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Al-Youbi received his bachelor’s and master’s degree in chemistry from King Abdulaziz University. He attended the University of Essex on a scholarship, where he received his PhD in physical chemistry in 1986.
Before being appointed as president of King Abdulaziz University in 2016, he served as vice president. He was a consultant at the Ministry of Higher Education, and was dean and vice-dean of the faculty of science, King Abdulaziz University. | 0 | Theoretical and Fundamental Chemistry |
William Carl Lineberger (born December 5, 1939-[https://jila.colorado.edu/news-events/news/remembering-jila-fellow-w-carl-lineberger October 17, 2023]) was an American chemist.
A native of Hamlet, North Carolina, William Carl Lineberger was born to parents Caleb Henry and Evelyn Pelot Cooper Lineberger on December 5, 1939. His mother was a former teacher and his father was a railroad worker. Through his mother, Lineberger is of French Huguenot descent. As a child, Lineberger was a Boy Scout and made Eagle rank. After completing his bachelors, masters and doctoral degrees at the Georgia Institute of Technology, Lineberger began teaching at his alma mater, leaving for a research position at the U. S. Army Ballistic Research Laboratory and later the Joint Institute for Laboratory Astrophysics. The University of Colorado at Boulder, one of two joint operators of JILA, hired Lineberger as an assistant professor in 1970. He was named E. U. Condon Distinguished Professor of Chemistry at the University of Colorado in 1985.
Over the course of his career, Lineberger received several awards. Among them are: the Herbert P. Broida Prize (1981) awarded by the American Physical Society, the Earle K. Plyler Prize for Molecular Spectroscopy (1992), Irving Langmuir Award (1996) and Peter Debye Award (2004) of the American Chemical Society, and the William F. Meggers Award in Spectroscopy (1989) from the Optical Society of America. Lineberger received the NAS Award in Chemical Sciences in 2015. Linberger is a member of the American Chemical Society as well as the National Academy of Sciences (1983) and American Academy of Arts and Sciences (1995). He is a fellow of the American Association for the Advancement of Science and the American Physical Society (1973). From 2011 to 2016, Lineberger served on the National Science Board and was nominated for a second term by Barack Obama in 2016. | 0 | Theoretical and Fundamental Chemistry |
Sauvagine has been shown to interact with corticotropin releasing factor receptors 1 and 2, and (as with other CRF-related peptides) is also bound by the corticotropin-releasing factor binding protein. | 1 | Applied and Interdisciplinary Chemistry |
CpG islands are commonly 200 to 2000 base pairs long, have a C:G base pair content >50%, and have frequent 5 → 3 CpG sequences. About 70% of human promoters located near the transcription start site of a gene contain a CpG island.
Promoters located at a distance from the transcription start site of a gene also frequently contain CpG islands. The promoter of the DNA repair gene ERCC1, for instance, was identified and located about 5,400 nucleotides upstream of its coding region. CpG islands also occur frequently in promoters for functional noncoding RNAs such as microRNAs and Long non-coding RNAs (lncRNAs). | 1 | Applied and Interdisciplinary Chemistry |
Hand-counting is a cheap and easy to conduct method to estimate the liberation characteristics of a bulk sample wither originating from run-of-mine material, a waste dump or for example exploration trenching. Analysis of particles in the size range 10-100mm has been conducted on a total sample mass of 10 tonnes. By visual inspection of trained personnel, a classification of each particle into different bins (e.g. lithology, grade) is possible and the distribution is determined by weighing each bin. A trained professional can quickly estimate the efficiency of a specific detection and process efficiency of sensor-based ore sorting knowing the sensor response of the mineralogy of ore in question and other process efficiency parameters. | 0 | Theoretical and Fundamental Chemistry |
The deepest gold mines of the Ancient world were found in the Maski region in Karnataka. There were ancient silver mines in northwest India. Dated to the middle of the 1st millennium BCE. gold and silver were also used for making utensils for the royal family and nobilities.the royal family wore costly fabrics that were made from gold and silver thin fibres embroidered or woven into fabrics or dress. | 1 | Applied and Interdisciplinary Chemistry |
In granulometry, the particle-size distribution (PSD) of a powder, or granular material, or particles dispersed in fluid, is a list of values or a mathematical function that defines the relative amount, typically by mass, of particles present according to size. Significant energy is usually required to disintegrate soil, etc. particles into the PSD that is then called a grain size distribution. | 0 | Theoretical and Fundamental Chemistry |
The ability of pitch to contaminate those in contact with it is mentioned by Dogberry, a character in Shakespeares Much Ado About Nothing', and the same point is made in a speech by Falstaff in Henry IV, Part 1, who refers to "ancient writers" who have made this observation. The Jewish deuterocanonical Book of Sirach states that "whoever touches pitch gets dirty, and whoever associates with a proud person becomes like him". | 0 | Theoretical and Fundamental Chemistry |
Due to the potential for wear protection at high temperatures beyond which conventional lubricants can be used, possible uses have been speculated in applications such as car engines, power generation and even aerospace, where there is an increasing demand for ever higher efficiency and thus operating temperature. | 1 | Applied and Interdisciplinary Chemistry |
The molecular demon switches mainly between two conformations. The first, or basic state, upon recognizing and binding the ligand or substrate following an induced fit, undergoes a change in conformation which leads to the second quasi-stable state: the protein-ligand complex. In order to reset the protein to its original, basic state, it needs ATP. When ATP is consumed or hydrolyzed, the ligand is released and the demon acquires again information reverting to its basic state. The cycle may start again. | 0 | Theoretical and Fundamental Chemistry |
The specific speed value for a turbine is the speed of a geometrically similar turbine which would produce unit power (one kilowatt) under unit head (one meter). The specific speed of a turbine is given by the manufacturer (along with other ratings) and will always refer to the point of maximum efficiency. This allows accurate calculations to be made of the turbine's performance for a range of heads.
Well-designed efficient machines typically use the following values: Impulse turbines have the lowest n values, typically ranging from 1 to 10, a Pelton wheel is typically around 4, Francis turbines fall in the range of 10 to 100, while Kaplan turbines are at least 100 or more, all in imperial units. | 1 | Applied and Interdisciplinary Chemistry |
Consider the Galvanic cell shown in the adjacent image: it is constructed with a piece of zinc (Zn) submerged in a solution of zinc sulfate () and a piece of copper (Cu) submerged in a solution of copper(II) sulfate (). The overall reaction is:
At the Zn anode, oxidation takes place (the metal loses electrons). This is represented in the following oxidation half reaction (note that the electrons are on the products side):
At the Cu cathode, reduction takes place (electrons are accepted). This is represented in the following reduction half reaction (note that the electrons are on the reactants side): | 0 | Theoretical and Fundamental Chemistry |
# Leave out the Bravais lattice type.
# Convert all symmetry elements with translational components into their respective symmetry elements without translation symmetry. (Glide planes are converted into simple mirror planes; screw axes are converted into simple axes of rotation.)
# Axes of rotation, rotoinversion axes, and mirror planes remain unchanged. | 0 | Theoretical and Fundamental Chemistry |
Elly Schwab-Agallidis (born Elly Agallidis, , ; – ) was a Greek physicist/physical chemist and one of the first women in Greece to be awarded a PhD in the field. She was the wife of Georg-Maria Schwab, who met her in Munich as the supervisor of the experimental work for her doctoral thesis; the couple then worked together as researchers in the Kanellopoulos Institute after they emigrated in Greece. Her most famous work concerned the properties and reactivity of parahydrogen. | 0 | Theoretical and Fundamental Chemistry |
Limit rods may be used in an expansion joint design to limit the axial compression or expansion. They allow the expansion joint to move over a range according to where the nut stops are placed along the rods. Limit rods are used to prevent bellows over-extension while restraining the full pressure thrust of the system. | 1 | Applied and Interdisciplinary Chemistry |
Dirubidium has several excited states, and spectral bands occur for transitions between these levels, combined with vibration. It can be studied by its absorption lines, or by laser induced-fluorescence. Laser induced-fluorescence can reveal the life-times of excited states.
In the absorption spectrum of rubidium vapour, Rb has a major effect. Single atoms of rubidium in the vapour cause lines in the spectrum, but the dimer causes wider bands to appear. The most severe absorption between 640 and 730 nm makes the vapour almost opaque from 670 to 700 nm, wiping out the far red end of the spectrum. This is the band due to X→B transition. From 430 to 460 nm there is a shark-fin shaped absorption feature due to X→E transitions. Another shark fin like effect around 475 nm s due to X→D transitions. There is also a small hump with peaks at 601, 603 and 605.5 nm 1→3 triplet transitions and connected to the diffuse series. There are a few more small absorption features in the near infrared.
There is also a dirubidium cation, Rb with different spectroscopic properties. | 0 | Theoretical and Fundamental Chemistry |
The metal can be situated in the repeat unit, the core or at the extremities as end-group. Elements often encountered are palladium and platinum. These metals can form octahedral six-coordinate M(IV) linking units from organic dihalides and the corresponding 4-coordinate M(II) monomers. Ferrocene-containing dendrimers and dendrimers with cobaltocene and arylchromiumtricarbonyl units have been reported in end-functional dendrimers.
Metallodendrimers can form as metal complexes with dendritic counter ions for example by hydrolysis of ester terminated PAMAM dendrimers with sodium hydroxide. | 0 | Theoretical and Fundamental Chemistry |
In a GC-O analysis, various methods are used to determine the odour contribution of a compound or the relative importance of each odorant. The methods can be categorised as (i) detection frequency, (ii) dilution to threshold and (iii) direct intensity. | 0 | Theoretical and Fundamental Chemistry |
A fusible alloy is a metal alloy capable of being easily fused, i.e. easily meltable, at relatively low temperatures. Fusible alloys are commonly, but not necessarily, eutectic alloys.
Sometimes the term "fusible alloy" is used to describe alloys with a melting point below . Fusible alloys in this sense are used for solder. | 1 | Applied and Interdisciplinary Chemistry |
When quality control of TEMPs is considered, a risk assessment needs to be conducted. A risk is defined as a "potentially unfavourable effect that can be attributed to the clinical use of advanced therapy medicinal products (ATMPs) and is of concern to the patient and/or to other populations (e.g. caregivers and off-spring)". Some risks include immunogenicity, disease transmission, tumor formation, treatment failure, undesirable tissue formation, and inadvertent germ transduction. A risk factor is defined as a "qualitative or quantitative characteristic that contributes to a specific risk following handling and/or administration of an ATMP". The integration of all available information on risks and risk factors is called risk profiling. Due to the fact that every TEMP is different, the risks associated with each one of them vary and, subsequently, the procedures that must be implemented to ensure its quality are also unique to the product. Once the risks associated with the TEMP are identified, the appropriate tests must be developed and validated accordingly. Thus, there is no standard set of tests for the quality control of TEMPs. The EMA has released a set of regulatory guidelines on the topics to be considered by companies involved in the development and marketing of medicines for use in the European Union. These guidelines have to be followed in order for the marketing authorization of a product to be issued. Fictitious examples of risk analysis for further elucidation of the process are provided in the EMA guidelines. | 1 | Applied and Interdisciplinary Chemistry |
The glycine cleavage system (GCS) is also known as the glycine decarboxylase complex or GDC. The system is a series of enzymes that are triggered in response to high concentrations of the amino acid glycine. The same set of enzymes is sometimes referred to as glycine synthase when it runs in the reverse direction to form glycine. The glycine cleavage system is composed of four proteins: the T-protein, P-protein, L-protein, and H-protein. They do not form a stable complex, so it is more appropriate to call it a "system" instead of a "complex". The H-protein is responsible for interacting with the three other proteins and acts as a shuttle for some of the intermediate products in glycine decarboxylation. In both animals and plants, the glycine cleavage system is loosely attached to the inner membrane of the mitochondria. Mutations in this enzymatic system are linked with glycine encephalopathy. | 1 | Applied and Interdisciplinary Chemistry |
Affinity chromatography is a method of separating a biomolecule from a mixture, based on a highly specific macromolecular binding interaction between the biomolecule and another substance. The specific type of binding interaction depends on the biomolecule of interest; antigen and antibody, enzyme and substrate, receptor and ligand, or protein and nucleic acid binding interactions are frequently exploited for isolation of various biomolecules. Affinity chromatography is useful for its high selectivity and resolution of separation, compared to other chromatographic methods. | 0 | Theoretical and Fundamental Chemistry |
Three factors define an ideal plasma:
*The plasma approximation: The plasma approximation applies when the plasma parameter Λ, representing the number of charge carriers within the Debye sphere is much higher than unity. It can be readily shown that this criterion is equivalent to smallness of the ratio of the plasma electrostatic and thermal energy densities. Such plasmas are called weakly coupled.
*Bulk interactions: The Debye length is much smaller than the physical size of the plasma. This criterion means that interactions in the bulk of the plasma are more important than those at its edges, where boundary effects may take place. When this criterion is satisfied, the plasma is quasineutral.
*Collisionlessness: The electron plasma frequency (measuring plasma oscillations of the electrons) is much larger than the electron–neutral collision frequency. When this condition is valid, electrostatic interactions dominate over the processes of ordinary gas kinetics. Such plasmas are called collisionless. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, Hückels rule predicts that a planar ring molecule will have aromatic properties if it has 4n + 2 π electrons, where n is a non-negative integer. The quantum mechanical basis for its formulation was first worked out by physical chemist Erich Hückel in 1931. The succinct expression as the 4n' + 2 rule has been attributed to W. v. E. Doering (1951), although several authors were using this form at around the same time.
In agreement with the Möbius–Hückel concept, a cyclic ring molecule follows Hückels rule when the number of its π-electrons equals 4n + 2, although clearcut examples are really only established for values of n = 0 up to about n = 6. Hückels rule was originally based on calculations using the Hückel method, although it can also be justified by considering a particle in a ring system, by the LCAO method and by the Pariser–Parr–Pople method.
Aromatic compounds are more stable than theoretically predicted using hydrogenation data of simple alkenes; the additional stability is due to the delocalized cloud of electrons, called resonance energy. Criteria for simple aromatics are:
# the molecule must have 4n + 2 (a so-called "Hückel number") π electrons (2, 6, 10, ...) in a conjugated system of p orbitals (usually on sp-hybridized atoms, but sometimes sp-hybridized);
# the molecule must be (close to) planar (p orbitals must be roughly parallel and able to interact, implicit in the requirement for conjugation);
# the molecule must be cyclic (as opposed to linear);
# the molecule must have a continuous ring of p atomic orbitals (there cannot be any sp atoms in the ring, nor do exocyclic p orbitals count). | 0 | Theoretical and Fundamental Chemistry |
* Ciliata: Oxytricha and Stylonychia, Paramecium, Tetrahymena, Oxytrichidae and probably Glaucoma chattoni.
* Dasycladaceae: Acetabularia, and Batophora.
* Diplomonadida: Hexamita inflata, Diplomonadida ATCC50330, and ATCC50380. | 1 | Applied and Interdisciplinary Chemistry |
The formulae for rokushō are not published widely or freely, but passed on in the Japanese craft tradition. However, some scholars have analysed samples of the material.
Premixed rokushō can be purchased outside Japan through specialty jewelry suppliers. Additionally, several different formulas have been proposed to replicate the traditional product for those who prefer to make their own:
* In a container made of glass, porcelain, or copper, dissolve 6g copper acetate, 2g calcium carbonate, and 2g sodium hydroxide in 150ml water. After a week, siphon or decant the clear liquid from the top; just before use, add another 2g copper sulfate.
* Dissolve 4g copper acetate, 1g copper nitrate, 1g cupric chloride, and 4g copper sulfate in 1 liter of distilled water.
* Dissolve 60g copper acetate and 60g copper sulfate in a 2-liter solution of white vinegar diluted 5-12% with water.
Rokusho is not used alone, but mixed with one or more other chemicals. Further, metal to be processed is cleaned in advance of treatment, using a mild acid bath (oxalic or sulfuric acids are frequently used), scrubbing with daikon radish or pumice, and/or a surface abrasive, and often treated after patination also. | 1 | Applied and Interdisciplinary Chemistry |
In a homogeneous crystalline structure, because of the uniform lattice structure of the metal ions, there is hardly any momentum transfer between the conduction electrons and the metal ions. However, this symmetry does not exist at the grain boundaries and material interfaces, and so here momentum is transferred much more vigorously. Since the metal ions in these regions are bonded more weakly than in a regular crystal lattice, once the electron wind has reached a certain strength, atoms become separated from the grain boundaries and are transported in the direction of the current. This direction is also influenced by the grain boundary itself, because atoms tend to move along grain boundaries.
Diffusion processes caused by electromigration can be divided into grain boundary diffusion, bulk diffusion and surface diffusion. In general, grain boundary diffusion is the major electromigration process in aluminum wires, whereas surface diffusion is dominant in copper interconnects. | 0 | Theoretical and Fundamental Chemistry |
Glugging (also referred to as "the glug-glug process") is the physical phenomenon which occurs when a liquid is poured rapidly from a vessel with a narrow opening, such as a bottle. It is a facet of fluid dynamics.
As liquid is poured from a bottle, the air pressure in the bottle is lowered, and air at higher pressure from outside the bottle is forced into the bottle, in the form of a bubble, impeding the flow of liquid. Once the bubble enters, more liquid escapes, and the process is repeated. The reciprocal action of glugging creates a rhythmic sound. The English word "glug" is onomatopoeic, describing this sound. Onomatopoeias in other languages include (German).
Academic papers have been written about the physics of glugging, and about the impact of glugging sounds on consumers' perception of products such as wine. Research into glugging has been done using high-speed photography.
Factors which affect glugging are the viscosity of the liquid, its carbonation, the size and shape of the container's neck and its opening (collectively referred to as "bottle geometry"), the angle at which the container is held, and the ratio of air to liquid in the bottle (which means that the rate and the sound of the glugging changes as the bottle empties). | 1 | Applied and Interdisciplinary Chemistry |
** HIBALL study by German and US institutions, Garching uses the high repetition rate of the RF accelerator driver to serve four reactor chambers and first-wall protection using liquid lithium inside the chamber cavity.
** Tore Supra construction starts at Cadarache, France. Its superconducting magnets will permit it to generate a strong permanent toroidal magnetic field.
** high-confinement mode (H-mode) discovered in tokamaks.
** JET, the largest operational magnetic confinement plasma physics experiment is completed on time and on budget. First plasmas achieved.
** The NOVETTE laser at LLNL comes on line and is used as a test bed for the next generation of ICF lasers, specifically the NOVA laser.
** The huge 10 beam NOVA laser at LLNL is completed and switches on in December. NOVA would ultimately produce a maximum of 120 kilojoules of infrared laser light during a nanosecond pulse in a 1989 experiment.
** National Academy of Sciences reviewed military ICF programs, noting HIF's major advantages clearly but averring that HIF was "supported primarily by other [than military] programs". The review of ICF by the National Academy of Sciences marked the trend with the observation: "The energy crisis is dormant for the time being." Energy becomes the sole purpose of heavy ion fusion.
** The Japanese tokamak, JT-60 completed. First plasmas achieved.
** The T-15, Soviet tokamak with superconducting helium-cooled coils completed.
** The Conceptual Design Activity for the International Thermonuclear Experimental Reactor (ITER), the successor to T-15, TFTR, JET and JT-60, begins. Participants include EURATOM, Japan, the Soviet Union and United States. It ended in 1990.
** The first plasma produced at Tore Supra in April.
** On March 23, two Utah electrochemists, Stanley Pons and Martin Fleischmann, announced that they had achieved cold fusion: fusion reactions which could occur at room temperatures. However, they made their announcements before any peer review of their work was performed, and no subsequent experiments by other researchers revealed any evidence of fusion. | 0 | Theoretical and Fundamental Chemistry |
The kiln is usually turned by means of a single Girth Gear surrounding a cooler part of the kiln tube, but sometimes it is turned by driven rollers. The gear is connected through a gear train to a variable-speed electric motor. This must have high starting torque to start the kiln with a large eccentric load. A 6 x 60 m kiln requires around 800 kW to turn at 3 rpm. The speed of material flow through the kiln is proportional to rotation speed; a variable-speed drive is needed to control this. When driving through rollers, hydraulic drives may be used. These have the advantage of developing extremely high torque. In many processes, it is dangerous to allow a hot kiln to stand still if the drive power fails. Temperature differences between the top and bottom of the kiln may cause the kiln to warp, and refractory is damaged. Hence, normal practice is to provide an auxiliary drive for use during power cuts. This may be a small electric motor with an independent power supply, or a diesel engine. This turns the kiln very slowly, but enough to prevent damage. | 1 | Applied and Interdisciplinary Chemistry |
In fluid dynamics, the Küssner effect describes the unsteady aerodynamic forces on an airfoil or hydrofoil caused by encountering a transverse gust. This is directly related to the Küssner function, used in describing the effect. Both the effect and function are named after Hans Georg Küssner (1900–1984), a German aerodynamics engineer.
Küssner derived an approximate model for an airfoil encountering a sudden step-like change in the transverse gust velocity; or, equivalently, as seen from a frame of reference moving with the airfoil: a sudden change in the angle of attack. The airfoil is modelled as a flat plate in a potential flow, moving with constant horizontal velocity. For this case he derived the impulse response function (known as Küssner function) needed to compute the unsteady lift and moment exerted by the air on the airfoil. | 1 | Applied and Interdisciplinary Chemistry |
The atoms in the GB are normally in a higher energy state than their equivalent in the bulk material. This is due to their more stretched bonds, which gives rise to a GB tension . This extra energy that the atoms possess is called the grain boundary energy, . The grain will want to minimize this extra energy, thus striving to make the grain boundary area smaller and this change requires energy.
"Or, in other words, a force has to be applied, in the plane of the grain boundary and acting along a line in the grain-boundary area, in order to extend the grain-boundary area in the direction of the force. The force per unit length, i.e. tension/stress, along the line mentioned is σGB. On the basis of this reasoning it would follow that:
with dA as the increase of grain-boundary area per unit length along the line in the grain-boundary area considered."
The GB tension can also be thought of as the attractive forces between the atoms at the surface and the tension between these atoms is due to the fact that there is a larger interatomic distance between them at the surface compared to the bulk (i.e. surface tension). When the surface area becomes bigger the bonds stretch more and the GB tension increases. To counteract this increase in tension there must be a transport of atoms to the surface keeping the GB tension constant. This diffusion of atoms accounts for the constant surface tension in liquids. Then the argument,
holds true. For solids, on the other hand, diffusion of atoms to the surface might not be sufficient and the surface tension can vary with an increase in surface area.
For a solid, one can derive an expression for the change in Gibbs free energy, dG, upon the change of GB area, dA. dG is given by
which gives
is normally expressed in units of while is normally expressed in units of since they are different physical properties. | 1 | Applied and Interdisciplinary Chemistry |
One example of crosstalk between proteins in a signalling pathway can be seen with cyclic adenosine monophosphate's (cAMP) role in regulating cell proliferation by interacting with the mitogen-activated protein (MAP) kinase pathway. cAMP is a compound synthesized in cells by adenylate cyclase in response to a variety of extracellular signals. cAMP primarily acts as an intracellular second messenger whose major intracellular receptor is the cAMP-dependent protein kinase (PKA) that acts through the phosphorylation of target proteins. The signal transduction pathway begins with ligand-receptor interactions extracellularly. This signal is then transduced through the membrane, stimulating adenylyl cyclase on the inner membrane surface to catalyze the conversion of ATP to cAMP.
ERK, a participating protein in the MAPK signaling pathway, can be activated or inhibited by cAMP. cAMP can inhibit ERKs in a variety of ways, most of which involve the cAMP-dependent protein kinase (PKA) and the inhibition of Ras-dependent signals to Raf-1. However, cAMP can also stimulate cell proliferation by stimulating ERKs. This occurs through the induction of specific genes via phosphorylation of the transcription factor CREB by PKA. Though ERKs do not appear to be a requirement for this phosphorylation of CREB, the MAPK pathway does play into crosstalk again, as ERKs are required to phosphorylate proteins downstream of CREB. Other known examples of the requirement of ERKs for cAMP-induced transcriptional effects include induction of the prolactin gene in pituitary cells, and of the dopamine beta-hydroxylate gene in pheochromocytomal cells (PC12). A number of diverse mechanisms exist by which cAMP can influence ERK signaling. Most mechanisms involving cAMP inhibition of ERKs uncouple Raf-1 from Ras activation through direct interaction of PKA with Raf-1 or indirectly through PKA interaction with the GTPase Rap1 (see figure 1). PKA may also negatively regulate ERKs by the activation of PTPases. Mechanisms for the activation of ERKs by cAMP are even more varied, usually including Rap1 or Ras, and even cAMP directly. | 1 | Applied and Interdisciplinary Chemistry |
A special type of bow, called a bulbous bow, is often used on large power vessels to reduce wave-making drag. The bulb alters the waves generated by the hull, by changing the pressure distribution ahead of the bow. Because of the nature of its destructive interference with the bow wave, there is a limited range of vessel speeds over which it is effective. A bulbous bow must be properly designed to mitigate the wave-making resistance of a particular hull over a particular range of speeds. A bulb that works for one vessels hull shape and one range of speeds could be detrimental to a different hull shape or a different speed range. Proper design and knowledge of a ships intended operating speeds and conditions is therefore necessary when designing a bulbous bow. | 1 | Applied and Interdisciplinary Chemistry |
For calculations with MEMO, a file must be provided which contains orography height and surface type for each grid location The following surface types are distinguished and must be stored as percentage:
* water (type: 1)
* arid land (type: 2)
* few vegetation (type: 3)
* farmland (type: 4)
* forest (type: 5)
* suburban area (type: 6)
* urban area (type: 7)
Only surface types 1–6 have to be stored. Type 7 is the difference between 100% and the sum of types 1–6. If the percentage of a surface type is 100%, then write the number 10 and for all other surface types the number 99.
The orography height is the mean height for each grid location above sea level in meter. | 1 | Applied and Interdisciplinary Chemistry |
Carbon nanotubes are meant to potentially solve the typical tradeoff between the permeability and the selectivity of RO membranes. CNTs present many ideal characteristics including: mechanical strength, electron affinity, and also exhibiting flexibility during modification. By restructuring carbon nanotubes and coating or impregnating them with other chemical compounds, scientists can manufacture these membranes to have all of the most desirable traits. The hope with CNT membranes is to find a combination of high water permeability while also decreasing the amount of neutral solutes taken out of the water. This would help decrease energy costs and the cost of remineralization after purification through the membrane. | 0 | Theoretical and Fundamental Chemistry |
In an octahedral complex, the molecular orbitals created by coordination can be seen as resulting from the donation of two electrons by each of six σ-donor ligands to the d-orbitals on the metal. In octahedral complexes, ligands approach along the x-, y- and z-axes, so their σ-symmetry orbitals form bonding and anti-bonding combinations with the d−y, d and d orbitals remain non-bonding orbitals. Some weak bonding (and anti-bonding) interactions with the s and p orbitals of the metal also occur, to make a total of 6 bonding (and 6 anti-bonding) molecular orbitals
In molecular symmetry terms, the six lone-pair orbitals from the ligands (one from each ligand) form six symmetry-adapted linear combinations (SALCs) of orbitals, also sometimes called ligand group orbitals (LGOs). The irreducible representations that these span are a, t and e. The metal also has six valence orbitals that span these irreducible representations - the s orbital is labeled a, a set of three p-orbitals is labeled t, and the d−y. The six σ-bonding molecular orbitals result from the combinations of ligand SALCs with metal orbitals of the same symmetry. | 0 | Theoretical and Fundamental Chemistry |
A different type of "blue roof" has been proposed by researchers at the Lawrence Berkeley National Laboratory, who researched a pigment used by the ancient Egyptians known as "Egyptian blue." This color, derived from calcium copper silicate, absorbs visible light, and emits light in the near-infrared range, helping keep roofs and walls cool. | 1 | Applied and Interdisciplinary Chemistry |
There have been several enantioselective versions of this reaction developed, and even employed in synthesis of complex molecules. Hoyvedas synthesis of (R')-(-)-sporochnol included an asymmetric copper-catalyzed allylic substitution with an organozinc nucleophile and peptide ligand.
A TaniaPHOS ligand, a ferrocenylphosphine, is used with a methyl Grignard nucleophile to form an allylic stereocenter towards the total synthesis of (S)-(-)-Zearalenone
Allylic substitutions are one class of the several types of reactions carried out by organocuprate reagents. | 0 | Theoretical and Fundamental Chemistry |
6-Phosphogluconolactone is an intermediate in the pentose phosphate pathway (PPP).
In the PPP pathway, it is produced from glucose-6-phosphate by glucose-6-phosphate dehydrogenase. It is then converted to 6-Phosphogluconic acid by 6-phosphogluconolactonase. | 1 | Applied and Interdisciplinary Chemistry |
* 2021, ACS Carothers Award
* 2019, DuPont Company Lavoisier Medal
* 2018, elected to the National Academy of Engineering
* 2018, named Fellow of the SPIE
* 2016, Perkin Medal, from the Society of Chemical Industry
* 2014, ACS Heroes of Chemistry, from the American Chemical Society (one of thirteen scientists from the Dow Chemical Company credited with the development of Dow AR Fast Etch Organic Bottom Antireflectant Coatings)
* 2013, SPIE C. Grant Willson Best Paper Award in Patterning Materials and Processes jointly with researchers at Dow and Texas A&M University, from SPIE for the paper "Bottom-up / top-down high-resolution, high-throughput lithography using vertically assembled block brush polymers". | 0 | Theoretical and Fundamental Chemistry |
Mixture fraction () is a quantity used in combustion studies that measures the mass fraction of one stream (usually the fuel stream) of a mixture formed by two feed streams, one the fuel stream and the other the oxidizer stream. Both the feed streams are allowed to have inert gases. The mixture fraction definition is usually normalized such that it approaches unity in the fuel stream and zero in the oxidizer stream. The mixture-fraction variable is commonly used as a replacement for the physical coordinate normal to the flame surface, in nonpremixed combustion. | 1 | Applied and Interdisciplinary Chemistry |
Some types of [http://www.epilepsy.com/ epilepsy] may be brought on due to a splice site mutation.
In addition to a mutation in a stop codon, a splice site mutation on the 3' strand was found in a gene coding for cystatin B in Progressive Myoclonus Epilepsy patients. This combination of mutations was not found in unaffected individuals. By comparing sequences with and without the splice site mutation, investigators were able to determine that a G-to-C nucleotide transversion occurs at the last position of the first intron. This transversion occurs in the region that codes for the cystatin B gene. Individuals suffering from Progressive Myoclonus Epilepsy possess a mutated form of this gene, which results in decreased output of mature mRNA, and subsequently decreases in protein expression.
A study has also shown that a type of Childhood Absence Epilepsy (CAE) causing febrile seizures may be linked to a splice site mutation in the sixth intron of the [https://www.ncbi.nlm.nih.gov/gene/2566 GABRG2 gene]. This splice site mutation was found to cause a nonfunctional GABRG2 subunit in affected individuals. According to this study, a point mutation was the culprit for the splice-donor site mutation, which occurred in intron 6. A nonfunctional protein product is produced, leading to the also nonfunctional subunit. | 1 | Applied and Interdisciplinary Chemistry |
Some available in situ measurement techniques include:
* Aerosol mass spectrometer (AMS)
* Differential mobility analyzer (DMA)
* Electrical aerosol spectrometer (EAS)
* Aerodynamic particle sizer (APS)
* Aerodynamic aerosol classifier (AAC)
* Wide range particle spectrometer (WPS)
* Micro-Orifice Uniform Deposit Impactor(MOUDI)
* Condensation particle counter (CPC)
* Epiphaniometer
* Electrical low pressure impactor (ELPI)
* Aerosol particle mass-analyser (APM)
* Centrifugal Particle Mass Analyser (CPMA) | 0 | Theoretical and Fundamental Chemistry |
The International Palladium Medal was instituted in 1958 and first awarded in 1961. The first recipient was Ernest-John Solvay. The medal has generally been given every two years.
The Société has also been involved in nominating and choosing the recipients of the Othmer Gold Medal and the Winthrop-Sears Medal, which are given yearly. | 1 | Applied and Interdisciplinary Chemistry |
This term has become very popular and commonly used in practice. But the appropriate expression is "enantioselective chromatography". Chiral chromatography has advanced to turn into the most preferred technique for the determination of enantiomeric purity as well as separation of pure enantiomers both on analytical and preparative scale. Chiral chromatographic assay is the first step in any study pertaining to enantioselective synthesis or separation. This includes the use of techniques viz. gas chromatography (GC), high performance liquid chromatography (HPLC), chiral supercritical fluid chromatography (SFC), capillary electrophoresis (CE) and thin-layer chromatography (TLC). The result of a literature survey done identifies HPLC-based chiral assays as the most dominating technology in use. An overview of various analytical methods engaged for chiral separation and analysis are listed in the table. | 0 | Theoretical and Fundamental Chemistry |
Deprotonation at the α-carbon of an oxazolidinone imide with a strong base such as lithium diisopropylamide selectively furnishes the (Z)-enolate, which can undergo stereoselective alkylation.
Activated electrophiles, such as allylic or benzylic halides, are very good substrates. | 0 | Theoretical and Fundamental Chemistry |
The Hamiltonian structure of surface gravity waves on a potential flow was discovered by Vladimir E. Zakharov in 1968, and rediscovered independently by Bert Broer and John Miles:
where the surface elevation and surface potential — which is the potential at the free surface — are the canonical variables. The Hamiltonian is the sum of the kinetic and potential energy of the fluid:
The additional constraint is that the flow in the fluid domain has to satisfy Laplace's equation with appropriate boundary condition at the bottom and that the potential at the free surface is equal to : | 1 | Applied and Interdisciplinary Chemistry |
Riveting is one of the most ancient metalwork joining processes. Its use declined markedly during the second half of the 20th century, but it still retains important uses in industry and construction, and in artisan crafts such as jewellery, medieval armouring and metal couture in the early 21st century. The earlier use of rivets is being superseded by improvements in welding and component fabrication techniques.
A rivet is essentially a two-headed and unthreaded bolt which holds two other pieces of metal together. Holes are drilled or punched through the two pieces of metal to be joined. The holes being aligned, a rivet is passed through the holes and permanent heads are formed onto the ends of the rivet utilizing hammers and forming dies (by either cold working or hotworking).
Rivets are commonly purchased with one head already formed.
When it is necessary to remove rivets, one of the rivet's heads is sheared off with a cold chisel. The rivet is then driven out with a hammer and punch. | 1 | Applied and Interdisciplinary Chemistry |
Bulgarian Professor Petko Dimitrov is the creator of the idea for the application of sapropel sediments from the bottom of the Black Sea as a natural ecological fertilizer and biological products. According to the Romanian tycoon Dinu Patriciu, the sapropel sediments have the potential to be a source of non-conventional energy. Patriciu has created a marine exploration project in the Black Sea which examines the sapropel sediments of that region. Sediment cores are collected and investigated by several universities and research institutes across the world. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, hydroamination is the addition of an bond of an amine across a carbon-carbon multiple bond of an alkene, alkyne, diene, or allene. In the ideal case, hydroamination is atom economical and green. Amines are common in fine-chemical, pharmaceutical, and agricultural industries. Hydroamination can be used intramolecularly to create heterocycles or intermolecularly with a separate amine and unsaturated compound. The development of catalysts for hydroamination remains an active area, especially for alkenes. Although practical hydroamination reactions can be effected for dienes and electrophilic alkenes, the term hydroamination often implies reactions metal-catalyzed processes. | 0 | Theoretical and Fundamental Chemistry |
Minimise the lateral pressure of the strings by adjusting the alignment tine bar to avoid the string being cut off. Have ceramic tube place over each aligning tine bar to act as bearing surface for the strings. | 0 | Theoretical and Fundamental Chemistry |
Helium-3 surface spin echo (HeSE) is an inelastic scattering technique in surface science that has been used to measure microscopic dynamics at well-defined surfaces in ultra-high vacuum. The information available from HeSE complements and extends that available from other inelastic scattering techniques such as neutron spin echo and traditional helium-4 atom scattering (HAS). | 0 | Theoretical and Fundamental Chemistry |
Certified reference materials (CRMs) are controls or standards used to check the quality and metrological traceability of products, to validate analytical measurement methods, or for the calibration of instruments. A certified reference material is a particular form of measurement standard.
Reference materials are particularly important for analytical chemistry and clinical analysis. Since most analytical instrumentation is comparative, it requires a sample of known composition (reference material) for accurate calibration. These reference materials are produced under stringent manufacturing procedures and differ from laboratory reagents in their certification and the traceability of the data provided.
Quality management systems involving laboratory accreditation under national and international accreditation/certification standards such as ISO/IEC 17025 require metrological traceability to Certified Reference Materials (where possible) when using reference materials for calibration.
Whilst Certified Reference Materials are preferred where available, their availability is limited. Reference Materials that do not meet all the criteria for certified reference materials are more widely available: the principal difference is the additional evidence of metrological traceability and statement of measurement uncertainty provided on the certificate for certified reference materials. | 0 | Theoretical and Fundamental Chemistry |
Pseudin-2 was shown to have potent antibacterial activity, but a lower cytotoxicity. The cytotoxicity of a peptide can be measured by its effect on human erythrocytes. It takes a lower concentration of Pseudin-2 to kill bacteria or fungi such as E. coli, S. aureus, and C. albicans than to kill human erythrocytes. It is hypothesized that Pseudin-2 binding to the cell membrane of the bacteria results in a conformational change in which the peptide forms an α-helical shape, which allows it to perform cell lysis by inserting itself in the hydrophobic portion of the membrane. This mechanism is applicable to similar amphipathic α-helical peptides created by many frog species, although most of these peptides aren't very potent against bacteria. By increasing the cationicity and amphipathic nature of the molecule, it is possible to create analogues of Pseudin-2 that are even more selective towards bacteria. This is done by substituting leucine residues with lysine residues and glycine residues with proline residues, which results in two shorter α-helices (linked by the substituted proline) that are more attuned to penetrating bacterial cell membranes. | 1 | Applied and Interdisciplinary Chemistry |
Yonekura shows the steel industry was central to the economic development of Japan. The nation's sudden transformation from feudal to modern society in the late nineteenth century, its heavy industrialization and imperialist war ventures in 1900–1945, and the post-World War II high-economic growth, all depended on iron and steel. The other great Japanese industries, such as shipbuilding, automobiles, and industrial machinery are closely linked to steel. From 1850 to 1970, the industry increased its crude steel production from virtually nothing to 93.3 million tons (the third largest in the world).
The government's activist Ministry of International Trade and Industry (MITI) played a major role in coordination. The transfer of technology from the West and the establishment of competitive firms involved far more than buying foreign hardware. MITI located steel mills and organized a domestic market; it sponsored Yawata Steel Company. Japanese engineers and entrepreneurs internally developed the necessary technological and organizational capabilities, planned the transfer and adoption of technology, and gauged demand and sources of raw materials and finances. | 1 | Applied and Interdisciplinary Chemistry |
It is common for two monochromators to be connected in series, with their mechanical systems operating in tandem so that they both select the same color. This arrangement is not intended to improve the narrowness of the spectrum, but rather to lower the cutoff level. A double monochromator may have a cutoff about one millionth of the peak value, the product of the two cutoffs of the individual sections. The intensity of the light of other colors in the exit beam is referred to as the stray light level and is the most critical specification of a monochromator for many uses. Achieving low stray light is a large part of the art of making a practical monochromator. | 0 | Theoretical and Fundamental Chemistry |
* The CAS database is the most comprehensive repository for data on organic compounds. The search tool SciFinder is offered.
* The Beilstein database contains information on 9.8 million substances, covers the scientific literature from 1771 to the present, and is today accessible via Reaxys. Structures and a large diversity of physical and chemical properties are available for each substance, with reference to original literature.
* PubChem contains 18.4 million entries on compounds and especially covers the field of medicinal chemistry.
A great number of more specialized databases exist for diverse branches of organic chemistry. | 0 | Theoretical and Fundamental Chemistry |
Radiopharmacology is radiochemistry applied to medicine and thus the pharmacology of radiopharmaceuticals (medicinal radiocompounds, that is, pharmaceutical drugs that are radioactive). Radiopharmaceuticals are used in the field of nuclear medicine as radioactive tracers in medical imaging and in therapy for many diseases (for example, brachytherapy). Many radiopharmaceuticals use technetium-99m (Tc-99m) which has many useful properties as a gamma-emitting tracer nuclide. In the book Technetium a total of 31 different radiopharmaceuticals based on Tc-99m are listed for imaging and functional studies of the brain, myocardium, thyroid, lungs, liver, gallbladder, kidneys, skeleton, blood and tumors.
The term radioisotope, which in its general sense refers to any radioactive isotope (radionuclide), has historically been used to refer to all radiopharmaceuticals, and this usage remains common. Technically, however, many radiopharmaceuticals incorporate a radioactive tracer atom into a larger pharmaceutically-active molecule, which is localized in the body, after which the radionuclide tracer atom allows it to be easily detected with a gamma camera or similar gamma imaging device. An example is fludeoxyglucose in which fluorine-18 is incorporated into deoxyglucose. Some radioisotopes (for example gallium-67, gallium-68, and radioiodine) are used directly as soluble ionic salts, without further modification. This use relies on the chemical and biological properties of the radioisotope itself, to localize it within the body. | 1 | Applied and Interdisciplinary Chemistry |
The reaction rate or rate of reaction is the speed at which a chemical reaction takes place, defined as proportional to the increase in the concentration of a product per unit time and to the decrease in the concentration of a reactant per unit time. Reaction rates can vary dramatically. For example, the oxidative rusting of iron under Earths atmosphere is a slow reaction that can take many years, but the combustion of cellulose in a fire is a reaction that takes place in fractions of a second. For most reactions, the rate decreases as the reaction proceeds. A reactions rate can be determined by measuring the changes in concentration over time.
Chemical kinetics is the part of physical chemistry that concerns how rates of chemical reactions are measured and predicted, and how reaction-rate data can be used to deduce probable reaction mechanisms. The concepts of chemical kinetics are applied in many disciplines, such as chemical engineering, enzymology and environmental engineering. | 0 | Theoretical and Fundamental Chemistry |
Since its original description in 1992, the CSI method has been used to characterize the secondary structure of thousands of peptides and proteins. Its popularity is largely due to the fact that it is easy to understand and can be implemented without the need for specialized computer programs. Even though the CSI method can be easily performed manually, a number of commonly used NMR data processing programs such as NMRView, NMR structure generation web servers such as [http://www.cs23d.ca/ CS23D] as well as various NMR data analysis web servers such as [http://randomcoilindex.com RCI], [http://www.preditor.ca/ Preditor] and PANAV have incorporated the CSI method into their software. | 0 | Theoretical and Fundamental Chemistry |
Calcein, also known as fluorexon, fluorescein complex, is a fluorescent dye with excitation and emission wavelengths of 495 and 515 nm, respectively, and has the appearance of orange crystals. Calcein self-quenches at concentrations above 70 mM and is commonly used as an indicator of lipid vesicle leakage. It has also been traditionally used as a complexometric indicator for titration of calcium ions with EDTA, and for fluorometric determination of calcium. | 0 | Theoretical and Fundamental Chemistry |
* Polyhydroxoalkanoates and polyesters obtained by enzyme-assisted esterification using lipases.<nowiki/>
* Heparin, heparan sulfate and other glycosaminoglycans and plant glycans.
*Polysaccharides such as cellulose, amylose, chitin and derivatives
*Natural and non-natural polynucleotides can be successfully obtained by enzyme-assisted synthesis using ligase- or polymerase-based approaches and template-assisted polymerisation.
Human-made biopolymers obtained through approaches that involve genetic engineering or recombinant DNA technology are different from synthetic biopolymers and should be referred to as artificial biopolymer (e.g., artificial protein, artificial polynucleotide, etc.). | 1 | Applied and Interdisciplinary Chemistry |
For an adsorption column, the column resin (the stationary phase) is composed of microbeads. Even smaller particles such as proteins, carbohydrates, metal ions, or other chemical compounds are conjugated onto the microbeads. Each binding particle that is attached to the microbead can be assumed to bind in a 1:1 ratio with the solute sample sent through the column that needs to be purified or separated.
Binding between the target molecule to be separated and the binding molecule on the column beads can be modeled using a simple equilibrium reaction K = [CS]/([C][S]) where K is the equilibrium constant, [C] and [S] are the concentrations of the target molecule and the binding molecule on the column resin, respectively. [CS] is the concentration of the complex of the target molecule bound to the column resin.
Using this as a basis, three different isotherms can be used to describe the binding dynamics of a column chromatography: linear, Langmuir, and Freundlich.
The linear isotherm occurs when the solute concentration needed to be purified is very small relative to the binding molecule. Thus, the equilibrium can be defined as:
:[CS] = K[C].
For industrial scale uses, the total binding molecules on the column resin beads must be factored in because unoccupied sites must be taken into account. The Langmuir isotherm and Freundlich isotherm are useful in describing this equilibrium. The Langmuir isotherm is given by:
:[CS] = (KS[C])/(1 + K[C]), where S is the total binding molecules on the beads.
The Freundlich isotherm is given by:
:[CS] = K[C]
The Freundlich isotherm is used when the column can bind to many different samples in the solution that needs to be purified. Because the many different samples have different binding constants to the beads, there are many different Ks. Therefore, the Langmuir isotherm is not a good model for binding in this case. | 0 | Theoretical and Fundamental Chemistry |
We have to distinguish between line source AAS (LS AAS) and continuum source AAS (CS AAS). In classical LS AAS, as it has been proposed by Alan Walsh, the high spectral resolution required for AAS measurements is provided by the radiation source itself that emits the spectrum of the analyte in the form of lines that are narrower than the absorption lines. Continuum sources, such as deuterium lamps, are only used for background correction purposes. The advantage of this technique is that only a medium-resolution monochromator is necessary for measuring AAS; however, it has the disadvantage that usually a separate lamp is required for each element that has to be determined. In CS AAS, in contrast, a single lamp, emitting a continuum spectrum over the entire spectral range of interest is used for all elements. Obviously, a high-resolution monochromator is required for this technique, as will be discussed later. | 0 | Theoretical and Fundamental Chemistry |
As a β-lactam antibiotic, piperacillin inhibits penicillin-binding proteins, preventing the spread of bacteria and infections. Responsible for catalyzing the cross-linkage between peptidoglycan strands that protect the bacterial cell from osmotic rupture, penicillin-binding proteins are unique to bacterial organisms, where every known bacteria with a peptidoglycan cell wall consists of homologous sub-families. By sharing a similar stereochemistry with the substrates that bind to penicillin-binding proteins, piperacillin is able to bind to serine residues found at the active site of the enzyme through the formation of a covalent complex, preventing other substrates from binding. Moreover, this leads to the release of autolysins that break down the bacteria's cell wall.
Some β-lactamase enzymes also consist of residue at their active site, enabling them to hydrolyze the β-lactam ring found within these antibiotics. However, this hydrolytic activity is inhibited when piperacillin works in conjunction with tazobactam. Tazobactam binds to these enzymes to form a stable acyl-enzyme complex; similar to one formed during the hydrolysis of the β-lactam ring. Thus, protecting piperacillin from hydrolysis.
The inclusion of a β-lactamase inhibitor does not always increase drug efficacy. Some bacteria may produce certain types of β-lactamase such as AmpC, which are intrinsically resistant to tazobactam. | 0 | Theoretical and Fundamental Chemistry |
Ertl was born in Stuttgart, Germany, where he studied physics from 1955 to 1957 at the Technical University of Stuttgart and then at the University of Paris (1957–1958) and Ludwig Maximilian University in Munich (1958–1959). He completed his Diplom in Physics at the Technical University of Stuttgart in 1961, followed his thesis advisor Heinz Gerischer from the Max Planck Institute for Metals Research in Stuttgart to Munich and received his PhD degree from the Technical University of Munich in 1965. | 0 | Theoretical and Fundamental Chemistry |
Electron transfer (ET) occurs when an electron relocates from an atom or molecule to another such chemical entity. ET is a mechanistic description of certain kinds of redox reactions involving transfer of electrons.
Electrochemical processes are ET reactions. ET reactions are relevant to photosynthesis and respiration and commonly involve transition metal complexes. In organic chemistry ET is a step in some commercial polymerization reactions. It is foundational to photoredox catalysis. | 0 | Theoretical and Fundamental Chemistry |
Mitigation of adverse impacts of runoff can take several forms:
* Land use development controls aimed at minimizing impervious surfaces in urban areas
* Erosion controls for farms and construction sites
* Flood control and retrofit programs, such as green infrastructure
* Chemical use and handling controls in agriculture, landscape maintenance, industrial use, etc.
Land use controls. Many world regulatory agencies have encouraged research on methods of minimizing total surface runoff by avoiding unnecessary hardscape. Many municipalities have produced guidelines and codes (zoning and related ordinances) for land developers that encourage minimum width sidewalks, use of pavers set in earth for driveways and walkways and other design techniques to allow maximum water infiltration in urban settings. An example of a local program specifying design requirements, construction practices and maintenance requirements for buildings and properties is in Santa Monica, California.
Erosion controls have appeared since medieval times when farmers realized the importance of contour farming to protect soil resources. Beginning in the 1950s these agricultural methods became increasingly more sophisticated. In the 1960s some state and local governments began to focus their efforts on mitigation of construction runoff by requiring builders to implement erosion and sediment controls (ESCs). This included such techniques as: use of straw bales and barriers to slow runoff on slopes, installation of silt fences, programming construction for months that have less rainfall and minimizing extent and duration of exposed graded areas. Montgomery County, Maryland implemented the first local government sediment control program in 1965, and this was followed by a statewide program in Maryland in 1970.
Flood control programs as early as the first half of the twentieth century became quantitative in predicting peak flows of riverine systems. Progressively strategies have been developed to minimize peak flows and also to reduce channel velocities. Some of the techniques commonly applied are: provision of holding ponds (also called detention basins or balancing lakes) to buffer riverine peak flows, use of energy dissipators in channels to reduce stream velocity and land use controls to minimize runoff.
Chemical use and handling. Following enactment of the U.S. Resource Conservation and Recovery Act (RCRA) in 1976, and later the Water Quality Act of 1987, states and cities have become more vigilant in controlling the containment and storage of toxic chemicals, thus preventing releases and leakage. Methods commonly applied are: requirements for double containment of underground storage tanks, registration of hazardous materials usage, reduction in numbers of allowed pesticides and more stringent regulation of fertilizers and herbicides in landscape maintenance. In many industrial cases, pretreatment of wastes is required, to minimize escape of pollutants into sanitary or stormwater sewers.
The U.S. Clean Water Act (CWA) requires that local governments in urbanized areas (as defined by the Census Bureau) obtain stormwater discharge permits for their drainage systems. Essentially this means that the locality must operate a stormwater management program for all surface runoff that enters the municipal separate storm sewer system ("MS4"). EPA and state regulations and related publications outline six basic components that each local program must contain:
* Public education (informing individuals, households, businesses about ways to avoid stormwater pollution)
* Public involvement (support public participation in implementation of local programs)
* Illicit discharge detection & elimination (removing sanitary sewer or other non-stormwater connections to the MS4)
* Construction site runoff controls (i.e. erosion and sediment controls)
* Post-construction (i.e. permanent) stormwater management controls
* Pollution prevention (e.g. improved chemical handling, including management of motor fuels and oil, fertilizers, pesticides and roadway deicers) and "good housekeeping" measures (e.g. system maintenance).
Other property owners which operate storm drain systems similar to municipalities, such as state highway systems, universities, military bases and prisons, are also subject to the MS4 permit requirements. | 1 | Applied and Interdisciplinary Chemistry |
The Stuart number (N), also known as magnetic interaction parameter, is a dimensionless number of fluids, i.e. gases or liquids.
It is defined as the ratio of electromagnetic to inertial forces, which gives an estimate of the relative importance of a magnetic field on a flow. The Stuart number is relevant for flows of conducting fluids, e.g. in fusion reactors, steel casters or plasmas. | 1 | Applied and Interdisciplinary Chemistry |
In humans, 5ALA is a precursor to heme. Biosynthesized, 5ALA goes through a series of transformations in the cytosol and finally gets converted to Protoporphyrin IX inside the mitochondria. This protoporphyrin molecule chelates with iron in presence of enzyme ferrochelatase to produce Heme.
Heme increases the mitochondrial activity thereby helping in activation of respiratory system Krebs Cycle and Electron Transport Chain leading to formation of adenosine triphosphate (ATP) for adequate supply of energy to the body. | 1 | Applied and Interdisciplinary Chemistry |
Studies of United States sewage in the late 1960s estimated mean per capita contributions of in urine and feces, in synthetic detergents, and lesser variable amounts used as corrosion and scale control chemicals in water supplies. Source control via alternative detergent formulations has subsequently reduced the largest contribution, but naturally the phosphorus content of urine and feces remained unchanged.
Phosphorus can be removed biologically in a process called enhanced biological phosphorus removal. In this process, specific bacteria, called polyphosphate-accumulating organisms (PAOs), are selectively enriched and accumulate large quantities of phosphorus within their cells (up to 20 percent of their mass).
Phosphorus removal can also be achieved by chemical precipitation, usually with salts of iron (e.g. ferric chloride) or aluminum (e.g. alum), or lime. This may lead to a higher sludge production as hydroxides precipitate and the added chemicals can be expensive. Chemical phosphorus removal requires significantly smaller equipment footprint than biological removal, is easier to operate and is often more reliable than biological phosphorus removal. Another method for phosphorus removal is to use granular laterite or zeolite.
Some systems use both biological phosphorus removal and chemical phosphorus removal. The chemical phosphorus removal in those systems may be used as a backup system, for use when the biological phosphorus removal is not removing enough phosphorus, or may be used continuously. In either case, using both biological and chemical phosphorus removal has the advantage of not increasing sludge production as much as chemical phosphorus removal on its own, with the disadvantage of the increased initial cost associated with installing two different systems.
Once removed, phosphorus, in the form of a phosphate-rich sewage sludge, may be sent to landfill or used as fertilizer in admixture with other digested sewage sludges. In the latter case, the treated sewage sludge is also sometimes referred to as biosolids. 22% of the world's phosphorus needs could be satisfied by recycling residential wastewater. | 1 | Applied and Interdisciplinary Chemistry |
* 1802 – Joseph Louis Gay-Lussac publishes Charless law, discovered (but unpublished) by Jacques Charles around 1787; this shows the dependency between temperature and volume. Gay-Lussac also formulates the law relating temperature with pressure (the pressure law, or Gay-Lussacs law)
* 1804 – Sir John Leslie observes that a matte black surface radiates heat more effectively than a polished surface, suggesting the importance of black-body radiation
* 1805 – William Hyde Wollaston defends the conservation of energy in On the Force of Percussion
* 1808 – John Dalton defends caloric theory in A New System of Chemistry and describes how it combines with matter, especially gases; he proposes that the heat capacity of gases varies inversely with atomic weight
* 1810 – Sir John Leslie freezes water to ice artificially
* 1813 – Peter Ewart supports the idea of the conservation of energy in his paper On the measure of moving force; the paper strongly influences Dalton and his pupil, James Joule
* 1819 – Pierre Louis Dulong and Alexis Thérèse Petit give the Dulong-Petit law for the specific heat capacity of a crystal
* 1820 – John Herapath develops some ideas in the kinetic theory of gases but mistakenly associates temperature with molecular momentum rather than kinetic energy; his work receives little attention other than from Joule
* 1822 – Joseph Fourier formally introduces the use of dimensions for physical quantities in his Théorie Analytique de la Chaleur
* 1822 – Marc Seguin writes to John Herschel supporting the conservation of energy and kinetic theory
* 1824 – Sadi Carnot analyzes the efficiency of steam engines using caloric theory; he develops the notion of a reversible process and, in postulating that no such thing exists in nature, lays the foundation for the second law of thermodynamics, and initiating the science of thermodynamics
* 1827 – Robert Brown discovers the Brownian motion of pollen and dye particles in water
* 1831 – Macedonio Melloni demonstrates that black-body radiation can be reflected, refracted, and polarised in the same way as light
* 1834 – Émile Clapeyron popularises Carnots work through a graphical and analytic formulation. He also combined Boyles Law, Charless Law, and Gay-Lussacs Law to produce a Combined Gas Law. PV/T = k
* 1841 – Julius Robert von Mayer, an amateur scientist, writes a paper on the conservation of energy, but his lack of academic training leads to its rejection
* 1842 – Mayer makes a connection between work, heat, and the human metabolism based on his observations of blood made while a ship's surgeon; he calculates the mechanical equivalent of heat
* 1842 – William Robert Grove demonstrates the thermal dissociation of molecules into their constituent atoms, by showing that steam can be disassociated into oxygen and hydrogen, and the process reversed
* 1843 – John James Waterston fully expounds the kinetic theory of gases, but according to D Levermore "there is no evidence that any physical scientist read the book; perhaps it was overlooked because of its misleading title, Thoughts on the Mental Functions."
* 1843 – James Joule experimentally finds the mechanical equivalent of heat
* 1845 – Henri Victor Regnault added Avogadro's Law to the Combined Gas Law to produce the Ideal Gas Law. PV = nRT
* 1846 – Grove publishes an account of the general theory of the conservation of energy in On The Correlation of Physical Forces
* 1847 – Hermann von Helmholtz publishes a definitive statement of the conservation of energy, the first law of thermodynamics | 0 | Theoretical and Fundamental Chemistry |
A typical LFER relation for predicting the equilibrium concentration of a compound or solute in the vapor phase to a condensed (or solvent) phase can be defined as follows (following M.H. Abraham and co-workers):
where is some free-energy related property, such as an adsorption or absorption constant, , anesthetic potency, etc. The lowercase letters (, , , , ) are system constants describing the contribution of the aerosol phase to the sorption process. The capital letters (, , , , ) are solute descriptors representing the complementary properties of the compounds. Specifically,
* is the gas–liquid partition constant on n-hexadecane at 298 K;
* = the excess molar refraction ( for n-alkanes).
* = the ability of a solute to stabilize a neighbouring dipole by virtue of its capacity for orientation and induction interactions;
* = the solute's effective hydrogen bond acidity; and
* = the solute's effective hydrogen-bond basicity.
The complementary system constants are identified as
* = the contribution from cavity formation and dispersion interactions;
* = the contribution from interactions with solute n-electrons and pi electrons;
* = the contribution from dipole-type interactions;
* = the contribution from hydrogen-bond basicity (because a basic sorbent will interact with an acidic solute); and
* = the contribution from hydrogen-bond acidity to the transfer of the solute from air to the aerosol phase.
Similarly, the correlation of solvent–solvent partition coefficients as , is given by
where is McGowan's characteristic molecular volume in cubic centimeters per mole divided by 100. | 0 | Theoretical and Fundamental Chemistry |
Macromolecules is a peer-reviewed scientific journal that has been published since 1968 by the American Chemical Society. Initially published bimonthly, it became monthly in 1983 and then, in 1990, biweekly. Macromolecules is abstracted and indexed in Scopus, EBSCOhost, PubMed, Web of Science, and SwetsWise. The editor-in-chief is Marc A. Hillmyer.
Its first editor was Dr. Field H. Winslow. | 0 | Theoretical and Fundamental Chemistry |
A selectable marker is carried by the vector to allow the selection of positively transformed cells. Antibiotic resistance is often used as marker, an example being the beta-lactamase gene, which confers resistance to the penicillin group of beta-lactam antibiotics like ampicillin. Some vectors contain two selectable markers, for example the plasmid pACYC177 has both ampicillin and kanamycin resistance gene. Shuttle vector which is designed to be maintained in two different organisms may also require two selectable markers, although some selectable markers such as resistance to zeocin and hygromycin B are effective in different cell types. Auxotrophic selection markers that allow an auxotrophic organism to grow in minimal growth medium may also be used; examples of these are LEU2 and URA3 which are used with their corresponding auxotrophic strains of yeast.
Another kind of selectable marker allows for the positive selection of plasmid with cloned gene. This may involve the use of a gene lethal to the host cells, such as barnase, Ccda, and the parD/parE toxins. This typically works by disrupting or removing the lethal gene during the cloning process, and unsuccessful clones where the lethal gene still remains intact would kill the host cells, therefore only successful clones are selected. | 1 | Applied and Interdisciplinary Chemistry |
*George Washington Carver's research in new agricultural products, crop rotation, and soil fertility at Tuskegee University between 1896 and 1943
*Isolation of antibiotics, including streptomycin (in 1943), by Selman Waksman at Rutgers University Cook Campus
*Columbia Dry Cell, the first sealed dry cell battery successfully manufactured for the mass market, by the National Carbon Company in 1896 | 1 | Applied and Interdisciplinary Chemistry |
The adsorption of ensemble molecules on a surface or interface can be divided into two processes: adsorption and desorption. If the adsorption rate wins the desorption rate, the molecules will accumulate over time giving the adsorption curve over time. If the desorption rate is larger, the number of molecules on the surface will decrease over time. The adsorption rate is dependent on the temperature, the diffusion rate of the solute (related to mean free path for pure gas), and the energy barrier between the molecule and the surface. The diffusion and key elements of the adsorption rate can be calculated using Fick's laws of diffusion and Einstein relation (kinetic theory).
Under ideal conditions, when there is no energy barrier and all molecules that diffuse and collide with the surface get adsorbed, the number of molecules adsorbed at a surface of area on an infinite area surface can be directly integrated from Fick's second law differential equation to be:
where is the surface area (unit m), is the number concentration of the molecule in the bulk solution (unit #/m), is the diffusion constant (unit m/s), and is time (unit s). Further simulations and analysis of this equation show that the square root dependence on the time is originated from the decrease of the concentrations near the surface under ideal adsorption conditions. Also, this equation only works for the beginning of the adsorption when a well-behaved concentration gradient forms near the surface. Correction on the reduction of the adsorption area and slowing down of the concentration gradient evolution have to be considered over a longer time.
Under real experimental conditions, the flow and the small adsorption area always make the adsorption rate faster than what this equation predicted, and the energy barrier will either accelerate this rate by surface attraction or slow it down by surface repulsion. Thus, the prediction from this equation is often a few to several orders of magnitude away from the experimental results. Under special cases, such as a very small adsorption area on a large surface, and under chemical equilibrium when there is no concentration gradience near the surface, this equation becomes useful to predict the adsorption rate with debatable special care to determine a specific value of in a particular measurement.
The desorption of a molecule from the surface depends on the binding energy of the molecule to the surface and the temperature. The typical overall adsorption rate is thus often a combined result of the adsorption and desorption. | 0 | Theoretical and Fundamental Chemistry |
Perindopril is a medication used to treat high blood pressure, heart failure, or stable coronary artery disease.
As a long-acting ACE inhibitor, it works by relaxing blood vessels and decreasing blood volume. As a prodrug, perindopril is hydrolyzed in the liver to its active metabolite, perindoprilat. It was patented in 1980 and approved for medical use in 1988.
Perindopril is taken in the form of perindopril arginine (with arginine, trade names include Coversyl, Coversum) or perindopril erbumine (with erbumine (tert-Butylamine), trade name Aceon). Both forms are therapeutically equivalent and interchangeable, but the dose prescribed to achieve the same effect differs between the two forms. It is also often combined with another medication, sometimes in the same tablet (see below). | 0 | Theoretical and Fundamental Chemistry |
Maria Salomea Skłodowska-Curie (; ; 7 November 1867 – 4 July 1934), known simply as Marie Curie ( , ), was a Polish and naturalised-French physicist and chemist who conducted pioneering research on radioactivity. She was the first woman to win a Nobel Prize, the first person to win a Nobel Prize twice, and the only person to win a Nobel Prize in two scientific fields. Her husband, Pierre Curie, was a co-winner of her first Nobel Prize, making them the first-ever married couple to win the Nobel Prize and launching the Curie family legacy of five Nobel Prizes. She was, in 1906, the first woman to become a professor at the University of Paris.
She was born in Warsaw, in what was then the Kingdom of Poland, part of the Russian Empire. She studied at Warsaws clandestine Flying University and began her practical scientific training in Warsaw. In 1891, aged 24, she followed her elder sister Bronisława to study in Paris, where she earned her higher degrees and conducted her subsequent scientific work. In 1895 she married the French physicist Pierre Curie, and she shared the 1903 Nobel Prize in Physics with him and with the physicist Henri Becquerel for their pioneering work developing the theory of "radioactivity"—a term she coined. In 1906 Pierre Curie died in a Paris street accident. Marie won the 1911 Nobel Prize in Chemistry for her discovery of the elements polonium and radium, using techniques she invented for isolating radioactive isotopes. Under her direction, the worlds first studies were conducted into the treatment of neoplasms by the use of radioactive isotopes. She founded the Curie Institute in Paris in 1920, and the Curie Institute in Warsaw in 1932; both remain major medical research centres. During World War I she developed mobile radiography units to provide X-ray services to field hospitals.
While a French citizen, Marie Skłodowska Curie, who used both surnames, never lost her sense of Polish identity. She taught her daughters the Polish language and took them on visits to Poland. She named the first chemical element she discovered polonium, after her native country. Marie Curie died in 1934, aged 66, at the sanatorium in Passy (), France, of aplastic anemia likely from exposure to radiation in the course of her scientific research and in the course of her radiological work at field hospitals during World War I. In addition to her Nobel Prizes, she received numerous other honours and tributes; in 1995 she became the first woman to be entombed on her own merits in the Paris , and Poland declared 2011 the Year of Marie Curie during the International Year of Chemistry. She is the subject of numerous biographical works. | 0 | Theoretical and Fundamental Chemistry |
Environmental water quality, also called ambient water quality, relates to water bodies such as lakes, rivers, and oceans. Water quality standards for surface waters vary significantly due to different environmental conditions, ecosystems, and intended human uses. Toxic substances and high populations of certain microorganisms can present a health hazard for non-drinking purposes such as irrigation, swimming, fishing, rafting, boating, and industrial uses. These conditions may also affect wildlife, which use the water for drinking or as a habitat. According to the EPA, water quality laws generally specify protection of fisheries and recreational use and require, as a minimum, retention of current quality standards. In some locations, desired water quality conditions include high dissolved oxygen concentrations, low chlorophyll-a concentrations, and high water clarity.
There is some desire among the public to return water bodies to pristine, or pre-industrial conditions. Most current environmental laws focus on the designation of particular uses of a water body. In some countries these designations allow for some water contamination as long as the particular type of contamination is not harmful to the designated uses. Given the landscape changes (e.g., land development, urbanization, clearcutting in forested areas) in the watersheds of many freshwater bodies, returning to pristine conditions would be a significant challenge. In these cases, environmental scientists focus on achieving goals for maintaining healthy ecosystems and may concentrate on the protection of populations of endangered species and protecting human health. | 0 | Theoretical and Fundamental Chemistry |
Emulsifying agents are effective at extinguishing fires on small, thin-layer spills of flammable liquids (class B fires). Such agents encapsulate the fuel in a fuel-water emulsion, thereby trapping the flammable vapors in the water phase. This emulsion is achieved by applying an aqueous surfactant solution to the fuel through a high-pressure nozzle. Emulsifiers are not effective at extinguishing large fires involving bulk/deep liquid fuels, because the amount of emulsifier agent needed for extinguishment is a function of the volume of the fuel, whereas other agents such as aqueous film-forming foam need cover only the surface of the fuel to achieve vapor mitigation. | 0 | Theoretical and Fundamental Chemistry |
Cosmogenic isotopes (or cosmogenic nuclides) are rare isotopes created when a high-energy cosmic ray interacts with the nucleus of an in situ atom. These isotopes are produced within earth materials such as rocks or soil, in Earth's atmosphere, and in extraterrestrial items such as meteorites. By measuring cosmogenic isotopes, scientists are able to gain insight into a range of geological and astronomical processes. There are both radioactive and stable cosmogenic isotopes. Some of these radioisotopes are tritium, carbon-14 and phosphorus-32. | 0 | Theoretical and Fundamental Chemistry |
Each action potential is followed by a refractory period, which can be divided into an absolute refractory period, during which it is impossible to evoke another action potential, and then a relative refractory period, during which a stronger-than-usual stimulus is required. These two refractory periods are caused by changes in the state of sodium and potassium channel molecules. When closing after an action potential, sodium channels enter an "inactivated" state, in which they cannot be made to open regardless of the membrane potential—this gives rise to the absolute refractory period. Even after a sufficient number of sodium channels have transitioned back to their resting state, it frequently happens that a fraction of potassium channels remains open, making it difficult for the membrane potential to depolarize, and thereby giving rise to the relative refractory period. Because the density and subtypes of potassium channels may differ greatly between different types of neurons, the duration of the relative refractory period is highly variable.
The absolute refractory period is largely responsible for the unidirectional propagation of action potentials along axons. At any given moment, the patch of axon behind the actively spiking part is refractory, but the patch in front, not having been activated recently, is capable of being stimulated by the depolarization from the action potential. | 0 | Theoretical and Fundamental Chemistry |
Chimpanzee age impacts the frequency of alarm signalling. Chimpanzees over 80 months of age are more likely to produce an alarm call than those less than 80 months of age. There are several hypotheses for this lack of alarm calling in infants zero to four years of age. The first hypothesis is a lack of motivation to produce alarm calls because of mothers in close proximity that minimize the infants perception of a threat or that respond to a threat before the infant can. Infants may also be more likely to use distress calls to catch their mothers attention in order for her to produce an alarm call. Infants might also lack the physical ability to produce alarm calls or lack the necessary experience to classify unfamiliar objects as dangerous and worthy of an alarm signal. Therefore, alarm calling may require advanced levels of development, perception, categorization, and social cognition. | 1 | Applied and Interdisciplinary Chemistry |
Another application for duplex sequencing is in the detection of DNA/RNA copy numbers by estimating the relative frequency of variants. A method for counting PCR template molecules with application to next-generation sequencing is an example. | 1 | Applied and Interdisciplinary Chemistry |
RHEED is an extremely popular technique for monitoring the growth of thin films. In particular, RHEED is well suited for use with molecular beam epitaxy (MBE), a process used to form high quality, ultrapure thin films under ultrahigh vacuum growth conditions. The intensities of individual spots on the RHEED pattern fluctuate in a periodic manner as a result of the relative surface coverage of the growing thin film. Figure 8 shows an example of the intensity fluctuating at a single RHEED point during MBE growth.
Each full period corresponds to formation of a single atomic layer thin film. The oscillation period is highly dependent on the material system, electron energy and incident angle, so researchers obtain empirical data to correlate the intensity oscillations and film coverage before using RHEED for monitoring film growth.
Video 1 depicts a metrology instrument recording the RHEED intensity oscillations and deposition rate for process control and analysis. | 0 | Theoretical and Fundamental Chemistry |
Whiskers can cause short circuits and arcing in electrical equipment. The phenomenon was discovered by telephone companies in the late 1940s and it was later found that the addition of lead to tin solder provided mitigation. The European Restriction of Hazardous Substances Directive (RoHS), which took effect on July 1, 2006, restricted the use of lead in various types of electronic and electrical equipment. This has driven the use of lead-free alloys with a focus on preventing whisker formation . Others have focused on the development of oxygen-barrier coatings to prevent whisker formation.
Airborne zinc whiskers have been responsible for increased system failure rates in computer server rooms. Zinc whiskers grow from galvanized (electroplated) metal surfaces at a rate of up to a millimeter per year with a diameter of a few micrometers. Whiskers can form on the underside of zinc electroplated floor tiles on raised floors. These whiskers can then become airborne within the floor plenum when the tiles are disturbed, usually during maintenance. Whiskers can be small enough to pass through air filters and can settle inside equipment, resulting in short circuits and system failure.
Tin whiskers do not have to be airborne to damage equipment, as they are typically already growing directly in the environment where they can produce short circuits, i.e., the electronic equipment itself. At frequencies above 6 GHz or in fast digital circuits, tin whiskers can act like miniature antennas, affecting the circuit impedance and causing reflections. In computer disk drives they can break off and cause head crashes or bearing failures. Tin whiskers often cause failures in relays and have been found upon examination of failed relays in nuclear power facilities. Pacemakers have been recalled due to tin whiskers. Research has also identified a particular failure mode for tin whiskers in vacuum (such as in space), where in high-power components a short-circuiting tin whisker is ionized into a plasma that is capable of conducting hundreds of amperes of current, massively increasing the damaging effect of the short circuit. The possible increase in the use of pure tin in electronics due to the RoHS directive drove JEDEC and IPC to release a tin whisker acceptance testing standard and mitigation practices guideline intended to help manufacturers reduce the risk of tin whiskers in lead-free products.
Silver whiskers often appear in conjunction with a layer of silver sulfide, which forms on the surface of silver electrical contacts operating in an atmosphere rich in hydrogen sulfide and high humidity. Such atmospheres can exist in sewage treatment plants and paper mills.
Whiskers over 20 µm in length were observed on gold-plated surfaces and noted in a 2003 NASA internal memorandum.
The effects of metal whiskering were chronicled on History Channels program Engineering Disasters' 19. | 1 | Applied and Interdisciplinary Chemistry |
Mg(I) dimers have also been researched for carbon monoxide, CO, activation. Further research regarding the synthesis of these complexes revealed that their behavior can be compared to low-valent f-blocks compounds concerning the reduction of CO, socyanides, and nitriles.
Computational studies carried out further reinforced this idea by showing parallels between CO activation with f-block metal hydride complexes. The researchers first started with Mg(I) dimers. These dimers were then hydrogenated in hopes of generating magnesium(II) dimers. Additionally, the hydrogenation of Mg(I) dimers in a CO atmosphere, led to Cross-Coupled alkoxy products. The mechanism in which this reaction proceeded was shown by the computational studies to proceed similarly to related reactions of f-block metal hydride complexes. More specifically, researchers drew a close analogy to the reactivity of [{(DippNacnac)Mg}] towards CO. After the reaction was carried out, the dimer was shown to have a similar reactivity towards CO that could also be shown in samarium(II) or uranium(III) complexes. This reaction could also illustrate the potential magnesium(I) dimers have for the conversion of H/CO mixtures. By using more reactive dimers, it was hypothesized that uses for the stoichiometric or catalytic transformation of CO/H mixtures to value added oxygenate products. Finally, the similarity to low-valent f-block complexes can give rise to a more affordable, nontoxic, and nonradioactive practices. Comparatively, the diamagnetic dimer could also a difference in electronic properties when compared to paramagnetic nature of the lanthanides and actinides. | 0 | Theoretical and Fundamental Chemistry |
Chen (2006) has located the origin of the statement of maximum power as a formal principle in a tentative proposal by Alfred J. Lotka (1922a, b). Lotkas statement sought to explain the Darwinian notion of evolution with reference to a physical principle. Lotkas work was subsequently developed by the systems ecologist Howard T. Odum in collaboration with the chemical engineer Richard C. Pinkerton, and later advanced by the engineer Myron Tribus.
While Lotka's work may have been a first attempt to formalise evolutionary thought in mathematical terms, it followed similar observations made by Leibniz and Volterra and Ludwig Boltzmann, for example, throughout the sometimes controversial history of natural philosophy. In contemporary literature it is most commonly associated with the work of Howard T. Odum.
The significance of Odum's approach was given greater support during the 1970s, amid times of oil crisis, where, as Gilliland (1978, pp. 100) observed, there was an emerging need for a new method of analysing the importance and value of energy resources to economic and environmental production. A field known as energy analysis, itself associated with net energy and EROEI, arose to fulfill this analytic need. However, in energy analysis intractable theoretical and practical difficulties arose when using the energy unit to understand, a) the conversion among concentrated fuel types (or energy types), b) the contribution of labour, and c) the contribution of the environment. | 0 | Theoretical and Fundamental Chemistry |
In eukaryotes, a corepressor is a protein that binds to transcription factors. In the absence of corepressors and in the presence of coactivators, transcription factors upregulate gene expression. Coactivators and corepressors compete for the same binding sites on transcription factors. A second mechanism by which corepressors may repress transcriptional initiation when bound to transcription factor/DNA complexes is by recruiting histone deacetylases which catalyze the removal of acetyl groups from lysine residues. This increases the positive charge on histones which strengthens the electrostatic attraction between the positively charged histones and negatively charged DNA, making the DNA less accessible for transcription.
In humans several dozen to several hundred corepressors are known, depending on the level of confidence with which the characterisation of a protein as a corepressors can be made. | 1 | Applied and Interdisciplinary Chemistry |
Example values of activity coefficients of sodium chloride in aqueous solution are given in the table. In an ideal solution, these values would all be unity. The deviations tend to become larger with increasing molality and temperature, but with some exceptions. | 0 | Theoretical and Fundamental Chemistry |
Gerel Ochir was born in Moscow on 17 July 1941. She gained an interest in geology at the age of 10 after her mother gave her a book on geology by Russian geochemist Alexander Fersman. She graduated from secondary school in Ulaanbaatar in 1958.
From 1959, Ochir attended Charles University in Prague. She earned a bachelor's degree in geology and petrography in 1964. She then spent a year with the Department of Geological Survey at the Central Geological Laboratory before she started teaching at the Mongolian State University (now Mongolian University of Science and Technology) in 1965. She later returned to Charles University, earning her RNDr. in geology and geochemistry in 1980. Ochir earned her PhD in petrology from the Irkutsk Institute of Geochemistry of the Siberian Branch of the Russian Academy of Sciences in 1978. Her thesis was on the "Petrology and geochemistry of granite with crystal-bearing pegmatites of Eastern Mongolia." Ochir earned her ScD in geochemistry, petrology, and metallogeny from the Vinogradov Institute of Geochemistry of the Russian Academy of Sciences in 1990. | 0 | Theoretical and Fundamental Chemistry |
https://web.archive.org/web/20160325004825/https://www.colorado.edu/physics/phys7550/phys7550_sp07/extras/Ramsey90_RMP.pdf | 0 | Theoretical and Fundamental Chemistry |
In quantum chemistry, the Dunham expansion is an expression for the rotational-vibrational energy levels of a diatomic molecule:
where and are the vibrational and rotational quantum numbers, and is the projection of along the internuclear axis in the body-fixed frame.
The constant coefficients are called Dunham parameters with representing the electronic energy. The expression derives from a semiclassical treatment of a perturbational approach to deriving the energy levels. The Dunham parameters are typically calculated by a least-squares fitting procedure of energy levels with the quantum numbers. | 0 | Theoretical and Fundamental Chemistry |
Heinz Falk studied chemistry at the University of Vienna starting in 1959 and completed his dissertation under his doctoral advisor, Karl Schlögl, in 1966. In 1971 Falk spent a year abroad to study at ETH Zürich. Upon his return to Vienna in 1972 he attained habilitation for organic chemistry at the University of Vienna. | 0 | Theoretical and Fundamental Chemistry |
Histamine N-methyltransferase (HNMT) is a protein encoded by the HNMT gene in humans. It belongs to the methyltransferases superfamily of enzymes and plays a crucial role in the inactivation of histamine, a biomolecule that is involved in various physiological processes. Methyltransferases are present in every life form including archaeans, with 230 families of methyltransferases found across species.
Specifically, HNMT transfers a methyl (-CH) group from S-adenosyl--methionine (SAM-e) to histamine, forming an inactive metabolite called N-methylhistamine, in a chemical reaction called N-methylation. In mammals, HNMT operates alongside diamine oxidase (DAO) as the only two enzymes responsible for histamine metabolism; however, what sets HNMT apart is its unique presence within the central nervous system (CNS), where it governs histaminergic neurotransmission, that is a process where histamine acts as a messenger molecule between the neurons—nerve cells—in the brain. By degrading and regulating levels of histamine specifically within the CNS, HNMT ensures the proper functioning of neural pathways related to arousal, appetite regulation, sleep-wake cycles, and other essential brain functions.
Research on knockout mice—that are genetically modified mice lacking the Hnmt gene—has revealed that the absence of this enzyme leads to increased brain histamine concentrations and behavioral changes such as heightened aggression and disrupted sleep patterns. These findings highlight the critical role played by HNMT in maintaining normal brain function through precise regulation of neuronal signaling involving histamine. Genetic variants affecting HNMT activity have also been implicated in various neurological disorders like Parkinson's disease and attention deficit disorder. | 1 | Applied and Interdisciplinary Chemistry |
In the case of bacteria, transposition mutagenesis is usually accomplished by way of a plasmid from which a transposon is extracted and inserted into the host chromosome. This usually requires a set of enzymes including transposase to be translated. The transposase can be expressed either on a separate plasmid, or on the plasmid containing the gene to be integrated. Alternatively, an injection of transposase mRNA into the host cell can induce translation and expression. Early transposon mutagenesis experiments relied on bacteriophages and conjugative bacterial plasmids for the insertion of sequences. These were very non-specific, and made it difficult to incorporate specific genes. A newer technique called shuttle mutagenesis uses specific cloned genes from the host species to incorporate genetic elements. Another effective approach is to deliver transposons through viral capsids. This facilitates integration into the chromosome and long-term transgene expression. | 1 | Applied and Interdisciplinary Chemistry |
The tensile strength of a material quantifies how much elongating stress the material will endure before failure. This is very important in applications that rely upon a polymer's physical strength or durability. For example, a rubber band with a higher tensile strength will hold a greater weight before snapping. In general, tensile strength increases with polymer chain length and crosslinking of polymer chains. | 0 | Theoretical and Fundamental Chemistry |
The molecular formula BaSO (molar mass: 233.39 g/mol, exact mass: 233.8570 u) may refer to:
*Barium sulfate
*Baryte (or barite), a mineral made of barium sulfate | 0 | Theoretical and Fundamental Chemistry |
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