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Another important area of nuclear chemistry is the study of how fission products interact with surfaces; this is thought to control the rate of release and migration of fission products both from waste containers under normal conditions and from power reactors under accident conditions. Like chromate and molybdate, the TcO anion can react with steel surfaces to form a corrosion resistant layer. In this way, these metaloxo anions act as anodic corrosion inhibitors. The formation of TcO on steel surfaces is one effect which will retard the release of Tc from nuclear waste drums and nuclear equipment which has been lost before decontamination (e.g. submarine reactors lost at sea). This TcO layer renders the steel surface passive, inhibiting the anodic corrosion reaction. The radioactive nature of technetium makes this corrosion protection impractical in almost all situations. It has also been shown that TcO anions react to form a layer on the surface of activated carbon (charcoal) or aluminium. A short review of the biochemical properties of a series of key long lived radioisotopes can be read on line.
Tc in nuclear waste may exist in chemical forms other than the TcO anion, these other forms have different chemical properties.
Similarly, the release of iodine-131 in a serious power reactor accident could be retarded by absorption on metal surfaces within the nuclear plant. | 0 | Theoretical and Fundamental Chemistry |
The following sections outline the method of MeDIP coupled with either high-resolution array hybridization or high-throughput sequencing. Each DNA detection method will also briefly describe post-laboratory processing and analysis. Different post-processing of the raw data is required depending on the technology used to identify the methylated sequences. This is analogous to data generated using ChIP-chip and ChIP-seq. | 1 | Applied and Interdisciplinary Chemistry |
The Creutz–Taube complex is a robust, readily analyzed, mixed-valence complex consisting of otherwise equivalent Ru(II) and Ru(III) centers bridged by the pyrazine. This complex serves as a model for the bridged intermediate invoked in inner-sphere electron transfer. | 0 | Theoretical and Fundamental Chemistry |
Two older prefixes still commonly used to distinguish diastereomers are threo and erythro. In the case of saccharides, when drawn in the Fischer projection the erythro isomer has two identical substituents on the same side and the threo isomer has them on opposite sides. When drawn as a zig-zag chain, the erythro isomer has two identical substituents on different sides of the plane (anti). The names are derived from the diastereomeric four-carbon aldoses erythrose and threose. These prefixes are not recommended for use outside of the realm of saccharides because their definitions can lead to conflicting interpretations.
Another threo compound is threonine, one of the essential amino acids. The erythro diastereomer of it is allothreonine. | 0 | Theoretical and Fundamental Chemistry |
If the hydration energy is greater than the lattice energy, then the enthalpy of solution is negative (heat is released), otherwise it is positive (heat is absorbed).
The hydration energy should not be confused with solvation energy, which is the change in Gibb's free energy (not enthalpy) as solute in the gaseous state is dissolved. If the solvation energy is positive, then the solvation process is endergonic; otherwise, it is exergonic.
For instance, water warms when treated with CaCl (anhydrous calcium chloride) as a consequence of the large heat of hydration. However, the hexahydrate, CaCl·6HO cools the water upon dissolution. The latter happens because the hydration energy does not completely overcome the lattice energy, and the remainder has to be taken from the water in order to compensate the energy loss.
The hydration energies of the gaseous Li, Na, and Cs are respectively 520, 405, and 265 kJ/mol. | 0 | Theoretical and Fundamental Chemistry |
In the Sn-Pb alloys, tensile strength increases with increasing tin content. Indium-tin alloys with high indium content have very low tensile strength.
For soldering semiconductor materials, e.g. die attachment of silicon, germanium and gallium arsenide, it is important that the solder contains no impurities that could cause doping in the wrong direction. For soldering n-type semiconductors, solder may be doped with antimony; indium may be added for soldering p-type semiconductors. Pure tin can also be used.
Various fusible alloys can be used as solders with very low melting points; examples include Fields metal, Lipowitzs alloy, Woods metal, and Roses metal. | 1 | Applied and Interdisciplinary Chemistry |
Elementary modes may be considered minimal realizable flow patterns through a biochemical network that can sustain a steady state. This means that elementary modes cannot be decomposed further into simpler pathways. All possible flows through a network can be constructed from linear combinations of the elementary modes.
The set of elementary modes for a given network is unique (up to an arbitrary scaling factor). Given the fundamental nature of elementary modes in relation to uniqueness and non-decomposability, the term `pathway' can be defined as an elementary mode. Note that the set of elementary modes will change as the set of expressed enzymes change during transitions from one cell state to another. Mathematically, the set of elementary modes is defined as the set of flux vectors, , that satisfy the steady state condition,
where is the stoichiometry matrix, is the vector of rates, the vector of steady state floating (or internal) species and , the vector of system parameters.
An important condition is that the rate of each irreversible reaction must be non-negative, .
A more formal definition is given by:
An elementary mode, , is defined as a vector of fluxes, , such that the three conditions listed in the following criteria are satisfied.
# The vector must satisfy: , that is: the steady state condition.
# For all irreversible reactions: . This means that all flow patterns must use reactions that proceed in their most natural direction. This makes the pathway described by the elementary mode a thermodynamically feasible pathway.
# The vector must be elementary. That is, it should not be possible to generate by combining two other vectors that satisfy the first and second requirements using the same set of enzymes that appear as non-zero entries in . In other words, it should not be possible to decompose into two other pathways that can themselves sustain a steady state. This is called elementarity. A more formal test is that the null space of the submatrix of that only involves the reactions of is of dimension one and has no zero entries. | 1 | Applied and Interdisciplinary Chemistry |
A severe shortage of potassium in body fluids may cause a potentially fatal condition known as hypokalemia. Hypokalemia typically results from loss of potassium through diarrhea, diuresis, or vomiting. Symptoms are related to alterations in membrane potential and cellular metabolism. Symptoms include muscle weakness and cramps, paralytic ileus, ECG abnormalities, intestinal paralysis, decreased reflex response and (in severe cases) respiratory paralysis, alkalosis and arrhythmia.
In rare cases, habitual consumption of large amounts of black licorice has resulted in hypokalemia. Licorice contains a compound (Glycyrrhizin) that increases urinary excretion of potassium. | 1 | Applied and Interdisciplinary Chemistry |
Sodium hydroxide is sometimes used during water purification to raise the pH of water supplies. Increased pH makes the water less corrosive to plumbing and reduces the amount of lead, copper and other toxic metals that can dissolve into drinking water. | 0 | Theoretical and Fundamental Chemistry |
Drug discovery and development requires the integration of multiple scientific and technological disciplines. These include chemistry, biology, pharmacology, pharmaceutical technology and extensive use of information technology. The latter is increasingly recognised as Pharmacoinformatics. Pharmacoinformatics relates to the broader field of bioinformatics. | 1 | Applied and Interdisciplinary Chemistry |
A Pd–Cu bimetallic system was not discovered until 2006 when Goossen et al. reported a decarboxylative cross-coupling of aryl halides with ortho-substituted aromatic carboxylic acids.
Through subsequent studies it was found that the use of aryl triflates allowed substrate scope for cross-coupling to be extended to some aromatic carboxylates lacking any ortho-substitution (less reactive). This was a result of the fact that any halide anion generated in the reaction inhibited the Cu-catalyzed decarboxylation process.
Further optimization of the system and catalyst conditions has made decarboxylative cross-coupling using bimetallic Pd–Cu systems applicable to organic synthesis, most predominantly in the formation of biaryls.
As well, the variability of this combined catalytic system allows for promotion of a large spectrum of reactions, including aryl ketone formation, c-heteroatom cross-coupling, and many others. | 0 | Theoretical and Fundamental Chemistry |
At low temperatures, has an A- hexagonal crystal structure. The metal atoms are surrounded by a 7 coordinate group of atoms, the oxygen ions are in an octahedral shape around the metal atom and there is one oxygen ion above one of the octahedral faces. On the other hand, at high temperatures lanthanum oxide converts to a C- cubic crystal structure. The ion is surrounded by six ions in a hexagonal configuration. | 0 | Theoretical and Fundamental Chemistry |
If an antigen can be recognized by more than one component of its structure, it is less likely to be "missed" by the immune system. Mutation of pathogenic organisms can result in modification of antigen—and, hence, epitope—structure. If the immune system "remembers" what the other epitopes look like, the antigen, and the organism, will still be recognized and subjected to the body's immune response. Thus, the polyclonal response widens the range of pathogens that can be recognized. | 1 | Applied and Interdisciplinary Chemistry |
The Finnish Alcoholic Beverages Act 1 March 2018 legalized the manufacture of fermented water and wine from fruits, berries and other carbohydrate sources, without the pretense of making proper wine. | 1 | Applied and Interdisciplinary Chemistry |
A common way to determine the coordination number of an atom is by X-ray crystallography. Related techniques include neutron or electron diffraction. The coordination number of an atom can be determined straightforwardly by counting nearest neighbors.
α-Aluminium has a regular cubic close packed structure, fcc, where each aluminium atom has 12 nearest neighbors, 6 in the same plane and 3 above and below and the coordination polyhedron is a cuboctahedron. α-Iron has a body centered cubic structure where each iron atom has 8 nearest neighbors situated at the corners of a cube.
The two most common allotropes of carbon have different coordination numbers. In diamond, each carbon atom is at the centre of a regular tetrahedron formed by four other carbon atoms, the coordination number is four, as for methane. Graphite is made of two-dimensional layers in which each carbon is covalently bonded to three other carbons; atoms in other layers are further away and are not nearest neighbours, giving a coordination number of 3.
For chemical compounds with regular lattices such as sodium chloride and caesium chloride, a count of the nearest neighbors gives a good picture of the environment of the ions. In sodium chloride each sodium ion has 6 chloride ions as nearest neighbours (at 276 pm) at the corners of an octahedron and each chloride ion has 6 sodium atoms (also at 276 pm) at the corners of an octahedron. In caesium chloride each caesium has 8 chloride ions (at 356 pm) situated at the corners of a cube and each chloride has eight caesium ions (also at 356 pm) at the corners of a cube. | 0 | Theoretical and Fundamental Chemistry |
The first known use of the word "aromatic" as a chemical term — namely, to apply to compounds that contain the phenyl radical — occurs in an article by August Wilhelm Hofmann in 1855. If this is indeed the earliest introduction of the term, it is curious that Hofmann says nothing about why he introduced an adjective indicating olfactory character to apply to a group of chemical substances only some of which have notable aromas. Also, many of the most odoriferous organic substances known are terpenes, which are not aromatic in the chemical sense. But terpenes and benzenoid substances do have a chemical characteristic in common, namely higher unsaturation indices than many aliphatic compounds, and Hofmann may not have been making a distinction between the two categories. | 0 | Theoretical and Fundamental Chemistry |
Dye-sensitized solar cells (DSSCs) are made of low-cost materials and do not need elaborate manufacturing equipment, so they can be made in a DIY fashion. In bulk it should be significantly less expensive than older solid-state cell designs. DSSC's can be engineered into flexible sheets and although its conversion efficiency is less than the best thin film cells, its price/performance ratio may be high enough to allow them to compete with fossil fuel electrical generation.
Typically a ruthenium metalorganic dye (Ru-centered) is used as a monolayer of light-absorbing material, which is adsorbed onto a thin film of titanium dioxide. The dye-sensitized solar cell depends on this mesoporous layer of nanoparticulate titanium dioxide (TiO) to greatly amplify the surface area (200–300 m/g , as compared to approximately 10 m/g of flat single crystal) which allows for a greater number of dyes per solar cell area (which in term in increases the current). The photogenerated electrons from the light absorbing dye are passed on to the n-type and the holes are absorbed by an electrolyte on the other side of the dye. The circuit is completed by a redox couple in the electrolyte, which can be liquid or solid. This type of cell allows more flexible use of materials and is typically manufactured by screen printing or ultrasonic nozzles, with the potential for lower processing costs than those used for bulk solar cells. However, the dyes in these cells also suffer from degradation under heat and UV light and the cell casing is difficult to seal due to the solvents used in assembly. Due to this reason, researchers have developed solid-state dye-sensitized solar cells that use a solid electrolyte to avoid leakage. The first commercial shipment of DSSC solar modules occurred in July 2009 from G24i Innovations. | 0 | Theoretical and Fundamental Chemistry |
Supramolecular catalysis is not a well-defined field but it generally refers to an application of supramolecular chemistry, especially molecular recognition and guest binding, toward catalysis. This field was originally inspired by enzymatic system which, unlike classical organic chemistry reactions, utilizes non-covalent interactions such as hydrogen bonding, cation-pi interaction, and hydrophobic forces to dramatically accelerate rate of reaction and/or allow highly selective reactions to occur. Because enzymes are structurally complex and difficult to modify, supramolecular catalysts offer a simpler model for studying factors involved in catalytic efficiency of the enzyme. Another goal that motivates this field is the development of efficient and practical catalysts that may or may not have an enzyme equivalent in nature.
A closely related field of study is asymmetric catalysis which requires molecular recognition to differentiate two chiral starting material or chiral transition states and thus it could be categorized as an area of supramolecular catalysis, but supramolecular catalysis however does not necessarily have to involve asymmetric reaction. As there is another Wikipedia article already written about small molecule asymmetric catalysts, this article focuses primarily on large catalytic host molecules. Non-discrete and structurally poorly defined system such as micelle and dendrimers are not included. | 0 | Theoretical and Fundamental Chemistry |
The great leonopteryx (Toruk in Navi, meaning last shadow) is the apex airborne predator native to Pandora. It is scientifically known as Leonopteryx rex, meaning "king lion-wing". The fierce beauty and nobility of the leonopteryx gave the species a place central to Navi lore and culture. The leonopteryx is scarlet with black stripes and a midnight blue crest on top of the head and on the lower jaw. It is celebrated in dance and song; elaborate totems symbolize both the fear and respect accorded to the creature. The leonopteryx is considered crucial to the Navi sense of destiny and interconnectedness. Prior to the events of the film, it had only been tamed five times, and Neytiri tells Jake that the riders (Toruk Makto) brought peace among the Pandoran tribes. This makes Jake the sixth Toruk Makto. He manages to capture one by jumping on it from above from his banshee but releases it after the battle with the humans has ended. The great leonopteryx and the banshee were designed with bright colors. Page based the colors on Earths birds, poison dart frogs, and monarch butterflies, though he altered the patterns so that their inspirations would not be so conspicuous to moviegoers. The skull and crest shapes appear to be derived from pterosaurs from the genus Tapejara. | 1 | Applied and Interdisciplinary Chemistry |
Buoyant density centrifugation (also isopycnic centrifugation or equilibrium density-gradient centrifugation) uses the concept of buoyancy to separate molecules in solution by their differences in density. | 0 | Theoretical and Fundamental Chemistry |
Klaus Schmiegel was born in Chemnitz, Germany on June 28, 1939. After he immigrated to the United States in 1951, Schmiegel received a B.S. in chemistry from the University of Michigan, an A.M. in organic chemistry from Dartmouth College, and a Ph.D. in organic chemistry from Stanford University. His strong educational background secured him a prestigious position as a senior organic chemist at Eli Lilly, a prominent pharmaceutical company. | 0 | Theoretical and Fundamental Chemistry |
As the aggregation process continues, larger clusters form. The growth occurs mainly through encounters between different clusters, and therefore one refers to cluster-cluster aggregation process. The resulting clusters are irregular, but statistically self-similar. They are examples of mass fractals, whereby their mass M grows with their typical size characterized by the radius of gyration R as a power-law
where d is the mass fractal dimension. Depending whether the aggregation is fast or slow, one refers to diffusion limited cluster aggregation (DLCA) or reaction limited cluster aggregation (RLCA). The clusters have different characteristics in each regime. DLCA clusters are loose and ramified (d ≈ 1.8), while the RLCA clusters are more compact (d ≈ 2.1). The cluster size distribution is also different in these two regimes. DLCA clusters are relatively monodisperse, while the size distribution of RLCA clusters is very broad.
The larger the cluster size, the faster their settling velocity. Therefore, aggregating particles sediment and this mechanism provides a way for separating them from suspension. At higher particle concentrations, the growing clusters may interlink, and form a particle gel. Such a gel is an elastic solid body, but differs from ordinary solids by having a very low elastic modulus. | 0 | Theoretical and Fundamental Chemistry |
*Monocytes / macrophages: the key chemokines that attract these cells to the site of inflammation include: CCL2, CCL3, CCL5, CCL7, CCL8, CCL13, CCL17 and CCL22.
*T-lymphocytes: the four key chemokines that are involved in the recruitment of T lymphocytes to the site of inflammation are: CCL2, CCL1, CCL22 and CCL17. Furthermore, CXCR3 expression by T-cells is induced following T-cell activation and activated T-cells are attracted to sites of inflammation where the IFN-y inducible chemokines CXCL9, CXCL10 and CXCL11 are secreted.
*Mast cells: on their surface express several receptors for chemokines: CCR1, CCR2, CCR3, CCR4, CCR5, CXCR2, and CXCR4. Ligands of these receptors CCL2 and CCL5 play an important role in mast cell recruitment and activation in the lung. There is also evidence that CXCL8 might be inhibitory of mast cells.
*Eosinophils: the migration of eosinophils into various tissues involved several chemokines of CC family: CCL11, CCL24, CCL26, CCL5, CCL7, CCL13, and CCL3. Chemokines CCL11 (eotaxin) and CCL5 (RANTES) acts through a specific receptor CCR3 on the surface of eosinophils, and eotaxin plays an essential role in the initial recruitment of eosinophils into the lesion.
*Neutrophils: are regulated primarily by CXC chemokines. An example CXCL8 (IL-8) is chemoattractant for neutrophils and also activating their metabolic and degranulation. | 1 | Applied and Interdisciplinary Chemistry |
The research shortened photosynthetic pathways in tobacco. Engineered crops grew taller and faster, yielding up to 40% more biomass. The study employed synthetic biology to construct new metabolic pathways and assessed their efficiency with and without transporter RNAi. The most efficient pathway increased light-use efficiency by 17%. | 0 | Theoretical and Fundamental Chemistry |
In principle one can calculate all the above thermodynamic observables from a single differential scanning calorimetry thermogram of the system assuming that the is independent of the temperature. However, it is difficult to obtain accurate values for this way. More accurately, the can be derived from the variations in vs. which can be achieved from measurements with slight variations in pH or protein concentration. The slope of the linear fit is equal to the . Note that any non-linearity of the datapoints indicates that is probably not independent of the temperature.
Alternatively, the can also be estimated from the calculation of the accessible surface area (ASA) of a protein prior and after thermal denaturation as follows:
For proteins that have a known 3d structure, the can be calculated through computer programs such as Deepview (also known as swiss PDB viewer). The can be calculated from tabulated values of each amino acid through the semi-empirical equation:
where the subscripts polar, non-polar and aromatic indicate the parts of the 20 naturally occurring amino acids.
Finally for proteins, there is a linear correlation between and through the following equation: | 0 | Theoretical and Fundamental Chemistry |
The maximum absorption of light is near 670 nm. The specifics of absorption depend on a number of factors, including protonation, adsorption to other materials, and metachromasy - the formation of dimers and higher-order aggregates depending on concentration and other interactions: | 0 | Theoretical and Fundamental Chemistry |
While at Strasbourg in 1981, Markovitsi joined the CNRS. Then she relocated to the Paris area, where she worked from 1985 until 2021 in the CEA Paris-Saclay, in joint research Laboratories of the CNRS and the French Alternative Energies and Atomic Energy Commission. From 2001 to 2014, she was the director of the Francis Perrin Laboratory (). After being appointed Emeritus Research Director, she moved to the Institut de Chimie Physique - Université Paris-Saclay.
Markovitsi served as president of the European Photochemistry Association from 2007 to 2010, and since 2014 she is the president of the [http://www.asianphotochem.com/doc/20230816_IFPwebpage.pdf International Foundation for Photochemistry]. | 0 | Theoretical and Fundamental Chemistry |
Supramolecular equivalent of step-growth mechanism is commonly known as isodesmic or equal-K model (K represents the total binding interaction between two neighboring monomers). In isodesmic supramolecular polymerization, no critical temperature or concentration of monomers is required for the polymerization to occur and the association constant between polymer and monomer is independent of the polymer chain length. Instead, the length of the supramolecular polymer chains rises as the concentration of monomers in the solution increases, or as the temperature decreases. In conventional polycondensation, the association constant is usually large that leads to a high degree of polymerization; however, a byproduct is observed. In isodesmic supramolecular polymerization, due to non-covalent bonding, the association between monomeric units is weak, and the degree of polymerization strongly depends on the strength of interaction, i.e. multivalent interaction between monomeric units. For instance, supramolecular polymers consisting of bifunctional monomers having single hydrogen bonding donor/acceptor at their termini usually end up with low degree of polymerization, however those with quadrupole hydrogen bonding, as in the case of ureidopyrimidinone motifs, result in a high degree of polymerization. In ureidopyrimidinone-based supramolecular polymer, the experimentally observed molecular weight at semi-dilute concentrations is in the order of 10 Dalton and the molecular weight of the polymer can be controlled by adding mono-functional chain-cappers. | 0 | Theoretical and Fundamental Chemistry |
Born in London to a silk merchant who died of tuberculosis when Ingold was five years old, Ingold began his scientific studies at Hartley University College at Southampton (now Southampton University) taking an external BSc in 1913 with the University of London. He then joined the laboratory of Jocelyn Field Thorpe at Imperial College, London, with a brief hiatus from 1918-1920 during which he conducted research into chemical warfare and the manufacture of poison gas with Cassel Chemical at Glasgow. Ingold received an MSc from the University of London and returned to Imperial College in 1920 to work with Thorpe. He was awarded a PhD in 1918 and a DSc in 1921. | 0 | Theoretical and Fundamental Chemistry |
Because of their importance in cell signaling and regulation, co-receptors have been implicated in a number of diseases and disorders. Co-receptor knockout mice are often unable to develop and such knockouts generally result in embryonic or perinatal lethality. In immunology in particular, the term "co-receptor" often describes a secondary receptor used by a pathogen to gain access to the cell, or a receptor that works alongside T cell receptors such as CD4, CD8, or CD28 to bind antigens or regulate T cell activity in some way. | 1 | Applied and Interdisciplinary Chemistry |
* 1950. Awarded the Corday-Morgan medal and Prize of the Chemical Society.
* 1955. Awarded the H G Smith Medal of the Royal Australian Chemical Institute.
* 1959. Elected Fellow of the Royal Society.
* 1959. Awarded the Royal Medal of the Royal Society of New South Wales.
* 1959. Elected Corresponding Member of the Finnish Chemical Society.
* 1961. Appointed Tilden Lecturer of the Chemical Society.
* 1967. Appointed Liversidge Lecturer of the Chemical Society.
* 1967. Created Knight Bachelor for services to science in the 1967 Birthday Honours.
* 1968. Awarded the Gold Medal of the Italian Chemical Society.
* 1968. Honorary Doctor of Science, University of East Anglia.
* 1968. Honorary Doctor of Science, City University, London.
* 1969. Awarded the Sigillum Magnum Medal, University of Bologna.
* 1969. Honorary Doctor of Science, University of New South Wales.
* 1971. Elected Honorary Member of the Accademia Peloritana (Sicily)
The Nyholm Prize for Inorganic Chemistry and the Nyholm Prize for Education, founded by the Chemical Society in 1973, are now awarded biennially by the Royal Society of Chemistry.
The mineral Nyholmite is named after Nyholm. It was discovered in Broken Hill in 2009 and its structure was elucidated by Elliot et al. | 0 | Theoretical and Fundamental Chemistry |
A combined sewer is a type of gravity sewer with a system of pipes, tunnels, pump stations etc. to transport sewage and urban runoff together to a sewage treatment plant or disposal site. This means that during rain events, the sewage gets diluted, resulting in higher flowrates at the treatment site. Uncontaminated stormwater simply dilutes sewage, but runoff may dissolve or suspend virtually anything it contacts on roofs, streets, and storage yards. As rainfall travels over roofs and the ground, it may pick up various contaminants including soil particles and other sediment, heavy metals, organic compounds, animal waste, and oil and grease. Combined sewers may also receive dry weather drainage from landscape irrigation, construction dewatering, and washing buildings and sidewalks.
Combined sewers can cause serious water pollution problems during combined sewer overflow (CSO) events when combined sewage and surface runoff flows exceed the capacity of the sewage treatment plant, or of the maximum flow rate of the system which transmits the combined sources. In instances where exceptionally high surface runoff occurs (such as large rainstorms), the load on individual tributary branches of the sewer system may cause a back-up to a point where raw sewage flows out of input sources such as toilets, causing inhabited buildings to be flooded with a toxic sewage-runoff mixture, incurring massive financial burdens for cleanup and repair. When combined sewer systems experience these higher than normal throughputs, relief systems cause discharges containing human and industrial waste to flow into rivers, streams, or other bodies of water. Such events frequently cause both negative environmental and lifestyle consequences, including beach closures, contaminated shellfish unsafe for consumption, and contamination of drinking water sources, rendering them temporarily unsafe for drinking and requiring boiling before uses such as bathing or washing dishes.
Mitigation of combined sewer overflows include sewer separation, CSO storage, expanding sewage treatment capacity, retention basins, screening and disinfection facilities, reducing stormwater flows, green infrastructure and real-time decision support systems.
This type of gravity sewer design is less often used nowadays when constructing new sewer systems. Modern-day sewer designs exclude surface runoff by building sanitary sewers instead, but many older cities and towns continue to operate previously constructed combined sewer systems. | 1 | Applied and Interdisciplinary Chemistry |
*DAD1 Defender against cell death
*DAP3 Involved in mediating interferon-gamma-induced cell death.
*DAXX Death Associated Protein 6 | 1 | Applied and Interdisciplinary Chemistry |
Molecular Physics is a peer-reviewed scientific journal covering research on the interface between chemistry and physics, in particular chemical physics and physical chemistry. It covers both theoretical and experimental molecular science, including electronic structure, molecular dynamics, spectroscopy, reaction kinetics, statistical mechanics, condensed matter and surface science. The journal was established in 1958 and is published by Taylor & Francis. According to the Journal Citation Reports, the journal has a 2021 impact factor of 1.937.
The current editor-in-chief is Professor George Jackson (Imperial College London). A reprint of the first editorial and a full list of editors since its establishment can be found in the issue celebrating 50 years of the journal. | 0 | Theoretical and Fundamental Chemistry |
TrkB agonists have received extensive interest from the scientific community resulting in the synthesis and biological evaluation of a large number of mimetics. Deoxygedunin, with a selective TrkB activity, is able to promote axon regeneration in topical treatments. Furthermore, it shows efficacy in two Parkinsons disease (PD) animal models, leading to the protection of locomotor function and the reduction of neuronal death in dopaminergic neurons. A number of studies corroborated that the flavonoid 7,8-Dihydroxyflavone (7,8-DHF) shows neuroprotection in PD and Huntingtons disease (HD) models together with antioxidant activity and enhancement of motor neuronal survival, motor function and spine density in amyotrophic lateral sclerosis (ALS) model. The benzothiazole riluzole exerts neuroprotective effects by increasing BDNF and GDNF levels with improvement of motor neuron survival. It has been approved for the treatment of ALS and delays the onset of ventilator-dependence or tracheostomy in some people and may increase survival by two to three months. Furthermore, several combinations of riluzole with other drugs are in clinical trials (NCT02588677, NCT03127267).
Brimonidine exerts neuroprotective effects in retinal ganglion cells (RGCs) through up-regulation of the expression of BDNF in these cells. It is used in the treatment of glaucoma as eye drops to reduce intraocular pressure (IOP) under the brand name Lumify®. Different drugs, used against PD also behave as neurotrophin mimetics such as rotigotine, selegiline, rasagiline, memantine and levodopa interacting with TrkB and increasing BDNF expression. Furthermore, of particular note, the groups of F. Longo and S. Massa discovered small molecule neurotrophic mimetics exhibiting specificity for TrkB at nanomolar concentrations. In particular, LM22A-4, prevents neuronal death in in vitro models of AD, HD and PD.
Among the peptidomimetic TrkB agonists, the dimeric dipeptide GSB-106 showed neurotrophic and neuroprotective effects by specific activation of TrkB and its signaling pathways. Furthermore, the tricyclic dimeric peptide TDP6 acts as a TrkB agonist mimicking BDNF and induces autophosphorylation of TrkB in primary oligodendrocyte cultures, leading to oligodendrocyte myelination. Regarding DHEA derivatives, the C17-spiroepoxy analogue, BNN-20, binds with high affinity to TrkB, showing antiapoptotic activity in vitro. Its neuroprotective activity was analyzed in the Weaver mouse genetic model of PD in which long term administration of BNN-20 protects the dopaminergic neurons by mimicking BDNF and induces antiapoptotic, antioxidant and anti-inflammatory effects. | 1 | Applied and Interdisciplinary Chemistry |
A hydrogen analyzer is a device used to measure the hydrogen concentration in steels and alloys when the hydrogen concentration is unknown. It also has industrial applications for corrosion monitoring. | 1 | Applied and Interdisciplinary Chemistry |
Photoluminescence spectroscopy is a widely used technique for characterisation of the optical and electronic properties of semiconductors and molecules. The technique itself is fast, contactless, and nondestructive. Therefore, it can be used to study the optoelectronic properties of materials of various sizes (from microns to centimeters) during the fabrication process without complex sample preparation. For example, photoluminescence measurements of solar cell absorbers can predict the maximum voltage the material could produce. In chemistry, the method is more often referred to as fluorescence spectroscopy, but the instrumentation is the same. The relaxation processes can be studied using time-resolved fluorescence spectroscopy to find the decay lifetime of the photoluminescence. These techniques can be combined with microscopy, to map the intensity (confocal microscopy) or the lifetime (fluorescence-lifetime imaging microscopy) of the photoluminescence across a sample (e.g. a semiconducting wafer, or a biological sample that has been marked with fluorescent molecules). Modulated photoluminescence is a specific method for measuring the complex frequency response of the photoluminescence signal to a sinusoidal excitation, allowing for the direct extraction of minority carrier lifetime without the need for intensity calibrations. It has been used to study the influence of interface defects on the recombination of excess carriers in crystalline silicon wafers with different passivation schemes. | 0 | Theoretical and Fundamental Chemistry |
Natural vanillin is extracted from the seed pods of Vanilla planifolia, a vining orchid native to Mexico, but now grown in tropical areas around the globe. Madagascar is presently the largest producer of natural vanillin.
As harvested, the green seed pods contain vanillin in the form of its β--glucoside; the green pods do not have the flavor or odor of vanilla.
After being harvested, their flavor is developed by a months-long curing process, the details of which vary among vanilla-producing regions, but in broad terms it proceeds as follows:
First, the seed pods are blanched in hot water, to arrest the processes of the living plant tissues. Then, for 1–2 weeks, the pods are alternately sunned and sweated: during the day they are laid out in the sun, and each night wrapped in cloth and packed in airtight boxes to sweat. During this process, the pods become dark brown, and enzymes in the pod release vanillin as the free molecule. Finally, the pods are dried and further aged for several months, during which time their flavors further develop. Several methods have been described for curing vanilla in days rather than months, although they have not been widely developed in the natural vanilla industry, with its focus on producing a premium product by established methods, rather than on innovations that might alter the product's flavor profile. | 0 | Theoretical and Fundamental Chemistry |
The level of complementarity of the mRNA SD sequence to the ribosomal ASD greatly affects the efficiency of translation initiation. Richer complementarity results in higher initiation efficiency. It is worth noting that this only holds up to a certain point - having too rich of a complementarity is known to paradoxically decrease the rate of translation as the ribosome then happens to be bound too tightly to proceed downstream.
The optimal distance between the RBS and the start codon is variable - it depends on the portion of the SD sequence encoded in the actual RBS and its distance to the start site of a consensus SD sequence. Optimal spacing increases the rate of translation initiation once a ribosome has been bound. The composition of nucleotides in the spacer region itself was also found to affect the rate of translation initiation in one study. | 1 | Applied and Interdisciplinary Chemistry |
In vascular plant biology, electro-osmosis is also used as an alternative or supplemental explanation for the movement of polar liquids via the phloem that differs from the cohesion-tension theory supplied in the mass flow hypothesis and others, such as cytoplasmic streaming. Companion cells are involved in the "cyclic" withdrawal of ions (K) from sieve tubes, and their secretion parallel to their position of withdrawal between sieve plates, resulting in polarisation of sieve plate elements alongside potential difference in pressure, and results in polar water molecules and other solutes present moved upward through the phloem.
In 2003, St Petersburg University graduates applied direct electric current to 10 mm segments of mesocotyls of maize seedlings alongside one-year linden shoots; electrolyte solutions present in the tissues moved toward the cathode that was in place, suggesting that electro-osmosis might play a role in solution transport through conductive plant tissues. | 0 | Theoretical and Fundamental Chemistry |
*1982 – Arnold O. Beckman Research Award, University of Illinois
*1983 – Established Investigator Award, American Heart Association
*2003 – Vilas Associate Award, UW-Madison | 1 | Applied and Interdisciplinary Chemistry |
IMes is an abbreviation for an organic compound that is a common ligand in organometallic chemistry. It is an N-heterocyclic carbene (NHC). The compound, a white solid, is often not isolated but instead is generated upon attachment to the metal centre.
First prepared by Arduengo, the heterocycle is synthesized by condensation of 2,4,6-trimethylaniline and glyoxal to give the diimine. In the presence of acid, the resulting glyoxal-bis(mesitylimine) condenses with formaldehyde to give the dimesitylimidazolium cation. This cation is the conjugate acid of the NHC. | 0 | Theoretical and Fundamental Chemistry |
For liquid solutions, the osmotic coefficient is often used to calculate the salt activity coefficient from the solvent activity, or vice versa. For example, freezing point depression measurements, or measurements of deviations from ideality for other colligative properties, allows calculation of the salt activity coefficient through the osmotic coefficient. | 0 | Theoretical and Fundamental Chemistry |
DEB theory has been extended into many directions, such as
*effects of changes in shape during growth (e.g. V1-morphs and V0-morphs)
*non-standard embryo->juvenile->adult transitions, for example in holometabolic insects
*inclusion of more types of food (substrate), which requires synthesizing units to model
*inclusion of more reserves (which is necessary for organisms that do not feed on other organisms) and more structures (which is necessary to deal with plants), or a simplified version of the model (DEBkiss) applicable in ecotoxicology
*the formation and excretion of metabolic products (which is a basis for syntrophic relationships, and useful in biotechnology)
*the production of free radicals (linked to size and nutritional status) and their effect on survival (aging)
*the growth of body parts (including tumours)
*effects of chemical compounds (toxicants) on parameter values and the hazard rate (which is useful to establish no effect concentrations for environmental risk assessment): the DEBtox method
*processes of adaptation (gene expression) to the availability of substrates (important in biodegradation)
A list and description of most common typified models can be found [http://www.debtheory.org/wiki/index.php?title=Typified_models here] . | 1 | Applied and Interdisciplinary Chemistry |
Metabolic pathways require tight regulation so that the proper compounds get produced in the proper amounts. Often, the first committed step is regulated by processes such as feedback inhibition and activation. Such regulation ensures that pathway intermediates do not accumulate, a situation that can be wasteful or even harmful to the cell. | 1 | Applied and Interdisciplinary Chemistry |
The Koenigs–Knorr reaction in organic chemistry is the substitution reaction of a glycosyl halide with an alcohol to give a glycoside. It is one of the oldest glycosylation reactions. It is named after Wilhelm Koenigs (1851–1906), a student of von Baeyer and fellow student with Hermann Emil Fischer, and Edward Knorr, a student of Koenigs.
In its original form, Koenigs and Knorr treated acetobromoglucose with alcohols in the presence of silver carbonate. Shortly afterwards Fischer and Armstrong reported very similar findings.
In the above example, the stereochemical outcome is determined by the presence of the neighboring group at C2 that lends anchimeric assistance, resulting in the formation of a 1,2-trans stereochemical arrangement. Esters (e.g. acetyl, benzoyl, pivalyl) generally provide good anchimeric assistance, whereas ethers (e.g. benzyl, methyl etc.) do not, leading to mixtures of stereoisomers. | 0 | Theoretical and Fundamental Chemistry |
William Leonard Pickard earned a scholarship to Princeton University but dropped out after one term, instead preferring to hang out at Greenwich Village jazz clubs in New York City. In 1971, he got a job as a research manager at the University of California, Berkeley in the Department of Bacteriology and Immunology, a job he held until 1974.
In December 1988, a neighbor reported a strange chemical odor coming from an architectural shop at a Mountain View, California industrial park. Federal agents arrived to find 200,000 doses of LSD and William Pickard inside. Pickard was charged with manufacturing LSD and served five years in prison.
By 1994, Pickard had enrolled at the John F. Kennedy School of Government at Harvard University. His studies focused on drug abuse in the former Soviet Union, where he theorized that the booming black market and many unemployed chemists could lead to a flood of the drug market.
In 2000, Pickard was arrested for manufacturing LSD in Kansas and was serving two life sentences at United States Penitentiary, Tucson. On July 27, 2020, Pickard was granted Compassionate Release from federal prison after serving 17 years of his sentence. | 1 | Applied and Interdisciplinary Chemistry |
Again under Thomsons leadership, Rutherford worked on the conductive effects of X-rays on gases, which led to the discovery of the electron, the results first presented by Thomson in 1897. Hearing of Henri Becquerels experience with uranium, Rutherford started to explore its radioactivity, discovering two types that differed from X-rays in their penetrating power. Continuing his research in Canada, in 1899 he coined the terms "alpha ray" and "beta ray" to describe these two distinct types of radiation.
In 1898, Rutherford was accepted to the chair of Macdonald Professor of physics position at McGill University in Montreal, Canada, on Thomson's recommendation. From 1900 to 1903, he was joined at McGill by the young chemist Frederick Soddy (Nobel Prize in Chemistry, 1921) for whom he set the problem of identifying the noble gas emitted by the radioactive element thorium, a substance which was itself radioactive and would coat other substances. Once he had eliminated all the normal chemical reactions, Soddy suggested that it must be one of the inert gases, which they named thoron. This substance was later found to be Rn, an isotope of radon. They also found another substance they called Thorium X, later identified as Rn, and continued to find traces of helium. They also worked with samples of "Uranium X" (protactinium), from William Crookes, and radium, from Marie Curie. Rutherford further investigated thoron in conjunction with R.B. Owens and found that a sample of radioactive material of any size invariably took the same amount of time for half the sample to decay (in this case, 11 minutes), a phenomenon for which he coined the term "half-life". Rutherford and Soddy published their paper "Law of Radioactive Change" to account for all their experiments. Until then, atoms were assumed to be the indestructible basis of all matter; and although Curie had suggested that radioactivity was an atomic phenomenon, the idea of the atoms of radioactive substances breaking up was a radically new idea. Rutherford and Soddy demonstrated that radioactivity involved the spontaneous disintegration of atoms into other, as yet, unidentified matter.
In 1903, Rutherford considered a type of radiation, discovered (but not named) by French chemist Paul Villard in 1900, as an emission from radium, and realised that this observation must represent something different from his own alpha and beta rays, due to its very much greater penetrating power. Rutherford therefore gave this third type of radiation the name of gamma ray. All three of Rutherfords terms are in standard use today – other types of radioactive decay have since been discovered, but Rutherfords three types are among the most common. In 1904, Rutherford suggested that radioactivity provides a source of energy sufficient to explain the existence of the Sun for the many millions of years required for the slow biological evolution on Earth proposed by biologists such as Charles Darwin. The physicist Lord Kelvin had argued earlier for a much younger Earth, based on the insufficiency of known energy sources, but Rutherford pointed out, at a lecture attended by Kelvin, that radioactivity could solve this problem. Later that year, he was elected as a member to the American Philosophical Society, and in 1907 he returned to Britain to take the chair of physics at the Victoria University of Manchester.
In Manchester, Rutherford continued his work with alpha radiation. In conjunction with Hans Geiger, he developed zinc sulfide scintillation screens and ionisation chambers to count alpha particles. By dividing the total charge they produced by the number counted, Rutherford decided that the charge on the alpha particle was two. In late 1907, Ernest Rutherford and Thomas Royds allowed alphas to penetrate a very thin window into an evacuated tube. As they sparked the tube into discharge, the spectrum obtained from it changed, as the alphas accumulated in the tube. Eventually, the clear spectrum of helium gas appeared, proving that alphas were at least ionised helium atoms, and probably helium nuclei. Ernest Rutherford was awarded the 1908 Nobel Prize in Chemistry "for his investigations into the disintegration of the elements, and the chemistry of radioactive substances". | 1 | Applied and Interdisciplinary Chemistry |
For solutions, a slightly different equation is used:
In this equation, α (Greek letter "alpha") is the measured rotation in degrees, l is the path length in decimeters, c is the concentration in g/mL, T is the temperature at which the measurement was taken (in degrees Celsius), and λ is the wavelength in nanometers.
For practical and historical reasons, concentrations are often reported in units of g/100mL. In this case, a correction factor in the numerator is necessary:
When using this equation, the concentration and the solvent may be provided in parentheses after the rotation. The rotation is reported using degrees, and no units of concentration are given (it is assumed to be g/100mL). The sign of the rotation (+ or −) is always given. If the wavelength of the light used is 589 nanometer (the sodium D line), the symbol “D” is used. If the temperature is omitted, it is assumed to be at standard room temperature (20 °C).
For example, the specific rotation of a compound would be reported in the scientific literature as:
: (c 1.00, EtOH) | 0 | Theoretical and Fundamental Chemistry |
The physician Valerius Cordus, son of the famous botanist Euricius Cordus, went through many woods and mountains discovering hundreds of new herbs. He gave lectures on Dioscorides at the University of Wittenberg, which experts from the university attended. Cordus had no intention of publishing his work. Five years after his death, a Materia Medica with commentaries was published. It contained the index of the Botanologicon, the outstanding work of his father Euricius, who developed a scientific classification of the plants. The following pages are on Gesner's Nomenclature, relating the different synonyms used for referring to the same plants of the Dioscorides work.
The abstracts of the lectures of Valerius Cordus go from page 449 to 553 as commentaries. This section consisted of a very refined explanation of Dioscorides teachings with more specifics on the variety of plants and habitats, and corrections of errors. Cordus refers to both his and his fathers observations. Eucharius Rösslin's herbal illustrations are prominent in this work, followed by 200 of Fuchs. This work and the model of botanical description and, many consider it the boldest innovation that was made by any botanist of the 16th century. | 1 | Applied and Interdisciplinary Chemistry |
Prior to the advent of computer-aided design (CAD) in the late 1980s, P&IDs were drawn by hand. The drawing template shown below, actual size 225.mm by 111 mm, is typical of those used to draw P&IDs.
Piping and instrumentation diagram manual drawing template (1980s). Symbol key: | 1 | Applied and Interdisciplinary Chemistry |
The pincer ligand is most often an anionic, two-electron donor to the metal centre. It consists of a rigid, planar backbone usually consisting of aryl frameworks and has two neutral, two-electron donor groups at the meta-positions. The general formula for pincer ligands is 2,6-(ER)CH – abbreviated ECE – where E is the two-electron donor and C is the ipso-carbon of the aromatic backbone (e.g. PCP – two phosphine donors). Due to the firm tridentate coordination mode, it allows the metal complexes to exhibit high thermal stability as well as air-stability. It also implies that a reduced number of coordination sites are available for reactivity, which often limits the number of undesirable products formed in the reaction due to ligand exchange, as this process is suppressed.
There are various types of pincer ligands that are used in transition metal catalysis. Often, they have the same two-electron donor flanking the metal centre, but this is not a requirement.
The most common pincer ligand designs are PCP, NCN, PCN, SCS, and PNO. Other elements that have been employed at different positions in the ligand are boron, arsenic, silicon, and even selenium.
By altering the properties of the pincer ligands, it is possible to significantly alter the chemistry at the metal centre. Changing the hardness/softness of the donor, using electron-withdrawing groups (EWGs) in the backbone, and the altering the steric constraints of the ligands are all methods used to tune the reactivity at the metal centre. | 0 | Theoretical and Fundamental Chemistry |
The Goldschmidt classification,
developed by Victor Goldschmidt (1888–1947), is a geochemical classification which groups the chemical elements within the Earth according to their preferred host phases into lithophile (rock-loving), siderophile (iron-loving), chalcophile (sulfide ore-loving or chalcogen-loving), and atmophile (gas-loving) or volatile (the element, or a compound in which it occurs, is liquid or gaseous at ambient surface conditions).
Some elements have affinities to more than one phase. The main affinity is given in the table below and a discussion of each group follows that table. | 0 | Theoretical and Fundamental Chemistry |
Small-scale cupellation is based on the same principle as the one done in a cupellation hearth; the main difference lies in the amount of material to be tested or obtained. The minerals have to be crushed, roasted and smelted to concentrate the metallic components to separate the noble metals. By the Renaissance the use of the cupellation processes was diverse: assay of ores from the mines, testing the amount of silver in jewels or coins or for experimental purposes. It was carried out in small shallow recipients known as cupels.
As the main purpose of small-scale cupellation was to assay and test minerals and metals, the matter to be tested must be carefully weighed. The assays were made in the cupellation or assay furnace, which needs to have windows and bellows to ascertain that the air oxidises the lead, as well as to be sure and prepared to take away the cupel when the process is complete. Pure lead must be added to the matter being tested to guarantee the further separation of the impurities. After the litharge has been absorbed by the cupel, buttons of silver were formed and settled in the middle of the cupel. If the alloy also contained a certain amount of gold, it settled with the silver, and both had to be separated by parting. | 1 | Applied and Interdisciplinary Chemistry |
During the 1970s the BNF became the BNF Metals Technology Centre and moved out of London to Grove Laboratories, Denchworth Road, Wantage, Oxfordshire. Recognising globalisation, membership was then opened to companies based overseas. In 1990 the BNF bought Fulmer Research Laboratories from the Institute of Physics and was renamed the BNF-Fulmer, then BNF (Fulmer Materials Centre). The laboratories were closed in 1992. | 1 | Applied and Interdisciplinary Chemistry |
The ocean can be conceptually divided into a surface layer within which water makes frequent (daily to annual) contact with the atmosphere, and a deep layer below the typical mixed layer depth of a few hundred meters or less, within which the time between consecutive contacts may be centuries. The dissolved inorganic carbon (DIC) in the surface layer is exchanged rapidly with the atmosphere, maintaining equilibrium. Partly because its concentration of DIC is about 15% higher but mainly due to its larger volume, the deep ocean contains far more carbon—it is the largest pool of actively cycled carbon in the world, containing 50 times more than the atmosphere—but the timescale to reach equilibrium with the atmosphere is hundreds of years: the exchange of carbon between the two layers, driven by thermohaline circulation, is slow.
Carbon enters the ocean mainly through the dissolution of atmospheric carbon dioxide, a small fraction of which is converted into carbonate. It can also enter the ocean through rivers as dissolved organic carbon. It is converted by organisms into organic carbon through photosynthesis and can either be exchanged throughout the food chain or precipitated into the oceans' deeper, more carbon-rich layers as dead soft tissue or in shells as calcium carbonate. It circulates in this layer for long periods of time before either being deposited as sediment or, eventually, returned to the surface waters through thermohaline circulation.
Oceans are basic (with a current pH value of 8.1 to 8.2). The increase in atmospheric CO shifts the pH of the ocean towards neutral in a process called ocean acidification. Oceanic absorption of CO is one of the most important forms of carbon sequestering. The projected rate of pH reduction could slow the biological precipitation of calcium carbonates, thus decreasing the ocean's capacity to absorb CO. | 0 | Theoretical and Fundamental Chemistry |
Glycogen is a multibranched polysaccharide of glucose that serves as a form of energy storage in animals, fungi, and bacteria. It is the main storage form of glucose in the human body.
Glycogen functions as one of three regularly used forms of energy reserves, creatine phosphate being for very short-term, glycogen being for short-term and the triglyceride stores in adipose tissue (i.e., body fat) being for long-term storage. Protein, broken down into amino acids, is seldom used as a main energy source except during starvation and glycolytic crisis (see bioenergetic systems).
In humans, glycogen is made and stored primarily in the cells of the liver and skeletal muscle. In the liver, glycogen can make up 5–6% of the organ's fresh weight: the liver of an adult, weighing 1.5 kg, can store roughly 100–120 grams of glycogen. In skeletal muscle, glycogen is found in a low concentration (1–2% of the muscle mass): the skeletal muscle of an adult weighing 70 kg stores roughly 400 grams of glycogen. Small amounts of glycogen are also found in other tissues and cells, including the kidneys, red blood cells, white blood cells, and glial cells in the brain. The uterus also stores glycogen during pregnancy to nourish the embryo.
The amount of glycogen stored in the body mostly depends on oxidative type 1 fibres, physical training, basal metabolic rate, and eating habits. Different levels of resting muscle glycogen are reached by changing the number of glycogen particles, rather than increasing the size of existing particles though most glycogen particles at rest are smaller than their theoretical maximum.
Approximately 4 grams of glucose are present in the blood of humans at all times; in fasting individuals, blood glucose is maintained constant at this level at the expense of glycogen stores, primarily from the liver (glycogen in skeletal muscle is mainly used as an immediate source of energy for that muscle rather than being used to maintain physiological blood glucose levels). Glycogen stores in skeletal muscle serve as a form of energy storage for the muscle itself; however, the breakdown of muscle glycogen impedes muscle glucose uptake from the blood, thereby increasing the amount of blood glucose available for use in other tissues. Liver glycogen stores serve as a store of glucose for use throughout the body, particularly the central nervous system. The human brain consumes approximately 60% of blood glucose in fasted, sedentary individuals.
Glycogen is an analogue of starch, a glucose polymer that functions as energy storage in plants. It has a structure similar to amylopectin (a component of starch), but is more extensively branched and compact than starch. Both are white powders in their dry state. Glycogen is found in the form of granules in the cytosol/cytoplasm in many cell types, and plays an important role in the glucose cycle. Glycogen forms an energy reserve that can be quickly mobilized to meet a sudden need for glucose, but one that is less compact than the energy reserves of triglycerides (lipids). As such it is also found as storage reserve in many parasitic protozoa. | 1 | Applied and Interdisciplinary Chemistry |
Dose-response curves can be constructed to describe response or ligand-receptor complex formation as a function of the ligand concentration. Antagonists make it harder to form these complexes by inhibiting interactions of the ligand with its receptor. This is seen as a change in the dose response curve: typically a rightward shift or a lowered maximum. A reversible competitive antagonist should cause a rightward shift in the dose response curve, such that the new curve is parallel to the old one and the maximum is unchanged. This is because reversible competitive antagonists are surmountable antagonists. The magnitude of the rightward shift can be quantified with the dose ratio, r. The dose ratio r is the ratio of the dose of agonist required for half maximal response with the antagonist present divided by the agonist required for half maximal response without antagonist ("control"). In other words, the ratio of the EC50s of the inhibited and un-inhibited curves. Thus, r represents both the strength of an antagonist and the concentration of the antagonist that was applied. An equation derived from the Gaddum equation can be used to relate r to , as follows:
where
* r is the dose ratio
*is the concentration of the antagonist
* is the equilibrium constant of the binding of the antagonist to the receptor
A Schild plot is a double logarithmic plot, typically as the ordinate and as the abscissa. This is done by taking the base-10 logarithm of both sides of the previous equation after subtracting 1:
This equation is linear with respect to , allowing for easy construction of graphs without computations. This was particular valuable before the use of computers in pharmacology became widespread. The y-intercept of the equation represents the negative logarithm of and can be used to quantify the strength of the antagonist.
These experiments must be carried out on a very wide range (therefore the logarithmic scale) as the mechanisms differ over a large scale, such as at high concentration of drug.
The fitting of the Schild plot to observed data points can be done with regression analysis. | 1 | Applied and Interdisciplinary Chemistry |
Many nuclear-derived transcription factors have played a role in respiratory chain expression. These factors may have also contributed to the regulation of mitochondrial functions. Nuclear respiratory factor (NRF-1) fuses to respiratory encoding genes proteins, to the rate-limiting enzyme in biosynthesis, and to elements of replication and transcription of mitochondrial DNA, or mtDNA. The second nuclear respiratory factor (NRF-2) is necessary for the production of cytochrome c oxidase subunit IV (COXIV) and Vb (COXVb) to be maximized.
The studying of gene sequences for the purpose of speciation and determining genetic similarity is just one of the many uses of modern day genetics, and the role that both types of genes have in that process is important. Though both nuclear genes and those within endosymbiotic organelles provide the genetic makeup of an organism, there are distinct features that can be better observed when looking at one compared to the other. Mitochondrial DNA is useful in the study of speciation as it tends to be the first to evolve in the development of a new species, which is different from nuclear genes' chromosomes that can be examined and analyzed individually, each giving its own potential answer as to the speciation of a relatively recently evolved organism.
Low-copy nuclear genes in plants are valuable for improving phylogenetic reconstructions, especially when universal markers like Chloroplast DNA, or cpDNA and Nuclear ribosomal DNA, or nrDNA fall short. Challenges in using these genes include limited universal markers and the complexity of gene families. Nonetheless, they are essential for resolving close species relationships and understanding plant phylogenetic studies. While using low-copy nuclear genes requires additional lab work, advances in sequencing and cloning techniques have made it more accessible. Fast-evolving introns in these genes can offer crucial phylogenetic insights near species boundaries. This approach, along with the analysis of developmentally important genes, enhances the study of plant diversity and evolution.
As nuclear genes are the genetic basis of all eukaryotic organisms, anything that can affect their expression therefore directly affects characteristics about that organism on a cellular level. The interactions between the genes of endosymbiotic organelles like mitochondria and chloroplasts are just a few of the many factors that can act on the nuclear genome. | 1 | Applied and Interdisciplinary Chemistry |
The MRI was first noticed in a non-astrophysical context by Evgeny Velikhov in 1959 when considering the stability of Couette flow of an ideal hydromagnetic fluid. His result was later generalized by Subrahmanyan Chandrasekhar in 1960. This mechanism was proposed by D. J. Acheson and Raymond Hide (1973) to perhaps play a role in the context of the Earth's geodynamo problem. Although there was some follow-up work in later decades (Fricke, 1969; Acheson and Hide 1972; Acheson and Gibbons 1978), the generality and power of the instability were not fully appreciated until 1991, when Steven A. Balbus and John F. Hawley gave a relatively simple elucidation and physical explanation of this important process. | 1 | Applied and Interdisciplinary Chemistry |
Dissolved organic matter is a heterogeneous pool of thousands, likely millions, of organic compounds. These compounds differ not only in composition and concentration (from pM to μM), but also originate from various organisms (phytoplankton, zooplankton, and bacteria) and environments (terrestrial vegetation and soils, coastal fringe ecosystems) and may have been produced recently or thousands of years ago. Moreover, even organic compounds deriving from the same source and of the same age may have been subjected to different processing histories prior to accumulating within the same pool of DOM.
Interior ocean DOM is a highly modified fraction that remains after years of exposure to sunlight, utilization by heterotrophs, flocculation and coagulation, and interaction with particles. Many of these processes within the DOM pool are compound- or class-specific. For example, condensed aromatic compounds are highly photosensitive, whereas proteins, carbohydrates, and their monomers are readily taken up by bacteria. Microbes and other consumers are selective in the type of DOM they utilize and typically prefer certain organic compounds over others. Consequently, DOM becomes less reactive as it is continually reworked. Said another way, the DOM pool becomes less labile and more refractory with degradation. As it is reworked, organic compounds are continually being added to the bulk DOM pool by physical mixing, exchange with particles, and/or production of organic molecules by the consumer community. As such, the compositional changes that occur during degradation are more complex than the simple removal of more labile components and resultant accumulation of remaining, less labile compounds.
Dissolved organic matter recalcitrance (i.e., its overall reactivity toward degradation and/or utilization) is therefore an emergent property. The perception of DOM recalcitrance changes during organic matter degradation and in conjunction with any other process that removes or adds organic compounds to the DOM pool under consideration.
The surprising resistance of high concentrations of DOC to microbial degradation has been addressed by several hypotheses. The prevalent notion is that the recalcitrant fraction of DOC has certain chemical properties, which prevent decomposition by microbes ("intrinsic stability hypothesis"). An alternative or additional explanation is given by the "dilution hypothesis", that all compounds are labile, but exist in concentrations individually too low to sustain microbial populations but collectively form a large pool. The dilution hypothesis has found support in recent experimental and theoretical studies. | 1 | Applied and Interdisciplinary Chemistry |
The specific mechanism that underlies monolayer evaporation resistance has been attributed to the physical barrier formed by the presence of these materials on the surface of the water (see figure). The extent to which a material can resist the evaporation of water is best treated on a case-by-case basis, however, a number of empirically derived formulas have been reported. Before the advent of surface spectroscopic techniques such as Brewster Angle Microscopy (BAM) and Glancing Incidence X-Ray reflectrometry (GIXD), it was thought that the intermolecular spacing between monolayer molecules was the largest determinant factor governing evaporation suppression. When the surface density of the monolayer was sufficiently small, water molecules were presumed to pass through the space between molecules. Scattering and imaging results, however, revealed that the intermolecular distance between monolayer molecules was essentially constant, and that evaporation was more likely at domain boundaries.
The factors governing the efficacy of an evaporation suppressing monolayer are the ability to remain tightly packed despite changes in surface pressure, the ability to adhere to the surface of water, and to neighbouring molecules. | 0 | Theoretical and Fundamental Chemistry |
In IUPAC nomenclature, 1,1-ethenediyl describes the connectivity >C=CH. The related species ethenylidenes have the connectivity =C=CH. | 0 | Theoretical and Fundamental Chemistry |
The Nigerian Society of Chemical Engineers (NSChE) is an organization for chemical engineers in Nigeria. NSChE was officially inaugurated on 12 March 1969 at a meeting at BP House in Lagos attended by twenty four Chemical Engineers, all trained abroad. In 1999 it became a Division of the Nigerian Society of Engineers. The Society publishes the Nigerian Society of Chemical Engineering Journal. | 1 | Applied and Interdisciplinary Chemistry |
This type of categorisation is from a pharmacological perspective and categorises them by their biological target. Drug classes that share a common molecular mechanism of action modulate the activity of a specific biological target. The definition of a mechanism of action also includes the type of activity at that biological target. For receptors, these activities include agonist, antagonist, inverse agonist, or modulator. Enzyme target mechanisms include activator or inhibitor. Ion channel modulators include opener or blocker. The following are specific examples of drug classes whose definition is based on a specific mechanism of action:
* 5-alpha-reductase inhibitor
* ACE inhibitor
* Alpha-adrenergic agonist
* Angiotensin II receptor antagonist
* Beta blocker
* Cholinergic
* Dopaminergic
* GABAergic
* Incretin mimetic
* Nonsteroidal anti-inflammatory drug − cyclooxygenase inhibitor
* Proton-pump inhibitor
* Renin inhibitor
* Selective glucocorticoid receptor modulator
* Serotonergic
* Statin – HMG-CoA reductase inhibitor | 1 | Applied and Interdisciplinary Chemistry |
Despite its limitations, the OR technique benefited from its close association with the development of the polymerase chain reaction. Kary Mullis, who also worked at Cetus, had synthesized the oligonucleotide probes being tested by Saiki and Erlich. Aware of the problems they were encountering, he envisioned an alternative method for analyzing the SCA mutation that would use components of the Sanger DNA sequencing technique. Realizing the difficulty of hybridizing an oligonucleotide primer to a single location in the genome, he considered using a second primer on the opposite strand. He then generalized that process and realized that repeated extensions of the two primers would lead to an exponential increase in the segment of DNA between the primers - a chain reaction of replication catalyzed by DNA polymerase.
As Mullis encountered his own difficulties in demonstrating PCR, he joined an existing group of researchers that were addressing the problems with OR. Together, they developed the combined PCR-OR assay. Thus, OR became the first method used to analyze PCR-amplified genomic DNA.
Mullis also encountered difficulties in publishing the basic idea of PCR (scientific journals rarely publish concepts without accompanying results). When his manuscript for the journal Nature was rejected, the basic description of PCR was hurriedly added to the paper originally intended to report the OR method (Mullis was also a co-author there). This OR paper thus became the first publication of PCR, and for several years would become the report most cited by other researchers. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, molecules with a non-collinear arrangement of two adjacent bonds have bent molecular geometry, also known as angular or V-shaped. Certain atoms, such as oxygen, will almost always set their two (or more) covalent bonds in non-collinear directions due to their electron configuration. Water (HO) is an example of a bent molecule, as well as its analogues. The bond angle between the two hydrogen atoms is approximately 104.45°. Nonlinear geometry is commonly observed for other triatomic molecules and ions containing only main group elements, prominent examples being nitrogen dioxide (NO), sulfur dichloride (SCl), and methylene (CH).
This geometry is almost always consistent with VSEPR theory, which usually explains non-collinearity of atoms with a presence of lone pairs. There are several variants of bending, where the most common is AXE where two covalent bonds and two lone pairs of the central atom (A) form a complete 8-electron shell. They have central angles from 104° to 109.5°, where the latter is consistent with a simplistic theory which predicts the tetrahedral symmetry of four sp hybridised orbitals. The most common actual angles are 105°, 107°, and 109°: they vary because of the different properties of the peripheral atoms (X).
Other cases also experience orbital hybridisation, but in different degrees. AXE molecules, such as SnCl, have only one lone pair and the central angle about 120° (the centre and two vertices of an equilateral triangle). They have three sp orbitals. There exist also sd-hybridised AX compounds of transition metals without lone pairs: they have the central angle about 90° and are also classified as bent. (See further discussion at VSEPR theory#Complexes with strong d-contribution). | 0 | Theoretical and Fundamental Chemistry |
Strongly alkaline soils are sodic and dispersive, with slow infiltration, low hydraulic conductivity and poor available water capacity. Plant growth is severely restricted because aeration is poor when the soil is wet; while in dry conditions, plant-available water is rapidly depleted and the soils become hard and cloddy (high soil strength). The higher the pH in the soil, the less water available to be distributed to the plants and organisms that depend on it. With a decreased pH, this does not allow for plants to uptake water like they normally would. This causes them to not be able to photosynthesize.
Many strongly acidic soils, on the other hand, have strong aggregation, good internal drainage, and good water-holding characteristics. However, for many plant species, aluminium toxicity severely limits root growth, and moisture stress can occur even when the soil is relatively moist. | 0 | Theoretical and Fundamental Chemistry |
Both of his early treatises, De natura boni and De bono, start with a metaphysical investigation into the concepts of the good in general and the physical good. Albert refers to the physical good as bonum naturae. Albert does this before directly dealing with the moral concepts of metaphysics. In Alberts later works, he says in order to understand human or moral goodness, the individual must first recognize what it means to be good and do good deeds. This procedure reflects Alberts preoccupations with neo-Platonic theories of good as well as the doctrines of Pseudo-Dionysius. Albert's view was highly valued by the Catholic Church and his peers. | 1 | Applied and Interdisciplinary Chemistry |
The phytoglobin-nitric oxide cycle is a metabolic pathway induced in plants under hypoxic conditions which involves nitric oxide (NO) and phytoglobin (Pgb). It provides an alternative type of respiration to mitochondrial electron transport under the conditions of limited oxygen supply. Phytoglobin in hypoxic plants acts as part of a soluble terminal nitric oxide dioxygenase system, yielding nitrate ion from the reaction of oxygenated phytoglobin with NO. Class 1 phytoglobins are induced in plants under hypoxia, bind oxygen very tightly at nanomolar concentrations, and can effectively scavenge NO at oxygen levels far below the saturation of cytochrome c oxidase. In the course of the reaction, phytoglobin is oxidized to metphytoglobin which has to be reduced for continuous operation of the cycle. Nitrate is reduced to nitrite by nitrate reductase, while NO is mainly formed due to anaerobic reduction of nitrite which may take place in mitochondria by complex III and complex IV in the absence of oxygen, in the side reaction of nitrate reductase, or by electron transport proteins on the plasma membrane. The overall reaction sequence of the cycle consumes NADH and can contribute to the maintenance of ATP level in highly hypoxic conditions. | 1 | Applied and Interdisciplinary Chemistry |
Disiamylborane is prepared by hydroboration of trimethylethylene with diborane. The reaction stops at the secondary borane due to steric hindrance.
Disiamylborane is relatively selective for terminal alkynes and alkenes vs internal alkynes and alkenes. Like most hydroboration, the addition proceeds in an anti-Markovnikov manner. It can be used to convert terminal alkynes, into aldehydes.
The hydroboration process proceeds via an initial dissociation of the dimer. | 0 | Theoretical and Fundamental Chemistry |
Phlogiston theory states that phlogisticated substances contain phlogiston and that they dephlogisticate when burned, releasing stored phlogiston, which is absorbed by the air. Growing plants then absorb this phlogiston, which is why air does not spontaneously combust and also why plant matter burns. This method of accounting for combustion was inverse to the oxygen theory by Antoine Lavoisier.
Joseph Blacks Scottish student Daniel Rutherford discovered nitrogen in 1772, and the pair used the theory to explain his results. The residue of air left after burning, in fact, a mixture of nitrogen and carbon dioxide, was sometimes referred to as phlogisticated air, having taken up all of the phlogiston. Conversely, when Joseph Priestley discovered oxygen, he believed it to be dephlogisticated air,' capable of combining with more phlogiston and thus supporting combustion for longer than ordinary air. | 1 | Applied and Interdisciplinary Chemistry |
The barrier for the rotation of the alkene about the M-centroid vector is a measure of the strength of the M-alkene pi-bond. Low symmetry complexes are suitable for analysis of these rotational barriers associated with the metal-ethene bond.In CpRh(CH)(CF), the ethene ligand is observed to rotate with a barrier near 12 kcal/mol but no rotation is observed for about the Rh-CF bond. | 0 | Theoretical and Fundamental Chemistry |
Fretting resistance is not an intrinsic property of a material, or even of a material couple. There are several factors affecting fretting behavior of a contact:
* Contact load
* Sliding amplitude
* Number of cycles
* Temperature
* Relative humidity
* Inertness of materials
* Corrosion and resulting motion-triggered contact insufficiency | 1 | Applied and Interdisciplinary Chemistry |
Food sticks easily to a bare metal cooking surface; it must either be oiled or seasoned before use. The coating known as seasoning is formed by a process of repeatedly layering extremely thin coats of oil on the cookware and oxidizing each layer with medium-high heat for a time. This process is known as "seasoning"; the color of the coating is commonly known as its "patina" - the base coat will darken with use.
To season cookware (e.g., to season a new pan, or to replace damaged seasoning on an old pan), the following is a typical process:
First the cookware is thoroughly cleaned to remove old seasoning, manufacturing residues or a possible manufacturer-applied anti corrosion coating and to expose the bare metal. If it is not pre-seasoned, a new cast-iron skillet or dutch oven typically comes from the manufacturer with a protective coating of wax or shellac; otherwise it would rust. This needs to be removed before the cookware is used. An initial scouring with hot soapy water will usually remove the protective coating. Alternatively, for woks, it is common to burn off the coating over high heat (outside or under a vent hood) to expose the bare metal surface. For already-used cookware that are to be re-seasoned, the cleaning process can be more complex, involving rust removal and deep cleaning (with strong soap or lye, or by burning in a campfire or self-cleaning oven) to remove existing seasoning and build-up.
Then several times the following is performed:
# Applying a very thin layer of animal fat or cooking oil (ranging from vegetable oil to lard, including many common food-grade oils).
# Polishing most of it off so that barely any remains or alternatively use a seasoning paste
# Heat the cookware to just below or just above the smoke point to generate a layer of seasoning.
The precise details of the seasoning process differ from one source to another, and there is much disagreement regarding the correct oil to use. There is also no clear consensus about the best temperature and duration. Lodge Manufacturing uses a proprietary soybean blend in their base coats as stated on their website, but states that all oils and fats can be used. The temperature recommended for seasoning varies from high temperatures above to temperatures below .
Seasoning a cast-iron or carbon steel wok is a common process in Asia and Asian-American culture. While the vegetable oil method of seasoning is also used in Asia, a traditional process for seasoning also includes the use of Chinese chives or scallions as part of the process. | 0 | Theoretical and Fundamental Chemistry |
Golgi enzymes play a key role in determining the synthesis of the various types of glycans. The order of action of the enzymes is reflected in their position in the Golgi stack: | 0 | Theoretical and Fundamental Chemistry |
The general equation for for species in a mixture of components is:
with
There are several different equation forms for and , the most general of which are shown above. | 0 | Theoretical and Fundamental Chemistry |
A glidants effect is due to the counter-action of factors that cause poor flowability of powders. For instance, correcting surface irregularity, reducing interparticular friction and decreasing surface charge. The result is a decrease in the angle of repose which is an indication of an enhanced powders flowability. | 1 | Applied and Interdisciplinary Chemistry |
A perturbation of nuclear spin orientations from equilibrium will occur only when an oscillating magnetic field is applied whose frequency ν sufficiently closely matches the Larmor precession frequency ν of the nuclear magnetization. The populations of the spin-up and -down energy levels then undergo Rabi oscillations, which are analyzed most easily in terms of precession of the spin magnetization around the effective magnetic field in a reference frame rotating with the frequency ν. The stronger the oscillating field, the faster the Rabi oscillations or the precession around the effective field in the rotating frame. After a certain time on the order of 2–1000 microseconds, a resonant RF pulse flips the spin magnetization to the transverse plane, i.e. it makes an angle of 90° with the constant magnetic field B ("90° pulse"), while after a twice longer time, the initial magnetization has been inverted ("180° pulse"). It is the transverse magnetization generated by a resonant oscillating field which is usually detected in NMR, during application of the relatively weak RF field in old-fashioned continuous-wave NMR, or after the relatively strong RF pulse in modern pulsed NMR. | 0 | Theoretical and Fundamental Chemistry |
The upper molecular-weight limit for a small molecule is approximately 900 daltons, which allows for the possibility to rapidly diffuse across cell membranes so that it can reach intracellular sites of action. This molecular weight cutoff is also a necessary but insufficient condition for oral bioavailability as it allows for transcellular transport through intestinal epithelial cells. In addition to intestinal permeability, the molecule must also possess a reasonably rapid rate of dissolution into water and adequate water solubility and moderate to low first pass metabolism. A somewhat lower molecular weight cutoff of 500 daltons (as part of the "rule of five") has been recommended for oral small molecule drug candidates based on the observation that clinical attrition rates are significantly reduced if the molecular weight is kept below this limit. | 1 | Applied and Interdisciplinary Chemistry |
A gasket used in a diamond anvil cell experiment is a thin metal foil, typically 0.3 mm in thickness, which is placed in between the diamonds. Desirable materials for gaskets are strong, stiff metals such as rhenium or tungsten. Steel is frequently used as a cheaper alternative for low pressure experiments. The above-mentioned materials cannot be used in radial geometries where the x-ray beam must pass through the gasket. Since they are not transparent to X-rays, if X-ray illumination through the gasket is required, lighter materials such as beryllium, boron nitride, boron or diamond are used as a gasket. Gaskets are preindented by the diamonds and a hole is drilled in the center of the indentation to create the sample chamber. | 0 | Theoretical and Fundamental Chemistry |
Seipin is a homo-oligomeric integral membrane protein in the endoplasmic reticulum (ER) that concentrates at junctions with cytoplasmic lipid droplets (LDs). Alternatively, seipin can be referred to as Berardinelli–Seip congenital lipodystrophy type 2 protein (BSCL2), and it is encoded by the corresponding gene of the same name, i.e. BSCL2. At protein level, seipin is expressed in cortical neurons in the frontal lobes, as well as motor neurons in the spinal cord. It is highly expressed in areas like the brain, testis and adipose tissue. Seipin's function is still unclear but it has been localized close to lipid droplets, and cells knocked out in seipin have anomalous droplets. Hence, recent evidence suggests that seipin plays a crucial role in lipid droplet biogenesis. | 1 | Applied and Interdisciplinary Chemistry |
To measure a PDRC surface's cooling power, the absorbed powers of atmospheric and solar radiations must be quantified. PDRC should not be measured when the surface is in a balanced or controlled state, but rather in a real-world setting. Standardized devices to measure PDRC effectiveness have been proposed.
Evaluating atmospheric downward longwave radiation based on "the use of ambient weather conditions such as the surface air temperature and humidity instead of the altitude-dependent atmospheric profiles," may be problematic since "downward longwave radiation comes from various altitudes of the atmosphere with different temperatures, pressures, and water vapor contents" and "does not have uniform density, composition, and temperature across its thickness." | 0 | Theoretical and Fundamental Chemistry |
Alogliptin is a dipeptidyl peptidase-4 inhibitor (DDP-4) that decreases blood sugar levels similar to other DPP-4 inhibitors. | 0 | Theoretical and Fundamental Chemistry |
Hyperpolarization is a change in membrane potential. Neuroscientists measure it using a technique known as patch clamping that allows them to record ion currents passing through individual channels. This is done using a glass micropipette, also called a patch pipette, with a 1 micrometer diameter. There is a small patch that contains a few ion channels and the rest is sealed off, making this the point of entry for the current. Using an amplifier and a voltage clamp, which is an electronic feedback circuit, allows the experimenter to maintain the membrane potential at a fixed point and the voltage clamp then measures tiny changes in current flow. The membrane currents giving rise to hyperpolarization are either an increase in outward current or a decrease in inward current. | 0 | Theoretical and Fundamental Chemistry |
War sand is sand contaminated by remains of projectiles used in war. This kind of sand has been found in Normandy, since the invasion of Normandy, among other places. In 1988, the sand on Omaha Beach was discovered to contain man-made metal and glass particles deriving from shrapnel; 4% of the sand in the sample was composed of shrapnel particles ranging in size between and . Researchers also discovered trace amounts of iron and glass beads in the sand, originating from the intense heat unleashed by munitions explosions in the air and sand. | 1 | Applied and Interdisciplinary Chemistry |
Different configurations can be used to perform Raman-SEC experiments. Raman scattering provides spectra with very weak Raman bands, therefore, a very well aligned optical configuration is required. Laser has to be focused on the electrode surface and an efficient collection of the scattered photons is mandatory. Many of the instruments used for Raman-SEC are based on the combination of a spectrometer, a potentiostat and a confocal microscope, since it is possible to focus and collect the scattered photons in a highly efficient way. Low resolution Raman spectrometers can be also used, providing suitable results. Using this setup, the sampling area is larger and average information about the electrode surface is obtained.
Typical configurations in Raman-SEC:
* Normal configuration. The laser beam samples the electrode/solution interface in a normal way respect to the electrode surface. The scattered radiation is collected, and the monochromator allows passing only the light beam with wavelengths different from that of the laser used.
* Inverted microscope. In this configuration the electrode/solution is sampled from behind the electrode, using optically transparent electrodes (OTE).
* Angular configuration. This configuration is usually selected when electrochemical techniques are combined with TERS.
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<br /> | 0 | Theoretical and Fundamental Chemistry |
The Portlethen Moss is a recognised nature preserve by the Scottish Wildlife Trust (with designation PLM076) and the Aberdeenshire Council. While peat cutting was conducted in prehistoric and Middle Ages times, there has been no harvesting of peat in the modern era. There is some ongoing loss of moss habitat from cattle grazing, but the most significant threat is from ongoing land development pressure; in fact, half of the Portlethen Moss has been lost to urban (low density) land development by the town of Portlethen during the period 1985 to 2005. Trampling is considered an insignificant threat due to the small animal or human presence in the existing nature reserve area; furthermore, cattle grazing, while ongoing, is deemed a much lesser current threat than population expansion pressure. Enrichment (addition of grazing animal manure) is not a major issue due to the low density of animals. As a net result damage to the primordial moss is considered extensive and widespread by the Scottish Wildlife Trust. The raised bog habitat of the Portlethen Moss is also protected by the United Kingdom Biodiversity Action Plan. | 1 | Applied and Interdisciplinary Chemistry |
Stephanopoulos has authored more than 400 journal articles on the topics of biotechnology, bioinformatics, and metabolic engineering. These include:
* Gregory Stephanopoulos, R. Aris, A. G. Fredrickson. "A stochastic analysis of the growth of competing microbial populations in a continuous biochemical reactor", Mathematical Biosciences 45, 99-135, (1979).
* Gregory Stephanopoulos, R. Aris, A. G. Fredrickson. "The growth of competing microbial populations in a CSTR with periodically varying inputs", AIChE Journal 25, 863-872, (1979).
* G. Stephanopoulos, A. G. Fredrickson. ""Coexistence of Photosynthetic Microorganisms with Growth Rates Depending on the Spectral Quality of Light", Bulletin of Mathematical Biology 41, 525-542, (1979).
* G. Stephanopoulos, A. G. Fredrickson. "The Effect of Spatial Inhomogeneities on the Coexistence of Competing Microbial Populations", Biotechnology and Bioengineering 21, 1491-1498, (1979).
* Rahul Singhvi, Amit Kumar, Gabriel P. Lopez, Gregory N. Stephanopoulos, D. I. Wang, George M. Whitesides, Donald E. Ingber "Engineering cell shape and function", Science, 264(5159), 696-698, (1994).
* Hal Alper, Curt Fischer, Elke Nevoigt, Gregory Stephanopoulos. "Tuning genetic control through promoter engineering", Proceedings of the National Academy of Sciences, 102(36), 12678, (2005).
* Parayil Kumaran Ajikumar, Wen-Hai Xiao, Keith E. J. Tyo, Yong Wang, Fritz Simeon, Effendi Leonard, Oliver Mucha, Too Heng Phon, Blaine Pfeifer, Gregory Stephanopoulos. "Isoprenoid pathway optimization for Taxol precursor overproduction in Escherichia coli", Science, 330(6000), 70-74, (2010).
* Christian M Metallo, Paulo A. Gameiro, Eric L. Bell, Katherine R. Mattaini, Juanjuan Yang, Karsten Hiller, Christopher M Jewell, Zachary R Johnson, Darrell J. Irvine, Leonard Guarente, Joanne K. Kelleher, Matthew G. Vander Heiden, Othon Iliopoulos, Gregory Stephanopoulos. "Reductive glutamine metabolism by IDH1 mediates lipogenesis under hypoxia", Nature, 481(7381), 380, (2012). | 1 | Applied and Interdisciplinary Chemistry |
*[http://shahid.mbc.net/media/video/28404/%D8%A3%D9%85_%D8%A8%D9%8A_%D8%B3%D9%8A_%D9%81%D9%8A_%D8%A3%D8%B3%D8%A8%D9%88%D8%B9_%D8%A7%D9%84%D8%AD%D9%84%D9%82%D8%A9_351 Report and Interview with Eng. Mohamed Osman Baloola in MBC in Week, MBC TV .(08:05 - 18:10) ]
*[http://www.alhurra.com/media/video/210481.html?z=0&zp=1 Report about Eng. Mohamed Osman Baloola in Alyoum , AlHurra TV (21:10-24:20)] | 0 | Theoretical and Fundamental Chemistry |
The flame point of a material is a temperature value at which sustained flame can be supported on the material once ignited by an external source. Once the flame point of a material is reached, it produces enough fuel vapors or oils to support continuous burning. | 0 | Theoretical and Fundamental Chemistry |
Sulfates in solution in contact with concrete can cause chemical changes to the cement, which can cause significant microstructural effects leading to the weakening of the cement binder (chemical sulfate attack). Sulfate solutions can also cause damage to porous cementitious materials through crystallization and recrystallization (salt attack). Sulfates and sulfites are ubiquitous in the natural environment and are present from many sources, including gypsum (calcium sulfate) often present as an additive in blended cements which include fly ash and other sources of sulfate. With the notable exception of barium sulfate, most sulfates are slightly to highly soluble in water. These include acid rain where sulfur dioxide in the airshed is dissolved in rainfall to produce sulfurous acid. In lightning storms, the dioxide is oxidized to trioxide making the residual sulfuric acid in rainfall even more highly acidic. Concrete sewage infrastructure is most commonly attacked by sulfuric acid and sulfate anions arising from the oxidation of sulfide present in the sewage. Sulfides are formed when sulfate-reducing bacteria present in sewer mains reduce the ubiquitous sulfate ions present in water drains into hydrogen sulfide gas (). is volatile and released from water in the sewage atmosphere. It dissolves in a thin film of water condensed onto the wall of the sewer ducts where it is also accompanied by hydrogeno-sulfide () and sulfide () ions. When and anions are further exposed to atmospheric oxygen or to oxygenated stormwater, they are readily oxidized and produce sulfuric acid (in fact acidic hydrogen ions accompanied by sulfate and bisulfate ions) according to the respective oxidation reactions:
or,
The corrosion often present in the crown (top) of concrete sewers is directly attributable to this process – known as crown rot corrosion. | 1 | Applied and Interdisciplinary Chemistry |
The portion of the MLSS that is actually eating the incoming food(in terms of COD & BOD) is referred to as the Mixed Liquor Volatile Suspended Solids (MLVSS). The volatile solids concentration in a sample of mixed liquor will consist mostly of microorganisms and organic matter. As a result, the volatile solids concentration of mixed liquor is approximately equal to the amount of microorganisms in the water and can be used to determine whether there are enough microorganisms present to purify the water | 0 | Theoretical and Fundamental Chemistry |
Amino acids can also be classified according to how many different amino acids they can be exchanged by through single nucleotide substitution.
* Typical amino acids - there are several other amino acids which they can change into through single nucleotide substitution. Typical amino acids and their alternatives usually have similar physicochemical properties. Leucine is an example of a typical amino acid.
* Idiosyncratic amino acids - there are few similar amino acids that they can mutate to through single nucleotide substitution. In this case most amino acid replacements will be disruptive for protein function. Tryptophan is an example of an idiosyncratic amino acid. | 1 | Applied and Interdisciplinary Chemistry |
Similar to DNA markers, these markers are typically composed of purified proteins whose molecular masses are already known. The list below outlines some of the proteins, as well as the molecular mass, that are commonly used when constructing a protein marker. | 1 | Applied and Interdisciplinary Chemistry |
N-linked glycosylation is a very prevalent form of glycosylation and is important for the folding of many eukaryotic glycoproteins and for cell–cell and cell–extracellular matrix attachment. The N-linked glycosylation process occurs in eukaryotes in the lumen of the endoplasmic reticulum and widely in archaea, but very rarely in bacteria. In addition to their function in protein folding and cellular attachment, the N-linked glycans of a protein can modulate a protein's function, in some cases acting as an on/off switch. | 0 | Theoretical and Fundamental Chemistry |
In geophysics, the Rayleigh number is of fundamental importance: it indicates the presence and strength of convection within a fluid body such as the Earths mantle. The mantle is a solid that behaves as a fluid over geological time scales. The Rayleigh number for the Earths mantle due to internal heating alone, Ra, is given by:
where:
*H is the rate of radiogenic heat production per unit mass
*η is the dynamic viscosity
*k is the thermal conductivity
*D is the depth of the mantle.
A Rayleigh number for bottom heating of the mantle from the core, Ra, can also be defined as:
where:
*ΔT is the superadiabatic temperature difference between the reference mantle temperature and the core–mantle boundary
*C is the specific heat capacity at constant pressure.
High values for the Earth's mantle indicates that convection within the Earth is vigorous and time-varying, and that convection is responsible for almost all the heat transported from the deep interior to the surface. | 1 | Applied and Interdisciplinary Chemistry |
Antidepressant exposure (including escitalopram) is associated with shorter duration of pregnancy (by three days), increased risk of preterm delivery (by 55%), lower birth weight (by 75 g), and lower Apgar scores (by <0.4 points). Antidepressant exposure is not associated with an increased risk of spontaneous abortion. There is a tentative association of SSRI use during pregnancy with heart problems in the baby. The advantages of their use during pregnancy may thus not outweigh the possible negative effects on the baby. | 0 | Theoretical and Fundamental Chemistry |
Other functional groups can undergo similar hydrolysis reactions. For instance, geminal trihalides (e.g. benzotrichloride) can be partially hydrolyzed to acyl halides (e.g. benzoyl chloride) in a similar way. Further hydrolysis yields carboxylic acids. | 0 | Theoretical and Fundamental Chemistry |
A photocarcinogen is a substance which causes cancer when an organism is exposed to it, then illuminated. Many chemicals that are not carcinogenic can be photocarcinogenic when combined with exposure to light, especially UV. This can easily be understood from a photochemical perspective: The reactivity of a chemical substance itself might be low, but after illumination it transitions to an excited state, which is chemically much more reactive and therefore potentially harmful to biological tissue and DNA. Light can also split photocarcinogens, releasing free radicals, whose unpaired electrons cause them to be extremely reactive.
The type of UV radiation determines the characteristics of photocarcinogenesis. For example, UVA radiation characteristically gives rise to reactive oxygen species (ROS) such as hydrogen peroxide whereas UVB radiation correlates with CPD lesions. The ROS are produced when endogenous photosensitizers are stimulated by UVA radiation. DNA absorption of UV radiation primarily leads to CPD and 6-4 lesions. The neighboring pyrimidines form a cyclobutane pyrimidine dimer in a CPD lesion. DNA absorption of UV radiation can also lead to TC, CC, and TT lesions but with much less frequency. The failure of DNA repair mechanisms to fix such lesions notably characterizes photocarcinogenesis.
In addition, UV radiation often increases the production of cytokines such as interleukin-10 which indirectly hinder antigen presentation in cells. Moreover, UV radiation frequently leads to mutations in the tumor suppressor gene p53 in photocarcinogenesis.
Determination of photocarcinogenicity can be accomplished using different techniques, including epidemiological studies and in-vivo studies. In one in-vivo technique, hairless mice are exposed to suspected photocarcinogens, and are then exposed to different wavelengths of light, ranging from visible to UV-B. Tumor incidence is compared to control mice that have not been exposed to the drug or chemical being tested.
Melanin is not a photocarcinogen, because it dissipates the excitation energy into small amounts of heat (see photoprotection). Oxybenzone (a component of some sunscreens) is suspected owing to its skin penetrating qualities and its production of free radicals. One medication that has been proven to be photocarcinogenic is psoralen. This drug is used in photodynamic therapy for many inflammatory skin conditions, where the drug is combined with skin exposure to UV light. Epidemiological studies dating back to the 1970s have shown a strong association between psoralen treatment and skin cancer incidence 5 to 15 years afterwards. A logistic regression study has shown that there is a positive association between citrus consumption, both in the form of fruit and fruit juice, and risk of developing melanoma. This increased risk is most profound in fair-skinned individuals. The reason for this correlation is the high concentration of the photocarcinogenic compound psoralen in citrus fruits. | 1 | Applied and Interdisciplinary Chemistry |
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