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Metals such as aluminum naturally form a passivating oxide layer which provides moderate protection against corrosion. The layer is strongly adherent to the metal surface, and it will regrow quickly if scratched off. In conventional anodizing, this layer of oxide is grown on the surface of the metal by the application of electrical potential, while the part is immersed in an acidic electrolyte.
In plasma electrolytic oxidation, higher potentials are applied. For example, in the plasma electrolytic oxidation of aluminum, at least 200 V must be applied. This locally exceeds the dielectric breakdown potential of the growing oxide film, and discharges occur. These discharges result in localized plasma reactions, with conditions of high temperature and pressure which modify the growing oxide. Processes include melting, melt-flow, re-solidification, sintering and densification of the growing oxide. One of the most significant effects, is that the oxide is partially converted from amorphous alumina into crystalline forms such as corundum (α-AlO) which is much harder. As a result, mechanical properties such as wear resistance and toughness are enhanced. | 1 | Applied and Interdisciplinary Chemistry |
To show how the Froude number is linked to general continuum mechanics and not only to hydrodynamics we start from the Cauchy momentum equation in its dimensionless (nondimensional) form. | 1 | Applied and Interdisciplinary Chemistry |
Aromatic acids are a type of aromatic compound. Included in that class are substances containing an aromatic ring and an organic acid functional group.
There are several categories of aromatic acids including:
*Phenolic acids: substances containing an aromatic ring and an organic carboxylic acid function (C6-C1 skeleton).
*Aromatic amino acids | 0 | Theoretical and Fundamental Chemistry |
Nyaya (न्याय) is a Sanskrit word which means justice, equality for all being, specially a collection of general or universal rules. In some contexts, it means model, axiom, plan, legal proceeding, judicial sentence, or judgment. Nyaya could also mean, "that which shows the way" tracing its Sanskrit etymology. In the theory of logic, and Indian texts discussing it, the term also refers to an argument consisting of an enthymeme or sometimes for any syllogism. In philosophical context, Nyaya encompasses propriety, logic and method.
Panini, revered Sanskrit grammarian, derives the "Nyaya" from the root "i" which conveys the same meaning as "gam" – to go. "Nyaya" signifying logic is there etymologically identical with "nigama" the conclusion of a syllogism.
Nyaya is related to several other concepts and words used in Indian philosophies: Hetu-vidya (science of causes), Anviksiki (science of inquiry, systematic philosophy), Pramana-sastra (epistemology, science of correct knowledge), Tattva-sastra (science of categories), Tarka-vidya (science of reasoning, innovation, synthesis), Vadartha (science of discussion) and Phakkika-sastra (science of uncovering sophism, fraud, error, finding fakes). Some of these subsume or deploy the tools of Nyaya. | 1 | Applied and Interdisciplinary Chemistry |
The sessile drop contact angle is measured by a contact angle goniometer using an optical subsystem to capture the profile of a pure liquid on a solid substrate. The angle formed between the liquid–solid interface and the liquid–vapor interface is the contact angle. Older systems used a microscope optical system with a back light. Current-generation systems employ high resolution cameras and software to capture and analyze the contact angle. Angles measured in such a way are often quite close to advancing contact angles. Equilibrium contact angles can be obtained through the application of well defined vibrations. | 0 | Theoretical and Fundamental Chemistry |
The PECT effect was first reported by Dr. F Lincoln Vogel in 1981 when studying how intercalation voltages could be used to provide an actuation force in graphitized carbon fibres. The research used sulphate (SO) ions from sulfuric acid to intercalate into the microstructure of carbon fibers, forming graphite intercalation compounds (GICs). It was hypothesized that an axial strain of up to 2% should be possible, however only 0.2% was observed due to experimental limitations.
The effect is often explained by the theories of Larché and Cahn who derived mathematical formulations for the equilibrium relationships between the electric potential, chemical potential, and mechanical stress in solid materials. In summary the theory states that solid materials under mechanical stress undergo a change in chemical potential, which in turn affects their electrical potential. | 0 | Theoretical and Fundamental Chemistry |
Arylsulfonyl chlorides are made industrially in a two-step, one-pot reaction from an arene (in this case, benzene) and chlorosulfuric acid:
The intermediate benzenesulfonic acid can be chlorinated with thionyl chloride as well. Benzenesulfonyl chloride, the most important sulfonyl halide, can also be produced by treating sodium benzenesulfonate with phosphorus pentachlorides.
Benzenediazonium chloride reacts with sulfur dioxide and hydrochloric acid to give the sulfonyl chloride:
For alkylsulfonyl chlorides, one synthetic procedure is the Reed reaction: | 0 | Theoretical and Fundamental Chemistry |
William Otto Frohring (July 1, 1893 – September 13, 1959) was an American biochemical researcher, inventor and business executive. He was a co-developer of "simulated milk adapted" (SMA), the first infant formula to be distributed in the United States and one of the most widely consumed infant formulas in the world.
Frohring held 15 patents, and led research in dairy products, and the refinement, synthesis and manufacture of vitamin products. | 0 | Theoretical and Fundamental Chemistry |
García Mancheño has received the following honors and awards during her career:
* 2019 invited speaker at Fulbright-Cottrell Junior Faculty Professional Development Workshop in Göttingen
* 2018 invited speaker at Fulbright-Cottrell Junior Faculty Professional Development Workshop in Berlin
* 2017 European Research Council Consolidator Grant (CoG). Frontiers in Catalytic Anion-Binding Chemistry (Max funding of €1,997,763)
*2016 ORCHEM Prize from the Liebig-Vereinigung für Organische Chemie of the Gesellschaft Deutscher Chemiker | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, the reyn is a British unit of dynamic viscosity,
named in honour of Osbourne Reynolds, for whom the Reynolds number is also named. | 1 | Applied and Interdisciplinary Chemistry |
The Arruda–Boyce model is based on the statistical mechanics of polymer chains. In this approach, each macromolecule is described as a chain of segments, each of length . If we assume that the initial configuration of a chain can be described by a random walk, then the initial chain length is
If we assume that one end of the chain is at the origin, then the probability that a block of size around the origin will contain the other end of the chain, , assuming a Gaussian probability density function, is
The configurational entropy of a single chain from Boltzmann statistical mechanics is
where is a constant. The total entropy in a network of chains is therefore
where an affine deformation has been assumed. Therefore the strain energy of the deformed network is
where is the temperature. | 0 | Theoretical and Fundamental Chemistry |
Standard cubic centimeters per minute (SCCM) is a unit used to quantify the flow rate of a fluid. 1 SCCM is identical to 1 cm³/min. Another expression of it would be Nml/min. These standard conditions vary according to different regulatory bodies. One example of standard conditions for the calculation of SCCM is = 0 °C (273.15 K) and = 1.01 bar (14.72 psia) and a unity compressibility factor = 1 (i.e., an ideal gas is used for the definition of SCCM) . This example is for the semi-conductor-manufacturing industry. | 1 | Applied and Interdisciplinary Chemistry |
Washing the polymer plates after they have been exposed to ultra-violet light may result in monomers entering the sewer system, eventually adding to the plastic content of the oceans. Current water purification installations are not able to remove monomer molecules from sewer water. Some monomers, such as styrene, are toxic or carcinogenic. | 0 | Theoretical and Fundamental Chemistry |
An antideuteron is the antimatter counterpart of the nucleus of deuterium, consisting of an antiproton and an antineutron. The antideuteron was first produced in 1965 at the Proton Synchrotron at CERN and the Alternating Gradient Synchrotron at Brookhaven National Laboratory. A complete atom, with a positron orbiting the nucleus, would be called antideuterium, but antideuterium has not yet been created. The proposed symbol for antideuterium is , that is, D with an overbar. | 0 | Theoretical and Fundamental Chemistry |
The first total synthesis of lupeol was reported by Gilbert Stork et al.
In 2009, Surendra and Corey reported a more efficient and enantioselective total synthesis of lupeol, starting from (1E,5E)-8-[(2S)-3,3-dimethyloxiran-2-yl]-2,6-dimethylocta-1,5-dienyl acetate by use of a polycyclization. | 0 | Theoretical and Fundamental Chemistry |
Mutations and loss of function of the Von Hippel-Lindau (VHL) tumor suppressor gene play a causal role in the pathogenesis of clear cell renal carcinomas (ccRCC), a pathological subtype that accounts for the majority kidney cancer each year. Mollapour work has shown that VHL ubiquitinates protein phosphatase-5 (PP5) for proteasomal degradation in a hypoxia- and prolyl-hydroxylation-independent manner. VHL-deficient ccRCC cell lines and patient tumors exhibit elevated PP5 levels. Downregulation of PP5 causes activation of the extrinsic apoptotic pathway in ccRCC cells, suggesting a prosurvival role for PP5 in kidney cancer.
Mollapour’s research group has been supported by grants from the National Institutes for General Medical Science and the National Cancer Institute to design and examine novel therapeutic strategies for patients with kidney, bladder and breast cancer. | 1 | Applied and Interdisciplinary Chemistry |
Lung surfactant is essential for effective ventilation as it modifies alveolar surface tension. IRDS is caused by a lung surfactant deficiency. Calfactant serves as a substitute for the natural surfactant. | 0 | Theoretical and Fundamental Chemistry |
Endomorphin-1 (EM-1) (amino acid sequence Tyr-Pro-Trp-Phe-NH) is an endogenous opioid peptide and one of the two endomorphins. It is a high affinity, highly selective agonist of the μ-opioid receptor, and along with endomorphin-2 (EM-2), has been proposed to be the actual endogenous ligand of the μ-receptor. EM-1 produces analgesia in animals and is equipotent with morphine in this regard. The gene encoding for EM-1 has not yet been identified, and it has been suggested that endomorphins could be synthesized by an enzymatic, non-ribosomal mechanism.
By combining N-terminal guadino modifications, a new class of endonmorphin-1 was synthesized, the range of their bioactivities were measured by radioligand binding assay in order to conclude its potency as an opioid. Endomorphin-1 has high affinity and specificity for opioid receptors for behavioral, physiological and pharmacological assays, it is also a potent analgesic agent which brings effects on cardiovascular, respiratory and gastrointestinal functions as well as in immune system responses. This endogenous opioid peptide can help with neuropathic pain without having the common side effects many neuropathic drugs caused which produces constipation. To make this drug side effect-free, a modification at the N-terminus by 2-aminodecainoic acid is made which in term showed an improve in the drug's metabolic stability along with improving its membrane permeability, while holding its high receptor binding affinity, helping the drug act as a potent agonist | 1 | Applied and Interdisciplinary Chemistry |
Eshelby was born at Puddington, Cheshire, the son of Captain Alan Douglas Eshelby and Phoebe Mason Hutchinson. He was educated at St Cyprian's School, Eastbourne and was due to go to Charterhouse School but developed rheumatic fever and received his secondary education privately at home. At about this time the family moved to Manor House at Farrington Gurney, Somerset where his tutors were the village schoolmaster and a local clergyman. He relied extensively on self-instruction and obtained a place in the Physics Department of Bristol University and was awarded a first class honours in physics in 1937. He then worked in a research laboratory under H W B Skinner and W Sucksmith on magnetism and the soft X-ray spectra of solids. | 1 | Applied and Interdisciplinary Chemistry |
A familiar example of the opposite, a shear thinning fluid, or pseudoplastic fluid, is wall paint: The paint should flow readily off the brush when it is being applied to a surface but not drip excessively. Note that all thixotropic fluids are extremely shear thinning, but they are significantly time dependent, whereas the colloidal "shear thinning" fluids respond instantaneously to changes in shear rate. Thus, to avoid confusion, the latter classification is more clearly termed pseudoplastic.
Another example of a shear thinning fluid is blood. This application is highly favoured within the body, as it allows the viscosity of blood to decrease with increased shear strain rate. | 1 | Applied and Interdisciplinary Chemistry |
Effective therapies to manage autism remain scarce. According to the exorphin theory of autism, an increase in the levels of exorphin is linked to symptoms of autism. Based on this concept, experiments have attempted to reduce the symptoms of autism by using large amounts of protease to break down exorphins before they are absorbed. Experiments have also attempted to enhance and utilize enzymes existing in the gut to break down exorphins in a similar fashion, since the production of exorphins within the gut is inevitable. | 1 | Applied and Interdisciplinary Chemistry |
Some members of this class of drugs inhibit the synthesis of cell walls in susceptible microbes by inhibiting peptidoglycan synthesis. The core class (including vancomycin) binds to acyl--alanyl--alanine in lipid II, preventing the addition of new units to the peptidoglycan. Of this core class, one may distinguish multiple generations: the first generation includes vancomycin and teicoplanin, while the semisynthetic second generation includes lipoglycopeptides like telavancin, oritavancin and dalbavancin. The extra lipophilicity not only enhances Lipid II binding, but also creates a second mechanism of action whereby the antibiotic dissolves into the membrane and makes it more permeable.
Corbomycin and complestatin are structurally and ancestrally related to vancomycin, but they work by inhibiting autolysins through binding to peptidoglycan, therefore preventing cell division, neither is an approved drug.
Ramoplanin, although a "glycopeptide" in the literal sense, has a quite different structural core. It not only binds to Lipid II, but also attacks MurG and transglycosylases (glycosyltransferases) which polymerize amino acid/sugar building blocks into peptidoglycan. It has been described as a "first-in-class" antibiotic, representing glycolipodepsipeptide antibiotics.
Bleomycin also has a different core. Its mode of action is also unrelated to the cell wall, instead causing DNA damage in tumor cells. | 0 | Theoretical and Fundamental Chemistry |
The cardiac action potential differs from the neuronal action potential by having an extended plateau, in which the membrane is held at a high voltage for a few hundred milliseconds prior to being repolarized by the potassium current as usual. This plateau is due to the action of slower calcium channels opening and holding the membrane voltage near their equilibrium potential even after the sodium channels have inactivated.
The cardiac action potential plays an important role in coordinating the contraction of the heart. The cardiac cells of the sinoatrial node provide the pacemaker potential that synchronizes the heart. The action potentials of those cells propagate to and through the atrioventricular node (AV node), which is normally the only conduction pathway between the atria and the ventricles. Action potentials from the AV node travel through the bundle of His and thence to the Purkinje fibers. Conversely, anomalies in the cardiac action potential—whether due to a congenital mutation or injury—can lead to human pathologies, especially arrhythmias. Several anti-arrhythmia drugs act on the cardiac action potential, such as quinidine, lidocaine, beta blockers, and verapamil. | 0 | Theoretical and Fundamental Chemistry |
As natural products, PXA and other phomoxanthones occur as secondary metabolites in fungi of the eponymous genus Phomopsis, most notably in the species Phomopsis longicolla. This fungus is an endophyte of the mangrove plant Sonneratia caseolaris. However, it has also been identified as a pathogen in other plants, such as the soybean plant in which it causes a disease called Phomopsis seed decay (PSD). | 1 | Applied and Interdisciplinary Chemistry |
Usually for acyclic systems trans isomers are more stable than cis isomers. This difference is attributed to the unfavorable steric interaction of the substituents in the cis isomer. Therefore, trans isomers have a less-exothermic heat of combustion, indicating higher thermochemical stability. In the Benson heat of formation group additivity dataset, cis isomers suffer a 1.10 kcal/mol stability penalty. Exceptions to this rule exist, such as 1,2-difluoroethylene, 1,2-difluorodiazene (FN=NF), and several other halogen- and oxygen-substituted ethylenes. In these cases, the cis isomer is more stable than the trans isomer. This phenomenon is called the cis effect. | 0 | Theoretical and Fundamental Chemistry |
pK values of amino acid side chains play an important role in defining the pH-dependent characteristics of a protein. The pH-dependence of the activity displayed by enzymes and the pH-dependence of protein stability, for example, are properties that are determined by the pK values of amino acid side chains.
The pK values of an amino acid side chain in solution is typically inferred from the pK values of model compounds (compounds that are similar to the side chains of amino acids). See Amino acid for the pK values of all amino acid side chains inferred in such a way. There are also numerous experimental studies that have yielded such values, for example by use of NMR spectroscopy.
The table below lists the model pK values that are often used in a protein pK calculation, and contains a third column based on protein studies. | 0 | Theoretical and Fundamental Chemistry |
In 2020, a large harmful algal bloom closed beaches in Poland and Finland, brought on by a combination of fertilizer runoff and extreme heat, posing a risk to flounder and mussel beds. This is seen by the Baltic Sea Action Group as a threat to biodiversity and regional fishing stocks. | 0 | Theoretical and Fundamental Chemistry |
The four-dimensional point groups (chiral as well as achiral) are listed in Conway and Smith, Section 4, Tables 4.1–4.3.
The following list gives the four-dimensional reflection groups (excluding those that leave a subspace fixed and that are therefore lower-dimensional reflection groups). Each group is specified as a Coxeter group, and like the polyhedral groups of 3D, it can be named by its related convex regular 4-polytope. Related pure rotational groups exist for each with half the order, and can be represented by the bracket Coxeter notation with a + exponent, for example [3,3,3] has three 3-fold gyration points and symmetry order 60. Front-back symmetric groups like [3,3,3] and [3,4,3] can be doubled, shown as double brackets in Coxeter's notation, for example with its order doubled to 240. | 0 | Theoretical and Fundamental Chemistry |
Rotary draw bending (RDB) is a precise technology, since it bends using tooling or "die sets" which have a constant center line radius (CLR), alternatively indicated as mean bending radius (Rm). Rotary draw benders can be programmable to store multiple bend jobs with varying degrees of bending. Often a positioning index table (IDX) is attached to the bender allowing the operator to reproduce complex bends which can have multiple bends and differing planes.
Rotary draw benders are the most popular machines for use in bending tube, pipe and solids for applications like: handrails, frames, motor vehicle roll cages, handles, lines and much more. Rotary draw benders create aesthetically pleasing bends when the right tooling is matched to the application.
CNC rotary draw bending machines can be very complex and use sophisticated tooling to produce severe bends with high quality requirements.
The complete tooling is required only for high-precision bending of difficult-to-bend tubes with relatively large OD/t (diameter/thickness) ratio and relatively small ratio between the mean bending radius Rm and OD. The use of axial boosting either on the tube free end or on the pressure die is useful to prevent excessive thinning and collapse of the extrados of the tube. The mandrel, with or without ball with spherical links, is mostly used to prevent wrinkles and ovalization. For relatively easy bending processes (that is, as the difficulty factor BF decreases), the tooling can be progressively simplified, eliminating the need for the axial assist, the mandrel, and the wiper die (which mostly prevents wrinkling). Furthermore, in some particular cases, the standard tooling must be modified in order to meet specific requirements of the products. | 1 | Applied and Interdisciplinary Chemistry |
In 1845, the first pipe was cast vertically in a pit and by the end of the century, all pipe was manufactured by this method. Using this method the slag would all collect at the top of the casting and could be removed by simply cutting off the end of the pipe. Pipes cast using this method often suffered from off centre bores caused by the core of the mould being placed off centre, resulting in one side of the pipe being thicker than the other. | 1 | Applied and Interdisciplinary Chemistry |
Trifluoroacetic acid (TFA) is an organofluorine compound with the chemical formula CFCOH. It is a haloacetic acid, with all three of the acetyl groups hydrogen atoms replaced by fluorine atoms. It is a colorless liquid with a vinegar-like odor. TFA is a stronger acid than acetic acid, having an acid ionisation constant, K', that is approximately 34,000 times higher, as the highly electronegative fluorine atoms and consequent electron-withdrawing nature of the trifluoromethyl group weakens the oxygen-hydrogen bond (allowing for greater acidity) and stabilises the anionic conjugate base. TFA is widely used in organic chemistry for various purposes. | 0 | Theoretical and Fundamental Chemistry |
An alternative form of the Arruda–Boyce model, using the first five terms of the inverse Langevin function, is
where is a material constant. The quantity can also be interpreted as a measure of the limiting network stretch.
If is the stretch at which the polymer chain network becomes locked, we can express the Arruda–Boyce strain energy density as
We may alternatively express the Arruda–Boyce model in the form
where and
If the rubber is compressible, a dependence on can be introduced into the strain energy density; being the deformation gradient. Several possibilities exist, among which the Kaliske–Rothert extension has been found to be reasonably accurate. With that extension, the Arruda-Boyce strain energy density function can be expressed as
where is a material constant and . For consistency with linear elasticity, we must have where is the bulk modulus. | 0 | Theoretical and Fundamental Chemistry |
Penicillamine, sold under the brand name of Cuprimine among others, is a medication primarily used for the treatment of Wilson's disease. It is also used for people with kidney stones who have high urine cystine levels, rheumatoid arthritis, and various heavy metal poisonings. It is taken by mouth.
Penicillamine was approved for medical use in the United States in 1970. It is on the World Health Organization's List of Essential Medicines. | 0 | Theoretical and Fundamental Chemistry |
Another form of amylase, β-amylase () (alternative names: 1,4-α--glucan maltohydrolase; glycogenase; saccharogen amylase) is also synthesized by bacteria, fungi, and plants. Working from the non-reducing end, β-amylase catalyzes the hydrolysis of the second α-1,4 glycosidic bond, cleaving off two glucose units (maltose) at a time. During the ripening of fruit, β-amylase breaks starch into maltose, resulting in the sweet flavor of ripe fruit. They belong to glycoside hydrolase family 14.
Both α-amylase and β-amylase are present in seeds; β-amylase is present in an inactive form prior to germination, whereas α-amylase and proteases appear once germination has begun. Many microbes also produce amylase to degrade extracellular starches. Animal tissues do not contain β-amylase, although it may be present in microorganisms contained within the digestive tract. The optimum pH for β-amylase is 4.0–5.0. | 1 | Applied and Interdisciplinary Chemistry |
* Phenol-Explorer ([http://www.phenol-explorer.eu phenol-explorer.eu]), a database dedicated to phenolics found in food by Augustin Scalbert, INRA Clermont-Ferrand, Unité de Nutrition Humaine (Human food unit)
* [http://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:33853 Phenols] at ChEBI (Chemical Entities of Biological Interest)
* [https://web.archive.org/web/20181002215232/https://www.ebi.ac.uk/chembldb/index.php ChEMBLdb], a database of bioactive drug-like small molecules by the European Bioinformatics Institute
* Foodb, a database of compounds found in food | 0 | Theoretical and Fundamental Chemistry |
Enumerating or counting structural isomers in general is a difficult problem, since one must take into account several bond types (including delocalized ones), cyclic structures, and structures that cannot possibly be realized due to valence or geometric constraints, and non-separable tautomers.
For example, there are nine structural isomers with molecular formula CHO having different bond connectivities. Seven of them are air-stable at room temperature, and these are given in the table below.
Two structural isomers are the enol tautomers of the carbonyl isomers (propionaldehyde and acetone), but these are not stable. | 0 | Theoretical and Fundamental Chemistry |
# For a Ca-looping cycle installed on a 500 MW power plant, the purge rate is 12.6 kg CaO/s.
# For the cement production process, 0.65 kg CaO is required/ kg cement produced.
# U.S. electric generation capacity (only fossil fuels): Natural gas = 415 GW, Coal= 318 GW & Petroleum = 51 GW
# Cement consumption in U.S. = 110,470 × 10 metric tons = 1.10470 × 10 metric tons = 1.10470 × 10 kg. | 1 | Applied and Interdisciplinary Chemistry |
Benson group-increment theory (BGIT), group-increment theory, or Benson group additivity uses the experimentally calculated heat of formation for individual groups of atoms to calculate the entire heat of formation for a molecule under investigation. This can be a quick and convenient way to determine theoretical heats of formation without conducting tedious experiments. The technique was developed by professor Sidney William Benson of the University of Southern California. It is further described in Heat of formation group additivity.
Heats of formations are intimately related to bond-dissociation energies and thus are important in understanding chemical structure and reactivity. Furthermore, although the theory is old, it still is practically useful as one of the best group-contribution methods aside from computational methods such as molecular mechanics. However, the BGIT has its limitations, and thus cannot always predict the precise heat of formation. | 0 | Theoretical and Fundamental Chemistry |
Common synthetic polymers that can be attacked include polypropylene and LDPE, where tertiary carbon bonds in their chain structures are the centres of attack. Ultraviolet rays interact with these bonds to form free radicals, which then react further with oxygen in the atmosphere, producing carbonyl groups in the main chain. The exposed surfaces of products may then discolour and crack, and in extreme cases, complete product disintegration can occur.
In fibre products like rope used in outdoor applications, product life will be low because the outer fibres will be attacked first, and will easily be damaged by abrasion for example. Discolouration of the rope may also occur, thus giving an early warning of the problem.
Polymers which possess UV-absorbing groups such as aromatic rings may also be sensitive to UV degradation. Aramid fibres like Kevlar, for example, are highly UV-sensitive and must be protected from the deleterious effects of sunlight. | 0 | Theoretical and Fundamental Chemistry |
Ethanol is the most commonly used biofuel and can be produced on large scale via fermentation. The maximum theoretical yield for the production of ethanol was achieved around 20 years. A plasmid that carried the pyruvate decarboxylase and alcohol dehydrogenase genes from the bacteria Z. mobilis was used by scientists. This was inserted into E. coli and resulted in an increased yield of ethanol. The genome of this E. coli strain, KO11, has more recently been sequenced and mapped. | 1 | Applied and Interdisciplinary Chemistry |
Electroreflectance is often used to determine band gaps and electric properties of thin films of weaker semiconducting materials. Two different examples are listed below. | 0 | Theoretical and Fundamental Chemistry |
Reactions of alkenyl- and alkynylaluminium compounds involve the transfer of a nucleophilic alkenyl or alkynyl group attached to aluminium to an electrophilic atom. Stereospecific hydroalumination, carboalumination, and terminal alkyne metalation are useful methods for generation of the necessary alkenyl- and alkynylalanes. | 0 | Theoretical and Fundamental Chemistry |
An ionic liquid (IL) is a salt in the liquid state at ambient conditions. In some contexts, the term has been restricted to salts whose melting point is below a specific temperature, such as . While ordinary liquids such as water and gasoline are predominantly made of electrically neutral molecules, ionic liquids are largely made of ions. These substances are variously called liquid electrolytes, ionic melts, ionic fluids, fused salts, liquid salts, or ionic glasses.
Ionic liquids have many potential applications. They are powerful solvents and can be used as electrolytes. Salts that are liquid at near-ambient temperature are important for electric battery applications, and have been considered as sealants due to their very low vapor pressure.
Any salt that melts without decomposing or vaporizing usually yields an ionic liquid. Sodium chloride (NaCl), for example, melts at into a liquid that consists largely of sodium cations () and chloride anions (). Conversely, when an ionic liquid is cooled, it often forms an ionic solid—which may be either crystalline or glassy.
The ionic bond is usually stronger than the Van der Waals forces between the molecules of ordinary liquids. Because of these strong interactions, salts tend to have high lattice energies, manifested in high melting points. Some salts, especially those with organic cations, have low lattice energies and thus are liquid at or below room temperature. Examples include compounds based on the 1-ethyl-3-methylimidazolium (EMIM) cation and include: EMIM:Cl, EMIMAc (acetate anion), EMIM dicyanamide, ()()·, that melts at ; and 1-butyl-3,5-dimethylpyridinium bromide which becomes a glass below .
Low-temperature ionic liquids can be compared to ionic solutions, liquids that contain both ions and neutral molecules, and in particular to the so-called deep eutectic solvents, mixtures of ionic and non-ionic solid substances which have much lower melting points than the pure compounds. Certain mixtures of nitrate salts can have melting points below 100 °C. | 0 | Theoretical and Fundamental Chemistry |
An MDC is constructed similarly to a microbial fuel cell by including two
chambers with two electrodes, an anode and a cathode, in addition to both a third chamber separated by an anion exchange membrane (AEM) and cation exchange membrane (CEM), and a peripheral, external circuit that is responsible for aerobic and anaerobic processes at each respective electrode. Organic matter from the sludge proliferates in the anode chamber and creates a biofilm that generates an electric current. The biofilm thus begins to oxidize the pollutants in the sludge by strictly adhering to the anode, freeing both electrons and protons from the bio-sludge, creating a current of atoms that are collected by the electrodes through circuit transportation. Electrical current is produced by the potential difference generated between the anode and cathode due to the aerobic nature of the cathode chamber. | 0 | Theoretical and Fundamental Chemistry |
E. coli has seven main sigma factors, five of which have a specific anti-sigma factor. The anti-sigma factor binding to its sigma factors depends upon environmental cues. This mechanism blocks the transcription of genes that are unnecessary in new conditions. The table below shows five sigma factors, what process it affects, and its corresponding anti-sigma factor. In E. coli, sigma factors transcribe their anti-sigma factors; this creates a negative feedback loop. The sigma factor can be regulated when the anti-sigma factor is transcribed and the anti-sigma factor when the sigmas gene is transcribed. Sigma factors 70 and 54 don't have specific anti-sigma factors; they have other negative feedback loop mechanisms. | 1 | Applied and Interdisciplinary Chemistry |
Diazomethane is an organic chemical compound with the formula CHN, discovered by German chemist Hans von Pechmann in 1894. It is the simplest diazo compound. In the pure form at room temperature, it is an extremely sensitive explosive yellow gas; thus, it is almost universally used as a solution in diethyl ether. The compound is a popular methylating agent in the laboratory, but it is too hazardous to be employed on an industrial scale without special precautions. Use of diazomethane has been significantly reduced by the introduction of the safer and equivalent reagent trimethylsilyldiazomethane. | 0 | Theoretical and Fundamental Chemistry |
Following the lead of Dachlauer and Jackel, contemporary routes to episulfides utilize a two-step method, converting an olefin to an epoxide followed by thiation using thiocyanate or thiourea.
Episulfides can also be prepared from cyclic carbonates, hydroxy mercaptans, hydroxyalkyl halides, dihaloalkanes, and halo mercaptans. The reaction of ethylene carbonate and KSCN gives ethylene sulfide:
The metal-catalyzed reaction of sulfur with alkenes has been demonstrated. | 0 | Theoretical and Fundamental Chemistry |
Cold filter plugging point (CFPP) is the lowest temperature, expressed in degrees Celsius (°C), at which a given volume of diesel type of fuel still passes through a standardized filtration device in a specified time when cooled under certain conditions. This test gives an estimate for the lowest temperature that a fuel will give trouble free flow in certain fuel systems. This is important as in cold temperate countries, a high cold filter plugging point will clog up vehicle engines more easily.
The test is important in relation to the use of additives that allow spreading the usage of winter diesel at temperatures below the cloud point. The tests according to EN 590 show that a CloudPoint of +1 °C can have a CFPP −10 °C. Current additives allow a CFPP of −20 °C to be based on diesel fuel with a CloudPoint of −7 °C.
The trustworthiness of the EN 590 have been criticized as being too low for modern diesel motors – the German ADAC has run a test series on customary winter diesel in a cold chamber. All diesel brands did exceed the legal minimum by 3 to 11 degrees in the laboratory according to the legal DIN test. One of the real diesel motors however stopped working even before the legal minimum was reached, presumably due to an undersized filter heater. Notably the experiments did not show a direct correlation between the CFPP value of the mineral oil and the cold start capability of the diesel motors – hence the automobile club suggest the creation of a new test standard. | 0 | Theoretical and Fundamental Chemistry |
An automated device for determining the coagulant dose is the Streaming Current Detector (SCD). The SCD measures the net surface charge of the particles and shows a streaming current value of 0 when the charges are neutralized (cationic coagulants neutralize the anionic colloids). At this value (0), the coagulant dose can be said to be optimum. | 1 | Applied and Interdisciplinary Chemistry |
Coenzyme A is available from various chemical suppliers as the free acid and lithium or sodium salts. The free acid of coenzyme A is detectably unstable, with around 5% degradation observed after 6 months when stored at −20 °C, and near complete degradation after 1 month at 37 °C. The lithium and sodium salts of CoA are more stable, with negligible degradation noted over several months at various temperatures. Aqueous solutions of coenzyme A are unstable above pH 8, with 31% of activity lost after 24 hours at 25 °C and pH 8. CoA stock solutions are relatively stable when frozen at pH 2–6. The major route of CoA activity loss is likely the air oxidation of CoA to CoA disulfides. CoA mixed disulfides, such as CoA-S–S-glutathione, are commonly noted contaminants in commercial preparations of CoA. Free CoA can be regenerated from CoA disulfide and mixed CoA disulfides with reducing agents such as dithiothreitol or 2-mercaptoethanol. | 1 | Applied and Interdisciplinary Chemistry |
Cell signaling or cell communication is important for cell regulation and for cells to process information from the environment and respond accordingly. Signaling can occur through direct cell contact or endocrine, paracrine, and autocrine signaling. Direct cell-cell contact is when a receptor on a cell binds a molecule that is attached to the membrane of another cell. Endocrine signaling occurs through molecules secreted into the bloodstream. Paracrine signaling uses molecules diffusing between two cells to communicate. Autocrine is a cell sending a signal to itself by secreting a molecule that binds to a receptor on its surface. Forms of communication can be through:
* Ion channels: Can be of different types such as voltage or ligand gated ion channels. They allow for the outflow and inflow of molecules and ions.
* G-protein coupled receptor (GPCR): Is widely recognized to contain seven transmembrane domains. The ligand binds on the extracellular domain and once the ligand binds, this signals a guanine exchange factor to convert GDP to GTP and activate the G-α subunit. G-α can target other proteins such as adenyl cyclase or phospholipase C, which ultimately produce secondary messengers such as cAMP, Ip3, DAG, and calcium. These secondary messengers function to amplify signals and can target ion channels or other enzymes. One example for amplification of a signal is cAMP binding to and activating PKA by removing the regulatory subunits and releasing the catalytic subunit. The catalytic subunit has a nuclear localization sequence which prompts it to go into the nucleus and phosphorylate other proteins to either repress or activate gene activity.
* Receptor tyrosine kinases: Bind growth factors, further promoting the tyrosine on the intracellular portion of the protein to cross phosphorylate. The phosphorylated tyrosine becomes a landing pad for proteins containing an SH2 domain allowing for the activation of Ras and the involvement of the MAP kinase pathway. | 1 | Applied and Interdisciplinary Chemistry |
*Because optical properties depend on suspended particle size, a stable synthetic material called "Formazin" with uniform particle size is often used as a standard for calibration and reproducibility. The unit is called Formazin Turbidity Unit (FTU).
*Nephelometric Turbidity Units (NTU) specified by United States Environmental Protection Agency is a special case of FTU, where a white light source and certain geometrical properties of the measurement apparatus are specified. (Sometimes the alternate form "nephelos turbidity units" is used)
*Formazin Nephelometric Units (FNU), prescribed for 9 measurements of turbidity in water treatment by ISO 7027, another special case of FTU with near infrared light (NIR) and 90° scatter.
*Formazin Attenuation Units (FAU) specified by ISO 7027 for water treatment standards for turbidity measurements at 0°, also a special case of FTU.
*Formazin Backscatter Units (FBU), not part of a standard, is the unit of optical backscatter detectors (OBS), measured at c. 180°, also a special case of FTU.
*European Brewery Convention (EBC) turbidity units
*Concentration Units (C.U.)
*Optical Density (O.D.)
*Jackson "Candle" Turbidity Units (JTU; an early measure)
*Helms Units
*American Society of Brewing Chemists (ASBC-FTU) turbidity units
*Brantner Haze Scale (BHS) and Brantner Haze Units (BHU) for purposefully hazy beer
*Parts Per Million of standard substance, such as PPM/DE (Kieselguhr)
*"Trübungseinheit/Formazin" (TE/F) a German standard, now replaced by the FNU unit.
*diatomaceous earth ("ppm SiO") an older standard, now obsolete
A more popular term for this instrument in water quality testing is a turbidimeter. However, there can be differences between models of turbidimeters, depending upon the arrangement (geometry) of the source beam and the detector. A nephelometric turbidimeter always monitors light reflected off the particles and not attenuation due to cloudiness. In the United States environmental monitoring the turbidity standard unit is called Nephelometric Turbidity Units (NTU), while the international standard unit is called Formazin Nephelometric Unit (FNU). The most generally applicable unit is Formazin Turbidity Unit (FTU), although different measurement methods can give quite different values as reported in FTU (see below).
Gas-phase nephelometers are also used to study the atmosphere. These can provide information on visibility and atmospheric albedo. | 0 | Theoretical and Fundamental Chemistry |
Carboxypeptidase A (CPA) contains a zinc (Zn) metal center in a tetrahedral geometry with amino acid residues in close proximity around zinc to facilitate catalysis and binding. Out of the 307 amino acids bonded in a peptide chain, the following amino acid residues are important for catalysis and binding; Glu-270, Arg-71, Arg-127, Asn-144, Arg-145, and Tyr-248. Figure 1 illustrates the tetrahedral zinc complex active site with the important amino acid residues that surround the complex.
The zinc metal is a strong electrophilic Lewis acid catalyst which stabilizes a coordinated water molecule as well as stabilizes the negative intermediates that occur throughout the hydrolytic reaction. Stabilization of both the coordinated water molecule and negative intermediates are assisted by polar residues in the active site which are in close proximity to facilitate hydrogen bonding.
The active site can be characterized into two sub-sites denoted as S’ and S. The S’ sub-site is the hydrophobic pocket of the enzyme, and Tyr-248 acts to ‘cap’ the hydrophobic pocket after substrate or inhibitor is bound (SITE). The hydrogen bonding from the hydroxyl group in Tyr-248 facilitates this conformation due to interaction with the terminal carboxylates of substrates that bind. Substantial movement is required for this enzyme and induced fit model explains how this interaction occurs.
A triad of residues interact to the C-terminal carboxylate through hydrogen bonding:
* Salt linkage with positively charged Arg-145
* Hydrogen bond from Tyr-248
* Hydrogen bond from the nitrogen of the Asn-144 amide | 1 | Applied and Interdisciplinary Chemistry |
Shotgun lipidomics is fast, highly sensitive, and it can identify hundreds of lipids missed by other methods — all with a much smaller tissue sample so that specific cells or minute biopsy samples can be examined. | 1 | Applied and Interdisciplinary Chemistry |
Trans-splicing is a form of splicing that removes introns or outrons, and joins two exons that are not within the same RNA transcript. Trans-splicing can occur between two different endogenous pre-mRNAs or between an endogenous and an exogenous (such as from viruses) or artificial RNAs. | 1 | Applied and Interdisciplinary Chemistry |
Thermodynamic power cycles are the basis for the operation of heat engines, which supply most of the world's electric power and run the vast majority of motor vehicles. Power cycles can be organized into two categories: real cycles and ideal cycles. Cycles encountered in real world devices (real cycles) are difficult to analyze because of the presence of complicating effects (friction), and the absence of sufficient time for the establishment of equilibrium conditions. For the purpose of analysis and design, idealized models (ideal cycles) are created; these ideal models allow engineers to study the effects of major parameters that dominate the cycle without having to spend significant time working out intricate details present in the real cycle model.
Power cycles can also be divided according to the type of heat engine they seek to model. The most common cycles used to model internal combustion engines are the Otto cycle, which models gasoline engines, and the Diesel cycle, which models diesel engines. Cycles that model external combustion engines include the Brayton cycle, which models gas turbines, the Rankine cycle, which models steam turbines, the Stirling cycle, which models hot air engines, and the Ericsson cycle, which also models hot air engines.
For example :--the pressure-volume mechanical work output from the ideal Stirling cycle (net work out), consisting of 4 thermodynamic processes, is:
For the ideal Stirling cycle, no volume change happens in process 4-1 and 2-3, thus equation (3) simplifies to: | 0 | Theoretical and Fundamental Chemistry |
An ATP test is the process of rapidly measuring active microorganisms in water through detection adenosine triphosphate (ATP). ATP is a molecule found only in and around living cells, and as such it gives a direct measure of biological concentration and health. ATP is quantified by measuring the light produced through its reaction with the naturally occurring enzyme firefly luciferase using a luminometer. The amount of light produced is directly proportional to the amount of biological energy present in the sample.
Second generation ATP tests are specifically designed for water, wastewater and industrial applications where, for the most part, samples contain a variety of components that can interfere with the ATP assay. | 0 | Theoretical and Fundamental Chemistry |
Carbon snake is a demonstration of the dehydration reaction of sugar by concentrated sulfuric acid. With concentrated sulfuric acid, granulated table sugar (sucrose) performs a degradation reaction which changes its form to a black solid-liquid mixture. The carbon snake experiment can sometimes be misidentified as the black snake, "sugar snake", or "burning sugar" reaction, all of which involve baking soda rather than sulfuric acid. | 1 | Applied and Interdisciplinary Chemistry |
Evaporation and condensation can give rise to both kinetic and equilibrium isotope effects. While equilibrium mass fractionation is present evaporation and condensation, it is negligible compared to kinetic effects. During condensation, the condensate is enriched in the light isotope, whereas in evaporation, the gas phase is enriched in the light isotope. Using the kinetic theory of gases, for Fe/Fe, a fractionation factor of α = 1.01835 for the evaporation of a pool containing equimolar amounts of Fe and Fe. In evaporation experiments, the evaporation of FeO at 1,823 K gave a fractionation factor of α = 1.01877. Presently, there have been no experimental attempts to determine the Fe/Fe fractionation factor of condensation. | 0 | Theoretical and Fundamental Chemistry |
Fluorogenic signaling oligonucleotide probes were reported for use to detect and isolate cells expressing one or more desired genes, including the production of multigene stable cell lines expressing heteromultimeric epithelial sodium channel (αβγ-ENaC), sodium voltage-gated ion channel 1.7 (NaV1.7-αβ1β2), four unique γ-aminobutyric acid A (GABAA) receptor ion channel subunit combinations α1β3γ2s, α2β3γ2s, α3β3γ2s and α5β3γ2s, cystic fibrosis conductance regulator (CFTR), CFTR-Δ508 and two G-protein coupled receptors (GPCRs). | 1 | Applied and Interdisciplinary Chemistry |
MERMOZ (also, MERMOZ project and Monitoring planEtary suRfaces with Modern pOlarimetric characteriZation) is an astrobiology project designed to remotely detect biosignatures of life. Detection is based on molecular homochirality, a characteristic property of the biochemicals of life. The aim of the project is to remotely identify and characterize life on the planet Earth from space, and to extend this technology to other solar system bodies and exoplanets. The project began in 2018, and is a collaboration of the University of Bern, University of Leiden and Delft University of Technology.
According to a member of the research team, “When light is reflected by biological matter, a part of the light’s electromagnetic waves will travel in either clockwise or counterclockwise spirals ... This phenomenon is called circular polarization and is caused by the biological matter’s homochirality.” These unique spirals of light indicate living materials; whereas, non-living materials do not reflect such unique spirals of light, according to the researchers.
The research team conducted feasibility studies, using a newly designed detection instrument, based on circular spectropolarimetry, and named FlyPol+ (an upgrade from the original FlyPol), by flying in a helicopter at an altitude of and velocity of for 25 minutes. The results were successful in remotely detecting living material, and quickly (within seconds) distinguishing living material from non-living material. The researchers concluded: "Circular spectropolarimetry can be a powerful technique to detect life beyond Earth, and we emphasize the potential of utilizing circular spectropolarimetry as a remote sensing tool to characterize and monitor in detail the vegetation physiology and terrain features of Earth itself."
The researchers next expect to scan the Earth from the International Space Station (ISS) with their detection instruments. One consequence of further successful studies is a possible pathfinder space mission, scheduled to launch in 2024. | 1 | Applied and Interdisciplinary Chemistry |
In 1942, on the recommendation of the Council for Scientific and Industrial Research (from 1949 Commonwealth Scientific and Industrial Research Organisation, or CSIRO), McTaggart was made its employee, working at first in facilities at Melbourne University then from later that year at Fishermans Bend when a new facility was opened there. His initial investigation was the chlorination of rutile found in Australian heavy beach sands which produced titanium tetrachloride; its importance in World War II then underway, was the dense white fume it produced on exposure to moist air, making it an effective smoke screen.
McTaggart's research in his position as Senior Principal Research Scientist headed a team including (in 1946) Ian Kraitzer, Chas Alsope, Margaret Ellis, Mick Bertrand and Joy Bear; and staff qualified in electronics; Keith Perger, appointed in 1962, replaced in 1968 by John A. Hamilton; and in glassblowing; in Port Melbourne Rudi Pillig transferred to the project from the Division of Chemical Physics, before which scientists including McTaggart and Newnham in the Minerals Utilization Section were themselves skilled glassblowers, and produced their own apparatus in glass or silica. | 0 | Theoretical and Fundamental Chemistry |
In addition to its well-known roles in the electron transport chain and cell apoptosis, according to a recent study cytochrome c can also act as an antioxidative enzyme in the mitochondria; it does so by removing superoxide (O) and hydrogen peroxide (HO) from mitochondria. Therefore, not only is cytochrome c required in the mitochondria for cellular respiration, but it is also needed in the mitochondria to limit the production of O and HO. | 1 | Applied and Interdisciplinary Chemistry |
The driving force behind radical clock reactions is their ability to rearrange. Some common radical clocks are radical cyclizations, ring openings, and 1,2-migrations. Two popular rearrangements are the cyclization of 5-hexenyl and the ring-opening of cyclopropylmethyl:
5-hexenyl radical undergoes cyclization to produce a five-membered ring because this is entropically and enthalpically more favored than the six-membered ring possibility. The rate-constant for this reaction is 2.3×10 s at 298 K.
Cyclopropylmethyl radical undergoes a very rapid ring opening rearrangement that relieves the ring strain and is enthalpically favorable. The rate-constant for this reaction is 8.6×10 s at 298 K.
In order to determine absolute rate constants for radical reactions, unimolecular clock reactions need to be calibrated for each group of radicals such as primary alkyls over a range of time. Through the usage of EPR spectroscopy, the absolute rate constants for unimolecular reactions can be measured with a variety of temperatures. The Arrhenius equation can then be applied to calculate the rate constant for a specific temperature at which the radical clock reactions are conducted.
When using a radical clock to study a reaction, there is an implicit assumption that the rearrangement rate of the radical clock is the same as when the rate of that rearrangement reaction rate is determined. A theoretical study of the rearrangement reactions of cyclobutylmethyl and of 5-hexenyl in a variety of solvents found that their reaction rates were only very slightly affected by the nature of the solvent.
The rates of radical clocks can be adjusted to increase or decrease by what types of substituents are attached to the radical clock. In the figure below, the rates of the radical clocks are shown with a variety of substituents attached to the clock.
By selecting among the general classes of radical clocks and the specific substituents on them, one can be chosen with a rate-constant suitable for studying reactions having a wide range of rates. Reactions having rates ranging from 10 to 10 M s have been studied using radical clocks. | 0 | Theoretical and Fundamental Chemistry |
The glass transition of a liquid to a solid-like state may occur with either cooling or compression. The transition comprises a smooth increase in the viscosity of a material by as much as 17 orders of magnitude within a temperature range of 500 K without any pronounced change in material structure. This transition is in contrast to the freezing or crystallization transition, which is a first-order phase transition in the Ehrenfest classification and involves discontinuities in thermodynamic and dynamic properties such as volume, energy, and viscosity. In many materials that normally undergo a freezing transition, rapid cooling will avoid this phase transition and instead result in a glass transition at some lower temperature. Other materials, such as many polymers, lack a well defined crystalline state and easily form glasses, even upon very slow cooling or compression. The tendency for a material to form a glass while quenched is called glass forming ability. This ability depends on the composition of the material and can be predicted by the rigidity theory.
Below the transition temperature range, the glassy structure does not relax in accordance with the cooling rate used. The expansion coefficient for the glassy state is roughly equivalent to that of the crystalline solid. If slower cooling rates are used, the increased time for structural relaxation (or intermolecular rearrangement) to occur may result in a higher density glass product. Similarly, by annealing (and thus allowing for slow structural relaxation) the glass structure in time approaches an equilibrium density corresponding to the supercooled liquid at this same temperature. T is located at the intersection between the cooling curve (volume versus temperature) for the glassy state and the supercooled liquid.
The configuration of the glass in this temperature range changes slowly with time towards the equilibrium structure. The principle of the minimization of the Gibbs free energy provides the thermodynamic driving force necessary for the eventual change. At somewhat higher temperatures than T, the structure corresponding to equilibrium at any temperature is achieved quite rapidly. In contrast, at considerably lower temperatures, the configuration of the glass remains sensibly stable over increasingly extended periods of time.
Thus, the liquid-glass transition is not a transition between states of thermodynamic equilibrium. It is widely believed that the true equilibrium state is always crystalline. Glass is believed to exist in a kinetically locked state, and its entropy, density, and so on, depend on the thermal history. Therefore, the glass transition is primarily a dynamic phenomenon. Time and temperature are interchangeable quantities (to some extent) when dealing with glasses, a fact often expressed in the time–temperature superposition principle. On cooling a liquid, internal degrees of freedom successively fall out of equilibrium. However, there is a longstanding debate whether there is an underlying second-order phase transition in the hypothetical limit of infinitely long relaxation times.
In a more recent model of glass transition, the glass transition temperature corresponds to the temperature at which the largest openings between the vibrating elements in the liquid matrix become smaller than the smallest cross-sections of the elements or parts of them when the temperature is decreasing. As a result of the fluctuating input of thermal energy into the liquid matrix, the harmonics of the oscillations are constantly disturbed and temporary cavities ("free volume") are created between the elements, the number and size of which depend on the temperature. The glass transition temperature T defined in this way is a fixed material constant of the disordered (non-crystalline) state that is dependent only on the pressure. As a result of the increasing inertia of the molecular matrix when approaching T, the setting of the thermal equilibrium is successively delayed, so that the usual measuring methods for determining the glass transition temperature in principle deliver T values that are too high. In principle, the slower the temperature change rate is set during the measurement, the closer the measured T value T approaches. Techniques such as dynamic mechanical analysis can be used to measure the glass transition temperature. | 0 | Theoretical and Fundamental Chemistry |
Flory and Stockmayer used a statistical approach to derive an expression to predict the gel point by calculating when approaches infinite size. The statistical approach assumes that (1) the reactivity of the functional groups of the same type is the same and independent of the molecular size and (2) there are no intramolecular reactions between the functional groups on the same molecule.
Consider the polymerization of bifunctional molecules , and multifunctional , where is the functionality. The extends of the functional groups are and , respectively. The ratio of all A groups, both reacted and unreacted, that are part of branched units, to the total number of A groups in the mixture is defined as . This will lead to the following reaction
The probability of obtaining the product of the reaction above is given by , since the probability that a B group reach with a branched unit is and the probability that a B group react with non-branched A is .
This relation yields to an expression for the extent of reaction of A functional groups at the gel point
where r is the ratio of all A groups to all B groups. If more than one type of multifunctional branch unit is present and average value is used for all monomer molecules with functionality greater than 2.
Note that the relation does not apply for reaction systems containing monofunctional reactants and/or both A and B type of branch units. | 0 | Theoretical and Fundamental Chemistry |
Flow conditioning makes a huge effect on the accuracy of liquid turbine meter which results in flow disturbances. These effects are mainly caused by debris on strainer screens, for various upstream piping geometries and different types of flow conditioners.
The effectiveness of a flow conditioner can be indicated by the following two key measurements:
* Percentage variation of an average meter factor over the defined range of flow disturbances for a given flow rate and inlet piping geometry. The lesser the value of percentage variation of an average meter factor over the range of flow disturbances, the better will be the performance of flow conditioner.
* Percentage meter factor repeatability for each flow disturbance, at a given flow rate and inlet piping geometry. The lesser the value of percentage meter factor repeatability at a given set of installation/operating conditions, the better will be the performance of flow conditioner. | 1 | Applied and Interdisciplinary Chemistry |
Loose Polyethylene sleeving was first developed by CIPRA (since 1979, DIPRA) in the US in 1951 for use in highly corrosive soil. It was employed more widely in the US in the late 1950s and first employed in the UK in 1965 and Australia in the mid-1960s. Loose Polyethylene Sleeving (LPS) remains as one of the most cost effective corrosion protection methods available today with a proven track record for reliability and effectiveness.
LPS comprises a loose sleeve of polyethylene that completely wraps the pipe, including the bells of any joints. The sleeving inhibits corrosion by a number of mechanisms. It physically separates the pipe from soil particles, preventing direct galvanic corrosion. By providing an impermeable barrier to ground water, the sleeve also inhibits the diffusion of oxygen to the ductile iron surface and limits the availability of electrolytes that would accelerate corrosion. It provides a homogeneous environment along the pipe surface so that corrosion occurs evenly over the pipe. The sleeve also restricts the availability of nutrients which could support sulfate-reducing bacteria, inhibiting microbially induced corrosion. LPS is not designed to be completely water-tight but rather to greatly restrict the movement of water to and from the pipe surface. Water present beneath the sleeve and in contact with the pipe surface is rapidly deoxygenated and depleted of nutrients and forms a stable environment in which limited further corrosion occurs. An improperly installed sleeve that continues to allow the free flow of ground water is not effective in inhibiting corrosion.
Polyethylene sleeves are available in a number of materials. The most common contemporary compositions are linear low-density polyethylene film which requires an 8 mil or 200 μm thickness and high-density cross-laminated polyethylene film which requires only a 4 mil or 100 μm thickness. The latter may or may not be reinforced with a scrim layer.
Polyethylene sleeving does have limitations. In European practice, its use in the absence of additional zinc and epoxy protective coatings is discouraged where natural soil resistivity is below 750 ohm/cm. Where resistivity is below 1500 ohm/cm and where the pipe is installed at or below the water table, where there are additional artificial soil contaminants and particularly stray currents again it is recommended for use in addition to zinc and epoxy coating. Because of the vulnerability of polyethylene to UV degradation, sleeving, or sleeved pipe should not be stored in sunlight, although carbon pigments included in the sleeving can provide some limited protection.
Polyethylene sleeving is standardised according to ISO 8180 internationally, AWWA C105 in the US, BS 6076 in the UK, and AS 3680 and AS 3681 in Australia. | 1 | Applied and Interdisciplinary Chemistry |
Hemoglobin variants are a part of the normal embryonic and fetal development. They may also be pathologic mutant forms of hemoglobin in a population, caused by variations in genetics. Some well-known hemoglobin variants, such as sickle-cell anemia, are responsible for diseases and are considered hemoglobinopathies. Other variants cause no detectable pathology, and are thus considered non-pathological variants.
In embryos:
* Gower 1 (ζε).
* Gower 2 (αε) ().
* Hemoglobin Portland I (ζγ).
* Hemoglobin Portland II (ζβ).
In fetuses:
* Hemoglobin F (αγ) ().
In neonates (newborns inmmediately after birth):
* Hemoglobin A (adult hemoglobin) (αβ) () – The most common with a normal amount over 95%
* Hemoglobin A (αδ) – δ chain synthesis begins late in the third trimester and, in adults, it has a normal range of 1.5–3.5%
* Hemoglobin F (fetal hemoglobin) (αγ) – In adults Hemoglobin F is restricted to a limited population of red cells called F-cells. However, the level of Hb F can be elevated in persons with sickle-cell disease and beta-thalassemia.
Abnormal forms that occur in diseases:
* Hemoglobin D – (αβ) – A variant form of hemoglobin.
* Hemoglobin H (β) – A variant form of hemoglobin, formed by a tetramer of β chains, which may be present in variants of α thalassemia.
* Hemoglobin Barts (γ) – A variant form of hemoglobin, formed by a tetramer of γ chains, which may be present in variants of α thalassemia.
* Hemoglobin S (αβ) – A variant form of hemoglobin found in people with sickle cell disease. There is a variation in the β-chain gene, causing a change in the properties of hemoglobin, which results in sickling of red blood cells.
* Hemoglobin C (αβ) – Another variant due to a variation in the β-chain gene. This variant causes a mild chronic hemolytic anemia.
* Hemoglobin E (αβ) – Another variant due to a variation in the β-chain gene. This variant causes a mild chronic hemolytic anemia.
* Hemoglobin AS – A heterozygous form causing sickle cell trait with one adult gene and one sickle cell disease gene
* Hemoglobin SC disease – A compound heterozygous form with one sickle gene and another encoding Hemoglobin C.
* Hemoglobin Hopkins-2 – A variant form of hemoglobin that is sometimes viewed in combination with Hemoglobin S to produce sickle cell disease. | 0 | Theoretical and Fundamental Chemistry |
Gough joined the School of Materials, Faculty of Science and Engineering at The University of Manchester, as a lecturer in 2002. She was quickly promoted to Senior lecturer and Reader in 2006 and 2010, respectively.
From 2012 to 2013 she was a Royal Academy of Engineering/Leverhulme Trust Senior Research Fellow. Gough was made full Professor in 2014.
Since then, she has continued her research in tissue engineering of mechanically sensitive connective tissues such as bone, cartilage, skeletal muscle and the intervertebral disc. This includes analysis and control of cells such as osteoblasts, chondrocytes, fibroblasts, keratinocytes, myoblasts and macrophages on a variety of materials and scaffolds. Her research also involves the development of scaffolds for tissue repair using novel hydrogels and magnesium alloys as various porous and fibrous materials. Gough has worked on the advisory board of the journal Biomaterials Science, and as part of the local organising committee for the World Biomaterials Congress. | 1 | Applied and Interdisciplinary Chemistry |
After the news about the curative properties of penicillin broke in an editorial in The Times on 27 August 1942, Fleming enjoyed the publicity, but Howard Florey did not: he feared that this would create a demand for penicillin that he did not yet have to give. When the press arrived at the Sir William Dunn School, he told his secretary to "send them packing". He also prohibited his team to speak to the press. Confusion resulted from the fact that both the mould juice and the drug produced from it were both called penicillin. Distorted and inaccurate accounts were published and broadcast giving Fleming credit for the development of penicillin, accounts that Fleming and St. Mary's Hospital made little or no effort to correct. The story the media wished to tell was the familiar one of the lone scientist and the serendipitous discovery. The British medical historian Bill Bynum later wrote:
In 1943, the Nobel committee received a single nomination for the Nobel Prize in Physiology or Medicine for Fleming and Florey from the British biochemist Rudolph Peters. The secretary of the Nobel committee, Göran Liljestrand, made an assessment of Fleming and Florey in the same year, but little was known about penicillin in Sweden at the time, and he concluded that more information was required. The following year, there was one nomination for Fleming alone and one for Fleming, Florey and Chain. Liljestrand and Nanna Svartz, the professor of medicine at the Karolinska Institute, considered their work, and while both judged Fleming and Florey equally worthy of a Nobel Prize, the Nobel committee was divided, and decided to award the prize that year instead to Joseph Erlanger and Herbert S. Gasser "for their discoveries relating to the highly differentiated functions of single nerve fibres".
There were a large number of nominations for Florey and Fleming or both in 1945, and one for Chain, from Liljestrand, who nominated all three. Liljestrand noted that thirteen of the first sixteen nominations that came in mentioned Fleming, but only three mentioned him alone. This time evaluations were made by Liljestrand, and , who endorsed all three.
There were rumours that the committee would award the prize to Fleming alone, or half to Fleming and one-quarter each to Florey and Chain. Fulton and Dale lobbied for the award to be given to Florey. The Nobel Assembly at the Karolinska Institute did consider awarding half to Fleming and one-quarter each to Florey and Chain, but in the end decided to divide it equally three ways. On 25 October 1945, it announced that Fleming, Florey and Chain equally shared the 1945 Nobel Prize in Physiology or Medicine "for the discovery of penicillin and its curative effect in various infectious diseases." When The New York Times announced that "Fleming and Two Co-Workers" had won the prize, Fulton demanded – and received – a correction in an editorial the next day.
Dorothy Hodgkin received the 1964 Nobel Prize in Chemistry "for her determinations by X-ray techniques of the structures of important biochemical substances." She became only the third woman to receive the Nobel Prize in Chemistry, after Marie Curie in 1911 and Irène Joliot-Curie in 1935. | 1 | Applied and Interdisciplinary Chemistry |
*Father - Grigory Vitalievich Khlopin (1863-1929).
*Mother - Ekaterina Alexandrovna, née Kavaderova (1865-1945) - a graduate of the Higher Womens Courses in St. Petersburg (verbal-historical and physical-mathematical faculties), was engaged in journalism. (at the time of G. V. Khlopins exile to the Urals in 1886), from 1905, when the Khlopins lived already in St. Petersburg, Ekaterina Alexandrovna was engaged in charity work. She died on the road during the re-evacuation of the State Radium University from Kazan to Leningrad.
**Brother - Nikolai Grigorievich Khlopin, a histologist.
Khlopin was first married to Nadezhda Pavlovna Annenkova (daughter of the Narodovtsy P. S. Annenkov[clarification]).
*A daughter (born 1913), whom they baptized in a church in Kuokkala.
*In 1920 he married Maria Alexandrovna Pasvik. | 0 | Theoretical and Fundamental Chemistry |
Ferdowsi (940–1020) was a Persian poet who lived in the Abbasid Caliphate. In Shahnameh, his national epic poem, Ferdowsi described a caesarean section performed on Rudaba. A special wine prepared by a Zoroastrian priest was used as an anesthetic for this operation.
Circa 1020, Ibn Sīnā (980–1037) in The Canon of Medicine described the "soporific sponge", a sponge imbued with aromatics and narcotics, which was to be placed under a patient's nose during surgical operations. Opium made its way from Asia Minor to all parts of Europe between the 10th and 13th centuries.
Throughout 1200 to 1500 AD in England, a potion called dwale was used as an anesthetic. This alcohol-based mixture contained bile, opium, lettuce, bryony, henbane, hemlock, and vinegar. Surgeons roused their patients by rubbing vinegar and salt on their cheekbones. One can find records of dwale in numerous literary sources, including Shakespeares Hamlet', and the John Keats poem "Ode to a Nightingale". In the 13th century, we have the first prescription of the "spongia soporifica"—a sponge soaked in the juices of unripe mulberry, flax, mandragora leaves, ivy, lettuce seeds, lapathum, and hemlock with hyoscyamus. After treatment and/or storage, the sponge could be heated and the vapors inhaled with anesthetic effect.
Alchemist Ramon Llull has been credited with discovering diethyl ether in 1275. Aureolus Theophrastus Bombastus von Hohenheim (1493–1541), better known as Paracelsus, discovered the analgesic properties of diethyl ether around 1525. It was first synthesized in 1540 by Valerius Cordus, who noted some of its medicinal properties. He called it oleum dulce vitrioli, a name that reflects the fact that it is synthesized by distilling a mixture of ethanol and sulfuric acid (known at that time as oil of vitriol). August Sigmund Frobenius gave the name Spiritus Vini Æthereus to the substance in 1730. | 1 | Applied and Interdisciplinary Chemistry |
Thiols, especially in the presence of base, are readily oxidized by reagents such as bromine and iodine to give an organic disulfide (R−S−S−R).
: 2 R−SH + Br → R−S−S−R + 2 HBr
Oxidation by more powerful reagents such as sodium hypochlorite or hydrogen peroxide can also yield sulfonic acids (RSOH).
: R−SH + 3 HO → RSOH + 3 HO
Oxidation can also be effected by oxygen in the presence of catalysts:
: 2 R–SH + O → RS−SR + HO
Thiols participate in thiol-disulfide exchange:
:RS−SR + 2 R′SH → 2 RSH + R′S−SR′
This reaction is important in nature. | 0 | Theoretical and Fundamental Chemistry |
Esters react with strong oxidizing acids, which may cause a violent reaction that is sufficiently exothermic to ignite the esters and the reaction products. Heat is also generated by the interaction of esters with alkali solutions. Very flammable hydrogen gas is generated by mixing esters with alkali metals and ionic hydrides. | 0 | Theoretical and Fundamental Chemistry |
Absorption of radiation by reactants of a reaction at equilibrium increases the rate of forward reaction without directly affecting the rate of the reverse reaction.
The rate of a photochemical reaction is proportional to the absorption cross section of the reactant with respect to the excitation source (σ), the quantum yield of reaction (Φ), and the intensity of the irradiation. In a reversible photochemical reaction between compounds A and B, there will therefore be a "forwards" reaction of at a rate proportional to and a "backwards" reaction of at a rate proportional to . The ratio of the rates of the forward and backwards reactions determines where the equilibrium lies, and thus the photostationary state is found at:
If (as is always the case to some extent) the compounds A and B have different absorption spectra, then there may exist wavelengths of light where σ is high and σ is low. Irradiation at these wavelengths will provide photostationary states that contain mostly B. Likewise, wavelengths that give photostationary states of predominantly A may exist. This is particularly likely in compounds such as some photochromics, where A and B have entirely different absorption bands. Compounds that may be readily switched in this way find utility in devices such as molecular switches and optical data storage. | 0 | Theoretical and Fundamental Chemistry |
uPVC or PVC-U, is a thermoplastic material derived from common salt and fossil fuels. The pipe material has the longest track record of all plastic materials. The first uPVC pipes were made in the 1930s. Beginning in the 1950s, uPVC pipes were used to replace corroded metal pipes and thus bring fresh drinking water to a growing rural and later urban population. uPVC pipes are certified safe for drinking water per NSF Standard 61 and used extensively for water distribution and transmission pipelines throughout North America and around the world. uPVC is allowed for waste lines in homes and is the most often used pipe for sanitary sewers.
Further pressure and non-pressure applications in the field of sewers, soil and waste, gas (low pressure) and cable protection soon followed. The material's contribution to public health, hygiene and well-being has therefore been significant.
Polyvinyl chloride or uPVC (unplasticized polyvinyl chloride) pipes are not well suited for hot water lines and have been restricted from inside water supply line use in the US for homes since 2006. Code IRC P2904.5 uPVC Not listed.
uPVC has high chemical resistance across its operating temperature range, with a broad band of operating pressures. Max operating temperature is reported at , and max working pressure: . Due to its long-term strength characteristics, high stiffness and cost effectiveness, uPVC systems account for a large proportion of plastic piping installations and some estimations put it that greater than of uPVC pipe are currently in service across applications. | 1 | Applied and Interdisciplinary Chemistry |
Commonly, isocyanides are synthesized by dehydration of formamides. The formamide can be dehydrated with toluenesulfonyl chloride, phosphorus oxychloride, phosgene, diphosgene, or the Burgess reagent in the presence of a base such as pyridine or triethylamine.
The formamide precursors are, in turn, prepared from amines by formylation with formic acid or formyl acetyl anhydride.or from the Ritter reaction of alkenes (and other sources of carbocations) and hydrogen cyanide. | 0 | Theoretical and Fundamental Chemistry |
The major steps in the sulfo-ED pathway are:
* oxidation of sulfoquinovose to sulfogluconolactone (catalyzed by sulfoquinovose dehydrogenase with NAD co-factor);
* hydrolysis of sulfogluconolactone to sulfogluconate acid (catalyzed by sulfogluconolactonase with water);
* dehydration of sulfogluconic acid to 2-keto-3,6-dideoxy-6-sulfogluconate (catalyzed by sulfogluconate dehydratase);
* retro-aldol cleavage of 2-keto-3,6-dideoxy-6-sulfogluconate to give pyruvate and (S)-sulfolactaldehyde (catalyzed by sulfoketogluconate dehydrogenase with NAD co-factor);
* oxidation of sulfolactaldehyde to (S)-sulfolactate (catalyzed by sulfolactaldehyde dehydrogenase with NAD co-factor). | 1 | Applied and Interdisciplinary Chemistry |
The simplest apparatus is a tubular setup known as a Venturi tube or simply a Venturi (plural: "Venturis" or occasionally "Venturies"). Fluid flows through a length of pipe of varying diameter. To avoid undue aerodynamic drag, a Venturi tube typically has an entry cone of 30 degrees and an exit cone of 5 degrees.
Venturi tubes are often used in processes where permanent pressure loss is not tolerable and where maximum accuracy is needed in case of highly viscous liquids. | 1 | Applied and Interdisciplinary Chemistry |
Arsenate esters, such as those that would be present in DNA, are generally expected to be orders of magnitude less stable to hydrolysis than corresponding phosphate esters. dAMAs, the structural arsenic analog of the DNA building block dAMP, has a half-life of 40 minutes in water at neutral pH. Estimates of the half-life in water of arsenodiester bonds, which would link the nucleotides together, are as short as 0.06 seconds—compared to 30 million years for the phosphodiester bonds in DNA. The authors speculate that the bacteria may stabilize arsenate esters to a degree by using poly-β-hydroxybutyrate (which has been found to be elevated in "vacuole-like regions" of related species of the genus Halomonas
) or other means to lower the effective concentration of water. Polyhydroxybutyrates are used by many bacteria for energy and carbon storage under conditions when growth is limited by elements other than carbon, and typically appear as large waxy granules closely resembling the "vacuole-like regions" seen in GFAJ-1 cells. The authors present no mechanism by which insoluble polyhydroxybutyrate may lower the effective concentration of water in the cytoplasm sufficiently to stabilize arsenate esters. Although all halophiles must reduce the water activity of their cytoplasm by some means to avoid desiccation, the cytoplasm always remains an aqueous environment. | 1 | Applied and Interdisciplinary Chemistry |
VR (Russian VX, VXr, Soviet V-gas, GOSNIIOKhT substance No. 33, Agent "November") is a "V-series" unitary
nerve agent closely related (it is an isomer) to the better-known VX nerve agent. It became a prototype for the series of Novichok agents. According to chemical weapons expert Jonathan Tucker, the first binary formulation developed under the Soviet Foliant program was used to make Substance 33, differing from VX only in the alkyl substituents on its nitrogen and oxygen atoms. "This weapon was given the code name Novichok." | 1 | Applied and Interdisciplinary Chemistry |
AEP publishes a quarterly magazine, the Environmental Monitor, which contains technical articles, legislative updates and other information useful to its members. As mentioned above the organization has developed a skilled legislative advocacy program, which is remarkable in its pursuit of clarity of language, efficient functioning of environmental review and ethical goals for its profession. AEP also provides annual recognition awards for excellence in various categories, provides members with information on career development and works to achieve standards for performance in the environmental disciplines.
Articles may include topics of air quality, habitat conservation, water quality, archaeology, urban planning, acoustics and other technical matters; however coverage is also given to legislation, AEP activities and professional career development. | 1 | Applied and Interdisciplinary Chemistry |
The environmental consequences of PFAS, especially from firefighting activities, has been recognized since the mid-1990s and came to prominence after the Buncefield explosion on 11 December 2005. In recent years the Environment Agency has undertaken a series of projects to understand the scale and nature of PFAS in the environment. The Drinking Water Inspectorate requires water companies to report concentrations of 47 PFAS. | 0 | Theoretical and Fundamental Chemistry |
Some amino acids are more likely to be replaced. One of the factors that influences this tendency is physicochemical distance. Example of a measure of amino acid can be Graurs Stability Index. The assumption of this measure is that the amino acid replacement rate and proteins evolution is dependent on the amino acid composition of protein. Stability index S of an amino acid is calculated based on physicochemical distances of this amino acid and its alternatives than can mutate through single nucleotide substitution and probabilities to replace into these amino acids. Based on Grantham's distance the most immutable amino acid is cysteine, and the most prone to undergo exchange is methionine. | 1 | Applied and Interdisciplinary Chemistry |
The fission sail is a type of spacecraft propulsion proposed by Robert Forward that uses fission fragments to propel a large solar sail-like craft. It is similar in concept to the fission-fragment rocket in that the fission by-products are directly harnessed as working mass, and differs primarily in the way that the fragments are used for thrust.
In the fission sail, the "rocket" is built in the form of a two-layer sheet, with some sort of absorber on one side, and nuclear fuel on the other. Atoms in the fuel that decay will release their fragments in random, but opposite, directions. In the simple case where the decay releases the fragments "front" and "rear", the rearward moving fragment generates thrust directly, while the frontward moving one is absorbed in the front half of the sail with no net contribution to thrust. The sail is not a nuclear reactor, and relies on natural decay rates for energy release. The thrust from such a system will always be very low, albeit extremely efficient.
Forward proposed the system as an "add on" to existing solar sails. Close to stars where the light density is high the sails work fine, but as they move past about 2 AU their thrust is too low to be useful. Forward suggested that coating the sail with fissionable material would provide thrust in this region, where maneuvering is no longer as important. Such a system would accelerate and maneuver based on solar energy for the start of its flight, and then continue to accelerate at a lower rate for long periods of time. | 0 | Theoretical and Fundamental Chemistry |
There are four main factors influencing photosynthesis and several corollary factors. The four main are:
* Light irradiance and wavelength
* Water absorption
* Carbon dioxide concentration
* Temperature.
Total photosynthesis is limited by a range of environmental factors. These include the amount of light available, the amount of leaf area a plant has to capture light (shading by other plants is a major limitation of photosynthesis), the rate at which carbon dioxide can be supplied to the chloroplasts to support photosynthesis, the availability of water, and the availability of suitable temperatures for carrying out photosynthesis. | 0 | Theoretical and Fundamental Chemistry |
Spectral hemispherical transmittance in frequency and spectral hemispherical transmittance in wavelength of a surface, denoted T and T respectively, are defined as
where
*Φ is the spectral radiant flux in frequency transmitted by that surface;
*Φ is the spectral radiant flux in frequency received by that surface;
*Φ is the spectral radiant flux in wavelength transmitted by that surface;
*Φ is the spectral radiant flux in wavelength received by that surface. | 0 | Theoretical and Fundamental Chemistry |
In 1798, Count Rumford published An Experimental Enquiry Concerning the Source of the Heat which is Excited by Friction, a report on his investigation of the heat produced while manufacturing cannons. He had found that boring a cannon repeatedly does not result in a loss of its ability to produce heat, and therefore no loss of caloric. This suggested that caloric could not be a conserved "substance", though the experimental uncertainties in his experiment were widely debated.
His results were not seen as a "threat" to caloric theory at the time, as this theory was considered to be equivalent to the alternative kinetic theory. In fact, to some of his contemporaries, the results added to the understanding of caloric theory.
Rumfords experiment inspired the work of James Prescott Joule and others towards the middle of the 19th century. In 1850, Rudolf Clausius published a paper showing that the two theories were indeed compatible, as long as the calorists principle of the conservation of heat was replaced by a principle of conservation of energy. Although compatible however, the theories differ significantly in their implications. In modern thermodynamics, heat is usually a transfer of kinetic energy of particles (atoms, molecules) from a hotter to a colder substance.
In later combination with the law of energy conservation, the caloric theory still provides a valuable analogy for some aspects of heat, for example, the emergence of Laplaces equation and Poissons equation in the problems of spatial distribution of heat and temperature. | 1 | Applied and Interdisciplinary Chemistry |
The Llewellyn separator is a membrane molecular separator, a device for interfacing the effluence from a gas chromatograph to the ion source input of a mass spectrometer by changing a rather large (e.g. 10^4 TorrLitre) dilute (e.g. 1 part of vapour in 10^5 parts of carrier gas) gas flow into a small(e.g. <10^-3 TorrLitre) concentrated flow that can be admitted to the vacuum of the mass spectrometer. It is typically based on the substance passing through a few silicone rubber membranes in series. In order for the molecules of interest to be enriched in relation to the small and light carrier gas molecules the former must be captured by (dissolved in) the membrane polymer. The selection properties may be augmented by a liquid stationary phase on the membrane. | 0 | Theoretical and Fundamental Chemistry |
Some forms of sexual dysfunction such as erectile dysfunction can be treated with drugs. Because of their effects, erectile dysfunction drugs are sometimes used for recreational purposes. Many drugs, both legal and illegal, some sold online, have side effects that affect the user's sexual function. Many drugs can cause loss of libido as a side effect.
Since a partial cause of the refractory period is the inhibition of dopamine by an orgasm-induced secretion of prolactin, such potent dopamine receptor agonists as cabergoline may help achieve multiple orgasms as well as the retention of sexual arousal for longer periods of time. | 1 | Applied and Interdisciplinary Chemistry |
Gastric organoids recapitulate at least partly the physiology of the stomach. Gastric organoids have been generated directly from pluripotent stem cells through the temporal manipulation of the FGF, WNT, BMP, retinoic acid and EGF signalling pathways in three-dimensional culture conditions. Gastric organoids have also been generated using LGR5 expressing stomach adult stem cells. Gastric organoids have been used as model for the study of cancer along with human disease and development. For example, one study investigated the underlying genetic alterations behind a patients metastatic tumor population, and identified that unlike the patients primary tumor, the metastasis had both alleles of the TGFBR2 gene mutated. To further assess the role of TGFBR2 in the metastasis, the investigators created organoids where TGFBR2 expression is knocked down, through which they were able to demonstrate that reduced TGFBR2 activity leads to invasion and metastasis of cancerous tumors both in vitro and in vivo. | 1 | Applied and Interdisciplinary Chemistry |
There are many types of coupled transition such as are observed in vibration–rotation spectra. The excited-state wave function is the product of two wave functions such as vibrational and rotational. The general principle is that the symmetry of the excited state is obtained as the direct product of the symmetries of the component wave functions. In rovibronic transitions, the excited states involve three wave functions.
The infrared spectrum of hydrogen chloride gas shows rotational fine structure superimposed on the vibrational spectrum. This is typical of the infrared spectra of heteronuclear diatomic molecules. It shows the so-called P and R branches. The Q branch, located at the vibration frequency, is absent. Symmetric top molecules display the Q branch. This follows from the application of selection rules.
Resonance Raman spectroscopy involves a kind of vibronic coupling. It results in much-increased intensity of fundamental and overtone transitions as the vibrations "steal" intensity from an allowed electronic transition. In spite of appearances, the selection rules are the same as in Raman spectroscopy. | 0 | Theoretical and Fundamental Chemistry |
* 1802 – Gay-Lussac first published the law that at constant pressure, the volume of any gas increases in proportion to its absolute temperature. Since in his paper announcing the law he cited earlier unpublished work on this subject by Jacques Charles, the law is usually called Charless Law, though some sources use the expression Gay-Lussacs Law. This law was independently and nearly simultaneously stated by John Dalton.
* 1804 – He and Jean-Baptiste Biot made a hydrogen-balloon ascent; a second ascent the same year by Gay-Lussac alone attained a height of in an early investigation of the Earth's atmosphere. He wanted to collect air samples at different heights to record differences in temperature and moisture.
* 1805 – Together with his friend and scientific collaborator Alexander von Humboldt, he discovered that the composition of the atmosphere does not change with decreasing pressure (increasing altitude). They also discovered that water is formed by two parts of hydrogen and one part of oxygen (by volume).
* 1808 – He was the co-discoverer of boron.
* 1808 – Discovery and announcement of the law of combining volumes of gases; published in 1809.
* 1810 – In collaboration with Louis Jacques Thénard, he developed a method for quantitative elemental organic combustion analysis by measuring the CO and HO evolved when an organic compound is fully oxidized by potassium chlorate. He also summarised the equation of alcoholic fermentation.
* 1811 – He recognized iodine as a new element, described its properties, and suggested the name iode.
* 1815 – He synthesized cyanogen, determined its empirical formula, and named it.
* 1824 – He developed an improved version of the burette that included a side arm, and coined the terms "pipette" and "burette" in an 1824 paper about the standardization of indigo solutions. | 1 | Applied and Interdisciplinary Chemistry |
In anhydrous rubidium rhodizonate , the rhodizonate anions are stacked in parallel columns, as are the rubidium ions. In the plane perpendicular to the columns, these are arranged as two interleaved hexagonal grids. The anions are planar.
Anhydrous potassium rhodizonate has a distinct but similar structure. The anions and cations are arranged in alternate planes. Within each plane, the anions are arranged in a hexagonal grid. Each potassium ion is arranged so that it connects symmetrically to eight oxygens of four anions, two from each adjacent plane. The anions are slightly twisted in the "boat" shape (with 0.108 Å of rms deviation from mean plane). Sodium rhodizonate has the same structure, with slightly more distorted anions (0.113 Å rms)
In solution, the rhodizonate anion is not hydrated. | 0 | Theoretical and Fundamental Chemistry |
The Historical Metallurgy Society is a British learned society providing an international forum for exchange of information and research in historical metallurgy. It was founded as the Historical Metallurgy Group in 1963. All aspects of the history of metals and associated materials are covered from prehistory to the present, from processes and production through technology and economics to archaeology and conservation.
The Historical Metallurgy Society origins were partly a response to the damage and destruction of many historically important metallurgical sites. Conservation, research and protection remain important parts of the society’s role.
Each year the society holds a two-day conference (usually in the United Kingdom) with a program of papers covering a particular area of metallurgical interest. In addition to this, it also runs other day meetings.
The Historical Metallurgy Society publishes Historical Metallurgy an internationally recognised peer-reviewed journal, published annually in two parts. The society also issues a newsletter The Crucible three times a year, and has published edited collections based on the papers given at several of its conferences in an Occasional Papers series.
The Historical Metallurgy Society is a company limited by guarantee (no. 1442508) and a registered charity (no. 279314). | 1 | Applied and Interdisciplinary Chemistry |
Trace fossils are important paleoecological and paleoenvironmental indicators, because they are preserved in situ, or in the life position of the organism that made them. Because identical fossils can be created by a range of different organisms, trace fossils can only reliably inform us of two things: the consistency of the sediment at the time of its deposition, and the energy level of the depositional environment. Attempts to deduce such traits as whether a deposit is marine or non-marine have been made, but shown to be unreliable. | 1 | Applied and Interdisciplinary Chemistry |
Platelet-derived growth factor receptors (PDGF-R) are cell surface tyrosine kinase receptors for members of the platelet-derived growth factor (PDGF) family. PDGF subunits -A and -B are important factors regulating cell proliferation, cellular differentiation, cell growth, development and many diseases including cancer. There are two forms of the PDGF-R, alpha and beta each encoded by a different gene. Depending on which growth factor is bound, PDGF-R homo- or heterodimerizes. | 1 | Applied and Interdisciplinary Chemistry |
Ocean gyres typically contain 5–6 trophic levels. The limiting factor for the number of trophic levels is the size of the phytoplankton, which are generally small in nutrient limited gyres. In low oxygen zones, oligotrophs are a large percentage of the phytoplankton.
At the intermediate level, small fishes and squid (especially ommastrephidae) dominate the nektonic biomass. They are important for the transport of energy from low trophic levels to high trophic levels. In some gyres, ommastrephidae are a major part of many animals' diets and can support the existence of large marine life. | 1 | Applied and Interdisciplinary Chemistry |
Micellar electrokinetic chromatography (MEKC) is a chromatography technique used in analytical chemistry. It is a modification of capillary electrophoresis (CE), extending its functionality to neutral analytes, where the samples are separated by differential partitioning between micelles (pseudo-stationary phase) and a surrounding aqueous buffer solution (mobile phase).
The basic set-up and detection methods used for MEKC are the same as those used in CE. The difference is that the solution contains a surfactant at a concentration that is greater than the critical micelle concentration (CMC). Above this concentration, surfactant monomers are in equilibrium with micelles.
In most applications, MEKC is performed in open capillaries under alkaline conditions to generate a strong electroosmotic flow. Sodium dodecyl sulfate (SDS) is the most commonly used surfactant in MEKC applications. The anionic character of the sulfate groups of SDS causes the surfactant and micelles to have electrophoretic mobility that is counter to the direction of the strong electroosmotic flow. As a result, the surfactant monomers and micelles migrate quite slowly, though their net movement is still toward the cathode. During a MEKC separation, analytes distribute themselves between the hydrophobic interior of the micelle and hydrophilic buffer solution as shown in figure 1.
Analytes that are insoluble in the interior of micelles should migrate at the electroosmotic flow velocity, , and be detected at the retention time of the buffer, . Analytes that solubilize completely within the micelles (analytes that are highly hydrophobic) should migrate at the micelle velocity, , and elute at the final elution time, . | 0 | Theoretical and Fundamental Chemistry |
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