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Archaeal transcription is the process in which a segment of archaeal DNA is copied into a newly synthesized strand of RNA using the sole Pol II-like RNA polymerase (RNAP). The process occurs in three main steps: initiation, elongation, and termination; and the end result is a strand of RNA that is complementary to a single strand of DNA. A number of transcription factors govern this process with homologs in both bacteria and eukaryotes, with the core machinery more similar to eukaryotic transcription.
Because archaea lack a membrane-enclosed nucleus like bacteria do, transcription and translation can happen at the same time on a newly-generated piece of mRNA. Operons are widespread in archaea. | 1 | Applied and Interdisciplinary Chemistry |
Bases: adenine (A), cytosine (C), guanine (G) and thymine (T) or uracil (U).
Amino acids: Alanine (Ala, A), Arginine (Arg, R), Asparagine (Asn, N), Aspartic acid (Asp, D), Cysteine (Cys, C), Glutamic acid (Glu, E), Glutamine (Gln, Q), Glycine (Gly, G), Histidine (His, H), Isoleucine (Ile, I), Leucine (Leu, L), Lysine (Lys, K), Methionine (Met, M), Phenylalanine (Phe, F), Proline (Pro, P), Serine (Ser, S), Threonine (Thr, T), Tryptophan (Trp, W), Tyrosine (Tyr, Y), Valine (Val, V). | 1 | Applied and Interdisciplinary Chemistry |
* Intercalating agents, such as ethidium bromide and proflavine, are molecules that may insert between bases in DNA, causing frameshift mutation during replication. Some such as daunorubicin may block transcription and replication, making them highly toxic to proliferating cells. | 0 | Theoretical and Fundamental Chemistry |
Although the FGF family of paracrine factors has a broad range of functions, major findings support the idea that they primarily stimulate proliferation and differentiation. To fulfill many diverse functions, FGFs can be alternatively spliced or even have different initiation codons to create hundreds of different FGF isoforms.
One of the most important functions of the FGF receptors (FGFR) is in limb development. This signaling involves nine different alternatively spliced isoforms of the receptor. Fgf8 and Fgf10 are two of the critical players in limb development. In the forelimb initiation and limb growth in mice, axial (lengthwise) cues from the intermediate mesoderm produces Tbx5, which subsequently signals to the same mesoderm to produce Fgf10. Fgf10 then signals to the ectoderm to begin production of Fgf8, which also stimulates the production of Fgf10. Deletion of Fgf10 results in limbless mice.
Additionally, paracrine signaling of Fgf is essential in the developing eye of chicks. The fgf8 mRNA becomes localized in what differentiates into the neural retina of the optic cup. These cells are in contact with the outer ectoderm cells, which will eventually become the lens.
Phenotype and survival of mice after knockout of some FGFR genes: | 1 | Applied and Interdisciplinary Chemistry |
The story of pantoprazole's discovery is a good example of the stepwise development of PPIs. The main focus of modification of timoprazole was the benzimidazole part of its structure. Addition of a trifluoromethyl group to the benzimidazole moiety led to a series of very active compounds with varying solution-stability. In general fluoro substituents were found to block metabolism at the point where they were attached. Later the more balanced fluoroalkoxy substituent, instead of the highly lipophilic and strongly electron-withdrawing trifluoromethyl substituent, led to highly active compounds with supposed longer half-lives and higher solution stability.
It was realized that activity was somehow linked to instability in solution and then came to the conclusion that the cyclic sulfenamides, formed in acidic conditions, were the active principle of the PPIs. Finally, it was understood that seemingly small alterations in the backbone of timoprazole led nowhere, and focus had to be centered on the substituents on the backbone. However, necessary intramolecular rearrangement of the benzimidazole into sulfenamide posed severe geometric constraints. Optimal compounds would be those that were stable at neutral pH but were quickly activated at low pH.
A clear-cut design of active inhibitors was still not possible because in the complex multi-step chemistry the influence of a substituent on each step in the cascade could be different, and therefore not predictable for the overall rate of the prerequisite acid activation. Smith Kline and French, that entered into collaboration with Byk Gulden mid-1984, greatly assisted in determining criteria for further development. From 1985, the aim was to identify a compound with good stability at neutral pH, sustaining this higher level of stability down to pH 5 but being rapidly activateable at lower pHs, combined with a high level of H/K ATPase inhibition. From the numerous already synthesized and tested compounds that fulfilled these criteria the most promising candidates were pantoprazole and its salt, pantoprazole sodium.
In 1986 pantoprazole sodium sesquihydrate was synthesized and from 1987 onwards the development of pantoprazole was switched to the sodium salt which is more stable and has better compatibility with other excipients used in the drug formulation.
Pantoprazole was identified after nearly seven years of research and registered for clinical use after a further seven years of development, and finally reached its first market in 1994 in Germany. During the course of the studies on pantoprazole, more than 650 PPIs had been synthesized and evaluated. Pantoprazole obtained high selection criteria in its development process — especially concerning the favorable low potential for interaction with other drugs. Good solubility of pantoprazole and a very high solution stability allowed it to become the first marketed PPI for intravenous use in critical care patients. | 1 | Applied and Interdisciplinary Chemistry |
The name γ-glutamyltransferase is preferred by the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology. The Expert Panel on Enzymes of the International Federation of Clinical Chemistry also used this name. The older name is gamma-glutamyl transpeptidase (GGTP). | 1 | Applied and Interdisciplinary Chemistry |
This is the most commonly used measurement system for measuring water supply in houses. The fluid, most commonly water, enters in one side of the meter and strikes the nutating disk, which is eccentrically mounted. The disk must then "wobble" or nutate about the vertical axis, since the bottom and the top of the disk remain in contact with the mounting chamber. A partition separates the inlet and outlet chambers. As the disk nutates, it gives direct indication of the volume of the liquid that has passed through the meter as volumetric flow is indicated by a gearing and register arrangement, which is connected to the disk. It is reliable for flow measurements within 1 percent. | 1 | Applied and Interdisciplinary Chemistry |
As a poet, over one hundred and sixty manuscript poems were written by Davy, the majority of which are found in his personal notebooks. Most of his written poems were not published, and he chose instead to share a few of them with his friends. Eight of his known poems were published. His poems reflected his views on both his career and also his perception of certain aspects of human life. He wrote on human endeavours and aspects of life like death, metaphysics, geology, natural theology and chemistry.
John Ayrton Paris remarked that poems written by the young Davy "bear the stamp of lofty genius". Davys first preserved poem entitled "The Sons of Genius" is dated 1795 and marked by the usual immaturity of youth. Other poems written in the following years, especially "On the Mounts Bay" and "St Michael's Mount", are descriptive verses.
Although he initially started writing his poems, albeit haphazardly, as a reflection of his views on his career and on life generally, most of his final poems concentrated on immortality and death. This was after he started experiencing failing health and a decline both in health and career. | 1 | Applied and Interdisciplinary Chemistry |
In statistical mechanics and information theory, the Fokker–Planck equation is a partial differential equation that describes the time evolution of the probability density function of the velocity of a particle under the influence of drag forces and random forces, as in Brownian motion. The equation can be generalized to other observables as well. The Fokker-Planck equation has multiple applications in information theory, graph theory, data science, finance, economics etc.
It is named after Adriaan Fokker and Max Planck, who described it in 1914 and 1917. It is also known as the Kolmogorov forward equation, after Andrey Kolmogorov, who independently discovered it in 1931. When applied to particle position distributions, it is better known as the Smoluchowski equation (after Marian Smoluchowski), and in this context it is equivalent to the convection–diffusion equation. When applied to particle position and momentum distributions, it is known as the Klein–Kramers equation. The case with zero diffusion is the continuity equation. The Fokker–Planck equation is obtained from the master equation through Kramers–Moyal expansion.
The first consistent microscopic derivation of the Fokker–Planck equation in the single scheme of classical and quantum mechanics was performed by Nikolay Bogoliubov and Nikolay Krylov. | 1 | Applied and Interdisciplinary Chemistry |
In Schoenflies notation, point groups are denoted by a letter symbol with a subscript. The symbols used in crystallography mean the following:
*C (for cyclic) indicates that the group has an n-fold rotation axis. C is C with the addition of a mirror (reflection) plane perpendicular to the axis of rotation. C is C with the addition of n mirror planes parallel to the axis of rotation.
*S (for Spiegel, German for mirror) denotes a group with only a 2n-fold rotation-reflection axis.
*D (for dihedral, or two-sided) indicates that the group has an n-fold rotation axis plus n twofold axes perpendicular to that axis. D has, in addition, a mirror plane perpendicular to the n-fold axis. D has, in addition to the elements of D, mirror planes parallel to the n-fold axis.
*The letter T (for tetrahedron) indicates that the group has the symmetry of a tetrahedron. T includes improper rotation operations, T excludes improper rotation operations, and T is T with the addition of an inversion.
*The letter O (for octahedron) indicates that the group has the symmetry of an octahedron (or cube), with (O) or without (O) improper operations (those that change handedness).
Due to the crystallographic restriction theorem, n = 1, 2, 3, 4, or 6 in 2- or 3-dimensional space.
D and D are actually forbidden because they contain improper rotations with n=8 and 12 respectively. The 27 point groups in the table plus T, T, T, O and O constitute 32 crystallographic point groups. | 0 | Theoretical and Fundamental Chemistry |
Thalidomide is used as a first-line treatment for multiple myeloma in combination with dexamethasone or with melphalan and prednisone to treat acute episodes of erythema nodosum leprosum, as well as for maintenance therapy.
The bacterium that causes tuberculosis (TB) is related to leprosy. Thalidomide may be helpful in some cases where standard TB drugs and corticosteroids are not sufficient to resolve severe inflammation in the brain.
It is used as a second-line treatment to manage graft-versus-host disease and aphthous stomatitis in children and has been prescribed for other conditions in children, including actinic prurigo and epidermolysis bullosa; the evidence for these uses is weak. It is recommended only as a third line treatment in graft-versus-host-disease in adults because of lack of efficacy and side effects observed in clinical trials. | 0 | Theoretical and Fundamental Chemistry |
Seventeen individuals, both men and women, journeyed across the remote region known as Arnhem Land in northern Australia for nine months. From varying disciplinary perspectives, and under the guidance of expedition leader Charles Mountford, they investigated the Indigenous populations and the environment of Arnhem Land. In addition to an ethnographer, archaeologist, photographer, and filmmaker, the expedition included a botanist, a mammalogist, an ichthyologist, an ornithologist, and a team of medical and nutritional scientists.
Their first base camp was Groote Eylandt in the Gulf of Carpentaria. Three months later they moved to Yirrkala on the Gove Peninsula and three months following that to Oenpelli (now Gunbalanya) in west Arnhem Land. The journey involved the collaboration of different sponsors and partners (among them the National Geographic Society, the Smithsonian Institution, and various agencies of the Commonwealth of Australia).
A Bulletin article in 1956 noted that the scientists collected 13,500 plants, 30,000 fish, 850 birds, 460 animals, thousands of implements, amounting to twenty-five tons, and photographed and filmed in colour and black-and-white and made tracings of cave-paintings from Chasm Island, Groote Eylandt and Oenpelli. The Australian Broadcasting Commission promoted the Expedition in its ABC Weekly magazine by appealing to readers curiosity about "...a fish that looks exactly like a leaf, a multi-coloured praying mantis, intricate string games the aborigines play, a fungus used to cure wounds..."
In the wake of the expedition came volumes of scientific publications. The legacy of the 1948 Arnhem Land Expedition is vast, complex, and, at times, contentious. Human remains collected by Setzler and later held by the Smithsonian Institution have since been repatriated to Gunbalanya. | 1 | Applied and Interdisciplinary Chemistry |
The Industrial Revolution was characterized by the use of steam power, the growth of factories, and the mass production of manufactured goods. In this case, coal became a mass necessity, “for it was a cheap and abundant source of energy” used to power steam engines, heat buildings, and generate electricity. With coal becoming a main source of energy, there was an increase in the employment of coal miners. With this increase in demand for labor came humanitarian issues. Notably, “Children were ideal employees because they could be paid less, were often of smaller size so could attend to tasks in tight spaces and were less likely to organize and strike against their pitiable working conditions.” | 1 | Applied and Interdisciplinary Chemistry |
The experimental facts collected on heavy fermion (HF) metals and two dimensional Helium-3 demonstrate that the quasiparticle effective mass M* is very large, or even diverges. Topological fermion condensation quantum phase transition (FCQPT) preserves quasiparticles, and forms flat energy band at the Fermi level. The emergence of FCQPT is directly related to the unlimited growth of the effective mass M*. Near FCQPT, M* starts to depend on temperature T, number density x, magnetic field B and other external parameters such as pressure P, etc. In contrast to the Landau paradigm based on the assumption that the effective mass is approximately constant, in the FCQPT theory the effective mass of new quasiparticles strongly depends on T, x, B etc. Therefore, to agree/explain with the numerous experimental facts, extended quasiparticles paradigm based on FCQPT has to be introduced. The main point here is that the well-defined quasiparticles determine the thermodynamic, relaxation, scaling and transport properties of strongly correlated Fermi systems and M* becomes a function of T, x, B, P, etc.
The data collected for very different strongly correlated Fermi systems demonstrate universal scaling behavior; in other words distinct materials with strongly correlated fermions unexpectedly turn out to be uniform, thus forming a new state of matter that consists of HF metals, quasicrystals, quantum spin liquid, two-dimensional Helium-3, and compounds exhibiting high-temperature superconductivity. | 0 | Theoretical and Fundamental Chemistry |
An inelastic collision, in contrast to an elastic collision, is a collision in which kinetic energy is not conserved due to the action of internal friction.
In collisions of macroscopic bodies, some kinetic energy is turned into vibrational energy of the atoms, causing a heating effect, and the bodies are deformed.
The molecules of a gas or liquid rarely experience perfectly elastic collisions because kinetic energy is exchanged between the molecules translational motion and their internal degrees of freedom with each collision. At any one instant, half the collisions are – to a varying extent – inelastic (the pair possesses less kinetic energy after the collision than before), and half could be described as “super-elastic” (possessing more' kinetic energy after the collision than before). Averaged across an entire sample, molecular collisions are elastic.
Although inelastic collisions do not conserve kinetic energy, they do obey conservation of momentum. Simple ballistic pendulum problems obey the conservation of kinetic energy only when the block swings to its largest angle.
In nuclear physics, an inelastic collision is one in which the incoming particle causes the nucleus it strikes to become excited or to break up. Deep inelastic scattering is a method of probing the structure of subatomic particles in much the same way as Rutherford probed the inside of the atom (see Rutherford scattering). Such experiments were performed on protons in the late 1960s using high-energy electrons at the Stanford Linear Accelerator (SLAC). As in Rutherford scattering, deep inelastic scattering of electrons by proton targets revealed that most of the incident electrons interact very little and pass straight through, with only a small number bouncing back. This indicates that the charge in the proton is concentrated in small lumps, reminiscent of Rutherford's discovery that the positive charge in an atom is concentrated at the nucleus. However, in the case of the proton, the evidence suggested three distinct concentrations of charge (quarks) and not one. | 0 | Theoretical and Fundamental Chemistry |
Charles B. Harris was born in New York City and spent most of his youth in Grosse Pointe. He attended the University of Michigan and received his bachelor's degree in 1963. In 1966 he received his Ph.D. in chemistry at the Massachusetts Institute of Technology under F. Albert Cotton. The following year, Harris went to the University of California, Berkeley, where he became a professor in the chemistry department. He headed this department from 2003 and was dean of the faculty from 2004 to 2007. In 2015 he retired. His research focus was in the field of ultrafast dynamics and electron dynamics as well as the dynamics of chemical reactions in liquids.
He educated multiple generations of scientists in chemical dynamics and ultrafast science who have since become leaders in the field including, as Ph.D. students, Paul Alivisatos, Michael D. Fayer, Roseanne Sension, Nien-hui Ge, Kelly Gaffney and as postdocs, Ahmed Zewail and Alan Campion. | 0 | Theoretical and Fundamental Chemistry |
In the early 1890s, Paul Ehrlich started to work with Emil Behring, professor of medicine at the University of Marburg. Behring had been investigating antibacterial agents and discovered a diphtheria antitoxin (that is, antibodies that target a biological toxin produced by the diphtheria bacteria Corynebacterium diphtheriae). (For that discovery, Bering was the first recipient of the Nobel Prize in Physiology or Medicine in 1901. Ehrlich was also nominated for that year.) From Behring's work, Ehrlich understood that antibodies produced in the blood could attack invading pathogens without any harmful effect on the body. He speculated that these antibodies act as bullets fired from a gun to target specific microbes. But after further research, he realised that antibodies sometimes failed to kill microbes. This led him to abandon his first concept of the magic bullet. | 1 | Applied and Interdisciplinary Chemistry |
The N-terminal maltase-glucoamylase enzymatic unit is in turn composed of 5 specific protein domains. The first of the 5 protein domains consist of a P-type trefoil domain containing a cysteine rich domain. Second is an N-terminal beta-sandwich domain, identified via two antiparallel beta pleated sheets. The third and largest domain consists of a catalytic (beta/alpha) barrel type domain containing two inserted loops. The fourth and 5th domains are C-terminal domains, similar to the N-terminal beta-sandwich domain. The N-terminal Maltase-glucoamylase does not have the +2/+3 sugar binding active sites and so it cannot bind to larger substrates. The N-terminal domain shows its optimal enzymatic affinity for substrates maltose, maltotriose, maltotetrose, and maltopentose. | 1 | Applied and Interdisciplinary Chemistry |
When a cluster of microparticles are trapped within a monochromatic laser beam, the organization of the microparticles within the optical trapping is heavily dependent on the redistributing of the optical trapping forces amongst the microparticles. This redistribution of light forces amongst the cluster of microparticles provides a new force equilibrium on the cluster as a whole. As such we can say that the cluster of microparticles are somewhat bound together by light. One of the first experimental evidence of optical binding was reported by Michael M. Burns, Jean-Marc Fournier, and Jene A. Golovchenko, though it was originally predicted by T. Thirunamachandran. One of the many recent studies on optical binding has shown that for a system of chiral nanoparticles, the magnitude of the binding forces are dependent on the polarisation of the laser beam and the handedness of interacting particles themselves, with potential applications in areas such as enantiomeric separation and optical nanomanipulation. | 1 | Applied and Interdisciplinary Chemistry |
In anatomic pathology, ammonical silver nitrate is used in the Fontana–Masson Stain, which is a silver stain technique used to detect melanin, argentaffin and lipofuscin in tissue sections. Melanin and the other chromaffins reduce the silver nitrate to metallic silver. | 0 | Theoretical and Fundamental Chemistry |
In QUADRISO particles a burnable neutron poison (europium oxide or erbium oxide or carbide) layer surrounds the fuel kernel of ordinary TRISO particles to better manage the excess of reactivity. If the core is equipped both with TRISO and QUADRISO fuels, at beginning of life neutrons do not reach the fuel of the QUADRISO particles because they are stopped by the burnable poison. During reactor operation, neutron irradiation of the poison causes it to "burn up" or progressively transmute to non-poison isotopes, depleting this poison effect and leaving progressively more neutrons available for sustaining the chain-reaction. This mechanism compensates for the accumulation of undesirable neutron poisons which are an unavoidable part of the fission products, as well as normal fissile fuel "burn up" or depletion. In the generalized QUADRISO fuel concept the poison can eventually be mixed with the fuel kernel or the outer pyrocarbon. The QUADRISO concept was conceived at Argonne National Laboratory. | 0 | Theoretical and Fundamental Chemistry |
A precursor to the Kurganov and Tadmor (KT) central scheme, (Kurganov and Tadmor, 2000), is the Nessyahu and Tadmor (NT) a staggered central scheme, (Nessyahu and Tadmor, 1990). It is a Riemann-solver-free, second-order, high-resolution scheme that uses MUSCL reconstruction. It is a fully discrete method that is straight forward to implement and can be used on scalar and vector problems, and can be viewed as a Rusanov flux (also called the local Lax-Friedrichs flux) supplemented with high order reconstructions. The algorithm is based upon central differences with comparable performance to Riemann type solvers when used to obtain solutions for PDE's describing systems that exhibit high-gradient phenomena.
The KT scheme extends the NT scheme and has a smaller amount of numerical viscosity than the original NT scheme. It also has the added advantage that it can be implemented as either a fully discrete or semi-discrete scheme. Here we consider the semi-discrete scheme.
The calculation is shown below:
Where the local propagation speed, , is the maximum absolute value of the eigenvalue of the Jacobian of over cells given by
and represents the spectral radius of
Beyond these CFL related speeds, no characteristic information is required.
The above flux calculation is most frequently called Lax-Friedrichs flux (though it's worth mentioning that such flux expression does not appear in Lax, 1954 but rather on Rusanov, 1961).
An example of the effectiveness of using a high resolution scheme is shown in the diagram opposite, which illustrates the 1D advective equation , with a step wave propagating to the right. The simulation was carried out on a mesh of 200 cells, using the Kurganov and Tadmor central scheme with Superbee limiter and used RK-4 for time integration. This simulation result contrasts extremely well against the above first-order upwind and second-order central difference results shown above. This scheme also provides good results when applied to sets of equations - see results below for this scheme applied to the Euler equations. However, care has to be taken in choosing an appropriate limiter because, for example, the Superbee limiter can cause unrealistic sharpening for some smooth waves.
The scheme can readily include diffusion terms, if they are present. For example, if the above 1D scalar problem is extended to include a diffusion term, we get
for which Kurganov and Tadmor propose the following central difference approximation,
Where,
Full details of the algorithm (full and semi-discrete versions) and its derivation can be found in the original paper (Kurganov and Tadmor, 2000), along with a number of 1D and 2D examples. Additional information is also available in the earlier related paper by Nessyahu and Tadmor (1990).
Note: This scheme was originally presented by Kurganov and Tadmor as a 2nd order scheme based upon linear extrapolation. A later paper (Kurganov and Levy, 2000) demonstrates that it can also form the basis of a third order scheme. A 1D advective example and an Euler equation example of their scheme, using parabolic reconstruction (3rd order), are shown in the parabolic reconstruction and Euler equation sections below. | 1 | Applied and Interdisciplinary Chemistry |
Fumagillin and the related fumagillol (the hydrolysis product) have been a target in total synthesis, with several reported successful strategies, racemic, asymmetric, and formal. | 0 | Theoretical and Fundamental Chemistry |
*Acid phosphatase test for semen
*Cobalt thiocyanate test for cocaine
*Duquenois-Levine reagent for cannabis
*Kastle-Meyer test for blood
*Malachite green test for blood
* Marquis reagent for narcotics and alkaloids
* Benzidine test for blood which changes from clear to blue in color with the presence of blood
* Luminol, phenolphthalein, Hemastix, Hemident, and Bluestar are all also used for blood testing | 0 | Theoretical and Fundamental Chemistry |
Sir Joseph Norman Lockyer (17 May 1836 – 16 August 1920) was an English scientist and astronomer. Along with the French scientist Pierre Janssen, he is credited with discovering the gas helium. Lockyer also is remembered for being the founder and first editor of the influential journal Nature. | 1 | Applied and Interdisciplinary Chemistry |
As of 2008, more than 700,000 crystal structures had been published and stored in crystal structure databases. The publishing rate has reached more than 50,000 crystal structures per year. These numbers refer to published and republished crystal structures from experimental data. Crystal structures are republished owing to corrections for symmetry errors, improvements of lattice and atomic parameters, and differences in diffraction technique or experimental conditions. As of 2016, there are about 1,000,000 molecule and crystal structures known and published, approximately half of them in open access.
Crystal structures are typically categorized as minerals, metals-alloys, inorganics, organics, nucleic acids, and biological macromolecules. Individual crystal structure databases cater for users in specific chemical, molecular-biological, or related disciplines by covering super- or subsets of these categories. Minerals are a subset of mostly inorganic compounds. The category ‘metals-alloys’ covers metals, alloys, and intermetallics. Metals-alloys and inorganics can be merged into ‘non-organics’. Organic compounds and biological macromolecules are separated according to molecular size. Organic salts, organometallics, and metalloproteins tend to be attributed to organics or biological macromolecules, respectively. Nucleic acids are a subset of biological macromolecules.
Comprehensiveness can refer to the number of entries in a database. On those terms, a crystal structure database can be regarded as comprehensive, if it contains a collection of all (re-)published crystal structures in the category of interest and is updated frequently. Searching for structures in such a database can replace more time-consuming scanning of the open literature. Access to crystal structure databases differs widely. It can be divided into reading and writing access. Reading access rights (search, download) affect the number and range of users. Restricted reading access is often coupled with restricted usage rights. Writing access rights (upload, edit, delete), on the other hand, determine the number and range of contributors to the database. Restricted writing access is often coupled with high data integrity.
In terms of user numbers and daily access rates, comprehensive and thoroughly vetted open-access crystal structure databases naturally surpass comparable databases with more restricted access and usage rights. Independent of comprehensiveness, open-access crystal structure databases have spawned open-source software projects, such as search-analysis tools, visualization software, and derivative databases. Scientific progress has been slowed down by restricting access or usage rights as well as limiting comprehensiveness or data integrity. Restricted access or usage rights are commonly associated with commercial crystal structure databases. Lack of comprehensiveness or data integrity, on the other hand, are associated with some of the open-access crystal structure databases other than the [http://www.crystallography.net/ Crystallography Open Database] (COD), and is "macromolecular open-access counterpart", the [http://www.wwpdb.org/ world wide Protein Database]. Apart from that, several crystal structure databases are freely available for primarily educational purposes, in particular mineralogical databases and [http://nanocrystallography.research.pdx.edu/search/edu/ educational offshoots of the COD] .
Crystallographic databases can specialize in crystal structures, crystal phase identification, crystallization, crystal morphology, or various physical properties. More integrative databases combine several categories of compounds or specializations. Structures of incommensurate phases, 2D materials, nanocrystals, thin films on substrates, and predicted crystal structures are collected in tailored special structure databases. | 0 | Theoretical and Fundamental Chemistry |
Other models exist to model more complex binary systems. The above theories operate on the assumption that the segregated atoms are non-interacting. If, in a binary system, adjacent adsorbate atoms are allowed an interaction energy , such that they can attract (when is negative) or repel (when is positive) each other, the solid-state analogue of the Fowler adsorption theory is developed as
When is zero, this theory reduces to that of Langmuir and McLean. However, as becomes more negative, the segregation shows progressively sharper rises as the temperature falls until eventually the rise in segregation is discontinuous at a certain temperature, as shown in the following figure.
Guttman, in 1975, extended the Fowler theory to allow for interactions between two co-segregating species in multicomponent systems. This modification is vital to explaining the segregation behavior that results in the intergranular failures of engineering materials. More complex theories are detailed in the work by Guttmann and McLean and Guttmann. | 0 | Theoretical and Fundamental Chemistry |
Reflection high energy electron diffraction (RHEED), is a technique used to characterize the surface of crystalline materials by reflecting electrons off a surface. As illustrated for the Ewald sphere construction in Figure 22, it uses mainly the higher-order Laue zones which have a reflection component. An experimental diffraction pattern is shown in Figure 23 and shows both rings from the higher-order Laue zones and streaky spots. RHEED systems gather information only from the surface layers of the sample, which distinguishes RHEED from other materials characterization methods that also rely on diffraction of electrons. Transmission electron microscopy samples mainly the bulk of the sample, although in special cases it can provide surface information. Low-energy electron diffraction (LEED) is also surface sensitive, and achieves surface sensitivity through the use of low energy electrons. The main uses of RHEED to date have been during thin film growth, as the geometry is amenable to simultaneous collection of the diffraction data and deposition. It can, for instance, be used to monitor surface roughness during growth by looking at both the shapes of the streaks in the diffraction pattern as well as variations in the intensities. | 0 | Theoretical and Fundamental Chemistry |
Pierre Jules César Janssen (22 February 1824 – 23 December 1907), usually known as Jules Janssen, was a French astronomer who, along with English scientist Joseph Norman Lockyer, is credited with discovering the gaseous nature of the solar chromosphere, and with some justification the element helium. | 1 | Applied and Interdisciplinary Chemistry |
Pro-oxidants are chemicals that induce oxidative stress, either by generating reactive oxygen species or by inhibiting antioxidant systems. The oxidative stress produced by these chemicals can damage cells and tissues, for example, an overdose of the analgesic paracetamol (acetaminophen) can fatally damage the liver, partly through its production of reactive oxygen species.
Some substances can serve as either antioxidants or pro-oxidants, depending on conditions. Some of the important conditions include the concentration of the chemical and if oxygen or transition metals are present. While thermodynamically very favored, reduction of molecular oxygen or peroxide to superoxide or hydroxyl radical respectively is spin forbidden. This greatly reduces the rates of these reactions, thus allowing aerobic life to exist. As a result, the reduction of oxygen typically involves either the initial formation of singlet oxygen, or spin–orbit coupling through a reduction of a transition-series metal such as manganese, iron, or copper. This reduced metal then transfers the single electron to molecular oxygen or peroxide. | 1 | Applied and Interdisciplinary Chemistry |
Septic tank and drain field microorganisms have very limited capability for catabolizing petroleum products and chlorinated solvents, and cannot remove dissolved metals; although some may be absorbed into septic tank sludge or drain field soils, and concentrations may be diluted by other groundwater in the vicinity of the drain field. Cleaning formulations may reduce drain field efficiency. Laundry bleach may slow or stop microbial activity in the drain field, and sanitizing or deodorizing chemicals may have similar effects. Detergents, solvents, and drain cleaners may transport emulsified, saponified or dissolved fats into the drain field before they can be catabolized into short-chain organic acids in the septic tank scum layer. | 1 | Applied and Interdisciplinary Chemistry |
It was formed by the intrusion of basaltic magma into Miocene salt deposits and subsequent hydrothermal activity. Phreatic eruptions took place here in 1926, forming Dallol Volcano; numerous other eruption craters dot the salt flats nearby. These craters are the lowest known subaerial volcanic vents in the world, at or more below sea level. In October 2004 the shallow magma chamber beneath Dallol deflated and fed a magma intrusion southwards beneath the rift. The most recent signs of activity occurred in January 2011 in what may have been a degassing event from deep below the surface. | 0 | Theoretical and Fundamental Chemistry |
Trans-spanning ligands are bidentate ligands that can span opposite sites of a complex with square-planar geometry. A wide variety of ligands that chelate in the cis fashion already exist, but very few can link opposite vertices on a coordination polyhedron. Early attempts to generate trans-spanning bidentate ligands relied on long hydrocarbon chains to link the donor functionalities, but such ligands often lead to coordination polymers. | 0 | Theoretical and Fundamental Chemistry |
If the Gaussian profile is centered at and the Lorentzian profile is centered at , the convolution is centered at and the characteristic function is:
The probability density function is simply offset from the centered profile by :
where:
The mode and median are both located at . | 0 | Theoretical and Fundamental Chemistry |
As shunt resistance decreases, the current diverted through the shunt resistor increases for a given level of junction voltage. The result is that the voltage-controlled portion of the I-V curve begins to sag far from the origin, producing a significant decrease in the terminal current I and a slight reduction in V. Very low values of R will produce a significant reduction in V. Much as in the case of a high series resistance, a badly shunted solar cell will take on operating characteristics similar to those of a resistor. These effects are shown for crystalline silicon solar cells in the I-V curves displayed in the figure to the right. | 0 | Theoretical and Fundamental Chemistry |
As discussed by Jin and Roberston in their review, silencing of a DNA repair gene by hypermethylation may be a very early step in progression to cancer. Such silencing is proposed to act similarly to a germ-line mutation in a DNA repair gene, and predisposes the cell and its descendants to progression to cancer. Another review also indicated an early role for hypermethylation of DNA repair genes in cancer. If a gene necessary for DNA repair is hypermethylated, resulting in deficient DNA repair, DNA damages will accumulate. Increased DNA damage tends to cause increased errors during DNA synthesis, leading to mutations that can give rise to cancer.
If hypermethylation of a DNA repair gene is an early step in carcinogenesis, then it may also occur in the normal-appearing tissues surrounding the cancer from which the cancer arose (the field defect). See the table below.
While DNA damages may give rise to mutations through error prone translesion synthesis, DNA damages can also give rise to epigenetic alterations during faulty DNA repair processes. The DNA damages that accumulate due to hypermethylation of the promoters of DNA repair genes can be a source of the increased epigenetic alterations found in many genes in cancers.
In an early study, looking at a limited set of transcriptional promoters, Fernandez et al. examined the DNA methylation profiles of 855 primary tumors. Comparing each tumor type with its corresponding normal tissue, 729 CpG island sites (55% of the 1322 CpG island sites evaluated) showed differential DNA methylation. Of these sites, 496 were hypermethylated (repressed) and 233 were hypomethylated (activated). Thus, there is a high level of promoter methylation alterations in tumors. Some of these alterations may contribute to cancer progression. | 1 | Applied and Interdisciplinary Chemistry |
Hemoglobin, which is the principal oxygen-carrier in humans, has four subunits in which the iron(II) ion is coordinated by the planar macrocyclic ligand protoporphyrin IX (PIX) and the imidazole nitrogen atom of a histidine residue. The sixth coordination site contains a water molecule or a dioxygen molecule. By contrast the protein myoglobin, found in muscle cells, has only one such unit. The active site is located in a hydrophobic pocket. This is important as without it the iron(II) would be irreversibly oxidized to iron(III). The equilibrium constant for the formation of HbO is such that oxygen is taken up or released depending on the partial pressure of oxygen in the lungs or in muscle. In hemoglobin the four subunits show a cooperativity effect that allows for easy oxygen transfer from hemoglobin to myoglobin.
In both hemoglobin and myoglobin it is sometimes incorrectly stated that the oxygenated species contains iron(III). It is now known that the diamagnetic nature of these species is because the iron(II) atom is in the low-spin state. In oxyhemoglobin the iron atom is located in the plane of the porphyrin ring, but in the paramagnetic deoxyhemoglobin the iron atom lies above the plane of the ring. This change in spin state is a cooperative effect due to the higher crystal field splitting and smaller ionic radius of Fe in the oxyhemoglobin moiety.
Hemerythrin is another iron-containing oxygen carrier. The oxygen binding site is a binuclear iron center. The iron atoms are coordinated to the protein through the carboxylate side chains of a glutamate and aspartate and five histidine residues. The uptake of O by hemerythrin is accompanied by two-electron oxidation of the reduced binuclear center to produce bound peroxide (OOH). The mechanism of oxygen uptake and release have been worked out in detail.
Hemocyanins carry oxygen in the blood of most mollusks, and some arthropods such as the horseshoe crab. They are second only to hemoglobin in biological popularity of use in oxygen transport. On oxygenation the two copper(I) atoms at the active site are oxidized to copper(II) and the dioxygen molecules are reduced to peroxide, .
Chlorocruorin (as the larger carrier erythrocruorin) is an oxygen-binding hemeprotein present in the blood plasma of many annelids, particularly certain marine polychaetes. | 1 | Applied and Interdisciplinary Chemistry |
Daltons law (also called Daltons law of partial pressures) states that in a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases. This empirical law was observed by John Dalton in 1801 and published in 1802. Dalton's law is related to the ideal gas laws. | 0 | Theoretical and Fundamental Chemistry |
Before the invention of artificial refrigeration technology, ice making by nocturnal cooling was common in both India and Iran.
In India, such apparatuses consisted of a shallow ceramic tray with a thin layer of water, placed outdoors with a clear exposure to the night sky. The bottom and sides were insulated with a thick layer of hay. On a clear night the water would lose heat by radiation upwards. Provided the air was calm and not too far above freezing, heat gain from the surrounding air by convection was low enough to allow the water to freeze.
In Iran, this involved making large flat ice pools, which consisted of a reflection pool of water built on a bed of highly insulative material surrounded by high walls. The high walls provided protection against convective warming, the insulative material of the pool walls would protect against conductive heating from the ground, the large flat plane of water would then permit evaporative and radiative cooling to take place. | 0 | Theoretical and Fundamental Chemistry |
The current production method includes two reaction steps with potentially hazardous azides. A reported azide-free Roche synthesis of tamiflu is summarised graphically below:
The synthesis commences from naturally available (−)-shikimic acid. The 3,4-pentylidene acetal mesylate is prepared in three steps: esterification with ethanol and thionyl chloride; ketalization with p-toluenesulfonic acid and 3-pentanone; and mesylation with triethylamine and methanesulfonyl chloride. Reductive opening of the ketal under modified Hunter conditions in dichloromethane yields an inseparable mixture of isomeric mesylates. The corresponding epoxide is formed under basic conditions with potassium bicarbonate. Using the inexpensive Lewis acid magnesium bromide diethyl etherate (commonly prepared fresh by the addition of magnesium
turnings to 1,2-dibromoethane in benzene:diethyl ether), the epoxide is opened with allyl amine to yield the corresponding 1,2-amino alcohol. The water-immiscible solvents methyl tert-butyl ether and acetonitrile are used to simplify the workup procedure, which involved stirring with 1 M aqueous ammonium sulfate. Reduction on palladium, promoted by ethanolamine, followed by acidic workup yielded the deprotected 1,2-aminoalcohol. The aminoalcohol was converted directly to the corresponding allyl-diamine in an interesting cascade sequence that commences with the unselective imination of benzaldehyde with azeotropic water removal in methyl tert-butyl ether. Mesylation, followed by removal of the solid byproduct triethylamine hydrochloride, results in an intermediate that was poised to undergo aziridination upon transimination with another equivalent of allylamine. With the librated methanesulfonic acid, the
aziridine opens cleanly to yield a diamine that immediately undergoes a second transimination. Acidic hydrolysis then removed the imine. Selective acylation with acetic anhydride (under buffered conditions, the 5-amino group is protonated owing to a considerable difference in pK, 4.2 vs 7.9, preventing acetylation) yields the desired N-acetylated product in crystalline form upon extractive workup. Finally, deallylation as above, yielded the freebase of oseltamivir, which was converted to the desired oseltamivir phosphate by treatment with phosphoric acid. The final product is obtained in high purity (99.7%) and an overall yield of 17-22% from (−)-shikimic acid. It is noted that the synthesis avoids the use of potentially explosive azide reagents and intermediates; however, the synthesis actually used by Roche uses azides. Roche has other routes to
oseltamivir that do not involve the use of (−)-shikimic acid as a chiral pool starting material, such as a Diels-Alder route involving furan and ethyl acrylate or an isophthalic acid route, which involves catalytic hydrogenation and enzymatic desymmetrization. | 0 | Theoretical and Fundamental Chemistry |
Currently, a limitation of the method is that the lengths of individual reads of DNA sequence are in the neighborhood of 300-500 nucleotides, shorter than the 800-1000 obtainable with chain termination methods (e.g. Sanger sequencing). This can make the process of genome assembly more difficult, particularly for sequences containing a large amount of repetitive DNA. Lack of proof-reading activity limits accuracy of this method. | 1 | Applied and Interdisciplinary Chemistry |
An estimated 550,000 people live in the triangle of death. The annual death rate per 100,000 inhabitants from liver cancer is approximately 38.4 for men and 20.8 for women in this area, as compared to the national average of 14. The death rate for bladder cancer and cancer of the central nervous system was also higher than the national average. The high death rates from cancers pointed towards the presence of illegal and improper hazardous waste disposal by various organized crime groups including the Camorra. The 2004 Lancet Oncology article noted, "Today, the difference between lawful management of waste and illegal manipulation with regard to their compliance with health regulations is very narrow, and the health risks are rising... The 5000 illegal or uncontrolled landfill sites in Italy drew particular criticism; Italy has already been warned twice for flouting the Hazardous Waste Directive and the Landfill Directive, and the EU has now referred Italy to the European Court of Justice for further action."
The report was met with criticism by the National Research Council, dismissing the methods used by Senior and Mazza as biased. Despite this, it sparked the first interest and concern into this matter, and has become the most cited source of evidence throughout the crisis.
Though some media outlets report France and Germany as waste sources, the EU has remained silent as to the sources of the waste in its criticism and demands of Italy. | 1 | Applied and Interdisciplinary Chemistry |
The US funded a magnetic mirror program in the late 1970s and early 1980s. This program resulted in a series of magnetic mirror devices including: 2X, Baseball I, Baseball II, the Tandem Mirror Experiment and upgrade, the Mirror Fusion Test Facility, and MFTF-B. These machines were built and tested at LLNL from the late 1960s to the mid-1980s. The final machine, MFTF cost 372 million dollars and was, at that time, the most expensive project in LLNL history. It opened on February 21, 1986, and immediately closed, allegedly to balance the federal budget. | 0 | Theoretical and Fundamental Chemistry |
Extrafarma is the drugstore chain owned by Ultrapar. The company is among the top 10 largest pharmacy chains in Brazil, with stores located throughout the north, northeast and southern regions of the country.
The company has more than 400 stores in 10 States and more than 7000 employees. | 1 | Applied and Interdisciplinary Chemistry |
Consider a steady plane emerging into the same fluid, a type of submerged jets from a narrow slit, which is supposed to be very small (such that the fluid loses memory of the shape and size of the slit far away from the origin, it remembers only the net momentum flux). Let the velocity be in Cartesian coordinate and the axis of the jet be axis with origin at the orifice. The flow is self-similar for large Reynolds number (the jet is so thin that varies much more rapidly in the transverse direction than the streamwise direction) and can be approximated with boundary layer equations.
where is the kinematic viscosity and the pressure is everywhere equal to the outside fluid pressure.
Since the fluid is at rest far away from the center of the jet
: as ,
and because the flow is symmetric about axis
: at ,
and also since there is no solid boundary and the pressure is constant, the momentum flux across any plane normal to the axis must be the same
is a constant, where which also constant for incompressible flow. | 1 | Applied and Interdisciplinary Chemistry |
Calcareous grassland is a form of grassland characteristic of soils containing much calcium carbonate from underlying chalk or limestone rock. | 0 | Theoretical and Fundamental Chemistry |
Thiosulfate (IUPAC-recommended spelling; sometimes thiosulphate in British English) is an oxyanion of sulfur with the chemical formula . Thiosulfate also refers to the compounds containing this anion, which are the salts of thiosulfuric acid, e.g. sodium thiosulfate . Thiosulfate also refers to the esters of thiosulfuric acid. The prefix thio- indicates that the thiosulfate is a sulfate with one oxygen replaced by sulfur. Thiosulfate is tetrahedral at the central S atom. Thiosulfate salts occur naturally. Thiosulfate ion has C symmetry, and is produced by certain biochemical processes. It rapidly dechlorinates water and is notable for its use to halt bleaching in the paper-making industry. Thiosulfate salts are mainly used in dying in textiles and the bleaching of natural substances.
Sodium thiosulfate, commonly called hypo (from "hyposulfite"), was widely used in photography to fix black and white negatives and prints after the developing stage; modern "rapid" fixers use ammonium thiosulfate as a fixing salt because it acts three to four times faster. Some bacteria can metabolise thiosulfates. | 1 | Applied and Interdisciplinary Chemistry |
A molecular probe is a group of atoms or molecules used in molecular biology or chemistry to study the properties of other molecules or structures. If some measurable property of the molecular probe used changes when it interacts with the analyte (such as a change in absorbance), the interactions between the probe and the analyte can be studied. This makes it possible to indirectly study the properties of compounds and structures which may be hard to study directly.
The choice of molecular probe will depend on which compound or structure is being studied as well as on what property is of interest. Radioactive DNA or RNA sequences are used in molecular genetics to detect the presence of a complementary sequence by molecular hybridization. | 1 | Applied and Interdisciplinary Chemistry |
* [https://vimeo.com/132472772 Towards a metabolism for synthetic cells] (video KNAW-symposium: Op jacht naar de minimale cel, 24 juni 2015 op Vimeo)
* [https://www.youtube.com/watch?v=O8BpEiYEvAU De mens als schepper] (The human being as creator. Unifocus on YouTube. Subtitles in English) | 0 | Theoretical and Fundamental Chemistry |
Chemotactic responses elicited by ligand-receptor interactions vary with the concentration of the ligand. Investigations of ligand families (e.g. amino acids or oligopeptides) demonstrates that chemoattractant activity occurs over a wide range, while chemorepellent activities have narrow ranges. | 1 | Applied and Interdisciplinary Chemistry |
The synthesis and degradation of sialic acid are distributed in different compartments of the cell. The synthesis starts in the cytosol, where N-acetylmannosamine 6 phosphate and phosphoenolpyruvate give rise to sialic acid. Later on, Neu5Ac 9 phosphate is activated in the nucleus by a cytidine monophosphate (CMP) residue through CMP-Neu5Ac synthase. Although the linkage between sialic acid and other compounds tends to be a α binding, this specific one is the only one that is a β linkage. CMP-Neu5Ac is then transported to the endoplasmic reticulum or the Golgi apparatus, where it can be transferred to an oligosaccharide chain, becoming a new glycoconjugate. This bond can be modified by O-acetylation or O-methylation. When the glycoconjugate is mature it is transported to the cell surface.
The sialidase is one of the most important enzymes of the sialic acid catabolism. It can cause the removal of sialic acid residues from the cell surface or serum sialoglycoconjugates. Usually, in higher animals, the glycoconjugates that are prone to be degraded are captured by endocytosis. After the fusion of the late endosome with the lysosome, lysosomal sialidases remove sialic acid residues. The activity of these sialidases is based on the removal of O-acetyl groups. Free sialic acid molecules are transported to the cytosol through the membrane of the lysosome. There, they can be recycled and activated again to form another nascent glycoconjugate molecule in the Golgi apparatus. Sialic acids can also be degraded to acylmannosamine and pyruvate with the cytosolic enzyme acylneuraminate lyase.
Some severe diseases can depend on the presence or absence of some enzymes related to the sialic acid metabolism. Sialidosis and Sialic acid deficiency with mutations in the NANS gene (see below) would be examples of this type of disorder. | 0 | Theoretical and Fundamental Chemistry |
Acetyl-CoA is a metabolic intermediate that is involved in many metabolic pathways in an organism. It is produced during the breakdown of glucose, fatty acids, and amino acids, and is used in the synthesis of many other biomolecules, including cholesterol, fatty acids, and ketone bodies. Acetyl-CoA is also a key molecule in the citric acid cycle, which is a series of chemical reactions that occur in the mitochondria of cells and is responsible for generating energy in the form of ATP.
In addition, acetyl-CoA is a precursor for the biosynthesis of various acetyl-chemicals, acting as an intermediate to transfer an acetyl group during the biosynthesis of those acetyl-chemicals. Acetyl-CoA is also involved in the regulation of various cellular mechanisms by providing acetyl groups to target amino acid residues for post-translational acetylation reactions of proteins. | 1 | Applied and Interdisciplinary Chemistry |
Patterson variously said it produced a hundred or two hundred times more power than it used. Clean Energy Technologies, Inc. (CETI) representatives promoting the device at the Power-Gen '95 Conference said that an input of 1 watt would generate more than 1,000 watts of excess heat (waste heat). This supposedly happens as hydrogen or deuterium nuclei fuse together to produce heat through a form of low energy nuclear reaction. The byproducts of nuclear fusion, e.g. a tritium nucleus and a proton or an He nucleus and a neutron, have not been detected in a reliable way, leading a vast majority of experts to think that no such fusion is taking place.
It is further claimed that if radioactive isotopes such as uranium are present, the cell enables the hydrogen nuclei to fuse with these isotopes, transforming them into stable elements and thus neutralizing the radioactivity; and this would be achieved without releasing any radiation to the environment and without expending any energy. A televised demonstration on June 11, 1997, on Good Morning America was not conclusive because there was no measurement of the radioactivity of the beads after the test, thus it cannot be discarded that the beads had simply absorbed the uranium ions and become radioactive themselves. In 2002, the neutralization of radioactive isotopes has only been achieved through intense neutron bombardment in a nuclear reactor or large scale high energy particle accelerator, and at a large expense of energy.
When asked about reliability in 1998, Gabe Collins, a chemical engineer at CETI, stated: "When they dont work, its mostly due to contamination. If you get any sodium in the system it kills the reaction – and since sodium is one of the more abundant elements, it's hard to keep it out."
Patterson has carefully distanced himself from the work of Fleischmann and Pons and from the label of "cold fusion", due to the negative connotations associated to them since 1989. Ultimately, this effort was unsuccessful, and not only did it inherit the label of pathological science, but it managed to make cold fusion look a little more pathological in the public eye. Some cold fusion proponents view the cell as a confirmation of their work, while critics see it as "the fringe of the fringe of cold fusion research", since it attempts to commercialize cold fusion on top of making bad science.
In 2002, John R. Huizenga, professor of nuclear chemistry at the University of Rochester, who was head of a government panel convened in 1989 to investigate the cold fusion claims of Fleischmann and Pons, and who wrote a book about the controversy, said "I would be willing to bet there's nothing to it", when asked about the Patterson Power Cell.
In 2006, Hideo Kozima, professor emeritus of physics at Shizuoka University, has suggested that the byproducts are consistent with cold fusion. | 0 | Theoretical and Fundamental Chemistry |
* Cannot revert to virulence meaning they cannot cause the disease they aim to protect against
* Safe for immunocompromised patients
* Can withstand changes in conditions (e.g. temperature, light exposure, humidity) | 1 | Applied and Interdisciplinary Chemistry |
A shadow wall is created when a light flashes upon a person or object in front of a phosphorescent screen which temporarily captures the shadow. The screen or wall is painted with a glow-in-the-dark product that contains phosphorescent compounds. Publicly, these shadow walls can be found at certain science museums. | 0 | Theoretical and Fundamental Chemistry |
The Shinnar–Le Roux (SLR) algorithm is a mathematical tool for generating frequency-selective radio frequency (RF) pulses in magnetic resonance imaging (MRI). Frequency selective pulses are used in MRI to isolate a slice through the subject for excitation, inversion and saturation.
Given a desired magnetization profile, determining the RF pulse that produces it is generally nonlinear, due to the non-linearity of the Bloch equations. At low tip angles, the RF excitation waveform can be approximated by the inverse Fourier Transform of the desired frequency profile, using the excitation kspace analysis. The small tip angle approximation continues to hold well for tip angles on the order of 90 degree. However, for tip angles greater than 90 degree, a different approach must be used.
A direct solution to the pulse design problem was independently proposed by Shinnar and Le Roux based on a discrete approximation to the spin domain version of the Bloch equations. | 0 | Theoretical and Fundamental Chemistry |
The rotating packs of disks (known as the media) are contained in a tank or trough and rotate at between 2 and 5 revolutions per minute. Commonly used plastics for the media are polyethylene, PVC and expanded polystyrene. The shaft is aligned with the flow of wastewater so that the discs rotate at right angles to the flow, with several packs usually combined to make up a treatment train. About 40% of the disc area is immersed in the wastewater.
Biological growth is attached to the surface of the disc and forms a slime layer. The discs contact the wastewater with the atmospheric air for oxidation as it rotates. The rotation helps to slough off excess solids. The disc system can be staged in series to obtain nearly any detention time or degree of removal required. Since the systems are staged, the culture of the later stages can be acclimated to the slowly degraded materials.
The discs consist of plastic sheets ranging from 2 to 4 m in diameter and are up to 10 mm thick. Several modules may be arranged in parallel and/or in series to meet the flow and treatment requirements. The discs are submerged in waste water to about 40% of their diameter. Approximately 95% of the surface area is thus alternately submerged in waste water and then exposed to the atmosphere above the liquid. Carbonaceous substrate is removed in the initial stage of RBC. Carbon conversion may be completed in the first stage of a series of modules, with nitrification being completed after the 5th stage. Most design of RBC systems will include a minimum of 4 or 5 modules in series to obtain nitrification of waste water. As the biofilm biomass changes from Carbon metabolizing to nitrifying, a visual colour change from grey/beige to brown can be seen which is illustrated by the adjacent photo.
Biofilms, which are biological growths that become attached to the discs, assimilate the organic materials (measured as BOD5) in the wastewater. Aeration is provided by the rotating action, which exposes the media to the air after contacting them with the wastewater, facilitating the degradation of the pollutants being removed. The degree of wastewater treatment is related to the amount of media surface area and the quality and volume of the inflowing wastewater.
RBC's regularly achieve the following effluent parameters for treated waste water: BOD5: 20 mg/L, Suspended Solids: 30 mg/L and Ammonia N: 20 mg/L. They consume very low power and make little noise due to the slow rotation of the rotor (2-5 RPM). They are generally considered very robust and low maintenance systems. Better discharge effluent parameters can be achieved by adding a tertiary polishing filter after the RBC to lower BOD5, SS and Ammonia Nitrogen. An additional UV or Chlorination step can achieve effluent parameters that make the water suitable for irrigation or toilet flushing. | 1 | Applied and Interdisciplinary Chemistry |
In 1826, French scientist and naval officer Captain Jules Dumont dUrville reported waves as high as in the Indian Ocean with three colleagues as witnesses, yet he was publicly ridiculed by fellow scientist François Arago. In that era, the thought was widely held that no wave could exceed . Author Susan Casey wrote that much of that disbelief came because there were very few people who had seen a rogue wave and survived; until the advent of steel double-hulled ships of the 20th century, "people who encountered rogue waves generally werent coming back to tell people about it." | 1 | Applied and Interdisciplinary Chemistry |
*The pi-pi charge-transfer interactions of bipyridinium with dioxyarenes or diaminoarenes have been used extensively for the construction of mechanically interlocked systems and in crystal engineering.
*The use of crown ether binding with metal or ammonium cations is ubiquitous in supramolecular chemistry.
*The formation of carboxylic acid dimers and other simple hydrogen bonding interactions.
*The complexation of bipyridines or terpyridines with ruthenium, silver or other metal ions is of great utility in the construction of complex architectures of many individual molecules.
*The complexation of porphyrins or phthalocyanines around metal ions gives access to catalytic, photochemical and electrochemical properties in addition to the complexation itself. These units are used a great deal by nature. | 0 | Theoretical and Fundamental Chemistry |
Chloroeremomycin was discovered by Eli Lilly in the 1980s. In the 1990s, researchers at Eli Lilly developed biphenyl-chloroeremomycin, now known as oritavancin, as a functionalized derivative of chloroeremomycin to combat rising antibacterial resistance to vancomycin. The chloroeremomycin gene cluster was sequenced by van Wageningen et al in 1998. After the publication, many groups expressed the genes and conducted experiments to understand how chloroeremomycin and, by extension, vancomycin are biosynthesized. | 0 | Theoretical and Fundamental Chemistry |
Light sheet fluorescence microscopy or selective plane imaging microscopy (SPIM) uses illumination that is done perpendicularly to the direction of observation, by using a thin sheet of (laser) light. Under certain conditions, this illumination principle can be combined with fluorescence correlation spectroscopy, to allow spatially resolved imaging of the mobility and interactions of fluorescing particles such as GFP labelled proteins inside living biological samples. | 0 | Theoretical and Fundamental Chemistry |
Many aspects of academic research and industrial research such as in pharmaceuticals, health products, and many others relies on accurate water analysis to identify substances of potential use, to refine those substances and to ensure that when they are manufactured for sale that the chemical composition remains consistent. The analytical methods used in these area can be very complex and may be specific to the process or area of research being conducted and may involve the use of bespoke analytical equipment. | 0 | Theoretical and Fundamental Chemistry |
One of the most well known epigenetic mechanisms that proline isomerization plays a role in is the modification of histone tails, specifically those of histone H3. Fpr4 is a PPIase, in the FK507BP group, that exhibits catalytic activity at the proline positions 16, 30, and 38 (also written P16, P30, and P38 respectively) on the N-terminal region of histone H3 in Saccharomyces cerevisiae. Fpr4s binding affinity is strongest at the P38 site, followed by P30 and then P16. However the catalytic efficiency, or the increase in isomerization rates, is highest at P16 and P30 equally, followed by P38 which exhibits a very small change in isomerization rates with the binding of Fpr4. Histone H3 has an important lysine residue at the 36 position (also written K36) on the N-terminal tail which can be methylated by Set2, a methyltransferase. Methylation of K36 is key to normal transcription elongation. Due to P38s proximity to K36, cross-talk between P38 isomerization and K36 methylation can occur. This means that isomer changes at the P38 position can affect methylation at the K36 position. In the cis position, P38 shifts the histone tail closer to the DNA, crowding the area around the tail. This can cause a decrease the ability of proteins to bind to the DNA and to the histone tail, including preventing Set2 from methylating K36. Also, this tail movement can increase the number interactions between the histone tail and the DNA, increasing likelihood of nucleosome formation and potentially leading to the creation of higher-order chromatin structure. In trans, P38 leads to the opposite effects: allowing for Set2 to methylate K36. Set2 is only affected by isomerization of P38 when creating a trimethylated K36 (commonly written as K36me3), however, and not K36me2. Fpr4 also binds to P32 in H4, though its effects are minimal.
In mammalian cells, the isomerization of H3P30 interacts with the phosphorylation of H3S28 (serine in the 28 position of histone H3) and the methylation of H3K27. hFKBP25 is a PPIase that is a homolog for Fpr4 in mammalian cells and is found to commonly be associated with the presence of HDACs. Cyp33 is a cyclophilin that has the ability to isomerize H3 proline residues at P16 and P30 positions. Histones H2A and H2B also have multiple proline residues near amino acids that when modified affect the activity surrounding the histone. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, a coupling reaction is a type of reaction in which two reactant molecules are bonded together. Such reactions often require the aid of a metal catalyst. In one important reaction type, a main group organometallic compound of the type R-M (where R = organic group, M = main group centre metal atom) reacts with an organic halide of the type R-X with formation of a new carbon-carbon bond in the product R-R. The most common type of coupling reaction is the cross coupling reaction.
Richard F. Heck, Ei-ichi Negishi, and Akira Suzuki were awarded the 2010 Nobel Prize in Chemistry for developing palladium-catalyzed cross coupling reactions.
Broadly speaking, two types of coupling reactions are recognized:
*Homocouplings joining two identical partners. The product is symmetrical
*Heterocouplings joining two different partners. These reactions are also called cross-coupling reactions. The product is unsymmetrical, . | 0 | Theoretical and Fundamental Chemistry |
As with experimental samples, the conditions of the gel can affect the molecular-weight size marker that runs alongside them. Factors such as buffer, charge/voltage, and concentration of gel can affect the mobility and/or appearance of your marker/ladder/standard. These elements need to be taken into consideration when selecting a marker and when analyzing the final results on a gel. | 1 | Applied and Interdisciplinary Chemistry |
Pempidine is an aliphatic, sterically hindered, cyclic, tertiary amine, which is a weak base: in its protonated form it has a pK of 11.25.
Pempidine is a liquid with a boiling point of 187–188 °C and a density of 0.858 g/cm.
Two early syntheses of this compound are those of Leonard and Hauck, and Hall. These are very similar in principle: Leonard and Hauck reacted phorone with ammonia, to produce 2,2,6,6-tetramethyl-4-piperidone, which was then reduced by means of the Wolff–Kishner reduction to 2,2,6,6-tetramethylpiperidine. This secondary amine was then N-methylated using methyl iodide and potassium carbonate.
Halls method involved reacting acetone with ammonia in the presence of calcium chloride to give 2,2,6,6-tetramethyl-4-piperidone, which was then reduced under Wolff–Kishner conditions, followed by N-methylation of the resulting 2,2,6,6-tetramethylpiperidine with methyl p'-toluenesulfonate. | 0 | Theoretical and Fundamental Chemistry |
Oxaziridines have been found to undergo rearrangement reactions via a radical mechanism when irradiated with UV light or in the presence of a single electron transfer reagent such as Cu. spirocylic oxaziridines undergo ring expansions to the corresponding lactam. The migrating substituent is determined by a stereoelectronic effect where the group trans to the lone pair on the nitrogen will always be the predominant migration product. In light of this effect, it is possible to take advantage of the chiral nitrogen due to high inversion barrier to direct the rearrangement. This phenomenon is demonstrated by observed selectivities in the rearrangements below. In the rearrangement on the left the thermodynamically unfavorable product is observed exclusively, while in the reaction on the right the product derived from the less stable radical intermediate is favored.
Aubé takes advantage of this rearrangement as the key step in his synthesis of (+)-yohimbine, a natural medicine classified by the NIH as possibly effective in the treatment of erectile dysfunction and the sexual problems caused by selective serotonin reuptake inhibitors.
It is also notable that oxaziridines will thermally rearrange to nitrones. Cis-trans selectivity of the resulting nitrone is poor, however, yields are good to excellent. It is thought that some oxaziridines racemize over time through a nitrone intermediate. | 0 | Theoretical and Fundamental Chemistry |
Using the distributed load equation provided the can be replaced with area of the piston surface where the pressure is acting on.
Where:
: represents the resultant force
: represents the radius of the piston
: is pi, approximately equal to 3.14159. | 1 | Applied and Interdisciplinary Chemistry |
Discharge cavitation occurs when the pump discharge pressure is extremely high, normally occurring in a pump that is running at less than 10% of its best efficiency point. The high discharge pressure causes the majority of the fluid to circulate inside the pump instead of being allowed to flow out the discharge. As the liquid flows around the impeller, it must pass through the small clearance between the impeller and the pump housing at extremely high flow velocity. This flow velocity causes a vacuum to develop at the housing wall (similar to what occurs in a venturi), which turns the liquid into a vapor. A pump that has been operating under these conditions shows premature wear of the impeller vane tips and the pump housing. In addition, due to the high pressure conditions, premature failure of the pump's mechanical seal and bearings can be expected. Under extreme conditions, this can break the impeller shaft.
Discharge cavitation in joint fluid is thought to cause the popping sound produced by bone joint cracking, for example by deliberately cracking one's knuckles. | 1 | Applied and Interdisciplinary Chemistry |
Deamination of guanine results in the formation of xanthine. Xanthine, however, still pairs with cytosine. | 1 | Applied and Interdisciplinary Chemistry |
Inside the body oxygen is delivered to cells and in the cells to mitochondria, where it is consumed in the process generating most of the energy required by the organism.
Mitochondrial respirometry measures the consumption of oxygen by the mitochondria without involving an entire living animal and is the main tool to study mitochondrial function. Three different types of samples may be subjected to such respirometric studies:
isolated mitochondria (from cell cultures, animals or plants); permeabilized cells (from cell cultures); and permeabilized fibers or tissues (from animals). In the latter two cases the cellular membrane is made permeable by the addition of chemicals leaving selectively the mitochondrial membrane intact. Therefore, chemicals that usually would not be able to cross the cell membrane can directly influence the mitochondria. By the permeabilization of the cellular membrane, the cell stops to exist as a living, defined organism, leaving only the mitochondria as still functional structures.
Unlike whole-animal respirometry, mitochondrial respirometry takes place in solution, i.e. the sample is suspended in a medium. Today mitochondrial respirometry is mainly performed with a closed-chamber approach. | 1 | Applied and Interdisciplinary Chemistry |
Callystatin A is a polyketide natural product from the leptomycin family of secondary metabolites. It was first isolated in 1997 from the marine sponge Callyspongia truncata which was collected from the Goto Islands in the Nagasaki Prefecture of Japan by the Kobayashi group. Since then its absolute configuration has been elucidated and callystatin A was discovered to have anti-fungal and anti-tumor activities with extreme potency against the human epidermoid carcinoma KB cells (IG = 10 pg/ml) and the mouse lymphocytic leukemia Ll210 cells (IG = 20 pg/ml). | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, alkyl nitrites are a group of organic compounds based upon the molecular structure , where R represents an alkyl group. Formally they are alkyl esters of nitrous acid. They are distinct from nitro compounds ().
The first few members of the series are volatile liquids; methyl nitrite and ethyl nitrite are gaseous at room temperature and pressure. The compounds have a distinctive fruity odor. Another frequently encountered nitrite is amyl nitrite (3-methylbutyl nitrite).
Alkyl nitrites were initially, and largely still are, used as medications and chemical reagents, a practice which began in the late 19th century. In their use as medicine, they are often inhaled for relief of angina and other heart-related symptoms of disease. However, when referred to as "poppers", alkyl nitrites represent recreational drugs. | 0 | Theoretical and Fundamental Chemistry |
It was found that the luciferase enzyme produced in fireflies is localized to the peroxisome within the photocytes. When mammalian cells were modified to produce the enzyme, it was found that they were targeted to the mammalian peroxisome as well. Because protein targeting to peroxisomes is not well understood, this finding is valuable for its potential to aid in the determination of peroxisome targeting mechanisms. If the cell produces a large amount of luciferase, some of the protein ends up in the cytoplasm. It is unknown what feature of the luciferase enzyme causes it to be targeted to the peroxisome since no particular protein sequences related to peroxisome targeting have been discovered. | 1 | Applied and Interdisciplinary Chemistry |
As of 2012, she is a full professor of inorganic chemistry and head of the research group Smart Biomaterials in the Department of Inorganic and Bioinorganic Chemistry of the Faculty of Pharmacy at Universidad Complutense de Madrid.
Vallet-Regí has written more than 600 articles and several books. She was the most-cited Spanish scientist, according to ISI Web of Knowledge, in the field of Materials Science in these past decades. | 0 | Theoretical and Fundamental Chemistry |
Several periods are attested at Hammeh. From bedrock upward, remains of Chalcolithic (ca. 4500-3000 BC) and Early Bronze Age (ca. 3000-2000 BC) occupation were found, followed by more substantial layers of Late Bronze Age (ca. 1600-1150 BC) material. Hammeh appears continuously settled through the Late Bronze Age and Iron Age I (ca. 1150-1000 BC), up to the moment when iron production started in the early Iron Age II (see van der Steen 2004).
At that point in time, domestic structures, at least in the excavated areas, cease to exist, and are covered, without a clear interruption, by a stratigraphically well defined phase of iron production. This phase has a complex internal layering, likely reflecting seasonal activity over an extended period of time. (Veldhuijzen 2005a).
This phase consists of large quantities of various types of slag, most belonging to a bloomery iron smelting operation, and a fraction to primary smithing (i.e. bloom-smithing or bloom consolidation).
Very soon or immediately after iron production ceased, habitation of the site resumed. This later Iron Age II phase seems to form the last extensive occupation of Tell Hammeh. Based on examination of the extensive pottery finds from this post-smelting phase, it can be assumed that the iron production activities must have ended no later than 750 BC. No settlement structures contemporary to the iron smelting phase are presently known from Tell Hammeh. | 1 | Applied and Interdisciplinary Chemistry |
Dynamic light scattering (DLS) is a technique in physics that can be used to determine the size distribution profile of small particles in suspension or polymers in solution. In the scope of DLS, temporal fluctuations are usually analyzed using the intensity or photon autocorrelation function (also known as photon correlation spectroscopy – PCS or quasi-elastic light scattering – QELS). In the time domain analysis, the autocorrelation function (ACF) usually decays starting from zero delay time, and faster dynamics due to smaller particles lead to faster decorrelation of scattered intensity trace. It has been shown that the intensity ACF is the Fourier transform of the power spectrum, and therefore the DLS measurements can be equally well performed in the spectral domain. DLS can also be used to probe the behavior of complex fluids such as concentrated polymer solutions. | 0 | Theoretical and Fundamental Chemistry |
As of 8 April 2013, 60 Eurobachelor, 36 Euromaster, and 1 Eurodoctorate labels have been awarded to 52 institutions and 3 consortia from 20 countries.
The countries that have been awarded labels include:
*Austria
*Belgium
*Czech Republic
*Estonia
*Finland
*France
*Germany
*Greece
*Hungary
*Ireland
*Italy
*Kazakhstan
*Morocco
*Netherlands
*Poland
*Portugal
*Slovakia
*Slovenia
*Spain
*United Kingdom | 1 | Applied and Interdisciplinary Chemistry |
BindingDB
is a public, web-accessible database of measured binding affinities, focusing chiefly on the interactions of proteins considered to be candidate drug-targets with ligands that are small, drug-like molecules. As of March, 2011, BindingDB contains about 650,000 binding data, for 5,700 protein targets and 280,000 small molecules. BindingDB also includes a small collection of host–guest binding data of interest to chemists studying supramolecular systems.
The purpose of BindingDB is to support medicinal chemistry and drug discovery via literature awareness and development of structure-activity relations (SAR and QSAR); validation of computational chemistry and molecular modelling approaches such as docking, scoring and free energy methods; chemical biology and chemical genomics; and basic studies of the physical chemistry of molecular recognition.
The data collection derives from a variety of measurement techniques, including enzyme inhibition and kinetics, isothermal titration calorimetry, NMR, and radioligand and competition assays. BindingDB includes data extracted from the scientific literature by the BindingDB project, selected PubChem confirmatory BioAssays, and ChEMBL entries for which a well-defined protein target ("TARGET_TYPE=PROTEIN") is provided. | 1 | Applied and Interdisciplinary Chemistry |
High levels of lactate dehydrogenase in cerebrospinal fluid are often associated with bacterial meningitis. In the case of viral meningitis, high LDH, in general, indicates the presence of encephalitis and poor prognosis. | 1 | Applied and Interdisciplinary Chemistry |
Open-channel flow can be classified and described in various ways based on the change in flow depth with respect to time and space. The fundamental types of flow dealt with in open-channel hydraulics are:
* Time as the criterion
** Steady flow
*** The depth of flow does not change over time, or if it can be assumed to be constant during the time interval under consideration.
** Unsteady flow
*** The depth of flow does change with time.
* Space as the criterion
** Uniform flow
*** The depth of flow is the same at every section of the channel. Uniform flow can be steady or unsteady, depending on whether or not the depth changes with time, (although unsteady uniform flow is rare).
** Varied flow
*** The depth of flow changes along the length of the channel. Varied flow technically may be either steady or unsteady. Varied flow can be further classified as either rapidly or gradually-varied:
**** Rapidly-varied flow
***** The depth changes abruptly over a comparatively short distance. Rapidly varied flow is known as a local phenomenon. Examples are the hydraulic jump and the hydraulic drop.
**** Gradually-varied flow
***** The depth changes over a long distance.
** Continuous flow
*** The discharge is constant throughout the reach of the channel under consideration. This is often the case with a steady flow. This flow is considered continuous and therefore can be described using the continuity equation for continuous steady flow.
** Spatially-varied flow
*** The discharge of a steady flow is non-uniform along a channel. This happens when water enters and/or leaves the channel along the course of flow. An example of flow entering a channel would be a road side gutter. An example of flow leaving a channel would be an irrigation channel. This flow can be described using the continuity equation for continuous unsteady flow requires the consideration of the time effect and includes a time element as a variable. | 1 | Applied and Interdisciplinary Chemistry |
The following table represents the closure temperatures of some materials. These values are the approximate values of the closure temperatures of certain minerals listed by the isotopic system being used. These values are approximations; better values of the closure temperature require more precise calculations and characterizations of the diffusion characteristics of the mineral grain being studied. | 0 | Theoretical and Fundamental Chemistry |
The theoretical plate concept was also adapted for chromatographic processes by Martin and Synge. The IUPAC's Gold Book provides a definition of the number of theoretical plates in a chromatography column.
The same equation applies in chromatography processes as for the packed bed processes, namely:
In packed column chromatography, the HETP may also be calculated with the Van Deemter equation.
In capillary column chromatography HETP is given by the Golay equation. | 1 | Applied and Interdisciplinary Chemistry |
Neglecting surface tension and viscosity, the equation was first derived by W. H. Besant in his 1859 book with the problem statement stated as An infinite mass of homogeneous incompressible fluid acted upon by no forces is at rest, and a spherical portion of the fluid is suddenly annihilated; it is required to find the instantaneous alteration of pressure at any point of the mass, and the time in which the cavity will be filled up, the pressure at an infinite distance being supposed to remain constant (in fact, Besant attributes the problem to Cambridge Senate-House problems of 1847). Besant predicted the time required to fill an empty cavity of initial radius to be
Lord Rayleigh found a simpler derivation of the same result, based on conservation of energy. The kinetic energy of the inrushing fluid is where is the time-dependent radius of the void, and the radial velocity of the fluid there. The work done by the fluid pressing in at infinity is , and equating these two energies gives a relation between and . Then, noting that , separation of variables gives Besants result. Rayleigh went further than Besant, in evaluating the integral (Eulers beta function) in terms of gamma functions. Rayleigh adapted this approach to the case of a cavity filled with an ideal gas (a bubble) by including a term for the work done compressing the gas.
For the case of the perfectly empty void, Rayleigh determined that the pressure in the fluid at a radius is given by:
When the void is at least one quarter of its initial volume, then the pressure decreases monotonically from at infinity to zero at . As the void shrinks further a pressure maximum, greater than appears at
very rapidly growing and converging on the void.
The equation was first applied to traveling cavitation bubbles by Milton S. Plesset in 1949 by including effects of surface tension. | 1 | Applied and Interdisciplinary Chemistry |
Respiration in cyanobacteria can occur in the thylakoid membrane alongside photosynthesis, with their photosynthetic electron transport sharing the same compartment as the components of respiratory electron transport. While the goal of photosynthesis is to store energy by building carbohydrates from CO, respiration is the reverse of this, with carbohydrates turned back into CO accompanying energy release.
Cyanobacteria appear to separate these two processes with their plasma membrane containing only components of the respiratory chain, while the thylakoid membrane hosts an interlinked respiratory and photosynthetic electron transport chain. Cyanobacteria use electrons from succinate dehydrogenase rather than from NADPH for respiration.
Cyanobacteria only respire during the night (or in the dark) because the facilities used for electron transport are used in reverse for photosynthesis while in the light. | 0 | Theoretical and Fundamental Chemistry |
In the kinetic proofreading schema, a time delay (equivalently, an irreversible intermediate stage) is introduced during the formation of the correct or incorrect complexes. This time delay reduces the production rates of both complexes but enhances the fidelity beyond the equilibrium limit. The irreversibility of the scheme requires an energy source. The time delay in kinetic proofreading is analogous to the spatial difference in conformational proofreading. However, the conformational proofreading can be an equilibrium scheme that does not consume energy. | 1 | Applied and Interdisciplinary Chemistry |
Polysome profiling is a technique in molecular biology that is used to study the association of mRNAs with ribosomes. It is important to note that this technique is different from ribosome profiling. Both techniques have been reviewed and both are used in analysis of the translatome, but the data they generate are at very different levels of specificity. When employed by experts, the technique is remarkably reproducible: the 3 profiles in the first image are from 3 different experiments. | 1 | Applied and Interdisciplinary Chemistry |
The litmus mixture has the CAS number 1393-92-6 and contains 10 to around 15 different dyes. All of the chemical components of litmus are likely to be the same as those of the related mixture known as orcein but in different proportions. In contrast with orcein, the principal constituent of litmus has an average molecular mass of 3300. Acid-base indicators on litmus owe their properties to a 7-hydroxyphenoxazone chromophore. Some fractions of litmus were given specific names including erythrolitmin (or erythrolein), azolitmin, spaniolitmin, leucoorcein, and leucazolitmin. Azolitmin shows nearly the same effect as litmus.
A recipe to make litmus out of the lichens, as outlined on a UC Santa Barbara website says: | 0 | Theoretical and Fundamental Chemistry |
According to Sazonov and Shaw, the dimensionless Bunsen coefficient is defined as "the volume of saturating gas, V1, reduced to T° = 273.15 K, p° = 1 bar, which is absorbed by unit volume V* of pure solvent at the temperature of measurement and partial pressure of 1 bar." If the gas is ideal, the pressure cancels out, and the conversion to is simply
with = 273.15K. Note, that according to this definition, the conversion factor is not temperature-dependent. Independent of the temperature that the Bunsen coefficient refers to, 273.15K is always used for the conversion. The Bunsen coefficient, which is named after Robert Bunsen, has been used mainly in the older literature, and IUPAC considers it to be obsolete. | 0 | Theoretical and Fundamental Chemistry |
Studies have shown that the binding of TFIIB to TBP is affected by the length of the polyglutamine tract in TBP. Extended polyglutamine tracts such as those found in neurodegenerative diseases cause increased interaction with TFIIB. This is thought to affect transcription in these diseases as it reduces the availability of TFIIB to other promoters in the brain as the TFIIB is instead interacting with the expanded polyglutamine tracts. | 1 | Applied and Interdisciplinary Chemistry |
Radioanalytical chemistry focuses on the analysis of sample for their radionuclide content. Various methods are employed to purify and identify the radioelement of interest through chemical methods and sample measurement techniques. | 0 | Theoretical and Fundamental Chemistry |
Degeneracy of the genetic code was identified by Lagerkvist. For instance, codons GAA and GAG both specify glutamic acid and exhibit redundancy; but, neither specifies any other amino acid and thus are not ambiguous or demonstrate no ambiguity.
The codons encoding one amino acid may differ in any of their three positions; however, more often than not, this difference is in the second or third position. For instance, the amino acid glutamic acid is specified by GAA and GAG codons (difference in the third position); the amino acid leucine is specified by UUA, UUG, CUU, CUC, CUA, CUG codons (difference in the first or third position); and the amino acid serine is specified by UCA, UCG, UCC, UCU, AGU, AGC (difference in the first, second, or third position).
Degeneracy results because there are more codons than encodable amino acids. For example, if there were two bases per codon, then only 16 amino acids could be coded for (4²=16). Because at least 21 codes are required (20 amino acids plus stop) and the next largest number of bases is three, then 4³ gives 64 possible codons, meaning that some degeneracy must exist. | 1 | Applied and Interdisciplinary Chemistry |
Explained briefly, NASBA works as follows:
#RNA template added to the reaction mixture, the first primer with the T7 promoter region on its 5 end attaches to its complementary site at the 3 end of the template.
#Reverse transcriptase synthesizes the opposite complementary DNA strand extending the 3' end of the primer, moving upstream along the RNA template.
#RNAse H destroys the RNA template from the DNA-RNA compound (RNAse H only destroys RNA in RNA-DNA hybrids, but not single-stranded RNA).
#The second primer attaches to the 5' end of the (antisense) DNA strand.
#Reverse transcriptase again synthesizes another DNA strand from the attached primer resulting in double stranded DNA.
#T7 RNA polymerase binds to the promoter region on the double strand. Since T7 RNA polymerase can only transcribe in the 3 to 5 direction the sense DNA is transcribed and an anti-sense RNA is produced. This is repeated, and the polymerase continuously produces complementary RNA strands of this template which results in amplification.
#Now a cyclic phase can begin similar to the previous steps. Here, however, the second primer first binds to the (-)RNA
#The reverse transcriptase now produces a (+)cDNA/(-)RNA duplex.
#RNAse H again degrades the RNA and the first primer binds to the now single stranded +(cDNA)
#The reverse transcriptase now produces the complementary (-)DNA, creating a dsDNA duplex
#Exactly like step 6, the T7 polymerase binds to the promoter region to produce (-)RNA, and the cycle is complete. | 1 | Applied and Interdisciplinary Chemistry |
* Димитров П. 1988. [https://www.researchgate.net/publication/312155281_Dalec_ot_bregove_i_farvateri_Far_from_the_coasts_and_waterways Далеч от брегове и фарватери]. Варна. Изд. „Галактика“. Библиотека „Нептун“, 161 с., doi:[https://doi.org/10.13140/RG.2.2.19449.36965/1 10.13140/RG.2.2.19449.36965/1]
* Димитров П., Д. Димитров. 2003. [https://www.researchgate.net/publication/290946364_Cerno_more_Potopt_i_drevnite_mitove Черно море, Потопът и древните митове]. „Славена“, Варна, ISBN 954-579-278-7, 91 с., doi:[https://doi.org/10.13140/RG.2.2.27133.05609 10.13140/RG.2.2.27133.05609]
** ((en)) Dimitrov P., D. Dimitrov. 2004. [https://www.researchgate.net/publication/290938137_The_Black_Sea_The_Flood_and_the_ancient_myths The Black Sea The Flood and the ancient myths]. „Slavena“, Varna, ISBN 954-579-335-X, 91 p., doi:[https://doi.org/10.13140/RG.2.2.18954.16327 10.13140/RG.2.2.18954.16327]
** ((ru)) Димитров П., Д. Димитров. 2008. [https://www.researchgate.net/publication/290946378_Cernoe_more_Potop_i_drevnie_mify Черное море, Потоп и древние мифы]. „Славена“, Варна, ISBN 954-579-278-7, 89 с., doi:[https://doi.org/10.13140/RG.2.2.23148.46729 10.13140/RG.2.2.23148.46729] | 0 | Theoretical and Fundamental Chemistry |
Ultraviolet radiation is used for very fine resolution photolithography, a procedure wherein a chemical called a photoresist is exposed to UV radiation that has passed through a mask. The exposure causes chemical reactions to occur in the photoresist. After removal of unwanted photoresist, a pattern determined by the mask remains on the sample. Steps may then be taken to "etch" away, deposit on or otherwise modify areas of the sample where no photoresist remains.
Photolithography is used in the manufacture of semiconductors, integrated circuit components, and printed circuit boards. Photolithography processes used to fabricate electronic integrated circuits presently use 193 nm UV and are experimentally using 13.5 nm UV for extreme ultraviolet lithography. | 0 | Theoretical and Fundamental Chemistry |
Excavations from sites where Indus Valley civilisation once flourished reveal usage of bronze for various purposes. Earliest known usage of bronze for art form can be traced back to 2500 BC. Dancing Girl of Mohenjo Daro is attributed for the same. Archaeologists working on excavation site at Kosambi in Uttar Pradesh unearthed a bronze figure of a Girl riding two bulls which is dated approximately between 2000 - 1750 BC further reveals the usage of bronze for casting into an art form during the Late Harappan period. Another such instance of a Late Harappan period bronze artifact was found at Daimbad in Maharashtra suggesting a possibility of a more widespread usage of bronze then localised to places around Indus Valley alone.
Bronze continued to be used as a metal for various statues and statuettes during Classical Period as can be seen from the Bronze hoard discovered in Chausa Bihar, which consisted of bronze statuettes dating between 2nd BC to 6th Century AD.
Bronze art picked up in South India during the Middle Ages during the rule of Pallava's, 8th Century Ardhaparyanka asana icon of Shiva is one notable artifact from this period. Bronze sculpting however peaked during the reign of Cholas (c. 850 CE - 1250 CE). Many of the bronze sculptures from this period are now present in various museums around the world. Nataraja statue found in the Metropolitan Museum of Art, New York City is a remarkable piece of sculpting from this period. | 1 | Applied and Interdisciplinary Chemistry |
Soil contamination from heavy elements can be found in the urban environments, which can be attributed to the transportation and industries along with the background levels (minerals-leaching heavy elements from weathering). Also, some of the most soil contaminated areas are around the mines such as the ones in Slovenia, Bosnia and Herzegovina, and in United States (Sulphur Bank Superfund Site, in California). In a study area, GIS is used for the analysis of spatial relationship of the contaminants within the soil. | 1 | Applied and Interdisciplinary Chemistry |
In the US, municipalities may require permits for building drainage systems as federal law requires water sent to storm drains to be free of certain contaminants and sediment.
In the UK, local authorities may have specific requirements for the outfall of a French drain into a ditch or watercourse. | 1 | Applied and Interdisciplinary Chemistry |
Erämetsä was an assistant geologist for the Geological Commission and made five exploration trips to Lapland.
He carried out a number of diamond surveys in the
Paatsjoki area of Petsamo in the 1930s, trying to verify reports of diamonds in the sands in that area. He concluded that what had been discovered was likely to have been spinel octahedra.
In 1939 Erämetsä and Thure Georg Sahama developed a new method for the separation of rare earths using chromatography. Their chromatographic separation method became a standard for the separation of rare earth and radioactive actinides into ion exchange resins.
Erämetsä worked as a lecturer in analytical chemistry at the Helsinki University of Technology (TKK) from 1940 to 1946 and then as a professor of inorganic chemistry from 1947 to 1973. During his time there, the department received new hardware including a spectrograph, Finland's first equipment for spark source mass spectrometry, and X-ray fluorescence equipment.
Large-scale industrial production of rare earths occurred in the 1960s at the Typpi Oy mills in Oulu, where lanthanide ores of the Kola Peninsula were being refined.
Erämetsä's most well-known, though controversial achievement, was the isolation of the element promethium from these natural sources. In 1965, he published a report stating that in 1964 he had successfully isolated isotopes of promethium from natural ores.
Erämetsä separated out traces of Pm from a rare earth concentrate purified from apatite,
resulting in an upper limit of 10 for the abundance of promethium in nature; this may have been produced by the natural nuclear fission of uranium, or by cosmic ray spallation of Nd.
The international scientific community was initially suspicious of the findings, as promethium had previously only be produced as a degradation product from the fission of uranium ore. Due to promethium's short half-life, its concentration in natural minerals was thought to be too small to be isolated. Subsequent findings were in line with those of Erämetsä.
Erämetsä and Allan Johansson used praseodymium to experiment with the development of a solid electrolyte fuel cell.
Erämetsä studied the presence of trace elements including rare earths in soils and plants such as lichens and mosses. He also studied of the presence of rare earths in the human body, over a period of many years. Results were negative from 1945 to 1969, when x-ray emission spectroscopy was introduced. With the new instruments, the researchers detected yttrium and other lanthanides. In one study, autopsies were performed on the bodies of people who had died in Helsinki hospitals. Yttrium was found in varying amounts and locations in the bodies of almost half of those examined (37/80).
Erämetsä was concerned with epidemiologic evidence of environmental factors affecting human health, cf. the presence of metals in drinking water and their possible relationships to coronary heart disease. | 1 | Applied and Interdisciplinary Chemistry |
;Myoglobin: Found in the muscle tissue of many vertebrates, including humans, it gives muscle tissue a distinct red or dark gray color. It is very similar to hemoglobin in structure and sequence, but is not a tetramer; instead, it is a monomer that lacks cooperative binding. It is used to store oxygen rather than transport it.
;Hemocyanin: The second most common oxygen-transporting protein found in nature, it is found in the blood of many arthropods and molluscs. Uses copper prosthetic groups instead of iron heme groups and is blue in color when oxygenated.
;Hemerythrin: Some marine invertebrates and a few species of annelid use this iron-containing non-heme protein to carry oxygen in their blood. Appears pink/violet when oxygenated, clear when not.
;Chlorocruorin: Found in many annelids, it is very similar to erythrocruorin, but the heme group is significantly different in structure. Appears green when deoxygenated and red when oxygenated.
;Vanabins: Also known as vanadium chromagens, they are found in the blood of sea squirts. They were once hypothesized to use the metal vanadium as an oxygen binding prosthetic group. However, although they do contain vanadium by preference, they apparently bind little oxygen, and thus have some other function, which has not been elucidated (sea squirts also contain some hemoglobin). They may act as toxins.
;Erythrocruorin: Found in many annelids, including earthworms, it is a giant free-floating blood protein containing many dozens—possibly hundreds—of iron- and heme-bearing protein subunits bound together into a single protein complex with a molecular mass greater than 3.5 million daltons.
;Leghemoglobin: In leguminous plants, such as alfalfa or soybeans, the nitrogen fixing bacteria in the roots are protected from oxygen by this iron heme containing oxygen-binding protein. The specific enzyme protected is nitrogenase, which is unable to reduce nitrogen gas in the presence of free oxygen.
;Coboglobin: A synthetic cobalt-based porphyrin. Coboprotein would appear colorless when oxygenated, but yellow when in veins. | 0 | Theoretical and Fundamental Chemistry |
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