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38,042,045 | https://en.wikipedia.org/wiki/44%20Ophiuchi | 44 Ophiuchi is a single star in the constellation Ophiuchus. It has the Bayer designation b Ophiuchi, while 44 Ophiuchi is the Flamsteed designation. It is visible to the naked eye as a faint, white-hued star with an apparent visual magnitude of 4.16. The distance to this object is approximately 83.2 light years based on parallax. It is drifting closer to the Earth with a heliocentric radial velocity of -37.2 km/s, and is predicted to come within around 585,000 years from now.
This is an Am star with a stellar classification of kA5hA9mF1III, indicating it has the luminosity class of a giant star with a spectrum that matches an A5 star based on the calcium K line, and an A9 star from the hydrogen and metal lines. It is around a billion years old with 1.77 times the mass of the Sun and 1.9 times the Sun's girth. The star is radiating 13 times the Sun's luminosity from its photosphere at an effective temperature of 7,559 K. It retains a moderately high rotation rate, showing a projected rotational velocity of 78 km/s.
References
F-type giants
A-type giants
Am stars
Ophiuchus
CD-24 13337
Ophiuchi, b
Ophiuchi, 44
Gliese and GJ objects
157792
085340
6486 | 44 Ophiuchi | Astronomy | 305 |
35,339,450 | https://en.wikipedia.org/wiki/Timestamping%20%28computing%29 | In computing, timestamping refers to the use of an electronic timestamp to provide a temporal order among a set of events.
Timestamping techniques are used in a variety of computing fields, from network management and computer security to concurrency control. For instance, a heartbeat network uses timestamping to monitor the nodes on a high availability computer cluster.
Timestamping computer files (updating the timestamp in the per-file metadata every time a file is modified) makes it possible to use efficient build automation tools.
See also
Trusted timestamping
Timestamp-based concurrency control
Lamport timestamp
References
Computer network security
Concurrency control
Transaction processing | Timestamping (computing) | Technology,Engineering | 134 |
56,907,265 | https://en.wikipedia.org/wiki/Clarke%27s%20equation | In combustion, Clarke's equation is a third-order nonlinear partial differential equation, first derived by John Frederick Clarke in 1978. The equation describes the thermal explosion process, including both effects of constant-volume and constant-pressure processes, as well as the effects of adiabatic and isothermal sound speeds. The equation reads as
or, alternatively
where is the non-dimensional temperature perturbation, is the specific heat ratio and is the relevant Damköhler number. The term describes the thermal explosion at constant pressure and the term describes the thermal explosion at constant volume. Similarly, the term describes the wave propagation at adiabatic sound speed and the term describes the wave propagation at isothermal sound speed. Molecular transports are neglected in the derivation.
It may appear that the parameter can be removed from the equation by the transformation , it is, however, retained here since may also appear in the initial and boundary conditions.
Example: Fast, non-diffusive ignition by deposition of a radially symmetric hot source
Suppose a radially symmetric hot source is deposited instantaneously in a reacting mixture. When the chemical time is comparable to the acoustic time, diffusion is neglected so that ignition is characterised by heat release by the chemical energy and cooling by the expansion waves. This problem is governed by the Clarke's equation with , where is the maximum initial temperature, is the temperature and is the Frank-Kamenetskii temperature ( is the gas constant and is the activation energy). Furthermore, let denote the distance from the center, measured in units of initial hot core size and be the time, measured in units of acoustic time. In this case, the initial and boundary conditions are given by
where , respectively, corresponds to the planar, cylindrical and spherical problems. Let us define a new variable
which is the increment of from its distant values. Then, at small times, the asymptotic solution is given by
As time progresses, a steady state is approached when and a thermal explosion is found to occur when , where is the Frank-Kamenetskii parameter; if , then in the planar case, in the cylindrical case and in the spherical case. For , the solution in the first approximation is given by
which shows that thermal explosion occurs at , where is the ignition time.
Generalised form
For generalised form for the reaction term, one may write
where is arbitrary function representing the reaction term.
See also
Frank-Kamenetskii theory
References
Partial differential equations
Fluid dynamics
Combustion | Clarke's equation | Chemistry,Engineering | 504 |
64,242,352 | https://en.wikipedia.org/wiki/Nitride%20fluoride | Nitride fluorides containing nitride and fluoride ions with the formula NF4-. They can be electronically equivalent to a pair of oxide ions O24-. Nitride fluorides were discovered in 1996 by Lavalle et al. They heated diammonium technetium hexafluoride to 300 °C to yield TcNF. Another preparation is to heat a fluoride compound with a nitride compound in a solid state reaction. The fluorimido ion is F-N2- and is found in a rhenium compound.
References
Nitrides
Fluorides
Mixed anion compounds | Nitride fluoride | Physics,Chemistry | 133 |
36,620,043 | https://en.wikipedia.org/wiki/Gallai%E2%80%93Hasse%E2%80%93Roy%E2%80%93Vitaver%20theorem | In graph theory, the Gallai–Hasse–Roy–Vitaver theorem is a form of duality between the colorings of the vertices of a given undirected graph and the orientations of its edges. It states that the minimum number of colors needed to properly color any graph equals one plus the length of a longest path in an orientation of chosen to minimize this path's The orientations for which the longest path has minimum length always include at least one
This theorem implies that every orientation of a graph with contains a simple directed path with this path can be constrained to begin at any vertex that can reach all other vertices of the oriented
Examples
A bipartite graph may be oriented from one side of the bipartition to the other. The longest path in this orientation has length one, with only two vertices. Conversely, if a graph is oriented without any three-vertex paths, then every vertex must either be a source (with no incoming edges) or a sink (with no outgoing edges) and the partition of the vertices into sources and sinks shows that it is
In any orientation of a cycle graph of odd length, it is not possible for the edges to alternate in orientation all around the cycle, so some two consecutive edges must form a path with three vertices. Correspondingly, the chromatic number of an odd cycle is three.
Proof
To prove that the chromatic number is greater than or equal to the minimum number of vertices in a longest path, suppose that a given graph has a coloring with colors, for some number . Then it may be acyclically oriented by numbering colors and by directing each edge from its lower-numbered endpoint to the higher-numbered endpoint. With this orientation, the numbers are strictly increasing along each directed path, so each path can include at most one vertex of each color, for a total of at most vertices per
To prove that the chromatic number is less than or equal to the minimum number of vertices in a longest path, suppose that a given graph has an orientation with at most vertices per simple directed path, for some Then the vertices of the graph may be colored with colors by choosing a maximal acyclic subgraph of the orientation, and then coloring each vertex by the length of the longest path in the chosen subgraph that ends at that vertex. Each edge within the subgraph is oriented from a vertex with a lower number to a vertex with a higher number, and is therefore properly colored. For each edge that is not in the subgraph, there must exist a directed path within the subgraph connecting the same two vertices in the opposite direction, for otherwise the edge could have been included in the chosen subgraph; therefore, the edge is oriented from a higher number to a lower number and is again properly
The proof of this theorem was used as a test case for a formalization of mathematical induction by
Category-theoretic interpretation
The theorem also has a natural interpretation in the category of directed graphs and graph homomorphisms. A homomorphism is a map from the vertices of one graph to the vertices of another that always maps edges to edges. Thus, a of an undirected may be described by a homomorphism from to the If the complete graph is given an orientation, it becomes a tournament, and the orientation can be lifted back across the homomorphism to give an orientation In particular, the coloring given by the length of the longest incoming path corresponds in this way to a homomorphism to a transitive tournament (an acyclically oriented complete graph), and every coloring can be described by a homomorphism to a transitive tournament in this
Considering homomorphisms in the other direction, instead of a directed has at most vertices in its longest path if and only if there is no homomorphism from the path graph
Thus, the Gallai–Hasse–Roy–Vitaver theorem can be equivalently stated as follows:For every directed there is a homomorphism from to the transitive tournament if and only if there is no homomorphism from the path In the case that is acyclic, this can also be seen as a form of Mirsky's theorem that the longest chain in a partially ordered set equals the minimum number of antichains into which the set may be This statement can be generalized from paths to other directed graphs: for every there is a dual directed such that, for every directed there is a homomorphism if and only if there is not a homomorphism to
History and related results
The Gallai–Hasse–Roy–Vitaver theorem has been repeatedly It is named after separate publications by and Roy credits the statement of the theorem to a conjecture in a 1958 graph theory textbook by It is a generalization of a much older theorem of László Rédei from 1934, that every tournament (an oriented complete graph) contains a directed Hamiltonian path. Rédei's theorem follows immediately from the Gallai–Hasse–Roy–Vitaver theorem applied to an undirected complete graph.
Instead of orienting a graph to minimize the length of its longest path, it is also natural to maximize the length of the shortest path, for a strong orientation (one in which every pair of vertices has a shortest path). Having a strong orientation requires that the given undirected graph be a bridgeless graph. For these graphs, it is always possible to find a strong orientation in which, for some pair of vertices, the shortest path length equals the length of the longest path in the given undirected
References
Graph coloring
Theorems in graph theory
Duality theories | Gallai–Hasse–Roy–Vitaver theorem | Mathematics | 1,121 |
1,996,117 | https://en.wikipedia.org/wiki/Thermalisation | In physics, thermalisation (or thermalization) is the process of physical bodies reaching thermal equilibrium through mutual interaction. In general, the natural tendency of a system is towards a state of equipartition of energy and uniform temperature that maximizes the system's entropy. Thermalisation, thermal equilibrium, and temperature are therefore important fundamental concepts within statistical physics, statistical mechanics, and thermodynamics; all of which are a basis for many other specific fields of scientific understanding and engineering application.
Examples of thermalisation include:
the achievement of equilibrium in a plasma.
the process undergone by high-energy neutrons as they lose energy by collision with a moderator.
the process of heat or phonon emission by charge carriers in a solar cell, after a photon that exceeds the semiconductor band gap energy is absorbed.
The hypothesis, foundational to most introductory textbooks treating quantum statistical mechanics, assumes that systems go to thermal equilibrium (thermalisation). The process of thermalisation erases local memory of the initial conditions. The eigenstate thermalisation hypothesis is a hypothesis about when quantum states will undergo thermalisation and why.
Not all quantum states undergo thermalisation. Some states have been discovered which do not (see below), and their reasons for not reaching thermal equilibrium are unclear .
Theoretical description
The process of equilibration can be described using the H-theorem or the relaxation theorem, see also entropy production.
Systems resisting thermalisation
Classical systems
Broadly-speaking, classical systems with non-chaotic behavior will not thermalise. Systems with many interacting constituents are generally expected to be chaotic, but this assumption sometimes fails. A notable counter example is the Fermi–Pasta–Ulam–Tsingou problem, which displays unexpected recurrence and will only thermalise over very long time scales. Non-chaotic systems which are pertubed by weak non-linearities will not thermalise for a set of initial conditions, with non-zero volume in the phase space, as stated by the KAM theorem, although the size of this set decreases exponentially with the number of degrees of freedom. Many-body integrable systems, which have an extensive number of conserved quantities, will not thermalise in the usual sense, but will equilibrate according to a generalized Gibbs ensemble.
Quantum systems
Some such phenomena resisting the tendency to thermalize include (see, e.g., a quantum scar):
Conventional quantum scars, which refer to eigenstates with enhanced probability density along unstable periodic orbits much higher than one would intuitively predict from classical mechanics.
Perturbation-induced quantum scarring: despite the similarity in appearance to conventional scarring, these scars have a novel underlying mechanism stemming from the combined effect of nearly-degenerate states and spatially localized perturbations, and they can be employed to propagate quantum wave packets in a disordered quantum dot with high fidelity.
Many-body quantum scars.
Many-body localisation (MBL), quantum many-body systems retaining memory of their initial condition in local observables for arbitrary amounts of time.
Other systems that resist thermalisation and are better understood are quantum integrable systems and systems with dynamical symmetries.
References
Thermodynamics | Thermalisation | Physics,Chemistry,Mathematics | 657 |
31,921,849 | https://en.wikipedia.org/wiki/Strange%E2%80%93Rahman%E2%80%93Smith%20equation | The Strange–Rahman–Smith equation is used in the cryoporometry method of measuring porosity.
NMR cryoporometry is a recent technique for measuring total porosity and pore size distributions. NMRC is based on two equations: the Gibbs–Thomson equation, which maps the melting point depression to pore size, and the Strange–Rahman–Smith equation, which maps the melted signal amplitude at a particular temperature to pore volume.
Equation
If the pores of the porous material are filled with a liquid, then the incremental volume of the pores with pore diameter between and may be obtained from the increase in melted liquid volume for an increase of temperature between and by:
Where: is the Gibbs–Thomson coefficient for the liquid in the pores.
References
Equations of physics | Strange–Rahman–Smith equation | Physics,Mathematics | 164 |
866,695 | https://en.wikipedia.org/wiki/Flora%20%28publication%29 | A Flora is a book or other work which describes the plant species occurring in an area or time period, often with the aim of allowing identification. The term is usually capitalized to distinguish it from the use of "flora" to mean the plants rather than their descriptions. Some classic and modern Floras are listed below.
Traditionally Floras are books, but some are now published on CD-ROM or websites. The area that a Flora covers can be either geographically or politically defined. Floras usually require some specialist botanical knowledge to use with any effectiveness.
A Flora often contains diagnostic keys. Often these are dichotomous keys, which require the user to repeatedly examine a plant, and decide which one of two alternatives given in the Flora best applies to the plant.
Floras produced at a local or regional level rarely contain identification keys. Instead they aim to impart more detailed understanding of the local status and distribution of that area's plants. Maps showing species distribution may be included, and nowadays are computer-generated from biological databases. Specific reference may be made to new arrivals and historic records in order to impart understanding of the changes in an area's vegetation over time.
Classic Floras
Europe
Sylva Hercynia, Johannes Thal. Germany 1588
Hortus Lusatiae, Johannes Franke. Germany 1594
Stirpium et fossilium Silesiae Catalogus, Caspar Schwenckfeldt. Germany 1600
Flora Jenensis, Heinrich Bernhard Rupp Germany, 1718.
Flora Suecica, Carl Linnaeus. 1745.
Flora Londinensis, William Curtis. England 1777–1798
Deutschlands_Flora_in_Abbildungen, Johann Georg Sturm. Germany 1796
Flora Graeca, John Sibthorp. (England) 1806–1840
Flora Danica, Simon Paulli. Denmark, 1847.
Flora von Deutschland, Österreich und der Schweiz, Otto Wilhelm Thomé. Germany 1886
Atlas des plantes de France, Amédée_Masclef. France 1891
Bilder ur Nordens Flora, Carl Axel Magnus Lindman. Sweden 1901-1905
India
Hortus indicus malabaricus, Hendrik van Rheede 1683–1703
Indonesia
Flora Javae, Carl Ludwig Blume and Joanne Baptista Fischer. 1828.
North America
Flora americae septentrionalis; or A Systematic Arrangement and Description of The Plants of North America, Frederick Pursh. (London) 1814.
Modern Floras
Americas
Caribbean
Britton, N. L., and Percy Wilson. Scientific Survey of Porto Rico and the Virgin Islands — Volume V, Part 1: Botany of Porto Rico and the Virgin Islands: Pandanales to Thymeleales. New York: New York Academy of Sciences, 1924.
Central & South America
Flora Brasiliensis
Flora of São Paulo in Brazil
Flora of Chile
Manual de Plantas de Costa Rica
Flora of Ecuador
Flora of Guatemala
Flora de Nicaragua
Flora of Peru
Flora of the Guianas
Flora of Panama
Flora del Paraguay
Flora of Suriname
Flora Mesoamericana (1994-ongoing) Introduction
Flora of the Venezuelan Guayana
Flora Neotropica (1968-ongoing) Organising committee website .
North America
Flora of North America
Kearney, Thomas H. Arizona Flora. University of California Press, 1940.
Hickman, James C., editor. The Jepson Manual: Higher Plants of California. University of California Press, 1993.
Hultén, Eric. Flora of Alaska and Neighboring Territories: A Manual of the Vascular Plants. Stanford University Press, 1968.
Radford, Albert E. Manual of the Vascular Flora of the Carolinas. University of North Carolina Press, 1968.
Wilhelm, G. and L. Rericha. Flora of the Chicago Region: A Floristic and Ecological Synthesis. Indiana Academy of Science, 2017.
Hitchcock, C. Leo, and Arthur Cronquist. Flora of the Pacific Northwest. University of Washington Press, 1973, 2018 (2nd edition). ; it is a compressed version of Hitchcock and Cronquist, Vascular Plants of the Pacific Northwest, University of Washington Press, 1955-1969 (5 volumes)
Cronquist, Arthur, Noel H. Holmgren, Patricia K. Holmgren, James L. Reveal and Rupert C. Barneby. Intermountain flora; vascular plants of the Intermountain West, U.S.A., New York Botanical Garden, 1972–2017 (9 volumes)
Chadde, Steve W.. A Great Lakes Wetland Flora. 2nd ed. Pocketflora Press, 2002.
Strausbaugh, P. D. and E. L. Core. Flora of West Virginia. 2nd ed. Seneca Books Inc., 1964.
Rhoads, A. F. and T. A Block. The Plants of Pennsylvania. University of Pennsylvania Press, 2000.
Britton, N. L. and Hon. A. Brown. An Illustrated Flora of the Northern United States and Canada. In three volumes. Dover Publications, 1913, 1970.
Stone, W. The Plants of Southern New Jersey. Annual Report of the State Museum of New Jersey, 1910.
Asia
China and Japan
Flora of China
Flora of China in eFloras
Flora of Japan
Southeast Asia
Flora of Thailand Flora of Thailand
Florae Siamensis Enumeratio
Flora Malesiana (1984-ongoing) About Flora Malesiana .
Flora of the Malay Peninsula
Flore du Cambodge, du Laos et du Viêtnam
Indian region and Sri Lanka
Flora of Bhutan
Flora of the Presidency of Madras by J.S. Gamble (1915–36)
Flora of Nepal
Bengal Plants by D. Prain (1903)
Flora of the upper Gangetic plains by J. F. Duthie (1903–29)
Botany of Bihar and Orissa by H.H. Haines (1921–25)
Flora of British India (1872–1897) by Sir J.D. Hooker
Middle East and western Asia
Flora of Turkey
Flora Iranica
Flora Palaestina:
M. Zohary (1966). Flora Palaestina part 1.
M. Zohary (1972). Flora Palaestina part 2.
N. Feinbrun (1978). Flora Palaestina part 3.
N. Feinbrun (1986). Flora Palaestina part 4.
A. Danin, (2004). Distribution Atlas of Plants in the Flora Palaestina Area (Flora Palaestina part 5).
Online updates: https://web.archive.org/web/20070828033350/http://flora.huji.ac.il/browse.asp?lang=en&action=showfile&fileid=14005
Australasia
Flora of Australia
Flora of New Zealand series:
Allan, H.H. 1961, reprinted 1982. Flora of New Zealand. Volume I: Indigenous Tracheophyta - Psilopsida, Lycopsida, Filicopsida, Gymnospermae, Dicotyledons. .
Moore, L.B.; Edgar, E. 1970, reprinted 1976. Flora of New Zealand. Volume II: Indigenous Tracheophyta - Monocotyledons except Graminae. .
Healy, A.J.; Edgar, E. 1980. Flora of New Zealand Volume III. Adventive Cyperaceous, Petalous & Spathaceous Monocotyledons. .
Webb, C.J.; Sykes, W.R.; Garnock-Jones, P.J. 1988. Flora of New Zealand Volume IV: Naturalised Pteridophytes, Gymnosperms, Dicotyledons. .
Edgar, E.; Connor, H.E. 2000. Flora of New Zealand Volume V: Grasses. .
Volumes I-V: First electronic edition, Landcare Research, June 2004. Transcribed by A.D. Wilton and I.M.L. Andres.
Galloway, D.J. 1985. Flora of New Zealand: Lichens. .
Croasdale, H.; Flint, E.A. 1986. Flora of New Zealand: Desmids. Volume I. .
Croasdale, H.; Flint, E.A. 1988. Flora of New Zealand: Desmids. Volume II. .
Croasdale, H.; Flint, E.A.; Racine, M.M. 1994. Flora of New Zealand: Desmids. Volume III. .
Sykes, W.R.; West, C.J.; Beever, J.E.; Fife, A.J. 2000. Kermadec Islands Flora - Special Edition. .
Pacific Islands
Flora Vitiensis Nova, a New Flora of Fiji
Manual of the Flowering Plants of Hawai‘i, Warren L. Wagner and Derral R. Herbst (1991) + suppl.
Flore de la Nouvelle-Calédonie (New Caledonia
Flore de la Polynésie Française (J. Florence, vol. 1 & 2, 1997 & 2004)
Europe
British Isles
Bowen, Humphry. The Flora of Berkshire. Oxford: Holywell Press, 1968. .
Morton, Osbourne. Marine Algae of Northern Ireland. Belfast: Ulster Museum, 1994.
Stace, Clive Anthony, and Hilli Thompson (illustrator). A New Flora of the British Isles. 2nd ed. Cambridge University Press, 1997. .
Beesley, S. and J. Wilde. Urban Flora of Belfast. Belfast: Institute of Irish Studies, Queen's University of Belfast, 1997.
Killick, John, Roy Perry and Stan Woodell. Flora of Oxfordshire. Pisces Publications, 1998. .
Bowen, Humphry. The Flora of Dorset. Pisces Publications, 2000. .
Milliken, William and Sam Bridgewater. Flora Celtica – Plants and people in Celtic Europe. Birlinn, 2004. . Paperback edition, 2013. .
Rest of Europe
Flora Europaea at the site of The Royal Botanical Gardens of Edinburgh Flora Europaea
Flora of Europe
Flora Gallica, published by Société Botanique de France
Flora iberica
Flora of Acores
Flora Danica
Flora of Romania
(Norwegian flora)
Africa and Madagascar
Flore du Gabon
Flore du Cameroun
Flora of Tropical Africa
Flora of Tropical East Africa
Flora of West Tropical Africa
Flore de la Côte d'Ivoire
Flora Capensis
Flora Zambesiaca
Flora of South Africa
Flore du Rwanda
Flore de Madagascar et des Comores
Flore pratique du Maroc
References
See also
List of electronic floras | Flora (publication) | Biology | 2,161 |
18,048,054 | https://en.wikipedia.org/wiki/Hypograph%20%28mathematics%29 | In mathematics, the hypograph or subgraph of a function is the set of points lying on or below its graph.
A related definition is that of such a function's epigraph, which is the set of points on or above the function's graph.
The domain (rather than the codomain) of the function is not particularly important for this definition; it can be an arbitrary set instead of .
Definition
The definition of the hypograph was inspired by that of the graph of a function, where the of is defined to be the set
The or of a function valued in the extended real numbers is the set
Similarly, the set of points on or above the function is its epigraph.
The is the hypograph with the graph removed:
Despite the fact that might take one (or both) of as a value (in which case its graph would be a subset of ), the hypograph of is nevertheless defined to be a subset of rather than of
Properties
The hypograph of a function is empty if and only if is identically equal to negative infinity.
A function is concave if and only if its hypograph is a convex set. The hypograph of a real affine function is a halfspace in
A function is upper semicontinuous if and only if its hypograph is closed.
See also
Citations
References
Mathematical analysis
Convex analysis | Hypograph (mathematics) | Mathematics | 291 |
5,292,574 | https://en.wikipedia.org/wiki/Lithium%20molybdate | Lithium molybdate (Li2MoO4) is a chemical compound. It is mainly used as an inhibitor in some types of industrial air conditioning.
Uses
Lithium molybdate is used as corrosion inhibitor in LiBr (Lithium bromide) absorption chiller for industrial central air conditioning. It is manufactured and shipped as either a colorless, transparent fluid or a white crystal powder. In either state it not classified as a hazardous material.
Li2MoO4 crystals have been found applicable for cryogenic phonon-scintillation detectors, which are used to investigate some rare nuclear processes. The use of Li2MoO4 ceramics for antennas has been studied due to their low loss dielectric properties and the possibility to fabricate them by a room-temperature densification method instead of conventional sintering.
Li2MoO4 (LMO) have also been used with hollow glass microspheres (HGMS) to make low permittivity composite which has been used to make lenses for lens antennas.
References
Molybdates
Lithium compounds
Phosphors and scintillators
Corrosion inhibitors | Lithium molybdate | Chemistry | 229 |
78,171,013 | https://en.wikipedia.org/wiki/Pseudonajatoxin%20b | Pseudonajatoxin b, or Pt-b, is a highly potent and lethal long-chain α-neurotoxin found in the venom of the eastern brown snake (Pseudonaja textilis). While the pharmacodynamics of pseudonajatoxin b are currently undocumented, α-neurotoxins are known to cause neuromuscular paralysis by blocking cholinergic neurotransmission.
Source
Pseudonajatoxin b is present in the venom of the highly lethal eastern brown snake, Pseudonaja textilis, which is the leading cause of snakebites in Australia. The concentration of pseudonajatoxin b in venom of South Australian specimens is up to a hundred times higher than in those from Queensland.
Chemistry
Structure and homology
Pseudonajatoxin b is composed of a single polypeptide chain of 71 amino acids and features five disulphide bridges. It exhibits 61-73% sequence homology with other long neurotoxins. Distinctive characteristics of pseudonajatoxin b include a high occurrence of proline residues, particularly at positions 49 and 54, where valines are usually present. Moreover, it contains an additional amino acid in the loop between Cys-46 and Cys-58.
Protein family
Pseudonajatoxin b is a type of three-finger toxin, which are characterized by a structure of three loops that emerge from a hydrophobic core. Specifically, it falls within the long-chain subfamily of the α-neurotoxin group.
Target and mechanism of action
Although the pharmacodynamics of pseudonajatoxin b have not been documented, α-neurotoxins generally exhibit some common traits.
Long-chain α-neurotoxins have been shown to bind with high affinity to both muscular and neuronal nicotinic acetylcholine receptors. These receptors serve as the primary mediator of muscle contraction in response to nerve impulses. Additionally, they are present in the central nervous system, where they play an important role in autonomic processes, including the regulation of heart rate and respiration.
By acting as competitive antagonists to acetylcholine, α-neurotoxins block acetylcholine from binding and subsequently prevent the activation of ion channels. This disruption in neurotransmission effectively leads to neuromuscular paralysis. Importantly, since the activation of nicotinic acetylcholine receptors requires the binding of two acetylcholine molecules, the blockage of just one binding site by an α-neurotoxin is sufficient to prevent channel opening. Furthermore, long-chain α-neurotoxins typically bind tightly and irreversibly to nicotinic receptors, resulting in permanent channel inactivation once they are bound.
Toxicity and treatment
Pseudonajatoxin b is a highly potent toxin, with a median lethal dose (LD50) of 15 pg/kg in mice. Although the specific lethal mechanisms of pseudonajatoxin b remain unknown, it is well established that both α-neurotoxins and the venom of P. textilis induce paralysis, leading to death through asphyxiation.
Currently, no treatment specific for pseudonajatoxin b has been documented. However, envenomation from Pseudonaja textilis can be treated with snake antivenom made from antibodies, specifically horse immuno-globulins. Despite this, studies have shown that brown snake antivenom has low efficacy against Pseudonaja textilis venom.
References
Snake toxins
Peptides
Neurotoxins | Pseudonajatoxin b | Chemistry | 751 |
9,703,509 | https://en.wikipedia.org/wiki/P25%20ISSI | The Project 25 Inter RF Subsystem Interface (P25 ISSI) is a non-proprietary interface that enables RF subsystems (RFSSs) built by different manufacturers to be connected together into wide area networks so that users on different networks can talk with each other. The wide area network connections using the ISSI provide an extended coverage area for subscriber units (SUs) that are roaming. The extended coverage area is important for public safety first responders that provide assistance in other jurisdictions during an emergency.
The ISSI supports the messaging, and procedures necessary to enable RFSSs to track and locate SUs, set up and teardown calls and transfer voice information to the SUs. The ISSI uses SIP and RTP protocols (standardized protocols) to provide the messaging between RFSSs.
The modern Land Mobile Radio (LMR) system includes many features in addition to voice communication. Many features will not work across systems connected using the ISSI. Whether a particular feature will work is determined by the systems and the particular ISSI implementation.
Overview of P25 ISSI Documentation Suite
The documentation suite which defines Scope One of the P25 ISSI consists of five standards.
ISSI Messages and Procedures for Voice Services
ISSI Measurement Methods for Voice Services
ISSI Performance Recommendations for Voice Services
ISSI Conformance Testing for Voice Services
ISSI Interoperability Testing for Voice Operations in Trunked Systems
A brief overview of each of these standards is provided in the subsections that follow.
ISSI Messages and Procedures for Voice Services
Scope One of the ISSI Messages and Procedures for Voice Services specifies the functional services of mobility management, call control and transmission control to provide trunked voice services for SU-to-SU and Group PTT calls involving multiple RFSSs.
Mobility management uses the SIP protocol and describes the messages and procedures necessary for RFSSs to perform registration, and affiliation across the ISSI for roaming SUs.
Call control also uses the SIP protocol and describes the messages and procedures necessary for RFSSs to set up and tear down a call, and manage RTP resources.
Transmission control uses the RTP protocol and describes the messages and procedures necessary for RFSSs to convey voice information, and manage voice call requests.
The functional service responsibilities of an RFSS in a call are dependent upon the type of call and also on the role of the RFSS in a call.
The specifications developed in the ISSI Messages and Procedures for Voice Services standard provide the fundamental starting point for the remaining standards in the ISSI suite of standards.
ISSI Measurement Methods for Voice Services
The ISSI Measurement Methods for Voice Services is based on the functional services and protocols defined in the ISSI Messages and Procedures for Voice Services standard.
Scope One of the ISSI Measurement Methods for Voice Services provides detailed measurement procedures to measure the ISSI Voice Service (IVS) Call Set-Up Delay (CSD) and IVS Message Transfer Delay (MTD) performance for SU-to-SU and Group calls.
IVS-CSD and IVS-MTD performance parameters are used to evaluate the delay associated with successful packet transfers across RFSSs and across the IP backbone connections that link adjacent RFSSs.
ISSI Performance Recommendations for Voice Services
The ISSI Performance Recommendations for Voice Services is a companion standard to the ISSI Measurement Methods for Voice Services standard. Scope One of the ISSI Performance Recommendations for Voice Services provides agreed upon (by manufacturers and end users) average and maximum values for the IVS-CSD and IVS-MTD performance parameters described in the ISSI Measurement Methods for Voice Services standard.
ISSI Conformance Testing for Voice Services
The ISSI Conformance testing for Voice Services defines a set of procedures to test the conformance between two RF Sub-systems using an IP backbone network. The procedures define reference-signaling sequences for SU-to-SU and Group call scenarios.
ISSI Interoperability Testing for Voice Operations in Trunked Systems
The ISSI Interoperability testing for Voice Operations in Trunked Systems defines procedures to test the interoperability of SUs, and RFSSs from different manufacturers while performing trunked voice operations in configurations that use the ISSI.
The trunked voice operations include registration of subscriber units, affiliation of subscriber units to the Subscriber Group Home, initiation of an SU-to-SU call, and initiation of a Group call.
See also
P25 Suite of Standards Overview
External links
https://web.archive.org/web/20111106042758/http://www.tiaonline.org/standards/ Telecommunications Industry Association, Standards Development Overview
https://web.archive.org/web/20120212013100/http://www.apcointl.org/frequency/project25/information.html APCO Project 25 Standards for Public Safety Digital Radio, Project 25 Homepage
http://www.p25.com/images/pdf/CodanTG-001-4-0-0P25TrainingGuide.pdf Daniels' P25 Radio System Training Guide
http://www-x.antd.nist.gov/proj25/ Department of Commerce ISSI Test and Evaluation Tools (DIETS) project at NIST.
http://valid8.com/solutions/p25-issi-cssi-conformance P25 Compliance Test Tools for ISSI & CSSI
Networking hardware
Networking standards | P25 ISSI | Technology,Engineering | 1,114 |
57,088,590 | https://en.wikipedia.org/wiki/American%20Union%20of%20Decorative%20Artists%20and%20Craftsmen | The American Union of Decorative Artists and Craftsmen (AUDAC) was an American society of designers and decorative artists that was active from 1928 until the early 1930s. The group aimed to bring modern principles of design, such as those promoted in Europe by the Wiener Werkstätte and the Bauhaus, to decorative arts in the United States.
History
The modernist furniture designer Paul T. Frankl immigrated from Vienna to New York in 1914. He worked to establish Europe's flourishing principles of contemporary design in the United States by writing books such as New Dimensions: The Decorative Arts of Today and by establishing a collective of fellow designers called the American Union of Decorative Artists and Craftsmen (AUDAC) in 1928. Early members included designers who exhibited at the American Designers' Gallery, which showed interiors and furnishings designed by contemporary New York designers, such as Donald Deskey and Ilonka Karasz.
AUDAC was modeled on European decorative arts societies such as the Société des Artistes Décorateurs in France. They published books on the new American design such as Modern American Design and Annual of American Design and put together influential exhibitions of their members' work, including one at the Brooklyn Museum in 1931 which showed work by Russel Wright, Ruth Reeves, and Rockwell Kent among many others.
The group was well known by the early 1930s when Radio City Music Hall commissioned Donald Deskey and other AUDAC members to design the fabrics, textiles, and furnishings for the interior. Many members (see list below) went on to long careers and well-known places in the history of twentieth-century design. However, due to the 1930s economic depression, the formal association was defunct by 1934.
Mission
AUDAC placed an ad in a supplement for the magazine Creative Art in March 1930 which listed contact information for many of its members and described the mission of the American Union of Decorative Artists and Craftsmen thus:
Members
AUDAC was founded by Paul T. Frankl in 1928. Their members included:
M. F. Agha
Richard F. Bach
Lucian Bernhard
M. D. C. Crawford
Donald Deskey
Alice Donaldson
Hugh Ferriss
Norman Bel Geddes
C. Adolph Glassgold
Wolfgang and Pola Hoffmann
Ellen M. Kern
Frederick John Kiesler
Peter Larsen
Robert Leonard
Marguerita Mergentime
Lewis Mumford
Ruth Reeves
Winold Reiss
Robert Schey
Lee Simonson
Edward Steichen
Edward Buk Ulreich
Kem Weber
Frank Lloyd Wright
Russel Wright
Paul M. Zimmermann
References
Sources
"American Union of Decorative Artist and Craftsmen" in Byars, Mel (2004). The Design Encyclopedia, New York: The Museum of Modern Art. |
External links
Modernism
Decorative arts
Graphic design
Industrial design
Textile design
Interior design | American Union of Decorative Artists and Craftsmen | Engineering | 546 |
59,609,094 | https://en.wikipedia.org/wiki/Lewis%27%20law | Lewis' law gives a relationship between the size and the shape of epithelial cells. It states that the average apical area of an epithelial cell is linearly related to its neighbor number . It is a phenomenological law that was first described in the cucumber epidermis by the morphologist Frederic Thomas Lewis in 1928. The simplest version of Lewis' law can be expressed as , which reads: The average apical area of a cell with neighbors (divided by the average apical area of all cells) is proportional to its shape. While neighbor number distributions change throughout organogenesis, the average neighbor number of epithelial cells is , which can be traced back to Euler's formula for polygons.
Discovery
Frederic Thomas Lewis noticed that epidermal cells display a patterning similar to froths, which led him to quantify and analyze the sizes and shapes of epidermal cells.
Confirmation and mechanism
A variety of empirical studies in different epithelial tissues have confirmed Lewis' law.
It has been suggested that the emergence of Lewis' law on the apical surface of epithelia is a result of the concurrence of
the tendency of cells to minimize intercellular contact surface energy, and
the distribution of apical cell areas (as a result of cellular processes such as cell division).
According to this theory, the observed tissue-specific polygon distributions and Lewis' law arise as a compromise in order to maintain tissue integrity.
Importance
In order to understand morphogenetic events, i.e. the growth and shaping of tissues and organs, it is necessary to analyze the packing of cells into tissues. In that context, an analysis of patterning processes can help to identify the underlying mechanisms that drive morphogenesis.
References
Epithelium
Biological theorems | Lewis' law | Biology | 366 |
3,043,713 | https://en.wikipedia.org/wiki/Leaf%20protein%20concentrate | Leaf protein concentrate (LPC) refers to the proteinaceous mass extracted from leaves. It can be a lucrative source of low-cost and sustainable protein for food as well as feed applications. Although the proteinaceous extracts from leaves have been described as early as 1773 by Rouelle, large scale extraction and production of LPC was pioneered post the World War II. In fact, many innovations and advances made with regards to LPC production occurred in parallel to the Green Revolution. In some respects, these two technologies were complimentary in that the Green Revolution sought to increase agrarian productivity through increased crop yields via fertiliser use, mechanisation and genetically modified crops, while LPC offered the means to better utilise available agrarian resources through efficient protein extraction.
Sources
Over the years, numerous sources have been experimented. Pirie and Telek described LPC production using a combination of pulping and heat coagulation. Leaves are typically sourced from shrubs or agricultural wastes given their ease of access and relative abundance. Trees are generally considered a poor source of leaf mass for the production of LPC given restrictions on the ease of access. Fallen leaves/leaf litter have negligible protein-content and are of no extractive value.
Plants belonging to the Fabaceae family such as clover, peas and legumes have also been prime candidates for LPC production. While most plants have a mean leaf protein content of 4 to 6% w/v. Fabaceae plants tend to have nearly double that value at 8 to 10% v/w, depending on the protein estimation method employed. Other non-traditional sources include agricultural wastes such as pea (Pisum sativum) pods, cauliflower (Brassica oleracea) leaves, as well as invasive plants such as gorse (Ulex europeaus), broom (Cytisus scoparius), and bracken (Pteridium aquilinum).
Methods of production
LPC production processes are two-staged, with the first focusing on the expression of leaf juice or production of a leaf extract, and the second being the purification or protein recovery stage that recovers protein from the solution.
The most commonly employed method of leaf protein extraction is pulping/juicing. Other assisted extraction methods have also been reported such as alkali treatment, pressurised extraction, and enzyme treatment Each method comes with its own advantages although pulping produces the most “native” protein composition and does not require significant investment in complex machinery.
Alkali extraction has been employed with some success although it significantly affects lysine and threonine residues in the protein. Pressurised extraction have limited success. Enzyme treatment is another well reported method which targets the plant cell wall to aid the release of bound proteins. However, enzymes are generally more expensive compared to physical or chemical methods of protein extraction.
Recovering the protein from the extract however is most critical to the nutritive value of the LPC. Commonly reported methods were heat coagulation, acid precipitation, ultrafiltration, solvent precipitation and chromatography.
Heat coagulation is the easiest and the oldest method of protein recovery, albeit the least preferred as most of the nutritive value of the LPC is lost. Acid precipitation is the most commonly employed method of protein recovery although it results in the loss of methionine and tryptophan in the LPC. Ultrafiltration is the most hardware demanding option for protein recovery although it serves more as a protein concentration step rather than complete recovery. Chromatographic methods may be used in tandem with ultrafiltration to help increase solute mass and subsequent recovery. Solvent precipitation is not often reported although it produces the highest protein recovery among other methods and preserves the nutritional integrity of the LPC. The extraction and purification methods are largely inter-compatible and may be employed depending on local facilities. Interestingly, the purity of the final LPC was influenced by the protein content in the initial leaf mass rather than the purification method employed. Furthermore, the amino acid composition of the LPC was dependent on the extraction method employed.
In laboratory conditions, protein fractions of 96% purity could be produced with a recovery of 56% w/w and an overall yield of 5.5%. Telek on the other hand experimented with numerous tropical plants at a large scale using a combination of pulping and heat coagulation. Yields were around 3% with protein recoveries <50%.
Depending on the purity of the recovered protein, they are either called leaf protein extract (<60% w/w), leaf protein concentrate (>60% w/w), or leaf protein isolate (>90% w/w), although publications use these terms interchangeably.
Composition
Whole leaf protein concentrate is a dark green substance with a texture similar to cheese. Approximately 60% of this is water, while the remaining dry matter is 9-11% nitrogen, 20-25% lipid, 5-10% starch and a variable amount of ash. It is a mixture of many individual proteins. Its flavour has been compared to spinach or tea.
Because the colour and taste may make it unpalatable for humans, LPC can instead be separated into green and white fractions. The green fraction has proteins mainly originating from the chloroplasts, while the white fraction has proteins mainly originating from the cytoplasm.
Applications
LPC was first suggested as a human food in the early 20th century, but it has not achieved much success, despite early promise. Norman Pirie, the Copley Medal winner from the UK, studied LPC and promoted its use for human consumption. He and his team developed machines for extraction of LPC, including low-maintenance "village units" intended for poor rural communities. These were installed in places such as villages in south India. The non profit organization, Leaf for Life, maintains a list of human edible leaves and provides recommendations for the top choices of plants.
There has recently been an interest in using LPCs as an alternative food (or resilient food) during times of catastrophe or food shortages. Such resilient food LPCs would be derived from widely geographically dispersed tree leaves from forests or agricultural waste.
LPC have been evaluated for infant weaning foods.
The increasing reliance on feedlot based animal rearing to satisfy human appetites for meat has increased demand for cheaper vegetable protein sources. This has recently led to renewed interest in LPC to reduce the use of human-edible vegetable protein sources in animal feed.
Leaf protein has had successful trials as a substitute for soy feed for chickens and pigs.
LPC from alfalfa can be included in feed for tilapia as a partial replacement for fish meal.
Amino acid composition
The amino acid composition of the LPC:
Dietary issues
Leaf protein is a good source of amino acids, with methionine being a limiting factor. It is nutritionally better than seed proteins and comparable to animal proteins (other than those in egg and milk).
In terms of digestibility, whole LPC has digestibility in the range 65–90%. The green fraction has a much lower digestibility that may be <50%, while the white fraction has digestibility >90%.
The challenges that have to be overcome using lucerne and cassava, two high density monoculture crops, include the high fiber content and other antinutritional factors, such as phytate, cyanide, and tannins.
Lablab beans, Moringa oleifera, tree collards and bush clover may also be used. Flavors of different species vary greatly.
For testing new leaf species for use as LPCs a non-targeted approach has been developed that uses an ultra-high-resolution hybrid ion trap orbitrap mass spectrometer with electrospray ionization coupled to an ultra-high pressure two-dimensional liquid chromatograph system. An open source software toolchain was also developed for automated non‐targeted screening of toxic compounds for LPCs. The process uses three tools: 1) mass spectrometry analysis with MZmine 2, 2) formula assignment with MFAssignR, and 3) data filtering with ToxAssign. Studies have looked at the potential for deciduous trees and coniferous tree leaves. The latter showed yields for LPC extraction from 1% to 7.5% and toxicity screenings confirm that coniferous trees may contain toxins that can be consumed in small amounts, and additional studies including measuring the quantity of each toxin are needed.
See also
Protein (nutrient)
Green Revolution
References
Bibliography
Nutrition
Meat substitutes
Vegetarianism
Leaves
Proteins
Perennial protein crops | Leaf protein concentrate | Chemistry | 1,752 |
1,814,932 | https://en.wikipedia.org/wiki/Butterfat | Butterfat or milkfat is the fatty portion of milk. Milk and cream are often sold according to the amount of butterfat they contain.
Composition
Butterfat is mainly composed of triglycerides. Each triglyceride contains three fatty acids. Butterfat triglycerides contain the following amounts of fatty acids (by mass fraction):
Butterfat contains about 3% trans fat, which is slightly less than 0.5 grams per US tablespoon. Trans fats occur naturally in meat and milk from ruminants. The predominant kind of trans fat found in milk is vaccenic fatty acid. Trans fats may be also found in some industrially produced foods, such as shortenings obtained by hydrogenation of vegetable oils. In light of recognized scientific evidence, nutritional authorities consider all trans fats equally harmful for health and recommend that their consumption be reduced to trace amounts.
However, two Canadian studies have shown that vaccenic acid could be beneficial compared to vegetable shortenings containing trans fats, or a mixture of pork lard and soy fat, by lowering total LDL and triglyceride levels. A study by the US Department of Agriculture showed that vaccenic acid raises both HDL and LDL cholesterol, whereas industrial trans fats only raise LDL with no beneficial effect on HDL.
U.S. standards
In the U.S., there are federal standards for butterfat content of dairy products. Many other countries also have standards for minimum fat levels in dairy products. Commercial products generally contain the minimum legal amount of fat with any excess being removed to make cream, a valuable commodity.
Milks
Non-fat milk, also labeled "fat-free milk" or "skim milk", contains less than 0.5% fat
Low-fat milk is 1% fat
Reduced-fat milk is 2% fat
Whole milk contains at least 3.25% fat
Cheeses
Dry curd and nonfat cottage cheese contain less than 0.5% fat
Lowfat cottage cheese contains 0.5–2% fat
Cottage cheese contains at least 4% fat
Swiss cheese contains at least 43% fat relative to the total solids
Cheddar cheese contains at least 50% fat relative to the total solids
Frozen desserts
Sherbet contains 1–2% fat
Lowfat ice cream, also called ice milk, contains no more than 2.6% fat
Ice cream contains at least 10% fat
Frozen custard, like ice cream, contains at least 10% fat, but it also must contain at least 1.4% egg yolk solids
Creams
Half and half contains 10.5–18% fat
Light cream and sour cream contain 18–30% fat
Light whipping cream (often called simply "whipping cream") contains 30–36% fat
Heavy cream contains a minimum of 36% fat
Manufacturer's cream (not federally regulated) contains 40% fat
Butter (including whipped butter) contains at least 80% fat
See also
Buttermilk
Clarified butter
List of dairy products
References
Dairy products
Food ingredients
Butter | Butterfat | Technology | 621 |
2,239,614 | https://en.wikipedia.org/wiki/Foil%20%28fluid%20mechanics%29 | A foil is a solid object with a shape such that when placed in a moving fluid at a suitable angle of attack the lift (force generated perpendicular to the fluid flow) is substantially larger than the drag (force generated parallel to the fluid flow). If the fluid is a gas, the foil is called an airfoil or aerofoil, and if the fluid is water the foil is called a hydrofoil.
Physics of foils
A foil generates lift primarily because of its shape and angle of attack. When oriented at a suitable angle, the foil deflects the oncoming fluid, resulting in a force on the foil in the direction opposite to the deflection. This force can be resolved into two components: lift and drag. This "turning" of the fluid in the vicinity of the foil creates curved streamlines which results in lower pressure on one side and higher pressure on the other. This pressure difference is accompanied by a velocity difference, via Bernoulli's principle, so for foils generating lift the resulting flowfield about the foil has a higher average velocity on one surface than on the other.
A more detailed description of the flowfield is given by the simplified Navier–Stokes equations, applicable when the fluid is incompressible. And since the effects of the compressibility of air at low speeds is negligible, these simplified equations can be used for airfoils as long as the airflow is substantially less than the speed of sound (up to about Mach 0.3). For hydrofoils at high speeds, of the order of according to Faltinsen, cavitation and ventilation – with air penetrating along the strut from the water surface to the foil – may occur. Both effects may have a substantial influence on the foil's lift.
Basic design considerations
The simplest type of foil is a flat plate. When set at an angle (the angle of attack) to the flow the plate will deflect the fluid passing over and under it, and this deflection will result in a lift force on the plate. However, while it does generate lift, it also generates a large amount of drag.
Since even a flat plate can generate lift, a significant factor in foil design is the minimization of drag. An example of this is the rudder of a boat or aircraft. When designing a rudder a key design factor is the minimization of drag in its neutral position, which is balanced with the need to produce sufficient lift with which to turn the craft at a reasonable rate.
Other types of foils, both natural and man-made, seen both in air and water, have features that delay or control the onset of lift-induced drag, flow separation, and stall (see Bird flight, Fin, Airfoil, Placoid scale, Tubercle, Vortex generator, Canard (close-coupled), Blown flap, Leading edge slot, Leading edge slats), as well as Wingtip vortices (see Winglet).
Lifted ability in air and water
The weight a foil can lift is proportional to its lift coefficient, the density of the fluid, the foil area and its speed squared. The following shows the lifting ability of a flat plate with span 10 metres and area 10 square metres moving at a speed of 10 m/s at different altitudes and water depths. It uses the lift at an altitude of 11 km as a datum to show how the lift increases with decreasing altitude (increasing air density). It also shows the influence of ground effect and then the effect of increase in density going from air to water.
height 11 km: lift 1.0 (datum for comparison)
5 m 3.4
in ground effect 4.1
water surface-planing 1,280
just submerged 1,420
depth 5 m 2,840
10 km 2,860
See also
Aircraft
Bilgeboard
Boomerang
Centerboard
Chord (aircraft)
Coanda effect
Diving plane
Drag coefficient
Flipper (anatomy)
Fluid dynamics
Formula One car
Keel (hydrodynamic)
Lift coefficient
NACA airfoil
Propeller
Sail (aerodynamics)
Skeg
Spoiler (automotive)
Surfboard fin
Wing
References
External links
Lift from Flow Turning
What is Lift?
Bernoulli and Newton
Effect of Shape on Lift
Incorrect Lift Theory
Penguin can fly
thresher shark swim towards scuba divers
Swimming with Wild Dolphins
Bird Flight II
Fluid dynamics
Aerodynamics | Foil (fluid mechanics) | Chemistry,Engineering | 886 |
8,918,557 | https://en.wikipedia.org/wiki/Ambush%20predator | Ambush predators or sit-and-wait predators are carnivorous animals that capture their prey via stealth, luring or by (typically instinctive) strategies utilizing an element of surprise. Unlike pursuit predators, who chase to capture prey using sheer speed or endurance, ambush predators avoid fatigue by staying in concealment, waiting patiently for the prey to get near, before launching a sudden overwhelming attack that quickly incapacitates and captures the prey.
The ambush is often opportunistic, and may be set by hiding in a burrow, by camouflage, by aggressive mimicry, or by the use of a trap (e.g. a web). The predator then uses a combination of senses to detect and assess the prey, and to time the strike. Nocturnal ambush predators such as cats and snakes have vertical slit pupils helping them to judge the distance to prey in dim light. Different ambush predators use a variety of means to capture their prey, from the long sticky tongues of chameleons to the expanding mouths of frogfishes.
Ambush predation is widely distributed in the animal kingdom, spanning some members of numerous groups such as the starfish, cephalopods, crustaceans, spiders, insects such as mantises, and vertebrates such as many snakes and fishes.
Strategy
Ambush predators usually remain motionless (sometimes hidden) and wait for prey to come within ambush distance before pouncing. Ambush predators are often camouflaged, and may be solitary. Pursuit predation becomes a better strategy than ambush predation when the predator is faster than the prey. Ambush predators use many intermediate strategies. For example, when a pursuit predator is faster than its prey over a short distance, but not in a long chase, then either stalking or ambush becomes necessary as part of the strategy.
Bringing the prey within range
Concealment
Ambush often relies on concealment, whether by staying out of sight or by means of camouflage.
Burrows
Ambush predators such as trapdoor spiders and Australian crab spiders on land and mantis shrimps in the sea rely on concealment, constructing and hiding in burrows. These provide effective concealment at the price of a restricted field of vision.
Trapdoor spiders excavate a burrow and seal the entrance with a web trapdoor hinged on one side with silk. The best-known is the thick, bevelled "cork" type, which neatly fits the burrow's opening. The other is the "wafer" type; it is a basic sheet of silk and earth. The door's upper side is often effectively camouflaged with local materials such as pebbles and sticks. The spider spins silk fishing lines, or trip wires, that radiate out of the burrow entrance. When the spider is using the trap to capture prey, its chelicerae (protruding mouthparts) hold the door shut on the end furthest from the hinge. Prey make the silk vibrate, and alert the spider to open the door and ambush the prey.
Camouflage
Many ambush predators make use of camouflage so that their prey can come within striking range without detecting their presence. Among insects, coloration in ambush bugs closely matches the flower heads where they wait for prey. Among fishes, the warteye stargazer buries itself nearly completely in the sand and waits for prey. The devil scorpionfish typically lies partially buried on the sea floor or on a coral head during the day, covering itself with sand and other debris to further camouflage itself. The tasselled wobbegong is a shark whose adaptations as an ambush predator include a strongly flattened and camouflaged body with a fringe that breaks up its outline. Among amphibians, the Pipa pipa's brown coloration blends in with the murky waters of the Amazon Rainforest which allows for this species to lie in wait and ambush its prey.
Aggressive mimicry
Many ambush predators actively attract their prey towards them before ambushing them. This strategy is called aggressive mimicry, using the false promise of nourishment to lure prey. The alligator snapping turtle is a well-camouflaged ambush predator. Its tongue bears a conspicuous pink extension that resembles a worm and can be wriggled around; fish that try to eat the "worm" are themselves eaten by the turtle. Similarly, some reptiles such as Elaphe rat snakes employ caudal luring (tail luring) to entice small vertebrates into striking range.
The zone-tailed hawk, which resembles the turkey vulture, flies among flocks of turkey vultures, then suddenly breaks from the formation and ambushes one of them as its prey. There is however some controversy about whether this is a true case of wolf in sheep's clothing mimicry.
Flower mantises are aggressive mimics, resembling flowers convincingly enough to attract prey that come to collect pollen and nectar. The orchid mantis actually attracts its prey, pollinator insects, more effectively than flowers do. Crab spiders, similarly, are coloured like the flowers they habitually rest on, but again, they can lure their prey even away from flowers.
Traps
Some ambush predators build traps to help capture their prey. Lacewings are a flying insect in the order Neuroptera. In some species, their larval form, known as the antlion, is an ambush predator. Eggs are laid in the earth, often in caves or under a rocky ledge. The juvenile creates a small, crater shaped trap. The antlion hides under a light cover of sand or earth. When an ant, beetle or other prey slides into the trap, the antlion grabs the prey with its powerful jaws.
Some but not all web-spinning spiders are sit-and-wait ambush predators. The sheetweb spiders (Linyphiidae) tend to stay with their webs for long periods and so resemble sit-and-wait predators, whereas the orb-weaving spiders (such as the Araneidae) tend to move frequently from one patch to another (and thus resemble active foragers).
Detection and assessment
Ambush predators must time their strike carefully. They need to detect the prey, assess it as worth attacking, and strike when it is in exactly the right place. They have evolved a variety of adaptations that facilitate this assessment. For example, pit vipers prey on small birds, choosing targets of the right size for their mouth gape: larger snakes choose larger prey. They prefer to strike prey that is both warm and moving; their pit organs between the eye and the nostril contain infrared (heat) receptors, enabling them to find and perhaps judge the size of their small, warm-blooded prey.
The deep-sea tripodfish Bathypterois grallator uses tactile and mechanosensory cues to identify food in its low-light environment. The fish faces into the current, waiting for prey to drift by.
Several species of Felidae (cats) and snakes have vertically elongated (slit) pupils, advantageous for nocturnal ambush predators as it helps them to estimate the distance to prey in dim light; diurnal and pursuit predators in contrast have round pupils.
Capturing the prey
Ambush predators often have adaptations for seizing their prey rapidly and securely. The capturing movement has to be rapid to trap the prey, given that the attack is not modifiable once launched. Zebra mantis shrimp capture agile prey such as fish primarily at night while hidden in burrows, striking very hard and fast, with a mean peak speed and mean duration of 24.98 ms.
Chameleons (family Chamaeleonidae) are highly adapted as ambush predators. They can change colour to match their surroundings and often climb through trees with a swaying motion, probably to mimic the movement of the leaves and branches they are surrounded by. All chameleons are primarily insectivores and feed by ballistically projecting their tongues, often twice the length of their bodies, to capture prey. The tongue is projected in as little as 0.07 seconds, and is launched at an acceleration of over 41 g. The power with which the tongue is launched, over 3000 W·kg−1, is more than muscle can produce, indicating that energy is stored in an elastic tissue for sudden release.
All fishes face a basic problem when trying to swallow prey: opening their mouth may pull food in, but closing it will push the food out again. Frogfishes capture their prey by suddenly opening their jaws, with a mechanism which enlarges the volume of the mouth cavity up to 12-fold and pulls the prey (crustaceans, molluscs and other whole fishes) into the mouth along with water; the jaws close without reducing the volume of the mouth cavity. The attack can be as fast as 6 milliseconds.
Taxonomic range
Ambush predation is widely distributed across the animal kingdom. It is found in many vertebrates including fishes such as the frogfishes (anglerfishes) of the sea bottom, and the pikes of freshwater; reptiles including crocodiles, snapping turtles, the mulga dragon, and many snakes such as the black mamba; mammals such as the cats; and birds such as the anhinga (darter). The strategy is found in several invertebrate phyla including arthropods such as mantises, purseweb spiders, and some crustaceans; cephalopod molluscs such as the colossal squid; and starfish such as Leptasterias tenera.
References
External links
Predation lecture University of Washington
Ethology
Predation
Articles containing video clips | Ambush predator | Biology | 1,935 |
20,250,365 | https://en.wikipedia.org/wiki/Geopolitical%20ontology | The FAO geopolitical ontology is an ontology developed by the Food and Agriculture Organization of the United Nations (FAO) to describe, manage and exchange data related to geopolitical entities such as countries, territories, regions and other similar areas.
Definitions and examples
An ontology is a kind of dictionary that describes information in a certain domain using concepts and relationships. It is often implemented using OWL (Web Ontology Language), an XML-based standard language that can be interpreted by computers.
A Concept is defined as abstract knowledge. For example, in the geopolitical ontology a non-self-governing territory and a geographical group are concepts. Concepts are explicitly implemented in the ontology with individuals and classes:
An individual is defined as an object perceived from the real world. In the geopolitical domain Ethiopia and the least developed countries group are individuals.
A class is defined as a set of individuals sharing common properties. In the geopolitical domain, Ethiopia, Republic of Korea and Italy are individuals of the class self-governing territory; and least developed countries is an individual of the class special group.
Relationships between concepts are explicitly implemented by:
Object properties between individuals of two classes. For example, has member and is in group properties, as shown in Figure 1.
Datatype properties between individuals and literals or XML datatypes. For example, the individual Afghanistan has the datatype property CodeISO3 with the value "AFG".
Restrictions in classes and/or properties. For example, the property official English name of the class self-governing territory has been restricted to have only one value, this means that a self-governing territory (or country) can only have one internationally recognized official English name.
The advantage of describing information in an ontology is that it enables to acquire domain knowledge by defining hierarchical structures of classes, adding individuals, setting object properties and datatype properties, and assigning restrictions.
FAO ontology
The geopolitical ontology provides names in seven languages (Arabic, Chinese, French, English, Spanish, Russian and Italian) and identifiers in various international coding systems (ISO2, ISO3, AGROVOC, FAOSTAT, FAOTERM, GAUL, UN, UNDP and DBPediaID codes) for territories and groups. Moreover, the FAO geopolitical ontology tracks historical changes from 1985 up until today; provides geolocation (geographical coordinates); implements relationships among countries and countries, or countries and groups, including properties such as has border with, is predecessor of, is successor of, is administered by, has members, and is in group; and disseminates country statistics including country area, land area, agricultural area, GDP or population.
The FAO geopolitical ontology provides a structured description of data sources. This includes: source name, source identifier, source creator and source's update date. Concepts are described using the Dublin Core vocabulary
In summary, the main objectives of the FAO geopolitical ontology are:
To provide the most updated geopolitical information (names, codes, relationships, statistics)
To track historical changes in geopolitical information
To improve information management and facilitate standardized data sharing of geopolitical information
To demonstrate the benefits of the geopolitical ontology to improve interoperability of corporate information systems
It is possible to download the FAO geopolitical ontology in OWL and RDF formats. Documentation is available in the FAO Country Profiles Geopolitical information web page.
Features of the FAO ontology
The geopolitical ontology contains :
Area types:
Territories: self-governing, non-self-governing, disputed, other.
Groups: organizations, geographic, economic and special groups.
Names (official, short and names for lists) in Arabic, Chinese, English, French, Spanish, Russian and Italian.
International codes: UN code – M49, ISO 3166 Alpha-2 and Alpha-3, UNDP code, GAUL code, FAOSTAT, AGROVOC FAOTERM and DBPediaID.
Coordinates: maximum latitude, minimum latitude, maximum longitude, minimum longitude.
Basic country statistics: country area, land area, agricultural area, GDP, population.
Currency names and codes.
Adjectives of nationality.
Relations:
Groups membership.
Neighbours (land border), administration of non-self-governing.
Historic changes: predecessor, successor, valid since, valid until.
Implementation into OWL
The FAO geopolitical ontology is implemented in OWL. It consists of classes, properties, individuals and restrictions. Table 1 shows all classes, gives a brief description and lists some individuals that belong to each class. Note that the current version of the geopolitical ontology does not provide individuals of the class "disputed" territories. Table 2 and Table 3 illustrate datatype properties and object properties.
Geopolitical ontology in Linked Open Data
The FAO Geopolitical ontology is embracing the W3C Linked Open Data (LOD) initiative and released its RDF version of the geopolitical ontology in March 2011.
The term 'Linked Open Data' refers to a set of best practices for publishing and connecting structured data on the Web. The key technologies that support Linked Data are URIs, HTTP and RDF.
The RDF version of the geopolitical ontology is compliant with all Linked data principles to be included in the Linked Open Data cloud, as explained in the following.
Resolvable http:// URIs
Every resource in the OWL format of the FAO Geopolitical Ontology has a unique URI. Dereferenciation was implemented to allow for three different URIs to be assigned to each resource as follows:
URI identifying the non-information resource
Information resource with an RDF/XML representation
Information resource with an HTML representation
In addition the current URIs used for OWL format needed to be kept to allow for backwards compatibility for other systems that are using them. Therefore, the new URIs for the FAO Geopolitical Ontology in LOD were carefully created, using “Cool URIs for Semantic Web” and considering other good practices for URIs, such as DBpedia URIs.
New URIs
The URIs of the geopolitical ontology need to be permanent, consequently all transient information, such as year, version, or format was avoided in the definition of the URIs. The new URIs can be accessed
For example, for the resource “Italy” the URIs are the following:
http://www.fao.org/countryprofiles/geoinfo/geopolitical/resource/Italy
identifies the non-information resource.
http://www.fao.org/countryprofiles/geoinfo/geopolitical/data/Italy
identifies the resource with an RDF/XML representation.
http://www.fao.org/countryprofiles/geoinfo/geopolitical/page/Italy
identifies the information resource with an HTML representation.
In addition, “owl:sameAs” is used to map the new URIs to the OWL representation.
Dereferencing URIs
When a non-information resource is looked up without any specific representation format, then the server needs to redirect the request to information resource with an HTML representation.
For example, to retrieve the resource “Italy”, which is a non-information resource, the server redirects to the HTML page of “Italy”.
At least 1000 triples in the datasets
The total number of triple statements in FAO Geopolitical Ontology is 22,495.
At least 50 links to a dataset already in the current LOD Cloud:
FAO Geopolitical Ontology has 195 links to DBpedia, which is already part of the LOD Cloud.
Access to the entire dataset
FAO Geopolitical Ontology provides the entire dataset as a RDF dump.
The RDF version of the FAO Geopolitical Ontology has been already registered in CKAN and it was requested to add it into the LOD Cloud.
Example of use
The FAO Country Profiles is an information retrieval tool which groups the FAO's vast archive of information on its global activities in agriculture and rural development in one single area and catalogues it exclusively by country.
The FAO Country Profiles system provides access to country-based heterogeneous data sources. By using the geopolitical ontology in the system, the following benefits are expected:
Enhanced system functionality for content aggregation and synchronization from the multiple source repositories.
Improved information access and browsing through comparison of data in neighbor countries and groups.
Figure 3 shows a page in the FAO Country Profiles where the geopolitical ontology is described.
See also
Agricultural Information Management Standards
AGROVOC
Country code
FAO Country Profiles
Global Administrative Unit Layers (GAUL)
International Organization for Standardization (ISO)
References
External links
Ontology (information science)
Knowledge representation
Country codes
Geographic data and information | Geopolitical ontology | Technology | 1,833 |
6,366 | https://en.wikipedia.org/wiki/Canis%20Major | Canis Major is a constellation in the southern celestial hemisphere. In the second century, it was included in Ptolemy's 48 constellations, and is counted among the 88 modern constellations. Its name is Latin for "greater dog" in contrast to Canis Minor, the "lesser dog"; both figures are commonly represented as following the constellation of Orion the hunter through the sky. The Milky Way passes through Canis Major and several open clusters lie within its borders, most notably M41.
Canis Major contains Sirius, the brightest star in the night sky, known as the "dog star". It is bright because of its proximity to the Solar System and its intrinsic brightness. In contrast, the other bright stars of the constellation are stars of great distance and high luminosity. At magnitude 1.5, Epsilon Canis Majoris (Adhara) is the second-brightest star of the constellation and the brightest source of extreme ultraviolet radiation in the night sky. Next in brightness are the yellow-white supergiant Delta (Wezen) at 1.8, the blue-white giant Beta (Mirzam) at 2.0, blue-white supergiants Eta (Aludra) at 2.4 and Omicron2 at 3.0, and white spectroscopic binary Zeta (Furud), also at 3.0. The red hypergiant VY CMa is one of the largest stars known, while the neutron star RX J0720.4-3125 has a radius of a mere 5 km.
History and mythology
In western astronomy
In ancient Mesopotamia, Sirius, named KAK.SI.SA2 by the Babylonians, was seen as an arrow aiming towards Orion, while the southern stars of Canis Major and a part of Puppis were viewed as a bow, named BAN in the Three Stars Each tablets, dating to around 1100 BC. In the later compendium of Babylonian astronomy and astrology titled MUL.APIN, the arrow, Sirius, was also linked with the warrior Ninurta, and the bow with Ishtar, daughter of Enlil. Ninurta was linked to the later deity Marduk, who was said to have slain the ocean goddess Tiamat with a great bow, and worshipped as the principal deity in Babylon. The Ancient Greeks replaced the bow and arrow depiction with that of a dog.
In Greek Mythology, Canis Major represented the dog Laelaps, a gift from Zeus to Europa; or sometimes the hound of Procris, Diana's nymph; or the one given by Aurora to Cephalus, so famed for its speed that Zeus elevated it to the sky. It was also considered to represent one of Orion's hunting dogs, pursuing Lepus the Hare or helping Orion fight Taurus the Bull; and is referred to in this way by Aratos, Homer and Hesiod. The ancient Greeks refer only to one dog, but by Roman times, Canis Minor appears as Orion's second dog. Alternative names include Canis Sequens and Canis Alter. Canis Syrius was the name used in the 1521 Alfonsine tables.
The Roman myth refers to Canis Major as Custos Europae, the dog guarding Europa but failing to prevent her abduction by Jupiter in the form of a bull, and as Janitor Lethaeus, "the watchdog". In medieval Arab astronomy, the constellation became al-Kalb al-Akbar, "the Greater Dog", transcribed as Alcheleb Alachbar by 17th century writer Edmund Chilmead. Islamic scholar Abū Rayḥān al-Bīrūnī referred to Orion as Kalb al-Jabbār, "the Dog of the Giant". Among the Merazig of Tunisia, shepherds note six constellations that mark the passage of the dry, hot season. One of them, called Merzem, includes the stars of Canis Major and Canis Minor and is the herald of two weeks of hot weather.
In non-western astronomy
In Chinese astronomy, the modern constellation of Canis Major is located in the Vermilion Bird (), where the stars were classified in several separate asterisms of stars. The Military Market () was a circular pattern of stars containing Nu3, Beta, Xi1 and Xi2, and some stars from Lepus. The Wild Cockerel () was at the centre of the Military Market, although it is uncertain which stars depicted what. Schlegel reported that the stars Omicron and Pi Canis Majoris might have been them, while Beta or Nu2 have also been proposed. Sirius was (), the Celestial Wolf, denoting invasion and plunder. Southeast of the Wolf was the asterism (), the celestial Bow and Arrow, which was interpreted as containing Delta, Epsilon, Eta and Kappa Canis Majoris and Delta Velorum. Alternatively, the arrow was depicted by Omicron2 and Eta and aiming at Sirius (the Wolf), while the bow comprised Kappa, Epsilon, Sigma, Delta and 164 Canis Majoris, and Pi and Omicron Puppis.
Both the Māori people and the people of the Tuamotus recognized the figure of Canis Major as a distinct entity, though it was sometimes absorbed into other constellations. , also called and , ("The Assembly of " or "The Assembly of Sirius") was a Māori constellation that included both Canis Minor and Canis Major, along with some surrounding stars. Related was , also called , the Mirror of , formed from an undefined group of stars in Canis Major. They called Sirius and , corresponding to two of the names for the constellation, though was a name applied to other stars in various Māori groups and other Polynesian cosmologies. The Tuamotu people called Canis Major , "the abiding assemblage of ".
The Tharumba people of the Shoalhaven River saw three stars of Canis Major as (Bat) and his two wives (Mrs Brown Snake) and (Mrs Black Snake); bored of following their husband around, the women try to bury him while he is hunting a wombat down its hole. He spears them and all three are placed in the sky as the constellation . To the Boorong people of Victoria, Sigma Canis Majoris was (which has become the official name of this star), and its flanking stars Delta and Epsilon were his two wives. The moon (, "native cat") sought to lure the further wife (Epsilon) away, but assaulted him and he has been wandering the sky ever since.
Characteristics
Canis Major is a constellation in the Southern Hemisphere's summer (or northern hemisphere's winter) sky, bordered by Monoceros (which lies between it and Canis Minor) to the north, Puppis to the east and southeast, Columba to the southwest, and Lepus to the west. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is "CMa". The official constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a quadrilateral; in the equatorial coordinate system, the right ascension coordinates of these borders lie between and , while the declination coordinates are between −11.03° and −33.25°. Covering 380 square degrees or 0.921% of the sky, it ranks 43rd of the 88 currently-recognized constellations in size.
Features
Stars
Canis Major is a prominent constellation because of its many bright stars. These include Sirius (Alpha Canis Majoris), the brightest star in the night sky, as well as three other stars above magnitude 2.0. Furthermore, two other stars are thought to have previously outshone all others in the night sky—Adhara (Epsilon Canis Majoris) shone at −3.99 around 4.7 million years ago, and Mirzam (Beta Canis Majoris) peaked at −3.65 around 4.42 million years ago. Another, NR Canis Majoris, will be brightest at magnitude −0.88 in about 2.87 million years' time.
The German cartographer Johann Bayer used the Greek letters Alpha through Omicron to label the most prominent stars in the constellation, including three adjacent stars as Nu and two further pairs as Xi and Omicron, while subsequent observers designated further stars in the southern parts of the constellation that were hard to discern from Central Europe. Bayer's countryman Johann Elert Bode later added Sigma, Tau and Omega; the French astronomer Nicolas Louis de Lacaille added lettered stars a to k (though none are in use today). John Flamsteed numbered 31 stars, with 3 Canis Majoris being placed by Lacaille into Columba as Delta Columbae (Flamsteed had not recognised Columba as a distinct constellation). He also labelled two stars—his 10 and 13 Canis Majoris—as Kappa1 and Kappa2 respectively, but subsequent cartographers such as Francis Baily and John Bevis dropped the fainter former star, leaving Kappa2 as the sole Kappa. Flamsteed's listing of Nu1, Nu2, Nu3, Xi1, Xi2, Omicron1 and Omicron2 have all remained in use.
Sirius is the brightest star in the night sky at apparent magnitude −1.46 and one of the closest stars to Earth at a distance of 8.6 light-years. Its name comes from the Greek word for "scorching" or "searing". Sirius is also a binary star; its companion Sirius B is a white dwarf with a magnitude of 8.4–10,000 times fainter than Sirius A to observers on Earth. The two orbit each other every 50 years. Their closest approach last occurred in 1993 and they will be at their greatest separation between 2020 and 2025. Sirius was the basis for the ancient Egyptian calendar. The star marked the Great Dog's mouth on Bayer's star atlas.
Flanking Sirius are Beta and Gamma Canis Majoris. Also called Mirzam or Murzim, Beta is a blue-white Beta Cephei variable star of magnitude 2.0, which varies by a few hundredths of a magnitude over a period of six hours. Mirzam is 500 light-years from Earth, and its traditional name means "the announcer", referring to its position as the "announcer" of Sirius, as it rises a few minutes before Sirius does. Gamma, also known as Muliphein, is a fainter star of magnitude 4.12, in reality a blue-white bright giant of spectral type B8IIe located 441 light-years from earth. Iota Canis Majoris, lying between Sirius and Gamma, is another star that has been classified as a Beta Cephei variable, varying from magnitude 4.36 to 4.40 over a period of 1.92 hours. It is a remote blue-white supergiant star of spectral type B3Ib, around 46,000 times as luminous as the sun and, at 2500 light-years distant, 300 times further away than Sirius.
Epsilon, Omicron2, Delta, and Eta Canis Majoris were called Al Adzari "the virgins" in medieval Arabic tradition. Marking the dog's right thigh on Bayer's atlas is Epsilon Canis Majoris, also known as Adhara. At magnitude 1.5, it is the second-brightest star in Canis Major and the 23rd-brightest star in the sky. It is a blue-white supergiant of spectral type B2Iab, around 404 light-years from Earth. This star is one of the brightest known extreme ultraviolet sources in the sky. It is a binary star; the secondary is of magnitude 7.4. Its traditional name means "the virgins", having been transferred from the group of stars to Epsilon alone. Nearby is Delta Canis Majoris, also called Wezen. It is a yellow-white supergiant of spectral type F8Iab and magnitude 1.84, around 1605 light-years from Earth. With a traditional name meaning "the weight", Wezen is 17 times as massive and 50,000 times as luminous as the Sun. If located in the centre of the Solar System, it would extend out to Earth as its diameter is 200 times that of the Sun. Only around 10 million years old, Wezen has stopped fusing hydrogen in its core. Its outer envelope is beginning to expand and cool, and in the next 100,000 years it will become a red supergiant as its core fuses heavier and heavier elements. Once it has a core of iron, it will collapse and explode as a supernova. Nestled between Adhara and Wezen lies Sigma Canis Majoris, known as Unurgunite to the Boorong and Wotjobaluk people, a red supergiant of spectral type K7Ib that varies irregularly between magnitudes 3.43 and 3.51.
Also called Aludra, Eta Canis Majoris is a blue-white supergiant of spectral type B5Ia with a luminosity 176,000 times and diameter around 80 times that of the Sun. Classified as an Alpha Cygni type variable star, Aludra varies in brightness from magnitude 2.38 to 2.48 over a period of 4.7 days. It is located 1120 light-years away. To the west of Adhara lies 3.0-magnitude Zeta Canis Majoris or Furud, around 362 light-years distant from Earth. It is a spectroscopic binary, whose components orbit each other every 1.85 years, the combined spectrum indicating a main star of spectral type B2.5V.
Between these stars and Sirius lie Omicron1, Omicron2, and Pi Canis Majoris. Omicron2 is a massive supergiant star about 21 times as massive as the Sun. Only 7 million years old, it has exhausted the supply of hydrogen at its core and is now processing helium. It is an Alpha Cygni variable that undergoes periodic non-radial pulsations, which cause its brightness to cycle from magnitude 2.93 to 3.08 over a 24.44-day interval. Omicron1 is an orange K-type supergiant of spectral type K2.5Iab that is an irregular variable star, varying between apparent magnitudes 3.78 and 3.99. Around 18 times as massive as the Sun, it shines with 65,000 times its luminosity.
North of Sirius lie Theta and Mu Canis Majoris, Theta being the most northerly star with a Bayer designation in the constellation. Around 8 billion years old, it is an orange giant of spectral type K4III that is around as massive as the Sun but has expanded to 30 times the Sun's diameter. Mu is a multiple star system located around 1244 light-years distant, its components discernible in a small telescope as a 5.3-magnitude yellow-hued and 7.1-magnitude bluish star. The brighter star is a giant of spectral type K2III, while the companion is a main sequence star of spectral type B9.5V. Nu1 Canis Majoris is a yellow-hued giant star of magnitude 5.7, 278 light-years away; it is at the threshold of naked-eye visibility. It has a companion of magnitude 8.1.
At the southern limits of the constellation lie Kappa and Lambda Canis Majoris. Although of similar spectra and nearby each other as viewed from Earth, they are unrelated. Kappa is a Gamma Cassiopeiae variable of spectral type B2Vne, which brightened by 50% between 1963 and 1978, from magnitude 3.96 or so to 3.52. It is around 659 light-years distant. Lambda is a blue-white B-type main sequence dwarf with an apparent magnitude of 4.48 located around 423 light-years from Earth. It is 3.7 times as wide as and 5.5 times as massive as the Sun, and shines with 940 times its luminosity.
Canis Major is also home to many variable stars. EZ Canis Majoris is a Wolf–Rayet star of spectral type WN4 that varies between magnitudes 6.71 and 6.95 over a period of 3.766 days; the cause of its variability is unknown but thought to be related to its stellar wind and rotation. VY Canis Majoris is a remote red hypergiant located approximately 3,800 light-years away from Earth. It is one of largest stars known (sometimes described as the largest known) and is also one of the most luminous with a radius varying from 1,420 to 2,200 times the Sun's radius, and a luminosity around 300,000 times greater than the Sun. Its current mass is about 17 ± 8 solar masses, having shed material from an initial mass of 25–32 solar masses. VY CMa is also surrounded by a red reflection nebula that has been made by the material expelled by the strong stellar winds of its central star. W Canis Majoris is a type of red giant known as a carbon star—a semiregular variable, it ranges between magnitudes 6.27 and 7.09 over a period of 160 days. A cool star, it has a surface temperature of around 2,900 K and a radius 234 times that of the Sun, its distance estimated at 1,444–1,450 light-years from Earth. At the other extreme in size is RX J0720.4-3125, a neutron star with a radius of around 5 km. Exceedingly faint, it has an apparent magnitude of 26.6. Its spectrum and temperature appear to be mysteriously changing over several years. The nature of the changes are unclear, but it is possible they were caused by an event such as the star's absorption of an accretion disc.
Tau Canis Majoris is a Beta Lyrae-type eclipsing multiple star system that varies from magnitude 4.32 to 4.37 over 1.28 days. Its four main component stars are hot O-type stars, with a combined mass 80 times that of the Sun and shining with 500,000 times its luminosity, but little is known of their individual properties. A fifth component, a magnitude 10 star, lies at a distance of . The system is only 5 million years old. UW Canis Majoris is another Beta Lyrae-type star 3000 light-years from Earth; it is an eclipsing binary that ranges in magnitude from a minimum of 5.3 to a maximum of 4.8. It has a period of 4.4 days; its components are two massive hot blue stars, one a blue supergiant of spectral type O7.5–8 Iab, while its companion is a slightly cooler, less evolved and less luminous supergiant of spectral type O9.7Ib. The stars are 200,000 and 63,000 times as luminous as the Sun. However the fainter star is the more massive at 19 solar masses to the primary's 16. R Canis Majoris is another eclipsing binary that varies from magnitude 5.7 to 6.34 over 1.13 days, with a third star orbiting these two every 93 years. The shortness of the orbital period and the low ratio between the two main components make this an unusual Algol-type system.
Seven star systems have been found to have planets. Nu2 Canis Majoris is an ageing orange giant of spectral type K1III of apparent magnitude 3.91 located around 64 light-years distant. Around 1.5 times as massive and 11 times as luminous as the Sun, it is orbited over a period of 763 days by a planet 2.6 times as massive as Jupiter. HD 47536 is likewise an ageing orange giant found to have a planetary system—echoing the fate of the Solar System in a few billion years as the Sun ages and becomes a giant. Conversely, HD 45364 is a star 107 light-years distant that is a little smaller and cooler than the Sun, of spectral type G8V, which has two planets discovered in 2008. With orbital periods of 228 and 342 days, the planets have a 3:2 orbital resonance, which helps stabilise the system. HD 47186 is another sunlike star with two planets; the inner—HD 47186 b—takes four days to complete an orbit and has been classified as a Hot Neptune, while the outer—HD 47186 c—has an eccentric 3.7-year period orbit and has a similar mass to Saturn. HD 43197 is a sunlike star around 183 light-years distant that has two planets: a hot Jupiter-size planet with an eccentric orbit. The other planet, HD 43197 c, is another massive Jovian planet with a slightly oblong orbit outside of its habitable zone.
Z Canis Majoris is a star system a mere 300,000 years old composed of two pre-main-sequence stars—a FU Orionis star and a Herbig Ae/Be star, which has brightened episodically by two magnitudes to magnitude 8 in 1987, 2000, 2004 and 2008. The more massive Herbig Ae/Be star is enveloped in an irregular roughly spherical cocoon of dust that has an inner diameter of and outer diameter of . The cocoon has a hole in it through which light shines that covers an angle of 5 to 10 degrees of its circumference. Both stars are surrounded by a large envelope of in-falling material left over from the original cloud that formed the system. Both stars are emitting jets of material, that of the Herbig Ae/Be star being much larger—11.7 light-years long. Meanwhile, FS Canis Majoris is another star with infra-red emissions indicating a compact shell of dust, but it appears to be a main-sequence star that has absorbed material from a companion. These stars are thought to be significant contributors to interstellar dust.
Deep-sky objects
The band of the Milky Way goes through Canis Major, with only patchy obscurement by interstellar dust clouds. It is bright in the northeastern corner of the constellation, as well as in a triangular area between Adhara, Wezen and Aludra, with many stars visible in binoculars. Canis Major boasts several open clusters. The only Messier object is M41 (NGC 2287), an open cluster with a combined visual magnitude of 4.5, around 2300 light-years from Earth. Located 4 degrees south of Sirius, it contains contrasting blue, yellow and orange stars and covers an area the apparent size of the full moon—in reality around 25 light-years in diameter. Its most luminous stars have already evolved into giants. The brightest is a 6.3-magnitude star of spectral type K3. Located in the field is 12 Canis Majoris, though this star is only 670 light-years distant. NGC 2360, known as Caroline's Cluster after its discoverer Caroline Herschel, is an open cluster located 3.5 degrees west of Muliphein and has a combined apparent magnitude of 7.2. Around 15 light-years in diameter, it is located 3700 light-years away from Earth, and has been dated to around 2.2 billion years old. NGC 2362 is a small, compact open cluster, 5200 light-years from Earth. It contains about 60 stars, of which Tau Canis Majoris is the brightest member. Located around 3 degrees northeast of Wezen, it covers an area around 12 light-years in diameter, though the stars appear huddled around Tau when seen through binoculars. It is a very young open cluster as its member stars are only a few million years old. Lying 2 degrees southwest of NGC 2362 is NGC 2354 a fainter open cluster of magnitude 6.5, with around 15 member stars visible with binoculars. Located around 30' northeast of NGC 2360, NGC 2359 (Thor's Helmet or the Duck Nebula) is a relatively bright emission nebula in Canis Major, with an approximate magnitude of 10, which is 10,000 light-years from Earth. The nebula is shaped by HD 56925, an unstable Wolf–Rayet star embedded within it.
In 2003, an overdensity of stars in the region was announced to be the Canis Major Dwarf, the closest satellite galaxy to Earth. However, there remains debate over whether it represents a disrupted dwarf galaxy or in fact a variation in the thin and thick disk and spiral arm populations of the Milky Way. Investigation of the area yielded only ten RR Lyrae variables—consistent with the Milky Way's halo and thick disk populations rather than a separate dwarf spheroidal galaxy. On the other hand, a globular cluster in Puppis, NGC 2298—which appears to be part of the Canis Major dwarf system—is extremely metal-poor, suggesting it did not arise from the Milky Way's thick disk, and instead is of extragalactic origin.
NGC 2207 and IC 2163 are a pair of face-on interacting spiral galaxies located 125 million light-years from Earth. About 40 million years ago, the two galaxies had a close encounter and are now moving farther apart; nevertheless, the smaller IC 2163 will eventually be incorporated into NGC 2207. As the interaction continues, gas and dust will be perturbed, sparking extensive star formation in both galaxies. Supernovae have been observed in NGC 2207 in 1975 (type Ia SN 1975a), 1999 (the type Ib SN 1999ec), 2003 (type 1b supernova SN 2003H), and 2013 (type II supernova SN 2013ai). Located 16 million light-years distant, ESO 489-056 is an irregular dwarf- and low-surface-brightness galaxy that has one of the lowest metallicities known.
References
Citations
Bibliography
External links
The Deep Photographic Guide to the Constellations: Canis Major
The clickable Canis Major
Warburg Institute Iconographic Database (medieval and early modern images of Canis Major)
Constellations listed by Ptolemy
Southern constellations | Canis Major | Astronomy | 5,433 |
42,058,042 | https://en.wikipedia.org/wiki/Cox%20ring | In algebraic geometry, a Cox ring is a sort of universal homogeneous coordinate ring for a projective variety, and is (roughly speaking) a direct sum of the spaces of sections of all isomorphism classes of line bundles. Cox rings were introduced by , based on an earlier construction by David A. Cox in 1995 for toric varieties.
See also
Cox–Zucker machine
References
Algebraic geometry | Cox ring | Mathematics | 78 |
711,902 | https://en.wikipedia.org/wiki/Julie%20Vinter%20Hansen | Julie Marie Vinter Hansen (20 July 1890 – 27 July 1960) was a Danish astronomer. She is the first woman to be obtain a scientific degree in astronomy in Denmark.
Life
Early life
Vinter Hansen was born in Copenhagen, Denmark.
Education
While studying at the University of Copenhagen, she was appointed as acomputer at the University's observatory in 1915. She was the first woman to hold an appointment at the University. She was later appointed observatory assistant and, in 1922, observer.
Career
Editor of Nordic Astronomy Review
She was a very energetic worker, who, along with her normal work of observing and performing mathematical reductions of observations took on the task of editing the Nordisk Astronomisk Tidsskrift (Nordic Astronomy Review).
International Astronomical Union
She later became Director of the International Astronomical Union's telegram bureau and Editor of its Circulars.
Work as Astronomer at University of Copenhagen
By 1939, Vinter Hansen was the First Astronomer at the Observatory of the University of Copenhagen, widely known for her accurate computation of orbits of minor planets and comets.
Tagea Brandt Rejselegat Award
In that 1939 she received the Tagea Brandt Rejselegat (travel award), given to women that have made big contributions on arts or science. With the award money (DKK 10.000 or 160,000 of actual US $) undertook a tour through the United States to Japan and back. On her return trip in 1940, the outbreak of World War II restricted her homeward journey.
Work in University of California
She was awarded a Martin Kellogg Fellowship at the University of California which allowed her to work for a time in the United States. Also in 1940 she was awarded the Annie J. Cannon Award in Astronomy.
Return to Denmark
Vinter Hansen was appointed Knight of the Order of the Dannebrog in 1956 and continued her career at the University of Copenhagen until 1960.
Death
Julie Vinter Hansen died in 1960, from a heart-failure just days before her retirement, in her beloved vacation destination, the Swiss mountain village of Mürren, and was buried in Copenhagen. The minor planet 1544 Vinterhansenia, discovered by Finnish astronomer Liisi Oterma in the 1940s, was named in her honour.
Awards
Knight of the Order of the Dannebrog (1956)
Annie J. Cannon Award in Astronomy (1940)
Martin Kellogg Fellowship
Tagea Brandt Rejselegat Award.
Further reading
Julie Vinter Hansen Papers, University Library, UC Santa Cruz
References
Sources
1890 births
1960 deaths
20th-century Danish astronomers
20th-century Danish women scientists
Recipients of the Annie J. Cannon Award in Astronomy
University of Copenhagen alumni
Academic staff of the University of Copenhagen
University of California, Berkeley faculty
Women astronomers
Scientists from Copenhagen
Danish women academics | Julie Vinter Hansen | Astronomy | 554 |
1,667,915 | https://en.wikipedia.org/wiki/Computer%20Shopper%20%28UK%20magazine%29 | Computer Shopper was a magazine published monthly between 1988 and 2020 in the UK by Dennis Publishing Ltd. It contained reviews of home computers, consumer technology and software as well as technology-focused news, analysis and feature articles.
The final editorial staff included Madeline Bennett (editor), David Ludlow (contributing editor) and James Archer (reviews editor). Contributors of columns, features and specialist reviews included Mel Croucher, Kay Ewbank, Simon Handby, Ben Pitt and David Crookes.
Content
The first section of the magazine was dedicated to columns, opinions and the Letters pages. This was followed by several news spreads on recent developments in the technology industry.
The magazine claimed the "UK's biggest reviews section" with much of the magazine devoted to product tests of the latest hardware. The reviews section was typically occupied by desktop PCs, laptops, PC components, smartphones, tablets, cameras, displays and printers. This section of new products was typically followed by two or three Group Tests which pitch ten or more similar products against one another to find an overall Best Buy. Previous tests included budget laptops, cloud storage providers, action cameras and gaming PCs.
The Best Buys section of the magazine was updated monthly to reflect the latest products the editorial team has deemed the overall best choice(s) in each area of consumer technology.
Two or three longer-form feature articles followed the reviews section, focusing on the wider world of technology and its applications in various industries. Later features included a history of coding, a guide on how to build racing, flight and train simulators as well as more consumer-focused features on broadband and mobile coverage. A retro section was also included.
The magazine was tailed by several tutorial pages including Advanced Projects, Multimedia Expert, Business Help and Helpfile.
The final page of the magazine was traditionally occupied by the Zygote column and the Great Moments in Computing comic.
See also
Computer Shopper (US magazine)
References
External links
1988 establishments in the United Kingdom
2020 disestablishments in the United Kingdom
2020 disestablishments in England
Amiga magazines
Defunct computer magazines published in the United Kingdom
Home computer magazines
Magazines established in 1988
Magazines published in London
Monthly magazines published in the United Kingdom | Computer Shopper (UK magazine) | Technology | 451 |
39,155,642 | https://en.wikipedia.org/wiki/Isocupressic%20acid | Isocupressic acid is a diterpene acid present in a variety of conifer needles. It induces abortion in cattle.
It is found in all parts of the ponderosa pine (Pinus ponderosa), especially the needles. This gives its toxic and abortifacient effects. It is also present in the lodgepole pine (P. contorta), the jeffrey pine (P. jeffreyi) and possibly in the monterey pine (P. radiata).
References
Pinus
Carboxylic acids
Diterpenes | Isocupressic acid | Chemistry | 116 |
39,543,128 | https://en.wikipedia.org/wiki/Koehler%20Depressing%20Carriage | The Koehler Depressing Carriage was a novel type of gun carriage invented in 1782 by Lt George Frederick Koehler of the Royal Artillery. It was devised to enable cannon to be fired at a steeply downward-facing angle and was made necessary by the peculiar circumstances that the British Army faced during the Great Siege of Gibraltar between 1779 and 1783. The carriage saw active service during the siege, when it was used to support the British counter-bombardment of Spanish and French artillery batteries during the successful defence of Gibraltar. Its success made Koehler famous and has been commemorated in a number of different forms over the last 230 years.
Background
During the Great Siege, the British garrison of Gibraltar faced a French and Spanish army entrenched on the low ground of the isthmus that links Gibraltar with Spain. The British controlled the high ground of the Rock of Gibraltar, which reaches a height of at its north end. Although this was a major advantage for the British gunners, as it gave them an increased range and a clear view of the enemy, it also posed significant problems. Enemies close to their positions could not be targeted as existing gun carriages would not allow the amount of vertical depression required to hit such a close target. Gunners tried to deal with this by propping up the rear of the carriages, but this was a clumsy solution that fixed the guns in position. It consequently exposed them to severe danger as they had to load the guns in full view of enemy counter-fire, rather than out of sight in an embrasure or battery.
Koehler's invention
Depressing carriages had been invented before – in the 15th century, a German engineer had devised a platform for a culverin that had four wheels and could be moved in two arcs for adjusting the elevation – but Koehler found a simple and effective solution that solved both the problems of elevation and recoil. It was based on an existing garrison carriage, a type of heavy gun carriage mounted on small wheels known as trucks. Koehler split the carriage in two horizontally, joining the two parts with a hinge created with a spindle at the front. This allowed the gun to be depressed to an angle of between 20 and 70 degrees. The cannonball and powder were held in place using wadding to secure them in the bore.
Koehler's design had the further advantage of absorbing the recoil caused by firing the gun. Ordinary carriages had no mechanism to absorb this recoil. The entire gun and mount would jump violently, causing the gun crew to have to reposition it before they could fire the next shot. Koehler's carriage mounted the gun on a sliding bed attached to the main body of the carriage via a vertical spindle. Firing the cannon forced the bed to slide upwards, rather than making the entire carriage recoil. As an eyewitness, John Drinkwater, noted, "the carriage, when the gun was depressed, seldom moved; the gun sliding upon the plank to which it was attached by the spindle, and returning to its former place with the most trifling assistance." This system was a forerunner of the recoil systems that are standard features of modern artillery pieces. The gun could be reversed on the carriage and fired upwards at angles of up to 45°, though according to Drinkwater "in that state [it] did not particularly excel." The design also enabled gunners to reload the cannon without exposing themselves to enemy fire, by rotating the sliding bed sideways.
The carriage was first put into operational use in the afternoon of 15 April 1782, when Koehler demonstrated it to the Governor of Gibraltar, General George Augustus Eliott, and other officers of the garrison. The target chosen was San Carlos Battery, a Spanish position some distant in the Lines of Contravallation. Drinkwater recorded that out of thirty rounds fired, twenty-eight hit the target. Koehler's carriage became a key advantage for the defenders of Gibraltar, contributing to the accuracy and speed of the British artillery, and became one of the most famous and successful examples of a special gun carriage. However, it had a significant flaw in that the angle of depression could only be adjusted in a number of large 'steps', making it difficult to aim at certain angles. This was resolved by an 1870s update to the design which saw the addition of a large wheel at the back, connected to a screw mechanism, which enabled fine tuning of the angle.
Commemoration
Koehler's invention has been commemorated in numerous works of art, models, sculptures, replicas and badges. The depressing gun carriage can be seen in the bottom-left corner of a famous 1787 portrait of General Eliott by Joshua Reynolds. It is still displayed on the badge of 22 (Gibraltar) Battery Royal Artillery, and the £10 note, £1 coin and 10p coin of the Gibraltar pound have all depicted the gun carriage. A replica of a Koehler gun carriage can be seen at Grand Casemates Square in Gibraltar's city centre, while in the Great Siege Tunnels, originally dug out during the siege itself, a reconstruction can be seen of how the depressing carriage would have been used.
References
Notes
Bibliography
Artillery components
Carriages and mountings
Fortifications in Gibraltar
18th century in technology | Koehler Depressing Carriage | Technology | 1,055 |
1,797,746 | https://en.wikipedia.org/wiki/Mural%20crown | A mural crown () is a crown or headpiece representing city walls, towers, or fortresses. In classical antiquity, it was an emblem of tutelary deities who watched over a city, and among the Romans a military decoration. Later the mural crown developed into a symbol of European heraldry, mostly for cities and towns, and in the 19th and 20th centuries was used in some republican heraldry.
Usage in ancient times
Early appearances of the mural crown occur in the Achaemenid Empire, where they resemble crenelations on Mesopotamian and Persian buildings.
In Hellenistic culture, a mural crown identified tutelary deities such as the goddess Tyche (the embodiment of the fortunes of a city, familiar to Romans as Fortuna), and Hestia (the embodiment of the protection of a city, familiar to Romans as Vesta). The high cylindrical polos of Rhea/Cybele too could be rendered as a mural crown in Hellenistic times, specifically designating the mother goddess as patron of a city.
The mural crown became an ancient Roman military decoration. The corona muralis (Latin for "walled crown") was a golden crown, or a circle of gold intended to resemble a battlement, bestowed upon the soldier who first climbed the wall of a besieged city or fortress to successfully place the standard (flag) of the attacking army upon it. The Roman mural crown was made of gold, and decorated with turrets, as is the heraldic version. As it was among the highest order of military decorations, it was not awarded to a claimant until after a strict investigation. The rostrata mural crown, composed of the rostra indicative of captured ships, was assigned as naval prize to the first in a boarding party, similar to the naval crown.
The Graeco-Roman goddess Roma's attributes on Greek coinage usually include her mural crown, signifying Rome's status as a loyal protector of Hellenic city-states.
Heraldic use
The Roman military decoration was subsequently employed in European heraldry, where the term denoted a crown modeled after the walls of a castle, which may be tinctured or (gold), argent (silver), gules (red), or proper (i.e. stone-coloured). In 19th-century Germany, mural crowns () came to be adopted for the arms of cities, with increasingly specific details: "Residential (i.e. having a royal residence) cities and capital towns usually bear a with five towers, large towns one with four towers, smaller towns one with three", observed Arthur Charles Fox-Davies, in A Complete Guide to Heraldry, adding "Strict regulations in the matter do not yet exist" and warning that the usage was not British.
Mural crowns were used, rather than royal crowns, for medieval and modern Italian . A mural-crowned lady, Italia Turrita, personifies Italy. In Italy, and some provinces and military corps have mural crowns on their coats of arms: gold with five towers for cities, and silver with nine-towered for others. The coat of arms of the Second Spanish Republic had a mural crown.
In the early 20th century Portugal established strict rules for its municipal heraldry, in which each coat of arms contains a mural crown, with three silver towers signifying a village or an urban parish, four silver towers representing a town, five silver towers standing for a city and five gold towers for a capital city. The Portuguese rules are also applied to most municipal coats of arms of Brazil and some other members of the Community of Portuguese Language Countries.
Romanian municipal coats of arms contain a mural crown, with one or three towers for villages and communes, five and seven towers for towns and municipalities.
The eagle on the coat of arms of Austria wears a mural crown to signify its status as a republic. This is in contrast to the royal crowns that adorned the double-headed eagle (and the imperial crown positioned above it) in the coat of arms of Austria-Hungary until their defeat in World War I. The mural-crowned eagle was abandoned under the clerico-fascist Federal State of Austria from 1934, but was reinstated in Allied-occupied Austria following World War II and remains in place to this day.
Examples from heraldry
See also
References
External links
Crowns in heraldry
Crowns (headgear)
Military awards and decorations of ancient Rome
Municipal coats of arms
National symbols of Italy
Iconography
Visual motifs | Mural crown | Mathematics | 898 |
11,183,776 | https://en.wikipedia.org/wiki/Penetration%20%28firestop%29 | A penetration, in firestopping, is an opening, such as one created by the use of a cast-in-place sleeve, in a wall or floor assembly required to have a fire-resistance rating, for the purpose of accommodating the passage of a mechanical, electrical, or structural penetrant.
The penetration may or may not contain a firestop system. A penetration (opening) may or may not include a penetrant (something passing through the opening).
See also
Sleeve (construction)
Passive fire protection
Annulus (firestop)
Joint (building)
Penetrant (mechanical, electrical, or structural)
Mortar (firestop)
Firestop pillow
Fire test
References
External links
Penetration seals (firestops) treatise by Warrington labs
Penetration seals (firestops) treatise by Nuclear Regulatory Commission
Penetration seal (firestop) vendor listings by Thomas Register
Passive fire protection
Building engineering
Firestops | Penetration (firestop) | Engineering | 183 |
2,030,723 | https://en.wikipedia.org/wiki/Cathedral%20hull | A cathedral hull is a hull shape used in modern boats, usually power-driven. It has sponsons which extend almost as far forward as the main hull. The airspace between the hulls may be very small or nonexistent.
Depending on the proportions of the sponsons and the depth of the main hull, the cathedral hull can approach the handling characteristics of either the Hickman sea sled, or the vee hull. The naval architect first credited with the successful use of the deep-vee hull form, C. Raymond Hunt, was involved in the design of the original 13’ Boston Whaler. It is cathedral hulled forward, but nearly a flat-bottomed scow at the stern.
The term "cathedral hull" refers to the resemblance of a section through an inverted boat to that of a medieval cathedral.
Characteristics
The cathedral hull configuration tends to result in a very broad bow; many such boats are completely rectangular. This provides the maximum cargo or working space for a given length and beam. The hull shape is also very stable compared to a conventional v-shaped bottom, and in either light chop conditions or above or so in certain conditions can be faster than a flat bottom, for the same weight, length and beam.
Cathedral hulls became popular in the 1960s and 1970s, when the use of fiberglass made economical production of this hull-form possible. The undesirable aspects of the cathedral hull are greater weight and cost, pounding in rough water, and a boxy appearance. Their advantages include high waterplane area at rest (good initial stability) a dry ride in light chop, and reasonable fuel economy at planing speeds. In exposed waters this hull form has been almost totally replaced by the modified-V and deep-V hull forms. After a period of reduced popularity, they live on in modified form as "deck boats" which are very popular in the inland lakes and rivers.
The cathedral hull design was originated by naval architect Richard C. Cole for Thunderbird boats in North Miami, Florida, in 1958.
See also
Tunnel hull
Supercavitation propeller
Hull
References
http://dictionary.reference.com/browse/cathedral+hull
https://web.archive.org/web/20101130124019/http://www.boatus.org/onlinecourse/reviewpages/boatusf/project/info1b.htm
http://www.huntdesigns.com/rayhunt.htm
Specific
Shipbuilding | Cathedral hull | Engineering | 514 |
14,057,170 | https://en.wikipedia.org/wiki/Alternaria%20consortialis | Alternaria consortialis is a fungal plant pathogen, infecting tomatoes and cucurbits. It also causes disease in caraway seedlings. It was found on fruits and vegetables in Saudi Arabia.
References
External links
USDA ARS Fungal Database
Fungal plant pathogens and diseases
Tomato diseases
Vegetable diseases
Pleosporaceae
Fungus species | Alternaria consortialis | Biology | 70 |
32,186,174 | https://en.wikipedia.org/wiki/Gymnosporangium%20clavariiforme | Gymnosporangium clavariiforme (tongues of fire) is a species of rust fungus which alternately infects Juniperus and hawthorns.
In junipers, the primary hosts, G. clavariiforme produces a set of orange tentacle-like spore tubes called telial horns. These horns expand and have a jelly like consistency when wet. The spores are released and travel on the wind until they infect a hawthorn tree.
On the secondary hosts, the fungus produces yellowish depressions on the leaves. It also infects the fruit, which grows whitish tubes like a Medusa head. These are the spore tubes. The spores must then infect a juniper to complete the life cycle.
The fungus does not cause serious damage to junipers, but hawthorns can suffer serious loss of haw production due to the effects of the fungus.
References
Further reading
Phillips, D. H., & Burdekin, D. A. (1992). Diseases of Forest and Ornamental Trees. Macmillan.
Scharpf, R. F., ed. (1993). Diseases of Pacific Coast Conifers. USDA Forest Service Agricultural Handbook 521.
External links
Pucciniales
Fungi described in 1786
Galls
Fungus species | Gymnosporangium clavariiforme | Biology | 256 |
31,440,136 | https://en.wikipedia.org/wiki/Pleurotoid%20fungi | Gilled fungi with laterally-attached fruiting bodies are classified as pleurotoid (Gr.: pleurē + ōtos + -oid, literally "side-ear form" or "having the likeness of Pleurotus ssp."). Pleurotoid fungi are typically wood-decay fungi and are found on dead and dying trees and coarse woody debris. The pleurotoid form is polyphyletic, having evolved a number of times within the Basidiomycota. Many species of pleurotoid fungi are commonly referred to as "oyster" mushrooms. Laterally-attached fungi with pores rather than gills are referred to as bracket fungi.
Genera
Agaricales
Cheimonophyllum
Crepidotus
Hohenbuehelia
Hypsizygus
Ossicaulis
Panellus
Phyllotopsis
Pleurocybella — Angel wings
Pleurotus — Oyster mushrooms
Resupinatus — Oysterlings
Schizophyllum
Tectella
Polyporales
Lentinus
Panus
Russulales
Lactifluus - some species
Lentinellus
Russula - some species
References
External links
Magic Mushrooms Effects & How To Grow Magic Mushrooms Retrieved 2020-10-06.
pleurotoid | Pleurotoid fungi | Biology | 257 |
9,048,103 | https://en.wikipedia.org/wiki/C7H8N4O2 | {{DISPLAYTITLE:C7H8N4O2}}
The molecular formula C7H8N4O2 (molar mass: 180.16 g/mol) may refer to:
Paraxanthine
Theobromine
Theophylline
Molecular formulas | C7H8N4O2 | Physics,Chemistry | 59 |
2,312,640 | https://en.wikipedia.org/wiki/Bioprocess | A bioprocess is a specific process that uses complete living cells or their components (e.g., bacteria, enzymes, chloroplasts) to obtain desired products.
Transport of energy and mass is fundamental to many biological and environmental processes. Areas, from food processing (including brewing beer) to thermal design of buildings to biomedical devices, manufacture of monoclonal antibodies to pollution control and global warming, require knowledge of how energy and mass can be transported through materials (momentum, heat transfer, etc.).
Cell bioprocessing
Cell therapy bioprocessing is a discipline that bridges the fields of cell therapy and bioprocessing (i.e., biopharmaceutical manufacturing), and is a sub-field of bioprocess engineering. The goals of cell therapy bioprocessing are to establish reproducible and robust manufacturing processes for the production of therapeutic cells. Commercially relevant bioprocesses will:
Produce products that maintain all of the quality standards of biopharmaceutical drugs
Supply both clinical and commercial quantities of therapeutic cells throughout the various stages of development. The processes and production technologies must be scalable, and
Control the cost of goods (CoGs) of the final drug product. This aspect is critical to building the foundation for a commercially viable industry.
Upstream bioprocessing
Therapeutic cell manufacturing processes can be separated into upstream processes and downstream processes. The upstream process is defined as the entire process from early cell isolation and cultivation, to cell banking and culture expansion of the cells until final harvest (termination of the culture and collection of the live cell batch).
Aside from technology challenges, concerning the scalability of culture apparatus, a number of raw material supply risks have emerged in recent years, including the availability of GMP grade fetal bovine serum.
The upstream part of a bioprocess refers to the first step in which microbes/cells are grown, e.g. bacterial or mammalian cell lines (see cell culture), in bioreactors. Upstream processing involves all the steps related to inoculum development, media development, improvement of inoculum by genetic engineering process, optimization of growth kinetics so that product development can improve tremendously. Fermentation has two parts: upstream and downstream. After product development, the next step is the purification of product for desired quality. When they reach the desired density (for batch and fed-batch cultures) they are harvested and moved to the downstream section of the bioprocess.
Downstream bioprocessing
The downstream part of a bioprocess refers to the part where the cell mass from the upstream are processed to meet purity and quality requirements. Downstream processing is usually divided into three main sections: cell disruption, a purification section and a polishing section.
The volatile products can be separated by distillation of the harvested culture without pre-treatment. Distillation is done at reduced pressure at continuous stills. At reduced pressure, distillation of product directly from fermentor may be possible. The steps of downstream processing are:
Separation of biomass: separating the biomass (microbial cells) generally carried out by centrifugation or ultra-centrifugation. If the product is biomass, then it is recovered for processing and spent medium is discarded. If the product is extra cellular the biomass will be discarded. Ultra filtration is an alternative to the centrifugation.
Cell disruption: If the desired product is intra cellular the cell biomass can be disrupted so that the product should be released. The solid-liquid is separated by centrifugation or filtration and cell debris is discarded.
Concentration of broth: The spent medium is concentrated if the product is extracellular.
Initial purification of metabolites: According to the physico-chemical nature of the product molecule several methods for recovery of product from the clarified fermented broth were used (precipitation, etc.)
De-watering: If low amount of product is found in very large volume of spent medium, the volume is reduced by removing water to concentrate the product. It is done by vacuum drying or reverse osmosis.
Polishing of metabolites: this is the final step of making the product 98 to 100% pure. The purified product is mixed with several inert ingredients called excipients. The formulated product is packed and sent to the market for the consumers.
See also
Adverse drug reaction
Adverse event
Assay sensitivity
Biomanufacturing
Bioprocess engineering
Biotechnology
Caco-2
Clinical study design
Good clinical practice
Good manufacturing practice
Keck Graduate Institute of Applied Life Sciences (KGI Amgen Bioprocessing Center)
References
Biotechnology | Bioprocess | Biology | 949 |
3,969,384 | https://en.wikipedia.org/wiki/Radiation%20Exposure%20Compensation%20Act | The United States Radiation Exposure Compensation Act (RECA) is a federal statute implemented in 1990, set to expire in July 2024, providing for the monetary compensation of people, including atomic veterans, who contracted cancer and a number of other specified diseases as a direct result of their exposure to atmospheric nuclear testing undertaken by the United States during the Cold War as residents, or their exposure to radon gas and other radioactive isotopes while undertaking uranium mining, milling or the transportation of ore.
The Act has been providing the following remunerations, unchanged since 1990 despite inflation:
$50,000 to individuals residing or working "downwind" of the Nevada Test Site
$75,000 for workers participating in atmospheric nuclear weapons tests
$100,000 for uranium miners, millers, and ore transporters
In all cases there are additional requirements which must be satisfied (proof of exposure, establishment of duration of employment, establishment of certain medical conditions, etc.).
In 2022, the law was to expire, and President Joe Biden extended the filing deadline for another two years.
Origins, 1979
Attempts to enact the legislation can be traced back to the late 1970s. In its fifth draft, a Bill entitled Radiation Exposure Compensation Act of 1979 was sponsored by Senator Ted Kennedy of Massachusetts. The Bill intended to make compensation available to persons exposed to fallout from nuclear weapons testing and for living uranium miners (or their survivors) who had worked in Utah, Colorado, New Mexico and Arizona between 1 January 1947 and 31 December 1961.
The Bill proposed to pay compensation to persons who lived within prescribed areas for at least a year, to persons who "died from, has or has had, leukaemia, thyroid cancer, bone cancer or any other cancer identified by an advisory board on the health effects of radiation and uranium exposure".
Fallout areas listed by the bill included counties in Utah and Nevada:
Utah counties included Millard, Sevier, Beaver, Iron, Washington, Kane, Garfiend, Piute, Wayne, San Juan, Grand, Carbon, Emery, Duchesne, Uintah, San Pete and Juab.
Nevada's "affected areas" were listed as the counties of White Pine, Nye, Lander, Lincoln and Eureka. The Bill as drafted, would have also compensated ranchers whose sheep died following nuclear weapons tests "Harry" (13 May 1959) and "Nancy" (24 May 1953).
Ten years later, Wayne Owens (D–UT introduced , which added uranium miners who worked in Wyoming to the list, and extended the eligible date rate for employed miners to between 1947 and 1971.
Implementation, 1990
Twelve years transpired before the bill was finally enacted. The Radiation Exposure Compensation Act was passed by Congress on October 5, 1990, and signed into law by President George H. W. Bush on October 15, 1990. In the successful bill it was written that Congress "apologizes on behalf of the nation" to individuals who were "involuntarily subjected to increased risk of injury and disease to serve the national security interests of the United States."
In some cases, it proved to be extremely difficult for people to receive their compensation, including cases filed by widows of uranium miners. Because many uranium miners were Native Americans, they did not have standard marriage licenses required to establish a legal connection to the deceased. In 1999, revisions were published in the Federal Register to assist in making award claims. Many mine workers and their families found the paperwork difficult and qualifications narrow and were declined compensation.
Exclusion
People living in the surrounding area near Trinity (the first nuclear test) site in New Mexico were, unlike the Nevada test site, unaware of the project and not included in the 1990 Radiation Exposure Compensation Act support for affected downwinders.
Compensation
The Act provides the following remunerations, as of 2023, unchanged since 1990 despite inflation:
$50,000 to individuals residing or working "downwind" of the Nevada Test Site
$75,000 for workers participating in atmospheric nuclear weapons tests
$100,000 for uranium miners, millers, and ore transporters
Eligibility
In order to be eligible for compensation, an affected uranium industry worker must have developed lung cancer, fibrosis of the lung, pulmonary fibrosis, cor pulmonale related to fibrosis of the lung, silicosis or pneumoconiosis following their employment. In the case of uranium mill workers and ore transporters, renal cancer and chronic renal disease are also compensable conditions.
Amendments and expiration
In 2000, amendments were passed which added two new claimant categories like uranium mill and ore workers, both eligible to receive as much money as uranium miners, added additional geographic regions to the "downwinders" provisions, changed some of the recognized illnesses, and lowered the threshold radiation exposure for uranium miners.
In 2002, additional amendments were passed as part of another bill, primarily fixing a number of draftsmanship errors in the previous amendments which had accidentally removed certain geographic areas from the original act and clarified a number of points.
In 2019, was introduced to extend RECA to 2045, expand downwinder eligibility to include Idaho, Montana, New Mexico, Guam, and Colorado, to expand uranium worker eligibility to those who worked after 1971, until 1990, also covering people involved in the cleanup of Enewetak Atoll of the Marshall Islands from 1977-1981, increase the compensation to $150,000 for all claimants, and to allow people exposed to atmospheric testing to receive the same medical benefits as Department of Energy workers, eligible under the Energy Employees Occupational Illness Compensation Program.
In 2022, the law was to expire, but President Joe Biden extended the filing deadline for another two years until July 2024.
For many years Senator Ben Ray Luján and other members of Congress have attempted to get compensation for those affected by the Trinity test. After the film Oppenheimer brought renewed attention to the test, the United States Senate approved the New Mexico downwinders' inclusion in the RECA amendment. To become law, the bill would also need to be passed by the United States House of Representatives.
Status of claims
It was initially expected that hundreds of compensation claims would be paid under the Act, a figure which later proved to be a gross underestimate.
As of 15 July 2012, 25,804 claims under the act had been approved (with 9,869 denied), expending a total of $1,707,998,044.
As of 19 November 2013, 43,068 claims were filed, 11,619 claims were denied, 748 claims were pending and 30,701 were awarded. These numbers did not include the Marshall Islands.
As of 2 March 2015, over $2 billion in total compensation had been paid to 32,000 successful claimants under the Act.
As of 16 March 2016, successful claims had been awarded to 19,555 downwinders, 3,963 onsite participants, 6,214 uranium miners, 1,673 uranium millers and 328 ore transporters.
As of 20 April 2018, 34,372 claims in total had been approved with total compensation paid at $2,243,205,380.
As of 12 January 2023, 40,274 claims have been approved with total compensation paid at $2,598,374,306. Successful claims include: 25,663 downwinders, 5,388 onsite participants, 6,896 uranium miners, 1,921 uranium millers and 406 ore transporters.
As of 15 July 2024, 41,900 claims have been approved with total compensation paid at $2,693,750,307. Successful claims include: 26,863 downwinders, 5,665 onsite participants, 6,996 uranium miners, 1,956 uranium millers and 420 ore transporters.
See also
Compensation scheme for radiation-linked diseases (United Kingdom)
Uranium mining and the Navajo people
Nuclear weapons and the United States
Pacific Proving Grounds
Radium and radon in the environment
Uranium mining in the United States
Uranium mining debate
Anti-nuclear movement in the United States
Nuclear labor issues
References
External links
Radiation Exposure Compensation Program home page
Radiation Exposure Compensation Act as amended (PDF/details) in the GPO Statute Compilations collection
Nuclear history of the United States
Navajo history
United States federal health legislation
1990 in American law
United States tort law
Occupational safety and health | Radiation Exposure Compensation Act | Chemistry,Materials_science | 1,713 |
64,189,898 | https://en.wikipedia.org/wiki/Lithium%20selenide |
Properties
Lithium selenide is an inorganic compound that formed by selenium and lithium. It is a selenide with a chemical formula Li2Se. Lithium selenide has the same crystal form as other selenides, which is cubic, belonging to the anti-fluorite structure, the space group is , each unit cell has 4 units.
Synthesis
Lithium Selenide can be synthesized via the reaction between 1.0 equivalents of grey elemental selenium and 2.1 equivalents of lithium trialkylborohydride. The reaction takes place in a solution of THF (tetrahydrofuran) under with stirring (minimum of 20 minutes) at room temperature according to the reaction below: To increase yields and harmful byproducts, naphthalene can be added to the reaction as a catalyst.
Se + 2Li(C2H5)3BH → Li2Se + 2(C2H5)3B + H2
Another method of synthesis involves the reduction of selenium with lithium in liquid ammonia. The Li2Se can be extracted after evaporation of the ammonia.
Uses
One of the most contemporary uses of Li2Se compounds is in the creation of high-density capacitors and batteries. Lithium selenide can act as an excellent prelithiation agent, which helps to prevent the loss of capacity and efficiency during the formation of the solid electrolyte interphase (SEI). Additionally, the high relative conductivity and solubility of the products of lithium selenide decomposition makes it an ideal prelithiation agent. No harmful byproducts or gases are created during this decomposition of Li2Se. One potential drawback to the use of Li2Se is the dissolution and shuttle problems inherent to the transition metals like selenide. To avoid this problem, evolving heterostructure materials can be used to inhibit the dissolution and shuttle effects of Li2Se.
References
Lithium compounds
Selenides
Fluorite crystal structure | Lithium selenide | Chemistry | 413 |
57,078,271 | https://en.wikipedia.org/wiki/Cardinal%20tree | A cardinal tree (or trie) of degree k, by analogy with cardinal numbers and by opposition with ordinal trees, is a rooted tree in which each node has positions for an edge to a child. Each node has up to children and each child of a given node is labeled by a unique integer from the set {1, 2, . . . , k}. For instance, a binary tree is a cardinal tree of degree 2.
References
Data types
Trees (data structures)
Knowledge representation
Abstract data types | Cardinal tree | Mathematics | 106 |
59,552,758 | https://en.wikipedia.org/wiki/NGC%20741 | NGC 741, also known as PGC 7252, is a formerly active radio galaxy in the constellation of Pisces. Located 74.13 Mpc away, NGC 741 is part of a group of galaxies including NGC 742 and PGC 7250. NGC 741 and NGC 742 recently collided, although the disruption was minor. Radio filaments have been found connecting NGC 741 to NGC 742, and due to the bent structure of the radio filaments, NGC 741 is estimated to be moving at 1400 km/s with respect to its local group, suggesting that ram-pressure stripping was created as a product of the former merger.
References
External links
Pisces (constellation)
741
Elliptical galaxies
007252
Radio galaxies
01413
4C objects | NGC 741 | Astronomy | 162 |
51,232,766 | https://en.wikipedia.org/wiki/Governing%20equation | The governing equations of a mathematical model describe how the values of the unknown variables (i.e. the dependent variables) change when one or more of the known (i.e. independent) variables change.
Physical systems can be modeled phenomenologically at various levels of sophistication, with each level capturing a different degree of detail about the system. A governing equation represents the most detailed and fundamental phenomenological model currently available for a given system.
For example, at the coarsest level, a beam is just a 1D curve whose torque is a function of local curvature. At a more refined level, the beam is a 2D body whose stress-tensor is a function of local strain-tensor, and strain-tensor is a function of its deformation. The equations are then a PDE system. Note that both levels of sophistication are phenomenological, but one is deeper than the other. As another example, in fluid dynamics, the Navier-Stokes equations are more refined than Euler equations.
As the field progresses and our understanding of the underlying mechanisms deepens, governing equations may be replaced or refined by new, more accurate models that better represent the system's behavior. These new governing equations can then be considered the deepest level of phenomenological model at that point in time.
Mass balance
A mass balance, also called a material balance, is an application of conservation of mass to the analysis of physical systems. It is the simplest governing equation, and it is simply a budget (balance calculation) over the quantity in question:
Differential equation
Physics
The governing equations in classical physics that are
lectured
at universities are listed below.
balance of mass
balance of (linear) momentum
balance of angular momentum
balance of energy
balance of entropy
Maxwell-Faraday equation for induced electric field
Ampére-Maxwell equation for induced magnetic field
Gauss equation for electric flux
Gauss equation for magnetic flux
Classical continuum mechanics
The basic equations in classical continuum mechanics are all balance equations, and as such each of them contains a time-derivative term which calculates how much the dependent variable change with time. For an isolated, frictionless / inviscid system the first four equations are the familiar conservation equations in classical mechanics.
Darcy's law of groundwater flow has the form of a volumetric flux caused by a pressure gradient. A flux in classical mechanics is normally not a governing equation, but usually a defining equation for transport properties. Darcy's law was originally established as an empirical equation, but is later shown to be derivable as an approximation of Navier-Stokes equation combined with an empirical composite friction force term. This explains the duality in Darcy's law as a governing equation and a defining equation for absolute permeability.
The non-linearity of the material derivative in balance equations in general, and the complexities of Cauchy's momentum equation and Navier-Stokes equation makes the basic equations in classical mechanics exposed to establishing of simpler approximations.
Some examples of governing differential equations in classical continuum mechanics are
Hele-Shaw flow
Plate theory
Kirchhoff–Love plate theory
Mindlin–Reissner plate theory
Vortex shedding
Annular fin
Astronautics
Finite volume method for unsteady flow
Acoustic theory
Precipitation hardening
Kelvin's circulation theorem
Kernel function for solving integral equation of surface radiation exchanges
Nonlinear acoustics
Large eddy simulation
Föppl–von Kármán equations
Timoshenko beam theory
Biology
A famous example of governing differential equations within biology is
Lotka-Volterra equations are prey-predator equations
Sequence of states
A governing equation may also be a state equation, an equation describing the state of the system, and thus actually be a constitutive equation that has "stepped up the ranks" because the model in question was not meant to include a time-dependent term in the equation. This is the case for a model of an oil production plant which on the average operates in a steady state mode. Results from one thermodynamic equilibrium calculation are input data to the next equilibrium calculation together with some new state parameters, and so on. In this case the algorithm and sequence of input data form a chain of actions, or calculations, that describes change of states from the first state (based solely on input data) to the last state that finally comes out of the calculation sequence.
See also
Constitutive equation
Mass balance
Master equation
Mathematical model
Primitive equations
References
Equations | Governing equation | Mathematics | 892 |
7,183,054 | https://en.wikipedia.org/wiki/Norilsk%20Nickel | Norilsk Nickel (), or Nornickel, is a Russian nickel and palladium mining and smelting company. Its largest operations are located in the Norilsk–Talnakh area near the Yenisei River in the north of Siberia. It also has holdings in Nikel, Zapolyarny, and Monchegorsk on the Kola Peninsula, in Harjavalta in western Finland, and in South Africa.
Headquartered in Moscow, Norilsk Nickel is the world's largest producer of refined nickel and the 11th largest copper producer.
The company is listed on MICEX-RTS. As of March 2021, its key shareholders were Vladimir Potanin's Olderfrey Holdings Ltd (34.59%) and Oleg Deripaska's Rusal (27.82%).
In December 2010, Norilsk Nickel made a share buyback offer for Rusal's 25% share in the company for $12 billion, but the offer was declined. In 2012, Potanin's Interros holding, Rusal, and Roman Abramovich signed a shareholder agreement on the size of dividend payouts to end a conflict over the matter, as well as issues around the company's broader strategy and management. The agreement expires on June 1, 2023, and the prospects of its extension or suspension are unclear. In March 2019, Abramovich sold a 1.7% stake in the company for $551 million, predominantly to British-based and Russian investors. Potanin and Deripaska's Rusal were blocked from purchasing any shares. In 2021, the company's revenue amounted to 856 billion rubles.
History
Mining began in the Norilsk area in the 1920s. The Soviet government established the Norilsk Combine in 1935 and passed control to the NKVD. In 1943, Norilsk produced 4,000 tonnes of refined nickel and in 1945 hit the target figure of 10,000 tonnes. The mining and metal production originally used forced labour from the Gulag system.
In 1993, after the fall of the Soviet Union, a joint-stock company called RAO Norilsk Nickel was created. Two years later, control over the deeply indebted company, which was bleeding cash at a rate of about $2 million a day against the background of falling nickel prices, was sold to a private company, Interros. By the end of privatization in 1997, the company had moved into the black, and workers were being paid. The current average pay exceeds $1,000 per month with an annual paid leave of two to three months. Nevertheless, the working and living conditions in Norilsk remain harsh, although they are improving as the company shuts down old factories that are the source of excessive pollution.
In July 2000, Norilsk Nickel joined forces with the St. Petersburg Research Institute of the Arctic and Antarctic (), to investigate the potential use of decommissioned nuclear powered submarines, both from the United States and Russia, to transport materials along the Northern Sea Route (). Overhaul and refit costs came to $72–80 million per submarine, which included modifying its ice-breaking bow to cut through ice up to 215 cm (85 in) thick in seawater and up to 150 cm (59 in) in the freshwater mouth of the Yenisei. Decommissioned Typhoon submarines were expected to transport up to 12,000 tonnes of supplies and nickel between Dudinka and either Murmansk or Arkhangelsk. In 2000, the Murmansk Shipping Company (MMP or MSCO) () provided icebreaker services at a charge of $11.35 per tonne of cargo. Three submarines - the project feasibility threshold - were scheduled for refit and overhaul between 2000 and 2003.
However, the stakeholders failed to reach an agreement as to who would conduct and cover the refit and overhaul of the submarines. Furthermore, money was not the only issue. Under the existing international agreements, decommissioned nuclear-powered submarines from the two countries’ navies had to be dismantled. Should this obstacle be addressed, subsequent ownership of the refitted submarines also remained unclear: whether they would remain the assets of the Ministry of Defense or would be transferred to another governmental agency. One of the options suggested by Nornickel was to establish a joint transportation company that would lease the vessels.
In 2002, Nornickel accounted for the most of MMP's shipping along the Northern Sea Route. In 2008, Aker Yards signed a contract with Norilsk Nickel for the delivery of four container/cargo ships for Arctic operations, with an option for a fifth.
In 2002, MMC Norilsk Nickel began purchasing gold mining assets, which were spun off in 2005 as Polyus Gold.
In 2003, the company took control of Stillwater Mining Company, the only palladium producer in the U.S. Stillwater operates a platinum group metals (PGM) facility in Stillwater, Montana. In November 2010, Norilsk Nickel announced the sale of Stillwater.
Throughout 2007, Norilsk acquired a host of mining and metallurgical assets abroad, transforming into a multinational company with operations in Australia, Botswana, Finland, Russia, South Africa, and the United States. Norilsk Nickel signed its key deal on June 28, 2007, acquiring about 90 percent of Canada's LionOre Mining International Ltd, the world's tenth-largest nickel producer at the time. This takeover, valued at $6.4 billion, was the biggest foreign acquisition by a Russian company at the time, making Norilsk Nickel the world's largest nickel producer.
On February 27, 2008, Norilsk Nickel diversified into the coal mining industry through North Star LLC by obtaining mining rights to the amount of 33.6 million rubles for the estimated 5.7 billion tonnes of coal at the Syradasai Field near the port of Dikson () in the Taymyrsky Dolgano-Nenetsky District (). In the coal mining industry, it competed with Rio Tinto and BHP Billiton. By the estimates of North Star LLC (), a firm affiliated with Nornickel, developing the field would require an investment of $1.5 billion, which including the necessary expansion of the port of Dikson, another Nornickel asset. The only competitor for the rights to the Syradasai Field was Golevskaya Mining Company LLC (). The Syradasai Field is 105 to 120 km southeast of Dikson in the Taimyr-Turukhansk support zone (). A 120-kilometer road and railway was expected to connect the deep-sea port on Cape Chaika to the massive coal deposit by 2019. CC VostokUgol () or Vostok Coal planned to export up to 10 million tonnes of coal annually from the open-pit mine to Western Europe and the Asia-Pacific regions.
In 2016 Nornickel ranked below 65 other oil, gas and mining companies in a list of 92 involved in onshore resource extraction above the Arctic Circle, in terms of handling indigenous rights.
In 2018, North Star LLC changed owners to become part of businessman Roman Trotsenko's AEON Group. Neither Nornickel nor AEON disclosed the transfer of ownership terms.
In the Arctic Environmental Responsibility Index (AERI), Norilsk Nickel is ranked No. 38 out of 120 oil, gas, and mining companies involved in resource extraction north of the Arctic Circle.
In April 2024, the United States and the United Kingdom announced a ban on imports of Russian aluminum, copper, and nickel. Due to sanctions, Norilsk Nickel planned to move some of its copper smelting to China and establish a joint venture with a Chinese company. Finished copper products would be sold as Chinese products to avoid Western sanctions. China is Norilsk Nickel's largest export market from 2023. Nickel is a critical metal in electric vehicle batteries, and palladium is critical element in catalytic converters, a component in natural gas vehicles. This plan was motivated not only by circumvent Western sanctions, but also China's significantly less stringent environmental standards than those in Russia.
Operations
Nornickel is Russia's largest non-ferrous metallurgy company and one of the 10 largest private enterprises in the country.
In 2019, the company produced 229,000 tonnes of nickel, 499,000 tonnes of copper, 2.9 million ounces of palladium, and 0.7 million ounces of platinum.
Globally, Nornickel ranks:
First in nickel production (accounting for 14% of global and 96% of Russian production). Bloomberg hails Nornickel as the world's most efficient nickel producer
First in palladium production with a share of 41%
Third in platinum production with a share of 10%
Nornickel also produces rhodium, cobalt, copper, silver, gold, iridium, ruthenium, selenium, tellurium, and sulfur.
Proven and possible reserves:
6.5 million tonnes of nickel
11.6 million tonnes of copper
118 million troy ounces of platinum-group metals
The company's revenue in 2020 reached $15.5 billion, with net profits of $3.6 billion.
Formed 250 million years ago during the eruption of the Siberian Traps igneous province (STIP), the Norilsk-Talnakh nickel deposits are the largest nickel-copper-palladium deposits in the world. The STIP disgorged over 1 million cubic kilometers of lava, a large portion of it through a series of flat-lying lava conduits below Norilsk and the Talnakh Mountains. The Siberian Traps are considered to be responsible for the late-Permian mass extinction event.
The district's first mineral resources were discovered in the 1840s when Alexander von Middendorff's expedition found the local coal deposits. In the 1860s, Friedrich Schmidt described the coal and surface copper ore found in the field that would later be called Norilsk 1. In the early days of the Soviet Union, Nikolay Urvantsev's expeditions revealed several industrially significant deposits. The 1930s saw the construction of the Norilsk Mining and Metallurgy Combine, which remains the pillar of local industry to date. The fields are located along the deep Norilsk-Khatanga Fault, and most mining operations employ underground methods. The area is believed to hold around 35% of the world's known nickel reserves, as well as 10% of its copper, 15% of its cobalt, and 40% of its platinum-group metals. The district's fields are divided into two clusters: the Norilsk Cluster in the southwest and the Talnakh Cluster in the northeast.
In 2022 Norilsk Nickel reiterated its output guidance for the year and said that operations remain uninterrupted. In the first update since the invasion of Ukraine, the miner said first-quarter nickel production increased 10% year-on-year to 52,000 tons. Palladium output declined 8% to 706,000 ounces and platinum fell by 12% to 163,000 ounces, but only from a higher-than-normal level a year ago.
Norilsk Ore Cluster
The cluster is located below Norilsk's city center and to the south of it, in the north-eastern part of the Norilsk Geological Basin. In 2021, Norilsk Nickel estimated the mineral reserves of the cluster at 156.6 million tonnes of ore, 400,000 tonnes of nickel, 600,000 tonnes of copper, and 25.6 million troy ounces of platinum-group metals. The rights to some of the cluster's deposits belong to Russian Platinum, but the corporation is unable to start mining because Nornickel, which controls the remote area's infrastructure, is blocking access. The two conflicting parties have a protracted history of negotiating a joint mining enterprise.
Norilsk 1 Field
The district's first actively developed field is located in the south of Norilsk's city center and to the south of the city. It is 30 to 350 meters thick. The northern part of the deposit consists of two branches: the “Coal Stream” and the “Bear Stream”. Extraction has been ongoing since the 1940s at the Zapolyarny Mine through both underground and open-pit mining of the Coal Stream and Bear Stream quarries. The reserves of its northern section have mostly been depleted, and mining in the Coal Stream quarry has ceased.
Russian Platinum obtained the mining rights to the southern section in 2012 but has not yet used them because of its conflict with Nornickel.
Norilsk 2 Field
The field is located near Mount Gudchikha to the east of Norilsk 1. In 1926, Nikolay Urvantsev discovered copper-nickel ore in the area, and mining began in the 1930s. However, the deposit turned out to be minor, and the decision was made to focus on Norilsk 1. Prospecting continued throughout the 1950s, but after the Talnakh Cluster was discovered, Norilsk 2 was abandoned.
Maslov Field
Located to the south of Norilsk 1, this field is believed to be an offshoot of the latter. Prospecting began here in the 1970s. The field stretches for over six kilometers from north to south and includes the northern and southern sections. Two by four kilometers in size, the northern section is up to 300 meters thick, while the southern estate, which is up to 400 meters thick, has an area of three by 1.5 kilometers[8]. The mining rights to the deposit belong to Nornickel, which in 2019 announced plans to launch an underground mining operation by 2029.
Chernogorskoye Field
The field is located to the east of the Maslov Field near Mount Chernaya. An intrusion with a mineral composition similar to that of Norilsk 1 is up to 200 meters thick. In 2021, Russian Platinum signed a memorandum with VEB.RF and VTB to develop the field. The plans include open-pit mining in the eastern field section with an option for the subsequent underground development of its western part.
Talnakh Ore Cluster
The cluster is located below the Talnakh District and to its northeast, in the southwest of the Kharayelakh Geological Basin. Following the discovery of its rich reserves of copper-and-nickel ore, the cluster became Norilsk's primary source of mineral resources. Its proven resources include over 100 kinds of ore minerals, many of which were previously unknown to science: talnakhite, godlevskite, shadlunite, taimyrite, sobolevskite, mayakite, and more. In 2021, Nornickel assessed the cluster's mineral reserves at 1,5 billion tonnes of ore, 11.2 million tonnes of nickel, 11.2 million tonnes of copper, and 231.7 million troy ounces of platinum-group metals.
Talnakh Field
The field stretches from north to south along the Norilsk-Khatanga Fault and includes its graben and the adjacent intrusions from the east. The primary development facilities are the Mayak, the Komsomolsky, and the Skalisty mines.
Oktyabrskoye Field
The field is located to the west of the Norilsk-Khatanga Fault. The primary development facilities are the Oktyabrsky and the Taimyrsky mines. The Oktyabrsky deposit accounts for about half of Norilsk Nickel's ore production.
Production divisions
The company currently has five core operational divisions in three countries:
The Polar Division of MMC Norilsk Nickel and ancillary activities, located on the Taimyr Peninsula
Kola MMC and ancillary activities, located on the Kola Peninsula (incorporating the Pechenganickel Combine in Nikel and Zapolyarny and the Severonickel Combine in Monchegorsk). The plant in Nikel closed in December 2020.
Norilsk Nickel Harjavalta, Finland's only nickel refining plant, purchased from OM Group in 2007
Norilsk Nickel Africa, which includes stakes in mines in Botswana (85% of Tati Nickel) and in South Africa (50% of Nkomati), both formerly owned by LionOre
Environmental problems
Norilsk Nickel is known to be one of Russia's largest industrial polluters, releasing approximately 1.9 million tonnes of sulfur dioxide into the air annually as of 2020, accounting for 1.9% of global emissions. Ore is smelted on site in Norilsk. The smelting is directly responsible for severe pollution, including acid rain and smog.
The pollution originating from the Kola division of the company was also affecting Norway, which has been offering financial support to clean up the operation since 1990. In December 2020, Norilsk Nickel shut down its old smelter in the town of Nikel on the Russia-Norway border.
In 2008, Rosprirodnadzor (the Federal Environmental, Industrial, and Nuclear Supervision Service of Russia) demanded that a 4.35-billion ruble ($60-million) fine be imposed on Nornickel for polluting minor rivers with wastewater.
The environmental problems at Norilsk stretch back for decades. Back in 2004, oligarch Mikhail Prokhorov claimed that Nornickel would resolve most of the area's environmental issues within 5–6 years. By 2008, this timeline had been moved to 2015. However, Nornickel claims to be a socially responsible business and invests in modernization.
Norilsk Nickel has been working consistently to reduce emissions of major air pollutants. In 2006, the company reported an investment of more than $5 million in the maintenance and overhaul of its dust-and-gas recovery and removal systems. The company asserts a commitment of nearly $1.4 million for its air pollution prevention plan. However, according to the official statistics, emissions remain extremely high. In 2006, Blacksmith Institute, an international non-profit organization, included Norilsk in its list of the world's 10 most polluted places. Nornickel wrote a protest letter but to no avail. According to local environmental experts, in spite of minor reductions in overall pollution levels, the levels of SO2, HS, phenol, formaldehyde, and dust have increased, with the levels of nickel and copper showing 50% growth. The morbidity rate remains stable, though the mortality rate is decreasing.
In 2010, Vladimir Putin visited Norilsk and complained about the pollution, threatening a “significant increase in environmental fines” if the company did not modernize its plant. By 2013, owner Vladimir Potanin had begun to invest in environmental measures. In June 2016, Norilsk shut down one of its factories, which was emitting 380,000 tonnes of sulfur dioxide every year, 25% of the total of sulfur emissions in the city, in an effort to clean up its environmental record. It also said it would invest 300 billion rubles to modernize manufacturing by 2020.
In 2016, Norilsk Nickel admitted that a spillage at one of its facilities had been responsible for a river in the Russian Arctic turning blood-red. The heavy rains on 5 September 2016 caused a filtration dam at the Nadezhda Plant to overflow into the Daldykan River. Indigenous groups have accused the company of lax safety standards.
At the end of 2016, Nornickel signed a contract with Canadian company SNC-Lavalin to introduce sulfur dioxide filtration and storage technologies on its plant in Norilsk in what was lauded as one of the largest environmental projects of its kind. Once the project reached completion in 2020, sulfur emissions dropped by up to 75%.
In April 2018, amid rising pressure from the Russian government and Western investment funds, the company announced its plans to invest in a processing plant worth $1 billion, which would convert sulfur dioxide produced during the metal smelting process into gypsum. The plant will be finished in 2022, in time for the company to meet its target of reducing harmful emissions by 75% and avoid financial fines 100 times higher than the current ones.
In 2019, the group's total environmental protection expenditures were reported to have rocketed by 117.9%. The cornerstone of Nornickel's environmental program is the $3.5-billion SO2 Project. Aimed at recycling toxic SO2 emissions, the goal of the project is to achieve a 75% cut in SO2 emissions in Nornickel's hometown of Norilsk by 2023, growing to 90% by 2025.
In 2020, Nornickel presented a new environmental strategy with ambitious targets to be reached by 2030 in six environmental protection areas. To honor its commitments, the company shut down Kola MMC's smelting shop in Nikel in 2020, eliminating 100% of sulfur dioxide emissions near the Russia-Norway border, followed by its copper smelter in Monchegorsk in March 2021. Combined with Nornickel's other green initiatives, these steps are expected to ensure an 85% decrease in sulfur dioxide pollution in the Murmansk Region by late 2021.
In December 2020, Norilsk Nickel reiterated plans to cut group sulfur dioxide emissions in the Norilsk area by 90% by 2025 from 2015 levels and earmarked $5.5 billion for environmental projects, including $3.6 billion for sulfur dioxide capture and processing.
2020 fuel spill
On May 29, 2020, a Soviet-era fuel storage tank owned by Nornickel subsidiary Norilsk-Taimyr Energy (NTEK) collapsed, flooding the nearby Daldykan River with some 20,000 tonnes of diesel. Russian President Vladimir Putin declared a state of emergency. The diesel oil was intended for the NTEK coal-fired combined heat and power plant as backup fuel. The fuel storage tank failed when the underlying permafrost began to soften. An area of up to 350 square kilometers (135 square miles) was contaminated. The cleanup efforts were complicated by a lack of roads and the river being too shallow for boats or barges to pass. Former deputy head of Rosprirodnadzor Oleg Mitvol estimated the clean-up cost at about 100 billion rubles ($1.5 billion) and set a timeline of five to 10 years. In September 2020, the company reported having collected more than 90% of the leaked fuel.
Environmental Resources Management, the international company which provides Norilsk Nickel with consulting services on environmental issues, identified the cause of the accident as subsidence resulting from the gradual melting of the permafrost on which the piles supporting the fuel storage tank stood. According to the results of the official investigation, some of the piles were shorter than the designed length and rested on the permafrost rather than being sunk into the bedrock. According to specialists, the average annual temperature in Russia is growing more than 2.5–2.8 times faster than the global average. Russia's Far North, including the Taymyr Peninsula, is heating up faster than anywhere else in the country, melting the permafrost on which many structures stand.
However, Zhanna Petukhova, director of the Arctic Permafrost Research Center, says that the tanks do in fact stand on piles driven into the bedrock, rather than the permafrost. She believes the accident is more likely to have been due to the poor condition of equipment dating back to the Soviet era.
In February 2021, the Krasnoyarsk Arbitration Court ordered Nornickel to pay 146 billion rubles ($2 billion) in compensation for the spill damage to support environmental projects in the Krasnoyarsk Territory. Nornickel had claimed the damages should be calculated at 21 billion rubles ($280 million).
Finland
Norilsk Nickel's nickel-cobalt refinery at Harjavalta, western Finland, released 66 tonnes of nickel as nickel sulphate into the local Kokemäenjoki (Kokemäki River) on 5–6 July 2014. Refinery coolant water recirculated from the river was accidentally contaminated by process water over a 30-hour period through an equipment failure. Nickel concentrations were 400 times normal levels, with the accident becoming the largest known leak in Finnish history. Elevated nickel values in river waters were recorded for ~20 days before declining to normal levels.
In December 2020, the company reported, citing a research paper, that the population of mussels in Kokemäenjoki had been recovering, purporting that the water protection measures had been successful and the burden on the river had been reduced.
Carbon footprint
Norilsk Nickel reported Total CO2e emissions (Direct + Indirect) for 31 December 2020 at 9,699 Kt (-253 /-2.5% y-o-y). There is little evidence of a consistent declining trend as yet.
Related organizations
The in St Petersburg is in charge of the design and construction of Nornickel's facilities. Gipronickel does research in every field of metallurgy, including extraction, patenting, design and more.
Norilsk Nickel uses the Yenisei River port of Dudinka to load its finished product on ships for export.
The Moscow-based Interros Holding Company is the controlling shareholder of Nornickel.
Nornickel also attempted to operate Nakety/Bogota, a nickel mine on the island of New Caledonia in the South Pacific, in partnership with Argosy Minerals of Australia but has withdrawn from this project.
In 2016, Nornickel established the Global Palladium Fund to promote industrial demand for palladium and to reduce volatility in the palladium market. The fund's objective is to act as a platform to facilitate cooperation between major palladium holders.
Competition
Nornickel's chief competitors in the production of nickel and of palladium are Vale, BHP and Anglo American Platinum.
Fleet
The company's fleet provides sea transportation of cargo and concentrates from Norilsk to ports with rail connections. In 2008, Norilsk Nickel commissioned the construction of five ice-breaking cargo freighters.
See also
Nickel mining and extraction
Copper mining and extraction
Emily Ann and Maggie Hays nickel mines
London Platinum and Palladium Market
London Metal Exchange
References
External links
The Moscow Times: Norilsk Nickel withdraws from Nakety Bogota project
MBendi's MMC Norilsk Nickel information page
The Metallurgical Complex at Norilsk in Siberia
JSC MMC Norilsk Nickel Company History
Russian metals firm admits spillage turned river blood red The Guardian, 2016.
Mining companies of Russia
Nickel mining companies
Copper mining companies of Russia
Palladium mining companies
Platinum mining companies
Companies based in Moscow
Krasnoyarsk Krai
Non-renewable resource companies established in 1993
1993 establishments in Russia
Companies listed on the Moscow Exchange
Companies in the MOEX
Norilsk
Vladimir Potanin | Norilsk Nickel | Chemistry | 5,531 |
31,281,413 | https://en.wikipedia.org/wiki/Gobar%20Times | Gobar Times is a monthly environmental education magazine for the young adult, published by the Centre for Science and Environment. It is published along with Down to Earth as a supplement. The magazine was first published in May, 1998 and has widespread circulation across India and abroad. The icon of the magazine, Pandit Gobar Ganesh, the pondering panditji is an Indian elderly who takes the reader through current issues, subjects and ideas relating to the environment. He is the icon whose brains can be picked for anything on earth. The current editor of the magazine is Sorit Gupto.
"Gobar" is the Hindi and Nepali word for "cow dung". It was chosen to capture the eco-philosophy and tradition of generating wealth from waste. Waste gobar serves as an insecticide and is used to plaster mud houses and is a waterproof coating for walls. It is also used to plaster floors to keep them cool. Gobar is the energy source for rural India. It is used as cooking fuel where people have no access to fuels like LPG. The greatest use of cow dung in India is in farming where it is used as natural manure for farmers' crops. In short, it's a mainstay of rural India, and an appropriate symbol for eco-friendly technology.
Anil Agarwal the founder-director of Centre for Science and Environment, India’s leading environmental NGO, aptly called ‘Gobar’ the symbol that embodies the spirit of the Indian environmental movement. As he correctly reflected, the widespread and diverse use of gobar in Indian society stands up to every principle of good environmentalism.
History
In May 1992, the Society for Environmental Communications started India’s only science and environment fortnightly, Down To Earth (DTE). Over the years the magazine has informed and inspired people about environmental threats facing India and the world - a dimension underplayed in mainstream media. In May, 1998, Gobar Times was first published as a supplement to DTE. Gobar Times reaches out to the young, encouraging them to take the lead and make a difference. It informs them and encourages them to save the environment by becoming an action-oriented, knowledgeable and aware community. The tone of the magazine is light-hearted, simple and thought-provoking. Every month the magazine comes up with an activity related center spread which can be pulled out and put up as a poster to encourage readers to become active participants. The magazine has recently entered into a partnership with the leading newspaper Hindustan Times. Readers can now get a glimpse of what Pandit Gobar Ganesh has to say as they read HTNext.
Green Schools Program
Conceptualized by the New Delhi–based Centre for Science and Environment(CSE), The Gobar Times Green Schools Program allows self-assessment of the environmental practices of a school by its students, using the "Green Schools Manual". This inspection or survey of environmental practices at schools is a way for them to audit their immediate environment across the key areas of water, air, land, energy and waste.
Water: To make the school water literate and teach ways of rainwater harvesting and recycling of waste water.
Air: Students check out the transport system of the school and understand how people commute to school. This further enables them to understand how transport policies affect air quality and how they can innovate and find ways of reducing emissions.
Land: The different plant and animal species on the school campus are identified by the students and a survey done on the use of pesticides in the school. Understanding the concept of carrying capacity.
Energy: The students study electricity and other forms of energy consumption on the school campus and explore ways in which it can be minimized.
Waste: Students find out how much and what type of waste the school is producing? Learn composting and waste segregation methods in the process.
Food: To make the students more conscious of the kind of food being promoted and consumed.
By the end of it all the program gives the students an opportunity to give a report card to the school on its environmental performance and practices. They conduct the audit with the help of an interesting handbook called the 'Green Schools Program Manual' (2019 Edition). This manual gives them step by step guidelines on how to conduct an environmental audit in the school.
The purpose of the Green Schools Program is to encourage and support schools to build up an environmentally aware, active and skilled community of teachers, students and parents. The schools may use the manual as part of their environmental studies program or to conduct activities in eco-clubs. The data collected by students is compiled and rated such that it becomes a self-assessment tool of environmental practices followed by the school. The aim of the rating is, to understand what can be done to improve the schools performance on its environmental sustainability index and to implement measurable changes over the coming years.
Awards
The Gobar Times Green Schools Awards is a platform to acknowledge and reward schools that have adopted the most innovative and effective practices to manage natural resources within their own premises. Schools send in their green reports to CSE. These reports undergo rigorous verification and selection and the best schools are awarded annually.
The top 10 schools of the country which have been working and have implemented tremendous improvement in their environmental practices are awarded the 'Change Makers' award. Schools participating for the first time are considered in the 'New Schools' category. They are judged basis involvement of students and teachers, and the quality of the reports submitted. Also schools which do not necessarily audit all areas but do exceptionally well in a single specific area of water, energy, land, air or waste apply for the coveted 'Best Managers' award.
Partners
The National Green Corps is a program of the Ministry of Environment and Forest, Government of India). State nodal offices and CSE partner in many states across India. As the Green Schools network is expanding, the awards are now also organized at the state level. The most resource efficient schools at the state level in different categories are nominated by state nodal agencies to compete for national awards with CSE in Delhi.
References
External links
Green Schools Programme - Official Website
Gobar Times - Official Website
Centre for Science and Environment- Official Website
1998 establishments in Delhi
Children's magazines published in India
Nature conservation in India
Education magazines
English-language magazines published in India
Environmental education
Environmental magazines
Magazines established in 1998
Magazines published in Delhi
Monthly magazines published in India | Gobar Times | Environmental_science | 1,297 |
33,032,599 | https://en.wikipedia.org/wiki/Bill%20Robinson%20%28scientist%29 | William Henry Robinson (2 October 1938 – 17 August 2011) was a New Zealand scientist and seismic engineer who invented the lead rubber bearing seismic isolation device. He grew up in West Auckland, New Zealand. He earned a master's degree at the Ardmore School of Engineering, then a PhD in physical metallurgy at the University of Illinois. Robinson was director of the DSIR's Physics and Engineering Laboratory between 1985 and 1991. He continued to invent and develop seismic isolation devices, travel and lecture until his early 70s.
Life's work
Robinson is most well known for his invention of the lead rubber bearing (LRB) seismic isolation device. He designed the LRB in 1974 while working as a scientist for DSIR (Department of Scientific and Industrial Research, New Zealand). As he was a public service employee when he invented the device, the LRB patent was owned by the state. The LRB is used under more than US$100 billion worth of structures around the world, including New Zealand's Te Papa Tongarewa (National Museum of New Zealand), the new Wellington Hospital, Victoria University Library and Parliament Buildings. Most significant bridges in NZ use base isolation technology.
LRBs are also under the Bhuj Hospital (India) and the C-1 building (Tokyo)—the largest building in the world that is protected by these devices. The Christchurch Women's Hospital is the only building in that city that uses LRBs and it was able to continue operating without any problems throughout the devastating earthquakes that occurred between September 2010 and June 2011.
During the severe 1994 Northridge earthquake in Los Angeles, the LRB-protected University of Southern California Teaching Hospital remained operational while the ten other hospitals in the area were so badly damaged that they had to be evacuated.
The William Clayton building in Wellington, New Zealand, was the first in the world to be base isolated with LRBs. It was built by the then Ministry of Works and Development.
The Ministry of Post and Telecommunications Computer Centre came through the 1995 Kobe quake unscathed and remained fully operational. This significant building is one that is pointed to as an example of how the lead rubber bearing technology saves a building and its contents. Following the Kobe quake there was a large uptake of seismic isolation technology and in particular the Lead Rubber Bearing in Japan.
The second region in which these devices have been well used is California, following the Los Angeles and Northridge earthquake in 1994. The first use of an LRB in the USA was in 1984. Base isolators have since been inserted under more than 100 bridges and 70 buildings in the USA. Building codes in that country require all new hospitals to implement base isolation technology to ensure that they can continue functioning after a major quake.
In more recent years severe earthquakes in India and Turkey have generated interest in seismic isolation technology and many new buildings and bridges are being fitted with seismic isolation.
The costs of using base isolation for large structures have been found to be recouped in only a few years as insurance premiums are reduced so dramatically.
Robinson also invented the Roball and the Roglider base isolation systems for medium-weight and low rise buildings, and the Lead Extrusion Damper, among other seismic isolation devices. He was founder, director and chief engineer of the world-leading seismic engineering company Robinson Seismic Ltd., which continues to test and manufacture his devices. In 1993 Robinson was co-author of An Introduction to Seismic Isolation, along with Ivan Skinner and Graeme McVerry.
Life
Robinson grew up in Auckland, where he attended Avondale College. After completing a master's degree in mechanical engineering at the University of Auckland's Ardmore campus, between 1958 and 1961, Robinson completed a PhD in Physical Metallurgy at the University of Illinois between 1962 and 1965, his thesis titled "High Temperature Internal Friction (Damping) in Potassium Chloride". During his time at Illinois, he spent a summer learning German so that he could complete the necessary reading for his research topic, due to the fact that a lot of important material in the field was published only in German. Following this he spent a short time as a research fellow in physics at the University of Sussex, from 1966 until 1967.
After returning to New Zealand in 1967 Robinson joined the DSIR Physics and Engineering Laboratory (PEL) as a scientist. His work included developing experimental techniques using ultrasonics in solid state physics and initiating a research programme in the Antarctic on sea ice (where he spent a few summers between 1978 and 1989). He also worked at the Scott Polar Research Institute in 1981–1982 (Cambridge, UK). He later became director of PEL (1985–91) and showed particular foresight in giving his full support to the new field of the High Temperature Superconductivity programme.
At the age of 52, Robinson suffered from a near-fatal stroke, spending 4 and a half months in hospital rehabilitation. His "indomitable spirit" enabled him to re-learn how to walk, write and drive, and within six months of the stroke he was back at work as a scientist. In 1995 he founded Robinson Seismic Ltd. to promote, develop and manufacture his seismic protection devices. He semi-retired during his 60s, spending most of his time on a lifestyle farm overlooking the Pacific Ocean, but continued to lecture, travel and develop his seismic engineering ideas part-time.
Robinson married in his early 20s and had three children.
Honours and awards
Robinson was a Fellow of the Royal Society of New Zealand. He was awarded: the Rutherford Medal (the Royal Society Gold Medal for Technology, 1999); an Honorary DSc from Victoria University of Wellington (1995); the Hutton Medal (NZ Institute of Physics, 1992); the ER Coopers Medal for Engineering Research (NZ Royal Society, 1991); the Michaelus Medal for Physics (University of Otago, 1976). He was appointed a Companion of the Queen's Service Order, for services to engineering, in the 2007 Queen's Birthday Honours.
The Robinson Research Institute was formed at Victoria University of Wellington in 2014, and "named to honour the late Dr Bill Robinson—inspirational scientist, seismic engineer and early champion of HTS [high-temperature superconductivity] technology".
In popular culture
On 2 October 2019, Google honoured Robinson by celebrating what would have been his 81st birthday with a Google Doodle.
References
External links
Building for earthquake resistance at Te Ara: The Encyclopedia of New Zealand.
Robinson Seismic - Our Story
Biography at Science Learn NZ
1938 births
2011 deaths
Earthquake engineering
Recipients of the Rutherford Medal
Scientists from Auckland
University of Auckland alumni
University of Illinois alumni
Companions of the Queen's Service Order
20th-century New Zealand scientists
20th-century New Zealand engineers
People of the Scott Polar Research Institute | Bill Robinson (scientist) | Engineering | 1,372 |
3,997,452 | https://en.wikipedia.org/wiki/RIAA%20equalization | RIAA equalization is a specification for the recording and playback of phonograph records, established by the Recording Industry Association of America (RIAA). The purposes of the equalization are to permit greater recording times (by decreasing the mean width of each groove), to improve sound quality, and to reduce the groove damage that would otherwise arise during playback.
The RIAA equalization curve was intended to operate as a de facto global industry standard for records since 1954, but when the change actually took place is difficult to determine.
Before then, especially from 1940, each record company applied its own equalization; over 100 combinations of turnover and rolloff frequencies were in use, the main ones being Columbia-78, Decca-U.S., European (various), Victor-78 (various), Associated, BBC, NAB, Orthacoustic, World, Columbia LP, FFRR-78 and microgroove, and AES. The obvious consequence was that different reproduction results were obtained if the recording and playback filtering were not matched.
The RIAA curve
RIAA equalization is a form of pre-emphasis on recording and de-emphasis on playback. A recording is made with the low frequencies reduced and the high frequencies boosted, and on playback, the opposite occurs. The net result is a flat frequency response, but with attenuation of high-frequency noise such as hiss and clicks that arise from the recording medium. Reducing the low frequencies also limits the excursions the cutter needs to make when cutting a groove. Groove width is thus reduced, allowing more grooves to fit into a given surface area, permitting longer recording times. This also reduces physical stresses on the stylus, which might otherwise cause distortion or groove damage during playback.
A potential drawback of the system is that rumble from the playback turntable's drive mechanism is amplified by the low-frequency boost that occurs on playback. Players must, therefore, be designed to limit rumble, more so than if RIAA equalization did not occur.
RIAA playback equalization is not a simple low-pass filter. It defines transition points in three places: 75 μs, 318 μs and 3180 μs, which correspond to 2122 Hz, 500.5 Hz and 50.05 Hz.
Mathematically, the pre-emphasis transfer function is expressed as follows, where T1=3180 μs, T2=318 μs, T3=75 μs:
Implementing this characteristic is not especially difficult, but is more involved than a simple amplifier. Practically every 20th century hi-fi preamplifier, integrated amplifier and receiver featured a built-in phono preamplifier with the RIAA characteristic. As more modern designs omitted the phonograph inputs, add-on phono preamplifiers with the RIAA equalization curve have become available. These adapt a magnetic phono cartridge to an unbalanced −10 dBv consumer line-level RCA input. Some modern turntables feature built-in preamplification to the RIAA standard. Special preamplifiers are also available for the various equalization curves used on pre-1954 records.
Digital audio editors often feature the ability to equalize audio samples using standard and custom equalization curves, removing the need for a dedicated hardware preamplifier when capturing audio with a computer. However, this can add an extra step in processing a sample, and may amplify or reduce audio quality deficiencies of the sound card being used to capture the signal.
History
Origins of pre-emphasis
Equalization practice for electrical recordings dates to the beginning of the art. In 1926, Joseph P. Maxwell and Henry C. Harrison from Bell Telephone Laboratories disclosed that the recording pattern of the Western Electric "rubber line" magnetic disc cutter had a constant-velocity characteristic. This meant that as frequency increased in the treble, recording amplitude decreased. Conversely in the bass, as frequency decreased, recording amplitude increased. Therefore, attenuating the bass frequencies was necessary below about 250 Hz, the bass turnover point, in the amplified microphone signal fed to the recording head. Otherwise, bass modulation became excessive and overcutting took place, with the cutter getting into the next record groove. When played back electrically with a magnetic pickup having a smooth response in the bass region, a complementary boost in amplitude at the bass turnover point was necessary. G. H. Miller in 1934 reported that when complementary boost at the turnover point was used in radio broadcasts of records, the reproduction was more realistic and many of the musical instruments stood out in their true form.
West in 1930 and later P. G. H. Voight (1940) showed that the early Wente-style condenser microphones contributed to a 4- to 6-dB midrange brilliance or pre-emphasis in the recording chain. This meant that the electrical recording characteristics of Western Electric licensees such as Columbia Records and Victor Talking Machine Company had a higher amplitude in the midrange region. Brilliance such as this compensated for dullness in many early magnetic pickups having drooping midrange and treble response. As a result, this practice was the empirical beginning of using pre-emphasis above 1,000 Hz in 78 and 33 rpm records, some 29 years before the RIAA curve.
Over the years, a variety of record equalization practices emerged, with no industry standard. For example, in Europe, for many years recordings required playback with a bass turnover setting of 250 to 300 Hz and a treble rolloff at 10,000 Hz ranging from 0 to −5 dB, or more. In the United States, practices varied and a tendency arose to use higher bass turnover frequencies, such as 500 Hz, as well as a greater treble rolloff such as −8.5 dB, and more. The purpose was to record higher modulation levels on the record.
Standardization
Evidence from the early technical literature concerning electrical recording suggests that serious efforts to standardize recording characteristics within an industry did not occur until 1942–1949. Before this time, electrical recording technology from company to company was considered a proprietary art all the way back to the 1925 Western Electric licensed method first used by Columbia and Victor. For example, what Brunswick did was different from the practices of Victor.
Broadcasters were faced with having to adapt daily to the varied recording characteristics of many sources - various makers of "home recordings" readily available to the public, European recordings, lateral cut transcriptions, and vertical cut transcriptions. Efforts were started in 1942 to standardize within the National Association of Broadcasters (NAB), later known as the National Association of Radio and Television Broadcasters. The NAB, among other items, issued recording standards in 1942 and 1949 for laterally and vertically cut records, principally transcriptions. A number of 78 rpm record producers, as well as early LP makers, also cut their records to the NAB lateral standard.
The lateral-cut NAB curve was remarkably similar to the NBC Orthacoustic curve, which evolved from practices within the National Broadcasting Company since the mid-1930s. Empirically, and not by any formula, the bass end of the audio spectrum below 100 Hz could be boosted somewhat to override system hum and turntable rumble noises. Likewise at the treble end beginning at 1,000 Hz, if audio frequencies were boosted by 16 dB at 10,000 Hz the delicate sibilant sounds of speech and high overtones of musical instruments could be heard despite the high background noise of shellac discs. When the record was played back using a complementary inverse curve (de-emphasis), signal-to-noise ratio was improved and the programming sounded more lifelike.
In a related area, around 1940 treble pre-emphasis similar to that used in the NBC Orthacoustic recording curve was first employed by Edwin Howard Armstrong in his system of frequency modulation (FM) radio broadcasting. FM radio receivers using Armstrong circuits and treble de-emphasis would render high-quality, wide-range audio output with low noise levels.
When the Columbia LP was released in June 1948, the developers subsequently published technical information about the 33 rpm, microgroove, long-playing record. Columbia disclosed a recording characteristic showing that it was like the NAB curve in the treble, but had more bass boost or pre-emphasis below about 150 Hz. The authors disclosed electrical network characteristics for the Columbia LP curve. Nevertheless, the curve was not yet based on mathematical formulae, at least not explicitly.
In 1951, at the beginning of the post-World War II high fidelity (hi-fi) popularity, the Audio Engineering Society (AES) developed a standard playback curve. This was intended for use by hi-fi amplifier manufacturers. If records were engineered to sound good on hi-fi amplifiers using the AES curve, this would be a worthy goal towards standardization. This curve was defined by the transition frequencies of audio filters and had a pole at 2.5 kHz (approximately 63.7 μs) and a zero at 400 Hz (approximately 397.9 μs).
RCA Victor and Columbia were in a "market war" concerning which recorded format was going to win: the Columbia LP versus the RCA Victor 45 rpm disc (released in February 1949). Besides also being a battle of disc size and record speed, there was a technical difference in the recording characteristics. RCA Victor was using "New Orthophonic", whereas Columbia was using their own LP curve.
Ultimately, the New Orthophonic curve was disclosed in a publication by R. C. Moyer of RCA Victor in 1953; additional background information about this evolution can also be found in another article of the same author, published in 1957. He traced the RCA Victor characteristics back to the Western Electric "rubber line" recorder in 1925 up to the early 1950s laying claim to long-held recording practices and reasons for major changes in the intervening years. The RCA Victor New Orthophonic curve was within the tolerances for the NAB/NARTB, Columbia LP, and AES curves. It eventually became the technical predecessor to the RIAA curve.
Between 1953 and 1956 (before the stereo LP in 1958), several standards bodies around the world adopted the same playback curve—identical to the RCA Victor New Orthophonic curve—which became standard throughout the national and international record markets. However, although these standards were all identical, no universal name was used. One of the standards was called simply "RIAA", and it is likely that this name was eventually adopted because it was memorable.
Some niche record cutters possibly were still using EQ curves other than the RIAA curve well into the 1970s. As a result, some audio manufacturers today produce phono equalizers with selectable EQ curves, including options for Columbia LP, Decca, CCIR, and TELDEC's Direct Metal Mastering.
The Mythical "Neumann pole"
The official RIAA standard defines three time-constants with pre-emphasis rising indefinitely above 75 μs, but in practice this is not possible. When the RIAA equalization standard was written the inherent bandwidth limitations of the recording equipment and cutting amplifier imposed their own ultimate upper limit on the pre-emphasis characteristic, so no official upper limit was included in the RIAA definition.
Modern systems have far wider potential bandwidth. An essential feature of all cutting amplifiers—including the Neumann cutting amplifiers—is a forcibly imposed high frequency roll-off above the audio band (>20 kHz). This implies two or more additional time constants to those defined by the RIAA curve. This is not standardized anywhere, but set by the maker of the cutting amplifier and associated electronics.
The so-called "Neumann pole" attempts to provide complementary correction for these unofficial time constants upon playback. However, there is no such pole.
Background
In 1995, an unqualified source erroneously suggested that Neumann cutting amplifiers applied a single high-frequency zero at 3.18 μs (about 50 kHz) and that a complementary zero should therefore be included upon playback. However, no such zero exists.
For example, the RIAA pre-emphasis in the popular Neumann SAB 74B equalizer applies a second-order roll off at 49.9 kHz, implemented by a Butterworth (maximally flat) active filter, plus an additional pole at 482 kHz. This cannot be compensated for by a simple zero even if it were necessary, and in any case, other amplifiers will differ. Correction upon playback is not, in fact, required, as it is taken into account at the cutting stage when manual equalization is applied while monitoring initial cuts on a standard RIAA playback system. Nevertheless, the use of the erroneous zero, misnamed "pole", remains a subject of some debate among amateur enthusiasts.
Many common phono preamplifier designs using negative feedback equalization include an unintentional zero at high frequencies, caused by using series negative feedback around a non-inverting gain stage, which cannot reduce the gain below 1. This was noted in the Lipshitz JAES paper, as t6, with equations and RC networks for a solution: all of which was missed by Wright, who claimed it was not mentioned by Lipshitz. This solution is implemented in some but not all affected phono preamplifiers.
IEC RIAA curve
In 1976, an alternative version of the replay curve (but not the recording curve) was proposed by the International Electrotechnical Commission, differing from the RIAA replay curve only in the addition of a pole at 7950 μs (approximately 20 Hz). The justification was to reduce the subsonic output of the phono amplifier caused by disk warp and turntable rumble.
This so-called IEC amendment to the RIAA curve is not universally seen as desirable, as it introduces considerable amplitude and—of more concern—phase errors into the low-frequency response during playback. The simple first-order roll-off also provides only very mild reduction of rumble, and many manufacturers consider that turntables, arm, and cartridge combinations should be of sufficient quality for problems not to arise.
Some manufacturers follow the IEC standard, others do not, while the remainder make this IEC-RIAA option user selectable. It remains subject to debate some 35 years later. This IEC Amendment was withdrawn in June 2009, though.
TELDEC/DIN Curve
Telefunken and Decca founded a record company (Teldec) that used a characteristic which was also proposed for German DIN standards in July 1957 (Entwurf DIN 45533, DIN 45536, and DIN 45537). Incidentally, this proposed standard defined exactly the same characteristic as the intermediate CCIR Recommendation No. 208 of 1956, which was valid until about mid-1959. Nevertheless, the proposed DIN standards were was adopted in April 1959 (DIN 45533:1959, DIN 45536:1959, and DIN 45537:1959): that is, at a time when the RIAA characteristic was already well-established; and it was in effect until November 1962, when the German DIN finally adopted the RIAA characteristic (DIN 45536:1962 and DIN 45537:1962). The extent of usage of the Teldec characteristic is unclear, though.
The time constants of the Teldec characteristic are 3180 μs (approximately 50 Hz), 318 μs (approximately 500 Hz), and 50 μs (approximately 3183 Hz), thus differing only in the third value from the corresponding RIAA values. Although the Teldec characteristic is close to the RIAA characteristic, it is different enough for recordings recorded with the former and played back with the latter to sound a little dull.
References
Notes
Bibliography
Powell, James R., Jr. The Audiophile's Technical Guide to 78 RPM, Transcription, and Microgroove Recordings. 1992; Gramophone Adventures, Portage, MI.
Powell, James R., Jr. Broadcast Transcription Discs. 2001; Gramophone Adventures, Portage, MI.
Powell, James R., Jr. and Randall G. Stehle. Playback Equalizer Settings for 78 RPM Recordings. Second Edition. 1993, 2001; Gramophone Adventures, Portage, MI.
External links
Playback equalization for 78rpm shellacs and pre-RIAA LPs (EQ curves, index of record labels): Audacity Wiki
Description and diagrams of RIAA equalization curve
Sample passive filter designs
Equalization
Audio engineering
Recorded music
Audio storage | RIAA equalization | Engineering | 3,333 |
72,147,712 | https://en.wikipedia.org/wiki/Porsche%20V4%20engine | The Porsche V4 engine is a two-liter, four-stroke, mono-turbocharged, V-4, racing engine, designed, developed, and built by German manufacturer Porsche, for their 919 Hybrid sports car prototype, between 2014 and 2017.
Background
The compact and lightweight engine was a 90-degree V4 cylinder bank mid-mounted mono-turbocharged petrol engine. It ran at 9,000 rpm, with performance coming from a direct fuel-injection system and a single Garrett-designed turbocharger with a dual overhead camshaft. It produced approximately and acted as a chassis load-bearing member. Due to the small size of the engine, the transmission casing was fitted to the rear suspension and was almost a third of the car's length. Engine air ingestion was achieved through a carbon-fiber-and-gold thermal wrapped airbox in its center. Front airflow was enabled by louvers along its flank, and a single curved roll-hoop intake was mounted on its roof to feed the carbon-fiber airbox.
Applications
Porsche 919 Hybrid
References
Porsche
Engines by model
Gasoline engines by model
Porsche in motorsport
V4 engines | Porsche V4 engine | Technology | 235 |
1,367,595 | https://en.wikipedia.org/wiki/Elemental%20analysis | Elemental analysis is a process where a sample of some material (e.g., soil, waste or drinking water, bodily fluids, minerals, chemical compounds) is analyzed for its elemental and sometimes isotopic composition. Elemental analysis can be qualitative (determining what elements are present), and it can be quantitative (determining how much of each is present). Elemental analysis falls within the ambit of analytical chemistry, the instruments involved in deciphering the chemical nature of our world.
History
Antoine Lavoisier is regarded as the inventor of elemental analysis as a quantitative, experimental tool to assess the chemical composition of a compound. At the time, elemental analysis was based on the gravimetric determination of specific absorbent materials before and after selective adsorption of the combustion gases. Today fully automated systems based on thermal conductivity or infrared spectroscopy detection of the combustion gases, or other spectroscopic methods are used.
CHNX analysis
For organic chemists, elemental analysis or "EA" almost always refers to CHNX analysis—the determination of the mass fractions of carbon, hydrogen, nitrogen, and heteroatoms (X) (halogens, sulfur) of a sample. This information is important to help determine the structure of an unknown compound, as well as to help ascertain the structure and purity of a synthesized compound. In present-day organic chemistry, spectroscopic techniques (NMR, both 1H and 13C), mass spectrometry and chromatographic procedures have replaced EA as the primary technique for structural determination. However, it still gives very useful complementary information.
The most common form of elemental analysis, CHNS analysis, is accomplished by combustion analysis. Modern elemental analyzers are also capable of simultaneous determination of sulfur along with CHN in the same measurement run.
Quantitative analysis
Quantitative analysis determines the mass of each element or compound present. Other quantitative methods include gravimetry, optical atomic spectroscopy, and neutron activation analysis.
Gravimetry is where the sample is dissolved, the element of interest is precipitated and its mass measured, or the element of interest is volatilized, and the mass loss is measured.
Optical atomic spectroscopy includes flame atomic absorption, graphite furnace atomic absorption, and inductively coupled plasma atomic emission spectroscopy, which probe the outer electronic structure of atoms.
Neutron activation analysis involves the activation of a sample matrix through the process of neutron capture. The resulting radioactive target nuclei of the sample begin to decay, emitting gamma rays of specific energies that identify the radioisotopes present in the sample. The concentration of each analyte can be determined by comparison to an irradiated standard with known concentrations of each analyte.
Qualitative analysis
To qualitatively determine which elements exist in a sample, the methods are mass spectrometric atomic spectroscopy, such as inductively coupled plasma mass spectrometry, which probes the mass of atoms; other spectroscopy, which probes the inner electronic structure of atoms such as X-ray fluorescence, particle-induced X-ray emission, X-ray photoelectron spectroscopy, and Auger electron spectroscopy; and chemical methods such as the sodium fusion test and Schöniger oxidation.
Analysis of results
The analysis of results is performed by determining the ratio of elements from within the sample and working out a chemical formula that fits with those results. This process is useful as it helps determine if a sample sent is the desired compound and confirms the purity of a compound. The accepted deviation of elemental analysis results from the calculated is 0.3%.
See also
Dumas method of molecular weight determination
References
Analytical chemistry
Materials science | Elemental analysis | Physics,Chemistry,Materials_science,Engineering | 738 |
57,701,673 | https://en.wikipedia.org/wiki/CD28%20family%20receptor | CD28 family receptors are a group of regulatory cell surface receptors expressed on immune cells. The CD28 family in turn is a subgroup of the immunoglobulin superfamily.
Two family members, CD28 and ICOS, act as positive regulators of T cell function while another three, BTLA, CTLA-4 and PD-1 act as inhibitors. Ligands for the CD28 receptor family include B7 family proteins.
CD28 receptors play a role in the development and proliferation of T cells. The CD28 receptors enhance signals from the T cell receptors (TCR) in order to stimulate an immune response and an anti-inflammatory response on regulatory T cells. Through the promotion of T cell function, CD28 receptors allow effector T cells to combat regulatory T cell-mediated suppression from adaptive immunity. CD28 receptors also elicit the prevention of spontaneous autoimmunity.
Function
CD28 receptors aid in other T cell processes such as cytoskeletal remodeling, production of cytokines and chemokines and intracellular biochemical reactions (i.e. phosphorylation, transcriptional signaling, and metabolism) that are key for T cell proliferation and differentiation. Ligation of CD28 receptors causes epigenetic, transcriptional and post-translational alterations in T cells. Specifically, CD28 costimulation controls many aspects within T cells, one being the expression of proinflammatory cytokine genes. A particular cytokine gene encodes for IL-2, which influences T cell proliferation, survival, and differentiation. The absence of CD28 costimulation results in the loss of IL-2 production causing the T cells to be anergic. Additionally, CD28 ligation causes arginine-methylation for many proteins. CD28 also drives transcription within T cells and produce signals that lead to IL-2 production and Bcl-xL regulation, an antiapoptotic protein, which are essential for T cell survival. CD28 receptors can be seen on 80% of human CD4+ and 50% of CD8+ T cells, in which this percentage decreases with age.
Clinical significance
Cancer
Some cancer cells evade destruction by the immune system through an of B7 ligands that bind to inhibitory CD28 family member receptors on immune cells. Antibodies directed against CD28 family members CTLA-4, PD-1, or their B7 ligands function as checkpoint inhibitors to overcome tumor immune tolerance and are clinically used in cancer immunotherapy.
Additionally, genetically engineered T cells containing CD28 and CD137 can be used in a molecularly targeted therapy response to a type of carcinomas called mesothelin. These T cells have a high affinity for human mesothelin. Upon mesothelin stimulation, the T cells proliferate, express an antiapoptotic gene, and secrete cytokines with the help of CD28 expression. When introduced to mice with pre-existing tumors, these T cells remove the tumors completely. The CD137 presence within the cells maintains the persistence of the engineered T cells. This interaction between engineered T cells with CD28 and CD137 are essential for immunotherapy, and show promise for directing T lymphocytes to tumor antigens and altering the tumor microenvironment for mesothelin.
HIV
The CD28 pathway is targeted by the human immunodeficiency virus (HIV) as the virus infects large numbers of normal cells. CD28 has effects on the transcription and stability of interleukin-2 and IFN-γ, cytokines that are important for immunity and stimulating NK cells. HIV alters the CD28 signaling as well as CD8 cells. As a result, there are reduced levels of CD8 cells, which express CD28, in individuals with HIV. With regards to subjects with both Hepatitis C Virus (HCV) and HIV, levels of CD8 cells are also reduced. CD28 signaling has a large role in the adaptive response to HCV and can increase morbidity for HCV/HIV coinfection within a subject. CD28 induces IL-2 secretion that increases IL-2 mRNA stability. CD28 costimulation influences the expression of key genes expressed in T cell differentiation. Tat, a regulatory protein that regulates viral transcription, increases the transcription of the HIV dsDNA. CD28 costimulation with the Tat protein can contribute to chronic immune hyperactivation seen among HIV-infected individuals. Thus, CD28 is an essential part of therapeutics for the infection and pathogenesis of HIV.
Hyper-induced inflammatory cytokines
Binding CD28 to superantigens can induce an overexpression of inflammatory cytokines which may be harmful. When CD28 interacts with coligand B7-2, these superantigens elicit T-cell hyperactivation. Superantigens can form this overexpression by controlling interactions between MHC-II and TCRs as well as increasing the B7-2 and CD28 costimulatory interactions. This is dangerous because the overexpression of inflammatory cytokines can cause toxic shock in an individual.
References
Receptors
Immunoglobulin superfamily
Immunology | CD28 family receptor | Chemistry,Biology | 1,083 |
59,844,792 | https://en.wikipedia.org/wiki/International%20Conference%20on%20Concurrency%20Theory | The International Conference on Concurrency Theory (CONCUR) is an academic conference in the field of computer science, with focus on the theory of concurrency and its applications. It is the flagship conference for concurrency theory according to the International Federation for Information Processing Working Group on Concurrency Theory (WP 1.8). The conference is organised annually since 1988. Since 2015, papers presented at CONCUR are published in the LIPIcs–Leibniz International Proceedings in Informatics, a "series of high-quality conference proceedings across all fields in informatics established in cooperation with Schloss Dagstuhl –Leibniz Center for Informatics". Before, CONCUR papers were published in the series Lecture Notes in Computer Science.
According to CORE Ranking, CONCUR has rank A ("excellent conference, and highly respected in a discipline area").
According to Google Scholar Metrics (as of 1. April 2023), CONCUR has H5-index 17 and H5-median 22.
Editions
35th CONCUR 2024: Calgary, Canada
34th CONCUR 2023: Antwerp, Belgium
33rd CONCUR 2022: Warsaw, Poland
32nd CONCUR 2021: Paris, France Online
31st CONCUR 2020: Vienna, Austria Online
30th CONCUR 2019: Amsterdam, the Netherlands
29th CONCUR 2018: Beijing, China
28th CONCUR 2017: Berlin, Germany
27th CONCUR 2016: Québec City, Canada
26th CONCUR 2015: Madrid, Spain
25th CONCUR 2014: Rome, Italy
24th CONCUR 2013: Buenos Aires, Argentina
23rd CONCUR 2012: Newcastle upon Tyne, UK
22nd CONCUR 2011: Aachen, Germany
21st CONCUR 2010: Paris, France
20th CONCUR 2009: Bologna, Italy
19th CONCUR 2008: Toronto, Canada
18th CONCUR 2007: Lisbon, Portugal
17th CONCUR 2006: Bonn, Germany
16th CONCUR 2005: San Francisco, CA, USA
15th CONCUR 2004: London, UK
14th CONCUR 2003: Marseille, France
13th CONCUR 2002: Brno, Czech Republic
12th CONCUR 2001: Aalborg, Denmark
11th CONCUR 2000: Pennsylvania State University, Pennsylvania, USA
10th CONCUR 1999: Eindhoven, The Netherlands
9th CONCUR 1998: Nice, France
8th CONCUR 1997: Warsaw, Poland
7th CONCUR 1996: Pisa, Italy
6th CONCUR 1995: Philadelphia, PA, USA
5th CONCUR 1994: Uppsala, Sweden
4th CONCUR 1993: Hildesheim, Germany
3rd CONCUR 1992: Stony Brook, NY, USA
2nd CONCUR 1991: Amsterdam, the Netherlands
1st CONCUR 1990: Amsterdam, the Netherlands
Concurrency: Theory, Language, And Architecture 1989: Oxford, UK
Concurrency 1988: Hamburg, Germany
Seminar on Concurrency 1984: Pittsburgh, PA, USA
Test-of-Time Award
In 2020, the International Conference on Concurrency Theory (CONCUR) and the IFIP Working Group 1.8 on Concurrency Theory
established the CONCUR Test-of-Time Award.
The goal of the Award is to recognize important achievements in concurrency theory that
have stood the test of time, and were published at CONCUR since its first edition in 1990.
Starting with CONCUR 2024, an award event will take
place every other year, and recognize one or two papers presented at CONCUR in the 4-year period from 20 to 17 years earlier.
From 2020 to 2023 two such award events are combined each year, in order to also recognize achievements that appeared
in the early editions of CONCUR.
2023
Period 2002–2005
Vincent Danos, Jean Krivine: "Reversible Communicating Systems." (CONCUR 2004)
2022
Period 2000–2003
Luca de Alfaro, Marco Faella, Thomas A. Henzinger, Rupak Majumdar & Mariëlle Stoelinga: "The Element of Surprise in Timed Games." (CONCUR 2003)
James J. Leifer & Robin Milner: "Deriving Bisimulation Congruences for Reactive Systems." (CONCUR 2000)
Period 1998–2001
Franck Cassez & Kim Larsen: "The Impressive Power of Stopwatches" (CONCUR 2000)
Christel Baier, Joost-Pieter Katoen & Holger Hermanns: "Approximate symbolic model checking of continuous-time Markov chains." (CONCUR 1999)
2021
Period 1996–1999
Rajeev Alur, Thomas A. Henzinger, Orna Kupferman & Moshe Y. Vardi: "Alternating Refinement Relations" (CONCUR 1998)
Ahmed Bouajjani, Javier Esparza & Oded Maler: "Reachability Analysis of Pushdown Automata: Application to Model-checking" (CONCUR 1997)
Period 1994–1997
Uwe Nestmann & Benjamin C. Pierce: "Decoding Choice Encodings" (CONCUR 1996)
David Janin & Igor Walukiewicz: "On the Expressive Completeness of the Propositional mu-Calculus with Respect to Monadic Second Order Logic." (CONCUR 1996)
2020
Period 1992–1995
Roberto Segala & Nancy Lynch: "Probabilistic Simulations for Probabilistic Processes" (CONCUR 1994)
Davide Sangiorgi: "A Theory of Bisimulation for the pi-Calculus" (CONCUR 1993)
Period 1990–1993
Rob van Glabbeek: "The Linear Time-Branching Time Spectrum" (CONCUR 1993)
Søren Christensen, Hans Hüttel & Colin Stirling: "Bisimulation Equivalence is Decidable for all Context-Free Processes" (CONCUR 1992)
Affiliated events
International Conference on Formal Modeling and Analysis of Timed Systems (FORMATS)
International Conference on Quantitative Evaluation of SysTems (QEST)
See also
List of computer science conferences
List of computer science conference acronyms
Outline of computer science
References
External links
DBLP Page of CONCUR Conferences
Computer science conferences | International Conference on Concurrency Theory | Technology | 1,237 |
60,027,450 | https://en.wikipedia.org/wiki/Target%20Malaria | Target Malaria is a not-for-profit international research consortium that aims to co-develop and share novel genetic technologies to help control malaria in Africa. The consortium brings together research institutes and universities from Africa, Europe and North America.
The project is working to develop genetically modified mosquitoes that carry a trait that would result in the reduction of malaria mosquito populations. Reducing the number of mosquitoes that can transmit the malaria parasite would lead to fewer malaria infections. The project’s novel genetic approach aims to be complementary to existing malaria control interventions. The project’s research is still at an early stage, and even though results so far have been promising, there is a long way to go.
The malaria burden in Africa
Every year, malaria kills half a million people and infects over 200 million people; a third of the world is at risk of contracting this disease transmitted by mosquitoes. The majority of the victims are children under the age of five living in Africa. While all regions in the world have made tremendous progress towards control and elimination of malaria, Africa accounts for 94% of malaria deaths in the world.
New vector control tools
According to the World Malaria Report 2020 published by the World Health Organization, despite tremendous progress in reducing malaria around the world, since 2015 this progress has slowed, stalling in the last three years. Current interventions, such as drug treatments, bed nets and insecticide spraying, have helped to lower the burden of malaria but have not been able to eradicate the disease in many countries. WHO warns that the global response to malaria has reached a “crossroads”: if new tools are not found, key targets of WHO’s global malaria strategy will likely be missed.
Gene drive for malaria control
Target Malaria is adapting a natural mechanism called a gene drive. The genetically modified mosquitoes carry a trait that targets their ability to reproduce. Gene drive ensures this modification is inherited at a higher rate than it normally would, thus reducing the fertility of the mosquito populations over time and ultimately their numbers. Gene drive technologies hold the promise of being a self-sustaining and cost-effective method to help in the fight against malaria by reducing the population of malaria mosquitoes. The WHO stated in its Position Statement on the evaluation and use of GMMs for the control of vector-borne diseases published on October 14, 2020: "In the spirit of fostering innovation, WHO takes the position that all potentially beneficial new technologies, including GMMs, should be investigated to determine whether they could be useful in the continued fight against diseases of public health concern. Such research should be conducted in steps and be supported by clear governance mechanisms to evaluate the health, environmental and ecological implications."
History and funding
Target Malaria started as a university-based research programme in 2005. Since 2012, the project has expanded to include scientists, social scientists, stakeholder engagement experts, regulatory affairs experts, project management teams, risk assessment specialists and communications professionals from Africa, Europe, and North America. The project receives core funding from the Bill and Melinda Gates Foundation. and from the Open Philanthropy Project Fund, an advised fund of Silicon Valley Community Foundation. Individual labs also received additional funding from a variety of sources to support their work, including but not limited to: DEFRA, The European Commission, MRC, NIH, Uganda Ministry of Health, Uganda National Council for Science & Technology, Wellcome Trust and the World Bank.
List of partner institutions
CDC Foundation, USA
Imperial College London, UK
Institut de Recherche en Sciences de la Santé – IRSS (Research Institute for Health Sciences, Burkina Faso)
Polo d’Innovazione di Genomica, Genetica e Biologia – PoloGGB, Italy
Uganda Virus Research Institute, Uganda
University of Ghana, Ghana
University of Oxford, UK
See also
Gene drive
Oxitec
Rat Guard
References
Genome editing
Genomics organizations
Insect-borne diseases
Malaria
Pest control | Target Malaria | Engineering,Biology | 779 |
18,674,875 | https://en.wikipedia.org/wiki/Turbine%20blade | A turbine blade is a radial aerofoil mounted in the rim of a turbine disc and which produces a tangential force which rotates a turbine rotor. Each turbine disc has many blades. As such they are used in gas turbine engines and steam turbines. The blades are responsible for extracting energy from the high temperature, high pressure gas produced by the combustor. The turbine blades are often the limiting component of gas turbines. To survive in this difficult environment, turbine blades often use exotic materials like superalloys and many different methods of cooling that can be categorized as internal and external cooling, and thermal barrier coatings. Blade fatigue is a major source of failure in steam turbines and gas turbines. Fatigue is caused by the stress induced by vibration and resonance within the operating range of machinery. To protect blades from these high dynamic stresses, friction dampers are used.
Blades of wind turbines and water turbines are designed to operate in different conditions, which typically involve lower rotational speeds and temperatures.
Introduction
In a gas turbine engine, a single turbine stage is made up of a rotating disk that holds many turbine blades and a stationary ring of nozzle guide vanes in front of the blades. The turbine is connected to a compressor using a shaft (the complete rotating assembly sometimes called a "spool"). Air is compressed, raising the pressure and temperature, as it passes through the compressor. The temperature is then increased by combustion of fuel inside the combustor which is located between the compressor and the turbine. The high-temperature, high-pressure gas then passes through the turbine. The turbine stages extract energy from this flow, lowering the pressure and temperature of the gas and transfer the kinetic energy to the compressor. The way the turbine works is similar to how the compressor works, only in reverse, in so far as energy exchange between the gas and the machine is concerned, for example. There is a direct relationship between how much the gas temperature changes (increase in compressor, decrease in turbine) and the shaft power input (compressor) or output (turbine).
For a turbofan engine the number of turbine stages required to drive the fan increases with the bypass-ratio unless the turbine speed can be increased by adding a gearbox between the turbine and fan in which case fewer stages are required. The number of turbine stages can have a great effect on how the turbine blades are designed for each stage. Many gas turbine engines are twin-spool designs, meaning that there is a high-pressure spool and a low-pressure spool. Other gas turbines use three spools, adding an intermediate-pressure spool between the high- and low-pressure spool. The high-pressure turbine is exposed to the hottest, highest-pressure air, and the low-pressure turbine is subjected to cooler, lower-pressure air. The difference in conditions leads to the design of high-pressure and low-pressure turbine blades that are significantly different in material and cooling choices even though the aerodynamic and thermodynamic principles are the same.
Under these severe operating conditions inside the gas and steam turbines, the blades face high temperature, high stresses, and potentially high vibrations. Steam turbine blades are critical components in power plants which convert the linear motion of high-temperature and high-pressure steam flowing down a pressure gradient into a rotary motion of the turbine shaft.
Environment and failure modes
Turbine blades are subjected to very strenuous environments inside a gas turbine. They face high temperatures, high stresses, and a potential environment of high vibration. All three of these factors can lead to blade failures, potentially destroying the engine, therefore turbine blades are carefully designed to resist these conditions.
Turbine blades are subjected to stress from centrifugal force (turbine stages can rotate at tens of thousands of revolutions per minute (RPM)) and fluid forces that can cause fracture, yielding, or creep failures. Additionally, the first stage (the stage directly following the combustor) of a modern gas turbine faces temperatures around , up from temperatures around in early gas turbines. Modern military jet engines, like the Snecma M88, can see turbine temperatures of . Those high temperatures can weaken the blades and make them more susceptible to creep failures. The high temperatures can also make the blades susceptible to corrosion failures. Finally, vibrations from the engine and the turbine itself can cause fatigue failures.
Materials
A limiting factor in early jet engines was the performance of the materials available for the hot section (combustor and turbine) of the engine. The need for better materials spurred much research in the field of alloys and manufacturing techniques, and that research resulted in a long list of new materials and methods that make modern gas turbines possible. One of the earliest of these was Nimonic, used in the British Whittle engines.
The development of superalloys in the 1940s and new processing methods such as vacuum induction melting in the 1950s greatly increased the temperature capability of turbine blades. Further processing methods like hot isostatic pressing improved the alloys used for turbine blades and increased turbine blade performance. Modern turbine blades often use nickel-based superalloys that incorporate chromium, cobalt, and rhenium.
Aside from alloy improvements, a major breakthrough was the development of directional solidification (DS) and single crystal (SC) production methods. These methods help greatly increase strength against fatigue and creep by aligning grain boundaries in one direction (DS) or by eliminating grain boundaries altogether (SC). SC research began in the 1960s with Pratt and Whitney and took about 10 years to be implemented. One of the first implementations of DS was with the J58 engines of the SR-71.
Another major improvement to turbine blade material technology was the development of thermal barrier coatings (TBC). Where DS and SC developments improved creep and fatigue resistance, TBCs improved corrosion and oxidation resistance, both of which became greater concerns as temperatures increased. The first TBCs, applied in the 1970s, were aluminide coatings. Improved ceramic coatings became available in the 1980s. These coatings increased turbine blade temperature capability by about 200 °F (90 °C). The coatings also improve blade life, almost doubling the life of turbine blades in some cases.
Most turbine blades are manufactured by investment casting (or lost-wax processing). This process involves making a precise negative die of the blade shape that is filled with wax to form the blade shape. If the blade is hollow (i.e., it has internal cooling passages), a ceramic core in the shape of the passage is inserted into the middle. The wax blade is coated with a heat-resistant material to make a shell, and then that shell is filled with the blade alloy. This step can be more complicated for DS or SC materials, but the process is similar. If there is a ceramic core in the middle of the blade, it is dissolved in a solution that leaves the blade hollow. The blades are coated with a TBC, and then any cooling holes are machined.
Ceramic matrix composites (CMC), where fibers are embedded in a matrix of polymer derived ceramics, are being developed for use in turbine blades. The main advantage of CMCs over conventional superalloys is their light weight and high temperature capability. SiC/SiC composites consisting of a silicon carbide matrix reinforced by silicon carbide fibers have been shown to withstand operating temperatures 200°-300 °F higher than nickel superalloys. GE Aviation successfully demonstrated the use of such SiC/SiC composite blades for the low-pressure turbine of its F414 jet engine.
List of turbine blade materials
Note: This list is not inclusive of all alloys used in turbine blades.
U-500 This material was used as a first stage (the most demanding stage) material in the 1960s, and is now used in later, less demanding, stages.
Rene 77
Rene N5
Rene N6
PWA1484
CMSX-4
CMSX-10
Inconel
IN-738 – GE used IN-738 as a first stage blade material from 1971 until 1984, when it was replaced by GTD-111. It is now used as a second stage material. It was specifically designed for land-based turbines rather than aircraft gas turbines.
GTD-111 Blades made from directionally solidified GTD-111 are being used in many GE Energy gas turbines in the first stage. Blades made from equiaxed GTD-111 are being used in later stages.
EPM-102 (MX4 (GE), PWA 1497 (P&W)) is a single crystal superalloy jointly developed by NASA, GE Aviation, and Pratt & Whitney for the High Speed Civil Transport (HSCT). While the HSCT program was cancelled, the alloy is still being considered for use by GE and P&W.
Nimonic 80a was used for the turbine blades on the Rolls-Royce Nene and de Havilland Ghost
Nimonic 90 was used on the Bristol Proteus.
Nimonic 105 was used on the Rolls-Royce Spey.
Nimonic 263 was used in the combustion chambers of the Bristol Olympus used on the Concorde supersonic airliner.
3D printed thermoplastic resin to create wind turbine blades is in development in a partnership between ORNL, NREL, and GE Renewable Energy.
Cooling
At a constant pressure ratio, thermal efficiency of the engine increases as the turbine entry temperature (TET) increases. However, high temperatures can damage the turbine, as the blades are under large centrifugal stresses and materials are weaker at high temperature. So, turbine blade cooling is essential for the first stages but since the gas temperature drops through each stage it is not required for later stages such as in the low pressure turbine or a power turbine. Current modern turbine designs are operating with inlet temperatures higher than 1900 kelvins which is achieved by actively cooling the turbine components.
Methods of cooling
Turbine blades are cooled using air, except for limited use of steam cooling in a combined cycle power plant. Water cooling has been extensively tested but has never been introduced. The General Electric "H" class gas turbine has cooled rotating blades and static vanes using steam from a combined cycle steam turbine although GE was reported in 2012 to be going back to air-cooling for its "FlexEfficiency" units. Liquid cooling seems to be more attractive because of high specific heat capacity and chances of evaporative cooling but there can be leakage, corrosion, choking and other problems which work against this method. On the other hand, air cooling allows the discharged air into main flow without any problem. Quantity of air required for this purpose is 1–3% of main flow and blade temperature can be reduced by 200–300 °C.
There are many techniques of cooling used in gas turbine blades; convection, film, transpiration cooling, cooling effusion, pin fin cooling etc. which fall under the categories of internal and external cooling. While all methods have their differences, they all work by using cooler air taken from the compressor to remove heat from the turbine blades.
Internal cooling
Convection cooling
It works by passing cooling air through passages internal to the blade. Heat is transferred by conduction through the blade, and then by convection into the air flowing inside of the blade. A large internal surface area is desirable for this method, so the cooling paths tend to be serpentine and full of small fins. The internal passages in the blade may be circular or elliptical in shape. Cooling is achieved by passing the air through these passages from hub towards the blade tip. This cooling air comes from an air compressor. In case of gas turbine the fluid outside is relatively hot which passes through the cooling passage and mixes with the main stream at the blade tip.
Impingement cooling
A variation of convection cooling, impingement cooling, works by hitting the inner surface of the blade with high velocity air. This allows more heat to be transferred by convection than regular convection cooling does. Impingement cooling is used in the regions of greatest heat loads. In case of turbine blades, the leading edge has maximum temperature and thus heat load. Impingement cooling is also used in mid chord of the vane. Blades are hollow with a core. There are internal cooling passages. Cooling air enters from the leading edge region and turns towards the trailing edge.
External cooling
Film cooling
Film cooling (also called thin film cooling), a widely used type, allows for higher cooling effectiveness than either convection and impingement cooling. This technique consists of pumping the cooling air out of the blade through multiple small holes or slots in the structure. A thin layer (the film) of cooling air is then created on the external surface of the blade, reducing the heat transfer from main flow, whose temperature (1300–1800 kelvins) can exceed the melting point of the blade material (1300–1400 kelvins). The ability of the film cooling system to cool the surface is typically evaluated using a parameter called cooling effectiveness. Higher cooling effectiveness (with maximum value of one) indicates that the blade material temperature is closer to the coolant temperature. In locations where the blade temperature approaches the hot gas temperature, the cooling effectiveness approaches to zero. The cooling effectiveness is mainly affected by the coolant flow parameters and the injection geometry. Coolant flow parameters include the velocity, density, blowing and momentum ratios which are calculated using the coolant and mainstream flow characteristics. Injection geometry parameters consist of hole or slot geometry (i.e. cylindrical, shaped holes or slots) and injections angle. A United States Air Force program in the early 1970s funded the development of a turbine blade that was both film and convection cooled, and that method has become common in modern turbine blades.
Injecting the cooler bleed into the flow reduces turbine isentropic efficiency; the compression of the cooling air (which does not contribute power to the engine) incurs an energetic penalty; and the cooling circuit adds considerable complexity to the engine. All of these factors have to be compensated by the increase in overall performance (power and efficiency) allowed by the increase in turbine temperature.
In recent years, researchers have suggested using plasma actuator for film cooling. The film cooling of turbine blades by using a dielectric barrier discharge plasma actuator was first proposed by Roy and Wang. A horseshoe-shaped plasma actuator, which is set in the vicinity of holes for gas flow, has been shown to improve the film cooling effectiveness significantly. Following the previous research,
recent reports using both experimental and numerical methods demonstrated the effect of cooling enhancement by 15% using a plasma actuator.
Cooling effusion
The blade surface is made of porous material which means having a large number of small orifices on the surface. Cooling air is forced through these porous holes which forms a film or cooler boundary layer. Besides this uniform cooling is caused by effusion of the coolant over the entire blade surface.
Pin fin cooling
In the narrow trailing edge film cooling is used to enhance heat transfer from the blade. There is an array of pin fins on the blade surface. Heat transfer takes place from this array and through the side walls. As the coolant flows across the fins with high velocity, the flow separates and wakes are formed. Many factors contribute towards heat transfer rate among which the type of pin fin and the spacing between fins are the most significant.
Transpiration cooling
This is similar to film cooling in that it creates a thin film of cooling air on the blade, but it is different in that air is "leaked" through a porous shell rather than injected through holes. This type of cooling is effective at high temperatures as it uniformly covers the entire blade with cool air. Transpiration-cooled blades generally consist of a rigid strut with a porous shell. Air flows through internal channels of the strut and then passes through the porous shell to cool the blade. As with film cooling, increased cooling air decreases turbine efficiency, therefore that decrease has to be balanced with improved temperature performance.
See also
Components of jet engines
Combustor
High temperature corrosion
Gas turbine
Superalloys
Notes
References
Bibliography
Engines | Turbine blade | Physics,Technology | 3,251 |
9,685,728 | https://en.wikipedia.org/wiki/Sexy%20son%20hypothesis | The sexy son hypothesis in evolutionary biology and sexual selection, proposed by Patrick J. Weatherhead and Raleigh J. Robertson of Queen's University in Kingston, Ontario in 1979, states that a female's ideal mate choice among potential mates is one whose genes will produce males with the best chance of reproductive success. This implies that other benefits the father can offer the mother or offspring are less relevant than they may appear, including his capacity as a parental caregiver, territory and any nuptial gifts. Fisher's principle means that the sex ratio (except in certain eusocial insects) is always near 1:1 between males and females, yet what matters most are her "sexy sons'" future breeding successes, more likely if they have a promiscuous father, in creating large numbers of offspring carrying copies of her genes. This sexual selection hypothesis has been researched in species such as the European pied flycatcher.
Context
Female mating preferences are widely recognized as being responsible for the rapid and divergent evolution of male secondary sex characteristics. In 1915, Ronald Fisher wrote:
Granted that while this taste and preference prevails among the females of the species, the males will grow more and more elaborate and beautiful tail feathers, the question must be answered "Why have the females this taste? Of what use is it to the species that they should select this seemingly useless ornament?"
The first step to a solution lies in the fact that the success of an animal in the struggle for existence is not measured only by the number of offspring which it produces and rears, but also by the probable success of these offspring. So that in selecting a mate from a number of different competitors, it is important to select that one which is most likely to produce successful children.
In 1976, prior to Weatherhead and Robertson's paper, Richard Dawkins had written in his book The Selfish Gene:
Ronald Fisher's principle, as published in his book The Genetical Theory of Natural Selection, is one of several possible explanations for the highly diverse and often astonishing ornaments of animals. If females choose physically attractive males, they will tend to get physically attractive sons, and, thus more grandchildren, because other choosy females will prefer their attractive, sexy sons. The theory will function regardless of the physical or behavioral trait a female chooses, as long as it is heritable (that is, the trait varies between individuals of the population), because it is possessing the trait that makes males attractive, and not the qualities of the trait in itself.
Once a preference becomes established, females choosing males with elaborate secondary sexual traits will produce sons that carry alleles for the trait and produce daughters that carry alleles for the preference, generating genetic coupling that will drive self-reinforcing coevolution of both trait and preference, due to the mating advantage of males with the trait, creating a Fisherian runaway sexy sons process. Similar models have been proposed for postcopulatory female preferences, such as the time at which females removed the male's sperm ampulla after mating. Sexual selection by direct and/or indirect benefits as well as sexual conflict determine the evolution of animal mating systems.
In its original context, the "narrow-sense sexy son hypothesis" of Weatherhead and Robertson refers to mating systems with care from both parents. In these mating systems, females that mate with a polygynous male normally receive less assistance than females mated with a monogamous male, and thus suffer from direct fitness consequences that have to be (at least) compensated for by the breeding successes of their sexy sons. On the other hand, a "broad-sense sexy son hypothesis" encompasses both polygyny and promiscuous mating systems, with and without care from both parents. Alatalo (1998) argues that the costs of any additional choice may be so minor that female choice for honestly signaling males, that is good genes, may evolve even if the indirect benefits on offspring quality are small. A similar argument can be made for the sexy son hypothesis if mates of attractive males do not suffer any direct fitness consequences.
Sexual conflict
Sexual conflict refers to the conflicting goals of breeding males and females. It describes the diverging interests of males and females in optimizing their fitness. From the viewpoint of any one partner, the best outcome would be for the partner's mate to care for the young, thus freeing up his or her own resources (e.g., time and energy) that s/he—but typically he—can invest in further sex that may create additional offspring. In polygynous mating systems, sexual conflict means the optimization of male reproductive success by having mated with multiple females, even though the reproductive success of a polygynously mated female is thereby reduced. Such can be the case for the Guianan cock-of-the-rocks, whose male members spend a majority of their time and energy maintaining their plumage and attempting to seek the most matings. Females, on the other hand, spend their time building and maintaining their nest where they will lay their eggs and raise the young.
Good genes theory
"Good genes" theory proposes that females select males seen to have genetic advantages that increase offspring quality. Increased viability of offspring provides compensation for any lower reproductive success that results from their being "picky". The good-gene hypothesis for polyandry proposes that when females encounter better males than their previous mates, they re-mate in order to fertilize their eggs with the better male's sperm.
Dung beetles who have selected mates with better genetics tend to have offspring that survive longer and are more able to reproduce than those that do not pick mates with genetic quality. This suggests that carefully choosing a mate is beneficial.
Another study notes that pronghorn females engage in an obvious and energetically expensive mate sampling process to identify vigorous males. Though each female selects independently, the outcome is that a small proportion of the herd's males sire most young. Offspring of attractive males were more likely to survive to weaning and to age classes as late as 5 years, apparently due to faster growth rates. Because pronghorn males do not have costly ornaments, the authors conclude that female choice for good genes can exist in the absence of obvious sexual selection cues such as elaborate antlers.
The sexy son hypothesis is closely related to the good genes assumption and the Fisherian runaway selection process. Like good genes, the sexy son hypothesis assumes the existence of indirect genetic benefits that are able to compensate for any inferior direct reproductive success (i.e., fewer offspring). The main difference between good genes and the sexy son hypothesis is that the latter assumes an indirect effect due to the attractiveness of the sons, whereas good genes focus on the viability of both sons and daughters. However, "attractiveness" is not narrowly defined, and can refer to every trait that increases a male's probability to become polygynous.
Sperm models
Good-sperm models predict positive genetic associations between a male's sperm competitiveness and the general viability of his offspring, whereas sexy-sperm models predict that multiple-mating females produce more grandchildren. As with precopulatory processes, postcopulatory models predict that the trait in males that determines fertilization success will become genetically coupled with the mechanism by which females choose the sperm of preferred males.
See also
Sexual selection in human evolution
Strategic pluralism
References
1979 introductions
Sexual selection
Evolutionary psychology
Evolutionary biology
Biological hypotheses
Ronald Fisher | Sexy son hypothesis | Biology | 1,515 |
15,074,660 | https://en.wikipedia.org/wiki/Mitochondrial%20ribosomal%20protein%20L12 | 39S ribosomal protein L12, mitochondrial is a protein that in humans is encoded by the MRPL12 gene.
Mammalian mitochondrial ribosomal proteins are encoded by nuclear genes and help in protein synthesis within the mitochondrion. Mitochondrial ribosomes (mitoribosomes) consist of a small 28S subunit and a large 39S subunit. They have an estimated 75% protein to rRNA composition compared to prokaryotic ribosomes, where this ratio is reversed. Another difference between mammalian mitoribosomes and prokaryotic ribosomes is that the latter contain a 5S rRNA. Among different species, the proteins comprising the mitoribosome differ greatly in sequence, and sometimes in biochemical properties, which prevents easy recognition by sequence homology. This gene encodes a 39S subunit protein which forms homodimers. In prokaryotic ribosomes, two L7/L12 dimers and one L10 protein form the L8 protein complex.
References
Further reading
Ribosomal proteins | Mitochondrial ribosomal protein L12 | Chemistry | 211 |
916,941 | https://en.wikipedia.org/wiki/Bulk%20movement | In cell biology, bulk flow is the process by which proteins with a sorting signal travel to and from different cellular compartments. In other words, bulk transport is a type of transport which involves the transport of large amount of substance like lipid droplets and solid food particles across plasma membrane by utilising energy. Special processes are involved in the transport of such large quantities of materials, which include endocytosis and exocytosis.
It is thought that cargo travels through the Golgi cisternae (from cis- to trans- Golgi) via bulk flow.
See also
Protein targeting
Vesicle (biology)
COPI
COPII
Mass flow
References
1. Rothman J.E. and Weiland F.T. Protein sorting by transport vesicles. Science 272. 227-234. 1996.
Protein targeting | Bulk movement | Biology | 169 |
6,424 | https://en.wikipedia.org/wiki/Corona%20Australis | Corona Australis is a constellation in the Southern Celestial Hemisphere. Its Latin name means "southern crown", and it is the southern counterpart of Corona Borealis, the northern crown. It is one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations. The Ancient Greeks saw Corona Australis as a wreath rather than a crown and associated it with Sagittarius or Centaurus. Other cultures have likened the pattern to a turtle, ostrich nest, a tent, or even a hut belonging to a rock hyrax.
Although fainter than its northern counterpart, the oval- or horseshoe-shaped pattern of its brighter stars renders it distinctive. Alpha and Beta Coronae Australis are the two brightest stars with an apparent magnitude of around 4.1. Epsilon Coronae Australis is the brightest example of a W Ursae Majoris variable in the southern sky. Lying alongside the Milky Way, Corona Australis contains one of the closest star-forming regions to the Solar System—a dusty dark nebula known as the Corona Australis Molecular Cloud, lying about 430 light years away. Within it are stars at the earliest stages of their lifespan. The variable stars R and TY Coronae Australis light up parts of the nebula, which varies in brightness accordingly.
Name
The name of the constellation was entered as "Corona Australis" when the International Astronomical Union (IAU) established the 88 modern constellations in 1922.
In 1932, the name was instead recorded as "Corona Austrina" when the IAU's commission on notation approved a list of four-letter abbreviations for the constellations.
The four-letter abbreviations were repealed in 1955. The IAU presently uses "Corona Australis" exclusively.
Characteristics
Corona Australis is a small constellation bordered by Sagittarius to the north, Scorpius to the west, Telescopium to the south, and Ara to the southwest. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is "CrA". The official constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a polygon of four segments (illustrated in infobox). In the equatorial coordinate system, the right ascension coordinates of these borders lie between and , while the declination coordinates are between −36.77° and −45.52°. Covering 128 square degrees, Corona Australis culminates at midnight around the 30th of June and ranks 80th in area. Only visible at latitudes south of 53° north, Corona Australis cannot be seen from the British Isles as it lies too far south, but it can be seen from southern Europe and readily from the southern United States.
Features
While not a bright constellation, Corona Australis is nonetheless distinctive due to its easily identifiable pattern of stars, which has been described as horseshoe- or oval-shaped. Though it has no stars brighter than 4th magnitude, it still has 21 stars visible to the unaided eye (brighter than magnitude 5.5). Nicolas Louis de Lacaille used the Greek letters Alpha through to Lambda to label the most prominent eleven stars in the constellation, designating two stars as Eta and omitting Iota altogether. Mu Coronae Australis, a yellow star of spectral type G5.5III and apparent magnitude 5.21, was labelled by Johann Elert Bode and retained by Benjamin Gould, who deemed it bright enough to warrant naming.
Stars
The only star in the constellation to have received a name is Alfecca Meridiana or Alpha CrA. The name combines the Arabic name of the constellation with the Latin for "southern". In Arabic, Alfecca means "break", and refers to the shape of both Corona Australis and Corona Borealis. Also called simply "Meridiana", it is a white main sequence star located 125 light years away from Earth, with an apparent magnitude of 4.10 and spectral type A2Va. A rapidly rotating star, it spins at almost 200 km per second at its equator, making a complete revolution in around 14 hours. Like the star Vega, it has excess infrared radiation, which indicates it may be ringed by a disk of dust. It is currently a main-sequence star, but will eventually evolve into a white dwarf; currently, it has a luminosity 31 times greater, and a radius and mass of 2.3 times that of the Sun. Beta Coronae Australis is an orange giant 474 light years from Earth. Its spectral type is K0II, and it is of apparent magnitude 4.11. Since its formation, it has evolved from a B-type star to a K-type star. Its luminosity class places it as a bright giant; its luminosity is 730 times that of the Sun, designating it one of the highest-luminosity K0-type stars visible to the naked eye. 100 million years old, it has a radius of 43 solar radii () and a mass of between 4.5 and 5 solar masses (). Alpha and Beta are so similar as to be indistinguishable in brightness to the naked eye.
Some of the more prominent double stars include Gamma Coronae Australis—a pair of yellowish white stars 58 light years away from Earth, which orbit each other every 122 years. Widening since 1990, the two stars can be seen as separate with a 100 mm aperture telescope; they are separated by 1.3 arcseconds at an angle of 61 degrees. They have a combined visual magnitude of 4.2; each component is an F8V dwarf star with a magnitude of 5.01. Epsilon Coronae Australis is an eclipsing binary belonging to a class of stars known as W Ursae Majoris variables. These star systems are known as contact binaries as the component stars are so close together they touch. Varying by a quarter of a magnitude around an average apparent magnitude of 4.83 every seven hours, the star system lies 98 light years away. Its spectral type is F4VFe-0.8+. At the southern end of the crown asterism are the stars Eta1 and Eta2 CrA, which form an optical double. Of magnitude 5.1 and 5.5, they are separable with the naked eye and are both white. Kappa Coronae Australis is an easily resolved optical double—the components are of apparent magnitudes 6.3 and 5.6 and are about 1000 and 150 light years away respectively. They appear at an angle of 359 degrees, separated by 21.6 arcseconds. Kappa2 is actually the brighter of the pair and is more bluish white, with a spectral type of B9V, while Kappa1 is of spectral type A0III. Lying 202 light years away, Lambda Coronae Australis is a double splittable in small telescopes. The primary is a white star of spectral type A2Vn and magnitude of 5.1, while the companion star has a magnitude of 9.7. The two components are separated by 29.2 arcseconds at an angle of 214 degrees.
Zeta Coronae Australis is a rapidly rotating main sequence star with an apparent magnitude of 4.8, 221.7 light years from Earth. The star has blurred lines in its hydrogen spectrum due to its rotation. Its spectral type is B9V. Theta Coronae Australis lies further to the west, a yellow giant of spectral type G8III and apparent magnitude 4.62. Corona Australis harbours RX J1856.5-3754, an isolated neutron star that is thought to lie 140 (±40) parsecs, or 460 (±130) light years, away, with a diameter of 14 km. It was once suspected to be a strange star, but this has been discounted.
Corona Australis Molecular Cloud
The Corona Australis Molecular Cloud is a dark molecular cloud just north of Beta Coronae Australis. Illuminated by a number of embedded reflection nebulae the cloud fans out from Epsilon Coronae Australis eastward along the constellation border with Sagittarius. It contains , Herbig–Haro objects (protostars) and some very young stars, being one of the closest star-forming regions, 430 light years (130 parsecs) to the Solar System, at the surface of the Local Bubble. The first nebulae of the cloud were recorded in 1865 by Johann Friedrich Julius Schmidt.
Between Epsilon and Gamma Coronae Australis the cloud consists of the particular dark nebula and star forming region Bernes 157. It is 55 by 18 arcminutes wide and possesses several stars around magnitude 13. These stars are dimmed by up to 8 magnitudes because of the obscuring dust clouds. At the center of the active star-forming region lies the Coronet cluster (also called R CrA Cluster), which is used in studying star and protoplanetary disk formation. R Coronae Australis (R CrA) is an irregular variable star ranging from magnitudes 9.7 to 13.9. Blue-white, it is of spectral type B5IIIpe. A very young star, it is still accumulating interstellar material. It is obscured by, and illuminates, the surrounding nebula, NGC 6729, which brightens and darkens with it. The nebula is often compared to a comet for its appearance in a telescope, as its length is five times its width. Other stars of the cluster include S Coronae Australis, a G-class dwarf and T Tauri star.
Nearby north, another young variable star, TY Coronae Australis, illuminates another nebula: reflection nebula NGC 6726/NGC 6727. TY Coronae Australis ranges irregularly between magnitudes 8.7 and 12.4, and the brightness of the nebula varies with it. Blue-white, it is of spectral type B8e. The largest young stars in the region, R, S, T, TY and VV Coronae Australis, are all ejecting jets of material which cause surrounding dust and gas to coalesce and form Herbig–Haro objects, many of which have been identified nearby.
Not part of it is the globular cluster known as NGC 6723, which can be seen adjacent to the nebulosity in the neighbouring constellation of Sagittarius, but is much much further away.
Deep sky objects
IC 1297 is a planetary nebula of apparent magnitude 10.7, which appears as a green-hued roundish object in higher-powered amateur instruments. The nebula surrounds the variable star RU Coronae Australis, which has an average apparent magnitude of 12.9 and is a WC class Wolf–Rayet star. IC 1297 is small, at only 7 arcseconds in diameter; it has been described as "a square with rounded edges" in the eyepiece, elongated in the north–south direction. Descriptions of its color encompass blue, blue-tinged green, and green-tinged blue.
Corona Australis' location near the Milky Way means that galaxies are uncommonly seen. NGC 6768 is a magnitude 11.2 object 35′ south of IC 1297. It is made up of two galaxies merging, one of which is an elongated elliptical galaxy of classification E4 and the other a lenticular galaxy of classification S0. IC 4808 is a galaxy of apparent magnitude 12.9 located on the border of Corona Australis with the neighbouring constellation of Telescopium and 3.9 degrees west-southwest of Beta Sagittarii. However, amateur telescopes will only show a suggestion of its spiral structure. It is 1.9 arcminutes by 0.8 arcminutes. The central area of the galaxy does appear brighter in an amateur instrument, which shows it to be tilted northeast–southwest.
Southeast of Theta and southwest of Eta lies the open cluster ESO 281-SC24, which is composed of the yellow 9th magnitude star GSC 7914 178 1 and five 10th to 11th magnitude stars. Halfway between Theta Coronae Australis and Theta Scorpii is the dense globular cluster NGC 6541. Described as between magnitude 6.3 and magnitude 6.6, it is visible in binoculars and small telescopes. Around 22000 light years away, it is around 100 light years in diameter. It is estimated to be around 14 billion years old. NGC 6541 appears 13.1 arcminutes in diameter and is somewhat resolvable in large amateur instruments; a 12-inch telescope reveals approximately 100 stars but the core remains unresolved.
Meteor showers
The Corona Australids are a meteor shower that takes place between 14 and 18 March each year, peaking around 16 March. This meteor shower does not have a high peak hourly rate. In 1953 and 1956, observers noted a maximum of 6 meteors per hour and 4 meteors per hour respectively; in 1955 the shower was "barely resolved". However, in 1992, astronomers detected a peak rate of 45 meteors per hour. The Corona Australids' rate varies from year to year. At only six days, the shower's duration is particularly short, and its meteoroids are small; the stream is devoid of large meteoroids. The Corona Australids were first seen with the unaided eye in 1935 and first observed with radar in 1955. Corona Australid meteors have an entry velocity of 45 kilometers per second. In 2006, a shower originating near Beta Coronae Australis was designated as the Beta Coronae Australids. They appear in May, the same month as a nearby shower known as the May Microscopids, but the two showers have different trajectories and are unlikely to be related.
History
Corona Australis may have been recorded by ancient Mesopotamians in the MUL.APIN, as a constellation called MA.GUR ("The Bark"). However, this constellation, adjacent to SUHUR.MASH ("The Goat-Fish", modern Capricornus), may instead have been modern Epsilon Sagittarii. As a part of the southern sky, MA.GUR was one of the fifteen "stars of Ea".
In the 3rd century BC, the Greek didactic poet Aratus wrote of, but did not name the constellation, instead calling the two crowns Στεφάνοι (Stephanoi). The Greek astronomer Ptolemy described the constellation in the 2nd century AD, though with the inclusion of Alpha Telescopii, since transferred to Telescopium. Ascribing 13 stars to the constellation, he named it Στεφάνος νοτιος (), "Southern Wreath", while other authors associated it with either Sagittarius (having fallen off his head) or Centaurus; with the former, it was called Corona Sagittarii. Similarly, the Romans called Corona Australis the "Golden Crown of Sagittarius". It was known as Parvum Coelum ("Canopy", "Little Sky") in the 5th century. The 18th-century French astronomer Jérôme Lalande gave it the names Sertum Australe ("Southern Garland") and Orbiculus Capitis, while German poet and author Philippus Caesius called it Corolla ("Little Crown") or Spira Australis ("Southern Coil"), and linked it with the Crown of Eternal Life from the New Testament. Seventeenth-century celestial cartographer Julius Schiller linked it to the Diadem of Solomon. Sometimes, Corona Australis was not the wreath of Sagittarius but arrows held in his hand.
Corona Australis has been associated with the myth of Bacchus and Stimula. Jupiter had impregnated Stimula, causing Juno to become jealous. Juno convinced Stimula to ask Jupiter to appear in his full splendor, which the mortal woman could not handle, causing her to burn. After Bacchus, Stimula's unborn child, became an adult and the god of wine, he honored his deceased mother by placing a wreath in the sky.
In Chinese astronomy, the stars of Corona Australis are located within the Black Tortoise of the North (北方玄武, Běi Fāng Xuán Wǔ). The constellation itself was known as ti'en pieh ("Heavenly Turtle") and during the Western Zhou period, marked the beginning of winter. However, precession over time has meant that the "Heavenly River" (Milky Way) became the more accurate marker to the ancient Chinese and hence supplanted the turtle in this role. Arabic names for Corona Australis include Al Ķubbah "the Tortoise", Al Ĥibā "the Tent" or Al Udḥā al Na'ām "the Ostrich Nest". It was later given the name Al Iklīl al Janūbiyyah, which the European authors Chilmead, Riccioli and Caesius transliterated as Alachil Elgenubi, Elkleil Elgenubi and Aladil Algenubi respectively.
The ǀXam speaking San people of South Africa knew the constellation as ≠nabbe ta !nu "house of branches"—owned originally by the Dassie (rock hyrax), and the star pattern depicting people sitting in a semicircle around a fire.
The indigenous Boorong people of northwestern Victoria saw it as Won, a boomerang thrown by Totyarguil (Altair). The Aranda people of Central Australia saw Corona Australis as a coolamon carrying a baby, which was accidentally dropped to earth by a group of sky-women dancing in the Milky Way. The impact of the coolamon created Gosses Bluff crater, 175 km west of Alice Springs. The Torres Strait Islanders saw Corona Australis as part of a larger constellation encompassing part of Sagittarius and the tip of Scorpius's tail; the Pleiades and Orion were also associated. This constellation was Tagai's canoe, crewed by the Pleiades, called the Usiam, and Orion, called the Seg. The myth of Tagai says that he was in charge of this canoe, but his crewmen consumed all of the supplies onboard without asking permission. Enraged, Tagai bound the Usiam with a rope and tied them to the side of the boat, then threw them overboard. Scorpius's tail represents a suckerfish, while Eta Sagittarii and Theta Corona Australis mark the bottom of the canoe. On the island of Futuna, the figure of Corona Australis was called Tanuma and in the Tuamotus, it was called Na Kaua-ki-Tonga.
See also
Corona Australis (Chinese astronomy)
Chamaeleon complex
References
Citations
Sources
Online sources
SIMBAD
External links
The Deep Photographic Guide to the Constellations: Corona Australis
Warburg Institute Iconographic Database (medieval and early modern images of Corona Australis)
Constellations
Constellations listed by Ptolemy
Mythological clothing
Roman mythology
Southern constellations | Corona Australis | Astronomy | 3,994 |
36,549,071 | https://en.wikipedia.org/wiki/Vortex%20sheet | A vortex sheet is a term used in fluid mechanics for a surface across which there is a discontinuity in fluid velocity, such as in slippage of one layer of fluid over another. While the tangential components of the flow velocity are discontinuous across the vortex sheet, the normal component of the flow velocity is continuous. The discontinuity in the tangential velocity means the flow has infinite vorticity on a vortex sheet.
At high Reynolds numbers, vortex sheets tend to be unstable. In particular, they may exhibit Kelvin–Helmholtz instability.
The formulation of the vortex sheet equation of motion is given in terms of a complex coordinate . The sheet is described parametrically by where is the arclength between coordinate and a reference point, and is time. Let denote the strength of the sheet, that is, the jump in the tangential discontinuity. Then the velocity field induced by the sheet is
The integral in the above equation is a Cauchy principal value integral. We now define as the integrated sheet strength or circulation between a point with arc length and the reference material point in the sheet.
As a consequence of Kelvin's circulation theorem, in the absence of external forces on the sheet, the circulation between any two material points in the sheet remains conserved, so . The equation of motion of the sheet can be rewritten in terms of and by a change of variable. The parameter is replaced by . That is,
This nonlinear integro-differential equation is called the Birkoff-Rott equation. It describes the evolution of the vortex sheet given initial conditions. Greater details on vortex sheets can be found in the textbook by Saffman (1977).
Diffusion of a vortex sheet
Once a vortex sheet, it will diffuse due to viscous action. Consider a planar unidirectional flow at ,
implying the presence of a vortex sheet at . The velocity discontinuity smooths out according to
where is the kinematic viscosity. The only non-zero vorticity component is in the direction, given by
.
Vortex sheet with periodic boundaries
A flat vortex sheet with periodic boundaries in the streamwise direction can be used to model a temporal free shear layer at high Reynolds number. Let us assume that the interval between the periodic boundaries is of length . Then the equation of motion of the vortex sheet reduces to
Note that the integral in the above equation is a Cauchy principal value integral. The initial condition for a flat vortex sheet with constant strength is . The flat vortex sheet is an equilibrium solution. However, it is unstable to infinitesimal periodic disturbances of the form . Linear theory shows that the Fourier coefficient grows exponentially at a rate proportional to . That is, higher the wavenumber of a Fourier mode, the faster it grows. However, a linear theory cannot be extended much beyond the initial state. If nonlinear interactions are taken into account, asymptotic analysis suggests that for large and finite , where is a critical value, the Fourier coefficient decays exponentially. The vortex sheet solution is expected to lose analyticity at the critical time. See Moore (1979), and Meiron, Baker and Orszag (1983).
The vortex sheet solution as given by the Birkoff-Rott equation cannot go beyond the critical time. The spontaneous loss of analyticity in a vortex sheet is a consequence of mathematical modeling since a real fluid with viscosity, however small, will never develop singularity. Viscosity acts a smoothing or regularization parameter in a real fluid. There have been extensive studies on a vortex sheet, most of them by discrete or point vortex approximation, with or without desingularization. Using a point vortex approximation and delta-regularization Krasny (1986) obtained a smooth roll-up of a vortex sheet into a double branched spiral. Since point vortices are inherently chaotic, a Fourier filter is necessary to control the growth of round-off errors. Continuous approximation of a vortex sheet by vortex panels with arc wise diffusion of circulation density also shows that the sheet rolls-up into a double branched spiral.
In many engineering and physical applications the growth of a temporal free shear layer is of interest. The thickness of a free shear layer is usually measured by momentum thickness, which is defined as
where and is the freestream velocity. Momentum thickness has the dimension of length and the non-dimensional momentum thickness is given by . Momentum thickness can be used to measure the thickness of a vortex layer.
See also
Vortex ring
Burgers vortex sheet
References
Fluid dynamics
Fluid dynamic instabilities | Vortex sheet | Chemistry,Engineering | 930 |
8,765,022 | https://en.wikipedia.org/wiki/Speed%20of%20electricity | The word electricity refers generally to the movement of electrons, or other charge carriers, through a conductor in the presence of a potential difference or an electric field. The speed of this flow has multiple meanings. In everyday electrical and electronic devices, the signals travel as electromagnetic waves typically at 50%–99% of the speed of light in vacuum. The electrons themselves move much more slowly. See drift velocity and electron mobility.
Electromagnetic waves
The speed at which energy or signals travel down a cable is actually the speed of the electromagnetic wave traveling along (guided by) the cable. I.e., a cable is a form of a waveguide. The propagation of the wave is affected by the interaction with the material(s) in and surrounding the cable, caused by the presence of electric charge carriers, interacting with the electric field component, and magnetic dipoles, interacting with the magnetic field component.
These interactions are typically described using mean field theory by the permeability and the permittivity of the materials involved.
The energy/signal usually flows overwhelmingly outside the electric conductor of a cable. The purpose of the conductor is thus not to conduct energy, but to guide the energy-carrying wave.
Velocity of electromagnetic waves in good dielectrics
The velocity of electromagnetic waves in a low-loss dielectric is given by
where
= speed of light in vacuum.
= the permeability of free space = 4π x 10−7 H/m.
= relative magnetic permeability of the material. Usually in good dielectrics, e.g. vacuum, air, Teflon, .
.
= the permittivity of free space = 8.854 x 10−12 F/m.
= relative permittivity of the material. Usually in good conductors e.g. copper, silver, gold, .
.
Velocity of electromagnetic waves in good conductors
The velocity of transverse electromagnetic (TEM) mode waves in a good conductor is given by
where
= frequency.
= angular frequency = 2f.
= conductivity of annealed copper = .
= conductivity of the material relative to the conductivity of copper. For hard drawn copper may be as low as 0.97.
.
and permeability is defined as above in
= the permeability of free space = 4π x 10−7 H/m.
= relative magnetic permeability of the material. Nonmagnetic conductive materials such as copper typically have a near 1.
.
This velocity is the speed with which electromagnetic waves penetrate into the conductor and is not the drift velocity of the conduction electrons. In copper at 60Hz, 3.2m/s. As a consequence of Snell's Law and the extremely low speed, electromagnetic waves always enter good conductors in a direction that is within a milliradian of normal to the surface, regardless of the angle of incidence.
Electromagnetic waves in circuits
In the theoretical investigation of electric circuits, the velocity of propagation of the electromagnetic field through space is usually not considered; the field is assumed, as a precondition, to be present throughout space. The magnetic component of the field is considered to be in phase with the current, and the electric component is considered to be in phase with the voltage. The electric field starts at the conductor, and propagates through space at the velocity of light, which depends on the material it is traveling through.
The electromagnetic fields do not move through space. It is the electromagnetic energy that moves. The corresponding fields simply grow and decline in a region of space in response to the flow of energy. At any point in space, the electric field corresponds not to the condition of the electric energy flow at that moment, but to that of the flow at a moment earlier. The latency is determined by the time required for the field to propagate from the conductor to the point under consideration. In other words, the greater the distance from the conductor, the more the electric field lags.
Since the velocity of propagation is very high – about 300,000 kilometers per second – the wave of an alternating or oscillating current, even of high frequency, is of considerable length. At 60 cycles per second, the wavelength is 5,000 kilometers, and even at 100,000 hertz, the wavelength is 3 kilometers. This is a very large distance compared to those typically used in field measurement and application.
The important part of the electric field of a conductor extends to the return conductor, which usually is only a few feet distant. At greater distance, the aggregate field can be approximated by the differential field between conductor and return conductor, which tend to cancel. Hence, the intensity of the electric field is usually inappreciable at a distance which is still small compared to the wavelength.
Within the range in which an appreciable field exists, this field is practically in phase with the flow of energy in the conductor. That is, the velocity of propagation has no appreciable effect unless the return conductor is very distant, or entirely absent, or the frequency is so high that the distance to the return conductor is an appreciable portion of the wavelength.
Charge carrier drift
The drift velocity deals with the average velocity of a particle, such as an electron, due to an electric field. In general, an electron will propagate randomly in a conductor at the Fermi velocity. Free electrons in a conductor follow a random path. Without the presence of an electric field, the electrons have no net velocity.
When a DC voltage is applied, the electron drift velocity will increase in speed proportionally to the strength of the electric field. The drift velocity in a 2 mm diameter copper wire in 1 ampere current is approximately 8 cm per hour. AC voltages cause no net movement. The electrons oscillate back and forth in response to the alternating electric field, over a distance of a few micrometers – see example calculation.
See also
Speed of light
Speed of gravity
Speed of sound
Telegrapher's equations
Reflections of signals on conducting lines
References
Further reading
Alfvén, H. (1950). Cosmical electrodynamics. Oxford: Clarendon Press
Alfvén, H. (1981). Cosmic plasma. Taylor & Francis US.
"Velocity of Propagation of Electric Field", Theory and Calculation of Transient Electric Phenomena and Oscillations by Charles Proteus Steinmetz, Chapter VIII, p. 394-, McGraw-Hill, 1920.
Fleming, J. A. (1911). Propagation of electric currents in telephone & telegraph conductors. New York: Van Nostrand
Electromagnetism
Electricity | Speed of electricity | Physics | 1,340 |
24,376,008 | https://en.wikipedia.org/wiki/C11H12O2 | {{DISPLAYTITLE:C11H12O2}}
The molecular formula C11H12O2 (molar mass: 176.21 g/mol) may refer to:
Allyl phenylacetate
Centalun
Cinnamyl acetate
2,2-Di-2-furylpropane
Ethyl cinnamate | C11H12O2 | Chemistry | 75 |
4,343,531 | https://en.wikipedia.org/wiki/Rica%20Erickson | Frederica Lucy "Rica" Erickson , née Sandilands, (10 August 1908 – 8 September 2009) was an Australian naturalist, botanical artist, historian, author and teacher. Without any formal scientific training, she wrote extensively on botany and birds, as well as genealogy and general history. Erickson authored ten books, co-authored four, was editor of twelve, and author or co-author of numerous papers and articles that have been printed in popular, scientific and encyclopaedic publications.
Biography
Born in Boulder, Western Australia, Erickson was the eldest of eight children of Phoebe Cooke and Christopher Sandilands, both of whom immigrated to Western Australia from Victoria in 1906, and met in the goldfield town. Christopher Sandilands was a farmer's son and worked at the Great Boulder Mine as a filter press hand. The family lived on Dwyer Street.
Christopher enlisted into the army and served in France during World War I. He returned home disabled and was unable to resume his work at the mine, consequently purchasing a block of virgin bush at Kendenup to begin farming as an orchardist. It was here that Rica met botanical artist Emily Pelloe in 1921. Pelloe was introduced after Jack De Garis, the publisher of Pelloe's books, gave the Sandilands family a gift of her just published Wildflowers of Western Australia as a Christmas present.
She returned to the goldfields to attend Eastern Goldfields High School, staying with her grandmother for five years. While living in Boulder she joined Girl Guides Australia where she developed an interest in birds and flowering plants. Choosing a career of teaching she was appointed as monitor teacher at her family town of Kendenup in 1924. After Kendenup, she was transferred to Mount Barker, Dumbleyung and Gnowangerup and in 1927 went to Perth and entered Claremont Teachers College for the required one year of training to become a country teacher. While there she met Dom Serventy and joined the Western Australian Naturalists' Club.
By 1931 she was teaching at isolated one-teacher schools such as Aurora between Cranbrook and Kojonup, and later at Young's Siding near Wilson Inlet, and Denmark. The countryside on the southern coast piqued an interest in orchids and coincided with the publication of her friend Emily Pelloe's second book, West Australian Orchids. Eminent orchidologists Edith Coleman and Dr. Richard Sanders Rogers were quoted extensively in Pelloe's book, and Erickson established contact, sending them sketches and pressings of orchids found in her region. Wilson Inlet was the site of many specimens painted in 1881 by Robert D. FitzGerald, who published the important work Australian Orchids. In Christmas 1931 she holidayed in Victoria and met Coleman and Rogers who encouraged her further study. Knowing she would be returning to a school posting near Wilson Inlet, Rogers instructed her on the finer details of painting the plants using pen and ink instead of pencil as she did previously.
After several years teaching on the southern coast of Western Australia, Erickson requested and received a transfer to the school at Bolgart north of Toodyay in 1934. It was here that she regularly passed by Hawthornden, the historic house of pioneer settler, botanist and naturalist James Drummond. Later she would write a detailed family history of the Drummond family, in The Drummonds of Hawthornden, as well as histories of the surrounding districts in The Victoria Plains and Old Toodyay and Newcastle. Another interest that she followed in Bolgart was bees and wasps, which she studied with the apiologist Tarlton Rayment.
In Bolgart she met share-farmer and future husband Sydney "Syd" Uden Erickson (1908–1987) and they were married in Fremantle in June 1936. The couple bought land at Bolgart in 1938, which they cleared and named Fairlea. They raised four children: Dorothy (born 1939), John (1940), Bethel (1942), and Robin (1943); the next few years were devoted largely to raising the children and establishing the farm. However Erickson maintained her interest in natural history and in 1951 published her first book, the self-illustrated Orchids of the West. This was followed by Triggerplants in 1958.
The state botanist Charles Gardner ran a wildflower tour in 1957 for the Midland Railway Road Service. The following year Erickson was invited to lead the tour, taking the opportunity for a paid holiday. In later years she led other groups of tourists on nature based tours in the south and north of the state.
In 1965 the couple travelled to Europe for a holiday where Rica spent some time studying Drummond's plant specimens at the Kew Gardens herbarium in London, which were sent from Western Australia in the mid-19th century. On their return, they retired from farm life and settled in the Perth suburb of Nedlands, where Erickson wrote several more books. She became a member of the Royal Western Australian Historical Society and her writing during this period focussed on the early days of the state's European settlement, and its convict era. She wrote a history of the society called Forty Years of the Royal Western Australian Historical Society: 1936–1976 which was published in Early Days. Assisted by a group of volunteers, she compiled the first three volumes of the Dictionary of Western Australians in time for Western Australia's sesquicentennial year of 1979.
In 1973 Flowers and Plants of Western Australia was first published. This book on Western Australian wildflowers and designed for popular use contained over 500 colour photographs and was the combined effort of Erickson as chairman and coordinator, Alex George and Neville Marchant as botanists, and Michael Morcombe as the photographer.
Syd died in 1987. Rica died on 8 September 2009 at Mosman Park.
Nature reserve
In 1964, the Bolgart Branch of the Country Women's Association petitioned the Victoria Plains Shire Council for the protection of of remaining forest along the Old Plains Road, about south-west of Calingiri, an important track through the bush which was blazed by Drummond in 1842. The reserve is located at .
The request was granted, and in 1996, following another request from the Association, the Department of Conservation and Land Management named Reserve 27595 the Rica Erickson Nature Reserve. Naming the reserve after a living person was an unusual step for the department's naming committee. Over three hundred people attended the official opening on 11 August 1996.
Awards and recognition
In 1980 she was awarded an honorary degree of doctor of letters from the University of Western Australia for her research and work in the field of botany. In the same year she was named Western Australian Citizen of the Year in the category of the Arts, Culture and Entertainment, and in 1987 was made a Member of the Order of Australia, "in recognition of service to the arts, particularly as an author and illustrator". Her botanical illustrations have been exhibited at the Art Gallery of Western Australia and Perth's Alexander Library.
In May 2007 she was awarded the Heritage Council of Western Australia individual award for her lifelong contribution to heritage in Western Australia.
Noted botanist Alex George with whom she co-wrote Flowers and Plants of Western Australia in 1973, wrote: "Rica Erickson has been one of the foremost amateur natural historians in Western Australia in the 20th Century."
Ronda Jamieson, Director of the J S Battye Library in Western Australia said "Rica Erickson is one of Western Australia's treasures". The State Library houses the Rica Erickson collection, a repository which includes manuscripts of her publications, background papers relating to the genealogical dictionaries, all of her published works, field journals, and 500 of her botanical art works. A website maintained by the library has been created as a tribute to her.
In 2004, Stephen Hopper and Andrew P. Brown named an orchid genus Ericksonella in her honour.
Works
The J S Battye Library holds some of her works.
Botany
Historical
Contributions to natural and general history books
Erickson was the head compiler of the Dictionary of Western Australians in its many volumes.
Papers and articles
Articles in The West Australian regarding natural history in the 1950s.
Springtime in the Stirlings – The West Australian 17 November 1951 p. 11 – Climbing Mondurup at the west end of the Range.
Australian Orchid Review
Australian Plants
Bird Study for Bird Lovers
The Emu: Official Organ of the Royal Australasian Ornithologists Union
Flowers & plants of Western Australia (with AS George AS, NG Marchant and MK Morcombe )(1986) (Reed, Sydney).
The Perth Mint Wildflower Chart
The Victorian Naturalist
The Western Australian Naturalist
Western Wildlife
Wild Life
Wildlife and Outdoors
Wildlife in Australia
Notes
Further reading
Layman, Lenore (editor) (2001) Rica's Stories/Rica Erickson Nedlands, W.A. Royal Western Australian Historical Society. – including the select bibliography pp. 243–247.
External links
Rica Erickson Home Page
Heritage Council of Western Australia – Awards Archive
1908 births
2009 deaths
20th-century Australian botanists
Australian naturalists
Australian nature writers
Orchidologists
Australian women centenarians
Australian taxonomists
Australian women historians
Botanical collectors active in Australia
Botanists active in Australia
Botany in Western Australia
Historians from Western Australia
Australian women biographers
Australian women botanists
Australian women educators
Women naturalists
Women science writers
Women taxonomists
Writers from Western Australia
Members of the Order of Australia
People from Boulder, Western Australia
20th-century Australian biographers
20th-century Australian women scientists
20th-century Australian women writers
20th-century naturalists
Western Australian schoolteachers
Botanical illustrators | Rica Erickson | Technology | 1,936 |
24,378,550 | https://en.wikipedia.org/wiki/C11H13N | {{DISPLAYTITLE:C11H13N}}
The molecular formula C11H13N (molar mass: 159.228 g/mol) may refer to:
Pargyline
2,3,4,5-Tetrahydro-1,5-methano-1H-3-benzazepine
Molecular formulas | C11H13N | Physics,Chemistry | 75 |
62,777,988 | https://en.wikipedia.org/wiki/LC3%20%28codec%29 | LC3 (Low Complexity Communication Codec) is an audio codec specified by the Bluetooth Special Interest Group (SIG) for the LE Audio audio protocol introduced in Bluetooth 5.2. It's developed by Fraunhofer IIS and Ericsson as the successor of the SBC codec.
LC3 provides higher audio quality and better Packet loss concealment than SBC, G.722 and Opus, according to subjective testing by the Bluetooth Special Interest Group and ETSI. The conclusion regarding Opus is disputed as the test only included speech audio, but the comparison was made to version 1.1.4 of the reference Opus encoder, using complexity level 0 at 32 kbps and relying on CELT (general audio) instead of the FEC-capable SILK (speech); the test also did not take into account the newer version 1.2 of the Opus encoder released in 2017, where significant improvements were made to low bitrate streams.
Supported systems:
Android 13; Google's liblc3 codec is open-source as a standalone GitHub project
Windows 11
Zephyr OS
Linux via bluez-alsa or BlueZ + PipeWire
LC3plus
LC3plus High Resolution mode is a codec defined by ETSI and is not compatible with the LC3 defined by Bluetooth SIG. It's included in the 2019 DECT standard.
On November 9, 2022, the Japan Audio Society (JAS) released a statement certifying LC3plus with the "Hi-Res AUDIO WIRELESS" logo. LC3plus is the 4th codec to receive this, alongside SCL6 (formerly known as MQair), LDAC and LHDC codecs.
The ETSI implementation of LC3plus is source-available software, subject to a ETSI Intellectual Property Rights Policy and the usual patent restrictions.
Fraunhofer defines a way to use LC3plus over A2DP.
See also
SBC (codec)
AptX
LDAC (codec)
LHDC (codec)
References
Audio codecs
Bluetooth | LC3 (codec) | Technology | 439 |
906,601 | https://en.wikipedia.org/wiki/Source-synchronous | Source-Synchronous clocking refers to a technique used for timing symbols on a digital interface. Specifically, it refers to the technique of having the transmitting device send a clock signal along with the data signals. The timing of the unidirectional data signals is referenced to the clock (often called the strobe) sourced by the same device that generates those signals, and not to a global clock (i.e. generated by a bus master). Compared to other digital clocking topologies like system-synchronous clocks, where a global clock source is fed to all devices in the system, a source-synchronous clock topology can attain far higher speeds.
This type of clocking is common in high-speed interfaces between micro-chips, including DDR SDRAM, SGI XIO interface, Intel Front Side Bus for the x86 and Itanium processors, HyperTransport, SPI-4.2 and many others.
Reasons for usage
A reason that source-synchronous clocking is useful is that it has been observed that all of the circuits within a given semiconductor device experience roughly the same process-voltage-temperature (PVT) variation. This means signal propagation delay experienced by the data through a device tracks the delay experienced by the clock through that same device over PVT. This advantage allows higher speed operation as compared to the traditional technique of providing the clock from a third device to both the transmitter and the receiver. Another benefit is that higher complexity data-recovery or clock-data-recovery circuits (such as PLLs) are not required when this technique is used.
Or rather than higher clock speeds, large systems that take advantage of source-synchronous clocking can have the benefit of a higher tolerance of PVT variation of its individual components.
Timing Analysis
Synchronous logic elements such as flip-flops have static timing criteria that must be satisfied in order for them to work correctly. In a system-synchronous clock topology where a skew-aligned clock is fed to all devices, the criteria are
A source-synchronous clock topology eliminates two of these factors, and . The former is eliminated since both clock and data signals are driven by identical flip-flops on the same silicon at the same temperature and voltage, thereby equalizing the seen by both clock and data. The latter is eliminated for the same reason - since the clock and data are driven by identical devices and (ideally) connected with wires of equal length, the skew between clock and data is greatly reduced. For this reason, can be reduced significantly. Since frequency is inversely proportional to clock period, the clock frequency increases as a result.
Drawbacks
One drawback of using source-synchronous clocking is the creation of a separate clock-domain at the receiving device, namely the clock-domain of the strobe generated by the transmitting device. This strobe clock-domain is often not synchronous to the core clock domain of the receiving device. For proper operation of the received data with other data already present in the device, an additional stage of synchronization logic is required to transfer the received data into the core clock-domain of the receiving device. This stage can often be found alongside source synchronous logic. This usually results in greater system complexity compared to globally clocked systems, but the benefits are generally much greater than this increase in complexity.
Implementation Variations
In bi-directional data transfer buses, two opposing unidirectional strobes can be sent from each device. Often the strobe is free running in this case. That is, the strobe continues to toggle whether there is data being transferred or not.
Another variation is the sharing of the same bus to transfer the strobe. In this case the strobe can only be transferred by the device that is sending the data and may require transmission of pre-ambles and post-ambles to indicate the start and end of the strobes. (Example: DDR2).
In large ASICs or processors, multiple strobes and data groups (data bits that are associated to the same strobe) may exist between the same two devices to account for the slightly different PVT variations in different regions of the same die.
See also
Clock recovery
8B/10B encoding
Synchronization (computer science)
External links
Overview of Memory Types and DDR Interface Design Implementation
Clock signal
Electrical circuits | Source-synchronous | Engineering | 920 |
37,237,169 | https://en.wikipedia.org/wiki/Affect%20%28education%29 | In education, affect is broadly defined as the attitudes, emotions, and values present in an educational environment. The two main types of affect are professional affect and student affect. Professional affect refers to the emotions and values presented by the teacher which are picked up by the student, while student affect refers to the attitudes, interests, and values acquired in the educational environment. While there is the possibility of overlap between student and professional affect, the terms are rarely used interchangeably by educational professionals, with student affect being reserved primarily for use to describe developmental activities present in a school which are not presented by the teacher.
The importance of affect in education has become a topic of increasing interest in the fields of psychology and education. It is a commonly held opinion that curriculum and emotional literacy should be interwoven. Examples of such curriculum include using English language to increase emotional vocabulary (see affect labeling), and writing about the self and history to discuss emotion in major events such as genocide. This type of curriculum is also known as therapeutic education. According to Ecclestone and Hayes, therapeutic education focuses on the emotional over the intellectual.
Educator attitudes
In order for such curriculum to be implemented, it is essential that educators be aware of the importance emotional literacy. Examination of educator and student attitudes towards emotional literacy is a common topic of research. Researchers have found that staff have conceptions of what constitutes emotional literacy, including being self-aware of one's own feelings, using emotional language, and being cognizant that children have feelings that need to be taken into account. In addition, staff discussed the necessity of having all educators dedicated to creating an emotionally literate school, and the detrimental effects of even one educator not supporting this initiative.
School attitudes
Roffey (2008) examined the influence of emotional literacy on the school as a whole using ecological analysis. It was found that positive change was gradual, and involved multiple elements. For instance, teachers who felt as though they were genuinely valued and were consulted about policy felt happier at work. In turn, these teachers felt better prepared to handle conflicts that arose inside the classroom, and when students experienced this positive approach they were more cooperative (see cooperative learning). This shows how incorporating emotional literacy into a child's education is a school-wide collaborative effort.
Funding
Examples of government funding of emotional literacy include Every Child Matters.
Criticisms
Criticisms of emotional literacy in curriculum revolves around the idea that it although well intended, it is designed to disempower students.
See also
Affect (psychology)
References
Emotion
Educational psychology | Affect (education) | Biology | 508 |
42,888,422 | https://en.wikipedia.org/wiki/Rock%20shed | A rock shed is a civil engineering structure used in mountainous areas where rock slides and land slides create highway closure problems. A rock shed is built over a roadway that is in the path of the slide. They are equally used to protect railroads. They are usually designed as a heavy reinforced concrete covering over the road, protecting the surface and vehicles from damage due to the falling rocks with a sloping surface to deflect slip material beyond the road, however an alternative is to include an impact-absorbing layer above the ceiling. A further use of this type of structure may be seen protecting the A4 road; although constructed primarily to alleviate risk from falling rocks from a limestone seam it also serves to protect against objects or persons falling from the Clifton Suspension Bridge where the height differential of approximately 70 metres from the bridge to the bottom of the Avon Gorge would give sufficient kinetic energy to even a relatively small item to cause injury on impact.
Examples of rock sheds
A4 road where it passes under the Clifton Suspension Bridge, Bristol, England, constructed in 1980
California State Route 1 at Pitkins Curve, just north of Limekiln State Park, constructed in 2014
Ferguson Rock Shed, to rectify a closure of California State Route 140 by a landslide in 2006, completion expected in the mid-2020s
External links
See also
Avalanche dam
Rock shelter
Snow shed
References
Civil engineering
Infrastructure | Rock shed | Engineering | 271 |
17,647,837 | https://en.wikipedia.org/wiki/Lenovo%203000 | Lenovo 3000 was a line of low-priced notebook and desktop computers designed by Lenovo Group targeting small businesses and individuals. It was replaced with the IdeaCentre and IdeaPad brands.
Background
The Lenovo 3000 series marked the debut of Lenovo branded products outside of China. First showcased in New York City on 23 February 2006, the line was intended to boost Lenovo's competitiveness internationally against rival brands like Dell and Hewlett-Packard. In addition, the 3000 series gave the company an independent identity: an identity separate from the Thinkpad line that Lenovo acquired in 2005 and defined its Westernised image since the acquisition.
In 2008, after introducing two new consumer brands, IdeaPad for laptops and IdeaCentre for desktops, Lenovo stopped selling its 3000 series models, although they continued to be sold in China in 2009.
Models
Desktops
Lenovo 3000 J
features both AMD and Intel processors
Lenovo 3000 H
Notebooks
First introduced in 2006, the Lenovo 3000 N100 and V100 offered Intel Core Duo processors, while the lower-end C series featured Pentium M and Celeron M processors. Its successors, C200, N200, V200 featured Core 2 Duo processors. Thereafter, came the N500, the G-series, and the B series
Lenovo 3000 C
C100, C200 - 15-inch XGA screen
Lenovo 3000 N
N100, N200 - 14.1-inch- and 15.4-inch- WXGA models
N500 - 15.4 inch screen.
Lenovo 3000 V
V100, V200 - 12.1-inch WXGA models
Lenovo 3000 G
G400, G410, G430, G450, G455, G510, G530, G550, and G560
Lenovo 3000 B Series
B450-B490 - 15.4 inch screen
References
External links
Introducing Lenovo 3000, Lenovo Group
3000
Consumer electronics brands
Computer-related introductions in 2006
Products and services discontinued in 2008 | Lenovo 3000 | Technology | 420 |
75,143,688 | https://en.wikipedia.org/wiki/Phlotoxin%201 | Phlotoxin (PhlTx1, μ-TRTX-Pspp-1) is a neurotoxin from the venom of the tarantula Phlogiellus that targets mostly voltage-sensitive sodium channels and mainly Nav1.7. The only non-sodium voltage-sensitive channel that is inhibited by Phlotoxin is Kv3.4. Nav1.4 and Nav1.6 seem to be Phlotoxin-1-sensitive to some extent as well.
Etymology
Another name for phlotoxin is μ-TRTX-Pspp-1: μ for NaV channel inhibition, then TRTX refers to theraphotoxin which refers to a group of toxins found in the Theraphosidae family.
Sources
Phlotoxin was first purified, characterized and sequenced from Phlogiellus sp. Phlogiellus is a genus of tarantulas. Its venom, which includes several neurotoxic peptides like phlotoxin, targets diverse ion channels and chemical receptors.
Chemistry
Structure
Phlotoxin-1 (PhlTx1), weighing around 4058.83 Da, is identified by a 34-amino acid sequence featuring three disulfide bridges and organized based on the Inhibitor Cystine Knot (ICK) architectural motif which is effective for its structural stabilization as three disulfide bonds are structured in a manner where two of them combine to create a circular arrangement, through which the third disulfide bond passes. It is classified to be a member of the NaV channel spider toxin (NaSpTx) family 1.
The structure of phlotoxin comprises six cysteine residues forming an ICK architecture fold, with amidation occurring at the C-terminus. "Cys2-Cys17, Cys9-Cys22, Cys16-Cys29" disulfide bridge organization. The proximity of Cys 16 and 17 makes it challenging to synthesize even though phlotoxin is commercially available.
Homology
The sequence similarity of PhlTx1 with other peptides does not exceed 59%. The closest match regarding inhibition IC50 for PhlTx1 is found in the NaSpTx family to HnTx-III or HwTx-I. It is basically classified under the NaSpTx family, due to the presence of disulfide bridges. PhlTx1 is categorized within the NaSpTx-1 family primarily because of its disulfide bridges. Notably, the inclusion of three proline residues (Pro11, Pro18, and Pro27) introduces the potential for Cis–trans isomerism. This dynamic property can influence the precise formation of secondary structures and the correct alignment of disulfide bridges, thereby impacting the overall structural integrity of the toxin.
Target
In examining the effects of PhlTx1 on the sodium channel Nav1.7/β1, it appears to share similarities with TTX (tetrodotoxin). Both PhlTx1 and TTX exhibit a capacity to block the channel pore, resulting in a noticeable decrease in sodium currents. Moreover, the behavior of the channel, as reflected in gating parameters, remains largely unaffected by the presence of PhlTx1. This observation suggests a comparable behavior between PhlTx1 and TTX in modulating the function of Nav1.7/β1 channels. The IC50 for PhlTx1 to inhibit Nav1.7 is 39 +/- 2 nM.
The PhlTx1 affects all hNav (human voltage-gated Na channels) channels to a different degree except hNav1.8. There is a poor selectivity of PhlTx1 towards the hNav1.1 and 1.3. It also has shown a high affinity towards hNav1.7.
Mode of action
The amino acids which are critical for binding of the hNaV1.7 subtype are identified by their substitution with alanine. When tryptophan at position 24, lysine at position 25 and tyrosine at position 26 are replaced with alanine, there is a complete loss of affinity. This highlights the critical role of these amino acids in the binding process to Nav1.7. Other substitutions, like alanine at position 1, serine at position 8, lysine at position 12 or 15, result in a slight change (less than 2.8-fold) in variant affinity, whereas substituting aspartate at position 7 leads to an increase in variant affinity (IC50 = 47.0 ± 40.9).
Therapeutic use
Phlotoxin-1 (PhlTx1) has demonstrated selectivity in inhibiting the voltage-gated sodium channel NaV1.7. Its potential as an antinociceptive agent became apparent when a loss-of-function mutation in the NaV1.7 gene resulted in a congenital inability to perceive pain. Notably, these peptides do not independently exhibit antinociceptive effects; however, when co-administered with exogenous opioids, they bring about analgesic effect, allowing for a significant reduction in opioid dosage. The mechanism underlying the synergistic effect of opioid receptor agonists with selective NaV1.7 inhibitors remains unknown, but this discovery presents a novel approach to pain management. The primary method for evaluating this property involves the formalin test. However, the poor selectivity towards the hNav1.5 and 1.6 subtypes may be associated with in vivo cardiac and neuromuscular side effects, respectively, which could limit its potential use as an analgesic molecule.
References
External links
Peptides
Spider toxins
Sodium channel blockers
Ion channel toxins | Phlotoxin 1 | Chemistry | 1,196 |
17,809,734 | https://en.wikipedia.org/wiki/Carumonam | Carumonam (INN) is a monobactam antibiotic. It is very resistant to beta-lactamases, which means that it is more difficult for bacteria to break down using β-lactamase enzymes.
References
Monobactam antibiotics
Thiazoles
Carbamates
Sulfamates | Carumonam | Chemistry | 65 |
40,313,295 | https://en.wikipedia.org/wiki/CMV423 | CMV423 (2-chloro-3-pyridin-3-yl-5,6,7,8-tetrahydroindolizine-1-carboxamide) is an experimental antiviral drug that has been studied for the treatment of cytomegalovirus (CMV) infection and human herpesvirus 6 (HHV-6) infection. The drug was investigated by Sanofi-Aventis, but its development was discontinued by 2018 before entering clinical trials.
References
Antiviral drugs
Abandoned drugs
Chloroarenes | CMV423 | Chemistry,Biology | 125 |
21,295,680 | https://en.wikipedia.org/wiki/Robotics%20middleware | Robotics middleware is middleware to be used in complex robot control software systems.
"...robotic middleware is designed to manage the complexity and heterogeneity of the hardware and applications, promote the integration of new technologies, simplify software design, hide the complexity of low-level communication and the sensor heterogeneity of the sensors, improve software quality, reuse robotic software infrastructure across multiple research efforts, and to reduce production costs."
It can be described as "software glue" to make it easier for robot builders focus on their specific problem area.
Robotics middleware projects
A wide variety of projects for robotics middleware exist, but no one of these dominates - and in fact many robotic systems do not use any middleware. Middleware products rely on a wide range of different standards, technologies, and approaches that make their use and interoperation difficult, and some developers may prefer to integrate their system themselves.
Player Project
The Player Project (formerly the Player/Stage Project) is a project to create free software for research into robotics and sensor systems. Its components include the Player network server and the Stage robot platform simulators. Although accurate statistics are hard to obtain, Player is one of the most popular open-source robot interfaces in research and post-secondary education. Most of the major intelligent robotics journals and conferences regularly publish papers featuring real and simulated robot experiments using Player and Stage.
RT-middleware
RT-middleware is a common platform standards for Robots based on distributed object technology. RT-middleware supports the construction of various networked robotic systems by the integration of various network-enabled robotic elements called RT-Components. The specification standard of RT-components is discussed and defined by the Object Management Group (OMG).
Urbi
Urbi is an open source cross-platform software platform in C++ used to develop applications for robotics and complex systems. It is based on the UObject distributed C++ component architecture. It also includes the urbiscript orchestration language which is a parallel and event-driven script language. UObject components can be plugged into urbiscript and appear as native objects that can be scripted to specify their interactions and data exchanges. UObjects can be linked to the urbiscript interpreter, or executed as autonomous processes in "remote" mode, either in another thread, another process, a machine on the local network, or a machine on a distant network.
MIRO
Miro is a distributed object oriented framework for mobile robot control, based on CORBA (Common Object Request Broker Architecture) technology.
The Miro core components have been developed under the aid of ACE (Adaptive Communications Environment), an object oriented multi-platform framework for OS-independent interprocess, network and real time communication. They use TAO (The ACE ORB) as their ORB (Object Request Broker), a CORBA implementation designed for high performance and real time applications.
Currently supported platforms include Pioneers, the B21, some robot soccer robots and various robotic sensors.
Orca
Orca describes its goals as:
to enable software reuse by defining a set of commonly-used interfaces;
to simplify software reuse by providing libraries with a high-level convenient API; and
to encourage software reuse by maintaining a repository of components.
They also state: "To be successful, we think that a framework with such objectives must be: general, flexible and extensible; sufficiently robust, high-performance and full-featured for use in commercial applications, yet sufficiently simple for experimentation in university research environments."
They describe their approach as:
adopts a Component-Based Software Engineering approach without applying any additional architectural constraints
uses a commercial open-source library for communication and interface definition
provides tools to simplify component development but makes them strictly optional to maintain full access to the underlying communication engine and services
uses cross-platform development tools
Orca software is released under LGPL and GPL licenses.
OpenRDK
OpenRDK is an open-source software framework for robotics for developing loosely coupled modules. It provides transparent concurrency management, inter-process (via sockets) and intra-process (via shared memory) blackboard-based communication and a linking technique that allows for input/output data ports conceptual system design. Modules for connecting to simulators and generic robot drivers are provided.
Rock
Rock (Robot Construction Kit), is a software framework for the development of robotic systems. The underlying component model is based on the Orocos RTT (Real Time Toolkit). Rock provides all the tools required to set up and run high-performance and reliable robotic systems for wide variety of applications in research and industry. It contains a rich collection of ready to use drivers and modules for use in your own system, and can easily be extended by adding new components.
ISAAC SDK / Simulation
ISAAC, The NVIDIA Isaac Software Development Kit (SDK) is a developer toolbox for accelerating the development and deployment of Artificial Intelligence-powered robots. The SDK includes the Isaac Robot Engine, packages with high-performance robotics algorithms (to perform perception and navigation), and hardware reference applications. Isaac Sim is a virtual robotics laboratory and a high-fidelity 3D world simulator. It accelerates research, design, and development in robotics by reducing cost and risk. Developers can quickly and easily train and test their robots in detailed, highly realistic scenarios. There is an open source community version available at GitHub with supported hardware platform includes BOM details, refer kaya-robot
ROS
ROS (Robot Operating System) is a collection of software frameworks for robot software development on a heterogeneous computer cluster. ROS provides standard operating system services such as hardware abstraction, low-level device control, implementation of commonly used functionality, message-passing between processes, and package management.
YARP
YARP is an open-source software package, written in C++ for interconnecting sensors, processors, and actuators in robots.
DDX
DDX (Dynamic Data eXchange) is (Linux/BSD/Unix) middleware developed by CSIRO to provide a lightweight real-time publish/subscribe service to distributed robot controllers. DDX allows a coalition of programs to share data at run-time through an efficient shared memory mechanism. Multiple machines can be linked by means of a global naming service and, when needed, data is multi-cast across machines. DDX was developed to automate a number of large mining machines: including draglines, LHD trucks, excavators and rock-breakers.
External links
BRICs: a European project that attempts to establish best practices in robot development
References
Robot operating systems
Robotics suites | Robotics middleware | Engineering | 1,349 |
73,730,263 | https://en.wikipedia.org/wiki/Gcore | Gcore is an edge AI, cloud, network, and security company founded in 2014 in Luxembourg. As of March 2024, its global network consists of over 180 Points of Presence (PoPs) on six continents. Gcore is partnering with NVIDIA to provide training and inference on cloud and edge infrastructure, aimed at accelerating artificial intelligence workloads.
History
Gcore was established in 2014 in Luxembourg. The company built its own content delivery network, originally designed for the needs of the entertainment industry. In 2016, Gcore's infrastructure included fifteen points of presence, many in regions not served by hyperscale cloud providers.
In 2020, the company entered partnership agreements with Intel and Equinix.
In 2022, Gcore partnered with Graphcore to launch the European AI Cloud, which uses technology to speed up machine learning tasks with ready-made AI infrastructure.
In March 2024, Gcore announced it had acquired a web application and API protection (WAAP) solution from StackPath.
In May 2024, former vice-chancellor of Germany and federal minister of Germany for health Philipp Rösler joined the Gcore board.
In April 2024, Gcore received a commendation in the Industry Innovation category at the NVIDIA Partner Network Awards EMEA for developing the first speech-to-text technology for Luxembourgish, using its LuxemBERT AI model.
In August 2024, Gcore was named as a Major Player in the IDC MarketScape report for European public cloud Infrastructure (IaaS) 2024 by IDC, the global market intelligence firm.
Network infrastructure
According to the company's website, Gcore has network locations in six continents: Europe, North America, Asia, South America, Africa, and Australia.
Products and services
Gcore provides content delivery network (CDN), cloud computing,virtual machines, bare-metal servers, object storage AI infrastructure and inference, Kubernetes, video streaming, DDoS mitigation, Web application and API protection (WAAP), Domain Name System (DNS), function as a service (FaaS) and logging as a Service (LaaS).
A January 18, 2022, review by TechRadar commend Gcore's large network and CDN analytics. However, the review noted that its support documentation could be more detailed.
In March 2023, Gcore offers a free speed test that helps check internet speed and the quality of a broadband and mobile connection.
Controversies
Correctiv and Tageszeitung reported that Gcore supported the distribution of the TV network RT until April 2023, which has been under sanctions by the EU since March 2022. However, Gcore denies the accusations.
References
External links
Cloud computing
Cloud computing providers
Cloud platforms
DDoS mitigation companies
Content delivery networks
Internet security
Software companies established in 2014
Software companies of Luxembourg
Artificial intelligence companies
Luxembourgian companies established in 2014 | Gcore | Technology | 585 |
994,531 | https://en.wikipedia.org/wiki/NGC%202477 | NGC 2477 (also known as Caldwell 71 or the Termite Hole Cluster) is an open cluster in the constellation Puppis. It contains about 300 stars, and was discovered by Abbé Lacaille in 1751. The cluster's age has been estimated at 700 million years.
Visual appearance
NGC 2477 is a stunning cluster, almost as extensive in the sky as the full moon. It has been called "one of the top open clusters in the sky", like a highly resolved globular cluster without the dense center characteristic of globular clusters. Burnham notes that several observers have remarked on its richness, and that although it is smaller than M46 (also an open cluster in Puppis), it is richer and more compact.
Distance
Burnham cites several published distances, ranging from to , where "ly" is the abbreviation for light year.
Notes
External links
2477
Open clusters
Puppis
071b
? | NGC 2477 | Astronomy | 189 |
57,956,353 | https://en.wikipedia.org/wiki/NextDC | NextDC (stylized as NEXTDC) is an Australian data centre operator. Headquartered in Brisbane, Queensland, NextDC is the largest listed developer and operator of data centres in Australia. , the company operates 13 data centres, with facilities in Melbourne, Sydney, Brisbane, Perth and Canberra.
History
NextDC was founded by Bevan Slattery in May 2010. It has been listed on the Australian Securities Exchange since December 2010.
Since June 2012, Craig Scroggie has assumed the role of Chief Executive Officer.
In 2015, NextDC was named by Deloitte as Australia's fastest growing technology company.
In July 2020, NextDC opened P2, its second data centre in Perth.
In November 2021, NextDC invested around $17 million for a 19.99% stake in AUCloud.
In February 2022, NextDC announced that it will invest more than $100 million to build a data centre on Pirie Street, Adelaide.
In April 2024, NextDC announced a $1.32 billion capital raise to accelerate the expansion of its data centre networks in Sydney and Melbourne.
The company's market capitalisation was valued at over $10 billion as of May 2024.
Data centres
Organisational structure
Board members
Douglas Flynn (Chairman)
Craig Scroggie (CEO and Managing Director)
Gregory Clark AC
Jennifer Lambert
Eileen Doyle
Stuart Davis
Steve Smith
Michael Helmer
Maria Leftakis
References
Data centers
Companies listed on the Australian Securities Exchange
Information technology companies of Australia
Technology companies established in 2010
2010 establishments in Australia | NextDC | Technology | 309 |
1,379,618 | https://en.wikipedia.org/wiki/Lithium%20diisopropylamide | Lithium diisopropylamide (commonly abbreviated LDA) is a chemical compound with the molecular formula . It is used as a strong base and has been widely utilized due to its good solubility in non-polar organic solvents and non-nucleophilic nature. It is a colorless solid, but is usually generated and observed only in solution. It was first prepared by Hamell and Levine in 1950 along with several other hindered lithium diorganylamides to effect the deprotonation of esters at the α position without attack of the carbonyl group.
Preparation and structure
LDA is commonly formed by treating a cooled (0 to −78 °C) mixture of tetrahydrofuran and diisopropylamine with n-butyllithium.
When dissociated, the diisopropylamide anion can become protonated to form diisopropylamine. Diisopropylamine has a pKa value of 36. Therefore, its conjugate base is suitable for the deprotonation of compounds with greater acidity, importantly, such weakly acidic compounds (carbon acids) of the type , where Z = C(O)R', C(O)OR' or CN. Conventional protic functional groups such as alcohols and carboxylic acids are readily deprotonated.
Like most organolithium reagents, LDA is not a salt, but is highly polar. It forms aggregates in solution, with the extent of aggregation depending on the nature of the solvent. In THF its structure is primarily that of a solvated dimer. In nonpolar solvents such as toluene, it forms a temperature-dependent oligomer equilibrium. At room temperature trimers and tetramers are the most likely structures. With decreasing temperature the aggregation extends to pentameric and higher oligomeric structures.
Solid LDA is pyrophoric, but its solutions are generally not. As such it is commercially available as a solution in polar aprotic solvents such as THF and ether; however, for small scale use (less than 50 mmol), it is common and more cost effective to prepare LDA in situ.
Kinetic vs thermodynamic bases
The deprotonation of carbon acids can proceed with either kinetic or thermodynamic reaction control. Kinetic controlled deprotonation requires a base that is sterically hindered and strong enough to remove the proton irreversibly. For example, in the case of phenylacetone, deprotonation can produce two different enolates. LDA has been shown to deprotonate the methyl group, which is the kinetic course of the deprotonation. To ensure the production of the kinetic product, a slight excess (1.1 equiv) of lithium diisopropylamide is used, and the ketone is added to the base at –78 °C. Because the ketone is quickly and quantitatively converted to the enolate and base is present in excess at all times, the ketone is unable to act as a proton shuttle to catalyze the gradual formation of the thermodynamic product. A weaker base such as an alkoxide, which reversibly deprotonates the substrate, affords the more thermodynamically stable benzylic enolate. An alternative to the weaker base is to use a strong base which is present at a lower concentration than the ketone. For instance, with a slurry of sodium hydride in THF or dimethylformamide (DMF), the base only reacts at the solution–solid interface. A ketone molecule might be deprotonated at the kinetic site. This enolate may then encounter other ketones and the thermodynamic enolate will form through the exchange of protons, even in an aprotic solvent which does not contain hydronium ions.
LDA can, however, act as a nucleophile under certain conditions.
See also
Lithium amide
Lithium bis(trimethylsilyl)amide (LiHMDS)
Lithium tetramethylpiperidide (LiTMP)
References
Diisopropylamino compounds
Lithium compounds
Metal amides
Non-nucleophilic bases
Organolithium compounds
Reagents for organic chemistry
Superbases | Lithium diisopropylamide | Chemistry | 914 |
10,660,660 | https://en.wikipedia.org/wiki/Other%20comprehensive%20basis%20of%20accounting | Other Comprehensive Basis of Accounting (OCBOA) in United States accounting refers to a system of accounting other than GAAP. As explained in the Journal of Accountancy,
under Statement on Auditing Standards (United States) No. 62, Special Reports, an OCBOA is any one of:
A statutory basis of accounting (for example, a basis of accounting that insurance companies use under the rules of a state insurance commission).
Income-tax-basis financial statements.
Cash-basis and modified-cash-basis financial statements.
Financial statements prepared using definitive criteria having substantial support in accounting literature that the preparer applies to all material items appearing in the statements (such as the price level basis of accounting).
In situations where GAAP-basis statements aren't necessary because of loan covenants, regulatory requirements or similar circumstances, an OCBOA may just be the answer.
See also
Comparison of cash method and accrual method of accounting
References
Accounting in the United States
Accounting systems | Other comprehensive basis of accounting | Technology | 200 |
51,711,705 | https://en.wikipedia.org/wiki/Approximate%20measures | Approximate measures are units of volumetric measurement which are not defined by a government or government-sanctioned organization, or which were previously defined and are now repealed, yet which remain in use.
It may be that all English-unit derived capacity measurements are derived from one original approximate measurement: the mouthful, consisting of about ounce, called the ro in ancient Egypt (their smallest recognized unit of capacity). The mouthful was still a unit of liquid measure during Elizabethan times. (The principal Egyptian standards from small to large were the ro, hin, hekat, and khar.)
Because of the lack of official definitions, many of these units will not have a consistent value.
United Kingdom
glass-tumbler
breakfast-cup
tea-cup
wine-glass
table-spoon
dessert-spoon
tea-spoon
black-jack
demijohn (dame-jeanne)
goblet
pitcher
gyllot (about equal to 1/2 gill)
noggin (1/4 pint)
nipperkin (measure for liquor, containing no more than 1/2 pint)
tumblerful (10 fl oz or 2 gills or 2 teacupsful)
apothecaries' approximate measures
teacupful = about 4 fl oz
wineglassful = about 2 fl oz
tablespoonful = about 1/2 fl oz
dessertspoonful = about 2 fl dr
teaspoonful = about 1 fl dr
drop = about minim
teacupful (5 fl oz, or 1 gill ibid)
wineglassful (2-1/2 fl oz or 1/2 gill or 1/2 teacupful or 1/4 tumblerful)
dessertspoonful (1/4 fl oz or 2 fl dr and equal to 2 teaspoonful or 1/2 tablespoonful)
teaspoonful (1/8 fl oz or 1 fl dr and also equal to 1/2 dessertspoonful or 1/4 tablespoonful)
United States
The vagueness of how these measures have been defined, redefined, and undefined over the years, both through written and oral history, is best exemplified by the large number of sources that need to be read and cross-referenced in order to paint even a reasonably accurate picture. So far, the list includes the United States Pharmacopoeia, U.S. FDA, NIST, A Manual of Weights, Measures, and Specific Gravity, State Board Questions and Answers, MediCalc, MacKenzie's Ten Thousand Receipts, Approximate Practical Equivalents, When is a Cup not a Cup?, Cook's Info, knitting-and.com., and Modern American Drinks.
Dashes, pinches, and smidgens are all traditionally very small amounts well under a teaspoon, but not more uniformly defined. In the early 2000s some companies began selling measuring spoons that defined a dash as teaspoon, a pinch as teaspoon, and a smidgen as teaspoon. Based on these spoons, there are two smidgens in a pinch and two pinches in a dash. However, the 1954 Angostura “Professional Mixing Guide” states that “a dash” is 1/6th of a teaspoon, or 1/48 of an ounce, and Victor Bergeron (a.k.a. Trader Vic, famous saloonkeeper), said that for bitters it was teaspoon, but fl oz for all other liquids.
References
Measurement | Approximate measures | Physics,Mathematics | 706 |
51,212,902 | https://en.wikipedia.org/wiki/Botanical%20Latin | Botanical Latin is a technical language based on Neo-Latin, used for descriptions of botanical taxa. Until 2012, International Code of Botanical Nomenclature mandated Botanical Latin to be used for the descriptions of most new taxa. It is still the only language other than English accepted for descriptions. The names of organisms governed by the Code also have forms based on Latin.
Botanical Latin is primarily a written language. It includes taxon names derived from any language or even arbitrarily derived, and consequently there is no single consistent pronunciation system. When speakers of different languages use Botanical Latin in speech, they use pronunciations influenced by their own languages, or, notably in French, there may be variant spellings based on the Latin. There are at least two pronunciation systems used for Latin by English speakers. Neither system, however, works across the full spectrum of botanical names, because many non-Latin words, such as people's names, have been used.
Origin
Alphonse Pyramus de Candolle described the language in 1880:
C'est le latin arrangé par Linné à l'usage des descriptions et, j'oserai dire, à l'usage de ceux qui n'aiment ni les complications grammaticales, ni les phrases disposées sens desus dessous." (Quoted by W. T. Stearn) [It is the Latin chosen by Linnaeus for the purpose of descriptions, and, I dare to say, for the use of those who love neither grammatical complications nor phrases arranged with senses on top of one another.]
De Candolle estimated that to learn Botanical Latin would take three months' work for an English speaker not already familiar with any language of Latin origin, and one month for an Italian.
William T. Stearn wrote:
Botanical Latin is best described as a modern Romance language of special technical application, derived from Renaissance Latin with much plundering of ancient Greek, which has evolved, mainly since 1700 and primarily through the work of Carl Linnaeus (1707–78), to serve as an international medium for the scientific naming of plants in all their vast numbers and manifold diversity. These include many thousands of plants unknown to the Greeks and Romans of classical times and for which names have had to be provided as a means of reference. Their description necessitates the recording of structures often too small for comprehension by the naked eye, hence unknown to the ancients and needing words with precise restricted applications foreign to classical Latin.
Orthography of taxon names
Latin names of organisms are generally used in English without alteration, but some informal derivatives are used as common names. For example, the -idae ending of subclass names is changed to -ids (e.g., Rosidae produces rosids); the subfamily ending -oideae is changed to -oids (e.g., Papilionoideae produces papilionoids). The -ids common names have, however also been adopted as rankless clade names, sometimes containing further -ids clade names, so that, for example, in the APG IV classification, rosids contain both fabids and malvids.
More extensive modifications to the spelling and pronunciation are routinely used in some other languages. French organism names are usually gallicized. For example: Chlorophyceae becomes Chlorophycées; Portulacineae becomes Portulacinées.
Alphabet
The Pre-Classical Latin alphabet consisted of 21 letters, to which y and z were added in the Classical epoch, w was later added, and the vowel/consonant pairs i and j, u and v, were later separated. This 26-letter alphabet is used for taxon names in Botanical Latin. Diacritics are not used in names, and a dieresis is considered an optional mark that does not affect spelling.
Pronunciation
Some English speakers, and some speakers of other languages, use the reconstructed pronunciation guide for Classical Latin when speaking Botanical Latin words. Latin names pronounced by gardeners and English botanists usually follow a system close to English. It differs greatly from classical pronunciation, and also from Ecclesiastical Latin pronunciation (which is based on Italian, and has, for example, c before i or e pronounced as ch).
Classical pronunciation
Every vowel is pronounced, except diphthongs, which are treated as single long vowels.
In classical Latin words of several syllables the stress falls on the syllable next to the last one (the penultimate) when this syllable is long ... e.g., for-mō'-sus, or when two consonants separate the two last vowels, e.g., cru-ěn'-tus ... on the last syllable but two (the antepenultimate) when the last but one is short, e.g. flō-ri-dus.
"These rules cannot satisfactorily be applied to all generic names and specific epithets commemorating persons. About 80 per cent of generic names and 30 per cent of specific epithets come from languages other than Latin and Greek. A simple and consistent method of pronouncing them does not exist."
The rules also create difficulties with the -ii and -iae endings derived from personal names, because the stress falls in a place that is not usual for those names.
English pronunciation
The following table is simplified from Stearn 1992. The pronunciation transcriptions for medical terminology in major medical dictionaries, such as Dorland’s Illustrated Medical Dictionary and Stedman's Medical Dictionary, match these values.
Resources
Online
Finding derivations /meanings for epithets. See, e.g.,: Plantillustrations.org: gracilis,-is,-e "slender", "thin", "graceful" (Site does not always give a derivation)
A Grammatical Dictionary of Botanical Latin (www.mobot.org)
International Code of Nomenclature for algae, fungi, and plants (Shenzhen Code) 2018
Books
Stearn, W.T. (2004) "Botanical Latin" (4th ed), Timber Press, Portland Oregon.
Backer, C.A. (1936) Verklarend woordenboek der wetenschappelijke namen van de in Nederland en Nederlandsch-Indië in het wild groeiende en in tuinen en parken gekweekte varens en hoogere planten (Edition Nicoline van der Sijs). (Explanatory dictionary of the scientific names of .. plants grown in the Netherlands and the Dutch East Indies...)
George, A. & Short, E. (2013) "A Primer of Botanical Latin with Vocabulary" Cambridge University Press
See also
Philosophia Botanica 1751, by Linnaeus, described as "The first textbook of descriptive systematic botany and botanical latin."
Syllable stress of Botanical Latin
Footnotes
References
Languages attested from the 18th century
Botanical nomenclature
Botany
Forms of Latin | Botanical Latin | Biology | 1,417 |
19,218,583 | https://en.wikipedia.org/wiki/Software%20feature | In software, a feature is an identifiable characteristic of a computer program.
Context
The term feature means the same for software as it does for any kind of system. For example, the British Royal Navy's HMS Dreadnought (1906) was considered an important milestone in naval technology because of its advanced features that did not exist in pre-dreadnought battleships.
Feature also applies to computer hardware. In the early history of computers, devices such as Digital Equipment Corporation's PDP-7 minicomputer (created in 1964) was noted for having a wealth of features, such as being the first version of the PDP minicomputer series to use wire wrap, as well as being the first to use the proprietary DEC Flip-Chip module which was invented in the same year.
Feature also applies to concepts such as a programming language.
The Python programming language is well-known for its feature of using whitespace characters (spaces and tabs) instead of curly braces to indicate different blocks of code.
Another similar high-level, object oriented programming language, Ruby, is noteworthy for using the symbols "@" and "$" to highlight different variable scopes, which the developers claim improves code readability. Its developers also claim that one of its important features is a high amount of flexibility.
The Institute of Electrical and Electronics Engineers (IEEE) defines feature in the (obsolete) standard for software test documentation IEEE 829 as a "distinguishing characteristic of a software item (e.g., performance, portability, or functionality)".
Although feature is typically used for a positive aspect of a software system, a software bug is also a feature but with negative value.
Examples
The terminal emulator xterm has many notable features, including compatibility with the X Window System, the ability to emulate a VT220 and VT320 terminal with ANSI color, and the ability to input escape sequences using a computer mouse or other similar device, and the ability to run on multiple different Unix-like operating systems (e.g. Linux, AIX, BSD, and HP-UX).
Feature-rich and feature creep
Feature-rich describes a software system as having many options and capabilities.
One mechanism for introducing feature-rich software to the user is the concept of progressive disclosure, a technique where features are introduced gradually as they become required, to reduce the potential confusion caused by displaying a wealth of features at once.
Sometimes, feature-rich is considered a negative attribute. The terms feature creep, software bloat, and featuritis refer to software that is overly feature-rich. This type of excessive inclusion of features is in some cases a result of design by committee.
To counteract the tendency of software developers to add additional, unnecessary features, the Unix philosophy was developed in the 1970s by Bell Labs employees working on the Unix operating system such as Ken Thompson and Dennis Ritchie. The philosophy can be summarized as: software programs should generally only complete one primary task and that "small is beautiful".
See also
Feature-oriented programming
Product family engineering
Software design
Software testing
Application lifecycle management
Feature creep
Scope creep
Overengineering
References
External links
Official IEEE website | Software feature | Technology | 644 |
24,127,347 | https://en.wikipedia.org/wiki/Galerina%20sulciceps | Galerina sulciceps is a dangerously toxic species of fungus in the family Strophariaceae, of the order Agaricales. It is distributed in tropical Indonesia and India, but has reportedly been found fruiting in European greenhouses on occasion. More toxic than the deathcap (Amanita phalloides), G. sulciceps has been shown to contain the toxins alpha- (α-), beta- (β-) and gamma- (γ-) amanitin; a series of poisonings in Indonesia in the 1930s resulted in 14 deaths from the consumption of this species. It has a typical "little brown mushroom" appearance, with few obvious external characteristics to help distinguish it from many other similar nondescript brown species. The fruit bodies of the fungus are tawny to ochre, deepening to reddish-brown at the base of the stem. The gills are well-separated, and there is no ring present on the stem.
History and taxonomy
This species was first described in the literature as Marasmius sulciceps by English Naturalist Miles Joseph Berkeley in 1848, based on a specimen found four years earlier growing on old wood in Ceylon (modern-day Sri Lanka). In 1898, Otto Kuntze transferred the species to Chamaeceras, a genus that has since been subsumed back into Marasmius. Because of its brown-colored spore print, Dutch mycologist Karel Bernard Boedijn transferred the species to the genus Phaeomarasmius 1938. In 1951, he redescribed the species and transferred it to its current position in Galerina. Rolf Singer's comprehensive taxonomical treatment of the Agaricales placed Galerina sulciceps in section Naucoriopsis of the genus Galerina, a subdivision first defined by French mycologist Robert Kühner in 1935. This section includes small brown-spored fungi what when young have a cap margin that is curved inward, and thin-walled, obtuse, or acute-ended pleurocystidia that are not broadly rounded at the top. All of the poisonous amatoxin-containing Galerina belong to section Naucoriopsis.
Description
The cap is initially egg-shaped in young specimens, but changes shape as it matures, becoming convex and later more or less flat with a central depression. At the center of the cap is a roughly spherical umbo – a nipple-like protrusion. The cap is hygrophanous, meaning it changes color depending on its state of hydration: the color is tawny in moist specimens, changing to ochre with dark brown edges when dried. The cap diameter is typically , with a surface that is smooth, and almost gelatinous in consistency. The edge of the cap is thin and wavy, and is often split open. The gills are broadly adnate (broadly attached to the stalk slightly above the bottom of the gill, with most of the gill fused to the stem) to slightly decurrent (running down the length of the stem). Interspersed between the gills are shorter gills, called lamellulae, that start from the cap but do not reach the stem. The gills are broad (up to 4 mm) and thick at the base (1 mm), and when mature can develop veins that run between the gills on the undersurface of the cap. The stem is long, thick, and usually attached centrally to the underside of the cap, although it may sometimes be slightly off-center. Stems are solid, cylindrical, and may be pruinose (dusted with a very fine layer of powder).
Berkeley's original description noted a resemblance to a small Marasmius peronatus, a mushroom today known as Gymnopus peronatus.
Microscopic characteristics
The spores are ellipsoid to almond-shaped, with dimensions of 7.2–9.7 by 4.5–5.8 μm. The basidia (spore-bearing cells) are cylindrical to slightly club-shaped, four-spored, and measure 30–45 by 5.5–6 μm. The sterigmata (projections of the basidia that attach the spores) are 5–6 μm long. The pleurocystidia (cystidia located in the gill face) are thin-walled, with long, somewhat cylindrical necks, and may range in color from translucent (hyaline) to pale brownish-yellow. They are typically 40 by 10.5 μm, although they may occasionally be larger—up to 142 by 18 by 8 μm. Cystidia in the gill edge—the cheilocystidia—are similar in appearance to the pleurocystidia. The hyphae of G. sulciceps have clamp connections—short branches connecting one cell to the previous cell to allow passage of the products of nuclear division.
Biochemistry
Galerina sulciceps is deadly poisonous; one author opines it to be "perhaps the most toxic mushroom known to man", while later studies of toxin concentrations in amanitin-containing mushrooms corroborate this view. The symptoms of poisoning attributed to the mushroom have been noted to be relatively unusual: a local anesthesic effect, "pins and needles" sensation, and nausea without vomiting. Although these clinical symptoms are inconsistent with those of amatoxin poisoning, the presence of α-, β- and γ- amanitins in this species has been verified with chromatographic analysis. Amatoxins damage the liver and kidney by binding irreversibly to RNA polymerase II. Three separate instances of poisoning in Indonesia involved 18 people, 14 of which died. Based on this set of occurrences, death occurs in 7–51 hours "unless the patient survives, which seems to depend on the quantity eaten and the vigor of the individual." Another death attributed to this mushroom was reported in Germany in the early 1980s. Severe poisonings have been treated with complete blood dialysis or liver transplants.
Habitat and distribution
This species grows on dead wood in tropical locales like Indonesia (Java and Sumatra), and near India (Sri Lanka), where it is prolific in some areas. It is not found in North America. In Germany, it has been found growing in greenhouses, and is known in the vernacular as the Gewächshaus-Häubling, meaning "greenhouse Galerina". In one instance, the mushroom was discovered fruiting in dense groups in pots of orchids standing on moist conifer sawdust.
See also
List of deadly fungi
References
Fungi described in 1847
Fungi of Sri Lanka
Poisonous fungi
Deadly fungi
Cortinariaceae
Fungi of Malaysia
Taxa named by Miles Joseph Berkeley
Fungus species | Galerina sulciceps | Biology,Environmental_science | 1,381 |
4,143,960 | https://en.wikipedia.org/wiki/Fibroblast%20growth%20factor | Fibroblast growth factors (FGF) are a family of cell signalling proteins produced by the macrophages. They are involved in a wide variety of processes, most notably as crucial elements for normal development in animal cells. Any irregularities in their function will lead to a range of developmental defects. These growth factors typically act as a systemic or locally circulating molecules of extracellular origin that activate cell surface receptors. A defining property of FGFs is that they bind to heparin and to heparan sulfate. Thus, some are sequestered in the extracellular matrix of tissues that contains heparan sulfate proteoglycans, and released locally upon injury or tissue remodeling.
Families
In humans, 23 members of the FGF family have been identified, all of which are structurally related signaling molecules:
Members FGF1 through FGF10 all bind fibroblast growth factor receptors (FGFRs). FGF1 is also known as acidic fibroblast growth factor, and FGF2 is also known as basic fibroblast growth factor.
Members FGF11, FGF12, FGF13, and FGF14, also known as FGF homologous factors 1-4 (FHF1-FHF4), have been shown to have distinct functions compared to the FGFs. Although these factors possess remarkably similar sequence homology, they do not bind FGFRs and are involved in intracellular processes unrelated to the FGFs. This group is also known as the intracellular fibroblast growth factor subfamily (iFGF).
Human FGF18 is involved in cell development and morphogenesis in various tissues including cartilage.
Human FGF20 was identified based on its homology to Xenopus FGF-20 (XFGF-20).
FGF15 through FGF23 were described later and functions are still being characterized. FGF15 is the mouse ortholog of human FGF19 (there is no human FGF15) and, where their functions are shared, they are often described as FGF15/19. In contrast to the local activity of the other FGFs, FGF15/19, FGF21 and FGF23 have hormonal systemic effects.
Receptors
The mammalian fibroblast growth factor receptor family has 4 members, FGFR1, FGFR2, FGFR3, and FGFR4. The FGFRs consist of three extracellular immunoglobulin-type domains (D1-D3), a single-span trans-membrane domain and an intracellular split tyrosine kinase domain. FGFs interact with the D2 and D3 domains, with the D3 interactions primarily responsible for ligand-binding specificity (see below). Heparan sulfate binding is mediated through the D3 domain. A short stretch of acidic amino acids located between the D1 and D2 domains has auto-inhibitory functions. This 'acid box' motif interacts with the heparan sulfate binding site to prevent receptor activation in the absence of FGFs.
Alternate mRNA splicing gives rise to 'b' and 'c' variants of FGFRs 1, 2 and 3. Through this mechanism, seven different signalling FGFR sub-types can be expressed at the cell surface. Each FGFR binds to a specific subset of the FGFs. Similarly, most FGFs can bind to several different FGFR subtypes. FGF1 is sometimes referred to as the 'universal ligand' as it is capable of activating all 7 different FGFRs. In contrast, FGF7 (keratinocyte growth factor, KGF) binds only to FGFR2b (KGFR).
The signalling complex at the cell surface is believed to be a ternary complex formed between two identical FGF ligands, two identical FGFR subunits, and either one or two heparan sulfate chains.
History
A mitogenic growth factor activity was found in pituitary extracts by Armelin in 1973 and further work by Gospodarowicz as reported in 1974 described a more defined isolation of proteins from cow brain extract which, when tested in a bioassay that caused fibroblasts to proliferate, led these investigators to apply the name "fibroblast growth factor." In 1975, they further fractionated the extract using acidic and basic pH and isolated two slightly different forms that were named "acidic fibroblast growth factor" (FGF1) and "basic fibroblast growth factor" (FGF2). These proteins had a high degree of sequence homology among their amino acid chains, but were determined to be distinct proteins.
Not long after FGF1 and FGF2 were isolated, another group of investigators isolated a pair of heparin-binding growth factors that they named HBGF-1 and HBGF-2, while a third group isolated a pair of growth factors that caused proliferation of cells in a bioassay containing blood vessel endothelium cells, which they called ECGF1 and ECGF2. These independently discovered proteins were eventually demonstrated to be the same sets of molecules, namely FGF1, HBGF-1 and ECGF-1 were all the same acidic fibroblast growth factor described by Gospodarowicz, et al., while FGF2, HBGF-2, and ECGF-2 were all the same basic fibroblast growth factor.
Functions
FGFs are multifunctional proteins with a wide variety of effects; they are most commonly mitogens but also have regulatory, morphological, and endocrine effects. They have been alternately referred to as "pluripotent" growth factors and as "promiscuous" growth factors due to their multiple actions on multiple cell types. Promiscuous refers to the biochemistry and pharmacology concept of how a variety of molecules can bind to and elicit a response from single receptor. In the case of FGF, four receptor subtypes can be activated by more than twenty different FGF ligands. Thus the functions of FGFs in developmental processes include mesoderm induction, anterior-posterior patterning, limb development, neural induction and neural development, and in mature tissues/systems angiogenesis, keratinocyte organization, and wound healing processes.
FGF is critical during normal development of both vertebrates and invertebrates and any irregularities in their function leads to a range of developmental defects.
FGFs secreted by hypoblasts during avian gastrulation play a role in stimulating a Wnt signaling pathway that is involved in the differential movement of Koller's sickle cells during formation of the primitive streak. Left, angiography of the newly formed vascular network in the region of the front wall of the left ventricle. Right, analysis quantifying the angiogenic effect.
While many FGFs can be secreted by cells to act on distant targets, some FGF act locally within a tissue, and even within a cell. Human FGF2 occurs in low molecular weight (LMW) and high molecular weight (HMW) isoforms. LMW FGF2 is primarily cytoplasmic and functions in an autocrine manner, whereas HMW FGF2s are nuclear and exert activities through an intracrine mechanism.
One important function of FGF1 and FGF2 is the promotion of endothelial cell proliferation and the physical organization of endothelial cells into tube-like structures. They thus promote angiogenesis, the growth of new blood vessels from the pre-existing vasculature. FGF1 and FGF2 are more potent angiogenic factors than vascular endothelial growth factor (VEGF) or platelet-derived growth factor (PDGF). FGF1 has been shown in clinical experimental studies to induce angiogenesis in the heart.
As well as stimulating blood vessel growth, FGFs are important players in wound healing. FGF1 and FGF2 stimulate angiogenesis and the proliferation of fibroblasts that give rise to granulation tissue, which fills up a wound space/cavity early in the wound-healing process. FGF7 and FGF10 (also known as keratinocyte growth factors KGF and KGF2, respectively) stimulate the repair of injured skin and mucosal tissues by stimulating the proliferation, migration and differentiation of epithelial cells, and they have direct chemotactic effects on tissue remodelling.
During the development of the central nervous system, FGFs play important roles in neural stem cell proliferation, neurogenesis, axon growth, and differentiation. FGF signaling is important in promoting surface area growth of the developing cerebral cortex by reducing neuronal differentiation and hence permitting the self-renewal of cortical progenitor cells, known as radial glial cells, and FGF2 has been used to induce artificial gyrification of the mouse brain. Another FGF family member, FGF8, regulates the size and positioning of the functional areas of the cerebral cortex (Brodmann areas).
FGFs are also important for maintenance of the adult brain. Thus, FGFs are major determinants of neuronal survival both during development and during adulthood.
Adult neurogenesis within the hippocampus e.g. depends greatly on FGF2. In addition, FGF1 and FGF2 seem to be involved in the regulation of synaptic plasticity and processes attributed to learning and memory, at least in the hippocampus.
The 15 exparacrine FGFs are secreted proteins that bind heparan sulfate and can, therefore, be bound to the extracellular matrix of tissues that contain heparan sulfate proteoglycans. This local action of FGF proteins is classified as paracrine signalling, most commonly through the JAK-STAT signalling pathway or the receptor tyrosine kinase (RTK) pathway.
Members of the FGF19 subfamily (FGF15, FGF19, FGF21, and FGF23) bind less tightly to heparan sulfates, and so can act in an endocrine fashion on far-away tissues, such as intestine, liver, kidney, adipose, and bone. For example:
FGF15 and FGF19 (FGF15/19) are produced by intestinal cells but act on FGFR4-expressing liver cells to downregulate the key gene (CYP7A1) in the bile acid synthesis pathway.
FGF23 is produced by bone but acts on FGFR1-expressing kidney cells to regulate the synthesis of vitamin D and phosphate homeostasis.
Structure
The crystal structures of FGF1 have been solved and found to be related to interleukin 1-beta. Both families have the same beta trefoil fold consisting of 12-stranded beta-sheet structure, with the beta-sheets are arranged in 3 similar lobes around a central axis, 6 strands forming an anti-parallel beta-barrel. In general, the beta-sheets are well-preserved and the crystal structures superimpose in these areas. The intervening loops are less well-conserved - the loop between beta-strands 6 and 7 is slightly longer in interleukin-1 beta.
Clinical applications
Dysregulation of the FGF signalling system underlies a range of diseases associated with the increased FGF expression. Inhibitors of FGF signalling have shown clinical efficacy. Some FGF ligands (particularly FGF2) have been demonstrated to enhance tissue repair (e.g. skin burns, grafts, and ulcers) in a range of clinical settings.
See also
Receptor tyrosine kinase
Granulocyte-colony stimulating factor (G-CSF)
Granulocyte-macrophage colony stimulating factor (GM-CSF)
Nerve growth factor (NGF)
Neurotrophins
Erythropoietin (EPO)
Thrombopoietin (TPO)
Myostatin (GDF8)
Growth differentiation factor 9 (GDF9)
Gyrification
Neurogenesis
References
External links
FGF5 in Hair Tonic Products
FGF1 in Cosmetic Products
Protein domains
Fibroblast growth factor
Morphogens | Fibroblast growth factor | Biology | 2,565 |
44,889,502 | https://en.wikipedia.org/wiki/Niobium%20capacitor | A niobium electrolytic capacitor (historically also Columbium capacitor) is an electrolytic capacitor whose anode (+) is made of passivated niobium metal or niobium monoxide, on which an insulating niobium pentoxide layer acts as a dielectric. A solid electrolyte on the surface of the oxide layer serves as the capacitor's cathode (−).
Niobium capacitors are available in SMD packaging and compete with tantalum chip capacitors in certain voltage and capacitance ratings. They are available with a solid manganese dioxide electrolyte.
Like most electrolytic capacitors, niobium capacitors are polarized components. Reverse voltages or ripple currents higher than specified tolerances can destroy the dielectric and thus the capacitor; the resulting short circuit can cause a fire or explosion in larger units.
Niobium capacitors were developed in the United States and the Soviet Union in the 1960s. Since 2002 they have been commercially available in the West, taking advantage of the lower cost and better availability of niobium relative to tantalum.
Basic information
Niobium is a sister metal to tantalum. Niobium has a similar melting point (2744 °C) to tantalum and exhibits similar chemical properties. The materials and processes used to produce niobium-dielectric capacitors are essentially the same as for existing tantalum-dielectric capacitors. However, niobium as a raw material is much more abundant in nature than tantalum and is less expensive. The characteristics of niobium electrolytic capacitors and tantalum electrolytic capacitors are roughly comparable.
Niobium electrolytic capacitors can be made with high purity niobium as the anode but the diffusion of oxygen from the dielectric (Nb2O5) into the niobium anode metal is very high, resulting in leakage current instability or even capacitor failures. There are two possible ways to reduce oxygen diffusion and improve leakage current stability – either by doping metallic niobium powders with nitride into passivated niobium nitride or using niobium oxide (NbO) as anode material. Niobium oxide is a hard ceramic material characterized by high metallic conductivity. Niobium oxide powder can be prepared in a similar structure to that of tantalum powder and can be processed in a similar way to produce capacitors. It also can be oxidized by anodic oxidation (anodizing, forming) to generate the insulating dielectric layer. Thus two types of niobium electrolytic capacitors are marketed, those using a passivated niobium anode and those using a niobium oxide anode. Both types use niobium pentoxide (Nb2O5) as the dielectric layer.
Anodic oxidation
Niobium, similarly to tantalum and aluminum, is a so-called valve metal. Placing such a metal in contact with an electrolytic bath and applying a positive voltage to it forms a layer of electrically insulating oxide whose thickness corresponds to the applied voltage. This oxide layer acts as the dielectric in an electrolytic capacitor.
This property of niobium was known since the beginning of the 20th century. Although niobium is more abundant in nature and less expensive than tantalum, its high melting point of 2744 °C hindered the development of niobium electrolytic capacitors.
In the 1960s, the higher availability of niobium ore compared with tantalum ore prompted research into niobium electrolytic capacitors in the Soviet Union. Here they served the same purpose as tantalum capacitors in the West. With the collapse of the Iron Curtain, the technology became better-known in the West, with major capacitor manufacturers taking interest in the late 1990s. The materials and processes used to produce niobium capacitors are essentially the same as for tantalum capacitors. Rising tantalum prices in 2000 and 2001 encouraged the development of niobium electrolytic capacitors with manganese dioxide and polymer electrolytes, which have been available since 2002.
Every electrolytic capacitor can be thought of as a "plate capacitor" whose capacitance increases with the electrode area (A) and the dielectric permittivity (ε), and decreases with the dielectric thickness (d).
The dielectric thickness of niobium electrolytic capacitors is very thin, in the range of nanometers per volt. This very thin dielectric layer, combined with a sufficiently high dielectric strength, allows niobium electrolytic capacitors to achieve a high volumetric capacitance comparable to tantalum capacitors.
The niobium anode material is manufactured from a powder sintered into a pellet with a rough surface structure intended to increase the electrode surface area A compared to a smooth surface with the same footprint. This increase in surface area can increase the capacitance by a factor of up to 200 for solid niobium electrolytic capacitors, depending on the rated voltage.
The properties of the niobium pentoxide dielectric layer, compared with a tantalum pentoxide layer, are given in the following table:
The higher permittivity and lower breakdown voltage of niobium pentoxide relative to tantalum pentoxide results in niobium capacitors and tantalum capacitors having similar sizes for a given capacitance and a rated voltage.
Basic construction of solid niobium electrolytic capacitors
A typical niobium capacitor is a chip capacitor and consists of niobium or niobium oxide powder pressed and sintered into a pellet as the anode of the capacitor, with the oxide layer of niobium pentoxide as dielectric, and a solid manganese dioxide electrolyte as the cathode.
Comparison of niobium and tantalum electrolytic capacitor types
The combination of anode materials for niobium and tantalum electrolytic capacitors and the electrolytes used has formed a wide variety of capacitor types with different properties. An outline of the main characteristics of the different types is shown in the table below.
Tantalum and niobium electrolytic capacitors with solid electrolyte as surface-mountable chip capacitors are mainly used in electronic devices in which little space is available or a low profile is required. They operate reliably over a wide temperature range without large parameter deviations.
Comparison of electrical parameters of niobium and tantalum capacitor types
In order to compare the different characteristics of the different electrolytic chip capacitor types, specimens with the same dimensions and of comparable capacitance and voltage are compared in the following table. In such a comparison the values for ESR and ripple current load are the most important parameters for the use of electrolytic capacitors in modern electronic equipment. The lower the ESR the higher the ripple current per volume, thus the better the functionality of the capacitor in the circuit.
(1) 100 μF/10 V, unless otherwise specified,
(2) calculated for a capacitor 100 μF/10 V,
History
The phenomenon that can electrochemically form an oxide layer on aluminum and metals like tantalum or niobium, blocking an electric current in one direction but allowing it to flow in the other direction, was discovered in 1875 by the French researcher Eugène Ducretet. He coined the term "valve metal" for such metals. Charles Pollak (born Karol Pollak) used this phenomenon for an idea of a polarized "Electric liquid capacitor with aluminum electrodes". In 1896 Pollak obtained a patent for the first electrolytic capacitor.
The first tantalum electrolytic capacitors with wound tantalum foils and non-solid electrolyte were developed in 1930 by Tansitor Electronics Inc., USA, and used for military purposes.
The development of solid electrolyte tantalum capacitors began in the early 1950s as a miniaturized, more reliable low-voltage support capacitor to complement the newly invented transistor. The solution found by R. L. Taylor and H. E. Haring of the Bell Labs was based on experience with ceramics. They ground down tantalum to a powder, pressed this powder into a cylindrical form and then sintered the powder particles into a pellet ("slug") at high temperatures, between 1500 and 2000 °C, under vacuum conditions. These first sintered tantalum capacitors used a non-solid electrolyte not consistent with the concept of solid state electronics. 1952 a targeted search in the Bell Labs for a solid electrolyte by D. A. McLean and F. S. Power led to the invention of manganese dioxide as a solid electrolyte for a sintered tantalum capacitor.
Electrical characteristics
Series-equivalent circuit
Niobium electrolytic capacitors as discrete components are not ideal capacitors, they have losses and parasitic inductive parts. All properties can be defined and specified by a series equivalent circuit composed out of an idealized capacitance and additional electrical components which model all losses and inductive parameters of a capacitor. In this series-equivalent circuit the electrical characteristics are defined by:
C, the capacitance of the capacitor
Rleakage, the resistance representing the leakage current of the capacitor
RESR, the equivalent series resistance which summarizes all ohmic losses of the capacitor, usually abbreviated as "ESR"
LESL, the equivalent series inductance which is the effective self-inductance of the capacitor, usually abbreviated as "ESL".
Using a series equivalent circuit instead of a parallel equivalent circuit is specified by IEC/EN 60384-1.
Capacitance standard values and tolerances
The electrical characteristics of niobium electrolytic capacitors depend on structure of the anode and the type of electrolyte. The capacitance value of the capacitor depends on measuring frequency and temperature. The rated capacitance value or nominal value is specified in the data sheets of the manufacturers and is symbolized CR CN. The standardized measuring condition for electrolytic capacitors is an AC measuring method with a frequency of 100/120 Hz. The AC measuring voltage shall not exceed 0,5 V AC-RMS.
The percentage of allowed deviation of the measured capacitance from the rated value is called capacitance tolerance. Electrolytic capacitors are available in different tolerance series, whose values are specified in the E series specified in IEC 60063. For abbreviated marking in tight spaces, a letter code for each tolerance is specified in IEC 60062.
rated capacitance, E3 series, tolerance ±20%, letter code "M"
rated capacitance, E6 series, tolerance ±20%, letter code "M"
rated capacitance, E12 series, tolerance ±10%, letter code "K"
Rated and category voltage
Referring to IEC/EN 60384-1 standard the allowed operating voltage for niobium capacitors is called "rated voltage UR " or "nominal voltage UN". The rated voltage UR is the maximum DC voltage or peak pulse voltage that may be applied continuously at any temperature within the rated temperature range TR (IEC/EN 60384-1).
The voltage proof of electrolytic capacitors decreases with increasing temperature. For some applications it is important to use a higher temperature range. Lowering the voltage applied at a higher temperature maintains safety margins. For some capacitor types therefore the IEC standard specifies a "temperature derated voltage" for a higher temperature, the "category voltage UC". The category voltage is the maximum DC voltage or peak pulse voltage that may be applied continuously to a capacitor at any temperature within the category temperature range TC. The relation between both voltages and temperatures is given in the picture right (or above, on mobile devices).
Lower voltage applied may have positive influences for tantalum (and niobium) electrolytic capacitors. Lowering the voltage applied increases the reliability and reduces the expected failure rate.
Applying a higher voltage than specified may destroy electrolytic capacitors.
Surge Voltage
The surge voltage indicates the maximum peak voltage value that may be applied to electrolytic capacitors during their application for a limited number of cycles. The surge voltage is standardized in IEC/EN 60384-1. For niobium electrolytic capacitors the surge voltage shall be not higher than round 1.3 times of the rated voltage, rounded off to the nearest volt.
The surge voltage applied to niobium capacitors may influence the capacitors failure rate.
Reverse voltage
Like other electrolytic capacitors, niobium electrolytic capacitors are polarized and require the anode electrode voltage to be positive relative to the cathode voltage.
Impedance, ESR and dissipation factor, ripple current, leakage current
General information to impedance, ESR, dissipation factor tan δ, ripple current, and leakage current see electrolytic capacitor
Reliability and life time
For general information on reliability and failure rate see electrolytic capacitor.
The life time, service life, load life or useful life of electrolytic capacitors is a special characteristic of non-solid electrolytic capacitors, especially non-solid aluminum electrolytic capacitors. Their liquid electrolyte can evaporate over time, leading to wear-out failures. Solid niobium capacitors with manganese dioxide electrolyte have no wear-out mechanism, so the constant failure rate lasts up to the point when all capacitors have failed. They don't have a life time specification like non-solid aluminum electrolytic capacitors.
However, solid polymer niobium electrolytic capacitors do have a life time specification. The electrolyte deteriorates by a thermal degradation mechanism of the conductive polymer. The electrical conductivity decreases, as a function of time, in agreement with a granular structure, in which aging is due to the shrinking of the conductive polymer grains. The life time of polymer electrolytic capacitors is specified in similar terms like non-solid e-caps but its life time calculation follows other rules leading to much longer operational life times.
Failure modes, self-healing mechanism and application rules
The different types of electrolytic capacitors show different behaviors in long-term stability, inherent failure modes and their self-healing mechanisms. Application rules for types with an inherent failure mode are specified to ensure capacitors high reliability and long life.
A rare failure in solid electrolytic capacitors is breakdown of the dielectric caused by faults or impurities. In niobium electrolytic capacitors the dielectric is niobium pentoxide (Nb2O5). Besides this pentoxide there is an additional niobium suboxide, niobium dioxide (NbO2). The NbO2 is a semi-conducting material with a higher conductivity than Nb2O5 but much lower than a short. In case of faults or impurities in the dielectric which evokes a partial dielectric breakdown the conducting channel would be effectively isolated by reduction of Nb2O5 into high ohmic NbO2 if energy is limited.
As more energy is applied to a faulty solid niobium eventually either the high ohmic NbO2 channel or the Nb2O5 dielectric breaks down and the capacitor exhibits a thermal runaway failure. In comparison to solid tantalum capacitors the thermal runaway of niobium anodes will occur at about three times higher power than of tantalum anodes. This gives a significant reduction (95%) of the ignition failure mode compared to solid tantalum capacitors.
The dielectric layer Nb2O5 of solid niobium electrolytic capacitors has a lower breakdown voltage proof than Ta2O5 in tantalum capacitors and therefore grows thicker per applied volt and so operates at lower field strength for a given voltage rating with the lower electrical stress the dielectric. In combination with niobium oxide anodes, which are more stable against oxygen diffusion that results in lower voltage derating rules compared with passivated niobium or tantalum anodes.
Additional information
Capacitor symbols
Electrolytic capacitor symbols
Polarity marking
Niobium capacitors are in general polarized components, with distinctly marked positive terminals. When subjected to reversed polarity (even briefly), the capacitor depolarizes and the dielectric oxide layer breaks down, which can cause it to fail even when later operated with correct polarity. If the failure is a short circuit (the most common occurrence), and current is not limited to a safe value, catastrophic thermal runaway may occur.
Standardization
The standardization for all electrical, electronic components and related technologies follows the rules given by the International Electrotechnical Commission (IEC), a non-profit, non-governmental international standards organization. The definition of the characteristics and the procedure of the test methods for capacitors for use in electronic equipment are set out in the generic specification:
IEC 60384-1, Fixed capacitors for use in electronic equipment – Part 1: Generic specification
Until now (2014) no IEC detail specification for niobium electrolytic capacitors is available.
For electronics manufacturers in the United States the EIA publish a standard for niobium and tantalum chip capacitors:
EIA-717-A Surface Mount Niobium and Tantalum Capacitor Qualification Specification
Features
Niobium capacitors serve as a replacement for tantalum capacitors
Niobium capacitors are available in SMD style, that makes them suitable for all portable electronic systems with flat design
Niobium capacitors have no inrush current limitation
Niobium capacitors are available with solid electrolyte for low ESR applications and stable electrical parameters
Niobium capacitors have a limited number of manufacturers (AVX and Vishay)
See also
Types of capacitor
References
Further reading
R. P. Deshpande, Capacitors: Technology and Trends, 9781259007316 – Capacitors : Technology and Trends by R P Deshpande - AbeBooks
D. Bach, Dissertation, 2009-06-05, Universität Karlsruhe (TH), EELS investigations of stoichiometric niobium oxides and niobium-based capacitors
Ch. Schnitter: The taming of niobium. In: Bayer research, Bayer AG, 2004 (2007-02-11), Wayback Machine
Niobium Powder for Electrolytic Capacitor, JFE Technical Report No. 6 (October 2005) PDF
Introduction to capacitors CapSite 2023
Capacitors | Niobium capacitor | Physics | 4,051 |
590,600 | https://en.wikipedia.org/wiki/Blohm%20%26%20Voss%20BV%20141 | The Blohm & Voss BV 141 (originally the Ha 141) was a World War II German tactical reconnaissance aircraft, notable for its uncommon structural asymmetry. Although the Blohm & Voss BV 141 performed well, it was never ordered into full-scale production, for reasons that included the unavailability of the preferred engine and competition from another tactical reconnaissance aircraft, the Focke-Wulf Fw 189.
Development
In 1937, the Reichsluftfahrtministerium (RLM/German Aviation Ministry) – issued a specification for a single-engine reconnaissance aircraft with optimal visual characteristics. The preferred contractor was Arado with the Ar 198, but the prototype proved unsuccessful. The eventual winner was the Focke-Wulf Fw 189 Uhu; even though its twin-boom design using two smaller engines did not match the requirement of a single engined aircraft. Blohm & Voss (Hamburger Flugzeugbau) although not invited to participate, pursued as a private venture something far more radical. The proposal of chief designer Dr. Richard Vogt was the uniquely asymmetric BV 141.
Design
The Plexiglas-glazed crew gondola on the starboard side strongly resembled that found on the Fw 189, and housed the pilot, observer and rear gunner, while the fuselage on the port side led smoothly from the BMW 132N radial engine to a tail unit.
At first glance, the placement of weight would have induced tendency to roll, but the weight was evenly supported by lift from the wings.
In terms of thrust vs drag asymmetry, the countering of induced yaw was a more complicated matter. At low airspeed, it was calculated to be mostly alleviated because of a phenomenon known as P-factor, while at normal airspeed it proved to be easily controlled with trimming.
The tailplane was symmetrical at first, but in the 141B it became asymmetrical – starboard tailplane virtually removed – to improve the rear gunner's fields of view and fire.
Operational history
The first prototype, the BV 141 V1 (D-ORJE) first flew on 25 February 1938, using an 865hp BMW 132N engine. Three prototypes and an evaluation batch of five BV 141As were produced, backed personally by Ernst Udet, but the RLM decided on 4 April 1940 that they were underpowered, although it was also noted they otherwise exceeded the requirements. By the time a batch of 12 BV 141Bs were built with the more powerful BMW 801 engine, they were too late to make an impression, as the RLM had already decided to put the Fw 189 into production.
An urgent need for BMW 801 engines for use in the Fw 190 fighter aircraft reduced the chance of the BV 141B being produced in quantity. The BV141 was never operational, though the B-02 (V-10) was evaluated in Autumn 1941 by Aufklärungsschule 1 (Reconnaissance school). Vogt came up with several other asymmetric designs, including the piston-jet P.194.01, but none of those were actually built. Several wrecked BV 141s were found by advancing Allied forces. One was captured by British forces and sent to England for examination. No examples survive today.
Variants
All 20 of the BV 141Bs that were ordered were produced and delivered. There exists a complete record of BV 141 production with either a German civil registration number or pre-military, four letter Stammkennzeichen factory radio code number.
Prototypes
Ha 141-0 - D-ORJE; original designation of the first aircraft completed with the stepped cockpit nacelle. Became the BV 141 V2.
BV 141 V1 - WNr 141-00-0171; D-OTTO then BL+AU, damaged
BV 141 V2 - WNr 141-00-0172; D-ORJE then PC+BA; chronologically, the first one built and the only one known under old "Ha" designation as "Ha 141"
BV 141 V3 - WNr 141-00-0359; D-OLGA then BL+AA
Pre-series BV 141A-0
BV 141A-01
(V4); WNr 01010360; D-OLLE; damaged
BV 141A-02
(V5); WNr 01010361; BL+AB
BV 141A-03
(V6); WNr 01010362; BL+AC
BV 141A-04
(V7); WNr 01010363; BL+AD
BV 141A-05
(V8); WNr 01010364; BL+AE
Pre-series BV 141B-0
The first to have BMW 801 engine. About 2 m longer and 2 m wider than A-05.
B-01 (V9) - WNr 0210001; NC+QZ; first flown 9 January 1941, had severe structural problem
B-02 (V10) - WNr 0210002; NC+RA; first flown 1 June 1941
B-03 (V11) - WNr 0210003; NC+RB
B-04 (V12) - WNr 0210004; NC+RC
B-05 (V13) - WNr 0210005; NC+RD
B-06 (V14) - WNr 0210006; NC+RE
B-07 (V15) - WNr 0210007; NC+RF
B-08 (V16) - WNr 0210008; NC+RG
B-09 (V17) - WNr 0210009; NC+RH
B-10 (V18) - WNr 0210010; NC+RI
Series BV 141B-1
WNr 0210011; GK+GA
WNr 0210012; GK+GB
WNr 0210013; GK+GC
WNr 0210014; GK+GD
WNr 0210015; GK+GE
WNr 0210016; GK+GF
WNr 0210017; GK+GG
WNr 0210018; GK+GH
WNr 0210019; GL+AG; rebuilt D-OTTO
WNr 0210020; GL+AH; rebuilt D-OLLE
Specifications (BV 141B-02 [V10])
See also
References
Notes
Citations
Bibliography
Green, William. Warplanes of the Third Reich. London: Macdonald and Jane's, 1979, pp. 81–86. .
Smith, J. Richard and Anthony Kay. German Aircraft of the Second World War. London: Putnam & Co, 1978, Third impression, pp. 66–71. .
Taylor, Michael. The World's Strangest Aircraft. London: Grange, 1999. .
Wood, Anthony and Bill Gunston. Hitler's Luftwaffe: A Pictorial History and Technical Encyclopedia of Hitler's Air Power in World War II. London: Salamander, 1977, p. 135. .
Further reading
External links
Blohm & Voss BV 141, VR Curassow.
Single-engined tractor aircraft
1930s German military reconnaissance aircraft
Asymmetrical aircraft
BV 141
Aircraft first flown in 1938 | Blohm & Voss BV 141 | Physics | 1,525 |
14,470,771 | https://en.wikipedia.org/wiki/Light%20effects%20on%20circadian%20rhythm | Light effects on circadian rhythm are the response of circadian rhythms to light.
Most animals and other organisms have a biological clock that synchronizes their physiology and behaviour with the daily changes in the environment. The physiological changes that follow these clocks are known as circadian rhythms. Because the endogenous period of these rhythms are approximately but not exactly 24 hours, these rhythms must be reset by external cues to synchronize with the daily cycles in the environment. This process is called entrainment. One of the most important cues to entrain circadian rhythms is light.
Mechanism
Light first passes into a mammal's system through the retina, then takes one of two paths: the light gets collected by rod cells and cone cells and the retinal ganglion cells (RGCs), or it is directly collected by these RGCs.
The RGCs use the photopigment melanopsin to absorb the light energy. Specifically, this class of RGCs being discussed is referred to as "intrinsically photosensitive", which just means they are sensitive to light. There are five known types of intrinsically photosensitive retinal ganglion cells (ipRGCs): M1, M2, M3, M4, and M5. Each of these differently ipRGC types have different melanopsin content and photosensitivity. These connect to amacrine cells in the inner plexiform layer of the retina. Ultimately, via this retinohypothalamic tract (RHT) the suprachiasmatic nucleus (SCN) of the hypothalamus receives light information from these ipRGCs.
The ipRGCs serve a different function than rods and cones, even when isolated from the other components of the retina, ipRGCs maintain their photo-sensitivity and as a result can be sensitive to different ranges of the light spectrum. Additionally, ipRGC firing patterns may respond to light conditions as low as 1 lux whereas previous research indicated 2500 lux was required to suppress melatonin production. Circadian and other behavioral responses have shown to be more sensitive at lower wavelengths than the photopic luminous efficiency function that is based on sensitivity to cone receptors.
The core region of the SCN houses the majority of light-sensitive neurons. From here, signals are transmitted via a nerve connection with the pineal gland that regulates various hormones in the human body.
There are specific genes that determine the regulation of circadian rhythm in conjunction with light. When light activates NMDA receptors in the SCN, CLOCK gene expression in that region is altered and the SCN is reset, and this is how entrainment occurs. Genes also involved with entrainment are PER1 and PER2.
Some important structures directly impacted by the light–sleep relationship are the superior colliculus-pretectal area and the ventrolateral pre-optic nucleus.
The progressive yellowing of the crystalline lens with age reduces the amount of short-wavelength light reaching the retina and may contribute to circadian alterations observed in older adulthood.
Effects
Primary
All of the mechanisms of light-affected entrainment are not yet fully known, however numerous studies have demonstrated the effectiveness of light entrainment to the day/night cycle. Studies have shown that the timing of exposure to light influences entrainment; as seen on the phase response curve for light for a given species. In diurnal (day-active) species, exposure to light soon after wakening advances the circadian rhythm, whereas exposure before sleeping delays the rhythm. An advance means that the individual will tend to wake up earlier on the following day(s). A delay, caused by light exposure before sleeping, means that the individual will tend to wake up later on the following day(s).
The hormones cortisol and melatonin are affected by the signals light sends through the body's nervous system. These hormones help regulate blood sugar to give the body the appropriate amount of energy that is required throughout the day. Cortisol levels are high upon waking and gradually decrease over the course of the day, melatonin levels are high when the body is entering and exiting a sleeping status and are very low over the course of waking hours. The earth's natural light-dark cycle is the basis for the release of these hormones.
The length of light exposure influences entrainment. Longer exposures have a greater effect than shorter exposures. Consistent light exposure has a greater effect than intermittent exposure. In rats, constant light eventually disrupts the cycle to the point that memory and stress coping may be impaired.
The intensity and the wavelength of light influence entrainment. Dim light can affect entrainment relative to darkness. Brighter light is more effective than dim light. In humans, a lower intensity short wavelength (blue/violet) light appears to be equally effective as a higher intensity of white light.
Exposure to monochromatic light at the wavelengths of 460 nm and 550 nm on two control groups yielded results showing decreased sleepiness at 460 nm tested over two groups and a control group. Additionally, in the same study but testing thermoregulation and heart rate researchers found significantly increased heart rate in 460 nm light over the course of a 1.5-hour exposure period.
In a study done on the effect of lighting intensity on delta waves, a measure of sleepiness, high levels of lighting (1700 lux) showed lower levels of delta waves measured through an EEG than low levels of lighting (450 lux). This shows that lighting intensity is directly correlated with alertness in an office environment.
Humans are sensitive to light with a short wavelength. Specifically, melanopsin is sensitive to blue light with a wavelength of approximately 480 nm. The effect this wavelength of light has on melanopsin leads to physiological responses such as the suppression of melatonin production, increased alertness, and alterations to the circadian rhythm.
Secondary
While light has direct effects on circadian rhythm, there are indirect effects seen across studies. Seasonal affective disorder creates a model in which decreased day length during autumn and winter increases depressive symptoms. A shift in the circadian phase response curve creates a connection between the amount of light in a day (day length) and depressive symptoms in this disorder. Light seems to have therapeutic antidepressant effects when an organism is exposed to it at appropriate times during the circadian rhythm, regulating the sleep-wake cycle.
In addition to mood, learning and memory become impaired when the circadian system shifts due to light stimuli, which can be seen in studies modeling jet lag and shift work situations. Frontal and parietal lobe areas involved in working memory have been implicated in melanopsin responses to light information.
"In 2007, the International Agency for Research on Cancer classified shift work with circadian disruption or chronodisruption as a probable human carcinogen."
Exposure to light during the hours of melatonin production reduces melatonin production. Melatonin has been shown to mitigate the growth of tumors in rats. By suppressing the production of melatonin over the course of the night rats showed increased rates of tumors over the course of a four-week period.
Artificial light at night causing circadian disruption additionally impacts sex steroid production. Increased levels of progestogens and androgens was found in night shift workers as compared to "working hour" workers.
The proper exposure to light has become an accepted way to alleviate some of the effects of seasonal affective disorder (SAD). In addition exposure to light in the morning has been shown to assist Alzheimer patients in regulating their waking patterns.
In response to light exposure, alertness levels can increase as a result of suppression of melatonin secretion. A linear relationship has been found between alerting effects of light and activation in the posterior hypothalamus.
Disruption of circadian rhythm as a result of light also produces changes in metabolism.
Measured lighting for rating systems
Historically light was measured in the units of luminous intensity (candelas), luminance (candelas/m2) and illuminance (lumen/m2). After the discovery of ipRGCs in 2002 additional units of light measurement have been researched in order to better estimate the impact of different inputs of the spectrum of light on various photoreceptors. However, due to the variability in sensitivity between rods, cones and ipRGCs and variability between the different ipRGC types a singular unit does not perfectly reflect the effects of light on the human body.
The accepted current unit is equivalent melanopic lux, which is a calculated ratio multiplied by the unit lux. The melanopic ratio is determined taking into account the source type of light and the melanopic illuminance values for the eye's photopigments. The source of light, the unit used to measure illuminance and the value of illuminance informs the spectral power distribution. This is used to calculate the Photopic illuminance and the melanopic lux for the five photopigments of the human eye, which is weighted based on the optical density of each photopigment.
The WELL Building standard was designed for "advancing health and well-being in buildings globally" Part of the standard is the implementation of Credit 54: Circadian Lighting Design. Specific thresholds for different office areas are designated in order to achieve credits. Light is measured at 1.2 m above the finished floor for all areas.
Work areas must have at least a value of 200 equivalent melanopic lux present for 75% or more work stations between the hours of 09:00 and 13:00 for each day of the year when daylight is incorporated into calculations. If daylight is not taken into account all workstations require lighting at the value of 150 equivalent melanopic lux or greater.
Living environments, which are bedrooms, bathrooms and rooms with windows, at least one fixture must provide a melanopic lux value of at least 200 during the day and a melanopic lux value less than 50 during the night, measured 0.76 m above the finished floor.
Breakrooms require an average melanopic lux of 250.
Learning areas require either that light models which may incorporate daylighting have an equivalent melanopic lux of 125 for at least 75% of desks for at least four hours per day or that ambient lights maintain the standard lux recommendations set forth by Table 3 of the IES-ANSI RP-3-13.
The WELL Building standard additionally provides direction for circadian emulation in multi-family residences. In order to more accurately replicate natural cycles lighting users must be able to set a wake and bed time. An equivalent melanopic lux of 250 must be maintained in the period of the day between the indicated wake time and two hours before the indicated bed time. An equivalent melanopic lux of 50 or less is required for the period of the day spanning from two hours before the indicated bed time through the wake time. In addition at the indicated wake time melanopic lux should increase from 0 to 250 over the course of at least 15 minutes.
Other factors
Although many researchers consider light to be the strongest cue for entrainment, it is not the only factor acting on circadian rhythms. Other factors may enhance or decrease the effectiveness of entrainment. For instance, exercise and other physical activity, when coupled with light exposure, results in a somewhat stronger entrainment response. Other factors such as music and properly timed administration of the neurohormone melatonin have shown similar effects. Numerous other factors affect entrainment as well. These include feeding schedules, temperature, pharmacology, locomotor stimuli, social interaction, sexual stimuli and stress.
Circadian-based effects have also been found on visual perception to discomfort glare. The time of day at which people are shown a light source that produces visual discomfort is not perceived evenly. As the day progress, people tend to become more tolerant to the same levels of discomfort glare (i.e., people are more sensitive to discomfort glare in the morning compared to later in the day.) Further studies on chronotype show that early chronotypes can also tolerate more discomfort glare in the morning compared to late chronotypes.
See also
Chronobiology
Circadian advantage
Circadian clock
Circadian oscillator
Circadian rhythm disorders
Electronic media and sleep
Light therapy
Scotobiology
References
Circadian rhythm
Circadian
Health effects by subject | Light effects on circadian rhythm | Physics,Biology | 2,549 |
44,126,100 | https://en.wikipedia.org/wiki/Hiizu%20Iwamura | is a Japanese chemist and Professor of Chemistry, Nihon University, as well as Professor Emeriti of the Institute for Molecular Science in Okazaki, the University of Tokyo, and Kyushu University in Japan.
Education
1957 B.S. Faculty of Science, The University of Tokyo
1962 D.Sci. in Chemistry, The University of Tokyo
Thesis: Intramolecular Hydrogen Bonding between Hydroxy Group and π-Electron Systems (Supervisors: Professors Yoshiyuki Urushibara and Michinori Oki)
Academic experience
1962-1966 Assistant Professor, The University of Tokyo
1966-1969 Lecturer, The University of Tokyo
1967-1969 Research Associate, University of Wisconsin (with Prof Howard E. Zimmerman)
1970-1977 Associate Professor, The University of Tokyo
November 1974-January 1975 DAAD Visiting Professor, University of Tübingen, Germany
1977-1988 Professor, Institute for Molecular Science, 1978-1987 Director of Division of Applied Molecular Science
1983-1985 Adjunct Professor, Faculty of Engineering, Nagoya University
1987-1995 Professor, The University of Tokyo
November, 1987 Visiting Professor, University of Chicago
1994-1998 Professor, Kyushu University, 1995-1998 Director, Institute for Fundamental Research in Organic Chemistry, Kyushu University
April–May, 1995 Visiting Professor, Louis Pasteur University, France
1998-2000 Professor, National Institution for Academic Degrees
2000-2005 Professor, University of the Air, 2001-2005 Director of Tokyo Bunkyo Study Center
2005-2010 Professor, Advanced Research Institute of Science and Humanity, Nihon University
2010–present Professor, College of Science and Technology, Nihon University
Professional activities
1979-1989 Associate and Titular Member, Commission on Organic Photochemistry, Division of Organic Chemistry, IUPAC
1992-1994 Member of the Board of Directors of the Chemical Society of Japan
1993-1994 Chairman, Kanto Section of the Chemical Society of Japan
1999-2012 Chairperson of the Committee for Validation and Examination for Degrees, National Institution for Academic Degrees and University Evaluation
2000-2005 Member of the Science Council of Japan
2005-2011 Corresponding Member of the Science Council of Japan
March 2000-February 2001 President Elect, the Chemical Society of Japan
March 2001-February 2002 President, The Chemical Society of Japan
2007-2008 The First President, Japan Union of Chemical Science and Technology
Journals involvement
1987-1996 Journal of Physical Organic Chemistry Editorial Board
1987-1992 New Journal of Chemistry, France, Advisory Board
1987-1999 Advances in Physical Organic Chemistry, Advisory Board
1988-2000 Chemical Reviews (American Chemical Society), Editorial Advisory Board
Chairmanship of conferences and symposia
June 1982 Oji International Seminar on Chemistry of Weak Molecular Interactions in Aichi
October 1992 International Conference on Chemistry and Physics of Molecule-Based Magnetic Materials in Tokyo
1990-1995 The Chemical Society of Japan Executive Committee for 1995-Chemical Congress of The Pacific Basin Societies in Honolulu
1995 The 6th Kyushu International Symposium on Physical Organic Chemistry
1995-2000 Vice-Chairman, 2000 Chemical Congress of the Pacific Basin Societies in Honolulu
September 1996 The 1st Gordon Research Conference on Organic Structure and Properties in Fukuoka
Awards and honors
1963 The Chemical Society of Japan Award for Young Scientist
November 1987 Julia and Edward Lee Lectureship from the University of Chicago
1992 The Chemical Society of Japan Award
1996 Purple Ribbon Medal of Japan (Shiju Hosho)
1998 Fujiwara Science Award
2001 Maria Sklodowska-Curie Medal from the Polish Chemical Society
2003 The Japan Academy Prize
2010 The Order of the Sacred Treasure
Major research interest and accomplishments
Organic molecule-based magnets, Radical and carbene chemistry, Correlated internal rotation (molecular gears), Organic reactions in sub- and supercritical water.
In 1984 he prepared hydrocarbon tri-carbene and tetra-carbene to demonstrate that their 2p-electron spins aligned in parallel and paramagnetic moments became greater than those of iron(III) and Gd(III) salts due to five 3d- and seven 4f-electron spins, respectively. The highest spin nona-carbene ever prepared had a S = 9 ground state (1993). Aminoxyl radicals and pyridylcarbenes were assembled into polymers by coordination with magnetic metal ions to give mixed metal-organic molecule-based magnets. They included a ferromagnet with the Curie temperature of 46 K (1996) and photomagnets where only the irradiated part become strongly magnetic (1997).
Earlier he designed and prepared a whole series of di-(9-triptycyl)X (X=CH2, NH, O, SiH2, S) as molecular cog-wheels and demonstrated that they undergo almost free correlated internal rotation (disrotation) by various physical and chemical measurements. Since the rapid internal rotation of the cog-wheels does not get off the track, the di-9-triptycyl compounds carrying different benzene ring(s) gave isolable stereoisomers due to the phase of the label in spite of the rapid internal rotation (1980).
More recently he developed a number of preparative organic reactions that proceed by way of aldol condensation and Michael addition in sub- or supercritical water in the absence of any added catalysts.
Selected bibliography
“Magnetic Behavior of Nonet Tetracarbene m-Phenylenebis[(diphenylmethylenen-3-yl)methylene]”, T. Sugawara, S. Bandow, K. Kimura, H. Iwamura, and K. Itoh, J. Am. Chem. Soc., 106 (1984) 6449-6450.
“High-spin organic molecules and spin alignment in organic molecular assemblies“, H. Iwamura, Adv. Phys. Org. Chem. 26 (1990) 179-253.
“A Branched-Chain Nonacarbene with a Nonadecet Ground State: A Step Nearer to Superparamagnetic Polycarbenes“, N. Nakamura, K. Inoue, and H. Iwamura, Angew. Chem., Inter. Ed. Engl., 32 (1993) 872-874.
“Studies of Organic Di-, Oligo-, and Polyradicals by Means of Their Bulk Magnetic Properties“, H. Iwamura and N. Koga, Acc. Chem. Res. 26, 346-351 (1993).
“Toward Dendritic Two-Dimensional Polycarbenes: Synthesis of "Starburst"-Type Nona- and Dodecadiazo Compound and Magnetic Study of Their Photoproduct”, K. Matsuda, N. Nakamura, K. Inoue, N. Koga, and H. Iwamura, Bull. Chem. Soc. Jpn. 69 (1996) 1483-1494.
“High-Spin Polynitroxide Radicals as Versatile Bridging Ligands for Transition Metal Complexes with High Ferri-/Ferromagnetic TC”, H. Iwamura, K. Inoue, and T. Hayamizu, Pure Appl. Chem. 68 (1996) 243-252.
“Formation of Ferromagnetic Chains by Photolysis of 1:1 Complexes of Bis(hexafluoro-acetylacetonato)copper(II) with Diazodi(4-pyridyl)methane”, Y. Sano, M. Tanaka, N. Koga, K. Matsuda, H. Iwamura, P. Rabu, and M. Drillon, J. Am. Chem. Soc. 119 (1997) 8246-8252.
“Magnetic Ordering in Metal Coordination Complexes with Aminoxyl Radicals”, H. Iwamura and K. Inoue, in Magnetism; Molecules to Materials II. Molecule-Based Materials, J. Miller and M. Drillon, Eds.; Wiley-VCH: Weinheim, Germany; Chapt. 2 (2001) 61-108.
“Organic Synthetic and Supramolecular Approaches to Free Radical-based Magnets”, H. Iwamura, Proc. Japan Acad., 81, Ser. B (2005) 233-243.
“What role has organic chemistry played in the development of molecule-based magnets?” H. Iwamura, Polyhedron 66 (2013) 3–14.
“Unconventional Synthesis and Conformational Flexibility of Bis(1-triptycyl) Ether”, Y. Kawada and H. Iwamura, J. Org. Chem., 45 (1980) 2547-2548.
“Crystal and Molecular Structure of Bis(9-triptycyl) Ether”, H. Iwamura, T. Ito, H. Ito, K. Toriumi, Y. Kawada, E. Osawa, T. Fujiyoshi, and C. Jaime, J. Am. Chem. Soc. 106, (1984) 4712-4717.
“Stereochemical Consequences of Dynamic Gearing”, H. Iwamura and K. Mislow, Acc. Chem. Res., 21 (1988) 175-182.
“Organic Reactions in Sub- and Supercritical Water in the Absence of Any Added Catalyst”, H. Iwamura, T. Sato, M. Okada, K. Sue and T. Hiaki, J. Res. Inst. Sci. Tech., Nihon Univ., 132 (2014) 1–9.
External links
Prof. Emeritus Hiizu Iwamura awarded the Order of the Sacred Treasure, Gold Rays with Neck Ribbon
ICMM 2O12 Olivier Kahn Lecture
References
Japanese organic chemists
Living people
Academic staff of the University of Tokyo
Academic staff of Nihon University
1934 births
Academic staff of Kyushu University
Recipients of the Medal with Purple Ribbon | Hiizu Iwamura | Chemistry | 2,019 |
78,762,546 | https://en.wikipedia.org/wiki/Darboux%20cyclide | A Darboux cyclide is an algebraic surface of degree at most 4 that contains multiple families of circles. Named after French mathematician Gaston Darboux who studied these surfaces in 1880, Darboux cyclides are a superset of Dupin cyclides and quadrics. These surfaces have applications in architectural geometry and computer-aided geometric design (CAGD).
Definition
A Darboux cyclide is defined as a surface whose equation in a Cartesian coordinate system has the form
where is a constant, is a polynomial of degree 1, and is a polynomial of degree at most 2 with coefficients that do not vanish simultaneously. If the left-hand side of this equation factors into non-constant polynomials with complex coefficients, the Darboux cyclide is called a reducible cyclide. A reducible cyclide either splits into a union of spheres/planes or degenerates to a curve in .
History
The mathematical study of Darboux cyclides began with Ernst Kummer's work in 1865, followed by significant contributions from Gaston Darboux in 1880. Julian Coolidge provided a comprehensive discussion of these surfaces in his 1916 monograph. After a period of reduced interest, geometers rediscovered these surfaces in the late 20th century, particularly due to their remarkable property of carrying multiple families of circles.
Properties and applications
Darboux cyclides can carry up to six families of real circles. That is, these circles lie entirely within the surface—they are contained within it as part of its geometric structure. These circle families manifest in two distinct types. The first type consists of paired families, where two families of circles are related such that any sphere through a circle of one family intersects the cyclide in a circle of the other family. The second type comprises single families, which arise when the cyclide is generated as a canal surface (the envelope of a one-parameter family of spheres).
A Möbius sphere (also known as an M-sphere) is the set given by the equation , where do not vanish simultaneously. Darboux cyclides can exhibit symmetry with respect to up to five pairwise orthogonal Möbius spheres, though at least one of these spheres must be imaginary; that is, one M-sphere has no real points at all.
Smooth Darboux cyclides can be classified topologically into three distinct categories: sphere-like surfaces, toruslike surfaces, and configurations consisting of two spheres.
In architectural geometry, Darboux cyclides have been applied in the rationalization of freeform structures–the process of taking a complex freeform architectural design and breaking it down into parts that can be manufactured and built while maintaining the designer's artistic intent. Their ability to carry multiple families of circles makes Darboux cyclides particularly useful in the design of circular arc structures and the creation of panels and supporting elements in architectural surfaces. The geometric properties of Darboux cyclides allow for efficient manufacturing processes and structural stability in architectural designs.
See also
Dupin cyclide
Möbius geometry
Algebraic surface
Architectural geometry
References
Algebraic surfaces
Differential geometry
Architectural elements
Computer-aided design | Darboux cyclide | Technology,Engineering | 640 |
67,582,789 | https://en.wikipedia.org/wiki/WASP-103 | WASP-103 is an F-type main-sequence star located 1,800 ± 100 light-years (550 ± 30 parsecs) away in the constellation Hercules. Its surface temperature is (K). The star's concentration of heavy elements is similar to that of the Sun. WASP-103 is slightly younger than the Sun at 4 billion years. The chromospheric activity of the star is elevated due to interaction with the giant planet on a close-in orbit.
A multiplicity survey in 2015 found a suspected stellar companion to WASP-103, at a projected separation of .
Planetary system
In 2014 one super-Jupiter planet, named WASP-103b, was discovered by the transit method. The planet is orbiting its host star in 22 hours and may be close to the limit of tidal disruption. Orbital decay was not detected by 2020. In early 2022, the planet was popularized because of its shape similar to a potato.
The planetary atmosphere contains water, and possibly hydrogen cyanide, titanium(II) oxide, or sodium. The planet has an elevated carbon to oxygen molar fraction of 0.9 or 1.35, therefore it is nearly certain to be a carbon planet.
The planetary equilibrium temperature is , although a big difference exists between the night side and day side. The dayside temperature is , while the night side temperature is .
References
External links
Hercules (constellation)
F-type main-sequence stars
Planetary transit variables
Planetary systems with one confirmed planet
J16371556+0711000 | WASP-103 | Astronomy | 311 |
2,502,261 | https://en.wikipedia.org/wiki/Fibonacci%20prime | A Fibonacci prime is a Fibonacci number that is prime, a type of integer sequence prime.
The first Fibonacci primes are :
2, 3, 5, 13, 89, 233, 1597, 28657, 514229, 433494437, 2971215073, ....
Known Fibonacci primes
It is not known whether there are infinitely many Fibonacci primes. With the indexing starting with , the first 37 indices n for which Fn is prime are :
n = 3, 4, 5, 7, 11, 13, 17, 23, 29, 43, 47, 83, 131, 137, 359, 431, 433, 449, 509, 569, 571, 2971, 4723, 5387, 9311, 9677, 14431, 25561, 30757, 35999, 37511, 50833, 81839, 104911, 130021, 148091, 201107.
(Note that the actual values Fn rapidly become very large, so, for practicality, only the indices are listed.)
In addition to these proven Fibonacci primes, several probable primes have been found:
n = 397379, 433781, 590041, 593689, 604711, 931517, 1049897, 1285607, 1636007, 1803059, 1968721, 2904353, 3244369, 3340367, 4740217, 6530879, 7789819, 10317107, 10367321.
Except for the case n = 4, all Fibonacci primes have a prime index, because if a divides b, then also divides (but not every prime index results in a Fibonacci prime). That is to say, the Fibonacci sequence is a divisibility sequence.
Fp is prime for 8 of the first 10 primes p; the exceptions are F2 = 1 and F19 = 4181 = 37 × 113. However, Fibonacci primes appear to become rarer as the index increases. Fp is prime for only 26 of the 1229 primes p smaller than 10,000. The number of prime factors in the Fibonacci numbers with prime index are:
0, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 3, 2, 1, 1, 2, 2, 2, 3, 2, 2, 2, 1, 2, 4, 2, 3, 2, 2, 2, 2, 1, 1, 3, 4, 2, 4, 4, 2, 2, 3, 3, 2, 2, 4, 2, 4, 4, 2, 5, 3, 4, 3, 2, 3, 3, 4, 2, 2, 3, 4, 2, 4, 4, 4, 3, 2, 3, 5, 4, 2, 1, ...
, the largest known certain Fibonacci prime is F201107, with 42029 digits. It was proved prime by Maia Karpovich in September 2023. The largest known probable Fibonacci prime is F10367321. It was found by Ryan Propper in July 2024.
It was proved by Nick MacKinnon that the only Fibonacci numbers that are also twin primes are 3, 5, and 13.
Divisibility of Fibonacci numbers
A prime divides if and only if p is congruent to ±1 modulo 5, and p divides if and only if it is congruent to ±2 modulo 5. (For p = 5, F5 = 5 so 5 divides F5)
Fibonacci numbers that have a prime index p do not share any common divisors greater than 1 with the preceding Fibonacci numbers, due to the identity:
For , Fn divides Fm if and only if n divides m.
If we suppose that m is a prime number p, and n is less than p, then it is clear that Fp cannot share any common divisors with the preceding Fibonacci numbers.
This means that Fp will always have characteristic factors or be a prime characteristic factor itself. The number of distinct prime factors of each Fibonacci number can be put into simple terms.
Fnk is a multiple of Fk for all values of n and k such that n ≥ 1 and k ≥ 1. It's safe to say that Fnk will have "at least" the same number of distinct prime factors as Fk. All Fp will have no factors of Fk, but "at least" one new characteristic prime from Carmichael's theorem.
Carmichael's Theorem applies to all Fibonacci numbers except four special cases: and If we look at the prime factors of a Fibonacci number, there will be at least one of them that has never before appeared as a factor in any earlier Fibonacci number. Let πn be the number of distinct prime factors of Fn.
If k | n then except for
If k = 1, and n is an odd prime, then 1 | p and
The first step in finding the characteristic quotient of any Fn is to divide out the prime factors of all earlier Fibonacci numbers Fk for which k | n.
The exact quotients left over are prime factors that have not yet appeared.
If p and q are both primes, then all factors of Fpq are characteristic, except for those of Fp and Fq.
Therefore:
The number of distinct prime factors of the Fibonacci numbers with a prime index is directly relevant to the counting function.
Rank of apparition
For a prime p, the smallest index u > 0 such that Fu is divisible by p is called the rank of apparition (sometimes called Fibonacci entry point) of p and denoted a(p). The rank of apparition a(p) is defined for every prime p. The rank of apparition divides the Pisano period π(p) and allows to determine all Fibonacci numbers divisible by p.
For the divisibility of Fibonacci numbers by powers of a prime, and
In particular
Wall–Sun–Sun primes
A prime p ≠ 2, 5 is called a Fibonacci–Wieferich prime or a Wall–Sun–Sun prime if where
and is the Legendre symbol:
It is known that for p ≠ 2, 5, a(p) is a divisor of:
For every prime p that is not a Wall–Sun–Sun prime, as illustrated in the table below:
The existence of Wall–Sun–Sun primes is conjectural.
Fibonacci primitive part
Because , we can divide any Fibonacci number by the least common multiple of all where . The result is called the primitive part of . The primitive parts of the Fibonacci numbers are
1, 1, 2, 3, 5, 4, 13, 7, 17, 11, 89, 6, 233, 29, 61, 47, 1597, 19, 4181, 41, 421, 199, 28657, 46, 15005, 521, 5777, 281, 514229, 31, 1346269, 2207, 19801, 3571, 141961, 321, 24157817, 9349, 135721, 2161, 165580141, 211, 433494437, 13201, 109441, ...
Any primes that divide and not any of the s are called primitive prime factors of . The product of the primitive prime factors of the Fibonacci numbers are
1, 1, 2, 3, 5, 1, 13, 7, 17, 11, 89, 1, 233, 29, 61, 47, 1597, 19, 4181, 41, 421, 199, 28657, 23, 3001, 521, 5777, 281, 514229, 31, 1346269, 2207, 19801, 3571, 141961, 107, 24157817, 9349, 135721, 2161, 165580141, 211, 433494437, 13201, 109441, 64079, 2971215073, 1103, 598364773, 15251, ...
The first case of more than one primitive prime factor is 4181 = 37 × 113 for .
The primitive part has a non-primitive prime factor in some cases. The ratio between the two above sequences is
1, 1, 1, 1, 1, 4, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 5, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 7, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 13, 1, 1, ....
The natural numbers n for which has exactly one primitive prime factor are
3, 4, 5, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 18, 20, 21, 22, 23, 24, 25, 26, 28, 29, 30, 32, 33, 34, 35, 36, 38, 39, 40, 42, 43, 45, 47, 48, 51, 52, 54, 56, 60, 62, 63, 65, 66, 72, 74, 75, 76, 82, 83, 93, 94, 98, 105, 106, 108, 111, 112, 119, 121, 122, 123, 124, 125, 131, 132, 135, 136, 137, 140, 142, 144, 145, ...
For a prime p, p is in this sequence if and only if is a Fibonacci prime, and 2p is in this sequence if and only if is a Lucas prime (where is the th Lucas number). Moreover, 2n is in this sequence if and only if is a Lucas prime.
The number of primitive prime factors of are
0, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 3, 1, 1, 1, 2, 1, 1, 2, 1, 2, 1, 1, 2, 2, 1, 1, 2, 1, 2, 1, 2, 2, 2, 1, 2, 1, 1, 2, 1, 1, 3, 2, 3, 2, 2, 1, 2, 1, 1, 1, 2, 2, 2, 2, 3, 1, 1, 2, 2, 2, 2, 3, 2, 2, 2, 2, 1, 1, 3, 2, 4, 1, 2, 2, 2, 2, 3, 2, 1, 1, 2, 1, 2, 2, 1, 1, 2, 2, 2, 2, 2, 3, 1, 2, 1, 1, 1, 1, 1, 2, 2, 2, ...
The least primitive prime factors of are
1, 1, 2, 3, 5, 1, 13, 7, 17, 11, 89, 1, 233, 29, 61, 47, 1597, 19, 37, 41, 421, 199, 28657, 23, 3001, 521, 53, 281, 514229, 31, 557, 2207, 19801, 3571, 141961, 107, 73, 9349, 135721, 2161, 2789, 211, 433494437, 43, 109441, 139, 2971215073, 1103, 97, 101, ...
It is conjectured that all the prime factors of are primitive when is a prime number.
Fibonacci numbers in prime-like sequences
Although it is not known whether there are infinitely primes in the Fibonacci sequence, Melfi proved that there are infinitely many primes among practical numbers, a prime-like sequence.
See also
Lucas number
References
External links
R. Knott Fibonacci primes
Caldwell, Chris. Fibonacci number, Fibonacci prime, and Record Fibonacci primes at the Prime Pages
Factorization of the first 300 Fibonacci numbers
Factorization of Fibonacci and Lucas numbers
Small parallel Haskell program to find probable Fibonacci primes at haskell.org
Classes of prime numbers
Fibonacci numbers
Unsolved problems in number theory | Fibonacci prime | Mathematics | 2,848 |
43,985,777 | https://en.wikipedia.org/wiki/Sugar%20Pine%20Dam | Sugar Pine Dam is an earthfill embankment dam in Placer County, California, approximately north of Foresthill. It impounds North Shirttail Creek, a tributary of the North Fork American River, and serves as the primary municipal water supply for the Foresthill community.
History
The dam was authorized in 1965 as part of the Auburn-Folsom South Unit of the Central Valley Project. Construction began in 1979, and the dam was completed in 1982. The project was transferred to the Foresthill Public Utility District for operation and maintenance in 1984. Although Sugar Pine Dam was funded through the Central Valley Project, it was never integrated into the project operationally, as it was intended to work with the never-completed Auburn Dam. The Sugar Pine Pipeline carries water from Sugar Pine Reservoir to the Foresthill area.
In 2003, the Foresthill Public Utility District purchased Sugar Pine Dam, reservoir, and the pipeline from the U.S. Bureau of Reclamation for $3.1 million. , the district provides water to 1,875 homes and 75 businesses in and around Foresthill.
See also
List of dams and reservoirs in California
References
Dams in California
Central Valley Project
Dams completed in 1982
1982 establishments in California
Earth-filled dams | Sugar Pine Dam | Engineering | 246 |
6,154,618 | https://en.wikipedia.org/wiki/Terminal%20Entry | Terminal Entry is a 1987 science fiction film directed by John Kincade, written by Mark Sobel, and starring Patrick Labyorteaux, Paul L. Smith, Edward Albert, Yaphet Kotto, and Kabir Bedi.
Plot
The film begins with Lady Electric and Bob. After being chased down another corridor and into an elevator where they both fall to their deaths Bob snaps out of his daydream at the last second. When he comes to, he finds his friends have lost the game in the same fashion. Later, when selecting another game to play on the "Outlaw BBS", they chose one called "Terminal Entry", however, this one is password protected. Thinking that the game was set up by members at MIT, Tom decides that he will crack the password and play it during a vacation planned up in the mountains for the weekend.
Colonel Styles and Captain Jackson inform General Stewart of the terrorist situation and request more men to help protect the border over a video conference. But the general is not convinced, so he decides to fly out and take command personally. The terrorist network commander watches a news cast on the television where General Stewart being interviewed by Dominique, the reporter who is also the love interest of Captain Jackson, and decides to place a hit on the general. But the plan was circumvented by Captain Jackson while escorting the general to his hotel.
Back at the dorm room, thinking they have been beaten again, the Caltech students just about give up on their game "Dr. Fly", when Gwen, a friend of Chris who was invited to the weekend retreat, beats the game with a single command. Meanwhile, the terrorist commander is reminded by his leader over another video conference the stakes of their operation and is given an initiation time frame for their coordinated attack. The Army unit makes progress in finding the communication network for the terrorist by locating the bulletin board system after searching through known listings. When they find the terrorist network they pose as Hassan, the terrorist they killed earlier, but Dan Jackson was distraught about being given the order to have his girlfriend Dominique assassinated.
During the weekend getaway, the teenage "hackers" fail to gain access to "Terminal Entry" through brute force password cracking, however when Bob drops one of his Twinkies on the keyboard, he enters the numbers "5.9.125.35 1/5.25.35" which was the same numbers as the measurements Lady Electric from the beginning of the movie had said to him. Upon gaining access, the group find a complex computer program which they think is a game.
The Army anti-terrorism unit tracks down the position of the terrorist command post, and initiate an assault on the location which is a warehouse in the middle of the desert. Before the commander escapes, he assigns the six students to take over command. When the students start playing the game, the commands they issue in play erupt in real life bombings, assassinations, and acts of terrorism. Some of which include a Russian peace delegate, an oil refinery in Los Angeles, airplanes flying in from Lisbon, and themselves.
Bob, not knowing the full impact of their influence, put the six of them on the hit list. Operator 23 was already dispatched before they could countermand the assignment. Coincidentally their car wouldn't start, so Bob leads the group back into the house to arm themselves. When night fell, a large group of terrorists descended upon the house. However, the anti-terrorist unit was one step ahead of the terrorists, and rescued the kids from their impending doom, then proceeded to eradicate the terrorist threat. During the fighting, Bob coaxed by his imagination, the voice in his head of Lady Electric, told him to go back inside to put his initials into the computer as the winner. At the end, even with the terrorists defeated, and the kids safe, Captain Jackson and Colonel Styles know the war is not over.
Cast
Paul L. Smith as Stewart
Yaphet Kotto as Colonel Styles
Heidi Helmer as Chris
Patrick Labyorteaux as Bob
Yvette Nipar as Tina
Rob Stone as Tom
Sam Temeles as Howie
Jill Terashita as Gwen
Kabir Bedi as Commander
Kavi Raz as Mahadi
Mazhar Khan as Abdul
Tracy Brooks Swope as Dominique
Edward Albert as Captain Danny Jackson
Barbara Edwards as Lady Electric
See also
Door Games
WarGames
External links
1987 films
Films about computing
1980s English-language films | Terminal Entry | Technology | 898 |
45,232,441 | https://en.wikipedia.org/wiki/Small%20molecule%20sensors | Small-molecule sensors are an effective way to detect the presence of metal ions in solution. Although many types exist, most small molecule sensors comprise a subunit that selectively binds to a metal that in turn induces a change in a fluorescent subunit. This change can be observed in the small molecule sensor's spectrum, which can be monitored using a detection system such as a microscope or a photodiode. Different probes exist for a variety of applications, each with different dissociation constants with respect to a particular metal, different fluorescent properties, and sensitivities. They show great promise as a way to probe biological processes by monitoring metal ions at low concentrations in biological systems. Since they are by definition small and often capable of entering biological systems, they are conducive to many applications for which other more traditional bio-sensing are less effective or not suitable.
Uses
Metal ions are essential to virtually all biological systems and hence studying their concentrations with effective probes is highly advantageous. Since metal ions are key to the causes of cancer, diabetes, and other diseases, monitoring them with probes that can provide insight into their concentrations with spatial and temporal resolution is of great interest to the scientific community. There are many applications that one can envision for small molecule sensors. It has been shown that one can use them to differentiate effectively between acceptable and harmful concentrations of mercury in fish. Further, since some types of neurons uptake zinc during their operation, these probes can be used as a way to track activity in the brain and could serve as an effective alternative to functional MRI. One can also track and quantify the growth of a cell, such as a fibroblast, that uptakes metal ions as it constructs itself. Numerous other biological processes can be tracked using small molecule sensors as many change metal concentrations as they occur, which can then be monitored. Still, the sensor must be tailored for its specific environment and sensing requirements. Depending on the application, the metal sensor should be selective for a certain type of metal, and especially needs to be able to bind its target metal with greater affinity than metals that naturally exist at high concentrations within the cell . Further, they should provide a response with a strong modulation in fluorescent spectrum and hence provide a high signal-to-noise ratio. Finally, it is essential that a sensor is not toxic to the biological system in which it is used.
Mechanisms of detection
Most detection mechanisms involved in small molecule sensors comprise some modulation in the fluorescent behavior of the sensing molecule upon binding the target metal. When a metal coordinates to such a sensor, it may either enhance or reduce the original fluorescent emission. The former is known as the Chelation Enhancement Fluorescence effect (CHEF), while the latter is called the Chelation Enhancement Quenching effect (CHEQ). By changing the intensity of emission at different wavelengths, the resulting fluorescent spectrum may attenuate, amplify, or shift upon the binding and dissociation of a metal. This shift in spectra can be monitored using a detector such as a microscope or a photodiode.
Listed below are some examples of mechanisms by which emission is modulated. Their participation in CHEQ or CHEF is dependent on the metal and small molecule sensor in question.
Primary Mechanisms of Detection
Paramagnetic Fluorescence Quenching, the allowance of new electronic states upon binding a paramagnetic metal atom
Photoinduced Electron Transfer (PET), the blocking of a lower energy state due to the binding of a metal atom.
Photoinduced Charge Transfer (PCT), the modulation of energy levels in a complex by charge transfer within a conjugated pi system.
Fluorescence Resonance Energy Transfer (FRET), the transfer of an exciton from a donor to an acceptor, modulating the emission spectrum.
Excimer/Exciplex formation, the formation of a state that is a hybrid of the ground and excited states. This has novel fluorescent properties.
Chemodosimeters, complexes that undergo irreversible reactions with other species upon binding a metal to form new compounds with novel fluorescent spectra.
Fluorophores
Fluorophores are essential to our measurement of the metal binding event, and indirectly, metal concentration. There are many types, all with different properties that make them advantageous for different applications. Some work as small metal sensors completely on their own while others must be complexed with a subunit that can chelate or bind a metal ion. Rhodamine for example undergoes a conformation change upon the binding of a metal ion. In so doing it switches between a colorless, non-fluorescent spirocyclic form to a fluorescent, pink open cyclic form. Quinoline based sensors have been developed that form luminescent complexes with Cd(II) and fluorescent ones with Zn(II). It is hypothesized to function by changing its lowest luminescent state from n–* to –* when coordinating to a metal.
When the Dansyl group DNS binds to a metal, it loses a sulfonamide hydrogen, causing fluorescence quenching via a PET or reverse PET mechanism in which an electron is transferred either to or from the metal that is bound.
Examples
Zinc
Zinc is one of the most common metal ions in biological systems. Small molecule sensors for it include:
ZX1, a compound comprizing a dipicolylamine (DPA) Zinc binding subunit that has greater affinity for Zinc than other species found in solution such as Ca and Mg.
Zinpyr-1 (ZP1), a compound containing a dichlorofluorescein fluorescent compound bound to two 2-picolamine (DPA) species that bind Zn(II). ZP1 is part of a family of zinc sensors known as the Zinpyr series, the members of which are variants on ZP1 to enable specific affinities and fluorescence profiles.
ZnAF-1 sensors that comprise an aryl donor and a xanthenone acceptor and have a large change in fluorescence upon binding Zn(II). They have been used to study uptake of Zn(II) in CA3 pyramidal neurons.
GFZnP: A novel 12-member family of fluorescent GFP chemosensors was prepared for the detection of Zn2+ in biological samples with two-photon microscopy. These are the combination of the 8-aminoquinoline motif and the GFP chromophore unit, resulting enhanced fluorescent response to the Zn2+. The most effective members are GFZnP ED, GFZnP Pic and GFZnP dipic. GFZnPs have a simple synthesis and commercially available making them one of the most easily accessible two-photon Zn2+ sensors. The spectroscopical characterization of the probe family highlights their bright fluorescent emission (ε x Φ > 200) at λem= 520 nm upon excitation by λex= 450 nm light. The 2P-action cross section of the probes reaches δ´Φcomp > 5 GM at λex, 2P=900 nm, with an increase up to 200-fold, which makes them one of the best two-photon probes for Zn2+.Most of the members of the sensor family, especially GFZnP ED, GFZnP Pic and GFZnP dipic, exhibit high selectivity for Zn2+ with an affinity in the nanomolar (nM) range, excellent water-solubility, and usability at a wide pH-range (pH > 6). The applicability of selected probes was demonstrated by epifluorescent and 2P microscopy on cultured cells and brain slices. This work expands the toolbox of efficient two-photon zinc sensors with a valuable new family.
GFZnP OMe: An alternate, GFP-based fluorescent Zn2+ sensor is published for two-photon microscopy and related biological and microscop application. It composed of an 8-methoxyquinoline scaffold. It has excellent photophysical characteristics including a 37-fold fluorescence enhancement with l(ex) = 440 nm and l(em) = 505 nm. The two-photon cross-section is as high as 73 GM at 880 nm.
GFZnP BIPY: A Zn2+ selective fluorescent chemosensor with a 2,2’-bipyridine chelator moiety. It was effective at physiologically relevant pH-range and excellent photophysical characteristics are reported, including a 53-fold fluorescence enhancement with excitation and emission maxima at 422 nm and 492 nm, respectively. High two-photon cross-section of 3.0 GM at 840 nm as well as excellent metal ion selectivity are reported. In vitro experiments on HEK 293 cell culture were carried out using two-photon microscopy demonstrating the applicability.
Copper
Copper is a biologically important metal to detect. It has many sensors developed for it including:
CTAP-1, a sensor that shows a response in the UV region when Cu(I) binds to an azatetrathiacrown motif that in turn excites a pyrazoline-based dye that is attached. To use the probe, one excites it at 365 nm. If it is bound to Cu, then it will increase its fluorescence intensity. CTAP-1 is effective as it has a large modulation in its spectrum upon binding Cu, and is selective for the binding of Cu over other metals.
Coppersensor-1 (CS1) that comprises a thioether rich motif that binds to Cu(I) causing the excitation of a boron-dipyrromethene (BODIPY) dye in the visible region. The probe has good selectivity for Cu(I) over alkaline earth metals, Cu(II), and d-block metals.
Iron
Iron is used a great deal in biological systems, a fact that is well known due to its role in Hemoglobin. For it, there are many small molecule sensors including:
Pryrene-TEMPO, in which the binding of iron to TEMPO quenches the fluorescence of pyrene when no Fe(II) is bound. Upon binding however, TEMPO is reduced and pyrene regains fluorescence. This probe is limited in that an analogous response can be generated by unwanted free radicals, and that it can only by used in acidic solution.
DansSQ, in which Fe(II) binding increases fluorescence at 460 nm. It consists of a Dansyl group bound to styrylquinoline and operates by the disruption of intra-molecular charge transfer upon the binding of Fe(II). It is limited in that it is only soluble in acetonitrile in 10% H2O.
Cobalt
Cobalt sensors have been made that capitalize on the breaking of C-O bonds by Co(II) in a fluorescent probe known as Cobalt Probe 1 (CP1).
Mercury
Mercury is a toxic heavy metal, and as such it is important to be able to detect it in biological systems. Sensors include:
Mercury Sensors (MS), a family of sensors that comprise complexes of fluorescein and napthofluorescein. The MS1 probe increases its emission upon binding of Hg(II), while maintaining great affinity for mercury over other heavy metal ions.
The S3 sensor is based on a BODIPY complex which undergoes a significant increase in fluorescence upon the binding of Hg(II).
MF1 uses a soft thioether chelator for Hg(II) bound to a fluorescein-like xanthenone reporter. It has good contrast upon binding mercury and good selectivity. MF1 is sensitive enough that it has been proposed to be used to test fish for toxic levels of mercury.
See also
Chelation
Luminescence
Fluorescence
Fluorophore
Biosensor
Deoxyribozyme
References
Photochemistry
Chemical reactions
Optoelectronics
Sensors | Small molecule sensors | Chemistry,Technology,Engineering | 2,491 |
8,665,986 | https://en.wikipedia.org/wiki/Verilog%20Procedural%20Interface | The Verilog Procedural Interface (VPI), originally known as PLI 2.0, is an interface primarily intended for the C programming language. It allows behavioral Verilog code to invoke C functions, and C functions to invoke standard Verilog system tasks. The Verilog Procedural Interface is part of the IEEE 1364 Programming Language Interface standard; the most recent edition of the standard is from 2005. VPI is sometimes also referred to as PLI 2, since it replaces the deprecated Program Language Interface (PLI).
While PLI 1 was deprecated in favor of VPI (aka. PLI 2), PLI 1 is still commonly used over VPI due to its much more widely documented tf_put, tf_get function interface that is described in many verilog reference books.
Use of C++
C++ is integrable with VPI (PLI 2.0) and PLI 1.0, by using the "extern C/C++" keyword built into C++ compilers.
Example
As an example, consider the following Verilog code fragment:
val = 41;
$increment(val);
$display("After $increment, val=%d", val);
Suppose the increment system task increments its first parameter by one. Using C and the VPI mechanism, the increment task can be implemented as follows:
// Implements the increment system task
static int increment(char *userdata) {
vpiHandle systfref, args_iter, argh;
struct t_vpi_value argval;
int value;
// Obtain a handle to the argument list
systfref = vpi_handle(vpiSysTfCall, NULL);
args_iter = vpi_iterate(vpiArgument, systfref);
// Grab the value of the first argument
argh = vpi_scan(args_iter);
argval.format = vpiIntVal;
vpi_get_value(argh, &argval);
value = argval.value.integer;
vpi_printf("VPI routine received %d\n", value);
// Increment the value and put it back as first argument
argval.value.integer = value + 1;
vpi_put_value(argh, &argval, NULL, vpiNoDelay);
// Cleanup and return
vpi_free_object(args_iter);
return 0;
}
Also, a function that registers this system task is necessary. This function is invoked prior to elaboration or resolution of references when it is placed in the externally visible vlog_startup_routines[] array.
// Registers the increment system task
void register_increment() {
s_vpi_systf_data data = {vpiSysTask, 0, "$increment", increment, 0, 0, 0};
vpi_register_systf(&data);
}
// Contains a zero-terminated list of functions that have to be called at startup
void (*vlog_startup_routines[])() = {
register_increment,
0
};
The C code is compiled into a shared object that will be used by the Verilog simulator. A simulation of the earlier mentioned Verilog fragment will now result in the following output:
VPI routine received 41
After $increment, val=42
See also
SystemVerilog DPI
Sources
IEEE Xplore
Sources for Verilog VPI interface
Teal, for C++
JOVE, for Java
Ruby-VPI, for Ruby
ScriptEDA, for Perl, Python, Tcl
Cocotb , for Python
OrigenSim, for Ruby
External links
Verilog PLI primer
Verilog VPI tutorial
IEEE standards | Verilog Procedural Interface | Technology | 857 |
65,927,172 | https://en.wikipedia.org/wiki/Smith%E2%80%93Wilson%20method | The Smith–Wilson method is a method for extrapolating forward rates. It is recommended by EIOPA to extrapolate interest rates. It was introduced in 2000 by A. Smith and T. Wilson for Bacon & Woodrow.
Mathematical formulation
Let UFR be some ultimate forward rate and be the time to the i'th maturity. Then defines the price of a zero-coupon bond at time t.
Where
and the symmetric W matrix is
and
,
,
.
References
A Technical Note on the Smith-Wilson Method, The Financial Supervisory Authority of Norway, (1 July 2010)
Lagerås, Andreas & Lindholm, Mathias. (2016). Issues with the Smith-Wilson method. Insurance: Mathematics and Economics. 71. 10.1016/j.insmatheco.2016.08.009.
Smith, A. and Wilson, T. (2000). Fitting Yield Curves with Long Term Constraints. Research report, Bacon & Woodrow.
Technical documentation of the methodology to derive EIOPA's risk-free interest rate term structures
Financial models
Fixed income analysis
Insurance
Mathematical finance | Smith–Wilson method | Mathematics | 225 |
42,381,107 | https://en.wikipedia.org/wiki/SensoMotoric%20Instruments | SensoMotoric Instruments (SMI) was a German provider of dedicated computer vision applications with a major focus on eye-tracking technology. SMI was founded in 1991 as a spin-off from academic and medical research at the Free University of Berlin. The company has its headquarters in Teltow near Berlin, Germany, offices in Boston, Massachusetts and San Francisco, California, in the United States, and a worldwide distributor and partner network.
SMI provided eye tracking systems for scientific research, professional solutions and OEM applications. The eye trackers can be combined with motion tracking systems, EEG, and other biometric data. They can be integrated into virtual reality CAVEs, head-mounted displayssuch as Google Glass or Oculus Rift, simulators, cars, or computers as a measurement or interaction modality.
History
The company was founded by Dr. Winfried Teiwes in 1991. SMI's first system 3D VOG was employed by the ESA, the NASA and on board the Russian space station Mir to analyze the effect of space missions on gravity-responsive torsional eye movements of astronauts. Gradually, the company shifted its focus from astronautics towards ophthalmology and scientific research. Dr. Teiwes remained the company's Managing Director until 2008, when Eberhard Schmidt took over this role. After the sale of the ENT productline to Interacoustics the diagnostics arm of William Demant Group in 2001, the spin-out of the retinal treatment activities into OD-OS in 2008, and the sale of the Ophthalmic division to Alcon in 2012, the company focused on scientific and professional eye tracking research solutions, virtual reality applications, and OEM integrations.
Technology and Products
The technology is based on the dark pupil and corneal reflection tracking: The cameras in the SMI eye trackers detect face, eyes, and pupils, as well as the corneal reflections from the infrared light sources, and calculate eye movements, gaze direction and points of regard. The sampling frequency of the eye trackers ranges from 30 Hz up to the kHz range.
On the hardware side, the company has three main product lines: mobile Eye Tracking Glasses (ETG), remote eye tracking systems (RED), and tower-mounted systems (Hi-Speed).
The software for experimental design and data analysis is called Experiment Suite and comes in different packages depending on the user's research interests.
Partnerships
At the 2014 Game Developers Conference, Sony unveiled the prototype InFamous: Second Son game for PlayStation 4, using SMI's RED-oem eye tracking system.
At the CES 2016, SMI demoed a new 250 Hz eye tracking system and a working foveated rendering solution. It resulted from a partnership with camera sensor manufacturer Omnivision who provided the camera hardware for the new system.
In 2015 DEWESoft together with SMI integrated the Eye Tracking Glasses into a driver machine monitoring and analysis platform for advanced driver-assistance systems (ADAS).
In 2014 Red Bull started using the Eye Tracking Glasses as part of their Red Bull Surf Science project. At the Game Developers Conference 2014, Sony unveiled the prototype of PlayStation 4 game Infamous: Second Son with the RED-oem eye tracking system integrated into it.
In 2013 TechViz integrated SMI's 3D Eye Tracking Glasses with TechViz 3D visualization software to enable eye tracking in a virtual reality CAVE. The 3D Eye Tracking Glasses were developed in partnership with Volfoni. In the same year, WorldViz started cooperating with SMI to enable calculation of intersects of gaze vectors with 3D objects and saving the data in one common database for deeper analysis. German Research Center for Artificial Intelligence (DFKI) used the Eye Tracking Glasses to create Talking Places the prototype of an interactive city guide.
In 2012, in partnership with Emotiv SMI developed a software package that combined the EEG data from the Emotiv EEG Neuroheadset with the eye tracking data. Neuromarketers can use this software to analyze consumer reactions to brands according to visual and emotional cues. Prentke Romich Company integrated SMI's NuEye eye-gaze accessory into its speech-generating platform for people with disabilities. The system allows users to control a communication device using only their eyes. Visual Interaction offers myGaze eye tracking accessory based on SMI technology with selected software packages for assistive applications.
Acquisition
It was reported that Apple acquired SMI in June 2017.
Awards
In 1992, SMI won the Berlin and Brandenburg Innovation Prize.
In 2009, SMI's iView X RED system received the iF Product Design Award.
See also
Biopac
Emotiv
Eye tracking
Video-oculography
Visual perception
References
Information technology companies of Germany
Data analysis software
Data collection in research
Companies based in Brandenburg
Physiological instruments
Vision | SensoMotoric Instruments | Technology,Engineering | 984 |
16,796,793 | https://en.wikipedia.org/wiki/HD%2040979%20b | HD 40979 b is an extrasolar planet orbiting the star HD 40979, was detected from the Lick and Keck observatories and photometric observations at Fairborn Observatory reveal low-amplitude brightness variations in HD 40979. It is thought to be a large gas giant planet. It was discovered in 2002 by Debra Fischer.
References
External links
Exoplanets discovered in 2002
Giant planets
Auriga
Exoplanets detected by radial velocity
de:HD 40979 b | HD 40979 b | Astronomy | 106 |
66,264 | https://en.wikipedia.org/wiki/Hexose | In chemistry, a hexose is a monosaccharide (simple sugar) with six carbon atoms. The chemical formula for all hexoses is , and their molecular weight is 180.156 g/mol.
Hexoses exist in two forms, open-chain or cyclic, that easily convert into each other in aqueous solutions. The open-chain form of a hexose, which usually is favored in solutions, has the general structure , where n is 1, 2, 3, 4, 5. Namely, five of the carbons have one hydroxyl functional group () each, connected by a single bond, and one has an oxo group (), forming a carbonyl group (). The remaining bonds of the carbon atoms are satisfied by seven hydrogen atoms. The carbons are commonly numbered 1 to 6 starting at the end closest to the carbonyl.
Hexoses are extremely important in biochemistry, both as isolated molecules (such as glucose and fructose) and as building blocks of other compounds such as starch, cellulose, and glycosides. Hexoses can form dihexose (like sucrose) by a condensation reaction that makes 1,6-glycosidic bond.
When the carbonyl is in position 1, forming an formyl group (), the sugar is called an aldohexose, a special case of aldose. Otherwise, if the carbonyl position is 2 or 3, the sugar is a derivative of a ketone, and is called a ketohexose, a special case of ketose; specifically, an n-ketohexose. However, the 3-ketohexoses have not been observed in nature, and are difficult to synthesize; so the term "ketohexose" usually means 2-ketohexose.
In the linear form, there are 16 aldohexoses and eight 2-ketohexoses, stereoisomers that differ in the spatial position of the hydroxyl groups. These species occur in pairs of optical isomers. Each pair has a conventional name (like "glucose" or "fructose"), and the two members are labeled "-" or "-", depending on whether the hydroxyl in position 5, in the Fischer projection of the molecule, is to the right or to the left of the axis, respectively. These labels are independent of the optical activity of the isomers. In general, only one of the two enantiomers occurs naturally (for example, -glucose) and can be metabolized by animals or fermented by yeasts.
The term "hexose" sometimes is assumed to include deoxyhexoses, such as fucose and rhamnose: compounds with general formula that can be described as derived from hexoses by replacement of one or more hydroxyl groups with hydrogen atoms.
Classification
Aldohexoses
The aldohexoses are a subclass of the hexoses which, in the linear form, have the carbonyl at carbon 1, forming an aldehyde derivative with structure . The most important example is glucose.
In linear form, an aldohexose has four chiral centres, which give 16 possible aldohexose stereoisomers (24), comprising 8 pairs of enantiomers. The linear forms of the eight -aldohexoses, in the Fischer projection, are
Of these -isomers, all except -altrose occur in living organisms, but only three are common: -glucose, -galactose, and -mannose. The -isomers are generally absent in living organisms; however, -altrose has been isolated from strains of the bacterium Butyrivibrio fibrisolvens.
When drawn in this order, the Fischer projections of the -aldohexoses can be identified with the 3-digit binary numbers from 0 to 7, namely 000, 001, 010, 011, 100, 101, 110, 111. The three bits, from left to right, indicate the position of the hydroxyls on carbons 4, 3, and 2, respectively: to the right if the bit value is 0, and to the left if the value is 1.
The chemist Emil Fischer is said to have devised the following mnemonic device for remembering the order given above, which corresponds to the configurations about the chiral centers when ordered as 3-bit binary strings:
All altruists gladly make gum in gallon tanks.
referring to allose, altrose, glucose, mannose, gulose, idose, galactose, talose.
The Fischer diagrams of the eight -aldohexoses are the mirror images of the corresponding -isomers; with all hydroxyls reversed, including the one on carbon 5.
Ketohexoses
A ketohexose is a ketone-containing hexose.
The important ketohexoses are the 2-ketohexoses, and the most important 2-ketose is fructose.
Besides the 2-ketoses, there are only the 3-Ketoses, and they do not exist in nature, although at least one 3-ketohexose has been synthesized, with great difficulty.
In the linear form, the 2-ketohexoses have three chiral centers and therefore eight possible stereoisomers (23), comprising four pairs of enantiomers. The four -isomers are:
The corresponding forms have the hydroxyls on carbons 3, 4,and 5 reversed. Below are
depiction of the eight isomers in an alternative style:
3-Ketohexoses
In theory, the ketohexoses include also the 3-ketohexoses, which have the carbonyl in position 3; namely . However, these compounds are not known to occur in nature, and are difficult to synthesize.
In 1897, an unfermentable product obtained by treatment of fructose with bases, in particular lead(II) hydroxide, was given the name glutose, a portmanteau of glucose and fructose, and was claimed to be a 3-ketohexose. However, subsequent studies showed that the substance was a mixture of various other compounds.
The unequivocal synthesis and isolation of a 3-ketohexose, xylo-3-hexulose, through a rather complex route, was first reported in 1961 by George U. Yuen and James M. Sugihara.
Cyclic forms
Like most monosaccharides with five or more carbons, each aldohexose or 2-ketohexose also exists in one or more cyclic (closed-chain) forms, derived from the open-chain form by an internal rearrangement between the carbonyl group and one of the hydroxyl groups.
The reaction turns the group into a hydroxyl, and the hydroxyl into an ether bridge () between the two carbon atoms, thus creating a ring with one oxygen atom and four or five carbons.
If the cycle has five carbon atoms (six atoms in total), the closed form is called a pyranose, after the cyclic ether tetrahydropyran, that has the same ring. If the cycle has four carbon atoms (five in total), the form is called furanose after the compound tetrahydrofuran. The conventional numbering of the carbons in the closed form is the same as in the open-chain form.
If the sugar is an aldohexose, with the carbonyl in position 1, the reaction may involve the hydroxyl on carbon 4 or carbon 5, creating a hemiacetal with five- or six-membered ring, respectively. If the sugar is a 2-ketohexose, it can only involve the hydroxyl in carbon 5, and will create a hemiketal with a five-membered ring.
The closure turns the carboxyl carbon into a chiral center, which may have either of two configurations, depending on the position of the new hydroxyl. Therefore, each hexose in linear form can produce two distinct closed forms, identified by prefixes "α" and "β".
It has been known since 1926 that hexoses in the crystalline solid state assume the cyclic form. The "α" and "β" forms, which are not enantiomers, will usually crystallize separately as distinct species. For example, -glucose forms an α crystal that has specific rotation of +112° and melting point of 146 °C, as well as a β crystal that has specific rotation of +19° and melting point of 150 °C.
The linear form does not crystallize, and exists only in small amounts in water solutions, where it is in equilibrium with the closed forms. Nevertheless, it plays an essential role as the intermediate stage between those closed forms.
In particular, the "α" and "β" forms can convert to into each other by returning to the open-chain form and then closing in the opposite configuration. This process is called mutarotation.
Chemical properties
Although all hexoses have similar structures and share some general properties, each enantiomer pair has its own chemistry. Fructose is soluble in water, alcohol, and ether. The two enantiomers of each pair generally have vastly different biological properties.
2-Ketohexoses are stable over a wide pH range, and with a primary pKa of 10.28, will only deprotonate at high pH, so are marginally less stable than aldohexoses in solution.
Natural occurrence and uses
The aldohexose that is most important in biochemistry is -glucose, which is the main "fuel" for metabolism in many living organisms.
The 2-ketohexoses psicose, fructose and tagatose occur naturally as the -isomers, whereas sorbose occurs naturally as the -isomer.
-Sorbose is commonly used in the commercial synthesis of ascorbic acid. -Tagatose is a rare natural ketohexose that is found in small quantities in food. -Fructose is responsible for the sweet taste of many fruits, and is a building block of sucrose, the common sugar.
Deoxyhexoses
The term "hexose" may sometimes be used to include the deoxyhexoses, which have one or more hydroxyls () replaced by hydrogen atoms (). It is named as the parent hexose, with the prefix "x-deoxy-", the x indicating the carbon with the affected hydroxyl. Some examples of biological interest are
-Fucose (6-deoxy--galactose)
-Rhamnose (6-deoxy--mannose)
-Quinovose (6-deoxy--glucose), found as part of the sulfolipid sulfoquinovosyl diacylglycerol (SQDG)
-Pneumose (6-deoxy--talose)
-Fuculose (6-deoxy--tagatose)
See also
Diose
Triose
Tetrose
Pentose
Heptose
Octose
References
External links
Monosaccharides | Hexose | Chemistry | 2,366 |
391,421 | https://en.wikipedia.org/wiki/Comparametric%20equation | A comparametric equation is an equation that describes a parametric relationship between a function and a dilated version of the same function, where the equation does not involve the parameter. For example, ƒ(2t) = 4ƒ(t) is a comparametric equation, when we define g(t) = ƒ(2t), so that we have g = 4ƒ no longer contains the parameter, t. The comparametric equation g = 4ƒ has a family of solutions, one of which is ƒ = t2.
To see that ƒ = t2 is a solution, we merely substitute back in: g = ƒ(2t) = (2t)2 = 4t2 = 4ƒ, so that g = 4ƒ.
Comparametric equations arise naturally in signal processing when we have multiple measurements of the same phenomenon, in which each of the measurements was acquired using a different sensitivity. For example, two or more differently exposed pictures of the same subject matter give rise to a comparametric relationship, the solution of which is the response function of the camera, image sensor, or imaging system. In this sense, comparametric equations are the fundamental mathematical basis for HDR (high dynamic range) imaging, as well as HDR audio.
Comparametric equations have been used in many areas of research, and have many practical applications to the real world. They are used in radar, microphone arrays, and have been used in processing crime scene video in homicide trials in which the only evidence against the accused was video recordings of the murder.
Solution
An existing solution is comparametric camera response function (CCRF) for real-time comparametric analysis. It has applications in the analysis of multiple images.
References
Related concepts
Parametric equation
Functional equation
Contraction mapping
Multivariable calculus
Equations | Comparametric equation | Mathematics | 370 |
5,401,558 | https://en.wikipedia.org/wiki/Cleaner%20production | Cleaner production is a preventive, company-specific environmental protection initiative. It is intended to minimize waste and emissions and maximize product output. By analysing the flow of materials and energy in a company, one tries to identify options to minimize waste and emissions out of industrial processes through source reduction strategies. Improvements of organisation and technology help to reduce or suggest better choices in use of materials and energy, and to avoid waste, waste water generation, and gaseous emissions, and also waste heat and noise.
Overview
The concept was developed during the preparation of the Rio Summit as a programme of UNEP (United Nations Environmental Programme) and UNIDO (United Nations Industrial Development Organization) under the leadership of Jacqueline Aloisi de Larderel, the former Assistant Executive Director of UNEP. The programme was meant to reduce the environmental impact of industry. It built on ideas used by the company 3M in its 3P programme (pollution prevention pays). It has found more international support than all other comparable programmes. The programme idea was described "...to assist developing nations in leapfrogging from pollution to less pollution, using available technologies". Starting from the simple idea to produce with less waste Cleaner Production was developed into a concept to increase the resource efficiency of production in general. UNIDO has been operating National Cleaner Production Centers and Programmes (NCPCs/NCPPs) with centres in Latin America, Africa, Asia and Europe.
Cleaner production is endorsed by UNEP's International Declaration on Cleaner Production, "a voluntary and public statement of commitment to the practice and promotion of Cleaner Production". Implementing guidelines for cleaner production were published by UNEP in 2001.
In the US, the term pollution prevention is more commonly used for cleaner production.
Options
Examples for cleaner production options are:
Documentation of consumption (as a basic analysis of material and energy flows, e. g. with a Sankey diagram)
Use of indicators and controlling (to identify losses from poor planning, poor education and training, mistakes)
Substitution of raw materials and auxiliary materials (especially renewable materials and energy)
Increase of useful life of auxiliary materials and process liquids (by avoiding drag in, drag out, contamination)
Improved control and automatisation
Reuse of waste (internal or external)
New, low waste processes and technologies
Initiatives
One of the first European initiatives in cleaner production was started in Austria in 1992 by the BMVIT (Bundesministerium für Verkehr, Innovation und Technologie). This resulted in two initiatives: "Prepare" and EcoProfit.
The "PIUS" initiative was founded in Germany in 1999. Since 1994, the United Nations Industrial Development Organization operates the National Cleaner Production Centre Programme with centres in Central America, South America, Africa, Asia, and Europe.
See also
Cradle-to-cradle design
Energy conservation
Environmental management
Environmental Quality Management
Green design
Industrial ecology
ISO 9001
ISO 14001
Source reduction)
Sustainability
Total quality management
Waste minimisation
Clean Production Agreement
References
Bibliography
Fresner, J., Bürki, T., Sittig, H., Ressourceneffizienz in der Produktion -Kosten senken durch Cleaner Production, , Symposion Publishing, 2009
Organisation For Economic Co-Operation And Development(OECD)(Hrsg.): Technologies For Cleaner Production And Products- Towards Technological Transformation For Sustainable Development. Paris: OECD, 1995 Google Books
Pauli, G., From Deep Ecology to The Blue Economy, 2011, ZERI
Schaltegger, S.; Bennett, M.; Burritt, R. & Jasch, C.: Environmental Management Accounting as a Support for Cleaner Production, in: Schaltegger, S.; Bennett, M.; Burritt, R. & Jasch, C. (Eds): Environmental Management Accounting for Cleaner Production. Dordrecht: Springer, 2008, 3-26
External links
Cleaner Production by sectors
Clean Production Council Chile Official site of the National Service that promotes Cleaner Production in that country.
Journal of Cleaner Production
National Pollution Prevention Roundtable Finds P2 Programs Effective (article)
Pollution prevention in China
Pollution prevention directory: TURI - Toxics Use Reduction Institute
United States National Pollution Prevention Information Center
United States Pollution Prevention Regional Information Center
Waste minimisation
Environmental engineering
Industrial ecology
Waste management concepts | Cleaner production | Chemistry,Engineering | 876 |
43,010,228 | https://en.wikipedia.org/wiki/WormBase | WormBase is an online biological database about the biology and genome of the nematode model organism Caenorhabditis elegans and contains information about other related nematodes. WormBase is used by the C. elegans research community both as an information resource and as a place to publish and distribute their results. The database is regularly updated with new versions being released every two months. WormBase is one of the organizations participating in the Generic Model Organism Database (GMOD) project.
Contents
WormBase comprises the following main data sets:
The annotated genomes of Caenorhabditis elegans, Caenorhabditis briggsae, Caenorhabditis remanei, Caenorhabditis brenneri, Caenorhabditis angaria, Pristionchus pacificus, Haemonchus contortus, Meloidogyne hapla, Meloidogyne incognita, Brugia malayi and Onchocerca volvulus;
Hand-curated annotations describing the function of ~20,500 C. elegans protein-coding genes and ~16,000 C. elegans non-coding genes;
Gene families;
Orthologies;
Genomic transcription factor binding sites
Comprehensive information on mutant alleles and their phenotypes;
Whole-genome RNAi (RNA interference) screens;
Genetic maps, markers and polymorphisms;
The C. elegans physical map;
Gene expression profiles (stage, tissue and cell) from microarrays, SAGE analysis and GFP promoter fusions;
The complete cell lineage of the worm;
The wiring diagram of the worm nervous system;
Protein-protein interaction Interactome data;
Genetic regulatory relationships;
Details of intra- and inter-specific sequence homologies (with links to other Model Organism Databases).
In addition, WormBase contains an up-to-date searchable bibliography of C. elegans research and is linked to the WormBook project.
Tools
WormBase offers many ways of searching and retrieving data from the database:
WormMart, Wiki - was a tool for retrieving varied information on many genes (or the sequences of those genes). This was the WormBase implementation of BioMart.
WormMine, Wiki - as of 2016, the primary data mining facility. This is the WormBase implementation of InterMine.
Genome Browser - browse the genes of C. elegans (and other species) in their genomic context
Textpresso - a search tool that queries published C. elegans literature (including meeting abstracts) and a subset of nematode literature.
Sequence curation
Sequence curation at WormBase refers to the maintenance and annotation of the primary genomic sequence and a consensus gene set.
Genome sequence
Even though the C. elegans genome sequence is the most accurate and complete eukaryotic genome sequence, it has continually needed refinement as new evidence has been created. Many of these changes were single nucleotide insertions or deletions, however several large mis-assemblies have been uncovered. For example, in 2005 a 39 kb cosmid had to be inverted. Other improvements have come from comparing genomic DNA to cDNA sequences and analysis of RNASeq high-throughput data. When differences between the genomic sequence and transcripts are identified, re-analysis of the original genomic data often leads to modifications of the genomic sequence.
The changes in the genomic sequence pose difficulties when comparing chromosomal coordinates of data derived from different releases of WormBase. There is a coordinate re-mapping program and mapping data are available to aid these comparisons.
Gene structure models
All the gene-sets of the WormBase species were initially generated by gene prediction programs. Gene prediction programs give a reasonable set of gene structures, but the best of them only predict about 80% of the complete gene structures correctly. They have difficulty predicting genes with unusual structures, as well as those with a weak translation start signal, weak splice sites or single exon genes. They can incorrectly predict a coding gene model where the gene is a pseudogene and they predict the isoforms of a gene poorly, if at all.
The gene models of C. elegans, C. briggsae, C. remanei, and C. brenneri genes are manually curated. The majority of gene structure changes have been based on transcript data from large scale projects such as Yuji Kohara's EST libraries, Mark Vidal's Orfeome project (worfdb.dfci.harvard.edu/) Waterston and Hillier's Illumina data and Makedonka Mitreva's 454 data. However, other data types (e.g. protein alignments, ab initio prediction programs, trans-splice leader sites, poly-A signals and addition sites, SAGE and TEC-RED transcript tags, mass-spectroscopic peptides, and conserved protein domains) are useful in refining the structures, especially where expression is low and so transcripts are not sufficiently available. When genes are conserved between the available nematode species, comparative analysis can also be very informative.
WormBase encourages researchers to inform them via the help-desk if they have evidence for an incorrect gene structure. Any cDNA or mRNA sequence evidence for the change should be submitted to EMBL/GenBank/DDBJ; this helps in the confirmation and evidence for the gene model as WormBase routinely retrieve sequence data from these public databases. This also makes the data public, allowing appropriate reference and acknowledgement to the researchers.
When any change is made to a CDS (or Pseudogene), the old gene model is preserved as a ‘history’ object. This will have a suffix name like: “AC3.5:wp119”, where ‘AC3.5’ is the name of the CDS and the ‘119’ refers to the database release in which the change was made. The reason for the change and the evidence for the change are added to the annotation of the CDS – these can be seen in the Visible/Remark section of the CDS's ‘Tree Display’ section on the WormBase web site.
Gene nomenclature
Genes
In WormBase, a Gene is a region that is expressed or a region that has been expressed and is now a Pseudogene. Genes have unique identifiers like ‘WBGene00006415’. All C. elegans WormBase genes also have a Sequence Name, which is derived from the cosmid, fosmid or YAC clone on which they reside, for instance F38H4.7, indicating it is on the cosmid ‘F38H4’, and there are at least 6 other genes on that cosmid. If a gene produces a protein that can be classified as a member of a family, the gene may also be assigned a CGC name like tag-30 indicating that this is the 30th member of the tag gene family. Assignment of gene family names is controlled by WormBase. Before publication, requests for names should be made in WormBase.
There are a few exceptions to this format, like the genes cln-3.1, cln-3.2, and cln-3.3 which all are equally similar to the human gene CLN3.
Gene GCG names for non-elegans species in WormBase have the 3-letter species code prepended, like Cre-acl-5, Cbr-acl-5, Cbn-acl-5.
A gene can be a Pseudogene, or can express one or more non-coding RNA genes (ncRNA) or protein-coding sequences (CDS).
Pseudogenes
Pseudogenes are genes that do not produce a reasonable, functional transcript. They may be pseudogenes of coding genes or of non-coding RNA and may be whole or fragments of a gene and may or may not express a transcript. The boundary between what is considered a reasonable coding transcript is sometimes subjective as, in the absence of other evidence, the use of weak splice sites or short exons can often produce a putative, though unsatisfactory, model of a CDS. Pseudogenes and genes with a problematic structure are constantly under review in WormBase and new evidence is used to try to resolve their status.
CDSs
Coding Sequences (CDSs) are the only part of a Gene's structure that is manually curated in WormBase. The structure of the Gene and its transcripts are derived from the structure of their CDSs.
CDSs have a Sequence Name that is derived from the same Sequence Name as their parent Gene object, so the gene ‘F38H4.7’ has a CDS called ‘F38H4.7’. The CDS specifies coding exons in the gene from the START (Methionine) codon up to (and including) the STOP codon.
Any gene can code for multiple proteins as a result of alternative splicing. These isoforms have a name that is formed from the Sequence Name of the gene with a unique letter appended. In the case of the gene bli-4 there are 6 known CDS isoforms, called K04F10.4a, K04F10.4b, K04F10.4c, K04F10.4d, K04F10.4e and K04F10.4f.
It is common to refer to isoforms in the literature using the CGC gene family name with a letter appended, for example pha-4a, however this has no meaning within the WormBase database and searches for pha-4a in WormBase will not return anything. The correct name of this isoform is either the CDS/Transcript name: F38A6.1a, or even better, the Protein name: WP:CE15998.
Gene transcripts
The transcripts of a gene in WormBase are automatically derived by mapping any available cDNA or mRNA alignments onto the CDS model. These gene transcripts will therefore often include the UTR exons surrounding the CDS. If there are no available cDNA or mRNA transcripts, then the gene transcripts will have exactly the same structure as the CDS that they are modelled on.
Gene transcripts are named after the Sequence Name of the CDS used to create them, for example, F38H4.7 or K04F10.4a.
However, if there is alternative splicing in the UTRs, which would not change the protein sequence, the alternatively spliced transcripts are named with a digit appended, for example: K04F10.4a.1 and K04F10.4a.2. If there are no isoforms of the coding gene, for example AC3.5, but there is alternative splicing in the UTRs, there will be multiple transcripts named AC3.5.1 and AC3.5.2, etc. If there are no alternate UTR transcripts the single coding_transcript is named the same as the CDS and does not have the .1 appended, as in the case of K04F10.4f.
Operons
Groups of genes which are co-transcribed as operons are curated as Operon objects. These have names like CEOP5460 and are manually curated using evidence from the SL2 trans-spliced leader sequence sites.
Non-coding RNA genes
There are several classes of non-coding RNA gene classes in WormBase:
tRNA genes are predicted by the program ‘tRNAscan-SE’.
rRNA genes are predicted by homology with other species.
snRNA genes are mainly imported from Rfam.
piRNA genes are from an analysis of the characteristic motif in these genes.
miRNA genes have mainly been imported from miRBase. They have the primary transcript and the mature transcript marked up. The primary transcript will have a Sequence name like W09G3.10 and the mature transcript will have a letter added to this name like W09G3.10a (and if there are alternative mature transcripts, W09G3.10b, etc.).
snoRNA genes are mainly imported from Rfam or from papers.
ncRNA genes that have no obvious other function but which are obviously not protein-coding and are not pseudogenes are curated. Many of these have conserved homology with genes in other species. A few of these are expressed on the reverse sense to protein-coding genes.
There is also one scRNA gene.
Transposons
Transposons are not classed as genes and so do not have a parent gene object. Their structure is curated as a Transposon_CDS object with a name like C29E6.6.
Other species
The non-elegans species in WormBase have genomes that have been assembled from sequencing technologies that do not involve sequencing cosmids or YACs. These species therefore do not have sequence names for CDSs and gene transcripts that are based on cosmid names. Instead they have unique alphanumeric identifiers constructed like the names in the table below.
Proteins
The protein products of gene are created by translating the CDS sequences. Each unique protein sequence is given a unique identifying name like WP:CE40440. Examples of the protein identifier names for each species in WormBase is given in the table, below.
It is possible for two CDS sequences from separate genes, within a species, to be identical and so it is possible to have identical proteins coded for by separate genes. When this happens, a single, unique identifying name is used for the protein even though it is produced by two genes.
ParaSite
WormBase ParaSite is a sub-portal for approximately 100 draft genomes of parasitic helminths (nematodes and platyhelminthes) developed at the European Bioinformatics Institute and Wellcome Trust Sanger Institute. All genomes are assembled and annotated. Additional information such as protein domains and Gene Ontology terms are also available. Gene trees allow the alignment of orthologues between parasitic worms, other nematodes and non-worm comparator species. A BioMart data-mining tool is offered to permit large scale access to the data.
WormBase management
WormBase is a collaboration among the European Bioinformatics Institute, Wellcome Trust Sanger Institute, Ontario Institute for Cancer Research, Washington University in St. Louis, and the California Institute of Technology. It is supported by the grant P41-HG002223 from the National Institutes of Health and the grant G0701197 from the British Medical Research Council . Caltech carries out the biological curation and develops the underlying ontologies, the EBI carries out sequence curation and computation as well as database builds, the Sanger is primarily involved in curation and display of parasitic nematode genomes and genes, and the OICR develops the website and main data mining tools.
See also
Flybase
Xenbase
Notes and references
External links
WormBase
WormBase ParaSite
The WormBook website, the online textbook companion to WormBase.
Textpresso, search engine for C. elegans and other biological literature.
WormBase Wiki
Release notes, details of the latest WormBase release
WormBase: better software, richer content Nucleic Acids Research article describing WormBase (2006).
Caenorhabditis elegans
Genetics databases
Genetics in the United Kingdom
Genomics organizations
Model organism databases
South Cambridgeshire District
Wellcome Trust | WormBase | Biology | 3,224 |
8,915,378 | https://en.wikipedia.org/wiki/Persin | Persin is a fungicidal toxin present in the avocado. Persin is an oil-soluble compound structurally similar to a fatty acid, a colourless oil, and it leaches into the body of the fruit from the seeds.
The relatively low concentrations of persin in the ripe pulp of the avocado fruit is generally considered harmless to humans. Negative effects in humans are primarily in allergic individuals. When persin is consumed by domestic animals through the leaves or bark of the avocado tree, or skins and seeds of the avocado fruit, it is toxic and dangerous.
Presence in the avocado plant
All parts of the avocado — the fruit, leaves, stems, and seeds — contain the toxin. The leaves are the most dangerous part.
Toxicity
Consumption of the leaves and bark of the avocado tree, or the skin and pit of the avocado fruit have been shown to have the following effects:
In birds, which are particularly sensitive to the avocado toxin, the symptoms are: increased heart rate, myocardial tissue damage, subcutaneous edema of the neck and pectoral regions, labored breathing, disordered plumage, unrest, weakness, apathy and anorexia. High doses cause acute respiratory syndrome (asphyxia), with death approximately 12 to 48 hours after consumption. Caged birds seem to be more sensitive to the effects of persin, whereas, for example, turkeys and chickens seem more resistant.
Lactating rabbits and mice: non-infectious mastitis and agalactia after consumption of leaves or bark.
Rabbits: cardiac arrhythmia, submandibular edema and death after consumption of leaves.
Cows and goats: mastitis, decreased milk production after consumption of leaves or bark. Goats develop severe mastitis after ingesting 20 g/kg of leaves, and 30 g/kg of leaves usually results in cardiac injury.
Horses: clinical effects occur mainly in mares, and includes noninfectious mastitis, as well as occasional gastritis and colic. Swelling of the head, tongue, and brisket may also be present.
Cats, dogs: mild stomach upset may occur, with potential to cause heart damage. Dogs might be more resistant.
Hares, pigs, rats, sheep, ostriches, chickens, turkeys and fish: symptoms of intoxication similar to those described above. The lethal dose is not known; the effect is different depending upon the animal species.
Mice: non-fatal injury to the lactating mammary gland from 60 to 100 mg/kg of persin. Necrosis of myocardial fibres with 100 mg/kg of persin. 200 mg/kg of persin is lethal.
Diagnosis
Diagnosis of avocado toxicosis relies on history of exposure and clinical signs. There are no readily available specific tests that confirm diagnosis.
Treatment
NSAIDs, pain relievers, medications for congestive heart failure.
Additional pharmacology
Animal studies show that exposure to persin leads to apoptosis in certain types of breast cancer cells. It has also been shown to enhance the cytotoxic effect of tamoxifen in vitro. Persin is however highly insoluble in aqueous solutions and more research will be needed to put it into a soluble tablet form.
References
Plant toxins
Veterinary toxicology
Acetate esters | Persin | Chemistry,Environmental_science | 697 |
2,018,285 | https://en.wikipedia.org/wiki/Polyketone | Polyketones are a family of high-performance thermoplastic polymers. The polar ketone groups in the polymer backbone of these materials gives rise to a strong attraction between polymer chains, which increases the material's melting point (255 °C for copolymer (carbon monoxide ethylene), 220 °C for terpolymer (carbon monoxide, ethylene, propylene). Trade names include Poketone, Carilon, Karilon, Akrotek, and Schulaketon. Such materials also tend to resist solvents and have good mechanical properties. Unlike many other engineering plastics, aliphatic polyketones such as Shell Chemicals' Carilon are relatively easy to synthesize and can be derived from inexpensive monomers. Carilon is made with a palladium(II) catalyst from ethylene and carbon monoxide. A small fraction of the ethylene is generally replaced with propylene to reduce the melting point somewhat. Shell Chemical commercially launched Carilon thermoplastic polymer in the U.S. in 1996, but discontinued it in 2000. Hyosung announced that they would launch production in 2015.
Industrial production
The ethylene-carbon monoxide co-polymer is most significant. Industrially, this polymer is synthesized either as a methanol slurry, or via a gas phase reaction with immobilized catalysts.
Polymerization mechanism
Initiation and termination
Where external initiation is not employed for the methanol system, initiation can take place via methanolysis of the palladium(II) precursor, giving either a methoxide or a hydride complex. Termination occurs also by methanolysis. Depending on the end of the growing polymer chain, this results in either an ester or a ketone end group, and regenerating the palladium methoxide or hydride catalysts respectively.
Propagation
A mechanism for the propagation of this reaction using a palladium(II)-phenanthroline catalyst has been proposed by Maurice Brookhart:
Polyketones are noted for having extremely low defects (double ethylene insertions or double carbonyl insertions, in red):
The activation barrier to give double carbonyl insertions is very high, so it does not occur. Brookhart's mechanistic studies show that the concentration of the alkyl-ethylene palladium complex required to give double ethylene insertions is very low at any one point:
Additionally, the Gibbs energy of activation of the alkyl-ethylene insertion is ~ 3 kcal/mol higher than the corresponding activation barrier for the alkyl-carbon monoxide insertion. As a result, defects occur at an extremely low rate (~ 1 part per million). The industrially-relevant palladium-dppp catalyst has also been investigated.
Importance of bidentate ligands
Where palladium(II) pre-catalysts bearing monodentate phosphine ligands are used in methanol, a relatively high fraction of methyl propionate is produced. In comparison, where chelating diphosphine ligands are used, this side-product is absent. This observation is rationalized: the bis(phosphine) complex can undergo cis-trans isomerization to give the sterically favored trans isomer. The propionyl ligand is now trans- to the open coordination site or ethylene ligand, and is unable to undergo migratory insertion. Instead, solvolysis by methanol occurs, which gives the undesired methyl propionate side-product.
Whereas much effort has involved discrete palladium complexes, an example in the patent literature claims that a combination of Lewis acid (aluminum, iron, or titanium halide) and a source of palladium (as a salt or the metal) is effective for making polyketone.
References
External links
Macrogalleria
Organic polymers
Thermoplastics | Polyketone | Chemistry | 820 |
51,623,631 | https://en.wikipedia.org/wiki/Discovery%20and%20development%20of%20gastrointestinal%20lipase%20inhibitors | Lipase inhibitors belong to a drug class that is used as an antiobesity agent. Their mode of action is to inhibit gastric and pancreatic lipases, enzymes that play an important role in the digestion of dietary fat. Lipase inhibitors are classified in the ATC-classification system as A08AB (peripherally acting antiobesity products).
Numerous compounds have been either isolated from nature, semi-synthesized, or fully synthesized and then screened for their lipase inhibitory activity but the only lipase inhibitor on the market (October 2016) is orlistat (Xenical, Alli).
Lipase inhibitors have also shown anticancer activity, by inhibiting fatty acid synthase.
Discovery of lipase inhibitors and their development
Pancreatic lipase inhibitor was originally discovered and isolated from fermented broth of the Streptomyces toxytricini bacterium in 1981 and named lipstatin. It is a selective and potent irreversible inhibitor of human gastric and pancreatic lipases. Tetrahydrolipstatin, more commonly known as orlistat, is a saturated derivative produced by hydrogenation. It was developed in 1983 by Hoffmann-La Roche and is a more simple and stable compound than lipstatin. For that reason orlistat was chosen over lipstatin for development as an anti-obesity drug. It is the only available FDA-approved oral lipase inhibitor and is known on the market as Xenical and Alli.
Initially orlistat was developed as a treatment for dyslipidemia, not as an anti-obesity agent. When researchers found out that it promotes less energy uptake, the focus was switched to obesity.
Orlistat has a few adverse effects. Most reported side effects are gastrointestinal; including liquid stools, steatorrhea and abdominal pain. More severe and serious are interactions between orlistat and anticoagulants when given in combination. It can increase INR which can lead to insufficient anticoagulant treatment and bleeding. These adverse effects of orlistat are more common early in the therapy but usually decrease with time. Pancreatic lipases do not only affect the hydrolysis of triglycerides but are also necessary for hydrolysis of fat soluble vitamins. Due to this, the absorption of fat-soluble vitamins may decrease. Therefore, it is recommended to take a multiple-vitamin supplement during orlistat therapy.
Cetilistat, a new lipase inhibitor, is an experimental drug for obesity. In October 2016 the drug was still in clinical trials.
Cetilistat was developed to overcome the adverse effects on the gastrointestinal tract of orlistat. It has a different structure but similar inhibition activity to the gastrointestinal lipase. However cetilistat interacts differently with the fat micelles from digested food, therefore it has less side effects and better tolerability.
Mechanism of action
The lipase inhibitors lipstatin and orlistat act locally in the intestinal tract. They are minimally absorbed in the circulation because of their lipophilicity. Hence, they do not affect systemic lipases.
The mechanism of lipase inhibitors in fat digestion is shown in figure 1. These inhibitors bind covalently as an ester to the serine hydroxyl group at the active site on pancreatic- and gastric lipases and form a stable complex.
This results in a conformational change in the enzyme which causes exposing of the catalytic active site. When the active site is exposed, the hydroxyl group on the serine residue is acylated. This leads to irreversible inactivation of the enzyme.
The inactive lipase is incapable of hydrolysing fats into absorbable fatty acids and monoglycerides, therefore triglycerides are excreted undigested with faeces. With this mode of action calorie uptake from fat in food is limited, hence body weight is reduced. The main role of lipase inhibitors is therefore to inhibit lipases in the gastrointestinal tract, but they do not have significant activity against proteases, amylases or other digestive enzymes.
Cetilistat has a bicyclic structure but lacks the β-lactone ring. It acts in a similar way as a typical lipase inhibitor that has the β-lactone structure.
Drug target
Lipases in the gastrointestinal tract play a critical role in fat digestion. More than 95% of fat in food consists of triglycerides, which are categorized based on the length of fatty acids connected to glyceride backbone. The length of long-chain triglycerides prevent their absorption through the intestinal mucosa. For that reason lipases in the gastrointestinal tract must hydrolyse it to smaller molecules, free fatty acids and monoglyceride, before absorption can occur.
Gastric lipase
Gastric- and lingual lipases are the two acidic lipolytic enzymes that origin preduodenal but the gastric lipase is in much higher levels in humans.
Gastric lipase is synthesized and secreted from gastric chief cells in the stomach and is stable at pH 1,5-8,
but has maximum activity at pH 3-6.
Fat digestion begins when gastric lipase hydrolyses dietary triglycerides, by cleaving only one long-, medium- or short-acyl chain from the glyceride backbone and release free fatty acids and diacylglycerols. The enzyme hydrolyses esters at position sn-3, the acyl chain at the bottom, more rapidly than esters at sn-1 position, the acyl chain on the top of the glyceride backbone. However the gastric lipase activity against phospholipids and cholesterol esters is poor.
Gastric lipase is composed of 379 amino acids. Fully glycosylated protein is 50kDa and unglycosylated enzyme is 43kDa. However deglycosylation of the enzyme does not affect the activity of the enzyme. The hydrophobic region around Ser152, which has the hexapeptide sequence Val-Gly-His-Ser-Gln-Gly, is essential for the catalytic activity of gastric lipase. At the N-terminal, Lys4 is necessary for the enzyme to bind at lipid-water interfaces.
Pancreatic lipase
Pancreatic lipase is the most important lipolytic enzyme in the gastrointestinal tract and is essential for fat digestion.
Pancreatic lipase is secreted from acinar cells in the pancreas and its secretion, with the pancreatic juice to the small intestine, is stimulated by hormones. These hormones are induced in the stomach by hydrolysed products in gastric digestion.
The pancreatic lipase is secreted to the small intestine where it is most active, at pH 7-7,5.
Pancreatic lipase hydrolyses triglycerides and diglycerides by cleaving acyl chains at the sn-1 and sn-3 position
and releases free fatty acids and 2-monoglycerides.
The pancreatic lipase consists of 465 amino acids. Schematic picture of pancreatic lipase is shown in figure 2. Pancreatic and gastric lipases share little homology but have the same hydrophobic region at the active site, which is important for the lipolytic activity. The hydrophobic region has the hexapeptide sequence Val-Gly-His-Ser-Gln-Gly and is at Ser153 in pancreatic lipases but Ser152 in gastric lipases.
Chemistry of lipase inhibitors
β-lactone class
The chemical structure of compounds play an important role in binding to their target. The most important and necessary chemical group for the binding and activity of these compounds is the β-lactone (beta-lactone) ring which is the central pharmacophore. The β-lactone moiety is shown in red in the structures in the table below.
Researches have shown that cleavage of the β-lactone ring results in loss of inhibitory activity of the inhibitors, which makes the β-lactone structure a crucial part in biological activity.
The lactone ring structure binds irreversibly to the active site of the lipase and forms covalent bond, which leads to inhibition.
Drugs of this class include:
Lipstatin, the first known lipase inhibitor, comes from a natural source. It has a β-propiolactone ring, which has a 2,3-trans-disubstituted linear alkyl chains located at the α- (C6) and β-site (C13) of the compound. It contains N-formyl-L-leucine amino acid connected to the β-alkyl chain via ester-bond. The structure of Lipstatin is shown in the table below.
Orlistat is a semi-synthetic compound, which has a similar structure to lipstatin. They differ only in the saturation of the β-alkyl chain, where orlistat is saturated while lipstatin has two double bonds in the side chain. The structure of orlistat is shown in the table from the last section.
Structure-activity relationship (SAR)
Most natural lipase inhibitors differ only in the structure of the side chains and the nature of the linked amino acids, but have the same β-lactone ring in (S)-configuration as a primary structure.
Besides the role of the β-lactone ring in structure-activity relationship, the nature of the functional groups (e.g. ester or ether and the chain length at the β-site) also matter. However a trans-position of the side-chains on the β-lactone ring is crucial for its activity.
Synthetic lipase inhibitor: cetilistat
Cetilistat is a synthetic lipase inhibitor. Instead of having a β-lactone structure like most of the lipase inhibitors, it has a bicyclic benzoxazinone ring. It is also a lipophilic compound but differs in the hydro- and lipophilic side chain.
The structure and more information about Cetilistat is shown in the table on the right.
Other lipase inhibitors
Other lipase inhibitors have been recognized, e.g. from different plant products. These include alkaloids, carotenoids, glycosides, polyphenols, polysaccharides, saponins and terpenoids. However, none of these have been used clinically as lipase inhibitors. More active lipase inhibitors are the lipophilic compounds from microbial sources.
Lipase inhibitors from microbial source can be divided into two classes based on their structure. Those who have a β-lactone ring are lipstatin, valilactone, percyquinin, panclicin A-E, ebelactone A and B, vibralactone and esterastin. Those who do not have a β-lactone ring are (E)-4-amino styryl acetate, ε–polylysine and caulerpenyne.
Lipase inhibitors have also been made synthetically, e.g. cetilistat, based on the structure of triglycerides and other natural lipase substrates. However, the synthetic lipase inhibitors differ in structure and some of them lack the β-lactone ring.
Additional activities
Potential for cancer treatment
As further discussed, orlistat is a pancreatic and gastric lipase inhibitor. Orlistat is also a potent thioesterase inhibitor and therefore inhibits fatty acid synthase (FAS). Since FAS is essential for tumor cells, for its growth and survival, and is upregulated and overexpressed in variety of tumors, scientists have high expectations for FAS as an oncology drug target. Orlistat inhibits FAS with the same mechanism as it does with pancreatic lipase, that is by binding covalently to the active serine site.
This effect of orlistat as a FAS-inhibitor was first identified in a high throughput screening for enzymes with prostate cancer inhibition activity. However FAS is resistant to many cancer medicines. Orlistat sensitizes these FAS resistance cancer drugs, by inhibiting FAS. There is a low FAS expression in normal tissues so the activity of orlistat on normal cells is limited.
Because of the difference in FAS expression between normal cells and cancer cells, orlistat selectively targets tumor cells. Due to this FAS is a potential drug target in cancer therapy.
Orlistat works locally in the intestines as a lipase inhibitor, and therefore suffers from several limitations in its development as a systemic drug. Its poor bioavailability and solubility are the main reasons to develop a new anticancer analogue to overcome these limitations.
References
Lipase inhibitors
Gastrointestinal lipase inhibitors | Discovery and development of gastrointestinal lipase inhibitors | Chemistry,Biology | 2,751 |
35,953,535 | https://en.wikipedia.org/wiki/Hausdorff%20completion | In algebra, the Hausdorff completion of a group G with filtration is the inverse limit of the discrete group . A basic example is a profinite completion. The image of the canonical map is a Hausdorff topological group and its kernel is the intersection of all : i.e., the closure of the identity element. The canonical homomorphism is an isomorphism, where is a graded module associated to the filtration.
The concept is named after Felix Hausdorff.
See also
linear topology
References
Nicolas Bourbaki, Commutative algebra
Commutative algebra | Hausdorff completion | Mathematics | 121 |
25,958,124 | https://en.wikipedia.org/wiki/MathJax | MathJax is a cross-browser JavaScript library that displays mathematical notation in web browsers, using MathML, LaTeX, and ASCIIMathML markup. MathJax is released as open-source software under the Apache License.
The MathJax project started in 2009 as the successor to an earlier JavaScript mathematics formatting library, jsMath, and is managed by the American Mathematical Society. The project was founded by the American Mathematical Society, Design Science, and the Society for Industrial and Applied Mathematics and is supported by numerous sponsors such as the American Institute of Physics and Stack Exchange.
MathJax is used by web sites including arXiv, Elsevier's ScienceDirect, MathSciNet, n-category cafe, MathOverflow, Wikipedia (on the backend), Scholarpedia, Project Euclid journals, IEEEXplore, Publons, Coursera, and the All-Russian Mathematical Portal.
Features
MathJax is downloaded as part of a web page, scans the page for mathematical markup, and typesets the mathematical information accordingly. Thus, MathJax requires no installation of software or extra fonts on the reader's system. This allows MathJax to run in any browser with JavaScript support, including mobile devices.
MathJax can display math by using a combination of HTML and CSS or by using the browser's native MathML support, when available. The exact method MathJax uses to typeset math is determined by the capabilities of the user's browser, fonts available on the user's system, and configuration settings. MathJax v2.0-beta introduced SVG rendering.
In the case of HTML and CSS typesetting, MathJax maximizes math display quality by using math fonts if available and by resorting to images for older browsers. For newer browsers that support web fonts, MathJax provides a comprehensive set of web fonts, which MathJax downloads as needed. If the browser does not support web fonts, MathJax checks whether valid fonts are available on the user's system. If this does not work, MathJax provides images of any symbols needed. MathJax can be configured to enable or disable web fonts, local fonts, and image fonts.
MathJax uses the STIX fonts for including mathematics in web pages. Installing the fonts on the local computer improves MathJax’s typesetting speed.
MathJax can display mathematical notation written in LaTeX or MathML markup. Because MathJax is meant only for math display, whereas LaTeX is a document layout language, MathJax only supports the subset of LaTeX used to describe mathematical notation.
MathJax also supports math accessibility by exposing MathML through its API to assistive technology software, as well as the basic WAI-ARIA "role" and older alt attributes.
The MathJax architecture is designed to support the addition of input languages and display methods in the future via dynamically loaded modules. MathJax also includes a JavaScript API for enumerating and interacting with math instances in a page.
Browser compatibility
MathJax renders math in most popular browsers, including Internet Explorer 6+, Firefox 3+, Google Chrome 0.3+, Safari 2.0+, Opera 9.5+, iPhone/iPad Safari, and the Android browser. Some older versions of browsers do not support web fonts (with the @font-face CSS construct), so they have to use MathJax image font mode. The browser compatibility list is available at the official site.
Plugin support
MathJax can be easily added to many popular web platforms.
Node.js
MathJax can be used in Node.js since version 3; for version 2, the MathJax-node library provides Node.js compatibility.
Equation-editor compatibility
Any MathJax equation displayed in a supported browser can be copied out in MathML or LaTeX format via "Show Math as" sub-menu if right-button clicked or control-clicked on it. Then it can be pasted in any equation editor that supports MathML or LaTeX, such as Mathematica, MathType, MathMagic, or Firemath, for re-use.
Equations generated in MathML or LaTeX format by any 3rd party equation editor can be used in MathJax enabled web pages.
TeX support
MathJax replicates the math environment commands of LaTeX. AMS-LaTeX math commands are supported via extensions. MathJax also supports TeX macros and miscellaneous formatting like \color and \underline.
MathML support
MathJax added partial support for MathML 2.0 and some MathML 3.0 constructs in its beta 2 release. MathJax supports presentation MathML and, as of version 2.2, provides experimental support for content MathML.
CDN servers
The MathJax site has been providing a content delivery network (CDN) where the JavaScript needed for MathJax to work can be loaded by the browser at run time from the CDN. This simplifies the installation and ensures the latest version of the library is always used. Over time usage of the server has grown from 1.3TB per month traffic in 2011 to 70TB per month in 2017. Due to increasing cost of hosting the server, the main CDN server shut down at the end of April 2017. Alternative third party CDN servers are available.
See also
:Category:Symbol typefaces
Google Chart API
KaTeX – JavaScript alternative to MathJax
References
External links
Official website
SimpleMathJax, a MediaWiki extension
MathJax, a MediaWiki extension
Free mathematics software
JavaScript libraries
Software using the Apache license
Symbol typefaces | MathJax | Mathematics | 1,209 |
8,917,050 | https://en.wikipedia.org/wiki/Journal%20of%20Environmental%20Psychology | The Journal of Environmental Psychology is a peer-reviewed academic journal published by Elsevier. Its founding editors were David Canter (University of Liverpool) and Kenneth Craik (University of California, Berkeley) back in 1981. From 2004 to 2016, Robert Gifford (University of Victoria) was the editor-in-chief. In 2017 and 2018, Florian G. Kaiser (Otto-von-Guericke University) and Jeffrey Joireman (Washington State University) were the co-chief editors. From 2019 to 2021 Sander van der Linden (University of Cambridge) was the Editor-in-Chief. Since 2021, Drs. Lindsay J. McCunn and Wesley Schultz have co-edited the journal.
The journal is the primary outlet for academic research in environmental psychology and reports scientific research on all human interactions with the built, social, and natural environment, with an emphasis on the individual and small-group level of analysis. The journal is published in association with the International Association of Applied Psychology (IAAP).
According to the Journal Citation Reports, Journal of Environmental Psychology had a 2020 impact factor of 5.192. This increased in 2021 to 7.649.
References
External links
Elsevier academic journals
English-language journals
Social psychology journals
Environmental social science journals
Academic journals established in 1980
Quarterly journals
Environmental psychology | Journal of Environmental Psychology | Environmental_science | 267 |
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