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Although a number of algaecides have been effective in killing algae, they have been used mostly in small bodies of water. For large algal blooms, however, adding algaecides such as silver nitrate or copper sulfate can have worse effects, such as killing fish outright and harming other wildlife. Cyanobacteria can also develop resistance to copper-containing algaecides, requiring a larger quantity of the chemical to be effective for HAB management, but introducing a greater risk to other species in the region. The negative effects can therefore be worse than letting the algae die off naturally.
In 2019, Chippewa Lake in Northeast Ohio became the first lake in the U.S. to successfully test a new chemical treatment. The chemical formula killed all of the toxic algae in the lake within a single day. The formula has already been used in China, South Africa and Israel.
In February 2020, Roodeplaat Dam in Gauteng Province, South Africa was treated with a new algicide formulation against a severe bloom of Microcystis sp. This formulation allows the granular product to float and slow-release its active ingredient, sodium percarbonate, that releases hydrogen peroxide (HO), on the water surface. Consequently, the effective concentrations are limited, vertically, to the surface of the water; and spatially to areas where cyanobacteria are abundant. This provide the aquatic organisms a "safe haven" in untreated areas and avoids the adverse effects associated with the use of standard algicides.
Bioactive compounds isolated from terrestrial and aquatic plants, particularly seaweeds, have seen results as a more environmentally friendly control for HABs. Molecules found in seaweeds such as Corallina, Sargassum, and Saccharina japonica have shown to inhibit some bloom-forming microalgae. In addition to their anti-microalgal effects, the bioactive molecules found in these seaweeds also have antibacterial, antifungal, and antioxidant properties. | 3 | Analytical Chemistry |
Microcins are all RiPPs produced by Enterobacteriaceae with a molecular weight <10 kDa. Many members of other RiPP families, such as microcin E492, microcin B17 (LAP) and microcin J25 (Lasso peptide) are also considered microcins. Instead of being classified based on posttranslational modifications or modifying enzymes, microcins are instead identified by molecular weight, native producer, and antibacterial activity. Microcins are either plasmid- or chromosome-encoded, but specifically have activity against Enerobacteriaceae. Because these organisms are also often producers of microcins, the gene cluster contains not only a precursor peptide and modification enzymes, but also a self-immunity gene to protect the producing strain, and genes encoding export of the natural product.
Microcins have bioactivity against Gram-negative bacteria but usually display narrow-spectrum activity due to hijacking of specific receptors involved in the transport of essential nutrients. | 1 | Biochemistry |
The slow-reacting substance of anaphylaxis or SRS-A is a mixture of the leukotrienes LTC4, LTD4 and LTE4. Mast cells secrete it during the anaphylactic reaction, inducing inflammation. It can be found in basophils.
It induces prolonged, slow contraction of smooth muscle and has a major bronchoconstrictor role in asthma. Compared to histamine, it is approximately 1000 times more potent and has a slower onset but longer duration of action. | 1 | Biochemistry |
Typically a traditional liquid rheostat consists of a steel cylinder (the negative), about in size, standing on insulators, in which was suspended a hollow steel cylinder. This acted as the positive electrode and was supported by a steel rope and insulator from an adjustable pulley. The water pipe connection included an insulated section. The tank contained salt water, but not at the concentration that could be described as “brine”. The whole device was fenced off for safety.
Operation was very simple, as adding more salt, more water or varying the height of the centre electrode would vary the load. The load proved to be quite stable, varying only slightly as the water heated up, which never came to boil. Power dissipation was about 1 megawatt, at a potential of about 700 volts and current of about 1,500 amperes.
Modern designs use stainless steel electrodes, and sodium carbonate, or other salts, and do not use the container as one electrode.
Systems with frequent starting may include water circulation to external heat exchangers. In such cases anti-freeze and anti-corrosion additives must be carefully chosen to not change the resistance or support the growth of algae or bacteria. | 7 | Physical 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. | 8 | Metallurgy |
The one-hybrid variation of this technique is designed to investigate protein–DNA interactions and uses a single fusion protein in which the AD is linked directly to the binding domain. The binding domain in this case however is not necessarily of fixed sequence as in two-hybrid protein–protein analysis but may be constituted by a library. This library can be selected against the desired target sequence, which is inserted in the promoter region of the reporter gene construct. In a positive-selection system, a binding domain that successfully binds the UAS and allows transcription is thus selected.
Note that selection of DNA-binding domains is not necessarily performed using a one-hybrid system, but may also be performed using a two-hybrid system in which the binding domain is varied and the bait and prey proteins are kept constant. | 1 | Biochemistry |
The condition that the ETH imposes on the diagonal elements of an observable is responsible for the equality of the predictions of the diagonal and microcanonical ensembles. However, the equality of these long-time averages does not guarantee that the fluctuations in time around this average will be small. That is, the equality of the long-time averages does not ensure that the expectation value of will settle down to this long-time average value, and then stay there for most times.
In order to deduce the conditions necessary for the observable's expectation value to exhibit small temporal fluctuations around its time-average, we study the mean squared amplitude of the temporal fluctuations, defined as
where is a shorthand notation for the expectation value of at time t. This expression can be computed explicitly, and one finds that
Temporal fluctuations about the long-time average will be small so long as the off-diagonal elements satisfy the conditions imposed on them by the ETH, namely that they become exponentially small in the system size. Notice that this condition allows for the possibility of isolated resurgence times, in which the phases align coherently in order to produce large fluctuations away from the long-time average. The amount of time the system spends far away from the long-time average is guaranteed to be small so long as the above mean squared amplitude is sufficiently small. If a system poses a dynamical symmetry, however, it will periodically oscillate around the long-time average. | 7 | Physical Chemistry |
Myo-inositol trispyrophosphate (ITPP), also known as OXY111A, is an inositol phosphate that causes a rightward shift in the oxygen hemoglobin dissociation curve through allosteric modulation of hemoglobin within red blood cells. It is an experimental drug intended to reduce tissue hypoxia. The effects appear to last roughly as long as the affected red blood cells remain in circulation. | 1 | Biochemistry |
Cholamine chloride hydrochloride is one of Good's buffers with a pH in the physiological range. Its pKa at 20°C is 7.10, making it useful in cell culture work. Its ΔpKa/°C is -0.027 and it has a solubility in water at 0°C of 4.2M. | 1 | Biochemistry |
A positioning goniometer or goniometric stage is a device that rotates an object precisely about a fixed axis in space. It is similar to a linear stage—however, rather than move linearly relative to its base, the stage platform rotates partially about a fixed axis above the mounting surface of the platform. Positioning goniometers typically use a worm drive with a partial worm wheel fixed to the underside of the stage platform meshing with a worm in the base. The worm gear may be rotated manually, or by a motor in automated positioning systems. | 7 | Physical Chemistry |
High performance affinity chromatography (HPAC) works by passing a sample solution through a column packed with a stationary phase that contains an immobilized biologically active ligand. The ligand is in fact a substrate that has a specific binding affinity for the target molecule in the sample solution. The target molecule binds to the ligand, while the other molecules in the sample solution pass through the column, having little or no retention. The target molecule is then eluted from the column using a suitable elution buffer.
This chromatographic process relies on the capability of the bonded active substances to form stable, specific, and reversible complexes thanks to their biological recognition of certain specific sample components. The formation of these complexes involves the participation of common molecular forces such as the Van der Waals interaction, electrostatic interaction, dipole-dipole interaction, hydrophobic interaction, and the hydrogen bond. An efficient, biospecific bond is formed by a simultaneous and concerted action of several of these forces in the complementary binding sites. | 3 | Analytical Chemistry |
Androsterone sulfate, also known as 3α-hydroxy-5α-androstan-17-one 3α-sulfate, is an endogenous, naturally occurring steroid and one of the major urinary metabolites of androgens. It is a steroid sulfate which is formed from sulfation of androsterone by the steroid sulfotransferase SULT2A1 and can be desulfated back into androsterone by steroid sulfatase. | 1 | Biochemistry |
Plastoquinone is found within photosystem II in two specific binding sites, known as Q and Q. The plastoquinone at Q, the primary binding site, is very tightly bound, compared to the plastoquinone at Q, the secondary binding site, which is much more easily removed. Q is only transferred a single electron, so it has to transfer an electron to Q twice before Q is able to pick up two protons from the stroma and be replaced by another plastoquinone molecule. The protonated Q then joins a pool of free plastoquinone molecules in the membrane of the thylakoid. The free plastoquinone molecules eventually transfer electrons to the water-soluble plastocyanin so as to continue the light-dependent reactions. There are additional plastoquinone binding sites within photosystem II (Q and possibly Q), but their function and/or existence have not been fully elucidated. | 5 | Photochemistry |
Unsaturated fluorocarbons are far more reactive than fluoroalkanes. Although difluoroacetylene is unstable (as is typical for related alkynes, see dichloroacetylene), hexafluoro-2-butyne and related fluorinated alkynes are well known. | 2 | Environmental Chemistry |
Lithium bis(trimethylsilyl)amide is a lithiated organosilicon compound with the formula . It is commonly abbreviated as LiHMDS or Li(HMDS) (lithium hexamethyldisilazide - a reference to its conjugate acid HMDS) and is primarily used as a strong non-nucleophilic base and as a ligand. Like many lithium reagents, it has a tendency to aggregate and will form a cyclic trimer in the absence of coordinating species. | 0 | Organic Chemistry |
Among several variants of thermal cracking methods (variously known as the "Shukhov cracking process", "Burton cracking process", "Burton-Humphreys cracking process", and "Dubbs cracking process") Vladimir Shukhov, a Russian engineer, invented and patented, the first in 1891 (Russian Empire, patent no. 12926, November 7, 1891). One installation was used to a limited extent in Russia, but development was not followed up; In the first decade of the 20th century the American engineers William Merriam Burton and Robert E. Humphreys independently developed and patented a similar process as U.S. patent 1,049,667 on June 8, 1908. Among its advantages was that both the condenser and the boiler were continuously kept under pressure.
In its earlier versions it was a batch process, rather than continuous, and many patents were to follow in the US and Europe, though not all were practical. In 1924, a delegation from the American Sinclair Oil Corporation visited Shukhov. Sinclair Oil apparently wished to suggest that the patent of Burton and Humphreys, in use by Standard Oil, was derived from Shukhovs patent for oil cracking, as described in the Russian patent. If that could be established, it could strengthen the hand of rival American companies wishing to invalidate the Burton-Humphreys patent. In the event Shukhov satisfied the Americans that in principle Burtons method closely resembled his 1891 patents, though his own interest in the matter was primarily to establish that "the Russian oil industry could easily build a cracking apparatus according to any of the described systems without being accused by the Americans of borrowing for free".
At that time, just a few years after the Russian Revolution and brutal Russian Civil War, the Soviet Union was desperate to develop industry and earn foreign exchange, so their oil industry eventually did obtain much of their technology from foreign companies, largely American. At about that time, fluid catalytic cracking was being explored and developed and soon replaced most of the purely thermal cracking processes in the fossil fuel processing industry. The replacement was not complete; many types of cracking, including pure thermal cracking, still are in use, depending on the nature of the feedstock and the products required to satisfy market demands. Thermal cracking remains important, for example in producing naphtha, gas oil, and coke, and more sophisticated forms of thermal cracking have been developed for various purposes. These include visbreaking, steam cracking, and coking. | 0 | Organic Chemistry |
The simplest materials characterization is the residue remaining after a reaction. For example, a combustion reaction could be tested by loading a sample into a thermogravimetric analyzer at normal conditions. The thermogravimetric analyzer would cause ion combustion in the sample by heating it beyond its ignition temperature. The resultant TGA curve plotted with the y-axis as a percentage of initial mass would show the residue at the final point of the curve.
Oxidative mass losses are the most common observable losses in TGA.
Studying the resistance to oxidation in copper alloys is very important. For example, NASA (National Aeronautics and Space Administration) is conducting research on advanced copper alloys for their possible use in combustion engines. However, oxidative degradation can occur in these alloys as copper oxides form in atmospheres that are rich in oxygen. Resistance to oxidation is significant because NASA wants to be able to reuse shuttle materials. TGA can be used to study the static oxidation of materials such as these for practical use.
Combustion during TG analysis is identifiable by distinct traces made in the TGA thermograms produced. One interesting example occurs with samples of as-produced unpurified carbon nanotubes that have a large amount of metal catalyst present. Due to combustion, a TGA trace can deviate from the normal form of a well-behaved function. This phenomenon arises from a rapid temperature change. When the weight and temperature are plotted versus time, a dramatic slope change in the first derivative plot is concurrent with the mass loss of the sample and the sudden increase in temperature seen by the thermocouple. The mass loss could result from particles of smoke released from burning caused by inconsistencies in the material itself, beyond the oxidation of carbon due to poorly controlled weight loss.
Different weight losses on the same sample at different points can also be used as a diagnosis of the sample's anisotropy. For instance, sampling the top side and the bottom side of a sample with dispersed particles inside can be useful to detect sedimentation, as thermograms will not overlap but will show a gap between them if the particle distribution is different from side to side. | 7 | Physical Chemistry |
One consequence of geometric strain on both the boron and the porphyrin moieties is unique reactivity. The Brothers group was able to demonstrate reductive coupling, wherein two BX units inside the porphyrin pocket become X-B-B-X, only occurs with X=Br and when the substrates are within the porphyrin pocket. DFT calculations show that for X=Cl or F, the reaction is endothermic and non-spontaneous. However, for X=Br, the reduction is spontaneous, which was consistent with experimental findings. Further, when the same reaction is simulated with two porphyrin halves ((dipyrromethene)BX), it is non-spontaneous even for X=Br, suggesting the steric strain of the porphyrin ring to be the driving force behind the reduction reaction. | 5 | Photochemistry |
A group of mostly desert plants called "C.A.M." plants (crassulacean acid metabolism, after the family Crassulaceae, which includes the species in which the CAM process was first discovered) open their stomata at night (when water evaporates more slowly from leaves for a given degree of stomatal opening), use PEPcase to fix carbon dioxide and store the products in large vacuoles. The following day, they close their stomata and release the carbon dioxide fixed the previous night into the presence of RuBisCO. This saturates RuBisCO with carbon dioxide, allowing minimal photorespiration. This approach, however, is severely limited by the capacity to store fixed carbon in the vacuoles, so it is preferable only when water is severely limited. | 5 | Photochemistry |
A negative balance is a result of energy intake being less than what is consumed in external work and other bodily means of energy expenditure.
The main cause is undereating due to a medical condition such as decreased appetite, anorexia nervosa, digestive disease, or due to some circumstance such as fasting or lack of access to food. Hyperthyroidism can also be a cause. | 1 | Biochemistry |
This compound is commercially available. It may be prepared by the methylation of 1,8-diaminonaphthalene with iodomethane or dimethyl sulfate. | 0 | Organic Chemistry |
While the formation of a sigma hole pair interaction is associated with energetic stabilization, this process is often thermodynamically disfavored as the energetic stabilization is often offset by a decrease in the entropy of the system. It has been shown that an enthalpy-entropy compensation relationship exists between the energetic and entropic changes associated with interactions, with more stabilizing interactions tending to result in larger entropy decreases. However, the decrease in entropy associated with the formation of a sigma hole interaction has been shown to approach a limiting value as the energetic favorability of the process is increased, and as such very energetically stabilizing interactions tend to be thermodynamically favored. There are additional factors that contribute to thermodynamic stability in the liquid and solid phases, which cannot be as easily modeled as gas phase interactions. As such, the favorability of a given sigma hole interaction in the liquid or solid phase may not necessarily match that of the gas phase equivalent. | 6 | Supramolecular Chemistry |
Aqueous monoethanolamine (MEA), diglycolamine (DGA), diethanolamine (DEA), diisopropanolamine (DIPA) and methyldiethanolamine (MDEA) are widely used industrially for removing carbon dioxide (CO) and hydrogen sulfide (HS) from natural gas and refinery process streams. They may also be used to remove CO from combustion gases and flue gases and may have potential for abatement of greenhouse gases. Related processes are known as sweetening. | 0 | Organic Chemistry |
Electrochemical methods, or electrolysis, can strip carbon dioxide directly from seawater. Electrochemical process are a type of ocean alkalinity enhancement, too. Some methods focus on direct removal (in the form of carbonate and gas) while others increase the alkalinity of seawater by precipitating metal hydroxide residues, which absorbs in a matter described in the ocean alkalinity enhancement section. The hydrogen produced during direct carbon capture can then be upcycled to form hydrogen for energy consumption, or other manufactured laboratory reagents such as hydrochloric acid.
However, implementation of electrolysis for carbon capture is expensive and the energy consumed for the process is high compared to other CDR techniques. In addition, research to assess the environmental impact of this process is ongoing. Some complications include toxic chemicals in wastewaters, and reduced DIC in effluents; both of these may negatively impact marine life. | 9 | Geochemistry |
The enthalpy of sublimation has commonly been predicted using the equipartition theorem. If the lattice energy is assumed to be approximately half the packing energy, then the following thermodynamic corrections can be applied to predict the enthalpy of sublimation. Assuming a 1 molar ideal gas gives a correction for the thermodynamic environment (pressure and volume) in which pV = RT, hence a correction of 1RT. Additional corrections for the vibrations, rotations and translation then need to be applied. From the equipartition theorem gaseous rotation and translation contribute 1.5RT each to the final state, therefore a +3RT correction. Crystalline vibrations and rotations contribute 3RT each to the initial state, hence −6RT. Summing the RT corrections; −6RT + 3RT + RT = −2RT. This leads to the following approximate sublimation enthalpy. A similar approximation can be found for the entropy term if rigid bodies are assumed. | 3 | Analytical Chemistry |
Classical analysis methods involve basic analytical methods widely used in laboratories. Gravimetric analysis measures the weight of the sample. Titrimetry is a family of techniques used to determine the concentration of an analyte. | 3 | Analytical Chemistry |
Retroposition accounts for approximately 10,000 gene-duplication events in the human genome, of which approximately 2-10% are likely to be functional. Such genes are called retrogenes and represent a certain type of retroposon. | 1 | Biochemistry |
The Bosch–Meiser process is an industrial process, which was patented in 1922 and named after its discoverers, the German chemists Carl Bosch and Wilhelm Meiser for the large-scale manufacturing of urea, a valuable nitrogenous chemical.
The whole process consists of two main equilibrium reactions, with incomplete conversion of the reactants.
* The first, called carbamate formation: the fast exothermic reaction of liquid ammonia with gaseous carbon dioxide () at high temperature and pressure to form ammonium carbamate ():
:(ΔH = −117 kJ/mol at 110 atm and 160 °C)
* The second, called urea conversion: the slower endothermic decomposition of ammonium carbamate into urea and water:
:(ΔH = +15.5 kJ/mol at 160–180 °C)
The overall conversion of and to urea is exothermic, with the reaction heat from the first reaction driving the second. The conditions that favor urea formation (high temperature) have an unfavorable effect on the carbamate formation equilibrium. The process conditions are a compromise: the ill-effect on the first reaction of the high temperature (around 190 °C) needed for the second is compensated for by conducting the process under high pressure (140–175 bar), which favors the first reaction. Although it is necessary to compress gaseous carbon dioxide to this pressure, the ammonia is available from the ammonia production plant in liquid form, which can be pumped into the system much more economically. To allow the slow urea formation reaction time to reach equilibrium, a large reaction space is needed, so the synthesis reactor in a large urea plant tends to be a massive pressure vessel. | 7 | Physical Chemistry |
In 1859, Henri Étienne Sainte-Claire Deville in France developed a method for making alumina by heating bauxite in sodium carbonate, NaCO, at 1200 °C, leaching the sodium aluminate formed with water, then precipitating aluminium hydroxide by carbon dioxide, CO, which was then filtered and dried. This process is known as the Deville process. In 1886, the Hall–Héroult electrolytic aluminium process was invented, and the cyanidation process was invented in 1887.
The Bayer process was invented in 1888 by Carl Josef Bayer. Working in Saint Petersburg, Russia to develop a method for supplying alumina to the textile industry (it was used as a mordant in dyeing cotton), Bayer discovered in 1887 that the aluminium hydroxide that precipitated from alkaline solution was crystalline and could be easily filtered and washed, while that precipitated from acid medium by neutralization was gelatinous and difficult to wash. The industrial success of this process caused it to replace the Le Chatelier process which was used to produce alumina from bauxite. The Deville process was abandoned in favor of the Bayer process, which marks the birth of the modern field of hydrometallurgy.
The engineering aspects of the process were improved upon to decrease the cost starting in 1967 in Germany and Czechoslovakia. This was done by increasing the heat recovery and using large autoclaves and precipitation tanks. To more effectively use energy, heat exchangers and flash tanks were used and larger reactors decreased the amount of heat lost. Efficiency was increased by connecting the autoclaves to make operation more efficient.
Today, the process produces nearly all the world's alumina supply as an intermediate step in aluminium production. | 8 | Metallurgy |
Smiths contributions to engineering education encompass work in cooperative learning and knowledge engineering applications. He published a paper in the Journal of Engineering Education', in 1981, introducing cooperative learning in engineering literature. During the early 1980s, he conducted some of the first randomized design empirical studies on cooperative learning in engineering classes. Subsequently, in the late 1980s, he transitioned from engineering research to education research, particularly focusing on cooperative learning and structured controversy, as his emphasis shifted towards teaching and research on project and knowledge management. This research addressed the critical needs of enhancing student learning, deepening understanding, and fostering collaborative skills. Beyond cooperative learning, his work included structured academic controversy, aimed at facilitating comprehensive understanding of complex issues through argument development and cooperative learning strategies.
Smith published books on this topic, including Active Learning: Cooperation in the College Classroom with David W. Johnson and Roger T. Johnson, providing strategies for college faculty to implement cooperative learning. They also co-authored Cooperative learning: Increasing College Faculty Instructional Productivity, in which they delved into the basics of cooperative learning, and he discussed how cooperative learning changed college teaching in New Paradigms for College Teaching that he co-edited with William E. Campbell. Later, in 2000, he wrote Teamwork and Project Management, where he emphasized key skills for engineering success, including teamwork, problem-solving, and project management. | 8 | Metallurgy |
pRb is a multifunctional protein with many binding and phosphorylation sites. Although its common function is seen as binding and repressing E2F targets, pRb is likely a multifunctional protein as it binds to at least 100 other proteins.
pRb has three major structural components: a carboxy-terminus, a "pocket" subunit, and an amino-terminus. Within each domain, there are a variety of protein binding sites, as well as a total of 15 possible phosphorylation sites. Generally, phosphorylation causes interdomain locking, which changes pRb's conformation and prevents binding to target proteins. Different sites may be phosphorylated at different times, giving rise to many possible conformations and likely many functions/activity levels. | 1 | Biochemistry |
Stable isotope mass spectrometry is conducted in the Department of Geography, and was recently used by the Landmark Trust to determine very precisely the age of the timber from Llwyn Celyn farmhouse to the year 1420. | 3 | Analytical Chemistry |
The nitrogen-vacancy center (N-V center or NV center) is one of numerous photoluminescent point defects in diamond. Its most explored and useful properties include its spin-dependent photoluminescence (which enables measurement of the electronic spin state using optically detected magnetic resonance), and its relatively long (millisecond) spin coherence at room temperature. The NV center energy levels are modified by magnetic fields, electric fields, temperature, and strain, which allow it to serve as a sensor of a variety of physical phenomena. Its atomic size and spin properties can form the basis for useful quantum sensors. It has also been explored for applications in quantum computing (e.g. for entanglement generation) and spintronics. | 7 | Physical Chemistry |
SDS may reduce the amount of bad breath-causing volatile sulfur compounds (VSCs) in the mouth. A series of small crossover studies (25–34 patients) have supported the efficacy of SLS in the reduction of VSCs, and its related positive impact on breath malodor, although these studies have been generally noted to reflect technical challenges in the control of study design variables. | 1 | Biochemistry |
To build a ground state without magnetic moment, valence bond states can be used, where two electron spins form a spin 0 singlet due to the antiferromagnetic interaction. If every spin in the system is bound like this, the state of the system as a whole has spin 0 too and is non-magnetic. The two spins forming the bond are maximally entangled, while not being entangled with the other spins. If all spins are distributed to certain localized static bonds, this is called a valence bond solid (VBS).
There are two things that still distinguish a VBS from a spin liquid: First, by ordering the bonds in a certain way, the lattice symmetry is usually broken, which is not the case for a spin liquid. Second, this ground state lacks long-range entanglement. To achieve this, quantum mechanical fluctuations of the valence bonds must be allowed, leading to a ground state consisting of a superposition of many different partitionings of spins into valence bonds. If the partitionings are equally distributed (with the same quantum amplitude), there is no preference for any specific partitioning ("valence bond liquid"). This kind of ground state wavefunction was proposed by P. W. Anderson in 1973 as the ground state of spin liquids and is called a resonating valence bond (RVB) state. These states are of great theoretical interest as they are proposed to play a key role in high-temperature superconductor physics. | 7 | Physical Chemistry |
Hydrogenolysis in the presence of a variety of palladium-based catalysts is the usual method for deprotection. Palladium on charcoal is typical.
Alternatively, HBr and strong Lewis acids have been used, provided that a trap is provided for the released benzyl carbocation.
When the protected amine is treated by either of the above methods (i.e. by catalytic hydrogenation or acidic workup), it yields a terminal carbamic acid which then readily decarboxylates to give the free amine.
2-Mercaptoethanol can also be used, in the presence of potassium phosphate in dimethylacetamide. | 0 | Organic Chemistry |
Soil organic matter is anything in the soil of biological origin. Carbon is its key component comprising about 58% by weight. Simple assessment of total organic matter is obtained by measuring organic carbon in soil. Living organisms (including roots) contribute about 15% of the total organic matter in soil. These are critical to operation of the soil carbon cycle. What follows refers to the remaining 85% of the soil organic matter - the non-living component.
As shown below, non-living organic matter in soils can be grouped into four distinct categories on the basis of size, behaviour and persistence. These categories are arranged in order of decreasing ability to decompose. Each of them contribute to soil health in different ways.
Dissolved organic matter (DOM): is the organic matter which dissolves in soil water. It comprises the relatively simple organic compounds (e.g. organic acids, sugars and amino acids) which easily decompose. It has a turnover time of less than 12 months. Exudates from plant roots (mucilages and gums) are included here.
Particulate organic matter (POM): is the organic matter that retains evidence of its original cellular structure, and is discussed further in the next section.
Humus: is usually the largest proportion of organic matter in soil, contributing 45 to 75%. Typically it adheres to soil minerals, and plays an important role structuring soil. Humus is the end product of soil organism activity, is chemically complex, and does not have recognisable characteristics of its origin. Humus is of very small unit size and has large surface area in relation to its weight. It holds nutrients, has high water holding capacity and significant cation exchange capacity, buffers pH change and can hold cations. Humus is quite slow to decompose and exists in soil for decades.
Resistant organic matter: has a high carbon content and includes charcoal, charred plant materials, graphite and coal. Turnover times are long and estimated in hundreds of years. It is not biologically active but contributes positively to soil structural properties, including water holding capacity, cation exchange capacity and thermal properties. | 9 | Geochemistry |
The terms "relative fluorescence units" (RFU) and "RFU peak" refer to measurements in electrophoresis methods, such as for DNA analysis. A "relative fluorescence unit" is a unit of measurement used in analysis which employs fluorescence detection. Fluorescence is detected using a charged coupled device (CCD) array, when the labeled fragments, which are separated within a capillary by using electrophoresis, are energized by laser light and travel across the detection window. A computer program measures the results, determining the quantity or size of the fragments, at each data point, from the level of fluorescence intensity. Samples which contain higher quantities of amplified DNA will have higher corresponding RFU values.
An "RFU peak" is a relative maximum point along a graph of the analyzed data. The data can be normalized to DNA input or additional normalizing genes. The RFU heights can range from 0 to several thousands. | 1 | Biochemistry |
2,4,6-Trichlorobenzoyl chloride is prepared by reacting 2,4,6-trichloroaniline with N-butyllithium in a carbon dioxide atmosphere. This produces 2,4,6-trichlorobenzoic acid, which can then be refluxed in thionyl chloride to form 2,4,6-trichlorobenzoyl chloride.
Since 2,4,6-trichlorobenzoic acid is produced as a by product of the esterification process, it can be refluxed again to recreate 2,4,6-trichlorobenzoyl chloride. | 0 | Organic Chemistry |
The chemical plant Chemko in Strážske (east Slovakia) was an important producer of polychlorinated biphenyls for the former communist bloc (Comecon) until 1984. Chemko contaminated a large part of east Slovakia, especially the sediments of the Laborec river and reservoir Zemplínska šírava. | 2 | Environmental Chemistry |
Amplified fragment length polymorphism (AFLP-PCR or AFLP) is a PCR-based tool used in genetics research, DNA fingerprinting, and in the practice of genetic engineering. Developed in the early 1990s by KeyGene, AFLP uses restriction enzymes to digest genomic DNA, followed by ligation of adaptors to the sticky ends of the restriction fragments. A subset of the restriction fragments is then selected to be amplified. This selection is achieved by using primers complementary to the adaptor sequence, the restriction site sequence and a few nucleotides inside the restriction site fragments (as described in detail below). The amplified fragments are separated and visualized on denaturing on agarose gel electrophoresis, either through autoradiography or fluorescence methodologies, or via automated capillary sequencing instruments.
Although AFLP should not be used as an acronym, it is commonly referred to as "Amplified fragment length polymorphism". However, the resulting data are not scored as length polymorphisms, but instead as presence-absence polymorphisms.
AFLP-PCR is a highly sensitive method for detecting polymorphisms in DNA. The technique was originally described by Vos and Zabeau in 1993. In detail, the procedure of this technique is divided into three steps:
#Digestion of total cellular DNA with one or more restriction enzymes and ligation of restriction half-site specific adaptors to all restriction fragments.
#Selective amplification of some of these fragments with two PCR primers that have corresponding adaptor and restriction site specific sequences.
#Electrophoretic separation of amplicons on a gel matrix, followed by visualisation of the band pattern. | 1 | Biochemistry |
Copper has two naturally occurring stable isotopes: Cu and Cu, which exist in the following natural abundances:
The isotopic composition of Cu is conventionally reported in delta notation (in ‰) relative to a NIST SRM 976 standard: | 9 | Geochemistry |
* [https://www.wikidata.org/wiki/Q101294270 Васина Т. А.] Формирование горнозаводских округов в конце XVIII — первой половине XIX веков на территории современной Удмуртии // Научный диалог — 2019. — вып. 7. — С. 222—239. — ISSN 2227-1295 — [https://www.nauka-dialog.ru/jour/article/view/1254 doi:10.24224/2227-1295-2019-7-222-239]
* Запарий В. В. [https://cyberleninka.ru/article/n/predystoriya-sozdaniya-metallurgii-na-urale|Предыстория создания металлургии на Урале] // Историко-экономические исследования : журнал. — Иркутск: Федеральное государственное бюджетное образовательное учреждение высшего образования «Байкальский государственный университет», 2015. — Т. 16, № 2. — С. 349—365. — ISSN 2308-2488. — doi:10.17150/2308-2588.2015.16(2).349-365.
* Запарий В. В. [https://cyberleninka.ru/article/n/metallurgiya-urala-v-epohu-potryaseniy-pervaya-mirovaya-i-grazhdanskaya-voyny Металлургия Урала в эпоху потрясений Первая мировая и Гражданская войны] // Историко-экономические исследования : журнал. — Иркутск: Федеральное государственное бюджетное образовательное учреждение высшего образования «Байкальский государственный университет», 2015. — Т. 16, № 1. — С. 67—108. — ISSN 2308-2488. — doi:10.17150/2308-2588.2015.16(1).67-108.
* Запарий В. В. [https://cyberleninka.ru/article/n/petrovskaya-modernizatsiya-i-metallurgiya-urala-1700-1725 Петровская модернизация и металлургия Урала (1700–1725)] // Историко-экономические исследования : журнал. — Иркутск: Федеральное государственное бюджетное образовательное учреждение высшего образования «Байкальский государственный университет», 2016. — Т. 17, № 1. — С. 95—140. — ISSN 2308-2488. — doi:10.17150/2308-2588.2016.17(1).95-140.
* Мударисов Р. З. [https://elar.urfu.ru/handle/10995/64248 К вопросу о кризисе горнозаводской промышленности Южного Урала в первой половине XIX века] // Урал индустриальный. Бакунинские чтения. Индустриальная модернизация России в XVIII–XXI вв.: материалы XIII Всероссийской научной конференции, Екатеринбург, 18—19 октября 2018 г.: в 2-х томах. — Екатеринбург: УрО РАН, 2018. — Т. 1. — С. 63—72. — ISBN 978-5-7691-2504-1.
* Пыхалов И. В. [https://cyberleninka.ru/article/n/razvitie-chyornoy-metallurgii-v-rossiyskoy-imperii Развитие чёрной металлургии в Российской империи] // Проблемы современной экономики : журнал. — СПб.: ООО «Научно-производственная компания «РОСТ», 2017. — № 1 (61). — С. 95—140. — ISSN 1818-3395. | 8 | Metallurgy |
When two fluorine atoms are in vicinal (i.e., adjacent) carbons, as in 1,2-difluoroethane (HFCCFH), the gauche conformer is more stable than the anti conformer—this is the opposite of what would normally be expected and to what is observed for most 1,2-disubstituted ethanes; this phenomenon is known as the gauche effect. In 1,2-difluoroethane, the gauche conformation is more stable than the anti conformation by 2.4 to 3.4 kJ/mole in the gas phase. This effect is not unique to the halogen fluorine, however; the gauche effect is also observed for 1,2-dimethoxyethane. A related effect is the alkene cis effect. For instance, the cis isomer of 1,2-difluoroethylene is more stable than the trans isomer.
There are two main explanations for the gauche effect: hyperconjugation and bent bonds. In the hyperconjugation model, the donation of electron density from the carbon–hydrogen σ bonding orbital to the carbon–fluorine σ antibonding orbital is considered the source of stabilization in the gauche isomer. Due to the greater electronegativity of fluorine, the carbon–hydrogen σ orbital is a better electron donor than the carbon–fluorine σ orbital, while the carbon–fluorine σ orbital is a better electron acceptor than the carbon–hydrogen σ orbital. Only the gauche conformation allows good overlap between the better donor and the better acceptor.
Key in the bent bond explanation of the gauche effect in difluoroethane is the increased p orbital character of both carbon–fluorine bonds due to the large electronegativity of fluorine. As a result, electron density builds up above and below to the left and right of the central carbon–carbon bond. The resulting reduced orbital overlap can be partially compensated when a gauche conformation is assumed, forming a bent bond. Of these two models, hyperconjugation is generally considered the principal cause behind the gauche effect in difluoroethane. | 0 | Organic Chemistry |
Membraneless organelles (MLOs), also known as biomolecular condensates, are a form of cell compartmentalization. Unlike classic membrane-bound organelles (e.g. mitochondrion, nucleus or lysosome), MLOs are not separated from their surroundings by a lipid bilayer. MLOs are mostly composed of proteins and nucleic acids, held together by weak intermolecular forces.
MLOs are present in the cytoplasm (e.g. stress granules, processing bodies) and in the nucleus (e.g. nucleolus, nuclear speckles). They have been shown to serve various functions: they can store and protect cellular material during stress conditions, they participate in gene expression and they are involved in the control of signal transduction.
It is now widely believed that MLOs form through LLPS. This was first proposed after observing that Cajal bodies and P granules show liquid-like properties, and was later confirmed by showing that liquid condensates can be reconstituted from purified protein and RNA in vitro. However, whether MLOs should be referred to as liquids, remains disputable. Even if initially they are liquid-like, over time some of them maturate into solids (gel-like or even crystalline, depending on the extent of spatial ordering within the condensate).
Many proteins participating in the formation of MLO contain so-called intrinsically disordered regions (IDRs), parts of the polypeptide chain that can adopt multiple secondary structures and form random coils in solution. IDRs can provide interactions responsible for LLPS, but over time conformational changes (sometimes promoted by mutations or post-translational modifications) may lead to the formation of higher ordered structures and solidification of MLOs. Some MLOs serve their biological role as solid particles (e.g. Balbiani body stabilised by β-sheet structure), but in many cases transformation from liquid to solid results in the formation of pathological aggregates. Examples of both liquid-liquid phase separating and aggregation-prone proteins include FUS, TDP-43 and hnRNPA1. Aggregates of these proteins are associated with neurodegenerative diseases (e.g. amyotrophic lateral sclerosis, or frontotemporal dementia). | 7 | Physical Chemistry |
In the case of ions it is common to speak about delocalized charge (charge delocalization). An example of delocalized charge in ions can be found in the carboxylate group, wherein the negative charge is centered equally on the two oxygen atoms. Charge delocalization in anions is an important factor determining their reactivity (generally: the higher the extent of delocalization the lower the reactivity) and, specifically, the acid strength of their conjugate acids. As a general rule, the better delocalized is the charge in an anion the stronger is its conjugate acid. For example, the negative charge in perchlorate anion () is evenly distributed among the symmetrically oriented oxygen atoms (and a part of it is also kept by the central chlorine atom). This excellent charge delocalization combined with the high number of oxygen atoms (four) and high electronegativity of the central chlorine atom leads to perchloric acid being one of the strongest known acids with a pK value of −10.
The extent of charge delocalization in an anion can be quantitatively expressed via the WAPS (weighted average positive sigma) parameter parameter and an analogous WANS (weighted average negative sigma) parameter is used for cations.
WAPS and WANS values are given in e/Å. Larger values indicate more localized charge in the corresponding ion. | 7 | Physical Chemistry |
Imd signalling regulates a number of effector peptides and proteins that are produced en masse following immune challenge. This includes many of the major antimicrobial peptide genes of Drosophila, particularly: Diptericin, Attacin, Drosocin, Cecropin, and Defensin. The Imd pathway regulates hundreds of genes after infection, however the antimicrobial peptides play one of the most essential roles of Imd signalling in defence. Flies lacking multiple antimicrobial peptide genes succumb to infections by a broad suite of Gram-negative bacteria. Classical thinking suggested that antimicrobial peptides worked as a generalist cocktail in defence, where each peptide provided a small and somewhat redundant contribution. However Hanson and colleagues found that single antimicrobial peptide genes displayed an unexpectedly high degree of specificity for defence against specific microbes. The fly Diptericin A gene is essential for defence against the bacterium Providencia rettgeri (also suggested by an earlier evolutionary study). A second specificity is encoded by Diptericin B, which defends flies against Acetobacter bacteria of the fly microbiome. A third specificity is encoded by the gene Drosocin. Flies lacking Drosocin are highly susceptible to Enterobacter cloacae infection. The Drosocin gene itself encodes two peptides (named Drosocin and Buletin), wherein it is specifically the Drosocin peptide that is responsible for defence against E. cloacae, while the Buletin peptide instead mediates a specific defence against another bacterium, Providencia burhodogranariea. These works accompany others on antimicrobial peptides and effectors regulated by the Drosophila Toll pathway, which also display a specific importance in defence against certain fungi or bacteria.
This work on Drosophila immune antimicrobial peptides and effectors has greatly revised the former view that such peptides are generalist molecules. The modern interpretation is now that specific molecules might provide a somewhat redundant layer of defence, but also single peptides can have critical importance, individually, against relevant microbes. | 1 | Biochemistry |
A reverberatory furnace is a metallurgical or process furnace that isolates the material being processed from contact with the fuel, but not from contact with combustion gases. The term reverberation is used here in a generic sense of rebounding or reflecting, not in the acoustic sense of echoing. | 8 | Metallurgy |
Single-drop microextraction (SDME) is a sample preparation technique in chemical test or analytical chemistry. SDME uses only a single drop of solvent to isolate and preconcentrate analytes from a sample matrix. The extremely low solvent use of SDME makes it cost-effective and less harmful to the environment, subscribing to the principles of green analytical chemistry.
In many chemical test procedures, sample preparation, often the time- and cost-determining step, is designed to isolate analytes from interferences and to provide (typically through enrichment) an analyte concentration suitable for detection. Liquid−liquid extraction (LLE) has long been a widely used technique for the preparation of aqueous samples. Numerous efforts have been made to improve upon the LLE technique for decades.
SDME using only one microdrop of organic solvent to perform LLE was first described in 1996 in Analytical Chemistry. [https://academictree.org/chemistry/peopleinfo.php?pid=844613 Liu] and Dasgupta described a microdrop LLE system with a drop (~1.3 microliter) of chloroform at the tip of a tube suspended in an aqueous drop to perform automatic drop-in-drop extraction and in situ optical detection. Jeannot and [https://academictree.org/chemistry/peopleinfo.php?pid=574033 Cantwell] introduced a method with a single drop (8 microliter) of n-octane at the end of a Teflon rod in a stirred aqueous sample solution to extract the analyte into the organic drop for GC analysis. Since its introduction, SDME has become a popular LLE technique because it is inexpensive, easy to operate, and uses only minuscule amount of solvent. | 3 | Analytical Chemistry |
Gecko feet are hydrophobic, but that is not the only property that assists in their self-cleaning nature. Estrada and Lin created polypropylene, polyethylene, and polycaprolactone nanofibers using a porous template. These nanofiber geometries were shown to be self-cleaning in fiber dimensions of 5, 0.6, and 0.2 microns. However, a hydrophobic surface alone does not explain the perpetually clean toe pad of the gecko, even in dry environments, where water is not available for self-cleaning. This resulting fouling is a common problem for reversible adhesives modeled after the gecko toe pad. Digital hyperextension, or a movement of the toe with each gecko step, contributes to the self-cleaning. A surface or system that mimics this dynamic self-cleaning process has yet to be developed. | 7 | Physical Chemistry |
As a consequence, the structure of any brush can be derived from the brush density profile . Indeed, the free end distribution is simply a convolution of the density profile with the free end distribution of a dry brush:
Correspondingly, the brush elastic free energy is given by:
This method has been used to derive wetting properties of polymer melts on polymer brushes of the same species and to understand fine interpenetration asymmetries between copolymer lamellae that may yield very unusual non-centrosymmetric lamellar structures. | 7 | Physical Chemistry |
The ascorbate-glutathione cycle, sometimes Foyer-Halliwell-Asada pathway, is a metabolic pathway that detoxifies hydrogen peroxide (HO), a reactive oxygen species that is produced as a waste product in metabolism. The cycle involves the antioxidant metabolites: ascorbate, glutathione and NADPH and the enzymes linking these metabolites.
In the first step of this pathway, HO is reduced to water by ascorbate peroxidase (APX) using ascorbate (ASC) as the electron donor. The oxidized ascorbate (monodehydroascorbate, MDA) is regenerated by monodehydroascorbate reductase (MDAR). However, monodehydroascorbate is a radical and if not rapidly reduced it disproportionates into ascorbate and dehydroascorbate (DHA). Dehydroascorbate is reduced to ascorbate by dehydroascorbate reductase (DHAR) at the expense of GSH, yielding oxidized glutathione (GSSG). Finally GSSG is reduced by glutathione reductase (GR) using NADPH as the electron donor. Thus ascorbate and glutathione are not consumed; the net electron flow is from NADPH to HO. The reduction of dehydroascorbate may be non-enzymatic or catalysed by proteins with dehydroascorbate reductase activity, such as glutathione S-transferase omega 1 or glutaredoxins.
In plants, the glutathione-ascorbate cycle operates in the cytosol, mitochondria, plastids and peroxisomes. Since glutathione, ascorbate and NADPH are present in high concentrations in plant cells it is assumed that the glutathione-ascorbate cycle plays a key role for HO detoxification. Nevertheless, other enzymes (peroxidases) including peroxiredoxins and glutathione peroxidases, which use thioredoxins or glutaredoxins as reducing substrates, also contribute to HO removal in plants. | 1 | Biochemistry |
* Fellow of the American Association for the Advancement of Science (1934)
* Fellow of the Indiana Academy of Science (1935)
* American Chemical Society
* Phi Beta Kappa
* Sigma Xi
* Tau Kappa Alpha
* Phi Lambda Upsilon
* Alpha Chi Sigma
* Lambda Chi Alpha | 3 | Analytical Chemistry |
Due to the versatility of SPR instrumentation, this technique pairs well with other approaches, leading to novel applications in various fields, such as biomedical and environmental studies.
When coupled with nanotechnology, SPR biosensors can use nanoparticles as carriers for therapeutic implants. For instance, in the treatment of Alzheimer's disease, nanoparticles can be used to deliver therapeutic molecules in targeted ways. In general, SPR biosensing is demonstrating advantages over other approaches in the biomedical field due to this technique being label-free, lower in costs, applicable in point-of-care settings, and capable of producing faster results for smaller research cohorts.
In the study of environmental pollutants, SPR instrumentation can be used as a replacement for former chromatography-based techniques. Current pollution research relies on chromatography to monitor increases in pollution in an ecosystem over time. When SPR instrumentation with a Kretschmann prism configuration was used in the detection of chlorophene, an emerging pollutant, it was demonstrated that SPR has similar precision and accuracy levels as chromatography techniques. Furthermore, SPR sensing surpasses chromatography techniques through its high-speed, straightforward analysis. | 7 | Physical Chemistry |
A Pesticide detection kit is a kit that scientific test kit detects the presence of pesticide residues. Various organizations create them, among them Defence Food Research Laboratory of India. | 1 | Biochemistry |
Its crystal structure has the tetragonal space group P4/nmm, which is a distorted version of the NHCl crystal structure; the unit cell has approximate dimensions 634×634×462 pm. The hydrogen bonding in the system causes the cations to orient such that the hydrogen atoms point toward the anions. | 0 | Organic Chemistry |
Moungi Bawendi (; born 15 March 1961) is an American–Tunisian–French chemist. He is currently the Lester Wolfe Professor at the Massachusetts Institute of Technology. Bawendi is known for his advances in the chemical production of high-quality quantum dots. In 2023 he was awarded the Nobel Prize in Chemistry. | 7 | Physical Chemistry |
The term "eutrophication" comes from the Greek eutrophos, meaning "well-nourished". Water bodies with very low nutrient levels are termed oligotrophic and those with moderate nutrient levels are termed mesotrophic. Advanced eutrophication may also be referred to as dystrophic and hypertrophic conditions. Thus, eutrophication has been defined as "degradation of water quality owing to enrichment by nutrients which results in excessive plant (principally algae) growth and decay."
Eutrophication was recognized as a water pollution problem in European and North American lakes and reservoirs in the mid-20th century. Breakthrough research carried out at the Experimental Lakes Area (ELA) in Ontario, Canada, in the 1970s provided the evidence that freshwater bodies are phosphorus-limited. ELA uses the whole ecosystem approach and long-term, whole-lake investigations of freshwater focusing on cultural eutrophication. | 2 | Environmental Chemistry |
Glucagon is traditionally a catabolic hormone, but also stimulates the anabolic process of gluconeogenesis by the liver, and to a lesser extent the kidney cortex and intestines, during starvation to prevent low blood sugar. It is the process of converting pyruvate into glucose. Pyruvate can come from the breakdown of glucose, lactate, amino acids, or glycerol. The gluconeogenesis pathway has many reversible enzymatic processes in common with glycolysis, but it is not the process of glycolysis in reverse. It uses different irreversible enzymes to ensure the overall pathway runs in one direction only. | 1 | Biochemistry |
The carbon-carbon single bond is weaker than C-H, O-H, N-H, H-H, H-Cl, C-F, and many double or triple bonds, and comparable in strength to C-O, Si-O, P-O, and S-H bonds, but is commonly considered as strong.
The values given above represent C-C bond dissociation energies that are commonly encountered; occasionally, outliers may deviate drastically from this range. | 0 | Organic Chemistry |
Adsorbed species on single crystal surfaces are frequently found to exhibit long-range ordering; that is to say that the adsorbed species form a well-defined overlayer structure. Each particular structure may only exist over a limited coverage range of the adsorbate, and in some adsorbate/substrate systems a whole progression of adsorbate structure are formed as the surface coverage is gradually increased.
The periodicity of the overlayer (which often is larger than that of the substrate unit cell) can be determined by low-energy electron diffraction (LEED), because there will be additional diffraction beams associated with the overlayer. | 7 | Physical Chemistry |
Monolayers have a multitude of applications both at the air-water and at air-solid interphases.
Nanoparticle monolayers can be used to create functional surfaces that have for instance anti-reflective or superhydrophobic properties.
Monolayers are frequently encountered in biology. A micelle is a monolayer, and the phospholipid lipid bilayer structure of biological membranes is technically two monolayers. Langmuir monolayers are commonly used to mimic cell membrane to study the effects of pharmaceuticals or toxins. | 7 | Physical Chemistry |
T4 bacteriophage uses anti-sigma factor to ruin the Escherichia coli polymerase in order that direct exclusive transcription of its own genes.
AsiA is an anti-sigma factor gene that is required for bacteriophage T4 to be developed). Which means that AsiA is an essential anti-sigma factor in bacteriophage. | 1 | Biochemistry |
This can be prevented by using sodium phosphate () instead of sodium carbonate as softening reagents. What happens is that its molecules will get inside the hair-line crack and block it, as a result of which sodium hydroxide, even if it is there, will not be able to come in contact with iron, and no reaction will be there. Adding tannin or lignin to boiler water blocks the hair-line cracks and prevents infiltration of NaOH into these areas. Adding NaSO to boiler water also blocks the hair-line cracks. | 8 | Metallurgy |
On 9 July 2014, the European Commission imposed fines of €427,700,000 on Laboratoires Servier and 5 companies which produce generics due to Serviers abuse of their dominant market position, in breach of European Union Competition law. Serviers strategy had included acquiring the principal source of generic production of Perindopril and entering into several pay-for-delay agreements with potential generic competitors. | 4 | Stereochemistry |
* 2011 National Science Foundation CAREER Award
* 2016 American Chemical Society Early-Career Award in Experimental Physical Chemistry
* 2019 Rice Institute of Biosciences and Bioengineering Hamill Innovation Award
* 2019 National Academy of Sciences Kavli Fellow
* 2020 National Science Foundation Award for Special Creativity | 7 | Physical Chemistry |
Intergenic regions may contain a number of functional DNA sequences such as promoters and regulatory elements, enhancers, spacers, and (in eukaryotes) centromeres. They may also contain origins of replication, scaffold attachment regions, and transposons and viruses.
Non-functional DNA elements such as pseudogenes and repetitive DNA, both of which are types of junk DNA, can also be found in intergenic regions—although they may also be located within genes in introns. It is possible that these regions contain as of yet unidentified functional elements, such as non-coding genes or regulatory sequences. This indeed occurs occasionally, but the amount of functional DNA discovered usually constitute only a tiny fraction of the overall amount of intergenic or intronic DNA. | 1 | Biochemistry |
A slip bond is a type of chemical noncovalent bond whose dissociation lifetime decreases with tensile force applied to the bond. This is the expected behaviour for chemical bonds, but exceptions, like catch bonds exist. | 1 | Biochemistry |
Transition metal nitrates form a variety of hydrates. The nitrate anion often binds to the metal, especially for those salts with fewer than six aquo ligands. Nitrates are uncommon in nature, so few minerals are represented here. Hydrated ferrous nitrate has not been characterized crystallographically. | 3 | Analytical Chemistry |
Triflic anhydride is prepared by dehydration of triflic acid using PO.
Triflic anhydride is useful for converting ketones into enol triflates.
In a representative application, is used to convert an imine into a NTf group. It will convert phenols into a triflic ester, which enables cleavage of the C-O bond. | 0 | Organic Chemistry |
Values of ΔH have been experimentally determined and are available in table form. Most general chemistry textbooks have appendixes including common ΔH values. There are several online tables available. A software offered with Active Thermochemical Tables (ATcT) provides more information online. | 7 | Physical Chemistry |
Cleaning surfaces in environments without water has been a challenge. Electric curtain devices were designed to remove particles by creating electric fields on the surface and carrying away particles due to their charged nature. It has been used in solar panels as well as 3D printers. | 7 | Physical Chemistry |
The dashboard provides support for mass spectrometry providing searches against the chemical data contained in the database based on mass and molecular formula. The dashboard has been applied to non-targeted analysis searching for "known unknowns". Both targeted mass spectrometry and non-targeted mass spectrometry are supported. The searches utilize a search based on "MS-Ready" forms of chemical compounds. Individual chemical substances are collapsed into a form that would be detected by mass spectrometry such that salts are desalted and neutralized and multi-component chemicals are separated into their individual components. | 2 | Environmental Chemistry |
Methyl isocyanate (MIC) is an organic compound with the molecular formula CHNCO. Synonyms are isocyanatomethane and methyl carbylamine. Methyl isocyanate is an intermediate chemical in the production of carbamate pesticides (such as carbaryl, carbofuran, methomyl, and aldicarb). It has also been used in the production of rubbers and adhesives. As an extremely toxic and irritating compound, it is very hazardous to human health. MIC was the principal toxicant involved in the Bhopal gas disaster, which eventually killed around 20,000 people in total as per official figures. It is also a very potent lachrymatory agent. | 9 | Geochemistry |
Capsiate (4-hydroxy-3-methoxybenzyl (E)-8-methyl-6-nonenoate) (CAS No. 205687-01-0)
Dihydrocapsiate (4-hydroxy-3-methoxybenzyl 8-methylnonanoate) (CAS No. 205687-03-2)
Nordihydrocapsiate (4-hydroxy-3-methoxybenzyl 7-methyloctanoate) (CAS No. 220012-53-3) | 1 | Biochemistry |
Anders Meibom (born 9 September 1969) is a Danish interdisciplinary scientist and former football player active in the field of bio-geochemistry. He is a professor at the École Polytechnique Fédérale de Lausanne (EPFL), where he heads the laboratory for biological geochemistry. | 9 | Geochemistry |
A selenenic acid is an organoselenium compound and an oxoacid with the general formula RSeOH, where R ≠ H. It is the first member of the family of organoselenium oxoacids, which also include seleninic acids and selenonic acids, which are RSeOH and RSeOH, respectively. Selenenic acids derived from selenoenzymes are thought to be responsible for the antioxidant activity of these enzymes. This functional group is sometimes called SeO-selenoperoxol. | 0 | Organic Chemistry |
If the solvent is a gas, only gases (non-condensable) or vapors (condensable) are dissolved under a given set of conditions. An example of a gaseous solution is air (oxygen and other gases dissolved in nitrogen). Since interactions between gaseous molecules play almost no role, non-condensable gases form rather trivial solutions. In the literature, they are not even classified as solutions, but simply addressed as homogeneous mixtures of gases. The Brownian motion and the permanent molecular agitation of gas molecules guarantee the homogeneity of the gaseous systems. Non-condensable gaseous mixtures (e.g., air/CO, or air/xenon) do not spontaneously demix, nor sediment, as distinctly stratified and separate gas layers as a function of their relative density. Diffusion forces efficiently counteract gravitation forces under normal conditions prevailing on Earth. The case of condensable vapors is different: once the saturation vapor pressure at a given temperature is reached, vapor excess condenses into the liquid state. | 7 | Physical Chemistry |
The parameters for water quality are determined by the intended use. Work in the area of water quality tends to be focused on water that is treated for potability, industrial/domestic use, or restoration (of an environment/ecosystem, generally for health of human/aquatic life). | 3 | Analytical Chemistry |
The first meeting of BOGS was held in Bangor (Wales) on 13–15 July 1988. The society meets annually, usually at (or near) a university department with links to research in organic geochemistry.
BOGS meetings are usually held over two days, and involve oral presentations (lasting 15 minutes), poster presentations and social events (i.e. evening meal).
Annual meetings have been held at Liverpool (1989), Bideford (1990), Newcastle-upon-Tyne (1992), Plymouth (1993), Aberdeen (1994), Bristol (1995), Liverpool (1996), Newcastle-upon-Tyne (1997), Plymouth (1998), York (1999), Bristol (2000), Gregynog, Wales (2001), Newcastle-upon-Tyne (2002), Plymouth (2003), Nottingham (2004), Liverpool (2005), Milton Keynes (2006). BOGS did not meet in 2007, as this would have clashed with the 23rd International Meeting of Organic Geochemistry (IMOG) event, which occurred a few months later in Torquay. Since 2007 BOGS has met at Newcastle (2008), Bristol (2009), Manchester (2010), Swansea (2011), Leeds (2012), Plymouth (2013), Liverpool (2014), Glasgow (2015), Imperial College London (2016) and Open University, Milton Keynes (2017). | 9 | Geochemistry |
Insertions are another common type of carbene reaction, a form of oxidative addition. Insertions may or may not occur in single step (see above). The end result is that the carbene interposes itself into an existing bond, preferably X–H (X not carbon), else C–H or (failing that) a C–C bond. Alkyl carbenes insert much more selectively than methylene, which does not differentiate between primary, secondary, and tertiary C-H bonds.
The 1,2-rearrangement produced from intramolecular insertion into a bond adjacent to the carbene center is a nuisance in some reaction schemes, as it consumes the carbene to yield the same effect as a traditional elimination reaction. Generally, rigid structures favor intramolecular insertions. In flexible structures, five-membered ring formation is preferred to six-membered ring formation. When such insertions are possible, no intermolecular insertions are seen. Both inter- and intra-molecular insertions admit asymmetric induction from a chiral metal catalyst. | 0 | Organic Chemistry |
As yttrium is chemically similar to lanthanides, it occurs in the same ores (rare-earth minerals) and is extracted by the same refinement processes. A slight distinction is recognized between the light (LREE) and the heavy rare-earth elements (HREE), but the distinction is not perfect. Yttrium is concentrated in the HREE group because of its ion size, though it has a lower atomic mass.
Rare-earth elements (REEs) come mainly from four sources:
* Carbonate and fluoride containing ores such as the LREE bastnäsite ((Ce, La, etc.)(CO)F) contain an average of 0.1% of yttrium compared to the 99.9% for the 16 other REEs. The main source for bastnäsite from the 1960s to the 1990s was the Mountain Pass rare earth mine in California, making the United States the largest producer of REEs during that period. The name "bastnäsite" is actually a group name, and the Levinson suffix is used in the correct mineral names, e.g., bästnasite-(Y) has Y as a prevailing element.
* Monazite ((Ce, La, etc.)PO), which is mostly phosphate, is a placer deposit of sand created by the transportation and gravitational separation of eroded granite. Monazite as an LREE ore contains 2% (or 3%) yttrium. The largest deposits were found in India and Brazil in the early 20th century, making those two countries the largest producers of yttrium in the first half of that century. Of the monazite group, the Ce-dominant member, monazite-(Ce), is the most common one.
* Xenotime, a REE phosphate, is the main HREE ore containing as much as 60% yttrium as yttrium phosphate (YPO). This applies to xenotime-(Y). The largest mine is the Bayan Obo deposit in China, making China the largest exporter for HREE since the closure of the Mountain Pass mine in the 1990s.
* Ion absorption clays or Lognan clays are the weathering products of granite and contain only 1% of REEs. The final ore concentrate can contain as much as 8% yttrium. Ion absorption clays are mostly in southern China. Yttrium is also found in samarskite and fergusonite (which also stand for group names).
One method for obtaining pure yttrium from the mixed oxide ores is to dissolve the oxide in sulfuric acid and fractionate it by ion exchange chromatography. With the addition of oxalic acid, the yttrium oxalate precipitates. The oxalate is converted into the oxide by heating under oxygen. By reacting the resulting yttrium oxide with hydrogen fluoride, yttrium fluoride is obtained. When quaternary ammonium salts are used as extractants, most yttrium will remain in the aqueous phase. When the counter-ion is nitrate, the light lanthanides are removed, and when the counter-ion is thiocyanate, the heavy lanthanides are removed. In this way, yttrium salts of 99.999% purity are obtained. In the usual situation, where yttrium is in a mixture that is two-thirds heavy-lanthanide, yttrium should be removed as soon as possible to facilitate the separation of the remaining elements.
Annual world production of yttrium oxide had reached by 2001; by 2014 it had increased to . Global reserves of yttrium oxide were estimated in 2014 to be more than . The leading countries for these reserves included Australia, Brazil, China, India, and the United States. Only a few tonnes of yttrium metal are produced each year by reducing yttrium fluoride to a metal sponge with calcium magnesium alloy. The temperature of an arc furnace of greater than 1,600 °C is sufficient to melt the yttrium. | 8 | Metallurgy |
The volume in the definition refers to the volume of the solution, not the volume of the solvent. One litre of a solution usually contains either slightly more or slightly less than 1 litre of solvent because the process of dissolution causes volume of liquid to increase or decrease. Sometimes the mass concentration is called titre. | 3 | Analytical Chemistry |
Many metathesis reactions with ruthenium catalysts are hampered by unwanted isomerization of the newly formed double bond, and it is believed that ruthenium hydrides that form as a side reaction are responsible. In one study it was found that isomerization is suppressed in the RCM reaction of diallyl ether with specific additives capable of removing these hydrides. Without an additive, the reaction product is 2,3-dihydrofuran and not the expected 2,5-dihydrofuran (together with the formation of ethylene gas). Radical scavengers, such as TEMPO or phenol, do not suppress isomerization; however, additives such as 1,4-benzoquinone or acetic acid successfully prevent unwanted isomerization. Both additives are able to oxidize the ruthenium hydrides which may explain their behavior.
Another common problem associated with RCM is the risk of catalyst degradation due to the high dilution required for some cyclizations. High dilution is also a limiting factor in industrial applications due to the large amount of waste generated from large-scale reactions at a low concentration. Efforts have been made to increase reaction concentration without compromising selectivity. | 0 | Organic Chemistry |
The metabolism of an animal is estimated by determining rates of carbon dioxide production (VCO) and oxygen consumption (VO) of individual animals, either in a closed or an open-circuit respirometry system. Two measures are typically obtained: standard (SMR) or basal metabolic rate (BMR) and maximal rate (VO2max). SMR is measured while the animal is at rest (but not asleep) under specific laboratory (temperature, hydration) and subject-specific conditions (e.g., size or allometry), age, reproduction status, post-absorptive to avoid thermic effect of food). VOmax is typically determined during aerobic exercise at or near physiological limits. In contrast, field metabolic rate (FMR) refers to the metabolic rate of an unrestrained, active animal in nature. Whole-animal metabolic rates refer to these measures without correction for body mass. If SMR or BMR values are divided by the body mass value for the animal, then the rate is termed mass-specific. It is this mass-specific value that one typically hears in comparisons among species. | 1 | Biochemistry |
"Amoxicillin" is the International Nonproprietary Name (INN), British Approved Name (BAN), and United States Adopted Name (USAN), while "amoxycillin" is the Australian Approved Name (AAN).
Amoxicillin is one of the semisynthetic penicillins discovered by former pharmaceutical company Beecham Group. The patent for amoxicillin has expired, thus amoxicillin and co-amoxiclav preparations are marketed under various brand names across the world. | 4 | Stereochemistry |
Precession electron diffraction is accomplished utilizing the standard instrument configuration of a modern TEM. The animation illustrates the geometry used to generate a PED pattern. Specifically, the beam tilt coils located pre-specimen are used to tilt the electron beam off of the optic axis so it is incident with the specimen at an angle, φ. The image shift coils post-specimen are then used to tilt the diffracted beams back in a complementary manner such that the direct beam falls in the center of the diffraction pattern. Finally, the beam is precessed around the optic axis while the diffraction pattern is collected over multiple revolutions.
The result of this process is a diffraction pattern that consists of a summation or integration over the patterns generated during precession. While the geometry of this pattern matches the pattern associated with a normally incident beam, the intensities of the various reflections approximate those of the kinematical pattern much more closely. At any moment in time during precession, the diffraction pattern consists of a Laue circle with a radius equal to the precession angle, φ. It is crucial to note that these snapshots contain far fewer strongly excited reflections than a normal zone axis pattern and extend farther into reciprocal space. Thus, the composite pattern will display far less dynamical character, and will be well suited for use as input into direct methods calculations. | 3 | Analytical Chemistry |
It is possible to combine the summation with the connectivity theorems to obtain closed expressions that relate the control coefficients to the elasticity coefficients. For example, consider the simplest non-trivial pathway:
We assume that and are fixed boundary species so that the pathway can reach a steady state. Let the first step have a rate and the second step . Focusing on the flux control coefficients, we can write one summation and one connectivity theorem for this simple pathway:
Using these two equations we can solve for the flux control coefficients to yield
Using these equations we can look at some simple extreme behaviors. For example, let us assume that the first step is completely insensitive to its product (i.e. not reacting with it), S, then . In this case, the control coefficients reduce to
That is all the control (or sensitivity) is on the first step. This situation represents the classic rate-limiting step that is frequently mentioned in textbooks. The flux through the pathway is completely dependent on the first step. Under these conditions, no other step in the pathway can affect the flux. The effect is however dependent on the complete insensitivity of the first step to its product. Such a situation is likely to be rare in real pathways. In fact the classic rate limiting step has almost never been observed experimentally. Instead, a range of limitingness is observed, with some steps having more limitingness (control) than others.
We can also derive the concentration control coefficients for the simple two step pathway: | 1 | Biochemistry |
The Chesapeake Bay forms a link in the Intracoastal Waterway, of the bays, sounds and inlets between the off-shore barrier islands and the coastal mainland along the Atlantic coast connecting the Chesapeake and Delaware Canal (linking the Bay to the north and the Delaware River) with the Albemarle and Chesapeake Canal (linking the Bay, to the south, via the Elizabeth River, by the cities of Norfolk and Portsmouth to the Albemarle Sound and Pamlico Sound in North Carolina and further to the Sea Islands of Georgia). A busy shipping channel (dredged by the U.S. Army Corps of Engineers since the 1850s) runs the length of the Bay, is an important transit route for large vessels entering or leaving the Port of Baltimore, and further north through the Chesapeake and Delaware Canal to the ports of Wilmington and Philadelphia on the Delaware River.
During the later half of the 19th century and the first half of the 20th century, the Bay was plied by passenger steamships and packet boat lines connecting the various cities on it, notably the Baltimore Steam Packet Company ("Old Bay Line").
In the later 20th century, a series of road crossings were built. One, the Chesapeake Bay Bridge (also known as the Governor William Preston Lane, Jr. Memorial Bridge) between the state capital of Annapolis, Maryland and Matapeake on the Eastern Shore, crossing Kent Island, was constructed 1949–1952. A second, parallel, span was added in 1973. The Chesapeake Bay Bridge–Tunnel, connecting Virginia's Eastern Shore with its mainland (at the metropolitan areas of Virginia Beach, Norfolk, Portsmouth, and Chesapeake), is approximately long; it has trestle bridges as well as two stretches of tunnels that allow unimpeded shipping; the bridge is supported by four man-made islands. The Chesapeake Bay Bridge–Tunnel was opened for two lanes in 1964 and four lanes in 1999. | 2 | Environmental Chemistry |
1/ In the 80's, diagnostic assays based on the Enzyme Linked Immunosorbent Assay (ELISA) method were already being developed for human and veterinary applications. Following the reports of the first use of ELISA to detect plant viruses by Voller and Clarke (1976), Dr. Sutula introduced in 1981 the first commercial kits for the detection of common viruses and bacteria in potato. These kits provided all of the components that were necessary to perform the test in a ready-to-use format, called PathoScreen®. He established collaborations with many plant pathologists all over the world to produce tests that are recognized worldwide for their quality and value.
2/ With two competing companies in Europe, Inotech, Basil, Switzerland and Boehringer Mannheim, Germany, Dr. Sutula pioneered the concept of "reagent sets"—matched, quality-controlled antibodies and antibody-enzyme conjugates that can be used to prepare and perform one's own test. He integrated these ideas into plant diagnostics, expanded the scope of diagnostic assays, and guided Agdia to a continuous company growth over the past 35 years.
3/ In response to many requests, he formed Agdia Testing Services in 1982, a unit of Agdia. Agdia currently offers more than 200 tests that use several technologies, such as ELISA, Recombinase Polymerase Amplification (RPA), Polymerase Chain Reaction (PCR), nucleic acid hybridization, immunochromatography, and Immunofluorescence assay (IFA), to detect viruses, viroids, bacteria, fungi, mycoplasma, insects, plant hormones, and proteins in conventional and genetically modified crops (GMO). He developed international sales and helped to establish Agdia-Biofords, French company based in Genopole Évry, in charge of product distribution in Europe, Africa and Middle East.
Dr. Sutula's vision was to make research on detecting plant pathogens available to many persons in worldwide agriculture and to package this technology into easy-to-perform, affordable tests. Now in retirement, Chet continues his special interest in simplifying complex chemistry and procedures into tests that are reliable and simple to perform. | 3 | Analytical Chemistry |
Mammalian-wide interspersed repeats (MIRs) are transposable elements in the genomes of some organisms and belong to the group of Short interspersed nuclear elements (SINEs). | 1 | Biochemistry |
The metallothermic reduction of anhydrous rare-earth fluorides to rare-earth metals is also referred to as the Ames process.
The study of rare earths was also advanced during World War II: Synthetic plutonium was believed to be rare-earth-like, it was assumed that knowledge of rare earths would assist in planning for and the study of transuranic elements; ion-exchange methods developed for actinide processing were forerunners to processing methods for rare-earth oxides; methods used for uranium were modified for plutonium, which were subsequently the basis for rare-earth metal preparation. | 8 | Metallurgy |
Salt compounds dissociate in aqueous solutions. This property is exploited in the process of salting out. When the salt concentration is increased, some of the water molecules are attracted by the salt ions, which decreases the number of water molecules available to interact with the charged part of the protein.
There are hydrophobic amino acids and hydrophilic amino acids in protein molecules.
After protein folding in aqueous solution, hydrophobic amino acids usually form protected hydrophobic areas while hydrophilic amino acids interact with the molecules of solvation and allow proteins to form hydrogen bonds with the surrounding water molecules. If enough of the protein surface is hydrophilic, the protein can be dissolved in water.
When salt is added to the solution, there is more frequent interaction between solvent molecules and salt ions. As a result, the protein and salt ions compete to interact with the solvent molecules with the result that there are fewer solvent molecules available for interaction with the protein molecules than before. The protein–protein interactions thus become stronger than the solvent–solute interactions and the protein molecules associate by forming hydrophobic interactions with each other. After dissociation in a given solvent, the negatively charged atoms from a chosen salt begin to compete for interactions with positively charged molecules present in the solution. Similarly, the positively charged cations compete for interactions with the negatively charged molecules of the solvent. This process is known as salting out.
Soaps are easily precipitated by concentrated salt solution, the metal ion in the salt reacts with the fatty acids forming back the soap and glycerin (glycerol). To separate glycerin from the soap, the pasty boiling mass is treated with brine (NaCl solution). Contents of the kettle salt out (separate) into an upper layer that is a curdy mass of impure soap and a lower layer that consists of an aqueous salt solution with the glycerin dissolved in it. The slightly alkaline salt solution, termed spent lye, is extracted from the bottom of the pan or kettle and may be subsequently treated for glycerin recovery. | 3 | Analytical Chemistry |
Zeise returned to Denmark in the autumn of 1819. The prospects were not bright for an appointment at the University, although he was likely the only scientifically trained chemist in the country at that time. However, he learned at the end of the year that he had received public funds to support his work in science. That same year the university rented an apartment in Nørregade for use as a physics workshop and for physics education. Ørsted converted the apartment kitchen into a menial little laboratory, over which Zeise was made responsible. In this, the so-called "Royal Science Laboratory", Zeise received 10 students in the first year to whom he lectured, both in the laboratory and partly in the physical workshop. In June 1822 Zeise was appointed extraordinary Professor of Chemistry. In 1824, Professor Ørsted selected a nearby farm as the site for what would later become the Danish Polytechnic Education Institution. It was decided to transform the large stable building in the courtyard into a dedicated chemical laboratory. When the Polytechnic College was eventually founded in 1829, Zeise was instrumental in getting the chemical laboratory expanded and organised.
In 1823 while still in the small laboratory at Nørregade he identified a new family of sulfur-containing compounds, calling them xanthates (xanthus, Greek "yellow") on account of the predominantly yellow colour of xanthate salts. Zeise was accordingly awarded a silver medal by the Royal Danish Academy of Sciences and Letters, and he became a member of that body the following year on the recommendation of Ørsted. In 1836 he became a Knight of the Order of the Dannebrog, a very high honour bestowed by the Danish monarch.
As a teacher Zeise demanded strict accuracy from his pupils; together with conscientiousness, order and diligence - the same qualities which so strongly animated him.
In February 1842 he married Maren Martine Bjerring. Zeise's health was fragile for much of his life and he suffered greatly, possibly due to his handling of noxious chemicals in poorly ventilated rooms. He died of tuberculosis in Copenhagen on 12 November 1847 and was buried in Assistens Cemetery in the same city. | 0 | Organic Chemistry |
A bridged nucleic acid (BNA) is a modified RNA nucleotide. They are sometimes also referred to as constrained or inaccessible RNA molecules. BNA monomers can contain a five-membered, six-membered or even a seven-membered bridged structure with a "fixed" C-endo sugar puckering. The bridge is synthetically incorporated at the 2, 4-position of the ribose to afford a 2, 4'-BNA monomer. The monomers can be incorporated into oligonucleotide polymeric structures using standard phosphoramidite chemistry. BNAs are structurally rigid oligo-nucleotides with increased binding affinities and stability. | 1 | Biochemistry |
Ca ions are an essential component of plant cell walls and cell membranes, and are used as cations to balance organic anions in the plant vacuole. The Ca concentration of the vacuole may reach millimolar levels. The most striking use of Ca ions as a structural element in algae occurs in the marine coccolithophores, which use Ca to form the calcium carbonate plates, with which they are covered.
Calcium is needed to form the pectin in the middle lamella of newly formed cells.
Calcium is needed to stabilize the permeability of cell membranes. Without calcium, the cell walls are unable to stabilize and hold their contents. This is particularly important in developing fruits. Without calcium, the cell walls are weak and unable to hold the contents of the fruit.
Some plants accumulate Ca in their tissues, thus making them more firm. Calcium is stored as Ca-oxalate crystals in plastids. | 1 | Biochemistry |
The process is named after the Italian physician, physicist, biologist and philosopher Luigi Galvani (9 September 1737 – 4 December 1798). The earliest known example of galvanized iron was discovered on 17th-century Indian armour in the Royal Armouries Museum collection in the United Kingdom.
The term "galvanized" can also be used metaphorically of any stimulus which results in activity by a person or group of people.
In modern usage, the term "galvanizing" has largely come to be associated with zinc coatings, to the exclusion of other metals. Galvanic paint, a precursor to hot-dip galvanizing, was patented by Stanislas Sorel, of Paris, on June 10, 1837, as an adoption of a term from a highly fashionable field of contemporary science, despite having no evident relation to it. | 8 | Metallurgy |
Heparin and heparan sulfate (HS) are mammalian glycosaminoglycans with the highest negative charge density of known biological macromolecules. They bind by ionic interactions with a variety of proteins. Heparin is widely used as an injectable anticoagulant. SFRP1 are heparin-binding proteins, with the heparin-binding domain within the C-terminal region of the SFRP1 protein. In vitro studies show that SFRP1 is stabilized by heparin, suggesting that heparin or endogenous heparan-sulfate proteoglycan (HSPG) has the potential to promote SFRP1/Wnt binding by serving as a scaffold to facilitate interaction between SFRP1 and Wnt proteins. Lowering HSPG levels in tissue have been shown to impair Wnt signaling in vivo, supporting the idea that HSPG plays an important role in Wnt signaling regulation. Furthermore, SFRP1 is tyrosine-sulfated at two N-terminal tyrosines; this modification is, however, inhibited by heparin. Tyrosine sulfation could partially destabilize the SFRP1 protein, which is supported by previous studies showing that SFRP1 is susceptible to degradation in the absence of heparin. The finding that heparin can inhibit intracellular post-translational modification of SFRP1 was surprising. This indicates that heparin may inhibit the process of tyrosine sulfation, for example, by tyrosyl-protein sulfotransferases enzymes or sulfate donor pathways. Since heparin is highly negatively charged and cannot permeate the membrane, it must activate a signal transduction pathway to carry out its effect. It is well known that fibroblast growth factors (FGFs) bind heparin with relatively high affinity. HSPGs have also been shown to be involved in FGF cell signaling. Zhong et al. revealed a specificity of FGFs and FGF receptors on SFRP1 accumulation, demonstrating that FGF and their receptors are involved in post-translational modification of SFRP1. As stated above, SFRP1 has been shown to attenuate the malignant phenotype and decrease the growth of tumors. Thus, Heparin is a potential drug that could be used to stabilize and accumulate SFRP1 in cancer cells. | 1 | Biochemistry |
Along with his interest in science, Fraser-Reid was an accomplished pianist and organist who gave recitals at notable venues such as St. George's Cathedral, Kingston, Jamaica (December 1986) and Cathedral de Seville, Spain (August 1995).
In the 1970s Fraser-Reid filed a lawsuit against a building contractor who had not followed municipal building codes. The case went all the way to the Supreme Court of Canada where Fraser-Reid prevailed, and "Fraser-Reid v Droumtsekas" is often cited in Canadian civil law. | 0 | Organic Chemistry |
Contact angle goniometers (q.v.)can also determine the surface tension for any liquid in gas or the interfacial tension between any two liquids. If the difference in densities between the two fluids is known, the surface tension or interfacial tension can be calculated by the pendant drop method. An advanced instrument often called a goniometer / tensiometer includes software tools that measure surface tension and interfacial tension using the pendant drop, inverted pendant drop, and sessile drop methods, in addition to contact angle. A centrifugal adhesion balance relates the contact angles to the adhesion of the drop to the surface. A gonioreflectometer measures the reflectivity of a surface at a number of angles. | 7 | Physical Chemistry |