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In order to convert the pressure into a shear stress, it is necessary to determine the component of the pressure that provides shear on the bed. For a channel that is at an angle from horizontal, the shear component of the stress acting on the bed , which is the component acting tangentially to the bed, equals the total pressure times the sine of the angle .
In natural rivers, the angle is typically very small. As a result, the small-angle formula states that:
The tangent of the angle is, by definition, equal to the slope of the channel, .
From this, we can arrive at the final form of the relation between bed shear stress and depth–slope product: | 1 | Applied and Interdisciplinary Chemistry |
The synchronizer acts as an external trigger for both the camera(s) and the laser. While analogue systems in the form of a photosensor, rotating aperture and a light source have been used in the past, most systems in use today are digital. Controlled by a computer, the synchronizer can dictate the timing of each frame of the CCD cameras sequence in conjunction with the firing of the laser to within 1 ns precision. Thus the time between each pulse of the laser and the placement of the laser shot in reference to the cameras timing can be accurately controlled. Knowledge of this timing is critical as it is needed to determine the velocity of the fluid in the PIV analysis. Stand-alone electronic synchronizers, called digital delay generators, offer variable resolution timing from as low as 250 ps to as high as several ms. With up to eight channels of synchronized timing, they offer the means to control several flash lamps and Q-switches as well as provide for multiple camera exposures. | 1 | Applied and Interdisciplinary Chemistry |
Oxidative phosphorylation (UK , US ) or electron transport-linked phosphorylation or terminal oxidation is the metabolic pathway in which cells use enzymes to oxidize nutrients, thereby releasing chemical energy in order to produce adenosine triphosphate (ATP). In eukaryotes, this takes place inside mitochondria. Almost all aerobic organisms carry out oxidative phosphorylation. This pathway is so pervasive because it releases more energy than alternative fermentation processes such as anaerobic glycolysis.
The energy stored in the chemical bonds of glucose is released by the cell in the citric acid cycle, producing carbon dioxide and the energetic electron donors NADH and FADH. Oxidative phosphorylation uses these molecules and O to produce ATP, which is used throughout the cell whenever energy is needed. During oxidative phosphorylation, electrons are transferred from the electron donors to a series of electron acceptors in a series of redox reactions ending in oxygen, whose reaction releases half of the total energy.
In eukaryotes, these redox reactions are catalyzed by a series of protein complexes within the inner membrane of the cells mitochondria, whereas, in prokaryotes, these proteins are located in the cells outer membrane. These linked sets of proteins are called the electron transport chain. In eukaryotes, five main protein complexes are involved, whereas in prokaryotes many different enzymes are present, using a variety of electron donors and acceptors.
The energy transferred by electrons flowing through this electron transport chain is used to transport protons across the inner mitochondrial membrane, in a process called electron transport. This generates potential energy in the form of a pH gradient and the resulting electrical potential across this membrane. This store of energy is tapped when protons flow back across the membrane and down the potential energy gradient, through a large enzyme called ATP synthase in a process called chemiosmosis. The ATP synthase uses the energy to transform adenosine diphosphate (ADP) into adenosine triphosphate, in a phosphorylation reaction. The reaction is driven by the proton flow, which forces the rotation of a part of the enzyme. The ATP synthase is a rotary mechanical motor.
Although oxidative phosphorylation is a vital part of metabolism, it produces reactive oxygen species such as superoxide and hydrogen peroxide, which lead to propagation of free radicals, damaging cells and contributing to disease and, possibly, aging and senescence. The enzymes carrying out this metabolic pathway are also the target of many drugs and poisons that inhibit their activities. | 1 | Applied and Interdisciplinary Chemistry |
Osborne Reynolds famously studied the conditions in which the flow of fluid in pipes transitioned from laminar flow to turbulent flow.
In his 1883 paper Reynolds described the transition from laminar to turbulent flow in a classic experiment in which he examined the behaviour of water flow under different flow velocities using a small stream of dyed water introduced into the centre of clear water flow in a larger pipe.
The larger pipe was glass so the behaviour of the layer of the dyed stream could be observed. At the end of this pipe, there was a flow control valve used to vary the water velocity inside the tube. When the velocity was low, the dyed layer remained distinct throughout the entire length of the large tube. When the velocity was increased, the layer broke up at a given point and diffused throughout the fluid's cross-section. The point at which this happened was the transition point from laminar to turbulent flow.
From these experiments came the dimensionless Reynolds number for dynamic similarity—the ratio of inertial forces to viscous forces. Reynolds also proposed what is now known as the Reynolds averaging of turbulent flows, where quantities such as velocity are expressed as the sum of mean and fluctuating components. Such averaging allows for bulk description of turbulent flow, for example using the Reynolds-averaged Navier–Stokes equations. | 1 | Applied and Interdisciplinary Chemistry |
As the pump and the probe beam must have the same exact frequency, the most convenient solution is for them to come from the same laser. The probe beam can be made of a reflection of the pump beam passed through neutral density filter to reduce its intensity. To fine-tune the frequency of the laser, a diode laser with a piezoelectric transducer that controls the cavity wavelength can be used. Due to photodiode noise, the laser frequency can be swept across the transition and the photodiode reading averaged over many sweeps.
In real atoms, there are sometimes more than two relevant transitions within the sample's Doppler profile (e.g. in alkali atoms with hyperfine interactions). This will generate the apparition of other dips in the absorption feature due to these new resonances in addition to crossover resonances. | 0 | Theoretical and Fundamental Chemistry |
Uridine diphosphate galactose (UDP-galactose) is an intermediate in the production of polysaccharides. It is important in nucleotide sugars metabolism, and is the substrate for the transferase B4GALT5. | 1 | Applied and Interdisciplinary Chemistry |
* [https://www.therminol.com/product/71093433?pn=Therminol-55-Heat-Transfer-Fluid Therminol 55] Heat Transfer Fluid
* [https://www.therminol.com/product/71093435?pn=Therminol-59-Heat-Transfer-Fluid Therminol 59] Heat Transfer Fluid
* [https://www.therminol.com/product/71093449?pn=Therminol-FF-(Flush-Fluid) Therminol FF] (Flush Fluid) | 1 | Applied and Interdisciplinary Chemistry |
To study charge transfer reactions of an ITIES, a four-electrode cell is used.
Two reference electrodes are used to control the polarisation of the interface, and two counter electrodes made of noble metals are used to pass the current. The aqueous supporting electrolyte must be hydrophilic, such as LiCl, and the organic electrolyte must be lipophilic, such as tetraheptylammonium tetra-pentafluorophenyl borate. | 0 | Theoretical and Fundamental Chemistry |
Thermal conductive heating is the application of heat to subsurface soils through conductive heat transfer. The source of the heat is applied via electric or gas powered thermal wells. Thermal wells are inserted vertically, or horizontally, in an array within the soil. Heat flows from the heating elements by conduction. The heating process causes contaminants to be vaporized or destroyed by means of:
# evaporation
# steam stripping
# hydrolysis
# oxidation
# pyrolysis
Vaporized contaminants are collected from vapor extraction wells and containerized for removal or recycling. | 1 | Applied and Interdisciplinary Chemistry |
To understand how presence of a futile cycle helps maintain low levels of ATP and generation heat in some species we look at metabolic pathways dealing with reciprocal regulation of glycolysis and gluconeogenesis.
The swim bladder of many fish; such as zebrafish for example - is an organ internally filled with gas that helps contribute to their buoyancy. These gas gland cell are found to be located where the capillaries and nerves are found. Analyses of metabolic enzymes demonstrated that a gluconeogenesis enzyme fructose-1,6- bisphosphatase (Fbp1) and a glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (Gapdh) are highly expressed in gas gland cells. The study signified that the characterization of the zebrafish swim bladder should not contain any expression fructose-1,6-bisphosphatase gene. The tissue of the swim bladder is known to be very high in glycogenic activity and lacking in gluconeogenesis, yet a predominant amount of Fbp was found to be expressed. This finding suggests that in the gas gland cell, Fbp forms an ATP-dependent metabolic futile cycle. Generation of heat is critically important for the gas gland cells to synthesize lactic acid because the process is strongly inhibited if ATP is accumulated.
Another example suggest that heat generation in fugu swim bladder will be transported out of the site of generation, however it may still be constantly recovered back through the rete mirabile so as to maintain the temperature of the gas gland higher than other areas of the body.
Another example of futile cycle benefiting in generation of heat is found in bumblebees. The futile cycle involving Fbp and Pfk is used by bumble bees to produce heat in flight muscles and warm up their bodies considerably at low ambient temperatures. | 1 | Applied and Interdisciplinary Chemistry |
When a crystal of a binary oxide is cleaved to generate two new surfaces, each solid's charge remains neutral. However, the structure of the two newly created surfaces may or may not be the same. If the structures are identical, the surface will be dipoleless and is considered a nonpolar surface. If the structures are different, the surface will have a strong dipole and is considered a polar surface. Examples of nonpolar surfaces include the rocksalt (100) surface, the rutile (100), (110) and (001) surfaces and the pervoskite (100) surface. An example of a polar surface is the rocksalt (111) surface. In general, a polar surface is less stable than a nonpolar surface because a dipole moment increases the surface Gibbs energy. Also, oxygen polar surfaces are more stable than metal polar surfaces because oxygen ions are more polarizable, which lowers the surface energy. | 0 | Theoretical and Fundamental Chemistry |
Christoph Weder was born on July 30, 1966. He began elementary school in Mülheim a. Main, Germany, in 1972 before moving to Thalwil, Switzerland, in 1974, where he completed elementary and secondary school. He then attended the high school Kantonsschule Enge in Zurich, from which he graduated in 1985. Following in the footsteps of his father, who was also a polymer chemist, Weder studied chemistry at the Swiss Federal Institute of Technology (ETH Zurich) in Zurich, where he received his diploma in chemistry in 1990. He then joined the research group of Professor Ulrich W. Suter as a doctoral student and in 1994 was awarded the degree of Doctor of Natural Sciences for his dissertation “New Polyamides with Stable Nonlinear Optical Properties.” While at ETH, Weder was also trained as a chemistry teacher and received his teaching certification in 1992. With a fellowship from the Swiss National Science Foundation, Weder then spent one year as a postdoctoral research fellow in the Department of Chemistry at the Massachusetts Institute of Technology, where he worked under the guidance of then-provost Mark S. Wrighton.
Weder returned to the Department of Materials of ETH Zurich in 1995, where he joined the group of Professor Paul Smith and continued to work on photofunctional polymers. Based on his habilitation thesis entitled “Polarizing Light with Polymers,” Weder received his habilitation and, bestowed with the venia legendi, became an independent lecturer in 1999. In 2001, Weder left ETH and joined Case Western Reserve University in Cleveland, Ohio, as an associate professor in the Department of Macromolecular Science and Engineering. He was promoted to professor in 2007, and in 2008 was named the F. Alex Nason Professor.
In 2009, Weder returned to Switzerland and joined the Adolphe Merkle Institute (AMI) as Professor of Polymer Chemistry and Materials. AMI, which was founded in 2008 thanks to a gift from Adolphe Merkle, is an interdisciplinary research center that focuses on fundamental and application-oriented research in soft nano- and materials sciences. In January 2010, Weder was appointed as the institute’s director, serving until April 2022.
Weder led a team that was awarded a grant from the Swiss National Science Foundation (SNSF) to establish the National Competence Center in Research (NCCR) Bio-Inspired Materials. He served as the center’s director from its launch in 2014 until 2020. The NCCRs are a research instrument of the Swiss National Science Foundation (SNSF) that aim to strengthen research in areas of strategic importance for the future of Swiss science, business and society.
Weder remains an adjunct professor at CWRU and has served as a visiting professor at Chulalongkorn University in Bangkok, Thailand since 2003. He serves as an Associate Editor of ACS Macro Letters and was a co-editor of the RSC Book Series Polymer Chemistry from 202-2021.
Weder has co-authored more than 300 peer-reviewed articles in scientific journals and over twenty book chapters. He also edited two books. As of March 2022, Weder has an h-index of 87 and his works have been cited more than 27,000 times.
Weder is a co-inventor of more than twenty patent families that protect technologies such as light-polarizing security features, mechanochromic materials, sea-cucumber inspired dynamic mechanical polymer nanocomposites, stimuli-responsive supramolecular polymers, materials for optical upconversion, shape memory polymers, and optical data storage systems. He was a co-founding board member of the ETH-spinoff company Omlidon Technologies, LLC (1999–2002), and served on the board of directors of Gel Instrumente AG (1994–2006).
Weder is the recipient of a 3M Non-Tenured Faculty Award, a DuPont Young Professor Award, an NSF Special Creativity Award, and the Case School of Engineering Award. He was awarded a prestigious European Research Council (ERC) Advanced Grant, and is a Fellow of the American Chemical Society’s Division of Polymer Chemistry. In 2017, he was nominated as a member of the Swiss Academy of Technical Sciences "in recognition of his pioneering work in the development of nanomaterials through combination of fundamental research and practical applications as well as his contribution to the successful establishment of the Adolphe Merkle Institute".
Weder is married and has three children. | 0 | Theoretical and Fundamental Chemistry |
As she neared the end of her doctorate in 1924, Irène Curie was asked to teach the precision laboratory techniques required for radiochemical research to the young chemical engineer Frédéric Joliot, whom she would later wed. From 1928 Joliot-Curie and her husband Frédéric combined their research efforts on the study of atomic nuclei. In 1932, Joliot-Curie and her husband Frédéric had full access to Maries polonium. Experiments were done using gamma rays to identify the positron. Though their experiments identified both the positron and the neutron, they failed to interpret the significance of the results and the discoveries were later claimed by Carl David Anderson and James Chadwick respectively. These discoveries would have secured greatness indeed, as together with J. J. Thomsons discovery of the electron in 1897, they finally replaced John Dalton's model of atoms as solid spherical particles.
However, in 1933, Joliot-Curie and her husband were the first to calculate the accurate mass of the neutron. The Joliot-Curies continued trying to get their name into the scientific community; in doing so they developed a new theory from an interesting experiment they conducted. During an experiment bombarding aluminium with alpha rays, they discovered that only protons were detected. Based on the undetectable electron and positron pair, they proposed that the protons changed into neutrons and positrons. Later in October 1933, this new theory was presented to the Seventh Solvay Conference. The Solvay Conferences consisted of prominent scientists in the physics and chemistry community. Irene and her husband presented their theory and results to their fellow scientists, but they received criticism of their finding from most of the 46 scientists attending. However they were able to build on the controversial theory later on.
In 1934, the Joliot-Curies finally made the discovery that sealed their place in scientific history. Building on the work of Marie and Pierre Curie, who had isolated naturally occurring radioactive elements, the Joliot-Curies realised the alchemist's dream of turning one element into another: creating radioactive nitrogen from boron, radioactive isotopes of phosphorus from aluminium, and silicon from magnesium. Irradiating the natural stable isotope of aluminium with alpha particles (i.e. helium nuclei) resulted in an unstable isotope of phosphorus: Al + He → P + n. This phosporus isotope is not found in nature and dacays emiting a positron. This discovery is formally known as positron emission or beta decay, where a proton in the radioactive nucleus changes to a neutron and releases a positron and an electron neutrino. By then, the application of radioactive materials for use in medicine was growing and this discovery allowed radioactive materials to be created quickly, cheaply, and plentifully. The Nobel Prize for chemistry in 1935 brought with it fame and recognition from the scientific community and Joliot-Curie was awarded a professorship at the Faculty of Science.
The work that Irènes laboratory pioneered in research into radium nuclei that led a separate group of German physicists, led by Otto Hahn, Lise Meitner, and Fritz Strassman, to discover nuclear fission: the splitting of the nucleus itself, emitting vast amounts of energy. Lise Meitners now-famous calculations actually disproved Irène's results to show that nuclear fission was possible.
In 1948, using work on nuclear fission, the Joliot-Curies along with other scientists created the first French nuclear reactor. The Joliot-Curies were a part of the organization in charge of the project, the Atomic Energy Commission, Commissariat à lénergie atomique (CEA). Irène was the commissioner of the CEA and Irènes husband, Frédéric, was the director of the CEA. The reactor, Zoé (Zéro énergie Oxyde et Eau lourde) used nuclear fission to generate five kilowatts of power. This was the beginning of nuclear energy as a source of power for France.
Years of working so closely with radioactive materials finally caught up with Joliot-Curie and she was diagnosed with leukemia. She had been accidentally exposed to polonium when a sealed capsule of the element exploded on her laboratory bench in 1946. Treatment with antibiotics and a series of operations relieved her suffering temporarily but her condition continued to deteriorate. Despite this, Joliot-Curie continued to work and in 1955 drew up plans for new physics laboratories at the Orsay Faculty of Sciences, which is now a part of the Paris-Saclay University, south of Paris. | 0 | Theoretical and Fundamental Chemistry |
The development of biomass in the form of aerobic granules is being studied for its application in the removal of organic matter, nitrogen and phosphorus compounds from wastewater.
Aerobic granules in an aerobic SBR present several advantages compared to conventional activated sludge process such as:
: Stability and flexibility: the SBR system can be adapted to fluctuating conditions with the ability to withstand shock and toxic loadings
: Low energy requirements: the aerobic granular sludge process has a higher aeration efficiency due to operation at increased height, while there are neither return sludge or nitrate recycle streams nor mixing and propulsion requirements
: Reduced footprint: The increase in biomass concentration that is possible because of the high settling velocity of the aerobic sludge granules and the absence of a final settler result in a significant reduction in the required footprint.
: Good biomass retention: higher biomass concentrations inside the reactor can be achieved, and higher substrate loading rates can be treated.
: Presence of aerobic and anoxic zones inside the granules: to perform simultaneously different biological processes in the same system (Beun et al. 1999 )
: Reduced investment and operational costs: the cost of running a wastewater treatment plant working with aerobic granular sludge can be reduced by at least 20% and space requirements can be reduced by as much as 75% (de Kreuk et al., 2004).
The HYBACS process has the additional benefit of being a flow-through process, thus avoiding the complexities of SBR systems. It is also readily applied to the upgrading of existing flow-through activated sludge processes, by installing the attached growth reactors upstream of the aeration tank. Upgrading to granular activated sludge process enables the capacity of an existing wastewater treatment plant to be doubled. | 1 | Applied and Interdisciplinary Chemistry |
The use of ion beams as a particle-beam weapon is theoretically possible, but has not been demonstrated. Electron beam weapons have been tested by the U.S. Navy in the early 20th century, but the hose instability effect prevents these from being accurate at a distance of over approximately 30 inches. See particle-beam weapon for more information on this type of weapon. | 0 | Theoretical and Fundamental Chemistry |
Conditions treated with combination therapy include tuberculosis, leprosy, cancer, malaria, and HIV/AIDS. One major benefit of combination therapies is that they reduce development of drug resistance since a pathogen or tumor is less likely to have resistance to multiple drugs simultaneously. Artemisinin-based monotherapies for malaria are explicitly discouraged to avoid the problem of developing resistance to the newer treatment.
Combination therapy may seem costlier than monotherapy in the short term, but when it is used appropriately, it causes significant savings: lower treatment failure rate, lower case-fatality ratios, fewer side-effects than monotherapy, slower development of resistance, and thus less money needed for the development of new drugs. | 1 | Applied and Interdisciplinary Chemistry |
MIKE BASIN is an extension of ArcMap (ESRI) for integrated water resources management and planning. It provides a framework for managers and stakeholders to address multi-sectoral allocation and environmental issues in river basins. It is designed to investigate water sharing issues at international or interstate level, and between competing groups of water users, including the environment. MIKE BASIN is developed by DHI. As of September 2014, MIKE BASIN is no longer available for order or download from DHI. It has been replaced by the application named MIKE HYDRO Basin. | 1 | Applied and Interdisciplinary Chemistry |
The evidence that arsenic may be a beneficial nutrient at trace levels below the background to which living organisms are normally exposed has been reviewed. Some organoarsenic compounds found in nature are arsenobetaine and arsenocholine, both being found in many marine organisms. Some As-containing nucleosides (sugar derivatives) are also known. Several of these organoarsenic compounds arise via methylation processes. For example, the mold Scopulariopsis brevicaulis produces significant amounts of trimethylarsine if inorganic arsenic is present. The organic compound arsenobetaine is found in some marine foods such as fish and algae, and also in mushrooms in larger concentrations. In clean environments, the edible mushroom species Cyanoboletus pulverulentus hyperaccumulates arsenic in concentrations reaching even 1,300 mg/kg in dry weight; cacodylic acid is the major As compound. A very unusual composition of organoarsenic compounds was found in deer truffles (Elaphomyces spp.). The average person's intake is about 10–50 µg/day. Values about 1000 µg are not unusual following consumption of fish or mushrooms; however, there is little danger in eating fish since this arsenic compound is nearly non-toxic.
A topical source of arsenic are the green pigments once popular in wallpapers, e.g. Paris green. A variety of illness have been blamed on this compound, although its toxicity has been exaggerated.
Trimethylarsine, once known as Gosio's gas, is an intensely malodorous organoarsenic compound that is commonly produced by microbial action on inorganic arsenic substrates.
Arsenic (V) compounds are easily reduced to arsenic (III) and could have served as an electron acceptor on primordial Earth. Lakes that contain a substantial amount of dissolved inorganic arsenic, harbor arsenic-tolerant biota. | 1 | Applied and Interdisciplinary Chemistry |
This is defined in Title 10, Section 20.1003, of the Code of Federal Regulations of the USA the CEDE dose (HE,50) as the sum of the products of the committed dose equivalents for each of the body organs or tissues that are irradiated multiplied by the weighting factors (W) applicable to each of those organs or tissues.
"The probability of occurrence of a stochastic effect in a tissue or organ is assumed to be proportional to the equivalent dose in the tissue or organ. The constant of proportionality differs for the various tissues of the body, but in assessing health detriment the total risk is required. This is taken into account using the tissue weighting factors, W, which represent the proportion of the stochastic risk resulting from irradiation of the tissue or organ to the total risk when the whole body is irradiated uniformly and H is the equivalent dose in the tissue or organ, T, in the equation:"
Committed Effective Dose Equivalent (CEDE) refers to the dose resulting from internal radiation exposures. The CEDE is combined with the Deep-Dose Equivalent (DDE), the dose from external whole body exposures, to produce the Total Effective Dose Equivalent (TEDE), the dose resulting from internal and external radiation exposures. | 0 | Theoretical and Fundamental Chemistry |
Historically, tailings were disposed of in the most convenient manner, such as in downstream running water or down drains. Because of concerns about these sediments in the water and other issues, tailings ponds came into use. The sustainability challenge in the management of tailings and waste rock is to dispose of material, such that it is inert or, if not, stable and contained, to minimise water and energy inputs and the surface footprint of wastes and to move toward finding alternate uses. | 1 | Applied and Interdisciplinary Chemistry |
In 1993 Ernst Homburg was senior research fellow at the Sidney M. Edelstein Center of the Hebrew University of Jerusalem.
In 1998/1999 he was a fellow at the Netherlands Institute of Advanced Study, Wassenaar.
In 2002 he was a fellow at the Max-Planck-Institut für Wissenschaftsgeschichte in Berlin.
In 2014 Homburg received the HIST Award for Outstanding Achievement in the History of Chemistry, from the Division History of Chemistry ("Hist") of the American Chemical Society (ACS). | 1 | Applied and Interdisciplinary Chemistry |
Notwithstanding these inventions of the Alexandrian school, its attention does not seem to have been directed to the motion of fluids; and the first attempt to investigate this subject was made by Sextus Julius Frontinus, inspector of the public fountains at Rome in the reigns of Nerva and Trajan. In his work De aquaeductibus urbis Romae commentarius, he considers the methods which were at that time employed for ascertaining the quantity of water discharged from ajutages (tubes), and the mode of distributing the waters of an aqueduct or a fountain. He remarked that the flow of water from an orifice depends not only on the magnitude of the orifice itself, but also on the height of the water in the reservoir; and that a pipe employed to carry off a portion of water from an aqueduct should, as circumstances required, have a position more or less inclined to the original direction of the current. But as he was unacquainted with the law of the velocities of running water as depending upon the depth of the orifice, the want of precision which appears in his results is not surprising. | 1 | Applied and Interdisciplinary Chemistry |
An NMR tube is a thin glass walled tube used to contain samples in nuclear magnetic resonance spectroscopy. Typically NMR tubes come in 5 mm diameters but 10 mm and 3 mm samples are known. It is important that the tubes are uniformly thick and well-balanced to ensure that NMR tube spins at a regular rate (i.e., they do not wobble), usually about 20 Hz in the NMR spectrometer. | 0 | Theoretical and Fundamental Chemistry |
The basic properties of two-dimensional stream functions can be summarized as follows:
# The x- and y-components of the flow velocity at a given point are given by the partial derivatives of the stream function at that point.
# The value of the stream function is constant along every streamline (streamlines represent the trajectories of particles in steady flow). That is, in two dimensions each streamline is a level curve of the stream function.
# The difference between the stream function values at any two points gives the volumetric flux through the vertical surface that connects the two points. | 1 | Applied and Interdisciplinary Chemistry |
* University Faculty Scholar
* Premier's Research Excellence Award
* Marilyn Robinson Award for Excellence in Teaching
* Alumni Western, Bank of Nova Scotia, University Students' Council Award for Excellence in Undergraduate Teaching (1997–98, 2001–02)
* Canadian National Congress-International Union Pure and Applied Chemistry (CNC-IUPAC) Award
* Ontario Confederation of University Faculty Associations Award for Excellence in University Teaching
* USC Teaching Honour Roll (2001–2005)
* NRC Research Associateship (1992–1994)
* NSERC Postdoctoral Scholarship (1992) – declined to take position at NRC
* NSERC Doctoral Prize finalist (1993)
* NSERC Postgraduate Scholarships (1988–1992)
* McMaster University Centennial Scholarships for Academic Excellence (1988–1992) | 0 | Theoretical and Fundamental Chemistry |
Leslie Eleazer Orgel FRS (12 January 1927 – 27 October 2007) was a British chemist. He is known for his theories on the origin of life. | 0 | Theoretical and Fundamental Chemistry |
In geometry, a Euclidean plane isometry is an isometry of the Euclidean plane, or more informally, a way of transforming the plane that preserves geometrical properties such as length. There are four types: translations, rotations, reflections, and glide reflections (see below ).
The set of Euclidean plane isometries forms a group under composition: the Euclidean group in two dimensions. It is generated by reflections in lines, and every element of the Euclidean group is the composite of at most three distinct reflections. | 0 | Theoretical and Fundamental Chemistry |
Diprotonation of [CBH] gives the neutral carborane CBH. Pyrolysis of this nido cluster gives closo-CBH. Chromate-oxidation of [CBH] results in deboronation, giving the CBH. This carborane features two CH vertices. | 0 | Theoretical and Fundamental Chemistry |
Bioaerosol transport and distribution is not consistent around the globe. While bioaerosols may travel thousands of kilometers before deposition, their ultimate distance of travel and direction is dependent on meteorological, physical, and chemical factors. The branch of biology that studies the dispersal of these particles is called Aerobiology. One study generated an airborne bacteria/fungi map of the United States from observational measurements, resulting community profiles of these bioaerosols were connected to soil pH, mean annual precipitation, net primary productivity, and mean annual temperature, among other factors. | 0 | Theoretical and Fundamental Chemistry |
For macroscopic bodies with known volumes and numbers of atoms or molecules per unit volume, the total van der Waals force is often computed based on the "microscopic theory" as the sum over all interacting pairs. It is necessary to integrate over the total volume of the object, which makes the calculation dependent on the objects shapes. For example, the van der Waals interaction energy between spherical bodies of radii R and R and with smooth surfaces was approximated in 1937 by Hamaker (using Londons famous 1937 equation for the dispersion interaction energy between atoms/molecules as the starting point) by:
where A is the Hamaker coefficient, which is a constant (~10 − 10 J) that depends on the material properties (it can be positive or negative in sign depending on the intervening medium), and z is the center-to-center distance; i.e., the sum of R, R, and r (the distance between the surfaces): .
The van der Waals force between two spheres of constant radii (R and R are treated as parameters) is then a function of separation since the force on an object is the negative of the derivative of the potential energy function,. This yields:
In the limit of close-approach, the spheres are sufficiently large compared to the distance between them; i.e., or , so that equation (1) for the potential energy function simplifies to:
with the force:
The van der Waals forces between objects with other geometries using the Hamaker model have been published in the literature.
From the expression above, it is seen that the van der Waals force decreases with decreasing size of bodies (R). Nevertheless, the strength of inertial forces, such as gravity and drag/lift, decrease to a greater extent. Consequently, the van der Waals forces become dominant for collections of very small particles such as very fine-grained dry powders (where there are no capillary forces present) even though the force of attraction is smaller in magnitude than it is for larger particles of the same substance. Such powders are said to be cohesive, meaning they are not as easily fluidized or pneumatically conveyed as their more coarse-grained counterparts. Generally, free-flow occurs with particles greater than about 250 μm.
The van der Waals force of adhesion is also dependent on the surface topography. If there are surface asperities, or protuberances, that result in a greater total area of contact between two particles or between a particle and a wall, this increases the van der Waals force of attraction as well as the tendency for mechanical interlocking.
The microscopic theory assumes pairwise additivity. It neglects many-body interactions and retardation. A more rigorous approach accounting for these effects, called the "macroscopic theory", was developed by Lifshitz in 1956. Langbein derived a much more cumbersome "exact" expression in 1970 for spherical bodies within the framework of the Lifshitz theory while a simpler macroscopic model approximation had been made by Derjaguin as early as 1934. Expressions for the van der Waals forces for many different geometries using the Lifshitz theory have likewise been published. | 0 | Theoretical and Fundamental Chemistry |
The INHIBIT logic gate incorporates a Tb ion in a chelate complex. This two-input logic gate is the first of its kind and displays non-commutative behavior with chemical inputs and a phosphorescence output. Whenever dioxygen (input “1”) is present, the system is quenched and no phosphorescence is observed (output “0”). The second input, H, must also be present for an output “1” to be observed. This is understood from a two-input INHIBIT truth table as included in Table 2. | 0 | Theoretical and Fundamental Chemistry |
* [http://www.aps.org/units/damop/ American Physical Society - Division of Atomic, Molecular & Optical Physics]
* [https://web.archive.org/web/20090927053332/http://ampd.epsdivisions.org/ European Physical Society - Atomic, Molecular & Optical Physics Division]
* [https://www.nsf.gov/funding/pgm_summ.jsp?pims_id=13622 National Science Foundation - Atomic, Molecular and Optical Physics]
* [http://cuaweb.mit.edu/ MIT-Harvard Center for Ultracold Atoms]
*[https://qfarm.stanford.edu Stanford QFARM Initiative for Quantum Science & Enginneering]
* [https://web.archive.org/web/20190101155151/http://jila.colorado.edu/research/atomic-molecular-physics/atomic-molecular-physics JILA - Atomic and Molecular Physics]
* [http://jqi.umd.edu/ Joint Quantum Institute at University of Maryland and NIST]
*[http://www.phy.ornl.gov/ ORNL Physics Division]
*[http://web.am.qub.ac.uk/ctamop/ Queen's University Belfast - Center for Theoretical, Atomic, Molecular and Optical Physics],
*[http://physics.berkeley.edu/research/atomic-molecular-and-optical-physics University of California, Berkeley - Atomic, Molecular and Optical Physics] | 0 | Theoretical and Fundamental Chemistry |
Liquid hydrophilic chemicals complexed with solid chemicals can be used to optimize solubility of hydrophobic chemicals. | 0 | Theoretical and Fundamental Chemistry |
When a molten metal is mixed with another substance, there are two mechanisms that can cause an alloy to form, called atom exchange and the interstitial mechanism. The relative size of each element in the mix plays a primary role in determining which mechanism will occur. When the atoms are relatively similar in size, the atom exchange method usually happens, where some of the atoms composing the metallic crystals are substituted with atoms of the other constituent. This is called a substitutional alloy. Examples of substitutional alloys include bronze and brass, in which some of the copper atoms are substituted with either tin or zinc atoms respectively.
In the case of the interstitial mechanism, one atom is usually much smaller than the other and can not successfully substitute for the other type of atom in the crystals of the base metal. Instead, the smaller atoms become trapped in the interstitial sites between the atoms of the crystal matrix. This is referred to as an interstitial alloy. Steel is an example of an interstitial alloy, because the very small carbon atoms fit into interstices of the iron matrix.
Stainless steel is an example of a combination of interstitial and substitutional alloys, because the carbon atoms fit into the interstices, but some of the iron atoms are substituted by nickel and chromium atoms. | 1 | Applied and Interdisciplinary Chemistry |
Although the ancient atomists works were unavailable, scholastic thinkers still had Aristotles critiques of atomism. Although the atomism of Epicurus had fallen out of favor in the centuries of Scholasticism, the minima naturalia of Aristotelianism received extensive consideration. Speculation on minima naturalia provided philosophical background for the mechanistic philosophy of early modern thinkers such as Descartes, and for the alchemical works of Geber and Daniel Sennert, who in turn influenced the corpuscularian alchemist Robert Boyle, one of the founders of modern chemistry.
A chief theme in late Roman and Scholastic commentary on this concept was reconciling minima naturalia with the general Aristotelian principle of infinite divisibility. Commentators like John Philoponus and Thomas Aquinas reconciled these aspects of Aristotle's thought by distinguishing between mathematical and "natural" divisibility. With few exceptions, much of the curriculum in the universities of Europe was based on such Aristotelianism for most of the Middle Ages. | 1 | Applied and Interdisciplinary Chemistry |
A number of models for the nucleus have also been proposed in which nucleons occupy orbitals, much like the atomic orbitals in atomic physics theory. These wave models imagine nucleons to be either sizeless point particles in potential wells, or else probability waves as in the "optical model", frictionlessly orbiting at high speed in potential wells.
In the above models, the nucleons may occupy orbitals in pairs, due to being fermions, which allows explanation of even/odd Z and N effects well known from experiments. The exact nature and capacity of nuclear shells differs from those of electrons in atomic orbitals, primarily because the potential well in which the nucleons move (especially in larger nuclei) is quite different from the central electromagnetic potential well which binds electrons in atoms. Some resemblance to atomic orbital models may be seen in a small atomic nucleus like that of helium-4, in which the two protons and two neutrons separately occupy 1s orbitals analogous to the 1s orbital for the two electrons in the helium atom, and achieve unusual stability for the same reason. Nuclei with 5 nucleons are all extremely unstable and short-lived, yet, helium-3, with 3 nucleons, is very stable even with lack of a closed 1s orbital shell. Another nucleus with 3 nucleons, the triton hydrogen-3 is unstable and will decay into helium-3 when isolated. Weak nuclear stability with 2 nucleons {NP} in the 1s orbital is found in the deuteron hydrogen-2, with only one nucleon in each of the proton and neutron potential wells. While each nucleon is a fermion, the {NP} deuteron is a boson and thus does not follow Pauli Exclusion for close packing within shells. Lithium-6 with 6 nucleons is highly stable without a closed second 1p shell orbital. For light nuclei with total nucleon numbers 1 to 6 only those with 5 do not show some evidence of stability. Observations of beta-stability of light nuclei outside closed shells indicate that nuclear stability is much more complex than simple closure of shell orbitals with magic numbers of protons and neutrons.
For larger nuclei, the shells occupied by nucleons begin to differ significantly from electron shells, but nevertheless, present nuclear theory does predict the magic numbers of filled nuclear shells for both protons and neutrons. The closure of the stable shells predicts unusually stable configurations, analogous to the noble group of nearly-inert gases in chemistry. An example is the stability of the closed shell of 50 protons, which allows tin to have 10 stable isotopes, more than any other element. Similarly, the distance from shell-closure explains the unusual instability of isotopes which have far from stable numbers of these particles, such as the radioactive elements 43 (technetium) and 61 (promethium), each of which is preceded and followed by 17 or more stable elements.
There are however problems with the shell model when an attempt is made to account for nuclear properties well away from closed shells. This has led to complex post hoc distortions of the shape of the potential well to fit experimental data, but the question remains whether these mathematical manipulations actually correspond to the spatial deformations in real nuclei. Problems with the shell model have led some to propose realistic two-body and three-body nuclear force effects involving nucleon clusters and then build the nucleus on this basis. Three such cluster models are the 1936 Resonating Group Structure model of John Wheeler, Close-Packed Spheron Model of Linus Pauling and the 2D Ising Model of MacGregor. | 0 | Theoretical and Fundamental Chemistry |
*Coley, N. G. [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1033981/ "The collateral sciences in the work of Golding Bird (1814-1854)"], Medical History, iss.4, vol.13, October 1969.
*Hemat, R. A. S. Water, Urotext 2009 .
*Lardner, Dionysius [https://books.google.com/books?id=FzoDAAAAQAAJ&pg=PA288 Electricity, Magnetism, and Acoustics], London: Spottiswoode & Co. 1856.
*Meyer, Moritz [https://books.google.com/books?id=1ZiZ78n7_XsC&pg=PA97 Electricity in its Relations to Practical Medicine], New York: D. Appleton and Co., 1869.
*Peña, Carolyn Thomas de la The Body Electric: How Strange Machines Built the Modern American, New York and London: New York University Press, 2005 .
*Powell, George Denniston The Practice of Medical Electricity, Dublin: Fannin & Co. 1869.
*Pulvermacher, Isaac Lewis "Improvement in voltaic batteries and apparatus for medical and other purposes", , issued 1 February 1853.
*Schlesinger, Henry The Battery: How Portable Power Sparked a Technological Revolution, Washington: Smithsonian Books, 2010 . | 0 | Theoretical and Fundamental Chemistry |
Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) is a protein that in humans is encoded by the PPARGC1A gene. PPARGC1A is also known as human accelerated region 20 (HAR20). It may, therefore, have played a key role in differentiating humans from apes.
PGC-1α is the master regulator of mitochondrial biogenesis. PGC-1α is also the primary regulator of liver gluconeogenesis, inducing increased gene expression for gluconeogenesis. | 1 | Applied and Interdisciplinary Chemistry |
For particles with the mass of a proton or greater, elastic scattering is one of the main methods by which the particles interact with matter. At relativistic energies, protons, neutrons, helium ions, and HZE ions will undergo numerous elastic collisions before they are dissipated. This is a major concern with many types of ionizing radiation, including galactic cosmic rays, solar proton events, free neutrons in nuclear weapon design and nuclear reactor design, spaceship design, and the study of the Earths magnetic field. In designing an effective biological shield, proper attention must be made to the linear energy transfer of the particles as they propagate through the shield. In nuclear reactors, the neutrons mean free path is critical as it undergoes elastic scattering on its way to becoming a slow-moving thermal neutron.
Besides elastic scattering, charged particles also undergo effects from their elementary charge, which repels them away from nuclei and causes their path to be curved inside an electric field. Particles can also undergo inelastic scattering and capture due to nuclear reactions. Protons and neutrons do this more often than heavier particles. Neutrons are also capable of causing fission in an incident nucleus. Light nuclei like deuterium and lithium can combine in nuclear fusion. | 0 | Theoretical and Fundamental Chemistry |
The thrust-to-weight ratio of jet engines with similar configurations varies with scale, but is mostly a function of engine construction technology. For a given engine, the lighter the engine, the better the thrust-to-weight is, the less fuel is used to compensate for drag due to the lift needed to carry the engine weight, or to accelerate the mass of the engine.
As can be seen in the following table, rocket engines generally achieve much higher thrust-to-weight ratios than duct engines such as turbojet and turbofan engines. This is primarily because rockets almost universally use dense liquid or solid reaction mass which gives a much smaller volume and hence the pressurization system that supplies the nozzle is much smaller and lighter for the same performance. Duct engines have to deal with air which is two to three orders of magnitude less dense and this gives pressures over much larger areas, which in turn results in more engineering materials being needed to hold the engine together and for the air compressor. | 1 | Applied and Interdisciplinary Chemistry |
The bottom of the salt pan () is typically composed of clay lined pools, basalt, sand, concrete, or tile. This keeps the salt from coming into contact with the silt beneath and becoming dirty. Every few days, or on occasion daily, the harvester (French: ) pushes or pulls the salt with a long wooden rake. This must be done carefully as the depth of the brine may be as little as and the clay bottom must not be penetrated at the risk of contaminating the salt. The salt is raked toward the sides of the pan where it is then shoveled into a pile and left to dry slightly before storing. of sel gris can be harvested in one day, whereas for fleurs de sel the daily yield is only . | 0 | Theoretical and Fundamental Chemistry |
Phosphoramide arises from the reaction of phosphoryl chloride with ammonia. In moist air, it hydrolyzes to an ammonium salt:
It reacts with sodium hydroxide with loss of ammonia:
The related thiophosphoryl triamide compound was made from the reaction of thiophosphoryl chloride with ammonia. | 0 | Theoretical and Fundamental Chemistry |
Many of the drugs in the same class exert additive effect as they have a similar therapeutic mechanism of action. For example, the calcium carbonate, magnesium, and aluminium salts are all antacids with the mechanism of using the negative ion to neutralize the acid in the stomach. The antacids have no interaction between them, so they would be considered to have additive effect when taken together.
Drugs that are in the same class, but do not have the same target, may also act additively by interacting with different targets in the same pathway. For example, propofol and sevoflurane can both produce anesthetic effects. Propofol can potentiate the activity of GABA receptor and act on α, β and γ subunits, while sevoflurane enhances the response of the GABA receptor to endogenous GABA by binding to the α1-subunit. By using Dixon up-down method, a trial has shown that the effect in producing anesthetic effects between propofol and sevoflurane is additive. | 1 | Applied and Interdisciplinary Chemistry |
The salen anion forms complexes with most transition metals. These complexes are usually prepared by the reaction of Hsalen ("proligand") with metal precursors containing built-in bases, such as alkoxides, metal amides, or metal acetate. The proligand may also be treated with a metal halide, with or without an added base. Lastly, the proligand may be deprotonated by a nonnucleophilic base, such as sodium hydride, before treatment with the metal halide. For example, Jacobsen's catalyst is prepared from the salen ligand precursor with manganese acetate. | 0 | Theoretical and Fundamental Chemistry |
In the last half-decade, coastal erosion in the form of inertial cavitation has been generally accepted. Bubbles in an incoming wave are forced into cracks in the cliff being eroded. Varying pressure decompresses some vapor pockets which subsequently implode. The resulting pressure peaks can blast apart fractions of the rock. | 1 | Applied and Interdisciplinary Chemistry |
A single-stranded genome that is used in both positive-sense and negative-sense capacities is said to be ambisense. Some viruses have ambisense genomes. Bunyaviruses have three single-stranded RNA (ssRNA) fragments, some of them containing both positive-sense and negative-sense sections; arenaviruses are also ssRNA viruses with an ambisense genome, as they have three fragments that are mainly negative-sense except for part of the 5′ ends of the large and small segments of their genome. | 1 | Applied and Interdisciplinary Chemistry |
This includes further education about microbial, molecular and cell biology. Classes can include cell biology, virology, microbial and plant biology | 1 | Applied and Interdisciplinary Chemistry |
The PFA-100 (Platelet Function Assay or Platelet Function Analyser) is a platelet function analyser that aspirates blood in vitro from a blood specimen into disposable test cartridges through a microscopic aperture cut into a biologically active membrane at the end of a capillary. The membrane of the cartridges are coated with collagen and adenosine diphosphate (ADP) or collagen and epinephrine inducing a platelet plug to form which closes the aperture.
The PFA test result is dependent on platelet function, plasma von Willebrand Factor level, platelet
number, and (to some extent) the hematocrit (that is, the percent composition of red blood cells in the sample).
The PFA test is initially performed with the Collagen/Epinepherine membrane. A normal Col/Epi closure time
(<180 seconds) excludes the presence of a significant platelet function defect.
If the Col/Epi closure time is prolonged (>180 seconds), the Col/ADP test is automatically
performed. If the Col/ADP result is normal (<120 seconds), aspirin-induced platelet dysfunction is
most likely.
Prolongation of both test results (Col/Epi >180 seconds, Col/ADP >120 seconds) may indicate
the following;
* Anemia (hematocrit <0.28)
* Thrombocytopenia (platelet count < 100 x 10/L)
* A significant platelet function defect other than aspirin
Once anemia and thrombocytopenia have been excluded, further evaluation to exclude von
Willebrand disease and inherited/acquired platelet dysfunction can be made. | 1 | Applied and Interdisciplinary Chemistry |
Other variations of the Grignard reagent have been discovered to improve the chemoselectivity of the Grignard reaction, which include but are not limited to: Turbo-Grignards, organocerium reagents, and organocuprate (Gilman) reagents. | 0 | Theoretical and Fundamental Chemistry |
Pioneer factors can function passively, by acting as a bookmark for the cell to recruit other transcription factors to specific genes in condensed chromatin. This can be important for priming the cell for a rapid response as the enhancer is already bound by a pioneer transcription factor giving it a head start towards assembling the transcription preinitiation complex. Hormone responses are often quickly induced in the cell using this priming method such as with the estrogen receptor. Another form of priming is when an enhancer is simultaneously bound by activating and repressing pioneer factors. This balance can be tipped by dissociation of one of the factors. In hepatic cell differentiation the activating pioneer factor FOXA1 recruits a repressor, grg3, that prevents transcription until the repressor is down-regulated later on in the differentiation process.
<br>
In a direct role pioneer factors can bind an enhancer and recruit activation complex that will modify the chromatin directly. The change in the chromatin changes the affinity, decreasing the affinity of the pioneer factor such that it is replaced by a transcription factor that has a higher affinity. This is a mechanism for the cell to switch a gene on was observed with glucocorticoid receptor recruiting modification factors that then modify the site to bind activated estrogen receptor which was coined as a “bait and switch” mechanism. | 1 | Applied and Interdisciplinary Chemistry |
In 2009, India's Chandrayaan-1 satellite and the National Aeronautics and Space Administration (NASA) Cassini spacecraft and Deep Impact probe each detected evidence of water by evidence of hydroxyl fragments on the Moon. As reported by Richard Kerr, "A spectrometer [the Moon Mineralogy Mapper, also known as "M3"] detected an infrared absorption at a wavelength of 3.0 micrometers that only water or hydroxyl—a hydrogen and an oxygen bound together—could have created." NASA also reported in 2009 that the LCROSS probe revealed an ultraviolet emission spectrum consistent with hydroxyl presence.
On 26 October 2020, NASA reported definitive evidence of water on the sunlit surface of the Moon, in the vicinity of the crater Clavius (crater), obtained by the Stratospheric Observatory for Infrared Astronomy (SOFIA). The SOFIA Faint Object infrared Camera for the SOFIA Telescope (FORCAST) detected emission bands at a wavelength of 6.1 micrometers that are present in water but not in hydroxyl. The abundance of water on the Moon's surface was inferred to be equivalent to the contents of a 12-ounce bottle of water per cubic meter of lunar soil.
The Chang'e 5 probe, which landed on the Moon on 1 December 2020, carried a mineralogical spectrometer that could measure infrared reflectance spectra of lunar rock and regolith. The reflectance spectrum of a rock sample at a wavelength of 2.85 micrometers indicated localized water/hydroxyl concentrations as high as 180 parts per million. | 0 | Theoretical and Fundamental Chemistry |
As a charged particle moves through a gravitational force or centrifugation, an electric potential is induced. While the particle moves, ions in the electric double layer lag behind creating a net dipole moment behind due to liquid flow. The sum of all dipoles on the particle is what causes sedimentation potential. Sedimentation potential has the opposite effect compared to electrophoresis where an electric field is applied to the system. Ionic conductivity is often referred to when dealing with sedimentation potential.
The following relation provides a measure of the sedimentation potential due to the settling of charged spheres. First discovered by Smoluchowski in 1903 and 1921. This relationship only holds true for non-overlapping electric double layers and for dilute suspensions. In 1954, Booth proved that this idea held true for Pyrex glass powder settling in a KCl solution. From this relation, the sedimentation potential, E, is independent of the particle radius and that E → 0, Φ → 0 (a single particle).
Smoluchowski's sedimentation potential is defined where ε is the permitivity of free space, D the dimensionless dielectric constant, ξ the zeta potential, g the acceleration due to gravity, Φ the particle volume fraction, ρ the particle density, ρ the medium density, λ the specific volume conductivity, and η the viscosity.
Smoluchowski developed the equation under five assumptions:
# Particles are spherical, nonconducting, and monodispersed.
# Laminar flow around the particles occurs (Reynolds number <1).
# Interparticle interactions are negligible.
# Surface conduction is negligible.
# The double-layer thickness 1/κ is small compared to the particle radius a (κa>>1).
Where D is the diffusion coefficient of the ith solute species, and n is the number concentration of electrolyte solution.
Ohshimas model was developed in 1984 and was originally used to analyze the sedimentation velocity of a single charged sphere and the sedimentation potential of a dilute suspension. The model provided below holds true for dilute suspensions of low zeta potential, i.e. e'ζ/κT ≤2 | 0 | Theoretical and Fundamental Chemistry |
The cytoplasmic polyhedrosis viruses (CPVs) form the genus Cypovirus of the family Reoviridae. CPVs are classified into 14 species based on the electrophoretic migration profiles of their genome segments. Cypovirus has only a single capsid shell, which is similar to the orthoreovirus inner core. CPV exhibits striking capsid stability and is fully capable of endogenous RNA transcription and processing. The overall folds of CPV proteins are similar to those of other reoviruses. However, CPV proteins have insertional domains and unique structures that contribute to their extensive intermolecular interactions. The CPV turret protein contains two methylase domains with a highly conserved helix-pair/β-sheet/helix-pair sandwich fold but lacks the β-barrel flap present in orthoreovirus λ2. The stacking of turret protein functional domains and the presence of constrictions and A spikes along the mRNA release pathway indicate a mechanism that uses pores and channels to regulate the highly coordinated steps of RNA transcription, processing, and release. | 1 | Applied and Interdisciplinary Chemistry |
Sodium hydroxide can form several hydrates , which result in a complex solubility diagram that was described in detail by Spencer Umfreville Pickering in 1893. The known hydrates and the approximate ranges of temperature and concentration (mass percent of NaOH) of their saturated water solutions are:
* Heptahydrate, : from −28 °C (18.8%) to −24 °C (22.2%).
* Pentahydrate, : from −24 °C (22.2%) to −17.7 °C (24.8%).
* Tetrahydrate, , α form: from −17.7 °C (24.8%) to 5.4 °C (32.5%).
* Tetrahydrate, , β form: metastable.
* Trihemihydrate, : from 5.4 °C (32.5%) to 15.38 °C (38.8%) and then to 5.0 °C (45.7%).
* Trihydrate, : metastable.
* Dihydrate, : from 5.0 °C (45.7%) to 12.3 °C (51%).
* Monohydrate, : from 12.3 °C (51%) to 65.10 °C (69%) then to 62.63 °C (73.1%).
Early reports refer to hydrates with n = 0.5 or n = 2/3, but later careful investigations failed to confirm their existence.
The only hydrates with stable melting points are (65.10 °C) and (15.38 °C). The other hydrates, except the metastable ones and (β) can be crystallized from solutions of the proper composition, as listed above. However, solutions of NaOH can be easily supercooled by many degrees, which allows the formation of hydrates (including the metastable ones) from solutions with different concentrations.
For example, when a solution of NaOH and water with 1:2 mole ratio (52.6% NaOH by mass) is cooled, the monohydrate normally starts to crystallize (at about 22 °C) before the dihydrate. However, the solution can easily be supercooled down to −15 °C, at which point it may quickly crystallize as the dihydrate. When heated, the solid dihydrate might melt directly into a solution at 13.35 °C; however, once the temperature exceeds 12.58 °C it often decomposes into solid monohydrate and a liquid solution. Even the n = 3.5 hydrate is difficult to crystallize, because the solution supercools so much that other hydrates become more stable.
A hot water solution containing 73.1% (mass) of NaOH is a eutectic that solidifies at about 62.63 °C as an intimate mix of anhydrous and monohydrate crystals.
A second stable eutectic composition is 45.4% (mass) of NaOH, that solidifies at about 4.9 °C into a mixture of crystals of the dihydrate and of the 3.5-hydrate.
The third stable eutectic has 18.4% (mass) of NaOH. It solidifies at about −28.7 °C as a mixture of water ice and the heptahydrate .
When solutions with less than 18.4% NaOH are cooled, water ice crystallizes first, leaving the NaOH in solution.
The α form of the tetrahydrate has density 1.33 g/cm. It melts congruously at 7.55 °C into a liquid with 35.7% NaOH and density 1.392 g/cm, and therefore floats on it like ice on water. However, at about 4.9 °C it may instead melt incongruously into a mixture of solid and a liquid solution.
The β form of the tetrahydrate is metastable, and often transforms spontaneously to the α form when cooled below −20 °C. Once initiated, the exothermic transformation is complete in a few minutes, with a 6.5% increase in volume of the solid. The β form can be crystallized from supercooled solutions at −26 °C, and melts partially at −1.83 °C.
The "sodium hydroxide" of commerce is often the monohydrate (density 1.829 g/cm). Physical data in technical literature may refer to this form, rather than the anhydrous compound. | 0 | Theoretical and Fundamental Chemistry |
Proteins, unlike nucleic acids, can have varying charges and complex shapes, therefore they may not migrate into the polyacrylamide gel at similar rates, or all when placing a negative to positive EMF on the sample. Proteins, therefore, are usually denatured in the presence of a detergent such as sodium dodecyl sulfate (SDS) that coats the proteins with a negative charge. Generally, the amount of SDS bound is relative to the size of the protein (usually 1.4g SDS per gram of protein), so that the resulting denatured proteins have an overall negative charge, and all the proteins have a similar charge-to-mass ratio. Since denatured proteins act like long rods instead of having a complex tertiary shape, the rate at which the resulting SDS coated proteins migrate in the gel is relative only to their size and not their charge or shape.
Proteins are usually analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), by native gel electrophoresis, by preparative native gel electrophoresis (QPNC-PAGE), or by 2-D electrophoresis.
Characterization through ligand interaction may be performed by electroblotting or by affinity electrophoresis in agarose or by capillary electrophoresis as for estimation of binding constants and determination of structural features like glycan content through lectin binding. | 1 | Applied and Interdisciplinary Chemistry |
Stokes, transitional and Newtonian settling describe the behaviour of a single spherical particle in an infinite fluid, known as free settling. However this model has limitations in practical application. Alternate considerations, such as the interaction of particles in the fluid, or the interaction of the particles with the container walls can modify the settling behaviour. Settling that has these forces in appreciable magnitude is known as hindered settling. Subsequently, semi-analytic or empirical solutions may be used to perform meaningful hindered settling calculations. | 0 | Theoretical and Fundamental Chemistry |
F decays predominantly by β emission, with a half-life of 109.8 min. It is made by proton bombardment of O in a cyclotron or linear particle accelerator. It is an important isotope in the radiopharmaceutical industry. For example, it is used to make labeled fluorodeoxyglucose (FDG) for application in PET scans. | 0 | Theoretical and Fundamental Chemistry |
The cAMP response element CREB is closely related to the cell decision to proliferate or not. Cells that are forced to overexpress AKT increase the amount of CREB and proliferation compared to wild type cells. These cells also express less glial and neural cell markers such as GFAP or β-tubulin. This is because CREB is a transcription factor that influences the transcription of cyclin A which promotes proliferation. For example, adult hippocampal neural progenitor cells need abeyance as stem cells to differentiate later. This is regulated by Shh. Shh works through a slow protein synthesis dependence, which stimulates other cascades that work synergistically with the PI3K/AKT pathway to induce proliferation. Then, the other pathway can be turned off and the effects of the PI3K/AKT pathway become insufficient in stopping differentiation. The specifics of this pathway are unknown. | 1 | Applied and Interdisciplinary Chemistry |
A nickel-catalyzed 1,n arylboration was developed in 2019 by Yin and coworkers and remains the only example of a chain-walking arylboration. This was accomplished via a nitrogen-based ligand and a three-component coupling. The general scheme plus proposed mechanism is shown. | 0 | Theoretical and Fundamental Chemistry |
Some oxidative additions proceed analogously to the well known bimolecular nucleophilic substitution reactions in organic chemistry. Nucleophilic attack by the metal center at the less electronegative atom in the substrate leads to cleavage of the R–X bond, to form an [M–R] species. This step is followed by rapid coordination of the anion to the cationic metal center. For example, reaction of a square planar complex with methyl iodide:
This mechanism is often assumed in the addition of polar and electrophilic substrates, such as alkyl halides and halogens. | 0 | Theoretical and Fundamental Chemistry |
Electrical implants are being used to relieve pain from rheumatoid arthritis. The electric implant is embedded in the neck of patients with rheumatoid arthritics, the implant sends electrical signals to electrodes in the vagus nerve. The application of this device is being tested an alternative to medicating people with rheumatoid arthritis for their lifetime. | 1 | Applied and Interdisciplinary Chemistry |
Shock hardening is a process used to strengthen metals and alloys, wherein a shock wave produces atomic-scale defects in the material's crystalline structure. As in cold work, these defects interfere with the normal processes by which metallic materials yield (plasticity), making materials stiffer, but more brittle. When compared to traditional cold work, such an extremely rapid process results in a different class of defect, producing a much harder material for a given change in shape. If the shock wave applies too great a force for too long, however, the rarefaction front that follows it can form voids in the material due to hydrostatic tension, weakening the material and often causing it to spall. Since voids nucleate at large defects, such as oxide inclusions and grain boundaries, high-purity samples with a large grain size (especially single crystals) are able to withstand greater shock without spalling, and can therefore be made much harder.
Shock hardening has been observed in many contexts:
Explosive forging uses the detonation of a high explosive charge to create a shockwave. This effect is used to harden rail track cast components and, coupled with the Misnay-Schardin effect, in the operation of explosively forged penetrators. Greater hardening can be achieved by using a lower quantity of an explosive with greater brisance, so that the force applied is greater but the material spends less time in hydrostatic tension.
Laser shock, similar to inertial confinement fusion, uses the ablation plume caused by a laser pulse to apply force to the laser's target. The rebound from the expelled matter can create very high pressures, and the pulse length of lasers is often quite short, meaning that good hardening can be achieved with little risk of spallation. Surface effects can also be achieved by laser treatment, including amorphization.
Light-gas guns have been used to study shock hardening. Although too labor-intensive for widespread industrial application, they do provide a versatile research testbed. They allow precise control of both magnitude and profile of the shock wave through adjustments to the projectile's muzzle velocity and density profile, respectively. Studies of various projectile types have been crucial in overturning a prior theory that spallation occurs at a threshold of pressure, independent of time. Instead, experiments show longer-lasting shocks of a given magnitude produce more material damage. | 1 | Applied and Interdisciplinary Chemistry |
Trimethylsilyl iodide is used to introduce the trimethylsilyl group onto alcohols (ROH):
:R-OH + TMSI → R-OTMS + HI
This type of reaction may be useful for gas chromatography analysis; the resultant silyl ether is more volatile than the underivatized original materials. However, for the preparation of bulk trimethylsilylated material, trimethylsilyl chloride may be preferred due to its lower cost.
TMSI reacts with alkyl ethers (ROR′), forming silyl ethers (ROSiMe) and iodoalkanes (RI) that can be hydrolyzed to alcohols (ROH).
Trimethylsilyl iodide is also used for the removing of the Boc protecting group, especially where other deprotection methods are too harsh for the substrate. | 0 | Theoretical and Fundamental Chemistry |
Protection quantities are calculated models, and are used as "limiting quantities" to specify exposure limits to ensure, in the words of ICRP, "that the occurrence of stochastic health effects is kept below unacceptable levels and that tissue reactions are avoided". These quantities cannot be measured in practice but their values are derived using models of external dose to internal organs of the human body, using anthropomorphic phantoms. These are 3D computational models of the body which take into account a number of complex effects such as body self-shielding and internal scattering of radiation. The calculation starts with organ absorbed dose, and then applies radiation and tissue weighting factors.
As protection quantities cannot practically be measured, operational quantities must be used to relate them to practical radiation instrument and dosimeter responses. | 0 | Theoretical and Fundamental Chemistry |
Vitamin A receptor, Stimulated by retinoic acid 6 or STRA6 protein was originally discovered as a transmembrane cell-surface receptor for retinol-binding protein. STRA6 is unique as it functions both as a membrane transporter and a cell surface receptor, particularly as a cytokine receptor. In fact, STRA6 may be the first of a whole new class of proteins that might be known as "cytokine signaling transporters." STRA6 is primarily known as the receptor for retinol binding protein and for its relevance in the transport of retinol to specific sites such as the eye (Vitamin A). It does this through the removal of retinol (ROH) from the holo-Retinol Binding Protein (RBP) and transports it into the cell to be metabolized into retinoids and/or kept as a retinylester. As a receptor, after holo-RBP is bound, STRA6 activates the JAK/STAT pathway, resulting in the activation of transcription factor, STAT5. These two functions—retinol transporter and cytokine receptor—while using different pathways, are processes that depend on each other. | 1 | Applied and Interdisciplinary Chemistry |
Although Berkeley began offering chemistry courses in 1869, the College was not officially established until 1872, awarding its first Ph.D. in 1885 to John Maxson Stillman, who later founded the chemistry department at Stanford University. A division of chemical engineering was formed in 1946, becoming a department in 1957. The department of chemical engineering changed its name to chemical and biomolecular engineering in 2010 to reflect the widening research interests of its faculty.
Faculty and researchers at the College and affiliated with Lawrence Berkeley National Laboratory are responsible for the discovery of sixteen elements, including berkelium, californium, and seaborgium, named after Nobel laureate, department chair, and alumnus Glenn Seaborg. | 1 | Applied and Interdisciplinary Chemistry |
Non-essential trace elements include silver (Ag), cadmium (Cd), mercury (Hg), and lead (Pb). They have no known biological function in mammals, with toxic effects even at low concentration.
The structural components of cells and tissues that are required in the diet in gram quantities daily are known as bulk elements. | 0 | Theoretical and Fundamental Chemistry |
Phosphodiesterases (PDEs) are a superfamily of enzymes. This superfamily is further classified into 11 families, PDE1 - PDE11, on the basis of regulatory properties, amino acid sequences, substrate specificities, pharmacological properties and tissue distribution. Their function is to degrade intracellular second messengers such as cyclic adenine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) which leads to several biological processes like effect on intracellular calcium level by the Ca pathway.
Phosphodiesterase 5 (PDE5) is widely expressed in several tissues in the body for example brain, lung, kidney, urinary bladder, smooth muscle and platelets. It is possible to prevent cGMP hydrolysis by inhibiting PDE5 and therefore treat diseases associated with low cGMP levels, because of this, PDE5 is an ideal target for the development of inhibitors. The therapeutic effects of PDE5 inhibition have been demonstrated in several cardiovascular conditions, chronic kidney disease and diabetes mellitus.
The major PDE5 inhibitors (a subset of the phosphodiesterase inhibitors) are sildenafil, tadalafil, vardenafil, and avanafil, and although all share the same mechanism of action each has unique pharmacokinetic and pharmacodynamic properties which dictate their suitability in various conditions and their side effect profile. | 1 | Applied and Interdisciplinary Chemistry |
Previous studies have shown that progesterone supports the normal development of neurons in the brain, and that the hormone has a protective effect on damaged brain tissue. It has been observed in animal models that females have reduced susceptibility to traumatic brain injury and this protective effect has been hypothesized to be caused by increased circulating levels of estrogen and progesterone in females. | 0 | Theoretical and Fundamental Chemistry |
In benzene the two cyclohexatriene Kekulé structures, first proposed by Kekulé, are taken together as contributing structures to represent the total structure. In the hybrid structure on the right, the dashed hexagon replaces three double bonds, and represents six electrons in a set of three molecular orbitals of π symmetry, with a nodal plane in the plane of the molecule.
In furan a lone pair of the oxygen atom interacts with the π orbitals of the carbon atoms. The curved arrows depict the permutation of delocalized π electrons, which results in different contributors. | 0 | Theoretical and Fundamental Chemistry |
Wide band gap semiconductors like tin oxide generally possess a high chemical stability and mobility, are cheap to fabricate and have a suitable band alignment, making these semiconductors often used in various electronics as thin film transistors, anodes in lithium ion batteries and as electron transport layer in solar cells. The large band gap of () and large binding energy () make it useful in ultraviolet based devices.
But a fundamental problem arises with its dipole forbidden band structure in bulk form: the transition from the valence to the conduction band is dipole forbidden since both types of states exist with even parity with the effect that band edge emission of is forbidden in nature. This can be offset by employing its reduced dimensional structure, partially destroying the crystal symmetry, turning the forbidden dipole transition into allowed ones. Observing optical transitions in at room temperature, however, is challenging due to the light absorbing efficiency in the UV region of the reduced structures being very weak and background scattering of electrons with lower energies. Using electroreflectance the optical transitions of thin films can be recovered: by placing a thin film in an electric field, the critical points of the optical transition will be enhanced while, due to a change in reflectivity, low energy background scattering is reduced. | 0 | Theoretical and Fundamental Chemistry |
This silicon α-effect was first observed in the late 1960s by researchers at Bayer AG as an increase in reactivity at the silicon atom for hydrolysis and was used for cross-linking of α-silane-terminated prepolymers. For a long time after that, people attributed this reactivity as silicon α-effect. However, the real mechanism beneath it had been debated for many years after this discovery. Generally, this effect has been rationalized as an intramolecular donor-acceptor interaction between the lone pair of the organofunctional group (such as NR, OC(O)R, N(H)COOMe) and the silicon atom. However, this hypothesis has been proved incorrect by Mitzel and coworkers and more experiments are needed to interpret this effect. | 0 | Theoretical and Fundamental Chemistry |
The selection rule for rotational transitions, derived from the symmetries of the rotational wave functions in a rigid rotor, is ΔJ = ±1, where J is a rotational quantum number. | 0 | Theoretical and Fundamental Chemistry |
Lecoq de Boisbaudran experimented with the precipitation of rare earth compounds from water solution using potassium sulfate to induce precipitation. He then measured the spectra of solutions in which the liquid served as a positive pole. Lecoq de Boisbaudran noted a spectral band in the yellow-green portion of the spectrum, indicative of a new element. In 1886 he succeeded in isolating a purified sample of the source of the new spectral band. He named the element dysprosium, meaning "difficult to obtain" in the Greek language. | 1 | Applied and Interdisciplinary Chemistry |
When a system contains two or more components whose concentration vary from point to point, there is a natural tendency for mass to be transferred, minimizing any concentration difference within the system. Mass transfer in a system is governed by Ficks first law: Diffusion flux from higher concentration to lower concentration is proportional to the gradient of the concentration of the substance and the diffusivity of the substance in the medium.' Mass transfer can take place due to different driving forces. Some of them are:
* Mass can be transferred by the action of a pressure gradient (pressure diffusion)
* Forced diffusion occurs because of the action of some external force
* Diffusion can be caused by temperature gradients (thermal diffusion)
* Diffusion can be caused by differences in chemical potential
This can be compared to Fick's law of diffusion, for a species A in a binary mixture consisting of A and B:
where D is the diffusivity constant. | 1 | Applied and Interdisciplinary Chemistry |
Atraric acid and N-butylbenzenesulfonamide are natural compounds with antiandrogen properties which have been purified from the bark of the African tree Pygeum africanum, see figures 9 and 10. In vitro assays have shown them both to be selective AR agonists and that they inhibit proliferation of several prostate cancer cell lines. Atraric acid also hinders extracellular matrix invasion and both compounds are able to prevent androgen-induced nuclear translocation of the AR. More potent derivatives are currently being synthesized in hope of improving the pharmacological profile of these two compounds. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, a template reaction is any of a class of ligand-based reactions that occur between two or more adjacent coordination sites on a metal center. In the absence of the metal ion, the same organic reactants produce different products. The term is mainly used in coordination chemistry. The template effects emphasizes the pre-organization provided by the coordination sphere, although the coordination modifies the electronic properties (acidity, electrophilicity, etc.) of ligands.
An early example is the dialkylation of a nickel dithiolate:
The corresponding alkylation in the absence of a metal ion would yield polymers. Crown ethers arise from dialkylations that are templated by alkali metals. Other template reactions include the Mannich and Schiff base condensations. The condensation of formaldehyde, ammonia, and tris(ethylenediamine)cobalt(III) to give a clathrochelate complex is one example.
The phosphorus analogue of an aza crown can be prepared by a template reaction. Where it is not possible to isolate the phosphine itself. | 0 | Theoretical and Fundamental Chemistry |
Schellman loops (also called Schellman motifs or paperclips) are commonly occurring structural features of proteins and polypeptides. Each has six amino acid residues (labelled residues i to i+5) with two specific inter-mainchain hydrogen bonds (as in lower figure, i) and a characteristic main chain dihedral angle conformation. The CO group of residue i is hydrogen-bonded to the NH of residue i+5 (colored orange in upper figure), and the CO group of residue i+1 is hydrogen-bonded to the NH of residue i+4 (beta turn, colored purple). Residues i+1, i+2, and i+3 have negative φ (phi) angle values and the phi value of residue i+4 is positive. Schellman loops incorporate a three amino acid residue RL nest (protein structural motif), in which three mainchain NH groups (from Schellman loop residues i+3 to i+5) form a concavity for hydrogen bonding to carbonyl oxygens. About 2.5% of amino acids in proteins belong to Schellman loops. Two websites are available for examining small motifs in proteins, Motivated Proteins: [http://motif.gla.ac.uk/motif/index.html]; or PDBeMotif: [http://www.ebi.ac.uk/pdbe-site/pdbemotif/].
The majority of Schellman loops (82%) occur at the C-terminus of an alpha-helix such that residues i, i+1, i+2 and i+3 are part of the helix. Over a quarter of helices (28%) have a C-terminal Schellman loop.
Occasional Schellman loops occur with seven instead of six residues. In these, the CO group of residue i is hydrogen-bonded to the NH of residue i+6, and the CO group of residue i+1 is hydrogen-bonded to the NH of residue i+5. Rare “left-handed” six-residue Schellman loops occur; these have the same hydrogen bonds, but residues i+1, i+2, and i+3 have positive φ values while the φ value of residue i+4 is negative; the nest is of the LR, rather than the RL, kind.
Amino acid propensities for the residues of the common type of Schellman loop have been described. Residue i+4 is the one most-highly conserved; it has positive φ values; 70% of amino acids are glycine and none are proline.
Consideration of the hydrogen bonding in the nests of Schellman loops bound to mainchain oxygens reveals two main types of arrangement: 1,3-bridged or not. In one (lower figure, ii) the first and third nest NH groups are bridged by an oxygen atom. In the other (lower figure, iv) the first NH group is hydrogen bonded to the CO group of an amino acid four residues behind in the sequence, and none of the nest NH groups are bridged. It seems that Schellman loops are less homogeneous than might have been expected.
The original Schellman criteria result in the inclusion of features not now regarded as Schellman loops. A newer set of criteria is given in the first paragraph. | 0 | Theoretical and Fundamental Chemistry |
When a system is at equilibrium under a given set of conditions, it is said to be in a definite thermodynamic state. The state of the system can be described by a number of state quantities that do not depend on the process by which the system arrived at its state. They are called intensive variables or extensive variables according to how they change when the size of the system changes. The properties of the system can be described by an equation of state which specifies the relationship between these variables. State may be thought of as the instantaneous quantitative description of a system with a set number of variables held constant.
A thermodynamic process may be defined as the energetic evolution of a thermodynamic system proceeding from an initial state to a final state. It can be described by process quantities. Typically, each thermodynamic process is distinguished from other processes in energetic character according to what parameters, such as temperature, pressure, or volume, etc., are held fixed; Furthermore, it is useful to group these processes into pairs, in which each variable held constant is one member of a conjugate pair.
Several commonly studied thermodynamic processes are:
* Adiabatic process: occurs without loss or gain of energy by heat
* Isenthalpic process: occurs at a constant enthalpy
* Isentropic process: a reversible adiabatic process, occurs at a constant entropy
* Isobaric process: occurs at constant pressure
* Isochoric process: occurs at constant volume (also called isometric/isovolumetric)
* Isothermal process: occurs at a constant temperature
* Steady state process: occurs without a change in the internal energy | 0 | Theoretical and Fundamental Chemistry |
High performance affinity chromatography (HPAC) works by passing a sample solution through a column packed with a stationary phase that contains an immobilized biologically active ligand. The ligand is in fact a substrate that has a specific binding affinity for the target molecule in the sample solution. The target molecule binds to the ligand, while the other molecules in the sample solution pass through the column, having little or no retention. The target molecule is then eluted from the column using a suitable elution buffer.
This chromatographic process relies on the capability of the bonded active substances to form stable, specific, and reversible complexes thanks to their biological recognition of certain specific sample components. The formation of these complexes involves the participation of common molecular forces such as the Van der Waals interaction, electrostatic interaction, dipole-dipole interaction, hydrophobic interaction, and the hydrogen bond. An efficient, biospecific bond is formed by a simultaneous and concerted action of several of these forces in the complementary binding sites. | 0 | Theoretical and Fundamental Chemistry |
SiGe thermocouples in an RTG convert heat directly into electricity. Thermoelectric power generation requires a constantly maintained temperature difference among the junctions of the two dissimilar metals (i.e. Si and Ge) to produce a low power closed circuit electric current without extra circuitry or external power sources.
A large array of SiGe thermocouples/unicouples form a thermopile that was incorporated into the design of radioisotope thermoelectric generators (RTGs) used in the missions Voyager, Galileo, Ulysses, Cassini, and New Horizons. On these spacecraft, Pu-238 dioxide fuel undergoes natural decay. The SiGe thermocouples/unicouples convert this heat to hundreds of Watts of electrical power. | 0 | Theoretical and Fundamental Chemistry |
The Schikorr reaction can occur in the process of anaerobic corrosion of iron and carbon steel in various conditions.
Anaerobic corrosion of metallic iron to give iron(II) hydroxide and hydrogen:
:3 (Fe + 2 HO → Fe(OH) + H)
followed by the Schikorr reaction:
:3 Fe(OH) → FeO + 2 HO + H
give the following global reaction:
:3 Fe + 6 HO → FeO + 2 HO + 4 H
:3 Fe + 4 HO → FeO + 4 H
At low temperature, the anaerobic corrosion of iron can give rise to the formation of "green rust" (fougerite) an unstable layered double hydroxide (LDH). In function of the geochemical conditions prevailing in the environment of the corroding steel, iron(II) hydroxide and green rust can progressively transform in iron(II,III) oxide, or if bicarbonate ions are present in solution, they can also evolve towards more stable carbonate phases such as iron carbonate (FeCO), or iron(II) hydroxycarbonate (Fe(OH)(CO), chukanovite) isomorphic to copper(II) hydroxycarbonate (Cu(OH)(CO), malachite) in the copper system. | 1 | Applied and Interdisciplinary Chemistry |
Xe isotopes are also promising in tracing mantle dynamics in Earths evolution. The first explicit recognition of non-atmospheric Xe in terrestrial samples came from the analysis of CO-well gas in New Mexico, displaying an excess of I-derived or primitive source Xe and high content in Xe due to the decay of U. At present, the excess of Xe and Xe has been widely observed in mid-ocean ridge basalt (MORBs) and Oceanic island basalt (OIBs). Because Xe receives more fissiogenic contribution than other heavy Xe isotopes, Xe (decay of I) and Xe are usually normalized to Xe when discussing Xe isotope trends of different mantle sources. MORBs Xe/Xe and Xe/Xe ratios lie on a trend from atmospheric ratios to higher values and seemingly contaminated by the air. Oceanic island basalt (OIBs) data lies lower than those in MORBs, implying different Xe sources for OIBs and MORBs.
The deviations in Xe/Xe ratio between air and MORBs show that mantle degassing occurred before I was extinct, otherwise Xe/Xe in the air would be the same as in the mantle. The differences in the Xe/Xe ratio between MORBs and OIBs may indicate that the mantle reservoirs are still not thoroughly mixed. The chemical differences between OIBs and MORBs still await discovery.
To obtain mantle Xe isotope ratios, it is necessary to remove contamination by atmospheric Xe, which could start before 2.5 billion years ago. Theoretically, the many non-radiogenic isotopic ratios (Xe/Xe, Xe/Xe, and Xe/Xe) can be used to accurately correct for atmospheric contamination if slight differences between air and mantle can be precisely measured. Still, we cannot reach such precision with current techniques. | 0 | Theoretical and Fundamental Chemistry |
Methylotrophic yeast metabolism differs from bacteria primarily on the basis of the enzymes used and the carbon assimilation pathway. Unlike bacteria which use bacterial MDH, methylotrophic yeasts oxidize methanol in their peroxisomes with a non-specific alcohol oxidase. This produces formaldehyde as well as hydrogen peroxide. Compartmentalization of this reaction in peroxisomes likely sequesters the hydrogen peroxide produced. Catalase is produced in the peroxisomes to deal with this harmful by-product. | 0 | Theoretical and Fundamental Chemistry |
Two modes can be used for this measurement. One is the isochromat mode, which scans the incident electron energy and keeps the detected photon energy constant. The other is the tunable photon energy mode, or spectrograph mode, which keeps the incident electron energy constant and measures the distribution of the detected photon energy. The latter can also measure the resonant inverse photoemission spectroscopy. | 0 | Theoretical and Fundamental Chemistry |
A rezas crystallization depends on the time it takes for layers of its chains to fold and orient themselves in the same direction. This time increases with a molecules weight and branching. The table below shows that the growth rate is higher for Sclair 14B.1 than Sclair 2907 (20%), where 2907 is less highly branched than 14B.1. Here Gc is the crystal growth rate, or how quickly it orders itself depending on the layers, and t is the time it takes to order. | 0 | Theoretical and Fundamental Chemistry |
Hepatitis B infection can be successfully controlled through the use of a recombinant subunit hepatitis B vaccine, which contains a form of the hepatitis B virus surface antigen that is produced in yeast cells. The development of the recombinant subunit vaccine was an important and necessary development because hepatitis B virus, unlike other common viruses such as polio virus, cannot be grown in vitro. | 1 | Applied and Interdisciplinary Chemistry |
IUPAC uses the prefix "isocyano" for the systematic nomenclature of isocyanides: isocyanomethane, isocyanoethane, isocyanopropane, etc.
The sometimes used old term "carbylamine" conflicts with systematic nomenclature. An amine always has three single bonds, whereas an isocyanide has only one single and one multiple bond.
The isocyanamide functional group consists of a amino group attached to an isocyano moiety.
for nomenclature as suffix of isonitrile or prefix of isocyano is used depending upon priority table. | 0 | Theoretical and Fundamental Chemistry |
Some manufacturers primarily produce left-hand drive vehicles, due to the larger or nearer market for such vehicles. For such models supplied to left-hand traffic markets, in the right-hand drive configuration, the manufacturer may reuse the same dashboard configuration as is used in the left-hand drive models, with the steering column and pedals moved to the right-hand side. Oft-used controls (such as audio volume and climate controls) that were placed near the left-hand driver for ease of access, are now situated on the far side of the center console for the right-hand driver. This may make them more difficult to reach quickly or without looking away from the road ahead.
In some cases, the manufacturer's dashboard design incorporates blanks and modular components, which permits the controls and underlying electronics to be rearranged to suit the right-hand drive model. This may be done in the factory, after import, or as an after-market modification. | 0 | Theoretical and Fundamental Chemistry |
Specialized proteins can unzip small segments of the DNA molecule when it is replicated or transcribed into RNA. But work published in 2015 illustrates how DNA opens on its own.
Simply twisting DNA can expose internal bases to the outside, without the aid of any proteins. Also, transcription itself contorts DNA in living human cells, tightening some parts of the coil and loosening it in others. That stress triggers changes in shape, most notably opening up the helix to be read. Unfortunately, these interactions are very difficult to study because biological molecules morph shapes so easily. In 2008 it was noted that transcription twists DNA, leaving a trail of undercoiled (or negatively supercoiled) DNA in its wake. Moreover, they discovered that the DNA sequence itself affects how the molecule responds to supercoiling.
For example, the researchers identified a specific sequence of DNA that regulates transcription speed; as the amount of supercoil rises and falls, it slows or speeds the pace at which molecular machinery reads DNA. It is hypothesized that these structural changes might trigger stress elsewhere along its length, which in turn might provide trigger points for replication or gene expression. This implies that it is a very dynamic process in which both DNA and proteins each influences how the other acts and reacts. | 1 | Applied and Interdisciplinary Chemistry |
The Chesapeake Bay watershed has been heavily impacted by natural forces such as erosion, tides, and a history of hurricanes and other storms. Along with environmental factors, the bay has been negatively impacted by humans since being settled in the 17th century, bringing with them problems like pollution, construction, and destruction of the environment. All of these circumstances have made it increasingly difficult for the MMAP to identify potential underwater archaeological sites. As sea levels rise and historically significant areas are sunk and covered in sediment, the MMAP relies on various pieces of equipment to locate these man-made anomalies but also ensure that the material being examined is kept intact. Using marine magnetometers (detects iron/absent space), side-scan sonar,(detects objects on sea floor), along with precise global positioning systems, Langley and the MMAP have been much more successful in locating submerged archaeological sites. After locating the site, Langley and her team have a strict process in order to preserve the site and its contents, allowing more accurate and thorough research to be conducted. The remains of nearly every site have been submerged in saltwater for sometimes centuries, the integrity of shipwrecks and other materials are fragile and careful precaution must be used when working with them. Taking photos and videos, creating maps, and constructing models are all a part of the process of preserving remains. Susan Langley notes herself, “If you have only ten percent of a ship’s hull, you can reconstruct the ship. Construction techniques can tell us about the people who built the vessels, artifacts can tell us about the people who profited from the ship’s trade, and eco-facts—evidence of insect infestation and organic remains, such as seeds, that are preserved in anaerobic, muddy environments—can tell us about the climate and season when a ship sank." Still, the MMAP makes it a point to publish their data and information once a site is officially identified; however, the details of the location are left out to sway would-be looters, who have plagued marine archaeologists for decades. | 1 | Applied and Interdisciplinary Chemistry |
When arachidonic acid is a substrate, isomers of hydroperoxyeicosatetraenoic acid (HPETEs) and hydroxyeicosatetraenoic acids (HETEs) are formed. | 1 | Applied and Interdisciplinary Chemistry |
When a sample such as blood or saliva is obtained, the DNA is only a small part of what is present in the sample. Before the DNA can be analyzed, it must be extracted from the cells and purified. There are many ways this can be accomplished, but all methods follow the same basic procedure. The cell and nuclear membranes need to be broken up to allow the DNA to be free in solution. Once the DNA is free, it can be separated from all other cellular components. After the DNA has been separated in solution, the remaining cellular debris can then be removed from the solution and discarded, leaving only DNA. The most common methods of DNA extraction include organic extraction (also called phenol chloroform extraction), Chelex extraction, and solid phase extraction. Differential extraction is a modified version of extraction in which DNA from two different types of cells can be separated from each other before being purified from the solution. Each method of extraction works well in the laboratory, but analysts typically select their preferred method based on factors such as the cost, the time involved, the quantity of DNA yielded, and the quality of DNA yielded. | 1 | Applied and Interdisciplinary Chemistry |
Infiltration reclaims stormwater runoff and allows for groundwater recharge. Runoff enters the soil and percolates through to the subsurface. The rate of infiltration is affected by soil compaction and storage capacity, and will decrease as the soil becomes saturated. The soil texture and structure, vegetation types and cover, water content of the soil, soil temperature, and rainfall intensity all play a role in controlling infiltration rate and capacity. Infiltration plays a critical role in LID site design. Some of the benefits of infiltration include improved water quality (as water is filtered through the soil) and reduction in runoff. When distributed throughout a site, infiltration can significantly help maintain the site's natural hydrology. | 1 | Applied and Interdisciplinary Chemistry |
The scattering cross section of an object () is defined by the time-averaged power of the scattered wave () divided by the intensity of the incident wave (): .
Starting with the assumptions that a plasma object is small relative to the incident wavelength, thin relative to the skin depth, unmagnetized, and homogenous, the scattering cross-section of the plasma object can be determined by the following equation, where is the electron charge, is the electron mass, is the number of unbound electrons in the plasma object, is the geometrically-determined depolarization factor, is the incident wave circular frequency, is the plasma frequency, and is the effective momentum-transfer collisional frequency (not to be confused with collisional frequency).
(The above equation is derived from the Drude-Lorentz-Sommerfeld model. It neglects transient effects of electron motion and is only qualitatively applicable to Rayleigh scattering due to neglecting evanescence effects - strict consideration of boundary conditions is often required to capture the case of negative permittivity.). The total cross section can related to the cross section of an individual electron () according to the equation , since the electron motion will be in phase assuming that the plasma object is small relative to the incident wavelength.
The scattering regime is determined by the dominant term in the denominator. Collisional scattering refers to the assumption that , allowing the total scattering cross section to be expressed as:
The collisional scattering cross-section can also be expressed in terms of the Thomson scattering cross section (), which is independent of the plasma geometry and collisional frequency according to the following equation. | 0 | Theoretical and Fundamental Chemistry |
The technique is commonly used for analyzing the chemical composition of metals, alloys, ceramics, and glasses. It is particularly useful for assessing the composition of individual particles or grains and chemical changes on the scale of a few micrometres to millimeters. The electron microprobe is widely used for research, quality control, and failure analysis. | 0 | Theoretical and Fundamental Chemistry |
Mixed-function oxidase is the name of a family of oxidase enzymes that catalyze a reaction in which each of the two atoms of oxygen in O is used for a different function in the reaction.
Oxidase is a general name for enzymes that catalyze oxidations in which molecular oxygen is the electron acceptor but oxygen atoms do not appear in the oxidized product. Often, oxygen is reduced to either water (cytochrome oxidase of the mitochondrial electron transfer chain) or hydrogen peroxide (dehydrogenation of fatty acyl-CoA in peroxisomes). Most of the oxidases are flavoproteins.
The name "mixed-function oxidase" indicates that the enzyme oxidizes two different substrates simultaneously. Desaturation of fatty acyl-CoA in vertebrates is an example of the mixed-function oxidase reaction. In the process, saturated fatty acyl-CoA and NADPH are oxidized by molecular oxygen (O) to produce monounsaturated fatty acyl-CoA, NADP and 2 molecules of water. | 1 | Applied and Interdisciplinary Chemistry |
A particular brand of gas-surface chemisorption is the dissociation of diatomic gas molecules, such as hydrogen, oxygen, and nitrogen. One model used to describe the process is precursor-mediation. The absorbed molecule is adsorbed onto a surface into a precursor state. The molecule then diffuses across the surface to the chemisorption sites. They break the molecular bond in favor of new bonds to the surface. The energy to overcome the activation potential of dissociation usually comes from translational energy and vibrational energy.
An example is the hydrogen and copper system, one that has been studied many times over. It has a large activation energy of 0.35 – 0.85 eV. The vibrational excitation of the hydrogen molecule promotes dissociation on low index surfaces of copper. | 0 | Theoretical and Fundamental Chemistry |
The oldest and most widely used expression systems are cell-based and may be defined as the "combination of an expression vector, its cloned DNA, and the host for the vector that provide a context to allow foreign gene function in a host cell, that is, produce proteins at a high level". Overexpression is an abnormally and excessively high level of gene expression which produces a pronounced gene-related phenotype.
There are many ways to introduce foreign DNA to a cell for expression, and many different host cells may be used for expression — each expression system has distinct advantages and liabilities. Expression systems are normally referred to by the host and the DNA source or the delivery mechanism for the genetic material. For example, common hosts are bacteria (such as E. coli, B. subtilis), yeast (such as S. cerevisiae) or eukaryotic cell lines. Common DNA sources and delivery mechanisms are viruses (such as baculovirus, retrovirus, adenovirus), plasmids, artificial chromosomes and bacteriophage (such as lambda). The best expression system depends on the gene involved, for example the Saccharomyces cerevisiae is often preferred for proteins that require significant posttranslational modification. Insect or mammal cell lines are used when human-like splicing of mRNA is required. Nonetheless, bacterial expression has the advantage of easily producing large amounts of protein, which is required for X-ray crystallography or nuclear magnetic resonance experiments for structure determination.
Because bacteria are prokaryotes, they are not equipped with the full enzymatic machinery to accomplish the required post-translational modifications or molecular folding. Hence, multi-domain eukaryotic proteins expressed in bacteria often are non-functional. Also, many proteins become insoluble as inclusion bodies that are difficult to recover without harsh denaturants and subsequent cumbersome protein-refolding.
To address these concerns, expressions systems using multiple eukaryotic cells were developed for applications requiring the proteins be conformed as in, or closer to eukaryotic organisms: cells of plants (i.e. tobacco), of insects or mammalians (i.e. bovines) are transfected with genes and cultured in suspension and even as tissues or whole organisms, to produce fully folded proteins. Mammalian in vivo expression systems have however low yield and other limitations (time-consuming, toxicity to host cells,..). To combine the high yield/productivity and scalable protein features of bacteria and yeast, and advanced epigenetic features of plants, insects and mammalians systems, other protein production systems are developed using unicellular eukaryotes (i.e. non-pathogenic <nowiki/>Leishmania<nowiki/> cells). | 1 | Applied and Interdisciplinary Chemistry |
The first part contains 60 multiple-choice questions. Each question has four answer choices. The questions are loosely grouped into 10 sets of 6 items; each set corresponds to a different chemistry topic. Typically, the topics are, in order, descriptive chemistry/laboratory techniques, stoichiometry, gases/liquids/solids, thermodynamics, kinetics, equilibrium, electrochemistry, electronic structure/periodic trends, bonding theories, and organic chemistry. There is no penalty for guessing; a student's score is equal to the number of questions answered correctly. One and a half hours (90 minutes) are allotted for this first part. | 1 | Applied and Interdisciplinary Chemistry |
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