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A recent study highlights the first report of thermo-responsive rare-earth elements (REE)-selective protein. The ELP and the REE-binding domain are genetically fused to form REE-selective and thermo-responsive genetically encoded ELP called RELP for the selective extraction and recovery of total REEs. RELP shows a selective and repeatable biosorption platform for REE recovery. The authors highlighted that technology can be adapted to recover other precious metals and commodities.
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Theoretical and Fundamental Chemistry
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Lithotrophic microbes are responsible for the phenomenon known as acid mine drainage. Typically occurring in mining areas, this process concerns the active metabolism of pyrites and other reduced sulfur components to sulfate. One example is the acidophilic bacterial genus, A. ferrooxidans, that use iron(II) sulfide (FeS) to generate sulfuric acid. The acidic product of these specific lithotrophs has the potential to drain from the mining area via water run-off and enter the environment.
Acid mine drainage drastically alters the acidity (pH values of 2 - 3) and chemistry of groundwater and streams, and may endanger plant and animal populations downstream of mining areas. Activities similar to acid mine drainage, but on a much lower scale, are also found in natural conditions such as the rocky beds of glaciers, in soil and talus, on stone monuments and buildings and in the deep subsurface.
| 1 |
Applied and Interdisciplinary Chemistry
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Particle size analyzers are used also in biology to measure protein aggregation.
DLS is a particularly appreciated technique for the characterization of nanoparticles designed for drug delivery, such as vaccines. DLS instruments are for instance part of the quality control process for mRNA vaccines formulated in lipid nanoparticle carriers.
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Theoretical and Fundamental Chemistry
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A decade after the discovery of RNAi mechanism in 1993, the pharmaceutical sector heavily invested in the research and development of siRNA therapy. There are several advantages that this therapy has over small molecules and antibodies. It can be administered quarterly or every six months. Another advantage is that, unlike small molecule and monoclonal antibodies that need to recognize specific conformation of a protein, siRNA functions by Watson-Crick basepairing with mRNA. Therefore, any target molecule that needs to be treated with high affinity and specificity can be selected if the right nucleotide sequence is available. One of the biggest challenges researchers needed to overcome was the identification and establishment of a delivery system through which the therapies would enter the body. And that the immune system often mistakes the RNAi therapies as remnants of infectious agents, which can trigger an immune response. Animal models did not accurately represent the degree of immune response that was seen in humans and despite the promise in the treatment investors divested away from RNAi.
However, there were a few companies that continued with the development of RNAi therapy for humans. Alnylam Pharmaceuticals, Sirna Therapeutics and Dicerna Pharmaceuticals are few of the companies still working on bringing RNAi therapies to market. It was learned that almost all siRNA therapies administered in the bloodstream accumulated in the liver. That is why most of the early drug targets were diseases that affected the liver. Repeated developmental work also shed light on improving the chemical composition of the RNA molecule to reduce the immune response, subsequently causing little to no side effects. Listed below are some of approved therapies or therapies in pipeline.
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Applied and Interdisciplinary Chemistry
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The constant momentum flux condition can be obtained by integrating the momentum equation across the jet.
where is used to simplify the above equation. The mass flux across any cross section normal to the axis is not constant, because there is a slow entrainment of outer fluid into the jet, and it's a part of the boundary layer solution. This can be easily verified by integrating the continuity equation across the boundary layer.
where symmetry condition is used.
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Applied and Interdisciplinary Chemistry
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Like the complex multicellularity seen in animals, the multicellularity of land plants is developmentally organized into tissue and organ units via transcription factor genes with homeotic effects.
Although plants have homeobox-containing genes, plant homeotic factors tend to possess MADS-box DNA binding domains.
Animal genomes also possess a small number MADS-box factors.
Thus, in the independent evolution of multicellularity in plants and animals, different eukaryotic transcription factor families were co-opted to serve homeotic functions.
MADS-domain factors have been proposed to function as co-factors to more specialized factors and thereby help to determine organ identity.
This has been proposed to correspond more closely to the interpretation of animal homeotics outlined by Michael Akam.
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Applied and Interdisciplinary Chemistry
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Clinical neurochemistry is the field of neurological biochemistry which relates biochemical phenomena to clinical symptomatic manifestations in humans. While neurochemistry is mostly associated with the effects of neurotransmitters and similarly functioning chemicals on neurons themselves, clinical neurochemistry relates these phenomena to system-wide symptoms. Clinical neurochemistry is related to neurogenesis, neuromodulation, neuroplasticity, neuroendocrinology, and neuroimmunology in the context of associating neurological findings at both lower and higher level organismal functions.
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Applied and Interdisciplinary Chemistry
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There are two causes of charge carrier motion and separation in a solar cell:
#drift of carriers, driven by the electric field, with electrons being pushed one way and holes the other way
#diffusion of carriers from zones of higher carrier concentration to zones of lower carrier concentration (following a gradient of chemical potential).
These two "forces" may work one against the other at any given point in the cell. For instance, an electron moving through the junction from the p region to the n region (as in the diagram at the beginning of this article) is being pushed by the electric field against the concentration gradient. The same goes for a hole moving in the opposite direction.
It is easiest to understand how a current is generated when considering electron-hole pairs that are created in the depletion zone, which is where there is a strong electric field. The electron is pushed by this field toward the n side and the hole toward the p side. (This is opposite to the direction of current in a forward-biased diode, such as a light-emitting diode in operation.) When the pair is created outside the space charge zone, where the electric field is smaller, diffusion also acts to move the carriers, but the junction still plays a role by sweeping any electrons that reach it from the p side to the n side, and by sweeping any holes that reach it from the n side to the p side, thereby creating a concentration gradient outside the space charge zone.
In thick solar cells there is very little electric field in the active region outside the space charge zone, so the dominant mode of charge carrier separation is diffusion. In these cells the diffusion length of minority carriers (the length that photo-generated carriers can travel before they recombine) must be large compared to the cell thickness. In thin film cells (such as amorphous silicon), the diffusion length of minority carriers is usually very short due to the existence of defects, and the dominant charge separation is therefore drift, driven by the electrostatic field of the junction, which extends to the whole thickness of the cell.
Once the minority carrier enters the drift region, it is swept across the junction and, at the other side of the junction, becomes a majority carrier. This reverse current is a generation current, fed both thermally and (if present) by the absorption of light. On the other hand, majority carriers are driven into the drift region by diffusion (resulting from the concentration gradient), which leads to the forward current; only the majority carriers with the highest energies (in the so-called Boltzmann tail; cf. Maxwell–Boltzmann statistics) can fully cross the drift region. Therefore, the carrier distribution in the whole device is governed by a dynamic equilibrium between reverse current and forward current.
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Theoretical and Fundamental Chemistry
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Whereas most meteorites originate from asteroids, the contrasting make-up of micrometeorites suggests that most originate from comets.
Fewer than 1% of MMs are achondritic and are similar to HED meteorites, which are thought to be from the asteroid 4 Vesta. Most MMs are compositionally similar to carbonaceous chondrites, whereas approximately 3% of meteorites are of this type. The dominance of carbonaceous chondrite-like MMs and their low abundance in meteorite collections suggests that most MMs derive from sources different from those of most meteorites. Since most meteorites derive from asteroids, an alternative source for MMs might be comets. The idea that MMs might originate from comets originated in 1950.
Until recently the greater-than-25-km/s entry velocities of micrometeoroids, measured for particles from comet streams, cast doubts against their survival as MMs. However, recent dynamical simulations suggest that 85% of cosmic dust could be cometary. Furthermore, analyses of particles returned from the comet, Wild 2, by the Stardust spacecraft show that these particles have compositions that are consistent with many micrometeorites. Nonetheless, some parent bodies of micrometeorites appear to be asteroids with chondrule-bearing carbonaceous chondrites.
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Theoretical and Fundamental Chemistry
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The reaction mechanism for an oxidation of an alcohol to an aldehyde according to the hypervalent twisting mechanism involves a ligand exchange reaction replacing the hydroxyl group by the alcohol followed by a twist and an elimination reaction. The twist is a requirement because the iodine to oxygen double bond is oriented out of plane with the alkoxy group and the concerted elimination would not be able to take place. This twist reaction is a rearrangement in which the oxygen atom is moved into a proper plane for a 5 membered cyclic transition state in the elimination reaction and is calculated by Computational chemistry to be the rate-determining step in the oxidation. The twist mechanism also explains why oxidation is faster for larger alcohols than for small alcohols. The twist is driven forward by the steric hindrance that exists between the ortho hydrogen atom and the protons from the alkoxy group and larger alkoxy groups create larger steric repulsion. The same computation predicts a much faster reacting IBX derivative with a 100 fold reaction rate when this ortho hydrogen atom is replaced by a methyl group thus facilitating the twist until the elimination reaction takes prevalence as the rate determining step.
IBX exists as two tautomers one of which is the carboxylic acid. The acidity of IBX which has been determined in water (pKa 2.4) and DMSO (pKa 6.65) is known to affect organic reactions, for instance acid-catalyzed isomerization accompanying oxidations.
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Theoretical and Fundamental Chemistry
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Praks and Brkić show one approximation of the Colebrook equation based on the Wright -function, a cognate of the Lambert W-function
:, , , and
The equation was found to match the Colebrook–White equation within 0.0012%.
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Applied and Interdisciplinary Chemistry
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The Ski complex is a multi-protein complex involved in the 3' end degradation of messenger RNAs in yeast.
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Applied and Interdisciplinary Chemistry
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Chance theories are based on the assumption that "Absolute asymmetric synthesis, i.e., the formation of enantiomerically enriched products from achiral precursors without the intervention of chiral chemical reagents or catalysts, is in practice unavoidable on statistical grounds alone".
Consider the racemic state as a macroscopic property described by a binomial distribution; the experiment of tossing a coin, where the two possible outcomes are the two enantiomers is a good analogy. The discrete probability distribution of obtaining n successes out of Bernoulli trials, where the result of each Bernoulli trial occurs with probability and the opposite occurs with probability is given by:
The discrete probability distribution of having exactly molecules of one chirality and of the other, is given by:
As in the experiment of tossing a coin, in this case, we assume both events ( or ) to be equiprobable, . The probability of having exactly the same amount of both enantiomers is inversely proportional to the square root of the total number of molecules . For one mol of a racemic compound, molecules, this probability becomes . The probability of finding the racemic state is so small that we can consider it negligible.
In this scenario, there is a need to amplify the initial stochastic enantiomeric excess through any efficient mechanism of amplification. The most likely path for this amplification step is by asymmetric autocatalysis. An autocatalytic chemical reaction is that in which the reaction product is itself a reactive, in other words, a chemical reaction is autocatalytic if the reaction product is itself the catalyst of the reaction. In asymmetric autocatalysis, the catalyst is a chiral molecule, which means that a chiral molecule is catalysing its own production. An initial enantiomeric excess, such as can be produced by polarized light, then allows the more abundant enantiomer to outcompete the other.
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Theoretical and Fundamental Chemistry
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An ideal surface is flat, rigid, perfectly smooth, chemically homogeneous, and has zero contact angle hysteresis. Zero hysteresis implies the advancing and receding contact angles are equal. In other words, only one thermodynamically stable contact angle exists. When a drop of liquid is placed on such a surface, the characteristic contact angle is formed as depicted in Figure 1. Furthermore, on an ideal surface, the drop will return to its original shape if it is disturbed. The following derivations apply only to ideal solid surfaces; they are only valid for the state in which the interfaces are not moving and the phase boundary line exists in equilibrium.
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Theoretical and Fundamental Chemistry
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Another popular method for decomplexation involves oxidation of a low valent complex. Oxidants include air, dioxirane, ceric ammonium nitrate (CAN), and halogens. Oxidants are selected to avoid reaction with the released organic ligand. Illustrative is the use of ferric chloride to release alkynes from Co(CR)(CO). One drawback to this method is that the organometallic center is usually destroyed. One example of oxidative decomplexation involves the CAN-induced release and trapping of cyclobutadiene from cyclobutadieneiron tricarbonyl.
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Theoretical and Fundamental Chemistry
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Mezlocillin is a broad-spectrum penicillin antibiotic. It is active against both Gram-negative and some Gram-positive bacteria. Unlike most other extended spectrum penicillins, it is excreted by the liver, therefore it is useful for biliary tract infections, such as ascending cholangitis.
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Theoretical and Fundamental Chemistry
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The nitrogen compounds through which excess nitrogen is eliminated from organisms are called nitrogenous wastes () or nitrogen wastes. They are ammonia, urea, uric acid, and creatinine. All of these substances are produced from protein metabolism. In many animals, the urine is the main route of excretion for such wastes; in some, it is the feces.
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Applied and Interdisciplinary Chemistry
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The β-agonsist that are clinically used are all substituted β-phenethylamine (see figure 5) and they have three kinds of phenyl rings shown in figure 4. They are called resorcinol ring, salicyl alcohol ring or N-formamide ring. The alcohol substituents in the phenyl ring are reactive and complicate the synthesis of the β-agonists. A protection step is needed while the N-residue is added in position R1 (figure 5). Another thing that complicates the synthesis is obtaining optically pure R (-) enantiomer of the compound. The stereochemistry is very important for activity because only the R (-) enantiomer is able to form the hydrogen bonds necessary to fit in the binding site and activate the β-receptor.
Salbutamol is usually inhaled in racemic mixtures (for example Ventolin). By treating asthma with optically pure (R)-salbutamol the risk of side effects, such as nervous system stimulatory effects and cardiac arrythmia, can be minimized. There are several routes for enantioselective synthesis, as well as methods for synthesis of the racemic mixture followed by chiral resolution.
Stereoselective synthesis of tributalin and salbutamol acetal can be done from O-protected-(R)-cyanohydrins. F. Effenberg, et al. describe a way for the synthesis. The main complications are to perform the deprotection step without racemization and to form a pure salt. A Ritter reaction can be used for an N-tertiary butylation. In this experiment deacetylation of (R)-salbutamol acetal was unsuccessful so it can not be used to obtain pure (R)-salbutamol. Figure 6 shows the main steps in the synthesis of salmeterol and tributalin.
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Applied and Interdisciplinary Chemistry
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Weatherization (American English) or weatherproofing (British English) is the practice of protecting a building and its interior from the elements, particularly from sunlight, precipitation, and wind, and of modifying a building to reduce energy consumption and optimize energy efficiency.
Weatherization is distinct from building insulation, although building insulation requires weatherization for proper functioning. Many types of insulation can be thought of as weatherization, because they block drafts or protect from cold winds. Whereas insulation primarily reduces conductive heat flow, weatherization primarily reduces convective heat flow.
In the United States, buildings use one third of all energy consumed and two thirds of all electricity. Due to the high energy usage, they are a major source of the pollution that causes urban air quality problems and pollutants that contribute to climate change. Building energy usage accounts for 49 percent of sulfur dioxide emissions, 25 percent of nitrous oxide emissions, and 10 percent of particulate emissions.
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Theoretical and Fundamental Chemistry
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He invented the first hardware security module (HSM), the so-called "Atalla Box", a security system that secures a majority of transactions from ATMs today. At the same time, Atalla contributed to the development of the personal identification number (PIN) system, which has developed among others in the banking industry as the standard for identification.
The work of Atalla in the early 1970s led to the use of hardware security modules. His "Atalla Box", a security system which encrypts PIN and ATM messages, and protected offline devices with an un-guessable PIN-generating key. He commercially released the "Atalla Box" in 1973. The product was released as the Identikey. It was a card reader and customer identification system, providing a terminal with plastic card and PIN capabilities. The system was designed to let banks and thrift institutions switch to a plastic card environment from a passbook program. The Identikey system consisted of a card reader console, two customer PIN pads, intelligent controller and built-in electronic interface package. The device consisted of two keypads, one for the customer and one for the teller. It allowed the customer to type in a secret code, which is transformed by the device, using a microprocessor, into another code for the teller. During a transaction, the customer's account number was read by the card reader. This process replaced manual entry and avoided possible key stroke errors. It allowed users to replace traditional customer verification methods such as signature verification and test questions with a secure PIN system.
A key innovation of the Atalla Box was the key block, which is required to securely interchange symmetric keys or PINs with other actors of the banking industry. This secure interchange is performed using the Atalla Key Block (AKB) format, which lies at the root of all cryptographic block formats used within the Payment Card Industry Data Security Standard (PCI DSS) and American National Standards Institute (ANSI) standards.
Fearful that Atalla would dominate the market, banks and credit card companies began working on an international standard. Its PIN verification process was similar to the later IBM 3624. Atalla was an early competitor to IBM in the banking market, and was cited as an influence by IBM employees who worked on the Data Encryption Standard (DES). In recognition of his work on the PIN system of information security management, Atalla has been referred to as the "Father of the PIN" and as a father of information security technology.
The Atalla Box protected over 90% of all ATM networks in operation as of 1998, and secured 85% of all ATM transactions worldwide as of 2006. Atalla products still secure the majority of the world's ATM transactions, as of 2014.
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Theoretical and Fundamental Chemistry
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Agrominerals (also known as stone bread or petrol fertilizer) are minerals of importance to agriculture and horticulture industries for they can provide essential plant nutrients. Some agrominerals occur naturally or can be processed to be used as alternative fertilizers or soil amendments. The term agromineral was created in the 19th century and is now one of the leading research topics for sustainable agriculture. These geomaterials are used to replenish the nutrients and amend soils. Agrominerals started with small uses most often seen in hobbyist gardening but are moving to a much larger scale such as commercial farming operations that take up 100's acres of land. In this transition the focus changed to be more on ground nutrients, mainly on the three major plant nutrients nitrogen (N), phosphorus (P), and potassium (K). Two of the three elements are only being harvested from a geomaterial called potash. Alternative sources are being researched, due to potash finite supply and cost.
The process of using agrominerals starts with crushing rocks into a "rock powder," than using the powder to replenish soil nutrients. The process of replenishing mineral levels in a soil is called soil remineralization. While studying alternative ways to replenish ground nutrients, it has been found that agrominerals can also help mitigate other issues such climate change, water preservation and soil management.
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Theoretical and Fundamental Chemistry
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In the glycolytic pathway, 1,3-bisphosphoglycerate is dephosphorylated to form 3-phosphoglyceric acid in a coupled reaction producing two ATP via substrate-level phosphorylation. The single phosphate group left on the 3-PGA molecule then moves from an end carbon to a central carbon, producing 2-phosphoglycerate. This phosphate group relocation is catalyzed by phosphoglycerate mutase, an enzyme that also catalyzes the reverse reaction.
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Theoretical and Fundamental Chemistry
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The Zerewitinoff determination or Zerevitinov determination is a quantitative chemical test for the determination of active hydrogens in a chemical substance. A sample is treated with the Grignard reagent, methylmagnesium iodide, which reacts with any acidic hydrogen atom to form methane. This gas can be determined quantitatively by measuring its volume. For example:
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Theoretical and Fundamental Chemistry
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The Boger pyridine synthesis is a cycloaddition approach to the formation of pyridines named after its inventor Dale L. Boger, who first reported it in 1981. The reaction is a form of inverse-electron demand Diels-Alder reaction in which an enamine reacts with a 1,2,4-triazine to form the pyridine nucleus. The reaction is especially useful for accessing pyridines that would be difficult or impossible to access via other methods and has been used in the total synthesis of several complicated natural products.
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Theoretical and Fundamental Chemistry
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Generally this topic is discussed when covering mass spectrometry and occurs generally by the same mechanisms.
To neutralize the positive charge on the ionization site a single two-electron transfer must be made. Neutralization of the positive charge at the ionization site is performed at the expense of the atom adjacent to the ionization site, transferring the positive charge to this atom as a result of the bond cleavage.
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Theoretical and Fundamental Chemistry
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In 1970-75, Giguère et al. observed infrared and Raman spectra of dilute aqueous solutions of trioxidane. In 2005, trioxidane was observed experimentally by microwave spectroscopy in a supersonic jet. The molecule exists in a skewed structure, with an oxygen–oxygen–oxygen–hydrogen dihedral angle of 81.8°. The oxygen–oxygen bond lengths of 142.8 picometer are slightly shorter than the 146.4 pm oxygen–oxygen bonds in hydrogen peroxide. Various dimeric and trimeric forms also seem to exist.
There is a trend of increasing gas-phase acidity and corresponding pK as the number of oxygen atoms in the chain increases in HOH structures (n=1,2,3).
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Theoretical and Fundamental Chemistry
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A smart fluid is a fluid whose properties (e.g. viscosity) can be changed by applying an electric field or a magnetic field.
The most developed smart fluids today are fluids whose viscosity increases when a magnetic field is applied. Small magnetic dipoles are suspended in a non-magnetic fluid, and the applied magnetic field causes these small magnets to line up and form strings that increase the viscosity. These magnetorheological or MR fluids are being used in the suspension of the 2002 model of the Cadillac Seville STS automobile and more recently, in the suspension of the second-generation Audi TT. Depending on road conditions, the damping fluids viscosity is adjusted. This is more expensive than traditional systems, but it provides better (faster) control. Similar systems are being explored to reduce vibration in washing machines, air conditioning compressors, rockets and satellites, and one has even been installed in Japans National Museum of Emerging Science and Innovation in Tokyo as an earthquake shock absorber.
Some haptic devices whose resistance to touch can be controlled are also based on these MR fluids.
Another major type of smart fluid are electrorheological or ER fluids, whose resistance to flow can be quickly and dramatically altered by an applied electric field (note, the yield stress point is altered rather than the viscosity). Besides fast acting clutches, brakes, shock absorbers and hydraulic valves, other, more esoteric, applications such as bulletproof vests have been proposed for these fluids.
Other smart fluids change their surface tension in the presence of an electric field. This has been used to produce very small controllable lenses: a drop of this fluid, captured in a small cylinder and surrounded by oil, serves as a lens whose shape can be changed by applying an electric field.
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Applied and Interdisciplinary Chemistry
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Risers, also known as feeders, are the most common way of providing directional solidification. It supplies liquid metal to the solidifying casting to compensate for solidification shrinkage. For a riser to work properly the riser must solidify after the casting, otherwise it cannot supply liquid metal to shrinkage within the casting. Risers add cost to the casting because it lowers the yield of each casting; i.e. more metal is lost as scrap for each casting. Another way to promote directional solidification is by adding chills to the mold. A chill is any material which will conduct heat away from the casting more rapidly than the material used for molding.
Risers are classified by three criteria. The first is if the riser is open to the atmosphere, if it is then it is called an open riser, otherwise it is known as a blind type. The second criterion is where the riser is located; if it is located on the casting then it is known as a top riser and if it is located next to the casting it is known as a side riser. Finally, if the riser is located on the gating system so that it fills after the molding cavity, it is known as a live riser or hot riser, but if the riser fills with materials that have already flowed through the molding cavity it is known as a dead riser or cold riser.
Riser aids are items used to assist risers in creating directional solidification or reducing the number of risers required. One of these items are chills which accelerate cooling in a certain part of the mold. There are two types: external and internal chills. External chills are masses of high-heat-capacity and high-thermal-conductivity material that are placed on an edge of the molding cavity. Internal chills are pieces of the same metal that is being poured, which are placed inside the mold cavity and become part of the casting. Insulating sleeves and toppings may also be installed around the riser cavity to slow the solidification of the riser. Heater coils may also be installed around or above the riser cavity to slow solidification.
| 1 |
Applied and Interdisciplinary Chemistry
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UNECE recognizes several rivers that cross international borders which flow into the Caspian Sea.
These are:
| 1 |
Applied and Interdisciplinary Chemistry
|
In aqueous solution, carbon dioxide forms carbonic acid
:CO + HO HCO
This reaction is very slow in the absence of a catalyst, but quite fast in the presence of the hydroxide ion
:CO + OH hydrogencarbonate|
A reaction similar to this is almost instantaneous with carbonic anhydrase. The structure of the active site in carbonic anhydrases is well known from a number of crystal structures. It consists of a zinc ion coordinated by three imidazole nitrogen atoms from three histidine units. The fourth coordination site is occupied by a water molecule. The coordination sphere of the zinc ion is approximately tetrahedral. The positively-charged zinc ion polarizes the coordinated water molecule, and nucleophilic attack by the negatively-charged hydroxide portion on carbon dioxide proceeds rapidly. The catalytic cycle produces the bicarbonate ion and the hydrogen ion as the equilibrium
:HCO + H
favours dissociation of carbonic acid at biological pH values.
| 1 |
Applied and Interdisciplinary Chemistry
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The Roman Bun Ingots are less pure than the earlier LBA examples and Tylecote suggests that they may be a direct product of smelting. Theoretically such an ingot could be formed in the base of the furnace. However, this is problematic in the case of the stamped examples as this would require the furnace to be dismantled or else have a short shaft to allow access for stamping. As a solution the furnace could have been tapped into a mould at the completion of smelting. It is possible that both methods were used as several of the ingots seem to have had additional metal poured onto the top in order to allow stamping.
| 1 |
Applied and Interdisciplinary Chemistry
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The principal components of volcanic gases are water vapor (HO), carbon dioxide (CO), sulfur either as sulfur dioxide (SO) (high-temperature volcanic gases) or hydrogen sulfide (HS) (low-temperature volcanic gases), nitrogen, argon, helium, neon, methane, carbon monoxide and hydrogen. Other compounds detected in volcanic gases are oxygen (meteoric), hydrogen chloride, hydrogen fluoride, hydrogen bromide, sulfur hexafluoride, carbonyl sulfide, and organic compounds. Exotic trace compounds include mercury, halocarbons (including CFCs), and halogen oxide radicals.
The abundance of gases varies considerably from volcano to volcano, with volcanic activity and with tectonic setting. Water vapour is consistently the most abundant volcanic gas, normally comprising more than 60% of total emissions. Carbon dioxide typically accounts for 10 to 40% of emissions.
Volcanoes located at convergent plate boundaries emit more water vapor and chlorine than volcanoes at hot spots or divergent plate boundaries. This is caused by the addition of seawater into magmas formed at subduction zones. Convergent plate boundary volcanoes also have higher HO/H, HO/CO, CO/He and N/He ratios than hot spot or divergent plate boundary volcanoes.
| 1 |
Applied and Interdisciplinary Chemistry
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Given two signals and , each of which possess power spectral densities and , it is possible to define a cross power spectral density (CPSD) or cross spectral density (CSD). To begin, let us consider the average power of such a combined signal.
Using the same notation and methods as used for the power spectral density derivation, we exploit Parseval's theorem and obtain
where, again, the contributions of and are already understood. Note that , so the full contribution to the cross power is, generally, from twice the real part of either individual CPSD. Just as before, from here we recast these products as the Fourier transform of a time convolution, which when divided by the period and taken to the limit becomes the Fourier transform of a cross-correlation function.
where is the cross-correlation of with and is the cross-correlation of with . In light of this, the PSD is seen to be a special case of the CSD for . If and are real signals (e.g. voltage or current), their Fourier transforms and are usually restricted to positive frequencies by convention. Therefore, in typical signal processing, the full CPSD is just one of the CPSDs scaled by a factor of two.
For discrete signals and , the relationship between the cross-spectral density and the cross-covariance is
| 0 |
Theoretical and Fundamental Chemistry
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Other effective molecules also came from industry during the period of 1970 to 1990, including anthracyclines and epipodophyllotoxins — both of which inhibited the action of topoisomerase II, an enzyme crucial for DNA synthesis.
| 1 |
Applied and Interdisciplinary Chemistry
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Deamination is the removal of an amino group from a molecule. Enzymes that catalyse this reaction are called deaminases.
In the human body, deamination takes place primarily in the liver; however, it can also occur in the kidney. In situations of excess protein intake, deamination is used to break down amino acids for energy. The amino group is removed from the amino acid and converted to ammonia. The rest of the amino acid is made up of mostly carbon and hydrogen, and is recycled or oxidized for energy. Ammonia is toxic to the human system, and enzymes convert it to urea or uric acid by addition of carbon dioxide molecules (which is not considered a deamination process) in the urea cycle, which also takes place in the liver. Urea and uric acid can safely diffuse into the blood and then be excreted in urine.
| 1 |
Applied and Interdisciplinary Chemistry
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*5.A.1 The Disulfide Bond Oxidoreductase D (DsbD) Family
*5.A.2 The Disulfide Bond Oxidoreductase B (DsbB) Family
*5.A.3 The Prokaryotic Molybdopterin-containing Oxidoreductase (PMO) Family
| 1 |
Applied and Interdisciplinary Chemistry
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In June 2012, the institution ASTM International organized a symposium on Geopolymer Binder Systems. The introduction to the symposium states: When performance specifications for Portland cement were written, non-portland binders were uncommon...New binders such as geopolymers are being increasingly researched, marketed as specialty products, and explored for use in structural concrete. This symposium is intended to provide an opportunity for ASTM to consider whether the existing cement standards provide, on the one hand, an effective framework for further exploration of geopolymer binders and, on the other hand, reliable protection for users of these materials.
The existing Portland cement standards are not adapted to geopolymer cements. They must be elaborated by an ad hoc committee. Yet, to do so, requires also the presence of standard geopolymer cements. Presently, every expert is presenting his own recipe based on local raw materials (wastes, by-products or extracted). There is a need for selecting the right geopolymer cement category. The 2012 State of the Geopolymer R&D, suggested to select two categories, namely:
* type 2 slag/fly ash-based geopolymer cement: fly ashes are available in the major emerging countries;
* ferro-sialate-based geopolymer cement: this geological iron-rich raw material is present in all countries throughout the globe.
along with the appropriate user-friendly geopolymeric reagent.
| 0 |
Theoretical and Fundamental Chemistry
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Silicon carbide can host point defects in the crystal lattice which are known as color centers. These defects can produce single photons on demand and thus serve as a platform for single-photon source. Such a device is a fundamental resource for many emerging applications of quantum information science. If one pumps a color center via an external optical source or electric current, the color center will be brought to the excited state and then relax with the emission of one photon.
One well known point defect in silicon carbide is the divacancy which has a similar electronic structure as the nitrogen-vacancy center in diamond. In 4H-SiC, the divacancy has four different configurations which correspond to four zero-phonon lines (ZPL). These ZPL values are written using the notation V-V and the unit eV: hh(1.095), kk(1.096), kh(1.119), and hk(1.150).
| 1 |
Applied and Interdisciplinary Chemistry
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Metallurgy derives from the Ancient Greek , , "worker in metal", from , , "mine, metal" + , , "work" The word was originally an alchemists term for the extraction of metals from minerals, the ending -urgy signifying a process, especially manufacturing: it was discussed in this sense in the 1797 Encyclopædia Britannica'.
In the late 19th century, metallurgys definition was extended to the more general scientific study of metals, alloys, and related processes. In English, the pronunciation is the more common one in the United Kingdom. The pronunciation is the more common one in the United States US and is the first-listed variant in various American dictionaries, including Merriam-Webster Collegiate and American Heritage'.
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Applied and Interdisciplinary Chemistry
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During the American Revolutionary War, a number of caves were mined for saltpeter to make gunpowder when supplies from Europe were embargoed. Abigail Adams reputedly also made gunpowder at her family farm in Massachusetts.
The New York Committee of Safety produced some essays on making gunpowder that were printed in 1776.
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Applied and Interdisciplinary Chemistry
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The formyl group readily oxidizes to the corresponding carboxyl group (). The preferred oxidant in industry is oxygen or air. In the laboratory, popular oxidizing agents include potassium permanganate, nitric acid, chromium(VI) oxide, and chromic acid. The combination of manganese dioxide, cyanide, acetic acid and methanol will convert the aldehyde to a methyl ester.
Another oxidation reaction is the basis of the silver-mirror test. In this test, an aldehyde is treated with Tollens reagent, which is prepared by adding a drop of sodium hydroxide solution into silver nitrate solution to give a precipitate of silver(I) oxide, and then adding just enough dilute ammonia solution to redissolve the precipitate in aqueous ammonia to produce complex. This reagent converts aldehydes to carboxylic acids without attacking carbon–carbon double bonds. The name silver-mirror test' arises because this reaction produces a precipitate of silver, whose presence can be used to test for the presence of an aldehyde.
A further oxidation reaction involves Fehling's reagent as a test. The complex ions are reduced to a red-brick-coloured precipitate.
If the aldehyde cannot form an enolate (e.g., benzaldehyde), addition of strong base induces the Cannizzaro reaction. This reaction results in disproportionation, producing a mixture of alcohol and carboxylic acid.
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Theoretical and Fundamental Chemistry
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Human activities have a major effect on the global sulfur cycle. The burning of coal, natural gas, and other fossil fuels has greatly increased the amount of sulfur in the atmosphere and ocean and depleted the sedimentary rock sink. Without human impact sulfur would stay tied up in rocks for millions of years until it was uplifted through tectonic events and then released through erosion and weathering processes. Instead it is being drilled, pumped and burned at a steadily increasing rate. Over the most polluted areas there has been a 30-fold increase in sulfate deposition.
Although the sulfur curve shows shifts between net sulfur oxidation and net sulfur reduction in the geologic past, the magnitude of the current human impact is probably unprecedented in the geologic record. Human activities greatly increase the flux of sulfur to the atmosphere, some of which is transported globally. Humans are mining coal and extracting petroleum from the Earths crust at a rate that mobilizes 150 x 10 gS/yr, which is more than double the rate of 100 years ago. The result of human impact on these processes is to increase the pool of oxidized sulfur (SO) in the global cycle, at the expense of the storage of reduced sulfur in the Earths crust. Therefore, human activities do not cause a major change in the global pools of sulfur, but they do produce massive changes in the annual flux of sulfur through the atmosphere.
When SO is emitted as an air pollutant, it forms sulfuric acid through reactions with water in the atmosphere. Once the acid is completely dissociated in water the pH can drop to 4.3 or lower causing damage to both man-made and natural systems. According to the EPA, acid rain is a broad term referring to a mixture of wet and dry deposition (deposited material) from the atmosphere containing higher than normal amounts of nitric and sulfuric acids. Distilled water (water without any dissolved constituents), which contains no carbon dioxide, has a neutral pH of 7. Rain naturally has a slightly acidic pH of 5.6, because carbon dioxide and water in the air react together to form carbonic acid, a very weak acid. Around Washington, D.C., however, the average rain pH is between 4.2 and 4.4. Since pH is on a log scale dropping by 1 (the difference between normal rain water and acid rain) has a dramatic effect on the strength of the acid. In the United States, roughly two thirds of all SO and one fourth of all NO come from electric power generation that relies on burning fossil fuels, like coal.
As it is an important nutrient for plants, sulfur is increasingly used as a component of fertilizers. Recently sulfur deficiency has become widespread in many countries in Europe. Because of actions taken to limit acid rains atmospheric inputs of sulfur continue to decrease, As a result, the deficit in the sulfur input is likely to increase unless sulfur fertilizers are used.
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Theoretical and Fundamental Chemistry
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Redox reactions are highly influential in wetland soil chemistry through transformations including those of carbon, sulfur, nitrogen. The abundance of oxygen changes the abundance of oxidized or reduced states of each compound. Areas of higher oxygen availability (aerobic) tend towards oxidized states and areas of low oxygen availability (anaerobic) tend towards reduced states. The abundance of each type results in a different ecosystem, as the plants and animals of the wetlands require specific conditions for their growth. Common wetland redox reactions include:
:2NO +10e +12H → N +6HO
:SO +8e +9H → HS +4HO
:CO +8e +8H → CH + 2HO
:MnO +2e +4H → Mn + 2HO
:Fe(OH) +e +3H → Fe + 3HO
Dredging allows for an increased flow of water through wetlands, causing anaerobic soil conditions. This change in wetland type results in a change in redox state for each reaction undergone and thus changes the plant species available to grow in those areas. The redox potential (Eh) can help to show the relationship of the redox reactions through the Nernst equation:
:Eh=E-(RT/nF)ln([Reductants]/[Oxidants][H])
This equation allows for the calculation of the extent of reaction between two redox systems and can be used, for example, to decide whether a particular reaction will go to completion or not.
An example of a change in these circumstances affecting the wetland system is in the transformation of pyrite (FeS) through the reduction of SO (found in seawater).
:Fe(OH) + e + H → Fe(OH) + HO
:SO + 6e + 8H → S + 4HO
:S + 2e + 2H → HS
:Fe(OH) + HS → FeS + 2HO
:FeS + S → FeS (pyrite)
The drainage of the resulted pyrite then results in oxidation to ferric hydroxide and sulfuric acid, causing extreme acidity (pH < 2).
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Theoretical and Fundamental Chemistry
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Değirmentepe or Değirmentepe Hüyük is an archaeological site which is located at 50 km north of the river Euphrates and at 24 km in the northeast of Malatya province in eastern Anatolia. It is now submerged in the reservoir area of the Karakaya and Atatürk dams. Rescue excavations were undertaken in under the supervision of Ufuk Esin of Istanbul University and interrupted in by flooding of the dams.
Four archaeological layers whose dates are determined by techniques such as C14 and traces of fusion have been discovered in this mound:
# Middle Ages (late Roman-Byzantine period)
# Iron Age (1000 BC)
# Bronze Age ancient I (Karaz or Khirbet Kerak culture, end of 4th millennium-beginning of 3rd millennium BCE)
# Chalcolithic Age (Ubaid period, second half of Vth millennium BCE.)
The Chalcolithic Değirmentepe level of Ubaid-4 of the second half of the Vth millennium BCE, of which the sites of Tülintepe, Seyh Hüyük and Kurban Hüyük are contemporary, contain skeletons of adolescents with skull deformed. The remains of this cultural phase belonging to the Chalcolithic are relatively well preserved. However, serious damage caused by occasional flooding of the Euphrates did occur, especially on architectural structures and the cemetery. Cranial deformities are not observed on human remains discovered and identified in Iron Age periods and medieval levels from Değrentepe.
The Chalcolithic period of this ancient village is characterized by rectangular mud brick houses that communicate with each other. We see the appearance of domestic animals such as dogs, sheeps, goats, pigs and Bovinae than at the beginning of the Chalcolithic. barley, wheat, oats, and peas were the most commonly cultivated plants.
Many potteries characteristic of Ubaid culture have been found at the site. Archaeologists have discovered 450 sealings there which indicate intensive commercial activities, and production management.
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Applied and Interdisciplinary Chemistry
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The condition that the ETH imposes on the diagonal elements of an observable is responsible for the equality of the predictions of the diagonal and microcanonical ensembles. However, the equality of these long-time averages does not guarantee that the fluctuations in time around this average will be small. That is, the equality of the long-time averages does not ensure that the expectation value of will settle down to this long-time average value, and then stay there for most times.
In order to deduce the conditions necessary for the observable's expectation value to exhibit small temporal fluctuations around its time-average, we study the mean squared amplitude of the temporal fluctuations, defined as
where is a shorthand notation for the expectation value of at time t. This expression can be computed explicitly, and one finds that
Temporal fluctuations about the long-time average will be small so long as the off-diagonal elements satisfy the conditions imposed on them by the ETH, namely that they become exponentially small in the system size. Notice that this condition allows for the possibility of isolated resurgence times, in which the phases align coherently in order to produce large fluctuations away from the long-time average. The amount of time the system spends far away from the long-time average is guaranteed to be small so long as the above mean squared amplitude is sufficiently small. If a system poses a dynamical symmetry, however, it will periodically oscillate around the long-time average.
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Theoretical and Fundamental Chemistry
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3D cell culturing by Magnetic Levitation Method (MLM) is the application of growing 3D tissue by inducing cells treated with magnetic nanoparticle assemblies in spatially varying magnetic fields, using neodymium magnetic drivers and promoting cell-to-cell interactions by levitating the cells up to the air/liquid interface of a standard petri dish. The magnetic nanoparticle assemblies consist of magnetic iron oxide nanoparticles, gold nanoparticles, and the polymer polylysine. 3D cell culturing is scalable, with the capability of culturing as few as 500 cells up to millions of cells, or from a single dish to high-throughput low volume systems. Once magnetized cultures are generated, they can also be used as the building block material, or the "ink" for the magnetic 3D bioprinting process.
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Theoretical and Fundamental Chemistry
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In alchemy, an athanor (, at-tannūr) is a furnace used to provide a uniform and constant heat for alchemical digestion. Etymologically, it descends from a number of Arabic texts of the period of the Caliphate which use the term "al-tannoor" in talismanic alchemy, meaning a bread-oven, from which the design portrayed evidently descends.
The athanor was also called Piger Henricus ("Slow Henry"), because it was chiefly used in slower operations, and because when once filled with coals, it keeps burning a long time. For this reason the Greeks referred to it as "giving no trouble", as it did not need to be continually attended. It was also called the Philosophical furnace, Furnace of Arcana, or popularly, the Tower furnace.
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Applied and Interdisciplinary Chemistry
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Organic phosphonium cations are lipophilic and can be useful in phase transfer catalysis, much like quaternary ammonium salts. Salts or inorganic anions and tetraphenylphosphonium () are soluble in polar organic solvents. One example is the perrhenate (PPh[ReO]).
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Theoretical and Fundamental Chemistry
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The electrolysis process, also known as the hydrometallurgical process, Roast-Leach-Electrowin (RLE) process, or electrolytic process, is more widely used than the pyrometallurgical processes.
The electrolysis process consists of 4 steps: leaching, purification, electrolysis, and melting and casting.
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Applied and Interdisciplinary Chemistry
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The net effect of soil liming on soil organic carbon is primarily the result of three processes.
# Increased plant productivity resulting in larger organic matter inputs. As soil liming ameliorates soil conditions that inhibit plant growth, an increase in plant productivity is expected. The higher yields resulting from lime applications will produce increased returns of organic matter to the soil in the form of dying roots and decaying crop residue.
# Increased organic matter mineralization due to a more favorable pH. Lime applications are known to have short-term stimulating effects on soil biological activity, thus favoring organic matter mineralization and very likely accelerating organic matter turnover rates in soil.
# Amelioration of soil structure leading to a reduction of mineralization by means of protecting soil organic carbon. Liming is known to ameliorate soil structure, as high Ca concentrations and high ionic strength in the soil solution enhance the flocculation of clay minerals and, in turn, form more stable soil aggregates.
An agricultural study at the Faculty of Forestry in Freising, Germany, that compared tree stocks two and twenty years after liming found that liming promotes nitrate leaching and decreases the phosphorus content of some leaves.
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Theoretical and Fundamental Chemistry
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Cyclamin is an irritant compound that causes gastroenteritis, bloody stools, dizziness, seizures and even death by asphyxiation. Studied by many physiologists, cyclamin was viewed merely as a local irritant. However, considering the toxic effects of cyclamin, this a misconception. The roots and bulbs of cyclamen plants containing cyclamin are known to cause severe diarrhea, nausea, vomiting and even death if eaten raw.
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Theoretical and Fundamental Chemistry
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Vargulin, also called Cypridinid luciferin, Cypridina luciferin, or Vargula luciferin, is the luciferin found in the ostracod Cypridina hilgendorfii, also named Vargula hilgendorfii. These bottom dwelling ostracods emit a light stream into water when disturbed presumably to deter predation. Vargulin is also used by the midshipman fish, Porichthys.
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Applied and Interdisciplinary Chemistry
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There are multiple technologies available that identify genetic variants. Each technology has advantages and disadvantages in terms of technical and financial factors. Two such technologies are microarrays and whole-genome sequencing.
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Applied and Interdisciplinary Chemistry
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In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions, or molecules in a crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric patterns that repeat along the principal directions of three-dimensional space in matter.
The smallest group of particles in the material that constitutes this repeating pattern is the unit cell of the structure. The unit cell completely reflects the symmetry and structure of the entire crystal, which is built up by repetitive translation of the unit cell along its principal axes. The translation vectors define the nodes of the Bravais lattice.
The lengths of the principal axes, or edges, of the unit cell and the angles between them are the lattice constants, also called lattice parameters or cell parameters. The symmetry properties of the crystal are described by the concept of space groups. All possible symmetric arrangements of particles in three-dimensional space may be described by the 230 space groups.
The crystal structure and symmetry play a critical role in determining many physical properties, such as cleavage, electronic band structure, and optical transparency.
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Theoretical and Fundamental Chemistry
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Though he later downplayed the hypothesis, Orgel, along with Francis Crick, proposed a detailed panspermia scenario for the origin of life on Earth, going so far as to suggest that life on Earth was designed by an alien species and sent to Earth. They proposed a design for the spaceship that aliens could have used to seed life on Earth.
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Theoretical and Fundamental Chemistry
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The principle behind fluorescence is that the fluorescent moiety contains electrons which can absorb a photon and briefly enter an excited state before either dispersing the energy non-radiatively or emitting it as a photon, but with a lower energy, i.e., at a longer wavelength (wavelength and energy are inversely proportional).
The difference in the excitation and emission wavelengths is called the Stokes shift, and the time that an excited electron takes to emit the photon is called a lifetime. The quantum yield is an indicator of the efficiency of the dye (it is the ratio of emitted photons per absorbed photon), and the extinction coefficient is the amount of light that can be absorbed by a fluorophore. Both the quantum yield and extinction coefficient are specific for each fluorophore and multiplied together calculates the brightness of the fluorescent molecule.
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Applied and Interdisciplinary Chemistry
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Sex and drugs date back to ancient humans and have been interlocked throughout human history. Both legal and illegal, the consumption of drugs and their effects on the human body encompasses all aspects of sex, including desire, performance, pleasure, conception, gestation, and disease.
There are many different types of drugs that are commonly associated with their effects on sex, including alcohol, cannabis, cocaine, MDMA, GHB, amphetamines, opioids, antidepressants, and many others.
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Applied and Interdisciplinary Chemistry
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The kinetic theory of gases entails that due to the microscopic reversibility of the gas particles' detailed dynamics, the system must obey the principle of detailed balance. Specifically, the fluctuation-dissipation theorem applies to the Brownian motion (or diffusion) and the drag force, which leads to the Einstein–Smoluchowski equation:where
* is the diffusion coefficient;
* is the "mobility", or the ratio of the particle's terminal drift velocity to an applied force, ;
* is the Boltzmann constant;
* is the absolute temperature.
Note that the mobility can be calculated based on the viscosity of the gas; Therefore, the Einstein–Smoluchowski equation also provides a relation between the mass diffusivity and the viscosity of the gas.
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Theoretical and Fundamental Chemistry
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The original Boger fluid was an aqueous solution, as were all the solutions synthesized until 1983, when organic Boger fluids were produced using a dilute solution of polyisobutylene (PIB) in a mixture of polybutene (PB) with a small quantity of kerosene oil added. From then on, most Boger fluids have been PIB - PB solutions. Other recipes include:
* polystyrene in oligomeric glycol (Solomon and Muller 1996)
* polyethylene oxide in polyethylene glycol (Dontula et al. 2004)
* polystyrene in dioctyl phthalate (Odell & Carrington 2006)
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Applied and Interdisciplinary Chemistry
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Smith earned a BS in Metallurgical Engineering from Michigan Technological University in 1969, subsequently working at an engineering firm in Moab, Utah. He returned to Michigan Tech to complete an M.S. degree in 1972 and then moved to Minneapolis for a research position at the University of Minnesota.
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Applied and Interdisciplinary Chemistry
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A variety of protective equipment may be used, including gas masks and respirators. In riot control situations, protesters sometimes use equipment (aside from simple rags or clothing over the mouth) such as swimming goggles and adapted water bottles, as well as covering as much skin as possible.
Activists in United States, the Czech Republic, Venezuela and Turkey have reported using antacid solutions such as Maalox diluted with water to repel effects of tear gas attacks, with Venezuelan chemist Mónica Kräuter recommending the usage of diluted antacids as well as baking soda. There have also been reports of these antacids being helpful for tear gas, and for capsaicin-induced skin pain.
During the 2019 Hong Kong protests, frontline protesters became adept at extinguishing tear gas: they formed special teams that spring into action as soon as it was fired. These individuals generally wear protective clothing, including heat-proof gloves, or cover their arms and legs with cling film to prevent the painful skin irritation. Canisters are sometimes picked up and lobbed back at police or extinguished straight away with water, or neutralized using objects such as traffic cones. They share information about models of 3M respirator filters which have been found to be most effective against tear gas, and where those models could be purchased. Other volunteers carry saline solutions to rinse the eyes of those affected. Similarly, Chilean protesters of Primera Línea have specialized individuals collecting and extinguishing the tear gas grenades. Others act as tear gas medics, while yet another group, the so-called shield-bearers, protect the protesters from the direct physical impact of the grenades.
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Applied and Interdisciplinary Chemistry
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Oxidation is the process of an element losing electrons. For example, iron will transfer two of its electrons to oxygen, forming an oxide. This occurs all throughout as an unintended part of the steelmaking process.
Oxygen blowing is a method of steelmaking where oxygen is blown through pig iron to lower the carbon content. Oxygen forms oxides with the unwanted elements, such as carbon, silicon, phosphorus, and manganese, which appear from various stages of the manufacturing process. These oxides will float to the top of the steel pool and remove themselves from the pig iron. However, some of the oxygen will also react with the iron itself.
Due to the high temperatures involved in smelting, oxygen in the air may dissolve into the molten iron while it is being poured. Slag, a byproduct left over after the smelting process, is used to further absorb impurities such as sulfur or oxides and protect steel from further oxidation. However, it can still be responsible for some oxidation.
Some processes, while still able to lead to oxidation, are not relevant to the oxygen content of steel during its manufacture. For example, rust is a red iron oxide that forms when the iron in steel reacts with the oxygen or water in the air. This usually only occurs once the steel has been in use for varying lengths of time. Some physical components of the steelmaking process itself, such as the electric arc furnace, may also wear down and oxidize. This problem is typically dealt with by the use of refractory metals, which resist environmental conditions.
If steel is not properly deoxidized, it will have lost various properties such as tensile strength, ductility, toughness, weldability, polishability, and machinability. This is due to forming non-metallic inclusions and gas pores, bubbles of gas that get trapped during the solidification process of steel.
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Applied and Interdisciplinary Chemistry
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The ISASMELT process is an energy-efficient smelting process that was jointly developed from the 1970s to the 1990s by Mount Isa Mines (a subsidiary of MIM Holdings and now part of Glencore) and the Government of Australia's CSIRO. It has relatively low capital and operating costs for a smelting process.
ISASMELT technology has been applied to lead, copper, and nickel smelting. As of 2021, 22 plants were in operation in eleven countries, along with three demonstration plants located at Mt Isa. The installed capacity of copper/nickel operating plants in 2020 was 9.76 million tonnes per year of feed materials and 750 thousand tonnes per year across lead operating plants.
Smelters based on the copper ISASMELT process are among the lowest-cost copper smelters in the world.
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Applied and Interdisciplinary Chemistry
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* (Biblical interpretation, the architecture of the Jewish Temple, ancient history, alchemy and the Apocalypse).
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Applied and Interdisciplinary Chemistry
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An example of a plumbide is CeRhPb. The lead atom has a coordination number of 12 in the crystal structure of this compound. It is bound to four rhodiums, six ceriums, and two other lead atoms in the crystal structure of the chemical.
Several other plumbides are the MPdPb plumbides, where M is a rare-earth element, and the intermetallic additionally contains a palladium. These plumbides tend to exhibit antiferromagnetism, and all of them are conductors.
A third plumbide is TiPb. Like the above plumbides, it is an intermetallic, but it only contains titanium as the other metal, and not any rare earths.
Plumbides can also be Zintl phase compounds, such as [K(18-crown-6)]KPb·(en). This is not a simple Zintl compound, but rather contains the organic molecules 18-crown-6 and ethylenediamine (en) in order to stabilize the crystal structure.
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Theoretical and Fundamental Chemistry
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NASAs Europa Clipper probe is designed as a flyby mission to Jupiters smallest Galilean moon, Europa. Set to launch in 2024, this probe will investigate the potential for habitability on Europa. Europa is one of the best candidates for biosignature discovery in the Solar System because of the scientific consensus that it retains a subsurface ocean, with two to three times the volume of water on Earth. Evidence for this subsurface ocean includes:
*Voyager 1 (1979): The first close-up photos of Europa are taken. Scientists propose that a subsurface ocean could cause the tectonic-like marks on the surface.
*Galileo (1997): The magnetometer aboard this probe detected a subtle change in the magnetic field near Europa. This was later interpreted as a disruption in the expected magnetic field due to the current induction in a conducting layer on Europa. The composition of this conducting layer is consistent with a salty subsurface ocean.
*Hubble Space Telescope (2012): An image was taken of Europa which showed evidence for a plume of water vapor coming off the surface.
The Europa Clipper probe will carry instruments to help confirm the existence and composition of a subsurface ocean and thick icy layer. In addition, it will map the surface to study features that may point to tectonic activity due to a subsurface ocean.
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Applied and Interdisciplinary Chemistry
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Niyazi Serdar Sarıçiftçi (born 1961 in Konya, Turkey) is a Turkish-Austrian physicist. He is professor for physical chemistry at the Johannes Kepler University (JKU) Linz. There, he leads the Institut for Physical Chemistry as well as the Institut for Organic Solar Cells (LIOS).
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Theoretical and Fundamental Chemistry
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The size of materials being processed in an operation is very important. Having oversize material being conveyed will cause damage to equipment and slow down production. Particle-size analysis also helps the effectiveness of SAG Mills when crushing material.
In the building industry, the particle size can directly affect the strength of the final material, as it observed for cement. Two of the most used techniques used for the particle size characterization of minerals are sieving and laser diffraction. These techniques are faster and cheaper compared to image-based techniques.
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Theoretical and Fundamental Chemistry
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;Pre-2004
*Organometallic C–H Bond Activation: An Introduction Alan S. Goldman and Karen I. Goldberg ACS Symposium Series 885, Activation and Functionalization of C–H Bonds, 2004, 1–43
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Theoretical and Fundamental Chemistry
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A superhydrophobic coating is a thin surface layer that repels water. It is made from superhydrophobic (ultrahydrophobicity) materials. Droplets hitting this kind of coating can fully rebound. Generally speaking, superhydrophobic coatings are made from composite materials where one component provides the roughness and the other provides low surface energy.
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Theoretical and Fundamental Chemistry
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There are currently two accepted models for the creation of human artificial chromosome vectors. The first is to create a small minichromosome by altering a natural human chromosome. This is accomplished by truncating the natural chromosome, followed by the introduction of unique genetic material via the Cre-Lox system of recombination. The second method involves the literal creation of a novel chromosome de novo. Progress regarding de novo HAC formation has been limited, as many large genomic fragments will not successfully integrate into de novo vectors. Another factor limiting de novo vector formation is limited knowledge of what elements are required for construction, specifically centromeric sequences. However, challenges involving centromeric sequences have begun to be overcome.
| 1 |
Applied and Interdisciplinary Chemistry
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Sieve analysis is often used because of its simplicity, cheapness, and ease of interpretation. Methods may be simple shaking of the sample in sieves until the amount retained becomes more or less constant. Alternatively, the sample may be washed through with a non-reacting liquid (usually water) or blown through with an air current.
Advantages: this technique is well-adapted for bulk materials. A large amount of materials can be readily loaded into sieve trays. Two common uses in the powder industry are wet-sieving of milled limestone and dry-sieving of milled coal.
Disadvantages: many PSDs are concerned with particles too small for separation by sieving to be practical. A very fine sieve, such as 37 μm sieve, is exceedingly fragile, and it is very difficult to get material to pass through it. Another disadvantage is that the amount of energy used to sieve the sample is arbitrarily determined. Over-energetic sieving causes attrition of the particles and thus changes the PSD, while insufficient energy fails to break down loose agglomerates. Although manual sieving procedures can be ineffective, automated sieving technologies using image fragmentation analysis software are available. These technologies can sieve material by capturing and analyzing a photo of material.
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Theoretical and Fundamental Chemistry
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Oxide fluxes are often combined to reduce volatility, viscosity, and reactivity towards the crucibles. Metallic fluxes aren't typically combined, as they do not suffer from the same volatility, viscosity, and reactivity issues. An ideal flux should have the following properties:
* Good solubility for desired compound at growth temperatures.
* Low melting point.
* Large gap between melting and boiling point.
* Easily removed from crystals.
* Unreactive with crucible and starting materials at growth temperatures.
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Theoretical and Fundamental Chemistry
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Metabolism and Hofmann elimination
Deacetylating vecuronium at position 3 results in a very active metabolite. In the case of rapacuronium the 3-deacylated metabolite is even more potent than rapacuronium. As long as the D-ring acetylcholine moiety is unchanged they retain their muscle relaxing effect. Mono-quaternary aminosteroids produced with deacylation in position 17 on the other hand are generally weak muscle relaxants. In the development of atracurium the main idea was to make use of Hofmann elimination of the muscle relaxant in vivo. When working with bisbenzyl-isoquinolinium types of molecules, inserting proper features into the molecule such as an appropriate electron withdrawing group then Hofmann elimination should occur at conditions in vivo. Atracurium, the resulting molecule, breaks down spontaneously in the body to inactive compounds and being especially useful in patients with kidney or liver failure. Cis-atracurium is very similar to atracurium except it is more potent and has a weaker tendency to cause histamine release.
Structure relations to onset time
The effect of structure on the onset of action is not very well known except that the time of onset appears inversely related to potency. In general mono-quaternary aminosteroids are faster than bis-quaternary compounds, which means they are also of lower potency. A possible explanation for this effect is that drug delivery and receptor binding are of a different timescale. Weaker muscle relaxants are given in larger doses so more molecules in the central compartment must diffuse into the effect compartment, which is the space within the mouth of the receptor, of the body. After delivery to the effect compartment then all molecules act quickly. Therapeutically this relationship is very inconvenient because low potency, often meaning low specificity can decrease the safety margin thus increasing the chances of side-effects. In addition, even though low potency usually accelerates onset of action, it does not guaranty a fast onset. Gallamine, for example, is weak and slow. When fast onset is necessary then succinylcholine or rocuronium are usually preferable.
Elimination
Muscle relaxants can have very different metabolic pathways and it is important that the drug does not accumulate if certain elimination pathways are not active, for example in kidney failure.
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Applied and Interdisciplinary Chemistry
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Surface run-off results in a significant amount of economic effects. Pine straws are cost effective ways of dealing with surface run-off. Moreover, Surface run-off can be reused through the growth of elephant mass. In Nigeria, elephant grass is considered to be an economical way in which surface run-off and erosion can be reduced. Also, China has suffered significant impact from surface run-off to most of their economical crops such as vegetables. Therefore, they are known to have implemented a system which reduced loss of nutrients (nitrogen and phosphorus) in soil.
| 1 |
Applied and Interdisciplinary Chemistry
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Stable isotope mass spectrometry is conducted in the Department of Geography, and was recently used by the Landmark Trust to determine very precisely the age of the timber from Llwyn Celyn farmhouse to the year 1420.
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Theoretical and Fundamental Chemistry
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PAF is a potent activator of platelet aggregation, inflammation, and anaphylaxis. It is similar to the ubiquitous membrane phospholipid phosphatidylcholine except that it contains an acetyl-group in the SN-2 position and the SN-1 position contains an ether-linkage. PAF signals through a dedicated G-protein coupled receptor, PAFR and is inactivated by PAF acetylhydrolase.
| 1 |
Applied and Interdisciplinary Chemistry
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Yakov Frenkel represented diffusion process in condensed matter as an ensemble of elementary jumps and quasichemical interactions of particles and defects. Henry Eyring applied his theory of absolute reaction rates to this quasichemical representation of diffusion. Mass action law for diffusion leads to various nonlinear versions of Fick's law.
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Theoretical and Fundamental Chemistry
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It is an aggressive electrophile and readily hydrolyzes to the strong acid triflic acid. It is very harmful to skin and eyes.
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Theoretical and Fundamental Chemistry
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Prof. Kotcherlakota Rangadhama Rao Memorial Lecture Award is given for the outstanding contributions in the subject of Spectroscopy in Physics. The award was established by the Indian National Science Academy of Calcutta in the year 1979. The honour is awarded to Indian citizens.
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Theoretical and Fundamental Chemistry
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Special, stringent care is required when handling aircraft hydraulic fluid, as it is critical to flight safety that it stay free from contamination. It is also necessary to strictly adhere to authorized references when servicing or repairing any aircraft system. Samples from aircraft hydraulic systems are taken during heavy aircraft maintenance checks (primarily C and D checks) to check contamination.
[http://everyspec.com/MIL-STD/MIL-STD-1100-1299/MIL-STD-1246C_NOTICE-1_21759/ Military Spec 1246C] is one fluid contamination specification.
The ISO fluid contamination scale assigns a contamination category based on particle size count and distribution.
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Applied and Interdisciplinary Chemistry
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Pullulan is generated by the microbial A. pullulans through the processing mainly of glucose, but can also be produced from maltose, fructose, galactose, sucrose, and mannose. In a commercial setting, pullulan is obtained from a strain of A. pullulans that is non-toxic, non-pathogenic, and unmodified genetically that is given a liquid form of starch in a set environment. The pullulan produced can be modified by different conditions such as the nutrients provided, temperature, pH, oxygen content, and other supplements. The microbial needs to be provided with a source of carbon and nitrogen in order to produce pullulan and the ratio of carbon to nitrogen needs to be precise in order to maximize pullulan production. Higher levels of nitrogen than carbon are required as excess carbon can decrease the efficiency of the enzymes and excess nitrogen can increase the production of biomass, but does not affect the pullulan production. Oxygen is also important for the proliferation of the A. pullulans cells and the production of pullulan. Further supplements can be used in order to increase the level of pullulan production, such as olive oil and tween 80.
While the manufacturing conditions of pullulan can be altered in order to increase yield, chemical modifications of pullulan can also be used to alter the properties of the pullulan. The unmodified structure of pullulan contains nine hydroxyl groups attached to the backbone of the molecule, and these hydroxyl groups can be replaced with other functional groups. Some examples of processes that can modify the functional groups of pullulan include sulfation, esterification, oxidation, etherification, copolymerization, amidification, and others. Pullulan can be given a negative charge through creating an ester linkage that attaches a carboxylate group to the hydroxyl, which yields a carboxymethyl pullulan. Pullulan is hydrophilic and can be modified to have hydrophobic functionality by adding a cholesterol group. The main benefit of the added hydrophobic functionality is that it makes it so the pullulan can form self assembling micelles. Another notable modification to pullulan is the acetylation of pullulan in order to create pullulan acetate (PA), which also has a hydrophobic functionality. PA has the benefit of forming self-assembled nanoparticles, which can simplify manufacturing of certain pullulan bioconjugates. Pullulan and pullulan derivatives can also be folated in order to improve cancer cell targeting as the nanoparticle can be endocytosed into the cancer cells through folate-mediated endocytosis.
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Applied and Interdisciplinary Chemistry
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Potential flow theory can also be used to model irrotational compressible flow. The derivation of the governing equation for from Eulers equation is quite straightforward. The continuity and the (potential flow) momentum equations for steady flows are given by
where the last equation follows from that fact that entropy is constant for a fluid particle and that square of the sound speed is . Eliminating from the two governing equations results in
The incompressible version emerges in the limit . Substituting here results in
where is expressed as a function of the velocity magnitude . For a polytropic gas, , where is the specific heat ratio and is the stagnation enthalpy. In two dimensions, the equation simplifies to
Validity: As it stands, the equation is valid for any inviscid potential flows, irrespective of whether the flow is subsonic or supersonic (e.g. Prandtl–Meyer flow). However in supersonic and also in transonic flows, shock waves can occur which can introduce entropy and vorticity into the flow making the flow rotational. Nevertheless, there are two cases for which potential flow prevails even in the presence of shock waves, which are explained from the (not necessairly potential) momentum equation written in the following form
where is the specific enthalpy, is the vorticity field, is the temperature and is the specific entropy. Since in front of the leading shock wave, we have a potential flow, Bernoulli's equation shows that is constant, which is also constant across the shock wave (Rankine–Hugoniot conditions) and therefore we can write
1) When the shock wave is of constant intensity, the entropy discontinuity across the shock wave is also constant i.e., and therefore vorticity production is zero. Shock waves at the pointed leading edge of two-dimensional wedge or three-dimensional cone (Taylor–Maccoll flow) has constant intensity. 2) For weak shock waves, the entropy jump across the shock wave is a third-order quantity in terms of shock wave strength and therefore can be neglected. Shock waves in slender bodies lies nearly parallel to the body and they are weak.
Nearly parallel flows: When the flow is predominantly unidirectional with small deviations such as in flow past slender bodies, the full equation can be further simplified. Let be the mainstream and consider small deviations from this velocity field. The corresponding velocity potential can be written as where characterizes the small departure from the uniform flow and satisfies the linearized version of the full equation. This is given by
where is the constant Mach number corresponding to the uniform flow. This equation is valid provided is not close to unity. When is small (transonic flow), we have the following nonlinear equation
where is the critical value of and is the specific volume. The transonic flow is completely characterized by the single parameter , which for polytropic gas takes the value . Under hodograph transformation, the transonic equation in two-dimensions becomes the Euler–Tricomi equation.
| 1 |
Applied and Interdisciplinary Chemistry
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A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings, but are usually discussed as a separate category. In an open valve, fluid flows in a direction from higher pressure to lower pressure. The word is derived from the Latin valva, the moving part of a door, in turn from volvere, to turn, roll.
The simplest, and very ancient, valve is simply a freely hinged flap which swings down to obstruct fluid (gas or liquid) flow in one direction, but is pushed up by the flow itself when the flow is moving in the opposite direction. This is called a check valve, as it prevents or "checks" the flow in one direction. Modern control valves may regulate pressure or flow downstream and operate on sophisticated automation systems.
Valves have many uses, including controlling water for irrigation, industrial uses for controlling processes, residential uses such as on/off and pressure control to dish and clothes washers and taps in the home. Valves are also used in the military and transport sectors. In HVAC ductwork and other near-atmospheric air flows, valves are instead called dampers. In compressed air systems, however, valves are used with the most common type being ball valves.
| 1 |
Applied and Interdisciplinary Chemistry
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There are multiple different ways to fix cultural eutrophication with raw sewage being a point source of pollution. For example, sewage treatment plants can be upgraded for biological nutrient removal so that they discharge much less nitrogen and phosphorus to the receiving water body. However, even with good secondary treatment, most final effluents from sewage treatment works contain substantial concentrations of nitrogen as nitrate, nitrite or ammonia. Removal of these nutrients is an expensive and often difficult process.
Laws regulating the discharge and treatment of sewage have led to dramatic nutrient reductions to surrounding ecosystems. Because a major contributor to the nonpoint source nutrient loading of water bodies is untreated domestic sewage, it is necessary to provide treatment facilities to highly urbanized areas, particularly those in developing countries, in which treatment of domestic waste water is a scarcity. The technology to safely and efficiently reuse wastewater, both from domestic and industrial sources, should be a primary concern for policy regarding eutrophication.
| 1 |
Applied and Interdisciplinary Chemistry
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Hull speed or displacement speed is the speed at which the wavelength of a vessel's bow wave is equal to the waterline length of the vessel. As boat speed increases from rest, the wavelength of the bow wave increases, and usually its crest-to-trough dimension (height) increases as well. When hull speed is exceeded, a vessel in displacement mode will appear to be climbing up the back of its bow wave.
From a technical perspective, at hull speed the bow and stern waves interfere constructively, creating relatively large waves, and thus a relatively large value of wave drag. Ship drag for a displacement hull increases smoothly with speed as hull speed is approached and exceeded, often with no noticeable inflection at hull speed.
The concept of hull speed is not used in modern naval architecture, where considerations of speed/length ratio or Froude number are considered more helpful.
| 1 |
Applied and Interdisciplinary Chemistry
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Organocatalysts for asymmetric synthesis can be grouped in several classes:
* Biomolecules: proline, phenylalanine. Secondary amines in general. The cinchona alkaloids, certain oligopeptides.
* Synthetic catalysts derived from biomolecules.
* Hydrogen bonding catalysts, including TADDOLS, derivatives of BINOL such as NOBIN, and organocatalysts based on thioureas
* Triazolium salts as next-generation Stetter reaction catalysts
Examples of asymmetric reactions involving organocatalysts are:
* Asymmetric Diels-Alder reactions
* Asymmetric Michael reactions
* Asymmetric Mannich reactions
* Shi epoxidation
* Organocatalytic transfer hydrogenation
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Theoretical and Fundamental Chemistry
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The quantum yield of photosynthesis, which is also the photochemical quenching of fluorescence, is calculated through the following equation:
Φ = (F-F)/F = F/F
F is the low fluorescence intensity, which is measured by a short light flash that is not strong enough to cause photochemistry, and thus induces fluorescence. F is the maximum fluorescence that can be obtained from a sample by measuring the highest intensity of fluorescence after a saturating flash. The difference between the measured values is the variable fluorescence F.
| 0 |
Theoretical and Fundamental Chemistry
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The isotopic reference frame of Standard Mean Ocean Water (SMOW) was established by Harmon Craig in 1961 by measuring δH and δO in samples of deep ocean water previously studied by Epstein & Mayeda (1953). Originally SMOW was a purely theoretical isotope ratio intended to represent the mean state of the deep ocean. In the initial work the isotopic ratios of deep ocean water were measured relative to NBS-1, a standard derived from the steam condensate of Potomac River water. Notably, this means SMOW was originally defined relative to NBS-1, and there was no physical SMOW solution. Following the advice of an IAEA advisory group meeting in 1966, Ray Weiss and Harmon Craig made an actual solution with the isotopic values of SMOW which they called Vienna Standard Mean Ocean Water (VSMOW). They also prepared a second hydrogen isotope reference material from firn collected at the Amundsen-Scott South Pole Station, initially called SNOW and later called Standard Light Antarctic Precipitation (SLAP). Both VSMOW and SLAP were distributed beginning in 1968. The isotopic characteristics of SLAP and NBS-1 were later evaluated by interlaboratory comparison through measurements against VSMOW (Gonfiantini, 1978). Subsequently, VSMOW and SLAP were used as the primary isotopic reference materials for the hydrogen isotope system for multiple decades. In 2006 the IAEA Isotope Hydrology Laboratory constructed new isotopic reference materials called VSMOW2 and SLAP2 with nearly identical δH and δO as VSMOW and SLAP. Hydrogen isotope working standards are currently calibrated against VSMOW2 and SLAP2 but are still reported on the scale defined by VSMOW and SLAP relative to VSMOW. Additionally, Greenland Ice Sheet Precipitation (GISP) δH has been measured to high precision in multiple labs, but different analytical facilities disagree on the value. These observations suggest GISP may have been fractionated during aliquoting or storage, implying that the reference material should be used with care.
| 0 |
Theoretical and Fundamental Chemistry
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Hydroalumination of alkynes may be either stereospecifically cis or trans depending on the conditions employed. When a dialkylalane such as di(isobutyl)aluminium hydride (DIBAL-H) is used, the hydrogen and aluminium delivered from the reagent end up cis in the resulting alkenylalane. This stereospecificity can be explained by invoking a concerted addition of the H–Al bond across the triple bond. In the transition state, partial positive charge builds up on the carbon forming a bond to hydrogen; thus, the carbon better able to stabilize a positive charge becomes attached to hydrogen in the product alkenylalane. Hydroaluminations of terminal alkynes typically produce terminal alkenylalanes as a result. Selectivity in hydroaluminations of internal alkynes is typically low, unless an electronic bias exists in the substrate (such as a phenyl ring in conjugation with the alkyne).
Stereospecific trans hydroalumination is possible through the use of lithium aluminium hydride. The mechanism of this transformation involves the addition of hydride to the carbon less able to stabilize the developing negative charge (viz., in the β position to an electron-withdrawing group). Coordination of aluminium to the resulting trans vinyl carbanion leads to the observed trans configuration of the product.
| 0 |
Theoretical and Fundamental Chemistry
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In molecular biology, gel extraction or gel isolation is a technique used to isolate a desired fragment of intact DNA from an agarose gel following agarose gel electrophoresis. After extraction, fragments of interest can be mixed, precipitated, and enzymatically ligated together in several simple steps. This process, usually performed on plasmids, is the basis for rudimentary genetic engineering.
After DNA samples are run on an agarose gel, extraction involves four basic steps: identifying the fragments of interest, isolating the corresponding bands, isolating the DNA from those bands, and removing the accompanying salts and stain.
To begin, UV light is shone on the gel in order to illuminate all the ethidium bromide-stained DNA. Care must be taken to avoid exposing the DNA to mutagenic radiation for longer than absolutely necessary. The desired band is identified and physically removed with a cover slip or razor blade. The removed slice of gel should contain the desired DNA inside. An alternative method, utilizing SYBR Safe DNA gel stain and blue-light illumination, avoids the DNA damage associated with ethidium bromide and UV light.
Several strategies for isolating and cleaning the DNA fragment of interest exist.
| 1 |
Applied and Interdisciplinary Chemistry
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Lovelock started defining the idea of a self-regulating Earth controlled by the community of living organisms in September 1965, while working at the Jet Propulsion Laboratory in California on methods of detecting life on Mars. The first paper to mention it was Planetary Atmospheres: Compositional and other Changes Associated with the Presence of Life, co-authored with C.E. Giffin. A main concept was that life could be detected in a planetary scale by the chemical composition of the atmosphere. According to the data gathered by the Pic du Midi observatory, planets like Mars or Venus had atmospheres in chemical equilibrium. This difference with the Earth atmosphere was considered to be a proof that there was no life in these planets.
Lovelock formulated the Gaia Hypothesis in journal articles in 1972 and 1974, followed by a popularizing 1979 book Gaia: A new look at life on Earth. An article in the New Scientist of February 6, 1975, and a popular book length version of the hypothesis, published in 1979 as The Quest for Gaia, began to attract scientific and critical attention.
Lovelock called it first the Earth feedback hypothesis, and it was a way to explain the fact that combinations of chemicals including oxygen and methane persist in stable concentrations in the atmosphere of the Earth. Lovelock suggested detecting such combinations in other planets' atmospheres as a relatively reliable and cheap way to detect life.
Later, other relationships such as sea creatures producing sulfur and iodine in approximately the same quantities as required by land creatures emerged and helped bolster the hypothesis.
In 1971 microbiologist Dr. Lynn Margulis joined Lovelock in the effort of fleshing out the initial hypothesis into scientifically proven concepts, contributing her knowledge about how microbes affect the atmosphere and the different layers in the surface of the planet. The American biologist had also awakened criticism from the scientific community with her advocacy of the theory on the origin of eukaryotic organelles and her contributions to the endosymbiotic theory, nowadays accepted. Margulis dedicated the last of eight chapters in her book, The Symbiotic Planet, to Gaia. However, she objected to the widespread personification of Gaia and stressed that Gaia is "not an organism", but "an emergent property of interaction among organisms". She defined Gaia as "the series of interacting ecosystems that compose a single huge ecosystem at the Earths surface. Period". The books most memorable "slogan" was actually quipped by a student of Margulis'.
James Lovelock called his first proposal the Gaia hypothesis but has also used the term Gaia theory. Lovelock states that the initial formulation was based on observation, but still lacked a scientific explanation. The Gaia hypothesis has since been supported by a number of scientific experiments and provided a number of useful predictions.
| 0 |
Theoretical and Fundamental Chemistry
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The main tools used to collect bioaerosols are collection plates, electrostatic collectors, mass spectrometers, and impactors, other methods are used but are more experimental in nature.<nowiki/> Polycarbonate (PC) filters have had the most accurate bacterial sampling success when compared to other PC filter options.
| 0 |
Theoretical and Fundamental Chemistry
|
Glucuronidation is often involved in drug metabolism of substances such as drugs, pollutants, bilirubin, androgens, estrogens, mineralocorticoids, glucocorticoids, fatty acid derivatives, retinoids, and bile acids. These linkages involve glycosidic bonds.
| 0 |
Theoretical and Fundamental Chemistry
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Sources:
The only parameter which characterizes the explosion is the Damköhler number . When is very high, conduction time is longer than the chemical reaction time and the system explodes with high temperature since there is not enough time for conduction to remove the heat. On the other hand, when is very low, heat conduction time is much faster than the chemical reaction time, such that all the heat produced by the chemical reaction is immediately conducted to the wall, thus there is no explosion, it goes to an almost steady state, Amable Liñán coined this mode as slowly reacting mode. At a critical Damköhler number the system goes from slowly reacting mode to explosive mode. Therefore, , the system is in steady state. Instead of solving the full problem to find this , Frank-Kamenetskii solved the steady state problem for various Damköhler number until the critical value, beyond which no steady solution exists. So the problem to be solved is
with boundary conditions
the second condition is due to the symmetry of the vessel. The above equation is special case of Liouville–Bratu–Gelfand equation in mathematics.
| 1 |
Applied and Interdisciplinary Chemistry
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Interfacial energy affects the mechanisms of grain boundary sliding and dislocation transmission. Higher interfacial energy promotes greater resistance to grain boundary sliding, as the higher energy barriers inhibit the relative movement of adjacent grains. Additionally, dislocations that encounter grain boundaries can either transmit across the boundary or be reflected back into the same grain. The interfacial energy influences the likelihood of dislocation transmission, with higher interfacial energy barriers impeding dislocation motion and enhancing grain boundary strengthening.
| 1 |
Applied and Interdisciplinary Chemistry
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UTP also has roles in mediating responses by extracellular binding to the P2Y receptors of cells. UTP and its derivatives are still being investigated for their applications in human medicine. However, there is evidence from various model systems to suggest it has applications in pathogen defense and injury repair. In mice UTP has been found to interact with P2Y4 receptors to mediate an enhancement in antibody production. In Schwannoma cells, UTP binds to the P2YP receptors in the event of damage. This leads to the downstream signal cascade that leads to the eventual injury repair.
| 1 |
Applied and Interdisciplinary Chemistry
|
Pancreatic lipase inhibitor was originally discovered and isolated from fermented broth of the Streptomyces toxytricini bacterium in 1981 and named lipstatin. It is a selective and potent irreversible inhibitor of human gastric and pancreatic lipases. Tetrahydrolipstatin, more commonly known as orlistat, is a saturated derivative produced by hydrogenation. It was developed in 1983 by Hoffmann-La Roche and is a more simple and stable compound than lipstatin. For that reason orlistat was chosen over lipstatin for development as an anti-obesity drug. It is the only available FDA-approved oral lipase inhibitor and is known on the market as Xenical and Alli.
Initially orlistat was developed as a treatment for dyslipidemia, not as an anti-obesity agent. When researchers found out that it promotes less energy uptake, the focus was switched to obesity.
Orlistat has a few adverse effects. Most reported side effects are gastrointestinal; including liquid stools, steatorrhea and abdominal pain. More severe and serious are interactions between orlistat and anticoagulants when given in combination. It can increase INR which can lead to insufficient anticoagulant treatment and bleeding. These adverse effects of orlistat are more common early in the therapy but usually decrease with time. Pancreatic lipases do not only affect the hydrolysis of triglycerides but are also necessary for hydrolysis of fat soluble vitamins. Due to this, the absorption of fat-soluble vitamins may decrease. Therefore, it is recommended to take a multiple-vitamin supplement during orlistat therapy.
Cetilistat, a new lipase inhibitor, is an experimental drug for obesity. In October 2016 the drug was still in clinical trials.
Cetilistat was developed to overcome the adverse effects on the gastrointestinal tract of orlistat. It has a different structure but similar inhibition activity to the gastrointestinal lipase. However cetilistat interacts differently with the fat micelles from digested food, therefore it has less side effects and better tolerability.
| 1 |
Applied and Interdisciplinary Chemistry
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Flutamide is an arylpropionamide analog with pure antiandrogenic properties, seen in figure 4. It is completely absorbed from the gastrointestinal tract after oral administration and undergoes extensive first pass metabolism to its active form, 2-hydroxyflutamide, and hydrolysis product, 3-trifluoromethyl-4-nitroaniline. Hydroxyflutamide is a more potent AR antagonist than flutamide in vivo, with higher binding affinity for the AR. Hydroxyflutamide has an elimination half-life of about 8 hours in humans. Hydrolysis of the amide bond represents the major metabolic pathway for this active metabolite. By reversing the stimulatory effect of DHT on ventral prostate weight, flutamide is approximately 2-fold more potent than cyproterone acetate. Hydroxyflutamide has relatively low binding affinity to AR and is therefore generally used at high doses in order to achieve complete AR blockage in therapy.
| 1 |
Applied and Interdisciplinary Chemistry
|
Plant defense signaling is activated by the pathogen-detecting receptors that are described in an above section. The activated receptors frequently elicit reactive oxygen and nitric oxide production, calcium, potassium and proton ion fluxes, altered levels of salicylic acid and other hormones and activation of MAP kinases and other specific protein kinases. These events in turn typically lead to the modification of proteins that control gene transcription, and the activation of defense-associated gene expression.
| 1 |
Applied and Interdisciplinary Chemistry
|
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