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In general terms, the free energy change (ΔG) of a reaction determines whether a chemical change will take place, but kinetics describes how fast the reaction is. A reaction can be very exothermic and have a very positive entropy change but will not happen in practice if the reaction is too slow. If a reactant can produce two products, the thermodynamically most stable one will form in general, except in special circumstances when the reaction is said to be under kinetic reaction control. The Curtin–Hammett principle applies when determining the product ratio for two reactants interconverting rapidly, each going to a distinct product. It is possible to make predictions about reaction rate constants for a reaction from free-energy relationships.
The kinetic isotope effect is the difference in the rate of a chemical reaction when an atom in one of the reactants is replaced by one of its isotopes.
Chemical kinetics provides information on residence time and heat transfer in a chemical reactor in chemical engineering and the molar mass distribution in polymer chemistry. It is also provides information in corrosion engineering. | 0 | Theoretical and Fundamental Chemistry |
Indoor tanning involves using a device that emits ultraviolet radiation to produce a cosmetic tan. Typically found in tanning salons, gyms, spas, hotels, and sporting facilities, and less often in private residences, the most common device is a horizontal tanning bed, also known as a sunbed or solarium. Vertical devices are known as tanning booths or stand-up sunbeds.
First introduced in the 1960s, indoor tanning became popular with people in the Western world, particularly in Scandinavia, in the late 1970s. The practice finds a cultural parallel in skin whitening in Asian countries, and both support multibillion-dollar industries. Most indoor tanners are women, 16–25 years old, who want to improve their appearance or mood, acquire a pre-holiday tan, or treat a skin condition.
Across Australia, Canada, Northern Europe and the United States, 18.2% of adults, 45.2% of university students, and 22% of adolescents had tanned indoors in the previous year, according to studies in 2007–2012. As of 2010 the indoor-tanning industry employed 160,000 in the United States, where 10–30 million tanners visit 25,000 indoor facilities annually. In the United Kingdom, 5,350 tanning salons were in operation in 2009. From 1997 several countries and US states banned under-18s from indoor tanning. The commercial use of tanning beds was banned entirely in Brazil in 2009 and Australia in 2015. , thirteen U.S. states and one territory have banned under-18s from using them, and at least 42 states and the District of Columbia have imposed regulations, such as requiring parental consent.
Indoor tanning is a source of UV radiation, which is known to cause skin cancer, including melanoma and skin aging, and is associated with sunburn, photodrug reactions, infections, weakening of the immune system, and damage to the eyes, including cataracts, photokeratitis (snow blindness) and eye cancer. Injuries caused by tanning devices lead to over 3,000 emergency-room cases a year in the United States alone. Physicians may use or recommend tanning devices to treat skin conditions such as psoriasis, but the World Health Organization does not recommend their use for cosmetic purposes. The WHO's International Agency for Research on Cancer includes tanning devices, along with ultraviolet radiation from the sun, in its list of group 1 carcinogens. Researchers at the Yale School of Public Health found evidence of addiction to tanning in a 2017 paper. | 0 | Theoretical and Fundamental Chemistry |
In particle physics and nuclear physics, the branching fraction (or branching ratio) for a decay is the fraction of particles which decay by an individual decay mode or with respect to the total number of particles which decay. It applies to either the radioactive decay of atoms or the decay of elementary particles. It is equal to the ratio of the partial decay constant to the overall decay constant. Sometimes a partial half-life is given, but this term is misleading; due to competing modes, it is not true that half of the particles will decay through a particular decay mode after its partial half-life. The partial half-life is merely an alternate way to specify the partial decay constant , the two being related through:
For example, for decays of Cs, 98.1% are ε (electron capture) or β (positron) decays, and 1.9% are β (electron) decays. The partial decay constants can be calculated from the branching fraction and the half-life of Cs (6.479 d), they are: 0.10 d (ε + β) and 0.0020 d (β). The partial half-lives are 6.60 d (ε + β) and 341 d (β). Here the problem with the term partial half-life is evident: after (341+6.60) days almost all the nuclei will have decayed, not only half as one may initially think.
Isotopes with significant branching of decay modes include copper-64, arsenic-74, rhodium-102, indium-112, iodine-126 and holmium-164. | 0 | Theoretical and Fundamental Chemistry |
Calcium silicate hydrates (or C-S-H) are the main products of the hydration of Portland cement and are primarily responsible for the strength of cement-based materials. They are the main binding phase ("the glue") in most concrete. Only well defined and rare natural crystalline minerals can be abbreviated as CSH while extremely variable and poorly ordered phases without well defined stoichiometry, as it is commonly observed in hardened cement paste (HCP), are denoted C-S-H. | 0 | Theoretical and Fundamental Chemistry |
The pathway bears resemblance to CAM; both act to concentrate around RuBisCO, thereby increasing its efficiency. CAM concentrates it temporally, providing during the day, and not at night, when respiration is the dominant reaction. plants, in contrast, concentrate spatially, with a RuBisCO reaction centre in a "bundle sheath cell" being inundated with . Due to the inactivity required by the CAM mechanism, carbon fixation has a greater efficiency in terms of PGA synthesis.
There are some /CAM intermediate species, such as Peperomia camptotricha, Portulaca oleracea, and Portulaca grandiflora. It was previously thought that the two pathways of photosynthesis in such plants could occur in the same leaves but not in the same cells, and that the two pathways could not couple but only occur side by side. It is now known, however, that in at least some species such as Portulaca oleracea, C and CAM photosynthesis are fully integrated within the same cells, and that CAM-generated metabolites are incorporated directly into the C cycle. | 0 | Theoretical and Fundamental Chemistry |
A double bond between two carbon atoms forces the remaining four bonds (if they are single) to lie on the same plane, perpendicular to the plane of the bond as defined by its π orbital. If the two bonds on each carbon connect to different atoms, two distinct conformations are possible, that differ from each other by a twist of 180 degrees of one of the carbons about the double bond.
The classical example is dichloroethene , specifically the structural isomer that has one chlorine bonded to each carbon. It has two conformational isomers, with the two chlorines on the same side or on opposite sides of the double bonds plane. They are traditionally called cis (from Latin meaning "on this side of") and trans ("on the other side of"), respectively; or Z and E' in the IUPAC recommended nomenclature. Conversion between these two forms usually requires temporarily breaking bonds (or turning the double bond into a single bond), so the two are considered different configurations of the molecule.
More generally, cis–trans isomerism (formerly called "geometric isomerism") occurs in molecules where the relative orientation of two distinguishable functional groups is restricted by a somewhat rigid framework of other atoms.
For example, in the cyclic alcohol inositol (a six-fold alcohol of cyclohexane), the six-carbon cyclic backbone largely prevents the hydroxyl and the hydrogen on each carbon from switching places. Therefore, one has different configurational isomers depending on whether each hydroxyl is on "this side" or "the other side" of the rings mean plane. Discounting isomers that are equivalent under rotations, there are nine isomers that differ by this criterion, and behave as different stable substances (two of them being enantiomers of each other). The most common one in nature (myo-inositol) has the hydroxyls on carbons 1, 2, 3 and 5 on the same side of that plane, and can therefore be called cis-1,2,3,5-trans-4,6-cyclohexanehexol. And each of these cis-trans isomers can possibly have stable "chair" or "boat" conformations (although the barriers between these are significantly lower than those between different cis-trans' isomers).
Cis and trans isomers also occur in inorganic coordination compounds, such as square planar complexes and octahedral complexes.
For more complex organic molecules, the cis and trans labels are ambiguous. The IUPAC recommends a more precise labeling scheme, based on the CIP priorities for the bonds at each carbon atom. | 0 | Theoretical and Fundamental Chemistry |
20β-Dihydroprogesterone (20β-DHP), also known as 20β-hydroxyprogesterone (20β-OHP), is an endogenous metabolite of progesterone which is formed by 20β-hydroxysteroid dehydrogenase (20β-HSD). It is a progestogen similarly to progesterone, with about 20 to 50% of the progestogenic activity of progesterone. It can be converted by 20β-HSD into progesterone in the uterus. The effects of 20β-HSD on the uterus, mammary glands, and in maintaining pregnancy have been studied. The progestogenic activity of 20β-HSD has also been characterized in women. | 1 | Applied and Interdisciplinary Chemistry |
Tanning booths (also known as stand-up sunbeds) are vertical enclosures; the tanner stands during exposure, hanging onto straps or handrails, and is surrounded by tanning bulbs. In most models, the tanner closes a door, but there are open designs too. Some booths use the same electronics and lamps as tanning beds, but most have more lamps and are likely to use 100–160 watt lamps. They often have a maximum session of 7–15 minutes. There are other technical differences, or degrees of intensity, but for all practical intents, their function and safety are the same as a horizontal bed. Booths have a smaller footprint, which some commercial operators find useful. Some tanners prefer booths out of concern for hygiene, since the only shared surface is the floor. | 0 | Theoretical and Fundamental Chemistry |
A photon absorbed by the manganese ions of the oxygen-evolving complex triggers inactivation of the oxygen-evolving complex. Further inhibition of the remaining electron transport reactions occurs like in the donor-side mechanism. The mechanism is supported by the action spectrum of photoinhibition. | 0 | Theoretical and Fundamental Chemistry |
International Standard ISO 20560-1 Safety information for the content of piping systems and tanks — Part 1: Piping systems was intended to replace the variety of regulations and standards across countries and regions. Basic identification colours and warning symbols identify the pipe contents and any hazards.
Pipe markers consists of 4 basic elements:
* Basic identification (background) colour, see table below, e.g. yellow for hazardous substance
* Name of the substance/content, e.g. NATURAL GAS
* Flow direction indicator arrows, ⇒
* Warning symbols, e.g. GHS symbol
Colours and substances are typically as follows:
International Standard ISO 20560-2 Safety information for the content of piping systems and tanks — Part 2: Tanks, provides a similar colour scheme for tanks. | 1 | Applied and Interdisciplinary Chemistry |
On selection as a remedy, implementation of SVE involves the following elements: system design, operation, optimization, performance assessment, and closure. Several guidance documents provide information on these implementation aspects. EPA and U.S. Army Corps of Engineers (USACE) guidance documents establish an overall framework for design, operation, optimization, and closure of a SVE system. The Air Force Center for Engineering and the Environment (AFCEE) guidance presents actions and considerations for SVE system optimization, but has limited information related to approaches for SVE closure and meeting remediation goals. Guidance from the Pacific Northwest National Laboratory (PNNL) supplements these documents by discussing specific actions and decisions related to SVE optimization, transition, and/or closure.
Design and operation of a SVE system is relatively straightforward, with the major uncertainties having to do with subsurface geology/formation characteristics and the location of contamination. As time goes on, it is typical for a SVE system to exhibit a diminishing rate of contaminant extraction due to mass transfer limitations or removal of contaminant mass. Performance assessment is a key aspect to provide input for decisions about whether the system should be optimized, terminated, or transitioned to another technology to replace or augment SVE. Assessment of rebound and mass flux provide approaches to evaluate system performance and obtain information on which to base decisions. | 1 | Applied and Interdisciplinary Chemistry |
With the velocity vector expanded as and similarly the body force vector , we may write the vector equation explicitly,
We arrive at these equations by making the assumptions that and the density is a constant. | 1 | Applied and Interdisciplinary Chemistry |
Protonation of basic sites in systems comprising a chromophore and a luminescent metal center leads the way for pH sensors. Some initially proposed systems were based on pyridine derivatives but these were not stable in water. More robust sensors have been proposed in which the core is a substituted macrocycle usually bearing phosphinate, carboxylate or four amide coordinating groups. It has been observed that lanthanide luminescent probe emission increases about six-fold when decreasing the pH of the solution from six to two. | 1 | Applied and Interdisciplinary Chemistry |
The original sequence is reconstructed from the reads using sequence assembly software. First, overlapping reads are collected into longer composite sequences known as contigs. Contigs can be linked together into scaffolds by following connections between mate pairs. The distance between contigs can be inferred from the mate pair positions if the average fragment length of the library is known and has a narrow window of deviation. Depending on the size of the gap between contigs, different techniques can be used to find the sequence in the gaps. If the gap is small (5-20kb) then the use of polymerase chain reaction (PCR) to amplify the region is required, followed by sequencing. If the gap is large (>20kb) then the large fragment is cloned in special vectors such as bacterial artificial chromosomes (BAC) followed by sequencing of the vector. | 1 | Applied and Interdisciplinary Chemistry |
When the temperature of concrete exceeds 65 °C for too long a time at an early age, the crystallization of ettringite (AFt) does not occur because of its higher solubility at elevated temperature and the then less soluble mono-sulfate (AFm) is formed. After dissipation of the cement hydration heat, temperature goes back to ambient and the temperature curves of the solubilities of AFt and AFm phases cross over. The mono-sulfate (AFm) now more soluble at low temperature slowly dissolves to recrystallize as the less soluble ettringite (AFt). AFt crystal structure hosts more water molecules than AFm. So, AFt has a higher molar volume than AFm because of its 32 HO molecules. During months, or years, after young concrete cooling, AFt crystallizes very slowly as small acicular needles and can exert a considerable crystallization pressure on the surrounding hardened cement paste (HCP). This leads to the expansion of concrete, to its cracking, and it can ultimately lead to the ruin of the affected structure. The characteristic feature of delayed ettringite formation (DEF) is a random honeycomb cracking pattern similar to this of the alkali-silica reaction (ASR). In fact, this typical crack pattern is common to all expansive internal reactions and also to restrained shrinkage where a rigid substrate or a dense rebar network prevents the movements of a superficial concrete layer. DEF is also known as internal sulfate attack (ISA). External sulfate attack (ESA) also involves ettringite (AFt) formation and deleterious expansion with the same harmful symptoms but requires an external source of sulfate anions in the surrounding terrains or environment. To avoid DEF or ISA reactions, the best way is to use a low CA (tri-calcium aluminate) cement precluding the formation of ettringite (AFt). Sulfate resisting (SR) cements have also a low content in AlO. DEF, or ISA, only affects the hardened cement paste (HCP) and leaves intact the aggregates.
DEF is exacerbated at high pH in cement with a too high content in alkalis and therefore in hydroxides. This is caused by the transformation of ettringite (AFt) into aluminoferrite monosulfate (AFm) under the action of the hydroxyl anions (OH) as schematized as follows:
: AFt + OH → AFm
The complete reaction can be derived from the molecular formulas of the reagents and products involved in the reaction. This reaction favors the dissolution of AFt and the formation of AFm. When combined, it is an aggravating factor of the harmful effect of too high temperatures. To minimize DEF, the use of low-alkali cements is also recommended. The detrimental crystallization of ettringite (AFt) preferentially occurs when concrete is exposed to water infiltrations and that the pH decreases due to the leaching of the (OH) ions: the reaction is reversed as when temperature decreases. | 1 | Applied and Interdisciplinary Chemistry |
In general, radical cyclization to produce small rings is difficult. However, it is possible to trap the cyclized radical before re-opening. This process can be facilitated by fragmentation (see the three-membered case below) or by stabilization of the cyclized radical (see the four-membered case). Five- and six-membered rings are the most common sizes produced by radical cyclization.
Polycycles and macrocycles can also be formed using radical cyclization reactions. In the former case, rings can be pre-formed and a single ring closed with radical cyclization, or multiple rings can be formed in a tandem process (as below). Macrocyclizations, which lack the FMO requirement of cyclizations of smaller substrates, have the unique property of exhibiting endo selectivity. | 0 | Theoretical and Fundamental Chemistry |
Agricultural chemistry encompases the science and technology of producing not only edible crops, but feedstocks for fuels ("biofuels") and materials. Ethanol fuel obtained by fermentation of sugars. Biodiesel is derived from fats, both animal- and plant-derived. Methane can be recovered from manure and other ag wastes by microbial action. Lignocellulose is a promising precursor to new materials. | 1 | Applied and Interdisciplinary Chemistry |
This chemical similarity can be exploited in cancer, where a protein may mutate into an "always on" (constitutively active) state. A mutation may occur to replace a tyrosine (which needs to be phosphorylated in order to activate the protein) with an aspartic acid (which would not need to be phosphorylated). In a laboratory setting, the use of recombinant proteins to artificially introduce phosphomimetics is a common tool for studying phosphorylation and protein activation. For example, the IRF3 protein must be phosphorylated for its normal activity (transcription of its target genes, like IFNβ), but when serine amino acid residues were mutated to aspartic acid, the activity increased 90-fold. Phosphomimetics are commonly used in a gain of function experiment with respect to phosphorylation. For example, aspartate mutants were successfully used to probe the biological function of the phosphorylation of a threonine residue of a ribosomal protein both in vivo and in vitro to investigate a gain-of-function mutation on a kinase that is related to Parkinson's disease. Phosphomimetics were also used to investigate the therapeutic potential of proteins or peptides. For example, phosphomimetic mutants (using glutamate to mimic serine phosphorylation) have been used to demonstrate that the phosphorylated glycoprotein may have stronger anti-melanoma effects that the wildtype protein. This approach is in particularly useful as up to three serine residues can be phosphoylated on the said protein, and hence phosphomimetic mutants are useful to probe the function of the individual phosphorylation. | 1 | Applied and Interdisciplinary Chemistry |
Protein crystallization is governed by the same physics that governs the formation of inorganic crystals. For crystallization to occur spontaneously, the crystal state must be favored thermodynamically. This is described by Gibb's free energy (∆G), defined as ∆G = ∆H- T∆S, which captures how the energetics of a process, ∆H, trades off with the corresponding change in entropy, ∆S. Entropy, roughly, describes the disorder of a system. Highly ordered states, such as protein crystals, are disfavored thermodynamically compared to more disordered states, such as solutions of proteins in solvent, because the transition to a more ordered state would decrease the total entropy of the system (positive ∆S). For crystals to form spontaneously, the ∆G of crystal formation must be negative. In other words, the entropic penalty must be paid by a corresponding decrease in the total energy of the system (∆H). Familiar inorganic crystals such as sodium chloride spontaneously form at ambient conditions because the crystal state decreases the total energy of the system. However, crystallization of some proteins under ambient conditions would both decrease the entropy (positive ∆S) and increase the total energy (positive ∆H) of the system, and thus does not occur spontaneously. To achieve crystallization of such proteins conditions are modified to make crystal formation energetically favorable. This is often accomplished by creation of a supersaturated solution of the sample. | 0 | Theoretical and Fundamental Chemistry |
Photolysis is performed resulting in photoactivation of the TIVA tag in the target cell or cells. Specifically, uncaging of the TIVA tag is accomplished using a 405-nm laser while measuring FRET excited by 514 nm. During this process, the mRNA-capturing moiety is released and subsequently anneals to the poly(A) tail of cellular mRNA. To confirm that the cell is not damaged during photolysis, the cell is imaged with the confocal microscope. | 1 | Applied and Interdisciplinary Chemistry |
Galen was a philosopher, physician, pharmacist and prolific medical writer. He compiled an extensive record of the medical knowledge of his day and added his own observations. He wrote on the structure of organs, but not their uses; the pulse and its association with respiration; the arteries and the movement of blood; and the uses of theriacs. "In treatises such as On Theriac to Piso, On Theriac to Pamphilius, and On Antidotes, Galen identified theriac as a sixty-four-ingredient compound, able to cure any ill known". His work was rediscovered in the 15th century and became the authority on medicine and healing for the next two centuries. His medicine was based on the regulation of the four humors (blood, phlegm, black bile, and yellow bile) and their properties (wet, dry, hot, and cold). | 1 | Applied and Interdisciplinary Chemistry |
The acoustical property of the speed of sound through a foam is of interest when analyzing failures of hydraulic components. The analysis involves calculating total hydraulic cycles to fatigue failure. The speed of sound in a foam is determined by the mechanical properties of the gas creating the foam: oxygen, nitrogen, or combinations.
Assuming that the speed of sound is based on the liquid's fluid properties leads to errors in calculating fatigue cycles and failure of mechanical hydraulic components. Using acoustical transducers and related instrumentation that set low limits (0–50,000 Hz with roll-off) causes errors. The low roll-off during measurement of actual frequency of acoustic cycles results in miscalculation due to actual hydraulic cycles in the possible ranges of 1–1000 MHz or higher. Instrumentation systems are most revealing when cycle bandwidths exceed the actual measured cycles by a factor of 10 to 100. Associated instrumentation costs also increase by factors of 10 to 100.
Most moving hydro-mechanical components cycle at 0–50 Hz, but entrained gas bubbles resulting in a foamy condition of the associated hydraulic fluid results in actual hydraulic cycles that can exceed 1000 MHz even if the moving mechanical components do not cycle at the higher cycle frequency. | 0 | Theoretical and Fundamental Chemistry |
Sepro designs and builds modular and mobile processing plants for a wide range of mineral applications. Complete plants can be assembled using Sepro manufactured equipment along with equipment from third-party vendors and sub-contractors.
Sepro Mobile Plants are designed to be easily re-locatable as they are mounted on road transportable custom built trailer assemblies. These include the Sepro Mobile Mill Plant and Sepro Mobile Flotation Plant, both of which were installed by Banks Island Gold Ltd at the company's Yellow Giant Gold Property on the coast of British Columbia. They can be designed to encompass a wide variety of process options from crushing through to the final concentrate collection.
Sepro Modular and Skid Mounted Plants are engineered around structural elements that are simple and easy to erect on site. These plants can be designed with larger equipment for higher tonnage applications than that of the Sepro Mobile Plants. One example is a 360 TPD Gold Processing Plant Sepro supplied to ProEurasia LCC for the Vladimirskaya Project in Russia. This included milling, gravity and smelting circuits.
Sepro also offers standard process modules which are designed around a single recovery or procession option. Dense Media Separation and Gravity Concentration are two examples of standard Sepro process modules. | 1 | Applied and Interdisciplinary Chemistry |
One example of controlling the environment to prevent or reduce corrosion is the practice of storing aircraft in deserts. These storage places are usually called aircraft boneyards. The climate is usually arid so this and other factors make it an ideal environment. | 1 | Applied and Interdisciplinary Chemistry |
In the medical field, microrobots that use swimming motions to move may make micromanipulations in unreachable environments.
The equation used for a blood vessel:
where,
: f = oscillation frequency of the microbot swimming motion
: D = blood vessel diameter
: V = unsteady viscoelastic flow
The Strouhal number is used as a ratio of the Deborah number (De) and Weissenberg number (Wi):
The Strouhal number may also be used to obtain the Womersley number (Wo). The case for blood flow can be categorized as an unsteady viscoelastic flow, therefore the Womersley number is
Or considering both equations, | 1 | Applied and Interdisciplinary Chemistry |
Perstraction has been combined with the ABE (acetone butanol ethanol) fermentation for butanol production. Butanol is toxic to the fermentation, therefore perstraction can be applied to remove the butanol from the vicinity of the bacteria as soon as it is produced. Liquid-liquid extraction (LLE) was combined with the ABE fermentation for in situ product recovery, but the extractants with the highest affinity for butanol tend to be toxic to the bacteria. The application of LLE would also require the extractant to be sterilised prior to contact with the fermentation broth. Perstraction can overcome these problems due to a membrane separating the fermentation broth from the extractant. As an in situ product recovery technique for the ABE fermentation perstraction is still in its development stages. | 0 | Theoretical and Fundamental Chemistry |
The development of VR started in 1957, after the Soviet Union obtained information about detection of high level of toxicity in phosphorylthiocholines (the same year Lars-Erik Tammelin published his first articles on fluorophosphorylcholines and phosphorylthiocholines in Acta Chemica Scandinavica) by a team from the Soviet Union's Scientific Research Institute No. 42 (NII-42). Sergei Zotovich Ivin, Leonid Soborovsky, and Iya Danilovna Shilakova jointly developed this analogue of VX. They completed their work in 1963 and were later awarded the Lenin Prize for their achievement. A binary weapon comprising two less toxic precursors which mixed during flight to form Substance 33 was later developed by a team led by Nikolai Kuznetsov.
In 1972 the Soviets opened Cheboksary Khimprom, a manufacturing plant for VR in Novocheboksarsk. All facilities in USSR produced 15,557 tons of VR according to their declaration to the Organisation for the Prohibition of Chemical Weapons (OPCW), although most if not all of this has now been destroyed under disarmament treaties. | 1 | Applied and Interdisciplinary Chemistry |
The Polevskoy Copper Smelting Plant (), also known as Polevaya or Poleva, was one of the major metallurgical facilities located in Polevskoy, in Sverdlovsk Oblast of Russia. | 1 | Applied and Interdisciplinary Chemistry |
Euhedral crystals have flat faces with sharp angles. The flat faces (also called facets) are oriented in a specific way relative to the underlying atomic arrangement of the crystal: They are planes of relatively low Miller index. This occurs because some surface orientations are more stable than others (lower surface energy). As a crystal grows, new atoms attach easily to the rougher and less stable parts of the surface, but less easily to the flat, stable surfaces. Therefore, the flat surfaces tend to grow larger and smoother, until the whole crystal surface consists of these plane surfaces. (See diagram on right.) | 0 | Theoretical and Fundamental Chemistry |
The Crams rule of asymmetric induction states In certain non-catalytic reactions that diastereomer will predominate, which could be formed by the approach of the entering group from the least hindered side when the rotational conformation of the C-C bond is such that the double bond is flanked by the two least bulky groups attached to the adjacent asymmetric center.The rule indicates that the presence of an asymmetric center in a molecule induces the formation of an asymmetric center adjacent to it based on steric hindrance (scheme 1').
The experiments involved two reactions. In experiment one 2-phenylpropionaldehyde (1, racemic but (R)-enantiomer shown) was reacted with the Grignard reagent of bromobenzene to 1,2-diphenyl-1-propanol (2) as a mixture of diastereomers, predominantly the threo isomer (see for explanation the Fischer projection).
The preference for the formation of the threo isomer can be explained by the rule stated above by having the active nucleophile in this reaction attacking the carbonyl group from the least hindered side (see Newman projection A) when the carbonyl is positioned in a staggered formation with the methyl group and the hydrogen atom, which are the two smallest substituents creating a minimum of steric hindrance, in a gauche orientation and phenyl as the most bulky group in the anti conformation.
The second reaction is the organic reduction of 1,2-diphenyl-1-propanone 2 with lithium aluminium hydride, which results in the same reaction product as above but now with preference for the erythro isomer (2a). Now a hydride anion (H) is the nucleophile attacking from the least hindered side (imagine hydrogen entering from the paper plane). | 0 | Theoretical and Fundamental Chemistry |
Isopentenyl pyrophosphate converts to geranyl pyrophosphate, the precursor to tens of thousands of terpeness and terpenoids. | 1 | Applied and Interdisciplinary Chemistry |
Dynamic nuclear polarization (DNP) results from transferring spin polarization from electrons to nuclei, thereby aligning the nuclear spins to the extent that electron spins are aligned. Note that the alignment of electron spins at a given magnetic field and temperature is described by the Boltzmann distribution under the thermal equilibrium. It is also possible that those electrons are aligned to a higher degree of order by other preparations of electron spin order such as: chemical reactions (leading to chemical-induced DNP, CIDNP), optical pumping and spin injection. DNP is considered one of several techniques for hyperpolarization. DNP can also be induced using unpaired electrons produced by radiation damage in solids.
When electron spin polarization deviates from its thermal equilibrium value, polarization transfers between electrons and nuclei can occur spontaneously through electron-nuclear cross relaxation or spin-state mixing among electrons and nuclei. For example, the polarization transfer is spontaneous after a homolysis chemical reaction. On the other hand, when the electron spin system is in a thermal equilibrium, the polarization transfer requires continuous microwave irradiation at a frequency close to the corresponding electron paramagnetic resonance (EPR) frequency. In particular, mechanisms for the microwave-driven DNP processes are categorized into the Overhauser effect (OE), the solid-effect (SE), the cross-effect (CE) and thermal-mixing (TM).
The first DNP experiments were performed in the early 1950s at low magnetic fields but until recently the technique was of limited applicability for high-frequency, high-field NMR spectroscopy, because of the lack of microwave (or terahertz) sources operating at the appropriate frequency. Today such sources are available as turn-key instruments, making DNP a valuable and indispensable method especially in the field of structure determination by high-resolution solid-state NMR spectroscopy. | 0 | Theoretical and Fundamental Chemistry |
Jostel's TSH index can be calculated with
from equilibrium serum concentrations of thyrotropin (TSH), free T4 (FT4) and a correction coefficient derived from the logarithmic standard model (β = 0.1345).
An alternative standardised form (standardised TSH index or sTSHI) is calculated with.
as a z-transformed value incorporating mean (2.7) and standard deviation (0.676) of TSHI in a reference population | 1 | Applied and Interdisciplinary Chemistry |
Immunofluorescence (IF) on ethanol-fixed neutrophils is used to detect ANCA, although formalin-fixed neutrophils may be used to help differentiate ANCA patterns. ANCA can be divided into four patterns when visualised by IF; cytoplasmic ANCA (c-ANCA), C-ANCA (atypical), perinuclear ANCA (p-ANCA) and atypical ANCA (a-ANCA), also known as x-ANCA. c-ANCA shows cytoplasmic granular fluorescence with central interlobular accentuation. C-ANCA (atypical) shows cytoplasmic staining that is usually uniform and has no interlobular accentuation. p-ANCA has three subtypes, classical p-ANCA, p-ANCA without nuclear extension and granulocyte specific-antinuclear antibody (GS-ANA). Classical p-ANCA shows perinuclear staining with nuclear extension, p-ANCA without nuclear extension has perinuclear staining without nuclear extension and GS-ANA shows nuclear staining on granulocytes only. a-ANCA often shows combinations of both cytoplasmic and perinuclear staining. | 1 | Applied and Interdisciplinary Chemistry |
AMGs may be integrated into cellular signaling pathways, influencing the transmission of signals related to energy status, nutrient availability, or stress. By modulating these signaling pathways, AMGs can indirectly regulate metabolic processes. | 1 | Applied and Interdisciplinary Chemistry |
Chloride inclusions (MgCl, NaCl, CaCl, …) are a special type of inclusion as they are liquid in liquid metal. When aluminium solidifies, they form spherical voids similar to hydrogen gas porosity but the void contains a chloride crystal formed when aluminium became colder. | 1 | Applied and Interdisciplinary Chemistry |
These luxurious products were most often sold in important jewellery stores. Sometimes the retailer's paper labels survived the cleaning attempts of the last decades, and these labels are always a keen addition for any collector. They confirm that silver overlay porcelain and glass was sold all over Germany.
Friedrich Deusch, the oldest and biggest firm, also sold internationally and even produced a large amount of silver overlay tableware for the Royal House of Saudi Arabia. Deusch is the only firm that has survived (as of 2013), although the focus of production has
changed from fine art to galvanizing parts for the automobile industry. In 1976, after three generations, the Deusch family relinquished interest in the firm of Friedrich Deusch and Company Today, there is scant knowledge and interest about this firm's history.
Veyhl (father and son) traveled a lot offering their newest items to different jewellery stores. Later, they opened their own shop in Plüderhausen (close to Schwäbisch Gmünd). Friedrich Wilhelm Spahr created timeless designs which can be found today all over Europe and even in the United States. These are rare, desirable and mostly exquisite.
Silver overlay was a very exclusive luxury ware from the beginning because of the very complicated and time-consuming steps of manufacturing. Silver overlay items were never mass-produced and were made in limited numbers. The development of silver overlay was forged by a technical alliance between artists, artisans and advances in chemistry, physics, electronics and, ultimately, the industrialized techniques of the late 19th century. The arts movements of the day were philosophically against industrialized techniques. Yet, ironically, many delightfully decorated pieces of silver overlay porcelain and glass can be seen with superb handicraft and Art Nouveau-inspired designs. Thus, while the handicraft movement died after a single incandescent generation, their designs live on, as do the stunning works of Friedrich Deusch, Friedrich Wilhelm Spahr, and Alfred & Manfred Vehyl. | 1 | Applied and Interdisciplinary Chemistry |
When a liquid drop strikes the surface of a liquid reservoir, it will either float, bounce, coalesce with the reservoir, or splash. In the case of floating, a drop will float on the surface for several seconds. Cleanliness of the liquid surface is reportedly very important in the ability of drops to float. Drop bouncing can occur on perturbed liquid surfaces. If the drop is able to rupture a thin film of gas separating it from the liquid reservoir, it can coalesce. Finally, higher Weber number drop impacts (with greater energy) produce splashing. In the splashing regime, the striking drop creates a crater in the fluid surface, followed by a crown around the crater. Additionally, a central jet, called the Rayleigh jet or Worthington jet, protrudes from the center of the crater. If the impact energy is high enough, the jet rises to the point where it pinches off, sending one or more droplets upward out of the surface. | 1 | Applied and Interdisciplinary Chemistry |
Flutamide, sold under the brand name Eulexin among others, is a nonsteroidal antiandrogen (NSAA) which is used primarily to treat prostate cancer. It is also used in the treatment of androgen-dependent conditions like acne, excessive hair growth, and high androgen levels in women. It is taken by mouth, usually three times per day.
Side effects in men include breast tenderness and enlargement, feminization, sexual dysfunction, and hot flashes. Conversely, the medication has fewer side effects and is better-tolerated in women with the most common side effect being dry skin. Diarrhea and elevated liver enzymes can occur in both sexes. Rarely, flutamide can cause liver damage, lung disease, sensitivity to light, elevated methemoglobin, elevated sulfhemoglobin, and deficient neutrophils. Numerous cases of liver failure and death have been reported, which has limited the use of flutamide.
Flutamide acts as a selective antagonist of the androgen receptor (AR), competing with androgens like testosterone and dihydrotestosterone (DHT) for binding to ARs in tissues like the prostate gland. By doing so, it prevents their effects and stops them from stimulating prostate cancer cells to grow. Flutamide is a prodrug to a more active form. Flutamide and its active form stay in the body for a relatively short time, which makes it necessary to take flutamide multiple times per day.
Flutamide was first described in 1967 and was first introduced for medical use in 1983. It became available in the United States in 1989. The medication has largely been replaced by newer and improved NSAAs, namely bicalutamide and enzalutamide, due to their better efficacy, tolerability, safety, and dosing frequency (once per day), and is now relatively little-used. It is on the World Health Organization's List of Essential Medicines. | 0 | Theoretical and Fundamental Chemistry |
Thiourea is an essential reagent in the Kurnakov test used to differentiate cis- and trans- isomers of certain square planar platinum complexes. The reaction was discovered in 1893 by Russian chemist Nikolai Kurnakov and is still performed as an assay for compounds of this type. | 0 | Theoretical and Fundamental Chemistry |
The chemical structure of penicillin was first suggested by Abraham in 1942. Dorothy Hodgkin determined the correct chemical structure of penicillin using X-ray crystallography at Oxford in 1945. In 1945, the US Committee on Medical Research and the British Medical Research Council jointly published in Science a chemical analyses done at different universities, pharmaceutical companies and government research departments. The report announced the existence of different forms of penicillin compounds which all shared the same structural component called β-lactam. The penicillins were designated by Roman numerals in UK (penicillin I, II, III and IV) in order of their discoveries, and known by letters (F, G, X, and K) referring to their origins or sources in the US, as below:
The chemical names were based on the side chains of the compounds. In 1948, Chain introduced the chemical names as standard nomenclature, remarking that this would "make the nomenclature as far as possible unambiguous".
In Kundl, Tyrol, Austria, in 1952, Hans Margreiter and Ernst Brandl of Biochemie developed the first acid-stable penicillin for oral administration, penicillin V. American chemist John C. Sheehan at the Massachusetts Institute of Technology (MIT) completed the first chemical synthesis of penicillin in 1957. Sheehan had started his studies into penicillin synthesis in 1948, and during these investigations developed new methods for the synthesis of peptides, as well as new protecting groups—groups that mask the reactivity of certain functional groups. Although the initial synthesis developed by Sheehan was not appropriate for mass production of penicillins, one of the intermediate compounds in Sheehan's synthesis was 6-aminopenicillanic acid (6-APA), the nucleus of penicillin.
An important development was the discovery of 6-APA itself. In 1957, researchers at the Beecham Research Laboratories in Surrey isolated 6-APA from the culture media of P. chrysogenum. 6-APA was found to constitute the core nucleus of penicillin (and subsequently many β-lactam antibiotics) and was easily chemically modified by attaching side chains through chemical reactions. The discovery was published Nature in 1959. This paved the way for new and improved drugs as all semisynthetic penicillins are produced from chemical manipulation of 6-APA.
The second-generation semisynthetic β-lactam antibiotic methicillin, designed to counter first-generation-resistant penicillinases, was introduced in the United Kingdom in 1959. Methicillin-resistant forms of S. aureus were first observed in the UK in 1960, less than a year later. It is likely that MRSA strains already existed many years before methicillin was introduced. This demonstrated that new drugs intended to circumvent known resistance mechanisms could be rendered ineffective by bacterial adaptations caused by the widespread use of other antibiotics. | 1 | Applied and Interdisciplinary Chemistry |
Born on 29 January 1917 as the fourth in a family of six children. Nyholms father, Eric Edward Nyholm (1878–1932) was a railway guard. Nyholms paternal grandfather, Erik Nyholm (1850–1887) was a coppersmith born in Nykarleby in the Swedish-speaking part of Finland, who migrated to Adelaide in 1873. Ronald Nyholm valued his Finnish roots and was particularly proud in his election in 1959 as Corresponding Member of the Finnish Chemical Society.
Hailing from the small mining town of Broken Hill, New South Wales, he was early exposed to the role of inorganic chemistry. He attended Burke Ward Public School and Broken Hill High School. Nyholm married Maureen Richardson of Epping, a suburb of Sydney, NSW, at the parish church in Kensington, London on 6 August 1948.
After graduating from Broken Hill High School, he attended the University of Sydney (BSc, 1938; MSc, 1942) and then University College London (PhD, 1950, supervised by Sir Christopher Ingold; D.Sc., 1953). On graduation Nyholm became a High School teacher – a contractual requirement of his scholarship to university. | 0 | Theoretical and Fundamental Chemistry |
There are many physical separation processes similar to the belt filter press used for dewatering, including centrifuges, vacuum-disc filters, and the plate and frame filter press. When compared to other compression filters, belt filters use relatively lower pressures. Although centrifuges have lower moisture content, lower costs and simpler operations in coal tails processing, belt filters tend to make less noise and have much quicker startup and shutdown times.
Belt filters are considered simple and reliable, with good availability, low staffing, easy maintenance and a long life. The belt filter is most advantageous when installed such that it is open and viewable at floor level for easier adjustment and monitoring. This is of course subject to what lighting and ventilation will allow.
The belt filter press is often used in wastewater treatment, and thus the odour of the feed sludge, volatile emissions and the chemicals used in treatment, may become a problem. One control method is to use odour-neutralizing chemicals such as potassium permanganate. However this only neutralizes odours and doesn’t affect any gases or chemicals involved. Although all problems can be controlled by enclosing the filter, the enclosure reduces essential visibility and easy access to the machine for maintenance and repairs, leading to the expensive automation of the process.
A belt filter press is also known for its high capacity throughput, as it is designed to handle excess capacity. It has low initial costs and low energy running costs, however, if throughput is less than 4 million gallons per day, the belt filter press may be less cost efficient than liquid transport, hiring a processing facility, or utilizing non-mechanical dewatering methods such as drying beds or reed beds.
Belt filters are less effective at processing some feeds. Unless the feed is well mixed from a digester, the use of belt filters will be more costly when processing a feed with varying solids content as this requires more operator attention, raising staffing costs. Feeds with high grease and oil content can lower the solids percentage in the cake by blinding the belt filter and all feeds need to be screened to protect the belt from being damaged by sharp objects. The type of feed may also affect the washing process. The belt filter needs to be washed frequently which consumes large amount of water and time. Water and time wastage, as well as the associated costs can be reduced by automating the washing system and using effluents. | 1 | Applied and Interdisciplinary Chemistry |
The pressure cell is connected to a source of compressed gas (such as Argon, Helium or Nitrogen). A capillary is placed through a ferrule in the cap so that one end is in contact with the liquid in the tube or vial. The distal end of the capillary is fritted to retain the particles while packing. Pressure from the compressed gas can be regulated to adjust the flow rate of the sample into the capillary. | 0 | Theoretical and Fundamental Chemistry |
Balle, Campbell, Keenan and Flygare demonstrated that the FTMW technique can be applied within a "free space cell" comprising an evacuated chamber containing a Fabry-Perot cavity. This technique allows a sample to be probed only milliseconds after it undergoes rapid cooling to only a few kelvins in the throat of an expanding gas jet. This was a revolutionary development because (i) cooling molecules to low temperatures concentrates the available population in the lowest rotational energy levels. Coupled with benefits conferred by the use of a Fabry-Perot cavity, this brought a great enhancement in the sensitivity and resolution of spectrometers along with a reduction in the complexity of observed spectra; (ii) it became possible to isolate and study molecules that are very weakly bound because there is insufficient energy available for them to undergo fragmentation or chemical reaction at such low temperatures. William Klemperer was a pioneer in using this instrument for the exploration of weakly bound interactions. While the Fabry-Perot cavity of a Balle-Flygare FTMW spectrometer can typically be tuned into resonance at any frequency between 6 and 18 GHz, the bandwidth of individual measurements is restricted to about 1 MHz. An animation illustrates the operation of this instrument which is currently the most widely used tool for microwave spectroscopy. | 0 | Theoretical and Fundamental Chemistry |
When pressure is applied on an incompressible fluid the velocity of the fluid will change. The fluid accelerates or decelerates depending on the relative direction of pressure with respect to the flow direction. This is because applying pressure on the fluid has caused momentum diffusion in that direction. Understanding the exact nature of diffusion is a key aspect towards understanding momentum diffusion due to pressure. | 1 | Applied and Interdisciplinary Chemistry |
Of the 25 known isotopes of sulfur, four are stable. In order of their abundance, those isotopes are S (94.93%), S (4.29%), S (0.76%), and S (0.02%). The δS value refers to a measure of the ratio of the two most common stable sulfur isotopes, S:S, as measured in a sample against that same ratio as measured in a known reference standard. The lowercase delta character is used by convention, to be consistent with use in other areas of stable isotope chemistry. That value can be calculated in per mil (‰, parts per thousand) as:
Less commonly, if the appropriate isotope abundances are measured, similar formulae can be used to quantify ratio variations between S and S, and S and S, reported as δS and δS, respectively. | 0 | Theoretical and Fundamental Chemistry |
In the protonation of an enolate ion, the kinetic product is the enol and the thermodynamic product is a ketone or aldehyde. Carbonyl compounds and their enols interchange rapidly by proton transfers catalyzed by acids or bases, even in trace amounts, in this case mediated by the enolate or the proton source.
In the deprotonation of an unsymmetrical ketone, the kinetic product is the enolate resulting from removal of the most accessible α-H while the thermodynamic product has the more highly substituted enolate moiety. Use of low temperatures and sterically demanding bases increases the kinetic selectivity. Here, the difference in pK between the base and the enolate is so large that the reaction is essentially irreversible, so the equilibration leading to the thermodynamic product is likely a proton exchange occurring during the addition between the kinetic enolate and as-yet-unreacted ketone. An inverse addition (adding ketone to the base) with rapid mixing would minimize this. The position of the equilibrium will depend on the countercation and solvent.
If a much weaker base is used, the deprotonation will be incomplete, and there will be an equilibrium between reactants and products. Thermodynamic control is obtained, however the reaction remains incomplete unless the product enolate is trapped, as in the example below. Since H transfers are very fast, the trapping reaction being slower, the ratio of trapped products largely mirrors the deprotonation equilibrium. | 0 | Theoretical and Fundamental Chemistry |
Following the unanimous ratification of the 1987 Montreal Protocolin response to concerns about the role of concentrations of chlorofluorocarbons (CFCs) in ozone layer-depletion in the stratospherea process was put into place to gradually phase out and replace CFC-13 and all the other CFCs. Research in the 1980s said that these man-made CFC compound compounds had opened a hole in ozone layer in the upper atmosphere or stratosphere that protects life on earth from UV radiation.
CFC-13s ozone depletion potential (ODP) is high 1 (CClF = 1)it is categorized as a Class I in the IPCCs list of ozone-depleting substances. CFC-13's radiative efficiency is high which results in a high global warming potential (GWPs) of 13 900 GWP-100 yr that is "surpassed by very few other greenhouse gases." It is categorized as a Class I in the list of ozone-depleting Substances. | 1 | Applied and Interdisciplinary Chemistry |
Nucleophiles add readily to the carbonyl group. In the product, the carbonyl carbon becomes sp-hybridized, being bonded to the nucleophile, and the oxygen center becomes protonated:
In many cases, a water molecule is removed after the addition takes place; in this case, the reaction is classed as an addition–elimination or addition–condensation reaction. There are many variations of nucleophilic addition reactions. | 0 | Theoretical and Fundamental Chemistry |
Theories of the structure of water involve three-dimensional networks of tetrahedra and chains and rings, linked via hydrogen bonding.
A polycatenated network, with rings formed from metal-templated hemispheres linked by hydrogen bonds, was reported in 2008.
In organic chemistry, hydrogen bonding is known to facilitate the formation of chain structures. 4-tricyclanol CHO, for example, shows catenated hydrogen bonding between the hydroxyl groups, leading to the formation of helical chains; crystalline isophthalic acid CHO is built up from molecules connected by hydrogen bonds, forming infinite chains.
In unusual conditions, a 1-dimensional series of hydrogen molecules confined within a single wall carbon nanotube is expected to become metallic at a relatively low pressure of 163.5 GPa. This is about 40% of the ~400 GPa thought to be required to metallize ordinary hydrogen, a pressure which is difficult to access experimentally. | 0 | Theoretical and Fundamental Chemistry |
The following Figure 9 summarizes the principle of interpretation of:
* Results measured by IRMS (isotopic deviation of δ C), which enables discrimination of plants according to their CO photosynthetic metabolism (C4 like can or maize versus C3 like beet, orange or grape)
* With results measured by SNIF-NMR ((D / H)I ) that can differentiate the botanical origin of sugars within the same metabolic group (beet versus orange or grape)
Values obtained on a test sample are then compared with the values of authentic samples (Database). | 0 | Theoretical and Fundamental Chemistry |
The Jameson Cell is a high-intensity froth flotation cell that was invented by Laureate Professor Graeme Jameson of the University of Newcastle (Australia) and developed in conjunction with Mount Isa Mines Limited ("MIM", a subsidiary of MIM Holdings Limited and now part of the Glencore group of companies). | 1 | Applied and Interdisciplinary Chemistry |
In fluid dynamics, Stokes problem also known as Stokes second problem or sometimes referred to as Stokes boundary layer or Oscillating boundary layer is a problem of determining the flow created by an oscillating solid surface, named after Sir George Stokes. This is considered one of the simplest unsteady problems that has an exact solution for the Navier–Stokes equations. In turbulent flow, this is still named a Stokes boundary layer, but now one has to rely on experiments, numerical simulations or approximate methods in order to obtain useful information on the flow. | 1 | Applied and Interdisciplinary Chemistry |
Global shortages of technetium-99m emerged in the late 2000s because two aging nuclear reactors (NRU and HFR) that provided about two-thirds of the world's supply of molybdenum-99, which itself has a half-life of only 66 hours, were shut down repeatedly for extended maintenance periods. In May 2009 the Atomic Energy of Canada Limited announced the detection of a small leak of heavy water in the NRU reactor that remained out of service until completion of the repairs in August 2010. After the observation of gas bubble jets released from one of the deformations of primary cooling water circuits in August 2008, the HFR reactor was stopped for a thorough safety investigation. NRG received in February 2009 a temporary license to operate HFR only when necessary for medical radioisotope production. HFR stopped for repairs at the beginning of 2010 and was restarted in September 2010.
Two replacement Canadian reactors (see MAPLE Reactor) constructed in the 1990s were closed before beginning operation, for safety reasons. A construction permit for a new production facility to be built in Columbia, MO was issued in May 2018. | 0 | Theoretical and Fundamental Chemistry |
Sewage treatment plants can have significant effects on the biotic status of receiving waters and can cause some water pollution, especially if the treatment process used is only basic. For example, for sewage treatment plants without nutrient removal, eutrophication of receiving water bodies can be a problem. | 1 | Applied and Interdisciplinary Chemistry |
HERVs are classified based on their homologies to animal retroviruses. Families belonging to Class I are similar in sequence to mammalian Gammaretroviruses (type C) and Epsilonretroviruses (Type E). Families belonging to Class II show homology to mammalian Betaretroviruses (Type B) and Deltaretroviruses (Type D). Families belonging to Class III are similar to foamy viruses. For all classes, if homologies appear well conserved in the gag, pol, and env gene, they are grouped into a superfamily. There are more Class I families known to exist. The families themselves are named in a less uniform manner, with a mixture of naming based on an exogenous retrovirus, the priming tRNA (HERV-W, HERV-K), or some neighboring gene (HERV-ADP), clone number (HERV-S71), or some amino acid motif (HERV-FRD). A proposed nomenclature aims to clean up the sometimes paraphyletic standards. | 1 | Applied and Interdisciplinary Chemistry |
Bases: adenine (A), cytosine (C), guanine (G) and thymine (T) or uracil (U).
Amino acids: Alanine (Ala, A), Arginine (Arg, R), Asparagine (Asn, N), Aspartic acid (Asp, D), Cysteine (Cys, C), Glutamic acid (Glu, E), Glutamine (Gln, Q), Glycine (Gly, G), Histidine (His, H), Isoleucine (Ile, I), Leucine (Leu, L), Lysine (Lys, K), Methionine (Met, M), Phenylalanine (Phe, F), Proline (Pro, P), Serine (Ser, S), Threonine (Thr, T), Tryptophan (Trp, W), Tyrosine (Tyr, Y), Valine (Val, V). | 1 | Applied and Interdisciplinary Chemistry |
Current living forms on Earth are essentially composed of four types of molecular entities: (i) nucleic acids, (ii) proteins, (iii) carbohydrates, and (iv) lipids. Nucleic acids (DNA and RNA) embody and express the genetic information and, together, constitute the genome and the apparatus for its expression (the genotype). Proteins, carbohydrates, and lipids form the structures, which harness and handle energy from the environment for organizing matter according to the instructions specified by the genotype, aiming to its conservation and transmission. The ensemble of proteins, carbohydrates, lipids and nucleic acids constitute the phenotype. Life is thus made of the interaction of metabolism and genetics, of the genotype with the phenotype. Both are built around the chemistry of the most common elements of the universe (hydrogen, oxygen, nitrogen, and carbon), important although ancillary roles being played by phosphorus and sulphur, and by other elements.
Given the overwhelming variety of the chemically conceivable molecules, the fact that in biological systems we observe only a small subset of organic molecules has raised questions how and which different reaction pathways could have plausibly lead to the synthesis of pre-biological molecules on the primordial Earth. These are the main objectives of prebiotic chemistry research. | 0 | Theoretical and Fundamental Chemistry |
* Bioassays. Test organisms are exposed to an environment and their response is measured. Typical organisms used in bioassays are certain species of plants, bacteria, fish, water fleas (Daphnia), and frogs.
* Community assessments. Also called biosurveys. An entire community of organisms is sampled to see what types of taxa remain. In aquatic ecosystems, these assessments often focus on invertebrates, algae, macrophytes (aquatic plants), fish, or amphibians. Rarely, other large vertebrates (reptiles, birds, and mammals) may be considered.
* Online biomonitoring devices. One example uses chemoreceptor cells of molluscs and similar animals to monitor their coastal and fresh water habitats. Different types of animals are used for this purpose either in the lab or in the field. The study of the opening and closing activity of clams valves is an example of one possible way to monitor in-situ' the quality of fresh and coastal waters. | 1 | Applied and Interdisciplinary Chemistry |
By improving water quality, reducing air temperatures and pollution, green infrastructure provides many public health benefits. Cooler and cleaner air can help reduce heat related illnesses like exhaustion and heatstroke, as well as respiratory problems like asthma. Cleaner and healthier waterways also means less illness from contaminated waters and seafood. Greener areas also promote physical activity and can boost mental health. | 1 | Applied and Interdisciplinary Chemistry |
The idea for anti-Stokes cooling was first advanced by Pringsheim in 1929. While Doppler cooling lowers the translational temperature of a sample, anti-Stokes cooling decreases the vibrational or phonon excitation of a medium. This is accomplished by pumping a substance with a laser beam from a low-lying energy state to a higher one with subsequent emission to an even lower-lying energy state. The principal condition for efficient cooling is that the anti-Stokes emission rate to the final state be significantly larger than that to other states as well as the nonradiative relaxation rate. Because vibrational or phonon energy can be many orders of magnitude larger than the energy associated with Doppler broadening, the efficiency of heat removal per laser photon expended for anti-Stokes cooling can be correspondingly larger than that for Doppler cooling. The anti-Stokes cooling effect was first demonstrated by Djeu and Whitney in CO gas. The first anti-Stokes cooling in a solid was demonstrated by Epstein et al. in 1980, in a ytterbium doped fluoride glass sample.
Potential practical applications for anti-Stokes cooling of solids include radiation balanced solid state lasers and vibration-free optical refrigeration. | 0 | Theoretical and Fundamental Chemistry |
After the petition was received, William Tilden, the President of the Chemical Society in 1905, led agreement from Council that the Petition should be acted upon and that the Society's byelaws should be modified to give qualified women all the privileges of fellows, except for the power to hold office or vote at meetings. However, when this was put to a vote, only 45 fellows showed up, and the motion was defeated. The subsequent discussions led to an eventual compromise in 1908 that women be admissible as "Subscribers" which would allow attendance at ordinary meetings, the use of the library, and the receipt of Society publications. Only 11 women joined as "Subscriber" in the period 1908 - 1919, when the category was abolished. After World War I, at an extraordinary general meeting on 8 May 1919, the Society under its then President James Dobbie resolved that women should be admitted on the same terms as men, and the corresponding byelaw was passed in 1920. The first woman fellow admitted was Ida Smedley (Mrs Maclean). | 1 | Applied and Interdisciplinary Chemistry |
Butyrate is produced by several fermentation processes performed by obligate anaerobic bacteria. This fermentation pathway was discovered by Louis Pasteur in 1861. Examples of butyrate-producing species of bacteria:
*Clostridium butyricum
*Clostridium kluyveri
*Clostridium pasteurianum
*Faecalibacterium prausnitzii
*Fusobacterium nucleatum
*Butyrivibrio fibrisolvens
*Eubacterium limosum
The pathway starts with the glycolytic cleavage of glucose to two molecules of pyruvate, as happens in most organisms. Pyruvate is oxidized into acetyl coenzyme A catalyzed by pyruvate:ferredoxin oxidoreductase. Two molecules of carbon dioxide () and two molecules of hydrogen () are formed as waste products. Subsequently, is produced in the last step of the fermentation. Three molecules of ATP are produced for each glucose molecule, a relatively high yield. The balanced equation for this fermentation is
Other pathways to butyrate include succinate reduction and crotonate disproportionation.
Several species form acetone and n-butanol in an alternative pathway, which starts as butyrate fermentation. Some of these species are:
*Clostridium acetobutylicum, the most prominent acetone and butanol producer, used also in industry
*Clostridium beijerinckii
*Clostridium tetanomorphum
*Clostridium aurantibutyricum
These bacteria begin with butyrate fermentation, as described above, but, when the pH drops below 5, they switch into butanol and acetone production to prevent further lowering of the pH. Two molecules of butanol are formed for each molecule of acetone.
The change in the pathway occurs after acetoacetyl CoA formation. This intermediate then takes two possible pathways:
*acetoacetyl CoA → acetoacetate → acetone
*acetoacetyl CoA → butyryl CoA → butyraldehyde → butanol
For commercial purposes Clostridium species are used preferably for butyric acid or butanol production.
The most common species used for probiotics is the Clostridium butyricum. | 1 | Applied and Interdisciplinary Chemistry |
During the 15th century, Leonardo da Vinci was one of the first to propose that mountain streams could result from the rise of water through small capillary cracks.
It is later, in the 17th century, that the theories about the origin of capillary action begin to appear. Jacques Rohault erroneously supposed that the rise of the liquid in a capillary could be due to the suppression of air inside and the creation of a vacuum. The astronomer Geminiano Montanari was one of the first to compare the capillary action to the circulation of sap in plants. Additionally, the experiments of Giovanni Alfonso Borelli determined in 1670 that the height of the rise was inversely proportional to the radius of the tube.
Francis Hauksbee, in 1713, refuted the theory of Rohault through a series of experiments on capillary action, a phenomenon that was observable in air as well as in vacuum. Hauksbee also demonstrated that the liquid rise appeared on different geometries (not only circular cross sections), and on different liquids and tube materials, and showed that there was no dependence on the thickness of the tube walls. Isaac Newton reported the experiments of Hauskbee in his work Opticks but without attribution.
It was the English physiologist James Jurin, who finally in 1718 confirmed the experiments of Borelli and the law was named in his honour. | 1 | Applied and Interdisciplinary Chemistry |
Protein adsorption refers to the adhesion of proteins to solid surfaces. This phenomenon is an important issue in the food processing industry, particularly in milk processing and wine and beer making. Excessive adsorption, or protein fouling, can lead to health and sanitation issues, as the adsorbed protein is very difficult to clean and can harbor bacteria, as is the case in biofilms. Product quality can be adversely affected if the adsorbed material interferes with processing steps, like pasteurization. However, in some cases protein adsorption is used to improve food quality, as is the case in fining of wines. | 1 | Applied and Interdisciplinary Chemistry |
Corrin is a heterocyclic compound. Although not known to exist on its own, the molecule is of interest as the parent macrocycle related to the cofactor and chromophore in vitamin B. Its name reflects that it is the "core" of vitamin B (cobalamins). Compounds with a corrin core are known as "corrins".
There are two chiral centres, which in natural compounds like cobalamin have the same stereochemistry. | 1 | Applied and Interdisciplinary Chemistry |
In 2008 the group of Barry M. Trost of Stanford University published the shortest synthetic route to date. | 0 | Theoretical and Fundamental Chemistry |
In 1980, Mingos was award the Corday-Morgan Medal and Prize of the Royal Society of Chemistry. He was elected a Fellow of the Royal Society (FRS) in 1992. | 0 | Theoretical and Fundamental Chemistry |
Day was a pioneer of materials chemistry, seeking unusual physical properties in inorganic and metal–organic compounds and models to explain them. He played a major role in the development of mixed-valence chemistry, and has carried out important and elegant experimental and theoretical work on the spectra, magnetic properties and conductivity of solid, inorganic complexes.
As a young researcher, he gave the first theoretically consistent description of the visible–ultraviolet spectra of vitamin B12 and its derivatives. Later, he put the assignment of inorganic charge-transfer spectra on a more rigorous basis; he correlated structures and physical properties of metal chain compounds and identified the first optically transparent ferromagnetic compounds by combined optical and neutron scattering methods. He also measured and systematised the optical properties of metamagnets.
Peter Day's graduate work initiated the study of mixed-valence compounds and led to the Robin-Day Classification of such species.
In 2012, he published a memoir about his life in science. | 0 | Theoretical and Fundamental Chemistry |
High photon intensity experiments can involve multiphoton processes with the absorption of integer multiples of the photon energy. In experiments that involve a multiphoton resonance, the intermediate is often a low-lying Rydberg state, and the final state is often an ion. The initial state of the system, photon energy, angular momentum and other selection rules can help in determining the nature of the intermediate state. This approach is exploited in resonance-enhanced multiphoton ionization spectroscopy (REMPI). The technique is in wide use in both atomic and molecular spectroscopy. An advantage of the REMPI technique is that the ions can be detected with almost complete efficiency and even time resolved for their mass. It is also possible to gain additional information by performing experiments to look at the energy of the liberated photoelectron in these experiments. | 0 | Theoretical and Fundamental Chemistry |
mA is not only found on mRNAs, various non-coding RNAs also contain this mark. For instance, XIST, the lncRNA that initiates X-inactivation, is enriched in mA. These mA are recognized and bound by the YTH domain protein YTHDC1. XIST mediated silencing of the X chromosome is negatively affected when XIST is not modified with mA.
RNA molecules containing mA are involved in UV-induced DNA damage repair mechanisms. When DNA is damaged, poly(A)+ transcripts containing numerous mA residues accumulate in the region. This facilitates the accessibility of DNA-repairing proteins, such as DNA polymerase K, so that they can fulfil their function. | 1 | Applied and Interdisciplinary Chemistry |
Formaldehyde can be determined in electroless copper plating solutions by the addition of an excess of sodium sulfite solution and titrating the liberated hydroxyl ion with standard acid.
: HC=O + HSO + HO → [HO-CH-SO] + OH | 0 | Theoretical and Fundamental Chemistry |
In working skeletal muscles and the brain, Phosphocreatine is stored as a readily available high-energy phosphate supply, and the enzyme creatine phosphokinase transfers a phosphate from phosphocreatine to ADP to produce ATP. Then the ATP releases giving chemical energy. This is sometimes erroneously considered to be substrate-level phosphorylation, although it is a transphosphorylation. | 1 | Applied and Interdisciplinary Chemistry |
The first heat-shrinkable sleeves were introduced as polyethylene pipeline coatings started to replace bituminous or tape coatings in the oil and gas industry. At the time, the processing for polyethylene to make the sleeve backing was new technology and the adhesives used in sleeves were much the same as those used on pipeline coating.
The technology used to make sleeves has advanced significantly since then, with new methods of cross-linking the polyolefin backings and new-generation adhesives that are formulated to provide performance under more-demanding pipeline conditions. | 1 | Applied and Interdisciplinary Chemistry |
Dynamic recrystallization is the process of removing the internal strain that remains in grains during deformation. This happens by the reorganization of a material with a change in grain size, shape, and orientation within the same mineral. When recrystallization occurs after deformation has come to an end and particularly at high temperatures, the process is called static recrystallization or annealing. Dynamic recrystallization results in grain size-reduction and static recrystallization results in the formation of larger equant grains.
Dynamic recrystallization can occur under a wide range of metamorphic conditions, and can strongly influence the mechanical properties of the deforming material. Dynamic recrystallization is the result of two end-member processes: (1) The formation and rotation of subgrains (rotation recrystallization) and (2) grain-boundary migration (migration recrystallization).
# Rotation recrystallization (subgrain rotation) is the progressive misorientation of a subgrain as more dislocations move into the dislocation wall (a zone of dislocations resulting from climb, cross-slip, and glide), which increases the crystallographic mismatch across the boundary. Eventually, the misorientation across the boundary is sufficiently large enough to recognize individual grains (usually 10–15° misorientation). Grains tend to be elongate or ribbon-shape, with many subgrains, with a characteristic gradual transition from low-angle subgrains to high-angle boundaries.
# Migration recrystallization (grain-boundary migration) is the processes by which a grain grows at the expense of the neighboring grains. At low temperatures, the mobility of the grain boundary may be local, and the grain boundary may bulge into a neighboring grain with a high dislocation density and form new, smaller, independent crystals by a process called low-temperature grain boundary migration, or bulging recrystallization. The bulges produced can separate from the original grain to form new grains by the formation of subgrain (low-angle) boundaries, which can evolve into grain boundaries, or by migration of the grain boundary. Bulging recrystallization often occurs along boundaries of old grains at triple junctions. At high temperatures, the growing grain has a lower dislocation density than the grain(s) consumed, and the grain boundary sweeps through the neighboring grains to remove dislocations by high-temperature grain-boundary migration crystallization. Grain boundaries are lobate with a variable grain size, with new grains generally larger than existing subgrains. At very high temperatures, grains are highly lobate or ameboid, but can be nearly strain-free. | 1 | Applied and Interdisciplinary Chemistry |
To dissipate the thermal load of main turbine exhaust steam, condensate from gland steam condenser, and condensate from Low Pressure Heater by providing a continuous supply of cooling water to the main condenser thereby leading to condensation.
The consumption of cooling water by inland power stations is estimated to reduce power availability for the majority of thermal power stations by 2040–2069. | 1 | Applied and Interdisciplinary Chemistry |
Otto studied chemistry at the University of Groningen and in 1994, he received his Master's degree, focusing on physical organic chemistry and biochemistry, with the distinction cum laude. In 1998, he obtained his PhD, again with the distinction cum laude, from his supervisor Prof. Jan B.F.N. Engberts for his thesis entitled Catalysis of Diels-Alder reactions in water.
After his subsequent research in both the United States (in 1998, with Prof. Steven L. Regen) at Lehigh University and in the United Kingdom (first with Prof. Jeremy K.M. Sanders and then, from 2001 onwards, as a Royal Society University Research Fellow, both at the University of Cambridge), he was appointed assistant professor at the University of Groningen in 2009. In 2011, he was promoted to associate professor and in 2016, to full professor. From 2014 to 2019, he coordinated the master's degree programme in chemistry.
Alongside his work at the university, Otto is also one of the six principal investigators of the Dutch national gravity programme for functional molecular systems (FMS; €26 million, over 10 years, 2013–2023). The ambition of this programme is to gain control over molecular self-assembly. With this technology, nanomotors could be made, for example, or biomaterials to repair damaged bodily tissues.
Otto was the lead applicant and chair of the European Cooperation in Science & Technology (COST) Action CM1304 (Emergence and Evolution of Complex Chemical Systems), which united more than 95 European research groups. He is the chair of the Gordon Research Conference on Systems Chemistry 2020 and is editor-in-chief of the Journal of Systems Chemistry.
Otto is a member of the Royal Dutch Chemical Society (KNCV), fellow of the Royal Society of Chemistry and member of the American Chemical Society. He is member of the steering committee of the Origins Center. The Origins Center is a Dutch research platform for scientists who are involved in the key questions of the Dutch Research Agenda on the origin, evolution and future of life on Earth and in the universe. Otto is active on several fronts in both the Netherlands and abroad. Otto was elected a member of the Royal Netherlands Academy of Arts and Sciences in 2020. | 0 | Theoretical and Fundamental Chemistry |
BLOSUM matrices are also used as a scoring matrix when comparing DNA sequences or protein sequences to judge the quality of the alignment. This form of scoring system is utilized by a wide range of alignment software including BLAST. | 1 | Applied and Interdisciplinary Chemistry |
Suppose the extent of the fluid domain be with representing a free surface. Then the solution as shown by Chia-Shun Yih in 1968 is given by
where | 1 | Applied and Interdisciplinary Chemistry |
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into oxides of nitrogen. Most commercially available nitric acid has a concentration of 68% in water. When the solution contains more than 86% , it is referred to as fuming nitric acid. Depending on the amount of nitrogen dioxide present, fuming nitric acid is further characterized as red fuming nitric acid at concentrations above 86%, or white fuming nitric acid at concentrations above 95%.
Nitric acid is the primary reagent used for nitration – the addition of a nitro group, typically to an organic molecule. While some resulting nitro compounds are shock- and thermally-sensitive explosives, a few are stable enough to be used in munitions and demolition, while others are still more stable and used as pigments in inks and dyes. Nitric acid is also commonly used as a strong oxidizing agent. | 0 | Theoretical and Fundamental Chemistry |
An anti-graffiti coating is a coating that prevents graffiti paint from bonding to surfaces.
Cleaning graffiti off buildings costs billions of dollars annually . Many cities have started anti-graffiti programs but vandalism is still a problem. Companies across the globe are attempting to develop coatings to prevent vandals from defacing public and private property. The coatings being developed can be the paint itself, or a clear coat added on top of existing paint or building facades. Depending on the substrate and the severity of graffiti, different coatings give different benefits and disadvantages. | 0 | Theoretical and Fundamental Chemistry |
Excitatory amino acids (EAA) will activate post-synaptic cells. inhibitory amino acids (IAA) depress the activity of post-synaptic cells. | 1 | Applied and Interdisciplinary Chemistry |
This experiment demonstrates the properties of acids, bases, pH indicators, and the properties of carbon dioxide. First, a large amount of universal indicator is added to water to facilitate the visual detection of changes in the solution's pH. Then, a few drops of ammonia (NH) or sodium hydroxide (NaOH) is mixed into the solution, which changes the color of the solution; the type of pH indicator used determines which colors are seen. Dry ice is subsequently added to form carbonic acid, changing the pH of the solution from basic to acidic. This causes the solution to change colors again. Simultaneously, a cloud of carbon dioxide is generated from the sublimation of dry ice due to the condensation of water vapor in the air. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, a pseudorotation is a set of intramolecular movements of attached groups (i.e., ligands) on a highly symmetric molecule, leading to a molecule indistinguishable from the initial one. The International Union of Pure and Applied Chemistry (IUPAC) defines a pseudorotation as a "stereoisomerization resulting in a structure that appears to have been produced by rotation of the entire initial molecule", the result of which is a "product" that is "superposable on the initial one, unless different positions are distinguished by substitution, including isotopic substitution."
Well-known examples are the intramolecular isomerization of trigonal bipyramidal compounds by the Berry pseudorotation mechanism, and the out-of-plane motions of carbon atoms exhibited by cyclopentane, leading to the interconversions it experiences between its many possible conformers (envelope, twist). Note, no angular momentum is generated by this motion. In these and related examples, a small displacement of the atomic positions leads to a loss of symmetry until the symmetric product re-forms (see image example below), where these displacements are typically along low-energy pathways. The Berry mechanism refers to the facile interconversion of axial and equatorial ligand in types of compounds, e.g. D-symmetric (shown). Finally, in a formal sense, the term pseudorotation is intended to refer exclusively to dynamics in symmetrical molecules, though mechanisms of the same type are invoked for lower symmetry molecules as well. | 0 | Theoretical and Fundamental Chemistry |
Sulfur in natural materials can vary widely in isotopic composition: compilations of the δS values of natural sulfur-containing materials include values ranging from −55‰ to 135‰ VCDT. The ranges of δS values vary across sulfur-containing materials: for example, the sulfur in animal tissue ranges from ~ −10 to +20‰ VCDT, while the sulfate in natural waters ranges from ~ −20 to +135‰ VCDT. The range of sulfur isotope abundances in different natural materials results from the isotope fractionation associated with natural processes like the formation and modification of those materials, discussed in the next section. | 0 | Theoretical and Fundamental Chemistry |
Naturally occurring strontium is nonradioactive and nontoxic at levels normally found in the environment, but Sr is a radiation hazard. Sr undergoes β decay with a half-life of 28.79 years and a decay energy of 0.546 MeV distributed to an electron, an antineutrino, and the yttrium isotope Y, which in turn undergoes β decay with a half-life of 64 hours and a decay energy of 2.28 MeV distributed to an electron, an antineutrino, and Zr (zirconium), which is stable. Note that Sr/Y is almost a pure beta particle source; the gamma photon emission from the decay of Y is so infrequent that it can normally be ignored.
Sr has a specific activity of 5.21 TBq/g. | 0 | Theoretical and Fundamental Chemistry |
The technique was developed in 1983 by Kary Mullis, PCR is now a common and important technique used in medical and biological research labs for a variety of applications.
PCR, or Polymerase Chain Reaction, is a widely used molecular biology technique to amplify a specific DNA sequence.
Amplification is achieved by a series of three steps:
1- Denaturation : In this step, the DNA is heated to 95 °C to dissociate the hydrogen bonds between the complementary base pairs of the double-stranded DNA.
2-Annealing : During this stage the reaction is cooled to 50-65 °C . This enables the primers to attach to a specific location on the single -stranded template DNA by way of hydrogen bonding.
3-Extension : A thermostable DNA polymerase which is Taq polymerase is commonly used at this step. This is done at a temperature of 72 °C . DNA polymerase adds nucleotides in the 5-6 direction and synthesizes the complementary strand of the DNA template . | 1 | Applied and Interdisciplinary Chemistry |
The first crystalline sponges developed by Makoto Fujita is [(Co(NCS))(TPT)], which is an infinitely extensive framework of Co octahedral complex. Each octahedral complex is composed of six Co(NCS) vertexes and four 2,4,6-tris(4-pyridyl)-1,3,5-triazine (TPT) ligands. Besides the basic octahedral cavity (ML), there are also two different cuboctahedral cavities (ML and ML) which can accommodate larger molecules, such as C, C.
In 2013, the Fujita and his team discovered that the [(ZnI)(TPT)] organometallic network can also act as a crystalline sponge. Because Zn crystalline sponges are less symmetrical (C) than Co crystalline sponges, the X-ray diffraction analysis of its guest molecules is easier to be elucidated.
The Zn-based sponges also have following advantages: (1) Pores sizes are suitable for accommodating general organic compounds (5 × 8Å), (2) The distribution of TPT ligand is flat, providing better stacking opportunity of aromatic guest compounds or C—H π interaction opportunity with aliphatic guest compounds, (3) The iodine atoms and the pyridinium protons can be hydrogen bond acceptors or donors, respectively. They would enhance the interaction between the substrate and the crystalline sponges, (4) The framework of Zn-based crystalline sponge is flexible to some extent. The molecule which is a little bit larger than the sponge cavity can still be accommodated via framework expansion to adjust the pore size. | 0 | Theoretical and Fundamental Chemistry |
A micellar cubic phase is a lyotropic liquid crystal phase formed when the concentration of micelles dispersed in a solvent (usually water) is sufficiently high that they are forced to pack into a structure having a long-ranged positional (translational) order. For example, spherical micelles a cubic packing of a body-centered cubic lattice. Normal topology micellar cubic phases, denoted by the symbol I, are the first lyotropic liquid crystalline phases that are formed by type I amphiphiles. The amphiphiles' hydrocarbon tails are contained on the inside of the micelle and hence the polar-apolar interface of the aggregates has a positive mean curvature, by definition (it curves away from the polar phase). The first pure surfactant system found to exhibit three different type I (oil-in-water) micellar cubic phases was observed in the dodecaoxyethylene mono-n-dodecyl ether (C12EO12)/water system.
Inverse topology micellar cubic phases (such as the Fd3m phase) are observed for some type II amphiphiles at very high amphiphile concentrations. These aggregates, in which water is the minority phase, have a polar-apolar interface with a negative mean curvature. The structures of the normal topology micellar cubic phases that are formed by some types of amphiphiles (e.g. the oligoethyleneoxide monoalkyl ether series of non-ionic surfactants are the subject of debate. Micellar cubic phases are isotropic phases but are distinguished from micellar solutions by their very high viscosity. When thin film samples of micellar cubic phases are viewed under a polarising microscope they appear dark and featureless. Small air bubbles trapped in these preparations tend to appear highly distorted and occasionally have faceted surfaces. A reversed micellar cubic phase has been observed, although it is much less common. It was observed that a reverse micellar cubic phase with Fd3m (Q227) symmetry formed in a ternary system of an amphiphilic diblock copolymer (EO17BO10, where EO represents ethylene oxide and BO represents butylene oxide), water, and p-xylene. | 0 | Theoretical and Fundamental Chemistry |
Electroslag remelting (ESR), also known as electro-flux remelting, is a process of remelting and refining steel and other alloys for mission-critical applications in aircraft, thermal power stations, nuclear power plants, military technology and others.
The electroslag remelting (ESR) process is used to remelt and refine steels and various super-alloys, resulting in high-quality ingots. This process can be started up through vacuum induction melting. The ESR process uses the as-cast alloy as a consumable electrode. Electric current (generally AC) is passed between the electrode and the new ingot, which is formed in the bottom of a water-cooled copper mold. The new ingot is covered in an engineered slag that is superheated by the electric current. The electrode tip is slowly melted from contact with the slag. These metal droplets travel through the slag to the bottom of the water-cooled mold and slowly freeze as the ingot is directionally solidified upwards from the bottom of the mold. The slag pool floats above the refined alloy, continuously floating upwards as the alloy solidifies. The molten metal is cleaned of impurities that chemically react with the slag or otherwise float to the top of the molten pool as the molten droplets pass through the slag.
Electroslag remelting uses highly reactive slags (calcium fluoride, lime, alumina, or other oxides are usually the main components) to reduce the amount of type-A sulfide present in biometal alloys. It is a common practice in European industries. ESR reduces other types of inclusions as well, and is seen as an alternative to the vacuum arc remelting (VAR) method that is prevalent in US industries.
An example of the use of the electro-slag refined (ESR) steel technique is the L30 tank gun.
CrNi60WTi is a stainless steel which is best formed by either electro-slag remelting or vacuum arc remelting. This alloy can be used for the construction of nuclear power plants. | 1 | Applied and Interdisciplinary Chemistry |
The final conversion of the common corrinoid intermediate 2 (fig. 6) from the two approaches into the target cobyric acid required the introduction of the two missing methyl groups at the meso positions of the corrin chromophore between rings A/B and C/D, as well as the conversion of all peripheral carboxyl functions into their amide form, except the critical carboxyl at the ring-D f-side chain (see fig. 6). These steps were collaboratively explored in strictly parallel fashion in both laboratories, the Harvard group using material produced via the A/B approach, the ETH group such prepared by the photochemical A/D approach.
The first decisive identification of a totally synthetic intermediate on the way to cobyric acid was carried out in February 1972 with a crystalline sample of totally synthetic dicyano-cobalt(III)-hexamethyl-cobyrinate-f-amide 3 (fig. 6), found to be identical in all data with a crystalline relay sample made from vitamin B by methanolysis to cobester 4, followed by partial ammonolysis and separation of the resulting mixture. At the time when Woodward announced the "Total Synthesis of Vitamin B" at the IUPAC conference in New Delhi in February 1972, the totally synthetic sample of the f-amide was one that had been made at ETH by the photochemical A/D approach, while the first sample of synthetic cobyric acid, identified with natural cobyric acid, had been obtained at Harvard by partial synthesis from B-derived f-amide relay material. Thus, the Woodward/Eschenmoser achievement around that time had been, strictly speaking, two total syntheses of cobyric acid, as well as two formal total syntheses of the vitamin.
In the later course of 1972, two crystalline epimers of totally synthetic dicyano-cobalt(III)-hexamethyl-cobyrinate-f- 3, as well as two crystalline epimers of the totally synthetic f-nitrile, all prepared via both synthetic approaches, were stringently identified chromatographically and spectroscopically with the corresponding B-derived substances. At Harvard, cobyric acid was then made also from totally synthetic f-amide 3 prepared via the A/B approach. Finally, in 1976 at Harvard, totally synthetic cobyric acid was converted into vitamin B via the pathway pioneered by . | 0 | Theoretical and Fundamental Chemistry |
Myogenin has been shown to interact with:
* MDFI,
* POLR2C,
* Serum response factor
* Sp1 transcription factor, and
* TCF3. | 1 | Applied and Interdisciplinary Chemistry |
Green infrastructure programs managed by EPA and partner organizations are intended to improve water quality generally through more extensive management of stormwater runoff. The practices are expected to reduce stress on traditional water drainage infrastructure--storm sewers and combined sewers—which are typically extensive networks of underground pipes and/or surface water channels in U.S. cities, towns and suburban areas. Improved stormwater management is expected to reduce the frequency of combined sewer overflows and sanitary sewer overflows, reduce the impacts of urban flooding, and provide other environmental benefits.
Though green infrastructure is yet to become a mainstream practice, many US cities have initiated its implementation to comply with their MS4 permit requirements. For example, the City of Philadelphia has installed or supported a variety of retrofit projects in neighborhoods throughout the city. Installed improvements include:
* permeable pavements in parks, basketball courts and parking lots
* rain gardens and bioretention systems at schools and other public facilities
* constructed wetlands for management of stormwater runoff.
Some of these facilities reduce the volume of runoff entering the city's aging combined sewer system, and thereby reduce the extent of system overflows during rainstorms.
Another U.S. example is the State of Marylands promotion of a program called "GreenPrint." GreenPrint Maryland is the first web-enabled map in the nation that shows the relative ecological importance of every parcel of land in the state. Combining color-coded maps, information layers, and aerial photography with public openness and transparency, Greenprint Maryland applies the best environmental science and Geographic Information Systems (GIS) to the urgent work of preserving and protecting environmentally critical lands. A valuable new tool not only for making land conservation decisions today, but for building a broader and better informed public consensus for sustainable growth and land preservation decisions into the future. The program was established in 2001 with the objective to "preserve an extensive intertwined network of lands vital to the long-term protection of the States natural resources, in concert with other Smart Growth initiatives."
In April 2011, EPA announced the Strategic Agenda to Protect Waters and Build More Livable Communities through Green Infrastructure and the selection of the first ten communities to be green infrastructure partners. The communities selected were: Austin, Texas; Chelsea, Massachusetts; the Northeast Ohio Regional Sewer District (Cleveland, Ohio); the City and County of Denver, Colorado; Jacksonville, Florida; Kansas City, Missouri; Los Angeles, California; Puyallup, Washington; Onondaga County and the City of Syracuse, New York; and Washington, D.C.
The Federal Emergency Management Agency (FEMA) is also promoting green infrastructure as a means of managing urban flooding (also known as localized flooding). | 1 | Applied and Interdisciplinary Chemistry |
Thermometric titrimetry is particularly suited to the determination of a range of analytes where a precipitate is formed by reaction with the titrant. In some cases, an alternative to traditional potentiometric titration practice can be offered. In other cases, reaction chemistries may be employed for which there is no satisfactory equivalent in potentiometric titrimetry. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, the capped trigonal prismatic molecular geometry describes the shape of compounds where seven atoms or groups of atoms or ligands are arranged around a central atom defining the vertices of an augmented triangular prism. This shape has C symmetry and is one of the three common shapes for heptacoordinate transition metal complexes, along with the pentagonal bipyramid and the capped octahedron.
Examples of the capped trigonal prismatic molecular geometry are the heptafluorotantalate () and the heptafluoroniobate () ions. | 0 | Theoretical and Fundamental Chemistry |
Isotopic analysis by nuclear magnetic resonance allows the user to quantify with great precision the differences of isotopic contents on each site of a molecule and thus to measure the specific natural isotope fractionation for each site of this molecule. The SNIF-NMR analytical method was developed to detect the (over) sugaring of wine and enrichment of grape musts, and is mainly used to check the authenticity of foodstuffs (such as wines, spirits, fruit juice, honey, sugar and vinegar) and to control the naturality of some aromatic molecules (such as vanillin, benzaldehyde, raspberry ketone and anethole). The SNIF-NMR method has been adopted by the International Organisation of Vine and Wine (OIV) and the European Union as an official method for wine analysis. It is also an official method adopted by the Association Of Analytical Chemists (AOAC) for analysis of fruit juices, maple syrup, vanillin, and by the European Committee for Standardization (CEN) for vinegar. | 0 | Theoretical and Fundamental Chemistry |
Almost two decades later, René Just Haüy introduced wooden crystal models to illustrate the two-dimensional drawings in the atlas volume of his "Traité de Minéralogie" (1801). For the production of crystal models, wood appeared to be much more convenient than clay. Especially pear wood permitted getting smooth faces, sharp edges and accurate dihedral angles required for the production of these three-dimensional objects. In general, the angular accuracy was very high and some models, especially those illustrating crystal twins and Haüy's figures of decrement, still appear as masterpieces of fine woodwork and carving. Skilful craftsmen such as Pleuvin, Beloeuf and Lambotin (to name only a few) became specialists in this field and the models they offered were highly esteemed.
Between 1802 and 1804, Martin van Marum bought 597 of these pear wood models, 550 of these are still present in the collection of Teylers Museum. Each model is labeled, mentioning a number and the name of the crystal form. This set is the most complete collection of Haüy crystal models that still survives. That Van Marum was able to acquire such a unique collection was due to his networking. Van Marum allowed Haüy as a member of the Hollandsche Maatschappij, a nomination to which Haüy attached great value. Haüy mentioned this membership in all of his publications.
After their introduction by Romé de l'Isle and Haüy, crystal models were increasingly demanded both by scholars for teaching purposes as well as by mineral collectors. The quality of the models improved due to the technical progress in their production. Several mineralogists and crystallographers started designing their own series of models. Although pear wood kept a prominent place, models were also manufactured using materials like plaster, cast iron, lead, brass, glass, porcelain, cardboard, etc. | 0 | Theoretical and Fundamental Chemistry |
The appropriate halocarbyne precursors of choice can be reacted with organolithium reagents to afford the respective lithiocarbyne derivate by virtue of lithium/halogen exchange. This species can serve as a lynchpin for subsequent carbide linkage with an additional metal complex. Phosphine-based analogues were first introduced by Templeton and co. These types of complexes can be characterized crystallographically and are distinguishable by their C symmetry. | 0 | Theoretical and Fundamental Chemistry |
In order to define and characterize a biosynthetic gene cluster, all the putative genes within said cluster must first be identified and their functions must be characterized. This can be performed by complementation and knock out experiments. In the process of characterizing putative genes, the genome under study becomes increasingly well understood as more interactions can be identified. Identification of putative genes is necessary to study genomic evolution, as significant proportion of genomes make up larger families of related genes. Genomic evolution occurs by processes such as duplication of individual genes, genome segments, or entire genomes. These processes can result in loss of function, altered function, or gain of function, and have drastic affects on the phenotype.
DNA mutations outside of a putative gene can act by positional effect, in which they alter the gene expression. These alterations leave the transcription unit and promoter of the gene intact, but may involve distal promoters, enhancer/silencer elements, or the local chromatin environment. These mutations can be associated with diseases or disorders associated with the gene.<br /> | 1 | Applied and Interdisciplinary Chemistry |
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