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The first generally accepted theory of ET was developed by Rudolph A. Marcus to address outer-sphere electron transfer and was based on a transition-state theory approach. The Marcus theory of electron transfer was then extended to include inner-sphere electron transfer by Noel Hush and Marcus. The resultant theory called Marcus-Hush theory, has guided most discussions of electron transfer ever since. Both theories are, however, semiclassical in nature, although they have been extended to fully quantum mechanical treatments by Joshua Jortner, Alexander M. Kuznetsov, and others proceeding from Fermi's golden rule and following earlier work in non-radiative transitions. Furthermore, theories have been put forward to take into account the effects of vibronic coupling on electron transfer; in particular, the PKS theory of electron transfer. In proteins, ET rates are governed by the bond structures: the electrons, in effect, tunnel through the bonds comprising the chain structure of the proteins. | 0 | Theoretical and Fundamental Chemistry |
Arsenic poisoning (or arsenicosis) is a medical condition that occurs due to elevated levels of arsenic in the body. If arsenic poisoning occurs over a brief period of time, symptoms may include vomiting, abdominal pain, encephalopathy, and watery diarrhea that contains blood. Long-term exposure can result in thickening of the skin, darker skin, abdominal pain, diarrhea, heart disease, numbness, and cancer.
The most common reason for long-term exposure is contaminated drinking water. Groundwater most often becomes contaminated naturally; however, contamination may also occur from mining or agriculture. It may also be found in the soil and air. Recommended levels in water are less than 10–50 µg/L (10–50 parts per billion). Other routes of exposure include toxic waste sites and pseudo-medicine. Most cases of poisoning are accidental. Arsenic acts by changing the functioning of around 200 enzymes. Diagnosis is by testing the urine, blood, or hair.
Prevention is by using water that does not contain high levels of arsenic. This may be achieved by the use of special filters or using rainwater. There is not good evidence to support specific treatments for long-term poisoning. For acute poisonings treating dehydration is important. Dimercaptosuccinic acid or dimercaptopropane sulfonate may be used while dimercaprol (BAL) is not recommended. Hemodialysis may also be used.
Through drinking water, more than 200 million people globally are exposed to higher-than-safe levels of arsenic. The areas most affected are Bangladesh and West Bengal. Exposure is also more common in people of low income and minorities. Acute poisoning is uncommon. The toxicity of arsenic has been described as far back as 1500 BC in the Ebers papyrus. | 1 | Applied and Interdisciplinary Chemistry |
pH partition is the tendency for acids to accumulate in basic fluid compartments, and bases to accumulate in acidic compartments. The reason for this phenomenon is that acids become negatively electric charged in basic fluids, since they donate a proton. On the other hand, bases become positively electric charged in acid fluids, since they receive a proton. Since electric charge decrease the membrane permeability of substances, once an acid enters a basic fluid and becomes electrically charged, then it cannot escape that compartment with ease and therefore accumulates, and vice versa with bases. | 1 | Applied and Interdisciplinary Chemistry |
The history and evolution of reversed phase stationary phases in described in detail in an article by Majors, Dolan, Carr and Snyder.
In the 1970s, most liquid chromatography runs were performed using solid particles as the stationary phases, made of unmodified silica gel or alumina. This type of technique is now referred to as normal-phase chromatography. Since the stationary phase is hydrophilic in this technique, and the mobile phase is non-polar (consisting of organic solvents such as hexane and heptane), biomolecules with hydrophilic properties in the sample adsorb to the stationary phase strongly. Moreover, they were not dissolved easily in the mobile phase solvents. At the same time hydrophobic molecules experience less affinity to the polar stationary phase, and elute through it early with not enough retention. This was the reasons why during the 1970s the silica based particles were treated with hydrocarbons, immobilized or bonded on their surface, and the mobile phases were switched to aqueous and polar in nature, to accommodate biomedical substances.
The use of a hydrophobic stationary phase and polar mobile phases is essentially the reverse of normal phase chromatography, since the polarity of the mobile and stationary phases have been inverted – hence the term reversed-phase chromatography. As a result, hydrophobic molecules in the polar mobile phase tend to adsorb to the hydrophobic stationary phase, and hydrophilic molecules in the sample pass through the column and are eluted first. Hydrophobic molecules can be eluted from the column by decreasing the polarity of the mobile phase using an organic (non-polar) solvent, which reduces hydrophobic interactions. The more hydrophobic the molecule, the more strongly it will bind to the stationary phase, and the higher the concentration of organic solvent that will be required to elute the molecule.
Many of the mathematical parameters of the theory of chromatography and experimental considerations used in other chromatographic methods apply to RP-LC as well (for example, the selectivity factor, chromatographic resolution, plate count, etc. It can be used for the separation of a wide variety of molecules. It is typically used for separation of proteins, because the organic solvents used in normal-phase chromatography can denature many proteins.
Today, RP-LC is a frequently used analytical technique. There are huge variety of stationary phases available for use in RP-LC, allowing great flexibility in the development of the separation methods. | 0 | Theoretical and Fundamental Chemistry |
The mitochondrial targeting signal also known as presequence is a 10-70 amino acid long peptide that directs a newly synthesized protein to the mitochondria. It is found at the N-terminus end consists of an alternating pattern of hydrophobic and positively charged amino acids to form what is called an amphipathic helix. Mitochondrial targeting signals can contain additional signals that subsequently target the protein to different regions of the mitochondria, such as the mitochondrial matrix or inner membrane. In plants, an N-terminal signal (or transit peptide) targets to the plastid in a similar manner. Like most signal peptides, mitochondrial targeting signals and plastid specific transit peptides are cleaved once targeting is complete. Some plant proteins have an N-terminal transport signal that targets both organelles often referred to as dual-targeted transit peptide. Approximately 5% of total organelle proteins are predicted to be dual-targeted however the specific number could be higher considering the variable degree of accumulation of passenger proteins in both organelles. The targeting specificity of these transit peptides depends on many factors including net charge and affinity between transit peptides and organelle transport machinery. | 1 | Applied and Interdisciplinary Chemistry |
De re metallica (Latin for On the Nature of Metals [Minerals]) is a book in Latin cataloguing the state of the art of mining, refining, and smelting metals, published a year posthumously in 1556 due to a delay in preparing woodcuts for the text. The author was Georg Bauer, whose pen name was the Latinized Georgius Agricola ("Bauer" and "Agricola" being respectively the German and Latin words for "farmer"). The book remained the authoritative text on mining for 180 years after its publication. It was also an important chemistry text for the period and is significant in the history of chemistry.
Mining was typically left to professionals, craftsmen and experts who were not eager to share their knowledge. Much experiential knowledge had been accumulated over the course of time. This knowledge was consecutively handed down orally within a small group of technicians and mining overseers. In the Middle Ages these people held the same leading role as the master builders of the great cathedrals, or perhaps also alchemists. It was a small, cosmopolitan elite within which existing knowledge was passed on and further developed but not shared with the outside world. Only a few writers from that time wrote anything about mining itself. Partly, that was because this knowledge was very difficult to access. Most writers also found it simply not worth the effort to write about it. Only in the Renaissance did this perception begin to change. With the improved transport and the invention of the printing press knowledge spread much more easily and faster than before. In 1500, the first printed book dedicated to mining engineering, called the Nützlich Bergbüchleyn ("The Useful Little Mining Book”) by Ulrich Rülein von Calw, was published. The most important works in this genre were, however, the twelve books of De Re Metallica by Georgius Agricola, published in 1556.
Agricola had spent nine years in the Bohemian town of Joachimsthal (now Jáchymov in the Czech Republic). After Joachimsthal, he spent the rest of his life in Chemnitz in Saxony, another prominent mining town in the Ore Mountains.
The book was greatly influential, and for more than a century after it was published, De Re Metallica remained a standard treatise used throughout Europe. The German mining technology it portrayed was acknowledged as the most advanced at the time, and the metallic wealth produced in German mining districts was the envy of many other European nations. The book was reprinted in a number of Latin editions, as well as in German and Italian translations. Publication in Latin meant that it could be read by any educated European of the time. The 292 superb woodcut illustrations and the detailed descriptions of machinery made it a practical reference for those wishing to replicate the latest in mining technology.
The drawings from which the woodcuts were made were done by an artist in Joachimsthal named Blasius Weffring or Basilius Wefring. The woodcuts were then prepared in the Froben publishing house by Hans Rudolf Manuel Deutsch and Zacharias Specklin.
In 1912, the first English translation of De Re Metallica was privately published in London by subscription. The translators were Herbert Hoover, a mining engineer (and later President of the United States), and his wife, Lou Henry Hoover, a geologist and Latinist. The translation is notable not only for its clarity of language, but for the extensive footnotes, which detail the classical references to mining and metals. Subsequent translations into other languages, including German, owe much to the Hoover translations, as their footnotes detail their difficulties with Agricola's invention of several hundred Latin expressions to cover Medieval German mining and milling terms that were unknown to classical Latin. The most important translation—outside English—was the one published by the Deutsches Museum in Munich. | 1 | Applied and Interdisciplinary Chemistry |
A baroclinic instability is a fluid dynamical instability of fundamental importance in the atmosphere and ocean. It can lead to the formation of transient mesoscale eddies, with a horizontal scale of 10-100 km. In contrast, flows on the largest scale in the ocean are described as ocean currents, the largest scale eddies are mostly created by shearing of two ocean currents and static mesoscale eddies are formed by the flow around an obstacle (as seen in the animation on eddy (fluid dynamics). Mesoscale eddies are circular currents with swirling motion and account for approximately 90% of the ocean's total kinetic energy. Therefore, they are key in mixing and transport of for example heat, salt and nutrients.
In a baroclinic medium, the density depends on both the temperature and pressure. The effect of the temperature on the density allows lines of equal density (isopycnals) and lines of equal pressure (isobars) to intersect. This is in contrast to a barotropic fluid, in which the density is only a function of pressure. For this barotropic case, isobars and isopycnals are parallel. The intersecting of isobars and isopycnals in a baroclinic medium may cause baroclinic instabilities to occur by the process of sloping convection. The sizes of baroclinic instabilities and therefore also the eddies they create scale with the Rossby radius of deformation, which strongly varies with latitude for the ocean. | 1 | Applied and Interdisciplinary Chemistry |
The helicity of a particle is positive ("right-handed") if the direction of its spin is the same as the direction of its motion. It is negative ("left-handed") if the directions of spin and motion are opposite. So a standard clock, with its spin vector defined by the rotation of its hands, has left-handed helicity if tossed with its face directed forwards.
Mathematically, helicity is the sign of the projection of the spin vector onto the momentum vector: "left" is negative, "right" is positive.
The chirality of a particle is more abstract: It is determined by whether the particle transforms in a right- or left-handed representation of the Poincaré group.
For massless particles – photons, gluons, and (hypothetical) gravitons – chirality is the same as helicity; a given massless particle appears to spin in the same direction along its axis of motion regardless of point of view of the observer.
For massive particles – such as electrons, quarks, and neutrinos – chirality and helicity must be distinguished: In the case of these particles, it is possible for an observer to change to a reference frame moving faster than the spinning particle, in which case the particle will then appear to move backwards, and its helicity (which may be thought of as "apparent chirality") will be reversed. That is, helicity is a constant of motion, but it is not Lorentz invariant. Chirality is Lorentz invariant, but is not a constant of motion: a massive left-handed spinor, when propagating, will evolve into a right handed spinor over time, and vice versa.
A massless particle moves with the speed of light, so no real observer (who must always travel at less than the speed of light) can be in any reference frame where the particle appears to reverse its relative direction of spin, meaning that all real observers see the same helicity. Because of this, the direction of spin of massless particles is not affected by a change of inertial reference frame (a Lorentz boost) in the direction of motion of the particle, and the sign of the projection (helicity) is fixed for all reference frames: The helicity of massless particles is a relativistic invariant (a quantity whose value is the same in all inertial reference frames) which always matches the massless particle's chirality.
The discovery of neutrino oscillation implies that neutrinos have mass, so the photon is the only confirmed massless particle; gluons are expected to also be massless, although this has not been conclusively tested. Hence, these are the only two particles now known for which helicity could be identical to chirality, and only the photon has been confirmed by measurement. All other observed particles have mass and thus may have different helicities in different reference frames. | 0 | Theoretical and Fundamental Chemistry |
Since natural amino acid residues are usually present in large quantities, it is often difficult to modify one single site. Strategies targeting the termini of protein have been developed, because they greatly enhanced the site selectivity of protein modification. One of the N- termini modifications involves the functionalization of the terminal amino acid. The oxidation of N-terminal serine and threonine residues are able to generate N-terminal aldehyde, which can undergo further bioorthogonal reactions (shown in the first reaction in Figure 4). Another type of modification involves the condensation of N-terminal cysteine with aldehyde, generating thiazolidine that is stable at high pH (second reaction in Figure 4). Using pyridoxal phosphate (PLP), several N-terminal amino acids can undergo transamination to yield N-terminal aldehyde, such as glycine and aspartic acid (third reaction in Figure 4).
An example of C-termini modification is the native chemical ligation (NCL), which is the coupling between a C-terminal thioester and a N-terminal cysteine (Figure 5). | 1 | Applied and Interdisciplinary Chemistry |
Cyclic olefin copolymer (COC) is an amorphous polymer made by several polymer manufacturers. COC is a relatively new class of polymers as compared to commodities such as polypropylene and polyethylene. This newer material is used in a wide variety of applications including packaging films, lenses, vials, displays, and medical devices. | 0 | Theoretical and Fundamental Chemistry |
Microstructure is the very small scale structure of a material, defined as the structure of a prepared surface of material as revealed by an optical microscope above 25× magnification. The microstructure of a material (such as metals, polymers, ceramics or composites) can strongly influence physical properties such as strength, toughness, ductility, hardness, corrosion resistance, high/low temperature behaviour or wear resistance. These properties in turn govern the application of these materials in industrial practice.
Microstructure at scales smaller than can be viewed with optical microscopes is often called nanostructure, while the structure in which individual atoms are arranged is known as crystal structure. The nanostructure of biological specimens is referred to as ultrastructure. A microstructure’s influence on the mechanical and physical properties of a material is primarily governed by the different defects present or absent of the structure. These defects can take many forms but the primary ones are the pores. Even if those pores play a very important role in the definition of the characteristics of a material, so does its composition. In fact, for many materials, different phases can exist at the same time. These phases have different properties and if managed correctly, can prevent the fracture of the material. | 1 | Applied and Interdisciplinary Chemistry |
In order to analyze a sample for its atomic constituents, it has to be atomized. The atomizers most commonly used nowadays are flames and electrothermal (graphite tube) atomizers. The atoms should then be irradiated by optical radiation, and the radiation source could be an element-specific line radiation source or a continuum radiation source. The radiation then passes through a monochromator in order to separate the element-specific radiation from any other radiation emitted by the radiation source, which is finally measured by a detector. | 0 | Theoretical and Fundamental Chemistry |
Metabolite damage can occur through enzyme promiscuity or spontaneous chemical reactions. Many metabolites are chemically reactive and unstable and can react with other cell components or undergo unwanted modifications. Enzymatically or chemically damaged metabolites are always useless and often toxic. To prevent toxicity that can occur from the accumulation of damaged metabolites, organisms have damage-control systems that:
# Reconvert damaged metabolites to their original, undamaged form (damage repair)
# Convert a potentially harmful metabolite to a benign one (damage pre-emption)
# Prevent damage from happening by limiting the build-up of reactive, but non-damaged metabolites that can lead to harmful products (directed overflow)
Damage-control systems can involve one or more specific enzymes. | 1 | Applied and Interdisciplinary Chemistry |
The noradrenaline system consists of around 15,000 neurons, primarily in the locus coeruleus. This is diminutive compared to the more than 100 billion neurons in the brain. As with dopaminergic neurons in the substantia nigra, neurons in the locus coeruleus tend to be melanin-pigmented. Noradrenaline is released from the neurons, and acts on adrenergic receptors. Noradrenaline is often released steadily so that it can prepare the supporting glial cells for calibrated responses. Despite containing a relatively small number of neurons, when activated, the noradrenaline system plays major roles in the brain including involvement in suppression of the neuroinflammatory response, stimulation of neuronal plasticity through LTP, regulation of glutamate uptake by astrocytes and LTD, and consolidation of memory. | 1 | Applied and Interdisciplinary Chemistry |
Mohamed M. Atalla (; August 4, 1924 – December 30, 2009) was an Egyptian-American engineer, physicist, cryptographer, inventor and entrepreneur. He was a semiconductor pioneer who made important contributions to modern electronics. He is best known for inventing, along with his colleague Dawon Kahng, the MOSFET (metal–oxide–semiconductor field-effect transistor, or MOS transistor) in 1959, which along with Atalla's earlier surface passivation processes, had a significant impact on the development of the electronics industry. He is also known as the founder of the data security company Atalla Corporation (now Utimaco Atalla), founded in 1972. He received the Stuart Ballantine Medal (now the Benjamin Franklin Medal in physics) and was inducted into the National Inventors Hall of Fame for his important contributions to semiconductor technology as well as data security.
Born in Port Said, Egypt, he was educated at Cairo University in Egypt and then Purdue University in the United States, before joining Bell Labs in 1949 and later adopting the more anglicized "John" or "Martin" M. Atalla as professional names. He made several important contributions to semiconductor technology at Bell Labs, including his development of the surface passivation process and his demonstration of the MOSFET with Kahng in 1959.
His work on MOSFET was initially overlooked at Bell, which led to his resignation from Bell and joining Hewlett-Packard (HP), founding its Semiconductor Lab in 1962 and then HP Labs in 1966, before leaving to join Fairchild Semiconductor, founding its Microwave & Optoelectronics division in 1969. His work at HP and Fairchild included research on Schottky diode, gallium arsenide (GaAs), gallium arsenide phosphide (GaAsP), indium arsenide (InAs) and light-emitting diode (LED) technologies. He later left the semiconductor industry, and became an entrepreneur in cryptography and data security. In 1972, he founded Atalla Corporation, and filed a patent for a remote Personal Identification Number (PIN) security system. In 1973, he released the first hardware security module, the "Atalla Box", which encrypted PIN and ATM messages, and went on to secure the majority of the world's ATM transactions. He later founded the Internet security company TriStrata Security in the 1990s. He died in Atherton, California, on December 30, 2009. | 0 | Theoretical and Fundamental Chemistry |
During the solidification of synthetic biofoams, fibers may be added as a reinforcement agent for the matrix. This additionally will create a heterogeneous nucleation site for the air pockets of the foam itself during the foaming process. However, as fiber content increases, it can begin to inhibit formation of the cellular structure of the matrix. | 0 | Theoretical and Fundamental Chemistry |
In materials science, critical resolved shear stress (CRSS) is the component of shear stress, resolved in the direction of slip, necessary to initiate slip in a grain. Resolved shear stress (RSS) is the shear component of an applied tensile or compressive stress resolved along a slip plane that is other than perpendicular or parallel to the stress axis. The RSS is related to the applied stress by a geometrical factor, , typically the Schmid factor:
where is the magnitude of the applied tensile stress, is the angle between the normal of the slip plane and the direction of the applied force, and is the angle between the slip direction and the direction of the applied force. The Schmid factor is most applicable to FCC single-crystal metals, but for polycrystal metals the Taylor factor has been shown to be more accurate. The CRSS is the value of resolved shear stress at which yielding of the grain occurs, marking the onset of plastic deformation. CRSS, therefore, is a material property and is not dependent on the applied load or grain orientation. The CRSS is related to the observed yield strength of the material by the maximum value of the Schmid factor:
CRSS is a constant for crystal families. Hexagonal close-packed crystals, for example, have three main families - basal, prismatic, and pyramidal - with different values for the critical resolved shear stress. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, a molecule experiences strain when its chemical structure undergoes some stress which raises its internal energy in comparison to a strain-free reference compound. The internal energy of a molecule consists of all the energy stored within it. A strained molecule has an additional amount of internal energy which an unstrained molecule does not. This extra internal energy, or strain energy, can be likened to a compressed spring. Much like a compressed spring must be held in place to prevent release of its potential energy, a molecule can be held in an energetically unfavorable conformation by the bonds within that molecule. Without the bonds holding the conformation in place, the strain energy would be released. | 0 | Theoretical and Fundamental Chemistry |
The track of the first competition is a gold surface, equipped with grooves to define race lanes in order to avoid losing vehicles. It is about 100 nanometres long, and includes two bends. It is located in a small enclosure cooled to -269°C under a primary vacuum of 10 mbar and is observed simultaneously by four scanning tunneling microscopes (STM) miniaturized for this event and operating on the same surface. Each microscope is responsible for driving a single vehicle (a single nanocar).
During this competition, the nanocars should move as far as possible on the gold track during the 36 hours race. Speeds of 5 nanometers per hour were expected. | 0 | Theoretical and Fundamental Chemistry |
A description of Debye–Hückel theory includes a very detailed discussion of the assumptions and their limitations as well as the mathematical development and applications.
A snapshot of a 2-dimensional section of an idealized electrolyte solution is shown in the picture. The ions are shown as spheres with unit electrical charge. The solvent (pale blue) is shown as a uniform medium, without structure. On average, each ion is surrounded more closely by ions of opposite charge than by ions of like charge. These concepts were developed into a quantitative theory involving ions of charge ze and ze, where z can be any integer. The principal assumption is that departure from ideality is due to electrostatic interactions between ions, mediated by Coulombs law: the force of interaction between two electric charges, separated by a distance, r' in a medium of relative permittivity ε is given by
It is also assumed that
*The solute is completely dissociated; it is a strong electrolyte.
*Ions are spherical and are not polarized by the surrounding electric field. Solvation of ions is ignored except insofar as it determines the effective sizes of the ions.
*The solvent plays no role other than providing a medium of constant relative permittivity (dielectric constant).
*There is no electrostriction.
*Individual ions surrounding a "central" ion can be represented by a statistically averaged cloud of continuous charge density, with a minimum distance of closest approach.
The last assumption means that each cation is surrounded by a spherically symmetric cloud of other ions. The cloud has a net negative charge. Similarly each anion is surrounded by a cloud with net positive charge. | 0 | Theoretical and Fundamental Chemistry |
In 2013, researchers reported that tramadol was found in relatively high concentrations (1%+) in the roots of the African pin cushion tree (Nauclea latifolia). In 2014, however, it was reported that the presence of tramadol in the tree roots was the result of tramadol having been administered to cattle by farmers in the region: tramadol and its metabolites were present in the animals' excreta, which contaminated the soil around the trees. Therefore, tramadol and its mammalian metabolites were found in tree roots in the far north of Cameroon, but not in the south where it is not administered to farm animals.
A 2014 editorial in Lab Times online contested the notion that tramadol in tree roots was the result of anthropogenic contamination, stating that samples were taken from trees that grew in national parks, where livestock were forbidden; it also quoted researcher Michel de Waard, who stated that "thousands and thousands of tramadol-treated cattle sitting around a single tree and urinating there" would be required to produce the concentrations discovered.
In 2015, radiocarbon analysis confirmed that the tramadol found in N. latifolia roots could not be plant-derived and was of synthetic origin. | 0 | Theoretical and Fundamental Chemistry |
Stereospecific cis-hydroalumination is possible through the use of dialkylalanes. The most common reagent used for this purpose is di(isobutyl)aluminium hydride (DIBAL-H). Analogous to hydroboration reactions with RBH, hydroalumination with RAlH leads to the attachment of aluminium at the carbon less able to stabilize developing positive charge (anti-Markovnikov selectivity). Metalation of terminal alkynes is a significant side reaction that occurs under these conditions. If metalation is desired, tertiary amine complexes of DIBAL-H are useful.
The use of silyl acetylenes avoids the problem of competitive metalation of terminal alkenes. The stereoselectivity of hydroalumination can be altered through a change in solvent: tertiary amine solvents provide the cis alkenylalane and hydrocarbon solvents provide the trans isomer.
Lithium aluminium hydride hydroaluminates alkynes to afford trans alkenylalanes. In equation (7) hydride adds to the terminal carbon, which places the developing negative charge next to the stabilizing phenyl substituent. | 0 | Theoretical and Fundamental Chemistry |
dimesitylborane is a dimer (CHMe)BH). It reacts only slowly with simple terminal alkenes. On the other hand, alkynes undergo monohydroboration with MesBH easily to produce alkenylboranes. | 0 | Theoretical and Fundamental Chemistry |
* A well-known electrosynthesis is the Kolbe electrolysis, in which two carboxylic acids decarboxylate, and the remaining structures bond together:
* A variation is called the non-Kolbe reaction when a heteroatom (nitrogen or oxygen) is present at the α-position. The intermediate oxonium ion is trapped by a nucleophile, usually solvent.
* Anodic electrosynthesis oxidize primary aliphatic amine to nitrile.
* Amides can be oxidized to N-acyliminium ions, which can be captured by various nucleophiles, for example:
:This reaction type is called a Shono oxidation. An example is the α-methoxylation of N-carbomethoxypyrrolidine
* Oxidation of a carbanion can lead to a coupling reaction for instance in the electrosynthesis of the tetramethyl ester of ethanetetracarboxylic acid from the corresponding malonate ester
* α-amino acids form nitriles and carbon dioxide via oxidative decarboxylation at AgO anodes (the latter is formed in-situ by oxidation of AgO):
* Cyanoacetic acid from cathodic reduction of carbon dioxide and anodic oxidation of acetonitrile.
* Propiolic acid is prepared commercially by oxidizing propargyl alcohol at a lead electrode.. | 0 | Theoretical and Fundamental Chemistry |
The partition coefficient between n-Octanol and water is known as the n-octanol-water partition coefficient, or K. It is also frequently referred to by the symbol P, especially in the English literature. It is also known as n-octanol-water partition ratio.
K, being a type of partition coefficient, serves as a measure of the relationship between lipophilicity (fat solubility) and hydrophilicity (water solubility) of a substance. The value is greater than one if a substance is more soluble in fat-like solvents such as n-octanol, and less than one if it is more soluble in water. | 0 | Theoretical and Fundamental Chemistry |
All three theories model the temperature dependence of k using an equation of the form
for some constant C, where α = 0, , and 1 give Arrhenius theory, collision theory, and transition state theory, respectively, although the imprecise notion of ΔE, the energy needed to overcome the activation barrier, has a slightly different meaning in each theory. In practice, experimental data does not generally allow a determination to be made as to which is "correct" in terms of best fit. Hence, it must be remembered that all three are conceptual frameworks that make numerous assumptions, both realistic and unrealistic, in their derivations. As a result, they are capable of providing different insights into a system. | 0 | Theoretical and Fundamental Chemistry |
Lauryldimethylamine oxide (LDAO), also known as dodecyldimethylamine oxide (DDAO), is an amine oxide–based zwitterionic surfactant, with a C (dodecyl) alkyl tail. It is one of the most frequently-used surfactants of this type. Like other amine oxide–based surfactants it is antimicrobial, being effective against common bacteria such as S. aureus and E. coli, however, it is also non-denaturing and may be used to solubilize proteins.
At high concentrations, LDAO forms liquid crystalline phases. Despite having only one polar atom that is able to interact with water – the oxygen atom (the quaternary nitrogen atom is hidden from intermolecular interactions), DDAO is a strongly amphiphilic surfactant: it forms normal micelles and normal liquid crystalline phases. High amphiphilicity of this surfactant can be explained by the fact that it forms not only very strong hydrogen bonds with water: the energy of DDAO – water hydrogen bond is about 50 kJ/mol, but it also has high experimental partition coefficient in non-polar medium, as characterized by experimental logP 5.284 | 0 | Theoretical and Fundamental Chemistry |
(AD 900–1500)
Utilitarian and ceremonial objects; objects of personal adornment
#Chiapa de Corzo, Chiapas
#El Paredón, Chiapas
#Polol, Guatemala
#Santa Rita Corozal, Belize
#Nojpetén, Guatemala
#Tikal, Guatemala
#Yaxhá, Guatemala
#Palenque, Chiapas
#Wild Cane Cay, Belize
#Lamanai, Belize | 1 | Applied and Interdisciplinary Chemistry |
In 1890, Sergei Winogradsky proposed a novel type of life process called "anorgoxydant". His discovery suggested that some microbes could live solely on inorganic matter and emerged during his physiological research in the 1880s in Strasbourg and Zürich on sulfur, iron, and nitrogen bacteria.
In 1897, Wilhelm Pfeffer coined the term "chemosynthesis" for the energy production by oxidation of inorganic substances, in association with autotrophic carbon dioxide assimilation—what would be named today as chemolithoautotrophy. Later, the term would be expanded to include also chemoorganoautotrophs, which are organisms that use organic energy substrates in order to assimilate carbon dioxide. Thus, chemosynthesis can be seen as a synonym of chemoautotrophy.
The term "chemotrophy", less restrictive, would be introduced in the 1940s by André Lwoff for the production of energy by the oxidation of electron donors, organic or not, associated with auto- or heterotrophy. | 1 | Applied and Interdisciplinary Chemistry |
Transition metal complexes often have spectacular colors caused by electronic transitions by the absorption of light. For this reason they are often applied as pigments. Most transitions that are related to colored metal complexes are either d–d transitions or charge transfer bands. In a d–d transition, an electron in a d orbital on the metal is excited by a photon to another d orbital of higher energy, therefore d–d transitions occur only for partially-filled d-orbital complexes (d). For complexes having d or d configuration, charge transfer is still possible even though d–d transitions are not. A charge transfer band entails promotion of an electron from a metal-based orbital into an empty ligand-based orbital (metal-to-ligand charge transfer or MLCT). The converse also occurs: excitation of an electron in a ligand-based orbital into an empty metal-based orbital (ligand-to-metal charge transfer or LMCT). These phenomena can be observed with the aid of electronic spectroscopy; also known as UV-Vis. For simple compounds with high symmetry, the d–d transitions can be assigned using Tanabe–Sugano diagrams. These assignments are gaining increased support with computational chemistry. | 0 | Theoretical and Fundamental Chemistry |
Some of the largest antidunes on Earth are formed by turbidity currents. One observed sediment-wave field is located on the lower continental slope off Guyana, South America. This sediment-wave field covers an area of at least 29 000 km at a water depth of 4400–4825 meters. These antidunes have wavelengths of 110–2600 m and wave heights of 1–15 m. Turbidity currents responsible for wave generation are interpreted as originating from slope failures on the adjacent Venezuela, Guyana and Suriname continental margins. Simple numerical modelling has been enabled to determine turbidity current flow characteristics across the sediment waves to be estimated: internal Froude number = 0.7–1.1, flow thickness = 24–645 m, and flow velocity = 31–82 cm·s. Generally, on lower gradients beyond minor breaks of slope, flow thickness increases and flow velocity decreases, leading to an increase in wavelength and a decrease in height. | 1 | Applied and Interdisciplinary Chemistry |
2-Methoxypropene is an ether with the chemical formula CHO. It is a reagent used in organic synthesis to introduce a protecting group for alcohols, and the conversion diols to the acetonide group.
2-Methoxypropene can be prepared by the elimination of methanol from dimethoxypropane, or by the addition of methanol to propyne or allene. | 0 | Theoretical and Fundamental Chemistry |
Cyproterone is a steroidal antiandrogen that competitively inhibits the binding of testosterone or DHT to AR. Cyproterone binds to ARs that are expressed by prostate cancer cells as well as to the AR that are expressed in the hypothalamus and pituitary. Therefore, cyproterone blocks the negative feedback of androgens at the hypothalamic-pituitary level leading to increased luteinizing hormone (LH) serum levels. This rise in LH levels causes an increase in serum testosterone levels and ultimately diminishes the ability of cyproterone to compete for AR binding and to block androgenic stimulation.
Cyproterone acetate was developed to overcome this problem. It is formed by adding an acetate group to cyproterone, see figure 3. Cyproterone acetate has a dual mode of action as it competes directly with DHT for binding to AR, but also inhibits gonadotropin secretion. It thereby reduces androgen, estrogen and LH levels. Cyproterone acetate acts both directly as an antiandrogen in prostate cancer cells and also functions to indirectly decrease serum testosterone levels. The latter causes the limitations of cyproterone acetate, which are central effects on androgen secretion, with subsequent loss of libido and sexual potency. Several reports also state that cyproterone acetate causes liver hyperplasia. These side effects gave pharmaceutical companies the incentive to search for alternative, "pure" NSAAs that would not have these side effects. Pure antiandrogens block the androgen receptor without exerting any agonistic or any other hormonal activity.
Flutamide became the first NSAA to be tested clinically. Later the NSAAs bicalutamide and nilutamide were developed. The alleged advantages of these compounds were that they did not affect libido or potency like the other centrally acting compounds under development, luteinizing-hormone-releasing hormone (LHRH) agonists and cyproterone acetate. But this theory did not prove to be true. These NSAAs eventually crossed the blood–brain barrier, like cyproterone acetate, leading to a subsequent increase in serum testosterone levels. | 1 | Applied and Interdisciplinary Chemistry |
* Anomeric effect
* Carbohydrate
* Carbohydrate conformation
* Disaccharide
* Glycosidic bond
* Monosaccharide
* Polysaccharide | 0 | Theoretical and Fundamental Chemistry |
In the English literature this reaction is sometimes called Baeyer–Drewsn reaction, although the author of the original paper was spelled Drewsn. | 0 | Theoretical and Fundamental Chemistry |
Some quinones, and phenoxynaphthacene quinone in particular, have photochromicity resulting from the ability of the phenyl group to migrate from one oxygen atom to another. Quinones with good thermal stability have been prepared, and they also have the additional feature of redox activity, leading to the construction of many-state molecular switches that operate by a mixture of photonic and electronic stimuli. | 0 | Theoretical and Fundamental Chemistry |
Closely related is mmCIF, macromolecular CIF, which is intended as an successor to the Protein Data Bank (PDB) format. It is now the default format used by the Protein Data Bank.
Also closely related is Crystallographic Information Framework, a broader system of exchange protocols based on data dictionaries and relational rules expressible in different machine-readable manifestations, including, but not restricted to, Crystallographic Information File and XML. | 0 | Theoretical and Fundamental Chemistry |
A total synthesis reported by Eli Lilly and the University of Southampton in 2007 also starts from isovanillin. The aldehyde group in its derivative 1 is converted to its amine by reductive amination with methylamine which is then protected as a BOC group in 2. The remainder of the carbon framework is added with chiral propargyl alcohol 3 (introducing the 4a stereocenter and obtained by chiral synthesis of the ketone with R-Alpine borane) in a Mitsunobu reaction to aryl ether 4. The trimethylsilyl protective group is removed by potassium carbonate in methanol and the subsequent enyne metathesis reaction with Grubbs' catalyst gives diene 5. A hydroboration–oxidation reaction converts 5 to alcohol 6 and an intramolecular Heck reaction affords tricycle 7 with alkene isomerization and establishment of the 8a stereocenter with correct stereochemistry based on chiral induction. The allyl alcohol group in 8 is introduced by selenoxide oxidation with an excess of the desired diastereomer. In the final step to galanthamine 9 the hydroxyl group is activated as the triflate and the amine group as the mesylate for intramolecular azepine ring closure via nucleophilic substitution (with 6% epimer formation). | 0 | Theoretical and Fundamental Chemistry |
In vehicles, a ducted fan is a method of propulsion in which a fan, propeller or rotor is surrounded by an aerodynamic duct or shroud which enhances its performance to create aerodynamic thrust or lift to transport the vehicle. | 0 | Theoretical and Fundamental Chemistry |
Cyanobacteria use the energy of sunlight to drive photosynthesis, a process where the energy of light is used to synthesize organic compounds from carbon dioxide. Because they are aquatic organisms, they typically employ several strategies which are collectively known as a " concentrating mechanism" to aid in the acquisition of inorganic carbon ( or bicarbonate). Among the more specific strategies is the widespread prevalence of the bacterial microcompartments known as carboxysomes, which co-operate with active transporters of CO and bicarbonate, in order to accumulate bicarbonate into the cytoplasm of the cell. Carboxysomes are icosahedral structures composed of hexameric shell proteins that assemble into cage-like structures that can be several hundreds of nanometres in diameter. It is believed that these structures tether the -fixing enzyme, RuBisCO, to the interior of the shell, as well as the enzyme carbonic anhydrase, using metabolic channeling to enhance the local concentrations and thus increase the efficiency of the RuBisCO enzyme. | 0 | Theoretical and Fundamental Chemistry |
The largest risk when using a separating funnel is that of pressure build-up. Pressure accumulates during mixing if a gas evolving reaction or physical change occurs. This problem can be easily handled by simply opening the stopper at the top of the funnel routinely while mixing. More standard procedure is to invert the separating funnel upside down, and open the stopcock to release the pressure, a step done repeatedly known as venting. This should be done with the tip of the funnel pointed away from the body. | 0 | Theoretical and Fundamental Chemistry |
Frzb (pronounced like the toy frisbee) is a Wnt-binding protein especially important in embryonic development. It is a competitor for the cell-surface G-protein receptor Frizzled.
Frizzled is a tissue polarity gene in Drosophila melanogaster and encodes integral proteins that function as cell-surface receptors for Wnts called serpentine receptors. The integral membrane proteins contain a cysteine-rich domain thought to be the Wnt binding domain in extracellular region. The signals are initiated at the 7 transmembrane domain and transmitted through receptor coupling to G-proteins.
This protein is expressed in chondrocytes making it important in skeletal development in the embryo and fetus. Frzb is localized in the extracellular plasma membrane. Unlike frizzled, frzb lacks the 7 transmembrane domains normally found in G-protein-coupled receptors. It is still considered a homolog of frizzled because it contains a Cysteine Rich Domain (CRD), and because of its intracellular C-terminus which is crucial for signaling. The CRD is highly conserved in diverse proteins, such as receptor tyrosine kinases and functions as a ligand binding domain. The C-terminal is a carboxyl terminus located intracellularly and is required for canonical signaling.
The serpentine receptors (frzb) couple binds to ligand (Wnt protein) and activates G-proteins. A signal transduction cascade results in the secretion of first and second group antagonists. First group antagonists are composed of secreted Frizzled Related protein family (Sfrp) and Wnt inhibitory factor (Wif). Both Srfp and Wif bind directly to Wnt proteins blocking activation of the receptor. Second group of antagonists contains a class of Wnt inhibitory proteins known as Frizzled Receptor-like Proteins (FRPs). FRPs bind to the LRP (low-density-lipoprotein-related protein) co-receptors blocking activation of the Wnt signaling pathway.
One such pathway that involves Frizzled (Fz) family is the Wnt/β-Catenin (β-Cat) signaling. β-Cat is an intracellular signal that is held in check by axin. In this pathway, the activation of Wnt receptors can be transduced by the canonical pathway via a series of phosphorylation steps leading to stabilization and nuclear import of β-Cat into the nucleus where β-Cat associates with T-cell factor (TCF), a DNA-binding protein family. The β-Cat and TCF complex activates target genes of the Wnt pathway. In the absence of Wnt, β-Catenin is phosphorylated by complex containing GSK3 (glycogen synthase kinase 3) which targets β-Cat for proteosomal degradation. In the nucleus, members of the T-cell factor (TCF) family of DNA-binding proteins repress Wnt targets along with co-repressors such as Groucho (Gro).
If Wnt is present it binds to Fz-LRP receptors causing axin to bind to intracellular domain of LRP and Fz. Dishevelled (Dvl) is a protein required for Wnt-dependent inhibition complex. The combination of LRP-axin induces Dvl phosphorylation (P) which blocks the APC-axin-GSK3 complex from phosphorylating β-Cat. The accumulated β-Cat then enters the nucleus and converts TCF into a transcriptional activator.
Defects in Frzb are associated with female-specific osteoarthritis (OA) susceptibility which is the most prevalent form of arthritis and common cause of disability.
https://web.archive.org/web/20070930043451/http://jcs.biologists.org/content/vol119/issue3/images/large/JCS02826F1.jpeg
Frzb (known as Frzb1 or Sfrp3, Secreted Frizzled Related Protein 3) was initially identified as a chondrogenic factor during bone morphogenesis, and was described as a novel marker of the neural crest-derived mesenchymal cells that contribute to dental follicle formation, the future periodontium. | 1 | Applied and Interdisciplinary Chemistry |
Salts of ATP can be isolated as colorless solids.
ATP is stable in aqueous solutions between pH 6.8 and 7.4 (in the absence of catalysts). At more extreme pH levels, it rapidly hydrolyses to ADP and phosphate. Living cells maintain the ratio of ATP to ADP at a point ten orders of magnitude from equilibrium, with ATP concentrations fivefold higher than the concentration of ADP. In the context of biochemical reactions, the P-O-P bonds are frequently referred to as high-energy bonds. | 1 | Applied and Interdisciplinary Chemistry |
If the data for different samples are going to be contrasted with each other, one can perform downsampling on the reads to achieve comparability. The reported sequencing coverage depth for reasonable analysis results was reported as bigger than 500 folds, thus any sample whose mean sequencing depth does not exceed the number can be dropped for more accurate outcomes. Also, EPIC-seq uses estimated expected cfDNA fragment length density of 140-185, based on chromatosomal length. The samples that have outlier fragment length density can be dropped for higher correlation results. As the last quality control step, mapping quality should be considered. A looser threshold can be dictated on EPIC-seq reads, compared to WGS, due to the TSS selection criteria imposed during design phases making the reads more unique for EPIC-seq. | 1 | Applied and Interdisciplinary Chemistry |
T5 retrofit conversion can maintain existing lighting levels with the higher efficiency of the T5 lamp. However, with kits that operates the lamp on the existing magnetic ballast, the efficiency drops and the lamp life is considerably shortened, as T5 lamps aren't designed to be operated on mains frequency but only on high frequency. | 1 | Applied and Interdisciplinary Chemistry |
Polysubstituted benzenes were originally synthesized by substitution reactions on aromatic precursors. However, these reactions can have low regioselectivity and are prone to over substitution. Directed ortho metalation requires precursors that are often unstable to metallating reagents. Both these synthetic routes pose issues in total synthesis. In 1984 a new synthetic strategy was developed by Rick Danheiser to address these shortcomings. | 0 | Theoretical and Fundamental Chemistry |
The concept of theoretical plates or trays applies to other processes as well, such as capillary electrophoresis and some types of adsorption. | 1 | Applied and Interdisciplinary Chemistry |
ChIP-on-chip (also known as ChIP-chip) is a technology that combines chromatin immunoprecipitation (ChIP) with DNA microarray ("chip"). Like regular ChIP, ChIP-on-chip is used to investigate interactions between proteins and DNA in vivo. Specifically, it allows the identification of the cistrome, the sum of binding sites, for DNA-binding proteins on a genome-wide basis. Whole-genome analysis can be performed to determine the locations of binding sites for almost any protein of interest. As the name of the technique suggests, such proteins are generally those operating in the context of chromatin. The most prominent representatives of this class are transcription factors, replication-related proteins, like origin recognition complex protein (ORC), histones, their variants, and histone modifications.
The goal of ChIP-on-chip is to locate protein binding sites that may help identify functional elements in the genome. For example, in the case of a transcription factor as a protein of interest, one can determine its transcription factor binding sites throughout the genome. Other proteins allow the identification of promoter regions, enhancers, repressors and silencing elements, insulators, boundary elements, and sequences that control DNA replication. If histones are subject of interest, it is believed that the distribution of modifications and their localizations may offer new insights into the mechanisms of regulation.
One of the long-term goals ChIP-on-chip was designed for is to establish a catalogue of (selected) organisms that lists all protein-DNA interactions under various physiological conditions. This knowledge would ultimately help in the understanding of the machinery behind gene regulation, cell proliferation, and disease progression. Hence, ChIP-on-chip offers both potential to complement our knowledge about the orchestration of the genome on the nucleotide level and information on higher levels of information and regulation as it is propagated by research on epigenetics.
__TOC__ | 1 | Applied and Interdisciplinary Chemistry |
A library is often prepared by random fragmentation of DNA and ligation of common adaptor sequences. However, the generated short reads challenge the identification of structural variants, such as indels, translocations, and duplication. Large regions of simple repeats can further complicate the alignment. Alternatively, a jumping library can be used with NGS for the mapping of structural variation and scaffolding of de novo assemblies.
Jumping libraries can be categorized according to the length of the incorporated DNA fragments. | 1 | Applied and Interdisciplinary Chemistry |
The loss of the in 1978 provided some of the first physical evidence of the existence of rogue waves. München was a state-of-the-art cargo ship with multiple water-tight compartments and an expert crew. She was lost with all crew, and the wreck has never been found. The only evidence found was the starboard lifeboat recovered from floating wreckage sometime later. The lifeboats hung from forward and aft blocks above the waterline. The pins had been bent back from forward to aft, indicating the lifeboat hanging below it had been struck by a wave that had run from fore to aft of the ship and had torn the lifeboat from the ship. To exert such force, the wave must have been considerably higher than . At the time of the inquiry, the existence of rogue waves was considered so statistically unlikely as to be near impossible. Consequently, the Maritime Court investigation concluded that the severe weather had somehow created an "unusual event" that had led to the sinking of the München.
In 1980, the MV Derbyshire was lost during Typhoon Orchid south of Japan, along with all of her crew. The Derbyshire was an ore-bulk oil combination carrier built in 1976. At 91,655 gross register tons, she wasand remainsthe largest British ship ever lost at sea. The wreck was found in June 1994. The survey team deployed a remotely operated vehicle to photograph the wreck. A private report published in 1998 prompted the British government to reopen a formal investigation into the sinking. The investigation included a comprehensive survey by the Woods Hole Oceanographic Institution, which took 135,774 pictures of the wreck during two surveys. The formal forensic investigation concluded that the ship sank because of structural failure and absolved the crew of any responsibility. Most notably, the report determined the detailed sequence of events that led to the structural failure of the vessel. A third comprehensive analysis was subsequently done by Douglas Faulkner, professor of marine architecture and ocean engineering at the University of Glasgow. His 2001 report linked the loss of the Derbyshire with the emerging science on freak waves, concluding that the Derbyshire was almost certainly destroyed by a rogue wave.
Work by sailor and author Craig B. Smith in 2007 confirmed prior forensic work by Faulkner in 1998 and determined that the Derbyshire was exposed to a hydrostatic pressure of a "static head" of water of about with a resultant static pressure of . This is in effect of seawater (possibly a super rogue wave) flowing over the vessel. The deck cargo hatches on the Derbyshire were determined to be the key point of failure when the rogue wave washed over the ship. The design of the hatches only allowed for a static pressure less than of water or , meaning that the typhoon load on the hatches was more than 10 times the design load. The forensic structural analysis of the wreck of the Derbyshire is now widely regarded as irrefutable.
In addition, fast-moving waves are now known to also exert extremely high dynamic pressure. Plunging or breaking waves are known to cause short-lived impulse pressure spikes called Gifle peaks. These can reach pressures of (or more) for milliseconds, which is sufficient pressure to lead to brittle fracture of mild steel. Evidence of failure by this mechanism was also found on the Derbyshire. Smith has documented scenarios where hydrodynamic pressure up to or over 500 metric tonnes/m could occur.
In 2004, an extreme wave was recorded impacting the Admiralty Breakwater, Alderney, in the Channel Islands. This breakwater is exposed to the Atlantic Ocean. The peak pressure recorded by a shore-mounted transducer was . This pressure far exceeds almost any design criteria for modern ships, and this wave would have destroyed almost any merchant vessel. | 1 | Applied and Interdisciplinary Chemistry |
The Bjerrum length (after Danish chemist Niels Bjerrum 1879–1958 ) is the separation at which the electrostatic interaction between two elementary charges is comparable in magnitude to the thermal energy scale, , where is the Boltzmann constant and is the absolute temperature in kelvins. This length scale arises naturally in discussions of electrostatic, electrodynamic and electrokinetic phenomena in electrolytes, polyelectrolytes and colloidal dispersions.
In standard units, the Bjerrum length is given by
where is the elementary charge, is the relative dielectric constant of the medium and is the vacuum permittivity.
For water at room temperature , so that
In Gaussian units, and the Bjerrum length has the simpler form
The relative permittivity ε of water decreases so strongly with temperature that the product (ε·T) decreases. Therefore, in spite of the (1/T) relation, the Bjerrum length λ increases with temperature, as shown in the graph. | 0 | Theoretical and Fundamental Chemistry |
Rust is associated with the degradation of iron-based tools and structures. As rust has a much higher volume than the originating mass of iron, its buildup can also cause failure by forcing apart adjacent parts — a phenomenon sometimes known as "rust packing". It was the cause of the collapse of the Mianus river bridge in 1983, when the bearings rusted internally and pushed one corner of the road slab off its support.
Rust was an important factor in the Silver Bridge disaster of 1967 in West Virginia, when a steel suspension bridge collapsed in less than a minute, killing 46 drivers and passengers on the bridge at the time. The Kinzua Bridge in Pennsylvania was blown down by a tornado in 2003, largely because the central base bolts holding the structure to the ground had rusted away, leaving the bridge anchored by gravity alone.
Reinforced concrete is also vulnerable to rust damage. Internal pressure caused by expanding corrosion of concrete-covered steel and iron can cause the concrete to spall, creating severe structural problems. It is one of the most common failure modes of reinforced concrete bridges and buildings. | 1 | Applied and Interdisciplinary Chemistry |
Real material systems always incorporate disorder. Examples are structural defects in the lattice or disorder due to variations of the chemical composition. Their treatment is extremely challenging for microscopic theories due to the lack of detailed knowledge about perturbations of the ideal structure. Thus, the influence of the extrinsic effects on the PL is usually addressed phenomenologically. In experiments, disorder can lead to localization of carriers and hence drastically increase the photoluminescence life times as localized carriers cannot as easily find nonradiative recombination centers as can free ones.
Researchers from the King Abdullah University of Science and Technology (KAUST) have studied the photoinduced entropy (i.e. thermodynamic disorder) of InGaN/GaN p-i-n double-heterostructure and AlGaN nanowires using temperature-dependent photoluminescence. They defined the photoinduced entropy as a thermodynamic quantity that represents the unavailability of a system's energy for conversion into useful work due to carrier recombination and photon emission. They have also related the change in entropy generation to the change in photocarrier dynamics in the nanowire active regions using results from time-resolved photoluminescence study. They hypothesized that the amount of generated disorder in the InGaN layers eventually increases as the temperature approaches room temperature because of the thermal activation of surface states, while an insignificant increase was observed in AlGaN nanowires, indicating lower degrees of disorder-induced uncertainty in the wider bandgap semiconductor. To study the photoinduced entropy, the scientists have developed a mathematical model that considers the net energy exchange resulting from photoexcitation and photoluminescence. | 0 | Theoretical and Fundamental Chemistry |
Chemistry:
* Inorganic chemistry
* Analytical chemistry
* Organic chemistry
* Physical chemistry
* Colloid chemistry
Chemical technology:
* Chemistry and Technology of basic organic and petrochemical synthesis
* Chemistry and Technology of organometallic compounds
* Chemical technology of natural energy and carbon materials
* Chemical Technology of Macromolecular Compounds
* Chemical technology of plastics and composite materials
* Technology for processing of elastomers
* Nanotechnology of organic photosensitive materials
* Processes and devices of chemical technologies
* Information Systems in Chemical Engineering and Biotechnology
* Chemical technology of fuel and gas
* Theoretical Foundations of Chemical Engineering
Biotechnology:
* Molecular and Cellular Biotechnology
* Chemistry and Technology of biologically active substances
* Technology of drugs
* Technology of biopharmaceuticals
* Technology of bioconversion of plant material
Materials science and technology of materials:
* Materials science and technology of nanomaterials and coatings
* Material science, the receipt and processing of inorganic powder and composite materials
* Theoretical and Applied Polymer Materials
* Physico-chemical studies of new materials and processes
* Physical materials and technology of electronic materials
Technosphere Safety:
* Protecting the environment
Standardization and Certification:
* Total Quality Management | 1 | Applied and Interdisciplinary Chemistry |
The desalinated water is stabilized to protect downstream pipelines and storage, usually by adding lime or caustic soda to prevent corrosion of concrete-lined surfaces. Liming material is used to adjust pH between 6.8 and 8.1 to meet the potable water specifications, primarily for effective disinfection and for corrosion control. Remineralisation may be needed to replace minerals removed from the water by desalination, although this process has proved to be costly and inconvenient in order to meet mineral demand by humans and plants as found in typical freshwater. For instance water from Israels national water carrier typically contains dissolved magnesium levels of 20 to 25 mg/liter, while water from the Ashkelon plant has no magnesium. Ashkelon water created magnesium-deficiency symptoms in crops, including tomatoes, basil, and flowers, and had to be remedied by fertilization. Israeli drinking water standards require a minimum calcium level of 20 mg/liter. Askelons post-desalination treatment uses sulfuric acid to dissolve calcite (limestone), resulting in calcium concentrations of 40 to 46 mg/liter, lower than the 45 to 60 mg/liter found in typical Israeli fresh water. | 0 | Theoretical and Fundamental Chemistry |
There are attempts to provide partition coefficients for drugs at a single-cell level. This strategy requires methods for the determination of concentrations in individual cells, i.e., with Fluorescence correlation spectroscopy or quantitative Image analysis. Partition coefficient at a single-cell level provides information on cellular uptake mechanism. | 0 | Theoretical and Fundamental Chemistry |
Barium nitrite can be made by reacting barium nitrate with lead metal sponge, or by reaction of lead nitrite with barium chloride. | 0 | Theoretical and Fundamental Chemistry |
Modafinil and armodafinil were studied as a complement to antipsychotic medications in the treatment of schizophrenia. They showed no effect on positive symptoms or cognitive performance. A 2015 meta-analysis found that modafinil and armodafinil may slightly reduce negative symptoms in people with acute schizophrenia, though they do not appear useful for people with the condition who are stable, with high negative symptom scores. Among medications demonstrated to be effective for reducing negative symptoms in combination with antipsychotics, modafinil and armodafinil are among the smallest effect sizes. | 0 | Theoretical and Fundamental Chemistry |
Charles Hatchett was born in Long Acre, London to John Hatchett (1729–1806), and Elizabeth Hatchett. John Hatchett was "(one of) the coachbuilders of London of the greatest celebrity". He later became a magistrate in Hammersmith. Charles Hatchett attended a private school, Fountayne's, in Marylebone Park, and was a self-taught mineralogist and analytical chemist.
On 24 March 1786, Charles Hatchett married Elizabeth Martha Collick (1756–1837) at St Martin-in-the-Fields. Their children included:
#John Charles Hatchett (bapt 27 January 1788 St Martin-in-the-Fields)
#His daughter, Anna Frederica Hatchett, married the chemist William Thomas Brande.
Following their marriage, Hatchett and his wife traveled extensively in Poland and Russia for 2 years before settling in Hammersmith. In 1790, Hatchett again had the opportunity to travel extensively, when his father sent him to deliver a coach to Catherine the Great in St. Petersburg. With an introduction from Sir Joseph Banks, he visited chemist Martin Klaproth, geologist and botanist Peter Pallas, Neapolitan mineralogist Andrea Savaresi, and other scientists.
In 1796 Hatchett took another long tour, this time through England and Scotland, where he visited geological sites, mines, and factories. His diary of this trip was edited by Arthur Raistrick and published in 1967 as The Hatchett diary: a tour through the counties of England and Scotland in 1796 visiting their mines and manufactories. | 1 | Applied and Interdisciplinary Chemistry |
Other factors such as iron-rich dust influx from large desert areas such as the Sahara are thought to play a role in causing HABs. Some algal blooms on the Pacific coast have also been linked to natural occurrences of large-scale climatic oscillations such as El Niño events. HABs are also linked to heavy rainfall. Although HABs in the Gulf of Mexico were witnessed in the early 1500s by explorer Cabeza de Vaca, it is unclear what initiates these blooms and how large a role nanthropogenic and natural factors play in their development. | 0 | Theoretical and Fundamental Chemistry |
The TRH test involves administration of a small amount of TRH intravenously, following which levels of TSH will be measured at several subsequent time points using samples of blood taken from a peripheral vein.
The test is used in the differential diagnosis of secondary and tertiary hypothyroidism. First, blood is drawn and a baseline TSH level is measured. Then, TRH is administered via a vein. After 30 minutes blood is drawn again and the levels of TSH are measured and compared to the baseline. Some authors recommend additional blood sampling at 15 minutes. In children, late blood sampling at 60 to 120 minutes is necessary.
An increase in the serum TSH level following TRH administration means that the cause of the hypothyroidism is in the hypothalamus (tertiary hypothyroidism), i.e. the hypothalamus is not producing TRH. Therefore, when TRH is given exogenously, TSH levels increase. If the increase in serum TSH level following TRH administration is absent or very slight, then the cause of the hypothyroidism is in the anterior pituitary gland, i.e. the pituitary is not secreting TSH. Therefore, even when TRH is given exogenously, TSH levels do not rise as the pituitary is diseased. | 1 | Applied and Interdisciplinary Chemistry |
A carbon source is a carbon-containing molecule that is used by an organism to synthesise biomass. Such sources may be organic or inorganic. Heterotrophs must use organic molecules as a source of both carbon and energy. In contrast, autotrophs may use inorganic materials as a source for both, such as inorganic chemical energy (chemolithotrophs) or light (photoautotrophs). The carbon cycle, which begins with an inorganic carbon source (such as carbon dioxide) and progresses through the biological carbon fixation process, includes the biological use of carbon as one of its components. | 1 | Applied and Interdisciplinary Chemistry |
The traditional approach to supramolecular catalysts focuses on the design of macromolecular receptor with appropriately placed catalytic functional groups. These catalysts are often inspired by the structure of enzymes with the catalytic group mimicking reactive amino acid residues, but unlike real enzymes, the binding sites of these catalysts are rigid structure made from chemical building blocks. All of the examples in this article are developed via the design approach.
Jeremy Sanders pointed out that the design approach has not been successful and has produced very few efficient catalysts because of rigidity of the supramolecules. He argued that rigid molecules with a slight mismatch to the transition state cannot be an efficient catalyst. Rather than investing so much synthesis effort on one rigid molecule that we cannot determine its precise geometry to the sub-angstrom level which is required for good stabilization, Sanders suggested the use of many small flexible building blocks with competing weak interactions so that it is possible for the catalyst to adjust its structure to accommodate the substrate better. There is a direct trade-off between the enthalpic benefit from flexible structure and the entropic benefit from rigid structure. Flexible structure could perhaps bind the transition state better but it allows more room for the substrates to move and vibrate. Most supramolecular chemists in the past prefer to build rigid structures out of fear of entropic cost.
This problem could perhaps be mended by Baker and Houk's "inside-out approach" which allows a systematic de novo enzyme development. This computational method starts simply with a predicted transition state structure and slowly builds outward by optimizing the arrangement of functional groups to stabilize the transition state. Then it fills out the remainder of the active site and, finally, it generates an entire protein scaffold that could contain the designed active site. This method could potentially be applied to supramolecular catalysis, although a plethora of chemical building blocks could easily overwhelm the computational model intended to work with 20 amino acids. | 0 | Theoretical and Fundamental Chemistry |
Escitalopram, sold under the brand names Lexapro and Cipralex, among others, is an antidepressant of the selective serotonin reuptake inhibitor (SSRI) class. Escitalopram is mainly used to treat major depressive disorder and generalized anxiety disorder. It is taken by mouth, available commercially as an oxalate salt exclusively.
Common side effects include trouble sleeping, nausea, sexual problems, and feeling tired. More serious side effects may include suicidal thoughts in people up to the age of 24 years. It is unclear if use during pregnancy or breastfeeding is safe. Escitalopram is the (S)-enantiomer of citalopram (which exists as a racemate), hence the name es-citalopram.
Escitalopram was approved for medical use in the United States in 2002. Escitalopram is rarely replaced by twice the dose of citalopram, though escitalopram is safer and more effective. It is on the World Health Organization's List of Essential Medicines. In 2021, it was the fifteenth most commonly prescribed medication in the United States, with more than 30million prescriptions. | 0 | Theoretical and Fundamental Chemistry |
As opposed to DNA gene editing techniques (e.g., using CRISPR-Cas proteins to make modifications directly to a defective gene), LEAPER targets editing messenger RNA (mRNA) for the same gene which is transcribed into a protein. Post-transcriptional RNA modification typically involves the strategy of converting adenosine-to-inosine (A-to-I) since inosine (I) demonstrably mimics guanosine (G) during translation into a protein. A-to-I editing is catalyzed by adenosine deaminase acting on RNA (ADAR) enzymes, whose substrates are double-stranded RNAs. Three human ADAR genes have been identified with ADAR1 (official symbol ADAR) and ADAR2 (ADARB1) proteins developed activity profiles. LEAPER achieves this targeted RNA editing through the use of short engineered ADAR-recruiting RNAs (). consist of endogenous ADAR1 proteins with several RNA binding domains (RBDs) fused with a peptide, CRISPR-Cas13b protein, and a guide RNA (gRNA) between 100 and 150 nt in length for high editing efficiency designed to recruit the chimeric ADAR protein to a target site.
This results in a change in which protein is synthesized during translation. | 1 | Applied and Interdisciplinary Chemistry |
Positive displacement flowmeters are very accurate and have high turndown. They can be used in very viscous, dirty and corrosive fluids and essentially require no straight runs of pipe for fluid flow stream conditioning though pressure drop can be an issue. They are widely used in the custody transfer of oils and liquid fluids (gasoline) and are applied on residential home natural gas and water metering. A diaphragm meter, with which most homes are equipped, is an example of a positive displacement meter. This type of meter is appealing in certain custody transfer flow applications where it is critical that the metering be functional in order for any flow to take place.
Positive displacement flowmeters, with internal wiping seals, produce the highest differential pressure (and subsequently greatest pressure drop head loss) of all the flowmeter types. Meters that rely on a liquid seal create a relatively low pressure drop.
Positive-displacement (PD) meters can measure both liquids and gases. Like turbine meters, PD flow meters work best with clean, non-corrosive, and non-erosive liquids and gases, although some models will tolerate some impurities. Because of their high accuracy, PD meters are widely used at residences to measure the amount of gas or water used. Other applications include: chemical injection, fuel measurement, precision test stands, high pressure, hydraulic testing, and similar precision applications.
Some designs require that only lubricating fluid be measured, because the rotors are exposed to the fluid. PD meters differ from turbine meters in that they handle medium and high-viscosity liquids well. For this reason, they are often used to measure the flow of hydraulic fluids. Compared with orifice-type meters, PD meters require very little straight upstream piping since they are not sensitive to uneven flow distribution across the area of the pipe. Positive displacement flow meters can provide better relative accuracy at low flows than orifice-type flow meters. However, a positive displacement meter can be considerably heavier and more costly than non-positive-displacement types such as orifice plates, magnetic or vortex flow meters. | 1 | Applied and Interdisciplinary Chemistry |
Without adharmastikaay, rest and stability is not possible in the universe. The principle of rest helps matter and the sentient that are liable to stay without moving, like the shade helps travellers. It does not stabilize those that move. According to Champat Rai Jain: | 1 | Applied and Interdisciplinary Chemistry |
Electroanalytical methods measure the electric potential in volts and/or the electric current in amps in an electrochemical cell containing the analyte. These methods can be categorized according to which aspects of the cell are controlled and which are measured. The three main categories are potentiometry (the difference in electrode potentials is measured), coulometry (the cells current is measured over time), and voltammetry (the cells current is measured while actively altering the cell's potential). | 0 | Theoretical and Fundamental Chemistry |
C plants capture carbon dioxide in their mesophyll cells (using an enzyme called phosphoenolpyruvate carboxylase which catalyzes the combination of carbon dioxide with a compound called phosphoenolpyruvate (PEP)), forming oxaloacetate. This oxaloacetate is then converted to malate and is transported into the bundle sheath cells (site of carbon dioxide fixation by RuBisCO) where oxygen concentration is low to avoid photorespiration. Here, carbon dioxide is removed from the malate and combined with RuBP by RuBisCO in the usual way, and the Calvin cycle proceeds as normal. The concentrations in the Bundle Sheath are approximately 10–20 fold higher than the concentration in the mesophyll cells.
This ability to avoid photorespiration makes these plants more hardy than other plants in dry and hot environments, wherein stomata are closed and internal carbon dioxide levels are low. Under these conditions, photorespiration does occur in C plants, but at a much lower level compared with C plants in the same conditions. C plants include sugar cane, corn (maize), and sorghum. | 0 | Theoretical and Fundamental Chemistry |
;1605:Sir Francis Bacon publishes The Proficience and Advancement of Learning, which contains a description of what would later be known as the scientific method.
;1605:Michal Sedziwój publishes the alchemical treatise A New Light of Alchemy which proposed the existence of the "food of life" within air, much later recognized as oxygen.
;1615:Jean Beguin publishes the Tyrocinium Chymicum, an early chemistry textbook, and in it draws the first-ever chemical equation.
;1637:René Descartes publishes Discours de la méthode, which contains an outline of the scientific method.
;1648:Posthumous publication of the book Ortus medicinae by Jan Baptist van Helmont, which is cited by some as a major transitional work between alchemy and chemistry, and as an important influence on Robert Boyle. The book contains the results of numerous experiments and establishes an early version of the law of conservation of mass.
;1661:Robert Boyle publishes The Sceptical Chymist, a treatise on the distinction between chemistry and alchemy. It contains some of the earliest modern ideas of atoms, molecules, and chemical reaction, and marks the beginning of the history of modern chemistry.
;1662:Robert Boyle proposes Boyle's law, an experimentally based description of the behavior of gases, specifically the relationship between pressure and volume.
;1735:Swedish chemist Georg Brandt analyzes a dark blue pigment found in copper ore. Brandt demonstrated that the pigment contained a new element, later named cobalt.
;1754:Joseph Black isolates carbon dioxide, which he called "fixed air".
;1757:Louis Claude Cadet de Gassicourt, while investigating arsenic compounds, creates Cadet's fuming liquid, later discovered to be cacodyl oxide, considered to be the first synthetic organometallic compound.
;1758:Joseph Black formulates the concept of latent heat to explain the thermochemistry of phase changes.
;1766:Henry Cavendish discovers hydrogen as a colorless, odourless gas that burns and can form an explosive mixture with air.
;1773–1774: Carl Wilhelm Scheele and Joseph Priestley independently isolate oxygen, called by Priestley "dephlogisticated air" and Scheele "fire air".
;1778:Antoine Lavoisier, considered "The father of modern chemistry", recognizes and names oxygen, and recognizes its importance and role in combustion.
;1787:Antoine Lavoisier publishes Méthode de nomenclature chimique, the first modern system of chemical nomenclature.
;1787:Jacques Charles proposes Charless law, a corollary of Boyles law, describes relationship between temperature and volume of a gas.
;1789:Antoine Lavoisier publishes Traité Élémentaire de Chimie, the first modern chemistry textbook. It is a complete survey of (at that time) modern chemistry, including the first concise definition of the law of conservation of mass, and thus also represents the founding of the discipline of stoichiometry or quantitative chemical analysis.
;1797:Joseph Proust proposes the law of definite proportions, which states that elements always combine in small, whole number ratios to form compounds.
;1800:Alessandro Volta devises the first chemical battery, thereby founding the discipline of electrochemistry. | 1 | Applied and Interdisciplinary Chemistry |
Grain refinement, also known as inoculation, is the set of techniques used to implement grain boundary strengthening in metallurgy. The specific techniques and corresponding mechanisms will vary based on what materials are being considered.
One method for controlling grain size in aluminum alloys is by introducing particles to serve as nucleants, such as Al–5%Ti. Grains will grow via heterogeneous nucleation; that is, for a given degree of undercooling beneath the melting temperature, aluminum particles in the melt will nucleate on the surface of the added particles. Grains will grow in the form of dendrites growing radially away from the surface of the nucleant. Solute particles can then be added (called grain refiners) which limit the growth of dendrites, leading to grain refinement. Al-Ti-B alloys are the most common grain refiner for Al alloys; however, novel refiners such as AlSc have been suggested.
One common technique is to induce a very small fraction of the melt to solidify at a much higher temperature than the rest; this will generate seed crystals that act as a template when the rest of the material falls to its (lower) melting temperature and begins to solidify. Since a huge number of minuscule seed crystals are present, a nearly equal number of crystallites result, and the size of any one grain is limited. | 1 | Applied and Interdisciplinary Chemistry |
In his later years, Ghiorso continued research toward finding superheavy elements, fusion energy, and innovative electron beam sources. He was a non-participating co-author of the experiments in 1999 that gave evidence of elements 116 and 118, which later turned out to be a case of scientific fraud perpetrated by the first author, Victor Ninov. He also had brief research interests in the free quark experiment of William Fairbank of Stanford, in the discovery of element 43, and in the electron disk accelerator, among others. | 1 | Applied and Interdisciplinary Chemistry |
Organic compounds may be classified in a variety of ways. One major distinction is between natural and synthetic compounds. Organic compounds can also be classified or subdivided by the presence of heteroatoms, e.g., organometallic compounds, which feature bonds between carbon and a metal, and organophosphorus compounds, which feature bonds between carbon and a phosphorus.
Another distinction, based on the size of organic compounds, distinguishes between small molecules and polymers. | 0 | Theoretical and Fundamental Chemistry |
Numerous reports have been published indicating that the glutamate/GABA–glutamine cycle is compromised in a variety of neurological disorders and conditions. Biopsies of sclerotic hippocampus tissue from human subjects with epilepsy have shown decreased glutamate–glutamine cycling. Another pathology in which the glutamate/GABA–glutamine cycle might be compromised is Alzheimers disease; NMR spectroscopy showed decreased glutamate neurotransmission activity and TCA cycling rate in patients with Alzheimers disease. Hyperammonemia in the brain, typically occurring as a secondary complication of primary liver disease and known as hepatic encephalopathy, is a condition that affects glutamate/GABA–glutamine cycling in the brain. Current research into autism also indicates potential roles for glutamate, glutamine, and/or GABA in autistic spectrum disorders. | 1 | Applied and Interdisciplinary Chemistry |
Apparent quantities can underline interactions in electrolyte – non-electrolyte systems which show interactions like salting in and salting out, but also give insights in ion-ion interactions, especially by their dependence on temperature. | 0 | Theoretical and Fundamental Chemistry |
One of the remarkable features of plasma electrolyte coatings is the presence of micro pores and cracks on the coating surface. Plasma electrolytic oxide coatings are generally recognized for high hardness, wear resistance, and corrosion resistance. However, the coating properties are highly dependent on the substrate used, as well as on the composition of the electrolyte and the electrical regime used (see Equipment used section, above).
Even on aluminium, the coating properties can vary strongly according to the exact alloy composition. For instance, the hardest coatings can be achieved on 2XXX series aluminium alloys, where the highest proportion of crystalline phase corundum (α-AlO) is formed, resulting in hardnesses of ~2000 HV, whereas coatings on the 5XXX series have less of this important constituent and are hence softer. Extensive work is being pursued by Prof. T. W. Clyne at the University of Cambridge to investigate the fundamental electrical and plasma physical processes involved in this process, having previously elucidated some of the micromechanical (& pore architectural), mechanical and thermal characteristics of PEO coatings. | 1 | Applied and Interdisciplinary Chemistry |
Knowledge base annotation is done based on the information of gene attribute, protein function and its metabolism. In this type of annotation more emphasis is given to genetic variation that disrupts the protein function domain, protein-protein interaction and biological pathway. The non-coding region of genome contain many important regulatory elements including promoter, enhancer and insulator, any kind of change in this regulatory region can change the functionality of that protein. The mutation in DNA can change the RNA sequence and then influence the RNA secondary structure, RNA binding protein recognition and miRNA binding activity. | 1 | Applied and Interdisciplinary Chemistry |
When red blood cells reach the end of their life due to aging or defects, they are removed from the circulation by the phagocytic activity of macrophages in the spleen or the liver or hemolyze within the circulation. Free hemoglobin is then cleared from the circulation via the hemoglobin transporter CD163, which is exclusively expressed on monocytes or macrophages. Within these cells the hemoglobin molecule is broken up, and the iron gets recycled. This process also produces one molecule of carbon monoxide for every molecule of heme degraded. Heme degradation is the only natural source of carbon monoxide in the human body, and is responsible for the normal blood levels of carbon monoxide in people breathing normal air.
The other major final product of heme degradation is bilirubin. Increased levels of this chemical are detected in the blood if red blood cells are being destroyed more rapidly than usual. Improperly degraded hemoglobin protein or hemoglobin that has been released from the blood cells too rapidly can clog small blood vessels, especially the delicate blood filtering vessels of the kidneys, causing kidney damage. Iron is removed from heme and salvaged for later use, it is stored as hemosiderin or ferritin in tissues and transported in plasma by beta globulins as transferrins. When the porphyrin ring is broken up, the fragments are normally secreted as a yellow pigment called bilirubin, which is secreted into the intestines as bile. Intestines metabolise bilirubin into urobilinogen. Urobilinogen leaves the body in faeces, in a pigment called stercobilin. Globulin is metabolised into amino acids that are then released into circulation. | 0 | Theoretical and Fundamental Chemistry |
Diazomethane and the safer analogue trimethylsilyldiazomethane methylate carboxylic acids, phenols, and even alcohols:
The method offers the advantage that the side products are easily removed from the product mixture. | 0 | Theoretical and Fundamental Chemistry |
The U.S. Environmental Protection Agency (EPA) is one of the many agencies that work with environmental engineers to solve key issues. An important component of EPA's mission is to protect and improve air, water, and overall environmental quality in order to avoid or mitigate the consequences of harmful effects. | 1 | Applied and Interdisciplinary Chemistry |
The International Chemistry Olympiad (IChO) is an annual academic competition for high school students. It is one of the International Science Olympiads. The first IChO was held in Prague, Czechoslovakia, in 1968. The event has been held every year since then, with the exception of 1971. The delegations that attended the first events were mostly countries of the former Eastern bloc and it was not until 1980, the 12th annual International Chemistry Olympiad, that the event was held outside of the bloc in Austria. Up to 4 students for each national team compete around July in both a theoretical and an experimental sections, with about half of the participants being awarded medals. | 1 | Applied and Interdisciplinary Chemistry |
Tissue engineering of oral mucosa combines cells, materials and engineering to produce a three-dimensional reconstruction of oral mucosa. It is meant to simulate the real anatomical structure and function of oral mucosa. Tissue engineered oral mucosa shows promise for clinical use, such as the replacement of soft tissue defects in the oral cavity. These defects can be divided into two major categories: the gingival recessions (receding gums) which are tooth-related defects, and the non tooth-related defects. Non tooth-related defects can be the result of trauma, chronic infection or defects caused by tumor resection or ablation (in the case of oral cancer). Common approaches for replacing damaged oral mucosa are the use of autologous grafts and cultured epithelial sheets. | 1 | Applied and Interdisciplinary Chemistry |
*Research on the atomic weight of oxygen conducted by Edward Morley at Case Western Reserve University, published in 1895
*Nylon, the first totally synthetic fiber used in consumer products, commercialized by DuPont in 1939
*First U.S. facility to produce acetyl chemicals commercially using coal gasification technology, opened by Eastman Chemical Company in 1983
*Riverside Laboratory for oil refining research, constructed by Universal Oil Products in 1921 | 1 | Applied and Interdisciplinary Chemistry |
Chemical synapses are biological junctions through which neurons' signals can be sent to each other and to non-neuronal cells such as those in muscles or glands. Chemical synapses allow neurons to form circuits within the central nervous system. They are crucial to the biological computations that underlie perception and thought. They allow the nervous system to connect to and control other systems of the body.
At a chemical synapse, one neuron releases neurotransmitter molecules into a small space (the synaptic cleft) that is adjacent to another neuron. The neurotransmitters are contained within small sacs called synaptic vesicles, and are released into the synaptic cleft by exocytosis. These molecules then bind to neurotransmitter receptors on the postsynaptic cell. Finally, the neurotransmitters are cleared from the synapse through one of several potential mechanisms including enzymatic degradation or re-uptake by specific transporters either on the presynaptic cell or on some other neuroglia to terminate the action of the neurotransmitter.
The adult human brain is estimated to contain from 10 to 5 × 10 (100–500 trillion) synapses. Every cubic millimeter of cerebral cortex contains roughly a billion (short scale, i.e. 10) of them. The number of synapses in the human cerebral cortex has separately been estimated at 0.15 quadrillion (150 trillion)
The word "synapse" was introduced by Sir Charles Scott Sherrington in 1897. Chemical synapses are not the only type of biological synapse: electrical and immunological synapses also exist. Without a qualifier, however, "synapse" commonly refers to chemical synapses. | 1 | Applied and Interdisciplinary Chemistry |
The folding of proteins from a primary (linear) sequence of amino acids to a three-dimensional structure is directed by all types of non-covalent interactions, including the hydrophobic forces and formation of intramolecular hydrogen bonds. Three-dimensional structures of proteins, including the secondary and tertiary structures, are stabilized by formation of hydrogen bonds. Through a series of small conformational changes, spatial orientations are modified so as to arrive at the most energetically minimized orientation achievable. The folding of proteins is often facilitated by enzymes known as molecular chaperones. Sterics, bond strain, and angle strain also play major roles in the folding of a protein from its primary sequence to its tertiary structure.
Single tertiary protein structures can also assemble to form protein complexes composed of multiple independently folded subunits. As a whole, this is called a protein's quaternary structure. The quaternary structure is generated by the formation of relatively strong non-covalent interactions, such as hydrogen bonds, between different subunits to generate a functional polymeric enzyme. Some proteins also utilize non-covalent interactions to bind cofactors in the active site during catalysis, however a cofactor can also be covalently attached to an enzyme. Cofactors can be either organic or inorganic molecules which assist in the catalytic mechanism of the active enzyme. The strength with which a cofactor is bound to an enzyme may vary greatly; non-covalently bound cofactors are typically anchored by hydrogen bonds or electrostatic interactions. | 0 | Theoretical and Fundamental Chemistry |
Two coils in an anti-Helmholtz configuration are used to generate a weak quadrupolar magnetic field; here, we will consider the coils as being separated along the -axis. In the proximity of the field zero, located halfway between the two coils along the -direction, the field gradient is uniform and the field itself varies linearly with position. For this discussion, consider an atom with ground and excited states with and , respectively, where is the magnitude of the total angular momentum vector. Due to the Zeeman effect, these states will each be split into sublevels with associated values of , denoted by (note that the Zeeman shift for the ground state is zero and that it will not be split into sublevels by the field). This results in spatially-dependent energy shifts of the excited-state sublevels, as the Zeeman shift is proportional to the field strength and in this configuration the field strength is linear in position. As a note, the Maxwell equation implies that the field gradient is twice as strong along the -direction than in the and -directions, and thus the trapping force along the -direction is twice as strong.
In combination with the magnetic field, pairs of counter-propagating circularly-polarized laser beams are sent in along three orthogonal axes, for a total of six MOT beams (there are exceptions to this, but a minimum of five beams is required to make a 3D MOT). The beams are red-detuned from the transition by an amount such that , or equivalently, , where is the frequency of the laser beams and is the frequency of the transition. The beams must be circularly polarized to ensure that photon absorption can only occur for certain transitions between the ground state and the sublevels of the excited state , where . In other words, the circularly-polarized beams enforce selection rules on the allowed electric dipole transitions between states.
At the center of the trap, the magnetic field is zero and atoms are "dark" to incident red-detuned photons. That is, at the center of the trap, the Zeeman shift is zero for all states and so the transition frequency from remains unchanged. The detuning of the photons from this frequency means that there will not be an appreciable amount of absorption (and therefore emission) by atoms in the center of the trap, hence the term "dark". Thus, the coldest, slowest moving atoms accumulate in the center of the MOT where they scatter very few photons.
Now consider an atom which is moving in the -direction. The Zeeman effect shifts the energy of the state lower in energy, decreasing the energy gap between it and the state; that is, the frequency associated with the transition decreases. Red-detuned photons, which only drive transitions, propagating in the -direction thus become closer to resonance as the atom travels further from the center of the trap, increasing the scattering rate and scattering force. When an atom absorbs a photon, it is excited to the state and gets a "kick" of one photon recoil momentum, , in the direction opposite to its motion, where . The atom, now in an excited state, will then spontaneously emit a photon in a random direction and after many absorption-spontaneous emission events, the atom will have, on average, been "pushed" back towards the field-zero of the trap. This trapping process will also occur for an atom moving in the -direction if photons are traveling in the -direction, the only difference being that the excitation will be from to <math>|J=1,m_J
=+1\rangle. Since the magnetic field gradient near the trap center is uniform, the same phenomenon of trapping and cooling occurs along the and -directions as well.
Mathematically, the radiation pressure force that atoms experience in a MOT is given by:
where is the damping coefficient, is the Landé g-factor and is the Bohr magneton. | 0 | Theoretical and Fundamental Chemistry |
Huntington's disease occurs when the cytosolic protein Huntingtin (Htt) has an additional 35 glutamine residues added to its amino terminal region. This modified form of Htt is called Htt. Htt makes Type 1 IP receptors more sensitive to IP, which leads to the release of too much Ca from the ER. The release of Ca from the ER causes an increase in the cytosolic and mitochondrial concentrations of Ca. This increase in Ca is thought to be the cause of GABAergic MSN degradation. | 1 | Applied and Interdisciplinary Chemistry |
P. rubens is a common fungus of indoor environment. Along with Cladosporium halotolerans and Aspergillus niger, it is one of the nuisance moulds when humidity is high. It is the most resilient mould as it needs less water for growth and propagation. It has a soft and velvety surface. The spore-bearing filaments, conidiophores are smooth and measure 200-300 µm in length. The hairy surface, penicilli are 8-12 µm long. The conidia are smooth-walled, ellipsoidal in shape, measuring 2.5-4.0 µm long, and are blue or bluish-green in colour. It exists in a number of strains, of which the most important are Fleming's strain (designated CBS 205.57 or NRRL 824 or IBT 30142) from which the first penicillin was discovered and the Wisconsin strain (NRRL1951) obtained from a cantaloupe in Peoria, Illinois, in 1944 and has been used for industrial production of penicillin G. The original Wisconsin strain itself has been produced in a variety of strains. | 1 | Applied and Interdisciplinary Chemistry |
The metabolism of drospirenone is extensive. It is metabolized into the acid form of drospirenone by opening of its lactone ring. The medication is also metabolized by reduction of its double bond between the C4 and C5 positions and subsequent sulfation. The two major metabolites of drospirenone are drospirenone acid and 4,5-dihydrodrospirenone 3-sulfate, and are both formed independently of the cytochrome P450 system. Neither of these metabolites are known to be pharmacologically active. Drospirenone also undergoes oxidative metabolism by CYP3A4. | 0 | Theoretical and Fundamental Chemistry |
A wide variety of absorption band and line shapes exist, and the analysis of the band or line shape can be used to determine information about the system that causes it. In many cases it is convenient to assume that a narrow spectral line is a Lorentzian or Gaussian, depending respectively on the decay mechanism or temperature effects like Doppler broadening. Analysis of the spectral density and the intensities, width and shape of spectral lines sometimes can yield a lot of information about the observed system like it is done with Mössbauer spectra.
In systems with a very large number of states like macromolecules and large conjugated systems the separate energy levels can't always be distinguished in an absorption spectrum. If the line broadening mechanism is known and the shape of then spectral density is clearly visible in the spectrum, it is possible to get the desired data. Sometimes it is enough to know the lower or upper limits of the band or its position for an analysis.
For condensed matter and solids the shape of absorption bands are often determined by transitions between states in their continuous density of states distributions. For crystals, the electronic band structure determines the density of states. In fluids, glasses and amorphous solids, there is no long range correlation and the dispersion relations are isotropic. For charge-transfer complexes and conjugated systems, the band width is complicated by a variety of factors, compared to condensed matter. | 0 | Theoretical and Fundamental Chemistry |
Feringa received his MSc degree with distinction from the University of Groningen in 1974. He subsequently obtained a PhD degree at the same university in 1978, with the thesis titled "Asymmetric oxidation of phenols. Atropisomerism and optical activity". Following a short period at Shell in the Netherlands and the United Kingdom, he was appointed as lecturer at the University of Groningen in 1984 and Full Professor, succeeding Prof Wijnberg, in 1988. His early career was focused on homogenous catalysis and oxidation catalysis, and especially on stereochemistry with major contributions in the field of enantioselective catalysis, including monophos ligand used in asymmetric hydrogenation, asymmetric conjugate additions of organometallic reagents, including the highly reactive organolithium reagents and organic photochemistry and stereochemistry. In the 1990s, Feringa's work in stereochemistry led to major contributions in photochemistry, resulting in the first monodirectional light driven molecular rotary motor and later a molecular car (a so-called nanocar) driven by electrical impulses.
Ben Feringa holds over 30 patents and has published over 650 peer reviewed research papers to date, cited more than 30,000 times and has an h-index in excess of 90. He has guided over 100 PhD students over his career. | 0 | Theoretical and Fundamental Chemistry |
The history of the periodic table is also a history of the discovery of the chemical elements. The first person in recorded history to discover a new element was Hennig Brand, a bankrupt German merchant. Brand tried to discover the philosophers stone—a mythical object that was supposed to turn inexpensive base metals into gold. In 1669, or later, his experiments with distilled human urine resulted in the production of a glowing white substance, which he called "cold fire" (kaltes Feuer'). He kept his discovery secret until 1680, when Anglo-Irish chemist Robert Boyle rediscovered phosphorus and published his findings. The discovery of phosphorus helped to raise the question of what it meant for a substance (any given variety of matter) to be an element, in a world where versions of atomic theory were only speculative and later understandings of the nature of substances were only beginning to become possible.
In 1661, Boyle defined elements as "those primitive and simple Bodies of which the mixt ones are said to be composed, and into which they are ultimately resolved."
In 1718, Étienne François Geoffroy's Affinity Table made use of several aspects — (1) tabular grouping and (2) correlation with chemical affinity — that would later be reprised.
In 1789, French chemist Antoine Lavoisier wrote Traité Élémentaire de Chimie (Elementary Treatise of Chemistry), which is considered to be the first modern textbook about chemistry. Lavoisier defined an element as a substance whose smallest units cannot be broken down into a simpler substance. Lavoisiers book contained a list of "simple substances" that Lavoisier believed could not be broken down further, which included oxygen, nitrogen, hydrogen, phosphorus, mercury, zinc and sulfur, which formed the basis for the modern list of elements. Lavoisiers list also included "light" and "caloric", which at the time were believed to be material substances. He classified these substances into metals and nonmetals. While many leading chemists refused to believe Lavoisiers new revelations, the Elementary Treatise was written well enough to convince the younger generation. However, Lavoisiers descriptions of his elements lack completeness, as he only classified them as metals and non-metals.
In 1808–10, British natural philosopher John Dalton published a method by which to arrive at provisional atomic weights for the elements known in his day, from stoichiometric measurements and reasonable inferences. Dalton's atomic theory was adopted by many chemists during the 1810s and 1820s.
In 1815, British physician and chemist William Prout noticed that atomic weights seemed to be multiples of that of hydrogen.
In 1817, German physicist Johann Wolfgang Döbereiner began to formulate one of the earliest attempts to classify the elements. In 1829, he found that he could form some of the elements into groups of three, with the members of each group having related properties. He termed these groups triads.
Definition of Triad law
"Chemically analogous elements arranged in increasing order of their atomic weights formed well marked groups of three called Triads in which the atomic weight of the middle element was found to be generally the arithmetic mean of the atomic weight of the other two elements in the triad.
#chlorine, bromine, and iodine
#calcium, strontium, and barium
#sulfur, selenium, and tellurium
#lithium, sodium, and potassium"
All those attempts to sort elements by atomic weights were inhibited by the inaccurate determination of weights, and not just slightly: carbon, oxygen and many other elements were believed to be half their actual masses (cf. the illustration by Dalton above), because only monatomic gases were believed to exist. Even though Amedeo Avogadro and, independently of him, André-Marie Ampère, proposed the solution in the form of diatomic molecules and Avogadros law already in the 1810s, it was not until after Stanislao Cannizzaros publications in late 1850s when the theory began to be widely considered.
In 1860, the modern scientific consensus emerged at the first international chemical conference, the Karlsruhe Congress, and a revised list of elements and atomic masses was adopted. It helped spur creation of more extensive systems. The first such system emerged in two years. | 1 | Applied and Interdisciplinary Chemistry |
Paucimannosidic proteins have been reported in vertebrates such as quail, chicken and in mammals, encompassing a limited diversity of paucimannosidic glycan structures. Early findings reported on paucimannosidic glycans on lysosomal glycoproteins in domestic animals. and human tissues, but have subsequently been found also to decorate non-lysosomal glycoproteins. Particularly, the granules of human neutrophils are a principal source of paucimannosidic proteins. Paucimannosidic proteins were also observed in human monocytes and macrophages and paucimannosidic immunoglycopeptides were found to be presented by SARS-CoV-2 challenged dendritic cells. Species within other classes under Animalia related to vertebrates were also documented to express paucimannosidic proteins. with some observations of unusual plant- and invertebrate-like paucimannosidic glycan structures | 1 | Applied and Interdisciplinary Chemistry |
In biology, scaffold proteins are crucial regulators of many key signalling pathways. Although scaffolds are not strictly defined in function, they are known to interact and/or bind with multiple members of a signalling pathway, tethering them into complexes. In such pathways, they regulate signal transduction and help localize pathway components (organized in complexes) to specific areas of the cell such as the plasma membrane, the cytoplasm, the nucleus, the Golgi, endosomes, and the mitochondria. | 1 | Applied and Interdisciplinary Chemistry |
There are three types of sweat glands: eccrine, apocrine, and apoeccrine. Apocrine glands are primarily responsible for body malodor and, along with apoeccrine glands, are mostly expressed in the axillary (underarm) regions, whereas eccrine glands are distributed throughout virtually all of the rest of the skin in the body, although they are also particularly expressed in the axillary regions, and contribute to malodor to a relatively minor extent. Sebaceous glands, another type of secretory gland, are not sweat glands but instead secrete sebum (an oily substance), and may also contribute to body odor to some degree.
The main odorous compounds that contribute to axillary odor include:
# Unsaturated or hydroxylated branched fatty acids, with the key ones being (E)-3-methyl-2-hexenoic acid (3M2H) and 3-hydroxy-3-methylhexanoic acid (HMHA)
# Sulfanylalkanols, particularly 3-methyl-3-sulfanylhexan-1-ol (3M3SH)
# Odoriferous androstane steroids, namely the pheromones androstenone (5α-androst-16-en-3-one) and androstenol (5α-androst-16-en-3α-ol)
These malodorous compounds are formed from non-odoriferous precursors that are secreted from apocrine glands and converted by various enzymes expressed in skin surface bacteria. The specific skin surface bacteria responsible are mainly Staphylococcus and Corynebacterium species.
The androstane steroids dehydroepiandrosterone sulfate (DHEA-S) and androsterone sulfate have been detected in an extract of axillary hairs together with high concentrations of cholesterol. Apocrine sweat contains relatively high amounts of androgens, for instance dehydroepiandrosterone (DHEA), androsterone, and testosterone, and the androgen receptor (AR), the biological target of androgens, is strongly expressed in the secretory cells of apocrine glands. In addition, 5α-reductase type I, an enzyme which converts testosterone into the more potent androgen dihydrotestosterone (DHT), has been found to be highly expressed in the apocrine glands of adolescents, and DHT has been found to specifically contribute to malodor as well. Starting at puberty, males have higher levels of androgens than do females and produce comparatively more axillary malodor. As such, it has been proposed that the higher axillary malodor seen in males is due to greater relative stimulation of axillary apocrine sweat glands by androgens. | 1 | Applied and Interdisciplinary Chemistry |
The first RBC was installed in West Germany in 1959, later it was introduced in the United States and Canada. In the United States, rotating biological contactors are used for industries producing wastewaters high in biochemical oxygen demand (BOD) (e.g., petroleum industry and dairy industry). In the UK, the first GRP RBC's - manufactured by KEE Process Ltd. originally known as KLARGESTER - go back to 1955.
A properly designed RBC produced a very high quality final effluent. However both the organic and hydraulic loading had to be addressed in the design phase.
In the 1980s problems were encountered in the USA prompting the Environmental Agency to commission a number of reports.
These reports identified a number of issues and criticized the RBC process. One author suggested that since manufacturers were aware of the problem, the problems would be resolved and suggested that design engineers should specify a long life.
Severn Trent Water Ltd, a large UK Water Company based in the Midlands, employed RBCs as the preferred process for their small works which amount to over 700 sites Consequently, long life was essential to compliance.
This issue was successfully addressed by Eric Findlay C Eng when he was employed by Severn Trent Water Ltd in the UK following a period of failure of a number of plants. As a result, the issue of short life failure became fully understood in the early 1990s when the correct process and hydraulic issues had been identified to produce a high quality nitrified effluent.
There are several other papers which address the whole issue of RBCs. Findlay also developed a system for repairing defective RBCs enabling shaft and frame life to be extended up to 30 years based on the Cranfield designed frame. Where additional capacity was required intermediate frames are used. | 1 | Applied and Interdisciplinary Chemistry |
Flutamide has been studied in the treatment of bulimia nervosa in women.
Flutamide was found to be effective in the treatment of obsessive–compulsive disorder (OCD) in men with comorbid Tourette's syndrome in one small randomized controlled trial. Conversely, it was ineffective in patients with OCD in another study. More research is necessary to determine whether flutamide is effective in the treatment of OCD. | 0 | Theoretical and Fundamental Chemistry |
James A. Rafferty, Vice President, Officers Committee member, Director, and member of the executive committee of Union Carbide, was an important figure in the petrochemical industry. Rafferty guided Union Carbides effort in developing the new industry of synthetic aliphatic chemicals (aliphatic compounds are one of the two main branches within organic chemistry) and was instrumental in the development of the liquid oxygen industry. Rafferty directed Union Carbide's collaboration with the United States government for the Manhattan Project and with the War Production Board for the synthetic rubber program during World War II.
Rafferty was born in Chicago, Illinois on May 4, 1886, and studied engineering and chemistry at the Illinois Institute of Technology (where Rafferty would later become a Trustee). After graduation in 1908, Rafferty worked for the People's Gas, Light, and Coke Company and then in 1917 joined the Linde Air Products Company, which later merged with three other companies to become Union Carbide.
Rafferty became general manager of the newly formed Union Carbide subsidiary, the Carbide and Carbon Chemicals Corporation (CCCC) in 1920. He became vice president in 1924, President in 1929, and chairman of the board in 1944. He was made president of the Bakelite Corporation in 1939 and Chairman of Bakelite in 1944. Under Rafferty's leadership, Carbide and Carbon Chemicals Corporation went on to become the second largest chemical company in the United States by 1948.
Rafferty became a Vice President of Union Carbide, the parent company of the CCCC, in 1938, a Director in 1941, and a member of the executive committee in 1944. Rafferty served as Chairman of the Union Carbide's new product development committee until his death on December 19, 1951.
As a result of lifetime achievements, Rafferty was awarded the Chemical Industry Medal in 1948. | 1 | Applied and Interdisciplinary Chemistry |
Considering a two dimensional flow in the plane, the flow velocity at any point at time can be expressed as – | 1 | Applied and Interdisciplinary Chemistry |
Direct energy conversion (DEC) or simply direct conversion converts a charged particle's kinetic energy into a voltage. It is a scheme for power extraction from nuclear fusion. | 0 | Theoretical and Fundamental Chemistry |
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