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This branch of engineering emerged gradually from chemical engineering as electrical power sources became available in the mid-19th century. Michael Faraday described his laws of electrolysis in 1833, relating for the first time the amount of electrical charge and converted mass. In 1886 Charles Martin Hall developed a cheap electrochemical process for extracting aluminium from its ore in molten salts, constituting the first true large-scale electrochemical industry. Later, Hamilton Castner improved the process aluminium manufacturing and devised the electrolysis of brine in large mercury cells for the production of chlorine and caustic soda, effectively founding the chlor-alkali industry with Karl Kellner in 1892. The next year, Paul L. Hulin patented filter-press type electrochemical cells in France. Charles Frederick Burgess developed the electrolytic refining of iron ca. 1904 and later ran a successful battery company. Burgess published one of the first texts on the field in 1920. Industrial electrochemistry followed an empirical approach during the first three decades of the 20th century.
After the Second World War, interest focused on the fundaments of electrochemical reactions. Among other developments, the potentiostat (1937) enabled such studies. A critical advance was provided by the work of Carl Wagner and Veniamin Levich in 1962, who linked the hydrodynamics of a flowing electrolyte towards a rotating disc electrode with the mass transport control of the electrochemical reaction through a rigorous mathematical treatment. The same year, Wagner described "The Scope of Electrochemical Engineering" for the first time as a separate discipline from a physicochemical perspective. During the 60s and 70s Charles W. Tobias, who is regarded as the "father of electrochemical engineering" by the Electrochemical Society, was concerned with ionic transport by diffusion, migration, and convection, exact solutions of potential and current distribution problems, conductance in heterogeneous media, quantitative description of processes in porous electrodes. Also in the 60s, John Newman pioneered the study of many of the physicochemical laws that govern electrochemical systems, demonstrating how complex electrochemical processes could be analysed mathematically to correctly formulate and solve problems associated with batteries, fuel cells, electrolyzer, and related technologies. In Switzerland, Norbert Ibl contributed to experimental and theoretical studies of mass transfer and potential distribution in electrolyses, especially at porous electrodes. Fumio Hine carried out equivalent developments in Japan. In addition, several individuals, including Kuhn, Kreysa, Rousar, Fleischmann, Alkire, Coeuret, Pletcher, and Walsh established many other training centers and, with their colleagues, developed important experimental and theoretical methods of study. Currently, the main tasks of electrochemical engineering consist of the development of efficient, safe, and sustainable technologies for the production of chemicals, metal recovery, remediation, and decontamination technologies as well as the design of fuel cells, flow batteries, and industrial electrochemical reactors.
The history of electrochemical engineering has been summarised by Wendt, Lapicque, and Stankovic. | 0 | Theoretical and Fundamental Chemistry |
In addition to her research and teaching career, Lathrop was involved in national societies. In 1966, she helped establish the SNM Medical Internal Radiation Dose Committee. She also was the first person to teach radiation safety to workers that would come into contact with radioactive material. After semi-retirement, she became very involved with the Daughters of the American Revolution and genealogy.
Lathrop retired in 2000 due to multiple cerebral ischemic attacks. She died in Las Cruces, New Mexico, on March 10, 2005, from complications caused by dementia.
Lathrop had five children. She had 10 grandchildren at the time of her death.
She died March 10, 2005. | 0 | Theoretical and Fundamental Chemistry |
Biomimicry is the imitation, or mimicry, of biological systems, models, or structures, in synthetic areas. Oftentimes, biological materials can produce structures, that have properties and qualities far exceeding what synthetic materials can achieve. Biomimicry is being used to create comparable properties in synthetic materials, particularly in wettability and self-cleaning abilities of self-cleaning surfaces. | 0 | Theoretical and Fundamental Chemistry |
Carboxypeptidase E (CPE), also known as carboxypeptidase H (CPH) and enkephalin convertase, is an enzyme that in humans is encoded by the CPE gene. This enzyme catalyzes the release of C-terminal arginine or lysine residues from polypeptides.
CPE is involved in the biosynthesis of most neuropeptides and peptide hormones. The production of neuropeptides and peptide hormones typically requires two sets of enzymes that cleave the peptide precursors, which are small proteins. First, proprotein convertases cut the precursor at specific sites to generate intermediates containing C-terminal basic residues (lysine and/or arginine). These intermediates are then cleaved by CPE to remove the basic residues. For some peptides, additional processing steps, such as C-terminal amidation, are subsequently required to generate the bioactive peptide, although for many peptides the action of the proprotein convertases and CPE is sufficient to produce the bioactive peptide. | 1 | Applied and Interdisciplinary Chemistry |
HACs were first constructed de novo in 1997 by adding alpha-satellite DNA to telomeric and genomic DNA in human HT1080 cells. This resulted in an entirely new microchromosome that contained DNA of interest, as well as elements allowing it to be structurally and mitotically stable, such as telomeric and centromeric sequences. Due to the difficulty of de novo HAC formation, this method has largely been abandoned. | 1 | Applied and Interdisciplinary Chemistry |
In the field of clinical imaging, with sufficient exposure, solarization of certain screen-film systems can occur which obscures details within the X-ray image and degrades the accuracy of the diagnosis. Even though degradation can occur this was found to be a rare phenomenon. | 0 | Theoretical and Fundamental Chemistry |
Abortive initiation occurs prior to promoter clearance.
# RNA polymerase binds to promoter DNA to form an RNA polymerase-promoter closed complex
# RNA polymerase then unwinds one turn of DNA surrounding the transcription start site to yield an RNA polymerase-promoter open complex
# RNA polymerase enters into abortive cycles of synthesis and releases short RNA products (contains less than 10 nucleotides)
# RNA polymerase escapes the promoter and enters into the elongation step of transcription | 1 | Applied and Interdisciplinary Chemistry |
FRET in lanthanide probes is a widely used technique to measure the distance between two points separated by approximately 15–100 Angstrom. Measurements can be done under physiological conditions in vitro with genetically encoded dyes, and often in vivo as well. The technique relies on a distant- dependent transfer of energy from a donor fluorophore to an acceptor dye. Lanthanide probes has been used to study DNA-protein interactions (using a terbium chelate complex) to measure distances in DNA complexes bent by the CAP protein. | 1 | Applied and Interdisciplinary Chemistry |
An energy diagram can be created based on the Enthalpy of Reaction of the individual steps. The energy diagram can be used to compare homogeneous and heterogeneous reactions: Due to the high activation energy of the dissociation of nitrogen, the homogeneous gas phase reaction is not realizable. The catalyst avoids this problem as the energy gain resulting from the binding of nitrogen atoms to the catalyst surface overcompensates for the necessary dissociation energy so that the reaction is finally exothermic. Nevertheless, the dissociative adsorption of nitrogen remains the rate-determining step: not because of the activation energy, but mainly because of the unfavorable pre-exponential factor of the rate constant. Although hydrogenation is endothermic, this energy can easily be applied by the reaction temperature (about 700 K). | 0 | Theoretical and Fundamental Chemistry |
The chloroplastida chloroplasts, or green chloroplasts, are another large, highly diverse primary chloroplast lineage. Their host organisms are commonly known as green algae and land plants. They differ from glaucophyte and red algal chloroplasts in that they have lost their phycobilisomes, and contain chlorophyll b instead. Most green chloroplasts are (obviously) green, though some arent, like some forms of Hæmatococcus pluvialis, due to accessory pigments that override the chlorophylls green colors. Chloroplastida chloroplasts have lost the peptidoglycan wall between their double membrane, leaving an intermembrane space. Some plants seem to have kept the genes for the synthesis of the peptidoglycan layer, though they've been repurposed for use in chloroplast division instead.
Most of the chloroplasts depicted in this article are green chloroplasts.
Green algae and plants keep their starch inside their chloroplasts, and in plants and some algae, the chloroplast thylakoids are arranged in grana stacks. Some green algal chloroplasts contain a structure called a pyrenoid, which is functionally similar to the glaucophyte carboxysome in that it is where RuBisCO and CO are concentrated in the chloroplast.
Helicosporidium is a genus of nonphotosynthetic parasitic green algae that is thought to contain a vestigial chloroplast. Genes from a chloroplast and nuclear genes indicating the presence of a chloroplast have been found in Helicosporidium even if nobody's seen the chloroplast itself. | 0 | Theoretical and Fundamental Chemistry |
Experimental error is usually assumed to affect the rate and not the substrate concentration , so is the dependent variable. As a result, both ordinate and abscissa are subject to experimental error, and so the deviations that occur due to error are not parallel with the ordinate axis but towards or away from the origin. As long as the plot is used for illustrating an analysis rather than for estimating the parameters, that matters very little. Regardless of these considerations various authors have compared the suitability of the various plots for displaying and analysing data. | 1 | Applied and Interdisciplinary Chemistry |
In the 1930s, USSR geochemist Alexander Fersman defined the relative abundance of chemical elements in geological objects, denoted in percents, as . This was in honor to the American geochemist Frank Wigglesworth Clarke, who pioneered in estimating the chemical composition of Earths crust, based on Clarke and colleagues extensive chemical analysis of numerous rock samples, throughout 1889 to 1924().
Examples based on Fersman's definition:
* : When the whole mass of a planet X is , and the mass of oxygen there is , then the weight clarke of oxygen in planet X is (dimensionless)
* : When the whole count of atoms in a rock Y is , and the atom count of silicon there is , then silicon's clarke of atom count in rock Y is (dimensionless)
* Fersmans "clarke of Earths crust" is the Earth's surface including 16 km-thick lithosphere, hydrosphere and atmosphere. | 0 | Theoretical and Fundamental Chemistry |
The earliest mention of the term can be found in a lecture given by Dr. Allan Macfadyen of the Jenner Institute of Preventative Medicine in 1902. Dr. Macfadyen described symbiotic fermentation as noting "a close relationship between the organisms at work, the action of one aiding or modifying the action of the other, whilst both members are more active as a results of the partnership." Fermentative microorganisms have had a deep history as seen by kefir and kumis fermentations of milk by Nomadic tribes in Russia, as well as Japanese koji fermentation (see Aspergillus oryzae).
In 1927, Dr. Aldo Castellani defined symbiotic fermentation as "two microorganisms neither of which alone produces fermentation with gas in certain carbohydrates, may do so when living in symbiosis or when artificially mixed." He based this definition on the observation that ordinary bakers yeast consisted of two or more microorganisms- Saccharomyces and Bacilli. He performed experiments to show that when two different Bacilli species were grown in culture together with maltose as the sugar, gas was produced as a result of symbiotic fermentation. Dr. Castellani also described symbiotic fermentation as a method to distinguish between Bacillus dysentariae Shiga (now Shigella dysentariae Shiga) and B. dysentariae Flexner (now Shigella flexneri) by fermenting each of them with Bacillus morgani (now Morganella morganii) in mannitol. The culture with Flexner would always produce gas and acid, while the culture with Shiga only produced acid. To summarize, one bacteria performs acid fermentation to produce acid from sugar, then the other bacteria performs gas fermentation using the acid products to produce gas. Thus creating a type of symbiotic relationship based on fermentation metabolism.
More recently, symbiotic fermentation is described in a traditional sense for the fermentation of food and beverage products. Biofilm aggregates of fermentative microorganisms are commonly associated with fermentation of many products including vinegar, sake, shochu, and kefir. In the U.S., kombucha has become a popular fermented beverage that is also a model of symbiotic fermentation. In kombucha, bacteria create the biofilm network that initiates SCOBY formation, while the yeast produce invertase that makes sugars available to the bacteria and yeast for fermentation. | 1 | Applied and Interdisciplinary Chemistry |
The effect of changing the temperature in the equilibrium can be made clear by 1) incorporating heat as either a reactant or a product, and 2) assuming that an increase in temperature increases the heat content of a system. When the reaction is exothermic (ΔH is negative and energy is released), heat is included as a product, and when the reaction is endothermic (ΔH is positive and energy is consumed), heat is included as a reactant. Hence, whether increasing or decreasing the temperature would favor the forward or the reverse reaction can be determined by applying the same principle as with concentration changes.
Take, for example, the reversible reaction of nitrogen gas with hydrogen gas to form ammonia:
:N(g) + 3 H(g) ⇌ 2 NH(g) ΔH = −92 kJ mol
Because this reaction is exothermic, it produces heat:
:N(g) + 3 H(g) ⇌ 2 NH(g) + heat
If the temperature were increased, the heat content of the system would increase, so the system would consume some of that heat by shifting the equilibrium to the left, thereby producing less ammonia. More ammonia would be produced if the reaction were run at a lower temperature, but a lower temperature also lowers the rate of the process, so, in practice (the Haber process) the temperature is set at a compromise value that allows ammonia to be made at a reasonable rate with an equilibrium concentration that is not too unfavorable.
In exothermic reactions, an increase in temperature decreases the equilibrium constant, K, whereas in endothermic reactions, an increase in temperature increases K.
Le Chateliers principle applied to changes in concentration or pressure can be understood by giving K a constant value. The effect of temperature on equilibria, however, involves a change in the equilibrium constant. The dependence of K on temperature is determined by the sign of ΔH. The theoretical basis of this dependence is given by the Van t Hoff equation. | 0 | Theoretical and Fundamental Chemistry |
Bridge expansion joints are designed to allow for continuous traffic between structures while accommodating movement, shrinkage, and temperature variations on reinforced and prestressed concrete, composite, and steel structures. They stop the bridge from bending out of place in extreme conditions, and also allow enough vertical movement to permit bearing replacement without the need to dismantle the bridge expansion joint. There are various types, which can accommodate movement from , including joints for small movement (EMSEAL BEJS, XJS, JEP, WR, WOSd, and Granor AC-AR), medium movement (ETIC EJ, Wd), and large movement (WP, ETIC EJF/Granor SFEJ).
Modular expansion joints are used when the movements of a bridge exceed the capacity of a single gap joint or a finger type joint. Modular multiple-gap expansion joints can accommodate movements in all directions and rotations about every axis. They can be used for longitudinal movements of as little as 160mm, or for very large movements of over 3000 mm. The total movement of the bridge deck is divided among a number of individual gaps which are created by horizontal surface beams. The individual gaps are sealed by watertight elastomeric profiles, and surface beam movements are regulated by an elastic control system. The drainage of the joint is via the drainage system of the bridge deck. Certain joints feature so-called “sinus plates” on their surface, which reduce noise from over-passing traffic by up to 80%.
Masonry control joints are also sometimes used in bridge slabs. | 1 | Applied and Interdisciplinary Chemistry |
This type of equipment has an eccentric drive or weights that causes the shaker to travel in an orbital path. The material rolls over the screen and falls with the induction of gravity and directional shifts. Rubber balls and trays provide an additional mechanical means to cause the material to fall through. The balls also provide a throwing action for the material to find an open slot to fall through.
The shaker is set a shallow angle relative to the horizontal level plane. Usually, no more than 2 to 5 degrees relative to the horizontal level plane.
These types of shakers are used for very clean cuts. Generally, a final material cut will not contain any oversize or any fines contamination.
These shakers are designed for the highest attainable quality at the cost of a reduced feed rate. | 1 | Applied and Interdisciplinary Chemistry |
Aquasomes have also shown promise as vaccine carriers. In a 2022 study by Jitendra et al., aquasomes prepared with hydroxyapatite and merozoite surface protein-119 (MSP-119) were shown to possess immunoadjuvant properties. Specifically, the small size and relatively large surface area of the nanoparticles contributed to their strong adsorption efficiency of immunogens, and showed slower antigen release and biodegradability in vitro compared to traditional adjuvants. These properties show promise for increasing the time that immunogens are present in vivo. This could increase the exposure of immunogens to antigen-presenting cells and lymphocytes and thus the immunological function of aquasome-based vaccines. Aquasomes prepared in such a manner were shown to induce significant release of antibodies of the immunoglobulin G class in addition to secretion of pro-inflammatory cytokines when compared to MSP-119 alone or MSP-119 with alum, a commonly used immunoadjuvant. These results indicate that aquasomes show promise as vaccine carriers due to their adjuvanticity and their ability to deliver vaccines to tissues. | 0 | Theoretical and Fundamental Chemistry |
These circuits can be modelled in silico to predict the dynamics of a genetic system. Having constructed a computational model of the natural circuit of interest, one can use the model to make testable predictions about circuit performance. When designing a synthetic circuit for a specific engineering task, a model is useful for identifying necessary connections and parameter operating regimes that give rise to a desired functional output. Similarly, when studying a natural circuit, one can use the model to identify the parts or parameter values necessary for a desired biological outcome. In other words, computational modelling and experimental synthetic perturbations can be used to probe biological circuits. However, the structure of the circuits have shown to not be a reliable indicator of the function that the regulatory circuit provides for the larger cellular regulatory network. | 1 | Applied and Interdisciplinary Chemistry |
The degree of dissociation in gases is denoted by the symbol , where refers to the percentage of gas molecules which dissociate. Various relationships between and exist depending on the stoichiometry of the equation. The example of dinitrogen tetroxide () dissociating to nitrogen dioxide () will be taken.
If the initial concentration of dinitrogen tetroxide is 1 mole per litre, this will decrease by at equilibrium giving, by stoichiometry, moles of . The equilibrium constant (in terms of pressure) is given by the equation
where represents the partial pressure. Hence, through the definition of partial pressure and using to represent the total pressure and to represent the mole fraction;
The total number of moles at equilibrium is , which is equivalent to . Thus, substituting the mole fractions with actual values in term of and simplifying;
This equation is in accordance with Le Chatelier's principle. will remain constant with temperature. The addition of pressure to the system will increase the value of , so must decrease to keep constant. In fact, increasing the pressure of the equilibrium favours a shift to the left favouring the formation of dinitrogen tetroxide (as on this side of the equilibrium there is less pressure since pressure is proportional to number of moles) hence decreasing the extent of dissociation . | 0 | Theoretical and Fundamental Chemistry |
In chemical terms, actinism is the property of radiation that lets it be absorbed by a molecule and cause a photochemical reaction as a result. Albert Einstein was the first to correctly theorize that each photon would be able to cause only one molecular reaction. This distinction separates photochemical reactions from exothermic reduction reactions triggered by radiation.
For general purposes, photochemistry is the commonly used vernacular rather than actinic or actino-chemistry, which are again more commonly seen used for photography or imaging. | 0 | Theoretical and Fundamental Chemistry |
The dissociation rate in chemistry, biochemistry, and pharmacology is the rate or speed at which a ligand dissociates from a protein, for instance, a receptor. It is an important factor in the binding affinity and intrinsic activity (efficacy) of a ligand at a receptor. The dissociation rate for a particular substrate can be applied to enzyme kinetics, including the Michaelis-Menten model. Substrate dissociation rate contributes to how large or small the enzyme velocity will be. In the Michaelis-Menten model, the enzyme binds to the substrate yielding an enzyme substrate complex, which can either go backwards by dissociating or go forward by forming a product. The dissociation rate constant is defined using K.
The Michaelis-Menten constant is denoted by K and is represented by the equation K= (K + K)/ K. The rates that the enzyme binds and dissociates from the substrate are represented by K and K respectively. K is also defined as the substrate concentration at which enzymatic velocity reaches half of its maximal rate. The tighter a ligand binds to a substrate, the lower the dissociation rate will be. K and K are proportional, thus at higher levels of dissociation, the Michaelis-Menten constant will be larger. | 0 | Theoretical and Fundamental Chemistry |
The shape of the semiintegral can be used as an easy method to measure the amount of ohmic drop of an electrochemical cell in cyclic voltammetry. Essentially the semiintegral of a cyclic voltammogram at a planar electrode (an electrode that obeys to the rules of planar diffusion) has the shape of a sigmoid while the original data is gauss-sigmoid convoluted. This enables the operator to optimize parameters necessary for positive feedback compensation in an easy manner. If ohmic drop distortion is present the two sigmoids for the forward and the backward scan are far away from congruence, the ohmic drop can be calculated from the deviation from congruence in these cases. In the example shown slight distortion is present, yet this does not have adverse effects on data quality. | 0 | Theoretical and Fundamental Chemistry |
Related to the title concept are the ideas of a van der Waals volume, V, and a van der Waals surface area, abbreviated variously as A, vdWSA, VSA, and WSA.
A van der Waals surface area is an abstract conception of the surface area of atoms or molecules from a mathematical estimation, either computing it from first principles or by integrating over a corresponding van der Waals volume.
In simplest case, for a spherical monatomic gas, it is simply the computed surface area of a sphere of radius equal to the van der Waals radius of the gaseous atom:
The van der Waals volume, a type of atomic or molecular volume, is a property directly related to the van der Waals radius, and is defined as the volume occupied by an individual atom, or in a combined sense, by all atoms of a molecule.
It may be calculated for atoms if the van der Waals radius is known, and for molecules if its atoms radii and the inter-atomic distances and angles are known.
As above, in simplest case, for a spherical monatomic gas, V is simply the computed volume of a sphere of radius equal to the van der Waals radius of the gaseous atom:
For a molecule, V is the volume enclosed by the van der Waals surface; hence, computation of V presumes ability to describe and compute a van der Waals surface. van der Waals volumes of molecules are always smaller than the sum of the van der Waals volumes of their constituent atoms, due to the fact that the interatomic distances resulting from chemical bond are less than the sum of the atomic van der Waals radii.
In this sense, a van der Waals surface of a homonuclear diatomic molecule can be viewed as an pictorial overlap of the two spherical van der Waals surfaces of the individual atoms, likewise for larger molecules like methane, ammonia, etc. (see images).
van der Waals radii and volumes may be determined from the mechanical properties of gases (the original method, determining the van der Waals constant), from the critical point (e.g., of a fluid), from crystallographic measurements of the spacing between pairs of unbonded atoms in crystals, or from measurements of electrical or optical properties (i.e., polarizability or molar refractivity).
In all cases, measurements are made on macroscopic samples and results are expressed as molar quantities. van der Waals volumes of a single atom or molecules are arrived at by dividing the macroscopically determined volumes by the Avogadro constant.
The various methods give radius values which are similar, but not identical—generally within 1–2 Å (100–200 pm).
Useful tabulated values of van der Waals radii are obtained by taking a weighted mean of a number of different experimental values, and, for this reason, different tables will be seen to present different values for the van der Waals radius of the same atom.
As well, it has been argued that the van der Waals radius is not a fixed property of an atom in all circumstances, rather, that it will vary with the chemical environment of the atom. | 0 | Theoretical and Fundamental Chemistry |
Perfluorohexane has extremely high global warming potential (GWP) of 9,300. This leads to a need to find low GWP alternative. Novec 649 was considered a good drop-in replacement in many applications due to its similar thermo-physical properties and having a global warming potential of 1. | 1 | Applied and Interdisciplinary Chemistry |
Trickling may have a variety of types of filter media used to support the biofilm. Types of media most commonly used include coke, pumice, plastic matrix material, open-cell polyurethane foam, clinker, gravel, sand and geotextiles. Ideal filter medium optimizes surface area for microbial attachment, wastewater retention time, allows air flow, resists plugging, is mechanically robust in all weathers allowing walking access across the filter, and does not degrade. Some residential systems require forced aeration units which will increase maintenance and operational costs.
Synthetic filter media may pose a significant risk of flammability as demonstrated in Christchurch, New Zealand in May 2022 when two large trickling filters filled with plastic filter bales caught fire. The resultant smell had a significant impact on many city residents and this event put out of action a significant proportion of the sewage treatment capacity. | 1 | Applied and Interdisciplinary Chemistry |
Cytochrome c has been used to detect peroxide production in biological systems. As superoxide is produced, the number of oxidised cytochrome c increases, and reduced cytochrome c decreases. However, superoxide is often produced with nitric oxide. In the presence of nitric oxide, the reduction of cytochrome c is inhibited. This leads to the oxidisation of cytochrome c to cytochrome c by peroxynitrous acid, an intermediate made through the reaction of nitric oxide and superoxide. Presence of peroxynitrite or HO and nitrogen dioxide NO in the mitochondria can be lethal since they nitrate tyrosine residues of cytochrome c, which leads to disruption of cytochrome c's function as an electron carrier in the electron transport chain. | 1 | Applied and Interdisciplinary Chemistry |
There are two suggested mechanisms behind physical hydrogel formation, the first one being the gelation of nanofibrous peptide assemblies, usually observed for oligopeptide precursors. The precursors self-assemble into fibers, tapes, tubes, or ribbons that entangle to form non-covalent cross-links. The second mechanism involves non-covalent interactions of cross-linked domains that are separated by water-soluble linkers, and this is usually observed in longer multi-domain structures. Tuning of the supramolecular interactions to produce a self-supporting network that does not precipitate, and is also able to immobilize water which is vital for to gel formation. Most oligopeptide hydrogels have a β-sheet structure, and assemble to form fibers, although α-helical peptides have also been reported. The typical mechanism of gelation involves the oligopeptide precursors self-assemble into fibers that become elongated, and entangle to form cross-linked gels.
One notable method of initiating a polymerization fuving involves the use of light as a stimulus. In this method, photoinitiators, compounds that cleave from the absorption of photons, are added to the precursor solution which will become the hydrogel. When the precursor solution is exposed to a concentrated source of light, usually ultraviolet irradiation, the photoinitiators will cleave and form free radicals, which will begin a polymerization reaction that forms crosslinks between polymer strands. This reaction will cease if the light source is removed, allowing the amount of crosslinks formed in the hydrogel to be controlled. The properties of a hydrogel are highly dependent on the type and quantity of its crosslinks, making photopolymerization a popular choice for fine-tuning hydrogels. This technique has seen considerable use in cell and tissue engineering applications due to the ability to inject or mold a precursor solution loaded with cells into a wound site, then solidify it in situ.
Physically crosslinked hydrogels can be prepared by different methods depending on the nature of the crosslink involved. Polyvinyl alcohol hydrogels are usually produced by the freeze-thawed technique. In this, the solution is frozen for a few hours, then thawed at room temperature, and the cycle is repeated until a strong and stable hydrogel is formed. Alginate hydrogels are formed by ionic interactions between alginate and double-charged cations. A salt, usually calcium chloride, is dissolved into an aqueous sodium alginate solution, that causes the calcium ions to create ionic bonds between alginate chains. Gelatin hydrogels are formed by temperature change. A water solution of gelatin forms an hydrogel at temperatures below 37–35 °C, as Van der Waals interactions between collagen fibers become stronger than thermal molecular vibrations. | 0 | Theoretical and Fundamental Chemistry |
Bromocresol purple is used in medical laboratories to measure albumin. Use of BCP in this application may provide some advantage over older methods using bromocresol green. In microbiology, it is used for staining dead cells based on their acidity, and for the isolation and assaying of lactic acid bacteria.
In photographic processing, it can be used as an additive to acid stop baths to indicate that the bath has reached neutral pH and needs to be replaced.
Bromocresol purple milk solids glucose agar is used as a medium used to distinguish dermatophytes from bacteria and other organisms in cases of ringworm fungus (T. verrucosum) infestation in cattle and other animals. | 0 | Theoretical and Fundamental Chemistry |
Ivan Ivanovich Ostromislensky (, also Iwan Ostromislensky) (9 September 1880 – 16 January 1939) was a Russian organic chemist. He is credited as the pioneer in studying polymerization of synthetic rubber as well as inventor of various industrial technologies for production of synthetic rubber, polymers and pharmaceuticals. | 0 | Theoretical and Fundamental Chemistry |
Biological oxidation processes are sensitive to temperature and, between 0 °C and 40 °C, the rate of biological reactions increase with temperature. Most surface aerated vessels operate at between 4 °C and 32 °C. | 1 | Applied and Interdisciplinary Chemistry |
Plutonium, like other actinides, readily forms a plutonium dioxide (plutonyl) core (PuO). In the environment, this plutonyl core readily complexes with carbonate as well as other oxygen moieties (OH, NO, NO, and SO) to form charged complexes which can be readily mobile with low affinities to soil.
*PuOCO
*PuO(CO)
*PuO(CO)
PuO formed from neutralizing highly acidic nitric acid solutions tends to form polymeric PuO which is resistant to complexation. Plutonium also readily shifts valences between the +3, +4, +5 and +6 states. It is common for some fraction of plutonium in solution to exist in all of these states in equilibrium.
Plutonium is known to bind to soil particles very strongly; see above for an X-ray spectroscopic study of plutonium in soil and concrete. While caesium has very different chemistry to the actinides, it is well known that both caesium and many actinides bind strongly to the minerals in soil. it has been possible to use Cs-labeled soil to study the migration of Pu and Cs is soils. It has been shown that colloidal transport processes control the migration of Cs (and will control the migration of Pu) in the soil at the Waste Isolation Pilot Plant. | 0 | Theoretical and Fundamental Chemistry |
Composite metal foam has shown an ability to shield against x-ray and neutron radiation, absorbs/mitigates shocks, sounds, and vibrations, and can withstand over 1,000,000 high load cycles, outperforming traditional solid metals in each case. | 0 | Theoretical and Fundamental Chemistry |
Radical cascades are those in which the
key step constitutes a radical reaction. The high reactivity of free radical
species renders radical-based synthetic approaches decidedly suitable for
cascade reactions.
One of the most widely recognized
examples of the synthetic utility of radical cascades is the cyclization
sequence employed in the total synthesis of (±)-hirsutene, in 1985 (Scheme 6). Herein, alkyl iodide 28 was converted to the primary radical
intermediate 29, which underwent a 5-exo-trig cyclization to afford reactive species 30. A subsequent 5-exo-dig radical cyclization lead to intermediate 31, which upon quenching gave the
target (±)-hirsutene (32) in 80%
overall yield.
A cascade radical process was also
used in one of the total syntheses of (–)-morphine (Scheme 7). Aryl bromide 33 was converted to the corresponding
radical species 34 by treatment with
tri-n-butyltin hydride. A 5-exo-trig cyclization then occurred to
give intermediate 35
stereoselectively in virtue of the stereochemistry of the ether linkage. In the
next step of the cascade, the geometric constraints of 35 forbid the kinetically favored 5-exo-trig cyclization pathway; instead secondary benzylic radical
species 36 was obtained via a
geometrically-allowed 6-endo-trig
cyclization. Subsequent elimination of the phenyl sulfinyl radical afforded
product 37 in 30% overall yield,
which was further elaborated to (–)-morphine (38). | 0 | Theoretical and Fundamental Chemistry |
One study used the water advancing contact angle to estimate the wettability of fifty-five oil reservoirs. De-oxygenated synthetic formation brine and dead anaerobic crude was tested on quartz and calcite crystals at reservoir temperature. Contact angles from 0 to 75 degrees were deemed water wet, 75 to 105 degrees as intermediate and 105 to 180 degrees as oil wet. Although the range of wettabilities were divided into three regions, these were arbitrary divisions. The wettability of different reservoirs can vary within the broad spectrum from strongly water-wet to strongly oil-wet.
Another study described two initial conditions as reference and non-reference for calculating cut-off values by using advancing and receding contact angles and spontaneous imbibition data. Limiting value between water wet and intermediate zones was described as 62-degree. Similarly, cut-off values for advancing contact angle is described as 0 to 62 degrees for water wet region, 62 to 133 degrees for Intermediate-wet zone, and 133 to 180 degrees for Oil wet zone.
Chilingar and Yen examined extensive research work on 161 limestone, dolomitic limestone, calcitic dolomite, and dolomite cores. Cut-off values classified as 160 to 180 degrees for strongly oil wet, 100 to 160 degrees for oil wet, 80 to 100 degrees intermediate wet, 80 to 20 degrees water wet and 0 to 20 strongly water wet.
Rise in core uses a combination of Chilingar et al. and Morrow wettability cut-off criteria. The contact angle range 80 – 100 degrees indicate neutral-wetness, the range 100 – 133 degrees indicate slight-oil wetness, the range 133 – 160 degrees indicate oil-wetness while the range 160- 180 degrees indicate strongly oil-wetness. The range 62 – 80 degrees indicate slight water wetness, the range 20 – 62 degrees indicate, water-wetness, while the range 0 – 20 degrees indicate strong water-wetness. | 1 | Applied and Interdisciplinary Chemistry |
Controlled radical polymerization, namely reversible addition−fragmentation chain-transfer polymerization (RAFT), is a common method for the polymerization of acrylates, methacrylates and acrylamides. Usually, a thiocarbonate is used in combination with an effective initiator for RAFT. The thiocarbonate moiety can be functionalized at the R-group for end group analysis. The end group is a result of the propagation of chain-transfer agents during the free-radical polymerization process. The end groups can subsequently be modified by the reaction of the thiocarbonylthio compounds with nucleophiles and ionic reducing agents.
The method for removal of thiocarbonyl containing end groups includes reacting the polymers containing the end-groups with en excess of radicals which add to the reactive C=S bond of the end group forming an intermediate radical (shown below). The remaining radical on the polymer chain can be hydrogenated by what is referred to as a trapping group and terminate; this results in a polymer that is free of the end groups at the α and ω positions.
Another method of end group removal for the thiocarbonyl containing end-groups of RAFT polymers is the addition of heat to the polymer; this is referred to as thermolysis. One method of monitoring thermolysis of RAFT polymers is by thermogravimetric analysis resulting in a weight-loss of the end group. An advantage of this technique is that no additional chemicals are required to remove the end group; however, it is required that the polymer be thermally stable to high temperature and therefore may not be effective for some polymers. Depending on the polymers sensitivity to ultraviolet radiation (UV) it has been reported in recent years that decomposition of end-groups can be effective, but preliminary data suggest that decomposition by UV leads to a change in the distribution of molecular weights of the polymer. | 0 | Theoretical and Fundamental Chemistry |
Several variations of thermal spraying are distinguished:
*Plasma spraying
*Detonation spraying
*Wire arc spraying
*Flame spraying
*High velocity oxy-fuel coating spraying (HVOF)
*High velocity air fuel (HVAF)
*Warm spraying
*Cold spraying
*Spray and Fuse
In classical (developed between 1910 and 1920) but still widely used processes such as flame spraying and wire arc spraying, the particle velocities are generally low (< 150 m/s), and raw materials must be molten to be deposited. Plasma spraying, developed in the 1970s, uses
a high-temperature plasma jet generated by arc discharge
with typical temperatures >15,000 K, which makes it
possible to spray refractory materials such as oxides, molybdenum, etc. | 1 | Applied and Interdisciplinary Chemistry |
The salt marsh plant Batis maritima contains the enzyme methyl chloride transferase that catalyzes the synthesis of CHCl from S-adenosine-L-methionine and chloride. This protein has been purified and expressed in E. coli, and seems to be present in other organisms such as white rot fungi (Phellinus pomaceus), red algae (Endocladia muricata), and the ice plant (Mesembryanthemum crystallinum), each of which is a known CHCl producer. | 1 | Applied and Interdisciplinary Chemistry |
Albert Ghiorso is credited with having co-discovered the following elements
* Americium ca. 1945 (element 95)
* Curium in 1944 (element 96)
* Berkelium in 1949 (element 97)
* Californium in 1950 (element 98)
* Einsteinium in 1952 (element 99)
* Fermium in 1953 (element 100)
* Mendelevium in 1955 (element 101)
* Nobelium in 1958–59 (element 102)
* Lawrencium in 1961 (element 103)
* Rutherfordium in 1969 (element 104)
* Dubnium in 1970 (element 105)
* Seaborgium in 1974 (element 106)
Ghiorso personally selected some of the names recommended by his group for the new elements. His original name for element 105 (hahnium) was changed by the International Union of Pure and Applied Chemistry (IUPAC) to dubnium, to recognize the contributions of the laboratory at Dubna, Russia, in the search for trans-fermium elements. His recommendation for element 106, seaborgium, was accepted only after extensive debate about naming an element after a living person. In 1999, evidence for two superheavy elements (element 116 and element 118) was published by a group in Berkeley. The discovery group intended to propose the name ghiorsium for element 118, but eventually the data were found to have been tampered and in 2002 the claims were withdrawn. Ghiorso's lifetime output comprised about 170 technical papers, most published in The Physical Review.
Ghiorso was famous among his colleagues for his endless stream of creative "doodles," which define an art form suggestive of fractals. He also developed a state-of-the-art camera for birdwatching, and was a constant supporter of environmental causes and organizations.
Several obituaries are available online, and a full-length biography is in preparation. | 1 | Applied and Interdisciplinary Chemistry |
The exact purity of very fine precious metals such as platinum, gold and silver can be of great interest. Based on the system of millesimal fineness, a metal is said to be one nine or one nine fine if it is 900 fine, or 90% pure. A metal that is 990 fine is then described as two nines fine and one that is 999 fine is described as three nines fine. Thus, nines are a logarithmic scale of purity for very fine precious metals. Similarly, percentages ending in a 5 have conventional names, traditionally the number of nines, then "five", so 999.5 fine (99.95% pure) is "three nines five", abbreviated 3N5.
Canada's Big Maple Leaf, a coin made of gold at 5N (99.999%) purity, stands as the purest gold coin ever minted, anywhere. The purest gold ever achieved was reportedly produced at the Perth Mint in 1957, at "almost six nines" (99.9999%) purity, as measured by the Worshipful Company of Goldsmiths of London. | 1 | Applied and Interdisciplinary Chemistry |
A water jet, or pump-jet, is a marine propulsion system that uses a jet of water. The mechanical arrangement may be a ducted propeller with nozzle, or a centrifugal compressor and nozzle. The pump-jet must be driven by a separate engine such as a Diesel or gas turbine. | 1 | Applied and Interdisciplinary Chemistry |
Taking into account the HiFIT process during development, on same load level and same lifetime, the construction can be slimmed down specifically. Extensive experimental investigations on structural details and FEM-supported-design methods has shown the high efficiency with conventional S235, S355J2 and fine grain steels, such as S460N, S690QL and even higher strength steels. The achievable material saving makes the HiFIT application in most applications already economically viable. Considering the additional benefit of the weight advantage e.g. the achievable payload in vehicles can be increased. | 1 | Applied and Interdisciplinary Chemistry |
The C-N distance in isocyanides is 115.8 pm in methyl isocyanide. The C-N-C angles are near 180°.
Akin to carbon monoxide, isocyanides are described by two resonance structures, one with a triple bond between the nitrogen and the carbon and one with a double bond between. The π lone pair of the nitrogen stabilizes the structure and is responsible of the linearity of isocyanides, although the reactivity of isocyanides reflects some carbene character, at least in a formal sense. Thus, both resonance structures are useful representations. They are susceptible to polymerization. | 0 | Theoretical and Fundamental Chemistry |
1. van Kretschmar, J. B., Bailey W. D., Arellano, C., Thompson, G. D., Sutula, C. L., Roe, R. M., Feeding disruption tests for monitoring the frequency of larval lepidopteran resistance to Cry1Ac, Cry1F, and Cry1Ab, Crop Prot. 30(7), 863-870 (2011)
2. Roe, R. M., W. D. Bailey, W. D., Gould, F., Sorenson, C. E., Kennedy, G. G., Bacheler, J. S., Rose, R. Hodgson, L. E., Sutula, C. L., Detection of resistant insects and IPM, Emerging technologies for integrated pest management concepts, research and implementation. Proceedings of a Conference, Raleigh, North Carolina, US, 8–10 March 1999. 2000 pp. 67–84. [Book ]
3. Zeng, F., Ramaswamy, S. B., Luttrell, R. G., Reed, J., Parker, C. D., Stewart, S., Harris, A., Knighten, K., Robbins, J., Xia, J. Q., Sutula, C. L., Comparison of monoclonal antibody and laboratory rearing techniques to identify Heliothentinaen (Lepidoptera: Noctuidae) eggs from Mississippi cotton fields, Environmental Entomology 28 (2): 275-281 (1999)
4. Yuen, G. Y., Xia, J. Q., Sutula, C. L., A Sensitive ELISA for Pythium ultimum Using Polyclonal and Species-Specific Monoclonal Antibodies, Plant Dis. 82(9), 1029-1032 (1998)
5. Xia, J. Q., Sutula, C. L., Marti, D., Development of a greenhouse test for tomato spotted wilt virus and impatiens necrotic spot virus, Acta Horticulturae 431:193-198 (1995)
6. Sutula, C. L., Gillett, J. M., Morrissey, S. M., Ramsdell, D. C., Interpreting ELISA data and establishing the positive-negative threshold, Plant Dis. 70(8s), 722 (1986)
7. Wershaw, R. L., Burcar, J. P., Sutula, C. L., Wiginton, B. L., Sodium humate solution studied with small-angle x-ray scattering, Science 157(3795), 1429-31 (1967)
8. Sutula, C. L., Wilson, J. E., Solid-like films at a moving interface, Society of Petroleum Engineers Journal 7(1), (1967)
9. Bartell, L. S., Sutula, C. L., Mechanically induced molecular reorientation in multimolecular films, The Journal of Physical Chemistry 67(11), 2413-2416 (1963)
10. Sutula, C. L., Bartell, L. S., Structure and molecular orientation in multimolecular films of long-chain n-hydrocarbon derivatives, The Journal of Physical Chemistry 66(6), 1010-1014 (1962) | 0 | Theoretical and Fundamental Chemistry |
Cellular noise is random variability in quantities arising in cellular biology. For example, cells which are genetically identical, even within the same tissue, are often observed to have different expression levels of proteins, different sizes and structures. These apparently random differences can have important biological and medical consequences.
Cellular noise was originally, and is still often, examined in the context of gene expression levels – either the concentration or copy number of the products of genes within and between cells. As gene expression levels are responsible for many fundamental properties in cellular biology, including cells' physical appearance, behaviour in response to stimuli, and ability to process information and control internal processes, the presence of noise in gene expression has profound implications for many processes in cellular biology. | 1 | Applied and Interdisciplinary Chemistry |
Dextrorphan was formerly a Schedule I controlled substance in the United States, but was unscheduled on October 1, 1976. | 0 | Theoretical and Fundamental Chemistry |
Animal research (on mice), which is pre-clinical, also found Retinoid acid, the bioactive metabolite of vitamin A, to have an effect on brain areas responsible for memory and learning. | 1 | Applied and Interdisciplinary Chemistry |
Waters was appointed as a lecturer in chemistry at the University of Auckland in 1961, rising to the rank of associate professor. In 1983, she joined Massey University as a senior research fellow and associate professor in chemistry, and in 2000 she was made a full professor at Massey's Albany campus. Following her retirement, she was conferred with the title of professor emeritus.
Her research focused on the determination of molecular structure using X-ray crystallography. An early publication by Waters was the first to describe the structure of a coordination complex containing a metal–hydrogen bond.
Waters served as president of the New Zealand Institute of Chemistry in 1989–1990, and was the first woman to hold the position. | 0 | Theoretical and Fundamental Chemistry |
Paralogs: FAM227A
Orthologs: FAM227B is present in Deuterostomia and Protostomia, dating as far back as porifera. FAM227B is not present in choanoflagellates, and gene alignment sequences have shown that FAM227B is a rapidly evolving gene due to its evolution trajectory compared to cytochrome c and fibrinogen alpha. | 1 | Applied and Interdisciplinary Chemistry |
Collective diffusion is the diffusion of a large number of particles, most often within a solvent.
Contrary to brownian motion, which is the diffusion of a single particle, interactions between particles may have to be considered, unless the particles form an ideal mix with their solvent (ideal mix conditions correspond to the case where the interactions between the solvent and particles are identical to the interactions between particles and the interactions between solvent molecules; in this case, the particles do not interact when inside the solvent).
In case of an ideal mix, the particle diffusion equation holds true and the diffusion coefficient D the speed of diffusion in the particle diffusion equation is independent of particle concentration. In other cases, resulting interactions between particles within the solvent will account for the following effects:
* the diffusion coefficient D in the particle diffusion equation becomes dependent of concentration. For an attractive interaction between particles, the diffusion coefficient tends to decrease as concentration increases. For a repulsive interaction between particles, the diffusion coefficient tends to increase as concentration increases.
* In the case of an attractive interaction between particles, particles exhibit a tendency to coalesce and form clusters if their concentration lies above a certain threshold. This is equivalent to a precipitation chemical reaction (and if the considered diffusing particles are chemical molecules in solution, then it is a precipitation). | 1 | Applied and Interdisciplinary Chemistry |
Bonnoris noted, “The environmental justice movement posits that the distribution of environmental harms and benefits should be fairly apportioned among all communities”. As Bonnoris argued, the burden of air pollution is disproportionally distributed among communities based on their racial, social or economic status. Disproportion distribution of air pollution among communities can be a violation of the Equal Protection Clause of the Constitution because it violates equal protection of residents’ public health.
Los Angeles is known for the nation's worst air quality and its “sharp inequalities in environmental exposures”. Wilmington, Los Angeles is a neighborhood located on the southern part of Los Angeles, California. 54,512 people live in Wilmington, the median household income is $40,627, about 86 percentage of them are Latino and only 5.1% of Wilmington residents 25 or older have a four-year degree.
Wilmington, most of its residents are ethnic minorities, is possible to bear more environmental burden than other communities in Los Angeles because it is located next to several sources of air pollution. For example, Wilmington has "the highest concentration of refineries in the State". Emissions from refineries in Wilmington include carbon dioxide, sulfur dioxide and benzene. Wilmington has higher concentration of diesel particulate matter due to emissions from diesel trucks from the ports of Los Angeles and Long Beach. The risks associated with diesel are often underestimated since existing epidemiological studies cannot isolate exposure to diesel PM. However, exposure to diesel particulate matter can cause “irritation to the eyes, nose, throat and lungs”, asthma, “exhaust immunological effects”, and cancer.
Several NGOs have worked to improve the accuracy of Wilmington air quality data and air quality in order to protect approximately 1400 children who live or visit schools or childcare facilities at Wilmington. The environmental group “Coalition For a Safe Environment” installed an air pollution monitoring devices on the residential buildings in Wilmington in order to prove that emissions from local oil refineries and diesel trucks to the ports pollute the air in Wilmington, disproportionately affecting Wilmington residents to suffer from health problems including lung diseases and respiratory diseases. | 1 | Applied and Interdisciplinary Chemistry |
There are over 300 types of ion channels just in the cells of the inner ear. Ion channels may be classified by the nature of their gating, the species of ions passing through those gates, the number of gates (pores), and localization of proteins.
Further heterogeneity of ion channels arises when channels with different constitutive subunits give rise to a specific kind of current. Absence or mutation of one or more of the contributing types of channel subunits can result in loss of function and, potentially, underlie neurologic diseases. | 1 | Applied and Interdisciplinary Chemistry |
Most plastic items, like packaging materials, are used briefly and only once. These rarely experience polymer degradation during their service-lives. Other items experience only gradual degradation from the natural environment. Some plastic items, however, can experience long service-lives in aggressive environments, particularly those where they are subject to prolonged heat or chemical attack. Polymer degradation can be significant in these cases and, in practice, is often only held back by the use of advanced polymer stabilizers. Degradation arising from the effects of heat, light, air and water is the most common, but other means of degradation exist.
The in-service degradation of mechanical properties is an important aspect which limits the applications of these materials. Polymer degradation caused by in-service degradation can cause life threatening accidents. In 1996, a baby was fed via a Hickman line and suffered an infection, when new connectors were used by a hospital. The reason behind this infection was the cracking and erosion of the pipes from the inner side due to contact with liquid media. | 0 | Theoretical and Fundamental Chemistry |
Pesticide residue refers to the pesticides that may remain on or in food, after they are applied to food crops. The maximum allowable levels of these residues in foods are stipulated by regulatory bodies in many countries. Regulations such as pre-harvest intervals also prevent harvest of crop or livestock products if recently treated in order to allow residue concentrations to decrease over time to safe levels before harvest. | 1 | Applied and Interdisciplinary Chemistry |
While statins may reduce CoQ in the blood it is unclear if they reduce CoQ in muscle. Evidence does not support that supplementation improves side effects from statins. However, a more recent metanalysis conducted in China, one of the world's largest producers of this supplement, concluded that, "CoQ supplementation ameliorated SAMSs [statin‐associated muscle symptoms], implying that CoQ supplementation might be a complementary approach to ameliorate statin‐induced myopathy." | 1 | Applied and Interdisciplinary Chemistry |
Collapsible flow is a phenomenon that occurs in steady flow in tubes with significant distensibility, or the capability of swelling or stretching, under conditions of lower internal pressure relative to pressure outside the tube. Such conditions occur rarely in industrial applications but are very common in biological studies such as blood flow in veins and air flow in lungs.
When a flow is driven through a deformable channel or tube, interactions between fluid-mechanical and elastic forces can lead to a variety of biologically significant phenomena, including nonlinear pressure-drop/flow-rate relations, wave propagation,
and the generation of instabilities. Understanding the physical origin and nature of these phenomena remains a significant experimental, analytical, and computational challenge, involving unsteady flows at low or high Reynolds numbers, large-amplitude fluid-structure interactions, free-surface flows, and intrinsically 2D or 3D motion. Whereas frequently the internal flow involves a single fluid
phase (albeit often of a complex biological fluid such as blood), in many instances the presence of two or more distinct flowing phases is of primary importance (as is the case for air-liquid flows in peripheral lung airways, for example). | 1 | Applied and Interdisciplinary Chemistry |
The EXPOSE-E experiments are:
* PROCESS, study photochemical organic compounds in Earth orbit. Relevant to comets, meteorites, Mars and Titan.
* ADAPT, study molecular adaptation strategies of microorganisms in analogues to meteoritic matter to different space and planetary UV climate conditions.
* PROTECT, study of spores' resistance to space conditions, and their ability to recover from the damages done by such an exposition. For planetary protection purposes.
* LiFE (Lichens and Fungi Experiment), study of radiations effect on lichens, fungi and symbiotes in space conditions.
* SEEDS, test plant seed as a terrestrial model for a panspermia vehicle and as a source of universal UV screens and study of their ability to resist radiations.
* Dosis, Dobis & R3D, passive dosimeters for ionizing radiation measurement and the R3D (Radiation Risk Radiometer-Dosimeter E) active radiation measuring instrument. | 1 | Applied and Interdisciplinary Chemistry |
Ramos, F.T.; Dores E.F.G.C.; Weber O.L.S.; Beber D.C.; Campelo Jr J.H.; Maia J.C.S. (2018) "Soil organic matter doubles the cation exchange capacity of tropical soil under no-till farming in Brazil". J Sci Food Agric. [http://onlinelibrary.wiley.com/doi/10.1002/jsfa.8881/abstract 10.1002/jsfa.8881] | 0 | Theoretical and Fundamental Chemistry |
Ferredoxins typically carry out a single electron transfer.
However a few bacterial ferredoxins (of the 2[4Fe4S] type) have two iron sulfur clusters and can carry out two electron transfer reactions. Depending on the sequence of the protein, the two transfers can have nearly identical reduction potentials or they may be significantly different.
Ferredoxins are one of the most reducing biological electron carriers. They typically have a mid point potential of -420 mV. The reduction potential of a substance in the cell will differ from its midpoint potential depending on the concentrations of its reduced and oxidized forms. For a one electron reaction, the potential changes by around 60 mV for each power of ten change in the ratio of the concentration. For example, if the ferredoxin pool is around 95% reduced, the reduction potential will be around -500 mV. In comparison, other biological reactions mostly have less reducing potentials: for example the primary biosynthetic reductant of the cell, NADPH has a cellular redox potential of -370 mV ( = -320 mV).
Depending on the sequence of the supporting protein ferredoxins have reduction potential from around -500mv to -340 mV. A single cell can have multiple types of ferredoxins where each type is tuned to optimally carry out different reactions. | 0 | Theoretical and Fundamental Chemistry |
Several of the principles which corpuscularianism proposed became tenets of modern chemistry.
*The idea that compounds can have secondary properties that differ from the properties of the elements which are combined to make them became the basis of molecular chemistry.
*The idea that the same elements can be predictably combined in different ratios using different methods to create compounds with radically different properties became the basis of stoichiometry, crystallography, and established studies of chemical synthesis.
*The ability of chemical processes to alter the composition of an object without significantly altering its form is the basis of fossil theory via mineralization and the understanding of numerous metallurgical, biological, and geological processes. | 1 | Applied and Interdisciplinary Chemistry |
As established by X-ray crystallography, octachlorodimolybdate(II) anion ([MoCl]) has an eclipsed conformation. This sterically unfavorable geometry is given as evidence for a quadruple bond between the Mo centers.
Experiments such as X-ray and electron diffraction analyses, nuclear magnetic resonance, microwave spectroscopies, and more have allowed researchers to determine which cycloalkane structures are the most stable based on the different possible conformations. Another method that was shown successful is molecular mechanics, a computational method that allows the total strain energies of different conformations to be found and analyzed. It was found that the most stable conformations had lower energies based on values of energy due to bond distances and bond angles.
In many cases, isomers of alkanes with branched chains have lower boiling points than those that are unbranched, which has been shown through experimentation with isomers of CH. This is because of a combination of intermolecular forces and size that results from the branched chains. The more branches that an alkane has, the more extended its shape is; meanwhile, if it is less branched then it will have more intermolecular attractive forces that will need to be broken which is the cause of the increased boiling point for unbranched alkanes. In another case, 2,2,3,3-tetramethylbutane is shaped more like an ellipsoid causing it to be able to form a crystal lattice which raises the melting point of the molecule because it will take more energy to transition from a solid to a liquid state. | 0 | Theoretical and Fundamental Chemistry |
Bravais lattices, also referred to as space lattices, describe the geometric arrangement of the lattice points, and therefore the translational symmetry of the crystal. The three dimensions of space afford 14 distinct Bravais lattices describing the translational symmetry. All crystalline materials recognized today, not including quasicrystals, fit in one of these arrangements. The fourteen three-dimensional lattices, classified by lattice system, are shown above.
The crystal structure consists of the same group of atoms, the basis, positioned around each and every lattice point. This group of atoms therefore repeats indefinitely in three dimensions according to the arrangement of one of the Bravais lattices. The characteristic rotation and mirror symmetries of the unit cell is described by its crystallographic point group. | 0 | Theoretical and Fundamental Chemistry |
Peri urban areas are often less densely populated than urban centers. Therefore, they have more space and on-site sanitation systems can be effective for solid and liquid treatment. In most such peri-urban areas, it is less likely that they will be connected to a conventional centralized sewerage system in the short or medium term. Therefore, these areas will rely on a mix of onsite-sanitation systems and services, decentralized wastewater management systems, or by condominial or simplified sewerage connected to decentralized or centralized treatment. In all of these situations, FSM is a necessary service to keep the sanitation systems functioning properly. | 1 | Applied and Interdisciplinary Chemistry |
The sievert (symbol: Sv) is a unit in the International System of Units (SI) intended to represent the stochastic health risk of ionizing radiation, which is defined as the probability of causing radiation-induced cancer and genetic damage. The sievert is important in dosimetry and radiation protection. It is named after Rolf Maximilian Sievert, a Swedish medical physicist renowned for work on radiation dose measurement and research into the biological effects of radiation.
The sievert is used for radiation dose quantities such as equivalent dose and effective dose, which represent the risk of external radiation from sources outside the body, and committed dose, which represents the risk of internal irradiation due to inhaled or ingested radioactive substances. According to the International Commission on Radiological Protection (ICRP), one sievert results in a 5.5% probability of eventually developing fatal cancer based on the disputed linear no-threshold model of ionizing radiation exposure.
To calculate the value of stochastic health risk in sieverts, the physical quantity absorbed dose is converted into equivalent dose and effective dose by applying factors for radiation type and biological context, published by the ICRP and the International Commission on Radiation Units and Measurements (ICRU). One sievert equals 100 rem, which is an older, CGS radiation unit.
Conventionally, deterministic health effects due to acute tissue damage that is certain to happen, produced by high dose rates of radiation, are compared to the physical quantity absorbed dose measured by the unit gray (Gy). | 0 | Theoretical and Fundamental Chemistry |
In 1850, Charles-Adolphe Wurtz described a colorless platinum tetrammine with the formula [Pt(etn)]Cl 2HO; Wolffram (H. Wolffram, Dissertation, Königsberg, 1900.), whom the compound is named after, obtained a red salt from this by action of hydrogen peroxide in hydrochloric acid, and initially considered it to be isomeric with Wurtz’s salt. With no known case of plato-tetrammine isomerism at the time, this prompted extensive discussion in the literature of the true nature and properties of Wolffram’s Red Salt. | 0 | Theoretical and Fundamental Chemistry |
Primary treatment is the "removal of a portion of the suspended solids and organic matter from the sewage".It consists of allowing sewage to pass slowly through a basin where heavy solids can settle to the bottom while oil, grease and lighter solids float to the surface and are skimmed off. These basins are called primary sedimentation tanks or primary clarifiers and typically have a hydraulic retention time (HRT) of 1.5 to 2.5 hours. The settled and floating materials are removed and the remaining liquid may be discharged or subjected to secondary treatment. Primary settling tanks are usually equipped with mechanically driven scrapers that continually drive the collected sludge towards a hopper in the base of the tank where it is pumped to sludge treatment facilities.
Sewage treatment plants that are connected to a combined sewer system sometimes have a bypass arrangement after the primary treatment unit. This means that during very heavy rainfall events, the secondary and tertiary treatment systems can be bypassed to protect them from hydraulic overloading, and the mixture of sewage and storm-water receives primary treatment only.
Primary sedimentation tanks remove about 50–70% of the suspended solids, and 25–40% of the biological oxygen demand (BOD). | 1 | Applied and Interdisciplinary Chemistry |
Ionochromic materials exist in a wide range of molecules, including organic molecules, pH-sensitive dyes and indicators, and other color-changing compounds with chromophores. Some of these molecules include phthalides, fluorans, and leucotriarylmethanes. | 0 | Theoretical and Fundamental Chemistry |
Sirpα migratory DCs (mDCs) form second subset of thymic DCs. They rise extrathymically, and were shown to present self antigens, especially blood-borne antigens, in the thymus, which they acquire in the periphery. They were also shown to be more efficient in T regulatory cells selection than clonal deletion. | 1 | Applied and Interdisciplinary Chemistry |
Flutamide has been found to be effective in the treatment of female pattern hair loss in a number of studies. In one study of 101 pre- and postmenopausal women, flutamide alone or in combination with an oral contraceptive produced a marked decrease in hair loss scores after 1 year of treatment, with maximum effect after 2 years of treatment and benefits maintained for another 2 years. In a small study of flutamide with an oral contraceptive, the medication caused an increase in cosmetically acceptance hair density in 6 of 7 women with diffuse scalp hair loss. In a comparative study, flutamide significantly improved scalp hair growth (21% reduction in Ludwig scores) in hyperandrogenic women after 1 year of treatment, whereas cyproterone acetate and finasteride were ineffective. | 0 | Theoretical and Fundamental Chemistry |
*Agnes Fay Morgan Research Award, Iota Sigma Pi, 2019
*Marshall University College of Science Distinguished Alumni Award, 2019
*Eli Lilly Young Investigator Award in Analytical Chemistry, 2018
*US HUPO Robert J. Cotter New Investigator Award, 2018
* NSF CAREER Award, 2015
* Arthur C. Neish Young Investigator Award, 2014
* NSF Graduate Research Fellowship, 2002-2005 | 0 | Theoretical and Fundamental Chemistry |
Progesterone is commercially produced by semisynthesis. Two main routes are used: one from yam diosgenin first pioneered by Marker in 1940, and one based on soy phytosterols scaled up in the 1970s. Additional (not necessarily economical) semisyntheses of progesterone have also been reported starting from a variety of steroids. For the example, cortisone can be simultaneously deoxygenated at the C-17 and C-21 position by treatment with iodotrimethylsilane in chloroform to produce 11-keto-progesterone (ketogestin), which in turn can be reduced at position-11 to yield progesterone. | 0 | Theoretical and Fundamental Chemistry |
One of the most basic tasks in spectroscopy is to characterize the spectrum of a light source: how much light is emitted at each different wavelength. The most straightforward way to measure a spectrum is to pass the light through a monochromator, an instrument that blocks all of the light except the light at a certain wavelength (the un-blocked wavelength is set by a knob on the monochromator). Then the intensity of this remaining (single-wavelength) light is measured. The measured intensity directly indicates how much light is emitted at that wavelength. By varying the monochromators wavelength setting, the full spectrum can be measured. This simple scheme in fact describes how some' spectrometers work.
Fourier-transform spectroscopy is a less intuitive way to get the same information. Rather than allowing only one wavelength at a time to pass through to the detector, this technique lets through a beam containing many different wavelengths of light at once, and measures the total beam intensity. Next, the beam is modified to contain a different combination of wavelengths, giving a second data point. This process is repeated many times. Afterwards, a computer takes all this data and works backwards to infer how much light there is at each wavelength.
To be more specific, between the light source and the detector, there is a certain configuration of mirrors that allows some wavelengths to pass through but blocks others (due to wave interference). The beam is modified for each new data point by moving one of the mirrors; this changes the set of wavelengths that can pass through.
As mentioned, computer processing is required to turn the raw data (light intensity for each mirror position) into the desired result (light intensity for each wavelength). The processing required turns out to be a common algorithm called the Fourier transform (hence the name, "Fourier-transform spectroscopy"). The raw data is sometimes called an "interferogram". Because of the existing computer equipment requirements, and the ability of light to analyze very small amounts of substance, it is often beneficial to automate many aspects of the sample preparation. The sample can be better preserved and the results are much easier to replicate. Both of these benefits are important, for instance, in testing situations that may later involve legal action, such as those involving drug specimens. | 0 | Theoretical and Fundamental Chemistry |
Also called Kharasch effect (named after Morris S. Kharasch), these reactions that do not involve a carbocation intermediate may react through other mechanisms that have regioselectivities not dictated by Markovnikov's rule, such as free radical addition. Such reactions are said to be anti-Markovnikov, since the halogen adds to the less substituted carbon, the opposite of a Markovnikov reaction.
The anti-Markovnikov rule can be illustrated using the addition of hydrogen bromide to isobutylene in the presence of benzoyl peroxide or hydrogen peroxide. The reaction of HBr with substituted alkenes was prototypical in the study of free-radical additions. Early chemists discovered that the reason for the variability in the ratio of Markovnikov to anti-Markovnikov reaction products was due to the unexpected presence of free radical ionizing substances such as peroxides. The explanation is that the O-O bond in peroxides is relatively weak. With the aid of light, heat, or sometimes even just acting on its own, the O-O bond can split to form 2 radicals. The radical groups can then interact with HBr to produce a Br radical, which then reacts with the double bond. Since the bromine atom is relatively large, it is more likely to encounter and react with the least substituted carbon since this interaction produces less static interactions between the carbon and the bromine radical. Furthermore, similar to a positive charged species, the radical species is most stable when the unpaired electron is in the more substituted position. The radical intermediate is stabilized by hyperconjugation. In the more substituted position, more carbon-hydrogen bonds are aligned with the radical's electron deficient molecular orbital. This means that there are greater hyperconjugation effects, so that position is more favorable. In this case, the terminal carbon is a reactant that produces a primary addition product instead of a secondary addition product.
A new method of anti-Markovnikov addition has been described by Hamilton and Nicewicz, who utilize aromatic molecules and light energy from a low-energy diode to turn the alkene into a cation radical.
Anti-Markovnikov behaviour extends to more chemical reactions than additions to alkenes. Anti-Markovnikov behaviour is observed in the hydration of phenylacetylene by auric catalysis, which gives acetophenone; although with a special ruthenium catalyst it provides the other regioisomer 2-phenylacetaldehyde:
Anti-Markovnikov behavior can also manifest itself in certain rearrangement reactions. In a titanium(IV) chloride-catalyzed formal nucleophilic substitution at enantiopure 1 in the scheme below, two products are formed – 2a and 2b Due to the two chiral centers in the target molecule, the carbon carrying chlorine and the carbon carrying the methyl and acetoxyethyl group, four different compounds are to be formed: 1R,2R- (drawn as 2b) 1R,2S- 1S,2R- (drawn as 2a) and 1S,2S- . Therefore, both of the depicted structures will exist in a D- and an L-form. :
This product distribution can be rationalized by assuming that loss of the hydroxy group in 1 gives the tertiary carbocation A, which rearranges to the seemingly less stable secondary carbocation B. Chlorine can approach this center from two faces leading to the observed mixture of isomers.
Another notable example of anti-Markovnikov addition is hydroboration. | 0 | Theoretical and Fundamental Chemistry |
The sessile drop method is another popular way to measure contact angles, and is done by placing a two-dimensional drop on a solid surface and controlling the volume of liquid in the drop. The sessile drop method and the captive bubble method are usually interchangeable in performing experiments as they are both based on the properties of symmetry. Specifically, the axis of symmetry of the drop or bubble makes the contact line of the drop or bubble with the solid surface circular. This creates an observable contact angle corresponding to the contact radius of the drop or bubble.
However, interacting with a rough homogeneous surface in measurements of contact angles, the drop and bubble each present different behaviours in the measuring process, which are related to the volume of liquid and contact angles.
# On a rough homogeneous surface, the observed contact angle may not represent the actual contact angle with a local slope since it may not be observable on a rough surface. The observed contact angle on a rough surface is also called an apparent angle which is equivalent to the sum of the intrinsic contact angle and the local surface slope at the tangent of the contact slope for a drop or bubble. With the sessile drop method, the observed contact angle usually underestimated the intrinsic contact angle, while the observed contact angle in the captive bubble method overestimates the intrinsic contact angle of the rough surface.
# If a graph is plotted respectively for the measurements of contact angles using the sessile drop method and the captive bubble method concerning the volume of liquid within the drop or bubble and the measured contact angle, the geometrical relationships illustrate different characteristics for each method. In consideration of the relationship between contact angles and the position of the contact for a certain volume in the drop or bubble, the highest and lowest possible contact angles on volume are dependent on each other differently in the two methods.
# For the amplitude of oscillations shown in the graph, both of the drop and the captive bubble display a similar order of magnitude at a relatively low contact angle. On the other hand, on a rough surface with a relatively high contact angle, the amplitude shown for the drop is larger than that of a captive bubble. The amplitude of oscillation of the lowest highest possible contact angle demonstrates the difference for the drop method and the captive bubble method, in which the amplitude of the graph of the captive bubble method is comparatively larger than that of the graph of the sessile drop method.
# In terms of the wavelength of the graph, the wavelength for both methods spans over a large range of volume of liquid on the solid surface. Differences in behaviours of the drop and the bubble vary from the lowest possible contact angles to the highest possible contact angle. | 0 | Theoretical and Fundamental Chemistry |
After an incident particle has fused with a parent nucleus, if the excitation energy is sufficient, the nucleus breaks into fragments. This is called scission, and occurs at about 10 seconds. The fragments can emit prompt neutrons at between 10 and 10 seconds. At about 10 seconds, the fragments can emit gamma rays. At 10 seconds β decay, β-delayed neutrons, and gamma rays are emitted from the decay products.
Typical fission events release about two hundred million eV (200 MeV) of energy, the equivalent of roughly >2 trillion kelvin, for each fission event. The exact isotope which is fissioned, and whether or not it is fissionable or fissile, has only a small impact on the amount of energy released. This can be easily seen by examining the curve of binding energy (image below), and noting that the average binding energy of the actinide nuclides beginning with uranium is around 7.6 MeV per nucleon. Looking further left on the curve of binding energy, where the fission products cluster, it is easily observed that the binding energy of the fission products tends to center around 8.5 MeV per nucleon. Thus, in any fission event of an isotope in the actinide mass range, roughly 0.9 MeV are released per nucleon of the starting element. The fission of U by a slow neutron yields nearly identical energy to the fission of U by a fast neutron. This energy release profile holds for thorium and the various minor actinides as well.
When a uranium nucleus fissions into two daughter nuclei fragments, about 0.1 percent of the mass of the uranium nucleus appears as the fission energy of ~200 MeV. For uranium-235 (total mean fission energy 202.79 MeV), typically ~169 MeV appears as the kinetic energy of the daughter nuclei, which fly apart at about 3% of the speed of light, due to Coulomb repulsion. Also, an average of 2.5 neutrons are emitted, with a mean kinetic energy per neutron of ~2 MeV (total of 4.8 MeV). The fission reaction also releases ~7 MeV in prompt gamma ray photons. The latter figure means that a nuclear fission explosion or criticality accident emits about 3.5% of its energy as gamma rays, less than 2.5% of its energy as fast neutrons (total of both types of radiation ~6%), and the rest as kinetic energy of fission fragments (this appears almost immediately when the fragments impact surrounding matter, as simple heat).
Some processes involving neutrons are notable for absorbing or finally yielding energy — for example neutron kinetic energy does not yield heat immediately if the neutron is captured by a uranium-238 atom to breed plutonium-239, but this energy is emitted if the plutonium-239 is later fissioned. On the other hand, so-called delayed neutrons emitted as radioactive decay products with half-lives up to several minutes, from fission-daughters, are very important to reactor control, because they give a characteristic "reaction" time for the total nuclear reaction to double in size, if the reaction is run in a "delayed-critical" zone which deliberately relies on these neutrons for a supercritical chain-reaction (one in which each fission cycle yields more neutrons than it absorbs). Without their existence, the nuclear chain-reaction would be prompt critical and increase in size faster than it could be controlled by human intervention. In this case, the first experimental atomic reactors would have run away to a dangerous and messy "prompt critical reaction" before their operators could have manually shut them down (for this reason, designer Enrico Fermi included radiation-counter-triggered control rods, suspended by electromagnets, which could automatically drop into the center of Chicago Pile-1). If these delayed neutrons are captured without producing fissions, they produce heat as well. | 0 | Theoretical and Fundamental Chemistry |
Many reactions produce carboxylic acids but are used only in specific cases or are mainly of academic interest.
* Disproportionation of an aldehyde in the Cannizzaro reaction
* Rearrangement of diketones in the benzilic acid rearrangement
* Involving the generation of benzoic acids are the von Richter reaction from nitrobenzenes and the Kolbe–Schmitt reaction from phenols. | 0 | Theoretical and Fundamental Chemistry |
The technique is closely related to using gas adsorption to measure pore sizes, but uses the Gibbs–Thomson equation rather than the Kelvin equation. They are both particular cases of the Gibbs Equations of Josiah Willard Gibbs: the Kelvin equation is the constant temperature case, and the Gibbs–Thomson equation is the constant pressure case.
This behaviour is closely related to the capillary effect and both are due to the change in bulk free energy caused by the curvature of an interfacial surface under tension.
The original equation only applies to isolated particles, but with the addition of surface interaction terms (usually expressed in terms of the contact wetting angle) can be modified to apply to liquids and their crystals in porous media. As such it has given rise to various related techniques for measuring pore size distributions. (See Thermoporometry and cryoporometry.)
The Gibbs–Thomson effect lowers both melting and freezing point, and also raises boiling point. However, simple cooling of an all-liquid sample usually leads to a state of non-equilibrium super cooling and only eventual non-equilibrium freezing. To obtain a measurement of the equilibrium freezing event, it is necessary to first cool enough to freeze a sample with excess liquid outside the pores, then warm the sample until the liquid in the pores is all melted, but the bulk material is still frozen. Then, on re-cooling the equilibrium freezing event can be measured, as the external ice will then grow into the pores.
This is in effect an "ice intrusion" measurement (cf. mercury intrusion), and as such in part may provide information on pore throat properties. The melting event can be expected to provide more accurate information on the pore body. | 0 | Theoretical and Fundamental Chemistry |
Cryptands enjoy some commercial applications (e.g. in homogenous-time-resolved-fluorescence, HTRF, technologies using Eu3+ as central ion). More importantly, they are reagents for the synthesis of inorganic and organometallic salts. Although more expensive and more difficult to prepare than crown ethers, cryptands bind alkali metals more strongly. They are especially used to isolate salts of highly basic anions. They convert solvated alkali metal cations into lipophilic cations, thereby conferring solubility in organic solvents to the resulting salts.
Referring to achievements that have been recognized in textbooks, cryptands enabled the synthesis of the alkalides and electrides. For example, addition of 2,2,2-cryptand to a solution of sodium in ammonia affords the salt [Na(2,2,2-crypt)]e, isolated a blue-black paramagnetic solid. Cryptands have also been used in the crystallization of Zintl ions such as .
Although rarely practical, cryptands can serve as phase transfer catalysts since their cationic complexes are lipophilic. | 0 | Theoretical and Fundamental Chemistry |
Human immunodeficiency virus (HIV) is a lentivirus that has two major species, HIV-1 which causes the majority of the epidemic, and HIV-2, a close relative whose distribution is concentrated in western Africa. HIV infection was first described in 1981 in San Francisco and New York City. In 1985, HIV was identified as the causative agent of acquired immune deficiency syndrome (AIDS) and its complete genome was immediately available. This knowledge paved the way for the development of selective inhibitors.
HIV-2 carries a slightly lower risk of transmission than HIV-1 and infection tends to progress more slowly to AIDS. In common usage HIV usually implies HIV-1.
HIV-1 protease is one of the best known aspartic proteases, and an attractive target for the treatment of AIDS.
After the discovery of HIV protease it only took 10 years for its first inhibitor to reach the market. The first reports of highly selective antagonists against the HIV protease were revealed in 1987. Phase I trials of saquinavir began in 1989 and it was the first HIV protease inhibitor to be approved for prescription use in 1995. Four months later, two other protease inhibitors, ritonavir and indinavir, were approved. In 2009, ten protease inhibitors have reached the market for treatment against HIV but one protease inhibitor, amprenavir, was withdrawn from the market in 2004. | 1 | Applied and Interdisciplinary Chemistry |
Zofenopril (INN) is a medication that protects the heart and helps reduce high blood pressure. It is an angiotensin-converting enzyme (ACE) inhibitor.
In small studies, zofenopril appeared significantly more effective in reducing hypertension than two older antihypertensive drugs, atenolol and enalapril, and was associated with fewer adverse effects.
Zofenopril is a prodrug with zofenoprilat as the active metabolite.
It was patented in 1978 and approved for medical use in 2000. | 0 | Theoretical and Fundamental Chemistry |
To collect the very fine particles a new technology is used in the field of "nano" spray drying. The reason is that common cyclone technology depends on the particle mass; particles smaller than 2 μm can't be separated and instead exit the system along with the exhaust gas.
The electrostatic particle collector charges the dry particles' surface and deflects them with an electrical field. To produce the electrical field, a high voltage (16 kV) is applied to a round collector tube. The electrical field builds up between the inner wall of the collector tube and the tips of a grounded star electrode. To have a low level of energy in the system the current is very low.
After getting deflected the particles stay at the inner wall of the particle collector tube and are completely uncharged. This separation method works fine for all kinds of materials.
The efficiency of the electrostatic particle collector is very high: 99% of all particles that enter the system are collected. | 0 | Theoretical and Fundamental Chemistry |
The cyclol fabric was shown to be implausible for several reasons. Hans Neurath and Henry Bull showed that the dense packing of side chains in the cyclol fabric was inconsistent with the experimental density observed in protein films. Maurice Huggins calculated that several non-bonded atoms of the cyclol fabric would approach more closely than allowed by their van der Waals radii; for example, the inner H and C atoms of the lacunae would be separated by only 1.68 Å (Figure 5). Haurowitz showed chemically that the outside of proteins could not have a large number of hydroxyl groups, a key prediction of the cyclol model, whereas Meyer and Hohenemser showed that cyclol condensations of amino acids did not exist even in minute quantities as a transition state. More general chemical arguments against the cyclol model were given by Bergmann and Niemann and by Neuberger. Infrared spectroscopic data showed that the number of carbonyl groups in a protein did not change upon hydrolysis, and that intact, folded proteins have a full complement of amide carbonyl groups; both observations contradict the cyclol hypothesis that such carbonyls are converted to hydroxyl groups in folded proteins. Finally, proteins were known to contain proline in significant quantities (typically 5%); since proline lacks the amide hydrogen and its nitrogen already forms three covalent bonds, proline seems incapable of the cyclol reaction and of being incorporated into a cyclol fabric. An encyclopedic summary of the chemical and structural evidence against the cyclol model was given by Pauling and Niemann. Moreover, a supporting piece of evidence—the result that all proteins contain an integer multiple of 288 amino-acid residues—was likewise shown to be incorrect in 1939.
Wrinch replied to the steric-clash, free-energy, chemical and residue-number criticisms of the cyclol model. On steric clashes, she noted that small deformations of the bond angles and bond lengths would allow these steric clashes to be relieved, or at least reduced to a reasonable level. She noted that distances between non-bonded groups within a single molecule can be shorter than expected from their van der Waals radii, e.g., the 2.93 Å distance between methyl groups in hexamethylbenzene. Regarding the free-energy penalty for the cyclol reaction, Wrinch disagreed with Pauling's calculations and stated that too little was known of intramolecular energies to rule out the cyclol model on that basis alone. In reply to the chemical criticisms, Wrinch suggested that the model compounds and simple bimolecular reactions studied need not pertain to the cyclol model, and that steric hindrance may have prevented the surface hydroxyl groups from reacting. On the residue-number criticism, Wrinch extended her model to allow for other numbers of residues. In particular, she produced a "minimal" closed cyclol of only 48 residues, and, on that (incorrect) basis, may have been the first to suggest that the insulin monomer had a molecular weight of roughly 6000 Da.
Therefore, she maintained that the cyclol model of globular proteins was still potentially viable and even proposed the cyclol fabric as a component of the cytoskeleton. However, most protein scientists ceased to believe in it and Wrinch turned her scientific attention to mathematical problems in X-ray crystallography, to which she contributed significantly. One exception was physicist Gladys Anslow, Wrinchs colleague at Smith College, who studied the ultraviolet absorption spectra of proteins and peptides in the 1940s and allowed for the possibility of cyclols in interpreting her results. As the sequence of insulin began to be determined by Frederick Sanger, Anslow published a three-dimensional cyclol model with sidechains, based on the backbone of Wrinchs 1948 "minimal cyclol" model. | 1 | Applied and Interdisciplinary Chemistry |
Albert Attalla died at Banner Thunderbird Medical Center on May 26, 2014, of cardiac arrest after suffering from a brain hemorrhage on May 12. His wife and middle daughter were by his side when he passed.
He donated his body to Research for Life and after all tissue samples were taken, his body was cremated and returned to his family.
Albert is mentioned in the "Pray for the Deceased" section of the Church of St. Thomas More June 22, 2014, bulletin. | 0 | Theoretical and Fundamental Chemistry |
MS-SnuPE employs the primer extension method initially designed for analyzing single-nucleotide polymorphisms. DNA is bisulfite-converted, and bisulfite-specific primers are annealed to the sequence up to the base pair immediately before the CpG of interest. The primer is allowed to extend one base pair into the C (or T) using DNA polymerase terminating dideoxynucleotides, and the ratio of C to T is determined quantitatively.
A number of methods can be used to determine this C:T ratio. At the beginning, MS-SnuPE relied on radioactive ddNTPs as the reporter of the primer extension. Fluorescence-based methods or Pyrosequencing can also be used. However, matrix-assisted laser desorption ionization/time-of-flight (MALDI-TOF) mass spectrometry analysis to differentiate between the two polymorphic primer extension products can be used, in essence, based on the GOOD assay designed for SNP genotyping. Ion pair reverse-phase high-performance liquid chromatography (IP-RP-HPLC) has also been used to distinguish primer extension products. | 1 | Applied and Interdisciplinary Chemistry |
Ellipsometry can also be done as imaging ellipsometry by using a CCD camera as a detector. This provides a real time contrast image of the sample, which provides information about film thickness and refractive index. Advanced imaging ellipsometer technology operates on the principle of classical null ellipsometry and real-time ellipsometric contrast imaging. Imaging ellipsometry is based on the concept of nulling. In ellipsometry, the film under investigation is placed onto a reflective substrate. The film and the substrate have different refractive indexes. In order to obtain data about film thickness, the light reflecting off of the substrate must be nulled. Nulling is achieved by adjusting the analyzer and polarizer so that all reflected light off of the substrate is extinguished. Due to the difference in refractive indexes, this will allow the sample to become very bright and clearly visible. The light source consists of a monochromatic laser of the desired wavelength. A common wavelength that is used is 532 nm green laser light. Since only intensity of light measurements are needed, almost any type of camera can be implemented as the CCD, which is useful if building an ellipsometer from parts. Typically, imaging ellipsometers are configured in such a way so that the laser (L) fires a beam of light which immediately passes through a linear polarizer (P). The linearly polarized light then passes through a quarter wavelength compensator (C) which transforms the light into elliptically polarized light. This elliptically polarized light then reflects off the sample (S), passes through the analyzer (A) and is imaged onto a CCD camera by a long working distance objective. The analyzer here is another polarizer identical to the P, however, this polarizer serves to help quantify the change in polarization and is thus given the name analyzer. This design is commonly referred to as a LPCSA configuration.
The orientation of the angles of P and C are chosen in such a way that the elliptically polarized light is completely linearly polarized after it is reflected off the sample. For simplification of future calculations, the compensator can be fixed at a 45 degree angle relative to the plane of incidence of the laser beam. This set up requires the rotation of the analyzer and polarizer in order to achieve null conditions. The ellipsometric null condition is obtained when A is perpendicular with respect to the polarization axis of the reflected light achieving complete destructive interference, i.e., the state at which the absolute minimum of light flux is detected at the CCD camera. The angles of P, C, and A obtained are used to determine the Ψ and Δ values of the material.
: and
where A and P are the angles of the analyzer and polarizer under null conditions respectively. By rotating the analyzer and polarizer and measuring the change in intensities of light over the image, analysis of the measured data by use of computerized optical modeling can lead to a deduction of spatially resolved film thickness and complex refractive index values.
Due to the fact that the imaging is done at an angle, only a small line of the entire field of view is actually in focus. The line in focus can be moved along the field of view by adjusting the focus. In order to analyze the entire region of interest, the focus must be incrementally moved along the region of interest with a photo taken at each position. All of the images are then compiled into a single, in focus image of the sample. | 0 | Theoretical and Fundamental Chemistry |
There are four known mammalian protein kinases that phosphorylate eIF2α, including PKR-like ER kinase (PERK, EIF2AK3), heme-regulated eIF2α kinase (HRI, EIF2AK1), general control non-depressible 2 (GCN2, EIF2AK4) and double stranded RNA dependent protein kinase (PKR, EIF2AK2). | 1 | Applied and Interdisciplinary Chemistry |
A wide variety of phenols undergo O-methylation to give anisole derivatives. This process, catalyzed by such enzymes as caffeoyl-CoA O-methyltransferase, is a key reaction in the biosynthesis of lignols, percursors to lignin, a major structural component of plants.
Plants produce flavonoids and isoflavones with methylations on hydroxyl groups, i.e. methoxy bonds. This 5-O-methylation affects the flavonoid's water solubility. Examples are 5-O-methylgenistein, 5-O-methylmyricetin, and 5-O-methylquercetin (azaleatin). | 0 | Theoretical and Fundamental Chemistry |
A crystallite is a small or even microscopic crystal which forms, for example, during the cooling of many materials. Crystallites are also referred to as grains.
Bacillite is a type of crystallite. It is rodlike with parallel longulites. | 1 | Applied and Interdisciplinary Chemistry |
Due to low emission rate experiments should be performed in ultrahigh vacuum (UHV). In some studies the materials were previously doped with tritium. MSGE rate then was measured by radioactivity outcome from the material under applied mechanical stress. | 0 | Theoretical and Fundamental Chemistry |
To determine five-day biochemical oxygen demand (BOD), several dilutions of a sample are analyzed for dissolved oxygen before and after a five-day incubation period at 20 °C in the dark. In some cases, bacteria are used to provide a standardized community to uptake oxygen while consuming the organic matter in the sample; these bacteria are known as "seed". The difference in DO and the dilution factor are used to calculated BOD. The resulting number (usually reported in parts per million or milligrams per liter) is useful in determining the relative organic strength of sewage or other polluted waters.
The BOD test is an example of analysis that determines classes of materials in a sample. | 0 | Theoretical and Fundamental Chemistry |
In oxidative phosphorylation, electrons are transferred from an electron donor such as NADH to an acceptor such as O through an electron transport chain, releasing energy. In photophosphorylation, the energy of sunlight is used to create a high-energy electron donor which can subsequently reduce oxidized components and couple to ATP synthesis via proton translocation by the electron transport chain.
Photosynthetic electron transport chains, like the mitochondrial chain, can be considered as a special case of the bacterial systems. They use mobile, lipid-soluble quinone carriers (phylloquinone and plastoquinone) and mobile, water-soluble carriers (cytochromes). They also contain a proton pump. The proton pump in all photosynthetic chains resembles mitochondrial Complex III. The commonly-held theory of symbiogenesis proposes that both organelles descended from bacteria. | 1 | Applied and Interdisciplinary Chemistry |
To place the sample under investigation into the x-ray beam, a sample holder is required. While in white-beam techniques a simple fixed holder is sometimes sufficient, experiments with monochromatic techniques typically require one or more degrees of freedom of rotational motion. Samples are therefore placed on a diffractometer, allowing to orient the sample along one, two or three axes. If the sample needs to be displaced, e.g. in order to scan its surface through the beam in several steps, additional translational degrees of freedom are required. | 0 | Theoretical and Fundamental Chemistry |
Liquid fuels are liquids containing dissolved nuclear fuel and have been shown to offer numerous operational advantages compared to traditional solid fuel approaches.
Liquid-fuel reactors offer significant safety advantages due to their inherently stable "self-adjusting" reactor dynamics. This provides two major benefits: virtually eliminating the possibility of a runaway reactor meltdown, and providing an automatic load-following capability which is well suited to electricity generation and high-temperature industrial heat applications.
Another major advantage of some liquid core designs is their ability to be drained rapidly into a passively safe dump-tank. This advantage was conclusively demonstrated repeatedly as part of a weekly shutdown procedure during the highly successful 4 year Molten Salt Reactor Experiment.
Another huge advantage of the liquid core is its ability to release xenon gas, which normally acts as a neutron absorber ( is the strongest known neutron poison and is produced both directly and as a decay product of as a fission product) and causes structural occlusions in solid fuel elements (leading to the early replacement of solid fuel rods with over 98% of the nuclear fuel unburned, including many long-lived actinides). In contrast, molten salt reactors (MSR) are capable of retaining the fuel mixture for significantly extended periods, which not only increases fuel efficiency dramatically but also incinerates the vast majority of its own waste as part of the normal operational characteristics. A downside to letting the escape instead of allowing it to capture neutrons converting it to the basically stable and chemically inert , is that it will quickly decay to the highly chemically reactive long lived radioactive , which behaves similar to other alkali metals and can be taken up by organisms in their metabolism. | 0 | Theoretical and Fundamental Chemistry |
SDS is not carcinogenic in low concentrations according to some studies. Like all detergents, sodium lauryl sulfate removes oils from the skin, and can cause skin and eye irritation. It has been shown to irritate the skin of the face, with prolonged and constant exposure (more than an hour) in young adults. SDS may worsen skin problems in individuals with chronic skin hypersensitivity, with some people being affected more than others. | 1 | Applied and Interdisciplinary Chemistry |
The following table and diagram show experimentally determined surface tensions in the mixture of water and propionic acid.
This example shows a good agreement between the published value a=2.6*10 and the calculated value a=2.59*10 at the smallest given mole fraction of 0.00861 but at higher concentrations of propionic acid the value of an increases considerably, showing deviations from the predicted value. | 0 | Theoretical and Fundamental Chemistry |
* Loading: Analogous to the starting stage, each module loads its specific amino acid onto its PCP-domain.
* Condensation: The C-domain catalyzes the amide bond formation between the thioester group of the growing peptide chain from the previous module with the amino group of the current module. The extended peptide is now attached to the current PCP-domain.
* Condensation-Cyclization: Sometimes the C-domain is replaced by a Cy-domain, which, in addition to the amide bond formation, catalyzes the reaction of the serine, threonine, or cysteine sidechain with the amide-N, thereby forming oxazolidines and thiazolidine, respectively.
* Epimerization: Sometimes an E-domain epimerizes the innermost amino acid of the peptide chain into the D-configuration.
* This cycle is repeated for each elongation module. | 1 | Applied and Interdisciplinary Chemistry |
One application for sodium tert-butoxide is as a non-nucleophilic base. It has been widely used in the Buchwald–Hartwig amination, as in this typical example:
Sodium tert-butoxide is used to prepare tert-butoxide complexes. For example hexa(tert-butoxy)ditungsten(III) is thus obtained by the salt metathesis reaction from a ditungsten heptachloride:
:NaWCl(THF) + 6 NaOBu-t → W(OBu-t) + 7 NaCl + 5 THF | 0 | Theoretical and Fundamental Chemistry |
A magnetohydrodynamic generator (MHD generator) is a magnetohydrodynamic converter that transforms thermal energy and kinetic energy directly into electricity. An MHD generator, like a conventional generator, relies on moving a conductor through a magnetic field to generate electric current. The MHD generator uses hot conductive ionized gas (a plasma) as the moving conductor. The mechanical dynamo, in contrast, uses the motion of mechanical devices to accomplish this.
MHD generators are different from traditional electric generators in that they operate without moving parts (e.g. no turbine) to limit the upper temperature. They therefore have the highest known theoretical thermodynamic efficiency of any electrical generation method. MHD has been extensively developed as a topping cycle to increase the efficiency of electric generation, especially when burning coal or natural gas. The hot exhaust gas from an MHD generator can heat the boilers of a steam power plant, increasing overall efficiency.
Practical MHD generators have been developed for fossil fuels, but these were overtaken by less expensive combined cycles in which the exhaust of a gas turbine or molten carbonate fuel cell heats steam to power a steam turbine.
MHD dynamos are the complement of MHD accelerators, which have been applied to pump liquid metals, seawater, and plasmas.
Natural MHD dynamos are an active area of research in plasma physics and are of great interest to the geophysics and astrophysics communities since the magnetic fields of the Earth and Sun are produced by these natural dynamos. | 1 | Applied and Interdisciplinary Chemistry |
Many organofluorine compounds are produced by electrofluorination. One manifestation of this technology is the Simons process, which can be described as:
:RC–H + HF → RC–F + H
In the course of a typical synthesis, this reaction occurs once for each C–H bond in the precursor. The cell potential is maintained near 5–6 V. The anode, the electrocatalyst, is nickel-plated. | 0 | Theoretical and Fundamental Chemistry |
Following the invention of X-ray crystallography techniques in the 1910s, the atomic structure of many compounds was investigated. Most metals have relatively simple structures. However, in 1923 Linus Pauling reported on the structure of the intermetallic NaCd, which had such a complicated structure he was unable to fully explain it. Thirty years later, he concluded that NaCd contains 384 sodium and 768 cadmium atoms in each unit cell.
Most physical properties of CMAs show distinct differences with respect to the behavior of normal metallic alloys and therefore these materials possess a high potential for technological application.
The European Commission funded the Network of Excellence CMA from 2005 to 2010, uniting 19 core groups in 12 countries. From this emerged the European Integrated Center for the Development of New Metallic Alloys and Compounds (previously C-MAC, now ECMetAC), which connects researchers at 21 universities. | 1 | Applied and Interdisciplinary Chemistry |
Prior to 1925, the materials used in implant surgery were primarily relatively pure metals. The success of these materials was surprising considering the relatively primitive surgical techniques. The 1930s marked the beginning of the era of better surgical techniques as well as the first use of alloys such as vitallium.
In 1969, L. L. Hench and others discovered that various kinds of glasses and ceramics could bond to living bone. Hench was inspired by the idea on his way to a conference on materials. He was seated next to a colonel who had just returned from the Vietnam War. The colonel shared that after an injury the bodies of soldiers would often reject the implant. Hench was intrigued and began to investigate materials that would be biocompatible. The final product was a new material which he called bioglass. This work inspired a new field called bioceramics. With the discovery of bioglass, interest in bioceramics grew rapidly.
On April 26, 1988, the first international symposium on bioceramics was held in Kyoto, Japan. | 0 | Theoretical and Fundamental Chemistry |
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