text stringlengths 105 4.57k | label int64 0 1 | label_text stringclasses 2
values |
|---|---|---|
A reverberatory furnace is a metallurgical or process furnace that isolates the material being processed from contact with the fuel, but not from contact with combustion gases. The term reverberation is used here in a generic sense of rebounding or reflecting, not in the acoustic sense of echoing. | 1 | Applied and Interdisciplinary Chemistry |
The capillary pressure developed within a liquid droplet/film can be calculated using the Young–Laplace equation (e.g.):
where:
* is the difference between the pressure across the liquid interface (Pa),
* is the surface tension of the liquid (N/m),
* is the unit normal pointing out of surface,
* are the principle radii of curvature at any point on the free surface of the liquid film or droplet (m).
If the liquid wets the contacting surfaces then this pressure difference is negative i.e. the pressure inside liquid is less than the ambient pressure, and if the liquid doesn't wet the contacting surfaces then the pressure difference is positive and liquid pressure is higher than the ambient pressure. | 1 | Applied and Interdisciplinary Chemistry |
Embryo transfer can be performed after various durations of embryo culture, conferring different stages in embryogenesis. The main stages at which embryo transfer is performed are cleavage stage (day 2 to 4 after co-incubation) or the blastocyst stage (day 5 or 6 after co-incubation).
Because in vivo, a cleavage stage embryo still resides in the fallopian tube and it is known that the nutritional environment of the uterus is different from that of the tube, it is postulated that this may cause stress on the embryo if transferred on day 3 resulting in reduced implantation potential. A blastocyst stage embryo does not have this problem as it is best suited for the uterine environment [https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD002118.pub5/full]
Embryos who reach the day 3 cell stage can be tested for chromosomal or specific genetic defects prior to possible transfer by preimplantation genetic diagnosis (PGD). Transferring at the blastocyst stage confers a significant increase in live birth rate per transfer, but also confers a decreased number of embryos available for transfer and embryo cryopreservation, so the cumulative clinical pregnancy rates are increased with cleavage stage transfer. It is uncertain whether there is any difference in live birth rate between transfer on day two or day three after fertilization.
Monozygotic twinning is not increased after blastocyst transfer compared with cleavage-stage embryo transfer.
There is a significantly higher odds of preterm birth (odds ratio 1.3) and congenital anomalies (odds ratio 1.3) among births having reached the blastocyst stage compared with cleavage stage. Because of increased female embryo mortality due to epigenetic modifications induced by extended culture, blastocyst transfer leads to more male births (56.1% male) versus 2 or 3 day transfer (a normal sex ratio of 51.5% male). | 1 | Applied and Interdisciplinary Chemistry |
Psycho-Active is developing a multi-fuel/air-hybrid chassis which is intended to serve as the foundation for a line of automobiles. Claimed performance is 50 hp/litre. The compressed air motor they use is called the DBRE or Ducted Blade Rotary Engine. | 1 | Applied and Interdisciplinary Chemistry |
A post–September 11 development, explosive detection systems have become a part of all US airports. These systems run on a host of technologies, many of them based on GC–MS. There are only three manufacturers certified by the FAA to provide these systems, one of which is Thermo Detection (formerly Thermedics), which produces the EGIS, a GC–MS-based line of explosives detectors. The other two manufacturers are Barringer Technologies, now owned by Smith's Detection Systems, and Ion Track Instruments, part of General Electric Infrastructure Security Systems. | 0 | Theoretical and Fundamental Chemistry |
Magnet-assisted transfection is a transfection method which uses magnetic interactions to deliver DNA into target cells. Nucleic acids are associated with magnetic nanoparticles, and magnetic fields drive the nucleic acid-particle complexes into target cells, where the nucleic acids are released. | 1 | Applied and Interdisciplinary Chemistry |
The HIV-1 RT is an asymmetric 1000-amino acid heterodimer composed of p66 (560 amino acids) and p51 subunits (440 amino acids). The p66 subunit has two domains, a polymerase and ribonuclease H. The polymerase domain contains four subdomains, which have been termed “fingers”, “palm”, “thumb” and “connection” and it is often compared to a right hand. The role of the p66 subunit is to carry out the activity of RT whereas it contains the active sites of the enzyme. The p51 is believed to play mainly a structural role. | 1 | Applied and Interdisciplinary Chemistry |
Because H is the lightest element, atmospheric H can readily be lost to space via Jeans escape, an irreversible process that drives Earth's net mass loss. Photolysis of heavier compounds not prone to escape, such as CH or HO, can also liberate H from the upper atmosphere and contribute to this process. Another major sink of free atmospheric H is photochemical oxidation by hydroxyl radicals (•OH), which forms water.
Anthropogenic sinks of H include synthetic fuel production through the Fischer-Tropsch reaction and artificial nitrogen fixation through the Haber-Bosch process to produce nitrogen fertilizers. | 1 | Applied and Interdisciplinary Chemistry |
At the end of the 19th century, the construction of the wealthy neighborhood of Circonvallazione a Monte significantly altered the area, when Corso Magenta and the Sant'Anna funicular were built immediately to the South of the convent. The religious buildings and the quaint village in which they are located have nonetheless remained intact and quiet to this day.
The Pharmacy is still active today. Several ancient recipes are still prepared and updated when necessary. The laboratories have been refurbished to reflect modern needs and the latest regulatory requirements.
After 1933, the Convent, the church and the pharmacy of Sant'Anna are accessible also with an elevator from the tunnel which connects Corso Magenta with the Elevator Magenta-Crocco. | 1 | Applied and Interdisciplinary Chemistry |
The height h of a liquid column is given by Jurin's law
where is the liquid-air surface tension (force/unit length), θ is the contact angle, ρ is the density of liquid (mass/volume), g is the local acceleration due to gravity (length/square of time), and r is the radius of tube.
As r is in the denominator, the thinner the space in which the liquid can travel, the further up it goes. Likewise, lighter liquid and lower gravity increase the height of the column.
For a water-filled glass tube in air at standard laboratory conditions, at 20°C, , and . Because water spreads on clean glass, the effective equilibrium contact angle is approximately zero. For these values, the height of the water column is
Thus for a radius glass tube in lab conditions given above, the water would rise an unnoticeable . However, for a radius tube, the water would rise , and for a radius tube, the water would rise . | 0 | Theoretical and Fundamental Chemistry |
In one study the usual regioselectivity of an alkyne hydrozirconation is reversed with the addition of zinc chloride:
One example of a one-pot hydrozirconation - carbonylation - coupling is depicted below:
With certain allyl alcohols, the alcohol group is replaced by nucleophilic carbon forming a cyclopropane ring: The selectivity of the hydrozirconation of alkynes has been studied in detail. Generally, the addition of the Zr–H proceeds via the syn-addition. The rate of addition to unsaturated carbon-carbon bonds is terminal alkyne > terminal alkene ≈ internal alkyne > disubstituted alkene Acyl complexes can be generated by insertion of CO into the C–Zr bond resulting from hydrozirconation. Upon alkene insertion into the zirconium hydride bond, the resulting zirconium alkyl undergoes facile rearrangement to the terminal alkyl and therefore only terminal acyl compounds can be synthesized in this way. The rearrangement most likely proceeds via β-hydride elimination followed by reinsertion. | 0 | Theoretical and Fundamental Chemistry |
The first example of ring-closing metathesis was reported by Dider Villemin in 1980 when he synthesized an Exaltolide precursor using a WCl/MeSn catalyzed metathesis cyclization in 60-65% yield depending on ring size (A). In the following months, Jiro Tsuji reported a similar metathesis reaction describing the preparation of a macrolide catalyzed by WCl and dimethyltitanocene (CpTiMe) in a modest 17.9% yield (B). Tsuji describes the olefin metathesis reaction as “…potentially useful in organic synthesis” and addresses the need for the development of a more versatile catalyst to tolerate various functional groups.
In 1987, Siegfried Warwel and Hans Kaitker published a synthesis of symmetric macrocycles through a cross-metathesis dimerization of starting cycloolefins to afford C, C, and C dienes in 58-74% yield, as well as C in 30% yield, using ReO on AlO and MeSn for catalyst activation.
After a decade since its initial discovery, Grubbs and Fu published two influential reports in 1992 detailing the synthesis of O- and N- heterocycles via RCM utilizing Schrock’s molybdenum alkylidene catalysts, which had proven more robust and functional group tolerant than the tungsten chloride catalysts. The synthetic route allowed access to dihydropyrans in high yield (89-93%) from readily available starting materials. In addition, synthesis of substituted pyrrolines, tetrahydropyridines, and amides were illustrated in modest to high yield (73-89% ). The driving force for the cyclization reaction was attributed to entropic favorability by forming two molecules per one molecule of starting material. The loss of the second molecule, ethylene, a highly volatile gas, drives the reaction in the forward direction according to Le Châtelier's principle.
In 1993, Grubbs and others not only published a report on carbocycle synthesis using a molybdenum catalyst, but also detailed the initial use of a novel ruthenium carbene complex for metathesis reactions, which later became a popular catalyst due to its extraordinary utility. The ruthenium catalysts are not sensitive to air and moisture, unlike the molybdenum catalysts. The ruthenium catalysts, known better as the Grubbs Catalysts, as well as molybdenum catalysts, or Schrock’s Catalysts, are still used today for many metathesis reactions, including RCM. Overall, it was shown that metal-catalyzed RCM reactions were very effective in C-C bond forming reactions, and would prove of great importance in organic synthesis, chemical biology, materials science, and various other fields to access a wide variety of unsaturated and highly functionalized cyclic analogues. | 0 | Theoretical and Fundamental Chemistry |
One approach to prevent PDs consists of physical-chemical optimization of the PCR system, i.e. changing the concentrations of primers, magnesium chloride, nucleotides, ionic strength and temperature of the reaction. This method is somewhat limited by the physical-chemical characteristics that also determine the efficiency of amplification of the target sequence in the PCR. Therefore, reducing PDs formation may also result in reduced PCR efficiency. To overcome this limitation, other methods aim to reduce the formation of PDs only, including primer design, and use of different PCR enzyme systems or reagents. | 1 | Applied and Interdisciplinary Chemistry |
When used as an indicator in an EDTA titration, the characteristic blue end-point is reached when sufficient EDTA is added and the metal ions bound to the indicator are chelated by EDTA, leaving the free indicator molecule.
Eriochrome Black T has also been used to detect the presence of rare earth metals. | 0 | Theoretical and Fundamental Chemistry |
A lead compound (, i.e. a "leading" compound, not to be confused with various compounds of the metallic element lead) in drug discovery is a chemical compound that has pharmacological or biological activity likely to be therapeutically useful, but may nevertheless have suboptimal structure that requires modification to fit better to the target; lead drugs offer the prospect of being followed by back-up compounds. Its chemical structure serves as a starting point for chemical modifications in order to improve potency, selectivity, or pharmacokinetic parameters. Furthermore, newly invented pharmacologically active moieties may have poor druglikeness and may require chemical modification to become drug-like enough to be tested biologically or clinically. | 1 | Applied and Interdisciplinary Chemistry |
Non-sequential double ionization is a process whose mechanism differs (in any detail) from the sequential one. For example, both the electrons leave the system simultaneously (as in alkaline earth atoms, see below), the second electron's liberation is assisted by the first electron (as in noble gas atoms, see below), etc.
The phenomenon of non-sequential double ionization was experimentally discovered by Suran and Zapesochny for alkaline earth atoms as early as 1975.
Despite extensive studies, the details of double ionization in alkaline earth atoms remain unknown. It is supposed that double ionization in this case is realized by transitions of both the electrons through the spectrum of autoionizing atomic states, located between the first and second ionization potentials.
For noble gas atoms, non-sequential double ionization was first observed by L'Huillier.
The interest to this phenomenon grew rapidly after it was rediscovered
in infrared fields and for higher intensities. Multiple ionization has also been observed.
The mechanism of non-sequential double ionization in noble gas atoms differs from the one in alkaline earth atoms. For noble gas atoms in infrared laser fields, following one-electron ionization, the liberated electron can recollide
with the parent ion.
This electron acts as an "atomic antenna", absorbing the
energy from the laser field between ionization and recollision and
depositing it into the parent ion. Inelastic scattering on the
parent ion results in further collisional excitation and/or
ionization. This mechanism is known as the three-step model of non-sequential double ionization, which is also closely related to the three step model of high harmonic generation.
Dynamics of double ionization within the three-step model strongly depends on the laser field intensity. The maximum energy (in atomic units) gained by the recolliding electron from the laser field is , where
is the ponderomotive energy, is the laser field strength, and is the laser frequency. Even when is far below ionization potential experiments have observed correlated ionization.
As opposed to the high- regime ()
in the low- regime () the assistance of the laser field during the
recollision is vital.
Classical and quantum analysis
of the low- regime
demonstrates the following two ways of electron ejection after the recollision: First, the two electrons can be freed with little time delay compared to the quarter-cycle of the driving laser field. Second, the time delay between the ejection of the
first and the second electron is of the order of the quarter-cycle of the driving field. In these two cases, the electrons appear in different quadrants of the correlated spectrum. If following the recollision, the electrons are ejected
nearly simultaneously, their parallel momenta have equal signs,
and both electrons are driven by the laser field in the same
direction toward the detector
. If after the recollision, the electrons are ejected with a substantial delay (quarter-cycle or
more), they end up going in the opposite directions. These two types of dynamics produce distinctly different correlated spectra (compare experimental results
with | 0 | Theoretical and Fundamental Chemistry |
In December 2004 plans were submitted, in partnership with Countryside Properties, to build an urban village over two-thirds of the site, comprising residential and business developments, a retail site and doctors surgery. MMC director Mark Russell stated that the plans were in everyones interests and would be carried out without harming the environment or causing problems with old asbestos: "At the end of the day this is a contaminated site with lots of old, ugly, dilapidated buildings on and it needs something doing with it. It is in everyone's interests that this happens." The planning application summary claimed: "of particular note is the absence of any asbestos contamination". A report submitted by the developers said only one out of the 86 soil tests they carried out showed any traces of asbestos dust, and that traces of lead and copper were more prevalent on the site. A working party of six councillors expressed concern that many areas on the site might have been unchecked, however, and Councillor Elwyn Watkins said that he had personally observed asbestos containing materials hanging on trees when he joined campaigners on the north side of the site. Heavy winds in January 2005 felled several trees, revealing asbestos-like fibres on the exposed roots. Residents eventually had the waste tested themselves at an independent laboratory where it was confirmed to be Amosite ("brown asbestos"), the most hazardous of the asbestos minerals because of its long persistence in the lungs of exposed people. | 1 | Applied and Interdisciplinary Chemistry |
Praseodymium(III) oxalate forms crystalline hydrates (light green crystals): Pr(CO)•10HO. The crystalline hydrate decomposes stepwise when heated: | 0 | Theoretical and Fundamental Chemistry |
The complex consists of three main proteins, the RNA helicase Ski2 and the proteins Ski3 and Ski8. This tetramer contains a 370 kDa core complex, containing N-terminal arms and C-terminal arms from Ski3. The helicase core of Ski2 is positioned by both the C-terminal of Ski3 and two subunits of Ski8. | 1 | Applied and Interdisciplinary Chemistry |
Polyurethanes contain multiple carbamate groups as part of their structure. The "urethane" in the name "polyurethane" refers to these carbamate groups; the term "urethane links" describe how carbamates polymerize. In contrast, the substance commonly called "urethane", ethyl carbamate, is neither a component of polyurethanes, nor is it used in their manufacture. Urethanes are usually formed by reaction of an alcohol with an isocyanate. Commonly, urethanes made by a non-isocyanate route are called carbamates.
Polyurethane polymers have a wide range of properties and are commercially available as foams, elastomers, and solids. Typically, polyurethane polymers are made by combining diisocyanates, e.g. toluene diisocyanate, and diols, where the carbamate groups are formed by reaction of the alcohols with the isocyanates:
:RN=C=O + R′OH → RNHC(O)OR′ | 0 | Theoretical and Fundamental Chemistry |
Hydrogen sulfide - a component of crude oil and natural gas and a by-product in anaerobic digestion of biomass - is also suitable for plasma-catalytic decomposition to produce hydrogen and elemental sulfur due to its weak binding energy.
The energy requirement for the production of hydrogen from HS is approx. 5 kWh/kg. | 0 | Theoretical and Fundamental Chemistry |
Vaisheshika (IAST: Vaiśeṣika; ; ) is one of the six schools of Hindu philosophy from ancient India. In its early stages, the Vaiśeṣika was an independent philosophy with its own metaphysics, epistemology, logic, ethics, and soteriology. Over time, the Vaiśeṣika system became similar in its philosophical procedures, ethical conclusions and soteriology to the Nyāya school of Hinduism, but retained its difference in epistemology and metaphysics.
The epistemology of the Vaiśeṣika school of Hinduism, like Buddhism, accepted only two reliable means to knowledge: direct observation and inference. The Vaiśeṣika school and Buddhism both consider their respective scriptures as indisputable and valid means to knowledge, the difference being that the scriptures held to be a valid and reliable source by Vaiśeṣikas were the Vedas.
The Vaiśeṣika school is known for its insights in naturalism. It is a form of atomism in natural philosophy. It postulated that all objects in the physical universe are reducible to paramāṇu (atoms), and one's experiences are derived from the interplay of substance (a function of atoms, their number and their spatial arrangements), quality, activity, commonness, particularity and inherence. Everything was composed of atoms, qualities emerged from aggregates of atoms, but the aggregation and nature of these atoms was predetermined by cosmic forces. Ājīvika metaphysics included a theory of atoms which was later adapted in the Vaiśeṣika school.
According to the Vaiśeṣika school, knowledge and liberation were achievable by a complete understanding of the world of experience.
Vaiśeṣika darshana was founded by Kaṇāda Kashyapa around the 6th to 2nd century BC. | 1 | Applied and Interdisciplinary Chemistry |
The term "ecosan" was first used in 1995 and the first project started in 1996 in Ethiopia, by an NGO called Sudea. A trio, Dr Torsten Modig, Umeå University, Almaz Terrefe, teamleader, and Gunder Edström, hygiene expert, chose an area in a dense urban area as a starting point. They used urine diverting dry toilets (UDDTs) coupled with reuse activities.
In the ecosan concept, human excreta and wastewater is regarded as a potential resource – which is why it has also been called "resource oriented sanitation". The term "productive sanitation" has also been in use since about 2006. | 1 | Applied and Interdisciplinary Chemistry |
N6-methyladenine (m6A) is the product of the addition of a methyl group (CH) at position 6 of the adenine. This modified nucleotide is absent from the vast majority of eukaryotes, with the exception of C. elegans, but is widespread in bacterial genomes, as part of the restriction modification or DNA repair systems. In Escherichia coli, adenine methylation is catalyzed by the adenine methyltransferase Dam (DNA adenine methyltransferase), which catalyses adenine methylation exclusively in the palindromic sequence GATC. Ectopic expression of Dam in eukaryotic cells leads to methylation of adenine in GATC sequences without any other noticeable side effect.
Based on this, DamID consists in fusing Dam to a protein of interest (usually a protein that interacts with DNA such as transcription factors) or a chromatin component. The protein of interest thus targets Dam to its cognate in vivo binding site, resulting in the methylation of neighboring GATCs. The presence of m6A, coinciding with the binding sites of the proteins of interest, is revealed by methyl PCR. | 1 | Applied and Interdisciplinary Chemistry |
Plotting the Nyquist diagram with a potentiostat and an impedance analyzer, most often included in modern potentiostats, allows the user to determine charge transfer resistance, double-layer capacitance and ohmic resistance. The exchange current density can be easily determined measuring the impedance of a redox reaction for .
Nyquist diagrams are made of several arcs for reactions more complex than redox reactions and with mass-transfer limitations. | 0 | Theoretical and Fundamental Chemistry |
Honeybees have very controlled patterns of movement, such as the waggle or tremble dance which serve to deliver specific coordinates of fruitful sources to potential foragers. Bumblebee movement is comparatively random and does not supply coordinates to other bees. Other experiments by Dornhaus and Chittka (2001) showed increased movement of successful foraging bees upon returning to the nest. Successful bees ran faster and longer compared to unsuccessful bees. A bee may spend several minutes running around the nest before flying out again. As the bee runs, it has been hypothesized that the bee may also offer a form of communication based on the buzzing sounds made from her wings. These excited runs serve in part to rouse other bees into foraging. | 1 | Applied and Interdisciplinary Chemistry |
The maskant to be used is determined primarily by the chemical used to etch the material, and the material itself. The maskant must adhere to the surface of the material, and it must also be chemically inert enough with regard to the etchant to protect the workpiece. Most modern chemical milling processes use maskants with an adhesion around ; if the adhesion is too strong, the scribing process may be too difficult to perform. If the adhesion is too low, the etching area may be imprecisely defined. Most industrial chemical milling facilities use maskants based upon neoprene elastomers or isobutylene-isoprene copolymers. | 1 | Applied and Interdisciplinary Chemistry |
A signal peptide (sometimes referred to as signal sequence, targeting signal, localization signal, localization sequence, transit peptide, leader sequence or leader peptide) is a short peptide (usually 16-30 amino acids long) present at the N-terminus (or occasionally nonclassically at the C-terminus or internally) of most newly synthesized proteins that are destined toward the secretory pathway.
These proteins include those that reside either inside certain organelles (the endoplasmic reticulum, Golgi or endosomes), secreted from the cell, or inserted into most cellular membranes. Although most type I membrane-bound proteins have signal peptides, most type II and multi-spanning membrane-bound proteins are targeted to the secretory pathway by their first transmembrane domain, which biochemically resembles a signal sequence except that it is not cleaved. They are a kind of target peptide. | 1 | Applied and Interdisciplinary Chemistry |
A. Cellular T cell response
The first evidence of survivin-specific CTL recognition and killing was shown in an assay wherein cytotoxic T cells (CTLs) induced lysis of B cells transfected to present survivin peptides on its surface. The naive CD8+ T cells were primed with dendritic cells and could therefore recognize the specific peptides of survivin presented on the surface Major Histocompatibility Complex I (MHC I) molecules of the B cells.
B. Humoral antibody response
Taking blood samples from cancer patients, scientists have found antibodies that are specific for survivin. These antibodies were absent in the blood samples of healthy normal patients. Therefore, this shows that survivin is able to elicit a full humoral immune response. This may prove useful, as one could measure the level of survivin-specific antibodies in the patient's blood as a monitor of tumour progression. In acquiring the humoral response to tumour antigens such as survivin, CD4+ T cells are activated to induce B cells to produce antibodies directed against the particular antigens.
The isolation of the antibodies specific for survivin peptides is useful, as one can look at the structure and sequence of the epitope binding groove of the antibody and, therefore, deduce possible epitopes that may fit in that particular antibody groove. Therefore, one can determine the particular peptide portion of the survivin protein that is bound most efficiently and most commonly by humoral antibodies generated against survivin. This will lead to the production of more specific survivin vaccines that contain a specific portion of the survivin protein that is known to elicit a good immune response, generate immune memory, and allow for protection from tumour development. | 1 | Applied and Interdisciplinary Chemistry |
*Addition reaction
**Aldol addition
**Electrophilic addition
**Michael addition
**Mukaiyama aldol addition
**Nucleophilic addition
*Cyclization
**Bergman cyclization
**Nazarov cyclization reaction
*Elimination reaction
**Beta elimination
**Cope elimination
**E1cB elimination reaction
**Hofmann elimination
*Organic redox reaction
**Cannizzaro reaction
**Oxidation
***Baeyer-Villiger oxidation
***Corey-Kim oxidation
***Dess-Martin oxidation
***Fleming-Tamao oxidation
***Jones oxidation
***Nucleophilic epoxidation
***Oppenauer oxidation
***Prilezhaev reaction
***Rubottom oxidation
***Schmidt reaction
***Swern oxidation
***Wacker-Tsuji oxidation
**Reduction
***Birch reduction
***Bouveault-Blanc reduction
***CBS reduction
***Clemmensen reduction
***Corey-Bakshi-Shibata reduction
***Corey–Itsuno reduction
***Fukuyama reduction
***Luche reduction
***Meerwein-Ponndorf-Verley reduction
***Rosenmund reduction
***Staudinger reduction
***Wolff-Kishner reduction
*Pericyclic reaction
**Cheletropic reaction
**Cycloaddition
***1,3-Dipolar cycloaddition
****Azide-alkyne Huisgen cycloaddition
***Diels–Alder reaction
***Nitrone-olefin (3+2) cycloaddition
***Staudinger ketene-imine cycloaddition
**Dyotropic reaction
**Electrocyclic reaction
**Group transfer reaction
**Sigmatropic reaction
*Polymerization
**Ring-opening metathesis polymerisation
*Rearrangement reaction
**Baker–Venkataraman rearrangement
**Beckmann rearrangement
**Benzilic acid rearrangement
**Brook rearrangement
**Claisen rearrangement
**Cope rearrangement
**Curtius rearrangement
**Fries rearrangement
**Ireland–Claisen rearrangement
**Newman–Kwart rearrangement
**Overman rearrangement
**Oxy-Cope rearrangement
**Pinacol rearrangement
**1,2-Wittig rearrangement
**2,3-Wittig rearrangement
*Substitution reaction
**Electrophilic aromatic substitution
**Nucleophilic aromatic substitution
**Electrophilic substitution
**Nucleophilic substitution
***S1 reaction
***S2 reaction
**Vicarious nucleophilic substitution | 0 | Theoretical and Fundamental Chemistry |
Glycolipids are important for cell recognition, and are important for modulating the function of membrane proteins that act as receptors. Glycolipids are lipid molecules bound to oligosaccharides, generally present in the lipid bilayer. Additionally, they can serve as receptors for cellular recognition and cell signaling. The head of the oligosaccharide serves as a binding partner in receptor activity. The binding mechanisms of receptors to the oligosaccharides depends on the composition of the oligosaccharides that are exposed or presented above the surface of the membrane. There is great diversity in the binding mechanisms of glycolipids, which is what makes them such an important target for pathogens as a site for interaction and entrance. For example, the chaperone activity of glycolipids has been studied for its relevance to HIV infection. | 0 | Theoretical and Fundamental Chemistry |
Thermal radiation is the emission of electromagnetic waves from all matter that has a temperature greater than absolute zero. Thermal radiation reflects the conversion of thermal energy into electromagnetic energy. Thermal energy is the kinetic energy of random movements of atoms and molecules in matter. It is present in all matter of nonzero temperature. These atoms and molecules are composed of charged particles, i.e., protons and electrons. The kinetic interactions among matter particles result in charge acceleration and dipole oscillation. This results in the electrodynamic generation of coupled electric and magnetic fields, resulting in the emission of photons, radiating energy away from the body. Electromagnetic radiation, including visible light, will propagate indefinitely in vacuum.
The characteristics of thermal radiation depend on various properties of the surface from which it is emanating, including its temperature and its spectral emissivity, as expressed by Kirchhoffs law. The radiation is not monochromatic, i.e., it does not consist of only a single frequency, but comprises a continuous spectrum of photon energies, its characteristic spectrum. If the radiating body and its surface are in thermodynamic equilibrium and the surface has perfect absorptivity at all wavelengths, it is characterized as a black body. A black body is also a perfect emitter. The radiation of such perfect emitters is called black-body radiation. The ratio of any bodys emission relative to that of a black body is the body's emissivity, so a black body has an emissivity of one.
Absorptivity, reflectivity, and emissivity of all bodies are dependent on the wavelength of the radiation. Due to reciprocity, absorptivity and emissivity for any particular wavelength are equal at equilibrium – a good absorber is necessarily a good emitter, and a poor absorber is a poor emitter. The temperature determines the wavelength distribution of the electromagnetic radiation.
The distribution of power that a black body emits with varying frequency is described by Plancks law. At any given temperature, there is a frequency f at which the power emitted is a maximum. Wiens displacement law, and the fact that the frequency is inversely proportional to the wavelength, indicates that the peak frequency f is proportional to the absolute temperature T of the black body. The photosphere of the sun, at a temperature of approximately 6000 K, emits radiation principally in the (human-)visible portion of the electromagnetic spectrum. Earths atmosphere is partly transparent to visible light, and the light reaching the surface is absorbed or reflected. Earths surface emits the absorbed radiation, approximating the behavior of a black body at 300 K with spectral peak at f. At these lower frequencies, the atmosphere is largely opaque and radiation from Earth's surface is absorbed or scattered by the atmosphere. Though about 10% of this radiation escapes into space, most is absorbed and then re-emitted by atmospheric gases. It is this spectral selectivity of the atmosphere that is responsible for the planetary greenhouse effect, contributing to global warming and climate change in general (but also critically contributing to climate stability when the composition and properties of the atmosphere are not changing). | 0 | Theoretical and Fundamental Chemistry |
According to the kinetic theory of gases, the kinetic energy for a gas at a temperature is
where is the mass of one molecule, is the root-mean-square speed of the molecules, and is the Boltzmann constant. The average molecular speed can be calculated from the Maxwell speed distribution
as (or, equivalently, ). The rate at which a gas of molar mass effuses (typically expressed as the number of molecules passing through the hole per second) is then
Here is the gas pressure difference across the barrier, is the area of the hole, is the Avogadro constant, is the gas constant and is the absolute temperature. Assuming the pressure difference between the two sides of the barrier is much smaller than , the average absolute pressure in the system (i.e. ), it is possible to express effusion flow as a volumetric flow rate as follows:
or
where is the volumetric flow rate of the gas, is the average pressure on either side of the orifice, and is the hole diameter. | 0 | Theoretical and Fundamental Chemistry |
The comparison of electrostatic surface potentials (ESPs) of aromatic rings in tryptophan, tyrosine, phenylalanine, and histidine suggests that electronic effects also play a role in the binding to glycans (see Figure 2). After normalizing the electron densities for surface area, the tryptophan still remains the most electron rich acceptor of interactions, suggesting a possible reason for its 9-fold prevalence in carbohydrate binding pockets. Overall, the electrostatic potential maps follow the prevalence trend of . | 1 | Applied and Interdisciplinary Chemistry |
Material properties such as strength, chemical reactivity, stress corrosion cracking resistance, weldability, deformation behavior, resistance to radiation damage, and magnetic susceptibility can be highly dependent on the material’s texture and related changes in microstructure. In many materials, properties are texture-specific, and development of unfavorable textures when the material is fabricated or in use can create weaknesses that can initiate or exacerbate failures. Parts can fail to perform due to unfavorable textures in their component materials. Failures can correlate with the crystalline textures formed during fabrication or use of that component. Consequently, consideration of textures that are present in and that could form in engineered components while in use can be a critical when making decisions about the selection of some materials and methods employed to manufacture parts with those materials. When parts fail during use or abuse, understanding the textures that occur within those parts can be crucial to meaningful interpretation of failure analysis data. | 1 | Applied and Interdisciplinary Chemistry |
Minimizing distortion of information is important in all spectrum analyzers. The FFT process applies windowing techniques to improve the output spectrum due to producing less side lobes. The effect of windowing may also reduce the level of a signal where it is captured on the boundary between one FFT and the next. For this reason FFT's in a Realtime spectrum analyzer are overlapped. Overlapping rate is approximately 80%. An analyzer that utilises a 1024-point FFT process will re-use approximately 819 samples from the previous FFT process. | 0 | Theoretical and Fundamental Chemistry |
The Diels–Reese Reaction is a reaction between hydrazobenzene and dimethyl acetylenedicarboxylate (or related esters) first reported in 1934 by Otto Diels and Johannes Reese. Later work by others extended the reaction scope to include substituted hydrazobenzenes. The exact mechanism is not known. By changing the acidic or basic nature of the solvent, the reaction gives different products. With acetic acid as solvent (acidic), the reaction gives an diphenylpyrazolone. With xylene as solvent (neutral), the reaction gives an indole. With pyridine as solvent (basic), the reaction gives a carbomethoxyquinoline which can be degraded to a dihydroquinoline. | 0 | Theoretical and Fundamental Chemistry |
Since the ions are charged, they cannot pass through cellular membranes via simple diffusion. Two different mechanisms can transport the ions across the membrane: active or passive transport.
An example of active transport of ions is the Na-K-ATPase (NKA). NKA is powered by the hydrolysis of ATP into ADP and an inorganic phosphate; for every molecule of ATP hydrolized, three Na are transported outside and two K are transported inside the cell. This makes the inside of the cell more negative than the outside and more specifically generates a membrane potential V of about .
An example of passive transport is ion fluxes through Na, K, Ca, and Cl channels. Unlike active transport, passive transport is powered by the arithmetic sum of osmosis (a concentration gradient) and an electric field (the transmembrane potential). Formally, the molar Gibbs free energy change associated with successful transport is where represents the gas constant, represents absolute temperature, is the charge per ion, and represents the Faraday constant.
In the example of Na, both terms tend to support transport: the negative electric potential inside the cell attracts the positive ion and since Na is concentrated outside the cell, osmosis supports diffusion through the Na channel into the cell. In the case of K, the effect of osmosis is reversed: although external ions are attracted by the negative intracellular potential, entropy seeks to diffuse the ions already concentrated inside the cell. The converse phenomenon (osmosis supports transport, electric potential opposes it) can be achieved for Na in cells with abnormal transmembrane potentials: at , the Na influx halts; at higher potentials, it becomes an efflux. | 0 | Theoretical and Fundamental Chemistry |
Minimizing harmful exposure to pesticides can be achieved by proper use of personal protective equipment, adequate reentry times into recently sprayed areas, and effective product labeling for hazardous substances as per FIFRA regulations. Training high-risk populations, including agricultural workers, on the proper use and storage of pesticides, can reduce the incidence of acute pesticide poisoning and potential chronic health effects associated with exposure. Continued research into the human toxic health effects of pesticides serves as a basis for relevant policies and enforceable standards that are health protective to all populations. | 1 | Applied and Interdisciplinary Chemistry |
The decay scheme of a radioactive substance is a graphical presentation of all the transitions occurring in a decay, and of their relationships. Examples are shown below.
It is useful to think of the decay scheme as placed in a coordinate system, where the vertical axis is energy, increasing from bottom to top, and the horizontal axis is the proton number, increasing from left to right. The arrows indicate the emitted particles. For the gamma rays (vertical arrows), the gamma energies are given; for the beta decay (oblique arrow), the maximum beta energy. | 0 | Theoretical and Fundamental Chemistry |
In case of a porous materials many issues have been raised both about the physical meaning of the calculated pore diameter and the real possibility to use this equation for the calculation of the contact angle of the solid, even if this method is often offered by much software as consolidated. Change of weight as a function of time is measured. | 0 | Theoretical and Fundamental Chemistry |
The Sherritt process is a hydrometallurgical process named for Sherritt Gordon Mines Ltd. (now Sherritt International) of Sherridon and Lynn Lake Manitoba Canada, based on the older Forward process developed by Dr. Frank Forward for the recovery of copper and nickel from those same mines. Nickel sulfide concentrates can be treated by either roasting or flash smelting to produce matte from which nickel and cobalt can be recovered hydrometallurgically, or they may be treated by an ammonia solution pressure leach. The residue is removed. A feed of matte and sulfide concentrate containing approximately 0.4% cobalt and 30% sulfur is pressure leached at elevated temperature and pressure in an ammoniacal solution to produce a solution of nickel, copper and cobalt. By boiling away the ammonia; copper is precipitated as a sulfide and sent to a smelter. Hydrogen sulfide is added to the autoclave to remove nickel sulfide and copper sulfide which is fed back to the leaching process. Air is then passed through the solution in the autoclave for oxyhydrolysis. The solution is then reduced with hydrogen, again at high temperature and pressure, to precipitate nickel powder (>99%). The remaining solution (containing approximately equal proportions of nickel and cobalt sulfides), is then adjusted (to a lower temperature and pressure) to precipitate the mixed sulfides and the fluid is concentrated and crystallized into ammonium sulfate ((NH)SO). The mixed sulfides are pressure leached with air and sulfuric acid. Ammonia is then added to remove potassium and iron as jarosite (KFe (OH)(SO)). More ammonia and air is added for oxidation. The solution is removed from the autoclave and sulfuric acid added to remove nickel as nickel(II) sulfate-ammonium sulfate hexahydrate ([NiSO]•[(NH)SO]•6HO) which is then sent to have its nickel recovered. The solution is then further reduced with more sulfuric acid and cobalt metal powder is added to aid in the nucleation of precipitants (seeding). Addition of hydrogen gas to saturation precipitates cobalt powder with a purity of approximately 99.6%. | 1 | Applied and Interdisciplinary Chemistry |
The force F(h) between two bodies is related to the interaction free energy U(h) as
where h is the surface-to-surface separation. Conversely, when the force profile is known, one can evaluate the interaction energy as
When one considers two planar walls, the corresponding quantities are expressed per unit area. The disjoining pressure is the force per unit area and can be expressed by the derivative
where W(h) is the surface free energy per unit area. Conversely, one has
The main restriction of the Derjaguin approximation is that it is only valid at distances much smaller than the size of the objects involved, namely h ≪ R and h ≪ R. Furthermore, it is a continuum approximation and thus valid at distances larger than the molecular length scale. Even when rough surfaces are involved, this approximation has been shown to be valid in many situations. Its range of validity is restricted to distances larger than the characteristic size of the surface roughness features (e.g., root mean square roughness). | 0 | Theoretical and Fundamental Chemistry |
Gustavs Vanags (10 March 1891 — 8 May 1965) was a Soviet and Latvian organic chemist, full member of Latvian SSR Academy of Sciences. He was also one of the signers of the Memorandum of Latvian Central Council in 1944. | 0 | Theoretical and Fundamental Chemistry |
From Isaiah: "And the people shall be as the burnings of lime: as thorns cut up shall they be burned in the fire"
Its use is mentioned in the Book of Amos (2:1): "I will not turn away the punishment thereof, because he burned the bones of the King of Edom into lime."
It was used in ancient formulas for white paint and cosmetic pigments, and in the cupellation process to separate silver from lead. | 0 | Theoretical and Fundamental Chemistry |
Yliaster or Iliaster, a term coined by Paracelsus, refers to "prime matter, consisting of body and soul".
Paracelsus described the Iliaster as the "completely healed human being who has burned away all the dross of his lower being and is free to fly as the Phoenix." It is most likely a portmanteau of the Greek hyle (matter) and Latin astrum (star). To Paracelsus, the Iliaster represented the two basic compounds of the cosmos, matter representing "below", and the stars representing "above". Paracelsus says this of the Yliaster while describing how fossils are trapped in wood:
In this sense, the Yliaster is the same as the Prima Materia. It is the formless base of all matter which is the raw material for the alchemical Great Work. | 1 | Applied and Interdisciplinary Chemistry |
Riboses 2 hydroxy group reacts with the phosphate linked 3 hydroxy group, making RNA too unstable to be used or synthesized reliably. To overcome this, a ribose analogue can be used. The most common RNA analogues are 2-O-methyl-substituted RNA, locked nucleic acid (LNA) or bridged nucleic acid (BNA), morpholino, and peptide nucleic acid (PNA). Although these oligonucleotides have a different backbone sugar—or, in the case of PNA, an amino acid residue in place of the ribose phosphate—they still bind to RNA or DNA according to Watson and Crick pairing while being immune to nuclease activity. They cannot be synthesized enzymatically and can only be obtained synthetically using the phosphoramidite strategy or, for PNA, other methods of peptide synthesis. | 1 | Applied and Interdisciplinary Chemistry |
An antibody titer is a measurement of how much antibody an organism has produced that recognizes a particular epitope. It is conventionally expressed as the inverse of the greatest dilution level that still gives a positive result on some test. ELISA is a common means of determining antibody titers. For example, the indirect Coombs test detects the presence of anti-Rh antibodies in a pregnant womans blood serum. A patient might be reported to have an "indirect Coombs titer" of 16. This means that the patients serum gives a positive indirect Coombs test at any dilution down to 1/16 (1 part serum to 15 parts diluent). At greater dilutions the indirect Coombs test is negative. If a few weeks later the same patient had an indirect Coombs titer of 32 (1/32 dilution which is 1 part serum to 31 parts diluent), this would mean that she was making more anti-Rh antibody, since it took a greater dilution to abolish the positive test.
Many traditional serological tests such as hemagglutination or complement fixation employ this principle. Such tests can typically be read visually, which makes them fast, cost-effective, and able to be deployed in a wide variety of laboratory environments. The interpretation of any serological titer result is guided by reference values that are specific to the antigen or antibody in question, so a titer of 1:32 may be below the cut-off for one test but above for another. | 1 | Applied and Interdisciplinary Chemistry |
Phenethylamine is a primary amine, the amino-group being attached to a benzene ring through a two-carbon, or ethyl group. It is a colourless liquid at room temperature that has a fishy odor, and is soluble in water, ethanol and ether. Its density is 0.964 g/ml and its boiling point is 195 °C. Upon exposure to air, it combines with carbon dioxide to form a solid carbonate salt. Phenethylamine is strongly basic, pK = 4.17 (or pK = 9.83), as measured using the HCl salt, and forms a stable crystalline hydrochloride salt with a melting point of 217 °C. | 1 | Applied and Interdisciplinary Chemistry |
The precedence for creating a pharmacopoeia went back to 1618 when the College of Physicians of London created their own London Pharmacopoeia to regulate the manufacture of medicine. The first edition of the Edinburgh Pharmacopoeia was created in a period of tension between physicians and surgeons and the College of Physicians in Edinburgh sought to regulate the practice of medicine by providing standardized recipes. The first item in the College of Physician's minutes in 1682 note the need for a committee for creating a pharmacopoeia.
The committee for the creation of the pharmacopoeia struggled for the next seventeen years, finally agreeing upon a text and publishing the first edition of the Edinburgh Pharmacopoeia in 1699. The first edition was rife with dispute amongst the College of Physicians. Robert Sibbald was a main figure in its eventual publication, however the College divided into two camps; the new science and Sibbald's dated faction. Members of the College not only disagreed on content of the pharmacopoeia, but style and structure as well. | 1 | Applied and Interdisciplinary Chemistry |
* The World Health Organization (WHO) published updated guidelines for drinking-water quality (GDWQ) in 2017.
*The International Organization for Standardization (ISO) published regulation of water quality in the section of ICS 13.060, ranging from water sampling, drinking water, industrial class water, sewage, and examination of water for chemical, physical or biological properties. ICS 91.140.60 covers the standards of water supply systems. | 0 | Theoretical and Fundamental Chemistry |
Oncometabolite dysregulation and cancer progression are linked to epigenetic changes in cancer cells. Several mechanisms have been linked to -2-hydroxyglutarate, succinate, and fumarate with the inhibition of α-KG–dependent dioxygenases, this causes epigenetic changes that affect the expression of genes involved in cell differentiation and the development of malignant characteristics. The group of Timothy A. Chan described a mechanism by which abnormal accumulation of the oncometabolite -2-hydroxyglutarate in brain tumor samples increased DNA methylation, a process that has been shown to play a key role in oncogenesis. On the other hand, in paraganglioma cells, succinate and fumarate were found to methylate histones, effectively silencing the genes PNMT and KRT19, which are involved in neuroendocrine differentiation and epithelial-mesenchymal transition, respectively. | 1 | Applied and Interdisciplinary Chemistry |
Benthic macroinvertebrates are found within the benthic zone of a stream or river. They consist of aquatic insects, crustaceans, worms and mollusks that live in the vegetation and stream beds of rivers. Macroinvertebrate species can be found in nearly every stream and river, except in some of the world's harshest environments. They also can be found in mostly any size of stream or river, prohibiting only those that dry up within a short timeframe. This makes the beneficial for many studies because they can be found in regions where stream beds are too shallow to support larger species such as fish. Benthic indicators are often used to measure the biological components of fresh water streams and rivers. In general, if the biological functioning of a stream is considered to be in good standing, then it is assumed that the chemical and physical components of the stream are also in good condition. Benthic indicators are the most frequently used water quality test within the United States. While benthic indicators should not be used to track the origins of stressors in rivers and streams, they can provide background on the types of sources that are often associated with the observed stressors. | 1 | Applied and Interdisciplinary Chemistry |
Despite GaAs-based photovoltaics being the clear champions of efficiency for solar cells, they have relatively limited use in today's market. In both world electricity generation and world electricity generating capacity, solar electricity is growing faster than any other source of fuel (wind, hydro, biomass, and so on) for the last decade. However, GaAs solar cells have not currently been adopted for widespread solar electricity generation. This is largely due to the cost of GaAs solar cells - in space applications, high performance is required and the corresponding high cost of the existing GaAs technologies is accepted. For example, GaAs-based photovoltaics show the best resistance to gamma radiation and high temperature fluctuations, which are of great importance for spacecraft. But in comparison to other solar cells, III-V solar cells are two to three orders of magnitude more expensive than other technologies such as silicon-based solar cells. The primary sources of this cost are the epitaxial growth costs and the substrate the cell is deposited on.
GaAs solar cells are most commonly fabricated utilizing epitaxial growth techniques such as metal-organic chemical vapor deposition (MOCVD) and hydride vapor phase epitaxy (HVPE). A significant reduction in costs for these methods would require improvements in tool costs, throughput, material costs, and manufacturing efficiency. Increasing the deposition rate could reduce costs, but this cost reduction would be limited by the fixed times in other parts of the process such as cooling and heating.
The substrate used to grow these solar cells is usually germanium or gallium arsenide which are notably expensive materials. One of the main pathways to reduce substrate costs is to reuse the substrate. An early method proposed to accomplish this is epitaxial lift-off (ELO), but this method is time-consuming, somewhat dangerous (with its use of hydrofluoric acid), and requires multiple post-processing steps. However, other methods have been proposed that use phosphide-based materials and hydrochloric acid to achieve ELO with surface passivation and minimal post-etching residues and allows for direct reuse of the GaAs substrate. There is also preliminary evidence that spalling could be used to remove the substrate for reuse. An alternative path to reduce substrate cost is to use cheaper materials, although materials for this application are not currently commercially available or developed.
Yet another consideration to lower GaAs solar cell costs could be concentrator photovoltaics. Concentrators use lenses or parabolic mirrors to focus light onto a solar cell, and thus a smaller (and therefore less expensive) GaAs solar cell is needed to achieve the same results. Concentrator systems have the highest efficiency of existing photovoltaics.
So, technologies such as concentrator photovoltaics and methods in development to lower epitaxial growth and substrate costs could lead to a reduction in the cost of GaAs solar cells and forge a path for use in terrestrial applications. | 0 | Theoretical and Fundamental Chemistry |
The practice of using colours to determine the temperature of a piece of (usually) ferrous metal comes from blacksmithing. Long before thermometers were widely available, it was necessary to know what state the metal was in for heat treating it and the only way to do this was to heat it up to a colour which was known to be best for the work. | 1 | Applied and Interdisciplinary Chemistry |
In the case of nucleic acids, the direction of migration, from negative to positive electrodes, is due to the naturally occurring negative charge carried by their sugar-phosphate backbone.
Double-stranded DNA fragments naturally behave as long rods, so their migration through the gel is relative to their size or, for cyclic fragments, their radius of gyration. Circular DNA such as plasmids, however, may show multiple bands, the speed of migration may depend on whether it is relaxed or supercoiled. Single-stranded DNA or RNA tends to fold up into molecules with complex shapes and migrate through the gel in a complicated manner based on their tertiary structure. Therefore, agents that disrupt the hydrogen bonds, such as sodium hydroxide or formamide, are used to denature the nucleic acids and cause them to behave as long rods again.
Gel electrophoresis of large DNA or RNA is usually done by agarose gel electrophoresis. See the "chain termination method" page for an example of a polyacrylamide DNA sequencing gel. Characterization through ligand interaction of nucleic acids or fragments may be performed by mobility shift affinity electrophoresis.
Electrophoresis of RNA samples can be used to check for genomic DNA contamination and also for RNA degradation. RNA from eukaryotic organisms shows distinct bands of 28s and 18s rRNA, the 28s band being approximately twice as intense as the 18s band. Degraded RNA has less sharply defined bands, has a smeared appearance, and the intensity ratio is less than 2:1. | 1 | Applied and Interdisciplinary Chemistry |
The affinity constants, k and k, of the 1879 paper can now be recognised as rate constants. The equilibrium constant, K, was derived by setting the rates of forward and backward reactions to be equal. This also meant that the chemical affinities for the forward and backward reactions are equal. The resultant expression
is correct even from the modern perspective, apart from the use of concentrations instead of activities (the concept of chemical activity was developed by Josiah Willard Gibbs, in the 1870s, but was not widely known in Europe until the 1890s). The derivation from the reaction rate expressions is no longer considered to be valid. Nevertheless, Guldberg and Waage were on the right track when they suggested that the driving force for both forward and backward reactions is equal when the mixture is at equilibrium. The term they used for this force was chemical affinity. Today the expression for the equilibrium constant is derived by setting the chemical potential of forward and backward reactions to be equal. The generalisation of the law of mass action, in terms of affinity, to equilibria of arbitrary stoichiometry was a bold and correct conjecture.
The hypothesis that reaction rate is proportional to reactant concentrations is, strictly speaking, only true for elementary reactions (reactions with a single mechanistic step), but the empirical rate expression
is also applicable to second order reactions that may not be concerted reactions. Guldberg and Waage were fortunate in that reactions such as ester formation and hydrolysis, on which they originally based their theory, do indeed follow this rate expression.
In general many reactions occur with the formation of reactive intermediates, and/or through parallel reaction pathways. However, all reactions can be represented as a series of elementary reactions and, if the mechanism is known in detail, the rate equation for each individual step is given by the expression so that the overall rate equation can be derived from the individual steps. When this is done the equilibrium constant is obtained correctly from the rate equations for forward and backward reaction rates.
In biochemistry, there has been significant interest in the appropriate mathematical model for chemical reactions occurring in the intracellular medium. This is in contrast to the initial work done on chemical kinetics, which was in simplified systems where reactants were in a relatively dilute, pH-buffered, aqueous solution. In more complex environments, where bound particles may be prevented from disassociation by their surroundings, or diffusion is slow or anomalous, the model of mass action does not always describe the behavior of the reaction kinetics accurately. Several attempts have been made to modify the mass action model, but consensus has yet to be reached. Popular modifications replace the rate constants with functions of time and concentration. As an alternative to these mathematical constructs, one school of thought is that the mass action model can be valid in intracellular environments under certain conditions, but with different rates than would be found in a dilute, simple environment .
The fact that Guldberg and Waage developed their concepts in steps from 1864 to 1867 and 1879 has resulted in much confusion in the literature as to which equation the law of mass action refers. It has been a source of some textbook errors. Thus, today the "law of mass action" sometimes refers to the (correct) equilibrium constant formula,
and at other times to the (usually incorrect) rate formula. | 0 | Theoretical and Fundamental Chemistry |
Francis Gordon Albert Stone CBE, FRS, FRSC (19 May 1925 – 6 April 2011), always known as Gordon, was a British chemist who was a prolific and decorated scholar. He specialized in the synthesis of main group and transition metal organometallic compounds. He was the author of more than 900 academic publications resulting in an h-index of 72 in 2011. | 0 | Theoretical and Fundamental Chemistry |
Ocean acidification is the ongoing decrease in the pH of the Earth's ocean. Between 1950 and 2020, the average pH of the ocean surface fell from approximately 8.15 to 8.05. Carbon dioxide emissions from human activities are the primary cause of ocean acidification, with atmospheric carbon dioxide () levels exceeding 410 ppm (in 2020). from the atmosphere is absorbed by the oceans. This chemical reaction produces carbonic acid () which dissociates into a bicarbonate ion () and a hydrogen ion (). The presence of free hydrogen ions () lowers the pH of the ocean, increasing acidity (this does not mean that seawater is acidic yet; it is still alkaline, with a pH higher than 8). Marine calcifying organisms, such as mollusks and corals, are especially vulnerable because they rely on calcium carbonate to build shells and skeletons.
A change in pH by 0.1 represents a 26% increase in hydrogen ion concentration in the world's oceans (the pH scale is logarithmic, so a change of one in pH units is equivalent to a tenfold change in hydrogen ion concentration). Sea-surface pH and carbonate saturation states vary depending on ocean depth and location. Colder and higher latitude waters are capable of absorbing more . This can cause acidity to rise, lowering the pH and carbonate saturation levels in these areas. Other factors that influence the atmosphere-ocean exchange, and thus local ocean acidification, include: ocean currents and upwelling zones, proximity to large continental rivers, sea ice coverage, and atmospheric exchange with nitrogen and sulfur from fossil fuel burning and agriculture.
Decreased ocean pH has a range of potentially harmful effects for marine organisms. These include reduced calcification, depressed metabolic rates, lowered immune responses, and reduced energy for basic functions such as reproduction. The effects of ocean acidification are therefore impacting marine ecosystems that provide food, livelihoods, and other ecosystem services for a large portion of humanity. Some 1 billion people are wholly or partially dependent on the fishing, tourism, and coastal management services provided by coral reefs. Ongoing acidification of the oceans may therefore threaten food chains linked with the oceans.
The United Nations Sustainable Development Goal 14 ("Life below Water") has a target to "minimize and address the impacts of ocean acidification". Reducing carbon dioxide emissions (i.e., climate change mitigation measures) is the only solution that addresses the root cause of ocean acidification. Mitigation measures which achieve carbon dioxide removal from the atmosphere would help to reverse ocean acidification. The more specific ocean-based mitigation methods (e.g. ocean alkalinity enhancement, enhanced weathering) could also reduce ocean acidification. These strategies are being researched, but generally have a low technology readiness level and many risks.
Ocean acidification has occurred previously in Earth's history. The resulting ecological collapse in the oceans had long-lasting effects on the global carbon cycle and climate. | 0 | Theoretical and Fundamental Chemistry |
Water vapor is common in the Solar System and by extension, other planetary systems. Its signature has been detected in the atmospheres of the Sun, occurring in sunspots. The presence of water vapor has been detected in the atmospheres of all seven extraterrestrial planets in the Solar System, the Earth's Moon, and the moons of other planets, although typically in only trace amounts.
Geological formations such as cryogeysers are thought to exist on the surface of several icy moons ejecting water vapor due to tidal heating and may indicate the presence of substantial quantities of subsurface water. Plumes of water vapor have been detected on Jupiters moon Europa and are similar to plumes of water vapor detected on Saturns moon Enceladus. Traces of water vapor have also been detected in the stratosphere of Titan. Water vapor has been found to be a major constituent of the atmosphere of dwarf planet, Ceres, largest object in the asteroid belt The detection was made by using the far-infrared abilities of the Herschel Space Observatory. The finding is unexpected because comets, not asteroids, are typically considered to "sprout jets and plumes." According to one of the scientists, "The lines are becoming more and more blurred between comets and asteroids." Scientists studying Mars hypothesize that if water moves about the planet, it does so as vapor.
The brilliance of comet tails comes largely from water vapor. On approach to the Sun, the ice many comets carry sublimes to vapor. Knowing a comets distance from the sun, astronomers may deduce the comets water content from its brilliance.
Water vapor has also been confirmed outside the Solar System. Spectroscopic analysis of HD 209458 b, an extrasolar planet in the constellation Pegasus, provides the first evidence of atmospheric water vapor beyond the Solar System. A star called CW Leonis was found to have a ring of vast quantities of water vapor circling the aging, massive star. A NASA satellite designed to study chemicals in interstellar gas clouds, made the discovery with an onboard spectrometer. Most likely, "the water vapor was vaporized from the surfaces of orbiting comets." Other exoplanets with evidence of water vapor include HAT-P-11b and K2-18b. | 1 | Applied and Interdisciplinary Chemistry |
With the development of bioconjugation technology, there are plenty of options to covalently ligating an artificial metal cofactor onto a protein: i) cysteine residue based chemistry like: Cys-meleimide, Cys-α-haloketone, Cys-benzylhalide chemistry and disulfide formation, ii) post-translational bioorthogonal modification based on Amber suppression (e.g., Click chemistry) and iii) enzyme active site modification (e.g., covalent bond formation between lipase and lipase inhibitor).
The video shows an example using reaction between cysteine residue and α-haloketone to introduce a phenanthroline ligand into an adipocyte lipid binding protein. In this context, the ArM can selectively hydrolyze certain racemic esters. | 0 | Theoretical and Fundamental Chemistry |
The Global Ocean Data Analysis Project (GLODAP) is a synthesis project bringing together oceanographic data, featuring two major releases as of 2018. The central goal of GLODAP is to generate a global climatology of the World Ocean's carbon cycle for use in studies of both its natural and anthropogenically forced states. GLODAP is funded by the National Oceanic and Atmospheric Administration, the U.S. Department of Energy, and the National Science Foundation.
The first GLODAP release (v1.1) was produced from data collected during the 1990s by research cruises on the World Ocean Circulation Experiment, Joint Global Ocean Flux Study and Ocean-Atmosphere Exchange Study programmes. The second GLODAP release (v2) extended the first using data from cruises from 2000 to 2013. The data are available both as individual "bottle data" from sample sites, and as interpolated fields on a standard longitude, latitude, depth grid. | 0 | Theoretical and Fundamental Chemistry |
Because the mechanically interlocked structures are maintained by bulky stoppers at the ends of the strings, if the bulky stoppers are removed, such as removed by a chemical stimulus, rings dethread from the axes. The drastic structural change can be used for programmed drug or gene delivery, of which drug or gene can be released with the rings when the stoppers are cut off at the specific destination.
For example, an enhanced gene delivery vehicle can be obtained by using a polyrotaxane formed by rings, backbones, then stoppers that linked by a disulfide bond (or other chemical bond that can be selected cleave in the body). The cation-functionalized polyrotaxanes can bind with pDNA to form complex through the electronstatic interaction. Glutathione (or other corresponding chemicals that can cleave the sensitive chemical bond) is over-expressed in the target cells. When the polyrotaxane/plasmid DNA (pDNA) complexes are uptaken by the target cells, intercellular glutathione could cleave the disulfide bond to cut off the stoppers at the end of polyrotaxanes, which results in the dissociation of the polyrotaxanes. As the rings dethread from the chain, pDNA is released with the ring molecules. | 0 | Theoretical and Fundamental Chemistry |
The final part dealt with the construction of oxetane ring D starting with protection of the alcohol group in 38 (Scheme 4). as a TROC alcohol 39 with 2,2,2-trichloroethyl chloroformate and pyridine. The OBOM group was replaced by a bromine group in three steps: deprotection to 40 with hydrochloric acid and sodium iodide, mesylation to 41 with mesyl chloride, DMAP and pyridine and nucleophilic substitution with inversion of configuration with lithium bromide to bromide 42. Because the oxidation of the alkene group to the diol 43 with osmium tetroxide was accompanied by the undesired migration of the benzoate group, this step was taken to completion with imidazole as 44. Two additional countermeasures were required: reprotection of the diol as the carbonate ester 45 with triphosgene and removal of the benzoate group (KCN) to alcohol 46 in preparation of the actual ring closure to the oxetane 47 with N,N-diisopropylethylamine. In the final steps the tertiary alcohol was acylated in 48, the TIPS group removed in 49 and the benzoate group re-introduced in 50.
Tail addition of the Ojima lactam 51 was not disclosed in detail but finally taxol 52 was formed in several steps similar to the other efforts. | 0 | Theoretical and Fundamental Chemistry |
The FIDA principle is based on measuring the change in the apparent size (diffusivity) of a selective indicator interacting with the analyte molecule. The apparent indicator size is measured by Taylor dispersion analysis in a capillary under hydrodynamic flow. | 1 | Applied and Interdisciplinary Chemistry |
Uranium tailings or uranium tails are a radioactive waste byproduct (tailings) of conventional uranium mining and uranium enrichment. They contain the radioactive decay products from the uranium decay chains, mainly the U-238 chain, and heavy metals. Long-term storage or disposal of tailings may pose a danger for public health and safety. | 0 | Theoretical and Fundamental Chemistry |
The involvement of Jander in the research on chemical warfare and his influence on the Kaiser Wilhelm Institute for Physical Chemistry and Elektrochemistry after he followed Fritz Haber as director, who was forced to resign due to the Law for the Restoration of the Professional Civil Service, have been a point of research of the Max Planck Society (The Max Planck Society is the successor organisation of the Kaiser Wilhelm Society). | 0 | Theoretical and Fundamental Chemistry |
The integral of thus yields the logarithm of the ratio of the upper and lower cut-offs. This number is known as the Coulomb logarithm and is designated by either or . It is the factor by which small-angle collisions are more effective than large-angle collisions. The Coulomb logarithm was introduced independently by Lev Landau in 1936 and Subrahmanyan Chandrasekhar in 1943. For many plasmas of interest it takes on values between and . (For convenient formulas, see pages 34 and 35 of the [https://www.nrl.navy.mil/ppd/content/nrl-plasma-formulary NRL Plasma formulary].) The limits of the impact parameter integral are not sharp, but are uncertain by factors on the order of unity, leading to theoretical uncertainties on the order of . For this reason it is often justified to simply take the convenient choice . The analysis here yields the scalings and orders of magnitude. | 0 | Theoretical and Fundamental Chemistry |
Trinitroethylorthoformate also known as TNEOF is an explosive with excellent chemical stability. It does not have hygroscopicity, does not dissolve in water, and does not react with acids. It decomposes in aqueous sodium hydroxide solution to release formaldehyde odor. The explosion point of TNEOF is 229 °C, though it begins to decompose at 190 °C. Its explosion heat is 6.3076 J/g and specific volume is 682 L/kg. Its structure is closely related to that of trinitroethylorthocarbonate (TNEOC). Both are highly explosive and very shock-sensitive, and may be dissolved in nitroalkanes to reduce their shock-sensitivity. | 0 | Theoretical and Fundamental Chemistry |
Biopesticides are certain types of pesticides derived from such natural materials as animals, plants, bacteria, and certain minerals. For example, canola oil and baking soda have pesticidal applications and are considered biopesticides. Biopesticides fall into three major classes:
* Microbial pesticides which consist of bacteria, entomopathogenic fungi or viruses (and sometimes includes the metabolites that bacteria or fungi produce). Entomopathogenic nematodes are also often classed as microbial pesticides, even though they are multi-cellular.
* Biochemical pesticides or herbal pesticides are naturally occurring substances that control (or monitor in the case of pheromones) pests and microbial diseases.
* Plant-incorporated protectants (PIPs) have genetic material from other species incorporated into their genetic material (i.e. GM crops). Their use is controversial, especially in many European countries. | 1 | Applied and Interdisciplinary Chemistry |
In May, researchers announced the first gene therapy trial for inherited retinal disease. The first operation was carried out on a 23-year-old British male, Robert Johnson, in early 2007. | 1 | Applied and Interdisciplinary Chemistry |
There are 5 core requirements when it comes to designing for LID.
# Conserve natural areas wherever possible (dont pave over the whole site if you dont need to).
# Minimize the development impact on hydrology.
# Maintain runoff rate and duration from the site (don't let the water leave the site).
# Scatter integrated management practices (IMPs) throughout your site – IMPs are decentralized, microscale controls that infiltrate, store, evaporate, and/or detain runoff close to the source.
# Implement pollution prevention, proper maintenance and public education programs. | 1 | Applied and Interdisciplinary Chemistry |
As described above, same-excess experiments are conducted with two or more experiments holding the excess, (e) constant while changing the absolute concentrations of the substrates (in this case, the catalyst is also treated as a substrate.) Note that this construction causes the number of equivalents and therefore the mole percentage of each reagent/catalyst to differ between reactions. These experiments enable one to artificially "enter" the reaction at any point, as the initial concentrations of one experiment (the intercepting reaction) are chosen to map directly onto the anticipated concentrations at some intermediate time, t, in another (the parent reaction). One would expect the reaction progress, described by the rate vs. substrate concentration plots detailed above, to map directly onto each other from that interception point onward. This will hold true, however, only if the rate of the reaction is not altered by changes to the active substrate/catalyst concentration (such as by catalyst activation, catalyst deactivation, or product inhibition) before that interception.
A perfect overlay of multiple experiments with the same-excess but different initial substrate loadings suggests that no changes in the active substrate/catalyst concentration occur over the course of the reaction. The failure of the plots to overlay is generally indicative of catalyst activation, deactivation, or product inhibition under the reaction conditions. These cases may be distinguished by the position of the reaction progress curves relative to each other. Intercepting reactions lying below (slower rates at the same substrate concentration) the parent reactions on the rate vs. substrate concentration plot, are indicative of catalyst activation under reaction conditions. Intercepting reactions lying above (faster rates at the same substrate concentration) the parent reactions on the rate vs. substrate concentration plot, are indicative of catalyst deactivation under reaction conditions; further experimentation is necessary to distinguish product inhibition from other forms of catalyst death.
One key difference between the intercepting reaction and the parent reaction described above is the presence of some amount of product in the parent reaction at the interception point. Product inhibition has long been known to influence catalyst efficiency of many systems, and in the case of same-excess experiments, it prevents the intercepting and parent reactions from overlaying. While same-excess experiments as described above cannot attribute catalyst deactivation to any particular cause, product inhibition can be probed by further experiments in which some initial amount of product is added to the intercepting reaction (designed to mimic the amount of product expected to be present in the parent reaction at the same substrate concentration). A perfect overlay of the rate vs. substrate concentration plots under same-excess-same product conditions indicates that product inhibition does occur under the reaction conditions used. While the failure of the rate vs. substrate concentration plots to overlay under same-excess-same product conditions does not preclude product inhibition, it does, at least, indicate that other catalyst deactivation paths must also be active.
Same-excess experiments probing catalyst deactivation and product inhibition are among the most widely used applications of reaction progress kinetic analysis. Among the numerous examples in the literature, some include investigation of the amino alcohol-catalyzed zinc alkylation of aldehydes, the amido-thiourea catalyzed asymmetric Strecker synthesis of unnatural amino acids, and the SOMO-activation of organocatalysts. | 0 | Theoretical and Fundamental Chemistry |
The prefix E/Z- can be used to indicate uncertainty in the E or Z isomers for an ene bond. For graphical representations, wavy single bonds are the standard way to represent unknown or unspecified stereochemistry or a mixture of isomers (as with tetrahedral stereocenters). A crossed double-bond has been used sometimes; it is no longer considered an acceptable style for general use by IUPAC but may still be required by computer software. | 0 | Theoretical and Fundamental Chemistry |
SELDI technology was developed by T. William Hutchens and Tai-Tung Yip at Baylor College of Medicine in 1993. Hutchens and Yip attached single-stranded DNA to agarose beads and used the beads to capture lactoferrin, an iron-binding glycoprotein, from preterm infant urine. The beads were incubated in the sample and then removed, washed, and analyzed with a MALDI-MS probe tip. This research led to the idea that MALDI surfaces could be derivatized with SEAC devices; the technique was later described by Hutchens and Yip in 1998.
SELDI technology was first commercialized by Ciphergen Biosystems in 1997 as the ProteinChip system, and is now produced and marketed by Bio-Rad Laboratories. | 1 | Applied and Interdisciplinary Chemistry |
Using only Hα chemical shifts and simple clustering rules (clusters of 3 or more vertical bars for beta strands and clusters of 4 or more vertical bars for alpha helices), the CSI is typically 75-80% accurate in the identification of secondary structures. This performance depends partly on the quality of the NMR data set as well as the technique (manual or programmatic) used to identify the protein secondary structures. As noted above, a consensus CSI method that filters upfield/downfield chemical shift changes in Cα, Cβ, and C' atoms in a similar manner to Hα shifts has also been developed. The consensus CSI combines the CSI plots from backbone H and C chemical shifts to generate a single CSI plot. It can be up to 85-90% accurate. | 0 | Theoretical and Fundamental Chemistry |
Photoreceptor cells are unusual cells in that they depolarize in response to absence of stimuli or scotopic conditions (darkness). In photopic conditions (light), photoreceptors hyperpolarize to a potential of −60 mV.
In the dark, cGMP levels are high and keep cGMP-gated sodium channels open allowing a steady inward current, called the dark current. This dark current keeps the cell depolarized at about −40 mV, leading to glutamate release which inhibits excitation of neurons.
The depolarization of the cell membrane in scotopic conditions opens voltage-gated calcium channels. An increased intracellular concentration of Ca causes vesicles containing glutamate, a neurotransmitter, to merge with the cell membrane, therefore releasing glutamate into the synaptic cleft, an area between the end of one cell and the beginning of another neuron. Glutamate, though usually excitatory, functions here as an inhibitory neurotransmitter.
In the cone pathway, glutamate:
* Hyperpolarizes on-center bipolar cells. Glutamate that is released from the photoreceptors in the dark binds to metabotropic glutamate receptors (mGluR6), which, through a G-protein coupling mechanism, causes non-specific cation channels in the cells to close, thus hyperpolarizing the bipolar cell.
* Depolarizes off-center bipolar cells. Binding of glutamate to ionotropic glutamate receptors results in an inward cation current that depolarizes the bipolar cell. | 1 | Applied and Interdisciplinary Chemistry |
Orosomucoid (ORM) or alpha-1-acid glycoprotein (αAGp, AGP or AAG) is an acute phase protein found in plasma. It is an alpha-globulin glycoprotein and is modulated by two polymorphic genes. It is synthesized primarily in hepatocytes and has a normal plasma concentration between 0.6–1.2 mg/mL (1–3% plasma protein). Plasma levels are affected by pregnancy, burns, certain drugs, and certain diseases, particularly HIV.
The only established function of ORM is to act as a carrier of basic and neutrally charged lipophilic compounds. In medicine, it is known as the primary carrier of basic (negatively charged) drugs (whereas albumin carries acidic (positively charged) and neutral drugs), steroids, and protease inhibitors. Aging causes a small decrease in plasma albumin levels; if anything, there is a small increase in alpha-1-acid glycoprotein. The effect of these changes on drug protein binding and drug delivery, however, appear to be minimal. AGP shows a complex interaction with thyroid homeostasis: AGP in low concentrations was observed to stimulate the thyrotropin (TSH) receptor and intracellular accumulation of cyclic AMP. High AGP concentrations, however, inhibited TSH signalling.
Alpha-1-acid glycoprotein has been identified as one of four potentially useful circulating biomarkers for estimating the five-year risk of all-cause mortality (the other three are albumin, very low-density lipoprotein particle size, and citrate).
Orosomucoid increases in amount in obstructive jaundice while it diminishes in hepatocellular jaundice and in intestinal infections. | 1 | Applied and Interdisciplinary Chemistry |
The thermodynamic description of gravity has a history that goes back at least to research on black hole thermodynamics by Bekenstein and Hawking in the mid-1970s. These studies suggest a deep connection between gravity and thermodynamics, which describes the behavior of heat. In 1995, Jacobson demonstrated that the Einstein field equations describing relativistic gravitation can be derived by combining general thermodynamic considerations with the equivalence principle. Subsequently, other physicists, most notably Thanu Padmanabhan, began to explore links between gravity and entropy. | 0 | Theoretical and Fundamental Chemistry |
Leopold Ružička (; born Lavoslav Stjepan Ružička; 13 September 1887 – 26 September 1976) was a Croatian-Swiss scientist and joint winner of the 1939 Nobel Prize in Chemistry "for his work on polymethylenes and higher terpenes" "including the first chemical synthesis of male sex hormones." He worked most of his life in Switzerland, and received eight doctorates honoris causa in science, medicine, and law; seven prizes and medals; and twenty-four honorary memberships in chemical, biochemical, and other scientific societies. | 0 | Theoretical and Fundamental Chemistry |
Mond gas could be produced and used more efficiently than other gases in the late 19th and early 20th century. The gas was used as fuel for street lighting and basic residential uses that required gas such as ovens, kilns, furnaces, and boilers. | 0 | Theoretical and Fundamental Chemistry |
Production of Mo by neutron activation of natural molybdenum, or molybdenum enriched in Mo, is another, currently smaller, route of production. | 0 | Theoretical and Fundamental Chemistry |
The compressibility factor is defined in thermodynamics and engineering frequently as:
where p is the pressure, is the density of the gas and is the specific gas constant, being the molar mass, and the is the absolute temperature (kelvin or Rankine scale).
In statistical mechanics the description is:
where p is the pressure, n is the number of moles of gas, is the absolute temperature, and is the gas constant, V is unit Volume
For an ideal gas the compressibility factor is per definition. In many real world applications requirements for accuracy demand that deviations from ideal gas behaviour, i.e., real gas behaviour, be taken into account. The value of generally increases with pressure and decreases with temperature. At high pressures molecules are colliding more often. This allows repulsive forces between molecules to have a noticeable effect, making the molar volume of the real gas () greater than the molar volume of the corresponding ideal gas (), which causes to exceed one. When pressures are lower, the molecules are free to move. In this case attractive forces dominate, making . The closer the gas is to its critical point or its boiling point, the more deviates from the ideal case. | 0 | Theoretical and Fundamental Chemistry |
The governing equations of LES are obtained by filtering the partial differential equations governing the flow field . There are differences between the incompressible and compressible LES governing equations, which lead to the definition of a new filtering operation. | 1 | Applied and Interdisciplinary Chemistry |
Following funding from the Wellcome Trust, from 2012 to 2015 the Guide to PHARMACOLOGY was expanded to include the biological targets of all prescription drugs and other likely targets of future small molecule drugs. Overviews of the key features of a wide range of targets are provided on the summary view pages, with detailed view pages providing more in-depth information on the properties of a selected subset of targets. As of January 2018 the Medicines for Malaria Venture is supporting a new extension to develop the [http://www.guidetomalariapharmacology.org Guide to Malaria Pharmacology]. The core GtoPdb continues to be supported by the British Pharmacological Society. | 1 | Applied and Interdisciplinary Chemistry |
The vorticity, , of a flow can be defined in terms of its flow velocity by
If the vorticity is zero, the flow is irrotational. | 1 | Applied and Interdisciplinary Chemistry |
Although rare, flutamide has been associated with severe hepatotoxicity and death. By 1996, 46 cases of severe cholestatic hepatitis had been reported, with 20 fatalities. There have been continued case reports since, including liver transplants and death. A 2021 review of the literature found 15 cases of serious hepatotoxicity in women treated with flutamide, including 7 liver transplantations and 2 deaths.
Based on the number of prescriptions written and the number of cases reported in the MedWatch database, the rate of serious hepatotoxicity associated with flutamide treatment was estimated in 1996 as approximately 0.03% (3 per 10,000). However, other research has suggested that the true incidence of significant hepatotoxicity with flutamide may be much greater, as high as 0.18 to 10%.
Flutamide is also associated with liver enzyme elevations in up to 42 to 62% of patients, although marked elevations in liver enzymes (above 5 times upper normal limit) occur only in 3 to 5%. The risk of hepatotoxicity with flutamide is much higher than with nilutamide or bicalutamide. Lower doses of the medication appear to have a possibly reduced but still significant risk. Liver function should be monitored regularly with liver function tests during flutamide treatment. In addition, due to the high risk of serious hepatotoxicity, flutamide should not be used in the absence of a serious indication.
The mechanism of action of flutamide-induced hepatotoxicity is thought to be due to mitochondrial toxicity. Specifically, flutamide and particularly its major metabolite hydroxyflutamide inhibit enzymes in the mitochondrial electron transport chain in hepatocytes, including respiratory complexes I (NADH ubiquinone oxidoreductase), II (succinate dehydrogenase), and V (ATP synthase), and thereby reduce cellular respiration via ATP depletion and hence decrease cell survival. Inhibition of taurocholate (a bile acid) efflux has also been implicated in flutamide-induced hepatotoxicity. In contrast to flutamide and hydroxyflutamide, which severely compromise hepatocyte cellular respiration in vitro, bicalutamide does not significantly do so at the same concentrations and is regarded as non-mitotoxic. It is thought that the nitroaromatic group of flutamide and hydroxyflutamide enhance their mitochondrial toxicity; bicalutamide, in contrast, possesses a cyano group in place of the nitro moiety, greatly reducing the potential for such toxicity.
The hepatotoxicity of flutamide appears to depend on hydrolysis of flutamide catalyzed by an arylacetamide deacetalyse enzyme. This is analogous to the hepatotoxicity that occurs with the withdrawn paracetamol (acetominophen)-related medication phenacetin. In accordance, the combination of paracetamol (acetaminophen) and flutamide appears to result in additive to synergistic hepatotoxicity, indicating a potential drug interaction.
Hepatotoxicity with flutamide may be cross-reactive with that of cyproterone acetate. | 0 | Theoretical and Fundamental Chemistry |
Two chemists generally expressed the composition of a mixture in terms of numerical values relating the amount of the product to describe the equilibrium state.
Cato Maximilian Guldberg and Peter Waage, building on Claude Louis Berthollet's ideas about reversible chemical reactions, proposed the law of mass action in 1864. These papers, in Danish, went largely unnoticed, as did the later publication (in French) of 1867 which contained a modified law and the experimental data on which that law was based.
In 1877 van t Hoff independently came to similar conclusions, but was unaware of the earlier work, which prompted Guldberg and Waage to give a fuller and further developed account of their work, in German, in 1879. Van t Hoff then accepted their priority. | 0 | Theoretical and Fundamental Chemistry |
Many of the competitive single-molecule sequencing methods rely on the incorporation of fluorescently labeled nucleotides. In next-generation sequencing, the fluorescence signal of clusters can be easily detected. However, when the same concept is applied to single-molecule sequencing, the largest complication results from the high error rates. Because it is difficult to detect single labeled molecules, these platforms suffer from low signal-to-noise ratios, often resulting in misdetection or non-detection of fluorescent signals. In the case of magnetic sequencing, the signal measured is the changes in distance between two ends of a hairpin. Such signal can be readily detected with standard cameras. Thus, the signals are easier to detect, even without the use of expensive imaging devices. | 1 | Applied and Interdisciplinary Chemistry |
One of the limitations of the Arrhenius definition is its reliance on water solutions. Edward Curtis Franklin studied the acid–base reactions in liquid ammonia in 1905 and pointed out the similarities to the water-based Arrhenius theory. Albert F.O. Germann, working with liquid phosgene, , formulated the solvent-based theory in 1925, thereby generalizing the Arrhenius definition to cover aprotic solvents.
Germann pointed out that in many solutions, there are ions in equilibrium with the neutral solvent molecules:
* solvonium ions: a generic name for positive ions. These are also sometimes called solvo-acids; when protonated solvent, they are lyonium ions.
* solvate ions: a generic name for negative ions. These are also sometimes called solve-bases; when deprotonated solvent, they are lyate ions.
For example, water and ammonia undergo such dissociation into hydronium and hydroxide, and ammonium and amide, respectively:
Some aprotic systems also undergo such dissociation, such as dinitrogen tetroxide into nitrosonium and nitrate, antimony trichloride into dichloroantimonium and tetrachloroantimonate, and phosgene into chlorocarboxonium and chloride:
A solute that causes an increase in the concentration of the solvonium ions and a decrease in the concentration of solvate ions is defined as an acid. A solute that causes an increase in the concentration of the solvate ions and a decrease in the concentration of the solvonium ions is defined as a base.
Thus, in liquid ammonia, (supplying ) is a strong base, and (supplying ) is a strong acid. In liquid sulfur dioxide (), thionyl compounds (supplying ) behave as acids, and sulfites (supplying ) behave as bases.
The non-aqueous acid–base reactions in liquid ammonia are similar to the reactions in water:
Nitric acid can be a base in liquid sulfuric acid:
The unique strength of this definition shows in describing the reactions in aprotic solvents; for example, in liquid :
Because the solvent system definition depends on the solute as well as on the solvent itself, a particular solute can be either an acid or a base depending on the choice of the solvent: is a strong acid in water, a weak acid in acetic acid, and a weak base in fluorosulfonic acid; this characteristic of the theory has been seen as both a strength and a weakness, because some substances (such as and ) have been seen to be acidic or basic on their own right. On the other hand, solvent system theory has been criticized as being too general to be useful. Also, it has been thought that there is something intrinsically acidic about hydrogen compounds, a property not shared by non-hydrogenic solvonium salts. | 0 | Theoretical and Fundamental Chemistry |
In the dynamics of fluid, a vortex is fluid that revolves around the axis line. This fluid might be curved or straight. Vortices form from stirred fluids: they might be observed in smoke rings, whirlpools, in the wake of a boat or the winds around a tornado or dust devil.
Vortices are an important part of turbulent flow. Vortices can otherwise be known as a circular motion of a liquid. In the cases of the absence of forces, the liquid settles. This makes the water stay still instead of moving.
When they are created, vortices can move, stretch, twist and interact in complicated ways. When a vortex is moving, sometimes, it can affect an angular position.
For an example, if a water bucket is rotated or spun constantly, it will rotate around an invisible line called the axis line. The rotation moves around in circles. In this example the rotation of the bucket creates extra force.
The reason that the vortices can change shape is the fact that they have open particle paths. This can create a moving vortex. Examples of this fact are the shapes of tornadoes and drain whirlpools.
When two or more vortices are close together they can merge to make a vortex. Vortices also hold energy in its rotation of the fluid. If the energy is never removed, it would consist of circular motion forever. | 1 | Applied and Interdisciplinary Chemistry |
Another type of entrainer is one that has a strong chemical affinity for one of the constituents. Using again the example of the water/ethanol azeotrope, the liquid can be shaken with calcium oxide, which reacts strongly with water to form the nonvolatile compound, calcium hydroxide. Nearly all of the calcium hydroxide can be separated by filtration and the filtrate redistilled to obtain 100% pure ethanol. A more extreme example is the azeotrope of 1.2% water with 98.8% diethyl ether. Ether holds the last bit of water so tenaciously that only a very powerful desiccant such as sodium metal added to the liquid phase can result in completely dry ether. Anhydrous calcium chloride is used as a desiccant for drying a wide variety of solvents since it is inexpensive and does not react with most nonaqueous solvents. Chloroform is an example of a solvent that can be effectively dried using calcium chloride. | 1 | Applied and Interdisciplinary Chemistry |
In medicinal chemistry and molecular biology, a pharmacophore is an abstract description of molecular features that are necessary for molecular recognition of a ligand by a biological macromolecule. IUPAC defines a pharmacophore to be "an ensemble of steric and electronic features that is necessary to ensure the optimal supramolecular interactions with a specific biological target and to trigger (or block) its biological response". A pharmacophore model explains how structurally diverse ligands can bind to a common receptor site. Furthermore, pharmacophore models can be used to identify through de novo design or virtual screening novel ligands that will bind to the same receptor. | 1 | Applied and Interdisciplinary Chemistry |
Nitrate salts are found naturally on earth in arid environments as large deposits, particularly of nitratine, a major source of sodium nitrate.
Nitrates are produced by a number of species of nitrifying bacteria in the natural environment using ammonia or urea as a source of nitrogen and source of free energy. Nitrate compounds for gunpowder were historically produced, in the absence of mineral nitrate sources, by means of various fermentation processes using urine and dung.
Lightning strikes in earth's nitrogen- and oxygen-rich atmosphere produce a mixture of oxides of nitrogen, which form nitrous ions and nitrate ions, which are washed from the atmosphere by rain or in occult deposition.
Nitrates are produced industrially from nitric acid. | 0 | Theoretical and Fundamental Chemistry |
The following is a list of structural features that can be elucidated by NMR:
* Chemical structure of each carbohydrate residue in a molecule, including
** carbon skeleton size and sugar type (aldose/ketose)
** cycle size (pyranose/furanose/linear)
** stereo configuration of all carbons (monosaccharide identification)
** stereo configuration of anomeric carbon (α/β)
** absolute configuration (D/L)
** location of amino-, carboxy-, deoxy- and other functions
* Chemical structure of non-carbohydrate residues in molecule (amino acids, fatty acids, alcohols, organic aglycons etc.)
* Substitution positions in residues
* Sequence of residues
* Stoichiometry of terminal residues and side chains
* Location of phosphate and sulfate diester bonds
* Polymerization degree and frame positioning (for polysaccharides) | 0 | Theoretical and Fundamental Chemistry |
This problem was addressed by George Keith Batchelor(1951), Keith Stewartson(1952) and many other researchers. Here the solution is not simple, because of the additional length scale imposed in the problem i.e., the distance between the two disks. In addition, the uniqueness and existence of a steady solution are also depend on the corresponding Reynolds number .<br />
Then the boundary conditions for the fluid are
In terms of , the upper wall location is simply . Thus, instead of the scalings
used before, it is convenient to introduce following transformation,
so that the governing equations become
with six boundary conditions
and the pressure is given by
Here boundary conditions are six because pressure is not known either at the top or bottom wall; is to be obtained as part of solution. For large Reynolds number , Batchelor argued that the fluid in the core would rotate at a constant velocity, flanked by two boundary layers at each disk for and there would be two uniform counter-rotating flow of thickness for . However, Stewartson predicted that for the fluid in the core would not rotate at , but just left with two boundary layers at each disk. It turns out, Stewartson predictions were correct (see Stewartson layer).
There is also an exact solution if the two disks are rotating about different axes but for . | 1 | Applied and Interdisciplinary Chemistry |
In a multiple-hearth roaster, the concentrate drops through a series of 9 or more hearths stacked inside a brick-lined cylindrical column. As the feed concentrate drops through the furnace, it is first dried by the hot gases passing through the hearths and then oxidized to produce calcine. The reactions are slow and can be sustained only by the addition of fuel. Multiple hearth roasters are unpressurized and operate at about . Operating time depends upon the composition of concentrate and the amount of the sulfur removal required. Multiple hearth roasters have the capability of producing a high-purity calcine. | 1 | Applied and Interdisciplinary Chemistry |
Margaret Douie Dougal ( – 1938, née Robertson, later Chaplin) was a British chemical publication indexer for fifteen years (1885–1909) for the Chemical Society. Dougal contributed to the compilation of volumes i-iii of A Collective Index of the Transactions, Proceedings and Abstracts of the Chemical Society. The then president of the Chemical society, Sir James Dewar, congratulated Dougal for her work as "an example of thoroughness and accuracy to her successors." The collected decennial indices were also prepared by Dougal; at the 1906 Annual Meeting of the Chemical Society it was noted that the Council "had pleasure in expressing the high appreciation of the ceaseless energy displayed by the indexer, Mrs. Margaret Dougal, on the completion of this valuable work."
Under Thomas Edward Thorpe, Dougal conducted inorganic chemistry research of mixed salts of chromium by testing their compositions. Research she conducted also provided insight on the stress and fracturing behavior of iron in Scottish craftsmanship and manufacturing in 1892.
Dougal was born Margaret Douie Robertson in Singapore in , the daughter of J.H. Robertson M.D.. She married William Dougal and, after his death, married Arnold Chaplin M.D. F.R.C.P. on 29 July 1909. She died in London on 9 November 1938 at the age of 79. | 0 | Theoretical and Fundamental Chemistry |
End groups are seen on all polymers and the functionality of those end groups can be important in determining the application of polymers. Each type of polymerization (free radical, condensation or etc.) has end groups that are typical for the polymerization, and knowledge of these can help to identify the type of polymerization method used to form the polymer. | 0 | Theoretical and Fundamental Chemistry |
1st International Symposium on Microscale Chemistry
May 2000 at Universidad Iberoamericana – Ciudad de Mexico
2nd International Symposium on Microscale Chemistry
13. – 15. December 2001 at Hong Kong Baptist University – Hong Kong [https://web.archive.org/web/20070930210616/http://www.hkbu.edu.hk/~chem/Photo_micro_2001.htm]
3rd International Symposium on Microscale Chemistry
18. – 20. May 2005 at Universidad Iberoamericana – Ciudad de Mexico [https://web.archive.org/web/20050521034123/http://www.cpe.fr/ectn-assoc/archives/lib/2005/N01/200501_3rd_IMCS_Announc.pdf]
4th International Symposium on Microscale Chemistry Bangkok, Thailand 2009
5th International Symposium on Microscale Chemistry Manila, Philippines, 2010
6th International Symposium on Microscale Chemistry Kuwait City, Kuwait, 2011
7th International Symposium on Microscale Chemistry Berlin, Germany, 2013
8th International Symposium on Microscale Chemistry Mexico City, Mexico, 2015
9th International Symposium on Microscale Chemistry Sendai, Japan, 2017
10th International Symposium on Microscale Chemistry, North-west University, Potchefstroom South Africa, 2019
11th International Symposium on Microscale Chemistry. On-line, United Kingdom, 2021 | 1 | Applied and Interdisciplinary Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.