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The self-ionization of water (also autoionization of water, and autodissociation of water, or simply dissociation of water) is an ionization reaction in pure water or in an aqueous solution, in which a water molecule, HO, deprotonates (loses the nucleus of one of its hydrogen atoms) to become a hydroxide ion, OH. The hydrogen nucleus, H, immediately protonates another water molecule to form a hydronium cation, HO. It is an example of autoprotolysis, and exemplifies the amphoteric nature of water. | 0 | Theoretical and Fundamental Chemistry |
Beractant, also known by the trade name of Survanta, is a modified bovine pulmonary surfactant containing bovine lung extract (phospholipids, neutral lipids,
fatty acids, and bovine surfactant proteins), to which synthetic DPPC, tripalmitin and palmitic acid are added. The composition provides 25 mg/mL phospholipids, 0.5 to 1.75 mg/mL triglycerides, 1.4 to 3.5 mg/mL free fatty acids, and <1.0 mg/mL total surfactant proteins. As an intratracheal suspension, it can be used for the prevention and treatment of neonatal respiratory distress syndrome. Survanta is manufactured by Abbvie. | 0 | Theoretical and Fundamental Chemistry |
The nucleus of deuterium is called a deuteron. It has a mass of (just over ).
The charge radius of the deuteron is .
Like the proton radius, measurements using muonic deuterium produce a smaller result: . | 0 | Theoretical and Fundamental Chemistry |
The spatial resolution achievable in topographic images can be limited by one or several of three factors:
the resolution (grain or pixel size) of the detector, the experimental geometry, and intrinsic diffraction effects.
First, the spatial resolution of an image can obviously not be better than the grain size (in the case of film) or the pixel size (in the case of digital detectors) with which it was recorded. This is the reason why topography requires high-resolution X-ray films or CCD cameras with the smallest pixel sizes available today. Secondly, resolution can be additionally blurred by a geometric projection effect. If one point of the sample is a "hole" in an otherwise opaque mask, then the X-ray source, of finite lateral size S, is imaged through the hole onto a finite image domain given by the formula
where I is the spread of the image of one sample point in the image plane, D is the source-to-sample distance, and d is the sample-to-image distance. The ratio S/D corresponds to the angle (in radians) under which the source appears from the position of the sample (the angular source size, equivalent to the incident divergence at one sample point). The achievable resolution is thus best for small sources, large sample distances, and small detector distances. This is why the detector (film) needed to be placed very close to the sample in the early days of topography; only at synchrotrons, with their small S and (very) large D, could larger values of d finally be afforded, introducing much more flexibility into topography experiments.
Thirdly, even with perfect detectors and ideal geometric conditions, the visibility of special contrast features, such as the images of single dislocations, can be additionally limited by diffraction effects.
A dislocation in a perfect crystal matrix gives rise to contrast only in those regions where the local orientation of the crystal lattice differs from average orientation by more than about the Darwin width of the Bragg reflection used. A quantitative description is provided by the dynamical theory of X-ray diffraction. As a result, and somehow counter-intuitively, the widths of dislocation images become narrower when the associated rocking curves are large. Thus, strong reflections of low diffraction order are particularly appropriate for topographic imaging. They permit topographists to obtain narrow, well-resolved images of dislocations, and to separate single dislocations even when the dislocation density in a material is rather high. In more unfavourable cases (weak, high-order reflections, higher photon energies), dislocation images become broad, diffuse, and overlap for high and medium dislocation densities. Highly ordered, strongly diffracting materials – like minerals or semiconductors – are generally unproblematic, whereas e.g. protein crystals are particularly challenging for topographic imaging.
Apart from the Darwin width of the reflection, the width of single dislocation images may additionally depend on the Burgers vector of the dislocation, i.e. both its length and its orientation (relative to the scattering vector), and, in plane wave topography, on the angular departure from the exact Bragg angle. The latter dependence follows a reciprocity law, meaning that dislocations images become narrower inversely as the angular distance grows. So-called weak beam conditions are thus favourable in order to obtain narrow dislocation images. | 0 | Theoretical and Fundamental Chemistry |
In the presence of lithium or aluminum amide bases, epoxides may open to give the corresponding allylic alcohols. Removal of a proton adjacent to the epoxide, elimination, and neutralization of the resulting alkoxide lead to synthetically useful allylic alcohol products. In reactions of chiral, non-racemic epoxides, the configuration of the allylic alcohol product matches that of the epoxide substrate at the carbon whose C–O bond does not break (the starred carbon below). Besides β-elimination some other reactions are possible, as metalation of the epoxide ring can take place competitively. Vinylogous eliminations are possible when the epoxide substrate is substituted with vinyl or dienyl groups. Unconstrained systems tend to form trans double bonds, as significant non-bonding interactions are avoided in the transition state for the formation of trans products (see equation (2) below). The strongly basic conditions required for most isomerizations of this type represent the reaction's primary disadvantage. | 0 | Theoretical and Fundamental Chemistry |
In fluid mechanics, the Rayleigh number (, after Lord Rayleigh) for a fluid is a dimensionless number associated with buoyancy-driven flow, also known as free (or natural) convection. It characterises the fluid's flow regime: a value in a certain lower range denotes laminar flow; a value in a higher range, turbulent flow. Below a certain critical value, there is no fluid motion and heat transfer is by conduction rather than convection. For most engineering purposes, the Rayleigh number is large, somewhere around 10 to 10.
The Rayleigh number is defined as the product of the Grashof number (), which describes the relationship between buoyancy and viscosity within a fluid, and the Prandtl number (), which describes the relationship between momentum diffusivity and thermal diffusivity: . Hence it may also be viewed as the ratio of buoyancy and viscosity forces multiplied by the ratio of momentum and thermal diffusivities: . It is closely related to the Nusselt number (). | 1 | Applied and Interdisciplinary Chemistry |
Al-Kindi was born in Kufa to an aristocratic family of the Arabian tribe of the Kinda, descended from the chieftain al-Ashath ibn Qays, a contemporary of Muhammad. The family belonged to the most prominent families of the tribal nobility of Kufa in the early Islamic period, until it lost much of its power following the revolt of Abd al-Rahman ibn Muhammad ibn al-Ashath. His father Ishaq was the governor of Basra and al-Kindi received his preliminary education there. He later went to complete his studies in Baghdad, where he was patronized by the Abbasid caliphs al-Mamun () and al-Mutasim (). On account of his learning and aptitude for study, al-Ma'mun appointed him to the House of Wisdom, a recently established center for the translation of Greek philosophical and scientific texts, in Baghdad. He was also well known for his beautiful calligraphy, and at one point was employed as a calligrapher by Caliph al-Mutawakkil ().
When al-Mamun died, his brother, al-Mutasim became caliph. Al-Kindis position would be enhanced under al-Mutasim, who appointed him as a tutor to his son. But on the accession of al-Wathiq (), and especially of al-Mutawakkil, al-Kindis star waned. There are various theories concerning this: some attribute al-Kindis downfall to scholarly rivalries at the House of Wisdom; others refer to al-Mutawakkils often violent persecution of unorthodox Muslims (as well as of non-Muslims); at one point al-Kindi was beaten and his library temporarily confiscated. Henry Corbin, an authority on Islamic studies, says that in 873, al-Kindi died "a lonely man", in Baghdad during the reign of al-Mutamid ().
After his death, al-Kindis philosophical works quickly fell into obscurity; many were lost even to later Islamic scholars and historians. Felix Klein-Franke suggests several reasons for this: aside from the militant orthodoxy of al-Mutawakkil, the Mongols also destroyed countless libraries during their invasion of Persia and Mesopotamia. However, he says the most probable cause of this was that his writings never found popularity amongst subsequent influential philosophers such as al-Farabi and Avicenna, who ultimately overshadowed him. His philosophical career peaked under al-Mutasim, to whom al-Kindi dedicated his most famous work, On First Philosophy, and whose son Ahmad was tutored by al-Kindi. | 1 | Applied and Interdisciplinary Chemistry |
The activity of calcifediol and calcitriol can be reduced by hydroxylation at position 24 by vitamin D3 24-hydroxylase, forming secalciferol and calcitetrol, respectively. | 1 | Applied and Interdisciplinary Chemistry |
In chemical kinetics, the Aquilanti–Mundim deformed Arrhenius model is a generalization of the standard Arrhenius law. | 0 | Theoretical and Fundamental Chemistry |
While the photothermal mechanism is universal, there could exist additional other mechanisms, superimposed on the photothermal mechanism, which may contribute significantly to the photoacoustic signal. These mechanisms are generally related to photophysical processes and photochemical reactions following light absorption: (1) change in the material balance of the sample or the gaseous phase around the sample; (2) change in the molecular organization, which results in molecular volume changes. Most prominent examples for these two kinds of mechanisms are in photosynthesis.
The first mechanism above is mostly conspicuous in a photosynthesizing plant leaf. There, the light induced oxygen evolution causes pressure changes in the air phase, resulting in a photoacoustic signal, which is comparable in magnitude to that caused by the photothermal mechanism. This mechanism was tentatively named "photobaric". The second mechanism shows up in photosynthetically active sub-cell complexes in suspension (e.g. photosynthetic reaction centers). There, the electric field which is formed in the reaction center, following the light induced electron transfer process, causes a micro electrostriction effect with a change in the molecular volume. This, in turn, induces a pressure wave which propagates in the macroscopic medium. Another case for this mechanism is Bacteriorhodopsin proton pump. Here the light induced change in the molecular volume is caused by conformational changes that occur in this protein following light absorption. | 0 | Theoretical and Fundamental Chemistry |
By replacing the nitrogen donor of a Tp ligand atoms with sulfur atoms, a class of ligands known as Tm can be made. These are related to the thioureas.¹; Several research groups including Anthony F. Hill's group have been working on this ligand class. To form NaTm {Na HB(mt)), Methimazole and sodium borohydride are heated together.
Coordination chemistry with ruthenium, rhodium, osmium, molybdenum, tungsten, and other metals has been reported. | 0 | Theoretical and Fundamental Chemistry |
This section will specifically address genome-wide CRISPR screens. For a review of CRISPR limitations see Lino et al. (2018) | 1 | Applied and Interdisciplinary Chemistry |
Primary ketimines can be synthesized via a Grignard reaction with a nitrile. This method is known as Moureu-Mignonac ketimine synthesis. For example, benzophenone imine can also be synthesized by addition of phenylmagnesium bromide to benzonitrile followed by careful hydrolysis (lest the imine be hydrolyzed):
:CHCN + CHMgBr → (CH)C=NMgBr
:(CH)C=NMgBr + HO → (CH)C=NH + MgBr(OH) | 0 | Theoretical and Fundamental Chemistry |
The most common bases used in plastic scintillators are the aromatic plastics, polymers with aromatic rings as pendant groups along the polymer backbone, amongst which polyvinyltoluene (PVT) and polystyrene (PS) are the most prominent. While the base does fluoresce in the presence of ionizing radiation, its low yield and negligible transparency to its own emission make the use of fluors necessary in the construction of a practical scintillator. Aside from the aromatic plastics, the most common base is polymethylmethacrylate (PMMA), which carries two advantages over many other bases: high ultraviolet and visible light transparency and mechanical properties and higher durability with respect to brittleness. The lack of fluorescence associated with PMMA is often compensated through the addition of an aromatic co-solvent, usually naphthalene. A plastic scintillator based on PMMA in this way boasts transparency to its own radiation, helping to ensure uniform collection of light.
Other common bases include polyvinyl xylene (PVX) polymethyl, 2,4-dimethyl, 2,4,5-trimethyl styrenes, polyvinyl diphenyl, polyvinyl naphthalene, polyvinyl tetrahydronaphthalene, and copolymers of these and other bases. | 0 | Theoretical and Fundamental Chemistry |
In 1976, environmentalists found PCBs in the sludge at Waukegan Harbor, the southwest end of Lake Michigan. They were able to trace the source of the PCBs back to the Outboard Marine Corporation that was producing boat motors next to the harbor. By 1982, the Outboard Marine Corporation was court-ordered to release quantitative data referring to their PCB waste released. The data stated that from 1954 they released 100,000 tons of PCB into the environment, and that the sludge contained PCBs in concentrations as high as 50%.
In 1989, during construction near the Zilwaukee bridge, workers uncovered an uncharted landfill containing PCB-contaminated waste which required $100,000 to clean up.
Much of the Great Lakes area were still heavily polluted with PCBs in 1988, despite extensive remediation work. | 1 | Applied and Interdisciplinary Chemistry |
The equations and their parameters are calibrated for adult humans with a body mass of 70 kg and a plasma volume of ca. 2.5 L. | 1 | Applied and Interdisciplinary Chemistry |
* Cells that are to be studied need to be collected.
* Breaking the cell membranes open exposes the DNA along with the cytoplasm within (cell lysis).
** Lipids from the cell membrane and the nucleus are broken down with detergents and surfactants.
** Breaking down proteins by adding a protease (optional).
** Breaking down RNA by adding an RNase (optional).
* The solution is treated with a concentrated salt solution (saline) to make debris such as broken proteins, lipids, and RNA clump together.
* Centrifugation of the solution, which separates the clumped cellular debris from the DNA.
* DNA purification from detergents, proteins, salts, and reagents is used during the cell lysis step. The most commonly used procedures are:
**Ethanol precipitation usually by ice-cold ethanol or isopropanol. Since DNA is insoluble in these alcohols, it will aggregate together, giving a pellet upon centrifugation. Precipitation of DNA is improved by increasing ionic strength, usually by adding sodium acetate.
** Phenol–chloroform extraction in which phenol denatures proteins in the sample. After centrifugation of the sample, denatured proteins stay in the organic phase while the aqueous phase containing nucleic acid is mixed with chloroform to remove phenol residues from the solution.
** Minicolumn purification relies on the fact that the nucleic acids may bind (adsorption) to the solid phase (silica or other) depending on the pH and the salt concentration of the buffer.
Cellular and histone proteins bound to the DNA can be removed either by adding a protease or having precipitated the proteins with sodium or ammonium acetate or extracted them with a phenol-chloroform mixture before the DNA precipitation.
After isolation, the DNA is dissolved in a slightly alkaline buffer, usually in a TE buffer, or in ultra-pure water. | 1 | Applied and Interdisciplinary Chemistry |
Nitrobenzene can be obtained by treating benzenediazonium fluoroborate with sodium nitrite in presence of copper. Alternatively, the diazotisation of the aniline can be conducted in presence of cuprous oxide, which generates cuprous nitrite in situ: | 0 | Theoretical and Fundamental Chemistry |
A temporary construction site has been set up alongside the basin to fabricate the gate housing structures to be positioned on the sea bed (Malamocco and Lido San Nicolò barriers, seven housing structures and two for the abutment connections for each barrier have been built).
In April 2014, the lock for the transit of large ships becomes operative to avoid interference with port activities when the gates are in operation.
Positioning of the gate housing structures for the Malamocco barrier was completed in October 2014.
The seabed in the area where the 19 gates will be installed has been reinforced.
Outside the inlet, a long curved breakwater designed to attenuate tidal currents and define a basin of calm water to protect the lock has been completed. | 1 | Applied and Interdisciplinary Chemistry |
Methane chlorination is a chain reaction. If only the products and reactants are analyzed, the result is:
However, this reaction has 3 intermediate reactants which are formed during a sequence of 4 irreversible second order reactions until we arrive at the final product. This is why it is called a chain reaction. Following only the carbon containing species in series:
Reactants:
Products:
The other species are reaction intermediates:
These are the set of irreversible second-order reactions:
These intermediate species' concentrations can be calculated by integrating the system of kinetic equations. The full reaction is a free radical propagation reaction which is filled out in detail below.
Initiation: This reaction can occur by thermolysis (heating) or photolysis (absorption of light) leading to the breakage of a molecular chlorine bond.
When the bond is broken it produces two highly reactive chlorine atoms.
Propagation: This stage has two distinct reaction classes. The first is the stripping of a hydrogen from the carbon species by the chlorine radicals. This occurs because chlorine atoms alone are unstable, and these chlorine atoms react with one the carbon species' hydrogens. The result is the formation of hydrochloric acid and a new radical methyl group.
These new radical carbon containing species now react with a second molecule. This regenerates the chlorine radical and the cycle continues. This reaction occurs because while the radical methyl species are more stable than the radical chlorines, the overall stability of the newly formed chloromethane species more than makes up the energy difference.
During the propagation of the reaction, there are several highly reactive species that will be removed and stabilized at the termination step.
Termination: This kind of reaction takes place when the radical species interact directly. The products of the termination reactions are typically very low yield in comparison to the main products or intermediates as the highly reactive radical species are in relatively low concentration in relation to the rest of the mixture. This kind of reaction produces stable side products, reactants, or intermediates and slows the propagation reaction by lowering the number of radicals available to propagate the chain reaction.
There are many different termination combinations, some examples are:
Union of methyl radicals from a C-C bond leading to ethane (a side product).
Union of one methyl radical to a Cl radical forming chloromethane (another reaction forming an intermediate).
Union of two Cl radicals to reform chlorine gas (a reaction reforming a reactant). | 0 | Theoretical and Fundamental Chemistry |
Macromolecular Chemistry and Physics was established in 1947 as Die Makromolekulare Chemie/Macromolecular Chemistry by Hermann Staudinger and obtained its current title in 1994. According to the Journal Citation Reports, the journal has a 2021 impact factor of 2.996. | 0 | Theoretical and Fundamental Chemistry |
Carboxypeptidase E functions in the production of nearly all neuropeptides and peptide hormones. The enzyme acts as an exopeptidase to activate neuropeptides. It does that by cleaving off basic C-terminal amino acids, producing the active form of the peptide. Products of carboxypeptidase E include insulin, the enkephalins, vasopressin, oxytocin, and most other neuroendocrine peptide hormones and neuropeptides.
It has been proposed that membrane-associated carboxypeptidase E acts as a sorting signal for regulated secretory proteins in the trans-Golgi network of the pituitary and in secretory granules; regulated secretory proteins are mostly hormones and neuropeptides. However, this role for carboxypeptidase E remains controversial, and evidence shows that this enzyme is not necessary for the sorting of regulated secretory proteins. | 1 | Applied and Interdisciplinary Chemistry |
All cells in animal body tissues are electrically polarized – in other words, they maintain a voltage difference across the cell's plasma membrane, known as the membrane potential. This electrical polarization results from a complex interplay between protein structures embedded in the membrane called ion pumps and ion channels. In neurons, the types of ion channels in the membrane usually vary across different parts of the cell, giving the dendrites, axon, and cell body different electrical properties. As a result, some parts of the membrane of a neuron may be excitable (capable of generating action potentials), whereas others are not. Recent studies have shown that the most excitable part of a neuron is the part after the axon hillock (the point where the axon leaves the cell body), which is called the axonal initial segment, but the axon and cell body are also excitable in most cases.
Each excitable patch of membrane has two important levels of membrane potential: the resting potential, which is the value the membrane potential maintains as long as nothing perturbs the cell, and a higher value called the threshold potential. At the axon hillock of a typical neuron, the resting potential is around –70 millivolts (mV) and the threshold potential is around –55 mV. Synaptic inputs to a neuron cause the membrane to depolarize or hyperpolarize; that is, they cause the membrane potential to rise or fall. Action potentials are triggered when enough depolarization accumulates to bring the membrane potential up to threshold. When an action potential is triggered, the membrane potential abruptly shoots upward and then equally abruptly shoots back downward, often ending below the resting level, where it remains for some period of time. The shape of the action potential is stereotyped; this means that the rise and fall usually have approximately the same amplitude and time course for all action potentials in a given cell. (Exceptions are discussed later in the article). In most neurons, the entire process takes place in about a thousandth of a second. Many types of neurons emit action potentials constantly at rates of up to 10–100 per second. However, some types are much quieter, and may go for minutes or longer without emitting any action potentials. | 0 | Theoretical and Fundamental Chemistry |
These phosphoric acids series are generally water-soluble considering the polarity of the molecules. Ammonium and alkali phosphates are also quite soluble in water. The alkaline earth salts start becoming less soluble and phosphate salts of various other metals are even less soluble. | 0 | Theoretical and Fundamental Chemistry |
Isomorphic Labs Limited is a London-based drug discovery company, which uses artificial intelligence for drug discovery. Isomorphic Labs was founded by Demis Hassabis. The company was incorporated on February 4, 2021 and announced on November 5, 2021. It was established under Alphabet Inc. as a spin-off from its AI research lab DeepMind. Hassabis is the CEO and founder.
The company draws upon DeepMind's AlphaFold 2 technology, which can be used to predict protein structures in the human body with high accuracy, allowing its researchers to find new target pathways for drug delivery.
In December 2022, Isomorphic Labs announced its second office location in Lausanne, Switzerland.
In January 2024, Isomorphic Labs partnered with Novartis AG and Eli Lilly & Company to work together on AI drug discovery and research. | 1 | Applied and Interdisciplinary Chemistry |
There are multiple ways to represent a pharmacogenomic genotype. A commonly used nomenclature system is to report haplotypes using a star (*) allele (e.g., CYP2C19 *1/*2). Single-nucleotide polymorphisms (SNPs) may be described using their assignment reference SNP cluster ID (rsID) or based on the location of the base pair or amino acid impacted. | 1 | Applied and Interdisciplinary Chemistry |
With the latest technologies, reduction of electricity requirements, and miniaturization of the needed power supplies, EC systems have now become affordable for water treatment plants and industrial processes worldwide. | 1 | Applied and Interdisciplinary Chemistry |
Phelps is involved in several outreach projects to increase youth participation in the fields of science, technology, engineering, and mathematics (STEM). She serves on ORNLs Educational Outreach Committee as its diversity chair for Knox County Schools. She has done outreach through the ASCEND program of the Alpha Kappa Alpha sororitys graduate chapter, establishing a program to teach robotics, drones, circuitry, and coding to inner city high school students in Knoxville. Phelps is also the Vice President of the board of Youth Outreach in Science, Technology, Engineering and Mathematics (YO-STEM).
Phelps was featured on the Oak Ridge Associated Universities STEM stories program, partnering with nearby schools in Tennessee. Phelps received the 2017 YWCA Knoxville Tribute to Women Award in the category Technology, Research, and Innovation. This award recognizes "local women who lead their fields in technology and excel in community service".
In 2019, the International Union of Pure and Applied Chemistry (IUPAC) featured Phelps in the Periodic Table of Younger Chemists in recognition of "her outstanding commitment to research and public engagement, as well as being an important advocate for diversity". She was one of two Oak Ridge National Laboratory researchers thus honored. Phelps is associated on this honorary periodic table with the element einsteinium, having along with others, including Julie Ezold, researched purification of einsteinium-254, and her fellow awardee, the post-doctoral researcher Nathan Brewer of Oak Ridge laboratory's Physics Division, is associated with the element tennessine. Their inclusion follows a competition by the IUPAC and the International Younger Chemists Network (IYCN).
At the December 6, 2019 TEDxNashvilleWomen, Phelps presented the talk "How I Claimed a Seat at the Periodic Table", where, according to TED Talks, she "debunk[ed] the myth of solitary genius and challenge[d] institutional elitism by sharing stories of women of color making their way in science". | 0 | Theoretical and Fundamental Chemistry |
These biological targets are conserved across species, making pharmaceutical pollution of the environment a danger to species who possess the same targets. For example, the synthetic estrogen in human contraceptives, 17-R-ethinylestradiol, has been shown to increase the feminization of fish downstream from sewage treatment plants, thereby unbalancing reproduction and creating an additional selective pressure on fish survival. Pharmaceuticals are usually found at ng/L to low-μg/L concentrations in the aquatic environment. Adverse effects may occur in non-target species as a consequence of specific drug target interactions. Therefore, evolutionarily well-conserved drug targets are likely to be associated with an increased risk for non-targeted pharmacological effects. | 1 | Applied and Interdisciplinary Chemistry |
These barriers are usually made out of zero-valent iron (ZVI) but can also be made with any other zero-valent metal. The most common way they are made is by filling a trench with ZVI, nanoscale iron, or palladium. Nanoscale iron particles can also be injected directly into the subsurface to treat plumes, and they have large surface areas and, therefore, high reactivities and can be distributed more evenly in the contamination site. Palladium's reaction rates are rapid. The main advantages of PRBs are that it can reduce many a variety of contaminants and it has no above-ground structure. Problems with PRBs include that even with well constructed barriers, there might be the problem of hydraulic short-circuiting. | 1 | Applied and Interdisciplinary Chemistry |
Blooming is commonly encountered in polymer additives such as stabilizers. Many polymers are essentially pure hydrocarbons whereas additives are often significantly more polar, this results their being forced out via hydrophobic forces. The blooming of additives may be desirable or undesirable. For example, the migration of antioxidants to the polymer surface may help it resist degradation. Conversely, the leaching of additives from packaging materials into foods, or the blooming of additives in biomedical devices is often of high concern. Regulations exist in many counties that require both the levels of blooming and the materials involved to be of a safe level, for example the international symbol for materials approved for food contact is a wine glass and a fork symbol. | 0 | Theoretical and Fundamental Chemistry |
Radial chromatography is a form of chromatography, a preparatory technique for separating chemical mixtures. It can also be referred to as centrifugal thin-layer chromatography. It is a common technique for isolating compounds and can be compared to column chromatography as a similar process. A common device used for this technique is a Chromatotron.
Here the solvent travels from the center of the circular chromatography silica layered on a plate towards the periphery. The entire system is kept covered in order to prevent evaporation of solvent while developing a chromatogram.
The wick at the center of system drips solvent into the system which the provides the mobile phase and moves the sample radially to form the sample spots of different compounds as concentric rings.
Continuous annular chromatography uses a stationary phase which is filled into an annular gap. The eluent is continuously fed across the whole bed interface also the feed is continuously fed at the top of the stationary however only at a certain point and not a cross the whole bed. The stationary phase is then rotated with a certain rotation speed. The rotation speed, eluent and feed flow rates have to be defined precisely such that the collector vessels only collect the correct substance. The retention times are transformed into the respective retention angles. | 0 | Theoretical and Fundamental Chemistry |
Konermann attended the prestigious Sächsisches Landesgymnasium Sankt Afra zu Meißen in Saxony, Germany, before matriculating in 2006 at ETH Zurich, where she completed her bachelor of science degree in neurobiology in three years.
She then moved to the United States and worked in the lab of Carlos Lois before entering the doctoral program in neuroscience at the Massachusetts Institute of Technology, receiving her Ph.D. in 2016 working in Feng Zhang's group. Since 2017, she has been an HHMI (Howard Hughes Medical Institute) Hanna H. Gray Fellow. She has also been a CZ Biohub Investigator and a postdoctoral fellow at the Salk Institute for Biological Studies and the University of California, Berkeley working with Patrick Hsu. In 2019, she joined Stanford as an assistant professor.
Konermann's research uses new genetic tools to identify and understand the workings of the "complex web of genes" that appear to make a person predisposed to the neurodegenerative Alzheimer’s disease.
21546 Konermann, a minor planet, was named after her, in honor of her 2006 second-place finish in the Intel International Science and Engineering Fair. At that time she was a senior at Sankt Afra in Meissen, Germany.
In June 2022, Konermann married Irish tech billionaire Patrick Collison, who is co-founder and CEO of Stripe, Inc., with whom she co-founded the Fast Grants and later the Arc Institute. Konermann met Collison during the 2004 EU Young Scientist competition. | 1 | Applied and Interdisciplinary Chemistry |
DNA molecules often have a preferred direction to bend, i.e., anisotropic bending. This is, again, due to the properties of the bases which make up the DNA sequence - a random sequence will have no preferred bend direction, i.e., isotropic bending.
Preferred DNA bend direction is determined by the stability of stacking each base on top of the next. If unstable base stacking steps are always found on one side of the DNA helix then the DNA will preferentially bend away from that direction. As bend angle increases then steric hindrances and ability to roll the residues relative to each other also play a role, especially in the minor groove. A and T residues will be preferentially be found in the minor grooves on the inside of bends. This effect is particularly seen in DNA-protein binding where tight DNA bending is induced, such as in nucleosome particles. See base step distortions above.
DNA molecules with exceptional bending preference can become intrinsically bent. This was first observed in trypanosomatid kinetoplast DNA. Typical sequences which cause this contain stretches of 4-6 T and A residues separated by G and C rich sections which keep the A and T residues in phase with the minor groove on one side of the molecule. For example:
The intrinsically bent structure is induced by the propeller twist of base pairs relative to each other allowing unusual bifurcated Hydrogen-bonds between base steps. At higher temperatures this structure is denatured, and so the intrinsic bend is lost.
All DNA which bends anisotropically has, on average, a longer persistence length and greater axial stiffness. This increased rigidity is required to prevent random bending which would make the molecule act isotropically. | 0 | Theoretical and Fundamental Chemistry |
The first suggestion of ADP-ribosylation surfaced during the early 1960s. At this time, Pierre Chambon and coworkers observed the incorporation of ATP into hen liver nuclei extract. After extensive studies on the acid insoluble fraction, several different research laboratories were able to identify ADP-ribose, derived from NAD, as the incorporated group. Several years later, the enzymes responsible for this incorporation were identified and given the name poly(ADP-ribose)polymerase. Originally, this group was thought to be a linear sequence of ADP-ribose units covalently bonded through a ribose glycosidic bond. It was later reported that branching can occur every 20 to 30 ADP residues.
The first appearance of mono(ADP-ribosyl)ation occurred a year later during a study of toxins: the diphtheria toxin of Corynebacterium diphtheriae was shown to be dependent on NAD in order for it to be completely effective, leading to the discovery of enzymatic conjugation of a single ADP-ribose group by mono(ADP-ribosyl)transferase.
It was initially thought that ADP-ribosylation was a post translational modification involved solely in gene regulation. However, as more enzymes with the ability to ADP-ribosylate proteins were discovered, the multifunctional nature of ADP-ribosylation became apparent. The first mammalian enzyme with poly(ADP-ribose)transferase activity was discovered during the late 1980s. For the next 15 years, it was thought to be the only enzyme capable of adding a chain of ADP-ribose in mammalian cells. During the late 1980s, ADP-ribosyl cyclases, which catalyze the addition of cyclic-ADP-ribose groups to proteins, were discovered. Finally, sirtuins, a family of enzymes that also possess NAD-dependent deacylation activity, were discovered to also possess mono(ADP-ribosyl)transferase activity. | 1 | Applied and Interdisciplinary Chemistry |
Antistasin contains an N- and a C-terminal domain which are similar in their amino acid sequences with ~40% identity and ~56% homology. Each of them contains a short β-sheet structure and 5 disulfide bonds. Only the N-terminal domain is necessary to inhibit Xa while the C-terminal domain does not contribute to the inhibitory properties due to differences in the 3 dimensional structure, even though the C-terminal domain has a strongly analogue pattern to the actual active site.
The interaction of antistasin with FXa involves both the active site and the inactive surface of FXa. The reactive site of antistasin formed by Arg-34 and Val-35 in the N-terminal domain suits the binding site of FXa, most likely the S1 pocket. At the same time, Glu-15 located outside the reactive site of antistasin fits to positively charged residues on the surface of FXa. The multiple binding is thermodynamically advantageous and leads to sub-nanomolar inhibition (Ki = 0.3–0.6 nM). | 1 | Applied and Interdisciplinary Chemistry |
In fluid dynamics, Taylor–Culick flow describes the axisymmetric flow inside a long slender cylinder with one end closed, supplied by a constant flow injection through the sidewall. The flow is named after Geoffrey Ingram Taylor and F. E. C. Culick. In 1956, Taylor showed that when a fluid forced into porous sheet of cone or wedge, a favorable longitudinal pressure gradient is set up in the direction of the flow inside the cone or wedge and the flow is rotational; this is in contrast in the vice versa case wherein the fluid is forced out of the cone or wedge sheet from inside in which case, the flow is uniform inside the cone or wedge and is obviously potential. Taylor also obtained solutions for the velocity in the limiting case where the cone or the wedge degenerates into a circular tube or parallel plates. Later in 1966, Culick found the solution corresponding to the tube problem, in problem applied to solid-propellant rocket combustion. Here the thermal expansion of the gas due to combustion occurring at
the inner surface of the combustion chamber (long slender cylinder) generates a flow directed towards the axis. | 1 | Applied and Interdisciplinary Chemistry |
The presence of ANAs in blood can be confirmed by a screening test. Although there are many tests for the detection of ANAs, the most common tests used for screening are indirect immunofluorescence and enzyme-linked immunosorbent assay (ELISA). Following detection of ANAs, various subtypes are determined. | 1 | Applied and Interdisciplinary Chemistry |
The herpes simplex virus is a human neurotropic virus. This is mostly examined for gene transfer in the nervous system. The wild type HSV-1 virus is able to infect neurons and evade the host immune response, but may still become reactivated and produce a lytic cycle of viral replication. Therefore, it is typical to use mutant strains of HSV-1 that are deficient in their ability to replicate. Though the latent virus is not transcriptionally apparent, it does possess neuron specific promoters that can continue to function normally. Antibodies to HSV-1 are common in humans, however complications due to herpes infection are somewhat rare. Caution for rare cases of encephalitis must be taken and this provides some rationale to using HSV-2 as a viral vector as it generally has tropism for neuronal cells innervating the urogenital area of the body and could then spare the host of severe pathology in the brain. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, alkynols (hydroxyalkynes) are organic compounds that contain both alkyne and alcohol functional groups. Thus, as structural features, they have a C≡C triple bond and a hydroxyl group. Some alkynols play a role as intermediates in the chemical industry.
The shortened term ynol typically refers to alkynols with the hydroxyl group affixed to one of the two carbon atoms composing the triple bond (), the triple-bond analogues to enols. Ynols can tautomerize to ketenes.
The deprotonated anions of ynols are known as ynolates, the triple-bond analogues to enolates. | 0 | Theoretical and Fundamental Chemistry |
Surface chemistry can be roughly defined as the study of chemical reactions at interfaces. It is closely related to surface engineering, which aims at modifying the chemical composition of a surface by incorporation of selected elements or functional groups that produce various desired effects or improvements in the properties of the surface or interface. Surface science is of particular importance to the fields of heterogeneous catalysis, electrochemistry, and geochemistry. | 0 | Theoretical and Fundamental Chemistry |
Elizabeth MacGregor Hardy (July 31, 1915 – June 26, 2008) was a North American chemist who discovered the Cope rearrangement while working in Arthur C. Cope's research group at Bryn Mawr College. The rearrangement drew upon the electronic models of Edward D. Hughes and Christopher Kelk Ingold, but also the non-electronic work of Rainer Ludwig Claisen and Ernst Tietze. | 0 | Theoretical and Fundamental Chemistry |
Nitrifying bacteria are chemolithotrophic organisms that include species of genera such as Nitrosomonas, Nitrosococcus, Nitrobacter, Nitrospina, Nitrospira and Nitrococcus. These bacteria get their energy from the oxidation of inorganic nitrogen compounds. Types include ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB). Many species of nitrifying bacteria have complex internal membrane systems that are the location for key enzymes in nitrification: ammonia monooxygenase (which oxidizes ammonia to hydroxylamine), hydroxylamine oxidoreductase (which oxidizes hydroxylamine to nitric oxide - which is further oxidized to nitrite by a currently unidentified enzyme), and nitrite oxidoreductase (which oxidizes nitrite to nitrate). | 1 | Applied and Interdisciplinary Chemistry |
To cope with high volume mass flows and for application, where a changing physical location of the sensor-based sorting process is of no benefit for the financial feasibility of the operation, stationary installations are applied. Another reason for applying stationary installations are multistage (Rougher, Scavenger, Cleaner) sensor-based ore sorting processes. Within stationary installations, sorters are usually located in parallel, which allows transport of the discharge fractions with one product and one waste belt respectively, which decreases plant footprint and amount of conveyors. | 0 | Theoretical and Fundamental Chemistry |
There is one assay office in Praha.
Assay Office was established by the Czech National Council Law No. 19/1993 Coll., concerning
the Administration Authorities of the Czech Republic in the Field of Hallmarking and Precious Metal Testing, from which the Assay Office competences and duties are resulting. The provision of the financing is included in the Law about Hallmarking and Precious Metal Testing (Hallmarking Act), No. 539/1992 Coll., and in the procedural Decree of the Federal Ministry of Economy (FME), No. 540/1992 Coll., according to which the Hallmarking Act is implemented. | 0 | Theoretical and Fundamental Chemistry |
Level P vectors are similar to level M constructs except that the BpiI sites are replaced by BsaI sites and the BsaI sites are replaced by BpiI sites. Several level M constructs with compatible fusion sites can be subcloned into a level P vector in one step. Theoretically, as many as 36 genes can be assembled in one construct using 6 parallel level M reactions (each required for assembly of 6 genes per level M construct) followed by one final level P reaction. In practice, fewer genes are usually assembled as most cloning projects do not require so many genes.
The structure of level M and P vectors is designed in a such as way that genes cloned in level P constructs can be further assembled in level M vectors. Repeated cloning in level M and P vectors forms a loop that can be repeated indefinitely to assemble progressively large constructs. | 1 | Applied and Interdisciplinary Chemistry |
Chiral oxazolidinones have been employed most widely in stereoselective aldol reactions.
Soft enolization with the Lewis acid dibutylboron triflate and the base diisopropylethylamine gives the (Z)-enolate, which undergoes a diastereoselective aldol reaction with an aldehyde substrate. The transformation is particularly powerful because it establishes two contiguous stereocenters simultaneously.
A model for the observed stereoselectivity can be found below. The syn-stereo relationship between the methyl group and the new secondary alcohol results from a six-membered ring Zimmerman-Traxler transition state, wherein the enolate oxygen and the aldehyde oxygen both coordinate boron. The aldehyde is oriented such that the hydrogen is placed in a pseudo-axial orientation to minimize 1,3-diaxial interactions. The absolute stereochemistry of the two stereocenters is controlled by the chirality in the auxiliary. In the transition structure, the auxiliary carbonyl is oriented away from the enolate oxygen so as to minimize the net dipole of the molecule; one face of the enolate is blocked by the substituent on the chiral auxiliary.
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Nonbonded 1,3-diaxial interaction energies are commonly used to approximate strain energy in cyclic molecules, as values for these interactions are available. By taking the difference in nonbonded interactions for each conformer, the equilibrium enthalpy can be estimated. The strain energy for methylidenecyclohexane has been calculated to be 4.5 kcalmol using estimations for 1,3-diaxial strain (0.9 kcalmol), methyl/hydrogen allylic strain (1.3kcalmol), and methyl/methyl allylic strain (7.6 kcalmol) values.
The strain energy in 1,8-dimethylnaphthalene was calculated to be 7.6 kcalmol and around 12-15 kcalmol for 4,5-dimethylphenanthrene. Allylic strain tends to be greater for cyclic molecules compared to olefins as strain energy increases with increasing rigidity of the system. An in depth summary of allylic strain in six membered rings has been presented in a review by Johnson, F. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, hydration energy (also hydration enthalpy) is the amount of energy released when one mole of ions undergoes hydration. Hydration energy is one component in the quantitative analysis of solvation. It is a particular special case of water. The value of hydration energies is one of the most challenging aspects of structural prediction. Upon dissolving a salt in water, the cations and anions interact with the positive and negative dipoles of the water. The trade-off of these interactions vs those within the crystalline solid comprises the hydration energy. | 0 | Theoretical and Fundamental Chemistry |
Hollow fiber membranes are ubiquitously used in industrial separations, especially the filtration of drinking water.
Industrial water filters are mainly equipped with ultrafiltration hollow fiber membranes. Domestic water filtration systems have microfiltration hollow fiber membranes. In microfiltration a membrane pore diameter of 0.1 micrometers cuts-off microorganisms like germs and bacteria, Giardia cysts and other intestinal parasites, as well removing sediments. Ultrafiltration membranes are capable of removing not only bacteria, but also viruses.
Hollow fibers are commonly used substrates for specialized bioreactor systems, with the ability of some hollow fiber cartridges to culture billions of anchorage-dependent cells within a relatively low (<100 mL) bioreactor volume.
Hollow fibers can be used for drug efficacy testing in cancer research, as an alternative to the traditional, but more expensive, xenograft model.
Hollow fiber membranes are used in Membrane oxygenators in extracorporeal membrane oxygenation which oxygenates blood, replacing lungs in critically ill patients. | 0 | Theoretical and Fundamental Chemistry |
cDNA molecules can be cloned by using restriction site linkers. Linkers are short, double stranded pieces of DNA (oligodeoxyribonucleotide) about 8 to 12 nucleotide pairs long that include a restriction endonuclease cleavage site e.g. BamHI. Both the cDNA and the linker have blunt ends which can be ligated together using a high concentration of T4 DNA ligase. Then sticky ends are produced in the cDNA molecule by cleaving the cDNA ends (which now have linkers with an incorporated site) with the appropriate endonuclease. A cloning vector (plasmid) is then also cleaved with the appropriate endonuclease. Following "sticky end" ligation of the insert into the vector the resulting recombinant DNA molecule is transferred into E. coli host cell for cloning. | 1 | Applied and Interdisciplinary Chemistry |
Common components of a phase diagram are lines of equilibrium or phase boundaries, which refer to lines that mark conditions under which multiple phases can coexist at equilibrium. Phase transitions occur along lines of equilibrium. Metastable phases are not shown in phase diagrams as, despite their common occurrence, they are not equilibrium phases.
Triple points are points on phase diagrams where lines of equilibrium intersect. Triple points mark conditions at which three different phases can coexist. For example, the water phase diagram has a triple point corresponding to the single temperature and pressure at which solid, liquid, and gaseous water can coexist in a stable equilibrium ( and a partial vapor pressure of ). The pressure on a pressure-temperature diagram (such as the water phase diagram shown) is the partial pressure of the substance in question.
The solidus is the temperature below which the substance is stable in the solid state. The liquidus is the temperature above which the substance is stable in a liquid state. There may be a gap between the solidus and liquidus; within the gap, the substance consists of a mixture of crystals and liquid (like a "slurry").
Working fluids are often categorized on the basis of the shape of their phase diagram. | 0 | Theoretical and Fundamental Chemistry |
Dennis Gail Peters (April 17, 1937 – April 13, 2020) was an American analytical chemist who specialized in electrochemistry and was named the Herman T. Briscoe Professor at Indiana University in 1975. Peters led his own research group at Indiana University in Bloomington, Indiana until his death in 2020. Peters' research focused on the electrochemical behavior of halogenated organic compounds, more recently moving to focus on transition metal catalysts in regards to the oxidation and reduction of organic species. He authored or co-authored over 210 publications and 5 analytical chemistry textbooks. | 0 | Theoretical and Fundamental Chemistry |
Anthocyanins generally are degraded at higher pH. However, some anthocyanins, such as petanin (petunidin 3-[6-O-(4-O-(E)-p-coumaroyl-O-α--rhamnopyranosyl)-β--glucopyranoside]-5-O-β--glucopyranoside), are resistant to degradation at pH 8 and may be used effectively as a food colorant. | 0 | Theoretical and Fundamental Chemistry |
Nearly 180 sites in all were used for this process, having a furnace, a forge or both between the 15th century and 18th century. Waterpower was the means of operating the bellows in the blast furnaces and for operating bellows and helve hammers in finery forges. Scattered through the Weald are ponds still to be found called ’Furnace Pond’ or ’Hammer Pond’. The iron was used for making household utensils, nails and hinges; and for casting cannon. The first blast furnace was recorded at Buxted in 1490.
The industry was at its peak towards the end of Queen Elizabeth Is reign. Most works were small, but at Brenchley one ironmaster employed 200 men. Most of them would have been engaged in mining ore and cutting wood (for charcoal), as the actual ironworks only required a small workforce. The wars fought during the reign of Henry VIII increased the need for armaments, and the Weald became the centre of an armaments industry. Cast-iron cannon were made in the Weald from 1543 when Buxteds Ralf Hogge cast the first iron cannon for his unlikely employer: a Sussex vicar who was gunstonemaker to the king.
In the 16th century and the early 17th century, the Weald was a major source of iron for manufacture in London, peaking at over 9000 tons per year in the 1590s. However, after 1650, Wealden production became increasingly focused on the production of cannon; and bar iron was only produced for local consumption. This decline may have begun as early as the 1610s, when Midland ironware began to be sold in London. Certainly after Swedish iron began to be imported in large quantities after the Restoration, Wealden bar iron seems to have been unable to compete in the London market.
Cannon production was a major activity in the Weald until the end of the Seven Years War, but a cut in the price paid by the Board of Ordnance drove several Wealden ironmasters into bankruptcy. They were unable to match the much lower price that was acceptable to the Scottish Carron Company, whose fuel was coke. A few ironworks continued operating on a very small scale. With no local source of mineral coal, the Wealden iron industry was unable to compete with the new coke-fired ironworks of the Industrial Revolution. The last to close was the forge at Ashburnham. Little survives of the furnace and forge buildings, although there are still scores of the industrys hammer and furnace ponds scattered throughout the Weald.
Steel production was never widespread in the Weald, with most high quality steel being imported from Spain, the Middle East, or Germany. A steel forge was built upstream from Newbridge Furnace on Ashdown Forest around 1505 but had ceased production by 1539. The Sydney family, with mills at Robertsbridge forge and at Sandhurst in Kent, produced steel using skilled German workers, but faced strong competition from German suppliers. In the 17th century a steel forge existed at Warbleton in Sussex. | 1 | Applied and Interdisciplinary Chemistry |
The term is known as the volume term. The volume of the nucleus is proportional to A, so this term is proportional to the volume, hence the name.
The basis for this term is the strong nuclear force. The strong force affects both protons and neutrons, and as expected, this term is independent of Z. Because the number of pairs that can be taken from A particles is , one might expect a term proportional to . However, the strong force has a very limited range, and a given nucleon may only interact strongly with its nearest neighbors and next nearest neighbors. Therefore, the number of pairs of particles that actually interact is roughly proportional to A, giving the volume term its form.
The coefficient is smaller than the binding energy possessed by the nucleons with respect to their neighbors (), which is of order of 40 MeV. This is because the larger the number of nucleons in the nucleus, the larger their kinetic energy is, due to the Pauli exclusion principle. If one treats the nucleus as a Fermi ball of nucleons, with equal numbers of protons and neutrons, then the total kinetic energy is , with the Fermi energy, which is estimated as 38 MeV. Thus the expected value of in this model is not far from the measured value. | 0 | Theoretical and Fundamental Chemistry |
Impure pyridine was undoubtedly prepared by early alchemists by heating animal bones and other organic matter, but the earliest documented reference is attributed to the Scottish scientist Thomas Anderson. In 1849, Anderson examined the contents of the oil obtained through high-temperature heating of animal bones. Among other substances, he separated from the oil a colorless liquid with unpleasant odor, from which he isolated pure pyridine two years later. He described it as highly soluble in water, readily soluble in concentrated acids and salts upon heating, and only slightly soluble in oils.
Owing to its flammability, Anderson named the new substance pyridine, after (pyr) meaning fire. The suffix idine was added in compliance with the chemical nomenclature, as in toluidine, to indicate a cyclic compound containing a nitrogen atom.
The chemical structure of pyridine was determined decades after its discovery. Wilhelm Körner (1869) and James Dewar (1871) suggested that, in analogy between quinoline and naphthalene, the structure of pyridine is derived from benzene by substituting one C–H unit with a nitrogen atom. The suggestion by Körner and Dewar was later confirmed in an experiment where pyridine was reduced to piperidine with sodium in ethanol. In 1876, William Ramsay combined acetylene and hydrogen cyanide into pyridine in a red-hot iron-tube furnace. This was the first synthesis of a heteroaromatic compound.
The first major synthesis of pyridine derivatives was described in 1881 by Arthur Rudolf Hantzsch. The Hantzsch pyridine synthesis typically uses a 2:1:1 mixture of a β-keto acid (often acetoacetate), an aldehyde (often formaldehyde), and ammonia or its salt as the nitrogen donor. First, a double hydrogenated pyridine is obtained, which is then oxidized to the corresponding pyridine derivative. Emil Knoevenagel showed that asymmetrically substituted pyridine derivatives can be produced with this process.
The contemporary methods of pyridine production had a low yield, and the increasing demand for the new compound urged to search for more efficient routes. A breakthrough came in 1924 when the Russian chemist Aleksei Chichibabin invented a pyridine synthesis reaction, which was based on inexpensive reagents. This method is still used for the industrial production of pyridine. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, Luke's variational principle is a Lagrangian variational description of the motion of surface waves on a fluid with a free surface, under the action of gravity. This principle is named after J.C. Luke, who published it in 1967. This variational principle is for incompressible and inviscid potential flows, and is used to derive approximate wave models like the mild-slope equation, or using the averaged Lagrangian approach for wave propagation in inhomogeneous media.
Luke's Lagrangian formulation can also be recast into a Hamiltonian formulation in terms of the surface elevation and velocity potential at the free surface. This is often used when modelling the spectral density evolution of the free-surface in a sea state, sometimes called wave turbulence.
Both the Lagrangian and Hamiltonian formulations can be extended to include surface tension effects, and by using Clebsch potentials to include vorticity. | 1 | Applied and Interdisciplinary Chemistry |
Calcium in a blood sample should be estimated when required medically. Calcium should be precipitated out of 0.1 mL of the blood sample serum as calcium oxalate. After that, the decomposition of the calcium oxalate should occur by heat. Then, the sample should be estimated colorimetrically by o-cresolphthalein complexone. The required liquid complexone is made by dissolving 10 mg o-cresolphthalein complexone in 50 mL alkaline borate, and then 50 mL of 0.05 N HCl are added to make the solution's pH 8.5. This method for calcium determination is efficient and effective, requiring a minimal amount of blood serum sample and a reasonable amount of time. | 0 | Theoretical and Fundamental Chemistry |
In the 8th edition of the International Patent Classification (IPC), which entered into force on January 1, 2006, a special subclass has been created for patent applications and patents related to inventions in the domain of combinatorial chemistry: "C40B". | 1 | Applied and Interdisciplinary Chemistry |
Much of the chemistry of glycosides is explained in the article on glycosidic bonds. For example, the glycone and aglycone portions can be chemically separated by hydrolysis in the presence of acid and can be hydrolyzed by alkali. There are also numerous enzymes that can form and break glycosidic bonds. The most important cleavage enzymes are the glycoside hydrolases, and the most important synthetic enzymes in nature are glycosyltransferases. Genetically altered enzymes termed glycosynthases have been developed that can form glycosidic bonds in excellent yield.
There are many ways to chemically synthesize glycosidic bonds. Fischer glycosidation refers to the synthesis of glycosides by the reaction of unprotected monosaccharides with alcohols (usually as solvent) in the presence of a strong acid catalyst. The Koenigs-Knorr reaction is the condensation of glycosyl halides and alcohols in the presence of metal salts such as silver carbonate or mercuric oxide. | 0 | Theoretical and Fundamental Chemistry |
A sump in a basement can be built in dry well form, allowing the sump pump to cycle less frequently (handling only occasional peak demand). A French drain can resemble a horizontal dry well that is not covered. A larger open pit or artificial swale that receives stormwater and dissipates it into the ground is called an infiltration basin or recharge basin. In places where the amount of water to be dispersed is not as large, a rain garden can be used instead.
A covered pit that disposes of the water component of sewage by the same principle as a dry well is called a cesspool. A septic drain field operates on the same slow-drain/large-area principle as an infiltration basin. | 1 | Applied and Interdisciplinary Chemistry |
Meteoroids enter Earths atmosphere from outer space traveling at hypersonic speeds of at least 11 km/s (7 mi/s) and often much faster. Despite moving through the rarified upper reaches of Earths atmosphere the immense speed at which a meteor travels nevertheless rapidly compresses the air in its path, creating a shock wave. The meteoroid then experiences what is known as ram pressure. As the air in front of the meteoroid is compressed its temperature quickly rises. This is not due to friction, rather it is simply a consequence of many molecules and atoms being made to occupy a smaller space than formerly. Ram pressure and the very high temperatures it causes are the reasons few meteors make it all the way to the ground and most simply burn up or are ablated into tiny fragments. Larger or more solid meteorites may explode instead in a meteor airburst. | 1 | Applied and Interdisciplinary Chemistry |
Born in New Plymouth on 10 April 1931, Waters was the son of Kathleen Emily Waters (née Morris) and Edwin Benjamin Waters. He was educated at New Plymouth Boys High School, and went on to study chemistry at Auckland University College, graduating Bachelor of Science in 1953, Master of Science with second-class honours the following year, and PhD in 1958. His doctoral thesis, supervised by David Hall, was titled The colour isomerism and structure of some copper co‑ordination compounds'.
In 1959, Waters married crystallographer Joyce Mary Partridge. | 0 | Theoretical and Fundamental Chemistry |
# Finite difference method proved to be convergent for the Navier–Stokes equations and the equations are numerically solved by the 1960s. It is proved that there are smooth and globally defined solutions to the Navier–Stokes equations in 2 dimensions.
# If the initial velocity is sufficiently small then the statement is true: there are smooth and globally defined solutions to the Navier–Stokes equations.
# Given an initial velocity there exists a finite time T, depending on such that the Navier–Stokes equations on have smooth solutions and . It is not known if the solutions exist beyond that "blowup time" T.
#Jean Leray in 1934 proved the existence of so-called weak solutions to the Navier–Stokes equations, satisfying the equations in mean value, not pointwise.
#Terence Tao in 2016 published a finite time blowup result for an averaged version of the 3-dimensional Navier–Stokes equation. He writes that the result formalizes a "supercriticality barrier" for the global regularity problem for the true Navier–Stokes equations, and claims that the method of proof hints at a possible route to establishing blowup for the true equations. | 1 | Applied and Interdisciplinary Chemistry |
Electrochemical fluorination (ECF) (also known as the Simons' process) involves electrolysis of a substrate dissolved in hydrogen fluoride. As fluorine is itself manufactured by the electrolysis of hydrogen fluoride, ECF is a rather more direct route to fluorocarbons. The process proceeds at low voltage (5 – 6 V) so that free fluorine is not liberated. The choice of substrate is restricted as ideally it should be soluble in hydrogen fluoride. Ethers and tertiary amines are typically employed. To make perfluorohexane, trihexylamine is used, for example:
The perfluorinated amine will also be produced: | 1 | Applied and Interdisciplinary Chemistry |
SMA actuators are typically actuated electrically, where an electric current results in Joule heating. Deactivation typically occurs by free convective heat transfer to the ambient environment. Consequently, SMA actuation is typically asymmetric, with a relatively fast actuation time and a slow deactuation time. A number of methods have been proposed to reduce SMA deactivation time, including forced convection, and lagging the SMA with a conductive material in order to manipulate the heat transfer rate.
Novel methods to enhance the feasibility of SMA actuators include the use of a conductive "lagging". this method uses a thermal paste to rapidly transfer heat from the SMA by conduction. This heat is then more readily transferred to the environment by convection as the outer radii (and heat transfer area) are significantly greater than for the bare wire. This method results in a significant reduction in deactivation time and a symmetric activation profile. As a consequence of the increased heat transfer rate, the required current to achieve a given actuation force is increased. | 1 | Applied and Interdisciplinary Chemistry |
An historical example, the Pratt & Whitney J58, illustrates the significance of using corrected values.
Rotating stall occurs at low corrected speeds so occurs during starting and also above idle. It may be relieved by opening a bleed valve to increase airflow. At very high flight speeds the compressor will return to this low corrected speed area so the same operating point occurs at low rotational speed on the ground and maximum rotational speed at mach 3 at high altitude. The stalling, low efficiency, blade vibration and failure that plagued low corrected speeds on the ground has returned at 100% rotor rpm at mach 3. The same operating point on the map has the same axial and peripheral mach numbers, same velocity triangles, same efficiency despite the actual rotor speed and compressor inlet temperature being 4750 RPM/60degF on the ground and 7,000RPM/over 600 degF at Mach 3. The same corrected operating point required the same solution to prevent stalling and increase efficiency which was to bleed air from the 4th compressor stage. | 0 | Theoretical and Fundamental Chemistry |
Growth factor receptor-bound protein 2, also known as Grb2, is an adaptor protein involved in signal transduction/cell communication. In humans, the GRB2 protein is encoded by the GRB2 gene.
The protein encoded by this gene binds receptors such as the epidermal growth factor receptor and contains one SH2 domain and two SH3 domains. Its two SH3 domains direct complex formation with proline-rich regions of other proteins, and its SH2 domain binds tyrosine phosphorylated sequences. This gene is similar to the sem-5 gene of Caenorhabditis elegans, which is involved in the signal transduction pathway. Two alternatively spliced transcript variants encoding different isoforms have been found for this gene. | 1 | Applied and Interdisciplinary Chemistry |
Vitamin B is the preeminent bioorganometallic species. Vitamin B is actually a collection of related enzyme cofactors, several of which contain cobalt–alkyl bonds, and is involved in biological methylation and 1,2-carbon rearrangement reactions. For a long time since its structure was elucidated by Hodgkin in 1955, it was believed to be the only example of a naturally occurring bioorganometallic system.
Several bioorganometallic enzymes carry out reactions involving carbon monoxide. Carbon monoxide dehydrogenase (CODH) catalyzes the water–gas shift reaction, which provides CO (through a nickelacarboxylate intermediate) for the biosynthesis of acetylcoenzyme A. The latter step is effected by the Ni–Fe enzyme CO-methylating acetyl-CoA synthase (ACS). CODH and ACS often occur together in a tetrameric complex, the CO being transported via a tunnel and the methyl group being provided by methyl cobalamin.
Hydrogenases are bioorganometallic in the sense that their active sites feature Fe–CO functionalities, although the CO ligands are only spectators. The binuclear [FeFe]-hydrogenases have a Fe(μ-SR)(μ-CO)(CO)(CN) active site connected to a 4Fe4S cluster via a bridging thiolate. The active site of the [NiFe]-hydrogenases are described as (NC)(OC)Fe(μ-SR)Ni(SR) (where SR is cysteinyl). Mononuclear [Fe]-hydrogenases contain an Fe(CO)(SR)(LX) active site, where LX is a 6-acylmethyl-2-pyridinol ligand, bound to the Fe center through the pyridyl nitrogen (L) and the acyl carbon (X). This class of hydrogenases thus provides examples of naturally occurring iron acyl complexes.
Methanogenesis, the biosynthesis of methane, entails as its final step, the scission of a nickel–methyl bond in cofactor F430.
The iron–molybdenum cofactor (FeMoco) of nitrogenases contains an FeC unit and is an example of an interstitial carbide found in biology.
The first example of a naturally-occurring arylmetal species, a pincer complex containing a nickel–aryl bond, has been reported to form the active site of lactate racemase. | 0 | Theoretical and Fundamental Chemistry |
IV dose 1-1.5mg/kg or 3 to 5 x ED
Paralysis occurs in one to two minutes.
Clinical duration of action (time from drug administration to recovery of single twich to 25% of baseline) is 7-12 minutes.
If IV access is unavailable, intramuscular administration 3-4mg/kg. Paralysis occurs at 4 minutes.
Use of succinylcholine infusion or repeated bolus administration increase the risk of Phase II block and prolonged paralysis. Phase II block occurs after large doses (>4mg/kg). This occurs when the post-synaptic membrane action potential returns to baseline in spite of the presence of succinylcholine and causes continued activation of nicotinic acetylcholine receptors. | 1 | Applied and Interdisciplinary Chemistry |
Mammalian FAS consists of a homodimer of two identical protein subunits, in which three catalytic domains in the N-terminal section (-ketoacyl synthase (KS), malonyl/acetyltransferase (MAT), and dehydrase (DH)), are separated by a core region (known as the interdomain) of 600 residues from four C-terminal domains (enoyl reductase (ER), -ketoacyl reductase (KR), acyl carrier protein (ACP) and thioesterase (TE)). The interdomain region allows the two monomeric domains to form a dimer.
The conventional model for organization of FAS (see the head-to-tail model on the right) is largely based on the observations that the bifunctional reagent 1,3-dibromopropanone (DBP) is able to crosslink the active site cysteine thiol of the KS domain in one FAS monomer with the phosphopantetheine prosthetic group of the ACP domain in the other monomer. Complementation analysis of FAS dimers carrying different mutations on each monomer has established that the KS and MAT domains can cooperate with the ACP of either monomer. and a reinvestigation of the DBP crosslinking experiments revealed that the KS active site Cys161 thiol could be crosslinked to the ACP 4'-phosphopantetheine thiol of either monomer. In addition, it has been recently reported that a heterodimeric FAS containing only one competent monomer is capable of palmitate synthesis.
The above observations seemed incompatible with the classical head-to-tail model for FAS organization, and an alternative model has been proposed, predicting that the KS and MAT domains of both monomers lie closer to the center of the FAS dimer, where they can access the ACP of either subunit (see figure on the top right).
A low resolution X-ray crystallography structure of both pig (homodimer) and yeast FAS (heterododecamer) along with a ~6 Å resolution electron cryo-microscopy (cryo-EM) yeast FAS structure have been solved. | 1 | Applied and Interdisciplinary Chemistry |
All the HIV protease inhibitors on the market contain a central core motif consisting of a hydroxyethylen scaffold, with the only exception being the central core of tipranavir, which is based on a coumarin scaffold. A very important group on the HIV protease inhibitors is a hydroxyl group on the core motif which forms a hydrogen bond with the carboxylic acid on the Asp-25 and Asp-25´ residues in the binding site. Hydrogen bonds between the water molecule, which is linked to Ile50 and Ile50, and carbonyl groups of the peptidomimetic inhibitors seem to connect them with the flap regions. On the other hand, on the nonpeptidic inhibitors, there is a proton acceptor which replaces the tetracoordinated water molecule and interacts directly with the two Ile50 residues on the flap of the enzyme. Specific pockets in the binding site of the HIV protease, often referred to as S1, S1,S2 and S2', recognize hydrophobic amino acids on natural substrates. The potency of inhibitors bearing hydrophobic groups complementing these areas is therefore increased. Some residues in the enzyme binding site are capable of forming hydrogen bonds with hydrophilic groups on the inhibitor, for example with the THF moieties on amprenavir and darunavir. Since darunavir has a bis-THF moiety, instead of a single THF moiety like on amprenavir, it can form more hydrogen bonds and increase binding energy. | 1 | Applied and Interdisciplinary Chemistry |
Between 3 and 10% of children taking amoxicillin (or ampicillin) show a late-developing (>72 hours after beginning medication and having never taken penicillin-like medication previously) rash, which is sometimes referred to as the "amoxicillin rash". The rash can also occur in adults and may rarely be a component of the DRESS syndrome.
The rash is described as maculopapular or morbilliform (measles-like; therefore, in medical literature, it is called "amoxicillin-induced morbilliform rash".). It starts on the trunk and can spread from there. This rash is unlikely to be a true allergic reaction and is not a contraindication for future amoxicillin usage, nor should the current regimen necessarily be stopped. However, this common amoxicillin rash and a dangerous allergic reaction cannot easily be distinguished by inexperienced persons, so a healthcare professional is often required to distinguish between the two.
A nonallergic amoxicillin rash may also be an indicator of infectious mononucleosis. Some studies indicate about 80–90% of patients with acute Epstein–Barr virus infection treated with amoxicillin or ampicillin develop such a rash. | 0 | Theoretical and Fundamental Chemistry |
Pervious concrete (also called porous concrete, permeable concrete, no fines concrete and porous pavement) is a special type of concrete with a high porosity used for concrete flatwork applications that allows water from precipitation and other sources to pass directly through, thereby reducing the runoff from a site and allowing groundwater recharge.
Pervious concrete is made using large aggregates with little to no fine aggregates. The concrete paste then coats the aggregates and allows water to pass through the concrete slab. Pervious concrete is traditionally used in parking areas, areas with light traffic, residential streets, pedestrian walkways, and greenhouses. It is an important application for sustainable construction and is one of many low impact development techniques used by builders to protect water quality. | 1 | Applied and Interdisciplinary Chemistry |
In aeroacoustics, jet noise is the field that focuses on the noise generation caused by high-velocity jets and the turbulent eddies generated by shearing flow. Such noise is known as broadband noise and extends well beyond the range of human hearing (100 kHz and higher). Jet noise is also responsible for some of the loudest sounds ever produced by mankind. | 1 | Applied and Interdisciplinary Chemistry |
Ming dynasty (1368–1644) authorities strongly disapproved of immortality elixirs, but the Jiajing Emperor (r. 1521–1567) supposedly died from consuming them. The emperor was interested in the art of immortality and put great confidence in Daoist physicians, magicians, and alchemists. One named Wang Jin 王金, who was appointed a Physician-in-Attendance in the Imperial Academy of Medicine, convinced the emperor that eating and drinking from vessels made of alchemical gold and silver would bring about immortality, but it only resulted in his death. Wang fled but was caught and exiled to the frontiers in 1570.
Li Shizhens classic 1578 Compendium of Materia Medica discusses the historical tradition of producing gold and cinnabar elixirs, and concludes, "(the alchemists) will never realise that the human body, which thrives on water and the cereals, is unable to sustain such heavy substances as gold and other minerals within the stomach and intestines for any length of time. How blind it is, in the pursuit of longevity, to lose ones life instead!". In another section, Li criticizes alchemists and pharmacologists for perpetuating the belief in mercury elixirs. | 1 | Applied and Interdisciplinary Chemistry |
Electrophoresis is used for estimating zeta potential of particulates, whereas streaming potential/current is used for porous bodies and flat surfaces.
In practice, the zeta potential of dispersion is measured by applying an electric field across the dispersion. Particles within the dispersion with a zeta potential will migrate toward the electrode of opposite charge with a velocity proportional to the magnitude of the zeta potential.
This velocity is measured using the technique of the laser Doppler anemometer. The frequency shift or phase shift of an incident laser beam caused by these moving particles is measured as the particle mobility, and this mobility is converted to the zeta potential by inputting the dispersant viscosity and dielectric permittivity, and the application of the Smoluchowski theories. | 0 | Theoretical and Fundamental Chemistry |
Filter papers are widely used in laboratory experiments across many different fields, from biology to chemistry. The type of filter used will differ according to the purpose of the procedure and the chemicals involved. Generally, filter papers are used with laboratory techniques such as gravity or vacuum filtration.
Historically, a type of soft, porous paper called charta emporetica was used in pharmacy as a filter and as packing paper. | 0 | Theoretical and Fundamental Chemistry |
Other phenomena in which large effects may be achieved faster than small effects are:
* Latent heat: Turning ice to water takes the same amount of energy as heating water from to .
* Leidenfrost effect: Lower temperature boilers can sometimes vaporize water faster than higher temperature boilers. | 0 | Theoretical and Fundamental Chemistry |
The evolution of hominoid communication is evident through chimpanzee hoo vocalizations and alarm calls. Researchers propose that communication evolved as natural selection diversified hoo vocalizations into context-dependent hoos for travel, rest, and threats. Context-dependent communication is beneficial and likely maintained by selection as it facilities cooperative activities and social cohesion between signallers and receivers that can increase the likelihood of survival. Alarm calls in chimpanzees also point to the evolution of hominoid language. Callers assess conspecifics' knowledge of threats, fill their need for information, and, in doing so, use social cues and intentionality to inform communication. Filling a gap in information and incorporating social cues and intentionality into communication are all components of human language. These shared elements between chimpanzee and human communication suggest an evolutionary basis, most likely that the last common human ancestor with chimpanzees also possessed these linguistic abilities. | 1 | Applied and Interdisciplinary Chemistry |
The ability of one compound to dissolve in another compound is called solubility. When a liquid can completely dissolve in another liquid the two liquids are miscible. Two substances that can never mix to form a solution are said to be immiscible.
All solutions have a positive entropy of mixing. The interactions between different molecules or ions may be energetically favored or not. If interactions are unfavorable, then the free energy decreases with increasing solute concentration. At some point, the energy loss outweighs the entropy gain, and no more solute particles can be dissolved; the solution is said to be saturated. However, the point at which a solution can become saturated can change significantly with different environmental factors, such as temperature, pressure, and contamination. For some solute-solvent combinations, a supersaturated solution can be prepared by raising the solubility (for example by increasing the temperature) to dissolve more solute and then lowering it (for example by cooling).
Usually, the greater the temperature of the solvent, the more of a given solid solute it can dissolve. However, most gases and some compounds exhibit solubilities that decrease with increased temperature. Such behavior is a result of an exothermic enthalpy of solution. Some surfactants exhibit this behaviour. The solubility of liquids in liquids is generally less temperature-sensitive than that of solids or gases. | 0 | Theoretical and Fundamental Chemistry |
Entropy generation and inefficiency in a PV cell is the result of photons more energetic than the band gap producing electrons with kinetic energy in addition to the potential energy provided by the band gap. Similarly, optical phonon energy in excess of the band gap generates an entropy flow in the pV cell, rather than electric power. The energy efficiency () is quantified by the ratio of the band gap and optical phonon energy, that is
<div class="center" style="width: auto; margin-left: auto; margin-right: auto;"><math>\begin{align}
\eta_{\phi}=\Delta E_{e,g}/E_{p,\mathrm{O}}.
\end{align}
In addition this typical inefficiency, hot optical phonon populations tend to downconvert into multiple low-energy, acoustic phonon modes (whereas photons typically do not downconvert into low energy infrared waves). This efficiency () is quantified by the tendency of a hot optical phonon to downconvert rather than generate an electron-hole pair, that is
<div class="center" style="width: auto; margin-left: auto; margin-right: auto;"><math>\begin{align}
\eta_{QE}=\dot{\gamma}_{e-p}^*=\frac{\dot{\gamma}_{e-p}}{\dot{\gamma}_{e-p}+\dot{\gamma}_{p-p}},
\end{align}
where is the rate of generation and is the rate of downconversion, i.e., the rate at which an optical phonon produces multiple low-energy, acoustic phonons. This provides a second entropy flow reducing the efficiency of a pV cell.
Finally, entropy is generated in both pV and PV cells due to the inefficient separation of the generated electrons and holes. This efficiency () is limited by the Carnot efficiency given by
<div class="center" style="width: auto; margin-left: auto; margin-right: auto;"><math>\begin{align}
\eta_\mathrm{C}=1-\frac{T_{pV}}{T_{p,\mathrm{O}}},
\end{align}
where is the temperature of the pV cell and is the temperature of the optical phonon population, as dictated by the Bose–Einstein statistics. This efficiency is reduced the smaller the band gap is in comparison to the thermal energy (, where is the Boltzmann constant and is the temperature). Indeed, the p-n junction efficiency is approximately
<div class="center" style="width: auto; margin-left: auto; margin-right: auto;"><math>\begin{align}
\eta_{pn} \simeq \eta_\mathrm{C} [1-0.75\exp(-0.1\Delta E_{e,g}/k_\mathrm{B} T_\mathrm{pV})].
\end{align}
Thus, the overall efficiency () is
<div class="center" style="width: auto; margin-left: auto; margin-right: auto;"><math>\begin{align}
\eta_\mathrm{pV} = \eta_\mathrm{C}\dot{\gamma}_{e-p}^*\frac{\Delta E_{e,g}}{E_{p,\mathrm{O}}} [1-0.75\exp(-0.1\Delta E_{e,g}/k_\mathrm{B} T_{pV})],
\end{align}
where the temperature independent terms become the material figure of merit (),
<div class="center" style="width: auto; margin-left: auto; margin-right: auto;"><math>\begin{align}
Z_\mathrm{pV} = \dot{\gamma}_{e-p}^*\frac{\Delta E_{e,g}}{E_{p,\mathrm{O}}}.
\end{align}
If the band gap and optical phonon mode are resonant, and the optical phonon tends to generate electrons, the phonovoltaic cell can approach the Carnot limit as . | 0 | Theoretical and Fundamental Chemistry |
Xe is the heaviest noble gas in the Earth's atmosphere. It has seven stable isotopes (Xe,Xe,Xe,Xe,Xe, Xe, Xe) and two isotopes (Xe, Xe) with long-lived half-lives. Xe has four synthetic radioisotopes with very short half-lives, usually less than one month.
Xenon-129 can be used to examine the early history of the Earth. Xe was derived from the extinct nuclide of iodine, iodine-129 or I (with a half-life of 15.7 Million years, or Myr), which can be used in iodine-xenon (I-Xe) dating. The production of Xe stopped within about 100 Myr after the start of the Solar System because I became extinct. In the modern atmosphere, about 6.8% of atmospheric Xe originated from the decay I in the first ~100 Myr of the Solar Systems history, i.e., during and immediately following Earths accretion.
Fissiogenic Xe isotopes were generated mainly from the extinct nuclide, plutonium-244 or Pu (half-life of 80 Myr), and also the extant nuclide, uranium-238 or U (half-life of 4468 Myr). Spontaneous fission of U has generated ~5% as much fissiogenic Xe as Pu. Pu and U fission produce the four fissiogenic isotopes, Xe, Xe, Xe, and Xe in distinct proportions. A reservoir that remains an entirely closed system over Earth's history has a ratio of Pu- to U-derived fissiogenic Xe reaching to ~27. Accordingly, the isotopic composition of the fissiogenic Xe for a closed-system reservoir would largely resemble that produced from pure Pu fission. Loss of Xe from a reservoir after Pu becomes extinct (500 Myr) would lead to a greater contribution of U fission to the fissiogenic Xe. | 0 | Theoretical and Fundamental Chemistry |
The modified Arrhenius equation makes explicit the temperature dependence of the pre-exponential factor. The modified equation is usually of the form
The original Arrhenius expression above corresponds to . Fitted rate constants typically lie in the range . Theoretical analyses yield various predictions for n. It has been pointed out that "it is not feasible to establish, on the basis of temperature studies of the rate constant, whether the predicted T dependence of the pre-exponential factor is observed experimentally". However, if additional evidence is available, from theory and/or from experiment (such as density dependence), there is no obstacle to incisive tests of the Arrhenius law.
Another common modification is the stretched exponential form
where β is a dimensionless number of order 1. This is typically regarded as a purely empirical correction or fudge factor to make the model fit the data, but can have theoretical meaning, for example showing the presence of a range of activation energies or in special cases like the Mott variable range hopping. | 0 | Theoretical and Fundamental Chemistry |
Lathrop was born in Lawton, Oklahoma, on June 16, 1915. She attended Oklahoma A&M, where she earned bachelors degrees in home economics and chemistry. She met her husband, Clarence Lathrop, while they were both studying for masters degrees in chemistry.. They married in 1938 and had five children.
Upon completion of their master's degrees in 1939, the couple first moved to New Mexico and then to Wyoming in 1941. Lathrop became a research assistant at the University of Wyoming where she focused her efforts on research pertaining to poisonous plants that grew on the Great Plains. In 1944, Lathrop and her family moved to Chicago where Clarence pursued a medical degree at Northwestern University. They divorced in 1976. | 0 | Theoretical and Fundamental Chemistry |
Simple:
* Strontium titanate
* Calcium titanate
* Lead titanate
* Bismuth ferrite
* Lanthanum ytterbium oxide
* Silicate perovskite
* Lanthanum manganite
* Yttrium aluminum perovskite (YAP)
* Lutetium aluminum perovskite (LuAP)
Solid solutions:
* Lanthanum strontium manganite
* LSAT (lanthanum aluminate – strontium aluminum tantalate)
* Lead scandium tantalate
* Lead zirconate titanate
* Methylammonium lead halide
* Methylammonium tin halide
* Formamidinium tin halide | 0 | Theoretical and Fundamental Chemistry |
With metals in group 4 or 5 a so-called edge-capped octahedral clusters are more common. Twelve halides are located along the edge of the octahedron and six are terminal. Examples of this structure type are tungsten(III) chloride, TaCl(HO), NbF, and NbF.
Many of the early metal clusters can only be prepared when they incorporate interstitial atoms. One example is ZrCCl. | 0 | Theoretical and Fundamental Chemistry |
The liquid is placed on horizontal plate and a shallow cone placed into it. The angle between the surface of the cone and the plate is around 1–2 degrees but can vary depending on the types of tests being run. Typically the plate is rotated and the torque on the cone measured. A well-known version of this instrument is the Weissenberg rheogoniometer, in which the movement of the cone is resisted by a thin piece of metal which twists—known as a torsion bar. The known response of the torsion bar and the degree of twist give the shear stress, while the rotational speed and cone dimensions give the shear rate. In principle the Weissenberg rheogoniometer is an absolute method of measurement providing it is accurately set up. Other instruments operating on this principle may be easier to use but require calibration with a known fluid.
Cone and plate rheometers can also be operated in an oscillating mode to measure elastic properties, or in combined rotational and oscillating modes. | 1 | Applied and Interdisciplinary Chemistry |
Methods of importance to cellular biology, such as fluorescence probes (e.g., FRAP, FRET and GFP) and imaging, will be covered as appropriate within the context of the content below.
A. Cellular Compartments of Prokaryotes and Eukaryotes: Organization, Dynamics and Functions
Cellular membrane systems (e.g., structure and transport across membrane)
Nucleus (e.g., envelope and matrix)
Mitochondria and chloroplasts (e.g., biogenesis and evolution)
B. Cell Surface and Communication
Extracellular matrix (including cell walls)
Cell adhesion and junctions
Signal transduction
Receptor function
Excitable membrane systems
C. Cytoskeleton, Motility and Shape
Regulation of assembly and disassembly of filament systems
Motor function, regulation and diversity
D. Protein, Processing, Targeting and Turnover
Translocation across membranes
Posttranslational modification
Intracellular trafficking
Secretion and endocytosis
Protein turnover (e.g., proteosomes, lysosomes, damaged protein response)
E. Cell Division, Differentiation and Development
Cell cycle, mitosis and cytokinesis
Meiosis and gametogenesis
Fertilization and early embryonic development (including positional information, homeotic genes, tissue-specific expression, nuclear and cytoplasmic interactions, growth factors and induction, environment, stem cells and polarity) | 1 | Applied and Interdisciplinary Chemistry |
Wave-making resistance is a form of drag that affects surface watercraft, such as boats and ships, and reflects the energy required to push the water out of the way of the hull. This energy goes into creating the wave. | 1 | Applied and Interdisciplinary Chemistry |
Semi-synthetic bio-hybrid channels constructed by modifications of natural ion channels had been constructed. Leveraging modern synthetic organic chemistry, these allows pinpoint modifications of existing structures to either elucidate their transport mechanisms or to graft on new functionalities.
Gramicidin and alamethicin had been popular starting points for selective modifications. The above diagram illustrates one example, where a crown-ether was fixed across the mouth of the ion-passing portal. This channel shows discrete conductance but different ion selectivity than wild type gramicidin in voltage-clamp experiments.
While modification of large protein channels using mutagenesis are generally considered out of the scope of synthetic channels, the demarcation is not sharp, as supramolecular or covalent bonding of cyclodextrins to alpha-hemolysin demonstrates. | 0 | Theoretical and Fundamental Chemistry |
Adding PDE5 inhibitors to SSRI drugs (e.g. paroxetine) for the treatment of premature ejaculation could result in better ejaculatory control according to recent studies. Possible mechanism is based on nitric oxide (NO)/cGMP transduction system as a central and peripheral mediator of inhibitory non-adrenergic, non-cholinergic nitrergic neurotransmission in the urogenital system. | 1 | Applied and Interdisciplinary Chemistry |
The protein AKT1 (also known as Protein Kinase B or PKB) in the PI3K/AKT/mTOR pathway is an important driver of the tumor glycolytic phenotype and stimulates ATP generation. AKT1 stimulates glycolysis by increasing the expression and membrane translocation of glucose transporters and by phosphorylating key glycolytic enzymes, such as hexokinase and phosphofructokinase 2. This leads to inhibition of forkhead box subfamily O transcription factors, leading to the increase of glycolytic capacity. Activated mTOR stimulates protein and lipid biosynthesis and cell growth in response to sufficient nutrient and energy conditions and is often constitutively activated during tumorigenesis. mTOR directly stimulates mRNA translation and ribosome biogenesis, and indirectly causes other metabolic changes by activating transcription factors such as hypoxia-inducible factor 1 (HIF1A). The subsequent HIF1-dependent metabolic changes are a major determinant of the glycolytic phenotype downstream of PI3K, AKT1 and mTOR. | 1 | Applied and Interdisciplinary Chemistry |
Enzyme-linked immunosorbent assay (ELISA) uses antigen-coated microtitre plates for the detection of ANAs. Each well of a microtitre plate is coated with either a single antigen or multiple antigens to detect specific antibodies or to screen for ANAs, respectively. The antigens are either from cell extracts or recombinant. Blood serum is incubated in the wells of the plate and is washed out. If antibodies that bind to antigen are present then they will remain after washing. A secondary anti-human antibody conjugated to an enzyme such as horseradish peroxidase is added. The enzyme reaction will produce a change in colour of the solution that is proportional to the amount of antibody bound to the antigen. There are significant differences in the detection of ANA by immunofluorescence and different ELISA kits and there is only a marginal agreement between these. A clinician must be familiar with the differences in order to evaluate the outcomes of the various assays. | 1 | Applied and Interdisciplinary Chemistry |
FASTpp measures the quantity of protein that resists digestion under various conditions. To this end, a thermostable protease is used, which cleaves specifically at exposed hydrophobic residues. The FASTpp assay combines the thermal unfolding, specificity of a thermostable protease for the unfolded fraction with the separation power of SDS-PAGE. Due to this combination, FASTpp can detect changes in the fraction folded over a large physico-chemical range of conditions including temperatures up to 85 °C, pH 6–9, presence or absence of the whole proteome. Applications range from biotechnology to study of point mutations and ligand binding assays. | 1 | Applied and Interdisciplinary Chemistry |
Rietti worked as a researcher at various Argentine universities and state agencies including the Department of Inorganic Chemistry and Physicochemistry at the University of Buenos Aires between 1955 and 1956. She was also a member of the board of directors of the Faculty of Exact and Natural Sciences of the University of Buenos Aires (UBA), where she witnessed the country's security forces breaking into the university during the events known as the Night of the Long Canes on 29 July 1966.
On that night, after police detained about 400 intellectuals, Sara and her husband Víctor moved from one police station to the next to free their colleagues from jail. As a result of the nationwide repression, numerous laboratories and libraries were destroyed and many scientists and academics were exiled or fled the country. Sara and Victor decided to remain in Argentina.
Rietti worked at the Latin American Publishing Center as director of the Scientific Collection between 1967 and 1969 and served on the board of that publisher between 1972 and 1992. Between 1973 and 1975, she was the coordination director of the National Institute of Industrial Technology.
In 1983, when science was again allowed to flourish in Argentina, the mathematician Manuel Sadosky appointed her Chief of Staff of the Secretary of Science and Technology, over which he presided, and in 1994 she was appointed academic coordinator of the Graduate Policy and Management of Science and Technology at the UBA. She was also a teacher advisor to the Rectorate there, a position she held until the end of her life. | 0 | Theoretical and Fundamental Chemistry |
The aim is to find new compounds or agents with improved properties such as a new mode of action or lower application rate. Another aim is to replace older pesticides which have been banned for reasons of toxicity or environmental harm or have become less effective due to development of resistance.
The process starts with testing (screening) against target organisms such as insects, fungi or plants. Inputs are typically random compounds, natural products, compounds designed to disrupt a biochemical target, compounds described in patents or literature, or biocontro<nowiki/>l organisms.
Compounds that are active in the screening process, known as hits or leads, cannot be used as pesticides, except for biocontrol organisms and some potent natural products. These lead compounds need to be optimised by a series of cycles of synthesis and testing of analogs. For approval by regulatory authorities for use as pesticides, the optimized compounds must meet several requirements. In addition to being potent (low application rate), they must show low toxicity, low environmental impact, and viable manufacturing cost. The cost of developing a pesticide in 2022 was estimated to be 350 million US dollars. It has become more difficult to find new pesticides. More than 100 new active ingredients were introduced in the 2000s and less than 40 in the 2010s. Biopesticides are cheaper to develop, since the authorities require less toxicological and environmental study. Since 2000 the rate of new biological product introduction has frequently exceeded that of conventional products.
More than 25% of existing chemical pesticides contain one or more chiral centres (stereogenic centres). Newer pesticides with lower application rates tend to have more complex structures, and thus more often contain chiral centres. In cases when most or all of the pesticidal activity in a new compound is found in one enantiomer (the eutomer), the registration and use of the compound as this single enantiomer is preferred. This reduces the total application rate and avoids the tedious environmental testing required when registering a racemate. However if a viable enantioselective manufacturing route cannot be found, then the racemate is registered and used.
Insecticides with systemic activity against sucking pests, which are safe to pollinators, are sought after, particularly in view of the partial bans on neonicotinoids. Revised 2023 guidance by registration authorities describes the bee testing that is required for new insecticides to be approved for commercial use. | 1 | Applied and Interdisciplinary Chemistry |
The hallmark of linear azol(in)e-containing peptide (LAP) biosynthesis is the formation of azol(in)e heterocycles from the nucleophilic amino acids serine, threonine, or cysteine. This is accomplished by three enzymes referred to as the B, C, and D proteins; the precursor peptide is referred to as the A protein, as in other classes.
The C protein is mainly involved in leader peptide recognition and binding and is sometimes called a scaffolding protein. The D protein is an ATP-dependent cyclodehydratase that catalyzes the cyclodehydration reaction, resulting in formation of an azoline ring. This occurs by direct activation of the amide backbone carbonyl with ATP, resulting in stoichiometric ATP consumption. The C and D proteins are occasionally present as a single, fused protein, as is the case for trunkamide biosynthesis. The B protein is a flavin mononucleotide (FMN)-dependent dehydrogenase which oxidizes certain azoline rings into azoles.
The B protein is typically referred to as the dehydrogenase; the C and D proteins together form the cyclodehydratase, although the D protein alone performs the cyclodehydration reaction. Early work on microcin B17 adopted a different nomenclature for these proteins, but a recent consensus has been adopted by the field as described above. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, IUPAC changed its definition of standard temperature and pressure in 1982:
* Until 1982, STP was defined as a temperature of 273.15 K (0 °C, 32 °F) and an absolute pressure of exactly 1 atm (101.325 kPa).
* Since 1982, STP has been defined as a temperature of 273.15 K (0 °C, 32 °F) and an absolute pressure of exactly 10 Pa (100 kPa, 1 bar).
NIST uses a temperature of 20 °C (293.15 K, 68 °F) and an absolute pressure of 1 atm (14.696 psi, 101.325 kPa). This standard is also called normal temperature and pressure (abbreviated as NTP). However, a common temperature and pressure in use by NIST for thermodynamic experiments is 298.15 K (25°C, 77°F) and 1 bar (14.5038 psi, 100 kPa). NIST also uses "15 °C (59 °F)" for the temperature compensation of refined petroleum products, despite noting that these two values are not exactly consistent with each other.
The ISO 13443 standard reference conditions for natural gas and similar fluids are and 101.325 kPa;
by contrast, the American Petroleum Institute adopts . | 0 | Theoretical and Fundamental Chemistry |
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