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The phenotype of each individual is modeled as the gene expression pattern at time . It is represented by a state vector in this model.
whose element denotes the expression state of gene i at time t. In the original Wagner model,
where 1 represents the gene is expressed while -1 implies the gene is not expressed. The expression pattern can only be ON or OFF. The continuous expression pattern between -1 (or 0) and 1 is also implemented in some other variants. | 1 | Applied and Interdisciplinary Chemistry |
Ge joined the University of Wisconsin–Madison as an assistant scientist, where she oversaw the mass spectrometry programme. She became an Associate Professor in 2015, and full Professor in 2019.
Ge develops high-resolution mass spectrometry proteomics to better understand cardiac disease. To image the very large proteins of human heart tissue, Ge combines fourier-transform ion cyclotron resonance (FT–ICR) mass spectrometry with electron-capture dissociation. She has worked to create a top-down disease proteomic platform that allows for the separation, detection and characterisation of the biomarkers of heart damage.
Nanoproteomics, a technique developed by Ge and co-workers, makes use of nanoparticles and high resolution mass spectrometry to capture and characterise cardiac troponins, including troponin I. Being able to test for and characterise troponin I would help with the early detection and diagnosis of heart disease. The peptide-functionalised superparamagnetic nanoparticles are combined with top-down mass spectrometry to identify the molecular fingerprints of troponins. Rather than just detecting cardiac troponins, which is possible using ELISA-based antibody testing, this higher level of characterisation will allow Ge to identify various forms of modified troponins, allowing a personalised understanding of cardiac disease.
Ge served on the board of the Top-Down Proteomics Consortium, on the editorial board of the Journal of Muscle Research and Cell Motility, as treasurer for the American Society for Mass Spectrometry (2016-2018).
[https://scholar.google.com/citations?user=Ymgpd5QAAAAJ&hl=en&oi=sra Ying Ge] publications indexed by Google Scholar. | 1 | Applied and Interdisciplinary Chemistry |
A melanomorph is a substance related to the pigment melanin. Melanomorphs originate from the aromatic amino acids tyrosine, tryptophan, and phenylalanine. They tend to absorb ultraviolet-B light, with peaks around 280 nanometers. See also Beer's Law. | 1 | Applied and Interdisciplinary Chemistry |
In fluid dynamics, a vortex (: vortices or vortexes) is a region in a fluid in which the flow revolves around an axis line, which may be straight or curved. Vortices form in stirred fluids, and may be observed in smoke rings, whirlpools in the wake of a boat, and the winds surrounding a tropical cyclone, tornado or dust devil.
Vortices are a major component of turbulent flow. The distribution of velocity, vorticity (the curl of the flow velocity), as well as the concept of circulation are used to characterise vortices. In most vortices, the fluid flow velocity is greatest next to its axis and decreases in inverse proportion to the distance from the axis.
In the absence of external forces, viscous friction within the fluid tends to organise the flow into a collection of irrotational vortices, possibly superimposed to larger-scale flows, including larger-scale vortices. Once formed, vortices can move, stretch, twist, and interact in complex ways. A moving vortex carries some angular and linear momentum, energy, and mass, with it. | 1 | Applied and Interdisciplinary Chemistry |
In cooperation with the chemical company BASF, Ralf Reski and coworkers established a collection of knockout mosses to use for gene identification. | 1 | Applied and Interdisciplinary Chemistry |
Adhesion is an essential process to epithelial cells so that epithelium can be formed and cells can be in permanent contact with extracellular matrix and other cells. Several pathways exist to accomplish this communication and adhesion with environment. But the main signalling pathways are the cadherin and integrin pathways.
The cadherin pathway is present in adhesion junctions or in desmosomes and it is responsible for epithelial adhesion and communication with adjacent cells. Cadherin is a transmembrane glycoprotein receptor that establishes contact with another cadherin present in the surface of a neighbour cell forming an adhesion complex. This adhesion complex is formed by β-catenin and α-catenin, and p120 is essential for its stabilization and regulation. This complex then binds to actin, leading to polymerization. For actin polymerization through the cadherin pathway, proteins of the Rho GTPases family are also involved. This complex is regulated by phosphorylation, which leads to downregulation of adhesion. Several factors can induce the phosphorylation, like EGF, HGF or v-Src. The cadherin pathway also has an important function in survival and proliferation because it regulates the concentration of cytoplasmic β-catenin. When β-catenin is free in the cytoplasm, normally it is degraded, however if the Wnt signalling is activated, β-catenin degradation is inhibited and it is translocated to the nucleus where it forms a complex with transcription factors. This leads to activation of genes responsible for cell proliferation and survival. So the cadherin-catenin complex is essential for cell fate regulation.
Integrins are heterodimeric glycoprotein receptors that recognize proteins present in the extracellular matrix, like fibronectin and laminin. In order to function, integrins have to form complexes with ILK and Fak proteins. For adhesion to the extracellular matrix, ILK activate the Rac and Cdc42 proteins and leading to actin polymerization. ERK also leads to actin polymerization through activation of cPLA2. Recruitment of FAK by integrin leads to Akt activation and this inhibits pro-apoptotic factors like BAD and Bax. When adhesion through integrins do not occur the pro-apoptotic factors are not inhibited and resulting in apoptosis. | 0 | Theoretical and Fundamental Chemistry |
Electrochemical impedance spectroscopy (EIS) involves measuring resistive and capacitive changes caused by a biorecognition event. Typically, a small amplitude sinusoidal electrical stimulus is applied, causing current to flow through the biosensor. The frequency is varied over a range to obtain the impedance spectrum. The resistive and capacitive components of impedance are determined from in phase and out of phase current responses. Typically, a conventional three-electrode system is made specific to the analyte by immobilizing a biorecognition element to the surface. A voltage is applied and the current is measured. The interfacial impedance between the electrode and solution changes as a result of the analyte binding. An impedance analyzer can be used to control and apply the stimulus as well as measure the impedance changes. | 1 | Applied and Interdisciplinary Chemistry |
Organic chemicals such as lactic acid and citric acid have been used to etch metals and create products as early as 400 BCE, when vinegar was used to corrode lead and create the pigment ceruse, also known as white lead. Most modern chemical milling methods involve alkaline etchants; these may have been used as early as the first century CE.
Armor etching, using strong mineral acids, was not developed until the fifteenth century. Etchants mixed from salt, charcoal, and vinegar were applied to plate armor that had been painted with a maskant of linseed-oil paint. The etchant would bite into the unprotected areas, causing the painted areas to be raised into relief. Etching in this manner allowed armor to be decorated as if with precise engraving, but without the existence of raised burrs; it also prevented the necessity of the armor being softer than an engraving tool. Late in the seventeenth century, etching became used to produce the graduations on measuring instruments; the thinness of lines that etching could produce allowed for the production of more precise and accurate instruments than were possible before. Not long after, it became used to etch trajectory information plates for cannon and artillery operators; paper would rarely survive the rigors of combat, but an etched plate could be quite durable. Often such information (normally ranging marks) was etched onto equipment such as stiletto daggers or shovels.
In 1782, the discovery was made by John Senebier that certain resins lost their solubility to turpentine when exposed to light; that is, they hardened. This allowed the development of photochemical milling, where a liquid maskant is applied to the entire surface of a material, and the outline of the area to be masked created by exposing it to UV light. Photo-chemical milling was extensively used in the development of photography methods, allowing light to create impressions on metal plates.
One of the earliest uses of chemical etching to mill commercial parts was in 1927, when the Swedish company Aktiebolaget Separator patented a method of producing edge filters by chemically milling the gaps in the filters. Later, around the 1940s, it became widely used to machine thin samples of very hard metal; photo-etching from both sides was used to cut sheet metal, foil, and shim stock to create shims, recording heat frets, and other components. | 1 | Applied and Interdisciplinary Chemistry |
Cited as coming from Bejan:
This equation
It was empirically determined by Globe and Dropkin in 1959: The containers used were around 5" in diameter and 2" high. | 1 | Applied and Interdisciplinary Chemistry |
Let , be the directions parallel to the flat plates, and the perpendicular direction, with being the gap between the plates (at ) and be the relevant characteristic length scale in the -directions. Under the limits mentioned above, the incompressible Navier–Stokes equations, in the first approximation becomes
where is the viscosity. These equations are similar to boundary layer equations, except that there are no non-linear terms. In the first approximation, we then have, after the non-slip boundary conditions at ,
The equation for is obtained from the continuity equation. Integrating the continuity equation from across the channel and imposing no-penetration boundary conditions at the walls, we have
which leads to the Laplace Equation:
This equation is supplemented by appropriate boundary conditions. For exmaple, no-penetration boundary conditions on the side walls become: , where is a unit vector perpendicular to the side wall (note that on the side walls, non-slip boundary conditions cannot be imposed). The boundary cal also be regions exposed to constant pressure in which a Dirichlet boundary conditions are appropirtae. Similayly, periodic boundary conditions can also be used. It can also be noted that the vertical velocity component in the first approximation is
While the velocity magnitude varies in the direction, the velocity-vector direction is independent of direction, that is to say, streamline patterns at each level are similar. Eliminating pressure in the above equation, one obtains
where is the vorticity in the direction. The streamline patterns thus correspond to potential flow (irrotational flow). Unlike potential flow, here the circulation around any closed contour , whether it encloses a solid object or not, is zero,
where the last integral is set to zero because is a single-valued function and the integration is done over a closed contour. If
then the depth-averaged velcity vector , satisfies Darcy's law, | 1 | Applied and Interdisciplinary Chemistry |
A crucible is a ceramic or metal container in which metals or other substances may be melted or subjected to very high temperatures. Although crucibles have historically tended to be made out of clay, they can be made from any material that withstands temperatures high enough to melt or otherwise alter its contents. | 0 | Theoretical and Fundamental Chemistry |
The term dispersion also refers to the physical property of the degree to which particles clump together into agglomerates or aggregates. While the two terms are often used interchangeably, according to ISO nanotechnology definitions, an agglomerate is a reversible collection of particles weakly bound, for example by van der Waals forces or physical entanglement, whereas an aggregate is composed of irreversibly bonded or fused particles, for example through covalent bonds. A full quantification of dispersion would involve the size, shape, and number of particles in each agglomerate or aggregate, the strength of the interparticle forces, their overall structure, and their distribution within the system. However, the complexity is usually reduced by comparing the measured size distribution of "primary" particles to that of the agglomerates or aggregates. When discussing suspensions of solid particles in liquid media, the zeta potential is most often used to quantify the degree of dispersion, with suspensions possessing a high absolute value of zeta potential being considered as well-dispersed. | 0 | Theoretical and Fundamental Chemistry |
In Sebastian Aniţa, Viorel Arnăutu, Vincenzo Capasso. An Introduction to Optimal Control Problems in Life Sciences and Economics (Birkhäuser. 2011), this equation appears as a special case of the Sharpe–Lotka–McKendrick’s equation; in the latter there is inflow, and the math is based on directional derivative. The McKendrick’s equation appears extensively in the context of cell biology as a good approach to model the eukaryotic cell cycle. | 1 | Applied and Interdisciplinary Chemistry |
The first step in the biological pump is the synthesis of both organic and inorganic carbon compounds by phytoplankton in the uppermost, sunlit layers of the ocean. Organic compounds in the form of sugars, carbohydrates, lipids, and proteins are synthesized during the process of photosynthesis:
CO + HO + light → CHO + O
In addition to carbon, organic matter found in phytoplankton is composed of nitrogen, phosphorus and various trace metals. The ratio of carbon to nitrogen and phosphorus varies from place to place, but has an average ratio near 106C:16N:1P, known as the Redfield ratio. Trace metals such as magnesium, cadmium, iron, calcium, barium and copper are orders of magnitude less prevalent in phytoplankton organic material, but necessary for certain metabolic processes and therefore can be limiting nutrients in photosynthesis due to their lower abundance in the water column.
Oceanic primary production accounts for about half of the carbon fixation carried out on Earth. Approximately 50–60 Pg of carbon are fixed by marine phytoplankton each year despite the fact that they account for less than 1% of the total photosynthetic biomass on Earth. The majority of this carbon fixation (~80%) is carried out in the open ocean while the remaining amount occurs in the very productive upwelling regions of the ocean. Despite these productive regions producing 2 to 3 times as much fixed carbon per area, the open ocean accounts for greater than 90% of the ocean area and therefore is the larger contributor. | 0 | Theoretical and Fundamental Chemistry |
Diphenyl diselenide and several benzylic selenides have been explored by Kwon et al. as photoiniferters in polymerization of styrene and methyl methacrylate. Their mechanism of control over polymerization is proposed to be similar to the dithiuram disulfide iniferters. However, their low transfer constants allow them to be used for block copolymer synthesis but give limited control over the molecular weight distribution. | 0 | Theoretical and Fundamental Chemistry |
Transferrin is a serum protein that carries iron through the bloodstream to the bone marrow, where red blood cells are manufactured, as well as to the liver and spleen. Structurally, transferrin is a polypeptide with two N-linked polysaccharide chains. These polysaccharide chains are branched with sialic acid residues. Sialic acid is a monosaccharide carbohydrate.
Various forms of transferrin exist, with differing levels of sialylation. The most common form is tetrasialotransferrin, with four sialic acid chains. In persons who consume significant quantities of alcohol (usually more than 4 or 5 alcoholic beverages a day for two weeks or more) , the proportion of transferrin with zero, one, or two sialic acid chains is increased. These are referred to as carbohydrate-deficient transferrins. These carbohydrate-deficient transferrins can be measured in the bloodstream, and are important markers for alcohol use disorder. | 1 | Applied and Interdisciplinary Chemistry |
Existing metabolic networks control the movement of molecules through their enzymatic steps by regulating enzymes that catalyze irreversible reactions. The movement of molecules through reversible steps is generally unregulated by enzymes, but rather regulated by the concentration of products and reactants. Irreversible reactions at regulated steps of a pathway have a negative free energy change, thereby promoting spontaneous reactions in one direction only. Reversible reactions have no or very small free energy change. As a result, the movement of molecules through a metabolic network is governed by simple chemical equilibria (at reversible steps), with specific key enzymes that are subject to regulation (at irreversible steps). This enzymatic regulation may be indirect, in the case of an enzyme being regulated by some cell signalling mechanism (like phosphorylation), or it may be direct, as in the case of allosteric regulation, where metabolites from a different portion of a metabolic network bind directly to and affect the catalytic function of other enzymes in order to maintain homeostasis.
A result that may seem at first counter intuitive, is that regulated steps tends to have small flux control coefficients. The reason is that these steps are part of a control system that stabilizes fluxes, hence a perturbation in the activity of a regulated step will inevitably trigger the control system to resist the perturbation, hence the flux control coefficients will tend to be small. This explains why, for example, that phosphofructokinase in glycolysis has such as small flux control coefficient. | 1 | Applied and Interdisciplinary Chemistry |
right|thumb|Example and diagram for p3
left|thumb|Cell structure for p3
* Orbifold signature:
* Coxeter notation: [(3,3,3)] or [3]
* Lattice: hexagonal
* Point group: C
* The group p3 has three different rotation centres of order three (120°), but no reflections or glide reflections.
Imagine a tessellation of the plane with equilateral triangles of equal size, with the sides corresponding to the smallest translations. Then half of the triangles are in one orientation, and the other half upside down. This wallpaper group corresponds to the case that all triangles of the same orientation are equal, while both types have rotational symmetry of order three, but the two are not equal, not each others mirror image, and not both symmetric (if the two are equal it is p6, if they are each others mirror image it is p31m, if they are both symmetric it is p3m1; if two of the three apply then the third also, and it is p6m). For a given image, three of these tessellations are possible, each with rotation centres as vertices, i.e. for any tessellation two shifts are possible. In terms of the image: the vertices can be the red, the blue or the green triangles.
Equivalently, imagine a tessellation of the plane with regular hexagons, with sides equal to the smallest translation distance divided by . Then this wallpaper group corresponds to the case that all hexagons are equal (and in the same orientation) and have rotational symmetry of order three, while they have no mirror image symmetry (if they have rotational symmetry of order six it is p6, if they are symmetric with respect to the main diagonals it is p31m, if they are symmetric with respect to lines perpendicular to the sides it is p3m1; if two of the three apply then the third also, it is p6m). For a given image, three of these tessellations are possible, each with one third of the rotation centres as centres of the hexagons. In terms of the image: the centres of the hexagons can be the red, the blue or the green triangles.
;Examples of group p3 | 0 | Theoretical and Fundamental Chemistry |
Galvanism influenced metaphysical thought in the domain of abiogenesis, the underlying process of the generation of living forms. In 1836, Andrew Crosse recorded what he referred to as "the perfect insect, standing erect on a few bristles which formed its tail," as having appeared during an experiment wherein he used electricity to produce mineral crystals. While Crosse himself never claimed to have generated the insects, even in private, the scientific world at the time viewed the connection between life and electricity to be sufficiently clear that he received threats against his life for this "blasphemy." | 0 | Theoretical and Fundamental Chemistry |
In isolated systems it is consistently observed that as time goes on internal rearrangements diminish and stable conditions are approached. Pressures and temperatures tend to equalize, and matter arranges itself into one or a few relatively homogeneous phases. A system in which all processes of change have gone practically to completion is considered in a state of thermodynamic equilibrium. The thermodynamic properties of a system in equilibrium are unchanging in time. Equilibrium system states are much easier to describe in a deterministic manner than non-equilibrium states. In some cases, when analyzing a thermodynamic process, one can assume that each intermediate state in the process is at equilibrium. Such a process is called quasistatic.
For a process to be reversible, each step in the process must be reversible. For a step in a process to be reversible, the system must be in equilibrium throughout the step. That ideal cannot be accomplished in practice because no step can be taken without perturbing the system from equilibrium, but the ideal can be approached by making changes slowly.
The very existence of thermodynamic equilibrium, defining states of thermodynamic systems, is the essential, characteristic, and most fundamental postulate of thermodynamics, though it is only rarely cited as a numbered law. According to Bailyn, the commonly rehearsed statement of the zeroth law of thermodynamics is a consequence of this fundamental postulate. In reality, practically nothing in nature is in strict thermodynamic equilibrium, but the postulate of thermodynamic equilibrium often provides very useful idealizations or approximations, both theoretically and experimentally; experiments can provide scenarios of practical thermodynamic equilibrium.
In equilibrium thermodynamics the state variables do not include fluxes because in a state of thermodynamic equilibrium all fluxes have zero values by definition. Equilibrium thermodynamic processes may involve fluxes but these must have ceased by the time a thermodynamic process or operation is complete bringing a system to its eventual thermodynamic state. Non-equilibrium thermodynamics allows its state variables to include non-zero fluxes, which describe transfers of mass or energy or entropy between a system and its surroundings. | 0 | Theoretical and Fundamental Chemistry |
The Small Molecule Pathway Database (SMPDB) is a comprehensive, high-quality, freely accessible, online database containing more than 600 small molecule (i.e. metabolic) pathways found in humans. SMPDB is designed specifically to support pathway elucidation and pathway discovery in metabolomics, transcriptomics, proteomics and systems biology. It is able to do so, in part, by providing colorful, detailed, fully searchable, hyperlinked diagrams of five types of small molecule pathways: 1) general human metabolic pathways; 2) human metabolic disease pathways; 3) human metabolite signaling pathways; 4) drug-action pathways and 5) drug metabolism pathways. SMPDB pathways may be navigated, viewed and zoomed interactively using a Google Maps-like interface. All SMPDB pathways include information on the relevant organs, subcellular compartments, protein cofactors, protein locations, metabolite locations, chemical structures and protein quaternary structures (Fig. 1). Each small molecule in SMPDB is hyperlinked to detailed descriptions contained in the HMDB or DrugBank and each protein or enzyme complex is hyperlinked to UniProt. Additionally, all SMPDB pathways are accompanied with detailed descriptions and references, providing an overview of the pathway, condition or processes depicted in each diagram. Users can browse the SMPDB (Fig. 2) or search its contents by text searching (Fig. 3), sequence searching, or chemical structure searching. More powerful queries are also possible including searching with lists of gene or protein names, drug names, metabolite names, GenBank IDs, Swiss-Prot IDs, Agilent or Affymetrix microarray IDs. These queries will produce lists of matching pathways and highlight the matching molecules on each of the pathway diagrams. Gene, metabolite and protein concentration data can also be visualized through SMPDB's mapping interface.
SMPDB is part of a suite of metabolomics databases that also includes Human Metabolome Database, DrugBank, and the Toxin and Toxin-Target Database (T3DB). While DrugBank includes information on 7000 drugs and >4200 non-redundant drug targets, enzymes, transporters, and carriers, HMDB houses over 40,000 small molecule metabolites found in the human body. The suite is complemented by T3DB with its over 3100 common toxic substances and over 1300 corresponding toxin targets. | 1 | Applied and Interdisciplinary Chemistry |
The split gene theory implies that structural features of split genes predicted from computer-simulated random sequences occur in eukaryotic split genes. This is borne out in most known split genes. The sequences exhibit a nearly perfect negative exponential distribution of ORF lengths. With rare exceptions, eukaryotic gene exons fall within the predicted 600 base maximum.
The theory correctly predicts that exons are delimited by stop codons, especially at the 3’ ends of exons. Actually they are precisely delimited more strongly at the 3’ ends of exons and less strongly at the 5’ ends in most known genes, as predicted. These stop codons are the most important functional parts of both splice junctions. The theory thus provides an explanation for the “conserved” splice junctions at the ends of exons and for the loss of these stop codons along with introns when they are spliced out. The theory correctly predicts that splice junctions are randomly distributed in eukaryotic DNA sequences. The theory correctly predicts that splice junctions present in transfer RNA genes and ribosomal RNA genes, do not contain stop codons. The lariat signal, another sequence involved in the splicing process, also contains stop codons.
The theory correctly predicts that introns are non-coding and that they are mostly non-functional. Except for some intron sequences including the donor and acceptor splice signal sequences and branch point sequences, and possibly the intron splice enhancers that occur at the ends of introns, which aid in the removal of introns, the vast majority of introns are devoid of any functions. The theory does not exclude rare sequences within introns that could be used by the genome and the cell, especially because introns are so long.
Thus, the theory's predictions are precisely corroborated by the major elements in modern eukaryotic genomes.
Comparative analysis of the modern genome data from several living organisms found that the characteristics of split genes trace back to the earliest organisms. These organisms could have contained the split genes and complex proteins that occur in today's living organisms.
Studies employing maximum likelihood analysis found that the earliest eukaryotic organisms contained the same genes as modern organisms with yet a higher intron density. Comparative genomics of many organisms including basal eukaryotes (considered to be primitive eukaryotic organisms such as Amoeboflagellata, Diplomonadida, and Parabasalia) showed that intron-rich split genes accompanied and spliceosome from modern organisms were present in their earliest forebears, and that the earliest organisms came with all the eukaryotic cellular components. | 1 | Applied and Interdisciplinary Chemistry |
Lightning strike protection minimizes damage to buildings during lightning terminations. This is usually accomplished by providing multiple interconnected pathways of low electrical impedance to the ground.
Copper and its alloys are the most common materials used in residential lightning protections, however in industrial, chemically corrosive environments, the copper may need to be clad in tin. Copper effectively facilitates the transmission of lightning energy to the ground because of its excellent electrical conductivity. Also, it bends easily compared to other conductor materials.
When copper roofing, gutters, and rain leaders are electrically bonded to an earth termination facility, a pathway of low electrical impedance to ground is provided, however without dedicated conduction pathways to concentrate the discharge channel, a disperse energized surface may not be the most desirable.
Because copper has a higher electrical conductivity than aluminium and its impedance during a lightning termination is less, copper allows for the use of less cross-sectional surface area per linear length, in its woven wires pathway than does aluminum. Also, aluminium cannot be used in poured concrete or for any component underground due to its galvanic properties.
To be effective, lightning protection systems generally maximize the surface area contact between the conductors and the earth through a ground grid of varying designs. To supplement grounding grids in low-conductivity earth, such as sand or rock, long, hollow copper tubes filled with metallic salts are available. These salts leach through holes in the tube, making the surrounding soil more conductive as well as increasing the overall surface area which decreases effective resistance.
Copper roofs may be used as part of a lightning protection scheme where the copper skin, gutters and rainwater pipes can be linked and bonded to an earth termination facility. The thickness of copper specified for roofing materials is usually adequate for lightning protection. A dedicated lightning protection system may be recommended to adequate lightning protection with an installed copper roof system. The system would include air terminals and intercepting conductors on the roof, a system of ground electrodes, and a system of down-conductors connecting the roof and ground components. It is recommended that the copper roof be bonded to the system of conductors. Bonding ensures that the conductors and roof remain at equipotential and reduce side flashing and possible roof damage. | 1 | Applied and Interdisciplinary Chemistry |
The world's largest form of storage for excess electricity, pumped-storage is a reversible hydroelectric plant. They are a net consumer of energy but provide storage for any source of electricity, effectively smoothing peaks and troughs in electricity supply and demand. Pumped storage plants typically use "spare" electricity during off peak periods to pump water from a lower reservoir to an upper reservoir. Because the pumping takes place "off peak", electricity is less valuable than at peak times. This less valuable "spare" electricity comes from uncontrolled wind power and base load power plants such as coal, nuclear and geothermal, which still produce power at night even though demand is very low. During daytime peak demand, when electricity prices are high, the storage is used for peaking power, where water in the upper reservoir is allowed to flow back to a lower reservoir through a turbine and generator. Unlike coal power stations, which can take more than 12 hours to start up from cold, a hydroelectric generator can be brought into service in a few minutes, ideal to meet a peak load demand. Two substantial pumped storage schemes are in South Africa, Palmiet Pumped Storage Scheme and another in the Drakensberg, Ingula Pumped Storage Scheme. | 1 | Applied and Interdisciplinary Chemistry |
Bone ash is a key raw material for bone china. Constituting around 50% of the body, it reacts with other raw materials in the body during firing to form, amongst other phases, anorthite.
In preparation for use in bone china, bones undergo multiple processing stages, including:
* Removal of any meat before being degreased.
* Calcination to around 1000 °C (1832 °F). This will remove all organic, and the bone is left sterilised.
* Being ground with water to fine particle size.
* Being partially dewatered.
Since the 1990s, the use of synthetic alternatives to bone ash, which are based on dicalcium phosphate and tricalcium phosphate, has increased. Significant amounts of bone china is produced using these synthetic alternatives rather than bone ash. | 0 | Theoretical and Fundamental Chemistry |
Although sedimentation might occur in tanks of other shapes, removal of accumulated solids is easiest with conveyor belts in rectangular tanks or with scrapers rotating around the central axis of circular tanks. Settling basins and clarifiers should be designed based on the settling velocity (v) of the smallest particle to be theoretically 100% removed. The overflow rate is defined as:
:Overflow rate (v ) = Flow of water (Q (m/s)) /(Surface area of settling basin (A(m))
In many countries this value is named as surface loading in m/h per m. Overflow rate is often used for flow over an edge (for example a weir) in the unit m/h per m.
The unit of overflow rate is usually meters (or feet) per second, a velocity. Any particle with settling velocity (v) greater than the overflow rate will settle out, while other particles will settle in the ratio v/v.
There are recommendations on the overflow rates for each design that ideally take into account the change in particle size as the solids move through the operation:
* Quiescent zones: per second
* Full-flow basins: per second
* Off-line basins: per second
However, factors such as flow surges, wind shear, scour, and turbulence reduce the effectiveness of settling. To compensate for these less than ideal conditions, it is recommended doubling the area calculated by the previous equation.
It is also important to equalize flow distribution at each point across the cross-section of the basin. Poor inlet and outlet designs can produce extremely poor flow characteristics for sedimentation.
Settling basins and clarifiers can be designed as long rectangles (Figure 1.a), that are hydraulically more stable and easier to control for large volumes. Circular clarifiers (Fig. 1.b) work as a common thickener (without the usage of rakes), or as upflow tanks (Fig. 1.c).
Sedimentation efficiency does not depend on the tank depth. If the forward velocity is low enough so that the settled material does not re-suspend from the tank floor, the area is still the main parameter when designing a settling basin or clarifier, taking care that the depth is not too low. | 0 | Theoretical and Fundamental Chemistry |
The US Institute of Medicine (IOM) updated Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for selenium in 2000. If there is not sufficient information to establish EARs and RDAs, an estimate designated Adequate Intake (AI) is used instead. The current EAR for selenium for people ages 14 and up is 45 μg/day. The RDA is 55 μg/day. RDAs are higher than EARs so as to identify amounts that will cover people with higher than average requirements. RDA for pregnancy is 60 μg/day. RDA for lactation is 70 μg/day. For children ages 1–13 years the RDA increases with age from 20 to 40 μg/day. As for safety, the IOM sets Tolerable upper intake levels (ULs) for vitamins and minerals when evidence is sufficient. In the case of selenium the UL is 400 μg/day. Collectively the EARs, RDAs, AIs and ULs are referred to as Dietary Reference Intakes (DRIs).
The European Food Safety Authority (EFSA) refers to the collective set of information as Dietary Reference Values, with Population Reference Intake (PRI) instead of RDA, and Average Requirement instead of EAR. AI and UL defined the same as in United States. For women and men ages 15 and older the AI is set at 70 μg/day. AI for pregnancy is 70 μg/day, for lactation 85 μg/day. For children ages 1–14 years the AIs increase with age from 15 to 55 μg/day. These AIs are higher than the U.S. RDAs. The European Food Safety Authority reviewed the same safety question and set its UL at 300 μg/day, which is lower than the U.S. value.
In the United States, selenium deficiency is not common. A federal survey of food consumption determined that for women and men over the age of 19, average consumption from foods and beverages was 89 and 125 μg/day, respectively. For women and men of all ages fewer than 3% consumed less than the EAR. | 1 | Applied and Interdisciplinary Chemistry |
The amount of strain energy in bicyclic systems is commonly the sum of the strain energy in each individual ring. This isn't always the case, as sometimes the fusion of rings induces some extra strain. | 0 | Theoretical and Fundamental Chemistry |
The centrifuge method relies on the following relationship between capillary pressure and gravity:
where:
: is the height of the capillary rise
: is gravity
: is the density of the wetting phase
: is the density of the non-wetting phase
The centrifugal force essentially serves as an applied capillary pressure for small test plugs, often composed of brine and oil. During the centrifugation process, a given amount of brine is expelled from the plug at certain centrifugal rates of rotation. A glass vial measures the amount of fluid as it is being expelled, and these readings result in a curve that relates rotation speeds with drainage amounts. The rotation speed is correlated to capillary pressure by the following equation:
where:
: is the radius of rotation of the bottom of the core sample
: is the radius of rotation of the top of the core sample
: is the rotational speed
The primary benefits to this method are that it's rapid (producing curves in a matter of hours) and is not restricted to being performed at certain temperatures.
Other methods include the Vapor Pressure Method, Gravity-Equilibrium Method, Dynamic Method, Semi-dynamic Method, and the Transient Method. | 1 | Applied and Interdisciplinary Chemistry |
Hydroxylamine-O-sulfonic acid (HOSA) or aminosulfuric acid is the inorganic compound with molecular formula HNOS that is formed by the sulfonation of hydroxylamine with oleum. It is a white, water-soluble and hygroscopic, solid, commonly represented by the condensed structural formula HNOSOH, though it actually exists as a zwitterion and thus is more accurately represented as HNOSO. It is used as a reagent for the introduction of amine groups (–NH), for the conversion of aldehydes into nitriles and alicyclic ketones into lactams (cyclic amides), and for the synthesis of variety of nitrogen-containing heterocycles. | 0 | Theoretical and Fundamental Chemistry |
Tablets are small, solid dosages suitable for the use of mucoadhesive coatings. The coating may be formulated to adhere to a specific mucosa, enabling both systemic and targeted local administration. Tablets are generally taken enterally, as the size and stiffness of the form results in poor patient compliance when administered through other routes. | 1 | Applied and Interdisciplinary Chemistry |
EmBiology (formerly EMBiology) is a web-based Software as a service tool from Elsevier in which researchers can view biological relationships between entities, such as genes, proteins, and cells.
Launched in 2023, EmBiology queries a Biological Knowledge Graph with 1.4 million entities connected by 15.7 million relationships. It uses a Sankey diagram to visualize search findings, and displays "snippets" of text from relevant scientific literature. | 1 | Applied and Interdisciplinary Chemistry |
In pulse-height analysis (PHA) mode, incoming pulses are characterized based on their amplitude (peak voltage). The output spectrum is a histogram of these pulses, where the height of each channel corresponds to the number pulses counted within a narrow range of amplitudes. The resolution of the output spectrum depends on the number of channels of the MCA, which is on the order of a few thousand for typical instruments.
In alpha-, beta-, and gamma spectroscopy, PHA is used to measure the energy distribution of particles emitted in nuclear decay. Incoming particles are absorbed by a detector medium and excite voltage pulses whose amplitudes are proportional to their energy. After many pulses have been counted, the output spectrum shows the energy distribution of the radiation incident on the detector. | 0 | Theoretical and Fundamental Chemistry |
It is used in a wide range of applications. For example, it is used as a catalyst for the hydrochlorination of acetylene, or the oxidation of sulfides. | 0 | Theoretical and Fundamental Chemistry |
The repulsive effects of the two lone pairs on the oxygen atom cause water to have a bent, not linear, molecular structure, allowing it to be polar. The hydrogen–oxygen–hydrogen angle is 104.45°, which is less than the 109.47° for ideal sp hybridization. The valence bond theory explanation is that the oxygen atoms lone pairs are physically larger and therefore take up more space than the oxygen atoms bonds to the hydrogen atoms. The molecular orbital theory explanation (Bents rule) is that lowering the energy of the oxygen atoms nonbonding hybrid orbitals (by assigning them more s character and less p character) and correspondingly raising the energy of the oxygen atoms hybrid orbitals bonded to the hydrogen atoms (by assigning them more p character and less s character) has the net effect of lowering the energy of the occupied molecular orbitals because the energy of the oxygen atoms nonbonding hybrid orbitals contributes completely to the energy of the oxygen atoms lone pairs while the energy of the oxygen atoms other two hybrid orbitals contributes only partially to the energy of the bonding orbitals (the remainder of the contribution coming from the hydrogen atoms' 1s orbitals). | 1 | Applied and Interdisciplinary Chemistry |
Efforts to elucidate the excited states of diphosphenes is important and valuable to realize the application of PP double bonds in molecular electronics. In triplets trans-HPPH, the P-P bond length is predicted to be 2.291 Å. It is not only longer than the P-P double bond in ground state trans-bis(2,4,6-tri-tert-butylphenyl)diphosphene, but also longer than that of P-P single bond in HPPH. Calculation of the dihedral angle of trans-HPPH suggests that it is almost 90 degree, which means the formation of and P-P bonds is forbidden and σ bond is enhanced. | 0 | Theoretical and Fundamental Chemistry |
The discovery of this type of mechanism to control the expression of genes in a biosynthetic operon lead to its identification in a wide variety of such operons for which repressors had never been discovered. For example: | 1 | Applied and Interdisciplinary Chemistry |
Mixtures of and are called Fenton reagent. If is replaced by , it is called Fenton-like reagent.
Numerous transition metal ions and their complexes in their lower oxidation states () were found to have the oxidative features of the Fenton reagent, and, therefore, the mixtures of these metal compounds with were named "Fenton-like" reagents. | 1 | Applied and Interdisciplinary Chemistry |
This section discusses fittings primarily used in pressurized piping systems, though there is some overlap with fittings for low-pressure or non-pressurized systems. Specialized fittings for the latter setups are discussed in the next major subsection. | 1 | Applied and Interdisciplinary Chemistry |
LEDs and laser diodes usually emit photons with energy close to and slightly larger than the band gap of the semiconductor material from which they are made. Therefore, as the band gap energy increases, the LED or laser color changes from infrared to red, through the rainbow to violet, then to UV. | 0 | Theoretical and Fundamental Chemistry |
Since 2016, Han Seo-jun, then associate professor at the Southern University of Science and Technology (SUSTech) in Shenzhen, with Zhang Renli and Qin Jinzhou, have used human embryo in gene-editing technology for assisted reproductive medicine. On 10 June 2017, a Chinese couple, an HIV-positive father and HIV-negative mother, pseudonymously called Mark and Grace, attended a conference held by He at SUSTech. They were offered in vitro fertilisation (IVF) along with gene-editing of their embryos so as to develop innate resistance to HIV infection in their offspring. They agreed to volunteer through informed consent and the experiment was carried out in secrecy. Six other couples having similar fertility problems were subsequently recruited. The couples were recruited through a Beijing-based AIDS advocacy group called Baihualin China League. When later examined, the consent forms were noted as incomplete and inadequate. The couple were reported to have agreed to this experiment because, by Chinese rules, normally HIV positive fathers were not allowed to have children using IVF.
When the place of the clinical experiment was investigated, SUSTech declared that the university was not involved and that He had been on unpaid leave since February 2018, and his department attested that they were unaware of the research project. | 1 | Applied and Interdisciplinary Chemistry |
In 1926, Raymond Pearl proposed that longevity varies inversely with basal metabolic rate (the "rate of living hypothesis"). Support for this hypothesis comes from the fact that mammals with larger body size have longer maximum life spans (large animals do have higher total metabolic rates, but the metabolic rate at the cellular level is much lower, and the breathing rate and heartbeat are slower in larger animals) and the fact that the longevity of fruit flies varies inversely with ambient temperature. Additionally, the life span of houseflies can be extended by preventing physical activity. This theory has been bolstered by several new studies linking lower basal metabolic rate to increased life expectancy, across the animal kingdom—including humans. Calorie restriction and reduced thyroid hormone levels, both of which decrease the metabolic rate, have been associated with higher longevity in animals.
However, the ratio of total daily energy expenditure to resting metabolic rate can vary between 1.6 and 8.0 between species of mammals. Animals also vary in the degree of coupling between oxidative phosphorylation and ATP production, the amount of saturated fat in mitochondrial membranes, the amount of DNA repair, and many other factors that affect maximum life span.
One problem with understanding the associations of lifespan and metabolism is that changes in metabolism are often confounded by other factors that may affect lifespan. For example under calorie restriction whole body metabolic rate goes down with increasing levels of restriction, but body temperature also follows the same pattern. By manipulating the ambient temperature and exposure to wind it was shown in mice and hamsters that body temperature is a more important modulator of lifespan than metabolic rate. | 1 | Applied and Interdisciplinary Chemistry |
The calculation of the structure factor for cases differing from ideal polymer chains can be quite cumbersome, and sometimes impossible to complete analytically. However, when the small-angle scattering condition is met, , the sinc term can be expanded so one gets:
and by utilising the definition of the radius of gyration:
where the final transition utilises once again the small-angle approximation.
We can thus approximate the scattering intensity in the small-angle regime as:
and by plotting vs. , a so-called "Guinier plot", we may determine the radius of gyration from the slope of this linear curve. This measure is one of many examples of how scattering experiments of polymers can reveal basic properties of those polymer chains. | 0 | Theoretical and Fundamental Chemistry |
One of the oldest methods is called the multiple tube method. In this method a measured sub-sample (perhaps 10 ml) is diluted with 100 ml of sterile growth medium and an aliquot of 10 ml is then decanted into each of ten tubes. The remaining 10 ml is then diluted again and the process repeated. At the end of 5 dilutions this produces 50 tubes covering the dilution range of 1:10 through to 1:10000.
The tubes are then incubated at a pre-set temperature for a specified time and at the end of the process the number of tubes with growth in is counted for each dilution. Statistical tables are then used to derive the concentration of organisms in the original sample. This method can be enhanced by using indicator medium which changes colour when acid forming species are present and by including a tiny inverted tube called a Durham tube in each sample tube. The Durham inverted tube catches any gas produced. The production of gas at 37 degrees Celsius is a strong indication of the presence of Escherichia coli. | 0 | Theoretical and Fundamental Chemistry |
Phosphoranes of the type RP=CR are more common and more important. Phosphoranes are also considered to be one of the resonance structures of ylides, these compounds feature a tetrahedral phosphorus center including a phosphorus–carbon double bond. These compounds are used as reagents in the Wittig reaction, for instance methylenetriphenylphosphorane or PhP=CH. | 0 | Theoretical and Fundamental Chemistry |
This study examined the clinical history of the CSF and urine of two Greek siblings who were both diagnosed with SR deficiency. Both siblings displayed delayed psychomotor development and a movement disorder. The diagnosis was confirmed by measuring the SR enzyme activity and mutation analysis. The mutation analysis of the gene was performed using genomic DNA isolated from blood samples. The results concluded that both patients have low concentrations of HVA and HIAA and high concentrations of sepiapterin in the CSF, but neopterin and biopterin were abnormal in only one sibling. The results of this research indicates that when diagnosing the SR deficiency, the quantification of sepiapterin in the CSF is more important and indicative of SR deficiency than using neopterin and biopterin alone. The results also show that the urine concentrations of neurotransmitter metabolites are abnormal in patients with this disorder. This finding may provide an initial and easier indication of the deficiency before CSF analysis is performed. | 1 | Applied and Interdisciplinary Chemistry |
Many modifications to the simple blade-element theory have been suggested in order to make it more complete and to improve its accuracy. Most of these modified theories attempt to take into account the blade interference, and, in some of them, attempts are also made to eliminate the inaccuracy due to the use of airfoil data from tests on wings having a finite aspect ratio, such as 6. The first modification to be made was in the nature of a combination of the simple Drzewiecki theory with the Froude momentum theory. | 1 | Applied and Interdisciplinary Chemistry |
In coordination chemistry, clathrochelates are ligands that encapsulate metal ions. Chelating ligands bind to metals more strongly than related monodentate ligands, and macrocyclic ligands bind more strongly than typical chelating ligands. It follows that bi- or polymacrocyclic ligands would bind to metals particularly strongly. Clathrochelates are usually derived from bimacrocyclic ligands.
The first examples were derived from the tris(dioximate)s of cobalt(III) and iron(II). The synthesis entails replacement of the hydrogen-bonded proton center with or group:
Also well known are the clathrochelates called sepulchrates derived from tris(ethylenediamine)cobalt(III):
The insertion and removal of metals from the binding pocket of clathrochelates can be very slow. For this reason, many clathrochelates are prepared by the reactions of pre-coordinated ligands. These reactions often do not directly break any metal-ligand bonds, but occur in the second coordination sphere. The slowness of the metal ion exchange enables certain experiments that would otherwise be difficult or impossible. For example, it is possible to optically resolve the equivalent of . In the absence of the special geometry imposed by the clathrochelate, the lifetime of Co(II)-amine complexes is typically very short. In this way, this family of complexes enables studies on self-exchange redox reactions between Co(II) and Co(III) partners that would be impossible with simpler ligand systems. | 0 | Theoretical and Fundamental Chemistry |
Histidine-tryptophan-ketoglutarate, or Custodiol HTK solution, is a high-flow, low-potassium preservation solution used for organ transplantation. The solution was initially developed by Hans-Jürgen Bretschneider.
HTK solution is intended for perfusion and flushing of donor liver, kidney, heart, lung and pancreas prior to removal from the donor and for preserving these organs during hypothermic storage and transport to the recipient. HTK solution is based on the principle of inactivating organ function by withdrawal of extracellular sodium and calcium, together with intensive buffering of the extracellular space by means of histidine/histidine hydrochloride, so as to prolong the period during which the organs will tolerate interruption of oxygenated blood. The composition of HTK is similar to that of intracellular fluid. All of the components of HTK occur naturally in the body. The osmolarity of HTK is 310 mOsm/L. | 1 | Applied and Interdisciplinary Chemistry |
The microprocessor complex is a protein complex involved in the early stages of processing microRNA (miRNA) and RNA interference (RNAi) in animal cells. The complex is minimally composed of the ribonuclease enzyme Drosha and the dimeric RNA-binding protein DGCR8 (also known as Pasha in non-human animals), and cleaves primary miRNA substrates to pre-miRNA in the cell nucleus. Microprocessor is also the smaller of the two multi-protein complexes that contain human Drosha. | 1 | Applied and Interdisciplinary Chemistry |
Simulation can be carried out at different effective plasmatic therapeutic level of the drugs to identify the level at which cardiotoxicity cannot be neglected. The data collected could be finally managed to create a score system aimed to define the torsadogenic risk, namely the risk of inducing torsade de pointes, of the new drugs.
A possible torsade de point risk score to assess cardiotoxicity could be:
where is the sum of all concentrations, [C] is the concentration taken into account, , is the total number of models in the population, and represents the number of models showing repolarization abnormalities. | 1 | Applied and Interdisciplinary Chemistry |
Often referred to as a bearing heater, the mains frequency unit employs standard transformer principles for its operation. An internal winding is wound around a laminated core similar to a standard mains transformer. The core is then passed through the work-piece and when the primary coil is energised, a magnetic flux is created around the core. The work-piece acts as a short circuit secondary of the transformer created, and due to the laws of induction, a current flows in the work-piece and heat is generated. The core is normally hinged or clamped in some way to allow loading or unloading, which is usually a manual operation. To cover variations in part diameter, the majority of units will have spare cores available which help to optimise performance. Once the part is heated to the correct temperature, assembly can take place either by hand or in the relevant jig or machine press. | 1 | Applied and Interdisciplinary Chemistry |
Anders Meibom (born 9 September 1969) is a Danish interdisciplinary scientist and former football player active in the field of bio-geochemistry. He is a professor at the École Polytechnique Fédérale de Lausanne (EPFL), where he heads the laboratory for biological geochemistry. | 0 | Theoretical and Fundamental Chemistry |
There are slight iron isotopic variations in the oceans relative to IRMM-014, which likely reflect variations in the biogeochemical cycling of iron within a given ocean basin. In the southeastern Atlantic, δFe values between -0.13 and +0.21‰ have been measured. In the north Atlantic, δFe values between -1.35 and +0.80‰ have been measured. In the equatorial Pacific δFe values between -0.03 and +0.58‰ have been measured. The supply of aerosol iron particles to the ocean have an isotopic composition of approximately 0‰. Dissolved iron riverine input to the ocean is isotopically light relative to igneous rocks, with δFe values between -1 and 0‰.
Most modern marine sediments have δFe values similar to those of igneous δFe values. Marine ferromanganese nodules have δFe values between -0.8 and 0‰. | 0 | Theoretical and Fundamental Chemistry |
Microarrays contain single-stranded oligonucleotides with sequences from the human genome to tile the region of interest fixed to the surface. Genomic DNA is sheared to form double-stranded fragments. The fragments undergo end-repair to produce blunt ends and adaptors with universal priming sequences are added. These fragments are hybridized to oligos on the microarray.
Unhybridized fragments are washed away and the desired fragments are eluted. The fragments are then amplified using PCR.
Roche NimbleGen was first to take the original DGS technology and adapt it for next-generation sequencing. They developed the Sequence Capture Human Exome 2.1M Array to capture ~180,000 coding exons. This method is both time-saving and cost-effective compared to PCR based methods. The Agilent Capture Array and the comparative genomic hybridization array are other methods that can be used for hybrid capture of target sequences. Limitations in this technique include the need for expensive hardware as well as a relatively large amount of DNA. | 1 | Applied and Interdisciplinary Chemistry |
The Great Calcite Belt (GCB) of the Southern Ocean is a region of elevated summertime upper ocean calcite concentration derived from coccolithophores, despite the region being known for its diatom predominance. The overlap of two major phytoplankton groups, coccolithophores and diatoms, in the dynamic frontal systems characteristic of this region provides an ideal setting to study environmental
influences on the distribution of different species within these taxonomic groups.
The Great Calcite Belt, defined as an elevated particulate inorganic carbon (PIC) feature occurring alongside seasonally elevated chlorophyll a in austral spring and summer in the Southern Ocean, plays an important role in climate fluctuations, accounting for over 60% of the Southern Ocean area (30–60° S). The region between 30° and 50° S has the highest uptake of anthropogenic carbon dioxide (CO) alongside the North Atlantic and North Pacific oceans. Knowledge of the impact of interacting environmental influences on phytoplankton distribution in the Southern Ocean is limited. For example, more understanding is needed of how light and iron availability or temperature and pH interact to control phytoplankton biogeography. Hence, if model parameterizations are to improve to provide accurate predictions of biogeochemical change, a multivariate understanding of the full suite of environmental drivers is required.
The Southern Ocean has often been considered as a microplankton-dominated (20–200 µm) system with phytoplankton blooms dominated by large diatoms and Phaeocystis sp. However, since the identification of the GCB as a consistent feature and the recognition of picoplankton (< 2 µm) and nanoplankton (2–20 µm) importance in high-nutrient, low-chlorophyll (HNLC) waters, the dynamics of small (bio)mineralizing plankton and their export need to be acknowledged. The two dominant biomineralizing phytoplankton groups in the GCB are coccolithophores and diatoms. Coccolithophores are generally found north of the polar front, though Emiliania huxleyi has been observed as far south as 58° S in the Scotia Sea, at 61° S across Drake Passage, and at 65°S south of Australia.
Diatoms are present throughout the GCB, with the polar front marking a strong divide between different size fractions. North of the polar front, small diatom species, such as Pseudo-nitzschia spp. and Thalassiosira spp., tend to dominate numerically, whereas large diatoms with higher silicic acid requirements (e.g., Fragilariopsis kerguelensis) are generally more abundant south of the polar front. High abundances of nanoplankton (coccolithophores, small diatoms, chrysophytes) have also been observed on the Patagonian Shelf and in the Scotia Sea. Currently, few studies incorporate small biomineralizing phytoplankton to species level. Rather, the focus has often been on the larger and noncalcifying species in the Southern Ocean due to sample preservation issues (i.e., acidified Lugol’s solution dissolves calcite, and light microscopy restricts accurate identification to cells > 10 µm. In the context of climate change and future ecosystem function, the distribution of biomineralizing phytoplankton is important to define when considering phytoplankton interactions with carbonate chemistry, and ocean biogeochemistry.
The Great Calcite Belt spans the major Southern Ocean circumpolar fronts: the Subantarctic front, the polar front, the Southern Antarctic Circumpolar Current front, and occasionally the southern boundary of the Antarctic Circumpolar Current. The subtropical front (at approximately 10 °C) acts as the northern boundary of the GCB and is associated with a sharp increase in PIC southwards. These fronts divide distinct environmental and biogeochemical zones, making the GCB an ideal study area to examine controls on phytoplankton communities in the open ocean. A high PIC concentration observed in the GCB (1 µmol PIC L) compared to the global average (0.2 µmol PIC L) and significant quantities of detached E. huxleyi coccoliths (in concentrations > 20,000 coccoliths mL) both characterize the GCB. The GCB is clearly observed in satellite imagery spanning from the Patagonian Shelf across the Atlantic, Indian, and Pacific oceans and completing Antarctic circumnavigation via the Drake Passage. | 0 | Theoretical and Fundamental Chemistry |
Spermine synthase (, spermidine aminopropyltransferase, spermine synthetase) is an enzyme that converts spermidine into spermine. This enzyme catalyses the following chemical reaction
: S-adenosylmethioninamine + spermidine S-methyl-5'-thioadenosine + spermine
Spermine synthase is an enzyme involved in polyamine biosynthesis. It is present in all eukaryotes and plays a role in a variety of biological functions in plants Its structure consists of two identical monomers of 41 kDa with three domains each, creating a homodimer formed via dimerization. The interactions between one of the three domains, the N-terminals of the monomers, is responsible for dimerization as that is where the active site is located; the central terminal consisting of four β- strands structurally forming a lid for the third domain, the C-terminal domain. | 1 | Applied and Interdisciplinary Chemistry |
As a postdoctoral researcher, Holmes worked on the total synthesis of Vitamin B with Albert Eschenmoser.
In 1972 he was appointed as a demonstrator to the University of Cambridge where he stayed for 32 years, ultimately as Professor of Organic and Polymer Chemistry, and Director of the Melville Laboratory for Polymer Synthesis where he oversaw the founding and initial decade of the Melville Laboratory.
Holmes early work at Cambridge expanded his interest in new techniques for synthesising small molecules that are biologically-active and practically-useful, including natural products (such as alkaloids) and peptidomimetics. In 1989, during systematic characterisation of a newly synthesised conductive polymer, Chloe Jennings working in Holmes research group observed that the polymer emitted light when a current was passed through it. An intensive period of research in Holmes group, and other polymer chemistry groups, led to the discovery of differently-coloured light-emitting polymers that spanned the visible colour spectrum. A subsequent collaboration with physicist Richard Friend and co-workers at Cambridges Cavendish Laboratory revealed the potential of these conjugated polymers for applications such as organic LEDs and rollable displays.
Friend and Holmes co-founded the company Cambridge Display Technology for commercial exploitation of these materials – an early success story of Silicon Fen.
In 2004 Holmes returned to his native Australia on a Federation Fellowship, to lead a group at the newly established Bio21 Institute. He has pursued the application of photovoltaic polymers to solar energy, and was instrumental in forming the Victorian Organic Solar Cell Consortium. He has also continued to develop new syntheses of novel, biologically-useful materials. An example is his groups' synthesis of phosphoinositides, amphiphilic phospholipids situated in the cell membrane, which collaborators at the Ludwig Institute for Cancer Research have used to probe the dynamics of signal transduction (intercellular signalling being an important component of many aspects of cell biology, including that of tumors).
Holmes has served on the editorial or advisory boards of numerous learned scientific journals, including Organic Letters, Chemical Communications and Angewandte Chemie. In 2006, his 1998 paper on electroluminescent polymers was the most highly cited paper in Angewandte Chemie's 120-year history. By August 2012 he had authored over 490 scientific papers and 52 patent applications.
In 2014 he was appointed as President of the Australian Academy of Science. | 0 | Theoretical and Fundamental Chemistry |
By reducing flow velocity to limit solids being transported along with fast flowing liquid, separation can occur. Approximately 35–60% of the solids is removed from dilute liquid slurry, with 10 minutes detention time, with a common detention time of 30 to 60 minutes. Due to the inadequate consideration of critical design criteria, most settling basins built were oversized and had low efficiency.
Settling basins used in dairy production reduce the nutrient-loading on a vegetative filter strip from lot runoff, thus decreasing the required lagoon volume for a new facility. Moreover, settling basins are useful to remove unwanted solid materials, such as hay, straw and feathers from the waste stream before flowing to the lagoon, aids to reduce smell and avoid crust formation on the lagoon surface. A baffle may be used to retain the floating solids removed. There are two types of settling basins, based on the method of removing solids. With one type, the solids are removed mechanically (after the free water has drained away), usually with a front-end or skid-steer loader. The other type uses hydraulic (pump) removal of the solids. Typically, pumping is initiated when the basin is half full of solids and the remainder is water. Vigorous agitation is needed to mix the liquid and the solids, preferably by propeller-type agitators or pumps with agitation nozzles. | 1 | Applied and Interdisciplinary Chemistry |
A defining feature of sand closures is the movement and subsequent loss of the construction material. The principle underpinning a sand closure relies on the production of more sand than what is lost during the process. Sand losses occur daily under average flow conditions through the closing gap, contingent upon the flow dynamics. In the context of "strength and load," the "strength" of a sand closure is represented by its production capacity, while the "load" is the resultant loss. A closure is deemed successful when the production exceeds the loss, leading to a gradual narrowing of the closing gap.
The production capacity, which includes a sufficiently large extraction site for the sand, must surpass the maximum anticipated loss during the closure operation. Consequently, the feasibility study for a (complete) sand closure must initially concentrate on identifying the phase associated with maximum losses. Employing hydraulic boundary conditions, the sand loss for each closure phase can be calculated and depicted graphically as illustrated. The horizontal axis in the diagram represents the closing gap's size, indicating that the depicted capacity is insufficient for a sand closure under these conditions.
A sand closure becomes viable if sufficient sand production can be sustained near the closure gap to overcome the phase with the highest losses. The essential criterion is that the average tidal loss remains lower than the production. However, considerable uncertainties exist in both the calculated losses and the anticipated production, necessitating careful attention. The loss curve, as a function of the closing gap area, typically exhibits a single peak. The maximal loss is usually found when the closing gap area is between 0 and 30% of its initial size. Hence, initial loss calculations can be restricted to this range of closing gap sizes.
Interestingly, the peak sand loss does not coincide with the near completion of the closure gap. Despite potentially high flow velocities, the eroded width of the closing hole is minimal, thus keeping overall sand losses low. Hydraulic boundary conditions can be determined using a storage/area approach.
In general, sand closures are theoretically feasible for maximum flow velocities up to approximately 2.0 to 2.5 m/s. Beyond these velocities, achieving a sand closure becomes virtually impossible due to the resulting flow rates, which are influenced by the reference flow rate U and the discharge coefficient μ. The discharge coefficient μ is affected by both friction and deceleration losses within the closing gap, with friction losses being notably significant due to the large dimensions of the sand dams. Consequently, the choice of gradient measurement distance significantly impacts the discharge coefficient, which exhibits considerable variability. However, this variability diminishes during the crucial final phase of the closure, where a value of 0.9 is recommended as a reasonable upper limit for the discharge coefficient. The actual flow velocity within the closing gap is determined by applying the storage area approach, adjusted by the discharge coefficient. | 1 | Applied and Interdisciplinary Chemistry |
The microscopic model and most optical properties of ensembles of the NV centers have been firmly established in the 1970s based on the optical measurements combined with uniaxial stress and on the electron paramagnetic resonance. However, a minor error in EPR results (it was assumed that illumination is required to observe NV EPR signals) resulted in the incorrect multiplicity assignments in the energy level structure. In 1991 it was shown that EPR can be observed without illumination, which established the energy level scheme shown above. The magnetic splitting in the excited state has been measured only recently.
The characterization of single NV centers has become a very competitive field nowadays, with many dozens of papers published in the most prestigious scientific journals. One of the first results was reported back in 1997. In that paper, it was demonstrated that the fluorescence of single NV centers can be detected by room-temperature fluorescence microscopy and that the defect shows perfect photostability. Also one of the outstanding properties of the NV center was demonstrated, namely room-temperature optically detected magnetic resonance. | 0 | Theoretical and Fundamental Chemistry |
The psychrometric chart depicts the changes of the cycle to the standard air conditioning cycle. First, the end state point 4 for air from the wheel represents a latent ratio increase (moisture removal) to about 45%, as opposed to the 25% of the typical coil shown. Secondly, the air quality delivered by the cycle is much dryer, about 55% RH (state point 4), rather than 98% with the standard coil (state point 4). Third, this is accomplished with a higher average evaporator temperature. Compare the midpoint of the evaporators temperature, line 1 to 4’, to the midpoint of the Cromer cycles evaporators temperature, line 2 to 3. These lines represent the work done by the coil on the air stream (its change in enthalpy). This is significant because, given a constant condenser temperature and equivalent change in enthalpy, the higher the evaporator coil temperature, the more efficient is the Carnot refrigeration cycle and the greater the energy efficiency a particular system can deliver.
Common dehumidification strategies include: reheating (electric or hot-gas bypass), where sensible heat is added to the air leaving the equipment; recuperative heat (run-around coils or heat pipes), where sensible heat is transferred from the return air to the supply air; or the Cromer cycle, where the latent heat of moisture sorption and evaporation is transferred from the return air to the supply air. These various strategies were compared in an ASHRAE Journal article that found that "the Cromer cycle produces similar enhanced dehumidification performance as is obtained with recuperative configurations." | 0 | Theoretical and Fundamental Chemistry |
*The lac operon consists of 3 structural genes, and a promoter, a terminator, regulator, and an operator. The three structural genes are: lacZ, lacY, and lacA.
**lacZ encodes β-galactosidase (LacZ), an intracellular enzyme that cleaves the disaccharide lactose into glucose and galactose.
** lacY encodes Beta-galactoside permease (LacY), a transmembrane symporter that pumps β-galactosides including lactose into the cell using a proton gradient in the same direction. Permease increases the permeability of the cell to β-galactosides.
** lacA encodes β-galactoside transacetylase (LacA), an enzyme that transfers an acetyl group from acetyl-CoA to thiogalactoside.
Only lacZ and lacY appear to be necessary for lactose catabolic pathway. | 1 | Applied and Interdisciplinary Chemistry |
* Bethea, R. M. 1978. Air Pollution Control Technology. New York: Van Nostrand Reinhold.
* National Asphalt Pavement Association. 1978. The Maintenance and Operation of Exhaust Systems in the Hot Mix Batch Plant. 2nd ed. Information Series 52.
* Perry, J. H. (Ed.). 1973. Chemical Engineers’ Handbook. 5th ed. New York: McGraw-Hill.
* Richards, J. R. 1995. Control of Particulate Emissions (APTI Course 413). U.S. Environmental Protection Agency.
* Richards, J. R. 1995. Control of Gaseous Emissions. (APTI Course 415). U.S. Environmental Protection Agency.
* Schifftner, K. C. 1979, April. Venturi scrubber operation and maintenance. Paper presented at the U.S. EPA Environmental Research Information Center. Atlanta, GA.
* Semrau, K. T. 1977. Practical process design of particulate scrubbers. Chemical Engineering. 84:87-91.
* U.S. Environmental Protection Agency. 1982, September. Control Techniques for Particulate Emissions from Stationary Sources. Vol. 1. EPA 450/3-81-005a.
* Wechselblatt, P. M. 1975. Wet scrubbers (particulates). In F. L. Cross and H. E. Hesketh (Eds.), Handbook for the Operation and Maintenance of Air Pollution Control Equipment. Westport: Technomic Publishing. | 0 | Theoretical and Fundamental Chemistry |
Molecular self-assembly is an important aspect of bottom-up approaches to nanotechnology. Using molecular self-assembly, the final (desired) structure is programmed in the shape and functional groups of the molecules. Self-assembly is referred to as a bottom-up manufacturing technique in contrast to a top-down technique such as lithography where the desired final structure is carved from a larger block of matter. In the speculative vision of molecular nanotechnology, microchips of the future might be made by molecular self-assembly. An advantage to constructing nanostructure using molecular self-assembly for biological materials is that they will degrade back into individual molecules that can be broken down by the body. | 0 | Theoretical and Fundamental Chemistry |
SAD analysis is widely used in material research for its relative simplicity and high information value. Once the sample is prepared and examined in a modern transmission electron microscope, the device allows for a routine diffraction acquisition in a matter of seconds. If the images are interpreted correctly, they can be used to identify crystal structures, determine their orientations, measure crystal characteristics, examine crystal defects or material textures. The course of analysis depends on whether the diffractogram depicts ring or spot diffraction pattern and on the quantity to be determined.
Software tools based on computer vision algorithms simplifies quantitative analysis. | 0 | Theoretical and Fundamental Chemistry |
Trandolapril is an ACE inhibitor used to treat high blood pressure. It may also be used to treat other conditions. It is similar in structure to another ramipril but has a cyclohexane group. It is a prodrug that must be metabolized into its active form. It has a longer half-life when compared to other agents in this class.
It was patented in 1981 and approved for medical use in 1993. It is marketed by Abbott Laboratories under the brand name Mavik. | 0 | Theoretical and Fundamental Chemistry |
KT5720 is a kinase inhibitor with specificity towards protein kinase A. It is a semi-synthetic derivative of K252a and analog of staurosporine. | 1 | Applied and Interdisciplinary Chemistry |
When Emerson exposed green plants to differing wavelengths of light, he noticed that at wavelengths of greater than 680 nm the efficiency of photosynthesis decreased abruptly despite the fact that this is a region of the spectrum where chlorophyll still absorbs light (chlorophyll is the green pigment in plants - it absorbs mainly the red and blue wavelengths from light). When the plants were exposed to short-wavelength light, (less than 660 nm), the efficiency also decreased.
Emerson then exposed the plants to both short and long wavelengths at the same time, causing the efficiency to increase greatly. He concluded that there must be two different photosystems involved in photosynthesis, one driven by short-wavelength light and one driven by long-wavelength (PS1 and PS2). They work together to enhance efficiency and convert the light energy to forms that can be absorbed by the plant.
The light excites the chlorophyll molecules at the reaction centre and causes an increase in energy. As the molecule becomes less excited, its energy is transported through a chain of electron carriers to the next photosystem which does much the same thing and produces energy-carrying organic molecules. | 0 | Theoretical and Fundamental Chemistry |
Shaving cream is an example of a complex fluid. Without stress, the foam appears to be a solid: it does not flow and can support (very) light loads. However, when adequate stress is applied, shaving cream flows easily like a fluid. On the level of individual bubbles, the flow is due to rearrangements of small collections of bubbles. On this scale, the flow is not smooth, but instead consists of fluctuations due to rearrangements of the bubbles and releases of stress. These fluctuations are similar to the fluctuations that are studied in earthquakes. | 1 | Applied and Interdisciplinary Chemistry |
Beryllium derivatives and reagents are often prepared by alkylation of beryllium chloride. Examples of known organoberyllium compounds are dineopentylberyllium, beryllocene (CpBe), diallylberyllium (by exchange reaction of diethyl beryllium with triallyl boron), bis(1,3-trimethylsilylallyl)beryllium and Be(mes)2. Ligands can also be aryls and alkynyls. | 0 | Theoretical and Fundamental Chemistry |
Initially, this particular lactoperoxidase-catalyzed compound was originally discovered while viewing the specific environment of cystic fibrosis patients' weakened respiratory immune system against bacterial infection.
Symptoms of cystic fibrosis include an inability to secrete sufficient quantities of SCN which results in a shortage of necessary hypothiocyanite, resulting in increasing mucous viscosity, inflammation and bacterial infection in the respiratory tract.
Lactoferrin with hypothiocyanite has been granted orphan drug status by the EMEA and the FDA.
Naturally, the discovery correlated with studies exploring different methods seeking to further gain alternative antibiotics, understanding that most older antibiotics are decreasing in effectiveness against bacteria with antibiotic resistance.
OSCN, which is not an antibiotic, has proved efficacy on superbugs including MRSA reference strains, BCC, Mucoid PA
Schema of LPO/SCN/HO in human lung: | 1 | Applied and Interdisciplinary Chemistry |
The Sandia method (also known as Veers method) is a method for generating a turbulent wind profile that can be used in aero-elastic software to evaluate the fatigue imparted on a turbine in a turbulent environment. That is, it generates time series of wind speeds at a set of points on a surface, say the plane of the rotor of a wind turbine. Analysis is performed initially in the frequency domain, where turbulence can be described quantitatively with more ease than the time domain. Then, the time series are obtained by inverse fast Fourier transforms.
In its original form, the Sandia method only simulates the u-component of the wind; that is, the wind was modelled as propagating in a direction perpendicular to the plane of the rotor. Work carried out by NREL, specifically Kelley, suggested that a considerable amount of turbulent energy existed in the v-component (the v-component is parallel to both the plane of the rotor and the Earth). As such, the Sandia method was upgraded such that it included the v-component and w-component. Further upgrades have been performed such that the wind profile exhibits cross-axis correlation (turbulent fluctuations in one component being somehow connected to turbulent fluctuations in another). However, these are not considered in this article. | 1 | Applied and Interdisciplinary Chemistry |
The integrated stress response is a cellular stress response conserved in eukaryotic cells that downregulates protein synthesis and upregulates specific genes in response to internal or environmental stresses. | 1 | Applied and Interdisciplinary Chemistry |
The relationship between humans and rivers, which represent freshwater environments, is complicated. Rivers serve primarily as a freshwater resource and as sinks for domestic and industrial waste water. The consequences from this usage occur from diverse activities and root themselves in complex, interdisciplinary systems and practices.
Environmental changes in rivers usually result from human development, such as population growth, the dependence on fossil resources, urbanization, global commerce and industrial and agricultural emission. Anthropogenic activities also include discrete elements like the use of fire, domestication of plants and animals, soil development, the establishment of settlements and irrigation. River ecosystems have been transformed downstream from the point of pollution. Active human transformations, river engineering, have altered the river systems and ecosystems. | 1 | Applied and Interdisciplinary Chemistry |
Although of no commercial significance, many other routes to benzene exist. Phenol and halobenzenes can be reduced with metals. Benzoic acid and its salts undergo decarboxylation to benzene. The reaction of the diazonium compound derived from aniline with hypophosphorus acid gives benzene. Alkyne trimerisation of acetylene gives benzene. Complete decarboxylation of mellitic acid gives benzene. | 1 | Applied and Interdisciplinary Chemistry |
In physics, the cross section is a measure of the probability that a specific process will take place in a collision of two particles. For example, the Rutherford cross-section is a measure of probability that an alpha particle will be deflected by a given angle during an interaction with an atomic nucleus. Cross section is typically denoted (sigma) and is expressed in units of area, more specifically in barns. In a way, it can be thought of as the size of the object that the excitation must hit in order for the process to occur, but more exactly, it is a parameter of a stochastic process.
When two discrete particles interact in classical physics, their mutual cross section is the area transverse to their relative motion within which they must meet in order to scatter from each other. If the particles are hard inelastic spheres that interact only upon contact, their scattering cross section is related to their geometric size. If the particles interact through some action-at-a-distance force, such as electromagnetism or gravity, their scattering cross section is generally larger than their geometric size.
When a cross section is specified as the differential limit of a function of some final-state variable, such as particle angle or energy, it is called a differential cross section (see detailed discussion below). When a cross section is integrated over all scattering angles (and possibly other variables), it is called a total cross section or integrated total cross section. For example, in Rayleigh scattering, the intensity scattered at the forward and backward angles is greater than the intensity scattered sideways, so the forward differential scattering cross section is greater than the perpendicular differential cross section, and by adding all of the infinitesimal cross sections over the whole range of angles with integral calculus, we can find the total cross section.
Scattering cross sections may be defined in nuclear, atomic, and particle physics for collisions of accelerated beams of one type of particle with targets (either stationary or moving) of a second type of particle. The probability for any given reaction to occur is in proportion to its cross section. Thus, specifying the cross section for a given reaction is a proxy for stating the probability that a given scattering process will occur.
The measured reaction rate of a given process depends strongly on experimental variables such as the density of the target material, the intensity of the beam, the detection efficiency of the apparatus, or the angle setting of the detection apparatus. However, these quantities can be factored away, allowing measurement of the underlying two-particle collisional cross section.
Differential and total scattering cross sections are among the most important measurable quantities in nuclear, atomic, and particle physics.
With light scattering off of a particle, the cross section specifies the amount of optical power scattered from light of a given irradiance (power per area). It is important to note that although the cross section has the same units as area, the cross section may not necessarily correspond to the actual physical size of the target given by other forms of measurement. It is not uncommon for the actual cross-sectional area of a scattering object to be much larger or smaller than the cross section relative to some physical process. For example, plasmonic nanoparticles can have light scattering cross sections for particular frequencies that are much larger than their actual cross-sectional areas. | 0 | Theoretical and Fundamental Chemistry |
Two different regimes may be distinguished in the nucleate boiling range. When the temperature difference is between approximately above T, isolated bubbles form at nucleation sites and separate from the surface. This separation induces considerable fluid mixing near the surface, substantially increasing the convective heat transfer coefficient and the heat flux. In this regime, most of the heat transfer is through direct transfer from the surface to the liquid in motion at the surface and not through the vapor bubbles rising from the surface.
Between above T, a second flow regime may be observed. As more nucleation sites become active, increased bubble formation causes bubble interference and coalescence. In this region the vapor escapes as jets or columns which subsequently merge into plugs of vapor.
Interference between the densely populated bubbles inhibits the motion of liquid near the surface. This is observed on the graph as a change in the direction of the gradient of the curve or an inflection in the boiling curve. After this point, the heat transfer coefficient starts to reduce as the surface temperature is further increased although the product of the heat transfer coefficient and the temperature difference (the heat flux) is still increasing.
When the relative increase in the temperature difference is balanced by the relative reduction in the heat transfer coefficient, a maximum heat flux is achieved as observed by the peak in the graph. This is the critical heat flux. At this point in the maximum, considerable vapor is being formed, making it difficult for the liquid to continuously wet the surface to receive heat from the surface. This causes the heat flux to reduce after this point. At extremes, film boiling commonly known as the Leidenfrost effect is observed.
The process of forming steam bubbles within liquid in micro cavities adjacent to the wall if the wall temperature at the heat transfer surface rises above the saturation temperature while the bulk of the liquid (heat exchanger) is subcooled. The bubbles grow until they reach some critical size, at which point they separate from the wall and are carried into the main fluid stream. There the bubbles collapse because the temperature of bulk fluid is not as high as at the heat transfer surface, where the bubbles were created. This collapsing is also responsible for the sound a water kettle produces during heat up but before the temperature at which bulk boiling is reached.
Heat transfer and mass transfer during nucleate boiling has a significant effect on the heat transfer rate. This heat transfer process helps quickly and efficiently to carry away the energy created at the heat transfer surface and is therefore sometimes desirable—for example in nuclear power plants, where liquid is used as a coolant.
The effects of nucleate boiling take place at two locations:
* the liquid-wall interface
* the bubble-liquid interface
The nucleate boiling process has a complex nature. A limited number of experimental studies provided valuable insights into the boiling phenomena, however these studies provided often contradictory data due to internal recalculation (state of chaos in the fluid not applying to classical thermodynamic methods of calculation, therefore giving wrong return values) and have not provided conclusive findings yet to develop models and correlations. Nucleate boiling phenomenon still requires more understanding. | 1 | Applied and Interdisciplinary Chemistry |
o-Cresolphthalein is a phthalein dye used as a pH indicator in titrations. It is insoluble in water but soluble in ethanol. Its solution is colourless below pH 8.2, and purple above 9.8. Its molecular formula is CHO. It is used medically to determine calcium levels in the human body, or to synthesize polyamides or polyimides. | 0 | Theoretical and Fundamental Chemistry |
The WGSR is exergonic, with the following thermodynamic parameters at room temperature (298 K):
In aqueous solution, the reaction is less exergonic. | 0 | Theoretical and Fundamental Chemistry |
Metagenomics is the study of genomic content of samples from same habitat, which is designed to determine the role and the extent of species diversity. Targeted or random sequencing are widely used with comparisons against sequence databases. Recent developments in sequencing technology increased the number of metagenomics samples. MEGAN is an easy to use tool for analysing such metagenomics data. First version of MEGAN was released in 2007 and the most recent version is MEGAN6. First version is capable of analysing taxonomic content of a single dataset while the latest version can analyse multiple datasets including new features (query different databases, new algorithm etc.). | 1 | Applied and Interdisciplinary Chemistry |
The Chemcatcher® concept was developed by Professors Richard Greenwood and Graham Mills at the University of Portsmouth, together with colleagues from Chalmers University of Technology, Sweden. The device is patented in a number of countries and the name is a registered trademark in Ireland and the United Kingdom
T.E. Laboratories (TelLab), based in Tullow, Ireland, holds the global licence to manufacture and sell Chemcatcher®. | 0 | Theoretical and Fundamental Chemistry |
The Δ splitting energy for tetrahedral metal complexes (four ligands), Δ is smaller than that for an octahedral complex. Consequently, tetrahedral complexes are almost always high spin Examples of low spin tetrahedral complexes include Fe(2-norbornyl), [Co(4-norbornyl)], and the nitrosyl complex Cr(NO)((N(tms)). | 0 | Theoretical and Fundamental Chemistry |
Norman Daly was awarded 6 patents in the years 1962–1973 relating to ion detection and mass spectrometers, from his work at the United Kingdom Atomic Energy Authority. | 0 | Theoretical and Fundamental Chemistry |
Medicinal Chemistry Research is a peer-reviewed scientific journal of medicinal chemistry emphasizing the structure-activity relationships of biologically active compounds. It was founded in 1991 by Alfred Burger (University of Virginia), who also founded the Journal of Medicinal Chemistry. The journal is currently edited by Longqin Hu. | 1 | Applied and Interdisciplinary Chemistry |
The naturally occurring calcium cycle has been altered by human intervention. Calcium is predominantly extracted from limestone deposits to be utilised by many industrial processes. Purification of iron ore and aluminium, replacing asbestos brake linings and some coatings for electric cables, are some of these major uses of calcium. Furthermore, calcium is used within the household to maintain alkaline pH of swimming pools, counteracting acidic disinfectants and in the food production industry to produce bicarbonate soda, some wines and dough.
With its widespread uses, a large volume of calcium must be obtained from mines and quarries to supply the high demand. As more limestone and water is removed from mines, underground stores of rock are often weakened making the ground more susceptible to sink holes. Sinkholes and mining both affect the presence of groundwater, potentially leading to a lower water table or altered pathways of flowing water. This may affect local ecosystems or farmland as the water supply is restricted. Additionally, the water that is released from mining areas will have higher concentrations of dissolved calcium. This can either be released into oceans or absorbed by the soil. Whilst not always detrimental, it alters the natural calcium cycle which may have flow-on effects for ecosystems. Furthermore, water being pumped from mines increases the danger of downstream flooding whilst simultaneously decreasing the volume on water in upstream reservoirs such as marshes, ponds of wetlands It is however important to note than limestone mining is comparatively less damaging than other mining process, with potential to restore the environment after the mine is no longer in use | 1 | Applied and Interdisciplinary Chemistry |
When used as an ingredient in food, antifoaming agents are intended to curb effusion or effervescence in preparation or serving. The agents are included in a variety of foods and in materials for food preparation; McDonald's includes polydimethylsiloxane (a type of silicone) in its oil to mitigate hazardous splashes of oil caused by foaming in fryers, so it has been listed as an ingredient in their chicken nuggets, french fries, and other fried menu items. | 0 | Theoretical and Fundamental Chemistry |
National Chemistry Day, first celebrated in 1987 by members of the American Chemical Society (ACS), educators and other individual volunteers, was a vision of the former ACS President Dr. George C. Pimentel. His goal was for ACS to hold a simultaneous event nationwide to impress on the public the importance of chemistry in everyday life. The first celebration was kicked off with a parade down the streets in Washington, D.C.
In 1989 the celebration was expanded to a biannual full-week event, and in 1993 National Chemistry Week became an annual celebration. | 1 | Applied and Interdisciplinary Chemistry |
Trimethylsilyl azide is incompatible with moisture, strong oxidizing agents, and strong acids. Azides are often explosive, as illustrated by their use in air bags. | 0 | Theoretical and Fundamental Chemistry |
A healthy American male soldier was given EA-3148, 1.15 µg/kg i.v.. Erythrocyte AChE values dropped precipitously to 22% of normal within 15 min of dosing and to 0% at 48 h; the value recovered to 88% of normal at 72 days post-exposure. Signs of toxicity were evident within 5-8 min of treatment in two comparably dosed subjects who felt dizzy, weak, tired, sweaty, and had hands and feet that were moist. Within 2 h post-exposure, these subjects reportedly were resting, eating, and feeling fine.
A U.S. Army report summarizing experience with EA-3148 noted anorexia, fatigue, poor sleep, unusual dreams, dizziness, euphoria, blurred vision, increased salivation, restlessness; decrements in a test of numerical facility in four individuals and exaggeration of a schizoid personality in one male soldier. | 1 | Applied and Interdisciplinary Chemistry |
The Deep-dose equivalent (DDE) is a measure of external radiation exposure defined by US regulations. It is reported alongside eye and shallow dose equivalents on typical US dosimetry reports. It represents the dose equivalent at a tissue depth of 1 cm (1000 mg/cm2) due to external whole-body exposure to ionizing radiation.
Dose due to external radiation tends to decrease with depth because of the shielding effects of outer tissues. The reference depth of 1 cm essentially discounts alpha and beta radiation that are easily shielded by the skin, clothing, and bone surface, while taking minimal credit for any self-shielding from the more penetrating gamma rays. This makes the deep-dose equivalent a conservative measure of internal organ exposure to external radiation, while eye and skin exposure to external radiation must be accounted differently. Deep-dose equivalent does include any contribution from internal contamination. | 0 | Theoretical and Fundamental Chemistry |
Click on genes, proteins and metabolites below to visit Gene Wiki pages and related Wikipedia articles. The pathway can be downloaded and edited at [http://www.wikipathways.org WikiPathways]. | 1 | Applied and Interdisciplinary Chemistry |
Zeta potential is the electrical potential at the slipping plane. This plane is the interface which separates mobile fluid from fluid that remains attached to the surface.
Zeta potential is a scientific term for electrokinetic potential in colloidal dispersions. In the colloidal chemistry literature, it is usually denoted using the Greek letter zeta (ζ), hence ζ-potential. The usual units are volts (V) or, more commonly, millivolts (mV). From a theoretical viewpoint, the zeta potential is the electric potential in the interfacial double layer (DL) at the location of the slipping plane relative to a point in the bulk fluid away from the interface. In other words, zeta potential is the potential difference between the dispersion medium and the stationary layer of fluid attached to the dispersed particle.
The zeta potential is caused by the net electrical charge contained within the region bounded by the slipping plane, and also depends on the location of that plane. Thus, it is widely used for quantification of the magnitude of the charge. However, zeta potential is not equal to the Stern potential or electric surface potential in the double layer, because these are defined at different locations. Such assumptions of equality should be applied with caution. Nevertheless, zeta potential is often the only available path for characterization of double-layer properties.
The zeta potential is an important and readily measurable indicator of the stability of colloidal dispersions. The magnitude of the zeta potential indicates the degree of electrostatic repulsion between adjacent, similarly charged particles in a dispersion. For molecules and particles that are small enough, a high zeta potential will confer stability, i.e., the solution or dispersion will resist aggregation. When the potential is small, attractive forces may exceed this repulsion and the dispersion may break and flocculate. So, colloids with high zeta potential (negative or positive) are electrically stabilized while colloids with low zeta potentials tend to coagulate or flocculate as outlined in the table.
Zeta potential can also be used for the pKa estimation of complex polymers that is otherwise difficult to measure accurately using conventional methods. This can help studying the ionisation behaviour of various synthetic and natural polymers under various conditions and can help in establishing standardised dissolution-pH thresholds for pH responsive polymers. | 0 | Theoretical and Fundamental Chemistry |
The Thorpe–Ingold effect, gem-dimethyl effect, or angle compression is an effect observed in chemistry where increasing steric hindrance favours ring closure and intramolecular reactions. The effect was first reported by Beesley, Thorpe, and Ingold in 1915 as part of a study of cyclization reactions. It has since been generalized to many areas of chemistry.
The comparative rates of lactone formation (lactonization) of various 2-hydroxybenzenepropionic acids illustrate the effect. The placement of an increasing number of methyl groups accelerates the cyclization process.
One application of this effect is addition of a quaternary carbon (e.g., a gem-dimethyl group) in an alkyl chain to increase the reaction rate and/or equilibrium constant of cyclization reactions. An example of this is an olefin metathesis reaction: In the field of peptide foldamers, amino acid residues containing quaternary carbons such as 2-aminoisobutyric acid are used to promote formation of certain types of helices.
One proposed explanation for this effect is that the increased size of the substituents increases the angle between them. As a result, the angle between the other two substituents decreases. By moving them closer together, reactions between them are accelerated. It is thus a kinetic effect.
The effect also has some thermodynamic contribution as the in silico strain energy decreases on going from cyclobutane to 1-methylcyclobutane and 1,1-dimethylcyclobutane by a value between 8 kcal/mole and 1.5 kcal/mole.
A noteworthy example of the Thorpe-Ingold effect in supramolecular catalysis is given by diphenylmethane derivatives provided with guanidinium groups. These compounds are active in the cleavage of the RNA model compound HPNP. Substitution of the methylene group of the parent diphenylmethane spacer with cyclohexylidene and adamantylidene moieties enhances catalytic efficiency, with gem dialkyl effect accelerations of 4.5 and 9.1, respectively. | 0 | Theoretical and Fundamental Chemistry |
Inclusions can create problems in the casting when they are large and in too high concentration. Here are examples of problems related to inclusions:
* Pinholes in light gauge foil
* Flange cracks in beverage containers
* Surface streaks in bright automotive trim and lithographic material
* Breakage in wire drawing operation
* Increased tool wear and tear
* Increased porosity
* Loss of pressure tightness of engine blocks
* Poor machinability
* Cosmetic defect in apparent surfaces
* Diminished mechanical properties (e.g. Ultimate Tensile Strength, Yield Strength, Elongation) | 1 | Applied and Interdisciplinary Chemistry |
Stiction refers to the characteristic of start-and-stop–type motion of a mechanical assembly. Consider a mechanical element slowly increasing an external force on an assembly at rest that is designed for the relative rotation or sliding of its parts in contact. The static contact friction between the assembly parts resists movement, causing the spring moments in the assembly to store mechanical energy. Any part of the assembly that can elastically bend, even microscopically, and exert a restoring force contributes a spring moment. Thus the "springs" in an assembly might not be obvious to the eye. The increasing external force finally exceeds the static friction resisting force, the spring moments, released, impulsively exert their restoring forces on both the moving assembly parts and, Newton's Third Law, in reaction on the external forcing element. The assembly parts then impulsively accelerate in motion with respect to each other though resisted by dynamic contact friction (in this context very much less than the static friction). However, the forcing element cannot accelerate at the same pace, fails to keep up and loses contact. The external force on the moving assembly momentarily drops to zero for lack of forcing mechanical contact even though the external force element continues its motion. The moving part then decelerates to a stop from the dynamic contact friction. The cycle repeats as the forcing element motion catches up to contact again. Stick, store spring energy, impulsively release spring energy, accelerate, decelerate, stop, stick. Repeat.
Stiction is a problem for the design and materials science of many moving linkages. This is particularly the case for linear sliding joints, rather than rotating pivots. Owing to simple geometry, the moving distance of a sliding joint in two comparable linkages is longer than the circumferential travel of a pivoting bearing, thus the forces involved (for equivalent work) are lower and stiction forces become proportionally more significant. This issue has often led to linkages being redesigned from sliding to purely pivoted structures, just to avoid problems with stiction. An example is the Chapman strut, a suspension linkage. | 0 | Theoretical and Fundamental Chemistry |
Historically it was assumed that the nucleation rate of new recrystallized grains would be determined by the thermal fluctuation model successfully used for solidification and precipitation phenomena. In this theory it is assumed that as a result of the natural movement of atoms (which increases with temperature) small nuclei would spontaneously arise in the matrix. The formation of these nuclei would be associated with an energy requirement due to the formation of a new interface and an energy liberation due to the formation of a new volume of lower energy material. If the nuclei were larger than some critical radius then it would be thermodynamically stable and could start to grow.
The main problem with this theory is that the stored energy due to dislocations is very low (0.1–1 J m) while the energy of a grain boundary is quite high (~0.5 J m). Calculations based on these values found that the observed nucleation rate was greater than the calculated one by some impossibly large factor (~10).
As a result, the alternate theory proposed by Cahn in 1949 is now universally accepted. The recrystallized grains do not nucleate in the classical fashion but rather grow from pre-existing sub-grains and cells. The incubation time is then a period of recovery where sub-grains with low-angle boundaries (<1–2°) begin to accumulate dislocations and become increasingly misoriented with respect to their neighbors. The increase in misorientation increases the mobility of the boundary and so the rate of growth of the sub-grain increases. If one sub-grain in a local area happens to have an advantage over its neighbors (such as locally high dislocation densities, a greater size or favorable orientation) then this sub-grain will be able to grow more rapidly than its competitors. As it grows its boundary becomes increasingly misoriented with respect to the surrounding material until it can be recognized as an entirely new strain-free grain. | 1 | Applied and Interdisciplinary Chemistry |
Magnesium ions (Mg) in cellular biology are usually in almost all senses opposite to Ca ions, because they are bivalent too, but have greater electronegativity and thus exert greater pull on water molecules, preventing passage through the channel (even though the magnesium itself is smaller). Thus, Mg ions block Ca channels such as (NMDA channels) and have been shown to affect gap junction channels forming electrical synapses. | 1 | Applied and Interdisciplinary Chemistry |
* Chaikin P. M. and Lubensky T. C. Principles of Condensed Matter Physics (Cambridge University Press, Cambridge) 1995, sect.9.
* Feynman R. P. Progress in Low Temperature Physics Vol.1, edited by C. Gorter (North Holland, Amsterdam) 1955. | 0 | Theoretical and Fundamental Chemistry |
Simple monosaccharides have a linear and unbranched carbon skeleton with one carbonyl (C=O) functional group, and one hydroxyl (OH) group on each of the remaining carbon atoms. Therefore, the molecular structure of a simple monosaccharide can be written as H(CHOH)(C=O)(CHOH)H, where ; so that its elemental formula is CHO.
By convention, the carbon atoms are numbered from 1 to x along the backbone, starting from the end that is closest to the C=O group. Monosaccharides are the simplest units of carbohydrates and the simplest form of sugar.
If the carbonyl is at position 1 (that is, n or m is zero), the molecule begins with a formyl group H(C=O)− and is technically an aldehyde. In that case, the compound is termed an aldose. Otherwise, the molecule has a ketone group, a carbonyl −(C=O)− between two carbons; then it is formally a ketone, and is termed a ketose. Ketoses of biological interest usually have the carbonyl at position 2.
The various classifications above can be combined, resulting in names such as "aldohexose" and "ketotriose".
A more general nomenclature for open-chain monosaccharides combines a Greek prefix to indicate the number of carbons (tri-, tetr-, pent-, hex-, etc.) with the suffixes "-ose" for aldoses and "-ulose" for ketoses. In the latter case, if the carbonyl is not at position 2, its position is then indicated by a numeric infix. So, for example, H(C=O)(CHOH)H is pentose, H(CHOH)(C=O)(CHOH)H is pentulose, and H(CHOH)(C=O)(CHOH)H is pent-3-ulose. | 0 | Theoretical and Fundamental Chemistry |
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