avatar, the Navi are an indigenous species that live on Pandora. They are humanoid in appearance and are tall, having pairs of eyes, ears, arms, legs and feet like humans, as well as a nose, a mouth, and expressions recognizable to humans. The Navi differ from humans in having blue striped skin, pointed and mobile ears, large eyes, catlike noses and tails, and hands each with three fingers and a thumb (hybrid avatars, on the other hand, retain the five-fingered hands of their human DNA). While taller than humans, they have narrower proportions in body frame. Their bones are reinforced with naturally occurring carbon fiber. The Navi also have a distinctive tendril feature protruding from the back of their heads, surrounded by hair (resembling a long plait or queue), feeding directly into the brain. This organ allows them to connect with other organisms, transferring electrochemical signals such as thoughts and memories. In the original script, Cameron refers to these as "Jubilees", although the word is not used in the film and may be changed by the time the novel is published. The Navi were initially conceived to be more alien in appearance. Cameron recalled when one of the main characters, Neytiri, was originally drawn, she had gills and other protuberances. In addition to feline features, the species were redesigned to seem more human so audiences could better relate to them.
The sequel, Avatar: The Way of Water, introduces Navi from the Metkayina tribe with a number of qualities that distinguish them from the blue-skinned Omatikaya clan in Avatar'. The Metkayina have evolved characteristics conducive to an aquatic lifestyle of swimming and diving. These adaptations include green/teal skin, stronger arms, thicker tails, inner eyelids.
According to Cameron, the appearance of the Navi character Neytiri had some specific inspirations and requirements: she was inspired by Raquel Welchs character in Fantastic Voyage and by Vampirella, noting in the latters case, "the fact [Vampirella] didnt exist didnt bother me because we have these quintessential female images in our mind, and in the case of the male mind, theyre grossly distorted. When you see something that reflects your id, it works for you.... Right from the beginning I said, Shes got to have tits, even though that makes no sense because her race, the Navi, arent placental mammals. I designed her costumes based on a taparrabo, a loincloth worn by Mayan Indians." This is somewhat of a non-sequitur because both marsupials (kangaroos, etc.) and monotremes (platypuses, etc.) are non-placental and yet both lactate. This objective of making the Navi as humanlike as possible can also be seen as an explanation as to why they are quadrupedal despite having evolved from common ancestors of the hexapodal lemurs seen in the film.
Cameron has described Avatar as more "science fantasy" than true science fiction and has said that he would explain in the novel for the film why in the fictional universe the Na'vi look like humans. | 1 | Applied and Interdisciplinary Chemistry |
A propelling nozzle produces a high velocity exhaust jet. Propelling nozzles turn internal and pressure energy into high velocity kinetic energy. The total pressure and temperature don't change through the nozzle but their static values drop as the gas speeds up.
The velocity of the air entering the nozzle is low, about Mach 0.4, a prerequisite for minimizing pressure losses in the duct leading to the nozzle. The temperature entering the nozzle may be as low as sea level ambient for a fan nozzle in the cold air at cruise altitudes. It may be as high as the 1000K exhaust gas temperature for a supersonic afterburning engine or 2200K with afterburner lit. The pressure entering the nozzle may vary from 1.5 times the pressure outside the nozzle, for a single stage fan, to 30 times for the fastest manned aircraft at Mach 3+.
Convergent nozzles are only able to accelerate the gas up to local sonic (Mach 1) conditions. To reach high flight speeds, even greater exhaust velocities are required, and so a convergent-divergent nozzle is needed on high-speed aircraft.
The engine thrust is highest if the static pressure of the gas reaches the ambient value as it leaves the nozzle. This only happens if the nozzle exit area is the correct value for the nozzle pressure ratio (npr). Since the npr changes with engine thrust setting and flight speed this is seldom the case. Also at supersonic speeds the divergent area is less than required to give complete internal expansion to ambient pressure as a trade-off with external body drag. Whitford gives the F-16 as an example. Other underexpanded examples were the XB-70 and SR-71.
The nozzle size, together with the area of the turbine nozzles, determines the operating pressure of the compressor. | 1 | Applied and Interdisciplinary Chemistry |
The Journal of Mining and Metallurgy, Section B: Metallurgy is a biannual peer-reviewed scientific journal that covers mining and metallurgy. The editor-in-chief is Dragana Živković (University of Belgrade). Publishing formats include original research articles, review articles, short notices, letters, and book reviews. | 1 | Applied and Interdisciplinary Chemistry |
* High upfront investment in materials and infrastructure.
* High operating costs mostly due to electricity, and system maintenance.
* A need for highly trained staff to monitor and operate the system.
* Higher greenhouse gas emissions than non-recirculating aquaculture. | 1 | Applied and Interdisciplinary Chemistry |
After graduating from Ohio University in 1950, Grasselli Brown was offered a job position at Standard Oil (now BP America) in Cleveland as a project leader. From 1950 to 1978, she worked closely with an instrument called an infrared spectrometer. This device is used to measure the absorbance, emission, and reflection of infrared light interacting with a molecule and also measures the vibrations of atoms to identify functional groups.
During her time at Standard Oil, Grasselli Brown used the infrared spectrometer to examine the concentration of materials, and sought to find industrial applications for it.
As a project leader, she analyzed the formulations of World War II German airplane fuels to understand how the German planes were able to extend their flight ranges. She also consulted with the coroner's office in Cleveland to analyze unknown samples at crime scenes.
In 1978, she became the manager of the analytical science laboratory, working there until 1983. In 1983, she became the director of the technological support department, working there until 1985, when she became the first female director of corporate research from 1985 to 1988. Grasselli Brown retired in January 1989 as the company's highest ranking female employee. | 0 | Theoretical and Fundamental Chemistry |
This was developed independently by R L Blaine of the American National Bureau of Standards, and uses a small glass kerosene manometer to apply suction to the powder bed. It differs from the other methods in that, because of uncertainty of the dimensions of the manometer tube, absolute results can't be calculated from the Carman equation. Instead, the apparatus must be calibrated using a known standard material. The original standards, supplied by NBS, were certified using the Lea and Nurse method. Despite this shortcoming, the Blaine method has become by far the most commonly used for cement materials, mainly because of the ease of maintenance of the apparatus and simplicity of the procedure. | 1 | Applied and Interdisciplinary Chemistry |
DNA concentration and purification has been achieved directly from tar sands samples resuspended in buffer using the SCODA technique. DNA sequencing was subsequently performed and tentatively over 200 distinct bacterial genomes have been identified. SCODA has also been used for purification of DNA from many other environmental sources. | 1 | Applied and Interdisciplinary Chemistry |
5-HT and 5-HT receptors are considered very similar, they share amino acid homology and their ligands expose similar binding properties thus they have similar pharmacophore. The pharmacophore model for these receptors ligands is qualitative and defines the relative positions of important groups. It is defined with following five main features: an aromatic group (usually the indole), protonated amine (a donor of hydrogen bond), acceptor of hydrogen bond, additional hydrogen bond site (both donor and acceptor) and hydrophobic region located between both hydrogen bond sites, see figure 2. The main binding points were concluded to be the protonated amine and the hydrogen bond site. It was observed that the double bond region in the indole was necessary for the agonism in this series of compounds. Figure 3 shows how different drugs fit the pharmacophore, with a C and N linked analogues of 5-HT agonist. The marked sites on the figure are responsible for the affinity. The pharmacophore can be characterized as amphipathic, that means that the structure has both hydrophobic and hydrophilic groups. | 1 | Applied and Interdisciplinary Chemistry |
Over-the-counter preparations containing dextromethorphan have been used in manners inconsistent with their labeling, often as a recreational drug. At doses much higher than medically recommended, dextromethorphan and its major metabolite, dextrorphan, acts as an NMDA receptor antagonist, which produces dissociative hallucinogenic states somewhat similar to ketamine and phencyclidine.
It may produce distortions of the visual field – feelings of dissociation, distorted bodily perception, excitement, and a loss of sense of time. Some users report stimulant-like euphoria, particularly in response to music. Dextromethorphan usually provides its recreational effects in a non-linear fashion, so that they are experienced in significantly varied stages. These stages are commonly referred to as "plateaus". These plateaus are numbered from one to four, with the first having the mildest effects to fourth being the most intense. Each plateau is said to come with different related effects and experiences.
The first plateau is said to induce music euphoria and mild stimulation, likened to that of MDMA. The second plateau is likened to a state of being on moderate amounts of alcohol and cannabis at the same time, featuring euphoria, sedation and minor hallucinations. The third plateau induces a significant dissociative state which can often cause anxiety in users. Reaching the fourth plateau is said to cause extreme sedation and a significant hallucinatory state as well as complete dissociation from reality. Teenagers tend to have a higher likelihood to use dextromethorphan-related drugs as they are easier to access, and an easier way to cope with psychiatric disorders. | 0 | Theoretical and Fundamental Chemistry |
In the scope of the ASP program, high purity germanium (HPGe) based portal monitors were evaluated. HPGe, having significantly better energy resolution than NaI(Tl), allows rather precise measurement of the isotopes contributing to gamma ray spectra. However, due to very high costs and major constraints such as cryo-cooling requirements, US government support for HPGe based portal monitors was dropped. | 0 | Theoretical and Fundamental Chemistry |
Low-pressure mercury lamps are very similar to a fluorescent lamp, with a wavelength of 253.7 nm (1182.5 THz).
The most common form of germicidal lamp looks similar to an ordinary fluorescent lamp but the tube contains no fluorescent phosphor. In addition, rather than being made of ordinary borosilicate glass, the tube is made of fused quartz or vycor 7913 glass. These two changes combine to allow the 253.7 nm ultraviolet light produced by the mercury arc to pass out of the lamp unmodified (whereas, in common fluorescent lamps, it causes the phosphor to fluoresce, producing visible light). Germicidal lamps still produce a small amount of visible light due to other mercury radiation bands.
An older design looks like an incandescent lamp but with the envelope containing a few droplets of mercury. In this design, the incandescent filament heats the mercury, producing a vapor which eventually allows an arc to be struck, short circuiting the incandescent filament.
As with all gas-discharge lamps, low- and high-pressure mercury lamps exhibit negative resistance and require the use of an external ballast to regulate the current flow. The older lamps that resembled an incandescent lamp were often operated in series with an ordinary 40 W incandescent "appliance" lamp; the incandescent lamp acted as the ballast for the germicidal lamp. | 0 | Theoretical and Fundamental Chemistry |
In the thorium cycle, fuel is formed when captures a neutron (whether in a fast reactor or thermal reactor) to become . This normally emits an electron and an anti-neutrino () by decay to become . This then emits another electron and anti-neutrino by a second decay to become , the fuel: | 0 | Theoretical and Fundamental Chemistry |
Mohamed researches diabetes due to a family history of suffering from the disease. His father, mother and brother are diabetics and his concern for the growing number of diabetics worldwide prompted his invention. He developed a remote monitoring and control system for diabetes symptoms. He set about creating an artificial pancreas and a remote system to monitor the stability of glucose levels in diabetics. The device, which can be linked to a hospital database system as well as family and friends, enables an immediate response if a medical situation arises. | 0 | Theoretical and Fundamental Chemistry |
Uniformity of Content is a pharmaceutical analysis parameter for the quality control of capsules or tablets. Multiple capsules or tablets are selected at random and a suitable analytical method is applied to assay the individual content of the active ingredient in each capsule or tablet.
The preparation complies if not more than one (all within limits) individual content is outside the limits of 85 to 115% of the average content and none is outside the limits of 75 to 125% of the average content. The preparation fails to comply with the test if more than 3 individual contents are outside the limits of 85 to 115% of the average content or if one or more individual contents are outside the limits of 75% to 125% of the average content. | 1 | Applied and Interdisciplinary Chemistry |
The light-harvesting complex (or antenna complex; LH or LHC) is an array of protein and chlorophyll molecules embedded in the thylakoid membrane of plants and cyanobacteria, which transfer light energy to one chlorophyll a molecule at the reaction center of a photosystem.
The antenna pigments are predominantly chlorophyll b, xanthophylls, and carotenes. Chlorophyll a is known as the core pigment. Their absorption spectra are non-overlapping and broaden the range of light that can be absorbed in photosynthesis. The carotenoids have another role as an antioxidant to prevent photo-oxidative damage of chlorophyll molecules. Each antenna complex has between 250 and 400 pigment molecules and the energy they absorb is shuttled by resonance energy transfer to a specialized chlorophyll-protein complex known as the reaction center of each photosystem. The reaction center initiates a complex series of chemical reactions that capture energy in the form of chemical bonds.
For photosystem II, when either of the two chlorophyll a molecules at the reaction center absorb energy, an electron is excited and transferred to an electron acceptor molecule, pheophytin, leaving the chlorophyll a in an oxidized state. The oxidised chlorophyll a replaces the electrons by photolysis that involves the oxidation of water molecules to oxygen, protons and electrons.
The N-terminus of the chlorophyll a-b binding protein extends into the stroma where it is involved with adhesion of granal membranes and photo-regulated by reversible phosphorylation of its threonine residues. Both these processes are believed to mediate the distribution of excitation energy between photosystems I and II.
This family also includes the photosystem II protein PsbS, which plays a role in energy-dependent quenching that increases thermal dissipation of excess absorbed light energy in the photosystem. | 0 | Theoretical and Fundamental Chemistry |
Another large class of non-coordinating anions are derived from carborane anion . Using this anion, the first example of a three-coordinate silicon compound, the salt [(mesityl)Si][HCBMeBr] contains a non-coordinating anion derived from a carborane. | 0 | Theoretical and Fundamental Chemistry |
Many ylides may be depicted by a multiple bond form in a resonance structure, known as the ylene form, while the actual structure lies in between both forms:
The actual bonding picture of these types of ylides is strictly zwitterionic (the structure on the right) with the strong Coulombic attraction between the "onium" atom and the adjacent carbon accounting for the reduced bond length. Consequently, the carbon anion is trigonal pyramidal. | 0 | Theoretical and Fundamental Chemistry |
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* The Geochemist's Workbench Commercial software from [http://www.gwb.com/ Aqueous Solutions LLC]
* [http://community.gwb.com/diagrams.php GWB Community Edition] Free community edition of the popular geochemical modeling software package.
* RockWorks Utilities Commercial software from RockWare, Inc.
* EnviroInsite Commercial software from HydroAnalysis, Inc.
* [http://python.hydrology-amsterdam.nl/ Python Scripts] Free open-source Python scripts that can plot stiff diagrams. | 0 | Theoretical and Fundamental Chemistry |
Medieval physicians routinely tasted urine and wrote discourses on their observations. Which physician originally thought that diabetes mellitus was a renal disorder because of glucose discharged in urine is apparently now lost to history. The discovery of insulin eventually led to a diabetes management focus on the pancreas. Traditional foci of therapeutic strategies for diabetes have been on enhancing endogenous insulin secretion and on improving insulin sensitivity.
In the previous decade the role of the kidney in the development and maintenance of high glucose levels has been examined. The role of the kidney led to the development of drugs that inhibit the sodium/glucose transporter 2 protein. Every day approximately 180 grams of glucose are filtered through the glomeruli and lost into the primary urine in healthy adults, but more than 90% of the glucose that is initially filtered is reabsorbed by a high capacity system controlled by SGLT-2 in the early convoluted segment of the proximal tubules. Almost all remaining filtered glucose is reabsorbed by sodium/glucose transporter 1 so under normal circumstances almost all filtered glucose will be reabsorbed and less than 100 mg of glucose finds its way into the urine of non-diabetic individuals. | 1 | Applied and Interdisciplinary Chemistry |
Simple chemical weapons were used sporadically throughout antiquity and into the Industrial age. It was not until the 19th century that the modern conception of chemical warfare emerged, as various scientists and nations proposed the use of asphyxiating or poisonous gases. So alarmed were nations that multiple international treaties, discussed below, were passed banning chemical weapons. This however did not prevent the extensive use of chemical weapons in World War I. The development of chlorine gas, among others, was used by both sides to try to break the stalemate of trench warfare. Though largely ineffective over the long run, it decidedly changed the nature of the war. In many cases the gases used did not kill, but instead horribly maimed, injured, or disfigured casualties. Some 1.3 million gas casualties were recorded, which may have included up to 260,000 civilian casualties.
The interwar period saw occasional use of chemical weapons, mainly by multiple European colonial forces to put down rebellions. The Italians also used poison gas during their 1936 invasion of Ethiopia. In Nazi Germany, much research went into developing new chemical weapons, such as potent nerve agents. However, chemical weapons saw little battlefield use in World War II. Both sides were prepared to use such weapons, but the Allied powers never did, and the Axis used them only very sparingly. The reason for the lack of use by the Nazis, despite the considerable efforts that had gone into developing new varieties, might have been a lack of technical ability or fears that the Allies would retaliate with their own chemical weapons. Those fears were not unfounded: the Allies made comprehensive plans for defensive and retaliatory use of chemical weapons, and stockpiled large quantities. Japanese forces used them more widely, though only against their Asian enemies, as they also feared that using it on Western powers would result in retaliation. Chemical weapons were frequently used against Kuomintang and Chinese communist troops. However, the Nazis did extensively use poison gas against civilians in the Holocaust. Vast quantities of Zyklon B gas and carbon monoxide were used in the gas chambers of Nazi extermination camps, resulting in the overwhelming majority of some three million deaths. This remains the deadliest use of poison gas in history.
The post-war era has seen limited, though devastating, use of chemical weapons. Some 100,000 Iranian troops were casualties of Iraqi chemical weapons during the Iran–Iraq War. Iraq used mustard gas and nerve agents against its own civilians in the 1988 Halabja chemical attack. The Cuban intervention in Angola saw limited use of organophosphates. The Syrian government has used sarin, chlorine, and mustard gas in the Syrian civil war generally against civilians. Terrorist groups have also used chemical weapons, notably in the Tokyo subway sarin attack and the Matsumoto incident. See also chemical terrorism. | 1 | Applied and Interdisciplinary Chemistry |
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