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The gel fragment is placed in a dialysis tube that is permeable to fluids but impermeable to molecules at the size of DNA, thus preventing the DNA from passing through the membrane when soaked in TE buffer. An electric field is established around the tubing (in a way similar to gel electrophoresis) long enough so that the DNA is removed from the gel but remains in the tube. The tube solution can then be pipetted out and will contain the desired DNA with minimal background. | 1 | Applied and Interdisciplinary Chemistry |
Falconbridge Limited in mid-1981 commissioned a copper smelter and refinery near Timmins, Ontario, to treat concentrate from its Kidd Mine. However, at the outset, the quality of the cathode copper produced in the Kidd refinery suffered from the presence of higher than usual concentrations of lead and selenium in the copper smelter’s anodes. Kidd cathode copper was not able to meet its customers’ specifications and obtaining product certification for the London Metal Exchange (“LME”) became a key focus.
After several process improvements were instigated, it was ultimately realised that the use of copper starter sheets was preventing the Kidd refinery meeting its cathode quality targets. Test work then began on the use of permanent stainless-steel cathodes. Preliminary tests using full-scale titanium blanks showed a reduction in the lead content of the cathode copper of a factor of four and a six-fold reduction in the selenium content, compared with the use of copper starter sheets.
The focus then shifted to developing a stripping machine, to develop stainless steel cathodes incorporating the existing header bars and evaluating edge-strip technology. The company’s board of directors gave approval for the conversion of the refinery to the Kidd technology in April 1985. The conversion was completed in 1986 and the Kidd refinery became the third to install permanent cathode and automated stripping technology.
Falconbridge began marketing the technology in 1992, after many requests from other refinery operators. Thus, the Kidd Process created competition between two suppliers of permanent cathode technology. The main differences between them were the cathode header bar, edge stripping and the stripping machine technology.
In contrast to the stainless steel header bar then used in the Isa Process cathode, the Kidd Process cathode used a solid copper header bar, which was welded onto the stainless steel sheet. This gave a lower voltage drop (by 8–10 millivolts) than the Isa Process cathode.
The Isa Process technology used the waxed edge at the bottom of the cathode plate to stop the copper depositing around the plate’s bottom to form a single mass of copper running from the top of one side of the cathode plate around the bottom to the top of the other side. The copper was stripped from the cathode plates as two separate sheets. The Kidd Process technology did not use wax, as it was thought that it could exacerbate the impurity problems with which the plant had been struggling. At Kidd, the stripping approach was to remove the copper from the cathode plate as a single V-shaped cathode product, akin to a taco shell.
The Kidd Process initially used a “carousel” stripping machine, but a linear installation was subsequently developed to provide machines with lower to medium stripping capacities for electrowinning plants and smaller refineries. The linear stripping machines, first installed in 1996, were more compact, less complex and had lower installation costs than the carousel machines. | 1 | Applied and Interdisciplinary Chemistry |
On the DO sag curve a minimum concentration occurs at some point, along a stream. If the Streeter–Phelps equation is differentiated with respect to time, and set equal to zero, the time at which the minimum DO occurs is expressed by
To find the value of the critical oxygen deficit, , the Streeter–Phelps equation is combined with the equation above, for the critical time, . Then the minimum dissolved oxygen concentration is
Mathematically it is possible to get a negative value of , even though it is not possible to have a negative amount of DO in reality.
The distance traveled in a river from a given point source pollution or waste discharge downstream to the (which is the minimum DO) is found by
where is the flow velocity of the stream. This formula is a good approximation as long as the flow can be regarded as a plug flow (turbulent). | 1 | Applied and Interdisciplinary Chemistry |
The outer surface of a rusticle is smooth red in appearance from the iron(III) oxide, while the core is bright orange due to the presence of crystals of goethite. There are several morphologies of the rusticle, some of which are conical, cylindrical, and rusticle on the seafloor. | 1 | Applied and Interdisciplinary Chemistry |
Atomic spectral lines are due to transitions of electrons between different atomic energy levels E, followed by emission of photons. Atomic levels are a manifestation of the electromagnetic interaction between electrons and nuclei. The energy levels of two atoms, the nuclei of which are different isotopes of the same element, are shifted one with respect to the other, despite the fact that the electric charges Z of the two isotopes are identical. This is so because isotopes differ by the number of neutrons, and therefore the masses and volumes of two isotopes are different; these differences give rise to the isotopic shift on atomic spectral lines.
In the case of two nuclear isomers, the number of protons and the number of neutrons are identical, but the quantum states and in particular the energy levels of the two nuclear isomers differ. This difference induces a difference in the electric charge distributions of two isomers and thus a difference δφ in the corresponding electrostatic nuclear potentials φ, which ultimately leads to a difference ΔE in the atomic energy levels. The isomeric shift on atomic spectral lines is then given by
where ψ is the wave function of the electron involved in the transition, e its electric charge, and the integration is performed over the electron coordinates.
The isotopic and the isomeric shift are similar in the sense that both are effects in which the finite size of the nucleus manifests itself and both are due to a difference in the electromagnetic interaction energy between the electrons and the nucleus of the atom. The isotopic shift had been known decades before the isomeric shift and provided useful but limited information about atomic nuclei. Unlike the isomeric shift, the isotopic shift was at first discovered in experiment and then interpreted theoretically (see also ). While in the case of the isotopic shift the determination of the interaction energy between electrons and nuclei is a relatively simple electromagnetic problem, for isomers the problem is more involved, since it is the strong interaction, which accounts for the isomeric excitation of the nucleus and thus for the difference of charge distributions of the two isomeric states. This circumstance explains in part why the nuclear isomeric shift was not discovered earlier: the appropriate nuclear theory and in particular the nuclear shell model were developed only in the late 1940s and early 1950s. As to the experimental observation of this shift, it also had to await the development of a new technique, that permitted spectroscopy with isomers, which are metastable nuclei. This too happened only in the 1950s.
While the isomeric shift is sensitive to the internal structure of the nucleus, the isotopic shift is (in a good approximation) not. Therefore, the nuclear physics information that can be obtained from the investigation of the isomeric shift, is superior to what can be obtained from isotopic-shift studies. The measurements through the isomeric shift of e.g. the difference of nuclear radii of the excited and ground state constitute one of the most sensitive tests of nuclear models. Moreover, combined with the Mössbauer effect, the isomeric shift constitutes at present a unique tool in many other fields besides physics. | 0 | Theoretical and Fundamental Chemistry |
LDH in humans uses His(193) as the proton acceptor, and works in unison with the coenzyme (Arg99 and Asn138), and substrate (Arg106; Arg169; Thr248) binding residues. The His(193) active site, is not only found in the human form of LDH, but is found in many different animals, showing the convergent evolution of LDH. The two different subunits of LDH (LDHA, also known as the M subunit of LDH, and LDHB, also known as the H subunit of LDH) both retain the same active site and the same amino acids participating in the reaction. The noticeable difference between the two subunits that make up LDHs tertiary structure is the replacement of alanine (in the M chain) with a glutamine (in the H chain). This tiny but notable change is believed to be the reason the H subunit can bind NAD faster, and the M subunits catalytic activity isnt reduced in the presence of acetylpyridine adenine dinucleotide, whereas the H subunits activity is reduced fivefold. | 1 | Applied and Interdisciplinary Chemistry |
This covers in more detail ways the environment can be protected through political means. This is done by introducing students to qualitative and quantitative tools in classes such as economics, sociology, political science and energy and resources. | 1 | Applied and Interdisciplinary Chemistry |
The importance of mediated transport proteins is visualized with the presence of mutations that render the transport proteins nonfunctional. A prime example of this are mutations found within the Archain 1 gene which codes for the transport proteins COPI and COPII. The main function of these transport proteins is to facilitate the passage of molecules from the endoplasmic reticulum to the golgi apparatus, and vice versa. The mutated ARCN1 gene gives rise to abnormal COPI who fails to transport type I collagen and leads to the secretion of collagen. Due to the fact that type I collagen is the main ingredient of connective tissue, such mutations are the cause of numerous severe skeletal disorders such as osteogenesis imperfecta and cranio-lenticulo-sutural dysplasia. Various variations of these disorders are characterized by visible physical dysplasia. This example highlights the importance of transport proteins, not only as a means for the passage of specific molecules across a membrane, but for proper bodily development. | 1 | Applied and Interdisciplinary Chemistry |
Carbon is present in all biological material including skeletal remains, charcoal and food residues and plays an integral role in the dating of materials, through radiocarbon dating. The ratio of different carbon isotopes naturally fluctuates over time, and, by analysing the composition of carbon dioxide (CO) in ancient air bubbles trapped in ice cores, a chronological record of these fluctuations can be constructed. Primary producers (such as grasses) absorb and sequester CO during photosynthesis, these plants are then eaten by consumers (such as cows, and later humans) which inherit this same CO signature. Therefore, by matching the carbon isotope ratios from a sample to ratios from the ice core record, the sample can be assigned to a broad period. After death, an organism no longer absorbs CO, Cs instability causes its concentration to decrease over time The predictable rate at which this occurs is known as an elements decay rate. | 0 | Theoretical and Fundamental Chemistry |
In 1899, physicists Ernest Rutherford (working in McGill University in Montreal, Canada) and Paul Villard (working in Paris) separated radiation into three types: eventually named alpha, beta, and gamma by Rutherford, based on penetration of objects and deflection by a magnetic field. Alpha rays were defined by Rutherford as those having the lowest penetration of ordinary objects.
Rutherfords work also included measurements of the ratio of an alpha particles mass to its charge, which led him to the hypothesis that alpha particles were doubly charged helium ions (later shown to be bare helium nuclei). In 1907, Ernest Rutherford and Thomas Royds finally proved that alpha particles were indeed helium ions. To do this they collected and purified the gas emitted by radium, a known alpha particle emitter, in a glass tube. An electric spark discharge inside the tube produced light. Subsequent study of the spectra of this light showed that the gas was helium and thus the alpha particles were indeed the helium ions.
Because alpha particles occur naturally, but can have energy high enough to participate in a nuclear reaction, study of them led to much early knowledge of nuclear physics. Rutherford used alpha particles emitted by radium bromide to infer that J. J. Thomsons Plum pudding model of the atom was fundamentally flawed. In Rutherfords gold foil experiment conducted by his students Hans Geiger and Ernest Marsden, a narrow beam of alpha particles was established, passing through very thin (a few hundred atoms thick) gold foil. The alpha particles were detected by a zinc sulfide screen, which emits a flash of light upon an alpha particle collision. Rutherford hypothesized that, assuming the "plum pudding" model of the atom was correct, the positively charged alpha particles would be only slightly deflected, if at all, by the dispersed positive charge predicted.
It was found that some of the alpha particles were deflected at much larger angles than expected (at a suggestion by Rutherford to check it) and some even bounced almost directly back. Although most of the alpha particles went straight through as expected, Rutherford commented that the few particles that were deflected was akin to shooting a fifteen-inch shell at tissue paper only to have it bounce off, again assuming the "plum pudding" theory was correct. It was determined that the atom's positive charge was concentrated in a small area in its center, making the positive charge dense enough to deflect any positively charged alpha particles that came close to what was later termed the nucleus.
Prior to this discovery, it was not known that alpha particles were themselves atomic nuclei, nor was the existence of protons or neutrons known. After this discovery, J.J. Thomsons "plum pudding" model was abandoned, and Rutherfords experiment led to the Bohr model and later the modern wave-mechanical model of the atom.
In 1917, Rutherford went on to use alpha particles to accidentally produce what he later understood as a directed nuclear transmutation of one element to another. Transmutation of elements from one to another had been understood since 1901 as a result of natural radioactive decay, but when Rutherford projected alpha particles from alpha decay into air, he discovered this produced a new type of radiation which proved to be hydrogen nuclei (Rutherford named these protons). Further experimentation showed the protons to be coming from the nitrogen component of air, and the reaction was deduced to be a transmutation of nitrogen into oxygen in the reaction
:N + α → O + p
This was the first discovered nuclear reaction.
To the adjacent pictures: According to the energy-loss curve by Bragg, it is recognizable that the alpha particle indeed loses more energy on the end of the trace. | 0 | Theoretical and Fundamental Chemistry |
The Gibson assembly method is a relatively straightforward DNA assembly method, requiring only a few additional reagents: the 5 T5 exonuclease, Phusion DNA polymerase, and Taq DNA ligase. The DNA fragments to be assembled are synthesised to have overlapping 5 and 3' ends in the order that they are to be assembled in. These reagents are mixed together with the DNA fragments to be assembled at 50 °C and the following reactions occur:
# The T5 exonuclease chews back DNA from the 5 end of each fragment, exposing 3 overhangs on each DNA fragment.
# The complementary overhangs on adjacent DNA fragments anneal via complementary base pairing.
# The Phusion DNA polymerase fills in any gaps where the fragments anneal.
# Taq DNA ligase repairs the nicks on both DNA strands.
Because the T5 exonuclease is heat labile, it is inactivated at 50 °C after the initial chew back step. The product is thus stable, and the fragments assembled in the desired order. This one-pot protocol can assemble up to 5 different fragments accurately, while several commercial providers have kits to accurately assemble up to 15 different fragments in a two-step reaction. However, while the Gibson assembly protocol is fast and uses relatively few reagents, it requires bespoke DNA synthesis as each fragment has to be designed to contain overlapping sequences with the adjacent fragments and amplified via PCR. This reliance on PCR may also affect the fidelity of the reaction when long fragments, fragments with high GC content or repeat sequences are used. | 1 | Applied and Interdisciplinary Chemistry |
In freshwater or estuarine systems close to land, nitrate can reach concentrations that are lethal to fish. While nitrate is much less toxic than ammonia, levels over 30 ppm of nitrate can inhibit growth, impair the immune system and cause stress in some aquatic species. Nitrate toxicity remains a subject of debate.
In most cases of excess nitrate concentrations in aquatic systems, the primary sources are wastewater discharges, as well as surface runoff from agricultural or landscaped areas that have received excess nitrate fertilizer. The resulting eutrophication and algae blooms result in anoxia and dead zones. As a consequence, as nitrate forms a component of total dissolved solids, they are widely used as an indicator of water quality. | 0 | Theoretical and Fundamental Chemistry |
For low energy photons the wavelength shift becomes negligible () and the Klein–Nishina formula reduces to the classical Thomson expression:
which is symmetrical in the scattering angle, i.e. the photon is just as likely to scatter backwards as forwards. With increasing energy this symmetry is broken and the photon becomes more likely to scatter in the forward direction. | 0 | Theoretical and Fundamental Chemistry |
The visual cycle occurs via G-protein coupled receptors called retinylidene proteins which consists of a visual opsin and a chromophore 11-cis-retinal. The 11-cis-retinal is covalently linked to the opsin receptor via Schiff base. When it absorbs a photon, 11-cis-retinal undergoes photoisomerization to all-trans-retinal, which changes the conformation of the opsin GPCR leading to signal transduction cascades which causes closure of cyclic GMP-gated cation channel, and hyperpolarization of the photoreceptor cell. Following photoisomerization, all-trans-retinal is released from the opsin protein and reduced to all-trans-retinol, which travels to the retinal pigment epithelium to be "recharged". It is first esterified by lecithin retinol acyltransferase (LRAT) and then converted to 11-cis-retinol by the isomerohydrolase RPE65. The isomerase activity of RPE65 has been shown; it is uncertain whether it also acts as the hydrolase. Finally, it is oxidized to 11-cis-retinal before traveling back to the photoreceptor cell outer segment where it is again conjugated to an opsin to form new, functional visual pigment (retinylidene protein), namely photopsin or rhodopsin. | 1 | Applied and Interdisciplinary Chemistry |
The dual tiling is called an order-7-3 floret pentagonal tiling, and is related to the floret pentagonal tiling. | 0 | Theoretical and Fundamental Chemistry |
Drinking birds, also known as insatiable birdies, dunking birds, drinky birds, water birds, dipping birds, and “Sippy Chickens” are toy heat engines that mimic the motions of a bird drinking from a water source. They are sometimes incorrectly considered examples of a perpetual motion device. | 0 | Theoretical and Fundamental Chemistry |
For the turbulent flow regime, the relationship between the Fanning friction factor and the Reynolds number is more complex and is governed by the Colebrook equation which is implicit in :
Various explicit approximations of the related Darcy friction factor have been developed for turbulent flow.
Stuart W. Churchill developed a formula that covers the friction factor for both laminar and turbulent flow. This was originally produced to describe the Moody chart, which plots the Darcy-Weisbach Friction factor against Reynolds number. The Darcy Weisbach Formula , also called Moody friction factor, is 4 times the Fanning friction factor and so a factor of has been applied to produce the formula given below.
* Re, Reynolds number (unitless);
* ε, roughness of the inner surface of the pipe (dimension of length);
* D, inner pipe diameter; | 1 | Applied and Interdisciplinary Chemistry |
* MT-CYB: mtDNA encoded cytochrome b; mutations associated with exercise intolerance
* CYC1: cytochrome c1
* CYCS: cytochrome c
* UQCRFS1: Rieske iron sulfur protein
* UQCRB: Ubiquinone binding protein, mutation linked with mitochondrial complex III deficiency nuclear type 3
* UQCRH: hinge protein
* UQCRC2: Core 2, mutations linked to mitochondrial complex III deficiency, nuclear type 5
* UQCRC1: Core 1
* UQCR: 6.4KD subunit
* UQCR10: 7.2KD subunit
* TTC19: Newly identified subunit, mutations linked to complex III deficiency nuclear type 2. Helps remove the N-terminal fragment of UQCRFS1, which would otherwise interfere with complex III function. | 1 | Applied and Interdisciplinary Chemistry |
* April 12, 1915 born in Milwaukee, Wisconsin
* 1936: BS, University of California, Berkeley (Chemistry)
* 1940: PhD, University of California, Berkeley (Physiology)
* 1936–1937: Paraffin Company, Inc., Control Chemist
* 1940–1941: University of California, Berkeley, Upjohn Fellow
* 1942–1943: Manhattan Project, Chicago Metallurgical Laboratory, Researcher
* 1943–1944: Manhattan Project, Oak Ridge Clinton Laboratory, Senior Chemist
* 1944–1945: Manhattan Project, Hanford Engineering Works (GE), Senior Chemist
* 1945–1974: University of California, Berkeley, Associate Professor to Professor of Chemistry
* 1963: elected to National Academy of Sciences
* 1974–1988: Hebrew University, Professor of Archeology and Chemistry
* 1988–1991: Lawrence Berkeley National Laboratory, Researcher
* August 3, 1991 died in Los Alamitos, California | 0 | Theoretical and Fundamental Chemistry |
* 2013 Royal Society of Chemistry Natural Product Report Lectureship Award
* 2011 UK's under 40 Organic Chemistry delegate for EuCheM’s Young Investigators Workshop
* 2011 Thieme Chemistry Journal Award
* 2006 Royal Society of Chemistry - Meldola prize | 0 | Theoretical and Fundamental Chemistry |
A salt with associated water of crystallization is known as a hydrate. The structure of hydrates can be quite elaborate, because of the existence of hydrogen bonds that define polymeric structures.
Historically, the structures of many hydrates were unknown, and the dot in the formula of a hydrate was employed to specify the composition without indicating how the water is bound. Per IUPAC's recommendations, the middle dot is not surrounded by spaces when indicating a chemical adduct. Examples:
* – copper(II) sulfate pentahydrate
* – cobalt(II) chloride hexahydrate
* – tin(II) (or stannous) chloride dihydrate
For many salts, the exact bonding of the water is unimportant because the water molecules are made labile upon dissolution. For example, an aqueous solution prepared from and anhydrous behave identically. Therefore, knowledge of the degree of hydration is important only for determining the equivalent weight: one mole of weighs more than one mole of . In some cases, the degree of hydration can be critical to the resulting chemical properties. For example, anhydrous is not soluble in water and is relatively useless in organometallic chemistry whereas is versatile. Similarly, hydrated is a poor Lewis acid and thus inactive as a catalyst for Friedel-Crafts reactions. Samples of must therefore be protected from atmospheric moisture to preclude the formation of hydrates.
Crystals of hydrated copper(II) sulfate consist of centers linked to ions. Copper is surrounded by six oxygen atoms, provided by two different sulfate groups and four molecules of water. A fifth water resides elsewhere in the framework but does not bind directly to copper. The cobalt chloride mentioned above occurs as and . In tin chloride, each Sn(II) center is pyramidal (mean angle is 83°) being bound to two chloride ions and one water. The second water in the formula unit is hydrogen-bonded to the chloride and to the coordinated water molecule. Water of crystallization is stabilized by electrostatic attractions, consequently hydrates are common for salts that contain +2 and +3 cations as well as −2 anions. In some cases, the majority of the weight of a compound arises from water. Glauber's salt, , is a white crystalline solid with greater than 50% water by weight.
Consider the case of nickel(II) chloride hexahydrate. This species has the formula . Crystallographic analysis reveals that the solid consists of subunits that are hydrogen bonded to each other as well as two additional molecules of . Thus one third of the water molecules in the crystal are not directly bonded to , and these might be termed "water of crystallization". | 0 | Theoretical and Fundamental Chemistry |
A retinalophototroph is one of two different types of phototrophs, and are named for retinal-binding proteins (microbial rhodopsins) they utilize for cell signaling and converting light into energy. Like all phototrophs, retinalophototrophs absorb photons to initiate their cellular processes. In contrast with chlorophototrophs, retinalophototrophs do not use chlorophyll or an electron transport chain to power their chemical reactions. This means retinalophototrophs are incapable of traditional carbon fixation, a fundamental photosynthetic process that transforms inorganic carbon (carbon contained in molecular compounds like carbon dioxide) into organic compounds. For this reason, experts consider them to be less efficient than their chlorophyll-using counterparts, chlorophototrophs. | 0 | Theoretical and Fundamental Chemistry |
Vectorette PCR is similar to PCR with the difference being that it is capable of obtaining the sequence desired for amplification from an already known primer site. While PCR needs information of already known sequences at both ends, Vectorette PCR only requires previous knowledge of one. This means that is able to apply the method of PCR which needs sequence information from both ends to fragments of DNA that contain the information of the sequence at only one end and not the other. In order to achieve this, there are specific steps that this method must first go through. These steps have been researched for the purpose of discovering the scientific uses of Vectorette PCR and how they can be applied. | 1 | Applied and Interdisciplinary Chemistry |
Like biotic molecules, position specific isotope enrichments in abiotic molecules can reflect the source of chemical precursors and synthesis pathways. The energy for abiotic reactions can come from many different sources, which will affect fractionation. For instance, metal catalysts can speed up abiotic reactions. Reactions can be slowed down or sped up by different temperature and pressure conditions, which will affect the equilibrium constant or activation energy of reversible and irreversible reactions, respectively.
For example, carbon in the interstellar medium and solar nebula partition into distinct states based on thermodynamic favorability. Measuring site-specific isotope enrichments of carbon from organic molecules extracted from carbonaceous chondrites can elucidate where each carbon atom comes from, and how organic molecules can be synthesized abiotically. More broadly, these isotope enrichments can provide information about physical processes in the region where the molecular precursors were formed, and where the molecule formed in the solar system (i.e., nucleosynthetic heterogeneity, mass independent fractionation, self-shielding, etc.).
Another example of distinct site-specific fractionations in abiotic molecules is Fischer-Tropsch-type synthesis, which is thought to produce abiogenic hydrocarbon chains. Through this reaction mechanism, site enrichments of carbon would deplete as carbon chain length increases, and be distinct from site-specific enrichments of hydrocarbons of biological origins. | 0 | Theoretical and Fundamental Chemistry |
In flash smelting, the concentrate is dispersed in an air or oxygen stream and the smelting reactions are largely completed while the mineral particles are still in flight. The reacted particles then settle in a bath at the bottom of the furnace, where they behave like calcine in a reverberatory furnace. A slag layer forms on top of the matte layer, and they can separately be tapped from the furnace. | 1 | Applied and Interdisciplinary Chemistry |
For an infinite three-dimensional lattice , defined by its primitive vectors and the subscript of integers , its reciprocal lattice with the integer subscript can be determined by generating its three reciprocal primitive vectors
where is the scalar triple product. The choice of these is to satisfy as the known condition (There may be other condition.) of primitive translation vectors for the reciprocal lattice derived in the heuristic approach above and the section multi-dimensional Fourier series. This choice also satisfies the requirement of the reciprocal lattice mathematically derived above. Using column vector representation of (reciprocal) primitive vectors, the formulae above can be rewritten using matrix inversion:
This method appeals to the definition, and allows generalization to arbitrary dimensions. The cross product formula dominates introductory materials on crystallography.
The above definition is called the "physics" definition, as the factor of comes naturally from the study of periodic structures. An essentially equivalent definition, the "crystallographer's" definition, comes from defining the reciprocal lattice . which changes the reciprocal primitive vectors to be
and so on for the other primitive vectors. The crystallographer's definition has the advantage that the definition of is just the reciprocal magnitude of in the direction of , dropping the factor of . This can simplify certain mathematical manipulations, and expresses reciprocal lattice dimensions in units of spatial frequency. It is a matter of taste which definition of the lattice is used, as long as the two are not mixed.
is conventionally written as or , called Miller indices; is replaced with , replaced with , and replaced with . Each lattice point in the reciprocal lattice corresponds to a set of lattice planes in the real space lattice. (A lattice plane is a plane crossing lattice points.) The direction of the reciprocal lattice vector corresponds to the normal to the real space planes. The magnitude of the reciprocal lattice vector is given in reciprocal length and is equal to the reciprocal of the interplanar spacing of the real space planes. | 0 | Theoretical and Fundamental Chemistry |
The equilibrium of this reaction shows a significant temperature dependence and the equilibrium constant decreases with an increase in temperature, that is, higher hydrogen formation is observed at lower temperatures. | 0 | Theoretical and Fundamental Chemistry |
Some hypotheses relating to diamond formation posit a possible role for cavitation—namely cavitation in the kimberlite pipes providing the extreme pressure needed to change pure carbon into the rare allotrope that is diamond. The loudest three sounds ever recorded, during the 1883 eruption of Krakatoa, are now understood as the bursts of three huge cavitation bubbles, each larger than the last, formed in the volcano's throat. Rising magma, filled with dissolved gasses and under immense pressure, encountered a different magma that compressed easily, allowing bubbles to grow and combine. | 1 | Applied and Interdisciplinary Chemistry |
Traditionally bun ingots were seen as a primary product of smelting, forming at the base of a furnace beneath a layer of less dense slag. However, experimental reconstruction of copper smelting showed that regular plano-convex ingots are difficult to form within the smelting furnace, producing only small ingots or copper prills that need to be remelted. High purity copper bun ingots found in Late Bronze Age Britain and the Mediterranean seem to have undergone a secondary refining procedure.
The metallographic structure and high iron compositions of some plano-convex ingots suggest that they are the product of primary smelting. Tylecote suggested that Roman plano-convex copper ingots may have been formed by tapping both slag and copper in one step into a mould or pit outside the furnace. A similar process was described by Agricola in book IX of his De Re Metallica and has been replicated experimentally. | 1 | Applied and Interdisciplinary Chemistry |
The coefficient of thermal expansion describes how the size of an object changes with a change in temperature. Specifically, it measures the fractional change in size per degree change in temperature at a constant pressure, such that lower coefficients describe lower propensity for change in size. Several types of coefficients have been developed: volumetric, area, and linear. The choice of coefficient depends on the particular application and which dimensions are considered important. For solids, one might only be concerned with the change along a length, or over some area.
The volumetric thermal expansion coefficient is the most basic thermal expansion coefficient, and the most relevant for fluids. In general, substances expand or contract when their temperature changes, with expansion or contraction occurring in all directions. Substances that expand at the same rate in every direction are called isotropic. For isotropic materials, the area and volumetric thermal expansion coefficient are, respectively, approximately twice and three times larger than the linear thermal expansion coefficient.
In the general case of a gas, liquid, or solid, the volumetric coefficient of thermal expansion is given by
The subscript "p" to the derivative indicates that the pressure is held constant during the expansion, and the subscript V stresses that it is the volumetric (not linear) expansion that enters this general definition. In the case of a gas, the fact that the pressure is held constant is important, because the volume of a gas will vary appreciably with pressure as well as temperature. For a gas of low density this can be seen from the ideal gas law. | 0 | Theoretical and Fundamental Chemistry |
Recent investigations suggest that complex I is a potent source of reactive oxygen species. Complex I can produce superoxide (as well as hydrogen peroxide), through at least two different pathways. During forward electron transfer, only very small amounts of superoxide are produced (probably less than 0.1% of the overall electron flow).
During reverse electron transfer, complex I might be the most important site of superoxide production within mitochondria, with around 3-4% of electrons being diverted to superoxide formation. Reverse electron transfer, the process by which electrons from the reduced ubiquinol pool (supplied by succinate dehydrogenase, glycerol-3-phosphate dehydrogenase, electron-transferring flavoprotein or dihydroorotate dehydrogenase in mammalian mitochondria) pass through complex I to reduce NAD to NADH, driven by the inner mitochondrial membrane potential electric potential. Although it is not precisely known under what pathological conditions reverse-electron transfer would occur in vivo, in vitro experiments indicate that this process can be a very potent source of superoxide when succinate concentrations are high and oxaloacetate or malate concentrations are low. This can take place during tissue ischaemia, when oxygen delivery is blocked.
Superoxide is a reactive oxygen species that contributes to cellular oxidative stress and is linked to neuromuscular diseases and aging. NADH dehydrogenase produces superoxide by transferring one electron from FMNH (or semireduced flavin) to oxygen (O). The radical flavin leftover is unstable, and transfers the remaining electron to the iron-sulfur centers. It is the ratio of NADH to NAD that determines the rate of superoxide formation. | 1 | Applied and Interdisciplinary Chemistry |
The magnitude and composition of the starvation response (i.e. metabolic adaptation) was estimated in a study of 8 individuals living in isolation in Biosphere 2 for two years. During their isolation, they gradually lost an average of 15% (range: 9–24%) of their body weight due to harsh conditions. On emerging from isolation, the eight isolated individuals were compared with a 152-person control group that initially had similar physical characteristics. On average, the starvation response of the individuals after isolation was a reduction in daily total energy expenditure. of the starvation response was explained by a reduction in fat-free mass and fat mass. An additional was explained by a reduction in fidgeting. The remaining was statistically insignificant. | 1 | Applied and Interdisciplinary Chemistry |
The Enders SAMP/RAMP hydrazone alkylation reaction is an asymmetric carbon-carbon bond formation reaction facilitated by pyrrolidine chiral auxiliaries. It was pioneered by E. J. Corey and Dieter Enders in 1976, and was further developed by Enders and his group. This method is usually a three-step sequence. The first step is to form the hydrazone between (S)-1-amino-2-methoxymethylpyrrolidine (SAMP) or (R)-1-amino-2-methoxymethylpyrrolidine (RAMP) and a ketone or aldehyde. Afterwards, the hydrazone is deprotonated by lithium diisopropylamide (LDA) to form an azaenolate, which reacts with alkyl halides or other suitable electrophiles to give alkylated hydrazone species with the simultaneous generation of a new chiral center. Finally, the alkylated ketone or aldehyde can be regenerated by ozonolysis or hydrolysis.
This reaction is a useful technique for asymmetric α-alkylation of ketones and aldehydes, which are common synthetic intermediates for medicinally interesting natural products and other related organic compounds. These natural products include (-)-C10-demethyl arteannuin B, the structural analog of antimalarial artemisinin, the polypropionate metabolite (-)-denticulatin A and B isolated from Siphonaria denticulata, zaragozic acid A, a potent inhibitor of sterol synthesis, and epothilone A and B, which have been proven to be very effective anticancer drugs. | 0 | Theoretical and Fundamental Chemistry |
The high surface tension of water causes droplets to assume a nearly spherical shape, since a sphere has minimal surface area, and this shape therefore minimizes the solid-liquid surface energy. On contact of liquid with a surface, adhesion forces result in wetting of the surface. Either complete or incomplete wetting may occur depending on the structure of the surface and the fluid tension of the droplet.
The cause of self-cleaning properties is the hydrophobic water-repellent double structure of the surface. This enables the contact area and the adhesion force between surface and droplet to be significantly reduced, resulting in a self-cleaning process.
This hierarchical double structure is formed out of a characteristic epidermis (its outermost layer called the cuticle) and the covering waxes. The epidermis of the lotus plant possesses papillae 10 μm to 20 μm in height and 10 μm to 15 μm in width on which the so-called epicuticular waxes are imposed. These superimposed waxes are hydrophobic and form the second layer of the double structure. This system regenerates. This biochemical property is responsible for the functioning of the water repellency of the surface.
The hydrophobicity of a surface can be measured by its contact angle. The higher the contact angle the higher the hydrophobicity of a surface. Surfaces with a contact angle < 90° are referred to as hydrophilic and those with an angle >90° as hydrophobic. Some plants show contact angles up to 160° and are called ultrahydrophobic, meaning that only 2–3% of the surface of a droplet (of typical size) is in contact. Plants with a double structured surface like the lotus can reach a contact angle of 170°, whereby the droplet's contact area is only 0.6%. All this leads to a self-cleaning effect.
Dirt particles with an extremely reduced contact area are picked up by water droplets and are thus easily cleaned off the surface. If a water droplet rolls across such a contaminated surface the adhesion between the dirt particle, irrespective of its chemistry, and the droplet is higher than between the particle and the surface. This cleaning effect has been demonstrated on common materials such as stainless steel when a superhydrophobic surface is produced. As this self-cleaning effect is based on the high surface tension of water it does not work with organic solvents. Therefore, the hydrophobicity of a surface is no protection against graffiti.
This effect is of a great importance for plants as a protection against pathogens like fungi or algae growth, and also for animals like butterflies, dragonflies and other insects not able to cleanse all their body parts.
Another positive effect of self-cleaning is the prevention of contamination of the area of a plant surface exposed to light resulting in reduced photosynthesis. | 0 | Theoretical and Fundamental Chemistry |
Biofoams are biological or biologically derived foams, making up lightweight and porous cellular solids. A relatively new term, its use in academia began in the 1980s in relation to the scum that formed on activated sludge plants.
Biofoams is a broad umbrella term that covers a large variety of topics including naturally occurring foams, as well as foams produced from biological materials such as soy oil and cellulose. Biofoams have been a topic of continuous research because synthesized biofoams are being considered as alternatives to traditional petroleum-based foams. Due to the variable nature of synthesized foams, they can have a variety of characteristics and material properties that make them suitable for packaging, insulation, and other applications. | 0 | Theoretical and Fundamental Chemistry |
The contribution of each gas to the enhanced greenhouse effect is determined by the characteristics of that gas, its abundance, and any indirect effects it may cause. For example, the direct radiative effect of a mass of methane is about 84 times stronger than the same mass of carbon dioxide over a 20-year time frame. Since the 1980s, greenhouse gas forcing contributions (relative to year 1750) are also estimated with high accuracy using IPCC-recommended expressions derived from radiative transfer models.
The concentration of a greenhouse gas is typically measured in parts per million (ppm) or parts per billion (ppb) by volume. A concentration of 420 ppm means that 420 out of every million air molecules is a molecule. The first 30 ppm increase in concentrations took place in about 200 years, from the start of the Industrial Revolution to 1958; however the next 90 ppm increase took place within 56 years, from 1958 to 2014. Similarly, the average annual increase in the 1960s was only 37% of what it was in 2000 through 2007.
Many observations are available online in a variety of Atmospheric Chemistry Observational Databases. The table below shows the most influential long-lived, well-mixed greenhouse gases, along with their tropospheric concentrations and direct radiative forcings, as identified by the Intergovernmental Panel on Climate Change (IPCC). Abundances of these trace gases are regularly measured by atmospheric scientists from samples collected throughout the world. It excludes water vapor because changes in its concentrations are calculated as a climate change feedback indirectly caused by changes in other greenhouse gases, as well as ozone, whose concentrations are only modified indirectly by various refrigerants that cause ozone depletion. Some short-lived gases (e.g. carbon monoxide, NOx) and aerosols (e.g. mineral dust or black carbon) are also excluded because of limited role and strong variation, alongwith minor refrigerants and other halogenated gases, which have been mass-produced in smaller quantities than those in the table. and Annex III of the 2021 IPCC WG1 Report
Mole fractions: μmol/mol = ppm = parts per million (10); nmol/mol = ppb = parts per billion (10); pmol/mol = ppt = parts per trillion (10).
The IPCC states that "no single atmospheric lifetime can be given" for CO. This is mostly due to the rapid growth and cumulative magnitude of the disturbances to Earth's carbon cycle by the geologic extraction and burning of fossil carbon. As of year 2014, fossil CO emitted as a theoretical 10 to 100 GtC pulse on top of the existing atmospheric concentration was expected to be 50% removed by land vegetation and ocean sinks in less than about a century, as based on the projections of coupled models referenced in the AR5 assessment. A substantial fraction (20–35%) was also projected to remain in the atmosphere for centuries to millennia, where fractional persistence increases with pulse size.
Values are relative to year 1750. AR6 reports the effective radiative forcing which includes effects of rapid adjustments in the atmosphere and at the surface. | 1 | Applied and Interdisciplinary Chemistry |
Bases: adenine (A), cytosine (C), guanine (G) and thymine (T) or uracil (U).
Amino acids: Alanine (Ala, A), Arginine (Arg, R), Asparagine (Asn, N), Aspartic acid (Asp, D), Cysteine (Cys, C), Glutamic acid (Glu, E), Glutamine (Gln, Q), Glycine (Gly, G), Histidine (His, H), Isoleucine (Ile, I), Leucine (Leu, L), Lysine (Lys, K), Methionine (Met, M), Phenylalanine (Phe, F), Proline (Pro, P), Serine (Ser, S), Threonine (Thr, T), Tryptophan (Trp, W), Tyrosine (Tyr, Y), and Valine (Val, V). | 1 | Applied and Interdisciplinary Chemistry |
The MDN measures total mercury concentrations on a weekly basis (methyl mercury is measured monthly at some sites), which provides wet deposition data for surface waters and other waterways. The goal is to deliver accurate information that allows researchers to evaluate the linkage between mercury and health, which is strengthened by its large spatial and temporal footprint. | 1 | Applied and Interdisciplinary Chemistry |
The surface energy is measured in units of joules per square meter, which is equivalent in the case of liquids to surface tension, measured in newtons per meter. The overall surface tension/energy of a liquid can be acquired through various methods using a tensiometer or using the pendant drop method and maximum bubble pressure method.
The interface tension at the interface of the probe liquid and the solid surface can additionally be viewed as being the result of different types of intermolecular forces. As such, surface energies can be subdivided according to the various interactions that cause them, such as the surface energy due to dispersive (e.g. van der Waals forces) and other interactions (e.g. hydrogen bonding, polar interactions, acid–base interactions, etc.). It is often useful for the sessile drop technique to use liquids that are known to be incapable of some of those interactions (see table 1). For example, the surface tension of all straight alkanes is said to be entirely dispersive, and all of the other components are zero. This is algebraically useful, as it eliminates a variable in certain cases and makes these liquids essential testing materials.
The overall surface energy, both for a solid and a liquid, is assumed traditionally to simply be the sum of the components considered. For example, the equation describing the subdivision of surface energy into the contributions of dispersive interactions and polar interactions would be
where σ is the total surface energy of the solid, σ and σ are respectively the dispersive and polar components of the solid surface energy,
σ is the total surface tension/surface energy of the liquid, and
σ and σ are respectively the dispersive and polar components of the surface tension.
In addition to the tensiometer and pendant drop techniques, the sessile drop technique can be used in some cases to separate the known total surface energy of a liquid into its components. This is done by reversing the above idea with the introduction of a reference solid surface that is assumed to be incapable of polar interactions, such as polytetrafluoroethylene (PTFE). | 0 | Theoretical and Fundamental Chemistry |
Development of theoretical models describing grain growth is an active field of research. Many models have been proposed for grain growth, but no theory has yet been put forth that has been independently validated to apply across the full range of conditions and many questions remain open. By no means is the following a comprehensive review. One recent theory of grain growth posits that normal grain growth only occurs in the polycrystalline systems with grain boundaries which have undergone roughening transitions, and abnormal and/or stagnant grain growth can only occur in the polycrystalline systems with non-zero GB (grain boundary) step free energy of grains. Other models explaining grain coarsening assert that disconnections are responsible for the motion of grain boundaries, and provide limited experimental evidence suggesting that they govern grain boundary migration and grain growth behavior. Other models have indicated that triple junctions play an important role in determining the grain growth behavior in many systems. | 1 | Applied and Interdisciplinary Chemistry |
Vanadium(III) bromide and molybdenum(IV) bromide were prepared by treatment of the higher chlorides with HBr. These reactions proceed via redox reactions: | 0 | Theoretical and Fundamental Chemistry |
In general α-Keggin anions are synthesized in acidic solutions. For example, 12-phosphotungstic acid is formed by condensing phosphate ion with tungstate ions. The heteropolyacid that is formed has the Keggin structure. | 0 | Theoretical and Fundamental Chemistry |
In the Conception Bay in Newfoundland, Southeastern coast of Canada, a series of Pre-Cambrian to Cambrian-linked volcanic rocks were silicified. The rocks mainly consist of rhyolitic and basaltic flows, with crystal tuffs and breccia interbedded. Regional silicification was taken place as a preliminary alteration process before other geochemical processes occurred. The source of silica near the area was from hot siliceous fluids from rhyolitic flow under a static condition. A significant portion of silica appeared in the form of white chalcedonic quartz, quartz veins as well as granular quartz crystal. Due to the difference in rock structures, silica replaces different materials in rocks of close locations. The following table shows the replacement of silica at different localities: | 0 | Theoretical and Fundamental Chemistry |
Unhindered aldimines tend to cyclize, as illustrated by the condensation of methylamine and formaldehyde, which gives the hexahydro-1,3,5-triazine.
Imine polymers (polyimines) can be synthesised from multivalent aldehydes and amines. The polymerisation reaction proceeds directly when the aldehyde and amine monomers are mixed together at room temperature. In most cases, (small) amounts of solvent may still be required. Polyimines are particularly interesting materials because of their application as vitrimers. Owing to the dynamic covalent nature of the imine bonds, polyimines can be recycled relatively easily. Furthermore, polyimines are known for their self-healing behaviour. | 0 | Theoretical and Fundamental Chemistry |
Shortly after World War II, a second approach to drug therapy of cancer began. Sidney Farber, a pathologist at Harvard Medical School, studied the effects of folic acid on leukemia patients. Folic acid, a vitamin crucial for DNA metabolism (the significance of DNA was not known at that time), had been discovered by Lucy Wills, when she was working in India, in 1937. It seemed to stimulate the proliferation of acute lymphoblastic leukemia (ALL) cells when administered to children with this cancer. In one of the first examples of rational drug design (rather than accidental discovery), Farber used folate analogues synthesized by Harriett Kiltie and Yellapragada Subbarow of Lederle Laboratories. These analogues — first aminopterin and then amethopterin (now methotrexate) were antagonistic to folic acid, and blocked the function of folate-requiring enzymes. When administered to children with ALL in 1948, these agents became the first drugs to induce remission in children with ALL. Remissions were brief, but the principle was clear — antifolates could suppress proliferation of malignant cells, and could thereby re-establish normal bone-marrow function. Farber met resistance to conducting his studies at a time when the commonly held medical belief was that leukemia was incurable, and that the children should be allowed to die in peace. Afterwards, Farber's 1948 report in the New England Journal of Medicine was met with incredulity and ridicule.
In 1947, Major League Baseball Hall of Famer Babe Ruth, who was battling nasopharyngeal cancer, became one of the first human subjects of pteroyl triglutamate (also known by its brand name Teropterin, and similar to aminopterin) treatment. Dr. Richard Lewisohn of Mount Sinai Hospital in New York administered the drug, and over the course of several months, Ruth's condition began to improve. However, Ruth died the following year.
In 1951, Jane C. Wright demonstrated the use of methotrexate in solid tumors, showing remission in breast cancer. Wright's group was the first to demonstrate use of the drug in solid tumors, as opposed to leukemias, which are cancers of the marrow. Several years later at the National Cancer Institute, Roy Hertz and Min Chiu Li then demonstrated complete remission in women with choriocarcinoma and chorioadenoma in 1956, discovering that methotrexate alone could cure choriocarcinoma (1958), a germ-cell malignancy that originates in trophoblastic cells of the placenta. In 1960 Wright et al. produced remissions in mycosis fungoides. | 1 | Applied and Interdisciplinary Chemistry |
The wetlands that surround the lake spread over an area of 0.63 km, and are enclosed into an ancient shoreline. The origin of this larger open water lake remains unclear. If the lake level has remained stable, then the reduction in lake size is solely due to the conversion of these open waters into wetlands. Alternatively, lake shrinking might reflect a slight lowering of the average lake level, possibly due to a more efficient drainage at the lake outlet. In any case, it cannot be excluded that the lake level reverts in the future to its ancient stand, flooding areas that have now been filled and urbanized. Besides, the outlet drains to a cave that might get partially of completely obstructed by debris following large storms. Water ponding upstream of the cave could result in an increase in the lake level of 4,0 ± 0,3 m before surface overflow is achieved near the cave. | 1 | Applied and Interdisciplinary Chemistry |
Ethers like diethyl ether and tetrahydrofuran (THF) can form highly explosive organic peroxides upon exposure to oxygen and light. THF is normally more likely to form such peroxides than diethyl ether. One of the most susceptible solvents is diisopropyl ether, but all ethers are considered to be potential peroxide sources.
The heteroatom (oxygen) stabilizes the formation of a free radical which is formed by the abstraction of a hydrogen atom by another free radical. The carbon-centered free radical thus formed is able to react with an oxygen molecule to form a peroxide compound. The process of peroxide formation is greatly accelerated by exposure to even low levels of light, but can proceed slowly even in dark conditions.
Unless a desiccant is used which can destroy the peroxides, they will concentrate during distillation, due to their higher boiling point. When sufficient peroxides have formed, they can form a crystalline, shock-sensitive solid precipitate at the mouth of a container or bottle. Minor mechanical disturbances, such as scraping the inside of a vessel or the dislodging of a deposit, merely twisting the cap may provide sufficient energy for the peroxide to explode or detonate. Peroxide formation is not a significant problem when fresh solvents are used up quickly; they are more of a problem in laboratories which may take years to finish a single bottle. Low-volume users should acquire only small amounts of peroxide-prone solvents, and dispose of old solvents on a regular periodic schedule.
To avoid explosive peroxide formation, ethers should be stored in an airtight container, away from light, because both light and air can encourage peroxide formation.
A number of tests can be used to detect the presence of a peroxide in an ether; one is to use a combination of iron(II) sulfate and potassium thiocyanate. The peroxide is able to oxidize the Fe ion to an Fe ion, which then forms a deep-red coordination complex with the thiocyanate.
Peroxides may be removed by washing with acidic iron(II) sulfate, filtering through alumina, or distilling from sodium/benzophenone. Alumina degrades the peroxides but some could remain intact in it, therefore it must be disposed of properly. The advantage of using sodium/benzophenone is that moisture and oxygen are removed as well. | 1 | Applied and Interdisciplinary Chemistry |
PAVA is used widely as a less lethal, temporary defence tool around the world including in the United Kingdom, India, Switzerland, and others. | 1 | Applied and Interdisciplinary Chemistry |
In molecular biology, intercellular adhesion molecules (ICAMs) and vascular cell adhesion molecule-1 (VCAM-1) are part of the immunoglobulin superfamily. They are important in inflammation, immune responses and in intracellular signalling events. The ICAM family consists of five members, designated ICAM-1 to ICAM-5. They are known to bind to leucocyte integrins CD11/CD18 such as LFA-1 and Macrophage-1 antigen, during inflammation and in immune responses. In addition, ICAMs may exist in soluble forms in human plasma, due to activation and proteolysis mechanisms at cell surfaces.
Mammalian intercellular adhesion molecules include:
* ICAM-1
* ICAM2
* ICAM3
* ICAM4
* ICAM5 | 1 | Applied and Interdisciplinary Chemistry |
Steric approach control is common in conjugate addition reactions. Thus, in cyclic substrates, a trans relationship between substituents on the α- and β-carbons is common. The configuration at the α-position is less predictable, especially in cases when epimerization can occur. On the basis of steric approach control, the new α-substituent is predicted to be trans to the new β-substituent, and this is observed in a number of cases. | 0 | Theoretical and Fundamental Chemistry |
Work performed in the Bradbury laboratory showed that nucleosomes reconstituted onto the 5S DNA positioning sequence were able to reposition themselves translationally onto adjacent sequences when incubated thermally. Later work showed that this repositioning did not require disruption of the histone octamer but was consistent with nucleosomes being able to "slide" along the DNA in cis. In 2008, it was further revealed that CTCF binding sites act as nucleosome positioning anchors so that, when used to align various genomic signals, multiple flanking nucleosomes can be readily identified. Although nucleosomes are intrinsically mobile, eukaryotes have evolved a large family of ATP-dependent chromatin remodelling enzymes to alter chromatin structure, many of which do so via nucleosome sliding. In 2012, Beena Pillai's laboratory has demonstrated that nucleosome sliding is one of the possible mechanism for large scale tissue specific expression of genes. The work shows that the transcription start site for genes expressed in a particular tissue, are nucleosome depleted while, the same set of genes in other tissue where they are not expressed, are nucleosome bound. | 1 | Applied and Interdisciplinary Chemistry |
Boiling is also a phase transition from the liquid phase to gas phase, but boiling is the formation of vapor as bubbles of vapor below the surface of the liquid. Boiling occurs when the equilibrium vapor pressure of the substance is greater than or equal to the atmospheric pressure. The temperature at which boiling occurs is the boiling temperature, or boiling point. The boiling point varies with the pressure of the environment. | 0 | Theoretical and Fundamental Chemistry |
A solar-powered desalination unit produces potable water from saline water by using a photovoltaic system to supply the energy. Solar power works well for water purification in settings lacking grid electricity and can reduce operating costs and greenhouse emissions. For example, a solar-powered desalination unit designed passed tests in Australia's Northern Territory.
Sunlight's intermittent nature makes output prediction difficult without an energy storage capability. However batteries or thermal energy storage systems can provide power when the sun does not. | 0 | Theoretical and Fundamental Chemistry |
Many C–H activation reactions, particularly those involving late transition metals, require carboxylate or carbonate bases. The need for this reaction component often suggests the occurrence of a CMD pathway. However, in order to be classified as CMD, the transition state does not need to involve the carboxylate as a ligand on the metal. Common sources of carboxylate include pivalate, acetate, and benzoate. | 0 | Theoretical and Fundamental Chemistry |
In common use, the research definition, including post-transition metals and metalloids, is extended to include compounds such as cementite, FeC. These compounds, sometimes termed interstitial compounds, can be stoichiometric, and share similar properties to the intermetallic compounds defined above. | 1 | Applied and Interdisciplinary Chemistry |
Leng has several roles, her most current is Chief Scientist for Environmental Change Adaptation and Resilience at the British Geological Survey. She is also Director of the Centre for Environmental Geochemistry, a collaboration between the British Geological Survey and the University of Nottingham, Leng leads research around environmental change, human impact, food security, and resource management. Leng has been involved in deep drilling as part of the International Continental Scientific Drilling Program, and worked in Lake Ohrid in Macedonia and Lake Chala in East Africa. She also heads the Stable Isotope Facility at the British Geological Survey, which is part of the National Environmental Isotope Facility. Stable isotopes can be used to better understand climate change and human-landscape interactions, with increasing importance on the Anthropocene and the modern calibration period; tracers of modern pollution; and understanding the hydrological cycle especially in areas suffering human impact. Leng takes part in expeditions, most recently the Natural Environment Research Council (NERC) mission called Ocean Regulation of Climate by Heat and Carbon Sequestration and Transports (ORCHESTRA). She actively blogs about her research.
Leng serves on the editorial board of the journals Quaternary Research, Quaternary Science Reviews, Scientific Reports and the Journal of Paleolimnology.
She has written several articles about successfully undertaking a PhD. | 0 | Theoretical and Fundamental Chemistry |
Joseph Louis Gay-Lussac (, , ; 6 December 1778 – 9 May 1850) was a French chemist and physicist. He is known mostly for his discovery that water is made of two parts hydrogen and one part oxygen by volume (with Alexander von Humboldt), for two laws related to gases, and for his work on alcohol–water mixtures, which led to the degrees Gay-Lussac used to measure alcoholic beverages in many countries. | 1 | Applied and Interdisciplinary Chemistry |
GPC is a type of chromatography in which analytes are separated, based on their size or hydrodynamic volume (radius of gyration). This differs from other chromatographic techniques, which depend upon chemical or physical interactions between the mobile and stationary phases to separate analytes. Separation occurs via the use of porous gel beads packed inside a column (see stationary phase (chemistry)). The principle of separation relies on the differential exclusion or inclusion of the macromolecules by the porous gel stationary phase. Larger molecules are excluded from entering the pores and elute earlier, while smaller molecules can enter the pores, thus staying longer inside the column. The entire process takes place without any interaction of the analytes with the surface of the stationary phase. The smaller analytes relative to the pore sizes can permeate these pores and spend more time inside the gel particles, increasing their retention time. Conversely, larger analytes relative to the pores sizes spend little if any time inside the column, hence they elute sooner. Each type of column has a range of molecular weights that can be separated, according to their pores sizes. If an analyte is too large relative to the column's pores, it will not be retained at all and will be totally excluded; conversely, if the analyte is small relative to the pores sizes, it will be totally permeating. Analytes that are totally excluded, elute with the free volume outside around the particles (V), the total exclusion limit, while analytes that are completely delayed, elute with the solvent, marking the total permeation volume of the column, including also the solvent held inside the pores (V). The total volume can be considered by the following equation, where V is the volume of the polymer gel and V is the total volume:
As can be inferred, there is a limited range of molecular weights that can be separated by each column, therefore the size of the pores for the packing should be chosen according to the range of molecular weight of analytes to be separated. For polymer separations the pore sizes should be on the order of the polymers being analyzed. If a sample has a broad molecular weight range it may be necessary to use several GPC columns with varying pores volumes in tandem to resolve the sample fully. | 0 | Theoretical and Fundamental Chemistry |
Progesterone is produced in high amounts in the ovaries (by the corpus luteum) from the onset of puberty to menopause, and is also produced in smaller amounts by the adrenal glands after the onset of adrenarche in both males and females. To a lesser extent, progesterone is produced in nervous tissue, especially in the brain, and in adipose (fat) tissue, as well.
During human pregnancy, progesterone is produced in increasingly high amounts by the ovaries and placenta. At first, the source is the corpus luteum that has been "rescued" by the presence of human chorionic gonadotropin (hCG) from the conceptus. However, after the 8th week, production of progesterone shifts to the placenta. The placenta utilizes maternal cholesterol as the initial substrate, and most of the produced progesterone enters the maternal circulation, but some is picked up by the fetal circulation and used as substrate for fetal corticosteroids. At term the placenta produces about 250 mg progesterone per day.
An additional animal source of progesterone is milk products. After consumption of milk products the level of bioavailable progesterone goes up. | 0 | Theoretical and Fundamental Chemistry |
With the ability of rapid screening of diverse compounds (such as small molecules or siRNAs) to identify active compounds, HTS has led to an explosion in the rate of data generated in recent years
Consequently, one of the most fundamental challenges in HTS experiments is to glean biochemical significance from mounds of data, which relies on the development and adoption of appropriate experimental designs and analytic methods for both quality control and hit selection
HTS research is one of the fields that have a feature described by John Blume, Chief Science Officer for Applied Proteomics, Inc., as follows: Soon, if a scientist does not understand some statistics or rudimentary data-handling technologies, he or she may not be considered to be a true molecular biologist and, thus, will simply become "a dinosaur." | 1 | Applied and Interdisciplinary Chemistry |
The chloroplast stroma contains many proteins, though the most common and important is RuBisCO, which is probably also the most abundant protein on the planet. RuBisCO is the enzyme that fixes CO into sugar molecules. In plants, RuBisCO is abundant in all chloroplasts, though in plants, it is confined to the bundle sheath chloroplasts, where the Calvin cycle is carried out in plants. | 0 | Theoretical and Fundamental Chemistry |
An acid is classified as "strong" when the concentration of its undissociated species is too low to be measured. Any aqueous acid with a pK value of less than 0 is almost completely deprotonated and is considered a strong acid. All such acids transfer their protons to water and form the solvent cation species (HO in aqueous solution) so that they all have essentially the same acidity, a phenomenon known as solvent leveling. They are said to be fully dissociated in aqueous solution because the amount of undissociated acid, in equilibrium with the dissociation products, is below the detection limit. = −1.4) behaves as a strong acid. When the ratio of water molecules to acid molecules in a solution of an acid is too small to fully solvate the dissociation products, dissociation is not complete, for example, with extremely concentrated solutions of sulfuric acid and hydrochloric acid.}}.
--> Likewise, any aqueous base with an association constant pK less than about 0, corresponding to pK greater than about 14, is leveled to OH and is considered a strong base.
Nitric acid, with a pK value of around −1.7, behaves as a strong acid in aqueous solutions with a pH greater than 1. At lower pH values it behaves as a weak acid.
pK values for strong acids have been estimated by theoretical means. For example, the pK value of aqueous HCl has been estimated as −9.3. | 0 | Theoretical and Fundamental Chemistry |
Vectorette PCR is a variation of polymerase chain reaction (PCR) designed in 1988. The original PCR was created and also patented during the 1980s. Vectorette PCR was first noted and described in an article in 1990 by John H. Riley and his team. Since then, multiple variants of PCR have been created. Vectorette PCR focuses on amplifying a specific sequence obtained from an internal sequence that is originally known until the fragment end. Multiple researches have taken this method as an opportunity to conduct experiments in order to uncover the potential uses that can be derived from Vectorette PCR. | 1 | Applied and Interdisciplinary Chemistry |
One-bond coupling is illustrated by PH where J(P,H) is 189 Hz. Two-bond couplings, e.g. PCH are an order of magnitude smaller. The situation for phosphorus-carbon couplings are more complicated since the two-bond couplings are often larger than one-bond couplings. The J(C,P) values for triphenylphosphine are respectively −12.5, 19.6, 6.8, and 0.3 for one-, two-, three-, and four-bond couplings. | 0 | Theoretical and Fundamental Chemistry |
Given a uniform velocity of a fluid at any position in space:
This flow is incompressible because the velocity is constant, the first derivatives of the velocity components are zero, and the total divergence is zero:
Given the circulation is always zero the flow is also irrotational, we can derive this from the Kelvin's circulation theorem and from the explicit computation of the vorticity:
Being incompressible and two-dimensional, this flow is constructed from a stream function:
from which
and in cylindrical coordinates:
from which
As usual the stream function is defined up to a constant value which here we take as zero. We can also confirm that the flow is irrotational from:
Being irrotational, the potential function is instead:
and therefore
and in cylindrical coordinates | 1 | Applied and Interdisciplinary Chemistry |
The advantage of the approximation arises because when considering a flow of, say, warm and cold water of density and one needs only to consider a single density : the difference is negligible. Dimensional analysis shows that, under these circumstances, the only sensible way that acceleration due to gravity should enter into the equations of motion is in the reduced gravity where
(Note that the denominator may be either density without affecting the result because the change would be of order
.) The most generally used dimensionless number would be the Richardson number and Rayleigh number.
The mathematics of the flow is therefore simpler because the density ratio , a dimensionless number, does not affect the flow; the Boussinesq approximation states that it may be assumed to be exactly one. | 1 | Applied and Interdisciplinary Chemistry |
CKLF1 is the first member of the CKLF-like MARVEL transmembrane domain-containing family of proteins to be defined and the most investigated of its four isoforms. Studies conducted in freshly isolated cells, cultured cells, animals, and tissue samples indicate that CKLF1 is a chemokine-like chemotactic factor that acts through the CCR4 receptors on human CD4+ Th2 lymphocytes, neutrophils, monocytes, macrophages, dendritic cells, and perhaps other CCR4-receptor bearing cells. Preliminary findings suggest that the actions of CKLF1 on these CCR4-bearing cells may contribute to the maturation of various tissues such as blood cells and skeletal muscle from their precursor cells and the regulation of allergic (e.g. asthma), autoimmune (e.g. rheumatoid arthritis and the antiphospholipid syndrome), and inflammatory (e.g. acute respiratory distress syndrome) disorders. Other studies have found that: 1) the benign fibrous skin tumor, keloids, had higher levels of CKLF1 and CKLF1 mRNA than nearby normal skin tissues; 2) CKLF1 levels were higher in ovarian carcinoma tissues than nearby normal ovary tissues and patients with higher levels of CKLF1 in their ovarian cancer tissues had a more aggressive cancer than patients with lover levels of the protein in their ovarian cancer tissues; and 3) the levels of CKLF1 protein were higher in cancerous than nearby normal liver tissues in patients with hepatocellular carcinoma (HCC) and patients with higher HCC tissue levels of CKLF1 had poorer overall survival times than patients with lower levels of this protein in their HCC tissues. These results suggest that high levels of CKLF1 promote the development and/or progression of these three neoplasms although further studies are required to further define these relationships and to determine if CKLF1 can be used as a marker for their severity and/or a therapeutic target for treating them. | 1 | Applied and Interdisciplinary Chemistry |
β-catenin has also been implicated in regulation of cell fates through asymmetric cell division in the model organism C. elegans. Similarly to the Xenopus oocytes, this is essentially the result of non-equal distribution of Dsh, Frizzled, axin and APC in the cytoplasm of the mother cell. | 1 | Applied and Interdisciplinary Chemistry |
The use of ractopamine in Russia is prohibited. On 6 June 2011, the Russian Ministry of Agriculture notified key meat import/exporters in Russia of a future prohibition of ractopamine in meat imported to Russia.
On 7 December 2012, the prohibition went into force, and pork and beef export to Russia required submission of compliance certificates confirming absence of ractopamine in exported meat. | 0 | Theoretical and Fundamental Chemistry |
The following analysis is taken largely from the work of Burton and Bush, and offers some mathematical insight into the role that flexibility plays in improving load-bearing characteristics of floating objects.
Consider two plates of infinite width, thickness , and length that are connected by a torsional spring with spring constant per unit width . Furthermore, let be the angle between a plate and the horizontal, and the from where the meniscus meets the plate to the horizontal. The distance from the undisturbed water line to the plate's outer edge is . The density of water is , the density of air is considered negligible, and the plate density, , shall be varied. All systems naturally assume a configuration that minimizes total energy. Thus, the goal of this analysis is to identify the configurations (i.e., values of and ) that result in a stable equilibrium for a given value of .
For a total system energy of , it is natural to distinguish sub-components:
<br />
:: Work done on the system
:: System potential energy
In defining , there are several associated components:
<br />
: is the work done on the interface by hydrostatic pressure
: is the work done on the plates by hydrostatic pressure
: is the work done on the plates by gravitational force
: is the work done on the plates by surface tension forces
Similarly, the system potential energy, , is taken to be composed of two terms:
<br />
: is the surface energy of the water/air interface
: is the energy stored in the torsional spring and is equal to
There are two ways in which the system energy can change by an incremental amount. The first is a translation of the center of mass of the plates by some distance . The second is an incremental change, in the hinge angle. Such a change will induce a new moment.
As mentioned, the system will seek the orientation that minimizes in order to find point of stable equilibrium. Writing out these terms more explicitly:
<br />
Here, is the equation air/water interface, is the incremental displacement of the interface, and is the surface tension of water.
For a given value of , stable equilibrium configurations are identified as being those values of and that satisfy
<br />
<br />
Taken in a different light, these conditions can be seen as identifying and that result in zero net force and zero net torque for a given . | 1 | Applied and Interdisciplinary Chemistry |
The benzyl halide 1 reacts with hexamine to a quaternary ammonium salt 3, each time just alkylating one nitrogen atom. Then the benzylammonium undergoes an acid-catalyzed hydrolysis process.
Depending on the hydrolysis conditions, the hexamine unit might instead break apart, leaving a benzyl amine (the Delépine reaction).
The reaction can also be applied to the oxidation of benzylic amines. In this way, m-xylylenediamine can be converted to isophthalaldehyde. | 0 | Theoretical and Fundamental Chemistry |
Angiogenin is a key protein implicated in angiogenesis in normal and tumor growth. Angiogenin interacts with endothelial and smooth muscle cells resulting in cell migration, invasion, proliferation and formation of tubular structures. Ang binds to actin of both smooth muscle and endothelial cells to form complexes that activate proteolytic cascades which upregulate the production of proteases and plasmin that degrade the laminin and fibronectin layers of the basement membrane. Degradation of the basement membrane and extracellular matrix allows the endothelial cells to penetrate and migrate into the perivascular tissue. Signal transduction pathways activated by Ang interactions at the cellular membrane of endothelial cells produce extracellular signal-related kinase1/2 (ERK1/2) and protein kinase B/Akt. Activation of these proteins leads to invasion of the basement membrane and cell proliferation associated with further angiogenesis. The most important step in the angiogenesis process is the translocation of Ang to the cell nucleus. Once Ang has been translocated to the nucleus, it enhances rRNA transcription by binding to the CT-rich (CTCTCTCTCTCTCTCTCCCTC) angiogenin binding element (ABE) within the upstream intergenic region of rDNA, which subsequently activates other angiogenic factors that induce angiogenesis.
However, angiogenin is unique among the many proteins that are involved in angiogenesis in that it is also an enzyme with an amino acid sequence 33% identical to that of bovine pancreatic ribonuclease (RNase A). Ang has the same general catalytic properties as RNase A, it cleaves preferentially on the 3' side of pyrimidines and follows a transphosphorylation/hydrolysis mechanism. Although angiogenin contains many of the same catalytic residues as RNase A, it cleaves standard RNA substrates 10–10 times less efficiently than RNase A. The reason for this inefficiency is due to the 117 residue consisting of a glutamine, which blocks the catalytic site. Removal of this residue through mutation increases the ribonuclease activity between 11 and 30 fold. Despite this apparent weakness, the enzymatic activity of Ang appears to be essential for biological activity: replacements of important catalytic site residues (histidine-13 and histidine-114) invariably diminish both the ribonuclease activity toward tRNA by 10,000 fold and almost abolishes angiogenesis activities completely. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, peptide synthesis is the production of peptides, compounds where multiple amino acids are linked via amide bonds, also known as peptide bonds. Peptides are chemically synthesized by the condensation reaction of the carboxyl group of one amino acid to the amino group of another. Protecting group strategies are usually necessary to prevent undesirable side reactions with the various amino acid side chains. Chemical peptide synthesis most commonly starts at the carboxyl end of the peptide (C-terminus), and proceeds toward the amino-terminus (N-terminus). Protein biosynthesis (long peptides) in living organisms occurs in the opposite direction.
The chemical synthesis of peptides can be carried out using classical solution-phase techniques, although these have been replaced in most research and development settings by solid-phase methods (see below). Solution-phase synthesis retains its usefulness in large-scale production of peptides for industrial purposes moreover.
Chemical synthesis facilitates the production of peptides that are difficult to express in bacteria, the incorporation of unnatural amino acids, peptide/protein backbone modification, and the synthesis of D-proteins, which consist of D-amino acids. | 1 | Applied and Interdisciplinary Chemistry |
Gaseous methylglyoxal has two carbonyl groups, an aldehyde and a ketone. In the presence of water, it exists as hydrates and oligomers. The formation of these hydrates is indicative of the high reactivity of MGO, which is relevant to its biological behavior. | 1 | Applied and Interdisciplinary Chemistry |
Advances in the field of recombinant protein engineering and expression, protein purification, NMR, X-ray crystallography and computational chemistry have improved the skills of drug designers to use data that have been gathered on the three-dimensional structures of protein ligand complexes.
Most bacterial species have various types of PBP which differ in various ways such as enzymatic function, molecular weight and the affinity for β-lactam antibiotics. There are two types of enzymes that are particularly interesting with regard to the binding site of β-lactams: PBP and β-lactamases. Target alterations in the binding site of PBP have led to high-level resistance of β-lactams among bacteria like staphylococci, enterococci and pneumococci.
For example, the binding site of PBP2 in Neisseria gonorrhoeae has been structurally determined and has three sequence motifs that can be seen in nearly all β-lactam interacting enzymes:
* SXXK motif is located at the N-terminal end of α2 helix and includes two residues that are important for the enzyme function.
** Ser-310 : Includes a serine nucleophile that is acylated by both peptide substrate and β-lactam antibiotics.
** Lys-313 : Plays an important role in providing the dense hydrogen bound network at the active site and is in distance of Ser 310, ASN-364 and the carbonyl backbone of Ser-362.
* SXN motif that includes Ser-362, Ser-363 and Asn-364
* KTG motif that includes Lys-497, Thr-498 and Gly-499
Research also implies that adjacent regions to the active site which differ between different PBP have significant influence on the rate of β-lactam acylation rate. | 1 | Applied and Interdisciplinary Chemistry |
Annual Review of Chemical and Biomolecular Engineering is an annual peer-reviewed scientific journal published by Annual Reviews, covering chemical and biomolecular engineering. The co-editors are Michael F. Doherty and Rachel A. Segalman. As of 2023, Journal Citation Reports, gives the journal an impact factor of 8.4. | 1 | Applied and Interdisciplinary Chemistry |
Radon-222 has been classified by International Agency for Research on Cancer as being carcinogenic to humans. In September 2009, the World Health Organization released a comprehensive global initiative on radon that recommended a reference level of 100 Bq/m for radon, urging establishment or strengthening of radon measurement and mitigation programs as well as development building codes requiring radon prevention measures in homes under construction.
Elevated lung cancer rates have been reported from a number of cohort and case-control studies of underground miners exposed to radon and its decay products but the main confounding factor in all miners' studies is smoking and dust. Up to the most of regulatory bodies there is sufficient evidence for the carcinogenicity of radon and its decay products in humans for such exposures. However, the discussion about the opposite results is still going on, especially a recent retrospective case-control study of lung cancer risk showed substantial cancer rate reduction between 50 and 123 Bq per cubic meter relative to a group at zero to 25 Bq per cubic meter. Additionally, the meta-analysis of many radon studies, which independently show radon risk increase, gives no confirmation of that conclusion: the joined data show log-normal distribution with the maximal value in zero risk of lung cancer below 800 Bq per cubic meter.
The primary route of exposure to radon and its progeny is inhalation. Radiation exposure from radon is indirect. The health hazard from radon does not come primarily from radon itself, but rather from the radioactive products formed in the decay of radon. The general effects of radon to the human body are caused by its radioactivity and consequent risk of radiation-induced cancer. Lung cancer is the only observed consequence of high concentration radon exposures; both human and animal studies indicate that the lung and respiratory system are the primary targets of radon daughter-induced toxicity.
Radon has a short half-life (3.8 days) and decays into other solid particulate radium-series radioactive nuclides.
Two of these decay products, polonium-218 and 214, present a significant radiologic hazard.
If the gas is inhaled, the radon atoms decay in the airways or the lungs, resulting in radioactive polonium and ultimately lead atoms attaching to the nearest tissue. If dust or aerosol is inhaled that already carries radon decay products, the deposition pattern of the decay products in the respiratory tract depends on the behaviour of the particles in the lungs. Smaller diameter particles diffuse further into the respiratory system, whereas the larger—tens to hundreds of micron-sized—particles often deposit higher in the airways and are cleared by the body's mucociliary staircase. Deposited radioactive atoms or dust or aerosol particles continue to decay, causing continued exposure by emitting energetic alpha radiation with some associated gamma radiation too, that can damage vital molecules in lung cells,
by either creating free radicals or causing DNA breaks or damage,
perhaps causing mutations that sometimes turn cancerous. In addition, through ingestion and blood transport, following crossing of the lung membrane by radon, radioactive progeny may also be transported to other parts of the body.
The risk of lung cancer caused by smoking is much higher than the risk of lung cancer caused by indoor radon. Radiation from radon has been attributed to increase of lung cancer among smokers too. It is generally believed that exposure to radon and cigarette smoking are synergistic; that is, that the combined effect exceeds the sum of their independent effects. This is because the daughters of radon often become attached to smoke and dust particles, and are then able to lodge in the lungs.
It is unknown whether radon causes other types of cancer, but recent studies suggest a need for further studies to assess the relationship between radon and leukemia.
The effects of radon, if found in food or drinking water, are unknown. Following ingestion of radon dissolved in water, the biological half-life for removal of radon from the body ranges from 30 to 70 minutes. More than 90% of the absorbed radon is eliminated by exhalation within 100 minutes, By 600 minutes, only 1% of the absorbed amount remains in the body. | 1 | Applied and Interdisciplinary Chemistry |
In his spare time Kowalski enjoyed horse-breeding and riding, sailing, hiking and backpacking, his Harley-Davidison motorcycle and skiing. According to Chemical & Engineering News, "After his retirement in 1999, Kowalski joined the Fort Lewis Mesa fire department in Durango, Colo., where he specialized in the handling of hazardous materials. Kowalski and his companion dog, Chaco-Bob, were a key part of the district’s canine search and rescue program." | 0 | Theoretical and Fundamental Chemistry |
The company was founded on June 15, 1917, with Spanish-French financial support, with a capital stock of 25 million pesetas. It was born in the context of a boom in Spanish industry, in the heat of the First World War. Two foreign capital companies were involved in its creation, the Sociedad Minera y Metalúrgica de Peñarroya (SMMP) and the Rio Tinto Company Limited (RTC), both of which became shareholders of the new company. The SECEM owned an important plant in Cordoba dedicated to copper metallurgy, brass production, manufacture of motors and electric transformers, etc. Over the years it ended up becoming one of the main companies in the sector, having also a great importance in the local context of Cordoba.
The company came to manufacture nearly 40% of all the electrolytic copper produced in Spain, being supplied to a large extent by the material coming from the Rio Tinto-Nerva mining basin. In this sense, SECEM became an important client of the Compañía Española de Minas de Río Tinto (CEMRT), and later the companies Río Tinto Patiño and Río Tinto Minera would have an important shareholding in SECEM. In spite of this privileged situation, the lack of internal competition meant that the machinery and technology of the Cordovan factory were not modernized, which in the long term would end up causing serious problems for SECEM's economic viability. Towards the end of the 1970s, the industrial crisis had a considerable impact on the copper sector. Taking advantage of this context, in May 1978 SECEM —with the financial support of Banco de Bilbao and Banco Hispano Americano— proceeded to acquire the companies Pradera Hermanos, Sociedad Industrial Asturiana and Earle; at the end of the year, all of these companies formed the conglomerate Ibercobre, which controlled 60% of the copper market.
The SECEM complex in Cordoba remained intact until 1989–1990, after the purchase of Ibercobre by the Finnish company Outokumpu, which decided to split it into three separate industries. | 1 | Applied and Interdisciplinary Chemistry |
Criegee intermediates are formed by the gas-phase reactions of alkenes and ozone in the Earths atmosphere. Ozone adds across the carbon–carbon double bond of the alkene to form a molozonide, which then decomposes to produce a carbonyl (RRCO) and a carbonyl oxide. The latter is known as the Criegee intermediate.
The alkene ozonolysis reaction is extremely exothermic, releasing about of excess energy. Therefore, the Criegee intermediates are formed with a large amount of internal energy. | 1 | Applied and Interdisciplinary Chemistry |
* Used from ~1837 to reduce local action which degraded operation of Voltaic piles. See History of the battery#Invention.
* To chemically reduce metallic ions in solution. See Jones reductor.
*To reduce ketones and aldehydes to alkanes via the Clemmensen reduction in acidic conditions. | 0 | Theoretical and Fundamental Chemistry |
Five major sources of dissolved silica to the marine environment can be distinguished:
* Riverine influx of dissolved silica to the oceans: 4.2 ± 0.8 × 10 g SiO yr
* Submarine volcanism and associated hydrothermal emanations: 1.9 ± 1.0 × 10 g SiO yr
* Glacial weathering: 2 × 10 g SiO yr
* Low temperature submarine weathering of oceanic basalts
* Some silica may also escape from silica-enriched pore waters of pelagic sediments on the seafloor
Once the organism has perished, part of the siliceous skeletal material dissolves, as it settles through the water column, enriching the deep waters with dissolved silica. Some of the siliceous scales can also be preserved over time as microfossils in deep-sea sediments, providing a window into modern and ancient plankton/protists communities. This biologic process has operated, since at least early Paleozoic time, to regulate the balance of silica in the ocean.
Radiolarians (Cambrian/Ordovician-Holocene), diatoms (Cretaceous-Holocene), and silicoflagellates (Cretaceous-Holocene) form the ocean's main contributors to the global silica biogenic cycle throughout geologic time. Diatoms account for 43% of the ocean primary production, and are responsible for the bulk of silica extraction from ocean waters in the modern ocean, and during much of the past fifty million years. In contrast, oceans of Jurassic and older ages, were characterized by radiolarians as major silica-utilizing phyla. Nowadays, radiolarians are the second (after diatoms) major producers of suspended amorphous silica in ocean waters. Their distribution ranges from the Arctic to the Antarctic, being most abundant in the equatorial zone. In equatorial Pacific waters, for example, about 16,000 specimens per cubic meter can be observed. | 1 | Applied and Interdisciplinary Chemistry |
The ability of AMGs modulating the metabolic capacities of their hosts can influence the abundance and distribution of specific microbial taxa. In turn, this shapes the overall composition of microbial communities, with potential cascading effects on higher trophic levels. | 1 | Applied and Interdisciplinary Chemistry |
Recently, CBED was applied to study graphene and other 2D monolayer crystals and van der Waals structures. For 2D crystals, the analysis of CBED patterns is simplified, because the intensity distribution in a CBED disk is directly related to the atomic arrangement in the crystal. The deformations at a nanometer resolution have been retrieved, the interlayer distance of a bilayer crystal has been reconstructed, and so on, by using CBED. | 0 | Theoretical and Fundamental Chemistry |
The courses of study are closely related to the research activities to provide interdisciplinary and research-oriented training.
The institute offers a broad bachelor programme with contents of marine, environmental and landscape-ecological sciences as well as four Master Programmes which are: Marine Environmental Sciences, Microbiology (held in English), Environmental Modelling and Marine Sensors. In cooperation with the ICBM, the Jade University of Applied Sciences offers a Bachelor Programme which is fundamental for marine engineering. The ICBM is ERASMUS exchange partner for students. | 0 | Theoretical and Fundamental Chemistry |
Top-down synthesis of the clusters can be achieved by the "etching" of larger metallic nanoparticles with redox-active, thiol-containing biomolecules. In this process, gold atoms on the nanoparticles' surface react with the thiol, dissolving as gold-thiolate complexes until the dissolution reaction stops; this leaves behind a residual species of thiolate-protected gold clusters that is particularly stable. This type of synthesis is also possible using other non thiol-based ligands. | 0 | Theoretical and Fundamental Chemistry |
The European Union defines a VOC as "any organic compound as well as the fraction of creosote, having at 293.15 K a vapour pressure of 0,01 kPa or more, or having a corresponding volatility under the particular conditions of use;". The VOC Solvents Emissions Directive was the main policy instrument for the reduction of industrial emissions of volatile organic compounds (VOCs) in the European Union. It covers a wide range of solvent-using activities, e.g. printing, surface cleaning, vehicle coating, dry cleaning and manufacture of footwear and pharmaceutical products. The VOC Solvents Emissions Directive requires installations in which such activities are applied to comply either with the emission limit values set out in the Directive or with the requirements of the so-called reduction scheme. Article 13 of The Paints Directive, approved in 2004, amended the original VOC Solvents Emissions Directive and limits the use of organic solvents in decorative paints and varnishes and in vehicle finishing products. The Paints Directive sets out maximum VOC content limit values for paints and varnishes in certain applications. The Solvents Emissions Directive was replaced by the Industrial Emissions Directive from 2013. | 0 | Theoretical and Fundamental Chemistry |
Microarray data is often normalized within arrays to control for systematic biases in dye coupling and hybridization efficiencies, as well as other technical biases in the DNA probes and the print tip used to spot the array. By minimizing these systematic variations, true biological differences can be found. To determine whether normalization is needed, one can plot Cy5 (R) intensities against Cy3 (G) intensities and see whether the slope of the line is around 1. An improved method, which is basically a scaled, 45 degree rotation of the R vs. G plot is an MA-plot. The MA-plot is a plot of the distribution of the red/green intensity ratio (M) plotted by the average intensity (A). M and A are defined by the following equations.
M is, therefore, the binary logarithm of the intensity ratio (or difference between log intensities) and A is the average log intensity for a dot in the plot. MA plots are then used to visualize intensity-dependent ratio of raw microarray data (microarrays typically show a bias here, with higher A resulting in higher |M|, i.e. the brighter the spot the more likely an observed difference between sample and control). The MA plot puts the variable M on the y-axis and A on the x-axis and gives a quick overview of the distribution of the data.
In many microarray gene expression experiments, an underlying assumption is that most of the genes would not see any change in their expression; therefore, the majority of the points on the y-axis (M) would be located at 0, since log(1) is 0. If this is not the case, then a normalization method such as LOESS should be applied to the data before statistical analysis. (On the diagram below see the red line running below the zero mark before normalization, it should be straight. Since it is not straight, the data should be normalized. After being normalized, the red line is straight on the zero line and shows as pink/black.) | 1 | Applied and Interdisciplinary Chemistry |
A mixture of racemic acid and meso-tartaric acid is formed when dextro-Tartaric acid is heated in water at 165 °C for about 2 days. meso-Tartaric acid can also be prepared from dibromosuccinic acid using silver hydroxide:
:HOCCHBrCHBrCOH + 2 AgOH → HOCCH(OH)CH(OH)COH + 2 AgBr
meso-Tartaric acid can be separated from residual racemic acid by crystallization, the racemate being less soluble. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, phosphonium coupling is a cross-coupling reaction for organic synthesis. It is a mild, efficient, chemoselective and versatile methodology for the formation of C–C, C–N, C–O, and C–S bond of unactivated and unprotected tautomerizable heterocycles. The method was originally reported in 2004. The C–OH bond of a tautomerizable heterocycle is activated with a phosphonium salt (PyBroP, PyBOP, BroP, or BOP), and subsequent functionalization with either a nucleophile through SNAr displacement or an organometallic through transition metal catalyzed cross coupling reaction. The in situ activation of the C-OH bond in phosphonium coupling has been applied to cross coupling reactions of tautomerizable heterocycles and arenols using other types of activating reagents.
Phosphonium coupling generates in situ a pseudo aryl or heteroaryl halide (the intermediate phosphonium species), which subsequently reacts with its coupling partner. | 0 | Theoretical and Fundamental Chemistry |
There are two primary approaches to the organic synthesis of catenanes. The first is to simply perform a ring-closing reaction with the hope that some of the rings will form around other rings giving the desired catenane product. This so-called "statistical approach" led to the first synthesis of a catenane; however, the method is highly inefficient, requiring high dilution of the "closing" ring and a large excess of the pre-formed ring, and is rarely used.
The second approach relies on supramolecular preorganization of the macrocyclic precursors utilizing hydrogen bonding, metal coordination, hydrophobic effect, or coulombic interactions. These non-covalent interactions offset some of the entropic cost of association and help position the components to form the desired catenane upon the final ring-closing. This "template-directed" approach, together with the use of high-pressure conditions, can provide yields of over 90%, thus improving the potential of catenanes for applications. An example of this approach used bis-bipyridinium salts which form strong complexes threaded through crown ether bis(para-phenylene)-34-crown-10.
Template directed syntheses are mostly performed under kinetic control, when the macrocyclization (catenation) reaction is irreversible. More recently, the groups of Sanders and Otto have shown that dynamic combinatorial approaches using reversible chemistry can be particularly successful in preparing new catenanes of unpredictable structure. The thermodynamically controlled synthesis provides an error correction mechanism; even if a macrocycle closes without forming a catenane it can re-open and yield the desired interlocked structure later. The approach also provides information on the affinity constants between different macrocycles thanks to the equilibrium between the individual components and the catenanes, allowing a titration-like experiment. | 0 | Theoretical and Fundamental Chemistry |
A second application in cement for the bulk material analyzer is raw mix proportioning. An analyzer placed just upstream of the raw mill can monitor the chemistry of the raw mix and automatically trigger an adjustment in the proportions of the reclaimed stockpile and the correctives. By doing so, the plant is able to reduce the variability in the raw mix, and later on the kiln feed. Consistent kiln feed chemistry in turn leads to lower fuel consumption per ton of clinker produced. | 0 | Theoretical and Fundamental Chemistry |
The surface tension of pure liquid water in contact with its vapor has been given by IAPWS as
where both and the critical temperature = 647.096 K are expressed in kelvins. The region of validity the entire vapor–liquid saturation curve, from the triple point (0.01 °C) to the critical point. It also provides reasonable results when extrapolated to metastable (supercooled) conditions, down to at least −25 °C. This formulation was originally adopted by IAPWS in 1976 and was adjusted in 1994 to conform to the International Temperature Scale of 1990.
The uncertainty of this formulation is given over the full range of temperature by IAPWS. For temperatures below 100 °C, the uncertainty is ±0.5%. | 0 | Theoretical and Fundamental Chemistry |
* 2005 IEEE Donald G. Fink Prize Paper Award
* 2008 Eurosensors Fellow
* 2011 DECHEMA Award of the Max Buchner Research Foundation | 0 | Theoretical and Fundamental Chemistry |
The winnowing-fan (λίκνον [líknon], also meaning a "cradle") featured in the rites accorded Dionysus and in the Eleusinian Mysteries: "it was a simple agricultural implement taken over and mysticized by the religion of Dionysus," Jane Ellen Harrison remarked. Dionysus Liknites ("Dionysus of the winnowing fan") was wakened by the Dionysian women, in this instance called Thyiades, in a cave on Parnassus high above Delphi; the winnowing-fan links the god connected with the mystery religions to the agricultural cycle, but mortal Greek babies too were laid in a winnowing-fan. In Callimachus Hymn to Zeus, Adrasteia lays the infant Zeus in a golden líknon, her goat suckles him and he is given honey. In the Odyssey, the dead oracle Teiresias tells Odysseus to walk away from Ithaca with an oar until a wayfarer tells him it is a winnowing fan (i.e., until Odysseus has come so far from the sea that people dont recognize oars), and there to build a shrine to Poseidon. | 0 | Theoretical and Fundamental Chemistry |
In a colloidal dispersion, the colloid-colloid interaction potential is approximated as the interaction potential between two hard spheres. For two hard spheres of diameter of , the interaction potential as a function of interparticle separation is:
called the hard-sphere potential where is the center-to-center distance between the spheres.
If both colloids and depletants are in a dispersion, there is interaction potential between colloidal particles and depletant particles that is described similarly by the hard-sphere potential. Again, approximating the particles to be hard-spheres, the interaction potential between colloids of diameter and depletant sols of diameter is:
where is the center-to-center distance between the spheres. Typically, depletant particles are very small compared to the colloids so
The underlying consequence of the hard-sphere potential is that dispersed colloids cannot penetrate each other and have no mutual attraction or repulsion. | 0 | Theoretical and Fundamental Chemistry |
Glycogen branching enzyme belongs to the α-amylase family of enzymes, which include α-amylases, pullulanas/isoamylase, cyclodextrin glucanotransferase (CGT), and branching enzyme. Shown by x-ray crystallography, glycogen branching enzyme has four marginally asymmetric units each that are organized into three domains: an amino-terminal domain, involved in determining the length of the chain transfer, a carboxyl-terminal domain, involved in substrate preference and catalytic capacity, and a central (α/β) barrel catalytic domain. The amino-terminal domain consists of 128 residues arranged in seven β-strands, the carboxyl-terminal domain with 116 residues also organized in seven β-strands, and the (α/β) barrel domain with 372 residues. While the central (α/β) barrel domain is common in members of the α-amylase family, numerous variations exist between the various barrel domains. Additionally, there are striking differences between the loops connecting elements of the secondary structure among these various α-amylase members, especially around the active site. In comparison to the other family members, glycogen binding enzyme has shorter loops, which result in a more open cavity, favorable to the binding of a bulkier substrate such as branched sugar. Through primary structure analysis and the x-ray crystallographic structures of the members of the α-amylase family, seven residue were conserved, Asp335, His340, Arg403, Asp 405, Glu458, His525, and Asp526 (E coli. numbering). These residues are implicated in catalysis and substrate binding.
Glycogen binding enzymes in other organisms have also been crystallized and structurally determined, demonstrating both similarity and variation to GBE found in Escherichia coli. | 1 | Applied and Interdisciplinary Chemistry |
Elliptc LCSs are closed and nested material surfaces that act as building blocks of the Lagrangian equivalents of vortices, i.e., rotation-dominated regions of trajectories that generally traverse the phase space without substantial stretching or folding. They mimic the behavior of Kolmogorov–Arnold–Moser (KAM) tori that form elliptic regions in Hamiltonian systems. There coherence can be approached either through their homogeneous material rotation or through their homogeneous stretching properties. | 1 | Applied and Interdisciplinary Chemistry |
Ca/calmodulin-dependent protein kinase II (CaMKII) plays a crucial role in a type of synaptic plasticity known as long-term potentiation (LTP) which requires the presence of calcium/calmodulin. CaMKII contributes to the phosphorylation of an AMPA receptor which increases the sensitivity of AMPA receptors. Furthermore, research shows that inhibiting CaMKII interferes with LTP. | 1 | Applied and Interdisciplinary Chemistry |
* Hawa Mahal of Jaipur, also utilizes the Venturi effect, by allowing cool air to pass through, thus making the whole area more pleasant during the high temperatures in summer.
* Large cities where wind is forced between buildings - the gap between the Twin Towers of the original World Trade Center was an extreme example of the phenomenon, which made the ground level plaza notoriously windswept. In fact, some gusts were so high that pedestrian travel had to be aided by ropes.
* In the south of Iraq, near the modern town of Nasiriyah, a 4000-year-old flume structure has been discovered at the ancient site of Girsu. This construction by the ancient Sumerians forced the contents of a nineteen kilometre canal through a constriction to enable the side-channeling of water off to agricultural lands from a higher origin than would have been the case without the flume. A recent dig by archaeologists from the British museum confirmed the finding. | 1 | Applied and Interdisciplinary Chemistry |
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