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Reactions of divinylcyclopropanes containing substituted double bonds are stereospecific with respect to the configurations at the double bonds—cis,cis isomers give cis products, while cis,trans isomers give trans products. Thus, chiral, non-racemic starting materials give rise to chiral products without loss of enantiomeric purity. In the example below, only the isomers depicted were observed in each case. | 0 | Theoretical and Fundamental Chemistry |
Mild steel (iron containing a small percentage of carbon, strong and tough but not readily tempered), also known as plain-carbon steel and low-carbon steel, is now the most common form of steel because its price is relatively low while it provides material properties that are acceptable for many applications. Mild steel contains approximately 0.05–0.30% carbon making it malleable and ductile. Mild steel has a relatively low tensile strength, but it is cheap and easy to form. Surface hardness can be increased with carburization.
The density of mild steel is approximately and the Young's modulus is .
Low-carbon steels display yield-point runout where the material has two yield points. The first yield point (or upper yield point) is higher than the second and the yield drops dramatically after the upper yield point. If a low-carbon steel is only stressed to some point between the upper and lower yield point then the surface develops Lüder bands. Low-carbon steels contain less carbon than other steels and are easier to cold-form, making them easier to handle. Typical applications of low carbon steel are car parts, pipes, construction, and food cans. | 1 | Applied and Interdisciplinary Chemistry |
Phosphoribosylaminoimidazole carboxylase is a fusion protein in plants and fungi, but consists of two non-interacting proteins in bacteria, PurK and PurE.
The crystal structure of PurE indicates a unique quaternary structure that confirms the octameric nature of the enzyme. | 1 | Applied and Interdisciplinary Chemistry |
The Transporter Classification Database (or TCDB) is an International Union of Biochemistry and Molecular Biology (IUBMB)-approved classification system for membrane transport proteins, including ion channels. | 1 | Applied and Interdisciplinary Chemistry |
Between 1963 and 1966, numerous scientific studies demonstrated the use of Tc as radiotracer or diagnostic tool. As a consequence the demand for Tc grew exponentially and by 1966, Brookhaven National Laboratory was unable to cope with the demand. Production and distribution of Tc generators were transferred to private companies. "TechneKow-CS generator", the first commercial Tc generator, was produced by Nuclear Consultants, Inc. (St. Louis, Missouri) and Union Carbide Nuclear Corporation (Tuxedo, New York). From 1967 to 1984, Mo was produced for Mallinckrodt Nuclear Company at the Missouri University Research Reactor (MURR).
Union Carbide actively developed a process to produce and separate useful isotopes like Mo from mixed fission products that resulted from the irradiation of highly enriched uranium (HEU) targets in nuclear reactors developed from 1968 to 1972 at the Cintichem facility (formerly the Union Carbide Research Center built in the Sterling forest in Tuxedo, New York ()). The Cintichem process originally used 93% highly enriched U-235 deposited as UO on the inside of a cylindrical target.
At the end of the 1970s, of total fission product radiation were extracted weekly from 20 to 30 reactor bombarded HEU capsules, using the so-called "Cintichem [chemical isolation] process." The research facility with its 1961 5-MW pool-type research reactor was later sold to Hoffman-LaRoche and became Cintichem Inc. In 1980, Cintichem, Inc. began the production/isolation of Mo in its reactor, and became the single U.S. producer of Mo during the 1980s. However, in 1989, Cintichem detected an underground leak of radioactive products that led to the reactor shutdown and decommissioning, putting an end to the commercial production of Mo in the USA.
The production of Mo started in Canada in the early 1970s and was shifted to the NRU reactor in the mid-1970s. By 1978 the reactor provided technetium-99m in large enough quantities that were processed by AECLs radiochemical division, which was privatized in 1988 as Nordion, now MDS Nordion. In the 1990s a substitution for the aging NRU reactor for production of radioisotopes was planned. The Multipurpose Applied Physics Lattice Experiment (MAPLE) was designed as a dedicated isotope-production facility. Initially, two identical MAPLE reactors were to be built at Chalk River Laboratories, each capable of supplying 100% of the worlds medical isotope demand. However, problems with the MAPLE 1 reactor, most notably a positive power co-efficient of reactivity, led to the cancellation of the project in 2008.
The first commercial Tc generators were produced in Argentina in 1967, with Mo produced in the CNEA's RA-1 Enrico Fermi reactor. Besides its domestic market CNEA supplies Mo to some South American countries. | 0 | Theoretical and Fundamental Chemistry |
At lower temperatures, more energy (i.e. - larger applied stress) is required to activate some slip systems. This is particularly evident in BCC materials, in which not all 5 independent slip systems are thermally activated at temperatures below the ductile-to-brittle transition temperature, or DBTT, so BCC specimens therefore become brittle. In general BCC metals have higher critical resolved shear stress values compared to FCC. However, the relationship between the CRSS and temperature and strain rate is worth examining further.
To understand the relationship between stress and temperature observed, we first divide the critical resolved shear stress into the sum of two components: an athermal term described as and a thermally dependent term known as where
can be attributed to the stresses involved with dislocation motion while dislocations move in long-range internal stress fields. These long-range stresses arise from the presence of other dislocations. however is attributed to short range internal stress fields that arise from defect atoms or precipitates within the lattice that are obstacles for dislocation glide. With increasing temperature, the dislocations within the material have sufficient energy to overcome these short-range stresses. This explains the trend in region I where stress decreases with temperature. At the boundary between region’s I and II, the term is effectively zero and the critical resolved shear stress is completely described by the athermal term, i.e. long-range internal stress fields are still significant. In the third region, diffusive processes begin to play a significant role in plastic deformation of the material and so the critically resolved shear stress decreases once again with temperature. Within region three, the equation suggested earlier no longer applies. Region I has a temperature upper bound of approximately while region III occurs at values where is the melting temperature of the material. The figure also shows the effect of increased strain rate generally increasing the critical resolved shear stress for a constant temperature as this increases the dislocation density in the material. Note that for intermediate temperatures, i.e. region II, there is a region where the strain rate has no effect on the stress. Increasing the strain rate does shift the graph to the right as more energy is needed to balance the short-term stresses with the resulting increased dislocation density.
The thermal component, can be expressed in the following manner.
Where is the thermal component at 0 K and is the temperature at which the thermal energy is sufficient to overcome the obstacles causing stress, i.e. the temperature at the transition from 1 to 2. The above equation has been verified experimentally. In general, the CRSS increases as the homologous temperature decreases because it becomes energetically more costly to activate the slip systems, although this effect is much less pronounced in FCC.
Solid solution strengthening also increases the CRSS compared to a pure single component material because the solute atoms distort the lattice, preventing the dislocation motion necessary for plasticity. With dislocation motion inhibited, it becomes harder to activate the necessary 5 independent slip systems, so the material becomes stronger and more brittle. | 1 | Applied and Interdisciplinary Chemistry |
Seminaphtharhodafluor or SNARF is a fluorescent dye that changes color with pH.
It can be used to construct optical biosensors that use enzymes that change pH.
The absorption peak of the derivative carboxy-SNARF at pH 6.0 is at wavelength (515 and) 550 nm, while that at pH 9.0 is at 575 nm.
The emission peak of carboxy-SNARF at pH 6.0 is at wavelength 585 nm, while that at pH 9.0 is at 640 nm.
SNARF-1 can serve as a substrate for the MRP1 (multidrug resistance-associated protein-1) drug transporter, to measure the activity of the MRP1 transporter. For this purpose, an acetomethoxyester group is added to SNARF-1. Cellular esterases cleave off SNARF-1, and its transport out of the cells can be measured by following the loss of fluorescence from the cells. | 1 | Applied and Interdisciplinary Chemistry |
In aromatic amines ("anilines"), nitrogen is often nearly planar owing to conjugation of the lone pair with the aryl substituent. The C-N distance is correspondingly shorter. In aniline, the C-N distance is the same as the C-C distances. | 0 | Theoretical and Fundamental Chemistry |
Outside the field of polarography, Harveys book Spectrochemical Procedures was the next earliest reference book to mention standard addition. Harveys approach, which involves the successive addition of standards, closely resembles the most commonly used method of standard addition today.
To apply this method, analysts prepare multiple solutions containing equal amounts of unknown and spike them with varying concentrations of the analyte. The amount of unknown and the total volume are the same across the standards and the only difference between the standards is the amount of analyte spiked. This leads to a linear relationship between the analyte signal and the amount of analyte added, allowing for the determination of the unknown's concentration by extrapolating the zero analyte signal. One disadvantage of this approach is that it requires sufficient amount of the unknown. When working with limiting amount of sample, an analyst might need to make a single addition, but it is generally considered a best practice to make at least two additions whenever possible.
Note that this is not limited to liquid samples. In atomic absorption spectroscopy, for example, standard additions are often used with solid as the sample.
In atomic emission spectroscopy, background signal cannot be resolved by standard addition. Thus, background signal must be subtracted from the unknown and standard intensities prior to extrapolating for the zero signal.
As this approach involves varying amount of standards added, it is often referred in the plural form as standard additions. | 0 | Theoretical and Fundamental Chemistry |
Transcription factor II H (TFH) is an important protein complex, having roles in transcription of various protein-coding genes and DNA nucleotide excision repair (NER) pathways. TFH first came to light in 1989 when general transcription factor-δ or basic transcription factor 2 was characterized as an indispensable transcription factor in vitro. This factor was also isolated from yeast and finally named TFH in 1992.
TFH consists of ten subunits, 7 of which (ERCC2/XPD, ERCC3/XPB, GTF2H1/p62, GTF2H4/p52, GTF2H2/p44, GTF2H3/p34 and GTF2H5/TTDA) form the core complex. The cyclin-activating kinase-subcomplex (CDK7, MAT1, and cyclin H) is linked to the core via the XPD protein. Two of the subunits, ERCC2/XPD and ERCC3/XPB, have helicase and ATPase activities and help create the transcription bubble. In a test tube, these subunits are only required for transcription if the DNA template is not already denatured or if it is supercoiled.
Two other TFH subunits, CDK7 and cyclin H, phosphorylate serine amino acids on the RNA polymerase II C-terminal domain and possibly other proteins involved in the cell cycle. Next to a vital function in transcription initiation, TFH is also involved in nucleotide excision repair. | 1 | Applied and Interdisciplinary Chemistry |
In a new bottle of soda, the concentration of carbon dioxide in the liquid phase has a particular value. If half of the liquid is poured out and the bottle is sealed, carbon dioxide will leave the liquid phase at an ever-decreasing rate, and the partial pressure of carbon dioxide in the gas phase will increase until equilibrium is reached. At that point, due to thermal motion, a molecule of CO may leave the liquid phase, but within a very short time another molecule of CO will pass from the gas to the liquid, and vice versa. At equilibrium, the rate of transfer of CO from the gas to the liquid phase is equal to the rate from liquid to gas. In this case, the equilibrium concentration of CO in the liquid is given by Henry's law, which states that the solubility of a gas in a liquid is directly proportional to the partial pressure of that gas above the liquid. This relationship is written as
where K is a temperature-dependent constant, P is the partial pressure, and c is the concentration of the dissolved gas in the liquid. Thus the partial pressure of CO in the gas has increased until Henry's law is obeyed. The concentration of carbon dioxide in the liquid has decreased and the drink has lost some of its fizz.
Henrys law may be derived by setting the chemical potentials of carbon dioxide in the two phases to be equal to each other. Equality of chemical potential defines chemical equilibrium. Other constants for dynamic equilibrium involving phase changes, include partition coefficient and solubility product. Raoults law defines the equilibrium vapor pressure of an ideal solution
Dynamic equilibrium can also exist in a single-phase system. A simple example occurs with acid-base equilibrium such as the dissociation of acetic acid, in an aqueous solution.
At equilibrium the concentration quotient, K, the acid dissociation constant, is constant (subject to some conditions)
In this case, the forward reaction involves the liberation of some protons from acetic acid molecules and the backward reaction involves the formation of acetic acid molecules when an acetate ion accepts a proton. Equilibrium is attained when the sum of chemical potentials of the species on the left-hand side of the equilibrium expression is equal to the sum of chemical potentials of the species on the right-hand side. At the same time, the rates of forward and backward reactions are equal to each other. Equilibria involving the formation of chemical complexes are also dynamic equilibria and concentrations are governed by the stability constants of complexes.
Dynamic equilibria can also occur in the gas phase as, for example when nitrogen dioxide dimerizes.
In the gas phase, square brackets indicate partial pressure. Alternatively, the partial pressure of a substance may be written as P(substance). | 0 | Theoretical and Fundamental Chemistry |
Ring-opening polymerization is an additive process but tends to give condensation-like polymers but follows the stoichiometry of addition polymerization. For example, polyethylene glycol is formed by opening ethylene oxide rings:
:HOCHCHOH + n CHO → HO(CHCHO)</sub>H
Nylon 6 (developed to thwart the patent on nylon 6,6) is produced by addition polymerization, but chemically resembles typical polyamides. | 0 | Theoretical and Fundamental Chemistry |
Databases containing biological targets information:
* Therapeutic Targets Database (TTD)
* [https://idrblab.org/drugmap/ DrugMap]
* DrugBank
* Binding DB | 1 | Applied and Interdisciplinary Chemistry |
Unlike in plants, animals do not have a pathway for the direct assimilation of inorganic sulfate into organic compounds. In animals, the primary source of sulfur is dietary methionine, an essential amino acid that contains a sulfur atom. Methionine is first converted to S-adenosylmethionine (SAM), a compound that is involved in many important biological processes, including DNA methylation and neurotransmitter synthesis.
SAM can then be used to synthesize other important sulfur-containing compounds such as cysteine, taurine, and glutathione. Cysteine is a precursor for the synthesis of several important proteins and peptides, as well as glutathione, a powerful antioxidant that protects cells from oxidative stress. Taurine is involved in a variety of physiological processes, including osmoregulation, modulation of calcium signaling, and regulation of mitochondrial function. | 1 | Applied and Interdisciplinary Chemistry |
First, the earlier theory which originated from the concept of a hypothetical medium referred as aether. Ether supposedly fills all evacuated or non-evacuated spaces. The transmission of light or of radiant heat are allowed by the propagation of electromagnetic waves in the aether. television and radio broadcasting waves are types of electromagnetic waves with specific wavelengths. All electromagnetic waves travel at the same speed; therefore, shorter wavelengths are associated with high frequencies. Since every body or fluid is submerged in the ether, due to the vibration of the molecules, any body or fluid can potentially initiate an electromagnetic wave. All bodies generate and receive electromagnetic waves at the expense of its stored energy.
In 1860, Gustav Kirchhoff published a mathematical description of thermal equilibrium (i.e. Kirchoffs law of thermal radiation). By 1884 the emissive power of a perfect blackbody was inferred by Josef Stefan using John Tyndalls experimental measurements, and derived by Ludwig Boltzmann from fundamental statistical principles. This relation is known as Stefan–Boltzmann law. | 0 | Theoretical and Fundamental Chemistry |
In many LMICs, fecal sludge is still not properly managed. This may be due to a lack of mandated institutions and low awareness of the impact of poor sanitation; a lack of technical expertise and experience; an inability to source funds for to purchase of vacuum trucks and treatment, as well as a lack of knowledge necessary to initiate and implement successful FSM programs. Another factor is that the transporting fecal sludge has a real cost to vacuum truck operators and there is thus an incentive to dispose of the untreated waste into the environment (primarily into waterways, but also directly onto the land.) Failure to properly manage fecal sludge can result in the poor performance of onsite sanitation facilities (OSSFs), fecal sludge overflowing from containments, and the unsafe emptying and dumping of untreated fecal sludge into the environment.
Fecal sludge contains pathogens, can generate odors and cause surface water pollution, as well as groundwater pollution. | 1 | Applied and Interdisciplinary Chemistry |
RNA secondary structure can be determined from atomic coordinates (tertiary structure) obtained by X-ray crystallography, often deposited in the Protein Data Bank. Current methods include 3DNA/DSSR and MC-annotate. | 0 | Theoretical and Fundamental Chemistry |
Although the diameter of the piston and the force exerted by a cylinder are related, they are not directly proportional to one another. Additionally, the typical mathematical relationship between the two assumes that the air supply does not become saturated. Due to the effective cross sectional area reduced by the area of the piston rod, the instroke force is less than the outstroke force when both are powered pneumatically and by same supply of compressed gas.
The relationship between the force, radius, and pressure can derived from simple distributed load equation:
Where:
: is the resultant force
: is the pressure or distributed load on the surface
: is the effective cross sectional area the load is acting on | 1 | Applied and Interdisciplinary Chemistry |
Many other methods have been developed to treat the contamination of dyes in a solution, including electrochemical degradation, ion exchange, laser degradation, and absorption onto various solids such as activated charcoal. | 0 | Theoretical and Fundamental Chemistry |
Thioacetic acid is prepared by the reaction of acetic anhydride with hydrogen sulfide:
It has also been produced by the action of phosphorus pentasulfide on glacial acetic acid, followed by distillation.
Thioacetic acid is typically contaminated by acetic acid.
The compound exists exclusively as the thiol tautomer, consistent with the strength of the double bond. Reflecting the influence of hydrogen-bonding, the boiling point (93 °C) and melting points are 20 and 75 K lower than those for acetic acid. | 0 | Theoretical and Fundamental Chemistry |
Non-biologic surface coatings will occur via two mechanisms, the first being direct hydrophobic interaction of the lipid tail with a hydrophobic surface resulting in a monolayer of FSL at the surface. The second surface coating will be through the formation of bilayers, which probably either encapsulate fibres or being via the hydrophilic F group. This is the expected mechanism by which FSLs bind to fibrous membranes such as paper and glass fibres. A recent study has found that when FSL Kode constructs are optimised, could in a few seconds glycosylate almost any non-biological surface including metals, glass, plastics, rubbers, and other polymers. | 1 | Applied and Interdisciplinary Chemistry |
Laboratory Proficiency Testing Program (LPTP) helps labs compete in the global marketplace by demonstrating that through participation they meet the highest international standards for accuracy, reliability, and compliance. | 0 | Theoretical and Fundamental Chemistry |
By placing the hybrid proteins under the control of IPTG-inducible lac promoters, they are expressed only on media supplemented with IPTG. Further, by including different antibiotic resistance genes in each genetic construct, the growth of non-transformed cells is easily prevented through culture on media containing the corresponding antibiotics. This is particularly important for counter selection methods in which a lack of interaction is needed for cell survival.
The reporter gene may be inserted into the E. coli genome by first inserting it into an episome, a type of plasmid with the ability to incorporate itself into the bacterial cell genome with a copy number of approximately one per cell.
The hybrid expression phagemids can be electroporated into E. coli XL-1 Blue cells which after amplification and infection with VCS-M13 helper phage, will yield a stock of library phage. These phage will each contain one single-stranded member of the phagemid library. | 1 | Applied and Interdisciplinary Chemistry |
Luciferins have been shown to be largely conserved among different species while luciferases show a greater degree of diversity. Eighty percent of the species that exhibit bioluminescence exist in aquatic habitats. | 1 | Applied and Interdisciplinary Chemistry |
Most chalconatronite formed on bronze and silver that have been treated with either sodium sesquicarbonate or sodium cyanide to prevent corrosion and bronze disease. The mineral has also been proven to form on the surface of copper artifacts after being treated with aqueous sodium carbonate. This formation by using sodium sesquicarbonate is undesirable by many antique collectors, as the mineral changes the patinas of copper artifacts. When the mineral forms, it can replace copper salts within the patina, and turn the color from a rich green to a blue-green or even black. | 1 | Applied and Interdisciplinary Chemistry |
In more general use, a calibration curve is a curve or table for a measuring instrument which measures some parameter indirectly, giving values for the desired quantity as a function of values of sensor output. For example, a calibration curve can be made for a particular pressure transducer to determine applied pressure from transducer output (a voltage). Such a curve is typically used when an instrument uses a sensor whose calibration varies from one sample to another, or changes with time or use; if sensor output is consistent the instrument would be marked directly in terms of the measured unit. | 1 | Applied and Interdisciplinary Chemistry |
A most serious objection to the formation of continuous, high embankments along rivers bringing down considerable quantities of detritus, especially near a place where their fall has been abruptly reduced by descending from mountain slopes onto alluvial plains, is the danger of their bed being raised by deposit, producing a rise in the flood-level, and necessitating a raising of the embankments if inundations are to be prevented. Longitudinal sections of the Po River, taken in 1874 and 1901, show that its bed was materially raised during this period from the confluence of the Ticino to below Caranella, despite the clearance of sediment effected by the rush through breaches. Therefore, the completion of the embankments, together with their raising, would only eventually aggravate the injuries of the inundations they have been designed to prevent, as the escape of floods from the raised river must occur sooner or later.
In the UK, problems of flooding of domestic properties around the turn of the 21st century have been blamed on inadequate planning controls which have permitted development on floodplains. This exposes the properties on the floodplain to flood, and the substitution of concrete for natural strata speeds the run-off of water, which increases the danger of flooding downstream. In the Midwestern United States and the Southern United States the term for this measure is channelization. Much of it was done under the auspices or overall direction of the United States Army Corps of Engineers. One of the most heavily channelized areas in the United States is West Tennessee, where every major stream with one exception (the Hatchie River) has been partially or completely channelized. | 1 | Applied and Interdisciplinary Chemistry |
Hybridization probes can be used to detect base flipping. This technique uses a molecule that has a complementary sequence to the sequence you would like to detect such that it binds to a single-strand of the DNA or RNA. Several hybridization probes have been used to detect base flipping. Potassium permanganate is used to detect thymine residues that have been flipped out by cytosine-C5 and adenine-N6 methyltransferases. Chloroacetaldehyde is used to detect cytosine residues flipped out by the HhaI DNA cytosine-5 methyltransferase (M. HhaI). | 1 | Applied and Interdisciplinary Chemistry |
Grafting to approach which is the most common and straightforward methodology refers to directly attaching the synthetic polymers to the target protein. This technique can be engineered for site-specific or random conjugation and, when compared to other conjugation methods, provides simple and thorough characterization of polymer before conjugation. And when using this method, the protein remains unaffected by polymerization methods. | 1 | Applied and Interdisciplinary Chemistry |
HCN has been measured in Titans atmosphere by four instruments on the Cassini space probe, one instrument on Voyager, and one instrument on Earth. One of these measurements was in situ, where the Cassini spacecraft dipped between above Titans surface to collect atmospheric gas for mass spectrometry analysis. HCN initially forms in Titan's atmosphere through the reaction of photochemically produced methane and nitrogen radicals which proceed through the HCN intermediate, e.g., (CH + N → HCN + H → HCN + H). Ultraviolet radiation breaks HCN up into CN + H; however, CN is efficiently recycled back into HCN via the reaction CN + CH → HCN + CH. | 0 | Theoretical and Fundamental Chemistry |
Given the above definitions the interaction Hamiltonian is
as stated. The next step is to find the Hamiltonian in the interaction picture, . The required unitary transformation is
where the 3rd step can be proved by using a Taylor series expansion, and using the orthogonality of the states and . Note that a multiplication by an overall phase of on a unitary operator does not affect the underlying physics, so in the further usages of we will neglect it. Applying gives:
Now we apply the RWA by eliminating the counter-rotating terms as explained in the previous section:
Finally, we transform the approximate Hamiltonian back to the Schrödinger picture:
The atomic Hamiltonian was unaffected by the approximation, so the total Hamiltonian in the Schrödinger picture under the rotating wave approximation is | 0 | Theoretical and Fundamental Chemistry |
Ferrocene is a redox-active organometallic compound which can be incorporated into various monomers and used to make polymers which can be tethered onto a surface. Vinylferrocene (ferroceneylethene) can be prepared by a Wittig reaction and then polymerized to form polyvinylferrocene (PVFc), an analog of polystyrene. Another polymer which can be formed is poly( ferrocenecarboxylate), PFcMA. Both PVFc and PFcMA have been tethered onto silica wafers and the wettability measured when the polymer chains are uncharged and when the ferrocene moieties are oxidised to produce positively charged groups, as illustrated at right. The contact angle with water on the PFcMA-coated wafers was 70° smaller following oxidation, while in the case of PVFc the decrease was 30°, and the switching of wettability has been shown to be reversible. In the PFcMA case, the effect of longer chains with more ferrocene groups (and also greater molar mass) has been investigated, and it was found that longer chains produce significantly larger contact angle reductions. | 0 | Theoretical and Fundamental Chemistry |
Because of the significant expenses and infrastructure required for accurate compound management (space requirements, robotics, IT support, analytical support, etc.) many companies choose to outsource this function to a company that specializes in this arena. It is important to work with a company that has significant experience in compound management due to the complexity of tracking not only inventory data, but also compound location, storage conditions, and compound integrity. This experience also is of paramount importance when knowing how to appropriately deal with the wide array of materials handled including, solids, liquids, volatile materials, sticky solids, oils, and gums as well as hazardous, flammable, hygroscopic and toxic compounds.
Customers can specify not only the quantity of material but also the exact vial and cap or plate for their specific application. The service provides enormous savings from a time perspective as researchers do not spend their valuable time on weighing hundreds of compounds or getting them into the correct format for their assay. It also dramatically reduces disposal costs since the exact amount of material required can be ordered rather than needing to order e.g. 100 g of material when only 0.1 g is needed for the experiment.
The high throughput analytical chemistry component of the company allows rapid validation that compounds are the correct material at the desired purity. While controlled storage conditions minimize degradation, customers may use this service to validate that the material they sent to outsourcing partner originally was correct and pure. Subsequently the service allows re-evaluation of compounds that may have decomposed during long term storage. The purification services complement the analytical services by allowing cost effective, environmentally friendly recovery of partially degraded reactive intermediates and HTS compounds at a fraction of the cost of synthesizing or purchasing these materials. | 1 | Applied and Interdisciplinary Chemistry |
To discuss the modeling of unresolved scales, first the unresolved scales must be classified. They fall into two groups: resolved sub-filter scales (SFS), and sub-grid scales(SGS).
The resolved sub-filter scales represent the scales with wave numbers larger than the cutoff wave number , but whose effects are dampened by the filter. Resolved sub-filter scales only exist when filters non-local in wave-space are used (such as a box or Gaussian filter). These resolved sub-filter scales must be modeled using filter reconstruction.
Sub-grid scales are any scales that are smaller than the cutoff filter width . The form of the SGS model depends on the filter implementation. As mentioned in the Numerical methods for LES section, if implicit LES is considered, no SGS model is implemented and the numerical effects of the discretization are assumed to mimic the physics of the unresolved turbulent motions. | 1 | Applied and Interdisciplinary Chemistry |
finds occasional use in organic synthesis, capitalizing on its Lewis acidity, its oxophilicity, and the electron-transfer properties of its reduced titanium halides. It is used in the Lewis acid catalysed aldol addition Key to this application is the tendency of to activate aldehydes (RCHO) by formation of adducts such as . | 0 | Theoretical and Fundamental Chemistry |
Temperature-programmed reduction is a technique for the characterization of solid materials and is often used in the field of heterogeneous catalysis to find the most efficient reduction conditions, an oxidized catalyst precursor is submitted to a programmed temperature rise while a reducing gas mixture is flowed over it. It was developed by John Ward Jenkins whilst developing heterogeneous catalysts for Shell Oil company, but was never patented. | 0 | Theoretical and Fundamental Chemistry |
To produce their metallic microlattice, the HRL/UCI/Caltech team first prepared a polymer template using a technique based on self-propagating waveguide formation, though it was noted that other methods can be used to fabricate the template. The process passed UV light through a perforated mask into a reservoir of UV-curable resin. Fiber-optic-like "self-trapping" of the light occurred as the resin cured under each hole in the mask, forming a thin polymer fiber along the path of the light. By using multiple light beams, multiple fibers could then interconnect to form a lattice.
The process was similar to photolithography in that it used a two-dimensional mask to define the starting template structure, but differed in the rate of formation: where stereolithography might take hours to make a full structure, the self-forming waveguide process allowed templates to be formed in 10–100 seconds. In this way, the process enables large free-standing 3D lattice materials to be formed quickly and scalably. The template was then coated with a thin layer of metal by electroless nickel plating, and the template is etched away, leaving a free-standing, periodic porous metallic structure. Nickel was used as the microlattice metal in the original report. Owing to the electrodeposition process, 7% of the material consisted of dissolved phosphorus atoms, and it contained no precipitates. | 0 | Theoretical and Fundamental Chemistry |
The satellite will carry a single instrument designed to make the most precise measurements of atmospheric carbon dioxide ever made from space. The instrument consists of three parallel, high-resolution spectrometers, integrated into a common structure and fed by a common telescope. The spectrometers will make simultaneous measurements of the carbon dioxide and molecular oxygen absorption of sunlight reflected off the same location on Earth's surface when viewed in the near-infrared part of the electromagnetic spectrum, invisible to the human eye.
As sunlight passes through Earths atmosphere and is reflected from Earths surface, molecules of atmospheric gases absorb very specific colors of light. If the light is divided into a rainbow of colors, called a spectrum, the specific colors absorbed by each gas appear as dark lines. Different gases absorb different colors, so the pattern of absorption lines provides a telltale spectral "fingerprint" for that molecule. OCO's spectrometers were designed to detect these molecular fingerprints.
Each of the three spectrometers was tuned to measure the absorption in a specific range of colors. Each of these ranges includes dozens of dark absorption lines produced by either carbon dioxide or molecular oxygen. The amount of light absorbed in each spectral line increases with the number of molecules along the optical path. OCO's spectrometers measure the fraction of the light absorbed in each of these lines with very high precision. This information was then to be analyzed to determine the number of molecules along the path between the top of the atmosphere and the surface.
If the amount of carbon dioxide varies from place to place, the amount of absorption will also vary. To resolve these variations, the observatory's instrument will record an image of the spectrum produced by each spectrometer three times every second as the satellite flies over the surface at more than four miles per second. This information would then be transmitted to the ground, where carbon dioxide concentrations would be retrieved in four separate footprints for each image collected. These spatially varying carbon dioxide concentration estimates would then be analyzed using global transport models, like those used for weather prediction, to infer the locations of carbon dioxide sources and sinks.
The OCO instrument was developed by Hamilton Sundstrand Sensor Systems in Pomona, California, and the Jet Propulsion Laboratory. | 1 | Applied and Interdisciplinary Chemistry |
Paschen's law requires that:
* There are already free electrons at the cathode () which can be accelerated to trigger impact ionization. Such so-called seed electrons can be created by ionization by natural radioactivity or cosmic rays.
* The creation of further free electrons is only achieved by impact ionization. Thus Paschen's law is not valid if there are external electron sources. This can, for example, be a light source creating secondary electrons by the photoelectric effect. This has to be considered in experiments.
* Each ionized atom leads to only one free electron. However, multiple ionizations occur always in practice.
* Free electrons at the cathode surface are created by the impacting ions. The problem is that the number of thereby created electrons strongly depends on the material of the cathode, its surface (roughness, impurities) and the environmental conditions (temperature, humidity etc.). The experimental, reproducible determination of the factor is therefore nearly impossible.
* The electrical field is homogeneous. | 0 | Theoretical and Fundamental Chemistry |
Herman T. Briscoe was born on November 6, 1893, in Shoals, Indiana. Briscoe received his teaching certificate in 1912 from Indiana University in Bloomington, Indiana and began teaching at his home high school in Shoals for three academic years before becoming principal of Shoals high school and later superintendent of Shoals school district. He returned to Indiana University, earning his A.B. degree in chemistry with high distinction in 1917. Briscoe would then enlist in the U.S. army as a private in May 1918, transferring to the Hercules Powder Company as a research chemist until his discharge in 1919. Between 1919 and 1922, Briscoe held successful teaching positions at Stark’s Military Academy, as an Austin Teaching Fellow at Harvard University, and at Colby College. Returning to Indiana University for a third time, Herman T. Briscoe received his A.M. and Ph.D. degrees in chemistry in 1924 under the guidance of Professor Frank C. Mathers.
Briscoe married Orah Elberta Briscoe (née Cole) in 1928. Orah, born in Liberty Center, IN in 1907, received her B.A. in Latin in 1929 and her M.A. in English in 1934. In 1929, their first child Catherine was born. They would have a total of 4 children. | 0 | Theoretical and Fundamental Chemistry |
The continent of stability is a hypothesised large group of nuclides with masses greater than 300 daltons that is stable against radioactive decay, consisting of freely flowing up quarks and down quarks rather than up and down quarks bound into protons and neutrons. Matter containing these nuclides is termed up-down quark matter (udQM). The continent of stability is named in analogy with the island of stability. However, if it exists, the range of charge and mass will be much greater than in the island. Quark matter composed of up quarks and down quarks is predicted to be a lower energy state than that which contains strange quarks (strange quark matter), and also lower than the combination of quarks in the form of hadrons found in normal atomic nuclei if there are over 300 protons and neutrons. The lower limit of 300 was calculated based on a surface tension model, where the surface has a higher energy than the interior of the piece of quark matter. In order to be the absolutely more stable form, the energy must be lower than that of the most stable normal matter, that is 930 MeV per baryon. If these quark matter nuclides exist, they would be stable against fission, as fission would increase the surface. The quark matter nuclide could absorb neutrons resulting in an increase in its mass.
The boundary to the continent of stability is determined by the situations where the Coulomb energy due to electric charge overcomes the binding energy, or where decay into atomic nuclei results in lower energy. The lowest energy mass number is proportional to the cube of the charge (atomic number). However, a range of charges is stable for each mass, and the range increases as the mass increases. This can result in very heavy nuclides with atomic numbers the same as existing known elements, and even zero-charge pieces of quark matter.
A proposed alternative form of quark matter known as strangelets contains strange quarks in addition to the up and down quarks. This would be neutral in charge, and thus not form atoms. udQM is probably lower energy than strangelets (uds-matter).
At the Large Hadron Collider, the ATLAS Collaboration is attempting to observe this kind of matter. | 0 | Theoretical and Fundamental Chemistry |
The double helix is an important tertiary structure in nucleic acid molecules which is intimately connected with the molecule's secondary structure. A double helix is formed by regions of many consecutive base pairs.
The nucleic acid double helix is a spiral polymer, usually right-handed, containing two nucleotide strands which base pair together. A single turn of the helix constitutes about ten nucleotides, and contains a major groove and minor groove, the major groove being wider than the minor groove. Given the difference in widths of the major groove and minor groove, many proteins which bind to DNA do so through the wider major groove. Many double-helical forms are possible; for DNA the three biologically relevant forms are A-DNA, B-DNA, and Z-DNA, while RNA double helices have structures similar to the A form of DNA. | 0 | Theoretical and Fundamental Chemistry |
Moungi Bawendi (; born 15 March 1961) is an American–Tunisian–French chemist. He is currently the Lester Wolfe Professor at the Massachusetts Institute of Technology. Bawendi is known for his advances in the chemical production of high-quality quantum dots. In 2023 he was awarded the Nobel Prize in Chemistry. | 0 | Theoretical and Fundamental Chemistry |
As key players in the carbon cycle, methylotrophs work to reduce global warming primarily through the uptake of methane and other greenhouse gases. In aqueous environments, methanogenic archaea produce 40-50% of the world's methane. Symbiosis between methanogens and methanotrophic bacteria greatly decreases the amount of methane released into the atmosphere.
This symbiosis is also important in the marine environment. Marine bacteria are very important to food webs and biogeochemical cycles, particularly in coastal surface waters but also in other key ecosystems such as hydrothermal vents. There is evidence of widespread and diverse groups of methylotrophs in the ocean that have potential to significantly impact marine and estuarine ecosystems. One-carbon compounds used as a carbon and energy source by methylotrophs are found throughout the ocean. These compounds include methane, methanol, methylated amines, methyl halides, and methylated sulfur compounds, such as dimethylsulfide (DMS) and dimethylsulfoxide (DMSO). Some of these compounds are produced by phytoplankton and some come from the atmosphere. Studies incorporating a wider range of one-carbon substrates have found increasing diversity of methylotrophs, suggesting that the diversity of this bacterial group has not yet fully been explored.
Because these compounds are volatile and impact the climate and atmosphere, research on the interaction of these bacteria with these one-carbon compounds can also help understanding of air-sea fluxes of these compounds, which impact climate predictions. For example, it is uncertain whether the ocean acts as a net source or sink of atmospheric methanol, but a diverse set of methylotrophs use methanol as their main energy source. In some regions, methylotrophs have been found to be a net sink of methanol, while in others a product of methylotroph activity, methylamine, has been found to be emitted from the ocean and form aerosols. The net direction of these fluxes depends on the utilization by methylotrophs.
Studies have found that methylotrophic capacity varies with the productivity of a system, so the impacts of methylotrophy are likely seasonal. Because some of the one-carbon compounds used by methylotrophs, such as methanol and TMAO, are produced by phytoplankton, their availability will vary temporally and seasonally depending on phytoplankton blooms, weather events, and other ecosystem inputs. This means that methylotrophic metabolism is expected to follow similar dynamics, which will then impact biogeochemical cycles and carbon fluxes.
Impacts of methylotrophs were also found in deep-sea hydrothermal vents. Methylotrophs, along with sulfur oxidizers and iron oxidizers, expressed key proteins associated with carbon fixation. These types of studies will contribute to further understanding of deep sea carbon cycling and the connectivity between deep ocean and surface carbon cycling. The expansion of omics technologies has accelerated research on the diversity of methylotrophs, their abundance and activity in a variety of environmental niches, and their interspecies interactions. Further research must be done on these bacteria and the overall effect of bacterial drawdown and transformation of one-carbon compounds in the ocean. Current evidence points to a potentially substantial role for methylotrophs in the ocean in the cycling of carbon but also potentially in the global nitrogen, sulfur and phosphorus cycles as well as the air-sea flux of carbon compounds, which could have global climate impacts.
The use of methylotrophs in the agricultural sector is another way in which they can potentially impact the environment. Traditional chemical fertilizers supply nutrients not readily available from soil but can have some negative environmental impacts and are costly to produce. Methylotrophs have high potential as alternative biofertilizers and bioinoculants due to their ability to form mutualistic relationships with several plant species. Methylotrophs provide plants with nutrients such as soluble phosphorus and fixed nitrogen and also play a role in the uptake of said nutrients. Additionally, they can help plants respond to environmental stressors through the production of phytohormones. Methylotrophic growth also inhibits the growth of harmful plant pathogens and induces systemic resistance. Methylotrophic biofertilizers used either alone or together with chemical fertilizers have been shown to increase both crop yield and quality without loss of nutrients. | 0 | Theoretical and Fundamental Chemistry |
Cellular ncRNA pools are known to be dynamically regulated and can have high degrees of variation between different cell types and developmental stages. Dysregulation of transfer RNAs (tRNAs), a type of ncRNA, has been linked to a diverse array of detrimental physiological conditions including neurological diseases and cancer. While characterization of transfer RNA (tRNAs) diversity is relevant to disease, current library preparation approaches are limited in their ability to capture highly modified tRNA bases, which block reverse transcriptase and interfere with the production of full-length cDNA intermediates needed for sequencing. To date, several cDNA library preparation techniques, including OTTR, have attempted to overcome these problems and improve our ability to characterize ncRNA pools. | 1 | Applied and Interdisciplinary Chemistry |
Progesterone is a naturally occurring pregnane steroid and is also known as pregn-4-ene-3,20-dione. It has a double bond (4-ene) between the C4 and C5 positions and two ketone groups (3,20-dione), one at the C3 position and the other at the C20 position. | 0 | Theoretical and Fundamental Chemistry |
The exploration of the antiangiogenic and immunomodulatory activities of thalidomide has led to the study and creation of thalidomide analogs. Celgene has sponsored numerous clinical trials with analogues to thalidomide, such as lenalidomide, that are substantially more powerful and have fewer side effects — except for greater myelosuppression. In 2005, Celgene received FDA approval for lenalidomide (Revlimid) as the first commercially useful derivative. Revlimid is available only in a restricted distribution setting to avoid its use during pregnancy. Further studies are being conducted to find safer compounds with useful qualities. Another more potent analog, pomalidomide, is now FDA approved. Additionally, apremilast was approved by the FDA in March 2014. These thalidomide analogs can be used to treat different diseases, or used in a regimen to fight two conditions.
Interest turned to pomalidomide, a derivative of thalidomide marketed by Celgene. It is a very active anti-angiogenic agent and also acts as an immunomodulator. Pomalidomide was approved in February 2013 by the FDA as a treatment for relapsed and refractory multiple myeloma. It received a similar approval from the European Commission in August 2013, and is expected to be marketed in Europe under the brand name Imnovid. | 0 | Theoretical and Fundamental Chemistry |
A bioindicator is an organism or biological response that reveals the presence of pollutants by the occurrence of typical symptoms or measurable responses and is, therefore, more qualitative.
These organisms (or communities of organisms) can be used to deliver information on alterations in the environment or the quantity of environmental pollutants by changing in one of the following ways: physiologically, chemically or behaviourally.
The information can be deduced through the study of:
# their content of certain elements or compounds
# their morphological or cellular structure
# metabolic biochemical processes
# behaviour
# population structure(s).
The importance and relevance of biomonitors, rather than man-made equipment, are justified by the observation that the best indicator of the status of a species or system is itself. Bioindicators can reveal indirect biotic effects of pollutants when many physical or chemical measurements cannot. Through bioindicators, scientists need to observe only the single indicating species to check on the environment rather than monitor the whole community. Small sets of indicator species can also be used to predict species richness for multiple taxonomic groups.
The use of a biomonitor is described as biological monitoring and is the use of the properties of an organism to obtain information on certain aspects of the biosphere. Biomonitoring of air pollutants can be passive or active. Experts use passive methods to observe plants growing naturally within the area of interest. Active methods are used to detect the presence of air pollutants by placing test plants of known response and genotype into the study area.
The use of a biomonitor is described as biological monitoring. This refers to the measurement of specific properties of an organism to obtain information on the surrounding physical and chemical environment.
Bioaccumulative indicators are frequently regarded as biomonitors. Depending on the organism selected and their use, there are several types of bioindicators. | 1 | Applied and Interdisciplinary Chemistry |
Brooker was educated at Hawarden Area School in North Canterbury from 1970 to 1982, and was dux of the school in her final year there. She went on to study chemistry at the University of Canterbury, first graduating Bachelor of Science with first-class honours, and then completing a PhD titled Synthesis and characterisation of polynuclear complexes with macrocyclic and related ligands under the supervision of Vickie McKee in 1989. | 0 | Theoretical and Fundamental Chemistry |
The technique was discovered by a team of researchers at Peking University in Beijing, China. The discovery was announced in the journal Nature Biotechnology in July 2019. | 1 | Applied and Interdisciplinary Chemistry |
By incorporating electron donors and electron acceptors into the supramolecular polymers, features of artificial photosynthesis can be replicated. | 0 | Theoretical and Fundamental Chemistry |
As with atorvastatin, simvastatin, and other statin drugs metabolized via CYP3A4, drinking grapefruit juice during lovastatin therapy may increase the risk of side effects. Components of grapefruit juice, the flavonoid naringin, or the furanocoumarin bergamottin inhibit CYP3A4 in vitro, and may account for the in vivo effect of grapefruit juice concentrate decreasing the metabolic clearance of lovastatin, and increasing its plasma concentrations. | 0 | Theoretical and Fundamental Chemistry |
Hydroelasticity is of concern in various areas of marine technology such as:
* High-speed craft.
* Ships with the phenomena springing and whipping affecting fatigue and extreme loading
* Large scale floating structures such as floating airports, floating bridges and buoyant tunnels.
* Marine Risers.
* Cable systems and umbilicals for remotely operated or tethered underwater vehicles.
* Seismic cable systems.
* Flexible containers for water transport, oil spill recovery and other purposes. | 1 | Applied and Interdisciplinary Chemistry |
In June, 1950, Drago graduated with a BS degree in chemistry from the University of Massachusetts Amherst. After he completed his time with the U.S. Air Force, he enrolled at Ohio State University under the GI bill, completing his Ph.D. degree on December 17, 1954, under Professor Harry Sisler. His thesis was entitled "Studies on the Synthesis of Chloramine and Hydrazine."
In 1955, he was hired at the University of Illinois at Urbana–Champaign Department of Chemistry, where he remained until 1982. In 1966, he published the textbook Physical Methods in Inorganic Chemistry. In 1982, he moved to the University of Florida as Graduate Research Professor of Chemistry. | 0 | Theoretical and Fundamental Chemistry |
G. I. Taylor gave the solution for a special case where , where is a constant in 1923. He showed that the separation satisfies the equation and also
Taylor also considered an example, a decaying system of eddies rotating alternatively in opposite directions and arranged in a rectangular array
which satisfies the above equation with , where is the length of the square formed by an eddy. Therefore, this system of eddies decays as
O. Walsh generalized Taylors eddy solution in 1992. Walshs solution is of the form , where and | 1 | Applied and Interdisciplinary Chemistry |
While a universally accepted definition of sustainability remains elusive, the Brundtland Commission of the United Nations defined sustainable development as development that meets the needs of the present without compromising the ability of future generations to meet their own needs. Sustainability, the long-term maintenance of responsibility, requires the reconciliation of environmental, social equity and economic demands. These "three pillars" of sustainability encompass the responsible management of resource use. Also, it can mean that we can use a resource which won't cease to be abundant despite increasing intake.
Copper is a sustainable material. Its durability offers long service with little maintenance. Its high electrical and thermal energy efficiencies reduce the waste of electrical energy. Its antimicrobial properties destroy pathogenic microorganisms that cause disease. And its high scrap value and ability to be continuously recycled without any loss in performance ensure its responsible management as a valuable resource.
Life cycle inventory (LCI) information on copper tube, sheet, and wire products, using ISO standards and covering the mining and primary copper production sectors (i.e., smelting and refining) is available. Used in life cycle assessments (LCAs), particularly in the building and construction sector, LCI datasets assist manufacturers of copper-containing products with compliance and voluntary improvement initiatives. They also support policy makers in the development of environmental guidelines and regulations with the aim of fostering sustainable development.
The long lifetime of copper roofing and cladding has a significant positive effect on whole life assessments of copper versus other materials in terms of embodied energy consumption (i.e., the total energy consumed during every phase of each lifecycle in MJ/m), CO generation, and cost. | 1 | Applied and Interdisciplinary Chemistry |
The table in Figure 2 summarizes the Möbius–Hückel concept. The columns specify whether one has a Möbius or a Hückel structure and the rows specify whether 4n + 2 electrons or 4n electrons are present. Depending on which is present, a Möbius or a Hückel system, one selects the first or the second column. Then depending on the number of electrons present, 4n + 2 or 4n, one selects the first or the second row.<Ref Name=HEZ1971/> | 0 | Theoretical and Fundamental Chemistry |
Salen complexes with d metal ions, such as Ni(salen), typically have a low-spin square planar molecular geometry in the coordination sphere.
Other metal–salen complexes may have additional ligands above the salen nitrogen–oxygen plane. Complexes with one extra ligand, such as VO(salen), may have a square pyramidal molecular geometry. Complexes with two extra ligands, such as Co(salen)Cl(py), may have octahedral geometry. Usually the MNO core is relatively planar, even though the ethylene backbone is skewed and the overall salen ligand takes a twisted C symmetry. Examples exist where ancillary ligands force the NO donors out of planarity. No evidence indicates that salen is a redox-noninnocent ligand. | 0 | Theoretical and Fundamental Chemistry |
Off-resin cyclization is a solid-phase synthesis of key intermediates, followed by the key cyclization in solution phase, the final deprotection of any masked side chains is also carried out in solution phase. This has the disadvantages that the efficiencies of solid-phase synthesis are lost in the solution phase steps, that purification from by-products, reagents and unconverted material is required, and that undesired oligomers can be formed if macrocycle formation is involved.
The use of pentafluorophenyl esters (FDPP, PFPOH) and BOP-Cl are useful for cyclising peptides. | 1 | Applied and Interdisciplinary Chemistry |
The primary application of TPEPICO is the production of internal energy selected ions to study their unimolecular dissociation dynamics as a function of internal energy. The electrons are extracted by a continuous electric field and are velocity map imaged depending on their initial kinetic energy. Ions are accelerated in the opposite direction and their mass is determined by time-of-flight mass spectrometry. The data analysis yields dissociation thresholds, which can be used to derive new thermochemistry for the sample.
The electron imager side can also be used to record photoionization cross sections, photoelectron energy and angular distributions. With the help of circularly polarized light, photoelectron circular dichroism (PECD) can be studied. A thorough understanding of PECD effects could help explain the homochirality of life. Flash pyrolysis can also be used to produce free radicals or intermediates, which are then characterized to complement e.g. combustion studies. In such cases, the photoion mass analysis is used to confirm the identity of the radical produced.
Photoelectron photoion coincidence spectroscopy can be used to shed light on reaction mechanisms, and can also be generalized to study double ionization in (photoelectron) photoion photoion coincidence ((PE)PIPICO), fluorescence using photoelectron photon coincidence (PEFCO), or photoelectron photoelectron coincidence (PEPECO). Times-of-flight of photoelectrons and photoions can be combined in a form of a map, which visualizes the dynamics of the dissociative ionization process. Ion–electron velocity vector correlation functions can be obtained in double imaging setups, in which the ion detector also delivers position information. | 0 | Theoretical and Fundamental Chemistry |
One of the first dendrimers, the Newkome dendrimer, was synthesized in 1985. This macromolecule is also commonly known by the name arborol. The figure outlines the mechanism of the first two generations of arborol through a divergent route (discussed below). The synthesis is started by nucleophilic substitution of 1-bromopentane by triethyl sodiomethanetricarboxylate in dimethylformamide and benzene. The ester groups were then reduced by lithium aluminium hydride to a triol in a deprotection step. Activation of the chain ends was achieved by converting the alcohol groups to tosylate groups with tosyl chloride and pyridine. The tosyl group then served as leaving groups in another reaction with the tricarboxylate, forming generation two. Further repetition of the two steps leads to higher generations of arborol.
Poly(amidoamine), or PAMAM, is perhaps the most well known dendrimer. The core of PAMAM is a diamine (commonly ethylenediamine), which is reacted with methyl acrylate, and then another ethylenediamine to make the generation-0 (G-0) PAMAM. Successive reactions create higher generations, which tend to have different properties. Lower generations can be thought of as flexible molecules with no appreciable inner regions, while medium-sized (G-3 or G-4) do have internal space that is essentially separated from the outer shell of the dendrimer. Very large (G-7 and greater) dendrimers can be thought of more like solid particles with very dense surfaces due to the structure of their outer shell. The functional group on the surface of PAMAM dendrimers is ideal for click chemistry, which gives rise to many potential applications.
Dendrimers can be considered to have three major portions: a core, an inner shell, and an outer shell. Ideally, a dendrimer can be synthesized to have different functionality in each of these portions to control properties such as solubility, thermal stability, and attachment of compounds for particular applications. Synthetic processes can also precisely control the size and number of branches on the dendrimer. There are two defined methods of dendrimer synthesis, divergent synthesis and convergent synthesis. However, because the actual reactions consist of many steps needed to protect the active site, it is difficult to synthesize dendrimers using either method. This makes dendrimers hard to make and very expensive to purchase. At this time, there are only a few companies that sell dendrimers; Polymer Factory Sweden AB commercializes biocompatible bis-MPA dendrimers and Dendritech is the only kilogram-scale producers of PAMAM dendrimers. NanoSynthons, LLC from Mount Pleasant, Michigan, USA produces PAMAM dendrimers and other proprietary dendrimers. | 0 | Theoretical and Fundamental Chemistry |
Fluoroantimonic acid (pH −31.3) is a mixture of hydrogen fluoride and antimony pentafluoride, containing various cations and anions (the simplest being and ). This mixture is a superacid that, in terms of corrosiveness, is trillions of times stronger than pure sulfuric acid when measured by its Hammett acidity function. It even protonates some hydrocarbons to afford pentacoordinate carbocations (carbonium ions). Like its precursor hydrogen fluoride, it attacks glass, but can be stored in containers lined with PTFE (Teflon) or PFA. | 0 | Theoretical and Fundamental Chemistry |
Bainite can essentially be regarded as martensite that tempers during the course of transformation. It forms at a higher temperature than martensite, and even the latter can autotemper. Because the transformation temperature is higher, the austenite itself is mechanically weak so that the shape deformation due to bainite is relaxed by the plastic deformation of the adjacent austenite. As a consequence, the growing plate of bainite is confronted by a forest of dislocations that eventually terminates its growth even before the plate has hit an austenite grain boundary. Plates of bainite can therefore be smaller than those of martensite in the same steel. The transformation then proceeds by a sub-unit mechanism involving the successive nucleation of new plates. | 1 | Applied and Interdisciplinary Chemistry |
Thermal desorption fundamentally involves collecting volatile organic compounds onto a sorbent, and then heating this sorbent in a flow of gas to release the compounds and concentrate them into a smaller volume.
Early thermal desorbers used just single-stage operation, whereby the volatiles collected on a sorbent tube were released by heating the tube in a flow of gas, from where they passed directly into the GC.
Modern thermal desorbers can also accommodate two-stage operation, whereby the gas stream from the sorbent tube (typically 100–200 mL) is collected on a narrower tube integral to the thermal desorber, called the focusing trap or cold trap. Heating this trap releases the analytes once again, but this time in an even smaller volume of gas (typically 100–200 μL), resulting in improved sensitivity and better GC peak shape.
Modern thermal desorbers can accommodate both single-stage and two-stage operation, although single-stage operation is now usually carried out using the focusing trap to collect the analytes, rather than a sorbent tube.
It is normal for the focusing trap to be held at or below room temperature, although a temperature no lower than 0 °C is sufficient for all but the most volatile analytes. Higher trap temperatures also reduce the amount of water condensing inside the trap (when transferred to the GC column, water can reduce the quality of the chromatography). | 0 | Theoretical and Fundamental Chemistry |
FAM227B is most highly expressed in the testis at 1.983 +/- 0.404 RPKM, in the kidney at 1.408 +/- 0.152 RPKM, in the adrenal at 1.177 +/- 0.088 RPKM, and in the thyroid 1.133 +/- 0.165 RPKM. It is also expressed to a lesser degree in the appendix, bone marrow, brain, colon, duodenum, endometrium, esophagus, fat, gall bladder, heart, liver, lung, lymph node, ovary, pancreas, placenta, prostate, salivary gland, skin, small intestine, spleen, stomach, and urinary bladder | 1 | Applied and Interdisciplinary Chemistry |
Aeronomy is the scientific study of the upper atmosphere of the Earth — the atmospheric layers above the stratopause — and corresponding regions of the atmospheres of other planets, where the entire atmosphere may correspond to the Earth's upper atmosphere or a portion of it. A branch of both atmospheric chemistry and atmospheric physics, aeronomy contrasts with meteorology, which focuses on the layers of the atmosphere below the stratopause. In atmospheric regions studied by aeronomers, chemical dissociation and ionization are important phenomena. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, deposition occurs when molecules settle out of a solution.
Deposition can be viewed as a reverse process to dissolution or particle re-entrainment. | 0 | Theoretical and Fundamental Chemistry |
More recent variations are built with a simple "waterfall" driven by gravity, using a simple PVC plumbing pipe to flow water down a piece of plastic knitting screen (also known as "plastic canvas"), which is roughed up to allow algae to attach. In almost every case, these homemade algae scrubbers reduced the nutrients to very low levels, and this reduced or eliminated all nuisance algae problems.
In addition, "turf" algae, which was the focus of Dr. Adey's dumping-bucket design, is replaced by "green hair algae". This is because turf algae tends to be dark brown and thick (like artificial turf on sports fields), and it blocks the light and water from reaching the screen. This slows the growth (and filtering) of the algae because the bottom layers of algae that are attached to the screen start to die and detach. Green algae, however (especially light-green hair algae), allows light and water to penetrate all the way down to the screen if the growth is kept less than 20 mm thick, which allows the algae to grow faster and absorb more nutrients without dying and losing attachment to the screen. This is fortunate because green hair algae is the exact type of algae that grows automatically in a properly constructed algae scrubber.
Some models also use up-flowing air bubbles. This version, which is basically the exact opposite of the waterfall, allows the algae scrubber to be placed underwater in the aquarium, sump or pond, instead of above it. This greatly simplifies construction, since the device does not need to be waterproof, and it allows placement of the scrubber into tight areas where there is no room above the water line. The design also keeps the algae from drying out in the event of a power failure, because all the algae is under water, and the design also removes almost all splashing. The up-flowing bubble design falls into three categories: those that attach to and shine through the aquarium (or sump) glass; those that float on top of the aquarium, sump or pond water surface; and those that go completely underwater like a submarine. | 0 | Theoretical and Fundamental Chemistry |
Epoxidation with dioxiranes refers to the synthesis of epoxides from alkenes using three-membered cyclic peroxides, also known as dioxiranes.
Dioxiranes are three-membered cyclic peroxides containing a weak oxygen-oxygen bond. Although they are able to effect oxidations of heteroatom functionality and even carbon-hydrogen bonds, they are most widely used as epoxidizing agents of alkenes. Dioxiranes are electrophilic oxidants that react more quickly with electron-rich than electron-poor double bonds; however, both classes of substrates can be epoxidized within a reasonable time frame. Dioxiranes may be prepared and isolated or generated in situ from ketones and potassium peroxymonosulfate (Oxone). In situ preparations may be catalytic in ketone, and if the ketone is chiral, enantioselective epoxidation takes place. The functional group compatibility of dioxiranes is limited somewhat, as side oxidations of amines and sulfides are rapid. Nonetheless, protocols for dioxirane oxidations are entirely metal free. The most common dioxiranes employed for synthesis are dimethyl dioxirane (DMD) and methyl(trifluoromethyl)dioxirane (TFD). | 0 | Theoretical and Fundamental Chemistry |
BIND was the first database of its kind to contain info on biomolecular interactions, reactions and pathways in one schema. It is also the first to base its ontology on chemistry which allows 3D representation of molecular interactions. The underlying chemistry allows molecular interactions to be described down to the atomic level of resolution.
PreBIND an associated system for data mining to locate biomolecular interaction information in the scientific literature. The name or accession number of a protein can be entered and PreBIND will scan the literature and return a list of potentially interacting proteins. BIND BLAST is also available to find interactions with proteins that are similar to the one specified in the query.
BIND offers several “features” that many other proteomics databases do not include. The authors of this program have created an extension to traditional IUPAC nomenclature to help describe post-translational modifications that occur to amino acids. These modifications include: acetylation, formylation, methylation, palmitoylation, etc. the extension of the traditional IUPAC codes allows these amino acids to be represented in sequence form as well. BIND also utilizes a unique visualization tool known as OntoGlyphs. The OntoGlyphs were developed based on Gene Ontology (GO) and provide a link back to the original GO information. A number of GO terms have been grouped into categories, each one representing a specific function, binding specificity, or localization in the cell. There are 83 OntoGlyph characters in total. There are 34 functional OntoGlyphs which contain information about the role of the molecule (e.g. cell physiology, ion transport, signaling). There are 25 binding OntoGlyphs which describe what the molecule binds (e.g. ligands, DNA, ions). The other 24 OntoGlyphs provide information about the location of the molecule within a cell (e.g. nucleus, cytoskeleton). The OntoGlyphs can be selected and manipulated to include or exclude certain characteristics from search results. The visual nature of the OntoGlyphs also facilitates pattern recognition when looking at search results. ProteoGlyphs are graphical representations of the structural and binding properties of proteins at the level of conserved domains. The protein is diagrammed as a straight horizontal line and glyphs are inserted to represent conserved domains. Each glyph is displayed to represent the relative position and length of its alignment in the protein sequence. | 1 | Applied and Interdisciplinary Chemistry |
Shq1, a protein thought to play a role in the stabilization and/or production of box H/ACA snoRNA, is still uncharacterized. It has been proposed that Shq1, along with Naf1p, is involved in the initial steps of the biogenesis of H/ACA box snoRNPs (box H/ACA snoRNAs form complexes with proteins, thereby forming snoRNPs) because of its association with certain snoRNP proteins during the snoRNP’s maturation, while showing very little association with the mature snoRNP complex. Despite the known involvement of Shq1 in H/ACA box snoRNP's production, the exact function of this protein in the overall rRNA processing pathway is still unknown. | 1 | Applied and Interdisciplinary Chemistry |
Photodynamic therapy (PDT) uses photooxygenation to destroy cancerous tissue. A photosensitizer is injected into the tumor and then specific wavelengths of light are exposed to the tissue to excite the Sens. The excited Sens generally follows a type I or II photooxygenation mechanism to result in oxidative damage to cells. Extensive oxidative damage to tumor cells will kill tumor cells. Also oxidative damage to nearby blood vessels will cause local agglomeration and cut off nutrient supply to the tumor, thus starving the tumor.
An important consideration when selecting the Sens to be used in PDT is the specific wavelength of light the Sens will absorb to reach an excited state. Since the maximum penetration of tissues is achieved around wavelengths of 800 nm, selecting Sens that absorb around this range is advantageous as it allows for PDT to be affective on tumors beneath the outer most layer of the dermis. The window of 800 nm light is most effective at penetrating tissues because at wavelengths shorter than 800 nm the light starts to be scattered by the macromolecules of cells and at wavelengths longer than 800 nm water molecules will begin to absorb the light and convert it into heat. | 0 | Theoretical and Fundamental Chemistry |
Examination of dimerized and trimerized natural products has shown that an element of bilateral symmetry is often present. Bilateral symmetry refers to a molecule or system that contains a C, C, or C point group identity. C symmetry tends to be much more abundant than other types of bilateral symmetry. This finding sheds light on how these compounds might be mechanistically created, as well as providing insight into the thermodynamic properties that make these compounds more favorable. Density functional theory (DFT), the Hartree–Fock method, and semiempirical calculations also show some favorability for dimerization in natural products due to evolution of more energy per bond than the equivalent trimer or tetramer. This is proposed to be due to steric hindrance at the core of the molecule, as most natural products dimerize and trimerize in a head-to-head fashion rather than head-to-tail. | 1 | Applied and Interdisciplinary Chemistry |
For an instance, in India the rainfall over the country is primarily orographic, associated with tropical depressions originating in the Arabian Sea and the Bay of Bengal. The summer monsoon accounts for more than 85 per cent of the precipitation. The uncertainty of occurrence of rainfall marked by prolonged dry spells and fluctuations in seasonal and annual rainfall is a serious problem for the country. Large parts of Haryana, Maharashtra, Andhra Pradesh, Rajasthan, Gujarat, Madhya Pradesh, Karnataka and Tamil Nadu are not only in deficit in rainfall but also subject to large variations, resulting in frequent droughts and causing immense hardship to the population and enormous loss to the nation. The water availability even for drinking purposes becomes critical, particularly in the summer months as the rivers dry up and the ground water recedes. Regional variations in the rainfall lead to situations when some parts of the country do not have enough water even for raising a single crop. On the other hand, excess rainfall occurring in some parts of the country creates havoc due to floods.
Irrigation using river water and ground water has been the prime factor for raising the food grain production in India from a mere 50 million tonnes in the 1950s to more than 200 million tonnes at present, leading India to attain self-sufficiency in food. Irrigated area has increased from 22 million hectares to 95 million hectares during this period. The population of India, which is around 1100 million at present, is expected to increase to 1500 to 1800 million in the year 2050 and that would require about 450 million tonnes of food grains. For meeting this requirement, it would be necessary to increase irrigation potential to 160 million hectares for all crops by 2050. India's maximum irrigation potential that could be created through conventional sources has been assessed to be about 140 million hectares. For attaining a potential of 160 million hectares, other strategies shall have to be evolved.
Floods are a recurring feature, particularly by the Brahmaputra and Ganga rivers, in which almost 60 per cent of the river flows of India occur. Flood damages, which were Rs. 52 crores in 1953, have gone up to Rs. 5,846 crores in 1998 with annual average being Rs. 1,343 crores affecting the States of Assam, Bihar, West Bengal and Uttar Pradesh along with untold human sufferings. On the other hand, large areas in the States of Rajasthan, Gujarat, Andhra Pradesh, Karnataka and Tamil Nadu face recurring droughts. As much as 85 percentage of drought prone area falls in these States. One of the most effective ways to increase the irrigation potential for increasing the food grain production, mitigating floods and droughts and reducing regional imbalance in the availability of water is the Inter Basin Water Transfer (IBWT) from the surplus rivers to deficit areas. Brahmaputra and Ganga particularly their northern tributaries, Mahanadi, Godavari and West Flowing Rivers originating from the Western Ghats are found to be surplus in water resources. If we can build storage reservoirs on these rivers and connect them to other parts of the country, regional imbalances could be reduced significantly and lot of benefits could be gained by way of additional irrigation, domestic and industrial water supply, hydropower generation, navigational facilities etc. | 1 | Applied and Interdisciplinary Chemistry |
Efrapeptins are peptides produced by fungi in the genus Tolypocladium that have antifungal, insecticidal, and mitochondrial ATPase inhibitory activities. They are produced via a biosynthetic pathway similar to, but simpler than, the ciclosporin pathway with nonribosomal peptide synthase (NRPS) and/or polyketide synthase (PKS) being the key elements.
The amino acid sequences of efrapeptins are:
:Efrapeptin F: Ac-Pip-Aib-Pip-Aib-Aib-Leu-bAla-Gly-Aib-Aib-Pip-Aib-Ala-Leu-Iva-Unk
:Efrapeptin G: Ac-Pip-Aib-Pip-Iva-Aib-Leu-bAla-Gly-Aib-Aib-Pip-Aib-Ala-Leu-Iva-Unk
::Aib: 2-methylalanine; Iva: 2-ethylalanine; Unk: does not match to a known amino acid | 0 | Theoretical and Fundamental Chemistry |
A-values help predict the conformation of cyclohexane rings. The most stable conformation will be the one which has the substituent or substituents equatorial. When multiple substituents are taken into consideration, the conformation where the substituent with the largest A-value is equatorial is favored.
The utility of A-values can be generalized for use outside of cyclohexane conformations. A-values can help predict the steric effect of a substituent. In general, the larger a substituents A-value, the larger the steric effect of that substituent. A methyl group has an A-value of 1.74 while tert-butyl group has an A-value of ~5. Because the A-value of tert-butyl is higher, tert'-butyl has a larger steric effect than methyl. This difference in steric effects can be used to help predict reactivity in chemical reactions. | 0 | Theoretical and Fundamental Chemistry |
Piperacillin is not absorbed orally, and must therefore be given by intravenous or intramuscular injection. It has been shown that the bactericidal actions of the drug do not increase with concentrations of piperacillin higher than 4-6× MIC, which means that the drug is concentration-independent in terms of its actions. Piperacillin has instead shown to offer higher bactericidal activity when its concentration remains above the MIC for longer periods of time (50% time above MIC showing the highest activity). This higher activity present in continuous dosing has not been directly linked to clinical outcomes, but however does show promise of lowering possibility of resistance and decreasing mortality.
Extending the time of piperacillin-tazobactam infusion allows the drugs to maintain the necessary concentrations needed within the body to prevent bacterial growth, enhancing bactericidal activity. The studies supporting this theory generally administered ~3.375 g of piperacillin-tazobactam every 8 hours during a 4-hour infusion, while for organisms with higher minimum inhibitory concentrations, ~4.5 g of piperacillin-tazobactam was administered every 6 hours during a 3-hour infusion.
The recommended doses provided by the BNFC for infants with hospital-acquired infections are 90 mg/kg every 8 hours for infants, a maximum of 4.5 g every 6 hours for children, and 4.5 g every 8 hours for children aged 12 and above. A dosage of 90 mg/kg every 6 hours is suggested for infants and children diagnosed with neutropenia. | 0 | Theoretical and Fundamental Chemistry |
Emission channeling is an experimental technique for identifying the position of short-lived radioactive atoms in the lattice of a single crystal.
When the radioactive atoms decay, they emit fast charged particles (e.g., α-particles and β-particles). Because of their charge, the emitted particles interact in characteristic ways with the electrons and nuclei of the crystal atoms, giving rise to channeling and blocking directions for the particle escaping the crystal. The intensity (or yield) of the emitted particles is therefore dependent on the position of the detector relative to crystal planes and axes. This fact is used to infer the location of the radioactive species in the lattice by varying the emission angles and subsequent comparison to simulation results. For the simulations, the manybeam formalism can be employed, and resolutions below 1 Å are achievable.
Among others, the technique has been used to determine the sites of manganese impurities implanted in semiconducting gallium arsenide: 70% occupy substitutional gallium sites and 28% are located at tetrahedral interstitial sites with arsenic as nearest neighbors. | 0 | Theoretical and Fundamental Chemistry |
With the late Professor Sir Nicholas Shackleton in charge, the focus of research shifted to marine isotope records, which document changes in the size of polar ice sheets and temperature changes. This research helped to establish the Milankovitch Theory as the most plausible explanation of glacial/interglacial changes over the past million years, and was continued to develop much more extensive geological timescales, covering the last 30 million years, on the basis of this hypothesis. Other areas researched by members of the laboratory include pollen records and tree rings as a proxy for past climate. The laboratory changed principal allegiance from the Department of Plant Sciences to the Department of Earth Sciences around 1995.
In 2005, after Nick Shackleton's retirement, the laboratory was incorporated into the building housing the Department of Earth Sciences, where it continues to operate. It is part of the inter-departmental Godwin Institute for Quaternary Research, a loose collection of Cambridge University research facilities and workers focused on research particularly addressing the history of the last 1.8 million years. | 0 | Theoretical and Fundamental Chemistry |
Depending on the mass of a star, the Oddo-Harkins pattern arises from the burning of progressively more massive elements within a collapsing dying star by fusion processes such as the proton-proton chain, the CNO cycle, and the triple-alpha process. The newly formed elements are ejected slowly via stellar wind, or in the explosion of a supernova, and will eventually join the rest of the galaxy's interstellar medium. | 0 | Theoretical and Fundamental Chemistry |
Tenuifolins are bio-active terpenoids. Tenuifolins inhibit beta-amyloid synthesis in vitro. Tenuifolins have nootropic activity in vivo via acetylcholinesterase inhibition and increased norepinephrine and dopamine production. | 0 | Theoretical and Fundamental Chemistry |
A low pressure ratio fan (such as that used on a high bypass ratio turbofan) has a range of working lines. At high flight speeds, the ram pressure ratio factors up the cold nozzle pressure ratio, causing the nozzle to choke. Above the choking condition, the working lines tend to coalesce into a unique steep straight line. When the nozzle unchokes, the working line starts to become more curved, reflecting the curvature of the nozzle characteristic. With falling flight Mach number, the cold nozzle pressure ratio decreases. Initially this has no effect upon the position of the working line, apart from the curved (unchoked) tail, which becomes longer. Eventually, the cold nozzle will become unchoked at lower flight Mach numbers, even at full throttle. The working lines will now become curved, gradually migrating towards surge as flight Mach number decreases. The lowest surge margin working line occurs at static conditions.
Owing to the nature of the constraints involved, the fan working lines of a mixed turbofan are somewhat steeper than those of the equivalent unmixed engine.
A fan may have two maps, one for the bypass (i.e. outer) section and one for the inner section which typically has longer, flatter, speed lines.
Military turbofans tend to have a much higher design fan pressure ratio than civil engines. Consequently, the final (mixed) nozzle is choked at all flight speeds, over most of the throttle range. However, at low throttle settings the nozzle will unchoke, causing the lower end of the working lines to have a short curved tail, particularly at low flight speeds.
However, ultra-high bypass ratio turbofans have a very low design fan pressure ratio (e.g. 1.2, on the bypass section). Consequently, even at cruise flight speeds, the cold (or mixed final) propelling nozzle may only be choked at high throttle settings. The fan working lines become more curved and migrate quickly towards surge as flight Mach number decreases. As a result, the static working line can be well into surge, particularly at low throttle settings.
One solution is to have a variable area cold (or mixed) nozzle. Increasing the nozzle area at low flight speeds brings the fan working line away from surge.
An alternative solution is to fit a variable pitch fan. Scheduling the pitch of the fan blades has no impact upon the position of the fan working lines, but can be used to move the surge line upwards, to improve fan surge margin. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, pyranose is a collective term for saccharides that have a chemical structure that includes a six-membered ring consisting of five carbon atoms and one oxygen atom (a heterocycle). There may be other carbons external to the ring. The name derives from its similarity to the oxygen heterocycle pyran, but the pyranose ring does not have double bonds. A pyranose in which the anomeric (hydroxyl group) at C(l) has been converted into an OR group is called a pyranoside. | 0 | Theoretical and Fundamental Chemistry |
Whether or not a given individuals brain can deal effectively with stress, and thus their susceptibility to depression, depends on the β-catenin in each persons brain, according to a study conducted at the Icahn School of Medicine at Mount Sinai and published November 12, 2014, in the journal Nature. Higher β-catenin signaling increases behavioral flexibility, whereas defective β-catenin signaling leads to depression and reduced stress management. | 1 | Applied and Interdisciplinary Chemistry |
Sum frequency generation spectroscopy uses two laser beams mixed at an interface to generate an output beam with a frequency equal to the sum of the two input frequencies. Sum frequency generation spectroscopy is used to analyze surfaces and interfaces, carrying complementary information to infrared and Raman spectroscopy. | 0 | Theoretical and Fundamental Chemistry |
NAPQI, also known as NAPBQI or N-acetyl-p-benzoquinone imine, is a toxic byproduct produced during the xenobiotic metabolism of the analgesic paracetamol (acetaminophen). It is normally produced only in small amounts, and then almost immediately detoxified in the liver.
However, under some conditions in which NAPQI is not effectively detoxified (usually in the case of paracetamol overdose), it causes severe damage to the liver. This becomes apparent 3–4 days after ingestion and may result in death from fulminant liver failure several days after the overdose. | 1 | Applied and Interdisciplinary Chemistry |
The exact solution of the Navier-Stokes solutions was verified experimentally by Zauner in 1985. Further analysis showed that the axial momentum flux decays slowly along the axis unlike the Schlichting jet solution and it is found that the Schneider flow becomes invalid when distance from the origin increases to a distance of the order exponential of square of the jet Reynolds number, thus the domain of validity of Schneider solution increases with increasing jet Reynolds number. | 1 | Applied and Interdisciplinary Chemistry |
Agroinfiltration is a method used in plant biology and especially lately in plant biotechnology to induce transient expression of genes in a plant, or isolated leaves from a plant, or even in cultures of plant cells, in order to produce a desired protein. In the method, a suspension of Agrobacterium tumefaciens is introduced into a plant leaf by direct injection or by vacuum infiltration, or brought into association with plant cells immobilised on a porous support (plant cell packs), whereafter the bacteria transfer the desired gene into the plant cells via transfer of T-DNA. The main benefit of agroinfiltration when compared to the more traditional plant transformation is speed and convenience, although yields of the recombinant protein are generally also higher and more consistent.
The first step is to introduce a gene of interest to a strain of Agrobacterium tumefaciens. Subsequently, the strain is grown in a liquid culture and the resulting bacteria are washed and suspended into a suitable buffer solution. For injection, this solution is then placed in a syringe (without a needle). The tip of the syringe is pressed against the underside of a leaf while simultaneously applying gentle counterpressure to the other side of the leaf. The Agrobacterium suspension is then injected into the airspaces inside the leaf through stomata, or sometimes through a tiny incision made to the underside of the leaf.
Vacuum infiltration is another way to introduce Agrobacterium deep into plant tissue. In this procedure, leaf disks, leaves, or whole plants are submerged in a beaker containing the solution, and the beaker is placed in a vacuum chamber. The vacuum is then applied, forcing air out of the intercellular spaces within the leaves via the stomata. When the vacuum is released, the pressure difference forces the "Agrobacterium" suspension into the leaves through the stomata into the mesophyll tissue. This can result in nearly all of the cells in any given leaf being in contact with the bacteria.
Once inside the leaf the Agrobacterium remains in the intercellular space and transfers the gene of interest as part of the Ti plasmid-derived T-DNA in high copy numbers into the plant cells. The gene transfer occurs when the plant signals are induced and physical contact is made between the plant cells and the bacteria. The bacteria create a mechanism that burrows a hole and transfers the new T-DNA strand into the plant cell. The T-DNA moves into the nucleus of the plant and begins to integrate into the plants chromosome. The gene is then transiently expressed through RNA synthesis from appropriate promoter sequences in all transfected cells (no selection for stable integration is performed). The plant can be monitored for a possible effect in the phenotype, subjected to experimental conditions or harvested and used for purification of the protein of interest. Many plant species can be processed using this method, but the most common ones are Nicotiana benthamiana and less often, Nicotiana tabacum'.
Transient expression in cultured plant cell packs is a new procedure, recently patented by the Fraunhofer Institute IVV, Germany. For this technique, suspension cultured cells of tobacco (e.g.: NT1 or BY2 cell lines of Nicotiana tabacum) are immobilised by filtration onto a porous support to form a well-aerated cell pack, then incubated with recombinant Agrobacterium for a time to allow T-DNA transfer, before refiltration to remove excess bacteria and liquid. Incubation of the cell pack in a humid environment for time periods up to several days allows transient expression of protein. Secreted proteins can be washed out of the cell pack by application of buffer and further filtration. | 1 | Applied and Interdisciplinary Chemistry |
In the Acerinox accident of 1998, the Spanish recycling company Acerinox accidentally melted down a mass of radioactive caesium-137 that came from a gamma-ray generator. | 0 | Theoretical and Fundamental Chemistry |
The versatility of spectroelectrochemistry is increasing due to the possibility of using several electrochemical techniques in different spectral regions depending on the purpose of the study and the information of interest.
The main advantages of spectroelectrochemical techniques are:
*The simultaneous information is obtained by different techniques in a single experiment, increasing the selectivity and the sensitivity.
*Both qualitative and quantitative information can be obtained.
*The possibility of working with a small amount of sample, saving it for future analysis.
Due to the high versatility of the technique, the field of applications is considerably wide.
*Study of reaction mechanisms, where the oxidation and reduction of the species involved in the reaction can be observed, as well as the generation of reaction intermediates.
*Characterization of organic and inorganic materials, that allow to understand the structure and properties of the material when is perturbed by a signal (electric, light, etc.).
*Development of spectroelectrochemical sensors, which are based on optical and electrical responses, capable of providing two independent signals about the same sample and offering a self-validated determination.
*Study of catalysts, obtaining relationships between the electrochemical and spectroscopic properties and their photochemical and photophysical behaviour.
*Study different processes and molecules in biotechnology, biochemistry or medicine.
*Determine specific properties and characteristics of new materials in fields such as energy or nanotechnology. | 0 | Theoretical and Fundamental Chemistry |
In many pairs of liquids, there is no uniformity of attractive forces, i.e., the adhesive (between dissimilar molecules) and cohesive forces (between similar molecules) are not uniform between the two liquids. Therefore, they deviate from Raoult's law, which applies only to ideal solutions. | 0 | Theoretical and Fundamental Chemistry |
Superose is a trade name for a collection of FPLC columns which are used in the automated separation of biological molecules. The different columns provided can separate a variety of macromolecules, ranging from small peptides and polysaccharides to DNA strands and entire viruses. The material inside the column is agarose based, meaning that it consists of sugars that are crosslinked to form a gel-like mass. The pores in this material have different sizes, and if a molecule is too big, it does not fit into the pores, meaning that it follows a shorter way to the end of the column.
The columns are placed in a holder, and a computerized pumping system pumps a watery solution, often a buffer through the column. A special injection loop allows the injection of the desired sample. | 1 | Applied and Interdisciplinary Chemistry |
Using a thin coat of polish can prevent tarnish from forming over these metals. Tarnish can be removed by using steel wool, sandpaper, emery paper, baking soda or a file to rub or polish the metal's dull surface. Fine objects (such as silverware) may have the tarnish electrochemically reversed (non-destructively) by resting the objects on a piece of aluminium foil in a pot of boiling water with a small amount of salt or baking soda, or it may be removed with a special polishing compound and a soft cloth. Gentler abrasives, like calcium carbonate, are often used by museums to clean tarnished silver as they cannot damage or scratch the silver and will not leave unwanted residues. | 1 | Applied and Interdisciplinary Chemistry |
Propranolol exist in two different enantiomers, (S)-(−)- and (R)-(+)-enantiomers. The (S)-isomer is 100-fold more potent than the (R)-isomer and that is the general rule for most β-blockers. It is possible to produce the (S)-propranolol enantiomer from α-naphthol and 3-bromopropanol as seen in figure 6. α-Naphthol and 3-bromopropanol are refluxed for 6 hours to give alcohol. The alcohol is oxidized by using 2-Iodoxybenzoic acid (IBX) to give aldehyde. The aldehyde is subjected to -proline catalyzed asymmetric α-aminoxylation and a reduction is made with NaBH in methanol. A diol is obtained by Pd/C-catalyzed hydrogenolysis. Finally the diol is converted to epoxide using the Mitsunobu reaction and stirred with isopropyl amine in CHCl to give (S)-propranolol. | 1 | Applied and Interdisciplinary Chemistry |
Karunadasa grew up in Colombo. She attended high school in Sri Lanka and was a student at Ladies College, Colombo. She thought that she would become a doctor, and eventually decided to apply to university in America. She attended Princeton University, where she worked with Robert Cava on the geometric magnetic frustration of metal oxides. Cavas excitement about research inspired Karunadasa to continue her own academic career. Graduating with a degree in chemistry and a certificate in materials science and engineering, Karunadasa joined the University of California, Berkeley for her doctoral studies. There she worked in the lab of Jeffrey R. Long on heavy-atom building units for magnetic materials and electrocatalysts for water splitting. Karunadasa continued her work on water-splitting electrocatalysts with Jeffrey R. Long and Christopher Chang as a postdoctoral fellow. The molybdenum-oxo metal complex synthesized by Karunadasa is around seventy times cheaper than platinum, the most commonly used metal catalyst in water splitting. She then moved to the California Institute of Technology, where she worked on catalysts for hydrocarbon oxidation with Harry B. Gray as a BP Postdoctoral Fellow. | 0 | Theoretical and Fundamental Chemistry |
Cervarix, GARDASIL and GARDASIL9 are three recombinant subunit vaccines licensed for the protection against HPV infection. They differ in the strains which they protect the patients from as Cervarix confers protection against type 16 and 18, Gardasil confers protection against type 6, 11, 16 and 18, and Gardasil 9 confers protection against type 6, 11, 16, 18, 31, 33, 45, 52, 58 respectively. The vaccines contain purified VLP of the major capsid L1 protein produced by recombinant Saccharomyces cerevisiae.
It has been shown in a 2014 systematic quantitative review that the bivalent HPV vaccine (Cervarix) is associated with pain (OR 3.29; 95% CI: 3.00–3.60), swelling (OR 3.14; 95% CI: 2.79–3.53) and redness (OR 2.41; 95% CI: 2.17–2.68) being the most frequently reported adverse effects. For Gardasil, the most frequently reported events were pain (OR 2.88; 95% CI: 2.42–3.43) and swelling (OR 2.65; 95% CI: 2.0–3.44).
Gardasil was discontinued in the U.S. on May 8, 2017, after the introduction of Gardasil 9 and Cervarix was also voluntarily withdrawn in the U.S. on August 8, 2016. | 1 | Applied and Interdisciplinary Chemistry |
POC is decomposed by a series of microbe-driven processes, such as methanogenesis and sulfate reduction, before burial in the seafloor. Degradation of POC also results in microbial methane production which is the main gas hydrate on the continental margins. Lignin and pollen are inherently resistant to degradation, and some studies show that inorganic matrices may also protect organic matter. Preservation rates of organic matter depend on other interdependent variables that vary nonlinearly in time and space. Although organic matter breakdown occurs rapidly in the presence of oxygen, microbes utilizing a variety of chemical species (via redox gradients) can degrade organic matter in anoxic sediments. The burial depth at which degradation halts depends upon the sedimentation rate, the relative abundance of organic matter in the sediment, the type of organic matter being buried, and innumerable other variables. While decomposition of organic matter can occur in anoxic sediments when bacteria use oxidants other than oxygen (nitrate, sulfate, Fe), decomposition tends to end short of complete mineralization. This occurs because of preferential decomposition of labile molecules over refractile molecules. | 0 | Theoretical and Fundamental Chemistry |
A number of factors can affect the migration of nucleic acids: the dimension of the gel pores (gel concentration), size of DNA being electrophoresed, the voltage used, the ionic strength of the buffer, and the concentration of intercalating dye such as ethidium bromide if used during electrophoresis.
Smaller molecules travel faster than larger molecules in gel, and double-stranded DNA moves at a rate that is inversely proportional to the logarithm of the number of base pairs. This relationship however breaks down with very large DNA fragments, and separation of very large DNA fragments requires the use of pulsed field gel electrophoresis (PFGE), which applies alternating current from different directions and the large DNA fragments are separated as they reorient themselves with the changing field.
For standard agarose gel electrophoresis, larger molecules are resolved better using a low concentration gel while smaller molecules separate better at high concentration gel. Higher concentration gels, however, require longer run times (sometimes days).
The movement of the DNA may be affected by the conformation of the DNA molecule, for example, supercoiled DNA usually moves faster than relaxed DNA because it is tightly coiled and hence more compact. In a normal plasmid DNA preparation, multiple forms of DNA may be present. Gel electrophoresis of the plasmids would normally show the negatively supercoiled form as the main band, while nicked DNA (open circular form) and the relaxed closed circular form appears as minor bands. The rate at which the various forms move however can change using different electrophoresis conditions, and the mobility of larger circular DNA may be more strongly affected than linear DNA by the pore size of the gel.
Ethidium bromide which intercalates into circular DNA can change the charge, length, as well as the superhelicity of the DNA molecule, therefore its presence in gel during electrophoresis can affect its movement. For example, the positive charge of ethidium bromide can reduce the DNA movement by 15%. Agarose gel electrophoresis can be used to resolve circular DNA with different supercoiling topology.
DNA damage due to increased cross-linking will also reduce electrophoretic DNA migration in a dose-dependent way.
The rate of migration of the DNA is proportional to the voltage applied, i.e. the higher the voltage, the faster the DNA moves. The resolution of large DNA fragments however is lower at high voltage. The mobility of DNA may also change in an unsteady field – in a field that is periodically reversed, the mobility of DNA of a particular size may drop significantly at a particular cycling frequency. This phenomenon can result in band inversion in field inversion gel electrophoresis (FIGE), whereby larger DNA fragments move faster than smaller ones. | 1 | Applied and Interdisciplinary Chemistry |
The standard enthalpy change of any reaction can be calculated from the standard enthalpies of formation of reactants and products using Hesss law. A given reaction is considered as the decomposition of all reactants into elements in their standard states, followed by the formation of all products. The heat of reaction is then minus the sum of the standard enthalpies of formation of the reactants (each being multiplied by its respective stoichiometric coefficient, ) plus' the sum of the standard enthalpies of formation of the products (each also multiplied by its respective stoichiometric coefficient), as shown in the equation below:
If the standard enthalpy of the products is less than the standard enthalpy of the reactants, the standard enthalpy of reaction is negative. This implies that the reaction is exothermic. The converse is also true; the standard enthalpy of reaction is positive for an endothermic reaction. This calculation has a tacit assumption of ideal solution between reactants and products where the enthalpy of mixing is zero.
For example, for the combustion of methane, :
However is an element in its standard state, so that , and the heat of reaction is simplified to
which is the equation in the previous section for the enthalpy of combustion . | 0 | Theoretical and Fundamental Chemistry |
The ground state destabilization theory proposes that the electron-electron repulsion between the alpha lone-pair and nucleophilic electron pair destabilize each other by electronic repulsion (filled–filled orbital interaction) thereby decreasing the activation barrier by increasing the ground state energy and making it more reactive. This explains the higher reactivity of α-nucleophiles, however, this electronic mechanism should also increase the basicity and, therefore, cannot fully explain the α-effect. | 0 | Theoretical and Fundamental Chemistry |
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