text
stringlengths 105
4.57k
| label
int64 0
1
| label_text
stringclasses 2
values |
|---|---|---|
In molecular biology, extracellular signal-regulated kinases (ERKs) or classical MAP kinases are widely expressed protein kinase intracellular signalling molecules that are involved in functions including the regulation of meiosis, mitosis, and postmitotic functions in differentiated cells. Many different stimuli, including growth factors, cytokines, virus infection, ligands for heterotrimeric G protein-coupled receptors, transforming agents, and carcinogens, activate the ERK pathway.
The term, "extracellular signal-regulated kinases", is sometimes used as a synonym for mitogen-activated protein kinase (MAPK), but has more recently been adopted for a specific subset of the mammalian MAPK family.
In the MAPK/ERK pathway, Ras activates c-Raf, followed by mitogen-activated protein kinase kinase (abbreviated as MKK, MEK, or MAP2K) and then MAPK1/2 (below). Ras is typically activated by growth hormones through receptor tyrosine kinases and GRB2/SOS, but may also receive other signals. ERKs are known to activate many transcription factors, such as ELK1, and some downstream protein kinases.
Disruption of the ERK pathway is common in cancers, especially Ras, c-Raf, and receptors such as HER2. | 1 | Applied and Interdisciplinary Chemistry |
Palladium complexes containing chiral phosphinooxazolines have been shown to be efficient catalysts for the Heck reaction. High yields and good to excellent enantioselectivities have been obtained, with the formation of by-products via C=C bond migration being greatly reduced. Pd-PHOX catalysts have also been used for intramolecular Heck reactions and examples exist where they have been shown to be superior to more common ligands such as BINAP. | 0 | Theoretical and Fundamental Chemistry |
For blast furnaces, direct reduction corresponds to the reduction of oxides by the carbon in the coke. However, in practice, direct reduction only plays a significant role in the final stage of iron reduction in a blast furnace, by helping to reduce wustite (FeO) to iron. In this case, the chemical reaction can be trivially described as follows:
FeO + C → Fe + CO consuming 155,15 kJ/mol
However, "in the solid state, there is virtually no reaction in the absence of gases, even between finely ground iron ore and coal powders. In other words, it seems certain that the reaction takes place via gases". This means that direct reduction most probably corresponds to the following chain of reactions:
FeO + CO → Fe + CO producing 17,45 kJ/mol (reduction by CO)
CO + C ⇌ 2 CO consuming 172,45 kJ/mol (Boudouard reaction) | 1 | Applied and Interdisciplinary Chemistry |
Work has been completed to construct a small craft harbour with double lock to guarantee transit of a large number of fishing vessels when the gates are in operation.
The sea-side basin has been temporarily drained and sealed for use as a construction site to fabricate the gate housing structures, as for the Lido north inlet barrier.
Positioning for the gate housing structures was completed in October 2014.
In the inlet channel, the seabed in the area where the 18 gates will be installed has been reinforced.
Outside the inlet, a long curved breakwater has been completed. | 1 | Applied and Interdisciplinary Chemistry |
The Porous Plate Method is an accurate way to understand capillary pressure relationships in fluid-air systems. In this process, a sample saturated with water is placed on a flat plate, also saturated with water, inside a gas chamber. Gas is injected at increasing pressures, thus displacing the water through the plate. The pressure of the gas represents the capillary pressure, and the amount of water ejected from the porous plate is correlated to the water saturation of the sample. | 1 | Applied and Interdisciplinary Chemistry |
Observations at the site have led scientists to believe that the area was flooded with water a number of times and was subjected to evaporation and desiccation. In the process sulfates were deposited. After sulfates cemented the sediments, hematite concretions grew by precipitation from groundwater. Some sulfates formed into large crystals which later dissolved to leave vugs. Several lines of evidence point toward an arid climate in the past billion years or so, but a climate supporting water, at least for a time, in the distant past. | 0 | Theoretical and Fundamental Chemistry |
In pre-modern medicine, "diarrhodon" (Gr , "compound of roses", from , "of roses") is a name given to diverse compositions, in which red roses are an ingredient.
Diarrhodon abbatis is a cordial powder, denominated from the Abbot who invented it. It consists of red roses, red and citron santals, lignum aloes, cinnamon, rhapontic, spikenard, ivory, harts-horn, saffron, mastic, pearls, ambergris, musk, etc. It was used to strengthen the heart, stomach, and liver, and to assist in digestion, and prevent vomiting.
Philip Barrough, author of the first textbook on medicine published in English, gives this description and recipe for diarrhodon abbatis:
:"Electarium Diarrhodon Abbatis mitigateth the heate of the stomacke and midrife, and yet notwithstanding furthereth their concoction, aswageth paine, and dissipateth wind.
::"R. Rosarum rubrarum oz. 1 1/2. Santali albi & rubri, ana dr. 2 1/2. Tragacanthe, Gummi Arabici, Eboris vsti, ana scr. ii. Mastiches, Spicae nardi, Cardamomi, succi Glycyrrhizae, Croci, Xyloales, Caryophyllorum, Galliae Muschatae, Anisi, Foeniculi, sem. Ocymi, Acinorum Berberis, sem. Scariolae, Portulacae & papaueris albi, quatuor sem. frigido. maiorum, Rheubarbari electi, Cinamomi, ana scr. i. Margaritarum, ossis e corde cerui, ana scr. 1/2. Caphurae gr. viii. Moschi, gr. iiii. Make thereof tablets with eight times so much sugar dissolved in Rosewater."
There is also trochisci diarrhodon, composed of red roses, scrapings of ivory, santals, liquorice, mastic, saffron, camphor, and rosewater. They were used to fortify the heart, stomach, and liver, and to stop dissenteries, and other fluxes of the belly.
Pillulae diarrhodon are composed of aloes, trochisci diarrhodon, wormwood leaves, mastic, and rock salt. They were used to purge, then fortify the stomach, promote digestion, and prevent bad breath.
A recipe for the intoxicating liquor known as "damnable hum" contains diarrhodon:
:"Take Species de Gemmis, Aromaticum Rosatum, Diarrhodon Abbatis, Lætificans Galeni, of each four drams, Loaf-sugar beaten to powder half a pound, small Aqua Vitæ three Pints, strong Angelica water one pint; mix all these together, and when you have drunk it to the Dregs, you may fill it up again with the same quantity of water. The same powders will serve twice, and after twice using it, it must be made new again."
American writer Samuel Woodworth makes reference to the concoction in an 1811 New Years Address written for the news carrier of The Columbian', apparently in reference to an article that appeared in the newspaper:
:"The Diarrhodon" you have heard expose
:The latent beauties of a modern Rose,
:And smiled to see the lively writer roast
:The doughty champion of the Morning Post. | 1 | Applied and Interdisciplinary Chemistry |
Hydrogen bromide is the inorganic compound with the formula . It is a hydrogen halide consisting of hydrogen and bromine. A colorless gas, it dissolves in water, forming hydrobromic acid, which is saturated at 68.85% HBr by weight at room temperature. Aqueous solutions that are 47.6% HBr by mass form a constant-boiling azeotrope mixture that boils at . Boiling less concentrated solutions releases HO until the constant-boiling mixture composition is reached.
Hydrogen bromide, and its aqueous solution, hydrobromic acid, are commonly used reagents in the preparation of bromide compounds. | 0 | Theoretical and Fundamental Chemistry |
The Fe-only hydrogenases are particularly common enzymes for synthetic organometallic chemists to mimic. This interest is motivated by the inclusion of high field ligands like cyano and CO (metal carbonyl) in the first coordination sphere of the pertinent di-iron cluster. Free cyano and carbonyl ligands are toxic to many biological systems. So, their inclusion in this system suggests they play pivotal roles. These high field ligands may ensure the iron centers at the active site remain in a low spin state throughout the catalytic cycle. In addition, there is bridging dithiolate between the two iron centers. This dithiolate has a three atom backbone in which the identity of the central atom is still undetermined; it models crystallographically as a CH, NH or O group. There is reason to believe that this central atom is an amine which functions as a Lewis base. This amine combined with Lewis acidic iron centers makes the enzyme a bifunctional catalyst which can split hydrogen between a proton acceptor and a hydride acceptor or produce hydrogen from a proton and hydride.
Since none of the ligands on the iron centers are part of the enzyme's amino acid backbone, they can not be investigated through site-directed mutagenesis, but enzyme mimicry is a feasible approach. | 1 | Applied and Interdisciplinary Chemistry |
Macrocycles are very useful in supramolecular chemistry, as they provide whole cavities that can completely surround guest molecules and may be chemically modified to fine-tune their properties.
*Cyclodextrins, calixarenes, cucurbiturils and crown ethers are readily synthesized in large quantities, and are therefore convenient for use in supramolecular systems.
*More complex cyclophanes, and cryptands can be synthesised to provide more tailored recognition properties.
*Supramolecular metallocycles are macrocyclic aggregates with metal ions in the ring, often formed from angular and linear modules. Common metallocycle shapes in these types of applications include triangles, squares, and pentagons, each bearing functional groups that connect the pieces via "self-assembly."
*Metallacrowns are metallomacrocycles generated via a similar self-assembly approach from fused chelate-rings. | 0 | Theoretical and Fundamental Chemistry |
Meitner's earliest research began at age eight, when she kept a notebook of her records underneath her pillow. She was particularly drawn to mathematics and science, and first studied colours of an oil slick, thin films, and reflected light. Women were not allowed to attend public institutions of higher education in Vienna until 1897, and she completed her final year of school in 1892. Her education included bookkeeping, arithmetic, history, geography, science, French and gymnastics.
The only career available to women was teaching, so she trained as a French teacher. Her sister Gisela passed the Matura, and entered medical school in 1900. In 1899, Meitner began taking private lessons with two other young women, cramming the missing eight years of secondary education into just two. Physics was taught by Arthur Szarvasy. In July 1901, the girls sat an external examination at the Akademisches Gymnasium. Only four out of fourteen girls passed, including Meitner and Henriette Boltzmann, the daughter of physicist Ludwig Boltzmann.
Meitner entered the University of Vienna in October 1901. She was particularly inspired by Boltzmann, and was said to often speak with contagious enthusiasm of his lectures. Her dissertation was supervised by Franz Exner and his assistant Hans Benndorf. Her thesis, titled ("Examination of a Maxwell Formula"), was submitted on 20 November 1905 and approved on 28 November. She was examined orally by Exner and Boltzmann on 19 December, and her doctorate was awarded on 1 February 1906. She became the second woman to earn a doctoral degree in physics at the University of Vienna, after Olga Steindler who had received her degree in 1903; the third was Selma Freud, who worked in the same laboratory as Meitner, and received her doctorate later in 1906. Meitner's thesis was published as ("Thermal Conduction in Inhomogeneous Bodies") on 22 February 1906.
Paul Ehrenfest asked her to investigate an article on optics by Lord Rayleigh that detailed an experiment that produced results that Rayleigh had been unable to explain. She was not only able to explain what was going on; she went further and made predictions based on her explanation, and then verified them experimentally, demonstrating her ability to carry out independent and unsupervised research.
While engaged in this research, Meitner was introduced by Stefan Meyer to radioactivity, then a very new field of study. She started with alpha particles. In her experiments with collimators and metal foil, she found that scattering in a beam of alpha particles increased with the atomic mass of the metal atoms. Later on, this led Ernest Rutherford to predict the nuclear atom. She submitted her findings to the Physikalische Zeitschrift on 29 June 1907. | 1 | Applied and Interdisciplinary Chemistry |
Plumbides can be formed when lead forms a Zintl phase compound with a more metallic element. One salt that can be formed this way is when cryptand reacts with sodium and lead in ethylenediamine (en) to produce [Pb], which is red in solution.
Lead can also create anions with tin, in a series of anions with the formula [SnPb].
Lead can also form the [Pb] anion, which is emerald green in solution. | 0 | Theoretical and Fundamental Chemistry |
Global steel production grew enormously in the 20th century from a mere 28 million tonnes at the beginning of the century to 781 million tons at the end. Per-capita steel consumption in the US peaked in 1977, then fell by half before staging a modest recovery to levels well below the peak. | 1 | Applied and Interdisciplinary Chemistry |
Studies of ephaptic coupling have also focused on its role in the synchronization and timing of action potentials in neurons. In the simpler case of adjacent fibers that experience simultaneous stimulation the impulse is slowed because both fibers are limited to exchange ions solely with the interstitial fluid (increasing the resistance of the nerve). Slightly offset impulses (conduction velocities differing by less than 10%) are able to exchange ions constructively and the action potentials propagate slightly out of phase at the same velocity.
More recent research, however, has focused on the more general case of electric fields that affect a variety of neurons. It has been observed that local field potentials in cortical neurons can serve to synchronize neuronal activity. Although the mechanism is unknown, it is hypothesized that neurons are ephaptically coupled to the frequencies of the local field potential. This coupling may effectively synchronize neurons into periods of enhanced excitability (or depression) and allow for specific patterns of action potential timing (often referred to as spike timing). This effect has been demonstrated and modeled in a variety of cases.
A hypothesis or explanation behind the mechanism is "one-way", "master-slave", or "unidirectional synchronization" effect as mathematical and fundamental property of non-linear dynamic systems (oscillators like neurons) to synchronize under certain criteria. Such phenomenon was proposed and predicted to be possible between two HR neurons, since 2010 in simulations and modeling work by Hrg. It was also shown that such unidirectional synchronization or copy/paste transfer of neural dynamics from master to slave neurons, could be exhibited in different ways. Hence the phenomenon is of not only fundamental interest but also applied one from treating epilepsy to novel learning systems. A study in July 2023 found that mathematical models of ephaptic coupling predicted in vivo data of neural activity. The authors likened the electric field to a conductor of an orchestra and neurons to the musicians. Then the field,like the conductor, listens to the music and guides the musicians accordingly. In an opinion paper, they also suggested that not only neurons but other parts of the cytoskeleton generate electromagnetic fields that influence individual neurons, and called this cytoelectric coupling. Synchronization of neurons is in principle unwanted behavior, as brain would have zero information or be simply a bulb if all neurons would synchronize. Hence it is a hypothesis that neurobiology and evolution of brain coped with ways of preventing such synchronous behavior on large scale, using it rather in other special cases.
As models of brain function using only neuronal and gap junction connections fail to explain its complexity, ephaptic coupling is being added more to the equation to try and explain the isopotentiality of cortical astrocytes to maintain the bioelectromagnetic crosstalk between neurons and astrocytes in the neocortex. | 1 | Applied and Interdisciplinary Chemistry |
Reaction systems that are less efficient or entirely inactive in the absence of carboxylate acids and bases are likely to occur through a concerted metalation protonation reaction pathway. An example of such a reaction with an sp C–H bond that was reported in 2007 by Keith Fagnou and coworkers is an intramolecular cyclization that uses a palladium catalyst.
A notable example of a reaction that is catalyzed by ruthenium in which directed metalation occurs through CMD was reported by Igor Larossa and coworkers in 2018. The ruthenium catalyst is functional group tolerant and enables the late stage synthesis of pharmaceutically relevant biaryls. | 0 | Theoretical and Fundamental Chemistry |
A solution of methyl(cyano)cuprate (Solution A) was prepared as follows: to a suspension of 0.35 g (3.91 mmol) of copper(I) cyanide in 5 mL of tetrahydrofuran under argon at 0° was added dropwise over about 5 minutes 2.76 mL of a solution of methyllithium in ethyl ether (1.4 M, 3.86 mmol). The colorless solution was stirred for 10 minutes at 0°, warmed to 25° over 30 minutes, then cooled again to 0°. Separately, a solution of the lithium salt of (±)-cis-4-benzyloxy-2,3-epoxy-1-butanol (Solution B) was prepared as follows: to a solution of 0.5 g (2.58 mmol) of the epoxy alcohol and 0.90 g (21.4 mmol) of lithium chloride in 10 mL of tetrahydrofuran under argon at −78° was added dropwise 1.65 mL of a solution of n-butyllithium in hexane (1.56 M, 2.58 mmol). The solution was stirred for 5 minutes at −78°, allowed to warm to 0°, and then stirred at that temperature for 10 minutes. The reaction was effected by the addition of Solution A to Solution B via cannula at 0° followed by warming to room temperature over 2 hours. The reaction mixture was then stirred for a further 12 hours and then cautiously treated with 5 mL of saturated aqueous ammonium chloride. The mixture was stirred for 1–2 hours to aid removal of copper residues. Ethyl ether (20 mL) was then added, and the organic layer was separated. The aqueous phase was extracted twice with 20 mL of ethyl ether, and the combined organic phases were dried over magnesium sulfate, filtered, and concentrated to give 0.51 g of the product as a colorless oil (95%), IR (film) 3400, 3100, 3060, 3030, 2970, 2930, 2870, 1600, 1500, 1465, 1445, 1385, 1370, 1320, 1285, 1210, 1180, 1120, 1100, 1075, 1030, 1020, 980, 905, 830, 750, 730, 710, 695 cm–1; 1H NMR (CDCl) δ 0.90 (t, J = 6.0 Hz, 3 H), 1.37–1.53 (m, 2 H), 3.20 (br s, 2 H), 3.40–3.65 (m, 4 H), 4.48 (s, 2 H), 7.29 (s, 5 H). | 0 | Theoretical and Fundamental Chemistry |
A special type of hypervalent molecules is hypervalent hydrides. Most known hypervalent molecules contain substituents more electronegative than their central atoms. Hypervalent hydrides are of special interest because hydrogen is usually less electronegative than the central atom. A number of computational studies have been performed on chalcogen hydrides and pnictogen hydrides. Recently, a new computational study has showed that most hypervalent halogen hydrides XH can exist. It is suggested that IH and IH are stable enough to be observable or, possibly, even isolable. | 0 | Theoretical and Fundamental Chemistry |
The wetted perimeter is the perimeter of the cross sectional area that is "wet". The length of line of the intersection of channel wetted surface with a cross sectional plane normal to the flow direction. The term wetted perimeter is common in civil engineering, environmental engineering, hydrology, geomorphology, and heat transfer applications; it is associated with the hydraulic diameter or hydraulic radius. Engineers commonly cite the cross sectional area of a river.
The wetted perimeter can be defined mathematically as
where l is the length of each surface in contact with the aqueous body.
In open channel flow, the wetted perimeter is defined as the surface of the channel bottom and sides in direct contact with the aqueous body. Friction losses typically increase with an increasing wetted perimeter, resulting in a decrease in head. In a practical experiment, one is able to measure the wetted perimeter with a tape measure weighted down to the river bed to get a more accurate measurement.
When a channel is much wider than it is deep, the wetted perimeter approximates the channel width. | 1 | Applied and Interdisciplinary Chemistry |
An important feature that has enabled the broad application of SPPS is the generation of extremely high yields in the coupling step. Highly efficient amide bond-formation conditions are required. To illustrate the impact of suboptimal coupling yields for a given synthesis, consider the case where each coupling step were to have at least 99% yield: this would result in a 77% overall crude yield for a 26-amino acid peptide (assuming 100% yield in each deprotection); if each coupling were 95% efficient, the overall yield would be 25%. and adding an excess of each amino acid (between 2- and 10-fold). The minimization of amino acid racemization during coupling is also of vital importance to avoid epimerization in the final peptide product.
Amide bond formation between an amine and carboxylic acid is slow, and as such usually requires coupling reagents or activators. A wide range of coupling reagents exist, due in part to their varying effectiveness for particular couplings, many of these reagents are commercially available. | 1 | Applied and Interdisciplinary Chemistry |
The Institute for Safe Medication Practices (ISMP) is an American 501(c)(3) organization focusing on the prevention of medication errors and promoting safe medication practices. It is affiliated with ECRI. | 1 | Applied and Interdisciplinary Chemistry |
E. coli use fermentation pathways as a final option for energy metabolism, as they produce very little energy in comparison to respiration.
Mixed acid fermentation in E. coli occurs in two stages. These stages are outlined by the biological database for E. coli, EcoCyc.
The first of these two stages is a glycolysis reaction. Under anaerobic conditions, a glycolysis reaction takes place where glucose is converted into pyruvate:
glucose → 2 pyruvate
There is a net production of 2 ATP and 2 NADH molecules per molecule of glucose converted. ATP is generated by substrate-level phosphorylation. NADH is formed from the reduction of NAD.
In the second stage, pyruvate produced by glycolysis is converted to one or more end products via the following reactions. In each case, both of the NADH molecules generated by glycolysis are reoxidized to NAD. Each alternative pathway requires a different key enzyme in E. coli. After the variable amounts of different end products are formed by these pathways, they are secreted from the cell. | 1 | Applied and Interdisciplinary Chemistry |
Green bridges are an ecotechnological in-situ bio remediation system. Their different physical and biological filters work in combination to remove suspended and dissolved impurities of water. Green bridge filters help in reducing the suspended solids by filtration process, reducing Chemical Oxygen Demand (COD)/Biochemical Oxygen Demand (BOD) by aerobic degradation. Green Bridges also help in the restoration of ecological food chain. | 1 | Applied and Interdisciplinary Chemistry |
According to one vendor, depressants "increase the efficiency of the flotation process by selectively inhibiting the interaction of one mineral with the collector." Thus a typical pulverized ore sample consists of many components, of which only one or a few are targets for the collector. Depressants bind to these other components, lest the collector be wasted by doing so. Depressants are selected for particular ores. Typical depressants are starch, polyphenols, lye, and lime. They are cheap, and oxygen-rich typically. | 1 | Applied and Interdisciplinary Chemistry |
In a common application, potassium thioacetate is combined with alkylating agents to give thioacetate esters (X = halide):
Hydrolysis of these esters affords thiols:
The thioacetate esters can also be cleaved with methanethiol in the presence of stoichiometric base, as illustrated in the preparation of pent-4-yne-1-thiol: | 0 | Theoretical and Fundamental Chemistry |
When two fluorine atoms are in vicinal (i.e., adjacent) carbons, as in 1,2-difluoroethane (HFCCFH), the gauche conformer is more stable than the anti conformer—this is the opposite of what would normally be expected and to what is observed for most 1,2-disubstituted ethanes; this phenomenon is known as the gauche effect. In 1,2-difluoroethane, the gauche conformation is more stable than the anti conformation by 2.4 to 3.4 kJ/mole in the gas phase. This effect is not unique to the halogen fluorine, however; the gauche effect is also observed for 1,2-dimethoxyethane. A related effect is the alkene cis effect. For instance, the cis isomer of 1,2-difluoroethylene is more stable than the trans isomer.
There are two main explanations for the gauche effect: hyperconjugation and bent bonds. In the hyperconjugation model, the donation of electron density from the carbon–hydrogen σ bonding orbital to the carbon–fluorine σ antibonding orbital is considered the source of stabilization in the gauche isomer. Due to the greater electronegativity of fluorine, the carbon–hydrogen σ orbital is a better electron donor than the carbon–fluorine σ orbital, while the carbon–fluorine σ orbital is a better electron acceptor than the carbon–hydrogen σ orbital. Only the gauche conformation allows good overlap between the better donor and the better acceptor.
Key in the bent bond explanation of the gauche effect in difluoroethane is the increased p orbital character of both carbon–fluorine bonds due to the large electronegativity of fluorine. As a result, electron density builds up above and below to the left and right of the central carbon–carbon bond. The resulting reduced orbital overlap can be partially compensated when a gauche conformation is assumed, forming a bent bond. Of these two models, hyperconjugation is generally considered the principal cause behind the gauche effect in difluoroethane. | 0 | Theoretical and Fundamental Chemistry |
The fraction collector is typically a rotating rack that can be filled with test tubes or similar containers. It allows samples to be collected in fixed volumes, or can be controlled to direct specific fractions detected as peaks of protein concentration, into separate containers.
Many systems include various optional components. A filter may be added between the mixer and column to minimize clogging. In large FPLC columns the sample may be loaded into the column directly using a small peristaltic pump rather than an injection loop. When the buffer contains dissolved gas, bubbles may form as pressure drops where the buffer exits the column; these bubbles create artifacts if they pass through the flow cells. This may be prevented by degassing the buffers, e.g. with a degasser, or by adding a flow restrictor downstream of the flow cells to maintain a pressure of 1-5 bar in the eluant line. | 0 | Theoretical and Fundamental Chemistry |
In 2010, CDP was called "The most powerful green NGO you've never heard of" by the Harvard Business Review. In 2012 it won the Zayed Future Energy Prize. | 1 | Applied and Interdisciplinary Chemistry |
In thermodynamics, an apparent molar property of a solution component in a mixture or solution is a quantity defined with the purpose of isolating the contribution of each component to the non-ideality of the mixture. It shows the change in the corresponding solution property (for example, volume) per mole of that component added, when all of that component is added to the solution. It is described as apparent because it appears to represent the molar property of that component in solution, provided that the properties of the other solution components are assumed to remain constant during the addition. However this assumption is often not justified, since the values of apparent molar properties of a component may be quite different from its molar properties in the pure state.
For instance, the volume of a solution containing two components identified as solvent and solute is given by
where is the volume of the pure solvent before adding the solute and its molar volume (at the same temperature and pressure as the solution), is the number of moles of solvent, is the apparent molar volume of the solute, and is the number of moles of the solute in the solution. By dividing this relation to the molar amount of one component a relation between the apparent molar property of a component and the mixing ratio of components can be obtained.
This equation serves as the definition of . The first term is equal to the volume of the same quantity of solvent with no solute, and the second term is the change of volume on addition of the solute. may then be considered as the molar volume of the solute if it is assumed that the molar volume of the solvent is unchanged by the addition of solute. However this assumption must often be considered unrealistic as shown in the examples below, so that
is described only as an apparent value.
An apparent molar quantity can be similarly defined for the component identified as solvent . Some authors have reported apparent molar volumes of both (liquid) components of the same solution. This procedure can be extended to ternary and multicomponent mixtures.
Apparent quantities can also be expressed using mass instead of number of moles. This expression produces apparent specific quantities, like the apparent specific volume.
where the specific quantities are denoted with small letters.
Apparent (molar) properties are not constants (even at a given temperature), but are functions of the composition. At infinite dilution, an apparent molar property and the corresponding partial molar property become equal.
Some apparent molar properties that are commonly used are apparent molar enthalpy, apparent molar heat capacity, and apparent molar volume. | 0 | Theoretical and Fundamental Chemistry |
The main theory that describes the rates of outer sphere electron transfer was developed by Rudolph A. Marcus in the 1950s. A major aspect of Marcus theory is the dependence of the electron transfer rate on the thermodynamic driving force (difference in the redox potentials of the electron-exchanging sites). For most reactions, the rates increase with increased driving force. A second aspect is that the rate of outer sphere electron-transfer depends inversely on the "reorganizational energy." Reorganization energy describes the changes in bond lengths and angles that are required for the oxidant and reductant to switch their oxidation states. This energy is assessed by measurements of the self-exchange rates (see below).
Outer sphere electron transfer is the most common type of electron transfer, especially in biochemistry, where redox centers are separated by several (up to about 11) angstroms by intervening protein. In biochemistry, there are two main types of outer sphere ET: ET between two biological molecules or fixed distance electron transfer, in which the electron transfers within a single biomolecule (e.g., intraprotein). | 0 | Theoretical and Fundamental Chemistry |
Chiral Lewis acids have proven useful in the ene reaction. When catalyzed by an achiral Lewis acid, the reaction normally provides good diastereoselectivity.
Good enantioselectivity has been observed when a chiral Lewis acid catalyst is used.
The enantioselectivity is believed to be due to the steric interactions between the methyl and phenyl group, which makes the transition structure of the iso product considerably more favorable. | 0 | Theoretical and Fundamental Chemistry |
Carboamination is an efficient method to access nitrogen-containing molecules, especially N-heterocycles. (+)-Preussin, a pyrrolidine alkaloid, can be easily prepared via this methodology.
(–)-Tylophorine is another example, which can be synthesized using carboamination reaction. | 0 | Theoretical and Fundamental Chemistry |
A biofilm is a community of microorganisms adsorbed to a surface. Microorganisms in biofilms are enclosed in a polymeric matrix consisting of exopolysaccharides, extracellular DNA and proteins. Seconds after a surface (usually metal) is placed in a solution, inorganic and organic molecules adsorb onto the surface. These molecules are attracted mainly by Coulombic forces (see above section), and can adhere very strongly to the surface. This first layer is called the conditioning layer, and is necessary for the microorganisms to bind to the surface. These microorganisms then attach reversibly by Van der Waals forces, followed by irreversible adhesion through self-produced attachment structures such as pili or flagella. Biofilms form on solid substrates such as stainless steel. A biofilm's enclosing polymeric matrix offers protection to its microbes, increasing their resistance to detergents and cleaning agents. Biofilms on food processing surfaces can be a biological hazard to food safety. Increased chemical resistance in biofilms can lead to a persistent contamination condition. | 1 | Applied and Interdisciplinary Chemistry |
The lake is mostly underlain by a mix of volcanic and plutonic igneous rock. Most of it is the same Archean basalt greenstone belt that predominates in the Yellowknife area. Running through the central portion from north northeast, under the heritage centre and Legislative Assembly building, to south southwest is a narrow belt of dacite flanked by two gabbro sills (one of which forms the largest island), with some more dacite under the visitors centre and the southern of the two points of the western peninsula. Small diabase dykes run through various portions of the bedrock, with the largest forming the elevated area at the lakes southeast corner. Quartz intrusions are visible in some areas.
Two local faults run across the south end of the lake. The stream from Robinson's Pond runs along the Pud Fault, which continues across the lakebed to McNiven Beach. At the south end is the larger Kam Fault, which when it was active had the same potential for earthquakes as the San Andreas Fault in the U.S. state of California. It divides the basalt from an area of lighter granite and granodiorite between the lake and the hospital.
There are also visible signs of the lakes glacial origins. Just south of Somba Ke Park on the east shore, the rock has striations and scour marks in the northeast-to-southwest direction of the glaciers' advance. The fine sand on the lake bed is also glacial residue. In some areas around the lake edge, the ground is underlain by permafrost at an average depth of .
Where soil exists around the lake, it is mostly silt and clay as opposed to the sand of neighboring New Town. It does not support buildings well, nor does it give way to bedrock at a uniform depth. The military building and visitor's centre both encountered construction difficulties due to this. | 1 | Applied and Interdisciplinary Chemistry |
The northern and southern hemispheres have atmospheric circulation systems that are sufficiently independent of each other that there is a noticeable time lag in mixing between the two. The atmospheric / ratio is lower in the southern hemisphere, with an apparent additional age of about 40 years for radiocarbon results from the south as compared to the north. This is because the greater surface area of ocean in the southern hemisphere means that there is more carbon exchanged between the ocean and the atmosphere than in the north. Since the surface ocean is depleted in because of the marine effect, is removed from the southern atmosphere more quickly than in the north. The effect is strengthened by strong upwelling around Antarctica. | 0 | Theoretical and Fundamental Chemistry |
η-bonding is the most common motif seen in coordination chemistry of dioxygen. Such complexes can be generated by treating low-valent metal complexes with oxygen. For example, Vaska's complex reversibly binds O (Ph = CH):
:IrCl(CO)(PPh) + O IrCl(CO)(PPh)O
The conversion is described as a 2 e redox process: Ir(I) converts to Ir(III) as dioxygen converts to peroxide. Since O has a triplet ground state and Vaskas complex is a singlet, the reaction is slower than when singlet oxygen is used. The magnetic properties of some η'-O complexes show that the ligand, in fact, is superoxide, not peroxide.
Most complexes of η-O are generated using hydrogen peroxide, not from O. Chromate ([CrO)]) can for example be converted to the tetraperoxide [Cr(O)]. The reaction of hydrogen peroxide with aqueous titanium(IV) gives a brightly colored peroxy complex that is a useful test for titanium as well as hydrogen peroxide. | 0 | Theoretical and Fundamental Chemistry |
The melanocortin system is one of the mammalian body's tools to regulate food intake in a push-pull fashion. The only neurons known to release melanocortins are located in the arcuate nucleus of the hypothalamus. However, [https://www.jidonline.org/article/S0022-202X(15)50783-5/pdf melanocortins are also produced by keratinocytes] in response to UV exposure. Accordingly, there is a subpopulation called POMC neurons and one called AgRP neurons. When POMC neurons release α-MSH, appetite is decreased. On the other hand, when AgRP neurons release AgRP, appetite is stimulated.
Leptin, the energy surfeit hormone, and Ghrelin, the hunger hormone, are upstream regulators of the melanocortin system in the brain. These hormones also regulate the release of peptides other than the melanocortins. Disturbance of the leptin-melanocortin pathway can lead to early onset obesity as well as various metabolic disorders and suppressed immune function. | 1 | Applied and Interdisciplinary Chemistry |
A method for phenolic content quantification is volumetric titration. An oxidizing agent, permanganate, is used to oxidize known concentrations of a standard solution, producing a standard curve. The content of the unknown phenols is then expressed as equivalents of the appropriate standard.
Some methods for quantification of total phenolic content are based on colorimetric measurements. Total phenols (or antioxidant effect) can be measured using the Folin-Ciocalteu reaction. Results are typically expressed as gallic acid equivalents (GAE). Ferric chloride (FeCl) test is also a colorimetric assay.
Lamaison and Carnet have designed a test for the determination of the total flavonoid content of a sample (AlCI method). After proper mixing of the sample and the reagent, the mixture is incubated for 10 minutes at ambient temperature and the absorbance of the solution is read at 440 nm. Flavonoid content is expressed in mg/g of quercetin.
Quantitation results produced by the means of diode array detector-coupled HPLC are generally given as relative rather than absolute values as there is a lack of commercially available standards for every phenolic molecules. The technique can also be coupled with mass spectrometry (for example, HPLC–DAD–ESI/MS) for more precise molecule identification. | 0 | Theoretical and Fundamental Chemistry |
The Jameson Cell can be used for the reverse flotation of silica from iron ore, where flotation columns have traditionally been used. | 1 | Applied and Interdisciplinary Chemistry |
The reaction mechanism is not clearly understood, but the textbook mechanism revolves around a palladium cycle which is in agreement with the "classical" cross-coupling mechanism, and a copper cycle, which is less well known. | 0 | Theoretical and Fundamental Chemistry |
Sir Geoffrey Wilkinson FRS (14 July 1921 – 26 September 1996) was a Nobel laureate English chemist who pioneered inorganic chemistry and homogeneous transition metal catalysis. | 0 | Theoretical and Fundamental Chemistry |
During operation of an electrochemical cell, chemical energy is transformed into electrical energy. This can be expressed mathematically as the product of the cells emf E measured in volts (V) and the electric charge Q' transferred through the external circuit.
:Electrical energy = EQ
Q is the cell current integrated over time and measured in coulombs (C); it can also be determined by multiplying the total number n of electrons transferred (measured in moles) times Faradays constant (F').
The emf of the cell at zero current is the maximum possible emf. It can be used to calculate the maximum possible electrical energy that could be obtained from a chemical reaction. This energy is referred to as electrical work and is expressed by the following equation:
where work is defined as positive when it increases the energy of the system.
Since the free energy is the maximum amount of work that can be extracted from a system, one can write:
A positive cell potential gives a negative change in Gibbs free energy. This is consistent with the cell production of an electric current from the cathode to the anode through the external circuit. If the current is driven in the opposite direction by imposing an external potential, then work is done on the cell to drive electrolysis.
A spontaneous electrochemical reaction (change in Gibbs free energy less than zero) can be used to generate an electric current in electrochemical cells. This is the basis of all batteries and fuel cells. For example, gaseous oxygen (O) and
hydrogen (H) can be combined in a fuel cell to form water and energy, typically a combination of heat and electrical energy.
Conversely, non-spontaneous electrochemical reactions can be driven forward by the application of a current at sufficient voltage. The electrolysis of water into gaseous oxygen and hydrogen is a typical example.
The relation between the equilibrium constant, K, and the Gibbs free energy for an electrochemical cell is expressed as follows:
Rearranging to express the relation between standard potential and equilibrium constant yields
At T = 298 K, the previous equation can be rewritten using the Briggsian logarithm as follows: | 0 | Theoretical and Fundamental Chemistry |
Aluminium (or aluminum) metal is very rare in native form, and the process to refine it from ores is complex, so for most of human history it was unknown. However, the compound alum has been known since the 5th century BCE and was used extensively by the ancients for dyeing. During the Middle Ages, its use for dyeing made it a commodity of international commerce. Renaissance scientists believed that alum was a salt of a new earth; during the Age of Enlightenment, it was established that this earth, alumina, was an oxide of a new metal. Discovery of this metal was announced in 1825 by Danish physicist Hans Christian Ørsted, whose work was extended by German chemist Friedrich Wöhler.
Aluminium was difficult to refine and thus uncommon in actual use. Soon after its discovery, the price of aluminium exceeded that of gold. It was reduced only after the initiation of the first industrial production by French chemist Henri Étienne Sainte-Claire Deville in 1856. Aluminium became much more available to the public with the Hall–Héroult process developed independently by French engineer Paul Héroult and American engineer Charles Martin Hall in 1886, and the Bayer process developed by Austrian chemist Carl Joseph Bayer in 1889. These processes have been used for aluminium production up to the present.
The introduction of these methods for the mass production of aluminium led to extensive use of the light, corrosion-resistant metal in industry and everyday life. Aluminium began to be used in engineering and construction. In World Wars I and II, aluminium was a crucial strategic resource for aviation. World production of the metal grew from 6,800 metric tons in 1900 to 2,810,000 metric tons in 1954, when aluminium became the most produced non-ferrous metal, surpassing copper.
In the second half of the 20th century, aluminium gained usage in transportation and packaging. Aluminium production became a source of concern due to its effect on the environment, and aluminium recycling gained ground. The metal became an exchange commodity in the 1970s. Production began to shift from developed countries to developing ones; by 2010, China had accumulated an especially large share in both production and consumption of aluminium. World production continued to rise, reaching 58,500,000 metric tons in 2015. Aluminium production exceeds those of all other non-ferrous metals combined. | 1 | Applied and Interdisciplinary Chemistry |
In ecology, the term productivity refers to the rate of generation of biomass in an ecosystem, usually expressed in units of mass per volume (unit surface) per unit of time, such as grams per square metre per day (g m d). The unit of mass can relate to dry matter or to the mass of generated carbon. The productivity of autotrophs, such as plants, is called primary productivity, while the productivity of heterotrophs, such as animals, is called secondary productivity.
The productivity of an ecosystem is influenced by a wide range of factors, including nutrient availability, temperature, and water availability. Understanding ecological productivity is vital because it provides insights into how ecosystems function and the extent to which they can support life. Productivity is typically divided into two categories: primary and secondary productivity. | 0 | Theoretical and Fundamental Chemistry |
The teapot effect, also known as dribbling, is a fluid dynamics phenomenon that occurs when a liquid being poured from a container runs down the spout or the body of the vessel instead of flowing out in an arc.
Markus Reiner coined the term "teapot effect" in 1956 to describe the tendency of liquid to dribble down the side of a vessel while pouring. Reiner received his PhD at TU Wien in 1913 and made significant contributions to the development of the study of flow behavior known as rheology. Reiner believed the teapot effect could be explained by Bernoullis principle, which states that an increase in the speed of a fluid is always accompanied by a decrease in its pressure. When tea is poured from a teapot, the liquids speed increases as it flows through the narrowing spout. This decrease in pressure was what Reiner thought to cause the liquid to dribble down the side of the pot.
However, a 2021 study found the primary cause of the phenomenon to be an interaction of inertia and capillary forces. The study found that the smaller the angle between the container wall and the liquid surface, the more the teapot effect is slowed down. | 1 | Applied and Interdisciplinary Chemistry |
Many prior technologies exist for preparing wide-gap diamond for use in electronic devices or as a substrate for single-crystal diamond growth. The more stable forms of carbon have lower gaps and different crystal structures, and their presence must be carefully controlled. The Marchywka Effect has been characterised and compared to alternative means to create a desired surface for several applications.
Removal of non-diamond carbon with wet chemicals had been accomplished by boiling in mixtures of sulfuric and chromic acid. When applied to a diamond substrate with an ion implantation damage profile as may be used for basic science, crystal growth, or device fabrication, the electrochemical approach makes it easier to preserve the thin film of less damaged diamond lying above the implant range, and it has been used in annealing experiments to fix the diamond after implantation damage has occurred. In some cases, thermal cycling may be an issue and selectivity to various masks may be important, so the lower temperatures and more flexible chemistry may offer benefits over prior art.
The method does not require the use of non-volatile materials such as chrome, possibly reducing contamination problems in some applications. The ability to control the etching direction and speed with an applied voltage or electrode configuration, as with electrochemical machining, gives additional capabilities not available with isotropic chemical-only approaches. Dry processing methods such as hot oxygen or plasmas can also burn off the graphite faster than the diamond, as can a simple acetylene torch. These require higher temperatures and do not have the same high selectivity that can be achieved with the electrochemical approach.
Surface termination is often an issue with both solid state and vacuum devices, and the details of final surface band structure have been compared with alternatives in various device structures. | 0 | Theoretical and Fundamental Chemistry |
A static gas mass spectrometer is one in which a gaseous sample for analysis is fed into the source of the instrument and then left in the source without further supply or pumping throughout the analysis. This method can be used for stable isotope analysis of light gases (as above), but it is particularly used in the isotopic analysis of noble gases (rare or inert gases) for radiometric dating or isotope geochemistry. Important examples are argon–argon dating and helium isotope analysis. | 0 | Theoretical and Fundamental Chemistry |
EPA first listed MTBE in 1998 as a candidate for development of a national Maximum Contaminant Level (MCL) standard in drinking water. As of 2020 the agency has not announced whether it will develop an MCL. EPA uses toxicity data in developing MCLs for public water systems.
California established a state-level MCL for MTBE, 13 micrograms per liter, in 2000. | 1 | Applied and Interdisciplinary Chemistry |
AUFS is an arbitrary but ubiquitous unit of UV absorbance intensity. It can be used in chemical analysis to quantify components in a mixture, as each components' integrated peak area correspond to their relative abundance. | 0 | Theoretical and Fundamental Chemistry |
Autophagy modulators are one type of method to enhance host cell functions. Pathogens like Mycobacterium tuberculosis (MTB), will be degraded in the autophagosome during an effective host response that will clear the bacteria. Because bacteria and other pathogens like MTB can take over cellular responses like autophagy, they can increase their survival in the body. By reactivating effective autophagy processes the pathogen could be cleared. Examples of this has been shown with MTB, and Listeria monocytogenes. OSU-03012 is thought to modulate autophagy in its effect on Salmonella enterica, and Francisella tularensis. | 1 | Applied and Interdisciplinary Chemistry |
Native ironwork in the Northwest Coast has been found in places like the Ozette Indian Village Archeological Site, where iron chisels and knives were discovered. These artifacts seem to have been crafted around 1613, based on the dendrochronological analysis of associated pieces of wood in the site, and were made out of drift iron from Asian (specifically Japanese) shipwrecks, which were swept by the Kuroshio Current towards the coast of North America.
The tradition of working with Asian drift iron was well-developed in the Northwest before European contact, and was present among several native peoples from the region, including the Chinookan peoples and the Tlingit, who seem to have had their own specific word for the metallic material, which was transcribed by Frederica De Laguna as gayES. The wrecking of Japanese and Chinese vessels in the North Pacific basin was fairly common, and the iron tools and weaponry they carried provided the necessary materials for the development of the local ironwork traditions among the Northwestern Pacific Coast peoples,
although there were also other sources of iron, like that from meteorites, which was occasionally worked using stone anvils. | 1 | Applied and Interdisciplinary Chemistry |
4-Nitrophenol irritates the eyes, skin, and respiratory tract. It may also cause inflammation of those parts. It has a delayed interaction with blood and forms methaemoglobin which is responsible for methemoglobinemia, potentially causing cyanosis, confusion, and unconsciousness. When ingested, it causes abdominal pain and vomiting. Prolonged contact with skin may cause allergic response. Genotoxicity and carcinogenicity of 4-nitrophenol are not known. The in mice is 282 mg/kg and in rats is 202 mg/kg (p.o.). | 0 | Theoretical and Fundamental Chemistry |
Microarrays usually consist of a grid of short nucleotide oligomers, known as "probes", typically arranged on a glass slide. Transcript abundance is determined by hybridisation of fluorescently labelled transcripts to these probes. The fluorescence intensity at each probe location on the array indicates the transcript abundance for that probe sequence. Groups of probes designed to measure the same transcript (i.e., hybridizing a specific transcript in different positions) are usually referred to as "probesets".
Microarrays require some genomic knowledge from the organism of interest, for example, in the form of an annotated genome sequence, or a library of ESTs that can be used to generate the probes for the array. | 1 | Applied and Interdisciplinary Chemistry |
The most common method is alkaline lysis, which involves the use of a high concentration of a basic solution, such as sodium hydroxide, to lyse the bacterial cells. When bacteria are lysed under alkaline conditions (pH 12.0–12.5) both chromosomal DNA and protein are denatured; the plasmid DNA however, remains stable. Some scientists reduce the concentration of NaOH used to 0.1M in order to reduce the occurrence of ssDNA. After the addition of acetate-containing neutralization buffer to lower the pH to around 7, the large and less supercoiled chromosomal DNA and proteins form large complexes and precipitate; but the small bacterial DNA plasmids stay in solution. | 1 | Applied and Interdisciplinary Chemistry |
SIR3 is principally involved in heterochromatin spreading, the silencing activity of the SIR protein complex. When overexpressed, SIR3 leads to spreading beyond the normal nucleation site. SIR3 can continue to operate at very low levels of SIR2 and SIR4, but not without them. It preferentially binds to unmodified nucleosomes (no acetylation at H4K16 or methylation at H3K79), and relies on SIR2's deacetylation of H4K16 to enhance silencing. H3K79 methylation by DOT1 methyltransferase inhibits SIR3, resulting in an unsilenced chromatin region. SIR3 is recruited to target sequence by the transcription factors RAP1 or ABF1. | 1 | Applied and Interdisciplinary Chemistry |
Microthermometry is the process of reheating a melt inclusion to its original melt temperature and then rapidly quenching to form a homogenous glass phase free of daughter minerals or vapor bubbles that may have been originally contained within the melt inclusion. | 0 | Theoretical and Fundamental Chemistry |
Aldehydes are commonly generated by alcohol oxidation. Industry oxidizes methanol to formaldehyde on a large scale, and, in the Wacker process, ethylene to acetaldehyde in the presence of copper and palladium catalysts (acetaldehyde is also produced on a large scale by acetylene hydration). "Green" and cheap oxygen is the oxidant of choice. For sensitive substrates, Oppenauer transfer oxidation avoids overoxidation to a carboxylic acid. When a mixture of products may be acceptable, hydroformylation directly adds a carbonyl to a olefin.
Laboratories may instead apply a wide variety of specialized oxidizing agents; chromium(VI) reagents are popular. Oxidation can be achieved by heating the alcohol with an acidified solution of potassium dichromate. In this case, excess dichromate will further oxidize the aldehyde to a carboxylic acid, so either the aldehyde is distilled out as it forms (if volatile) or milder reagents such as PCC are used.
A variety of reagent systems achieve aldehydes under chromium-free conditions. One such are the hypervalent organoiodine compounds (i.e., IBX acid, Dess–Martin periodinane), although these often also oxidize the α position. A Lux-Flood acid will activate other pre-oxidized substrates: various sulfoxides (e.g. the Swern oxidation), or amine oxides (e.g., the Ganem oxidation). Sterically-hindered nitroxyls (i.e., TEMPO) can catalyze aldehyde formation with a cheaper oxidant.
Alternatively, vicinal diols or their oxidized sequelae (acyloins or α-hydroxy acids) can be oxidized with cleavage to two aldehydes or an aldehyde and carbon dioxide. | 0 | Theoretical and Fundamental Chemistry |
Non-viral methods present certain advantages over viral methods, with simple large scale production and low host immunogenicity being just two. Previously, low levels of transfection and expression of the gene held non-viral methods at a disadvantage; however, recent advances in vector technology have yielded molecules and techniques with transfection efficiencies similar to those of viruses. | 1 | Applied and Interdisciplinary Chemistry |
Many, but not all, diesel trains use only friction brakes (as do cars and trucks) to slow or stop the train. This wears the discs and pads, introducing particulates into the atmosphere. Electric trains predominantly use the motors in regeneration mode to slow the train, producing almost zero particulates. The technology does not yet exist to stop the train completely. Using this technology would improve the health of the nation but in particular for people who live closer to the railway. In addition, regenerative braking saves energy and is more efficient and thus helps the low-carbon economy. Diesel trains also generate soot and particulates from the engines, often clearly visible in the air. Electrification vastly reduces or even eliminates this problem, thus bringing cleaner and healthier air. | 1 | Applied and Interdisciplinary Chemistry |
Ruppeiner geometry is thermodynamic geometry (a type of information geometry) using the language of Riemannian geometry to study thermodynamics. George Ruppeiner proposed it in 1979. He claimed that thermodynamic systems can be represented by Riemannian geometry, and that statistical properties can be derived from the model.
This geometrical model is based on the inclusion of the theory of fluctuations into the axioms of equilibrium thermodynamics, namely, there exist equilibrium states which can be represented by points on two-dimensional surface (manifold) and the distance between these equilibrium states is related to the fluctuation between them. This concept is associated to probabilities, i.e. the less probable a fluctuation between states, the further apart they are. This can be recognized if one considers the metric tensor g in the distance formula (line element) between the two equilibrium states
where the matrix of coefficients g is the symmetric metric tensor which is called a Ruppeiner metric, defined as a negative Hessian of the entropy function
where U is the internal energy (mass) of the system and N refers to the extensive parameters of the system. Mathematically, the Ruppeiner geometry is one particular type of information geometry and it is similar to the Fisher-Rao metric used in mathematical statistics.
The Ruppeiner metric can be understood as the thermodynamic limit (large systems limit) of the more general Fisher information metric. For small systems (systems where fluctuations are large), the Ruppeiner metric may not exist, as second derivatives of the entropy are not guaranteed to be non-negative.
The Ruppeiner metric is conformally related to the Weinhold metric via
where T is the temperature of the system under consideration. Proof of the conformal relation can be easily done when one writes down the first law of thermodynamics (dU=TdS+...) in differential form with a few manipulations. The Weinhold geometry is also considered as a thermodynamic geometry. It is defined as a Hessian of the internal energy with respect to entropy and other extensive parameters.
It has long been observed that the Ruppeiner metric is flat for systems with noninteracting underlying statistical mechanics such as the ideal gas. Curvature singularities signal critical behaviors. In addition, it has been applied to a number of statistical systems including Van der Waals gas. Recently the anyon gas has been studied using this approach. | 0 | Theoretical and Fundamental Chemistry |
In fluid mechanics, Kelvins minimum energy theorem (named after William Thomson, 1st Baron Kelvin who published it in 1849) states that the steady irrotational motion of an incompressible fluid occupying a simply connected region has less kinetic energy than any other motion with the same normal component of velocity at the boundary (and, if the domain extends to infinity, with zero value values there)'. | 1 | Applied and Interdisciplinary Chemistry |
Full spectral imaging (FSI) is a form of imaging spectroscopy and is the successor to hyperspectral imaging. Full spectral imaging was developed to improve the capabilities of remote sensing including Earth remote sensing. | 0 | Theoretical and Fundamental Chemistry |
A sonic black hole, sometimes called a dumb hole or acoustic black hole, is a phenomenon in which phonons (sound perturbations) are unable to escape from a region of a fluid that is flowing more quickly than the local speed of sound. They are called sonic, or acoustic, black holes because these trapped phonons are analogous to light in astrophysical (gravitational) black holes. Physicists are interested in them because they have many properties similar to astrophysical black holes and, in particular, emit a phononic version of Hawking radiation. This Hawking radiation can be spontaneously created by quantum vacuum fluctuations, in close analogy with Hawking radiation from a real black hole. On the other hand, the Hawking radiation can be stimulated in a classical process. The boundary of a sonic black hole, at which the flow speed changes from being greater than the speed of sound to less than the speed of sound, is called the event horizon. | 1 | Applied and Interdisciplinary Chemistry |
Research on the cytotoxic and anticlastogenic activities of the cyclamen genus has been limited. In the 1950s and 1960s little research was done on the toxic saponin cyclamin, but no further investigation has recently been performed. Cyclamin, a triterpenoid pentasaccharidic saponin, has previously been extracted from different cyclamen species, including Cyclamen mirabile, Cyclamen trocopteranthum, Cyclamen libanoticum and Cylamen persicum. | 0 | Theoretical and Fundamental Chemistry |
Heart failure is one of the leading causes of death. In 2013, an estimate of 17.3 million deaths per year out of the 54 million total deaths was caused by cardiovascular diseases, meaning that 31.5% of the world's total death was caused by this. Often, the only viable treatment for end-stage heart failure is organ transplantation. Currently organ supply is insufficient to meet the demand, which presents a large limitation in an end-stage treatment plan. A theoretical alternative to traditional transplantation processes is the engineering of personalized bioartificial hearts. Researchers have had many successful advances in the engineering of cardiovascular tissue and have looked towards using decellularized and recellularized cadaveric hearts in order to create a functional organ. Decellularization-recellularization involves using a cadaveric heart, removing the cellular contents while maintaining the protein matrix (decellularization), and subsequently facilitating growth of appropriate cardiovascular tissue inside the remaining matrix (recellularization).
Over the past years, researchers have identified populations of cardiac stem cells that reside in the adult human heart. This discovery sparked the idea of regenerating the heart cells by taking the stem cells inside the heart and reprogramming them into cardiac tissues. The importance of these stem cells are self-renewal, the ability to differentiate into cardiomyocytes, endothelial cells and smooth vascular muscle cells, and clonogenicity. These stem cells are capable of becoming myocytes, which are for stabilizing the topography of the intercellular components, as well as to help control the size and shape of the heart, as well as vascular cells, which serve as a cell reservoir for the turnover and the maintenance of the mesenchymal tissues. However, in vivo studies have demonstrated that the regenerative ability of implanted cardiac stem cells lies in the associated macrophage-mediated immune response and concomitant fibroblast-mediated wound healing and not in their functionality, since these effects were observed for both live and dead stem cells. | 1 | Applied and Interdisciplinary Chemistry |
Increased endocannabinoid signaling within the central nervous system promotes sleep-inducing effects. Intercerebroventricular administration of anandamide in rats has been shown to decrease wakefulness and increase slow-wave sleep and REM sleep. Administration of anandamide into the basal forebrain of rats has also been shown to increase levels of adenosine, which plays a role in promoting sleep and suppressing arousal. REM sleep deprivation in rats has been demonstrated to increase CB1 receptor expression in the central nervous system. Furthermore, anandamide levels possess a circadian rhythm in the rat, with levels being higher in the light phase of the day, which is when rats are usually asleep or less active, since they are nocturnal. | 1 | Applied and Interdisciplinary Chemistry |
Most analytical instruments produce a signal even when a blank (matrix without analyte) is analyzed. This signal is referred to as the noise level. The instrument detection limit (IDL) is the analyte concentration that is required to produce a signal greater than three times the standard deviation of the noise level. This may be practically measured by analyzing 8 or more standards at the estimated IDL then calculating the standard deviation from the measured concentrations of those standards.
The detection limit (according to IUPAC) is the smallest concentration, or the smallest absolute amount, of analyte that has a signal statistically significantly larger than the signal arising from the repeated measurements of a reagent blank.
Mathematically, the analyte's signal at the detection limit () is given by:
where, is the mean value of the signal for a reagent blank measured multiple times, and is the known standard deviation for the reagent blank's signal.
Other approaches for defining the detection limit have also been developed. In atomic absorption spectrometry usually the detection limit is determined for a certain element by analyzing a diluted solution of this element and recording the corresponding absorbance at a given wavelength. The measurement is repeated 10 times. The 3σ of the recorded absorbance signal can be considered as the detection limit for the specific element under the experimental conditions: selected wavelength, type of flame or graphite oven, chemical matrix, presence of interfering substances, instrument... . | 0 | Theoretical and Fundamental Chemistry |
Many limepits were sunken in the ground at a depth of between 2.5 and 5 meters and 3 to 4.5 meters in diameter, in a circular fashion, and some were built with a retaining wall along the inside for support, usually constructed of uncut field-stones. Simpler limepits were made without supportive walls. In the following account, Abu-Rabiʻa describes the practice of Bedouins in the Negev, during the late 19th and early 20th-century:
In Palestine, the principal fuel used to keep the lime-kiln burning was the dried brushwood of prickly burnet (Sarcopoterium spinosum) and savory (Satureja thymbra), where often camel loads of this dried wood would be hauled to the lime-kiln. Monolithic stone structures were already in use for burning limestone (nāri) during the Ottoman period, throughout the Levant. Modern kilns for burning lime first appeared in Palestine during the British Mandate. | 1 | Applied and Interdisciplinary Chemistry |
Methyl metabolism is very ancient and can be found in all organisms on earth, from bacteria to humans, indicating the importance of methyl metabolism for physiology. Indeed, pharmacological inhibition of global methylation in species ranging from human, mouse, fish, fly, roundworm, plant, algae, and cyanobacteria causes the same effects on their biological rhythms, demonstrating conserved physiological roles of methylation during evolution. | 0 | Theoretical and Fundamental Chemistry |
Geostationary Carbon Cycle Observatory (GeoCarb) was an intended NASA Venture-class Earth observation mission that was designed to measure the carbon cycle. Originally intended to be mounted on a commercial geostationary communication satellite operated by SES S.A., a lack of hosting opportunities drove NASA to seek a standalone spacecraft to carry GeoCarb. GeoCarb was to be stationed over the Americas and make observations between 50° North and South latitudes. Its primary mission was to conduct observations of vegetation health and stress, as well as observe the processes that govern the carbon exchange of carbon dioxide, methane, and carbon monoxide between the land, atmosphere, and ocean.
GeoCarb was a joint collaboration between NASA's Ames Research Center, Goddard Space Flight Center, and Jet Propulsion Laboratory; the University of Oklahoma; Colorado State University; the Lockheed Martin Advanced Technology Center of Palo Alto, California; and SES Government Solutions (now SES Space & Defense) of Reston, Florida.
On 29 November 2022, NASA announced the cancellation of development of the GeoCarb mission, citing cost overruns and the availability of other options to measure and observe greenhouse gases, like the EMIT instrument on the ISS and the upcoming Earth System Observatory. | 1 | Applied and Interdisciplinary Chemistry |
Antoine-Laurent de Lavoisier ( ; ; 26 August 17438 May 1794), also Antoine Lavoisier after the French Revolution, was a French nobleman and chemist who was central to the 18th-century chemical revolution and who had a large influence on both the history of chemistry and the history of biology.
It is generally accepted that Lavoisier's great accomplishments in chemistry stem largely from his changing the science from a qualitative to a quantitative one. Lavoisier is most noted for his discovery of the role oxygen plays in combustion. He named oxygen (1778), recognizing it as an element, and also recognized hydrogen as an element (1783), opposing the phlogiston theory. Lavoisier helped construct the metric system, wrote the first extensive list of elements, and helped to reform chemical nomenclature. He predicted the existence of silicon (1787) and discovered that, although matter may change its form or shape, its mass always remains the same. His wife and laboratory assistant, Marie-Anne Paulze Lavoisier, became a renowned chemist in her own right.
Lavoisier was a powerful member of a number of aristocratic councils, and an administrator of the Ferme générale. The Ferme générale was one of the most hated components of the Ancien Régime because of the profits it took at the expense of the state, the secrecy of the terms of its contracts, and the violence of its armed agents. All of these political and economic activities enabled him to fund his scientific research. At the height of the French Revolution, he was charged with tax fraud and selling adulterated tobacco, and was guillotined despite appeals to spare his life in recognition of his contributions to science. | 1 | Applied and Interdisciplinary Chemistry |
Mitochondria and other membranous organelles are normally enriched in the PNP region of peripheral myelinated axons, especially those large caliber axons. The actual physiological role of this accumulation and factors that regulate it are not understood; however, it is known that mitochondria are usually present in areas of the cell that expresses a high energy demand. In these same regions, they are also understood to contain growth cones, synaptic terminals, and sites of action potential initiation and regeneration, such as the nodes of Ranvier. In the synaptic terminals, mitochondria produce the ATP needed to mobilize vesicles for neurotransmission. In the nodes of Ranvier, mitochondria serve as an important role in impulse conduction by producing the ATP that is essential to maintain the activity of energy-demanding ion pumps. Supporting this fact, about five times more mitochondria are present in the PNP axoplasm of large peripheral axons than in the corresponding internodal regions of these fibers. | 1 | Applied and Interdisciplinary Chemistry |
An antagonist of a prostaglandin E2 receptor has been shown to serve as an affective contraceptive for female macaques while unaffecting their menstrual cyclicity as well as hormonal patterns. The exact reason behind the reduced amount of successful pregnancies of primates during the study is unclear due a number of possibilities that may affect such result.
Inhibition of the prostaglandin E2 EP receptor has been shown to inhibit tumor growth, angiogenesis, lymphangiogenesis, and metastasis. | 1 | Applied and Interdisciplinary Chemistry |
Euro banknotes are recommended since it is made of paper and it is legally permitted to artistically mutilate it or burn in small amounts. Moreover, there are no depictions of any persons on the banknotes.
Aside from banknotes, a similar experiment can be performed by using towels, paper or exam paper. | 1 | Applied and Interdisciplinary Chemistry |
The Kantrowitz limit demonstrates the amount of contraction, or change in two-dimensional cross-section area, that a hypersonic inlet can employ while successfully starting an engine inlet (or avoiding the expelling of the hypersonic inlet shock wave). | 1 | Applied and Interdisciplinary Chemistry |
As a dis-Ability rights activist, Perera has promoted the concept of establishing a society that does not marginalise or discriminate against people on the basis of limited mobility, either for short time, or long time or life time in attending to normal day-to-day life – the principal problem in this context.
He is a fervent advocate of built environments and facilities that are a joy rather than a trial to use by everyone. He has constantly used the weapon of persuasion to convince people that the cumulative result of even small changes could be substantial.
Perera has also pioneered the campaign in Sri Lanka for accessible tourism, recognising it as an overlooked growth market and new profit resource for Sri Lanka.
Perera was also instrumental in proposing to the Sri Lanka Standards Institution (SLSI) and paving the way in persuading them to establish the first Sri Lanka standard for design in building construction SLS ISO TR 9527:2006 in 2007, a fact which Dr. A. R. L. Wijesekera, the then Chairman SLSI, recognised as an achievement of national importance. | 0 | Theoretical and Fundamental Chemistry |
Blood based protein biomarkers are often used as a diagnostic test that usually monitor one or more protein that are indicative of the presence of disease or disorder or the presence of a disease/disorder subphtnotype. Such a Blood based protein biomarker-based test can aoften be used Bas prognosticator of disease outcome. An example is neuronal Ubiquitin carboxy-terminal hydrolase L1 (UCH-L1) and Glial fibrillary acidic protein (GFAP) can aid in the diagnosis of the presence a cranial lesion among moderate to mild TBI patients that is otherwise only diagnosable with the use of a CT scan of the head. | 1 | Applied and Interdisciplinary Chemistry |
Normally, when a metallic material cools, the individual atoms solidify in strong, repeating patterns to form a crystalline solid. However, in melt spinning, the melt is quenched (cooled) so rapidly that the atoms don't have time to form these ordered structures before they completely solidify. Instead, the atoms are solidified in positions resembling their liquid state. This physical structure gives rise to the magnetic and electric properties of amorphous metals. | 1 | Applied and Interdisciplinary Chemistry |
The hybrid flow battery uses one or more electroactive components deposited as a solid layer. The major disadvantage is the loss decoupled energy and power as seen in full flow batteries from using a solid state electrode. The cell contains one battery electrode and one fuel cell electrode. This type is limited in energy by the electrode surface area. Hybrid flow batteries include the zinc–bromine, zinc–cerium, soluble lead–acid, and iron-salt flow batteries. Weng et al. reported a vanadium–metal hydride rechargeable hybrid flow battery with an experimental OCV of 1.93 V and operating voltage of 1.70 V, relatively high values among rechargeable flow batteries with aqueous electrolytes. This hybrid battery consists of a graphite felt positive electrode operating in a mixed solution of and , and a metal hydride negative electrode in KOH aqueous solution. The two electrolytes of different pH are separated by a bipolar membrane. The system demonstrated good reversibility and high efficiencies in coulomb (95%), energy (84%), and voltage (88%). They reported further improvements of this redox couple with achievements of increased current density, inclusion of larger 100 cm electrodes, and the operation of 10 large cells in series. Preliminary data using a fluctuating simulated power input tested the viability toward kWh scale storage. In 2016, a high energy density Mn(VI)/Mn(VII)-Zn hybrid flow battery was proposed.
A prototype zinc–polyiodide flow battery demonstrated an energy density of 167 Wh/L (watt-hours per liter). Older zinc–bromide cells reach 70 Wh/L. For comparison, lithium iron phosphate batteries store 233 Wh/L. The zinc–polyiodide battery is claimed to be safer than other flow batteries given its absence of acidic electrolytes, nonflammability and operating range of that does not require extensive cooling circuitry, which would add weight and occupy space. One unresolved issue is zinc buildup on the negative electrode that can permeate the membrane, reducing efficiency. Because of the Zn dendrite formation, Zn-halide batteries cannot operate at high current density (> 20 mA/cm) and thus have limited power density. Adding alcohol to the electrolyte of the ZnI battery can help with the problem. The drawbacks of Zn/I RFB lie at the high cost of Iodide salts (> $20 / Kg); limited area capacity of Zn deposition also losing the decoupled energy and power; and Zn dendrite formation.
When the battery is fully discharged, both tanks hold the same electrolyte solution: a mixture of positively charged zinc ions () and negatively charged iodide ion, (). When charged, one tank holds another negative ion, polyiodide, (). The battery produces power by pumping liquid from external tanks into the batterys stack area where the liquids are mixed. Inside the stack, zinc ions pass through a selective membrane and change into metallic zinc on the stacks negative side. To further increase the energy density of the zinc–iodide flow battery, bromide ions () are used as the complexing agent to stabilize the free iodine, forming iodine–bromide ions () as a means to free up iodide ions for charge storage.
Proton flow batteries (PFB) integrate a metal hydride storage electrode into a reversible proton exchange membrane (PEM) fuel cell. During charging, PFB combines hydrogen ions produced from splitting water with electrons and metal particles in one electrode of a fuel cell. The energy is stored in the form of a solid-state metal hydride. Discharge produces electricity and water when the process is reversed and the protons are combined with ambient oxygen. Metals less expensive than lithium can be used and provide greater energy density than lithium cells. | 0 | Theoretical and Fundamental Chemistry |
Charge modulation spectroscopy is an electro-optical spectroscopy technique tool. It is used to study the charge carrier behavior of organic field-effect transistors. It measures the charge introduced optical transmission variation by directly probing the accumulation charge at the burning interface of semiconductor and dielectric layer where the conduction channel forms. | 0 | Theoretical and Fundamental Chemistry |
SRAS (spatially resolved acoustic spectroscopy) a non-destructive acoustic microscopy microstructural-crystallographic characterization technique commonly used in the study of crystalline or polycrystalline materials. The technique can provide information about the structure and crystallographic orientation of the material. Traditionally, the information provided by SRAS has been acquired by using diffraction techniques in electron microscopy - such as EBSD. The technique was patented in 2005, .
SRAS measures the surface acoustic wave velocity across a specimen, the surface acoustic wave (SAW) velocity is in turn a function of the material state, including parameters such as crystallographic orientation, elastic constants, temperature and stress. | 0 | Theoretical and Fundamental Chemistry |
The shock wave may be described as a compression front in a supersonic flow field, and the flow process across the front results in an abrupt change in fluid properties. The thickness of the shock wave is comparable to the mean free path of the gas molecules in the flow field. In other words, shock is a thin region where large gradients in temperature, pressure and velocity occur, and where the transport phenomena of momentum and energy are important. The normal shock wave is a compression front normal to the flow direction. However, in a wide variety of physical situations, a compression wave inclined at an angle to the flow occurs. Such a wave is called an oblique shock. Indeed, all naturally occurring shocks in external flows are oblique. | 1 | Applied and Interdisciplinary Chemistry |
Slow-tight inhibition occurs when the initial enzyme–inhibitor complex EI undergoes conformational isomerism (a change in shape) to a second more tightly held complex, EI*, but the overall inhibition process is reversible. This manifests itself as slowly increasing enzyme inhibition. Under these conditions, traditional Michaelis–Menten kinetics give a false value for K, which is time–dependent. The true value of K can be obtained through more complex analysis of the on (k) and off (k) rate constants for inhibitor association with kinetics similar to irreversible inhibition. | 1 | Applied and Interdisciplinary Chemistry |
The elements of the space group fixing a point of space are the identity element, reflections, rotations and improper rotations, including inversion points. | 0 | Theoretical and Fundamental Chemistry |
RNA may be too complex to be the first nucleic acid, so before the RNA world several simpler nucleic acids that differ in the backbone, such as GNA, PNA, and TNA have been offered as candidates for the first nucleic acids. | 1 | Applied and Interdisciplinary Chemistry |
Metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements, their inter-metallic compounds, and their mixtures, which are known as alloys.
Metallurgy encompasses both the science and the technology of metals, including the production of metals and the engineering of metal components used in products for both consumers and manufacturers. Metallurgy is distinct from the craft of metalworking. Metalworking relies on metallurgy in a similar manner to how medicine relies on medical science for technical advancement. A specialist practitioner of metallurgy is known as a metallurgist.
The science of metallurgy is further subdivided into two broad categories: chemical metallurgy and physical metallurgy. Chemical metallurgy is chiefly concerned with the reduction and oxidation of metals, and the chemical performance of metals. Subjects of study in chemical metallurgy include mineral processing, the extraction of metals, thermodynamics, electrochemistry, and chemical degradation (corrosion). In contrast, physical metallurgy focuses on the mechanical properties of metals, the physical properties of metals, and the physical performance of metals. Topics studied in physical metallurgy include crystallography, material characterization, mechanical metallurgy, phase transformations, and failure mechanisms.
Historically, metallurgy has predominately focused on the production of metals. Metal production begins with the processing of ores to extract the metal, and includes the mixture of metals to make alloys. Metal alloys are often a blend of at least two different metallic elements. However, non-metallic elements are often added to alloys in order to achieve properties suitable for an application. The study of metal production is subdivided into ferrous metallurgy (also known as black metallurgy) and non-ferrous metallurgy, also known as colored metallurgy.
Ferrous metallurgy involves processes and alloys based on iron, while non-ferrous metallurgy involves processes and alloys based on other metals. The production of ferrous metals accounts for 95% of world metal production.
Modern metallurgists work in both emerging and traditional areas as part of an interdisciplinary team alongside material scientists and other engineers. Some traditional areas include mineral processing, metal production, heat treatment, failure analysis, and the joining of metals (including welding, brazing, and soldering). Emerging areas for metallurgists include nanotechnology, superconductors, composites, biomedical materials, electronic materials (semiconductors) and surface engineering. Many applications, practices, and devices associated or involved in metallurgy were established in ancient India and China, such as the innovation of the wootz steel , bronze, blast furnace, cast iron, hydraulic-powered trip hammers, and double acting piston bellows. | 1 | Applied and Interdisciplinary Chemistry |
Supercritical angle fluorescence microscopy (SAF) is a technique to detect and characterize fluorescent species (proteins, biomolecules, pharmaceuticals, etc.) and their behaviour close or even adsorbed or linked at surfaces. The method is able to observe molecules in a distance of less than 100 to 0 nanometer from the surface even in presence of high concentrations of fluorescent species around. Using an aspheric lens for excitation of a sample with laser light, fluorescence emitted by the specimen is collected above the critical angle of total internal reflection selectively and directed by a parabolic optics onto a detector. The method was invented in 1998 in the laboratories of Stefan Seeger at University of Regensburg/Germany and later at University of Zurich/Switzerland. | 0 | Theoretical and Fundamental Chemistry |
Two effects which are closely related to pyroelectricity are ferroelectricity and piezoelectricity. Normally materials are very nearly electrically neutral on the macroscopic level. However, the positive and negative charges which make up the material are not necessarily distributed in a symmetric manner. If the sum of charge times distance for all elements of the basic cell does not equal zero the cell will have an electric dipole moment (a vector quantity). The dipole moment per unit volume is defined as the dielectric polarization. If this dipole moment changes with the effect of applied temperature changes, applied electric field, or applied pressure, the material is pyroelectric, ferroelectric, or piezoelectric, respectively.
The ferroelectric effect is exhibited by materials which possess an electric polarization in the absence of an externally applied electric field such that the polarization can be reversed if the electric field is reversed. Since all ferroelectric materials exhibit a spontaneous polarization, all ferroelectric materials are also pyroelectric (but not all pyroelectric materials are ferroelectric).
The piezoelectric effect is exhibited by crystals (such as quartz or ceramic) for which an electric voltage across the material appears when pressure is applied. Similar to pyroelectric effect, the phenomenon is due to the asymmetric structure of the crystals that allows ions to move more easily along one axis than the others. As pressure is applied, each side of the crystal takes on an opposite charge, resulting in a voltage drop across the crystal.
Pyroelectricity should not be confused with thermoelectricity: In a typical demonstration of pyroelectricity, the whole crystal is changed from one temperature to another, and the result is a temporary voltage across the crystal. In a typical demonstration of thermoelectricity, one part of the device is kept at one temperature and the other part at a different temperature, and the result is a permanent voltage across the device as long as there is a temperature difference. Both effects convert temperature change to electrical potential, but the pyroelectric effect converts temperature change over time into electrical potential, while the thermoelectric effect converts temperature change with position into electrical potential. | 0 | Theoretical and Fundamental Chemistry |
Project SUNSHINE was a series of research studies that began in 1953 to ascertain the impact of radioactive fallout on the worlds population. The project was initially kept secret, and only became known publicly in 1956. Commissioned jointly by the United States Atomic Energy Commission and USAF Project Rand, SUNSHINE sought to examine the long-term effects of nuclear radiation on the biosphere due to repeated nuclear detonations of increasing yield. With the conclusion from Project GABRIEL that radioactive isotope Sr-90 represented the most serious threat to human health from nuclear fallout, Project SUNSHINE sought to measure the global dispersion of Sr-90 by measuring its concentration in the tissues and bones of the dead. Of particular interest was tissue from the young, whose developing bones have the highest propensity to accumulate Sr-90 and thus the highest susceptibility to radiation damage. SUNSHINE elicited a great deal of controversy when it was revealed that many of the remains sampled were utilized without prior permission from relatives of the dead, which wasnt known until many years later. | 0 | Theoretical and Fundamental Chemistry |
The simplest liquid crystal phase is the nematic. In a nematic phase, organic molecules lack a crystalline positional order, but do self-align with their long axes roughly parallel. The molecules are free to flow and their center of mass positions are randomly distributed as in a liquid, but their orientation is constrained to form a long-range directional order.
The word nematic comes from the Greek (), which means "thread". This term originates from the disclinations: thread-like topological defects observed in nematic phases.
Nematics also exhibit so-called "hedgehog" topological defects. In two dimensions, there are topological defects with topological charges and . Due to hydrodynamics, the defect moves considerably faster than the defect. When placed close to each other, the defects attract; upon collision, they annihilate.
Most nematic phases are uniaxial: they have one axis (called a directrix) that is longer and preferred, with the other two being equivalent (can be approximated as cylinders or rods). However, some liquid crystals are biaxial nematic, meaning that in addition to orienting their long axis, they also orient along a secondary axis. Nematic crystals have fluidity similar to that of ordinary (isotropic) liquids but they can be easily aligned by an external magnetic or electric field. Aligned nematics have the optical properties of uniaxial crystals and this makes them extremely useful in liquid-crystal displays (LCD).
Nematic phases are also known in non-molecular systems: at high magnetic fields, electrons flow in bundles or stripes to create an "electronic nematic" form of matter. | 0 | Theoretical and Fundamental Chemistry |
Mandelonitrile, with the formula CHCH(OH)CN, occurs in small amounts in the pits of some fruits. Related cyanogenic glycosides are known, such as amygdalin.
Glycolonitrile, also called hydroxyacetonitrile or formaldehyde cyanohydrin, is the organic compound with the formula HOCHCN. It is the simplest cyanohydrin, being derived from formaldehyde. | 0 | Theoretical and Fundamental Chemistry |
Since the deep sea cores became available in the 1960s, paleoclimatic indices of planktonic foraminifera from marine sediments have been used for paleoclimatic reconstruction. Among the early pioneers to apply foraminifera latitudinal abundances, Ericson and Wollin (1968) succeeded in establishing the Pleistocene glacial and interglacial cycles based on the ratios of cold and warm water species in tropical sediments. Similar work was extended to subantarctic region by Kennett (1970), who, based on subpolar cold and warm water planktonic foraminferal species, reconstructed paleoclimatic changes in the Pleistocene, consistent in trends with those established in the tropical region.
When drilling cores, which recovered longer sediment columns than piston cores, came along, paleoclimatic reconstruction investigations were pushed back further in geological times. A climatic curve in the Oligocene was constructed in the Gulf of Mexico by using warm water indicators (Turborotalia pseudoampliapertura, Globoquadrina tripartita, Dentoglobigerina globularis, Dentoglobigerina baroemoenensis, “Globigerina” ciperoensis and Globigerinoides groups, and Cassigerinella chipolensis) and cold water indicators (Catapsydrax spp., Globorotaloides spp., Subbotina angiporoides group, Globigerina s. str., and the tenuitellids). A more extensive geographic coverage was investigated by Spezzaferri in 1995, who analyzed samples from drilling cores in the Atlantic, Indian and South Pacific Oceans and identified and grouped foraminifera into warmer, cooler, warm-temperate and cool-temperate indices. A paleoclimatic curve in the Oligocene and Miocene transition period was established and the curve was supported by the isotope data.
A more sophisticated approach to reconstruct paleoclimate involves using factor analysis. Thompson (1981) was able to relate six foraminiferal assemblages from core top samples to present water masses in the western North Pacific. A transfer function was generated to link the assemblages to sea surface temperatures. A paleotemperature curve for the past 150,000 years was reconstructed by applying this transfer function to old sediments in the cores.
Similar technique has been applied to the Eocene and Oligocene sediments and the forams have been categorized in surface, intermediate and deep water-mass groups. Thus water-mass stratification, in addition to paleotemperature fluctuation has been reconstructed. | 0 | Theoretical and Fundamental Chemistry |
Due to the similar aqueous chemistries of aluminium and iron, it has been long thought that an analogous iron polycation should be isolatable from water. Moreover, in 2007, the structure of ferrihydrite was determined and shown to be built of iron Keggin ions. This further captured scientists' imagination and drive to isolate the iron Keggin ion. In 2015, the iron Keggin ion was isolated from water, but as a polyanion with a −17 charge; and protecting chemistry was required. Iron-bound water is very acidic; so it is difficult to capture the intermediate Keggin ion form without bulky and nonprotic ligands instead of the water that is found in the aluminum Keggin ion. However, more important in this synthesis was the bismuth () counterions that provided high positive charge to stabilize the high negative charge of the heptadecavalent polyanion. | 0 | Theoretical and Fundamental Chemistry |
Technical journals published on behalf of ASM include:
* Alloy Digest
* International Materials Reviews (IMR)
* Journal of Failure Analysis & Prevention (JFAP)
* Journal of Materials Engineering and Performance (JMEP)
* Journal of Phase Equilibria and Diffusion (JPED)
* Journal of Thermal Spray Technology (JTST)
* Metallography, Microstructure, and Analysis (MMA)
* Metallurgical and Materials Transactions A and B (MetTransA & MetTransB)
* Shape Memory and Superelasticity. | 1 | Applied and Interdisciplinary Chemistry |
The effects of anaerobic corrosion are evident when evaluating the safety of chemical waste disposal. Currently, the permanent disposal of nuclear waste is commonly in deep geological repositories (DGR) that use copper coating to prevent metal corrosion. In the DGR, four major types of corrosion are expected to occur, including oxygen-driven, radiation-influenced, anaerobic, and microbiologically-influenced corrosion. Of these, the most notable process is the microbiologically-influenced corrosion in terms of the magnitude of corrosion. The ability of microorganisms such as SRB to survive in a wide range of environments also lends to their relevance when considering the threat of corrosion to permanent chemical waste disposal. | 1 | Applied and Interdisciplinary Chemistry |
Except in acid or siliceous igneous rocks containing greater than 66% of silica, known as felsic rocks, quartz is not abundant in igneous rocks. In basic rocks (containing 20% of silica or less) it is rare for them to contain as much silicon, these are referred to as mafic rocks. If magnesium and iron are above average while silica is low, olivine may be expected; where silica is present in greater quantity over ferromagnesian minerals, such as augite, hornblende, enstatite or biotite, occur rather than olivine. Unless potash is high and silica relatively low, leucite will not be present, for leucite does not occur with free quartz. Nepheline, likewise, is usually found in rocks with much soda and comparatively little silica. With high alkalis, soda-bearing pyroxenes and amphiboles may be present. The lower the percentage of silica and alkali's, the greater is the prevalence of plagioclase feldspar as contracted with soda or potash feldspar.
Earths crust is composed of 90% silicate minerals and their abundance in the Earth is as follows: plagioclase feldspar (39%), alkali feldspar (12%), quartz (12%), pyroxene (11%), amphiboles (5%), micas (5%), clay minerals (5%); the remaining silicate minerals make up another 3% of Earths crust. Only 8% of the Earth is composed of non-silicate minerals such as carbonates, oxides, and sulfides.
The other determining factor, namely the physical conditions attending consolidation, plays, on the whole, a smaller part, yet is by no means negligible. Certain minerals are practically confined to deep-seated intrusive rocks, e.g., microcline, muscovite, diallage. Leucite is very rare in plutonic masses; many minerals have special peculiarities in microscopic character according to whether they crystallized in-depth or near the surface, e.g., hypersthene, orthoclase, quartz. There are some curious instances of rocks having the same chemical composition, but consisting of entirely different minerals, e.g., the hornblendite of Gran, in Norway, which contains only hornblende, has the same composition as some of the camptonites of the same locality that contain feldspar and hornblende of a different variety. In this connection, we may repeat what has been said above about the corrosion of porphyritic minerals in igneous rocks. In rhyolites and trachytes, early crystals of hornblende and biotite may be found in great numbers partially converted into augite and magnetite. Hornblende and biotite were stable under the pressures and other conditions below the surface, but unstable at higher levels. In the ground-mass of these rocks, augite is almost universally present. But the plutonic representatives of the same magma, granite, and syenite contain biotite and hornblende far more commonly than augite. | 0 | Theoretical and Fundamental Chemistry |
Mill scale is sought after by select abstract expressionist artists as its effect on steel can cause unpredicted and seemingly random abstract organic visual effects. Although the majority of mill scale is removed from steel during its passage through scale breaker rolls during manufacturing, smaller structurally inconsequential residue can be visible. Leveraging this processing vestige by accelerating its corrosive effects through the metallurgical use of phosphoric acid or in conjunction with selenium dioxide can create a high contrast visual substrate onto which other compositional elements can be added. | 1 | Applied and Interdisciplinary Chemistry |
According to the U.S. Department of Agriculture, the Dietary Reference Intakes, which is the "highest level of daily nutrient intake that is likely to pose no risk of adverse health effects" specify 10 mg/day for most people, corresponding to 10 L of fluoridated water with no risk. For young children the values are smaller, ranging from 0.7 mg/d to 2.2 mg/d for infants. Water and food sources of fluoride include community water fluoridation, seafood, tea, and gelatin.
Soluble fluoride salts, of which sodium fluoride is the most common, are toxic, and have resulted in both accidental and self-inflicted deaths from acute poisoning. The lethal dose for most adult humans is estimated at 5 to 10 g (which is equivalent to 32 to 64 mg elemental fluoride per kg body weight). A case of a fatal poisoning of an adult with 4 grams of sodium fluoride is documented, and a dose of 120 g sodium fluoride has been survived. For sodium fluorosilicate (NaSiF), the median lethal dose (LD) orally in rats is 125 mg/kg, corresponding to 12.5 g for a 100 kg adult.
Treatment may involve oral administration of dilute calcium hydroxide or calcium chloride to prevent further absorption, and injection of calcium gluconate to increase the calcium levels in the blood. Hydrogen fluoride is more dangerous than salts such as NaF because it is corrosive and volatile, and can result in fatal exposure through inhalation or upon contact with the skin; calcium gluconate gel is the usual antidote.
In the higher doses used to treat osteoporosis, sodium fluoride can cause pain in the legs and incomplete stress fractures when the doses are too high; it also irritates the stomach, sometimes so severely as to cause ulcers. Slow-release and enteric-coated versions of sodium fluoride do not have gastric side effects in any significant way, and have milder and less frequent complications in the bones. In the lower doses used for water fluoridation, the only clear adverse effect is dental fluorosis, which can alter the appearance of children's teeth during tooth development; this is mostly mild and is unlikely to represent any real effect on aesthetic appearance or on public health. Fluoride was known to enhance the measurement of bone mineral density at the lumbar spine, but it was not effective for vertebral fractures and provoked more non vertebral fractures. In areas that have naturally occurring high levels of fluoride in groundwater which is used for drinking water, both dental and skeletal fluorosis can be prevalent and severe.
A popular urban myth claims that the Nazis used fluoride in concentration camps, but there is no historical evidence to prove this claim. | 1 | Applied and Interdisciplinary Chemistry |
S&S has also been used in RNA splicing research in many animals and plants.
The mRNA splicing plays a fundamental role in gene functional regulation. Very recently, it has been shown that A to G conversions at splice sites can lead to mRNA mis-splicing in Arabidopsis. The splicing and exon–intron junction prediction coincided with the GT/AG rule (S&S) in the Molecular characterization and evolution of carnivorous sundew (Drosera rotundifolia L.) class V b-1,3-glucanase. Unspliced (LSDH) and spliced (SSDH) transcripts of NAD+ dependent sorbitol dehydroge nase (NADSDH) of strawberry (Fragaria ananassa Duch., cv. Nyoho) were investigated for phytohormonal treatments.
Ambra1 is a positive regulator of autophagy, a lysosome-mediated degradative process involved both in physiological and pathological conditions. Nowadays, this function of Ambra1 has been characterized only in mammals and zebrafish. Diminution of rbm24a or rbm24b gene products by morpholino knockdown resulted in significant disruption of somite formation in mouse and zebrafish. Dr.Senapathy algorithm used extensively to study intron-exon organization of fut8 genes. The intron-exon boundaries of Sf9 fut8 were in agreement with the consensus sequence for the splicing donor and acceptor sites concluded using S&S. | 1 | Applied and Interdisciplinary Chemistry |
Coupon holders are used to fix corrosion coupons inside a pipe or tank and attaches itself to a solid plug or hollow plug. They are usually made from stainless steel 316/316L or Monel and inconel or other corrosion resistant materials. | 1 | Applied and Interdisciplinary Chemistry |
In 2003, ATSDR released public health assessments that evaluated the potential health effects of pollution left behind by the United States Navy in Vieques, Puerto Rico. The public health assessments noted that residents of the island were exposed to environmental contamination at such low levels that no harmful health effects were expected, and the agency concluded that there was "no apparent public health hazard." In 2009, however, ATSDR announced that it had identified gaps in environmental data and planned to take a "fresh look" at Vieques by reviewing studies on the island. | 1 | Applied and Interdisciplinary Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.