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Surface tension draws fluid from capillaries to the alveolar spaces. Surfactant reduces fluid accumulation and keeps the airways dry by reducing surface tension. | 0 | Theoretical and Fundamental Chemistry |
The rate of this kind of reaction does not depend on the substrate concentration, . Thus the concentration decreases linearly.
:The integrated rate law of zero order kinetics is:
In order to find the half-life, we have to replace the concentration value for the initial concentration divided by 2: and isolate the time:This formula indicates that the half-life for a zero order reaction depends on the initial concentration and the rate constant. | 0 | Theoretical and Fundamental Chemistry |
Many scientific endeavors are dependent upon accurate quantification of drugs and endogenous substances in biological samples; the focus of bioanalysis in the pharmaceutical industry is to provide a quantitative measure of the active drug and/or its metabolite(s) for the purpose of pharmacokinetics, toxicokinetics, bioequivalence and exposure–response (pharmacokinetics/pharmacodynamics studies). Bioanalysis also applies to drugs used for illicit purposes, forensic investigations, anti-doping testing in sports, and environmental concerns.
Bioanalysis was traditionally thought of in terms of measuring small molecule drugs. However, the past twenty years has seen an increase in biopharmaceuticals (e.g. proteins and peptides), which have been developed to address many of the same diseases as small molecules. These larger biomolecules have presented their own unique challenges to quantification. | 0 | Theoretical and Fundamental 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. | 0 | Theoretical and Fundamental Chemistry |
Embedded in the thylakoid membranes are important protein complexes which carry out the light reactions of photosynthesis. Photosystem II and photosystem I contain light-harvesting complexes with chlorophyll and carotenoids that absorb light energy and use it to energize electrons. Molecules in the thylakoid membrane use the energized electrons to pump hydrogen ions into the thylakoid space, decreasing the pH and turning it acidic. ATP synthase is a large protein complex that harnesses the concentration gradient of the hydrogen ions in the thylakoid space to generate ATP energy as the hydrogen ions flow back out into the stroma—much like a dam turbine.
There are two types of thylakoids—granal thylakoids, which are arranged in grana, and stromal thylakoids, which are in contact with the stroma. Granal thylakoids are pancake-shaped circular disks about 300–600 nanometers in diameter. Stromal thylakoids are helicoid sheets that spiral around grana. The flat tops and bottoms of granal thylakoids contain only the relatively flat photosystem II protein complex. This allows them to stack tightly, forming grana with many layers of tightly appressed membrane, called granal membrane, increasing stability and surface area for light capture.
In contrast, photosystem I and ATP synthase are large protein complexes which jut out into the stroma. They can't fit in the appressed granal membranes, and so are found in the stromal thylakoid membrane—the edges of the granal thylakoid disks and the stromal thylakoids. These large protein complexes may act as spacers between the sheets of stromal thylakoids.
The number of thylakoids and the total thylakoid area of a chloroplast is influenced by light exposure. Shaded chloroplasts contain larger and more grana with more thylakoid membrane area than chloroplasts exposed to bright light, which have smaller and fewer grana and less thylakoid area. Thylakoid extent can change within minutes of light exposure or removal. | 0 | Theoretical and Fundamental Chemistry |
Zircon (ZrSiO) is commonly found in felsic igneous rock. Because both Ce and Ce can substitute for zirconium, Zircon often has a positive Ce anomaly. Ce substitutes with Zr much more easily than Ce because Ce (ionic radius 0.97Å) has the same charge and a similar ionic radius as Zr (ionic radius 0.84Å). Therefore, the oxidation state of the magma is what determines the Ce anomaly in Zircon. If the oxygen fugacity is high, more Ce will oxidize to Ce and create a larger positive Ce anomaly in the zircon structure. At lower levels of oxygen fugacity, the level of Ce anomaly will also be lower. | 0 | Theoretical and Fundamental Chemistry |
In combustion processes, the reaction rate is dependent on temperature in the following form (Arrhenius law),
where is the activation energy, and is the universal gas constant. In general, the condition is satisfied, where is the burnt gas temperature. This condition forms the basis for activation energy asymptotics. Denoting for unburnt gas temperature, one can define the Zel'dovich number and heat release parameter as follows
In addition, if we define a non-dimensional temperature
such that approaching zero in the unburnt region and approaching unity in the burnt gas region (in other words, ), then the ratio of reaction rate at any temperature to reaction rate at burnt gas temperature is given by
Now in the limit of (large activation energy) with , the reaction rate is exponentially small i.e., and negligible everywhere, but non-negligible when . In other words, the reaction rate is negligible everywhere, except in a small region very close to burnt gas temperature, where . Thus, in solving the conservation equations, one identifies two different regimes, at leading order,
*Outer convective-diffusive zone
*Inner reactive-diffusive layer
where in the convective-diffusive zone, reaction term will be neglected and in the thin reactive-diffusive layer, convective terms can be neglected and the solutions in these two regions are stitched together by matching slopes using method of matched asymptotic expansions. The above mentioned two regime are true only at leading order since the next order corrections may involve all the three transport mechanisms. | 1 | Applied and Interdisciplinary Chemistry |
At length-scales larger than the persistence length, the entropic flexibility of DNA is remarkably consistent with standard polymer physics models, such as the Kratky-Porod worm-like chain model. Consistent with the worm-like chain model is the observation that bending DNA is also described by Hooke's law at very small (sub-piconewton) forces. For DNA segments less than the persistence length, the bending force is approximately constant and behaviour deviates from the worm-like chain predictions.
This effect results in unusual ease in circularising small DNA molecules and a higher probability of finding highly bent sections of DNA. | 0 | Theoretical and Fundamental Chemistry |
Compared to time domain reflectometer (TDR), FD sensors are cheaper to build and have a faster response time. However, because of the complex electrical field around the probe, the sensor needs to be calibrated for different soil types. Some commercial sensors have been able to remove the soil type sensitivity by using a high frequency. | 0 | Theoretical and Fundamental Chemistry |
Herbicide volatilisation or spray drift may result in herbicide affecting neighboring fields or plants, particularly in windy conditions. Sometimes, the wrong field or plants may be sprayed due to error. | 1 | Applied and Interdisciplinary Chemistry |
The Dortmund Data Bank was founded in the 1970s at the University of Dortmund in Germany. The original reason for starting a vapor–liquid phase equilibria data collection was the development of the group contribution method UNIFAC which allows to estimate vapor pressures of mixtures.
The DDB has since been extended to many other properties and has increased dramatically in size also because of intensive (German) government aid. The funding has ended and the further development and maintenance is performed by DDBST GmbH, a company founded by members of the industrial chemistry chair of the Carl von Ossietzky University of Oldenburg, Germany.
Additional contributors are the DECHEMA, the FIZ CHEMIE (Berlin), the Technical University in Tallinn, and others. | 0 | Theoretical and Fundamental Chemistry |
In addition to water and ammonia, the clouds in the atmospheres of the gas giant planets contain ammonium sulfides. The reddish-brownish clouds are attributed to polysulfides, arising from the exposure of the ammonium sulfides to light. | 1 | Applied and Interdisciplinary Chemistry |
(See also Bridgman's thermodynamic equations for the use of exact differentials in the theory of thermodynamic equations)
Suppose we have five state functions , and . Suppose that the state space is two-dimensional and any of the five quantities are differentiable. Then by the chain rule
but also by the chain rule:
and
so that (by substituting (2) and (3) into (1)):
which implies that (by comparing (4) with (1)):
Letting in (5) gives:
Letting in (5) gives:
Letting and in (7) gives:
using ( gives the triple product rule: | 0 | Theoretical and Fundamental Chemistry |
Ancient milk glasses used crystals of calcium antimonate, formed in the melt from calcium present in the glass and an antimony additive. Opaque yellow glasses contained crystals of lead antimonate; bindheimite mineral may have been used as the additive. Under oxidizing condition, lead also forms incompletely dissolved lead pyroantimonate (PbSbO). From 2nd century BC tin oxide appears in use as opacifier, likely in the form of cassiterite mineral. Opaque yellow can be produced as lead stannate; the color is paler than the lead antimonate one. Later calcium and sodium phosphates became used; bone ash contains calcium phosphate in a high proportion. Calcium fluoride was also used, especially in China.
For dental ceramics, several approaches are in use. Spodumene or mica crystals can be precipitated. Fluorides of aluminium, calcium, barium, and magnesium can be used with suitable heat treatment. Tin oxide can be used, but zirconia and titania give better results; for titania, the appropriate resulting particle size is between submicron to 20 μm. Another desirable opacifier is zinc oxide.
Opacifiers must also form small particles in the system. Opacifiers are generally inert. | 0 | Theoretical and Fundamental Chemistry |
Compressed-air engines were used in trams and shunters, and eventually found a successful niche in mining locomotives, although in the end they were replaced by electric trains, underground. Over the years designs increased in complexity, resulting in a triple expansion engine with air-to-air reheaters between each stage. For more information see Fireless locomotive and Mekarski system. | 1 | Applied and Interdisciplinary Chemistry |
The Griess test is an analytical chemistry test which detects the presence of nitrite ion in solution. One of its most important uses is the determination of nitrite in drinking water. The Griess diazotization reaction, on which the Griess reagent relies, was first described in 1858 by Peter Griess. The test has also been widely used for the detection of nitrates (N-oxidation state = 5+), which are a common component of explosives, as they can be reduced to nitrites (N-oxidation state = 3+) and detected with the Griess test. | 0 | Theoretical and Fundamental Chemistry |
In the 15th century, the finery process, another process which shares the air-blowing principle with the Bessemer process, was developed in Europe. In 1740, Benjamin Huntsman developed the crucible technique for steel manufacture, at his workshop in the district of Handsworth in Sheffield. This process had an enormous impact on the quantity and quality of steel production, but it was unrelated to the Bessemer-type process employing decarburization.
The Japanese may have made use of a Bessemer-type process, which was observed by European travellers in the 17th century. The adventurer Johan Albrecht de Mandelslo describes the process in a book published in English in 1669. He writes, "They have, among others, particular invention for the melting of iron, without the using of fire, casting it into a tun done about on the inside without about half a foot of earth, where they keep it with continual blowing, take it out by ladles full, to give it what form they please." According to historian Donald Wagner, Mandelslo did not personally visit Japan, so his description of the process is likely derived from accounts of other Europeans who had traveled to Japan. Wagner believes that the Japanese process may have been similar to the Bessemer process, but cautions that alternative explanations are also plausible. | 1 | Applied and Interdisciplinary Chemistry |
Trail pheromone deposition from an organism is correlated with its environment. In the event where a food source is identified and a trail pheromone is deposited, certain wildlife may flock towards or away from the trail causing temporary or dispersal of the population or individual. With relocation of wildlife, surrounding plant life may change as well; for example, pollen attached to the migrating organism is also relocating, thus may potentially regenerate in different patches. | 1 | Applied and Interdisciplinary Chemistry |
All sulfate-reducing organisms are strict anaerobes. Because sulfate is energetically stable, before it can be metabolized it must first be activated by adenylation to form APS (adenosine 5’-phosphosulfate) thereby consuming ATP. The APS is then reduced by the enzyme APS reductase to form sulfite () and AMP. In organisms that use carbon compounds as electron donors, the ATP consumed is accounted for by fermentation of the carbon substrate. The hydrogen produced during fermentation is actually what drives respiration during sulfate reduction. | 1 | Applied and Interdisciplinary Chemistry |
Count median aerodynamic diameter (CMAD) is only used rarely. Half of the particles (by count) of a given aerosol have the aerodynamic diameter smaller than the CMAD, and the other half larger. A similar quantity, count median (geometric) diameter (CMD) is more common. | 0 | Theoretical and Fundamental Chemistry |
Porphyrin complexes consist of a square planar MN core. The periphery of the porphyrins, consisting of sp-hybridized carbons, generally display small deviations from planarity. "Ruffled" or saddle-shaped porphyrins is attributed to interactions of the system with its environment. Additionally, the metal is often not centered in the N plane. For free porphyrins, the two pyrrole protons are mutually trans and project out of the N plane. These nonplanar distortions are associated with altered chemical and physical properties. Chlorophyll-rings are more distinctly nonplanar, but they are more saturated than porphyrins. | 1 | Applied and Interdisciplinary Chemistry |
A monoisotopic element is an element which has only a single stable isotope (nuclide). There are 26 such elements, as listed.
Stability is experimentally defined for chemical elements, as there are a number of stable nuclides with atomic numbers over ~40 which are theoretically unstable, but apparently have half-lives so long that they have not been observed either directly or indirectly (from measurement of products) to decay.
Monoisotopic elements are characterized, except in one case, by odd numbers of protons (odd Z), and even numbers of neutrons. Because of the energy gain from nuclear pairing, the odd number of protons imparts instability to isotopes of an odd Z, which in heavier elements requires a completely paired set of neutrons to offset this tendency into stability. (The five stable nuclides with odd Z and odd neutron numbers are hydrogen-2, lithium-6, boron-10, nitrogen-14, and tantalum-180m1.)
The single monoisotopic exception to the odd Z rule is beryllium; its single stable, primordial isotope, beryllium-9, has 4 protons and 5 neutrons. This element is prevented from having a stable isotope with equal numbers of neutrons and protons (beryllium-8, with 4 of each) by its instability toward alpha decay, which is favored due to the extremely tight binding of helium-4 nuclei. It is prevented from having a stable isotope with 4 protons and 6 neutrons by the very large mismatch in proton/neutron ratio for such a light element. (Nevertheless, beryllium-10 has a half-life of 1.36 million years, which is too short to be primordial, but still indicates unusual stability for a light isotope with such an imbalance.) | 0 | Theoretical and Fundamental Chemistry |
Sewage treatment plants (STP) based on activated sludge often cover large surface areas, necessitated mainly by the large settling tanks. To build compact STP's, biomass can be grown as biofilms on a carrier material, or as fast settling aerobic granular sludge without a carrier. Recent research showed the advantages of a discontinuously fed system, in which it is possible to grow stable granulated sludge under aerobic conditions.
Simultaneous Chemical oxygen demand, and Nitrogen and Phosphorus removal, can be easily integrated in a discontinuous fed system. Because of the high settling capacity of the granules, the use of a traditional settler is unnecessary. Therefore, the installation can be built very compact, needing only 20% of the surface area of conventional activated sludge systems. | 1 | Applied and Interdisciplinary Chemistry |
Only certain combinations of symmetry elements are possible in a space group. Translations are always present, and the space group P1 has only translations and the identity element. The presence of mirrors implies glide planes as well, and the presence of rotation axes implies screw axes as well, but the converses are not true. An inversion and a mirror implies two-fold screw axes, and so on. | 0 | Theoretical and Fundamental Chemistry |
The table below lists some of the properties of the BTX aromatic hydrocarbons, all of which are liquids at typical room conditions: | 0 | Theoretical and Fundamental Chemistry |
Patients receiving chronic treatment are relatively resistance to nondepolarising NMBAs due to the accelerated clearance. | 1 | Applied and Interdisciplinary Chemistry |
Flush toilets often have some siphon effect as the bowl empties.
Some toilets also use the siphon principle to obtain the actual flush from the cistern. The flush is triggered by a lever or handle that operates a simple diaphragm-like piston pump that lifts enough water to the crest of the siphon to start the flow of water which then completely empties the contents of the cistern into the toilet bowl. The advantage of this system was that no water would leak from the cistern excepting when flushed. These were mandatory in the UK until 2011.
Early urinals incorporated a siphon in the cistern which would flush automatically on a regular cycle because there was a constant trickle of clean water being fed to the cistern by a slightly open valve. | 1 | Applied and Interdisciplinary Chemistry |
Host-directed therapeutics, also called host targeted therapeutics, act via a host-mediated response to pathogens rather than acting directly on the pathogen, like traditional antibiotics. They can change the local environment in which the pathogen exists to make it less favorable for the pathogen to live and/or grow. With these therapies, pathogen killing, e.g.bactericidal effects, will likely only occur when it is co-delivered with a traditional agent that acts directly on the pathogen, such as an antibiotic, antifungal, or antiparasitic agent. Several antiviral agents are host-directed therapeutics, and simply slow the virus progression rather than kill the virus. Host-directed therapeutics may limit pathogen proliferation, e.g., have bacteriostatic effects. Certain agents also have the ability to reduce bacterial load by enhancing host cell responses even in the absence of traditional antimicrobial agents. | 1 | Applied and Interdisciplinary Chemistry |
Chargaff's rules (given by Erwin Chargaff) state that in the DNA of any species and any organism, the amount of guanine should be equal to the amount of cytosine and the amount of adenine should be equal to the amount of thymine. Further, a 1:1 stoichiometric ratio of purine and pyrimidine bases (i.e., ) should exist. This pattern is found in both strands of the DNA. They were discovered by Austrian-born chemist Erwin Chargaff in the late 1940s. | 1 | Applied and Interdisciplinary Chemistry |
In spectroscopy a band head is the abrupt edge of a spectroscopic band. When a band is described as degrading to the violet, it means that for wavelengths above the band head wavelength, the spectrum is dark as the band comes to a sudden stop(just above/after the head), and below the wavelength the brightness of the band weakens gradually. A band that degrades to the red, conversely means that the band head is a lower limit on wavelength for the band, and it fades off toward longer wavelengths, which in visible light is the red end of the spectrum.
If a band spectrum is examined at high resolution it consists of many lines. At a band head the numbers often increase to a limit, or otherwise a series of lines may approach from one side and then reverse at the band head. The lines pile up on top of each other at the band head, and may not be viewed separately. They have become unresolvable. | 0 | Theoretical and Fundamental Chemistry |
Due to the threat of punishment and the potential scrutiny he feared from his peers within the scientific community, Newton may have deliberately left his work on alchemical subjects unpublished. Newton was well known as being highly sensitive to criticism, such as the numerous instances when he was criticized by Robert Hooke, and his admitted reluctance to publish any substantial information regarding calculus before 1693. A perfectionist by nature, Newton also refrained from publication of material that he felt was incomplete, as evident from a 38-year gap from Newton's conception of calculus in 1666 and its final full publication in 1704, which would ultimately lead to the infamous Leibniz–Newton calculus controversy.
Most of the scientists manuscript heritage after his death passed to John Conduitt, the husband of his niece Catherine. To evaluate the manuscripts, physician Thomas Pellet was involved, who decided that only "the Chronology of Ancient Kingdoms", an unreleased fragment of "Principia", "Observations upon the Prophesies of Daniel and the Apocalypse of St. John" and "Paradoxical Questions Concerning the Morals and Actions of Athanasius and His Followers" were suitable for publication. The remaining manuscripts, according to Pellet, were "foul draughts of the Prophetic stile" and were not suitable for publication. After the death of J. Conduitt in 1737, manuscripts were transferred to Catherine, who unsuccessfully tried to publish theological notes of her uncle. She consulted with Newtons friend, the theologian Arthur Ashley Sykes (1684–1756). Sykes kept 11 manuscripts for himself, and the rest of the archive passed into the family of Catherines daughter, who married the John Wallop, Viscount Lymington, and was then owned by the Earls of Portsmouth. Sykes documents after his death came to the Rev. Jeffery Ekins (d. 1791) and were kept in the family of the latter until they were presented to the New College, Oxford in 1872. Until the mid-19th century, few had access to the Portsmouth collection, including David Brewster, a renowned physicist and biographer of Newton. In 1872, the fifth Earl of Portsmouth transferred part of the manuscripts (mainly of a physical and mathematical nature) to Cambridge University.
In 1936, a collection of Isaac Newtons unpublished works were auctioned by Sothebys on behalf of Gerard Wallop, 9th Earl of Portsmouth. Known as the "Portsmouth Papers", this material consisted of 329 lots of Newtons manuscripts, over a third of which were filled with content that appeared to be alchemical in nature. At the time of Newtons death this material was considered "unfit to publish" by Newton's estate, and consequently fell into obscurity until their somewhat sensational reemergence in 1936.
At the auction many of these documents, along with Newtons death mask, were purchased by economist John Maynard Keynes, who throughout his life collected many of Newtons alchemical writings. Much of the Keynes collection later passed to eccentric document collector Abraham Yahuda, who was himself a vigorous collector of Isaac Newton's original manuscripts.
Many of the documents collected by Keynes and Yahuda are now in the Jewish National and University Library in Jerusalem. In recent years, several projects have begun to gather, catalogue, and transcribe the fragmented collection of Newtons work on alchemical subjects and make them freely available for on-line access. Two of these are The Chymistry of Isaac Newton Project supported by the U.S. National Science Foundation, and The Newton Project' supported by the U.K. Arts and Humanities Research Board. In addition, The Jewish National and University Library has published a number of high-quality scanned images of various Newton documents. | 1 | Applied and Interdisciplinary Chemistry |
Through a variety of physical and chemical processes, chemical elements change in concentration and move around in what are called geochemical cycles. An understanding of these changes requires both detailed observation and theoretical models. Each chemical compound, element or isotope has a concentration that is a function of position and time, but it is impractical to model the full variability. Instead, in an approach borrowed from chemical engineering, geochemists average the concentration over regions of the Earth called geochemical reservoirs. The choice of reservoir depends on the problem; for example, the ocean may be a single reservoir or be split into multiple reservoirs. In a type of model called a box model, a reservoir is represented by a box with inputs and outputs.
Geochemical models generally involve feedback. In the simplest case of a linear cycle, either the input or the output from a reservoir is proportional to the concentration. For example, salt is removed from the ocean by formation of evaporites, and given a constant rate of evaporation in evaporite basins, the rate of removal of salt should be proportional to its concentration. For a given component , if the input to a reservoir is a constant and the output is for some constant , then the mass balance equation is
This expresses the fact that any change in mass must be balanced by changes in the input or output. On a time scale of , the system approaches a steady state in which . The residence time is defined as
where and are the input and output rates. In the above example, the steady-state input and output rates are both equal to , so .
If the input and output rates are nonlinear functions of , they may still be closely balanced over time scales much greater than the residence time; otherwise, there will be large fluctuations in . In that case, the system is always close to a steady-state and the lowest order expansion of the mass balance equation will lead to a linear equation like Equation (). In most systems, one or both of the input and output depend on , resulting in feedback that tends to maintain the steady-state. If an external forcing perturbs the system, it will return to the steady-state on a time scale of . | 0 | Theoretical and Fundamental Chemistry |
In 2010, Shanon was awarded the Chevening Scholarship to pursue his Master of Arts (MA) in Religion in Contemporary Society at Kings College London. He completed his MA in 2011 and won the Shelford MA Prize from Kings School of Arts and Humanities.
He is currently a doctoral candidate at King's College London. | 1 | Applied and Interdisciplinary Chemistry |
Bromocresol purple (BCP) or 5′,5″-dibromo-o-cresolsulfophthalein, is a dye of the triphenylmethane family (triarylmethane dyes) and a pH indicator. It is colored yellow below pH 5.2, and violet above pH 6.8. In its cyclic sulfonate ester form, it has a pK value of 6.3, and is usually prepared as a 0.04% aqueous solution. | 0 | Theoretical and Fundamental Chemistry |
The strontium radioisotopes are very important, as strontium is a calcium mimic which is incorporated in bone growth and therefore has a great ability to harm humans. On the other hand, this also allows Sr to be used in the open source radiotherapy of bone tumors. This tends to be used in palliative care to reduce the pain due to secondary tumors in the bones.
Strontium-90 is a strong beta emitter with a half-life of 28.8 years. Its fission product yield decreases as the mass of the fissile nuclide increases - fission of produces more than fission of with fission of in the middle. A map of Sr contamination around Chernobyl has been published by the IAEA. Due to its very small neutron absorption cross section, Strontium-90 is poorly suited for thermal neutron induced nuclear transmutation as a way of disposing of it.
Strontium-90 has been used in radioisotope thermoelectric generators (RTGs) in the past because of its relatively high power density (0.95 W/g for the metal, 0.46 W/g for the commonly used inert perovskite form Strontium titanate) and because it is easily extracted from spent fuel (both native Strontium metal and Strontium oxide react with water by forming soluble Strontium hydroxide). However, the increased availability of renewable energy for off-grid applications formerly served by RTGs as well as concern about orphan sources has led to a nigh-total abandonment of in RTGs. The few (largely space based) applications for RTGs that still exist are largely supplied by despite its higher cost, as it has a higher power density, longer half life and is easier shielded since it is an alpha emitter while Strontium-90 is a beta emitter. | 0 | Theoretical and Fundamental Chemistry |
With the Bay of Fundy having the highest tidal range in the world, most rivers draining into the upper bay between Nova Scotia and New Brunswick have significant tidal bores. They include:
* The Petitcodiac River formerly had the highest bore in North America at over in height, but causeway construction between Moncton and Riverview in the 1960s led to subsequent extensive sedimentation which reduced the bore to little more than a ripple. After considerable political controversy, the causeway gates were opened on April 14, 2010, as part of the Petitcodiac River Restoration Project and the tidal bore began to grow again. The restoration of the bore has been sufficient that in July 2013, professional surfers rode a -high wave up the Petitcodiac River from Belliveau Village to Moncton to establish a new North American record for continuous surfing.
* The Shubenacadie River in Nova Scotia. When the tidal bore approaches, completely drained riverbeds are filled. It has caused the deaths of several tourists who were in the riverbeds when the bore came in. Tour boat operators offer rafting excursions in the summer.
* The bore is fastest and highest on some of the smaller rivers that connect to the bay including the River Hebert and Maccan River on the Cumberland Basin, the St. Croix and Kennetcook rivers in the Minas Basin, and the Salmon River in Truro. | 1 | Applied and Interdisciplinary Chemistry |
Non-viral vectors for gene therapy present certain advantages over viral methods, such as large scale production and low host immunogenicity. However, non-viral methods initially produced lower levels of transfection and gene expression, and thus lower therapeutic efficacy. Newer technologies offer promise of solving these problems, with the advent of increased cell-specific targeting and subcellular trafficking control.
Methods for non-viral gene therapy include the injection of naked DNA, electroporation, the gene gun, sonoporation, magnetofection, the use of oligonucleotides, lipoplexes, dendrimers, and inorganic nanoparticles. These therapeutics can be administered directly or through scaffold enrichment.
More recent approaches, such as those performed by companies such as Ligandal, offer the possibility of creating cell-specific targeting technologies for a variety of gene therapy modalities, including RNA, DNA and gene editing tools such as CRISPR. Other companies, such as Arbutus Biopharma and Arcturus Therapeutics, offer non-viral, non-cell-targeted approaches that mainly exhibit liver trophism. In more recent years, startups such as Sixfold Bio, GenEdit, and Spotlight Therapeutics have begun to solve the non-viral gene delivery problem. Non-viral techniques offer the possibility of repeat dosing and greater tailorability of genetic payloads, which in the future will be more likely to take over viral-based delivery systems.
Companies such as Editas Medicine, Intellia Therapeutics, CRISPR Therapeutics, Casebia, Cellectis, Precision Biosciences, bluebird bio, Excision BioTherapeutics, and Sangamo have developed non-viral gene editing techniques, however frequently still use viruses for delivering gene insertion material following genomic cleavage by guided nucleases. These companies focus on gene editing, and still face major delivery hurdles.
BioNTech, Moderna Therapeutics and CureVac focus on delivery of mRNA payloads, which are necessarily non-viral delivery problems.
Alnylam, Dicerna Pharmaceuticals, and Ionis Pharmaceuticals focus on delivery of siRNA (antisense oligonucleotides) for gene suppression, which also necessitate non-viral delivery systems.
In academic contexts, a number of laboratories are working on delivery of PEGylated particles, which form serum protein coronas and chiefly exhibit LDL receptor mediated uptake in cells in vivo. | 1 | Applied and Interdisciplinary Chemistry |
Henry Walter Bates (1825–1892) was an English explorer-naturalist who surveyed the Amazon rainforest with Alfred Russel Wallace in 1848. While Wallace returned in 1852, Bates remained for over a decade. Batess field research included collecting almost a hundred species of butterflies from the families Ithomiinae and Heliconiinae, as well as thousands of other insects specimens. In sorting these butterflies into similar groups based on appearance, inconsistencies began to arise. Some appeared superficially similar to others, so much so that even Bates could not tell some species apart based only on wing appearance. However, closer examination of less obvious morphological characters seemed to show that they were not even closely related. Shortly after his return to England, he read a paper on his theory of mimicry at a meeting of the Linnean Society of London on 21 November 1861, which was then published in 1862 as Contributions to an Insect Fauna of the Amazon Valley in the societys Transactions. He elaborated on his experiences further in The Naturalist on the River Amazons.
Bates put forward the hypothesis that the close resemblance between unrelated species was an antipredator adaptation. He noted that some species showed very striking coloration and flew in a leisurely manner, almost as if taunting predators to eat them. He reasoned that these butterflies were unpalatable to birds and other insectivores, and were thus avoided by them. He extended that logic to forms that closely resembled such protected species and mimicked their warning coloration but not their toxicity.
This naturalistic explanation fitted well with the recent account of evolution by Wallace and Charles Darwin, as outlined in his famous 1859 book The Origin of Species. Because the Darwinian explanation required no supernatural forces, it met with considerable criticism from anti-evolutionists, both in academic circles and in the broader social realm. | 1 | Applied and Interdisciplinary Chemistry |
ISO standard 1133-1 governs the procedure for measurement of the melt flow rate. The procedure for determining MFI is as follows:
# A small amount of the polymer sample (around 4 to 5 grams) is taken in the specially designed MFI apparatus. A die with an opening of typically around 2 mm diameter is inserted into the apparatus.
# The material is packed properly inside the barrel to avoid formation of air pockets.
# A piston is introduced which acts as the medium that causes extrusion of the molten polymer.
# The sample is preheated for a specified amount of time: 5 min at 190 °C for polyethylene and 6 min at 230 °C for polypropylene.
# After the preheating a specified weight is introduced onto the piston. Examples of standard weights are 2.16 kg, 5 kg, etc.
# The weight exerts a force on the molten polymer and it immediately starts flowing through the die.
# A sample of the melt is taken after the desired period of time and is weighed accurately.
# MFI is expressed in grams of polymer per 10 minutes of duration of the test.
Synonyms of Melt Flow Index are Melt Flow Rate and Melt Index. More commonly used are their abbreviations: MFI, MFR and MI.
Confusingly, MFR may also indicate "melt flow ratio", the ratio between two melt flow rates at different gravimetric weights. More accurately, this should be reported as FRR (flow rate ratio), or simply flow ratio. FRR is commonly used as an indication of the way in which rheological behavior is influenced by the molecular mass distribution of the material.
formerly: (MFI = Melt Flow Index) → currently: (MFR = Melt mass-Flow Rate)
formerly: (MVI = Melt Volume Index) → currently: (MVR = Melt Volume-flow Rate)
formerly: (MFR = Melt Flow Ratio) → currently: (FRR = Flow Rate Ratio)
The flow parameter that is readily accessible to most processors is the MFI. MFI is often used to determine how a polymer will process. However, MFI takes no account of the shear, shear rate or shear history and as such is not a good measure of the processing window of a polymer. It is a single-point viscosity measurement at a relatively low shear rate and temperature. Earlier, it was often said that MFI give a ‘dot’ when actually what is needed is a ‘plot’ for the polymer processors. However, this is not true now because of a unique approach developed for estimating the rheogram merely from the knowledge of the MFI.
The MFI device is not an extruder in the conventional polymer processing sense in that there is no screw to compress, heat and shear the polymer. MFI additionally does not take account of long chain branching nor the differences between shear and elongational rheology. Therefore, two polymers with the same MFI will not behave the same under any given processing conditions.
The relationship between MFI and temperature can be used to obtain the activation energies for polymers. The activation energies developed from MFI values has the advantage of simplicity and easy availability. The concept of obtaining activation energy from MFI can be extended to copolymers as well wherein there exists an anomalous temperature dependence of melt viscosity leading to the existence of two distinct values of activation energies for each copolymer.
For a detailed numerical simulation of the melt flow index, see or. | 0 | Theoretical and Fundamental Chemistry |
This process allows for reheating of one or more melt inclusions in a furnace held at a constant pressure of one atmosphere to their original melt temperatures and then rapidly quenching in water to produce a homogenous glass phase. | 0 | Theoretical and Fundamental Chemistry |
Titer (American English) or titre (British English) is a way of expressing concentration. Titer testing employs serial dilution to obtain approximate quantitative information from an analytical procedure that inherently only evaluates as positive or negative. The titer corresponds to the highest dilution factor that still yields a positive reading. For example, positive readings in the first 8 serial, twofold dilutions translate into a titer of 1:256 (i.e., 2). Titres are sometimes expressed by the denominator only, for example 1:256 is written 256.
The term also has two other, conflicting meanings. In titration, the titer is the ratio of actual to nominal concentration of a titrant, e.g. a titer of 0.5 would require 1/0.5 = 2 times more titrant than nominal. This is to compensate for possible degradation of the titrant solution. Second, in textile engineering, titre is also a synonym for linear density. | 1 | Applied and Interdisciplinary Chemistry |
In 2007 a new family of triazole NNRTIs was presented by researchers from the pharmaceutical company Ardea Biosciences. The selected candidate from the screening executed was RDEA806 belonging to the family of triazoles. It has similar resistance profile against selected NNRTI resistant HIV-1 strains to other next generation NNRTIs. The candidate entered phase IIb clinical trials in the end of 2009, but no further trial have been initiated. Ardea was sold to AstraZeneca in 2012. | 1 | Applied and Interdisciplinary Chemistry |
The result of a T-RFLP profiling is a graph called electropherogram which is an intensity plot representation of an electrophoresis experiment (gel or capillary). In an electropherogram the X-axis marks the sizes of the fragments while the Y-axis marks the fluorescence intensity of each fragment. Thus, what appears on an electrophoresis gel as a band appears as a peak on the electropherogram whose integral is its total fluorescence. In a T–RFLP profile each peak assumingly corresponds to one genetic variant in the original sample while its height or area corresponds to its relative abundance in the specific community. Both assumptions listed above, however, are not always met. Often, several different bacteria in a population might give a single peak on the electropherogram due to the presence of a restriction site for the particular restriction enzyme used in the experiment at the same position. To overcome this problem and to increase the resolving power of this technique a single sample can be digested in parallel by several enzymes (often three) resulting in three T-RFLP profiles per sample each resolving some variants while missing others. Another modification which is sometimes used is to fluorescently label the reverse primer as well using a different dye, again resulting in two parallel profiles per sample each resolving a different number of variants.
In addition to convergence of two distinct genetic variants into a single peak artifacts might also appear, mainly in the form of false peaks. False peaks are generally of two types: background “noises” and “pseudo” TRFs. Background (noise) peaks are peaks resulting from the sensitivity of the detector in use. These peaks are often small in their intensity and usually form a problem in case the total intensity of the profile is low (i.e. low concentration of DNA). Because these peaks result from background noise they are normally irreproducible in replicate profiles, thus the problem can be tackled by producing a consensus profile from several replicates or by eliminating peaks below a certain threshold. Several other computational techniques were also introduced in order to deal with this problem. Pseudo TRFs, on the other hand, are reproducible peaks and are linear to the amount of DNA loaded. These peaks are thought to be the result of ssDNA annealing on to itself and creating double stranded random restriction sites which are later recognized by the restriction enzyme resulting in a terminal fragment which does not represent any genuine genetic variant. It has been suggested that applying a DNA exonuclease such as the Mung bean exonuclease prior to the digestion stage might eliminate such artifact. | 1 | Applied and Interdisciplinary Chemistry |
Three patients' deaths have been reported in gene therapy trials, putting the field under close scrutiny. The first was that of Jesse Gelsinger, who died in 1999, because of immune rejection response. One X-SCID patient died of leukemia in 2003. In 2007, a rheumatoid arthritis patient died from an infection; the subsequent investigation concluded that the death was not related to gene therapy. | 1 | Applied and Interdisciplinary Chemistry |
Some trace fossils can be used as local index fossils, to date the rocks in which they are found, such as the burrow Arenicolites franconicus which occurs only in a layer of the Triassic Muschelkalk epoch, throughout wide areas in southern Germany.
The base of the Cambrian period is defined by the first appearance of the trace fossil Treptichnus pedum.
Trace fossils have a further utility, as many appear before the organism thought to create them, extending their stratigraphic range. | 1 | Applied and Interdisciplinary Chemistry |
Other compounds having different elements in the corners, various atoms or groups bonded to the corners are all part of this class of structures.
Inorganic cubane-type clusters include selenium tetrachloride, tellurium tetrachloride, and sodium silox.
Cubane clusters are common throughout bioinorganic chemistry. Ferredoxins containing [FeS] iron–sulfur clusters are pervasive in nature. The four iron atoms and four sulfur atoms form an alternating arrangement at the corners. The whole cluster is typically anchored by coordination of the iron atoms, usually with cysteine residues. In this way, each Fe center achieves tetrahedral coordination geometry. Some [FeS] clusters arise via dimerization of square-shaped [FeS] precursors. Many synthetic analogues are known including heterometallic derivatives.
Several alkyllithium compounds exist as clusters in solution, typically tetramers, with the formula [RLi]. Examples include methyllithium and tert-butyllithium. The individual RLi molecules are not observed. The four lithium atoms and the carbon from each alkyl group bonded to them occupy alternating vertices of the cube, with the additional atoms of the alkyl groups projecting off their respective corners.
Octaazacubane is a hypothetical allotrope of nitrogen with formula N; the nitrogen atoms are the corners of the cube. Like the carbon-based cubane compounds, octaazacubane is predicted to be highly unstable due to angle strain at the corners, and it also does not enjoy the kinetic stability seen for its organic analogues. | 0 | Theoretical and Fundamental Chemistry |
The Pleuger rudder (also known as a Dutch rudder) is a power assisted ship's rudder. It creates a flow of water in the direction the rudder points powered by an auxiliary electric motor. This aids maneuverability at low speeds greatly, since it operates on a similar principle to a thruster.
A ducted propeller is mounted as an integral part of the rudder and is fixed to it. The duct is a Kort nozzle and enables the propeller to develop more thrust than an unducted propeller.
The Pleuger rudder is necessarily mounted in the flow from the main engine's propeller in a ship with an odd number of propellers. If the Pleuger and the main engine are run at the same time, the Pleuger can often be torn away. The thrust produced by the Pleuger rudder is sufficient to power the ship in slow speed maneuvers when the force required to move the vessel is relatively small.
The Pleuger rudder is meant to be assisting in the fast maneuverability of ships, in tight harbor operations. Thus, it is only an improvement of rudder by controlling the water flow pattern passing a rudder and thus giving it an artificial flow and thus an extra power to steer even in slow engine r.p.m. It is absolutely not a substitute for a propeller, without which the mammoth energy required to propel a ship through the water is hard to generate. | 1 | Applied and Interdisciplinary Chemistry |
Inevitably, [4+4] photocycloadditions carry the side reaction of [2+2] photocycloadditions. However, since these reactions are reversible, the most stable product may be formed through thermodynamic control. | 0 | Theoretical and Fundamental Chemistry |
Although isomerization of proteins has been known about since 1968 when it was discovered by C. Tanford, proline isomerization and its use as a noncovalent histone tail modification was not discovered until 2006 by Nelson and his colleagues. | 0 | Theoretical and Fundamental Chemistry |
Essentially there are two types of chiral inversion, unidirectional and bidirectional. Inversion process is dependent on species and substrate.
;Unidirectional: chiral inversion (enzyme mediated) was described only with 2-arylpropionate nonsteroidal anti-inflammatory drugs (NSAIDs), namely ibuprofen, ketoprofen, fenoprofen, benoxaprophen, etc. For this group, only S-enantiomer (eutomer) is active i.e. has analgesic and anti-inflammatory effect. In the body, only inactive R-enantiomer can undergo chiral inversion by hepatic enzymes into the active S-enantiomer and not vice versa. The “inactive” R-isomer (distomer) may be responsible for the gastrointestinal irritation and related side-effects associated with NSAIDs. In certain situations, carbenicillin, ethiazide, etoposide, zopiclone, pantoprazole, clopidogrel, ketorolac, albendazole-sulfoxide, lifibrol, and 5-aryl-thiazolidinedione also go through unidirectional chiral inversion. Chiral inversions were found to happen in a group of important compounds called α-amino acids. Amino acids exist in two mirror-image versions (D- and L- configurations). Several D-amino acids, like D-methionine, D-proline, D-serine, D-alanine, D-aspartate, D-leucine, and D-phenylalanine, have been shown to go through unidirectional chiral inversion in mammals.
;Bidirectional: chiral inversion or racemization type of inversion is shown by pharmaceutical drugs including 3-hydroxy-benzodiazapine class of drugs (oxazepam, lorazepam, temazepam), thalidomide, and tiaprofenic acid. A brief list of select pharmaceutical drugs that go through chiral inversion are presented in Table below.. | 0 | Theoretical and Fundamental Chemistry |
At the northern end there are salt flats, which include a wetland of international importance. This area is preserved as a natural park administered by the regional government: the (‘San Pedro del Pinatar salt flats and sand beaches’). The microbes that live in this coastal lagoon have been recently described.
The islets and the few coastal places without permanent human constructions are a protected landscape: the (‘Mar Menor open areas and islands’).
In 1994 the Mar Menor was included on the Ramsar Convention list for the conservation and sustainable utilisation of wetlands.
The Mar Menor is also part of a Specially Protected Area of Mediterranean Importance and is a Special Protection Area (ZEPA in Spanish) for bird life.
In July 2016 pollution was reportedly so severe as to render the area close to ecological collapse, following 18 years of neglected warnings. The public prosecutors office is investigating allegations of negligence against the relevant authorities, which are governed by the conservative Peoples Party
In May 2017 all beaches of the Mar Menor were stripped of their Blue Flag status as a result of the polluted condition of the Mar Menor in 2016.
In October 2019 the pollution entering after floods in September led to thousands of dead fish lining the beaches, having suffocated due to a lack of oxygen. Intensive farming in surrounding areas leads to high levels of nitrates, ammonium and phosphates from fertilizers being washed into the lagoon, causing eutrophication, an excessive growth of algae and bacteria that deprives the water of oxygen.
A similar event occurred in August 2021, with four to five tons of dead fish being removed from the lagoon within a week. Shortly thereafter, a large demonstration took place, with 70,000 people surrounding the entire lagoon on August 28, 2021. | 1 | Applied and Interdisciplinary Chemistry |
The evidence suggests that there is a general interdependence between base composition patterns and coding region availability. The coding region is thought to contain a higher GC-content than non-coding regions. There is further research that discovered that the longer the coding strand, the higher the GC-content. Short coding strands are comparatively still GC-poor, similar to the low GC-content of the base composition translational stop codons like TAG, TAA, and TGA.
GC-rich areas are also where the ratio point mutation type is altered slightly: there are more transitions, which are changes from purine to purine or pyrimidine to pyrimidine, compared to transversions, which are changes from purine to pyrimidine or pyrimidine to purine. The transitions are less likely to change the encoded amino acid and remain a silent mutation (especially if they occur in the third nucleotide of a codon) which is usually beneficial to the organism during translation and protein formation.
This indicates that essential coding regions (gene-rich) are higher in GC-content and more stable and resistant to mutation compared to accessory and non-essential regions (gene-poor). However, it is still unclear whether this came about through neutral and random mutation or through a pattern of selection. There is also debate on whether the methods used, such as gene windows, to ascertain the relationship between GC-content and coding region are accurate and unbiased. | 1 | Applied and Interdisciplinary Chemistry |
Methylated DNA immunoprecipitation (MeDIP or mDIP) is a large-scale (chromosome- or genome-wide) purification technique in molecular biology that is used to enrich for methylated DNA sequences. It consists of isolating methylated DNA fragments via an antibody raised against 5-methylcytosine (5mC). This technique was first described by Weber M. et al. in 2005 and has helped pave the way for viable methylome-level assessment efforts, as the purified fraction of methylated DNA can be input to high-throughput DNA detection methods such as high-resolution DNA microarrays (MeDIP-chip) or next-generation sequencing (MeDIP-seq). Nonetheless, understanding of the methylome remains rudimentary; its study is complicated by the fact that, like other epigenetic properties, patterns vary from cell-type to cell-type. | 1 | Applied and Interdisciplinary Chemistry |
Current researchers have developed gene transfer systems on the basis of conservative transposition which can integrate new DNA in both invertebrates and vertebrate genomes. Scientists alter the genetic sequence of a transposon in a laboratory setting, then insert this sequence into a vector which is then inserted into a target cell. The transposase coding region of these transposons is replaced by a gene of interest intended to be integrated into the genome. Conservative transposition is induced by the expression of transposase from another source within the cell, since the transposon no longer contains the transposase coding region to be self sufficient. Generally a second vector is prepared and inserted into the cell for expression of transposase. This technique is used in transgenesis and insertional mutagenesis research fields. The Sleeping Beauty transposon system is an example of gene transfer system developed for use in vertebrates. Further development in integration site preferences of transposable elements is expected to advance the technologies of human gene therapy. | 1 | Applied and Interdisciplinary Chemistry |
The western meadow vole (Microtus drummondii) is a species of North American vole found in midwestern and western Canada and the United States, and formerly in Mexico. It was formerly considered conspecific with the eastern meadow vole (M. pennsylvanicus), but genetic studies indicate that it is a distinct species. | 1 | Applied and Interdisciplinary Chemistry |
* Further muscle development (especially upper body)
* Increased sweat and changes in body odor
* Prominence of veins and coarser skin
* Alterations in blood lipids (cholesterol and triglycerides)
* Increased red blood cell count | 1 | Applied and Interdisciplinary Chemistry |
The siRNA-induced post transcriptional gene silencing is initiated by the assembly of the RNA-induced silencing complex (RISC). The complex silences certain gene expression by cleaving the mRNA molecules coding the target genes. To begin the process, one of the two siRNA strands, the guide strand (anti-sense strand), will be loaded into the RISC while the other strand, the passenger strand (sense strand), is degraded. Certain Dicer enzymes may be responsible for loading the guide strand into RISC. Then, the siRNA scans for and directs RISC to perfectly complementary sequence on the mRNA molecules. The cleavage of the mRNA molecules is thought to be catalyzed by the Piwi domain of Argonaute proteins of the RISC. The mRNA molecule is then cut precisely by cleaving the phosphodiester bond between the target nucleotides which are paired to siRNA residues 10 and 11, counting from the 5end. This cleavage results in mRNA fragments that are further degraded by cellular exonucleases. The 5 fragment is degraded from its 3 end by exosome while the 3 fragment is degraded from its 5 end by 5 -3' exoribonuclease 1(XRN1). Dissociation of the target mRNA strand from RISC after the cleavage allow more mRNA to be silenced. This dissociation process is likely to be promoted by extrinsic factors driven by ATP hydrolysis.
Sometimes cleavage of the target mRNA molecule does not occur. In some cases, the endonucleolytic cleavage of the phosphodiester backbone may be suppressed by mismatches of siRNA and target mRNA near the cleaving site. Other times, the Argonaute proteins of the RISC lack endonuclease activity even when the target mRNA and siRNA are perfectly paired. In such cases, gene expression will be silenced by an miRNA induced mechanism instead
Piwi-interacting RNAs are responsible for the silencing of transposons and are not siRNAs. PIWI-interacting RNAs (piRNAs) are a recently-discovered class of small non-coding RNAs (ncRNAs) with a length of 21-35 nucleotides. They play a role in gene expression regulation, transposon silencing, and viral infection inhibition. Once considered as "dark matter" of ncRNAs, piRNAs emerged as important players in multiple cellular functions in different organisms. | 1 | Applied and Interdisciplinary Chemistry |
A sublimatory or sublimation apparatus is equipment, commonly laboratory glassware, for purification of compounds by selective sublimation. In principle, the operation resembles purification by distillation, except that the products do not pass through a liquid phase. | 0 | Theoretical and Fundamental Chemistry |
Since they were discovered in the mid-1960s, histone modifications have been predicted to affect transcription. The fact that most of the early post-translational modifications found were concentrated within the tail extensions that protrude from the nucleosome core lead to two main theories regarding the mechanism of histone modification. The first of the theories suggested that they may affect electrostatic interactions between the histone tails and DNA to "loosen" chromatin structure. Later it was proposed that combinations of these modifications may create binding epitopes with which to recruit other proteins. Recently, given that more modifications have been found in the structured regions of histones, it has been put forward that these modifications may affect histone-DNA and histone-histone interactions within the nucleosome core. Modifications (such as acetylation or phosphorylation) that lower the charge of the globular histone core are predicted to "loosen" core-DNA association; the strength of the effect depends on location of the modification within the core.
Some modifications have been shown to be correlated with gene silencing; others seem to be correlated with gene activation. Common modifications include acetylation, methylation, or ubiquitination of lysine; methylation of arginine; and phosphorylation of serine. The information stored in this way is considered epigenetic, since it is not encoded in the DNA but is still inherited to daughter cells. The maintenance of a repressed or activated status of a gene is often necessary for cellular differentiation. | 1 | Applied and Interdisciplinary Chemistry |
When water is added to cement, each of the compounds undergoes hydration and contributes to the final state of the concrete. Only calcium silicates contribute to the strength. Tricalcium silicate is responsible for most of the early strength (first 7 days). Dicalcium silicate, which reacts more slowly, only contributes to late strength.
Calcium silicate hydrate (also shown as C-S-H) is a result of the reaction between the silicate phases of Portland cement and water. This reaction typically is expressed as:
also written in cement chemist notation, (CCN) as:
: 2 + 7 H → + 3 CH + heat
or, tricalcium silicate + water → calcium silicate hydrate + calcium hydroxide + heat
The stoichiometry of C-S-H in cement paste is variable and the state of chemically and physically bound water in its structure is not transparent, which is why "-" is used between C, S, and H.
Synthetic C-S-H can be prepared from the reaction of CaO and SiO in water or through the double precipitation method using various salts. These methods provide the flexibility of producing C-S-H at specific C/S (Ca/Si, or CaO/SiO) ratios. The C-S-H from cement phases can also be treated with an ammonium nitrate solution in order to induce calcium leaching, and so to achieve a given C/S ratio. | 0 | Theoretical and Fundamental Chemistry |
Aerobic granular sludge can be formed by applying specific process conditions that favour slow growing organisms such as PAOs (polyphosphate accumulating organisms) and GAOs (glycogen accumulating organisms). Another key part of granulation is selective wasting whereby slow settling floc-like sludge is discharged as waste sludge and faster settling biomass is retained. This process has been commercialized as Nereda process. | 1 | Applied and Interdisciplinary Chemistry |
The book An Album of Fluid Motion is a collection of black-and-white photographs of flow visualizations for different types of fluid flows. These flows include:
*Creeping flow
*Laminar flow
*Flow separation
*Vortices
*Fluid instability
*Fluid turbulence
*Free-surface flow
*Natural convection
*Subsonic flow
*Shock waves
*Supersonic flow
The book was self-published by its editor, Milton Van Dyke, fluid mechanics professor at Stanford University. | 1 | Applied and Interdisciplinary Chemistry |
Perhaps the simplest definition of electronegativity is that of Leland C. Allen, who has proposed that it is related to the average energy of the valence electrons in a free atom,
where ε are the one-electron energies of s- and p-electrons in the free atom and n are the number of s- and p-electrons in the valence shell. It is usual to apply a scaling factor, 1.75×10 for energies expressed in kilojoules per mole or 0.169 for energies measured in electronvolts, to give values that are numerically similar to Pauling electronegativities.
The one-electron energies can be determined directly from spectroscopic data, and so electronegativities calculated by this method are sometimes referred to as spectroscopic electronegativities. The necessary data are available for almost all elements, and this method allows the estimation of electronegativities for elements that cannot be treated by the other methods, e.g. francium, which has an Allen electronegativity of 0.67. However, it is not clear what should be considered to be valence electrons for the d- and f-block elements, which leads to an ambiguity for their electronegativities calculated by the Allen method.
On this scale, neon has the highest electronegativity of all elements, followed by fluorine, helium, and oxygen. | 0 | Theoretical and Fundamental Chemistry |
Calfactant, also known as Infasurf, is an intratracheal suspension derived from the natural surfactant in calf lungs. It is used in premature infants with lung surfactant deficiency that causes infant respiratory distress syndrome (IRDS). | 0 | Theoretical and Fundamental Chemistry |
Salting in refers to the effect where increasing the ionic strength of a solution increases the solubility of a solute, such as a protein. This effect tends to be observed at lower ionic strengths.
Protein solubility is a complex function of physicochemical nature of the protein, pH, temperature, and the concentration of the salt used. It also depends on whether the salt is kosmotropic, whereby the salt will stabilize water. The solubility of proteins usually increases slightly in the presence of salt, referred to as "salting in". However, at high concentrations of salt, the solubility of the proteins drop sharply and proteins can precipitate out, referred to as "salting out". | 0 | Theoretical and Fundamental Chemistry |
Many thiolate complexes are prepared by redox reactions. Organic disulfides oxidize low valence metals, as illustrated by the oxidation of titanocene dicarbonyl:
Some metal centers are oxidized by thiols, the coproduct being hydrogen gas:
These reactions may proceed by the oxidative addition of the thiol to Fe(0).
Thiols and especially thiolate salts are reducing agents. Consequently, they induce redox reactions with certain transition metals. This phenomenon is illustrated by the synthesis of cuprous thiolates from cupric precursors:
:4 HSCH + 2 CuO → 2 Cu(SCH) + (CHS) + 2 HO
Thiolate clusters of the type [FeS(SR)] occur in iron–sulfur proteins. Synthetic analogues can be prepared by combined redox and salt metathesis reactions:
:4 FeCl + 6 NaSR + 6 NaSH → Na[FeS(SR)] + 10 NaCl + 4 HCl + HS + RS | 0 | Theoretical and Fundamental Chemistry |
A heptose is a monosaccharide with seven carbon atoms.
They have either an aldehyde functional group in position 1 (aldoheptoses) or a ketone functional group in position 2, 3 or 4 (ketoheptoses). Ketoheptoses have 4 chiral centers, whereas aldoheptoses have 5. | 1 | Applied and Interdisciplinary Chemistry |
Copper tubes are made from the large billets of copper that are gradually worked and drawn down to the required size. As the tubes are drawn they are heat treated to produce the correct mechanical properties. The organic oils and greases used to lubricate the tubes during the drawing processes are broken down during the heat treatment and gradually coat the tube with a film of carbon. If the carbon is left in the bore of the tube then it disrupts the formation of the protective scale and allows the initiation of pits in the wall. The presence of deleterious films, such as carbon, has been prohibited by the British Standards in copper tubes since 1969. All copper tubes for water service are treated, usually by sand (or other nonferrous medium) blasting or acid pickling, to remove any films produced during manufacture with the result that Type 1 pitting initiated by carbon films is now very rare. | 1 | Applied and Interdisciplinary Chemistry |
The airborne visible/infrared imaging spectrometer (AVIRIS) is the second in a series of imaging spectrometer instruments developed at the Jet Propulsion Laboratory (JPL) for Earth remote sensing. This instrument uses scanning optics and four spectrometers to image a 614-pixel swath simultaneously in 224 adjacent spectral bands. | 0 | Theoretical and Fundamental Chemistry |
C-alkylation is a process for the formation of carbon-carbon bonds. The largest example of this takes place in the alkylation units of petrochemical plants, which convert low-molecular-weight alkenes into high octane gasoline components. Electron-rich species such as phenols are also commonly alkylated to produce a variety of products; examples include linear alkylbenzenes used in the production of surfactants like LAS, or butylated phenols like BHT, which are used as antioxidants. This can be achieved using either acid catalysts like Amberlyst, or Lewis acids like aluminium. On a laboratory scale the Friedel–Crafts reaction uses alkyl halides, as these are often easier to handle than their corresponding alkenes, which tend to be gasses. The reaction is catalysed by aluminium trichloride. This approach is rarely used industrially as alkyl halides are more expensive than alkenes. | 0 | Theoretical and Fundamental Chemistry |
Anthropogenic sources emit about 142 teragrams (1.42 × 10 kg) of carbon per year in the form of VOCs.
The major source of man-made VOCs are:
* Fossil fuel use and production, e.g. incompletely combusted fossil fuels or unintended evaporation of fuels. The most prevalent VOC is ethane, a relatively inert compound.
* Solvents used in coatings, paints, and inks. Approximately 12 billion litres of paint are produced annually. Typical solvents include aliphatic hydrocarbons, ethyl acetate, glycol ethers, and acetone. Motivated by cost, environmental concerns, and regulation, the paint and coating industries are increasingly shifting toward aqueous solvents.
* Compressed aerosol products, mainly butane and propane, estimated to contribute 1.3 billion tonnes of VOC emissions per year globally.
* Biofuel use, e.g., cooking oils in Asia and bioethanol in Brazil.
* Biomass combustion, especially from rain forests. Although combustion principally releases carbon dioxide and water, incomplete combustion affords a variety of VOCs. | 0 | Theoretical and Fundamental Chemistry |
Cerevisterol (5α-ergosta-7,22-diene-3β,5,6β-triol) is a sterol. Originally described in the 1930s from the yeast Saccharomyces cerevisiae, it has since been found in several other fungi and, recently, in deep water coral. Cerevisterol has some in vitro bioactive properties, including cytotoxicity to some mammalian cell lines. | 1 | Applied and Interdisciplinary Chemistry |
Particle aggregation is a widespread phenomenon, which spontaneously occurs in nature but is also widely explored in manufacturing. Some examples include.
Formation of river delta. When river water carrying suspended sediment particles reaches salty water, particle aggregation may be one of the factors responsible for river delta formation. Charged particles are stable in river's fresh water containing low levels of salt, but they become unstable in sea water containing high levels of salt. In the latter medium, the particles aggregate, the larger aggregates sediment, and thus create the river delta.
Papermaking. Retention aids are added to the pulp to accelerate paper formation. These aids are coagulating aids, which accelerate the aggregation between the cellulose fibers and filler particles. Frequently, cationic polyelectrolytes are being used for that purpose.
Water treatment. Treatment of municipal waste water normally includes a phase where fine solid particles are removed. This separation is achieved by addition of a flocculating or coagulating agent, which induce the aggregation of the suspended solids. The aggregates are normally separated by sedimentation, leading to sewage sludge. Commonly used flocculating agents in water treatment include multivalent metal ions (e.g., Fe or Al), polyelectrolytes, or both.
Cheese making. The key step in cheese production is the separation of the milk into solid curds and liquid whey. This separation is achieved by inducing the aggregation processes between casein micelles by acidifying the milk or adding rennet. The acidification neutralizes the carboxylate groups on the micelles and induces the aggregation. | 0 | Theoretical and Fundamental Chemistry |
* vials of dry chemicals
* metal wires, such as copper, nickel or zinc
* metal filings, such as iron
* graphite rods
* a balance and weights
* a measuring cylinder
* a thermometer
* a magnifying glass
* pipettes
* beakers, retorts, flasks, test tubes, U-tubes or other reaction vessels
* cork stoppers
* watch glasses
* glass and rubber tubing
* test tube holders, retort stands and clamps
* an alcohol burner or other heat source
* a filter funnel and filter paper
* universal indicator paper or litmus paper
* safety goggles
* an instruction manual | 1 | Applied and Interdisciplinary Chemistry |
The name octasulfur is the most commonly used for this chemical. It is systematically named cyclo-octasulfur (which is the preferred IUPAC name) and cyclooctasulfane. It is also the final member of the thiocane heterocylic series, where every carbon atom is substituted with a sulfur atom, thus this sulfur allotrope is systematically named octathiocane as well. | 1 | Applied and Interdisciplinary Chemistry |
Catalyst poisons lower catalyst activity. They are usually impurities in the synthesis gas. Permanent poisons cause irreversible loss of catalytic activity, while temporary poisons lower the activity while present. Sulfur compounds, phosphorus compounds, arsenic compounds, and chlorine compounds are permanent poisons. Oxygenic compounds like water, carbon monoxide, carbon dioxide, and oxygen are temporary poisons.
Although chemically inert components of the synthesis gas mixture such as noble gases or methane are not strictly poisons, they accumulate through the recycling of the process gases and thus lower the partial pressure of the reactants, which in turn slows conversion. | 0 | Theoretical and Fundamental Chemistry |
A number of schools have been named after Albert, including Albertus Magnus High School in Bardonia, New York; Albertus Magnus Lyceum in River Forest, Illinois; and Albertus Magnus College in New Haven, Connecticut.
Albertus Magnus Science Hall at Thomas Aquinas College, in Santa Paula, California, is named in honor of Albert. The main science buildings at Providence College and Aquinas College in Grand Rapids, Michigan, are also named after him.
The central square at the campus of the University of Cologne features a statue of Albert and is named after him. Made by Gerhard Marcks around 1950s, this statue is one of four replicas found in different places around the world (along with University of Jena, University of the Andes, and University of Houston).
The Academy for Science and Design in New Hampshire honored Albert by naming one of its four houses Magnus House.
As a tribute to the scholar's contributions to the law, the University of Houston Law Center displays a statue of Albert. It is located on the campus of the University of Houston.
The Albertus-Magnus-Gymnasium is found in Rottweil, Germany.
In Managua, Nicaragua, the Albertus Magnus International Institute, a business and economic development research center, was founded in 2004.
In the Philippines, the Albertus Magnus Building at the University of Santo Tomas that houses the Conservatory of Music, College of Tourism and Hospitality Management, College of Education, and UST Education High School is named in his honor. The Saint Albert the Great Science Academy in San Carlos City, Pangasinan, which offers preschool, elementary and high school education, takes pride in having St. Albert as their patron saint. Its main building was named Albertus Magnus Hall in 2008. San Alberto Magno Academy in Tubao, La Union is also dedicated in his honor. This century-old Catholic high school continues to live on its vision-mission up to this day, offering Senior High school courses.
Due to his contributions to natural philosophy, the bacterium Agrobacterium albertimagni, the plant species Alberta magna, the crustacean Bodigiella albertimagni, the fossil brachiopod Albasphe albertimagni, and the asteroid 20006 Albertus Magnus were named after him.
Numerous Catholic elementary and secondary schools are named for him, including schools in Toronto; Calgary; Cologne; and Dayton, Ohio.
The Albertus typeface is named after him.
At the University of Notre Dame du Lac in Notre Dame, Indiana, the Zahm Hall Chapel is dedicated to St. Albert the Great. Fr. John Zahm, C.S.C., after whom the mens residence hall is named, looked to St. Alberts example of using religion to illumine scientific discovery. Fr. Zahms work with the Bible and evolution is sometimes seen as a continuation of St. Alberts legacy.
The second largest student's fraternity of the Netherlands, located in the city of Groningen, is named [https://www.albertus.nl Albertus Magnus], in honor of the saint.
The Colegio Cientifico y Artistico de San Alberto, Hopelawn, New Jersey, USA with a sister school in Nueva Ecija, Philippines was founded in 1986 in honor of him who thought and taught that religion, the sciences and the arts may be advocated as subjects which should not contradict each other but should support one another to achieve wisdom and reason.
The Vosloorus catholic parish (located in Vosloorus Extension One, Ekurhuleni, Gauteng, South Africa) is named after the saint.
The [https://www.kath-ka-hardt.de/html/st_antonius_egg_leo.html catholic parish] in Leopoldshafen, near Karlsruhe in Germany is also named after him also considering the huge research center of the Karlsruhe Institute of Technology nearby, as he is the patron saint of scientists.
Since the death of King Albert I, the Kings Feast is celebrated in Belgium on Alberts feast day.
Edinburghs Catholic Chaplaincy serving the citys universities, is named after St Albert.
Sant'Alberto Magno is a titular church in Rome. | 1 | Applied and Interdisciplinary Chemistry |
Organisms such as limpets and sea stars use suction and mucus-like slimes to create Stefan adhesion, which makes pull-off much harder than lateral drag; this allows both attachment and mobility. Spores, embryos and juvenile forms may use temporary adhesives (often glycoproteins) to secure their initial attachment to surfaces favorable for colonization. Tacky and elastic secretions that act as pressure-sensitive adhesives, forming immediate attachments on contact, are preferable in the context of self-defense and predation. Molecular mechanisms include non-covalent interactions and polymer chain entanglement. Many biopolymers – proteins, carbohydrates, glycoproteins, and mucopolysaccharides – may be used to form hydrogels that contribute to temporary adhesion. | 1 | Applied and Interdisciplinary Chemistry |
There are several options to address biogenic sulfide corrosion problems: impairing HS formation, venting out the HS or using materials resistant to biogenic corrosion. For example, sewage flows more rapidly through steeper gradient sewers reducing time available for hydrogen sulfide generation. Likewise, removing sludge and sediments from the bottom of the pipes reduces the amount of anoxic areas responsible for sulfate reducing bacteria growth. Providing good ventilation of sewers can reduce atmospheric concentrations of hydrogen sulfide gas and may dry exposed sewer crowns, but this may create odor issues with neighbors around the venting shafts. Three other efficient methods can be used involving continuous operation of mechanical equipment: chemical reactant like calcium nitrate can be continuously added in the sewerage water to impair the HS formation, an active ventilation through odor treatment units to remove HS, or an injection of compressed air in pressurized mains to avoid the anaerobic condition to develop. In sewerage areas where biogenic sulfide corrosion is expected, acid resistant materials like calcium aluminate cements, PVC or vitrified clay pipe may be substituted to ordinary concrete or steel sewers.
Existing structures that have extensive exposure to biogenic corrosion such as sewer manholes and pump station wet wells can be rehabilitated. Rehabilitation can be done with materials such as a structural epoxy coating, this epoxy is designed to be both acid resistant and strengthen the compromised concrete structure. | 1 | Applied and Interdisciplinary Chemistry |
The driving force for titanium foam's replacement of existing materials in the aerospace sector results from the following five factors:
*Weight reduction: as a substitute for steels and nickel-based superalloys;
*Application temperature: as a substitute for aluminum and nickel-based alloys and steels
*Corrosion resistance: as a substitute for aluminum alloys and low-alloyed steels
*Galvanic compatibility: with polymer matrix composites as substitutes for aluminum alloys
*Space constraints: as substitutes for aluminum alloys and steels
The most urgent problem of engineering and its advanced branch of aerospace engineering is the efficient use of materials as well as increased service life. | 0 | Theoretical and Fundamental Chemistry |
The underlying flame physics can be understood with the help of an idealized model consisting of a uniform one-dimensional tube of unburnt and burned gaseous fuel, separated by a thin transitional region of width in which the burning occurs. The burning region is commonly referred to as the flame or flame front. In equilibrium, thermal diffusion across the flame front is balanced by the heat supplied by burning.
Two characteristic timescales are important here. The first is the thermal diffusion timescale , which is approximately equal to
where is the thermal diffusivity. The second is the burning timescale that strongly decreases with temperature, typically as
where is the activation barrier for the burning reaction and is the temperature developed as the result of burning; the value of this so-called "flame temperature" can be determined from the laws of thermodynamics.
For a stationary moving deflagration front, these two timescales must be equal: the heat generated by burning is equal to the heat carried away by heat transfer. This makes it possible to calculate the characteristic width of the flame front:
thus
Now, the thermal flame front propagates at a characteristic speed , which is simply equal to the flame width divided by the burn time:
This simplified model neglects the change of temperature and thus the burning rate across the deflagration front. This model also neglects the possible influence of turbulence. As a result, this derivation gives only the laminar flame speed—hence the designation . | 0 | Theoretical and Fundamental Chemistry |
Most of the applications of polymers with this effect are only suggestions for now, many possibilities have been proposed, but so far only a few have been used, the most important being medical devices and automotive elements, although the greatest success has been achieved with heat-shrinkable polyethylene, which is also an exception in the programming step, since it is processed in a different way. | 0 | Theoretical and Fundamental Chemistry |
Most commercial Mo/Tc generators use column chromatography, in which Mo in the form of molybdate, MoO is adsorbed onto acid alumina (AlO). When the Mo-99 decays it forms pertechnetate TcO, which, because of its single charge, is less tightly bound to the alumina. Pouring normal saline solution through the column of immobilized Mo elutes the soluble Tc, resulting in a saline solution containing the Tc as pertechnetate, with sodium as the counterion.
The solution of sodium pertechnetate may then be added in an appropriate concentration to the pharmaceutical kit to be used, or sodium pertechnetate can be used directly without pharmaceutical tagging for specific procedures requiring only the TcO as the primary radiopharmaceutical. A large percentage of the Tc generated by a Mo/Tc generator is produced in the first 3 parent half-lives, or approximately one week. Hence, clinical nuclear medicine units purchase at least one such generator per week or order several in a staggered fashion. | 0 | Theoretical and Fundamental Chemistry |
A bubble is made of transparent water enclosing transparent air. However, the soap film is as thin as the visible light wavelength, resulting in optical interference. This creates iridescence which, together with the bubbles spherical shape and fragility, contributes to its magical effect on children and adults alike. Each colour is the result of varying thicknesses of soap bubble film. Tom Noddy (who featured in the second episode of Marcus du Sautoys The Code) gave the analogy of looking at a contour map of the bubbles' surface. However, it has become a challenge to produce artificially coloured bubbles.
Byron, Melody & Enoch Swetland invented a patented non-toxic bubble (Tekno Bubbles) that glow under UV lighting. These bubbles look like ordinary high quality "clear" bubbles under normal lighting, but glow when exposed to true UV light. The brighter the UV lighting, the brighter they glow. The family sold them worldwide, but has since sold their company.
Adding coloured dye to bubble mixtures fails to produce coloured bubbles, because the dye attaches to the water molecules as opposed to the surfactant. Therefore, a colourless bubble forms with the dye falling to a point at the base. Dye chemist Dr. Ram Sabnis has developed a lactone dye that sticks to the surfactants, enabling brightly coloured bubbles to be formed. Crystal violet lactone is an example. Another man named Tim Kehoe invented a coloured bubble which loses its colour when exposed to pressure or oxygen, which he is now marketing online as Zubbles, which are non-toxic and non-staining. In 2010, Japanese astronaut Naoko Yamazaki demonstrated that it is possible to create coloured bubbles in microgravity. The reason is that the water molecules are spread evenly around the bubble in the low-gravity environment. | 1 | Applied and Interdisciplinary Chemistry |
The reactions best for pressure (geobarometers) are ones that have a large change in molar volume during the reaction. Higher pressures cause the reaction to decrease in total volume, and lighter pressures allow reaction to increase in total volume. Therefore, based on the proportion of minerals that have larger volumes versus the proportion of minerals that have smaller volumes, the pressure of the environment during the reaction can be calculated, as a function of temperature. Experiments must be done to calibrate each reaction and determine the rate at which the volume changes with changes in pressure. | 0 | Theoretical and Fundamental Chemistry |
The Otto Laporte Award (1972–2003) was an annual award by the American Physical Society (APS) to "recognize outstanding contributions to fluid dynamics" and to honour Otto Laporte (1902–1971). It was established as the Otto Laporte Memorial Lectureship by the APS Division of Fluid Dynamics in 1972, and became an APS award in 1985. The Otto Laporte Award was merged into the Fluid Dynamics Prize in 2004, in order to obtain one major prize in fluid dynamics by the APS. | 1 | Applied and Interdisciplinary Chemistry |
Nucleic acids consist of a chain of linked units called nucleotides. Each nucleotide consists of three subunits: a phosphate group and a sugar (ribose in the case of RNA, deoxyribose in DNA) make up the backbone of the nucleic acid strand, and attached to the sugar is one of a set of nucleobases. The nucleobases are important in base pairing of strands to form higher-level secondary and tertiary structures such as the famed double helix.
The possible letters are A, C, G, and T, representing the four nucleotide bases of a DNA strand – adenine, cytosine, guanine, thymine – covalently linked to a phosphodiester backbone. In the typical case, the sequences are printed abutting one another without gaps, as in the sequence AAAGTCTGAC, read left to right in the 5 to 3 direction. With regards to transcription, a sequence is on the coding strand if it has the same order as the transcribed RNA.
One sequence can be complementary to another sequence, meaning that they have the base on each position in the complementary (i.e., A to T, C to G) and in the reverse order. For example, the complementary sequence to TTAC is GTAA. If one strand of the double-stranded DNA is considered the sense strand, then the other strand, considered the antisense strand, will have the complementary sequence to the sense strand. | 1 | Applied and Interdisciplinary Chemistry |
Ionic compounds normally dissociate into their constituent ions when they dissolve in water. For example, for silver chloride:
The expression for the equilibrium constant for this reaction is:
where is the thermodynamic equilibrium constant and braces indicate activity. The activity of a pure solid is, by definition, equal to one.
When the solubility of the salt is very low the activity coefficients of the ions in solution are nearly equal to one. By setting them to be actually equal to one this expression reduces to the solubility product expression:
For 2:2 and 3:3 salts, such as CaSO and FePO, the general expression for the solubility product is the same as for a 1:1 electrolyte
: (electrical charges are omitted in general expressions, for simplicity of notation)
With an unsymmetrical salt like Ca(OH) the solubility expression is given by
Since the concentration of hydroxide ions is twice the concentration of calcium ions this reduces to
In general, with the chemical equilibrium
and the following table, showing the relationship between the solubility of a compound and the value of its solubility product, can be derived.
Solubility products are often expressed in logarithmic form. Thus, for calcium sulfate, with , . The smaller the value of K, or the more negative the log value, the lower the solubility.
Some salts are not fully dissociated in solution. Examples include MgSO, famously discovered by Manfred Eigen to be present in seawater as both an inner sphere complex and an outer sphere complex. The solubility of such salts is calculated by the method outlined in dissolution with reaction. | 0 | Theoretical and Fundamental Chemistry |
Atta-ur-Rahman (Urdu: عطاالرحمان; b. 22 September 1942), h-index 75, with 36,000 citations is a Pakistani organic chemist and is currently serving as Professor Emeritus at the International Center for Chemical and Biological Sciences at the University of Karachi and as Chairman of PM Task Force on Science and Technology. He has twice served as the President of Pakistan Academy of Sciences (2003-2006, and 2011–2014). He was the Federal Minister of Science and Technology (2000-2002), Federal Minister of Education (2002) and Chairman Higher Education Commission with status of Federal Minister (2002-2008) He is also the President of the Network of Academies of Sciences in Countries of the Organisation of Islamic Countries (NASIC). After returning to Pakistan from Cambridge after completing his tenure as Fellow of Kings College, Cambridge University, he contributed to the development of the International Center for Chemical and Biological Sciences at the University of Karachi, and transforming the landscape of higher education, science and technology of Pakistan. He is Fellow of Royal Society (London), Life Fellow of Kings College, Cambridge University, UK.,, Academician Chinese Academy of Sciences and Professor Emeritus at University of Karachi | 0 | Theoretical and Fundamental Chemistry |
Muscle is a naturally aligned organ, with individual muscle fibers packed together into larger units called muscle fascicles. The uniaxial alignment of muscle fibers allows them to simultaneously contract in the same direction and properly propagate force on the bones via the tendons. Approximately 45% of the human body is composed of muscle tissue, and this tissue can be classified into three different groups: skeletal muscle, cardiac muscle, and smooth muscle. Muscle plays a role in structure, stability, and movement in mammalian bodies. The basic unit for a muscle is a muscle fiber, which is made up of myofilaments actin and myosin. This muscle fiber contains sarcomeres which generate the force required for contraction.
A major focus of muscle tissue engineering is to create constructs with the functionality of native muscle and ability to contract. To this end, alignment of the tissue engineered construct is extremely important. It has been shown that cells grown on substrates with alignment cues form more robust muscle fibers. Several other design criteria considered in muscle tissue engineering include the scaffold porosity, stiffness, biocompatibility, and degradation timeline. Substrate stiffness should ideally be in the myogenic range, which has been shown to be 10-15 kPa.
The purpose of muscle tissue engineering is to reconstruct functional muscular tissue which has been lost via traumatic injury, tumor ablation, or functional damage caused by myopathies. Until now, the only method used to restore muscular tissue function and aesthetic was free tissue transfer. Full function is typically not restored, however, which results in donor site morbidity and volume deficiency. The success of tissue engineering as it pertains to the regeneration of skin, cartilage, and bone indicates that the same success will be found in engineering muscular tissue. Early innovations in the field yielded in vitro cell culturing and regeneration of muscle tissue which would be implanted in the body, but advances in recent years have shown that there may be potential for in vivo muscle tissue engineering using scaffolding. | 1 | Applied and Interdisciplinary Chemistry |
Cation-exchange capacity is defined as the amount of positive charge that can be exchanged per mass of soil, usually measured in cmol/kg. Some texts use the older, equivalent units me/100g or meq/100g. CEC is measured in moles of electric charge, so a cation-exchange capacity of 10 cmol/kg could hold 10 cmol of Na cations (with 1 unit of charge per cation) per kilogram of soil, but only 5 cmol Ca (2 units of charge per cation).
Cation-exchange capacity arises from various negative charges on soil particle surfaces, especially those of clay minerals and soil organic matter. Phyllosilicate clays consist of layered sheets of aluminium and silicon oxides. The replacement of aluminium or silicon atoms by other elements with lower charge (e.g. Al replaced by Mg) can give the clay structure a net negative charge. This charge does not involve deprotonation and is therefore pH-independent, and called permanent charge. In addition, the edges of these sheets expose many acidic hydroxyl groups that are deprotonated to leave negative charges at the pH levels in many soils. Organic matter also makes a very significant contribution to cation exchange, due to its large number of charged functional groups. CEC is typically higher near the soil surface, where organic matter content is highest, and declines with depth. The CEC of organic matter is highly pH-dependent.
Cations are adsorbed to soil surfaces by the electrostatic interaction between their positive charge and the negative charge of the surface, but they retain a shell of water molecules and do not form direct chemical bonds with the surface. Exchangeable cations thus form part of the diffuse layer above the charged surface. The binding is relatively weak, and a cation can easily be displaced from the surface by other cations from the surrounding solution. | 0 | Theoretical and Fundamental Chemistry |
Given the definition of the elasticity coefficient in terms of a partial derivative, it is possible, for example, to determine the elasticity of an arbitrary rate law by differentiating the rate law by the independent variable and scaling. For example, the elasticity coefficient for a mass-action rate law such as:
where is the reaction rate, the reaction rate constant, is the ith chemical species involved in the reaction and the ith reaction order, then the elasticity, can be obtained by differentiating the rate law with respect to and scaling:
That is, the elasticity for a mass-action rate law is equal to the order of reaction of the species.
For example the elasticity of A in the reaction where the rate of reaction is given by: , the elasticity can be evaluated using:
Elasticities can also be derived for more complex rate laws such as the Michaelis–Menten rate law. If
then it can be easily shown than
This equation illustrates the idea that elasticities need not be constants (as with mass-action laws) but can be a function of the reactant concentration. In this case, the elasticity approaches unity at low reactant concentration (s) and zero at high reactant concentration.
For the reversible Michaelis–Menten rate law:
where is the forward , the forward , the equilibrium constant and the reverse , two elasticity coefficients can be calculated, one with respect to substrate, S, and another with respect to product, P. Thus:
where is the mass-action ratio, that is . Note that when p = 0, the equations reduce to the case for the irreversible Michaelis–Menten law.
As a final example, consider the Hill equation:
where n is the Hill coefficient and is the half-saturation coefficient (cf. Michaelis–Menten rate law), then the elasticity coefficient is given by:
Note that at low concentrations of S the elasticity approaches n. At high concentrations of S the elasticity approaches zero. This means the elasticity is bounded between zero and the Hill coefficient. | 0 | Theoretical and Fundamental Chemistry |
Carbohydrate markers are employed in a technique known as polysaccharide analysis by carbohydrate gel electrophoresis (PACE), which is a measurable separation technique.
It allows for the analysis of enzyme hydrolysis products. It has been used in applications such as characterizing enzymes involved in hemicellulose degradation, determining the structure of hemicellulose polysaccharides, and analysis of enzymatic cleavage of cellulose products.
PACE depends on derivitization, which is the conversion of a chemical compound into a derivative. Here monosaccharides, oligosaccharides, and polysaccharides are the compounds of interest. They are labeled at their reducing ends with a fluorescent label (i.e. a fluorophore). This derivitization with a fluorophore permits both separation on a gel under the desired circumstances and fluorescence imaging of the gel. In this case, a polyacrylamide gel is used.
As with DNA, RNA, and protein electrophoresis, markers are run alongside the samples of interest in carbohydrate gel electrophoresis. The markers consist of oligosaccharides of known molecular weight. Like the samples of interest, the marker is also derivitized with a fluorophore (usually with 8-aminonaphthalene-1,3,6-trisulfonic acid (ANTS) or 2-aminoacridone). | 1 | Applied and Interdisciplinary Chemistry |
The photosynthetic partner in a lichen is called a photobiont. The photobionts in lichens come from a variety of simple prokaryotic and eukaryotic organisms. In the majority of lichens the photobiont is a green alga (Chlorophyta) or a cyanobacterium. In some lichens both types are present; in such cases, the alga is typically the primary partner, with the cyanobacteria being located in cryptic pockets. Algal photobionts are called phycobionts, while cyanobacterial photobionts are called cyanobionts. About 90% of all known lichens have phycobionts, and about 10% have cyanobionts. Approximately 100 species of photosynthetic partners from 40 genera and five distinct classes (prokaryotic: Cyanophyceae; eukaryotic: Trebouxiophyceae, Phaeophyceae, Chlorophyceae) have been found to associate with the lichen-forming fungi.
Common algal photobionts are from the genera Trebouxia, Trentepohlia, Pseudotrebouxia, or Myrmecia. Trebouxia is the most common genus of green algae in lichens, occurring in about 40% of all lichens. "Trebouxioid" means either a photobiont that is in the genus Trebouxia, or resembles a member of that genus, and is therefore presumably a member of the class Trebouxiophyceae. The second most commonly represented green alga genus is Trentepohlia. Overall, about 100 species of eukaryotes are known to occur as photobionts in lichens. All the algae are probably able to exist independently in nature as well as in the lichen.
A "cyanolichen" is a lichen with a cyanobacterium as its main photosynthetic component (photobiont). Most cyanolichen are also ascolichens, but a few basidiolichen like Dictyonema and Acantholichen have cyanobacteria as their partner.
The most commonly occurring cyanobacterium genus is Nostoc. Other common cyanobacterium photobionts are from Scytonema. Many cyanolichens are small and black, and have limestone as the substrate. Another cyanolichen group, the jelly lichens of the genera Collema or Leptogium are gelatinous and live on moist soils. Another group of large and foliose species including Peltigera, Lobaria, and Degelia are grey-blue, especially when dampened or wet. Many of these characterize the Lobarion communities of higher rainfall areas in western Britain, e.g., in the Celtic rain forest. Strains of cyanobacteria found in various cyanolichens are often closely related to one another. They differ from the most closely related free-living strains.
The lichen association is a close symbiosis. It extends the ecological range of both partners but is not always obligatory for their growth and reproduction in natural environments, since many of the algal symbionts can live independently. A prominent example is the alga Trentepohlia, which forms orange-coloured populations on tree trunks and suitable rock faces. Lichen propagules (diaspores) typically contain cells from both partners, although the fungal components of so-called "fringe species" rely instead on algal cells dispersed by the "core species".
The same cyanobiont species can occur in association with different fungal species as lichen partners. The same phycobiont species can occur in association with different fungal species as lichen partners. More than one phycobiont may be present in a single thallus.
A single lichen may contain several algal genotypes. These multiple genotypes may better enable response to adaptation to environmental changes, and enable the lichen to inhabit a wider range of environments. | 1 | Applied and Interdisciplinary Chemistry |
Two-stroke, Four-stroke, and continuous machine are very different from each other. However it was shown that there is a quantum regime where all these machines become thermodynamically equivalent to each other. While the intra cycle dynamics in the equivalence regime is very different in different engine types, when the cycle is completed they all turn out to provide the same amount of work and consume the same amount of heat (hence they share the same efficiency as well). This equivalence is associated with a coherent work extraction mechanism and has no classical analogue. These quantum features have been demonstrated experimentally. | 0 | Theoretical and Fundamental Chemistry |
Alpha spectrometry (also known as alpha(-particle) spectroscopy) is the quantitative study of the energy of alpha particles emitted by a radioactive nuclide that is an alpha emitter.
As emitted alpha particles are mono-energetic (i.e. not emitted with a spectrum of energies, such as beta decay) with energies often distinct to the decay they can be used to identify which radionuclide they originated from. | 0 | Theoretical and Fundamental Chemistry |
In the field of physical chemistry, a nonthermal surface reaction refers to an elementary reaction between a thermally accommodated adsorbed surface species and a reactant which has not yet thermally accommodated to the surface.
The two main mechanisms classified as nonthermal are the Eley-Rideal and hot atom mediated mechanisms. | 0 | Theoretical and Fundamental Chemistry |
Hyperconjugation can be used to rationalize a variety of chemical phenomena, including the anomeric effect, the gauche effect, the rotational barrier of ethane, the beta-silicon effect, the vibrational frequency of exocyclic carbonyl groups, and the relative stability of substituted carbocations and substituted carbon centred radicals, and the thermodynamic Zaitsev's rule for alkene stability. More controversially, hyperconjugation is proposed by quantum mechanical modeling to be a better explanation for the preference of the staggered conformation rather than the old textbook notion of steric hindrance. | 0 | Theoretical and Fundamental Chemistry |
Metal carbonyls react with reducing agents such as metallic sodium or sodium amalgam to give carbonylmetalate (or carbonylate) anions:
:Mn(CO) + 2 Na → 2 Na[Mn(CO)]
For iron pentacarbonyl, one obtains the tetracarbonylferrate with loss of CO:
:Fe(CO) + 2 Na → Na[Fe(CO)] + CO
Mercury can insert into the metal–metal bonds of some polynuclear metal carbonyls:
:Co(CO) + Hg → (CO)Co−Hg−Co(CO) | 0 | Theoretical and Fundamental Chemistry |
The general steps to prepare a complementary DNA (cDNA) library for sequencing are described below, but often vary between platforms.
# RNA Isolation: RNA is isolated from tissue and mixed with Deoxyribonuclease (DNase). DNase reduces the amount of genomic DNA. The amount of RNA degradation is checked with gel and capillary electrophoresis and is used to assign an RNA integrity number to the sample. This RNA quality and the total amount of starting RNA are taken into consideration during the subsequent library preparation, sequencing, and analysis steps.
#RNA selection/depletion: To analyze signals of interest, the isolated RNA can either be kept as is, enriched for RNA with 3 polyadenylated (poly(A)) tails to include only eukaryotic mRNA, depleted of ribosomal RNA (rRNA), and/or filtered for RNA that binds specific sequences (RNA selection and depletion methods table, below). RNA molecules having 3 poly(A) tails in eukaryotes are mainly composed of mature, processed, coding sequences. Poly(A) selection is performed by mixing RNA with oligomers covalently attached to a substrate, typically magnetic beads. Poly(A) selection has important limitations in RNA biotype detection. Many RNA biotypes are not polyadenylated, including many noncoding RNA and histone-core protein transcripts, or are regulated via their poly(A) tail length (e.g., cytokines) and thus might not be detected after poly(A) selection. Furthermore, poly(A) selection may display increased 3' bias, especially with lower quality RNA. These limitations can be avoided with ribosomal depletion, removing rRNA that typically represents over 90% of the RNA in a cell. Both poly(A) enrichment and ribosomal depletion steps are labor intensive and could introduce biases, so more simple approaches have been developed to omit these steps. Small RNA targets, such as miRNA, can be further isolated through size selection with exclusion gels, magnetic beads, or commercial kits.
#cDNA synthesis: RNA is reverse transcribed to cDNA because DNA is more stable and to allow for amplification (which uses DNA polymerases) and leverage more mature DNA sequencing technology. Amplification subsequent to reverse transcription results in loss of strandedness, which can be avoided with chemical labeling or single molecule sequencing. Fragmentation and size selection are performed to purify sequences that are the appropriate length for the sequencing machine. The RNA, cDNA, or both are fragmented with enzymes, sonication, or nebulizers. Fragmentation of the RNA reduces 5 bias of randomly primed-reverse transcription and the influence of primer binding sites, with the downside that the 5 and 3' ends are converted to DNA less efficiently. Fragmentation is followed by size selection, where either small sequences are removed or a tight range of sequence lengths are selected. Because small RNAs like miRNAs are lost, these are analyzed independently. The cDNA for each experiment can be indexed with a hexamer or octamer barcode, so that these experiments can be pooled into a single lane for multiplexed sequencing. | 1 | Applied and Interdisciplinary Chemistry |
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